bluuebunny/crossref_metadata_2025 huggingface dataset:
Specific mechanism of use‐dependent channel block of calcium‐permeable AMPA receptors provides activity‐dependent inhibition of glutamatergic neurotransmission
Authors: Zaitsev A. V. , Kim K. K. , Fedorova I. M. , Dorofeeva N. A. , Magazanik L. G. , Tikhonov D. B.
Published: April 2011

Non‐technical summary  Calcium‐permeable (CP) AMPA receptors play an important role in many synaptic functions and neuronal death. In this study, we investigated the blocking activity of a selective CP‐AMPAR channel blocker, IEM‐1925, and discovered that the blocker preferentially inhibits receptor activity at an increased frequency of synapse stimulation and in the continuous presence of the agonist. The activity‐dependent block described in this study may serve as a useful means for answering important questions about the specific role of CP‐AMPARs, as it opens a new way to modulate CP‐AMPAR‐mediated transmission using a physiologically relevant approach. It allows for the examination of specific involvement of CP‐AMPARs in the physiological and pathological processes, including high‐frequency synaptic activity or increase of the steady‐state glutamate concentration.
An Approach to Constraint-Based and Mass-Customizable Product Design
Authors: Nordin Axel , Hopf Andreas , Motte Damien , Bjärnemo Robert , Eckhardt Claus-Christian
Published: April 2011

In traditional product development, several iterations are usually necessary to obtain a successful compromise between constraints emanating from engineering, manufacturing, and aesthetics. Moreover, this approach to product development is not well suited for true mass-customization, as the manufacturing company remains in control of all aspects of the shape of the product-to-be. In this article, we propose an alternative approach that would (1) allow for an improved integration of industrial design into the product development process and (2) enhance the creative repertoire of industrial designers, which (3) would result in significantly improved prospects for mass-customization. The industrial design process may benefit from using advanced and aesthetically interesting morphologies emanating from the areas of mathematics and nature. Such complex morphologies can only be manipulated (analyzed and represented) by means of specific algorithms. On one hand, this requires a shift from established industrial design practice, where the industrial designer is in total control of the product form; on the other hand, it makes it fully possible to compute form so that it complies with engineering and manufacturing constraints. In this setup, the industrial designer still has control of the final result, in that she or he can choose from a set of valid forms. This approach would greatly reduce the number of iterations in the product development process between industrial design, engineering, and production. Naturally, such an approach also allows for advanced mass-customization by allowing consumers to use these tools. Within this approach, a table generation system has been developed: A system that generates tables whose support structure is based on a Voronoi diagram that fulfills structural and manufacturing constraints while being aesthetically appealing.
Creeping Contours: A Multilabel Image Segmentation Method for Extracting Boundary Surfaces of Parts in Volumetric Images
Authors: Shammaa Haitham , Suzuki Hiromasa , Ohtake Yutaka
Published: April 2011

In this work, we introduce a method named creeping contours for image segmentation into component parts for the purpose of extracting the boundary surfaces of these parts. Creeping contours are contours that expand following a speed function defined by the gradient and curvature at contour points, starting from an initial contour position defined either manually or automatically. Contours in the image creep simultaneously at different speeds, while labels are assigned to contour pixels by the defined creeping condition. We also demonstrate the effectiveness of the proposed method by segmenting 2D grayscale images and 3D volumetric computed tomography images of mechanical parts into multiple segments and generating the boundary surfaces of these parts.
Proactive Assembly Oriented Design Approach Based on the Deployment of Functional Requirements
Authors: Demoly Frédéric , Troussier Nadège , Eynard Benoît , Falgarone Hugo , Fricero Benoît , Gomes Samuel
Published: April 2011

Concurrent engineering and integrated design have been a major issue over the past two decades especially considering design for X stakes. This paper describes a new proposal of integrated product-process design approach in order to improve the efficiency and the robustness of the assembly process planning phase. The proposed method illustrates how to consider functional requirements and technical constraints as early as possible to improve design principles and define the best assembly sequences fulfilling these requirements. Lastly, the proposed research is applied on an aeronautic case study for illustrating the potential benefits of such an approach in terms of taking account of assembly knowledge in the early product development stages.
Modal Analysis of a Loudspeaker and Its Associated Acoustic Pressure Field
Authors: Kuo Derek , Shiah Y. C. , Huang Jin H.
Published: April 2011

This paper presents a modal analysis and the sound pressure field for the vibrator membrane of an actual portable loudspeaker. Unlike the conventional way to model the membrane’s edge under a simply supported condition, the present approach takes the glued edge to be elastically supported. With theoretical derivations for such treatment, this paper also presents the associated near-field and far-field sound pressures that have not been reported in the open literature. Fundamentally, calculation of the near-field sound pressure solution for the elastically supported membrane has difficulty with numerical convergence. In this paper, integral regularization is employed to enforce the convergence. From the viewpoint of acoustic engineers, the analysis may effectively help to tailor the design of a loudspeaker that caters to consumers’ preference.
Estimating Severity of Damage in Lattice Structures Utilizing Substructure Modal Data
Authors: Fang Hui
Published: April 2011

