bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between ophthalmological and neuropaediatric findings in children adopted from Eastern Europe
Authors: Andersson Grönlund Marita , Landgren Magnus , Strömland Kerstin , Aring Eva , Svensson Leif , Tuvemo Torsten , Hellström Ann
Published: March 2009

Purpose:  This study aimed to evaluate and relate visual function, ocular dimensions and neuropaediatric findings in adoptees from Eastern Europe.

Methods:  We studied 72 of 99 children, born during 1990–95 and adopted from Eastern Europe to western Sweden during 1993–97. The children (mean age 7.5 years, range 4.8–10.5 years; 41 boys, 31 girls) were examined after a mean period of 5 years post‐adoption by a multidisciplinary team. Correlations between ophthalmological findings and neuropaediatric data were analysed.

Results:  Bivariate and regression analyses indicate a significant positive correlation between visual acuity (VA) and perceptual organization (p < 0.001), as well as between strabismus and verbal comprehension (p < 0.02). Fetal alcohol syndrome (FAS) was correlated with low VA (p < 0.02), subnormal stereovision (p < 0.009) and small optic discs (p < 0.02). Small head circumference was related to low VA (p < 0.015) and small optic discs (p < 0.03). Furthermore, small optic discs were related to low birthweight (p < 0.005) and preterm birth (p < 0.01). Large optic cups were correlated with poorer perceptual organization (p < 0.02).

Conclusions:  In this group of adoptees from Eastern Europe, ophthalmological findings were correlated to neuropaediatric findings, especially those arising from prenatal adverse events resulting in growth deficiency and central nervous system damage. Therefore, it is important and valuable with an ophthalmological examination in children adopted from Eastern Europe.
Comparison of laser in situ keratomileusis reoperation outcomes with the Moria M2 head 90 and 130 following previous photorefractive keratectomy or laser in situ keratomileusis
Authors: Pitkänen Antti , Pietilä Juhani , Mäkinen Petri , Huhtala Anne , Uusitalo Hannu
Published: March 2009

Purpose:  To compare the Moria Model Two (M2) automated microkeratome with the head 90 (intended to create a 120‐μm flap) to the head 130 (intended to create a 160‐μm flap) in reoperations following previous photorefractive keratectomy (PRK) or laser‐assisted in situ keratomileusis (LASIK) in terms of accuracy, predictability, safety and complications of the procedure.

Methods:  Eighty‐five eyes of 70 consecutive patients received LASIK with the Moria M2 microkeratome. Nine previously PRK‐operated eyes were reoperated with the head 90 and 37 eyes were reoperated with the head 130. Repeated LASIK was performed on 16 eyes with the head 90 and on 23 eyes with head the 130. Flap dimensions were measured and correlated to preoperative parameters.

Results:  The average flap thickness in the previously PRK‐operated eyes was 115.1 μm [range 82–137 μm, standard deviation (SD) 17.9] with the head 90 and 131.2 μm (range 105–171 μm, SD 19.8) with the head 130. In the previously LASIK‐operated eyes, the mean flap thickness was 139.2 μm (range 92–182 μm, SD 23.8) with the head 90 and 141.9 μm (range 109–179 μm, SD 15.2) with the head 130. There were no free or incomplete flaps or flaps with buttonholes in the study. There was no statistically significant difference in postoperative uncorrected visual acuity (UCVA) between the groups.

Conclusion:  In eyes with previous PRK or LASIK, LASIK reoperation offers a safe alternative for improving refractive outcomes. The Moria M2 head 90, especially in LASIK‐operated eyes, does not cut thinner flaps compared to the head 130.
Molecular characterization of the symbionts associated with marine nematodes of the genus Robbea‡
Authors: Bayer Christoph , Heindl Niels R. , Rinke Christian , Lücker Sebastian , Ott Joerg A. , Bulgheresi Silvia
Published: March 2009

Marine nematodes that carry sulfur‐oxidizing bacteria on their cuticle (Stilbonematinae, Desmodoridae) migrate between oxidized and reduced sand layers thereby supplying their symbionts with oxygen and sulfide. These symbionts, in turn, constitute the worms' major food source. Due to the accessibility, abundance and relative simplicity of this association, stilbonematids may be useful to understand symbiosis establishment. Nevertheless, only the symbiont of Laxus oneistus has been found to constitute one single phylotype within the Gammaproteobacteria. Here, we characterized the symbionts of three yet undescribed nematodes that were morphologically identified as members of the genus Robbea. They were collected at the island of Corsica, the Cayman Islands and the Belize Barrier Reef. The surface of these worms is covered by a single layer of morphologically undistinguishable bacteria. 18S rDNA‐based phylogenetic analysis showed that all three species belong to the Stilbonematinae, although they do not form a distinct cluster within that subfamily. 16S rDNA‐based analysis of the symbionts placed them interspersed in the cluster comprising the sulfur‐oxidizing symbionts of L. oneistus and of marine gutless oligochaetes. Finally, the presence and phylogeny of the aprA gene indicated that the symbionts of all three nematodes can use reduced sulfur compounds as an energy source.
Estimating leukocyte, platelet, and erythrocyte counts in rats by blood smear examination
Authors: Durbin Cathy , Guo Kevin , Hoffman Wherly , Eric Schultze A. , White Sandy
Published: March 2009

Background: The CBC is an essential test for assessing the health of rats used in drug development studies. Because of limited blood volume, estimates of cell counts from a blood smear would be valuable when other analytical methods of enumerating cells are not possible or available.

