Showing papers by "University of Miami published in 2000"

Managerial Ties and Firm Performance in a Transition Economy: The Nature of a Micro-Macro Link

Abstract: Using survey data from China, we demonstrate that managers' micro interpersonal ties with top executives at other firms and with government officials help improve macro organizational performance This micro-macro link differs among firms with different (1) ownership types, (2) business sectors, (3) sizes, and (4) industry growth rates In addition, managerial ties were found to be necessary but insufficient for good performance; a number of traditional strategy variables also drive performance Theoretically, the findings point to the importance of the social context in which managerial ties are embedded Empirically, this study provides the first set of quantitative data demonstrating both the extent and limits to which managerial ties are beneficial in a transition economy

Technology Readiness Index (Tri): A Multiple-Item Scale to Measure Readiness to Embrace New Technologies

Abstract: The role of technology in customer-company interactions and the number of technology-based products and services have been growing rapidly. Although these developments have benefited customers, the...

Artificial Molecular Machines.

Abstract: The miniaturization of components used in the construction of working devices is being pursued currently by the large-downward (top-down) fabrication. This approach, however, which obliges solid-state physicists and electronic engineers to manipulate progressively smaller and smaller pieces of matter, has its intrinsic limitations. An alternative approach is a small-upward (bottom-up) one, starting from the smallest compositions of matter that have distinct shapes and unique properties-namely molecules. In the context of this particular challenge, chemists have been extending the concept of a macroscopic machine to the molecular level. A molecular-level machine can be defined as an assembly of a distinct number of molecular components that are designed to perform machinelike movements (output) as a result of an appropriate external stimulation (input). In common with their macroscopic counterparts, a molecular machine is characterized by 1) the kind of energy input supplied to make it work, 2) the nature of the movements of its component parts, 3) the way in which its operation can be monitored and controlled, 4) the ability to make it repeat its operation in a cyclic fashion, 5) the timescale needed to complete a full cycle of movements, and 6) the purpose of its operation. Undoubtedly, the best energy inputs to make molecular machines work are photons or electrons. Indeed, with appropriately chosen photochemically and electrochemically driven reactions, it is possible to design and synthesize molecular machines that do work. Moreover, the dramatic increase in our fundamental understanding of self-assembly and self-organizational processes in chemical synthesis has aided and abetted the construction of artificial molecular machines through the development of new methods of noncovalent synthesis and the emergence of supramolecular assistance to covalent synthesis as a uniquely powerful synthetic tool. The aim of this review is to present a unified view of the field of molecular machines by focusing on past achievements, present limitations, and future perspectives. After analyzing a few important examples of natural molecular machines, the most significant developments in the field of artificial molecular machines are highlighted. The systems reviewed include 1) chemical rotors, 2) photochemically and electrochemically induced molecular (conformational) rearrangements, and 3) chemically, photochemically, and electrochemically controllable (co-conformational) motions in interlocked molecules (catenanes and rotaxanes), as well as in coordination and supramolecular complexes, including pseudorotaxanes. Artificial molecular machines based on biomolecules and interfacing artificial molecular machines with surfaces and solid supports are amongst some of the cutting-edge topics featured in this review. The extension of the concept of a machine to the molecular level is of interest not only for the sake of basic research, but also for the growth of nanoscience and the subsequent development of nanotechnology.

The impact of technology on the quality-value-loyalty chain: A research agenda

Abstract: In this article, the authors first propose a simple model summarizing the key drivers of customer loyalty. Then, on the basis of this model and drawing on key insights from the preceding articles in this issue, they outline a set of issues for further research related to the quality-value-loyalty chain. Next, the authors develop a conceptual framework that integrates the quality-value-loyalty chain with the “pyramid model,” which emphasizes the increasing importance of technology-customer, technology-employee, and technology-company linkages in serving customers. Using this integrated framework as a spring-board, they identify a number of avenues for additional inquiry pertaining to the three types of linkages.

Connectivity of marine populations: open or closed?

