Land surface changes effect the regional climate due to the complex coupling of land-atmosphere interactions. From 1995 to 2000, a decrease in the vegetation density and an increase in ground-level thermodynamic activ...Land surface changes effect the regional climate due to the complex coupling of land-atmosphere interactions. From 1995 to 2000, a decrease in the vegetation density and an increase in ground-level thermodynamic activity has been documented by multiple data sources in Northwest China, including meteorological, reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF), National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and TIROS Operational Vertical Sounder (TOVS) satellite remote sensing data. As the ground-level thermodynamic activity increases, humid air from the surrounding regions converge toward desert (and semi-desert) regions, causing areas with high vegetation cover to become gradually more arid. Furthermore, land surface changes in Northwest China are responsible for a decrease in total cloud cover, a decline in the fraction of low and middle clouds, an increase in high cloud cover (due to thermodynamic activity) and other regional climatic adaptations. It is proposed that, beginning in 1995, these cloud cover changes contributed to a "green- house" effect, leading to the rapid air temperature increases and other regional climate impacts that have been observed over Northwest China.展开更多
This paper investigates the spatial effect of environmental regulation measures on the upgrading of industrial structure in the integrated development strategy of Beijing-Tianjin-Hebei region and its surrounding areas...This paper investigates the spatial effect of environmental regulation measures on the upgrading of industrial structure in the integrated development strategy of Beijing-Tianjin-Hebei region and its surrounding areas.In order to reflect the effect of the environmental regulation and different regulation measures more truly,this paper constructs indices of the environmental regulation measures through the results of policy texts quantification.On the basis of the previous research,this paper divides environmental regulation into the following types:personnel and administrative measures of command and control;market-oriented fiscal,taxation,financial and other economic measures;guidance measures.Spatial panel regression results show that administrative measures of command control and market-oriented fiscal measures have a significant role in promoting regional industrial structure upgrading,but not conducive to the advancement of the industrial structure of adjacent areas.Their roles in promoting and inhibition are counteracted,which causes the total effect of industrial structure upgrading of Beijing-Tianjin-Hebei and the surrounding areas are not significant.Personnel measures,financial measures,other economic measures and guidance measures do not have the short-term effect and spatial effect on the upgrading of industrial structure.展开更多
Leptomeningeal metastasis is an uncommon but serious complication in patients with advanced cancers. Leptomeningeal metastasis is diagnosed in approximately 5% of the patients, most commonly among patients with cancer...Leptomeningeal metastasis is an uncommon but serious complication in patients with advanced cancers. Leptomeningeal metastasis is diagnosed in approximately 5% of the patients, most commonly among patients with cancers of breast and lung, melanoma, and gastrointestinal malignancies. Treatment goal is to improve survival and quality of the patients. Use of targeted therapies and immunotherapy has led to improved survival of patients with non-small cell lung cancer (NSCLC). In this article, we review emerging data on use of mutation-specific agents and immunotherapy in the treatment of leptomeningeal metastasis among patients with NSCLC.展开更多
By the end of the 21st century, mean sea surface temperatures are expected to increase 4?C, while atmospheric CO2 concentrations are predicted to triple causing seawater to become acidic. These compounding effects wil...By the end of the 21st century, mean sea surface temperatures are expected to increase 4?C, while atmospheric CO2 concentrations are predicted to triple causing seawater to become acidic. These compounding effects will undoubtedly have major consequences for the organisms and processes in the oceans. Bacterioplankton play a vital role in the marine carbon cycle and the oceans’ ability to sequester CO2. We utilized pCO2 perturbation experiments to investigate the effects of ocean acidity and elevated temperature on bacterioplankton community structure and metabolism. Terminal-restriction fragment length polymorphism (T-RFLP) of small subunit ribosomal (SSU) genes revealed that bacterioplankton incubated in lower pH conditions exhibited a reduction of species richness, evenness, and overall diversity, relative to those incubated in ambient pH conditions. Non-metric multidimensional scaling (MDS) of T-RFLP data resulted in clustering by pH suggesting that pH influenced the structure of these communities. Shifts in the dominant members of bacterioplankton communities incubated under different pH were observed in both T-RFLP and SSU clone library analyses. Both ambient and low pH communities were dominated by Gammaproteobacteria and Alphaproteobacteria, although abundance of Alphaproteobacteria increased in communities incubated at lower pH. This was expressed by the gamma to alpha ratio dropping from ~9 to 4, respectively. In general, the representative taxa from these two classes were distinctly different between the treatments, with a few taxa found to be persistent in both treatments. Changes in the structure of bacterioplankton communities coincided with significant changes to their overall metabolism. Bacterial production rates decreased, while bacterial respiration increased under lower pH conditions. This study highlights the ability of bacterioplankton communities to respond to ocean acidification both structurally and metabolically, which may have significant implications for their ecological function in the marine carbon cycle and the ocean’s response to global climate change.展开更多