Objective: The purpose of this study was to develop a statistical model to accurately estimate WBC, platelet (PLT), and RBC counts in blood smears from rats.

Method: Blood smears and quantitative cell counts were obtained from vehicle‐treated male and female Fischer 344 rats (n=65) involved in a variety of studies. The numbers of WBCs, PLTs, and RBCs were estimated in 10 fields in the monolayer of smears using × 20 (WBC) or × 100 (PLT, RBC) objectives. Using a statistical model and the quantitative cell counts obtained on an ADVIA 120 hematology analyzer, formulas were developed to predict the quantitative counts from the estimates.

Results: Data were log‐transformed before analysis. A formula was derived using the slope and intercept of the regression line between cell estimates and ADVIA counts to predict WBC, PLT, and RBC counts based only on estimates. A second formula was developed for situations in which limited quantitative analyses may be available, and resulted in even more accurately predicted counts from smear estimates.

Conclusion: The formulas developed in this study can be a valuable tool in estimating cell counts from a blood smear when cell counting instruments are not available or when an instrument cell count needs to be verified. These formulas may be useful in the assessment of rat blood in discovery and lead optimization studies.
What is your diagnosis? Intra‐abdominal mass aspirate from a spayed dog with abdominal pain
Authors: Putwain Sarah , Archer Joy
Published: March 2009

Abstract:An 8‐year‐old, spayed female Labrador Retriever was presented for evaluation of unwillingness to exercise. On clinical examination abdominal pain was elicited, and a midabdominal mass was detected in survey radiographs. Ultrasound‐guided fine‐needle aspiration of the intra‐abdominal mass was done. The cytologic findings indicated chronic granulomatous inflammation with reactive fibroplasia, cholesterol crystals, and extracellular foreign material. The foreign material consisted of opaque, basophilic fragments of uniform width (5–10 μm) and variable length (30–180 μm) and was observed extracellularly and within macrophages. The material was birefringent under polarized light. Histologic examination of the excised mass confirmed the cytologic findings and a diagnosis of gossypiboma (textiloma) was made, consistent with retention of a surgical sponge. This case provides a unique example of the utility of fine‐needle aspiration for the diagnosis of gossypiboma.
What is your diagnosis? Vertebral mass in a dog
Authors: Khachatryan Artashes R. , Wills Tamara B. , Potter Kathleen A.
Published: March 2009

Abstract: A 1‐year‐old, castrated male, mixed‐breed dog was presented for sporadic episodes of kyphosis, tremors, and vocalizing. On neurologic examination, the lesion was localized to spinal cord segments T3–L3. Magnetic resonance imaging of the spine showed an expansile mass occupying most of the ventral aspect of the spinous process of T6. Fine‐needle aspirates of the mass were examined cytologically. A moderately cellular population of pleomorphic spindle cells and abundant mucinous matrix were observed. The cytologic diagnosis was spindle cell neoplasia, with myxosarcoma and fibrosarcoma as the primary differential diagnoses. The dog was euthanized. Histopathologic evaluation of the mass and surrounding tissue confirmed a low‐grade spindle cell sarcoma, with severe compressive myelopathy and mild neutrophilic inflammation. The neoplastic cells stained positive for mucopolysaccharides with Alcian blue, resulting in a final diagnosis of low‐grade (grade 1) myxosarcoma. Fine‐needle aspiration was useful in making a preliminary diagnosis of myxosarcoma in this case. Myxosarcoma should be included in the differential diagnosis for a vertebral mass in a young dog.
Accuracy and Convergence Using a Local Interaction Simulation Approach in One, Two, and Three Dimensions
Authors: Sundararaman Shankar , Adams Douglas E.
Published: March 2009

Guided waves are utilized in structural health monitoring for identifying damage in material components. Simulations can be used to examine how elastic waves propagate in components to help in selecting measurement and data analysis techniques. In this work, the influence of grid size and the frequency sample rate on the amplitude accuracy and convergence of local interaction simulation approach/sharp interface model (LISA/SIM) numerical simulations are studied as they pertain to guided wave propagation in structural materials. These issues are studied in all three dimensions, and amplitude distortion with respect to the Courant–Friedrich–Lewy criterion is explored. The LISA/SIM enables accurate and fast modeling of localized and sharp changes in material properties across interfaces associated with heterogeneities and/ or boundaries. The validity of the simulation is demonstrated by comparing simulated responses with experimentally measured data. Additionally, Lamb wave dispersion curves are extracted through the course of the convergence study using a broadband pulse and the two-dimensional fast Fourier transform method.
Evaluation of Mixed-Mode Stress Intensity Factors for a Sharp Notch-tip With Curved and Stressed Edges
Authors: Chang J. H. , Fan J. F.
Published: March 2009

