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BISC219/F13: RNAi Lab 8
Lab 8: Heat Shock Proteins (HSP's) and Heat Shock Factor -1 (HSF-1)
Background materials for HSP's, HSF-1 and the reporter assay are provided by Cassandra Theusch and Peter Kuhn; Elisabeth A. Cox and Theresa M. Grana.
Although "heat shock proteins" are best characterized in associated with temperature, mounting evidence suggests that heat shock proteins are expressed and play vital roles during many types of cell stress. Heat shock proteins work by helping other proteins fold properly and have been classified in a functional category of proteins called molecular chaperones. Molecular chaperones catalyze the folding of a newly-translated peptide into the secondary and tertiary structures that characterize the mature protein product. Improperly-folded proteins are unstable, prone to aggregation, and dysfunctional.
Correct protein folding is extremely important for protein and cell function. . Alterations in protein structure, including secondary and tertiary structure, lead to altered protein function. Similarly, improperly or incompletely folded proteins are likely to be dysfunctional and lead to complications for the cell. It should come as no surprise that improper protein folding in cells of the human body can lead to severe diseases. For example, transmissible spongiform encephalopathies (TSE's), such as mad cow disease, chronic wasting disease, and Creutzfield-Jakob disease, are the result of improperly-folded proteins called prions. A buildup of prions interferes with cell functions and leads to apoptosis (programmed cell death). Other protein folding diseases exhibit similar pathological mechanisms. Alzheimer's disease is thought to result from the aggregation of improperly-folded amyloid protein. Amyloid plaques accumulate in the brain and damage surrounding neurons as they grow. Certain types of cancer are associated with molecular chaperone dysfunction, which allows tumor cells to grow abnormally and survive adverse conditions.
Heat shock factor 1 (HSF-1) is a transcription factor which is required for transcription/expression of genes encoding many subtypes of heat shock proteins. Under normal cell conditions, HSF-1 expressed in the cytoplasm migrates occasionally, in small amounts, to the nucleus to activate transcription of genes encoding heat shock proteins to carry out normal cell functions. During a cell's response to stressful conditions, HSF-1 is activated in large amounts, polymerizes, and migrates from the cytoplasm to the nucleus to search out recognized promoter sequences. This high level expression of heat shock proteins allows for refolding of proteins following stress and recovery of protein function. The specific mechanisms and molecular triggers of HSF-1 activation and migration are still unclear. Some evidence points to certain subtypes of heat shock proteins binding with and phosphorylating HSF-1 during the stress response. Yet other HSP's may have roles inhibiting HSF-1, although scientists are still working to identify all the facets of HSF-1 regulation. More broadly, the types of stressful cellular stimuli which activate HSF-1 also have yet to be elucidated. This is a hot area of research currently, where scientists are hoping to answer some important questions about how cells respond to stressful stimuli. Perhaps your investigations will contribute to this research!
GFP and the reporter assay
A reporter assay is commonly used to assess the activity of transcription factors within a cell. You will use reporter assays to determine functional expression of the transcription factor HSF-1. A reporter assay exploits the expression of a measurable (or visible) protein, in this case GFP. The gene encoding GFP is transgenically engineered to lie downstream of a promoter to which the transcription factor binds and initiates transcription. This engineered "transgene" can be incorporated into the genome of an organism, such as C. elegans. Therefore, when conditions are right and the transcription factor's expression is high enough, reporter gene is transcribed, and this can be measured by the amount of reporter protein produced.
Green fluorescent protein (GFP) is a commonly-used reporter protein, and, as its name suggests, is a fluorescent protein used in countless ways to visualize and quantify cellular molecules and processes. Originally, GFP was identified in and isolated from the marine jellyfish Aequorea victoria. However, modern advances in molecular biology have produced transgenic forms of GFP to more aptly suit certain experimental requirements. Due to the explosion of discoveries through experiments using GFP, the 2008 Nobel Prize in Chemistry was awarded to Martin Chalfie, Osamu Shimomura, and Roger Tsien for the initial discovery of GFP.
Your experiments will use a transgenic C. elegans strain which has been engineered to contain within its genome a reporter gene. This reporter construct encodes GFP under the control of a hsp-16.2 promoter. (Normally, expression of hsp-16.2 genes results in HSP-16.2 protein production.) HSP-16.2 is one subtype in the family of heat shock proteins, and therefore, it carries out molecular chaperone duties when it is present in the cell. HSF-1 binds to and initiates transcription via the promoter to hsp-16.2. Genetic engineers merely chopped out the promoter to hsp-16.2, pasted it onto the gene encoding GFP, and inserted the combo into a worm's genome – a reporter gene was born!
Figure 1: Construction of the GFP reporter transgene. The promoter region of hsp-16.2 was pasted onto the gene encoding GFP. Therefore, transcriptional activity at the hsp promoter can be measured by the levels of GFP in the cell.
Under normal conditions, HSF-1 is present in cells, but its low level of activation cannot be directly measured using the techniques you will use in lab. When a cell is stressed, HSF-1 is phosphorylated and activated in the large amounts measurable using this GFP reporter assay. Activated HSF-1 up-regulates the transcription of the hsp16.2/gfp transgene, which allows measurement of activation through detection of GFP using fluorescence microscopy.
Lab 8: Series 3- Creating the feeding strain of bacteria for RNAi in C. elegans
In order for RNAi to be successful we must insert the plasmid expressing dsRNA of our C. elegans gene of interest into the bacteria that will make lots of double stranded RNA. We will then feed the bacteria that is full of double stranded RNA specific to our gene of interest to our worms. The process of inserting the plasmid into bacteria is called transformation. Transformation, either chemically or electrically, opens up pores or channels in the bacterial membrane that allows for uptake of the plasmid DNA.
Precise pipetting is required for transformation to be effective. Your instructor will demonstrate the correct technique. If you have any questions, please consult with her/him before proceeding with any micropipetting.
To recap what has been done in order for your to be ready to do today's work:
Yesterday you inoculated a few milliliters of LB broth containing E. coli that we are sure have maintained our genetically engineered plasmid, pPD129.36, modified to contain an antibiotic resistance gene to ampicillin and all or part of the C. elegans hsf-1 gene that you want to investigate. You added ampicillin to the broth to ensure that the plasmid DNA would be maintained by the cells. Overnight the bacteria have grown to high density and the plasmid DNA has undergone many replications. However since you started with a single colony of bacteria and that colony grew from a single transformed cell, all the copies of the plasmid DNA in your overnight culture should be identical ("clones" of one another). To isolate the plasmid DNA from this bacterial strain that expresses C. elegans hsf-1 , you will perform what is commonly called a "mini-prep". This term distinguishes the procedure from a "maxi-" or "large scale-prep" which involves a larger volume of cells and additional steps of purification. The overall goal of each "prep" is the same--to separate the plasmid DNA from the chromosomal DNA so that a certain gene on the plasmid DNA can be studied further.
Synopsis of Today's Work
Today you will transform the isolated plasmid DNA, pPD129.36+hsf-1, into an IPTG inducible strain of E. coli called HT115(DE3), and spread the transformed bacteria onto LB agar media supplemented with ampicillin (resistance conferred by a gene expressed from the plasmid).
Part 1: Plasmid DNA Isolation
What's Happening in Your MiniPrep
To isolate plasmid DNA from an overnight culture of cells, the media is removed from the cells by centrifugation. The cells are resuspended in "Solution I" which contains Tris to buffer the cells and EDTA to bind divalent cations in the lipid bilayer, thereby weakening the cell envelope. Upon the addition of "Solution II," the chromosomal DNA and the plasmid DNA are denatured by the sodium hydroxide, and the cellular proteins and lipids are dissolved by the detergent, sodium dodecyl sulfate (SDS). The pH of the solution is returned to neutral by the potassium acetate in "Solution III." At neutral pH the SDS precipitates from solution, carrying with it the dissolved proteins and lipids. In addition, the DNA strands renature at neutral pH. The chromosomal DNA, which is much longer than the plasmid DNA, renatures as a tangle that gets trapped in the SDS precipitate. The plasmid DNA renatures normally and stays in a water based solution. In this way the plasmid DNA is separated from the chromosomal DNA, the proteins and the lipids of the cell. Plasmid DNA can be precipitated out of solution in absolute ethanol and then put back into solution (in an appropriate concentration) in water. The ingredients and concentrations of a stock solution of all reagents (such as Solutions I, II, and III) can be found in the Media Recipes section of this section of the wiki.
