检索结果-南通市图书馆

Insect Science 2014年第4期21卷 477-485页

作者： Christina l. Mogren William E. Walton John T. Trumble Department of Entomology University of California Riverside CA 92521 USA

Arsenic contamination of global water supplies has come to the forefront in policy decisions in recent decades. However, the effects of arsenic on lower trophic levels of insects inhabiting contaminated ecosystems are not well understood. One approach to document both acute and sublethal effects of toxicants like arsenic is to assay them in combination with microbial pathogens to evaluate shifts in survival curves of the test organisms. larvae of Culex quinquefasciatus and Culex tarsalis were reared in water containing 0 or 1 000μg/l of arsenate or arsenite. Fourth instars were then exposed to a range of doses of Bacillus thuringiensis subsp, israelensis （Bti） or lysinibacillus sphaericus （ls）, with shifts in lethal concentrations determined. Arsenic accumulation in 4th instars was also quantified, and a relative growth index （RGI） calculated for the treatments and compared to controls. larvae of both species accumulated between 4 447 ± 169 ng As/g and 6 983 4- 367 ng As/g, though RGI values indicated accumulation did not affect growth and development. In all cases, the lC50＇s and lC90＇s of Cx. quinquefasciatus exposed jointly with arsenic and Bti/ls were higher than Cx. tarsafis. Cx. tarsafis reared in arsenite showed a significant reduction in their Bti lC90 values compared to the control, indicating a sublethal effect of Bti. When exposed jointly with ls, arsenite was more toxic than arsenate in Cx. tarsalis. Overall, these results indicate tolerance of these Culex species to arsenic exposures, and why this may occur is discussed.

关键词： arsenate arsenite Bsph Bti Culex tarsalis Culex quinquefasciatus

Influence of Al_2O_3 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2014年第4期10卷 375-383页

作者： l.SUVARNA RAJU A.KUMAR Department of Mechanical Engineering KITS(S) Huzurabad Telangana India Department of Mechanical Engineering NIT Warangal Telangana India

The influence of three factors, such as volume percentage of reinforcement particles(i.e. Al2O3), tool tilt angle and concave angle of shoulder, on the mechanical properties of Cue Al2O3 surface composites fabricated via friction stir processing was studied. Taguchi method was used to optimize these factors for maximizing the mechanical properties of surface composites. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. It was found that Al2O3 particles are uniformly dispersed in the stir zone. The tensile properties of the surface composites increased with the increase in the volume percentage of the Al2O3 reinforcement *** is due to the addition of the reinforcement particles which increases the temperature of recrystallization by pinning the grain boundaries of the copper matrix and blocking the movement of the dislocations. The observed mechanical properties are correlated with microstructure and fracture features.

关键词：表面复合材料材料力学性能颗粒搅拌制造摩擦 Taguchi法微观

Preparation of synthetic rutile via selective sulfation of ilmenite with(NH4)2SO4 followed by targeted removal of impurities

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2017年第6期25卷 821-828页

作者： Weizao liu Xiaomei Wang Zhenpu lu Hairong Yue Bin liang li lü Chun li College of Chemical Engineering Sichuan University Chengdu 610065 Chino

This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e., selectively sulfating ilmenite, which was realized via roasting ilmenite with(NH_4)_2SO_4followed by selective thermal decomposition of the sulfated ilmenite, and targeted leaching of the impurities. The effects of the process parameters were systematically investigated. The results showed that the optimum sulfation conditions were a mass ratio of(NH_4)_2SO_4to ilmenite of 14, temperature of 360 °C, and time of 120 min with a sulfation ratio of ~ 95%. The optimum thermal decomposition conditions were480 °C in N_2 atmosphere, and nearly all Ti OSO_4 were decomposed with co-decomposition of Fe SO_4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 °C and 120 min. Under those conditions, 94.2% iron was removed with a Ti O_2 dissolution loss b 1%. For alkali leaching, 67% Si O_2 was removed in 5 wt% Na OH at102 °C for 1 h. A synthetic rutile with a Ti O_2 content N 92 wt% and total Mg O + Ca O b 1.5 wt% was *** on these results, a schematic flowsheet was proposed. Additionally, it was found that the decomposition of Fe SO_4 mixed with Ti OSO_4 under N_2was inhibited due to its oxidation to a higher thermal stability Fe_2(SO_4)_3by oxygen emitted from the decomposition of Ti OSO_4. At the same time, Ti OSO_4 decomposition was promoted due to the immediate in situ consumption of oxygen by Fe SO_4. The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition.

