text:
|Publication number
|Publication type
|Publication date
|Aug 26, 1969
|Filing date
|Aug 5, 1965
|Priority date
|Aug 5, 1965
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|Publication number
|Booth Robert Ben, Mead Linda Clarendon
|Original Assignee
|American Cyanamid Co
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|BiBTeX, EndNote, RefMan
|Patent Citations (6), Referenced by (76), Classifications (14)
|External Links: USPTO, USPTO Assignment, Espacenet
United States Patent 3,463,730 PREVENTION OF AND REMOVAL OF SCALE FORMATION IN WATER SYSTEMS Robert Ben Booth, Stamford, and Linda Clarendon Mead, Greenwich, Conn., assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Aug. 5, 1965, Ser. No. 477,604
Int. Cl. C02b 1/20 US. Cl. 210--58 15 Claims ABSTRACT OF THE DISCLOSURE Formation of hard adherent scale deposits of insoluble salts particularly carbonates and sulfates of metals such as calcium or other alkaline earth metals, and/or iron which may include particles of silt or silica, are inhibited, controlled or prevented on, or removed from (a) the walls of evaporators, cooling towers, heat exchangers, boilers and devices where a thermal gradient exists or areas where catalytically active sites induce scale formation in aqueous systems by (-b) from about A to 100 parts per million of a hydrolyzed polyacrylarnide having (c) from about to 50% unhydrolyzed amide groups and (d) a molecular weight of about 1,000 to 8,000. The polymer is useful alone, and in cooperation with other sequestrants and chelating agents.
This invention relates to a process of controlling or preventing the formation of adherent deposits of salts from water, particularly during distillation, evaporation heat exchanging processes, filtration, flow, circulation and transportation and storage, by the use of a small but effective amount of a hydrolyzed polyacrylamide having from about 10% to about 50% of unhydrolyzed amide groups and a molecular weight of about 1,000 to about 8,000; and to a composition containing such polymer.
More particularly, the invention relates to the process of preventing the formation of hard adherent scales or deposits on containing vessels, which scales are at least in part composed of the compounds of the alkaline earths or iron, from aqueous solutions in such vessels; including such deposits which have in their structure silt or sediment particles of silica or clay or other materials which are basically insoluble in water but are locked into place in a matrix composed of the alkaline earth or iron compounds.
In a broad sense the invention relates to the control of the characteristics of formation of adherent deposits of both comparatively soluble and comparatively insoluble salts. The control of insoluble salts, especially calcium carbonate, and also calcium sulfate, is the most important and broadest teaching. Incipient deposits to be controlled may be regarded as (a) temperature induced precipitates as, for example, in heat exchangers and boilers where a thermal gradient exists which tends to increase the rate of deposition; b) surface-modified deposition in which the surface has active centers which appear to catalytically control the rate of attainment of equilibria and, hence, induce the rapid deposition of insoluble deposits (this phenomena is particularly of interest in filter media where there is a comparatively large surface as well as pipes and other vessels in which there is some agitation); (c) incrustations in which finely-divided silica or clay particles are incorporated in deposits on surfaces, thereby both increasing the rate of buildup and the hardness of the deposit while rendering such deposit more resistant to either mechanical or chemical attack; (d) precipitation induced by a change in conditions such as the pH or concentration ice of one of the components or by evaporation of water to increase concentrations. Scale formation is increased by a drift in the pH toward such a range in which a component is less soluble, or a change in concentration as, for example, absorption of the carbon dioxide from the air in cooling towers, which additional carbon dioxide by the law of mass action tends to precipitate out with calcium as a calcium carbonate. These phenomena are not necessarily completely independent as more than one of them may be contributing toward the production of deposits. Deposition may occur from a system in equilibrium in which a change in conditions causes a component to become insoluble or it may occur in a metastable system where calcium carbonate, for example, is present in a supersaturated solution, and which system is seeking but has not yet reached equilibrium.
The problem of scale formation has its largest application where there are interfacial problems involved. Of particular importance are boilers, pipe lines, heat exchangers, and other thermal transfer equipment made of metal, particularly carbon steel. The surface of steel appears to be peculiarly susceptible to and perhaps even might be considered catalytic in promoting scale formation. The results in the present invention are consistent with the theory that a thin monomolecular layer of the low molecular weight polyelectrolyte forms on steel or other surface, or at least the more active centers, and protects the surface, or at least alters the interfacial relationship between the surface and the scale forming elements, so that the tendency of scale to adhere is markedly reduced; and, additionally, the crystal characteristics of precipitating hardness, such as carbonates and sulfates of calcium, are so altered that the crystals are smaller, poorly formed and more easily removed with less of a tendency to adhere than in the absence of the low molecular weight polyelectrolyte.
Another area of major importance is: in filtration. Filter media, which may be fiber filter cloths, steel filter cloths, cellulose paper, glass cloth, or synthetic fibers such as nylon or polyester filters, or other filter material, appear to have active centers or some type of sites which tend to increase the tendency of the carbonates and/or sulfates of calcium to precipitate on such filter surfaces, clogging and blinding the filter surfaces, thus reducing the filtering rate and requiring that the filter surface be changed, cleaned, or that it be treated with an acid to react chemically with and remove the scale formed. As is common in many heterogenous reaction mechanisms, the theory and proof of theory is either ambiguous or difficult because the actual areas involved and the mass present at the area at a given time is such a small fraction of the total mass present.
The alkaline carbonates and/or sulfates appear to come out as hard dense crystals on solid surfaces. In the presence of the present polymer, the precipitates are finer and more irregular.
The problem of scale formation is a very serious one, both for domestic water supplies, where plumbing is gradually plugged up, and also for steam boilers, where formation of scale in the boiler tubes is a serious matter and once deposited is dilficult to remove.
This problem is aggravated, particularly in certain industrial operations such as cooling operations, where waters containing salts, mineral matter, slimes and other sediments even in small quantities are the only waters economically available. In such cases, the alkaline earth compounds which deposit out of the waters tend to cement together the silt or sediment particles as a strongly adherent scale or concretion which causes blockage of and interferes with water flow in industrial processing such as cooling, heat exchanging, filtering, evaporation, air-conditioning and the like.
The present invention prevents the formation of hard adherent scale by adding small amounts of a hydrolyzed polyacrylamide having from to 50% unhydrolyzed amide groups, and preferably from about 20% to about 40%.
In addition to the proportion of amide groups, there is a very vital and critical limitation on molecular weight which must be well below 10,000 and should be from 1,000 to 8,000, preferably 4,000 to 7,000. This is a vital and essential feature of the invention, as high molecular weight hydrolyzed polyacrylamide results in flocculation rather than the prevention of scale formation. Different theorie are propounded to explain the very different results obtained with the low molecular weight hydrolyzed polyacrylamides of the present invention. Such theory is in part set forth herein, but the invention is not predicated upon such theories. Importantly, scale formation is greatly reduced, the amount of alkaline earth metal salts remaining in solution is higher and, importantly, the precipitates which do form are light and amorphous and are readily removed; whereas in the absence of the hydrolyzed low molecular weight polyacrylamides, hard, adherent, crystalline scale deposits result which can only be removed from walls of vessels by vigorous scrubbing or other abrasion procedures or chemicals too corrosive for routine use.
An unhydrolyzed polyacrylamide of the same molecular weight is not nearly as satisfactory as a scale inhibitor or antiprecipitant or crystal habit modifier.
Even though at least 50% of the amide groups are hydrolyzed, the designation low molecular weight hydrolyzed polyacrylamide is chosen because it fits in well with current trade usage and is descriptive and distinguishing. The polymer can properly be termed a polycarboxyethylene-polycarbamylethylene long chain carbon-to-carbon polymer. It is a polyelectrolyte. In the acid form the polymer has the probable formula:
where n and m are Whole numbers, such that n is at least about as large as m, and not more than about 9 times as large as m, and n and m and x have such size that the total molecular weight is between 1,000 and 8,000, preferably between 4,000 and 7,000, and the two groups may occur in random order and orientation.
From polymerization theory one end of the chain in polymerization is a free radical, with which the vinyl group of a monomer molecule reacts. The high catalyst ratio permits a theory that sulfonate groups are formed on the end of, and terminate chain growth. This causes the relatively low molecular weight. This is consistent with the theory that the sul'fonate groups are themselves reactive with calcium and barium ions, and hence alter the reactivity in crystal growth. The relatively low polymer weight permits the relative number of sulfonate groups to make a greater contribution.
