293 research outputs found
Dopant Induced Stabilization of Silicon Cluster at Finite Temperature
With the advances in miniaturization, understanding and controlling
properties of significant technological systems like silicon in nano regime
assumes considerable importance. It turns out that small silicon clusters in
the size range of 15-20 atoms are unstable upon heating and in fact fragment in
the temperature range of 1200 K to 1500 K. In the present work we demonstrate
that it is possible to stabilize such clusters by introducing appropriate
dopant (in this case Ti). Specifically, by using the first principle density
functional simulations we show that Ti doped Si, having the Frank-Kasper
geometry, remains stable till 2200 K and fragments only above 2600 K. The
observed melting transition is a two step process. The first step is initiated
by the surface melting around 600 K. The second step is the destruction of the
cage which occurs around 2250 K giving rise to a peak in the heat capacity
curve.Comment: 6 pages, 8 Figs. Submitted to PR
Survey on Classification of Online Reviews Based on Social Networking
For what reason would individuals like to vote in favor of or against content at some online groups and not at others? Social foraging hypothesis, mainly research on insect and other animal information sharing behavior, it provides new approach. Obtaining ideas from social searching hypothesis, this survey suggests that four components drive individuals' goal to vote online content (positive or negative): 1) altruistic intentions; 2) identification with the community; 3) data quality; and 4) learning self-adequacy. The survey show was tried in a study of online news groups. It found that positive voting goal was anticipated by altruistic motives, identification with the community, and learning self-adequacy. Data quality is critical for positive voting; however, it works in a indirect way through cultivating more group recognition. Negative voting expectation was anticipated by altruistic motives and data quality. Earlier research has connected through searching hypothesis to people acting alone, e.g., when an individual uses Google to search for data on the web. This survey grows the utilization of searching hypothesis to the group surroundings where people give votes to impact others in their selected group. The discoveries advance our insight about content voting and give suggestions to experts of voting systems
Raman Signatures of Strong Kitaev Exchange Correlations in (NaLi)IrO : Experiments and Theory
Inelastic light scattering studies on single crystals of
(NaLi)IrO ( and ) show a polarization
independent broad band at ~2750 cm with a large band-width ~cm. For NaIrO the broad band is seen for temperatures ~K and persists inside the magnetically ordered state. For Li doped
samples, the intensity of this mode increases, shifts to lower wave-numbers and
persists to higher temperatures. Such a mode has recently been predicted
(Knolle et.al.) as a signature of the Kitaev spin liquid. We assign the
observation of the broad band to be a signature of strong Kitaev-exchange
correlations. The fact that the broad band persists even inside the
magnetically ordered state suggests that dynamically fluctuating moments
survive even below . This is further supported by our mean field
calculations. The Raman response calculated in mean field theory shows that the
broad band predicted for the spin liquid state survives in the magnetically
ordered state near the zigzag-spin liquid phase boundary. A comparison with the
theoretical model gives an estimate of the Kitaev exchange interaction
parameter to be ~meV.Comment: 14pages 4 figure
Evolutionary dynamics of the most populated genotype on rugged fitness landscapes
We consider an asexual population evolving on rugged fitness landscapes which
are defined on the multi-dimensional genotypic space and have many local
optima. We track the most populated genotype as it changes when the population
jumps from a fitness peak to a better one during the process of adaptation.
This is done using the dynamics of the shell model which is a simplified
version of the quasispecies model for infinite populations and standard
Wright-Fisher dynamics for large finite populations. We show that the
population fraction of a genotype obtained within the quasispecies model and
the shell model match for fit genotypes and at short times, but the dynamics of
the two models are identical for questions related to the most populated
genotype. We calculate exactly several properties of the jumps in infinite
populations some of which were obtained numerically in previous works. We also
present our preliminary simulation results for finite populations. In
particular, we measure the jump distribution in time and find that it decays as
as in the quasispecies problem.Comment: Minor changes. To appear in Phys Rev
Quantum entanglement in the NMR implementation of the Deutsch-Jozsa algorithm
A scheme to execute an n-bit Deutsch-Jozsa (D-J) algorithm using n qubits has
been implemented for up to three qubits on an NMR quantum computer. For the one
and two bit Deutsch problem, the qubits do not get entangled, hence the NMR
implementation is achieved without using spin-spin interactions. It is for the
three bit case, that the manipulation of entangled states becomes essential.