For a sharp notch with curved edges and subjected to surface tractions along the edges, the fracture parameters (in particular, the stress intensity factors and the size of a singular-dominant zone) are significantly affected by the near-tip geometric and loading conditions. In this paper, a pair of contour integrals termed JkR is presented for calculating the mixed-mode stress intensity factors at such a sharp notch-tip. Furthermore, by proper use of the integrals, the extent of the singular-dominant zone can be effectively characterized. Since no a priori auxiliary (or, complementary) solutions are required in its formulation, the approach appears to be feasible for problems of arbitrary notch angles and curved shapes. Also, no special treatments are required for the modeling of the near-tip singular behavior so that the integration can be performed by direct use of numerical schemes such as finite element method.
Identification of Linear Structural Systems With a Limited Set of Input-Output Measurements
Authors: Yu Jun , Imbimbo Maura , Betti Raimondo
Published: March 2009

In this paper, a methodology is presented for the identification of the complete mass, damping, and stiffness matrices of a dynamical system using a limited number of time histories of the input excitation and of the response output. Usually, in this type of inverse problems, the common assumption is that the excitation and the response are recorded at a sufficiently large number of locations so that the full-order mass, damping, and stiffness matrices can be estimated. However, in most applications, an incomplete set of recorded time histories is available and this impairs the possibility of a complete identification of a second-order model. In this proposed approach, all the complex eigenvectors are correctly identified at the instrumented locations (either at a sensor or at an actuator location). The remaining eigenvector components are instead obtained through a nonlinear least-squares optimization process that minimizes the output error between the measured and predicted responses at the instrumented locations. The effectiveness of this approach is shown through numerical examples and issues related to its robustness to noise polluted measurements and to uniqueness of the solution are addressed.
A Screw Theory of Timoshenko Beams
Authors: Selig J. M. , Ding Xilun
Published: March 2009

In this work, the classic theory of Timoshenko beams is revisited using screw theory. The theory of screws is familiar from robotics and the theory of mechanisms. A key feature of the screw theory is that translations and rotations are treated on an equal footing and here this means that bending, torsion, and extensions can all be considered together in a particularly simple manner. By combining forces and torques into a six-dimensional vector called a wrench, Hooke’s law for the Timoshenko beam can be written in a very simple form. From here simple expressions can be found for the kinetic and potential energy densities of the beam. Hence equations of motion for small vibrations of the beam can be easily derived. The screw theory also leads to a new understanding of the boundary conditions for beams. It is demonstrated that simple boundary conditions are closely related to mechanical joints. In order to set up the boundary conditions for a beam attached to a joint, a system of wrenches dual to the screws representing the freedoms of the joint must be found. Finally, a screw version of the Rayleigh–Ritz numerical method is introduced. An example is investigated in which the boundary conditions on the beam lead to vibrational modes of the beam involving bending, torsion, and extension at the same time.
An Inviscid Solution for Modeling of Tornadolike Vortices
Authors: Xu Zhuyun , Hangan Horia
Published: March 2009

An inviscid tornadolike vortex is analytically modeled using a free narrow jet solution combined with a modified Rankine vortex. An empirical and simplified solution to existing models is defined for flows similar to the ones simulated in Ward-type vortex chambers. Velocity profiles are calculated for a particular swirl ratio Sr=0.28. The model shows reasonable agreement with existing experimental measurements by Baker (1981, “Boundary Layers in Laminar Vortex Flows,” Ph.D. thesis, Purdue University, West Lafayette, IN) and the numerical simulation by Wilson and Rotunno (1986, “Numerical Simulation of a Laminar End-Wall Vortex and Boundary Layer,” Phys. Fluids, 29(12), pp. 3993–4005).
Effective Properties of Carbon Nanotube and Piezoelectric Fiber Reinforced Hybrid Smart Composites
Authors: Ray M. C. , Batra R. C.
Published: March 2009

We propose a new hybrid piezoelectric composite comprised of armchair single-walled carbon nanotubes and piezoelectric fibers as reinforcements embedded in a conventional polymer matrix. Effective piezoelectric and elastic properties of this composite have been determined by a micromechanical analysis. Values of the effective piezoelectric coefficient e31 of this composite that accounts for the in-plane actuation and of effective elastic properties are found to be significantly higher than those of the existing 1–3 piezoelectric composites without reinforced with carbon nanotubes.
An Experimental Study of Contact Forces During Oblique Elastic Impact
Authors: Garland Philip P. , Rogers Robert J.
Published: March 2009

