bluuebunny/crossref_metadata_2025 huggingface dataset:
Health Disparities in Lifestyle Choices Among Hypertensive Korean Americans, Non-Hispanic Whites, and Blacks
Authors: Kim Mi Ja , Ahn Yang-Heui , Chon Chris , Bowen Phyllis , Khan Shaheen
Published: May 2005

Purpose and Methods. To describe medication profile, diet, and exercise/physical activity in hypertensive Korean Americans, a convenience sample of 100 hypertensive Korean Americans (KAs) at two KA health clinics were interviewed by bilingual Korean nurses using questions from the 1988-1994 Third National Health and Nutrition Examination Survey (NHANES III). One hundred age- and gender-matched hypertensive non-Hispanic Whites and 100 Blacks were randomly selected from the NHANES III dataset, and results were compared to describe the health disparities in lifestyle choices among the three groups. Results. The medication profile among the three groups was similar. A majority of members of all three groups had been told by health professionals to exercise for hypertension. KAs made significantly less effort to reduce salt in their diets than did members of the other two groups (p < .05). Fewer KAs than non-Hispanic Whites or Blacks were following their health professionals’advice to control or lose weight for their high blood cholesterol levels. KAs had the lowest body mass index and were older and more educated than members of the other two groups. KAs’ primary reasons for using the KA clinic were the respect they received and the use of the Korean language. Implications. KA health professionals need to teach their patients more about the importance of health-promoting lifestyles for hypertension and its contributing factors. More KA hypertensive patients should follow the advice of health professionals on healthy lifestyles. Nurses should continue to treat patients with respect and provide care with sensitivity to language needs of patients.
Accelerated decline in lung function in smoking women with airway obstruction: SAPALDIA 2 cohort study
Authors: Downs Sara H , Brändli Otto , Zellweger Jean-Pierre , Schindler Christian , Künzli Nino , Gerbase Margaret W , Burdet Luc , Bettschart Robert , Zemp Elisabeth , Frey Martin , Keller Roland , Tschopp Jean-Marie , Leuenberger Philippe , Ackermann-Liebrich Ursula ,   the SAPALDIA team
Published: May 2005

Background

The aim was to determine if effects from smoking on lung function measured over 11 years differ between men and women.

Methods

In a prospective population based cohort study (Swiss Study on Air Pollution and Lung Diseases in Adults) current smokers in 1991 (18 – 60 yrs) were reassessed in 2002 (n = 1792). Multiple linear regression was used to estimate effects from pack-years of cigarettes smoked to 1991 and mean packs of cigarettes smoked per day between 1991 and 2002 on change in lung volume and flows over the 11 years.

Results

In both sexes, packs smoked between assessments were related to lung function decline but pack-years smoked before 1991 were not. Mean annual decline in FEV1was -10.4 mL(95%CI -15.3, -5.5) per pack per day between assessments in men and -13.8 mL(95%CI-19.5,-8.1) in women. Decline per pack per day between 1991 and 2002 was lower in women who smoked in 1991 but quit before 2002 compared to persistent smokers (-6.4 vs -11.6 mL, p = 0.05) but this was not seen in men (-14.3 vs -8.8 mL p = 0.49). Smoking related decline was accelerated in men and women with airway obstruction, particularly in women where decline in FEV1was three fold higher in participants with FEV1/FVC<0.70 compared to other women (-39.4 vs -12.2 mL/yr per pack per day, p < 0.002).

Conclusion

There are differences in effects from smoking on lung function between men and women. Lung function recovers faster in women quitters than in men. Women current smokers with airway obstruction experience a greater smoking related decline in lung function than men.
Exercise training improves aerobic endurance and musculoskeletal fitness in female cardiac transplant recipients
Authors: Haykowsky Mark , Riess Kenneth , Figgures Linda , Kim Daniel , Warburton Darren , Jones Lee , Tymchak Wayne
Published: May 2005

Aim

Female cardiac transplant recipients' aerobic capacity is 60% lower than sex and age-predicted values. The effect of exercise training on restoring the impaired aerobic endurance and muscle strength in female cardiac transplant recipients is not known. This study examined the effect that aerobic and strength training have on improving aerobic endurance and muscle strength in female cardiac transplant recipients.

Methods

20 female cardiac transplant recipients (51 ± 11 years) participated in this investigation. The subjects performed a baseline six-minute walk test and a leg-press strength test when they were discharged following cardiac transplantation. The subjects then participated in a 12-week exercise program consisting of aerobic and lower extremity strength training. Baseline assessments were repeated following completion of the exercise intervention.

Results

At baseline, the cardiac transplant recipients' aerobic endurance was 50% lower than age-matched predicted values. The training program resulted in a significant increase in aerobic endurance (pre-training: 322 ± 104 m vs. post-training: 501 ± 99 m, p < 0.05) and leg-press strength (pre-training: 48 ± 16 kg. vs. post-training: 78 ± 27 kg, p < 0.05).

