We designed micromechanical experiments to examine the deformation behaviors of austenitic stainless steels fabricated by additive manufacturing. Micro-pillars containing different dislocation cell ...sizes were produced from the bulk specimen, and were mechanically tested for direct assessment of cell size reliance of yield and plastic deformation processes. The results highlight the cruciality of dislocation density in determining the yield strength of additively manufactured stainless steels, challenging the previous viewpoint that the strength scales with the cell size. However, dislocation nucleation and hardening of these micro-pillars were found to be cell size-correlated, with easier dislocation nucleation for micro-pillars containing smaller cells.
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Autonomous underwater vehicle plays a more and more important role in the exploration of marine resources. Path planning and obstacle avoidance is the core technology to realize the autonomy of AUV, ...which will determine the application prospect of AUV. This paper mainly describes the state-of-the-art methods of path planning and obstacle avoidance for AUV and aims to become a starting point for researchers who are initiating their endeavors in this field. Moreover, the objective of this paper is to give a comprehensive overview of work on recent advances and new breakthroughs, also to discuss some future directions worthy to research in this area. The focus of this article is put on these path planning algorithms that deal with constraints and characteristics of AUV and the influence of marine environments. Since most of the time AUV will operate in the environments full of obstacles, we divide path planning methods of AUV into two categories: global path planning with known static obstacles, and local path planning with unknown and dynamic obstacles. We describe the basic principles of each method and survey most related work to them. An in-depth discussion and comparisons between different path planning algorithms are also provided. Lastly, we propose some potential future research directions that are worthy to investigate in this field.
•State-of-the-art and new breakthroughs of path planning and obstacle avoidance methods for AUV•Studies applied to physical AUV platform and real marine environment.•Comparisons and discussions about path planning methods for obstacle avoidance.•Potential future research directions worthy to investigate in this field.
Satellite‐based technologies that track individual animal movements enable the mapping of their spatial and temporal patterns of occurrence. This is particularly useful in poorly studied or remote ...regions where there is a need for the rapid gathering of relevant ecological knowledge to inform management actions. One such region is East Asia, where many intertidal habitats are being degraded at unprecedented rates and shorebird populations relying on these habitats show rapid declines.
We examine the utility of satellite tracking to accelerate the identification of coastal sites of conservation importance in the East Asian–Australasian Flyway. In 2015–2017, we used solar‐powered satellite transmitters to track the migration of 32 great knots (Calidris tenuirostris), an “Endangered” shorebird species widely distributed in the Flyway and fully dependent on intertidal habitats for foraging during the non‐breeding season.
From the great knot tracks, a total of 92 stopping sites along the Flyway were identified. Surprisingly, 63% of these sites were not known as important shorebird sites before our study; in fact, every one of the tracked individuals used sites that were previously unrecognized.
Site knowledge from on‐ground studies in the Flyway is most complete for the Yellow Sea and generally lacking for Southeast Asia, Southern China and Eastern Russia.
Synthesis and applications. Satellite tracking highlighted coastal habitats that are potentially important for shorebirds but lack ecological information and conservation recognition, such as those in Southern China and Southeast Asia. At the same time, the distributional data of tracked individuals can direct on‐ground surveys at the lesser known sites to collect information on bird numbers and habitat characteristics. To recognize and subsequently protect valuable coastal habitats, filling knowledge gaps by integrating bird tracking with ground‐based methods should be prioritized.
