bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Studies of the Effects of Active and Passive Circulation Enhancement Concepts on Wind Turbine Performance
Authors: Tongchitpakdee Chanin , Benjanirat Sarun , Sankar Lakshmi N.
Published: October 2006

The aerodynamic performance of a wind turbine rotor equipped with circulation enhancement technology (trailing-edge blowing or Gurney flaps) is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory Phase VI horizontal axis wind turbine is chosen as the baseline configuration. Experimental data for the baseline case is used to validate the flow solver, prior to its use in exploring these concepts. Calculations have been performed for axial and yawed flow at several wind conditions. Results presented include radial distribution of the normal and tangential forces, shaft torque, root flap moment, and surface pressure distributions at selected radial locations. At low wind speed (7m∕s) where the flow is fully attached, it is shown that a Coanda jet at the trailing edge of the rotor blade is effective at increasing circulation resulting in an increase of lift and the chordwise thrust force. This leads to an increased amount of net power generation compared to the baseline configuration for moderate blowing coefficients (Cμ⩽0.075). A passive Gurney flap was found to increase the bound circulation and produce increased power in a manner similar to Coanda jet. At high wind speed (15m∕s) where the flow is separated, both the Coanda jet and Gurney flap become ineffective. The effects of these two concepts on the root bending moments have also been studied.
Characterization of Three-Dimensional Effects for the Rotating and Parked NREL Phase VI Wind Turbine
Authors: Schmitz Sven , Chattot Jean-Jacques
Published: October 2006

This paper addresses three-dimensional effects which are pertinent to wind turbine aerodynamics. Two computational models were applied to the National Renewable Energy Laboratory Phase VI Rotor under rotating and parked conditions, a vortex line method using a prescribed wake, and a parallelized coupled Navier-Stokes/vortex-panel solver (PCS). The linking of the spanwise distribution of bound circulation between both models enabled the quantification of three-dimensional effects with PCS. For the rotating turbine under fully attached flow conditions, the effects of the vortex sheet dissipation and replacement by a rolled-up vortex on the computed radial force coefficients were investigated. A quantitative analysis of both radial pumping and Coriolis effect, known as the Himmelskamp effect, was performed for viscous as well as inviscid flow. For the parked turbine, both models were applied at various pitch angles corresponding to fully attached as well as stalled flow. For partially stalled flow, computed results revealed a vortical structure trailing from the blade’s upper surface close to the 40% radial station. This trailing vortex was documented as a highly unsteady flow structure in an earlier detached eddy simulation by another group, however, it was not directly observed experimentally but only inferred. Computed results show very good agreement with measured wind tunnel data for the PCS model. Finally, a new method for extracting three-dimensional airfoil data is proposed that is particularly well suited for highly stalled flow conditions.
Impact and Dispersion of Liquid Filled Cylinders
Authors: Borg John , Bartyczak Susan , Swanson Nancy , Cogar John R.
Published: October 2006

The computational and experimental results of impact loading a thin wall liquid filled cylindrical target within a vacuum chamber are presented. The impact velocity ranges from 2.2 to 4.2km∕s. Both experimental and computational results are presented. It will be shown that impact dynamics and the early time fluid expansion are well modeled and understood. This includes the mass distribution and resulting expansion velocity. However, the late time dynamics, which includes the liquid breakup and droplet formation process of impacted liquid filled cylinders, is not well understood.
Optimization of an Innovative Rotary Shaft Pump (RSP)
Authors: Allen Jacob C. , Ligrani Phillip M.
Published: October 2006

This paper describes the optimization of rotary shaft pump performance, which is accomplished by comparing the performance of four different centrifugal rotary pump configurations: hooked blades pump, backward-curved blades ID=12.7mm pump, contoured base pump, and backward-curved blades ID=19.1mm pump. Each of these devices utilizes a unique and simple impeller design where the blades are directly integrated into a shaft with an outer diameter of 25.4mm. Presented for each pump are performance data including volumetric flow rate, pump head, and hydraulic efficiency. When pumping water, the most optimal arrangement with the hooked impeller blades produces a maximum flow rate of 3.22L∕min and a pump head as high as 0.97m.
A Comparative Study of DES and URANS for Flow Prediction in a Two-Pass Internal Cooling Duct
Authors: Viswanathan Aroon K. , Tafti Danesh K.
Published: October 2006

The capabilities of the detached eddy simulation (DES) and the unsteady Reynolds averaged Navier-Stokes (URANS) versions of the 1988 k-ω model in predicting the turbulent flow field in a two-pass internal cooling duct with normal ribs is presented. The flow is dominated by the separation and reattachment of shear layers; unsteady vorticity induced secondary flows and strong streamline curvature. The techniques are evaluated in predicting the developing flow at the entrance to the duct and downstream of the 180deg bend, fully developed regime in the first pass, and in the 180deg bend. Results of mean flow quantities, secondary flows, and the average friction factor are compared to experiments and large-eddy simulations (LES). DES predicts a slower flow development than LES, whereas URANS predicts it much earlier than LES computations and experiments. However, it is observed that as fully developed conditions are established, the capability of the base model in predicting the flow is enhanced by the DES formulation. DES accurately predicts the flow both in the fully developed region as well as the 180deg bend of the duct. URANS fails to predict the secondary flows in the fully developed region of the duct and is clearly inferior to DES in the 180deg bend.
Experimental Examination of Unsteady Friction Models for Transient Pipe Flow Simulation
Authors: Adamkowski Adam , Lewandowski Mariusz
Published: October 2006

