bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a mechanical testing assay for fibrotic murine liver
Authors: Barnes Stephanie L. , Lyshchik Andrej , Washington Mary K. , Gore John C. , Miga Michael I.
Published: November 2007

In this article, a novel protocol for mechanical testing, combined with finite element modeling, is presented that allows the determination of the elastic modulus of normal and fibrotic murine livers and is compared to an independent mechanical testing method. The novel protocol employs suspending a portion of murine liver tissue in a cylindrical polyacrylamide gel, imaging with a microCT, conducting mechanical testing, and concluding with a mechanical property determination via a finite element method analysis. More specifically, the finite element model is built from the computerized tomography (CT) images, and boundary conditions are imposed in order to simulate the mechanical testing conditions. The resulting model surface stress is compared to that obtained during mechanical testing, which subsequently allows for direct evaluation of the liver modulus. The second comparison method involves a mechanical indentation test performed on a remaining liver lobe for comparison. In addition, this lobe is used for histological analysis to determine relationships between elasticity measurements and tissue health. This complete system was used to study 14 fibrotic livers displaying advanced fibrosis (injections with irritant), three control livers (injections without irritant), and three normal livers (no injections). The moduli evaluations for nondiseased livers were estimated as and for indenter and model‐gel‐tissue (MGT) assay tests, respectively. Moduli estimates for diseased liver ranged from and for indenter and MGT assay tests, respectively. The MGT modulus, though not equivalent to the modulus determined by indentation, demonstrates a high correlation, thus indicating a relationship between the two testing methods. The results also showed a clear difference between nondiseased and diseased livers. The developed MGT assay system is quite compact and could easily be utilized for controlled evaluation of soft‐tissue moduli as shown here. In addition, future work will add the correlative method of elastography such that direct controlled validation of measurement on tissue can be determined.
Improved arterial spin labeling method: Applications for measurements of cerebral blood flow in human brain at high magnetic field MRI
Authors: Jahng Geon‐Ho , Weiner Michael W. , Schuff Norbert
Published: November 2007

Measurements of cerebral blood flow (CBF) with arterial spin labeling (ASL) MRI are challenging primarily due to a poor signal‐to‐noise (SNR) ratio. Therefore, methods that improve SNR and minimize measurement errors can play a significant role for better estimations of CBF. The purpose of this work was to develop an ASL method for measurements of CBF at high magnetic field strength. In the proposed multislice ASL method, using in‐plane double inversion for labeling, stationary spins are kept at equilibrium to avoid relaxation effects, while blood water is labeled using a lower magnetic field gradient. Improvement for CBF measurements is demonstrated on subjects and by comparison with other multislice ASL MRI methods at 1.5 Tesla. Furthermore, echo‐planar imaging (EPI) and Turbo‐FLASH (TFL) at 4 T MRI are compared for mapping CBF in human brain using various postlabeling delay times. CBF maps were obtained and analyzed within region‐of‐interests encompassing either gray matter or white matter. Elimination of dependence of stationary spins in conjunction with avoidance of magnetization transfer mismatch between labeling and control scans lead to improved CBF measurements. Although measurements of CBF in brain tissue are feasible at 4 T using either EPI or TFL, TFL reduced contaminations from an intravascular signal and susceptibility‐related artifacts, providing overall more robust CBF measurements than EPI. Therefore, the proposed ASL method in combination with TFL should be used for measuring CBF of human brain at 4T.
Quantification of accuracy of the automated nonlinear image matching and anatomical labeling (ANIMAL) nonlinear registration algorithm for 4D CT images of lung
Authors: Heath E. , Collins D. L. , Keall P. J. , Dong L. , Seuntjens J.
Published: November 2007

The performance of the ANIMAL (Automated Nonlinear Image Matching and Anatomical Labeling) nonlinear registration algorithm for registration of thoracic 4D CT images was investigated. The algorithm was modified to minimize the incidence of deformation vector discontinuities that occur during the registration of lung images. Registrations were performed between the inhale and exhale phases for five patients. The registration accuracy was quantified by the cross‐correlation of transformed and target images and distance to agreement (DTA) measured based on anatomical landmarks and triangulated surfaces constructed from manual contours. On average, the vector DTA between transformed and target landmarks was . Comparing transformed and target 3D triangulated surfaces derived from planning contours, the average target volume (GTV) center‐of‐mass shift was and the 3D DTA was . An average DTA of was obtained for all planning structures. All DTA metrics were comparable to inter observer uncertainties established for landmark identification and manual contouring.
FEATURE EXTRACTION BASED ON DIRECT CALCULATION OF MUTUAL INFORMATION
Authors: KWAK NOJUN
Published: November 2007

In many pattern recognition problems, it is desirable to reduce the number of input features by extracting important features related to the problems. By focusing on only the problem-relevant features, the dimension of features can be greatly reduced and thereby can result in a better generalization performance with less computational complexity. In this paper, we propose a feature extraction method for handling classification problems. The proposed algorithm is used to search for a set of linear combinations of the original features, whose mutual information with the output class can be maximized. The mutual information between the extracted features and the output class is calculated by using the probability density estimation based on the Parzen window method. A greedy algorithm using the gradient descent method is used to determine the new features. The computational load is proportional to the square of the number of samples. The proposed method was applied to several classification problems, which showed better or comparable performances than the conventional feature extraction methods.
A MODIFIED MULTIPHASE LEVEL SET EVOLUTION SCHEME FOR AERIAL IMAGE SEGMENTATION
Authors: WEI WANG , XIN YANG
Published: November 2007

