Showing papers by "University of Florida published in 1991"
TL;DR: This article reviewed the book "A Theory of Goal Setting and Task Performance" by Edwin A. Locke and Gary P. Latham and found it to be a good introduction to goal setting and task performance.
Abstract: The article reviews the book “A Theory of Goal Setting and Task Performance,” by Edwin A. Locke and Gary P. Latham.
5,435 citations
TL;DR: The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues.
Abstract: Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.
4,292 citations
TL;DR: In this paper, the authors present an overall picture of immigration in the United States and explore points of destination patterns of settlement and the formation and function of new ethnic communities in urban areas; the incorporation of immigrants in the U.S. economy; immigrant politics; psychological aspects of immigration; the learning of English; and the origins of illegal immigrants.
Abstract: The authors present an overall picture of immigration in the United States. The first chapter describes migrant characteristics and countries of origin. The following chapters explore points of destination patterns of settlement and the formation and function of new ethnic communities in urban areas; the incorporation of immigrants in the U.S. economy; immigrant politics; psychological aspects of immigration; the learning of English; and the origins of illegal immigrants. (ANNOTATION)
1,411 citations
TL;DR: The process by which spatial cues are used for localizing a sound source in a free-field listening situation is summarized, and current evidence does not support the view that auditory motion perception is anything more than detection of changes in static location over time.
Abstract: In keeping with our promise earlier in this review, we summarize here the process by which we believe spatial cues are used for localizing a sound source in a free-field listening situation. We believe it entails two parallel processes: 1. The azimuth of the source is determined using differences in interaural time or interaural intensity, whichever is present. Wightman and colleagues (1989) believe the low-frequency temporal information is dominant if both are present. 2. The elevation of the source is determined from spectral shape cues. The received sound spectrum, as modified by the pinna, is in effect compared with a stored set of directional transfer functions. These are actually the spectra of a nearly flat source heard at various elevations. The elevation that corresponds to the best-matching transfer function is selected as the locus of the sound. Pinnae are similar enough between people that certain general rules (e.g. Blauert's boosted bands or Butler's covert peaks) can describe this process. Head motion is probably not a critical part of the localization process, except in cases where time permits a very detailed assessment of location, in which case one tries to localize the source by turning the head toward the putative location. Sound localization is only moderately more precise when the listener points directly toward the source. The process is not analogous to localizing a visual source on the fovea of the retina. Thus, head motion provides only a moderate increase in localization accuracy. Finally, current evidence does not support the view that auditory motion perception is anything more than detection of changes in static location over time.
1,181 citations
TL;DR: In this paper, four new questions tapping internal political efficacy were added to the 1988 National Election Study, and inter-item correlations among these questions indicate high internal consistency, that by both exploratory and confirmatory factor analysis the items measure a single concept distinct from external efficacy and political trust, that the measurement model is robust across major subgroups, and that the overall scale is externally valid and provides a good distribution of efficacy scores across the population.
Abstract: Political efficacy has been studied extensively since the 1950s, hut analysts have never been fully satisfied with its measurement. After considerable testing, four new questions tapping internal political efficacy were added to the 1988 National Election Study. Our investigation shows that inter-item correlations among these questions indicate high internal consistency, that by both exploratory and confirmatory factor analysis the items measure a single concept distinct from external efficacy and political trust, that the measurement model is robust across major subgroups, and that the overall scale is externally valid and provides a good distribution of efficacy scores across the population. Further, the results of an order experiment in the survey suggest that responses are unaffected by mode of presentation. In short, the four new questions constitute the most satisfactory measure of internal political efficacy to date.
800 citations
TL;DR: In this paper, a pictorial instrument was developed to examine perceptions of body figure in a cross-sectional survey of 1118 preadolescent children, and the results showed that the perceived body figure was associated with a negative image of the human body.
Abstract: A pictorial instrument was developed to examine perceptions of body figure in a cross-sectional survey of 1118 preadolescent children
758 citations
Patent•
25 Oct 1991TL;DR: A hybrid gene vector suitable for introducing foreign DNA into a mammalian cell comprising the foreign DNA ligated to an AAV genome was proposed in this article, and a method of constructing the hybrid vector was presented.
