Showing papers by "Linköping University published in 1997"

Worldwide variations in prevalence of symptoms of allergic rhinoconjunctivitis in children: the International Study of Asthma and Allergies in Childhood (ISAAC)

Abstract: Background: As part of the International Study of Asthma and Allergies in Childhood (ISAAC), prevalence surveys were conducted among representative samples of school children from locations in Europe, Asia, Africa, Australasia, North and South America Subjects: 257,800 children aged 6-7 years from 91 centres in 38 countries, and 463,801 children aged 13-14 years from 155 centres in 56 countries Methods: Written symptom questionnaires were translated from English into the local language for self-completion by the 13-14-year-olds and completion by the parents of the 6-7-year-olds Rhinitis was described as a problem with sneezing, or a runny, or blocked nose when you (your child) DID NOT have a cold or the flu Additional questions were asked about rhinitis associated with itchy-watery eyes, interference with activities and a history of hay fever ever Results: The prevalence of rhinitis with itchy-watery eyes (“rhinoconjunctivitis”) in the past year varied across centres from 08%(to 149% in the 6-7-year-olds and from 14% to 397% in the 13-14-year-olds Within each age group, the global pattem was broadly consistent across each of the symptom categories In centres of higher prevalence there was great variability in the proportion of rhinoconjunctivitis labelled as hay fever The lowest prevalences of rhinoconjunctivitis were found in parts of eastern Europe south and central Asia High prevalences were reported from centres in several regions Conclusion: These results suggest substantial worldwide variations in the prevalence and labelling of symptoms of allergic rhinoconjunctivitis which require further study These differences, if real, may offer important clues to environmental influences on allergy

Low-Molecular-Weight Heparin (Fragmin) During Instability in Coronary Artery Disease (FRISC)

Abstract: This study evaluated whether the low-molecular-weight (LMW) heparin dalteparin sodium (Fragmin) had protective effects against cardiac events in aspirin-treated patients with unstable coronary artery syndromes. Patients (n = 1,506) with unstable angina or non-Q-wave myocardial infarction were randomized to double-blind, placebo-controlled treatment with LMW heparin. The treatment was given as subcutaneous injections: 120 U/kg body weight/12 hours during the first 5-7 days and 7,500 U once daily during the following 35-45 days. The primary endpoint, death or myocardial infarction after 6 days, showed a 3% (4.7%-1.7%) absolute and a 65% relative reduction in the LMW heparin group. There was a 6.8% (15.5%-8.7%) absolute and a 47% relative reduction of urgent revascularization or need for heparin or nitroglycerin infusions in combination with the primary endpoint. After 40 days there was an absolute reduction of death or myocardial infarction of 2.8% (10.7%-7.9%) and its combination with incapacitating angina was reduced by 5.9% (30.7%-24.8%). The survival analysis indicated a reactivation of the instability soon after lowering the dose at 5-7 days. With long-term follow-up, 3-4 months after termination of LMW heparin, the differences between groups were no longer statistically significant. However, the cumulative reduction in death, myocardial infarction, and revascularization because of incapacitating angina of 5.1% (25.3%-20.4%) was maintained. No cerebral and few major bleeds occurred. Compliance was adequate. Thus, subcutaneous LMW heparin protects against cardiac events in the acute phase of unstable coronary artery disease. The subcutaneous regimen also allows prolongation of treatment in the outpatient setting, which might maintain the initial benefits over a longer period.

System Level Hardware/Software Partitioning Based on Simulated Annealing and Tabu Search

Abstract: This paper presents two heuristics for automatic hardware/software partitioning of system level specifications. Partitioning is performed at the granularity of blocks, loops, subprograms, and processes with the objective of performance optimization with a limited hardware and software cost. We define the metric values for partitioning and develop a cost function that guides partitioning towards the desired objective. We consider minimization of communication cost and improvement of the overall parallelism as essential criteria during partitioning. Two heuristics for hardware/software partitioning, formulated as a graph partitioning problem, are presented: one based on simulated annealing and the other on tabu search. Results of extensive experiments, including real-life examples, show the clear superiority of the tabu search based algorithm.

