A methodology for estimating airborne virus exposures in indoor environments using the spatial distribution of expiratory aerosols and virus viability characteristics

This study investigated the feasibility of using the spatial distribution of expiratory aerosols and the viability functions of airborne viruses to estimate exposures to airborne viruses in an indoor environment under imperfectly mixed condition. A method adopting this approach was tested in an air-conditioned hospital ward. Artificial coughs were produced by aerosolizing a simulated respiratory fluid containing a known concentration of benign bacteriophage. The bacteriophage exposures estimated on the basis of the spatial aerosol distributions and its viability function were in reasonable agreement with those measured directly by biological air sampling and culturing. The ventilation flow and coughing orientation were found to play significant roles in aerosol transport, leading to different spatial distribution patterns in bacteriophage exposure. Bacteriophage exposures decreased with lateral distance from the infector when the infector coughed vertically upward. In contrast, exposures were constant or even increased with distance in the case of lateral coughing. The possibility of incorporating the proposed exposure estimation into a dose-response model for infection risk assessment was discussed. The study has also demonstrated the potential application of viability functions of airborne viral pathogens in exposure assessment and infection risk analysis, which are often unavailable in literature for some important communicable diseases. PRACTICAL IMPLICATIONS: The proposed method makes use of the viability function of the virus and the spatial distribution of the expiratory aerosols for virus exposure estimation. Spatial differences in aerosol distribution and its influences on virus exposure in an air space can be determined. Variations in infectious dose with carrier aerosol size could also be considered. The proposed method may serve as a tool for further investigation of ventilation design and infection control in clinical or other indoor environments.     

Disinfection of circulating water systems by ultraviolet light and halogenation

Continuous ultraviolet light (u.v.) and chemical disinfection of circulating water systems were evaluated. Direct comparisons of the biocidal effectiveness of u.v. light vs halogenation were tested with Legionella spp and Pseudomonas aeruginosa because of their association with the acquisition of overt clinical disease from water-containing appliances. Findings indicated that six species of Legionella and P. aeruginosa were killed by a moderate level of u.v. radiation. L. pneumophila and other bacteria in a circulating water system were effectively killed by a biocidal u.v. light. However, free chlorine levels needed to kill Legionella, Pseudomonas, and Flavobacterium within 1 min were found to be greater than 4 mg ml^?1. Data from a long-term field trial with u.v. light treatment of evaporative condenser water showed a significant reduction in numbers of bacteria. Ultraviolet disinfection of hospital hydrotherapy whirlpools confirmed the utility of this mode of disinfection under circumstances where chlorination may not be practical for medical reasons. These findings were confirmed during investigations of halogenated or u.v.-treated public hot tub/whirlpools. The effectiveness of routine chemical disinfection for controlling microbial flora in a cooling tower was also evaluated. The 2 month survey indicated that the numbers of bacteria, including Legionella, were not affected by two biocides that were used. The observations made during this investigation support the conclusion that u.v. light disinfection of water-containing systems may be an appropriate alternative or supplement to chemical biocides.     

以美国景观设计市场化经营为鉴,审视中国的发展

加利福尼亚作为美国自然环境多样化和文化多元的地区,景观设计在历史上形成了独具特色的风格.在二战以后社会变革和产业复兴中,景观设计学在私营领域得到了巨大发展,涌现了大量的事务所.通过介绍笔者在加州的实践二例,并从多学科合作的设计方法、与不同主体的沟通策略、发展开放空间以及城市复兴的经济和社会考虑等多个方面,阐述了景观设计的意义,并强调私营部门的积极作用,以期对中国的景观设计学发展有所助益.     

触摸富饶的土地:创新校园设计重建学生与中国农业景观联系

沈阳建筑大学新校园设计是中国景观设计领域的一项真正创新之作--它在中国社会结构不断加宽的裂缝上架起了一座桥梁.农业是中国社会最根本的特征之一,然而近25年的经济繁荣使人们的关注逐渐背离农业:大学生梦想着建立新的公司,企业家成为他们心目中的英雄.虽然仍有数亿农民依靠土地生活,然而在年轻人的认识里,农民是不受重视和尊敬的群体.任何唤起和提高学生对农业文明的认识的尝试都与现代主流媒体、全球化以及普遍的价值取向相违背.     

Isolation and characterization of biologically metal-doped protein as semiconducting biopolymer

Metal-doped (Cu₂O, CdO and PbO) muscle protein from fish (Clarious batracus Lin.) was isolated, purified and characterized for its potential as semiconducting biopolymer. The initial characterization of the isolated protein was carried out by circular dichrosim (CD), FTIR and AAS. Protein thin film was prepared using polyvinyl alcohol (PVA) and characterized for its surface morphology by SEM/EDAX and crystallinity by XRD spectrum. The physical properties such as Raman shift, optical coefficient and electron transfer reaction such as electrical conductivity, temperature dependent conductivity and cyclic voltammeter (CV) were studied. The present study concludes that the Cd and Cu-doped fish protein behaves like semiconductor and has the potential application in molecular electronics like protein semiconductors, protein based (proton exchange membrane) fuel cell, drug delivery and nanotechnology.     

