Showing papers by "University of Arkansas published in 1992"

Multicultural Counseling Competencies and Standards: A Call to the Profession

Abstract: In April 1991, the Association for Multicultural Counseling and Development (AMCD) approved a document outlining the need and rationale for a multicultural perspective in counseling. The work of the Professional Standards committee went much further in proposing 31 multicultural counseling competencies and strongly encouraged the American Association for Counseling and Development (AACD) and the counseling profession to adopt these competencies in accreditation criteria. The hope was to have the competencies eventually become a standard for curriculum reform and training of helping professionals.

The calculation of ab initio molecular geometries: efficient optimization by natural internal coordinates and empirical correction by offset forces

Abstract: Two suggestions are made to increase the efficiency and accuracy of ab initio optimization of molecular geometries. To improve the convergence of the optimization, a set of internal coordinates, the natural valence coordinates, is suggested. These coordinates originate from vibrational spectroscopy and reduce both harmonic and anharmonic coupling terms in the potential function as much as possible in a purely geometrical definition. The natural valence coordinates are local, eliminate most redundancies, and conform to local pseudosymmetry. Special attention has been paid to ring systems. A computer program has been included in our program system TX90 to generate the natural internal coordinates automatically. The usefulness of these coordinates is demonstrated by numerous examples of ab initio geometry optimization. Starting with a geometry preoptimized by molecular mechanics and using a simple diagonal estimate of the Hessian in conjunction with the GDIIS optimization technique, we usually achieved convergence in 8-15 steps, even for large molecules. It is demonstrated that, due to the reduction in anharmonic couplings, natural coordinates are superior to Cartesian or other simple internal coordinates, even when an accurate initial Hessian is available. Constrained optimization and the location of transition states are also discussed. The gradient optimization method has been generalized to handle redundancies; this is necessary in some complex polycyclic molecules and is illustrated on, among others, the porphine molecule. To increase the accuracy of relatively low-level calculations, empirical corrections to ab initio SCF geometries are suggested in the form of “offset forces” acting along bonds. We recommend offset forces for the most important bonds, to be used with the 4-21G(*) and the 6-31G* basis sets. Based on 130 comparisons, the mean absolute error between theoretical and experimental bond lengths is reduced this way from 0.014 to 0.005 A.

Interaction of Nest Predation and Food Limitation in Reproductive Strategies

Abstract: Heritable reproductive strategies that yield the greatest lifetime production of surviving offspring are favored by natural selection. I consider a reproductive strategy to be the complement of behaviors and traits associated with reproduction that influence lifetime reproductive success. Trade-offs among standard life history traits (e.g., clutch size, growth rate, juvenile and adult mortality) influence success of reproductive strategies (see reviews by Stearns, 1976; Martin, 1987). In addition, energy allocation between reproduction and other activities can influence expression of traits such as clutch size (Cody 1966). However, for organisms that care for their young, success of traits is also strongly affected by the amount of energy and time allocated to care of young by parents (Trivers, 1972, 1974; Low, 1978; Clutton-Brock, 1984). In other words, allocation of energy and time among different activities within reproduction can be as important as allocation between reproduction and other activities.

Geometry optimization in redundant internal coordinates

Abstract: The gradient geometry‐optimization procedure is reformulated in terms of redundant internal coordinates. By replacing the matrix inverse with the generalized inverse, the usual Newton–Raphson–type algorithms can be formulated in exactly the same way for redundant and nonredundant coordinates. Optimization in redundant coordinates is particularly useful for bridged polycyclic compounds and cage structures where it is difficult to define physically reasonable redundancy‐free internal coordinates. This procedure, already used for the geometry optimization of porphine, C20N4H14, is illustrated here at the ab initio self‐consistent‐field level for the four‐membered ring azetidine, for bicyclo[2.2.2]octane, and for the four‐ring system C16O2H22, the skeleton of taxol.