Abstract: Most marine populations are thought to be well connected via long-distance dispersal of larval stages. Eulerian and Lagrangian flow models, coupled with linear mortality estimates, were used to examine this assumption. The findings show that when simple advection models are used, larval exchange rates may be overestimated; such simplistic models fail to account for a decrease of up to nine orders of magnitude in larval concentrations resulting from diffusion and mortality. The alternative process of larval retention near local populations is shown to exist and may be of great importance in the maintenance of marine population structure and management of coastal marine resources.

Research Methodology In Management: Current Practices, Trends, And Implications For Future Research

Abstract: This study is a comparison of the strategies employed in management research in two periods, 1995–97 and 1985–87. Through a content analysis of articles from the Academy of Management Journal, Admi...

Neurodevelopmental and Functional Outcomes of Extremely Low Birth Weight Infants in the National Institute of Child Health and Human Development Neonatal Research Network, 1993–1994

Abstract: Objectives. The purposes of this study were to report the neurodevelopmental, neurosensory, and functional outcomes of 1151 extremely low birth weight (401–1000 g) survivors cared for in the 12 participating centers of the National Institute of Child Health and Human Development Neonatal Research Network, and to identify medical, social, and environmental factors associated with these outcomes. Study Design. A multicenter cohort study in which surviving extremely low birth weight infants born in 1993 and 1994 underwent neurodevelopmental, neurosensory, and functional assessment at 18 to 22 months9 corrected age. Data regarding pregnancy and neonatal outcome were collected prospectively. Socioeconomic status and a detailed interim medical history were obtained at the time of the assessment. Logistic regression models were used to identify maternal and neonatal risk factors for poor neurodevelopmental outcome. Results. Of the 1480 infants alive at 18 months of age, 1151 (78%) were evaluated. Study characteristics included a mean birth weight of 796 ± 135 g, mean gestation (best obstetric dates) 26 ± 2 weeks, and 47% male. Birth weight distributions of infants included 15 infants at 401 to 500 g; 94 at 501 to 600 g; 208 at 601 to 700 g; 237 at 701 to 800 g; 290 at 801 to 900 g; and 307 at 901 to 1000 g. Twenty-five percent of the children had an abnormal neurologic examination, 37% had a Bayley II Mental Developmental Index Conclusion. ELBW infants are at significant risk of neurologic abnormalities, developmental delays, and functional delays at 18 to 22 months9 corrected age.

Practice parameter: Screening and diagnosis of autism Report of the Quality Standards Subcommittee of the American Academy of Neurology and the Child Neurology Society

Abstract: Autism is a common disorder of childhood, affecting 1 in 500 children. Yet, it often remains unrecognized and undiagnosed until or after late preschool age because appropriate tools for routine developmental screening and screening specifically for autism have not been available. Early identification of children with autism and intensive, early intervention during the toddler and preschool years improves outcome for most young children with autism. This practice parameter reviews the available empirical evidence and gives specific recommendations for the identification of children with autism. This approach requires a dual process: 1) routine developmental surveillance and screening specifically for autism to be performed on all children to first identify those at risk for any type of atypical development, and to identify those specifically at risk for autism; and 2) to diagnose and evaluate autism, to differentiate autism from other developmental disorders.

The influence of cause-related marketing on consumer choice: Does one good turn deserve another?

Abstract: Are consumers more likely to select brands offered by companies that engage in cause-related marketing (CRM)? Somewhat surprisingly, little evidence exists that directly addresses this issue. Accordingly, the present examination investigates whether and when CRM efforts influence consumer choice. The results from several studies indicate that information regarding a company’s support of social causes can affect choice. However, CRM’s influence on choice is found to depend on the perceived motivation underlying the company’s CRM efforts as well as whether consumers must trade off company sponsorship of causes for lower performance or higher price. The results also indicate that CRM cues affect choice primarily through compensatory strategies involving trade-offs rather than through noncompensatory strategies. Implications of the current findings for existing theory are discussed along with directions for future research.

Rapid changes in the hydrologic cycle of the tropical Atlantic during the last glacial.

