Local heating effects on flow and heat transfer in microchannels

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.A series of numerical investigations was conducted to explore the effects of temperature-dependent viscosity and thermal conductivity on two-dimensional low Reynolds number convection of water in microchannels with locally heating. An emphasis was addressed on the fundamental characteristics of flow and thermal re-development at different localized heat fluxes and different inlet temperatures. The velocity field is highly coupled with temperature distribution and distorted through the variations of viscosity and thermal conductivity. The induced cross-flow velocity has a marked contribution to the convection. The heat transfer enhancement due to viscosity-variation is pronounced, though the axial convection introduced by thermal-conductivity-variation is insignificant unless for the cases of very low Reynolds numbers. The heat transfer enhancement is described by defining the peak value and location of relative Nusselt number distribution as ΔNu%max and Xmax. Strong nonlinear interaction mechanism prevails in the correlation of ΔNu%max and Xmax due to high heat flux condition and dramatic rise of liquid temperature.This study is supported by the National Natural Science Foundation of China (Grant No. 50636030)

Fano-Rashba effect in thermoelectricity of a double quantum dot molecular junction

We examine the relation between the phase-coherent processes and spin-dependent thermoelectric effects in an Aharonov-Bohm (AB) interferometer with a Rashba quantum dot (QD) in each of its arm by using the Green's function formalism and equation of motion (EOM) technique. Due to the interplay between quantum destructive interference and Rashba spin-orbit interaction (RSOI) in each QD, an asymmetrical transmission node splits into two spin-dependent asymmetrical transmission nodes in the transmission spectrum and, as a consequence, results in the enhancement of the spin-dependent thermoelectric effects near the spin-dependent asymmetrical transmission nodes. We also examine the evolution of spin-dependent thermoelectric effects from a symmetrical parallel geometry to a configuration in series. It is found that the spin-dependent thermoelectric effects can be enhanced by controlling the dot-electrode coupling strength. The simple analytical expressions are also derived to support our numerical results

Tunneling magnetoresistance in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junctions

published_or_final_versio

Investigation on the Dispersal Characteristics of Liquid Breakup in Vacuum

This work presents an experimental study on the dispersal characteristics of a liquid jet ejecting into vacuum. The liquid breaking experiments of several kinds of liquid under different pressure and temperature conditions are carried out in a flash chamber. The stability of the jet and the sizes of the droplets or the icing particles formed during liquid flashing dispersing are analyzed. The influences of the superheat degree, spray velocity, and the mass of the volatile liquid mixing in the nonvolatile liquid on these characteristics are discussed. Moreover, the applicability of the two definitions of superheat degree is discussed. The results show that the superheat degree is an important parameter influencing the pattern of the breaking liquid, and the jet velocity has a large influence on the distribution of particle sizes. In addition, mixing some volatile liquid with nonvolatile liquid can enhance the dispersion of the latter

C-Reactive Protein Promotes Diabetic Kidney Disease in db/db Mice via the CD32b-Smad3-mTOR signaling Pathway

published_or_final_versio

Correlation between promoter methylation of p14ARF, TMS1/ASC, and DAPK, and p53 mutation with prognosis in cholangiocarcinoma

<p>Abstract</p> <p>Background</p> <p>To study the methylation status of genes that play a role in the p53-Bax mitochondrial apoptosis pathway and its clinical significance in cholangiocarcinoma.</p> <p>Patients and Methods</p> <p>Out of 36 cases cholangiocarcinoma patients from April 2000 to May 2005 were collected.Promoter hypermethylation of <it>DAPK</it>, <it>p14^ARF</it>, and <it>ASC </it>were detected by methylation-specific PCR on cholangiocarcinoma and normal adjacent tissues samples. Mutation of the p53 gene was examined by automated sequencing. Correlation between methylation of these genes and/or <it>p53 </it>mutation status with clinical characteristics of patients was investigated by statistical analysis.</p> <p>Results</p> <p>We found 66.7% of 36 cholangiocarcinoma patients had methylation of at least one of the tumor suppressor genes analyzed. <it>p53 </it>gene mutation was found in 22 of 36 patients (61.1%). Combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation was detected in 14 cases (38.9%). There were statistically significant differences in the extent of pathologic biology, differentiation, and invasion between patients with combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation compared to those without (P < 0.05). The survival rate of patients with combined <it>DAPK, p14^ARF, and ASC </it>methylation and <it>p53 </it>mutation was poorer than other patients (<it>P </it>< 0.05).</p> <p>Conclusion</p> <p>Our study indicates that methylation of <it>DAPK, p14^ARF, and ASC </it>in cholangiocarcinoma is a common event. Furthermore, <it>p53 </it>mutation combined with <it>DAPK, p14^ARF, and/or ASC </it>methylation correlates with malignancy and poor prognosis.</p

Chlorophyll derivatives/MXene hybrids for photocatalytic hydrogen evolution: Dependence of performance on the central coordinating metals

Development of efficient photocatalytic hydrogen evolution reaction (HER) with illumination of visible light is challenging. In this work, five chlorophyll derivatives (M-Chls; M = H2/Cu/Ni/Co/Zn) with different central ions in its cyclic tetrapyrrole ring including free base, copper, nickel, cobalt, and zinc were synthesized and employed as the effective visible-light harvester for efficient HER. In addition, two-dimensional (2D) noble metal-free co-catalyst Ti3C2Tx MXene was used as an excellent electron capturer due to its outstanding conductivity property. These M-Chls are modified on the surface of Ti3C2Tx MXene with 2D accordion-like morphology by means of a simple deposition process to form noble metal-free Chl/Ti3C2Tx-based photocatalysts for HER. It is found that the best HER performance as high as 49 μmol/h/gcat was achieved with the Co-Chl@Ti3C2Tx hybrid, which was much higher than those of other M-Chl@Ti3C2Tx composites. This research provides a specific way to synthesize low-cost and environmentally friendly natural Chls for developing highly efficient photocatalytic HER through molecular engineering