bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Head Tracking Method
Authors: Wang Yong Jun , Xu Jing Shuo , Li Lin
Published: April 2014

Head tracking technique plays an important role in the modern war. Because it is directly related to target capture rate. To adapt to rapid attitude position of the helmet, a novel real-time head tracking technology based on Micro-Electro-Mechanical Systems inertial navigation system (MEMS-INS) and Charge Coupled Device (CCD) is put forward. This method not only considers the spatial limitations of the helmet, but also takes into account the complementarity between inertial method and optical method. Firstly, the fundamental principle of head attitude measurement based on MEMS-INS/CCD is introduced. The state space model of the helmet attitude measurement is then built. In the end, feasibility of this method is validated by simulation. Simulation results show that head misalignment angle error can be estimated and reaches anticipated precision2 in 10 seconds. The helmet real-time tracking can be completed.
Effect of Size of Graphite Flakes on the Physical Properties of the Graphite Materials
Authors: Sun Shu Jie , Liu Xiu Jun , Li Tong Qi , Fan Zhen , Feng Zhi Hai
Published: April 2014

Mesophase pitch and natural graphite flake were applied as raw materials to prepare the graphite materials by a hot-pressing technique at a relatively low temperature. In this work, the effect of mean size of natural graphite flake on physical properties and microstructure of the graphite materials were investigated. X-ray analyses, field emission scanning electron microscopy and polarized light microscopy observations indicate that the graphite blocks have highly preferred structural orientation perpendicular to the hot-pressing direction. Results shows that the graphite materials have a low electrical resistivity of 2.45μΩ·m and a high thermal conductivity of 498 W/m·K ,as well as a high bending strength of 26.71 MPa when the mean size of graphite flake in raw materials was 425μm.
Controllable Self-Assembly of 9,10-Diphenylanthracene into Micro-Nanostructures from 0-Dimension to 3-Dimension by Simple Post-Drying Thermal Annealing Method
Authors: Sun Jing Wei , Ouyang Mi , Zhang Cheng
Published: April 2014

A post-drying thermal annealing method is proposed to successfully fabricate micro-/nanostructures with 9,10-diphenylanthracene (DPA). Through varying operating temperature, different morphologies from 0-D to 3-D of pure DPA self-assembly were achieved and studied by SEM, XRD and PL spectra. The morphology transformation mechanism was also investigated. These results indicate that varying annealing temperature is an effective way to control the supramolecular architectures of DPA. In addition, such in situ fabrication on a substrate will provide possibility for manufacture of electronic devices which normally require surface deposition of nanomaterials.
Research on the Sol-Gel Method of Preparing Ternary Nano SiO2-Al2O3-TiO2 Materials
Authors: Chen Ying , Liu Peng , Yu Zhi Wu
Published: April 2014

Tetraethyl orthosilicate (TEOS), butyl titanate [Ti (OBu)4] and aluminium isopropoxide were used as molecular precursor of ternary nanoSiO2-Al2O3-TiO2 materials. The influences of temperature and the dosage of compounds on the characteristic of ternary nanomaterials were investigated. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to investigate the characteristics of the nanomaterials synthesized by the sol-gel method. In addition, the adsorption of nanomaterials for different kinds of surfactants was also studied. Results revealed that the influences of temperature, compounds dosages and water on the size of ternary nanomaterials had a significant impact. With the increase of ammonia dosage, the concentration of the OH- ion became higer, and system showed a faster reaction rate. The higer temperature of the system was, the larger size of the ternary nanomaterials was. Moreover, the higer tempreature woule also lead to divide into layer and precipitate. Optimal parameters can be chosen to prepare monodispersed ternary nanoSiO2-Al2O3-TiO2 materials. Results also showed that the surface characteristic of ternary nanoSiO2-Al2O3-TiO2 particles differed from nanosilica, which manifested in forms of the adsorption dosage of surfactants.
Assessment on the Collection Efficiency of an Aerosol Sampler in Micro and Nanoparticles Environment
Authors: Yang Yi , Mao Ping , Feng Shu Yan , Zhang Jin Hua
Published: April 2014

The collection efficiency (CE) of an aerosol sampler is usually assessed dependently by using a sampler with higher CE and higher sampling accuracy or comparing the grain size distribution, concentration and/or other characteristics of the collected dust to that of the original dust, instead of the sampler itself. To establish a simple method for the assessment on the collection efficiency (CE) of an aerosol sampler, a self-dependent method was derived to calculate the CE of an aerosol sampler, which was patented with the number of ZL200910233001.X by the State Intellectual Property Office of China. According to the patent method, two or more uniform aerosol samplers of the same model were connected in series the inlet of a sampler was connected directly with the outlet of another sampler. The CE (η) of the aerosol sampler can be calculated by a simple equation as:η=1-m2/m1, in whichm1andm2is the weight of the aerosol particles collected by sampler 1# and sampler 2# in the connection sequence, respectively. A cascade impactor sampler was used to sample in a micrometer particle (d50=2.5 μm) aerosol environment and a nanoparticle (d50=42 nm) aerosol environment which were formed artificially in a glove box, as well as a workplace environment which manufactured nanometer powders. The sampling test results indicated that the cascade impactor sampler showed relative high CE (99.51%) for micrometer aerosol but a little bit low CE (95.2%) for nanoparticle aerosol. However, a low CE (93.93%) was calculated out by the method because of low concentration aerosol nanoparticles in the workplace environment, which result to big testing errors. It was found that the assessment result on collection efficiency of a sampler is highly affected by the subsequent analytical methods and detection accuracies after the sampling process. If the precision of the electronic balance was improved to a reasonable higher order of magnitude, the cascade impactor sampler can hopefully show much higher collection efficiency on nanoparticle aerosols.
Numerical Simulation of Microstructure Evolution in AZ31 Magnesium Alloy during Equal Channel Angular Pressing
Authors: Ren Guo Cheng , Lin Xiao Juan , Xu Shu Bo
Published: April 2014

