Effect of interplanetary magnetic field B_(x)on the polar electrojets as observed by CHAMP and Swarm satellites

Based on 16 years of magnetic field observations from CHAMP and Swarm satellites,this study investigates the influence of the Interplanetary Magnetic Field(IMF)Bx component on the location and peak current density of the polar electrojets(PEJs).We find that the IMF Bx displays obvious local time,seasonal,and hemispherical effects on the PEJs,as follows:(1)Compared to other local times,its influence is weakest at dawn and dusk.(2)In the midnight sectors of both hemispheres,the IMF Bx tends to amplify the westward PEJ when it is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere;this effect is relatively stronger in the local winter hemisphere.(3)At noontime,the IMF Bx intensifies the eastward current when it is<0 in the Northern Hemisphere;in the Southern Hemisphere when it is>0,it reduces the westward current;this effect is notably more prominent in the local summer hemisphere.(4)Moreover,the noontime eastward current shifts towards higher latitudes,while the midnight westward current migrates towards lower latitudes when IMF Bx is<0 in the Northern Hemisphere and when it is>0 in the Southern Hemisphere.

美国哥伦比亚大学图书馆的“战略方向”

美国哥伦比亚大学图书馆2015年秋开始实施"战略方向"流程,以阐明愿景,"战略方向"确定为"致力于包容、提升知识、激发探索、促进发现、塑造话语和赋予员工权利"。文章概述北美大学图书馆的战略规划趋势,分析哥伦比亚大学图书馆"战略方向"的制定过程及其评估。

哥伦比亚大学图书馆张学良私人图书经眼记

本文首先概述哥伦比亚大学图书馆张学良口述史及其档案收藏的复杂情况,其次介绍和分析张学良私人图书的种类和内容,最后讨论图书馆在资源有限的情况下如何处理获赠的名人私藏图书。

陈纳德智囊魏劳尔与中国国防物资供应公司

作为陈纳德智囊的魏劳尔(Whiting Willauer,1906—1962)对中国国防物资供应公司(China Defense Supplies,Inc.)、飞虎队和民航空运大队等抗日战争时期重要组织的建立和运作,都起了非同一般的作用。本文主要利用普林斯顿大学的魏劳尔档案,特别是其中的国防物资供应公司的主题文件、与宋子文信函以及魏劳尔的日记和回忆等,来分析魏劳尔在国防物资供应公司重大事务中的作用和对飞虎队的贡献。作为宋子文和国防物资供应公司主要助手的魏劳尔在抗战时期是一位谋士和斗士,正是魏劳尔强调的“国防物资供应公司想象力”(CDS Imagination)和创造力,以及魏劳尔与宋子文之间的彼此信任关系,使国防物资供应公司能高效和成功地运作并创造奇迹。

Phase field modeling of dendrite growth

Single dendrite and multi-dendrite growth for Al-2 mol pct Si alloy during isothermal solidification are simulated by phase field method. In the case of single equiaxed dendrite growth, the secondary and the necking phenomenon can be observed. For multi-dendrite growth, there exists the competitive growth among the dendrites during solidification. As solidification proceeds, growing and coarsening of the primary arms occurs, together with the branching and coarsening of the secondary arms. When the diffusion fields of dendrite tips come into contact with those of the branches growing from the neighboring dendrites, the dendrites stop growing and being to ripen and thicken.

Parameters Sensitivity Analysis and Correction for Concrete Damage Plastic Model

In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through a convenient cube unit test was conducted. The results showed that the peak strength strain was independent of the hardening ductility parameter DH,but affected by AH,BH,and CH. The softening ductility was mainly related to the softening ductility parameter AS,but not affected by the damage ductility exponent BS. In case that the model with default parameters failed to match the AS-controlled damage softening phase,an optimized model with an AS correction was developed. The corrected model with the AS value of 2 matched well with the code model,and exhibited good feasibility in predicting the stress-strain curve of different grades of concrete. Moreover,the practicability of the corrected model was further validated by the conventional triaxial test. The simulated curve exhibited favorable consistence with the trial curve. Therefore,the model with parameter correction could provide a prospective reference for predicting the mechanical properties of concrete.

