Room temperature continuous-wave operation of GaInNAs/GaAs VCSELsgrown by chemical beam epitaxy with output power exceeding 1 mW

The authors present a near 1200 nm wavelength vertical-cavity surface-emitting laser (VCSEL) the active region of which is formed by GaInNAs/GaAs quantum wells grown by chemical beam epitaxy. Room temperature continuous-wave operation has been demonstrated with a high slope efficiency of 0.23 W/A, a high output power of over 1.0 mW, and a singlemode output power of 0.34 mW. The fabricated devices with different aperture sizes show low threshold currents of 1.2-2.1 mA and a record low threshold current density of 2.6 kA/cm² in GaInNAs VCSELs     

Oxidation and stress relief in air at room temperature of amorphous silicon hydrogenated in a glow discharge

Glow-discharge-hydrogenated amorphous silicon (a-Si : H) was found to be oxidized in the following two ways after exposing to air at room temperature; first, thin oxide films grew uniformly on the a-Si : H, slowly with increase of exposure time; secondly, oxide with a columnar morphology grew rapidly with the increase of exposure time and the cross section of the columnar oxide was small. Mechanical stress caused by the differences of the thermal expansion coefficient and the crystallographical structure between the a-Si : H and substrates was relieved with the increase in the amount of the columnar oxide.     

Crystalline Sodium Selenocarboxylates – synthesis and characterization

A series of sodium selenocarboxylates 2 were isolated from the reaction of diacyl selenides with sodium ethanolate and characterized. A convenient preparation of the sodium salts 2 by the direct reaction of acyl chlorides with sodium selenide was also established. The salts are colourless to slightly pale yellow crystals and labile towards moisture. They readily react with alkyl iodides at room temperature to give the corresponding Se-alkyl esters 3 .     

Chemical‐Free Approach for Z‐Isomerization of Lycopene in Tomato Powder: Hot Air and Superheated Steam Heating above the Melting Point of Lycopene

Z‐isomers of lycopene exhibit higher bioavailability and antioxidant capacity than those of the all‐E‐isomer. Therefore, it is important to develop an efficient and environmentally friendly procedure for Z‐isomerization. The current methods for Z‐isomerization of (all‐E)‐lycopene use toxic chemicals such as organic solvents and catalysts. This study is aimed to develop a chemical‐free method for Z‐isomerization of (all‐E)‐lycopene in tomato powder by hot air and superheated steam heating. The Z‐isomerization reaction is promoted by heating above the melting point of lycopene. When heated with superheated steam, the thermal decomposition of lycopene is suppressed compared to that when heated with hot air. When tomato powder is heated at 240 °C for 5 min by superheated steam, the total Z‐isomer content and remaining lycopene are 69.0% and 90.7%, respectively, while with hot air heating, the total Z‐isomer content and remaining lycopene are 69.9% and 68.0%, respectively. These results indicate that the thermal Z‐isomerization of lycopene occurs in the molten state and heating in a low oxygen atmosphere suppresses the thermal decomposition of lycopene. Practical Applications: Tomato powder rich in lycopene Z‐isomers is an important ingredient for the food and animal feed industries. Since Z‐isomers of lycopene are more soluble in solvents including ethanol which is a low‐toxicity and environmentally friendly solvent, the efficiency of lycopene extraction with ethanol can be improved by using the Z‐isomer‐rich tomato powder as a raw material. The obtained Z‐isomer‐rich extract has a high added value because the Z‐isomers have higher bioavailability and antioxidant capacity than those of the all‐E‐isomer. In addition, since lycopene Z‐isomers exhibit higher accumulation efficiency and better color improvement in hen egg yolks than those of the all‐E‐isomer, Z‐isomer‐rich tomato powder is an effective animal feed.     

Crystal Structure and Microwave dielectric Properties of Ba(Zn1/3Ta2/3)O3–(Sr,Ba)(Ga1/2Ta1/2)O3 Ceramics

The microwave dielectric properties and crystal structure of Ba(Zn_1/3Ta_2/3)O₃– (Sr,Ba)(Ga_1/2Ta_1/2)O₃ ceramics were investigated in the present study. The Q value of Ba(Zn_1/3Ta_2/3)O₃ was improved by adding 5 mol% Sr(Ga_1/2Ta_1/2)O₃. The maximum Q value of Q × f = 162000 GHz was obtained at 0.95Ba(Zn_1/3Ta_2/3)O₃. 0.05Sr(Ga_1/2Ta_1/2)O₃. For this composition, a lattice super structure caused by hexagonal ordering was observed. A further improvement in the Q value was attained when some Sr was replaced with Ba, and 0.95Ba(Zn_1/3Ta_2/3)O₃· 0.05(Sr_0.25Ba_0.75)(Ga_1/2Ta_1/2)O₃ exhibited a maximum Q value such that Q × f = 210000 GHz. Despite the increased Q value with the replacement of Sr by Ba, the c/a value, which indicates the degree of lattice distortion, remained constant near 3/2. The Q value thus improved without lattice distortion in the system Ba(Zn_1/3Ta_2/3)O₃-(Sr,Ba)(Ga_1/2Ta_1/2)O₃, whereas the improvement of Q value increased with lattice distortion in the solid solution system with Ba(Zn_1/3Ta_2/3)O₃ as an end member.     