Vegetation and soil within estuarine ecosystems play an integral role in ecological processes within pocket estuaries. However, physical barriers, caused by culverts diminish hydrological inputs, sediment exchange, an...Vegetation and soil within estuarine ecosystems play an integral role in ecological processes within pocket estuaries. However, physical barriers, caused by culverts diminish hydrological inputs, sediment exchange, and habitat connectivity. The restoration of estuaries by bridge replacement reconnects <span>the aquatic corridor, however, the recovery of plant communities and soil s</span>ubstrate is not well understood. This observational study monitored four estuary restoration sites of variable ages (0 - 12 years) in Western Washington, USA. Plant community composition, soil organic carbon, organic matter, and soil nutrients were assessed. Percent soil carbon was different among the pre-restoration and youngest (3-year) post-restoration site (<i>P</i> = 0.03), suggesting an initial decrease in carbon and organic matter during restoration. Both N and P were deficient at the newest, lower restoration site, presumably linked to the lack of organic matter required for adequate cation exchange capacity and nutrient/plant exchange (<i>P</i> < 0.05). Plant species diversity was higher at the intermediate (9-year) and oldest post-restoration sites (12-year;<i>P</i> = 0.02). Vegetation composition was primarily native species with few invasive plants present. The results of this study illustrate that tidal marsh plant communities are influenced by the development of salinity and vertical gradients with older sites having an increase in species diversity. Future surveys are ongoing to <span>better understand how these sites recover organic matter and tidal marsh co</span>mmunities to form adequate estuarine habitat over time.展开更多
The impact of chestnut blight, caused by the fungal pathogen Cryphonectria parasitica, has diminished in Europe due to a natural biological control caused by hypovirus infection. Hypovirulence-mediated biological cont...The impact of chestnut blight, caused by the fungal pathogen Cryphonectria parasitica, has diminished in Europe due to a natural biological control caused by hypovirus infection. Hypovirulence-mediated biological control has been far less successful in North America meriting further evaluation of field isolates that have the ability to produce non-lethal cankers, generate hypovirulent inoculum, and exhibit a greater ecological fitness in forest systems. In this study, Cryphonectria hypoviruses (CHV) CHV3-County Line, CHV1-Euro7, and CHV1-Ep713 were evaluated in five different isolates of C. parasitica. One hundred and eighty cankers representing each treatment combination were initiated on American chestnut sprouts in the Monongahela National Forest, West Virginia, USA. The size of cankers, the persistence of hypovirulent (HV) isolates, stroma production, and hypovirus transmission to conidia were assessed four and 12 months after canker expansion. CHV3-County Line infected isolates produced significantly smaller cankers than the isolates infected with either CHV1-type. With regard to CHV1-Euro7 isolates, the fungal genome appeared to contribute to the differences in canker size. After four months, HV isolates harboring either CHV1-type (30%) were retrieved at a significantly higher rate than isolates containing CHV3-County Line (14%). After 12 months, the HV recovery was similar among the three hypoviruses indicating smaller cankers will maintain their HV status after one year. Very few stroma were produced after one year in the field from HV isolates. In vitro, CHV3-County Line (49%) had a significantly lower rate of hypovirus transmission to conidia when compared to CHV1-Euro7 (87%) and CHV1-Ep713 (80%). Significant differences existed among the five different isolates indicating HV transmission is dependent on the fungal genome. This research provided additional evidence that each hypovirus interacts with its host differently and certain isolate/hypovirus combinations have better biological control potential than others.展开更多
New LIDAR (Light Detection and Ranging) and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly v...New LIDAR (Light Detection and Ranging) and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly visible on LIDAR and sonar images. Many previously unknown faults criss-cross the islands and large fault scarps are visible on sonar imagery along the margins of the larger islands. Sonar images of sea floor morphology show many submerged faults as long linear scarps with relief up to 300m (1,000 fl), some of which visibly truncate geologic structures. The San Juan Lopez fault, the largest fault in the islands, extends for at least 65 km (40 mi) from Stuart Island to Rosario strait with a scarp up to 330m (1,000 it) high. Since 1975, the basic structural framework of the San Juan Islands has been considered to consist of five stacked thrust faults, the Rosario, Orcas, Haro, Lopez, and Buck Bay faults, constituting the San Juan Thrust (Nappe) System that has shuffled together far distant terranes. However, the new LIDAR and sonar imagery shows that most of the mapped extent of these postulated faults are actually segments of high angle, dipslip faults and are not thrust faults at all. Thus, the San Juan Thrust (Nappe) System does not exist. The age of these faults is not accurately known and more than one period of high angle faulting may have occurred. Faults shown on L1DAR images of the surface of the islands appear as visible gashes, etched out by erosion of fault zones with few fault scarps. However, the sea floor faults have bold relief and high scarps. A late Pleistocene moraine lies undisturbed across the San Juan Lopez fault.展开更多
Numerical simulation of the bifurcation of Bingham fluid streamline topologies in rectangular double-lid-driven cavity, with varying aspect (height to width) ratio A, is presented. The lids on the top and bottom move ...Numerical simulation of the bifurcation of Bingham fluid streamline topologies in rectangular double-lid-driven cavity, with varying aspect (height to width) ratio A, is presented. The lids on the top and bottom move at the same speed but in opposite directions so that symmetric flow patterns are generated. Similar to the Newtonian case, bifurcations occur as the aspect ratio decreases. Special to Bingham fluids, the non-Newtonian indicator, Bingham number B, also governs the bifurcation besides the bifurcation parameter A.展开更多
