bluuebunny/crossref_metadata_2025 huggingface dataset:
Are All Caregivers Created Equal? Stress in Caregivers to Adults With and Without Dementia
Authors: Bertrand Rosanna M. , Fredman Lisa , Saczynski Jane
Published: July 2006

Objectives: Caregiving for older adults is stressful; however, by treating caregivers as a homogenous group, it is possible that stress-related factors are misrepresented for some. This study of 349 elderly caregivers explored mediators of the caregiving/ stress relationship for caregivers to adults with ( n = 106), and without ( n = 243) dementia. Methods: The sample was from the Caregiver Study of Osteoporotic Fractures (CG-SOF), ancillary to SOF, a four-site cohort of 9,704 women. Results:Stress was higher ( p < .001) in dementia than nondementia caregivers ( m= 19.85; 16.45). For caregivers overall, intensity and recipient problems were associated with stress but mediated through role captivity. However, relationships differed when stratified by recipient dementia status. Only recipient problems among nondementia caregivers was mediated through captivity. Discussion: Results confirm previous findings of lower stress among nondementia caregivers and suggest that different factors influence caregivers' appraisal of the situation, including their perception of stress, based on recipients' dementia status.
Health Effects of Managed Care Among the Near-Elderly
Authors: Xu Xiao , Jensen Gail A.
Published: July 2006

Objectives: The authors evaluate whether enrolling in a health maintenance organization (HMO) or preferred provider organization (PPO) affects the health of adults ages 55 to 64, relative to fee-for-service plans. Methods: A nationwide random sample of 4,044 adults with employer-sponsored health insurance is drawn from the 1994 to 2000 waves of the Health and Retirement Study. Multinomial logit regressions are estimated for self-reported general health status, first using a sample of all near-elders, then using subsamples of near-elders with and without longstanding chronic health conditions. The possibility of selection bias into managed care plans is considered and explicitly addressed in model estimation. Results: We find no ill effects of HMOs on health status, and older adults with a history of chronic health conditions actually fare better upon enrolling in these plans. Discussion: More research is needed to understand the reasons for the observed beneficial effects of managed care.
Using Probability vs. Nonprobability Sampling to Identify Hard-to-Access Participants for Health-Related Research
Authors: Feild Lucy , Pruchno Rachel A. , Bewley Jennifer , Lemay Edward P. , Levinsky Norman G.
Published: July 2006

This article compares the recruitment costs and participant characteristics associated with the use of probability and nonprobability sampling strategies in a longitudinal study of older hemodialysis patients and their spouses. Contrasts were made of people who accrued to the study based on probability and nonprobability sampling strategies. Probability-based sampling was more time-efficient and cost-effective than nonprobability sampling. There were no significant differences between the respondents identified through probability and nonprobability sampling on age, gender, years married, education, work status, and professional job status. Respondents from the probability sample were more likely to be Protestant and less likely to be Catholic than those from the nonprobability sample. Respondents from the probability sample were more likely to be Black, whereas those from the nonprobability sample were more likely to be White. There are strengths and shortcomings associated with both nonprobability and probability sampling. Researchers need to consider representativeness and external validity issues when designing sampling and related recruitment plans for health-related research.
Caught between freedom and control: ‘ordinary’ people’s discursive positioning on an Israeli prime-time talk show
Authors: Hamo Michal
Published: July 2006

The article discusses the democratizing potential of the talk show genre by exploring the discursive positioning of anonymous lay participants in the Israeli prime-time talk show Live. Quantitative analyses of three measures of participation reveal that anonymous guests take fewer turns, intervene less and self-select less than famous and semi-famous guests on the show. Qualitative analyses reveal a dialectical response by the host to anonymous guests’ initiative behavior. Such behavior is encouraged and supported when it conforms to a prototypical view of the anonymous guest as communicatively inferior, but is perceived as challenging and sanctioned when guests go beyond this prototypical view and exhibit high degrees of communicative competence. This dialectic is discussed as evidence of the embeddedness of conversational patterns of self-selection within an institutional framework of asymmetric control, meriting a multi-layered approach to semi-institutional discourse. The article concludes with a cultural and institutional contextualization of the findings.
Thanks for the Compliment? Emotional Reactions to Group-Level Versus Individual-Level Compliments and Insults
Authors: Garcia Amber L. , Miller Daniel A. , Smith Eliot R. , Mackie Diane M.
Published: July 2006

The current research investigated participants' reactions to positive and negative comments directed toward them as individuals or as members of a social group. Using both perspective-taking (Studies 1 and 2) and actual interaction methodologies (Study 3), three studies found that participants generally responded negatively to negative comments regardless of the level of identity to which the comment was directed. Positive comments were generally viewed positively, except when the comment was directed at the group and was stereotype relevant. When the latter was the case, participants reported increased anger and desires to attack (and avoid) the speaker. Furthermore, these negative feelings and action tendencies were partially mediated by an attribution to prejudice to the speaker.
Intergroup Contact and Grandparent–Grandchild Communication: The Effects of Self-Disclosure on Implicit and Explicit Biases Against Older People
Authors: Tam Tania , Hewstone Miles , Harwood Jake , Voci Alberto , Kenworthy Jared
Published: July 2006

