bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on the Fracture Mechanism of Carbon Nanotubes
Authors: Zhang Fei-Hu , Zhang Hua-Li , Zhao Hang
Published: June 2009

Carbon nanotubes (CNT) has a property of rebound elasticity, which is induced barely no fracture even bending to a greet extent due to its perfect structural integrity. Resent studies have been carried out on the plastic formation and fracture process of CNT by calculation and dynamics simulation. In this paper, the radial fracture of CNT was found feasible even though CNT has high tenacity, hard to allocation and detection for its nano-scale size. Both ramped load and constant load scratch tests were conducted on CNTs using a Nano Indetenter to investigate the pattern alteration and the critical behavior of radial fracture. Fracture caused by nano-scratching was observed after scratching. The scratch resistance of CNT and the evolution of friction coefficient during scratching were analyzed, and the critical load of fracture was obtained also, which led to a new understanding of the origin of the fracture mechanism of CNTs.
Dual Layer Photoresist and Back Sputtering Applied in Lift-Off Technique
Authors: Zhang Lu , Zhang Le , Wang Ying , Yang Zhenchuan , Yan Guizhen
Published: June 2009

Lift-off has been widely used in microfabrication process. In normal lift-off process, after photolithography and developing, a thin layer of residua will remain on the exposed substrate. To remove the residua, descum and back sputtering are required before metal sputtering. However, because of the high temperature of descum process and high energy induced by ion bombardment during back sputtering, the up inner angle of photoresist will increase in normal lift-off process. The metal films will deposit on the sidewall of the photoresist, and adhere to the substrate even after the photoresist removal. In order to overcome these problems, a lift-off process adopting dual layer photoresist is introduced in this paper, and high quality metallic pattern could be made.
Characterization of Piezoelectric Response of PZT Nanofibers
Authors: Xu Shiyou , Challa Vinod , Shi Yong
Published: June 2009

This paper reports the characterization of piezoelectric response of the Lead Zirconate Titanate (PbZr52Ti48O3) PZT nanofibers by three-point bending test using dynamic mechanical analyzer (DMA). PZT nanofibers were fabricated by sol-gel electrospinning process. The diameters of the fiber obtained were from 50 to 150 nm. The fiber consists of nanocrystal grains with average grain size of 10 nm. Titanium strip was used as substrate to collect the nanofibers for the three-point bending test to demonstrate the piezoresponse. The output voltage from the nanofibers under 0.5% strain was 0.17±0.005V, which was recorded by Labview. These results have shown that PZT nanofibers have great potential for nano sensor and actuator applications.
Optical Limiting Performance of ZnS Nanotube
Authors: Chang Qing , Chang Cun , Ye Hongan , Song Yinglin
Published: June 2009

Optical limiting (OL) performances of ZnS nanotube and ZnS nanoparticle in N, N dimethyllformaide (DMF) were comparatively investigated by using nanosecond laser pulses at 532 nm. Experimental results indicate that the shapes of ZnS nanomaterials have effect on their OL performances, and ZnS nanotube exhibits stronger OL performance than ZnS nanoparticle. The results were analyzed by use of the Maxwell-Garnett Effective Medium theory (MGT).
Image-Based Displacement Measurement System for the Characterization of Mechanical Properties of Thin Films
Authors: Ha Jong-Eun , Park Jun-Hyub , An Joong-Hyok , Kim Yun-Jae
Published: June 2009

This paper proposes a method for the direct measurement of displacement through the analysis of image. We designed specimen with indicator for the image-based displacement measurement system. First, illumination system for the simple processing of image is investigated. We found that backlight system gives a high contrast image for measurement. Measurement could be done by finding the positions of 8 rectangular-shape indicators. This is done by the analysis of intensity profile along vertical direction in each region of interest. In each region of interest we find two positions of peaks. Also, for easy setup procedure, region of interest is found automatically through the analysis of edge projection profile along the horizontal direction. Current system uses two types CCD camera with image size of 640×480 pixels and 1600×1200 pixels. The number of pixel is important to resolution of measurement. To gain confidence in reliability of the system, pre-test using the Al-3%Ti thin film was performed, which is widely used in the switches and other MEMS devices. The specimen was fabricated with dimensions of 1000μm long, 1.0μm thickness, and width of 50μm. Tensile tests were performed and measured displacement using the developed system and capacitance type displacement sensor, simultaneously. Current systems are implemented on PC with 2.7GHz CPU with 752Mbyte memory and we can obtain measurements rate of 10Hz. It is possible to measure fatigue property of thin films with easy setup and accuracy by proposed system.
Mechanism for Size Dependence of Light Emission From ZnO Nanocrystallites
Authors: Zhao Fuli , Wang Xiaofang , Xie Pingbo , Xu Ningsheng , Xu Zhizhan
Published: June 2009

Broadband light emission of different sized ZnO nanoparticles (17 nm to 300 nm) has been measured under picosecond laser excitation. Each spectrum consists of three Gaussian components including one emerging inside band-gap. Such inside band-gap band shows a clear dependence of the weighted intensity on the sizes of nanoparticles. Originated from our simplified one-dimensional (1D) model it has been qualitatively deduced that such size dependence match with the surface-state modified band structure. Additionally, a critical grain size as 110 nm for surface states recombination of ZnO nanoparticles has been found experimentally.
Research Progress and Problems of Heat-Transfer Properties of Nanofluids
Authors: Zhu Dongsheng , Li Xinfang
Published: June 2009

