The effect of indoor daylight spectrum and intensity on viability of indoor pathogens on different surface materials

Built environments play a key role in the transmission of infectious diseases. Ventilation rates, air temperature and humidity affect airborne transmission while cleaning protocols, material properties and light exposure can influence viability of pathogens on surfaces. We investigated how indoor daylight intensity and spectrum through electrochromic (EC) windows can impact the growth rate and viability of indoor pathogens on different surface materials (polyvinyl chloride (PVC) fabric, polystyrene (PS), and glass) compared to traditional blinds. Our results showed that tinted EC windows let in higher energy, shorter wavelength daylight than those with clear window and blind. The growth rates of pathogenic bacteria and fungi were significantly lower in spaces with EC windows compared to blinds: nearly 100% growth rate reduction was observed when EC windows were in their clear state followed by 41-100% reduction in bacterial growth rate and 26-42% reduction in fungal growth rate when EC windows were in their darkest tint. Moreover, bacterial viabilities were significantly lower on PVC fabric when they were exposed to indoor light at EC-tinted window. These findings are deemed fundamental to the design of healthy modern buildings, especially those that encompass sick and vulnerable individuals.

Evaluation of Salmonella Biofilm Cell Transfer from Common Food Contact Surfaces to Beef Products

Meat contamination by Salmonella enterica is a serious public health concern. Available studies have suggested that biofilm formation at processing plants and the contaminated contact surfaces might contribute to meat contamination. Since bacteria transfer from contact surfaces to food products via direct contact has been deemed as the most common transmission route that could lead to contamination, we evaluated the effect of Salmonella biofilm forming ability, contact surface materials, and beef surface tissue types on Salmonella biofilm transfer from hard surfaces to beef products. Salmonella biofilms developed on common contact surface stainless steel (S.S) and polyvinylchloride (P.V.C) were transferred consecutively via direct contacts of 30 sec each to either lean muscle or adipose tissue surfaces of 15 pieces of beef trim. Our results showed that Salmonella biofilm cells could be effectively transferred multiple times from contact surface to beef trim as enumerable Salmonella cells could be detected on most of the meat samples. Bacterial biofilm forming ability had the most significant impact (p<0.05) on transfer efficiency as the strong biofilm forming strains not only transferred higher amounts of bacteria after each contact, but also contaminated more meat samples with enumerable Salmonella cells compared to the weak biofilm formers. Contact surface materials could affect transferability as Salmonella biofilms on S.S surface appeared to transfer more efficiently compared to those on P.V.C surface. Conversely, the two types of meat surface tissues showed no significant difference (p>0.05) on biofilm transfer efficiency. Furthermore, biofilm - contacted beef trim without enumerable Salmonella cells all exhibited positive Salmonella prevalence after enrichment. Our study demonstrated the high potential of Salmonella biofilms on common contact surfaces to cause product cross contamination in meat processing plants.

Online Measurement of the Elastic Recovery Value of Machined Surface in Milling Titanium Alloy

In the machining of titanium alloy, the elastic recovery of the machined surface will cause strong friction between the tool flank and the workpiece surface, which will result in the tool wear and the poor machined surface. This paper designed a new online measuring system to monitor the elastic recovery behavior of Ti6Al4V alloy in dry milling based on the digital image correlation (DIC). DIC measurement principle were analyzed and the orthogonal milling experiments were carried out under different cutting conditions. Because of the complexity of metal cutting environment such as high temperature and chip splash, and the micro scale of elastic recovery of metal machined surface materials, DIC non-contact sensor was designed to measure the deformation of machined surface materials in titanium alloy milling. The displacement data obtained from the experiment were analyzed, and the calculation method of the elastic recovery value of the machined surface was obtained. The measured data were compared with those in other literature. The focus of this paper is to explore the availability of DIC measuring instrument for measurement of elastic recovery in titanium alloy milling. This method can be extended to the measurement of machining of other difficult machining materials.

Developing Prototype Simulants for Surface Materials and Morphology of Near Earth Asteroid 2016 HO3

There are a variety of applications for asteroid simulants in asteroid studies for science advances as well as technology maturation. For specific purpose, it usually requires purpose-specialized simulant. In this study, we designed and developed a set of prototype simulants as S-type asteroid surface materials analogue based on H, L, and LL ordinary chondrites’ mineralogy and terrestrial observations of near-earth asteroid 2016 HO3, which is the Chinese sample return mission target. These simulants are able to simulate morphology and reflectance characteristics of asteroid (469219) 2016 HO3 and, thus, to be used for engineering evaluation of the optical navigation system and the sampling device of the spacecraft during the mission phase. Meanwhile, these prototype simulants are easily to modify to reflect new findings on the asteroid surface when the spacecraft makes proximate observations.

Capability of Remote Sensing Images to Distinguish the Urban Surface Materials: A Case Study of Venice City

Many countries share an effort to understand the impact of growing urban areas on the environment. Spatial, spectral, and temporal resolutions of remote sensing images offer unique access to this information. Nevertheless, their use is limited because urban surface materials exhibit a great diversity of types and are not well spatially and spectrally distinguishable. This work aims to quantify the effect of these spatial and spectral characteristics of urban surface materials on their retrieval from images. To avoid other sources of error, synthetic images of the historical center of Venice were analyzed. A hyperspectral library, which characterizes the main materials of Venice city and knowledge of the city, allowed to create a starting image at a spatial resolution of 30 cm and spectral resolution of 3 nm and with a spectral range of 365–2500 nm, which was spatially and spectrally resampled to match the characteristics of most remote sensing sensors. Linear spectral mixture analysis was applied to every resampled image to evaluate and compare their capabilities to distinguish urban surface materials. In short, the capability depends mainly on spatial resolution, secondarily on spectral range and mixed pixel percentage, and lastly on spectral resolution; impervious surfaces are more distinguishable than pervious surfaces. This analysis of capability behavior is very important to select more suitable remote sensing images and/or to decide the complementarity use of different data.