This study investigated contact and ageism on both the implicit and the explicit level. We examined the role of grandparent–grandchild communication (in terms of self-disclosure) and its relations to anxiety and empathy in improving intergenerational attitudes. Analyses revealed that: (1) quantity and quality of contact with older people (other than grandparents) predict higher levels of self-disclosure (to one's grandparent); (2) quantity (but not quality) of contact with older people is associated with more favorable implicit associations with them, while quality of contact is associated with more favorable explicit attitudes; and (3) higher levels of self-disclosure to grandparents are associated with empathy and reduced anxiety, which in turn are associated with more positive explicit attitudes toward older adults. We explain our findings in light of the environmental associations model (Karpinsky & Hilton, 2001)—that quantity of contact, or mere exposure to older people, drives the Implicit Association Test effect. The model sheds light on the mediational roles of interpersonal variables (self-disclosure, anxiety, and empathy with a grandparent) in intergenerational contact.
Minority Influence is Facilitated When the Communication Employs Linguistic Abstractness
Authors: Sigall Harold , Mucchi-Faina Angelica , Mosso Cristina
Published: July 2006

An experiment tested the hypothesis that minority influence is enhanced when the source of a persuasive communication employs abstract, as opposed to concrete, language. This hypothesis and the research testing it links ideas from two heretofore separate areas of inquiry: minority influence and linguistic abstraction.

It is well known that minority influence increases when the minority is perceived to be consistent. Work on linguistic abstraction has established that when abstract language is used to describe an act, it implies that the act reflects stable, trans-situational characteristics of the actor, whereas concrete language implies that the act reflects isolated, situationally bounded events. We suggest that abstract language therefore conveys greater conviction and thereby increases perceived consistency and, in turn, minority influence.

Source (majority, minority) and language abstractness (abstract, concrete) of a persuasive communication were manipulated. Results revealed that a minority (but not a majority) source was seen as more consistent when using abstract (vs. concrete) language. Although there were no differences among conditions on direct influence, a statistically significant interaction was observed for indirect influence: the abstract-minority source had significantly more indirect influence than did the concrete-minority source, whereas the indirect influence of the majority communicator was not affected by language abstractness.
Linking healthcare associated norovirus outbreaks: a molecular epidemiologic method for investigating transmission
Authors: Lopman Ben A , Gallimore Chris , Gray Jim J , Vipond Ian B , Andrews Nick , Sarangi Joyshri , Reacher Mark H , Brown David W
Published: July 2006

Background

Noroviruses are highly infectious pathogens that cause gastroenteritis in the community and in semi-closed institutions such as hospitals. During outbreaks, multiple units within a hospital are often affected, and a major question for control programs is: are the affected units part of the same outbreak or are they unrelated transmission events? In practice, investigators often assume a transmission link based on epidemiological observations, rather than a systematic approach to tracing transmission.

Here, we present a combined molecular and statistical method for assessing:

1) whether observed clusters provide evidence of local transmission and

2) the probability that anecdotally|linked outbreaks truly shared a transmission event.

Methods

76 healthcare associated outbreaks were observed in an active and prospective surveillance scheme of 15 hospitals in the county of Avon, England from April 2002 to March 2003. Viral RNA from 64 out of 76 specimens from distinct outbreaks was amplified by reverse transcription-PCR and was sequenced in the polymerase (ORF 1) and capsid (ORF 2) regions. The genetic diversity, at the nucleotide level, was analysed in relation to the epidemiological patterns.

Results

Two out of four genetic and epidemiological clusters of outbreaks were unlikely to have occurred by chance alone, thus suggesting local transmission. There was anecdotal epidemiological evidence of a transmission link among 5 outbreaks pairs. By combining this epidemiological observation with viral sequence data, the evidence of a link remained convincing in 3 of these pairs. These results are sensitive to prior beliefs of the strength of epidemiological evidence especially when the outbreak strains are common in the background population.

Conclusion

The evidence suggests that transmission between hospitals units does occur. Using the proposed criteria, certain hypothesized transmission links between outbreaks were supported while others were refuted. The combined molecular/epidemiologic approach presented here could be applied to other viral populations and potentially to other pathogens for a more thorough view of transmission.
Analysis of RNA splicing defects in PITX2 mutants supports a gene dosage model of Axenfeld-Rieger syndrome
Authors: Maciolek Nicole L , Alward Wallace LM , Murray Jeffrey C , Semina Elena V , McNally Mark T
Published: July 2006

Background

Axenfeld-Rieger syndrome (ARS) is associated with mutations in thePITX2gene that encodes a homeobox transcription factor. Several intronicPITX2mutations have been reported in Axenfeld-Rieger patients but their effects on gene expression have not been tested.

Methods

We present two new families with recurrentPITX2intronic mutations and usePITX2cminigenes and transfected cells to address the hypothesis that intronic mutations effect RNA splicing. ThreePITX2mutations have been analyzed: a G>T mutation within the AG 3' splice site (ss) junction associated with exon 4 (IVS4-1G>T), a G>C mutation at position +5 of the 5' (ss) of exon 4 (IVS4+5G>C), and a previously reported A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G).

Results

Mutation IVS4+5G>C showed 71% retention of the intron between exons 4 and 5, and poorly expressed protein. Wild-type protein levels were proportionally expressed from correctly spliced mRNA. The G>T mutation within the exon 4 AG 3'ss junction shifted splicing exclusively to a new AG and resulted in a severely truncated, poorly expressed protein. Finally, the A>G substitution at position -11 of the 3'ss of exon 5 shifted splicing exclusively to a newly created upstream AG and resulted in generation of a protein with a truncated homeodomain.