Abstract: Sedimentary time series of color reflectance and major element chemistry from the anoxic Cariaco Basin off the coast of northern Venezuela record large and abrupt shifts in the hydrologic cycle of the tropical Atlantic during the past 90,000 years. Marine productivity maxima and increased precipitation and riverine discharge from northern South America are closely linked to interstadial (warm) climate events of marine isotope stage 3, as recorded in Greenland ice cores. Increased precipitation at this latitude during interstadials suggests the potential for greater moisture export from the Atlantic to Pacific, which could have affected the salinity balance of the Atlantic and increased thermohaline heat transport to high northern latitudes. This supports the notion that tropical feedbacks played an important role in modulating global climate during the last glacial period.

Biodiversity and systematics of basidiomycetous yeasts as determined by large-subunit rDNA D1/D2 domain sequence analysis.

Abstract: The molecular systematics of 337 strains of basidiomycetous yeasts and yeast-like fungi, representing 230 species in 18 anamorphic and 24 teleomorphic genera, was determined by sequence analysis of the D1/D2 region of the large-subunit rDNA. The data were compared with published sequences of other basidiomycetous fungi. The results demonstrated that the yeast species and genera are phylogenetically distributed among the Microbotryum, Sporidiobolus, Agaricostilbum and Erythrobasidium clades of the Urediniomycetes; the Tremellales, Trichosporonales ord. nov., Filobasidiales and Cystofilobasidiales clades of the Hymenomycetes; and the Ustilaginales, Microstromatales and Malasseziales clades of the Ustilaginomycetes. Genera such as Bensingtonia, Cryptococcus, Rhodotorula and Sporobolomyces are polyphyletic, i.e. they occur in two or more clades. In contrast, other genera, e.g. Bullera, Cystofilobasidium, Fellomyces, Filobasidiella, Filobasidium, Kondoa, Kurtzmanomyces, Leucosporidium, Rhodosporidium, Sporidiobolus and Udeniomyces, are monophyletic. The majority of the species can be identified using D1/D2 analyses, although the internal transcribed spacer region is required to distinguish closely related species. The intergenic spacer region is recommended for additional differentiation of species and strains.

The Antecedents and Consequences of Customer-Centric Marketing:

Abstract: As we enter the twenty-first century, the marketing function remains concerned with serving customers and consumers effectively. The authors propose that just as the marketing function gradually shifted from mass marketing to segmented marketing in the twentieth century, it will increasingly move toward customer-centric marketing in the next century. In the practice of customer-centric marketing, the marketing function seeks to fulfill the needs and wants of each individual customer. The antecedents of customer-centric marketing are the increasing pressure on firms to improve marketing productivity, increasing market diversity in household and business markets, and technology applicability. On the basis of the shift toward customer-centric marketing, the authors expect increased importance of marketing as a “supply management” function, customer outsourcing, cocreation marketing, fixedcost marketing, and customer-centric organizations. This article highlights the implications of customer-centric marketing as well as the boundary conditions that will affect its adoption.

Recommendations for the establishment of primary stroke centers

Abstract: ObjectiveTo develop recommendations for the establishment and operation of primary stroke centers as an approach to improve the medical care of patients with stroke.ParticipantsMembers of the Brain Attack Coalition (BAC), a multidisciplinary group of representatives from major professional organizations involved with delivering stroke care. Supplemental input was obtained from other experts involved in acute stroke care.EvidenceA review of literature published from 1966 to March 2000 was performed using MEDLINE. More than 600 English-language articles that had evidence from randomized clinical trials, meta-analyses, care guidelines, or other appropriate methods supporting specific care recommendations for patients with acute stroke that could be incorporated into a stroke center model were selected.Consensus ProcessArticles were reviewed initially by 1 author (M.J.A.). Members of the BAC reviewed each recommendation in the context of current practice parameters, with special attention to improving the delivery of care to patients with acute stroke, cost-effectiveness, and logistical issues related to the establishment of primary stroke centers. Consensus was reached among all BAC participants before an element was added to the list of recommendations.ConclusionsRandomized clinical trials and observational studies suggest that several elements of a stroke center would improve patient care and outcomes. Key elements of primary stroke centers include acute stroke teams, stroke units, written care protocols, and an integrated emergency response system. Important support services include availability and interpretation of computed tomography scans 24 hours everyday and rapid laboratory testing. Administrative support, strong leadership, and continuing education are also important elements for stroke centers. Adoption of these recommendations may increase the use of appropriate diagnostic and therapeutic modalities and reduce peristroke complications. The establishment of primary stroke centers has the potential to improve the care of patients with stroke.

