bluuebunny/crossref_metadata_2025 huggingface dataset:
Why Does A Small Power Lead? ASEAN Leadership in Asia–Pacific Regionalism
Authors: Kim Min‐hyung
Published: April 2012

Asia–Pacific regionalism is quite different from its counterparts in other regions of the world. Most notably, it displays an extremely low level of institutionalization and is led by a small/weak power (i.e., ASEAN), rather than major powers in the region. ASEAN leadership stressing dialogue and consensus without enforcement mechanisms inevitably produces weak regional institutions that are ineffective in resolving region‐wide security and economic problems. Contending that the main source of the small power‐driven (i.e., ASEAN‐led) Asia–Pacific regionalism is the influence rivalry and leadership competition among the three major powers (the USA, China, and Japan) in the region, this article seeks to articulate the conditions under which the weak power of ASEAN takes the lead in the process of regional security and economic cooperation.
Intestinal transporters for endogenic and pharmaceutical organic anions: the challenges of deriving in-vitro kinetic parameters for the prediction of clinically relevant drug–drug interactions
Authors: Grandvuinet Anne Sophie , Vestergaard Henrik Tang , Rapin Nicolas , Steffansen Bente
Published: April 2012

Objectives

This review provides an overview of intestinal human transporters for organic anions and stresses the need for standardization of the various in-vitro methods presently employed in drug–drug interaction (DDI) investigations.

Key findings

Current knowledge on the intestinal expression of the apical sodium-dependent bile acid transporter (ASBT), the breast cancer resistance protein (BCRP), the monocarboxylate transporters (MCT) 1, MCT3-5, the multidrug resistance associated proteins (MRP) 1–6, the organic anion transporting polypetides (OATP) 2B1, 1A2, 3A1 and 4A1, and the organic solute transporter α/β (OSTα/β) has been covered along with an overview of their substrates and inhibitors. Furthermore, the many challenges in predicting clinically relevant DDIs from in-vitro studies have been discussed with focus on intestinal transporters and the various methods for deducting in-vitro parameters for transporters (Km/Ki/IC50, efflux ratio). The applicability of using a cut-off value (estimated based on the intestinal drug concentration divided by the Ki or IC50) has also been considered.

A re-evaluation of the current approaches for the prediction of DDIs is necessary when considering the involvement of other transporters than P-glycoprotein. Moreover, the interplay between various processes that a drug is subject to in-vivo such as translocation by several transporters and dissolution should be considered.
Application of double patterning technology to fabricate optical elements: Process simulation, fabrication, and measurement
Authors: Babin S. , Glushenko G. , Weber T. , Kaesebier T. , Kley E.-B. , Szeghalmi A.
Published: April 2012

Double patterning is an important technique for the improvement of spatial resolution in fabricated micro and nanostructures. In this paper, we investigated and applied the double patterning technique to fabricate diffractive optical elements. Simulations of multiple dry etch and film deposition steps were performed to study and optimize the vertical profiles of the fabricated patterns. Etch and deposition characteristics were varied to study their impact on the resulting vertical profile of the metal layers. The influence of the linewidth of the initial resist pattern and the process-induced tapering of the grating tops on the optical performance were investigated in particular. A variably shaped electron-beam lithography system was used for the fabrication of the initial resist pattern. The spatial frequency was then doubled by means of double patterning. Broadband aluminum and iridium wire grid polarizers were fabricated for applications down to the UV range with a feature size of 30 nm, a period of 100 nm, and a vertical aspect ratio of about 5:1. Optical measurements have confirmed the designed optical properties.
Optimized generation of high resolution breast anthropomorphic software phantoms
Authors: Pokrajac David D. , Maidment Andrew D. A. , Bakic Predrag R.
Published: April 2012

Purpose:

The authors present an efficient method for generating anthropomorphic software breast phantoms with high spatial resolution. Employing the same region growing principles as in their previous algorithm for breast anatomy simulation, the present method has been optimized for computational complexity to allow for fast generation of the large number of phantoms required in virtual clinical trials of breast imaging.

Methods:

The new breast anatomy simulation method performs a direct calculation of the Cooper's ligaments (i.e., the borders between simulated adipose compartments). The calculation corresponds to quadratic decision boundaries of a maximuma posteriori classifier. The method is multiscale due to the use of octree‐based recursive partitioning of the phantom volume. The method also provides user‐control of the thickness of the simulated Cooper's ligaments and skin.

Results:

Using the proposed method, the authors have generated phantoms with voxel size in the range of (25–1000 μm)3/voxel. The power regression of the simulation time as a function of the reciprocal voxel size yielded a log‐log slope of 1.95 (compared to a slope of 4.53 of our previous region growing algorithm).

Conclusions:

A new algorithm for computer simulation of breast anatomy has been proposed that allows for fast generation of high resolution anthropomorphic software phantoms.
Time‐delayed summation as a means of improving resolution on fast rotating computed tomography systems
Authors: Nowak Tristan , Hupfer Martin , Althoff Felix , Brauweiler Robert , Eisa Fabian , Steiding Christian , Kalender Willi A.
Published: April 2012

Purpose:

Modern computed tomography (CT) systems are supporting increasingly fast rotation speeds, which are a prerequisite for fast dynamic acquisition, e.g. in perfusion imaging, and for new modalities such as dedicated breast CT, where breathhold scanning is indicated. However, not all detector technologies are supporting the high frame rates that are necessary to retain high resolution for objects far away from the isocenter. Even on systems that would support a sufficiently high frame rate, the necessary bandwidth of the data transfer from the rotating gantry stills remains challenging. The authors evaluated a pixel shifting technique termed time‐delayed summation (TDS) as a method of increasing resolution on fast rotating CT systems without the need to increase the frame rate.

