A survey and tutorial of wireless relay network protocols based on network coding

Ever since the wireless relay network (RN) was introduced, it has led to the discovery of several new protocols, which have been consistently improved by researchers to overcome many constraints such as throughput, capacity bound, symbol error rate, outage probability, and power allocations. Meanwhile, network coding (NC) was invented as an efficient technique to address these problems. To the best of our knowledge, there has been no comprehensive discussion about wireless-RN modes in the literature. We therefore provide a tutorial concerning the basic concepts of NC, dealing with the classification of particular relay modes, and presenting new wireless-RN protocols with/without NC in this paper. Under appropriate categories (i.e., fixed and dynamic), much attention has been given to various proposed wireless-RN protocols because they may differ individually depending on their processing at relay nodes and network topology. We compare the available wireless-RN protocols with/without NC, and conclude that the wireless-RN based on NC outperforms the traditional wireless-RN in certain scenarios.     

Distribution of Pb, As, Cd, Sn and Hg in soil, sediment and surface water of the tropical river watershed, Terengganu (Malaysia)

Hydrogeochemistry and distribution of Pb, As, Cd, Sn and Hg in soils (n = 53), sediments (n = 42) and surface waters (n = 51) of the tropical Terengganu River basin, northeast coast of Peninsular Malaysia, were investigated. The order of abundance of the elements in soils followed granite > metasedimentary > Quaternary deposit ? volcanic with slight enrichment as compared to the upper continental crust. Both soils and sediments registered the order of concentration of Pb > Sn > As ? Cd ? Hg with an enrichment factor (EF) < 6 for sediments indicating slight enrichment representing the regional background and less likely due to the anthropogenic activity related input. SEM analysis revealed the presence of Malayaite (CaSnOSiO₄) explaining elevated Sn concentration (up to ∼34 mg/kg; 3 times the upper continental crust) in soils. Soil Pb distribution showed the geology as the primary control.Dissolved concentrations of As showed an increasing and Cd decreasing with distance from upstream to downstream along the river flow path. Lake surface waters registered 16 times higher Cd concentrations (average ∼ 14.21 μg/L) than the river waters, but lake sediments registered lower Cd concentration than the river sediments (average ∼ 0.45 mg/kg) revealing Eh, pH and TDS control. Dissolved average Hg concentration (∼0.04 μg/L) was measured to be lower than the tropical river waters from the Central Africa river, but higher than the Mekong and the Amazon Rivers.     

Supermacroporous poly(vinyl alcohol)-carboxylmethyl chitosan-poly(ethylene glycol) scaffold: an in vitro and in vivo pre-assessments for cartilage tissue engineering

This study aims to pre-assess the in vitro and in vivo biocompatibility of poly(vinyl alcohol)-carboxylmethyl-chitosan-poly(ethylene glycol) (PCP) scaffold. PCP was lyophilised to create supermacroporous structures. 3-(4, 5-dimethyl-thiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and immunohistochemistry (IHC) were used to evaluate the effectiveness of PCP scaffolds for chondrocytes attachment and proliferation. The ultrastructural was assessed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Extracellular matrix (ECM) formation was evaluated using collagen type-II staining, glycosaminoglycan (GAG) and collagen assays. Histological analysis was conducted on 3-week implanted Sprague–Dawley rats. The MTT, IHC, SEM and TEM analyses confirm that PCP scaffolds promoted cell attachment and proliferation in vitro. The chondrocyte-PCP constructs secreted GAG and collagen type-II, both increased significantly from day-14 to day-28 (P < 0.05). PCP scaffolds did not elicit any adverse effects on the host tissue, but were partially degraded. These results suggest that supermacroporous PCP is a biocompatible scaffold for clinical applications.     