Effects of a Warm Oceanic Feature on Hurricane Opal

Abstract: On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf of Mexico over a 14-h period upon encountering a warm core ring (WCR) in the ocean shed by the Loop Current during an upper-level atmospheric trough interaction. Based on historical hydrographic measurements placed within the context of a two-layer model and surface height anomalies (SHA) from the radar altimeter on the TOPEX mission, upperlayer thickness fields indicated the presence of two warm core rings during September and October 1995. As Hurricane Opal passed directly over one of these WCRs, the 1-min surface winds increased from 35 to more than 60 m s21, and the radius of maximum wind decreased from 40 to 25 km. Pre-Opal SHAs in the WCR exceeded 30 cm where the estimated depth of the 208C isotherm was located between 175 and 200 m. Subsequent to Opal’s passage, this depth decreased approximately 50 m, which suggests upwelling underneath the storm track due to Ekman divergence. The maximum heat loss of approximately 24 Kcal cm22 relative to depth of the 268C isotherm was a factor of 6 times the threshold value required to sustain a hurricane. Since most of this loss occurred over a period of 14 h, the heat content loss of 24 Kcal cm22 equates to approximately 20 kW m22. Previous observational findings suggest that about 10%‐15% of upper-ocean cooling is due to surface heat fluxes. Estimated surface heat fluxes based upon heat content changes range from 2000 to 3000 W m 22 in accord with numerically simulated surface heat fluxes during Opal’s encounter with the WCR. Composited AVHRR-derived SSTs indicated a2 8‐38C cooling associated with vertical mixing in the along-track direction of Opal except over the WCR where AVHRR-derived and buoy-derived SSTs decreased only by about 0.58‐18C. Thus, the WCR’s effect was to provide a regime of positive feedback to the hurricane rather than negative feedback induced by cooler waters due to upwelling and vertical mixing as observed over the Bay of Campeche and north of the WCR.

The role of microbes in accretion, lamination and early lithification of modern marine stromatolites

Abstract: For three billion years, before the Cambrian diversification of life, laminated carbonate build-ups called stromatolites were widespread in shallow marine seas. These ancient structures are generally thought to be microbial in origin and potentially preserve evidence of the Earth's earliest biosphere. Despite their evolutionary significance, little is known about stromatolite formation, especially the relative roles of microbial and environmental factors in stromatolite accretion. Here we show that growth of modern marine stromatolites represents a dynamic balance between sedimentation and intermittent lithification of cyanobacterial mats. Periods of rapid sediment accretion, during which stromatolite surfaces are dominated by pioneer communities of gliding filamentous cyanobacteria, alternate with hiatal intervals. These discontinuities in sedimentation are characterized by development of surface films of exopolymer and subsequent heterotrophic bacterial decomposition, forming thin crusts of microcrystalline carbonate. During prolonged hiatal periods, climax communities develop, which include endolithic coccoid cyanobacteria. These coccoids modify the sediment, forming thicker lithified laminae. Preservation of lithified layers at depth creates millimetre-scale lamination. This simple model of modern marine stromatolite growth may be applicable to ancient stromatolites.

The Concept of Theme as Used in Qualitative Nursing Research

Abstract: The concept of theme is critical to the accurate interpretation of qualitative data. A literature review of qualitative research methodology and nursing research studies reveals considerable diversity in the identification of themes, the interpretation of the concept, and its function in data analysis. Part of the problem is the transfer of research methods from other disciplines to the study of nursing phenomena. The transfer often results in a blending of distinct research methods that compromises methodological rigor in data analysis and theory generation. A definition of theme is developed from the literature review and interdisciplinary definitions and descriptions. Five aspects of a theme and criteria foundational to the definition and concept of theme are identified. Implications of the concept of theme are presented for the conduct and application of research findings to the practice and development of nursing science.