Frequently and conveniently the polymer is added as an alkali metal salt, usually the sodium salt. Potassium, ammonium or other soluble salts may be used, and all of the acidic hydrogens need not be replaced, nor of those replaced need the cation be the same. As the polymer is used in dilute solution, and the cation, be it alkali metal or hydrogen, etc., is dissociated to an extent that varies with the concentration of other cations present, the polymer at the time of action can be considered in a transient state, and for purposes of convenience, the name of the acid form is used for identification Without the intention that the polymer be in such acid form. Also, small numbers of nitriloethylene linkages, from acrylonitrile, or other vinyl compounds may be in the chain without deleteriously affecting the action, and in such minor quantities that positive identification of their presence or absence is diflicult.
One of the big advantages of the present invention is that the polymers can be prepared from technical grade components, and the final polymer may in part be used as a dry powder added when desired, or as an aqueous solution, or as a powder or solution containing the residues from catalyst systems, or organic or inorganic salts, compounds and impurities inherently present in the starting materials from components used in synthesis. The low requirements for process purity of the polymer permits grades of acrylamide or acrylonitrile, or acrylic acid and its salts, to be used in synthesis that are less pure than required for fiber formation, or high molecular weight polymers, thus conferring a distinct commercial advantage in synthesis. These monomers in high grade or purified form may be utilized as starting materials, if economically available. The hydrolyzed polyacrylamide can be prepared by first polymerizing acrylamide and then hydrolyzing some of the amide groups, or concurrent polymerization and hydrolysis or it may be made by other means, including copolymerization of acrylic acid and acrylamide, or hydrolysis of polyacrylon'itrile, etc. In any event, there are the proper proportions of amide groups and the remainder being carboxyl groups, usually in the form of an alkali metal salt. The term hydrolyzed polyacrylamide is used as convenient understandable terminology rather than to limit the process of manufacture.
High molecular weight polyelectrolytes, that is polymers from about 10,000 up, and for best results in the range of 100,000 to 20,000,000 have been used as flocculants. As fiocculants, one theory is that one part of the long polymer chain attaches to one solid particle and another part attaches to another particle, which holds the particles together forming fiocs, almost like grapes in a bunch. The phenomena of fluocculation is markedly different from the prevention of adherence of deposits of the present invention and the same polymer at the same molecular weight cannot be optimum for both. The present low molecular weight hydrolyzed polyacrylamide acts in part as a dispersant or deflocculant, a diametrically opposed objective from that of the higher molecular weight polyelectrolytes used as fiocculants.
The present problem of scale inhibition and preventing the formation of solid deposits, primarily of calcium and which may have other insoluble materials in the matrix, has certain theoretical concepts which may involve chelation, sequestration, antiprecipitation and antinucleation as Well as dispersion and the modification of crystal structure. These concepts are both chemical and physical and involve the action of additives with stoichiometric equivalents of the compounds in solution or greater than stoichiometric quantities, and the inhibition of neucleation or inactivation of nuclei to prevent precipitation or to slow down precipitation long enough to permit a processing operation to take place. The dispersion of suspended solids or of precipitated solids is likewise a significant factor. The modification of crystal structure and the formation of non-adherent deposits plays an important role. These phenomena, singly or in partial and total combination and cooperation and interaction probably account for the action of the low molecular weight hydrolyzed polyacrylamide herein described. It is obvious that even a theoretical expanation is difficult to provide because the complexity of the factors involved and their probable interaction.
Uniquely, the low molecular weight hydrolyzed polyacrylamide is advantageously present with added soluble inorganic salts which enhance the action of these polymers by improving their dispersing properties. The desirability of the presence of such salts, particularly sodium sulfate has an added and unexpected economic advantage. The low molecular weight polymers of the present invention are economically produced by polymerizing acrylamide with redox catalysts such as a mixture of sodium metabisulfite and sodium persulfate at a comparatively high catalyst usage. About 5% of the catalyst by weight of the monomer gives extremely rapid polymerization and chain termination to result in lower molecular weight polymers. The residues after the interaction of the components of the redox catalyst, as well as any residual sodium sulfate which may have been present with the monomer is desirably retained with the polymer. The polyacrylamide is conveniently hydrolyzed with caustic, such as sodium hydroxide, and again residual caustic can conveniently be left with the polymer after it has been hydrolyzed so as to leave from about 50% to about amide groups on the chain. Fortunately and fortuitously, the catalyst system is such that even less purified grades of polyacrylamide may be used in the production and, hence, a final product is obtained which may have at least 20% to 30% of sodium sulfate and/or sodium chloride and/ or caustic present. Such salt containing low molecular weight hydrolized polyacrylamide operates not only with maximum efficiency as compared with a pure polymer, but in many instances even with improved results, so that the unique and highly unexpected result is obtained with a more economical product, which not only does not require purification, but actually in some systems is more elfective than if purified.
The partially hydrolyzed polyacrylamide with a molecular weight of 1,000 to 8,000 is water soluble. It is readily soluble to the extent of at least 25% at room temperature. The polymer may be added dry, and permitted to dissolve during use. Solution is so rapid that only sufficient agitation is required to cause uniform mixing, and yet any amount of agitation is not deleterious. Alternatively, the polymer can be dissolved in water and added as 0.1% to 25 solution for operations in which liquid feeding is more convenient and, in fact, may be used as a synthesis mixture without drying where logistics are such that this procedure is most economical.
This case of addition is in marked contrast to the high molecular weight polyacrylarnides and polyacrylamide hydrolytes used for flocculation which require much time and care to dissolve the polymer without the production of gel clots and which polymer must be added as a dilute solutionfrequently less than one-half of 1% in order that the viscosity be low enough for convenience in handling as a liquid. For flocculation, agitation is often kept to a minimum, to avoid degradation of the polymer.
The present hydrolyzed low molecular weight polyacrylamide in one specific embodiment is a dry light cream colored solid having a molecular weight of 6,000, a polymer content of 75%, with the polymer being 75% carboxyl and 25 amide, and the diluents being primarily sodium and ammonium sulfates and sodium hydroxide. The pH of a 1% solution is 10.8 and of a 10% solution 12.1. The viscosity at 1% solution is 1.3 centipoises and the solubility is over 25 in solutions having a useful viscosity, that is thin enough to be added and readily dispersed. If the point of use is close to the point of manufacture the polymer can be moved by pipe line or as a liquid. For greater distances, or for long-term storage, the product is drum dried. Not all of the known useful properties of the material are here claimed as the material is known to be useful as a drilling mud additive, as a sequestrant, a descalant, a boiler water additive, an additive in the electrodeposition of metals, and in heating and air-conditioning equipment, both in circuits which are exposed to the air and, therefore, subject to absorb carbon dioxide, and in closed systems where the absorption of carbon dioxide is not a problem. It is useful in the evaporation and desalting of sea water, as well as various other brines and is useful in controllin scales and encrustations and a wide variety of chemical processing, including treating hard water, to assist in the control of scale and deposits which are independent of or induced by added chemicals in processing equipment and machinery such as tanks, pipes, pumps, filters, filter media, as a detergent for use with or independent of other detergents and surfactants; in metal cleaning, the processing of ores, including flotation, cyanidation, filtration, etc. It may be used to assist in dispersing mineral products as may be desired in degritting clay, classification of clay fractions, classification of other minerals such as asbestos, and processing sewage and industrial wastes and as a dispersant for pigments, fillers, carbon blacks, paper coatings, and in conjunction with other sequestrants, chelating agents, or antinucleating agents in chemical processing or heat exchange or paper making.
Concurrent usage with other additives The present low molecular weight hydrolyzed polyacrylamide is not only effective in its own right as an antiprecipitant, sequestrant and chelating agent, but also is effectively blended with conventional agents used for such purpose with advantage. Among the chelating agents and sequestrants and antiprecipitants which may be used advantageously in combination with the low molecular weight hydrolyzed polyacrylamide are:
Ethylenediamine tetraacetic acid Nitrilotrisacetic acid Hydroxyethylethylene diamine triacetic acid Trisodium bis(1-carboxy-1-hydroxyethyl)phosphinic acid Sodium N,Nbis (Z-hydroxyethyl) glycinate Lignin compounds, including sulfonates Polyphosphates Inorganic polyacids, e.g., polymolybdates and polytungstates Polysaccharides Citric acid Glutamic acid Heptagluconic acid Tannic acids Salts of the above compounds Other sequestrants which give other useful compounds in combination are set forth in conventional texts, such as: Mantel and Calvin, Chemistry of the Metal Chelate Compounds," Prentice Hall, New York (1953), and Bailar, The Chemistry of the Coordination Compounds, Reinhold Publishing Corp., New York (1956).