Plasmid DNA Isolation
Only one of your two overnight cultures should appear cloudy with bacterial growth. If your control is cloudy, please inform your instructor. (You can find the ingredients and concentrations for ingredients of Solutions I, II, and III in the Series 3 Media Recipes page.
- To start the plasmid DNA isolation, label 2 microfuge tubes with pPD129.36+hsf-1 (our plasmid name + our C. elegans gene), plus your initials and team color.
- Check to be sure that your cells have not settled. If they have, mix the cultures but do NOT invert them because they will leak. Then pour some of the overnight culture so that both microfuge tubes are almost full. If you are nervous about pouring the bacteria, you can pipet 750 microliters into each tube twice, so that there is a total of 1.5 ml in each tube. The exact volume doesn't matter but the tubes should be quite full when you close the cap.
- Place the tubes in the room temperature microfuge so that the hinges of each cap is facing out. Paying attention to this small detail will help you know where in the tube to find your pellets. While it is not essential to do this in this step, it is a good habit to get into since sometimes pellets are very small and hard to see. Be sure your tubes are balanced, then spin the tubes for two minutes at 8,000 rpm. Check the rcf speed of the centrifuge while it is spinning (by hitting the toggle that changes the readout) and record the rcf's in your lab notebook. Relative centrifugal force (rcf) is what should be used in M&M to describe your speed since it is universal and rpm is rotor and centrifuge dependent.
- If the supernatant is not clear, recentrifuge until it is. When the supernatant is clear, pour it into the waste beaker that is on your bench, then flick the tube with the cap open to remove the last few drops of liquid. The cell pellet will not fall out.
- Resuspend your cell pellets COMPLETELY in 100 microliters of solution I. Pipet up and down until ALL of the cells are uniformly suspended in Solution I. Be sure to change tips between samples. Leave the cells at room temperature as you prepare solution II.
- To make solution II, mix 500 microliters of 2% SDS with 500 microliters of 0.4M NaOH in a microfuge tube. Close the cap and invert the tube several times to mix the contents. Add 200 microliters of solution II to each miniprep and invert the tubes five or six times to mix. In some cases the minipreps may appear to "clear" but don't worry if you don't see a big change in yours. Place the tubes on ice for five minutes.
- Add 150 microliters of solution III to each miniprep and immediately vortex each tube for 10 seconds with your vortex set at the highest setting. White clumps should appear in the solution after you vortex it. Place the tubes in the room temperature microfuge and spin for 3 minutes at the HIGHEST speed.
- While the minipreps are spinning, label another set of microfuge tubes with the name of the plasmid (pPD12936+hsf-1)and your initials or team color. The new tubes can be left at room temperature.
- A white pellet should be visible when you remove your minipreps from the microfuge. Use your P1000 to transfer 400 microliters of each supernatant to the appropriate clean microfuge tube. It's OK to leave some of the supernatant behind. Try to avoid transferring the white pellet.
- Add 1 ml of room temperature 100% ethanol to each new tube. The tubes will be quite full. Close the caps and invert the tubes at least five times to thoroughly mix the contents.
- Spin the tubes in the room temperature microfuge for 2 minutes at HIGHEST speed. It is important to orient your tubes so that the hinges are up this time, as the pellets are expected to be barely visible.
- Pour off the supernatants into the waste beaker on your bench then flick out the last few drops. The tubes do not have to be completely dry.
- Carefully, wash the pellets with 500 microliters of 80% ethanol. (You may need to make a few mls of 80% ETOH from the 100% ethanol stock provided). When you wash the pellets, add the 80% ethanol slowly and carefully, so that the liquid flows down the side of the tube away from the pellet. After the ethanol has been dispensed, immediately remove it with the same tip, making sure to keep the tip on the side of the tube that doesn't have your pellet. Some liquid will remain in the tube, and it can and must be removed using your P200, set to 100 microliters. Try to remove as much of the ethanol as you can (without removing your pellet!). The pelleted DNA will have to be completely dry before you add water or your DNA will not go into solution.
- After all the DNA pellets have been washed, put your tubes with their caps open in the SpeedVac that is at the back of the lab. If you were able to remove most of the ethanol with the P200, then after two or three minutes the last drops of ethanol will have evaporated and the pellet will be barely visible. If the DNA pellet is invisible please see your instructor to determine how much water to use in the next step.
- If you have a visible pellet of DNA, add 30 microliters of sterile water to each tube and vortex each tube enough for all of the DNA to be off the wall of the tube and into solution. The pelleted plasmid DNA must dissolve completely in the water. The liquid can be brought back to the bottom of the tubes by spinning for a few seconds in the microfuge. You can then combine the dissolved plasmid DNA into one of the two tubes so that you have approximately 60 microliters of plasmid DNA as one aliquot. Store the DNA on ice until you are ready to use part of it and then give the rest to your instructor to freeze. DO NOT DISCARD ANY OF YOUR PLASMID ISOLATE!
Part 2: Measuring the concentration of plasmid DNA using the NanoDropper
Proper transformation requires the concentration of bacteria to plasmid DNA to be right. We will use a nano-dropper to determine the concentration of the plasmid DNA from a previous plasmid isolation procedure.
Use the ThermoScientific NanoDrop Spectrophotometer in L308 to measure DNA by taking Absorbance at A260nm. This spectrophotometer uses only 1 microliter of sample and does not require cuvettes. The sample is held in place by fiber optic technology and surface tension that holds the sample in place between two optical surfaces that define the pathlength vertically and dynamically. Measurement can be assessed in a range of 2 to 3700nm/microliter dsDNA. These are expensive machines so make sure you follow the directions carefully and ask your instructor for guidance as needed.
More information is available from the manufacturer's website at: | http://www.nanodrop.com/HowItWorks.aspx
Using the Nanodropper
1. Clean the upper and lower optical surfaces of the sample retension device by pipetting 2 microliters of clean deionized water onto the lower optical surface. Close the lever arm and tap it a few times to bathe the upper optical surface. Lift the lever arm and wipe off both optical surfaces with a Kimwipe.
2. Open the NanoDrop software from the Desktop of the computer and select the nucleic acids module.
3. Initialize the machine by placing 1 microliter of clean deionized water onto the lower optic surface, lower the lever arm, and select initialize from the NanoDrop software. Once initialization is complete (~10sec.), clean both optical surfaces with a Kimwipe.
4. Perform a blank measurement by loading 1 microliter of purified deionized water.
Note that as in traditional spectroscopy, the blank will be subtracted from subsequent measurements. If you want to determine the contribution of a specific buffer or diluent, measure the buffer first using distilled water as a blank. If the buffer does not contribute to the A 260nm reading, then deionized water is fine to use as the blank. The water or buffer should always be measured to be sure that the instrument has been zeroed properly. The measurement of water or buffer should be zero or very close. All measurements are automatically normalized to 340nm.
5. Measure the nucleic acid sample by loading 1microliter of sample and selecting "measure". Record your DNA concentration in your lab notebook and on the tube of plamid DNA. Once the measurement is complete. Clean both optical surfaces with a Kimwipe and the machine is ready for the next sample.
You should ensure that the appropriate constant (50 for dsDNA or 40 for RNA) has been chosen. The software automatically calculates the nucleic acid concentration. If the calculation is done by hand, the A260nm is represented as a 1cm path for convenience, even though 1-nm and 0.2nm paths are actually used during the measurement cycle.
Clean Up
When the last sample was been measured, clean the sampling device by repeating step 1.
Part 3: Transformation of plasmid DNA into E. coli strain HT115(DE3)
The competent HT115(DE3) bacterial cells are on the instructor's bench. You will transform some of your plasmid DNA into these bacteria. The cells are very fragile, so treat them gently.
The genotype of the HT115(DE3) cells is: F-, mcrA, mcrB, IN(rrnD-rrnE)1, rnc14::Tn10(DE3 lysogen: lavUV5 promoter -T7 polymerase) (IPTG-inducible T7 polymerase) (RNAse III minus). This strain grows on LB or 2XYT plates. This strain is tetracycline resistant. The most important things about this strain is:
- It has an IPTG inducible T7 polymerase. The chemical IPTG (Isopropyl β-D-1-thiogalactopyranoside) is a lactose mimic and is commonly used to induce the production of large amounts of protein. In this case when the cells are incubated with IPTG lots of the polymerase T7 is made. This T7 polymerase binds to T7 specific promoters on the plasmid and transcribes lots of our gene of interest.
