Showing papers by "Dartmouth College published in 2002"

Microbial cellulose utilization: fundamentals and biotechnology.

Abstract: Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

Phylogenies and Community Ecology

Abstract: ▪ Abstract As better phylogenetic hypotheses become available for many groups of organisms, studies in community ecology can be informed by knowledge of the evolutionary relationships among coexisting species. We note three primary approaches to integrating phylogenetic information into studies of community organization: 1. examining the phylogenetic structure of community assemblages, 2. exploring the phylogenetic basis of community niche structure, and 3. adding a community context to studies of trait evolution and biogeography. We recognize a common pattern of phylogenetic conservatism in ecological character and highlight the challenges of using phylogenies of partial lineages. We also review phylogenetic approaches to three emergent properties of communities: species diversity, relative abundance distributions, and range sizes. Methodological advances in phylogenetic supertree construction, character reconstruction, null models for community assembly and character evolution, and metrics of community ...

The Dynamic Resource-Based View: Capability Lifecycles

Abstract: This article introduces the concept of the capability lifecycle (CLC), which articulates general patterns and paths in the evolution of organizational capabilities over time. The capability lifecycle provides a structure for a more comprehensive approach to dynamic resource-based theory. The analysis incorporates the founding, development, and maturity of capabilities in a manner that helps to explain the sources of heterogeneity in organizational capabilities. In addition, the analysis includes the "branching" of an original capability into several possible altered forms.

Testing Trade-Off and Pecking Order Predictions About Dividends and Debt

Abstract: Confirming predictions shared by the trade-off and pecking order models, more profitable firms and firms with fewer investments have higher dividend payouts. Confirming the pecking order model but contradicting the trade-off model, more profitable firms are less levered. Firms with more investments have less market leverage, which is consistent with the trade-off model and a complex pecking order model. Firms with more investments have lower long-term dividend payouts, but dividends do not vary to accommodate shortterm variation in investment. As the pecking order model predicts, short-term variation in investment and earnings is mostly absorbed by debt. The finance literature offers two competing models of financing decisions. In the trade-off model, firms identify their optimal leverage by weighing the costs and benefits of an additional dollar of debt. The benefits of debt include, for example, the tax deductibility of interest and the reduction of free cash flow problems. The costs of debt include potential bankruptcy costs and agency conflicts between stockholders and bondholders. At the leverage optimum, the benefit of the last dollar of debt just offsets the cost. The tradeoff model makes a similar prediction about dividends. Firms maximize value by selecting the dividend payout that equates the costs and benefits of the last dollar of dividends. Myers (1984) develops an alternative theory known as the pecking order model of financing decisions. The pecking order arises if the costs of issuing new securities overwhelm other costs and benefits of dividends and debt. The financing costs that produce pecking order behavior include the transaction costs associated with new issues and the costs that arise because of management’s superior information about the firm’s prospects and the value of its risky securities. Because of these costs, firms finance new investments first with retained earnings, then with safe debt, then with risky debt, and finally, under duress, with equity. As a result, variation in a firm’s leverage

Collaborative Care Management of Late-Life Depression in the Primary Care Setting: A Randomized Controlled Trial