Nano-Scale heat transfer is becoming a research upsurge over the world and the abnormal heat-transfer behaviour of nanofluids represents one of the hottest spots in this area. To promote the rapid progress of nanofluids, the preparation techniques of nanofluids are introduced, and the research progress and existing problems of the heat-transfer properties of nanofluids are discussed. Moreover, the prospect and development direction of nanofluids are presented.
Performance Analysis of Composite Sorbents in Thermal Energy Storage System
Authors: Zhu Dongsheng , Li Xuebo , Wu Huijun , Wang Nan
Published: June 2009

Composite adsorbents, prepared by impregnating hygroscopic salt into silica gel pores are considered as promising storage materials in space heating for their high specific storage density and low regenerating temperature. In this paper, a numerical model of the adsorber heat exchanger was developed. Four kinds of composite adsorbents were tested under different conditions. The experiments were conducted to investigate the effect of their nature, the regenerating temperature, the air flow rate and number of transfer unit on the thermal storage performances. The results reveal that thermal storage performances increases significantly with CaCl2 concentration ranged from 10% to 40%. COP declines with the regenerating temperature and air flow rate, ranged from 80°C to 90°C and 4 m3/min to 6 m3/min respectively, while NTU is another case. The optimization of thermal performance of TES can be achieved by compromising between the above factors.
Plasmonic-Enhanced Radiative Transfer Through Nanoscale Aperture Antennas
Authors: Jin Eric X. , Wang Liang , Xu Xianfan
Published: June 2009

Nanoscale ridge aperture antenna as a nanoscale high transmission optical device is demonstrated. High transfer efficiency and confined radiation are achieved simultaneously in the near field compared with regularly-shaped apertures. The radiation enhancement is attributed to the fundamental electromagnetic field propagating in the TE10 mode concentrated in the gap between the ridges. The transfer efficiency is further enhanced through plasmon excitation and resonance. This paper reports spectroscopic measurements of radiative transfer through bowtie shape ridge aperture antennas. Resonance in these aperture antennas and its relation with the aperture geometry are investigated. The near-field radiation through the bowtie aperture and the regular nanoaperture is also mapped with near-field scanning optical microscopy. It is revealed that plasmon excitation and resonance contribute to the radiation enhancement through the ridge aperture antennas.
Coherent Phonon Excitation by Ultrafast Pulse Trains
Authors: Wu Alexander Q. , Xu Xianfan
Published: June 2009

Time resolved reflectivity of bismuth thin film evaporated on a silicon substrate is measured by an 80 femtosecond (fs) laser at a center wavelength of 800 nm. The reflectivity data reveal that coherent optical phonons (A1g) near 2.9 THz (1 THz = 1012 Hz) are excited by the 80 fs laser pulses. Analyses of the reflectivity data reveal key parameters related to electron and phonon dynamics, including phonon excitation and de-phasing and electron-phonon energy coupling. It is also found that the phonon frequency peaks are red-shifted and broadened at higher laser fluences. We also show that the phonon oscillation can be manipulated by specifically designed ultrafast pulse trains with different pulse separation times.
Study to Enhance the Micro-Level in USM
Authors: Jia Baoxian , Bian Wenfeng , Zhao Wansheng , Wang Zhenlong
Published: June 2009

With the wide applications of the hard brittle materials in micro electromechanical system (MEMS), the high precision micromachining technology of hard brittle materials has become an important subject. In order to enhance the machining accuracy and the degree of the micro ultrasonic machining (USM), the key technologies in micro USM are discussed. They include high precision machine body, rotated tool, on-line tool preparation, applying vibration to the workpiece, choosing the parameters of micro tool and so on. The buckling dynamic stability of the micro tool is analyzed. It not only depends on the static pressure but also on the ultrasonic amplitude. The formula for calculating the critical length of the tool is given. It can solve the problem of the tool’s bend, breakage, and deteriorating the hole shape accuracy in machining process caused by the improper choice of tool length, static pressure and ultrasonic amplitude. The experiment is carried out on the micro USM system, and the machined samples are presented.
Experimental Study on Characteristics of Nanofluid for Low-Temperature Phase Change Cool Storage
Authors: Long Jianyou , Zhu Dongsheng , He Qinbo
Published: June 2009

The TiO2-BaCl2-H2O nanofluid with 1.13% volume fraction of TiO2, which has the dimension of 20nm, was prepared by supersonic oscillator with hydrophilic dispersant. BaCl2 solution and TiO2-BaCl2-H2O nanofluid were tested by the experiments of freezing. The experimental results show that nanofluid has remarkably lower subcooling degree than BaCl2 solution, and the cool storage capacity of the nanofluid is larger than that of BaCl2 solution. Comparing with BaCl2 solution, the heat transfer characteristic of the nanofluid is remarkably improved for the added nanoparticles.
Magnetic Nanomaterial and Its Applications in Biomedicine
Authors: Gu Ning , Zhang Song
Published: June 2009

Being one kind of functional nanomaterials of importance, magnetic nanomaterial with various excellent properties could be used in many fields, such as information, mechanics, and biomedicine. The main possible applications of magnetic nanomaterial in biomedicine will be described with the focus on the earlier diagnosis and effective treatment of tumors. Also our recent interrelated results are included.
MOS Capacitor Micro Sensor Array for Hydrogen Gas Measurement
Authors: Hu Cheng , Qu Xidong , Wu Q. M. Jonathan , Chapman Glenn
Published: June 2009

