Electroosmotically enhanced microchannel heat sinks

The present study investigates the microchannel heat sink for pure electroosmotic, pressure-driven, and mixed (electroosmotic and pressure-driven) flows. A three-dimensional numerical analysis is performed for electroosmotic and mixed flows. Electroosmotic flow (EOF) induced in an ionic solution in the presence of surface charge and electric field is investigated with hydrodynamic pressure-driven flow (PDF) to enhance heat removal through the microchannel heat sink. In a pressure-driven microchannel heat sink, the application of an external electric field increases the flow rate that consequently reduces the thermal resistance. The effects of ionic concentration represented by the zeta potential and Debye thickness are studied with the various steps of externally applied electric potential. A higher value of zeta potential leads to higher flow rate and lower thermal resistance, which consequently reduce the temperature of the microprocessor chip and load of the micropump used to supply coolant to the microchannels. This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee Afzal Husain received B.E. and M.Tech. degrees in Mechanical Engineering with specialization in Thermal Sciences from Aligarh Muslim University, India in 2003 and 2005, respectively. Currently he is pursuing Ph.D. degree in Thermodynamics and Fluid Mechanics in Inha University, Republic of Korea. His research interests are numerical analysis and optimization of heat transfer systems using computational fluid dynamics and surrogate models, development of heat transfer augmentation techniques for conventional and micro systems, thermal analysis of microelectromechanical systems (MEMS), and electronic cooling. Kwang-Yong Kim received a B.S. degree from Seoul National University in 1978, and his M.S. and Ph.D. degrees from Korea Advanced Institute of Science and Technology (KAIST), Korea, in 1981 and 1987, respectively. Presently, he is professor and chairman, School of Mechanical Engineering, Inha University, Incheon, Korea. Prof. Kim is presently the editor-in-chief of Transactions of Korean Society of Mechanical Engineers (KSME), the editor-in-chief of International Journal of Fluid Machinery and Systems (IJFMS), and chief vice president of Korean Fluid Machinery Association (KFMA). Prof. Kim is Fellow of American Society of Mechanical Engineers (ASME).     

Structure and Charge-Transfer Mechanism in Y1?x Ca x Ba2Cu3O7?δ Through Direct Doping

Here we study the effect of Ca doping on the charge-transfer mechanism of polycrystalline YBa₂Cu₃O_7??? compound. The samples of composition Y_1?x Ca _x Ba₂Cu₃O_7??? (x=0.00,0.05,0.10,0.20 and 0.30) are synthesized through standard solid-state reaction route. Carrier doping is controlled by annealing of samples in oxygen and subsequently in reducing atmosphere. Samples are investigated using resistivity, dc magnetization (M?CT) and magnetization with field (M?CH) measurements. With increase of Ca the transition temperature (T _c) decreases in oxygenated samples, whereas the same increases in reduced samples. Further reduction of samples at higher temperatures (>600?°C) though results in non-superconducting nature up to Ca concentration of x=0.20, the x=0.30 sample is superconducting below 30?K. This provides a remarkably simple and effective way to study the relationship between structure, superconductivity, and associated electronic properties. Variation in Cu₁?CO₄, Cu₂?CO₄ and Cu₂?CO₂ bond lengths with oxygen content, is seen through the structural refinement of XRD pattern. The effective coordination of Cu₂ atom with oxygen changes with the change in these bond lengths and hence the holes in the CuO₂ planes. The charge-transfer mechanism from CuO _x chains to CuO₂ planes and thus effective hole doping is discussed in the context of the results observed.     

Thermally assisted ECR etching of CdTe in CCl2F2/Ar discharge under different gas flow ratio

II–VI compounds have attracted increasing attention, primarily because of the large range of energy band gaps available. ECR plasma etching of CdTe in a CCl₂F₂/Ar discharge with rf biasing were investigated at different temperature and different flow rate ratio. The etch rate increases with the increase in flow rate of reactive gas and temperature. The use of ECR conditions with additional rf biasing provides the good etching of the surface and fast etch rates. The etch depths were measured by Dektek profilometry and the surface morphology with scanning electron microscopy. This paper reports the thermal effect on the etch process of CdTe and the effect of various gas flow rates and ratio between CCl₂F₂ and Ar.     

