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- Baureus Koch, Catrin, et al.
(author)
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Interaction between weak low frequency magnetic fields and cell membranes.
- 2003
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In: Bioelectromagnetics. - : Wiley. - 0197-8462. ; 24:6, s. 395-402
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Journal article (peer-reviewed)abstract
- The question of whether very weak low frequency magnetic fields can affect biological systems, has attracted attention by many research groups for quite some time. Still, today, the theoretical possibility of such an interaction is often questioned and the site of interaction in the cell is unknown. In the present study, the influence of extremely low frequency (ELF) magnetic fields on the transport of Ca2+ was studied in a biological system consisting of highly purified plasma membrane vesicles. We tested two quantum mechanical theoretical models that assume that biologically active ions can be bound to a channel protein and influence the opening state of the channel. Vesicles were exposed for 30 min at 32 °C and the calcium efflux was studied using radioactive 45Ca as a tracer. Static magnetic fields ranging from 27 to 37 T and time varying magnetic fields with frequencies between 7 and 72 Hz and amplitudes between 13 and 114 T (peak) were used. We show that suitable combinations of static and time varying magnetic fields directly interact with the Ca2+ channel protein in the cell membrane, and we could quantitatively confirm the model proposed by Blanchard. Bioelectromagnetics 24:395-402, 2003. © 2003 Wiley-Liss, Inc.
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| 3. |
- Blaudez, D., et al.
(author)
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Differential responses of ectomycorrhizal fungi to heavy metals in vitro
- 2000
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In: Mycological Research. - : Elsevier. - 0953-7562 .- 1469-8102. ; 104:11, s. 1366-1371
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Journal article (peer-reviewed)abstract
- Thirty-nine ectomycorrhizal isolates of Paxillus involutus, Pisolithus tinctorius, Suillus bovinus, S. luteus and S. variegatus were tested on cadmium, copper, nickel and zinc amended media to determine their in vitro tolerance, measured as inhibition of biomass production. Twenty-one isolates were from heavy metal polluted sites, whereas the others were from non-contaminated soils. There was a strong interspecific variation in metal tolerance. S. luteus, S. variegatus and P. tinctorius were more tolerant of Cu, Cd and Zn when compared with P. involutus, whereas the reverse was true for Ni. A high intraspecific heterogeneity in metal tolerance was also found. EC50 values for isolates originating from polluted sites were not statistically different from EC50 values for isolates originating from non-contaminated sites. The findings are discussed in relation to the potential benefits of ectomycorrhizal fungi in protecting their host plants from metal contamination.
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| 4. |
- Jacob, AP, et al.
(author)
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Ultrathin oxynitridation process through ion implantation in a poly Si1-xGex gate MOS capacitor
- 2003
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In: Materials Science in Semiconductor Processing. - : Elsevier Science B.V., Amsterdam.. - 1369-8001 .- 1873-4081. ; 6:03-Jan, s. 37-41
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Journal article (peer-reviewed)abstract
- Effect of temperature and time of heat treatment on the distribution of ion-implanted nitrogen in poly Si0.65Ge0.35 gate MOS samples was studied. Secondary ion mass spectrometry (SIMS) was used for the qualitative analysis of the nitrogen distribution. Rapid thermal processing was carried out for a temperature range of 950-1070degreesC for the redistribution of ions. The nitrogen implantation doses were 5 x 10(14) cm(-2), 2 x 10(15) cm(-2) and 5 x 10(15) cm(-2), all with an implantation energy of 50 keV. For a uniform distribution of nitrogen in the SiO2 region, an optimal temperature at a well calibrated time must be applied and this depends on the implantation dose. For medium and high concentrations the optimal conditions were 1050degreesC and 15s, and 1070degreesC and 15s, respectively. A uniform nitrogen distribution could be obtained throughout the SiO2 film. Prolonged heat treatment can cause degradation of the oxide layer and movement of the nitrogen and oxygen into the channel and the poly-Si0.65Ge0.35 layer.
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| 5. |
- Knudsen, Jacob, et al.
(author)
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Dynamic stability of weakly damped oscillators with elastic impacts and wear
- 2003
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In: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 263:1, s. 175-204
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Journal article (peer-reviewed)abstract
- The dynamics of non-linear oscillators comprising of a single-degree-of-freedom system and beams with elastic two-sided amplitude constraints subject to harmonic loads is analyzed. The beams are clamped at one end, and constrained against unilateral contact sites near the other end. The structures are modelled by a Bernoulli-type beam supported by springs using the finite element method. Rayleigh damping is assumed. Symmetric and elastic double-impact motions, both harmonic and sub-harmonic, are studied by way of a Poincaré mapping that relates the states at subsequent impacts. Stability and bifurcation analyses are performed for these motions, and domains of instability are delineated. Impact work rate, which is the rate of energy dissipation to the impacting surfaces, is evaluated and discussed. In addition, an experiment conducted by Moon and Shaw on the vibration of a cantilevered beam with one-sided amplitude constraining stop is modelled. Bifurcation observed in the experiment could be captured
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| 6. |
- Knudsen, Jacob, et al.
