381 research outputs found
Extreme magnetic field variations during the October 2003 superstorm
From October to November, 2003 the sun became very active. The plural numbers of active region appeared on the solar surface. The most prominent one was the number 486, which yielded extremely large flares X17/4B at 0951UT on October 28, and X10/2B at 2037UT on October 29. These big flares hurled massive coronal mass ejections (CMEs) toward the earth. In this paper the solar-terrestrial relationship during the October super magnetic storms is discussed. Two fast moving clouds of gas from the sun swept the earth and sparked extreme geomagnetic storms producing the big ground magnetic field depressions of approximately - 350nT and - 400nT of Dst. Several interesting magnetic field variations observed in interplanetary space and their relationships to the ground magnetic field variations are discussed. Topics are as follows: 1) magnetic field polarity changes of the north-south component Bz of interplanetary magnetic field conveyed with the interplanetary coronal mass ejections (ICMEs) and their response to the magnetic field variations on the ground, 2) large amplitude tail flapping motions observed in the distant tail at about - 160Re, 3) large amplitude Pc 5 oscillations globally observed on the ground during the recovery phase of the super magnetic storm, and 4) large amplitude Pc 3 ULF waves observed in space from upstream through the magnetosheath to the dusk-side outer magnetosphere
Interval Analysis of Worst-case Stationary Moments for Stochastic Chemical Reactions with Uncertain Parameters
The dynamics of cellular chemical reactions are variable due to stochastic
noise from intrinsic and extrinsic sources. The intrinsic noise is the
intracellular fluctuations of molecular copy numbers caused by the
probabilistic encounter of molecules and is modeled by the chemical master
equation. The extrinsic noise, on the other hand, represents the intercellular
variation of the kinetic parameters due to the variation of global factors
affecting gene expression. The objective of this paper is to propose a
theoretical framework to analyze the combined effect of the intrinsic and the
extrinsic noise modeled by the chemical master equation with uncertain
parameters. More specifically, we formulate a semidefinite program to compute
the intervals of the stationary solution of uncertain moment equations whose
parameters are given only partially in the form of the statistics of their
distributions. The semidefinite program is derived without approximating the
governing equation in contrast with many existing approaches. Thus, we can
obtain guaranteed intervals of the worst possible values of the moments for all
parameter distributions satisfying the given statistics, which are
prohibitively hard to estimate from sample-path simulations since sampling from
all possible uncertain distributions is difficult. We demonstrate the proposed
optimization approach using two examples of stochastic chemical reactions and
show that the solution of the optimization problem gives practically useful
upper and lower bounds of the statistics of the stationary copy number
distributions
Stochastic Estimation of Nuclear Level Density in the Nuclear Shell Model: An Application to Parity-Dependent Level Density in Ni
We introduce a novel method to obtain level densities in large-scale
shell-model calculations. Our method is a stochastic estimation of eigenvalue
count based on a shifted Krylov-subspace method, which enables us to obtain
level densities of huge Hamiltonian matrices. This framework leads to a
successful description of both low-lying spectroscopy and the experimentally
observed equilibration of and states in Ni in a
unified manner.Comment: 13 pages, 4 figure
Detection of the onset time of Pi 2 pulsations by using wavelet analysis
We have developed an algorithm for automatic detection of the onset of Pi 2 pulsations by using the wavelet transform. It is found that the Cauchy wavelet with proper parameters has a time resolution higher than that of the Gabor wavelet, and is suitable for detecting Pi 2 onset. It is revealed that the time of power peak of the Cauchy wavelet transform is given within one to three minutes after the onset of Pi 2. This time lag has been automatically compensated in the present algorithm, and it is shown that the onset time of almost all Pi 2 events can be determined with an accuracy of one minute
Similarity and dissimilarity of conjugate relationships of Pi magnetic pulsations observed during excellent similar auroras
Similarity and dissimilarity of conjugate relationships of Pi magnetic pulsations observed during excellent similar auroras at the conjugate stations, Tjornes in Iceland and Syowa Station in Antarctica are examined. The study revealed that characteristic Pi pulsations, Pi 2 pulsations and impulsive Pi 1 pulsations were prominently observed with a close relationship to aurora activities. During the substorm growth phase they showed a good similarity between the conjugate stations. How ever, at the onset of substorm expansion, the appearance of Pi pulsations showed prominent dissimilarity between the conjugate stations, suggesting that there might be some asymmetry of the ionosphere and magnetosphere conditions in between the northern and the southern hemispheres
