148 research outputs found
The effect of disorder on phases across two-dimensional thermal melting
We study melting in a two-dimensional system of classical particles with
Gaussian-core interactions in disordered environments. The pure system
validates the conventional two-step melting with a hexatic phase intervening
between the solid and the liquid. This picture is modified in the presence of
pinning impurities. A random distribution of pinning centers forces a
hexatic-like low temperature phase that transits into a liquid at a single
melting temperature . In contrast, pinning centers located
at randomly chosen sites of a perfect crystal anchors a solid at low
temperatures which undergoes a direct transition to the liquid at . Thus, the two-step melting is lost in either cases of disorder.
We discuss the characteristics of melting depending on the nature of the
impurities.Comment: 12 pages, 13 figure
A numerical renormalization group study of laser induced freezing
We study the phenomenon of laser induced freezing, within a numerical
renormalization scheme which allows explicit comparison with a recent defect
mediated melting theory. Precise values for the `bare' dislocation fugacities
and elastic moduli of the 2-d hard disk system are obtained from a constrained
Monte Carlo simulation sampling only configurations {\em without} dislocations.
These are used as inputs to appropriate renormalization flow equations to
obtain the equilibrium phase diagram which shows excellent agreement with
earlier simulation results. We show that the flow equations need to be correct
at least up to third order in defect fugacity to reproduce meaningful results.Comment: Minor Corrections; Combined version of Europhys. Lett. 67 (2004) p.
814 and Europhys. Lett. 68 (2004) p. 16
S-Duality in N=4 Yang-Mills Theories
Evidence in favor of S-duality in supersymmetric Yang-Mills
theories in four dimensions and with general compact, simple gauge groups is
presented. (Contribution to the Proceedings of the Strings '95 conference,
March 13-18, 1995, USC, and the Proceedings of the Trieste Conference on
S-Duality and Mirror Symmetry, June 5-9, 1995.)Comment: 11 page
A CdZnTeSe Gamma Spectrometer Trained by Deep Convolutional Neural Network for Radioisotope Identification
We report the implementation of a deep convolutional neural network to train a high-resolution room-temperature CdZnTeSe based gamma ray spectrometer for accurate and precise determination of gamma ray energies for radioisotope identification. The prototype learned spectrometer consists of a NI PCI 5122 fast digitizer connected to a pre-amplifier to recognize spectral features in a sequence of data. We used simulated preamplifier pulses that resemble actual data for various gamma photon energies to train a CNN on the equivalent of 90 seconds worth of data and validated it on 10 seconds worth of simulated data
Calculation of density fluctuation in inflationary epoch
Starting from an initial state of thermal equilibrium, we derive an
expression for the quantum fluctuation in the energy density during the
inflationary epoch in terms of the mode functions for the inflaton field. The
effect of this particular initial state is not washed out in the final formula,
contrary to what is usually believed. Numerically, however, the effect is
completely negligible, validating the use of the two point function in the
vacuum state. We also point out the requirement of conventional quantum field
theory during inflation, that the quantum fluctuation in a wavelength must be
evaluated, at the latest, when the wavelength crosses the Hubble length, in
contrast to the usual practice in the literature.Comment: 12 pages, latex, 1 figure, axodra
Radiosensitization with an inhibitor of poly(ADP-ribose) glycohydrolase: A comparison with the PARP1/2/3 inhibitor olaparib
Upon DNA binding the poly(ADP-ribose) polymerase family of enzymes (PARPs) add multiple ADP-ribose subunits to themselves and other acceptor proteins. Inhibitors of PARPs have become an exciting and real prospect for monotherapy and as sensitizers to ionising radiation (IR). The action of PARPs are reversed by poly(ADP-ribose) glycohydrolase (PARG). Until recently studies of PARG have been limited by the lack of an inhibitor. Here, a first in class, specific, and cell permeable PARG inhibitor, PDD00017273, is shown to radiosensitize. Further, PDD00017273 is compared with the PARP1/2/3 inhibitor olaparib. Both olaparib and PDD00017273 altered the repair of IR-induced DNA damage, resulting in delayed resolution of RAD51 foci compared with control cells. However, only PARG inhibition induced a rapid increase in IR-induced activation of PRKDC (DNA-PK) and perturbed mitotic progression. This suggests that PARG has additional functions in the cell compared with inhibition of PARP1/2/3, likely via reversal of tankyrase activity and/or that inhibiting the removal of poly(ADP-ribose) (PAR) has a different consequence to inhibiting PAR addition. Overall, our data are consistent with previous genetic findings, reveal new insights into the function of PAR metabolism following IR and demonstrate for the first time the therapeutic potential of PARG inhibitors as radiosensitizing agents
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