New single-clock CMOS latches and flipflops with improved speed and power savings

Abstract: New dynamic, semistatic, and fully static single-clock CMOS latches and flipflops are proposed. By removing the speed and power bottlenecks of the original true-single-phase clocking (TSPC) and the existing differential latches and flipflops, both delays and power consumptions are considerably reduced. For the nondifferential dynamic, the differential dynamic, the semistatic, and the fully static flipflops, the best reduction factors are 1.3, 2.1, 2.2, and 2.4 for delays and 1.9, 3.5, 3.4, and 6.5 for power-delay products with an average activity ratio (0.25), respectively. The total and the clocked transistor numbers are decreased. In the new differential flipflops, clock loads are minimized and logic-related transistors are purely n-type in both n- and p-latches, giving additional speed advantage to this kind of CMOS circuits.

The Many Meanings of Occupational Competence and Qualification

Abstract: The last decade has witnessed an increasing focus, both in research and in the policy debate on human resource development (HRD) and work‐based education and training, as instruments for enhancing productivity, competitiveness, and economic growth. Unfortunately, the increasing interest in these issues has only, to a limited extent, been followed by more profound changes in existing practices concerning HRD, training and other forms of competence development in firms and agencies. Outlines a conceptual framework that might be used as a point of departure for theoretical and empirical analyses of the concepts of occupational competence and qualification, and of the role of HRD and vocational education and training (VET) in the formation of competences and in the promotion of social innovation.

Cloning of two candidate tumor suppressor genes within a 10 kb region on chromosome 13q14, frequently deleted in chronic lymphocytic leukemia.

Abstract: Previous studies have indicated the presence of a putative tumor suppressor gene on chromosome 13q14, commonly deleted in patients with B-cell chronic lymphocytic leukemia (B-CLL). We have previously defined a minimally deleted region of 130 kb centromeric to the marker D13S272, and constructed a PAC and cosmid contig encompassing this area. In the present study we have made a detailed restriction and transcriptional map of the region of interest. Using these tools we have screened a panel of 206 primary CLL clones and three cell lines. In five CLL cases we found limited deletions defining the region of interest to an area of no more than 10 kb. Two adjacent genes, termed Leu1 and Leu2 (leukemia-associated gene 1 and 2), were mapped to the minimally deleted region, with several patients showing deletion borders within these genes. The Leu1 and Leu2 genes show little homology to previously published genes at the nucleotide and expected translated amino acid sequence level. Mutational analysis of the Leu1 and 2 genes in 170 CLL samples revealed no small intragenic mutations or point mutations. However, in all cases of 13q14 loss examined, the first exon of both genes, which are only 300 bp apart, were deleted. We conclude that the Leu1 and Leu2 genes are strong candidates as tumor suppressor gene(s) involved in B-CLL leukemogenesis.

Direct SCF direct static-exchange calculations of electronic spectra

Abstract: Applications of the direct SCF direct static-exchange method are reviewed for three different types of systems (free molecules, polymers, and surface adsorbates) and for six types of spectroscopy (X-ray absorption-, -emission-, and -shake-up spectroscopy, ultraviolet photoelectron emission, X-ray Raman and circular dichroism spectroscopy.

Poly(3,4‐ethylenedioxythiophene) as Electrode Material in Electrochemical Capacitors

Abstract: We have investigated the conjugated polymer poly(3,4-ethylenedioxythiophene) as electrode material in electrochemical supercapacitor. The conjugated polymer is prepared by chemical polymerization in the form of thin films on nonconducting plastic substrates. One film is electrochemically reduced to the neutral state, while the other is kept in the as-prepared, doped state. The films are thin immersed in a liquid organic electrolyte. In the charged state the supercapacitor cell voltage is 0.8 V and the energy density is measured to 1 to 4 Wh/kg of active electrode material, depending on the current density used during discharge. The power density (delivered energy/discharge time) also depends on the current density and at the highest current densities investigated (1 mA/cm 2 ) it reaches 2.5 kW/kg of active electrode material.

