计算流体力学(CFD)模拟机械通气时下气道气流流场特性的方法及其可行性研究

目的 探索计算流体力学（computational fluid dynamics,CFD）技术模拟机械通气状态下呼吸系统内部气流流动的可行性,为CFD技术应用于机械通气的气流流场模拟奠定基础。方法 选取1名健康的中年男性志愿者进行头颈部加胸部MRI扫描,将获得的图像保存为DICOM格式导入Mimics17.0医学图像软件中构建气道三维模型,用Geomagic Studio 12软件进行网格划分后导入Ansys 14.5软件进行CFD模拟计算,对机械通气气道内部气流流场变化进行动态分析。结果 基于MRI图像数据构建气道三维模型,划分网格后对CFD模拟施加不同流速的入口边界条件,分析流速分布、壁压力分布、流场线变化情况以及局部管壁剪切应力的变化情况。结论 基于影像数据对气道进行三维重建,通过对模型进行CFD模拟发现,入口流速与气道内流体流速分布、壁剪切应力及壁压力均呈正相关,入口高流速易在气道分叉处形成涡流。     

Effect of Polymer Drag Reducer on Rheological Properties of Rocket Kerosene Solutions

Adding drag reduction agent (DRA) to rocket kerosene is an effective way to reduce the pipeline resistance of rocket kerosene transportation systems. However, so far, there have been few research reports on the effect of DRA on the rheological properties of rocket kerosene solution, especially from a microscopic perspective. In this study, coarse-grained molecular dynamics simulations were conducted to investigate the rheological properties of rocket kerosene solutions with DRAs of different chain lengths and concentrations. The results showed that the viscosity of DRA—kerosene solution is generally higher than that of pure kerosene at a low shear rate, while with an increase in shear rate, the viscosity of DRA—kerosene solution decreases rapidly and finally tends to become similar to that of pure kerosene. The shear viscosity of DRA—kerosene solution increases with an increase in chain length and concentration of polymers. Through observing the morphologic change of DRA molecules and analyzing the radius of gyration and the mean-squared end-to-end distance of polymers, it was confirmed that the rheological properties of DRA—kerosene solutions are strongly related to the degree of entanglement of polymer chains. The simulation results provide microscopic insights into the rheological behavior of DRA—kerosene solutions and clarify the intrinsic relation between the morphologic change of polymer molecules and the rheological properties of DRA—kerosene solutions.     

我国中医药胃肠动力基础实验方法研究进展

中药在胃肠动力动物基础实验研究,目前主要采用胃排空小肠推进率测定法、胃肠道腔外电桥式应力传感器记录法、胃肠激素测定(胃泌素、胃动素、生长抑素等)、免疫组织化学方法、离体体胃肠平滑肌肌条动力测定、胃肠内压描记法.采用最佳的实验研究方法,对中药的研究和认知具有重要的临床意义.     

Population interconnectivity over the past 120,000 years explains distribution and diversity of Central African hunter-gatherers

The evolutionary history of African hunter-gatherers holds key insights into modern human diversity. Here, we combine ethnographic and genetic data on Central African hunter-gatherers (CAHG) to show that their current distribution and density are explained by ecology rather than by a displacement to marginal habitats due to recent farming expansions, as commonly assumed. We also estimate the range of hunter-gatherer presence across Central Africa over the past 120,000 years using paleoclimatic reconstructions, which were statistically validated by our newly compiled dataset of dated archaeological sites. Finally, we show that genomic estimates of divergence times between CAHG groups match our ecological estimates of periods favoring population splits, and that recoveries of connectivity would have facilitated subsequent gene flow. Our results reveal that CAHG stem from a deep history of partially connected populations. This form of sociality allowed the coexistence of relatively large effective population sizes and local differentiation, with important implications for the evolution of genetic and cultural diversity in Homo sapiens.

