Modelling and fabrication of wide temperature range Al0.24Ga0.76As/GaAs Hall magnetic sensors

Silicon Hall-effect sensors have been widely used in industry and research fields due to their straightforward fabrication process and CMOS compatibility. However, as their material property limitations, technicians usually implement complex CMOS circuits to improve the sensors’ performance including temperature drift and offset compensation for fitting tough situation, but it is no doubt that it increases the design complexity and the sensor area. Gallium arsenide (GaAs) is a superior material of Hall-effect device because of its large mobility and stable temperature characteristics. Concerning there is no specified modelling of GaAs Hall-effect device, this paper investigated its modelling by using finite element method (FEM) software Silvaco TCAD^® to help and guide GaAs Hall-effect device fabrication. The modeled sensor has been fabricated and its experimental results are in agreement with the simulation results. Comparing to our previous silicon Hall-effect sensor, the GaAs Hall-effect sensor demonstrates potential and reliable benchmark for the future Hall magnetic sensor developments.     

Cyclic preference scheduling of nurses using a Lagrangian-based heuristic

This paper addresses the problem of developing cyclic schedules for nurses while taking into account the quality of individual rosters. In this context, quality is gauged by the absence of certain undesirable shift patterns. The problem is formulated as an integer program (IP) and then decomposed using Lagrangian relaxation. Two approaches were explored, the first based on the relaxation of the preference constraints and the second based on the relaxation of the demand constraints. A theoretical examination of the first approach indicated that it was not likely to yield good bounds. The second approach showed more promise and was subsequently used to develop a solution methodology that combined subgradient optimization, the bundle method, heuristics, and variable fixing. After the Lagrangian dual problem was solved, though, there was no obvious way to perform branch and bound when a duality gap existed between the lower bound and the best objective function value provided by an IP-based feasibility heuristic. This led to the introduction of a variable fixing scheme to speed convergence. The full algorithm was tested on data provided by a medium-size U.S. hospital. Computational results showed that in most cases, problem instances with up to 100 nurses and 20 rotational profiles could be solved to near-optimality in less than 20 min.     

Iron oxide/gold nanoparticles‐decorated reduced graphene oxide nanohybrid as the thermo‐radiotherapy agent

The main focus of the current study is the fabrication of a multifunctional nanohybrid based on graphene oxide (GO)/iron oxide/gold nanoparticles (NPs) as the combinatorial cancer treatment agent. Gold and iron oxide NPs formed on the GONPs via the in situ synthesis approach. The characterisations showed that gold and iron oxide NPs formed onto the GO. Cell toxicity assessment revealed that the fabricated nanohybrid exhibited negligible toxicity against MCF‐7 cells in low doses (<50 ppm). Temperature measurement showed a time and dose‐dependent heat elevation under the interaction of the nanohybrid with the radio frequency (RF) wave. The highest temperature was recorded using 200 ppm concentration nanohybrid during 40 min exposure. The combinatorial treatments demonstrated that the maximum cell death (average of 53%) was induced with the combination of the nanohybrid with RF waves and radiotherapy (RT). The mechanistic study using the flow cytometry technique illustrated that early apoptosis was the main underlying cell death. Moreover, the dose enhancement factor of 1.63 and 2.63 were obtained from RT and RF, respectively. To sum up, the authors’ findings indicated that the prepared nanohybrid could be considered as multifunctional and combinatorial cancer therapy agents.Inspec keywords: radiation therapy, toxicology, gold, biomedical materials, nanofabrication, nanoparticles, iron compounds, cancer, nanomedicine, cellular biophysics, tumours, graphene compounds, biothermicsOther keywords: graphene oxide nanohybrid, combinatorial cancer treatment agent, cell toxicity assessment, MCF‐7 cells, dose‐dependent heat elevation, multifunctional cancer therapy agents, thermoradiotherapy agent, graphene oxide‐iron oxide‐gold nanoparticles, temperature measurement, radiofrequency wave, flow cytometry, time 40.0 min, CO‐FeO‐Au     

Emergence of non-group A streptococcal necrotizing diabetic foot infections

Recently the authors have noted a disturbing trend toward an increased incidence of necrotizing infections caused by non-group A streptococcal species. This article describes the typical clinical course of such an infection. Prompt surgical intervention, coupled with an antibiotic regimen aimed at mitigating exotoxin release, may be both limb- and life-preserving.     

Placental chorioangioma: prenatal diagnosis and clinical significance

We report the prenatal diagnosis of placental chorioangioma in a 32-week intrauterine pregnancy associated with polyhydramnios and enlarged fetal cardiac size that resulted in intrauterine fetal death. Ultrasound appearance, pathophysiology, and clinical significance of this entity are discussed.     

Size effect and fracture energy studies using compact compression specimens

The size effect has been investigated and fracture energy, G_F, determined for a range of different strength concretes. The test specimen geometry used in the study was a compact compression prism. Five sizes of geometrically similar specimens with increasing square cross-sectional area (length=depth) and constant thickness (100 mm) were used in the experimental work; the length/depth dimensions of the test specimens were 100, 150, 200, 300, and 400 mm, giving an overall size range ratio of 1:4. The grades of concrete used in this study were C50, C70, C80, C90, and the maximum coarse aggregate (crushed limestone) size was 10 mm. A strong size effect was observed in the results and it is concluded that the test geometry is good for size effect studies in concrete. Furthermore, it was observed that with increasing strength the size effect becomes more pronounced as the brittleness is increased.

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Résumé On a étudie l'effet de taille et l'énergie de rupture, G_F, déterminés pour une gamme de bétons ayant des résistances différentes. La géométrie des éprouvettes choisie pour cette étude était le prisme compact de compression. Cinq tailles d'éprouvettes de géométrie similaire, ayant une épaisseur constante (100 mm) et de section transversale carrée (longueur=profondeur) croissante ont été utilisées pour ce travail. Les dimensions longueur/profondeur des éprouvettes étaient de 100, 150, 200, 300 et 400 mm, résultant en un rapport général de 1:4. Les bétons utilisés dans cette étude étaient de qualités C50, C70, C80 et C90, et la dimension maximale des granulats (calcaire concassé) était de 10 mm. On a observé dans les résultats un fort effet de taille et on a conclu que la géométrie utilisée pour l'essai convient pour des études d'effet de taille sur le béton. Qui plus est, on a observé qu'avec une résistance croissante, l'effet de taille devient plus prononcé lorsque la fragilité augmente.

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Editorial note Prof. Benjamin I. G. Barr is a RILEM Senior Member. He participates in the Editorial Group of TC 909-FMA, “Fracture Mechanics of Concrete-Applications”, and is a member of TC 162-TDF, “Test and Design Methods for Steel Fibre reinforced Concrete” and TC QFS, “Size effect and Scaling of Quasibrittle Fracture”.     

Simultaneous adsorption of a mixture of paraquat and dye by NaY zeolite covered with alkylsilane

The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites.