bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcatheter Closure of Ruptured Sinus of Valsalva Aneurysm
Authors: ARORA RAMESH , TREHAN VIJAY , RANGASETTY UMA MAHESH C. , MUKHOPADHYAY SAIBAL , THAKUR ASHISH K. , KALRA G.S.
Published: February 2004

Percutaneous transcatheter closure of ruptured sinus of valsalva aneurysm was attempted in eight patients between January 1995 and March 2003 as an alternative strategy to surgery as this technique at present is an accepted therapeutic modality for various intracardiac defects. The age range was 14–35 years, all were male, seven in symptomatic class III and one in class IV on medical treatment. Two‐dimensional and color Doppler echocardiography revealed rupture of an aneurysm of right coronary sinus into right ventricle in five and noncoronary sinus into right atrium in three and none had associated ventricular septal defect. The echo estimated size of the defect was 7–12 mm. On cardiac catheterization left ventricular end‐diastolic pressure ranged from 20 to 40 mmHg and the calculated Qp/Qs ratio was 2–3.5. In all patients the defect was crossed retrogradely from the aortic side and over an arterio‐venous wire loop after balloon sizing, devices were successfully deployed by antegrade venous approach (Rashkind umbrella device in two and Amplatzer occluders in six, which included Amplatzer duct occluder in five and Amplatzer septal occluder in one). One patient who had residual shunt developed hemolysis on the next day and was taken up for reintervention. That patient continued to have intermittent hemolysis and was sent for surgical repair. On follow‐up (2–96 months), there was no device embolization, infective endocarditis, and aortic regurgitation. One patient died of progressive congestive heart failure while other six are asymptomatic. These data highlight that transcatheter closure is feasible and effective, especially safe with the available Amplatzer devices. Definitely, it has the advantage of obviating open heart surgery but complete occlusion is mandatory to prevent hemolysis and infective endocarditis. (J Interven Cardiol 2004;17:53–58)
Application of red laser video‐rate scanning confocal microscopy to in vivo assessment of tubular function in the rat: selective action of diuretics on tubular diameter
Authors: Simeoni M. , Boyde A. , Shirley D. G. , Capasso G. , Unwin R. J.
Published: February 2004

This study examined the use of a red laser illuminated, video‐rate scanning confocal reflection microscopy (VRSCM) system, with improved structural and functional imaging at high temporal resolution, to visualize physiological changes in the kidney in response to pharmacological stimuli. We applied VRSCM to superficial nephrons in vivo and measured temporal changes in the diameter of proximal and/or distal tubular segments in response to the administration of three major classes of diuretics with known selective actions at specific nephron sites. Mannitol caused measurable increases in both proximal and distal tubular diameter, whereas frusemide and hydrochlorothiazide caused dilation of the distal tubules only. The findings indicate that VRSCM is capable of detecting and quantifying predicted dynamic changes in renal tubular diameter.
Role of sex, gonadectomy and sex hormones in the development of nitric oxide inhibition‐induced hypertension
Authors: Sáinz Juan , Osuna Antonio , Wangensteen Rosemary , Luna Juan de Dios , Rodríguez‐Gómez Isabel , Duarte Juan , Moreno Juan Manuel , Vargas Félix
Published: February 2004

In this study we have evaluated the influence of sex, gonadectomy and sex hormones on the development of l‐NAME‐induced hypertension in the rat, focusing our investigation on blood pressure (BP), plasma renin activity (PRA), cardiac hypertrophy and proteinuria. Three experiments were performed to investigate: (i) the influence of sex on the development of l‐NAME‐induced hypertension; (ii) the effects of gonadectomy on the dimorphism of l‐NAME‐induced hypertension; and (iii) the effects of testosterone in ovariectomized female and of 17β‐oestradiol in orchidectomized male rats. Male l‐NAME‐treated rats had higher BP values than females. Orchidectomy of l‐NAME‐treated rats reduced BP to the levels of females and ovariectomy did not affect hypertension in females. Oestrogenized and orchidectomized males had a BP level similar to intact female l‐NAME‐treated rats. However, androgenization and ovariectomy did not change BP in female l‐NAME‐treated rats. PRA was greater in intact male l‐NAME hypertensive rats than in female rats, and gonadectomy protected against the increase in PRA such that PRA was similar among all the groups. Intact female hypertensive rats showed significantly greater ventricular hypertrophy compared with male hypertensive rats. Male l‐NAME hypertensive rats had increased proteinuria that was not present in female rats. Moreover, testosterone increased proteinuria in males and females regardless of the BP level. Male l‐NAME‐treated rats developed higher BP, PRA and proteinuria than female rats, but were more resistant to the development of cardiac hypertrophy. The higher PRA of male l‐NAME‐treated rats might be involved in the sex‐dependent dimorphism of this model of hypertension.
Dynamics of Flexible Structures With Nonlinear Joints
Authors: Sarkar Sunetra , Venkatraman Kartik , Dattaguru B.
Published: February 2004