摘要
基于卫星技术追踪动物个体的移动，能展示其时空分布格局。这种方法尤其适用于偏远或缺乏相关研究的地区，用于快速收集对生境管理和保护有用的生态学信息。东亚地区的潮间带湿地正受到大规模的破坏，依赖这些湿地的涉禽种群数量亦急剧下降, 而有关涉禽对这个区域的利用却所知甚少。
我们检验能否使用卫星追踪技术来快速识别东亚─澳大利西亚迁飞路线上具有重要保护意义的地点。2015–2017年间，我们使用太阳能卫星发射器追踪了32只大滨鹬 (Calidris tenuirostris)的迁徙活动。大滨鹬是一种广泛分布在此迁飞路线上的濒危涉禽，它们在繁殖季以外完全依赖潮间带湿地觅食。
根据卫星追踪数据，一共获取了大滨鹬在此迁飞路线上的92个迁徙停歇地点。出乎意料的是，其中63%的停歇地点在此之前并未被识别为涉禽的重要栖息地，并且所有追踪个体都曾停歇在这些以往未被识别为重要栖息地的地点。
在此迁飞路线上，实地调查数据最完善的是黄海地区，而东南亚、中国南部以及俄罗斯远东地区普遍缺乏实地调查数据。
结论及应用：卫星追踪研究结果强调了涉禽潜在的重要滨海栖息地，尤其是那些目前仍缺乏生态学数据和保护价值认知的栖息地，例如中国南部和东南亚的滨海区域。与此同时，卫星跟踪的个体分布数据可用于指导在信息缺乏的地点开展地面调查，以便更有效地收集鸟类数量和生境特征的数据。为了确认并保护那些具有保护价值的滨海栖息地，必须优先考虑将卫星追踪和地面调查两种方法相结合以填补相关知识的空缺。
Satellite tracking highlighted coastal habitats that are potentially important for shorebirds but lack ecological information and conservation recognition, such as those in Southern China and Southeast Asia. At the same time, the distributional data of tracked individuals can direct on‐ground surveys at the lesser known sites to collect information on bird numbers and habitat characteristics. To recognize and subsequently protect valuable coastal habitats, filling knowledge gaps by integrating bird tracking with ground‐based methods should be prioritized.
Chemosensory proteins (CSP) are soluble carrier proteins that may function in odorant reception in insects. CSPs have not been thoroughly studied at whole-genome level, despite the availability of ...insect genomes. Here, we identified/reidentified 283 CSP genes in the genomes of 22 mosquitoes. All 283 CSP genes possess a highly conserved OS-D domain. We comprehensively analyzed these CSP genes and determined their conserved domains, structure, genomic distribution, phylogeny, and evolutionary patterns. We found an average of seven CSP genes in each of 19 Anopheles genomes, 27 CSP genes in Cx. quinquefasciatus, 43 in Ae. aegypti, and 83 in Ae. albopictus. The Anopheles CSP genes had a simple genomic organization with a relatively consistent gene distribution, while most of the Culicinae CSP genes were distributed in clusters on the scaffolds. Our phylogenetic analysis clustered the CSPs into two major groups: CSP1-8 and CSE1-3. The CSP1-8 groups were all monophyletic with good bootstrap support. The CSE1-3 groups were an expansion of the CSP family of genes specific to the three Culicinae species. The Ka/Ks ratios indicated that the CSP genes had been subject to purifying selection with relatively slow evolution. Our results provide a comprehensive framework for the study of the CSP gene family in these 22 mosquito species, laying a foundation for future work on CSP function in the detection of chemical cues in the surrounding environment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Identifying where and when population ‘bottlenecks’ occur is critical to the conservation of migratory species, many of which are declining precipitously worldwide. Especially challenging is the ...evaluation of changes to staging sites. These sites are indispensable links in the migratory cycle but are typically used only briefly.
We devised a field‐based approach to assess the quality and carrying capacity of a critical staging site in Nanpu, China, for the declining, migratory Red Knot (Calidris canutus rogersi & C. c. piersmai) during northward migration. The Nanpu tidal flat supports 50,000–100,000 Red Knots annually, and while there, the knots feed almost exclusively on the bivalve Potamocorbula laevis. We simultaneously monitored changes in the abundance of Red Knots and bivalves across this entire staging site in spring 2018.
After taking into account potential competition with other shorebird species, we estimated that the Nanpu tidal flat was capable of supporting approximately 1.46–1.70 times the observed level of Red Knot usage of this site, and therefore is operating below, but close to, carrying capacity with respect to food resources for Red Knots. This result suggests that any further habitat loss or degradation at this site could harm the Red Knot population along the entire East Asian‐Australasian Flyway.
Synthesis and applications. Quantitative monitoring and evaluation of habitat quality of staging sites are essential to successfully conserve declining migratory species. In particular, researchers and conservation practitioners should incorporate both population size and staging duration to more accurately assess the importance of different sites and to quantify how changes in staging habitat quality may translate into changes in the population sizes of migratory species at both local and global scales.
