bluuebunny/crossref_metadata_2025 huggingface dataset:
A Biomechanical and Finite Element Analysis of Femoral Neck Notching During Hip Resurfacing
Authors: Davis Edward T. , Olsen Michael , Zdero Rad , Papini Marcello , Waddell James P. , Schemitsch Emil H.
Published: March 2009

Hip resurfacing is an alternative to total hip arthroplasty in which the femoral head surface is replaced with a metallic shell, thus preserving most of the proximal femoral bone stock. Accidental notching of the femoral neck during the procedure may predispose it to fracture. We examined the effect of neck notching on the strength of the proximal femur. Six composite femurs were prepared without a superior femoral neck notch, six were prepared in an inferiorly translated position to create a 2 mm notch, and six were prepared with a 5 mm notch. Six intact synthetic femurs were also tested. The samples were loaded to failure axially. A finite element model of a composite femur with increasing superior notch depths computed maximum equivalent stress and strain distributions. Experimental results showed that resurfaced synthetic femurs were significantly weaker than intact femurs (mean failure of 7034 N, p<0.001). The 2 mm notched group (mean failure of 4034 N) was significantly weaker than the un-notched group (mean failure of 5302 N, p=0.018). The 5 mm notched group (mean failure of 2808 N) was also significantly weaker than both the un-notched and the 2 mm notched groups (p<0.001, p=0.023, respectively). The finite element model showed the maximum equivalent strain in the superior reamed cancellous bone increasing with corresponding notch size. Fracture patterns inferred from equivalent stress distributions were consistent with those obtained from mechanical testing. A superior notch of 2 mm weakened the proximal femur by 24%, and a 5 mm notch weakened it by 47%. The finite element analysis substantiates this showing increasing stress and strain distributions within the prepared femoral neck with increasing notch depth.
Microindentation of the Young Porcine Ocular Lens
Authors: Reilly Matthew , Ravi Nathan
Published: March 2009

Debate regarding the mechanisms of how the eye changes focus (accommodation) and why this ability is lost with age (presbyopia) has recently been rejoined due to the advent of surgical procedures for the correction of presbyopia. Due to inherent confounding factors in both in vivo and in vitro measurement techniques, mechanical modeling of the behavior of the ocular lens in accommodation has been attempted to settle the debate. However, a paucity of reliable mechanical property measurements has proven problematic in the development of a successful mechanical model of accommodation. Instrumented microindentation was utilized to directly measure the local elastic modulus and dynamic response at various locations in the lens. The young porcine lens exhibits a large modulus gradient with the highest modulus appearing at the center of the nucleus and exponentially decreasing with distance. The loss tangent was significantly higher in the decapsulated lens and the force waveform amplitude decreased significantly upon removal of the lens capsule. The findings indicate that localized measurements of the lens’ mechanical properties are necessary to achieve accurate quantitative parameters suitable for mechanical modeling efforts. The results also indicate that the lens behaves as a crosslinked gel rather than as a collection of individual arched fiber cells.
Design and Subspace System Identification of an Ex Vivo Vascular Perfusion System
Authors: El-Kurdi Mohammed S. , Vipperman Jeffrey S. , Vorp David A.
Published: March 2009

Numerical algorithms for subspace system identification (N4SID) are a powerful tool for generating the state space (SS) representation of any system. The purpose of this work was to use N4SID to generate SS models of the flowrate and pressure generation within an ex vivo vascular perfusion system (EVPS). Accurate SS models were generated and converted to transfer functions (TFs) to be used for proportional integral and derivative (PID) controller design. By prescribing the pressure and flowrate inputs to the pumping components within the EVPS and measuring the resulting pressure and flowrate in the system,_four TFs were estimated;_two for a flowrate controller (HRP,f and HRPP,f) and two for a pressure controller (HRP,p and HRPP,p). In each controller,_one TF represents a roller pump (HRP,f and HRP,p),_and the other represents a roller pump and piston in series (HRPP,f and HRPP,p). Experiments to generate the four TFs were repeated five times (N=5) from which average TFs were calculated. The average model fits, computed as the percentage of the output variation (to_the_prescribed_inputs) reproduced by the model, were 94.93±1.05% for HRP,p, 81.29±0.20% for HRPP,p, 94.45±0.73% for HRP,f, and 77.12±0.36% for HRPP,f. The simulated step, impulse, and frequency responses indicate that the EVPS is a stable system and can respond to signals containing power of up to 70_Hz.
Static Friction Model of Elastic-Plastic Contact Behavior of Surface With Elliptical Asperities
Authors: Jeng Yeau-Ren , Peng Shin-Rung
Published: March 2009

The friction coefficient (μ) of a contact surface with elliptical asperities is examined at various values of the plasticity index (ψ), the effective radius ratio (γ), the shear-strength-pressure proportionality constant (c), and the dimensionless limiting interfacial shear strength (τ¯m). The results demonstrate that the friction coefficient of the contact system increases with an increasing value of γ but decreases with an increasing value of ψ. Furthermore, it is shown that Amonton’s law is applicable for contact systems with either a low ψ and a high τ¯m or a high ψ and a low τ¯m. Analyzing the ratio of the nonelastic contact area, it is found that the asperities of a surface characterized by a large γ generally deform elastically at all values of the plasticity index, while those of a surface with a larger c deform plastically, particularly for surfaces with higher values of τ¯m and ψ. Finally, an inspection of the critical dimensionless real contact area shows that the contact mode of the surface is determined primarily by the value of the effective radius ratio.
Simulation of Damage Percolation Within Aluminum Alloy Sheet
Authors: Orlov O. S. , Worswick M. J. , Maire E. , Lloyd D. J.
Published: March 2009