The paper presents a comparative analysis of calculations performed basing on the selected unsteady friction models and their validation based on the results of own experimental tests. The computer code developed for predicting transient pipe flows includes the models of: Zielke, Trikha, Vardy and Brown, Zarzycki, and Brunone et al. Our own experiments have been conducted at a test rig designed and constructed at the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences (IMP PAN) in Gdansk in order to test transient pipe flows in a wide range of Reynolds numbers. The results following from this analysis enable the quantitative and qualitative assessment of the models under consideration.
Numerical Prediction Method for Growth and Deformation of Filter Cakes
Authors: Parry A. J.
Published: October 2006

During filtration of a fluid-solid mixture, a filter cake composed of solids is formed on the upstream side of the permeable interface—the filtrate or clean fluid passes through but not the solids. This paper describes a multi-dimensional calculation framework to carry out numerical simulations of growth and deformation of a filter cake. Two examples of cake growth and deformation phenomena of interest to the oil industry are the sticking of drill string within a wellbore and the sealing of wellbore sections by expandable packers. The calculation algorithm is based on the algebraic slip mixture model, involving the solution of a non-linear transport equation for solids concentration and the mass- and momentum-conservation equations of the mixture for the velocity and pressure field. The matrix stress and flow permeability are expressed as functions of solids concentration. The viscosity in the momentum equations is modeled using the Bingham approach and proportionality between yield stress and solids matrix pressure. Velocity and pressure fields are split into filtration and deformation components, thus permitting a stable calculation scheme. The simulated results match reasonably experimental observations.
A Low-Reynolds Number Explicit Algebraic Stress Model
Authors: Rahman M. M. , Siikonen T.
Published: October 2006

A low-Reynolds number extension of the explicit algebraic stress model, developed by Gatski and Speziale (GS) is proposed. The turbulence anisotropy Πb and production to dissipation ratio P∕ϵ are modeled that recover the established equilibrium values for the homogeneous shear flows. The devised (Πb, P∕ϵ) combined with the model coefficients prevent the occurrence of nonphysical turbulence intensities in the context of a mild departure from equilibrium, and facilitate an avoidance of numerical instabilities, involved in the original GS model. A new near-wall damping function fμ in the eddy viscosity relation is introduced. To enhance dissipation in near-wall regions, the model constants Cϵ(1,2) are modified and an extra positive source term is included in the dissipation equation. A realizable time scale is incorporated to remove the wall singularity. The turbulent Prandtl numbers σ(k,ϵ) are modeled to provide substantial turbulent diffusion in near-wall regions. The model is validated against a few flow cases, yielding predictions in good agreement with the direct numerical simulation and experimental data.
Study of Drag Forces on a Designed Surface in Bubbly Water Lubrication Using Electrolysis
Authors: Chen Haosheng , Li Jiang , Chen Darong
Published: October 2006

To study the drag reduction effect of a bubbly fluid, a pin-disk experiment is performed on the Universal Micro Tribotester system. Bubbles are generated by water electrolysis in holes that are specially designed on the disk surface. Experiment result shows that the drag force experiences a dynamic process, both drag reduction and drag increment effects appear in the process depending on the bubble behavior. This process is numerically simulated using computational fluid dynamics (CFD), and the explanations for the drag variation are given based on the analysis of drag forces on each wall of the disk surface. The drag reduction occurs when the bubble fills the hole, as the viscous drag on the air-liquid surface is small, and the pressure drag is reduced as the side wall of the hole is covered by the bubble. The drag increment is thought to be caused by the increment of the fluid viscosity when the bubble leaves the hole and flows in the fluid.
Use of Protein Microarrays To Define the Humoral Immune Response in Leprosy Patients and Identification of Disease-State-Specific Antigenic Profiles
Authors: Groathouse Nathan A. , Amin Amol , Marques Maria Angela M. , Spencer John S. , Gelber Robert , Knudson Dennis L. , Belisle John T. , Brennan Patrick J. , Slayden Richard A.
Published: October 2006

Although the global prevalence of leprosy has decreased over the last few decades due to an effective multidrug regimen, large numbers of new cases are still being reported, raising questions as to the ability to identify patients likely to spread disease and the effects of chemotherapy on the overall incidence of leprosy. This can partially be attributed to the lack of diagnostic markers for different clinical states of the disease and the consequent implementation of differential, optimal drug therapeutic strategies. Accordingly, comparative bioinformatics andMycobacterium lepraeprotein microarrays were applied to investigate whether leprosy patients with different clinical forms of the disease can be categorized based on differential humoral immune response patterns. Evaluation of sera from 20 clinically diagnosed leprosy patients using native protein and recombinant protein microarrays revealed unique disease-specific, humoral reactivity patterns. Statistical analysis of the serological patterns yielded distinct groups that correlated with phenolic glycolipid I reactivity and clinical diagnosis, thus demonstrating that leprosy patients, including those diagnosed with the paucibacillary, tuberculoid form of disease, can be classified based on humoral reactivity to a subset ofM. lepraeprotein antigens produced in recombinant form.
VirulentSalmonella entericaSerovar Typhimurium Evades Adaptive Immunity by Preventing Dendritic Cells from Activating T Cells
Authors: Tobar Jaime A. , Carreño Leandro J. , Bueno Susan M. , González Pablo A. , Mora Jorge E. , Quezada Sergio A. , Kalergis Alexis M.
Published: October 2006

