Showing papers by "University of Michigan published in 1994"
TL;DR: The prevalence of psychiatric disorders is greater than previously thought to be the case, and morbidity is more highly concentrated than previously recognized in roughly one sixth of the population who have a history of three or more comorbid disorders.
Abstract: Background: This study presents estimates of lifetime and 12-month prevalence of 14 DSM-III-R psychiatric disorders from the National Comorbidity Survey, the first survey to administer a structured psychiatric interview to a national probability sample in the United States. Methods: The DSM-III-R psychiatric disorders among persons aged 15 to 54 years in the noninstitutionalized civilian population of the United States were assessed with data collected by lay interviewers using a revised version of the Composite International Diagnostic Interview. Results: Nearly 50% of respondents reported at least one lifetime disorder, and close to 30% reported at least one 12-month disorder. The most common disorders were major depressive episode, alcohol dependence, social phobia, and simple phobia. More than half of all lifetime disorders occurred in the 14% of the population who had a history of three or more comorbid disorders. These highly comorbid people also included the vast majority of people with severe disorders. Less than 40% of those with a lifetime disorder had ever received professional treatment, and less than 20% of those with a recent disorder had been in treatment during the past 12 months. Consistent with previous risk factor research, it was found that women had elevated rates of affective disorders and anxiety disorders, that men had elevated rates of substance use disorders and antisocial personality disorder, and that most disorders declined with age and with higher socioeconomic status. Conclusions: The prevalence of psychiatric disorders is greater than previously thought to be the case. Furthermore, this morbidity is more highly concentrated than previously recognized in roughly one sixth of the population who have a history of three or more comorbid disorders. This suggests that the causes and consequences of high comorbidity should be the focus of research attention. The majority of people with psychiatric disorders fail to obtain professional treatment. Even among people with a lifetime history of three or more comorbid disorders, the proportion who ever obtain specialty sector mental health treatment is less than 50%. These results argue for the importance of more outreach and more research on barriers to professional help-seeking.
11,648 citations
TL;DR: In this paper, the authors question the economic benefits of improving customer satisfaction and question whether there are economic benefits to improving quality and customer satisfaction, and they also question the link between quality and satisfaction.
Abstract: Are there economic benefits to improving customer satisfaction? Many firms that are frustrated in their efforts to improve quality and customer satisfaction are beginning to question the link betwe...
5,428 citations
TL;DR: In this paper, Bergami et al. developed a model to explain how images of one's work organization shape the strength of his or her identification with the organization and how members assess the attractiveness of these images by how well the image preserves the continuity of their self-concept, provides distinctiveness, and enhances self-esteem.
Abstract: We thank Massimo Bergami, Arthur Brief, Mason Carpenter, Brian Golden, Frances Hauge, Rod Kramer, Sharon Lobel, Reuben McDaniel, Debra Meyerson, Wendy Penner, Sandy Piderit, Linda Pike, Mlchael Pratt, Robert Quinn, Anat Rafaeli, Lance Sandelands, Bob Sutton, David Whetten, Batia Wiesenfeld, and three anonymous reviewers for comments on earlier drafts of this paper. We develop a model to explain how images of one's work organization shape the strength of his or her identification with the organization. We focus on two key organizational images: one based on what a member believes is distinctive, central, and enduring about his or her organization and one based on a member's beliefs about what outsiders think about the organization. According to the model, members assess the attractiveness of these images by how well the image preserves the continuity of their self-concept, provides distinctiveness, and enhances self-esteem. The model leads to a number of propositions about how organizational identification affects members' patterns of social interaction.'
4,469 citations
3,857 citations
TL;DR: This survey characterizes an emerging research area, sometimes called coordination theory, that focuses on the interdisciplinary study of coordination, that uses and extends ideas about coordination from disciplines such as computer science, organization theory, operations research, economics, linguistics, and psychology.
