5,736 research outputs found
Influence of Fermion Velocity Renormalization on Dynamical Mass Generation in QED
We study dynamical fermion mass generation in (2+1)-dimensional quantum
electrodynamics with a gauge field coupling to massless Dirac fermions and
non-relativistic scalar bosons. We calculate the fermion velocity
renormalization and then examine its influence on dynamical mass generation by
using the Dyson-Schwinger equation. It is found that dynamical mass generation
takes place even after including the scalar bosons as long as the bosonic
compressibility parameter is sufficiently small. In addition, the fermion
velocity renormalization enhances the dynamically generated mass.Comment: 6 pages, 3 figures, Chinese Physics Letter, Vol 29, page 057401(2012
Modelling the Mechanical Behaviour of a Pharmaceutical Tablet Using PDEs.
yesDetailed design of pharmaceutical tablets is essential nowadays in order to produce robust tablets with tailor-made properties. Compressibility and compactibility are the main compaction properties involved in the design and development of solid dosage forms. The data obtained from measured forces and displacements of the punch are normally analysed using the Heckel model to assess the mechanical behaviour of pharmaceutical powders. In this paper, we present a technique for shape modelling of pharmaceutical tablets based on the PDE method. We extended the formulation of the PDE method to a higher dimensional space in order to generate a solid tablet and a cuboid mesh is created to represent the tablet¿s components. We also modelled the displacement components of a compressed PDE- based representation of a tablet by utilising the solution of the axisymmetric boundary value problem for a finite cylinder subject to a uniform axial load. The experimental data and the results obtained from the developed model are shown in Heckel plots and a good agreement is found between both.Available in full text since 5th Feb 2013 following the publisher's embargo period
Neutron Transfer reactions induced by 8Li on 9Be
Angular distributions for the elastic scattering of 8Li on 9Be and the
neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been
measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for
8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between
the experimental differential cross section and finite-range DWBA calculations
with the code FRESCO. The spectroscopic factors obtained are compared to shell
model calculations and to other experimental values from (d,p) reactions. Using
the present values for the spectroscopic factor, cross sections for the direct
neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the
framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR
The Physical Origins of Entropy Production, Free Energy Dissipation and their Mathematical Representations
A complete mathematical theory of nonequilibrium thermodynamics of stochastic
systems in terms of master equations is presented. As generalizations of
isothermal entropy and free energy, two functions of states play central roles:
the Gibbs entropy and the relative entropy , which are related via the
stationary distribution of the stochastic dynamics. satisfies the
fundamental entropy balance equation with entropy production
rate and heat dissipation rate , while . For
closed systems that satisfy detailed balance: . For open system
one has where the housekeeping heat
was first introduced in the phenomenological nonequilibrium steady state
thermodynamics. Entropy production consists of free energy dissipation
associated with spontaneous relaxation, , and active energy pumping that
sustains the open system . The amount of excess heat involved in the
relaxation .Comment: 4 pages, no figure
The Measure-theoretic Identity Underlying Transient Fluctuation Theorems
We prove a measure-theoretic identity that underlies all transient
fluctuation theorems (TFTs) for entropy production and dissipated work in
inhomogeneous deterministic and stochastic processes, including those of Evans
and Searles, Crooks, and Seifert. The identity is used to deduce a tautological
physical interpretation of TFTs in terms of the arrow of time, and its
generality reveals that the self-inverse nature of the various trajectory and
process transformations historically relied upon to prove TFTs, while necessary
for these theorems from a physical standpoint, is not necessary from a
mathematical one. The moment generating functions of thermodynamic variables
appearing in the identity are shown to converge in general only in a vertical
strip in the complex plane, with the consequence that a TFT that holds over
arbitrary timescales may fail to give rise to an asymptotic fluctuation theorem
for any possible speed of the corresponding large deviation principle. The case
of strongly biased birth-death chains is presented to illustrate this
phenomenon. We also discuss insights obtained from our measure-theoretic
formalism into the results of Saha et. al. on the breakdown of TFTs for driven
