bluuebunny/crossref_metadata_2025 huggingface dataset:
Emergence rate of the time-domain Green’s function from the ambient noise cross-correlation function
Authors: Sabra Karim G. , Roux Philippe , Kuperman W. A.
Published: December 2005

It has been demonstrated experimentally and theoretically that an estimate of the Green’s function between two receivers can be obtained from the time derivative of the long-time average ambient noise function cross-correlation function between these two receivers. The emergence rate of the deterministic coherent arrival times of the cross-correlation function, which yield an estimate of the Green’s function, from the recordings of an isotropic distribution of random noise sources is studied by evaluating the amplitude of the variance of the cross-correlation function. The leading term in the expression of the variance depends on the recorded energy by both receivers and the time-bandwidth product of the recordings. The variance of the time derivative of the correlation function has a similar dependency. These simple analytic formulas show a good agreement with the variance determined experimentally for the correlation of ocean ambient noise for averaging time varying from 1 to 33min. The data were recorded in shallow water at a depth of 21-m water depth in the frequency band [300–530Hz] for receivers separation up to 28m.
Optimal active noise control in large rooms using a “locally global” control strategy
Authors: Li Desheng , Hodgson Murray
Published: December 2005

The feasibility of applying active noise control in large rooms, in which global control is very difficult, is investigated. Local control can only ensure sound attenuation near error-sensor positions. Considering that workers usually work only in certain regions of a workroom, a new “locally global” control strategy is proposed. The objective is to reduce the acoustic potential energy in the target region. Compared to local control, “locally global” control ensures overall noise reduction over the target region. Compared to global control, it allows the number of control channels to be significantly reduced. The placements of the control loudspeakers and error microphones must be optimized to ensure that, while the sum of the squared sound pressures at the error sensors is minimized, the potential energy in the target region is reduced. Room sound fields are modeled using the image-source method and point sources. Genetic algorithms are used to optimize the locations of the control loudspeakers and error microphones. Both numerical and experimental results are presented. The sensitivities of control performance to variations in the excitation frequency, the control-source positions, and the error-sensor locations are investigated.
Origin of the double- and multi-pulse structure of echolocation signals in Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis)
Authors: Li Songhai , Wang Kexiong , Wang Ding , Akamatsu Tomonari
Published: December 2005

The signals of dolphins and porpoises often exhibit a multi-pulse structure. Here, echolocation signal recordings were made from four geometrically distinct positions of seven Yangtze finless porpoises temporarily housed in a relatively small, enclosed area. Some clicks demonstrated double-pulse, and others multi-pulse, structure. The interpulse intervals between the first and second pulse of the double- and multi-pulse clicks were significantly different among data from the four different positions (p<0.01, one-way ANOVA). These results indicate that the interpulse interval and structure of the double- and multi-pulse echolocation signals depend on the hydrophone geometry of the animal, and that the double- and multi-pulse structure of echolocation signals in Yangtze finless porpoise is not caused by the phonating porpoise itself, but by the multipath propagation of the signal. Time delays in the 180° phase-shifted surface reflection pulse and the nonphase-shifted bottom reflection pulse of the multi-pulse structures, relative to the direct signal, can be used to calculate the distance to a phonating animal.
Coupled flexural-longitudinal wave motion in a finite periodic structure with asymmetrically arranged transverse beams
Authors: Friis Lars , Ohlrich Mogens
Published: December 2005

A companion paper [J. Acoust. Soc. Am. 118, 3010–3020 2005] has examined the phenomena of flexural-longitudinal wave coupling in a practically undamped and semi-infinite periodic waveguide with structural side-branches. The effect of structural damping on wave coupling in such a waveguide is examined in the first part of the present paper, and the damping-dependent decrease in wave coupling is revealed for a structure with multiresonant side-branches. In the second part, the simplifying semi-infinite assumption is relaxed and general expressions for the junction responses of finite and multicoupled periodic systems are derived as a generalization of the governing expressions for finite, mono-coupled periodic systems [Ohlrich, J. Sound Vib. 107, 411–434 (1986)]. The present derivation of the general frequency response of a finite system utilizes the eigenvectors of displacement responses and wave forces that are associated with the characteristic wave-types, which can exist in a multicoupled periodic system [Mead, J. Sound Vib. 40, 19–39 (1975)]. The third part of the paper considers a finite specific test-structure with eight periodic elements and with structural terminations at the extreme ends. Audio-frequency vibration responses of this tri-coupled periodic structure are predicted numerically over a broad range of frequencies and a very good agreement is found with the measurement results obtained from an experiment with a nominally identical, periodic test-structure which is freely suspended.
Boosting Immune Response to Hepatitis B DNA Vaccine by Coadministration of Prothymosin α-Expressing Plasmid
Authors: Jin Yanwen , Cao Cheng , Li Ping , Liu Xuan , Huang Wei , Li Chufang , Ma Qingjun
Published: December 2005

DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. However, compared to conventional vaccines, DNA vaccines usually induce poor antibody responses. In this study, we report that coadministration of a hepatitis B virus (HBV) DNA vaccine with prothymosin α as an adjuvant improves antibody responses to HBV S antigen. We also observed higher seroconversion rates and higher antibody titers. Prothymosin α appears to increase the number and affinity of hepatitis B surface antigen-specific, gamma interferon-secreting T cells and to enhance cellular immune response to the PreS2S DNA vaccine. Interestingly, administering the DNA separately from the prothymosin α plasmid abrogated the enhancement of DNA vaccine potency. The results suggest that prothymosin α may be a promising adjuvant for DNA vaccines.
Induction of Antigen-Specific Th1-Type Immune Responses by Gamma-Irradiated RecombinantBrucella abortusRB51
Authors: Sanakkayala Neelima , Sokolovska Anna , Gulani Jatinder , HogenEsch Harm , Sriranganathan Nammalwar , Boyle Stephen M. , Schurig Gerhardt G. , Vemulapalli Ramesh
Published: December 2005

