Showing papers by "University of Connecticut published in 2002"

Thermal Barrier Coatings for Gas-Turbine Engine Applications

Abstract: Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities.

Evidence of the effect of trust building technology in electronic markets: price premiums and buyer behavior

Abstract: Despite the wide use of reputational mechanisms such as eBay's Feedback Forum to promote trust, empirical studies have shown conflicting results as to whether online feedback mechanisms induce trust and lead to higher auction prices. This study examines the extent to which trust can be induced by proper feedback mechanisms in electronic markets, and how some risk factors play a role in trust formation. Drawing from economic, sociological, and marketing theories and using data from both an online experiment and an online auction market, we demonstrate that appropriate feedback mechanisms can induce calculus-based credibility trust without repeated interactions between two transacting parties. Trust can mitigate information asymmetry by reducing transaction-specific risks, therefore generating price premiums for reputable sellers. In addition, the research also examines the role that trust plays in mitigating the risks inherent in transactions that involve very expensive products.

Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones.

Abstract: Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate the "strength–endurance continuum". Subjects were divided into four groups: a low repetition group (Low Rep, n=9) performing 3–5 repetitions maximum (RM) for four sets of each exercise with 3 min rest between sets and exercises, an intermediate repetition group (Int Rep, n=11) performing 9–11 RM for three sets with 2 min rest, a high repetition group (High Rep, n=7) performing 20–28 RM for two sets with 1 min rest, and a non-exercising control group (Con, n=5). Three exercises (leg press, squat, and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g., maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion) were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization. Maximal strength improved significantly more for the Low Rep group compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion significantly increased at the end of the study for only the High Rep group. All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups. However, the percentage of type IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups. These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a significant increase in MHCIIa. No significant changes in fiber-type composition were found in the control samples. Although all three training regimens resulted in similar fiber-type transformations (IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects. Overall, however, these data demonstrate that both physical performance and the associated physiological adaptations are linked to the intensity and number of repetitions performed, and thus lend support to the "strength–endurance continuum".

Roles of heat-shock proteins in innate and adaptive immunity

Abstract: Heat-shock proteins (HSPs) are the most abundant and ubiquitous soluble intracellular proteins. In single-cell organisms, invertebrates and vertebrates, they perform a multitude of housekeeping functions that are essential for cellular survival. In higher vertebrates, their ability to interact with a wide range of proteins and peptides--a property that is shared by major histocompatibility complex molecules--has made the HSPs uniquely suited to an important role in organismal survival by their participation in innate and adaptive immune responses. The immunological properties of HSPs enable them to be used in new immunotherapies of cancers and infections.

Prokaryotic Evolution in Light of Gene Transfer

Abstract: Accumulating prokaryotic gene and genome sequences reveal that the exchange of genetic information through both homology-dependent recombination and horizontal (lateral) gene transfer (HGT) is far more important, in quantity and quality, than hitherto imagined. The traditional view, that prokaryotic evolution can be understood primarily in terms of clonal divergence and periodic selection, must be augmented to embrace gene exchange as a creative force, itself responsible for much of the pattern of similarities and differences we see between prokaryotic microbes. Rather than replacing periodic selection on genetic diversity, gene loss, and other chromosomal alterations as important players in adaptive evolution, gene exchange acts in concert with these processes to provide a rich explanatory paradigm-some of whose implications we explore here. In particular, we discuss (1) the role of recombination and HGT in giving phenotypic "coherence" to prokaryotic taxa at all levels of inclusiveness, (2) the implications of these processes for the reconstruction and meaning of "phylogeny," and (3) new views of prokaryotic adaptation and diversification based on gene acquisition and exchange.

Shifting Paradigms: From Flexner to Competencies

Abstract: Realizing medical education is on the brink of a major paradigm shift from structure- and process-based to competency-based education and measurement of outcomes, the authors reviewed the existing medical literature to provide practical insight into how to accomplish full implementation and evaluation of this new paradigm. They searched Medline and the Educational Resource Information Clearinghouse from the 1960s until the present, reviewed the titles and abstracts of the 469 articles the search produced, and chose 68 relevant articles for full review. The authors found that in the 1970s and 1980s much attention was given to the need for and the development of professional competencies for many medical disciplines. Little attention, however, was devoted to defining the benchmarks of specific competencies, how to attain them, or the evaluation of competence. Lack of evaluation strategies was likely one of the forces responsible for the threedecade lag between initiation of the movement and widespread adoption. Lessons learned from past experiences include the importance of strategic planning and faculty and learner buy-in for defining competencies. In addition, the benchmarks for defining competency and the thresholds for attaining competence must be clearly delineated. The development of appropriate assessment tools to measure competence remains the challenge of this decade, and educators must be responsible for studying the impact of this paradigm shift to determine whether its ultimate effect is the production of more competent physicians. Acad. Med. 2002;77:361‐367.