A combined experimental and analytical approach is used to study damage initiation and evolution in three-dimensional second phase particle fields. A three-dimensional formulation of a damage percolation model is developed to predict damage nucleation and propagation through random-clustered second phase particle fields. The proposed approach is capable of capturing the three-dimensional character of damage phenomena and the three stages of ductile fracture, namely, void nucleation, growth, and coalescence, at the level of discrete particles. An in situ tensile test with X-ray tomography is utilized to quantify material damage during deformation in terms of the number of nucleated voids and porosity. The results of this experiment are used for both the development of a clustering-sensitive nucleation criterion and the validation of the damage percolation predictions. The evolution of damage in aluminum alloy AA5182 has been successfully predicted to match that in the in situ tensile specimen. Two forms of second phase particle field input data were considered: (1) that measured directly with X-ray tomography and (2) fields reconstructed statistically from two-dimensional orthogonal sections. It is demonstrated that the adoption of a cluster-sensitive void nucleation criterion, as opposed to a cluster-insensitive nucleation criterion, has a significant effect in promoting predicted void nucleation to occur within particle clusters. This behavior leads to confinement of void coalescence to within clusters for most of the duration of deformation followed by later development of a macrocrack through intracluster coalescence. The measured and reconstructed second phase particle fields lead to similar rates of predicted damage accumulation and can be used interchangeably in damage percolation simulations.
Critical Review and Appraisal of Traditional and New Procedures for the Quantification of Creep Fracture Behavior Using 1Cr–1Mo–0.25V Steel
Authors: Evans M.
Published: March 2009

The approaches traditionally used to quantify creep and creep fracture are critically assessed and reviewed in relation to a new approach proposed by Wilshire and Scharning. The characteristics, limitations, and predictive accuracies of these models are illustrated by reference to information openly available for the bainitic 1Cr–1Mo–0.25V steel. When applied to this comprehensive long-term data set, the estimated 100,000–300,000 h strength obtained from the older so called traditional methods varied considerably. Further, the isothermal predictions from these models became very unstable beyond 100,000 h. In contrast, normalizing the applied stress through an appropriate ultimate tensile strength value not only reduced the melt to melt scatter in rupture life, but also the 100,000 h strengths determined from this model for this large scale test program are predicted very accurately by extrapolation of creep life measurements lasting less than 5000 h. The approach therefore offers the potential for reducing the scale and cost of current procedures for acquisition of long-term engineering design data.
High Velocity Oblique Impact and Coefficient of Restitution for Head Disk Interface Operational Shock
Authors: Katta Raja R. , Polycarpou Andreas A. , Hanchi Jorge V. , Crone Robert M.
Published: March 2009

With the increased use of hard disk drives (HDDs) in mobile and consumer applications combined with the requirement of higher areal density, there is enhanced focus on reducing head disk spacing, and consequently there is higher susceptibility of slider/disk impact damage during HDD operation. To investigate this impact process, a dynamic elastic-plastic finite element model of a sphere (representing a slider corner) obliquely impacting a thin-film disk was created to study the effect of the slider corner radius and the impact velocity on critical contact parameters. To characterize the energy losses due to the operational shock impact damage, the coefficient of restitution for oblique elastic-plastic impact was studied using the finite element model. A modification to an existing physics-based elastic-plastic oblique impact coefficient of restitution model was proposed to accurately predict the energy losses for a rigid sphere impacting a half-space. The analytical model results compared favorably to the finite element results for the range from low impact angles (primarily normal impacts) to high impact angles (primarily tangential impacts).
Basic Electrochemical Thermodynamic Studies of Fuel Cells Using MALT2
Authors: Williams M. , Horita T. , Yamagi K. , Sakai N. , Yokokawa H.
Published: March 2009

There are at least four basic fuel cell thermodynamic features: maximum intrinsic thermal efficiency (electrical efficiency), reversible potential, and two new ones—intrinsic cooling requirement and intrinsic exergetic efficiency. A basic electrochemical thermodynamic analysis of fuel cells using MALT reveals that it is probably for thermodynamic reasons that cooling strategies other than excess oxidant, such as water cooling, have generally been adopted for lower temperature fuel cells such as polymer electrolyte fuel cell (PEFC) and phosphoric acid fuel cell (PAFC). One can mathematically demonstrate that for a simple hybrid system, any fuel cell, any operating temperature, and any pressure, the maximum reversible work is equal to the free energy of reaction at the standard state. This study gives information of new opportunity fuels having increasing importance is all future energy scenarios. The results of this analysis show that ammonia and direct methanol give greater maximum intrinsic thermal efficiency than hydrogen oxidation. From these simple studies alone, one would conclude that the great payoff in terms of theoretical efficiency potential for research is direct carbon fuel cell (DCFT), PEFC, and direct oxidation of methane, intermediate temperature solid oxide fuel cell (SOFC), and simple fuel cell turbine hybrids.
Advances in Research, Development, and Testing of Single Cells at Forschungszentrum Jülich
Authors: Haanappel V. A. C. , Jordan N. , Mai A. , Mertens J. , Serra J. M. , Tietz F. , Uhlenbruck S. , Vinke I. C. , Smith M. J. , de Haart L. G. J.
Published: March 2009