Reconstruction and Analysis of Spring Rainfall over the Southeastern U.S. for the Past 1000 Years

Abstract: Tree-ring chronologies can provide surprisingly accurate estimates of the natural variability of important climate parameters such as precipitation and temperature during the centuries prior to the industrial Revolution. Bald cypress tree-ring chronologies have been used to reconstruct spring rainfall for the past 1000 years in North Carolina, South Carolina, and Georgia. These rainfall reconstructions explain from 54% to 68% of the spring rainfall variance in each state, and are well verified against independent rainfall measurements. In fact, these tree-ring data explain only 6% to 13% less statewide rainfall variance than is explained by the same number of instrumental raingage records. The reconstructions indicate that the spring rainfall extremes and decade-long regimes witnessed during the past century of instrumental observation have been a prominent feature of southeastern United States climate over the past millennium. These spring rainfall regimes are linked in part to anomalies in the seasonal expansion and migration of the subtropical anticyclone over the North Atlantic. The western sector of the Bermuda high often ridges strongly westward into the southeastern United States during dry springs, but during wet springs it is usually located east of its mean position and well offshore. Similar anomalies in the western sector of themore » Bermuda high occurred during multidecadal regimes of spring rainfall over the Southeast. During the relatively dry springs from 1901 to 1939, the high often ridged into the Southeast, but the western periphery of the high was more frequently located offshore during the relatively wet period from 1940 to 1980. Spring and summer rainfall extremes and decade-long regimes over the Southeast are frequently out of phase, and the tendency for wet (dry) springs to be followed by dry (wet) summers also appears to reflect anomalies in the zonal position of the Bermuda high during spring and summer.« less

Dispositional affect and work-related stress.

Abstract: Trait negative affectivity (NA) has been asserted to be a factor that spuriously inflates relationships between self-reported stressors and self-reported strain outcomes. We tested this hypothesis with conventional work stress instrument responses and physiological assessments obtained from 311 fire and police department employees. Confirmatory factor analyses indicated that NA did not measure a factor in common with measures of subjective strain. Latent-variable structural equations analyses, however, found that estimating the effects of NA on strain significantly attenuated the effects of work stressors. NA had no correlation with physiological stress outcomes. Trait positive affectivity did not attenuate relationships between work stressors and either subjective or objective stress outcomes. Implications for work stress research methodology and recommendations are discussed.

Differential Effectiveness of Applicant Impression Management Tactics on Employment Interview Decisions1

Abstract: It has been a commonly held belief for some time that applicants attempt to manage impressions of interviewers in the employment interview process, but only recently have researchers begun to examine systematically the tactics applicants use, and how effective they are. The present study contrasted two sets of impression management tactics used by applicants and observed their effects on interviewer decisions in a controlled laboratory experiment. An applicant who employed self-focused-type impression management tactics was rated higher, received more recommendations for a job offer, and received fewer rejections from business students, who had just completed an interviewer training program, than when he used other-focused-type tactics. The implications of these results in terms of both theory and practice are discussed.

Path analysis of rice yield and yield components as affected by seeding rate

Abstract: Understanding relationships among rice (Oryza sativa L.) yield and yield components (panicle density, filled grain per panicle, unfilled grain per panicle, and grain weight) is critical to utilizing these relationships effectively. Interrelationships among rice yield and yield components for direct-seeded rice cultural systems using path-coefficient analysis that describes a priori cause-and-effect relationships have not been shown. Our objective was to study direct-seeded rice yield and yield component relationships as affected by seeding rates using path-coefficient analysis. «Lemont», a semidwarf rice, was seeded at 43, 85, 128, 170, and 213 kg ha −1 in four environments between 1986 and 1988 (...)

Sorption of heavy metals by the soil fungi Aspergillus niger and Mucor rouxii

Abstract: Sorption of the nitrate salts of cadmium(II), copper(II), lanthanum(III) and silver(I) by two fungi, Aspergillus niger and Mucor rouxii, was evaluated using Freundlich adsorption isotherms and energy dispersive X-ray electron microscopy. The linearized Freundlich isotherm described the metal sorption data well for metal concentrations of 5 μm-1 Mm metal. Differences in metal binding were observed among metals, as well as between fungal species. Calculated Freundlich K values indicated that metal binding decreased in the order La3+ ⩾ Ag+ > Cu2+ > Cd2+. However, sorption of Ag+ was greater than that of La3+ from solutions of 0.1 and 1 mM metal and likely due to precipitation at the cell wall surface. At the 1 mM initial concentration, there were no significant differences between the two fungi in metal sorption, except for Ag+ binding. At the 5 μM concentration, there was no difference between the fungi in their sorption capacities for the four metals. Electron microscopy-energy dispersive X-ray analysis indicated that silver precipitated onto cells as colloidal silver. The results indicate that Freundlich isotherms may be useful for describing short-term metal sorption by fungal biomass and for comparison with other soil constituents in standardized systems.

16S rRNA-based probes and polymerase chain reaction method to detect Listeria monocytogenes cells added to foods.