The microstructure and material properties of AZ31 magnesium alloy are very sensitive to process parameters, which directly determine the service properties. To explore and understand the deformation behavior and the optimization of the deformation process, the microstructure evolution during equal channel angular pressing was predicted by using the DEFORM-3D software package at different temperature. To verify the finite element simulation results, the microstructure across the transverse direction of the billet was measured. The results show that the effects strain and deformation temperatures on the microstructure evolution of AZ31 magnesium during ECAP process are significant, and a good agreement between the predicted and experimental results was obtained, which confirmed that the derived dynamic recrystallization mathematical models can be successfully incorporated into the finite element model to predict the microstructure evolution of ECAP process for AZ31 magnesium.
Viscous Dissipation of Polymer Melt in Micro Channels and Macro Channels
Authors: Xu Bin , An Xiao Yu , Li Liang Chao , Li Guang Ming
Published: April 2014

Viscous dissipation is the key factor impacting flowing characteristics of polymer melt. In order to study the difference between micro scale and macro scale, experimental studies of viscous dissipation at various shear rate were investigated with several polymers, including PMMA and HDPE, at different temperature when melts flow through 1000μm,500μm,350μm diameter channels of identical aspects ratio in the paper. The results indicate that the temperature rises caused by viscous dissipation increase with increasing shear rate and the temperature rise for some shear rate decreases with increasing melts temperature. The temperature rises decrease significantly with the reduction of the characteristic size of micro channel at the same shear rate. However, the average temperature rises per unit length increase when the character size of channel decreases. This indicates the shear friction gradually increases with the decrease of channel characteristic size. Therefore polymer melt viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions.
Nucleation and Growth Characteristics of Bubble in Subcooled Flow Boiling in Microchannel
Authors: Qiu Chao , Zhang Hui Chen
Published: April 2014

Dynamic characteristics of micro bubble are the key for its applications. A thermal bubble is produced on the wall of microchannel with flowing fluid. Generation of bubble, including nucleation and growth, is observed and measured with different volume flow rates. The results show that nucleation becomes more difficult and instable with volume flow rate increasing. Bubble growth could be divided into three stages, while the second stage becomes shorter and even disappears as volume flow rate increasing. When volume flow rate increases suddenly, bubble shrinks, and it is more remarkable for larger volume flow rate. Furthermore it needs more time for bubble to reach and keep the minimum volume.
The Tunable Optofluidics Waveguide Design Based on the Novel Dual Side-Coupled Cavities Plasmonic Structure
Authors: Li Teng Long , Liang Rui Sheng , Mo Wen Hao , Luo Liang Bing , He Ming Jia , Wang Yu Ruo
Published: April 2014

We present a tunable wavelength filter in plasmonic metaldielectricmetal (MIM) side-coupled-cavity waveguide with optofluidics pump system proposed to realize tunable mechanism. The peak wavelength can shift by manipulating the length of liquid column and the effective refractive index. The finite difference time domain method is used in the numerically simulated experiment and the resonant wavelengths from 1000 to around 1800nm had been analyzed. The results reveal that the resonant wavelengths are proportional to the liquid volume length and refractive index of liquid in the cavity. This waveguide filter can be used in integrated optical circuits.
Research about Flexible PDMS Micro-Perforated Panel Based on MEMS Silicon Mold
Authors: Ping Hao Yue , Wu Shao Hua , Zhao Zhan , Kong De Yi , Du Li Dong , Fang Zhen
Published: April 2014

Micro-perforated panel (MPP) is known for its remarkable noise absorption capability and has been studied and developed for decades. Although the panel and cavity walls of traditional MPP are rigid, some previous works have shown that the absorption bandwidth of flexible MPP can be improved by the vibration of the panel. But this result is only tested at low frequencies. In this paper, the flexible MPP aiming at high frequency range is studied under a control experiment. But the perforations of high frequency MPP are in the range of micron and difficult to be fabricated in traditional mechanical methods. A new process, based on MEMS silicon mold technology and PDMS casting method, is developed to meet this challenge. Experimental results show that the noise absorption bandwidth of flexible MPP does get widened conspicuously only at a little sacrifice of absorption peak.
Research of Micro-Inertial Device High-Aspect-Ratio Etching Parameters
Authors: Shi Gui Xiong , Jia Shi Xing , Jiang Guo Qin , Zhu Jian
Published: April 2014

This is mainly due to the high chemical reactivity and spontaneous etching nature of the fluorine radicals towards silicon, and the high volatility of the silicon fluorides as reaction products. Anisotropy can only be achieved by the inclusion of sidewall passivation schemes to the process. The existing approaches to deep reactive ion etching (DRIE) of silicon are distinguished by the way sidewall passivation is achieved, the key to anisotropy and overall performance of the etch process. Cryogenic etching and the so-called Bosch process with alternating etch and passivation cycles are the two most well-known high-aspect-ratio silicon etch processes and are discussed in this paper.
A New Method to Analyze the Stiffness of MEMS Accelerometer
Authors: Liu Hai Tao , Wen Zhi Yu , Shang Zheng Guo , Chen Li
Published: April 2014