Palladium-MOS hydrogen sensors have wide applications in the industries. This paper presents a novel design and development of a hydrogen sensor and sensor array based on MOS capacitor structure. An empirical model for sensors’ response to hydrogen concentrations is established and validated. Experimental results demonstrate that the sensor is highly sensitive to hydrogen gas, is capable of not only hydrogen leaks detection, but leaks location, and gas distribution monitoring.
Properties of HDPE/Clay/Wood Nanocomposites
Authors: Wu Q. , Lei Y. , Yao F. , Xu Y. , Lian K.
Published: June 2009

Composites based on high density polyethylene (HDPE), pine flour, and organic clay were made by melt compounding and injection molding. The influence of clay on crystallization behavior, mechanical properties, water absorption, and thermal stability of HDPE/pine composites were investigated. The HDPE/pine composites containing exfoliated clay were made by a two-step melt compounding procedure with a maleated polyethylene (MAPE) as a compatibilizer. Adding 2% clay to a HDPE/pine composite without MAPE decreased the crystallization temperature (Tc) and rate, and the crystallinity level. When 2% MAPE was added, the Tc and crystallization rate increased, but the crystallinity level was lowered. The flexural strength and the tensile strength of HDPE/pine composites increased 19.6% and 24.2% respectively with addition of 1% clay but then decreased slightly as the clay content was increased to 3%. The tensile modulus and tensile elongation were increased 11.8% and 13% respectively with addition of 1% clay but the storage and loss moduli barely change as the clay content was increased to 3%. The impact strength was lowered 7.5% by adding 1% clay, but did not decrease further as more clay was added. The moisture content and thickness swelling of the HDPE/pine composites was reduced by the clay, but did not improve the thermal stability.
Large-Scale Synthesis of Monodisperse Nanocrystals via Microreaction
Authors: Yang Hongwei , Luan Weiling , Tu Shan-Tung
Published: June 2009

A microfluidic reactor was set up to synthesize quantum dots (QDs) in large scale. The increased reaction channels in an individual reactor lead to improved throughput while maintaining sufficient residence time for the nucleation and growth of QDs. Uniform reaction conditions in the four capillaries realized by our set-up result in superior stability of the whole system. Organometallic synthesis of CdSe was chosen as a model system to evaluate the reactor, the absorption spectra of samples collected from different streams at various time intervals are indistinguishable from each other. By systematically varying the reaction parameters, fairly monodisperse CdSe NCs was produced with three times throughput higher than the conventional single-channel counterpart, and the FWHM of the PL. peaks can be controlled in the range from 37nm to 44nm. The large-scale synthesis route is characterized as excellent reproducibility, low-cost, fast reaction, and mass-production, by which 12ml CdSe NCs solution can be produced within 1h with the reaction time of 21s.
Micro Hydrogen Gas Sensor Based on Bi-Te Film Couples and Pt/ACC
Authors: Huang Hu , Zhang Jian-Song , Luan Weiling , Tu Shan-Tung , Yang Shang-Kuo
Published: June 2009

TE (Thermoelectric) materials have been widely used in clean energy system as low-power generator and Peliter cooler, due to its salient features of being compact, light-weighted, noiseless in operation, highly reliable, and environment friendly. Recently, another application has been explored on TE materials as gas sensors based on Seebeck effect and exothermic reaction of hydrogen oxidation on catalyst. In this paper, a TE hydrogen gas sensor with a simple structure, low energy consumption and a high sensitivity was reported. Bi-Te (bismuth telluride) with a high Seebeck coefficient at room-temperature was deposited onto thin glass substrates by RF magnetron sputtering technology. Four pairs of PN film couples were connected in series to improve the output voltage. Pt/ ACC (Activated Carbon Fiber Cloth) was mounted at the joint of PN couples, acting as catalyst so as to accelerate the oxidation of hydrogen. The influences of reduction temperature and Pt content on the generated temperature difference were investigated. The voltage output and selectivity to combustible gas mixture were measured. Experimental results showed that when exposed to 3vol% H2/ air, as-prepared sensor gave out a high output signal of 33.1mV, and the response time was about 50s with recovery time of 50s.
Guided Self-Assembly via Designed Strain Field
Authors: Lu Wei
Published: June 2009

We apply an elastic field to the substrate to guide the self-assembly of domain patterns on its surface. The effect of arbitrary three dimensional external loading is found to be characterized by a single two dimensional parameter—a surface stain field of the substrate. A non-uniform strain field significantly influences the size, shape and orientation of self-assembled features, and may induce the formation of pattern colonies. It is shown that a pattern orientates normal to the strain gradient direction. An applied load anchors the position of a self-assembled pattern relative to the substrate, where a colony boundary resides on the strain gradient region. The work suggests a method of strain field design to make various monolayer patterns for nanofabrication.
Further Experimental Studies on Flow Boiling Instabilities in Parallel Microchannels
Authors: Wang G. D. , Cheng Ping , Wu H. Y.
Published: June 2009

A simultaneous visualization and measurement study has been carried out to investigate flow boiling instabilities of water in parallel microchannels at various heat fluxes and mass fluxes. Eight parallel silicon microchannels, with an identical trapezoidal cross-section having a hydraulic diameter of 186 μm and a length of 30 mm, were used in this experiment. It was found that the flow boiling pattern depended on the heat to mass flux ratio q/G. Stable flow boiling regimes existed for q/G < 0.96 kJ/kg and q/G > 2.14 kJ/kg whereas unstable flow boiling existed in the range of 0.96 kJ/kg < q/G < 2.14 kJ/kg. At a given heat flux in the unstable flow boiling regime, the mass flux decreases continuously to a constant value after a sufficiently long time, and eventually reaches a stable flow boiling mode. It was found that the physical mechanism for the unstable boiling flow is owing to bubble expansion in both upstream and downstream direction. In particular, the expansion of bubble upstream will increase the upstream wall temperature, and the temperature of entire microchannel will eventually reach a steady state, i.e., a stable flow boiling regime.
The UTAM Nano-Patterning: A New Surface Nano-Patterning Technique in Fabricating Ordered Arrayed Surface Nanostructures
Authors: Lei Yong , Wilde Gerhard
Published: June 2009

