Microbial stability evaluation of cement-based waste forms at different waste to cement ratio

An evaluation of the effect of differences in chromium nitrate to cement ratio on the microbial stability of a chromium nitrate/cement waste form, as reflected in the leaching of chromium, calcium, magnesium and aluminum; was carried out in this study. An increase in the proportion of chromium in the waste form from 4.8 to 8.7% had no noticeable effect on microbial stability, with the total chromium leached essentially unchanged. Further increases in the proportion of chromium in the waste form from 8.7 to 10.7%, and from 10.7 to 15.9% resulted in a substantial decrease in microbial stability, with 3-fold and 1.3-fold increase in the total chromium leached, respectively, observed. For calcium, increases in the chromium proportion were accompanied with increases in the total calcium leached even though the increases were not in direct proportion to the increases in chromium proportion. For magnesium and aluminum, increases in the proportion of chromium within the range 4.8-10.7% were accompanied with increases in the total respective metals leached, with minor variation for each metal. On the whole, the maximum percentage chromium leached from the different waste forms was substantially lower than those of the other metals.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

Performance of a liquid thermal-diffusion column with temperature asymmetry over the width

The theory of thermal diffusion [1] employs an idealized model in which the temperature at all points on the hot or cold surface is assumed to be the same. In practice, however, such a model cannot be realized, since even the most careful design of the column will result in asymmetry in the temperature distributions on these surfaces. This asymmetry is more pronounced in liquid columns because of the small width of the annulus, and so the column acquires parasitic convection [1], which results in resolution worse than theory predicts. The origin of this effect, which is extremely undesirable in practical operation is explained in Fig. 1a [1]. The azimuthal temperature gradient in regions I and II causes the mean temperature of the liquid to vary, so the liquid as a whole moves in one direction in region I and in the opposite direction in region II; in each of these regions there are also two flows caused by the radial temperature gradient, which is incorporated in the theory of the column.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 5, pp. 809–817, November 1970.One prime and two primes refer, respectively, to the column parts shown in Fig. 1 as I and II.     

气候变化与青藏高原工程设计

最近半个世纪,青藏高原地面气候发生了一定变化,主要表现在地面平均气温明显上升,冬季、夜间和城镇区域气温上升尤其显著,多数地区降水量呈现不同程度增加。气候变暖对高原地区自然和人类系统产生了一定影响。预计未来青藏高原气候总体将继续趋向变暖,这可能对冰冻圈、河湖系统、陆地植被、农业自然条件、能源气候资源、交通和水利设施、城镇人居环境等产生明显影响。与生态保护和经济社会发展有关的各类大型工程的规划、设计和维护,需要考虑今后气候变化的可能影响,及早制定可行的适应性措施。     

基于沉浸理论的农区畜牧业服务设计研究

目的 探究沉浸理论介入农区畜牧业服务设计的策略,构建更具用户体验感的农区畜牧业服务设计系统。方法 根据沉浸理论的内涵与我国农区畜牧业发展现状,分析沉浸理论介入农区畜牧业服务设计的经济价值、社会价值和文化价值,针对农区畜牧业存在的问题及沉浸理论可行性分析,构建沉浸理论下的农区畜牧业服务设计策略。结果 首先对河南省新野县畜牧业现状进行调研分析;其次基于服务设计思维与设计策略进行服务系统图及蓝图设计,并进一步设计以用户为中心的服务载体——恒永牧场APP、畜牧市集及配套应用小程序,来实现新野农区畜牧业用户的沉浸式体验;最后通过沉浸效果评估,验证了沉浸理论介入农区畜牧业的可行性及重要性。结论 沉浸理论的融入能够改善用户体验,促进农区畜牧业的高质量发展,为我国畜牧业服务系统的创新设计提供了新的思路和方法。     

水下夹芯复合空腔结构声学特性试验研究

引入空腔改善夹芯复合结构低频段吸声性能。建立了三种典型水下声隐身结构声学系统模型,在数值分析吸声性能影响因素基础上,运用脉冲声管试验方法,分析了空气背衬“硬”边界条件和水背衬“软”边界条件下,有无空腔试样、不同空腔间距、空腔形状和深度对谐振吸声峰值及峰值频率等的影响。试验结果表明,空腔显著改善了夹芯复合结构低频段吸声性能;空气背衬下,空腔间距越小,首阶谐振吸声峰值越大,峰值频率越低,水背衬条件下则相反;空腔体积越大,首阶谐振吸声峰值越小,峰值频率越低。     

血吸虫病控制新策略的研究

目的:我国血吸虫病的传播与自然生态环境和社会经济等因素关系密切,采取以前的防治策略难以控制湖沼型血吸虫病的传播.研究旨在探索以控制传染源为主的湖沼型血吸虫病流行区综合防治新策略的效果.方法:选取了江西省鄱阳湖地区、每年常规实施化疗防治措施的2个干预村和2个对照村进行现场研究.新的干预措施于2005年全面实施,主要措施包括封洲禁牧、"以机代牛"、改水改厕、渔船民粪便管理等措施,并强化健康教育措施,以降低人和耕牛作为钉螺传染源的作用.并于2005-2008年间连续观测了人群感染率、钉螺感染率以及哨鼠感染率的变化情况.结果:干预措施实施后,经3个传播季节后干预组的血吸虫人群感染率降到1.0%以下,其中爱国村从11.3%降到0.7%,新和村从4.0%降到0.9%(两两比较均P<0.001),且在第4个传播季节后分别持续下降至0.2%和0%.而对照组人群感染率出现上下波动,但仍维持在原来的基线水平.干预组一个草洲上的感染性钉螺密度在4个传播季节后分别从2.2%和0.3%下降到0%(两两比较均P<0.01),而暴露于水体中的哨鼠感染率从79.3%降至0%(P<0.001).结论:以传染源控制为主综合性防治策略能有效地降低日本血吸虫病在耕牛、人群和钉螺间的传播,这一策略现已被采纳为中国新的血吸虫病防治策略.     

In vivo and in vitro tracking of erosion in biodegradable materials using non-invasive fluorescence imaging

The design of erodible biomaterials relies on the ability to program the in vivo retention time, which necessitates real-time monitoring of erosion. However, in vivo performance cannot always be predicted by traditional determination of in vitro erosion, and standard methods sacrifice samples or animals, preventing sequential measures of the same specimen. We harnessed non-invasive fluorescence imaging to sequentially follow in vivo material-mass loss to model the degradation of materials hydrolytically (PEG:dextran hydrogel) and enzymatically (collagen). Hydrogel erosion rates in vivo and in vitro correlated, enabling the prediction of in vivo erosion of new material formulations from in vitro data. Collagen in vivo erosion was used to infer physiologic in vitro conditions that mimic erosive in vivo environments. This approach enables rapid in vitro screening of materials, and can be extended to simultaneously determine drug release and material erosion from a drug-eluting scaffold, or cell viability and material fate in tissue-engineering formulations.     

深孔台阶爆破近远区振动特征的试验研究

为了探索深孔台阶爆破在近区和远区的振动特征,以现场试验为基础,利用回归分析、随机分析及小波包分解技术,从爆破振动信号的衰减规律、三分量特征、随机特征及能量分布等方面对二者进行了对比研究,结果显示:振速三分量在近区的K、α值均大于远区,远区各分量的α值更为接近。振速三分量在远区的相关系数大于近区,且更接近1,三分量中垂向分量的相关系数最大。近区当比例距离小于5时,径向振速最大,比例距离大于等于5时,垂向振速最大。远区的垂向振速最大。无论在近区还是远区,切向振速一般最小。振速三分量在近区的变异系数大于远区,径向振速的变异系数在近区和远区较为接近。最大段药量或爆心距增加时,近区及远区的能量均向低频带流动,近区的移动速度更快,同时近区及远区能量分布的频带宽度也将趋于集中,近区的频带宽度更宽。     

Nonresponsiveness of the rat liver to alkylating carcinogens given by gavage.

Carcinogenic alkylating agents administered orally are metabolized in the liver and alkylate DNA in liver cells of rats and hamsters. They frequently, but not always, induce liver tumors, in addition to tumors of other organs. Directly acting alkylating agents, such as alkylnitrosoureas and alkylnitrosocarbamates, rarely induce liver tumors, although they alkylate DNA in liver cells. The methylating agents nitrosodimethylamine and azoxymethane induce high incidences of liver tumors in rats when given in drinking water, but few or no liver tumors when given by gavage, although the total dose and the weekly dose were the same in either regimen. In contrast, methylnitrosoethylamine and nitrosodiethylamine give rise to liver tumors in rats in high incidences whether given by gavage or in drinking water. Sharp differences are also observed with other nitrosamines, such as those containing a propyl group with an oxygen substituent in the 2-position. These discrepancies indicate that, in addition to alkylation of DNA, pharmacokinetics of dosing and distribution and other reactions of the carcinogen are the dominant factors in determining the development of tumors in the liver.     

