Using autocorrelation information of the pseudorange errors generated by se- lective availability (SA) frequency dithering, we have constructed a simple first order stochas- tic model for SA effects. This model has be...Using autocorrelation information of the pseudorange errors generated by se- lective availability (SA) frequency dithering, we have constructed a simple first order stochas- tic model for SA effects. This model has been used in a Kalman filter to account for the stochastic behavior of SA dithering in estimating satellite clock information in wide area dif- ferential GPS. We have obtained fifteen percent improvement in the user positioning using the correlation information on the satellite clock information in a Kalman filter, when comparing the results obtained using a regular least square estimation.展开更多
Background: While mental health among collegiate athletes is receiving increased attention, research on factors surrounding collegiate athletes' decision to seek mental health services is limited. The goal of the ...Background: While mental health among collegiate athletes is receiving increased attention, research on factors surrounding collegiate athletes' decision to seek mental health services is limited. The goal of the present review was to analyze and synthesize the current literature concerning collegiate athletes' utilization of mental health services, including the facilitators of and barriers to use of these services.Methods: The analysis was guided and organized using a socio-ecological framework, which considered the unique context in which collegiate athletes study and perform. A total of 21 articles, published between 2005 and 2016, which concern U.S. collegiate athletes' mental health services utilization(MHSU) were selected and included for the final analysis. Conceptualizations and operationalizations of MHSU were compared and contrasted. Facilitators of and barriers to athletes MHSU were examined and summarized while appropriately considering the proximity of each factor(facilitator or barrier) to the athletes.Results: Results showed variations in conceptualizations and operationalizations of MHSU in the articles analyzed, which made interpretation and cross comparison difficult. Collegiate athletes are willing to utilize mental health services, but gender, perceived stigma, peer norms—for athletes and coaches—plus service availability impact their MHSU.Conclusion: Key stakeholders, administrators, and public health officials should partner to eliminate MHSU barriers, support facilitators, and generally empower collegiate athletes to actively manage their mental health.展开更多
In China, the income tax of enterprise is very different between foreign funded enterprises and other domestic enterprises. It is believed that this discrimination is harmful to the entire economy. So there is a refor...In China, the income tax of enterprise is very different between foreign funded enterprises and other domestic enterprises. It is believed that this discrimination is harmful to the entire economy. So there is a reform in the tax system to build a uniform enterprise income tax. This is a significant reform in China's tax system, so every decision about this have to count the cost and the benefit carefully. The author has introduced the Computable General Equilibrium (CGE) to simulate this new tax system and value its benefit and cost. There are two different models in the paper; they are of different assumptions and for different purposes. Model I is a static CGE model and model II is a Ramsey Dynamic model. The static model is mainly used for comparative static approach to examine how the tax reform will change the endogenous variables. According to the results of the model, more goods will be produced by both of the DFEs and FIEs after the tax reform in the medium and low tax effective tax rate situations. If the nominal tax rates decrease 24.24% (from 33% to 25%), the enterprise income tax will only reduce 19.36% and the total tax revenue will only reduce 1.911%. The dynamic model will concentrate on the costs and benefits during the transition. From the results of the model, a lower tax rate will increase the level of investment, capital stock, capital prices, wage rate and also the growth rates through transition. If the capital tax rates are changed gradually, the fluctuating of transition will be smoothed a little.展开更多