A new surface nano-patterning technique, the so-called UTAM nano-patterning approach, is reported here in this paper. Using the UTAM nano-patterning technique, large-scale arrays of highly ordered nanostructures (nanoparticles and nanoholes) in the range of square centimeters have been fabricated on substrates in a massive parallel way. The resulting nanostructures are characterized by highly defined and controllable size, shape, composition, and spacing of the nanostructures. By changing the structural parameters of the nanoparticles, the properties of the nanoparticle arrays can be tuned. This non-lithographic surface nano-patterning approach provides an efficient and low-cost alternative in fabricating large-scale ordered arrays of surface nanostructures.
An Integrated Approach for Virtual Microstructure Generation and Micro-Mechanics Modelling for Micro-Forming Simulation
Authors: Ho Kar Cheong , Zhang Nan , Lin Jianguo , Dean Trevor Anthony
Published: June 2009

To aid FE simulation for forming micro-components, an integrated approach is proposed to generate virtual microstructure for micro-mechanics modelling. Based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micro-materials. The input data of the system are physical parameters of a material, including average, minimum and maximum grain sizes. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation and a method has been developed to solve the probability equation. These are the basis for the development of the VGRAIN system, which can be used to generate different grain structures and shapes that follow a certain pattern according to the probability theory. Statistical analyses have been carried out to investigate the distribution of generated virtual grains. The generated virtual microstructure is then implemented in the commercial FE code, ABAQUS, for mesh generation and micro-mechanics analysis using crystal plasticity equations for FCC materials. The crystal plasticity model is implemented in the commercial FE code, ABAQUS, through the used-defined subroutine, UMAT. FE analyses have been carried out to investigate size effects and localised necking encountered in micro-forming processes.
Toward the Next Generation Micro-Nanosystems: Technology and Industry Development in Japan
Authors: Adachi Junji , Adegawa Shunichi , Aoyagi Keiichi
Published: June 2009

MEMS industry in Japan has successfully taken off and been expected its rapid expansion, and is classified as a priority technology in the 3rd Science and Technology Basic Plan. Further involvement from the government in support technology development and commercialization is essential to achieve competitive advantage of the industry. In relation with the large anticipation of MEMS industry, Micromachine Center recently launched MEMS Industry Forum (MIF) in order to support MEMS industry development in collaboration with the government, the academia and the industry. Primary activities of MIF are policies proposal to the government, supporting the national project implementation, education, MEMS foundry service network and so on. The new national project, conducted by New Energy and Industrial Technology development Organization (NEDO), launched in July, 2006. The project focuses upon technology development on highly integrated MEMS, such as MEMS/MEMS, CMOS/MEMS and Nano/MEMS integrations, and its final goal is to commercialize the next generation MEMS devices and systems in five to ten years.
Formation of surface-grafted polymeric amphiphilic coatings comprising ethylene glycol and fluorinated groups and their response to protein adsorption
Authors: Arifuzzaman Shafi , Özçam Ali E. , Efimenko Kirill , Fischer Daniel A. , Genzer Jan
Published: June 2009

Amphiphilic polymer coatings were prepared by first generating surface-anchored polymer layers of poly(2-hydroxyethyl methacrylate) (PHEMA) on top of flat solid substrates followed by postpolymerization reaction on the hydroxyl terminus of HEMA’s pendent group using three classes of fluorinating agents, including organosilanes, acylchlorides, and trifluoroacetic anhydride (TFAA). The distribution of the fluorinated groups inside the polymer brushes was assessed by means of a suite of analytical probes, including contact angle, ellipsometry, infrared spectroscopy, atomic force microscopy, and near-edge x-ray absorption fine structure spectroscopy. While organosilane modifiers were found to reside primarily close to the tip of the brush, acylchlorides penetrated deep inside PHEMA thus forming random copolymers P(HEMA-co-fHEMA). The reaction of TFAA with the PHEMA brush led to the formation of amphiphilic diblocks, PHEMA-b-P(HEMA-co-fHEMA), whose bottom block comprised unmodified PHEMA and the top block was made of P(HEMA-co-fHEMA) rich in the fluorinated segments. This distribution of the fluorinated groups endowed PHEMA-b-P(HEMA-co-fHEMA) with responsive properties; while in hydrophobic environment P(HEMA-co-fHEMA) segregated to the surface, when in contact with a hydrophilic medium, PHEMA partitioned at the brush surface. The surface activity of the amphiphilic coatings was tested by studying the adsorption of fibrinogen (FIB). While some FIB adsorption occurred on most coatings, the ones made by TFAA modification of PHEMA remained relatively free of FIB.
Experimental and theoretical investigation of chain length and surface coverage on fouling of surface grafted polypeptoids
Authors: Statz Andrea R. , Kuang Jinghao , Ren Chunlai , Barron Annelise E. , Szleifer Igal , Messersmith Phillip B.
Published: June 2009