The focus of the present study is to use a technique based on Fourier approximation and Galerkin error minimization to determine periodic solutions of nonlinear jointed flexible structures, and study the effect of joint nonlinearity on the global dynamics of an otherwise linear flexible structure. Results presented here show that the Fourier-Galerkin algorithm is a fast tool for computing periodic motion of nonlinear dynamic systems as compared to time-integration, and the effect of nonlinear joints on the dynamics of an otherwise linear flexible structure modeled as a multi degree of freedom system can be significant.
Application of a Nonlinear Modal Instability Approach to Brake Systems
Authors: Sinou Jean-Jacques , Thouverez Fabrice , Jezequel Louis
Published: February 2004

A method, called the Complex NonLinear Modal Analysis (CNLMA), is proposed for the calculation of the periodic solutions of nonlinear mechanical systems with continued nonlinearities. The equivalent linearization concept and the notion of nonlinear complex modes are applied in order to analyze the steady-state responses of autonomous nonlinear systems. The CNLM-Analysis appears very interesting in regard to computational time; it also necessitates very few computer resources. This method was applied to study instability phenomena in a nonlinear model with a constant brake friction coefficient.
Vibration Confinement via Optimal Eigenvector Assignment and Piezoelectric Networks
Authors: Tang J. , Wang K. W.
Published: February 2004

The underlying principle for vibration confinement is to alter the structural vibration modes so that the corresponding modal components have much smaller amplitude in concerned area than in the remaining part of the structure. In this research, the state-of-the-art in vibration confinement technique is advanced in two correlated ways. First, a new eigenstructure assignment algorithm is developed to more directly suppress vibration in regions of interest. This algorithm is featured by the optimal selection of achievable eigenvectors that minimizes the eigenvector components at concerned region by using the Rayleigh Principle. Second, the active control input is applied through an active-passive hybrid piezoelectric network. With the introduction of circuitry elements, which are much easier to implement than changing or adding mechanical components, the state matrices can be reformed and the design space for eigenstructure assignment can be greatly enlarged. To maximize the system performance, a simultaneous optimization/optimal eigenvector assignment approach to decide the passive and active parameters concurrently is outlined. The merits of the proposed system and scheme are demonstrated and analyzed using numerical examples.
Shaking-Table Control by Real-Time Compensation of the Reaction Force Caused by a Nonlinear Specimen
Authors: Dozono Yoshihiro , Horiuchi Toshihiko , Katsumata Hideo , Konno Takao
Published: February 2004

An improved shaking-table control method has been developed. This method compensates the reaction force caused by a nonlinear specimen in real time, and thus maintains a desired table acceleration. To do so, it identifies the difference between the desired and the actual transfer characteristics of the shaking table, then compensates for the difference. Because the required time for this combination of identification and compensation is less than one second, the method can compensate, in real time, for the disturbance caused by a nonlinear specimen. By means of a series of experiments, it is confirmed that the method can maintain a desired table acceleration even when a nonlinear specimen is under excitation.
Experimental and Analytical Study of Free Lift-Off Motion Induced Slip Behavior of Rectangular Rigid Bodies
Authors: Taniguchi Tomoyo
Published: February 2004

The mechanism of the slip of a rectangular rigid body during free lift-off motion is investigated analytically and experimentally. Equations of motion of slipping rectangular rigid body during free lift-off motion are derived by the variational approach. The time histories of both slip and lift-off motions are numerically computed and compared with corresponding experimental results to discuss the analytical accuracy; given an initial enforced lift-off angle to the rectangular rigid body and then gently released. The mechanical energy balance of simultaneous slip and lift-off motions is clarified to explain the considerable reduction of lift-off angle due to the slip.
Nonlinear Seismic Responses of Container Cranes Including the Contact Problem Between Wheels and Rails
Authors: Kobayashi Nobuyuki , Kuribara Hiroshi , Honda Tomokazu , Watanabe Masahiro
Published: February 2004

This paper presents a modeling method based on multibody dynamics formulation for simulating the three-dimensional nonlinear seismic response of a large, movable container crane, including the contact problem regarding the wheels attached to the bottom of its legs and the rails on which they ride. As a container crane is large and flexible structure, its wheels should be lifted up and derailed due to the seismic excitation. The contact configuration and the contact forces between the wheels and the rail or the ground that significantly affect the seismic response of the structure are classified and calculated in reference to geometric relationships between contact-judging markers on the wheels and the rails. It is found that the numerical simulations with the presented modeling method quite accurately simulates the nonlinear seismic response of a container crane including the uplifting and derailment behavior of the wheels that is found in large-scale model shaking tests.
Insights Gleaned From NRC-BNL Benchmark Evaluation of Seismic Analysis Methods for Non-Classically Damped Coupled Systems
Authors: Xu J. , DeGrassi G. , Chokshi N.
Published: February 2004