Fatty acids(FAs) in sediment collected from three different stations in the Yellow Sea and the East China Sea were analyzed for their distributions and to determine evidence of harmful algal blooms in the sediment cor...Fatty acids(FAs) in sediment collected from three different stations in the Yellow Sea and the East China Sea were analyzed for their distributions and to determine evidence of harmful algal blooms in the sediment core.Less diverse FAs were found in the Yellow Sea(YS) station,whereas in the two stations of the East China Sea(ECS) the FAs were more diverse.Concentrations of some FA species in the two ECS stations displayed an occasional surge in their vertical profile.The highest concentration of FAs was found in the surface layer of station QT3(43.28 μg g^(-1)).Monounsaturated FAs were more susceptible to degradation compared to their saturated counterparts,and changes of 16:0,18:2 and 20:5 accounted for the most variability in total concentrations of FAs as those species made up most of the quantified FAs.The origins of the major fraction of FAs were attributed to autotrophic sources,and bacterial FAs accounted for only a small fraction of the total FAs in the region.Nutrient availability was a possible regulating factor controlling bacteria abundances in marine sediments in the ECS and the YS.A principal component analysis(PCA) was applied to analyze the FA dataset and to reveal the principal environmental factors that control the composition of FAs in the sediments.PC2,which explains 15% of the variance,was estimated to reflect the diagenetic effects on the FA compositional changes in sediments influenced by bacterial degradation.展开更多
In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin (Mb) were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood ...In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin (Mb) were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood (ML), neighbor joining (NJ), unweighted pair group method with arithmetic means (UPGMA) and maximum parsimony (MP) methods in comparison with the conventional molecular markers, mitochondrial cytochrome b (cyt-b) and cytochrome c oxidase subunit I (COI). The phylogenetic trees drawn based on Mb sequences were similar to those by the traditional classification based on the other molecular markers. The primary and secondary structures, as well as the modeled tertiary structures of Mbs were similar to each other, but were clearly distinguishable among those species. Such differences in structure would be associated with adaptation of Mb molecule to the physiological conditions of each species. These results suggest that Mb can be a molecular marker for the phylogenetic relationship of fish.展开更多
Educational achievement and age correlatives may have significant bearings on generation, maintenance, and sustenance of environment to disseminate education for comprehensive development of learners as permeation of ...Educational achievement and age correlatives may have significant bearings on generation, maintenance, and sustenance of environment to disseminate education for comprehensive development of learners as permeation of learning and its diffusion rate may vary depending upon different achievements on literacy scale for different age groups. More so, for disable learners as such learners need additional initiatives and assisting environment of even more literate fellow beings constituting surroundings. From this perspective, this paper makes a descriptive analytical effort to present census (2011) results in evaluating overall literacy position and that for disable ones alongwith environment availability through simple statistical tools展开更多
The climate,mainly the water availability and temperature,drives the renewal of biomass inseasonal forest ecosystem,and the greenness and leaf area of its canopy are responsive climate variations.This study verified ...The climate,mainly the water availability and temperature,drives the renewal of biomass inseasonal forest ecosystem,and the greenness and leaf area of its canopy are responsive climate variations.This study verified models to explain the phenomenon of leaf production and deciduousness by time,with LAI(Leaf Area Index),NDVI(Normalized Difference VegetationIndex)and climate variables,on period 2011-2016. The data were obtained in satellite images and in plots installed at forestmonitoring sites,visited monthly.The analysis incorporated the water balance.Three equations were compared,two alreadypublished and the equation that was adjusted in this work.The model was improved and validated with new variables and data.It is possible to estimate the fall and renew of leaves biomass in semideciduous forests with reasonable precision.展开更多
