8,834 research outputs found
The guanine nucleotide exchange factor RIC8 regulates conidial germination through Gα proteins in Neurospora crassa.
Heterotrimeric G protein signaling is essential for normal hyphal growth in the filamentous fungus Neurospora crassa. We have previously demonstrated that the non-receptor guanine nucleotide exchange factor RIC8 acts upstream of the Gα proteins GNA-1 and GNA-3 to regulate hyphal extension. Here we demonstrate that regulation of hyphal extension results at least in part, from an important role in control of asexual spore (conidia) germination. Loss of GNA-3 leads to a drastic reduction in conidial germination, which is exacerbated in the absence of GNA-1. Mutation of RIC8 leads to a reduction in germination similar to that in the Δgna-1, Δgna-3 double mutant, suggesting that RIC8 regulates conidial germination through both GNA-1 and GNA-3. Support for a more significant role for GNA-3 is indicated by the observation that expression of a GTPase-deficient, constitutively active gna-3 allele in the Δric8 mutant leads to a significant increase in conidial germination. Localization of the three Gα proteins during conidial germination was probed through analysis of cells expressing fluorescently tagged proteins. Functional TagRFP fusions of each of the three Gα subunits were constructed through insertion of TagRFP in a conserved loop region of the Gα subunits. The results demonstrated that GNA-1 localizes to the plasma membrane and vacuoles, and also to septa throughout conidial germination. GNA-2 and GNA-3 localize to both the plasma membrane and vacuoles during early germination, but are then found in intracellular vacuoles later during hyphal outgrowth
Numerical simulations of mixed states quantum computation
We describe quantum-octave package of functions useful for simulations of
quantum algorithms and protocols. Presented package allows to perform
simulations with mixed states. We present numerical implementation of important
quantum mechanical operations - partial trace and partial transpose. Those
operations are used as building blocks of algorithms for analysis of
entanglement and quantum error correction codes. Simulation of Shor's algorithm
is presented as an example of package capabilities.Comment: 6 pages, 4 figures, presented at Foundations of Quantum Information,
16th-19th April 2004, Camerino, Ital
Polarized micro-Raman studies of femtosecond laser written stress-induced optical waveguides in diamond
Understanding the physical mechanisms of the refractive index modulation
induced by femtosecond laser writing is crucial for tailoring the properties of
the resulting optical waveguides. In this work we apply polarized Raman
spectroscopy to study the origin of stress-induced waveguides in diamond,
produced by femtosecond laser writing. The change in the refractive index
induced by the femtosecond laser in the crystal is derived from the measured
stress in the waveguides. The results help to explain the waveguide
polarization sensitive guiding mechanism, as well as providing a technique for
their optimization.Comment: 5 pages, 4 figure
Orbits and Pulsations of the Classical ζ Aurigae Binaries
We have derived new orbits for ζ Aur, 32 Cyg, and 31 Cyg with observations from the Tennessee State University (TSU) Automatic Spectroscopic Telescope, and used them to identify nonorbital velocities of the cool supergiant components of these systems. We measure periods in those deviations, identify unexpected long-period changes in the radial velocities, and place upper limits on the rotation of these stars. These radial-velocity variations are not obviously consistent with radial pulsation theory, given what we know about the masses and sizes of the components. Our concurrent photometry detected the nonradial pulsations driven by tides (ellipsoidal variation) in both ζ Aur and 32 Cyg, at a level and phasing roughly consistent with simple theory to first order, although they seem to require moderately large gravity darkening. However, the K component of 32 Cyg must be considerably bigger than expected, or have larger gravity darkening than ζ Aur, to fit its amplitude. However, again there is precious little evidence for the normal radial pulsation of cool stars in our photometry. Hα shows some evidence for chromospheric heating by the B component in both ζ Aur and 32 Cyg, and the three stars show among them a meager ~2-3 outbursts in their winds of the sort seen occasionally in cool supergiants. We point out two fundamental questions in the interpretation of these stars: (1) whether it is appropriate to model the surface brightness as gravity darkening and (2) whether much of the nonorbital velocity structure may actually represent changes in the convective flows in the stars\u27 atmospheres