This paper presents an overview of the main advances in solid oxide fuel cells (SOFCs) research and development (R&D), measurement standardization, and quality assurance in SOFC testing at the Forschungszentrum Jülich. These activities have resulted in both a significant improvement of the electrochemical performance and a better understanding of the electrochemical behavior of SOFCs. Research and development of SOFCs was mainly focused on two types of anode-supported cells, namely, those employing either La0.65Sr0.3MnO3 (LSM) or La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode materials. In both cases the optimization of processing and microstructural parameters resulted in satisfactory power output and long-term stability at reduced operation temperatures. Standardization and quality assurance in SOFC testing was also addressed with the goal of producing consistent and reliable tests and measurement results. At present, under optimized experimental conditions, SOFCs with LSM or LSCF cathodes can deliver a power output of about 1.0 W/cm2 and 1.9 W/cm2 at 800°C (700 mV), respectively.
Fabrication of High Precision PEMFC Membrane Electrode Assemblies by Sieve Printing Method
Authors: Andrade Alexandre B. , Bejarano Martha L. Mora , Cunha Edgar F. , Robalinho Eric , Linardi Marcelo
Published: March 2009

A sieve printing technique has been developed for the preparation of gas diffusion electrodes for proton exchange membrane fuel cells (PEMFCs). The results of the preparation of membrane electrode assemblies (MEAs) are shown to be faster and highly reproducible by using the sieve printing and hot pressing method. These results were compared with those obtained by spray and hot pressing method. The experiments were carried out in a 25 cm2 single PEM fuel cell with platinum loadings of 0.4 mg Pt cm−2 and 0.6 mg Pt cm−2 on the anode and cathode, respectively. Scanning electron microscopy analysis was used to investigate the electrodes’ morphology. The performance of the MEAs was measured by polarization curves. It was observed that the sieve printing technique is highly reproducible and significantly more accurate and faster than the spray one. Sieve printing technique can be easily scaled up and is very adequate for high volume production with low-cost. Such features allow manufacturing large active areas for power stack fabrication. In addition, this deposition technique has produced MEAs with a 39.8% higher power density at 0.6 V when compared with the spray one.
Creep Relaxation of an Elastic–Perfectly Plastic Hemisphere in Fully Plastic Contact
Authors: Goedecke Andreas , Mock Randolf
Published: March 2009

A set of finite element simulations was performed to analyze the creep behavior of an elastic–perfectly plastic hemisphere in contact with a rigid flat. This study focuses on the time-dependent stress relaxation of a fully plastic asperity. Assuming a Garofalo (hyperbolic sine) type material creep law, the asperity shows two distinct phases of relaxation. In the first phase, the asperity creeps with an accelerated creep rate and shows a contact area increase similar to that of a cylindrical geometry. In the second phase, no contact area change can be measured and the asperity creeps with a slower rate. Empirical evolution laws for the asperity creep behavior are presented, analyzing the influence of both material and geometrical parameters. The results are interpreted in terms of transient friction.
Transient Thermomechanical Analysis of Sliding Electrical Contacts of Elastoplastic Bodies, Thermal Softening, and Melting Inception
Authors: Chen W. Wayne , Wang Q. Jane , Kim Wansik
Published: March 2009

Sliding electrical contacts are found in many electromechanical devices, such as relays, switches, and resistance spot welding. Temperature rise due to sliding friction and electrical current may be the major source of sliding electrical contact deterioration. This paper reports the development of a three-dimensional thermo-elasto-plastic contact model of counterformal bodies, which takes into account transient heat flux, temperature-dependent strain hardening behavior, and a realistic heat partition between surfaces. Transient contact simulations induce a significant increase in computational burden. The discrete convolution and fast Fourier transform and the conjugate gradient method are utilized to improve the computation efficiency. The present model is used to study the case of a half-space sliding over a stationary sphere, and both are made of 7075 aluminum alloy; the contact resistance is considered mainly due to the surface oxide film. The simulation results indicate that the transient contact model is able to capture the history of plastic deformation accumulation and the material melting inception.
Effect of Coating Thickness on the Friction Coefficients and Torque-Tension Relationship in Threaded Fasteners
Authors: Nassar Sayed A. , Zaki Amro M.
Published: March 2009

This paper experimentally investigates the effect of coating thickness on the thread, bearing friction coefficients, and torque-tension relationship in threaded fasteners, as well as an investigation into the effect of coating thickness on surface roughness properties. The torque-tension relationship is highly sensitive to frictional changes. Two different coating thicknesses are investigated using two bolt thread pitch; test data are collected for a preselected level of bolt tension. The experimental setup collects real-time data on the tightening torque, bolt tension, and the corresponding reaction torque. Test data are used for calculating the thread and bearing friction coefficients, as well as the overall torque-tension relationship for two different coating thicknesses. The study would provide an insight into the variation in the torque-tension relationship, which is a key factor that significantly affect the reliability and safety of bolted assemblies in many mechanical and structural applications.
Load-Independent Spin Power Losses of a Spur Gear Pair: Model Formulation
Authors: Seetharaman S. , Kahraman A.
Published: March 2009

