Understanding the mechanisms underlying plant responses to climate change is an important step toward developing effective mitigation strategies. Polyploidy is an important evolutionary trait that can influence the ca...Understanding the mechanisms underlying plant responses to climate change is an important step toward developing effective mitigation strategies. Polyploidy is an important evolutionary trait that can influence the capacity of plants to adapt to climate change. The environmental flexibility of polyploids suggests their resiliency to climate change, however, such hypotheses have not yet received empirical evidence. To understand how ploidy level may influence response to climate change, we modeled the current and future distribution of 54 Crataegus species under moderate to severe environments and compared the range change between diploids and polyploids. The majority of studied species are predicted to experience considerable range expansion. We found a negative interaction between ploidy and ecoregions in determining the response to climate change. In extreme environments, polyploids are projected to experience a higher range expansion than diploids with climate change, while the opposite is true for moderate environments. The range expansion of Crataegus species can be attributed to their tolerance for a wide range of environmental conditions. Despite the higher tolerance of polyploids to extreme environments, they do not necessarily outperform diploids in moderate environments, which can be attributed to the varying nature of species interactions along a stress gradient.展开更多
Eight temperate deciduous tree species, Acer rubrum L., A. saccharinum L., A. saccharum Marsh., Belluta alleghaniensis Britton., Fraxinus nigra Marsh., Quercus rubra L., Titia americana L., and Ulmus americana L. in e...Eight temperate deciduous tree species, Acer rubrum L., A. saccharinum L., A. saccharum Marsh., Belluta alleghaniensis Britton., Fraxinus nigra Marsh., Quercus rubra L., Titia americana L., and Ulmus americana L. in eastern North America, were selected to explore relationship between the northward distribution of temperate tree species and climatic factors. For each species, more than 30 sites at their north limits of distribution were obtained from their distribution maps, and 11 climatic indices at the north limits were computed. The standardized standard deviation (SD) method, which compares the magnitude of variance of climatic indices, was used to detect which climatic parameter was the most important for explaining northward distribution of these species. We presume that the climatic parameter that has the smallest variance at the north limit would be assigned as the dominant climatic factor for limiting the distribution of this species. The results derived from the standardized SD method indicated that the SD value of warmth index (WI) and/or annual biotemperature (ABT) were the smallest among the 11 climatic indices. Since both WI and ABT represent growing season temperature, it suggested that growing season temperature was the most important climatic factor for explaining the northward distribution of these temperate tree species. The relationships between several climatic indices, WI, coldness index (CI), annual precipitation (AP), annual range of temperature (ART) and humid/arid index were also analyzed. As a result, at the north limits of all these species, both WI and CI decreased with an increase of AP, and CI increased with an increase of ART. Besides growing season temperature, precipitation and climatic continentality also have influence on the northward distribution of the temperate trees in eastern North America.展开更多
The disjunct distribution of plants between eastern Asia(EA) and North America(NA) is one of the most well-known biogeographic patterns. However, the formation and historical process of this pattern have been long deb...The disjunct distribution of plants between eastern Asia(EA) and North America(NA) is one of the most well-known biogeographic patterns. However, the formation and historical process of this pattern have been long debated. Chamaecyparis is a good model to test previous hypotheses about the formation of this disjunct pattern as it contains six species disjunctly distributed in EA, western North America(WNA)and eastern North America(ENA). In this study, we applied ecological niche models to test the formation of the disjunct pattern of Chamaecyparis. The model calibrated with the EA species was able to predict the distribution of eastern NA species well, but not the western NA species. Furthermore, the eastern Asian species were shown to have higher niche overlap with the eastern North American species. The EA species were also shown to share more similar habitats with ENA species than with WNA species in the genus. Chamaecyparis species in WNA experienced a significant niche shift compared with congeneric species. Chamaecyparis had a low number of suitable regions in Europe and the middle and western NA during the Last Glacial Maximum(LGM) period, and became extinct in the former region whereas it retains residual distribution in the latter. The extirpations in western NA and Europe in response to the late Neogene and Quaternary climatic cooling and the more similar habitats between ENA and EA ultimately shaped the current intercontinental disjunct distribution of Chamaecyparis. Both current hypotheses may be also jointly applied to explain more eastern Asian and eastern North American disjunctions observed today.展开更多
