Equivalent Weights Research Articles

Raman study of water in Nafion-117 membranes

We report on a Raman scattering study of the state of water in the acid form of the perfluorosulfonate exchanger membrane Nafion-117 in H 2O- and D 2O-wet conditions. The data reveal that in Nafion-117 (molecular weight 1100), as distinct from Nafion with higher molecular weights (1200 and 1400), practically all water molecules participate in OH · · · H bonding rather than linking to the fluorocarbon matrix. Moreover, the shifts of the OH and OD bands in Nafion-1100 towards higher frequencies as compared to Nafion of larger equivalent weights (1200 and 1400) implies that the state of water in Nafion-117 is more bulk-like than in the higher molecular weight membranes.

Microelectrode Investigation of Oxygen Permeation in Perfluorinated Proton Exchange Membranes with Different Equivalent Weights

Oxygen concentrations (Cb) and diffusion coefficients (D) in various proton exchange membranes were measured using chronoamperometry at microelectrodes. These measurements were made under conditions similar to those prevailing in proton‐exchange‐membrane fuel cells. Knowledge of the D and Cb, parameters is essential for the determination of oxygen permeation in the catalytic layers of gas diffusion electrodes, which could be rate limiting in these low‐temperature fuel cells. Furthermore, the D and Cb values also provide the permeation rates of oxygen through the bulk of the proton conducting membrane. It was found that the concentration of oxygen increased and the diffusion coefficient decreased with increasing equivalent weight of the membranes. These results were interpreted using a model based on the microstructure of the swollen membranes separated into two phases, one hydrophobic and the other hydrophilic, with distinctly different ‐permeation properties. According to this model the relative amounts of the two phases in the membranes, caused by the different water contents, determine the solubility and diffusion coefficient in the different membrane materials.

Morphological Changes and Facilitated Transport Characteristics for Nafion Membranes of Various Equivalent Weights

Perfluorosulfonic acid materials such as Nafion1 that have been exchanged with Ag(I) ion have been shown to exhibit high selectivities with respect to membrane separations of mixtures of unsaturate...

Selection for carcass and feedlot traits considering alternative slaughter end points and optimized management.

Profit was defined as a function of the genotype of animals and variables controlled by management. Alternative parameterizations of management variables were examined to compare the effect of controlling age at slaughter, weight at slaughter, or fat depth at slaughter. The various parameterizations are shown to result in equivalent economic weights for genetic variables, provided management variables are optimized for the current genotype. The implication is that economic weights and selection indexes can be conveniently calculated for age constant end points even though commercial production may involve weight or backfat depth constant slaughter points. An example of selection for profit in the feedlot phase of beef production is presented. Three genotype-management combinations were considered. Economic weights and subsequent selection index weights were shown to depend on both average genotypic means and management (feeding and marketing program) factors.

Organotitanium(IV)-Catalyzed Cyclopolymerizations of 1,2-Diisocyanates and Cyclocopolymerizations of Monoisocyanates with 1,2-Diisocyanates

1,2-Diisocyanates were cyclopolymerized using CpTiCl 2 N(CH 3 ) 2 . Treatment of 1,2-diisocyanatodecane with CpTiCl 2 N(CH 3 ) 2 in THF effected its cyclopolymerization with stoichiometric control over molecular weight and with M w /M n ranging from 1.2 to 1.8. IR, 1 H NMR, and 13 C NMR spectra of the resulting polymers indicate that the monomer underwent complete cyclization. Studies of the solution properties of poly(1,2-diisocyanatodecane) showed that it maintains a smaller hydrodynamic volume than poly(n-hexyl isocyanate) at equivalent molecular weights. Living poly(n-hexyl isocyanate) was end-capped with blocks of poly(1,2-diisocyanatopropane) and poly(1,2-diisocyanatodecane). TGA and DSC studies of these block copolymers showed that the individual block segments decomposed at the same temperatures as their respective homopolymers. Random copolymerizations of n-hexyl isocyanate with 1,2-diisocyanatopropane and 1,2-diisocyanatodecane were conducted. TGA studies of these macromolecules showed that the decomposition temperature of the copolymer was a function of its 1,2-diisocyanate content, and the incorporation ofa relatively high mole percent of the diisocyanate monomer was necessary to observe an increase in the decomposition onset of the copolymer.

