319 research outputs found
Editorial honoring the 2018 reviewers for JGR Space Physics
The Editors of the Journal of Geophysical Research Space Physics would like to honor and thank the 2018 manuscript reviewers for the journal. This is a large‐scale, community‐wide effort for which 1,358 scientists submitted 3,027 reviews in 2018. We understand that this is a volunteer task and we greatly appreciate your time and effort to fulfill this service role back to the research community
Cosmic histories of star formation and reionization: An analysis with a power-law approximation
With a simple power-law approximation of high-redshift () star
formation history, i.e., , we
investigate the reionization of intergalactic medium (IGM) and the consequent
Thomson scattering optical depth for cosmic microwave background (CMB) photons.
A constraint on the evolution index is derived from the CMB optical
depth measured by the {\it Wilkinson Microwave Anisotropy Probe} (WMAP)
experiment, which reads ,
where the free parameter is the number of the escaped
ionizing ultraviolet photons per baryon. Moreover, the redshift for full
reionization, , can also be expressed as a function of as well as
. By further taking into account the implication of the
Gunn-Peterson trough observations to quasars for the full reionization
redshift, i.e., , we obtain
and .
For a typical number of of ionizing photons released per baryon of
normal stars, the fraction of these photons escaping from the stars, , can be constrained to within the range of .Comment: 10 pages, 4 figures, accepted for publication in JCA
Domain Wall Spacetimes: Instability of Cosmological Event and Cauchy Horizons
The stability of cosmological event and Cauchy horizons of spacetimes
associated with plane symmetric domain walls are studied. It is found that both
horizons are not stable against perturbations of null fluids and massless
scalar fields; they are turned into curvature singularities. These
singularities are light-like and strong in the sense that both the tidal forces
and distortions acting on test particles become unbounded when theses
singularities are approached.Comment: Latex, 3 figures not included in the text but available upon reques
ЭНДОГЕННАЯ ОПИОИДНАЯ СИСТЕМА КАК ЗВЕНО СРОЧНОЙ И ДОЛГОВРЕМЕННОЙ АДАПТАЦИИ ОРГАНИЗМА К ЭКСТРЕМАЛЬНЫМ ВОЗДЕЙСТВИЯМ. ПЕРСПЕКТИВЫ КЛИНИЧЕСКОГО ПРИМЕНЕНИЯ ОПИОИДНЫХ ПЕПТИДОВ
It has been well established that opioid peptides (OPs) affect various hormonal systems. Opioids exhibit stress-limiting and gastro-protective effects in stressed animals, acting via μ- and δ-opioid receptors (OR). Peripheral μ-OR stimulation by endogenous and exogenous opioids increases cardiac tolerance to pathological consequences of stress. Enhancement of prostacyclin synthesis, decrease of thromboxane production as well as suppression of lipid peroxidation can be directly responsible for cardioprotective effects of OPs in stressed animals. Adaptive responses are accompanied by increased OP levels in blood and tissues. Reduction of ventricular arrhythmias induced by repeated short-term immobilization stress is mediated via μ-OR stimulation by endogenous opioids, while δ-OR account for an antiarrhythmic effect of adaptation to chronic intermittent hypobaric hypoxia. The mechanism of infarct size-limiting effect of continuous normobaric hypoxia involves both μ- and δ-OR stimulation. Peptide OR agonists can be considered in future clinical practice for treatment of withdrawal syndrome, stress-related cardiac disease or myocardial injury caused by ischemia-reperfusion insult. Установлено, что опиоидные пептиды (ОП) влияют на различные гормональные системы. Опиоиды оказывают стресс-лимитирующий и гастропротекторный эффект на стрессированных особей, действуя на μ- и δ-опиоидные рецепторы (ОР). Стимуляция периферических μ-ОР эндо- и экзогенными опиоидами способствует повышению толерантности сердца к патогенному действию стресса. Усиление синтеза простациклина, снижение продукции тромбоксана, а также подавление процессов пероксидного окисления липидов (ПОЛ) могут иметь прямое отношение к кардиопротекторному эффекту ОП у стрессированных животных. Адаптация сопровождается увеличением содержания ОП в крови и тканях экспериментальных животных. Снижение частоты возникновения желудочковых аритмий, индуцированное повторными иммобилизациями, опосредуется через стимуляцию μ-ОР эндогенными опиоидами, в то время как δ-ОР ответственны за антиаритмический эффект адаптации к периодической гипобарической гипоксии. Инфаркт-лимитирующий эффект адаптации к непрерывной нормобарической гипоксии зависит от активации μ- и δ-ОР. Пептидные агонисты ОР в будущем могут найти применение в клинической практике в лечении абстинентного синдрома, стресс-индуцированных заболеваний сердца или повреждений миокарда, вызванных ишемией и реперфузией.