Under the auspices of the US Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) developed a comprehensive program to evaluate state-of-the-art methods and computer programs for seismic analysis of typical coupled nuclear power plant (NPP) systems with non-classical damping. In this program, four benchmark models of coupled building-piping/equipment systems with different damping characteristics were developed and analyzed by BNL for a suite of earthquakes. The BNL analysis was carried out by the Wilson-θ time domain integration method with the system-damping matrix computed using a synthesis formulation as presented in a companion paper [Xu, J., 2003, Nuclear Eng. Des. These benchmark problems were subsequently distributed to and analyzed by program participants applying their uniquely developed methods and computer programs. This paper presents the insights gleaned from the participants’ analyses, and the comparison of their results to the BNL time history solutions. The participant’s results established using complex modal time history methods showed close agreement with the BNL solutions, while the analyses produced with either complex-mode response spectrum methods or classical normal-mode response spectrum method, in general, produced relatively conservative results, when averaged over a suite of earthquakes. However, when coupling due to damping is significant, complex-mode response spectrum methods performed better than the classical normal-mode response spectrum method. Furthermore, as part of the program objectives, a parametric assessment is performed aiming at evaluating the applicability and sensitivity of various analysis methods to problems with different dynamic characteristics unique to coupled NPP systems. It is believed that the findings and insights learned from this program are useful in developing new acceptance criteria and providing guidance for future regulatory activities involving licensing applications of these alternate methods to coupled systems.
Design of Earthquake Resistant Server Computer Structures
Authors: Notohardjono Budy D. , Wilcoski James , Gambill James B.
Published: February 2004

This paper presents the design features of an electrical equipment frame structure that can withstand a severe earthquake test profile. Original designs of these structures were optimized to survive shock and shipping vibrations only, since the majority of products experience shock and vibrations during transportation. Shock and vibration found in the shipping environment are oriented in the vertical direction only. Increased concerns for equipment survivability and safety during seismic events have driven new requirements for consideration when designing equipment’s frame structure and incorporation of tests having earthquake profiles into testing regimes. This adds horizontal components of vibration into design considerations and demands design compromises that will optimize performance for both horizontal and vertical vibrations. Frame and assembly mounting design for both orientations will be discussed and test criteria specifically for vertical vibration will be described in order to compare to tests geared toward combinations of vertical and horizontal vibrations. Structures created under these new requirements are rigid in all three axes, especially in the horizontal direction where low frequency seismic vibrations can induce large displacement of the frame members and subassemblies installed in the frame. Both the subassembly components and the frame assembly must be modified to reach the optimum design for multi-directional vibration. The development of the frame structure and related hardware involves extensive uniaxial and triaxial earthquake simulation testing in both raised floor and non-raised floor environments. The dynamic responses of the system under different earthquake test profiles are recorded and analyzed in both the time and frequency domains. The computer frame and anchorage system must have adequate strength and stiffness for earthquake induced forces to prevent human injury and potential system damage. However, this same frame and anchorage system must also meet the potentially conflicting requirement of ensuring continued system operation by limiting transmitted accelerations to acceptable levels at critical system components such as hard drives.
Failure Behavior of Piping Systems With Wall Thinning Under Seismic Loading
Authors: Nakamura Izumi , Otani Akihito , Shiratori Masaki
Published: February 2004

Shaking table tests of three-dimensional piping models with degradation were conducted in order to investigate the influence of degradation on dynamic behavior and failure modes of piping systems. The degradation condition induced in the piping models was about 50 percent full circumferential wall thinning at elbows. Four types of models were made for the shaking table tests by varying the location of wall thinning in the piping models. These models were excited under the same input acceleration until the models failed and a leak of pressurized internal water occurred. Through these tests, the change of the vibration characteristics and processes to failure of degraded piping models were obtained. The deformation of the piping models tended to concentrate on the degraded elbows, and the damage was concentrated on the weakest elbow in the piping models. The failure mode of the piping models was a low-cycle fatigue failure at the weakest elbow.
An Experimental Study of Particle Damping for Beams and Plates
Authors: Xu Zhiwei , Wang Michael Yu , Chen Tianning
Published: February 2004

This paper describes an experimental investigation of a particle damping method for a beam and a plate. Tungsten carbide particles are embedded within longitudinal (and latitudinal) holes drilled in the structure, as a simple and passive means for vibration suppression. Unlike in traditional damping materials, mechanisms of energy dissipation of particle damping are highly nonlinear and primarily related to friction and impact phenomena. Experiments are conducted with a number of arrangements of the packed particles including different particle sizes and volumetric packing ratios. The results show that the particle damping is remarkably effective and that strong attenuations are achieved within a broad frequency range. The effects of the system parameters including particle size, packing ratio and particle material are studied by broadband and narrowband random excitations. The experimental results confirm a numerical prediction that shear friction in the longitudinal (and the latitudinal) directions is effective as the major contributing mechanism of damping in the case. Another unique feature of linear decay in free vibrations is also observed in this case of particle damping.
Covariance Control of Nonlinear Dynamic Systems via Exact Stationary Probability Density Function
Authors: Elbeyli O. , Sun J. Q.
Published: February 2004

This paper presents a method for designing covariance type controls of nonlinear stochastic systems. The method consists of two steps. The first step is to find a class of nonlinear feedback controls with undetermined gains such that the exact stationary PDF of the response is obtainable. The second step is to select the control gains in the context of the covariance control method by minimizing a performance index. The exact PDF makes the solution process of optimization very efficient, and the evaluation of expectations of nonlinear functions of the response very accurate. The theoretical results of various orders of response moments by the present method have been compared with Monte Carlo simulations. Special cases are studied when the approximate methods based on the maximum entropy principle or other closure schemes leads less accurate response estimates, while the present method still works fine.
A Dynamical Systems Approach to Failure Prognosis
Authors: Chelidze David , Cusumano Joseph P.
Published: February 2004