Brownian particles
Plasmonic Metasurfaces with High UVâ Vis Transmittance for Photopatterning of Designer Molecular Orientations
Recent developments of utilizing plasmonic metasurfaces in photopatterning of designer molecular orientations have facilitated numerous new applications of liquid crystals; while the optical efficiency of the metamasks remains a critical issue, especially in the UV region. Here a new design of plasmonic metasurfaces made of parallelepiped arrays is presented which yield very high and broadband transmission in the UVâ vis wavelength range. It is shown that this plasmonic metamask exhibits two polarization peaks originated from a cavity mode and lattice resonance respectively and demonstrated that complex designer molecular orientations can be photopatterned by using this metamask with significantly reduced exposure time. This type of highâ efficiency broadband plasmonic metasurfaces is not only important for high resolution photopatterning of molecular orientation but also tailorable for various other flat optics applications in the UV and near UV regions.Spatially variant molecular orientations are central to many liquid crystal applications. Here a new design of plasmonic metasurfaces with ultrahigh optical transmissions as metamasks for photopatterning arbitrary designer molecular orientations is presented and it is demonstrated that such metamasks can significantly reduce the exposure time of the photopatterning.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149547/1/adom201900117-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149547/2/adom201900117.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149547/3/adom201900117_am.pd
Dynamic Control of Fraud Information Spreading in Mobile Social Networks
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordMobile social networks (MSNs) provide real-time information services to individuals in social communities through mobile devices. However, due to their high openness and autonomy, MSNs have been suffering from rampant rumors, fraudulent activities, and other types of misuses. To mitigate such threats, it is urgent to control the spread of fraud information. The research challenge is: how to design control strategies to efficiently utilize limited resources and meanwhile minimize individuals' losses caused by fraud information? To this end, we model the fraud information control issue as an optimal control problem, in which the control resources consumption for implementing control strategies and the losses of individuals are jointly taken as a constraint called total cost, and the minimum total cost becomes the objective function. Based on the optimal control theory, we devise the optimal dynamic allocation of control strategies. Besides, a dynamics model for fraud information diffusion is established by considering the uncertain mental state of individuals, we investigate the trend of fraud information diffusion and the stability of the dynamics model. Our simulation study shows that the proposed optimal control strategies can effectively inhibit the diffusion of fraud information while incurring the smallest total cost. Compared with other control strategies, the control effect of the proposed optimal control strategies is about 10% higher.National Natural Science Foundation of China (NSFC)Fundamental Research Funds for the Central Universitie
Nf1 haploinsufficiency alters myeloid lineage commitment and function, leading to deranged skeletal homeostasis
Although nullizygous loss of NF1 leads to myeloid malignancies, haploinsufficient loss of NF1 (Nf1) has been shown to contribute to osteopenia and osteoporosis which occurs in approximately 50% of neurofibromatosis type 1 (NF1) patients. Bone marrow mononuclear cells of haploinsufficient NF1 patients and Nf1(+/-) mice exhibit increased osteoclastogenesis and accelerated bone turnover; however, the culprit hematopoietic lineages responsible for perpetuating these osteolytic manifestations have yet to be elucidated. Here we demonstrate that conditional inactivation of a single Nf1 allele within the myeloid progenitor cell population (Nf1-LysM) is necessary and sufficient to promote multiple osteoclast gains-in-function, resulting in enhanced osteoclastogenesis and accelerated osteoclast bone lytic activity in response to proresorptive challenge in vivo. Surprisingly, mice conditionally Nf1 heterozygous in mature, terminally differentiated osteoclasts (Nf1-Ctsk) do not exhibit any of these skeletal phenotypes, indicating a critical requirement for Nf1 haploinsufficiency at a more primitive/progenitor stage of myeloid development in perpetuating osteolytic activity. We further identified p21Ras-dependent hyperphosphorylation of Pu.1 within the nucleus of Nf1 haploinsufficient myelomonocytic osteoclast precursors, providing a novel therapeutic target for the potential treatment of NF1 associated osteolytic manifestations
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