This paper newly develops a method for the damage severity estimate for lattice structures based on the employment of the substructure potential energy (SPE). While all existing damage severity estimation methods that utilize modal data are either employing an iterative solution procedure or requiring spatially complete information, the SPE method is an exact, noniterative solution method and only requires substructure modal data. The performance of the proposed method is presented for beam-type and plate-type lattice structures based on synthetic data generated from finite element models.
Experimental Investigation of the Hydraulic and Thermal Performance of a Phase Change Material Slurry in the Heat Exchangers
Authors: Zhang P. , Ma Z. W. , Wang R. Z.
Published: April 2011

The application of phase change material slurry to the refrigeration and air conditioning system opens a new way for energy saving and reduction of the quantity of refrigerant in the system involved because it can serve as both the energy storage and the transportation media in the secondary loop, which is responsible for distributing the cooling power. In the present study, the experimental investigations of the forced flow and heat transfer characteristics of tetrabutylammonium bromide (TBAB) clathrate hydrate slurry (CHS) in both the plate heat exchanger (PHE) and the double-tube heat exchanger (DHE) are carried out. It is found out that the pressure drop in the PHE is about 3.0–50.0 kPa at the flow rate of 2.5–13.0 L/min (0.15–0.78 m3∕h)and is about 1.0–27.0 kPa at the flow rate of 3.0–14.0 L/min (0.18–0.84 m3∕h) in the DHE, which is nearly 2 times of that of the chilled water. The overall heat transfer coefficient is in the range of 2500–5000 W/(m2 K) for TBAB CHS in the PHE and is about 1500–3500 W/(m2 K) in the DHE, which are both higher than that of TBAB aqueous solution flow because of the involvement of the phase change of TBAB CHS.
On the potential of ultrasound elastography for pressure ulcer early detection
Authors: Deprez Jean‐François , Brusseau Elisabeth , Fromageau Jérémie , Cloutier Guy , Basset Olivier
Published: April 2011

Purpose:

Pressure ulcers are areas of soft tissue breakdown induced by a sustained mechanical stress that damages the skin and underlying tissues. They represent a considerable burden to the society in terms of health care and cost. Yet, techniques for prevention and detection of pressure ulcers still remain very limited. In this article, the authors investigated the potential of ultrasound elastography for pressure ulcer early detection. Elastography is an imaging technique providing local information on biological tissue mechanical properties. It is relevant for pressure ulcer detection as this pathology is associated with a gradual stiffening of damaged tissues, beginning in the deeper tissues and progressing toward the skin surface.

Methods:

A 2D ultrasound elastography method was proposed and its ability in terms of pressure ulcer detection was validated through numerical simulations and physical acquisitions on pressure ulcer mimicking phantoms.In vivo experiments on a rat model are also reported. A maintained pressure was applied on the animal thigh, with a view to generate a pressure ulcer, and ultrasound data were acquired and processed before and after application of this pressure.

Results:

Numerical simulations demonstrated that a pressure ulcer can theoretically be detected at a very early stage with ultrasound elastography. Even when the ulcer region was characterized by a low stiffening (ratio of 1.8 relative to normal tissues), the corresponding elastogram clearly underlined the pathological area. This observation was confirmed by the results obtained on a physical phantom mimicking a pressure ulcer at an early stage. Computed elastograms showed strain differences between areas mimicking healthy and pathological tissues. Results corresponding toin vivo experiments revealed a difference in the way tissues behaved before and after the pressure was applied on the animal thigh, which strongly suggests the presence of a pathological area.

Conclusions:

Experiments demonstrated that ultrasound elastography is a promising technique for pressure ulcer detection, especially at an early stage of the pathology, when the disease is still visually undetectable. In the absence of any gold standard method, this is also a first step toward the development of a quantitative technique.
A spatially encoded dose difference maximal intensity projection map for patient dose evaluation: A new first line patient quality assurance tool
Authors: Hu Weigang , Graff Pierre , Boettger Thomas , Pouliot Jean
Published: April 2011

Purpose:

To develop a spatially encoded dose difference maximal intensity projection (DD‐MIP) as an online patient dose evaluation tool for visualizing the dose differences between the planning dose and dose on the treatment day.

Methods:

Megavoltage cone‐beam CT (MVCBCT) images acquired on the treatment day are used for generating the dose difference index. Each index is represented by different colors for underdose, acceptable, and overdose regions. A maximal intensity projection (MIP) algorithm is developed to compress all the information of an arbitrary 3D dose difference index into a 2D DD‐MIP image. In such an algorithm, a distance transformation is generated based on the planning CT. Then, two new volumes representing the overdose and underdose regions of the dose difference index are encoded with the distance transformation map. The distance‐encoded indices of each volume are normalized using the skin distance obtained on the planning CT. After that, two MIPs are generated based on the underdose and overdose volumes with green‐to‐blue and green‐to‐red lookup tables, respectively. Finally, the two MIPs are merged with an appropriate transparency level and rendered in planning CT images.

Results:

The spatially encoded DD‐MIP was implemented in a dose‐guided radiotherapy prototype and tested on 33 MVCBCT images from six patients. The user can easily establish the threshold for the overdose and underdose. A 3% difference between the treatment and planning dose was used as the threshold in the study; hence, the DD‐MIP shows red or blue color for the dose difference or , respectively. With such a method, the overdose and underdose regions can be visualized and distinguished without being overshadowed by superficial dose differences.

