The vertical distribution of magnetotactic bacteria along various physico-chemical gradients in freshwater microcosms was analyzed by a combined approach of viable cell counts, 16S rRNA gene ...analysis, microsensor profiling and biogeochemical methods. The occurrence of magnetotactic bacteria was restricted to a narrow sediment layer overlapping or closely below the maximum oxygen and nitrate penetration depth. Different species showed different preferences within vertical gradients, but the largest proportion (63–98%) of magnetotactic bacteria was detected within the suboxic zone. In one microcosm the community of magnetotactic bacteria was dominated by one species of a coccoid “
Alphaproteobacterium”, as detected by denaturing gradient gel electrophoresis in sediment horizons from 1 to 10 mm depth. Maximum numbers of magnetotactic bacteria were up to 1.5
×
10
7 cells/cm
3, which corresponded to 1% of the total cell number in the upper sediment layer. The occurrence of magnetotactic bacteria coincided with the availability of significant amounts (6–60 μM) of soluble Fe(II), and in one sample with hydrogen sulfide (up to 40 μM). Although various trends were clearly observed, a strict correlation between the distribution of magnetotactic bacteria and individual geochemical parameters was absent. This is discussed in terms of metabolic adaptation of various strains of magnetotactic bacteria to stratified sediments and diversity of the magnetotactic bacterial communities.
This paper describes an advanced concept for an electronically steerable antenna for mobile satellite communications. The antenna consists of eight stacked patches, mounted on a heptagonal surface. ...By switching between either single elements or combinations of two active elements hemispherical coverage can be reached. The realization of an inertial sensor system and an active power control makes the antenna suitable for worldwide L-band satellite communications. Typical applications for this antenna are boats, ships, trains and trucks.
The recent spatial and temporal coincidence of the blazar TXS 0506+056 with the IceCube detected neutrino event IC-170922A has opened up a realm of multi-messenger astronomy with blazar jets as a ...plausible site of cosmic-ray acceleration. After TXS 0506+056, a second blazar, BZB J0955+3551, has recently been found to be spatially coincident with the IceCube detected neutrino event IC-200107A and undergoing its brightest X-ray flare measured so far. Here, we present the results of our multi-frequency campaign to study this peculiar event that includes observations with the NuSTAR, Swift, NICER, and 10.4 m Gran Telescopio Canarias (GTC). The optical spectroscopic observation from GTC secured its redshift as \(z=0.55703^{+0.00033}_{-0.00021}\) and the central black hole mass as 10\(^{8.90\pm0.16}~M_{\odot}\). Both NuSTAR and NICER data reveal a rapid flux variability albeit at low-significance (\(\lesssim3.5\sigma\)). We explore the origin of the target photon field needed for the photo-pion production using analytical calculations and considering the observed optical-to-X-ray flux level. We conclude that seed photons may originate from outside the jet, similar to that reported for TXS 0506+056, although a scenario invoking a co-moving target photon field (e.g., electron-synchrotron) can not be ruled out. The electromagnetic output from the neutrino-producing photo-hadronic processes are likely to make only a sub-dominant contribution to the observed spectral energy distribution suggesting that the X-ray flaring event may not be directly connected with IC-200107A.
The record of climatic change in shallow marine, coastal, and adjacent lowland areas has been investigated by three different approaches. A mass balance study focused on the interaction between ...sea-level rise and Holocene sediment accumulation in the coastal lowland area between the Ems and Weser rivers on the German North Sea coast. This region, which comprises various sedimentary environments, such as barrier islands, sheltered and open tidal flats, bay flats, and estuaries, is highly suitable for such quantitative studies, which can be used to create a model for general mass transport and accumulation processes connected with transgressions over coastal lowlands.
An integrated geochemical and microfacies study was made to assess the response of shallow marine, intertidal, and limnic-semiterrestrial environments to the climate-controlled Holocene sea-level rise. The factors controlling the development of various palaeoenvironments were estimated from the distribution of biomarkers, major and trace elements, diatoms, foraminifera and sedimentary structures observed at high resolution in core sections. These data complement those of conventional geological, lithostratigraphical, archaeological and geobotanical investigations.
The extensive raised bogs which occur in the Pleistocene hinterland, adjacent to the coastal zone, provided an excellent opportunity to examine peat formation in response to climatic changes in the past. On the basis of a large number of 14C-age determinations special attention was paid to the onset and regional expansion of raised bogs in this region and to the question of whether or not the formation of raised bog peat started synchronously in one or in a series of different phases.
