91,275 research outputs found
Gene expression analysis in microdissected renal tissue - Current challenges and strategies
The architecture and compartmentalization of the kidney has stimulated the development of an array of microtechniques to study the functional differences between the distinct nephron segments. With the vast amounts of genomic sequence data now available, the groundwork has been laid for a comprehensive characterization of the molecular pathways defining the differences in nephron function. With the development of sensitive gene expression techniques the tools for a comprehensive molecular analysis of specific renal microenvironments have been provided: Quantitative RT-PCR technologies now allow the analysis of specific mRNAs from as little as single microdissected renal cells. A more global view of gene expression regulation is a logical development from the application of large scale profiling techniques. In this review, we will discuss the power and pitfalls of these approaches, including their potential for the functional characterization of nephron heterogeneity and diagnostic application in renal disease. Copyright (C) 2002 S. Karger AG, Basel
Study of actinide chemistry in saturated potassium fluoride solution
Study concerning the chemistry of actinides in saturated KF solution included work with neptunium, uranium, and americium. Solubilities, absorption spectra, oxidation-reduction reactions, and solid compounds which can be produced in KF solution were examined. The information is used for preparation of various materials from salts of the actinides
Microscopic chaos and diffusion
We investigate the connections between microscopic chaos, defined on a
dynamical level and arising from collisions between molecules, and diffusion,
characterized by a mean square displacement proportional to the time. We use a
number of models involving a single particle moving in two dimensions and
colliding with fixed scatterers. We find that a number of microscopically
nonchaotic models exhibit diffusion, and that the standard methods of chaotic
time series analysis are ill suited to the problem of distinguishing between
chaotic and nonchaotic microscopic dynamics. However, we show that periodic
orbits play an important role in our models, in that their different properties
in chaotic and nonchaotic systems can be used to distinguish such systems at
the level of time series analysis, and in systems with absorbing boundaries.
Our findings are relevant to experiments aimed at verifying the existence of
chaoticity and related dynamical properties on a microscopic level in diffusive
systems.Comment: 28 pages revtex, 14 figures incorporated with epsfig; see also
chao-dyn/9904041; revised to clarify the definition of chaos and include
discussion of a mixed model with both square and circular scatterer
Atmospheric turbulence and superstatistics
Nonequilibrium systems with large-scale fluctuations of a suitable system
parameter are often effectively described by a superposition of two statistics,
a superstatistics. Here we illustrate this concept by analysing experimental
data of fluctuations in atmospheric wind velocity differences at Florence
airport.Comment: 9 pages, 4 figures. New version to appear in Europhysics News (2005
Geodynamics Branch research report, 1982
The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies
N-body Monte Carlo simulation of specific lunar orbiter missions
N-body Monte Carlo simulation of specific lunar orbiter mission
The Delta-Delta Intermediate State in 1S0 Nucleon-Nucleon Scattering From Effective Field Theory
We examine the role of the Delta-Delta intermediate state in low energy NN
scattering using effective field theory. Theories both with and without pions
are discussed. They are regulated with dimensional regularization and MSbar
subtraction. We find that the leading effects of the Delta-Delta state can be
absorbed by a redefinition of the contact terms in a theory with nucleons only.
It does not remove the requirement of a higher dimension operator to reproduce
data out to moderate momentum. The explicit decoupling of the Delta-Delta state
is shown for the theory without pions.Comment: 16 pages, 3 figures, uses harvma
Coherent pumping of a Mott insulator: Fermi golden rule versus Rabi oscillations
Cold atoms provide a unique arena to study many-body systems far from
equilibrium. Furthermore, novel phases in cold atom systems are conveniently
investigated by dynamical probes pushing the system out of equilibrium. Here,
we discuss the pumping of doubly-occupied sites in a fermionic Mott insulator
by a periodic modulation of the hopping amplitude. We show that deep in the
insulating phase the many-body system can be mapped onto an effective two-level
system which performs coherent Rabi oscillations due to the driving. Coupling
the two-level system to the remaining degrees of freedom renders the Rabi
oscillations damped. We compare this scheme to an alternative description where
the particles are incoherently pumped into a broad continuum.Comment: 4 pages, 3 figure
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