4,244 research outputs found
String-- and Brane--Localized Causal Fields in a Strongly Nonlocal Model
We study a weakly local, but nonlocal model in spacetime dimension
and prove that it is maximally nonlocal in a certain specific quantitative
sense. Nevertheless, depending on the number of dimensions , it has
string--localized or brane--localized operators which commute at spatial
distances. In two spacetime dimensions, the model even comprises a covariant
and local subnet of operators localized in bounded subsets of Minkowski space
which has a nontrivial scattering matrix. The model thus exemplifies the
algebraic construction of local observables from algebras associated with
nonlocal fields.Comment: paper re-written with a change of emphasis and new result
An operator expansion for integrable quantum field theories
A large class of quantum field theories on 1+1 dimensional Minkowski space,
namely, certain integrable models, has recently been constructed rigorously by
Lechner. However, the construction is very abstract and the concrete form of
local observables in these models remains largely unknown. Aiming for more
insight into their structure, we establish a series expansion for observables,
similar but not identical to the well-known form factor expansion. This
expansion will be the basis for a characterization and explicit construction of
local observables, to be discussed elsewhere. Here, we establish the expansion
independent of the localization aspect, and analyze its behavior under
space-time symmetries. We also clarify relations with deformation methods in
quantum field theory, specifically, with the warped convolution in the sense of
Buchholz and Summers.Comment: minor corrections and clarifications, as published in J. Phys A; 24
page
Scaling limits of integrable quantum field theories
Short distance scaling limits of a class of integrable models on
two-dimensional Minkowski space are considered in the algebraic framework of
quantum field theory. Making use of the wedge-local quantum fields generating
these models, it is shown that massless scaling limit theories exist, and
decompose into (twisted) tensor products of chiral, translation-dilation
covariant field theories. On the subspace which is generated from the vacuum by
the observables localized in finite light ray intervals, this symmetry can be
extended to the M\"obius group. The structure of the interval-localized
algebras in the chiral models is discussed in two explicit examples.Comment: Revised version: erased typos, improved formulations, and corrections
of Lemma 4.8/Prop. 4.9. As published in RMP. 43 pages, 1 figur
Impedance measurements and simulations on the TCT and TDI LHC collimators
The LHC collimation system is a critical element for
the safe operation of the LHC machine and it is subject
to continuous performance monitoring, hardware upgrade
and optimization. In this work we will address the impact
on impedance of the upgrades performed on the injection
protection target dump (TDI), where the absorber material
has been changed to mitigate the device heating observed
in machine operation, and on selected secondary (TCS) and
tertiary (TCT) collimators, where beam position monitors
(BPM) have been embedded for faster jaw alignment. Con-
cerning the TDI, we will present the RF measurements per-
formed before and after the upgrade, comparing the result
to heating and tune shift beam measurements. For the TCTs,
we will study how the higher order modes (HOM) intro-
duced by the BPM addition have been cured by means of
ferrite placement in the device. The impedance mitigation
campaign has been supported by RF measurements whose
results are in good agreement with GdfidL and CST simula-
tions. The presence of undamped low frequency modes is
proved not to be detrimental to the safe LHC operation
Partial Homology Relations - Satisfiability in terms of Di-Cographs
Directed cographs (di-cographs) play a crucial role in the reconstruction of
evolutionary histories of genes based on homology relations which are binary
relations between genes. A variety of methods based on pairwise sequence
comparisons can be used to infer such homology relations (e.g.\ orthology,
paralogy, xenology). They are \emph{satisfiable} if the relations can be
explained by an event-labeled gene tree, i.e., they can simultaneously co-exist
in an evolutionary history of the underlying genes. Every gene tree is
equivalently interpreted as a so-called cotree that entirely encodes the
structure of a di-cograph. Thus, satisfiable homology relations must
necessarily form a di-cograph. The inferred homology relations might not cover