Brucella abortusstrain RB51 is an attenuated rough mutant used as the live vaccine against bovine brucellosis in the United States and other countries. We previously reported the development of strain RB51 as a bacterial vaccine vector for inducing Th1-type immune responses against heterologous proteins. Because safety concerns may preclude the use of strain RB51-based recombinant live vaccines, we explored the ability of a gamma-irradiated recombinant RB51 strain to induce heterologous antigen-specific immune responses in BALB/c mice. Exposure of strain RB51G/LacZ expressingEscherichia coliβ-galactosidase to a minimum of 300 kilorads of gamma radiation resulted in complete loss of replicative ability. These bacteria, however, remained metabolically active and continued to synthesize β-galactosidase. A single intraperitoneal inoculation of mice with 109CFU equivalents of gamma-irradiated, but not heat-killed, RB51G/LacZ induced a β-galactosidase-specific Th1-type immune response. Though no obvious differences were detected in immune responses toB. abortus-specific antigens, mice vaccinated with gamma-irradiated, but not heat-killed, RB51G/LacZ developed significant protection against challenge with virulentB. abortus. In vitro experiments indicated that gamma-irradiated and heat-killed RB51G/LacZ induced maturation of dendritic cells; however, stimulation with gamma-irradiated bacteria resulted in more interleukin-12 secretion. These results suggest that recombinant RB51 strains exposed to an appropriate minimum dose of gamma radiation are unable to replicate but retain their ability to stimulate Th1 immune responses against the heterologous antigens and confer protection againstB. abortuschallenge in mice.
Immunoglobulin E Binding Reactivity of a Recombinant Allergen Homologous to α-Tubulin from
Tyrophagus putrescentiae
Authors: Jeong Kyoung Yong , Lee Haeseok , Lee Jae Sik , Lee Jongweon , Lee In-Yong , Ree Han-Il , Hong Chein-Soo , Park Jung Won , Yong Tai-Soon
Published: December 2005

Storage mites may cause allergic respiratory diseases in urban areas as well as pose an occupational hazard in rural areas. Characterization of storage mite allergens is important for the development of diagnostic and therapeutic agents against mite-associated allergic disorders. Here we report on the cloning and expression of α-tubulin from the storage mite (
Tyrophagus putrescentiae
). The deduced amino acid sequence of the α-tubulin from the storage mite showed as much as 97.3% identity to the α-tubulin sequences from other organisms. The highly conserved amino acid sequences of α-tubulins across different species of mites may indicate that cross-reactivity for this potential allergen exists. The frequency of immunoglobulin E reactivity of this recombinant protein is 29.3% in sera from storage mite-allergic subjects.
A VISUALIZATION ENVIRONMENT FOR PLANNING
Authors: VRAKAS DIMITRIS , VLAHAVAS IOANNIS
Published: December 2005

This article presents ViTAPlan-2, a visual tool for adaptive planning that is build on top of HAPRC, a rule-configurable planning system, which automatically adapts to each problem, in order to achieve best performance. Apart from HAPRC, ViTAPlan can be interfaced with any other planning system that supports the PDDL language. More than just being a user friendly environment for executing the underlying planner, the tool serves as a unified planning environment for encoding a new problem problem, solving it, visualizing the solution and monitoring its execution on a simulation of the problem's word. The tool consists of various sub-systems, each one accompanied by a graphical interface, that collaborate with each other and assist the user, whether he is a knowledge engineer, a domain expert, an academic or even an end user in industry, to carry out complex planning tasks.
A ROBUST FUZZY LOGIC PATH TRACKER FOR NON-HOLONOMIC MOBILE ROBOTS
Authors: MOUSTRIS G. , TZAFESTAS S. G.
Published: December 2005

In this paper the path tracking problem for non-holonomic mobile robots is dealt with. The model used is known as the Dubins Car model. A robust fuzzy logic controller that steers the car to the appropriate direction is proposed. A technique called "spatial window technique" which greatly increases the overall performance of the control scheme is also introduced. The simulations of this scheme show that the path following problem is treated very adequately and the noise tolerance of the overall system is high.
AN EVOLVABLE HARDWARE LAYER FOR GLOBAL AND LOCAL LEARNING OF MOTOR CONTROL IN A HEXAPOD ROBOT
Authors: GALLAGHER JOHN C.
Published: December 2005

The use of Genetic Algorithms (GAs) to evolve Continuous Time Recurrent Neural Networks (CTRNNs) for locomotion control of a hexapod robot was demonstrated in previous work. Those controllers were shown to be robust to loss of sensory information and other peripheral variations and their operation was explained through qualitative dynamical systems analysis. Although real robot controllers were fielded, our prior methods contained drawbacks limiting the attractiveness of their implementation as real devices. These included centralization of the evolutionary learning algorithms and the inability of those algorithms to evolve effective controllers without inclusion of a priori architectural knowledge. In this paper, we will introduce a generic neuromorphic Evolvable Hardware (EH) learning architecture and show how it can be used to overcome these previous difficulties. We will also introduce a novel modification to previously reported EH methods that improves search efficacy. We will discuss our previous work, introduce relevant concepts from the emerging field of evolvable hardware as well as our chip, and show how it can be used to deliver effective and practical locomotion control. We will focus especially on the integrated systems abilities to self-heal and reconfigure while in service and will examine centralized, decentralized, and hybrid learning configurations.
SINGLE-STEP SYNTHESIS OF COBALT-OXIDE SHELLED NANOCARBONS
Authors: LIU LIHONG
Published: December 2005