A physics-based fluid mechanics model is proposed to predict spin power losses of gear pairs due to oil churning and windage. While the model is intended to simulate oil churning losses in dip-lubricated conditions, certain components of it apply to air windage losses as well. The total spin power loss is defined as the sum of (i) power losses associated with the interactions of individual gears with the fluid, and (ii) power losses due to pumping of the oil at the gear mesh. The power losses in the first group are modeled through individual formulations for drag forces induced by the fluid on a rotating gear body along its periphery and faces, as well as for eddies formed in the cavities between adjacent teeth. Gear mesh pumping losses will be predicted analytically as the power loss due to squeezing of the lubricant, as a consequence of volume contraction of the mesh space between mating gears as they rotate. The model is applied to a unity-ratio spur gear pair to quantify the individual contributions of each power loss component to the total spin power loss. The influence of operating conditions, gear geometry parameters, and lubricant properties on spin power loss are also quantified at the end. A companion paper (Seetharaman et al., 2009, “Oil Churning Power Losses of a Gear Pair: Experiments and Model Validation,” ASME J. Tribol., 131, p. 022202) provides comparisons to experiments for validation of the proposed model.
Failure Analysis of a Fibrous Composite Half-Space Subjected to
Uniform Surface Line Load
Authors: Gururaja Suhasini , Ramulu Mamidala
Published: March 2009

Unidirectional fiber-reinforced plastic (UD-FRP) laminates have been modeled previously as an equivalent quasihomogeneous monoclinic half-space subjected to an inclined line load on the surface using Lekhnitskii’s formulation simulating the orthogonal edge trimming loads in UD-FRPs. In continuation, failure analysis of the aforementioned composite half-space has been carried out in the present investigation based on Tsai–Wu criterion. In particular, the failure behavior of the half-space laminate with respect to the fiber orientation, load inclination angle, and spatial coordinates has been examined in detail. The motivation behind such a study lies in correlating the failure behavior of the half-space laminate with the machining damage observed during orthogonal edge trimming experiments. The present work strives at identifying this relationship and, in the process, understanding the physics of orthogonal cutting of UD-FRP laminates.
Asperity Creep Measured by the Reflection of Ultrasound at Rough Surface Contact
Authors: Gonzalez-Valadez M. , Dwyer-Joyce R. S.
Published: March 2009

The asperity contact regions in static contact are subjected to very high stress. Deformation is plastic and the material can suffer localized creep that is not usually observed at conventional stress levels. Creep of the asperity contacts causes an increase in contact area and hence an increase in the adhesive component of friction. The strains are so small compared with the bulk deflections that they are hard to measure by displacement of strain transducers. However, one measurement approach is to use the reflection of an ultrasonic pulse since this depends only on the interface behavior, specifically its stiffness. In this study, ultrasound was used to investigate the increase in interfacial stiffness with time. A power law relationship between stiffness and hold time was observed for both steel and aluminum surfaces pressed together. An analytical model that assumes a simple geometry for the contact has been developed. A single asperity was considered to determine the geometry of the whole interface by superposition. The stiffness predicted by the model was compared with experimental data and was used to determine the creep rate exponent for the material.
THREE-DIMENSIONAL CR-SUBMANIFOLDS IN THE NEARLY KÄHLER 6-SPHERE WITH ONE-DIMENSIONAL NULLITY
Authors: DJORIĆ MIRJANA , VRANCKEN LUC
Published: March 2009

In this paper, we study certain three-dimensional CR-submanifolds M of the nearly Kähler 6-dimensional sphere S6(1). It is well known that there does not exist a three-dimensional totally geodesic proper CR-submanifold in S6(1). In this paper we obtain a classification of the 3-dimensional CR-submanifolds which are the closest possible to totally geodesic submanifolds, i.e. those that admit a one-dimensional nullity distribution.
HARMONIC CONTACT METRIC STRUCTURES AND SUBMERSIONS
Authors: VERGARA-DIAZ E. , WOOD C. M.
Published: March 2009

We study harmonic almost contact structures in the context of contact metric manifolds, and an analysis is carried out when such a manifold fibres over an almost Hermitian manifold, as exemplified by the Boothby–Wang fibration. Two types of almost contact metric warped products are also studied, relating their harmonicity to that of the almost Hermitian structure on the base or fibre.
RIEMANNIAN GEOMETRY OF HARTOGS DOMAINS
Authors: DI SCALA ANTONIO J. , LOI ANDREA , ZUDDAS FABIO
Published: March 2009

Let DF = {(z0, z) ∈ ℂn | |z0|2 < b, ||z||2 < F(|z0|2)} be a strongly pseudoconvex Hartogs domain endowed with the Kähler metric gF associated to the Kähler form [Formula: see text].

