578 research outputs found
Solid state microwave source development program Final report
Microstrip oscillator for solid state microwave sourc
Strange matrix elements of the nucleon
Results for the disconnected contributions to matrix elements of the vector
current and scalar density have been obtained for the nucleon from the Wilson
action at beta=6 using a stochastic estimator technique and 2000 quenched
configurations. Various methods for analysis are employed and chiral
extrapolations are discussed.Comment: Lattice2002(matrixel), 3 pages, 3 figure
Using Cash-To-Cash To Benchmark Service Industry Performance
The cash-to-cash (C2C) metric is a measurement tool which may be used to bridge the management of firms and functions in a supply chain. C2C can be used by management to improve firm liquidity position and overall firm value. Measuring C2C also offers a consistent measure across time, helps to identify the greatest leverage points and opportunities for improvement, serves as a means to set goals for improvement within the supply chain, and can help to optimize the entire supply chain, instead of sub-optimizing individual portions. In this study, the authors illustrate the calculation of cash-to-cash, investigate changes in C2C between product and service industries to identify key differences, review and discuss key leverage points of C2C, and provide insights for today’s service industry managers to understand the C2C metric from both accounting and supply chain management perspectives. Data in this study can also be used for benchmarking purposes
The use of oscillatory signals in the study of genetic networks
The structure of a genetic network is uncovered by studying its response to
external stimuli (input signals). We present a theory of propagation of an
input signal through a linear stochastic genetic network. It is found that
there are important advantages in using oscillatory signals over step or
impulse signals, and that the system may enter into a pure fluctuation
resonance for a specific input frequency.Comment: 46 pages, 5 figures. Submitted to PNAS on May 27th 2004. The paper is
under consideratio
What Do We Know About the Strange Magnetic Radius?
We analyze the q^2-dependence of the strange magnetic form factor, \GMS(q^2),
using heavy baryon chiral perturbation theory (HBChPT) and dispersion
relations. We find that in HBChPT a significant cancellation occurs between the
O(p^2) and O(p^3) loop contributions. Consequently, the slope of \GMS at the
origin displays an enhanced sensitivity to an unknown O(p^3) low-energy
constant. Using dispersion theory, we estimate the magnitude of this constant,
show that it may have a natural size, and conclude that the low-q^2 behavior of
\GMS could be dominated by nonperturbative physics. We also discuss the
implications for the interpretation of parity-violating electron scattering
measurements used to measure \GMS(q^2).Comment: 9 pages, Revtex, 2 ps figure
Length, Protein-Protein Interactions, and Complexity
The evolutionary reason for the increase in gene length from archaea to
prokaryotes to eukaryotes observed in large scale genome sequencing efforts has
been unclear. We propose here that the increasing complexity of protein-protein
interactions has driven the selection of longer proteins, as longer proteins
are more able to distinguish among a larger number of distinct interactions due
to their greater average surface area. Annotated protein sequences available
from the SWISS-PROT database were analyzed for thirteen eukaryotes, eight
bacteria, and two archaea species. The number of subcellular locations to which
each protein is associated is used as a measure of the number of interactions
to which a protein participates. Two databases of yeast protein-protein
interactions were used as another measure of the number of interactions to
which each \emph{S. cerevisiae} protein participates. Protein length is shown
to correlate with both number of subcellular locations to which a protein is
associated and number of interactions as measured by yeast two-hybrid
experiments. Protein length is also shown to correlate with the probability
that the protein is encoded by an essential gene. Interestingly, average
protein length and number of subcellular locations are not significantly
different between all human proteins and protein targets of known, marketed
drugs. Increased protein length appears to be a significant mechanism by which
the increasing complexity of protein-protein interaction networks is
accommodated within the natural evolution of species. Consideration of protein
length may be a valuable tool in drug design, one that predicts different
strategies for inhibiting interactions in aberrant and normal pathways.Comment: 13 pages, 5 figures, 2 tables, to appear in Physica
Cell cycle-dependent variations in protein concentration
Computational modeling of biological systems has become an effective tool for analyzing cellular behavior and for elucidating key properties of the intricate networks that underlie experimental observations. While most modeling techniques rely heavily on the concentrations of intracellular molecules, little attention has been paid to tracking and simulating the significant volume fluctuations that occur over each cell division cycle. Here, we use fluorescence microscopy to acquire single cell volume trajectories for a large population of Saccharomyces cerevisiae cells. Using this data, we generate a comprehensive set of statistics that govern the growth and division of these cells over many generations, and we discover several interesting trends in their size, growth and protein production characteristics. We use these statistics to develop an accurate model of cell cycle volume dynamics, starting at cell birth. Finally, we demonstrate the importance of tracking volume fluctuations by combining cell division dynamics with a minimal gene expression model for a constitutively expressed fluorescent protein. The significant oscillations in the cellular concentration of a stable, highly expressed protein mimic the observed experimental trajectories and demonstrate the fundamental impact that the cell cycle has on cellular functions
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