In this paper, we report a simple solid-state method for fabricating cobalt-oxide–carbon core-shell nanostructures. With this technique, various forms of nanocarbons such as nanotubes, polyhedrons and onions can be generated via pyrolyzing cobalt–complex xerogels at 150 ~ 340°C. The thus-formed nanocarbons can be protected by cobalt-oxide matrix up to 1000°C in air atmosphere. Cobalt-oxide shelled or unshelled nanocarbons can be controlled by choosing a suitable complexing agent for the xerogel precursors. In particular, glycine has been proven to be a good complexing agent for low-temperature formation of unshelled nanocarbons and high-temperature generation of shelled nanocarbons.
CARBON NANOTUBE PROBE FOR SCANNING TUNNELING MICROSCOPY
Authors: XIAO BING , ALBIN SACHARIA
Published: December 2005

A simple technique was developed to fabricate carbon nanotube (CNT) probes for scanning tunneling microscope (STM). Multi-walled nanotubes were grown on the apex of the electro-chemically etched tungsten ( W ) tip using thermal chemical vapor deposition (CVD) at normal pressure with H 2 and C 2 H 2. Nickel ( Ni ) nanoparticles, which were used as the catalyst for CNT synthesis, were applied to the tip apex by dipping the W tip into the Ni nanopowder suspension in ethanol. The diameters of grown nanotubes were in the range of 20 nm to 100 nm. Their lengths were generally less than 1 μm and controlled by growth time. The technique can be readily applied to mass production of CNT STM probes without the use of any sophisticated and expensive equipments. The performance of the fabricated CNT tips was assessed by producing STM images of atomic-resolution.
INVESTIGATION OF THERMAL EFFECT OF MICROSTRUCTURES FABRICATED VIA FOCUSED ION BEAM RASTER SCANNING
Authors: FU YONGQI , QIAN HAIXIA , NGOI BRYAN KOK ANN , ZHOU WEI
Published: December 2005

Microstructures fabricated by use of focused ion beam (FIB) direct scanning is useful for microsystems. However, a new phenomenon was found recently by our experimental results. After the FIB bombardment in the defined area, the microstructures were formed under the competence between the ion sputtering induced surface roughening and surface diffusion induced surface smoothing. The process was called self-organized formation. The generated microstructures were characterized by atomic force microscope (AFM). The measured results show that the dimensions of the microstructures were changed with time. In other word, the measured results were different between the samples just processed and that one finished over one week, and the former with smaller dimensions than the latter. The reason maybe due to the thermal effect induced by the FIB bombardment. We called it a natural annealing. The fabricated microstructures were not in stable state due to the internal stress caused by ion sputtering and thermal diffusion. At initial state, it is in dynamic balance. After the natural annealing with several days, the dynamic balance is changed by the thermal diffusion which caused the dimensions of the microstructures varied continuously. In addition, the surface oxidation is also another factor.
EVALUATION OF CURRENT-CARRYING WIRES FOR MANIPULATION OF MAGNETIC MICRO/NANOPARTICLES FOR BIOMEDICAL APPLICATIONS
Authors: RAMADAN QASEM , SAMPER VICTOR , POENAR DANIEL , YU CHEN
Published: December 2005

In this study we present a set of guidelines for the design of current carrying micro-conductors/micro-coils (MCs) for magnetic nanoparticles manipulation in biomedical applications. Precise spatial manipulation requires steep magnetic field gradients and due to the consequences of scaling laws, these gradients should be maximized as the size of the particle reduces. Conventional planar coils have many construction and functional limitations, such as generating only small magnetic field gradients, Joule heating, and limited ability to move particles with high spatial resolution. On the other hand, micro-coils can provide a satisfactory solution to all these problems. The geometrical and structural parameters play significant roles in determining the ability to move guide and transport nanoparticles.

Design guidelines were generated from a detailed theoretical treatment and finite element analysis (FEA). The spatial distributions of magnetic fields, field gradients and magnetic forces on particles were simulated using FEA for different geometrical/structural parameters and wire arrangements. An array of wires create a chain of magnetic potential wells that are controllable in terms of magnitude and direction and therefore can be used to control the motion and position of magnetic nano-particles by tuning the current through the array.
MECHANICAL PROPERTIES OF FERROELECTRIC CERAMIC NANOCOMPOSITES
Authors: LEE KWOK LUN , SOH AI KAH , WANG XIAO XING , KWOK KIN WING
Published: December 2005

The micro- and nano-indentation techniques and compression tests were employed to determine the mechanical properties of PZT based composites dispersed with Al 2 O 3 nano-particles for comparison. Compared with the reduced modulus, the nano-hardness, which exhibited indentation size effect (ISE), seemed to be more sensitive to the indentation depth. The true hardness values were deduced, based on the modified proportional specimen resistance (PSR) model, from the depth sensing machine and micro-indenter. Both the micro- and nano-hardness of the nano-composites confirmed that the hardness was best improved by addition of 0.5wt% of Al 2 O 3.
MICROMECHANICAL MODELING OF NANOSTRUCTURED MATERIALS BY POLYCLUSTERING TECHNIQUE
Authors: DOBOVŠEK IGOR
Published: December 2005