Statewide Truck Transportation Planning: Methodology and Case Study

An alternate approach for truck transportation planning at the state level is presented using a case study application in the State of Iowa. The method was based on some freight modeling concepts and available freight data sets. However, the model takes advantage of two concepts: unconstrained highway capacities and the decomposition of commodities, resulting in manageable data and modeling requirements. Identification of significant economic sectors, selection of appropriate productivity measures, estimation of truck freight volumes for each sector individually, and estimation of routing of truck traffic on major highway routes are major elements of the planning method. The case study used two industrial sectors—food and kindred products, and machinery products—which accounted for the largest portion of state employment in nonservice sectors and the largest truck traffic generated in the state. A simplistic transportation network was used to demonstrate the modeling procedure. The analysis uses county-level employment and population to estimate zonal freight tonnage. The truck share of generated freight was estimated as the total freight generated less the freight tonnage shipped by rail. A gravity model was used to distribute the truck tonnage among origin-destination pairs, using travel time as the impedance on highway links. Estimated truck flows were converted to vehicle trips on least time highway routes using typical vehicle equivalent weights.

Synthesis and Properties of a Novel Fluorine-Containing Alicyclic Diepoxide

A novel fluorine-containing alicyclic diepoxide resin, the diglycidyl ether of bis(1,1,1,3,3,3-hexafluoropropyl)cyclohexane (CHEP), has been synthesized using benzene, hexafluoroacetone, and epichlorohydrin. The CHEPs, consisting of a mixture of 1,3- and 1,4-isomers, whose epoxy equivalent weights are 270 and 290, are liquids with viscosities of 5000 and 30 000 cP at 25 °C, whereas the 1,4-isomer CHEP is a solid resin. The liquid CHEPs show low refractive indexes of ∼1.405 due to the high fluorine content of more than 43 wt %. They also show high optical transparency to UV because they are nonaromatic hydrocarbons. The CHEPs can be cured by heat or UV irradiation in the presence of curing agents. The cured resins show refractive indexes of less than 1.45, and a 1-mm-thick film has a high transparency of more than 80%, which includes Fresnel's reflection loss at both sides of the film/air interfaces, at wavelengths from 0.5 to 1.6 μm. The glass transition temperature is up to 53 °C, and tensile shear strength to quartz glass is more than 100 kg/cm2.

Bioavailable Herbicide Residues in Turfgrass Clippings Used for Mulch Adversely Affect Plant Growth

Grass clippings may comprise a minimum of 35% of yard waste. We investigated whether bioavailable herbicide residues in grass clippings used as mulch would be toxic to desirable plants. In each of three experiments, tall fescue (Festuca arundinacea Schreb.) was treated with a mixture of 2,4-D + dicamba + MCPP at 0.5 g total a.i./m2. Clippings were collected at 1-, 5-, 10-, and 15-day postspray intervals. Clippings at gram equivalent weights relative to desired mulching depths were applied to tomato (Lycopersicon esculentum L.), cucumber (Cucumis sativus L.), salvia (Salvia splendens F.), and marigold (Tagetes tenuifolia Cav.) grown in pots. Plant dry-weight comparisons were made at two destructive harvest intervals, from 2 to 5 weeks after mulching. No mulch and nontreated mulch treatments were used as controls. Growth of tomato and marigold was enhanced when nontreated grass mulch was used compared to no mulch, but growth of cucumber and salvia was not enhanced. The bioavailable residues relative to the postspray interval (1 to 15 days) influenced growth of all species. Mulching depth affected growth of all species, except salvia. Herbicide-treated mulch reduced dry weight by ≤80% for cucumber, 73% for tomato, 65% for marigold, and 34% for salvia compared to controls. Herbicide residues apparently increased with mulching depth, resulting in a cumulative effect inhibiting plant growth. Chemical names used: 2,4-dichlorophenoxyacetic acid (2,4-D); 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP); and 3,6-dichloro-o-anisic acid (dicamba).

