3,023 research outputs found
Transient Reward Approximation for Continuous-Time Markov Chains
We are interested in the analysis of very large continuous-time Markov chains
(CTMCs) with many distinct rates. Such models arise naturally in the context of
reliability analysis, e.g., of computer network performability analysis, of
power grids, of computer virus vulnerability, and in the study of crowd
dynamics. We use abstraction techniques together with novel algorithms for the
computation of bounds on the expected final and accumulated rewards in
continuous-time Markov decision processes (CTMDPs). These ingredients are
combined in a partly symbolic and partly explicit (symblicit) analysis
approach. In particular, we circumvent the use of multi-terminal decision
diagrams, because the latter do not work well if facing a large number of
different rates. We demonstrate the practical applicability and efficiency of
the approach on two case studies.Comment: Accepted for publication in IEEE Transactions on Reliabilit
EXPRESSION OF A FUNCTIONAL CHIMERIC lg-MHC CLASS II PROTEIN
composed of the a- and ß-chains of the MHC class I1
I-E molecule fused to antibody V regions derived
from anti-human CD4 mAb MT310. Expression vectors
were constructed containing the functional,
rearranged gene segments coding for the V region
domains of the antibody H and L chains in place of
the first domains of the complete structural genes
of the I-E a- and ß-chains, respectively. Celltsr ansfected
with both hybrid genes expressed a stable
protein product on the cell surface. The chimeric
molecule exhibited the idiotype of the antibody
MT310 as shown by binding to the anti-idiotypic
mAb 20-46. A protein of the anticipated molecular
mass was immunoprecipitated witha nti-mouse IgG
antiserum. Furthermore, human soluble CD4 did
bind to thetr ansfected cell line, demonstrating that
the chimeric protein possessed the binding capacity
of the original mAb. Thus, the hybrid molecule retained:
1) the properties of a MHC class I1 protein
with regardt o correct chain assembly and transport
to the cell surface: as well as 2) the Ag binding
capacity of the antibody genes used. Thgee neration
of hybrid MHC class I1 molecules with highly specific,
non-MHC-restricted bindingc apacities will be
useful for studying MHC class 11-mediated effector
functions such as selection of the T cell repertoire
in thymus of transgenic mice
The determinants of urban household poverty in Malaysia
Since independence in 1950s Malaysia has been
recognised as one of the more successful countries
in fighting poverty: head count ratio came down to
5.7 percent by 2004. However the recent process
of rapid urbanization has led to an increase of
urban poverty aggravated further by the 1997
Asian financial crisis. It is important to understand
the nature and scale of urbanization, the various
driving forces that affect it and the determinants of
urban poverty as linked to this process. Our paper
identifies the determinants of urban poverty in
Malaysia using a logistic regression. Multiple
regression model which used to be the main tool of
analysis in this kind of studies has been criticised
for a number of drawbacks and binary probit or
logit models have been proposed as alternative and
widely used. Previous studies have used income to identify poor
households. We have two problems with this
procedure. First, the official poverty line in
Malaysia is an consumption expenditure. Secondly
data on household incomes are known to be less
reliable than consumption data obtained from
household expenditure surveys. We therefore
compare a person’s consumption expenditure with
the poverty line to determine its poverty status.
This agrees with the idea that poverty is the
inability to attain a critical minimum amount of
consumption. We study the effect of human
capital, region of residence and other household
characteristics on urban poverty using this
benchmark
A sample of 2,403 urban households from the
2004-05 Household Expenditure Survey (HES) has
been used in this research. We first estimate the
probability of households with specified
characteristics to fall below Malaysia’s official
poverty line. Results show that human capital significantly reduces the chance of being poor
while migrant workers are more prone to poverty.