The finite element method to obtain the stiffness of MEMS (Micro-Electro-Mechanical Systems) accelerometer is difficult to give an exact expression, so a new method to analyze the stiffness of MEMS accelerometer was purposed. Both Mechanics and electricity analysis were used to calculate the stiffness of vacuum microelectronic accelerometer developed in our laboratory, and the control and detection circuits were design according to the result. Finally, the sensitivity, linearity and other performance were measured through the static gravitational field experiments; the least squares curve fitting correlation coefficient 0.9999 and linear 0.9%. The result shows that this method to analyze the stiffness of the stiffness of vacuum microelectronics accelerometer is correct and feasible, and this method can also be applied to other MEMS accelerometer with symmetrical structure and electrostatic force balance mode.
ZnO/Graphene Composites: Synthesis, Characterization and Optical Properties
Authors: Hu Ling Wei , Tian Hua , Zhang Yu Xia , Lu Kun , Jing Ai Hua
Published: April 2014

ZnO/graphene composites has been synthesized using a one-pot hydrothermal method at moderate temperature of 90°C. Hydrothermal growth was done in an aqueous solution consisting of 20 mL graphene oxide (GO) solution (0.25 mg/mL) with equimolar of zinc acetate [ZAc, Zn (CH3COO)2·2H2 and hexamethylenetetramine (HMTA, C6H12N4). The as-synthesized composites was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results of the characterization indicate that GO was reduced to graphene in the growth process, while ZnO in the form of quantum dots (QDs) or nanoparticles embedded in the graphene sheet. The composites synthesized by this method will have potential applications in bioimaging, gas sensing, optoelectrical materials and devices. The photoluminescence (PL) of the conposites was also investigated.
Cantilever Piezoelectric Micro-Pump Modeling Based on Bond Graph Port
Authors: Cao Dong Xing , Jia Qiu Ling , Lei Li Zhu , Xin Zhao Feng , Mi Jia Jia
Published: April 2014

Micro-pump is a fundamental component of micro-fluid machine, which has obtained an extensive use in medical care, bio-engineering, and the other fields. Its application will continuously be expanded. Its structure is different from the conventional mechanical pump as its size and flow limit, thus it is difficult to directly apply traditional method to micro-pump modeling. Firstly, the paper introduces the structure of the cantilever piezoelectric micro-pump, in which its input/output can be seen as two separate one-way valves, and its structure can be simplified for a simple beam model. Secondly, presents a port model based on bond graph port analysis, and selects the basic components in order to understand the micro-fluid characteristics of the micro-pump. Finally, gives the result of simulation to obtain the process of the volume change of micro-pump companying with the input pressure and the displacement of deformable film..
Study of a Temperature Detection Sensor in Road Surface Sensors System
Authors: Dong Xue Peng , Han Lei , Yin Gang Yi , Cai Lei
Published: April 2014

Road surface sensors system, which monitors the road conditions and raises an alarm when necessary, plays a very important role in the safety of transportation. The temperature detection sensor is used to measure the temperature on and beneath the road surface. It synthetically estimates the road conditions in cooperation with other sensors, such as water film sensor, salinity sensor and so on. In this paper, the theory, circuit structure and testing method of the temperature detection sensor have been introduced, and the data processing pattern and accuracy of results have been improved.
Nanoindentation Measurements in Non-Oriented Silicon Steel at Elevated Temperatures
Authors: Gavendová Petra , Kováč František , Petryshynets Ivan , Sopko Martin , Molnárová Mária
Published: April 2014

The present work deals about nanoindentation measurements between particular grains with various orientation at room and at elevated temperatures ( 100°C, 200°C, 250°C). Nanohardness measurements were carried out in non-oriented silicon steel with columnar microstructure, in order to evaluate local variation of work hardening as function of crystallographic orientation. The dependence of texture on the applied condition was studied by EBSD (Electron Backscatter Diffraction) analysis. Hardness was shown to decrease with increasing temperature in each of individual grains. The differences of hardness values were observed also between particular grain orientations.
Changes in Mechanical Properties and Microstructure after Quasi-Static and Dynamic Tensile Loading
Authors: Zubko Pavol , Vojtko Marek , Pešek Ladislav , Német Miroslav , Bekeč Pavel
Published: April 2014

Dual phase (DP), interstitial free (IF) and advanced high strength low alloy steel (HSLA)sheets have been successfully used for different components of car body. DP and HSLA are used ascrash resistant and IF as cover or “skin” of car body. The development of new vehicles nowadays isbeing driven by the need to simultaneously reduce mass and increase of passenger and pedestriansafety as well as costs saving through cold forming instead of hot forming. Limited publishedinformation is available on the changes in microstructure of these steel grades at different highstrain rates [1-3].This paper deals with changes of mechanical properties, microstructure and fractography of threesteel grades, which were tested at quasi static (10-3 s-1) and high strain rate (3000 s-1). Themicrostructures were characterized in terms of ferrite grain size, aspect ratio of ferrite andelongation of constituent phases. Deformed and undeformed specimens were compared to assess thechanges in the microstructure. The fracture appearance analysis indicates that the fracture patternunder high strain rates is mainly ductile, regardless of steel grades. The microstructure changessignificantly during the deformation process under both quasi-static and dynamic tension in allinvestigated steels. The plastic deformation in ferrite dominates in this process.
Structure Stability of Ni-Base and Co-Base Alloys
Authors: Podhorná Božena , Andršová Irena , Dobrovská Jana , Vodárek Vlastimil , Hrbáček Karel
Published: April 2014