This paper describes an innovative aerial images segmentation algorithm. The algorithm is based upon the knowledge of image multiscale geometric analysis using contourlet transform, which can extract the image's intrinsic geometrical structure efficiently. The contourlet transform is introduced to represent the most distinguished and the rotation invariant features of the image. A modified Mumford–Shah model is applied to segment the aerial image by a multifeature level set evolution. To avoid possible local minima in the level set evolution, we adjust the weighting coefficients of the multiscale features in different evolution periods, i.e. the global features have bigger weighting coefficients at the beginning stages which roughly define the shape of the contour, then bigger weighting coefficients are assigned to the detailed features for segmenting the precise shape. When the algorithm is applied to segment the aerial images with several classes, satisfied experimental results are achieved by the proposed method.
A WILD KNOT 𝕊2↪ 𝕊4AS LIMIT SET OF A KLEINIAN GROUP: INDRA'S PEARLS IN FOUR DIMENSIONS
Authors: HINOJOSA GABRIELA
Published: November 2007

The purpose of this paper is to construct an example of a 2-knot wildly embedded in 𝕊4as the limit set of a Kleinian group. We find that these wild 2-knots are nowhere PL and yet these knots have very interesting topological properties.
WHERE THE LINKS–GOULD INVARIANT FIRST FAILS TO DISTINGUISH NONMUTANT PRIME KNOTS
Authors: DE WIT DAVID , LINKS JON
Published: November 2007

It is known that the first two-variable Links–Gould quantum link invariant LG ≡ LG2,1 is more powerful than the HOMFLYPT and Kauffman polynomials, in that it distinguishes all prime knots (including reflections) of up to 10 crossings. Here we report investigations which greatly expand the set of evaluations of LG for prime knots. Through them, we show that the invariant is complete, modulo mutation, for all prime knots (including reflections) of up to 11 crossings, but fails to distinguish some nonmutant pairs of 12-crossing prime knots. As a byproduct, we classify the mutants within the prime knots of 11 and 12 crossings. In parallel, we learn that LG distinguishes the chirality of all chiral prime knots of at most 12 crossings. We then demonstrate that every mutation-insensitive link invariant fails to distinguish the chirality of a number of 14-crossing prime knots. This provides 14-crossing examples of chiral prime knots whose chirality is undistinguished by LG.
THE 2-BRIDGE KNOTS OF UP TO 16 CROSSINGS
Authors: DE WIT DAVID
Published: November 2007

For any given number of crossings c, there exists a formula to determine the number of 2-bridge knots of c crossings, and indeed it is a simple matter to actually construct presentations of these knots. However, the determination of whether a given (prime) knot is a 2-bridge knot remains a nontrivial exercise, and we have no procedure to determine bridge numbers more generally. Herein, we identify the 2-bridge knots within the Hoste–Thistlethwaite–Weeks tables of prime knots of up to 16 crossings by an exhaustive search of a larger set of 2-bridge knots. As the unknot is the only knot with bridge number 1, this yields a lower bound of 3 for the bridge numbers of the remaining knots.
THE COVERAGE PROBLEM IN THREE-DIMENSIONAL WIRELESS SENSOR NETWORKS
Authors: HUANG CHI-FU , TSENG YU-CHEE , LO LI-CHU
Published: November 2007

One of the fundamental issues in sensor networks is the coverage problem, which reflect-show well a sensor network is monitored or tracked by sensors. In this paper, we formulate this problem as a decision problem, whose goal is to determine whether every point in the servicearea of the sensor network is covered by at least α sensors, where ff is a given parameter andthe sensing regions of sensors are modeled by balls (not necessarily of the same radius). This problem in a 2D space is solved in [10] with an efficient polynomial-time algorithm (in termsof the number of sensors). In this paper, we show that tackling this problem in a 3D space is still feasible within polynomial time. Further, the proposed solution can be easily translated intoan efficient polynomial-time distributed protocol. We demonstrate an application of the derived result by proposing an energy-conserving scheduling protocol.
DISTRIBUTED ALGORITHMS FOR BUILDING HAMILTONIAN CYCLES IN k-ARY n-CUBES AND HYPERCUBES WITH FAULTY LINKS
Authors: STEWART IAIN A.
Published: November 2007

We derive a sequential algorithm Find-Ham-Cycle with the following property. On input: k and n (specifying the k-ary n-cube [Formula: see text]); F, a set of at most 2n − 2 faulty links; and v , a node of [Formula: see text], the algorithm outputs nodes v + and v − such that if Find-Ham-Cycle is executed once for every node v of [Formula: see text] then the node v + (resp. v −) denotes the successor (resp. predecessor) node of v on a fixed Hamiltonian cycle in [Formula: see text] in which no link is in F. Moreover, the algorithm Find-Ham-Cycle runs in time polynomial in n and log k. We also obtain a similar algorithm for an n-dimensional hypercube with at most n − 2 faulty links. We use our algorithms to obtain distributed algorithms to embed Hamiltonian cycles k-ary n-cubes and hypercubes with faulty links; our hypercube algorithm improves on a recently-derived algorithm due to Leu and Kuo, and our k-ary n-cube algorithm is the first distributed algorithm for embedding a Hamiltonian cycle in a k-ary n-cube with faulty links.
MULTISCALE NEUROFUZZY MODELS FOR FORECASTING IN TIME SERIES DATABASES
Authors: KUMAR ASHWANI , AGRAWAL D. P. , JOSHI S. D.
Published: November 2007

