Molecular Study of the Persistence of Infectious Human Norovirus on Food-Contact Surfaces

The aim of this study was to investigate the effect of relative humidity (RH) and temperature on norovirus (NoV) persistence as infectious particles on food-contact surfaces such as stainless steel and polyvinyl chloride (PVC). For this purpose, a new method combining enzymatic digestion with molecular beacon-based NASBA targeting the ORF1-ORF2 domain was developed to discriminate between infectious and noninfectious NoV. Stainless steel and PVC disks were contaminated with known amounts of human NoV and kept for 56 days at 7 and 20°C at high (86% ± 4%) and low (30% ± 10%) RH. NoV retained its putative infectivity for 56 days on PVC and for 49 days on stainless steel at 7°C and for 7 and 28 days, respectively, at low and high RH at 20°C on both tested surfaces. These results confirm that NoV persists in an infective state on inert surfaces for long periods of time and consequently may cause illness. The new molecular approach to detecting infectious NoV on inert surfaces may provide valuable information for evaluating environmental surface decontamination strategies.     

纳滤膜过滤MBR出水的污染原因与清洗方法

为研究膜-生物反应器(MBR)出水对纳滤膜的污染原因及清洗方法,使用场发射扫描电镜、傅立叶变换红外光谱仪、原子力显微镜和接触角仪对经MBR出水污染的纳滤膜表面污染层进行了检测,结果表明,纳滤膜表面污染物包括有机物和无机物,所含元素包括磷、镁等,对经过不同清洗步骤的膜表面进行的检测表明,柠檬酸清洗可以去除镁和大部分磷,这些物质主要以无机形态存在于膜面污染物中;后续NaOH清洗可以进一步去除磷,这部分磷主要来自有机酸、有机磷或蛋白质等膜面污染物.污染使膜表面粗糙度由79.5 nm增大至111.2 nm,但接触角由55.6°变为62.1°,表明亲水性变化不大;酸洗后表面粗糙度显著减小至51.9 nm,接触角变为96.0°,表明有机污染物暴露出来,膜面呈现疏水性;再经碱洗后,膜面粗糙度与亲水性均接近于新膜.这些结果说明,先酸洗后碱洗的方法可以去除绝大部分的膜面污染物,进一步推知膜污染初期主要为有机污染,之后无机物的作用使污染进一步加重.     

Enzymatic preparation of hydrophobic biomass with one-pot synthesis and the oil removal performance

Oil pollution is causing deleterious damage to aquatic ecosystems and human health. The utilization of agricultural waste such as corn stalk (CS) to produce biosorbents has been considered an ecofriendly and efficient approach for removing oil. However, most previous studies focused on the modification of the whole CS, which is inefficient due to the heterogeneity of CS. In this study, corn stalk pith (CP), which has excellent amphipathic characteristics, was selected to prepare a high-efficienc...     

Effect of Capacitor Discharge Welding on Single-Crystal Metals

The objective of this study was to investigate the use of capacitor discharge welding (CDW) as a suitable technique for joining metal single crystals by studying the effect of CDW on the microstructure of single-crystal copper. According to solidification theory, single-crystal formation requires high thermal gradients and moderate solidification rates. Therefore, an initial analysis was performed to determine if single-crystal CDW would result in a single-crystal microstructure. Joints were made using samples with joining surfaces at 0°, 15°, 30°, and 45° to the (111) crystal plane. Results show that single-crystal copper can be joined using CDW without the formation of voids and grain boundaries at the weld centerline. Average etch-pit densities after CDW are lower than those reported in the literature for single-crystal copper, suggesting minimal microstructural disruption. Crystal orientation does not seem to have any effect on fusion zone thickness or etch-pit density. Further work is needed to evaluate the effect of crystal orientation on void content in single-crystal copper welds made by CDW.     