Data-based perfect-deficit approach to understanding climate extremes and forest carbon assimilation capacity
Several lines of evidence suggest that the warming climate plays a vital role in driving certain types of extreme weather. The impact of warming and of extreme weather on forest carbon assimilation capacity is poorly known. Filling this knowledge gap is critical towards understanding the amount of carbon that forests can hold. Here, we used a perfect-deficit approach to identify forest canopy photosynthetic capacity (CPC) deficits and analyze how they correlate to climate extremes, based on observational data measured by the eddy covariance method at 27 forest sites over 146 site-years. We found that droughts severely affect the carbon assimilation capacities of evergreen broadleaf forest (EBF) and deciduous broadleaf forest. The carbon assimilation capacities of Mediterranean forests were highly sensitive to climate extremes, while marine forest climates tended to be insensitive to climate extremes. Our estimates suggest an average global reduction of forest CPC due to unfavorable climate extremes of 6.3 Pg C (~5.2% of global gross primary production) per growing season over 2001–2010, with EBFs contributing 52% of the total reduction
Unified dark energy models : a phenomenological approach
A phenomenological approach is proposed to the problem of universe
accelerated expansion and of the dark energy nature. A general class of models
is introduced whose energy density depends on the redshift in such a way
that a smooth transition among the three main phases of the universe evolution
(radiation era, matter domination, asymptotical de Sitter state) is naturally
achieved. We use the estimated age of the universe, the Hubble diagram of Type
Ia Supernovae and the angular size - redshift relation for compact and
ultracompact radio structures to test whether the model is in agreement with
astrophysical observation and to constrain its main parameters. Although
phenomenologically motivated, the model may be straightforwardly interpreted as
a two fluids scenario in which the quintessence is generated by a suitably
chosen scalar field potential. On the other hand, the same model may also be
read in the context of unified dark energy models or in the framework of
modified Friedmann equation theories.Comment: 12 pages, 10 figures, accepted for publication on Physical Review
Identifying topological edge states in 2D optical lattices using light scattering
We recently proposed in a Letter [Physical Review Letters 108 255303] a novel
scheme to detect topological edge states in an optical lattice, based on a
generalization of Bragg spectroscopy. The scope of the present article is to
provide a more detailed and pedagogical description of the system - the
Hofstadter optical lattice - and probing method. We first show the existence of
topological edge states, in an ultra-cold gas trapped in a 2D optical lattice
and subjected to a synthetic magnetic field. The remarkable robustness of the
edge states is verified for a variety of external confining potentials. Then,
we describe a specific laser probe, made from two lasers in Laguerre-Gaussian
modes, which captures unambiguous signatures of these edge states. In
particular, the resulting Bragg spectra provide the dispersion relation of the
edge states, establishing their chiral nature. In order to make the Bragg
signal experimentally detectable, we introduce a "shelving method", which
simultaneously transfers angular momentum and changes the internal atomic
state. This scheme allows to directly visualize the selected edge states on a
dark background, offering an instructive view on topological insulating phases,
not accessible in solid-state experiments.Comment: 17 pages, 10 figures. Revised and extended version, to appear in EJP
Special Topic for the special issue on "Novel Quantum Phases and Mesoscopic
Physics in Quantum Gases". Extended version of arXiv:1203.124
Metal enrichment processes
There are many processes that can transport gas from the galaxies to their
environment and enrich the environment in this way with metals. These metal
enrichment processes have a large influence on the evolution of both the
galaxies and their environment. Various processes can contribute to the gas
transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy
interactions and others. We review their observational evidence, corresponding
simulations, their efficiencies, and their time scales as far as they are known
to date. It seems that all processes can contribute to the enrichment. There is
not a single process that always dominates the enrichment, because the
efficiencies of the processes vary strongly with galaxy and environmental
properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 17; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Identification of alpha-enolase as an autoantigen in lung cancer: Its overexpression is associated with clinical outcomes
Purpose: Although existence of humoral immunity has been previously shown in malignant pleural effusions, only a limited number of immunogenic tumor-associated antigens (TAA) have been identified and associated with lung cancer. In this study, we intended to identify more TAAs in pleural effusion-derived tumor cells. Experimental Design: Using morphologically normal lung tissues as a control lysate in Western blotting analyses, 54 tumor samples were screened with autologous effusion antibodies. Biochemical purification and mass spectrometric identification of TAAs were done using established effusion tumor cell lines as antigen sources. We identified a p48 antigen as of-enolase (ENO1). Semiquantitative immunohistochemistry was used to evaluate expression status of ENO1 in the tissue samples of 80 patients with non-small cell lung cancer (NSCLC) and then correlated with clinical variables. Results: Using ENO1-specifc antiserum, up-regulation of ENO1 expression in effusion tumor cells from 11 of 17 patients was clearly observed compared with human normal lung primary epithelial and non-cancer-associated effusion cells. Immunohistochemical studies consistently showed high level of ENO1 expression in all the tumors we have examined thus far. Log-rank and Cox's analyses of ENO1 expression status revealed that its expression level in primary tumors was a key factor contributing to overall- and progression-free survivals of patients (P < 0.05). The same result was also obtained in the early stage of NSCLC patients, showing that tumors expressing relatively higher ENO1 level were tightly correlated with poorer survival outcomes. Conclusions: Our data strongly support a prognostic role of ENO1 in determining tumor malignancy of patients with NSCLC
Evaluation of the impact of orally administered carbohydrates on postprandial blood glucose levels in different pre-clinical models
ABSTRACT We developed a pre-clinical model in which to evaluate the impact of orally administered carbohydrates on postprandial blood glucose levels. For this purpose, we compared the effects of different carbohydrates with well-established glycemic indexes. We orally administered (gavage) increasing amounts (0.2, 0.4, 0.6, 0.8, and 1.0 g/kg) of sucrose and lactose to rats which had been fasted for 6 h or 15 h, respectively. In part of the experiments we administered frutose (gavagem). Three different models were compared for measuring postprandial blood glucose levels: a) evaluation of interstitial glucose concentrations by using a real time continuous glucose monitoring system; b) evaluation of glucose levels in blood obtained from the rat tail; c) evaluation of serum glucose levels in blood collected after decapitation. Our results showed that blood obtained from the tails of 15-h fasted rats was the best model in which to evaluate the effect of carbohydrates on postprandial blood glucose levels
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