Conclusions:

A DD‐MIP algorithm was developed that compresses information from 3D into a single or two orthogonal projections while hinting the user whether the dose difference is on the skin surface or deeper.
Dose response of alanine detectors irradiated with carbon ion beams
Authors: Herrmann Rochus , Jäkel Oliver , Palmans Hugo , Sharpe Peter , Bassler Niels
Published: April 2011

Purpose:

The dose response of the alanine detector shows a dependence on particle energy and type when irradiated with ion beams. The purpose of this study is to investigate the response behavior of the alanine detector in clinical carbon ion beams and compare the results to model predictions.

Methods:

Alanine detectors have been irradiated with carbon ions with an energy range of 89–400 MeV/u. The relative effectiveness of alanine has been measured in this regime. Pristine and spread out Bragg peak depth‐dose curves have been measured with alanine dosimeters. The track structure based alanine response model developed by Hansen and Olsen has been implemented in the Monte Carlo codeFLUKA and calculations were compared to experimental results.

Results:

Calculations of the relative effectiveness deviate less than 5% from the measured values for monoenergetic beams. Measured depth‐dose curves deviate from predictions in the peak region, most pronounced at the distal edge of the peak.

Conclusions:

The used model and its implementation show a good overall agreement for quasimonoenergetic measurements. Deviations in depth‐dose measurements are mainly attributed to uncertainties of the detector geometry implemented in the Monte Carlo simulations.
Elastic registration of multimodal prostate MRI and histology via multiattribute combined mutual information
Authors: Chappelow Jonathan , Bloch B. Nicolas , Rofsky Neil , Genega Elizabeth , Lenkinski Robert , DeWolf William , Madabhushi Anant
Published: April 2011

Purpose:

By performing registration of preoperative multiprotocolin vivo magnetic resonance (MR) images of the prostate with corresponding whole‐mount histology (WMH) sections from postoperative radical prostatectomy specimens, an accurate estimate of the spatial extent of prostate cancer (CaP) on in vivo MR imaging (MRI) can be retrospectively established. This could allow for definition of quantitative image‐based disease signatures and lead to development of classifiers for disease detection on multiprotocol in vivo MRI. Automated registration of MR and WMH images of the prostate is complicated by dissimilar image intensities, acquisition artifacts, and nonlinear shape differences.

Methods:

The authors present a method for automated elastic registration of multiprotocolin vivo MRI and WMH sections of the prostate. The method, multiattribute combined mutual information (MACMI), leverages all available multiprotocol image data to drive image registration using a multivariate formulation of mutual information.

Results:

Elastic registration using the multivariate MI formulation is demonstrated for 150 corresponding sets of prostate images from 25 patient studies with T2‐weighted and dynamic‐contrast enhanced MRI and 85 image sets from 15 studies with an additional functional apparent diffusion coefficient MRI series. Qualitative results of MACMI evaluation via visual inspection suggest that an accurate delineation of CaP extent on MRI is obtained. Results of quantitative evaluation on 150 clinical and 20 synthetic image sets indicate improved registration accuracy using MACMI compared to conventional pairwise mutual information‐based approaches.

Conclusions:

The authors' approach to the registration ofin vivo multiprotocol MRI and ex vivo WMH of the prostate using MACMI is unique, in that (1) information from all available image protocols is utilized to drive the registration with histology, (2) no additional, intermediate ex vivo radiology or gross histology images need be obtained in addition to the routinely acquired in vivo MRI series, and (3) no corresponding anatomical landmarks are required to be identified manually or automatically on the images.
Deconvolution by finite‐size‐source effects of x‐ray phase‐contrast images
Authors: De Caro Liberato , Scattarella Francesco , Tangaro Sabina , Pelliccia Daniele , Giannini Cinzia , Bottigli Ubaldo , Bellotti Roberto
Published: April 2011

Purpose:

In the hard x‐ray region, the cross sections for the phase shift of low‐ elements are about 1000 times larger than the absorption ones. As a consequence, phase contrast is detectable even when absorption contrast is minimal or absent. Therefore, phase‐contrast imaging could become a valid alternative to absorption contrast without delivering high dose to tissue/human body parts.

Methods:

To enhance the quality of phase‐contrast images without increasing the dose, a possible approach could be the partial deconvolution of the finite source size effects by experimental phase‐contrast images. The deconvolution procedure, the authors propose, employs the acquisition of two images on a suitable well‐known test sample, one in contact and the other in phase‐contrast conditions. Both acquired images are used along with a simulated phase‐contrast image (obtained from the test sample in ideal conditions of pointlike source illumination) to correctly retrieve the experimental source distribution function. This information allows a generic experimental phase‐contrast image, acquired in the same conditions, to be partially deconvolved by finite source size effects.

Results:

The performed experimental tests indicate that deconvolved images are equivalent to those which would be obtained with a source 40% smaller than the actual size. In turn, this finding is equivalent to an increase of the “effective” lateral spatial coherence length. The corresponding quality improvement of the phase‐contrast imaging is directly deducible by the presence of many Fresnel fringes, much better visible with respect to the original experimental phase‐contrast images.

