351 research outputs found
Covariant derivative expansion of fermionic effective action at high temperatures
We derive the fermionic contribution to the 1-loop effective action for A_4
and A_i fields at high temperatures, assuming that gluon fields are slowly
varying but allowing for an arbitrary amplitude of A_4.Comment: RevTex 4, 11 pages, 3 figures. Version 2: Typos corrected; magnetic
fields restricted to parallel sector. Version accepted for publication in PR
Covariant derivative expansion of Yang-Mills effective action at high temperatures
Integrating out fast varying quantum fluctuations about Yang--Mills fields
A_i and A_4, we arrive at the effective action for those fields at high
temperatures. Assuming that the fields A_i and A_4 are slowly varying but that
the amplitude of A_4 is arbitrary, we find a non-trivial effective gauge
invariant action both in the electric and magnetic sectors. Our results can be
used for studying correlation functions at high temperatures beyond the
dimensional reduction approximation, as well as for estimating quantum weights
of classical static configurations such as dyons.Comment: Minor changes. References added. Paper accepted for publication in
Phys.Rev.
Differential Geometry applied to Acoustics : Non Linear Propagation in Reissner Beams
Although acoustics is one of the disciplines of mechanics, its
"geometrization" is still limited to a few areas. As shown in the work on
nonlinear propagation in Reissner beams, it seems that an interpretation of the
theories of acoustics through the concepts of differential geometry can help to
address the non-linear phenomena in their intrinsic qualities. This results in
a field of research aimed at establishing and solving dynamic models purged of
any artificial nonlinearity by taking advantage of symmetry properties
underlying the use of Lie groups. The geometric constructions needed for
reduction are presented in the context of the "covariant" approach.Comment: Submitted to GSI2013 - Geometric Science of Informatio
Ergodic properties of a generic non-integrable quantum many-body system in thermodynamic limit
We study a generic but simple non-integrable quantum {\em many-body} system
of {\em locally} interacting particles, namely a kicked model of spinless
fermions on 1-dim lattice (equivalent to a kicked Heisenberg XX-Z chain of 1/2
spins). Statistical properties of dynamics (quantum ergodicity and quantum
mixing) and the nature of quantum transport in {\em thermodynamic limit} are
considered as the kick parameters (which control the degree of
non-integrability) are varied. We find and demonstrate {\em ballistic}
transport and non-ergodic, non-mixing dynamics (implying infinite conductivity
at all temperatures) in the {\em integrable} regime of zero or very small kick
parameters, and more generally and important, also in {\em non-integrable}
regime of {\em intermediate} values of kicked parameters, whereas only for
sufficiently large kick parameters we recover quantum ergodicity and mixing
implying normal (diffusive) transport. We propose an order parameter (charge
stiffness ) which controls the phase transition from non-mixing/non-ergodic
dynamics (ordered phase, ) to mixing/ergodic dynamics (disordered phase,
D=0) in the thermodynamic limit. Furthermore, we find {\em exponential decay of
time-correlation function} in the regime of mixing dynamics.
The results are obtained consistently within three different numerical and
analytical approaches: (i) time evolution of a finite system and direct
computation of time correlation functions, (ii) full diagonalization of finite
systems and statistical analysis of stationary data, and (iii) algebraic
construction of quantum invariants of motion of an infinite system, in
particular the time averaged observables.Comment: 18 pages in REVTeX with 14 eps figures included, Submitted to
Physical Review
Foraging on human-derived foods by urban bird species
Capsule: Providing peanuts on bird feeders was shown to attract more individuals and more species than providing cheese or bread. Aims: To investigate how the provision of different human-derived foods affected visit rates of urban birds at bird feeders. Methods: A fully replicated study design was set up in parkland, offering a binary choice from three food types (peanuts, bread and cheese) on bird tables. Birds were observed by using a scan-sample method. Results: Peanuts attracted more visits, and a greater diversity of bird species, than cheese or bread. This preference was strongest for Blue Tits Cyanistes caeruleus and Great Tits Parus major, whereas European Robins Erithacus rubecula visited all food types equally, and Blackbirds Turdus merula preferred cheese. Bread was the most consumed food type when measured by mass, but this could be linked to varying bite sizes. Conclusion: Our results indicate that birds preferred to visit feeding stations with the most protein- and energy-rich foods, but that some birds still chose the carbohydrate-rich bread. The findings indicate that peanuts, rather than household scraps like bread and cheese, attract the highest number of species and individuals to bird tables. The findings will be of interest to the public and to organizations providing information on bird feeding for recreational purposes
Reporting of quality attributes in scientific publications presenting biosimilarity assessments of (intended) biosimilars: a systematic literature review
Last years, more than 46 unique biosimilars were approved by EMA and/or US-FDA following patent expiration of reference products. Biosimilars are not identical like generics, but highly similar versions where demonstrating biosimilarity of quality attributes (QAs) to a reference product is the basis of development and regulatory approval. Information on QAs assessed to establish biosimilarity may not always be publicly available, although this information is imperative to understand better the science behind biosimilars approval. This study aims to identify QA types reported in publications presenting biosimilarity assessments of (intended) biosimilars over time. English full-text publications presenting biosimilarity assessments of QAs for (intended) biosimilars between 2000 and 2019 identified from PubMed and EMBASE. Publication characteristics and QAs classified into: structural (physicochemical properties, primary structure, higher-order structures (HOSs), post-translational modifications (PTMs), and purity and impurities) and functional (biological and immunochemical activities) were extracted from publications. Seventy-nine publications were identified (79% open-access, 75% industry-sponsored, 62% including unapproved biosimilars, and 66% involving antibodies). Reporting frequencies varied for QA types: biological activity (94%), physicochemical properties (81%), PTMs (79%), primary structure (77%) purity and impurities (73%), HOSs (58%), and immunochemical activity (41%). The number of publications increased from 6 (7%) during 2009–2011 to 62 (79%) during 2015–2019. Eighteen (28%) publications reported all QA types relevant to an active-biological-substance. Reporting of most QA types increased over time that most evidenced by immunochemical activity (from 0% to 47%) which occured after EMA monoclona