Understanding traders\u27 regional arbitage : the case of rice traders in Antananarivo, Madagascar
Many studies find that agricultural markets in developing countries are poorly integrated spatially. Traders\u27 regional arbitrage plays a key role in integrating markets across space. We investigate the performance of regional arbitrage and the associated obstacles for rice traders in Antananarivo, Madagascar. On the basis of a trader-level biweekly survey spanning 2012–2013, we find that traders are not fully exploiting the regional arbitrage opportunities: most of them fail to purchase from the cheapest district and are paying higher prices than those in the cheapest district. One apparent obstacle is obtaining price information from many different regions. To reduce search costs, we provided regional price information via SMS to randomly selected traders, but found that this had a null-effect on improving arbitrage performance. Traders tend to concentrate on trading with a few fixed districts, even if they are informed about cheaper prices in other new districts, because they worry about quality uncertainty and the trustworthiness of new partners. These findings suggest that not only transmission of price information but also issues related to produce quality and matching prevent the performance of arbitrage and market integration
Rice flows across regions in Madagascar
Although spatial disintegration of rice markets in Madagascar has been well documented, little is known about actual rice flows across regions. Using weekly collected unique data from rice markets in 22 regional capital cities for one year, this study explores the physical distribution of rice in Madagascar and reveals that rice flows from sufficient regions to deficit regions, along with geographical proximity, have positive effects on rice flow. In contrast, season factors, such as harvest/non-harvest periods and weather conditions have a negligible effect on rice flow. These findings suggest that rice flows generally follow a rational pattern despite the fact that market indicators indicate that rice trade across regions is underdeveloped
Is there any premium for unobservable quality? : a hedonic price analysis of the Malagasy rice market
This paper examines if consumers pay a premium for unobservable quality in the absence of quality standards and/or quality grading systems and, if so, how they assess that unobservable quality, using a rice retail market in Madagascar as an example. In Madagascar, the lack of quality standards and/or grading systems for rice makes is considered to be one of the causes of the rice market\u27s spatial disintegration. Thus, quality standards and grading systems will be necessary to increase the market\u27s efficiency. We hypothesize that consumers and retailers use product origin and rice name as observable indictors of unobservable quality and test the hypothesis using hedonic price regressions. We find that the interaction terms of product origin and rice name significantly affect the price after controlling for both observable quality and spatial and temporal price variation, but that the contribution of product origin and rice name to rice price variation is smaller than spatial and temporal factors. We thus conclude that consumers pay a premium for unobservable quality throughout Madagascar. This finding implies that quality standards and/or grading systems will work in the Malagasy market and that improving market infrastructure such as roads and storage will make them even more effective
Essential roles of angiotensin II in vascular endothelial growth factor expression in sleep apnea syndrome
SummaryBackgroundHypoxia-induced endothelial cell dysfunction has been implicated in increased cardiovascular disease associated with obstructive sleep apnea syndrome (OSAS). OSAS mediates hypertension by stimulating angiotensin II (Ang II) production. Hypoxia and Ang II are the major stimuli of vascular endothelial growth factor (VEGF), which is a potent angiogenic cytokine and also contributes to the atherogenic process itself.Methods & resultsWe observed serum Ang II and VEGF levels and peripheral blood mononuclear cell (PBMC) and neutrophil VEGF expression. Compared to controls, subjects with OSAS had significantly increased levels of serum Ang II and VEGF and VEGF mRNA expression in their leukocytes. To examine whether Ang II stimulates VEGF expression in OSAS, we treated PBMCs obtained from control subjects with Ang II and with an Ang II receptor type 1 (AT1) blocker, olmesartan. We observed an increased expression of VEGF in the Ang II-stimulated PBMCs and decreased in VEGF mRNA and protein expression in the PBMCs treated with olmesartan.ConclusionsThese findings suggest that the Ang II-AT1 receptors pathway potentially are involved in OSAS and VEGF-induced vascularity and that endothelial dysfunction might be linked to this change in Ang II activity within leukocytes of OSAS patients
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