This paper contains several results on the Riemannian geometry of these domains. These are summarized in Theorems 1.1–1.3. In the first one we prove that if DF admits a non-special geodesic (see definition below) through the origin whose trace is a straight line then DF is holomorphically isometric to an open subset of the complex hyperbolic space. In the second theorem we prove that all the geodesics through the origin of DF do not self-intersect, we find necessary and sufficient conditions on F for DF to be geodesically complete and we prove that DF is locally irreducible as a Riemannian manifold. Finally, in Theorem 1.3, we compare the Bergman metric gB and the metric gF in a bounded Hartogs domain and we prove that if gB is a multiple of gF, namely gB = λ gF, for some λ ∈ ℝ+, then DF is holomorphically isometric to an open subset of the complex hyperbolic space.
ORBITAL APPROACH TO MICROSTATE FREE ENTROPY
Authors: HIAI FUMIO , MIYAMOTO TAKUHO , UEDA YOSHIMICHI
Published: March 2009

Motivated by Voiculescu's liberation theory, we introduce the orbital free entropy χorbfor non-commutative self-adjoint random variables (also for "hyperfinite random multi-variables"). Besides its basic properties, the relation of χorbwith the usual free entropy χ is shown. Moreover, the dimension counterpart δ0, orbof χorbis discussed, and we obtain the relation between δ0, orband the original free entropy dimension δ0together with applications to δ0itself.
SECURE, LOW-COST PROTOTYPE DESIGN OF UNDERWATER ACOUSTIC SENSOR NETWORKS
Authors: HU FEI , TILGHMAN PAUL , MOKEY STEVEN , BYRON JAMES , SACKETT ANDREW
Published: March 2009

Underwater Wireless Sensor Networks are essentially different from terrestrial RF-based sensor networks due to its highly variable and long acoustic delay. This paper describes our hardware/software co-design of low-cost underwater sensor nodes for deployment in a shallow underwater environment. Each sensor is comprised of a DSP board responsible for modulation/demodulation and sensor readings, as well as an analog board responsible for signal strength amplification and signal conditioning.
IMPROVED NET REWRITING SYSTEMS–EXTENDED PETRI NETS SUPPORTING DYNAMIC CHANGES
Authors: LI JUN , DAI XIANZHONG , MENG ZHENGDA , XU LIBO
Published: March 2009

The existing extensions of Petri nets supporting dynamic changes cannot ensure preservation of desired properties of the modeled systems. This paper tries to address this problem. By extending the structure of the net rewriting system (NRS) and modifying the specification of its rewriting rule, we present improved net rewriting system (INRS). INRS enjoys four important properties, i.e., locality, transitivity, reflexivity, and reversibility. A practical system subject to dynamic changes can be modeled by an INRS, and its desired properties can be preserved with the state evolvement of the INRS. The property-preserving principles of INRS and their strict proofs are provided as well. Finally, a case study is provided to demonstrate the modeling of an automated manufacturing cell with changeable structure using an INRS. The result shows that the desired properties of the cell are still preserved despite its model evolvement.
AN ELECTROSTATIC DISCHARGE FREE BOOTSTRAPPED BiCMOS INVERTER CIRCUIT BASED ON PARASITIC DIODE
Authors: TOOPRAKAI SIRAPHOP (PAIBOON) , DEJHAN KOBCHAI
Published: March 2009

Electrostatic discharge (ESD) free bootstrapped BiCMOS inverter circuit is proposed. The proposed driver circuit uses the bootstrapped technique; the transistor base voltage is higher than the supply voltage. The input of circuit is arranged to protect the electrostatic discharge problem, and the output waveform is able to have full swing. The proposed circuit consumes low power with small delay time. The transistors in the circuit operate with high performance and efficiency.
A NEW APPROACH FOR THE ANALYSIS OF THE TRANSIENT AND STEADY STATE OF PIECEWISE-LINEAR CIRCUITS BY NEURAL NETWORKS
Authors: TUNTAŞ REMZI , DEMIR YAKUP , KÖKSAL MUHAMMET
Published: March 2009

This paper presents a new approach based on Feed-Forward multilayered Neural Networks (FNNs) for the transient and steady-state analysis of piecewise-linear circuits. Nonlinear circuits are changed by linear circuits containing switches together with some state matrices and control inequalities by using piecewise linearization approach. One of the two problems arising in the analysis of these circuits is that control inequalities belonging to piecewise linearized components and control times for internally or externally controlled components is needed to determine switching times. Another is that the analysis time is very long. The proposed approach is considered as the solution to the problems. FNNs are used for modeling the piecewise linear circuits. By using the obtained model networks, the switching sequence and switching times from one state to another for transient and steady states are determined. The transient and steady-state solutions are fast accomplished through this knowledge. As an example, a nonlinear circuit is used for demonstrating the utility of the proposed approach, and the results are compared with that of the model constructed at Matlab/Simulink. Example circuit is analyzed in the time of 1 h 42 min by using the proposed approach but the time of 2 h 27 min by Matlab/Simulink. Moreover, simulation results demonstrate that the proposed approach yields more accurate approximation for the switched nonlinear circuits.
REDUCTION, RECONSTRUCTION, AND SKEW-PRODUCT DECOMPOSITION OF SYMMETRIC STOCHASTIC DIFFERENTIAL EQUATIONS
Authors: LÁZARO-CAMÍ JOAN-ANDREU , ORTEGA JUAN-PABLO
Published: March 2009