Objective: The purpose of this study was to compare the effectiveness of a thorough sonographic oocyte retrieval to a routine in vitro fertilization retrieval to induce ovulation, pregnancy, and endocrine changes in p...Objective: The purpose of this study was to compare the effectiveness of a thorough sonographic oocyte retrieval to a routine in vitro fertilization retrieval to induce ovulation, pregnancy, and endocrine changes in patients with polycystic ovarian syndrome in their post-in vitro fertilization cycles. Study design: Sixty-four patients from a tertiary infertility clinic, with clomiphene citrate-resistant polycystic ovarian syndrome and who were undergoing in vitro fertilization, were assigned randomly into 2 groups. Group 1 (n = 34) had a thorough (every possible follicle punctured) sonographic oocyte retrieval, and group 2 (n = 30) had a routine (only follicles that were likely to contain oocytes) in vitro fertilization retrieval. These patients who did not conceive in their in vitro fertilization cycle were monitored with ultrasound scanning for evidence of ovulation, pregnancy, before and after day 3 gonadotropin,and steroid hormone levels. Analysis of variance and the Student t test were used for statistical significance. Results: Ovulation rates of 53% (18/34) and cumulative pregnancy rate of 44% (8/18) were observed in group 1, with no ovulations in group 2. Significant decreases in luteinizing hormone/FSH ratio (4.1 to 1.7) and testosterone (1.2 to 0.7 ng/mL) occurred after treatment in the thorough sonographic oocyte retrieval group, with no change after routine in vitro fertilization. Operating time was increased signifi cantly in the thorough sonographic oocyte retrieval group (45 vs 24 minutes) in group 2. Conclusion: Thorough sonographic oocyte retrieval during in vitro fertilization cycle can produce significant improvements in the endocrinologic abnormalities, ovulation, and pregnancies that are comparable with ovarian wedge resection in patients with clomiphene citrate-resistant polycystic ovarian syndrome.展开更多
Objective: The purpose of this study was to compare the effectiveness of low-dose human chorionic gonadotropin (hCG) in the late follicular phase to induce ovulation and its endocrine response in patients who had prev...Objective: The purpose of this study was to compare the effectiveness of low-dose human chorionic gonadotropin (hCG) in the late follicular phase to induce ovulation and its endocrine response in patients who had previously failed to ovulate on clomiphene citrate (CC) alone. Design: A total of 67 patients from a private tertiary infertility clinic, who had produced a dominant follicle 12 mm or larger but 20 mm or smaller on a prior CC cycle at 100 mg but had failed to ovulate, were prospectively randomly assigned to groups. Group 1 repeated the 100 mg dose of CC but started a 200 IU hCG intramuscular injection daily when the largest follicle was 12 mm or larger mean diameter. Group 2 received a 150 mg dose of CC and both groups were monitored with transvaginal ultrasound and serum levels of E2,P4, and testosterone. Ultrasound measurements of follicle number and growth, ovulation, pregnancy rates, and serum hormonal levels were recorded and compared between the 2 groups. Analysis of variance and Student t test were used for statistical significance. Results: The low-dose hCG group had significantly higher percentage of ovulatory cycles (57% vs 7% P < .001), peak E2 levels (378 pg/mL vs125 pg/mL P < .01), and pregnancy rates (18% vs 0% P < .001). This group showed no evidence of premature leutinization from the hCG with preovulatory P4 levels less than 1.0 ng/mL and a slight increase in androgen levels. Conclusion: The use of micro-dose hCG after CC in the late follicular phase results in continued follicle growth, increased E2 levels, ovulation, and pregnancies. This treatment offers an efficient and cost-effective alternative before gonadotropin therapy for this type of patient.展开更多
Although the carbon pricing policy is a critical driving factor that will help China achieve economic growth,energy transition,and dual climate change mitigation goals,the kind of carbon pricing policy that will compl...Although the carbon pricing policy is a critical driving factor that will help China achieve economic growth,energy transition,and dual climate change mitigation goals,the kind of carbon pricing policy that will complement the country's current development situation remains controversial.We apply the World Induced Technical Change Hybrid(WITCH)model to explore the heterogeneity and synergy of different carbon pricing policies,and the results indicate that it will be challenging to achieve carbon neutrality before 2060.The study find that the combined policy-a mix of carbon tax and carbon market policies--has the optimal emission reduction effect but comes with the highest economic cost,proving to be unsuitable in the long run.The carbon tax policy is an important transitional means to assist in emission reduction,which can serve as an important supplement to carbon market policy and be phased out after the market mechanism matures.展开更多
Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administrat...Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administration (NOAA-AVHRR)'s Leaf Area Index (LAI) satellite images. Results suggest that from 1982 to 2000 global climate change has contributed to an increase in vegetation cover in the Qinghai-Tibet Plateau. The correlation between rainfall and LAI EOF PC1 and PC2 indicates that rainfall is the major climatic factor influencing interannual variations of average vegetation cover throughout the entire Plateau. However, annual mean vegetation cover trends in the Qinghai-Tibet Plateau are mainly out of phase with air temperature increasing, which is primarily responsible for nonsynchro- nous changes of vegetation cover. In the southern ridge of the Qinghai-Tibet Plateau, recent warming trends contribute to humid weather and favorable conditions for vegetation growth. By contrast, higher temperatures have led to arid conditions and insufficient rainfall in the northern part of the Plateau, leading to drought and other climatic conditions which are not conducive to increased vegetation cover.展开更多
An emerging business model increasingly used by companies in the online software market is to provide both a free basic version and a paid premium version for a service or a product to customers. Such a setting is oft...An emerging business model increasingly used by companies in the online software market is to provide both a free basic version and a paid premium version for a service or a product to customers. Such a setting is often called freemium model. The existence of the free version can reduce the customer uncertainty regarding the evaluation of the commercial software and make use of network effect to improve the firm's profit. However, the freemium model may also have the cannibalization effect which can hurt the profit. Hence, the from needs to determine the optimal content for the free version and the optimal price for the premium version to maximize its profit. In this paper, thst, we obtain the optimal decisions of the freemium model and their properties. Second, we compare the freemium model with the traditional charge-for-everything model that all content of the product need to be charged in terms of the profit, customer welfare, and social welfare. The results show that when customer underestimates the value of the software significantly and the true value of the software is high enough, the freemium model can generate higher profit, higher customer welfare, and higher social welfare. Otherwise, the freemium model may not deliver the desired results.展开更多