We present certain aspects of theoretical modeling of nanostructured materials with some degree of local order. The topological structure of local short-range order versus the long-range spatial heterogeneity of the nanostructure as a whole is described in terms of Voronoi polyhedra, so that the resulting topological tessellations form groups of polyclusters. For so obtained geometry of polycluster microstructure we describe the transition from micro to macro domain by using a generalized theory of micromorphic continuum, where polyclusters are considered as individual elements of micromorphic continuum. Then the master equations of micromorphic continuum can be perceived as a fundamental set of field equations that are needed for further theoretical development of the model. The semi-discrete nature of field variables, which describes the kinematics of deformation in polyclusters, leads to the natural choice of a pair potential function for modeling a short-range order.
PRECIPITATION OF CALCIUM PHOSPHATE IN THE PRESENCE OF DOUBLE HYDROPHILIC BLOCK COPOLYMER PEO-b-PMAA
Authors: TJANDRA WILIANA , RAVI PALANISWAMY , TAM KAM CHIU , YAO JIA
Published: December 2005

Polyethylene oxide-block-polymethacrylic acid (PEO-b-PMAA) copolymer was employed as template for the controlled precipitation of calcium phosphate from aqueous solution at different pH values. Two interesting superstructures of an organized inorganic/organic hybrid material were characterized by electron microscopy. At pH of 4, a nested structure was obtained, which consists of hybrid nanofilaments. The fibers originate from a core of similar size to the primary polymer aggregates, suggesting that cooperative interactions at a local level between dissolving calcium phosphate clusters and disassembling polymer units could be responsible for the highly anisotropic nature of the secondary growth process. At pH of 9, a fractal induced growth morphology was obtained through the mineralization process. Such calcium phosphate/polymer nanohybrids with complex morphologies are interesting and may find application as novel ceramics precursors, reinforcing fillers, or biomedical implants.
THE INFLUENCE OF AMORPHOUS PHASE TO PLASTIC HARDNESS OF SUPER- AND ULTRAHARD NANOCOMPOSITES
Authors: MOTO KEBA , ABUBAKAR ZUFAR , SETIARINI LIA
Published: December 2005

Hardness and yield stress of (polycrystalline) materials typically increase with decreasing grain size. However, in nanocomposites materials which consist of nanocrystalline phase (filler) embedded in amorphous phase (matrix), the hardness relation to the crystallite size curve shifts due to amorphous fraction. Experimental data show that some coatings have very different hardness ( H v > 40-105 GPa ) even though they have similar grain (nanocrystalline) size. The shifting of hardness versus crystallite size curve in nanocomposites is of particular interest. Here we use mechanical system modeling to determine the plastic hardness based on displacement of nanocrystallines during indentation process in nanocomposite nc - TiN/a - Si 3 N 4. Our hypothesis is that the nanocrystalline behave like a rigid body that move relative to each other under shear condition by indentation load. This relative movement is retarded by drag force from the surface friction between nanocrystals and amorphous phase. Our findings indicated that the influence of amorphous content in nanocomposites shift the plastic hardness as the amorphous fraction is varied. In the range of 3-13 nm grain size, one can construct several hardness versus crystallite size curve by varying the amorphous fraction. The experimental data of nanocomposite nc - TiN/a - Si 3 N 4/ a -& nc - TiSi 2 agree well with our calculation results.
GROWTH OF CARBON NANOTUBE BUNDLES ON MICROSCRATCHED SURFACES
Authors: HUANG LEI , LAU S. P. , SUN Z. , TEO KENNETH B. K. , TAY B. K.
Published: December 2005

In this paper, we demonstrated a roughness dependent chemical vapor deposition (CVD) process to selectively grow aligned carbon nanotube bundles on silicon substrates with microscratches. Our results show that the aligned nanotubes of uniform length (around 2 μm) and diameter (20~30 nm) are assembled to nanotube bundles and in-plane vertically aligned with the microscratches. The microscratch-selective nanotube growth offers a promising approach for the fabrication of 3-D nanotube architectures in a single CVD process.
GROWTH AND STRUCTURAL STUDY OF NANOCRYSTALLINE TITANIUM OXIDE AND ZIRCONIUM OXIDE THIN FILMS DEPOSITED AT LOW TEMPERATURES
Authors: TAY B. K. , ZHAO Z. W. , LAU S. P. , GAO J. X.
Published: December 2005

Titanium oxide and zirconium oxide thin films were deposited at low temperatures (not exceeding 350°C) by off-plane filtered cathodic vacuum arc (FCVA). The film structures were studied by XRD and Raman spectra. For titanium oxide thin films, amorphous structure remains up to 230°C, and anatase film with the crystallite size of 16 nm is observed at 330°C as confirmed by XRD and Raman analysis. For zirconium oxide, the film structure develops from amorphous at room temperature to polycrystalline state at 150°C and above. Moreover, for the crystallized films, preferred orientation is along [-111] direction. At 150°C the films possess nano-sized crystallites (less than 15 nm). For these two kinds of metal oxide thin films, surface roughness both increases with the growth temperature.
CONSTRUCTION OF MOLECULAR SENSORS FOR PROTONS USING π-CONJUGATED MOLECULES
Authors: KOYAMA EMIKO , TOKUHISA HIDEO , BELAISSAOUI ABDELHAK , NAGAWA YOSHINOBU , KANESATO MASATOSHI , ISHIDA TAKAO
Published: December 2005