The 1995 Clinical Research Award

Pediatric patients with severe burns exhibit growth delays. This study investigates weight history after discharge. Twenty-seven children with burns covering more than 40% of their total body surface area were studied from admission until 2 to 4 years after injury. Younger children decreased their weights for height; older patients mainly increased theirs. Alterations during the first year of follow-up correlated with alterations until 2 and 3 years (r = 0.91 and r = 0.76, respectively). Once initiated, net weight gain continued, whereas net weight losses diminished with time. Preburn equivalent weights, however, could not be reached within 3 years. Special attention must be paid to children who are close to or less than their ideal body weights at the time of injury, especially if they are young, because further weight loss may be critical. Outpatient nutritional therapy should be focused to control these developments.

Quantization and the foundations of chemistry

The mass relationships associated with a system of chemical equations are studied in a general way as a linear algebraic structure; initially the linear space is represented in terms of the matrix relations of stoichiometry, and subsequently more abstractly in terms of linear operators working on a carrier space. Various mathematical structures arise naturally so that ultimately the framework might be extended to a Hilbert space. The determination of a consistent set of atomic weights from the directly accessible experimental information recorded in equivalent weights was a notorious indeterminate problem in the nineteenth century. The indeterminacy arises in the present formalism because of the freedom to represent the linear space in terms of any valid basis, while the physical interpretation requires the selection of a privileged representation. It is argued that at a fundamental level this should arise through quantization, and the paper represents a first step in that direction by formulating the sto...

Studies on Methanol Crossover in Liquid-Feed Direct Methanol PEM Fuel Cells

The performance of liquid feed direct methanol fuel cells using various types of Nafion membranes as the solid polymer electrolyte have been studied. The rate of fuel crossover and electrical performance has been measured for cells with Nafion membranes of various thicknesses and equivalent weights. The crossover rate is found to decrease with increasing thickness and applied current. The dependence of crossover rate on current density can be understood in terms of a simple linear diffusion model which suggests that the crossover rate can be influenced by the electrode structure in addition to the membrane. The studies suggest that Nafion EW 1500 is a very promising alternate to Nafion EW 1100 for direct methanol fuel cells.

Genetically size-scaled growth and composition of Dorset and Suffolk rams

AbstractThirty-four Dorset and 34 Suffolk rams were slaughtered in pairs within breed at birth, weaning, at monthly intervals to 420 days and then at bimonthly intervals until 600 days to compare factors used to estimate mature size and to determine how genetic size-scaling affects the comparison of body composition between breeds. At equal empty body weights there were no detectable differences between the breeds in amounts of water, protein or ash but Dorsets contained more lipid. Dorset and Suffolk asymptotic values of water (40 and 61 kg), water-plus-protein-plus-ash (51 and 77 kg), metacarpal bone length (127 and 147 mm) and metacarpal bone weight (59 and 101 g) were used to estimate mature size. Regardless of the estimator of mature size, there were no significant differences between breeds in degree of maturity at a given metabolic age. At the same degree of maturity within the estimators of mature size, there were no differences between breeds in the degree of maturity of water, protein or ash, with the exception of small differences in protein for two of the mature size indicators. Because lipid appeared to accumulate without limit in these sheep, the mature body was assumed to contain 300 g lipid per kg. Using this proportion to estimate amount of mature lipid, there was a higher degree of maturity of lipid for Suffolk than for Dorset rams at equal degrees of maturity of water, water-plus-protein-plus-ash or metacarpal bone weight. Thus, Dorsets with greater lipid content at equivalent empty body weights were leaner than Suffolks when adjusted for mature size.

