Preparation of dendritic waterborne polyurethane-urea/Ni–Zn ferrite composite coatings and investigation of their microwave absorption properties

This study shows the preparation of microwave absorbing composite material by using Ni–Zn ferrite filler and dendritic waterborne polyurethane-urea (WPU) polymer as a matrix. Initially, waterborne polyurethane prepolymers were synthesized by using PEG1500 (WPU1) and PPG1000 (WPU2) polyols via prepolymer mixing process. Then, chain extended with water in the presence of hexamethylenetetramine (HMTA) as crosslinker. Then, 1/1 (w/w) amount of Ni–Zn ferrite was dispersed in the WPU polymer to be converted into a microwave absorbing composite coating (CWPU1 and CWPU2). Structural, mechanical and morphological properties were investigated. The microwave absorption measurements were performed by using transmission/reflection method via waveguide method in the frequency range of 8.2–12.4 GHz. Permittivity and permeability measurements were performed in the frequency range of 8.2–12.4 GHz. It has been found that CWPU1 which was prepared by using WPU1 polymer indicated broader microwave absorption between 9.4 and 11.7 GHz due to its dendritic structure. Besides, permittivity and permeability results indicated that CWPU1 and CWPU2 have distinctive magnetic properties.     

Current transport mechanisms and trap state investigations in (Ni/Au)-AlN/GaN Schottky barrier diodes

The current transport mechanisms in (Ni/Au)-AlN/GaN Schottky barrier diodes (SBDs) were investigated by the use of current-voltage characteristics in the temperature range of 80-380 K. In order to determine the true current transport mechanisms for (Ni/Au)-AlN/GaN SBDs, by taking the J_s(tunnel), E₀, and R_s as adjustable fit parameters, the experimental J-V data were fitted to the analytical expressions given for the current transport mechanisms in a wide range of applied biases and at different temperatures. Fitting results show the weak temperature dependent behavior in the saturation current and the temperature independent behavior of the tunneling parameters in this temperature range. Therefore, it has been concluded that the mechanism of charge transport in (Ni/Au)-AlN/GaN SBDs, along the dislocations intersecting the space charge region, is performed by tunneling.In addition, in order to analyze the trapping effects in (Ni/Au)-AlN/GaN SBDs, the capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics were measured in the frequency range 0.7-50 kHz. A detailed analysis of the frequency-dependent capacitance and conductance data was performed, assuming the models in which traps are located at the heterojunction interface. The density (D_t) and time constants (τ_t) of the trap states have been determined as a function of energy separation from the conduction-band edge (E_c − E_t) as D_t≅(5-8)×10¹², respectively.     

Color removal from textile dyebath effluents in a zeolite fixed bed reactor: determination of optimum process conditions using Taguchi method

Taguchi method was applied as an experimental design to determine optimum conditions for color removal from textile dyebath house effluents in a zeolite fixed bed reactor. After the parameters were determined to treat real textile wastewater, adsorption experiments were carried out. The breakthrough curves for adsorption studies were constructed under different conditions by plotting the normalized effluent color intensity (C/C(0)) versus time (min) or bed volumes (BV). The chosen experimental parameters and their ranges are: HTAB concentration (C(htab)), 1-7.5 gL(-1); HTAB feeding flowrate (Q(htab)), 0.015-0.075 L min(-1); textile wastewater flowrate (Q(dye)), 0.025-0.050 L min(-1) and zeolite bed height (H(bed)), 25-50 cm, respectively. Mixed orthogonal array L(16) (4(2)x2(2)) for experimental plan and the larger the better response category were selected to determine the optimum conditions. The optimum conditions were found to be as follows: HTAB concentration (C(htab))=1g L(-1), HTAB feeding flowrate (Q(htab))=0.015 L min(-1), textile wastewater flowrate (Q(dye))=0.025 L min(-1) and bed height (H(bed))=50 cm. Under these conditions, the treated wastewater volume reached a maximum while the bed volumes (BV) were about 217. While HTAB concentration, gL(-1) (A); zeolite bed height, cm (D) and wastewater flowrate, L min(-1) (C) were found to be significant parameters, respectively, whereas, HTAB flowrate, L min(-1) (B) was found to be an insignificant parameter.     

Growth and Evapotranspiration of Okra (Abelmoschus Esculentus L.) as Influenced by Salinity of Irrigation Water

The effects of irrigation water salinity on growth, yield, and water consumption of okra was investigated with a pot experiment. For this purpose, five irrigation water salinity levels with electrical conductivities of 1.5, 2.5, 3.5, 5.0, and 7.0?dS/m and tap water as a control treatment were used in a randomized design with five replications. Irrigation practices were realized by considering the weight of each pot. Threshold soil salinity and slope values of the yield response to soil salinity level were determined to be 3.48?dS/m and 4.2%, respectively, for fruit yield, 4.24?dS/m and 7.0% for vegetative dry weight, and 6.0?dS/m and 7.9% for root dry weight. The results revealed that okra was moderately tolerant to salinity. Increasing soil salinity levels caused significant decreases in plant water consumption. Plant water consumption decreased by 2.43% per unit increase in soil salinity. Plant coefficient (Ky) was 1.26. Saline irrigation water treatments altered Cl, Mg, Ca, and Na accumulations in leaves, whereas only Na accumulation in fruits was observed.     