Abstract: This survey characterizes an emerging research area, sometimes called coordination theory, that focuses on the interdisciplinary study of coordination. Research in this area uses and extends ideas about coordination from disciplines such as computer science, organization theory, operations research, economics, linguistics, and psychology.A key insight of the framework presented here is that coordination can be seen as the process of managing dependencies among activities. Further progress, therefore, should be possible by characterizing different kinds of dependencies and identifying the coordination processes that can be used to manage them. A variety of processes are analyzed from this perspective, and commonalities across disciplines are identified. Processes analyzed include those for managing shared resources, producer/consumer relationships, simultaneity constraints, and task/subtask dependencies.Section 3 summarizes ways of applying a coordination perspective in three different domains:(1) understanding the effects of information technology on human organizations and markets, (2) designing cooperative work tools, and (3) designing distributed and parallel computer systems. In the final section, elements of a research agenda in this new area are briefly outlined.
3,447 citations
TL;DR: This article compares the disablement experiences of people who acquire chronic conditions early in life and those who acquire them in mid or late life (late-life disability), which can help inform research and public health activities.
3,149 citations
TL;DR: The amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records as discussed by the authors, but only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation.
2,421 citations
TL;DR: Gilligan translated this question into research by subjecting the abstraction of universal and discrete agency to comparative research into female behavior evaluated on its own terms and revealed women to be more concrete in their thinking and more attuned to "fairness" while men acted on abstract reasoning and "rules of justice" as discussed by the authors.
Abstract: justice. Women, by contrast, were believed to be at a lower stage because they were found to have a sense of agency still tied primarily to their social relationships and to make political and moral decisions based on context-specific principles based on these relationships rather than on the grounds of their own autonomous judgments. Students of gender studies know well just how busy social scientists have been kept by their efforts to come up with ever more sociological "alibis" for the question of why women did not act like men. Gilligan's response was to refuse the terms of the debate altogether. She thus did not develop yet another explanation for why women are "deviant." Instead, she turned the question on its head by asking what was wrong with the theory a theory whose central premises defines 50% of social beings as "abnormal." Gilligan translated this question into research by subjecting the abstraction of universal and discrete agency to comparative research into female behavior evaluated on its own terms The new research revealed women to be more "concrete" in their thinking and more attuned to "fairness" while men acted on "abstract reasoning" and "rules of justice." These research findings transformed female otherness into variation and difference but difference now freed from the normative de-
2,345 citations
TL;DR: It is found that family income and poverty status are powerful correlates of the cognitive development and behavior of children, even after accounting for other differences--in particular family structure and maternal schooling--between low- and high-income families.
Abstract: We consider 3 questions regarding the effects of economic deprivation on child development. First, how are developmental outcomes in childhood affected by poverty and such poverty correlates as single parenthood, ethnicity, and maternal education? Second, what are the developmental consequences of the duration and timing of family economic deprivation? And, third, what is the comparative influence of economic deprivation at the family and neighborhood level? We investigate these issues with longitudinal data from the Infant Health and Development Program. We find that family income and poverty status are powerful correlates of the cognitive development and behavior of children, even after accounting for other differences--in particular family structure and maternal schooling--between low- and high-income families. While the duration of poverty matters, its timing in early childhood does not. Age-5 IQs are found to be higher in neighborhoods with greater concentrations of affluent neighbors, while the prevalence of low-income neighbors appears to increase the incidence of externalizing behavior problems.
2,180 citations
TL;DR: This chapter discusses the gamma-aminobutyric acid (GABA) receptor channels, which are the most abundant inhibitory neurotransmitter in the CNS.
Abstract: This chapter discusses the gamma-aminobutyric acid (GABA) receptor channels, which are the most abundant inhibitory neurotransmitter in the CNS. Following release from presynaptic vesicles, GABA exerts fast inhibitory effects by interacting with GABA receptors, whose primary function is to hyperpolarize neuronal membranes in mature CNS neurons. GABA receptors are found both presynaptically, where they decrease the likelihood of neurotransmitter release, and postsynaptically, where they decrease the likelihood of neuronal firing. There are two types of GABA receptor, termed GABA A and GABA B receptors. GABA A receptors are fast-activating Clˉ channels from the Cys-loop family of ligand-gated ion channels. Activation of GABA A receptors causes membrane hyperpolarization by allowing Clˉ influx, reflecting the relatively low concentration of Clˉ found intracellularly in most adult CNS neurons. GABA A receptors can also mediate depolarizing responses in most immature CNS neurons and in mature peripheral neurons.
