Letter to the editor

Fifty-one surficial sediment samples were collected from 21 stations situated in the nearshore area of the central Red Sea. Sediments were analysed for the major elements Ca, Mg, Al and Fe and the trace elements Mn, Cu, Zn, Ni, Cr, Co, Cd and Pb. The major grain-size classes gravel, sand and mud as well as organic carbon and carbonates were determined. Some samples were subjected to X-ray mineralogy. Sediments were generally coarse-grained but the fine fraction increased in the sheltered areas. The major mineralogical constituents of the sediments were carbonate minerals (calcite and aragonite) and detrital silicates (quartz and feldspars). Organic carbon was low (0.38%) in the northern part of the area but greatly increased in areas receiving direct sewage discharge (1-9.5%). Concentrations of trace elements were highly variable and appeared to be related to the grain size and the mineralogical composition. Generally, trace element concentrations were positively correlated with the mud and Al and Fe contents. In the polluted sites these regular associations were perturbed and trace elements were associated with organic matter. Element/Al ratios were used to group the sampling sites according to their degree of enrichment. The resulting order was different from that based on the absolute concentrations. The use of a combination of the element/Al ratio and the absolute concentration resulted in the distinction of highly and moderately contaminated and uncontaminated sites.     

The Retrogradation of Concentrated Wheat Starch Systems

The ageing of non‐expanded wheat starch extrudates containing 37% and 51% water on a dry solids basis (d.s.b.) at 25°C was studied using Differential Scanning Calorimetry (DSC), Wide Angle X‐ray Diffraction (XRD), proton Nuclear Magnetic Resonance (NMR) relaxometry and Dynamic Mechanical Thermal Analysis (DMTA). The retrogradation rate increased with water content (∼0.02 h⁻¹ at 37% water (d.s.b.) compared to ∼0.06 h⁻¹ at 51%). While a good correlation was found between the DSC, XRD and NMR data, the kinetics of retrogradation measured by DMTA was delayed. The findings were interpreted in terms of the different molecular processes probed by the different techniques. In addition to the kinetics, information on the physical structure of the partially crystalline retrograded materials were obtained. DSC suggested a broad bimodal melting behaviour, which was attributed to the melting of the crystalline structure followed by the dissociation of the double helices. XRD suggested that at both water contents, the recrystallisation of amylopectin led principally to the A‐polymorph. DMTA suggested a significant interaction between the amorphous and crystalline phases, with a requirement of a minimum relative crystallinity index of ∼0.8 (e.g. ∼80% of the crystallinity index of the fully retrograded material), before any increase in the elastic modulus (at 25°C) was measured.     

Optimal homotopy asymptotic method for heat transfer in hollow sphere with robin boundary conditions

In this article, we have investigated heat transfer from a hollow sphere using a powerful and relatively new semi‐analytic technique known as the optimal homotopy asymptotic method (OHAM). Robin boundary conditions are applied on both the inner and outer surfaces. The effects of Biot numbers, uniform heat generation, temperature‐ dependent thermal conductivity, and temperature parameters on the dimensionless temperature and heat transfer are investigated. The results of OHAM are compared with a numerical method and are found to be in good agreement. It is shown that the dimensionless temperature increases with an increase in Biot number at the inner surface and temperature and heat generation parameters, whereas it decreases with an increase in the Biot number at the outer surface and the dimensionless thermal conductivity and radial distance parameters. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res 43(2): 124‐133, 2014; Published online 20 June 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21067     

Nanoscale heat transfer investigation of an array of impinging jet systems with different working fluids under crossflow with and without pin fins

In the current numerical study, the thermal and flow field performance of an array of confined multiple jets with air, water, and water‐Al₂O₃ nanofluid in the maximum crossflow configuration over the target plate with and without pin fins is investigated. The numerical results are validated with the experimental data; it is found that a reasonable prediction related to heat transfer can be made. For this study, steady‐state Reynolds‐averaged Navier‐Stokes simulations with the shear‐stress transport $k‐\omega$ turbulence model in ANSYS Fluent were performed. The simulations are performed with volumetric concentration $?=0.2\%$ to 3% and the jet's Reynolds number Re = 15 000 to 35 000. In all cases, the jet outlet‐to‐target plate distance $Z/D$ is 3. It is found that the increase in values of the volumetric concentration of nanoparticles results in a decrease of the Nusselt number and an increase of the convective heat transfer coefficient. This is because there is an increase in thermal conductivity of the working fluid with the increase in the volumetric concentration of nanoparticles for the same Reynolds number. About 81.5% and 89.1% enhancement in the average heat transfer flux values is observed for flat and pin fin‐roughened target plates, respectively, for $?=3\%$.     