Conclusion

Aerobic and strength training are effective interventions that can partially restore the impaired aerobic endurance and strength found in female cardiac transplant recipients.
Creatine synthesis and transport during rat embryogenesis: Spatiotemporal expression of AGAT, GAMT and CT1
Authors: Braissant Olivier , Henry Hugues , Villard Anne-Marie , Speer Oliver , Wallimann Theo , Bachmann Claude
Published: May 2005

Background

Creatine (Cr) is synthesized by a two-step mechanism involving arginine:glycine amidinotransferase (AGAT) and guanidinoacetate methyltransferase (GAMT), and is taken up by cells through a specific Cr transporter, CT1. Recently, genetic defects of this pathway have been described, that lead to Cr deficiency, neurological symptoms in early infancy and severe neurodevelopmental delay. To investigate the involvement of Cr synthesis and uptake pathways during embryonic development, we determined the spatiotemporal expression of AGAT, GAMT and CT1 during the rat embryogenesis, at the mRNA and protein level.

Results

We show that AGAT and GAMT are expressed in hepatic primordium as soon as 12.5 days, then progressively acquire their adult pattern of expression, with high levels of AGAT in kidney and pancreas, and high levels of GAMT in liver and pancreas. AGAT and CT1 are prominent in CNS, skeletal muscles and intestine, where they appear earlier than GAMT. High levels of CT1 are found in epithelia.

Conclusion

Our results suggest that de novo synthesis of Cr by AGAT and GAMT, as well as cellular Cr uptake by CT1, are essential during embryonic development. This work provides new clues on how creatine can be provided to developing tissues, and suggests that Cr deficiencies might induce irreversible damages already in utero, particularly on the nervous system.
PAX6 mutations: genotype-phenotype correlations
Authors: Tzoulaki Ioanna , White Ian MS , Hanson Isabel M
Published: May 2005

Background

The PAX6 protein is a highly conserved transcriptional regulator that is important for normal ocular and neural development. In humans, heterozygous mutations of the PAX6 gene cause aniridia (absence of the iris) and related developmental eye diseases. PAX6 mutations are archived in the Human PAX6 Allelic Variant Database, which currently contains 309 records, 286 of which are mutations in patients with eye malformations.

Results

We examined the records in the Human PAX6 Allelic Variant Database and documented the frequency of different mutation types, the phenotypes associated with different mutation types, the contribution of CpG transitions to the PAX6 mutation spectrum, and the distribution of chain-terminating mutations in the open reading frame. Mutations that introduce a premature termination codon into the open reading frame are predominantly associated with aniridia; in contrast, non-aniridia phenotypes are typically associated with missense mutations. Four CpG dinucleotides in exons 8, 9, 10 and 11 are major mutation hotspots, and transitions at these CpG's account for over half of all nonsense mutations in the database. Truncating mutations are distributed throughout the PAX6 coding region, except for the last half of exon 12 and the coding part of exon 13, where they are completely absent. The absence of truncating mutations in the 3' part of the coding region is statistically significant and is consistent with the idea that nonsense-mediated decay acts on PAX6 mutant alleles.

Conclusion

The PAX6 Allelic Variant Database is a valuable resource for studying genotype-phenotype correlations. The consistent association of truncating mutations with the aniridia phenotype, and the distribution of truncating mutations in the PAX6 open reading frame, suggests that nonsense-mediated decay acts on PAX6 mutant alleles.
Use of SNPs to determine the breakpoints of complex deficiencies, facilitating gene mapping in Caenorhabditis elegans
Authors: Kadandale Pavan , Geldziler Brian , Hoffmann Melissa , Singson Andrew
Published: May 2005

Background

Genetic deletions or deficiencies have been used for gene mapping and discovery in various organisms, ranging from the nematodeCaenorhabditis elegansall the way to humans. One problem with large deletions is the determination of the location of their breakpoints. This is exacerbated in the case of complex deficiencies that delete a region of the genome, while retaining some of the intervening sequence. Previous methods, using genetic complementation or cytology were hampered by low marker density and were consequently not very precise at positioning the breakpoints of complex deficiencies. The identification of increasing numbers of Single Nucleotide Polymorphisms (SNPs) has resulted in the use of these as genetic markers, and consequently in their utilization for defining the breakpoints of deletions using molecular biology methods.

Results

Here, we show that SNPs can be used to help position the breakpoints of a complex deficiency inC. elegans. The technique uses a combination of genetic crosses and molecular biology to generate robust and highly reproducible results with strong internal controls when trying to determine the breakpoints of deficiencies. The combined use of this technique and standard genetic mapping allowed us to rapidly narrow down the region of interest in our attempts to clone a gene.

Conclusion

Unlike previous methods used to locate deficiency breakpoints, our technique has the advantage of not being limited by the amount of starting material. It also incorporates internal controls to eliminate false positives and negatives. The technique can also easily be adapted for use in other organisms in which both genetic deficiencies and SNPs are available, thereby aiding gene discovery in these other models.
No role for quality scores in systematic reviews of diagnostic accuracy studies
Authors: Whiting Penny , Harbord Roger , Kleijnen Jos
Published: May 2005

Background

There is a lack of consensus regarding the use of quality scores in diagnostic systematic reviews. The objective of this study was to use different methods of weighting items included in a quality assessment tool for diagnostic accuracy studies (QUADAS) to produce an overall quality score, and to examine the effects of incorporating these into a systematic review.