This article summarises results of structure stability investigation of cast Ni-base and Co-base alloys after prolonged high temperature exposure at 900-1100 °C. Cast Ni (Co)-Cr-W-C alloys are resistant to high-temperature corrosion, due to high chromium content. Their heat resistance is caused by presence of carbides, which are stable at very high temperatures. Carbides precipitate in shape of large plate-like particles or carbide eutectics at casting cell boundaries, thus forming carbide skeleton of the alloy. Carbide morphology and temperature stability depends on chemical composition of the alloy, e.g. carbide content, type and content of carbide-forming elements. Microstructure changes were evaluated by stereological analysis and X ray-spectral microanalysis.
Study of Fracture Feature of Titanium Based Alloys for Biocompatible Implants after Removal from Human Body
Authors: Losertová Monika , Drápala Jaromír , Konečná Kateřina , Pleva Leopold
Published: April 2014

The study of microstructure and fracture surfaces was performed on specimens of reconstruction plate, reconstruction nail and elastic nail. The composition and phase analysis of microstructure was performed by scanning electron microscope (SEM) JEOL JSM - 6490LV equipped with EDS INCA X - ACT probe. Examination of fracture surfaces by SEM confirmed that damage was not simply due to fatigue but contained evidence of corrosion and mechanical fretting as well.
Prediction of Ternary Fe-B-Cr Phase Diagram
Authors: Homolová Viera
Published: April 2014

Fe-B-Cr ternary system and its binary subsystems have been studied with aim to develop database of parameters for various thermodynamic calculations of complex systems with boron (for example modified ferritic and austenitic steels for energy industry). All corresponding binary phase diagram were calculated with software THERMO-CALC. Prediction of ternary phase diagram for the Fe-B-Cr system was modelled with using binary data of corresponding subsystems. The prediction was compared with available literature experimental results of phase analysis. The experimental results were used for modifying of the phase diagram prediction by Calphad-method. In future the modified prediction is going to be compared with our experimental results of phase analysis of prepared model alloys to receive most reliable phase diagram of the system.
High Cr-Ni Cast Iron Base Deposits with Tantalum Carbide Particles Produced by Plasma Spraying
Authors: Hoshiyama Yasuhiro , Otani Toshiaki , Miyake Hidekazu
Published: April 2014

Fe-C-Ta-Cr-Ni alloy powder in diameter of 32-53 μm made by argon atomization was low-pressure plasma sprayed to produce high Cr-Ni cast iron base deposits with finely dispersed tantalum carbide particles. The as-sprayed deposit formed on a water-cooled substrate consisted of γFe, αFe and carbide. The fine precipitates of approximately 0.1 μm in the as-sprayed deposit formed on a water-cooled substrate were carbide. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The hardness of deposit decreases with increasing heat treatment temperature. The wear resistance of as-sprayed deposit formed on a non-cooled substrate was higher than that of the deposit heat-treated at 1273 K. The as-sprayed deposit and deposit heat-treated at 1273 K hade higher wear resistance than a commercial stainless steel.
Thermal Spray Technology and Casting in Renovation of Friction Bearings Surface
Authors: Švejcar Jiří , Čelko Ladislav , Dvořáček Emil , Klakurková Lenka , Juliš Martin , Slámečka Karel , Zapletal Josef
Published: April 2014

The contribution deals with an analysis of thick wear-resistant coatings produced on the surface of cast iron friction bearings by means of twin wire arc spraying or by pouring, with the aim of comparing the two manufacturing technologies. In addition to a detailed analysis of the microstructure and phase composition of the two types of coating, their mechanical and adhesion properties were established (using tensile and shear stress testing methods as well as cyclic thermal shocks).
Effect of Experimental Factors on Hardness Measurement Using the UCI Technique
Authors: Burik Peter , Pešek Ladislav
Published: April 2014

The work experimentally analyses the effect of various factors on hardness measured values on thin steel sheets using Ultrasonic Contact Impedance (UCI) technique. The conditions experimentally used are compared with that according the ASTM A 1038-08 standard. UCI is an experimental technique for indirect hardness measurement. The equipment uses a Vickers indenter and the hardness measurement is based on the change of the resonance frequency during indenter ́s penetration [.The UCI hardness may depend on some factors, therefore optimal measurement conditions must be determined. The effect of distance between indents, zinc coating, sample weight, sample mounting and adhesive material for sample fixation were determined.
Precipitation in Surface Zone of Continuously-Cast Slab of ULC/IF Steel Microalloyed with Titanium
Authors: Longauerová Margita , Hurakova Maria , Longauer Svätoboj
Published: April 2014

The aim of this work was to analyze the morphology and distribution of the microalloy precipitates in the slab surface zone of ULC/IF steel microalloyed with titanium. The slab was made by continuous casting using two different slab pulling rates. Transient slabs were pulled with pulling rate 0.4 m/min at the start and 0.8 m/min at the end of the slab. It was confirmed that morphology of the particles evaluated in the surface areas of slab were globular, cubical or elliptical shape and have been identified as of TiS, TiN and TiC. At the lower drawing rate particles from the middle cut-out from an area with coarse ferritic grains at the slab surface attained an mean size of 2r = 41.8 nm, and from an area with fine ferritic grains they attained an mean size of 2r = 32.5 nm. At the higher drawing rate particles in the middle cut-out attained an mean size of 2r= 63.5 nm. The coarser particles were found in areas with coarse ferrite grains and at higher pulling speed.
Sensitization of Tumor Cells to NK Cell-Mediated Killing by Proteasome Inhibition
Authors: Hallett William H.D. , Ames Erik , Motarjemi Milad , Barao Isabel , Shanker Anil , Tamang David L. , Sayers Thomas J. , Hudig Dorothy , Murphy William J.
Published: April 2014