GRACE-based estimates for groundwater storage(GWS)changes in North America substantially depend upon correction of glacialisostatic adjustment(GIA)effects,which are usually removed with GIA models.In this study,GIA ef...GRACE-based estimates for groundwater storage(GWS)changes in North America substantially depend upon correction of glacialisostatic adjustment(GIA)effects,which are usually removed with GIA models.In this study,GIA effects are eliminated by employing an independent separation approach with the aid of Global Navigation Satellite System(GNSS)vertical velocity data.Our goal is to provide an independent estimate for monthly GWS changes within North America in 1-degree-grids and their trends over the whole GRACE mission lifetime from April 2002 to June 2017.This estimate is derived from the release-6 version of GRACE monthly level-2 data,GNSS data,land surface models for soil moisture and snow wa-ter equivalent,and satellite altimetric lake leveldata.We find a GWS anomaly in form of an increasing trend in Saskatchewan,which affects the Saskatchewan Province and the states of Montana,North Dakota and Minnesota,and 4 GWS anomalies with declining trends in Nevada,California,Arizona and Texas,respec-tively.The monthly changes of these GWS anomalies,except for the one in Nevada,are validated by well level data.We provide results for average monthly GWS changes and the trends for the 5 anomalies but also in separate form for the 13 affected states or provinces.The increasing trends of the Saskatchewan GWS anomaly and the affected 3 states are related to increasing precipitation and can be elucidated by the decreasing drought intensity level.On the contrary,the declining trends in GWS can be explained by weakening precipitation and are mostly supported by the increasing drought intensity level in the other 4 anomalies and the affected states,which are Nevada,California,Arizona,New Mexico,Texas,Oklahoma,Kansas,and Colorado.Ourestimates of monthly GWS changes and their trendscan serveas alternativeand beneficial input for the sustainable management of groundwater resources in North America.展开更多
The latitudinal richness gradient is a frequent topic of study on the modern landscape,but its history in deep time is much less well known.Here,we preliminarily evaluated the paleolatitudinal richness gradient of vas...The latitudinal richness gradient is a frequent topic of study on the modern landscape,but its history in deep time is much less well known.Here,we preliminarily evaluated the paleolatitudinal richness gradient of vascular plants for the Eocene(56-33.9 million years ago) and Oligocene(33.9-23 million years ago) epochs of North America north of IVlexico using 201 fossil floras.We calculated the direction and shape of the gradient using quadratic regression to detect linear and curvilinear trends.We performed regressions for the Eocene and Oligocene as well as for informal time intervals within the Eocene:early,middle,and middle + late.We found that quadratic models better explain the data than linear models for both epochs as well as for the early Eocene.A roughly linear trend in the middle and middle + late intervals may reflect limited sampling of high latitude floras for those times.The curvilinear relationship was weak for the Eocene and the model showed a peak in richness at 45.5°N.The curvilinear relationship was much stronger for the Oligocene and the peak occurred at 48.5°N.In the Eocene,the mid-latitude peak in richness may be explained by mean annual temperature,which was probably higher at some mid-latitudes than at lower ones.For the Oligocene,the peak in richness at midlatitudes may be explained by evolutionary diversification within the temperate zone or by increased aridity at low latitudes.We also assessed the latitudinal richness gradient of genera within modern floras in North America north of Mexico and we found a weak,curvilinear trend with a peak in richness at 31.5°N.Our results suggest that the latitudinal genus richness gradient of vascular plants in North America continued to develop into its modern structure following the Oligocene.展开更多
In this study, the Palmer Drought Severity Index （PDSI） was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent ...In this study, the Palmer Drought Severity Index （PDSI） was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America： a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nin？a event was considered during 1997–2003.展开更多
Under recent Arctic warming,boreal winters have witnessed severe cold surges over both Eurasia and North America,bringing about serious social and economic impacts.Here,we investigated the changes in daily surface air...Under recent Arctic warming,boreal winters have witnessed severe cold surges over both Eurasia and North America,bringing about serious social and economic impacts.Here,we investigated the changes in daily surface air temperature(SAT)variability during the rapid Arctic warming period of 1988/89–2015/16,and found the daily SAT variance,mainly contributed by the sub-seasonal component,shows an increasing and decreasing trend over eastern Eurasia and North America,respectively.Increasing cold extremes(defined as days with daily SAT anomalies below 1.5 standard deviations)dominated the increase of the daily SAT variability over eastern Eurasia,while decreasing cold extremes dominated the decrease of the daily SAT variability over North America.The circulation regime of cold extremes over eastern Eurasia(North America)is characterized by an enhanced high-pressure ridge over the Urals(Alaska)and surface Siberian(Canadian)high.The data analyses and model simulations show the recent strengthening of the high-pressure ridge over the Urals was associated with warming of the Barents–Kara seas in the Arctic region,while the high-pressure ridge over Alaska was influenced by the offset effect of Arctic warming over the East Siberian–Chukchi seas and the Pacific decadal oscillation(PDO)–like sea surface temperature(SST)anomalies over the North Pacific.The transition of the PDO-like SST anomalies from a positive to negative phase cancelled the impact of Arctic warming,reduced the occurrence of extreme cold days,and possibly resulted in the decreasing trend of daily SAT variability in North America.The multi-ensemble simulations of climate models confirmed the regional Arctic warming as the driver of the increasing SAT variance over eastern Eurasia and North America and the overwhelming effect of SST forcing on the decreasing SAT variance over North America.Therefore,the regional response of winter cold extremes at midlatitudes to the Arctic warming could be different due to the distinct impact of decadal SST anomalies.展开更多
