Blackening of aluminium-zinc (galvalume) coatings for solar energy utilization

The authors have reported a method for immersion blackening of Galvalume coatings for use as a selective surface for solar collectors. Such coatings have a solar absorptance () of 0.90–0.92 and thermal emittance (ε) of 0.25–0.40. The coating has moderate corrosion resistance. In order to improve this, a post-treatment is necessary. The post-treated coatings in dichromate solution offer good corrosion resistance. Thermal cycling tests show that the coatings are stable to 220°C. Tape tests show that the coating is strongly adherent.     

Purifying genomic DNA from whole blood on automated, high-throughput, and moderate-throughput platforms

We describe three new automated methods for purifying genomic DNA from whole blood. The MagneSil^® Blood Genomic, Max Yield System uses MagneSil^® paramagnetic particles (PMPs) in a 96-well format to purify the maximal amount of DNA from a 200-μL blood sample. In contrast, the MagneSil^® ONE, Fixed Yield Blood Genomic System uses MagneSil^® Fixed Yield PMPs to purify a normalized amount of DNA from 60 μL of blood in a 96-well format. These methods are implemented on the Beckman Coulter Biomek^® FX automated workstation. The MagneSil^® KF Genomic System uses MagneSil^® PMPs to purify DNA from 1 to 15 samples of 200-μL blood using the moderate-throughput Thermo Electron KingFisher^® mL instrument.The MagneSil^® Blood Genomic System typically yields > 4 μg per 200 μL of whole blood, depending on the white blood cell content. The MagneSil^® ONE System is best suited where there is a requirement for purification of a narrow concentration range of DNA. This system purifies 1 μg (±50%) of DNA from 60 μL of blood. The MagneSil^® KF System purifies 2 to 6 μg of DNA from 200 μL of blood. DNA purified using all of these methods is suitable for PCR, STR, READIT^® SNP genotype analysis, and multiplexed PCR analysis.     

Strain energy release rates for an interface crack in orthotropic media--a finite element investigation

Strain energy release rate (SERR) components for an interface crack in two-dimensional orthotropic media were obtained using finite element (FE) analysis. The elastic analysis of interface cracks results in oscillatory singularity. This is prevalent over a very small zone near the crack-tip, where the traction free crack faces undergo unacceptable deformations resulting in the interpenetration of crack faces. The individual and total strain energy release rates are calculated using modified crack closure integral (MCCI) method. Although the total SERR converges, it is observed that the individual SERR components are dependent on the values of the smallest element size (Δa) at the crack-tip. It is observed that both the crack opening and sliding displacements are oscillatory when the interpenetration is allowed in the contact zone. The contact zone length (r_c) calculated using Suo's analytical expression [Singularities, interfaces and cracks in dissimilar anisotropic media. Proc. Royal Soc. London, Ser A427 (1990) 331] is in good agreement with the results from FE analysis and MCCI calculations. However, for the chosen material properties, the estimated contact zone length based on the analytical expression proposed by Ni and Nemat-Nasser [J. Mech. Phys. Solids 39 (1991) 113] exhibits a large deviation from the present FE results. It is seen that the mode-II behavior dominates the crack growth, even under mode-I loading.     

Exact realisation of 2-dimensional digital filters by separable filters

A scheme for the exact realisation of 2-dimensional digital filters by using separable filters is proposed. The desired impulse response is obtained by a process of successive corrections. The performance criterion in terms of computing speed is compared with that of another existing technique.     

Ligands for selective metal ion extraction: A molecular modeling approach

We present a density functional theory (DFT) based study on interaction of alkali metal cations (Li⁺ and Na⁺) with macrocyclic crown ethers of different ring sizes. The minimum energy structures, binding energies, and binding enthalpies of crown ether–cation complexes have been determined with a correlated hybrid density functional, namely Becke’s three-parameter functional, B3LYP using a split valence basis function, 6-311++G(d, p). Geometry optimizations for all the crown ether–cation complexes were carried out with several initial guess structures based on semi-empirical PM3 optimized results. For both metal ions, the calculated values of binding energy and binding enthalpy increase with the increase in size of the crown ether ring, i.e. with the increase in the number of donor oxygen atoms in crown ether. The calculated values of gas phase binding energy for lithium ions are always higher than those for sodium ions in the case of all macrocyclic crown ethers studied at present. The calculated values of binding enthalpy are in good agreement with the reported experimental data.     

Measurement of principal permeability with the channel flow experiment

A framework for channel flow permeability measurement in resin transfer molding (RTM) is developed in this paper. For the channel flow experiment, five possible experimental configurations are identified, of which two have not yet been mentioned in the literature. Starting from effective permeability, the entity measured in the experiment, explicit formulas for principal permeability and its orientation in two and three dimensions are developed. These formulas are applied to (published) experimental results that demonstrate their validity. The practical problems that prevent three-dimensional permeability measurement are discussed. Next, a framework for two-dimensional channel flow permeability measurement is proposed. All known channel flow permeability measurement methods are classified according to this new framework, and where appropriate, differences are discussed. An important finding emerging from this comparison is that two different definitions of Darcy's law are used today in permeability measurement.     