Multiscale neurofuzzy modeling combines the multiresolution property of the wavelet transform with the regression ability of neurofuzzy systems. A wavelet transform is used to decompose the time series into varying scales of resolution so that the underlying temporal structures of the original time series become more tractable; the decomposition is additive in detail and approximation. A neurofuzzy system is then trained on each of the relevant resolution scales (i.e. those scales where significant events are detected); and individual wavelet forecasts are recombined to form the overall forecast. The neurofuzzy models developed in this paper are based on Mamdani and Takagi–Sugeno–Kang approaches to the problem of fuzzy modeling based on the strategy knowledge expressed by the input-output data. Within these approaches, the proposed Neural-Fuzzy Inference System (NFIS) provides several methods that represent different alternatives in the fuzzy modeling process and how they can be integrated with the learning power of neural networks. Simulation results carried out on a forecasting problem associated with stock market, are included to demonstrate the potential of the proposed forecasting scheme.
WAVELET-BASED BASE LINE WANDERING REMOVAL AND R PEAK AND QRS COMPLEX DETECTION
Authors: SHANTHA SELVA KUMARI R. , SADASIVAM V.
Published: November 2007

Wavelet transform has emerged as a powerful tool for time-frequency analysis and signal coding favored for the interrogation of complex non-stationary signals such as the ECG signal. Measurement of timing intervals of ECG signal by automated system is highly superior to its subjective analysis. The timing interval is found from the onset and offset of the wave components of the ECG signal. Since the Daubechies wavelet is similar to the shape of the ECG signal, better detection is achieved. Discrete Wavelet Transform is easier to implement, provides multiresolution and also reduces the computational time, and thus, is used. In the pre-processing step, the base line wandering is removed from the ECG signal. Then the R peak and the QRS complexes are detected. Twenty five records from the MIT-BIH arrhythmia database are used to evaluate the proposed method. Sensitivity and positive prediction are used as performance measures. This method is very simple and detects all the R peaks (sensitivity = 100% and positive prediction = 99.86%). That is, false positive detection is very negligible and false negative detection is zero. The performance of the proposed method is better than other methods that exist in the literature.
CONVERGENCE OF AN ITERATIVE NONLINEAR SCHEME FOR DENOISING OF PIECEWISE CONSTANT IMAGES
Authors: PLONKA GERLIND , MA JIANWEI
Published: November 2007

In this paper we present a new efficient iterative nonlinear scheme for recovering of a piecewise constant image from an observed image containing additive noise. We apply an adaptive neighborhood filter which comes from robust statistics and completely rejects outliers being greater than a certain constant. We prove that the iterated application of the scheme leads to a piecewise constant image. This observation generalizes the known results on convergence of nonlinear diffusion schemes to a constant steady-state. Moreover, we show that the partition of the image determining the piecewise constant steady-state after an infinite iteration process can already be found after a finite number of iteration steps. This result can be used for a fast approximation of the piecewise constant image by a mean value procedure. We examine the relations of our scheme to average and bilateral filtering, diffusion filtering and wavelet shrinkage. Numerical experiments illustrate the performance of the algorithm.
WAVELET-BASED ADAPTIVE COLLOCATION METHOD FOR THE RESOLUTION OF NONLINEAR PDEs
Authors: KARAMI A. , KARIMI H. R. , MOSHIRI B. , JABEDAR MARALANI P.
Published: November 2007

Theoretical modeling of dynamic processes in chemical engineering often implies the numeric solution of one or more partial differential equations. The complexity of such problems is increased when the solutions exhibit sharp moving fronts. An efficient adaptive multiresolution numerical method is described for solving systems of partial differential equations. This method is based on multiresolution analysis and interpolating wavelets, that dynamically adapts the collocation grid so that higher resolution is automatically attributed to domain regions where sharp features are present. Space derivatives were computed in an irregular grid by cubic splines method. The effectiveness of the method is demonstrated with some relevant examples in a chemical engineering context.
CLIFFORD ALGEBRA Cl3,0-VALUED WAVELET TRANSFORMATION, CLIFFORD WAVELET UNCERTAINTY INEQUALITY AND CLIFFORD GABOR WAVELETS
Authors: BAHRI MAWARDI , HITZER ECKHARD S. M.
Published: November 2007