Numerous strategies exist to prevent biological fouling of surfaces in physiological environments; the authors’ strategy focuses on the modification of surfaces with poly-N-substituted glycine oligomers (polypeptoids). The authors previously reported the synthesis and characterization of three novel polypeptoid polymers that can be used to modify titanium oxide surfaces, rendering the surfaces resistant to adsorption of proteins, to adhesion of mammalian and bacterial cells, and to degradation by common protease enzymes. In this study, they investigated the effect of polypeptoid chain length on the antifouling properties of the modified surfaces. For these experiments, they used poly(N-methoxyethyl) glycines with lengths between 10 and 50 repeat units and determined the influence of chain length on coating thickness and density as well as resistance to protein adsorption and cellular adhesion. Short-term protein resistance remained low for all polymers, as measured by optical waveguide light mode spectroscopy, while fibroblast adhesion after several weeks indicated reduced fouling resistance for the polypeptoid-modified surfaces with the shortest chain length polymer. Experimental observations were compared to predictions obtained from a molecular theory of polymer and protein adsorption. Good agreement was found between experiment and theory for the chain length dependence of peptoid grafting density and for protein adsorption as a function of peptoid grafting density. The theoretical predictions provide specific guidelines for the surface coverage for each molecular weight for optimal antifouling. The predictions show the relationship between polymer layer structure and fouling.
Measuring cell adhesion forces during the cell cycle by force spectroscopy
Authors: Weder Gilles , Vörös Janos , Giazzon Marta , Matthey Nadège , Heinzelmann Harry , Liley Martha
Published: June 2009

Force spectroscopy has been used to measure the adhesion of Saos-2 cells to a glass surface at different phases of the cell cycle. The cells were synchronized in three phases of the cell cycle: G1, S, and G2M. Cells in these phases were compared with unsynchronized and native mitotic cells. Individual cells were attached to an atomic force microscope cantilever, brought into brief contact with the glass surface, and then pulled off again. The force-distance curves obtained allowed the work and maximum force of detachment as well as the number, amplitude, and position of discrete unbinding steps to be determined. A statistical analysis of the data showed that the number of binding proteins or protein complexes present at the cell surface and their binding properties remain similar throughout the cell cycle. This, despite the huge changes in cell morphology and adhesion that occur as the cells enter mitosis. These changes are rather associated with the changes in cytoskeletal organization, which can be quantified by force spectroscopy as changes in cell stiffness.
Bio-organism sensing via surface enhanced Raman spectroscopy on controlled metal/polymer nanostructured substrates
Authors: Demirel M. C. , Kao P. , Malvadkar N. , Wang H. , Gong X. , Poss M. , Allara D. L.
Published: June 2009

A new class of nonlithographically prepared surface enhanced Raman spectroscopy (SERS) substrates based on metalized, nanostructured poly(p-xylylene) films has been developed and optimized for surface plasmon response with a view to applications of SERS detection of microbial pathogens, specifically, bacteria and viruses. The main emphasis has been on achieving high spot to spot, sample to sample reproducibility of the SERS signals while maintaining useful enhancement factors. The use of these surfaces, metalized with either Ag or Au, provides a noninvasive and nondestructive method for spectral fingerprint analyses of both bacteria and viruses. Examples are given for the detection of bacteria (E. coli and B. cereus) and viruses (respiratory syncytial virus and Coxsackievirus). Our method is able to distinguish Gram positive from Gram negative bacterial strains as well as enveloped and nonenveloped viruses. The results demonstrate the development of a new class of SERS substrates which can provide rapid, selective identification of infectious agents without amplification of cultures.
LXR Regulates Cholesterol Uptake Through Idol-Dependent Ubiquitination of the LDL Receptor
Authors: Zelcer Noam , Hong Cynthia , Boyadjian Rima , Tontonoz Peter
Published: June 2009

Idolizing Cholesterol Control

The low-density lipoprotein receptor (LDLR) removes LDL, the so-called “bad” cholesterol particles, from the blood through a mechanism that involves LDL binding and internalization into liver cells. Because the LDLR plays a pivotal role in heart disease risk, there is substantial interest in understanding how its expression is regulated, and a large body of previous work has established the importance of transcriptional control. A new study identifies a signaling pathway that appears to regulate the LDLR at the level of protein degradation.

Zelcer
et al.

(p.
100
, published online 11 June) show that a sterol-responsive transcription factor called LXR induces the expression of Idol (for inducible degrader of the LDLR), a protein that triggers ubiquitination of the receptor and targets it for degradation. Activation of this pathway suppresses cellular uptake of LDL and, in a mouse model, leads to higher plasma LDL levels, raising the possibility that the pathway could be targeted pharmacologically to control plasma cholesterol levels.
Experimental Realization of a Three-Dimensional Topological Insulator, Bi
2
Te
3
Authors: Chen Y. L. , Analytis J. G. , Chu J.-H. , Liu Z. K. , Mo S.-K. , Qi X. L. , Zhang H. J. , Lu D. H. , Dai X. , Fang Z. , Zhang S. C. , Fisher I. R. , Hussain Z. , Shen Z.-X.
Published: June 2009

Topological Insulators

Topological insulators are a recently discovered state of matter, in which the bulk is an insulator while the surface is metallic with counterpropagating spin states. The surface states are protected by the topology, or structure, of the Fermi surface in the bulk gap and are described by a Dirac cone showing linear dispersion behavior meeting at the Dirac point.

Chen
et al.