BACKGROUND Large inter-individual and inter-population differences in the susceptibility to and outcome of severe acute respiratory syndrome coronavirus 2 or coronavirus disease 2019(COVID-19)have been noted.Understan...BACKGROUND Large inter-individual and inter-population differences in the susceptibility to and outcome of severe acute respiratory syndrome coronavirus 2 or coronavirus disease 2019(COVID-19)have been noted.Understanding these differences and how they influence vulnerability to infection and disease severity is critical to public health intervention.AIM To analyze and compare the profile of COVID-19 cases between China and North America as two regions that differ in many environmental,host and healthcare factors related to disease risk.METHODS We conducted a meta-analysis to examine and compare demographic information,clinical symptoms,comorbidities,disease severity and levels of disease biomarkers of COVID-19 cases from clinical studies and data from China(105 studies)and North America(19 studies).RESULTS COVID-19 patients from North America were older than their Chinese counterparts and with higher male:Female ratio.Fever,cough,fatigue and dyspnea were the most common clinical symptoms in both study regions(present in about 30%to 75%of the cases in both regions).Meta-analysis for the prevalence of comorbidities(such as obesity,hypertension,diabetes,cardiovascular diseases,chronic obstructive pulmonary disease,cancer,and chronic kidney diseases)in COVID-19 patients were all significantly more prevalent in North America compared to China.Comorbidities were positively correlated with age but at a significantly younger age range in China compared to North American.The most prevalent infection outcome was acute respiratory distress syndrome which was 2-fold more frequent in North America than in China.Levels of C-reactive protein were 4.5-fold higher in the North American cases than in cases from China.CONCLUSION The differences in the profile of COVID-19 cases from China and North America may relate to differences in environmental-,host-and healthcare-related factors between the two regions.Such inter-population differences-together with intrapopulation variability-underline the need to characterize the effect of health inequities and inequalities on public health response to COVID-19 and can assist in preparing for the re-emergence of the epidemic.展开更多
In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the are...In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event （c.1400-1900 A.D.）, it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event （6,000 years B.P.）, the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United States were able to migrate up the Saskatchewan River system as far as Lake Louise, Alberta. On the southern Prairies, the many small sloughs and lakes dried up. During the maximum of the Late Wisconsin Glacial event （15,000 years B.P.）, the Arctic Front had moved south to the vicinity of 30°N, while there had been a southward movement of the Zone of Intertropical Convergence from the equator to about 10°S. The mP air was also very strong and dumped enormous quantities of snow in the glaciated Canadian Cordillera, but it does not appear to have moved south any distance into the northern United States, witness the limited glaciation and widespread permafrost that developed there. Instead, there is evidence for buffering of the climatic changes in the closed basins in the northern Cordillera of the contiguous United States. The source of the cT air mass had moved south into the northern part of South America, permitting an exchange of savannah biota between the two continents. An extensive area of white dune sands inundated both savannah and forest along the inland hills in Guyana. This parallels the massive changes in African climatology during the last Ice Age （Fairbridge, 1964）. If these changes occurred each time there was a major glaciation in the Northern Hemisphere, this would explain the movement of biota from all terrestrial environments between the two American continents in the last 2 million years. A similar northward movement of climatic belts occurred in South America, with the cA air from Antarctica expanding northwards into southern Argentina and Chili. However paucity of data and the potential effects of El Ni o and the Southern Oscillation make it difficult toprovide details of the changes there in the present state of knowledge. This technique of studying the mechanisms of present-day climatic changes and applying the results to past climatic events has considerable potential for elucidating past climatic changes elsewhere in continental regions. This may prove particularly valuable in studying the Siberian anticyclone that is the main cause of the distribution of permafrost, but this will need international cooperation to be successful.展开更多
Paleoclimatic settings have been reconstructed for the Campanian using original oxygenisotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP h...Paleoclimatic settings have been reconstructed for the Campanian using original oxygenisotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes （95, 98, 102, 390A, and 392A） in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific （to 24.2℃） and the eastern circum-Pacific （to 26.4℃） areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland （22.4-25.5℃）, which agrees with the data on the Campanian Barykovskaya flora in high latitudes （Golovneva and Herman, 1998） and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska （19.4℃） and the Koryak Upland （22.4-25.5℃）, we also expect Latest Campauian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main dimatic tendency during the Campanian （with the exception of Latest Campanian） has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin （Krilyon） marine basin. In contrary to Huber＇s et al. （2002） assumption, we expect warm greenhouse conditions during the most part of the Campanian.展开更多