Methods:

In TDS mode, detector pixel values are shifted along rows during image acquisition to compensate for detector motion. In order to fully exploit TDS, focal spot position control (FSC) was used in combination with TDS. FSC applies a counter movement to the x‐ray focal spot during image acquisition such that it is kept fixed in space. As a proof of concept, measurements were performed on a prototype photon counting detector capable of TDS. The detector was mounted on a movable table and a gold wire phantom was imaged with different TDS settings and detector velocities. Additionally, simulations of a broad range of TDS and FSC settings on two different modalities, a clinical CT scanner and a breast CT scanner, and two different detector geometries, flat and cylindrical, were performed to assess the gain in resolution and contrast in cylindrical water phantoms containing a small wire at distances from the phantom center varied from 5% to 90% of the phantom radius. As figures of merit, the modulation transfer function (MTF) at 10% and the maximum contrast were used and compared against the respective values when using step‐and‐shoot acquisition, which means stopping the rotation when a projection image is acquired.

Results:

Measurements showed that detector movement and the resulting blurring of the wire projections were compensated to the expected degree when using the appropriate number of TDS shifts per frame (TDS factor). Using simulations it was found that when using the optimal TDS factor, over 90% of the resolution achieved in step‐and‐shot mode was reached for all investigated wire positions. TDS showed better performance on a cylindrical detector that on the same system with a flat detector. TDS factors that were deviating from the optimum by more than 1 shift led to a performance below that of standard continuous acquisition.

Conclusions:

The findings of this study encourage the combined usage of TDS and FSC in systems that require fast rotation. The integration of TDS in state‐of‐the‐art x‐ray detectors is feasible.
A Large Bioactive BMP Ligand with Distinct Signaling Properties Is Produced by Alternative Proconvertase Processing
Authors: Akiyama Takuya , Marqués Guillermo , Wharton Kristi A.
Published: April 2012

Mutations in an evolutionarily conserved processing site in bone morphogenetic proteins are associated with developmental disorders.
Science Signaling
Podcast: 3 April 2012
Authors: Sabatini David M. , Baur Joseph A. , VanHook Annalisa M.
Published: April 2012

Rapamycin’s effects on longevity and insulin sensitivity are mediated by different molecular targets.
Dissecting Rapamycin Responses
Authors: Ray L. Bryan
Published: April 2012

The effect of the drug rapamycin on life span can be separated from its effects on metabolism.
Sleeping Around the Clock
Authors: Ray L. Bryan
Published: April 2012

Two proteins that regulate cell division also regulate sleep in
Drosophila
.
Summary of Ceftaroline Activity against Pathogens in the United States, 2010: Report from the Assessing Worldwide Antimicrobial Resistance Evaluation (AWARE) Surveillance Program
Authors: Flamm Robert K. , Sader Helio S. , Farrell David J. , Jones Ronald N.
Published: April 2012

The
A
ssessing
W
orldwide
A
ntimicrobial
R
esistance
E
valuation (AWARE) surveillance program is a sentinel resistance monitoring system designed to track the activity of ceftaroline and comparator agents. In the United States, a total of 8,434 isolates were collected during the 2010 surveillance program from 65 medical centers distributed across the nine census regions (5 to 10 medical centers per region). All organisms were isolated from documented infections, including 3,055 (36.2%) bloodstream infections, 2,282 (27.1%) respiratory tract infections, 1,965 (23.3%) acute bacterial skin and skin structure infections, 665 (7.9%) urinary tract infections, and 467 (5.5%) miscellaneous other infection sites. Ceftaroline was the most potent β-lactam agent tested against staphylococci. The MIC
90
values were 1 μg/ml for methicillin-resistant
Staphylococcus aureus
(MRSA; 98.4% susceptible) and 0.5 μg/ml for methicillin-resistant coagulase-negative staphylococci (CoNS). Ceftaroline was 16- to 32-fold more potent than ceftriaxone against methicillin-susceptible staphylococcal strains. All staphylococcus isolates (
S. aureus
and CoNS) were inhibited at ceftaroline MIC values of ≤2 μg/ml. Ceftaroline also displayed potent activity against streptococci (MIC
90
, 0.015 μg/ml for beta-hemolytic streptococci; MIC
90
, 0.25 μg/ml for penicillin-resistant
Streptococcus pneumoniae
). Potent activity was also shown against Gram-negative pathogens (
Haemophilus influenzae
,
Haemophilus parainfluenzae
, and
Moraxella catarrhalis
). Furthermore, wild-type strains of
Enterobacteriaceae
(non-extended-spectrum β-lactamase [ESBL]-producing strains and non-AmpC-hyperproducing strains) were often susceptible to ceftaroline. Continued monitoring through surveillance networks will allow for the assessment of the evolution of resistance as this new cephalosporin is used more broadly to provide clinicians with up-to-date information to assist in antibiotic stewardship and therapeutic decision making.
Pharmacokinetic/Pharmacodynamic Predictors of Clinical Potency for Hepatitis C Virus Nonnucleoside Polymerase and Protease Inhibitors
Authors: Reddy Micaela B. , Morcos Peter N. , Le Pogam Sophie , Ou Ying , Frank Karl , Lave Thierry , Smith Patrick
Published: April 2012

