21,815 research outputs found
Measurements of the Influence of Acceleration and Temperature of Bodies on their Weight
A brief review of experimental research of the influence of acceleration and
temperatures of test mass upon gravitation force, executed between the 1990s
and the beginning of 2000 is provided.Results of weighing a rotor of a
mechanical gyroscope with a horizontal axis, an anisotropic crystal with the
big difference of the speed of longitudinal acoustic waves, measurements of
temperature dependence of weight of metal bars of non-magnetic materials, and
also measurement of restitution coefficients at quasi-elastic impact of a steel
ball about a massive plate are given. A negative temperature dependence of the
weight of a brass core was measured. All observably experimental effects, have
probably a general physical reason connected with the weight change dependent
upon acceleration of a body or at thermal movement of its microparticles.Comment: 7 pages, 6 figures. Presented at the 5-th Symposium on New Frontiers
and Future Concepts (STAIF-2008
Forager bees (Apis mellifera) highly express immune and detoxification genes in tissues associated with nectar processing.
Pollinators, including honey bees, routinely encounter potentially harmful microorganisms and phytochemicals during foraging. However, the mechanisms by which honey bees manage these potential threats are poorly understood. In this study, we examine the expression of antimicrobial, immune and detoxification genes in Apis mellifera and compare between forager and nurse bees using tissue-specific RNA-seq and qPCR. Our analysis revealed extensive tissue-specific expression of antimicrobial, immune signaling, and detoxification genes. Variation in gene expression between worker stages was pronounced in the mandibular and hypopharyngeal gland (HPG), where foragers were enriched in transcripts that encode antimicrobial peptides (AMPs) and immune response. Additionally, forager HPGs and mandibular glands were enriched in transcripts encoding detoxification enzymes, including some associated with xenobiotic metabolism. Using qPCR on an independent dataset, we verified differential expression of three AMP and three P450 genes between foragers and nurses. High expression of AMP genes in nectar-processing tissues suggests that these peptides may contribute to antimicrobial properties of honey or to honey bee defense against environmentally-acquired microorganisms. Together, these results suggest that worker role and tissue-specific expression of AMPs, and immune and detoxification enzymes may contribute to defense against microorganisms and xenobiotic compounds acquired while foraging
Availability analysis of terrestrial free space optical (FSO) link using visibility data measured in tropical region
Haze and rain are the most impairments factors to free space optical (FSO) links. These weather conditions limit the visibility, and thereby causes high attenuation of the optical signal. This high attenuation reduces the availability performance of the FSO link. This study evaluates the performance of a terrestrial FSO link under tropical climate conditions. The performance analysis is evaluate over 5 km link distance. The cumulative distribution function (CDF) of the received signal to noise ratio (SNR) is used to study the outage performance of the FSO link under haze conditions. The performance analysis is based on three years measured visibility data in Malaysia. Based on the statistical analysis, link availability of 99.99% can be achieved for 37.44 dB SNR over 1 km link distance. Carrier class availability “five nine” can be achieved for 20 dBm transmission power using 1550 nm wavelength
On the Efficient Calculation of a Linear Combination of Chi-Square Random Variables with an Application in Counting String Vacua
Linear combinations of chi square random variables occur in a wide range of
fields. Unfortunately, a closed, analytic expression for the pdf is not yet
known. As a first result of this work, an explicit analytic expression for the
density of the sum of two gamma random variables is derived. Then a
computationally efficient algorithm to numerically calculate the linear
combination of chi square random variables is developed. An explicit expression
for the error bound is obtained. The proposed technique is shown to be
computationally efficient, i.e. only polynomial in growth in the number of
terms compared to the exponential growth of most other methods. It provides a
vast improvement in accuracy and shows only logarithmic growth in the required
precision. In addition, it is applicable to a much greater number of terms and
currently the only way of computing the distribution for hundreds of terms. As
an application, the exponential dependence of the eigenvalue fluctuation
probability of a random matrix model for 4d supergravity with N scalar fields
is found to be of the asymptotic form exp(-0.35N).Comment: 21 pages, 19 figures. 3rd versio
Quantised orbital angular momentum transfer and magnetic dichroism in the interaction of electron vortices with matter
Following the very recent experimental realisation of electron vortices, we
consider their interaction with matter, in particular the transfer of orbital
angular momentum in the context of electron energy loss spectroscopy, and the
recently observed dichroism in thin film magnetised iron samples. We show here
that orbital angular momentum exchange does indeed occur between electron
vortices and the internal electronic-type motion, as well as center of mass
motion of atoms in the electric dipole approximation. This contrasts with the
case of optical vortices where such transfer only occurs in transitions
involving multipoles higher than the dipole. The physical basis of the observed
dichroism is explained
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