A large amount of palm oil mill effluent is one of the issues faced by palm oil producers in Indonesia. To alleviate the environmental pollution, it is necessary to reduce the problem by using it as a liquid organic f...A large amount of palm oil mill effluent is one of the issues faced by palm oil producers in Indonesia. To alleviate the environmental pollution, it is necessary to reduce the problem by using it as a liquid organic fertilizer. A pot experiment to determine the effects of mill effluent on growth of palm oil seedlings (Elaeis guineensis Jacq.), availability and uptake of macronutrients was conducted in Tandun Plantation Unit, province of Riau, Indonesia. The experiment used a randomized block design, consisting nine combinations of mill effluent doses (3.2, 6.4 and 9.6 L) and recommended fertilizer doses (100%, 75%, 50% NPKMg) in 20 kg soil and one control. The experiment was replicated three times. The results showed that plant height, stem diameter and number of fronds of palm oil seedlings at 26 weeks after planting (WAP) were significantly affected by application of 9.6 L mill effluent with 50%-75% NPKMg, The enhancement of soil organic C (Co,g) content, soil pH and cation exchange capacity due to the application of 9.6 L mill effluent combined with 50% NPKMg caused the availability of soil P and total N (Ntot) increased significantly, while exchangeable K was affected by application of 6.4 L mill effluent combined with 100% NPKMg. All treatments did not affect soil exchangeable Mg. A positive correlation between availability of soil N, P, K and its uptake by palm oil seedlings at 26 WAP were indicated by r = 0.61, 0.63 and 0.57, respectively.展开更多
Motion event typology predicts that languages can be divided into either satellite-framed, verb-framed or serial-framed languages. However, an increasing number of studies show that languages within the same type pred...Motion event typology predicts that languages can be divided into either satellite-framed, verb-framed or serial-framed languages. However, an increasing number of studies show that languages within the same type predispose their speakers to describe motion events differently. Based on the narrative behavior of 15 native speakers, we provide evidence that suggests Tunisian Arabic (TA) is an untypical verb-framed language. One the one hand, TA conflates motion and path meanings in the main verb, and native speakers adhere to the boundary-crossing constraint. On the other hand, the availability of a rich manner verb lexicon combined with the availability of mono-verbal clauses ready to be coordinated asyndetically, encourages TA speakers to attend to the manner of motion more often than reported for a typical verb-framed language (e.g., Spanish). Based on these fmdings, we conclude that predictions based on motion event typology are best considered as guidelines, and not as an accurate reflection of how motion meanings may be lexicalized and expressed in individual languages展开更多
Sunscreen application is a common strategy used to prevent the damage induced by UV radiations. In the last 30 years a variety of protective agents against UV exposure have been developed: physical filters, chemical ...Sunscreen application is a common strategy used to prevent the damage induced by UV radiations. In the last 30 years a variety of protective agents against UV exposure have been developed: physical filters, chemical filters and organic filters. Physical filters are the safest: they scatter and reflect UV rays, but are difficult to apply on the skin. Chemical filters are capable of absorbing these rays, they are cosmetically pleasant, but recent studies suggest a toxicological nature for some of these agents. Organic filters are the newest advance in sun products. Since 2003 the COLIPA Index [Europe] has regulated sun product availability on the market. In the USA, the FDA establishes the classification and the safety of sun products, which are considered topical medical drugs. This article summarizes the dermatologist's point of view, according to the patient's request, professional ethics and increasing offer of sun product.展开更多
In general, the energy storage in facilities to intermittent sources is provided by a battery of accumulators. Having found that the duration of life of chemical accumulators is strongly shortened in the northern regi...In general, the energy storage in facilities to intermittent sources is provided by a battery of accumulators. Having found that the duration of life of chemical accumulators is strongly shortened in the northern regions of Cameroon and that this has a considerable impact on the operating costs and the reliability of power plants to intermittent sources, this work proposes to find an alternative to these chemical accumulators rendered vulnerable by the high temperatures. It reviews all energy storage techniques and makes a choice (the CAES (compressed air energy storage)) based on thermal robustness. It proposes a new technique of restitution of the energy by producing an artificial wind from the compressed air. The feedback loop thus obtained by the compressor-tank-wind subsystem is studied from a series of manipulations and its efficiency is determined. To automate the operation of this system, a controller is required. The operating logic of the controller is provided in function of the precise states of the load, the tank and the natural sources.展开更多