Methods

We developed five schemes for weighting QUADAS to produce quality scores. We used three methods to investigate the effects of quality scores on test performance. We used a set of 28 studies that assessed the accuracy of ultrasound for the diagnosis of vesico-ureteral reflux in children.

Results

The different methods of weighting individual items from the same quality assessment tool produced different quality scores. The different scoring schemes ranked different studies in different orders; this was especially evident for the intermediate quality studies. Comparing the results of studies stratified as "high" and "low" quality based on quality scores resulted in different conclusions regarding the effects of quality on estimates of diagnostic accuracy depending on the method used to produce the quality score. A similar effect was observed when quality scores were included in meta-regression analysis as continuous variables, although the differences were less apparent.

Conclusion

Quality scores should not be incorporated into diagnostic systematic reviews. Incorporation of the results of the quality assessment into the systematic review should involve investigation of the association of individual quality items with estimates of diagnostic accuracy, rather than using a combined quality score.
Low back pain in military recruits in relation to social background and previous low back pain. A cross-sectional and prospective observational survey
Authors: Hestbaek Lise , Larsen Kristian , Weidick Flemming , Leboeuf-Yde Charlotte
Published: May 2005

Background

Traditionally, studies on the etiology of low back pain have been carried out in adult populations. However, since low back pain often appears early in life, more research on young populations is needed. This study focuses on the importance of social background factors and previous low back pain in the development of low back pain in military recruits.

Methods

During a three-month period, Danish military recruits with different social backgrounds live and work under the same conditions. Thus, there is an opportunity to investigate the influence of social background on the development of low back pain, when persons are removed from their usual environment and submitted to a number of new stressors. In addition, the importance of the recruits' previous low back pain history in relation to low back pain during military service was studied. This was done by means of questionnaires to 1,711 recruits before and after this three-month period.

Results

Sedentary occupation was negatively associated with long-lasting low back pain (>30 days during the past year) at baseline with an odds ratios of 0.55 (95% CI: 0.33–0.90). This effect vanished during service. Having parents with higher education increased the risk of low back pain during service (OR: 1.9;1.2–3.0, for the highest educated group), but not of the consequences (leg pain and exemption from duty), whereas high IQ decreased the risk of these consequences (odds ratios as low as 0.2;0.1–0.8 for exemption from duty in the group with highest IQ). Long-lasting low back pain prior to service increased the risk of long-lasting low back pain (OR: 4.8;2.1–10.8), leg pain (OR: 3.3;1.3–8.3) and exemption from duty during service (OR: 5.9;2.4–14.8).

Conclusion

Sedentary occupation is negatively associated with low back pain at baseline. This protective effect disappears, when the person becomes physically active. For predicting trouble related to the low back during service, the duration of low back pain prior to service and IQ-level are the most important factors.
Aberrations of TACC1 and TACC3 are associated with ovarian cancer
Authors: Lauffart Brenda , Vaughan Mary M , Eddy Roger , Chervinsky David , DiCioccio Richard A , Black Jennifer D , Still Ivan H
Published: May 2005

Background

Dysregulation of the human Transforming Acidic Coiled Coil (TACC) genes is thought to be important in the development and progression of multiple myeloma, breast and gastric cancer. Recent, large-scale genomic analysis and Serial Analysis of Gene Expression data suggest that TACC1 and TACC3 may also be involved in the etiology of ovarian tumors from both familial and sporadic cases. Therefore, the aim of this study was to determine the occurrence of alterations of these TACCs in ovarian cancer.

Methods

Detection and scoring of TACC1 and TACC3 expression was performed by immunohistochemical analysis of the T-BO-1 tissue/tumor microarray slide from the Cooperative Human Tissue Network, Tissue Array Research Program (TARP) of the National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. Tumors were categorized as either positive (greater than 10% of cells staining) or negative. Statistical analysis was performed using Fisher's exact test and p < 0.05 (single comparisons), and p < 0.02 (multiple comparisons) were considered to be significant. Transgenomics WAVE high performance liquid chromatography (dHPLC) was used to pre-screen the TACC3 gene in constitutional DNA from ovarian cancer patients and their unaffected relatives from 76 families from the Gilda Radner Familial Ovarian Cancer Registry. All variant patterns were then sequenced.

Results

This study demonstrated absence of at least one or both TACC proteins in 78.5% (51/65) of ovarian tumors tested, with TACC3 loss observed in 67.7% of tumors. The distribution pattern of expression of the two TACC proteins was different, with TACC3 loss being more common in serous papillary carcinoma compared with clear cell carcinomas, while TACC1 staining was less frequent in endometroid than in serous papillary tumor cores. In addition, we identified two constitutional mutations in the TACC3 gene in patients with ovarian cancer from the Gilda Radner Familial Ovarian Cancer Registry. These patients had previously tested negative for mutations in known ovarian cancer predisposing genes.