Abstract: ContextFew depressed older adults receive effective treatment in primary care settings.ObjectiveTo determine the effectiveness of the Improving Mood–Promoting Access to Collaborative Treatment (IMPACT) collaborative care management program for late-life depression.DesignRandomized controlled trial with recruitment from July 1999 to August 2001.SettingEighteen primary care clinics from 8 health care organizations in 5 states.ParticipantsA total of 1801 patients aged 60 years or older with major depression (17%), dysthymic disorder (30%), or both (53%).InterventionPatients were randomly assigned to the IMPACT intervention (n = 906) or to usual care (n = 895). Intervention patients had access for up to 12 months to a depression care manager who was supervised by a psychiatrist and a primary care expert and who offered education, care management, and support of antidepressant management by the patient's primary care physician or a brief psychotherapy for depresssion, Problem Solving Treatment in Primary Care.Main Outcome MeasuresAssessments at baseline and at 3, 6, and 12 months for depression, depression treatments, satisfaction with care, functional impairment, and quality of life.ResultsAt 12 months, 45% of intervention patients had a 50% or greater reduction in depressive symptoms from baseline compared with 19% of usual care participants (odds ratio [OR], 3.45; 95% confidence interval [CI], 2.71-4.38; P<.001). Intervention patients also experienced greater rates of depression treatment (OR, 2.98; 95% CI, 2.34-3.79; P<.001), more satisfaction with depression care (OR, 3.38; 95% CI, 2.66-4.30; P<.001), lower depression severity (range, 0-4; between-group difference, −0.4; 95% CI, −0.46 to −0.33; P<.001), less functional impairment (range, 0-10; between-group difference, −0.91; 95% CI, −1.19 to −0.64; P<.001), and greater quality of life (range, 0-10; between-group difference, 0.56; 95% CI, 0.32-0.79; P<.001) than participants assigned to the usual care group.ConclusionThe IMPACT collaborative care model appears to be feasible and significantly more effective than usual care for depression in a wide range of primary care practices.

Finding the Self? An Event-Related fMRI Study

Abstract: Researchers have long debated whether knowledge about the self is unique in terms of its functional anatomic representation within the human brain. In the context of memory function, knowledge about the self is typically remembered better than other types of semantic information. But why does this memorial effect emerge? Extending previous research on this topic (see Craik et al., 1999), the present study used event-related functional magnetic resonance imaging to investigate potential neural substrates of self-referential processing. Participants were imaged while making judgments about trait adjectives under three experimental conditions (self-relevance, other-relevance, or case judgment). Relevance judgments, when compared to case judgments, were accompanied by activation of the left inferior frontal cortex and the anterior cingulate. A separate region of the medial prefrontal cortex was selectively engaged during self-referential processing. Collectively, these findings suggest that self-referential processing is functionally dissociable from other forms of semantic processing within the human brain.

IRT1, an Arabidopsis Transporter Essential for Iron Uptake from the Soil and for Plant Growth

Abstract: Plants are the principal source of iron in most diets, yet iron availability often limits plant growth. In response to iron deficiency, Arabidopsis roots induce the expression of the divalent cation transporter IRT1. Here, we present genetic evidence that IRT1 is essential for the uptake of iron from the soil. An Arabidopsis knockout mutant in IRT1 is chlorotic and has a severe growth defect in soil, leading to death. This defect is rescued by the exogenous application of iron. The mutant plants do not take up iron and fail to accumulate other divalent cations in low-iron conditions. IRT1‐green fluorescent protein fusion, transiently expressed in culture cells, localized to the plasma membrane. We also show, through promoter:: � -glucuronidase analysis and in situ hybridization, that IRT1 is expressed in the external cell layers of the root, specifically in response to iron starvation. These results clearly demonstrate that IRT1 is the major transporter responsible for high-affinity metal uptake under iron deficiency.

An Economic Approach to Social Capital

Abstract: A standard optimal investment model can be used to analyse an individual's decision to accumulate social capital. We analyse six facts that support the predictions of this individual-based approach: (1) social capital first rises and then falls with age, (2) social capital declines with expected mobility, (3) social capital rises in occupations with greater returns to social skills, (4) social capital is higher among homeowners, (5) social connections fall sharply with physical distance, (6) people who invest in human capital also invest in social capital. We fail to find robust evidence that social capital investments fall with the value of time or that geographic/religious groups generate social capital complementarities.