Electronic structure of the GaAs:MnGa center

Abstract: The excitation spectrum of the 0.11-eV Mn acceptor in GaAs has been thoroughly investigated by uniaxial stress and Zeeman fourier transform infrared spectroscopy. The results give strong evidence for the ${3\mathrm{d}}^{5}$ +shallow hole model for the ${\mathrm{Mn}}^{0}$ center. The deformation potentials as well as the g values determined for the hole are in close agreement with those previously reported for the ${1\mathrm{S}}_{3\mathrm{/}2}$(${\mathrm{\ensuremath{\Gamma}}}_{8}$) state for shallow acceptors in GaAs. All experimental results are in accordance with a J=1 ground-state level derived from exchange coupling of the shallow ${1\mathrm{S}}_{3\mathrm{/}2}$(${\mathrm{\ensuremath{\Gamma}}}_{8}$) hole and the S=5/2 ${\mathrm{Mn}}^{\mathrm{\ensuremath{-}}}$ core. A splitting between J=2 and J=1 levels in the range from 9 to 12 meV is inferred and is considerably larger than the 2\char21{}3 meV splitting previously suggested

Posttraumatic stress reactions after emergency cesarean section

Abstract: Background. The study aimed at answering the following questions: Do women experience emergency cesarean section as traumatic?Do women experience any posttraumatic stress reactions or even posttrau...

High Temperature Sensors Based on Metal–Insulator–Silicon Carbide Devices

Abstract: High temperature gas sensors based on catalytic metal-insulator-silicon carbide (MISiC) devices are developed both as capacitors and Schottky diodes. A maximum operation temperature of 1000 degrees C is obtained for capacitors based on 4H-SiC, and all sensors work routinely for several weeks at 600 degrees C. Reducing gases like hydrocarbons and hydrogen lower the flat band voltage of the capacitor and the barrier height of the diode. The time constants for the gas response are in the order of milliseconds and because of this good performance the sensors are tested for combustion engine control. For temperatures around 600 degrees C total combustion occurs on the sensor surface and the signal is high for fuel in excess and low for air in excess. At temperatures around 400 degrees C the response is more linear. The high temperature operation causes interdiffusion of the metal and insulator layers in these devices; and this interdiffusion has been studied. At sufficiently high temperatures the inversion capacitance shows different levels for hydrogen free and hydrogen containing ambients, which is suggested to be due to a reversible hydrogen annealing effect at the insulator-silicon carbide interface.

Cost and effectiveness analysis of chiropractic and physiotherapy treatment for low back and neck pain. Six-month follow-up.

Abstract: Study design A randomized, clinical trial was conducted in which patients with back/neck problems, visiting a general practitioner, were allocated to chiropractic or physiotherapy as primary management. Objectives To compare outcome and costs of chiropractic and physiotherapy in managing patients with low back or neck pain. Summary of background data Earlier studies on the treatment of back pain by spinal manipulation have shown inconsistent results. When a "new" strategy--chiropractic--in the treatment of back pain was introduced in public health care in Sweden, there was a need to compare the effects and costs of chiropractic with the established physiotherapy. Methods Three hundred twenty-three patients aged 18 to 60 years who had no contraindications to manipulation and who had not been treated within the previous month were included in the study. Treatment was carried out at the discretion of the therapist. Outcome measures were primarily changes in pain intensity and general health, both assessed with visual analog scale and Oswestry pain disability questionnaire. Direct and indirect costs were measured. Results For patients with low back or neck pain visiting the general practitioner in primary care, both chiropractic and physiotherapy as primary treatment reduced the symptoms. No difference in outcome or direct or indirect costs between the two groups could be seen, nor in subgroups defined as duration, history, or severity. Conclusions The effectiveness and total costs of chiropractic or physiotherapy as primary treatment were similar to reach the same result after treatment and after 6 months.