Conclusion

When combined, our data suggest that aberrations of TACC genes, and TACC3 in particular, underlie a significant proportion of ovarian cancers. Thus, TACC3 could be a hitherto unknown endogenous factor that contributes to ovarian tumorigenesis.
Predictors of serum dioxin levels among adolescent boys in Chapaevsk, Russia: A cross-sectional pilot study
Authors: Hauser Russ , Williams Paige , Altshul Larisa , Korrick Susan , Peeples Lynne , Patterson Donald G , Turner Wayman E , Lee Mary M , Revich Boris , Sergeyev Oleg
Published: May 2005

Background

Toxicological studies and limited human studies have demonstrated associations between exposure to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) and adverse developmental and reproductive health effects. Given that children may be particularly susceptible to reproductive and developmental effects of organochlorines, and the paucity of information available regarding childhood exposures to dioxins in particular, we undertook a pilot study to describe the distribution of, and identify potential predictors of exposure to, dioxin-like compounds and dioxins among adolescent boys in Chapaevsk, Russia. The pilot study was also designed to guide the development of a large prospective cohort study on the relationship of exposure to PCDDs, PCDFs, and PCBs with growth and pubertal development in peri-pubertal Chapaevsk boys.

Methods

221 boys age 14 to 17 participated in the pilot study. Each of the boys, with his mother, was asked to complete a nurse-administered detailed questionnaire on medical history, diet, and lifestyle. The diet questions were used to measure the current and lifetime consumption of locally grown or raised foods. Blood samples from 30 of these boys were sent to the Centers for Disease Control and Prevention (CDC) for analysis of dioxins, furans and PCBs.

Results

The median (25th, 75th percentile) concentrations for total PCDDs, PCDFs and coplanar PCBs were 95.8 pg/g lipids (40.9, 144), 33.9 pg/g lipids (20.4, 61.8), and 120 pg/g lipids (77.6, 157), respectively. For WHO-TEQs, the median (25th, 75th percentile) for total PCDDs, PCDFs, and coplanar PCBs were 0.29 (0.1, 9.14), 7.98 (5.27, 12.3), and 7.39 (4.51, 11.9), respectively. Although TCDD was largely non-detectable, two boys had high TCDD levels (17.9 and 21.7 pg/g lipid). Higher serum levels of sum of dioxin-like compounds and sum of dioxin TEQs were positively associated with increased age, consumption of fish, local meats other than chicken, PCB 118, and inversely with weeks of gestation.

Conclusion

The total TEQs among Chapaevsk adolescents were higher than most values previously reported in non-occupationally exposed populations of comparable or even older ages. Dietary consumption of local foods, as well as age and weeks of gestation, predicted dioxin exposure in this population.
Analysis of memory T lymphocyte activity following stimulation with overlapping HLA-A*2402, A*0101 and Cw*0402 restricted CMV pp65 peptides
Authors: Ghei Monica , Stroncek David F , Provenzano Maurizio
Published: May 2005

The continuous efforts aimed at the identification of new immune epitopes across the MHC system has led to the discovery that more than one peptide may be restricted to the same HLA antigen and function as an immune determinant for that association. The aim of this study was to compare the ability of two overlapping peptides, the nonamer (9-mer) cytomegalovirus (CMV) pp65341–349 (QYDPVAALF) and the decamer (10-mer) CMV pp65341–350 (QYDPVAALFF), and the esadecamer (16-mer) peptide containing both the 9-mer and 10-mer sequences, CMV pp65340–355 (RQYDPVAALFFFDIDL), to stimulate and maintain over time a T cell immune reactivation by HLA-A*2402, A*0101, and Cw*0402 cells from CMV-seropositive subjects. The 9-mer, 10-mer, and 16-mer peptides effectively stimulated CTLs from HLA-A*2402, HLA-A*0101, and HLA-Cw*0402 CMV seropositive donors. This data confirms that both the 9-mer and the 10-mer peptides are promiscuous and are not restricted to a single HLA antigen. CMV pp65341–349 and CMV pp65341–350 have the ability to produce CMV-specific CTLs in subjects with several different HLA types, presenting a practical advantage over other peptides that are restricted only to a single HLA antigen, and thus being optimal for CMV adoptive immune therapy. Moreover, since the 16-mer peptide encompasses both the 9-mer and 10-mer peptides, it may be better than either of these peptides for CMV adoptive immune therapy.
Conservation of functional domains and limited heterogeneity of HIV-1 reverse transcriptase gene following vertical transmission
Authors: Sundaravaradan Vasudha , Hahn Tobias , Ahmad Nafees
Published: May 2005

Background

The reverse transcriptase (RT) enzyme of human immunodeficiency virus type 1 (HIV-1) plays a crucial role in the life cycle of the virus by converting the single stranded RNA genome into double stranded DNA that integrates into the host chromosome. In addition, RT is also responsible for the generation of mutations throughout the viral genome, including in its own sequences and is thus responsible for the generation of quasi-species in HIV-1-infected individuals. We therefore characterized the molecular properties of RT, including the conservation of functional motifs, degree of genetic diversity, and evolutionary dynamics from five mother-infant pairs following vertical transmission.