Conclusion

This is the first direct evidence to support aberrant RNA splicing as the mechanism underlying the disorder in some patients and suggests that the magnitude of the splicing defect may contribute to the variability of ARS phenotypes, in support of a gene dosage model of Axenfeld-Rieger syndrome.
The 5'-end transitional CpGs between the CpG islands and retroelements are hypomethylated in association with loss of heterozygosity in gastric cancers
Authors: Kim Young-Ho , Hong Seung-Jin , Jung Yu-Chae , Kim Sung-Ja , Seo Eun-Joo , Choi Sang-Wook , Rhyu Mun-Gan
Published: July 2006

Background

A loss of heterozygosity (LOH) represents a unilateral chromosomal loss that reduces the dose of highly repetitive Alu, L1, and LTR retroelements. The aim of this study was to determine if the LOH events can affect the spread of retroelement methylation in the 5'-end transitional area between the CpG islands and their nearest retroelements.

Methods

The 5'-transitional area of all human genes (22,297) was measured according to the nearest retroelements to the transcription start sites. For 50 gastric cancer specimens, the level of LOH events on eight cancer-associated chromosomes was estimated using the microsatellite markers, and the 5'-transitional CpGs of 20 selected genes were examined by methylation analysis using the bisulfite-modified DNA.

Results

The extent of the transitional area was significantly shorter with the nearest Alu elements than with the nearest L1 and LTR elements, as well as in the extragenic regions containing a higher density of retroelements than in the intragenic regions. The CpG islands neighbouring a high density of Alu elements were consistently hypomethylated in both normal and tumor tissues. The 5'-transitional methylated CpG sites bordered by a low density of Alu elements or the L1 and LTR elements were hypomethylated more frequently in the high-level LOH cases than in the low-level LOH cases.

Conclusion

The 5'-transitional methylated CpG sites not completely protected by the Alu elements were hypomethylated in association with LOH events in gastric cancers. This suggests that an irreversible unbalanced decrease in the genomic dose reduces the spread of L1 methylation in the 5'-end regions of genes.
Psychosocial factors and distress: a comparison between ethnic Norwegians and ethnic Pakistanis in Oslo, Norway
Authors: Syed Hammad Raza , Dalgard Odd Steffen , Dalen Ingvild , Claussen Bjørgulf , Hussain Akthar , Selmer Randi , Ahlberg Nora
Published: July 2006

Background

In the Norwegian context, higher mental distress has been reported for the non-Western immigrants compared to the ethnic Norwegians and Western immigrants. This high level of distress is often related to different socio-economic conditions in this group. No efforts have been made earlier to observe the impact of changed psychosocial conditions on the state of mental distress of these immigrant communities due to the migration process. Therefore, the objective of the study was to investigate the association between psychological distress and psychosocial factors among Pakistani immigrants and ethnic Norwegians in Oslo, and to investigate to what extent differences in mental health could be explained by psychosocial and socioeconomic conditions.

Method

Data was collected from questionnaires as a part of the Oslo Health Study 2000–2001. 13581 Norwegian born (attendance rate 46%) and 339 ethnic Pakistanis (attendance rate 38%) in the selected age groups participated. A 10-item version of Hopkins Symptom Checklist (HSCL) was used as a measure of psychological distress.

Results

Pakistanis reported less education and lower employment rate than Norwegians (p < 0.005). The Pakistani immigrants also reported higher distress, mean HSCL score 1.53(1.48–1.59), compared to the ethnic Norwegians, HSCL score 1.30(1.29–1.30). The groups differed significantly (p < 0.005) with respect to social support and feeling of powerlessness, the Pakistanis reporting less support and more powerlessness. The expected difference in mean distress was reduced from 0.23 (0.19–0.29) to 0.07 (0.01–0.12) and 0.12 (0.07–0.18) when adjusted for socioeconomic and social support variables respectively. Adjusting for all these variables simultaneously, the difference in the distress level between the two groups was eliminated

Conclusion

Poor social support and economic conditions are important mediators of mental health among immigrants. The public health recommendations/interventions should deal with both the economic conditions and social support system of immigrant communities simultaneously.
Technology Development to Explore the Relationship Between Oral Health and the Oral Microbial Community
Authors: Starke E Michelle L , Smoot James C , Smoot Laura M , Liu Wen-Tso , Chandler Darrell P , Lee Hyun H , Stahl David A
Published: July 2006

The human oral cavity contains a complex microbial community that, until recently, has not been well characterized. Studies using molecular tools have begun to enumerate and quantify the species residing in various niches of the oral cavity; yet, virtually every study has revealed additional new species, and little is known about the structural dynamics of the oral microbial community or how it changes with disease. Current estimates of bacterial diversity in the oral cavity range up to 700 species, although in any single individual this number is much lower. Oral microbes are responsible for common chronic diseases and are suggested to be sentinels of systemic human diseases. Microarrays are now being used to study oral microbiota in a systematic and robust manner. Although this technology is still relatively young, improvements have been made in all aspects of the technology, including advances that provide better discrimination between perfect-match hybridizations from non-specific (and closely-related) hybridizations. This review addresses a core technology using gel-based microarrays and the initial integration of this technology into a single device needed for system-wide studies of complex microbial community structure and for the development of oral diagnostic devices.
Tracheotomy does not affect reducing sedation requirements of patients in intensive care – a retrospective study
Authors: Veelo Denise P , Dongelmans Dave A , Binnekade Jan M , Korevaar Johanna C , Vroom Margreeth B , Schultz Marcus J
Published: July 2006

Introduction

Translaryngeal intubated and ventilated patients often need sedation to treat anxiety, agitation and/or pain. Current opinion is that tracheotomy reduces sedation requirements. We determined sedation needs before and after tracheotomy of intubated and mechanically ventilated patients.