Trade liberalization, exit, and productivity improvements: Evidence from Chilean plants

Abstract: This paper empirically investigates the effects of liberalized trade on plant productivity in the case of Chile. Chile presents an interesting setting to study this relationship since it underwent a massive trade liberalization that significantly exposed its plants to competition from abroad during the late 1970s and early 1980s. Methodologically, I approach this question in two steps. In the first step, I estimate a production function to obtain a measure of plant productivity. I estimate the production function semiparametrically to correct for the presence of selection and simultaneity biases in the estimates of the input coefficients required to construct a productivity measure. I explicitly incorporate plant exit in the estimation to correct for the selection problem induced by liquidated plants. These methodological aspects are important in obtaining a reliable plant-level productivity measure based on consistent estimates of the input coefficients. In the second step, I identify the impact of trade on plants' productivity in a regression framework allowing variation in productivity over time and across traded- and nontraded-goods sectors. Using plant-level panel data on Chilean manufacturers, I find evidence of within plant productivity improvements that can be attributed to a liberalized trade for the plants in the import-competing sector. In many cases, aggregate productivity improvements stem from the reshuffling of resources and output from less to more efficient producers.

The Equity Premium

Abstract: We estimate the equity premium using dividend and earnings growth rates to measure the expected rate of capital gain. Our estimates for 1951 to 2000, 2.55 percent and 4.32 percent, are much lower than the equity premium produced by the average stock return, 7.43 percent. Our evidence suggests that the high average return for 1951 to 2000 is due to a decline in discount rates that produces a large unexpected capital gain. Our main conclusion is that the average stock return of the last half-century is a lot higher than expected. THE EQUITY PREMIUM—the difference between the expected return on the market portfolio of common stocks and the risk-free interest rate—is important in portfolio allocation decisions, estimates of the cost of capital, the debate about the advantages of investing Social Security funds in stocks, and many other applications. The average return on a broad portfolio of stocks is typically used to estimate the expected market return. The average real return for 1872 to 2000 on the S&P index ~a common proxy for the market portfolio, also used here! is 8.81 percent per year. The average real return on sixmonth commercial paper ~a proxy for the risk-free interest rate! is 3.24 percent. This large spread ~5.57 percent! between the average stock return and the interest rate is the source of the so-called equity premium puzzle: Stock returns seem too high given the observed volatility of consumption ~Mehra and Prescott ~1985!!. We use fundamentals ~dividends and earnings! to estimate the expected stock return. Along with other evidence, the expected return estimates from fundamentals help us judge whether the realized average return is high or low relative to the expected value. The logic of our approach is straightforward. The average stock return is the average dividend yield plus the average rate of capital gain:

Links between worlds: unraveling migratory connectivity

Abstract: Migration is the regular seasonal movement of animals from one place to another, often from a breeding site to a nonbreeding site and back. Because the act of migration makes it difficult to follow individuals and populations year round, our understanding of the ecology and evolution of migrating organisms, particularly birds, has been severely impeded. Exciting new advances in satellite telemetry, genetic analyses and stable isotope chemistry are now making it possible to determine the population and geographical origin of individual birds. Here, we review these new approaches and consider the relevance of understanding migratory connectivity to ecological, evolutionary and conservation issues.

The birth of capabilities: market entry and the importance of pre-history

Abstract: We analyze the birth of capabilities and resources within organizations and within industries, and their historical antecedents, at the time of market entry. We find a consistent theme: the greater the similarity between pre-entry firm resources and the required resources in an industry, the greater the likelihood that a firm will enter that particular industry, and the greater the likelihood that the firm will survive and prosper. In addition, resource gaps affect the likelihood, speed and mode of entry.

Matrix metalloproteinases: a tail of a frog that became a prince

Abstract: It is 40 years since the first member of what came to be known as the matrix metalloproteinase (MMP) family was described. Structural, molecular and biochemical approaches have subsequently contributed to piecing together the puzzle of how MMPs work, and how they contribute to various disease processes.

Accurate prediction of ferrite core loss with nonsinusoidal waveforms using only Steinmetz parameters

Abstract: An improved calculation of ferrite core loss for nonsinusoidal waveforms separates a flux trajectory into major and minor loops via a new recursive algorithm. It is highly accurate and outperforms two previous methods for our measured data. The only characteristics of the material required are the standard Steinmetz-equation parameters.