The combination of angina pectoris, angiographically normal epicardial coronary arteries, and a positive exercise test is referred to as syndrome X. Previous studies have demonstrated an impaired ...coronary flow reserve and a peripheral vascular dysfunction, suggesting that vascular abnormalities in syndrome X may not be confined to the heart. The aim of this study was to investigate whether any vascular disorder of syndrome X is due to intrinsic structural or functional disturbances in resistance arteries. We compared 16 patients with syndrome X (56.6 ± 1.2 years, 3 men) with 15 matched control subjects. Myocardial blood flow was measured with
13N-ammonia positron emission tomography. Forearm blood flow was measured in the brachial artery with high-resolution ultrasound. Gluteal subcutaneous resistance arteries were dissected and mounted on a myograph for measurement of active tension development, lumen diameter, and media thickness. Baseline myocardial blood flow was similar in patients and controls, but dipyridamole-induced hyperemia was decreased in patients (1.67 ± 0.13 vs 2.31 ± 0.12 ml/min/g, p <0.01). Patients and controls had similar baseline forearm blood flow, but hyperemic flow after transient occlusion of the brachial artery was impaired in patients (198 ± 20 vs 273 ± 32 ml/min, p <0.05). Isolated resistance arteries showed no differences in constriction to noradrenaline, or relaxation to acetylcholine, dipyridamole, or nitroglycerin. Furthermore, the ratio between media thickness and lumen diameter were similar in syndrome X patients and controls. Our data show that when compared with a well-matched control group, syndrome X patients have a decreased coronary and peripheral vasodilator capacity. However, this is not reflected by functional abnormalities or structural changes as evaluated in subcutaneous resistance arteries. We conclude that syndrome X is not a generalized intrinsic abnormality of the resistance circulation.
As known from studies in animal and human subjects, ozone can exert effects on the immune response including allergic sensitisation and allergen responsiveness. The objective of the present study was ...to assess the changes in lymphocyte subsets in bronchoalveolar lavage fluid (BALF) after single and repeated ozone exposures. Twenty-three healthy subjects underwent single exposures to 200 ppb ozone or filtered air (FA), as well as repeated exposures to 200 ppb ozone on four consecutive days, each during 4 h of intermittent exercise. Bronchoalveolar lavage was performed 20 h after the single exposure or the last of the repeated exposures. Lymphocytes were identified by sideward scatter and CD45 expression, and their subsets by eight different panels of antibodies. Checksums were calculated to assess the validity of the results. The percentage and the absolute number of lymphocytes, mostly comprising T-lymphocytes (CD2+; overall mean 98.8%), increased after single (P < 0.05; each), but not after repeated ozone exposure, compared with FA (7.4 vs 5.8 vs 6.5%; 680 vs 419 vs 301 x 10(3)). In addition, we observed small but statistically significant changes in the proportions of lymphocyte subpopulations. The percentage of CD4+ lymphocytes increased after single (P < 0.05) and repeated ozone exposure (P < 0.01), whereas the percentage of CD8+ cells decreased after repeated exposure (P < 0.05). The proportion of activated lymphocytes (CD25+) was elevated after repeated, compared with single, ozone exposure (P < 0.01), and the percentages of natural killer (NK) cells were decreased after both single (P < 0.05) and repeated (P < 0.01) exposures. Our data suggest that single but not repeated ozone exposures cause a change in absolute numbers of lymphocytes in BALF, whereas the proportions of lymphocyte subsets are affected by single as well as repeated exposures.
Ice rafting in the Lower Saxonian Wadden Sea, northwest Germany, in winter 1995–1996 had a dramatic effect on surface sediments. At the beginning of a longer-term biogeochemical study, the ...investigated area (six sampling sites) comprised beds of the mussel
Mytilus edulis which disappeared under the severe weather conditions. Large amounts of sediment were eroded and redeposited. Evidence for emplaced biodeposits was given by TOC measurements and molecular distribution profiles of
n- and
iso/anteiso-fatty acids and of sterols. Absolute concentrations of fatty acids and sterols in 1996 were lower than in 1995, despite a higher organic carbon content in 1996 (>1.4% compared to 0.8%). This indicates that redeposition was accompanied by a decrease in the labile organic matter fraction by oxidation. After removal of the mussels, the sedimentary organic matter composition was nearly uniform at all sampling sites. This was manifested in
n-fatty acid distribution patterns, relative proportions of algal to terrigenous and bacterial acids, cholestanol/cholesterol ratios and sterol distributions. An enormous diatom bloom of
Coscinodiscus concinnus in spring 1996 caused an increase in the amounts of
n-C
14 and
n-C
16 fatty acids in the surface sediments. These fatty acids then dominated the distribution patterns of almost all samples investigated.
This paper proposes a frequency domain model to predict conducted electromagnetic interferences (EMI) caused by a converter. In the model, the nonlinear and time-variant semiconductor switches of the ...converter are replaced by voltage sources characterized by measurements during operation of the converter. A vector network analyzer (VNA) measurement method is presented to characterize the disturbance path from the voltage sources to the line impedance stabilization network (LISN). The approach shows that the main resonances of the disturbance voltage at the LISN are caused by the coupling path, which is linear and time-invariant. Based on this knowledge, a frequency domain simulation of the coupling path is performed. The simulation reproduces the measured coupling path very well. Based on the analysis of the electromagnetic potential at selected resonance frequencies, an electrical circuit is designed that accurately describes EMC root-causes of the converter.
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