Results

The RT open reading frame was maintained with a frequency of 87.2% in five mother-infant pairs' sequences following vertical transmission. There was a low degree of viral heterogeneity and estimates of genetic diversity in mother-infant pairs' sequences. Both mothers and infants RT sequences were under positive selection pressure, as determined by the ratios of non-synonymous to synonymous substitutions. Phylogenetic analysis of 132 mother-infant RT sequences revealed distinct clusters for each mother-infant pair, suggesting that the epidemiologically linked mother-infant pairs were evolutionarily closer to each other as compared with epidemiologically unlinked mother-infant pairs. The functional domains of RT which are responsible for reverse transcription, DNA polymerization and RNase H activity were mostly conserved in the RT sequences analyzed in this study. Specifically, the active sites and domains required for primer binding, template binding, primer and template positioning and nucleotide recruitment were conserved in all mother-infant pairs' sequences.

Conclusion

The maintenance of an intact RT open reading frame, conservation of functional domains for RT activity, preservation of several amino acid motifs in epidemiologically linked mother-infant pairs, and a low degree of genetic variability following vertical transmission is consistent with an indispensable role of RT in HIV-1 replication in infected mother-infant pairs.
Age and kidney function are the primary correlates of fasting plasma total homocysteine levels in non-diabetic and diabetic adults. Results from the 1999–2002 National Health and Nutrition Examination Survey
Authors: Duncan Glen E , Li Sierra M , Zhou Xiao-Hua
Published: May 2005

Background

Plasma total homocysteine (tHcy) is commonly elevated in persons with diabetes. This may be due to effects of insulin and/or glucose and/or metabolic control on the metabolism or plasma levels of tHcy. This study examined the effects of fasting plasma glucose status on fasting tHcy levels among adults without diabetes, and diabetes per se among adults with a self-report history of diabetes.

Methods

Analysis of data on adults (≥ 20y) who had fasted at least 8 hours, from the National Health and Nutrition Examination Survey (1999–2000 and 2001–2002). Subjects with no self-report history of diabetes were grouped according to fasting plasma glucose status as normal (< 100 mg/dL = NFG, n = 2,244), impaired (≥ 100 < 126 mg/dL = IFG, n = 1,108), or a provisional diagnosis of diabetes (≥ 126 mg/dL = DFG, n = 133). Subjects with a self-report history of diabetes (n = 275) were examined separately.

Results

Fasting tHcy was higher (Ps < 0.01) among non-diabetic subjects with DFG and IFG, compared to NFG (median [95% confidence interval] = 8.6 [8.0–9.2], 8.3 [8.1–8.5], and 7.4 [7.3–7.5] μmol/L, respectively). Diabetic subjects had levels similar to non-diabetic subjects with DFG and IFG (8.3 [7.9–8.6] μmol/L). Age and estimated creatinine clearance were strong correlates of fasting tHcy among non-diabetic subjects (r = 0.38 to 0.44 and r = -0.35 to -0.46, respectively) and diabetic subjects (r = 0.41 and r = -0.46, respectively) (Ps < 0.001), while fasting glucose and glycohemoglobin (HbA1c) were weaker (but still significant) correlates of tHcy in non-diabetic and diabetic subjects. Fasting glucose status was not a significant independent predictor of fasting tHcy levels in non-diabetic subjects, and HbA1c was not a significant independent predictor of tHcy in diabetic subjects (Ps > 0.05).

Conclusion

Fasting tHcy levels are elevated among non-diabetic adults with elevated fasting glucose levels, compared to persons with normal fasting glucose levels, and among diabetic adults. However, elevations in fasting tHcy appear to be mediated primarily by age and kidney function, and not by measures of glucose metabolism.
Spared Nerve Injury Rats Exhibit Thermal Hyperalgesia on an Automated Operant Dynamic Thermal Escape Task
Authors: Baliki Marwan , Calvo Oscar , Chialvo Dante R , Apkarian A Vania
Published: May 2005

Well-established methods are available to measure thermal and mechanical sensitivity in awake behaving rats. However, they require experimenter manipulations and tend to emphasize reflexive behaviors. Here we introduce a new behavioral test, with which we examine thermal sensitivity of rats with neuropathic injury. We contrast thermal hyperalgesia between spared nerve injury and chronic constriction injury rats. This device is a fully automated thermal sensitivity assessment tool designed to emphasize integrated learned responses to thermal painful and non-painful stimuli that are applied dynamically to a surface on which the animal is standing. It documents escape behavior in awake, unrestrained animals to innocuous and noxious heating of the floor where the animal is located. Animals learn to minimize pain by escaping to the opposite non-heated side; escape latency is recorded. On this device, thermal stimulus-response curves showed > 6°C leftward shift in both groups of neuropathic rats. In contrast, when these animals were tested on hotplate the stimulus-response shift was < 2°C. Spared nerve injury rats showed even less evidence for thermal hyperalgesia when thermal sensitivity was tested by measuring paw withdrawal to infrared heating, plantar test. The implications of test dependent magnitude of thermal hyperalgesia are discussed from the viewpoint of the tests used, as well as the animal models studied. It is argued that the dynamic thermal operant task reveals the relevance of the neuropathic injury associated pain-like behavior in relation to the whole organism.
The practical utility of incorporating model selection uncertainty into prognostic models for survival data
Authors: Augustin Nicole , Sauerbrei Willi , Schumacher Martin
Published: May 2005