Bortezomib is a proteasome inhibitor that has direct antitumor effects. We and others have previously demonstrated that bortezomib could also sensitize tumor cells to killing via the death ligand, TRAIL. NK cells represent a potent antitumor effector cell. Therefore, we investigated whether bortezomib could sensitize tumor cells to NK cell-mediated killing. Preincubation of tumor cells with bortezomib had no effect on short-term NK cell killing or purified granule killing assays. Using a 24-h lysis assay, increases in tumor killing was only observed using perforin-deficient NK cells, and this increased killing was found to be dependent on both TRAIL and FasL, correlating with an increase in tumor Fas and DR5 expression. Long-term tumor outgrowth assays allowed for the detection of this increased tumor killing by activated NK cells following bortezomib treatment of the tumor. In a tumor purging assay, in which tumor:bone marrow cell mixtures were placed into lethally irradiated mice, only treatment of these mixtures with a combination of NK cells with bortezomib resulted in significant tumor-free survival of the recipients. These results demonstrate that bortezomib treatment can sensitize tumor cells to cellular effector pathways. These results suggest that the combination of proteasome inhibition with immune therapy may result in increased antitumor efficacy.
Loss of IL-7R and IL-15R Expression Is Associated with Disappearance of Memory T Cells in Respiratory Tract following Influenza Infection
Authors: Shen Ching-Hung , Ge Qing , Talay Oezcan , Eisen Herman N. , García-Sastre Adolfo , Chen Jianzhu
Published: April 2014

Following influenza virus infection, memory CD8 T cells are found in both lymphoid and nonlymphoid organs, where they exhibit striking differences in survival. We have assessed persistence, phenotype, and function of memory CD8 T cells expressing the same TCR in the airways, lung parenchyma, and spleen following influenza virus infection in mice. In contrast to memory CD8 T cells in the spleen, those residing in the airways gradually lost expression of IL-7R and IL-15R, did not respond to IL-7 and/or IL-15, and exhibited poor survival both in vivo and in vitro. Following adoptive transfer into the airways, splenic memory CD8 T cells also down-regulated IL-7R and IL-15R expression and failed to undergo homeostatic proliferation. Thus, although cytokines IL-7 and IL-15 play an essential role in memory CD8 T cell homeostasis in lymphoid organs, the levels of IL-7R and IL-15R expression likely set a threshold for the homeostatic regulation of memory CD8 T cells in the airways. These findings provide a molecular explanation for the gradual loss of airway memory CD8 T cells and heterosubtypic immunity following influenza infection.
Baculovirus-Infected Insect Cells Expressing Peptide-MHC Complexes Elicit Protective Antitumor Immunity
Authors: Jordan Kimberly R. , McMahan Rachel H. , Oh Jason Z. , Pipeling Matthew R. , Pardoll Drew M. , Kedl Ross M. , Kappler John W. , Slansky Jill E.
Published: April 2014

Evaluation of T cell responses to tumor- and pathogen-derived peptides in preclinical models is necessary to define the characteristics of efficacious peptide vaccines. We show in this study that vaccination with insect cells infected with baculoviruses expressing MHC class I linked to tumor peptide mimotopes results in expansion of functional peptide-specific CD8+ T cells that protect mice from tumor challenge. Specific peptide mimotopes selected from peptide-MHC libraries encoded by baculoviruses can be tested using this vaccine approach. Unlike other vaccine strategies, this vaccine has the following advantages: peptides that are difficult to solublize can be easily characterized, bona fide peptides without synthesis artifacts are presented, and additional adjuvants are not required to generate peptide-specific responses. Priming of antitumor responses occurs within 3 days of vaccination and is optimal 1 wk after a second injection. After vaccination, the Ag-specific T cell response is similar in animals primed with either soluble or membrane-bound Ag, and CD11c+ dendritic cells increase expression of maturation markers and stimulate proliferation of specific T cells ex vivo. Thus, the mechanism of Ag presentation induced by this vaccine is consistent with cross-priming by dendritic cells. This straightforward approach will facilitate future analyses of T cells elicited by peptide mimotopes.
CD62L (L-Selectin) Down-Regulation Does Not Affect Memory T Cell Distribution but Failure to Shed Compromises Anti-Viral Immunity
Authors: Richards Hannah , Longhi M. Paula , Wright Kate , Gallimore Awen , Ager Ann
Published: April 2014

The down-regulation of CD62L that accompanies T lymphocyte activation is thought to redirect cells away from lymph nodes to sites of infection. In this study, CD62L was maintained on Ag-activated T cells and their distribution, and ability to clear pathogen from peripheral sites determined. CD62L was down-regulated on Ag-specific CD8 T cells in lungs of C57BL/6 mice but maintained in CD62L transgenic mice at day 8 after influenza infection. However, the numbers of influenza-specific CD8 T cells recruited were similar in CD62L transgenic and C57BL/6 mice. Memory CD8 T cell numbers in the lungs and noninvolved organs 100 days after primary infection were similar in CD62L transgenic and C57BL/6 mice, despite differing CD62L expression. Transgenic mice expressing wild-type CD62L cleared a recombinant vaccinia virus expressing an influenza-derived CD8 T cell epitope as efficiently as C57BL/6 mice. However, transgenic mice expressing a protease resistant mutant of CD62L showed significantly delayed viral clearance, despite normal CTL generation and the presence of CD107a and IFN-γ expressing influenza-specific CD8 T cells. These results demonstrate that CD62L down-regulation is not required for CD8 memory cells to home to sites of infection. However, their ability to clear virus is significantly compromised if CD62L shedding is abrogated.
Nuclear Export of NF90 to Stabilize IL-2 mRNA Is Mediated by AKT-Dependent Phosphorylation at Ser647 in Response to CD28 Costimulation
Authors: Pei Yuan , Zhu Ping , Dang Yongjun , Wu Jiaxue , Yang Xianmei , Wan Bo , Liu Jun O. , Yi Qing , Yu Long
Published: April 2014