Effect of Individual Housing and Other Experimental Design Factors on Tumor Incidence in B6C3F1 Mice

Effect of Individual Housing and Other Experimental Design Factors on Tumor Incidence in B6C3F1 Mice. J Haseman, J. K., Bourbina, J., and Eustis, S. L. (1994). Fundam. Appl. Toxicol. 23, 44-52.The effects of individual housing and other experimental design factors on body weight, survival, and tumor incidence in 72 control groups of B6C3F1 mice were evaluated. Individually housed males showed a greatly reduced incidence of dermal/subcutaneous tumors and an improved survival relative to group-housed animals. However, there were significant body weight increases in individually housed males and females and an associated marked increase in liver tumor incidence in both sexes and a lesser increase in lung neoplasms in males. Body weights of mice as young as 19 weeks of age were predictive of subsequent liver tumor incidence. There were no major differences in tumor rates among the various types of control groups, and differences in tumor rates among laboratories were not significant for most tumors. Differences among animal suppliers may have contributed to the time-related decreased incidence of malignant lymphoma observed in control mice, particularly in females. Comparisons with earlier control tumor rates suggest that there has been little change in tumor incidence for control groups having approximately equivalent body weights. However, control groups with heavier animals have shown a striking increase in the incidence of liver tumors. The National Toxicology Program recently returned to its earlier practice of group-housing female mice, and this should reduce the incidence of liver tumors in this sex-species group. However, if measures are not taken to reduce body weights, male mice (which continue to be individually housed because of fighting problems among group-housed animals) will likely continue to show a high incidence of liver tumors and possibly also lung neoplasms.

Effect of Individual Housing and Other Experimental Design Factors on Tumor Incidence in B6C3F1 Mice

The effects of individual housing and other experimental de sign factors on body weight, survival, and tumor incidence in 72 control groups of B6C3F1 mice were evaluated. Individually housed males showed a greatly reduced incidence of dermal/subcutaneous tumors and an improved survival relative to group-housed animals. However, there were significant body weight increases in individually housed males and females and an associated marked increase in liver tumor incidence in both sexes and a lesser increase in lung neoplasms in males. Body weights of mice as young as 19 weeks of age were predictive of subsequent liver tumor incidence. There were no major differ ences in tumor rates among the various types of control groups, and differences in tumor rates among laboratories were not sig nificant for most tumors. Differences among animal suppliers may have contributed to the time-related decreased incidence of malignant lymphoma observed in control mice, particularly in females. Comparisons with earlier control tumor rates suggest that there has been little change in tumor incidence for control groups having approximately equivalent body weights. However, control groups with heavier animals have shown a striking increase in the incidence of liver tumors. The National Toxicology Program recently returned to its earlier practice of group-housing female mice, and this should reduce the incidence of liver tumors in this sex-species group. However, if measures are not taken to reduce body weights, male mice (which continue to be individually housed because of fighting problems among group-housed animals) will likely continue to show a high incidence of liver tumors and possibly also lung neoplasms.

Degradable polyurethane networks based on d,l-lactide, glycolide, ε-caprolactone, and trimethylene carbonate homopolyester and copolyester triols

