3,297 research outputs found
Non-Markovian Dynamics of Charge Carriers in Quantum Dots
We have investigated the dynamics of bound particles in multilevel
current-carrying quantum dots. We look specifically in the regime of resonant
tunnelling transport, where several channels are available for transport.
Through a non-Markovian formalism under the Born approximation, we investigate
the real-time evolution of the confined particles including transport-induced
decoherence and relaxation. In the case of a coherent superposition between
states with different particle number, we find that a Fock-space coherence may
be preserved even in the presence of tunneling into and out of the dot.
Real-time results are presented for various asymmetries of tunneling rates into
different orbitals.Comment: 9 pages, 3 figures, International Workshop on Physics-Based
Mathematical Models for Low-Dimensional Semiconductor Nanostructures. BIRS,
November 18-23, 200
Bose Condensation and the BTZ Black Hole
Although all popular approaches to quantum gravity are able to recover the
Bekenstein-Hawking entropy-area law in the thermodynamic limit, there are
significant differences in their descriptions of the microstates and in the
application of statistics. Therefore they can have significantly different
phenomenological implications. For example, requiring indistinguishability of
the elementary degrees of freedom should lead to changes in the black hole's
radiative porperties away from the thermodynamic limit and at low temperatures.
We demonstrate this for the Ba\~nados-Teitelboim-Zanelli (BTZ) black hole. The
energy eigenstates and statistical entropy in the thermodynamic limit of the
BTZ black hole were obtained earlier by us via symmetry reduced canonical
quantum gravity. In that model the BTZ black hole behaves as a system of
Bosonic mass shells moving in a one dimensional harmonic trap. Bose
condensation does not occur in the thermodynamic limit but this system
possesses a finite critical temperature, , and exhibits a large condensate
fraction below when the number of shells is finite.Comment: 5 pages, 5 figures. Published versio
The Quantum States and the Statistical Entropy of the Charged Black Hole
We quantize the Reissner-Nordstr\"om black hole using an adaptation of
Kucha\v{r}'s canonical decomposition of the Kruskal extension of the
Schwarzschild black hole. The Wheeler-DeWitt equation turns into a functional
Schroedinger equation in Gaussian time by coupling the gravitational field to a
reference fluid or dust. The physical phase space of the theory is spanned by
the mass, , the charge, , the physical radius, , the dust proper time,
, and their canonical momenta. The exact solutions of the functional
Schroedinger equation imply that the difference in the areas of the outer and
inner horizons is quantized in integer units. This agrees in spirit, but not
precisely, with Bekenstein's proposal on the discrete horizon area spectrum of
black holes. We also compute the entropy in the microcanonical ensemble and
show that the entropy of the Reissner-Nordstr\"om black hole is proportional to
this quantized difference in horizon areas.Comment: 31 pages, 3 figures, PHYZZX macros. Comments on the wave-functional
in the interior and one reference added. To appear in Phys. Rev.
Toward a Midisuperspace Quantization of LeMaitre-Tolman-Bondi Collapse Models
LeMa\^\i tre-Tolman-Bondi models of spherical dust collapse have been used
and continue to be used extensively to study various stellar collapse
scenarios. It is by now well-known that these models lead to the formation of
black holes and naked singularities from regular initial data. The final
outcome of the collapse, particularly in the event of naked singularity
formation, depends very heavily on quantum effects during the final stages.
These quantum effects cannot generally be treated semi-classically as quantum
fluctuations of the gravitational field are expected to dominate before the
final state is reached. We present a canonical reduction of LeMa\^\i
tre-Tolman-Bondi space-times describing the marginally bound collapse of
inhomogeneous dust, in which the physical radius, , the proper time of the
collapsing dust, , and the mass function, , are the canonical
coordinates, , and on the phase space. Dirac's
constraint quantization leads to a simple functional (Wheeler-DeWitt) equation.
The equation is solved and the solution can be employed to study some of the
effects of quantum gravity during gravitational collapse with different initial
conditions.Comment: 9 pages, 1 figure, Latex file. Minor corrections made. A general
solution of the constraints is presented. Revised version to appear in Phys.
Rev.