The protonation/deprotonation response of a novel bipyridine containing (phenylene-ethynylene) thiol adsorbed to a Au surface was investigated with scanning tunneling microscopy (STM). STM results show reversible changes in the average heights (~50 spots) and the height distribution arising from protonation/deprotonation.
INFLUENCE OF ELECTRODE–MOLECULE INTERFACE ON ELECTRON TRANSPORT
Authors: BAI PING , LI ERPING , COLLIER PETER A.
Published: December 2005

We have studied the metal-molecule interface linkage effects of metal-molecule-metal systems by first principles method, which is based on density functional theory (DFT) and nonequilibrium Green's functions (NEGF) to calculate the electron transport of open metal-molecule-metal systems. Metal electrodes are described through 3-D atomic model instead of a non-atomic (like Jellium model) description. Several open systems are constructed, optimized and simulated. Sulphur atom (S) and cyano-group (CN) are employed to connect Au electrodes and molecule borazine/benzene. The density of states (DOS) and the transmission functions (TF) of constructed systems are investigated. Results show that DOS of the systems are affected little but transmission properties a lot by terminal groups CN and S. The peaks in the TF mismatch with those in DOS and the mismatch resulting from terminal group CN is larger than it from terminal atom S. Calculated transmission functions show that the systems with terminal group CN present better conductance at lower bias and this effect is much more significant in the borazine systems than that in the benzene systems.
OPTICAL NONLINEARITY OF Au METAL NANOPARTICLE DISPERSED (Ba,Sr)TiO3 THIN FILMS
Authors: LEE KYEONG-SEOK , KIM IN-HO , CHEONG BYUNGKI , KIM WON-MOK , YOON SEUNG-HYUN , CHO KYU-MAN , JUN HEE-SUN , KIM DO-SEOK
Published: December 2005

Nearly spherical Au nanoparticles of about 3.83 nm diameter were embedded into the ( Ba , Sr ) TiO 3 matrix using alternating sputtering method, showing the characteristic surface plasmon resonance absorption band at 571 nm. Dispersion in the third-order optical nonlinearity was investigated at several wavelengths from 450 to 680 nm around the resonance peak by a single beam Z-scan technique with a wavelength tunable picosecond laser system. The real and imaginary parts of third-order nonlinear susceptibility were resolved and the relative contributions are quantitatively compared at each wavelength. The maximum absolute value of third-order susceptibility as large as 4.312 × 10-8 esu was obtained at the surface plasmon frequency. The temporal response was also characterized by the femtosecond time-resolved optical Kerr gate measurement and the nonlinear response time was evaluated to be 192 fs at the laser wavelength of 800 nm.
DEVELOPMENT OF NOVEL LEAD-FREE SOLDER COMPOSITES USING CARBON NANOTUBE REINFORCEMENTS
Authors: NAI S. M. L. , GUPTA M. , WEI J.
Published: December 2005

In this study, Sn - Ag - Cu based nanocomposites with carbon nanotubes (CNTs) as reinforcements were successfully synthesized via the powder metallurgy technique. Lead-free solder powders were firstly blended together with varying weight percentages of CNTs. The materials were then compacted, sintered and finally extruded at room temperature. The extruded materials were characterized for their microstructural, thermal and mechanical properties. The porosity of the nanocomposites was observed to increase with increasing weight percentages of CNTs, accordingly the density of the nanocomposites was reduced. Thermomechanical analysis of the solder nanocomposites showed that the use of CNTs as reinforcements decreased the average coefficient of thermal expansion of the solder matrix. Furthermore, the results of mechanical properties characterization revealed that the addition of CNTs aids in enhancing the microhardness and the overall strength of the nanocomposite solder. An attempt is made in the present study to correlate the variation in weight percentages of the carbon nanotubes with the properties of the resultant nanocomposite materials.
RIPPLE FORMATION ON InP SURFACE IRRADIATED WITH FEMTOSECOND LASER
Authors: QIAN H. X. , ZHOU W. , ZHENG H. Y.
Published: December 2005

Single crystalline InP was ablated with linearly p-polarized femtosecond laser in air. Ripples with orientation parallel to the laser polarization direction were formed at low laser fluence. Analyses by EDX reveal In oxides and P oxides on the surface. Micro Raman spectroscopy of the laser irradiated surface indicates presence of stresses and possible formation of InP nanocrystals due to the femtosecond laser irradiation.
NANOSECOND RESOLUTION IN FINGERPRINT IMAGING USING OPTICAL TECHNIQUE
Authors: DINISH U. S. , CHAO Z. X. , SEAH L. K. , MURUKESHAN V. M.
Published: December 2005

The extension of fluorescence measurements of samples from steady state to dynamic methods offers the possibility to extract valuable information at the micro and nano level. Imaging of fluorescent samples with nanosecond resolution often imposes challenging problems, especially when dealing with very weak optical and electrical signals. In this context, this paper discusses the detection of latent fingerprint samples with nanosecond resolution. Imaging of fingerprint samples, which are deposited on strongly fluorescing substrates, is carried out by the subsequent suppression of the unwanted background fluorescence emissions using the time-resolved optical technique. "signature" characterisation of fingerprint samples treated with fluorescent magnetic powders is also carried out.
ATOMISTIC MODELING OF THE EFFECT OF TWINS ON PLASTIC DEFORMATION IN NANOCRYSTALLINE COBALT
Authors: ZHENG G. P.
Published: December 2005