Waterproof and translucent wings at the same time: problems and solutions in butterflies

Although the colour of butterflies attracts the most attention, the waterproofing properties of their wings are also extremely interesting. Most butterfly wings are considered “super-hydrophobic” because the contact angle (CA) with a water drop exceeds 150°. Usually, butterfly wings are covered with strongly overlapping scales; however, in the case of transparent or translucent wings, scale cover is reduced; thus, the hydrophobicity could be affected. Here, we present a comparative analysis of wing hydrophobicity and its dependence on morphology for two species with translucent wings Parantica sita (Nymphalidae) and Parnassius glacialis (Papilionidae). These species have very different life histories: P. sita lives for up to 6 months as an adult and migrates over long distance, whereas P. glacialis lives for less than 1 month and does not migrate. We measured the water CA and analysed wing morphology with scanning electron microscopy and atomic force microscopy. P. sita has super-hydrophobic wing surfaces, with CA > 160°, whereas P. glacialis did not (CA = 100–135°). Specialised scales were found on the translucent portions of P. sita wings. These scales were ovoid and much thinner than common scales, erect at about 30°, and leaving up to 80% of the wing surface uncovered. The underlying bare wing surface had a remarkable pattern of ridges and knobs. P. glacialis also had over 80% of the wing surface uncovered, but the scales were either setae-like or spade-like. The bare surface of the wing had an irregular wavy smooth pattern. We suggest a mode of action that allows this super-hydrophobic effect with an incompletely covered wing surface. The scales bend, but do not collapse, under the pressure of a water droplet, and the elastic recovery of the structure at the borders of the droplet allows a high apparent CA. Thus, P. sita can be translucent without losing its waterproof properties. This characteristic is likely necessary for the long life and migration of this species. This is the first study of some of the effects on the hydrophobicity of translucency through scales’ cover reduction in butterfly wings and on the morphology associated with improved waterproofing. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

低温硝基苯降解菌的筛选及降解特性研究

从被硝基苯污染的某河流底泥中分离到能在低温下生长并能以硝基苯为唯一碳源的7株细菌,其中菌株NB1在温度从2.5～35 ℃范围内时都可以生长并矿化20 mg/L的硝基苯,最适宜的生长温度为25 ℃左右;当培养温度为5 ℃时,该菌株在pH为6～9范围内可以快速降解20 mg/L硝基苯,偏碱性的条件比酸性条件更适合其生长;不超过100 mg/L的硝基苯可以被该细菌完全降解.通过生理生化反应特性、菌体形态以及16S rDNA序列测定结果,确定NB1为恶臭假单胞菌(Pseudomonas putida).不同温度条件,特别是低温下该菌株对硝基苯的快速降解特性为低温环境硝基苯污染的生物修复提供了可能.     

城市生活垃圾滚筒筛分选特性研究

滚筒筛筛分是生活垃圾分选中常用的工艺,国内目前有关滚筒筛分选生活垃圾的研究尚不多见.因此,本实验通过自行设计的一台处理能力为150kg.h-1的滚筒筛,采用实际生活垃圾进行分选实验,确定最佳运行参数范围.结果表明,当滚筒筛孔径为120mm时,在V实测/V极限（V实测为滚筒转动时实时测定转速,V极限为物料与滚筒一起转动时...     

回转窑热解气化炉处理生活垃圾特性

基于目前固定床热解气化法在常温下进行存在燃气热值和气化效率较低、燃料适用范围小和预处理复杂等问题,采用控制变量法设计探究了不同预热空气温度和过量空气系数对小型回转窑式热解气化炉处理村镇生活垃圾的影响.结果表明:预热空气温度升高有利于垃圾热解气化产气,但有一定的局限性,当温度超过600 ℃时垃圾的气化产气明显下降;当过量空气系数为0.4时,垃圾的热解气化效率达到最大值,并且焦油产量最小.垃圾原样在过量空气系数为0.4、空气预热温度为500 ℃下对底渣、飞灰进行重金属含量的分析测试结果显示,飞灰中的铅含量远高于GB 18598—2001《危险废物填埋污染控制标准》相关标准限值,需要经过处理才能排放,二英采样分析结果显示其含量均低于GB 18485—2014《生活垃圾焚烧污染控制标准》限值.研究显示,该回转窑式热解气化工艺处理生活垃圾的最佳过量空气系数为0.4,最佳空气预热温度为500 ℃,在此最佳工况条件下焦油产量小,飞灰及焦渣中重金属含量小,ρ(二英)低于0.10 ng/m3.      

