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Anders Persson

Publications and source records attributed to Anders Persson.

12 recordsLinked to original sources
PubMed2006

High-intensity laser-driven proton acceleration: influence of pulse contrast.

Proton acceleration from the interaction of ultra-short laser pulses with thin foil targets at intensities greater than 10(18) W cm(-2) is discussed. An overview of the physical processes giving rise to the generation of protons with multi-MeV energies, in well defined beams with excellent spatial quality, is presented. Specifically, the discussion centres on the influence of laser pulse contrast on the spatial and energy distributions of accelerated proton beams. Results from an ongoing experimental investigation of proton acceleration using the 10 Hz multi-terawatt Ti:sapphire laser (35f s, 35 TW) at the Lund Laser Centre are discussed. It is demonstrated that a window of amplified spontaneous emission (ASE) conditions exist, for which the direction of proton emission is sensitive to the ASE-pedestal preceding the peak of the laser pulse, and that by significantly improving the temporal contrast, using plasma mirrors, efficient proton acceleration is observed from target foils with thickness less than 50 nm.

Journal Article↗
PubMed2006

Research ethics and the development of medical biotechnology.

Commercial funding is of most importance for the development of new biomedical technologies such as xenotransplantation. The dependence of such funding may, however, carry certain risks from an ethical point of view. In this article some of these risks are exemplified and it is argued that the adherence to basic research ethical norms are of vital importance for the field of xenotransplantation to develop properly.

Animals↗
PubMed2006

Leachability testing of sludge from street gullies.

Sludge from gullies, on two types of streets with different traffic intensity, was investigated using two recommended EU methods for leachability testing of waste: a two-stage batch test and an up-flow percolation test. The main purpose of this investigation was to gain more knowledge about these leaching test methods to be able to make future decisions on the general applicability of the proposed tests. A number of parameters were determined in the sludge as well as in the eluates obtained from the two leaching tests. These include pH, conductivity, dissolved organic carbon and inorganic ions as chloride ions. A number of metals as Cd, Cr, Cu, Hg, Ni and Zn, were determined by inductive coupled plasmamass spectrometry and organic compounds were screened by high performance liquid chromatography-diode array UV detection and gas chromatography-mass spectrometry. It was found that the concentrations of metals and organic compounds in the sludge were several orders of magnitudes higher than the actual eluate concentrations. For all metals the concentrations were well below the proposed limit values for non-hazardous waste included in the Council decision document 2003/33/EC. Generally, concentrations obtained in batch test were equal or higher than from percolation tests. The repeatability of the percolation and the batch test were in average 28 and 17%, respectively.

Refuse Disposal↗
PubMed2006

Linking patch-use behavior, resource density, and growth expectations in fish.

Optimality theory rests on the assumptions that short-term foraging decisions are driven by variation in environmental quality, and that these decisions have important implications for long-term fitness. These assumptions, however, are rarely tested in a field setting. We linked behavioral foraging decisions in food patches with measures of environmental quality covering larger spatial (resource density) or temporal (growth parameters) scales. In 10 lakes, we measured the food density at which benthic fish give up foraging in experimental food patches (giving-up density, GUD), quantified the biomass of benthic invertebrates, and calculated the maximum individual size (L(infinity)) of bream (Abramis brama L.), a typical benthivore in these lakes. We found positive relationships between resource density and both GUD and L(infinity), and a positive relationship between L(infinity) and GUD. Prey characterized as vulnerable to predation contributed most to the relationships between resource density and either GUD or L(infinity). A path analysis showed that resource density and L(infinity) directly explained 54% and 28%, respectively, of the variation in GUD, whereas 86% of the variation in L(infinity) was explained by resource density, with mostly indirect contribution from GUD. We conclude that the short-term foraging behavior of benthivores matched our expectations based on optimality theory by being positively linked to variables on environmental quality operating at both a larger spatial scale and a longer temporal scale.

Animals↗
PubMed2005

The effects of spatial food distribution and group size on foraging behaviour in a benthic fish.

Animals foraging in heterogeneous environments benefit from information on local resource density because it allows allocation of foraging effort to rich patches. In foraging groups, this information may be obtained by individuals through sampling or by observing the foraging behaviour of group members. We studied the foraging behaviour of goldfish (Carassius auratus) groups feeding in pools on resources distributed in patches. First, we determined if goldfish use sampling information to distinguish between patches of different qualities, and if this allowed goldfish to benefit from a heterogeneous resource distribution. Then, we tested if group size affected the time dedicated to food searching and ultimately foraging success. The decision of goldfish to leave a patch was affected by whether or not they found food, indicating that goldfish use an assessment rule. Giving-up density was higher when resources were highly heterogeneous, but overall gain was not affected by resource distribution. We did not observe any foraging benefits of larger groups, which indicate that grouping behaviour was driven by risk dilution. In larger groups the proportion searching for food was lower, which suggests interactions among group members. We conclude that competition between group members affects individual investments in food searching by introducing the possibility for alternative strategies, such as scrounging or resource monopolisation.

Animals↗
PubMed2005

Amplitude and phase control of attosecond light pulses.

We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms.