With the development of high-speed railways in China,more than 2000 high-speed trains will be put into use.Safety and efficiency of railway transportation is increasingly important.We have designed a high availability...With the development of high-speed railways in China,more than 2000 high-speed trains will be put into use.Safety and efficiency of railway transportation is increasingly important.We have designed a high availability quadruple vital computer (HAQVC) system based on the analysis of the architecture of the traditional double 2-out-of-2 system and 2-out-of-3 system.The HAQVC system is a system with high availability and safety,with prominent characteristics such as fire-new internal architecture,high efficiency,reliable data interaction mechanism,and operation state change mechanism.The hardware of the vital CPU is based on ARM7 with the real-time embedded safe operation system (ES-OS).The Markov modeling method is designed to evaluate the reliability,availability,maintainability,and safety (RAMS) of the system.In this paper,we demonstrate that the HAQVC system is more reliable than the all voting triple modular redundancy (AVTMR) system and double 2-out-of-2 system.Thus,the design can be used for a specific application system,such as an airplane or high-speed railway system.展开更多
Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availab...Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availability. However, little is known about how lizard trophic ecology varies with elevation. In this study, we analyze diet, prey availability, prey selection, and trophic niche width in the lacertid lizard Psammodromus algirus along a 2,200-m elevational gradient in the Sierra Nevada (SE Spain). The analysis of fecal samples has shown that Orthoptera, Formicidae, Hemiptera, Coleoptera, and Araneae are the main prey, although, according to their abundance in pitfall traps, Formicidae and Coleoptera are rejected by the lizard whereas Orthoptera, Hemiptera, and Araneae are preferred. Prey abundance and diversity increase with elevation and diet subtly varies along with the elevational gradient. The consumption of Coleoptera increases with elevation probably as a consequence of the lizard foraging more in open areas while basking. The electivity for Araneae increases with elevation. Araneae are rejected in the lowlands--where they are rela- tively abundant--whereas, at high elevation, this lizard positively selects them, despite they being less abundant. The lizard trophic niche width expands with elevation due to concomitant greater prey diversity and hence this lizard feeds on more prey types in highlands. Although no sex difference in diet has been found, the trophic niche is broader in females than males. As a whole, alpine lizards show a trophic niche simitar to that found at lower elevat(ons, suggesting that P. algirus is well adapted to the harsh environment found in alpine areas.展开更多
Synthetic macrocyclic host molecules always play an essential role in the establishment and development of supramolecular chemistry. Along with the continuous interests in the study of classical macrocycles, recent de...Synthetic macrocyclic host molecules always play an essential role in the establishment and development of supramolecular chemistry. Along with the continuous interests in the study of classical macrocycles, recent decades have witnessed the emergence and rapid development of the chemistry and supramolecular chemistry of novel and functional macrocycles. Owing to their easy availability, a self-tunable V-shaped cavity resulted from 1,3-alternate conformation, and diversified electronic features steered by the interplay between heteroatom linkages and aromatic rings, heteracalixaromatics act as a type of versatile and powerful macrocyclic hosts in molecular recognition and fabrication of supramolecular systems. Very recently, by means of engineering the bond connectivity or the recombination of chemical bonds within heteracalixaromatics, we have devised coronarenes, a new generation of macrocycles. In this concise review, macrocyclic and supramolecular chemistry of coronarenes are summarized in the order of their syntheses, structural features, molecular recognition and self-assembly properties. In the last part of this article, personal perspectives on the study of macrocyclic and supramolecular chemistry will also be discussed.展开更多
