Graphitized carbon foams(GFms)were prepared using mesophase pitch(MP)as a raw material by foaming(450℃),pre-oxidation(320℃),carbonization(1000℃)and graphitization(2800℃).The differences in structure and properties...Graphitized carbon foams(GFms)were prepared using mesophase pitch(MP)as a raw material by foaming(450℃),pre-oxidation(320℃),carbonization(1000℃)and graphitization(2800℃).The differences in structure and properties of GFms prepared from different MP precursors pretreated by ball milling or liquid phase extraction were investigated and compared,and semi-quantitative calculations were conducted on the Raman and FTIR spectra of samples at each preparation stage.Semi-quantitat-ive spectroscopic analysis provided detailed information on the structure and chemical composition changes of the MP and GFm de-rived from it.Combined with microscopic observations,the change from precursor to GFm was analyzed.The results showed that ball milling concentrated the distribution of aromatic molecules in the pitch,which contributed to uniform foaming to give a GFm with a uniform pore distribution and good properties.Liquid phase extraction helped remove light components while retaining large aromatics to form graphitic planes with the largest average size during post-treatment to produce a GFm with the highest degree of graphitization and the fewest open pores,giving the best compression resistance(2.47 MPa),the highest thermal conductivity(64.47 W/(m·K))and the lowest electrical resistance(13.02μΩ·m).Characterization combining semi-quantitative spectroscopic ana-lysis with microscopic observations allowed us to control the preparation of the MP-derived GFms.展开更多
The fracture properties of epoxy asphalt mixtures （EAM） are evaluated based on J-integral and ultimate strength. Totally 60 semi-circular bending （SCB）specimens cored from superpave gyratory compactor （SGC）with ...The fracture properties of epoxy asphalt mixtures （EAM） are evaluated based on J-integral and ultimate strength. Totally 60 semi-circular bending （SCB）specimens cored from superpave gyratory compactor （SGC）with three groups of notch depths are tested at the temperature of - 10 and 20 ℃. The experimental results reveal good repeatability in EAM characterization. The tensile strength ratio of SCB to the indirect tensile test （IDT） is at a range of 1.4 to 1.7, and the ultimate strength of EAM is exponentially dependent on the notch depths. At the test temperatures, the critical J-integral value of EAM is much higher than that of hot mix asphalt（ HMA） with thermoplastic asphalt binder. The response mode of EAM changes from ductile mode to brittle mode and the fracture energy increases 30% when temperature decreases from 20 to - 10℃, while its critical J-integral value decreases only 15%. It is concluded that EAM has better fracture resistance than thermo-plastic HMA; more fracture energy is needed to initiate cracks in EAM at low temperature, and the cracks propagate more rapidly than at room temperature.展开更多
AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis.METHODS: From 2001 to October 200...AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis.METHODS: From 2001 to October 2003, we studied GIB in 13 502 workers constructing the railroad on Mountain Tanggula which is 4905 m above the sea level. The incidence of GIB in workers at different altitudes was recorded. Endoscopy was performed when the workers evacuated to Golmud (2808 m) and Xining (2261 m). The available data on altitude GIB were analyzed.RESULTS: The overall incidence of GIB was 0.49% in 13 502 workers. The incidence increased with increasing altitude. The onset of symptoms in most patients was within three weeks after arrival at high altitude. Bleeding manifested as hematemesis, melaena or hematochezia, and might be occult. Endoscopic examination showed that the causes of altitude GIB included hemorrhage gastritis, gastric ulcer, duodenal ulcer, and gastric erosion. Experimental studies suggested that acute gastric mucosal lesion (AGML) could be induced by hypoxic and cold stress, which might be the pathogenesis of altitude GIB. Those who consumed large amount of alcohol, aspirin or dexamethasone were at a higher risk of developing GIB. Persons who previously suffered from peptic ulcer or high-altitude polycythemia were also at risk of developing GIB. Early diagnosis, evacuation, and treatment led to early recovery. CONCLUSION: GIB is a potentially life threatening disease, if it is not treated promptly and effectively. Early diagnosis, treatment and evacuation lead to an early recovery. Death due to altitude GIB can be avoided if early symptoms and signs are recognized.展开更多
Glaciers in the western Nyainqentanglha Range are an important source of water for social and economic development. Changes in their area were derived from two Chinese glacier inventories; one from the 197o 1：5o,ooo ...Glaciers in the western Nyainqentanglha Range are an important source of water for social and economic development. Changes in their area were derived from two Chinese glacier inventories; one from the 197o 1：5o,ooo scale Chinese Topographic Maps series and the other from Landsat TM/ETM＋ images acquired in 2009. Analyses also included boundaries from 2000 and 2014 Landsat TM/ETM＋ images. A continuing and accelerating shrinkage of glaciers occurred here from 1970 to 2014, with glacier area decreasing by 244.38±29.48 km^2 （27.4%±3.3%） or 0.62%±0.08% a^-1. While this is consistent with a changing climate, local topographic parameters, such as altitude, slope, aspect and debris cover, are also important influences. Recession is manifested by a rise in the elevation of the glacier terminus. The shrinkage of glaciers with NE, N and NW orientations exceeded that of other aspects, and glaciers with SE and S orientations experienced less shrinkage. Changes in the average positive difference of glaciation （PDG） show that the western Nyainqentanglha Range has unfavorable conditions for glacier maintenance which is being exacerbated by a warming climate since 1970.展开更多
Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are character...Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue （conspecific skin extract） alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water （control） and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks （12 and 14） of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1） the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2） this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 （1）： 36-42, 2010].展开更多
Since the 1980s and 1980s, a new trend in the discipline of Translation Studies has emerged beyond the boundaries of Europe. Scholars from post-colonial nations like Canada, India, China, Africa, and Latin America hav...Since the 1980s and 1980s, a new trend in the discipline of Translation Studies has emerged beyond the boundaries of Europe. Scholars from post-colonial nations like Canada, India, China, Africa, and Latin America have argued that translation was used in the past as a means of depriving the colonised people of their voice. In the colonial structure, the hegemonic culture used to dominate, making the others subservient. Translation in the colonial period reflected that hierarchy. In this light, decades after the independence of India, translation from a reverse direction, that is, rendering popular English texts in minority languages, may be seen as a process of＂writing back＂. Even if the original text concerned is not a ＂political＂ writing, and the translation is apparently meant for ＂safer-zones＂ such as ＂young students＇ literature＂, a tendency of claiming cultural equality, overlapping the translator＇s own cultural and literary heritage with the original author＇s, can be discovered. This paper attempts to focus on these issues in a particular text—the 1995 Bengali translation of Marie Corelli＇s 1921 science-fiction, The Secret Power. The purpose of this paper is to explore how Sudhindranath Raha has intermingled Biblical references and Western contexts with allusions to Indian culture and Sanskrit literature, thereby claiming a space for mutual understanding and respect between two cultures.展开更多
文摘Graphitized carbon foams(GFms)were prepared using mesophase pitch(MP)as a raw material by foaming(450℃),pre-oxidation(320℃),carbonization(1000℃)and graphitization(2800℃).The differences in structure and properties of GFms prepared from different MP precursors pretreated by ball milling or liquid phase extraction were investigated and compared,and semi-quantitative calculations were conducted on the Raman and FTIR spectra of samples at each preparation stage.Semi-quantitat-ive spectroscopic analysis provided detailed information on the structure and chemical composition changes of the MP and GFm de-rived from it.Combined with microscopic observations,the change from precursor to GFm was analyzed.The results showed that ball milling concentrated the distribution of aromatic molecules in the pitch,which contributed to uniform foaming to give a GFm with a uniform pore distribution and good properties.Liquid phase extraction helped remove light components while retaining large aromatics to form graphitic planes with the largest average size during post-treatment to produce a GFm with the highest degree of graphitization and the fewest open pores,giving the best compression resistance(2.47 MPa),the highest thermal conductivity(64.47 W/(m·K))and the lowest electrical resistance(13.02μΩ·m).Characterization combining semi-quantitative spectroscopic ana-lysis with microscopic observations allowed us to control the preparation of the MP-derived GFms.
基金Specialized Research Fund for the Doctoral Program ofHigher Education(No20070286009)the Preresearch Project of the National Natural Science Foundation of Southeast University ( NoKJ2009388)
文摘The fracture properties of epoxy asphalt mixtures （EAM） are evaluated based on J-integral and ultimate strength. Totally 60 semi-circular bending （SCB）specimens cored from superpave gyratory compactor （SGC）with three groups of notch depths are tested at the temperature of - 10 and 20 ℃. The experimental results reveal good repeatability in EAM characterization. The tensile strength ratio of SCB to the indirect tensile test （IDT） is at a range of 1.4 to 1.7, and the ultimate strength of EAM is exponentially dependent on the notch depths. At the test temperatures, the critical J-integral value of EAM is much higher than that of hot mix asphalt（ HMA） with thermoplastic asphalt binder. The response mode of EAM changes from ductile mode to brittle mode and the fracture energy increases 30% when temperature decreases from 20 to - 10℃, while its critical J-integral value decreases only 15%. It is concluded that EAM has better fracture resistance than thermo-plastic HMA; more fracture energy is needed to initiate cracks in EAM at low temperature, and the cracks propagate more rapidly than at room temperature.