- RNAse III minus. The strain is lacking the RNAse III enzyme which typically breaks down double stranded RNAs. We want double stranded RNAs to accumulate.
The prep staff prepared these competent HT115(DE3) cells for you using the Inoue Method Media:Inoue bacterial transformation.doc. Reference: Inoue H., Nojima H., and Okayama H. 1990. High efficiency transformation of Escherichia coli with plasmids. Gene 96: 23-28. The cells were made competent to take up free plasmid DNA by this treatment. This treatment makes the cell wall and membrane more permeable and our transformation efficiency much greater but it weakens the cells; therefore you must keep them cold and mix them gently throughout the transformation (no vortexing!).
- Obtain a tube containing 50 μL of competent cells from your instructor.
- Label the top or the side of the tube with HT115(DE3), pPD12936+hsf-1, and your initials or team color.
- Consult with your instructor to determine how much of your plasmid DNA you should add to the cells to start the transformation. When you have determined the correct vol., pipet between 1μL and 10μL of your plasmid DNA to the tube. (The volume you should use is dependent on the conc. you achieved in your mini-prep.) Pipet up and down once to mix the DNA and the cells. Close the cap and let the transformation mixture sit on ice for 10 minutes.
- Heat shock by incubating the transformation mix at 42°C for 90 seconds, exactly. This step must be timed exactly. Remove the tube at the end of 90 seconds directly into to your ice bucket (carry your ice bucket over to the heat block) while you get your LB ready.
- Consult your instructor to determine the volume of warm LB broth you should add (usually between 250-500 microliters) to the transformation mix. LB aliquots can be found in the 37°C incubator near the lab door. When pipetting the media, remember to release your thumb on your micropipet slowly, to avoid splashing the liquid on the end of the barrel. The barrel is not sterile and if you see the liquid touch it, then discard the media in the waste beaker and try again with a new tip.
- Once you have added the LB, close the cap and invert the tube once or twice to mix the contents. Incubate at 37°C for 30-60 minutes in the bench top incubator/ mixer with occasional gentle mixing.
- While the plasmid DNA is being taken up by the competent cells and the new genes provided by the plasmid are being expressed by the bacteria, label one LB + amp agar plate and one LB + amp + tet plate. Label the bottom of the two plates with the strain's identity (HT115(DE3)), the plasmid used (pPD12936+hsf-1), the date, your initials and team color. You must label the bottom of the plated since the tops are easily switched. Put these plates in the hood with the blower on and with the lid ajar to dry the surface of the agar for about 10 minutes or until the surface looks dry but is not badly dehydrated.
- Once the transformation mix has incubated at 37°C for 30-60 minutes, invert it to mix the contents and pipet 100 microliters of transformed cells onto the center of each of your labeled plates. Pour 5-10 glass beads onto the plates. Put the lid back on and gently swirl the beads all over the agar to spread the transformed bacteria around. When you are done pour the beads into the beaker with disinfectant near the sink.
- Replace the lids and leave the agar plates undisturbed for a few minutes to allow for the liquid to be absorbed by the agar.
- Once they have dried enough that the surface does not appear wet, invert the plates (lid side down) and incubate them at 37°C for 24 hours. The plates should be incubated with the agar side up so that condensation will not drip onto the surface of the agar and smear the colonies that will be growing there.
- Save the remaining transformation mix for 24 hours or until we are sure that there is at least one colony growing on each of your plates.
What would it mean if you had no colonies on your plate? Normally, you would expect to have around 100 pale color colonies on each plate. If you have at least one well isolated colony on the plate, you're all set. After the 24 hour growth period the plate should be placed in the rack in the refrigerator labeled with your lab day. You will use a single colony from the plate to make an overnight broth culture on the day before next lab. If you have no colonies on one or more of your plates, please notify your instructor right away.
Before leaving lab today, give the rest of your isolated plasmid DNA to your instructor in a labeled microfuge tube. Make sure your tube is labeled with your name, lab day, plasmid name, DNA concentration and color coded with a piece of tape in your team color.
To do on the day before the next lab
You and your partner will return to the lab to make an overnight broth culture of your selected colony as described below. This process will create a sub-culture of many identical copies of the bacteria containing the plasmid carrying the construct to RNAi the gene that you want to study.
- Find your plate in the glass front refrigerator in a rack labeled with your lab day. Select a colony to start your overnight culture. At this point, ALL of your colonies should contain your plasmid of interest.
- Begin by obtaining two tubes of LB broth (each will have 5 ml of broth) from the refrigerator in the back left hand corner of the room.
- Add 5 microliters of the 50mg/ml ampicillin stock (also found in the refrigerator with the broth) to each tube. Calculate the effective concentration of ampicillin that you have in your LB tube (remember V1 x C1= V2 x C2) and record that information in your lab notebook.
- Gently swirl your LB +amp broth to mix the contents.
- Label the two sterile glass culture tubes with tape in your team color. Label one with "pPD129.36 hsf-1" and your initials. Label the other with your initials only.
- Inoculate the broth with your bacteria by using a sterile disposable loop to scrape your candidate colony off the plate. Be sure not to touch the plate with the loop except on the desired colony and don't pick up any satellite colonies! Gently swirl the loop in the LB+amp broth - you should be able to see the colony come off the loop. The second tube of broth labeled with just your initials is a control and should not be inoculated with bacteria as it is your control for contamination.
- Balance the 2 tubes across from each other on the rotating wheel in the 37C incubator at the front of the room when you come in the door.
- Incubate these broth cultures at 37°C overnight. Do not forget to make sure the wheel is rotating when you leave!


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subset: commoncrawl


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Understanding Rankings and Related Concepts in DEtools[rifsimp]
Ranking Defined
Properties of a Ranking
A ranking is essentially an ordering of all indeterminates in a system. To introduce rankings, we must first introduce some related concepts.
Dependent variable
This term describes any unknown function that is present in the input system. As an example, consider a system involving f(x,y) and its derivatives, g(x,y) and its derivatives, and exp(x). In a calculation, you may want to view f(x,y) as the solving variable, and g(x,y) as a parameter. Even in this case, these are both considered to be dependent variables. Because exp(x) is a known function, it is not considered to be a dependent variable.
Independent variable
For a problem containing f(x,y) and its derivatives, g(x,y) and its derivatives, and exp(x), x and y are the independent variables.
Any unknown not having a dependency, and not occurring in a dependency, is considered to be a constant. This is true even if it appears in a known function. For example, in the equation a*f(x,y)+sin(c)*g(x,y), both a and c are considered to be constants.
Note: The distinction between independent variables and constants is vital, since mistaking one for the other will not give a valid result for a system. For information on the specification of independent variables, please see rifsimp[options].
An indeterminate can be any constant, dependent variable, or derivative of a dependent variable. This does not include any known functions or independent variables. This is exactly the group of items that a ranking is defined for.
With these definitions, a more precise definition of ranking for a system is now possible:
A ranking is a strict ordering of all indeterminates appearing in a system in the course of a calculation. Note that it is necessary to define a ranking that works for more than just the indeterminates appearing in the initial system, because higher derivatives may appear in the course of the algorithm. For example, if the initial system contains only second order derivatives in the dependent variables, the specified ranking may need to be able to rank much higher order derivatives, as these may appear in a run of the algorithm.
Leading Indeterminate
The leading indeterminate of an equation is defined as the indeterminate in that equation that is of the highest rank (maximal with respect to the ranking).
The concept of a leading indeterminate is important for understanding how the rifsimp algorithm works, because any equation in which the leading indeterminate appears linearly is solved with respect to that indeterminate.
Rankings have a number of properties, some of which are required for the proper performance and termination of the algorithm, others of which may be helpful in tackling specific systems.
In any of the descriptions below, v1 and v2 are indeterminates that may depend on some of x1, x2, x3, ...
Preservation of ranking under differentiation
Given a ranking v1 > v2, this ranking also holds after equal differentiation of both v1 and v2 with respect to any independent variable, for all v1, v2 where v1 and v2 are indeterminates.