Action, Emotion, and Personality: Emerging Conceptual Integration

Abstract: Several literatures converge on the idea that approach and positive affect related to goal pursuit are managed by one self-regulatory system and that avoidance (or withdrawal) and negative affect related to threats are managed by a second self-regulatory system. After briefly reviewing these literatures, the authors consider the relation of these themes to the broader domain of personality. In particular, they map individual differences in the responsivity of the approach system onto the personality dimension of extraversion and map individual differences in the responsivity of the withdrawal system onto the dimension of neuroticism. This mapping requires a slight refocusing of current conceptions of extraversion and neuroticism. However, such a refocusing brings a gain as well as a cost: In particular, it would embed these dimensions more explicitly in a process-oriented conceptualization of action control.

A metabotropic glutamate receptor variant functions as a taste receptor.

Abstract: Sensory transduction for many taste stimuli such as sugars, some bitter compounds and amino acids is thought to be mediated via G protein-coupled receptors (GPCRs), although no such receptors that respond to taste stimuli are yet identified. Monosodium L-glutamate (L-MSG), a natural component of many foods, is an important gustatory stimulus believed to signal dietary protein. We describe a GPCR cloned from rat taste buds and functionally expressed in CHO cells. The receptor couples negatively to a cAMP cascade and shows an unusual concentration-response relationship. The similarity of its properties to MSG taste suggests that this receptor is a taste receptor for glutamate.

How effective are one-to-one tutoring programs in reading for elementary students at risk for reading failure? A meta-analysis of the intervention research

Abstract: A meta-analysis of supplemental, adult-instructed one-to-one reading interventions for elementary students at risk for reading failure was conducted. Reading outcomes for 42 samples of students (N = 1,539) investigated in 29 studies reported between 1975 and 1998 had a mean weighted effect size of 0.41 when compared with controls. Interventions that used trained volunteers or college students were highly effective. For Reading Recovery interventions, effects for students identified as discontinued were substantial, whereas effects for students identified as not discontinued were not significantly different from zero. Two studies comparing one-to-one with small-group supplemental instruction showed no advantage for the one-to-one programs.

American thyroid association guidelines for detection of thyroid dysfunction

Abstract: Objective To define the optimal approach to identify patients with thyroid dysfunction. Participants The 8-member Standards of Care Committee of the American Thyroid Association prepared a draft, which was reviewed by the association's 780 members, 50 of whom responded with suggested revisions. Evidence Relevant published studies were identified through MEDLINE and the association membership's personal resources. Consensus Process Consensus was reached at group meetings. The first draft was prepared by a single author (P.W.L.) after group discussion. Suggested revisions were incorporated after consideration by the committee. Conclusions The American Thyroid Association recommends that adults be screened for thyroid dysfunction by measurement of the serum thyrotropin concentration, beginning at age 35 years and every 5 years thereafter. The indication for screening is particularly compelling in women, but it can also be justified in men as a relatively cost-effective measure in the context of the periodic health examination. Individuals with symptoms and signs potentially attributable to thyroid dysfunction and those with risk factors for its development may require more frequent serum thyrotropin testing.

Regret: A Model of its Antecedents and Consequences in Consumer Decision Making

Abstract: The article develops a model of regret and tests it via four studies. Study 1 develops a multi-item measure of regret and distinguishes it from satisfaction. It also shows that, while satisfaction directly influences both repurchase and complaint intentions, regret directly influences only repurchase intentions, and its effect on complaint intentions is fully mediated via satisfaction. Study 2 examines the antecedents and moderators of regret. It shows that regret is experienced even in the absence of information on a better-forgone outcome. Furthermore, the moderating effect of three situation-specific characteristics (outcome valence, status quo preservation, and reversibility of the outcome) is examined. Studies 3 and 4 examine the cognitive process underlying the experiencing of regret in the absence of information on a better-forgone outcome. Generation of counterfactuals is identified as the cognitive mechanism that engenders regret. Results show that counterfactuals are most likely to be generated when the chosen outcome is negative and not the status quo.

Salvage surgery for patients with recurrent squamous cell carcinoma of the upper aerodigestive tract: when do the ends justify the means?