IL-2 is one of the most important cytokines required for T cell-mediated immune responses. Costimulation of CD28 in T cells up-regulates IL-2 mRNA levels via transcription activation and mRNA stabilization. Upon T cell activation, NF90, an AU-rich element (ARE)-binding protein, translocates from the nucleus into the cytoplasm, where it binds to the ARE-containing 3′ untranslated regions of IL-2 mRNA and slows down degradation of IL-2 mRNA. The translocation of NF90 is mediated through a nuclear export signal at its N terminus, but how it is triggered is still unclear. Phosphorylation of ARE-binding proteins has been reported as a signal transduction pathway to stabilize ARE-containing transcripts. In this study, we demonstrate that AKT phosphorylates NF90 on Ser647 upon CD28 costimulation. This phosphorylation is necessary for nuclear export of NF90 and IL-2 mRNA stabilization by this protein, because a mutation at Ser647 abolished both functions. We observed that treatment of cells with CD28 costimulation induced distinct increase in phosphorylation of AKT and NF90 at Ser647 concomitantly. Phosphorylation at Ser647 of NF90 up-regulated IL-2 production in response to CD28 costimulation. In vivo and in vitro data support a model in which CD28 costimulation activates AKT to phosphorylate NF90 at Ser647 and phosphorylation triggers NF90 to relocate to the cytoplasm and stabilize IL-2 mRNA.
Targeted Deletion of fgl2 Leads to Impaired Regulatory T Cell Activity and Development of Autoimmune Glomerulonephritis
Authors: Shalev Itay , Liu Hao , Koscik Cheryl , Bartczak Agata , Javadi Mojib , Wong Kit Man , Maknojia Asif , He Wei , Liu Ming Feng , Diao Jun , Winter Erin , Manuel Justin , McCarthy Doug , Cattral Mark , Gommerman Jennifer , Clark David A. , Phillips M. James , Gorczynski Reginald R. , Zhang Li , Downey Greg , Grant David , Cybulsky Myron I. , Levy Gary
Published: April 2014

Mice with targeted deletion of fibrinogen-like protein 2 (fgl2) spontaneously developed autoimmune glomerulonephritis with increasing age, as did wild-type recipients reconstituted with fgl2−/− bone marrow. These data implicate FGL2 as an important immunoregulatory molecule and led us to identify the underlying mechanisms. Deficiency of FGL2, produced by CD4+CD25+ regulatory T cells (Treg), resulted in increased T cell proliferation to lectins and alloantigens, Th 1 polarization, and increased numbers of Ab-producing B cells following immunization with T-independent Ags. Dendritic cells were more abundant in fgl2−/− mice and had increased expression of CD80 and MHCII following LPS stimulation. Treg cells were also more abundant in fgl2−/− mice, but their suppressive activity was significantly impaired. Ab to FGL2 completely inhibited Treg cell activity in vitro. FGL2 inhibited dendritic cell maturation and induced apoptosis of B cells through binding to the low-affinity FcγRIIB receptor. Collectively, these data suggest that FGL2 contributes to Treg cell activity and inhibits the development of autoimmune disease.
Cutting Edge: A Key Pathogenic Role of IL-27 in T Cell- Mediated Hepatitis
Authors: Siebler Juergen , Wirtz Stefan , Frenzel Christian , Schuchmann Marcus , Lohse Ansgar W. , Galle Peter R. , Neurath Markus F.
Published: April 2014

The signals driving T cell activation in T cell-mediated fulminant hepatitis are not fully understood. In this study, we identify the cytokine IL-27p28/EBI3 as a major pathogenic factor in the ConA model of T cell-mediated hepatitis. We found an up-regulation of hepatic EBI3 and p28 expression and augmented levels of IL-27 in wild-type mice after ConA administration, suggesting a potential pathogenic role of this cytokine in ConA hepatitis. Consistently, IL-27 EBI3-deficient mice were almost completely protected from ConA-induced liver damage. Such protection was associated with reduced levels of IFN-γ and its signaling proteins pSTAT-1 and T-bet. Finally, in vivo blockade of IL-27 function using a soluble IL-27 receptor fusion protein led to reduced pSTAT1 levels and suppression of liver injury. Taken together, these data demonstrate a key pathogenic role of IL-27 in T cell-mediated liver injury. Furthermore, in vivo blockade of IL-27 emerges as a novel potential therapy for T cell-mediated hepatitis.
Antigen-Driven Interactions with Dendritic Cells and Expansion of Foxp3+ Regulatory T Cells Occur in the Absence of Inflammatory Signals
Authors: Chappert Pascal , Leboeuf Marylène , Rameau Philippe , Stockholm Daniel , Liblau Roland , Danos Olivier , Davoust Jean M. , Gross David-Alexandre
Published: April 2014

