Showing papers by "Maastricht University published in 1995"

Local Search in Combinatorial Optimization

Abstract: computational bounds for local search in combinatorial local search algorithms for combinatorial problems local search algorithms for solving the combinatorial a dual local search framework for combinatorial the max-min ant system and local search for combinatorial a framework for local combinatorial optimization problems local search in combinatorial optimization mifou local search in combinatorial optimization radarx heuristics and local search paginas.fe.up local search in combinatorial optimization banani local search in combinatorial optimization integrating interval estimates of global optima and local local search in combinatorial optimization holbarto a fuzzy valuation-based local search framework for local search in combinatorial optimization gbv gentle introduction to local search in combinatorial e cient local search for several combinatorial introduction: combinatorial problems and search on application of the local search optimization online local search for combinatorial optimisation problems how to choose solutions for local search in multiobjective a hybrid of inference and local search for distributed on set-based local search for multiobjective combinatorial localsolver: black-box local search for combinatorial on local optima in multiobjective combinatorial sets of interacting scalarization functions in local introduction e r optimization online estimation-based local search for stochastic combinatorial advanced search combinatorial problems sas/or user's guide: local search optimization how easy is local search? univerzita karlova metaheuristic search for combinatorial optimization local search genetic algorithms for the job shop towards a formalization of combinatorial local search dynamic and adaptive neighborhood search in combinatorial global search in combinatorial optimization using a framework for the development of local search heuristics a feasibility-preserving local search operator for hybrid metaheuristics in combinatorial optimization: a survey consultant-guided search algorithms with local search for a new optimization algorithm for combinatorial problems hybrid metaheuristics in combinatorial optimization: a survey network algorithms colorado state university model-based search for combinatorial optimization: a local and global optimization stochastic local search algorithms for multiobjective corso (collaborative reactive search optimization local search in combinatorial optimization zaraa

Continuous nitric oxide synthesis by inducible nitric oxide synthase in normal human airway epithelium in vivo

Abstract: Nitric oxide (NO) is an important mediator of inflammatory responses in the lung and a key regulator of bronchomotor tone. An airway NO synthase (NOS; EC 1.14.13.39) has been proposed as a source of endogenous NO in the lung but has not been clearly defined. Through molecular cloning, we conclusively demonstrate that NO synthesis in normal human airways is due to the continuous expression of the inducible NOS (iNOS) isoform in airway epithelial cells. Although iNOS mRNA expression is abundant in airway epithelial cells, expression is not detected in other pulmonary cell types, indicating that airway epithelial cells are unique in the continuous pattern of iNOS expression in the lung. In situ analysis reveals all airway epithelial cell types express iNOS. However, removal of epithelial cells from the in vivo airway environment leads to rapid loss of iNOS expression, which suggests expression is dependent upon conditions and/or factors present in the airway. Quantitation of NOS activity in epithelial cell lysates indicates nanomolar levels of NO synthesis occur in vivo. Remarkably, the high-level iNOS expression is constant in airway epithelium of normal individuals over time. However, expression is strikingly decreased by inhaled corticosteroids and beta-adrenergic agonists, medications commonly used in treatment of inflammatory airway diseases. Based upon these findings, we propose that respiratory epithelial cells are key inflammatory cells in the airway, functioning in host defense and potentially playing a role in airway inflammation.

Potential impact of global climate change on malaria risk.

Abstract: The biological activity and geographic distribution of the malarial parasite and its vector are sensitive to climatic influences, especially temperature and precipitation. We have incorporated General Circulation Model-based scenarios of anthropogenic global climate change in an integrated linked-system model for predicting changes in malaria epidemic potential in the next century. The concept of the disability-adjusted life years is included to arrive at a single measure of the effect of anthropogenic climate change on the health impact of malaria. Assessment of the potential impact of global climate change on the incidence of malaria suggests a widespread increase of risk due to expansion of the areas suitable for malaria transmission. This predicted increase is most pronounced at the borders of endemic malaria areas and at higher altitudes within malarial areas. The incidence of infection is sensitive to climate changes in areas of Southeast Asia, South America, and parts of Africa where the disease is less endemic; in these regions the numbers of years of healthy life lost may increase significantly. However, the simulated changes in malaria risk must be interpreted on the basis of local environmental conditions, the effects of socioeconomic developments, and malaria control programs or capabilities.