In view of the abrupt and phased features of natural gas consumption,this paper attempts to predict natural gas consumption in China with a refined forecasting approach.First,we establish a Markov switching(MS)model t...In view of the abrupt and phased features of natural gas consumption,this paper attempts to predict natural gas consumption in China with a refined forecasting approach.First,we establish a Markov switching(MS)model to identify the phase characteristics after eliminating change points in the natural gas consumption sequence,using the product partition model(PPM).The results show that there are"rapid growth"and"slow growth"regimes in the development process of natural gas consumption in China.Second,the Bayesian model average(BMA)method is employed to determine the core determinants of natural gas consumption under sub-regimes,and it is determined that there are significant differences in the influencing factors under different regimes and periods.Third,this paper establishes the BMA model of the"rapid growth"regime after predicting the state of future natural gas consumption in China.We find that,compared to some other models,the BMA model that fully recognizes the regime without considering change points has the best predictive performance.Finally,the results of static and dynamic scenario analyses show that natural gas consumption continues to rise in 2019 and has obvious seasonal charac-teristics,while possible ultra-rapid growth of consumption in the future provides a new requirement for the supply of natural gas.展开更多
One of the surprises in the run up to,and during,the United Nations’International Year of Light and Light-based Technologies(IYL)in 2015 was the nearly universal lack of awareness of how life depends completely on li...One of the surprises in the run up to,and during,the United Nations’International Year of Light and Light-based Technologies(IYL)in 2015 was the nearly universal lack of awareness of how life depends completely on light,and of the widening role of photonics-based technologies in our lives today.I recognize how little credit or attention we also give to oxygen or water.Like the light from the sun that brings and sustains life,and that eons ago brought most of the energy we now consume,these crucial contributors to life are rarely thought of,not only by the general public but even within the technical community.On being reminded of what photonics enables today,practitioners of photonics were however quick to acknowledge the increasing role of photonics in modern life.That was one of one of the successes of the IYL.展开更多
Gold has multiple attributes and its price is affected by various factors in the market.This paper studies the dynamic relationship between the gold price returns and its affecting factors.Then we use the STL-ETS,neur...Gold has multiple attributes and its price is affected by various factors in the market.This paper studies the dynamic relationship between the gold price returns and its affecting factors.Then we use the STL-ETS,neural network and Bayesian structural time series model to predict the gold price returns,and compare their performance with the benchmark models.The results show that the shocks of crude oil returns and VIX have the positive effect on gold price returns,the shocks of the US dollar index have the negative effect on gold price returns.And the fluctuation of gold price returns mainly depends on crude oil price returns shocks.STL-ETS model can accurately fit the fluctuation trend of the gold price returns and improve prediction accuracy.展开更多
From Newton’s third law,which is known as the principle of actio et reactio1,we expect the forces between interacting particles to be equal and opposite for closed systems.Otherwise,“nonreciprocal”forces can arise....From Newton’s third law,which is known as the principle of actio et reactio1,we expect the forces between interacting particles to be equal and opposite for closed systems.Otherwise,“nonreciprocal”forces can arise.2 This has been shown theoretically in the interaction between dissimilar optically trapped particles that are mediated by an external field.3 As a result,despite the incident external field not having a transverse component of momentum,the particle pair experiences a force in a direction that is transverse to the light propagation direction.3,4 In this letter,we directly measure the net nonreciprocal forces in electrodynamically interacting asymmetric nanoparticle dimers and nanoparticle structures that are illuminated by plane waves and confined to pseudo one-dimensional geometries.We show via electrodynamic theory and simulations that interparticle interactions cause asymmetric scattering from heterodimers.Therefore,the putative nonreciprocal forces are actually a consequence of momentum conservation.Our study demonstrates that asymmetric scatterers exhibit directed motion due to the breakdown of mirror symmetry in their electrodynamic interactions with external fields.展开更多
This article examines the various ways in which the Northern Wei emperor Wenchengdi (440465; r. 452-465) was portrayed to his subjects. As is the case with many monarchs in many countries, he played different parts ...This article examines the various ways in which the Northern Wei emperor Wenchengdi (440465; r. 452-465) was portrayed to his subjects. As is the case with many monarchs in many countries, he played different parts before different groups. For his soldiers, he was represented as a great hunter and marksman; to farmers in the lowlands, as a caring protector and benefactor; to potentially rebellious groups on the periphery, as a strong and steady observer of their actions. At the same time, it was in his reign that the Northern Wei court began efforts to use Buddhism as an overarching way to justify rule to all within the realm, by initiating construction of the famous cave-temples at Yungang, where "Buddhas became emperors and emperors Buddhas." The spectacles through which Wenchengdi was portrayed are contextualized by a parallel examination of the very difficult life of the person behind the pomp and circumstance.展开更多
基金jointly supported by the Key Project of Chinese Academy of Sciences(Grant No.KZCX3-SW-221)the National Natural Science Foundation of China(Grant Nos.40675047 and 40233027).