The present low molecular weight hydrolyzed polyacrylamide is also useful in conjunction with acids or bases used for cleaning deposits from pipes, vessels, tanks, radiators, pipe lines, watermains, sewage lines, and other locations where deposits already formed, either from calcium carbonate alone, or in conjunction with silt and/or other salts are already in place, and mud removal. The present low molecular weight hydrolyzed polyacrylamide is useful alone in loosening and removing such deposits, and aids in solvent, detergent or acid or base attack because once particles are loosened, the polymer tends to keep them suspended.
From common ion effect, and solubility product theory, in thermodynamically stable systems, it is obvious that a more efiicient scavenging of calcium is required Where a high carbonate or sulfate concentration is present. In cooling towers, and aerated systems, such concentrations cannot be conveniently reduced, and hence, the highly efficient present concepts of calcium inactivation are more important than in systems where lime may be high, but low carbonate concentration prevents calcium carbonate build-up.
It should be noted that the hydrolyzed polyacrylamide of the present invention does not act purely as a sequestrant, although this phenomena may be present. The drastic change in the nature of any precipitates which form on the walls of vessels or pipes is not purely a sequestration phenomenon. It is not known exactly what mechanism produces the new effect. Accordingly, the invention is not limited to any theory of action, and any statement of theory is to assist in understanding the invention, not limit the invention.
The low molecular weight hydrolyzed polyacrylamides of the present invention are especially useful in the treatment of water containing silts, mineral matter, slimes and other sediments, including such waters from natural sources, by-product and reused waters from industrial processing operations, and also domestic and industrial waste waters. The solids in such waters tend to settle out to coat containing vessels, clog pipes, and decrease the etficiency of heat exchangers, radiators of various types, evaporators, boilers, automobile cooling systems and other cooling equipment. In hard waters, this problem is aggravated by the deposits and encrustations of alkaline earth metal compounds and salts which also form and act as cementing materials for deposited mineral matter. Calcium carbonate and sulfate are one of the most common components. Removal of the combined agglomerate is difficult and costly. The use of the low molecular weight hydrolyzed polyacrylamides of the present invention provides a solution of the problem of handling such waters. These polymers are dispersants and keep fine solids in suspension, thus preventing their sedimentation to form hard adherent deposits. These polymers also prevent the formation of hard deposits by keeping alkaline earth metal compounds in solution as described above. Thus the use of these polymers eliminates the formation of agglomerates composed of the settled solid materials combined with the deposits of alkaline earth compounds and solves the diflicult problems involved in utilizing silt-containing hard waters.
In quantitative dispersing tests on samples of clays and limonite, hematite, coal, slate, limestone, and other mineral and ore slimes, the hydrolyzed polyacrylamides herein described have been found to be more efficient dispersants than polyphosphates, lignin sulfonates, and sodium silicate, frequently being 3 to times more effective.
The low molecular weight hydrolyzed polyacrylamides are beneficial in evaporation and distillation processes used for the treatment of salt waters, brackish waters, sea and ocean waters, brines, etc. in the recovery of water and concentration of valuable components. Without the polymer, the salt deposits from such treatments form hard and difiiculty removable deposits on heating coils and heated surfaces. The use of a fractional part to a few parts per million of the polymers of the present invention in the desalting of water by evaporation produces salt deposits which are readily removed from heating coils by simple brushing operations, and often the force of flowing water is suificient to render such deposits self-cleaning.
The invention will also be described in conjunction with the specific examples, in which the parts are by weight unless otherwise specified. Molecular Weights are weight average molecular weights for polymers.
Example l.Calcium carbonate sequestration vs. tripolyphosphate Two water solutions were prepared: one containing 0.04% calcium hydroxide and the second 0.05% sodium bicarbonate. 250 ml. samples of the first solution were prepared, to which were added varying amounts of the sodium salt of hydrolyzed polyacrylamide of about 6,000 molecular weight containing about unhydrolyzed amide groups. The amounts ran from 0.75 to 10 p.p.m. To each sample of the first solution was added an equal volume of the second solution, and the combined solutions permitted to stand for one hour. The pH was 11.5. The system was then filtered to collect the precipitate which formed.
To a second set of samples of the first solution there were added corresponding amounts of sodium tripolyphosphate. An equal volume of the second solution was added. These mixed solutions were also permitted to stand for the same time, followed by filtration to collect the precipitate which formed. A control test was run in which the solutions were mixed, but no hydrolyzed polyacrylamide was present. The nature of the precipitates was quite dilferent. Those samples which received varying amounts of the hydrolyzed polyacrylamide showed calcium carbonate precipitates which were light, amorphous and free-flowing instead of the dense, crystalline, adherent properties formed in the control tests. The light, amorphous products were readily removed from the vessels, whereas the control samples produced precipitates which adhered strongly to the walls and bottom of the container and were dislodged only by vigorous scrubbing. The containers were glass beakers.
Each precipitate was analyzed for calcium content by dissolving in 6 N hydrochloric acid followed by titrating the calcium with ethylene diamine tetraacetic acid. This was compared with the control solution to which neither hydrolyzed polyacrylamide nor sodium tripolyphosphate had been added, and the carbonate held in solution was determined as the diiference between that found in the control and that found in each of the precipitates of the treated solutions.
Experimental results show:
CALCIUM CARBONA'IE HELD IN SOLUTION Low Molecular-Weight Hydrolyzed Polyacrylamide Sodium Tripolyphosphate P.p.n1. Calcium P.p.m. P.p.rn. Calcium P.p.rn. Polymer Carbonate held Polyphosphate Carbonate Held Added in Solution Added in Solution Example 2.-Calciun1 carbonate precipitation control degree of hydrolysis Two solutions were prepared, Solution I containing 0.04% CaO and Solution II containing 0.05% NaI-ICO To a 250 ml. aliquot of Solution I, hydrolyzed polyacrylamides and a polyacrylic acid were added in concentrations ranging from 0.75 p.p.m. to 2.0 p.p.m. in a series of separate tests. A 250 ml. aliquot of Solution II was then added. The resulting solution was then allowed to stand one hour and filtered. The calcium in the precipitates which were filtered off was determined by an EDTA (ethylene diamine tetraacetic acid) titration. A control was conducted similarly, except that the hydrolyzed polyacrylamides and the polyacrylic acid were omitted.
In one series of tests, a hydrolyzed polyacrylamide of 6,000 molecular weight was used and 70% of the contained amide groupings were hydrolyzed to COONa groupings. In a second series of tests, a hydrolyzed polyacrylamide of 6,000 molecular weight and of the contained amide groupings were hydrolyzed to COONa groupings. The low molecular weight hydrolyzed polyacrylamide used contained about 25% Na SO The table shows real polymer content. In the third series of tests, a polyacrylic acid of 23,000 molecular weight was used, as free acid.
The results of these tests are summarized in the following table:
P.p.m. hydrolyzed P.p.m. calcium Rpm. calcium P.p.rn. hydrolyzed P.p.m. calcium pol acrylamide P.p.rn. calcium carbonate carbonate 90 a GOONa precipitated held in solution P.p.m. calcium P.p.m. calcium P.p.m. polyacrylic carbonate carbonate acid precipitated held in solution The hydrolyzed polyacrylamide containing 70% COONa was more efiicient in holding calcium carbonate in solution than the po-lyacrylic acid since 0.75-1.50 p.p.m. of this hydrolyzed polyacrylamide held 128-142 p.p.m. calcium carbonate in solution as compared to 49-118 p.p.m. calcium carbonate with 1-2 p.p.m. polyacrylic acid.
Also, the hydrolyzed polyacrylamide containing 90% COONa was more efiicient in holding calcium carbonate in solution than the polyacrylic acid since 0.75-1.50 ppm. of this hydrolyzed polyacrylamide held 99-118 p.p.m. calcium carbonate in solution as compared to 49- 118 p.p.m. calcium carbonate with 1-2 p.p.m. polyacrylic acid.
The low molecular weight hydrolyzed polyacrylamide causes a variation in crystal form that is readily apparent under a microscope. The crystals are smaller. Some of them even exhibit Brownian movement. Thus, they are readily dispersible and suspendable. The crystals lose their characteristic morphology, the edges become rounder, the faces smaller, anhedral rather than euhed-ral. The change is from flat rods and plates to more equant crystals. The crystals pack more like marbles in a bag than bricks in a wall, and hence the precipitated material is more readily removed.