The characteristics of interannual fluctuations of the surface air temperature over North America are investigated by using the surface air temperature data of 130 stations during 1941 through 1980. It is found that t...The characteristics of interannual fluctuations of the surface air temperature over North America are investigated by using the surface air temperature data of 130 stations during 1941 through 1980. It is found that the surface air temperature bears about ten-year time scale oscillation over the southeastern and northwestern North America and along the west coast of the United States, and it has the characteristics of quasibiennial oscillation over the eastern North America. The ten-year scale oscillation of the surface air temperature is related to that of the sea surface temperature (SST) of North Pacific through the PNA pattern atmospheric circulation anomaly over North Pacific through North America. It is shown that the North Pacific SST has a closer association with the surface air temperature over North America than the central and eastern equatorial Pacific SST. The characteristics of the seasonal variations of the relationship between the North Pacific SST and the surface air temperature over North America are also analyzed.展开更多
Endoscopic submucosal dissection(ESD)and related procedures are minimally invasive and cost-effective alternates to surgery.However,there is no approved or listed current procedural terminology(CPT)for ESD.We aimed to...Endoscopic submucosal dissection(ESD)and related procedures are minimally invasive and cost-effective alternates to surgery.However,there is no approved or listed current procedural terminology(CPT)for ESD.We aimed to review the current reimbursement process hurdles for ESD procedures in private practice model in United States.We reviewed the data of two advanced endoscopists(one in New York and other in Pennsylvania State)performing ESD in their private practice set-ups.We found the reimbursement process was complex,with number of refusals varied from 0-9 for ESD procedures.It was not paid at all in 8.3%of cases by the medical insurance.Endoscopic mucosal resection,which is considered inferior as compared to ESD,but has a listed CPT,was denied in only 0.83%cases.Our data highlights the billing hurdles by the endoscopists to adopt ESD-related procedures in private practice model.展开更多
Sekeres et al. （1） conducted a multicenter randomized, controlled trial to compare whether azacitidine-based combinations with lenalidomide or vorinostat produce superior overall response rates to azacitidine in the...Sekeres et al. （1） conducted a multicenter randomized, controlled trial to compare whether azacitidine-based combinations with lenalidomide or vorinostat produce superior overall response rates to azacitidine in the treatment of myelodysplastic syndromes （MDS）. In that trial, 224 patients with higher-risk MDS and 53 with chronic myelomonocytic leukemia （CMML） were enrolled and randomly assigned to the ＂azacitidine＂ group, ＂azacitidine plus lenalidomide＂ group or ＂azacitidine plus vorinostat＂ group. The researchers found that patients with MDS treated with azacitidine-based combinations had similar response rate to azacitidine monotherapy. Using genomic mutation analysis, they found that the overall response rate to azacitidine-based treatment was higher for patients with mutations in DNMT3A and lower for those with mutations in SRSF2. Whereas in another study, Welch et al. enrolled 26 patients with MDS and 90 with acute myeloid leukemia （AML） who were treated with decitabine, and they found that patients with TP53 mutations had a higher response rate, but not those with DNMT3A mutations （2）. We propose that this big discrepancy in the conclusions between the two studies might have been caused by the presence of many co-interacting factors, e.g. study aims, DNA demethylating agents, treatment protocols, and patient sources.展开更多
China issues 2nd warning for Chrysler Jeep China’s top quality watchdog on November 16 issued its second warming regarding potential safety hazards in U.S au-
Through the analysis of ensembles of coupled model simulations and projections collected from CMIP3 and CMIP5, we demonstrate that a fundamental spatial scale limit might exist below which useful additional refinement...Through the analysis of ensembles of coupled model simulations and projections collected from CMIP3 and CMIP5, we demonstrate that a fundamental spatial scale limit might exist below which useful additional refinement of climate model predictions and projections may not be possible. That limit varies among climate variables and from region to region. We show that the uncertainty（noise） in surface temperature predictions（represented by the spread among an ensemble of global climate model simulations） generally exceeds the ensemble mean（signal） at horizontal scales below 1000 km throughout North America, implying poor predictability at those scales. More limited skill is shown for the predictability of regional precipitation. The ensemble spread in this case tends to exceed or equal the ensemble mean for scales below 2000 km. These findings highlight the challenges in predicting regionally specific future climate anomalies, especially for hydroclimatic impacts such as drought and wetness.展开更多
Versatile sports goods and keepfit apparatus and easy-to-carry tourist equipment are important in many Western world households in the craze for body-building and travel. In the North American market, the sales volume...Versatile sports goods and keepfit apparatus and easy-to-carry tourist equipment are important in many Western world households in the craze for body-building and travel. In the North American market, the sales volume of sports goods and tourist equipment every year is worth about US$100 million.展开更多
