37 research outputs found
Spin Gauge Theory of Gravity in Clifford Space: A Realization of Kaluza-Klein Theory in 4-Dimensional Spacetime
A theory in which 4-dimensional spacetime is generalized to a larger space,
namely a 16-dimensional Clifford space (C-space) is investigated. Curved
Clifford space can provide a realization of Kaluza-Klein theory. A covariant
Dirac equation in curved C-space is explored. The generalized Dirac field is
assumed to be a polyvector-valued object (a Clifford number) which can be
written as a superposition of four independent spinors, each spanning a
different left ideal of Clifford algebra. The general transformations of a
polyvector can act from the left and/or from the right, and form a large gauge
group which may contain the group U(1)xSU(2)xSU(3) of the standard model. The
generalized spin connection in C-space has the properties of Yang-Mills gauge
fields. It contains the ordinary spin connection related to gravity (with
torsion), and extra parts describing additional interactions, including those
described by the antisymmetric Kalb-Ramond fields.Comment: 57 pages; References added, section 2 rewritten and expande
Axiomatic geometric formulation of electromagnetism with only one axiom: the field equation for the bivector field F with an explanation of the Trouton-Noble experiment
In this paper we present an axiomatic, geometric, formulation of
electromagnetism with only one axiom: the field equation for the Faraday
bivector field F. This formulation with F field is a self-contained, complete
and consistent formulation that dispenses with either electric and magnetic
fields or the electromagnetic potentials. All physical quantities are defined
without reference frames, the absolute quantities, i.e., they are geometric
four dimensional (4D) quantities or, when some basis is introduced, every
quantity is represented as a 4D coordinate-based geometric quantity comprising
both components and a basis. The new observer independent expressions for the
stress-energy vector T(n)(1-vector), the energy density U (scalar), the
Poynting vector S and the momentum density g (1-vectors), the angular momentum
density M (bivector) and the Lorentz force K (1-vector) are directly derived
from the field equation for F. The local conservation laws are also directly
derived from that field equation. The 1-vector Lagrangian with the F field as a
4D absolute quantity is presented; the interaction term is written in terms of
F and not, as usual, in terms of A. It is shown that this geometric formulation
is in a full agreement with the Trouton-Noble experiment.Comment: 32 pages, LaTex, this changed version will be published in Found.
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The Schroedinger Problem, Levy Processes Noise in Relativistic Quantum Mechanics
The main purpose of the paper is an essentially probabilistic analysis of
relativistic quantum mechanics. It is based on the assumption that whenever
probability distributions arise, there exists a stochastic process that is
either responsible for temporal evolution of a given measure or preserves the
measure in the stationary case. Our departure point is the so-called
Schr\"{o}dinger problem of probabilistic evolution, which provides for a unique
Markov stochastic interpolation between any given pair of boundary probability
densities for a process covering a fixed, finite duration of time, provided we
have decided a priori what kind of primordial dynamical semigroup transition
mechanism is involved. In the nonrelativistic theory, including quantum
mechanics, Feyman-Kac-like kernels are the building blocks for suitable
transition probability densities of the process. In the standard "free" case
(Feynman-Kac potential equal to zero) the familiar Wiener noise is recovered.
In the framework of the Schr\"{o}dinger problem, the "free noise" can also be
extended to any infinitely divisible probability law, as covered by the
L\'{e}vy-Khintchine formula. Since the relativistic Hamiltonians
and are known to generate such laws, we focus on
them for the analysis of probabilistic phenomena, which are shown to be
associated with the relativistic wave (D'Alembert) and matter-wave
(Klein-Gordon) equations, respectively. We show that such stochastic processes
exist and are spatial jump processes. In general, in the presence of external
potentials, they do not share the Markov property, except for stationary
situations. A concrete example of the pseudodifferential Cauchy-Schr\"{o}dinger
evolution is analyzed in detail. The relativistic covariance of related waveComment: Latex fil
The size criteria in minimally invasive video-assisted thyroidectomy
