Showing papers by "University at Buffalo published in 1999"

A Comparative Study of Unit Root Tests with Panel Data and a New Simple Test

Abstract: The panel data unit root test suggested by Levin and Lin (LL) has been widely used in several applications, notably in papers on tests of the purchasing power parity hypothesis. This test is based on a very restrictive hypothesis which is rarely ever of interest in practice. The Im–Pesaran–Shin (IPS) test relaxes the restrictive assumption of the LL test. This paper argues that although the IPS test has been offered as a generalization of the LL test, it is best viewed as a test for summarizing the evidence from a number of independent tests of the sample hypothesis. This problem has a long statistical history going back to R. A. Fisher. This paper suggests the Fisher test as a panel data unit root test, compares it with the LL and IPS tests, and the Bonferroni bounds test which is valid for correlated tests. Overall, the evidence points to the Fisher test with bootstrap-based critical values as the preferred choice. We also suggest the use of the Fisher test for testing stationarity as the null and also in testing for cointegration in panel data.

A New Estimate of Transaction Costs

Abstract: Transaction costs are important for a host of empirical analyses from market efficiency to international market research. But transaction costs estimates are not always available, or where available, are cumbersome to use and expensive to purchase. We present a model that requires only the time series of daily security returns to endogenously estimate the effective transaction costs for any firm, exchange, or time period. The feature of the data that allows for the estimation of transaction costs is the incidence of zero returns. Incorporating zero returns in the return-generating process, the model provides continuous estimates of average round-trip transaction costs from 1963 to 1990 that are 1.2% and 10.3% for large and small decile firms, respectively. These estimates are highly correlated (85%), with the most commonly used transaction cost estimators. How much does it cost to trade common stock? The Plexus Group (1996) estimated that trading costs are at least 1.0-2.0% of market value for institutions trading the largest NYSE/AMEX firms. Such trades account for more than 20% of reported trading volume. Stoll and Whaley (1983) reported quoted spread and commission costs of 2.0% for the largest NYSE size decile to 9.0% for the small decile. Bwardwaj and Brooks (1992) reported median quoted spread and commission costs between 2.0% for NYSE securities with prices greater than $20.00 and 12.5% for securities priced less than $5.00. These costs are important in determining investment performance and "can substantially reduce or possibly outweigh the expected value created by an investment strategy" [Keim and Madhavan (1995)]. This article is based on a portion of the first chapter of David A. Lesmond's dissertation entitled: "Trans

Intermittent Administration of Inhaled Tobramycin in Patients with Cystic Fibrosis

Abstract: Background and Methods We conducted two multicenter, double-blind, placebo-controlled trials of intermittent administration of inhaled tobramycin in patients with cystic fibrosis and Pseudomonas aeruginosa infection. A total of 520 patients (mean age, 21 years) were randomly assigned to receive either 300 mg of inhaled tobramycin or placebo twice daily for four weeks, followed by four weeks with no study drug. Patients received treatment or placebo in three on–off cycles for a total of 24 weeks. The end points included pulmonary function, the density of P. aeruginosa in sputum, and hospitalization. Results The patients treated with inhaled tobramycin had an average increase in forced expiratory volume in one second (FEV1) of 10 percent at week 20 as compared with week 0, whereas the patients receiving placebo had a 2 percent decline in FEV1 (P<0.001). In the tobramycin group, the density of P. aeruginosa decreased by an average of 0.8 log10 colony-forming units (CFU) per gram of expectorated sputum from w...