In this paper, it is shown how continuous Clifford Cl3,0-valued admissible wavelets can be constructed using the similitude group SIM(3), a subgroup of the affine group of ℝ3. We express the admissibility condition in terms of a Cl3,0Clifford Fourier transform and then derive a set of important properties such as dilation, translation and rotation covariance, a reproducing kernel, and show how to invert the Clifford wavelet transform of multivector functions. We invent a generalized Clifford wavelet uncertainty principle. For scalar admissibility constant, it sets bounds of accuracy in multivector wavelet signal and image processing. As concrete example, we introduce multivector Clifford Gabor wavelets, and describe important properties such as the Clifford Gabor transform isometry, a reconstruction formula, and an uncertainty principle for Clifford Gabor wavelets.
QUANTUM COMPUTATIONAL FINITE-VALUED LOGICS
Authors: BERTINI CESARINO , LEPORINI ROBERTO
Published: November 2007

The theory of logical gates in quantum computation has suggested new forms of quantum logic, called quantum computational logics. The basic semantic idea is the following: the meaning of a sentence is identified with a quantum information quantity, represented by a quregister (a system of qudits) or, more generally, by a mixture of quregisters (called qumix), whose dimension depends on the logical complexity of the sentence. At the same time, the logical connectives are interpreted as logical operations defined in terms of quantum logical gates. Physical models of quantum computational logics can be built by means of Mach-Zehnder interferometers.
CONTROLLABLE ADIABATIC MANIPULATION OF THE QUBIT STATE
Authors: BERMAN G. P. , BISHOP A. R. , BORGONOVI F. , TSIFRINOVICH V. I.
Published: November 2007

We propose a scheme which implements a controllable change of the state of the target spin qubit in such a way that both the control and the target spin qubits remain in their ground states. The interaction between the two spins is mediated by an auxiliary spin, which can transfer to its excited state. Our scheme suggests a possible relationship between the gate and adiabatic quantum computation.
A CURVATURE DEPENDENT BOUND FOR ENTANGLEMENT CHANGE IN CLASSICALLY CHAOTIC SYSTEMS
Authors: GHIKAS DEMETRIS P. K. , STAMATIOU GEORGE
Published: November 2007

Using the Calogero–Moser model and the Nakamura–Lakshmanan equations of motion for eigenvalues and eigenfunctions associated with a multi-partite quantum system, we prove an inequality between the mean bi-partite entanglement rate of change under the variation of a critical parameter and the level-curvature. This provides an upper bound for the rate of production or destruction of entanglement induced dynamically. We then investigate the dependence of the upper bound on the degree of chaos of the system, which in turn, through the inequality, gives a measure of the stability of the entangled state. Our analytical results are supported by extensive numerical calculations.
SIMPLE FAULT-TOLERANT ENCODING OVER q-ARY CSS QUANTUM CODES
Authors: SALAS PEDRO J.
Published: November 2007

CSS codes are a subfamily of stabilizer codes especially appropriate for fault-tolerant quantum computations. A very simple method is proposed to encode a general qudit when a Calderbank–Shor–Steane quantum code, defined over a q-ary alphabet, is used.
QUANTUM KOLMOGOROV COMPLEXITY AND ITS APPLICATIONS
Authors: MORA CATERINA E. , BRIEGEL HANS J. , KRAUS BARBARA
Published: November 2007

Kolmogorov complexity is a measure of the information contained in a binary string. We investigate here the notion of quantum Kolmogorov complexity, a measure of the information required to describe a quantum state. We show that for any definition of quantum Kolmogorov complexity measuring the number of classical bits required to describe a pure quantum state, there exists a pure n-qubit state which requires exponentially many bits of description. This is shown by relating the classical communication complexity to the quantum Kolmogorov complexity. Furthermore, we give some examples of how quantum Kolmogorov complexity can be applied to prove results in different fields, such as quantum computation and thermodynamics, and we generalize it to the case of mixed quantum states.
QUANTUM AUCTIONS
Authors: HOGG TAD , HARSHA PAVITHRA , CHEN KAY-YUT
Published: November 2007

We present a quantum auction protocol using superpositions to represent bids and distributed search to identify the winner(s). Measuring the final quantum state gives the auction outcome while simultaneously destroying the superposition. Thus, non-winning bids are never revealed. Participants can use entanglement to arrange for correlations among their bids, with the assurance that this entanglement is not observable by others. This protocol is useful for information hiding applications, such as partnership bidding with allocative externality or concerns about revealing bidding preferences. The protocol applies to a variety of auction types, e.g. first or second price, and to auctions involving either a single item or arbitrary bundles of items (i.e. combinatorial auctions). We analyze the game-theoretical behavior of the quantum protocol for the simple case of a sealed-bid quantum, and show how a suitably designed adiabatic search reduces the possibilities for bidders to game the auction. This design illustrates how incentive rather that computational constraints affect quantum algorithm choices.
S. POMBEGENE REGULATORY NETWORK INFERENCE USING THE FUZZY LOGIC NETWORK
Authors: CAO YINGJUN , YU LINGCHU , TOKUTA ALADE , WANG PAUL P.
Published: November 2007