Interaction of Heat Shock Proteins with Peptides and Antigen Presenting Cells: Chaperoning of the Innate and Adaptive Immune Responses

Abstract: Heat shock proteins are abundant soluble intracellular proteins, present in all cells. Members of the heat shock protein family bind peptides including antigenic peptides generated within cells. Heat shock proteins also interact with antigen presenting cells through CD91 and other receptors, eliciting a cascade of events including re-presentation of heat shock protein-chaperoned peptides by MHC, translocation of NFκB into the nuclei and maturation of dendritic cells. These consequences point to a key role of heat shock proteins in fundamental immunological phenomena such as activation of antigen presenting cells, indirect presentation (or cross-priming), and chaperoning of peptides during antigen presentation. Heat shock proteins appear to have been involved in innate immune responses since the emergence of phagocytes in early multicellular organisms and to have been commandeered for adaptive immune responses with the advent of specificity. These properties of heat shock proteins also allow them to be use...

Modularity in technology and organization

Abstract: This paper is an attempt to raid both the literature on modular design and the literature on property rights to create the outlines of a modularity theory of the firm . Such a theory will look at firms, and other organizations, in terms of the partitioning of rights—understood as protected spheres of authority—among cooperating parties. And it will assert that organizations reflect nonmodular structures, that is, structures in which decision rights, rights of alienation, and residual claims to income do not all reside in the same hands. © 2002 Elsevier Science B.V. All rights reserved.

Cognitive functioning of long-term heavy cannabis users seeking treatment.

Abstract: ContextCognitive impairments are associated with long-term cannabis use, but the parameters of use that contribute to impairments and the nature and endurance of cognitive dysfunction remain uncertain.ObjectiveTo examine the effects of duration of cannabis use on specific areas of cognitive functioning among users seeking treatment for cannabis dependence.Design, Setting, and ParticipantsMultisite retrospective cross-sectional neuropsychological study conducted in the United States (Seattle, Wash; Farmington, Conn; and Miami, Fla) between 1997 and 2000 among 102 near-daily cannabis users (51 long-term users: mean, 23.9 years of use; 51 shorter-term users: mean, 10.2 years of use) compared with 33 nonuser controls.Main Outcome MeasuresMeasures from 9 standard neuropsychological tests that assessed attention, memory, and executive functioning, and were administered prior to entry to a treatment program and following a median 17-hour abstinence.ResultsLong-term cannabis users performed significantly less well than shorter-term users and controls on tests of memory and attention. On the Rey Auditory Verbal Learning Test, long-term users recalled significantly fewer words than either shorter-term users (P = .001) or controls (P = .005); there was no difference between shorter-term users and controls. Long-term users showed impaired learning (P = .007), retention (P = .003), and retrieval (P = .002) compared with controls. Both user groups performed poorly on a time estimation task (P<.001 vs controls). Performance measures often correlated significantly with the duration of cannabis use, being worse with increasing years of use, but were unrelated to withdrawal symptoms and persisted after controlling for recent cannabis use and other drug use.ConclusionsThese results confirm that long-term heavy cannabis users show impairments in memory and attention that endure beyond the period of intoxication and worsen with increasing years of regular cannabis use.

How Children Use Input to Acquire a Lexicon

Abstract: The contributions of social processes and computational processes to early lexical development were evaluated. A re-analysis and review of previous research cast doubt on the sufficiency of social approaches to word learning. An empirical investigation of the relation of social-pragmatic and data-providing features of input to the productive vocabulary of sixty-three 2-year-old children revealed benefits of data provided in mother-child conversation, but no effects of social aspects of those conversations. The findings further revealed that the properties of data that benefit lexical development in 2-year-olds are quantity, lexical richness, and syntactic complexity. The nature of the computational mechanisms implied by these findings is discussed. An integrated account of the roles of social and computational processes to lexical development is proposed.