We present reduction and reconstruction procedures for the solutions of symmetric stochastic differential equations, similar to those available for ordinary differential equations. In addition, we use the local tangent-normal decomposition, available when the symmetry group is proper, to construct local skew-product splittings in a neighborhood of any point in the open and dense principal orbit type. The general methods introduced in the first part of the paper are then adapted to the Hamiltonian case, which is studied with special care and illustrated with several examples. The Hamiltonian category deserves a separate study since in that situation the presence of symmetries implies in most cases the existence of conservation laws, mathematically described via momentum maps, that should be taken into account in the analysis.
MOLECULAR DYNAMICS STUDY OF THE TRANSCRIPTIONAL RECOGNITION MECHANISM OF HEME ACTIVATE PROTEIN (HAP)
Authors: ZHAO XI , HUANG XU-RI , SUN CHIA-CHUNG
Published: March 2009

The heme activate protein (HAP) is a model system for understanding protein–DNA interactions and allosteric mechanisms in gene regulation. Despite the wealth of biochemical data provided by extensive mutations of HAP, the specific recognition mechanism of the target DNA by HAP has remained elusive. This paper gives the results of a study using molecular dynamics simulations performed for a single DNA fragment (USACYC7) and three protein–DNACYC7complex crystal structures: the HAP-wt and two HAP mutants — HAP-PC7: S63G; HAP-18: S63R. Comparative molecular dynamics simulations reveal that the distributions of protein–DNA interactions recognizing the key base steps (CGC) are consistent with their transcriptional activities. Relative to the similar conformations of three bound DNA, the different flexibilities in involving DNA recognition regions: N-term Arm and Zn 2 Cys 6 Binuclear Cluster in three HAPs may result in a variety of protein–DNA recognitions. Despite different intensities of motions, the essential dynamics (ED) analysis shows that the internal motions of three protein–DNA complexes are similar: three proteins all slide along DNA to find their target sites. Thus, under this condition, during the recognition process, the flexibility of the DNA recognizing regions (N-term Arm and Zn 2 Cys 6 Binuclear Cluster regions) plays a crucial role in determining the abilities of protein's recognizing DNA: the higher is its flexibility, the faster it slides along the DNA to find the targeted DNA.
THEORETICAL STUDY ON THE INTERACTION SCHEMES OF β-CYCLODEXTRIN WITH ACETOVANILLONE
Authors: XING SHENG-KAI , ZHANG CHONG , AI HONG-QI , ZHAO QIANG , ZHANG QIAN , SUN DE-ZHI
Published: March 2009

The inclusion process of β-cyclodextrin (β-CD) with Acetovanillone (Ace) was studied by using PM3 method, and the single-point energy of the inclusion complex was calculated at the level of B3LYP/6-31G*. The calculated data suggest that (1) the inclusion complex formed by Ace entering into the cavity of β-CD from its wide side (the secondary hydroxyl group side) is more stable than that from its narrow side (the primary hydroxyl group side); (2) the formation of the inclusion complex is probably an enthalpy-driven process; (3) the more the charge transfers, the more unstable the inclusion complex is. In addition to the inclusion schemes, other seven interaction schemes of the Ace with β-CD were also investigated and the results suggest that all these schemes should exist in actual experiment.
TDDFT STUDY OF NUCLEOBASE THIOANALOGUES AND OXO-DERIVATIVES EXCITED STATES
Authors: GOMZI VJERAN
Published: March 2009

Thioanalogues of nucleic-acid bases have been shown to be the place of preferential charge or energy localization when incorporated in the system of respective regular bases. Most evidence of such behavior is based on experiments using γ-ray or other ionizing radiation. Here time dependent density functional theory (TDDFT) has been applied to investigate singlet and triplet excited state spectra of thioanalogues and some oxo-derivatives of nucleic-acid bases and compare the spectra to the calculated spectra of the regular bases as well as to the existing experimental data. It has been shown that thioanalogues have lower excitation singlet and triplet energies than are the respective energies in the regular bases. Energy localization on thioanalogues and their spectroscopic properties are related to the effect of sulfur substitution in such systems.
PRESSURE INDUCED STRUCTURAL PHASE TRANSITION AND SUPERCONDUCTIVITY IN TITANIUM METAL
Authors: AMAL RAJ A.
Published: March 2009

The electronic band structure, density of states, structural phase transition, and superconducting transition temperature under normal and high pressures are reported for titanium ( Ti ). The normal pressure band structure and density of states of hcp- Ti agree well with the previous calculations. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s, p → d transition. On the basis of band structure and total energy results obtained using full potential linear muffin-tin orbital method (FP LMTO), we predict a phase transformation sequence of α (hcp) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis we predict a δ (distorted bcc) phase which is not stable at any high pressures. According to the present calculation, at normal pressure, the superconducting transition of hcp- Ti occurs at 0.36 K which is in agreement with the experimental observation of 0.4 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp- Ti . On further increase of pressure Tc begins to decrease at a rate of 1.464 K/Mbar.
OPTIMALLY CONTROLLED VIBRATIONAL POPULATION TRANSFER IN A DIATOMIC QUANTUM SYSTEM
Authors: KUMAR PRAVEEN , SHARMA SITANSH , SINGH HARJINDER
Published: March 2009