Low and high speed impacts frequently occur in many mechanical processes. Although widely studied, rarely are normal and tangential force time-waveforms measured, as generally these are very difficult measurements to do accurately. This paper presents, for the first time, a comprehensive set of experimentally obtained contact force waveforms during oblique elastic impact for a range of initial velocities and incidence angles. The experimental apparatus employed in this study was a simple pendulum consisting of a spherical steel striker suspended from a steel wire. The contact force time-waveforms were collected using a tri-axial piezoelectric force transducer sandwiched between a spherical target cap and a large block. The measured contact forces showed that loading was essentially limited to the normal and tangential directions in the horizontal plane. Analysis of the maximum normal and tangential forces for the near glancing angles of incidence indicated a friction coefficient that varies linearly with initial tangential velocity. The essential features of tangential force reversal during impact predicted by previous continuum models are confirmed by the experimental force results.
An Argument Against Augmenting the Lagrangean for Nonholonomic Systems
Authors: Roithmayr Carlos M. , Hodges Dewey H.
Published: March 2009

Although it is known that correct dynamical equations of motion for a nonholonomic system cannot be obtained from a Lagrangean that has been augmented with a sum of the nonholonomic constraint equations weighted with multipliers, previous publications suggest otherwise. One published example that was proposed in support of augmentation purportedly demonstrates that an accepted method fails to produce correct equations of motion whereas augmentation leads to correct equations. This present paper shows that, in fact, the opposite is true. The correct equations, previously discounted on the basis of a flawed application of the Newton–Euler method, are verified by using Kane’s method together with a new approach for determining the directions of constraint forces.
Feasibility of Metallic Structural Heat Pipes as Sharp Leading Edges for Hypersonic Vehicles
Authors: Steeves Craig A. , He Ming Y. , Kasen Scott D. , Valdevit Lorenzo , Wadley Haydn N. G. , Evans Anthony G.
Published: March 2009

Hypersonic flight with hydrocarbon-fueled airbreathing propulsion requires sharp leading edges. This generates high temperatures at the leading edge surface, which cannot be sustained by most materials. By integrating a planar heat pipe into the structure of the leading edge, the heat can be conducted to large flat surfaces from which it can be radiated out to the environment, significantly reducing the temperatures at the leading edge and making metals feasible materials. This paper describes a method by which the leading edge thermal boundary conditions can be ascertained from standard hypersonic correlations, and then uses these boundary conditions along with a set of analytical approximations to predict the behavior of a planar leading edge heat pipe. The analytical predictions of the thermostructural performance are verified by finite element calculations. Given the results of the analysis, possible heat pipe fluid systems are assessed, and their applicability to the relevant conditions determined. The results indicate that the niobium alloy Cb-752, with lithium as the working fluid, is a feasible combination for Mach 6–8 flight with a 3 mm leading edge radius.
Scattering by a Cavity in an Exponentially Graded Half-Space
Authors: Martin P. A.
Published: March 2009

An inhomogeneous half-space containing a cavity is bonded to a homogeneous half-space. Waves are incident on the interface and the problem is to calculate the scattered waves. For a circular cavity in an exponentially graded half-space, it is shown how to solve the problem by constructing an appropriate set of multipole functions. These functions are singular on the axis of the cavity, they satisfy the governing differential equation in each half-space, and they satisfy the continuity conditions across the interface between the two half-spaces. Seven recent publications are criticized: They do not take proper account of the interface between the two half-spaces.
Analysis of Non-Newtonian Reactive Flow in a Cylindrical Pipe
Authors: Makinde Oluwole Daniel
Published: March 2009

In this paper, a mathematical investigation on the effect of convective cooling on a reactive third-grade fluid flowing steadily through a cylindrical pipe is performed. It is assumed that the system exchange heat, with the ambient following Newton’s cooling law and the reaction, is exothermic under Arrhenius kinetics, neglecting the consumption of the material. The simplified governing nonlinear equations of momentum and energy are obtained and solved using a special type of the Hermite–Padé approximation technique. The important properties of the overall flow structure including velocity field, temperature field, bifurcations, and thermal criticality conditions are discussed.
Time-Derivative Preconditioning Methods for Multicomponent Flows—Part II: Two-Dimensional Applications
Authors: Housman Jeffrey A. , Kiris Cetin C. , Hafez Mohamed M.
Published: March 2009

A time-derivative preconditioned system of equations suitable for the numerical simulation of multicomponent/multiphase inviscid flows at all speeds was described in Part I of this paper. The system was shown to be hyperbolic in time and remain well conditioned in the incompressible limit, allowing time marching numerical methods to remain an efficient solution strategy. Application of conservative numerical methods to multicomponent flows containing sharp fluid interfaces was shown to generate nonphysical pressure and velocity oscillations across the contact surface, which separates the fluid components. It was demonstrated using the one-dimensional Riemann problem that these oscillations may lead to stability problems when the interface separates fluids with large density ratios, such as water and air. The effect of which leads to the requirement of small physical time steps and slow subiteration convergence for the implicit time marching numerical method. Alternatively, the nonconservative and hybrid formulations developed by the present authors were shown to eliminate this nonphysical behavior. While the nonconservative method did not converge to the correct weak solution for flow containing shocks, the hybrid method was able to capture the physically correct entropy solution and converge to the exact solution of the Riemann problem as the grid is refined. In Part II of this paper, the conservative, nonconservative, and hybrid formulations described in Part I are implemented within a two-dimensional structured body-fitted overset grid solver, and a study of two unsteady flow applications is reported. In the first application, a multiphase cavitating flow around a NACA0015 hydrofoil contained in a channel is solved, and sensitivity to the cavitation number and the spatial order of accuracy of the discretization are discussed. Next, the interaction of a shock moving in air with a cylindrical bubble of another fluid is analyzed. In the first case, the cylindrical bubble is filled with helium gas, and both the conservative and hybrid approaches perform similarly. In the second case, the bubble is filled with water and the conservative method fails to maintain numerical stability. The performance of the hybrid method is shown to be unchanged when the gas is replaced with a liquid, demonstrating the robustness and accuracy of the hybrid approach.
Solar Power Wires Based on Organic Photovoltaic Materials
Authors: Lee Michael R. , Eckert Robert D. , Forberich Karen , Dennler Gilles , Brabec Christoph J. , Gaudiana Russell A.
Published: March 2009