1,991 citations
TL;DR: A Cognitive Performance Scale (CPS) is designed that uses MDS data to assign residents into easily understood cognitive performance categories, and should prove useful to clinicians and investigators using the MDS to determine a resident's cognitive assets.
Abstract: Background Chronic cognitive impairment is a major problem in U.S. nursing homes, yet traditional assessment systems in most facilities included only limited information on cognitive status. Following the Congressional mandate in the Omnibus Reconciliation Act of 1987 (OBRA '87), U.S. nursing homes now complete the Minimum Data Set (MDS), a standardized, comprehensive assessment of each resident's functional, medical, psychosocial, and cognitive status. We designed a Cognitive Performance Scale (CPS) that uses MDS data to assign residents into easily understood cognitive performance categories. Methods Information was drawn from three data sets, including two multistate data sets constructed for the Health Care Financing Administration. The prevalence and reliability of the MDS cognitive performance variables were established when assessed by trained nursing personnel. Five selected MDS items were combined to create the single, functionally meaningful seven-category hierarchical Cognitive Performance Scale. Results The CPS scale corresponded closely with scores generated by the Mini-Mental State Examination and the Test for Severe Impairment, nursing judgments of disorientation, and neurological diagnoses of Alzheimer's disease and other dementias. Conclusions The new CPS provides a functional view of cognitive performance, using readily available MDS data. It should prove useful to clinicians and investigators using the MDS to determine a resident's cognitive assets.
Book•
01 Jan 1994TL;DR: The origins of Mating Behavior What Women Want Men Want Something Else Casual Sex Attracting A Partner Staying Together Sexual Conflict Breaking Up Changes Over Time Harmony Between The Sexes as mentioned in this paper
Abstract: Origins of Mating Behavior What Women Want Men Want Something Else Casual Sex Attracting A Partner Staying Together Sexual Conflict Breaking Up Changes Over Time Harmony Between The Sexes
TL;DR: The identification of VHL mutations in a majority of localized and advanced sporadic renal carcinomas and in a second form of hereditary renal carcinoma indicates that the VHL gene plays a critical part in the origin of this malignancy.
Abstract: Multiple, bilateral renal carcinomas are a frequent occurrence in von Hippel-Lindau (VHL) disease. To elucidate the aetiological role of the VHL gene in human kidney tumorigenesis, localized and advanced tumours from 110 patients with sporadic renal carcinoma were analysed for VHL mutations and loss of heterozygosity (LOH). VHL mutations were identified in 57% of clear cell renal carcinomas analysed and LOH was observed in 98% of those samples. Moreover, VHL was mutated and lost in a renal tumour from a patient with familial renal carcinoma carrying the constitutional translocation, t(3;8)(p14;q24). The identification of VHL mutations in a majority of localized and advanced sporadic renal carcinomas and in a second form of hereditary renal carcinoma indicates that the VHL gene plays a critical part in the origin of this malignancy.
TL;DR: This paper proposed a framework for representing personality constructs at four levels of abstraction, i.e., partial disaggregation, total aggregation, partial aggregation and total disaggregation models, where each dimension is either freely correlated with the other dimensions or loading on one or more order factors.
Abstract: This article proposes a framework for representing personality constructs at four levels of abstraction. The total aggregation model is the composite formed by the sum of scores on all items in a scale. The partial aggregation model treats separate dimensions of a personality construct as indicators of a single latent variable, with each dimension being an aggregation of items. The partial disaggregation model represents each dimension as a separate latent variable, either freely correlated with the other dimensions or loading on one or more than one higher order factor; the measures of the dimensions are multiple indicators formed as aggregates of subsets of items. The total disaggregation model also represents each dimension as a separate latent variable but, unlike the partial disaggregation model, uses each item in the scale as an indicator of its respective factor. Illustrations of the models are provided on the State Self‐Esteem Scale—including tests of psychometric properties, invariance, and gener...
