756 research outputs found
Study of the wind speed, rainfall and storm surges for the Scheldt estuary in Belgium
The Belgian coast and the Scheldt estuary are important for the Belgian economy. Coastal flood risks tend to increase due to climate change. This study was set out to investigate the wind speed, surges and rainfall in the Scheldt estuary. The study explored the changes in mean and extreme winds according to the recent ENSEMBLES climate models and examined the dependency of extremes between surge with wind speed and surge with rainfall. The dependence analysis between surge and wind speed aimed to investigate whether climatic changes in wind speed can be transferred to changes in surge, while the existence of dependence between surge and rainfall would require climate scenarios for rainfall upstream in the Scheldt basin to be correlated with climate scenarios for the downstream surge boundary. A special dependence measure χ, developed by Buishand (1984) and Coles et al (2000) was followed. Data was extracted and processed using Matlab and CDO. The analysis of wind speeds showed that future wind speeds in the estuary (based on the climate models) will remain stable in comparison with the past wind speeds. Also, wind direction will be mainly from 180°-300°, although slight shifts might appear towards more frequent south western winds. From the study of dependency, there was no significant dependency between sea surge at Oostende coast and rainfall at different stations. The definition of significant dependency is strong or conservative. Above all, the extremes events are more or less dependent. While the study has not found significant changes in wind speed and only slight changes in wind direction, it is important to further investigate the impact of these changes on the Scheldt estuary using hydrodynamic models. The assessment of changes in extreme rainfall and sea surge need to be further studied
The effect of nuclear deformation on level statistics
We analyze the nearest neighbor spacing distributions of low-lying 2+ levels
of even-even nuclei. We grouped the nuclei into classes defined by the
quadrupole deformation parameter (Beta2). We calculate the nearest neighbor
spacing distributions for each class. Then, we determine the chaoticity
parameter for each class with the help of the Bayesian inference method. We
compare these distributions to a formula that describes the transition to chaos
by varying a tuning parameter. This parameter appears to depend in a
non-trivial way on the nuclear deformation, and takes small values indicating
regularity in strongly deformed nuclei and especially in those having an oblate
deformation.Comment: 10 Pages, 6 figure
An assessment of hydrogen fuel cell vehicles in Malaysia
Hydrogen Fuel Cell Vehicles (HFCV) as a backstop technology has the potential to meet energy security needs especially in the transportation sector of the economy. A good number of studies assessing the acceptance of HFCV as a renewable energy source in relation to other economic factors indicate that HFCV can meet increasing energy consumption needs, significantly reduce CO2 emission and increase energy security of a country. Scientific evidence has shown that the adoption of hydrogen pathway is expected to have beneficial economic and environmental impact. The momentum of current research in this area is focused on optimizing the potential benefits. This article highlights issues and prospects, energy security, economic and environmental impact of HFCV in the Malaysian context. Key methods and assumptions of the literature are duly discussed to lessen these concerns and to help the research community towards the development of HFCV that is expected to benefit and bring forth effective prospects to Malaysia and elsewhere
Random matrix theory within superstatistics
We propose a generalization of the random matrix theory following the basic
prescription of the recently suggested concept of superstatistics. Spectral
characteristics of systems with mixed regular-chaotic dynamics are expressed as
weighted averages of the corresponding quantities in the standard theory
assuming that the mean level spacing itself is a stochastic variable. We
illustrate the method by calculating the level density, the
nearest-neighbor-spacing distributions and the two-level correlation functions
for system in transition from order to chaos. The calculated spacing
distribution fits the resonance statistics of random binary networks obtained
in a recent numerical experiment.Comment: 20 pages, 6 figure
Spectral fluctuation properties of spherical nuclei
The spectral fluctuation properties of spherical nuclei are considered by use
of NNSD statistic. With employing a generalized Brody distribution included
Poisson, GOE and GUE limits and also MLE technique, the chaoticity parameters
are estimated for sequences prepared by all the available empirical data. The
ML-based estimated values and also KLD measures propose a non regular dynamic.