Abstract: A hybrid gene vector suitable for introducing foreign DNA into a mammalian cell comprising the foreign DNA ligated to an AAV genome; a method of constructing the hybrid gene vector; a method of transducing foreign DNA into mammalian cells comprising infecting the cells with the above hybrid gene vector and a method of rescuing foreign DNA from mammalian cells utilizing helper virus.
711 citations
TL;DR: The authors found that between 77 and 97 percent of the downward bias in previous spread estimates is caused by time variation in expected returns and/or partial price adjustments, and that adverse selection component accounts for a much smaller proportion (8 to 13 percent) of the quoted spread, at least for small trades, than the proportion (over 40 percent) previously reported in the literature.
Abstract: We show that time variation in expected returns and/or partial price adjustments lead to a downward bias in previous estimators of both the spread and its components. We introduce a new approach that provides unbiased and efficient estimators of the components of the spread. We find that between 77 and 97 percent of the downward bias in previous spread estimates is caused by time variation in expected returns. More importantly, the adverse-selection component, though significant, accounts for a much smaller proportion (8 to 13 percent) of the quoted spread, at least for small trades, than the proportion (over 40 percent) previously reported in the literature. Order processing costs are the predominant component of quoted spreads. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.
683 citations
TL;DR: Findings of intense and dynamic NPY neurosecretory activity within a discrete hypothalamic site in association with an increased drive for food consumption demonstrate that NPY release in the PVN is an important orexigenic signal for periodic eating behavior.
Abstract: Feeding in mammals is a periodic behavior; however, knowledge of how the brain signals an intermittent eating pattern is scanty. Recent indirect evidence indicates that one of the signals encoded in the structure of neuropeptide Y (NPY) is to stimulate robust feeding. Therefore, two series of experiments were undertaken to characterize NPY secretion within the paraventricular nucleus (PVN) in association with eating behavior in the rat. Dynamic changes in NPY concentration in several hypothalamic sites and release in the PVN were assessed before and during the course of food consumption in rats trained to eat daily only for 4 h. Only in the PVN were NPY concentrations elevated before the introduction of food and, thereafter, levels decreased significantly during the course of eating. A similar temporal pattern in NPY release into the PVN interstitium was evident in samples collected by push-pull cannula perfusion in unrestrained rats. In addition, in food-deprived rats displaying a robust drive for feeding, NPY release in the PVN was also markedly enhanced in the shape of high-amplitude secretory episodes as compared to a lower release rate in rats receiving food ad libitum. The higher rate of NPY release in fasted rats returned to the control range after 24 h of ad libitum food supply. These findings of intense and dynamic NPY neurosecretory activity within a discrete hypothalamic site in association with an increased drive for food consumption demonstrate that NPY release in the PVN is an important orexigenic signal for periodic eating behavior. These results have important global implications for elucidating the underlying causes of the pathophysiology of eating disorders--anorexia nervosa, bulimia, and obesity--as well as constituting a specific contextual model for the formulation and testing of suitable NPY receptor agonists and antagonists for therapeutic intervention.
673 citations
TL;DR: The results indicate that VP1 is a novel transcription factor possibly involved in potentiation of a seed-specific hormone response and could be functionally replaced by the activation sequence of the herpes simplex virus VP16 protein.
652 citations
TL;DR: The results indicate that it is possible to significantly expand the bioactive composition range through microstructural control made possible by sol-gel processing techniques.
Abstract: Bioactive glass powders, with a composition of SiO2-CaO-P2O5,have been successfully synthesized via a sol-gel process at considerably loer temperatures than required for conventional melting method. Bioactive glass powders made via conventional methods form an interfacial bond wih none when they are implanted. Bonding is correlated with the formation of a surface hydroxyapatite layer. This study examinded the formation of a hydroxyapatite layer in Tris-buffered solution as a function of SiO2 content of sol-gel derived powders. A FT-IRRS technique was used to monitor the formation of the hydroxyapatite on the surface of the powders. X-ray diffraction analysis and BET were also used to characterize the chemical and physical properties of the sol-gel derived bioactive powders. It was discovered that: (a) the rate of hydroxyapatite formation decreased wih increasing SiO2 content for powders whose SiO2 content was less than 90 mol%; (b) a hydroxyapatite film does not form for the powders whose SiO2 content is more than 90 mol%; (c) the SiO2 limit, beyond which the powders lost their bioactivity, was much higher for bioactive glass powders mad through sol-gel process (90%) than those made by conventional melting methods (60%). These results indicate that it is possible to significantly expand the bioactive composition range through microstructural control made possible by sol-gel processing techniques.