Conclusions:

The use of a test standard sample, always possible in every experimental setup, to partially deconvolve the finite‐size‐source blurring effects shows that higher quality phase‐contrast images could be readily available, making easier diagnoses and tissue/sample analyses. The method could give, in the future, the possibility to further lower the delivered dose to patients, organs, and tissues when compact room‐sized and brilliant microfocus x‐ray sources will be available for clinical applications in hospitals.
An opposite view data replacement approach for reducing artifacts due to metallic dental objects
Authors: Yazdi Mehran , Lari Meghdad Asadi , Bernier Gaston , Beaulieu Luc
Published: April 2011

Purpose:

To present a conceptually new method for metal artifact reduction (MAR) that can be used on patients with multiple objects within the scan plane that are also of small sized along the longitudinal (scanning) direction, such as dental fillings.

Methods:

The proposed algorithm, named opposite view replacement, achieves MAR by first detecting the projection data affected by metal objects and then replacing the affected projections by the corresponding opposite view projections, which are not affected by metal objects. The authors also applied a fading process to avoid producing any discontinuities in the boundary of the affected projection areas in the sinogram. A skull phantom with and without a variety of dental metal inserts was made to extract the performance metric of the algorithm. A head and neck case, typical of IMRT planning, was also tested.

Results:

The reconstructed CT images based on this new replacement scheme show a significant improvement in image quality for patients with metallic dental objects compared to the MAR algorithms based on the interpolation scheme. For the phantom, the authors showed that the artifact reduction algorithm can efficiently recover the CT numbers in the area next to the metallic objects.

Conclusions:

The authors presented a new and efficient method for artifact reduction due to multiple small metallic objects. The obtained results from phantoms and clinical cases fully validate the proposed approach.
Performance of topological texture features to classify fibrotic interstitial lung disease patterns
Authors: Huber Markus B. , Nagarajan Mahesh B. , Leinsinger Gerda , Eibel Roger , Ray Lawrence A. , Wismüller Axel
Published: April 2011

Purpose:

Topological texture features were compared in their ability to classify “honeycombing,” a morphological pattern that is considered indicative for the presence of fibrotic interstitial lung disease in high‐resolution computed tomography (HRCT) images.

Methods:

For 14 patients with known occurrence of honeycombing, a stack of 70 axial, lung kernel reconstructed images was acquired from HRCT chest exams. A set of 964 regions of interest of both healthy and pathological (356) lung tissue was identified by an experienced radiologist. Texture features were extracted using statistical features (Stat), six properties calculated from gray‐level co‐occurrence matrices (GLCMs), Minkowski dimensions (MDs), and three Minkowski functionals (MFs) (e.g., MF.Euler). A naïve Bayes (NB) and ‐nearest‐neighbor (‐NN) classifier, a multilayer radial basis functions network (RBFN), and a support vector machine with a radial basis function (SVMrbf) kernel were optimized in a tenfold cross‐validation for each texture vector, and the classification accuracy was calculated on independent test sets as a quantitative measure of automated tissue characterization. A Wilcoxon signed‐rank test was used to compare two accuracy distributions and the significance thresholds were adjusted for multiple comparisons by the Bonferroni correction.

Results:

The best classification results were obtained by the MF features, which performed significantly better than all the standard Stat, GLCM, and MD features for both classifiers. The highest accuracies were found for MF.Euler (93.6%, 94.9%, 94.2%, and 95.0% for NB, ‐NN, RBFN, and SVMrbf, respectively). The best groups of standard texture features were a Stat and GLCM (“homogeneity”) feature set (up to 91.8%).

Conclusions:

The results indicate that advanced topological texture features derived from MFs can provide superior classification performance in computer‐assisted diagnosis of fibrotic interstitial lung disease patterns when compared to standard texture analysis methods.
Crescent artifacts in cone‐beam CT
Authors: Giles William , Bowsher James , Li Hao , Yin Fang‐Fang
Published: April 2011

Purpose:

In image‐guided radiation therapy, cone‐beam CT has been adopted for three‐dimensional target localization in the treatment room. In many of these cone‐beam CT images, dark and light crescent artifacts can be seen. This study investigates potential causes of this artifact and a technique for mitigating the crescents.

Methods:

Three deviations from an ideal geometry were simulated to assess their ability to cause crescent artifacts: Bowtie filter sag, x‐ray tube sag, and x‐ray tube rotation. The magnitudes of these deviations were estimated by matching shifts in simulated projections to those observed with clinical systems. To correct the artifacts, angle‐dependent blank projections were acquired and incorporated into image reconstruction. The degree of artifact reduction was evaluated with varying numbers (1–380) of blank projections. Scanner‐acquired phantom and patient studies were conducted to demonstrate the effectiveness of the proposed correction method.

Results:

All three investigated causes of the crescent artifact introduced similar mismodeling of the acquired projections and similar crescent artifacts. The deviations required for these artifacts were in the range of 0.5–5 mm or 0.1°. RMS error is reduced from to for 1–380 blank projections over a 200° scan angle. In the patient and phantom studies, reconstructions that utilized 380 blank projections largely mitigated the crescent artifacts.

