1,491 research outputs found
Evolution of Parton Fragmentation Functions at Finite Temperature
The first order correction to the parton fragmentation functions in a thermal
medium is derived in the leading logarithmic approximation in the framework of
thermal field theory. The medium-modified evolution equations of the parton
fragmentation functions are also derived. It is shown that all infrared
divergences, both linear and logarithmic, in the real processes are canceled
among themselves and by corresponding virtual corrections. The evolution of the
quark number and the energy loss (or gain) induced by the thermal medium are
investigated.Comment: 21 pages in RevTex, 10 figure
Ironic effects of thought suppression: a meta-analysis
The ironic effect of thought suppression refers to the phenomenon in which individuals trying to rid their mind of a target thought ironically experience greater levels of occurrence and accessibility of the thought compared to individuals that deliberately concentrate on the thought (Wegner, 1994). Ironic effects occurring after thought suppression, also known as rebound effects, have been consistently detected by previous meta-analyses. However, ironic effects that occur during thought suppression, also known as immediate enhancement effects, have been found to be largely absent. In the current meta-analysis, we test Wegner’s original proposition that detection of immediate enhancement effects is dependent on the cognitive load experienced by individuals when enacting thought suppression. Given that thought suppression is an effortful cognitive process, it is proposed that the introduction of additional cognitive load would compete for the allocation of existing cognitive resources and impair capacity for thought suppression. Studies (k = 31) consistent with Wegner’s original thought suppression paradigm were analysed. Consistent with our predictions, rebound effects were observed regardless of cognitive load while immediate enhancement effects were only observed in the presence of cognitive load. Implications are discussed in light of ironic process theory and suggestions for future thought suppression research provided
Modulating the catalytic activity of enzyme-like nanoparticles through their surface functionalization
The inclusion of transition metal catalysts into nanoparticle scaffolds permits the creation of catalytic nanosystems (nanozymes) able to imitate the behaviour of natural enzymes. Here we report the fabrication of a family of nanozymes comprised of bioorthogonal ruthenium catalysts inserted in the protective monolayer of gold nanoparticles. By introducing simple modifications to the functional groups at the surface of the nanozymes, we have demonstrated control over the kinetic mechanism of our system. Cationic nanozymes with hydrophobic surface functionalities tend to replicate the classical Michaelis Menten model, while those with polar groups display substrate inhibition behaviour, a key mechanism present in 20% of natural enzymes. The structural parameters described herein can be used for creating artificial nanosystems that mimic the complexity observed in cell machinery. © 2018 The Royal Society of Chemistry
The Hydrodynamics of M-Theory
We consider the low energy limit of a stack of N M-branes at finite
temperature. In this limit, the M-branes are well described, via the AdS/CFT
correspondence, in terms of classical solutions to the eleven dimensional
supergravity equations of motion. We calculate Minkowski space two-point
functions on these M-branes in the long-distance, low-frequency limit, i.e. the
hydrodynamic limit, using the prescription of Son and Starinets
[hep-th/0205051]. From these Green's functions for the R-currents and for
components of the stress-energy tensor, we extract two kinds of diffusion
constant and a viscosity. The N dependence of these physical quantities may
help lead to a better understanding of M-branes.Comment: 1+19 pages, references added, section 5 clarified, eq. (72) correcte
Pluripotency and the endogenous retrovirus HERVH: Conflict or serendipity?