TL;DR: In this paper, the authors argue that cointegration is a long-run concept and hence requires long spans of data to give tests for co-integration much power rather than merely large numbers of observations.
TL;DR: Reproductive mechanisms, primarily mating preferences, result in 27% fewer MHC-homozygous offspring than expected from random mating, and mating preferences are strong enough to account for most of the MHC genetic diversity found in natural populations of Mus.
Abstract: Because of the central role of major histocompatibility complex (MHC) genes in immune recognition, it is often assumed that parasite-driven selection maintains the unprecendented genetic diversity of these genes. But associations between MHC genotype and specific infectious diseases have been difficult to identify with a few exceptions such as Marek's disease and malaria. Alternatively, MHC-related reproductive mechanisms such as selective abortion and mating preferences could be responsible for the diversity. To determine both the nature and strength of selection operating on MHC genes by we have studied components of selection in seminatural populations of mice (Mus musculus domesticus). Here we assess MHC-related patterns of reproduction and early (preweaning) mortality by analysing 1,139 progeny born in nine populations, and 662 progeny from laboratory matings. Reproductive mechanisms, primarily mating preferences, result in 27% fewer MHC-homozygous offspring than expected from random mating. MHC genotype had no detectable influence on neonatal (preweaning) mortality. These mating preferences are strong enough to account for most of the MHC genetic diversity found in natural populations of Mus.
TL;DR: In this paper, a composite model of limb praxis processing is proposed, supported by a series of dissociations noted in the performance of apraxic patients, i.e., die separability of production from reception, the selectivity of input modalities, an assembled route of imitation, and the possible fragmentation of semantics into an action and a nonaction system.
Abstract: This paper is devoted to the development of a composite model of limb praxis processing that is supported by a series of dissociations noted in the performance of apraxic patients. These dissociations include die separability of praxis production from praxis reception, the selectivity of input modalities, an “assembled” route of praxis imitation, and the possible fragmentation of semantics into an action and a nonaction system.
TL;DR: A new voice source model that accounted for certain physiological aspects of vocal fold motion was developed and tested using speech synthesis, and applications include synthesis of natural sounding speech, synthesis and modeling of vocal disorders, and the development of speaker independent (or adaptive) speech recognition systems.
Abstract: The purpose of this study was to examine several factors of vocal quality that might be affected by changes in vocal fold vibratory patterns. Four voice types were examined: modal, vocal fry, falsetto, and breathy. Three categories of analysis techniques were developed to extract source‐related features from speech and electroglottographic (EGG) signals. Four factors were found to be important for characterizing the glottal excitations for the four voice types: the glottal pulse width, the glottal pulse skewness, the abruptness of glottal closure, and the turbulent noise component. The significance of these factors for voice synthesis was studied and a new voice source model that accounted for certain physiological aspects of vocal fold motion was developed and tested using speech synthesis. Perceptual listening tests were conducted to evaluate the auditory effects of the source model parameters upon synthesized speech. The effects of the spectral slope of the source excitation, the shape of the glottal excitation pulse, and the characteristics of the turbulent noise source were considered. Applications for these research results include synthesis of natural sounding speech, synthesis and modeling of vocal disorders, and the development of speaker independent (or adaptive) speech recognition systems.
TL;DR: These mutants were functionally equivalent to the previous plasmid-based strains for the fermentation of xylose and glucose to ethanol and exceeded theoretical limits on the basis of added sugars because of the additional production of ethanol from the catabolism of complex nutrients.