Example 3 Saturated calcium sulfate solutions in water, (0.21% CaSO were prepared. 500 m1. samples of the solution were treated with various amounts of a low molecular weight hydrolyzed polyacrylamide as described in Example 1; again the additions being from 1 to 10 p.p.m. One of the samples was used as a control, to which no hydrolyzed polyacrylamide was added. All samples were then concentrated by boiling down to a volume of about 125 ml. Precipitation of calcium sulfate, of course, occurred during the evaporation and was filtered off. The calcium sulfate content of the filtrate was then determined. The results are shown in the following table:
Hydrolyzed Percent (32150 in solution polyacrylamide p.p.m.: after evaporation As in Example 1, the structure of the deposited calcium sulfate was modified by the hydrolyzed polyac-rylamide. The calcium sulfate was amorphous in structure as compared to the crystalline deposit obtained in the control test. The deposits formed in the presence of the hydrolyzed polyacrylamide were readily dislodged and removed from the walls and bottom of the containing vessel, whereas in the control test a strongly adhering deposit formed, which was diflicult to remove and had to be scraped or scrubbed off.
5 Example 4.-Delay in precipitation To separate 100 ml. samples of an aqueous solution containing 5,000 p.p.m. of sulfate ion as sodium sulfate, 1-2 p.p.m. of low molecular Weight hydrolyzed polyacrylamide, molecular weight about 6,000, about 70% hydrolyzed, were added, with one such sample as a control. To the samples water solutions of calcium chloride were added to produce calcium ion concentrations of from 2,000 to 10,000 p.p.m. The solutions were then all observed to notice the effect of hydrolyzed polyacrylamide on the formation of a precipitate of calcium sulfate. The results of the tests are shown in the following table:
Hydrolyzed Time (hours) before polyacrylamide precipitation occurred Example 5 A series of precipitation observations were made in accordance with Example 4 but using solutions containing stoichiometric quantities of calcium and sulfate ions in various concentrations. The result is shown in the table:
Hydrolyzed Time (hours) before OaSO4 polyacrylarnide precipitation occurred Example 6 The procedure of Example 5 was followed with solutions containing rvarious amounts of barium and sulfate ions in stoichiometric amounts. The results are as given in the following table. No precipitation was observed over a two-hour period.
50 PARTS PER MINUTE Hydrolyzed BaSO Polyacrylamide 1O 1-25 Example 7 Samples of water containing 115 p.p.m. hardness and 10 p.p.m. of the sodium salts of hydrolyzed polyacrylamides of varying molecular Weight and earboxyl content were heated on an electric hot plate. The water level in the beaker was maintained constant by the addition of water from a constant level device until 20 liters of the water were evaporated. A control test was conducted similarly except that no polymer was added to the water at the start of the evaporation.
During the evaporation, a scale deposit formed on the areas of the beaker which were heated, particularly on the bottom in contact with the electric hot plate. The deposit formed in the absence of the hydrolyzed polyacrylamide was hard and adherent, while in the presence of the hydrolyzed polyacrylamide the deposit was readily dislodged. The quantity of scale deposited in the various tests is shown in the following table:
Percent amide groups hydrolyzed to COONa Wt. of scale, g.
6,000 53 0. 130 Control, no polymer 0. 326
Example 8 Twelve liters of a Connecticut tap water were concentrated to a volume of 400 'ml. by adding the water in 500-ml. stages to a vented autoclave heated and maintained at 200 pounds per square inch (gage) pressure. The solid residue remaining after this operation was fine, dense and strongly adherent to the autoclave.
Separate l2-liter samples of the same water were pretreated with various hydrolyzed polyacrylamides and similarly concentrated. The hydrolyzed polyacrylamides used are as follows:
Percent amide groups M01. wt. hydrolyzed to COONa P.p.m. added In all cases the addition of the hydrolyzed polyacrylamide to the water prevented the formation of deposits which adhered strongly to the autoclave. The deposits formed from the pretreated waters were loose, amorphous and readily movable. In the control test deposits were firmly adherent to the walls and bottom.
Example 9 The alkaline-lime-cyanide solutions obtained in the cyanidation of a Philippine gold ore were removed from the ore and treated with 0.32 lb. zinc dust per ton to precipitate the gold which was recovered by filtration. Because of the formation of finely-divided deposits of calcium salts on the filter cloths, filters tended to clog and it was necessary to stop the operation twice per week to permit acid washing of the filters to dissolve these deposits. The addition of 2 p.p.m. of the hydrolyzed polyacrylamide product described in Example 4 prior to the filtration operation inhibited the formation of the deposits of calcium salts. Acid washing of the filters was reduced to once per month, thus reducing down time of the filters and maintenance costs by about 87%. Gold losses were also reduced by the use of the hydrolyzed polyacrylamide from 3.5 cents per ton to 2.5 cents per I011.
Example 10 The concentrate obtained in the flotation of a copper ore was settled in a thickener by the use of 2.0 lb. lime/ ton. The alkaline underflow from the thickener was filtered for shipment to smelting operations. A deposit of lime salts built up and clogged the filter such that weekly shutdowns were required to permit acid washing of the filters to remove the deposits. The addition of 1.5 p.p.m. of the potassium salt of a hydrolyzed polyacrylamide of about 6,000 molecular weight, containing carboxyl as acrylic acid, to the thickener underflow eliminated the deposition of lime salts and permitted continuous operation of the filters without shutdown for cleanouts.
Example 11 A South American copper ore containing about 2% Cu was ground to minus 65 mesh, conditioned with 4.0 lb./ton sulfuric acid, 0.15 lb./ton cresylic acid as frother, and 0.1 lb./ton sodium diethylmonothiophosphate as collector and floated for 7 minutes. In the resulting concentrate assaying 23.42% Cu, 84.1% of the total copper was recovered. The copper and iron contents of water in which the ore was suspended during the flotation operation were 360 ppm. copper and 110 p.p.m. iron and served as interferences during the concentration of copper by flotation.
The ore was similarly treated except that 5 p.p.m. of the sodium salt of hydrolyzed polyacrylamide (molecular weight-6,000; hydrolyzed) were added following the sulfuric acid and before the addition of the cresylic acid and monothiophosphate collector. The use of the hydrolyzed polyacrylamide and subsequent flotation for 7 minutes improved the copper recovery to 89.3% in a concentrate assaying 28.76% Cu.
Example 12 A copper ore containing about 1.2% Cu in an alkaline gangue consisting of calcium and magnesium carbonates and some calcium phosphate is wet ground to about 5% plus 65 mesh. Lime and magnesium salts are dissolved during the grinding in sufficient quantity to interfere with flotation so that only 79.3% of the copper in a concentrate assaying 25.12% Cu is recovered by the use of 0.1 lb./ton amyl xanthate and 0.045 1b./ton of a higher alcohol frother.
The addition of 10 p.p.m. of the hydrolyzed polyacrylamide, 70% carboxylated as described in Example 2, eliminates the interference of the dissolved salts. Subsequent flotation with the xanthate-higher alcohol combination gives a copper recovery of 85.6% in a concentrate assaying 28.47% Cu.
Example 13 The concentrate obtained in the flotation of a copper ore was settled in a thickener by the use of 2.0 lb. lime/ton. The alkaline underflow from the thickener was filtered for shipment to smelting operations. A deposit of lime salts built up and clogged the filter to the extent that weekly shutdowns are required to permit acid washing of the filters to remove the deposits. The addition of 1.5 ppm. of sodium salt of the hydrolyzed polyacrylamide to the thickener underfiow eliminated the deposition of lime salts and permitted continuous operation of the filters without shutdown for cleanouts over periods of at least thirty days.
Example 14 The following controlled experiments demonstrate the efficiency of the hydrolyzed polyacrylamides herein described in the treatment and utilization of hard waters containing suspended solids such as clay, silts, ore and mineral fines, etc.
The test apparatus consisted of a heating block capable of holding six copper specimens which act as the heat transfer surface. The specimens were polished and weighed before and after a trial run. The heating block was maintained at a temperature of C.i2 C. The circulating water temperature was held at 40-45 'C. by means of a stainless steel cooling coil introduced into the cooling water sump. The cooling water being tested was circulated over the copper specimens through a plastic head. The flow velocity along a radius of the test sample ranged from 5 feet per second at the center to 0.5 feet per second at the circumference.
The composition of test solution is given in the following table:
P.p.m. CaCl to give Ca as CaCO 700 MgCl to give Mg as CaCO 200 Total Hardness as CaCO 900 M. O. Alkalinity as CaCO 20 NaCl to give Cl as Cl 500 Na SO to give S as $0., 500 CuSO to give Cu as Cu 0.2 FeSO to give Fe as Fe 0.2 NaHCO as CaCO 460 PH adjusted to 8.0.