It has been observed by experiments and computer simulations that deformation twinning and grown-in twins play important roles during the plastic deformation in nanocrystalline (nc) metals. In this study, molecular dynamics simulation is employed to investigate the role of grown-in twins in the tensile deformation of hexagonal close-packed nc cobalt. Plastic deformation processes in three types of nc samples, namely nc-cobalt without twins, with (0002) twin faults and with (1121) twins, are compared. The results show that the pre-existing twins significantly lower the mechanical strength and do not enhance the ductility of nc cobalt. Instead deformation induced hcp-to-fcc allotropic transformation is found to result in remarkable strain hardening in the modeled nc cobalt.
Deficiency of LKB1 in heart prevents ischemia-mediated activation of AMPKα2 but not AMPKα1
Authors: Sakamoto Kei , Zarrinpashneh Elham , Budas Grant R. , Pouleur Anne-Catherine , Dutta Anindya , Prescott Alan R. , Vanoverschelde Jean-Louis , Ashworth Alan , Jovanović Aleksandar , Alessi Dario R. , Bertrand Luc
Published: December 2005

Recent studies indicate that the LKB1 is a key regulator of the AMP-activated protein kinase (AMPK), which plays a crucial role in protecting cardiac muscle from damage during ischemia. We have employed mice that lack LKB1 in cardiac and skeletal muscle and studied how this affected the activity of cardiac AMPKα1/α2 under normoxic, ischemic, and anoxic conditions. In the heart lacking cardiac muscle LKB1, the basal activity of AMPKα2 was vastly reduced and not increased by ischemia or anoxia. Phosphorylation of AMPKα2 at the site of LKB1 phosphorylation (Thr172) or phosphorylation of acetyl-CoA carboxylase-2, a downstream substrate of AMPK, was ablated in ischemic heart lacking cardiac LKB1. Ischemia was found to increase the ADP-to-ATP (ADP/ATP) and AMP-to-ATP ratios (AMP/ATP) to a greater extent in LKB1-deficient cardiac muscle than in LKB1-expressing muscle. In contrast to AMPKα2, significant basal activity of AMPKα1 was observed in the lysates from the hearts lacking cardiac muscle LKB1, as well as in cardiomyocytes that had been isolated from these hearts. In the heart lacking cardiac LKB1, ischemia or anoxia induced a marked activation and phosphorylation of AMPKα1, to a level that was only moderately lower than observed in LKB1-expressing heart. Echocardiographic and morphological analysis of the cardiac LKB1-deficient hearts indicated that these hearts were not overtly dysfunctional, despite possessing a reduced weight and enlarged atria. These findings indicate that LKB1 plays a crucial role in regulating AMPKα2 activation and acetyl-CoA carboxylase-2 phosphorylation and also regulating cellular energy levels in response to ischemia. They also provide genetic evidence that an alternative upstream kinase can activate AMPKα1 in cardiac muscle.
ANG II induces apoptosis of human vascular smooth muscle via extrinsic pathway involving inhibition of Akt phosphorylation and increased FasL expression
Authors: Li Yangxin , Song Yao-Hua , Mohler Jessica , Delafontaine Patrick
Published: December 2005

In addition to well-documented vascular growth-promoting effects, ANG II exerts proapoptotic effects that are poorly understood. IGF-1 is a potent survival factor for human vascular smooth muscle cells (hVSMC), and its antiapoptotic effects are mediated via the IGF-1 receptor (IGF-1R) through a signaling pathway involving phosphatidylinositol 3-kinase and Akt. We hypothesized that there would be cross talk between ANG II proapoptotic effects and IGF-1 survival effects in hVSMC. To investigate ANG II-induced apoptosis and the potential involvement of IGF-1, we exposed quiescent and nonquiescent hVSMC to ANG II. ANG II induced apoptosis only in nonquiescent cells but stimulated hypertrophy in quiescent cells. ANG II-induced apoptosis was characterized by marked inhibition of Akt phosphorylation and stimulation of membrane Fas ligand (FasL) expression, caspase-8 activation, and a reduction in soluble FasL expression. Adenovirally mediated overexpression of Akt rescued hVSMC from ANG II-induced apoptosis. IGF-1R activation increased Akt phosphorylation and soluble FasL expression, and these effects were completely blocked by coincubating hVSMC with ANG II. In conclusion, ANG II-induced apoptosis of hVSMC is characterized by marked inhibition of Akt phosphorylation and stimulation of an extrinsic cell death signaling pathway via upregulation of membrane FasL expression, caspase-8 activation, and a reduction in soluble FasL expression. Furthermore, ANG II antagonizes the antiapoptotic effect of IGF-1 by blocking its ability to increase Akt phosphorylation and soluble FasL. These findings provide novel insights into ANG II-induced apoptotic signaling and have significant implication for understanding ANG II-induced remodeling in hypertension and atherosclerosis.
Nitric oxide-endothelin-1 interactions after surgically induced acute increases in pulmonary blood flow in intact lambs
Authors: Oishi Peter , Azakie Anthony , Harmon Cynthia , Fitzgerald Robert K. , Grobe Albert , Xu Jie , Hendricks-Munoz Karen , Black Stephen M. , Fineman Jeffrey R.
Published: December 2005