移动床生物膜反应器载体亲水改性的试验研究

采用聚合物共混法研究载体亲水性改善的可行性,在此基础上研究电晕处理对亲水性能强化的效果和持续性.结果表明,共混方式能够改善载体亲水性能,接触角从108°降至88°,载体表面已经呈亲水性;电晕处理能够强化亲水性能,接触角可进一步降低至72°,但强化效果持续时间短.从检测指标和检测方法2方面建立载体生物学性能评价体系,研究亲水性能改善对载体生物学性能的影响.对比电晕处理前后载体,经20 d生物学性能试验检测表明,亲水性能经电晕处理强化的载体启动快,启动第2 d COD和NH⁺₄-N去除率就分别高达80%和97%,同期未电晕处理载体仅为61%和63%;后期两者处理效果基本持平,说明电晕改性初期效果明显,而持续时间有限;也表明所建立的生物学性能评价体系快速可靠.     

Efficacy of Cinnamaldehyde Against Enteric Viruses and Its Activity After Incorporation Into Biodegradable Multilayer Systems of Interest in Food Packaging

Cinnamaldehyde (CNMA), an organic compound that gives cinnamon its flavor and odor, was investigated for its virucidal activity on norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), and hepatitis A virus (HAV). Initially, different concentrations of CNMA (0.1, 0.5 and 1 %) were individually mixed with each virus at titers of ca. 6–7 log₁₀ TCID₅₀/ml and incubated 2 h at 4 and 37 °C. CNMA was effective in reducing the titers of norovirus surrogates in a dose-dependent manner after 2 h at 37 °C, while HAV titers were reduced by 1 log₁₀ after treatment with 1 % of CNMA. When incubation time was extended, HAV titers were reduced by 3.4 and 2.7 log₁₀ after overnight incubation at 37 °C with 1 and 0.5 % of CNMA, respectively. Moreover, this paper analyzed, for the first time, the antiviral activity of adding an active electrospun interlayer based on zein and CNMA to a polyhydroxybutyrate packaging material (PHB) in a multilayer form. Biodegradable multilayer systems prepared with 2.60 mg/cm² (~9.7 %) of CNMA completely inactivated FCV according to ISO 22196:2011, while MNV titers were reduced by 2.75 log₁₀. When the developed multilayer films were evaluated after one month of preparation or at 25 °C, the antiviral activity was reduced as compared to freshly prepared multilayer films evaluated at 37 °C. The results show the excellent potential of this system for food contact applications as well as for active packaging technologies in order to maintain or extend food quality and safety.     

T型槽密封结构的有限元分析及试验验证

目的通过有限元分析,实现T型密封结构的优化设计。方法利用ABAQUS建立液压系统用T型槽密封结构的二维轴对称模型,分析计算密封结构中过渡圆角、槽宽、倾斜角度等对密封圈应力分布、接触应力的影响,通过设计密封圈老化寿命试验,验证分析结论。结果随着过渡圆角(R0.5～R2)的增大、倾斜角度(10°～3°)的减小,密封圈的局部应力最大值和接触应力均减小。随着槽宽(10～18mm)的增加,密封圈的局部应力最大值逐渐增加,接触应力逐渐减小。分析用密封结构的接触应力均大于密封介质压力0.7 MPa。最终通过试验证实了分析用密封结构均满足密封性能,且不合理的设计会降低密封圈寿命。结论在密封介质压力较小的情况下,建议选用较大的过渡圆角(推荐值为R2),较小的倾斜角度(推荐值为5°～6°)及槽宽(推荐值为密封圈截面直径的1.2～1.5倍)。     

包埋厌氧氨氧化的脱氮特性及其微生物群落结构

采用聚乙二醇二丙烯酸酯作为载体,分别以N,N,N,‘N’-四甲基乙二胺（TEMED）,过硫酸钾（KPS）作为促进剂和引发剂,对厌氧氨氧化菌进行包埋固定化.采用正交试验优化包埋条件,得到的最佳条件为：10% PEGDA单体,0.25% KPS,0.5% TEMED,最佳的操作条件为：聚合温度20℃,聚合时间控制在5min左右,菌胶比选取1：1.包埋颗粒的连续流实验表明,颗粒经过短暂的活性恢复后,脱氮效果不断提升,并且对水力负荷的提高有一定的抗冲击能力.扫描电镜（SEM）表明本实验包埋材料具有很好的生物相容性,且具有良好的传质性能.高通量测序显示,稳定运行一段时间后,颗粒内微生物多样性略有减小,厌氧氨氧化功能菌Candidatus Kuenenia占整个微生物体系比例由6.58%上升至9.8%,微生物种群的变化说明了包埋后厌氧氨氧化性能能够得到更大的提升.     