A Review of the Alleged Health Hazards of Monosodium Glutamate

Monosodium glutamate (MSG) is an umami substance widely used as flavor enhancer. Although it is generally recognized as being safe by food safety regulatory agencies, several studies have questioned its long‐term safety. The purpose of this review was to survey the available literature on preclinical studies and clinical trials regarding the alleged adverse effects of MSG. Here, we aim to provide a comprehensive overview of the reported possible risks that may potentially arise following chronic exposure. Preclinical studies have associated MSG administration with cardiotoxicity, hepatotoxicity, neurotoxicity, low‐grade inflammation, metabolic disarray, and premalignant alterations, along with behavioral changes. However, in reviewing the available literature, we detected several methodological flaws, which led us to conclude that these studies have limited relevance for extrapolation to dietary human intake of MSG risk exposure. Clinical trials have focused mainly on MSG effects on food intake and energy expenditure. Besides its well‐known impact on food palatability, MSG enhances salivary secretion and interferes with carbohydrate metabolism, while the impact on satiety and post‐meal recovery of hunger varied in relation to meal composition. Reports on MSG hypersensitivity or links of its use to increased pain sensitivity and atopic dermatitis were found to have little supporting evidence. Many of the reported negative health effects of MSG have little relevance for chronic human exposure and are poorly informative as they are based on excessive dosing that does not meet with levels normally consumed in food products. We conclude that further clinical and epidemiological studies are needed, with an appropriate design, accounting for both added and naturally occurring dietary MSG.     

Energy-efficient routing for correlated data in wireless sensor networks

In this paper, we investigate the reduction in the total energy consumption of wireless sensor networks using multi-hop data aggregation by constructing energy-efficient data aggregation trees. We propose an adaptive and distributed routing algorithm for correlated data gathering and exploit the data correlation between nodes using a game theoretic framework. Routes are chosen to minimize the total energy expended by the network using best response dynamics to local data. The cost function that is used for the proposed routing algorithm takes into account energy, interference and in-network data aggregation. The iterative algorithm is shown to converge in a finite number of steps. Simulations results show that multi-hop data aggregation can significantly reduce the total energy consumption in the network.     

桥梁结构状态参数监测技术研究现状

桥梁的自然老化、劣化将会影响其安全与正常使用,甚至造成重大的人员伤亡和财产损失,已成为交通运输部门关注的问题。为了有效维护桥梁和确保其安全运行,监测桥梁结构的关键状态参数对于全面及时反映桥梁工作状态和进一步开展安全性评估极为重要。综述了桥梁结构的应变、挠度、振动等关键状态参数监测技术的研究进展,并分析了这些监测技术的基本原理、性能、应用范围,同时,对未来桥梁结构状态参数监测的发展提出了建议。     

热烈欢迎下一代照明技术可调白光LED的到来

单一的白光LED难以满足色彩与照明的应用需求．可调LED将是更好的选择 随着固态照明技术的性能与效率不断超越传统照明技术,该新技术得到了广泛应用。不过,如果我们只是用静态白光LED来取代传统技术的话,就难以真正发挥固态照明技术的全部潜力,不能充分实现产品的特色化。在智能驱动器支持下,LED照明灯具不仅能取代白光照明,而且还能实现新的功能,而这些功能用传统的照明技术是很难实现的。     

Statistical investigation of wave power potential in the North Aegean Sea

Clean Technologies and Environmental Policy - Wave energy is recognized as a significant renewable energy source with a high energy density and very low environmental impact. Today, in parallel...     

Selective and Sustainable Production of Sub-terminal Hydroxy Fatty Acids by a Self-Sufficient CYP102 Enzyme from Bacillus Amyloliquefaciens

Enzymatic hydroxylation of fatty acids by Cytochrome P450s (CYPs) offers an eco-friendly route to hydroxy fatty acids (HFAs), high-value oleochemicals with various applications in materials industry and with potential as bioactive compounds. However, instability and poor regioselectivity of CYPs are their main drawbacks. A newly discovered self-sufficient CYP102 enzyme, BAMF0695 from Bacillus amyloliquefaciens DSM 7, exhibits preference for hydroxylation of sub-terminal positions (ω-1, ω-2, and ω-3) of fatty acids. Our studies show that BAMF0695 has a broad temperature optimum (over 70 % of maximal enzymatic activity retained between 20 to 50 °C) and is highly thermostable (T₅₀ >50 °C), affording excellent adaptive compatibility for bioprocesses. We further demonstrate that BAMF0695 can utilize renewable microalgae lipid as a substrate feedstock for HFA production. Moreover, through extensive site-directed and site-saturation mutagenesis, we isolated variants with high regioselectivity, a rare property for CYPs that usually generate complex regioisomer mixtures. BAMF0695 mutants were able to generate a single HFA regiosiomer (ω-1 or ω-2) with selectivities from 75 % up to 91 %, using C12 to C18 fatty acids. Overall, our results demonstrate the potential of a recent CYP and its variants for sustainable and green production of high-value HFAs.