In this paper, a previously published damage tracking method is extended to provide failure prognosis, and applied experimentally to an electromechanical system with a failing supply battery. The method is based on a dynamical systems approach to the problem of damage evolution. In this approach, damage processes are viewed as occurring in a hierarchical dynamical system consisting of a “fast,” directly observable subsystem coupled to a “slow,” hidden subsystem describing damage evolution. Damage tracking is achieved using a two-time-scale modeling strategy based on phase space reconstruction. Using the reconstructed phase space of the reference (undamaged) system, short-time predictive models are constructed. Fast-time data from later stages of damage evolution of a given system are collected and used to estimate a tracking function by calculating the short time reference model prediction error. In this paper, the tracking metric based on these estimates is used as an input to a nonlinear recursive filter, the output of which provides continuous refined estimates of the current damage (or, equivalently, health) state. Estimates of remaining useful life (or, equivalently, time to failure) are obtained recursively using the current damage state estimates under the assumption of a particular damage evolution model. The method is experimentally demonstrated using an electromechanical system, in which mechanical vibrations of a cantilever beam are dynamically coupled to electrical oscillations in an electromagnet circuit. Discharge of a battery powering the electromagnet (the “damage” process in this case) is tracked using strain gauge measurements from the beam. The method is shown to accurately estimate both the battery state and the time to failure throughout virtually the entire experiment.
Plasma characteristics in pulsed direct current reactive magnetron sputtering of aluminum nitride thin films
Authors: Lee Jung W. , Cuomo Jerome J. , Bourham Mohamed
Published: February 2004

Plasma diagnostics is important to identify plasma parameters and generate reproducible plasma in magnetron sputtering. Langmuir probes have been used to measure local plasma parameters such as electron temperature (Te), charge densities (ne and ni), and plasma potential (Vp). Pulsed direct current (dc) power in the midfrequency range (50–250 kHz) has been used in growing insulating films without charging accumulations at target. Recent investigations showed increased energetic particle bombardment of the substrate in pulsed power. In this work, aluminum nitride thin films were fabricated by pulsed dc power sputter deposition. The argon and nitrogen plasma was characterized by Langmuir probe measurement. The electron temperature in argon and nitrogen plasma was observed to increased from 3.06 to 5.32 eV when the pulsed dc frequency increased from 75 to 250 kHz. The ion density and energy flux were found to increase with frequency. This is believed to be from the stochastic heating generated by the fast oscillation in the target voltage wave form. The measured plasma characteristics were correlated with the crystal orientation of AlN thin films. The crystal structure of AlN thin films changed to (002) preferred orientations as the ion and energy flux increased.
Preparation of TiN films by arc ion plating using dc and pulsed biases
Authors: Huang M. D. , Lee Y. P. , Dong C. , Lin G. Q. , Sun C. , Wen L. S.
Published: February 2004

TiN hard coatings were prepared by arc ion plating with both direct current (dc) and pulsed biases. An extensive investigation was undertaken to determine the effects of the substrate temperature on the mechanical properties and the microstructures of films. The results show that the substrate temperature is decreased evidently when a pulsed bias instead of a dc one is employed. At the same time, the microstructures and the properties are also improved. A low-temperature arc ion plating can be realized by using pulsed biases.
Trace moisture emissions from heated metal surfaces in hydrogen service
Authors: Funke Hans H. , Yao Jianlong , Raynor Mark W.
Published: February 2004

The formation of trace moisture by exposure of dry heated surfaces of 316 L stainless-steel, Restek Silcosteel®, and nickel 1/8 in. outer diameter line segments to purified Ar and H2 was studied using atmospheric pressure ionization mass spectrometry at flow rates of 2 slpm. Prior to H2 exposure, adsorbed moisture was removed by heating incrementally to 500 °C in an argon matrix, where the Restek Silcosteel® material released a maximum of 50 ppb moisture at 300 °C and moisture spikes from the Ni and stainless-steel surfaces reached several 100 ppb. Upon exposure to H2, persistent low ppb moisture emissions due to the reduction of surface oxide species were observed at temperatures as low as 100 °C. Spikes at 300–500 °C ranged from ∼100 ppb for the stainless-steel lines to 400 ppb for the Restek Silcosteel® material. The observed moisture emissions have to be considered as a potential contamination source for high-purity processes utilizing H2 purge at elevated temperatures.
Nonselective and smooth etching of GaN/AlGaN heterostructures by Cl2/Ar/BCl3 inductively coupled plasmas
Authors: Han Yanjun , Xue Song , Wu Tong , Wu Zhen , Guo Wenping , Luo Yi , Hao Zhibiao , Sun Changzheng
Published: February 2004

