Optimization of arsenite removal by adsorption onto organically modified montmorillonite clay: Experimental & theoretical approaches

Arsenic is a critical contaminant for aqueous environments as it poses harmful health risks. To meet the stringent regulations regarding the presence of arsenic in aqueous solutions, the feasibility of montmorillonite clay modified with hexadecyltrimethyl ammonium chloride as the adsorbent was tested for the removal of arsenic ions from aqueous solutions. A scanning electron microscopy (SEM) study confirmed that the organically modified nanoclay (ONC) adsorbent had a porous structure with a vast adsorbent surface.The x-ray fluorescence (XRF) analysis proved the presence of carbon in the structure of the modified nanoclay that can be evidence for the creation of ONC. The x-ray diffraction (XRD) analysis results confirm the existence of four main groups of minerals, carbonate (Calcite), clay (Askmtyt and Kandyt), silicate (Quartz), and phyllosilicate (Kaolinite), in the ONC structure.The influence of various parameters such as solution pH, adsorbent dosage, initial arsenite concentration, and contact time on arsenic adsorption onto ONC was investigated. A 2⁵ full factorial central composite experimental design was applied. A central composite design under response surface methodology (RSM) was employed to investigate the effects of independent variables on arsenite removal and to determine the optimum condition. The experimental values were in a good fit with the ones predicted by the model. The optimal operating points (adsorbent dosage: 3.7 g L^?1, surfactant dosage: 3 g L^?1 and the contact time: 37.2min) giving maximum arsenite removal (95.95%) were found using Solver “Add-ins” in Microsoft Excel 2010.     

An integrated approach of form finding and construction simulation for glass fiber‐reinforced polymer elastic gridshells

Glass fiber‐reinforced polymer (GFRP) elastic gridshell is composed of long continuous GFRP tubes and achieves its shape through the elastic deformations during the lifting construction process. However, the complicated mechanical behaviors during the practical forming process are rarely examined in the previous researches. In this research, an innovative approach consolidating the form‐finding analysis and the construction simulation is proposed for the GFRP elastic gridshells. The integrated approach, which is developed with the ABAQUS and Python, is based on finite element analysis and iterative optimization; therefore, the mechanical deformations of gridshell can be accurately taken into account. The procedure of the integrated analysis is comprehensively presented by taking a typical double‐hump gridshell as an example. The form‐finding results (i.e., the flat lattices) derived from the iteration are found to be insensitive to the initial input. The structural behavior indexes (e.g., deflections, support reactions, and sectional stresses) during the lifting construction process are also available in the analysis. Based on the indexes, some general structural features of such gridshells are concluded. The achievements provide novel perspectives for the form‐finding analysis of GFRP elastic gridshells where lifting construction is involved, which is beneficial for the design and analysis of such structures.     

A study on the extraction of essential oil of Persian black cumin using static supercritical CO2 extraction,and comparison with hydro-distillation extraction method

The essential oil of Persian black cumin was extracted using static supercritical CO₂ technique at different temperatures, extraction times, and number of extractions. The composition of extracted oil was measured by GC-MS analysis and 25 components were identified. It was found that the oil recovery was reduced by increasing the temperature. Maximum recovery was achieved at two-step extraction that was about 49%. Both dissolution rate and solubility limited the oil recovery at the tested extraction conditions. The oxygenate components have less dissolution rate than the terpenes. The application of experimental data for design of an efficient dynamic extraction system was discussed.     

Quantitative Assessment of Point-of-Care 3D-Printed Patient-Specific Polyetheretherketone (PEEK) Cranial Implants

Recent advancements in medical imaging, virtual surgical planning (VSP), and three-dimensional (3D) printing have potentially changed how today’s craniomaxillofacial surgeons use patient information for customized treatments. Over the years, polyetheretherketone (PEEK) has emerged as the biomaterial of choice to reconstruct craniofacial defects. With advancements in additive manufacturing (AM) systems, prospects for the point-of-care (POC) 3D printing of PEEK patient-specific implants (PSIs) have emerged. Consequently, investigating the clinical reliability of POC-manufactured PEEK implants has become a necessary endeavor. Therefore, this paper aims to provide a quantitative assessment of POC-manufactured, 3D-printed PEEK PSIs for cranial reconstruction through characterization of the geometrical, morphological, and biomechanical aspects of the in-hospital 3D-printed PEEK cranial implants. The study results revealed that the printed customized cranial implants had high dimensional accuracy and repeatability, displaying clinically acceptable morphologic similarity concerning fit and contours continuity. From a biomechanical standpoint, it was noticed that the tested implants had variable peak load values with discrete fracture patterns and failed at a mean (SD) peak load of 798.38 ± 211.45 N. In conclusion, the results of this preclinical study are in line with cranial implant expectations; however, specific attributes have scope for further improvements.     