(p.
178
, published online 11 June) provide a comprehensive photoemission study on Bi
2
Te
3
showing that it too falls into the category of topological band insulators. Moreover, there is just a single surface state with a single Dirac point in the photoemission spectrum. The identification of a material with a single Dirac point removes the ambiguity arising from multiple surface states and provides an ideal test-bed to probe the physics of these exotic new materials.
Genome-Wide RNAi Screen Identifies Genes Involved in Intestinal Pathogenic Bacterial Infection
Authors: Cronin Shane J. F. , Nehme Nadine T. , Limmer Stefanie , Liegeois Samuel , Pospisilik J. Andrew , Schramek Daniel , Leibbrandt Andreas , Simoes Ricardo de Matos , Gruber Susanne , Puc Urszula , Ebersberger Ingo , Zoranovic Tamara , Neely G. Gregory , von Haeseler Arndt , Ferrandon Dominique , Penninger Josef M.
Published: June 2009

Innate Immunity in the Fly Gut

Drosophila melanogaster
is an important model system to study innate immunity, being both easy to manipulate and lacking an adaptive immune system. In order to identify genes that regulate innate immunity,

Cronin
et al.

(p.
340
; published online 11 June) performed an RNA interference screen on flies infected with the oral bacterial pathogen,
Serratia marcescens
. Genes involved in intestinal immunity and regulation of hemocytes, macrophage-like cells critical for phagocytosis and killing of the bacteria, were identified. Several hundred genes conferred either enhanced susceptibility or resistance to bacterial infection. Furthermore, the JAK/STAT signaling pathway was activated in intestinal stem cells after bacterial infection, resulting in enhanced susceptibility to infection, most likely through regulation of intestinal stem cell homeostasis.
Food restriction promotes downregulation of myocardial L-type Ca2+ channels
Authors: De Tomasi Loreta Casquel , Bruno Alessandro , Sugizaki Mário Mateus , Lima-Leopoldo Ana Paula , Nascimento André Ferreira , Júnior Silvio Assis de Oliveira , Pinotti Matheus Fécchio , Padovani Carlos Roberto , Leopoldo André Soares , Cicogna Antonio Carlos
Published: June 2009

Food restriction (FR) has been shown to impair myocardial performance. However, the mechanisms behind these changes in myocardial function due to FR remain unknown. Since myocardial L-type Ca2+ channels may contribute to the cardiac dysfunction, we examined the influence of FR on L-type Ca2+ channels. Male 60-day-old Wistar rats were fed a control or a restricted diet (daily intake reduced to 50% of the amount of food consumed by the control group) for 90 days. Myocardial performance was evaluated in isolated left ventricular papillary muscles. The function of myocardial L-type Ca2+ channels was determined by using a pharmacological Ca2+ channel blocker, and changes in the number of channels were evaluated by mRNA and protein expression. FR decreased final body weights, as well as weights of the left and right ventricles. The Ca2+ channel blocker diltiazem promoted a higher blockade on developed tension in FR groups than in controls. The protein content of L-type Ca2+ channels was significantly diminished in FR rats, whereas the mRNA expression was similar between groups. These results suggest that the myocardial dysfunction observed in previous studies with FR animals could be caused by downregulation of L-type Ca2+ channels.
URB597, an inhibitor of fatty acid amide hydrolase, reduces hyperalgesia in diabetic rats
Authors: Hasanein Parisa , Parviz Mohsen , Keshavarz Mansoor , Roohbakhsh Ali
Published: June 2009

Diabetic rats display increased pain responses after injection of formalin into the paw or thermal stimulation of the tail, suggesting the presence of hyperalgesia. In this study, we investigated the efficacy of URB597 (0.1, 0.3, and 0.5 mg/kg, i.p.), an inhibitor of endocannabinoids metabolism, on 2 models of experimental hyperalgesia in streptozotocin (STZ)-induced diabetic rats. Animals were divided into control, URB597-treated control (0.1, 0.3, and 0.5 mg/kg), diabetic, and URB597-treated diabetic (0.1, 0.3, and 0.5 mg/kg) groups. Formalin and tail-flick tests were performed 4 and 8 weeks after the onset of hyperglycemia, respectively. Diabetes caused significant hyperalgesia during these tests. URB597 (0.3 and 0.5 mg/kg) reversed chemical and thermal hyperalgesia in diabetic rats. Administration of URB597 at a dose of 0.1 mg/kg did not alter pain-related behaviors in control and diabetic groups compared with those of the respective control groups. URB597 treatment did not affect body weight or plasma glucose level of treated animals compared with nontreated animals. This study shows that increasing endocannabinoid neurotransmission with URB597 displays efficacy in chemical and thermal models of diabetic hyperalgesia. It also suggests that URB597 is a promising tool for treatment of painful diabetic neuropathy.
Mechanism of glucocorticoid-induced oxidative stress in rat hippocampal slice cultures
Authors: You Jung-Man , Yun Su-Jin , Nam Kyong Nyon , Kang Chulhun , Won Ran , Lee Eunjoo H.
Published: June 2009