基金Supported by the grant LS-CNNSF-30393130, and 973 Program 2006 CB 504100, CB708514, China
文摘AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis.METHODS: From 2001 to October 2003, we studied GIB in 13 502 workers constructing the railroad on Mountain Tanggula which is 4905 m above the sea level. The incidence of GIB in workers at different altitudes was recorded. Endoscopy was performed when the workers evacuated to Golmud (2808 m) and Xining (2261 m). The available data on altitude GIB were analyzed.RESULTS: The overall incidence of GIB was 0.49% in 13 502 workers. The incidence increased with increasing altitude. The onset of symptoms in most patients was within three weeks after arrival at high altitude. Bleeding manifested as hematemesis, melaena or hematochezia, and might be occult. Endoscopic examination showed that the causes of altitude GIB included hemorrhage gastritis, gastric ulcer, duodenal ulcer, and gastric erosion. Experimental studies suggested that acute gastric mucosal lesion (AGML) could be induced by hypoxic and cold stress, which might be the pathogenesis of altitude GIB. Those who consumed large amount of alcohol, aspirin or dexamethasone were at a higher risk of developing GIB. Persons who previously suffered from peptic ulcer or high-altitude polycythemia were also at risk of developing GIB. Early diagnosis, evacuation, and treatment led to early recovery. CONCLUSION: GIB is a potentially life threatening disease, if it is not treated promptly and effectively. Early diagnosis, treatment and evacuation lead to an early recovery. Death due to altitude GIB can be avoided if early symptoms and signs are recognized.
基金supported by the fundamental program from the Ministry of Science and Technology of China(MOST)(Grant No.2013FY111400)the National Natural Science Foundation of China(Grant No.41190084)+1 种基金the MOST Technology Oriented Project(Grant No.2012BAC19B07)The second Chinese Glacier Inventory was a product of the previous MOST Project(Grant No.2006FY110200)
文摘Glaciers in the western Nyainqentanglha Range are an important source of water for social and economic development. Changes in their area were derived from two Chinese glacier inventories; one from the 197o 1：5o,ooo scale Chinese Topographic Maps series and the other from Landsat TM/ETM＋ images acquired in 2009. Analyses also included boundaries from 2000 and 2014 Landsat TM/ETM＋ images. A continuing and accelerating shrinkage of glaciers occurred here from 1970 to 2014, with glacier area decreasing by 244.38±29.48 km^2 （27.4%±3.3%） or 0.62%±0.08% a^-1. While this is consistent with a changing climate, local topographic parameters, such as altitude, slope, aspect and debris cover, are also important influences. Recession is manifested by a rise in the elevation of the glacier terminus. The shrinkage of glaciers with NE, N and NW orientations exceeded that of other aspects, and glaciers with SE and S orientations experienced less shrinkage. Changes in the average positive difference of glaciation （PDG） show that the western Nyainqentanglha Range has unfavorable conditions for glacier maintenance which is being exacerbated by a warming climate since 1970.
基金provided by the Undergraduate Research Opportunities Program of Boston University
文摘Olfactory cues that indicate predation risk elicit a number of defensive behaviors in fishes, but whether they are sufficient to also induce morphological defenses has received little attention. Cichlids are characterized by a high level of morphological plasticity during development, and the few species that have been tested do exhibit defensive behaviors when exposed to alarm cues released from the damaged skin of conspecifics. We utilized young juvenile Nicaragua cichlids Hypsophrys nicaraguensis to test if the perception of predation risk from alarm cue （conspecific skin extract） alone induces an increased relative body depth which is a defense against gape-limited predators. After two weeks of exposure, siblings that were exposed to conspecific alarm cue increased their relative body depth nearly double the amount of those exposed to distilled water （control） and zebrafish Danio rerio alarm cue. We repeated our measurements over the last two weeks （12 and 14） of cue exposure when the fish were late-stage juveniles to test if the rate of increase was sustained; there were no differences in final dimensions between the three treatments. Our results show that 1） the Nicaragua cichlid has an innate response to conspecific alarm cue which is not a generalized response to an injured fish, and 2） this innate recognition ultimately results in developing a deeper body at a stage of the life history where predation risk is high [Current Zoology 56 （1）： 36-42, 2010].
文摘Since the 1980s and 1980s, a new trend in the discipline of Translation Studies has emerged beyond the boundaries of Europe. Scholars from post-colonial nations like Canada, India, China, Africa, and Latin America have argued that translation was used in the past as a means of depriving the colonised people of their voice. In the colonial structure, the hegemonic culture used to dominate, making the others subservient. Translation in the colonial period reflected that hierarchy. In this light, decades after the independence of India, translation from a reverse direction, that is, rendering popular English texts in minority languages, may be seen as a process of＂writing back＂. Even if the original text concerned is not a ＂political＂ writing, and the translation is apparently meant for ＂safer-zones＂ such as ＂young students＇ literature＂, a tendency of claiming cultural equality, overlapping the translator＇s own cultural and literary heritage with the original author＇s, can be discovered. This paper attempts to focus on these issues in a particular text—the 1995 Bengali translation of Marie Corelli＇s 1921 science-fiction, The Secret Power. The purpose of this paper is to explore how Sudhindranath Raha has intermingled Biblical references and Western contexts with allusions to Indian culture and Sanskrit literature, thereby claiming a space for mutual understanding and respect between two cultures.