关键词： Synthetic rutile Ilmenite Titania Ammonium sulfate Thermal decomposition

Opposite Interplay Between the Canonical WNT/β-Catenin Pathway and PPAR Gamma： A Potential Therapeutic Target in Gliomas

在线全文

学校读者我要写书评

暂无评论

Neuroscience Bulletin 2018年第3期34卷 573-588页

作者： AlexANDre Vallée Yves lecarpentier Rémy Guillevin Jean-Noёl Vallée laboratory of Mathematics and Applications Unites Mixtes de Recherche (UMR) Centre National de la Recherche Scientifique (CNRS) 7348 University of Poitiers PoitiersFrance Delegation a la Recherche Clinique et a l'Innovation (DRCI) Hopital Foch Suresnes France Centre de Recherche Clinique Grand Hopital de l'EstFrancilien Meaux France DACTIM UMR CNRS 7348 University of Poitiers et CHU de Poitiers Poitiers France CHU Amiens Picardie University of Picardie Jules VerneAmiens France

In gliomas, the canonical Wingless/Int（WNT）/b-catenin pathway is increased while peroxisome proliferator-activated receptor gamma（PPAR-c） is *** two systems act in an opposite manner. This review focuses on the interplay between WNT/b-catenin signaling and PPAR-c and their metabolic implications as potential therapeutic target in gliomas. Activation of the WNT/bcatenin pathway stimulates the transcription of genes involved in proliferation, invasion, nucleotide synthesis,tumor growth, and angiogenesis. Activation of PPAR-c agonists inhibits various signaling pathways such as the JAK/STAT, WNT/b-catenin, and PI3 K/Akt pathways,which reduces tumor growth, cell proliferation, cell invasiveness, and angiogenesis. Nonsteroidal anti-inflammatory drugs, curcumin, antipsychotic drugs, adiponectin,and sulforaphane downregulate the WNT/b-catenin pathway through the upregulation of PPAR-c and thus appear to provide an interesting therapeutic approach for ***（TMZ） is an antiangiogenic agent. The downstream action of this opposite interplay may explain the TMZ-resistance often reported in gliomas.

关键词： WNT/beta-catenin pathway PPAR gamma Glioma STAT3 pathway PI3K/Akt pathway NSAID Curcumin

APPROXIMATION BY SOME OPERATORS OF SZASZ-MIRAKYAN TYPE

在线全文

学校读者我要写书评

暂无评论

Analysis in Theory and Applications 2004年第1期20卷 1-15页

作者： l.Rempulska Z.Walczak Poznan University of Technology PolandPoznan University of Technology Poland

In this paper we give theorems on the degree of approximation of functions of one and two variables by certain operators of the Szasz-Mirakyan type.

关键词： Szasz-Mirakyan operator approximation theorem polynomial weighted space

Preparation of Chinese fir wood/MMT nanocomposites and the factors affecting it

在线全文

学校读者我要写书评

暂无评论

Forestry Studies in China 2007年第1期9卷 45-50页

作者： lü Wen-hua Zhao Guang-jie Faculty of Wood Science and Decoration Engineering Southwest Forestry College Kunming 650224 E R. China Research Institute of Wood Industry Chinese Academy of Forestry B eijing 100091 E R. China College of Material Science and Technology Beijing Forestry University Beijing 100083 E R. China

The nano intercalation compounding of wood and MMT has important implications for the modification of wood and for the development of new materials. With water-soluble phenol formaldehyde resin as an intermediary, the nanocomposites of Chinese fir （Cunningharnia lanceolata） wood and montmorillonite （MMT） were prepared via three impregnation methods, i.e. normal pressure, once and twice vacuum methods. Based on the weight percent gain （WPG） of impregnated wood, the effects of compounding wood and MMT in terms of concentration, impregnating temperature and time, wood moisture content and wood extraction treatments, on sapwood and heartwood are discussed. Results show that： 1） the optimum MMT concentration in the impregnation solution is 3% for sapwood and 5% for heartwood; 2） room temperature is suitable in practice; 3） treatment pressure should be set at a high enough value in order to ensure sufficient permeation; 4） the effects of different impregnation methods on sapwood and heartwood are different, the heartwood extractives affect WPG significantly; cell wall permeability of sapwood is better than that of heartwood; 5） the cold water, hot water and benzene-ethanol solution extractions can all greatly improve the permeability of heartwood, hot water can dissolve some hemicellulose of low aggregation and hot water extraction improves wood cell wall permeability; 6） with an increase in wood moisture content, the permeable space in wood is reduced, but with a certain amount of water, instantaneous spaces are created and the permeation dynamic increases. This effect is especially apparent for difficult impregnating situations in heartwood and impregnation under normal pressure.

