Double-active-layer index-guided InGaAsP-InP laser diode

A buried crescent InGaAsP-InP laser with two active layers was fabricated to study the temperature behavior of the double-carrier-confinement structure. An anomalously high characteristic temperature T0 was measured, and optical switching behavior was observed. A mode analysis and numerical calculation using a rate equation approach explained qualitatively very well the experimental results. It was revealed that both the Auger recombination in this special double-active-layer configuration and the temperature-dependent leakage current, which leads to uniform carrier distribution in both active regions, are essential to increase T0

Optimization of cool roof and night ventilation in office buildings: A case study in Xiamen, China

Increasing roof albedo (using a “cool” roof) and night ventilation are passive cooling technologies that can reduce the cooling loads in buildings, but existing studies have not comprehensively explored the potential benefits of integrating these two technologies. This study combines an experiment in the summer and transition seasons with an annual simulation so as to evaluate the thermal performance, energy savings and thermal comfort improvement that could be obtained by coupling a cool roof with night ventilation. A holistic approach integrating sensitivity analysis and multi-objective optimization is developed to explore key design parameters (roof albedo, night ventilation air change rate, roof insulation level and internal thermal mass level) and optimal design options for the combined application of the cool roof and night ventilation. The proposed approach is validated and demonstrated through studies on a six-storey office building in Xiamen, a cooling-dominated city in southeast China. Simulations show that combining a cool roof with night ventilation can significantly decrease the annual cooling energy consumption by 27% compared to using a black roof without night ventilation and by 13% compared to using a cool roof without night ventilation. Roof albedo is the most influential parameter for both building energy performance and indoor thermal comfort. Optimal use of the cool roof and night ventilation can reduce the annual cooling energy use by 28% during occupied hours when air-conditioners are on and reduce the uncomfortable time slightly during occupied hours when air-conditioners are off

Combined High Power and High Frequency Operation of InGaAsP/InP Lasers at 1.3μm

A simultaneous operation of a semiconductor laser at high power and high speed was demonstrated in a buried crescent laser on a P-InP substrate. In a cavity length of 300μm, a maximum CW power of 130mW at room temperature was obtained in a junction-up mounting configuration. A 3dB bandwidth in excess of 12GHz at an output power of 52mW was observed

Parametric study of cavity length and mirror reflectivity in ultralow threshold quantum well InGaAs/AlGaAs lasers

Record low CW threshold currents of 16 μA at-room temperature and 21 μA at cryogenic temperature have been demonstrated in buried heterostructure strained layer, single quantum well InGaAs/AlGaAs lasers with a short cavity length and high reflectivity coatings

An advanced meshless method for time fractional diffusion equation

Recently, because of the new developments in sustainable engineering and renewable energy, which are usually governed by a series of fractional partial differential equations (FPDEs), the numerical modelling and simulation for fractional calculus are attracting more and more attention from researchers. The current dominant numerical method for modeling FPDE is Finite Difference Method (FDM), which is based on a pre-defined grid leading to inherited issues or shortcomings including difficulty in simulation of problems with the complex problem domain and in using irregularly distributed nodes. Because of its distinguished advantages, the meshless method has good potential in simulation of FPDEs. This paper aims to develop an implicit meshless collocation technique for FPDE. The discrete system of FPDEs is obtained by using the meshless shape functions and the meshless collocation formulation. The stability and convergence of this meshless approach are investigated theoretically and numerically. The numerical examples with regular and irregular nodal distributions are used to validate and investigate accuracy and efficiency of the newly developed meshless formulation. It is concluded that the present meshless formulation is very effective for the modeling and simulation of fractional partial differential equations

Possible role of spinal astrocytes in maintaining chronic pain sensitization: review of current evidence with focus on bFGF/JNK pathway