Abstract: A rapid polymerase chain reaction (PCR) method was developed for detection of Listeria monocytogenes in foods. This method used a pair of primers based on a unique region in the 16S rRNA sequence of L. monocytogenes, which were previously reported by us to yield a specific nucleic acid probe. Our method included use of a shorter denaturing time, a shorter annealing time, a rapid transition, and an increase in the number of cycles, resulting in good sensitivity. Just 3 h for PCR plus 1 h for electrophoresis was required. Additional time for DNA isolation and DNA hybridization was not needed. This method detected as few as 2 to 20 CFU of L. monocytogenes in pure cultures and as few as 4 to 40 CFU of L. monocytogenes in inoculated (10(8) CFU), diluted food samples. Seven of eight foods, including four poultry products, gave positive results. Only one food sample, soft cheese, gave interference. An internal probe hybridization test was used to confirm that the PCR products were from L. monocytogenes. A specificity test indicated that this PCR method was positive for all 13 strains of L. monocytogenes tested but negative for the other 6 species of Listeria, including 6 strains of L. innocua, and negative for 17 other gram-positive and gram-negative bacteria tested. Images

Nucleotide and amino acid sequence of pap-gene (pediocin AcH production) in Pediococcus acidilactici H.

Abstract: N-terminal analysis of purified pediocin AcH produced a partial sequence of 23 amino acids This sequence matched perfectly with a segment of 23 amino acids in a 62 amino acid molecule generated from the 186 nucleotide sequence open reading frame in a Hind III fragment in pSMB74 encoding pap-gene (pediocin AcH production) It is suggested that the molecule is translated as inactive prepediocin AcH of 62 amino acids Then through enzymatic modifications the leader segment of 18 amino acids is removed from the NH2-terminal The remaining segment of 44 amino acids is active pediocin AcH of 4628 Mr

The effects of furfural on ethanol production by saccharomyces cereyisiae in batch culture

Abstract: Browning reaction products such as furfural and 5-hydroxy-methyl-furfural (HMF) have been shown to inhibit microbial growth and metabolism in ethanol fermentations using Saccharomyces cerevisiae. This paper quantifies the extent of furfural inhibition on yeast growth, glucose utilization, and ethanol production as a function of inoculum size (0.1–9 gl−1. Batch culture experiments were conducted using furfural concentrations in the range of 0 to 2.0 gl−1. and mathematical correlations were proposed and tested. The results indicate that the specific growth rate decreased with increasing furfural concentration and inoculum size, while the maintenance coefficients were unaffected. The apparent and true cell yield coefficients on glucose were depressed with the addition of furfural. Specific production rates were unaffected at the furfural levels used but ethanol inhibition was apparent. The specific production rate was less inhibited by ethanol at higher inoculum sizes. Global specific productivities were not affected by the presence of furfural. At a 0.1 gl−1. inoculum size, furfural depletion was complete within 15–20 h, depending upon the furfural concentration employed. At higher inoculum levels (2–9 gl−1. all furfural was depleted in less than 5 h.

Preparation and Solid-state Structures of (Cyanophenyl)dithia- and (Cyanophenyl)diselenadiazolyl Radicals