Development of a multiple sclerosis functional composite as a clinical trial outcome measure

Abstract: The primary clinical outcome measure for evaluating multiple sclerosis in clinical trials has been Kurtzke's expanded disability status scale (EDSS). New therapies appear to favourably impact the course of multiple sclerosis and render continued use of placebo control groups more difficult. Consequently, future trials are likely to compare active treatment groups which will most probably require increased sample sizes in order to detect therapeutic efficacy. Because more responsive outcome measures will be needed for active arm comparison studies, the National Multiple Sclerosis Society's Advisory Committee on Cinical Trials of New Agents in Multiple Sclerosis appointed a Task Force that was charged with developing improved clinical outcome measures. This Task Force acquired contemporary clinical trial and historical multiple sclerosis data for meta-analyses of primary and secondary outcome assessments to provide a basis for recommending a new outcome measure. A composite measure encompassing the major clinical dimensions of arm, leg and cognitive function was identified and termed the multiple sclerosis functional composite (MSFC). The MSFC consists of three objective quantitative tests of neurological function which are easy to administer. Change in this MSFC over the first year of observation predicted subsequent change in the EDSS, suggesting that the MSFC is more sensitive to change than the EDSS. This paper provides details concerning the development and testing of the MSFC.

Effectiveness of assistive technology and environmental interventions in maintaining independence and reducing home care costs for the frail elderly. A randomized controlled trial.

Abstract: Context Home environmental interventions (EIs) and assistive technology (AT) devices have the potential to increase independence for community-based frail elderly persons, but their effectiveness has not been demonstrated. Objective To evaluate a system of AT-EI service provision designed to promote independence and reduce health care costs for physically frail elderly persons. Design Randomized controlled trial. Setting and participants A total of 104 home-based frail elderly persons living in western New York were assigned to 1 of 2 groups (52 treatment, 52 control). Intervention All participants underwent a comprehensive functional assessment and evaluation of their home environment. Participants in the treatment group received AT and EIs based on the results of the evaluation. The control group received "usual care services." Main outcome measures Functional status as measured by the Functional Independence Measure (FIM) and the Craig Handicap Assessment and Reporting Technique; pain as measured by the Functional Status Instrument; and health care costs including the costs. Results After the 18-month intervention period, the treatment groups showed significant decline for FIM total score and FIM motor score, but there was significantly more decline for the control group. Functional Status Instrument pain scores increased significantly more for the control group. In a comparison of health care costs, the treatment group expended more than the control group for AT and EIs. The control group required significantly more expenditures for institutional care. There was no significant difference in total in-home personnel costs, although there was a large effect size. The control group had significantly greater expenditures for nurse visits and case manager visits. Conclusion The frail elderly persons in this trial experienced functional decline over time. Results indicate rate of decline can be slowed, and institutional and certain in-home personnel costs reduced through a systematic approach to providing AT and EIs.

Relationship of Stress, Distress, and Inadequate Coping Behaviors to Periodontal Disease

Abstract: Background: The association of stress, distress, and coping behaviors with periodontal disease was assessed. Methods: A cross-sectional study of 1,426 subjects between the ages of 25 and 74 years in Erie County, New York, was carried out to assess these relationships. Subjects were asked to complete a set of 5 psychosocial questionnaires which measure psychological traits and attitudes including discrete life events and their impact; chronic stress or daily strains; distress; coping styles and strategies; and hassles and uplifts. Clinical assessment of supragingival plaque, gingival bleeding, subgingival calculus, probing depth, clinical attachment level (CAL) and radiographic alveolar crestal height (ACH) was performed, and 8 putative bacterial pathogens from the subgingival flora measured. Results: Reliability of subjects' responses and internal consistencies of all the subscales on the instruments used were high, with Cronbach's alpha ranging from 0.88 for financial strain to 0.99 for job strain, uplif...

Relation of weight and rate of increase in weight during childhood and adolescence to body size, blood pressure, fasting insulin, and lipids in young adults. The Minneapolis Children's Blood Pressure Study.

Abstract: Background—Weight gain is of concern during early development because adult obesity and its cardiovascular consequences appear to have their origins during childhood. Insulin resistance is known to be related to obesity. Thus, weight gain beginning in childhood may influence the development of insulin-induced cardiovascular risk during adulthood. Methods and Results—We monitored 679 individuals from 7.7±0.1 years of age with repeated measures of height, weight, and systolic blood pressure (SBP) until 23.6±0.2 years of age, when blood samples were obtained for measurements of insulin and lipids. Initial childhood weight, body mass index (BMI), and height were significantly correlated with young adult weight, BMI, and height and with fasting insulin, lipids, and SBP. The increases in weight and BMI but not height during childhood were significantly related to the young adult levels of insulin, lipids, and SBP. Conclusions—These data suggest that weight gain in excess of normal growth during childhood is a d...