文摘Land surface changes effect the regional climate due to the complex coupling of land-atmosphere interactions. From 1995 to 2000, a decrease in the vegetation density and an increase in ground-level thermodynamic activity has been documented by multiple data sources in Northwest China, including meteorological, reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF), National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and TIROS Operational Vertical Sounder (TOVS) satellite remote sensing data. As the ground-level thermodynamic activity increases, humid air from the surrounding regions converge toward desert (and semi-desert) regions, causing areas with high vegetation cover to become gradually more arid. Furthermore, land surface changes in Northwest China are responsible for a decrease in total cloud cover, a decline in the fraction of low and middle clouds, an increase in high cloud cover (due to thermodynamic activity) and other regional climatic adaptations. It is proposed that, beginning in 1995, these cloud cover changes contributed to a "green- house" effect, leading to the rapid air temperature increases and other regional climate impacts that have been observed over Northwest China.
基金We are grateful to the financial support from the National Natural Science Foundation of China[Grant number:71874074,Grant number:71433005,Grant number:71804063]Humanities and Social Science Fund of Ministry of Education of China[Grant number:18YJC630208,Grant number:19YJC810007]。
文摘This paper investigates the spatial effect of environmental regulation measures on the upgrading of industrial structure in the integrated development strategy of Beijing-Tianjin-Hebei region and its surrounding areas.In order to reflect the effect of the environmental regulation and different regulation measures more truly,this paper constructs indices of the environmental regulation measures through the results of policy texts quantification.On the basis of the previous research,this paper divides environmental regulation into the following types:personnel and administrative measures of command and control;market-oriented fiscal,taxation,financial and other economic measures;guidance measures.Spatial panel regression results show that administrative measures of command control and market-oriented fiscal measures have a significant role in promoting regional industrial structure upgrading,but not conducive to the advancement of the industrial structure of adjacent areas.Their roles in promoting and inhibition are counteracted,which causes the total effect of industrial structure upgrading of Beijing-Tianjin-Hebei and the surrounding areas are not significant.Personnel measures,financial measures,other economic measures and guidance measures do not have the short-term effect and spatial effect on the upgrading of industrial structure.
文摘Leptomeningeal metastasis is an uncommon but serious complication in patients with advanced cancers. Leptomeningeal metastasis is diagnosed in approximately 5% of the patients, most commonly among patients with cancers of breast and lung, melanoma, and gastrointestinal malignancies. Treatment goal is to improve survival and quality of the patients. Use of targeted therapies and immunotherapy has led to improved survival of patients with non-small cell lung cancer (NSCLC). In this article, we review emerging data on use of mutation-specific agents and immunotherapy in the treatment of leptomeningeal metastasis among patients with NSCLC.
文摘By the end of the 21st century, mean sea surface temperatures are expected to increase 4?C, while atmospheric CO2 concentrations are predicted to triple causing seawater to become acidic. These compounding effects will undoubtedly have major consequences for the organisms and processes in the oceans. Bacterioplankton play a vital role in the marine carbon cycle and the oceans’ ability to sequester CO2. We utilized pCO2 perturbation experiments to investigate the effects of ocean acidity and elevated temperature on bacterioplankton community structure and metabolism. Terminal-restriction fragment length polymorphism (T-RFLP) of small subunit ribosomal (SSU) genes revealed that bacterioplankton incubated in lower pH conditions exhibited a reduction of species richness, evenness, and overall diversity, relative to those incubated in ambient pH conditions. Non-metric multidimensional scaling (MDS) of T-RFLP data resulted in clustering by pH suggesting that pH influenced the structure of these communities. Shifts in the dominant members of bacterioplankton communities incubated under different pH were observed in both T-RFLP and SSU clone library analyses. Both ambient and low pH communities were dominated by Gammaproteobacteria and Alphaproteobacteria, although abundance of Alphaproteobacteria increased in communities incubated at lower pH. This was expressed by the gamma to alpha ratio dropping from ~9 to 4, respectively. In general, the representative taxa from these two classes were distinctly different between the treatments, with a few taxa found to be persistent in both treatments. Changes in the structure of bacterioplankton communities coincided with significant changes to their overall metabolism. Bacterial production rates decreased, while bacterial respiration increased under lower pH conditions. This study highlights the ability of bacterioplankton communities to respond to ocean acidification both structurally and metabolically, which may have significant implications for their ecological function in the marine carbon cycle and the ocean’s response to global climate change.
