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51.
Anna Klisiska-Kopacz Renata Tilova Grzegorz Adamski Roman Kozowski 《Journal of Cultural Heritage》2010,11(4):950-410
Mercury porosimetry was applied to the study of pore structure of the historic Roman cement mortars representative of different locations in Europe and time periods as well as different application techniques from architectural castings to in situ formed renders and profiles. Three categories of pores were found to coexist in the mortars. The finest pores, with diameters below 0.1 μm, are present within the hardened aged Roman cement matrix. The larger ‘air’ pores, with diameters between 0.2–2 μm, are due to the evaporation of the excess unbound water and restricted hydration. Pores larger than 2 μm are rare and, in general, can be related to microcracking induced by shrinkage drying and mortar weathering. The mortars have rarely been found to develop a dense fine-porous microstructure characteristic of the ideal conditions of moist-curing; massive architectural castings being the only exception identified. The presence of larger ‘air’ pores was, in turn, almost universally observed. The investigations of the freshly prepared Roman cement mortars have revealed that the restricted hydration could be due to the exposure of the freshly laid surface to dry real-world external environments, a high water-to-cement ratio in the original mortars, or the drawing of water from the stucco mass due to insufficient pre-wetting of the porous masonry. The insufficient reactivity of historic cements, resulting from a high content of over-burned, non-reactive cement components or coarseness of the cement grains, could be another reason for yielding poorly hydrated mortars in the past. In general, Roman cement stuccoes are in an excellent state of preservation in spite of their usual exposure to polluted urban environments for more than a century. Therefore, the coexistence of Roman cement mortars of widely different pore structures has not brought about any problems of incompatibility which field observations could reveal. The Roman cement repair materials have been found to develop pore structures similar to those of historic mortars. Therefore, they are in broad terms compatible with historic masonry or stuccoes. However, the porosity and strength of the repair materials can be controlled by a careful manipulation of the water-to-cement ratio of the mix to adapt them better to the properties of the host material. 相似文献
52.
Georgina L. Kent Brian Dawson Lars R. McNaughton Gregory R. Cox Louise M. Burke Peter Peeling 《Journal of sports sciences》2019,37(3):339-346
This investigation assessed the effect of dietary nitrate (NO3?) supplementation, in the form of beetroot juice (BR), on repeat-sprint performance in normoxia and normobaric hypoxia. 12 male team-sport athletes (age 22.3 ± 2.6 y, VO2peak 53.1 ± 8.7 mL.kg?1.min?1) completed three exercise trials involving a 10 min submaximal warm-up and 4 sets of cycling repeat-sprint efforts (RSE; 9 × 4 s) at sea level (CON), or at 3000 m simulated altitude following acute supplementation (140 mL) with BR (HYPBR; 13 mmol NO3?) or NO3–depleted BR placebo (HYPPLA). Peak (PPO) and mean (MPO) power output, plus work decrement were recorded during the RSE task, while oxygen consumption (VO2) was measured during the warm-up. There were no significant differences observed between HYPBR and HYPPLA for PPO or MPO; however, work decrement was reduced in the first RSE set in HYPBR compared with HYPPLA. There was a moderate effect for VO2 to be lower following BR at the end of the 10 min warm-up (ES = 0.50 ± 0.51). Dietary NO3? may not improve repeat-sprint performance in hypoxia but may reduce VO2 during submaximal exercise. Therefore, BR supplementation may be more effective for performance improvement during predominantly aerobic exercise. 相似文献
53.
Sam Robertson Bart Spencer Nicole Back Damian Farrow 《Journal of sports sciences》2019,37(11):1280-1285
Representative learning design provides a framework for the extent to which practice simulates key elements of a performance setting. Improving both the measurement and analysis of representative learning design would allow for the refinement of sports training environments that seek to replicate competition conditions and provide additional context to the evaluation of athlete performance. Using rule induction, this study aimed to develop working models for the determination of high frequency, representative events in Australian Rules football kicking. A sample of 9005 kicks from the 2015 Australian Football League season were categorised and analysed according to the following constraints: type of pressure, kick distance, possession source, time in possession, velocity and kick target. The Apriori algorithm was used to develop two models. The first consisted of 10 rules containing the most commonly occurring constraint sets occurring during the kick in AF, with support values ranging from 0.15 to 0.22. None of the rules contained more than three constraints and confidence values ranged from 0.63 to 0.84. The second model considered ineffective and effective kick outcomes and displayed 70% classification accuracy. This research provides a measurement approach to determine the degree of representativeness of sports practice and is directly applicable to various team sports. 相似文献
54.