Near-far effects in land mobile random access networks withnarrow-band Rayleigh fading channels

The near-far effect of random access protocols in mobile radio channels with receiver capture is investigated. To this end, the probability of successful reception of a packet from a terminal at a known distance from the central receiver is obtained taking into account Rayleigh fading, UHF propagation attenuation, and the statistics of contending packet traffic in radio nets employing slotted ALOHA, carrier sense multiple access (CSMA) or inhibit sense multiple access (ISMA) protocols. Various models of receiver capture are compared, namely packet error rates for synchronous detection in slow- and fast-fading channels, and the probability that the signal-to-interference ratio is above a required threshold     

Instructional desensitization: A semantic behavior treatment of anxiety disorder.

Explored the efficacy of instructional desensitization (ID) in the treatment of public speaking anxiety, using 30 speech-anxious undergraduates as Ss. Three self-report measures of confidence, affect, and anxiousness were completed by Ss, and 20 behavioral manifestations of anxiety were observed during Ss' delivery of a 4-min speech. Ss were randomly assigned to ID, placebo, or waiting list groups. Ss in the placebo group were led to believe that they were receiving a new form of therapy. Results show that ID Ss showed a significant decrement in their anxiety reactions as measured by objective and subjective anxiety measures. A significant anxiety decrement was also found in placebo Ss. However, self-report gains were not verified by objective observations. It is concluded that ID is a new semantic behavior therapy intervention that may have beneficial effects in the treatment of a broad variety of anxiety disorders. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signal amplification strategy using gold/N ‐trimethyl chitosan/iron oxide magnetic composite nanoparticles as a tracer tag for high‐sensitive electrochemical detection

This study presents a novel signal amplification method for high‐sensitive electrochemical immunosensing. Gold (Au)/N ‐trimethyl chitosan (TMC)/iron oxide (Fe₃ O₄) (shell/shell/core) nanocomposite was used as a tracing tag to label antibody. The tag was shown to be capable of amplifying the recognition signal by high‐density assembly of Au nanoparticles (NPs) on TMC/Fe₃ O₄ particles. The remarkable conductivity of AuNPs provides a feasible pathway for electron transfer. The method was found to be simple, reliable and capable of high‐sensitive detection of human serum albumin as a model, down to 0.2 pg/ml in the range of 0.25–1000 pg/ml. Findings of the present study would create new opportunities for sensitive and rapid detection of various analytes.Inspec keywords: gold, filled polymers, conducting polymers, iron compounds, magnetic particles, nanoparticles, nanocomposites, nanosensors, electrochemical sensors, proteins, molecular biophysics, biomagnetism, biosensorsOther keywords: signal amplification strategy, gold‐N‐trimethyl chitosan‐iron oxide magnetic composite nanoparticles, tracer tag, high‐sensitive electrochemical detection, high‐sensitive electrochemical immunosensing, antibody, high‐density assembly, AuNP conductivity, electron transfer, human serum albumin, FeO‐Au     

A multiplier-less digital design of a bio-inspired stimulator to suppress synchronized regime in a large-scale,sparsely connected neural network

Excessive synchronous firing of neurons is the sign of several neurological disorders such as Parkinson and epilepsy. In addition, growing evidence suggests that astrocytes have significant roles in neural synchronization. Drawing on these concepts and based on the latest studies, a bio-inspired stimulator which essentially is a dynamical model of the astrocyte biophysical model is proposed. The performance of the proposed bio-inspired stimulator is investigated on a large-scale, sparsely connected neural network which models a local cortical population. Next, a multiplier-less digital circuit for the bio-inspired stimulator is designed, and finally, the complete digital circuit of the closed-loop system is implemented in hardware on the ZedBoard development kit. Considering software simulations and hardware FPGA implementation, the proposed bio-inspired stimulator is able to prevent the hyper-synchronous neural firing in a network of excitatory and inhibitory neurons. Based on the obtained results, it is demonstrated that the proposed stimulator has a demand-controlled characteristic and can be a good candidate as a new deep brain stimulation (DBS) technique to effectively suppress the hyper-synchronous neural oscillations.

     

Chemical mechanism of precipitate formation and pH effect on the morphology and thermochemical co-precipitation of W–Cu nanocomposite powders

W–25%Cu composite powder was produced via thermochemical procedure. Copper nitrate and sodium tungstate salts were used as Cu and W containing precursors, respectively. Aqueous solutions of these salts were reacted under several different pH conditions. It was found that the products of all stages involving Cu₂WO₄(OH)₂ and CuWO₄·2H₂O as raw precipitates, CuWO_4−x, CuO, and WO₃ as calcined powders, and W–Cu reduced composite powders possessed similar compositions in different pH conditions. But changing the reaction pH in the range of 3–13 was found to markedly influence the microstructure of the products. At low and medium pH precipitates were in the form of large monolithic agglomerates while in high pH smaller cotton like agglomerates were formed. At low and medium pH conditions simple ion replacement was found to be dominant mechanism of precipitation while in high pH Cu(NH₃)₄²⁺ complex ion was formed and ligand exchange was the dominant mechanism of precipitation.