20,338 research outputs found
Monadicity of the Bousfield-Kuhn functor
We consider the localization of the -category of spaces at the -periodic equivalences, the case being rational homotopy theory. We prove that this localization is for equivalent to algebras over a certain monad on the -category of -local spectra. This monad is built from the Bousfield--Kuhn functor
Ten milliparsec-scale structure of the nucleus region in Centaurus A
We present the results of a VLBI Space Observatory Programme (VSOP)
observation of the subparsec structure in Centaurus A at 4.9 GHz. Owing to its
proximity, our Centaurus A space-VLBI image is one of the highest spatial
resolution images of an AGN ever made -- 0.01 pc per beam. The elongated core
region is resolved into several components over 10 milli-arcseconds long (0.2
pc) including a compact component of brightness temperature 2.2x10^10K. We
analyze the jet geometry in terms of collimation. Assuming the strongest
component to be the core, the jet opening angle at ~ 5,000 r_s (Schwarzchild
radii) from the core is estimated to be ~ 12 degree, with collimation of the
jet to ~ 3 degree continuing out to ~ 20,000 r_s. This result is consistent
with previous studies of the jet in M87, which favor MHD disk outflow models.
Future space VLBI observations at higher frequencies will probably be able to
image the collimation region, within 1,000 r_s of the center of Centaurus A,
together with the accretion disk itself.Comment: 12 pages, 6 figures, accepted for publication in PASJ, Vol.57 No.6,
VSOP special issu
Anomalous Hall effect in granular ferromagnetic metals and effects of weak localization
We theoretically investigate the anomalous Hall effect in a system of
dense-packed ferromagnetic grains in the metallic regime. Using the formalism
recently developed for the conventional Hall effect in granular metals, we
calculate the residual anomalous Hall conductivity and
resistivity and weak localization corrections to them for both
skew-scattering and side-jump mechanisms. We find that, unlike for
homogeneously disordered metals, the scaling relation between and
the longitudinal resistivity does not hold. The weak localization
corrections, however, are found to be in agreement with those for homogeneous
metals. We discuss recent experimental data on the anomalous Hall effect in
polycrystalline iron films in view of the obtained results.Comment: published version, 10 pages, 6 figure
Response of single junction GaAs/GaAs and GaAs/Ge solar cells to multiple doses of 1 MeV electrons
A comparison of the radiation tolerance of MOCVD-grown GaAs cells and GaAs/Ge cells was undertaken using 1 MeV electrons. The GaAs/Ge cells are somewhat more tolerant of 1 MeV electron irradiation and more responsive to annealing than are the GaAs/GaAs cells examined in this study. However, both types of cells suffer a greater degradation in efficiency than has been observed in other recent studies. The reason for this is not certain, but it may be associated with an emitter thickness which appears to be greater than desired. The deep level transient spectroscopy (DLTS) spectra following irradiation are not significantly different for the GaAs/Ge and the GaAs/GaAs cells, with each having just two peaks. The annealing behavior of these peaks is also similar in the two samples examined. It appears that no penalty in radiation tolerance, and perhaps some benefit, is associated with fabricating MOCVD GaAs cells on Ge substrates rather than GaAs substrates
Defect healing at room temperature in pentacene thin films and improved transistor performance
We report on a healing of defects at room temperature in the organic
semiconductor pentacene. This peculiar effect is a direct consequence of the
weak intermolecular interaction which is characteristic of organic
semiconductors. Pentacene thin-film transistors were fabricated and
characterized by in situ gated four-terminal measurements. Under high vacuum
conditions (base pressure of order 10E-8 mbar), the device performance is found
to improve with time. The effective field-effect mobility increases by as much
as a factor of two and mobilities up to 0.45 cm2/Vs were achieved. In addition,
the contact resistance decreases by more than an order of magnitude and there
is a significant reduction in current hysteresis. Oxygen/nitrogen exposure and
annealing experiments show the improvement of the electronic parameters to be
driven by a thermally promoted process and not by chemical doping. In order to
extract the spectral density of trap states from the transistor
characteristics, we have implemented a powerful scheme which allows for a
calculation of the trap densities with high accuracy in a straightforward
fashion. We show the performance improvement to be due to a reduction in the
density of shallow traps <0.15 eV from the valence band edge, while the
energetically deeper traps are essentially unaffected. This work contributes to
an understanding of the shallow traps in organic semiconductors and identifies
structural point defects within the grains of the polycrystalline thin films as
a major cause.Comment: 13 pages, 13 figures, to be published in Phys. Rev.