Modification of CeO2-ZrO2 catalyst by potassium for NOx-assisted soot oxidation

Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method.The ageing treatment was performed in static air at 800°C for 20 hr to evaluate the thermal stability of the catalyst.The catalysts were characterized by X-ray diffraction,BET surface area,oxygen storage capacity,NOx-temperature programmed desorption and soot-temperature programmed oxidation measurements.By introduction of potassium,the maximum soot oxidation rate temperature(Tm) of the ceria-zirconia based catalyst de...     

Physical conditions for trapping air by a microtrichia-covered insect cuticle during temporary submersion

The intertidal midge Clunio, which reproduces on exposed rocky seashores, becomes enclosed in an irregularly shaped air bubble during short submersion by incoming waves. This water-repellent property of Clunio’s cuticle is caused by a complete cover of hydrophobic microtrichia offering an effective surf tolerance. These microtrichia not only trap a thin air layer above the cuticle but also maintain a larger air bubble between the insect’s ventral side and legs. The effectiveness of the water repellence was quantitatively characterised on the basis of a known model (Crisp and Thorpe, Discuss Faraday Soc 3:210–220, 1948). The parameters of the model are the contact angle θ (>90°) at the contact line of air/water/microtrichia and the distance between individual microtrichia and their radius. When the microtrichia are 1.1 μm apart and have a radius of 0.1 μm and an estimated contact angle θ of 140°, the air layer is stable against hydrostatic pressures of up to 3 m water column. As shown by a modified version of the model, considerably larger air bubbles can be trapped by the microtrichia cover of the legs up to distances of 0.5 mm from the body. The widely spaced (about 8 μm apart) and longer setae of Clunio are not involved in the formation of air layers and air bubble.     

Effects of acidic deposition on the erosion of carbonate stone — experimental results from the U.S. National Acid Precipitation Assessment Program (NAPAP)

One of the goals of NAPAP-sponsored research on the effects of acidic deposition on carbonate stone has been to quantify the incremental effects of wet and dry deposition of hydrogen ion, sulfur dioxide and nitrogen oxides on stone erosion. Test briquettes and slabs of freshly quarried Indiana limestone and Vermont marble have been exposed to ambient environmental conditions in a long-term exposure program. Physical measurements of the recession of test stones exposed to ambient conditions at an angle of 30° to horizontal at the five NAPAP materials exposure sites range from ∼ 15 to ∼ 30 μm yr⁻¹ for marble, and from ∼ 25 to ∼ 45 μm yr⁻¹ for limestone, and are approximately double the recession estimates based on the observed calcium content of run-off solutions from test slabs. The difference between the physical and chemical recession measurements is attributed to the loss of mineral grains from the stone surfaces that are not measured in the run-off experiments. The erosion due to grain loss does not appear to be influenced by rainfall acidity, however, preliminary evidence suggests that grain loss may be influenced by dry deposition of sulfur dioxide between rainfall events. Chemical analyses of the run-off solutions and associated rainfall blanks suggest that ∼ 30% of erosion by dissolution can be attributed to the wet deposition of hydrogen ion and the dry deposition of sulfur dioxide and nitric acid between rain events. The remaining ∼ 70% of erosion by dissolution is accounted for by the solubility of carbonate stone in rain that is in equilibrium with atmospheric carbon dioxide (“clean rain”). These results are for marble and limestone slabs exposed at an angle of 30° from horizontal. The relative contribution of sulfur dioxide to chemical erosion is significantly enhanced for stone slabs having an inclination of 60° or 85°. The dry deposition of alkaline particulate material has a mitigating effect at the two urban field exposure sites at Washington, DC, and Steubenville, OH.     