each pair of genes and thus, provide only partial knowledge on the full set of
homology relations. Moreover, for particular pairs of genes, it might be known
with a high degree of certainty that they are not orthologs (resp.\ paralogs,
xenologs) which yields forbidden pairs of genes. Motivated by this observation,
we characterize (partial) satisfiable homology relations with or without
forbidden gene pairs, provide a quadratic-time algorithm for their recognition
and for the computation of a cotree that explains the given relations
Osteoimmune Interaction and TH-1/TH-2 Ratio in Jawbone Marrow Defects: An Underestimated Association – Original Research
Johann Lechner,1 Volker von Baehr,2 Florian Notter,1 Fabian Schick1 1Clinic for Integrative Dentistry, Munich, Germany; 2Department of Immunology and Allergology, Institute for Medical Diagnostics, Berlin, GermanyCorrespondence: Johann Lechner, Gruenwalder Str. 10A, Munich, 81547, Germany, Tel +49 89 697 0129, Fax +49 89 692 5830, Email [email protected]: Osteoimmunology recognizes the relationship between bone cells and immune cells. Chronic osteoimmune dysregulation is present in bone marrow defects of the jaw (BMDJ) as fatty-degenerative osteonecrosis (FDOJ). In comparison to samples from healthy jaw bone, the cytokine analysis of samples of BMDJ/FDOJ from 128 patients showed downregulated TNF-α and IL-6 expression and the singular overexpression of the chemokine RANTES/CCL5.Aim and Objectives: This paper raises the question of whether the osteoimmune defects due to incomplete wound healing in BMDJ/FDOJ in 128 patients are related to dysregulation of the Th1/Th2 ratio and regulatory T cell (T-reg) expression in a control group of 197 BMDJ/FDOJ patients, each presenting with BMDJ/FJOD and one of seven different immune disorders.Material and Methods: In the control group, serum concentrations of the cytokines IFN-y and IL-4 were determined after stimulated cytokine release and displayed as Th1/Th2 ratios.Results: Data show a shift in Th2 in more than 80% (n = 167) of the control cohort of 197 chronically ill patients with concomitant BMDJ/FDOJ. In these 167 subjects, the Th1/Th2 ratio was 1.900 pg/mL, indicating strongly downregulated immune activity.Discussion: BMDJ/FDOJ is characterized by a lack of Th1 cytokines and an excessive expression of RANTES/CCL5 and IL-1ra and, thus, the inversion of an acute inflammatory cytokine pattern. In contrast, abdominal fat contains a very high proportion of regulatory Th1 cells and produces an inflammatory immune response through the high overexpression of TNF-α and IL-6. The lack of Th1 activation in BMDJ/FDOJ areas inhibits normal wound healing and supports the persistence of BMDJ/FDOJ.Conclusion: The Th1/Th2 ratio requires greater consideration, especially with respect to wound healing following dental surgical interventions, such as jaw surgery, implantation and augmentation, to avoid the emergence of the osteoimmune situation that is characteristic of BMDJ/FDOJ. Keywords: osteoimmunology, T-cells, Th1/Th2 shift, jawbone, osteoclastogenesis, RANTES/CCL
Recommended from our members
Weak intermolecular interactions in an ionically bound molecular adsorbate: cyclopentadienyl=Cu(111)
The dissociative adsorption of cyclopentadiene (C5H6) on Cu(111) yields a cyclopentadienyl (Cp) species with strongly anionic characteristics. The Cp potential energy surface and frictional coupling to the substrate are determined from measurements of dynamics of the molecule together with density functional calculations. The molecule is shown to occupy degenerate threefold adsorption sites and molecular motion is characterized by a low diffusional energy barrier of 40 +/- 3 meV with strong frictional dissipation. Repulsive dipole-dipole interactions are not detected despite charge transfer from substrate to adsorbate
Do work placements improve final year academic performance or do high-calibre students choose to do work placements?
This study investigates whether the completion of an optional sandwich work placement enhances student performance in final year examinations. Using Propensity Score Matching, our analysis departs from the literature by controlling for self-selection. Previous studies may have overestimated the impact of sandwich work placements on performance because it might be the case that high-calibre students choose to go on placement. Our results, utilising a large student data set, indicate that self-selection is present, but the effects of a placement on student performance still have an impact. This robust finding is found to be of a remarkably similar magnitude across two UK universities
- …