Predictions of disease outcome in prognostic factor models are usually based on one selected model. However, often several models fit the data equally well, but these models might differ substantially in terms of included explanatory variables and might lead to different predictions for individual patients. For survival data, we discuss two approaches to account for model selection uncertainty in two data examples, with the main emphasis on variable selection in a proportional hazard Cox model. The main aim of our investigation is to establish the ways in which either of the two approaches is useful in such prognostic models. The first approach is Bayesian model averaging (BMA) adapted for the proportional hazard model, termed ‘approx. BMA’ here. As a new approach, we propose a method which averages over a set of possible models using weights estimated from bootstrap resampling as proposed by Buckland et al., but in addition, we perform an initial screening of variables based on the inclusion frequency of each variable to reduce the set of variables and corresponding models. For some necessary parameters of the procedure, investigations concerning sensible choices are still required. The main objective of prognostic models is prediction, but the interpretation of single effects is also important and models should be general enough to ensure transportability to other clinical centres. In the data examples, we compare predictions of our new approach with approx. BMA, with ‘conventional’ predictions from one selected model and with predictions from the full model. Confidence intervals are compared in one example. Comparisons are based on the partial predictive score and the Brier score. We conclude that the two model averaging methods yield similar results and are especially useful when there is a high number of potential prognostic factors, most likely some of them without influence in a multivariable context. Although the method based on bootstrap resampling lacks formal justification and requires some ad hoc decisions, it has the additional positive effect of achieving model parsimony by reducing the number of explanatory variables and dealing with correlated variables in an automatic fashion.
A latent variable scorecard for neonatal baby frailty
Authors: Bowden Jack , Whittaker Joe
Published: May 2005

A latent variable frailty model is built for data coming from a neonatal study conducted to investigate whether the presence of a particular hospital service given to families with premature babies has a positive effect on their care requirements within the first year of life. The predicted value of the latent frailty term from information obtained from the family in advance of the birth furnishes an overall measure of the quality of health of the baby. This identifies families at risk. Maximum likelihood and Bayesian approaches are used to estimate the effect of the variables on the value of the latent baby frailty and for prediction of health complications. It is found that these give much the same estimates of regression coefficients, but that the variance components are the more difficult to estimate. We indicate how the findings from the model may be presented as a scorecard for predicting frailty, and so be useful to doctors working in hospital neonatal units. New information about a baby is automatically combined with the current score to provide an up-to-date score, so that rapid decisions for taking appropriate action are made more possible. A diagnostic procedure is proposed to assess how well the independence assumptions of the model are met in fitting to this data. It is concluded that the frailty model provides an informative summary of the data from this neonatal study.
Sporadic and Continuous Clearing Policies for a Production/Inventory System Under an M/G Demand Process
Authors: Perry David , Stadje Wolfgang , Zacks Shelemyahu
Published: May 2005

A production/inventory system is filled continuously at rate 1 and satisfies demands of i.i.d. random sizes that arrive at Poisson times. For this system we consider two clearing policies. Under sporadic review, clearing takes place after a random time independent of the content process. Under continuous review, the system is cleared as soon as the inventory level reaches some pre-specified threshold. We derive explicit results for the associated expected discounted cost functionals under both types of clearing.
A Conic Programming Approach to Generalized Tchebycheff Inequalities
Authors: Zuluaga Luis F. , Peña Javier F.
Published: May 2005

Consider the problem of finding optimal bounds on the expected value of piecewise polynomials over all measures with a given set of moments. This is a special class of generalized Tchebycheff inequalities in probability theory. We study this problem within the framework of conic programming. Relying on a general approximation scheme for conic programming, we show that these bounds can be numerically computed or approximated via semidefinite programming. We also describe some applications of this class of generalized Tchebycheff inequalities in probability, finance, and inventory theory.
A Multiexchange Local Search Algorithm for the Capacitated Facility Location Problem
Authors: Zhang Jiawei , Chen Bo , Ye Yinyu
Published: May 2005

We present a multiexchange local search algorithm for approximating the capacitated facility location problem (CFLP), where a new local improvement operation is introduced that possibly exchanges multiple facilities simultaneously. We give a tight analysis for our algorithm and show that the performance guarantee of the algorithm is between 3 + 2√2 − ε and 3 + 2√2 + ε for any given constant ε > 0. The previously known best approximation ratio for the CFLP is 7.88, as shown by Mahdian and Pál (2003. Universal facility location. Proc. 11th Annual Eur. Sympos. Algorithms (ESA), 409–421), based on the operations proposed by Pál et al. (2001. Facility location with hard capacities. Proc. 42nd IEEE Sympos. Foundations Comput. Sci. (FOCS), 329–338). Our upper bound 3+2√2+ε also matches the best-known ratio, obtained by Chudak and Williamson (1999. Improved approximation algorithm for capacitated facility location problems. Proc. 7th Conf. Integer Programming Combin. Optim. (IPCO), 99–113), for the CFLP with uniform capacities. In order to obtain the tight bound of our new algorithm, we make interesting use of the notion of exchange graph of Pál et al. and techniques from the area of parallel machine scheduling.
Asymptotic Behavior of Internet Congestion Controllers in a Many-Flows Regime
Authors: Deb Supratim , Shakkottai Sanjay , Srikant R.
Published: May 2005