Prolonged stress results in elevation of glucocorticoid (GC) hormones, which can have deleterious effects in the brain. The hippocampus, which has a high concentration of glucocorticoid receptors, is especially vulnerable to increasing levels of GCs. GCs have been suggested to endanger hippocampal neurons by exacerbating the excitotoxic glutamate–calcium–reactive oxygen species (ROS) cascade. In an effort to reveal the mechanisms underlying GC-mediated hippocampal neurotoxicity, we aimed to clarify the molecular pathway of GC-induced ROS increase by using organotypic hippocampal slice cultures. Assays for ROS, using 2′,7′-dichlorodihydrofluorescein diacetate fluorescence, showed that treatment of synthetic GC, dexamethasone (DEX) significantly enhanced ROS levels. Time course and dose response analyses indicated that peak amount of ROS was generated at 4 h after treatment with 50 µmol/L DEX. By contrast, other steroid hormones, progesterone and estradiol did not influence ROS production. N-acetyl-l-cysteine completely suppressed ROS produced by DEX. Propidium iodide staining exhibited prominent cell death in the hippocampal layer after 96 h of DEX treatment. RU486, a GC receptor antagonist, almost completely blocked the effect of DEX on ROS production and cell death, indicating that DEX-induced ROS overproduction and hippocampal death are mediated via GC receptors. Real-time reverse transcriptase PCR analysis demonstrated that after DEX treatment the level of glutathione peroxidase mRNA was decreased whereas that of NADPH oxidase mRNA was significantly enhanced. These findings suggest that excess GCs cause hippocampal damage by regulating genes involved in ROS generation.
Chunghyuldan attenuates brain microglial inflammatory response
Authors: Nam Kyong Nyon , Jung Hoon-Ji , Kim Mi-Hyun , Kang Chulhun , Jung Woo-Sang , Cho Ki-Ho , Lee Eunjoo H.
Published: June 2009

Microglial cells are the prime effectors in immune and inflammatory responses of the central nervous system (CNS). During pathological conditions, the activation of these cells helps restore CNS homeostasis. However, chronic microglial activation endangers neuronal survival through the release of various proinflammatory molecules and neurotoxins. Thus, negative regulators of microglial activation have been considered as potential therapeutic candidates to target stroke and neurodegenerative diseases. Chunghyuldan, a combinatorial drug consisting of Scutellariae Radix, Coptidis Rhizoma, Phellodendri Cortex, Gardeniae Fructus, and Rhei Rhizoma, has an inhibitory effect on stroke recurrence in patients with small-vessel disease. It has also been reported to confer antihypertensive, antihyperlipidemic, and antiinflammatory effects. The aim of this study was to examine whether Chunghyuldan suppresses microglial activation. Chunghyuldan was effective at inhibiting LPS-induced nitric oxide (NO) release from rat brain microglia. Real-time reverse transcriptase PCR analysis revealed that pretreatment of rat brain microglia with Chunghyuldan attenuated the LPS-induced expression of mRNAs encoding inducible NO synthase, tumor necrosis factor (TNF)-α, interleukin-1β, and cyclooxygenase-2. In rat brain microglia, Chunghyuldan reduced the LPS-stimulated production of TNF-α and prostaglandin E2. In addition, Chunghyuldan significantly decreased LPS-induced phosphorylation of the ERK1/2 and p38 signaling proteins. These results suggest that Chunghyuldan provide neuroprotection by reducing the release of various proinflammatory molecules from activated microglia.
Evaluation of the antidiabetic potential of selected medicinal plant extracts from the Canadian boreal forest used to treat symptoms of diabetes: part II
Authors: Harbilas Despina , Martineau Louis C. , Harris Cory S. , Adeyiwola-Spoor Danielle C.A. , Saleem Ammar , Lambert Jennifer , Caves Dayna , Johns Timothy , Prentki Marc , Cuerrier Alain , Arnason John T. , Bennett Steffany A.L. , Haddad Pierre S.
Published: June 2009

Among the Cree of northern Quebec, the disproportionately high rate of diabetic complications is largely due to the cultural inadequacy of modern therapies for type 2 diabetes. To establish culturally adapted antidiabetic treatments, our team identified several candidate plant species used by the Cree to treat symptoms of diabetes. An initial study focused on 8 species and revealed that most possess significant in vitro antidiabetic activity. The purpose of the present study was to assess a further 9 species identified through the ethnobotanical survey. Crude plant extracts were screened for (i) potentiation of basal and insulin-stimulated glucose uptake by skeletal muscle cells (C2C12) and adipocytes (3T3-L1); (ii) potentiation of glucose-stimulated insulin secretion by pancreatic β cells (βTC); (iii) potentiation of adipogenesis in 3T3-L1 cells; (iv) protection against glucose toxicity and glucose deprivation in PC12-AC neuronal precursor cells; and (v) diphenylpicrylhydrazyl (DPPH) oxygen free radical scavenging. Four species potentiated basal glucose uptake in muscle cells or adipocytes, one species being as potent as metformin. Adipogenesis was accelerated by 4 species with a potency roughly half that of rosiglitazone. Five species protected PC12-AC cells against glucose toxicity and 4 protected against glucose deprivation. Five species exhibited antioxidant activity comparable to ascorbic acid. However, no species increased insulin secretion. The present study revealed that Gaultheria hispidula , Rhododendron tomentosum , and Vaccinium vitis-idaea exhibit a promising profile of antidiabetic potential and are good candidates for more in-depth evaluation.
Continuous therapy with transdermal nitroglycerin does not affect biomarkers of vascular inflammation and injury in healthy volunteers
Authors: Thomas George R. , DiFabio Jonathan M. , Gori Tommaso , Jenkins David J.A. , Parker John D.
Published: June 2009

