501 research outputs found
New Lncs to mesendoderm specification.
Mammalian genomes are pervasively transcribed generating thousands of long noncoding RNAs (lncRNAs) with emergent regulatory roles. Many of these lncRNAs exhibit highly specialised expression patterns during development and typically flank and regulate key developmental factors. In this review, we discuss and summarise the latest advances in our understanding of the roles of lncRNAs during mesendoderm (ME) specification, a key step during gastrulation and the formation of the primitive streak (PS)
Conformal Spinning Quantum Particles in Complex Minkowski Space as Constrained Nonlinear Sigma Models in U(2,2) and Born's Reciprocity
We revise the use of 8-dimensional conformal, complex (Cartan) domains as a
base for the construction of conformally invariant quantum (field) theory,
either as phase or configuration spaces. We follow a gauge-invariant Lagrangian
approach (of nonlinear sigma-model type) and use a generalized Dirac method for
the quantization of constrained systems, which resembles in some aspects the
standard approach to quantizing coadjoint orbits of a group G. Physical wave
functions, Haar measures, orthonormal basis and reproducing (Bergman) kernels
are explicitly calculated in and holomorphic picture in these Cartan domains
for both scalar and spinning quantum particles. Similarities and differences
with other results in the literature are also discussed and an extension of
Schwinger's Master Theorem is commented in connection with closure relations.
An adaptation of the Born's Reciprocity Principle (BRP) to the conformal
relativity, the replacement of space-time by the 8-dimensional conformal domain
at short distances and the existence of a maximal acceleration are also put
forward.Comment: 33 pages, no figures, LaTe
Creating a Perioperative Glycemic Control Program
Hyperglycemia in the surgical population is a recognized risk factor for postoperative complications; however, there is little literature to date regarding the management of hyperglycemia in the perioperative period. Here, we detail the strategies that our institutions have employed to identify and treat hyperglycemia in patients with diabetes who present for surgery. Our approach focuses on the recognition of hyperglycemia and metabolic abnormalities, control of glucose levels via insulin infusion when needed, monitoring for hypoglycemia and a comprehensive multidisciplinary approach that provides standardized recommendations for patients at all points in care as they transition from the preoperative clinic into the operating room, and then into the hospital
Problems With Complex Actions
We consider Euclidean functional integrals involving actions which are not
exclusively real. This situation arises, for example, when there are -odd
terms in the the Minkowski action. Writing the action in terms of only real
fields (which is always possible), such terms appear as explicitly imaginary
terms in the Euclidean action. The usual quanization procedure which involves
finding the critical points of the action and then quantizing the spectrum of
fluctuations about these critical points fails. In the case of complex actions,
there do not exist, in general, any critical points of the action on the space
of real fields, the critical points are in general complex. The proper
definition of the function integral then requires the analytic continuation of
the functional integration into the space of complex fields so as to pass
through the complex critical points according to the method of steepest
descent. We show a simple example where this procedure can be carried out
explicitly. The procedure of finding the critical points of the real part of
the action and quantizing the corresponding fluctuations, treating the
(exponential of the) complex part of the action as a bounded integrable
function is shown to fail in our explicit example, at least perturbatively.Comment: 6+epsilon pages, no figures, presented at Theory CANADA
Electromagnetic characterization of conformal antennas
The ultimate objective of this project is to develop a new technique which permits an accurate simulation of microstrip patch antennas or arrays with various feed, superstrate and/or substrate configurations residing in a recessed cavity whose aperture is planar, cylindrical or otherwise conformed to the substructure. The technique combines the finite element and boundary integral methods to formulate a system suitable for solution via the conjugate gradient method in conjunction with the fast Fourier transform. The final code is intended to compute both scattering and radiation patterns of the structure with an affordable memory demand. With upgraded capabilities, the four included papers examined the radar cross section (RCS), input impedance, gain, and resonant frequency of several rectangular configurations using different loading and substrate/superstrate configurations
Identifying Amidyl Radicals for Intermolecular C-H Functionalizations
Recent studies have demonstrated the capabilities of amidyl radicals to facilitate a range of intermolecular functionalizations of unactivated, aliphatic C-H bonds. Relatively little information is known regarding the important structural and electronic features of amidyl and related radicals that impart efficient reactivity. Herein, we evaluate a diverse range of nitrogen-centered radicals in unactivated, aliphatic C-H chlorinations. These studies establish the salient features of nitrogen-centered radicals critical to these reactions in order to expedite the future development of new site-selective, intermolecular C-H functionalizations
Path integration and perturbation theory with complex Euclidean actions
The Euclidean path integral quite often involves an action that is not
completely real {\it i.e.} a complex action. This occurs when the Minkowski
action contains -odd CP-violating terms. Analytic continuation to Euclidean
time yields an imaginary term in the Euclidean action. In the presence of
imaginary terms in the Euclidean action, the usual method of perturbative
quantization can fail. Here the action is expanded about its critical points,
the quadratic part serving to define the Gaussian free theory and the higher
order terms defining the perturbative interactions. For a complex action, the
critical points are generically obtained at complex field configurations. Hence
the contour of path integration does not pass through the critical points and
the perturbative paradigm cannot be directly implemented. The contour of path
integration has to be deformed to pass through the complex critical point using
a generalized method of steepest descent, in order to do so. Typically, what is
done is that only the real part of the Euclidean action is considered, and its
critical points are used to define the perturbation theory. In this article we
present a simple 0+1-dimensional example, of scalar fields interacting with
a U(1) gauge field, in the presence of a Chern-Simons term, where
alternatively, the path integral can be done exactly, the procedure of
deformation of the contour of path integration can be done explicitly and the
standard method of only taking into account the real part of the action can be
followed. We show explicitly that the standard method does not give a correct
perturbative expansion.Comment: 11 pages, no figures, version to be published in PR
Covariance of noncommutative Grassmann star product
Using the Coherent states of many fermionic degrees of freedom labeled by
Gra\ss mann variables, we introduce the noncommutative (precisely non
anticommutative) Gra\ss mann star product. The covariance of star product under
unitary transformations, particularly canonical ones, is studied. The super
star product, based on supercoherent states of supersymmetric harmonic
oscillator, is also considered
Renormalization of the Hamiltonian and a geometric interpretation of asymptotic freedom
Using a novel approach to renormalization in the Hamiltonian formalism, we
study the connection between asymptotic freedom and the renormalization group
flow of the configuration space metric. It is argued that in asymptotically
free theories the effective distance between configuration decreases as high
momentum modes are integrated out.Comment: 22 pages, LaTeX, no figures; final version accepted in Phys.Rev.D;
added reference and appendix with comment on solution of eq. (9) in the tex
Extended Voros product in the coherent states framework
Using coherent states of the Weyl-Heisenberg algebra , extended Voros
products and Moyal brakets are derived.
The covariance of Voros product under canonical transformations is discussed.
Star product related to Barut-Girardello coherent states of the Lie algebra
is also considered. The star eigenvalue problem of singular harmonic
osillator is investigated
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