Electrochemical reaction engineering of polymer electrolyte fuel cell

Although fuel cells can be considered as a type of reactor, methods of kinetic analysis and reactor modeling from the viewpoint of chemical reaction engineering have not yet been established. The rate of an electrochemical reaction is a function of concentration, temperature, and interfacial potential difference (or electromotive force). This study examined the cathode reaction in a polymer electrolyte fuel cell, in which oxygen and protons react over platinum in the catalyst layer (CL). The effects of the oxygen partial pressure and the cathode electromotive force on the reaction rate were assessed. Resistance to proton transport increases the electromotive force and reducing the reaction rate. It was established that the effectiveness factor of the cathode CL is determined by competition between the reaction and mass transport of oxygen and protons. Two dimensionless moduli that govern the cathode behavior are proposed as a means of depicting the processes in the cell. © 2016 American Institute of Chemical Engineers AIChE J, 63: 249–256, 2017     

Synthesis of Dense Lead Titanate Ceramics with Submicrometer Grains by Spark Plasma Sintering

Dense PbTiO₃ ceramics consisting of submicrometer-sized grains were prepared using the spark-plasma-sintering (SPS) method. Hydrothermally prepared PbTiO₃ (0.1 μm) was used as a starting powder. The powder was densified to ≳98% of the theoretical X-ray density by the SPS process. The average grain size of the spark-plasma-sintered ceramics (SPS ceramics) was ≲1 μm, even after sintering at 900°–1100°C, because of the short sintering period (1–3 min). The measured permittivity of the SPS ceramics showed almost no frequency dependence over the range 10¹–10⁶ Hz, mainly because pores were absent from the ceramics. The coercive field of the SPS ceramics was somewhat higher than that of conventionally sintered ceramics, which could be attributed to the small-grained microstructures of the SPS ceramics.     

X型聚丙烯纤维力学性能试验研究

针对日本生产的X型聚丙烯纤维,采用微机控制电子万能试验机,对其抗拉强度、断裂伸长率、弹性模量等力学指标进行了试验,并与分别经过pH值为12.5的碱溶液和120℃的烘箱处理后的纤维力学性能进行了对比.试验结果表明:① X型聚丙烯纤维拉伸强度高、弹性模量大、延性好;②纤维耐碱、耐热性能好,经碱溶液处理后,纤维拉伸强度、弹性模量和断裂伸长率分别达到处理前的93.8%、96.3%、89.6%;经耐热处理后,纤维拉伸强度、弹性模量和断裂伸长率分别达到处理前的98.7%、99.4%、93.4%.     

The Role of Autophagy in Chemical Proteasome Inhibition Model of Retinal Degeneration

We recently demonstrated that chemical proteasome inhibition induced inner retinal degeneration, supporting the pivotal roles of the ubiquitin–proteasome system in retinal structural integrity maintenance. In this study, using beclin1-heterozygous (Becn1-Het) mice with autophagic dysfunction, we tested our hypothesis that autophagy could be a compensatory retinal protective mechanism for proteasomal impairment. Despite the reduced number of autophagosome, the ocular tissue morphology and intraocular pressure were normal. Surprisingly, Becn1-Het mice experienced the same extent of retinal degeneration as was observed in wild-type mice, following an intravitreal injection of a chemical proteasome inhibitor. Similarly, these mice equally responded to other chemical insults, including endoplasmic reticulum stress inducer, N-methyl-D-aspartate, and lipopolysaccharide. Interestingly, in cultured neuroblastoma cells, we found that the mammalian target of rapamycin-independent autophagy activators, lithium chloride and rilmenidine, rescued these cells against proteasome inhibition-induced death. These results suggest that Becn1-mediated autophagy is not an effective intrinsic protective mechanism for retinal damage induced by insults, including impaired proteasomal activity; furthermore, autophagic activation beyond normal levels is required to alleviate the cytotoxic effect of proteasomal inhibition. Further studies are underway to delineate the precise roles of different forms of autophagy, and investigate the effects of their activation in rescuing retinal neurons under various pathological conditions.