Organic photovoltaics in a flexible wire format has potential advantages that are described in this paper. A wire format requires long-distance transport of current that can be achieved only with conventional metals, thus eliminating the use of transparent oxide semiconductors. A phase-separated, photovoltaic layer, comprising a conducting polymer and a fullerene derivative, is coated onto a thin metal wire. A second wire, coated with a silver film, serving as the counter electrode, is wrapped around the first wire. Both wires are encased in a transparent polymer cladding. Incident light is focused by the cladding onto to the photovoltaic layer even when it is completely shadowed by the counter electrode. Efficiency values of the wires range from 2.79% to 3.27%.
Lung cancer mortality and fibre exposures among North Carolina asbestos textile workers
Authors: Loomis D , Dement J M , Wolf S H , Richardson D B
Published: March 2009

Objective:

To describe mortality among workers exposed to chrysotile asbestos and evaluate the relationship between lung cancer and asbestos fibre exposure.

Methods:

Workers employed for at least 1 day between 1 January 1950 and 31 December 1973 in any of four plants in North Carolina, USA that produced asbestos textile products were enumerated. Vital status was ascertained through 31 December 2003. Historical exposures to asbestos fibres were estimated from work histories and 3578 industrial hygiene measurements taken in 1935–1986. Mortality of the cohort was compared with that of the national population via standardised mortality ratios (SMRs). Exposure–response relationships for lung cancer were examined within the cohort using Poisson regression to compute adjusted mortality rate ratios.

Results:

Follow-up of 5770 workers included in the cohort resulted in 181 640 person-years of observation, with 2583 deaths from all causes and 277 from lung cancer. Mortality from all causes, all cancers and lung cancer was significant higher than expected, with SMRs of 1.47 for all causes, 1.41 for all cancer and 1.96 (95% CI 1.73 to 2.20) for lung cancer. SMRs for pleural cancer, mesothelioma and pneumoconiosis were also elevated. The risk of lung cancer and asbestosis increased with cumulative fibre exposure (RR 1.102 per 100 fibre-year/ml, 95% CI 1.044 to 1.164, and RR 1.249 per 100 fibre-year/ml, 95% CI 1.186 to 1.316, respectively, for total career exposure).

Conclusions:

This study provides further evidence that exposure to chrysotile asbestos in textile manufacturing is associated with increased risk of lung cancer, asbestosis cancer of the pleura and mesothelioma.
SOME PROBLEMS OF NANOPROBE MODELING
Authors: ANDRIANOV SERGE N. , EDAMENKO NIKOLAY S. , TERESHONKOV YURY V.
Published: March 2009

We treat here the process of simulation of ion micro- and nanoprobes in detail using the matrix formalism for Lie algebraic tools. Similar approach allows realizing necessary analytical and numerical modeling procedures.

Nowadays ion micro- and nanoprobes are extensively applied in different branches of science and industry. It is known that similar facilities are very sensitive to certain of steering parameters of the systems. In other words, similar beam lines are high precision systems, requiring preliminary modeling for thorough analysis of possible optimal working regimes. In this paper we consider analytical and numerical models, which allow one to study effect of various aberrations on basic beam characteristics. Research process performs from linear to nonlinear model with step by step including nonlinear effects of different nature.

Previous papers of the authors consider some aspects of nonlinear models. The present paper deals with full conception of modeling process, generalizing most essential aberrations and providing adequate solution methods.
BEAM-BASED FEEDBACK SYSTEM FOR THE INTERNATIONAL LINEAR COLLIDER
Authors: IVANOV VALENTIN
Published: March 2009

The algorithms and computer codes for linac Feedback system were developed at SLAC during 1991–2004. The efficiency of that system have been demonstrated for the SLC, CLIC, TESLA and NLC projects. International Linear Collider (ILC) has its own features. Ground motion (GM) oscillations play a dominant role here. It forced to implement a new version of the Linac Feedback Simulation Code based on the previous developments. A set of benchmark tests and realistic simulations for the whole ILC structure have been performed. The effects of different GM models, BPM resolution, time intervals, initial misalignments, a dispersion-free steering (DFS), and a quad jitter have been studied.
GREEN'S FUNCTION TECHNIQUE IN FORMING INTENSIVE BEAMS
Authors: IVANOV VALENTIN
Published: March 2009