In this paper, we first study the stability and convergence property of fuzzy logic networks (FLN). A random approach is adopted to simulate the convergence speed and steady-state properties based on four fuzzy logical functions. The simulation results show that MV logical function causes the system to be on the edge of chaos when the number of nodes increases. Thus this logical function is more useful to infer real complex networks, such as gene regulatory networks. Then, a novel gene regulatory network inference algorithm based on the FLN theory is proposed and tested. The algorithm uses fuzzy logical functions to model gene regulatory relationships, and the degrees of regulations are represented as the length of accumulated distances during a period of time intervals. Based on the assumption that the distribution of connectivity in yeast protein-protein networks follows the Zipf's law, the criteria for algorithm parameter quantifications are deduced. One unique feature of this algorithm is that it makes limited a priori assumptions concerning the modeling; hence the algorithm is categorized as a data-driven algorithm. The algorithm was applied to the S. pombe time-series dataset and 407 cell cycle regulated genes were used. The algorithm inferred 59 functionally verified regulations, 47 regulations involving genes with unknown functions, and 19 dubious regulations. The 125 regulatory pairs involve 108 genes, and the average connectivity of the inferred network, 1.157, confirms the Zipf's law.
DIFFUSION IN SIMULATED SiO2 NANOPARTICLES
Authors: HOANG VO VAN
Published: November 2007

Diffusion in liquid SiO 2 nanoparticle with the diameter of 4 nm has been studied in a spherical model containing 2214 atoms via Molecular Dynamics simulation (MD). Diffusion constant of atomic species has been calculated over temperatures ranged from 2100 K to 7000 K and compared with those observed for the bulk. We found that temperature dependence of diffusion constant of atomic species in nanoparticle shows an Arrhenius law at temperatures above 2100 K and at T > 4200 K , it deviates from an Arrhenius law. However, unlike those observed in the bulk at T > 4200 K , it does not show a power law, D ~ (T - Tc)γ. Moreover, at relatively low temperatures, diffusion constant in nanoparticle is higher than that in the bulk indicating the surface dynamics effects.
CHARGE TRANSPORT THROUGH CARBON NANOTUBE OR FULLERENE–MOLECULE–SILICON JUNCTIONS
Authors: FAN FU-REN F. , CHEN BO , FLATT AUSTEN K. , TOUR JAMES M. , BARD ALLEN J.
Published: November 2007

We report here the current–voltage (i–V) characteristics of several (n++- Si /MNOPE/ C 60/ Pt -tip) or (n++- Si /MNOPE/SWCNT/ Pt -tip) junctions, where MNOPE = 2'-mononitro-4, 4'-bis(phenylethynyl)-1-phenylenediazonium and SWCNT = single wall carbon nanotube. A layer of C 60 or SWCNT-derivatized MNOPE has strong effect on the i–V behavior of the junctions, including rectification, negative differential resistance (NDR) and switching behaviors. The i–V curve of a grafted molecular monolayer (GMM) of MNOPE atop n++- Si shows NDR behavior, whereas those of C 60- and SWCNT-derivatized GMMs of MNOPE on n++- Si show strong rectifying behavior with opposite rectification polarities. With C 60, larger currents were found with negative tip bias, while with SWCNT, the forward top bias was positive. Because C 60 tends to be a good electron acceptor and SWCNTs tend to be good electron donors, they show different i–V behavior, as observed. Some of the (n++- Si /MNOPE/SWCNT/ Pt -tip) junctions also show reversible bistable switching behavior.
Endovascular Therapies for Peripheral Arterial Disease
Authors: White Christopher J. , Gray William A.
Published: November 2007

Peripheral arterial disease is one manifestation of systemic atherosclerosis. The prevalence of peripheral arterial disease increases with the age of the population. It is important to remember the significant association of coincident coronary artery disease, which is the major cause of mortality in these patients. Remarkable technological advances in the past decade, along with patient preference, have shifted revascularization strategies from traditional open surgical approaches toward lower-morbidity percutaneous endovascular treatments. The availability of stents, more than any other advance, has fueled the growth of catheter-based procedures by improving the safety, durability, and predictability of percutaneous revascularization.
A Direct Micromechanical Approach toward the Development of Quadratic Stress Gradient Failure Criteria for Textile Composites
Authors: Karkkainen Ryan L. , Sankar Bhavani V. , Tzeng Jerome T.
Published: November 2007

Based upon previous results of direct micromechanical method (DMM) analysis of the representative volume element (RVE) of a plain-weave textile composite, two methods for predicting failure envelopes are presented: a parametric ellipse-fitting scheme, and a 27-term quadratic stress-gradient failure criterion. Both include the consideration of micro level stress gradients and effectively predict failure in agreement with the DMM. The parametric ellipse-fitting method was found to agree with DMM results to within a few percent. The quadratic failure criterion was found to agree within 9.3%, but the method is more robust in its ability to predict failure for complex loading cases.
Investigation on the Reduction of In-Plane Compressive Strength in Thick Preconditioned Composite Panels
Authors: Zhou G. , Rivera L.A.
Published: November 2007

