Showing papers by "Uppsala University published in 1996"

Ecological immunology: costly parasite defences and trade-offs in evolutionary ecology

Abstract: In the face of continuous threats from parasites, hosts have evolved an elaborate series of preventative and controlling measures - the immune system - in order to reduce the fitness costs of parasitism. However, these measures do have associated costs. Viewing an individual's immune response to parasites as being subject to optimization in the face of other demands offers potential insights into mechanisms of life history trade-offs, sexual selection, parasite-mediated selection and population dynamics. We discuss some recent results that have been obtained by practitioners of this approach in natural and semi-natural populations, and suggest some ways in which this field may progress in the near future.

Hypertension and Associated Metabolic Abnormalities — The Role of Insulin Resistance and the Sympathoadrenal System

Abstract: Abnormalities of glucose, insulin, and lipoprotein metabolism are common in patients with hypertension. These changes can also be discerned in normotensive first-degree relatives of hypertensive patients. They are not present in patients with secondary forms of hypertension, do not necessarily improve when blood pressure is lowered pharmacologically, and may even be made worse by some forms of antihypertensive treatment. These metabolic abnormalities may play a part in both the pathogenesis and the complications of hypertension in many patients. We hypothesize that the metabolic abnormalities are linked to the hypertension by a pathophysiologic process that involves the sympathoadrenal system and exerts . . .

Testing differentiation in diploid populations

Abstract: We examine the power of different exact tests of differentiation for diploid populations. Since there is not necessarily random mating within populations, the appropriate hypothesis to construct exact tests is that of independent sampling of genotypes. There are two categories of tests, Fsrestimator tests and goodness of fit tests. In this latter category, we distinguish “allelic statistics”, which account for the nature of alleles within genotypes, from “genotypic statistics” that do not. We show that the power of Fs+stimator tests and of allelic goodness of fit tests are similar when sampling is balanced, and higher than the power of genotypic goodness of fit tests. When sampling is unbalanced, the most powerful tests are shown to belong to the allelic goodness of fit group.

Spectroscopy Made Easy: A New Tool for Fitting Observations with Synthetic Spectra

Abstract: We describe a new software package that may be used to determine stellar and atomic parameters by matching observed spectra with synthetic spectra generated from parameterized atmospheres. A nonlinear least squares algorithm is used to solve for any subset of allowed parameters, which include atomic data (loggf and van der Waals damping constants), model atmosphere specications (Te ,l og g), elemental abundances, and radial, turbulent, and rotational velocities. LTE synthesis software handles discontiguous spectral intervals and complex atomic blends. As a demonstration, we t 26 Fe I lines in the NSO Solar Atlas (Kurucz et al. 1984), determining various solar and atomic parameters.

Relation of size at birth to non-insulin dependent diabetes and insulin concentrations in men aged 50-60 years

Abstract: Objective: To establish whether the relation between size at birth and non-insulin dependent diabetes is mediated through impaired β cell function or insulin resistance. Design: Cohort study. Setting: Uppsala, Sweden. Subjects: 1333 men whose birth records were traced from a cohort of 2322 men born during 1920-4 and resident in Uppsala in 1970. Main outcome measures: Intravenous glucose tolerance test at age 50 years and non-insulin dependent diabetes at age 60 years. Results: There was a weak inverse correlation (r=-0.07, P=0.03) between ponderal index at birth and 60 minute insulin concentrations in the intravenous glucose tolerance test at age 50 years. This association was stronger (r=-0.19, P=0.001) in the highest third of the distribution of body mass index than in the other two thirds (P=0.01 for the interaction between ponderal index and body mass index). Prevalence of diabetes at age 60 years was 8% in men whose birth weight was less than 3250 g compared with 5% in men with birth weight 3250 g or more (P=0.08; 95% confidence interval for difference −0.3% to 6.8%). There was a stronger association between diabetes and ponderal index: prevalence of diabetes was 12% in the lowest fifth of ponderal index compared with 4% in the other four fifths (P=0.001; 3.0% to 12.6%). Conclusion: These results confirm that reduced fetal growth is associated with increased risk of diabetes and suggest a specific association with thinness at birth. This relation seems to be mediated through insulin resistance rather than through impaired β cell function and to depend on an interaction with obesity in adult life.

Armaments and ornaments: an evolutionary explanation of traits of dual utility

Abstract: Secondary sexual characters in many species function both in male-male competition and as cues for female choice. Based on a literature compilation of existing knowledge of traits with this dual fu ...

The dynamics of operational sex ratios and competition for mates.

