Pulse-Shape discrimination with the Counting Test Facility

Pulse shape discrimination (PSD) is one of the most distinctive features of liquid scintillators. Since the introduction of the scintillation techniques in the field of particle detection, many studies have been carried out to characterize intrinsic properties of the most common liquid scintillator mixtures in this respect. Several application methods and algorithms able to achieve optimum discrimination performances have been developed. However, the vast majority of these studies have been performed on samples of small dimensions. The Counting Test Facility, prototype of the solar neutrino experiment Borexino, as a 4 ton spherical scintillation detector immersed in 1000 tons of shielding water, represents a unique opportunity to extend the small-sample PSD studies to a large-volume setup. Specifically, in this work we consider two different liquid scintillation mixtures employed in CTF, illustrating for both the PSD characterization results obtained either with the processing of the scintillation waveform through the optimum Gatti's method, or via a more conventional approach based on the charge content of the scintillation tail. The outcomes of this study, while interesting per se, are also of paramount importance in view of the expected Borexino detector performances, where PSD will be an essential tool in the framework of the background rejection strategy needed to achieve the required sensitivity to the solar neutrino signals.Comment: 39 pages, 17 figures, submitted to Nucl. Instr. Meth.

Nucleocytoplasmic transport: a thermodynamic mechanism

The nuclear pore supports molecular communication between cytoplasm and nucleus in eukaryotic cells. Selective transport of proteins is mediated by soluble receptors, whose regulation by the small GTPase Ran leads to cargo accumulation in, or depletion from the nucleus, i.e., nuclear import or nuclear export. We consider the operation of this transport system by a combined analytical and experimental approach. Provocative predictions of a simple model were tested using cell-free nuclei reconstituted in Xenopus egg extract, a system well suited to quantitative studies. We found that accumulation capacity is limited, so that introduction of one import cargo leads to egress of another. Clearly, the pore per se does not determine transport directionality. Moreover, different cargo reach a similar ratio of nuclear to cytoplasmic concentration in steady-state. The model shows that this ratio should in fact be independent of the receptor-cargo affinity, though kinetics may be strongly influenced. Numerical conservation of the system components highlights a conflict between the observations and the popular concept of transport cycles. We suggest that chemical partitioning provides a framework to understand the capacity to generate concentration gradients by equilibration of the receptor-cargo intermediary.Comment: in press at HFSP Journal, vol 3 16 text pages, 1 table, 4 figures, plus Supplementary Material include

A New Approach to Probabilistic Programming Inference

We introduce and demonstrate a new approach to inference in expressive probabilistic programming languages based on particle Markov chain Monte Carlo. Our approach is simple to implement and easy to parallelize. It applies to Turing-complete probabilistic programming languages and supports accurate inference in models that make use of complex control flow, including stochastic recursion. It also includes primitives from Bayesian nonparametric statistics. Our experiments show that this approach can be more efficient than previously introduced single-site Metropolis-Hastings methods.Comment: Updated version of the 2014 AISTATS paper (to reflect changes in new language syntax). 10 pages, 3 figures. Proceedings of the Seventeenth International Conference on Artificial Intelligence and Statistics, JMLR Workshop and Conference Proceedings, Vol 33, 201

Quality management and profitability linkage: Does the length of QM adoption act as the moderating variable?

Manufacturing companies in Malaysia have never had it so tough. They are now confronting increasing prices of oil and raw materials, high advancement in innovation and technology, as well as high customer expectation on the quality of products and services. In addition, managers of these companies are well aware of the increasing competitive pressures in the world market. It is clear today that these pressures are due largely to the increased performance of those firms that have successfully implemented quality improvement.This paper presents the findings from an empirical study examining the relationship between quality management (QM) practices and profitability in the electronics and electrical industry in Malaysia. It is said that QM has the potential to not only enhance production efficiency and effectiveness, but also improves bottom-line results. Much has been written about the relationship between QM and performance. However, the link of QM practices to profitability in the electronics and electrical industry in Malaysia has not been fully addressed in empirical studies. To address this issue, this paper investigates the impact of QM practices on profitability in the Malaysian electronics and electrical industry using correlation, multiple regression,and hierarchical regression analyses. The findings revealed that quality measurement, supplier relations, and benchmarking in particular, appear to be of primary importance and exhibit significant impact on profitability. Findings of the study provided a striking demonstration of the importance of implementing effective QM practices for the electronics and electrical industry in Malaysia in enhancing its profitability. However, the study failed to provide the statistical evidence of the existence of the moderating effect of the length of QM adoption on the QM and profitability linkage