Washington University in St. Louis1, Stanford University2, National Institutes of Health3, Pennsylvania State University4, Harvard University5, Vanderbilt University6, University of Tennessee Health Science Center7, University of Washington8, Case Western Reserve University9, George Washington University10, Johns Hopkins University11, Baylor College of Medicine12, Howard University13, University of California, Los Angeles14, University of Michigan15
TL;DR: It is concluded that ulcer patients with H. pylori infection require treatment with antimicrobial agents in addition to antisecretory drugs whether on first presentation with the illness or on recurrence.
Abstract: The National Institutes of Health Consensus Development Conference onHelicobacter pyloriin Peptic Ulcer Disease brought together specialists in gastroenterology, surgery, infectious diseases, epidemiology, and pathology, as well as the public to address the following questions: (1) What is the causal relationship ofH pylorito upper gastrointestinal disease? (2) How does one diagnose and eradicateH pyloriinfection? (3) Does eradication ofH pyloriinfection benefit the patient with peptic ulcer disease? (4) What is the relationship betweenH pyloriinfection and gastric malignancy? (5) WhichH pylori—infected patients should be treated? (6) What are the most important questions that must be addressed by future research inH pyloriinfections? Following 1½ days of presentations by experts and discussion by the audience, a consensus panel weighed the evidence and prepared their consensus statement. Among their findings, the consensus panel concluded that (1) ulcer patients withH pyloriinfection require treatment with antimicrobial agents in addition to antisecretory drugs whether on first presentation with the illness or on recurrence; (2) the value of treating of nonulcerative dyspepsia patients withH pyloriinfection remains to be determined; and (3) the interesting relationship betweenH pyloriinfection and gastric cancers requires further exploration. (JAMA. 1994;272:65-69)
TL;DR: Endoglin is identified as the HHT gene mapping to 9q3 and HHT is established as the first human disease defined by a mutation in a member of the TGF-β receptor complex.
Abstract: Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent haemorrhage. Linkage for some families has been established to chromosome 9q33−q34. In the present study, endoglin, a transforming growth factor beta (TGF-beta) binding protein, was analysed as a candidate gene for the disorder based on chromosomal location, expression pattern and function. We have identified mutations in three affected individuals: a C to G substitution converting a tyrosine to a termination codon, a 39 base pair deletion and a 2 base pair deletion which creates a premature termination codon. We have identified endoglin as the HHT gene mapping to 9q3 and have established HHT as the first human disease defined by a mutation in a member of the TGF-beta receptor complex.
TL;DR: A comprehensive overview of disk array technology and implementation topics such as refining the basic RAID levels to improve performance and designing algorithms to maintain data consistency are discussed.
Abstract: Disk arrays were proposed in the 1980s as a way to use parallelism between multiple disks to improve aggregate I/O performance. Today they appear in the product lines of most major computer manufacturers. This article gives a comprehensive overview of disk arrays and provides a framework in which to organize current and future work. First, the article introduces disk technology and reviews the driving forces that have popularized disk arrays: performance and reliability. It discusses the two architectural techniques used in disk arrays: striping across multiple disks to improve performance and redundancy to improve reliability. Next, the article describes seven disk array architectures, called RAID (Redundant Arrays of Inexpensive Disks) levels 0–6 and compares their performance, cost, and reliability. It goes on to discuss advanced research and implementation topics such as refining the basic RAID levels to improve performance and designing algorithms to maintain data consistency. Last, the article describes six disk array prototypes of products and discusses future opportunities for research, with an annotated bibliography disk array-related literature.
Book•
01 Jan 1994TL;DR: This book discusses the importance of Vitality and Growth Throughout Your Teaching Career, and how to become more Strategic and Self-Regulated Learners in the College Classroom.