Predicting Returns with Financial Ratios

Abstract: This article provides a new test of the predictive ability of aggregate financial ratios. Predictive regressions are subject to small-sample biases, but the correction in previous studies can substantially understate forecasting power. Dividend yield predicts aggregate market returns from 1946 - 2000, as well as in various subperiods. Book-to-market and the earnings-price ratio predict returns during the shorter 1963 - 2000 sample. The evidence remains strong despite the unusual price run-up in recent years.

Building brand equity through corporate societal marketing

Abstract: Marketers have shown increasing interest in the use of corporate societal marketing (CSM) programs. In this article, the authors describe six means by which CSM programs can build brand equity: (1) building brand awareness, (2) enhancing brand image, (3) establishing brand credibility, (4) evoking brand feelings, (5) creating a sense of brand community, and (6) eliciting brand engagement. The authors also address three key questions revolving around how CSM programs have their effects, which cause the firm should choose, and how CSM programs should be branded. The authors offer a series of research propositions throughout and conclude by outlining a set of potential future research directions.

Unwarranted variations in healthcare delivery: implications for academic medical centres

Abstract: Everyday clinical practice is characterised by wide variations that cannot be explained by illness severity or patient preference. Professor Wennberg examines the causes for these variations and suggests ways to remedy the situation Academic medicine has had only limited success in improving the scientific basis of everyday clinical practice, even within the walls of its own hospitals. Patterns of practice among academic medical centres—as among other institutions—are often idiosyncratic and unscientific, and local medical opinion and local supply of resources are more important than science in determining how medical care is delivered. In short, after nearly 100 years of academic medicine as we know it, much of medicine in the United States remains empirical. The evaluative clinical sciences—those disciplines whose role in medicine is to evaluate medical theory, understand patient preferences, and improve systems—are capable of improving the scientific basis of clinical practice and warrant high priority in the national research agenda and full adoption into medical school curriculums. These sciences are essential to the development of organised healthcare systems in the 21st century, not least because they expose unwarranted variations in care and can be used to remedy them. #### Summary box I will begin with a summary of the facts of unwarranted variations in clinical practice, derived from the Dartmouth Atlas of Health Care project, a US national study of traditional (fee for service) Medicare. The atlas project reports on the rates of …

Transcriptional regulation of collagenase (MMP-1, MMP-13) genes in arthritis: integration of complex signaling pathways for the recruitment of gene-specific transcription factors

Abstract: Matrix metalloproteinase (MMP)-1, MMP-8 and MMP-13 are interstitial collagenases that degrade type II collagen in cartilage; this is a committed step in the progression of rheumatoid arthritis and osteoarthritis. Of these enzymes, the expression of MMP-1 and MMP-13 is substantially increased in response to IL-1 and tumor necrosis factor-α, and elevated levels of these collagenases are observed in arthritic tissues. Therefore, cytokine-mediated MMP-1 and MMP-13 gene regulation is an important issue in arthritis research. In this review, we discuss current models of MMP-1 and MMP-13 transcriptional regulation, with a focus on signaling intermediates and transcription factors that may be future targets for the development of new arthritis drugs.

Expression of the IRT1 metal transporter is controlled by metals at the levels of transcript and protein accumulation.

Abstract: Iron, an essential nutrient, is not readily available to plants because of its low solubility. In addition, iron is toxic in excess, catalyzing the formation of hydroxyl radicals that can damage cellular constituents. Consequently, plants must carefully regulate iron uptake so that iron homeostasis is maintained. The Arabidopsis IRT1 gene is the major transporter responsible for high-affinity iron uptake from the soil. Here, we show that the steady state level of IRT1 mRNA was induced within 24 h after transfer of plants to iron-deficient conditions, with protein levels peaking 72 h after transfer. IRT1 mRNA and protein were undetectable 12 h after plants were shifted back to iron-sufficient conditions. Overexpression of IRT1 did not confer dominant gain-of-function enhancement of metal uptake. Analysis of 35S-IRT1 transgenic plants revealed that although IRT1 mRNA was expressed constitutively in these plants, IRT1 protein was present only in the roots when iron is limiting. Under these conditions, plants that overexpressed IRT1 accumulated higher levels of cadmium and zinc than wild-type plants, indicating that IRT1 is responsible for the uptake of these metals and that IRT1 protein levels are indeed increased in these plants. Our results suggest that the expression of IRT1 is controlled by two distinct mechanisms that provide an effective means of regulating metal transport in response to changing environmental conditions.

