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排序方式: 共有331条查询结果,搜索用时 15 毫秒
1.
Carrara Gabriel R. Burle Leonardo M. Medeiros Dianne S. V. de Albuquerque Célio Vinicius N. Mattos Diogo M. F. 《电信纪事》2020,75(3-4):163-174
Annals of Telecommunications - Blockchain is a disruptive technology that relies on the distributed nature of the peer-to-peer network while performing an agreement, or consensus, a mechanism to... 相似文献
2.
Second home tourism studies have found that there are environmental concerns which arise through the development and continued use of a second home. The majority of these studies, however, have been conducted in the Global North, and no research of this kind has yet been conducted in South Africa. This study, therefore, aims to investigate the environmental implications of second home tourism in Hartbeespoort, South Africa, with special reference to the perceptions second home owners hold with regards to their impacts on the environment. The perception held by majority of second home owner respondents is that neither they, nor their households, impact upon the environment. This perception brings the environmental sustainability of second home tourism in South Africa into question. 相似文献
3.
Dianne Smith 《Color research and application》2019,44(4):581-594
How we understand and recall colour in the environments we encounter is reliant on the context. Drawing on a repeated experience of the author in a rural Indian village, a number of questions were raised regarding visual distinctiveness and its impact on the identity of place embedded in the memories of the village. A photographic walk‐through was undertaken to determine the existing colour palette and its relationship to the character of the memories of the village. Combined with observations and theory drawn from the literature, it is proposed that considering the experience from a pluralist perspective enables insights to emerge. In this case, colour moments and colour contrast are key attributes of memories and identity construction for the village visitor. 相似文献
4.
This paper deals with the incorporation of glass cullet in cement-based materials. The aim is to help understand the differing behaviours observed depending on the particle size of the glass: the use of fine powders usually improves the concrete properties due to pozzolanic reaction, while coarse aggregates are generally detrimental for concrete due to alkali-silica reaction. It is shown that the lack of swelling of gels resulting from the reaction of glass fines can be partly due to the nature of these gels. The comparative investigation carried out on reaction products resulting from glass grains of various sizes, in the presence of both portlandite Ca(OH)2 and C3S (tricalcium silicate: 3CaO · SiO2), has shown that glass aggregates produce detrimental gels while glass fines produce gels that help to improve concrete properties. 相似文献
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As a widely recognised feature of work activity, procedural violations have been of considerable interest to human factors specialists, and several models have been proposed to aid in understanding their occurrence. A common feature of these models is that they depict violations as being, to a greater or lesser extent, intentional; therefore, rule-related behaviour could be reconceptualised as an exercise in decision-making. In this paper, we examine anaesthetists’ use of rules from the perspective of naturalistic decision-making. Doing so suggests that their rule-related behaviour is a product of the extent to which following a rule is consistent with other principles that guide their decision-making. Observational and interview data from 23 consultant anaesthetists indicated the presence of three such principles: “doing the right thing”; “doing what works in the circumstances”; and “using one’s skills and expertise”. Hence, rule-related behaviour in this setting is better understood as a form of situated action than as the following or breaking of rules per se. We discuss the implications of this view for understanding why violations occur, and how to address them. 相似文献
6.
Cross-talk between the sympathetic nervous system (SNS) and immune system is vital for health and well-being. Infection, tissue injury and inflammation raise firing rates of sympathetic nerves, increasing their release of norepinephrine (NE) in lymphoid organs and tissues. NE stimulation of β2-adrenergic receptors (ARs) in immune cells activates the cAMP-protein kinase A (PKA) intracellular signaling pathway, a pathway that interfaces with other signaling pathways that regulate proliferation, differentiation, maturation and effector functions in immune cells. Immune–SNS cross-talk is required to maintain homeostasis under normal conditions, to develop an immune response of appropriate magnitude after injury or immune challenge, and subsequently restore homeostasis. Typically, β2-AR-induced cAMP is immunosuppressive. However, many studies report actions of β2-AR stimulation in immune cells that are inconsistent with typical cAMP–PKA signal transduction. Research during the last decade in non-immune organs, has unveiled novel alternative signaling mechanisms induced by β2-AR activation, such as a signaling switch from cAMP–PKA to mitogen-activated protein kinase (MAPK) pathways. If alternative signaling occurs in immune cells, it may explain inconsistent findings of sympathetic regulation of immune function. Here, we review β2-AR signaling, assess the available evidence for alternative signaling in immune cells, and provide insight into the circumstances necessary for “signal switching” in immune cells. 相似文献
7.
On the origin of the blue/green color of blast‐furnace slag‐based materials: Sulfur K‐edge XANES investigation 下载免费PDF全文
Mohend Chaouche Xiao Xiao Gao Martin Cyr Marine Cotte Laurent Frouin 《Journal of the American Ceramic Society》2017,100(4):1707-1716
Slag‐based materials including mortars, concretes, Ca‐geopolymers, etc., are known to display a fascinating blue/green color upon hydration. This specific color is of particular concern in applications where visual esthetics are important. Yet only limited studies have been devoted to this phenomenon so far and its origin remains unexplained. It has sometimes been attributed, without any experimental evidence, to the presence of polysulfur species in the slag. To address the origin of this coloration, sulfur K‐edge X‐ray absorption near edge structure (XANES) spectroscopy was used to investigate the evolution of the speciation of sulfur during slag hydration. Three methods of slag activation were considered: thermal, portland cement, and sodium silicate. The impact of the activation method on the sulfur K‐edge XANES spectrum was examined first. Then, a comparison was made between the XANES of blue and white samples or zones with or without the blue color within the same sample. Independently of the activation route, the blue color was found to be unambiguously related to the presence of a prepeak in the corresponding XANES spectrum. This feature was absent for white samples or white zones. The prepeak, which was located at lower energy than the peak corresponding to the most common reduced sulfur species, was attributed to the presence of the trisulfur radical anion S3?. This blue chromophore is known to be at the origin of the deep blue color of the stone lapis lazuli or the ultramarine pigment (derived from lazurite). 相似文献
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Dianne L. Poster Maria J. Lopez de Alda Michele M. Schantz Lane C. Sander Stephen A. Wise Mark G. Vangel 《Polycyclic Aromatic Compounds》2013,33(2):141-191
The National Institute of Standards and Technology (NIST) has recently issued three Standard Reference Materials (SRMs) related to diesel particulate matter: SRM 1650a, Diesel Particulate Matter; SRM 2975, Diesel Particulate Matter (Industrial Forklift); and SRM 1975, Diesel Particulate Extract. These three materials have certified and reference concentrations for selected polycyclic aromatic hydrocarbons (PAHs) including many alkyl-substituted compounds. SRM 1650a is the reissue of an existing material and SRMs 2975 and 1975 represent new materials. The characterization of the PAH content of these three diesel particulate-related SRMs is presented with a discussion of the approach for the certification of PAH concentrations. In addition, the physical and biological characterization of these materials is discussed. A review of customer reported uses of these SRMs in the chemical, physical, and biological sciences is also provided. 相似文献