A systematic study of the nonselective and smooth etching of GaN/AlGaN heterostructures was performed using Cl2/Ar/BCl3 inductively coupled plasmas (ICPs). Nonselective etching can be realized by adjusting the BCl3 ratio in the Cl2/Ar/BCl3 mixture (20%–60%), increasing the ICP power, and decreasing the chamber pressure. Surface morphology of the etched heterostructures strongly depends on the gas chemistry and the chamber pressure, whereas selectivity and surface morphology show a slight dependence on the dc bias and total flow rate. Specifically, with the addition of 20% BCl3 to Cl2/Ar (4:1) gas mixture, nonselective etching of GaN/Al0.28Ga0.72N heterostructures at a high etch rate is maintained and the surface root-mean-square roughness is reduced from 10.6 nm to 0.5 nm, which is smoother than the as-grown sample. Auger electron spectroscopy analysis shows that the effective removal of residual oxygen from the surface of AlGaN during the etching process is crucial to the nonselective and smooth etching of GaN/AlGaN herterostructures at high etch rate.
Zirconia-alumina nanolaminate for perforated pitting corrosion protection of stainless steel
Authors: Gaertner W. F. , Hoppe E. E. , Omari M. A. , Sorbello R. S. , Aita C. R.
Published: February 2004

The subject of this article is control of perforated pit growth in 316L stainless steel by application of an artificial overlayer film. The protection afforded by 250 nm thick films with two ZrO2–Al2O3 nanolaminate architectures, single-layer ZrO2, and single-layer Al2O3 under cyclic polarization in saline electrolyte is reported here. The post-exposure morphology is characterized by scanning electron microscopy with in situ electron energy dispersive spectroscopy. The films’ diverse behavior is analyzed in terms of a model for perforated pit growth that requires partial pit occlusion until an autocatalytic geometry is established. The results show that the key property a film must have to arrest the development of autocatalytic geometry is the capability to fracture locally so that the electrolyte from the pit freely mixes with the bulk electrolyte and the pit interior becomes passivated. We show how a nanolaminate with 5.0 nm tetragonal ZrO2–5.0 nm amorphous Al2O3 bilayers sustains local fracture (blow holes) without widespread cracking and is protective against perforated pit growth.
Characterization of graded InGaN/GaN epilayers grown on sapphire
Authors: Song T. L. , Chua S. J. , Fitzgerald E. A. , Chen P. , Tripathy S.
Published: February 2004

Atomic force microscopy, scanning electron microscopy, micro-Raman, and photoluminescence techniques have been used to characterize graded InGaN/GaN epilayers grown on sapphire. These graded InGaN/GaN can be employed as buffers that can relax the strain arising from the lattice and thermal mismatch in nitride epilayers grown on sapphire. Compared to the conventional two-step high temperature bulk GaN, an enhanced strain relaxation was observed in the GaN grown on a gradually graded InGaN buffer with an intermediate thin GaN layer. The function of the intermediate layer was to progressively relax the strain that built up in the InGaN layer after a certain thickness. The optimum growth conditions of the intermediate layer play a major role in promoting the suppression and filling of the V-pits in the GaN cap layer, and were empirically found to be a thin 10 nm GaN grown at 750 °C and annealed at 1000 °C. Based on the statistical distribution of the size of the V-pits opening, the formation of V-pits was also investigated.
Preferred orientation and film structure of TaN films deposited by reactive magnetron sputtering
Authors: Noda Suguru , Tepsanongsuk Kun , Tsuji Yoshiko , Kajikawa Yuya , Ogawa Yoshifumi , Komiyama Hiroshi
Published: February 2004

The structural evolution of tantalum nitride (TaN) films deposited by reactive rf magnetron sputtering were investigated in detail by using transmission electron microscopy (TEM) and x-ray diffractometry (XRD) for a wide range of thickness from 2 nm to 2 μm under various N2/Ar flow ratios from 0 to 20 vol % on both amorphous SiO2 (a-SiO2) and randomly oriented polycrystalline fcc TaN (poly-fcc-TaN) substrates. Although the films had various crystalline structures [including tetragonal Ta, bcc Ta(N), and fcc TaN] of different preferred orientation (PO) and had amorphous phases depending on deposition conditions, the formation mechanism of these structures was systematically explained by mapping them on 2D graphs of film thickness vs N2/Ar flow ratio. The texture map of films deposited on a-SiO2 substrates reflected both nucleation and growth stages, whereas that of films deposited on poly-fcc-TaN substrates reflected mainly the growth stage. Comparison of these two maps allowed the nucleation and growth processes to be separately discussed. For films deposited at 4 vol % N2/Ar ratio on a-SiO2 substrates, an amorphous phase initially appeared when the film thickness was 1.8–3.5 nm. When the film thickness was about 7 nm, nucleation occurred to form fcc TaN without any PO. When the thickness was about 100 nm, (111) PO appeared. Finally, when the thickness exceeded 200 nm, (200) PO dominated the film. Cross-sectional TEM micrographs revealed that evolutionary selection growth occurred when the film was 200-nm-thick to cause the PO change. (111) PO was preferred at relatively low (2–3 vol %) and high (⩾10 vol %) N2/Ar ratios, whereas (200) was preferred at medium N2/Ar ratio (4–7 vol %).
High temperature processing of TiO2 thin films for application in silicon solar cells
Authors: Richards Bryce S. , Richards S. Raymond , Boreland Matthew B. , Jamieson David N.
Published: February 2004