Abstract: Zymomonas mobilis genes for pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adhB) were integrated into the Escherichia coli chromosome within or near the pyruvate formate-lyase gene (pfl) Integration improved the stability of the Z mobilis genes in E coli, but further selection was required to increase expression Spontaneous mutants were selected for resistance to high level of chloramphenicol that also expressed high levels of the Z mobilis genes Analogous mutants were selected for increased expression of alcohol dehydrogenase on aldehyde indicator plates These mutants were functionally equivalent to the previous plasmid-based strains for the fermentation of xylose and glucose to ethanol Ethanol concentrations of 544 and 416 g/liter were obtained from 10% glucose and 8% xylose, respectively The efficiency of conversion exceeded theoretical limits (051 g of ethanol/g of sugar) on the basis of added sugars because of the additional production of ethanol from the catabolism of complex nutrients Further mutations were introduced to inactivate succinate production (frd) and to block homologous recombination (recA)
Journal Article•
TL;DR: In this article, an unsymmetric-pattern multifrontal method based on dense matrix kernels was proposed to solve sparse matrix factorization problems with repetitive structure in the matrix by factorizing more than one pivot in each frontal matrix, enabling the use of Level 2 and Level 3 BLAS.
Abstract: Sparse matrix factorization algorithms for general problems are typically characterized by irregular memory access patterns that limit their performance on parallel-vector supercomputers. For symmetric problems, methods such as the multifrontal method avoid indirect addressing in the innermost loops by using dense matrix kernels. However, no efficient LU factorization algorithm based primarily on dense matrix kernels exists for matrices whose pattern is very unsymmetric. We address this deficiency and present a new unsymmetric-pattern multifrontal method based on dense matrix kernels. As in the classical multifrontal method, advantage is taken of repetitive structure in the matrix by factorizing more than one pivot in each frontal matrix, thus enabling the use of Level 2 and Level 3 BLAS. The performance is compared with the classical multifrontal method and other unsymmetric solvers on a CRAY C-98.
TL;DR: In this article, the results of experiments designed to identify the process(es) responsible for nonequilibrium sorption of hydrophobic organic chemicals (HOCs) by natural sorbents are reported.
Abstract: The results of experiments designed to identify the process(es) responsible for nonequilibrium sorption of hydrophobic organic chemicals (HOCs) by natural sorbents are reported. The results of experiments performed with natural sorbents were compared to rate data obtained from systems wherein rate-limited sorption was caused by specific sorbate-sorbent interactions. This comparison showed that chemical nonequilibrium associated with specific sorbate-sorbent interactions does not significantly contribute to the rate-limited sorption of HOCs by natural sorbents. Transport-related nonequilibrium was also shown to not be a factor for the systems investigated. Hence, attempts were made to interpret the data in terms of two, sorption-related, diffusive mass-transfer conceptual models: retarded intraparticle diffusion and intraorganic matter diffusion. The analyses provide strong evidence that intraorganic matter diffusion was responsible for the nonequilibrium sorption exhibited by the systems investigated in this paper.
TL;DR: In this paper, the authors examined the losses realized in bank failures during the period 1985 through mid-year 1988, using data from the Federal Deposit Insurance Corporation (FDIC) as the difference between the book value of assets and the recovery value net of the direct expenses associated with the failure.
Abstract: This paper examines the losses realized in bank failures Losses are measured as the difference between the book value of assets and the recovery value net of the direct expenses associated with the failure I find the loss on assets is substantial, averaging 30 percent of the failed bank's assets Direct expenses associated with bank closures average 10 percent of assets An empirical analysis of the determinants of these losses reveals a significant difference in the value of assets retained by the FDIC and similar assets assumed by acquiring banks THE 1980S HAVE WITNESSED an unprecedented number of commercial bank and savings and loan failures For example, between 1982 and year-end 1988, 791 commercial banks failed, more than twice the number of failures that occurred in the previous 40 years1 The magnitude and sources of the losses realized in these and future bank failures have important implications for the adequacy of the deposit insurance fund and the resources of the Resolution Trust Corporation, as well as the efficacy of the policies these agencies use to dispose of a filed institution's assets2 In this paper I examine the losses realized in bank failures during the period 1985 through mid-year 1988 Losses are measured using data from the Federal Deposit Insurance Corporation (FDIC) as the difference between the book value of a bank's assets at the time of its closure and the value of the assets in an FDIC receivership or the value of the assets to an acquirer This measure of loss I refer to as "loss on assets" Losses include expenses incurred in the liquidation and sale of assets, losses associated with forced liquidation including lost charter value (ie, the value of the right to continue to operate) and past unrealized losses (ie, losses on assets that occur prior to the bank's failure but are not reported on the bank's balance sheet at the time of the failure)3
TL;DR: It is found that RHD subjects performed normally in their ability to infer the emotion conveyed by sentences describing situations, but RHD patients were impaired in relation to both LHD and NC in the capacity to judge the emotional content of sentences depicting facial, prosodic, and gestural expressions.