Mortality, disability, and nursing home use for persons with and without hip fracture: a population-based study

Abstract: OBJECTIVES: To compare persons with and without hip fracture for subsequent mortality and change in disability and nursing home (NH) use. DESIGN: Population-based historical cohort study. SETTING: Olmsted County, Minnesota. PARTICIPANTS: All residents who experienced a first hip fracture between January 1, 1989, and December 31, 1993, and, for each case, a resident of the same sex and similar age who had not experienced a hip fracture and was seen by a local care provider. MEASUREMENTS: Data on disability (Rankin score), comorbidity (Charlson Index), and NH residency before baseline (fracture date for cases and registration date for controls) were obtained by review of complete community-based medical records. The records were then reviewed from baseline through December 31, 1994, for Rankin disability at 1 month and 1 year, all NH admissions and discharges, and date of death for those who died. RESULTS: There were 312 cases and 312 controls (81% female, mean age ± standard deviation = 81 ± 12 years). Before baseline, cases had higher comorbidity (45% vs 30% had Charlson Index ≥ 1, P < .001) and disability (mean Rankin score = 2.5 ± 1.1 vs 2.2 ± 1.1, P < .001) and were more likely to be in a NH (28% vs 18%, P < .001) than controls. One year after baseline, estimated mortality was 20% (95% confidence interval (CI) = 16–24) for cases vs 11% (95% CI = 8–15) for controls, 51% of cases versus 16% of controls had a level of disability one or more units worse than before baseline (P < .001), and the cumulative incidence of first NH admission was 64% (95% CI = 58–71) for cases versus 7% (95% CI = 4–11) for controls. The risk of NH admission for cases relative to controls diminished over time, but remained elevated 5 years after the event (risk ratio = 20.0 at 3 months and 2.1 at 5 years), but, in persons admitted to a nursing home, cases were two times more likely than controls to be discharged alive within a year (P < .001). CONCLUSIONS: Hip fracture is an important contributor to disability and NH use, but the potential savings from hip fracture prophylaxis may be overestimated by studies that fail to consider differential risk, mortality, and long-term follow-up.

Ideas, Politics, and Public Policy

Abstract: ▪ Abstract Scholars have become acutely interested in how behavior driven by ideas rather than self-interest determines policy-making outcomes. This review examines the literature on this subject. It differentiates among the types of ideas that may affect policy making (i.e., cognitive paradigms, world views, norms, frames, and policy programs) and identifies some of the persistent difficulties associated with studying how ideas shape policy. In particular, studies often do a poor job pinpointing the causal mechanisms that link ideas to policy-making outcomes. More attention needs to be paid to articulating the causal processes through which ideas exert effects. Suggestions for future scholarship that might improve this situation are offered. These include identifying the actors who seek to influence policy making with their ideas, ascertaining the institutional conditions under which these actors have more or less influence, and understanding how political discourse affects the degree to which policy ide...