Congestion controllers for the Internet are typically designed based on deterministic delay differential equation models. In this paper, we consider the case of a single link accessed by many TCP-like congestion-controlled flows and uncontrolled flows that are modeled as stochastic disturbances. We show that if the number of flows is large and the link capacity is scaled in proportion to the number of users, then under appropriate conditions, the trajectory of the stochastic system is eventually well approximated by the trajectory of a delay-differential equation. Our analysis also throws light on the choice of various parameters that ensure global asymptotic stability of the limiting deterministic system in the presence of feedback delay. Numerical examples with some popular congestion feedback mechanisms validate the parameter choices from the analysis. The results indicate that a system with multiple TCP-like flows is globally stable (and thus, that a deterministic model is reasonable if the number of flows is large) as long as the product of the throughput and feedback delay per flow is not very small.
Submodularity, Supermodularity, and Higher-Order Monotonicities of Pseudo-Boolean Functions
Authors: Foldes Stephan , Hammer Peter L.
Published: May 2005

Classes of set functions defined by the positivity or negativity of the higher-order derivatives of their pseudo-Boolean polynomial representations generalize those of monotone, supermodular, and submodular functions. In this paper, these classes are characterized by functional inequalities and are shown to be closed both under algebraic closure conditions and a local closure criterion. It is shown that for every m ≥ 1, in addition to the class of all set functions, there are only three other classes satisfying these algebraic and local closure conditions: those having positive, respectively negative, mth-order derivatives, and those having a polynomial representation of degree less than m.
Robust Dynamic Programming
Authors: Iyengar Garud N.
Published: May 2005

In this paper we propose a robust formulation for discrete time dynamic programming (DP). The objective of the robust formulation is to systematically mitigate the sensitivity of the DP optimal policy to ambiguity in the underlying transition probabilities. The ambiguity is modeled by associating a set of conditional measures with each state-action pair. Consequently, in the robust formulation each policy has a set of measures associated with it. We prove that when this set of measures has a certain “rectangularity” property, all of the main results for finite and infinite horizon DP extend to natural robust counterparts. We discuss techniques from Nilim and El Ghaoui [17] for constructing suitable sets of conditional measures that allow one to efficiently solve for the optimal robust policy. We also show that robust DP is equivalent to stochastic zero-sum games with perfect information.
The Continuous Mixing Polyhedron
Authors: Van Vyve Mathieu
Published: May 2005

We analyze the polyhedral structure of the sets PCMIX = {(s, r, z) ∈ R × R+n × Zn ∣ s + rj + zj ≥ fj, j = 1, …, n} and P+CMIX = PCMIX ∩ {s ≥ 0}. The set P+CMIX is a natural generalization of the mixing set studied by Pochet and Wolsey [15, 16] and Günlük and Pochet [8] and recently has been introduced by Miller and Wolsey [12]. We introduce a new class of valid inequalities that has proven to be sufficient for describing conv(PCMIX). We give an extended formulation of size O(n) × O(n2) variables and constraints and indicate how to separate over conv(PCMIX) in O(n3) time. Finally, we show how the mixed integer rounding (MIR) inequalities of Nemhauser and Wolsey [14] and the mixing inequalities of Günlük and Pochet [8] constitute special cases of the cycle inequalities.
On the Lipschitz Continuity of the Solution Map in Semidefinite Linear Complementarity Problems
Authors: Balaji R. , Parthasarathy T. , Raman D. Sampangi , Vetrivel V.
Published: May 2005

In this paper, we investigate the Lipschitz continuity of the solution map in semidefinite linear complementarity problems. For a monotone linear transformation defined on the space of real symmetric n × n matrices, we show that the Lipschitz continuity of the solution map implies the globally uniquely solvable (GUS)-property. For Lyapunov transformations with the Q-property, we prove that the Lipschitz continuity of the solution map is equivalent to the strong monotonicity property. For the double-sided multiplicative transformations, we show that the Lipschitz continuity of the solution map implies the GUS-property.
On the Average Waiting Time for Regular Routing to Deterministic Queues
Authors: Hordijk Arie , van der Laan Dinard
Published: May 2005

We consider a deterministic queueing system in which N ≥ 2 servers of different speeds operate in parallel. Each service in queue i takes the deterministic time Si. Identical customers arrive exactly one per time unit, and it is desirable to route them to the queues so that the average waiting time (we consider as waiting time the time a customer waits in the buffer of a queue, and thus the service time is not included in this) is minimized. We provide an algorithm to compute lower and upper bounds on this quantity. The upper bound is found by showing that there is a periodic policy for which the average waiting time is no greater than the lower bound plus (N / 2) − 1. Thus, the bounds coincide when N = 2. For obtaining the lower bound, we give explicit formulae for the average waiting time in case of regular routing to a deterministic queue.
Sensitivity Analysis for Cone-Constrained Optimization Problems Under the Relaxed Constraint Qualifications
Authors: Arutyunov Aram V. , Izmailov Alexey F.
Published: May 2005

