A 350-year-long, well-dated δ18 O stalagmite record from the summer rainfall region in South Africa is positively correlated with regional air surface temperatures at interannual time scales. The ...coldest period documented in this record occurred between 1690 and 1740, slightly lagging the Maunder Minimum (1645-1710). A temperature reconstruction, based on the correlation between regional surface temperatures and the stalagmite δ18 O variations, indicates that parts of this period could have been as much as 1.4°C colder than today. Significant cycles of 22, 11 and 4.8 years demonstrate that the solar magnetic and the El Niño-Southern Oscillation cycle could be important drivers of multidecadal to interannual climate variability in this region. The observation that the most important driver of stalagmite δ18 O on interannual time scales from this subtropical region is regional surface temperature cautions against deterministic interpretations of δ18 O variations in low-latitude stalagmites as mainly driven by the amount of precipitation.
The Cryogenic Dark Matter Search (CDMS) experiment employs ultra-cold solid-state detectors to search for rare events resulting from WIMP-nucleus scattering. An innovative detector packaging and ...readout system has been developed to meet the unusual combination of requirements for: low temperature, low radioactivity, low energy threshold, and large channel count. Features include use of materials with low radioactivity such as multi-layer KAPTON laminates for circuit boards; immunity to microphonic noise via a vacuum coaxial wiring design, manufacturability, and modularity.
The detector readout design had to accommodate various electronic components which have to be operated in close proximity to the detector as well maintaining separate individual temperatures (ranging from 600
mK to 150
K) in order to achieve optimal noise performance. The paper will describe the general electrical, thermal, and mechanical designs of the CDMS readout system, as well as presenting the theoretical and measured performance of the detector readout channels.
CDMS-II uses detectors known as Z-sensitive ionization phonons (ZIPs) to search for weakly interacting massive particles (WIMPs), a very promising candidate for the dark matter in the universe. The ...most recent data run utilized 12 ZIP detectors (six Ge and six Si) running for
1
2
year at the Soudan deep underground laboratory (780
m below surface), resulting in the current world's highest sensitivity to WIMP–nucleon coherent interaction D.S. Akerib, et al., Phys. Rev. Lett. 93 (2004) 211301. The CDMS-II experiment is approved to run 30 ZIPs until summer 2007 and its goal is to another order of magnitude increase in sensitivity to WIMPs. We present the detector preparation steps leading to the production of the CDMS-II detectors to be used in this final run.
In species reproducing both sexually and asexually clones are often more common in recently established populations. Earlier studies have suggested that this pattern arises due to natural selection ...favouring generally or locally successful genotypes in new environments. Alternatively, as we show here, this pattern may result from neutral processes during species’ range expansions. We model a dioecious species expanding into a new area in which all individuals are capable of both sexual and asexual reproduction, and all individuals have equal survival rates and dispersal distances. Even under conditions that favour sexual recruitment in the long run, colonization starts with an asexual wave. After colonization is completed, a sexual wave erodes clonal dominance. If individuals reproduce more than one season, and with only local dispersal, a few large clones typically dominate for thousands of reproductive seasons. Adding occasional long‐distance dispersal, more dominant clones emerge, but they persist for a shorter period of time. The general mechanism involved is simple: edge effects at the expansion front favour asexual (uniparental) recruitment where potential mates are rare. Specifically, our model shows that neutral processes (with respect to genotype fitness) during the population expansion, such as random dispersal and demographic stochasticity, produce genotype patterns that differ from the patterns arising in a selection model. The comparison with empirical data from a post‐glacially established seaweed species (Fucus radicans) shows that in this case, a neutral mechanism is strongly supported.
Obstructive sleep apnea is common among patients with atrial fibrillation, but the prevalence and risk factors for atrial fibrillation among patients who are being investigated on suspicion of sleep ...apnea are not well known. The aim of the study was to estimate the prevalence of atrial fibrillation among patients investigated for suspected obstructive sleep apnea and to identify risk factors for atrial fibrillation among them.
The prevalence of atrial fibrillation was investigated among 201 patients referred for suspected obstructive sleep apnea. Patients without known atrial fibrillation were investigated with a standard 12-lead ECG at hospital and short intermittent handheld ECG recordings at home, during 14 days.
Atrial fibrillation occurred in 13 of 201 subjects (6.5%), and in 12 of 61 men aged 60 years and older (20%). The prevalence of atrial fibrillation increased with sleep apnea severity (p = 0.038). All patients with atrial fibrillation were men and all had sleep apnea. Age 60 or older, the occurrence of central sleep apnea and diabetes mellitus were independent risk factors for atrial fibrillation after adjustments for body mass index, gender, sleep apnea and cardiovascular disease.
Atrial fibrillation is common among subjects referred for sleep apnea investigation and the prevalence of atrial fibrillation increases with sleep apnea severity. Independent risk factors for atrial fibrillation among patients investigated for suspected obstructive sleep apnea include the occurrence of coexisting central sleep apnea, age 60 years or older and diabetes mellitus.
