2,370 research outputs found
Cavity optomechanics with stoichiometric SiN films
We study high-stress SiN films for reaching the quantum regime with
mesoscopic oscillators connected to a room-temperature thermal bath, for which
there are stringent requirements on the oscillators' quality factors and
frequencies. Our SiN films support mechanical modes with unprecedented products
of mechanical quality factor and frequency reaching Hz. The SiN membranes exhibit a low optical absorption
characterized by Im at 935 nm, representing a 15 times
reduction for SiN membranes. We have developed an apparatus to simultaneously
cool the motion of multiple mechanical modes based on a short, high-finesse
Fabry-Perot cavity and present initial cooling results along with future
possibilities.Comment: 4 pages, 5 figure
Self-consistent treatment of the self-energy in nuclear matter
The influence of hole-hole propagation in addition to the conventional
particle-particle propagation, on the energy per nucleon and the momentum
distribution is investigated. The results are compared to the
Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and
conventional choice for the single-particle spectrum. The Bethe-Goldstone
equation has been solved using realistic interactions. Also, the structure
of nucleon self-energy in nuclear matter is evaluated. All the self-energies
are calculated self-consistently. Starting from the BHF approximation without
the usual angle-average approximation, the effects of hole-hole contributions
and a self-consistent treatment within the framework of the Green function
approach are investigated. Using the self-consistent self-energy, the hole and
particle self-consistent spectral functions including the particle-particle and
hole-hole ladder contributions in nuclear matter are calculated using realistic
interactions. We found that, the difference in binding energy between both
results, i.e. BHF and self-consistent Green function, is not large. This
explains why is the BHF ignored the 2h1p contribution.Comment: Preprint 20 pages including 15 figures and one tabl
Utilization of Agricultural Waste in Treating Water Pollutants
This study investigated the applicability of chemically (phosphoric acid) activated bagasse pith and date pits in the adsorption of water pollutants. The textural properties including porous parameters, monolayer equivalent surface area, total pore volumes, average pore radius, Methylene blue number and other physic-chemical characterization were investigated. The activated carbons were analyzed for moisture content, ash content. Ultimate analysis was done by using CHNS analyzer (Cairo University, Micro-analytical Center). To investigate the effect of phosphoric acid on the raw material, thermo gravimetric analysis (TGA) and differential thermo gravimetric (DTG) recordings were determined. The adsorption of heavy metals as pollutants, including Co, Sr, Cu, Cs, Pb, Cd, Ni, Fe, Zn, was studied in a batch experiments. Comparison of date pits activated carbon with commercial activated carbon was done, and the results indicated that using of prepared activated carbon for removal of Co, Sr, Cu, Cs, Pb, Cd, Ni, Fe, Zn was more effective than commercial activated carbon
Scalar FCNC and rare top decays in a two Higgs doublet model "for the top"
In the so called two Higgs doublet model for the top-quark (T2HDM), first
suggested by Das and Kao, the top quark receives a special status, which endows
it with a naturally large mass, and also potentially gives rise to large flavor
changing neutral currents (FCNC) only in the up-quark sector. In this paper we
calculate the branching ratio (BR) for the rare decays t->ch and h->tc (h is a
neutral Higgs) in the T2HDM, at tree level and at 1-loop when it exceeds the
tree-level. We compare our results to predictions from other versions of 2HDM's
and find that the scalar FCNC in the T2HDM can play a significant role in these
decays. In particular, the 1-loop mediated decays can be significantly enhanced
in the T2HDM compared to the 2HDM of types I and II, in some instances reaching
BR~10^-4 which is within the detectable level at the LHC.Comment: added two references. 15 pages, 14 figure
Energy and Momentum densities of cosmological models, with equation of state , in general relativity and teleparallel gravity
We calculated the energy and momentum densities of stiff fluid solutions,
using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes,
in both general relativity and teleparallel gravity. In our analysis we get
different results comparing the aforementioned complexes with each other when
calculated in the same gravitational theory, either this is in general
relativity and teleparallel gravity. However, interestingly enough, each
complex's value is the same either in general relativity or teleparallel
gravity. Our results sustain that (i) general relativity or teleparallel
gravity are equivalent theories (ii) different energy-momentum complexes do not
provide the same energy and momentum densities neither in general relativity
nor in teleparallel gravity. In the context of the theory of teleparallel
gravity, the vector and axial-vector parts of the torsion are obtained. We show
that the axial-vector torsion vanishes for the space-time under study.Comment: 15 pages, no figures, Minor typos corrected; version to appear in
International Journal of Theoretical Physic
