Effect of Temperature Variation on the Characteristics of Microwave Power AlGaN/GaN MODFET

The prime motivation for developing the proposed model of AlGaN/GaN microwave power device is to demonstrate its inherent ability to operate at much higher temperature. An investigation of temperature model of a 1 μm gate AlGaN/GaN enhancement mode n-type modulation-doped field effect transistor (MODFET) is presented. An analytical temperature model based on modified charge control equations is developed. The proposed model handles higher voltages and show stable operation at higher temperatures. The investigated temperature range is from 100 °K–600 °K. The critical parameters of the proposed device are the maximum drain current (I_Dmax), the threshold voltage (V_th), the peak dc trans-conductance (g_m), and unity current gain cut-off frequency (f_T). The calculated values of f_T (10–70 GHz) at elevated temperature suggest that the operation of the proposed device has sufficiently high current handling capacity. The temperature effect on saturation current, cutoff frequency, and trans-conductance behavior predict the device behavior at elevated temperatures. The analysis and simulation results on the transport characteristics of the MODFET structure is compared with the previously measured experimental data at room temperature. The calculated critical parameters suggest that the proposed device could survive in extreme environments.     

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

Bismuth‐based compounds have recently gained increasing attention as potentially nontoxic and defect‐tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, one such compound is explored in detail through theory and experiment: bismuth oxyiodide (BiOI). BiOI thin films are grown by chemical vapor transport and found to maintain the same tetragonal phase in ambient air for at least 197 d. The computations suggest BiOI to be tolerant to antisite and vacancy defects. All‐inorganic solar cells (ITO|NiO_x|BiOI|ZnO|Al) with negligible hysteresis and up to 80% external quantum efficiency under select monochromatic excitation are demonstrated. The short‐circuit current densities and power conversion efficiencies under AM 1.5G illumination are nearly double those of previously reported BiOI solar cells, as well as other bismuth halide and chalcohalide photovoltaics recently explored by many groups. Through a detailed loss analysis using optical characterization, photoemission spectroscopy, and device modeling, direction for future improvements in efficiency is provided. This work demonstrates that BiOI, previously considered to be a poor photocatalyst, is promising for photovoltaics.     

Estimating cholera risk from an exploratory analysis of its association with satellite-derived land surface temperatures

Occurrence and growth of Vibrio cholerae, the causative agent of cholera, is linked to modalities of elevated temperatures and heavy precipitation. Previous studies have employed temperature- and satellite-derived precipitation data to determine the risk of cholera, but predictions were limited because of the coarse spatial resolution of temperature data (about 50 km). Cholera estimation has a severe impact on those in vulnerable regions with marginal civil infrastructure and those suffering additional damage after a natural disaster. In this study, a new remote-sensing data-based algorithm is proposed that includes a pathway to associate coarse-resolution cholera prediction with high-resolution land surface temperature (LST) dataset. The algorithm allows identification and prediction of regions with elevated risk of cholera at least four weeks in advance. Additionally, it employs a hierarchical structure comprising long-term anomalous LST values to determine hot spots of potential Vibrio cholerae. The algorithm was tested in five cholera epidemic regions of Sub-Saharan Africa (Mozambique, Central African Republic, Cameroon, South Sudan, and Rwanda), with realistic accuracy in demarcating regions where human cholera cases had been reported.     

Nanocellulose-Based Composites and Bioactive Agents for Food Packaging

Global environmental concern, regarding the use of petroleum-based packaging materials, is encouraging researchers and industries in the search for packaging materials from natural biopolymers. Bioactive packaging is gaining more and more interest not only due to its environment friendly nature but also due to its potential to improve food quality and safety during packaging. Some of the shortcomings of biopolymers, such as weak mechanical and barrier properties can be significantly enhanced by the use of nanomaterials such as nanocellulose (NC). The use of NC can extend the food shelf life and can also improve the food quality as they can serve as carriers of some active substances, such as antioxidants and antimicrobials. The NC fiber-based composites have great potential in the preparation of cheap, lightweight, and very strong nanocomposites for food packaging. This review highlights the potential use and application of NC fiber-based nanocomposites and also the incorporation of bioactive agents in food packaging.     

Use of Lactobacillus rossiae DC05 for bioconversion of the major ginsenosides Rb1 and Re into the pharmacologically active ginsenosides C-K and Rg2

Rb1 and Re are the major ginsenosides in protopanaxadiol and protopanaxatriol with contents of 38.89 and 13.34%, respectively. β-Glucosidase-producing food grade Lactobacillus rossiae DC05 was isolated from kimchi using esculin-MRS agar and an enzyme of L. rossiae DC05 was used for bioconversion of the major ginsenosides Rb1 and Re. Strain DC05 showed strong activity in converting ginsenosides Rb1 and Re into the minor ginsenosides compound-K and Rg2, respectively. Within 4 days, 100% of ginsenoside Rb1 was decomposed and converted into C-K, while 85% of Re was decomposed and converted into Rg2 after 6 days of incubation. The biosynthesis rate of ginsenoside C-K was 72.88%, and the biosynthesis rate of Rg2 was 53.94%. Strain DC05 hydrolyzed ginsenosides Rb1 and Re along the pathway Rb1→Rd→F2→CK and the pathway Re→Rg2, respectively. The optimum temperature and pH of the enzyme were 30°C and 7.0, respectively.     