Although pain is regarded traditionally as neuronally mediated, recent progress shows an important role of spinal glial cells in persistent pain sensitization. Mounting evidence has implicated spinal microglia in the development of chronic pain (e.g. neuropathic pain after peripheral nerve injury). Less is known about the role of astrocytes in pain regulation. However, astrocytes have very close contact with synapses and maintain homeostasis in the extracellular environment. In this review, we provide evidence to support a role of spinal astrocytes in maintaining chronic pain. In particular, c-Jun N-terminal kinase (JNK) is activated persistently in spinal astrocytes in a neuropathic pain condition produced by spinal nerve ligation. This activation is required for the maintenance of neuropathic pain because spinal infusion of JNK inhibitors can reverse mechanical allodynia, a major symptom of neuropathic pain. Further study reveals that JNK is activated strongly in astrocytes by basic fibroblast growth factor (bFGF), an astroglial activator. Intrathecal infusion of bFGF also produces persistent mechanical allodynia. After peripheral nerve injury, bFGF might be produced by primary sensory neurons and spinal astrocytes because nerve injury produces robust bFGF upregulation in both cell types. Therefore, the bFGF/JNK pathway is an important signalling pathway in spinal astrocytes for chronic pain sensitization. Investigation of signaling mechanisms in spinal astrocytes will identify new molecular targets for the management of chronic pain

In vitro Anti-Gastric Tumor Activities and Possible Mechanisms of Action of Paederosidic Acid from Paederia scandens (Lour) Merrill

Purpose: To evaluate the anti-tumor activity and explore the possible mechanisms of action of paederosidic acid isolated from Paederia scandens (Lour.) Merrill.Methods: Paederosidic acid (PA) was isolated from P. scandens and identified by spectroscopic methods. The cytotoxic effects of PA in gastric cancer cell lines (MGC-803, BGC-823, and SGC-7901 cells) were assayed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). Apoptosis of PA in SGC-7901 cells was evaluated by DAPI staining. To investigate the possible mechanisms of apoptosis, the effect of PA on C-caspase-3, C-caspase-9, Bcl-2 and Bax expressions in SGC-7901 cells were assayed by Western blot analysis.Results: PA exerted significant inhibitory effects on MGC-803, BGC-823, and SGC-7901 cells with 50 % inhibitory concentration (IC50) values of 42.2, 43.7, and 30.5 μM, respectively, and in a concentration-dependent manner. Subsequently, SGC-7901 cells were selected for further studies. After treatment with PA, obvious condensation of the nucleus was observed in fluorescence photomicrographs, which is a  characteristic of apoptosis. In addition, caspase-3, caspase-9 proteins and Bax were significantly  up-regulated (p < 0.05), whereas Bcl-2 was significantly down-regulated (p < 0.05) by PA in a concentration-dependent  manner.Conclusion: PA has significant anti-tumor activity on SGC-7901 cells in vitro, and the possible mechanism of action may be related to PA-induced apoptosis via mitochondria-mediated apoptosis pathway.Keywords: Paederosidic acid, Paederia scandens, Anti-tumor activity, Apoptosis, Gastric cance

Very High Modulation Efficiency of Ultralow Threshold Current Single Quantum Well InGaAs Lasers

A record high current modulation efficiency of 5 GHz/[sqrt](mA) has been demonstrated in an ultralow threshold strained layer single quantum well InGaAs laser

Effects of natural soiling and weathering on cool roof energy savings for dormitory buildings in Chinese cities with hot summers

Roofs with high-reflectance (solar reflectance) coating, commonly known as cool roofs, can stay cool in the sun, thereby reducing building energy consumption and mitigating the urban heat island. However, chemical-physical degradation and biological growth can decrease their solar reflectance and the ability to save energy. In this study, the solar spectral reflectance of 12 different roofing products with an initial albedo of 0.56–0.90 was measured before exposure and once every three months over 32 months. Specimens were exposed on the roofs of dormitory buildings in Xiamen and Chengdu, each major urban areas with hot summers. The albedos of high and medium-lightness coatings stabilized in the ranges 0.45–0.62 and 0.36–0.59 in both cities, respectively. This study yielded albedo loss exceeded those reported in the latest Chinese standard by 0.08–0.15. Finally, DesignBuilder (EnergyPlus) simulations estimate that a new cool roof with albedo 0.78 on a six-story dormitory building will yield annual site energy savings (heating and cooling) for the top floor, which are 8.01 kWh/m2 (24.2%) and 9.12 kWh/m2 (26.3%) per unit floor area in Xiamen and Chengdu, respectively; while an aged cool roof with albedo 0.45 and 0.56 will yield the annual savings by 5.12 kWh/m2 (15.4%) and 2.47 kWh/m2 (10.5%) in these two cities