文摘Vegetation and soil within estuarine ecosystems play an integral role in ecological processes within pocket estuaries. However, physical barriers, caused by culverts diminish hydrological inputs, sediment exchange, and habitat connectivity. The restoration of estuaries by bridge replacement reconnects <span>the aquatic corridor, however, the recovery of plant communities and soil s</span>ubstrate is not well understood. This observational study monitored four estuary restoration sites of variable ages (0 - 12 years) in Western Washington, USA. Plant community composition, soil organic carbon, organic matter, and soil nutrients were assessed. Percent soil carbon was different among the pre-restoration and youngest (3-year) post-restoration site (<i>P</i> = 0.03), suggesting an initial decrease in carbon and organic matter during restoration. Both N and P were deficient at the newest, lower restoration site, presumably linked to the lack of organic matter required for adequate cation exchange capacity and nutrient/plant exchange (<i>P</i> < 0.05). Plant species diversity was higher at the intermediate (9-year) and oldest post-restoration sites (12-year;<i>P</i> = 0.02). Vegetation composition was primarily native species with few invasive plants present. The results of this study illustrate that tidal marsh plant communities are influenced by the development of salinity and vertical gradients with older sites having an increase in species diversity. Future surveys are ongoing to <span>better understand how these sites recover organic matter and tidal marsh co</span>mmunities to form adequate estuarine habitat over time.
文摘The impact of chestnut blight, caused by the fungal pathogen Cryphonectria parasitica, has diminished in Europe due to a natural biological control caused by hypovirus infection. Hypovirulence-mediated biological control has been far less successful in North America meriting further evaluation of field isolates that have the ability to produce non-lethal cankers, generate hypovirulent inoculum, and exhibit a greater ecological fitness in forest systems. In this study, Cryphonectria hypoviruses (CHV) CHV3-County Line, CHV1-Euro7, and CHV1-Ep713 were evaluated in five different isolates of C. parasitica. One hundred and eighty cankers representing each treatment combination were initiated on American chestnut sprouts in the Monongahela National Forest, West Virginia, USA. The size of cankers, the persistence of hypovirulent (HV) isolates, stroma production, and hypovirus transmission to conidia were assessed four and 12 months after canker expansion. CHV3-County Line infected isolates produced significantly smaller cankers than the isolates infected with either CHV1-type. With regard to CHV1-Euro7 isolates, the fungal genome appeared to contribute to the differences in canker size. After four months, HV isolates harboring either CHV1-type (30%) were retrieved at a significantly higher rate than isolates containing CHV3-County Line (14%). After 12 months, the HV recovery was similar among the three hypoviruses indicating smaller cankers will maintain their HV status after one year. Very few stroma were produced after one year in the field from HV isolates. In vitro, CHV3-County Line (49%) had a significantly lower rate of hypovirus transmission to conidia when compared to CHV1-Euro7 (87%) and CHV1-Ep713 (80%). Significant differences existed among the five different isolates indicating HV transmission is dependent on the fungal genome. This research provided additional evidence that each hypovirus interacts with its host differently and certain isolate/hypovirus combinations have better biological control potential than others.
文摘New LIDAR (Light Detection and Ranging) and sonar imagery have revealed remarkable geomorphic details never seen before and not visible by any other means. Numerous faults and other geologic structures are plainly visible on LIDAR and sonar images. Many previously unknown faults criss-cross the islands and large fault scarps are visible on sonar imagery along the margins of the larger islands. Sonar images of sea floor morphology show many submerged faults as long linear scarps with relief up to 300m (1,000 fl), some of which visibly truncate geologic structures. The San Juan Lopez fault, the largest fault in the islands, extends for at least 65 km (40 mi) from Stuart Island to Rosario strait with a scarp up to 330m (1,000 it) high. Since 1975, the basic structural framework of the San Juan Islands has been considered to consist of five stacked thrust faults, the Rosario, Orcas, Haro, Lopez, and Buck Bay faults, constituting the San Juan Thrust (Nappe) System that has shuffled together far distant terranes. However, the new LIDAR and sonar imagery shows that most of the mapped extent of these postulated faults are actually segments of high angle, dipslip faults and are not thrust faults at all. Thus, the San Juan Thrust (Nappe) System does not exist. The age of these faults is not accurately known and more than one period of high angle faulting may have occurred. Faults shown on L1DAR images of the surface of the islands appear as visible gashes, etched out by erosion of fault zones with few fault scarps. However, the sea floor faults have bold relief and high scarps. A late Pleistocene moraine lies undisturbed across the San Juan Lopez fault.
文摘Numerical simulation of the bifurcation of Bingham fluid streamline topologies in rectangular double-lid-driven cavity, with varying aspect (height to width) ratio A, is presented. The lids on the top and bottom move at the same speed but in opposite directions so that symmetric flow patterns are generated. Similar to the Newtonian case, bifurcations occur as the aspect ratio decreases. Special to Bingham fluids, the non-Newtonian indicator, Bingham number B, also governs the bifurcation besides the bifurcation parameter A.