(author)
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Impact oscillations and wear of loosely supported rod subject to harmonic load
- 2004
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In: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 278:4-5, s. 1025-1050
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Journal article (peer-reviewed)abstract
- The non-linear dynamic behaviour of a damped rod oscillator with elastic two-sided amplitude constraints is analyzed using finite element method. Symmetric and asymmetric elastic double-impact motions, both harmonic and sub-harmonic, are studied by way of a Poincaré mapping that relates the states at subsequent impacts. It is found that by increasing the forcing frequency (ω) for the beam at a certain frequency a stable period one motion turns into a stable period two motion without bifurcation and subsequently moves to an infinite number of solutions characteristic of chaotic behaviour through a cyclic fold bifurcation. By further increasing ω a series of windows in the bifurcation diagram (impact velocity vs. ω) comprising periodic solutions within the chaotic domain appear. The kinds of bifurcations involved are discussed. Furthermore, impact work-rate of the beam, i.e., the rate of energy dissipation to the impacting surfaces, is calculated. Computations show that the work-rate for asymmetric orbits is substantially higher than for symmetric orbits at or near the same frequency. For the vibro-impacting beam, under conditions that exhibit a stable attractor, calculation of work-rate allows prediction of the "lifetime" of the contacting beam due to fretting-wear damage by extending the stable branch and using the local gap between contacting surfaces as a control parameter
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| 8. |
- Salford, Leif, et al.
(author)
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Nerve cell damage in mammalian brain after exposure to microwaves from GSM mobile phones.
- 2003
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In: Environmental Health Perspectives. - 1552-9924. ; 111:7, s. 881-883
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Journal article (peer-reviewed)abstract
- The possible risks of radio-frequency electromagnetic fields for the human body is a growing concern for our society. We have previously shown that weak pulsed microwaves give rise to a significant leakage of albumin through the blood-brain barrier. In this study we investigated whether a pathologic leakage across the blood-brain barrier might be combined with damage to the neurons. Three groups each of eight rats were exposed for 2 hr to Global System for Mobile Communications (GSM) mobile phone electromagnetic fields of different strengths. We found highly significant (p < 0.002) evidence for neuronal damage in the cortex, hippocampus, and basal ganglia in the brains of exposed rats. Key words: blood-brain barrier, central nervous system, microwaves, mobile phones, neuronal damage, rats.
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| 9. |
- Twigger, S, et al.
(author)
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Rat Genome Database : A comparative genomics platform for rat mouse and human.
- 2001
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In: Journal of Molecular Medicine. - : Springer. - 0946-2716 .- 1432-1440. ; , s. B30-
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Conference paper (peer-reviewed)abstract
- The Rat Genome Database (RGD) is a NIH funded project who’s stated mission is “to collect, consolidate, and integrate data generated from ongoing rat genetic and genomic research efforts and make these data widely available to the scientific community.” In a collaboration between the Medical College of Wisconsin, the Jackson Lab, the National Center for Biotechnology and Information and the Genetics Lundberg Laboratory, Gothenburg, Sweden, RGD has been created to meet these stated aims. The primary focus of RGD is to aid Rat researchers in their work studying the rat as a model organism for human disease. To support these studies we have integrated a large amount of rat genetic and genomic resources in RGD and these are constantly being expanded through ongoing literature curation. One of the major features of RGD version 1.1, released in January of this year, is incorporation of QTL data to facilitate physiological genomics studies relating disease with the genome. In addition, a dynamic sequence-based homology tool is in final testing which will enable Rat, Mouse and Human researchers to view mapped genes and sequences and their locations in the other two organisms. We hope to release this tool in the second quarter of 2001. This will facilitate the application of results in one species to experiments in another species. In collaboration with the Mouse Genome Database and NCBI, close links are being created between RGD and MGD, LocusLink and UniGene to increase access to each set of data. To support its other general functions RGD has a variety of tools available for the rat researcher, plus ones that are equally useful to researchers working in other organisms and a sampling of these tools will be presented. Thus RGD is not only a valuable resource for those working with the rat but also for researchers in other model organisms wishing to harness the existing genetic and physiological data available in the rat to complement their own work.
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