The cultural dimension of sustainability as the fourth pillar of the overall sustainable development framework encompasses both tangible and intangible cultures.In this study,tangible culture refers to the home enviro...The cultural dimension of sustainability as the fourth pillar of the overall sustainable development framework encompasses both tangible and intangible cultures.In this study,tangible culture refers to the home environments of Chinese residents in China and North America,while intangible culture refers to their faiths and belief systems,in other words,their philosophy and religion,reflected(or not)in their home environments.The paper argues that Chinese philosophy and religion have historically contributed to Chinese people’s environmental ethics and their health and happiness.Set within this context,the paper presents the author’s two empirical research findings on Chinese residents’philosophy and religion in contemporary China and North America.Quantitative and qualitative data were collected by asking Chinese residents the same research question in the 2007-2008 onsite survey and follow-up interviews in Beijing and Suzhou of China,and the 2013 online survey and follow-up interviews in the US and Canada.The findings show a significantly higher percentage of ethnic Chinese in North America holds traditional Chinese faiths than those in China,though Western cultural infiltration is also happening to them.Nevertheless,due to the limited number of participants,the findings may only be indicative.展开更多
RITM is participating in Techtextil North America 2009, April 21-23 2009, in Las Vegas, (NV, USA), the premier North American tradeshow for technical textiles and nonwovens. In its booth, RITM will present
文摘Understanding the mechanisms underlying plant responses to climate change is an important step toward developing effective mitigation strategies. Polyploidy is an important evolutionary trait that can influence the capacity of plants to adapt to climate change. The environmental flexibility of polyploids suggests their resiliency to climate change, however, such hypotheses have not yet received empirical evidence. To understand how ploidy level may influence response to climate change, we modeled the current and future distribution of 54 Crataegus species under moderate to severe environments and compared the range change between diploids and polyploids. The majority of studied species are predicted to experience considerable range expansion. We found a negative interaction between ploidy and ecoregions in determining the response to climate change. In extreme environments, polyploids are projected to experience a higher range expansion than diploids with climate change, while the opposite is true for moderate environments. The range expansion of Crataegus species can be attributed to their tolerance for a wide range of environmental conditions. Despite the higher tolerance of polyploids to extreme environments, they do not necessarily outperform diploids in moderate environments, which can be attributed to the varying nature of species interactions along a stress gradient.
文摘Eight temperate deciduous tree species, Acer rubrum L., A. saccharinum L., A. saccharum Marsh., Belluta alleghaniensis Britton., Fraxinus nigra Marsh., Quercus rubra L., Titia americana L., and Ulmus americana L. in eastern North America, were selected to explore relationship between the northward distribution of temperate tree species and climatic factors. For each species, more than 30 sites at their north limits of distribution were obtained from their distribution maps, and 11 climatic indices at the north limits were computed. The standardized standard deviation (SD) method, which compares the magnitude of variance of climatic indices, was used to detect which climatic parameter was the most important for explaining northward distribution of these species. We presume that the climatic parameter that has the smallest variance at the north limit would be assigned as the dominant climatic factor for limiting the distribution of this species. The results derived from the standardized SD method indicated that the SD value of warmth index (WI) and/or annual biotemperature (ABT) were the smallest among the 11 climatic indices. Since both WI and ABT represent growing season temperature, it suggested that growing season temperature was the most important climatic factor for explaining the northward distribution of these temperate tree species. The relationships between several climatic indices, WI, coldness index (CI), annual precipitation (AP), annual range of temperature (ART) and humid/arid index were also analyzed. As a result, at the north limits of all these species, both WI and CI decreased with an increase of AP, and CI increased with an increase of ART. Besides growing season temperature, precipitation and climatic continentality also have influence on the northward distribution of the temperate trees in eastern North America.
基金funded by grants from the Ministry of Science and Technology of China, Basic Research Project(No. 2013FY112600)the Talent Project of Yunnan Province(No. 2011CI042)
文摘The disjunct distribution of plants between eastern Asia(EA) and North America(NA) is one of the most well-known biogeographic patterns. However, the formation and historical process of this pattern have been long debated. Chamaecyparis is a good model to test previous hypotheses about the formation of this disjunct pattern as it contains six species disjunctly distributed in EA, western North America(WNA)and eastern North America(ENA). In this study, we applied ecological niche models to test the formation of the disjunct pattern of Chamaecyparis. The model calibrated with the EA species was able to predict the distribution of eastern NA species well, but not the western NA species. Furthermore, the eastern Asian species were shown to have higher niche overlap with the eastern North American species. The EA species were also shown to share more similar habitats with ENA species than with WNA species in the genus. Chamaecyparis species in WNA experienced a significant niche shift compared with congeneric species. Chamaecyparis had a low number of suitable regions in Europe and the middle and western NA during the Last Glacial Maximum(LGM) period, and became extinct in the former region whereas it retains residual distribution in the latter. The extirpations in western NA and Europe in response to the late Neogene and Quaternary climatic cooling and the more similar habitats between ENA and EA ultimately shaped the current intercontinental disjunct distribution of Chamaecyparis. Both current hypotheses may be also jointly applied to explain more eastern Asian and eastern North American disjunctions observed today.