Abstract: The preparation and solid-state characterization of the dimers of the cyanophenyl-substituted 1,2,3,5-dithia- and 1,2,3,5-diselenadiazolyl radicals [NCC6H4CN2E2]· (E = S, Se) are described. Crystals of the 4-cyanophenyl derivatives 4 are triclinic, space group P¯1. The radicals dimerize in a cofacial fashion, with mean intradimer E- - -E spacings of 3.104/3.233 A (E = S/Se). The dimer units form ribbonlike arrays connected by head-to-tail CN- - -E contacts. The ribbons are packed in an antiparallel fashion with no close interdimer E- - -E contacts. The 3-cyanophenyl sulfur derivative 5 crystallizes in two phases. The α-phase, along with the isomorphous selenium compound, belongs to the monoclinic space group P21/n. As in the 4-cyano derivatives, the radicals dimerize cofacially, generating ribbons connected by head-to-tail CN- - -E contacts. The ribbons, however, are layered with CN2E2 rings oriented into stacks parallel to the a axis. In addition to short intradimer E- - -E contacts (mean values = 3.13 (2)/3.27 (4) A for E = S/Se), there are relatively short interdimer E- - -E contacts (mean values = 4.26 (5)/4.15 (5) A (E = S/Se) along the stacking axis. The β-phase of the 3-cyanophenyl sulfur compound 5, monoclinic space group P21/n, forms discrete dimers associated in a trans antarafacial fashion, with intradimer S- - -S contacts of 3.121 (1) A; there are no close interdimer S- - -S contacts. The 2-cyanophenyl selenium derivative 6 crystallizes in the polar space group P21. In this structure also the dimer units are laced together by short CN- - -Se contacts. The dimers form stacks parallel to the b axis, with mean intradimer and interdimer Se- - -Se contacts of 3.312/4.083 A, respectively. Lattice constants for the six structures are: 4 (E = S), C8H4N3S2, a = 10.466 (3) A, b = 10.342 (2) A, c = 9.169 (2) A, α = 104.97 (2)°, β = 112.97 (2)°, γ = 69.84 (2)°, V = 849.0 (3) A3, Z = 4; 4 (E = Se), C8H4N3Se2, a = 10.478 (4) A, b = 10.780 (4) A, c = 9.432 (4) A, α = 107.16 (3)°, β = 115.23 (2)°, γ = 68.39 (3)°, V = 883.8 (6) A3, Z = 4; 5 (E = S, α-phase), C8H4N3S2, a = 7.295 (3) A, b = 20.488 (2) A, c = 11.276 (2) A, β = 95.54 (2)°, V = 1676.0 (7) A3, Z = 8; 5 (E = Se), C8H4N3Se2, a = 7.364 (8) A, b = 21.085 (2) A, c = 11.119 (4) A, β = 94.91 (5)°, V = 1720 (7) A3, Z = 8; 5 (E = S, β-phase), C8H4N3S2, a = 8.782 (1) A, b = 5.638 (1) A, c = 17.128 (4) A, β = 102.94 (2)°, V = 826.5 (6) A3, Z = 4; 6 (E = Se), C8H4N3Se2, a = 7.301 (1) A, b = 11.883 (2) A, c = 10.186 (1) A, β = 101.50 (1)°, V = 866.1 (5) A3, Z = 4.

Health status and needs of migrant farm workers in the United States: a literature review.

Abstract: Migrant farmworkers lead a hard life filled with strenuous work, stress, and anxiety about employment; live under substandard conditions; and rarely get the health care they require. Preventive care is a luxury they cannot afford. Year-round nutritious meals are rarely possible, due to long working hours, traveling, and living in housing without adequate cooking and refrigeration facilities. Children may attend up to six or more schools during the course of a school year. Crowded housing conditions support the invasion of parasites, infectious diseases, and viral infections. Dermatological conditions from working around a wide variety of plants, dirt, and in the sun are frequent. Exposure to pesticides, herbicides, and other chemical additives creates the likelihood of acute reactions, such as headaches and rashes, and also puts workers at risk of developing chronic diseases as the level of exposure rises because of accumulation and mix of various chemicals. Yet, we know little about the health status of this population. We are unable to estimate crude death rates, age-specific death rates, or prevalence rates of most common causes of death, such as heart disease,cancer and stroke. There is no information about occupational accident rates, infectious disease rates, or even postneonatal mortality. We do know that when migrants go to a clinic, they are often likely to have the chronic conditions of hypertension or diabetes. They present symptoms of acute conditions such as dental problems, dermatitis, otitis media among children, and acute upper respiratory infections. Women frequently need obstetrical care, reflected (ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative structure-activity relationship investigation of the role of hydrophobicity in regulating mutagenicity in the Ames test: 2. Mutagenicity of aromatic and heteroaromatic nitro compounds in Salmonella Typhimurium TA100.

Abstract: A quantitative structure-activity relationship (QSAR) has been derived for the mutagenic activity of 117 aromatic and heteroaromatic nitro compounds acting on Salmonella typhimurium TA100. Relative mutagenic activity is bilin-early dependent on hydrophobicity, with an optimal log P of 5.44, and is linearly dependent on the energy of the lowest unoccupied molecular orbital of the nitro compound. The dependence of mutagenic activity on hydrophobicity and electronic effects is very similar for TA98 and TA100. Mutagenic activity in TA100 does not depend on the size of the aromatic ring system, as its does in TA9. The effect of the choice of assay organism, TA98 versus TA100, on nitroarene QSAR is seen to be similar to the effect previously found for aminoarenes. Lateral verification of QSARs is presented as a tool for establishing the significance of a new QSAR.

Premating isolation is determined by larval substrates in cactophilic drosophila mojavensis.