We present the local sensitivity analysis for cone-constrained optimization problems under the CQ-type conditions significantly weaker than those traditionally used in this context. Our basic sensitivity results are established under the first or second-order sufficient optimality conditions combined with the estimate of the distance to the feasible set of the perturbed problem. We demonstrate how such an estimate can be obtained under the assumptions weaker than Robinson’s CQ, and establish the corresponding sensitivity results. Finally, we apply our results to sensitivity analysis and relaxation schemes for mathematical programs with complementarity constraints.
The effects of adult guidance and peer discussion on the development of children's representations: Evidence from the training of pedestrian skills
Authors: Tolmie Andrew , Thomson James A. , Foot Hugh C. , Whelan Kirstie , Morrison Sheila , McLaren Brian
Published: May 2005

It was hypothesized that practical training is effective in improving children's pedestrian skills because adult scaffolding and peer discussion during training specifically promote E3 level representation (linguistically‐encoded, experientially‐grounded, generalizable knowledge), as defined byKarmiloff‐Smith's (1992)representational redescription (RR) model. Two studies were conducted to examine in detail the impact of this social input in the context of simulation‐based training in roadside search skills. A group of 5–8‐year‐olds were pre‐tested on ability to detect relevant road‐crossing features. They then participated in four training sessions designed to promote attunement to these, under peer discussion versus adult guidance conditions (Study 1), and adult–child versus adult–group conditions (Study 2). Performance at post‐test was compared with that of controls who underwent no training. Study 1 found that children in the adult guidance condition improved significantly more than those in the peer discussion or control conditions, and this improvement was directly attributable to appropriation of E3 level representations from adult dialogue. Study 2 found that progress was greater still when adult scaffolding was supplemented by peer discussion, with E3 level representation attributable to the children's exploration of conflicting ideas. The implications of these findings for the RR model and for practical road safety education are discussed.
Self‐enhancement, crash‐risk optimism and the impact of safety advertisements on young drivers
Authors: Harré Niki , Foster Susan , O'Neill Maree
Published: May 2005

In Study 1, young drivers (aged between 16 and 29 years, N=314) rated their driving attributes relative to their peers. They also rated their likelihood of being involved in a crash relative to their peers (crash‐risk optimism), their crash history, stereotype of the young driver, and concern over another health issue. A self‐enhancement bias was found for all items in which self/other comparisons were made. These items formed two major factors, perceived relative driving ability and perceived relative driving caution. These factors and perceived luck relative to peers in avoiding crashes significantly predicted crash‐risk optimism. In Study 2, an experimental group of young drivers (N=173) watched safety advertisements that showed drinking and dangerous driving resulting in a crash, and a control group (N=193) watched advertisements showing people choosing not to drive after drinking. Each group then completed the self/other comparisons used in Study 1. The same factors were found, but only driving caution significantly predicted crash‐risk optimism. The experimental group showed more self‐enhancement on driving ability than the control group. In both studies, men showed substantially more self‐enhancement than women about their driving ability. Implications for safety interventions are discussed.
Perceptual adaptation affects attractiveness of female bodies
Authors: Winkler Christopher , Rhodes Gillian
Published: May 2005

We investigated whether short durations (5 minutes) of exposure to distorted bodies can change subsequent perceptions of attractiveness and normality. Participants rated 110 female bodies, varying in width, on either their attractiveness or normality before and after exposure to either extremely narrow (−50% of original width in Experiments 1 and 2) or extremely wide bodies (+50% of original width in Experiment 1, and +70% of original width in Experiment 2). In both experiments, the most attractive and most normal looking bodies became significantly and substantially narrower after exposure to narrow bodies. The most normal looking body changed significantly after exposure to wide bodies, but the most attractive body did not. These results show that perceptions of body attractiveness can be influenced by experience, but that there is an asymmetry between the effects of exposure to narrow and wide bodies. We consider a possible mechanism for this unexpected asymmetry, as well as possible implications for the effects of media exposure on body‐image. The most attractive body shape was consistently narrower than the most normal looking body shape. Substantial changes in what looked normal were accompanied by congruent changes in what looked attractive, suggesting that a normal or average body shape may function as a reference point against which body attractiveness is judged.
Signal regularity and the mindlessness model of vigilance
Authors: Helton William S. , Hollander Todd D. , Warm Joel S. , Matthews Gerald , Dember William N. , Wallaart Matthew , Beauchamp Gerald , Parasuraman Raja , Hancock Peter A.
Published: May 2005

Robertson, Manly, Andrade, Baddeley, and Yiend (1997) have proposed that detection failures in vigilance tasks result from a ‘mindless’ withdrawal of attentional effort from the monitoring assignment. To explore that view, they modified the traditional vigilance task, in which observers make button‐press responses to signify the detection of rarely occurring critical signals, to one in which button‐press responses acknowledge frequently occurring non‐signal events and response withholding signifies signal detection. This modification is designed to promote a mindless withdrawal of attentional effort from the task through routinization. The present study challenges the validity of the mindlessness model by showing that with both types of task, observers utilize subtle patterns in the temporal structure of critical signal appearances to develop expectations about the time course of those appearances that affect performance efficiency. Such expectations enhance performance on the traditional vigilance task, but degrade performance on the modified task.