Several congenital heart defects require surgery that acutely increases pulmonary blood flow (PBF). This can lead to dynamic alterations in postoperative pulmonary vascular resistance (PVR) and can contribute to morbidity and mortality. Thus the objective of this study was to determine the role of nitric oxide (NO), endothelin (ET)-1, and their interactions in the alterations of PVR after surgically induced increases in PBF. Twenty lambs underwent placement of an aortopulmonary vascular graft. Lambs were instrumented to measure vascular pressures and PBF and studied for 4 h. Before and after shunt opening, lambs received an infusion of saline ( n = 9), tezosentan, an ETA- and ETB-receptor antagonist ( n = 6), or Nω-nitro-l-arginine (l-NNA), a NO synthase (NOS) inhibitor ( n = 5). In control lambs, shunt opening increased PBF by 117.8% and decreased PVR by 40.7% ( P < 0.05) by 15 min, without further changes thereafter. Plasma ET-1 levels increased 17.6% ( P < 0.05), and total NOS activity decreased 61.1% ( P < 0.05) at 4 h. ET-receptor blockade (tezosentan) prevented the plateau of PBF and PVR, such that PBF was increased and PVR was decreased compared with controls at 3 and 4 h ( P < 0.05). These changes were associated with an increase in total NOS activity (+61.4%; P < 0.05) at 4 h. NOS inhibition (l-NNA) after shunt placement prevented the sustained decrease in PVR seen in control lambs. In these lambs, PVR decreased by 15 min ( P < 0.05) but returned to baseline by 2 h. Together, these data suggest that surgically induced increases in PBF are limited by vasoconstriction, at least in part by an ET-receptor-mediated decrease in lung NOS activity. Thus NO appears to be important in maintaining a reduction in PVR after acutely increased PBF.
Evidence that inhibition of tubular cell apoptosis protects against renal damage and development of fibrosis following ureteric obstruction
Authors: Docherty Neil G. , O'Sullivan Orfhlaith E. , Healy Declan A. , Fitzpatrick John M. , Watson R. William G.
Published: December 2005

Ureteric obstruction is frequently encountered in primary care urology and can lead to damage to the ipsilateral kidney. Relief of all types of obstruction generally leads to the normalization of any deterioration in renal function noted at diagnosis. However, some evidence from animal models suggests that obstruction can cause progressive deleterious effects on renal function and blood pressure control, especially in the presence of preexisting pathologies such as essential hypertension. The last 10 years have seen a proliferation of studies in rodents wherein complete unilateral ureteric obstruction has been used as a model of renal fibrosis. However, the relevance of the findings to human obstructive uropathy has, in many cases, not been the primary aim. In this review, we outline the major events linking damage to the renal parenchyma and cell death to the evolution of fibrosis following obstruction. Special focus is given to the role of apoptosis as a major cause of cell death during and post-complete ureteric obstruction. Several interventions that reduce tubular apoptosis are discussed in terms of their ability to prevent subsequent progression to end-organ damage and fibrosis.
Plasma arginine-vasopressin following experimental stroke: effect of osmotherapy
Authors: Chang Yi , Chen Tsung-Ying , Chen Chih-Hung , Crain Barbara J. , Toung Thomas J. K. , Bhardwaj Anish
Published: December 2005

Neurohumoral responses have been implicated in the pathogenesis of ischemia-evoked cerebral edema. In a well-characterized animal model of ischemic stroke, the present study was undertaken to 1) study the profile of plasma arginine-vasopressin (AVP), and 2) determine whether osmotherapy with mannitol and various concentrations of hypertonic saline (HS) solutions influence plasma AVP levels. Halothane-anesthetized adult male Wistar rats were subjected to 2 h of middle cerebral artery occlusion with the intraluminal filament technique. Plasma AVP levels (means ± SD) were significantly elevated at 24 h (42 ± 21 pg/ml), 48 h (50 ± 28 pg/ml), and 72 h (110 ± 47 pg/ml), and returned to baseline at 96 h (22 ± 15 pg/ml) following middle cerebral artery occlusion compared with sham-operated controls (14 ± 7 pg/ml). Plasma AVP levels at 72 h were significantly attenuated with 7.5% HS (37 ± 8 pg/ml; 360 ± 11 osmol/l) compared with 0.9% saline (73 ± 6; 292 ± 6 osmol/l), 3% HS (66 ± 8 pg/ml; 303 ± 12 osmol/l), or mannitol (74 ± 9 pg/ml; 313 ± 14 osmol/l) treatment. HS (7.5%) significantly attenuated water content in the ipsilateral and contralateral hemispheres compared with surgical shams, 0.9% saline, 3% HS, and mannitol treatments. Peak plasma AVP levels were not associated with direct histopathological injury to the anterior hypothalamus. Attenuation of brain water content with 7.5% HS treatment coincides with attenuated serum AVP levels, and we speculate that this may represent one additional mechanism by which osmotherapy attenuates edema associated with ischemic stroke.
Spatiotemporal Activity Patterns During Respiratory Rhythmogenesis in the Rat Ventrolateral Medulla
Authors: Fisher Jonathan A. N. , Marchenko Vitaliy A. , Yodh Arjun G. , Rogers Robert F.
Published: December 2005

One of the most important brain rhythms is that which generates involuntary breathing movements. The lower brain stem contains neural circuitry for respiratory rhythm generation in mammals. To date, microsectioning and selective lesioning studies have revealed anatomical regions necessary for respiratory rhythmogenesis. Although respiratory neurons distributed within these regions can be identified by their firing patterns in different phases of the respiratory cycle, conventional electrophysiology techniques have limited the study of spatial organization within this network. Optical imaging techniques offer the potential for monitoring the spatiotemporal activity of large groups of neurons simultaneously. Using high-speed voltage-sensitive dye imaging and spatial correlation analysis in an arterially perfused in situ preparation of the juvenile rat, we determined the spatial distribution of respiratory neuronal activity in a region of the ventrolateral respiratory group containing the pre-Bötzinger complex (pBC) during spontaneous eupneic breathing. While distinctly pre- and postinspiratory-related responses were spatially localizable on length scales less than 100 μm, we found the studied area on whole exhibited a spatial mixture of phase-spanning and postinspiratory-related activity. Additionally, optical recordings revealed significant widespread hyperpolarization, suggesting inhibition in the same region during expiration. This finding is consistent with the hypothesis that inhibitory neurons play a crucial role in the inspiration-expiration phase transition in the pBC. To our knowledge this is the first optical imaging of a near fully intact in situ preparation that exhibits both eupneic respiratory activity and functional reflexes.
Electrophysiological Heterogeneity of Spinally Projecting Serotonergic and Nonserotonergic Neurons in the Rostral Ventromedial Medulla
Authors: Zhang Liang , Sykes Kenneth T. , Buhler Amber V. , Hammond Donna L.
Published: December 2005