Dendritic cells (DCs) constitute the link between innate and adaptive immunity by directly recognizing pathogen-associated molecular patterns (PAMPs) in bacteria and by presenting bacterial antigens to T cells. Recognition of PAMPs renders DCs as professional antigen-presenting cells able to prime naïve T cells and initiate adaptive immunity against bacteria. Therefore, interfering with DC function would promote bacterial survival and dissemination. Understanding the molecular mechanisms that have evolved in virulent bacteria to evade activation of adaptive immunity requires the characterization of virulence factors that interfere with DC function.Salmonella entericaserovar Typhimurium, the causative agent of typhoid-like disease in the mouse, can prevent antigen presentation to T cells by avoiding lysosomal degradation in DCs. Here, we show that this feature of virulentSalmonellaapplies in vivo to prevent activation of adaptive immunity. In addition, this attribute of virulentSalmonellarequires functional expression of a type three secretion system (TTSS) and effector proteins encoded within theSalmonellapathogenicity island 2 (SPI-2). In contrast to wild-type virulentSalmonella, mutant strains carrying specific deletions of SPI-2 genes encoding TTSS components or effectors proteins are targeted to lysosomes and are no longer able to prevent DCs from activating T cells in vitro or in vivo. SPI-2 mutant strains are attenuated in vivo, showing reduced tissue colonization and enhanced T-cell activation, which confers protection against a challenge with wild-type virulentSalmonella. Our data suggest that impairment of DC function by the activity of SPI-2 gene products is crucial forSalmonellapathogenesis.
Acquisition of Avian PathogenicEscherichia coliPlasmids by a CommensalE. coliIsolate Enhances Its Abilities To Kill Chicken Embryos, Grow in Human Urine, and Colonize the Murine Kidney
Authors: Skyberg Jerod A. , Johnson Timothy J. , Johnson James R. , Clabots Connie , Logue Catherine M. , Nolan Lisa K.
Published: October 2006

We have found an avian pathogenicEscherichia coli(APEC) plasmid, pAPEC-O2-ColV, which contains many of the genes associated with APEC virulence and also shows similarity in content to a plasmid and pathogenicity island of human uropathogenicE. coli(UPEC). To test the possible role of this plasmid in virulence, it was transferred by conjugation along with a large R plasmid, pAPEC-O2-R, into a commensal avianE. colistrain. The transconjugant was compared to recipient strain NC, UPEC strain HE300, and donor strain APEC O2 using various assays, including lethality for chicken embryos, growth in human urine, and ability to cause urinary tract infection in mice. The transconjugant killed significantly more chicken embryos than did the recipient. In human urine, APEC O2 grew at a rate equivalent to that of UPEC strain HE300, and the transconjugant showed significantly increased growth compared to the recipient. The transconjugant also significantly outcompeted the recipient in colonization of the murine kidney. These findings suggest that APEC plasmids, such as pAPEC-O2-ColV, contribute to the pathogenesis of avian colibacillosis. Moreover, since avianE. coliand their plasmids may be transmitted to humans, evaluation of APEC plasmids as possible reservoirs of urovirulence genes for human UPEC may be warranted.
Mice Naturally Resistant to
Yersinia pestis
Δ
pgm
Strains Commonly Used in Pathogenicity Studies
Authors: Congleton Yasemin H. K. , Wulff Christine R. , Kerschen Edward J. , Straley Susan C.
Published: October 2006

We report that females of some substrains of inbred mouse strain 129 are resistant to systemic plague due to conditionally virulent Δ
pgm
strains of
Yersinia pestis
; however, fully virulent
Y. pestis
is not attenuated in these mice. Therefore, these mice offer a powerful system in which to map in parallel host resistance traits and opposing bacterial virulence properties for plague.
Comparison of the Serological Responses toMoraxella catarrhalisImmunoglobulin D-Binding Outer Membrane Protein and the Ubiquitous Surface Proteins A1 and A2
Authors: Tan Thuan Tong , Christensen Jens Jørgen , Dziegiel Morten Hanefeld , Forsgren Arne , Riesbeck Kristian
Published: October 2006