摘要
全球的迁徙候鸟数量都在急剧下降。识别出影响它们种群数量变化的关键栖息地和生活史阶段，对于 保护这些快速减少的迁徙物种而言至关重要。尽管候鸟每年利用中停地的时间较为短暂，中停地在候鸟的迁徙和生存过程中却起着举足轻重的作用。然而，如何量化和评估中停地的栖息地质量及其对于候鸟 种群的影响却颇具挑战。
本研究设计了㇐套基于野外调查的中停地栖息地质量及环境承载力评估方案，并以每年春季北迁期间 在河北南堡滩涂停歇的红腹滨鹬 (Calidris canutus rogersi & C. c. piersmai) 作为研究对象，测试了该方案 的可行性。每年春天约有5‐10万只红腹滨鹬到访南堡，它们主要取食滩涂中的光滑河篮蛤 (Potamocorbula laevis) 进行能量补给。2018年春季，我们对整个南堡滩涂的红腹滨鹬和光滑河篮蛤数量 变化进行了持续监测。
将其他鸻鹬类的种间竞争影响考虑在内，南堡滩涂的红腹滨鹬环境承载力约为当年实际种群利用强度 的1.46‐1.70倍。综合分析表明，南堡滩涂上红腹滨鹬的食物利用强度十分接近其环境承载力，因此，当 地栖息地质量的变化可能会极大地影响整个东亚‐澳大利西亚迁飞区的红腹滨鹬种群数量。
综述和应用:针对重要中停地的栖息地质量监测和评估对于保护那些数量快速下降的候鸟种群具有十 分重要的意义。在科学研究和实际保护工作中，人们尤其需要同时考虑整个迁徙季节中的中停地候鸟数 量变化及其停留时长，从而更为准确地评估不同中停地对于候鸟的重要性，进而定量化地研究和预测栖 息地质量变化将如何影响候鸟的种群数量。
Quantitative monitoring and evaluation of habitat quality of staging sites are essential to successfully conserve declining migratory species. In particular, researchers and conservation practitioners should incorporate both population size and staging duration to more accurately assess the importance of different sites and to quantify how changes in staging habitat quality may translate into changes in the population sizes of migratory species at both local and global scales.
There is no Diophantine quintuple Bo He; Alain Togbé; Volker Ziegler
Transactions of the American Mathematical Society,
05/2019, Letnik:
371, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A set of m positive integers \{a_1, a_2, \ldots , a_m\} is called a Diophantine m-tuple if a_i a_j + 1 is a perfect square for all 1 \le i < j \le m. Dujella proved that there is no Diophantine ...sextuple and that there are at most finitely many Diophantine quintuples. In particular, a folklore conjecture concerning Diophantine m-tuples states that no Diophantine quintuple exists at all. We prove this conjecture.
•We study the online presale model of fresh produce from a competitive perspective.•Impact of an online grocery entry on the existing physical store is investigated.•We characterize pricing strategy ...equilibrium for the store and the online grocery.•We identify the conditions under which the store should alter its pricing strategy.
The fresh produce market is one of the last unexplored spaces for e-commerce and has attracted the entrance of many e-commerce firms in recent years; these firms are likely to influence the traditional fresh produce sales channels. The online presale of fresh produce can lower the circulation loss rate while traditional sales channels suffer from a huge waste in the circulation. In this paper, we study the online presale model of fresh produce from a competitive perspective. We examine the pricing and order decisions of one online grocery and one physical store. By examining the physical store with and without the online grocery, we investigate the impact of the entry of an online grocery on the physical store. We first identify two pricing strategies, penetration-pricing and skimming-pricing, for the physical store and two pricing strategies for the online grocery, and then identify the conditions under which pricing equilibrium will occur. We find that the store does not necessarily alter its pricing strategy after the online grocery enters the market. When the physical store uses the penetration-pricing strategy to compete with the online grocery for Internet shoppers, it may fail to achieve that goal if the online grocery's delivery cost is low and if the Internet shoppers account for a relatively low proportion of shoppers. Alternatively, the physical store may fail if the online grocery's delivery cost is not high and if the circulation loss rate of fresh produce is high.