HL-1M装置边缘扰动和流速的实验研究

利用一组马赫探针研究HL-1M装置刮离层和边缘等离子体流在欧姆放电、壁硼化、偏压抽气孔栏、偏压电极、低混杂波电流驱动、电子回旋共振加热、弹丸注入、分子束注入、激光吹气和补充送气等情况下的平行流马赫数、离子饱和电流扰动、平行流速度剪切和极向流速度的分布。实验中发现局部等离子体电位快速变化，改变了电场分布，改变了边缘等离子体的流速和方向。从而改善了等离子体约束性能。     

生物质与生活垃圾共气化过程重金属的迁移转化规律

为了研究流化床生物质气化协同处置生活垃圾衍生燃料过程中重金属的迁移转化规律,在湖北某循环流化床气化炉耦合燃煤发电厂进行掺烧试验。研究表明重金属主要赋存于飞灰和炉渣中。空白工况下86.2%的Cr赋存于飞灰中,13.3%于炉渣中;75.5%的Pb在飞灰中,23.8%在炉渣中;79.5%的As迁移至飞灰中,11.7%在炉渣中。RDF工况下75.8%的Cr迁移至飞灰,20.7%迁移至炉渣;44.6%的Pb存在于飞灰中,52%存在于炉渣。协同处置后,重金属在飞灰和炉渣中的分配比例明显发生了变化,飞灰中重金属含量减少12.5%~31.3%,炉渣中重金属增加7.33%~20.1%,气化气的引入改变了炉内重金属的分配情况。协同处置可以有效处理生活垃圾,对固废中的热量进行资源化利用,且出炉物料中重金属含量均低于我国现行标准限值。     

Modification of the phased-tracking method for reduction of artifacts in estimated artery wall deformation

Noninvasive measurement of mechanical properties, such as elasticity, of the arterial wall, is useful for diagnosis of atherosclerosis. For assessment of mechanical properties, it is necessary to measure the deformation of the arterial wall. In this study, a modification of the previously proposed phased-tracking method was conducted to improve measurement of the small change in thickness (deformation) of the arterial wall due to the heartbeat. In our previous method, a set of two points along an ultrasonic beam was initially assigned, and the change in thickness of the layer between these two points during an entire cardiac cycle was estimated. In motion estimation with ultrasound, the motion of an interface or a scatterer, which generates an echo, can be obtained by estimating the change in time delay of the echo. For example, in the case of a carotid artery of a healthy subject, there are only two dominant echoes from the lumen-intima and media-adventitia interfaces. Thus, only the displacements of the lumen-intima and media-adventitia interfaces can be estimated, which means that ultrasound can estimate only the change in distance (thickness) between these two interfaces. However, even in this case, our previous method gives different estimates of the change in thickness, depending on the depths (positions in the arterial radial direction) of the two initially assigned points. In this study, modifications of the previous method in terms of the strategy for assignment of layers and the required thickness of an assigned layer were made to reduce such an artificial spatial variation in the estimated changes in thickness. Using the proposed method, errors in estimated changes in thickness were reduced from 21.2 +/- 24.1% to 0.19 +/- 0.04% (mean +/- standard deviation) in simulation experiments. As in the case of the simulation experiments, the spatial variation in estimated changes in thickness also was reduced in in vivo experiments in a carotid artery of a healthy subject and in vitro experiments using two excised, diseased arteries.     

Damage in biocomposites: Stiffness evolution of aligned plant fibre composites during monotonic and cyclic fatigue loading

The non-linear stress–strain behaviour of plant fibre composites is well-known in the scientific community. Yet, the important consequences of this, in terms of the evolution of stiffness as a function of applied strain and cycles to failure, are not well-studied in literature. This is despite the fact that stiffness degradation is a well-accepted indicator of damage in a composite material, and is regularly used as a component failure criterion. This article systematically explores the evolution of stiffness of various aligned plant fibre composites, subjected to (i) monotonic loading, (ii) low-cycle, repeated progressive loading, and (iii) fatigue loading. The evolution in stiffness in plant fibre composites is found to be complex: structural changes in the elementary fibre cell wall and damage development in the composite have often competing effects on stress–strain behaviour. Indeed, the evolution in stiffness of plant fibre composites is found to be unlike that typically observed in traditional composites, and therefore needs to be taken into account in the design of structural components.     