Remnants of ancient retroviral infections during evolution litter all mammalian genomes. In modern humans, such endogenous retroviral (ERV) sequences comprise at least 8% of the genome. While ERVs and other types of transposable elements undoubtedly contribute to the genomic "junk yard", functions for some ERV sequences have been demonstrated, with growing evidence that ERVs can be important players in gene regulatory processes. Here we focus on one particular large family of human ERVs, termed HERVH, which several recent studies suggest has a key regulatory role in human pluripotent stem cells. Remarkably, this is not the first instance of an ERV controlling pluripotency. We speculate as to why this convergent evolution might have come about, suggesting that it may reflect selection on the virus to extend the time available for transposition. Alternatively it may reflect serendipity alone
Quark Coulomb Interactions and the Mass Difference of Mirror Nuclei
We study the Okamoto-Nolen-Schiffer (ONS) anomaly in the binding energy of
mirror nuclei at high density by adding a single neutron or proton to a quark
gluon plasma. In this high-density limit we find an anomaly equal to two-thirds
of the Coulomb exchange energy of a proton. This effect is dominated by quark
electromagnetic interactions---rather than by the up-down quark mass
difference. At normal density we calculate the Coulomb energy of neutron matter
using a string-flip quark model. We find a nonzero Coulomb energy because of
the neutron's charged constituents. This effect could make a significant
contribution to the ONS anomaly.Comment: 4 pages, 2 figs. sub. to Phys. Rev. Let
Energy Loss of a Heavy Quark Produced in a Finite Size Medium
We study the medium-induced energy loss suffered by a
heavy quark produced at initial time in a quark-gluon plasma, and escaping the
plasma after travelling the distance . The heavy quark is treated
classically, and within the same framework consistently
includes: the loss from standard collisional processes, initial bremsstrahlung
due to the sudden acceleration of the quark, and transition radiation. The
radiative loss {\it induced by rescatterings} is not
included in our study. For a ultrarelativistic heavy quark with momentum p
\gsim 10 {\rm GeV}, and for a finite plasma with L_p \lsim 5 {\rm fm}, the
loss is strongly suppressed compared to the stationary
collisional contribution . Our results
support that is the dominant contribution to the heavy quark
energy loss (at least for L_p \lsim 5 {\rm fm}), as indeed assumed in most of
jet-quenching analyses. However they might raise some question concerning the
RHIC data on large electron spectra.Comment: 18 pages, 3 figures. New version clarified and simplified. A critical
discussion added in section 2, and previous sections 3 and 4 have been merged
together. Main results are unchange
Birman-Wenzl-Murakami Algebra and the Topological Basis
In this paper, we use entangled states to construct 9x9-matrix
representations of Temperley-Lieb algebra (TLA), then a family of 9x9-matrix
representations of Birman-Wenzl-Murakami algebra (BWMA) have been presented.
Based on which, three topological basis states have been found. And we apply
topological basis states to recast nine-dimensional BWMA into its
three-dimensional counterpart. Finally, we find the topological basis states
are spin singlet states in special case.Comment: 11pages, 1 figur
Saturation and parton level Cronin effect: enhancement vs suppression of gluon production in p-A and A-A collisions
We note that the phenomenon of perturbative saturation leads to transverse
momentum broadening in the spectrum of partons produced in hadronic collisions.
This broadening has a simple interpretation as parton level Cronin effect for
systems in which saturation is generated by the "tree level" Glauber-Mueller
mechanism. For systems where the broadening results form the nonlinear QCD
evolution to high energy, the presence or absence of Cronin effect depends
crucially on the quantitative behavior of the gluon distribution functions at
transverse momenta kt outside the so called scaling window. We discuss the
relation of this phenomenon to the recent analysis by Kharzeev-Levin-McLerran
of the momentum and centrality dependence of particle production in
nucleus-nucleus collisions at RHIC.Comment: 22 pages LaTex, 7 eps-figures, discussion of evolved gluon
distribution revised significantl
Some Bianchi Type III String Cosmological Models with Bulk Viscosity
We investigate the integrability of cosmic strings in Bianchi III space-time
in presence of a bulk viscous fluid by applying a new technique. The behaviour
of the model is reduced to the solution of a single second order nonlinear
differential equation. We show that this equation admits an infinite family of
solutions. Some physical consequences from these results are also discussed.Comment: 12 pages, no figure. To appear in Int. J. Theor. Phy
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