Maternal essential fatty acid patterns during normal pregnancy and their relationship to the neonatal essential fatty acid status

Abstract: Although essential fatty acids (EFA) and their longer chain, more unsaturated derivatives play a major role during pregnancy, hardly any information is available with respect to the course of the maternal EFA status during an uncomplicated pregnancy and its relationship to the neonatal EFA status. Therefore, a longitudinal study was started in which 110 pregnant women gave repeated blood samples from the 10th week of gestation until delivery. After birth a blood sample from the umbilical vein and a maternal venous blood sample were collected as well, and 6 months after delivery a final blood sample from the mother was taken. The absolute (mg/l) and relative (% total fatty acids) amounts of the fatty acids in plasma phospholipids were determined. The total amounts of fatty acids increased significantly during pregnancy. This pattern was similar for the individual fatty acids and fatty acid families. The relative amount of linoleic acid (18:2n-6) did not change during pregnancy, whereas the relative amount of arachidonic acid (20:4n-6) decreased. Despite maternal mobilization of docosahexaenoic acid (22:6n-3, DHA), suggested by a temporary increase in the DHA status until 18 weeks gestation, the DHA status steadily declined thereafter. This pattern was associated with a progressive increase in the DHA deficiency index in maternal blood throughout pregnancy and resulted in a sub-optimal neonatal DHA status. The overall maternal EFA status also declined steadily during pregnancy. Therefore, the question arises whether the mother, under the prevailing dietary conditions, is able to meet the high fetal requirement for EFA.

What makes a tutor effective? A structural-equations modeling approach to learning in problem-based curricula.

Abstract: Purpose To test and further develop a causal model of the influence of tutor behaviors on student achievement and interest in the context of problem-based learning. Method Data from 524 tutorial groups involving students participating in the four-year undergraduate health sciences curriculum at the University of Limburg in 1992-93 were analyzed. The tutorial groups were guided by 261 tutors. Overall, 3,792 data records were studied, with each student participating in an average of 2.3 groups. Correlations among tutors' social-congruence, expertise-use, and cognitive-congruence behaviors, small-group functioning, and student' self-study time, intrinsic interest in subject matter, and level of achievement were analyzed using structural-equations modeling. This statistical technique allows the investigator to test causal hypotheses on correlational data by comparing the structure of data with a theoretical model. Results After minor adaptations, the hypothesized causal model of the effective tutor fitted the data extremely will. Each tutor's level of expertise use and social congruence not only directly affected his or her level of cognitive congruence but also affected other elements of the model. Level of social congruence influenced group functioning in a direct fashion, while expertise use had a slightly negative effect on the students' level of self-study time and a slightly positive effect on level of achievement. As hypothesized, the level of cognitive congruence influenced tutorial-group functioning. Level of group functioning affected self-study time and intrinsic interest. Finally, time spent on self-study influenced level of achievement. Conclusion The results suggest that subject-matter expertise; a commitment to students' learning and their lives in a personal, authentic way; and the ability to express oneself in the language used by the student are all determinants of learning in problem-based curricula. The theory of the effective tutor, presented in this article, merges two different perspectives prevalent in the literature. One perspective emphasizes the personal qualities of the tutor: his or her ability to communicate with students in an informal way, coupled with an empathic attitude that enables the tutor to encourage student learning by creating an atmosphere in which open exchange of ideas is facilitated. The other stresses the tutor's subject-matter knowledge as a determinant of learning. The data presented in this article suggest that what is needed, really, is much of both.

The impact of social influences in the context of attitude, self-efficacy, intention, and previous behavior as predictors of smoking onset

Abstract: Three different constructs for measuring social influence were utilized in the present study to explain adolescents' present and future smoking behavior at 6 (T2), 12 (T3), and 18 months (T4) after the first test. Social influence was assessed by measuring the social norms, perceived smoking behavior, and direct pressure. The impact of the social influence constructs was also assessed in the context of broader models, including attitudes and self-efficacy expectations, intention, and previous behavior. The three social influence measures correlated significantly with intention and behavior. Stepwise regression analyses showed that perceived behavior and pressure made significant contributions, after entering social norms, in explaining actual and future adolescent smoking behavior. Adding attitudes and self-efficacy increased the predictive power of the model significantly. In agreement with the theory of Fishbein & Ajzen (1975), intention was the most powerful predictor in explaining present and future smoking behavior. Attitudes, self-efficacy, and the social influences also made small unique contributions improving the explanatory power by approximately 5%. Previous behavior, however, had a substantial unique contribution in predicting future behavior after attitudes, social influences, self-efficacy, and intention were entered in the equations. Since social influences may exert their impact via different routes, it is recommended that smoking prevention programs discuss not only overt pressures such as direct pressure from peers, parents, and media, but also address the more covert social pressures such as modeling and the adolescents' ability to cope with these covert influences. Furthermore, norms on nonsmoking should be made explicit.