Note: You must restrict yourself to non-vanishing indeterminates (for example, for h(x) > g(x,y), differentiation with respect to y makes h(x) vanish, so the rule does not apply).
This property is required for the proper running of rifsimp. Once an equation is solved for the leading indeterminate, any differentiation of that equation (assuming that the leading indeterminate does not vanish) is also in solved form with respect to its new leading indeterminate (the derivative of the prior leading indeterminate).
Positive ranking
Given a ranking >, it must be true that diff(v1,x1) > v1 for all indeterminates v1 and all independent variables x1, as long as diff(v1,x1) is nonzero.
This property is required for the proper running of rifsimp, because it prevents any infinite chain of differential substitutions from occurring.
As an example, consider the solved form of the equation u[t]-u[tt] = 0 under a non-positive ranking u[t] = u[tt]. Differential elimination of the derivative u[xt] with respect to this equation will give u[xtt], then u[xttt], then u[xtttt], and so on. It will never terminate.
Total-degree ranking
Let dord() give the total differential order of an indeterminate with respect to all independent variables. Then for v1 and v2 derivatives of the same dependent variable, given a ranking >, then dord(v1) larger than dord(v2) implies v1 > v2.
For rifsimp to run correctly, a ranking does not have to be total degree. In some cases this does allow rifsimp to run faster, however. For those familiar with Groebner basis theory, a total degree ranking is similar to a total degree Groebner basis ordering, because calculations usually terminate more quickly than they would with a lexicographic ordering.
Orderly ranking
A ranking is said to be orderly if, for any indeterminate, no infinite sets of indeterminates that are lower in the ordering exist.
As an example of a ranking that is not orderly, we consider a ranking of f(x), g(x), and of all derivatives. If we choose to solve a system using rifsimp for f(x) in terms of g(x) (by specification of only f(x) in the solving variables), then this is not an orderly ranking, because g(x) and all of its derivatives are of lower rank than f(x) and any of its derivatives.
For rifsimp to run correctly, using the defaults for nonlinear equations, a ranking is not required to be orderly (see rifsimp[nonlinear].)
The Default ranking
The rifsimp default ranking is an orderly, total-degree ranking that is both positive and preserved under differentiation. Note that if the solving variables are specified, we may no longer be using the default ranking (since specification of solving variables alters the ranking. See "Specification of a ranking" below.
On input, rifsimp assumes that all dependent variables present in the input system are solving variables, and that all constants are to be viewed as parameters. The set of dependent variables is then sorted alphabetically, along with the set of constants. In contrast, the set of independent variables is ordered based on order of appearance in the dependency lists of the dependent variables.
A description of the sorting method for independent variables can be found in the "Specification of a ranking" section. Note that this sort is used to break ties for derivatives of equal differential order (under some circumstances).
Under the above restriction, the default ranking is defined by the following algorithm, which returns true if v1 is greater than v2 with respect to the default ordering (and false if v1 is less than v2).
# Criterion 1: Solving variables
If v1 is a solving variable, and v2 is not, then
If v2 is a solving variable, and v1 is not, then
# Criterion 2: Total Degree
If dord(v1) is larger than dord(v2), then
If dord(v2) is larger than dord(v1), then
# Criterion 3: Independent Variable Differential Order
Loop i := each independent variable in sorted order
If diff. order of v1 in i is larger than order of v2 in i, then
If diff. order of v2 in i is larger than order of v1 in i, then
end loop
# Criterion 4: Dependent Variable
If dependent var for v1 occurs before v2, then
If dependent var for v2 occurs before v1, then
The following examples are for a system containing f(x,y,z), g(x,y), and h(x,z), and derivatives with the constants a and b. The system is recognized with the following (already sorted):
Dependent Variables
Independent Variables
So, by default, f, g, and h are considered solving variables, and a and b parameters.
When the criteria are considered in order, any pair of distinct indeterminates are ranked by exactly one of them (as the ranking process then stops and returns the result). Of course to reach, say, criterion 3, criteria 1 and 2 must not differentiate the inputs. The following is a list of examples of each criterion in action:
Criterion 1
Criterion 2
Criterion 3
Criterion 4
Equivalence classes
Any step of the ranking process can be viewed as separating all possible indeterminates into a sorted chain of equivalence classes. When considering all criterion simultaneously, the size of each equivalence class must be exactly one. Sometimes viewing the ranking from the point of view of equivalence classes helps visualize how ranking is performed. As an example, we illustrate the equivalence classes for the prior example for each criterion considered independently of the other criteria:
Criterion 1: Rank solving variables higher than parameters
Criterion 2: Rank by differential order
Criterion 3: Rank by differential degree in each independent variable in turn
Criterion 4: Rank by dependent variable or constant name
So the process is equivalent to determining in which equivalence class each indeterminate falls, and checking if this criterion distinguishes the two input indeterminates.
Specification of a ranking
Three options can be used to control the ranking in rifsimp. Two of these perform simple modifications to the default ranking, while the third allows complete control of the ranking.
Specification of solve variables
As mentioned in the "Default ranking" section, specification of solving variables in a manner or order different from the default order changes the ranking. The solving variables can be specified in two ways:
1. Simple List
When the vars parameter is entered as a simple list, it affects the ranking in the following ways:
Criterion 1 of the default ranking is changed to add an additional class of indeterminates, which is specified by the solving variables. Specifically, any indeterminate mentioned in vars is ranked higher than any indeterminate not in vars. Any dependent variables not mentioned in vars are still ranked higher than any constants not mentioned in vars.
As an example, suppose an input system contained f(x,y,z), g(x,y), h(x,z), a, b, and c. If vars had been specified as [f(x,y,z),b,h(x,y)], then f, h, any f or h derivatives, and the constant c would be ranked higher than g and any g derivatives, which would be ranked higher than the constants a and b. Using equivalence classes, criterion 1 becomes
where the new equivalence class is on the right.
Criterion 4 of the default ranking is changed to reflect the same order as the specified vars, so when criterion 4 is reached, f is ranked higher than b, which in turn is ranked higher than g, which in turn is ranked higher than h, and so on.
Using equivalence classes, we have the following:
This is an unusual ranking (since it allows for c to be solved in terms of h, g, and derivatives of g), but it was chosen to highlight the flexibility of rankings.
2. Nested List
This is just a variation of the simple list specification that allows multiple equivalence classes to be specified. It is activated by the presence of a list in the vars input. When this specification is used, every entry in the vars list is interpreted as an equivalence class (even if it is not a list itself). This is best illustrated by an example. Use the same system as the prior example. If vars is specified as [f(x,y,z),[g(x,y),c]], we notice that the second entry is a list, so the equivalence classes for criterion 1 become
An equivalence class has been added for f and its derivatives, then one for g and c, and g derivatives, then the two that are created by default.
We can interpret this as "solve for f in terms of all other indeterminates; if the expression does not contain an f, then solve for g or c in terms of all other indeterminates, and so on".
Criterion 4 is changed to reflect the order in which the entries of vars appear in their equivalence classes:
Option: indep=[...]
This option allows for specification of the independent variables, but modifies the ordering as well. Put simply, it specifies the order in which criterion 3 looks at the dependent variables.
First, recall how the default ordering works. To begin with, the set of independent variables is sorted alphabetically. Then, the set of independent variables is sorted based on their occurrence in the dependent variable lists, where the dependent variable lists are considered in the same order in which they are ranked. If the order of a dependency list disagrees with the order of another dependency list, only the one of higher rank one is used.
As an example, consider a system containing f(x,y), g(y,x). In this case the independent variables are sorted in the order [x,y] if f is ranked higher than g, but in the order [y,x] if the reverse is true.
For a system containing f(x,y), g(x,z), the independent variables are sorted [x,y,z], because ties are broken alphabetically.
The specification of indep=[...] enforces the order specified in the list, so if the input contains f(x,y,z) and h(x,y,z) and we specify [z,x,y], then the independent variables are ordered as specified.
These two ways of controlling the ordering of a system are sufficient for most purposes, but you can also fully specify the exact ordering to be used for a system.