TL;DR: In this article, the authors argue that individuals store their components of organizational routines in procedural memory, which is memory for how things are done that is relatively automatic and inarticulate, and encompasses both cognitive and motor activities.
Abstract: Organizational routines-multi-actor, interlocking, reciprocally-triggered sequences of actions-are a major source of the reliability and speed of organizational performance. Without routines, organizations would lose efficiency as structures for collective action. But these frequently repeated action sequences can also occasionally give rise to serious suboptimality, hampering performance when they are automatically transferred onto inappropriate situations.
While the knowledgeable design and redesign of routines presents a likely lever for those wishing to enhance organizational performance, the lever remains difficult to grasp because routines are hard to observe, analyze, and describe. This paper argues that new work in psychology on "procedural" memory may help explain how routines arise, stabilize and change. Procedural memory has close links to notions of individual skill and habit. It is memory for how things are done that is relatively automatic and inarticulate, and it encompasses both cognitive and motor activities.
We report an experiment in which paired subjects developed interlocked task performance patterns that display the chief characteristics of organizational routines. We show evidence from their behavior supporting the claim that individuals store their components of organizational routines in procedural memory. If routines are stored as distributed procedural memories, this may be the source of distinctive properties reported by observers of organizational routines. The paper concludes with implications for both research and practice.
TL;DR: This paper summarized a set of social and psychological factors that Eccles and her colleagues have been studying for the past 15 years in an effort to understand the occupational and educational choices of women and men.
Abstract: Despite recent efforts to increase the participation of women in advanced educational training and high-status professional fields, women and men are still concentrated in different occupations and educational programs, and women are still underrepresented in many high-status occupational fields—particularly those associated with physical science, engineering, and applied mathematics. Many factors, ranging from outright discrimination to the processes associated with gender role socialization, contribute to these gendered patterns of educational and occupational choices. This paper summarizes a set of social and psychological factors that Eccles and her colleagues have been studying for the past 15 years in an effort to understand the occupational and educational choices of women and men. The paper summarizes the key features of the theoretical model they developed and provides an overview of the empirical support now available for key aspects of this model. The implications of this model for understandin...
TL;DR: Basic descriptive findings from new research on the epidemiology of drug dependence syndromes are reported, conducted as part of the National Comorbidity Survey (NCS).
Abstract: Studying prevalence of Diagnostic and Statistical Manual (3rd ed., rev., American Psychiatric Association, 1987) drug dependence among Americans 15-54 years old, we found about 1 in 4 (24%) had a history of tobacco dependence; about 1 in 7 (14%) had a history of alcohol dependence; and about 1 in 13 (7.5%) had a history of dependence on an inhalant or controlled drug. About one third of tobacco smokers had developed tobacco dependence and about 15% of drinkers had become alcohol dependent. Among users of the other drugs, about 15% had become dependent. Many more Americans age 15-54 have been affected by dependence on psychoactive substances than by other psychiatric disturbances now accorded a higher priority in mental health service delivery systems, prevention, and sponsored research programs. The aim of this article is to report basic descriptive findings from new research on the epidemiology of drug dependence syndromes, conducted as part of the National Comorbidity Survey (NCS). In this study, our research team secured a nationally representative sample and applied standardized diagnostic assessments in a way that allows direct comparisons across prevalence estimates and cor
TL;DR: A predictive algorithm is formulated in order to apply the flux balance model to describe unsteady-state growth and by-product secretion in aerobic batch, fed-batch, and anaerobic batch cultures.
