CO Oxidation over Pd Catalyst Supported on Porous TiO2 Prepared by Plasma Electrolytic Oxidation (PEO) of a Ti Metallic Carrier

A porous TiO₂ layer was prepared with the plasma electrolytic oxidation (PEO) of Ti. In a further step, Pd was deposited on the TiO₂ surface layer using the adsorption method. The activity of the Pd/TiO₂/Ti catalyst was investigated during the oxidation of CO to CO₂ in a mixture of air with 5% CO. The structure of the catalytic active layer was studied using a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray diffraction (XRD). The PEO process provided a porous TiO₂ layer with a uniform thickness in the range of 5–10 µm, which is desirable for the production of Pd-supported catalysts. A TOF-SIMS analysis showed the formation of Pd nanoparticles after the adsorption treatment. The conversion of CO to CO₂ in all samples was achieved at 150–280 °C, depending on the concentration of Pd. The composition of Pd/ TiO₂/Ti was determined using ICP-MS. The optimum concentration of Pd on the surface of the catalyst was approximately 0.14% wt. This concentration was obtained when a 0.4% PdCl₂ solution was used in the adsorption process. Increasing the concentration of PdCl₂ did not lead to a further improvement in the activity of Pd/ TiO₂/Ti.     

The Genomic Evolution and the Transmission Dynamics of H6N2 Avian Influenza A Viruses in Southern China

In China, the broad prevalence of H6 subtype influenza viruses, increasingly detected in aquatic birds, promotes their exchange materials with other highly pathogenic human-infecting H5N1, H5N6, and H7N9 influenza viruses. Strikingly, some H6 subtype viruses can infect pigs, dogs, and humans, posing risks to public health. In this study, 9 H6N2 viruses recovered from waterfowl species in the Guangdong province of China in 2018 were isolated and sequenced. Phylogenetic analysis revealed that the genome sequences of these H6N2 viruses belonged to Group I, except for the NP gene in Group III. Coalescent analyses demonstrated that the reassortment of NA and NS genes have occurred in two independent clusters, suggesting H6 subtype viruses had been undergoing a complex reassortant. To examine the evolutionary dynamics and the dissemination of the H6 subtype viruses, a Bayesian stochastic search variable selection was performed for results showing higher viral migration rates between closer provinces, including Guangdong, Jiangxi, Guangxi, and Fujian. Notably, the transmission routes of the H6 subtype viruses were concentrated in Jiangxi Province, the most frequent location for input and output transmission and a region containing Poyang Lake, a well-known wintering site for migration birds. We also found that the aquatic birds, especially ducks, were the most common input source of the viral transmission. In addition, we also found that eight positively selected amino acid sites were identified in HA protein. Given their continuous dissemination and the broad prevalence of the H6 subtype influenza viruses, continued surveillance is warranted in the future.     

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.     

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.     

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。     

云南省瑞丽市新型冠状病毒肺炎暴发疫情传播力和控制效果模型分析

目的 针对2021年3月末瑞丽市COVID-19疫情暴发,本研究应用更新方程模拟COVID-19在瑞丽市的传播过程,快速测算其传播的流行病学参数传播序列间隔(SI)、再生数(R)及其在加强防控措施干预下的变化,为边境地区疫情防控策略提供科学依据。方法 收集官方网站公布的2021年3月30日至4月16日瑞丽市的病例信息,用Excel 2019软件进行流行病学分析,使用R 4.0.5软件建立更新方程模型,用马尔可夫链蒙特卡罗算法(MCMC)采样计算各参数值的中位数与95%置信区间,对不同索引病例情况下疫情发展进行预测,研究疫情防控政策执行效果。结果 2021年3月30日至4月16日,瑞丽市累计报告确诊病例90例,无症状感染者43例,共133例,其中19例无症状感染者转为确诊病例,确诊病例和无症状感染者的年龄中位数分别为32、28岁。通过模型得到SI中位数约为5.00(95%CI: 4.22～7.31)天,标准差中位数约为24.67(95%CI: 12.05～27.91)天; 在疫情暴发较早阶段,再生数R约为1.42(95%CI: 1.31～1.80),加强防控措施后1周内,R下降至0.58(95%CI: 0.07～0.72),位于临界值1.0以下; 模型预测4月17日以后,每天新增感染者数量≤1例。结论 在合理推测索引病例的前提下,更新方程模型能较好地拟合疫情数据,其预测瑞丽市的疫情将在短时间内得到控制。瑞丽市的防控措施和经验可为类似边境地区的防疫工作提供有益借鉴。     

