3,617 research outputs found
Updates in metabolomics tools and resources: 2014-2015
Data processing and interpretation represent the most challenging and time-consuming steps in high-throughput metabolomic experiments, regardless of the analytical platforms (MS or NMR spectroscopy based) used for data acquisition. Improved machinery in metabolomics generates increasingly complex datasets that create the need for more and better processing and analysis software and in silico approaches to understand the resulting data. However, a comprehensive source of information describing the utility of the most recently developed and released metabolomics resources—in the form of tools, software, and databases—is currently lacking. Thus, here we provide an overview of freely-available, and open-source, tools, algorithms, and frameworks to make both upcoming and established metabolomics researchers aware of the recent developments in an attempt to advance and facilitate data processing workflows in their metabolomics research. The major topics include tools and researches for data processing, data annotation, and data visualization in MS and NMR-based metabolomics. Most in this review described tools are dedicated to untargeted metabolomics workflows; however, some more specialist tools are described as well. All tools and resources described including their analytical and computational platform dependencies are summarized in an overview Table
Quantum Gravity as a Dissipative Deterministic System
It is argued that the so-called holographic principle will obstruct attempts
to produce physically realistic models for the unification of general
relativity with quantum mechanics, unless determinism in the latter is
restored. The notion of time in GR is so different from the usual one in
elementary particle physics that we believe that certain versions of hidden
variable theories can -- and must -- be revived. A completely natural procedure
is proposed, in which the dissipation of information plays an essential role.
Unlike earlier attempts, it allows us to use strictly continuous and
differentiable classical field theories as a starting point (although discrete
variables, leading to fermionic degrees of freedom, are also welcome), and we
show how an effective Hilbert space of quantum states naturally emerges when
one attempts to describe the solutions statistically. Our theory removes some
of the mysteries of the holographic principle; apparently non-local features
are to be expected when the quantum degrees of freedom of the world are
projected onto a lower-dimensional black hole horizon. Various examples and
models illustrate the points we wish to make, notably a model showing that
massless, non interacting neutrinos are deterministic.Comment: 20 pages plain TeX, 2 figures PostScript. Added some further
explanations, and the definitions of `beable' and `changeable'. A minor error
correcte
Monopole Condensation and Color Confinement
New evidence is discussed of monopole condensation in the vacuum of SU(2) and
SU(3) gauge theories. Monopoles defined by different abelian projections do
condense in the transition to the confined phase and show the same behavior.
For SU(2) critical indices are determined by finite size scaling analysis and
the results agree with the 3d Ising Model, as expected.Comment: LATTICE98(confinement),3 pages,4 figure
A Mean Field Approximation to the Worldsheet Model of Planar phi^3 Field Theory
We develop an approximation scheme for our worldsheet model of the sum of
planar diagrams based on mean field theory. At finite coupling the mean field
equations show a weak coupling solution that resembles the perturbative
diagrams and a strong coupling solution that seems to represent a tensionless
soup of field quanta. With a certain amount of fine-tuning, we find a solution
of the mean field equations that seems to support string formation.Comment: 27 pages, 10 figures, typos corrected, appendix on slowly varying
mean fields adde
Vortices versus monopoles in color confinement
We construct the creation operator of a vortex for SU(2) pure gauge theory
using the methods developed for monopoles. We interpret its vacuum expectation
value as a disorder parameter for the deconfinement phase transition and find
that it behaves in the vacuum in a similar way to monopoles. Results are
extrapolated to the thermodynamical limit using finite-size scaling.Comment: Talk presented at Lattice2000 (Topology and Vacuum), 4 page
Black Hole Evaporation without Information Loss
An approach to black hole quantization is proposed wherein it is assumed that
quantum coherence is preserved. A consequence of this is that the Penrose
diagram describing gravitational collapse will show the same topological
structure as flat Minkowski space. After giving our motivations for such a
quantization procedure we formulate the background field approximation, in
which particles are divided into "hard" particles and "soft" particles. The
background space-time metric depends both on the in-states and on the
out-states. We present some model calculations and extensive discussions. In
particular, we show, in the context of a toy model, that the -matrix
describing soft particles in the hard particle background of a collapsing star
is unitary, nevertheless, the spectrum of particles is shown to be
approximately thermal. We also conclude that there is an important topological
constraint on functional integrals.Comment: 35 pages (including Figures); TEX, 3 figures in postscrip
Subcritical String and Large N QCD
We pursue the possibility of using subcritical string theory in 4 space-time
dimensions to establish a string dual for large N QCD. In particular we study
the even G-parity sector of the 4 dimensional Neveu-Schwarz dual resonance
model as the natural candidate for this string theory. Our point of view is
that the open string dynamics given by this model will {\it determine} the
appropriate subcritical closed string theory, a tree level background of which
should describe the sum of planar multi-loop open string diagrams. We examine
the one loop open string diagram, which contains information about the closed
string spectrum at weak coupling. Higher loop open string diagrams will be
needed to determine closed string interactions. We also analyze the field
theory limit of the one loop open string diagram and recover the correct
running coupling behavior of the limiting gauge theory.Comment: 18 pages, 2 figures, error in eqs 46 and 47 correcte
Chern-Simons term in the 4-dimensional SU(2) Higgs Model
Using Seiberg's definition for the geometric charge in SU(2) lattice gauge
theory, we have managed to apply it also to the Chern-Simons term. We checked
the periodic structure and determined the Chern-Simons density on small
lattices and with L=4,\, 6,\mbox{ and }8 near the
critical region in the SU(2) Higgs model. The data indicate that tunneling is
increased at high temperature.Comment: 7 pages plus 4 PS figure
Symmetry breaking via fermion 4-point functions
We construct the effective action and gap equations for nonperturbative
fermion 4-point functions. Our results apply to situations in which fermion
masses can be ignored, which is the case for theories of strong flavor
interactions involving standard quarks and leptons above the electroweak scale.
The structure of the gap equations is different from what a naive
generalization of the 2-point case would suggest, and we find for example that
gauge exchanges are insufficient to generate nonperturbative 4-point functions
when the number of colors is large.Comment: 36 pages, uses Revtex and eps files for figure
- …