Also, spherical odd-mass nuclei in the mass region, exhibit a slight deviation
to the GUE spectral statistics rather than the GOE.Comment: 10 pages, 2 figure
Superstatistical random-matrix-theory approach to transition intensities in mixed systems
We study the fluctuation properties of transition intensities applying a
recently proposed generalization of the random matrix theory, which is based on
Beck and Cohen's superstatistics. We obtain an analytic expression for the
distribution of the reduced transition probabilities that applies to systems
undergoing a transition out of chaos. The obtained distribution fits the
results of a previous nuclear shell model calculations for some electromagnetic
transitions that deviate from the Porter-Thomas distribution. It agrees with
the experimental reduced transition probabilities for the 26A nucleus better
than the commonly used chi-squared distribution.Comment: 14 pages, 3 figure
Kappa-deformed random-matrix theory based on Kaniadakis statistics
We present a possible extension of the random-matrix theory, which is widely
used to describe spectral fluctuations of chaotic systems. By considering the
Kaniadakis non-Gaussian statistics, characterized by the index {\kappa}
(Boltzmann-Gibbs entropy is recovered in the limit {\kappa}\rightarrow0), we
propose the non-Gaussian deformations ({\kappa} \neq 0) of the conventional
orthogonal and unitary ensembles of random matrices. The joint eigenvalue
distributions for the {\kappa}-deformed ensembles are derived by applying the
principle maximum entropy to Kaniadakis entropy. The resulting distribution
functions are base invarient as they depend on the matrix elements in a trace
form. Using these expressions, we introduce a new generalized form of the
Wigner surmise valid for nearly-chaotic mixed systems, where a
basis-independent description is still expected to hold. We motivate the
necessity of such generalization by the need to describe the transition of the
spacing distribution from chaos to order, at least in the initial stage. We
show several examples about the use of the generalized Wigner surmise to the
analysis of the results of a number of previous experiments and numerical
experiments. Our results suggest the entropic index {\kappa} as a measure for
deviation from the state of chaos. We also introduce a {\kappa}-deformed
Porter-Thomas distribution of transition intensities, which fits the
experimental data for mixed systems better than the commonly-used
gamma-distribution.Comment: 18 pages, 8 figure
Multiplex shRNA screening of germ cell development by in vivo transfection of mouse testis
Spermatozoa are one of the few mammalian cell types that cannot be fully derived in vitro, severely limiting the application of modern genomic techniques to study germ cell biology. The current gold standard approach of characterizing single-gene knockout mice is slow as generation of each mutant line can take 6–9 months. Here, we describe an in vivo approach to rapid functional screening of germline genes based on a new nonsurgical, nonviral in vivo transfection method to deliver nucleic acids into testicular germ cells. By coupling multiplex transfection of short hairpin RNA (shRNA) constructs with pooled amplicon sequencing as a readout, we were able to screen many genes for spermatogenesis function in a quick and inexpensive experiment. We transfected nine mouse testes with a pilot pool of RNA interference (RNAi) against well-characterized genes to show that this system is highly reproducible and accurate. With a false negative rate of 18% and a false positive rate of 12%, this method has similar performance as other RNAi screens in the well-described Drosophila model system. In a separate experiment, we screened 26 uncharacterized genes computationally predicted to be essential for spermatogenesis and found numerous candidates for follow-up studies. Finally, as a control experiment, we performed a long-term selection screen in neuronal N2a cells, sampling shRNA frequencies at five sequential time points. By characterizing the effect of both libraries on N2a cells, we show that our screening results from testis are tissue-specific. Our calculations indicate that the current implementation of this approach could be used to screen thousands of protein-coding genes simultaneously in a single mouse testis. The experimental protocols and analysis scripts provided will enable other groups to use this procedure to study diverse aspects of germ cell biology ranging from epigenetics to cell physiology. This approach also has great promise as an applied tool for validating diagnoses made from medical genome sequencing, or designing synthetic biological sequences that can act as potent and highly specific male contraceptives
- …