Abstract: In sexually reproducing animals, individuals of one sex may have to compete for access to mating partners of the opposite sex. The operational sex ratio (OSR) is central in predicting the intensity of mating competition and which sex is competing for which. Thanks to recent theoretical and empirical advances, particularly by exploring the concept of OSR, sexual selection studies today are becoming more fine-tuned and dynamic. The original role of parental investment in predicting sexual selection has recently been complemented by the use of sexual differences in potential reproductive rates (PRR).

UPPAAL—a tool suite for automatic verification of real-time systems

Abstract: Uppaal is a tool suite for automatic verification of safety and bounded liveness properties of real-time systems modeled as networks of timed automata. It includes: a graphical interface that supports graphical and textual representations of networks of timed automata, and automatic transformation from graphical representations to textual format, a compiler that transforms a certain class of linear hybrid systems to networks of timed automata, and a model-checker which is implemented based on constraint-solving techniques. Uppaal also supports diagnostic model-checking providing diagnostic information in case verification of a particular real-time systems fails.

The risk of stomach cancer in patients with gastric or duodenal ulcer disease.

Abstract: Background Helicobacter pylori infection, now considered to be a cause of gastric cancer, is also strongly associated with gastric and duodenal ulcer disease. The discovery of these relations has brought the long-controversial connection between peptic ulcers and gastric cancer into focus. Methods We estimated the risk of stomach cancer in a large cohort of hospitalized patients with gastric or duodenal ulcers, as recorded in the Swedish Inpatient Register between 1965 and 1983. Altogether, 57,936 patients were followed through 1989, for an average of 9.1 years. The standardized incidence ratio — the ratio of the observed number of cancers to the number expected on the basis of the incidence in the Swedish population at large — was used as a measure of relative risk. Results After peaking in the first 3 years of follow-up, the standardized incidence ratio for gastric cancer among 29,287 patients with gastric ulcers leveled off at 1.8 (95 percent confidence interval, 1.6 to 2.0) and remained significantly ...

Cohort studies of fat intake and the risk of breast cancer--a pooled analysis.

Abstract: Background. Experiments in animals, international correlation comparisons, and case-control studies support an association between dietary fat intake and the incidence of breast cancer. Most cohort studies do not corroborate the association, but they have been criticized for involving small numbers of cases, homogeneous fat intake, and measurement errors in estimates of fat intake. Methods. We identified seven prospective studies in four countries that met specific criteria and analyzed the primary data in a standardized manner. Pooled estimates of the relation of fat intake to the risk of breast cancer were calculated, and data from study-specific validation studies were used to adjust the results for measurement error. Results. Information about 4980 cases from studies including 337,819 women was available. When women in the highest quintile of energy-adjusted total fat intake were compared with women in the lowest quintile, the multivariate pooled relative risk of breast cancer was 1.05 (95 percent confidence interval, 0.94 to 1.16). Relative risks for saturated, monounsaturated, and polyunsaturated fat and for cholesterol, considered individually, were also close to unity. There was little overall association between the percentage of energy intake from fat and the risk of breast cancer, even among women whose energy intake from fat was less than 20 percent. Correcting for error in the measurement of nutrient intake did not materially alter these findings. Conclusions. We found no evidence of a positive association between total dietary fat intake and the risk of breast cancer. There was no reduction in risk even among women whose energy intake from tat was less than 20 percent of total energy intake. In the context of the Western lifestyle, lowering the total intake of fat in midlife is unlikely to reduce the risk of breast cancer substantially. Chemicals/CAS: Dietary Fats

Relation Between Troponin T and the Risk of Subsequent Cardiac Events in Unstable Coronary Artery Disease

Abstract: Background Early risk assessment is important in patients with unstable coronary artery disease, ie, unstable angina or non–Q-wave myocardial infarction. Some previous small studies have indicated that patients with unstable angina and elevation of troponin T (tn-T) have worse short-term and long-term prognoses. In this study, the prognostic value of tn-T was evaluated and compared with other early available risk indicators. Methods and Results Nine hundred seventy-six patients participating in a randomized study of low-molecular-weight heparin in unstable coronary artery disease were followed for 5 months after the index episode. The risk of cardiac events increased with increasing maximal levels of tn-T obtained in the initial 24 hours. The lowest quintile (<0.06 μg/L) constituted a low-risk group, the second quintile (0.06 to 0.18 μg/L) an intermediate-risk group, and the three highest quintiles (≥0.18 μg/L) a high-risk group, with 4.3%, 10.5%, and 16.1% risk of either myocardial infarction or cardiac ...