Cooperative Enhancement of Two-Photon Absorption in Multi-branched Structures

Abstract: Recent reports of molecular structures with considerably enhanced two-photon absorption cross-section have generated considerable interest in this phenomenon from both fundamental and applications perspectives. In this letter, we report cooperative enhancement of two-photon absorption in multi-branched structures which may lead to new design criteria for development of highly efficient two-photon materials. The multi-branched structures were synthesized using coupling of two and three two-photon active asymmetric donor−acceptor chromophores linked together by a common amine group. The two-photon cross-sections measured both with nanosecond and femtosecond pulses show that the value for the trimer is more than six times larger than that for the monomer, and not just three times larger as expected from the number density increase.

A review of integrated analysis of production–distribution systems

Abstract: This paper reviews recent work on integrated analysis of production-distribution systems, and identifies important areas where further research is needed. By integrated analysis we understand analysis performed on models that integrate decisions of different production and distribution functions for a simultaneous optimization. We review work that explicitly considers the transportation system in the analysis, since we are interested in the following questions: (i) how have logistics aspects been included in the integrated analysis? and (ii) what competitive advantages, if any, have been obtained from the integration of the distribution function to other production functions within a company and among different companies? In our review we also mention whether the work has been done at the strategic level, i.e., if it concerns the design of the distribution system, or at the tactical level, i.e., if it concerns optimization problems for which the characteristics of the distribution system are provided.

Construct and concurrent validity of the Hopkins Verbal Learning Test - Revised

Abstract: The present investigation examined the validity of the revised Hopkins Verbal Learning Test (HVLT-R). In a principal components analysis with varimax rotation, measures of new learning and delayed ...

Intersegmental Dynamics Are Controlled by Sequential Anticipatory, Error Correction, and Postural Mechanisms

Abstract: Intersegmental dynamics are controlled by sequential anticipatory, error correction, and positional control mechanisms. The purpose of this study is to examine the mechanisms underlying control of ...

Electromagnetic interference shielding using continuous carbon-fiber carbon-matrix and polymer-matrix composites

Abstract: A carbon-matrix composite with continuous carbon-fibers was found to be an excellent electromagnetic interference (EMI) shielding material with shielding effectiveness 124 dB, low surface impedance and high reflectivity in the frequency range from 0.3 MHz to 1.5 GHz. The shielding effectiveness of polymer-matrix composites with continuous carbon-fibers was less and that of polymer-matrix composites with discontinuous fillers was even less. The addition of 2.9 vol.% discontinuous 0.1 μm diameter carbon-filaments between the layers of conventional 7 μm diameter continuous carbon-fibers in a composite degraded the shielding effectiveness. The dominant mechanism of EMI shielding for both carbon-matrix and polymer-matrix continuous carbon-fiber composites is reflection.

Efficacy and current limitations of intravascular stents for intracranial internal carotid, vertebral, and basilar artery aneurysms

Abstract: Object. Results of previous in vitro and in vivo experimental studies have suggested that placement of a porous stent within the parent artery across the aneurysm neck may hemodynamically uncouple the aneurysm from the parent vessel, leading to thrombosis of the aneurysm. For complex wide-necked aneurysms, a stent may also aid packing of the aneurysm with Guglielmi detachable coils (GDCs) by acting as a rigid scaffold that prevents coil herniation into the parent vessel. Recently, improved stent system delivery technology has allowed access to the tortuous vascular segments of the intracranial system. The authors report here on the use of intracranial stents to treat aneurysms involving different segments of the internal carotid artery (ICA), the vertebral artery (VA), and the basilar artery (BA). Methods. Ten patients with intracranial aneurysms located at ICA segments (one petrous, two cavernous, and three paraclinoid aneurysms), the VA proximal to the posterior inferior cerebellar artery origin (one an...

Spatial distribution and habitat characterization of anopheline mosquito larvae in Western Kenya.