基金This work is funded by the National Key R&D Program of China(2017YFA0603103)the National Natural Science Foundation of China(41974009 and 42004007)+1 种基金Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-DQC042 and QYZDJ-SSW-DQC027)Alberta Innovates(the Groundwater Recharge in the Prairies project)。
文摘GRACE-based estimates for groundwater storage(GWS)changes in North America substantially depend upon correction of glacialisostatic adjustment(GIA)effects,which are usually removed with GIA models.In this study,GIA effects are eliminated by employing an independent separation approach with the aid of Global Navigation Satellite System(GNSS)vertical velocity data.Our goal is to provide an independent estimate for monthly GWS changes within North America in 1-degree-grids and their trends over the whole GRACE mission lifetime from April 2002 to June 2017.This estimate is derived from the release-6 version of GRACE monthly level-2 data,GNSS data,land surface models for soil moisture and snow wa-ter equivalent,and satellite altimetric lake leveldata.We find a GWS anomaly in form of an increasing trend in Saskatchewan,which affects the Saskatchewan Province and the states of Montana,North Dakota and Minnesota,and 4 GWS anomalies with declining trends in Nevada,California,Arizona and Texas,respec-tively.The monthly changes of these GWS anomalies,except for the one in Nevada,are validated by well level data.We provide results for average monthly GWS changes and the trends for the 5 anomalies but also in separate form for the 13 affected states or provinces.The increasing trends of the Saskatchewan GWS anomaly and the affected 3 states are related to increasing precipitation and can be elucidated by the decreasing drought intensity level.On the contrary,the declining trends in GWS can be explained by weakening precipitation and are mostly supported by the increasing drought intensity level in the other 4 anomalies and the affected states,which are Nevada,California,Arizona,New Mexico,Texas,Oklahoma,Kansas,and Colorado.Ourestimates of monthly GWS changes and their trendscan serveas alternativeand beneficial input for the sustainable management of groundwater resources in North America.
文摘The latitudinal richness gradient is a frequent topic of study on the modern landscape,but its history in deep time is much less well known.Here,we preliminarily evaluated the paleolatitudinal richness gradient of vascular plants for the Eocene(56-33.9 million years ago) and Oligocene(33.9-23 million years ago) epochs of North America north of IVlexico using 201 fossil floras.We calculated the direction and shape of the gradient using quadratic regression to detect linear and curvilinear trends.We performed regressions for the Eocene and Oligocene as well as for informal time intervals within the Eocene:early,middle,and middle + late.We found that quadratic models better explain the data than linear models for both epochs as well as for the early Eocene.A roughly linear trend in the middle and middle + late intervals may reflect limited sampling of high latitude floras for those times.The curvilinear relationship was weak for the Eocene and the model showed a peak in richness at 45.5°N.The curvilinear relationship was much stronger for the Oligocene and the peak occurred at 48.5°N.In the Eocene,the mid-latitude peak in richness may be explained by mean annual temperature,which was probably higher at some mid-latitudes than at lower ones.For the Oligocene,the peak in richness at midlatitudes may be explained by evolutionary diversification within the temperate zone or by increased aridity at low latitudes.We also assessed the latitudinal richness gradient of genera within modern floras in North America north of Mexico and we found a weak,curvilinear trend with a peak in richness at 31.5°N.Our results suggest that the latitudinal genus richness gradient of vascular plants in North America continued to develop into its modern structure following the Oligocene.
基金supported by the NSFC project (Grant Nos. 40905037, 40775055,40705016, and 40828004)the NSFC key program(Grant No. 40830956)
文摘In this study, the Palmer Drought Severity Index （PDSI） was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America： a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nin？a event was considered during 1997–2003.
基金This study was jointly supported by the National Key R&D Program(Grant No.2018YFC1505904)the National Natural Science Foundation of China(Grant Nos.41830969 and 41705052)the Basic Scientific Research and Operation Foundation of CAMS(Grant No.2018Z006).
文摘Under recent Arctic warming,boreal winters have witnessed severe cold surges over both Eurasia and North America,bringing about serious social and economic impacts.Here,we investigated the changes in daily surface air temperature(SAT)variability during the rapid Arctic warming period of 1988/89–2015/16,and found the daily SAT variance,mainly contributed by the sub-seasonal component,shows an increasing and decreasing trend over eastern Eurasia and North America,respectively.Increasing cold extremes(defined as days with daily SAT anomalies below 1.5 standard deviations)dominated the increase of the daily SAT variability over eastern Eurasia,while decreasing cold extremes dominated the decrease of the daily SAT variability over North America.The circulation regime of cold extremes over eastern Eurasia(North America)is characterized by an enhanced high-pressure ridge over the Urals(Alaska)and surface Siberian(Canadian)high.The data analyses and model simulations show the recent strengthening of the high-pressure ridge over the Urals was associated with warming of the Barents–Kara seas in the Arctic region,while the high-pressure ridge over Alaska was influenced by the offset effect of Arctic warming over the East Siberian–Chukchi seas and the Pacific decadal oscillation(PDO)–like sea surface temperature(SST)anomalies over the North Pacific.The transition of the PDO-like SST anomalies from a positive to negative phase cancelled the impact of Arctic warming,reduced the occurrence of extreme cold days,and possibly resulted in the decreasing trend of daily SAT variability in North America.The multi-ensemble simulations of climate models confirmed the regional Arctic warming as the driver of the increasing SAT variance over eastern Eurasia and North America and the overwhelming effect of SST forcing on the decreasing SAT variance over North America.Therefore,the regional response of winter cold extremes at midlatitudes to the Arctic warming could be different due to the distinct impact of decadal SST anomalies.