Low temperature deposited coatings have the potential to reduce the production costs of silicon (Si) photovoltaic devices, such as the buried-contact (BC) solar cell. This work investigates the potential of titanium dioxide (TiO2) films to replace silicon dioxide (SiO2) or nitride coatings currently implemented in the BC fabrication sequence, which requires films to be stable at temperatures up to 1000 °C in a variety of gas atmospheres. The authors demonstrate that: (i) TiO2 films do not reduce the bulk minority carrier lifetime of the silicon wafer after lengthy high temperature processing, however chemical reduction of the TiO2 film can occur if samples are not loaded in an oxygen-containing ambient; (ii) a thin SiO2 passivation layer can be formed at the TiO2:Si interface by performing a brief oxidation after TiO2 film deposition; (iii) while TiO2 coatings function as a phosphorus diffusion barrier, reactions between TiO2 and the phosphorus source result in irreversible damage to the TiO2 film; (iv) phosphorus-doped TiO2 films can act as an n-type dopant source, however further reactions with phosphorus limit the usefulness of the film. Thus, TiO2 films are compatible with the high temperature processing required for BC solar cells, but not with any phosphorus diffusion steps.
Effect of deposition parameters on properties of ITO films prepared by reactive middle frequency pulsed dual magnetron sputtering
Authors: Rogozin A. I. , Vinnichenko M. V. , Kolitsch A. , Möller W.
Published: February 2004

ITO layers with low resistivity and high visible transmittance were produced by means of middle frequency reactive dual magnetron sputtering. The influence of base pressure, Ar/O2 ratio and magnetron pulse duration on the film composition, structure, electrical, and optical properties has been investigated. The deposition rate is proportional to the magnetron operation power at changing pulse duration and constant Ar and O2 flows. At enhanced O2 flows an onset of the magnetron target oxidation is discussed as a reason for the decrease of the deposition rate. The presence of water vapor in the residual gas is determined to be a reason for deterioration of resistivity and optical transmittance observed for ITO films produced at a base pressures higher than 5⋅10−4 Pa. It is demonstrated that spectroscopic ellipsometry can be used as a noncontact tool to monitor the resistivity of ITO films.
Chemical bonds of fluorocarbon films which can be a source of CFx radicals
Authors: Takada N. , Iida T. , Shibagaki K. , Sasaki K.
Published: February 2004

Some experiments reported previously [e.g., K. Sasaki et al., J. Appl. Phys. 88, 5585 (2000)] show that fluorocarbon films can be a source of CFx radicals in fluorocarbon plasmas. In the present article, we examined the relationship between the degree of surface production and the chemical bonds of fluorocarbon films synthesized by various fluorocarbon plasmas with the addition of H2. The degree of surface production was evaluated from the absolute flux of CFx (x=1,2) radicals desorbed from fluorocarbon films. The composition of the chemical bonds was analyzed by x-ray photoelectron spectroscopy. As a result, significant surface production (>3×1015 cm−2 s−1) was observed when fluorocarbon film had the dominant –CF2 bond. The change in the dominant bond from –CF2 to –C–C resulted in the decrease in the degree of surface production.
Growth and characterization of cubic CdS epilayers on GaAs substrates
Authors: Yu Young-Moon , Lee Ki-Seon , O Byungsung , Yu Pyeong Yeol , Kim Chang-Soo , Choi Yong Dae , Yun Hee-Joong
Published: February 2004

Cubic CdS epilayers were grown on (100) GaAs substrate by hot-wall epitaxy. X-ray diffraction and photoluminescence measurements revealed that the hexagonal phase was dominant in the layers grown at low temperatures, and the cubic phase became dominant with increasing growth temperature. The photoluminescence emission lines in cubic CdS were identified.
Analytical modeling of rarefied Poiseuille flow in microchannels
Authors: Yuhong Sun , Chan W. K.
Published: February 2004

The prediction of rarefied gas flow in the transition regime remains an obstacle due to its complexity. The moment method is commonly used in kinetic theory of gases to obtain approximate solutions in this regime, though substantial effort is still needed either numerically or mathematically. In this article Grad’s 13-moment method was first applied to the derivation of a new governing equation for Poiseuille flow in microchannels and novel boundary conditions were introduced. For validation purposes, Poiseuille flow in micro channels was investigated. The flow rate and velocity profiles were obtained analytically. The results were compared with the linearized Boltzmann equation and available experimental data. The error is within 10% in both slip and transition regimes. This shows a substantial improvement over first-, and second-order slip models where the errors can be as high as several tens or even hundreds of percent. The major attraction of the current approach is that it allows a simple analytical equation to explain the effects of various forces on the velocity profiles, flow rates, and pressure distributions.
Fabrication of iron (III) oxide doped polystyrene shells
Authors: Cai Pei-jun , Tang Yong-jian , Zhang Lin , Du Kai , Feng Chang-gen
Published: February 2004