The evolutionary history of African hunter-gatherers may hold key insights into patterns and processes behind the evolution of modern human diversity. Recent genomic studies have revealed that these populations represent the oldest and most diverse human genetic lineages and have been genetically differentiated from one another since the origin of humans (1–3) (SI Appendix, Table S1). Therefore, a first question is whether their current ecological niches were also characteristic of early Homo sapiens populations. However, genetic data alone can neither determine the geographic distribution of hunter-gatherers in the past nor demonstrate a deep history of adaptation of hunter-gatherers to their current environments. In fact, various studies have proposed that farming expansions within the past 5,000 years (in particular by the ancestors of Bantu speakers) would have only recently displaced hunter-gatherers to marginalized regions less favorable to agriculture (such as rainforests and deserts) (4–7).For example, the central part of Africa, between latitudes 5°N and 5°S currently is inhabited by ∼20 scattered hunter-gatherer ethnic groups (8). These Central African hunter-gatherers (CAHG) form a genetic clade thought to have diverged from other African populations as far back as 120,000 to 200,000 years ago (2, 9). The lack of any major linguistic specificity between them is often implied to reflect extensive contacts with surrounding farmer populations (8, 10), and seen as evidence of recent displacement into marginal forest environments by expanding farming populations. However, anthropologists have remarked on the huge variability in lifestyle, habitat, techniques, and tools between CAHG (11), suggestive of long-term cultural diversification and adaptation to forest environments. Research on the drivers of demography and adaptation of CAHG populations remains extremely limited, which can be partially attributed to the lack of archaeological and osteological data resulting from a rapid disintegration of fossil remains in the rainforest’s acidic soils, in addition to social instability in the region (12). Therefore, we are still left with crucial questions regarding the time depth of occupation of Central Africa by hunter-gatherers, the breadth of the niche exploited by earlier populations in the region, and variations in levels of interconnectivity at different points in time.To address those questions, we first compiled ethnographic data on the distribution of 749 camps from 11 hunter-gatherer groups extending from West to East Central Africa. We used them as inputs for environmental niche models (ENMs) to determine the relative influence of several bioclimatic and ecological factors, as well as the presence of farming populations, on the distribution and abundance of CAHG (13, 14). Then, we used high-resolution paleoclimatic reconstructions and topographic maps to make continuous predictions about where CAHG could have lived over the past 120,000 years and the potential extension of their interaction networks. Next, we compiled all reliably dated archaeological assemblages ascribed to hunter-gatherer groups in the Congo Basin (n = 168) and confirmed the model’s ability to predict the location and date of the sites. We further contextualized genomic estimates of population divergences with changes in population densities and interpopulation connectivity predicted by our model. Last, we complemented these analyses with a detailed assessment of present and historical gene flow between nine CAHG populations (n = 265 individuals), which we used to assess recent interactions between previously diverged CAHG populations, after farming expansions. Our study therefore provides a causal link between past environmental changes and human population dynamics over evolutionary time, by predicting where and when populations across Central Africa could have exchanged genetic and/or cultural information throughout their evolutionary history.     

Thoughts on how to think (and talk) about RNA structure

Recent events have pushed RNA research into the spotlight. Continued discoveries of RNA with unexpected diverse functions in healthy and diseased cells, such as the role of RNA as both the source and countermeasure to a severe acute respiratory syndrome coronavirus 2 infection, are igniting a new passion for understanding this functionally and structurally versatile molecule. Although RNA structure is key to function, many foundational characteristics of RNA structure are misunderstood, and the default state of RNA is often thought of and depicted as a single floppy strand. The purpose of this perspective is to help adjust mental models, equipping the community to better use the fundamental aspects of RNA structural information in new mechanistic models, enhance experimental design to test these models, and refine data interpretation. We discuss six core observations focused on the inherent nature of RNA structure and how to incorporate these characteristics to better understand RNA structure. We also offer some ideas for future efforts to make validated RNA structural information available and readily used by all researchers.     

Molecular Dynamics Simulation Study on the Interactions of Mixed Cationic/Anionic Collectors on Muscovite (001) Surface in Aqueous Solution

In this study, the adsorption mechanisms of dodecylamine hydrochloride(DDAHC), sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate(SDBS), and their mixed anionic/cationic collectors at ten different molar ratios on a muscovite (Mcv) surface in neutral aqueous solution were assessed by molecular dynamics simulations (MDS). According to the snapshot, interaction energy, radial distribution function (RDF), and density profile between the Mcv surface and collector molecules, the individual DDAHC collector was an effective collector for the flotation of Mcv. The molar ratio of anionic/cationic collectors was determined to be an essential factor in the flotation recovery of Mcv. The DDAHC collector was involved in the adsorption of the mixed anionic/cationic collectors on the Mcv (001) surface, whereas SDS and SDBS collectors were co-adsorbed with DDAHC. The mixed cationic/anionic collector showed the best adsorption on the Mcv surface in a molar ratio of 2. Additionally, SDBS, which has one more benzene ring than SDS, was more likely to form spherical micelles with DDAHC, thus resulting in better adsorption on the Mcv surface. The results of micro-flotation experiments indicated that the DDAHC collector could improve the flotation recovery of Mcv in neutral aqueous solution, which was in agreement with MDS-derived findings. In conclusion, DDAHC alone is the optimum collector for Mcv flotation under the neutral aqueous conditions, while the mixture of DDAHC and SDBS collectors (molar ratio = 2:1) exhibits the similar flotation performance.     