Methods

We performed a retrospective analysis of the use of morphine, midazolam and propofol in patients before and after tracheotomy.

Results

Of 1,788 patients admitted to our intensive care unit during the study period, 129 (7%) were tracheotomized. After the exclusion of patients who received a tracheotomy before or at the day of admittance, 117 patients were left for analysis. The daily dose (DD; the amount of sedatives for each day) divided by the mean daily dose (MDD; the mean amount of sedatives per day for the study period) in the week before and the week after tracheotomy was 1.07 ± 0.93 DD/MDD versus 0.30 ± 0.65 for morphine, 0.84 ± 1.03 versus 0.11 ± 0.46 for midazolam, and 0.62 ± 1.05 versus 0.15 ± 0.45 for propofol (p < 0.01). However, when we focused on a shorter time interval (two days before and after tracheotomy), there were no differences in prescribed doses of morphine and midazolam. Studying the course in DD/MDD from seven days before the placement of tracheotomy, we found a significant decline in dosage. From day -7 to day -1, morphine dosage (DD/MDD) declined by 3.34 (95% confidence interval -1.61 to -6.24), midazolam dosage by 2.95 (-1.49 to -5.29) and propofol dosage by 1.05 (-0.41 to -2.01). After tracheotomy, no further decrease in DD/MDD was observed and the dosage remained stable for all sedatives. Patients in the non-surgical and acute surgical groups received higher dosages of midazolam than patients in the elective surgical group. Time until tracheotomy did not influence sedation requirements. In addition, there was no significant difference in sedation between different patient groups.

Conclusion

In our intensive care unit, sedation requirements were not further reduced after tracheotomy. Sedation requirements were already sharply declining before tracheotomy was performed.
Clusters and knowledge: local buzz, global pipelines and the process of knowledge creation
Authors: Bathelt Harald , Malmberg Anders , Maskell Peter
Published: July 2006

The paper is concerned with spatial clustering of economic activity and its relation to the spatiality of knowledge creation in interactive learning processes. It questions the view that tacit knowledge transfer is confined to local milieus whereas codified knowledge may roam the globe almost frictionlessly. The paper highlights the conditions under which both tacit and codified knowledge can be exchanged locally and globally. A distinction is made between, on the one hand, the learning processes taking place among actors embedded in a community by just being there dubbed buzz and, on the other, the knowledge attained by investing in building channels of communication called pipelines to selected providers located outside the local milieu. It is argued that the co-existence of high levels of buzz and many pipelines may provide firms located in outward-looking and lively clusters with a string of particular advantages not available to outsiders. Finally, some policy implications, stemming from this argument, are identified.
Evaluating the role of human papillomavirus vaccine in cervical cancer prevention
Authors: Kang Minhee , Lagakos Stephen W
Published: July 2006

Persistent genital infection with human papillomavirus (HPV) is a natural candidate as a surrogate marker for cervical cancer because of the strong epidemiologic and molecular evidence that HPV infection is the causative agent for almost all cervical cancers. However, while infection with high-risk types of HPV appears to be necessary for the development of cervical cancer, most infections are controlled by host immune response and do not lead to cancer in the vast majority of infected women. Because diagnostic tests cannot distinguish a persistent infection in the pathogenesis of cervical cancer from a transient infection, it is difficult to describe the disease mechanism as a progressive process based on observations. Therefore, the disease pathogenesis pathway does not fit into the usual surrogate marker framework, raising practical concerns about using HPV infection as a surrogate for a clinical endpoint in vaccine trials. In this paper, we describe the challenges in defining HPV infection as a surrogate endpoint in a HPV vaccine trial that is aimed at reducing cervical cancer rates and examine potential effects of the vaccine. We then outline some issues in the design and analysis of HPV vaccine trials, including the use of operationally defined HPV infection events meant to capture persistent infections. We conclude with a recommendation for a multi-state model that uses HPV infection to help explain the mechanisms of vaccine action rather than validate it as an endpoint substitute.
American Society of Clinical Oncology Clinical Practice Guideline for the Use of Larynx-Preservation Strategies in the Treatment of Laryngeal Cancer
Authors: Pfister David G. , Laurie Scott A. , Weinstein Gregory S. , Mendenhall William M. , Adelstein David J. , Ang K. Kian , Clayman Gary L. , Fisher Susan G. , Forastiere Arlene A. , Harrison Louis B. , Lefebvre Jean-Louis , Leupold Nancy , List Marcy A. , O'Malley Bernard O. , Patel Snehal , Posner Marshall R. , Schwartz Michael A. , Wolf Gregory T.
Published: July 2006

Purpose

To develop a clinical practice guideline for treatment of laryngeal cancer with the intent of preserving the larynx (either the organ itself or its function). This guideline is intended for use by oncologists in the care of patients outside of clinical trials.