A type of iron (III) oxide doped plastic shell used for inertial confinement fusion experiments has been fabricated by emulsion techniques. Three different phases of solution (W1, O, and W2) are used for the fabrication process. The W1 phase is a 1 wt % of sodium lauryl sulfate in water. This W1 phase solution is mixed with a 3 wt % Fe2O3–polystyrene (PS) solution in benzene-dichloroethane (O phase) while stirring. The resulting emulsion (W1/O) is poured into a 3 wt % aqueous polyvinyl alcohol solution (W2 phase) while stirring. The resulting emulsion (W1/O/W2) is then heated to evaporate benzene and dichloroethane, and thus a solid Fe2O3–PS shell is formed. The diameter and wall thickness of the shells range from 150 to 500 μm and 5 to 15 μm, respectively. The average surface roughness of the shells is 40 nm, similar to that of the usual PS shells.
Effects of mesh-assisted carbon plasma immersion ion implantation on the surface properties of insulating silicon carbide ceramics
Authors: Fu Ricky K. Y. , Fu Ka Leung , Tian Xiubo , Chu Paul K.
Published: February 2004

Plasma immersion ion implantation (PIII) is an effective materials modification and synthesis technique but has seldom been applied to ceramic materials due to the high electrical resistance that reduces the ion bombardment energy and sometimes causes serious electrical arcing in the instrument. Even in cases where PIII is applicable, the surface properties of the implanted insulating materials can be seriously affected due to the low ion energy and materials damage from electrical arcing. In order to enhance the surface and mechanical properties such as wear resistance of ceramic materials used in many industrial applications, surface modification is needed. In this work, we conduct carbon implantation into sintered α-SiC (silicon carbides that are widely used in vacuum ceramic bearings) using mesh-assisted plasma immersion ion implantation to enhance the surface properties. The use of a conducting grid is necessitated by the high electrical resistance that induces a large voltage drop across the substrate when a negative voltage is applied to the back of the specimen. The rough surfaces make direct assessment of the shallow depth profiles difficult and so we directly measure the hardness and surface friction coefficients, both of which are significantly enhanced after implantation. Our data suggest different wear mechanisms for the unimplanted and implanted samples as inferred from the surface topography and wear tracks.
Effect of ion beam energy on magnetic properties of CoCrPt and CoPt thin films
Authors: Zhang Jinqiu , Wang Haifeng , Alex Michael , Miloslavsky Lena
Published: February 2004

The magnetic properties of Cr/CoPt and Cr/CoCrPt thin films prepared by ion beam deposition with Xe ions (0.6–1.5 kV) have been investigated. The effect of ion beam energy on the structural and magnetic properties has been studied. A strong dependence of in-plane coercivity on the beam energy was observed and the coercivity increased with beam energy for both CoPt and CoCrPt thin films. With increasing beam energy from 600 to 1500 eV, the coercivity for CoPt thin films increased from 1700 to 2100 Oe. In addition, CoPt thin films have a greater advantage over CoCrPt thin films. A 40% increase in coercivity for CoPt thin films was obtained at the same remanent magnetization-thickness (Mrt) product as compared to CoCrPt. A minimum thickness of 20 Å for the Cr underlayer and 600 eV beam energy were required for constant coercivity and Mrt. X-ray diffraction studies indicated that CoPt(101̄0) texture and in-plane hcp c-axis orientation were enhanced with increased beam energy. The increase of coercivity with beam energy is attributed to an increase in the peak intensity ratio (101̄0)/(0002). The decrease of grain size for CoPt(101̄0) texture with beam energy was attributed to contribute to improvement in coercivity. Compositional analysis using inductively coupled plasma indicated that the Pt content in CoPt thin films increased with beam energy. The increase of Pt content in the thin films accompanied by an increase in the d spacing (lattice constant) improved in-plane coercivity. From magnetic force microscopy studies, lower inter-granular exchange coupling was observed at higher beam energy.
Improving Classroom Behavior
Authors: Blanton Patricia
Published: February 2004

Frustration with one's ability to deal with classroom discipline is cited as a primary problem facing new teachers and a major factor in teacher retention. As a novice teacher, perhaps you had never been in a classroom where you felt as if the teacher was not in control until it came your time to be the “teacher.” Now you are faced with what you expect your students to do and the reality of what they actually will do. How do you develop and nurture a classroom environment where learning is the primary objective of both the students and the teacher? While there is no magic formula that will work for everyone, there are some guidelines to follow and pitfalls to avoid that can increase your chances for success.
Carbon and Nitrogen Isotopic Anomalies in an Anhydrous Interplanetary Dust Particle
Authors: Floss Christine , Stadermann Frank J. , Bradley John , Dai Zu Rong , Bajt Saša , Graham Giles
Published: February 2004

Because hydrogen and nitrogen isotopic anomalies in interplanetary dust particles have been associated with carbonaceous material, the lack of similar anomalies in carbon has been a major conundrum. We report here the presence of a
13
C depletion associated with a
15
N enrichment in an anhydrous interplanetary dust particle. Our observations suggest that the anomalies are carried by heteroatomic organic compounds. Theoretical models indicate that low-temperature formation of organic compounds in cold interstellar molecular clouds can produce carbon and nitrogen fractionations, but it remains to be seen whether the specific effects observed here can be reproduced.
Many Perspectives, No Consensus
Authors: Carstairs-McCarthy Andrew
Published: February 2004

Language Evolution
. Morten H. Christiansen and Simon Kirby, Eds. Oxford University Press, Oxford, 2003. 413 pp. $98, £60. ISBN 0-19-924483-9. Paper, $26.95, £17.95. ISBN 0-19-924484-7. Studies in the Evolution of Language.