Flavonoids as phospholipase A2 inhibitors: importance of their structure for selective inhibition of group II phospholipase A2.

Abstract: The inhibitory effect of the plant flavonoid, rutin, on group I phospholipase A2 (PLA2-I) from porcine pancreas and Naja naja, and on group II phospholipase A2 (PLA2-II) from Vipera russelli and Crotalus atrox was investigated. Rutin efficiently inhibited PLA2-II from both Vipera russelli and Crotalus atrox but was only a weak inhibitor of PLA2-I from porcine pancreas and Naja naja. The lack of strong inhibition of pancreatic PLA2-I was not due to contaminating proteins in the enzyme preparation, since the same weak inhibition was obtained against pancreatic PLA2 purified to homogeneity as judged by two-dimensional gel electrophoresis. Rutin also efficiently inhibited human PLA2-II from synovial fluid but was only a weak inhibitor of human PLA2-I from pancreatic juice, suggesting that rutin is a selective PLA2-I from porcine pancreas. The results obtained indicate that the hydroxyl group in 5-position as well as the double bond and the double-bonded oxygen in the oxane ring are all important for the overall ability of flavonoids to inhibit PLA2 activity, and that the hydroxyl groups in 3'- and 4'- position are required for selective inhibition of PLA2-II.

Cyclic HIV-1 Protease Inhibitors Derived from Mannitol: Synthesis, Inhibitory Potencies, and Computational Predictions of Binding Affinities

Abstract: Ten C2-symmetric cyclic urea and sulfamide derivatives have been synthesized from l-mannonic γ-lactone and d-mannitol. The results of experimental measurement of their inhibitory potencies against HIV-1 protease were compared to calculated free energies of binding derived from molecular dynamics (MD) simulations. The compounds were selected, firstly, to enable elucidation of the role of stereochemistry for binding affinity (1a−d) and, secondly, to allow evaluation of the effects of variation in the link to the P1 and P1‘ phenyl groups on affinity (1a and 2−5). Thirdly, compounds with hydrogen bond-accepting or -donating groups attached to the phenyl groups in the P2 and P2‘ side chains (6 and 7) were selected. Binding free energies were estimated by a linear response method, whose predictive power for estimating binding affinities from MD simulations was demonstrated.

In Vitro Plasma Protein Adsorption on ω-Functionalized Alkanethiolate Self-Assembled Monolayers

Abstract: In Vitro Plasma Protein Adsorption on -Functionalized Alkanethiolate Self-Assembled Monolayers

YopK of Yersinia pseudotuberculosis controls translocation of Yop effectors across the eukaryotic cell membrane.

Abstract: Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins a ...

Computing Circumscription Revisited: A Reduction Algorithm

Abstract: In recent years, a great deal of attention has been devoted to logics of common-sense reasoning. Among the candidates proposed, circumscription has been perceived as an elegant mathematical technique for modeling nonmonotonic reasoning, but difficult to apply in practice. The major reason for this is the second-order nature of circumscription axioms and the difficulty in finding proper substitutions of predicate expressions for predicate variables. One solution to this problem is to compile, where possible, second-order formulas into equivalent first-order formulas. Although some progress has been made using this approach, the results are not as strong as one might desire and they are isolated in nature. In this article, we provide a general method that can be used in an algorithmic manner to reduce certain circumscription axioms to first-order formulas. The algorithm takes as input an arbitrary second-order formula and either returns as output an equivalent first-order formula, or terminates with failure. The class of second-order formulas, and analogously the class of circumscriptive theories that can be reduced, provably subsumes those covered by existing results. We demonstrate the generality of the algorithm using circumscriptive theories with mixed quantifiers (some involving Skolemization), variable constants, nonseparated formulas, and formulas with n-ary predicate variables. In addition, we analyze the strength of the algorithm, compare it with existing approaches, and provide formal subsumption results.