文摘Objective: The purpose of this study was to compare the effectiveness of a thorough sonographic oocyte retrieval to a routine in vitro fertilization retrieval to induce ovulation, pregnancy, and endocrine changes in patients with polycystic ovarian syndrome in their post-in vitro fertilization cycles. Study design: Sixty-four patients from a tertiary infertility clinic, with clomiphene citrate-resistant polycystic ovarian syndrome and who were undergoing in vitro fertilization, were assigned randomly into 2 groups. Group 1 (n = 34) had a thorough (every possible follicle punctured) sonographic oocyte retrieval, and group 2 (n = 30) had a routine (only follicles that were likely to contain oocytes) in vitro fertilization retrieval. These patients who did not conceive in their in vitro fertilization cycle were monitored with ultrasound scanning for evidence of ovulation, pregnancy, before and after day 3 gonadotropin,and steroid hormone levels. Analysis of variance and the Student t test were used for statistical significance. Results: Ovulation rates of 53% (18/34) and cumulative pregnancy rate of 44% (8/18) were observed in group 1, with no ovulations in group 2. Significant decreases in luteinizing hormone/FSH ratio (4.1 to 1.7) and testosterone (1.2 to 0.7 ng/mL) occurred after treatment in the thorough sonographic oocyte retrieval group, with no change after routine in vitro fertilization. Operating time was increased signifi cantly in the thorough sonographic oocyte retrieval group (45 vs 24 minutes) in group 2. Conclusion: Thorough sonographic oocyte retrieval during in vitro fertilization cycle can produce significant improvements in the endocrinologic abnormalities, ovulation, and pregnancies that are comparable with ovarian wedge resection in patients with clomiphene citrate-resistant polycystic ovarian syndrome.
文摘Objective: The purpose of this study was to compare the effectiveness of low-dose human chorionic gonadotropin (hCG) in the late follicular phase to induce ovulation and its endocrine response in patients who had previously failed to ovulate on clomiphene citrate (CC) alone. Design: A total of 67 patients from a private tertiary infertility clinic, who had produced a dominant follicle 12 mm or larger but 20 mm or smaller on a prior CC cycle at 100 mg but had failed to ovulate, were prospectively randomly assigned to groups. Group 1 repeated the 100 mg dose of CC but started a 200 IU hCG intramuscular injection daily when the largest follicle was 12 mm or larger mean diameter. Group 2 received a 150 mg dose of CC and both groups were monitored with transvaginal ultrasound and serum levels of E2,P4, and testosterone. Ultrasound measurements of follicle number and growth, ovulation, pregnancy rates, and serum hormonal levels were recorded and compared between the 2 groups. Analysis of variance and Student t test were used for statistical significance. Results: The low-dose hCG group had significantly higher percentage of ovulatory cycles (57% vs 7% P < .001), peak E2 levels (378 pg/mL vs125 pg/mL P < .01), and pregnancy rates (18% vs 0% P < .001). This group showed no evidence of premature leutinization from the hCG with preovulatory P4 levels less than 1.0 ng/mL and a slight increase in androgen levels. Conclusion: The use of micro-dose hCG after CC in the late follicular phase results in continued follicle growth, increased E2 levels, ovulation, and pregnancies. This treatment offers an efficient and cost-effective alternative before gonadotropin therapy for this type of patient.
基金supported by the National Natural Science Foundation of China(71874133)the Youth Innovation Team of Shaanxi Universities,and the Annual Basic Scientific Research Project of Xidian University(2019).
文摘Although the carbon pricing policy is a critical driving factor that will help China achieve economic growth,energy transition,and dual climate change mitigation goals,the kind of carbon pricing policy that will complement the country's current development situation remains controversial.We apply the World Induced Technical Change Hybrid(WITCH)model to explore the heterogeneity and synergy of different carbon pricing policies,and the results indicate that it will be challenging to achieve carbon neutrality before 2060.The study find that the combined policy-a mix of carbon tax and carbon market policies--has the optimal emission reduction effect but comes with the highest economic cost,proving to be unsuitable in the long run.The carbon tax policy is an important transitional means to assist in emission reduction,which can serve as an important supplement to carbon market policy and be phased out after the market mechanism matures.
基金国家重点基础研究发展计划(批准号:2006CB403607)国家自然科学基金(批准号:40675047,40605023)+1 种基金中国科学院创新项目(批准号:KZCX2-YW-219)A Western Washington University Summer Research Grant联合资助
基金the National Basic Research Program of China (Grant No. 2006CB403607)the National Natural Science Foundation of China (Grant Nos. 40675047 and 40605023)+1 种基金the Key Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-219)a Western Washington University summer research grant
文摘Empirical Orthogonal Function (EOF) analysis and the related Principal Components (PC) analysis are used to extract valuable vegetation cover derived information from the National Oceanic and Atmos- pheric Administration (NOAA-AVHRR)'s Leaf Area Index (LAI) satellite images. Results suggest that from 1982 to 2000 global climate change has contributed to an increase in vegetation cover in the Qinghai-Tibet Plateau. The correlation between rainfall and LAI EOF PC1 and PC2 indicates that rainfall is the major climatic factor influencing interannual variations of average vegetation cover throughout the entire Plateau. However, annual mean vegetation cover trends in the Qinghai-Tibet Plateau are mainly out of phase with air temperature increasing, which is primarily responsible for nonsynchro- nous changes of vegetation cover. In the southern ridge of the Qinghai-Tibet Plateau, recent warming trends contribute to humid weather and favorable conditions for vegetation growth. By contrast, higher temperatures have led to arid conditions and insufficient rainfall in the northern part of the Plateau, leading to drought and other climatic conditions which are not conducive to increased vegetation cover.