The effect of adding varying quantities of a hydrolyzed polyacrylamide (with about 54% of the amide groups hydrolyzed to COONa groups) to the above solution containing 500 ppm. kaolin clay is shown in the following table. The weights of deposits are those found on the copper specimens after 20 hours of continuous operation. 20
Test solution (pH=8.0)--500 p.p.m. clay Concentration (p.p.m.) of hydrolyzed Weight (mg.)
Generally similar results were obtained with hydrolyzed polyacrylamides in which 60 to 90% of the amide groups had been hydrolyzed to COONa groups. In contrast, 60 ppm. sodium lignin sulfonate are required to get a reduction of about 50% of the weight of the deposit. Modification of crystal size, shape, and texture, as described in the foregoing examples, was evident in the solutions to which the hydrolyzed polyacrylamides had been added.
We claim:
1. A process for the control of hard, adherent scales on the walls of vessels or pipes containing an aqueous system having present therein compounds of alkaline earth metals or iron which comprises:
adding to an aqueous system having present therein alkaline earth metal or iron compounds a small but effective amount of a polymer selected from polymers Which in the acid form have the formula:
10 70 1 0H 11 1 1112 In x where n and m are whole numbers such that n is at least as large as m, and not more than 9 times as large as m, and x is a value such that the molecular weight is about 1,000 to about 8,000 and water soluble salts thereof.
2. A process according to claim 1 in which the polymer has from about 20% to about 40% unhydrolyzed amide groups.
3. A process according to claim 2 in which the molec ular weight of the polymer is between 4,000 to 7,000.
4. A process according to claim 1 in which the aqueous solution is ordinary tap water.
5. A process according to claim 2 in which the aqueous solution is ordinary tap water.
6. A process according to claim 3 in which the aqueous solution is ordinary tap water.
7. A process according to claim 1 in which the aqueous system contains alkaline earth metals compounds.
8. A process for the inhibition of formations of hard adherent scales on the walls of steel pipes or vessels from solutions containing alkaline earth metals compounds and in which solutions are suspended silts or sediment particles, comprising adding a small but effective amount of the polymer of claim 1.
9. The process of claim 8 in which the alkaline earth metal compound is predominantly calcium as a carbonate. 10. A process for causing calcium carbonate to precipitate out from an aqueous system as a soft fluffy precipitate which comprises adding to the aqueous system a small but effective amount of the polymer defined in claim 9 as its sodium salt while said system is substantially free 10 from insoluble calcium salts, then modifying the system so that calcium carbonate is precipitated out as a soft non-adherent precipitate.
11. The process of claim 10 in which the precipitation of calcium carbonate is induced by the increase in temperature and volatilization of part of the water from the system.
12. The process of claim 10 in which the precipitation of calcium carbonate is induced by the increase in concentration of the carbonate ion.
13. The process of claim 11 in which the said polymer is present at a concentration between about A and 100 parts per million.
14. The process of claim 12 in which the said polymer is present at a concentration between about A and 100 parts per million.
15. A process for the control of hard, adherent scale of alkaline earth metal salts selected from the group consisting of calcium sulfate and barium sulfate on the walls of vessels or pipes containing aqueous systems having present therein sulfate ions and alkaline earth metal ions selected from the group consisting of calcium ions and barium ions, comprising:
adding to an aqueous system having present therein sulfate ions and alkaline earth metal ions selected from the group consisting of calcium ions and barium ions from A to 100 parts per million of a polymer selected from polymers which in the acid form have the formula:
4 where n and m are whole numbers such that n is at least as large as m, and not more than 9 times as large as m, and x is a value such that the molecular weight is about 1,000 to about 8,000 and water soluble salts thereof, said calcium ions or barium ions and sulfate ions being present in scale forming quantities, under scale forming conditions, whereby the calcium sulfate or barium sulfate is caused to partially remain in solution, and partially precipitate out in soft readily removable form.
References Cited UNITED STATES PATENTS 2,327,302 8/1943 Dittmar 252--180 2,783,200 2/1957 Crum et al. 252180 2,820,777 1/1958 Suen et al 26089.7 2,980,610 4/ 1961 Ruehrwein 252-180 3,022,279 2/1962 Proffitt 26089.7 3,215,680 11/1965 Kolodny 252180 US. Cl. X.R.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,465,750 Dated Augpst 26, 1969 Inventor(s) ROBERT BEN BOOTH 8c LINDA CLARENDON MEAD It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
001. 10, line 50 change "PARTS PER MINUTE" to read QPO O Col. 1, line 55 change "teaching" to read reaching Signed and sealed this 19th day of October 1971.
(SEAL) Attest:
EDWARD MEETCHERJ'R. ROBERT GO'I'TSCHALK Acting Commissioner of Patents Attesting Officer USCOMM-DC 60376-969 i u s covilmnun rnmnuc orncl H69 OJ66-J3-l FORM PO-105O (10-69l
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|European Classification


text:
It's Early in the Flu Season But a Strain Isn't Waiting
Published: December 3, 1993
ATLANTA, Dec. 2— Though the flu season is barely under way, a harsh strain of influenza has already made an appearance this year in 17 states.
Through late November, health officials in three states reported outbreaks of the Beijing flu, and 14 states reported sporadic cases.
"When the predominant strain is the Beijing, a lot of the population tends to be susceptible," said Nancy Arden, chief of influenza epidemiology for the Centers for Disease Control and Prevention in Atlanta. "Things seem to be happening a little bit earlier than usual this season."
Flu kills an average 20,000 people a year, Dr. Arden said. Federal health officials recommended today that people at high risk of death from the flu, including the elderly, people with heart and lung diseases or those with immune deficiencies, be vaccinated.
The flu season typically begins in November. Outbreaks usually don't occur until December or January. But this season started in August when Louisiana reported cases of the Beijing flu in a nursing home and on a barge. Beijing is Worst Strain
"It's hard to say when we might see a peak of activity," Ms. Arden said.
Last year's season was dominated by the Type B flu strain, which is mild and typically infects children and young adults.
Type A flu, which caused an epidemic in 1991, is the harshest and is most deadly to the elderly and people with chronic diseases. Beijing is the worst strain of Type A flu, Ms. Arden said.
The C.D.C. said that it was not too late to get a flu shot for protection against this season's strain.
The three states that reported outbreaks of the Beijing flu through Nov. 23 were Idaho, Montana and Wyoming. The 14 states that reported sporadic cases were Alaska, California, Colorado, Connecticut, Hawaii, Louisiana, New Mexico, New York, North Carolina, Ohio, Oregon, South Dakota, Texas and West Virginia.

subset: commoncrawl


text:
SCCE Chennai
St. Christophers College Of Education
Tamil Nadu
UGC, NAAC, Govt. of India
Total Students
Fees Range
How to reach
St. Christophers College Of Education is situated at No: 63, E.V.K. Sampath Road, Vepery, Chennai 600 007. in Chennai.
Courses Offered
- 1 Years
- B.Ed.
- Languages / Arts / Literature
- 1 Years
- B.Ed.
- Languages / Arts / Literature
- 1 Years
- B.Ed.
- Languages / Arts / Literature
- 1 Years
- B.Ed.
- Languages / Arts / Literature
- 1 Years
- B.Ed.
- Languages / Arts / Literature
St. Christophers College Of Education - SCCE Chennai - SCCE
St. Christopher's College of Education was started in 1923 with a class of 12 LT students and 4 faculty members of three different nationalities. This Residential College is situated in Tamil Nadu, South India. The College is affiliated to the Tamil Nadu Teachers Education University and prepares students for the D.El.Ed., B.Ed., M.Ed., and M.Phil. Degree Examinations. The college has been recognized to conduct research leading to Ph.D. The College was accredited at Five Star Status and reaccredited at 'A' level by NAAC, UGC of Govt. of India. The College is also the recipient of the National Gold Star Award from the International Business Management, New Delhi for its outstanding achievements in the field of education. In keeping with the vision of the college which is 'To provide women, special consideration being given to the poor and the needy, with professional and general education of the highest order on Christian lines', the college has been doing pioneering service in integrating the efforts for excellence in Christian values also.
Nearby Hangout
|Food & Entertainment
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Why join St Christopher College of Education Vepery Chennai
Institute Has Well Furnished Class Rooms.