Studying the causes of parasite geographic distribution is relevant to understand ecological and evolutionary processes that affect host populations as well as for species conservation. Temperature is one of the most ...Studying the causes of parasite geographic distribution is relevant to understand ecological and evolutionary processes that affect host populations as well as for species conservation. Temperature is one of the most important environmental variables affecting parasite distribution, as raising temperatures positively affect development, reproduction, and rate of transmission of both endo- and ectoparasites. In this context, it is generally accepted that, in mountains, parasite abundance decreases with elevation. However, empirical evidence on this topic is limited. In the present study, we analyzed the elevational variation of hemoparasites and ectoparasites of a lizard, Psammodromus algirus, along a 2,200-m elevational gradient in Sierra Nevada (SE Spain). As pre- dicted, ectoparasite (mites, ticks, mosquitoes, and sandflies) abundance decreased with elevation. However, hemoparasite prevalence and intensity in the lizard augmented with altitude, showing a pattern contrary to their vectors (mites). We suggest that tolerance to hemoparasites may increase with elevation as a consequence of lizards at high altitudes taking advantage of increased body condition and food availability, and reduced oxidative stress. Moreover, lizards could have been selected for higher resistance against hemoparasites at lowlands (where higher rates of replication are expected), thus reducing hemoparasite prevalence and load. Our findings imply that, in a scen- ario of climate warming, populations of lizards at high elevation may face increased abundance of ectoparasites, accompanied with strong negative effects.展开更多
基金Project Supported by the Hong Kong Polytechnic University Research Grand(No. 353/392
文摘Using autocorrelation information of the pseudorange errors generated by se- lective availability (SA) frequency dithering, we have constructed a simple first order stochas- tic model for SA effects. This model has been used in a Kalman filter to account for the stochastic behavior of SA dithering in estimating satellite clock information in wide area dif- ferential GPS. We have obtained fifteen percent improvement in the user positioning using the correlation information on the satellite clock information in a Kalman filter, when comparing the results obtained using a regular least square estimation.
文摘Background: While mental health among collegiate athletes is receiving increased attention, research on factors surrounding collegiate athletes' decision to seek mental health services is limited. The goal of the present review was to analyze and synthesize the current literature concerning collegiate athletes' utilization of mental health services, including the facilitators of and barriers to use of these services.Methods: The analysis was guided and organized using a socio-ecological framework, which considered the unique context in which collegiate athletes study and perform. A total of 21 articles, published between 2005 and 2016, which concern U.S. collegiate athletes' mental health services utilization(MHSU) were selected and included for the final analysis. Conceptualizations and operationalizations of MHSU were compared and contrasted. Facilitators of and barriers to athletes MHSU were examined and summarized while appropriately considering the proximity of each factor(facilitator or barrier) to the athletes.Results: Results showed variations in conceptualizations and operationalizations of MHSU in the articles analyzed, which made interpretation and cross comparison difficult. Collegiate athletes are willing to utilize mental health services, but gender, perceived stigma, peer norms—for athletes and coaches—plus service availability impact their MHSU.Conclusion: Key stakeholders, administrators, and public health officials should partner to eliminate MHSU barriers, support facilitators, and generally empower collegiate athletes to actively manage their mental health.
文摘In China, the income tax of enterprise is very different between foreign funded enterprises and other domestic enterprises. It is believed that this discrimination is harmful to the entire economy. So there is a reform in the tax system to build a uniform enterprise income tax. This is a significant reform in China's tax system, so every decision about this have to count the cost and the benefit carefully. The author has introduced the Computable General Equilibrium (CGE) to simulate this new tax system and value its benefit and cost. There are two different models in the paper; they are of different assumptions and for different purposes. Model I is a static CGE model and model II is a Ramsey Dynamic model. The static model is mainly used for comparative static approach to examine how the tax reform will change the endogenous variables. According to the results of the model, more goods will be produced by both of the DFEs and FIEs after the tax reform in the medium and low tax effective tax rate situations. If the nominal tax rates decrease 24.24% (from 33% to 25%), the enterprise income tax will only reduce 19.36% and the total tax revenue will only reduce 1.911%. The dynamic model will concentrate on the costs and benefits during the transition. From the results of the model, a lower tax rate will increase the level of investment, capital stock, capital prices, wage rate and also the growth rates through transition. If the capital tax rates are changed gradually, the fluctuating of transition will be smoothed a little.
