51 research outputs found
The Arctic summer atmosphere: an evaluation of reanalyses using ASCOS data
The Arctic has experienced large climate changes over recent decades, the
largest for any region on Earth. To understand the underlying reasons for
this climate sensitivity, reanalysis is an invaluable tool. The Arctic
System Reanalysis (ASR) is a regional reanalysis, forced by ERA-Interim at
the lateral boundaries and incorporating model physics adapted to Arctic
conditions, developed to serve as a state-of-the-art, high-resolution
synthesis tool for assessing Arctic climate variability and monitoring
Arctic climate change.
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We use data from Arctic Summer Cloud-Ocean Study (ASCOS) to evaluate the
performance of ASR and ERA-Interim for the Arctic Ocean. The ASCOS field
experiment was deployed on the Swedish icebreaker <i>Oden</i> north of
87° N in the Atlantic sector of the Arctic during August and early
September 2008. Data were collected during the transits from and to
Longyearbyen and the 3-week ice drift with <i>Oden</i> moored to a drifting
multiyear ice floe. These data are independent and detailed enough to
evaluate process descriptions.
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The reanalyses captures basic meteorological variations coupled to the
synoptic-scale systems, but have difficulties in estimating clouds and
atmospheric moisture. While ERA-Interim has a systematic warm bias in the
lowest troposphere, ASR has a cold bias of about the same magnitude on
average. The results also indicate that more sophisticated descriptions of
cloud microphysics in ASR did not significantly improve the modeling of
cloud properties compared to ERA-Interim. This has consequences for the
radiation balance, and hence the surface temperature, and illustrate how a
modeling problem in one aspect of the atmosphere, here the clouds, feeds
back to other parameters, especially near the surface and in the boundary
layer
Sequential changes in hematologic and biochemical parameters in African tick bite fever
ObjectivesTo evaluate the sequential changes and to estimate the frequencies of abnormalities in some commonly measured biological variables in patients with African tick bite fever (ATBF), an emerging spotted fever group (SFG) rickettsiosis in international travelers to rural sub-Saharan Africa.MethodsA study was done of hemoglobin, total leukocyte count, absolute lymphocyte count, blood platelet count and serum levels of C-reactive protein (S-CRP), alanine aminotransferase (S-ALAT), aspartate aminotransferase, lactic dehydrogenase, Îł-glutamyl transferase, alkaline phosphatase, bilirubin, sodium and creatinine during the first two weeks of illness and prior to the institution of antirickettsial therapy in 108 patients with travel-associated ATBF.ResultsThere were significant falls in mean total leukocyte count, mean absolute lymphocyte count, and mean platelet count, and significant increases in mean S-CRP and S-ALAT. During the first ten days of illness, elevated S-CRP, lymphopenia and elevated S-ALAT were detected in 91.7%, 73.3% and 40.7% of patients, respectively. Most abnormalities were mild. For 55 patients who underwent both S-CRP and absolute lymphocyte count determination, at least one parameter was abnormal in 52 (94.5%) patients.ConclusionsThe sequential changes in many biological parameters during the acute phase of ATBF mimic those reported in other SFG rickettsioses. Mild abnormalities are frequent, with increased S-CRP and lymphopenia being the two most consistent findings
Probing Colored Particles with Photons, Leptons, and Jets
If pairs of new colored particles are produced at the Large Hadron Collider,
determining their quantum numbers, and even discovering them, can be
non-trivial. We suggest that valuable information can be obtained by measuring
the resonant signals of their near-threshold QCD bound states. If the particles
are charged, the resulting signatures include photons and leptons and are
sufficiently rich for unambiguously determining their various quantum numbers,
including the charge, color representation and spin, and obtaining a precise
mass measurement. These signals provide well-motivated benchmark models for
resonance searches in the dijet, photon+jet, diphoton and dilepton channels.
While these measurements require that the lifetime of the new particles be not
too short, the resulting limits, unlike those from direct searches for pair
production above threshold, do not depend on the particles' decay modes. These
limits may be competitive with more direct searches if the particles decay in
an obscure way.Comment: 39 pages, 9 figures; v2: more recent searches include
Behaviour of Solitary Adult Scandinavian Brown Bears (Ursus arctos) when Approached by Humans on Foot
Successful management has brought the Scandinavian brown bear (Ursus arctos L.) back from the brink of extinction, but as the population grows and expands the probability of bear-human encounters increases. More people express concerns about spending time in the forest, because of the possibility of encountering bears, and acceptance for the bear is decreasing. In this context, reliable information about the bear's normal behaviour during bear-human encounters is important. Here we describe the behaviour of brown bears when encountering humans on foot. During 2006–2009, we approached 30 adult (21 females, 9 males) GPS-collared bears 169 times during midday, using 1-minute positioning before, during and after the approach. Observer movements were registered with a handheld GPS. The approaches started 869±348 m from the bears, with the wind towards the bear when passing it at approximately 50 m. The bears were detected in 15% of the approaches, and none of the bears displayed any aggressive behaviour. Most bears (80%) left the initial site during the approach, going away from the observers, whereas some remained at the initial site after being approached (20%). Young bears left more often than older bears, possibly due to differences in experience, but the difference between ages decreased during the berry season compared to the pre-berry season. The flight initiation distance was longer for active bears (115±94 m) than passive bears (69±47 m), and was further affected by horizontal vegetation cover and the bear's age. Our findings show that bears try to avoid confrontations with humans on foot, and support the conclusions of earlier studies that the Scandinavian brown bear is normally not aggressive during encounters with humans
Characterization of the interphase in PPO/PMMA blends compatibilized by P(S-g-EO)
The influence of a poly(styrene-graft-ethylene oxide) (P(S-g-EO)) copolymer on poly(2,6-dimethyl-p-phenylene oxide)/poly(methyl methacrylate) (PPO/PMMA) blends was studied by a number of different techniques in order to characterize the properties of the interphase. Scanning electron microscopy shows that the copolymer reduces the dispersed phase size, and dynamic mechanical spectroscopy (DMS) reveals a new micromechanical transition in the ternary blends. These effects are shown to be caused by a copolymer-rich interphase with a certain volume fraction and with its own characteristic properties. Solid-state nuclear magnetic resonance (NMR) relaxation times indicate that the poly(ethylene oxide) side chains of the copolymer are partially miscible with PMMA in the ternary blends, which suggests that the interphase does not only consist of pure copolymer
Studies of the accuracy of the guinea pig test for estimating antigenicity of poliomyelitis virus preparations
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