基于衍生展示模型的协同工作方法

在基于3DE平台的船舶设计流程中,各专业之间协同工作仍存在一些问题,特别是由于船舶结构原生模型比较复杂,数据量大,调取耗时长,并容易引起系统崩溃,是结构专业与其它专业的协同工作的一个重大障碍。为解决这一问题,有针对性地对3DE平台模型轻量化进行研究,对3DE平台衍生展示模型这一轻量化模型的特性与协同设计的需要进行对比分析,综合其包括数据更新在内的各项特性,探索出一种基于衍生展示模型协同工作方法,解决了模型调取存在的问题,提高了设计人员的工作效率。

胡适荣誉博士学位考之一:纽约州立大学荣誉博士学位

半个多世纪以来胡适一生获授三十五个荣誉博士学位成为公论。胡适去世前和去世后半个多世纪以来,他的敌人、朋友、无数的崇拜者和研究者,不曾有任何疑问。笔者秉承胡适“不疑处有疑”的学术精神,近年来,对此公论正本清源;对胡适三十五个荣誉博士学位,以及其他荣誉博士学位,乃至与荣誉博士学位有同样殊荣的大学毕业典礼演讲,做了详尽的档案研究和系统的调查考证。本文以普遍认可的胡适1942年获授纽约州立大学文学博士学位为例,通过查找档案文献来研究胡适的荣誉博士学位的实际情况:胡适获授纽约州立大学博士学位实为子虚乌有,他获授的是纽约州大学院的荣誉博士学位。本文有助于更深地理解胡适在中美文化交流上的特殊地位以及看似简单实则复杂的美国教育制度。

Two birds with one stone:Construction of bifunctional-POSS hybridized boron-silicon ceramicized phenolic composites and its ablation behavior

To further enhance the ablation resistance properties of thermosetting phenolic resin matrix composites,in this work,bifunctional alkalic heptaphenyltrisilanol sodium salt polyhedral oligomeric silsesquioxane was utilized to catalyze the synthesis of boron phenolic resin and provide silicon source to obtain boron-silicon hybrid phenolic resin(BPOSSPR)with excellent ablative resistance.BPOSSPR possesses a low cur-ing activation energy(101.4 kJ/mol)and excellent thermal properties(initial decomposition temperature was 453.0℃and char yield at 1000℃was 72.7%).The mechanical and thermal insulation properties of carbon fiber reinforced BPOSSPR composites(CF/BPOSSPR)and high silica fiber reinforced BPOSSPR composites(HSF/BPOSSPR)are significantly enhanced.The linear ablation rate and mass ablation rate of CF/BPOSSPR are as low as 0.003 mm/s and 0.0354 g/s;those of HSF/BPOSSPR are 0.119 mm/s and 0.0264 g/s.The ablation-resistance mechanism of BPOSSPR composites is mainly due to the formation of ceramic thermal barrier layers under high temperature conditions,such as B_(2)O_(3),SiO_(2),borosilicate glass,SiC,which might play an effective role in protecting against heat flow erosion.As a result of these ex-cellent properties,the innovative heat shielding BPOSSPR composites could offer the ability to tolerate harsher environment in future aerospace applications.

Targeted Degradation of DNA/RNA Binding Proteins via Covalent Hydrophobic Tagging

Targeted protein degradation(TPD)holds great promise for biological inquiry and therapeutic development.However,it still remains elusive to destruct DNA/RNA binding proteins(DBPs/RBPs)previously deemed undruggable.Herein,we report ligandassisted covalent hydrophobic tagging(LACHT)as a modular strategy for TPD of these difficult-totarget proteins.Guided by a noncovalent protein ligand,LACHT leverages a reactive N-acyl-N-alkyl sulfonamide group to covalently label the protein target with a hydrophobic adamantane,which further engages the cellular quality control mechanism to induce proteolytic degradation.Using a smallmolecule ligand,we demonstrated that LACHT allowed TPD of a DBP,bromodomain-containing protein 4,in human leukemia cells with high efficiency.Mechanistic studies revealed that LACHT-mediated TPD dependent on ligand-directed irreversible tagging and the covalently labeled proteins underwent polyubiquitination before removal through both the proteasome and the lysosome.Furthermore,when an RNA ligand was employed,we showed that LACHT also enabled TPD of an RBP,Lin28a,leading to upregulation of its downstream let-7 miRNA.This study thus provides a generalizable platform to expand the TPD toolbox for biomedical applications.