Smart cure cycles for the adhesive joint of composite structures at cryogenic temperatures

Adhesive joints are employed for composite structures used at the cryogenic temperatures such as LNG (liquefied natural gas) insulating tanks and satellite structures. The strength of the adhesive joints at the cryogenic temperatures is influenced by the property variation of adhesive and the thermal residual stress generated due to the large temperature difference (ΔT) from the adhesive bonding process to the operating temperature. Therefore, in this work, the strength and thermal residual stress of the epoxy adhesive at cryogenic temperatures were measured with respect to cure cycle. Also, the cure cycles composed of gradual heating, rapid cooling and reheating steps were applied to the adhesive joints to reduce the thermal residual stress in the adhesive joints with short curing time. Finally, a smart cure method was developed to improve the adhesive joint strength and to reduce the cure time for the composite sandwich structures at cryogenic temperatures.     

The residual pattern of double thin-film over-etching for the fabrication of continuous patterns with dimensions varying from 50 nm to millimeters over a large area

Attempts at heavy edge over-etching of a single thin film under a photoresist to leave behind a residual smaller patterned line as a mask for nanostructure fabrication frequently fail due to detachment of the photoresist above it. We have accordingly developed a technique named 'residual pattern of double thin-film over-etching' (RDTO) to obtain a nanoscale residual pattern of the bottom thin film after extensive edge over-etching. When Au and Cr were used as the top and bottom thin films, respectively, heavy over-etching of Cr for use as a mask for nanopatterning of the underlying silicon substrate was feasible. Three patterns were fabricated for demonstration of the RDTO technique, and nanopatterns with linewidths as small as 50?nm were obtained. More importantly, our technique allows the fabrication of a single pattern with feature dimensions that vary continuously from a few tens of nanometers to a few millimeters at different positions. In addition, we have developed simple models to analyze the hydrodynamic and surface tension effects during the over-etching procedure to show the feasibility of RDTO. This technique will find diverse applications in micro-?and nano-fluidics, lab-on-a-chip nano-arrays and biomedical engineering.     

Complications of home hemodialysis

Home hemodialysis is regaining popularity as a treatment choice for end-stage kidney disease. This trend is fueled by numerous reports of better survival and improved quality of life with primarily home-based more frequent and/or longer hours of hemodialysis. Home hemodialysis in the contemporary era is generally very safe. Advances in machine technology have reduced technical complications and longer and more frequent treatments have reduced the risk of hypotension and cardiovascular instability. A successful home hemodialysis program must focus on patient safety to prevent serious hemorrhage from needle dislodgement and enable an aseptic cannulation technique. In addition, vigilance in relation to machine maintenance procedures and attention to water quality are key skills that patients must acquire for optimal outcomes. The possibility of increased septic events with longer and more frequent hemodialysis regimens performed in the home, the long-term psychosocial effects of home hemodialysis, and the best methods for maintaining compliance of patients in the long term are of particular contemporary interest.     

Materials design principles of ancient fish armour

Knowledge of the structure-property-function relationships of dermal scales of armoured fish could enable pathways to improved bioinspired human body armour, and may provide clues to the evolutionary origins of mineralized tissues. Here, we present a multiscale experimental and computational approach that reveals the materials design principles present within individual ganoid scales from the 'living fossil' Polypterus senegalus. This fish belongs to the ancient family Polypteridae, which first appeared 96 million years ago during the Cretaceous period and still retains many of their characteristics. The mechanistic origins of penetration resistance (approximating a biting attack) were investigated and found to include the juxtaposition of multiple distinct reinforcing composite layers that each undergo their own unique deformation mechanisms, a unique spatial functional form of mechanical properties with regions of differing levels of gradation within and between material layers, and layers with an undetectable gradation, load-dependent effective material properties, circumferential surface cracking, orthogonal microcracking in laminated sublayers and geometrically corrugated junctions between layers.     

Carbon nanotubes and mesenchymal stem cells: biocompatibility, proliferation and differentiation

The synergy of the unique properties of carbon nanotubes (CNT) with the remarkable potential of human mesenchymal stem cells (hMSC) provides an exciting opportunity for novel therapeutic modalities. However, little is known about the impact of CNT on hMSC behavior. We report the effect of CNT on hMSC renewal, metabolic activity, and differentiation. Furthermore, we tracked the intracellular movement of CNT through the cytoplasm to a nuclear location and assessed effects on cellular ultra structure.