Conclusions:

Small deviations from an ideal geometry can result in crescent artifacts due to steep gradients in the bowtie filter. Angle‐dependent blank projections can largely alleviate the artifacts.
Objective method to report planner‐independent skin/rib maximal dose in balloon‐based high dose rate (HDR) brachytherapy for breast cancer
Authors: Kim Yongbok , Trombetta Mark G.
Published: April 2011

Purpose:

An objective method was proposed and compared with a manual selection method to determine planner‐independent skin and rib maximal dose in balloon‐based high dose rate (HDR) brachytherapy planning.

Methods:

The maximal dose to skin and rib was objectively extracted from a dose volume histogram (DVH) of skin and rib volumes. A virtual skin volume was produced by expanding the skin surface in three dimensions (3D) external to the breast with a certain thickness in the planning computed tomography (CT) images. Therefore, the maximal dose to this volume occurs on the skin surface the same with a conventional manual selection method. The rib was also delineated in the planning CT images and its maximal dose was extracted from its DVH. The absolute and relative maximal skin and rib dose differences between the manual selection method and the objective method were measured for 50 balloon‐based HDR (25 MammoSite® and 25 Contura®) patients.

Results:

The deviation of maximal dose difference was of the prescribed dose (PD). No statistical difference was observed between MammoSite® and Contura® patients for both Abdiff and Rediff[%] values. However, a statistically significant difference ( value ) was observed in maximal rib dose difference compared with maximal skin dose difference for both Abdiff ( vs ) and Rediff[%] ( vs ). In general, rib has a more irregular contour and it is more proximally located to the balloon for 50 HDR patients. Due to the inverse square law factor, more dose difference was observed in higher dose range compared with lower dose range : vs with value of 0.0049. However, the Rediff[%] analysis eliminated the inverse square factor and there was no statistically significant difference between high and low dose ranges.

Conclusions:

The objective method using volumetric information of skin and rib can determine the planner‐independent maximal dose compared with the manual selection method. However, the difference was of PD, on average, if appropriate attention is paid to selecting a manual dose point in 3D planning CT images.
Saturn’s Curiously Corrugated C Ring
Authors: Hedman M. M. , Burns J. A. , Evans M. W. , Tiscareno M. S. , Porco C. C.
Published: April 2011

Spacecraft observations show that Saturn’s and Jupiter’s rings preserve records of recent interplanetary debris collisions.
Logical recruitment
Authors: Reffold Pippa
Published: April 2011

When the word ‘recruitment’ is mentioned, many people go into a cold sweat. Finding a new person to suit the practice may be a daunting task and can seem a difficult and subjective process. In this article, Pippa Reffold explains how to go about recruitment in a logical manner to ensure that you find the right person who is a good fit for your practice.
Tobacco and poverty: evidence from Vietnam
Authors: Efroymson Debra , Pham Hoang Anh , Jones Lori , FitzGerald Sian , Thu Le Thi , Thu Hien Le Thi
Published: April 2011

This review examined existing evidence to investigate the link between tobacco and poverty in Vietnam, to assess the impact of tobacco control policies on employment related to tobacco consumption and to identify information gaps that require further research for the purposes of advocating stronger tobacco control policies. A Medline, PubMed and Google Scholar search identified studies addressing the tobacco and poverty association in Vietnam using extensive criteria. In all, 22 articles related either to tobacco and health or economics, or to the potential impact of tobacco control policies, were identified from titles, abstracts or the full text. 28 additional publications were identified by other means. PHA, LTT and LTTH reviewed the publications and prepared the initial literature review. There is extensive evidence that tobacco use contributes to poverty and inequality in Vietnam and that tobacco control policies would not have a negative impact on overall employment. Tobacco use wastes household and national financial resources and widens social inequality. The implementation and enforcement of a range of tobacco control measures could prove beneficial not only to improve public health but also to alleviate poverty.
BIAS STRESS AND MEASUREMENT OF CHARACTERISTICS OF HYDROGENATED AMORPHOUS-SILICON THIN FILM TRANSISTORS USING ALTERNATING CURRENT DRIVING PULSE
Authors: LEE HO NYEON , JUNG DUCK HYEONG , LEE YUN HO
Published: April 2011

A thin film transistor (TFT) characteristics measuring and bias stress applying system using an alternating current (AC) pulse sequence similar to a real driving pulse was developed to study the properties of hydrogenated amorphous-silicon (a-Si:H) TFTs under real operating conditions. Using this system, the application of a gate bias stress and the measurement of source-to-drain current were performed successfully. Degradation of the TFT transfer curve depended on the ratio of on time to off time for a fixed on time; a longer off time made the shift of threshold voltage V TH smaller. In addition, degradation of transfer curves depended on the frequency of the driving pulse; a higher frequency pulse produced a larger degradation. These results could originate from the dependence of the direction of V TH shift on the polarity of the gate bias, and the differences of injection barrier height and the mobility of the electron and hole. Using the AC driving pulse and the transient measurement system proposed in this study may be useful in understanding the response of TFTs under real operating conditions.
VARIATIONAL COMPUTATIONS FOR EXCITONS IN QUANTUM DOTS: A QUANTUM MONTE CARLO STUDY
Authors: YILDIZ A. , ŞAKİROĞLU S. , DOĞAN Ü. , AKGÜNGÖR K. , EPİK H. , SÖKMEN İ. , SARI H. , ERGÜN Y.
Published: April 2011

