600 research outputs found
Time-dependent quantum transport: an exact formulation based on TDDFT
An exact theoretical framework based on Time Dependent Density Functional
Theory (TDDFT) is proposed in order to deal with the time-dependent quantum
transport in fully interacting systems. We use a \textit{partition-free}
approach by Cini in which the whole system is in equilibrium before an external
electric field is switched on. Our theory includes the interactions between the
leads and between the leads and the device. It is well suited for calculating
measurable transient phenomena as well as a.c. and other time-dependent
responses. We show that the steady-state current results from a
\textit{dephasing mechanism} provided the leads are macroscopic and the device
is finite. In the d.c. case, we obtain a Landauer-like formula when the
effective potential of TDDFT is uniform deep inside the electrodes.Comment: final version, 7 pages, 1 figur
Scaling of Heteroepitaxial Island Sizes
Monte Carlo simulations of an atomistic solid-on-solid model are used to
study the effect of lattice misfit on the distribution of two-dimensional
islands sizes as a function of coverage in the submonolayer
aggregation regime of epitaxial growth. Misfit promotes the detachment of atoms
from the perimeter of large pseudomorphic islands and thus favors their
dissolution into smaller islands that relieve strain more efficiently. The
number density of islands composed of atoms exhibits scaling in the form
\mbox{)} where is the average island size. Unlike the
case of homoepitaxy, a rate equation theory based on this observation leads to
qualitatively different behavior than observed in the simulations.Comment: 10 pages, LaTeX 2.09, IC-DDV-94-00
Revealing the true partitioning character of zirconium in additively manufactured polycrystalline superalloys
International audienc
Complement-Like Protein TEP1 Is a Determinant of Vectorial Capacity in the Malaria Vector Anopheles gambiae
AbstractAnopheles mosquitoes are major vectors of human malaria in Africa. Large variation exists in the ability of mosquitoes to serve as vectors and to transmit malaria parasites, but the molecular mechanisms that determine vectorial capacity remain poorly understood. We report that the hemocyte-specific complement-like protein TEP1 from the mosquito Anopheles gambiae binds to and mediates killing of midgut stages of the rodent malaria parasite Plasmodium berghei. The dsRNA knockdown of TEP1 in adults completely abolishes melanotic refractoriness in a genetically selected refractory strain. Moreover, in susceptible mosquitoes this knockdown increases the number of developing parasites. Our results suggest that the TEP1-dependent parasite killing is followed by a TEP1-independent clearance of dead parasites by lysis and/or melanization. Further elucidation of the molecular mechanisms of TEP1-mediated parasite killing will be of great importance for our understanding of the principles of vectorial capacity in insects
A general method to determine replica symmetry breaking transitions
We introduce a new parameter to investigate replica symmetry breaking
transitions using finite-size scaling methods. Based on exact equalities
initially derived by F. Guerra this parameter is a direct check of the
self-averaging character of the spin-glass order parameter. This new parameter
can be used to study models with time reversal symmetry but its greatest
interest concerns models where this symmetry is absent. We apply the method to
long-range and short-range Ising spin glasses with and without magnetic field
as well as short-range multispin interaction spin glasses.Comment: 5 pages, 4 figures, Revtex fil
In Vivo Identification of Novel Regulators and Conserved Pathways of Phagocytosis in A. gambiae
SummaryAnopheles gambiae uses effective immune responses, including phagocytosis, to fight microbial infection. We have developed a semiquantitative phagocytosis test and used it in conjunction with dsRNA gene silencing to test the in vivo roles of 71 candidate genes in phagocytosis of Escherichia coli and Staphylococcus aureus. Here, we show that inactivation of 26 genes changes the phagocytic activity by more than 45% and that two pathways similar to those that mediate apoptotic cell removal in Caenorhabditis elegans are used in A. gambiae for phagocytosis of microorganisms. Simultaneous inactivation of the identified regulators of phagocytosis and conserved components defining each signaling pathway permitted provisional assignment of the novel regulators to one or the other pathway. Pathway inactivation enhances at least three times the ability of E. coli and S. aureus to proliferate in the mosquito. Interestingly, mosquito survival is not compromised even if both pathways are perturbed simultaneously
Thermo-mechanical analysis of dental silicone polymers
Soft lining materials are used to replace the inner surface of a conventional complete denture, especially for weak elderly patients, with delicate health who cannot tolerate the hard acrylic denture base. Most of these patients have fragile supporting mucosa, excessive residual ridge resorption, particularly on the mandibular arch. The application of a soft liner to the mandibular denture allows absorbing impact forces during mastication and relieving oral mucosa. Actually, the silicone rubbers constitute the main family of commercialised soft lining materials. This study was conducted to understand the relationships between the mechanical properties and the physical structure of polysiloxanes. For this purpose, a series of polysiloxanes of various chemical compositions have been investigated. The evolution of their physical structure as a function of temperature has been followed by differential scanning calorimetry (DSC). In order to facilitate comparisons, the mechanical modulus has been analysed upon the same heating rate using dynamic mechanical analysis (DMA). Polysiloxanes actually commercialised as soft denture liners are three-dimensional networks: the flexibility of chains allows a crystalline organisation in an amorphous phase leading to the low value of the shear modulus. The dynamic mechanical analysis shows that they are used in the rubbery state. So, polysiloxanes have steady mechanical properties during physiological utilisation
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