This analysis was conducted to determine whether the hepatitis C virus (HCV) viral kinetics (VK) model can predict viral load (VL) decreases for nonnucleoside polymerase inhibitors (NNPolIs) and protease inhibitors (PIs) after 3-day monotherapy studies of patients infected with genotype 1 chronic HCV. This analysis includes data for 8 NNPolIs and 14 PIs, including VL decreases from 3-day monotherapy, total plasma trough concentrations on day 3 (
C
min
), replicon data (50% effective concentration [EC
50
] and protein-shifted EC
50
[EC
50,PS
]), and for PIs, liver-to-plasma ratios (LPRs) measured
in vivo
in preclinical species. VK model simulations suggested that achieving additional log
10
VL decreases greater than one required 10-fold increases in the
C
min
. NNPolI and PI data further supported this result. The VK model was successfully used to predict VL decreases in 3-day monotherapy for NNPolIs based on the EC
50,PS
and the day 3
C
min
. For PIs, however, predicting VL decreases using the same model and the EC
50,PS
and day 3
C
min
was not successful; a model including LPR values and the EC
50
instead of the EC
50,PS
provided a better prediction of VL decrease. These results are useful for designing phase 1 monotherapy studies for NNPolIs and PIs by clarifying factors driving VL decreases, such as the day 3
C
min
and the EC
50,PS
for NNPolIs or the EC
50
and LPR for PIs. This work provides a framework for understanding the pharmacokinetic/pharmacodynamic relationship for other HCV drug classes. The availability of mechanistic data on processes driving the target concentration, such as liver uptake transporters, should help to improve the predictive power of the approach.
Impact of Two-Component Regulatory Systems PhoP-PhoQ and PmrA-PmrB on Colistin Pharmacodynamics in Pseudomonas aeruginosa
Authors: Ly Neang S. , Yang Jenny , Bulitta Jurgen B. , Tsuji Brian T.
Published: April 2012

The
in vitro
pharmacodynamics of colistin against
Pseudomonas aeruginosa
PAO1 wild-type and isogenic knockout strains of
phoP
and
pmrA
were evaluated. Colistin killing at subinhibitory concentrations was greater against the
phoP
and
pmrA
mutants than the wild type within the first 8 h: the concentration that results in 50% of maximal effect (EC
50
) of the
pmrA
mutant (0.413 mg/liter) was less than that of the wild type (0.718 mg/liter) (
P
< 0.05). An
in vitro
pharmacodynamic model simulating human colistin regimens displayed initial killing followed by regrowth in the
phoP
mutant and gradual regrowth in the
pmrA
mutant and wild type.
Involvement of Mismatch Repair in the Reciprocal Control of Motility and Adherence of Uropathogenic Escherichia coli
Authors: Cooper Lauren A. , Simmons Lyle A. , Mobley Harry L. T.
Published: April 2012

Type 1 fimbriae and flagella, two surface organelles critical for colonization of the urinary tract by uropathogenic
Escherichia coli
(UPEC), mediate opposing virulence objectives. Type 1 fimbriae facilitate adhesion to mucosal cells and promote bacterial persistence in the urinary tract, while flagella propel bacteria through urine and along mucous layers during ascension to the upper urinary tract. Using a transposon screen of the
E. coli
CFT073
fim
locked-ON (L-ON) mutant, a construct that constitutively expresses type 1 fimbriae and represses motility, we identified six mutants that exhibited a partial restoration of motility. Among these six mutated genes was
mutS
, which encodes a component of the methyl-directed mismatch repair (MMR) system. When complemented with
mutS in trans
, motility was again repressed. To determine whether the MMR system, in general, is involved in this reciprocal control, we characterized the effects of gene deletions of other MMR components on UPEC motility. Isogenic deletions of
mutS
,
mutH
, and
mutL
were constructed in both wild-type CFT073 and
fim
L-ON backgrounds. All MMR mutants showed an increase in motility in the wild-type background, and Δ
mutH
and Δ
mutS
mutations increased motility in the
fim
L-ON background. Cochallenge of the wild-type strain with an MMR-defective strain showed a subtle but significant competitive advantage in the bladder and spleen for the MMR mutant using the murine model of ascending urinary tract infection after 48 h. Our findings demonstrate that the MMR system generally affects the reciprocal regulation of motility and adherence and thus could contribute to UPEC pathogenesis during urinary tract infections.
Neutralizing Antibodies Elicited by a Novel Detoxified Pneumolysin Derivative, PlyD1, Provide Protection against Both Pneumococcal Infection and Lung Injury
Authors: Salha Danielle , Szeto Jason , Myers Lisa , Claus Carol , Sheung Anthony , Tang Mei , Ljutic Belma , Hanwell David , Ogilvie Karen , Ming Marin , Messham Benjamin , van den Dobbelsteen Germie , Hopfer Robert , Ochs Martina M. , Gallichan Scott
Published: April 2012