Phase II Study of Cetuximab in Combination with Docetaxel in Patients with Recurrent and/or Metastatic Squamous Cell Carcinoma of the Head and Neck after Platinum-Containing Therapy: A Multicenter Study of the Arbeitsgemeinschaft Internistische Onkologie
Background: Cetuximab and docetaxel have single-agent activity in squamous cell carcinoma of the head and neck (SCCHN). The efficacy of their combination was evaluated in platinum-pretreated patients with recurrent and/or metastatic SCCHN. Patients and Methods: A total of 84 patients were treated with docetaxel 35 mg/m2 weekly for a maximum of 6 cycles and concomitant cetuximab 250 mg/m2 weekly until disease progression or unacceptable toxicity. The primary endpoint was the objective response rate and secondary endpoints included the response rate in relation to platinum sensitivity, progression-free survival (PFS), overall survival (OS) and toxicity. Results: Nine (11%) patients achieved a partial response and 34 (40%) stable disease, resulting in a disease control rate of 51%. Response to treatment was 49% in previously platinum-sensitive and 50% in previously platinum-resistant disease. The median PFS was 3.1 months and the median OS 6.7 months. The most common grade 3 or 4 adverse events were mucositis (8%), pneumonia (8%), fatigue (8%) and skin reactions (14%). Sepsis occurred in 3 patients. Conclusion: Cetuximab plus docetaxel is an active treatment regimen with moderate toxicity in SCCHN patients. However, no superiority in comparison with monotherapy could be shown. Responsiveness and survival were independent of previous platinum sensitivity
Azimuthal asymmetries in lepton-pair production at a fixed-target experiment using the LHC beams (AFTER)
A multi-purpose fixed-target experiment using the proton and lead-ion beams
of the LHC was recently proposed by Brodsky, Fleuret, Hadjidakis and Lansberg,
and here we concentrate our study on some issues related to the spin physics
part of this project (referred to as AFTER). We study the nucleon spin
structure through and processes with a fixed-target experiment using
the LHC proton beams, for the kinematical region with 7 TeV proton beams at the
energy in center-of-mass frame of two nucleons GeV. We calculate
and estimate the azimuthal asymmetries of unpolarized and
dilepton production processes in the Drell--Yan continuum region and at the
-pole. We also calculate the , and
azimuthal asymmetries of and dilepton production
processes with the target proton and deuteron longitudinally or transversally
polarized in the Drell--Yan continuum region and around resonances region.
We conclude that it is feasible to measure these azimuthal asymmetries,
consequently the three-dimensional or transverse momentum dependent parton
distribution functions (3dPDFs or TMDs), at this new AFTER facility.Comment: 15 pages, 40 figures. Version accepted for publication in EPJ
Nonperturbative renormalization group approach to frustrated magnets
This article is devoted to the study of the critical properties of classical
XY and Heisenberg frustrated magnets in three dimensions. We first analyze the
experimental and numerical situations. We show that the unusual behaviors
encountered in these systems, typically nonuniversal scaling, are hardly
compatible with the hypothesis of a second order phase transition. We then
review the various perturbative and early nonperturbative approaches used to
investigate these systems. We argue that none of them provides a completely
satisfactory description of the three-dimensional critical behavior. We then
recall the principles of the nonperturbative approach - the effective average
action method - that we have used to investigate the physics of frustrated
magnets. First, we recall the treatment of the unfrustrated - O(N) - case with
this method. This allows to introduce its technical aspects. Then, we show how
this method unables to clarify most of the problems encountered in the previous
theoretical descriptions of frustrated magnets. Firstly, we get an explanation
of the long-standing mismatch between different perturbative approaches which
consists in a nonperturbative mechanism of annihilation of fixed points between
two and three dimensions. Secondly, we get a coherent picture of the physics of
frustrated magnets in qualitative and (semi-) quantitative agreement with the
numerical and experimental results. The central feature that emerges from our
approach is the existence of scaling behaviors without fixed or pseudo-fixed
point and that relies on a slowing-down of the renormalization group flow in a
whole region in the coupling constants space. This phenomenon allows to explain
the occurence of generic weak first order behaviors and to understand the
absence of universality in the critical behavior of frustrated magnets.Comment: 58 pages, 15 PS figure
Critical behavior of the two-dimensional N-component Landau-Ginzburg Hamiltonian with cubic anisotropy
We study the two-dimensional N-component Landau-Ginzburg Hamiltonian with
cubic anisotropy. We compute and analyze the fixed-dimension perturbative
expansion of the renormalization-group functions to four loops. The relations
of these models with N-color Ashkin-Teller models, discrete cubic models,
planar model with fourth order anisotropy, and structural phase transition in
adsorbed monolayers are discussed. Our results for N=2 (XY model with cubic
anisotropy) are compatible with the existence of a line of fixed points joining
the Ising and the O(2) fixed points. Along this line the exponent has
the constant value 1/4, while the exponent runs in a continuous and
monotonic way from 1 to (from Ising to O(2)). For N\geq 3 we find a
cubic fixed point in the region , which is marginally stable or
unstable according to the sign of the perturbation. For the physical relevant
case of N=3 we find the exponents and at the cubic
transition.Comment: 14 pages, 9 figure
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