Electronic Modulation of Nickel Disulfide toward Efficient Water Electrolysis

Developing highly efficient earth‐abundant nickel‐based compounds is an important step to realize hydrogen generation from water. Herein, the electronic modulation of the semiconducting NiS₂ by cation doping for advanced water electrolysis is reported. Both theoretical calculations and temperature‐dependent resistivity measurements indicate the semiconductor‐to‐conductor transition of NiS₂ after Cu incorporation. Further calculations also suggest the advantages of Cu dopant to cathodic water electrolysis by bringing Gibbs free energy of H adsorption at both Ni sites and S sites much closer to zero. It is noteworthy that water dissociation on Cu‐doped NiS₂ (Cu‐NiS₂) surface is even more favorable than those on NiS₂ and Pt(111). Thus, the prepared Cu‐NiS₂ shows noticeably improved performance toward alkaline hydrogen and oxygen evolution reactions (HER and OER). Specifically, it requires merely 232 mV OER overpotential to drive 10 mA cm^?2; in parallel with Tafel slopes of 46 mV dec^?1. Regarding HER, an onset overpotential of only 68 mV is achieved. When integrated as both electrodes for water electrolysis, Cu‐NiS₂ needs only 1.64 V to drive 10 mA cm^?2, surpassing the state‐of‐the‐art Ir/C–Pt/C couple (1.71 V). This work opens up an avenue to engineer low‐cost and earth‐abundant catalysts performing on par with the noble‐metal‐based one for water splitting.     

In situ transesterification of coconut oil using mixtures of methanol and tetrahydrofuran

The conventional biodiesel production method requires oil extraction followed by transesterification with methanol. The solubility of vegetable oils in methanol is low which decreases the overall rate of reaction. To eliminate the oil extraction step and improve the overall reaction rate, simultaneous extraction, esterification and transesterification were conducted by directly mixing methanol and tetrahydrofuran (THF) co-solvent and sulfuric acid catalyst with ground, desiccated coconut meat (copra) in a batch process and continuing the reaction until the system reached steady state. After separation of the mixture, yield was obtained by measuring the content of triglycerides, diglycerides and monoglycerides in the biodiesel phase. The yield increases with THF:methanol ratio, methanol:oil molar ratio and temperature. Within the range of conditions tested, the highest yield achieved was 96.7% at 60 °C, THF:methanol volume ratio of 0.4 and methanol:oil molar ratio of 60:1. The methanol:oil molar ratio is necessarily high in order to completely wet the copra mass, but is still lower than in previous studies by other researchers on in situ transesterification. Product assays show that the resulting biodiesel product is similar to conventionally produced coconut biodiesel. The results indicate that the in situ transesterification of copra using methanol/THF mixtures merits further study.     

Numerical Study of a Full-wavelength Dipole Antenna on a GaAs Membrane Structure at Terahertz Frequency

In this paper, a full-wavelength dipole antenna, supported by a GaAs membrane structure, is examined. The antenna was designed with both high input resistance and high radiation efficiency to improve the overall efficiency of a terahertz photomixer design. The geometrical effects of the GaAs membrane structure on the overall antenna performance were investigated through an optimization process. To supply DC bias to the antenna, a bias line with a photonic bandgap (PBG) structure was designed and optimized. The resulting antenna had a 2742-Ω input resistance and a 65% radiation efficiency, corresponding to an approximately 44% total efficiency at the 1.05-THz resonance frequency. The proposed antenna is expected to efficiently generate THz waves and be applicable to many practical applications where large coverage (detection area), easy alignment, and high scanning speed, rather than high-resolution, are preferred.     

Radical and incremental creativity: Antecedents and processes.