Abstract: Studies were conducted to characterize larval habitats of anopheline mosquitoes and to analyze spatial heterogeneity of mosquito species in the Suba District of western Kenya. A total of 128 aquatic habitats containing mosquito larvae were sampled, and 2,209 anopheline and 10,538 culicine larvae were collected. The habitats were characterized based on size, pH, distance to the nearest house and to the shore of Lake Victoria, coverage of canopy, surface debris, algae and emergent plants, turbidity, substrate, and habitat types. Microscopic identification of third- and fourth-instar anopheline larvae did not yield any Anopheles funestus or other anophelines. A total of 829 An. gambiae s.l. larvae from all habitats were analyzed further by rDNA-polymerase chain reaction to identify individual species within the An. gambiae species complex. Overall, An. arabiensis was the predominant species (63.4%), and An. gambiae was less common (31.4%). The species composition of An. gambiae s.l. varied significantly among the sampling sites throughout Suba District. The larval habitats in the southern area of the district had a higher proportion of An. gambiae than in the northern area. Multiple logistic analysis did not detect any significant association between the occurrence of anopheline larvae and habitat variables, and principal component analysis did not identify key environmental factors associated with the abundance of An. gambiae. However, significant spatial heterogeneity in the relative abundance of An. gambiae within the Suba district was detected. When the effect of larval habitat locality was considered in the analysis, we found that the distance to the nearest house and substrate type were significantly associated with the relative abundance of An. gambiae. Future studies integrating detailed water chemistry analysis, remote sensing technology, and the ecology of predators may be required to further elucidate the mechanisms underlying the observed spatial variation of anopheline larval distribution.

Selective transfer of endogenous metabolites through gap junctions composed of different connexins.

Abstract: Selective transfer of endogenous metabolites through gap junctions composed of different connexins

Well-Being Therapy: Conceptual and Technical Issues

Abstract: Well-being therapy is a short-term, well-being-enhancing psychotherapeutic strategy. It is based on Carol D. Ryff’s multidimensional model of psychological well-being, encompassing environmental maste

Development of an Attitudes Toward Health Care Teams Scale.

Abstract: The authors describe the development and psychometric testing across three study phases of an Attitudes Toward Health Care Teams Scale. The measure contains two subscales: Quality of Care/Process (14 items) and Physician Centrality (6 items). The Quality of Care/Process subscale measures team members' perceptions of the quality of care delivered by health care teams and the quality of teamwork to accomplish this. The Physician Centrality subscale measures team members' attitudes toward physicians' authority in teams and their control over information about patients. Tests of reliability and validity demonstrate that each subscale is a strong measure of its respective underlying concept. The measure has potential for use as a research tool and as a pre- and posttest tool for educational interventions with teams and for evaluating clinically based team training programs for medical and health professions students and residents.

Characterization of potential endocrine-related health effects at low-dose levels of exposure to PCBs.

Abstract: This article addresses issues related to the characterization of endocrine-related health effects resulting from low-level exposures to polychlorinated biphenyls (PCBs). It is not intended to be a comprehensive review of the literature but reflects workshop discussions. "The Characterizing the Effects of Endocrine Disruptors on Human Health at Environmental Exposure Levels," workshop provided a forum to discuss the methods and data needed to improve risk assessments of endocrine disruptors. This article contains an overview of endocrine-related (estrogen and thyroid system) interactions and other low-dose effects of PCBs. The data set on endocrine effects includes results obtained from mechanistic methods/ and models (receptor based, metabolism based, and transport protein based), as well as from (italic)in vivo(/italic) models, including studies with experimental animals and wildlife species. Other low-dose effects induced by PCBs, such as neurodevelopmental and reproductive effects and endocrine-sensitive tumors, have been evaluated with respect to a possible causative linkage with PCB-induced alterations in endocrine systems. In addition, studies of low-dose exposure and effects in human populations are presented and critically evaluated. A list of conclusions and recommendations is included.

Work stress and alcohol use.