Methods

A multidisciplinary Expert Panel determined the clinical management questions to be addressed and reviewed the literature available through November 2005, with emphasis given to randomized controlled trials of site-specific disease. Survival, rate of larynx preservation, and toxicities were the principal outcomes assessed. The guideline underwent internal review and approval by the Panel, as well as external review by additional experts, members of the American Society of Clinical Oncology (ASCO) Health Services Committee, and the ASCO Board of Directors.

Results

Evidence supports the use of larynx-preservation approaches for appropriately selected patients without a compromise in survival; however, no larynx-preservation approach offers a survival advantage compared with total laryngectomy and adjuvant therapy with rehabilitation as indicated.

Recommendations

All patients with T1 or T2 laryngeal cancer, with rare exception, should be treated initially with intent to preserve the larynx. For most patients with T3 or T4 disease without tumor invasion through cartilage into soft tissues, a larynx-preservation approach is an appropriate, standard treatment option, and concurrent chemoradiotherapy therapy is the most widely applicable approach. To ensure an optimum outcome, special expertise and a multidisciplinary team are necessary, and the team should fully discuss with the patient the advantages and disadvantages of larynx-preservation options compared with treatments that include total laryngectomy.
Availability of periodically inspected systems with Markovian wear and shocks
Authors: Kharoufeh Jeffrey P. , Finkelstein Daniel E. , Mixon Dustin G.
Published: July 2006

We analyze a periodically inspected system with hidden failures in which the rate of wear is modulated by a continuous-time Markov chain and additional damage is induced by a Poisson shock process. We explicitly derive the system's lifetime distribution and mean time to failure, as well as the limiting average availability. The main results are illustrated in two numerical examples.
Average optimality for Markov decision processes in borel spaces: a new condition and approach
Authors: Guo Xianping , Zhu Quanxin
Published: July 2006

In this paper we study discrete-time Markov decision processes with Borel state and action spaces. The criterion is to minimize average expected costs, and the costs may have neither upper nor lower bounds. We first provide two average optimality inequalities of opposing directions and give conditions for the existence of solutions to them. Then, using the two inequalities, we ensure the existence of an average optimal (deterministic) stationary policy under additional continuity-compactness assumptions. Our conditions are slightly weaker than those in the previous literature. Also, some new sufficient conditions for the existence of an average optimal stationary policy are imposed on the primitive data of the model. Moreover, our approach is slightly different from the well-known ‘optimality inequality approach’ widely used in Markov decision processes. Finally, we illustrate our results in two examples.
Boundedly rational quasi-Bayesian learning in coordination games with imperfect monitoring
Authors: Chen Hsiao-Chi , Chow Yunshyong , Hsieh June
Published: July 2006

In this paper we study players' long-run behaviors in evolutionary coordination games with imperfect monitoring. In each time period, signals corresponding to players' underlying actions, instead of the actions themselves, are observed. A boundedly rational quasi-Bayesian learning process is proposed to extract information from the realized signals. We find that players' long-run behaviors depend not only on the correlations between actions and signals, but on the initial probabilities of risk-dominant and non-risk-dominant equilibria being chosen. The conditions under which risk-dominant equilibrium, non-risk-dominant equilibrium, and the coexistence of both equilibria emerges in the long run are shown. In some situations, the number of limiting distributions grows unboundedly as the population size grows to infinity.
Limit distribution of distances in biased random tries
Authors: Aguech Rafik , Lasmar Nabil , Mahmoud Hosam
Published: July 2006

The trie is a sort of digital tree. Ideally, to achieve balance, the trie should grow from an unbiased source generating keys of bits with equal likelihoods. In practice, the lack of bias is not always guaranteed. We investigate the distance between randomly selected pairs of nodes among the keys in a biased trie. This research complements that of Christophi and Mahmoud (2005); however, the results and some of the methodology are strikingly different. Analytical techniques are still useful for moments calculation. Both mean and variance are of polynomial order. It is demonstrated that the standardized distance approaches a normal limiting random variable. This is proved by the contraction method, whereby the limit distribution is shown to approach the fixed-point solution of a distributional equation in the Wasserstein metric space.
On a random-coefficient AR(1) process with heavy-tailed renewal switching coefficient and heavy-tailed noise
Authors: Leipus Remigijus , Paulauskas Vygantas , Surgailis Donatas
Published: July 2006

We discuss the limit behavior of the partial sums process of stationary solutions to the (autoregressive) AR(1) equation Xt = atXt−1 + εt with random (renewal-reward) coefficient, at, taking independent, identically distributed values Aj ∈ [0,1] on consecutive intervals of a stationary renewal process with heavy-tailed interrenewal distribution, and independent, identically distributed innovations, εt, belonging to the domain of attraction of an α-stable law (0 < α ≤ 2, α ≠ 1). Under suitable conditions on the tail parameter of the interrenewal distribution and the singularity parameter of the distribution of Aj near the unit root a = 1, we show that the partial sums process of Xt converges to a λ-stable Lévy process with index λ < α. The paper extends the result of Leipus and Surgailis (2003) from the case of finite-variance Xt to that of infinite-variance Xt.
On the time behaviour of Okazaki fragments
Authors: Bartoszek Krzysztof , Bartoszek Wojciech
Published: July 2006

We find explicit analytical formulae for the time dependence of the probability of the number of Okazaki fragments produced during the process of DNA replication. This extends a result of Cowan on the asymptotic probability distribution of these fragments.
Moments of a Markov-modulated, irreducible network of fluid queues
Authors: Rabehasaina Landy
Published: July 2006