5 Type Courses Available
- 5 UG Courses
St. Christophers College Of Education Placements
The institute provides placement assistance to all its students. The dedicated placement cell regularly conducts grooming sessions of the students in areas like soft skills, interview facing skills, behavioral skills hereby making them industry-fit. In the recent years the college has witnessed some well known recruitment companies walking-in and being invited for campus placements
Visiting Companies
Student Placement
The college continues to provide a rich environment which is intellectually stimulating and aesthetically pleasing. The hostel provides a wholesome atmosphere for living and learning. The hostel has been extended with a few more rooms in the year 2009. The hostel mess has been renovated with new flooring extending its way upto the corridor of the hostel down stairs. The existing hostel has been extended with 5 single rooms, a Dining Hall and a Study Hall in the first floor. The institute tries to utilize all possible opportunities, to inculcate a proper sense of values through the curriculum and also develop an understanding of the critical factors affecting us today.The life of a student is a busy, wholesome one filled with new and varied things to do. The most important aspect of on-campus life is the opportunity it offers to develop self-discipline, inter-personal relationship and the sense of community responsibility along with the academic work. As staff we endeavour to inculcate in our students the habit of honest.
Nearby popular spots within 5 KM from the campus
|Southern Spice (Restaurant)
|Escape (Movie Theater)
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|Hotel Saravana Bhavan (Restaurant)
|Devi Cineplex (Movie Theater)
|Fusion 9 (Restaurant)
|Ega Theatre (Movie Theater)
|Hotel Apoorva Sangeetha (Restaurant)
|Mathsya Restaurant (Restaurant)
|Kefi Restaurant (Restaurant)
|Udipi Hotel Sudha (Restaurant)
|Cafe Coffee Day (Cafe)
|Sangam Multiplex (Movie Theater)
|Tamil Nadu Government Multi Super Specialty Hospital (Hospital)
|Regional Institute of Ophthalmology and Government Ophthalmic Hospital, Chennai (Hospital)
|Apollo Children's Hospital (Hospital)
|Influence (Spa)
|Apollo First Med Hospitals (Hospital)
|Express Avenue (Shopping Mall)
|Abirami Mega Mall (Shopping Mall)
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text:
Long Bar
Long Bar is now closed as part of our restoration programme and is slated for a grand reopening in the middle of 2018, along with the rest of the hotel. The Singapore Sling will still continue to be served at it's temporary new home, the Bar & Billiard Room. For more details on our restoration, please click here.
Home of the Singapore Sling, this two-storey bar located on the second floor of Raffles Singapore is the place where travellers undergo one of the truest rites of passage of travel. While there, sip on the world-famous pink cocktail, created in 1915 by bar captain Ngiam Tong Boon, and toss peanut shells onto the floor - the only place in Singapore where "littering" is permitted. The menu offers a mélange of cocktails and non-alcoholic concoctions, together with traditional pub favourites.
The earthy interiors are inspired by Malayan plantation life in the 1920s. Oriental carpets are overlain on tiled floors and the furniture is traditional stained cane and rattan. A charming timber spiral staircase connects the two levels of the Long Bar with the seating above interspersed with teak lounge chairs.
For Reservations & Enquiries:
Tel: +65 64121816
Email: firstname.lastname@example.com
Long Bar welcomes walk-in guests and does not accept reservations.


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Swan Environmental Pvt. Ltd., was established in by qualified and experienced professionals from various fields of activity. The company SWAN name has been specified with an aim of covering all types of instruments for measuring the quality of Soil, Water, Air & Noise. At SWAN we have 8 departments viz., Academia, Agri-Food Tec, Enviro Tec, Health & Safety Tec, Pharma ...
based in Madhapur, INDIA.
Pumping & Valves. The Maher Corporation has been servicing the local needs of the New England water & wastewater community for more than 30 years. We are proud to have been selected to represent over 35 Companies producing quality products used in protecting our environment and providing the highest quality drinking water for the consumer.
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Representing water and wastewater equipment manufacturers in the municipal industry throughout the southeast. Since 1988, Eco-Tech Inc. has provided sales and service of engineered equipment to the municipal water and wastewater industry. With a strong emphasis on comprehensive solutions, Eco-Tech Inc. acts as a regional equipment supplier for the municipal water and ...
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TROOPER BASEBALL - The Sheridan Troopers and Laurel Dodgers got one game in Wednesday night before weather washed out game two of the Doubleheader.
The Troopers came out on top to run their record to 35-15 overall and it was a very entertaining game.
The Troops jumped out to a 5-0 lead after two innings but Laurel would score six times in the 4th inning to take the lead and add another run in the 5th to make it 7-5 then the Troopers bats woke up scoring three in the 6th inning and went onto the 8-7 victory.
TROOPER BASEBALL - The Sheridan Troopers start at six game Homestand tonight against the Laurel, Montana Dodgers the Doubleheader will start at 5:00 and we will broadcast the first game of the live on 14-10 KWYO.
This weekend they host two games with Cody Saturday afternoon starting at 1:00 and Sunday they have two with Rapid City Post #320 also at 1:00.
Along with the home games this week the Troops host their youth baseball camp at Thorne-Rider stadium tomorrow and Friday.
TROOPER BASEBALL - The Sheridan Troopers went 3-3 at a tournament in Cheyenne over the weekend they closed out the tournament with two victories Saturday and dropped a 3-2 decision against Cheyenne Post #6 Sunday.
Tomorrow evening they will start at six game Homestand it will begin against Laurel, Montana the Doubleheader will start at 5:00 and we will broadcast the first game of the live on 14-10 KWYO.
Then on the weekend they host two games with Cody Saturday afternoon starting at 1:00 and Sunday they have two with Rapid City Post #320 also at 1:00.
TROOPER BASEBALL - The Sheridan Troopers lost the opener of the Cheyenne Post 6 tournament Thursday dropping a 9-0 game against Greely, Colorado.
They will play two games today they have the Cheyenne Hawks this afternoon and with play Cheyenne Post 6 tonight they also have games tomorrow and Sunday.
Starting next week on Wednesday they will play six straight at home it will start against Laurel, Montana, Head coach Ben Phillips.
KENDRICK GOLF COURSE - Kendrick golf course will host the Sheridan city championship next weekend Saturday and Sunday July 8th and 9th.
Kendrick golf course Professional Brian James says the City championship is great tradition for local golfers.
TROOPER BASEBALL - The Sheridan Troopers picked up another victory in Rapid City Tuesday winning 15-0 behind the pitching of Quinton Brooks they head to Cheyenne for a tournament tomorrow.
The pitching has been the key the Troopers success most of the season and Head coach Ben Phillips says the entire staff has been solid for the most part for the last two months.
Here are the results from the Bank of the West Cup held Sunday June 25, 3:00 p.m. at the Big Horn Equestrian Center:
R.R. Williams & Associates defeated Big Horn Beverage 12-5.
MVP was Joe Fitzsimons of R.R. Williams.
Best Playing Pony was Joe Fitzsimons' mare "Gavilan".
R.R. Williams & Associates:
#1 Kris Bowman / Morgan Bowman
#2 Trent Passini
#3 Joe Fitzsimons
#4 Richard Dudman
TROOPER BASEBALL - The Sheridan Troopers are coming off a Doubleheader sweep at Cody Head coach Ben Phillips says pitching played a big factor in both victories.
The play a Doubleheader at Rapid City Post #320 today they head to Cheyenne for a tournament Thursday they'll play four games.
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How to Defeat the final boss in the game Magicka
The most popular game on Steam right now is the whimsical adventure, Magicka. This tutorial shows you a few strategies when you reach the final boss and must defeat him to win the game. Best tip: use the machine gune.


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Trump's nomination of Clovis violates the 2008 Farm Bill, which s...
Posted Dec. 12, 2013 / Posted by: Kate Colwell
WASHINGTON, D.C.—In response to a letter from 25 Congressional leaders to President Obama on the State Department's review of the Keystone XL pipeline, Friends of the Earth Senior Campaigner Ross Hammond issued the following statement:
"We applaud Rep. Grijalva and other members of Congress for sending this important message to President Obama. The conflicts of interest in the State Department's tainted review of Keystone XL have become so obvious that the only reasonable choice is for the Inspector General to be given a chance to finish his job before the environmental review is completed.
"While ERM claimed on its application that it had no conflicts of interest, we now know that ERM lied to get the job. ERM's work for TransCanada and over a dozen oil companies with a financial stake in the pipeline being built should have disqualified it. These facts should be enough to call into question ERM's disputed analysis of the environmental impacts of the pipeline.
"President Obama came into office promising the most transparent government in history. We expect him to live up to his word and make sure that Keystone XL is fairly evaluated."
# # #
Ross Hammond, (415) 559-5082, firstname.lastname@example.com
Daniel Kessler, (510) 501-1779, email@example.com
Categories: Climate and Energy, News Releases« Back to main page
Trump's nomination of Clovis violates the 2008 Farm Bill, which s...