Conjugated polymer surfaces and interfaces

Abstract: The doping of a conjugated polymer, polyacetylene, to a state of high electrical conductivity in 1977 marked a distinct step in interest in the electronic and transport properties of electrically conducting organic materials Since 1990, however, undoped semiconducting conjugated polymers have emerged as potentially useful electronic materials in a variety of electronic and optoelectronic applications In the context of polymer–based electronic device applications, it is of critical importance to understand the nature of the electronic structure of the polymer surface and the polymer–metal interface It has been shown that, especially for conjugated polymers, photoelectron spectroscopy provides a maximum amount of both chemical and electronic structural information within a single measurement technique This contribution contains an overview of some details of the early stages of interface formation with metals on the surfaces of conjugated polymers and model molecular solids, as studied using photoelectron spectroscopy The materials chosen are especially of interest in connection with polymer-based light emitting devices, or LEDs Specifically, the materials involved include poly( p –phenylenevinylene), or PPV, and a series of substituted PPVs, as well as a diphenylpolyene molecule for PPV, namely, α,ω–diphenyltetradecaheptaene Some general trends in the behaviour of light–metal atoms on the clean surfaces of conjugated polymers are pointed out Some consequences, based upon the information obtained in the studies reviewed, are highlighted Finally, two recent issues, which are studied by the methods used for the metal–on–polymer interfaces studies, are covered: the role of water vapour on the electronic structure of PPV; and the use of phase–separated polymer blends to increase the quantum efficiency of blue light emitting diodes

Ergonomics, quality and continuous improvement--conceptual and empirical relationships in an industrial context.

Abstract: This paper reviews the literature comparing the fields of ergonomics and quality, mainly in an industrial context, including mutual influences, similarities and differences. Relationships between ergonomics and the factors: work conditions, product design, ISO 9000, continuous improvements and TQM are reviewed in relation to the consequence, application, and process domains. The definitions of ergonomics and quality overlap substantially. Quality deficiencies, human errors and ergonomics problems often have the same cause, which in many cases can be traced to the design of work, workplace and environment e.g. noise, light, postures, loads, pace and work content. In addition, the possibility of performing to a high standard at work is an important prerequisite for satisfaction and well-being. Contradictions between the two fields have been identified in the view of concepts such as standardization, reduction of variability and copying of best practice, requiring further research. The field of quality would gain by incorporating ergonomics knowledge, especially in the areas of work design and human capability, since these factors are decisive for human performance and also therefore the performance of the systems involved. The field of ergonomics, on the other hand, would benefit from developing a stronger emphasis on methodologies and structures for improvement processes, including a clearer link with leadership and company strategies. Just as important is a further development of practicable participative ergonomics methods and tools for use at workplaces by the workers themselves, in order to integrate the top-down and the bottom-up processes and achieve better impact. Using participative processes for problem-solving and continuous improvement, focusing ergonomics and quality jointly has a great potential for improving working conditions and quality results simultaneously, and satisfying most of the interested parties.

Growth of SiC by Hot-Wall CVD and HTCVD

Abstract: A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The reactor concept is based on a hot-wall type susceptor which, due to the unique design, is very power efficient. Four different susceptors are discussed in terms of quality and uniformity of the grown material. The films are grown using the silane–propane–hydrogen system on off-axis (0001) 6H- and 4H-SiC substrates. Layers with doping levels in the low 1014 cm—3 showing strong free exciton emission in the photoluminescence spectra may readily be grown reproducibly in this system. The quality of the grown layers is also confirmed by the room temperature minority carrier lifetimes in the microsecond range and the optically detected cyclotron resonance data which give mobilities in excess of 100000 cm2/Vs at 6 K. Finally, a brief description will be given of the HTCVD technique which shows promising results in terms of high quality material grown at high growth rates.

The initial reactions of TiO2 with blood.