Experimental observation of the effect of astigmatic aperture lens on the spectral switches of polychromatic Gaussian beam

Experimental results of a study, conducted to investigate the effect of an astigmatic aperture lens on the spectral switches observed with spatially coherent polychromatic light, are reported. It is found that the spectrum at the observation plane exhibits anomalous behavior after passing through the astigmatic aperture lens. It is shown that at a particular position of the aperture, the spectrum splits into two halves, while at other positions the spectrum either shifts towards lower frequencies (red shift) or shifts towards higher frequencies (blue shift). These spectral changes take place in the vicinity of the dark region of the diffraction pattern. Experimental observations show that the behavior of the spectral switch is affected by the astigmatism of the lens. It is found that the spectral minimum value and the transition height of the spectral switch change as the astigmatism of the lens changes. Moreover, the critical position of the aperture where spectral switch occurs also changes with the astigmatism of the lens. The results are consistent with the theoretical predictions [Pan, L.; Lü, B. Opt. Commun. 2004, 234, 13–22].     

Nuclear Export Inhibitor KPT-8602 Synergizes with PARP Inhibitors in Escalating Apoptosis in Castration Resistant Cancer Cells

Aberrant nuclear protein transport, often observed in cancer, causes mislocalization-dependent inactivation of critical cellular proteins. Earlier we showed that overexpression of exportin 1 is linked to higher grade and Gleason score in metastatic castration resistant prostate cancer (mCRPC). We also showed that a selective inhibitor of nuclear export (SINE) selinexor and second generation eltanexor (KPT-8602) could suppress mCRPC growth, reduce androgen receptor (AR), and re-sensitize to androgen deprivation therapy. Here we evaluated the combination of KPT-8602 with PARP inhibitors (PARPi) olaparib, veliparib and rucaparib in 22rv1 mCRPC cells. KPT-8602 synergized with PARPi (CI < 1) at pharmacologically relevant concentrations. KPT-8602-PARPi showed superior induction of apoptosis compared to single agent treatment and caused up-regulation of pro-apoptotic genes BAX, TP53 and CASPASE 9. Mechanistically, KPT-8602-PARPi suppressed AR, ARv7, PSA and AR targets FOXA1 and UBE2C. Western blot analysis revealed significant down-regulation of AR, ARv7, UBE2C, SAM68, FOXA1 and upregulation of cleaved PARP and cleaved CASPASE 3. KPT-8602 with or without olaparib was shown to reduce homologous recombination-regulated DNA damage response targets including BRCA1, BRCA2, CHEK1, EXO1, BLM, RAD51, LIG1, XRCC3 and RMI2. Taken together, this study revealed the therapeutic potential of a novel combination of KPT-8602 and PARP inhibitors for the treatment of mCRPC.     

Analysis of cold flow fluidization test results for various biomass fuels

A systematic theoretical and experimental study was conducted to obtain hydrodynamic properties such as particle size diameter, bulk density, fluidizing velocity, etc. for locally available biomass residue fuels in Malaysia like rice husk, sawdust, peanut shell, coconut shell, palm fiber as well as coal and bottom ash. The tests were carried out in a cold flow fluidization bed chamber of internal diameter 60 mm with air as fluidizing medium. The height of the chamber could be raised up to 630 mm by five separate cylindrical rings. Bed-pressure drop was measured as a function of superficial air velocity over a range of bed heights for each individual type of particle. The data were used to determine minimum fluidization velocity, which could be used to compare with theoretical values. The particle size of biomass residue fuel was classified according to Gildart's distribution diagram. The results show that Gildart's particle size (B) for sawdust, coal bottom ash, coconut shell have good fluidizing properties compared to rice husk, type (D) or palm fiber, type (A). The bulk density and voidage are found to be main factors contributing to fluidizing quality of the bed.     

Transient analysis of parallel plate forced circulation solar water heating system

In this paper, a transient analysis of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank has been presented for a parallel flat plate collector. The effect of various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day viz. 26 January 1980 in Delhi.     

Effect of tin oxide nanoparticle binding on the structure and activity of α-amylase from Bacillus amyloliquefaciens

Proteins adsorbed on nanoparticles (NPs) are being used in biotechnology, biosensors and drug delivery. However, understanding the effect of NPs on the structure of proteins is still in a nascent state. In the present paper tin oxide (SnO2) NPs were synthesized by the reaction of SnCl4·5H2O in methanol via the sol-gel method and characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The binding of these SnO2-NPs with α-amylase was investigated by using UV-vis, fluorescence and circular dichroism (CD) spectroscopic techniques. A strong quenching of tryptophan fluorescence intensity in α-amylase was observed due to formation of a ground state complex with SnO2-NPs. Far-UV CD spectra showed that the secondary structure of α-amylase was changed in the presence of NPs. The Michaelis-Menten constant (K(m)), was found to be 26.96 and 28.45 mg ml(-1), while V(max) was 4.173 and 3.116 mg ml(-1) min(-1) for free and NP-bound enzyme, respectively.