文摘BACKGROUND Large inter-individual and inter-population differences in the susceptibility to and outcome of severe acute respiratory syndrome coronavirus 2 or coronavirus disease 2019(COVID-19)have been noted.Understanding these differences and how they influence vulnerability to infection and disease severity is critical to public health intervention.AIM To analyze and compare the profile of COVID-19 cases between China and North America as two regions that differ in many environmental,host and healthcare factors related to disease risk.METHODS We conducted a meta-analysis to examine and compare demographic information,clinical symptoms,comorbidities,disease severity and levels of disease biomarkers of COVID-19 cases from clinical studies and data from China(105 studies)and North America(19 studies).RESULTS COVID-19 patients from North America were older than their Chinese counterparts and with higher male:Female ratio.Fever,cough,fatigue and dyspnea were the most common clinical symptoms in both study regions(present in about 30%to 75%of the cases in both regions).Meta-analysis for the prevalence of comorbidities(such as obesity,hypertension,diabetes,cardiovascular diseases,chronic obstructive pulmonary disease,cancer,and chronic kidney diseases)in COVID-19 patients were all significantly more prevalent in North America compared to China.Comorbidities were positively correlated with age but at a significantly younger age range in China compared to North American.The most prevalent infection outcome was acute respiratory distress syndrome which was 2-fold more frequent in North America than in China.Levels of C-reactive protein were 4.5-fold higher in the North American cases than in cases from China.CONCLUSION The differences in the profile of COVID-19 cases from China and North America may relate to differences in environmental-,host-and healthcare-related factors between the two regions.Such inter-population differences-together with intrapopulation variability-underline the need to characterize the effect of health inequities and inequalities on public health response to COVID-19 and can assist in preparing for the re-emergence of the epidemic.
文摘In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event （c.1400-1900 A.D.）, it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event （6,000 years B.P.）, the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United States were able to migrate up the Saskatchewan River system as far as Lake Louise, Alberta. On the southern Prairies, the many small sloughs and lakes dried up. During the maximum of the Late Wisconsin Glacial event （15,000 years B.P.）, the Arctic Front had moved south to the vicinity of 30°N, while there had been a southward movement of the Zone of Intertropical Convergence from the equator to about 10°S. The mP air was also very strong and dumped enormous quantities of snow in the glaciated Canadian Cordillera, but it does not appear to have moved south any distance into the northern United States, witness the limited glaciation and widespread permafrost that developed there. Instead, there is evidence for buffering of the climatic changes in the closed basins in the northern Cordillera of the contiguous United States. The source of the cT air mass had moved south into the northern part of South America, permitting an exchange of savannah biota between the two continents. An extensive area of white dune sands inundated both savannah and forest along the inland hills in Guyana. This parallels the massive changes in African climatology during the last Ice Age （Fairbridge, 1964）. If these changes occurred each time there was a major glaciation in the Northern Hemisphere, this would explain the movement of biota from all terrestrial environments between the two American continents in the last 2 million years. A similar northward movement of climatic belts occurred in South America, with the cA air from Antarctica expanding northwards into southern Argentina and Chili. However paucity of data and the potential effects of El Ni o and the Southern Oscillation make it difficult toprovide details of the changes there in the present state of knowledge. This technique of studying the mechanisms of present-day climatic changes and applying the results to past climatic events has considerable potential for elucidating past climatic changes elsewhere in continental regions. This may prove particularly valuable in studying the Siberian anticyclone that is the main cause of the distribution of permafrost, but this will need international cooperation to be successful.
文摘Paleoclimatic settings have been reconstructed for the Campanian using original oxygenisotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes （95, 98, 102, 390A, and 392A） in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific （to 24.2℃） and the eastern circum-Pacific （to 26.4℃） areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland （22.4-25.5℃）, which agrees with the data on the Campanian Barykovskaya flora in high latitudes （Golovneva and Herman, 1998） and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska （19.4℃） and the Koryak Upland （22.4-25.5℃）, we also expect Latest Campauian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main dimatic tendency during the Campanian （with the exception of Latest Campanian） has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin （Krilyon） marine basin. In contrary to Huber＇s et al. （2002） assumption, we expect warm greenhouse conditions during the most part of the Campanian.