Streptococcus pneumoniae
pneumolysin (PLY) is a virulence factor that causes toxic effects contributing to pneumococcal pneumonia. To date, deriving a PLY candidate vaccine with the appropriate detoxification and immune profile has been challenging. A pneumolysin protein that is appropriately detoxified and that retains its immunogenicity is a desirable vaccine candidate. In this study, we assessed the protective efficacy of our novel PlyD1 detoxified PLY variant and investigated its underlying mechanism of protection. Results have shown that PlyD1 immunization protected mice against lethal intranasal (i.n.) challenge with pneumococci and lung injury mediated by PLY challenge. Protection was associated with PlyD1-specific IgG titers and
in vitro
neutralization titers. Pretreatment of PLY with PlyD1-specific rat polyclonal antiserum prior to i.n. delivery of toxin reduced PLY-mediated lung lesions, interleukin-6 (IL-6) production, and neutrophil infiltration into lungs, indicating that protection from lung lesions induced by PLY is antibody mediated. Preincubation of PLY with a neutralizing monoclonal PLY antibody also specifically reduced the cytotoxic effects of PLY after i.n. inoculation in comparison to nonneutralizing monoclonal antibodies. These results indicate that the induction of neutralizing antibodies against PLY can contribute to protection against bacterial pneumonia by preventing the development of PLY-induced lung lesions and inflammation. Our detoxified PlyD1 antigen elicits such PLY neutralizing antibodies, thus serving as a candidate vaccine antigen for the prevention of pneumococcal pneumonia.
ANRS–COM'TEST: description of a community-based HIV testing intervention in non-medical settings for men who have sex with men
Authors: Champenois Karen , Le Gall Jean-Marie , Jacquemin Cédric , Jean Sophie , Martin Cyril , Rios Laura , Benoit Olivier , Vermoesen Stéphanie , Lert France , Spire Bruno , Yazdanpanah Yazdan
Published: April 2012

Objective

To describe a community-based HIV testing programme.

Design and setting

An intervention of HIV voluntary testing conducted in non-medical settings in four French cities.

Participants

Men who have sex with men (MSM).

Intervention

Counselling and rapid HIV testing staffed by trained personnel from an HIV/AIDS community-based organisation.

Primary and secondary outcome measures

The population that has taken hold of the intervention and the satisfaction of participants. Data were collected on demographics, HIV testing history, sexual practices and satisfaction with the testing programme.

Results

532 MSM were tested between February 2009 and June 2010, of whom 49 (9%) were tested two or more times. 468 MSM (88%) had casual male partners in the previous 6 months, and 152 (35%) reported having unprotected anal intercourse with risky casual partners (HIV infected or HIV serostatus unknown). 159 men (30%) had not been tested in the previous 2 years, and 50 (31%) of whom had unprotected anal intercourse with risky casual partners. Among the 15 patients who tested positive (2.8%), 12 (80%) received confirmation and were linked to care (median CD4 cell count =550/mm3). Satisfaction was high: 92% reported being ‘very satisfied’ with their experience. Steps of counselling and testing procedure were respected by testers and difficulties in handling tests were rare.

Conclusions

This community-based HIV testing programme reached high-risk MSM, of whom a substantial proportion had not been tested lately. This novel service supplements pre-existing HIV testing services and increases access to HIV testing in high-risk groups.
ON THE ORIGIN OF PROBABILITY IN QUANTUM MECHANICS
Authors: HSU STEPHEN D. H.
Published: April 2012

I give a brief introduction to many worlds or "no wave function collapse" quantum mechanics, suitable for non-specialists. I then discuss the origin of probability in such formulations, distinguishing between objective and subjective notions of probability.
DESCRIPTION OF (PSEUDO-)RAPIDITY DENSITY AND TRANSVERSE MOMENTUM DISTRIBUTIONS IN A WIDE ENERGY RANGE $(\sqrt{s} = 22.4\hbox{--}7000~{\rm GeV})$
Authors: OHSAWA AKINORI , SHIBUYA EDISON HIROYUKI , TAMADA MASANOBU
Published: April 2012

The rapidity density and transverse momentum distributions of produced particles in multiple particle production are formulated assuming that the produced particles are emitted isotropically from several emitting centers. The energy distribution of produced particles in the rest frames of respective emitting centers is that of the Tsallis statistics. The distribution of emitting centers is flat with slanting cuts at both shoulders on the rapidity axis in the center of mass system. The formulation includes six adjustable parameters, among which four are energy dependent and more important and are determined so that the transverse momentum and the (pseudo-)rapidity density distributions fit to the data at various energies. The energy dependences of the four parameters, determined empirically, reproduce quite well the energy dependence of the average transverse momentum, that of the pseudo-rapidity density at η* = 0 and that of the charged multiplicity. The energy dependence of the inelasticity is either increasing or decreasing from the assumed value of K = 0.5 at [Formula: see text], due to lack of experimental data at the most-forward rapidity region. The pseudo-rapidity density distribution at LHC energy [Formula: see text] expected by the present formulation is compared with those by the other models.
COMMENT ON "DIMENSION OF THE MODULI SPACE AND HAMILTONIAN ANALYSIS OF BF FIELD THEORIES"
Authors: MONDRAGON MAURICIO
Published: April 2012