Continuous exposure to nitroglycerin (GTN) results in development of tolerance and is associated with increased free radical production and abnormal endothelial function. Elevated plasma biomarkers of inflammation have been shown to be associated with endothelial dysfunction in most cardiovascular conditions. It remains unclear whether exposure to GTN is also associated with increased biomarkers of endothelial and vascular injury or vascular inflammation. In an investigator-blind study, a total of 28 healthy volunteers were randomized to continuous therapy with GTN (0.6 mg/h 24 h/day for 7 days) or no therapy. Venous blood was collected on day 0 and day 7. Plasma levels of markers such as asymmetric dimethyl-arginine (ADMA), human soluble P-selectin, interleukin-6, tumor necrosis factor-α, intercellular adhesion molecule-1, and oxidized low-density lipoproteins were measured. The levels of blood markers on day 0 were similar in the control and GTN-treated groups. After 7 days of GTN exposure, there were no significant changes in the different markers of vascular inflammation and injury either in the GTN or control group (all p > 0.5). The present study documents that prolonged continuous therapy with transdermal GTN therapy is not associated with changes in markers of vascular inflammation and injury.
Infarct size is increased in female post-MI rats treated with rapamycin
Authors: Lajoie Claude , El-Helou Viviane , Proulx Cindy , Clément Robert , Gosselin Hugues , Calderone Angelino
Published: June 2009

Rapamycin represents a recognized drug-based therapeutic approach to treat cardiovascular disease. However, at least in the female heart, rapamycin may suppress the recruitment of putative signalling events conferring cardioprotection. The present study tested the hypothesis that rapamycin-sensitive signalling events contributed to the cardioprotective phenotype of the female rat heart after an ischemic insult. Rapamycin (1.5 mg/kg) was administered to adult female Sprague–Dawley rats 24 h after complete coronary artery ligation and continued for 6 days. Rapamycin abrogated p70S6K phosphorylation in the left ventricle of sham rats and the noninfarcted left ventricle (NILV) of 1-week postmyocardial-infarcted (MI) rats. Scar weight (MI 0.028 ± 0.006, MI+rapamycin 0.064 ± 0.004 g) and surface area (MI 0.37 ± 0.08, MI+rapamycin 0.74 ± 0.03 cm2) were significantly larger in rapamycin-treated post-MI rats. In the NILV of post-MI female rats, rapamycin inhibited the upregulation of eNOS. Furthermore, the increased expression of collagen and TGF-β3 mRNAs in the NILV were attenuated in rapamycin-treated post-MI rats, whereas scar healing was unaffected. The present study has demonstrated that rapamycin-sensitive signalling events were implicated in scar formation and reactive fibrosis. Rapamycin-mediated suppression of eNOS and TGF-β3 mRNA in post-MI female rats may have directly contributed to the larger infarct and attenuation of the reactive fibrotic response, respectively.
Effect of winter torpor upon antioxidative defence in Helix pomatia
Authors: Nowakowska Anna , Świderska-Kołacz Grażyna , Rogalska Justyna , Caputa Michał
Published: June 2009

Arousal of land snails from torpor is inseparably connected with an increase in oxygen consumption leading to oxidative stress. Therefore, activity of antioxidant defence system (antioxidant enzymes and reduced glutathione) and degree of oxidative damage (concentration of malondialdehyde as an index of lipid peroxidation) in the snail Helix pomatia L., 1758 were tested to check whether torpid snails are able to activate their antioxidative defence against oxidative damage prior to arousal from winter torpor. Snails, which were collected from their natural habitats, were tested at the beginning, in the middle part, and at the end of winter torpor. Active snails collected in autumn and spring were taken as control groups. Snails were immediately killed and their foot, hepatopancreas, and kidney were used for the biochemical assays. Winter torpor induced significant changes in activities of the crucial antioxidant substances. The lowest activities were observed at the beginning of torpor, whereas activity of some of these enzymes was significantly enhanced prior to spring arousal. Reduced glutathione concentration did not show time-dependent changes during winter torpor. MDA (1,3-propanedial) level was elevated in the kidney and foot but was unchanged in the hepatopancreas. In conclusion, the snail H. pomatia is able to maintain REDOX balance necessary to prevent oxidative injury during arousal.
Limited behavioural thermoregulation by adult upriver-migrating sockeye salmon (Oncorhynchus nerka) in the Lower Fraser River, British Columbia
Authors: Donaldson M. R. , Cooke S. J. , Patterson D. A. , Hinch S. G. , Robichaud D. , Hanson K. C. , Olsson I. , Crossin G. T. , English K. K. , Farrell A. P.
Published: June 2009

The objective of this study was to combine radio telemetry with individual thermal loggers to assess the extent to which adult migrating sockeye salmon ( Oncorhynchus nerka (Walbaum in Artedi, 1792)) behaviourally thermoregulate during their migration through the Fraser River mainstem, British Columbia. The Fraser mainstem represents a region of the migration route that contains some of the highest mean temperatures encountered by sockeye salmon during their life history. We found that throughout the study area, individual sockeye salmon body temperatures occasionally deviated from ambient temperatures (ΔT), yet individuals maintained a ΔT of –1 °C or cooler for only 5% of their migration through the study region. There were moderate mean deviations of ΔT in two segments that are known to contain thermally stratified waters. In one of the study segments with the greatest ΔT, mean body temperatures decreased as river temperatures increased and ΔT became increasingly positive with higher river discharge rates, but these relationships were not observed in any of the other study segments. No relationship existed between ΔT and migration rate. While periodic associations with cool water were evident, mean body temperatures were not significantly different than mean river temperatures throughout the lower Fraser mainstem. This finding raises further conservation concerns for vulnerable Fraser River sockeye stocks that are predicted to encounter increasing peak summer river temperatures in the coming decades.