Several trifunctional, hydroxy-telechelic polyester and poly(ester-carbonate) homopolymers and copolymers were synthesized by the triol-initiated, ring-opening bulk polymerization of d,l-lactide, glycolide, ε-caprolactone, and/or trimethylene carbonate. The molar compositions of the copolymers were determined from 13C n.m.r. spectra; hydroxy equivalent weights were determined by acetylation titration, and the glass transition temperatures ( T g) and melting points were determined by differential scanning calorimetry (d.s.c.). Crosslinked polyurethane networks were prepared by reacting the hydroxy-telechelic prepolymers with tolylene diisocyanate. Network characterization included determination of sol content by solvent extraction, T g by d.s.c., tensile properties by stress-strain measurements, and degradation properties by hydrolytic degradation studies. Equilibrium swelling results indicated that the per cent weight gains correlated well with the prepolymer hydroxy equivalent weights, with the exception of the poly(glycolide- co-trimethylene carbonate) network. The poly( d,l-lactide) and poly( d,l-lactide- co-trimethylene carbonate) (PLTMC) networks had the highest tensile strengths of 49.60 and 41.27 MPa, respectively, and glass transition temperatures of 51.3 and 21.3°C, respectively. All other networks were highly flexible with tensile strengths of 12 MPa or less. Hydrolytic degradation studies were conducted by placing network samples in a solution of phosphate-buffered saline (pH = 7.4) at 37°C. Weight uptake of buffer and weight loss of the networks were monitored gravimetrically over time. Tensile properties, monitored as a function of degradation time, indicated that the poly(ε-caprolactone- co- d,l-lactide) and PLTMC networks displayed a linear loss of strength with respect to weight during the first 30 days of degradation; the other networks degraded either too slowly or too quickly to establish such a linear relationship.

Synthesis and characterization of linear and three-arm star radial poly(styrene- b-isobutylene- b-styrene) block copolymers using blocked dicumyl chloride or tricumyl chloride/TiCl 4/pyridine initiating system

Linear and three-arm star styrene- b-isobutylene- b-styrene block copolymers were synthesized by living cationic polymerization using ring-substituted di- or tricumyl chloride, respectively, as initiator, TiCl 4 as coinitiator, pyridine as an electron donor and 2,6-di-tert-butylpyridine as a proton trap in a 60 40 ( v v ) methylcyclohexane/methyl chloride solvent mixture at − 80°C. The polymers had equivalent compositions and segmental molecular weights allowing the effect of molecular geometry on sample morphology and physical properties to be determined. The samples exhibited a dual-phase morphology consisting of cylindrical polystyrene domains dispersed within a matrix of polyisobutylene; polymer geometry was found to have a significant effect on the tensile properties, with the three-arm star sample displaying a tensile strength twice that of the linear sample. In addition, the three-arm star block copolymer was found to have a higher rubbery plateau modulus than the linear block copolymer. Due to their perfectly saturated mid-block, polyisobutylene-based block copolymers were found to be much more thermally stable than the closely related styrene- b-(ethylene- co-l-butene)- b-styrene block copolymers (hydrogenated polybutadiene centre block).

Effects of Addition of an Electrolyte on Size Exclusion Chromatography of Polyamides Using Hexafluoro-2-Propanol as Mobile Phase

Abstract Polyelectrolyte effects for polyamides and poly(methyl metha-crylate)(PMMA) used as calibration standards and the suppression of these effects by the addition of sodium trifluoroacetate to the mobile phase were shown and discussed. The addition of the electrolyte helped to the disaggregation of the polymer samples by breaking down hydrogen bonding. Besides the disaggregation of the polymer samples, the addition of the electrolyte caused the change of the retention volume and peak width of PMMA. Elution of PMMA having higher molecular weight than 6×104 was retarded and that having smaller one than 6×104 was hastened by the addition of the electrolyte. Peak width of PMMA became also narrower in about 20%. PMMA equivalent molecular weights of polyamides were plotted against real molelcular weights of the polyamides measured by end group analysis and next equations were obtained. log Mnylon 6 = -i. 53402 +1.352 log MPMMA eq log Mnylon 6 6 = -4.88506 + 2.143 log MpMMA eq

Oxygen permeation through perfluorinated carboxylate ion exchange membranes

Permeation of oxygen through perfluorinated carboxylate membranes (Flemion ®) of different counterions and equivalent weights (EW = 700 and 800) was investigated. Solubilities and diffusion coefficients of oxygen in the membranes were determined by an electrochemical monitoring technique using solid polymer electrolyte composite electrodes. The solubilities were close to the values in perfluorocarbon media rather than to the value in water. The solubility decreased with increasing water content of the membranes. The diffusion coefficient in 700 EW membranes increased with increasing water content, while that in 800 EW membranes decreased slightly. On the basis of these results, the diffusion path of oxygen through the membranes was discussed in terms of morphological properties of perfluorinated ion exchange membranes.