The purpose of this Comment is to point out that the results presented in the appendix of M. Mondragon and M. Montesinos, J. Math. Phys.47, 022301 (2006) provides a generic method so as to deal with cases as those of Sec. 6 of R. Cartas-Fuentevilla, A. Escalante-Hernández, and J. Berra-Montiel, Int. J. Mod. Phys. A26, 3013 (2011). The results already reported are: the canonical analysis, the transformations generated by the constraints, and the analysis of the reducibility of the constraints for SO (3, 1) and SO (4) four-dimensional BF theory coupled or not to a cosmological constant. But such results are generic and hold actually for any Lie algebra having a nondegenerate inner product invariant under the action of the gauge group.
MINIMAL UNKNOTTING SEQUENCES OF REIDEMEISTER MOVES CONTAINING UNMATCHED RII MOVES
Authors: HAYASHI CHUICHIRO , HAYASHI MIWA , SAWADA MINORI , YAMADA SAYAKA
Published: April 2012

Arnold introduced invariants J+, J- and St for generic planar curves. It is known that both J+/2 + St and J-/2 + St are invariants for generic spherical curves. Applying these invariants to underlying curves of knot diagrams, we can obtain lower bounds for the number of Reidemeister moves required for unknotting. J- /2 + St works well to count the minimum number of unmatched RII moves. However, it works only up to a factor of two for RI moves. Let w denote the writhe for a knot diagram. We show that J-/2 + St ± w/2 also gives sharp counts for the number of required RI moves, and demonstrate that it gives a precise estimate for a certain family of diagrams of the unknot with the underlying curve r = 2 + cos (nθ/(n + 1)), (0 ≤ θ ≤ 2(n + 1)π).
HIGH-ORDER RADIATION BOUNDARY CONDITIONS FOR STRATIFIED MEDIA AND CURVILINEAR COORDINATES
Authors: HAGSTROM THOMAS
Published: April 2012

Optimized local radiation boundary conditions to truncate the computational domain by a rectangular boundary have been constructed for acoustic waves propagating into a homogeneous, isotropic far field. Here we try to achieve comparable efficiencies in stratified media and cylindrical coordinates. We find that conditions constructed for homogeneous media are highly effective in the stratified case. On the circle we derive boundary conditions by optimizing a semidiscretized perfectly matched layer. Though we are unsuccessful in matching the accuracies of the Cartesian case, our experiments show that older sequences based on the progressive wave expansion are surprisingly efficient.
A SCENARIO STUDY FOR IMPROVING COST-EFFECTIVENESS IN ACOUSTIC TIME-REVERSAL SOURCE RELOCATION IN AN URBAN ENVIRONMENT
Authors: LIU LANBO , XIE HAO , ALBERT DONALD G. , ELLER PAUL R. , CHENG JING-RU C.
Published: April 2012

Through finite difference time domain (FDTD) numerical simulation, we have studied the possible observation settings to improve the cost effectiveness in time-reversal (TR) source relocation in a two-dimensional (2D) urban setting under a number of typical scenarios. All scenario studies were based on the FDTD computation of the acoustic wave field resulted from an impulse source, propagated through an artificial village composed of 15 buildings and a set of sources and receivers, a typical urban setting has been extensively analyzed in previous studies. The FDTD numerical modeling code can be executed on an off-the-shelf graphic processor unit (GPU) that increases the speed of the time-reversal calculations by a factor of 200. With this approach the computational results lead to some significant conclusions. In general, using only one non-line-of-sight (NLOS) single receiver is not enough to do a quality work to re-locate the source via time-reversal. This is particularly true when there are more than one path between the source and this receiver with similar wave energy travel time. However, when the single sensor is located in an acoustic channel, reverberation inside the waveguide may increase the effective aperture of the single receiver enough to give a good location. It is equivalent to say that the waveguide and the single receiver form a "virtual array". It appears that a sensor array with a minimum number of three receivers might be the most cost-effective way to carry out TR source relocation in an urban environment. The most optimal geometry of a sensor array with a minimum number of three receivers could be an equal side-length triangle. Simple analysis showed that by this setup it is possible to catch sound sources from almost all possible azimuths. Effective source relocation essentially depends on the geometry, relativity to the scatters, etc. of the sensing array. Generally, adding another single sensor relatively far away from the main array will not improve the results. It is practically useful and achievable to have a sensor array mounted on the outside of a single building, and in these cases successful source relocations were obtained. As stated by the fundamental TR theory, increasing the number of scatters, here, increasing the number of buildings will definitely be helpful to increase the effectiveness of TR source relocation.
EXTENSION OF THE PUFEM TO ELASTIC WAVE PROPAGATION IN LAYERED MEDIA
Authors: LAGHROUCHE O. , EL-KACIMI A. , TREVELYAN J.
Published: April 2012

This work deals with the extension of the partition of unity finite element method (PUFEM) "(Comput. Meth. Appl. Mech. Eng.139 (1996) pp. 289–314; Int. J. Numer. Math. Eng.40 (1997) 727–758)" to solve wave problems involving propagation, transmission and reflection in layered elastic media. The proposed method consists of applying the plane wave basis decomposition to the elastic wave equation in each layer of the elastic medium and then enforce necessary continuity conditions at the interfaces through the use of Lagrange multipliers. The accuracy and effectiveness of the proposed technique is determined by comparing results for selected problems with known analytical solutions. Complementary results dealing with the modeling of pure Rayleigh waves are also presented where the PUFEM model incorporates information about the pressure and shear waves rather than the Rayleigh wave itself.
LOW- TO MID-FREQUENCY SCATTERING FROM ELASTIC OBJECTS ON A SAND SEA FLOOR: SIMULATION OF FREQUENCY AND ASPECT DEPENDENT STRUCTURAL ECHOES
Authors: ZAMPOLLI MARIO , ESPANA AUBREY L. , WILLIAMS KEVIN L. , KARGL STEVEN G. , THORSOS ERIC I. , LOPES JOSEPH L. , KENNEDY JERMAINE L. , MARSTON PHILIP L.
Published: April 2012