Advanced specification of a ranking
This method requires a bit of description first:
Say that we have a system with n independent variables (we call these x1,...,xn), and m dependent variables (we call these V1,...,Vm). For each derivative, we can then construct a list of n+m elements, where the first n elements are the differentiations of the derivative with respect to the corresponding independent variable, and the remaining m elements are all zero, except for the one that corresponds to the dependent variable of the derivative.
Ranking examples:
Say that we have a system with independent variables indep = [x,y,z], and dependent variables [f,g,h,s]. Then the vector for g[xxz] can be constructed as [2,0,1, 0,1,0,0]. This vector then contains all the information required to identify the original derivative. From the last four items in the list, we see that our dependent variable is g (since the 1 corresponds to the placement of g in the dependent variable list). We can also see from the first three elements of the list that it is differentiated twice with respect to x, 0 times with respect to y, and once with respect to z (where we are matching up the first three elements of the list to the corresponding independent variables).
With the same system, we may obtain:
Now we have specified a way to turn each derivative into a list of integer values. Using this, we now can create a new list called a criterion, which must be of the same length and must be specified with integer values. The dot product of the derivative list and the criterion is called the weight of that derivative with respect to the criterion.
So for the above example, if we specified the criterion list to be [1,0,0, 0,0,0,0], then g[xxz] would have weight 2, f[xyz] would have weight 1, h[xxxxx] would have weight 5, and so on.
Now when two derivatives are being compared with respect to one of these list criteria, the ranking would be determined by their respective weights. So, for example, f[xyz] < g[xxz] with respect to [1,0,0, 0,0,0,0], because weightfxyz=1 is less than weightgxxz=2 with respect to [1,0,0, 0,0,0,0].
The new ranking can then be constructed as a list of these criteria which, during a comparison, are calculated and compared in order. The construction of a ranking in this way is called a Janet ranking.
As an example, we can construct the default ranking as a criterion list for the example system as:
ranking = [
# This corresponds to criterion 1
# This corresponds to criterion 2
# These three lines are criterion 3
# This corresponds to criterion 4
So if we compared f[xyz] to f[xyy], the weights for the first entry would be 1 and 1, for the second entry 3 and 3, for the third entry 1 and 1, and for the fourth entry 1 and 2, at which point it is recognized that f[xyz] < f[xyy].
Specification of the ranking to rifsimp
The ranking is specified on the command line to rifsimp as ranking = list of criteria, where the criterion list is as described above. We recommend that you specify the dependent variables and independent variables so that the order is known and the ranking behaves as expected.
Additional notes
In the event that the input ranking does not fully specify a ranking (two different indeterminates are not ranked differently by the input ranking), the default ranking is then used (see examples). If the system contains constants, and any of the entries of the input ranking do not have corresponding entries for these constants, then the entries are padded with zeros.
For examples we will take as input single equations or a system of decoupled equations and observe their solved form in the output. They will be solved for their leading indeterminate.
By default, the above will be solved for the g derivative, as f and g have equal weight (criterion 1). The equation is differential order 2, so this narrows it down to the three second order derivatives (criterion 2), but x derivatives are of greater weight than y derivatives (criterion 3), so the equation will be solved for g[xx]:
So how can we solve for f instead? The obvious way is to give f more weight than g by declaring it as the solving variable by using vars (alter criterion 1):
What if we wanted to solve for the y derivative of f? Well, we could then also weight y derivatives greater using indep:
Good, but what if we want to solve for the t derivative of f. This is an unusual example because we are solving for a lower order derivative in terms of higher order derivatives. We could specify a new ranking that weights t derivatives higher than everything else:
With the above ranking, f is always greater than g, and t derivatives are always greater than x or y derivatives of any order. We have to declare the order of occurrence in the command line arguments so that we can match the independent and dependent variables to the sample_rank table. (These are typed in above for visualization.)
Note: We did not specify a full ranking, but instead specified as much as we required, then let the default ranking take over.
Note that a ranking like the one above is natural for certain classes of equations. As an example, consider the heat equation u[t] = u[xx]+u[yy]+u[zz] where the form of the solved equation is only physically meaningful when solving for the time derivatives in terms of the space derivatives, even when the space derivatives are of higher differential order.
As a final example, we construct a strange ranking that weights t derivatives twice as heavily as x derivatives. This is done for the following:
See Also
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stuff about fashion blogging, again, again
So I just watched Jefferson Hack's interview with Imran Amed of the Business of Fashion for the thousandth time, because it makes me very happy, and very optimistic about this digital age, which is so big that it's beyond any of us and we have no clue what to do with it, and about fashion in general.
Don't you love this guy? I like how, among many other things, he said magazines are only more important now that there's no need for news and there can be substantial content. For me, there are only a few magazines whose more news-type stuff I read (Interview, T, Vogue US) and the others I really just look at the editorial content.
Aaaaand I smiled at what he said about bloggers. Does this mean I think I deserve to be sitting front row, or at all, at a few shows? Hell no, and it's never because of my blog alone, it's because I'm affiliated with a project or magazine that has me there, but I'm happy to write about what I saw and how I feel about it on the blog as well, and hear what my commenters thought, and maybe this reaches a different demographic of people than a magazine or newspaper, because anything can only reach so many people before there have to be some that can't identify with it. This doesn't mean anyone has to be all print, or all blogs. No one is going to stop reading a magazine they like because they started reading a blog. Blogs are not magazines, they are not alternatives to magazines, and they usually have different goals than magazines, though it doesn't even make sense to generalize it that way because each blog or magazine has a different goal from the next. It just means that you can hear from someone with years in the industry and someone who is more outside of it; you can hear different opinions from people with different backgrounds, and this ultimately makes for a more interesting discussion. I don't think the digital age means that bloggers, not magazines or critics, decide what's cool or what people wear; I think it means that no one really decides that now, because there are so many points of views. I know that I don't try to give any advice about what people should wear, because I just would like everyone to wear what they want. This larger discussion sort of forces people to be more creative and honest, which is a good thing, no? All this Internet-ness makes fashion about a conversation anyone can take part in, which is, in my opinion, more democratic and interesting.
Still, I didn't turn in my vote for the CFDA -- it's a different thing, because my opinion on my blog is less determining of someone else's fate than a CFDA vote. I can post a rap about Rei Kawakubo and write about the magic of Celine for this blog, but I can't hold that kind of responsibility for another person's career. I just want to be a part of the conversation.
Sooo, speaking of industry pioneers doing interviews with the Business of Fashion...
45 comments:
- Maile John said...
My heart races watching this interview! I love Jefferson's idea on satellite blogs, its brilliant!
- July 13, 2010 2:04 PM
- Sonia said...
I completely agree - I love blogs, but I'm not parting with my glossies any time soon! You're very smart y'know, and I admire your CFDA vote decision-thing a lot. So yay!
Also jealous of the Londoners! Business of fashion <3
Sonia xo - July 13, 2010 2:04 PM
- Rheanne said...
love this ♥
Love, x - July 13, 2010 2:06 PM
- Erin said...
Oh. My. God.
I have been seriously scarred for life by the above comment...
I really agree with you on the whole thing with blogs not being an alternative to magazines. I read your blog AND Vogue, not one or the other!
-Erin - July 13, 2010 2:08 PM
- Exercises in Style said...
definitely right..I love blogs because somehow they give us the chance to be part of fashion world, but still I love to flip trought magazine's pages! great blog yours!
- July 13, 2010 2:13 PM
- nobody said...
you have a good point of view. the most horrible thing about bloggers is that they believe they're creating the fashion, that they're ruling its world, because they have 5000 of readers who say that they're cute.
- July 13, 2010 2:13 PM
- sarah said...
i don't know if i think bloggers should be able to have a voice in fashion? is it more democratic in a way (voice of the people and all that)? or is it just the voices of a select group (yet again)?
- July 13, 2010 2:19 PM
- J. Fonte for RogueRanting.com said...
Ditto on what you said about blogs not being a replacement for glossies.
Blogs don't have editorials- or Emmanuelle Alt. LOL. - July 13, 2010 2:19 PM
- Maxens M. Finch said...
You made me learn something, didn't know this guy. I feel a bit stupid, but thanks.
- July 13, 2010 2:21 PM
- Tavi said...
sarah-I don't think it's just the voice of a select group STILL, only switched over to bloggers as opposed to editors/critics. I don't think there IS a select group because now everyone can have an opinion. If that makes sense.