Moraxella catarrhalisimmunoglobulin D-binding protein (MID) is a complex antigen with unique immunoglobulin D (IgD)-binding, adhesion, and hemagglutination properties. Previous studies have shown that antibodies raised against MID764-913in rabbits inhibitedM. catarrhalisadhesion to human alveolar epithelial cells, and immunization with MID764-913resulted in an increased pulmonary clearance in a murine model. Strong immune responses against MID have also consistently been shown in humans. Here, the MID-specified IgG responses were compared to those of ubiquitous surface proteins A1 and A2 (UspA1/A2) using a series of recombinant fragments that spanned all three proteins. Sera were obtained from young children, aged 6 months to 1 year (n= 8) and 2 to 3 years (n= 15), and healthy adults (n= 16). Acute- and convalescent-phase sera from chronic obstructive pulmonary disease (COPD) patients withM. catarrhalisinfective exacerbations (n= 23) were also analyzed. Young children, who are at risk ofM. catarrhalisinfection, had low levels of anti-MID and anti-UspA1/A2 antibodies. Healthy adults and the majority of COPD patients (16/23) had high levels of antibodies directed against, among others, the adhesive domain of MID and the fibronectin- and C3-binding domains of UspA1/A2. Among eight COPD patients in whom a rise in antibody levels could be detected, these functional domains were also the main regions targeted by the antibodies. In addition, human IgG directed against MID was bactericidal and anti-MID antibodies were additive to antibodies targeting UspA1/A2. Hence, the functional domains in these three antigens may have significant potential in a future vaccine againstM. catarrhalis.
Alpha-Toxin ofClostridium perfringensIs Not an Essential Virulence Factor in Necrotic Enteritis in Chickens
Authors: Keyburn Anthony L. , Sheedy Scott A. , Ford Mark E. , Williamson Mark M. , Awad Milena M. , Rood Julian I. , Moore Robert J.
Published: October 2006

TheClostridium perfringensalpha-toxin has previously been implicated as the major virulence factor in necrotic enteritis in chickens, although definitive proof has not been reported. In this study an alpha-toxin mutant was constructed in a virulent chicken isolate and shown to retain full virulence in a chicken disease model. These results demonstrated that alpha-toxin is not an essential virulence factor in the pathogenesis of necrotic enteritis in chickens.
Novel Surface Structures Are Associated with the Adhesion of
Actinobacillus actinomycetemcomitans
to Collagen
Authors: Ruiz Teresa , Lenox Christopher , Radermacher Michael , Mintz Keith P.
Published: October 2006

Actinobacillus actinomycetemcomitans
is a gram-negative, facultative, anaerobic bacterium that colonizes the human oral cavity and the upper respiratory tract. This bacterium is strongly associated with localized aggressive periodontitis and adult periodontitis and is the causative agent for other serious systemic infections. Recently, we have identified a protein, EmaA (extracellular matrix protein adhesin A), that mediates the adhesion of
A. actinomycetemcomitans
to collagen. The conserved sequence and predicted secondary structure suggest that EmaA is an orthologue of the
Yersinia enterocolitica
adhesin YadA. Electron microscopy examinations of
A. actinomycetemcomitans
have identified antenna-like protrusions associated with the surface of the bacterium. These structures are absent on
emaA
mutant strains and can be restored by transformation of the mutant strain with
emaA
in
trans
. The loss of these structures is associated with a decrease in the binding of this bacterium to collagen. The antenna-like structures are composed of a long rod that terminates in an ellipsoidal head region. The analysis of these structures using image processing techniques has provided an initial estimate of the overall dimensions, which suggests that the appendages are oligomeric structures formed by either three or four subunits. Together, the data suggest that
emaA
is required for the expression of novel appendages on the surface of
A. actinomycetemcomitans
that mediate the adhesion of the bacterium to collagen.
Immunostimulatory Activity of RecombinantMycobacterium bovisBCG That Secretes Major Membrane Protein II ofMycobacterium leprae
Authors: Makino Masahiko , Maeda Yumi , Inagaki Katsuya
Published: October 2006

We previously demonstrated that major membrane protein II (MMP-II) is one of the immunodominant antigens (Ags) ofMycobacterium lepraecapable of activating T cells through Toll-like receptor 2. Based on the observation thatMycobacterium bovisBCG secreting a 30-kDa protein offered better protection against tuberculosis, we constructed a recombinant BCG strain (BCG-SM) that secretes MMP-II to improve the potency of BCG against leprosy. The secreted MMP-II protein from BCG-SM stimulated monocyte-derived dendritic cells (DC) to produce interleukin-12. DC infected with BCG-SM expressed MMP-II on their surfaces, and MMP-II expression was suppressed by the pretreatment of DC with chloroquine. These results indicated that secreted MMP-II was processed by DC for higher expression levels on their surfaces. In addition, BCG-SM phenotypically activated DC and induced higher expression levels of major histocompatibility complex, CD86, and CD83 Ags on DC than did vector control BCG (BCG-pMV). The DC infected with BCG-SM more efficiently stimulated naïve and memory CD4+T cells and memory CD8+T cells to produce gamma interferon than did those infected with BCG-pMV. However, naïve CD8+T cells were significantly activated only when they were stimulated with BCG-SM-infected DC. When CD8+T cells were cocultured with BCG-SM-infected DC, the proportion of perforin-producing T cells was significantly higher than that in cells cocultured with BCG-pMV-infected DC. Moreover, MMP-II-specific memory T cells were more efficiently produced in mice inoculated with BCG-SM than in mice inoculated with BCG-pMV. Taken together, these results indicate that BCG capable of secreting the immunodominant Ag is more potent in the stimulation of T cells.
Random Mutagenesis of Helicobacter pylori vacA To Identify Amino Acids Essential for Vacuolating Cytotoxic Activity
Authors: McClain Mark S. , Czajkowsky Daniel M. , Torres Victor J. , Szabo Gabor , Shao Zhifeng , Cover Timothy L.
Published: October 2006