This paper investigates the effects of damage characteristics and local curvature change on the residual compressive strength (RCS) of flat 4-mm thick carbon/epoxy panels through the examination of their buckling behavior. The damage was induced by impact, quasi-static loading and embedment of artificial delamination for a variety of damage areas, intensities and different local curvature changes. The embedment technique of artificial delaminations allowed the separation of the damage from the local curvature change. Panels with no or less significant damage in conjunction with no or little local curvature change failed in end crushing because of large membrane reaction, in-plane shear resistance and flexural rigidity. Prebuckling and Poisson's effect dictated their compressive behavior. Panels with significant damage followed the sequential behavior of prebuckling, local buckling, global buckling and ultimate failure in the mid-section region. Their RCSs were dictated by a combination of delamination size, intensity and local curvature change. Propagation of the damage with certain size and intensity associated with reduced flexural rigidity in the damaged area led to the local-to-global buckling transition and the panels failed at the global buckling-to-postbuckling transition at a nodal line. The effect of increasing the panel thickness on the ratio of RCS to a baseline value was not straightforward due to the end crushing failure of the thicker intact panels.
Preparation of High Loading Magnesium Hydroxide Flame Retardant Polypropylene by Solid State Shear Milling
Authors: Liu Yuan , Li Jie , Wang Qi
Published: November 2007

Due to high loading level and poor compatibility, magnesium hydroxide (MH) flame retardant polypropylene (PP) has poor processability and seriously deteriorated material performance. We adopted a novel processing technology, solid state shear milling (S3M) by using our self-designed pan-mill equipment, to prepare even MH/PP composite powder, as the flame retardant master batch to be added to the virgin PP. This original method can achieve efficient pulverization of PP, a high degree of blending, and even dispersion of MH in the resin, thus effectively controlling the dispersion phase in solid state. Simultaneously, mechanochemical effects of S3M can induce chemical interaction between PP and MH, and improve their compatibility. Compared with conventional melt processing, S3M can greatly enhance the melt flowability, and greatly modify the melt processability of the composite materials. Also, pre-compounded through S3M, MH flame retardant PP shows remarkably enhanced flame retardancy and mechanical performance, therefore showing promise to prepare high performance composite materials with high loading level for commercial applications.
A Silicone Treatment Compared to Traditional Natural Fiber Treatments: Effect on the Mechanical and Viscoelastic Properties of Jute—Vinylester Laminates
Authors: Stocchi A. , Bernal C. , Vázquez A. , Biagotti J. , Kenny J.
Published: November 2007

In this work vinylester—matrix composites reinforced with woven jute fabrics were investigated. The effect of a simple fiber treatment with silicone on the mechanical and viscoelastic response in comparison to traditional treatments was analyzed. Unless the composite with acetylated fibers, all composites exhibited higher values of rubbery storage modulus than the matrix. All treated fiber composites have similar damping capacities. Furthermore, silicone had a plasticizing effect on the vinylester matrix. The composites with washed fibers and with fibers treated with silicone exhibited slightly higher stiffness and strength values than other treated fiber composites. In addition to its experimental simplicity, the treatment with silicone also allowed us to obtain the composites with best combination of stiffness, strength, and toughness.
Microstructure, Hardness, and Bending Strength of Carbon Nanotube—Iron Aluminide Composites
Authors: Pang L.X. , Sun K.N. , Ren S. , Sun C. , Bi J.Q.
Published: November 2007

Iron aluminide (Fe3Al) composites reinforced with ~3 wt% of carbon nanotube (CNT) were fabricated by hot press consolidation. Ambient-temperature mechanical properties of the iron aluminide—CNT composites were determined. The hardness, compressive yield strength, and bending strength hardness of composites were higher by 63%, 1%, and 5%, respectively. Microscopic examination of the composite showed the added CNTs still keep their tubular structure. The preliminary results on the processing and improvement in mechanical properties of CNT-reinforced iron aluminide matrix composites are being reported here for the first time.
Synthesis and Characterization of Nanoalumina—Styrene Acrylonitrile High Impact Composite as a Plausible Civilian Armour Material
Authors: Singh Dhananjay , Rai K.N. , Jayasimha T. , Kumar Anil
Published: November 2007

Nanoalumina particles, prepared by autoignition of aluminum nitrate with urea, were made compatible with the styrene—acrylonitrile copolymer syrup (in its own monomer) by chemical modification using methacrylol isocyanate. The polymer syrup prepared this way was applied between two PMMA sheets of 10 cm × 10 cm × 2 mm dimension each and the composite thus prepared was tested with a bullet firing machine as well as a drop weight impact testing machine. The impact strength measurements of a two plate composite using both these procedures showed that the impact resistance was found to double in the case of a chemically modified nanoalumina composite. The impact energy needed to fracture the multilayered composites can be modeled by a quadratic expression involving the number of layers. A ten-layer PMMA sheet can withstand as much as 110 J impact energy without any noticeable damage. The ten-layer composite was not penetrated by a 0.32 IOF revolver having a bullet mass of 9.9 g and muzzle velocity of 236 ± 7 m/s (muzzle energy of 275 J). The eleven-layers composite was further tested by a Sub Machine Gun Carbine 9 mm 1A1, having a bullet mass of 11.9 g and muzzle velocity of 390 m/s (muzzle energy of 900 J) which produced an ordinary indent with no penetration.
Statistical Energy and Failure Analysis of CFRP Compression Behavior Using a Uniaxial Microbuckling Model
Authors: Guimard J.M. , Allix O. , Pechnik N. , Thevenet P.
Published: November 2007