- July 13, 2010 2:22 PM
- Contact said...
im equally jealous of those in london... that video is very inspiring!
heelsandinspiration.blogspot.com - July 13, 2010 2:56 PM
- Deano SC said...
22nd 7:30 syked!
- July 13, 2010 3:00 PM
I think the whole editor vrs.fashion bloggers is pointless. The more people that have views and opinions on things and the more people that have a love for something the better it will be because were all giving different opinions. If an editor really loved fashion than they wouldnt care about letting bloggers in on it because the more people in fashion the better it will get. Great video and post! Can't wait till thursday!
WWW.TheLevelHeadedChild.blogspot.com - July 13, 2010 3:01 PM
- Leslie said...
i am constantly puzzled over the blogger/editor rivalry because the two are completely incomparable in my mind. i am someone who, for the most part, does not buy magazines because i feel like they are so full of plastic content (but i understand most people do. and i totally don't think magazines are going away anytime soon, because like he said, people want that experience, the spatial relationship to things. there is no sublime future, so people need to stop freaking out that books are going to disappear within our lifetime). i pick up a us vogue (for example) and the space isn't being used to start a conversation with the clothes or the idea, it's just being filled up for the sake of being filled up. editors and creative directors don't work to challenge their readers ideas about new styles or ideas; they just try and shove this idea of a luxury fantasy lifestyle as far down your throat as they possibly can. it's so weird because editors and magazines have the accessibility and the edibility to content and ideas that bloggers strive for and yet they remain completely static--whereas bloggers are curators of constant visual streams of consciousness and yet there is still this limit on the visual aspect because, well, not all of us get sent miu miu clothes to take pictures with. but i mean, duh, blogs are so completely personal. i totally lost my train of thought, whatever, i wrote a blog entry a while ago about raging about editorial content or lack thereof, if anyone cares enough to read it. http://jellybones.net/blog/?p=622
i think the point i was trying to make before that whole wall of text appeared was that yes!!! technology rocks!!! and this dude is totally brilliant--what he said about tilda creating a fashion video was great. i mean it seems such a complete waste to me for any photo shoot, music video, ANYTHING to just be on default, to JUST be aesthetics. no, generation y is not the underdogs and no, we don't (can't) really stick it to the man anymore, but we aren't completely bubble-headed consumers of plastic culture! we are probably the first total generation of users, who constantly upload personal content (pictures, videos, blogging, whatever) and it's not meaningless temporary culture--it's turning into something totally permanent. i mean most people who start fashion blogs aren't consumers of high end fashion, i don't think most of us are convinced by agenda, inc.'s belief system on luxury brands or lifestyles. most of us aren't interested the business or the commercial side of fashion, right? i think what blogs have contributed to was the validity of fashion as an art and not just a craft, and we should move in that direction, or else life will just be that scene in the september issue where all the dudes in penguin suits get together for breakfast and complain about how prada rain boots are totally uncommercial and how the hell are we going to market this stuff. - July 13, 2010 3:22 PM
- ADNA said...
Just to let you know, I envy you I still can't believe you got those Miu Miu shoes! And second, how old are you now about 14? I admire your blog and have seen it grow, keep up the good work! Regardless of what critics say, I consider you as an inspiration to me and the little thoughts I put into my blog. (=
- July 13, 2010 3:32 PM
Here here for bloggers!
- July 13, 2010 4:53 PM
- Miscellaneous said...
Hello "Tavi-Titties",
In light of the fact that Tavi is 14, I have alerted Blogspot and the Police. I suggest anyone else who reads this blog, feel free to also contact Blogspot.
With an uncle who works internationally combatting child pornography, I suggest choosing your words wisely. - July 13, 2010 4:54 PM
- KARLITO said...
Magazines are fun to read and then having a blog to read that talks about what you just read is even more fun. I love reading people's opinions and enlightening me to things I might have missed.
- July 13, 2010 5:17 PM
- Richard Kilroy said...
I agree with what you have to say totally, I've always believed that having something print is something you can treasure, such as photography and illustration, whereas articles and discussion can be suited any medium!
I actually want to send you a copy of my new fanzine on fashion illustration as I think / hope you'll really like it! how do I go about posting you a copy?
www.richardkilroy.com/decoy.html - July 13, 2010 5:21 PM
- Unknown said...
Tavi, after seeing you mentioned and photographed here and there, I had to come see what all the to-do was about. After reading through some of your posts, it is easy to see that you are a smart, witty girl with your own style. I admire you for following your muse at such a young age.
With that said, as an older (wow, that makes me feel old) style blogger, I can say that I agree with you about the editors vs bloggers controversy. I wish the hoopla about bloggers trying to take over the universe would die down. We are living in a digital age and it's cheaper and more convenient for people to gather their information online. Niche magazines will always have a following if they are good. There are certainly some magazines I will not give up, no matter how good the web gets. It's nice to sit on the porch with a magazine in hand. It's like reading a real book vs a digital book--not the same experience and cannot really be substituted if you like the vintage feel of holding a real book or magazine. I think magazines are starting to reach out to bloggers to ensure that they don't die out. I've been receiving many more pitches and things of that nature from magazines. I like to think that we can work together to really shape a more democratic look at beauty and fashion.
And lastly, to address your first part about Seventeen, thank you. As a woman, mother, and one-time mental health counselor, I appreciate the fact that you took the time to publish this on your highly visible blog. THIS is how we make change. This is how we get away from the industry standard of using unhealthy models and convincing a good portion of our population that they are not only unhealthy, but ugly. Shame on Seventeen. Drugs also lead to poor decision making, which is MUCH scarier than being overweight. Good for you for catching that poor marketing. Keep up the wonderful work! - July 13, 2010 5:51 PM
- SabinePsynopsis said...
That was interesting. I think he put the change of how we use/perceive media these days very well. But 40 quid for the N. Massenet interview... Ouch!
- July 13, 2010 5:56 PM
- lily said...
awww. the video didn't work for me. What I love about your blog is that the parts where all you do is post up pictures, links and videos is just as interesting as your actually talking. On an average tumblr, the pictures are SO BORING. but here on yours they introduce me to a whole new world! please don't stop!
- July 13, 2010 7:47 PM
I do think blogs compete a lil bit with Magazines... Actually the internet in general just competes with magazines... and like you said this does push people to be more creative which is really good! Some magazines are still not realizing this. I think that in this time Magazines have to become collectible items... everything on them have to be so unique an amazing that people will really want to buy them and keep them. Like in the past Vogue used to have amazing editorials and worked with all kinds of artists For example Salvador Dali made the cover of Vogue... an amazing painter! Not like now a days where Vogue is just this pretty cover with boring editorials
- July 13, 2010 10:37 PM
- Unknown said...
Very interesting post thank you!
Long life to the magazines!!!!
-the diary of a fashion stylist- - July 14, 2010 12:49 AM
- Tayler Worrell said...
wow aghhghghaghhg. I got an email about this and i want to go so incredibly bad. this interview makes me so excited about the industry and my opinions and future in it! and your review nailed it. it really did. thanks for posting!
www.bighairandbikinis.blogspot.com/ - July 14, 2010 2:35 AM
- zoomslow said...
"rap about Rei Kawakubo" <3 :-)
- July 14, 2010 2:50 AM
- Unknown said...
Great, interesting post!
www.eighteenthnyc.com - July 14, 2010 10:58 AM
- Unknown said...
That was very interesting .
- July 14, 2010 12:36 PM
- cancercowboy said...
- This comment has been removed by the author.
- July 14, 2010 3:50 PM
- cancercowboy said...
the problem is that the internet as a whole makes the sales figures go down. and that reduces the amount of ads quasi automatically.
plus, the publishing houses are forced to sell their ad space cheaper. don't know if thats true for US fashion magazines, but i know it applies to german newspapers and news magazines, with just a few exceptions.
this has a bunch of consequences and none of them are particularly good for editorial independence. most mags ain't here to educate or provide a forum for discussion; they are advertisement platforms, sadly. thats where they make most of their revenue, not with selling actual printed material.
communication between readers and writers beyond the 'letters to the editor' is a rare thing. Magazines have to change to continue their existence and thats hard but inevitable if they wanna stay (or again become) relevant.
the other alternative is of course to regulate the internet much sharper and to control the upload and use of content way stricter than ever. - July 14, 2010 3:53 PM
- Masha said...
yeah there are so many informations now from blogs, magazines, tv, radio. and all this information is really different. So the smart people are the choice, the smart people will not prefer to read or just a magazine or just a blog, the smart people will take all interesting for him information, will mix all that and will create a his point of view, his style. With all this information we can be unique!
http://leblogdemasha.blogspot.com/ - July 15, 2010 1:24 AM
Thanks for this blog post! I actually referenced it in my London College of Fashion interview yesterday (had to write about digital media vs. magazines). I agree that magazines and blogs generally have different aims, and a blog is not a magazine. Personally I like both, but for different reasons. I really hope that the quality of writing in magazines does not become compromised by the number of adverts or promotions in them, whilst I also hope that websites do not start charging money to read online content (as some British papers have threatened to do).