Beekeepers, farmworkers, and concerned Cincinnati residents gathered ou...
Tell Donald Trump not to appoint corporate cronies in our government.
It's time to combat climate change and earn royalties for Earth.You can help. Lets do this.


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Baraggan Luisenbarn (Regan Kirkhope) (born March 30th 30XXX) Is A Unknown Origined UFC Fighter That Is Named Under Baraggan Luisenbarn In The UFC, As A Former UFC Fighter And A Zombie Overlord, He Fought Bravely With His Old And Golden Pride. Baraggan Luisenbarn Still Fights In The UFC, In The Machinima Sports Industry, Baraggan Luisenbarn Fought With The Red Corner Along With Lyoto Machida, Tito Ortiz, Rampage Jackson, Chuck Liddell, Batista, And A Few Others, In The Previous Team Battles, Baraggan Luisenbarn Used To Team Up With Haku Yowane, Knuckle Sister Scoff, Sektor, Cyrax, Sheeva, And Samus.
Baraggan Luisenbarn Is Expected To Fight His Enemy Jamie Anderson In Another UFC Battle Against Him, He's Also Predicted To Fight Scoff And Lyoto Machida In a Triple Threat Match Handicap Style 1 on 2. He Has Won His Way To The Belt After A Few Years After His Experiance And Training A New UFC Fighter From Westerville Ohio, Doug Daniel. Baraggan Luisenbarn Will Keep His Best Interest Up And Train The Newly UFC Rookie, Doug Daniel In A Gentle Kind Of Way.


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HCV genotype 1a shows a better virological response to antiviral therapy than HCV genotype 1b
Hepatobiliary and pancreatic disorders
The impact of viral subtype on the rate of sustained virological response (SVR) to antiviral therapy in patients chronically infected with hepatitis C genotype 1 subtype 1a and 1b has not been extensively investigated. The aim of this study is to determine whether the HCV genotype 1 subtypes 1a and 1b respond differently to treatment with PEGylated interferon (PEG-IFN) plus ribavirin.
For 48 weeks, 388 "naïve"genotype 1 patients were treated weekly with PEG-IFN α-2a or PEG-INF α-2b combined with daily ribavirin (1000–1200 mg/day). The numbers of patients in whom HCV-RNA was undetectable were compared after 4 (rapid virological response, RVR), 12 (early virological response, EVR), and 48 (end treatment virological response, ETR) weeks of treatment as well as 24 weeks after the last treatment (sustained virological response, SVR).
The rate of SVR was higher in subtype 1a patients than subtype 1b patients (55% vs. 43%; p < 0.02). Multiple logistic regression analysis showed that infection with genotype 1a (odds ratio(OR) : 1.8; 95% confidence interval (CI): 1.4 to 4.1), age < 50 years (OR:7.0; 95% CI 1.1 to 21.2), alanine aminotransferase level (ALT)<100 IU/ml (OR:2.1; 95% CI: 1.3 to3.5), HCV-RNA < 5.6 log10 IU/ml (OR: 3.2; 95% CI: 2.7 to 6.9) and fibrosis score < S3 (OR: 3.8; 95% CI:3.2 to 7.4), were all independent predictors of SVR.
Dual antiviral therapy is more effective against HCV subtype 1a than against subtype 1b and this difference is independent of other factors that may favour viral clearance.
Trial registration
ClinicalTrials.gov Identifier: NCT01342003
Despite the promise of new antiviral drugs that can act directly on hepatitis C viral replication such as protease and polymerase inhibitors, a 48 weeks course of PEGylated interferon (PEG-INF) combined with ribavirin remains the current standard treatment for genotype 1 chronic hepatitis C (CHC)
We have performed an observational study on a large cohort of "naïve" HCV patients to evaluate the influence of HCV subtypes 1 on the response to treatment with PEG-INF plus ribavirin.
A total of 11 regional centres affiliated with the CLEO Group partecipate in the study between February 2007 and October 2010. Eligible subjects were naïve patients infected with HCV genotype 1 virus who met the internationally recognised criteria for treatment (elevation of aminotransferases and inflammation and/ or fibrosis at liver biopsy). The exclusion criteria included co-infection with human immunodeficiency virus (HIV) or hepatitis B virus (HBV), alcohol intake averaging greater than 20 g per day, active drug abuse, chronic systemic disease, psychiatric disorders, autoimmune disease, pregnancy or lactation. The following data were collected: age, gender, body mass index (BMI) and Ishak score of liver biopsy
All patients received Peg-IFN α-2a at 180 μg/week or PEG-INF α-2b at 1.5 μg/kg/week combined with ribavirin at 1000 mg/day if the body weight was < 75 Kg or 1200 mg/day if the body weight was > 75 kg. The dose of PEG-INF and ribavirin were modified as necessary according to the standard criteria and protocol
HCVRNA quantification
Quantitative determination of HCVRNA (TaqMan Roche Diagnostics). was performed before the treatment. The TaqMan value used to determine the response was 15 IU/ml. The TaqMan method is a standardised technique that was used in all the CLEO group centres beginning in December 2007. HCVRNA level was expressed as log10 IU/ml. HCVRNA was measured before the treatment, at weeks 4,12,24,48 of treatment and 24 weeks after the final treatment. HCV genotyping was performed using a hybridisation technique (INNOLiPA HCV Immunogenetics).
Statistical analysis
All analysis were performed on the basis of the intention to treat (ITT);i.e., the denominator included all subjects who received at least 1 dose of treatment.
Statistical analysis was performed using the Epiinfo software package. All Data were expressed as the median and range for discrete variables and as counts and percentages for qualitative variables. The differences between the groups were compared using non parametric tests (the Mann Whitney U test for continuous variables and χ2 test for parametric variables). A p value of < 0.05 was considered to be significant.
The crude odds ratios (O.R s) for the association of SVR with different variables were evaluated by univariate analysis. The following variables were analyzed: sex, age (cut-off 50 years), ALT (cut-off 100 IU/ml), gamma-glutamyltranspeptidase (GGT), BMI (cut-off 24.9), HCV-RNA (cut-off 400,000 IU/ml), HCV genotype 1 subtype ( 1a or 1b), liver biopsy grade and stage score, and type of PEGylated interferon received. The adjusted O.R. were calculated by multiple logistic regression analysis in order to identify independent predictors of SVR. Adjustment were made for all of the variables considered at univariate analyses.
The study was approved by a central ethic committee (San Camillo Hospital Rome Italy).
The study included 388 patients; of these 165 were infected with HCV genotype 1 subtype 1a (42.5%) and 223 with subtype 1b (57.5%). On average, subtype 1a patients were younger and had lower baseline HCV-RNA levels than subtype 1b patients. All the baseline characteristics of the 388 patients are reported in Table
Virological response
At week 4 of treatment HCV-RNA was undetectable (RVR) in 77 genotype 1a patients (47%) and in 83 genotype 1b patients (37%) ( p < 0.07). At week 12 of treatment 91 genotype 1a patients (55%) and 99 genotype 1b patients (44%) had undetectable HCV-RNA (early virological response; EVR) (p < 0.04). At the end of treatment 108 genotype 1a patients (65%) and 131 genotype 1b patients (58%) had undetectable HCV-RNA (p = n.s). Seventeen (10%) of the genotype 1a patients and 32 (14%) of the genotype 1b had detectable HCVRNA at week 12 but not at week 24 (slow responders) (p = ns).At the end of the treatment, there were 16 (9%) relapsed patients in the genotype 1a group and 35(15%) in the genotype 1b group (p = ns). Sustained virological response was attained in 91 genotype 1a patients (55%) and 96 genotype 1b patients (43%) ( p < 0.02). A total of 18 genotype 1a and 16 genotype 1b patients discontinued all treatments at some time during the study owing due adverse events (Figure
Figure 1
Rapid virological response (RVR), early virological response (EVR), end treatment virological response (ETR), sustained virological response (SVR) and drop out in genotype 1 subtypes 1a and 1b patients
Rapid virological response (RVR), early virological response (EVR), end treatment virological response (ETR), sustained virological response (SVR) and drop out in genotype 1 subtypes 1a and 1b patients.
Sustained virological response
The overall rate of SVR was 48.2%. Subtype 1a, age < 50 years, ALT value < 100 IU/ml, HCV-RNA < 400.000IU/ml (< 5 .60 log10 IU/ml), and fibrosis score ≤ S3 were all factors predisposing to SVR (Table
Cross-tabulation of RVR vs.SVR showed that the positive predictive value (PPV) of RVR for the achievement of SVR was 82.0% for subtype 1a and 77.4% for subtype 1b (data not shown).