Production and mechanical properties (strength, wear, and fracture toughness) of chilled aluminum-quartz castable particulate composite

Structural composite materials offer an excellent opportunity to produce components that achieve weight savings and improved mechanical properties. This paper describes a chilled Al-quartz particulate composite that can be cast using metallic and nonmetallic chill blocks, much like nonreinforced aluminum, using conventional aluminum casting equipments. Unlike other metal matrix composites (MMCs), this material is produced economically by a simple ingot metallurgical process. An overview of the production process is given along with the techniques used for fabricating the chilled composite. The material’s mechanical properties, particularly its strength, wear resistance, fracture toughness, and hardness, are discussed in some detail. These properties offer attractive design opportunities for a variety of automotive, aerospace, and structural applications. The composite developed is shown to provide significant weight savings over ferrous metals. The present investigation aims at producing cast aluminum alloy-quartz particulate composites in molds, containing metallic and non metallic chill blocks, by dispersing quartz particles in molten aluminum alloy, above the liquidus temperature, the size of the particles dispersed being between 60 and 100 μm. The dispersoid being added ranges from 3 to 9 wt.% in steps of 3%. The resulting composites cast using chill blocks were tested for thier mechanical properties.     

A practical randomization approach of deterministic equation to determine probabilistic fatigue and fracture behaviours based on small experimental data sets

This paper outlines a new technique to address the paucity of data in determining fatigue and fracture performances based on reliability concepts. Two new randomized models of time-dependent processes are presented for estimating the P–a–t and P–S–N curves, by using a randomization approach of deterministic equations, dealing with small sample numbers of data. The confidence level formulations for these curves are also given. The concepts are then applied for the determination of the P–a–t and P–S–N curves. Two sets of fatigue and fracture tests for these curves are conducted to validate the presented method, demonstrating the practical use of the proposed technique.     

Optical Biosensors for Virus Detection: Prospects for SARS-CoV-2/COVID-19

The recent pandemic of the novel coronavirus disease 2019 (COVID-19) has caused huge worldwide disruption due to the lack of available testing locations and equipment. The use of optical techniques for viral detection has flourished in the past 15 years, providing more reliable, inexpensive, and accurate detection methods. In the current minireview, optical phenomena including fluorescence, surface plasmons, surface-enhanced Raman scattering (SERS), and colorimetry are discussed in the context of detecting virus pathogens. The sensitivity of a viral detection method can be dramatically improved by using materials that exhibit surface plasmons or SERS, but often this requires advanced instrumentation for detection. Although fluorescence and colorimetry lack high sensitivity, they show promise as point-of-care diagnostics because of their relatively less complicated instrumentation, ease of use, lower costs, and the fact that they do not require nucleic acid amplification. The advantages and disadvantages of each optical detection method are presented, and prospects for applying optical biosensors in COVID-19 detection are discussed.     

Extensively drug-resistant tuberculosis in children with Human immunodeficiency virus in rural South Africa

背景:全球均有对广泛耐药结核病的文献报道,但对儿童广泛耐药结核病的文献报道非常罕见.目的:报告南非农村地区广泛耐药结核病患儿的特征.设计:在南非共和国图盖拉渡口地区,对2006年1月-2007年12月间登记的经痰培养确诊为广泛耐药结核病的患儿进行了回顾性评估.从患儿病案中获得其人口统计学、临床和微生物学信息.结果:4例6～8岁的儿童为广泛耐药结核病患者.其中2例患儿先前有结核病史.4例患儿均为感染了人类免疫缺陷病毒的孤儿,其中3例在诊断患有广泛耐药结核病之前已接受了高效抗逆转录病毒治疗.在接受标准化抗广泛耐药结核病和高效抗逆转录病毒治疗后,所有患儿的临床表现、影像学均改善,痰培养阴转.其中2例患儿较好地耐受了抗广泛耐药结核病和高效抗逆转录病毒同时治疗.另外2例出现了环丝氨酸相关的神经精神系统不良反应.4例患儿的存活时间均超过24个月,广泛耐药结核病均得到治愈.在诊断为广泛耐药结核病之前,这些患儿在儿科病房的平均住院时间为8个月(5～17个月),包括3个月的住院重叠期.结论:广泛耐药结核病依靠微生物学来确诊,合并艾滋病的广泛耐药结核病患者也能被成功诊断.尽管需要对同时接受两种治疗的潜在交叉毒性开展更多的研究,但本研究显示患儿同时接受抗广泛耐药结核病和高效抗逆转录病毒治疗是可行且有效的.