The numerical extensions of the Green's function technique have been used to represent a space charge of intensive beams in three-dimensional (3D) case. The introduced tri-linear approximation helps to avoid the numerical noise of space charge density on the beam boundary, peculiar to the commonly used piecewise-constant approximation. Both artificial and real singularities for the potential and field gradients have been analyzed. The efficiency of the suggested numerical algorithms has been demonstrated by benchmark tests. The design of the electron gun for an X-band sheet-beam klystron has been done using these algorithms.
BEAM DYNAMICS OPTIMIZATION FOR THE XFEL PHOTO INJECTOR
Authors: KRASILNIKOV MIKHAIL
Published: March 2009

The main challenge for the European XFEL photo injector is the production of 1 nC electron beams with a normalized transverse emittance of 0.9 mm mrad. The photo injector setup consists of a 1.5-cell L-band rf gun cavity supplied with solenoids for beam focusing and emittance compensation and the first accelerating section with 8 TESLA superconducting cavities. The first 4 cavities are used as a booster to provide by proper choice of its position, gradient and phase matching conditions for the emittance conservation.

For optimization of the beam dynamics in the photo injector, a staged algorithm, based on ASTRA simulations, has been developed. The first stage considers the emission of electrons from a photo cathode. The cathode laser energy and its transverse parameters are adjusted to produce a bunch charge of 1 nC in presence of space charge forces (including image charge at the cathode) and Schottky-like effects. The second stage contains rf gun cavity and solenoid optimization. The booster position, gradient and initial phase are optimized at the third stage yielding the minimum emittance at the photo injector exit. Results of the XFEL photo injector optimization will be presented.

Besides simulations experimental studies towards XFEL photo injector are carried out. The photo injector test facility at DESY in Zeuthen (PITZ) develops photo injectors for FELs, including FLASH and the European XFEL. A thorough comparison of measured data with results of beam dynamics simulations is one of the main PITZ goals. Detailed experimental studies on photo emission processes, thermal emittance, transverse and longitudinal phase space of the electron beam are being performed together with beam dynamics simulations. This aims to result in better understanding of beam dynamics in high brightness photo injectors. Experimentally obtained photo injector characteristics (like thermal emittance) have to be used in an additional optimization of the photo injector resulting in more realistic beam dynamics simulations. Results of these studies will be reported as well.
ROBUST STABILITY ANALYSIS OF LINEAR PERIODIC SYSTEMS WITH TIME DELAY
Authors: LETYAGINA OLGA N. , ZHABKO ALEXEY P.
Published: March 2009

In this paper, a procedure for construction of quadratic Lyapunov-Krasovskii functionals for linear time delay systems with periodic coefficients is proposed. Functionals are used to derive robust stability conditions. The problem of computation of Lyapunov matrices for functionals is reduced to computation of solutions of an auxiliary two-point boundary problem for a special delay free system of matrix equation.
EVOLUTIONARY ALGORITHM FOR THE NEUTRINO FACTORY FRONT END DESIGN
Authors: POKLONSKIY ALEXEY A. , NEUFFER DAVID
Published: March 2009

The Neutrino Factory is an important tool in the long-term neutrino physics program. Substantial effort is put internationally into designing this facility in order to achieve desired performance within the allotted budget. This accelerator is a secondary beam machine: neutrinos are produced by means of the decay of muons. Muons, in turn, are produced by the decay of pions, produced by hitting the target by a beam of accelerated protons suitable for acceleration. Due to the physics of this process, extra conditioning of the pion beam coming from the target is needed in order to effectively perform subsequent acceleration. The subsystem of the Neutrino Factory that performs this conditioning is called Front End, its main performance characteristic is the number of the produced muons.

Evolutionary Algorithms demonstrated themselves as a reliable and efficient tool for exploration, optimization and ultimately decision-making during the design process. In this work we describe the scenario for the Neutrino Factory Front End production optimization via the GATool Evolutionary Algorithm implemented in COSY Infinity and discuss the results of this optimization.
CALCULATION OF NONLINEAR TUNE SHIFT USING BEAM POSITION MEASUREMENT RESULTS
Authors: SNOPOK PAVEL , BERZ MARTIN , JOHNSTONE CAROL
Published: March 2009

The calculation of the nonlinear tune shift with amplitude based on the results of measurements and the linear lattice information is discussed. The tune shift is calculated based on a set of specific measurements and some extra information which is usually available, namely that about the size and particle distribution in the beam and the linear optics effect on the particles. The method to solve this problem uses the technique of normal form transformation.