The ant fauna of a tropical rain forest: estimating species richness three different ways

Abstract: Species richness is an important characteristic of ecological communities, but it is difficult to quantify. We report here a thorough inventory of a tropical rain forest ant fauna and use it to evaluate species richness estimators. The study was carried out in ;1500 ha of lowland rain forest at La Selva Biological Station, Costa Rica. Diverse methods were used, including canopy fogging, Malaise traps, Berlese samples, Winkler samples, baiting, and manual search. Workers of 437 ant species were encountered. The abundance distribution was clearly lognormal, and the distribution emerged from a veil line with each doubling of sampling effort. Three richness estimates were calculated: the area under the fitted lognormal distribution, the asymptote of the Michaelis-Menten equation fit to the species accumulation curve, and the Incidence-based Coverage Estimator (ICE). The per- formance of the estimators was evaluated with sample-based rarefaction plots. The inventory was nearly complete because the species accumulation curve approached an asymptote, the richness estimates were very close to the observed species richness, and the uniques and duplicates curves were both declining. None of the richness estimators was stable in sample- based rarefaction plots, but regions of stability of estimators occurred. The explanation of rarity is one key to understanding why richness estimates fail. Fifty-one species (12% of the total) were still uniques (known from only one sample) at the end of the inventory. The rarity of 20 of these species was explained by ''edge effects'': ''methodological edge species'' (possibly abundant at the site but difficult to sample because of their microhabitat), and ''geographic edge species,'' known to be common in habitats or regions outside of La Selva. Rarity of 31 species remained unexplained. Most of the 51 rare species were known from additional collections outside of La Selva, either in other parts of Costa Rica or in other countries. Only six species were ''global uniques,'' known to date from only one sample on Earth. The study demonstrates that patterns of species occurrence early in an inventory may be inadequate to estimate species richness, but that relatively complete inventories of species-rich arthropod communities are possible if multiple sampling methods and extensive effort are applied.

An exact method for the stability analysis of time-delayed linear time-invariant (LTI) systems

Abstract: A general class of linear time invariant systems with time delay is studied. Recently, they attracted considerable interest in the systems and control community. The complexity arises due to the exponential type transcendental terms in their characteristic equation. The transcendentality brings infinitely many characteristic roots, which are cumbersome to elaborate as evident from the literature. A number of methodologies have been suggested with limited ability to assess the stability in the parametric domain of time delay. This study offers an exact, structured and robust methodology to bring a closure to the question at hand. Ultimately we present a unique explicit analytical expression in terms of the system parameters which not only reveals the stability regions (pockets) in the domain of time delay, but it also declares the number of unstable characteristic roots at any given pocket. The method starts with the determination of all possible purely imaginary (resonant) characteristic roots for any positive time delay. To achieve this a simplifying substitution is used for the transcendental terms in the characteristic equation. It is proven that the number of such resonant roots for a given dynamics is finite. Each one of these roots is created by infinitely many time delays, which are periodically distributed. An interesting property is also claimed next, that the root crossing directions at these locations are invariant with respect to the delay and dependent only on the crossing frequency. These two unique findings facilitate a simple and practical stability method, which is the highlight of the work.

The use of reduced healing times on ITI implants with a sandblasted and acid-etched (SLA) surface: early results from clinical trials on ITI SLA implants.

Abstract: Summary: ITI® dental implants are available with two bone-anchoring surfaces, a titanium plasma-sprayed (TPS) surface, and a recently introduced sandblasted and acid-etched (SLA) surface. Cell culture and animal tests demonstrate that the SLA surface stimulates bone cell differentiation and protein production, has large amounts of bone-to-implant contact, and results in large removal torque values in functional testing of the bone contact. As a result of these studies, a prospective human clinical trial was initiated to determine whether the 4.1 mm diameter SLA ITI® solid screw implants could be predictably and safely restored as early as six weeks after implant placement surgery. The protocol restricted the use of the reduced healing time to a) healthy patients with sufficient bone volume to surround the implant, and b) those patients who had good bone quality (classes I-III) at the implant recipient site. Patients with poorer bone quality (class IV) did not have restorations until 12 weeks after implant placement. The clinical trial is an ongoing multicenter trial, with six centers in four countries, and with follow-up over five years. The primary outcome variable was abutment placement with a 35 Ncm force, with no countertorque and no pain or rotation of the implant. A secondary outcome was implant success, as defined by no mobility, no persistent pain or infection, and no peri-implant radiolucency. To date, 110 patients with 326 implants have completed the one-year post-loading recall visit, while 47 patients with 138 implants have completed the two-year recall. Three implants were lost prior to abutment connection. Prosthetic restoration was commenced after shortened healing times on 307 implants. The success rate for these implants, as judged by abutment placement, was 99.3% (with an average healing time of 49 days). Life table analyses demonstrated an implant success rate of 99.1%, both for 329 implants at one year and for 138 implants at two years. In the 24-month period after restoration, no implant losses were reported for the 138 implants. These results demonstrate that, under defined conditions, solid screw ITI® implants with an SLA endosseous surface can be restored after approximately six weeks of healing with a high predictability of success, defined by abutment placement at 35 Ncm without countertorque, and with subsequent implant success rates of greater than 99% two years after restoration.

