The muscles semitendinosus (ST) and psoas major (PM) were removed from chilled young bull carcasses 24 h after slaughter and stored at 4 °C. At the 1st, 6th and 12th day of post-mortem ageing the chemical composition (moisture, fat, protein, collagen) and contents of free, immobilized and unfreezable water in the muscles were estimated. The muscle steaks were boiled at 100 °C, roasted at 170 °C or fried at 160 °C to an internal temperature of 75 °C, and the amounts of total, free, immobilized, and unfreezable water in heated muscles were evaluated. The unfreezable water was estimated by DSC. In the raw muscles immobilized water constituted 74–75%, free water 16.6–17.6% and unfreezable water 7–8% of the total water. Independent of time of ageing, PM muscle contained significantly more free water than ST muscle. During post-mortem ageing, changes in free, immobilized and unfreezable water in muscles were not significant. The level of free water was highest in boiled and least in fried meat, however the amount of immobilized water was highest in fried and lowest in boiled meat. The amount of unfreezable water in muscles heated after 12 days of post-mortem ageing decreased. 相似文献
The IMPROVE (Interagency Monitoring of PROtected Visual Environments) network monitors the attenuation of light by PM2.5 samples (fine particulate matter, Daero = 2.5 μm) routinely collected on polytetrafluoroethylene (PTFE) filters throughout the United States. The results of this measurement have long been reported as an indicator of absorption, with no rigorous calibration as such. Filter-based absorption measurements more conventionally employ optically thick quartz- or glass-fiber collection media, for which a substantial calibration literature offers algorithms to correct for particle scattering and filter loading effects. PTFE membranes are optically thinner and less homogeneous than the fiber media, but they avoid interference from adsorbed organic gases that is associated with quartz and glass fiber media. IMPROVE's measurement system is a hybrid of integrating sphere and integrating plate that records the light backscattered as well as transmitted by each filter. This article introduces and validates a theory-based model for calibration and data reduction that accounts for particle scattering effects as well as variations in filter optics. Tests based on historical analyses of field blanks and recent reanalyses of archived samples establish that the current system has operated with a stable calibration since 2003.
The newly calibrated IMPROVE absorption values correlate strongly with the refractory carbon fraction reported by thermal-optical analysis as “elemental” (EC). EC is sometimes treated as the only significant light absorber in PM2.5, but the general decline observed between 2005 and 2014 in IMPROVE EC was not accompanied by a comparable decline in IMPROVE absorption. Absorption also exhibits a distinct association with Fe concentrations, which at IMPROVE sites are attributable mainly to mineral dusts and have generally held steady or risen since 2003. An increased relative contribution by mineral dusts can explain some, but not all, of the observed difference between recent absorption and EC trends. 相似文献
Highly ordered hexagonal nanopatterns of gold clusters on glass substrates were used as anchoring points for the specific attachment of fluorescence dyes and proteins labeled with fluorescence dyes. Thiol- or disulfide-containing linker molecules were used for the binding to the gold dots. In order to ensure specific binding on the gold dots only, the surface area in between the dots was protected against unspecific adsorption. For the attachment of polar low-molecular-weight fluorescence dyes, an octadecyltrichlorosilane self-assembled monolayer was prepared on the surface in between the gold dots, whereas a layer prepared from star-shaped poly(ethylene oxide-stat-propylene oxide) prepolymers was used to prevent unspecific adsorption of proteins between the gold dots. Fluorescence microscopy proved the specific binding of the dyes as well as of the proteins. Scanning force microscopy studies show that each gold dot is only capable of binding one protein at a time. 相似文献
Measurement in ergonomics science has not kept pace with theorizing. As a result, it is rare to find measures of human performance that are simultaneously objective, quantitative, sensitive, and theoretically grounded. This article proposes a new set of measures, based on the abstraction hierarchy (AH) framework, that satisfies all of these criteria. Each level of the AH can be used to define a quantitative state space that can serve as a frame of reference for objective measurement. These state spaces are complementary because they provide different views of the same human-environment behaviour. Collectively, this set of measures can be used to determine if a participant is strongly or weakly coupled to functional or physical distal properties of the work domain. Data from a longitudinal study are used as a case study to test the value of these novel measures. The empirical results show that these AH-based measures provide unique insight into participants' behaviour that was not revealed by many, more traditional measures of performance. Because it is theoretically grounded, the set of measures proposed here has the potential to be generalized to diverse work domains for which it is possible to develop an AH representation. 相似文献
