1,485 research outputs found
Fluids, Anomalies and the Chiral Magnetic Effect: A Group-theoretic Formulation
It is possible to formulate fluid dynamics in terms of group-valued
variables. This is particularly suited to the cases where the fluid has
nonabelian charges and is coupled to nonabelian gauge fields. We explore this
formulation further in this paper. An action for a fluid of relativistic
particles (with and without spin) is given in terms of the Lorentz and Poincare
(or de Sitter) groups. Considering the case of particles with flavor
symmetries, a general fluid action which also incorporates all flavor anomalies
is given. The chiral magnetic and chiral vorticity effects as well as the
consequences of the mixed gauge-gravity anomaly are discussed.Comment: 17 pages, version to be published in Phys Rev
A Rare Case of Reversible Encephalopathy Syndrome Accompanying Late Postpartum Eclampsia or Hypertensive Encephalopathy-A Clinical Dilemma
Posterior Reversible Encephalopathy Syndrome (PRES) refers to a clinic-radiologic diagnosis. Clinically it is characterized by non specific symptoms such as headache, confusion, visual disturbances and seizures. The radiological findings in PRES are thought to be due to vasogenic oedema, predominantly in the posterior cerebral hemispheres, and are reversible with appropriate management. We report a case of reversible encephalopathy diagnosed by MRI scan occurring in atypical areas like the caudate and lentiform nuclei of the brain following an uneventful lower segment caesarean section in a normotensive patient, who was successfully treated with antihypertensives, anticonvulsants and supportive treatment. The differential diagnosis of convulsions in the post-partum period is discussed
Bulk and Edge excitations in a quantum Hall ferromagnet
In this article, we shall focus on the collective dynamics of the fermions in
a quantum Hall droplet. Specifically, we propose to look at the
quantum Hall ferromagnet. In this system, the electron spins are ordered in the
ground state due to the exchange part of the Coulomb interaction and the Pauli
exclusion principle. The low energy excitations are ferromagnetic magnons. To
provide a means for describing these magnons, we shall discuss a method of
introducing collective coordinates in the Hilbert space of many-fermion
systems. These collective coordinates are bosonic in nature. They map a part of
the fermionic Hilbert space into a bosonic Hilbert space. Using this technique,
we shall interpret the magnons as bosonic collective ex citations in the
Hilbert space of the many-electron Hall system. By considering a Hall droplet
of finite extent, we shall also obtain the effective Lagrangian governing the
spin collective excitations at the edge of the sample.Comment: Plain TeX 18 Pages Proceedings for the Y2K conference on strongly c
orrelated fermionic systems, Calcutta, Indi
Interference Alignment in Regenerating Codes for Distributed Storage: Necessity and Code Constructions
Regenerating codes are a class of recently developed codes for distributed
storage that, like Reed-Solomon codes, permit data recovery from any arbitrary
k of n nodes. However regenerating codes possess in addition, the ability to
repair a failed node by connecting to any arbitrary d nodes and downloading an
amount of data that is typically far less than the size of the data file. This
amount of download is termed the repair bandwidth. Minimum storage regenerating
(MSR) codes are a subclass of regenerating codes that require the least amount
of network storage; every such code is a maximum distance separable (MDS) code.
Further, when a replacement node stores data identical to that in the failed
node, the repair is termed as exact.
The four principal results of the paper are (a) the explicit construction of
a class of MDS codes for d = n-1 >= 2k-1 termed the MISER code, that achieves
the cut-set bound on the repair bandwidth for the exact-repair of systematic
nodes, (b) proof of the necessity of interference alignment in exact-repair MSR
codes, (c) a proof showing the impossibility of constructing linear,
exact-repair MSR codes for d < 2k-3 in the absence of symbol extension, and (d)
the construction, also explicit, of MSR codes for d = k+1. Interference
alignment (IA) is a theme that runs throughout the paper: the MISER code is
built on the principles of IA and IA is also a crucial component to the
non-existence proof for d < 2k-3. To the best of our knowledge, the
constructions presented in this paper are the first, explicit constructions of
regenerating codes that achieve the cut-set bound.Comment: 38 pages, 12 figures, submitted to the IEEE Transactions on
Information Theory;v3 - The title has been modified to better reflect the
contributions of the submission. The paper is extensively revised with
several carefully constructed figures and example
Explicit Construction of Optimal Exact Regenerating Codes for Distributed Storage
Erasure coding techniques are used to increase the reliability of distributed
storage systems while minimizing storage overhead. Also of interest is
minimization of the bandwidth required to repair the system following a node
failure. In a recent paper, Wu et al. characterize the tradeoff between the
repair bandwidth and the amount of data stored per node. They also prove the
existence of regenerating codes that achieve this tradeoff.
In this paper, we introduce Exact Regenerating Codes, which are regenerating
codes possessing the additional property of being able to duplicate the data
stored at a failed node. Such codes require low processing and communication
overheads, making the system practical and easy to maintain. Explicit
construction of exact regenerating codes is provided for the minimum bandwidth
point on the storage-repair bandwidth tradeoff, relevant to
distributed-mail-server applications. A subspace based approach is provided and
shown to yield necessary and sufficient conditions on a linear code to possess
the exact regeneration property as well as prove the uniqueness of our
construction.
Also included in the paper, is an explicit construction of regenerating codes
for the minimum storage point for parameters relevant to storage in
peer-to-peer systems. This construction supports a variable number of nodes and
can handle multiple, simultaneous node failures. All constructions given in the
paper are of low complexity, requiring low field size in particular.Comment: 7 pages, 2 figures, in the Proceedings of Allerton Conference on
Communication, Control and Computing, September 200
OVERVIEW OF FORMULATION, MANUFACTURE AND APPLICATIONS OF MINI TABLETS
Mini tablets, recent trend of solid dosage form, made remarkable contribution to avoid certain obstacles in people’s mind and offered best therapeutic benefits, flexible dose and combined released pattern. Mini tablets were developed and reported as patient friendly with increased patient acceptance. Mini tablets were made into modified release system for better dose and prolong drug release. They offer the advantage of reduced dose dumping and increased effect of drug by localization. Manufacture of mini tablets are similar to conventional tablets but need a change in tooling, equipment and specifications. Evaluation parameters found to be similar with conventional tablets but doses are variable. Mini tablets can also be encapsulated and hence different drug combinations are tried and found useful
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