基金supported by the National Key Research and Development Program of China(No.2016YFA0601302)the National Natural Science Foundation of China(No.41676067)+2 种基金the Fundamental Research Funds for the Central Universities(No.201762030)the National Natural Science Foundation for Creative Groups(No.41521064)the‘111’Program of Marine Chemistry(No.B13030)
文摘Fatty acids(FAs) in sediment collected from three different stations in the Yellow Sea and the East China Sea were analyzed for their distributions and to determine evidence of harmful algal blooms in the sediment core.Less diverse FAs were found in the Yellow Sea(YS) station,whereas in the two stations of the East China Sea(ECS) the FAs were more diverse.Concentrations of some FA species in the two ECS stations displayed an occasional surge in their vertical profile.The highest concentration of FAs was found in the surface layer of station QT3(43.28 μg g^(-1)).Monounsaturated FAs were more susceptible to degradation compared to their saturated counterparts,and changes of 16:0,18:2 and 20:5 accounted for the most variability in total concentrations of FAs as those species made up most of the quantified FAs.The origins of the major fraction of FAs were attributed to autotrophic sources,and bacterial FAs accounted for only a small fraction of the total FAs in the region.Nutrient availability was a possible regulating factor controlling bacteria abundances in marine sediments in the ECS and the YS.A principal component analysis(PCA) was applied to analyze the FA dataset and to reveal the principal environmental factors that control the composition of FAs in the sediments.PC2,which explains 15% of the variance,was estimated to reflect the diagenetic effects on the FA compositional changes in sediments influenced by bacterial degradation.
文摘In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin (Mb) were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood (ML), neighbor joining (NJ), unweighted pair group method with arithmetic means (UPGMA) and maximum parsimony (MP) methods in comparison with the conventional molecular markers, mitochondrial cytochrome b (cyt-b) and cytochrome c oxidase subunit I (COI). The phylogenetic trees drawn based on Mb sequences were similar to those by the traditional classification based on the other molecular markers. The primary and secondary structures, as well as the modeled tertiary structures of Mbs were similar to each other, but were clearly distinguishable among those species. Such differences in structure would be associated with adaptation of Mb molecule to the physiological conditions of each species. These results suggest that Mb can be a molecular marker for the phylogenetic relationship of fish.
文摘Educational achievement and age correlatives may have significant bearings on generation, maintenance, and sustenance of environment to disseminate education for comprehensive development of learners as permeation of learning and its diffusion rate may vary depending upon different achievements on literacy scale for different age groups. More so, for disable learners as such learners need additional initiatives and assisting environment of even more literate fellow beings constituting surroundings. From this perspective, this paper makes a descriptive analytical effort to present census (2011) results in evaluating overall literacy position and that for disable ones alongwith environment availability through simple statistical tools
文摘The climate,mainly the water availability and temperature,drives the renewal of biomass inseasonal forest ecosystem,and the greenness and leaf area of its canopy are responsive climate variations.This study verified models to explain the phenomenon of leaf production and deciduousness by time,with LAI(Leaf Area Index),NDVI(Normalized Difference VegetationIndex)and climate variables,on period 2011-2016. The data were obtained in satellite images and in plots installed at forestmonitoring sites,visited monthly.The analysis incorporated the water balance.Three equations were compared,two alreadypublished and the equation that was adjusted in this work.The model was improved and validated with new variables and data.It is possible to estimate the fall and renew of leaves biomass in semideciduous forests with reasonable precision.
文摘A large amount of palm oil mill effluent is one of the issues faced by palm oil producers in Indonesia. To alleviate the environmental pollution, it is necessary to reduce the problem by using it as a liquid organic fertilizer. A pot experiment to determine the effects of mill effluent on growth of palm oil seedlings (Elaeis guineensis Jacq.), availability and uptake of macronutrients was conducted in Tandun Plantation Unit, province of Riau, Indonesia. The experiment used a randomized block design, consisting nine combinations of mill effluent doses (3.2, 6.4 and 9.6 L) and recommended fertilizer doses (100%, 75%, 50% NPKMg) in 20 kg soil and one control. The experiment was replicated three times. The results showed that plant height, stem diameter and number of fronds of palm oil seedlings at 26 weeks after planting (WAP) were significantly affected by application of 9.6 L mill effluent with 50%-75% NPKMg, The enhancement of soil organic C (Co,g) content, soil pH and cation exchange capacity due to the application of 9.6 L mill effluent combined with 50% NPKMg caused the availability of soil P and total N (Ntot) increased significantly, while exchangeable K was affected by application of 6.4 L mill effluent combined with 100% NPKMg. All treatments did not affect soil exchangeable Mg. A positive correlation between availability of soil N, P, K and its uptake by palm oil seedlings at 26 WAP were indicated by r = 0.61, 0.63 and 0.57, respectively.