Biodiversity, invasion resistance, and marine ecosystem function: reconciling pattern and process

Abstract: A venerable generalization about community resistance to invasions is that more diverse communities are more resistant to invasion. However, results of experimental and observational studies often conflict, leading to vigorous debate about the mechanistic importance of diversity in determining invasion success in the field, as well as other eco- system properties, such as productivity and stability. In this study, we employed both field experiments and observational approaches to assess the effects of diversity on the invasion of a subtidal marine invertebrate community by three species of nonindigenous ascidians (sea squirts). In experimentally assembled communities, decreasing native diversity in- creased the survival and final percent cover of invaders, whereas the abundance of individual species had no effect on these measures of invasion success. Increasing native diversity also decreased the availability of open space, the limiting resource in this system, by buffering against fluctuations in the cover of individual species. This occurred because temporal patterns of abundance differed among species, so space was most consistently and completely occupied when more species were present. When we held diversity constant, but manipulated resource availability, we found that the settlement and recruitment of new invaders dramatically increased with increasing availability of open space. This suggests that the effect of diversity on invasion success is largely due to its effects on resource (space) availability. Apart from invasion resistance, the increased temporal stability found in more diverse communities may itself be considered an enhancement of ecosystem func- tion. In field surveys, we found a strong negative correlation between native-species richness and the number and frequency of nonnative invaders at the scale of both a single quadrat (25 3 25 cm), and an entire site (50 3 50 m). Such a pattern suggests that the means by which diversity affects invasion resistance in our experiments is important in determining the distribution of invasive species in the field. Further synthesis of mechanistic and ob- servational approaches should be encouraged, as this will increase our understanding of the conditions under which diversity does (and does not) play an important role in deter- mining the distribution of invaders in the field.

Determinants of trust in a service provider: the moderating role of length of relationship

Abstract: Trust is a key factor in the establishment of long‐term relationships between service representatives and their customers. Prior research has documented that both “person‐related” (e.g. empathy, politeness and customer/service representative similarity) and “offer‐related” (customization, competence, reliability and promptness) service representative characteristics have an impact on trust. However, the relative importance of these characteristics, and in some cases the direction of their relationships with trust, has varied across studies. In this paper, we posit a contingency model of trust, suggesting that the effects of the above variables on trust are moderated by length of the customer/service provider relationship. Our model is tested in a business‐to‐business context by means of a mail survey involving 677 small business owners. The small business owners provided data about their relationships with their insurance industry service providers. Our results demonstrate how service representatives and firms can work toward the establishment of trust with their clients under varying market conditions.

A controlled trial of rasagiline in early Parkinson disease: The tempo study

Abstract: CONTEXT Monotherapy with rasagiline mesylate may be useful in early Parkinson disease (PD). OBJECTIVE To evaluate the safety and efficacy of the selective monoamine oxidase type B inhibitor rasagiline. DESIGN Multicenter, 26-week, parallel-group, randomized, double-blind, placebo-controlled clinical trial. SETTING Academically based movement disorders clinics. PATIENTS Patients with early PD not requiring dopaminergic therapy (n = 404). INTERVENTION Research participants were randomized to rasagiline mesylate at dosages of 1 mg or 2 mg per day or matching placebo. A 1-week escalation period was followed by a 25-week maintenance period. MAIN OUTCOME MEASURE The primary prespecified measure of efficacy was the change in the total Unified Parkinson's Disease Rating Scal score between baseline and 26 weeks of treatment, comparing each active treatment group with the placebo group. RESULTS Monotherapy with rasagiline was effective in this 26-week study. The adjusted effect size for the total Unified Parkinson's Disease Rating Scale was -4.20 units comparing 1 mg of rasagiline and placebo (95% confidence interval, -5.66 to -2.73 units; P<.001) and -3.56 units comparing a 2-mg dosage and placebo (95% confidence interval, -5.04 to -2.08 units; P<.001). There were no meaningful differences in the frequency of adverse events or premature withdrawals among the treatment groups. CONCLUSIONS Rasagiline is effective as monotherapy for patients with early PD. The 2 dosages in this trial were both effective relative to placebo. Further study is warranted to evaluate the longer-term effects of rasagiline in PD.

