5,088 research outputs found
Empirical prediction of traffic noise transmission loss across plenum windows
A parametric study on the traffic noise transmission loss across plenum windows was carried out experimentally in this investigation in an attempt to establish a simple empirical model for predicting this transmission loss. A total of fourteen full scale plenum windows were included in this study. The results of a site mockup measurement were used for model validation. The present model was developed based on the existing plenum chamber theory in which the sound fields inside the plenum window cavities were assumed to make up of a diffracted wave and a reverberant field. Results suggest that both the diffracted and reverberant field inside the plenum window cavities are weaker than those assumed in existing plenum chamber theory. It is found that a model, which assumes frequency-independent diffraction directivity and percentage reverberant field attenuation, gives the best prediction of traffic noise transmission loss. This prediction model is also able to predict site test results with good accurac
Magneto-transport in a quantum network: Evidence of a mesoscopic switch
We investigate magneto-transport properties of a shaped three-arm
mesoscopic ring where the upper and lower sub-rings are threaded by
Aharonov-Bohm fluxes and , respectively, within a
non-interacting electron picture. A discrete lattice model is used to describe
the quantum network in which two outer arms are subjected to binary alloy
lattices while the middle arm contains identical atomic sites. It is observed
that the presence of the middle arm provides localized states within the band
of extended regions and lead to the possibility of switching action from a high
conducting state to a low conducting one and vice versa. This behavior is
justified by studying persistent current in the network. Both the total current
and individual currents in three separate branches are computed by using
second-quantized formalism and our idea can be utilized to study magnetic
response in any complicated quantum network. The nature of localized
eigenstates are also investigated from probability amplitudes at different
sites of the quantum device.Comment: 7 pages, 9 figure
An efficient ant colony system based on receding horizon control for the aircraft arrival sequencing and scheduling problem
The aircraft arrival sequencing and scheduling (ASS) problem is a salient problem in air traffic control (ATC), which proves to be nondeterministic polynomial (NP) hard. This paper formulates the ASS problem in the form of a permutation problem and proposes a new solution framework that makes the first attempt at using an ant colony system (ACS) algorithm based on the receding horizon control (RHC) to solve it. The resultant RHC-improved ACS algorithm for the ASS problem (termed the RHC-ACS-ASS algorithm) is robust, effective, and efficient, not only due to that the ACS algorithm has a strong global search ability and has been proven to be suitable for these kinds of NP-hard problems but also due to that the RHC technique can divide the problem with receding time windows to reduce the computational burden and enhance the solution's quality. The RHC-ACS-ASS algorithm is extensively tested on the cases from the literatures and the cases randomly generated. Comprehensive investigations are also made for the evaluation of the influences of ACS and RHC parameters on the performance of the algorithm. Moreover, the proposed algorithm is further enhanced by using a two-opt exchange heuristic local search. Experimental results verify that the proposed RHC-ACS-ASS algorithm generally outperforms ordinary ACS without using the RHC technique and genetic algorithms (GAs) in solving the ASS problems and offers high robustness, effectiveness, and efficienc
Observation of Enhanced Beaming from Photonic Crystal Waveguides
We report on the experimental observation of the beaming effect in photonic
crystals enhanced via surface modes. We experimentally map the spatial field
distribution of energy emitted from a subwavelength photonic crystal waveguide
into free-space, rendering with crisp clarity the diffractionless beaming of
energy. Our experimental data agree well with our numerical studies of the
beaming enhancement in photonic crystals with modulated surfaces. Without loss
of generality, we study the beaming effect in a photonic crystal scaled to
microwave frequencies and demonstrate the technological capacity to deliver
long-range, wavelength-scaled beaming of energy.Comment: 4 pages, 6 figure
A new "polarized version" of the Casimir Effect is measurable
We argue that the exactly computable, angle dependent, Casimir force between