Abstract: Objectives/Hypotheses: Salvage surgery is widely viewed as a “double-edged sword.” It is the best option for many patients with recurrent cancer of the upper aerodigestive tract, especially when original therapy included irradiation, yet it may provide only modest benefit at high personal cost to the patient. The stakes are high because alternatives are of limited value. The primary objective of this study was to fully assess the value of salvage surgical procedures in the treatment of local and regional recurrence. The following hypotheses were developed to focus the study design and data analysis. 1) The efficacy of salvage surgery correlates recurrent stage, recurrent site, and time to presalvage recurrence. 2) The economic and noneconomic costs of salvage surgery increase with higher recurrent stage. 3) Information relating the value of salvage surgery to recurrent stage and recurrent site will be useful to these patients and the physicians who treat them. Study Design: Two complimentary methods of investigation were used: a meta-analysis of the published literature and a prospective observational study of patients undergoing salvage surgery for recurrent cancer of the upper aerodigestive tract. Methods: The meta-analysis combined 32 published reports to obtain an estimate of average treatment effect for salvage surgery with regard to survival, disease-free survival, surgical complications, and operative mortality. The prospective observational study included detailed data in 109 patients who underwent salvage surgery. In addition to parameters studied in the meta-analysis, we obtained baseline and interval quality of life data (Functional Living Index for Cancer [FLIC] scores), baseline and interval performance status evaluations (Performance Status Scale for Head and Neck Cancer Patients [PSS head and neck scores]), length of hospital stay, and hospital and physician charges, and related this data primarily to recurrent stage, recurrent site, and time to presalvage recurrence. Results: The weighted average of 5-year survival in the meta-analysis was 39% in 1,080 patients from 28 different institutions. In the prospective study, median disease-free survival was 17.9 months in 109 patients, and this correlated strongly with recurrent stage, weakly with recurrent site, and not at all with time to presalvage recurrence. Noneconomic costs for patients and economic costs correlated with recurrent stage, but not with site. Baseline FLIC and PSS head and neck scores correlated with recurrent stage, but not with site. After salvage surgery the percentage of patients reaching or exceeding baseline was 51% for FLIC scores, and this differed significantly with recurrent stage. Postoperative interval “success” in PSS head and neck subscale scores for diet and eating in public also correlated with recurrent stage. Conclusions: Overall, the expected efficacy for salvage surgery in patients with recurrent head and neck cancer was surprisingly good, but success was limited and costs were great in stage III and, especially, in stage IV recurrences. A strong correlation of efficacy and noneconomic costs with recurrent stage allowed the creation of expectation profiles that may be useful to patients. Additional systematic clinical research is needed to improve results. In the end, the decision to undergo salvage surgery should be a personal choice made by the patient after honest and compassionate discussion with his or her surgeon.

Sources of Escherichia coli in a coastal subtropical environment.

Abstract: Sources of Escherichia coli in a coastal waterway located in Ft. Lauderdale, Fla., were evaluated. The study consisted of an extensive program of field measurements designed to capture spatial and temporal variations in E. coli concentrations as well as experiments conducted under laboratory-controlled conditions. E. coli from environmental samples was enumerated by using a defined substrate technology (Colilert-18). Field sampling tasks included sampling the length of the North Fork to identify the river reach contributing high E. coli levels, autosampler experiments at two locations, and spatially intense sampling efforts at hot spots. Laboratory experiments were designed to simulate tidal conditions within the riverbank soils. The results showed that E. coli entered the river in a large pulse during storm conditions. After the storm, E. coli levels returned to baseline levels and varied in a cyclical pattern which correlated with tidal cycles. The highest concentrations were observed during high tide, whereas the lowest were observed at low tide. This peculiar pattern of E. coli concentrations between storm events was caused by the growth of E. coli within riverbank soils which were subsequently washed in during high tide. Laboratory analysis of soil collected from the riverbanks showed increases of several orders of magnitude in soil E. coli concentrations. The ability of E. coli to multiply in the soil was found to be a function of soil moisture content, presumably due to the ability of E. coli to outcompete predators in relatively dry soil. The importance of soil moisture in regulating the multiplication of E. coli was found to be critical in tidally influenced areas due to periodic wetting and drying of soils in contact with water bodies. Given the potential for growth in such systems, E. coli concentrations can be artificially elevated above that expected from fecal impacts alone. Such results challenge the use of E. coli as a suitable indicator of water quality in tidally influenced areas located within tropical and subtropical environments.