We study a network of fluid queues in which exogenous arrivals are modulated by a continuous-time Markov chain. Service rates in each queue are proportional to the queue size, and the network is assumed to be irreducible. The queue levels satisfy a linear, vector-valued differential equation. We obtain joint moments of the queue sizes recursively, and deduce the Laplace transform of the queue sizes in the stationary regime.
On extreme ruinous behaviour of Lévy insurance risk processes
Authors: Klüppelberg C. , Kyprianou A. E.
Published: July 2006

In this short note we show how new fluctuation identities and their associated asymptotics, given in Vigon (2002), Klüppelberg et al. (2004) and Doney and Kyprianou (2006), provide the basis for establishing, in an elementary way, asymptotic overshoot and undershoot distribitions for a general class of Lévy insurance risk processes. The results bring the earlier conclusions of Asmussen and Klüppelberg (1996) for the Cramér-Lundberg process into greater generality.
The control of sexual identity in theDrosophilagermline
Authors: Casper Abbie , Van Doren Mark
Published: July 2006

Whether to be male or female is a critical decision in development. Nowhere is this more important than in the germ cells, which must produce either the sperm or eggs necessary for the perpetuation of the species. How does a germ cell make this decision and how is it executed? One thing that is clear is that this process is very different in germ cells compared with other cells of the embryo. Here, we explore how sexual identity is established in the Drosophila germline, how this affects other aspects of germ cell development and what studies in Drosophila can teach us about mammalian germ cells.
Brachyury is required for elongation and vasculogenesis in the murine allantois
Authors: Inman Kimberly E. , Downs Karen M.
Published: July 2006

Mouse conceptuses homozygous for mutations in brachyury (T)exhibit a short, misshapen allantois that fails to fuse with the chorion. Ultimately, mutant embryos die during mid-gestation. In the 60 years since this discovery, the role of T in allantoic development has remained obscure. T protein was recently identified in several new sites during mouse gastrulation, including the core of the allantois, where its function is not known. Here, using molecular, genetic and classical techniques of embryology,we have investigated the role of T in allantoic development. Conceptuses homozygous for the TCurtailed(TC) mutation (TC/TC)exhibited allantoic dysmorphogenesis shortly after the allantoic bud formed. Diminution in allantoic cell number and proliferation was followed by cell death within the core. Fetal liver kinase (Flk1)-positive angioblasts were significantly decreased in TC/TC allantoises and did not coalesce into endothelial tubules, possibly as a result of the absence of platelet endothelial cell adhesion molecule 1 (Pecam1), whose spatiotemporal relationship to Flk1 suggested a role in patterning the umbilical vasculature. Remarkably, microsurgical perturbation of the wild-type allantoic core phenocopied the TC/TCvascularization defect, providing further support that an intact core is essential for vascularization. Last, abnormalities were observed in the TC/TC heart and yolk sac, recently reported sites of T localization. Our findings reveal that T is required to maintain the allantoic core, which is essential for allantoic elongation and vascular patterning. In addition, morphological defects in other extraembryonic and embryonic vascular organs suggest a global role for T in vascularization of the conceptus.
A signalling relay involving Nodal and Delta ligands acts during secondary notochord induction inCionaembryos
Authors: Hudson Clare , Yasuo Hitoyoshi
Published: July 2006

The notochord is one of the defining features of chordates. The ascidian notochord is a rod like structure consisting of a single row of 40 cells. The anterior 32 `primary' notochord cells arise from the A-line (anterior vegetal)blastomeres of the eight-cell stage embryo, whereas the posterior 8`secondary' notochord cells arise from the B-line (posterior vegetal)blastomeres of the eight-cell stage embryo. Specification of notochord precursors within these two lineages occurs in a spatially and temporally distinct manner. We show that specification of the secondary but not the primary notochord in Ciona intestinalis requires a relay mechanism involving two signalling pathways. First, we show evidence that acquisition of secondary notochord fate is dependent upon lateral Nodal signalling sources,situated in the adjacent b-line animal cells. Expression of the notochord specific gene Ci-Brachyury in the secondary notochord precursor was downregulated following selective inhibition of Nodal signal reception in B-line derivatives and also, strikingly, following selective inhibition of Nodal signal reception in A-line cell derivatives. Within the A-line, Nodal signals are required for localised expression of Delta2, which encodes a divergent form of Delta ligand. Using four distinct reagents to inhibit Delta2/Notch signals, we showed that Delta2 signalling from A-line cells, which activates the Notch/Su(H) pathway in adjacent B-line cells, is required for specification of the secondary notochord precursor. We propose a model whereby laterally produced Nodal acts to specify the secondary notochord precursor both directly in the B-line cells and via Delta2 induction in adjacent A-line cells.
The Fes/Fer non-receptor tyrosine kinase cooperates with Src42A to regulate dorsal closure inDrosophila
Authors: Murray Michael J. , Davidson Catherine M. , Hayward Neil M. , Brand Andrea H.
Published: July 2006