Keep up the great work, Tavi!
http://soulisrainingclothes.blogspot.com - July 21, 2010 7:41 AM
- sami said...
please please please,hepl me. What can i do to my blog have a lot of vistis??? You are the most, and i think i have style but i haven,t publicity. My outfits are cheaps and chics ;) and i,ve todas las ganas del mundo de triunfar en la moda. Si tienes unos minutos libres, sería un placer para mi que te metieras en mi blog.Eres un crac y yo, tambien;)))! besos desde España.(y mil gracias tengas o no tengas tiempo)
http://www.mientrasmevisto.com - July 22, 2010 5:09 PM
- SOJOURNED IN STYLE said...
i read about imran amed in a magazine and was really fascinated by his perspective but i agreee with you on the blog and magazine comparison :)
- July 24, 2010 1:22 PM
- Blioux Studio said...
Great interview but the stained curtain drives me banana cakes! It's about fashion people...details count.
I think however you want to get your voice out is your prerogative and it's the readers prerogative to look at and read what they want and disseminate what's important to them. Digital media might make glossies better. Use high quality images, laid out in a creative way on great paper and people can pay for quality glossies and save advertising for the digital world. - July 25, 2010 6:39 PM
- Unknown said...
Finally someone who agrees with me on NOT TELLING OTHER PEOPLE WHAT TO WEAR. It really pisses me off when someone insults someone else's clothing for being "different", or when magazines run "hot and not" lists. I think anyone who dares to wear something "weird" deserves a medal!
- July 26, 2010 9:20 PM
- Izzen said...
http://izzenxoxo.blogspot.com/ - July 29, 2010 4:23 PM
- La Clochard said...
"I don't give a shit!" hahahahah yes, I love this guy!
kisses from Spain :) - July 31, 2010 12:02 AM
- Teetho said...
I know that I don't try to give any advice about what people should wear, because I just would like everyone to wear what they want. This larger discussion sort of forces people to be more creative and honest, which is a good thing, no? All this Internet-ness makes fashion about a conversation anyone can take part in, which is, in my opinion, more democratic and interesting. bookmark
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Personal information collected online may be combined with information you provide to us through other sources We may also remove your personal identifiers (your name, email address, social security number, etc). In this case, you would no longer be identified as a single unique individual. Once we have de-identified information, it is non-personal information and we may treat it like other non-personal information. Finally, we may use your personal information to protect our rights or property, or to protect someone's health, safety or welfare, and to comply with a law or regulation, court order or other legal process.
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How Is Personal Information Used For Communications?
We may contact you periodically by e-mail, mail or telephone to provide information regarding programmes, products, services and content that may be of interest to you. In addition, some of the features on this web site allow you to communicate with us using an online form. If your communication requests a response from us, we may send you a response via e-mail. The e-mail response or confirmation may include your personal information. We cannot guarantee that our e-mails to you will be secure from unauthorized interception.
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We have implemented generally accepted standards of technology and operational security in order to protect personally-identifiable information from loss, misuse, alteration, or destruction. Only authorized personnel and third party vendors have access to your personal information, and these employees and vendors are required to treat this information as confidential. Despite these precautions, we cannot guarantee that unauthorized persons will not obtain access to your personal information.
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Children's Privacy
Kilo will not intentionally collect any personal information (such as a child's name or email address) from children under the age of 13. If you think that we have collected personal information from a child under the age of 13, please contact us.
Kilo reserves the right to modify this statement at any time. Any changes to this Privacy Policy will be listed in this section, and if such changes are material, a notice will be included on the homepage of the web site for a period of time. If you have any questions about privacy at any websites operated by Kilo or about our website practices, please contact us at: hello @ usekilo . com
About this Cookie Policy
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Jan 24, 2024Avoid Seed Corn Maggots in Spring Melons (2024)
Spring melon planting is getting underway with a few cantaloupe fields under plastic, and Yuma beds being prepared and planted. One field I observed last week being listed had excessive produce crop residue in and on top of the beds. I immediately thought of the threat of seed corn maggots on early planted melons with the cooler soil temperatures we see this time of the year. Seed corn maggot (SCM) is a pest that should be avoided whenever possible since control after the fact is near impossible. SCM are always a concern in melon crops planted during late January and February, and are most prevalent under cool, wet conditions. SCM can cause significant stand reductions in melons and other large seeded crops (e.g., cotton, corn, beans) due to the maggots feeding on germinating seed, roots and stems of young seedlings and transplants. If larvae populations are high in the soil, replanting parts or all of an infested field is often necessary. Not only is this an inconvenience to the grower, but replanting is expensive and can disrupt harvest schedules. Unfortunately, once maggots have been found infesting the soil during stand establishment, there is usually nothing you can do. Thus, avoidance of the problem is the most effective way of preventing stand reductions. First, weather plays a major role in determining the damage potential for SCM. Melon stands are more susceptible to SCM during wet, cool spring weather in which seed germination is slowed or delayed. These conditions (low soil temperatures, rainfall, and/or excessive irrigation) give SCMs a chance to develop in the soil and attack the seeds before they can emerge. SCM larvae will begin developing at soil temperatures as low as 50 °F. The minimum temperature for melon germination is 60 °F. Current soil temperatures at planting depth have been a bit below 60 °F for the past 2 weeks, giving SCM the advantage. However, I've also observed SCMs take down direct seeded cantaloupe and transplanted watermelon stands established under warm, dry conditions when flies were abundant. Secondly, our cropping system plays a key role. Melon crops following produce are the most often attacked because SCM adults are attracted to freshly tilled soils with high levels of decomposing organic matter and will readily lay eggs in the soil (particularly moist soil). This includes heavy plant residue remaining after harvest of the previous lettuce or brassica crop, as well as applications of composted manure prior to planting. Growers would be encouraged to delay planting melons into fields under these conditions. However, if growers decide to plant in these conditions, then it would be wise to use a preventative insecticide applied in-furrow at planting to minimize the impact from SCM and give seedlings a fighting chance. A few alternatives are available that have shown activity against SCM and may be practical for their management in spring melons. For more information, visit Seed Corn Maggot in Spring Melons, 2024.
To contact John Palumbo go to: email@example.com


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Struggling to build your organization's ability to work with data? Use our hands-on learning program to kickstart your data culture.
Data is everywhere right now. But many organizations like yours are struggling to figure out how to build capacity to work with data. You don't need a data scientist; you need a data culture.
For the first time, the numbers [from our grantees] were consistent
- Erika Lapsys, Telluride Foundation
Use our self-service learning program to facilitate fun, creative introductions for the non-technical folks in your organization. These are not boring spreadsheet trainings. The free tools and activites below are hands-on and designed to meet people where they are across your organization and build their capacity to work with data. Try to kickstart your data culture by running one activity per month as a brown bag lunch. The videos and facilitation guides below will lead you through running them yourself. People at more than 30 organizations have done so already - from a local public library, to the World Food Progam.
How do you build a data culture? Use our videos and guides to run one activity a month at brown bag lunches in your org.
The Data Process
Here's a process we introduce to get you from data to impactful story. Keep scrolling down to learn about the activities we offer for you to run at each step along the way.
Warm Ups
Before jumping into finding data or telling stories, it's important to do some warm ups to activate your organization's data mindset. Warm ups are quick, fun, hands-on activities designed to activate conversation, catalyze creative ideas and build confidence to take the next step. For example, lead colleagues to Build Data Sculptures with craft materials to explore different ways to communicate the same simple data set. Working with pompons, pipe cleaners, or other local materials changes how you approach data, letting you focus on playfully quick ways to look for stories. Deconstruct a dataviz to build your skills in understanding data visualizations, and developing a strong data-driven narrative arc of your own.