Synthetic hydrophilic polymers

Synthetic hydrophilic polymers find promising applications in pharmacology, biotechnology and chemistry. The biocompatibility, biodegradability and pharmacological activity of these polymers depend much on their hydrophilic nature. This article summarizes the recent developments in the utilization of the different classes of these hydrophilic polymers as pharmacologically active agents, for enzyme modification and as catalysts and supports for chemical reactions.     

Experimental Evaluation of Cutter Orientation When Ball Nose End Milling Inconel 718™

High-speed machining (HSM), specifically end milling and ball end cutting, is attracting interest in the aerospace industry for the machining of complex 3D aerofoil surfaces in titanium alloys and nickel-based superalloys. Following a brief introduction on HSM and related aerospace work, the paper reviews published data on the effect of cutter/workpiece orientation, also known as engagement or tilt angle, on tool performance. Such angles are defined as ±β_fN and ±β_f.Experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force, and workpiece surface roughness when high-speed ball end milling Inconel 718™. Dry cutting was performed using 8 mm diameter PVD-coated solid carbide cutters with the workpiece mounted at an angle of 45° from the cutter axis.A horizontal downward (-β_fN) cutting orientation provided the best tool life with cut lengths ∼50% longer than for all other directions (+β_fN, +β_f, and –β_f). Evaluation of cutting forces and associated spectrum analysis of results indicated that cutters employed in a horizontal downward direction produced the least vibration. This contributed to improved workpiece surface roughness, with typical mean values of ∼0.4 μm Ra as opposed to ∼1.25 μm Ra when machining in the vertical downward (–β_f) direction.     

Groundwater-dependent irrigation costs and benefits for adaptation to global change

The effects of a 1.5 °C global change on irrigation costs and carbon emissions in a groundwater-dependent irrigation system were assessed in the northwestern region of Bangladesh and examined at the global scale to determine possible global impacts and propose necessary adaptation measures. Downscaled climate projections were obtained from an ensemble of eight general circulation models (GCMs) for three representative concentration pathways (RCPs), RCP2.6, RCP4.5, and RCP8.5 and were used to generate the 1.5 °C warming scenarios. A water balance model was used to estimate irrigation demand, a support vector machine (SVM) model was used to simulate groundwater levels, an energy-use model was used to estimate carbon emissions from the irrigation pump, and a multiple linear regression (MLR) model was used to simulate the irrigation costs. The results showed that groundwater levels would likely drop by only 0.03 to 0.4 m under a 1.5 °C temperature increase, which would result in an increase in irrigation costs and carbon emissions ranging from 11.14 to 148.4 Bangladesh taka (BDT) and 0.3 to 4% CO₂ emissions/ha, respectively, in northwestern Bangladesh. The results indicate that the impacts of climate change on irrigation costs for groundwater-dependent irrigation would be negligible if warming is limited to 1.5 °C; however, increased emissions, up to 4%, from irrigation pumps can have a significant impact on the total emissions from agriculture. This study revealed that similar impacts from irrigation pumps worldwide would result in an increase in carbon emissions by 4.65 to 65.06 thousand tons, based only on emissions from groundwater-dependent rice fields. Restricting groundwater-based irrigation in regions where the groundwater is already vulnerable, improving irrigation efficiency by educating farmers and enhancing pump efficiency by following optimum pumping guidelines can mitigate the impacts of climate change on groundwater resources, increase farmers’ profits, and reduce carbon emissions in regions with groundwater-dependent irrigation.     

Nocturnal variation of air-surface temperature gradients for typical urban and rural surfaces

The nocturnal variation of the standard atmospheric air-ground surface temperature gradient under fair weather conditions is considered. A semi-analytical model in the form of an exponential response function is proposed and experimentally verified against field observations conducted by the author at Haifa (ca 32°N) and by others at various geographical locations. The proposed model is intended to predict the sought gradient variation with the aid of an experimentally derived parameter (a time constant) which is directly proportional to the thermal inertia of the substrate matter beneath the surface in question. Among the impervious ground-cover types widely encountered in urban environments, concrete surfaces exhibit the highest time constant of about 10 h, while that of bare dry rural soil is 6.5 h. Turf and wet soil surfaces, common in rural environments, have time constants of 3.6 and 10.8 h, respectively. Applicability of the proposed model to the exterior surfaces of building-envelope elements is also discussed, as are the implications of the present findings regarding the causative factors of urban heat islands.