Six-year results of hydroxyapatite-coated total hip replacement.

Abstract: We present the 5.6- to 7.6-year results of our first 118 hydroxyapatite (HA)-coated total hip replacements in patients under 66 years of age. The titanium femoral component has proximal HA coating and was usually articulated with an HA-coated threaded cup. The HA coating of 50 microns thickness has a porosity of below 3%, 97% HA purity and 65% crystallinity. The survival rate at a mean of six years was 100% for the HA-coated stems and 99% for the HA-threaded cups. The average Harris hip score at one year was 96, and at three years and thereafter 98. There was a very low incidence of early pain after surgery. Serial radiographs showed rapid bony integration of implants with evidence of bone apposition on the coating within six months. By Engh's criteria, all the femoral components had confirmed bone ongrowth after three years. We found no deterioration of results with time, and consider that our clinical and radiological results show that HA coatings can provide early pain relief and durable implant fixation.

Mosaicism of autosomes and sex chromosomes in morphologically normal, monospermic preimplantation human embryos.

Abstract: We have previously detected chromosome abnormalities in human embryos whilst identifying the sex for preimplantation diagnosis of X-linked disease. In this study we assess the incidence of these abnormalities, both for sex chromosomes and autosomes 1 and 17, using dual fluorescent in situ hybridization (FISH). Sixty-nine normally fertilized embryos of good morphology at the 6-10 cell stage (day 3 post-insemination) were examined. The embryos were spread whole using HCl and Tween 20 to dissolve the cytoplasm. Thirty-four embryos were analyzed for the sex chromosomes and 35 for autosomes 1 and 17. All probes were directly labelled with fluorochromes allowing analysis in 2 h. Control lymphocytes demonstrated that the probes were of high specificity. For the sex chromosomes, five embryos were mosaic (15 per cent) with the remaining 29 being uniformly XX or XY. In no case was an XX nucleus found in an otherwise XY embryo, indicating that even though mosaicism for the sex chromosomes is present, such abnormalities would not lead to a misdiagnosis of sex. For the autosomes, 16 embryos were abnormal (46 per cent); one embryo was triploid, one was monosomic for chromosome 1, and ten others were diploid mosaics (three diploid/aneuploid, three diploid/polyploid, and four diploid/haploid). A further four embryos had variable chromosome numbers in the majority of nuclei which appeared to be the result of uncontrolled mitotic division. The presence of haploidy or double monosomy, which occurred in 15 per cent of nuclei, has important implications for the diagnosis of trisomies and dominant disorders.

The Maastricht Protocol for the Measurement of Body Composition and Energy Expenditure with Labeled Water

Abstract: An update of practical aspects of the use of labeled water for the measurement of total body water (TBW) and energy expenditure (EE) is presented as applied in Maastricht, The Netherlands. We use a 10-hour equilibration period. The isotopes for the measurement of TBW and EE are routinely administered, after collecting a background urine sample, as a last consumption before the night. Our data show an underestimate of TBW measured with isotope dilution after 4 hours (in the morning), a discrepancy which increases with the size of TBW. No such relation and no significant differences were found after 10-hour (overnight) equilibration. The ratio between the dilution space for deuterium and oxygen-18 is higher than the earlier figure of 1.03, especially in adult subjects with a high body fat content. For an observation period of EE over two weeks, samples from the second and the last voiding on the first, mid, and last day of the observation period are collected. Differences in EE calculated from morning and evening samples within the first and second week allow detection of sampling errors and if so, samples are excluded from the final calculation. Differences of EE between weeks 1 and 2 allow a check for the consistency of the subjects' physical activity level and usually fall within 10% of the average EE over the total observation interval.

