5,347 research outputs found
Fourier's Law from Schroedinger Dynamics
We consider a class of one-dimensional chains of weakly coupled many level
systems. We present a theory which predicts energy diffusion within these
chains for almost all initial states, if some concrete conditions on their
Hamiltonians are met. By numerically solving the time dependent Schroedinger
equation, we verify this prediction. Close to equilibrium we analyze this
behavior in terms of heat conduction and compute the respective coefficient
directly from the theory.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
Pressure buildup during CO2 injection in brine aquifers using the Forchheimer equation
If geo-sequestration of CO2 is to be employed as a key emissions reduction method in the global effort to mitigate climate change, simple yet robust screening of the risks of disposal in brine aquifers will be needed. There has been significant development of simple analytical and semi-analytical techniques to support screening analysis and performance assessment for potential carbon sequestration sites. These techniques have generally been used to estimate the size of CO2 plumes for the purpose of leakage rate estimation. A common assumption has been that both the fluids and the geological formation are incompressible. Consequently, calculation of pressure distribution requires the specification of an arbitrary radius of influence. In this talk, a new similarity solution is derived using the method of matched asymptotic expansions. By allowing for slight compressibility in the fluids and formation, the solution improves on previous work by not requiring the specification of an arbitrary radius of influence. A large-time approximation of the solution is then extended to account for non-Darcy inertial effects using the Forchheimer equation. Both solutions are verified by comparison with finite difference solutions. The results show that inertial losses will often be comparable, and sometimes greater than, the viscous Darcy-like losses associated with the brine displacement, although this is strongly dependent on formation porosity and permeability
Dynamical Surface Gravity in Spherically Symmetric Black Hole Formation
We study dynamical surface gravity in a general spherically symmetric setting
using Painlev\'{e}-Gullstrand (PG) coordinates. Our analysis includes several
definitions that have been proposed in the past as well as two new definitions
adapted to PG coordinates. Various properties are considered, including general
covariance, value at extremality, locality and static limit. We illustrate with
specific examples of "dirty" black holes that even for spacetimes possessing a
global timelike Killing vector, local definitions of surface gravity can differ
substantially from "non-local" ones that require an asymptotic normalization
condition. Finally, we present numerical calculations of dynamical surface
gravity for black hole formation via spherically symmetric scalar field
collapse. Our results highlight the differences between the various definitions
in a dynamical setting and provide further insight into the distinction between
local and non-local definitions of surface gravity.Comment: Final version to appear in Phys. Rev. D. Slight name change, further
improvements to numerics and presentation, 25 pages, 7 figure
Selfdual 2-form formulation of gravity and classification of energy-momentum tensors
It is shown how the different irreducibility classes of the energy-momentum
tensor allow for a Lagrangian formulation of the gravity-matter system using a
selfdual 2-form as a basic variable. It is pointed out what kind of
difficulties arise when attempting to construct a pure spin-connection
formulation of the gravity-matter system. Ambiguities in the formulation
especially concerning the need for constraints are clarified.Comment: title changed, extended versio
Sex-partitioning of the <i>Plasmodium falciparum</i> stage V gametocyte proteome provides insight into <i>falciparum</i>-specific cell biology
One of the critical gaps in malaria transmission biology and surveillance is our lack of knowledge about Plasmodium falciparum gametocyte biology, especially sexual dimorphic development and how sex ratios that may influence transmission from the human to the mosquito. Dissecting this process has been hampered by the lack of sex-specific protein markers for the circulating, mature stage V gametocytes. The current evidence suggests a high degree of conservation in gametocyte gene complement across Plasmodium, and therefore presumably for sex-specific genes as well. To better our understanding of gametocyte development and subsequent infectiousness to mosquitoes, we undertook a Systematic Subtractive Bioinformatic analysis (filtering) approach to identify sex-specific P. falciparum NF54 protein markers based on a comparison with the Dd2 strain, which is defective in producing males, and with syntenic male and female proteins from the reanalyzed and updated P. berghei (related rodent malaria parasite) gametocyte proteomes. This produced a short list of 174 male- and 258 female-enriched P. falciparum stage V proteins, some of which appear to be under strong diversifying selection, suggesting ongoing adaptation to mosquito vector species. We generated antibodies against three putative female-specific gametocyte stage V proteins in P. falciparum and confirmed either conserved sex-specificity or the lack of cross-species sex-partitioning. Finally, our study provides not only an additional resource for mass spectrometry-derived evidence for gametocyte proteins but also lays down the foundation for rational screening and development of novel sex-partitioned protein biomarkers and transmission-blocking vaccine candidates
Dynamic spin-Hall effect and driven spin helix for linear spin-orbit interactions
We derive boundary conditions for the electrically induced spin accumulation
in a finite, disordered 2D semiconductor channel. While for DC electric fields
these boundary conditions select spatially constant spin profiles equivalent to
a vanishing spin-Hall effect, we show that an in-plane ac electric field
results in a non-zero ac spin-Hall effect, i.e., it generates a spatially
non-uniform out-of-plane polarization even for linear intrinsic spin-orbit
interactions. Analyzing different geometries in [001] and [110]-grown quantum
wells, we find that although this out-of-plane polarization is typically
confined to within a few spin-orbit lengths from the channel edges, it is also
possible to generate spatially oscillating spin profiles which extend over the
whole channel. The latter is due to the excitation of a driven spin-helix mode
in the transverse direction of the channel. We show that while finite
frequencies suppress this mode, it can be amplified by a magnetic field tuned
to resonance with the frequency of the electric field. In this case, finite
size effects at equal strengths of Rashba- and Dresselhaus SOI lead to an
enhancement of the magnitude of this helix mode. We comment on the relation
between spin currents and boundary conditions.Comment: 10 pages, 5 figures, added references, corrected typos, extended
section V, VI
Driven Spin Systems as Quantum Thermodynamic Machines: Fundamental Limits
We show that coupled two level systems like qubits studied in quantum
information can be used as a thermodynamic machine. At least three qubits or
spins are necessary and arranged in a chain. The system is interfaced between
two split baths and the working spin in the middle is externally driven. The
machine performs Carnot-type cycles and is able to work as heat pump or engine
depending on the temperature difference of the baths and the energy
differences in the spin system . It can be shown that the efficiency
is a function of and .Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.
Cdc53p acts in concert with Cdc4p and Cdc34p to control the G1 to S phase transition and identifies a conserved family of proteins
Regulation of cell cycle progression occurs in part through the targeted degradation of both activating and inhibitory subunits of the cyclin-dependent kinases. During G1, CDC4, encoding a WD-40 repeat protein, and CDC34, encoding a ubiquitin-conjugating enzyme, are involved in the destruction of these regulators. Here we describe evidence indicating that CDC53 also is involved in this process. Mutations in CDC53 cause a phenotype indistinguishable from those of cdc4 and cdc34 mutations, numerous genetic interactions are seen between these genes, and the encoded proteins are found physically associated in vivo. Cdc53p defines a large family of proteins found in yeasts, nematodes, and humans whose molecular functions are uncharacterized. These results suggest a role for this family of proteins in regulating cell cycle proliferation through protein degradation
Produção de farinha mista de mandioca e castanha-do-brasil.
bitstream/item/63916/1/Oriental-Doc227.pd
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