Compression failure followed by fragmentation is a pre-eminent energy absorption mechanism in fiber-reinforced composites and, therefore, it is often used in crash absorption devices. Fragmentation is the last stage of degradation leading to total failure of a carbon fiber reinforced plastic (CFRP) laminate in compression. Micromechanical studies have shown that this phenomenon is initiated mainly by a microbuckling mechanism which depends on microstructural imperfections (fiber misalignment and matrix plasticity). As far as energy absorption and dedicated modeling strategies are concerned, the question is whether the failure scenario is dependent on these imperfections in terms of dissipated energy. In this context, we used a one-dimensional microscale approach to model plastic microbuckling and evaluate the corresponding dissipated energy for a realistic range of microstructural parameters (with statistical treatment). Contrary to our expectations and to the well-known sensitivity of the peak loads, these energies seem unaffected by microscopic parameters. In conclusion, we propose some ideas on how to include the main aspects of fragmentation, which can occur in composite materials under in-plane compression loading, on the mesoscale.
A Generalized Analytical Modeling of Grid Stiffened Composite Structures
Authors: Li Guoqiang , Cheng Jinquan
Published: November 2007

With the advancement of manufacturing technology, advanced grid stiffened (AGS) composite structures have been extensively studied recently due to their superior structural performance at a lower cost. Currently, the theoretical analysis involving AGS structures without fillers (empty bay) is dominated by the smeared method and finite element analysis (FEA). Obviously, the smeared method averages the local information and fails to predict structural behavior when the length scale (contact area) of the external load is smaller than the length scale (size) of the unit cell. This is because the actual structural behavior heavily depends on the spatial location of the applied load (at the rib, node, or cell). The limitation of FEA persists in its difficulty in conducting structural optimization. For AGS structures with fillers (filled bay), the interaction between the filler and the grid skeleton offers a higher level of challenge to theoretical modeling. In this study, a generalized analytical model was developed to predict the static structural behavior without smearing. This model was generalized in such a way that it unified the analysis of both empty bay and filled bay and could be reduced to conventional laminated composite or sandwich composite. This model was developed based on the classical lamination theory by treating the bay area as inclusion and the physical discontinuity between the rib and the bay was considered by introducing a stiffness distribution function. Using Hamilton's variational principle, the governing equation and boundary condition were obtained. The variable coefficient differential equation was solved by Fourier series expansion technique. The model was first validated by a numerical result found in the literature. Parametric studies were then conducted to evaluate the effect of various design parameters on the structural behavior subjected to both distributed load and concentrated load.
Frequency Analysis of Stress Waves in Testing 3-D Angle-interlock Woven Composite at High Strain Rates
Authors: Sun Baozhong , Gu Bohong
Published: November 2007

This article presents Fourier transform and wavelet packet analysis of stress waves in a split Hopkinson pressure bar apparatus where the compressive behaviors of 3-D angle-interlock woven composite were tested at strain rate of 800/s, 1600/s and 2100/s. The stress waves in incident and transmission bar are transformed into frequency domain to analyze the impact energy spectrum under different lengths and impact velocities of the strike bar. It was found that the energy-frequency distribution is irrelevant to impact velocity and will be left-shifted when the length of the striker bar (i.e., width of incident stress wave) increases. The impact energy is mainly concentrated on the low-frequency region. The wavelet packet analysis of the incident and transmission stress waves shows that the transform coefficients decrease from the low-frequency region to the high-frequency region. Furthermore, the coefficients in the high-frequency region only occur at the ascending and descending part of stress waves. Based on the time-frequency analysis results, a unique start point of the stress wave can be determined for the stress-time and strain-time history calculation. This method can improve the calculation precision of stress—strain curves of the 3-D woven composite under different strain rate compression. The calculating results indicate that the stress—strain curves of the 3-D angle-interlock woven composites are sensitive to strain rate. The compressive modulus, maximum compressive stress linearly increases with strain rate. The failure strain decreases when the strain rate increases. This start point determination method can also be extended to high strain rate tests (including compression, tension, etc.) of other materials with split Hopkinson bar apparatus.
Effects of Hygrothermal Conditions and UV Radiation on UHMWPE Fibers/Nanofiber—Epoxy Composites
Authors: Jana S. , Zhong W.H.
Published: November 2007

Nanofiber-epoxy with reactive graphitic nanofibers (r-GNFs) showed an improvement in adhesion properties in ultra-high molecular weight polyethylene (UHMWPE) fibers/epoxy resin composite (bundle/tow form) in our previous experiments. In this study, moisture absorption characteristics of pure-epoxy, nanofiber-epoxy materials and their UHMWPE bundle composites were investigated under hygrothermal aging and UV conditions. For the matrix specimens the weight gain deviated from Fick's law, and thus, a two-stage model, which includes both diffusion and structural relaxation, was applied to analyze the moisture absorption behaviors. For the bundle composites the results indicated that the weight gain showed compatibility with Fick's law. The UHMWPE fiber composite with nanofiber-epoxy containing 0.3 wt% r-GNF loading resulted in the lowest rate of water absorption. Bundle composites were also exposed to accelerated UV aging conditions. The UV test results showed that the plateau stress and ultimate tensile strength of the bundle composites have been reduced. However, the ductility of the UHMWPE composites was increased due to the plasticization in hygrothermal aging tests.
Marital Quality in the Context of Mild Cognitive Impairment
Authors: Garand Linda , Dew Mary Amanda , Urda Bridget , Lingler Jennifer Hagerty , DeKosky Steven T. , Reynolds Charles F.
Published: November 2007