VacA is a secreted toxin that plays a role in
Helicobacter pylori
colonization of the stomach and may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. In this study, we analyzed a library of plasmids expressing randomly mutated forms of recombinant VacA and identified 10 mutant VacA proteins that lacked vacuolating cytotoxic activity when added to HeLa cells. The mutations included six single amino acid substitutions within an amino-terminal hydrophobic region and four substitutions outside the amino-terminal hydrophobic region. All 10 mutations mapped within the p33 domain of VacA. By introducing mutations into the
H. pylori
chromosomal
vacA
gene, we showed that secreted mutant toxins containing V21L, S25L, G121R, or S246L mutations bound to cells and were internalized but had defects in vacuolating activity. In planar lipid bilayer and membrane depolarization assays, VacA proteins containing V21L and S25L mutations were defective in formation of anion-selective membrane channels, whereas proteins containing G121R or S246L mutations retained channel-forming capacity. These are the first point mutations outside the amino-terminal hydrophobic region that are known to abrogate vacuolating toxin activity. In addition, these are the first examples of mutant VacA proteins that have defects in vacuolating activity despite exhibiting channel activities similar to those of wild-type VacA.
Costs and compensation of work-related injuries in British Columbia sawmills
Authors: Alamgir Hasanat , Tompa Emile , Koehoorn Mieke , Ostry Aleck , Demers Paul A
Published: October 2006

Objective:To estimate the costs of work-related injury in a cohort of sawmill workers in British Columbia from the perspective of the workers’ compensation system.

Methods:Hospital discharge records were extracted from 1989 to 1998 for a cohort of 5786 actively employed sawmill workers. A total of 173 work-related injury cases were identified from these records using theInternational classification of diseases—ninth revision (ICD-9) external cause of injury codes and the responsibility of payment schedule. Workers’ compensation records were extracted and matched with hospital records by dates and ICD-9 diagnosis codes. All costs were converted into 1995 constant Canadian dollars using the Provincial General Consumer Price Index for the non-healthcare costs and Medical Consumer Price Index for the healthcare costs. A 5% discounting rate was applied to adjust for the time value of money. For the uncompensated cases, costs were imputed from the compensated cases using the median cost for a similar nature of injury.

Results:370 hospitalisation events due to injury were captured, and by either of the two indicators (E Codes or payment schedules), 173 (47%) hospitalisation events due to injury, were identified as work related. The median healthcare cost was $4377 and the median non-healthcare cost was $16 559 for a work-related injury. The median non-healthcare and healthcare costs by injury were falls, $19 978 and $5185; struck by falling object, $32 398 and $8625; struck against, $12 667 and $5741; machinery related, $26 480 and $6643; caught in or between, $24 130 and $4389; and overexertion, $7801 and $2710. The total cost was $10 374 115 for non-healthcare and $1 764 137 for healthcare. The compensation agency did not compensate $874 871 (8.4%) of the non-healthcare costs and $200 588 (11.4%) of the healthcare costs.

Conclusion:Eliminating avoidable work-related injury events can save valuable resources.
Spreading of occupational allergens: laboratory animal allergens on hair-covering caps and in mattress dust of laboratory animal workers
Authors: Krop Esmeralda J M , Doekes Gert , Stone Martin J , Aalberse Rob C , van der Zee Jaring S
Published: October 2006

Background:Family members of laboratory animal workers are at risk of developing allergy to laboratory animals. Little is known about the spreading of laboratory animal allergens outside the animal facilities.

Objective:To assess the presence of laboratory animal allergens in dust collected from mattresses of laboratory animal workers and unexposed controls.

Methods:Mouse and rat urinary proteins were measured in samples of mattress dust collected by laboratory animal workers and unexposed controls. In addition, rat and mouse allergens were determined in extracts of hair-covering caps, used during laboratory animal work, to estimate spreading of allergen through dust captured on hair. Allergen concentrations on hair caps were compared with exposure measured by personal airborne dust sampling.

Results:Levels of rat urinary allergens (RUA) and mouse urinary allergens (MUA) and mouse urinary protein (MUP) 8, a specific pheromone-binding mouse allergen, were significantly higher in mattress samples of laboratory animal workers than in those of controls. Hair-covering caps used in animal facilities harboured large amounts of RUA and MUA, which correlated significantly with exposure measured by the personal sampling technique in the animal facility.

Conclusions:Occupational laboratory animal allergens are detectable in mattress dust of laboratory animal workers. Transfer of allergens via uncovered hair of animal workers is likely contributing to this phenomenon. This study stresses the importance of using hair caps to prevent spreading of occupational allergens.
ON THE SPECTRUM OF PRIMORDIAL DENSITY FLUCTUATIONS
Authors: POLLOCK M. D.
Published: October 2006

The problem of the origin and spectrum of cosmic density fluctuations is discussed, especially with reference to the heterotic superstring theory of Gross et al. It is shown that primordial variation of the gravitational constant, due to its renormalization by higher-derivative terms [Formula: see text] dependent on the moduli, or the Harrison mechanism applied at the Hagedorn temperature T H = 1.14 × 1017 GeV (where we have argued that the four-dimensional theory decompactifies to higher dimensions), both naturally give rise to the scale-invariant spectrum of Zeldovich with a density contrast δ ~ 10-4-10-3, as required by the indeterminacy principle and for galaxy formation in the Universe.
COSMOLOGICAL DYNAMICS OF DILATONIC (PHANTOM) DARK ENERGY MODEL
Authors: HUANG Z. G. , LU H. Q.
Published: October 2006

