293 research outputs found
Calculation of nanowire thermal conductivity using complete phonon dispersion relations
The lattice thermal conductivity of crystalline Si nanowires is calculated.
The calculation uses complete phonon dispersions, and does not require any
externally imposed frequency cutoffs. No adjustment to nanowire thermal
conductivity measurements is required. Good agreement with experimental results
for nanowires wider than 35 nm is obtained. A formulation in terms of the
transmission function is given. Also, the use of a simpler, nondispersive
"Callaway formula", is discussed from the complete dispersions perspective.Comment: 4 pages, 3 figures. Accepted in Phys. Rev.
Permutation complexity of the fixed points of some uniform binary morphisms
An infinite permutation is a linear order on the set N. We study the
properties of infinite permutations generated by fixed points of some uniform
binary morphisms, and find the formula for their complexity.Comment: In Proceedings WORDS 2011, arXiv:1108.341
EphA4 signaling regulates phospholipase Cgamma1 activation, cofilin membrane association, and dendritic spine morphology
Specialized postsynaptic structures known as dendritic spines are the primary sites of glutamatergic innervation at synapses of the CNS. Previous studies have shown that spines rapidly remodel their actin cytoskeleton to modify their shape and this has been associated with changes in synaptic physiology. However, the receptors and signaling intermediates that restructure the actin network in spines are only beginning to be identified. We reported previously that the EphA4 receptor tyrosine kinase regulates spine morphology. However, the signaling pathways downstream of EphA4 that induce spine retraction on ephrin ligand binding remain poorly understood. Here, we demonstrate that ephrin stimulation of EphA4 leads to the recruitment and activation of phospholipase Cgamma1 (PLCgamma1) in heterologous cells and in hippocampal slices. This interaction occurs through an Src homology 2 domain of PLCgamma1 and requires the EphA4 juxtamembrane tyrosines. In the brain, PLCgamma1 is found in multiple compartments of synaptosomes and is readily found in postsynaptic density fractions. Consistent with this, PLC activity is required for the maintenance of spine morphology and ephrin-induced spine retraction. Remarkably, EphA4 and PLC activity modulate the association of the actin depolymerizing/severing factor cofilin with the plasma membrane. Because cofilin has been implicated previously in the structural plasticity of spines, this signaling may enable cofilin to depolymerize actin filaments and restructure spines at sites of ephrin-EphA4 contact
S-, P- and D-wave resonances in positronium-sodium and positronium-potassium scattering
Scattering of positronium (Ps) by sodium and potassium atoms has been
investigated employing a three-Ps-state coupled-channel model with Ps(1s,2s,2p)
states using a time-reversal-symmetric regularized electron-exchange model
potential fitted to reproduce accurate theoretical results for PsNa and PsK
binding energies. We find a narrow S-wave singlet resonance at 4.58 eV of width
0.002 eV in the Ps-Na system and at 4.77 eV of width 0.003 eV in the Ps-K
system. Singlet P-wave resonances in both systems are found at 5.07 eV of width
0.3 eV. Singlet D-wave structures are found at 5.3 eV in both systems. We also
report results for elastic and Ps-excitation cross sections for Ps scattering
by Na and K.Comment: 9 pages, 5 figures, Accepted in Journal of Physics
Thermopower of a 2D electron gas in suspended AlGaAs/GaAs heterostructures
We present thermopower measurements on a high electron mobility
two-dimensional electron gas (2DEG) in a thin suspended membrane.We show that
the small dimension of the membrane substantially reduces the thermal
conductivity compared to bulk material so that it is possible to establish a
strong thermal gradient along the 2DEG even at a distance of few micrometers.
We find that the zero-field thermopower is significantly affected by the micro
patterning. In contrast to 2DEGs incorporated in a bulk material, the diffusion
contribution to the thermopower stays dominant up to a temperature of 7 K until
the phonon-drag becomes strong and governs the run of the thermopower. We also
find that the coupling between electrons and phonons in the phonon-drag regime
is due to screened deformation potentials, in contrast to piezoelectric
coupling found with bulk phonons.Comment: 7 page
Infinite permutations vs. infinite words
I am going to compare well-known properties of infinite words with those of
infinite permutations, a new object studied since middle 2000s. Basically, it
was Sergey Avgustinovich who invented this notion, although in an early study
by Davis et al. permutations appear in a very similar framework as early as in
1977. I am going to tell about periodicity of permutations, their complexity
according to several definitions and their automatic properties, that is, about
usual parameters of words, now extended to permutations and behaving sometimes
similarly to those for words, sometimes not. Another series of results concerns
permutations generated by infinite words and their properties. Although this
direction of research is young, many people, including two other speakers of
this meeting, have participated in it, and I believe that several more topics
for further study are really promising.Comment: In Proceedings WORDS 2011, arXiv:1108.341
Vacation posts on Facebook:A model for incidental vicarious travel consumption
Vicarious consumption of travel is ubiquitous. However little is known about the psychological processes this initiates or the potential for resultant behaviors beyond direct steps toward patronage. We address this gap through developing and testing the incidental vicarious travel consumption model (IVTCM), which draws from well-established knowledge of the self-concept and compensatory consumption. In the context of vicariously consuming idyllic vacation posts on Facebook, the model identifies the following: individuals’ travel-related self-discrepancies may become active, leading to feelings of dejection, initiating five possible compensatory consumption behaviors (Direct, Symbolic, Dissociation, Escapism, Fluid). A sequential mixed-method design (total n=860) provides support for the IVTCM. The primary contributions of the paper are as follows: first the IVTCM can be used to understand different forms of vicarious travel consumption. Second, specific understanding on the impact of idyllic vacation posts is contributed, furthering knowledge on the role of social media within touris
Isolation of a euryhaline microalgal strain, Tetraselmis sp CTP4, as a robust feedstock for biodiesel production
Bioprospecting for novel microalgal strains is key to improving the feasibility of microalgae-derived biodiesel production. Tetraselmis sp. CTP4 (Chlorophyta, Chlorodendrophyceae) was isolated using fluorescence activated cell sorting (FACS) in order to screen novel lipid-rich microalgae. CTP4 is a robust, euryhaline strain able to grow in seawater growth medium as well as in non-sterile urban wastewater. Because of its large cell size (9-22 mu m), CTP4 settles down after a six-hour sedimentation step. This leads to a medium removal efficiency of 80%, allowing a significant decrease of biomass dewatering costs. Using a two-stage system, a 3-fold increase in lipid content (up to 33% of DW) and a 2-fold enhancement in lipid productivity (up to 52.1 mg L-1 d(-1)) were observed upon exposure to nutrient depletion for 7 days. The biodiesel synthesized from the lipids of CTP4 contained high levels of oleic acid (25.67% of total fatty acids content) and minor amounts of polyunsaturated fatty acids with >= 4 double bonds (< 1%). As a result, this biofuel complies with most of the European (EN14214) and American (ASTM D6751) specifications, which commonly used microalgal feedstocks are usually unable to meet. In conclusion, Tetraselmis sp. CTP4 displays promising features as feedstock with lower downstream processing costs for biomass dewatering and biodiesel refining
Author Correction: Elucidating causative gene variants in hereditary Parkinson’s disease in the Global Parkinson’s Genetics Program (GP2)
Correction to: npj Parkinson’s Disease, published online 27 June 2023 In this article the Global Parkinson’s Genetics Program (GP2) members names and affiliations were missing in the main author list of the Original article which are listed in the below
- …