The scattering from roughly meter-sized targets, such as pipes, cylinders and unexploded ordnance shells in the 1–30 kHz frequency band is studied by numerical simulations and compared to experimental results. The numerical tool used to compute the frequency and aspect-dependent target strength is a hybrid model, consisting of a local finite-element model for the vicinity of the target, based on the decomposition of the three-dimensional scattering problem for axially symmetric objects into a series of independent two-dimensional problems, and a propagation model based on the wavenumber spectral integral representation of the Green's functions for layered media.
STOCHASTIC QUASI-GEOSTROPHIC EQUATION
Authors: RÖCKNER MICHAEL , ZHU RONGCHAN , ZHU XIANGCHAN
Published: April 2012

In this note we study the 2D stochastic quasi-geostrophic equation in 𝕋2 for general parameter α ∈ (0, 1) and multiplicative noise. We prove the existence of martingale solutions and pathwise uniqueness under some condition in the general case, i.e. for all α ∈ (0, 1). In the subcritical case α > 1/2, we prove existence and uniqueness of (probabilistically) strong solutions and construct a Markov family of solutions. In particular, it is uniquely ergodic for α > 2/3 provided the noise is non-degenerate. In this case, the convergence to the (unique) invariant measure is exponentially fast. In the general case, we prove the existence of Markov selections.
ASYMPTOTIC EXPANSIONS FOR THE GAUSSIAN UNITARY ENSEMBLE
Authors: HAAGERUP UFFE , THORBJØRNSEN STEEN
Published: April 2012

Let g : ℝ → ℂ be a C∞-function with all derivatives bounded and let tr n denote the normalized trace on the n × n matrices. In Ref. 3 Ercolani and McLaughlin established asymptotic expansions of the mean value 𝔼{ tr n(g(Xn))} for a rather general class of random matrices Xn, including the Gaussian Unitary Ensemble (GUE). Using an analytical approach, we provide in the present paper an alternative proof of this asymptotic expansion in the GUE case. Specifically we derive for a [Formula: see text] random matrix Xn that [Formula: see text] where k is an arbitrary positive integer. Considered as mappings of g, we determine the coefficients αj(g), j ∈ ℕ, as distributions (in the sense of L. Schwarts). We derive a similar asymptotic expansion for the covariance Cov { Tr n[f(Xn)], Tr n[g(Xn)]}, where f is a function of the same kind as g, and Tr n = n tr n. Special focus is drawn to the case where [Formula: see text] and [Formula: see text] for λ, μ in ℂ\ℝ. In this case the mean and covariance considered above correspond to, respectively, the one- and two-dimensional Cauchy (or Stieltjes) transform of the [Formula: see text].
EFFECT OF PARTICLE SIZE ON SATURATION MAGNETIZATION AND MAGNETIC ANISOTROPY OF Ni0.65Zn0.35Fe2O4 NANOPARTICLES
Authors: VARMA M. CHAITANYA , KUMAR A. MAHESH , CHOUDARY G. S. V. R. K. , RAO K. H.
Published: April 2012

Ni 0.65 Zn 0.35 Fe 2 O 4 nanoparticles synthesized by sol–gel process have been subjected to various annealing temperatures with a view of obtaining size dependent properties and critical length. X-ray diffraction, transmission electron microscopy, VSM and ESR experiments were carried out as a function of crystallite size. From the ESR spectra it has been observed that the sample annealed at 1025°C has least magnetic anisotropy. The observed variations in saturation magnetization and coercive field have been explained in terms of magnetic anisotropy.
SIMULATION OF THE ELASTIC PROPERTIES OF REINFORCED KEVLAR-GRAPHENE COMPOSITES
Authors: ZYSKIN M. , MARTIROSYAN KAREN S.
Published: April 2012

The compressive strength of unidirectional fiber composites in the form of Kevlar yarn with a thin outer layer of graphene was investigated and modeled. Such fiber structure may be fabricated by using a strong chemical bond between Kevlar yarn and graphene sheets. Chemical functionalization of graphene and Kevlar may be achieved by modification of appropriate surface-bound functional (e.g., carboxylic acid) groups on their surfaces. In this report we studied elastic response to unidirectional in-plane applied load with load peaks along the diameter. The 2D linear elasticity model predicts that significant strengthening occurs when graphene outer layer radius is about 4% of kevlar yarn radius. The polymer chains of Kevlar are linked into locally planar structure by hydrogen bonds across the chains, with transversal strength considerably weaker than longitudinal one. This suggests that introducing outer enveloping layer of graphene, linked to polymer chains by strong chemical bonds may significantly strengthen Kevlar fiber with respect to transversal deformations.
Leveraging Strength-Based Dynamic Information Flow Analysis to Enhance Data Value Prediction
Authors: Ghandour Walid J. , Akkary Haitham , Masri Wes
Published: April 2012

Value prediction is a technique to increase
parallelism
by attempting to overcome serialization constraints caused by true data dependences. By predicting the outcome of an instruction before it executes, value prediction allows data dependent instructions to issue and execute speculatively, hence increasing parallelism when the prediction is correct. In case of a misprediction, the execution is redone with the corrected value. If the benefit from increased parallelism outweighs the misprediction recovery penalty, overall performance could be improved. Enhancing performance with value prediction therefore requires highly accurate prediction methods. Most existing general value prediction techniques are local, that is, future outputs of an instruction are predicted based on outputs from previous executions of the same instruction.

