RESUMEN

Identifying the time of ovulation is an important process for women seeking and avoiding pregnancy. Luteinizing hormone (LH) plays an important role in ovulation, which is very important in the reproductive mechanism. Therefore, detecting the LH level is of great importance in monitoring ovulation. In this study, sensitive, rapid and selective electrochemical biosensors were developed to detect LH quantitatively from human urine samples and to monitor the ovulation period. Isopotential region and current density optimization studies revealed that sensors with an electrode width and spacing of 1 mm had the optimum performance. Electrochemical impedance spectra evidenced immobilization of DSP self-assembled monolayers and anti-LH-beta antibody on the surface. While the mobile phone vibrator led to a 3.5-fold enhancement in response signals, the agitation system developed resulted in a 10-fold improvement. The sensors displayed detection limits of 1.02 and 1.53 mIU/ml in the range of 0-40 mIU/ml LH concentration obtained using two statistical approaches. Additionally, the sensors showed no cross-reactivity to hCG, which is very similar in structure and is widely reported to have high cross-reactivity.

Asunto(s)

RESUMEN

Ir is one of the most efficient oxygen evolution reaction (OER) catalysts; however, it is also one of the rarest and most expensive elements. Therefore, it is highly desirable to develop Ir catalysts with nanostructures that reduce Ir consumption by maximizing the surface-to-volume ratio without limiting the mass transport of reactants and products of reactions. Ir OER catalysts on a template that consisted of porous nanotubes (PNTs) based on Ni are fabricated. The Ir/Ni PNTs offer multiple benefits, including high catalytic performance (potential of 1.500 V vs. reversible hydrogen electrode (RHE) at an operating current density of 10 mA cm-2 and Tafel slope of 44.34 mV decade-1 ), minimal use of Ir (mass activity of 3273 A g-1 at 1.53 V vs RHE), and facile mass transport through the NT-sidewall pores (stable operation for more than 10 h). The Ir/Ni PNTs are also applied to a tandem device, consisting of a Cu(In,Ga)Se2 -based photocathode and halide perovskite photovoltaic cell, for unassisted water splitting. A solar-to-hydrogen conversion efficiency that exceeded 10% is also demonstrated, which is nearly 1% point greater than when a planar Ir film is used as the anode instead of Ir/Ni PNTs.

RESUMEN

Small pore zeolites with chabazite structure have been commercialized for selective catalytic reduction (SCR) of nitrogen oxides (NOx) with ammonium (NH3) from diesel exhaust. However, conventional zeolite synthesis processes detrimental effects on the environment due to the consumption of large amount of water, organic templates. Thus, this study proposed a green synthesis process with addition of minimal amount of water, structure directing agent and shortened steps to prepare nano-sized SSZ-13 (0.12 µm) using trans-crystallization strategy and exhibited enhanced performance for NOx removal after copper ion-exchange. The operation temperature window (NOx conversion >90 %) as well as the SO2 and H2O resistance over the green-route prepared nano-sized SSZ-13 (178-480 °C) outperformed the conventional SSZ-13 (29.8 µm, 211-438 °C) mainly due to the much shorter diffusion path. This clearly implied that the mass transportation was key for NH3-SCR of NOx on such small pore zeolite catalysts, which was further confirmed via an in-depth mass transportation calculation process. These results demonstrate that the Cu-nano-sized SSZ-13 prepared by the environmental benign route has great potential to act as a new generation of deNOx catalyst for diesel exhaust and provided a guideline for researchers to develop new methods to synthesize nano-catalysts for air pollution control.

RESUMEN

In this study, we synthesize two layered and amorphous structures of germanium phosphide (GeP5) and compare their electrochemical performances to better understand the role of layered, crystalline structures and their ability to control large volume expansions. We compare the results obtained with those of previous, conventional viewpoints addressing the effectiveness of amorphous phases in traditional anodes (Si, Ge, and Sn) to hinder electrode pulverization. By means of both comprehensive experimental characterizations and density functional theory calculations, we demonstrate that layered, crystalline GeP5 in a hybrid structure with multiwalled carbon nanotubes exhibits exceptionally good transport of electrons and electrolyte ions and tolerance to extensive volume changes and provides abundant reaction sites relative to an amorphous structure, resulting in a superior solid-electrolyte interphase layer and unprecedented initial Coulombic efficiencies in both Li-ion and Na-ion batteries. Moreover, the hybrid delivers excellent rate-capability (symmetric and asymmetric) performance and remarkable reversible discharge capacities, even at high current rates, realizing ultradurable cycles in both applications. The findings of this investigation are expected to offer insights into the design and application of layered materials in various devices.

RESUMEN

Porous solid with multimodal pore size distribution provides plenty of advantages including large specific surface area and superior mass transportation to achieve high gas-sensing performances. In this study, α-Fe2O3 nanoparticles with bimodal porous structures were prepared successfully through a nanocasting pathway, adopting the bicontinuous 3D cubic symmetry mesoporous silica KIT-6 as the hard template. Its structure and morphology were characterized by X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, and so on. Furthermore, the gas sensor fabricated from this material exhibited excellent gas-sensing performance to several volatile organic compounds (acetone, ethyl acetate, isopropyl alcohol, n-butanol, ethanol, and methanol), such as ultrahigh sensitivity, rapid response speed (less than 10 s) and recovery time, good reproducibility, as well as stability. These would be associated with the desirable pore structure of the material, facilitating the molecules diffusion toward the entire sensing surface, and providing more active sensing sites for analytical gas.

RESUMEN

This work is related to billiards and their applications in geometric optics. It is known that perfectly invisible bodies with mirror surface do not exist. It is, therefore, natural to search for bodies that are, in a sense, close to invisible. We introduce a visibility index of a body measuring the mean angle of deviation of incident light rays, and derive a lower estimate for this index. This estimate is a function of the body's volume and of the minimal radius of a ball containing the body. This result is far from being final and opens a possibility for further research.

RESUMEN

Fine particles(PM2.5) collected by two middle volume air samplers in the suburbs of Baoding and the urban area of Beijing during Jan 10th to 17th, 2015, were used to compare the community characteristics of cultivable bacteria in the two sites. In this study, we observed the particle morphology of PM2.5 using a field emission scanning electron microscope (FESEM), analyzed the air mass transportation source of the two sampling sites by the NOAA/ARL HYSPLIT-4 backward trajectory model, and measured the concentrations of the major water-soluble ions and heavy metal elements in the PM2.5 samples using ion chromatography, continuous flow analyzer and ICP-MS. The results indicated that, the cultivable bacteria of PM2.5 contained three phyla, which were Firmicutes, Actinobacteria and α-Proteobacteria. Nine genera and 17 species of cultivable airborne bacteria were isolated and identified. The most abundant phylum was Firmicutes. The Gram-positive bacteria accounted for more than 90%. The spore-forming Bacillus which was the dominant species contributed 68.15% and 75% to the total bacteria in urban Beijing and the suburbs of Baoding, respectively. The difference in the community structure of PM2.5's cultivable bacteria in the two sampling areas may be affected by PM2.5's physical and chemical properties and air mass transportation.

Asunto(s)