Household size, race and regions are also
important determinants of poverty outcome in
urban Malaysia. Then we analyse the sensitivity of
the probability estimates to shift of the poverty line
over a reasonable range. Effects of education,
number of children, number of male adults,
number of elderly, foreign migrant-headed
household, Chinese household and households
living in Region 1 on poverty are robust over the
shifts. The findings have important policy
implications for Malaysian government which has
pledged to reduce overall poverty rate to 2.8
percent and eradicate hardcore poverty by 2010
under the Ninth Malaysian Plan
2 kirja Karl Morgensternile, Candau
http://tartu.ester.ee/record=b1783199~S1*es
Social Preferences and the Efficiency of Bilateral Exchange
Under what conditions do social preferences, such as altruism or a concern for fair outcomes, generate efficient trade? I analyze theoretically a simple bilateral exchange game: Each player sequentially takes an action that reduces his own material payoff but increases the other player’s. Each player’s preferences may depend on both his/her own material payoff and the other player’s. I identify necessary conditions and sufficient conditions on the players’ preferences for the outcome of their interaction to be Pareto efficient. The results have implications for interpreting the rotten kid theorem, gift exchange in the laboratory, and gift exchange in the field
A high-flux BEC source for mobile atom interferometers
Quantum sensors based on coherent matter-waves are precise measurement
devices whose ultimate accuracy is achieved with Bose-Einstein condensates
(BEC) in extended free fall. This is ideally realized in microgravity
environments such as drop towers, ballistic rockets and space platforms.
However, the transition from lab-based BEC machines to robust and mobile
sources with comparable performance is a challenging endeavor. Here we report
on the realization of a miniaturized setup, generating a flux of quantum degenerate Rb atoms every 1.6s. Ensembles of atoms can be produced at a 1Hz rate. This is achieved by loading a
cold atomic beam directly into a multi-layer atom chip that is designed for
efficient transfer from laser-cooled to magnetically trapped clouds. The
attained flux of degenerate atoms is on par with current lab-based BEC
experiments while offering significantly higher repetition rates. Additionally,
the flux is approaching those of current interferometers employing Raman-type
velocity selection of laser-cooled atoms. The compact and robust design allows
for mobile operation in a variety of demanding environments and paves the way
for transportable high-precision quantum sensors.Comment: 22 pages, 6 figure
Protein Kinase CK2 Controls CaV2.1-Dependent Calcium Currents and Insulin Release in Pancreatic β-cells
The regulation of insulin biosynthesis and secretion in pancreatic β-cells is essential for glucose homeostasis in humans. Previous findings point to the highly conserved, ubiquitously expressed serine/threonine kinase CK2 as having a negative regulatory impact on this regulation. In the cell culture model of rat pancreatic β-cells INS-1, insulin secretion is enhanced after CK2 inhibition. This enhancement is preceded by a rise in the cytosolic Ca2+ concentration. Here, we identified the serine residues S2362 and S2364 of the voltage-dependent calcium channel CaV2.1 as targets of CK2 phosphorylation. Furthermore, co-immunoprecipitation experiments revealed that CaV2.1 binds to CK2 in vitro and in vivo. CaV2.1 knockdown experiments showed that the increase in the intracellular Ca2+ concentration, followed by an enhanced insulin secretion upon CK2 inhibition, is due to a Ca2+ influx through CaV2.1 channels. In summary, our results point to a modulating role of CK2 in the CaV2.1-mediated exocytosis of insulin
Controlling germanium CMP selectivity through slurry mediation by surface active agents
Due to copyright restrictions, the access to the full text of this article is only available via subscription.New developments and device performance requirements in microelectronics industry add to the challenges in chemical mechanical planarization (CMP) process. One of the recently introduced materials to semiconductor manufacturing is germanium which enables improved device performance through better channel mobility in shallow trench isolation (STI) applications for advanced circuits. This paper focuses on controlling germanium/silica selectivity for advanced STI CMP applications through slurry modification by surface active agents. Surface adsorption characteristics of cationic and anionic surfactants on germanium and silica wafers are analyzed in order to control selectivity as well as the defectivity performance of the CMP applications. The effects of surfactant charge and concentration (up to self-assembly) are studied in terms of slurry stability, material removal rates and surface defectivity. Surface charge manipulation by the surfactant adsorption on the germanium surface is presented as the main criteria on the selection of the proper surfactant/oxidizer systems for CMP. The outlined correlations are systematically presented to highlight slurry modification criteria for the desired selectivity results. Consequently, the paper evaluates the slurry selectivity control and improvement criteria for the new materials introduced to microelectronics applications with CMP requirement by evaluating the germanium silica system as a model application.European Commissio
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