Pd-catalyzed cross-coupling reactions have become essential tools for the construction of carbon–carbon and carbon–heteroatom bonds. Over the last three decades, great efforts have been made with ...cross-coupling chemistry in the discovery, development, and commercialization of innovative new pharmaceuticals and agrochemicals (mainly herbicides, fungicides, and insecticides). In view of the growing interest in both modern crop protection and cross-coupling chemistry, this review gives a comprehensive overview of the successful applications of various Pd-catalyzed cross-coupling methodologies, which have been implemented as key steps in the synthesis of agrochemicals (on R&D and pilot-plant scales) such as the Heck, Suzuki, Sonogashira, Stille, and Negishi reactions, as well as decarboxylative, carbonylative, α-arylative, and carbon–nitrogen bond bond-forming cross-coupling reactions. Some perspectives and challenges for these catalytic coupling processes in the discovery of agrochemicals are briefly discussed in the final section. The examples chosen demonstrate that cross-coupling chemistry approaches open-up new, low-cost, and more efficient industrial routes to existing agrochemicals, and such methods also have the capability to lead the new generation of pesticides with novel modes of action for sustainable crop protection.
Cancer-related fatigue, one of the most frequent side-effects of cancer treatment, affects the well-being of patients. Despite the fact that the estimated prevalence and risk factors of ...cancer-related fatigue are widely reported, these results have not been synthesized.
To systematically assess the prevalence of cancer-related fatigue, including stratification by fatigue degree, sex, age, therapeutic method, cancer-related fatigue scales, countries, and risk factors for cancer-related fatigue.
Systematic literature review and meta-analysis.
PubMed, Cochrane Library, Web of Science, CINAHL Plus, China Knowledge Resource Integrated Database (CNKI), Wanfang Database, Chinese Biomedical Database (CBM), and Weipu Database (VIP) were comprehensively searched for observational studies investigating the prevalence and risk factors of cancer-related fatigue from inception to March 31st, 2019.
Original journal articles were included which met the inclusion criteria. The quality of the included studies was evaluated independently by two investigators. Meta-analysis was conducted using Stata 12.0 software package, with estimates of cancer-related fatigue from pooled using a random-effects model.
In total, 2641 articles were screened and data from 84 studies involving 144,813 subjects were used in meta-analysis. The prevalence of cancer-related fatigue in individual studies varied from 14.03% to 100%. The pooled prevalence of cancer-related fatigue was 52% (95% confidence interval, CI: 48% to 56%, I2 = 99.7%, P < 0.0001). After controlling for confounding variables, the following risk factors were associated with cancer-related fatigue: poor performance status (odds ratio, OR = 6.58, 95% CI: 2.60 to 16.67, I2 = 75.2%, P < 0.0001), chemoradiotherapy (OR = 2.25, 95% CI: 1.90 to 2.67, I2 =0%, P<0.0001), female sex (OR = 2.07, 95% CI: 1.51 to 2.84, I2 = 41.2%, P<0.0001), insomnia (OR = 2.83, 95% CI: 1.22 to 6.57, I2 = 98.3%, P = 0.015), neuroticism (OR = 1.23, 95% CI: 1.05 to 1.43, I2 = 88.9%, P = 0.01), pain (OR = 2.64, 95% CI: 1.20 to 5.80, I2 = 95.3%, P = 0.016), and depression (OR = 2.23, 95% CI: 1.70 to 2.93, I2 = 98.1%, P < 0.0001).
The current analysis indicates an overall pooled prevalence of cancer-related fatigue of 52%. Poor performance status, chemoradiotherapy, female sex, insomnia, neuroticism, pain, and depression were identified as risk factors for cancer-related fatigue. Understanding the risk factors of cancer-related fatigue can provide the healthcare personnel with the theoretical basis for the management and treatment of the patients.
Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe3C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) ...electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe3C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm−2 in peak power density) and an aprotic Li–O2 battery (8749 mAh g−1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe3C contribution to the catalyst performance, suggesting Fe3C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.
An Fe–N–C catalyst is derived from dual metal–organic frameworks through facile pyrolysis, affording excellent oxygen reduction catalytic performance in alkaline/acidic half‐cells, a H2–O2 proton exchange membrane fuel cell, and a Li–O2 battery. The excellent catalytic performance benefits from density populated Fe–Fe3C@Fe–N–C dual active sites, hierarchical porosities for mass transport, and partial carbon graphitization for charge transfer.
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