Electrochemical Performance of Grids of Lead-acid Batteries made from Pb-0.8%Ca-1.1%Sn Alloys Containing Cu, As and Sb Impurities in the presence of phosphoric acid
Electrochemical performance of grids of lead-acid Batteries manufactured from Pb-0.8%Ca-1.1%Sn alloys containing Cu, As and Sb impurities at 0.1 wt% level were studied in 4.0 M H2SO4 without and with 0.4 M H3PO4. The presence of impurities in the alloy or addition of H3PO4 was found to suppress the corrosion rate. H3PO4 increased the rates of both hydrogen and oxygen evolution reactions at high overpotentials for all alloys. Except for Cu-containing alloy, H3PO4 had a slight positive effect on PbO2 formation.The self-discharge of PbO2 under polarization or opencircuitconditions increased in the presence of H3PO4 but the positive grid corrosion decreased, except for the As-containing alloy. Impurity-containing alloys showed significantly lower self-discharge rate in the presence of H3PO4 than in its absence. Impedance measurement was able to detect and quantify the formation of the highly insulating inner PbO layer beneath the outer PbSO4 layer and its transformation to the conducting PbO2, during the oxidation of alloys under constant current conditions.H3PO4 significantly enhanced the formation of PbO in thepresence of impurities, especially Sb
Energy and Momentum Distributions of Kantowski and Sachs Space-time
We use the Einstein, Bergmann-Thomson, Landau-Lifshitz and Papapetrou
energy-momentum complexes to calculate the energy and momentum distributions of
Kantowski and Sachs space-time. We show that the Einstein and Bergmann-Thomson
definitions furnish a consistent result for the energy distribution, but the
definition of Landau-Lifshitz do not agree with them. We show that a signature
switch should affect about everything including energy distribution in the case
of Einstein and Papapetrou prescriptions but not in Bergmann-Thomson and
Landau-Lifshitz prescriptions.Comment: 12 page
Smart Bagged Tree-based Classifier optimized by Random Forests (SBT-RF) to Classify Brain- Machine Interface Data
Brain-Computer Interface (BCI) is a new technology that uses electrodes and sensors to connect machines and computers with the human brain to improve a person\u27s mental performance. Also, human intentions and thoughts are analyzed and recognized using BCI, which is then translated into Electroencephalogram (EEG) signals. However, certain brain signals may contain redundant information, making classification ineffective. Therefore, relevant characteristics are essential for enhancing classification performance. . Thus, feature selection has been employed to eliminate redundant data before sorting to reduce computation time. BCI Competition III Dataset Iva was used to investigate the efficacy of the proposed system. A Smart Bagged Tree-based Classifier (SBT-RF) technique is presented to determine the importance of the features for selecting and classifying the data. As a result, SBT-RF is better at improving the mean accuracy of the dataset. It also decreases computation cost and training time and increases prediction speed. Furthermore, fewer features mean fewer electrodes, thus lowering the risk of damage to the brain. The proposed algorithm has the greatest average accuracy of ~98% compared to other relevant algorithms in the literature. SBT-RF is compared to state-of-the-art algorithms based on the following performance metrics: Confusion Matrix, ROC-AUC, F1-Score, Training Time, Prediction speed, and Accuracy
Scanning tunneling spectroscopy characterization of the pseudogap and the x = 1/8 anomaly in La2-xSrxCuO4 thin films
Using scanning tunneling spectroscopy we examined the local density of states
of thin c-axis La2-xSrxCuO4 films, over wide doping and temperature ranges. We
found that the pseudogap exists only at doping levels lower than optimal. For x
= 0.12, close to the 'anomalous' x = 1/8 doping level, a zero bias conductance
peak was the dominant spectral feature, instead of the excepted V- shaped
(c-axis tunneling) gap structure. We have established that this surprising
effect cannot be explained by tunneling into (110) facets. Possible origins for
this unique behavior are discussed.Comment: 15 pages, 6 figure
DGGE-RAPD analysis as a useful tool for cultivar identification
Denaturing gradient gel electrophoresis-random amplified polymorphic DNA (DGGE-RAPD) was used to overcome the main drawbacks of RAPD (i.e., the low levels of reproducibility and polymorphism). As a model, six barley cultivars of known origin were tested for RAPD markers using DGGE methodology with 29 arbitrary primers. Among a total of 418 bands observed, as high as 99 were polymorphic. Comparison between agarose-RAPD and DGGE-RAPD revealed that the latter was highly reproducible and gave higher level of polymorphism and consequently more markers. The relationships among barley cultivars derived from this study based on DGGE-RAPD are consistent with the known lineage of these cultivars. In conclusion, we recommend the use of DGGE-RAPD as an alternative tool to the more costly DNA-based analysis in cultivar identification in laboratories with limited funds.Key words: Denaturing gradient gel electrophoresis-random amplified polymorphic DNA, artificial heteroduplex, dendogram, lineage
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