A time-dependent formulation of quantum control is employed to investigate optimally controlled vibrational population transfer in a diatomic quantum system. The problem of finding the optimal laser field needed to achieve a specific quantum transition from an initial state to the desired target goal is formulated using an iterative method and the conjugate gradient method (CGM). The time-dependent Schrödinger equation is solved with interaction of laser radiation with matter included within a dipole approximation in the Hamiltonian. Appropriate boundary conditions are chosen for the evolution problem. The control objective is chosen as the value of transition probability from an initial state to a target state. A comparison is made between the results obtained using the iterative method and the CGM for optimization. Finally, quantum bits are encoded using the vibrational states of the diatomic in the regime of low-vibrational excitation.
ENVIRONMENTAL MANAGEMENT FRAMEWORKS AS AN ALTERNATIVE TO FARM-LEVEL EIA IN A GLOBAL BIODIVERSITY HOTSPOT: A PROPOSAL FROM THE CAPE FLORISTIC REGION, SOUTH AFRICA
Authors: DE VILLIERS CHARL C. , HILL RICHARD C.
Published: March 2009

Cultivation has been the primary driver of habitat transformation in South Africa. This paper explores the effectiveness of agricultural and, latterly, Environmental Impact Assessment (EIA) authorisation procedures in stemming biodiversity loss resulting from cultivation in the lowlands of the Cape Floristic Region, a global biodiversity hotspot. Owing to an activity-based focus, agri-environmental regulation has been largely unable to mitigate the cumulative effects of large-scale land clearance in threatened ecosystems. Case studies in the Sandveld and Slanghoek districts are used to argue that revised EIA regulations published in 2006 partly perpetuate the structural shortcomings of activity-based EIA. An ecosystem-based strategy for agri-environmental screening in biodiversity hotspots is introduced, drawing on conservation plans, the agricultural LandCare programme and the provision for Environmental Management Frameworks (EMF) in the 2006 EIA regulations. "Agri-EMFs", as a collaborative initiative that involves government, agricultural and non-governmental representatives, may present an effective alternative to the inefficiencies of project-level EIA.
Development and Validation of a Cervical Cancer Screening Self-Efficacy Scale for Low-Income Mexican American Women
Authors: Fernández María E. , Diamond Pamela M. , Rakowski William , Gonzales Alicia , Tortolero-Luna Guillermo , Williams Janet , Morales-Campos Daisy Y.
Published: March 2009

Although self-efficacy, a construct from social cognitive theory, has been shown to influence other screening behaviors, few measures currently exist for measuring Papanicolaou test self-efficacy. This article describes the development and psychometric testing of such a measure for Mexican American women. Data from two separate samples of Mexican American women ages ≥50 years, obtained as part of a study to develop and evaluate a breast and cervical cancer screening educational program, were used in the current study. Exploratory factor analysis indicated a single-factor solution and all item loadings were >0.73. Confirmatory analysis confirmed a single-factor structure with all standardized loadings >0.40 as hypothesized. The eight-item self-efficacy scale showed high internal consistency (Cronbach's α = 0.95). As hypothesized, self-efficacy was correlated with knowledge, prior experience, and screening intention. Logistic regression supported the theoretical relationship that women with higher self-efficacy were more likely to have had a recent Papanicolaou test. Findings showed a significant increase in self-efficacy following the intervention, indicating that the measure has good sensitivity to change over time. (Cancer Epidemiol Biomarkers Prev 2009;18(3):866–75)
Family History and Risk of Renal Cell Carcinoma: Results from a Case-Control Study and Systematic Meta-Analysis
Authors: Clague Jessica , Lin Jie , Cassidy Adrian , Matin Surena , Tannir Nizar M. , Tamboli Pheroze , Wood Christopher G. , Wu Xifeng
Published: March 2009

We conducted a case-control analysis, a family-based population analysis, and a meta-analysis to assess the role of family history of cancer and kidney cancer in association with the risk of renal cell carcinoma (RCC). A total of 325 cases and 329 controls were identified from an ongoing case-control study of RCC. Study variables were assessed through 45-minute structured face-to-face interviews. In the case-control analysis, a family history of any cancer (in first-degree relatives) was associated with a nonsignificant 1.2-fold increase in RCC risk [95% confidence interval (95% CI), 0.8-1.6]. The risk increased to 1.7 and became significant when the relative was a sibling (95% CI, 1.1-2.5). A family history of kidney cancer (kidney cancer in first-degree relatives) was associated with a 4.3-fold significantly increased risk of RCC (95% CI, 1.6-11.9). The cases reported a total of 2,536 first-degree relatives of which 21 (0.8%) had kidney cancer, and the controls reported a total of 2,333 first-degree relatives of which 5 (0.2%) had kidney cancer (P = 0.003). In the family-based population analysis, a family history of kidney cancer was associated with a 2.8-fold increased risk of RCC (95% CI, 1.0-7.8). The meta-analysis further confirmed this significant association with a 2.2-fold increased risk of RCC (95% CI, 1.6-2.9). To our knowledge, this is the first study to use three analytic strategies to investigate the association between a family history of kidney cancer and risk of RCC, and the first systematic evaluation of the relative risk for developing RCC associated with family history.(Cancer Epidemiol Biomarkers Prev 2008;18(3):801–7)
Trends in Colorectal Cancer Screening Utilization among Ethnic Groups in California: Are We Closing the Gap?
Authors: Maxwell Annette E. , Crespi Catherine M.
Published: March 2009

Background: Given the low prevalence of and racial/ethnic disparities in colorectal cancer screening, it is important to monitor whether prevalence and disparities are increasing or decreasing over time.