Abstract: Employees who drink heavily or who abuse or are dependent on alcohol can undermine a workforce's overall health and productivity. To better understand the reasons behind employee abusive drinking and to develop more effective ways of preventing problem drinking in the workforce, researchers have developed a number of paradigms that guide their research. One such paradigm is the alienation/stress paradigm, which suggests that employee alcohol use may be a direct or indirect response to physical and psychosocial qualities of the work environment. Although in the alcohol literature, work alienation and work stress traditionally have been treated as separate paradigms, compelling reasons support subsuming the work-alienation paradigm under a general work-stress paradigm. Researchers have developed several models to explain the relationship between work stress and alcohol consumption: the simple cause-effect model, the mediation model, the moderation model, and the moderated mediation model. Of these, the moderated mediation model particularly stands out, because it simultaneously addresses the two fundamental issues of how and when work stressors are related to alcohol use. Recent research supports a relation of work-related stressors to elevated alcohol consumption and problem drinking. Future research should focus on the relation between work stressors and alcohol use among adolescents and young adults, because they are just entering the workforce and are the most likely to engage in heavy drinking. Longitudinal studies also are needed to better explain the relation between work stress and alcohol use.

Effects of luteolin and quercetin, inhibitors of tyrosine kinase, on cell growth and metastasis-associated properties in A431 cells overexpressing epidermal growth factor receptor

Abstract: 1. Flavonoids display a wide range of pharmacological properties including anti-inflammatory. Anti-mutagenic, anti-carcinogenic and anti-cancer effects. Here, we evaluated the effects of eight flavonoids on the tumour cell proliferation, cellular protein phosphorylation, and matrix metalloproteinase (MMPs) secretion. 2. Of the flavonoids examined, luteolin (Lu) and quercetin (Qu) were the two most potent agents, and significantly inhibited A431 cell proliferation with IC50 values of 19 and 21 micronM, respectively. 3. The epidermal growth factor (EGF) (10 nM) promoted growth of A431 cells (+25+/-4.6%) and mediated epidermal growth factor receptor (EGFR) tyrosine kinase activity and autophosphorylation of EGFR were inhibited by Lu and Qu. At concentration of 20 micronM, both Lu and Qu markedly decreased the levels of phosphorylation of A431 cellular proteins, including EGFR. 4. A431 cells treated with Lu or Qu exhibited protuberant cytoplasmic blebs and progressive shrinkage morphology. Lu and Qu also time-dependently induced the appearance of a ladder pattern of DNA fragmentation, and this effect was abolished by EGF treatment. 5. The addition of EGF only marginally diminished the inhibitory effect of luteolin and quercetin on the growth rate of A431 cells, treatment of cellular proteins with EGF and luteolin or quercetin greatly reduced protein phosphorylation, indicating Lu and Qu may act effectively to inhibit a wide range of protein kinases, including EGFR tyrosine kinase. 6. EGF increased the levels of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), while Lu and Qu appeared to suppress the secretion of these two MMPs in A431 cells. 7. Examination of the relationship between the chemical structure and inhibitory effects of eight flavonoids reveal that the double bond between C2 and C3 in ring C and the OH groups on C3' and C4' in ring B are critical for the biological activities. 8. This study demonstrates that the inhibitory effects of Lu and Qu, and the stimulatory effects of EGF, on tumour cell proliferation, cellular protein phosphorylation, and MMP secretion may be mediated at least partly through EGFR. This study supports the idea that Lu and Qu may have potential as anti-cancer and anti-metastasis agents.

Surgery-related factors and local recurrence of Wilms tumor in National Wilms Tumor Study 4.

Abstract: ObjectiveTo assess the prognostic factors for local recurrence in Wilms tumor.Summary Background DataCurrent therapy for Wilms tumor has evolved through four studies of the National Wilms Tumor Study Group. As adverse prognostic factors were identified, treatment of children with Wilms tumor has bee

Access to coronary artery bypass surgery by race/ethnicity and gender among patients who are appropriate for surgery.

Abstract: Objective.The study sought to determine if there were race/ethnicity or gender differences in access to coronary artery bypass graft (CABG) surgery among patients who have been designated as appropriate and as necessary for that surgery according to the RAND methodology.Methods.RAND appropriateness