Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visit...Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visitation and accessibility.First,the global and local accessibility indexes of each park unit are computed based on an accessibility model that takes into account the surrounding population and its proximity to the park unit.Integrated in the model is a distance decay coefficient that is derived from U.S.national park visitor surveys and therefore pertinent to the case of study.Then correlation analysis is performed between park visitation and accessibility based on park types,regions,and visitation types.Results show that total visitation is positively related to accessibility in National Memorials,Military Parks and Battlefield Parks/Sites but negatively related to accessibility in national parks and national monuments.However,recreational overnight stay visits are commonly negatively correlated to accessibility for almost all park types.Moreover,local accessibility index displays enhanced correlation coefficients with improved significance levels in many categories of analysis.Results suggest that historical/cultural national parks which often show positive correlations tend to attract more local visitors,but nature-based parks which mainly show negative correlations tend to attract more distant visitors.展开更多
Discussions about the U. S-Iraq war would last for years, but the war will surely produce long-term influences on international strategic structure and China’s security environment. The feature and influence of the w...Discussions about the U. S-Iraq war would last for years, but the war will surely produce long-term influences on international strategic structure and China’s security environment. The feature and influence of the war are determined by the America’ purposes in launching the war, which, in the common.展开更多
As the hegemonic country in the world system, U. S. national strategy is global and multi-directional. Since September 11, 2001, America has made series of adjustments in its global strategy, including adjustment in s...As the hegemonic country in the world system, U. S. national strategy is global and multi-directional. Since September 11, 2001, America has made series of adjustments in its global strategy, including adjustment in security focus and change of security means. Come what may, since America has become the superpower in the world system, its national strategy has always been between offensive and integration. In a sense, current American strategy is the combination of the two. Although different government would tilt toward one direction, none展开更多
OBJECTIVE To compare the outcomes of transapical transcatheter aortic valve replacement(TA-TAVR)and surgical aortic valve replacement(SAVR)using a large US population sample.METHODS The U.S.National Inpatient Sample w...OBJECTIVE To compare the outcomes of transapical transcatheter aortic valve replacement(TA-TAVR)and surgical aortic valve replacement(SAVR)using a large US population sample.METHODS The U.S.National Inpatient Sample was queried for all patients who underwent TA-TAVR or SAVR during the years2016-2017.The primary outcome was all-cause in-hospital mortality.Secondary outcomes were in-hospital stroke,pericardiocentesis,pacemaker insertion,mechanical ventilation,vascular complications,major bleeding,acute kidney injury,length of stay,and cost of hospitalization.Outcomes were modeled using multi-variable logistic regression for binary outcomes and generalized linear models for continuous outcomes.RESULTS A total of 1560 TA-TAVR and 44,280 SAVR patients were included.Patients who underwent TA-TAVR were older and frailer.Compared to SAVR,TA-TAVR correlated with a higher mortality(4.5%vs.2.7%,effect size(SMD)=0.1)and higher periprocedural complications.Following multivariable analysis,both TA-TAVR and SAVR had a similar adjusted risk for in-hospital mortality.TA-TAVR correlated with lower odds of bleeding with(adjusted OR(aOR)=0.26;95%CI:0.18-0.38;P<0.001),and a shorter length of stay(adjusted mean ratio(aMR)=0.77;95%CI:0.69-0.84;P<0.001),but higher cost(aMR=1.18;95%CI:1.10-1.28;P<0.001).No significant differences in other study outcomes.In subgroup analysis,TA-TAVR in patients with chronic lung disease had higher odds for mortality(aOR=3.11;95%CI:1.37-7.08;P=0.007).CONCLUSION The risk-adjusted analysis showed that TA-TAVR has no advantage over SAVR except for patients with chronic lung disease where TA-TAVR has higher mortality.展开更多
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science ...The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.展开更多
基金supported by the National Nature Science Foundation of China (Grant No. 41401604)the Central Universities Fund Project of Southwest Minzu University (Grant No. 2019SYB07)
文摘Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visitation and accessibility.First,the global and local accessibility indexes of each park unit are computed based on an accessibility model that takes into account the surrounding population and its proximity to the park unit.Integrated in the model is a distance decay coefficient that is derived from U.S.national park visitor surveys and therefore pertinent to the case of study.Then correlation analysis is performed between park visitation and accessibility based on park types,regions,and visitation types.Results show that total visitation is positively related to accessibility in National Memorials,Military Parks and Battlefield Parks/Sites but negatively related to accessibility in national parks and national monuments.However,recreational overnight stay visits are commonly negatively correlated to accessibility for almost all park types.Moreover,local accessibility index displays enhanced correlation coefficients with improved significance levels in many categories of analysis.Results suggest that historical/cultural national parks which often show positive correlations tend to attract more local visitors,but nature-based parks which mainly show negative correlations tend to attract more distant visitors.
文摘Discussions about the U. S-Iraq war would last for years, but the war will surely produce long-term influences on international strategic structure and China’s security environment. The feature and influence of the war are determined by the America’ purposes in launching the war, which, in the common.
文摘As the hegemonic country in the world system, U. S. national strategy is global and multi-directional. Since September 11, 2001, America has made series of adjustments in its global strategy, including adjustment in security focus and change of security means. Come what may, since America has become the superpower in the world system, its national strategy has always been between offensive and integration. In a sense, current American strategy is the combination of the two. Although different government would tilt toward one direction, none
文摘OBJECTIVE To compare the outcomes of transapical transcatheter aortic valve replacement(TA-TAVR)and surgical aortic valve replacement(SAVR)using a large US population sample.METHODS The U.S.National Inpatient Sample was queried for all patients who underwent TA-TAVR or SAVR during the years2016-2017.The primary outcome was all-cause in-hospital mortality.Secondary outcomes were in-hospital stroke,pericardiocentesis,pacemaker insertion,mechanical ventilation,vascular complications,major bleeding,acute kidney injury,length of stay,and cost of hospitalization.Outcomes were modeled using multi-variable logistic regression for binary outcomes and generalized linear models for continuous outcomes.RESULTS A total of 1560 TA-TAVR and 44,280 SAVR patients were included.Patients who underwent TA-TAVR were older and frailer.Compared to SAVR,TA-TAVR correlated with a higher mortality(4.5%vs.2.7%,effect size(SMD)=0.1)and higher periprocedural complications.Following multivariable analysis,both TA-TAVR and SAVR had a similar adjusted risk for in-hospital mortality.TA-TAVR correlated with lower odds of bleeding with(adjusted OR(aOR)=0.26;95%CI:0.18-0.38;P<0.001),and a shorter length of stay(adjusted mean ratio(aMR)=0.77;95%CI:0.69-0.84;P<0.001),but higher cost(aMR=1.18;95%CI:1.10-1.28;P<0.001).No significant differences in other study outcomes.In subgroup analysis,TA-TAVR in patients with chronic lung disease had higher odds for mortality(aOR=3.11;95%CI:1.37-7.08;P=0.007).CONCLUSION The risk-adjusted analysis showed that TA-TAVR has no advantage over SAVR except for patients with chronic lung disease where TA-TAVR has higher mortality.
文摘The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