文摘Motion event typology predicts that languages can be divided into either satellite-framed, verb-framed or serial-framed languages. However, an increasing number of studies show that languages within the same type predispose their speakers to describe motion events differently. Based on the narrative behavior of 15 native speakers, we provide evidence that suggests Tunisian Arabic (TA) is an untypical verb-framed language. One the one hand, TA conflates motion and path meanings in the main verb, and native speakers adhere to the boundary-crossing constraint. On the other hand, the availability of a rich manner verb lexicon combined with the availability of mono-verbal clauses ready to be coordinated asyndetically, encourages TA speakers to attend to the manner of motion more often than reported for a typical verb-framed language (e.g., Spanish). Based on these fmdings, we conclude that predictions based on motion event typology are best considered as guidelines, and not as an accurate reflection of how motion meanings may be lexicalized and expressed in individual languages
文摘Sunscreen application is a common strategy used to prevent the damage induced by UV radiations. In the last 30 years a variety of protective agents against UV exposure have been developed: physical filters, chemical filters and organic filters. Physical filters are the safest: they scatter and reflect UV rays, but are difficult to apply on the skin. Chemical filters are capable of absorbing these rays, they are cosmetically pleasant, but recent studies suggest a toxicological nature for some of these agents. Organic filters are the newest advance in sun products. Since 2003 the COLIPA Index [Europe] has regulated sun product availability on the market. In the USA, the FDA establishes the classification and the safety of sun products, which are considered topical medical drugs. This article summarizes the dermatologist's point of view, according to the patient's request, professional ethics and increasing offer of sun product.
文摘In general, the energy storage in facilities to intermittent sources is provided by a battery of accumulators. Having found that the duration of life of chemical accumulators is strongly shortened in the northern regions of Cameroon and that this has a considerable impact on the operating costs and the reliability of power plants to intermittent sources, this work proposes to find an alternative to these chemical accumulators rendered vulnerable by the high temperatures. It reviews all energy storage techniques and makes a choice (the CAES (compressed air energy storage)) based on thermal robustness. It proposes a new technique of restitution of the energy by producing an artificial wind from the compressed air. The feedback loop thus obtained by the compressor-tank-wind subsystem is studied from a series of manipulations and its efficiency is determined. To automate the operation of this system, a controller is required. The operating logic of the controller is provided in function of the precise states of the load, the tank and the natural sources.
基金Project(No.2009BAG12A05) supported by the National Key Technology R&D Program of China
文摘With the development of high-speed railways in China,more than 2000 high-speed trains will be put into use.Safety and efficiency of railway transportation is increasingly important.We have designed a high availability quadruple vital computer (HAQVC) system based on the analysis of the architecture of the traditional double 2-out-of-2 system and 2-out-of-3 system.The HAQVC system is a system with high availability and safety,with prominent characteristics such as fire-new internal architecture,high efficiency,reliable data interaction mechanism,and operation state change mechanism.The hardware of the vital CPU is based on ARM7 with the real-time embedded safe operation system (ES-OS).The Markov modeling method is designed to evaluate the reliability,availability,maintainability,and safety (RAMS) of the system.In this paper,we demonstrate that the HAQVC system is more reliable than the all voting triple modular redundancy (AVTMR) system and double 2-out-of-2 system.Thus,the design can be used for a specific application system,such as an airplane or high-speed railway system.