Effects of Heat Treatment on the Nutritional Value of Conventional and Low Trypsin Inhibitor Soybeans for Chicks

Two experiments were conducted to assess the nutritional value of conventional and low trypsin inhibitor (TI) soybeans when fed in raw or heated form for chicks. In Experiment 1, four replicates of eight chicks per pen were fed corn-based diets (19% CP, 3,158 kcal ME/kg) containing raw or heated conventional soybeans, raw or heated low TI soybeans, or conventional soybean meal (44% CP) plus oil. Heating was achieved by autoclaving the soybeans for 20 min at 110 C. Treatments were the same in Experiment 2 except that the soybeans were heated for 20 or 40 min. The TI activity of the low TI soybeans was approximately one-half that of the raw conventional soybeans (9.6 versus 22.1 mg/g). Heating reduced the TI activity of both types of soybeans. Chick growth, feed utilization, and apparent retention of dietary DM and N were markedly depressed and pancreatic hypertrophy occurred when the raw conventional soybeans were fed. Depressions in performance and N retention and increases in pancreatic weights also occurred when chicks were fed raw low TI soybeans, but the responses were not as pronounced as when raw conventional soybeans were fed. Heat treatment reduced the TI activity of both types of soybeans and resulted in improved chick weight gain, feed:gain, and dietary DM and N retention, and reduced pancreatic weights (P < .01). In Experiment 1, chicks fed low TT soybeans heated for 20 min performed as well and had equivalent pancreas weights as those fed soybean meal. In Experiment 2, chicks fed either type of soybean heated for 40 min did not perform as well as those fed soybean meal. The results indicate that low TI soybeans are nutritionally superior to conventional soybeans, but some heating is required to maximize their nutritional value.

New epoxy‐terminated oligoesters: Precursors to totally biodegradable networks

AbstractTwo types of novel biodegradable epoxy resins, carrying cycloaliphatic‐epoxy and glycidyl ester end‐groups, have been synthesized from hydroxy‐telechelic oligoesters. The cycloaliphatic‐epoxy end‐groups were based on either methyl cis‐4‐cyclohexene‐2‐(carboxylic acid)‐1‐carboxylate or 3‐cyclohexene‐1‐carboxylic acid. These compounds were reacted with hydroxy‐telechelic poly(ε‐caprolactone‐co‐D,L‐lactide) oligoesters, yielding cycloaliphatic‐olefin‐terminated oligomers. Conversion of the olefin to the epoxide groups was achieved using a phase transfer epoxidation with an inorganic peracid derived from the reaction of phosphoric acid, sodium tungstate, and hydrogen peroxide. Aliquat 336, a quaternary ammonium salt, acted as the phase transfer catalyst. Nearly theoretical conversion of hydroxy to epoxy end‐groups was achieved in only one case, however, alternative variations of this method of synthesis show promise. To prepare glycidyl ester‐terminated prepolymers, hydroxy‐telechelic poly(ε‐caprolactone) oligoesters were reacted with succinic anhydride, in 1,2‐dichloroethane with 1‐methylimidazole as catalyst, resulting in (carboxylic acid)‐terminated oligomers. After conversion of the end‐groups to the potassium carboxylate salt by titration with methanolic KOH, the isolated salt was dried and reacted with epibromohydrin in acetonitrile at reflux, using an 18‐C‐6 crown ether as the phase transfer catalyst, thus preparing the (glycidyl ester)‐telechelic prepolymer. Epoxide equivalent weights differed by 2.7–7.1% from the theoretical values. These cycloaliphatic‐epoxide and glycidyl ester‐terminated prepolymers may be crosslinked with anhydrides or amines, respectively, to produce totally bioabsorbable networks. © 1993 John Wiley &amp; Sons, Inc.