The Systematic Refinement for the Phase Change and Conversion Reactions Arising from the Lithiation of Magnetite Nanocrystals

Nanostructured materials can exhibit phase change behavior that deviates from the macroscopic phase behavior. This is exemplified by the ambiguity for the equilibrium phases driving the first open‐circuit voltage (OCV) plateau for the lithiation of Fe₃O₄ nanocrystals. Adding complexity, the relaxed state for Li_xFe₃O₄ is observed to be a function of electrochemical discharge rate. The phases occurring on the first OCV plateau for the lithiation of Fe₃O₄ nanocrystals have been investigated with density functional theory (DFT) through the evaluation of stable, or hypothesized metastable, reaction pathways. Hypotheses are evaluated through the systematic combined refinement with X‐ray absorption spectroscopy (XAS), X‐ray diffraction (XRD) measurements, neutron‐diffraction measurements, and the measured OCV on samples lithiated to x = 2.0, 3.0, and 4.0 in Li_xFe₃O₄. In contrast to the Li–Fe–O bulk phase thermodynamic pathway, Fe⁰ is not observed as a product on the first OCV plateau for 10–45 nm nanocrystals. The phase most consistent with the systematic refinement is LiFe₃O₄, showing Li+Fe cation disorder. The observed equilibrium concentration for conversion to Fe⁰ occurs at x = 4.0. These definitive phase identifications rely heavily on the systematic combined refinement approach, which is broadly applicable to other nano‐ and mesoscaled systems that have suffered from difficult or crystallite‐size‐dependent phase identification.     

Towards 5G: Context Aware Resource Allocation for Energy Saving

With the objective of providing high quality of service (QoS), 5G system will need to be context-aware that uses context information in a real-time mode depends on network, devices, applications, and the environment of users’. In order to continue enjoying the benefits provided by future technologies such as 5G, we need to find solutions for reducing energy consumption. One promising solution is taking advantage of the context information available in today’s networks. In this paper, we take a step towards 5G by utilizing context information in the scheduling process as conventional packet scheduling algorithms are mainly designed for increasing throughput but not for the energy saving. We investigate a Context Aware Scheduling (CAS) algorithm which considers the context information of users along with conventional metrics for scheduling. An information model of context awareness along with a context aware framework for resource management is also presented in this paper. CAS is simulated applying a system level simulator and the results obtained show that considerable amount of energy is saved by utilizing the context information compare to conventional scheduling algorithms.     

Synthesis and activity of a trinuclear platinum complex: [{trans-PtCl(NH3)2}2mu-{trans-Pt(3-hydroxypyridine)2(H2N(CH2)6NH2)2}]Cl4 in ovarian cancer cell lines

This paper describes the synthesis, characterisation, and cytotoxicity of a novel trinuclear platinum complex code named TH1. In addition to its activity against human ovarian cancer cell lines: A2780, A2780(cisR), and A2780(ZD0473R), cell uptake, DNA-binding, and the nature of the compound interaction with pBR322 plasmid DNA have been determined. TH1 is found to be significantly more cytotoxic than cisplatin - two times more active than cisplatin against the parent cell line A2780, thirteen times more active against the cisplatin-resistant cell line A2780(cisR) and 11.5 times more active against the cell line A2780(ZD0473R). Whereas the resistance factors for cisplatin as applied to the cell lines A2780 and A2780(cisR), and A2780 and A2780(ZD0473R) are 12.9 and 3.0 respectively, the corresponding values for TH1 are 1.98 and 0.5. The results suggest that TH1 has been able to significantly overcome resistance in A2780(cisR) and A2780(ZD0473R) cell lines. Whereas cisplatin binds with DNA forming mainly intrastrand GG adduct that causes local bending of a DNA strand, TH1 should bind with DNA forming mainly interstrand GG adducts that would cause more of a global change in DNA conformation. Provided it has favourable toxicity profile, TH1 has the potential to be developed into a highly active anticancer drug with a wider spectrum of activity than cisplatin.     

22 nm silicon nanowire gas sensor fabricated by trilayer nanoimprint and wet etching

In this work, we demonstrate the fabrication of silicon nanowires down to 22 nm wide using trilayer nanoimprint lithography and wet etching. Using the same template prepared by E-beam lithography (EBL), nanowires with top width of 22 nm and 75 nm are fabricated on boron-doped top silicon layer of SOI substrate. The two samples are tested in 250 ppm NO₂ ambient for gas detection. The 22 nm wide one shows a much higher relative sensitivity than the 75 nm wide one. The simulation which calculates the carrier density by solving Poisson equation was carried out and the results well explain the sensitivity disparity between the two samples.     

Effects of large scale eddies and stagnation surfaces on microcrystallization

A Lagrangian marker particle (LMP) method is applied to measure the toroidal large-scale eddies (LSEs) and their enveloping stagnation surfaces in a 280 l bottom-sweeping model crystallizer. The trajectories of a 0.4 cm diameter LMP show that these stagnation surfaces inhibit transport. Analysis shows that the velocity component normal to stagnation surfaces vanish. Therefore, stagnation surfaces act as a semi-permeable barriers to particle transport. Microconductivity measurements show that the stagnation surfaces are leaky at the molecular scale. Thus particle transport through stagnation surfaces is size-dependent. The LMP measurements reveal the structure of the LSEs. This consists of (1) an upward-swirling flow adjacent to the tank perimeter extending from the bottom to the top of the tank, (2) a central, quiescent zone, and (3) a downward return flow between (1) and (2) through a system of nested, smaller diameter, secondary toroidal flows concentric with the impeller axis. A cylindrical stagnation surface surrounds the central quiescent zone. These results are corroborated by measurements of inhomogeneous concentration profiles in an industrial scale 2000 l batch crystallizer. This leads to an understanding of the effects of LSEs on silver halide microcrystal particle size distribution in the industrial scale crystallizer.