Abstract: Premating isolation among geographically isolated populations of Drosophila mojavensis is an often cited example of incipient speciation (Wasserman and Koepfer, 1977; Zouros and D'Entremont, 1980; Markow, 1981, 1991; Markow et aI., 1983; Markow and Toolson, 1990; Koepfer, 1987a, 1987b; Krebs, 1990; Krebs and Markow, 1989; Heed, 1978, 1982; Heed and Mangan, 1986; Wasserman, 1982; Ehrman and Wasserman, 1987; Kaneshiro and Giddings, 1987). In laboratory tests, when mainland females from Sonora, Mexico, or Arizona are allowed to choose between males originating from the mainland or Baja California during courtship, mainland females and Baja males do not mate as frequently as all other male-female combinations causing low but significant one-way behavioral isolation. Since D. mojavensis have relatively simple courtship rituals that do not vary geographically (Markow, 1981; Krebs and Markow, 1989), determining the mechanism for the origin of this reproduction isolation is ofgreat interest. At least three hypotheses have been advanced: I) reproductive character displacement (Wasserman and Koepfer, 1977); 2) use of different host plants for feeding and oviposition that have caused physiological shifts in some traits such as cuticular hydrocarbons, contact pheromones in this species (Markow et aI., 1983; Markow and Toolson, 1990); and 3) correlated responses in behavior resulting from adaptation to different host cacti due to genetic correlations between premating behavior and some component of fitness associated with differential host plant use (Etges, 1990). The latter two hypotheses may not be mutually exclusive, but suggest an important role of host cactus use on patterns of adult mate choice. Almost all D. mojavensis in Baja California use agria cactus, Stenocereus gummosus, and most mainland Sonora and Arizona populations use organ pipe cactus, S. thurberi (Heed and Mangan, 1986). Variation in the profiles of adult cuticular hydrocarbons (CHCs) has been shown to influence mate choice in D. mojavensis (Markow and Toolson, 1990) and other drosophilid species (Antony and Jallon, 1982; Jallon and David, 1987; Cobb and Jallon, 1990). The preadult environment may influence adult CHC profiles because some adult cuticle precursors are assimilated during larval stages in holometabolous insects such as D. pseudoobscura (Toolson and Kuper-Simbron, 1989). The type ofculture medium used for rearing larvae also can alter patterns of male mate choice in D. pegasa (Wasserman and Zweig, 1991). All measurements of premating isolation in D. mojavensis have heretofore been made under laboratory conditions with flies reared on artificial media. Thus, artificial environmental conditions might influence adult mating behavior or physiological responses that are important in mate choice. CHC profiles differ between lab and wild adults (Toolson et aI., 1990). The purpose of this study was to test the influences of rearing D. mojavensis in agria and organ pipe cultures on premating isolation between populations.

Effects of Six Modifications on the Incidence and Levels of Spoilage and Pathogenic Organisms on Commercially Processed Postchill Broilers

Abstract: A combination of six processing modifications was evaluated in five commercial broiler processing facilities. These modifications included: counter current scalding; addition of a bird wash at the exit of the scalder; addition of 20 ppm total chlorine to the bird wash in the picking room, the water used on the transfer belt, and the final wash; and addition of chlorine in the chill water at a level to allow for 1 to 5 ppm free chlorine in the overflow from the chill tank. The modifications were based on recommendations suggested by the National Broiler Council and approved by the Food Safety and Inspection Service. Aerobic plate counts decreased in all five plants when modifications were incorporated. Coliform counts decreased significantly in two of the five plants, and E. coli counts decreased significantly in three of the five plants. Levels of Salmonella spp. and Listeria monocytogenes were reduced significantly in two of the five plants, and those of Campylobacter jejuni/coli were reduced significantly in four of the five plants. Incidence of these same pathogens was also reduced significantly by the processing modifications in two of the five plants. Reduction in incidence was independent of specific pathogen or plant. Levels of Salmonella spp. and L. monocytogenes on postchill carcasses were extremely low in all five plants, while those of C. jejuni/coli were higher. This latter organism is, however, more susceptible to environmental conditions. Based on the results of this study, the National Broiler Council's Board of Directors voted in February 1992 that all members of council voluntarily adopt the modifications presented here.