Persistent pulmonary hypertension of the newborn in the era before nitric oxide: practice variation and outcomes.

Abstract: Objectives. In the era before widespread use of inhaled nitric oxide, to determine the prevalence of persistent pulmonary hypertension (PPHN) in a multicenter cohort, demographic descriptors of the population, treatments used, the outcomes of those treatments, and variation in practice among centers. Study Design. A total of 385 neonates who received ≥50% inspired oxygen and/or mechanical ventilation and had documented evidence of PPHN (2D echocardiogram or preductal or postductal oxygen difference) were tracked from admission at 12 Level III neonatal intensive care units. Demographics, treatments, and outcomes were documented. Results. The prevalence of PPHN was 1.9 per 1000 live births (based on 71 558 inborns) with a wide variation observed among centers (.43–6.82 per 1000 live births). Neonates with PPHN were admitted to the Level III neonatal intensive care units at a mean of 12 hours of age (standard deviation: 19 hours). Wide variations in the use of all treatments studied were found at the centers. Hyperventilation was used in 65% overall but centers ranged from 33% to 92%, and continuous infusion of alkali was used in 75% overall, with a range of 27% to 93% of neonates. Other frequently used treatments included sedation (94%; range: 77%–100%), paralysis (73%; range: 33%–98%), and inotrope administration (84%; range: 46%–100%). Vasodilator drugs, primarily tolazoline, were used in 39% (range: 13%–81%) of neonates. Despite the wide variation in practice, there was no significant difference in mortality among centers. Mortality was 11% (range: 4%–33%). No specific therapy was clearly associated with a reduction in mortality. To determine whether the therapies were equivalent, neonates treated with hyperventilation were compared with those treated with alkali infusion. Hyperventilation reduced the risk of extracorporeal membrane oxygenation without increasing the use of oxygen at 28 days of age. In contrast, the use of alkali infusion was associated with increased use of extracorporeal membrane oxygenation (odds ratio: 5.03, compared with those treated with hyperventilation) and an increased use of oxygen at 28 days of age. Conclusions. Hyperventilation and alkali infusion are not equivalent in their outcomes in neonates with PPHN. Randomized trials are needed to evaluate the role of these common therapies.

Blunt splenic injury in adults: Multi-institutional Study of the Eastern Association for the Surgery of Trauma.

Abstract: Background: Nonoperative management of blunt injury to the spleen in adults has been applied with increasing frequency. However, the criteria for nonoperative management are controversial. The purpose of this multi-institutional study was to determine which factors predict successful observation of blunt splenic injury in adults. Methods: A total of 1,488 adults (>15 years of age) with blunt splenic injury from 27 trauma centers in 1997 were studied through the Multi-institutional Trials Committee of the Eastern Association for the Surgery of Trauma. Statistical analysis was performed with analysis of variance and extended X 2 test. Data are expressed as mean ± SD; a value of p 15 were successfully observed. Frequency of immediate operation correlated with American Association for the Surgery of Trauma (AAST) grades of splenic injury: I (23.9%), II (22.4%), III (38.1%), IV (73.7%), and V (94.9%) (p < 0.05). Of patients initially managed nonoperatively, the failure rate increased significantly by AAST grade of splenic injury: I (4.8%), II (9.5%), III (19.6%), IV (33.3%), and V (75.0%) (p < 0.05). A total of 60.9% of the patients failed nonoperative management within 24 hours of admission; 8% failed 9 days or later after injury. Laparotomy was ultimately performed in 19.9% of patients with small hemoperitoneum, 49.4% of patients with moderate hemoperitoneum, and 72.6% of patients with large hemoperitoneum. Conclusion: In this multicenter study, 38.5% of adults with blunt splenic injury went directly to laparotomy. Ultimately, 54.8% of patients were successfully managed nonoperatively; the failure rate of planned observation was 10.8%, with 60.9% of failures occurring in the first 24 hours. Successful nonoperative management was associated with higher blood pressure and hematocrit, and less severe injury based on ISS, Glasgow Coma Scale, grade of splenic injury, and quantity of hemoperitoneum.