Species sensitivity of zeolite minerals for uptake of mercury solutes
The uptake of inorganic Hg2+ and organometallic CH3Hg+ from aqueous solutions by 11 different natural zeolites has been investigated using a batch distribution coefficient (Kd) method and supported by a preliminary voltammetric study. The effect of mercury concentration on theKd response is shown over an environmentally appropriate concentration range of 0.1-5 ppm inorganic and organometallic Hg using a batch factor of 100 ml g−1 and 20 h equilibration. Analcime and a Na-chabazite displayed the greatest methylmercury uptakes (Kd values at 1.5 ppm of 4023 and 3456, respectively), with mordenite as the smallest at 578. All uptake responses were greater for methylmercury than for the inorganic mercuric nitrate solutions, suggesting a distinctive sensitivity of zeolites to reaction with different types of solute species. It is likely that this sensitivity is attributable to the precise nature of the resultant Hg-zeolite bonds. Additionally, both the Si-Al ratio and the Na content of the initial natural zeolite samples are shown to influence the Kd responses, with positive correlations between Kd and Na content for all zeolites excluding mordenite
Chemical Cryptology of Cancer’s Histone Code
Somatic mutations in non-Hodgkin's lymphoma frequently activate EZH2, a protein methyltransferase responsible for H3K27 trimethylation. In this issue of Chemistry and Biology, Bradley and coworkers describe a new set of EZH2 inhibitors amenable to probing the targetable role of H3K27 trimethylation in lymphoma
No roots, no fruits: Marcel Tanner's scholarly contribution, achievements in capacity building, and impact in global health
On 1 October 2022, Marcel Tanner celebrated his 70th birthday with his family and friends on the River Rhein in Basel. Trained in epidemiology (Ph.D.) and public health (MPH), Tanner devoted his entire working life to research, teaching, and capacity building. Indeed, he built up productive partnerships, fostered multinational consortia, served on numerous scientific and strategic advisory boards, and contributed measurably to improving people’s health and well-being. We systematically searched the Web of Science Core Collection to identify Tanner’s scholarly contribution and pursued an in-depth analysis of his scientific oeuvre including the main areas of research, pathogens, diseases, and health systems, and the geographical foci of his scholarly activities. Additionally, we examined Tanner’s impact on personal and institutional capacity building in the arena of global health. We also invited a handful of colleagues to describe their experiences while working with Marcel Tanner. What transpires is a considerable breadth and depth of peer-reviewed publications in tropical medicine; epidemiology, environmental, and occupational health; parasitology; and infectious diseases. More than a third of the 622 peer-reviewed articles, the first piece published in 1978, focused on various aspects of the protozoan parasite Plasmodium and the disease it causes: malaria. Tanner trained, taught, and inspired generations of students, scientists, and practitioners all over the world. His unique ability to bring people and institutions together to work in partnership is at the heart of an impactful career in global health
When general practitioners don't feel appreciated by their patients: prospective effects on well-being and work-family conflict in a Swiss Longitudinal Study
Background: Impaired well-being and high work-family conflict are critical issues among GPs. This research examined an understudied psychosocial risk factor for these outcomes, namely GPs' perception that they invest more in the relationship with their patients than what they receive in return (i.e. lack of reward in their relationship with patients). Objective: To test the effect of lack of reward as a risk factor for poor well-being and work-family conflict among GPs. Methods: Longitudinal study (12 months time lag). 272 GPs in Switzerland [mean age 54.5 (SD = 8.3), 73% male] volunteered to participate in the study. 270 participants completed the baseline survey and 252 completed the follow-up survey. Of these, six retired between the baseline and the follow-up survey, resulting in a sample size of 246 participants at t2. Outcome measures were burnout, sleep problems, self-perceived health and work-family conflict. Results: Strength and direction of prospective effects were tested using cross-lagged models. Lack of reward was related to an increase in emotional exhaustion (β = 0.15), sleep problems (β = 0.16) and work-family conflict (β = 0.19) and a decrease in self-perceived health (β = −0.17). Effects on depersonalization and personal accomplishment were not significant. Regarding reversed effects of impaired well-being on lack of reward, emotional exhaustion (β = 0.14) and self-perceived health (β = −0.13) predicted future level of lack of reward. Conclusion: Lack of reward by patients is a risk factor in GPs' mental healt
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