BACKGROUND: Thyroid size is a very important criteria of MIVAT exclusion because the working space provided by the technique is limited. The aim of this work has been to verify the suitability of MIVAT and its applicability in clinical practice, not only in patients with a thyroid volume up to 25 ml but also in patients with a thyroid volume included from 25 to 50 ml. METHODS: From January 2003 to February 2006, 33 patients have been selected for MIVAT. A completely gasless procedure was carried out through a central 20 to 35 mm skin incision performed "high" between the cricoid and jugular notch. RESULTS: The patients were separated in 2 groups. The first group (less than 25 ml) included 23 patients, the second group (from 25 to 50 ml) included 10 patients. The skin incision performed was from 20 to 25 mm (mean 23.61 mm ± 1.83) long in the first group and from 25 to 35 mm (mean 27.8 mm ± 2.20) long in the second one; this difference is significant (t test p < 0.001). CONCLUSION: Our study suggest that the MIVAT using for thyroids bigger than 25 ml and up to 50 ml in volume is feasible and safe. This way allows more patients, excluded before, to take the advantages of minimally invasive approach
PD-L1 Overexpression, SWI/SNF Complex Deregulation, and Profound Transcriptomic Changes Characterize Cancer-Dependent Exhaustion of Persistently Activated CD4+ T Cells
Growing tumors avoid recognition and destruction by the immune system. During
continuous stimulation of tumor-infiltrating lymphocytes (TILs) by tumors, TILs become functionally
exhausted; thus, they become unable to kill tumor cells and to produce certain cytokines and lose
their ability to proliferate. This collectively results in the immune escape of cancer cells. Here, we
show that breast cancer cells expressing PD-L1 can accelerate exhaustion of persistently activated
human effector CD4+ T cells, manifesting in high PD-1 and PD-L1 expression level son T cell surfaces,
decreased glucose metabolism genes, strong downregulation of SWI/SNF chromatin remodelingcomplex subunits, and p21 cell cycle inhibitor upregulation. This results in inhibition of T cell
proliferation and reduction of T cell numbers. The RNAseq analysis on exhausted CD4+ T cells
indicated strong overexpression of IDO1 and genes encoding pro-inflammatory cytokines and
chemokines. Some interleukins were also detected in media from CD4+ T cells co-cultured with
cancer cells. The PD-L1 overexpression was also observed in CD4+ T cells after co-cultivation with
other cell lines overexpressing PD-L1, which suggested the existence of a general mechanism of CD4+
T cell exhaustion induced by cancer cells. The ChIP analysis on the PD-L1 promoter region indicated
that the BRM recruitment in control CD4+ T cells was replaced by BRG1 and EZH2 in CD4+ T cells
strongly exhausted by cancer cells. These findings suggest that epi-drugs such as EZH2 inhibitors
may be used as immunomodulators in cancer treatment
Wealth Formation by Economic Agents and Their International Mobility: Towards an Eclectic Migration Decision-support Framework
International migration has been a major influence on the economic and social development of nations. Nevertheless, a vast majority of the global population continues to reside in their country of birth. While income/wealth differentials between states create centrifugal forces responsible for migration, impediments to International mobility of human, financial, physical and social capital assets work in the centripetal direction. This paper reviews a large segment of the extant literature on International migration to probe economic influences on people's International mobility and immobility decisions. It aims to refine and extend the neoclassical foundations of migration theory and to outline how potentially complex decision mechanisms used by potentially mobile economic agents may be modified to simplify the complexity inherent in such choices so that immobility is often a default outcome of indecision
SWP73 Subunits of Arabidopsis SWI/SNF Chromatin Remodeling Complexes Play Distinct Roles in Leaf and Flower Development.
Arabidopsis thaliana SWP73A and SWP73B are homologs of mammalian BRAHMA-associated factors (BAF60s) that tether SWITCH/SUCROSE NONFERMENTING chromatin remodeling complexes to transcription factors of genes regulating various cell differentiation pathways. Here, we show that Arabidopsis thaliana SWP73s modulate several important developmental pathways. While undergoing normal vegetative development, swp73a mutants display reduced expression of FLOWERING LOCUS C and early flowering in short days. By contrast, swp73b mutants are characterized by retarded growth, severe defects in leaf and flower development, delayed flowering, and male sterility. MNase-Seq, transcript profiling, and ChIP-Seq studies demonstrate that SWP73B binds the promoters of ASYMMETRIC LEAVES1 and 2, KANADI1 and 3, and YABBY2, 3, and 5 genes, which regulate leaf development and show coordinately altered transcription in swp73b plants. Lack of SWP73B alters the expression patterns of APETALA1, APETALA3, and the MADS box gene AGL24, whereas other floral organ identity genes show reduced expression correlating with defects in flower development. Consistently, SWP73B binds to the promoter regions of APETALA1 and 3, SEPALLATA3, LEAFY, UNUSUAL FLORAL ORGANS, TERMINAL FLOWER1, AGAMOUS-LIKE24, and SUPPRESSOR OF CONSTANS OVEREXPRESSION1 genes, and the swp73b mutation alters nucleosome occupancy on most of these loci. In conclusion, SWP73B acts as important modulator of major developmental pathways, while SWP73A functions in flowering time control