Foxp3+ regulatory T cells (Tregs) play a pivotal role in the maintenance of peripheral T cell tolerance and are thought to interact with dendritic cells (DC) in secondary lymphoid organs. We analyzed here the in vivo requirements for selective expansion of Ag-specific Treg vs CD4+CD25− effector T cells and engagement of Ag-specific Treg-DC interactions in secondary lymphoid organs. Using i.v. Ag delivery in the absence of inflammation, we found that CD4+CD25+Foxp3+ Tregs undergo vigorous expansion and accumulate whereas naive CD4+CD25−Foxp3− T cells undergo abortive activation. Quantifying directly the interactions between Tregs and CD11c+ DC, we found that Tregs establish cognate contacts with endogenous CD11c+ DC in spleen and lymph nodes at an early time point preceding their expansion. Importantly, we observed that as few as 103 Tregs selectively expanded by i.v. Ag injection are able to suppress B and T cell immune responses in mouse recipients challenged with the Ag. Our results demonstrate that Tregs are selectively mobilized by Ag recognition in the absence of inflammatory signals, and can induce thereafter potent tolerance to defined Ag targets.
Macrophages Driven to a Novel State of Activation Have Anti-Inflammatory Properties in Mice
Authors: Brem-Exner Beate G. , Sattler Christine , Hutchinson James A. , Koehl Gudrun E. , Kronenberg Katharina , Farkas Stefan , Inoue Seiichiro , Blank Christian , Knechtle Stuart J. , Schlitt Hans J. , Fändrich Fred , Geissler Edward K.
Published: April 2014

Recurrent episodes of inflammation underlie numerous pathologies, notably those of inflammatory bowel diseases. In this study, we describe a population of macrophages in a novel state of activation that mitigates colitis in mice. The cells responsible for this effect, called IFN-γ-stimulated monocyte-derived cells (IFNγ-MdC), derive from mouse spleen, blood, and bone marrow monocytes and are distinguished from known macrophage populations by mode of generation, cell surface phenotype, and function. IFNγ-MdC only arise when macrophages are cultivated in the presence of CD40L-expressing CD4+ T cells, M-CSF, and IFN-γ. IFNγ-MdC express markers including F4/80, CD11b/c, CD86, and CD274; they are negative for CD4, CD8, Gr1, CD19, CD80, and CD207. Functionally, IFNγ-MdC are defined by their capacity to enrich cocultured T cell populations for CD4+CD25+Foxp3+ regulatory cells; this enrichment, constituting up to 60% or more of residual lymphocytes, is attributed to an expansion, but also to a cell contact and caspase-dependent depletion of activated T cells. In mice, IFNγ-MdC delivered i.v. traffic to gut-associated peripheral lymphoid tissues, including the mesenteric lymph nodes, Peyer’s patches, and colonic mucosa, and promote the clinical and histological resolution of chronic colitis. We conclude that IFNγ-MdC represent macrophages in a novel state of activation, possessing multiple T cell-suppressive effects with therapeutic potential for the treatment of autoimmune inflammation.
Molecular Design of the Cαβ Interface Favors Specific Pairing of Introduced TCRαβ in Human T Cells
Authors: Voss Ralf-Holger , Willemsen Ralph A. , Kuball Jürgen , Grabowski Margarete , Engel Renate , Intan Ratna S. , Guillaume Philippe , Romero Pedro , Huber Christoph , Theobald Matthias
Published: April 2014

A promising approach to adoptive transfer therapy of tumors is to reprogram autologous T lymphocytes by TCR gene transfer of defined Ag specificity. An obstacle, however, is the undesired pairing of introduced TCRα- and TCRβ-chains with the endogenous TCR chains. These events vary depending on the individual endogenous TCR and they not only may reduce the levels of cell surface-introduced TCR but also may generate hybrid TCR with unknown Ag specificities. We show that such hybrid heterodimers can be generated even by the pairing of human and mouse TCRα- and TCRβ-chains. To overcome this hurdle, we have identified a pair of amino acid residues in the crystal structure of a TCR that lie at the interface of associated TCR Cα and Cβ domains and are related to each other by both a complementary steric interaction analogous to a “knob-into-hole” configuration and the electrostatic environment. We mutated the two residues so as to invert the sense of this interaction analogous to a charged “hole-into-knob” configuration. We show that this inversion in the CαCβ interface promotes selective assembly of the introduced TCR while preserving its specificity and avidity for Ag ligand. Noteworthily, this TCR modification was equally efficient on both a Mu and a Hu TCR. Our data suggest that this approach is generally applicable to TCR independently of their Ag specificity and affinity, subset distribution, and species of origin. Thus, this strategy may optimize TCR gene transfer to efficiently and safely reprogram random T cells into tumor-reactive T cells.
Pro-IL-16 Recruits Histone Deacetylase 3 to the Skp2 Core Promoter through Interaction with Transcription Factor GABP
Authors: Zhang Yujun , Tuzova Marina , Xiao Zhi-Xiong J. , Cruikshank William W. , Center David M.
Published: April 2014

Pro-IL-16 is a PDZ domain-containing protein expressed in T cells. Our previous work showed that upon activation of normal T cells, pro-IL-16 mRNA and protein are diminished in close correlation to the down-regulation of p27KIP1 protein. In addition, we showed that pro-IL-16 regulates the transcription of Skp2, the mechanism of which, however, remains elusive. In this study, we identified GA binding protein β1 subunit (GABPβ1) and histone deacetylase 3 (HDAC3) as binding partners of pro-IL-16. Interestingly, both GABPβ1 and HDAC3 have canonical PDZ-binding motifs and specifically bind to the first and second PDZ domain of pro-IL-16, respectively. Heat shock cognate protein 70 (HSC70) also copurified with the GST-PDZ1-containing fragment but lacks a C-terminal PDZ binding motif, suggesting that it binds through a different mechanism. We further showed that pro-IL-16 is located in a GABP transcriptional complex bound to the Skp2 promoter. In addition, we demonstrated that HDAC activity is critical for pro-IL-16-induced cell cycle arrest. Taken altogether, these data suggest that pro-IL-16 forms a complex with GABPβ1 and HDAC3 in suppressing the transcription of Skp2. Thus, this study has revealed a novel mechanism with which pro-IL-16 regulates T cell growth through the Skp2-p27KIP1 pathway.
Lineage-Specific Transition of Histone Signatures in the Killer Cell Ig-Like Receptor Locus from Hematopoietic Progenitor to NK Cells
Authors: Santourlidis Simeon , Graffmann Nina , Christ Julia , Uhrberg Markus
Published: April 2014

