An optimization-based "phase field" model for polycrystalline ferroelectrics

An optimization-based computational model is proposed to study domain evolution in polycrystalline ferroelectrics composed of numerous grains, each of which consists of multiple domains. Domain switching is realized by an optimization process to minimize the free energy of each grain. Similar to phase field modeling, no priori domain-switching criterion is imposed in the proposed model. Moreover, by focusing on the volume fractions of domains only, the computational complexity of this model becomes much smaller and the domain textures evolution can be captured. Simulation results on both tetragonal and rhombohedral lead titanate zirconate ceramics illustrate the efficiency of this model. © 2010 American Institute of Physics.published_or_final_versio

Super-resolution time delay estimation in multipath environments

The problem of super-resolution time delay estimation in multipath environments is addressed in this paper. Two cases, active and passive systems, are considered. The time delay estimation is first converted into a sinusoidal parameter estimation problem. Then the sinusoidal parameters are estimated by generalizing the Multiple Signal Classification (MUSIC) algorithm for single-experiment data. The proposed method, referred to as the MUSIC-type algorithm, approximates the Cramer-Rao bound (CRB) in terms of the mean square errors (MSEs) for different signal-to-noise ratios (SNRs) and separations of muitipath components. Simulation results show that the MUSIC-type algorithm performs better than the classical correlation approach and the conventional MUSIC method for the closely spaced components in muitipath environments.published_or_final_versio

Iterative CZT-based frequency offset estimation for frequency-selective channels

In this paper, we present an accurate frequency offset estimation method for frequency-selective channels. Through the iterative use of the chirp z-transform (CZT) algorithm, an accurate frequency offset estimator is proposed, approaching the Cramer-Rao Bound (CRB) even at low signal-to-noise ratio (SNR). Further, the estimation can be achieved within one block of training sequence, thus avoiding the transmission of repetitive known blocks as is usually required in many conventional methods. Meanwhile, the overall complexity is acceptable. More importantly, the CZT operation can utilize the fast Fourier transform (FFT) structure that is favourable for digital signal processor (DSP) implementation. Simulation results show that two or at most three iterations of the CZT computation are sufficient for an accurate frequency offset estimation in the SNR range from 0 dB to 30 dB. © 2005 IEEE.published_or_final_versio

In situ loading and delivery of short single- And double-stranded dna by supramolecular organic frameworks

Short DNA represents an important class of biomacromolecules that are widely applied in gene therapy, editing, and modulation. However, the development of simple and reliable methods for their intracellular delivery remains a challenge. Herein, we describe that seven water-soluble, homogeneous supramolecular organic frameworks (SOFs) with a well-defined pore size and high stability in water that can accomplish in situ inclusion of single-stranded (ss) and double-stranded (ds) DNA (21, 23, and 58 nt) and effective intracellular delivery (including two noncancerous and six cancerous cell lines). Fluorescence quenching experiments for single and double endlabeled ss- and ds-DNA support that the DNA sequences can be completely enveloped by the SOFs. Confocal laser scanning microscopy and flow cytometry reveal that five of the SOFs exhibit excellent delivery efficiencies that, in most of the studied cases, outperform the commercial standard Lipo2000, even at low SOF-nucleic acid ratios. In addition to high delivery efficiencies, the watersoluble, self-assembled SOF carriers have a variety of advantages, including convenient preparation, high stability, and in situ DNA inclusion, which are all critical for practical applications in nucleic acid delivery

Improving polymer solar cell performances by manipulating the self-organization of polymer

We have investigated driving force effects on the ordering of polymer, which is a key factor of self-assembly of soft materials. By turning the substrate up-side-down, the downward driving force can form in solution film-growth process and affect the self-organization of polymer chains and domains. We introduce Brown's capillarity theory [J. Polym. Sci., Polym. Phys. Ed. 22, 423 (1956)] to describe the film formation. Our results show that the better chain and lamellae packing of polymer make hole transport, carrier balance, and power conversion efficiency of annealed and unannealed devices improve even with thick active-layers as compared to conventional devices. © 2011 American Institute of Physics.published_or_final_versio