In this article, we investigate leveraging
strength-based dynamic information flow analysis
to enhance data value prediction. We use dynamic information flow analysis (DIFA) to determine when a specific value predictor can perform well and even outperform other predictors. We apply information theory to mathematically prove the validity and benefits of correlating value predictors. We also introduce the concept of the
linear
value predictors, a new technique that predicts a new value from another one using a linear relation. We finally present a variant of stride predictor that we call
update stride
.

We then conduct an empirical analysis using
Pin
, a dynamic binary instrumentation tool, and
DynFlow
, a dynamic information flow analysis tool, that we apply to programs from the SPECjvm2008 and Siemens benchmarks. Our empirical measurements support our mathematical theory and allow us to make important observations on the relation between predictability of data values and information flow. Our analysis and empirical results show that the values of a set of selected variables can be predicted with a very high accuracy, up to 100%. Such prediction is based on the previous history and/or the values of one or more other
source
variables that have strong information flow into the predicted variable. Using our selection criteria, we show that a DIFA-directed predictor outperforms hardware value prediction for all subject programs, and sometimes by a significant margin. This was observed even when using an ideal tagged hardware value prediction table that does not suffer from aliasing or capacity misses.
Dataflow Tomography
Authors: Mazloom Bita , Mysore Shashidhar , Tiwari Mohit , Agrawal Banit , Sherwood Tim
Published: April 2012

It is not uncommon for modern systems to be composed of a variety of interacting services, running across multiple machines in such a way that most developers do not really understand the whole system. As abstraction is layered atop abstraction, developers gain the ability to compose systems of extraordinary complexity with relative ease. However, many software properties, especially those that cut across abstraction layers, become very difficult to understand in such compositions. The communication patterns involved, the privacy of critical data, and the provenance of information, can be difficult to find and understand, even with access to all of the source code. The goal of Dataflow Tomography is to use the inherent information flow of such systems to help visualize the interactions between complex and interwoven components across multiple layers of abstraction. In the same way that the injection of short-lived radioactive isotopes help doctors trace problems in the cardiovascular system, the use of “data tagging” can help developers slice through the extraneous layers of software and pin-point those portions of the system interacting with the data of interest. To demonstrate the feasibility of this approach we have developed a prototype system in which tags are tracked both through the machine and in between machines over the network, and from which novel visualizations of the whole system can be derived. We describe the system-level challenges in creating a working system tomography tool and we qualitatively evaluate our system by examining several example real world scenarios.
Multimodal recognition of reading activity in transit using body-worn sensors
Authors: Bulling Andreas , Ward Jamie A. , Gellersen Hans
Published: April 2012

Reading is one of the most well-studied visual activities. Vision research traditionally focuses on understanding the perceptual and cognitive processes involved in reading. In this work we recognize reading activity by jointly analyzing eye and head movements of people in an everyday environment. Eye movements are recorded using an electrooculography (EOG) system; body movements using body-worn inertial measurement units. We compare two approaches for continuous recognition of reading: String matching (STR) that explicitly models the characteristic horizontal saccades during reading, and a support vector machine (SVM) that relies on 90 eye movement features extracted from the eye movement data. We evaluate both methods in a study performed with eight participants reading while sitting at a desk, standing, walking indoors and outdoors, and riding a tram. We introduce a method to segment reading activity by exploiting the sensorimotor coordination of eye and head movements during reading. Using person-independent training, we obtain an average precision for recognizing reading of 88.9% (recall 72.3%) using STR and of 87.7% (recall 87.9%) using SVM over all participants. We show that the proposed segmentation scheme improves the performance of recognizing reading events by more than 24%. Our work demonstrates that the joint analysis of eye and body movements is beneficial for reading recognition and opens up discussion on the wider applicability of a multimodal recognition approach to other visual and physical activities.
Reinforcement learning utilizes proxemics
Authors: Kastanis Iason , Slater Mel
Published: April 2012

A reinforcement learning (RL) method was used to train a virtual character to move participants to a specified location. The virtual environment depicted an alleyway displayed through a wide field-of-view head-tracked stereo head-mounted display. Based on proxemics theory, we predicted that when the character approached within a personal or intimate distance to the participants, they would be inclined to move backwards out of the way. We carried out a between-groups experiment with 30 female participants, with 10 assigned arbitrarily to each of the following three groups: In the Intimate condition the character could approach within 0.38m and in the Social condition no nearer than 1.2m. In the Random condition the actions of the virtual character were chosen randomly from among the same set as in the RL method, and the virtual character could approach within 0.38m. The experiment continued in each case until the participant either reached the target or 7 minutes had elapsed. The distributions of the times taken to reach the target showed significant differences between the three groups, with 9 out of 10 in the Intimate condition reaching the target significantly faster than the 6 out of 10 who reached the target in the Social condition. Only 1 out of 10 in the Random condition reached the target. The experiment is an example of applied presence theory: we rely on the many findings that people tend to respond realistically in immersive virtual environments, and use this to get people to achieve a task of which they had been unaware. This method opens up the door for many such applications where the virtual environment adapts to the responses of the human participants with the aim of achieving particular goals.
Self-localizing smart camera networks
Authors: Shirmohammadi Babak , Taylor Camillo J.
Published: April 2012