文摘Mountains imply enormous environmental variation, with alpine habitats entailing harsh environ- ments, especially for ectotherms such as lizards. This environmental variability also may imply variation in prey availability. However, little is known about how lizard trophic ecology varies with elevation. In this study, we analyze diet, prey availability, prey selection, and trophic niche width in the lacertid lizard Psammodromus algirus along a 2,200-m elevational gradient in the Sierra Nevada (SE Spain). The analysis of fecal samples has shown that Orthoptera, Formicidae, Hemiptera, Coleoptera, and Araneae are the main prey, although, according to their abundance in pitfall traps, Formicidae and Coleoptera are rejected by the lizard whereas Orthoptera, Hemiptera, and Araneae are preferred. Prey abundance and diversity increase with elevation and diet subtly varies along with the elevational gradient. The consumption of Coleoptera increases with elevation probably as a consequence of the lizard foraging more in open areas while basking. The electivity for Araneae increases with elevation. Araneae are rejected in the lowlands--where they are rela- tively abundant--whereas, at high elevation, this lizard positively selects them, despite they being less abundant. The lizard trophic niche width expands with elevation due to concomitant greater prey diversity and hence this lizard feeds on more prey types in highlands. Although no sex difference in diet has been found, the trophic niche is broader in females than males. As a whole, alpine lizards show a trophic niche simitar to that found at lower elevat(ons, suggesting that P. algirus is well adapted to the harsh environment found in alpine areas.
基金supported by the National Natural Science Foundation of China (21732004, 21421064, 91427301, 21132005)Tsinghua University
文摘Synthetic macrocyclic host molecules always play an essential role in the establishment and development of supramolecular chemistry. Along with the continuous interests in the study of classical macrocycles, recent decades have witnessed the emergence and rapid development of the chemistry and supramolecular chemistry of novel and functional macrocycles. Owing to their easy availability, a self-tunable V-shaped cavity resulted from 1,3-alternate conformation, and diversified electronic features steered by the interplay between heteroatom linkages and aromatic rings, heteracalixaromatics act as a type of versatile and powerful macrocyclic hosts in molecular recognition and fabrication of supramolecular systems. Very recently, by means of engineering the bond connectivity or the recombination of chemical bonds within heteracalixaromatics, we have devised coronarenes, a new generation of macrocycles. In this concise review, macrocyclic and supramolecular chemistry of coronarenes are summarized in the order of their syntheses, structural features, molecular recognition and self-assembly properties. In the last part of this article, personal perspectives on the study of macrocyclic and supramolecular chemistry will also be discussed.
文摘Studying the causes of parasite geographic distribution is relevant to understand ecological and evolutionary processes that affect host populations as well as for species conservation. Temperature is one of the most important environmental variables affecting parasite distribution, as raising temperatures positively affect development, reproduction, and rate of transmission of both endo- and ectoparasites. In this context, it is generally accepted that, in mountains, parasite abundance decreases with elevation. However, empirical evidence on this topic is limited. In the present study, we analyzed the elevational variation of hemoparasites and ectoparasites of a lizard, Psammodromus algirus, along a 2,200-m elevational gradient in Sierra Nevada (SE Spain). As pre- dicted, ectoparasite (mites, ticks, mosquitoes, and sandflies) abundance decreased with elevation. However, hemoparasite prevalence and intensity in the lizard augmented with altitude, showing a pattern contrary to their vectors (mites). We suggest that tolerance to hemoparasites may increase with elevation as a consequence of lizards at high altitudes taking advantage of increased body condition and food availability, and reduced oxidative stress. Moreover, lizards could have been selected for higher resistance against hemoparasites at lowlands (where higher rates of replication are expected), thus reducing hemoparasite prevalence and load. Our findings imply that, in a scen- ario of climate warming, populations of lizards at high elevation may face increased abundance of ectoparasites, accompanied with strong negative effects.