parallel plates with different directions of conductivity can be measured.Comment: One Figure, 11 page
On complex surfaces diffeomorphic to rational surfaces
In this paper we prove that no complex surface of general type is
diffeomorphic to a rational surface, thereby completing the smooth
classification of rational surfaces and the proof of the Van de Ven conjecture
on the smooth invariance of Kodaira dimension.Comment: 34 pages, AMS-Te
Increased Levels of Circulating and Tissue mRNAs of Oct-4, Sox-2, Bmi-1 and Nanog is ESCC Patients: Potential Tool for Minimally Invasive Cancer Diagnosis
Background Early stages of esophageal cancer lack a specific symptom, a reliable biomarker and accurate non-invasive diagnostic modalities prompting the pressing need for identification of a marker for early diagnosis of this disease. Methods In the present study we investigated the levels of circulating and tissue mRNAs of Oct-3/4, Sox-2, Nanog and Bmi-1 in esophageal cancer patients using Reverse-Transcription Polymerase Chain Reaction (RT-PCR) with the aim of evaluating their potential as minimally invasive diagnostic markers. Result Increased transcript levels of Oct-4, Sox-2, Bmi-1 and Nanog were detected in (92%), (95%), (75%) and (67%) of the esophageal cancer tissues, respectively as compared with the matched distant normals. Conclusion Interestingly, most of the preneoplastic tissues exhibited increased transcript levels of these stemness markers suggesting their role in early stages of esophageal tumorigenesis. Furthermore, the detection of elevated levels of circulating mRNAs of Oct-4 and Nanog in sera of esophageal cancer patients emphasizes their potential as minimally invasive diagnostic markers for esophageal cancer
Charge and spin ordering in Nd{1/3}Sr{2/3}FeO{3}
We have investigated the charge and spin ordering in Nd{1/3}Sr{2/3}FeO{3}
with neutron diffraction technique. This sample undergoes a charge ordering
transition accompanying charge disproportionation of 2Fe4+ -> Fe3+ + Fe5+. We
measured the superlattice reflections due to the charge and spin ordering, and
confirmed that charges and spins order simultaneously at Tco = 185 K. The
ordering pattern of charges and spins in this sample can be viewed as three
dimensional stripe order, and is compared with two dimensional stripe order
observed in other transition metal oxides.Comment: REVTeX, 4 pages, 3 figures, to be published in J. Phys. Chem. Solid
Cysteine 893 is a target of regulatory thiol modifications of GluA1 AMPA receptors
Recent studies indicate that glutamatergic signaling involves, and is regulated by, thiol modifying and redox-active compounds. In this study, we examined the role of a reactive cysteine residue, Cys-893, in the cytosolic C-terminal tail of GluA1 AMPA receptor as a potential regulatory target. Elimination of the thiol function by substitution of serine for Cys-893 led to increased steady-state expression level and strongly reduced interaction with SAP97, a major cytosolic interaction partner of GluA1 C-terminus. Moreover, we found that of the three cysteine residues in GluA1 C-terminal tail, Cys-893 is the predominant target for Snitrosylation induced by exogenous nitric oxide donors in cultured cells and lysates. Co-precipitation experiments provided evidence for native association of SAP97 with neuronal nitric oxide synthase (nNOS) and for the potential coupling of Ca2+- permeable GluA1 receptors with nNOS via SAP97. Our results show that Cys-893 can serve as a molecular target for regulatory thiol modifications of GluA1 receptors, including the effects of nitric oxide.Peer reviewe
Elementary excitations in one-dimensional spin-orbital models: neutral and charged solitons and their bound states
We study, both numerically and variationally, the interplay between different
types of elementary excitations in the model of a spin chain with anisotropic
spin-orbit coupling, in the vicinity of the "dimer line" with an exactly known
dimerized ground state. Our variational treatment is found to be in a
qualitative agreement with the exact diagonalization results. Soliton pairs are
shown to be the lowest excitations only in a very narrow region of the phase
diagram near the dimer line, and the phase transitions are always governed by
magnon-type excitations which can be viewed as soliton-antisoliton bound
states. It is shown that when the anisotropy exceeds certain critical value, a
new phase boundary appears. In the doped model on the dimer line, the exact
elementary charge excitation is shown to be a hole bound to a soliton. Bound
states of those "charged solitons" are studied; exact solutions for N-hole
bound states are presented.Comment: 11 pages revtex, 6 figure
- …