In this paper, we study the cosmological dynamics of dilatonic dark energy model and its phantom model — with negative kinetic energy. When the potential is taken as the form [Formula: see text], we investigate the existence of a late time attractor solution, and find out the sufficient condition. One interesting feature found by us is that the evolutions of components of comic density are locally fluctuating on the way to the late time attractor. But this local fluctuation cannot hold the trend that the equation of state ω evolves to -1 and the cosmic density parameter Ωσ evolves to 1, which are important features for a dark energy model that can meet the current observations.
GRAVITY OF A STATIC MASSLESS SCALAR FIELD AND A LIMITING SCHWARZSCHILD-LIKE GEOMETRY
Authors: GAUDIN M. , GORINI V. , KAMENSHCHIK A. , MOSCHELLA U. , PASQUIER V.
Published: October 2006

We study a set of static solutions of the Einstein equations in the presence of a massless scalar field and establish their connection to the Kantowski–Sachs cosmological solutions based on some kind of duality transformations. The physical properties of the limiting case of an empty hyperbolic space–time (pseudo-Schwarzschild geometry) are analyzed in some detail.
GRAVITATIONAL COLLAPSE OF AN ANISOTROPIC FLUID WITH SELF-SIMILARITY OF THE SECOND KIND
Authors: BRANDT C. F. C. , CHAN R. , DA SILVA M. F. A. , VILLAS DA ROCHA JAIME F.
Published: October 2006

We study the evolution of an anisotropic fluid with kinematic self-similarity of the second kind. We found a class of solution to the Einstein field equations by assuming an equation of state where the radial pressure of the fluid is proportional to its energy density (pr = ωρ) and that the fluid moves along time-like geodesics. The self-similarity requires ω = -1. The energy conditions, geometrical and physical properties of the solutions are studied. We have found that, depending on the self-similar parameter α, they may represent a black hole or a naked singularity.
SOME FURTHER ANALYTICAL PROPERTIES OF THE CONSTANT CORRELATION MODEL FOR PORTFOLIO SELECTION
Authors: KWAN CLARENCE C. Y.
Published: October 2006

The constant correlation model is a mean-variance portfolio selection model where, for a given set of risky securities, the correlation of returns between any pair of different securities is considered to be the same. Support for the model is from previous empirical evidence that sample averages of correlations outperform various more sophisticated models in forecasting the correlation matrix, an important input component for portfolio analysis. To enable a better understanding of the constant correlation model, this study identifies some additional analytical properties of the model and relates them to familiar portfolio concepts. By comparing computational times for portfolio construction with and without simplifying the correlation matrix in a simulation study, this study also confirms the model's computational advantage. This study is intended to provide further analytical support for the model as a viable, simple alternative to those portfolio selection models where input requirements and the attendant computations are more burdensome.
OPTIMAL HEDGING OF DERIVATIVES WITH TRANSACTION COSTS
Authors: AURELL ERIK , MURATORE-GINANNESCHI PAOLO
Published: October 2006

We investigate the optimal strategy over a finite time horizon for a portfolio of stock and bond and a derivative in an multiplicative Markovian market model with transaction costs (friction). The optimization problem is solved by a Hamilton–Jacobi–Bellman equation, which by the verification theorem has well-behaved solutions if certain conditions on a potential are satisfied. In the case at hand, these conditions simply imply arbitrage-free ("Black–Scholes") pricing of the derivative. While pricing is hence not changed by friction allow a portfolio to fluctuate around a delta hedge. In the limit of weak friction, we determine the optimal control to essentially be of two parts: a strong control, which tries to bring the stock-and-derivative portfolio towards a Black–Scholes delta hedge; and a weak control, which moves the portfolio by adding or subtracting a Black–Scholes hedge. For simplicity we assume growth-optimal investment criteria and quadratic friction.
THE EXPONENT EXPANSION: AN EFFECTIVE APPROXIMATION OF TRANSITION PROBABILITIES OF DIFFUSION PROCESSES AND PRICING KERNELS OF FINANCIAL DERIVATIVES
Authors: CAPRIOTTI LUCA
Published: October 2006

A computational technique borrowed from the physical sciences is introduced to obtain accurate closed-form approximations for the transition probability of arbitrary diffusion processes. Within the path integral framework the same technique allows one to obtain remarkably good approximations of the pricing kernels of financial derivatives. Several examples are presented, and the application of these results to increase the efficiency of numerical approaches to derivative pricing is discussed.
COLOR IMAGE RETRIEVAL BASED ON COLOR-TEXTURE-EDGE FEATURE HISTOGRAMS
Authors: YU SHENGSHENG , HUANG CHAOBING , ZHOU JINGLI
Published: October 2006