Calogero Guccio Domenico Lisi Marco Martorana Anna Mignosa 《Journal of Cultural Economics》2017,41(2):129-154
The relationship between culture and tourism has been widely investigated from different perspectives. A large strand of literature studies the role of cultural heritage to attract tourists, while a rich bulk of studies on cultural participation investigates the impact of tourism flows on the demand for culture. Another aspect worth investigating relates to the link between cultural participation and the performance of tourism destinations (TDs), as a higher cultural participation in an area could boost the performance in the management of tourism resources. However, so far, this issue has been disregarded in the literature, and this paper aims at filling this gap. Specifically, it studies the effect of cultural participation on TDs’ performance using a conditional efficiency approach that ensures robust inference on the role of environmental factors. We employ data on the Italian regions for the period 2004–2010, and we explore the role of cultural participation for tourism by using several indicators. Our findings offer empirical support to the positive role of cultural participation and, thus, suggest that public cultural policies might also boost the efficiency of the tourism sector. 相似文献
55.
In Western societies scientists are increasingly expected to seek media exposure and cooperate with industry. Little attention
has been given to the way such expectations affect the role of scientific experts in society. To investigate scientists’ own
perspectives on these issues eight exploratory, in-depth interviews were conducted in Denmark with reputable nutrition scientists.
Additionally, eight interviews were held with ‘key informants’ from the field of nutrition policy. It was found that nutrition
scientists experience two dilemmas: first, between their aspiration to make a collective impact on public health and the powerful
incentives of each to appear frequently in the media with new messages; second, between their need to cooperate with the food
industry for financial reasons and their fear that this may compromise their independence and scientific integrity. It is
argued that the dilemmas identified in this study should be dealt with openly by the relevant groups of scientists. 相似文献
56.
Museums,schools and geographies of cultural value 总被引:1,自引:0,他引:1
This article explores a paradox and a possibility that have emerged from two pieces of policy-related research concerning educational use of museums within England. The paradox relates to the use of museums which, whilst widely perceived as rather elitist institutions, appear from a postcode analysis of school visits to museums to be visited by large numbers of schools located in areas of social deprivation. The present analysis further explores this paradox, drawing on revised postcode analysis and governmental indices of multiple deprivation and income deprivation affecting children. The analysis supports the contention that museums attracted visits from schools located in areas with some of the highest levels of deprivation, although it suggests that this result needs to be considered in relation to regional differences in areas of social deprivation, the location of museums and the differences between individual and area-based measures of deprivation. Attention is then drawn to the potential of considering museums through a geographical perspective, and specifically through Foucault's notions of primary, secondary and tertiary spatializations. It is argued that primary spatializations encompasses how museums are conceptualized and classified; secondary spatializations concern how various elements of museums are articulated together; and tertiary spatializations relate to the placement of museums in wider societal contexts and processes. It is suggested that the postcode analysis of school visits points both to the significance of considering tertiary spatializations relating to the social circumstances of museum visitors but also raised questions concerning primary spatializations of museums. Attention is drawn to changes in the classification and grouping of museums, and how these often encompass geographically based criteria related to the social reach of museums. The article ends by considering the degree to which museums might seek to further change their primary spatialization to reflect tertiary spatializations relating to cultural value. 相似文献
57.
58.
Efthimiadou A Asimakopoulos B Nikolettos N Giatromanolaki A Sivridis E Lialiaris TS Papachristou DN Kontoleon E 《Journal of sports sciences》2006,24(8):849-854
Although angiogenetic therapy using recombinant growth factors holds much hope for the treatment of ischaemic diseases, there are still many unanswered questions, including the method of administration, the correct dose of these factors, and the duration of the therapeutic approach. Exercise has also been suggested to induce neovascularizaiton in muscles. We evaluated the angiogenetic effects of the intramuscular administration of basic-fibroblast growth factor (b-FGF) and acidic-fibroblast growth factor (a-FGF) in rat heart, compared with rats who exercised daily. In conclusion, both the intramuscular administration of b-FGF and exercise increased significantly angiogenesis in the heart in contrast to the intramuscular administration of a-FGF, which was ineffective. 相似文献
59.
A study is made of separability conditions for the Helmholtz and Laplace equations. Attention is confined to the most useful case for physical applications; namely,
- 1.
- (a) The coordinate system is either cylindrical or it has rotational symmetry, and 相似文献
60.