Physicochemical studies of mild steel corrosion and atmospheric corrosivity mapping of Karachi: An important harbor city of modern Maritime Silk Route

This paper has reported physicochemical features of mild steel's corrosion products and provided atmospheric corrosivity maps of Karachi harbor city, drafted on the basis of spatial distribution of corrosion data from July 2018 to June 2019 at 10 different urban, industrial, and marine test sites. Exposure tests have been performed to study atmospheric corrosivity, corrosion products, and corrodants including chloride, sulfur dioxide, time of wetness (TOW), and corrosion rate as per ISO and ASTM standards. Scanning electron microscope, Fourier-transform infrared spectroscopy, and X-ray diffraction have corroborated the presence of lepidocrocite, goethite, magnetite, and quartz phases at almost all the test sites, with slight variations in their morphologies and quantities. The data analysis has revealed that TOW is a major detrimental factor to accelerate corrosion of mild steel at Karachi city. The corrosivity category of all urban and marine test sites is found in C₄–C₅ range, whereas for industrial test sites, it is found in C₃–C₅ range. Resultant corrosivity maps have shown that the prevailing atmosphere is significantly corrosive at Karachi harbor city. This study has furnished a novel product of atmospheric corrosivity map, which is the first-ever corrosivity map for Pakistan.     

Double Charge Transfer Dominates in Carrier Localization in Low Bandgap Sites of Heterogeneous Lead Halide Perovskites

Heterogeneous organic-inorganic halide perovskites possess inherent non-uniformities in bandgap that are sometimes engineered and exploited on purpose, like in quasi-2D perovskites. In these systems, charge carrier and excitation energy migration to lower-bandgap sites are key processes governing luminescence. The question, which of them dominates in particular materials and under specific experimental conditions, still remains unanswered, especially when charge carriers comprise excitons. In this study transient absorption (TA) and transient photoluminescence (PL) techniques are combined to address the excited state dynamics in quasi-2D and other heterogeneous perovskite structures in broad temperature range, from room temperature down to 15 K. The data provide clear evidence that charge carrier transfer rather than energy migration dominates in heterogeneous quasi-2D perovskite films.     

Electrical detection of cancer biomarker using aptamers with nanogap break-junctions

Epidermal growth factor receptor (EGFR) is a cell surface protein overexpressed in cancerous cells. It is known to be the most common oncogene. EGFR concentration also increases in the serum of cancer patients. The detection of small changes in the concentration of EGFR can be critical for early diagnosis, resulting in better treatment and improved survival rate of cancer patients. This article reports an RNA aptamer based approach to selectively capture EGFR protein and an electrical scheme for its detection. Pairs of gold electrodes with nanometer separation were made through confluence of focused ion beam scratching and electromigration. The aptamer was hybridized to a single stranded DNA molecule, which in turn was immobilized on the SiO(2) surface between the gold nanoelectrodes. The selectivity of the aptamer was demonstrated by using control chips with mutated non-selective aptamer and with no aptamer. Surface functionalization was characterized by optical detection and two orders of magnitude increase in direct current (DC) was measured when selective capture of EGFR occurred. This represents an electronic biosensor for the detection of proteins of interest for medical applications.     

Copper(II) tetrafluoroborate as a mild and efficient catalyst for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones under solvent-free conditions

A simple, mild and efficient procedure for the synthesis of dihydropyrimidinones using copper(II) tetrafluoroborate as a new catalyst is described under solvent-free conditions in shorter reaction times at room temperature.     

A Three-Dimensional Real-Time Gait-Based Age Detection System Using Machine Learning

Human biometric analysis has gotten much attention due to its widespread use in different research areas, such as security, surveillance, health, human identification, and classification. Human gait is one of the key human traits that can identify and classify humans based on their age, gender, and ethnicity. Different approaches have been proposed for the estimation of human age based on gait so far. However, challenges are there, for which an efficient, low-cost technique or algorithm is needed. In this paper, we propose a three-dimensional real-time gait-based age detection system using a machine learning approach. The proposed system consists of training and testing phases. The proposed training phase consists of gait features extraction using the Microsoft Kinect (MS Kinect) controller, dataset generation based on joints’ position, pre-processing of gait features, feature selection by calculating the Standard error and Standard deviation of the arithmetic mean and best model selection using R² and adjusted R² techniques. T-test and ANOVA techniques show that nine joints (right shoulder, right elbow, right hand, left knee, right knee, right ankle, left ankle, left, and right foot) are statistically significant at a 5% level of significance for age estimation. The proposed testing phase correctly predicts the age of a walking person using the results obtained from the training phase. The proposed approach is evaluated on the data that is experimentally recorded from the user in a real-time scenario. Fifty (50) volunteers of different ages participated in the experimental study. Using the limited features, the proposed method estimates the age with 98.0% accuracy on experimental images acquired in real-time via a classical general linear regression model.