This study examined the passive membrane and action potential properties of serotonergic and nonserotonergic neurons in the rostral ventromedial medulla (RVM) of the rat using whole cell patch-clamp recording techniques in the slice. Serotonergic neurons were identified by immunoreactivity for tryptophan hydroxylase (TrpH). Spinally projecting neurons were retrogradely labeled with 1′-dioactadecyl-3,3,3′,3′-tetramethylindocarbodyanine perchlorate (DiI). Three types of neurons were identified within both spinally projecting serotonergic and nonserotonergic populations. Type 1 neurons exhibited irregular or sporadic spontaneous activity interspersed with periods of quiescence. Type 2 neurons were not spontaneously active and were additionally discriminated by a more negative resting membrane potential and a larger-amplitude action potential. Type 3 neurons fired repetitively without pause. Serotonergic neurons had a higher membrane resistance and greater action potential half-width than their nonserotonergic counterparts and rarely exhibited a fast afterhyperpolarization. Serotonergic type 3 neurons also fired more slowly and regularly than nonserotonergic type 3 neurons. Comparison of electrophysiological and immunohistochemical characteristics suggested that the smallest type 3 serotonergic neurons had an increased risk of immunohistochemical “misclassification” due to failure to detect TrpH, possibly due to more complete dialysis of intracellular contents during lengthy recordings. This risk was minimal for type 1 or 2 serotonergic neurons. The three different types of spinally projecting serotonergic neurons also differed markedly in their responsiveness to the mu opioid receptor agonist D-Ala2, NMePhe4, Gly5-ol]enkephalin. These results provide important new electrophysiological and pharmacological evidence for a significant heterogeneity among spinally projecting serotonergic RVM neurons. They may also provide a basis for resolving the controversy concerning the role of serotonergic RVM neurons in opioid analgesia.
Spatial Distribution of Osteocyte Lacunae in Equine Radii and Third Metacarpals: Considerations for Cellular Communication, Microdamage Detection and Metabolism
Authors: Skedros John G. , Grunander Todd R. , Hamrick Mark W.
Published: December 2005

Osteocytes, which are embedded in bone matrix, are the most abundant cells in bone. Despite the ideal location of osteocytes to sense the local environment and influence bone remodeling, their functions, and the relative importance of these functions, remain controversial. In this study, we tested several hypotheses that address the possibilities that population densities of osteocyte lacunae (Ot.Lc.N/B.Ar) correlate with strain-, remodeling- or metabolism-related aspects of the local biomechanical environments of mid-third diaphyseal equine radii and third metacarpals from skeletally mature animals. Ot.Lc.N/B.Ar data, quantified in multiple cortical locations, were analyzed for possible correlations with (1) structural and material characteristics (e.g., cortical thickness, percent ash, secondary osteon population density, mean osteon cross-sectional area, and predominant collagen fiber orientation), (2) strain characteristics, including prevalent/predominant strain magnitude and mode (tension, compression, shear), (3) hypothesized strain-mode-related microdamage characteristics, which might be perceived by osteocyte ‘operational’ networks, and (4) variations in remodeling dynamics and/or metabolism (i.e. presumably higher in endocortical regions than in other transcortical locations). Results showed relatively uniform Ot.Lc.N/B.Ar between regions with highly non-uniform strain and strain-related environments and markedly heterogeneous structural and material organization. These results suggest that population densities of these cells are poorly correlated with mechanobiological characteristics, including local variations in metabolic rate and strain magnitude/mode. Although osteocytes hypothetically evolved both as strain sensors and fatigue damage sensors able to direct the removal of damage as needed, the mechanisms that govern the distribution of these cells remain unclear. The results of this study provide little or no evidence that the number of osteocyte lacunae has a functional role in mechanotransduction pathways that are typically considered in bone adaptation.
Expression and Localization of Chromogranin A Gene and Protein in Human Submandibular Gland
Authors: Saruta Juri , Tsukinoki Keiichi , Sasaguri Kenichi , Ishii Hidenori , Yasuda Masanori , Osamura Yoshiyuki R. , Watanabe Yoshihisa , Sato Sadao
Published: December 2005

Human saliva chromogranin A (CgA) is clinically promising as a psychological stress marker. However, expression of CgA is poorly understood in humans, although salivary gland localization of CgA in other mammals, such as rodents and horses, has been demonstrated. In the present study, we investigated the expression and localization of CgA in the human submandibular gland (HSG) using various methods. CgA was consistently localized in serous and ductal cells in HSG, as detected by immunohistochemistry and in situhybridization. Reactivity was stronger in serous cells than in ductal cells. In addition, strong immunoreactivity for CgA was observed in the saliva matrix of ductal cavities. Western blotting gave one significant immunoreactive band of 68 kDa in the adrenal gland, HSG and saliva. Finally, CgA was detected in secretory granules of serous and ductal cells by immunoelectron microscopy. In conclusion, CgA in humans is produced by HSG and secreted into saliva.