The proposed model for the nonlinear tune shift calculation is compared to both the numerical results for the nonlinear model of the Tevatron accelerator and the independent approximate formula for the tune shift by Meller et al. The proposed model shows a discrepancy of about 2%.
RECENT PROGRESS ON THE 6D COOLING SIMULATIONS IN THE GUGGENHEIM CHANNEL
Authors: SNOPOK PAVEL , HANSON GAIL , KLIER AMIT
Published: March 2009

The RFOFO ring is considered to be one of the most promising six-dimensional cooling channels proposed for the future muon collider. It has a number of advantages over other cooling channels, but it also has certain drawbacks. The injection and extraction issue as well as the absorber overheating are its main problems. In this article the simulations of a possible solution to these problems, the RFOFO helix, commonly referred to as the Guggenheim channel, are studied in detail. The details of the tracking studies of both the idealized and realistic lattices are presented and compared to the performance of the underlying RFOFO cooling ring design.
PLASMA STABILIZATION BASED ON MODEL PREDICTIVE CONTROL
Authors: SOTNIKOVA MARGARITA
Published: March 2009

The nonlinear model predictive control algorithms for plasma current and shape stabilization are proposed. Such algorithms are quite suitable for the situations when the plant to be controlled has essentially nonlinear dynamics. Besides that, predictive model based control algorithms allow to take into account a lot of requirements and constraints involved both on the controlled and manipulated variables. The significant drawback of the algorithms is that they require a lot of time to compute control input at each sampling instant. In this paper the model predictive control algorithms are demonstrated by the example of plasma vertical stabilization for ITER-FEAT tokamak. The tuning of parameters of algorithms is performed in order to decrease computational load.
SPECTRAL APPROACH TO H-OPTIMIZATION OF PLASMA CONTROL
Authors: VEREMEY EVGENY
Published: March 2009

This paper presents a spectral approach to H-optimal linear synthesis with the application for tokamak plasma control systems. Two main problems of a synthesis are discussed: the mean square optimization and the appropriate guaranteeing interpretation. The simple computational technique to solve these problems is proposed. Their implementation is illustrated by the example on the base of one variant of ITER tokamak model for the plasma vertical feedback control.
COMPUTATION OF HIGH-ORDER MAPS TO MULTIPLE MACHINE PRECISION
Authors: WITTIG ALEXANDER , BERZ MARTIN
Published: March 2009

The Beam Dynamics simulation package in COSY INFINITY is built upon a differential algebra data type. With it, it is possible to compute transfer maps or arbitrary systems to arbitrary order. However, this data type is limited by the precision of the underlying floating point number model provided by the computer processor.

We will present a method to extend the effective precision of the calculations based purely on standard floating point operations. Those algorithms are then integrated into the differential algebra data type to efficiently extend the available precision, without unnecessarily affecting overall efficiency. To that effect, the precision of each coefficient is adjusted automatically during the calculation.

We will then proceed to show the effectiveness of our implementation by calculating high precision maps of combinations of homogeneous dipole segments, for which the exact results are known, and comparing the high precision coefficients with the results produced by the traditional COSY beam physics package.
BIAS DEPENDENCE OF SPIN TRANSFER TORQUE IN A MAGNETIC TUNNEL JUNCTION
Authors: CUI J. , YANG Y. H. , WANG J.
Published: March 2009

We report a theoretical study on the bias dependence of the current-induced torque in the noncollinear ferromagnet/barrier/ferromagnet (FM) tunnel junction. By using the Keldysh–Green function technique, we derived an analytic expression of the spin transfer torque (STT) based on a continuum model. It was found that for finite bias, the torque induced by current increases monotonically with bias and is nearly antisymmetric with regard to the current direction, which agrees with the experimental observation on the STT in the spin valve system.
AN EXTENDED OV MODEL WITH CONSIDERATION OF DRIVER'S MEMORY
Authors: TANG T. Q. , HUANG H. J. , ZHAO S. G. , XU G.
Published: March 2009

In this paper, the optimal velocity (OV) model is extended to take account of the effect that the driver's memory has on the car-following behavior. The stability condition of the proposed model is obtained by using linear stability theory. The modified Korteweg-de Vries (mKdV) equation is obtained and solved. Traffic flows in the headway-sensitivity space are classified into three types as stable, metastable and unstable. Both analytical and simulation results show that introduction of driver's memory in the acceleration can improve the stability of traffic flow. It is also found that the stable region will be enlarged with the increase of the past information considered. Finally, numerical tests show that properly considering driver's memory can improve the stability of traffic flow.
PRESSURE-INDUCED ELECTRONIC PHASE TRANSITIONS AND SUPERCONDUCTIVITY IN TITANIUM
Authors: IYAKUTTI K. , NIRMALA LOUIS C. , ANURATHA S. , MAHALAKSHMI S.
Published: March 2009

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium ( Ti ) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB 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. At ambient pressure, the superconducting transition occurs at 0.354 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. The highest value of Tc(P) estimated is 5.043 K for hcp–Ti , 4.538 K for ω– Ti and 4.85 K for bcc – Ti . From this, it is inferred that the maximum value of Tc(P) is rather insensitive to the crystal structure of Ti . The nonlinearities in Tc(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω- Ti > hcp - Ti > bcc- Ti > γ- Ti .
MELTING OF THE VORTEX LATTICE IN LAYERED SUPERCONDUCTORS
Authors: FENG BO , WU ZHIGANG , LI DINGPING
Published: March 2009