Fes/Fer non-receptor tyrosine kinases regulate cell adhesion and cytoskeletal reorganisation through the modification of adherens junctions. Unregulated Fes/Fer kinase activity has been shown to lead to tumours in vivo. Here, we show that Drosophila Fer localises to adherens junctions in the dorsal epidermis and regulates a major morphological event, dorsal closure. Mutations in Src42A cause defects in dorsal closure similar to those seen in dfer mutant embryos. Furthermore, Src42Amutations enhance the dfer mutant phenotype, suggesting that Src42A and DFer act in the same cellular process. We show that DFer is required for the formation of the actin cable in leading edge cells and for normal rates of dorsal closure. We have isolated a gain-of-function mutation in dfer(dfergof) that expresses an N-terminally fused form of the protein, similar to oncogenic forms of vertebrate Fer. dfergof blocks dorsal closure and causes axon misrouting. We find that in dfer loss-of-function mutants β-catenin is hypophosphorylated, whereas in dfergof β-catenin is hyperphosphorylated. Phosphorylated β-catenin is removed from adherens junctions and degraded, thus implicating DFer in the regulation of adherens junctions.
Conserved regulation and role ofPitx2in situs-specific morphogenesis of visceral organs
Authors: Shiratori Hidetaka , Yashiro Kenta , Shen Michael M. , Hamada Hiroshi
Published: July 2006

Pitx2 is expressed in developing visceral organs on the left side and is implicated in left-right (LR) asymmetric organogenesis. The asymmetric expression of Pitx2 is controlled by an intronic enhancer (ASE) that contains multiple Foxh1-binding sites and an Nkx2-binding site. These binding sites are essential and sufficient for asymmetric enhancer activity and are evolutionarily conserved among vertebrates. We now show that mice that lack the ASE of Pitx2(Pitx2ΔASE/ΔASEmice) fail to manifest left-sided Pitx2 expression and exhibit laterality defects in most visceral organs, although the position of the stomach and heart looping remain unaffected. Asymmetric Pitx2expression in some domains, such as the common cardinal vein, was found to be induced by Nodal signaling but to be independent of the ASE of Pitx2. Expression of Pitx2 appears to be repressed in a large portion of the heart ventricle and atrioventricular canal of wild-type mice by a negative feedback mechanism at a time when the gene is still expressed in its other domains. Rescue of the early phase of asymmetric Pitx2 expression in the left lateral plate of Pitx2ΔASE/ΔASEembryos was not sufficient to restore normal organogenesis, suggesting that continuous expression of Pitx2 in the lineage of the left lateral plate is required for situs-specific organogenesis.
Specification of theC. elegansMS blastomere by the T-box factor TBX-35
Authors: Broitman-Maduro Gina , Lin Katy Tan-Hui , Hung Wendy W. K. , Maduro Morris F.
Published: July 2006

In C. elegans, many mesodermal cell types are made by descendants of the progenitor MS, born at the seven-cell stage of embryonic development. Descendants of MS contribute to body wall muscle and to the posterior half of the pharynx. We have previously shown that MS is specified by the activity of the divergent MED-1,2 GATA factors. We report that the MED-1,2 target gene tbx-35, which encodes a T-box transcription factor, specifies the MS fate. Embryos homozygous for a putative tbx-35-null mutation fail to generate MS-derived pharynx and body muscle, and instead generate ectopic PAL-1-dependent muscle and hypodermis, tissues normally made by the C blastomere. Conversely, overexpression of tbx-35 results in the generation of ectopic pharynx and muscle tissue. The MS and E sister cells are made different by transduction of a Wnt/MAPK/Src pathway signal through the nuclear effector TCF/POP-1. We show that in E, tbx-35 is repressed in a Wnt-dependent manner that does not require activity of TCF/POP-1, suggesting that an additional nuclear Wnt effector functions in E to repress MS development. Genes of the T-box family are known to function in protostomes and deuterostomes in the specification of mesodermal fates. Our results show that this role has been evolutionarily conserved in the early C. elegans embryo, and that a progenitor of multiple tissue types can be specified by a surprisingly simple gene cascade.
Determination of Copper(II) Ion by Differential Pulse Voltammetry Used a Glassy Carbon Electrode with a Nafion® Film
Authors: Nakabayashi Yasuo , Imai Hiromu
Published: July 2006

The determination of Cu2+ by differential pulse voltammetry was carried out using a chemically modified electrode coated with a Nafion® film to the surface of a glassy carbon electrode (GC/NAF electrode). This method, which is based on the principle of ion-exchange equilibria between Nafion® and imidazole–copper(II) complex ions, is applicable to the determination of traces of Cu2+ by a measurement of the reduction current of the Cu(II) complex ions incorporated into the Nafion® film. The procedure is as follows: immerse the GC/NAF electrode in 10 cm3 of a sample solution containing traces (concentration, < 1.0 × 10−6 M) of Cu2+, 1.0 × 10−2 M of imidazole as the complexing agent, and 0.5 M of NaBr as the supporting electrolyte, and record the differential pulse voltammogram after stirring for 15 min at 25 °C. The reduction peak current obtained from this voltammogram was recoganize to be proportional to the Cu2+ concentration in the range of 1.0 × 10−7 to 1.0 × 10−6 M at pH 6.0 and 1.0 × 10−8 to 1.0 × 10−7 M at pH 7.0, respectively. The relative standard deviations for the peak currents obtained from four repeated determinations were 1.2 and 1.5% for 5.0 × 10−7 M of Cu2+ at pH 6.0 and 5.0 × 10−8 M of Cu2+ at pH 7.0, respectively. The diverse metal ions which coexist with Cu2+ at pH 6.0 did not interfere up to about a 100-fold excess of Mn2+, Co2+, Ni2+, and Cd2+, except for about a 10-fold excess of Fe3+, and about a 50-fold excess of Zn2+ for the Cu2+ concentration. This method was applied to the determination of Cu2+ in both waste- and river-water samples.
Regioisomeric Formation of Acenaphtho[1,2-e][1,2,4]triazolo[3,4-c][1,2,4]triazines and Their Acyclic C-Nucleoside Analogues
Authors: Rashed Nagwa , Shoukry Mahmoud , El Ashry El Sayed H
Published: July 2006