A study of variational wave functions for calculation of the ground-state energies of excitons confined in a two-dimensional (2D) disc-like and three-dimensional (3D) spherical parabolic GaAs quantum dots (QDs) is presented. We have used four variational trial wave functions constructed as the harmonic-oscillator basis multiplied by different correlation functions. The proposed correlation function formed by including linear expansion in terms of Hylleraas-like coordinates to the Jastrow factor is able to capture nearly exactly the ground-state energies of 3D excitons, and it properly account for the results of 2D excitons. Quantum Monte Carlo techniques combined with the proposed wave function are a powerful tool for studying excitons in parabolic QDs.
THE PROPERTIES OF PROTON CONDUCTIVITY ALONG THE HYDROGEN-BONDED MOLECULAR SYSTEMS WITH DAMPING UNDER INFLUENCES OF THERMAL PERTURBATION AND STRUCTURE NONUNIFORMITY
Authors: PANG XIAO-FENG , YU JIA-FENG , ZENG HONG-JUAN
Published: April 2011

The effects of structure nonuniformity and thermal perturbation on properties of proton conductivity in hydrogen-bonded systems with damping exposed in an externally applied electric-field have been numerically studied by fourth order Runge–Kutta method in our soliton model. The results obtained show that the proton-soliton is very robust against the structure disorder including the fluctuation of the force constant and disorder in the sequence of masses and thermal perturbation and damping effect of medium, its velocity of conductivity increases with increasing externally applied electric-field and with decreasing damping coefficient of medium, but the proton-soliton disperses at quite great fluctuations of force constant and damping coefficient. In the meantime, the proton-soliton in ice crystals is thermally stable in the region of temperature of T ≤ 273 K. From the numerical simulation, we find out that the mobility (or velocity) of proton conduction in ice is a nonmonotonic function of temperature in the temperature region of 170–273 K, i.e., it increases initially, reaches a maximum at about 191.4 K, subsequently decreases to a minimum at about 211.6 K, and then increases again. This changed rule of mobility obtained consists qualitatively with its experimental datum in ice in the same temperature region. Thus these results provide an evidence for the soliton excited in the hydrogen-bonded systems.
TENSILE PROPERTY AND CRACK PROPAGATION BEHAVIOR OF TUNGSTEN ALLOYS
Authors: SONG WEIDONG , LIU HAIYAN , NING JIANGUO
Published: April 2011

In situ SEM experimental system is employed to investigate the mechanical characteristics and the fracture behavior of 91W–6.3Ni–2.7Fe tungsten alloys. The crack initiation and propagation of tungsten alloys under tensile loadings are examined. Multi-particle unit cell models containing the microstructure characteristics of tungsten alloys are established. Fixed-point iteration method is firstly used for the multi-particle unit cell's boundary condition. By adopting the method, real displacement constrained conditions are applied on the multi-particle unit cell models. The mechanical and fracture behaviors of tungsten alloys under tensile loading are simulated. The effects of tungsten content, particle shape, particle size, and interface strength on the mechanical properties of tungsten alloys are analyzed. The relationship between the mechanical behaviors and the microstructure parameters is studied. A good agreement is obtained between the experimental results and the numerical predictions, verifying the rationality of the FE models using the fixed-point iteration method.
CROSS-CORRELATION ANALYSIS IN MIXED TRAFFIC FLOW TIME SERIES
Authors: XU S. Y. , SUN H. J. , WU J. J.
Published: April 2011

In this paper, we investigate the complexity behind the mixed traffic flow time series generated by multi-lane cellular automaton model. Throughout the paper, the cross-correlation coefficient is introduced to characterize the time series. It is found that there exists a critical vehicle density S, when S < S1 and the ratio of slow vehicle R > 0.01, the cross-correlation coefficient r is larger than 0.5, which indicates a significant linear correlation. Otherwise, the cross-correlation coefficient r < 0.5 which corresponds to a weak linear correlation. That is to say, the vehicle density plays an important role in the cross-correlation coefficient. Additionally, we also found that the asymmetric lane-change probability has no great influence on the cross-correlation coefficient.
DEPHASING OF QD EXCITON ORBITAL AND SPIN STATES DUE TO HYBRIDIZATION WITH BULK COLLECTIVE EXCITATIONS
Authors: JACAK W. , KRASNYJ J. , JACAK L. , DONDEROWICZ W.
Published: April 2011