Abstract: Flux balance models of metabolism use stoichiometry of metabolic pathways, metabolic demands of growth, and optimality principles to predict metabolic flux distribution and cellular growth under specified environmental conditions. These models have provided a mechanistic interpretation of systemic metabolic physiology, and they are also useful as a quantitative tool for metabolic pathway design. Quantitative predictions of cell growth and metabolic by-product secretion that are experimentally testable can be obtained from these models. In the present report, we used independent measurements to determine the model parameters for the wild-type Escherichia coli strain W3110. We experimentally determined the maximum oxygen utilization rate (15 mmol of O2 per g [dry weight] per h), the maximum aerobic glucose utilization rate (10.5 mmol of Glc per g [dry weight] per h), the maximum anaerobic glucose utilization rate (18.5 mmol of Glc per g [dry weight] per h), the non-growth-associated maintenance requirements (7.6 mmol of ATP per g [dry weight] per h), and the growth-associated maintenance requirements (13 mmol of ATP per g of biomass). The flux balance model specified by these parameters was found to quantitatively predict glucose and oxygen uptake rates as well as acetate secretion rates observed in chemostat experiments. We have formulated a predictive algorithm in order to apply the flux balance model to describe unsteady-state growth and by-product secretion in aerobic batch, fed-batch, and anaerobic batch cultures. In aerobic experiments we observed acetate secretion, accumulation in the culture medium, and reutilization from the culture medium. In fed-batch cultures acetate is cometabolized with glucose during the later part of the culture period.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The authors summarizes problems with congruence indices, presents an alternative approach that overcomes these problems, and illustrates this approach using data from two samples, and recommends the use and further development of this approach.
TL;DR: Lakes are a small but potentially important conduit for carbon from terrestrial sources to the atmospheric sink, and the potential efflux of CO2 from lakes is about half as large as riverine transport of organic plus inorganic carbon to the ocean.
Abstract: Data on the partial pressure of carbon dioxide (CO2) in the surface waters from a large number of lakes (1835) with a worldwide distribution show that only a small proportion of the 4665 samples analyzed (less than 10 percent) were within ±20 percent of equilibrium with the atmosphere and that most samples (87 percent) were supersaturated. The mean partial pressure of CO2 averaged 1036 microatmospheres, about three times the value in the overlying atmosphere, indicating that lakes are sources rather than sinks of atmospheric CO2. On a global scale, the potential efflux of CO2 from lakes (about 0.14 x 1015 grams of carbon per year) is about half as large as riverine transport of organic plus inorganic carbon to the ocean. Lakes are a small but potentially important conduit for carbon from terrestrial sources to the atmospheric sink.
TL;DR: The paper describes the space-alternating generalized EM (SAGE) method, which updates the parameters sequentially by alternating between several small hidden-data spaces defined by the algorithm designer, and proves that the sequence of estimates monotonically increases the penalized-likelihood objective, derive asymptotic convergence rates, and provide sufficient conditions for monotone convergence in norm.
Abstract: The expectation-maximization (EM) method can facilitate maximizing likelihood functions that arise in statistical estimation problems. In the classical EM paradigm, one iteratively maximizes the conditional log-likelihood of a single unobservable complete data space, rather than maximizing the intractable likelihood function for the measured or incomplete data. EM algorithms update all parameters simultaneously, which has two drawbacks: 1) slow convergence, and 2) difficult maximization steps due to coupling when smoothness penalties are used. The paper describes the space-alternating generalized EM (SAGE) method, which updates the parameters sequentially by alternating between several small hidden-data spaces defined by the algorithm designer. The authors prove that the sequence of estimates monotonically increases the penalized-likelihood objective, derive asymptotic convergence rates, and provide sufficient conditions for monotone convergence in norm. Two signal processing applications illustrate the method: estimation of superimposed signals in Gaussian noise, and image reconstruction from Poisson measurements. In both applications, the SAGE algorithms easily accommodate smoothness penalties and converge faster than the EM algorithms. >
TL;DR: The results indicate that the MNSI is a good screening tool for diabetic neuropathy and that the MDNS coupled with nerve conductions provides a simple means to confirm this diagnosis.