This article describes a novel approach to localizing networks of embedded cameras and sensors. In this scheme, the cameras and the sensors are equipped with controllable light sources (either visible or infrared), which are used for signaling. Each camera node can then determine automatically the bearing to all of the nodes that are visible from its vantage point. By fusing these measurements with the measurements obtained from onboard accelerometers, the camera nodes are able to determine the relative positions and orientations of other nodes in the network.

The method uses angular measurements derived from images, rather than range measurements derived from time-of-flight or signal attenuation. The scheme can be implemented relatively easily with commonly available components, and it scales well since the localization calculations exploit the sparse structure of the system of measurements. Additionally, the method provides estimates of camera orientation which cannot be determined solely from range measurements.

The localization technology could serve as a basic capability on which higher-level applications could be built. The method could also be used to automatically survey the locations of sensors of interest, to implement distributed surveillance systems, or to analyze the structure of a scene, based on images obtained from multiple registered vantage points. It also provides a mechanism for integrating the imagery obtained from the cameras with the measurements obtained from distributed sensors.
Practical RSA signature scheme based on periodical rekeying for wireless sensor networks
Authors: Chang Shih-Ying , Lin Yue-Hsun , Sun Hung-Min , Wu Mu-En
Published: April 2012

Broadcast is an efficient communication channel on wireless sensor networks. Through authentic broadcast, deployed sensors can perform legitimate actions issued by a base station. According to previous literature, a complete solution for authentic broadcast is digital signature based on asymmetric cryptography. However, asymmetric cryptography utilizes expensive operations, which result in computational bottlenecks. Among these cryptosystems, Elliptic Curve Cryptography (ECC) seems to be the most efficient and the most popular choice. Unfortunately, signature verification in ECC is not efficient enough. In this article, we propose an authentic broadcast scheme based on RSA. Unlike conventional approaches, the proposed scheme adopts short moduli to enhance performance. Meanwhile, the weakness of short moduli can be fixed with rekeying strategies. To minimize the rekeying overhead, a Multi-Modulus RSA generation algorithm, which can reduce communication overhead by 50%, is proposed. We implemented the proposed scheme on MICAz. On 512-bit moduli, each verification spends at most 0.077 seconds, which is highly competitive with other public-key cryptosystems.
Utility-based bandwidth adaptation in mission-oriented wireless sensor networks
Authors: Eswaran Sharanya , Misra Archan , Bergamaschi Flavio , Porta Thomas La
Published: April 2012

This article develops a utility-based optimization framework for resource sharing by multiple competing missions in a mission-oriented wireless sensor network (WSN) environment. Prior work on network utility maximization (NUM) based optimization has focused on unicast flows with sender-based utilities in either wireline or wireless networks. In this work, we develop a generalized NUM model to consider three key new features observed in mission-centric WSN environments: i) the definition of the utility of an individual mission (receiver) as a joint function of data from multiple sensor sources; ii) the consumption of each sender's (sensor) data by multiple missions; and iii) the multicast-tree-based dissemination of each sensor's data flow, using link-layer broadcasts to exploit the “wireless broadcast advantage” in data forwarding. We show how a price-based, distributed protocol (WSN-NUM) can ensure optimal and proportionally fair rate allocation across multiple missions, without requiring any coordination among missions or sensors. We also discuss techniques to improve the speed of convergence of the protocol, which is essential in an environment as dynamic as the WSN. Further, we analyze the impact of various network and protocol parameters on the bandwidth utilization of the network, using a discrete-event simulation of a stationary wireless network. Finally, we corroborate our simulation-based performance results of the WSN-NUM protocol with an implementation of an 802.11b network.
Exploiting media stream similarity for energy-efficient decoding and resource prediction
Authors: Hamers Juan , Eeckhout Lieven
Published: April 2012

This article introduces a novel approach to energy-efficient media stream decoding that is based on the notion of media stream similarity. The key idea is that platform-independent scenarios with similar decoding complexity can be identified within and across media streams. A device that decodes a media stream annotated with scenario information can then adjust its processor clock frequency and voltage level based on these scenarios for lower energy consumption. Our evaluation, done using the H.264 AVC decoder and 12 reference video streams, shows an average energy reduction of 44% while missing less than 0.2% of the frame deadlines using scenario-driven video decoding.

An additional application of scenario-based media stream annotation is to predict required resources (compute power and energy) for consuming a given service on a given device. Resource prediction is extremely useful in a client-server setup in which the client requests a media service from the server or content provider. The content provider (in cooperation with the client) can then determine what service quality to deliver, given the client's available resources. Scenario-aware resource prediction can predict (compute power and energy) consumption with errors less than 4% (and an overall average 1.4% error).