Recruitment and reinforcement: maintaining epigenetic silencing

Cells need to appropriately balance transcriptional stability and adaptability in order to maintain their identities while responding robustly to various stimuli. Eukaryotic cells use an elegant "epigenetic" system to achieve this functionality. "Epigenetics" is referred to as heritable information beyond the DNA sequence, including histone and DNA modifications, nc RNAs and other chromatin-related components. Here, we review the mechanisms of the epigenetic inheritance of a repressive chromatin state,with an emphasis on recent progress in the field. We emphasize that(i) epigenetic information is inherited in a relatively stable but imprecise fashion;(ii) multiple cis and trans factors are involved in the maintenance of epigenetic information during mitosis; and(iii) the maintenance of a repressive epigenetic state requires both recruitment and self-reinforcement mechanisms.These mechanisms crosstalk with each other and form interconnected feedback loops to shape a stable epigenetic system while maintaining certain degrees of flexibility.

Co-or Ni-modified Sn-MnO_(x) low-dimensional multi-oxides for high-efficient NH_(3)-SCR De-NO_(x):Performance optimization and reaction mechanism

NH_(3)-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis method.Due to its strong oxidation performance,Sn-MnO_(x) was prone to side reactions between NO,NH_(3)and O_(2),resulting in the generation of more NO_(2)and N_(2)O,here most of N_(2)O was driven from the non-selective oxidation of NH_(3),while a small part generated from the side reaction between NH_(3)and NO_(2).Co or Ni doping into Sn-MnO_(x) as solid solution components obviously stronged the electronic interaction for actively mobilization and weakened the oxidation performance for signally reducing the selective tendency of side reactions to N_(2)O.The optimal modification resulted in improving the surface area and enhancing the strong interaction between polyvalent cations in Co/Ni-Mn-SnO_(2)to provide more surface adsorbed oxygen,active sites of Mn^(3+) and Mn^(4+),high-content Sn^(4+) and plentiful Lewis-acidity for more active intermediates,which significantly broadened the activity window of Sn-MnOx,improved the N^(2) selectivity by inhibiting N_(2)O formation,and also contributed to an acceptable resistances to water and sulfur.At low reaction temperatures,the SCR reactions over three catalysts mainly obeyed the typical Elye-rideal(E-R)routs via the reactions of adsorbed L-NH_(x)(x=3,2,1)and B-NH_(4)^(+) with the gaseous NO to generate N_(2) but also N_(2)O by-products.Except for the above basic E-R reactions,as increasing the reaction temperature,the main adsorbed NO_(x)-species were bidentate nitrates that were also active in the Langmuir-Hinshelwood reactions with adsorbed L-NH_(x) species over Co/Ni modified Mn-SnO_(2) catalyst.

Novel Mn-Ce bi-oxides loaded on 3D monolithic nickel foam for low-temperature NH_(3)-SCR de-NO_(x):Preparation optimization and reaction mechanism

This study explored the superior citrate method(CM)to synthesize Mn-Ce bi-oxides on 3 D monolithic Ni-foam(NF)catalysts for the selective catalytic reduction of NO by NH_(3)(NH_(3)-SCR).The 17 wt%Mn(7)Ce(3)O_(x)/NF(CM-17)catalyst shows the NO_(x)conversion of 98.7%at 175℃and 90%in the presence of 10 vol%H2 O.It is revealed that the combination of surface-active oxygen(formed by high-level oxygen vacancies)and strongly oxidized Mn4+species promots the Fast-SCR reactions,in which Mn4+species play a leading role in NH_(3)-SCR reaction,and the unsaturated Ni atoms and also Ce3+species promote electron exchange and thus improve the redox performance.The coexistence mechanisms of Fast-SCR reactions and E-R pathways are observed over Mn-CeO_(x)/NF catalyst,which may be promoted by the Br?nsted sites at low temperature.In addition,the heat resistance,stability,3 D monolithic porous structure and excellent physical properties of foam nickel provide a unique growth substrates for catalysts preparation and reaction sites for NO_(x)purification.Therefore,industrial application of Mn-Ce bioxides loaded on 3 D monolithic is proposed to be achieved through reasonable preparation methods.

Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China

The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of northeast China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.