Efficient mixed-spectrum estimation with applications to target feature extraction

Abstract: We present a decoupled parameter estimation (DPE) algorithm for estimating sinusoidal parameters from both 1-D and 2-D data sequences corrupted by autoregressive (AR) noise. In the first step of the DPE algorithm, we use a relaxation (RELAX) algorithm that requires simple fast Fourier transforms (FFTs) to obtain the estimates of the sinusoidal parameters. We describe how the RELAX algorithm may be used to extract radar target features from both 1-D and 2-D data sequences. In the second step of the DPE algorithm, a linear least-squares approach is used to estimate the AR noise parameters. The DPE algorithm is both conceptually and computationally simple. The algorithm not only provides excellent estimation performance under the model assumptions, in which case the estimates obtained with the DPE algorithm are asymptotically statistically efficient, but is also robust to mismodeling errors.

Business Networks and Cooperation in International Business Relationships

Abstract: Cooperative relationships between firms can be better understood if they are examined in the context of a network of connected business relationships. Based on research on business relationships and business networks, this paper formulates a LISREL model that analyses cooperation in international business relationships between suppliers and customer firms. Theory suggests that cooperation can raise the value of business relationships, and that business network connections have an impact on cooperation. The model is investigated in a sample of 136 international business relationships. The analysis shows that relationship profitability is directly affected by relationship commitment and, indirectly through commitment, by business network connections.

Review of Some Basic Characteristics of the Atmospheric Surface Layer

Abstract: Some of the fundamental issues of surface layer meteorology are critically reviewed For the von Karman constant (k), values covering the range from 032 to 065 have been reported Most of the data are, however, found in a rather narrow range between 039 and 041 Plotting all available atmospheric data against the so-called roughness Reynolds number, Reo = u * z 0/v or against the surface Rossby number, Ro0 = G/f z 0 gives no clear indication of systematic trend It is concluded that k is indeed constant in atmospheric surface-layer flow and that its value is the same as that found for laboratory flows, ie about 040

Use of non-crystallographic symmetry in protein structure refinement.

Abstract: Several methods to assess the (dis)similarity of protein structures objectively are described, some of which, when applied to non-crystallographically related protein models, are able to discriminate between significant differences and `random noise'. Some of these methods have been used to investigate a sample of several hundred protein structures which have been solved by means of X-ray crystallography in order to investigate the extent to which non-crystallographically related protein models differ from one another. It is shown that the extent of such differences is largely dependent on the resolution of the data used for the determination and refinement of the structure and, measured by some statistics, even varies essentially linearly with the resolution. The implications of these findings for the strategies used to refine structures with non-crystallographic symmetry, in particular at low resolution, are discussed. Finally, two examples are given of recent structure determinations from this laboratory in which the presence (and employment) of non-crystallographic symmetry was crucial to the solution and refinement of the structure.

Synchronized terrestrial-atmospheric deglacial records around the North Atlantic

Abstract: On the basis of synchronization of three carbon-14 (C-14)-dated lacustrine sequences from Sweden With tree ring and ice core records, the absolute age of the Younger Dryas-Preboreal climatic shift was determined to be 11,450 to 11,390 +/- 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising Delta(14)C values, is evident in all records and indicates an ocean ventilation change. This cooling is similar to earlier deglacial coolings, and box-model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the North Atlantic heat conveyor, although the Younger Dryas may have begun as an anomalous meltwater event.

Flora of Ethiopia and Eritrea

Abstract: After several years of planning and fund-hunting the Flora of Ethiopia project was launched in 1980, funded by SAREC (Swedish Agency for Research Cooperation with Developing Countries) with the aim of producing a Flora of Ethiopia, training of Ethiopian students to Ph.D. in Systematic Botany, and strengthening the National Herbarium in Addis Ababa and its library. Four Ethiopian botanists have now received their Ph.D. in Uppsala and a considerable number of collections has been added in the National Herbarium. Vol. 3 of the Flora was published in 1989 and thanks to the combined efforts of many botanists accounts for most of the remaining families for Flora of Ethiopia are now available in a more or less finalized version.

Emotional Expression in Music Performance: Between the Performer's Intention and the Listener's Experience:

Abstract: Nine professional musicians were instructed to perform short melodies using various instruments - the violin, electric guitar, flute, and singing voice - so as to communicate specific emotional characters to listeners. The performances were first validated by having listeners rating the emotional expression and then analysed with regard to their physical characteristics, e.g. tempo, dynamics, timing, and spectrum. The main findings were that (a) the performer's expressive intention had a marked effect on all analysed variables; (b) the performers showed many similarities as well as individual differences in emotion encoding; (c) listeners were generally successful in decoding the intended expression; and (d) some emotional characters seemed easier to communicate than others. The reported results imply that we are unlikely to find performance rules independent of instrument, musical style, performer, or listener.