The structure function of the vortex lattice of layered superconductor is calculated to one-loop order. Based on a phenomenological melting criterion concerning the Debye–Waller factor, we calculate the melting line of the vortex lattice, and compare our results to Monte Carlo simulation and experiment. We find that our results are in good agreement with the Monte Carlo results. Moreover, our analytic calculation of the melting line of BSCCO fits the experiment reasonably.
DEVELOPING A TOOL FOR A QUALITATIVE MEASUREMENT OF PINNING FORCES USING ROTATIONAL MAGNETIZATION EXPERIMENTS
Authors: OBAIDAT I. M.
Published: March 2009

We have investigated the behavior of vortices in a polycrystalline YBa 2 Cu 3 O 7-δ disk sample using rotational magnetization-vector (RMV) measurements. The measurements were conducted in the field-cooled (FC) and the zero-field cooled (ZFC) states for several values of applied magnetic field parallel to the sample surface at 4.2 K and for various angles of rotation (θ rot ) up to 360°. The total magnetic flux density, B, in the sample at any rotational angle was considered to be composed of two types of vortices: weakly pinned vortices that rotate frictionally in the opposite direction of sample rotation and strongly pinned vortices that rotate rigidly in the same direction of sample rotation. From the rate of change of these two types of vortices and the rate of change of B, we were able to develop a tool to qualitatively describe the average strength of pinning centers in high-temperature superconductors.
QUANTUM SIZE EFFECTS OF HYDROGEN IMPURITY AT OFF-CENTER DONOR ATOM IN SPHERICAL QUANTUM DOTS
Authors: HUANG YUNG SHENG , HUANG JUNG SHENG , LEE KUAN WEI , CHANG FANG-LING
Published: March 2009

We obtain the numerical solutions for a single electron energy level of a hydrogen impurity confined inside an off-center donor in a spherical quantum dot. The energy spectrum of single electron impurity for off-center donor atom subject to screened Coulomb's attractive potential barrier well is presented. Using B-spline finite element method, we generate a complete set of wavefunctions within the central unit cell, and through the perturbation theory, the whole energy spectrum of an impurity at low temperature can be explored. We find that the energy splitting and different related magnetic quantum number ml, i.e., (n, l, ml) varies with quantum dot size. This is due to the fact that quantum confinement effect lifts the degeneracy which comes from the Coulomb interaction. On the other hand, the phenomena of energy spectrum splitting under this model is an analogous case, considering that degeneracy of hydrogen energy levels in free space has been lifted by an external magnetic field (Zeeman effect).
DYNAMICS OF VISCOUS DISSIPATIVE GRAVITATIONAL COLLAPSE: A FULL CAUSAL APPROACH
Authors: HERRERA L. , DI PRISCO A. , FUENMAYOR E. , TROCONIS O.
Published: March 2009

The Misner and Sharp approach to the study of gravitational collapse is extended to the viscous dissipative case in both the streaming out and the diffusion approximations. The dynamical equation is then coupled to causal transport equations for the heat flux, the shear, and the bulk viscosity, in the context of Israel–Stewart theory, without excluding the thermodynamics viscous/heat coupling coefficients. The result is compared with previous works where these later coefficients were neglected and viscosity variables were not assumed to satisfy causal transport equations. Prospective applications of this result to some astrophysical scenarios are discussed.
THE COSMOLOGICAL DYNAMICS OF INTERACTING HOLOGRAPHIC DARK ENERGY MODEL
Authors: SETARE M. R. , VAGENAS ELIAS C.
Published: March 2009

Motivated by the recent observations for cosmic acceleration and the suitable evolution of the universe provided an interaction (decay of dark energy to matter) is incorporated in a cosmological model, we study the cosmological evolution of the interacting holographic dark energy scenario. Critical points are derived and their corresponding cosmological models are presented. The dynamical character of these models is revealed.
EXTENDED STRUCTURE OF GALAXIES AND COSMIC ENERGY EQUATION
Authors: AHMAD FAROOQ , WAHID ABDUL , MALIK MANZOOR A. , MASOOD SAJAD
Published: March 2009

We derive the cosmic energy equation for extended mass structures (i.e., galaxies with halos) which cluster gravitationally in the expanding universe. From this cosmic energy equation, we study the quasi-static evolution for nonpoint mass system of galaxies. Using this cosmic energy equation, we examine the growth of correlation potential energy for the extended masses. We also derive the expression for virial mass and try to account for the dark matter present in the halos of the galaxies.
WKB-TYPE APPROXIMATION TO NONCOMMUTATIVE QUANTUM COSMOLOGY
Authors: MENA E. , OBREGÓN O. , SABIDO M.
Published: March 2009

In this paper, we develop and apply the WKB-type approximation to several examples of noncommutative quantum cosmology, obtaining the time evolution of the noncommutative universe. This is accomplished by starting from a noncommutative quantum formulation of cosmology, where the noncommutativity is introduced by a deformation on the minisuperspace variables. This procedure gives a straightforward algorithm to incorporate noncommutativity into cosmology and inflation.