General Competencies And Accreditation In Graduate Medical Education

Abstract: Many have recommended changing the professional development of physicians Concluding that further educational process specification was inadequate, the Accreditation Council for Graduate Medical Education (ACGME) decided to specify six general competencies of graduate medical education (GME): patient care; medical knowledge; practice-based learning and improvement; professionalism; interpersonal skills and communication; and systems-based practice Coupling them with a developmental view of professional knowledge and skill acquisition, the ACGME invited further specification and development of desired learning from the extended medical specialty community, including the specialty boards This collaborative process offers a model of the role accrediting agencies can play in fostering workforce developmental change

Enhancing breast tumor detection with near-field imaging

Abstract: This article outlines the main features of active, passive, and hybrid systems under investigation for breast cancer detection. Our main focus is on active microwave systems, in particular microwave tomography and confocal microwave imaging.

Geography And The Debate Over Medicare Reform

Abstract: Medicare spending varies more than twofold among regions, and the variations persist even after differences in health are corrected for. Higher levels of Medicare spending are due largely to increased use of "supply-sensitive" services--physician visits, specialist consultations, and hospitalizations, particularly for those with chronic illnesses or in their last six months of life. Also, higher spending does not result in more effective care, elevated rates of elective surgery, or better health outcomes. To improve the quality and efficiency of care, we propose a new approach to Medicare reform based on the principles of shared decision making and the promotion of centers of medical excellence. We suggest that our proposal be tested in a major demonstration project

Illness management and recovery: a review of the research.

Abstract: Illness management is a broad set of strategies designed to help individuals with serious mental illness collaborate with professionals, reduce their susceptibility to the illness, and cope effectively with their symptoms. Recovery occurs when people with mental illness discover, or rediscover, their strengths and abilities for pursuing personal goals and develop a sense of identity that allows them to grow beyond their mental illness. The authors discuss the concept of recovery from psychiatric disorders and then review research on professional-based programs for helping people manage their mental illness. Research on illness management for persons with severe mental illness, including 40 randomized controlled studies, indicates that psychoeducation improves people's knowledge of mental illness; that behavioral tailoring helps people take medication as prescribed; that relapse prevention programs reduce symptom relapses and rehospitalizations; and that coping skills training using cognitive-behavioral te...

Detection of Ductal Carcinoma In Situ in Women Undergoing Screening Mammography

Abstract: Background: With the large number of women having mammography—an estimated 28.4 million U.S. women aged 40 years and older in 1998—the percentage of cancers detected as ductal carcinoma in situ (DCIS), which has an uncertain prognosis, has increased. We pooled data from seven regional mammography registries to determine the percentage of mammographically detected cancers that are DCIS and the rate of DCIS per 1000 mammograms. Methods: We analyzed data on 653 833 mammograms from 540 738 women between 40 and 84 years of age who underwent screening mammography at facilities participating in the National Cancer Institute’s Breast Cancer Surveillance Consortium (BCSC) throughout 1996 and 1997. Mammography results were linked to population-based cancer and pathology registries. We calculated the percentage of screen-detected breast cancers that were DCIS, the rate of screen-detected DCIS per 1000 mammograms by age and by previous mammography status, and the sensitivity of screening mammography. Statistical tests were two-sided. Results: A total of 3266 cases of breast cancer were identified, 591 DCIS and 2675 invasive breast cancer. The percentage of screendetected breast cancers that were DCIS decreased with age (from 28.2% [95% confidence interval (CI) = 23.9% to 32.5%] for women aged 40–49 years to 16.0% [95% CI = 13.3% to 18.7%] for women aged 70–84 years). However, the rate of screen-detected DCIS cases per 1000 mammograms increased with age (from 0.56 [95% CI = 0.41 to 0.70] for women aged 40–49 years to 1.07 [95% CI = 0.87 to 1.27] for women aged 70–84 years). Sensitivity of screening mammography in all age groups combined was higher for detecting DCIS (86.0% [95% CI = 83.2% to 88.8%]) than it was for detecting invasive breast cancer (75.1% [95% CI = 73.5% to 76.8%]). Conclusions: Overall, approximately 1 in every 1300 screening mammography examinations leads to a diagnosis of DCIS. Given uncertainty about the natural history of DCIS, the clinical significance of screen-detected DCIS needs further investigation. [J Natl Cancer Inst 2002;94: 1546–54]