Abstract: Previous research has established that patients with right hemisphere damage (RHD) are impaired in the comprehension of emotional prosody and facial expression. There are several explanations for this impairment. It may reflect defective acoustic and visuospatial analysis, disruption of nonverbal communicative representations, or a disturbance in the comprehension of emotional meaning. In order to examine these hypotheses, we asked RHD patients, left hemisphere damaged patients (LHD) and normal controls (NC) to judge the emotional content of sentences describing nonverbal expressions, and sentences describing emotional situations. We found that RHD subjects performed normally in their ability to infer the emotion conveyed by sentences describing situations. However, RHD patients were impaired in relation to both LHD and NC in the capacity to judge the emotional content of sentences depicting facial, prosodic, and gestural expressions, suggesting a disruption of nonverbal communicative representations.
01 Nov 1991
TL;DR: It is found that for time series of different complexities there are optimal neural network topologies and parameters that enable them to learn more efficiently and are also parsimonious in their data requirements.
Abstract: We discuss the results of a comparative study of the performance of neural networks and conventional methods in forecasting time series Our work was initially inspired by previously published work
TL;DR: A protein kinase that requires calcium but not calmodulin or phospholipids for activity has been purified from soybean and is established as a prototype for a new family of calcium-regulated protein kinases.
Abstract: Calcium can function as a second messenger through stimulation of calcium-dependent protein kinases. A protein kinase that requires calcium but not calmodulin or phospholipids for activity has been purified from soybean. The kinase itself binds calcium with high affinity. A complementary DNA clone for this kinase has been identified; it encodes a protein with a predicted molecular mass of 57,175 daltons. This protein contains a catalytic domain similar to that of calmodulin-dependent kinases and a calmodulin-like region with four calcium binding domains (EF hands). The predicted structure of this kinase explains its direct regulation via calcium binding and establishes it as a prototype for a new family of calcium-regulated protein kinases.
TL;DR: The Multi-Hospital Eastern Atlantic Restenosis Trial group obtained follow-up angiography in 510 patients with 598 successfully dilated coronary lesions who were enrolled in a controlled trial of the effects of a single dose of methylprednisolone on restenosis after coronary angioplasty to indicate that the probability of restenotic after angiopLasty is determined predominantly by the characteristics of the lesion being dilated.
TL;DR: In this article, a high-resolution reconstruction of Caribbean climate is presented based on O-18/O-16 ratios in ostracod shells from Lake Miragoane, Haiti.
Abstract: A high-resolution reconstruction of Caribbean climate is presented based on O-18/O-16 ratios in ostracod shells from Lake Miragoane, Haiti. The variations which are found can be largely explained by orbitally induced variations in seasonal insolation which modified the intensity of the annual cycle.
TL;DR: The influence of teacher beliefs on curriculum implementation was explored in two different contexts as discussed by the authors, where two middle-level teachers implemented a 20-lesson curriculum package in the presence of participant observers.