根管超声冲洗的计算流体动力学分析

目的 应用计算机模型分析当超声工作尖位于根管内一定深度时冲洗液的计算流体动力学特点,以期为临床应用提供参考.方法 首先使用扫描激光振测系统扫描超声工作尖,分析其在一定功率下的振动特点.然后应用ICEM CFD 18.0软件建立根管超声冲洗模型,设置超声工作尖放置的位置为距根尖止点1 mm,通过FLUENT 18.0软件...     

Thermodynamic and Kinetic Binding Behaviors of Human Serum Albumin to Silver Nanoparticles

A nanoparticle, under biological milieu, is inclined to be combined with various biomolecules, particularly protein, generating an interfacial corona which provides a new biological identity. Herein, the binding interaction between silver nanoparticles (AgNPs) and human serum albumin (HSA) was studied with transmission electron microscopy (TEM), circular dichroism (CD), and multiple spectroscopic techniques. Due to the ground state complex formed mainly through hydrophobic interactions, the fluorescence titration method proved that intrinsic fluorescence for HSA was probably statically quenched by AgNPs. The complete thermodynamic parameters were derived, indicating that the interaction between HSA and AgNPs is an entropy-driven process. Additionally, synchronous fluorescence and CD spectrum results suggested the conformational variation it has upon binding to AgNPs and the α-helix content has HSA visibly decreased. The kinetic experiments proved the double hysteresis effect has in HSA’s binding to the AgNPs surface. Moreover, the binding has between HSA and AgNPs follows the pseudo-second-order kinetic characteristic and fits the Freundlich model for multilayer adsorption. These results facilitate the comprehension about NPs’ underlying biological effects under a physiological environment and promote the secure applications of NPs biologically and medically.     

交联羧甲基壳聚糖树脂的制备及其对尿素的吸附性能研究

目的研究交联羧甲基壳聚糖对尿素吸附剂性能。方法以壳聚糖为原料,用微波辐射法制成了羧甲基壳聚糖,再通过戊二醛交联,制成了交联羧甲基壳聚糖。研究了交联羧甲基壳聚糖对尿素的吸附性能,探讨了吸附时间、溶液的pH值、吸附温度、尿素的起始浓度、交联程度等对吸附的影响。结果交联羧甲基壳聚糖对尿素具有较高的吸附容量和较高的选择性,在戊二醛用量为4 mL、pH值为8、尿素的初始浓度为2mg/mL时,其吸附量达90.5 mg/g。结论交联羧甲基壳聚糖对尿素的吸附性能较好,是一种具有发展前景的尿素吸附剂材料。     

犬迷走神经干切断术对Oddi括约肌的影响

 目的 建立双侧迷走神经干切断术动物模型,研究迷走神经对Oddi括约肌(Sphincter of Oddi,SO)的调节作用.方法 成年杂种犬禁食16～18 h(可自由饮水)麻醉后,实验组行膈肌水平双侧迷走神经干切断术加幽门成形术,对照组仅行幽门成形术.手术8周后行Oddi括约肌测压(SOM)及肌电记录(SOE),SOM和SOE前超声检查测定胆总管内径,SOM和SOE后取胆囊内胆汁肉眼观察.结果 对照组比较,实验组胆总管内压明显升高,内径明显增粗,胆汁内全部出现絮状泥沙样沉淀;实验组SO基础压明显升高,收缩幅度、频率及收缩时间无显著性变化,慢波幅度明显升高,快波无显著性变化.结论 迷走神经对SO运动具有抑制作用,膈肌水平双侧迷走神经干切断术导致SO肌电慢波幅度明显增高,基础压明显提高,胆道动力学发生明显变化.