Profound behavioral changes in persons with dementia often negatively affect the quality of marital relationships. Yet, little is known about the extent to which the marital relationship may be affected when the care recipient has milder degrees of cognitive impairment. This study characterizes marital quality among 27 adults who live with a spouse with mild cognitive impairment (MCI). This study demonstrates that at mild levels of cognitive impairment, specific behaviors in the affected person are distressing and may degrade the quality of the marital relationship. These results have implications for clinical practice and the delivery of health care and social services to these families. It is important to develop interventions to address the needs of these individuals and their caregivers. Results of this study suggest the need for mental health interventions designed to preserve the quality of these marital relationships.
Effect of coaching on psychological adjustment in patients with spinocerebellar degeneration: a pilot study
Authors: Izumi Shin-Ichi , Ando Kiyoshi , Ono Masafumi , Suzukamo Yoshimi , Michimata Akira , Fukuhara Shunichi
Published: November 2007

Objective: To examine effect of coaching intervention on psychological adjustment to illness and health-related QOL (HRQOL) in patients with spinocerebellar degeneration.

Design: Randomized controlled trial.

Subjects: Twelve independently living patients with spinocerebellar degeneration aged 20—65 years old, without cognitive impairment or psychiatric disorder received coaching intervention, which was postponed in another 12 (control).

Interventions: Three physician coaches telephoned assigned patients for 15—30 minutes in each of 10 weekly coaching sessions over three months.

Main outcome measures: Primary endpoints were HRQOL (SF-36) and psychological adjustment to illness (Nottingham Adjustment Scale, Japanese version; NAS-J).

Results: Two-way analysis of variance (group × time) showed statistically significant main effects of time for vitality (F = 5.00; P = 0.036), anxiety/depression (F = 5.15; P = 0.033), and locus of control (F = 5.58; P = 0.027), indicating improvement of scores over time in both coaching and control groups. No main effect of group or interaction was seen. However analysis of covariance with baseline scores as the covariate showed the coaching group to have better self-efficacy scores than controls at follow-up (least-square mean, experimental group, 65.1; control group, 52.7; P = 0.037).

Conclusion: Carefully structured telephone coaching can improve self-efficacy in patients with spinocerebellar degeneration.
Group physical activity for demented older adults — feasibility and effectiveness
Authors: Netz Yael , Axelrad Salit , Argov Ester
Published: November 2007

Objectives: (1) To examine the feasibility of group physical activity in a day-care routine. (2) To assess the impact of this programme on functional fitness.

Design: Ten-week observational period, followed by 12 weeks of intervention in randomized controlled design, followed by 12 weeks of intervention only.

Setting: A day-care centre for demented older individuals.

Participants: Twenty-nine demented (Mini-Mental State Exam score 13.3 ± 5.83) day-care attendees, mean ± SD age 76.9 ± 6.72.

Intervention: Group physical activity vs. social activity, followed by increased-intensity physical activity for both groups.

Measurements: Performance rate (PR) in physical activity sessions, Timed Get Up and Go (TGUG), Sit-to-Stand (STS) and Functional Reach (FR).

Results: Approximately 60% of the participants performed almost all movements or repetitions in both intervention phases. No improvements were observed following the first phase of physical activity. A reduction of 3.2 seconds (±1.2 SE) was noted in the time needed to perform the TGUG following the increased-intensity physical activity.

Conclusion: A carefully tailored group physical activity, conducted twice weekly with a group of 12—15 participants in a medium size room, and led by a physical activity teacher assisted by a staff aide, is feasible. Although physical activity performed mainly while sitting is ineffective, it can be effective to a meaningful degree when performed while standing or walking.
Daily physical activities of patients with chronic pain or fatigue versus asymptomatic controls. A systematic review
Authors: van Weering Marit , Vollenbroek-Hutten M.M.R. , Kotte E.M. , Hermens H.J.
Published: November 2007

Objective: To gain an insight into the daily physical activity levels of patients with chronic pain or fatigue compared with asymptomatic controls.

Data sources: MEDLINE, EMBASE, PsycINFO, Picarta, Cochrane Database of Systematic Reviews, reference tracking and a manual search of relevant journals.

Review methods: A systematic, computerized database search of the medical databases up to September 2006 was performed. In addition, a hand search of relevant journals was carried out. Appropriate studies reported on the daily physical activities of adult patients with chronic pain or fatigue and included an asymptomatic control group. Two reviewers independently carried out methodological quality assessment and data extraction. A qualitative analysis was performed.

Results: Twelve studies were included, involving five different syndromes. Results show large heterogeneity in methods used and syndromes investigated, which limited evidence. Eleven different methods were used to assess daily physical activities resulting in 16 different outcome parameters. There seem to be differences between the different syndromes, but results are not conclusive. Eight studies reported a lower physical activity level in patients compared with controls. There seems to be a difference in results between studies using objective versus those using subjective methods.

Conclusions: Results reported in the literature with respect to the activity level of patients with chronic pain or fatigue compared with controls were too heterogeneous to give sufficient evidence and were not conclusive.