Enhancing Syntactic Competency Of Engineering Students In English Using CLIL
Content and Language Integrated Learning (CLIL) may be seen as a type of instruction where students can study foreign languages and specialized material concurrently, depending on the subject matter. By striking a balance between professional education and the acquisition of foreign language abilities, CLIL greatly enhances students' motivation, responsibility, and personal growth. CLIL is a type of bilingual education where students study foreign languages and subject material at the same time. Through teaching trials, the efficacy of the CLIL technique as an academic subject for second-year mechanical engineering students was examined in this study. Mechanical engineering second semester students are taken into consideration. Subject and English professors provided ideas for the "definitions" for the elements utilized in the Engineering Practice Lab, which were taken from the Professional English curriculum. Only mechanical engineering students taking English as a supplement are the topic of this study. The main research approach is educational experiments; alternative research methods include survey questionnaires that are used as pre- and post-tests at the start and finish of the study. Based on the survey questionnaire responses, a statistical assessment of the students' syntactic proficiency was conducted. The study's findings demonstrate students' interest in developing their definition-building abilities with favorable opinions on CLIL.
 
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
Globalization And Its Effect On Post-Millennium Literature
Globalization, as a slowly spreading risk factor, covers almost the whole country with its full force. Literature and literary studies have evolved into a space for the evocation, promotion and interpretation of various social, political, literary and cultural ideas in the world of globalization. Indian Literature after Independence of India has seen some significant changes in the literary writings. Today, the younger generation in the country is searching for a new identity and they are at the intersection of Individuality, Culture and Society. In the world of literature, the call-center generation sees itself as India’s cultural commissars, projecting India as a land of illumination and emancipation. The major Samson of the youth lies in the power of the youth through the unlimited consumption of natural and human resources. The novels of the millennium assist us in dispelling the myth that contemporary writing is only for the light entertainment of the younger generations.
 
Candidate alzheimer’s disease biomarker mir-483-5p lowers tau phosphorylation by direct erk1/2 repression
MicroRNAs have been demonstrated as key regulators of gene expression in the etiology of a range of diseases including Alzheimer’s disease (AD). Recently, we identified miR-483-5p as the most upregulated miRNA amongst a panel of miRNAs in blood plasma specific to prodromal, early-stage Alzheimer’s disease patients. Here, we investigated the functional role of miR-483-5p in AD pathology. Using TargetScan and miRTarBase, we identified the microtubule-associated protein MAPT, often referred to as TAU, and the extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2), known to phosphorylate TAU, as predicted direct targets of miR-483-5p. Employing several functional assays, we found that miR-483-5p regulates ERK1 and ERK2 at both mRNA and protein levels, resulting in lower levels of phosphorylated forms of both kinases. Moreover, miR-483-5p-mediated repression of ERK1/2 resulted in reduced phosphorylation of TAU protein at epitopes associated with TAU neurofibrillary pathology in AD. These results indicate that upregulation of miR-483-5p can decrease phosphorylation of TAU via ERK pathway, representing a compensatory neuroprotective mechanism in AD pathology. This miR-483-5p/ERK1/TAU axis thus represents a novel target for intervention in AD.This work has been supported by the Polish National Science Centre grant OPUS 2018/29 /B/NZ7/02757, by the EU Horizon 2020 FETOPEN grant, agreement no 737390 (ArrestAD), and by the funding from the Polish Ministry of Science and Higher Education within 2016-2020 funds for the implementation of international projects (agreement no 3548/H2020/COFUND/2016/2). A.F. research internship in Portugal was supported by Erasmus fellowship
Mass Quantization of the Schwarzschild Black Hole
We examine the Wheeler-DeWitt equaton for a static, eternal Schwarzschild
black hole in Kucha\v r-Brown variables and obtain its energy eigenstates.
Consistent solutions vanish in the exterior of the Kruskal manifold and are
non-vanishing only in the interior. The system is reminiscent of a particle in
a box. States of definite parity avoid the singular geometry by vanishing at
the origin. These definite parity states admit a discrete energy spectrum,
depending on one quantum number which determines the Arnowitt-Deser-Misner
(ADM) mass of the black hole according to a relation conjectured long ago by
Bekenstein, . If attention is restricted only to these
quantized energy states, a black hole is described not only by its mass but
also by its parity. States of indefinite parity do not admit a quantized mass
spectrum.Comment: Change in eq. (13). Factors of 4 cleaned up. Refs. adde
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