The interactions through scalar J-couplings in NMR spin systems have been
exploited to implement entangling transformations required for the three bit
D-J algorithm.Comment: 4-pages in revtex with 5 eps figure included using psfi
Contrasting X-ray/UV time-lags in Seyfert 1 galaxies NGC 4593 and NGC 7469 using AstroSat observations
We study accretion disk-corona connection in Seyfert 1 galaxies using
simultaneous UV/X-ray observations of NGC 4593 (July 14-18, 2016) and NGC 7469
(October 15-19, 2017) performed with AstroSat. We use the X-ray (0.5-7.0 keV)
data acquired with the Soft X-ray Telescope (SXT) and the UV (FUV: 130-180 nm,
NUV: 200-300 nm) data obtained with the Ultra-Violet Imaging Telescope (UVIT).
We also use the contemporaneous Swift observations of NGC 4593 and demonstrate
AstroSat's capability for X-ray/UV correlation studies. We performed UV/X-ray
cross-correlation analysis using the Interpolated and the Discrete
Cross-Correlation Functions and found similar results. In the case of NGC 4593,
we found that the variations in the X-rays lead to those in the FUV and NUV
bands by ~ 38 ks and ~ 44 ks, respectively. These UV lags favour the disk
reprocessing model, they are consistent with the previous results within
uncertainties. In contrast, we found an opposite trend in NGC 7469 where the
soft X-ray variations lag those in the FUV and NUV bands by ~ 41 ks and ~ 49
ks, respectively. The hard lags in NGC 7469 favour the Thermal Comptonization
model. Our results may provide direct observational evidence for the variable
intrinsic UV emission from the accretion disk which acts as the seed for
thermal Comptonization in a hot corona in a lamp-post like geometry. The
non-detection of disk reverberation photons in NGC 7469, using AstroSat data,
is most likely due to a high accretion rate resulting in a hot accretion disk
and large intrinsic emission.Comment: 14 pages, 20 figures, Accepted for publication in MNRA
Use of Quadrupolar Nuclei for Quantum Information processing by Nuclear Magnetic Resonance: Implementation of a Quantum Algorithm
Physical implementation of Quantum Information Processing (QIP) by
liquid-state Nuclear Magnetic Resonance (NMR), using weakly coupled spin-1/2
nuclei of a molecule, is well established. Nuclei with spin1/2 oriented in
liquid crystalline matrices is another possibility. Such systems have multiple
qubits per nuclei and large quadrupolar couplings resulting in well separated
lines in the spectrum. So far, creation of pseudopure states and logic gates
have been demonstrated in such systems using transition selective
radio-frequency pulses. In this paper we report two novel developments. First,
we implement a quantum algorithm which needs coherent superposition of states.
Second, we use evolution under quadrupolar coupling to implement multi qubit
gates. We implement Deutsch-Jozsa algorithm on a spin-3/2 (2 qubit) system. The
controlled-not operation needed to implement this algorithm has been
implemented here by evolution under the quadrupolar Hamiltonian. This method
has been implemented for the first time in quadrupolar systems. Since the
quadrupolar coupling is several orders of magnitude greater than the coupling
in weakly coupled spin-1/2 nuclei, the gate time decreases, increasing the
clock speed of the quantum computer.Comment: 16 pages, 3 figure
Green nanotechnology of MGF‑AuNPs for immunomodulatory intervention in prostate cancer therapy
Abstract Men with castration-resistant prostate cancer (CRPC) face poor prognosis and increased risk of treatment-incurred adverse effects resulting in one of the highest mortalities among patient population globally. Immune cells act as double-edged sword depending on the tumor microenvironment, which leads to increased infiltration of pro-tumor (M2) macrophages. Development of new immunomodulatory therapeutic agents capable of targeting the tumor microenvironment, and hence orchestrating the transformation of pro-tumor M2 macrophages to anti-tumor M1, would substantially improve treatment outcomes of CRPC patients. We report, herein, Mangiferin functionalized gold nanoparticulate agent (MGF-AuNPs) and its immunomodulatory characteristics in treating prostate cancer. We provide evidence of immunomodulatory intervention of MGF-AuNPs in prostate cancers through observations of enhanced levels of anti-tumor cytokines (IL-12 and TNF-α) with concomitant reductions in the levels of pro-tumor cytokines (IL-10 and IL-6). In the MGF-AuNPs treated groups, IL-12 was elevated to ten-fold while TNF-α was elevated to about 50-fold, while IL-10 and IL-6 were reduced by two-fold. Ability of MGF-AuNPs to target splenic macrophages is invoked via targeting of NF-kB signaling pathway. Finally, therapeutic efficacy of MGF-AuNPs, in treating prostate cancer in vivo in tumor bearing mice, is described taking into consideration various immunomodulatory interventions triggered by this green nanotechnology-based nanomedicine agent
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