文摘An emerging business model increasingly used by companies in the online software market is to provide both a free basic version and a paid premium version for a service or a product to customers. Such a setting is often called freemium model. The existence of the free version can reduce the customer uncertainty regarding the evaluation of the commercial software and make use of network effect to improve the firm's profit. However, the freemium model may also have the cannibalization effect which can hurt the profit. Hence, the from needs to determine the optimal content for the free version and the optimal price for the premium version to maximize its profit. In this paper, thst, we obtain the optimal decisions of the freemium model and their properties. Second, we compare the freemium model with the traditional charge-for-everything model that all content of the product need to be charged in terms of the profit, customer welfare, and social welfare. The results show that when customer underestimates the value of the software significantly and the true value of the software is high enough, the freemium model can generate higher profit, higher customer welfare, and higher social welfare. Otherwise, the freemium model may not deliver the desired results.
基金The paper is supported by the National Natural Science Foundation of China(NSFC)under grant No.71473155the New Star of Youth Science and Technology Plan Project in China’s Shaanxi Province with No.2016KJXX-142016 Annual Basic Scientific Research Project of Xidian University with No.JB160603.
文摘In view of the abrupt and phased features of natural gas consumption,this paper attempts to predict natural gas consumption in China with a refined forecasting approach.First,we establish a Markov switching(MS)model to identify the phase characteristics after eliminating change points in the natural gas consumption sequence,using the product partition model(PPM).The results show that there are"rapid growth"and"slow growth"regimes in the development process of natural gas consumption in China.Second,the Bayesian model average(BMA)method is employed to determine the core determinants of natural gas consumption under sub-regimes,and it is determined that there are significant differences in the influencing factors under different regimes and periods.Third,this paper establishes the BMA model of the"rapid growth"regime after predicting the state of future natural gas consumption in China.We find that,compared to some other models,the BMA model that fully recognizes the regime without considering change points has the best predictive performance.Finally,the results of static and dynamic scenario analyses show that natural gas consumption continues to rise in 2019 and has obvious seasonal charac-teristics,while possible ultra-rapid growth of consumption in the future provides a new requirement for the supply of natural gas.
文摘One of the surprises in the run up to,and during,the United Nations’International Year of Light and Light-based Technologies(IYL)in 2015 was the nearly universal lack of awareness of how life depends completely on light,and of the widening role of photonics-based technologies in our lives today.I recognize how little credit or attention we also give to oxygen or water.Like the light from the sun that brings and sustains life,and that eons ago brought most of the energy we now consume,these crucial contributors to life are rarely thought of,not only by the general public but even within the technical community.On being reminded of what photonics enables today,practitioners of photonics were however quick to acknowledge the increasing role of photonics in modern life.That was one of one of the successes of the IYL.
基金supported by the National Natural Science Foundation of China(NSFC)(71874133)the Annual Basic Scientific Research Project of Xidian University(2019)
文摘Gold has multiple attributes and its price is affected by various factors in the market.This paper studies the dynamic relationship between the gold price returns and its affecting factors.Then we use the STL-ETS,neural network and Bayesian structural time series model to predict the gold price returns,and compare their performance with the benchmark models.The results show that the shocks of crude oil returns and VIX have the positive effect on gold price returns,the shocks of the US dollar index have the negative effect on gold price returns.And the fluctuation of gold price returns mainly depends on crude oil price returns shocks.STL-ETS model can accurately fit the fluctuation trend of the gold price returns and improve prediction accuracy.
基金support from the Vannevar Bush Faculty Fellowship programsponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research through grant N00014-16-1-2502supported by the U.S.Department of Energy,Office of Science,under Contract No.DE-AC02-06CH11357.
文摘From Newton’s third law,which is known as the principle of actio et reactio1,we expect the forces between interacting particles to be equal and opposite for closed systems.Otherwise,“nonreciprocal”forces can arise.2 This has been shown theoretically in the interaction between dissimilar optically trapped particles that are mediated by an external field.3 As a result,despite the incident external field not having a transverse component of momentum,the particle pair experiences a force in a direction that is transverse to the light propagation direction.3,4 In this letter,we directly measure the net nonreciprocal forces in electrodynamically interacting asymmetric nanoparticle dimers and nanoparticle structures that are illuminated by plane waves and confined to pseudo one-dimensional geometries.We show via electrodynamic theory and simulations that interparticle interactions cause asymmetric scattering from heterodimers.Therefore,the putative nonreciprocal forces are actually a consequence of momentum conservation.Our study demonstrates that asymmetric scatterers exhibit directed motion due to the breakdown of mirror symmetry in their electrodynamic interactions with external fields.
文摘This article examines the various ways in which the Northern Wei emperor Wenchengdi (440465; r. 452-465) was portrayed to his subjects. As is the case with many monarchs in many countries, he played different parts before different groups. For his soldiers, he was represented as a great hunter and marksman; to farmers in the lowlands, as a caring protector and benefactor; to potentially rebellious groups on the periphery, as a strong and steady observer of their actions. At the same time, it was in his reign that the Northern Wei court began efforts to use Buddhism as an overarching way to justify rule to all within the realm, by initiating construction of the famous cave-temples at Yungang, where "Buddhas became emperors and emperors Buddhas." The spectacles through which Wenchengdi was portrayed are contextualized by a parallel examination of the very difficult life of the person behind the pomp and circumstance.