This study extends creativity theory and research by differentiating between 2 distinct forms of creative performance: radical and incremental. It also examines the differential effects of certain antecedents on these two forms of creativity. Results demonstrate that intrinsic motivation, problem-driven, and abstract theory-related creative ideas are associated mostly with radical creativity, whereas extrinsic motivation and ideas that are solution-driven and developed on the basis of concrete practices are linked more closely to incremental creativity. Theoretical and managerial implications are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Fast and accurate statistical characterization of standard cell libraries

With devices entering the nanometer scale process-induced variations, intrinsic variations and reliability issues impose new challenges for the electronic design automation industry. Design automation tools must keep the pace of technology and keep predicting accurately and efficiently the high-level design metrics such as delay and power. Although it is the most time consuming, Monte Carlo is still the simplest and most employed technique for simulating the impact of process variability at circuit level. This work addresses the problem of efficient alternatives for Monte Carlo for modeling circuit characteristics under statistical variability. This work employs the error propagation technique and Response Surface Methodology for substituting Monte Carlo simulations for library characterization.The techniques are validated and compared using a production level cell library using a state-of-the-art 32 nm technology node and statistical device compact model. They require electrical simulation effort linear to the number of devices, thus from one to two orders of magnitude speed-up is obtained compared to Monte Carlo analysis with the error on standard deviation and mean being smaller than 2% for the Response Surface Methodology, as compared to errors of 7% when using linear sensitivity analysis.     

In vitro skin permeation and retention of paromomycin from liposomes for topical treatment of the cutaneous leishmaniasis

Paromomycin (PA), a very hydrophilic antibiotic, has been tested as an alternative topical treatment against cutaneous leishmaniasis (CL). Although this treatment has shown promising results, it has not been successful in accelerating the recovery in most cases. This could be attributed to the low skin penetration of PA. Liposomal formulations usually provide sustained and enhanced drug levels in skin. The aim of this study was to prepare liposomal formulations containing PA and to investigate their potential as topical delivery systems of this antileishmanial. Large multilamellar vesicles (MLVs) were prepared by conventional solvent evaporation method. Large unilamellar vesicles (LUVs) were prepared by reverse-phase evaporation method. The lipids used were soybean phosphatidylcholine (PC) and PC:cholesterol (CH) (molar ratio 1:1). The skin permeation experiments across stripped and normal hairless mice skin were performed in modified Franz diffusion cells. The PA entrapment in LUV liposomes (20.4 ± 2.2%) was higher than that observed for MLV liposomes (7.5 ± 0.9%). Drug entrapment was 41.9 ± 6.2% and 27.2 ± 2.4% for PC and PC:CH LUV, respectively. The skin permeation was 1.55 ± 0.31%, 1.29 ± 0.40%, 0.20 ± 0.08%, and 0.50 ± 0.19% for PC LUV, PC:CH LUV, empty LUV + PA and aqueous solution, respectively. Controlled topical delivery, across stripped skin, was observed for PA entrapped in LUV liposomes.     

Control of macrophage responses on hydrophobic and hydrophilic carbon nanostructures

This study monitored the expression of cytokines by macrophages and synaptic antigens on macrophages in contact with hydrophobic (water contact angle was 140°) and hydrophilic (water completely adsorbed within 5 s) carbon nanostructures. Results indicated that hydrophilic carbon nanofibers (CNFs) generated the smallest inflammatory response from macrophages compared to hydrophobic CNFs and titanium (which is a conventional prosthetic implant material). Specifically, hydrophilic CNFs triggered less pro-inflammatory cytokine (e.g., tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6)) secretion from macrophages than hydrophobic CNFs. Results further revealed that hydrophobic CNFs activated macrophage cytoskeleton changes in a time dependent manner, whereas hydrophilic CNFs did not. Lastly, although additional tests are needed, the net analysis of macrophage expression of co-stimulatory molecules (e.g., CD80 and CD86) demonstrated that hydrophobic CNFs may ultimately lead to increased T-cell activation than hydrophilic CNFs. In summary, this study suggests that the wettability of carbon nanostructured materials may be potentially linked to macrophage behavior to induce or minimize inflammation.     

Optimal control of vibration by multiple tuned liquid dampers using Taguchi method

Journal of Mechanical Science and Technology - This paper investigates the multiple tuned liquid dampers (MTLD), which consist of a number of MTLD whose first natural frequencies of sloshing are...