Magnetoresistance in LaFe11.2Co0.7Si1.1 compound

Magnetoresistance has been studied in LaFe/sub 11.2/Co/sub 0.7/Si/sub 1.1/ compound. The ferromagnetic ordering at Curie temperature T/sub C/ of 274 K was found being accompanied by a drastic negative lattice expansion due to the strong structural and magnetic interplay. Such a simultaneous magnetic and lattice change would cause changes in transport properties. The measured transport properties indicate that the transition can be induced by temperature or applied magnetic field. The sample shows a metallic character below T/sub C/, whereas the electrical resistance decreases dramatically and then recovers the metal-like behavior above T/sub C/. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase of field leads to an increase of resistance at temperatures near but above T/sub C/, which is a result of the field-induced metamagnetic transition from paramagnetic to ferromagnetic state.published_or_final_versio

Ameliorative Effects of Neurolytic Celiac Plexus Block on Stress and Inflammation in Rats with Partial Hepatectomy

Purpose: To investigate effects of neurolytic celiac plexus block (NCPB) on stress and inflammation in rats with partial hepatectomy (PH).Methods: A model of PH rat was established, and serum C-reactive protein (CRP); corticosterone (GC); adrenocorticotropin (ACTH); noradrenaline (NA); adrenalin (AD); aspartate transaminase (AST); alanine transaminase (ALT); as well as tumor necrosis factor-α (TNF-α); interleukin (IL)-1β and IL-6; high mobility group box1 (HMGB1); and nitric oxide (NO) concentrations in serum assessed after PH. Additionally, Western blotting was performed to determine the effect of NCPB on expressions of glucocorticoid receptors (GR), inhibitor of nuclear factor kappa B (IκB), p65, c-Jun and inducible nitric oxide synthase (iNOS) of PH rats, as well as assay effects of NCPB on nuclear translocation of GR, c- Jun and p65. DNA binding activities of nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1) were also determined.Results: NCPB reduced AST and ALT (P < 0.05), decreased secretion of inflammatory cytokines and NO (P < 0.05), as well as decreased CRP, GC, ACTH, NA and AD after PH (p < 0.05). NCPB increased expressions of GR and IκB, but expressions of p65, c-Jun, and iNOS (p < 0.05). Additionally, NCPB increased nuclear translocation of GR (p < 0.01), but decreased nuclear translocation of p65 and c-Jun after PH (p < 0.05). Additionally, DNA binding activity of NF-κB and AP-1 was decreased by NCPB (p < 0.05).Conclusion: The results indicate that NCPB treatment can significantly inhibit stress and inflammation in PH rats.Keywords: Neurolytic celiac plexus block, Cytokine, Nuclear translocation, Partial hepatectomy, Stress, Inflammatio

Thickness dependence of microstructures in La0.8Ca0.2MnO3 thin films

The thickness dependence of microstructures of La0.8Ca0.2MnO3 (LCMO)/SrTiO3 (STO) thin films was investigated by high-resolution x-ray diffraction, small angle x-ray reflection, grazing incidence x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The results show that all the LCMO films are well oriented in (00l) direction perpendicular to the substrate surface. Self-organized crystalline grains with a tetragonal shape are uniformly distributed on the film surface, indicating the deposition condition being of benefit to the formation of the crystalline grains. With increasing the film thickness, the crystalline quality of the LCMO film is improved, while the surface becomes rougher. There exists a nondesigned cap layer on the upper surface of the LCMO layer for all the samples. The mechanism is discussed briefly.published_or_final_versio

Optical frequency synthesizer with an integrated erbium tunable laser.

Optical frequency synthesizers have widespread applications in optical spectroscopy, frequency metrology, and many other fields. However, their applicability is currently limited by size, cost, and power consumption. Silicon photonics technology, which is compatible with complementary-metal-oxide-semiconductor fabrication processes, provides a low-cost, compact size, lightweight, and low-power-consumption solution. In this work, we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser. The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser. A 20 nm tuning range from 1544 to 1564 nm is achieved with ~10-13 frequency instability at 10 s averaging time. Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates. This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale low-cost optical frequency synthesizers

Extracts of Feijoa Inhibit Toll-Like Receptor 2 Signaling and Activate Autophagy Implicating a Role in Dietary Control of IBD

Inflammatory bowel disease (IBD) is a heterogeneous chronic inflammatory disease affecting the gut with limited treatment success for its sufferers. This suggests the need for better understanding of the different subtypes of the disease as well as nutritional interventions to compliment current treatments. In this study we assess the ability of a hydrophilic feijoa fraction (F3) to modulate autophagy a process known to regulate inflammation, via TLR2 using IBD cell lines