In this paper, two novel texture descriptors and two novel edge descriptors are proposed, which are low-dimension, effective, and are obtained by a relative simple approach. The two texture descriptors are the directional difference unit and the gradient unit histogram, which are rotation invariant. The two edge descriptors are the quantized max-min difference histogram and the quantized fuzzy entropy histogram, the former is more suitable for describing the images with relatively regular texture characteristic, the latter is more suitable for describing the images with relatively regular structure characteristic or no regular characteristic. Combing color descriptor, texture descriptor and edge descriptor to form hybrid visual feature index to retrieve natural color images, this method is insensitive to image rotation and translation. Experimental results show that the method achieves better performance than other recent relevant methods.
INSIGHT OF FUZZY NEURAL SYSTEMS IN THE APPLICATION OF HANDWRITTEN DIGITS CLASSIFICATION
Authors: NG GEOK SEE , ERDOGAN SEVKI , SHI DAMING , WAHAB ABDUL
Published: October 2006

There have been many applications in the area of handwritten character recognition. Over the last decade much research has gone into developing algorithms to accurately convert captured images of handwriting to text. At the same time, research into neuro fuzzy classification models has proven to solve many complex problems. In this paper, Adaptive Neuro Fuzzy Inference System (ANFIS) and Evolving Fuzzy Neural Network (EFuNN) was investigated and studied in detail on how these two models can be used to perform handwritten digits classification. Results of the experiments show great potential of the EFuNN over the ANFIS for practical implementation of the handwritten digit recognition.
HARMONIC INTERPOLATION FOR IMAGE COMPRESSION
Authors: HARDY ALEXANDRE , STEEB WILLI-HANS
Published: October 2006

Harmonic interpolation has been shown to produce smooth interpolating curves when applied to points in 2D or 3D space. The techniques used in harmonic interpolation can be applied equally well to image data. In this paper, harmonic interpolation is used to interpolate the colors in an image. We identify certain properties of harmonic interpolation which allows us to transform the image into another image more suitable for conventional compression techniques to be applied. The properties identified also allow for further compression of the image in addition to conventional compression techniques. We apply the algorithm to a variety of images and present the results.
IMAGE SEGMENTATION USING NCUT IN THE WAVELET DOMAIN
Authors: REGENTOVA EMMA , YAO DONGSHENG , LATIFI SHAHRAM , ZHENG JUN
Published: October 2006

A new image segmentation method is developed that combines the advantage of the normalized cuts (Ncut) algorithm to solve the perceptual grouping problem by means of graph partitioning, and the ability of wavelet transform to capture image features by decomposing signal both in time and frequency. We derive image features from orientation histograms defined on the detail subbands of the discrete wavelet transform. The segmentation is implemented by partitioning a graph representing an image at the coarsest transform level, while the weights of the graph are calculated from all the scales. Due to the reduced dimensionality of the dataset, the speed of Ncut is increased. Even though segmentation is carried out at a coarsest level of transform, the results are accurate for images of different structural contents, including textures.
Recovery of mucosal barrier function in ischemic porcine ileum and colon is stimulated by a novel agonist of the ClC-2 chloride channel, lubiprostone
Authors: Moeser Adam J. , Nighot Prashant K. , Engelke Kory J. , Ueno Ryuji , Blikslager Anthony T.
Published: October 2006

Previous studies utilizing an ex vivo porcine model of intestinal ischemic injury demonstrated that prostaglandin (PG)E2stimulates repair of mucosal barrier function via a mechanism involving Cl−secretion and reductions in paracellular permeability. Further experiments revealed that the signaling mechanism for PGE2-induced mucosal recovery was mediated via type-2 Cl−channels (ClC-2). Therefore, the objective of the present study was to directly investigate the role of ClC-2 in mucosal repair by evaluating mucosal recovery in ischemia-injured intestinal mucosa treated with the selective ClC-2 agonist lubiprostone. Ischemia-injured porcine ileal mucosa was mounted in Ussing chambers, and short-circuit current ( Isc) and transepithelial electrical resistance (TER) were measured in response to lubiprostone. Application of 0.01–1 μM lubiprostone to ischemia-injured mucosa induced concentration-dependent increases in TER, with 1 μM lubiprostone stimulating a twofold increase in TER (ΔTER = 26 Ω·cm2; P < 0.01). However, lubiprostone (1 μM) stimulated higher elevations in TER despite lower Iscresponses compared with the nonselective secretory agonist PGE2(1 μM). Furthermore, lubiprostone significantly ( P < 0.05) reduced mucosal-to-serosal fluxes of3H-labeled mannitol to levels comparable to those of normal control tissues and restored occludin localization to tight junctions. Activation of ClC-2 with the selective agonist lubiprostone stimulated elevations in TER and reductions in mannitol flux in ischemia-injured intestine associated with structural changes in tight junctions. Prostones such as lubiprostone may provide a selective and novel pharmacological mechanism of accelerating recovery of acutely injured intestine compared with the nonselective action of prostaglandins such as PGE2.
Dual alterations in casein kinase I-ε and GSK-3β modulate β-catenin stability in hyperproliferating colonic epithelia
Authors: Umar Shahid , Wang Yu , Morris Andrew P. , Sellin Joseph H.
Published: October 2006