Joint erosions and patients with early rheumatoid arthritis

Abstract: The development of changes on X-rays in patients with rheumatoid arthritis (RA), as described in the literature, is presented. Prospective studies on patients with early disease show that approximately 75% of the patients have joint erosions. The majority of patients develop the first erosions during the first 2 yr of the disease. The rate of progression, expressed as newly eroded joints or increase in radiographic damage, is highest during the early years of the disease. Joints in the feet erode earlier than those in the hands. Moreover, more joints are affected in the feet than in the hands. Exact data on the involvement of large joints are scarce, but the progression of RA in small and large joints correlates well. Over half of the patients develop an involvement of the cervical spine during the first 10 yr of the disease. The percentage of patients with cervical subluxation increases steeply with disease duration.

Anal Dynamic Graciloplasty in the Treatment of Intractable Fecal Incontinence

Abstract: Background In patients with intractable fecal incontinence, conventional treatment is not always successful. Dynamic graciloplasty (transposition of the gracilis muscle to the anus with the implantation of stimulating electrodes) was developed to provide such patients with functional neosphincters. We evaluated the clinical results of this new surgical approach and the effects on quality of life. Methods We treated 52 patients with dynamic graciloplasty. The clinical results of treatment were evaluated in an interview, by anal manometry, and by enema testing. The degree of continence was scored. To assess quality of life, four questionnaires were administered (parts 1 and 2 of the Nottingham Health Profile, the State –Trait Anxiety Inventory, and the Self-rating Depression scale). Results Among the 52 patients, 38 (73 percent) were continent after a median follow-up of 2.1 years. At 52 weeks the patients' condition had improved with respect to the median frequency of defecation (from five to two times per...

Car Versus Public Transportation? The Role of Social Value Orientations in a Real-Life Social Dilemma1

Abstract: This research evaluates the role of social value orientations (i.e., preferences for distribution of outcomes for the self and others) in decisions as how to commute. It was proposed that the commuting situation could be viewed either as an environmental issue, reflecting the decision structure of an N-person Prisoner’s Dilemma, or as an accessibility problem, reflecting the decision structure of an N-person Chicken Dilemma. On the basis of interdependence theory (Kelley & Thibaut, 1978) it was predicted that people who are primarily concerned with the collective welfareprosocial individuals-would prefer commuting by public transportation when other commuters were expected to go by public transportation. On the other hand, it was hypothesized that people who are primarily concerned with their own well-beingproself individuals-would prefer commuting by public transportation when others were expected to go by car. The obtained findings were consistent with these expectations. Practical and theoretical implications regarding the link between social value orientations and environmentally relevant behavior will be discussed.

The Effect of Different Dosages of Caffeine on Endurance Performance Time

Abstract: The effect of different dosages of caffeine (0-5-9-13 mg.kg body weight-1) on endurance performance was examined. Nine well-trained cyclists participated in this study (VO2max 65.1 +/- 2.6 ml.kg-1.min-1). Caffeine capsules were administered in random order and double-blind. One hour after capsule ingestion, subjects cycled until exhaustion at 80% Wmax on an electromagnetically braked cycle ergometer. Blood samples were taken before, during and after the exercise test. Before and after the test a urine sample was obtained. A significant increase in endurance performance was found for all caffeine tests compared to placebo (endurance time 47 +/- 13, 58 +/- 11, 59 +/- 12 and 58 +/- 12 min for 0, 5, 9 and 13 mg.kg-1 body weight, respectively). No differences were found in endurance performance between the three caffeine dosages which indicates that no dose-response relation of caffeine and endurance performance was found. An increased free fatty acid and glycerol concentration was found after caffeine consumption compared with placebo. The mean urinary caffeine concentrations after exercise were 4.8 +/- 1.8, 8.9 +/- 5.2 and 14.9 +/- 6.9 micrograms.ml-1 urine for 5, 9 and 13 mg of caffeine.kg-1 body weight. Only the lowest dose of caffeine resulted in urine caffeine concentrations below the doping limit of the International Olympic Committee of 12 micrograms.ml-1 urine in all individuals. It is concluded that caffeine is an ergogenic aid that stimulates endurance performance. A dose-response relation between caffeine and endurance time was not found for the dose-range investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of vitamin K in bone metabolism.