文摘The characteristics of interannual fluctuations of the surface air temperature over North America are investigated by using the surface air temperature data of 130 stations during 1941 through 1980. It is found that the surface air temperature bears about ten-year time scale oscillation over the southeastern and northwestern North America and along the west coast of the United States, and it has the characteristics of quasibiennial oscillation over the eastern North America. The ten-year scale oscillation of the surface air temperature is related to that of the sea surface temperature (SST) of North Pacific through the PNA pattern atmospheric circulation anomaly over North Pacific through North America. It is shown that the North Pacific SST has a closer association with the surface air temperature over North America than the central and eastern equatorial Pacific SST. The characteristics of the seasonal variations of the relationship between the North Pacific SST and the surface air temperature over North America are also analyzed.
文摘Endoscopic submucosal dissection(ESD)and related procedures are minimally invasive and cost-effective alternates to surgery.However,there is no approved or listed current procedural terminology(CPT)for ESD.We aimed to review the current reimbursement process hurdles for ESD procedures in private practice model in United States.We reviewed the data of two advanced endoscopists(one in New York and other in Pennsylvania State)performing ESD in their private practice set-ups.We found the reimbursement process was complex,with number of refusals varied from 0-9 for ESD procedures.It was not paid at all in 8.3%of cases by the medical insurance.Endoscopic mucosal resection,which is considered inferior as compared to ESD,but has a listed CPT,was denied in only 0.83%cases.Our data highlights the billing hurdles by the endoscopists to adopt ESD-related procedures in private practice model.
文摘Sekeres et al. （1） conducted a multicenter randomized, controlled trial to compare whether azacitidine-based combinations with lenalidomide or vorinostat produce superior overall response rates to azacitidine in the treatment of myelodysplastic syndromes （MDS）. In that trial, 224 patients with higher-risk MDS and 53 with chronic myelomonocytic leukemia （CMML） were enrolled and randomly assigned to the ＂azacitidine＂ group, ＂azacitidine plus lenalidomide＂ group or ＂azacitidine plus vorinostat＂ group. The researchers found that patients with MDS treated with azacitidine-based combinations had similar response rate to azacitidine monotherapy. Using genomic mutation analysis, they found that the overall response rate to azacitidine-based treatment was higher for patients with mutations in DNMT3A and lower for those with mutations in SRSF2. Whereas in another study, Welch et al. enrolled 26 patients with MDS and 90 with acute myeloid leukemia （AML） who were treated with decitabine, and they found that patients with TP53 mutations had a higher response rate, but not those with DNMT3A mutations （2）. We propose that this big discrepancy in the conclusions between the two studies might have been caused by the presence of many co-interacting factors, e.g. study aims, DNA demethylating agents, treatment protocols, and patient sources.
文摘China issues 2nd warning for Chrysler Jeep China’s top quality watchdog on November 16 issued its second warming regarding potential safety hazards in U.S au-
基金partially supported by the NSF(Grant No.AGS-1305798)the ONR(Grant No.N000140910526)
文摘Through the analysis of ensembles of coupled model simulations and projections collected from CMIP3 and CMIP5, we demonstrate that a fundamental spatial scale limit might exist below which useful additional refinement of climate model predictions and projections may not be possible. That limit varies among climate variables and from region to region. We show that the uncertainty（noise） in surface temperature predictions（represented by the spread among an ensemble of global climate model simulations） generally exceeds the ensemble mean（signal） at horizontal scales below 1000 km throughout North America, implying poor predictability at those scales. More limited skill is shown for the predictability of regional precipitation. The ensemble spread in this case tends to exceed or equal the ensemble mean for scales below 2000 km. These findings highlight the challenges in predicting regionally specific future climate anomalies, especially for hydroclimatic impacts such as drought and wetness.
文摘Versatile sports goods and keepfit apparatus and easy-to-carry tourist equipment are important in many Western world households in the craze for body-building and travel. In the North American market, the sales volume of sports goods and tourist equipment every year is worth about US$100 million.
文摘The cultural dimension of sustainability as the fourth pillar of the overall sustainable development framework encompasses both tangible and intangible cultures.In this study,tangible culture refers to the home environments of Chinese residents in China and North America,while intangible culture refers to their faiths and belief systems,in other words,their philosophy and religion,reflected(or not)in their home environments.The paper argues that Chinese philosophy and religion have historically contributed to Chinese people’s environmental ethics and their health and happiness.Set within this context,the paper presents the author’s two empirical research findings on Chinese residents’philosophy and religion in contemporary China and North America.Quantitative and qualitative data were collected by asking Chinese residents the same research question in the 2007-2008 onsite survey and follow-up interviews in Beijing and Suzhou of China,and the 2013 online survey and follow-up interviews in the US and Canada.The findings show a significantly higher percentage of ethnic Chinese in North America holds traditional Chinese faiths than those in China,though Western cultural infiltration is also happening to them.Nevertheless,due to the limited number of participants,the findings may only be indicative.
文摘RITM is participating in Techtextil North America 2009, April 21-23 2009, in Las Vegas, (NV, USA), the premier North American tradeshow for technical textiles and nonwovens. In its booth, RITM will present