Abstract: The influence of teacher beliefs on curriculum implementation was explored in two different contexts. Two middle-level teachers implemented a 20-lesson curriculum package in the presence of participant observers. Data sources included field notes and interview transcripts. The data were reviewed daily and tentative assertions were developed. Assertions and their accompanying evidence were examined weekly for recurring patterns. Case studies of the belief structures of each teacher were then prepared. In both cases, four major categories of beliefs appeared to influence curriculum implementation. These included beliefs about how students learn, a teacher's role in the classroom, the ability levels of students in a particular age group, and the relative importance of content topics. Both teachers believed that the most important student outcome is factual knowledge, that middle-grade students learn through repeated drill and practice, and that middle school students require a great deal of direction. The teachers' beliefs differed in other areas, including beliefs about a teacher's role in the classroom and beliefs regarding the curriculum and its content topics. Although certain components of both teachers' belief structures enhanced the success of curriculum implementation, overall their existing belief structures were incongruent with the underlying philosophy of the intended curriculum, thus hampering successful implementation.
TL;DR: CO2 exerts secondary effects in growth regulation, probably at the molecular level, that are not predictable from its primary biochemical role in carboxylation, and a reduction in net photosynthesis and rubisco activity is not inevitable under CO2 enrichment, as exemplified by field-grown soybeans and salt marsh species.
Abstract: . The global uptake of CO2 in photosynthesis is about 120 gigatons (Gt) of carbon per year. Virtually all passes through one enzyme, ribulose bisphosphate carboxylase/oxygenase (rubisco), which initiates both the photosynthetic carbon reduction, and photorespiratory carbon oxidation, cycles. Both CO2 and O2 are substrates; CO2 also activates the enzyme. In C3 plants, rubisco has a low catalytic activity, operates below its Km (CO2), and is inhibited by O2. Consequently, increases in the CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually enhances the productivity of C3 plants, but the effect is marginal in C4 species. It also causes acclimation in various ways: anatomically, morphologically, physiologically or biochemically. So, CO2 exerts secondary effects in growth regulation, probably at the molecular level, that are not predictable from its primary biochemical role in carboxylation. After an initial increase with CO2 enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in field studies, that is ultimately mediated by a decline in rubisco activity, though the RuBP/Pi-regeneration capacities of the plant may play a role. The decline is due to decreased rubisco protein, activation state, and/or specific activity, and it maintains the rubisco fixation and RuBP/Pi regeneration capacities in balance. Carbohydrate accumulation is sometimes associated with reduced net photosynthesis, possibly causing feedback inhibition of the RuBP/Piregeneration capacities, or chloroplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction in net photosynthesis and rubisco activity is not inevitable under CO2 enrichment. Strong sinks or rapid translocation may avoid such acclimation responses. Over geological time, aquatic autotrophs and terrestrial C4 and CAM plants have genetically adapted to a decline in the external CO2/O2 ratio, by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibition of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation compatible with a high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating mechanisms acclimate to the external CO2, being suppressed at high-CO2. It is unclear, whether a doubling in atmospheric CO2 will be sufficient to cause a de-adaptive trend in the rubisco kinetics of future C3 plants, producing higher catalytic activities.
TL;DR: The relationship between the substitution in use approach to product-market structure and cognitive accounts of product category structures is investigated in terms of the role of product usage context and it is shown that distinctive usages predict similarity judgments, whereas usage versatility predicts prototypicality.
Abstract: The relationship between the substitution in use approach to product-market structure and cognitive accounts of product category structures is investigated in terms of the role of product usage con...
TL;DR: Productivities, yields, and final ethanol concentrations achieved from xylose with recombinant E. coli exceeded the reported values with other organisms.
Abstract: The conversion of xylose to ethanol by recombinant Escherichia coli has been investigated in pH-controlled batch fermentations. Chemical and environmental parameters were varied to determine tolerance and to define optimal conditions. Relatively high concentrations of ethanol (56 g/L) were produced from xylose with excellent efficiencies. Volumetric productivities of up to 1.4 g ethanol/L h were obtained. Productivities, yields, and final ethanol concentrations achieved from xylose with recombinant E. coli exceeded the reported values with other organisms. In addition to xylose, all other sugar constituents of biomass (glucose, mannose, arabinose, and galactose) were efficiently converted to ethanol by recombinant E. coli. Unusually low inocula equivalent to 0.033 mg of dry cell weight/L were adequate for batch fermentations. The addition of small amounts of calcium, magnesium, and ferrous ions stimulated fermentation. The inhibitory effects of toxic compounds (salts, furfural, and acetate) which are present in hemicellulose hydrolysates were also examined.