Safety profile
Eighteen subtype 1a (11%) and 16 subtype 1b (7%) patients stopped antiviral treatment due to adverse effects. Six patients stopped during the first month of treatment and the remaining patients during the following months. The percentage of patients in both groups whose treatment dose were decreased due to adverse events were comparable: 9.6% (16 patients) for subtype 1a and 10.7% (24 patients) for subtype 1b. Anaemia was the most frequent cause of dose reduction. Total discontinuation, dose modifications and adverse events related to treatment are showed in Table
We have conducted a large observational study to assess the influence of viral subtype within HCV genotype 1 on the virological response to antiviral treatment in naïve HCV patients. Logistic regression analysis showed that HCV subtype 1a, mild liver fibrosis scored as less than S3 (Ishak score), HCV-RNA level less than 5.6 log10 IU/ml, age less than 50 years, and ALT level less than 100 IU/ml were all independent predictors of SVR.
Many efforts have been made to identify predictors of SVR to antiviral treatment in the difficult-to- treat chronic hepatitis C genotype 1 patients. Liver histology and viral HCV-RNA levels seem to be particularly important predictor of response in these patients. A recent study by Cheng et al. showed that naïve genotype-1 patients with advanced fibrosis were less likely to achieve SVR than those without advanced fibrosis
Genotype 1 subtypes 1a and 1b are the most common HCV genotypes in the United State. These subtypes are also predominant in Europe and subtype 1b is responsible for up to 73% of HCV infection in Japan. Zein et al. found that patients with HCV subtype 1b were older on average than those infected with other genotypes and that subtype 1b may have been present in some countries before the other genotypes. All patients who acquired HCV before 1955 were infected with subtype 1b. Subtype 1a was introduced in the late 1950s and then, it became the most prevalent genotype
While we observed in dual antiviral therapy a better SVR of genotype 1a respect to genotype 1b patients, genotype 1a presents higher virologic failure respect to genotype 1b in patients treated with triple antiviral combination therapy including protease inhibitors Boceprevir or Telaprevir. Overall, the barrier to resistance is lower in genotype 1a than in genotype 1b strains, resulting in higher breakthrough rates in the former
In our study we found similar SVR in patients treated with pegylated interferon alfa-2a and alfa 2-b, this is in agreement with Ideal and AIFA study
The interleukin-28B (IL28B) polymorphism has been reported to influence viral kinetics and SVR in genotype 1 patients
Finally, we would like to emphasise that this study was conducted in "real- world- patients", thus providing a representative picture of HCV treatment.
While in triple antiviral combination therapy including protease inhibitors Boceprevir or Telaprevir genotype 1a presents higher virologic failure respect to genotype 1b patients, we observed in dual antiviral therapy a better SVR of genotype 1a respect to genotype 1b patients that is independent of other factors that may favour viral clearance.
Competing interests
All the authors declares the they not have received reimbursements, fees, funding, or salary from an organization that may in any way gain or lose financially from the publication of this manuscript, either now or in the future. All the authors declares that they do not hold any stocks or shares in an organization that may in any way gain or lose financially from the publication of this manuscript, either now or in the future. All the authors declare that they do not hold or apply any patents relating to the content of the manuscript. All the authors declare that they have not received reimbursements, fees, funding, or salary from an organization that holds or has applied for patents relating to the content of the manuscript. All the Authors declare that they not have any other financial competing interests.
Authors' contributions
AMP Concept-Design-Manuscript editing-Manuscript review-Manuscript preparation, Data acquisition MR Concept-Design-Literature search manuscript review, manuscript preparation, TS Statistical analysis, manuscript editing, manuscript review. LN Data acquisition, literature search. FM Data acquisition, manuscript review. CP Data acquisition, manuscript preparation, analysis of laboratory data. GB Statistical analysis ,Manuscript review. RM Data acquisition and manuscript review. EM Manuscript editing, Data acquisition. AP Data acquisition. MEB Manuscript review, data acquisition. CM Data acquisition. PV statistical analysis, data acquisition, manuscript editing. AA Manuscript editing, literature search. MM Literature search, data acquisition. CD Manuscript preparation, Data acquisition, Concept. LM Manuscript review, Data acquisition. OM Laboratory analysis, Data acquisition. UVG data acquisition. Manuscript preparation. CF Manuscript review and preparation, critical review of the mauscript AB Manuscript preparation, Data acquisition. GB Data acquisition, Manuscript preparation-Literature search, Manuscript review. All the authors read and approved the final manuscript
PROVE1 Study Team. Telaprevir with peginterferon and ribavirin for chronic HCV genotype 1 infection
SPRINT-1 investigators. Efficacy of boceprevir, an NS3 protease inhibitor, in combination with peginterferon alfa-2b and ribavirin in treatment-naive patients with genotype 1hepatitis C infection (SPRINT-1): an open-label, randomised, multicentre phase 2 trial
Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection
PEGASYS International Study Group. Peginterferon-alpha2a and ribavirin combination therapy in chronic hepatitis C: a randomized study of treatment duration and ribavirin dose
Low virological response and high relapse rates in hepatitis C genotype 1 patients with advanced fibrosis despite adequate therapeutic dosing
Peginterferon alfa-2b plus ribavirin for naïve patients with genotype 1 chronic hepatitis C: a randomized controlled trial
Effectiveness of hepatitis C virus treatment in real life practice: a prospective observational multicenter study in Italy (PROBE)
Influence of the HCV subtype on the virological response to pegylated interferon and ribavirin therapy
Influence of genotype 1 subtypes on the virus response to Peg interferon alpha-2a plus ribavirin therapy
PEG-IFN for chronic hepatitis C in clinical practice: the prospective phase of the AIFA study
Formulation and application of a numerical scoring system for assessing histological activity in asymptomatic chronic active hepatitis
American Gastroenterological association technical review on the management of hepatitis C
Hepatitis C virus genotypes in United States: epidemiology, pathogenicity, and response to interferon therapy
Clinical significance of hepatitis C virus genotypes
BERNAR-1 Study Group. A randomized open label, multicenter studyevaluating the efficacy of peginterferon alfa 2a, in combination with ribavirin, in naïve and relapsed chronic hepatitis C patient
Predictive value of rapid virological response and early virological response on sustained virological response in HCV patients treated with pegylated interferon alpha-2a and ribavirin
Resistance to direct antiviral agents in patients with hepatitis C virus infection
Peginterferon alfa-2b or alfa-2a with ribavirin for treatment of hepatitis C infection
Peginterferon alfa-2a plus ribavirin is nore effective than peginterferon alfa-2b plus ribavirin for treating chronic hepatitis C virus infection
Randomized study of peginterferon alfa2a plus ribavirin vs peginterferon alfa2b plus ribavirin in chronic hepatitis C
Comparative trials of peginterferon alfa-2a and peginterferon alfa-2b for chronic hepatitis C
Interleukin-28B polymorphism improves viral kinetics and is the strongestpretreatment predictor of sustained virologic response in genotype 1 hepatitis C virus
Pre-publication history
The pre-publication history for this paper can be accessed here:


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Some people practice meditation because it's the in thing to do. Popularized by the media and celebrities alike, meditation holds the promise of helping one to become rich and maybe even just a little famous.
For others, however, meditation is an entirely different thing all together. Not only is the practice used to reduce stress and anxiety and as a means to think more clearly in difficult situations, meditation is used as a way for these people to better get to know their true selves.
In this Q & A Intent post, Deepak Chopra reflects on meditation as a way to access one's core self, and in that, the freedom from one's mental conditioning.
For knowing your true self, I know of nothing better than starting a meditation. A silent meditation practice will give you the experience of your core self that lies beyond your thoughts, feelings and mental conditioning. Finding your essential nature independent of your past pain and confusion is not only illuminating, but it is also helpful in continuing your healing process. When you discover your true self, you know that your real self can never be hurt, clouded, or traumatized and this provides the understanding and security from which you can let go of the pain of the past.
Read more from Chopra on meditation and finding your true self here.


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SI (Systems Integration) has a deep understanding of the fresh produce sector and the problems that often occur during fruit and vegetable processing. That's why Integreater has been specifically developed to work with the perishable nature of these raw materials and short lead times.
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We went through a vigorous systems selection process and felt that Systems Integration can provide our business with market-leading consultancy, services and solutions.
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Dean Fowler, General Manager, R&G Herbs
If you work within this challenging sector and would like to discuss ways to improve efficiency, call 01543 444 555 to talk to one of our food productivity experts or email email@example.com to find out more about our fresh produce productivity software.