The clonal distribution and stable expression of killer cell Ig-like receptor (KIR) genes is epigenetically regulated. To assess the epigenetic changes that occur during hemopoietic development we examined DNA methylation and chromatin structure of the KIR locus in early hemopoietic progenitor cells and major lymphocyte lineages. In hemopoietic progenitor cells, KIR genes exhibited the major hallmarks of epigenetic repression, which are dense DNA methylation, inaccessibility of chromatin to Micrococcus nuclease digest, and a repressive histone signature, characterized by strong H3K9 dimethylation and reduced H4K8 acetylation. In contrast, KIR genes of NK cells showed active histone signatures characterized by absence of H3K9 dimethylation and presence of H4K8 acetylation. Histone modifications correlated well with the competence of different lymphocyte lineages to express KIR; whereas H4K8 acetylation was high in NK and CD8+ T cells, it was almost absent in CD4+ T cells and B cells and, in the latter case, replaced by H3K9 dimethylation. In KIR-competent lineages, active histone signatures were also observed in silent KIR genes and in this case found in combination with dense DNA methylation of the promoter and nearby regions. The study suggests a two-step model of epigenetic regulation in which lineage-specific acquisition of euchromatic histone marks is a prerequisite for subsequent gene-specific DNA demethylation and expression of KIR genes.
Suppression of LethalPlasmodium yoeliiMalaria following Protective Immunization Requires Antibody-, IL-4-, and IFN-γ-Dependent Responses Induced by Vaccination and/or Challenge Infection
Authors: Petritus Patricia M. , Burns James M.
Published: April 2014

Immunization with Plasmodium yoelii merozoite surface protein (PyMSP)-8 protects mice from lethal malaria but does not prevent infection. Using this merozoite surface protein-based vaccine model, we investigated vaccine- and infection-induced immune responses that contribute to protection. Analysis of prechallenge sera from rPyMSP-8-immunized C57BL/6 and BALB/c mice revealed high and comparable levels of Ag-specific IgG, but differences in isotype profile and specificity for conformational epitopes were noted. As both strains of mice were similarly protected against P. yoelii, we could not correlate vaccine-induced responses with protection. However, passive immunization studies suggested that protection resulted from differing immune responses. Studies with cytokine-deficient mice showed that protection was induced by immunization of C57BL/6 mice only when IL-4 and IFN-γ were both present. In BALB/c mice, the absence of either IL-4 or IFN-γ led to predictable shifts in the IgG isotype profile but did not reduce the magnitude of the Ab response induced by rPyMSP-8 immunization. Immunized IL-4−/− BALB/c mice were solidly protected against P. yoelii. To our surprise, immunized IFN-γ−/− BALB/c mice initially controlled parasite growth but eventually succumbed to infection. Analysis of cytokine production revealed that P. yoelii infection induced two distinct peaks of IFN-γ that correlated with periods of controlled parasite growth in intact, rPyMSP-8-immunized BALB/c mice. Maximal parasite growth occurred during a period of sustained TGF-β production. Combined, the data indicate that induction of protective responses by merozoite surface protein-based vaccines depends on IL-4 and IFN-γ-dependent pathways and that vaccine efficacy is significantly influenced by host responses elicited upon infection.
TLR3 Increases Disease Morbidity and Mortality from Vaccinia Infection
Authors: Hutchens Martha , Luker Kathryn E. , Sottile Peter , Sonstein Joanne , Lukacs Nicholas W. , Núñez Gabriel , Curtis Jeffrey L. , Luker Gary D.
Published: April 2014

Innate immunity is required for effective control of poxvirus infections, but cellular receptors that initiate the host response to these DNA viruses remain poorly defined. Given this information and the fact that functions of TLRs in immunity to DNA viruses remain controversial, we investigated effects of TLR3 on pathogenesis of vaccinia virus, a prototype poxvirus. We used a recombinant strain Western Reserve vaccinia virus that expresses firefly luciferase to infect wild-type C57BL/6 and TLR3−/− mice through intranasal inoculation. Bioluminescence imaging showed that TLR3−/− mice had substantially lower viral replication in the respiratory tract and diminished dissemination of virus to abdominal organs. Mice lacking TLR3 had reduced disease morbidity, as measured by decreased weight loss and hypothermia after infection. Importantly, TLR3−/− mice also had improved survival relative to wild-type mice. Infected TLR3−/− mice had significantly reduced lung inflammation and recruitment of leukocytes to the lung. Mice lacking TLR3 also had lower levels of inflammatory cytokines, including IL-6, MCP-1, and TNF-α in serum and/or bronchoalveolar lavage fluid, but levels of IFN-β did not differ between genotypes of mice. To our knowledge, our findings show for the first time that interactions between TLR3 and vaccinia increase viral replication and contribute to detrimental effects of the host immune response to poxviruses.