9,591 research outputs found
Matrix Formulation of Hamiltonian Structures of Constrained KP Hierarchy
We give a matrix formulation of the Hamiltonian structures of constrained KP
hierarchy. First, we derive from the matrix formulation the Hamiltonian
structure of the one-constraint KP hierarchy, which was originally obtained by
Oevel and Strampp. We then generalize the derivation to the multi-constraint
case and show that the resulting bracket is actually the second Gelfand-Dickey
bracket associated with the corresponding Lax operator. The matrix formulation
of the Hamiltonian structure of the one-constraint KP hierarchy in the form
introduced in the study of matrix model is also discussedComment: 19 pages, Revtex, no figures. Minor changes, reference correcte
Impact of 2-bromopropane on mouse embryonic stem cells and related regulatory mechanisms
2-Bromopropane (2-BP), a cleaning agent, is used as an alternative to ozone-depleting solvents. Previously, 2-BP was shown to have cytotoxic effects on mouse blastocysts and is associated with defects in their subsequent development, both in vitro and in vivo. In addition, it was found that 2-BP also has cytotoxic effects on oocyte maturation and subsequent pre- and post implantation development in vitro and in vivo, and significantly reduces the rate of oocyte maturation, fertilization, and embryonic development in vitro. This study shows that 2-BP (5 to 10 ÎŒM) induces apoptotic processes in mouse embryonic stem cells (ESC-B5), but exerts no effects at treatment dosages below 5 ÎŒM. In ESC-B5 cells, 2-BP directly increased the content of reactive oxygen species (ROS), significantly increased the cytoplasmic free calcium and nitric oxide (NO) levels, triggered a loss of mitochondrial membrane potential (MMP), activated caspases-9 and -3, and induced cell death. Pre-treatment with NO scavengers suppressed the apoptotic biochemical changes induced by 10 ÎŒM 2-BP and promoted the gene expression levels of p53 and p21, which are involved in apoptotic signaling. These results demonstrate for the first time that 2-BP triggers apoptosis in mouse embryonic stem cells via ROS, NO and the activation of mitochondria-dependent cell death signaling.Keywords: 2-Bromopropane, apoptosis, oxidative stress, calcium, nitric oxideAfrican Journal of Biotechnology Vol. 12(20), pp. 3012-302
"An Econometric Analysis of SARS and Avian Flu on International Tourist Arrivals to Asia"
This paper compares the impacts of SARS and human deaths arising from Avian Flu on international tourist arrivals to Asia. The effects of SARS and human deaths from Avian Flu will be compared directly according to human deaths. The nature of the short run and long run relationship is examined empirically by estimating a static line fixed effect model and a difference transformation dynamic model, respectively. Empirical results from the static fixed effect and difference transformation dynamic models are consistent, and indicate that both the short run and long run SARS effect have a more significant impact on international tourist arrivals than does Avian Flu. In addition, the effects of deaths arising from both SARS and Avian Flu suggest that SARS is more important to international tourist arrivals than is Avian Flu. Thus, while Avian Flu is here to stay, its effect is currently not as significant as that of SARS.
Complete Agent-driven Model-based System Testing for Autonomous Systems
In this position paper, a novel approach to testing complex autonomous
transportation systems (ATS) in the automotive, avionic, and railway domains is
described. It is intended to mitigate some of the most critical problems
regarding verification and validation (V&V) effort for ATS. V&V is known to
become infeasible for complex ATS, when using conventional methods only. The
approach advocated here uses complete testing methods on the module level,
because these establish formal proofs for the logical correctness of the
software. Having established logical correctness, system-level tests are
performed in simulated cloud environments and on the target system. To give
evidence that 'sufficiently many' system tests have been performed with the
target system, a formally justified coverage criterion is introduced. To
optimise the execution of very large system test suites, we advocate an online
testing approach where multiple tests are executed in parallel, and test steps
are identified on-the-fly. The coordination and optimisation of these
executions is achieved by an agent-based approach. Each aspect of the testing
approach advocated here is shown to either be consistent with existing
standards for development and V&V of safety-critical transportation systems, or
it is justified why it should become acceptable in future revisions of the
applicable standards.Comment: In Proceedings FMAS 2021, arXiv:2110.1152
On the Pitfalls of Resource Augmentation Factors and Utilization Bounds in Real-Time Scheduling
In this paper, we take a careful look at speedup factors, utilization bounds, and capacity augmentation bounds. These three metrics have been widely adopted in real-time scheduling research as the de facto standard theoretical tools for assessing scheduling algorithms and schedulability tests. Despite that, it is not always clear how researchers and designers should interpret or use these metrics. In studying this area, we found a number of surprising results, and related to them, ways in which the metrics may be misinterpreted or misunderstood. In this paper, we provide a perspective on the use of these metrics, guiding researchers on their meaning and interpretation, and helping to avoid pitfalls in their use. Finally, we propose and demonstrate the use of parametric augmentation functions as a means of providing nuanced information that may be more relevant in practical settings
A Bayesian measurement error model for two-channel cell-based RNAi data with replicates
RNA interference (RNAi) is an endogenous cellular process in which small
double-stranded RNAs lead to the destruction of mRNAs with complementary
nucleoside sequence. With the production of RNAi libraries, large-scale RNAi
screening in human cells can be conducted to identify unknown genes involved in
a biological pathway. One challenge researchers face is how to deal with the
multiple testing issue and the related false positive rate (FDR) and false
negative rate (FNR). This paper proposes a Bayesian hierarchical measurement
error model for the analysis of data from a two-channel RNAi high-throughput
experiment with replicates, in which both the activity of a particular
biological pathway and cell viability are monitored and the goal is to identify
short hair-pin RNAs (shRNAs) that affect the pathway activity without affecting
cell activity. Simulation studies demonstrate the flexibility and robustness of
the Bayesian method and the benefits of having replicates in the experiment.
This method is illustrated through analyzing the data from a RNAi
high-throughput screening that searches for cellular factors affecting HCV
replication without affecting cell viability; comparisons of the results from
this HCV study and some of those reported in the literature are included.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS496 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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