Abstract: Vitamin K is a cofactor required for the formation of gamma-carboxyglutamate (Gla) residues in proteins. Osteoblasts produce at least three different Gla-containing proteins: osteocalcin, matrix Gla-protein, and protein S. After cellular secretion of these proteins, the main part of each remains bound to the hydroxyapatite matrix in bone, but their function remains unclear. Part of the newly synthesized osteocalcin is also set free into the bloodstream, where it may be used as a diagnostic marker for bone formation. Several studies have demonstrated that a poor vitamin K status is associated with an increased risk of osteoporotic bone fractures. Whether vitamin K supplementation will reduce the rate of bone loss in postmenopausal women remains a matter of debate.

The efficacy of traction for back and neck pain : a systematic, blinded review of randomized clinical trial methods

Abstract: Background and Purpose. The purpose of this study was to conduct a systematic analysis of the literature to assess the efficacy of traction for patients with neck or back pain. Subjects. For this purpose, randomized clinical trials comparing traction with other treatments were selected. Methods. A computer-aided search of the literature was conducted for relevant articles, followed by blinded assessment of the methods of the studies. The main outcome measures were (1) scoring for quality of the designated conduct of studies (based on a methodological checklist with four main categories: study population, interventions, measurement of effect, and data presentation) and the main conclusions of author(s) with regard to traction and (2) calculation of confidence intervals and power of the studies. Results. Only three studies scored more than 50 points (maximum score=100 points), suggesting that most of the selected studies were of poor quality. None of these three studies showed favorable results for traction. Only four studies, of which one scored more than 50 points, had an acceptable power (1−β>80%). Conclusion and Discussion. The available reports of studies on the efficacy of traction for back and neck pain do not allow clear conclusions due to the methodological flaws in their design and conduct. Most studies lacked power (1−β) due to small sample sizes. To date, no conclusions can be drawn about whether a specific traction modality for back or neck pain is effective, or more efficacious than other treatments. There are no clear indications, however, that traction is an ineffective therapy for back and neck pain. Further trials are needed in which much more attention should be paid to proper design and conduct, as well as to clear descriptions of crucial methodological features and results.

Discrimination between myocardial and skeletal muscle injury by assessment of the plasma ratio of myoglobin over fatty acid-binding protein.

Abstract: Background Myoglobin and fatty acid–binding protein (FABP) each are useful as early biochemical markers of muscle injury. We studied whether the ratio of myoglobin over FABP in plasma can be used to distinguish myocardial from skeletal muscle injury. Methods and Results Myoglobin and FABP were assayed immunochemically in tissue samples of human heart and skeletal muscle and in serial plasma samples from 22 patients with acute myocardial infarction (AMI), from 9 patients undergoing aortic surgery (causing injury of skeletal muscles), and from 10 patients undergoing cardiac surgery. In human heart tissue, the myoglobin/FABP ratio was 4.5 and in skeletal muscles varied from 21 to 73. After AMI, the plasma concentrations of both proteins were elevated between ≈1 and 15 to 20 hours after the onset of symptoms. In this period, the myoglobin/FABP ratio was constant both in subgroups of patients receiving and those not receiving thrombolytics and amounted to 5.3±1.2 (SD). In serum from aortic surgery patients, bo...

Increased resting energy expenditure and weight loss are related to a systemic inflammatory response in lung cancer patients

Abstract: PURPOSETo determine whether an increased resting energy expenditure (REE) and weight loss in lung cancer patients are related to a systemic inflammatory response.MATERIALS AND METHODSREE was measured by indirect calorimetry using a ventilated hood system. Soluble tumor necrosis factor receptor 55 (sTNF-R55) and sTNF-R75, soluble intercellular adhesion molecule (sICAM)-1, soluble E (sE)-selectin, lipopolysaccharide (LPS)-binding protein (LBP), interleukin (IL)-6, and TNF-alpha were measured using sandwich enzyme-linked immunosorbent assay (ELISA), and C-reactive protein (CRP) was measured by turbidimetry. A cross-sectional study was performed to compare inflammatory mediators between hypermetabolic (REE/Harris Benedict [HB] equation > or = 110%) versus normometabolic (REE/HB < 110%) patients and between patients who lost weight (more than 10% loss of preillness weight) versus those whose weight remained stable.RESULTSEighty-seven patients with primary non-small-cell lung cancer were consecutively entered o...