Graphene Oxide Assemblies for Sustainable Clean-Water Harvesting and Green-Electricity Generation

CONSPECTUS:The urgent problems of water scarcity and the energy crisis have given rise to the development of a range of sustainable technologies with the great advancement of nanotechnologies and advent of attractive nanomaterials.Graphene oxides(GO),a derivative of graphene with an atom-thin thickness and abundant oxygen-containing functional groups(such as−OH,−COOH),are water-soluble and can be assembled into a variety of structures(such as fiber,membrane,and foam)with great potential in environmental and energy-related fields.As a typical precursor of graphene,GO can be easily reduced to graphene by chemical or thermal treatments to demonstrate excellent photothermal properties as well as tunable thermal conduction,which is highly desirable for efficient solar-driven water evaporation.The intrinsic large specific area of GO nanosheets can provide enough sites for ions adsorption and its porous assemblies facilitate the transport of water.In addition,the abundant functional groups allow the spontaneous adsorption of water molecules from the ambient environment and give birth to movable ions(usually protons)under the solvation effect.Once a chemical gradient is formed on the component,a remarkable electricity is generated from the directional transport of protons.Thanks to the excellent chemical properties of GO nanosheets,a wide range of assemblies with 1D aligned fibers,2D layered membranes and 3D porous foam can be easily fabricated by wet-spinning,solution-filtration,and freezingdrying methods.The various GO assemblies are able to exhibit abundant functions with remarkable weaving capability for GO fibers,superior flexibility for GO membranes,and exceptional adsorption capacity for GO foams.In light of all the advantages,GO and its assemblies are remarkably promising in the fields of sustainable development to meet the pressing challenges of water and energy crisis.In this Account,we will discuss the progress of clean-water production and green-electricity generation technologies based on GO assemblies.The fundamental working mechanism,optimization strategies,and promising applications are explored with an emphasis on the materials development.We also discuss the functions of GO assemblies in the water and electricity generation process and present their limitations and possible solutions.Current challenges and promising directions for the development of clean-water production and green-electricity generation are also demonstrated for their realistic implementations.We anticipate that this Account would promote more efforts toward fundamental research on graphene functionalization and encourage a broad exploration on the application of graphene assemblies in clean-water production and electric power generation systems.

Use of copper-cysteamine nanoparticles to simultaneously enable radiotherapy,oxidative therapy and immunotherapy for melanoma treatment

Dear Editor,Melanoma,squamous cell carcinoma(SCC),and basal cell carcinoma(BCC)are three major types of skin cancer.Among them,melanoma is the most severe form and accounts for~4%of all newly diagnosed cancers annually in the United States.It is estimated that approximately 9500 people are diagnosed with skin cancer every day,and more than 1 million Americans are living with melanoma.Melanoma treatment is still a major challenge in the clinic.Photodynamic therapy(PDT)is composed of targeted ablation and immune activation,is less invasive than other therapies and has been widely used in the treatment of various cancers.

Selectivity of biopolymer membranes using HepG2 cells

Bioartificial liver(BAL)system has emerged as an alternative treatment to bridge acute liver failure to either liver transplantation or liver regeneration.One of the main reasons that the efficacy of the current BAL systems was not convincing in clinical trials is attributed to the lack of friendly interface between the membrane and the hepatocytes in liver bioreactor,the core unit of BAL system.Here,we systematically compared the biological responses of hepatosarcoma HepG2 cells seeded on eight,commercially available biocompatible membranes made of acetyl cellulose–nitrocellulose mixed cellulose(CA–NC),acetyl cellulose(CA),nylon(JN),polypropylene(PP),nitrocellulose(NC),polyvinylidene fluoride(PVDF),polycarbonate(PC)and polytetrafluoroethylene(PTFE).Physicochemical analysis and mechanical tests indicated that CA,JN and PP membranes yield high adhesivity and reasonable compressive and/or tensile features with friendly surface topography for cell seeding.Cells prefer to adhere on CA,JN,PP or PTFE membranes with high proliferation rate in spheriod-like shape.Actin,albumin and cytokeratin 18 expressions are favorable for cells on CA or PP membrane,whereas protein filtration is consistent among all the eight membranes.These results further the understandings of cell growth,morphology and spreading,as well as protein filtration on distinct membranes in designing a liver bioreactor.