We analyze theoretically a hybridization type dressing of orbital (i.e., charge) and spin degrees of freedom of excitations captured in semiconductor quantum dot with band phonons and magnons (the latter for magnetic semiconductor surroundings), as a mechanism of dephasing of rapidly excited dot exciton state. Within the Green function approach we derive our previously formulated heuristic general rule for estimation of corresponding dephasing time-rate. The pure dephasing (off-diagonal decoherence) of quantum dot exciton resulting due to this dressing is studied, for both orbital and spin states of the exciton. A significant difference between phonon-induced (for charge) and magnon-assisted (for spin) quantum dot exciton dephasing is indicated as the result of the spin conservation, which leads to the disappearance of the exciton spin pure-dephasing at T = 0 (freezing out of spin dephasing), in contrary to the exciton charge dephasing caused by phonons, which maintains strong even at T = 0.
INFORMATION ASYMMETRY IN PRICING OF CREDIT DERIVATIVES
Authors: HILLAIRET CAROLINE , JIAO YING
Published: April 2011

We study the pricing of credit derivatives with asymmetric information. The managers have complete information on the value process of the firm and on the default threshold, while the investors on the market have only partial observations, especially about the default threshold. Different information structures are distinguished using the framework of enlargement of filtrations. We specify risk neutral probabilities and we evaluate default sensitive contingent claims in these cases.
PORTFOLIO OPTIMIZATION UNDER PARTIAL INFORMATION WITH EXPERT OPINIONS
Authors: FREY RÜDIGER , GABIH ABDELALI , WUNDERLICH RALF
Published: April 2011

This paper investigates optimal portfolio strategies in a market with partial information on the drift. The drift is modelled as a function of a continuous-time Markov chain with finitely many states which is not directly observable. Information on the drift is obtained from the observation of stock prices. Moreover, expert opinions in the form of signals at random discrete time points are included in the analysis. We derive the filtering equation for the return process and incorporate the filter into the state variables of the optimization problem. This problem is studied with dynamic programming methods. In particular, we propose a policy improvement method to obtain computable approximations of the optimal strategy. Numerical results are presented at the end.
NOVEL REVERSIBLE FAULT TOLERANT ERROR CODING AND DETECTION CIRCUITS
Authors: HAGHPARAST MAJID , NAVI KEIVAN
Published: April 2011

Reversible logic is an emerging area of research, having applications in nanotechnology, low power CMOS design, quantum computing, and DNA computing. In this paper, two different parity-preserving reversible error coding and detection circuits are studied. First we propose two new reversible Hamming code generator circuits. One of them is parity-preserve. We also propose a new parity-preserving reversible Hamming code error detector circuit. The proposed parity-preserving reversible Hamming code generator (PPHCG) and error detector circuits provide single error correction–double error detection (SEC–DED). The designs are better than the existing counterparts in terms of quantum cost (QC), number of constant inputs, and number of garbage outputs. Then we propose parity-preserving reversible cyclic code encoder/decoder circuits for the first time. A parity-preserving reversible D flip-flop is also proposed. Equivalent quantum representation of two parity-preserving 4 ∗ 4 reversible gates, IG, and PPHCG, are also proposed. We show for the first time that IG has a QC of only 7 and PPHCG has a QC of only 6.
MAGNETIC FLUX SENSITIVITY OF THE POPULATION AND THE PANCHARATNAM PHASE FOR A SINGLE COOPER-PAIR BOX
Authors: BOUCHENE M. A. , ABDEL-ATY M.
Published: April 2011

We study the behaviour of a single Cooper-pair box with a SQUID loop interacting with a magnetic field. We demonstrate the strong dependence of the population and the Pancharatnam phase on the magnetic flux and study the modifications when a temporal drift is present on the magnetic field. Moreover, we show that the Pancharatnam phase is more sensitive to the excitation parameters than the populations, suggesting a sensitive method for controlling the system and/or detecting flux variations.
LIMIT THEOREMS FOR A LOCALIZATION MODEL OF 2-STATE QUANTUM WALKS
Authors: MACHIDA TAKUYA
Published: April 2011

We consider 2-state quantum walks (QWs) on the line, which are defined by two matrices. One of the matrices operates the walk at only half-time. In the usual QWs, localization does not occur at all. However, our walk can be localized around the origin. In this paper, we present two limit theorems, that is, one is a stationary distribution and the other is a convergence theorem in distribution.
PERFECT STATE TRANSFER, GRAPH PRODUCTS AND EQUITABLE PARTITIONS
Authors: GE YANG , GREENBERG BENJAMIN , PEREZ OSCAR , TAMON CHRISTINO
Published: April 2011

We describe new constructions of graphs which exhibit perfect state transfer on continuous-time quantum walks. Our constructions are based on generalizations of the double cones and variants of the Cartesian graph products (which include the hypercube). We also describe a generalization of the path collapsing argument (which reduces questions about perfect state transfer to simpler weighted multigraphs) for graphs with equitable distance partitions.
Learning for Chocolate
Authors: Landay Susan
Published: April 2011

Giving the gift of chocolate may go a long way in the classroom. Susan Landay not only shares her love of chocolate, but discusses how to recognize and inspire participation and performance.
A robust link-translating proxy server mirroring the whole web
Authors: Mao Ziqing , Herley Cormac
Published: April 2011

Link-translating proxies are widely used for anonymous browsing, policy circumvention and WebVPN functions. These are implemented by encoding the destination URL in the path of the URL submitted to the proxy and rewriting all links before returning the document to the client. Commonly these are based on the CGIProxy implementation or a variant. While popular, broken links and very slow load times are common. This is so, since the use of scripting languages makes finding and translating links (the essential task of such a proxy) very difficult. Some web-sites become entirely non-functional when loaded.