Servitization of manufacturing in the new ICTs era: A survey on operations management

Servitization of manufacturing has become one of the main pathways for transition and upgrade in the manufacturing industry. New information and communication technologies (ICTs), such as the Internet of Things, Big Data, and Cloud Computing have enabled the servitization of manufacturing in terms of value creation, resource management, and supply chain management. This study presents a comprehensive review on the servitization in operations management in the era of new ICTs. A new value chain framework is proposed under the business model that revolves around servitization, which showcases the new activities and ways of implementation in the era of new ICTs. The virtualization, configuration, and evaluation of integrated manufacturing and service resources are analyzed. In particular, the methods used in new ICT-supported resource management platforms are surveyed. Problems in the supply chain management in manufacturing services (including the selection of partners, as well as the coordination, planning, and scheduling among members) are presented. This study concludes with a discussion on state-of-the-art servitization in operations management in the era of new ICTs.     

Continuity and Discontinuity of Collaboration Behaviour since 1800 — from a Bibliometric Point of View

Time-series of collaboration trends indicated through co-authorships are examined from 1800 to presence in mathematics, logic, and physics. In physics, the share of co-authored papers expands in the second half of the19th century, in mathematics in the first decades of the 20th century, in logic in the second half of the 20th century. Subdisciplines of mathematics, of physics, and areas of logic show large differences in their respective propensities to collaborate. None of the existing explanatory approaches meets this heterogeneity; the most salient feature is a propensitiy to collaborate in fields where theoretical and applied research is combined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Application of corporate social responsibility approach in Bulgaria to support sustainable tourism development

The rapidly developing tourism industry in Bulgaria in the last 15?years, especially at the Black sea coast, contributed to an entire change in the accommodation sector. The growth was due to unseen construction of new accommodation facilities and entire renovation of the existing ones. At the same time the tourism industry suffers from many social problems: lack of staff, shortage of qualified staff especially in the high-star hotels, very high rate of turnover, flow of Bulgarian staff abroad. The bigger mobility of the employees is facilitated by the seasonal character of the industry, knowledge of foreign languages, difference in payments, as well as in the nature of work. Overall, this leads to lost training investments, reduces the incentives for employers to provide training, causes lower quality services in hotels, and finally impacts negatively the competitiveness of the hotel sector in Bulgaria and its sustainable development. The paper presents the practical experience and conclusions from a corporate social responsibility (CSR) assessment in 25 Bulgarian hotels regarding the social issues of the CSR: human resource management, occupational safety and health, human and labour rights, stakeholder and community involvement, customer satisfaction. The most important social problems identified are: deficiency in management skills, deficiency in organised (external) stakeholder dialogue, lack of qualified staff in certain professions, lack of investment in training, high turnover, low motivation, conflicts related to wage levels, overtime, etc. A set of key performance indicators related to social responsibility is suggested and analysed. The benchmarking process is discussed and exemplary benchmarks are quoted. The most frequently proposed measures by the hotel CSR teams to improve the social responsibility in the hotels are reviewed.     

In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria

Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.     

Effect of micro-randomness on macroscopic properties and fracture of laminates

Composite materials demonstrate a considerable extent of heterogeneity. A non-uniform spatial distribution of reinforcement results in variations of local properties of fibrous laminates. This non-uniformity not only affects effective properties of composite materials but is also a crucial factor in initiation and development of damage and fracture processes that are also spatially non-uniform. Such randomness in microstructure and in failure evolution is responsible for non-uniform distributions of stresses in composite specimens even under externally uniform loading, resulting, for instance, in a random distribution of matrix cracks in cross-ply laminates. The paper deals with statistical features of a distribution of carbon fibres in a transversal cross-sectional area in a unidirectional composite with epoxy matrix, based on various approaches used to quantify its microscopic randomness. A random character of the fibres’ distribution results in fluctuations of local elastic moduli in composites, the bounds of which depend on the characteristic length scale. A lattice model to study damage and fracture evolution in laminates, linking randomness of microstructure with macroscopic properties, is discussed. An example of simulations of matrix cracking in a carbon fibre/epoxy cross-ply laminate is given.