Contributors offer a variety of perspectives--from fields such as anthropology, archaeology, cognitive science, linguistics, evolutionary biology, neuroscience, and psychology--on the origins, evolution, and uniqueness of human language.
Of Towers, Walls, and Fields: Perspectives on Language in Science
Authors: Montgomery Scott
Published: February 2004

Language in science is in the midst of change and appears dominated by two contradictory trends. Globalization of scientific English seems to promise greater international unity, while growth of field-specific jargon suggests communicational diaspora. Real in part, each trend is complex and multileveled, and includes elements of convergence and divergence, along with important implications for the present and future of technical knowledge.
Software and the Future of Programming Languages
Authors: Aho Alfred V.
Published: February 2004

Although software is the key enabler of the global information infrastructure, the amount and extent of software in use in the world today are not widely understood, nor are the programming languages and paradigms that have been used to create the software. The vast size of the embedded base of existing software and the increasing costs of software maintenance, poor security, and limited functionality are posing significant challenges for the software R&D community.
The Future of Language
Authors: Graddol David
Published: February 2004

The world's language system is undergoing rapid change because of demographic trends, new technology, and international communication. These changes will affect both written and spoken communication. English may not be the dominant language of the future, and the need to be multilingual will be enhanced. Although many languages are going extinct, new ones are emerging in cities and extended social groups.
Carcinogen derived biomarkers: applications in studies of human exposure to secondhand tobacco smoke
Authors: Hecht S S
Published: February 2004

Objective:To review the literature on carcinogen derived biomarkers of exposure to secondhand tobacco smoke (SHS). These biomarkers are specifically related to known carcinogens in tobacco smoke and include urinary metabolites, DNA adducts, and blood protein adducts.

Method:Published reviews and the current literature were searched for relevant articles.

Results:The most consistently elevated biomarker in people exposed to SHS was 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (NNAL-Gluc), urinary metabolites of the tobacco specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The tobacco specificity of this biomarker as well as its clear relation to an established lung carcinogen are particularly appropriate for its application in studies of SHS exposure.

Conclusion:The results of the available carcinogen derived biomarker studies provide biochemical data which support the conclusion, based on epidemiologic investigations, that SHS causes lung cancer in non-smokers.
A prospective study of household smoking bans and subsequent cessation related behaviour: the role of stage of change
Authors: Pizacani B A , Martin D P , Stark M J , Koepsell T D , Thompson B , Diehr P
Published: February 2004

Objective:To assess the degree to which smokers living with a full household ban on smoking change their cessation related behaviour.

Design, setting, and participants:Prospective cohort study; follow up of a population based cohort of 1133 smokers, identified from a 1997 telephone survey of adult Oregonians. After a median of 21 months, 565 were located and reinterviewed.

Main outcome measures:Quit attempts, time until relapse, and smoking cessation, defined as seven day and 90 day sustained abstinence at follow up.

Results:A full ban at baseline was associated with a doubling of the odds of a subsequent quit attempt (odds ratio (OR)  =  2.0, 95% confidence interval (CI), 1.0 to 3.9). Among respondents in the preparation stage at baseline (intention to quit in the next month with a quit attempt in the previous year), a full ban was associated with a lower relapse rate (hazard ratio  =  0.5 (95% CI, 0.2 to 0.9)), while for those in precontemplation/contemplation (no intention to quit or intention to quit within the next six months, respectively), there was no significant association between full ban and relapse rate. For respondents in preparation, those with a full ban had over four times the odds of being in cessation for seven or more days before the follow up call (OR  =  4.4 (1.1 to 18.7)), but for those in precontemplation/contemplation, full bans were unrelated to cessation.

Conclusions:Full household bans may facilitate cessation among smokers who are preparing to quit by increasing quit attempts. They may also prolong time to relapse among those smokers.
Determination of tar, nicotine, and carbon monoxide yields in the mainstream smoke of selected international cigarettes
Authors: Calafat A M , Polzin G M , Saylor J , Richter P , Ashley D L , Watson C H
Published: February 2004

Objective:Survey of nicotine, tar, and carbon monoxide (CO) smoke deliveries from 77 cigarette brands purchased in 35 countries was conducted using a standardised machine smoking method. The goal of this study was to determine regional variations and differences in the tar, nicotine, and CO smoke yields of a cigarette brand manufactured by a leading transnational corporation and of non-US locally popular cigarette brands.

Design:The majority of the cigarettes were purchased in each of the participating countries by delegate members of the World Health Organization and forwarded to the Centers for Disease Control and Prevention for analysis. Smoke deliveries were determined using a standardised smoking machine method and subsequent gravimetric and gas chromatography analysis.

Results:The smoke deliveries varied widely. Mainstream smoke deliveries varied from 6.8 to 21.6 mg tar/cigarette, 0.5 to 1.6 mg nicotine/cigarette, and 5.9 to 17.4 mg CO/cigarette. In addition to the smoke deliveries, the cigarettes were examined to determine physical parameters such as filter composition, length, and ventilation levels.

Conclusion:Analysis of the smoke deliveries suggested that cigarettes from the Eastern Mediterranean, Southeast Asia, and Western Pacific WHO regions tended to have higher tar, nicotine, and CO smoke deliveries than did brands from the European, American, or African WHO regions surveyed.