Abstract: OBJECTIVE Early diagnosis of distal symmetric sensorimotor polyneuropathy, a common complication of diabetes, may decrease patient morbidity by allowing for potential therapeutic interventions. We have designed an outpatient program to facilitate diagnosis of diabetic neuropathy. RESEARCH DESIGN AND METHODS Patients are initially administered a brief questionnaire and screening examination, designated the Michigan Neuropathy Screening Instrument (MNSI). Diabetic neuropathy is confirmed in patients with a positive assessment by a quantitative neurological examination coupled with nerve conduction studies, designated the Michigan Diabetic Neuropathy Score (MDNS). In this study, 56 outpatients with confirmed type I or II diabetes were administered the standardized quantitative components required to diagnose and stage diabetic neuropathy according to the San Antonio Consensus Statement (1) and the Mayo Clinic protocol (2). These same patients were then assessed with the MNSI and the MDNS. RESULTS Of 29 patients with a clinical MNSI score > 2, 28 had neuropathy. Twenty-eight patients with an MDNS of ≥ 7 had neuropathy, while 21 non-neuropathic patients had a score ≤ 6. Of 35 patients with diabetic neuropathy, 34 had ≥ 2 abnormal nerve conductions. Twenty-one normal patients and one patient with neuropathy had ≤ 1 abnormal nerve conduction. CONCLUSIONS The results indicate that the MNSI is a good screening tool for diabetic neuropathy and that the MDNS coupled with nerve conductions provides a simple means to confirm this diagnosis.
TL;DR: Increases in urethral closure pressure during a cough probably arise because the urethra is compressed against a hammock-like supportive layer, rather than the Urethra being truly "intraabdominal."
TL;DR: The flux balance methodology allows the quantitative interpretation of metabolic physiology, gives an interpretation of experimental data, provides a guide to metabolic engineering, enables optimal medium formulation, and provides a method for bioprocess optimization.
Abstract: Recently, there has been an increasing interest in stoichiometric analysis of metabolic flux distributions. Flux balance methods only require information about metabolic reaction stoichiometry, metabolic requirements for growth, and the measurement of a few strain–specific parameters. This information determines the domain of stoichiometrically allowable flux distributions that may be taken to define a strain's “metabolic genotype”. Within this domain a single flux distribution is sought based on assumed behavior, such as maximal growth rates. The optimal flux distributions are calculated using linear optimization and may be taken to represent the strain's “metabolic phenotype” under the particular conditions. This flux balance methodology allows the quantitative interpretation of metabolic physiology, gives an interpretation of experimental data, provides a guide to metabolic engineering, enables optimal medium formulation, and provides a method for bioprocess optimization. This spectrum of applications, and its ease of use, makes the metabolic flux balance model a potentially valuable approach for the design and optimization of bioprocesses.
TL;DR: The authors provides a critical look at recent empirical work in international trade theory and addresses the issue of why empirical work has perhaps not been as influential as it could have been, and also provides several suggestions on directions for future empirical research in International Trade.
Abstract: This paper provides a critical look at recent empirical work in international trade theory. The paper addresses the issue of why empirical work in international trade has perhaps not been as influential as it could have been. The paper also provides several suggestions on directions for future empirical research in international trade.
TL;DR: It is shown that results previously reported for indices of SES hold separately for education and income and that the interaction between age and SES can be substantially explained by the greater exposure of lower SES persons to a wide range of psychosocial risk factors to health.
Abstract: The way health varies with age is importantly stratified by socioeconomic status (SES)--specifically, education and income. Prior theory and cross-sectional data suggest that among higher SES persons the onset of health problems is usually postponed until rather late in life, while health declines are prevalent in lower SES groups by middle age. Thus, SES differences in health are small in early adulthood, but increase with age until relatively late in life, when they diminish due to selection or greater equalization of health risks and protections. The present paper strengthens our causal and interpretive understanding of these phenomena by showing: (1) that results previously reported for indices of SES hold separately for education and income; (2) that the interaction between age and SES (i.e., education or income) in predicting health can be substantially explained by the greater exposure of lower SES persons to a wide range of psychosocial risk factors to health, especially in middle and early old age, and, to a lesser degree, the greater impact of these risk factors on health with age; and (3) that results (1) and (2) generally hold in short-term longitudinal as well as in cross-sectional data. Implications for science and policy in the areas of aging, health, and social stratification are discussed.