The oxidative cyclization of the ethylidene derivative of 3-hydrazinoacenaphtho[1,2-e][1,2,4]triazine (2) gave regioselectively the angular isomer 1-methylacenaphtho[1,2-e][1,2,4]triazolo[3,4-c][1,2,4]triazine (5). Its linear isomer 10-methylacenaphtho[1,2-e][1,2,4]triazolo[4,3-b][1,2,4]triazine (4) was synthesized by the condensation of acenaphthenequinone (6) with 3,4-diamino-5-methyl-4H-1,2,4-triazole. Condensation of 2 with a number of monosaccharides afforded the respective hydrazones 9 whose oxidative cyclization gave the corresponding 1-(polyhydroxyalkyl)acenaphtho[1,2-e][1,2,4]triazolo[3,4-c][1,2,4]triazine (10). Acetylation of 9 and 10 gave 3-[N-acetyl-N′-(polyacetoxyalkylidene)hydrazino]acenaphtho[1,2-e][1,2,4]triazine (11) and 1-(polyacetoxyalkyl)acenaphtho[1,2-e][1,2,4]triazolo[3,4-c][1,2,4]triazine (13) respectively. Periodate oxidation of 9e gave 3-(2-oxoethylidenehydrazino)acenaphtho[1,2-e][1,2,4]triazine (14).
Stereodivergent Synthesis of Optically Active α-Hydroxy Acids via Diastereoselective Reduction of α-Keto Esters Derived from l-Quebrachitol
Authors: Akiyama Takahiko , Nishimoto Hiroyuki , Kuwata Takaaki , Ozaki Shoichiro
Published: July 2006

Reduction of an α-keto ester derived from chiral cyclitol, readily available from l-quebrachitol, with K-Selectride proceeded via re-face attack of the ketone with high diastereoselectivity to obtain the α-hydroxy ester in 92% de. On the other hand, reduction of the α-keto ester with K-Selectride in the presence of 18-Crown-6 took place via si-face attack of the ketone to furnish the corresponding α-hydroxy ester in 92% de. Thus both enantiomers of mandelic acid were obtained in optically pure form.
Nucleophilic Substitution Reaction of 2,3,5,6-Tetrachloronitrobenzene with Primary and Secondary Amines under High Pressure
Authors: Ibata Toshikazu , Zou Xinzhuo , Demura Tetsuo
Published: July 2006

Nucleophilic substitution of 2,3,5,6-tetrachloronitrobenzene with secondary amines such as morpholine, piperidine, pyrrolidine, diethylamine, and ethylmethylamine, and primary amines such as aniline, benzylamine, butylamine, isobutylamine, s-butylamine, and t-butylamine, under high pressure of 0.6 GPa at 50 °C for 1—40 h in tetrahydrofuran gave nitro group substitution products together with ortho-mono-, meta-mono-, ortho-ortho-, and ortho-meta-dichloro substitution products. The ratio of these products depends on the bulkiness and amount of amines and the reaction conditions. The selectivity of the nitro group substitution and chlorine substitution depends mainly on the bulkiness of amines.
Polarization Modulation Fourier Transform Infrared Studies of the Effects of Self-Assembly Time on the Order and Orientation of 11-Ferrocenyl-1-undecanethiol Monolayers on Gold
Authors: Sato Yukari , Frey Brian L , Corn Robert M , Uosaki Kohei
Published: July 2006

The effects of self-assembly time on the order and orientation of 11-ferrocenyl-1-undecanethiol (FcC11SH) molecular layers on gold were studied with polarization modulation Fourier transform infrared spectroscopy. A comparison between the intensity of the asymmetric methylene stretching mode of a 1-octadecanethiol monolayer and that of the FcC11SH molecular layer confirmed that the FcC11SH molecules formed a self-assembled monolayer on the gold surface. The conformational order of the monolayer increased with longer self-assembly time as evidenced by a decrease in the vibrational frequencies of the methylene stretching modes and a decrease in the full width at half maximum of these bands. The peak area of the asymmetric methylene stretch also decreased with longer self-assembly time, implying that the FcC11SH molecules stood more erect with respect to the gold surface as the monolayer self-assembled.
Direct Evidence for the Imidic Acid Mechanism of Proton Exchange in N-Methyl Amides
Authors: Wang Wei-Hsien , Hsieh Hsing-Ching
Published: July 2006

Proton exchange of N-methyl amides with general acid catalysis in aqueous solution was studied by NMR. Rate coefficients were determined by NMR lineshape analysis of the N-methyl protons. The imidic acid mechanism is favored by amides with electron-withdrawing substituents. Only the imidic acid mechanism is expected to show general acid catalysis, and this mechanism was observed with Brønsted α = 0.16 for the Z proton of N-methylformamide. No general acid catalysis was observed for N-methyl-2-chloroacetamide and N,N′-dimethylmalonamide which exchange protons via the imidic acid mechanism. This result is attributed to their Z conformations.