关键词： Cunninghamia lanceolata wood montmorillonite (MMT) nano intercalation compounding affecting factors

Formation building and collision avoidance for a fleet of NAOs based on optical sensor with local positions and minimum communication

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2019年第5期62卷 214-236页

作者： Xiaomin WANG lorenzo BENOZZI Benoit ZERR Zexiao XIE Hélène THOMAS Benoit ClEMENT Engineering college Ocean University of China

Multi-robot system has become a research hotspot because of low demand on the sensors’ accuracy, high reliability, and high efficiency. To put all the robots together, formation control is a crucial problem. In this paper, we propose a local position-based method to plan trajectories and build a pyramid pattern for a fleet of NAOs in the obstacle-free environment by refering to the position-based method and giving an O(n log n) collision avoidance strategy inspired from one graph theory, where the local positions are estimated from optical sensors. To get the local positions, an integrated image processing method is developped. Firstly a mask-base is generated to store the features of NAOs, and a cross-correlation method is introduced to recognize the NAO. Subsequently, the distance and angle models are proposed to get the local information from a single image. Then, a visual compass is introduced to obtain the orientation of one NAO. After the local information exchange by the WiFi communication, a neighbor-check method is put foward to distinguish the homogeneous NAOs(all the NAOs look like the same). Further, a common frame is constructed as an artificial global frame, and straight non-intercrossing trajectories are planned according to the O(n log n) collision avoidance strategy. At last, the performance of our proposed local position-based method is verified by the simulations with up to 15 robots and the indoor experiments with 3 NAOs in a real environment. The convergence of the method has been demonstrated in both obstacle-free and static obstacle environments.

关键词： formation building a fleet of NAOs optical sensor visual compass local positions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

基于STM32的宠物自动喂食器系统设计

农业装备与车辆工程 2024年第8期62卷 158-160页

作者：汤文祺黄略起曹玉华广东白云学院智能制造工程学院广东广州510450

针对因人们长期外出无法及时喂养宠物的问题,提出一种利用远程控制技术的宠物自动喂食器系统设计方案。该喂食器以STM32单片机为核心控制OlED的显示及称重模块和舵机,实现了定时定量加食,并可按照用户设定的时间定时发出语音播报吸引宠... 详细信息

针对因人们长期外出无法及时喂养宠物的问题,提出一种利用远程控制技术的宠物自动喂食器系统设计方案。该喂食器以STM32单片机为核心控制OlED的显示及称重模块和舵机,实现了定时定量加食,并可按照用户设定的时间定时发出语音播报吸引宠物进食;利用ESP8266开发移动端APP对系统进行远程功能控制,用户可设置喂食时间、食物分量等参数,操作界面简单。经测试,该系统可以在室温环境下正常工作,称重误差能够控制在5%以内,满足宠物喂食的精度要求;该宠物自动喂食器硬件简单、运行成本低,可实现对宠物的自动定时定量喂食功能。

关键词：单片机自动喂食器称重 APP

STUDY ON PTA ClAD (Cr,Fe)_7C_3/γ-Fe CERAMAl COMPOSITE COATING

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English letters) 2005年第6期18卷 695-700页

作者： J.B. liu J.H. Huang l.M. Wang Department of Mechanical and Electronic Engineering Weifang University Weifang 261061 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.

关键词： plasma transferred arc ( PTA ) cladding ( Cr Fe )7C3/γ-Fe coating,microstructure wear

Geochemical Evaluation of the Permian Ecca Shale in Eastern Cape Province, South Africa:Implications for Shale Gas Potential

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2018年第3期92卷 1193-1217页

作者： Christopher BAIYEGUNHI Kuiwu lIU Nicola WAGNER Oswald GWAVAVA Temitope l.OlONINIYI Department of Geology University of Fort Hare Department of Geology University of Johannesburg

Shale gas has been the exploration focus for future energy supply in South Africa in recent time. Specifically, the Permian black shales of the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations are considered to be most prospective rocks for shale gas exploration. In this study,outcrop and core samples from the Ecca Group were analyzed to assess their total organic carbon(TOC), organic matter type, thermal maturity and hydrocarbon generation potential. These rocks have TOC ranging from 0.11 to 7.35 wt%. The genetic potential values vary from 0.09 to 0.53 mg HC/g,suggesting poor hydrocarbon generative potential. Most of the samples have Hydrogen Index(HI) values of less than 50 mg HC/g TOC, thus suggesting Type-Ⅳ kerogen. Tmax values range from 318℃ to601℃, perhaps indicating immature to over-maturity of the samples. The vitrinite reflectance values range from 2.22% to 3.93%, indicating over-maturity of samples. Binary plots of HI against Oxygen Index(OI), and HI versus Tmax show that the shales are of Type II and mixed Type Ⅱ-Ⅲ *** on the geochemical data, the potential source rocks are inferred as immature to over-matured and having present-day potential to produce gas.

关键词： geochemistry organic matter type thermal maturity hydrocarbons Ecca Group South Africa