No abstract

An effective method for performing the thermal optimization of fully confined pin-fin heat sinks under constraints of pressure drop, mass, and space limitations has been successfully developed. This study shows how automated design optimization techniques can be successfully applied to optimal design of pin-fin heat sinks, which allows the thermal engineer to meet several design objectives and constraints simultaneously. The thermal and hydrodynamic models for pin-fin heat sinks have been developed. A statistical method for sensitivity analysis of the design factors, including the size of heat source and sink footprint, conductivity of sink base, fin material, fin pitch, fin diameter, fin height, thickness of sink base, and upstream mass flowrate, is performed to determine the key factors that are critical to the design. A response surface methodology is then applied to establish regression models for the thermal resistance and pressure drop in terms of the design factors with an experimental design. By employing the gradient-based numerical optimization technique, a series of constrained optimal designs can be efficiently performed. Comparisons between these predicted optimal designs and those evaluated by the theoretical calculations and numerical simulations are made with satisfactory agreements.

The emerging Weyl semi‐metals with robust topological surface states are very promising candidates to rationally develop new‐generation electrocatalysts for dye‐sensitized solar cells (DSSCs). In this study, a chemical vapor deposition (CVD) method to synthesize highly crystalline Weyl semi‐metallic MoxW1‐xTe2 nanocrystals, which are applied for the counter electrode (CE) of DSSCs for the first time, are employed. By controlling the temperature‐dependent phase‐engineered synthesis, the nanocrystal grown at 760 °C exhibits the mixed phases of semiconducting Td‐ & 2H‐Mo0.32W0.67Te2.01 with charge carrier density of (1.20 ± 0.02) × 1019 cm−3; whereas, the nanocrystal synthesized at 820 °C shows a single phase of semi‐metallic Td‐Mo0.29W0.72Te1.99 with much higher carrier density of (1.59 ± 0.04) × 1020 cm−3. In the cyclic voltammetry (CV) analysis over 200 cycles, the MoxW1‐xTe2‐based electrodes show better stability in the I−/I3− electrolyte than a Pt electrode. In DSSC tests, a Td‐Mo0.29W0.72Te1.99‐decorated CE achieves the efficiency (η) of 8.85%, better than those CEs fabricated with Td‐ & 2H‐Mo0.32W0.67Te2.01 (7.81%) and sputtered Pt (8.01%). The electrochemical impedance spectra reveal that the Td‐Mo0.29W0.72Te1.99 electrode possesses low charge‐transfer resistance in electrocatalytic reactions. These exceptional properties make Weyl semi‐metallic Td‐MoxW1‐xTe2 a potential electrode material for a wide variety of electrocatalytic applications.

The short and long isoforms of the dopamine D2 receptor (D2S and D2L respectively) are highly expressed in the striatum. Functional D2 receptors activate an intracellular signalling pathway that includes a cAMP-independent route involving Akt/GSK3 (glycogen synthase kinase 3). To investigate the Akt/GSK3 response to the seldom-studied D2S receptor, we established a rat D2S receptor-expressing cell line [HEK (human embryonic kidney)-293/rD2S]. We found that in HEK-293/rD2S cells, the D2/D3 agonists bromocriptine and quinpirole significantly induced Akt and GSK3 phosphorylation, as well as ERK1/2 (extracellular-signal-regulated kinase 1/2) activation. The D2S receptor-induced Akt signals were profoundly inhibited by the internalization blockers monodansyl cadaverine and concanavalin A. Activation of the D2S receptor in HEK-293/rD2S cells appeared to trigger Akt/phospho-Akt translocation to the cell membrane. In addition to our cell culture experiments, we studied D2 receptor-dependent Akt in vivo by systemic administration of the D2/D3 agonist quinpirole. The results show that quinpirole evoked Akt-Ser473 phosphorylation in the ventral striatum. Furthermore, intra-accumbens administration of wortmannin, a PI3K (phosphoinositide 3-kinase) inhibitor, significantly suppressed the quinpirole-evoked behavioural activation. Overall, we demonstrate that activation of the dopamine D2S receptor stimulates Akt/GSK3 signalling. In addition, in vivo Akt activity in the ventral striatum appears to play an important role in systemic D2/D3 agonist-induced behavioural activation.

A hierarchical urchin-like structure of CoSe2/CoSeO3 (denoted as CoSe2/CoSeO3-UL) is synthesized by a one-step hydrothermal method and investigated as the electro-catalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs).

Boron nitride (BN) is newly introduced as a nonmetal electrocatalyst for the counter electrode of a dye-sensitized solar cell (DSSC). By applying a conductive binder of sulfonated poly(thiophene-3-[2-(2methoxyethoxy)ethoxy]-2,5-diyl) (s-PT), the BN/s-PT composite film was successfully wrapped around each carbon fiber (CF) in the flexible carbon cloth (CC) substrate via a low-cost drop-coating method. Each CF in the CC provided a one-dimensional electron transfer core, and the wrapped BN/s-PT composite film functioned as the mesoporous electro-catalytic shell. Compared to pristine BN and pristine s-PT electrodes, the electrochemical and impedance performances of the BN/s-PT composite film were incredibly enhanced because of the synergetic effect of the BN nanoparticle and the s-PT binder; the former offered a large active surface area and a high intrinsic heterogeneous rate constant, and the latter formed fast electron transfer matrices. With a proper BN weight percentage among BN/s-PT solutions, the best DSSC coupling with a BN/s-PT composite counter electrode exhibited a good cell efficiency (η) of 9.21% at 1 sun, showing a great potential to substitute the expensive platinum (8.11%). At the dim light environment (i.e., T5 fluorescent illumination), the DSSC reached attractive η′s of 21.02% (6000 lux), 19.52% (3000 lux), and 17.48% (1000 lux).

No abstract

No abstract