The purpose of this paper is to present a philosophical aspect of the ecology of human-machine systems by exploring the potential application of the basic pattern referred to as the golden section to workplace design and human body dimensions. Studies of stairway and industrial knife designs confirm that subjects prefer workplace and tool dimensions that are related to their human body segment lengths. In this paper, it is suggested that for each task or equipment there are different body segments which should be considered as a transitional element harmonizing a human body with its workplace. Hence, for a knife design - grip size circumference and blade length, for stairway design - length of foot and height of a riser. The psychophysical assessments affirm an existence of the golden section in workplace/tool design as a preferred design harmonizing an individual's body dimensions with work demands. 相似文献
The symbol grounding problem (SGP), which remains difficult for AI and philosophy of information, was recently scrutinised by Taddeo and Floridi (Solving the symbol grounding problem: A critical review of fifteen years of research. Journal of Experimental & Theoretical Artificial Intelligence, 17, 419–445, 2005; A praxical solution of the symbol grounding problem. Minds and machines, 17, 369–389, doi:10.1007/s11023-007-9081-32005, 2007). However, their own solution to SGP, underwritten by Action-based Semantics, although different from other solutions, does not seem to be satisfactory. Moreover, it does not satisfy the authors' principle, which they dub ‘Zero Semantic Commitment Condition’. In this paper, Taddeo and Floridi's solution is criticised in particular because of the excessively liberal relationship between symbols and internal states of agents, which is conceived in terms of levels of abstraction. Also, the notion of action seems to be seriously defective in their theory. Due to the lack of the possibility of symbols to misrepresent, the grounded symbols remain useless for the cognitive system itself, and it is unclear why they should be grounded in the first place, as the role of grounded symbols is not specified by the proposed solution. At the same time, it is probably one of the best-developed attempts to solve SGP and shows that naturalised semantics can benefit from taking artificial intelligence seriously. 相似文献
Copper (Cu) is an essential element involved in various metabolic processes in plants, but at concentrations above the threshold level, it becomes a potential stress factor. The effects of two different cytokinins, kinetin (KIN) and 6-benzylaminopurine (BAP), on chlorophyll a fluorescence parameters, stomatal responses and antioxidation mechanisms in castor (Ricinus communis L.) under Cu2+ toxicity was investigated. Ricinus communis plants were exposed to 80 and 160 μM CuSO4 added to the growth medium. Foliar spraying of 15 μM KIN and BAP was carried out on these seedlings. The application of these cytokinins enhanced the tissue water status, chlorophyll contents, stomatal opening and photosynthetic efficiency in the castor plants subjected to Cu2+ stress. The fluorescence parameters, such as Fm, Fv/Fo, Sm, photochemical and non-photochemical quantum yields, energy absorbed, energy trapped and electron transport per cross-sections, were more efficiently modulated by BAP application than KIN under Cu2+ toxicity. There was also effective alleviation of reactive oxygen species by enzymatic and non-enzymatic antioxidation systems, reducing the membrane lipid peroxidation, which brought about a relative enhancement in the membrane stability index. Of the various treatments, 80 µM CuSO4 + BAP recorded the highest increase in photosynthetic efficiency compared to other cytokinin treatments. Therefore, it can be concluded that BAP could effectively alleviate the detrimental effects of Cu2+toxicity in cotyledonary leaves of R. communis by effectively modulating stomatal responses and antioxidation mechanisms, thereby enhancing the photosynthetic apparatus’ functioning. 相似文献
This paper presents mechanochemical synthesis as an alternative to the traditional high-temperature synthesis of advanced electrotechnical ceramic materials with a perovskite-type structure. The reaction conditions for high-energy ball milling, e.g. reaction environment, energy of milling and additives to BaTiO3 such as metallic iron or zirconia from the exfoliation of the milling vessel and grinding media are discussed. 相似文献