The effect of sodium chloride on the glass transition of potato and cassava starches at low moisture contents

The effect of NaCl on the glass transition of cassava and potato starches at low water levels (<20% dwb) was investigated. Sodium chloride (up to 6% of the starch dry weight) was mixed thoroughly with cassava and potato starches using a twin-screw extruder. The samples were equilibrated over saturated salt solutions (LiCl, CH₃COOK, MgCl₂, NaBr, CuCl₂ and NaCl) to give a range of moisture contents. The addition of sodium chloride caused a considerable reduction in the DSC measured glass transition temperature for both starches. For example, the T_g of cassava starch without and with 6% NaCl equilibrated at relative humidity of 11% was 166 and 136 °C, respectively. Similar reductions were found for potato starch. Although the starch sorption isotherms are affected by the addition of salt when T_g is plotted against water content as opposed to relative humidity a T_g reduction on salt addition is still observed. The possible reasons for the plasticization of starch by salt are discussed.     

Ray theory design of hyperbolic secant horn

It is shown that ray theory can be used in designing a microwave horn with a hyperbolic secant refractive-index profile. The horn is short in length, has constant phase across the plane aperture and tapered illumination in the E-plane, resulting in a radiation pattern with low sidelobes. Experimental verification has been made on a model operating around a frequency of 10 GHz.     

Placental transfer and maternally acquired neonatal IgG immunity in human immunodeficiency virus infection

PURPOSE: The effect of the sensitizer razoxane on soft tissue sarcomas (STS) was prospectively evaluated in a randomized, controlled trial. The main purpose of the study was to determine the response rates and local control under the combined treatment compared to irradiation alone. METHODS AND MATERIALS: Between 1978 and 1988, 144 patients entered the study; 130 were evaluable for response, toxicity, or survival. The patients were randomized to receive radiotherapy alone or radiotherapy with razoxane. They were divided into postoperative cases and patients with gross disease (unresectable primaries, recurrent disease, or metastatic disease). The median radiation dose was 60 Gy postoperatively, and 56-58 Gy in patients with gross disease. The dose difference has palliative reasons. Razoxane was given orally at a daily dose of 150 mg/m2 during the time of the radiotherapy, starting 5 days before the first irradiation. In general, the groups were comparable as to their prognostic factors. There was some imbalance, however, in favor of the postoperative group reveiving radiotherapy alone. RESULTS: Between the patient groups treated postoperatively in an adjuvant form, there were no substantial differences in local control and survival. Among 82 patients with gross disease, the treatment with radiotherapy and razoxane led to an increased response rate compared to photon irradiation alone (74 vs. 49%). The local control rate was likewise improved (64 vs. 30%;p < 0.05). The acute toxicity was somewhat higher in the sensitizer arm, but there was no difference in the occurrence of late complications. CONCLUSIONS: Radiotherapy combined with razoxane seems to improve the local control in inoperable, residual, or recurrent STS compared to radiotherapy alone. The combined treatment is a fairly well tolerated procedure at low costs. It can be recommended for inoperable primary STS or gross disease after incomplete resection, conditions which are still associated with limited local control and a grave prognosis.     

Technique for fast and accurate prediction of antenna far-field patterns

A technique for the fast prediction of antenna far-field patterns is described in which a pillbox antenna is used as the probe. The processing involves transformation of 1-D arrays, and the validation is provided by comparing the measured and predicted patterns of a parabolic reflector.     

Machine Learning with Dimensionality Reduction for DDoS Attack Detection

With the advancement of internet, there is also a rise in cybercrimes and digital attacks. DDoS (Distributed Denial of Service) attack is the most dominant weapon to breach the vulnerabilities of internet and pose a significant threat in the digital environment. These cyber-attacks are generated deliberately and consciously by the hacker to overwhelm the target with heavy traffic that genuine users are unable to use the target resources. As a result, targeted services are inaccessible by the legitimate user. To prevent these attacks, researchers are making use of advanced Machine Learning classifiers which can accurately detect the DDoS attacks. However, the challenge in using these techniques is the limitations on capacity for the volume of data and the required processing time. In this research work, we propose the framework of reducing the dimensions of the data by selecting the most important features which contribute to the predictive accuracy. We show that the ‘lite’ model trained on reduced dataset not only saves the computational power, but also improves the predictive performance. We show that dimensionality reduction can improve both effectiveness (recall) and efficiency (precision) of the model as compared to the model trained on ‘full’ dataset.