Methods: We estimated the prevalence of colorectal cancer screening by year (2001, 2003, and 2005), modality (endoscopy, fecal occult blood test, either), and recency (ever had, up-to-date) for the California population as a whole, major racial/ethnic groups (White, Black, Latino, Asian), and selected Asian subgroups (Chinese, Filipino, Japanese, Korean, Vietnamese) using data from the California Health Interview Survey. All prevalence estimates were age- and gender-standardized.

Results: From 2001 to 2005, prevalence of up-to-date screening increased significantly among Whites and Latinos but not among Blacks and Asian Americans. Screening prevalence varied substantially among Asian subgroups, with Korean, Filipino, and Vietnamese Americans having the lowest prevalence. Korean Americans were the only group in the analysis with a significant decline in screening prevalence from 2001 to 2005. The gap between the highest and the lowest up-to-date screening prevalence using any screening modality, exhibited by Japanese and Korean Americans, increased from 18% in 2001 to 30% in 2005.

Conclusions: Findings suggest that we need to intensify efforts to increase colorectal cancer screening, especially among Korean Americans but also among Filipinos, Vietnamese, and Latinos. (Cancer Epidemiol Biomarkers Prev 2009;18(3):752–9)
Texture Features from Mammographic Images and Risk of Breast Cancer
Authors: Manduca Armando , Carston Michael J. , Heine John J. , Scott Christopher G. , Pankratz V. Shane , Brandt Kathy R. , Sellers Thomas A. , Vachon Celine M. , Cerhan James R.
Published: March 2009

Mammographic percent density (PD) is a strong risk factor for breast cancer, but there has been relatively little systematic evaluation of other features in mammographic images that might additionally predict breast cancer risk. We evaluated the association of a large number of image texture features with risk of breast cancer using a clinic-based case-control study of digitized film mammograms, all with screening mammograms before breast cancer diagnosis. The sample was split into training (123 cases and 258 controls) and validation (123 cases and 264 controls) data sets. Age-adjusted and body mass index (BMI)–adjusted odds ratios (OR) per SD change in the feature, 95% confidence intervals, and the area under the receiver operator characteristic curve (AUC) were obtained using logistic regression. A bootstrap approach was used to identify the strongest features in the training data set, and results for features that validated in the second half of the sample were reported using the full data set. The mean age at mammography was 64.0 ± 10.2 years, and the mean time from mammography to breast cancer was 3.7 ± 1.0 (range, 2.0-5.9 years). PD was associated with breast cancer risk (OR, 1.49; 95% confidence interval, 1.25-1.78). The strongest features that validated from each of several classes (Markovian, run length, Laws, wavelet, and Fourier) showed similar ORs as PD and predicted breast cancer at a similar magnitude (AUC = 0.58-0.60) as PD (AUC = 0.58). All of these features were automatically calculated (unlike PD) and measure texture at a coarse scale. These features were moderately correlated with PD (r = 0.39-0.76), and after adjustment for PD, each of the features attenuated only slightly and retained statistical significance. However, simultaneous inclusion of these features in a model with PD did not significantly improve the ability to predict breast cancer. (Cancer Epidemiol Biomarkers Prev 2009;18(3):837–45)
The Relationship between Gene-Specific DNA Methylation in Leukocytes and Normal Colorectal Mucosa in Subjects with and without Colorectal Tumors
Authors: Ally Mina Sarah , Al-Ghnaniem Reyad , Pufulete Maria
Published: March 2009

CpG island methylation in the promoter regions of tumor suppressor genes has been shown to occur in normal colonic tissue and can distinguish between subjects with and without colorectal neoplasms. It is unclear whether this relationship exists in other tissues such as blood. We report the relationship between estrogen receptor gene (estrogen receptor α) methylation in leukocyte and normal colonic tissue DNA in subjects with and without colorectal neoplasia. DNA was extracted from frozen stored whole blood samples of 27 subjects with cancer, 30 with adenoma, 16 with hyperplastic polyps, and 57 disease-free subjects. DNA methylation in seven CpG sites close to the transcription start of estrogen receptor α was quantitated using pyrosequencing and expressed as a methylation index (average methylation across all CpG sites analyzed). Estrogen receptor α methylation in leukocyte DNA was compared with estrogen receptor α methylation in normal colonic mucosa DNA that had been previously determined in the same subjects. Estrogen receptor α was partially methylated (median, 4.3%; range, 0.0-12.6%) in leukocyte DNA in all subjects, with no significant difference between disease groups (P > 0.05). Estrogen receptor α methylation in leukocytes was 60% lower than estrogen receptor α methylation in normal colonic tissue (P < 0.001). Estrogen receptor α methylation in colonic tissue (P < 0.001) and smoking (P = 0.016) were determinants of estrogen receptor α methylation in leukocytes, independent of age, body mass index, gender, and disease status. In conclusion, there was a positive relationship between estrogen receptor α methylation in leukocytes and colonic tissue in subjects with and without colorectal tumors. However, unlike in colonic tissue, estrogen receptor α methylation in leukocytes was unable to distinguish between disease groups. (Cancer Epidemiol Biomarkers Prev 2009;18(3):922–8)