Citrobacter rodentium is an attaching and effacing intestinal murine pathogen which shares similar virulence strategies with the human pathogens enteropathogenic- and enterohemorrhagic Escherichia ...coli to infect their host. C. rodentium is spontaneously cleared by healthy wild-type (WT) mice whereas mice lacking Muc2 or specific immune regulatory genes demonstrate an impaired ability to combat the pathogen. Here we demonstrate that apical formyl peptide receptor 2 (Fpr2) expression increases in colonic epithelial cells during C. rodentium infection. Using a conventional inoculum dose of C. rodentium, both WT and Fpr2
−/−
mice were infected and displayed similar signs of disease, although Fpr2
−/−
mice recovered more slowly than WT mice. However, Fpr2
−/−
mice exhibited increased susceptibility to C. rodentium colonization in response to low dose infection: 100% of the Fpr2
−/−
and 30% of the WT mice became colonized and Fpr2
−/−
mice developed more severe colitis and more C. rodentium were in contact with the colonic epithelial cells. In line with the larger amount of C. rodentium detected in the spleen in Fpr2
−/−
mice, more C. rodentium and enteropathogenic Escherichia coli translocated across an in vitro mucosal surface to the basolateral compartment following FPR2 inhibitor treatment. Fpr2
−/−
mice also lacked the striated inner mucus layer that was present in WT mice. Fpr2
−/−
mice had decreased mucus production and different mucin O-glycosylation in the colon compared to WT mice, which may contribute to their defect inner mucus layer. Thus, Fpr2 contributes to protection against infection and influence mucus production, secretion and organization.
Objectives The worldwide rapid increase in antibiotic-resistant bacteria has made efforts to prolong the lifespan of existing antibiotics very important. Antibiotic resistance often confers a fitness ...cost in the bacterium. Resistance may thus be reversible if antibiotic use is discontinued or reduced. To examine this concept, we performed a 24 month voluntary restriction on the use of trimethoprim-containing drugs in Kronoberg County, Sweden. Methods The intervention was performed on a 14 year baseline of monthly data on trimethoprim resistance and consumption. A three-parameter mathematical model was used to analyse the intervention effect. The prerequisites for reversion of resistance (i.e. fitness cost, associated resistance and clonal composition) were studied on subsets of consecutively collected Escherichia coli from urinary tract infections. Results The use of trimethoprim-containing drugs decreased by 85% during the intervention. A marginal but statistically significant effect on the increase in trimethoprim resistance was registered. There was no change in the clonal composition of E. coli and there was no measurable fitness cost associated with trimethoprim resistance in clinical isolates. The frequency of associated antibiotic resistances in trimethoprim-resistant isolates was high. Conclusions A lack of detectable fitness cost of trimethoprim resistance in vitro together with a strong co-selection of other antibiotics could explain the rather disappointing effect of the intervention. The result emphasizes the low possibility of reverting antibiotic resistance once established and the urgent need for the development of new antibacterial agents.
In May 2013, Italy declared a national outbreak of hepatitis A, which also affected several foreign tourists who had recently visited the country. Molecular investigations identified some cases as ...infected with an identical strain of hepatitis A virus subgenotype IA. After additional European Union/European Economic Area (EU/EEA) countries reported locally acquired and travel-related cases associated with the same outbreak, an international outbreak investigation team was convened, a European outbreak case definition was issued and harmonisation of the national epidemiological and microbiological investigations was encouraged. From January 2013 to August 2014, 1,589 hepatitis A cases were reported associated with the multistate outbreak; 1,102 (70%) of the cases were hospitalised for a median time of six days; two related deaths were reported. Epidemiological and microbiological investigations implicated mixed frozen berries as the vehicle of infection of the outbreak. In order to control the spread of the outbreak, suspected or contaminated food batches were recalled, the public was recommended to heat-treat berries, and post-exposure prophylaxis of contacts was performed. The outbreak highlighted how large food-borne hepatitis A outbreaks may affect the increasingly susceptible EU/EEA general population and how, with the growing international food trade, frozen berries are a potential high-risk food.
Long term variability of Cygnus X-1 Grinberg, V; Leutenegger, M A; Hell, N ...
Astronomy and astrophysics (Berlin),
04/2015, Letnik:
576
Journal Article
Recenzirano
Odprti dostop
Binary systems with an accreting compact object offer a unique opportunity to investigate the strong, clumpy, line-driven winds of early-type supergiants by using the compact object's X-rays to probe ...the wind structure. We analyze the two-component wind of HDE 226868, the 09.7Iab giant companion of the black hole Cyg X-1, using 4.77 Ms Rossi X-ray Timing Explorer (RXTE) observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-Abbott-Klein wind: as it does not incorporate clumping, the model does not describe the observations well. A qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could either be due to lack of a focussed wind component in the model or to a more complicated clump structure.
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