Asking Questions
What questions can (and cannot) be answered with data? And once you are staring at some rows and columns, how do you start to make sense of the data in front of you? In this stage, you learn to take the first step in the data analysis process by asking good questions. Use WTFcsv to quickly summarize spreadsheet data, brainstorm questions about it, potential connections to other data sets, and potential biases you might bring to it. Remember – the data never speaks for itself – you help it speak by asking better and better questions. Fill in a Paper Spreadsheet to introduce people to various types of data and help them think about how people fill it in.
Gathering Data
Often you don't recognize the data you already have! Data is all around, but can be difficult to identify and describe. You need the right data to tell a strong story. As they say, "garbage in, garbage out." You also need to remember that a single data set may not be able to answer your questions. Combining datasets is often the best way to create a more fleshed out story. Use Connect the Dots to explore crowd-sourcing data from your audience to analyze together as a network. Or Use WTFcsv to think about how to gather the data you need to answer a question.
Analyzing Data
Data can be intimidating, especially when it comes to analyzing it. But remember, most of statistics is just special ways of counting. We're all pretty good at counting! Establishing a data culture doesn't mean that we will all be statistical wizards but it does mean learning enough about analysis to understand its creative potential. The data analysis process is an opportunity to bring people together. There are many ways to do this to find a story. Use WordCounter to learn about analyzing text data to find stories. Use Connect the Dots to collaboratively analyze a network graph. Use SameDiff to learn about how algorithms can help you analyze data in more abstract ways.
Telling Your Story
Telling your story is where the rubber hits the road. Numbers alone are not enough to make your case or move people to action. You have to give your data some context, and stitch it together into a narrative so that people can understand it. Sketch a story with WordCounter to practice communicating a data-driven story visually. Make a Word Web to move from abstract ideas and numbers into concrete visual symbols. Remix an Infographic to practice telling the same story in diffferent ways.
Try It Out
How do you know if your story is working? Does the data you included support the narrative you are telling? It can be very difficult to put yourself in the shoes of your audience and try to understand what kind of story will change their worldview or move them to action. And you might have multiple audiences. Each potential audience brings different beliefs and experiences to understanding your message. Try out ConvinceMe to practice telling different stories to different audiences. Write a Data Storybook to practice writing compelling narrative arcs that are supported by the data you are working with.
Connect with Others
Trying to build a data culture can be a lonely effort in organizations that haven't recognized the importance of data. Join the Data Culture discussion group to connect with others and reflect on how these activities are working, or not working, for your organization.
Join the discussion groupAbout Us
The Data Culture Project is an initiative of DataBasic.io. We've pulled together the years of work with nonprofits into one place to help you build a data culture. DataBasic.io is the brainchild of Catherine D'Ignazio and Rahul Bhargava.


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Python | Program to find factorial of a number
This is an example of how to find the factorial of a number in python.
The factorial of a number is a product of all the positive integers less than or equal to that number.
For example, the factorial of 5 is 5x4x3x2x1 = 120
Factorial is not defined for negative integers, and the factorial of zero is one, 0! = 1.
Check here for factorial recursive way
n = int(input('Enter no.:'))
fact = 1
for i in range(1,n+1):
fact *= i
Output for the above code
>>> ====================== RESTART: E:\py\factorial.py ====================== Enter no.:5 120
let's modify the code to handle number less than or equal to zero
n = int(input('Enter no.:'))
fact = 1
if n < 0:
print(f"Sorry, factorial does not exist for {n}, negative number")
elif n == 0:
print("The factorial of 0 is 1")
for i in range(1,n+1):
fact *= i
Output for the above code
>>> ====================== RESTART: E:\py\factorial.py ====================== Enter no.:5 120 >>> ====================== RESTART: E:\py\factorial.py ====================== Enter no.:0 The factorial of 0 is 1 >>> ====================== RESTART: E:\py\factorial.py ====================== Enter no.:-5 Sorry, factorial does not exist for -5, negative number
Tips and Tricks
What is pass in Python?
Python | Pass Statement
The pass statement is used as a placeholder for future code. It represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written.
def myfunction():
How can you generate random numbers?
Python | Generate random numbers
Python provides a module called random using which we can generate random numbers. e.g: print(random.random())
We have to import a random module and call the random() method as shown below:
import random
The random() method generates float values lying between 0 and 1 randomly.
To generate customized random numbers between specified ranges, we can use the randrange() method
Syntax: randrange(beginning, end, step)
import random
What is lambda in Python?
Python | Lambda function
A lambda function is a small anonymous function. This function can have any number of parameters but, can have just one statement.
lambda arguments : expression
a = lambda x,y : x+y
print(a(5, 6))
It also provides a nice way to write closures. With that power, you can do things like this.
def adder(x):
return lambda y: x + y
add5 = adder(5)
add5(1) #6
As you can see from the snippet of Python, the function adder takes in an argument x and returns an anonymous function, or lambda, that takes another argument y. That anonymous function allows you to create functions from functions. This is a simple example, but it should convey the power lambdas and closures have.
What is swapcase() function in the Python?
Python | swapcase() Function
It is a string's function that converts all uppercase characters into lowercase and vice versa. It automatically ignores all the non-alphabetic characters.
string = "IT IS IN LOWERCASE."
How to remove whitespaces from a string in Python?
Python | strip() Function | Remove whitespaces from a string
To remove the whitespaces and trailing spaces from the string, Python provides a strip([str]) built-in function. This function returns a copy of the string after removing whitespaces if present. Otherwise returns the original string.
string = " Python "
What is the usage of enumerate() function in Python?
Python | enumerate() Function
The enumerate() function is used to iterate through the sequence and retrieve the index position and its corresponding value at the same time.
lst = ["A","B","C"]
print (list(enumerate(lst)))
Can you explain the filter(), map(), and reduce() functions?
Python | filter(), map(), and reduce() Functions
- filter() function accepts two arguments, a function and an iterable, where each element of the iterable is filtered through the function to test if the item is accepted or not.
>>> set(filter(lambda x:x>4, range(7))) # {5, 6}
map() function calls the specified function for each item of an iterable and returns a list of result
>>> set(map(lambda x:x**3, range(7))) # {0, 1, 64, 8, 216, 27, 125}
reduce() function reduces a sequence pair-wise, repeatedly until we arrive at a single value..
>>> reduce(lambda x,y:y-x, [1,2,3,4,5]) # 3
Let's understand this:
5-2=3Hence, 3.
What is a namedtuple?
Python | namedtuple
A namedtuple will let us access a tuple's elements using a name/label. We use the function namedtuple() for this, and import it from collections.
>>> from collections import namedtuple
>>> result=namedtuple('result','Physics Chemistry Maths')
#declaring the tuple
>>> Chris=result(Physics=86,Chemistry=92,Maths=80)
>>> Chris.Chemistry
# 92
Write a code to add the values of same keys in two different dictionaries and return a new dictionary.
We can use the Counter method from the collections module
from collections import Counter
dict1 = {'a': 5, 'b': 3, 'c': 2}
dict2 = {'a': 2, 'b': 4, 'c': 3}
new_dict = Counter(dict1) + Counter(dict2)
# Print: Counter({'a': 7, 'b': 7, 'c': 5})
Python In-place swapping of two numbers
Python | In-place swapping of two numbers
>>> a, b = 10, 20
>>> print(a, b)
10 20
>>> a, b = b, a
>>> print(a, b)
20 10
Reversing a String in Python
Python | Reversing a String
>>> x = 'PythonWorld'
>>> print(x[: : -1])
Python join all items of a list to convert into a single string
Python | Join all items of a list to convert into a single string
>>> x = ["Python", "Online", "Training"]
>>> print(" ".join(x))
Python Online Training
python return multiple values from functions
Python | Return multiple values from functions
>>> def A():
return 2, 3, 4
>>> a, b, c = A()
>>> print(a, b, c)
2 3 4
Python Print String N times
Python | Print String N times
>>> s = 'Python'
>>> n = 5
>>> print(s * n)
Python check the memory usage of an object
Python | Check the memory usage of an object
>>> import sys
>>> x = 100
>>> print(sys.getsizeof(x))