Molecular Dynamics Investigation of Spreading Performance of Physiological Saline on Surface

Physiological saline is an indispensable element for maintaining the functions of life. The spreading performance of physiological saline droplets on the surface of graphene under different NaCl concentrations and electric field intensities was studied in the present work. The results show that the increase in NaCl concentration reduces the displacement vector value of molecules in droplets. In addition, NaCl is easy to aggregate on the surface of graphene. The increase in NaCl concentration makes it more difficult for droplets to penetrate the surface of graphene, and the penetration angle of droplets increases with the rise in NaCl concentration. With the increase in electric field intensity, the wetting effect of droplets is more obvious. The greater the electric field intensity is, the smaller the penetration angle is, which is mainly due to the polarity of water molecules. This study has reference significance for the study of body fluid volatilization on the human surface.     

2008-2009年长江三峡库区万州农村成蚊监测结果分析

目的掌握三峡水库万州农村蚊媒数量变化规律及种群构成情况,为做好蚊媒等传染病防治和蚊类危害预测预报提供科学依据。方法用人工小时法和诱蚊灯法,定点、定时调查,对捕获蚊虫进行分类鉴定统计。结果 2008-2009年2种方法共诱捕成蚊229561只。经鉴定分类,捕获成蚊隶属1目1科2亚科4属5种。骚扰阿蚊为优势种,占捕蚊总数的69.80%,其次为致倦库蚊占15.59%,中华按蚊占8.56%,三带喙库蚊占6.00%。诱蚊灯法人房2008-2009年平均总成蚊密度分别为247.3和145.8只/（灯·晚）,猪圈分别为933.5和1166.1只/（灯·晚）,牛棚年平均成蚊总密度分别为1835.2和1203.3只/（灯·晚）。人工小时法人房总成蚊平均密度为94.03只/人工小时,猪圈为254.46只/人工小时。结论人工小时法和诱蚊灯法调查获得的蚊类种群密度消长及其种群构成指标,是万州农村乃至三峡库区的第一手资料,将会对三峡库区蚊媒等传染病的防治和蚊虫危害治理有重要价值和意义。     

滨州市1984～2001年流行性出血热流行动态及其影响因素的分析

目的分析研究本地区流行性出血热流行动态和相关的影响因素，为防治计划的制订提供科学依据。方法对18年来的疫情动态进行分析，与鼠密度、温度、湿度、降雨量及人均收入、习俗、生活卫生状况等进行相关分析。结果1984年发现首例病人至2001年共发病4589例，病死29例；发病最小年龄3岁，最大年龄86岁；7—9岁的儿童发病率最高，其次是10—34岁的青少年及壮年；男性发病率是女性的2．10倍；农民发病率最高，其次是工人(包括打工)；3—6月是高发期，8—10月是低发期；18年间有流行期和非流行期，发病率的高低与人们的户外活动的多少有关，与鼠密度的大小和鼠活动的习性有关；人们不良习俗、生活卫生状况亦是造成发病率升高的一个重要原因。结论实施的以灭鼠为主的预防措施不能从根本上控制疫倩的流行。疫苗接种能起到有效的免疫屏障作用。今后实施以疫苗接种和灭鼠为主的综合性防治措施，就会取得有效控制的效果。     

Discovery of a High Affinity Adenosine A1/A3 Receptor Antagonist with a Novel 7-Amino-pyrazolo[3,4-d]pyridazine Scaffold

Here we describe the design and synthesis of pyrazolo[3,4-d]pyridazines as adenosine receptor (AR) ligands. We demonstrate that the introduction of a 3-phenyl group, together with a 7-benzylamino and 1-methyl group at the pyrazolopyridazine scaffold, generated the antagonist compound 10b, which displayed 21 nM affinity and a residence time of ∼60 min, for the human A₁R, 55 nM affinity and a residence time of ∼73 min, for the human A₃R and 1.7 μΜ affinity for the human A_2BR while not being toxic. Strikingly, the 2-methyl analog of 10b, 15b, had no significant affinity. Docking calculations and molecular dynamics simulations of the ligands inside the orthosteric binding area suggested that the 2-methyl group in 15b hinders the formation of hydrogen bonding interactions with N^6.55 which are considered critical for the stabilization inside the orthosteric binding cavity. We, therefore, demonstrate that 10a is a novel scaffold for the development of high affinity AR ligands. From the mutagenesis experiments the biggest effect was observed for the Y271^7.46A mutation which caused an ∼10-fold reduction in the binding affinity of 10b.