Jungle fowl–domestic fowl relationships: a use of DNA fingerprinting

Abstract: There has been a long and continuing interest among poultry breeders and scientists in relationships of domestic fowl with their jungle fowl ancestor. Recent commercial practices in poultry breeding have greatly changed and improved the meat and egg stocks available for the production of food. There is concern, however, that artificial selection for traits of economic importance has caused a narrowing of the genetic base and subsequent reduction in genetic variability. Because continued progress in the achievement of increased growth or egg production depends heavily on genetic variability, its present status is of interest. Current techniques in molecular biology allow estimations to be made of genetic distance among populations. This paper reviews DNA fingerprinting in poultry using results from this technique to survey genetic diversity among jungle fowl, domestic fowl representative of stocks from several decades ago and today's commercial broilers and layers. The genetic distance between wild jungle fowl and layers has been found to be similar to that between wild jungle fowl and broilers. Within the two types of modern commercial fowl there is less genetic diversity among broiler than layer stocks.

Genetic engineering of redox donor sites : measurement of intracomplex electron transfer between ruthenium-65-cytochrome b5 and cytochrome c

Abstract: The de novo design and synthesis of ruthenium-labeled cytochrome b5 that is optimized for the measurement of intracomplex electron transfer to cytochrome c are described. A single cysteine was substituted for Thr-65 of rat liver cytochrome b5 by recombinant DNA techniques [Stayton, P. S., Fisher, M. T., & Sligar, S. G. (1988) J. Biol. Chem. 263, 13544-13548]. The single sulfhydryl group on T65C cytochrome b5 was then labeled with [4-(bromomethyl)-4'-methylbipyridine] (bisbipyridine)ruthenium2+ to form Ru-65-cyt b5. The ruthenium group at Cys-65 is only 12 A from the heme group of cytochrome b5 but is not located at the binding site for cytochrome c. Laser excitation of the complex between Ru-65-cyt b5 and cytochrome c results in electron transfer from the excited state Ru(II*) to the heme group of Ru-65-cyt b5 with a rate constant greater than 10(6) s-1. Subsequent electron transfer from the heme group of Ru-65-cyt b5 to the heme group of cytochrome c is biphasic, with a fast-phase rate constant of (4 +/- 1) x 10(5) s-1 and a slow-phase rate constant of (3 +/- 1) x 10(4) s-1. This suggests that the complex can assume two different conformations with different electron-transfer properties. The reaction becomes monophasic and the rate constant decreases as the ionic strength is increased, indicating dissociation of the complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Avoidance of antinutritive plant defense : role of midgut pH in Colorado potato beetle

Abstract: The fate of the tomato foliar phenolic, chlorogenic acid, in the digestive systems of Colorado potato beetleLeptinotarsa decemlineata (Coleoptera: Chrysomelidae) andHelicoverpa tea (Lepidoptera: Noctuidae) is compared. In larvalH. zea and other lepidopteran species previously examined, approximately 35–50% of the ingested chlorogenic acid was oxidized in the digestive system by foliar phenolic oxidases (i.e., polyphenol oxidase and peroxidase) from the tomato plant. The oxidized form of chlorogenic acid, chlorogenoquinone, is a potent alkylator of dietary protein and can exert a strong antinutritive effect upon larvae through chemical degradation of essential amino acids. In contrast, inL. decemlineata less than 4% of the ingested dose of chlorogenic acid was bound to protein. In vitro experiments to determine the influence of pH on covalent binding of chlorogenic acid to protein showed that 30–45% less chlorogenic acid bound to protein at pHs representative of the beetle midgut (pH 5.5–6.5) than at a pH representing the lepidopteran midgut (pH 8.5). At an acidic pH, considerably more of the alkylatable functional groups of amino acids (−NH2, −SH) are in the nonreactive, protonated state. Hence, polyphenol oxidases are unlikely to have significant antinutritive effects against the Colorado potato beetle and may not be a useful biochemical source of resistance against this insect. The influence of feeding by larval Colorado potato beetle on foliar polyphenol oxidase activity in tomato foliage and its possible significance to interspecific competition is also considered.

A compositional classification scheme for meteoritic chondrules.

Abstract: A compositionally based classification scheme for chondrules is proposed that will help in systematizing the wealth of data available and disentangling the effects of nebular and subsequent processes. The classification is not by texture or the composition of a single phase, or a mixture of these two, but rather is a comprehensive, systematic approach which uses the composition of the two main chondrule components. This scheme is applicable to over 95 percent of the chondrules and is easily applied using an electron microprobe. It stresses the original diversity of the chondrules and the complex yet facile way in which they respond to parent-body metamorphism. Results using this classification scheme suggest that arguments against an important role of chondrules in determining the compositional trends of the chondrites have been premature.