Cutting Edge: Requirement for IL-15 in the Generation of Primary and Memory Antigen-Specific CD8 T Cells

Abstract: IL-15 and IL-15Rα are required for generation of memory-phenotype CD8 T cells in unimmunized mice. However, the role of IL-15 in primary expansion and generation of Ag-specific memory CD8 T cells in vivo has not been investigated. We characterized the CD8 T cell response against vesicular stomatitis virus (VSV) in IL-15 −/− and IL-15Rα −/− mice. Surprisingly, IL-15 was required for primary expansion of VSV-specific CD8 T cells. The generation of VSV-specific memory CD8 T cells was also impaired without IL-15 signaling, and this defect correlated with a decrease in memory CD8 T cell turnover. Despite minimal proliferation without IL-15, a subset of memory cells survived long-term. IL-15Rα expression was low on naive CD8 T cells, up-regulated on Ag-specific effector cells, and sustained on memory cells. Thus, IL-15 was important for the generation and the subsequent maintenance of antiviral memory CD8 T cells.

The Divided Welfare State: The Battle over Public and Private Social Benefits in the United States

Abstract: Part I. The American Welfare Regime: 1. The politics of public and private social benefits Part II. The Politics of Public and Private Pensions: 2. Connected at birth: public and private pensions before 1945 3. Sibling rivalry: public and private pensions after 1945 Part III. The Politics of Public and Private Health Insurance: 4. Seeds of exceptionalism: public and private health insurance before 1945 5. The elusive cure: public and private health insurance after 1945 Part IV. The Formation and Future of the American Welfare Regime: 6. The formation of the American welfare regime 7. The future of the American welfare regime.

Apical limit of root canal instrumentation and obturation, part 2. A histological study.

Abstract: The results of an in vivo histological study involving apical and periapical tissues following root canal therapy after different observation periods demonstrated the most favourable histological conditions when the instrumentation and obturation remained at or short of the apical constriction. This was the case in the presence of vital or necrotic pulps, also when bacteria had penetrated the foramen and were present in the periapical tissues. When the sealer and/or the gutta-percha was extruded into the periapical tissue, the lateral canals and the apical ramifications, there was always a severe inflammatory reaction including a foreign body reaction despite a clinical absence of pain.

International Union of Pharmacology. XXXIV. Lysophospholipid Receptor Nomenclature

Abstract: The lysophospholipids, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), are now recognized as important extracellular signaling molecules. These lipid mediators are pleiotropic; among the most common cellular responses are mitogenesis, cell survival (anti-apoptosis), inhibition of adenylyl cyclase and calcium mobilization. Physiologic events associated with these mediators include platelet aggregation, vasopressor activity, wound healing, immune modulation, and angiogenesis. Many of the actions of LPA and S1P are mediated through a set of eight G protein-coupled receptors. Five of these are S1P-prefering while the remaining three are LPA receptors. These receptors are expressed widely and in aggregate signal through a variety of heterotrimeric G proteins. The lysophospholipid receptor family is referred to commonly as the "Edg" group (e.g., Edg-1, Edg-2, etc.). Herein, the molecular pharmacology of the lysophospholipid receptors is reviewed briefly, and a rational nomenclature for LPA and S1P receptors that is consistent with the International Union of Pharmacology guidelines is proposed.

Moderators of the Relationship Between Work-Family Conflict and Career Satisfaction

Abstract: In this study, we examined the moderating effects of individual differences and sources of support on the negative relationship between work-family conflict and career satisfaction. Data from 975 managers indicated that the relationship was significant for women irrespective of age but was significant for men only in later career. Moreover, the relationship was stronger for individuals who were in the minority gender in their work groups, but it was weaker for those who had strong community ties. Implications are discussed.

A Bayesian approach to inferring population structure from dominant markers

Abstract: Molecular markers derived from polymerase chain reaction (PCR) amplification of genomic DNA are an important part of the toolkit of evolutionary geneticists. Random amplified polymorphic DNA markers (RAPDs), amplified fragment length polymorphisms (AFLPs) and intersimple sequence repeat (ISSR) polymorphisms allow analysis of species for which previous DNA sequence information is lacking, but dominance makes it impossible to apply standard techniques to calculate F-statistics. We describe a Bayesian method that allows direct estimates of FST from dominant markers. In contrast to existing alternatives, we do not assume previous knowledge of the degree of within-population inbreeding. In particular, we do not assume that genotypes within populations are in Hardy-Weinberg proportions. Our estimate of FST incorporates uncertainty about the magnitude of within-population inbreeding. Simulations show that samples from even a relatively small number of loci and populations produce reliable estimates of FST. Moreover, some information about the degree of within-population inbreeding (FIS) is available from data sets with a large number of loci and populations. We illustrate the method with a reanalysis of RAPD data from 14 populations of a North American orchid, Platanthera leucophaea.