Optimization in the Natural Sciences: 30th Euro Mini-Conference, EmC-ONS 2014, Aveiro, Portugal, February 5-9, 2014: revised selected papers
This book constitutes the refereed proceedings of the 30th Euro Mini-Conference, EmC-ONS 2014, held in Aveiro, Portugal, in February 2014. The 13 revised full papers presented were carefully reviewed and selected from 70 submissions. The papers are organized in topical sections on dynamical systems; optimization and applications; modeling and statistical techniques for data analysis
Mathematical retroreflectors
Retroreflectors are optical devices that reverse the direction of incident
beams of light. Here we present a collection of billiard type retroreflectors
consisting of four objects; three of them are asymptotically perfect
retroreflectors, and the fourth one is a retroreflector which is very close to
perfect. Three objects of the collection have recently been discovered and
published or submitted for publication. The fourth object - notched angle - is
a new one; a proof of its retroreflectivity is given.Comment: 32 pages, 19 figure
A dynamical model for the dusty ring in the Coalsack
Lada et al. recently presented a detailed near-infrared extinction map of
Globule G2 in the Coalsack molecular cloud complex, showing that this starless
core has a well-defined central extinction minimum. We propose a model for G2
in which a rapid increase in external pressure is driving an approximately
symmetric compression wave into the core. The rapid increase in external
pressure could arise because the core has recently been assimilated by the
Coalsack cloud complex, or because the Coalsack has recently been created by
two large-scale converging flows. The resulting compression wave has not yet
converged on the centre of the core, so there is a central rarefaction. The
compression wave has increased the density in the swept-up gas by about a
factor of ten, and accelerated it inwards to speeds of order . It is shown that even small levels of initial turbulence destroy the
ring seen in projection almost completely. In the scenario of strong external
compression that we are proposing this implies that the initial turbulent
energy in this globule is such that .
Protostar formation should occur in about .Comment: Accepted for publication in A&
Reliable estimation of prediction uncertainty for physico-chemical property models
The predictions of parameteric property models and their uncertainties are
sensitive to systematic errors such as inconsistent reference data, parametric
model assumptions, or inadequate computational methods. Here, we discuss the
calibration of property models in the light of bootstrapping, a sampling method
akin to Bayesian inference that can be employed for identifying systematic
errors and for reliable estimation of the prediction uncertainty. We apply
bootstrapping to assess a linear property model linking the 57Fe Moessbauer
isomer shift to the contact electron density at the iron nucleus for a diverse
set of 44 molecular iron compounds. The contact electron density is calculated
with twelve density functionals across Jacob's ladder (PWLDA, BP86, BLYP, PW91,
PBE, M06-L, TPSS, B3LYP, B3PW91, PBE0, M06, TPSSh). We provide systematic-error
diagnostics and reliable, locally resolved uncertainties for isomer-shift
predictions. Pure and hybrid density functionals yield average prediction
uncertainties of 0.06-0.08 mm/s and 0.04-0.05 mm/s, respectively, the latter
being close to the average experimental uncertainty of 0.02 mm/s. Furthermore,
we show that both model parameters and prediction uncertainty depend
significantly on the composition and number of reference data points.
Accordingly, we suggest that rankings of density functionals based on
performance measures (e.g., the coefficient of correlation, r2, or the
root-mean-square error, RMSE) should not be inferred from a single data set.
This study presents the first statistically rigorous calibration analysis for
theoretical Moessbauer spectroscopy, which is of general applicability for
physico-chemical property models and not restricted to isomer-shift
predictions. We provide the statistically meaningful reference data set MIS39
and a new calibration of the isomer shift based on the PBE0 functional.Comment: 49 pages, 9 figures, 7 table
- …