Head injury and the risk of AD in the MIRAGE study

Abstract: Objectives: It has been suggested in some studies that head injury is a risk factor for AD, and that this risk is heightened among carriers of the APOE -e4 allele. We examined the effects of head injury and APOE genotype on AD risk in a large family study. Subjects: A total of 2,233 probands who met criteria for probable or definite AD and their 14,668 first-degree family members (4,465 parents, 7,694 siblings, and 2,509 spouses) were ascertained at 13 centers in the United States, Canada, and Germany participating in the MIRAGE (Multi-Institutional Research in Alzheimer Genetic Epidemiology) project. Information on head injury was collected by interview of multiple informants and review of medical records. Nondemented relatives and spouses served as control subjects for this study. Methods: Odds of AD for head trauma with or without loss of consciousness were computed by comparing probands with unaffected spouses using conditional logistic regression analysis. To account for the unique biologic relationship between probands and their parents and siblings, odds of AD were computed using a generalized estimating equation (GEE) Poisson regression approach. GEE logistic regression was used to examine the joint effects of APOE genotype and head injury on the odds of AD in probands and a control group comprised of unaffected siblings and spouses. Results: Comparison of probands with their unaffected spouses yielded odds ratios for AD of 9.9 (95% CI, 6.5 to 15.1) for head injury with loss of consciousness and 3.1 (2.3 to 4.0) for head injury without loss of consciousness. The corresponding odds derived from the comparison of probands with their parents and sibs were 4.0 (2.9 to 5.5) for head injury with loss of consciousness and 2.0 (1.5 to 2.7) for head injury without loss of consciousness. Head injury without loss of consciousness did not significantly increase the risk of AD in spouses (OR = 1.3; 95% CI, 0.4 to 4.1). The joint effects of head injury and APOE genotype were evaluated in a subsample of 942 probands and 327 controls (spouses and siblings). Head injury increased the odds of AD to a greater extent among those lacking e4 (OR = 3.3) than among e4 heterozygotes (OR = 1.8) or homozygotes (OR = 1.3). Conclusion: Head injury is a risk factor for AD. The magnitude of the risk is proportional to severity and heightened among first-degree relatives of AD patients. The influence of head injury on the risk of AD appears to be greater among persons lacking APOE -e4 compared with those having one or two e4 alleles, suggesting that these risk factors may have a common biologic underpinning.

The use of stable isotopes to study ecosystem gas exchange.

Abstract: Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem re- search is increasing. In this review we introduce and dis- cuss the relevant details underlying the use of carbon and oxygen isotopic compositions in ecosystem gas ex- change research. The current use and potential develop- ments of stable isotope measurements together with con- centration and flux measurements of CO2 and water va- por are emphasized. For these applications it is critical to know the isotopic identity of specific ecosystem compo- nents such as the isotopic composition of CO 2 , organic matter, liquid water, and water vapor, as well as the associated isotopic fractionations, in the soil-plant- atmosphere system. Combining stable isotopes and con- centration measurements is very effective through the use of "Keeling plots." This approach allows the identifi- cation of the isotopic composition and the contribution of ecosystem, or ecosystem components, to the exchange fluxes with the atmosphere. It also allows the estimation of net ecosystem discrimination and soil disequilibrium effects. Recent modifications of the Keeling plot ap- proach permit examination of CO2 recycling in ecosys- tems. Combining stable isotopes with dynamic flux mea- surements requires precision in isotopic sampling and analysis, which is currently at the limit of detection. Combined with the micrometeorological gradient ap- proach (applicable mostly in grasslands and crop fields), stable isotope measurements allow separation of net CO 2 exchange into photosynthetic and soil respiration compo- nents, and the evapotranspiration flux into soil evapora- tion and leaf transpiration. Similar applications in con- junction with eddy correlation techniques (applicable to forests, in addition to grasslands and crop fields) are more demanding, but can potentially be applied in com- bination with the Keeling plot relationship. The advance and potential in using stable isotope measurements should make their use a standard component in the limit- ed arsenal of ecosystem-scale research tools.