General decidability theorems for infinite-state systems

Abstract: Over the last few years there has been an increasing research effort directed towards the automatic verification of infinite state systems. This paper is concerned with identifying general mathematical structures which can serve as sufficient conditions for achieving decidability. We present decidability results for a class of systems (called well-structured systems), which consist of a finite control part operating on an infinite data domain. The results assume that the data domain is equipped with a well-ordered and well-founded preorder such that the transition relation is "monotonic" (is a simulation) with respect to the preorder. We show that the following properties are decidable for well-structured systems: reachability; eventuality; and simulation. We also describe how these general principles subsume several decidability results from the literature about timed automata, relational automata, Petri nets, and lossy channel systems.

The structure and function of hyaluronan: An overview

Abstract: Hyaluronan is a major component of synovial tissue and fluid as well as other soft connective tissues. It is a high-Mr polysaccharide which forms entangled networks already at dilute concentrations (< 1 mg/mL) and endows its solutions with unique rheological properties. Physiological functions of hyaluronan (lubrication, water homeostasis, macromolecular filtering, exclusion, etc.) have been ascribed to the properties of these networks. Recently a number of specific interactions between hyaluronan and a group of proteins named hyaladherins have also pointed towards a role of hyaluronan in recognition and the regulation of cellular activities. Many more or less well documented hypotheses have been proposed for the function of hyaluronan in joints, for example, that it should lubricate, protect cartilage surfaces, scavenge free radicals and debris, keep the joint cavities open, form flow barriers in the synovium and prevent capillary growth.

Studies on the role of the Arabidopsis gene MONOPTEROS in vascular development and plant cell axialization.

Abstract: In the embryo of Arabidopsis thaliana (L.) Heynh., formation of the hypocotyl/root axis is initiated at the early-globular stage, recognizable as oriented expansion of formerly isodiametric cells. The process depends on the activity of the gene MONOPTEROS (MP); mp mutant embryos fail to produce hypocotyl and radicle. We have analyzed the morphology and anatomy of mp mutant plants throughout the Arabidopsis life cycle. Mutants form largely normal rosettes and root systems, but inflorescences either fail to form lateral flowers or these flowers are greatly reduced. Furthermore, the auxin transport capacity of inflorescence axes is impaired and the vascular strands in all analyzed organs are distorted. These features of the mutant phenotype suggest that the MP gene promotes cell axialization and cell file formation at multiple stages of plant development.

Heparan sulfate: a piece of information.

Abstract: The sulfated glycosaminoglycans, heparan sulfate and heparin, are increasingly implicated in cell-biological processes such as cytokine action, cell adhesion, and regulation of enzymic catalysis. These activities generally depend on interactions of the polysaccharides with proteins, mediated by distinct saccharide sequences, and expressed at various levels of specificity, selectivity, and molecular organization. The formation of heparin/ heparan sulfate in the cell requires an elaborate biosynthetic machinery, that is conceived in terms of a novel model of glycosaminoglycan assembly and processive modification. Recent advances in the identification and molecular analysis of the enzymes and other proteins involved in the biosynthesis provide novel tools to study the regulation of the process, presently poorly understood, at the subcellular and cellular levels. The potential medical importance of heparin-related compounds is likely to promote the biotechnological exploitation of components of the biosynthetic machinery.

An adaptive filtering approach to spectral estimation and SAR imaging

Abstract: We present an adaptive FIR filtering approach, which is referred to as the amplitude and phase estimation of a sinusoid (APES), for complex spectral estimation. We compare the APES algorithm with other FIR filtering approaches including the Welch (1967) and Capon (1969) methods. We also describe how to apply the FIR filtering approaches to target range signature estimation and synthetic aperture radar (SAR) imaging. We show via both numerical and experimental examples that the adaptive FIR filtering approaches such as Capon and APES can yield more accurate spectral estimates with much lower sidelobes and narrower spectral peaks than the FFT method, which is also a special case of the FIR filtering approach. We show that although the APES algorithm yields somewhat wider spectral peaks than the Capon method, the former gives more accurate overall spectral estimates and SAR images than the latter and the FFT method.

Increase in Testicular Cancer Incidence in Six European Countries: a Birth Cohort Phenomenon

Abstract: Background: For unknown reasons, the age-standardized incidence of testicular cancer has shown a rapid increase in virtually all countries (mostly Western) studied. For populations with a sufficiently long period of cancer registration, this development c