This paper proposes a novel architecture for a link-translating proxy. By using a sub-domain mapping technique we entirely eliminate the need to translate (or even find") relative links in content. This makes the link rewriting algorithm very simple and robust. We have implemented, deployed, and tested the proxy extensively. We conducted a comparison between the our proxy and CGIProxy. Both the theoretical analysis and experimental evaluation show that our proxy is significantly better in terms of robustness, performance, and security. We call our system Address Bar Only Proxy or ABOProxy. We suggest several novel applications.
Parallel memory prediction for fused linear algebra kernels
Authors: Karlin Ian , Jessup Elizabeth , Belter Geoffrey , Siek Jeremy G.
Published: April 2011

The performance of many scientific programs is limited by data movement. Loop fusion is one optimization used to increase the speed of memory bound operations. To automate loop fusion for matrix computations, we developed the Build to Order (BTO) compiler. Within BTO, an analytic memory model efficiently and accurately reduces the number of serial loop fusion options considered. In this paper, we extend the model to shared memory parallel machines. We detail the differences between parallel and serial memory use and runtime prediction and explain the changes made to include parallel machines in the model. Analysis of the parallel model's predictions show that when it is included in BTO it will reduce the search space of considered routines.
Should we worry about memory loss?
Authors: Perks O. , Hammond S. D. , Pennycook S. J. , Jarvis S. A.
Published: April 2011

In recent years the High Performance Computing (HPC) industry has benefited from the development of higher density multi-core processors. With recent chips capable of executing up to 32 tasks in parallel, this rate of growth also shows no sign of slowing. Alongside the development of denser micro-processors has been the considerably more modest rate of improvement in random access memory (RAM). The effect has been that the available memory-per-core has reduced and current projections suggest that this is set to reduce still further.

In this paper we present three studies into the use and measurement of memory in parallel applications; our aim is to capture, understand and, if possible, reduce the memory-per-core needed by complete multi-component applications. First, we present benchmarked memory usage and runtimes of a six scientific benchmarks, which represent algorithms that are common to a host of production-grade codes. Memory usage of each benchmark is measured and reported for a variety of compiler toolkits, and we show >30% variation in memory high-water mark requirements between compilers. Second, we utilise this benchmark data combined with runtime data, to simulate via the Maui scheduler simulator, the effect on a multi-science workow if memory-per-core is reduced from 1.5GB-per-core to only 256MB. Finally, we present initial results from a new memory profiling tool currently in development at the University of Warwick. This tool is applied to a finite-element benchmark and is able to map high-water-mark memory allocations to individual program functions. This demonstrates a lightweight and accurate method of identifying potential memory problems, a technique we expect to become commonplace as memory capacities decrease.
A statistical performance model of the opteron processor
Authors: Cook Jeanine , Cook Jonathan , Alkohlani Waleed
Published: April 2011

Cycle-accurate simulation is the dominant methodology for processor design space analysis and performance prediction. However, with the prevalence of multi-core, multi-threaded architectures, this method has become highly impractical as the sole means for design due to its extreme slowdowns. We have developed a statistical technique for modeling multicore processors that is based on Monte Carlo methods. Using this method, processor models of contemporary architectures can be developed and applied to performance prediction, bottleneck detection, and limited design space analysis. To date, we have accurately modeled the IBM Cell, the Intel Itanium, and the Sun Niagara 1 and Niagara 2 processors [23, 22, 8]. In this paper, we present a work in progress which is applying this methodology to an out-of-order execution processor. We present the initial single-core model and results for the AMD Barcelona (Opteron) processor.
Energy-aware metrics for benchmarking heterogeneous systems
Authors: McIntosh-Smith Simon , Wilson Terry , Crisp Jon , Ibarra Amaurys Ávila , Sessions Richard B.
Published: April 2011

With the advent of heterogeneous computing systems consisting of multi-core CPUs and many-core GPUs, robust methods are needed to facilitate fair benchmark comparisons between different systems. In this paper we present a benchmarking methodology for measuring a number of performance metrics for heterogeneous systems. Methods for comparing performance and energy efficiency are included. Consideration is given to further metrics, such as associated runnings costs and even carbon emissions. We give a case study for these metrics applied to BUDE, a molecular mechanics-based docking application that has been ported to OpenCL at the University of Bristol.
Limitations of matrix completion via trace norm minimization
Authors: Shi Xiaoxiao , Yu Philip S.
Published: April 2011

In recent years, compressive sensing attracts intensive attentions in the field of statistics, automatic control, data mining and machine learning. It assumes the sparsity of the dataset and proposes that the whole dataset can be reconstructed by just observing a small set of samples. One of the important approaches of compressive sensing is trace norm minimization, which can minimize the rank of the data matrix under some conditions. For example, in collaborative filtering, we are given a small set of observed item ratings of some users and we want to predict the missing values in the rating matrix. It is assumed that the users' ratings are affected by only a few factors and the resulting rating matrix should be of low rank. In this paper, we analyze the issues related to trace norm minimization and find an unexpected result that trace norm minimization often does not work as well as expected.