Journal Article↗
PubMed2003

Comparative genome- and proteome analysis of cerebral cortex from MK-801-treated rats.

cDNA microarrays and two-dimensional gel-electrophoresis in combination with mass spectrometry, were used to screen alterations in mRNA and protein levels, respectively, in cerebral cortex of MK-801-treated rats. The rats were divided in two groups; group 1 (short-term treated) and group 2 (long-term treated). In group 1, four genes were up-regulated and five down-regulated. In group 2, seven genes were up-regulated and six down-regulated. In group 1, the levels of one protein was increased and eight proteins reduced. In group 2, the levels of two proteins were increased and four proteins reduced. Several of the altered genes (casein kinase 2, glutamic acid decarboxylase, synaptotagmin, gamma aminobutyric acid [GABA] transporter, creatine kinase, and cytochrome c oxidase) and proteins (superoxide dismutase, hsp 60, hsp 72 and gamma-enolase) have previously been connected to schizophrenia. Alterations of the genes (microglobulin, c-jun proto-oncogene, 40S ribosomal protein S19, adenosine diphosphate (ADP)-ribosylation factors, platelet-derived growth factor, fructose-bisphophate aldolase A, and myelin proteolipid) and the proteins (stathmin, H+-transp. Adenosine triphosphate (ATP) synthase, pyruvate dehydrogenase, beta-actin and alpha-enolase), have not, to our knowledge, earlier been implicated in schizophrenia pathology. Overall, these results with a combined approach of genomics and proteomics add to the validity of subchronic N-methyl-D-aspartate (NMDA)-receptor antagonist treatment as an animal model of schizophrenia.

Animals↗
PubMed2002

Budesonide CIR capsules (once or twice daily divided-dose) in active Crohn's disease: a randomized placebo-controlled study in the United States.

OBJECTIVES: Budesonide controlled ileal release (CIR) capsules deliver budesonide, a glucocorticosteroid with high topical and low systemic activity, to the distal ileum and the proximal colon. In four previous controlled trials in Crohn's disease, remission rates ranged from 51% to 69%. We sought to evaluate the efficacy and safety of this drug in a population of patients in the United States with Crohn's disease. METHODS: In this multicenter, double blind, randomized trial, 200 patients in the United States with mild to moderate Crohn's disease (Crohn's Disease Activity Index [CDAI] between 200 and 450) involving the distal ileum and/or ascending colon received 9 mg of budesonide CIR once daily, 4.5 mg b.i.d., or placebos for 8 wk. The primary outcome was remission defined by a CDAI of 150 or less. RESULTS: Remission was achieved in 48%, 53%, and 33% with 9 mg once daily, 4.5 mg b.i.d., and placebos, respectively, after 8 wk of treatment. Differences between the groups were not significant. The differences in mean change from baseline CDAI between the combined budesonide and placebo groups was significant (p < 0.05). There was no difference in observed adverse events between treatment groups, although a modest decrease in plasma cortisol levels was observed relative to the placebo (p < 0.01). CONCLUSIONS: Treatment of symptomatic Crohn's disease with budesonide CIR capsules (9 mg daily) was safe, and remission rates were similar to those achieved in previous trials. Although the remission rate did not significantly differ from the placebo response in this study, there was a significant change in the mean CDAI from baseline in the combined treatment groups relative to the placebo.

Adult↗
PubMedDate not supplied

Full body virtual autopsies using a state-of-the-art volume rendering pipeline.

This paper presents a procedure for virtual autopsies based on interactive 3D visualizations of large scale, high resolution data from CT-scans of human cadavers. The procedure is described using examples from forensic medicine and the added value and future potential of virtual autopsies is shown from a medical and forensic perspective. Based on the technical demands of the procedure state-of-the-art volume rendering techniques are applied and refined to enable real-time, full body virtual autopsies involving gigabyte sized data on standard GPUs. The techniques applied include transfer function based data reduction using level-of-detail selection and multi-resolution rendering techniques. The paper also describes a data management component for large, out-of-core data sets and an extension to the GPU-based raycaster for efficient dual TF rendering. Detailed benchmarks of the pipeline are presented using data sets from forensic cases.

Algorithms↗
PubMedDate not supplied

The ADL ability and use of technical aids in persons with late effects of polio.

OBJECTIVE: The purpose of this study was to describe functional performance in activities of daily living (ADL) and the use of technical aids among persons with late effects of polio. METHOD: Abilities in ADL of 150 participants 20 to 82 years of age were assessed with the Sunnaas Index of ADL, and the participants' use of technical aids was recorded. RESULTS: The activities in which most participants were independent were eating, daily hygiene, and communication. Many needed technical aids, adaptation of their homes, or both to perform mobility-related activities and to dress or undress, take a bath or shower, cook, or manage toilet visits. In total, 86 (57%) used mobility aids such as canes, crutches, and walkers. Thirty-one (21%) used wheelchairs within or outside the home. Bath and shower aids were the most commonly used technical aids other than mobility aids. The activity where most participants depended on others was housework. CONCLUSION: In spite of their disabilities, most participants performed well in many ADL, functioning independently by using technical aids and by living in an adapted environment.

Activities of Daily Living↗