Abstract: The natural titanium oxide (TiO2) layer of commercial sheet titanium was dissolved in hydrofluoric acid. A new oxide layer was grown by oxidation in nitric acid or by annealing at 700 degrees C in air. At this temperature, reaction with nitrogen is unlikely. The purity of the oxidized sheet-titanium surfaces was investigated by Auger spectroscopy. The composition of both surfaces was TiO2 with carbon impurities. The carbon content of the acid-oxidized titanium was 20 +/- 2%, and the carbon content of the heat-oxidized titanium was 14 +/- 2% The initial reactions of the TiO2 surfaces with blood were investigated by short-time exposure to capillary blood and by detection of surface-adsorbed plasma proteins and cells with immunofluorescence. Antibodies specific to fibrinogen, complement factor C1q, prothrombin/thrombin, and platelet membrane antigen were used, and the fluorescence was quantitated by computer-aided image analysis. The results show that serine proteases are the dominating proteins adsorbed onto annealed titanium (C1q = 67 +/- 4.6; pt/t = 97 +/- 0.2; fib = 47 +/- 0.2). The adsorption of serine proteases was lower and the amount of fibrinogen was higher on the acid-oxidized surface (C1q = 46.3 +/- 2.6; pt/t = 25 +/- 2.9; fib = 64 +/- 0.7). Platelets adhered and spread on the annealed titanium surface within 5 sec of blood-material contact. The number of adhering platelets was higher on the acid-oxidized surface.

Avoided and avoidable risks of cancer.

Abstract: Despite the considerable efforts and funds devoted to cancer research over several decades, cancer still remains a mainly lethal disease. Cancer incidence and mortality have not declined at the same rate as other major causes of death, indicating that primary prevention remains a most valuable approach to decrease mortality. There is general agreement that environmental exposures are variously involved in the causation of the majority of cancer cases and that at least half of all cancers could be avoided by applying existing etiologic knowledge. There is disagreement, however, regarding the proportion of cancer risks attributable to specific etiological factors, including diet, occupation and pollution. Estimates of attributable risks are largely based today on unverified assumptions and the calculation of attributable risks involves taking very unequal evidence of various types of factors and treating them equally. Effective primary prevention resulting in a reduction of cancer risk can be obtained by: (i) a reduction in the number of carcinogens to which humans are exposed; or (ii) a reduction of the exposure levels to carcinogens. Exposure levels that could be seen as sufficiently low when based on single agents, may actually not be safe in the context of the many other concomitant carcinogenic and mutagenic exposures. The list of human carcinogens and of their target organs might be quite different if: (i) epidemiological data were available for a larger proportion of human exposures for which there is experimental evidence of carcinogenicity; (ii) more attention was paid to epidemiological evidence that is suggestive of an exposure-cancer association, but is less than sufficient, particularly in identifying target organs; and (iii) experimental evidence of carcinogenicity, supported by mechanistic considerations, were more fully accepted as predictions of human risk.

Skeletal Muscle Fatigue and Endurance in Young and Old Men and Women

Abstract: The effects of increasing age on skeletal muscle fatigue and endurance were assessed in 22 healthy young (14 men and 8 women; mean age, 28 +/- 6 years) and 16 healthy old (8 men and 8 women; mean age, 73 +/- 3 years) individuals. All subjects performed 100 repeated maximum dynamic knee extensions at 90 degrees.s-1 (1.57 rad.s-1) using an isokinetic dynamometer (Cybex II). Peak torque was recorded during every contraction, and for each individual the maximal voluntary contraction (MVC), the fatigue rate, the endurance level, and the relative reduction in muscle force were determined. MVC and endurance level were significantly lower in old men and women, but there was no discernible difference in relative muscle force reduction and fatigue rate between young and old individuals. We conclude that thigh muscles of older individuals are weaker than those of younger individuals, but relative to their strength, older individuals have similar properties as younger individuals with respect to muscle fatigue and endurance.