Casein kinase I (CKI)-ε and GSK-3β phosphorylate β-catenin at Ser45(β-cat45) and Thr41/Ser37,33(β-cat33,37,41) residues, thereby facilitating its ubiquitination and proteasomal degradation. We used a Citrobacter rodentium-induced transmissible murine colonic hyperplasia (TMCH) model to determine Ser/Thr phosphorylation and biological function of β-catenin during crypt hyperproliferation. TMCH was associated with 3-fold and 3.3-fold increases in CKI-ε cellular abundance and 2-fold and 1.8-fold increase in its activity at 6 and 12 days after infection, respectively. β-Catenin coimmunoprecipitated with both cellular and nuclear CKI-ε and cellular axin at these time points. Cellular β-catenin was constitutively phosphorylated at Ser45and underwent subcellular redistribution to cytoskeletal and nuclear fractions at days 6 and 12 of TMCH, respectively. β-cat33,37,41, however, exhibited only subtle changes in either phosphorylation status or subcellular distribution even after blocking proteasomal degradation in vivo. Interestingly, GSK-3β underwent increased phosphorylation at Ser9, leading to 40% and 70% decreases in its activity at these time points, respectively. Coimmunoprecipitation studies exhibited strong association of GSK-3β with PKC-ζ at either time point. Cellular β-cat45stabilized and, along with unphosphorylated β-catenin, underwent nuclear translocation, associated with nuclear accumulated Tcf-4 and cAMP response element binding protein binding protein, and was significantly acetylated, leading to increases in DNA binding. Priming of β-catenin at Ser45exists in vivo. However, β-cat45does not necessarily enter the degradation pathway. Impairment in linking β-cat45to subsequent GSK-3β-mediated phosphorylation and degradation may account for increased steady-state levels of both unphosphorylated as well as Ser45-phosphorylated β-catenin, which may be causally linked to increases in cell census during TMCH.
Creatine supplementation attenuates corticosteroid-induced muscle wasting and impairment of exercise performance in rats
Authors: Menezes Luciana Gomes , Sobreira Cláudia , Neder Luciano , Rodrigues-Júnior Antonio Luis , Baddini Martinez José A.
Published: October 2006

The objective of the present study was to investigate whether creatine (Cr) could attenuate the deleterious effects of high doses of dexamethasone (Dexa) on body mass, exercise performance, and respiratory variables of rodents. Forty-four Wistar rats performed incremental maximal exercise tests. They were then assigned to four groups: G1: subcutaneous (SC) and intraperitoneal (IP) saline; G2: SC saline and IP Cr (250 mg·kg−1·day−1); G3: SC Dexa (7.5 mg·kg−1·day−1) and IP saline; G4: SC Dexa and IP Cr. New exercise tests and analysis of the respiratory pattern under resting conditions and after stimulation with doxapram (2 mg/kg IP) were performed after 18 days. Post- minus pretreatment differences were compared between groups. G3 and G4 showed a significant impairment in body mass gain compared with G1 and G2 ( P < 0.05) (G1: 65.3 ± 26.1, G2: 93.1 ± 27.4, G3: −18.4 ± 20.1, G4: 9.8 ± 23.1 kg × 10−3). Similar results were observed for maximal oxygen consumption (G1: 9.5 ± 8.5, G2: 25.8 ± 14.5, G3: −25.5 ± 6.0, G4: −4.8 ± 9.5 ml·kg−1·min−1) and test duration (G1: 43.0 ± 45.0, G2: 72.0 ± 59.5, G3: −165.0 ± 60.6, G4: −48.0 ± 48.5 s). Simultaneous use of Cr significantly attenuated the Dexa-induced impairment of the last two variables. Cr attenuated Dexa-induced gastrocnemius and diaphragm muscle weight losses and the atrophy of gastrocnemius type IIb fibers. Cr supplementation had only small effects on Dexa-induced respiratory changes. These results suggest that Cr may play a role in the prophylaxis or treatment of steroid-induced myopathy.
Field Trial on Caries Prevention with Xylitol Candies among Disabled School Students
Authors: Honkala E. , Honkala S. , Shyama M. , Al-Mutawa S.A.
Published: October 2006

Background: In a 1999 survey high caries levels were found among physically disabled school students in Kuwait. Objectives: A field study was planned to test the efficacy of xylitol candies in preventing caries among individuals in two special schools in Kuwait. Methods: Altogether 176 students were examined in 2002 and 145 (105 in xylitol group and 40 in the control group) after 18 months’ intervention. The WHO criteria were used in recording caries according to surfaces (third molars were excluded) by 2 calibrated examiners (E.H., M.S.). The students were allocated to the xylitol group only if the parent/caregiver returned the informed consent form. School health nurses distributed xylitol candies to the students 3 times during the school day (after breakfast and lunch, and before leaving the school). Results: In the xylitol group, the baseline DS and DMFS scores were 3.4 and 8.2 and in the follow-up 1.9 and 7.1, respectively. In the control group, the baseline scores were DS 3.9 and DMFS 9.8, and the follow-up scores DS 3.9 and DMFS 13.2. Conclusion: Xylitol seemed to have a strong preventive and a clear remineralizing effect on caries.
Caries-Preventive Effect of Chlorhexidine Gel Applications among High-Risk Children
Authors: Petti S. , Hausen H.
Published: October 2006

Evidence on the caries-preventive effect of chlorhexidine (CHX) among high-risk children is inconclusive, possibly because obscured by fluoride exposure. We investigated the effect of CHX among initially 3-year-old subjects whose baseline d3ft was = 0 and whose only regular fluoride exposure came from toothpaste. The subjects were assigned to three groups: high-risk test (HRT, n = 70), high-risk control (HRC, n = 71), and low-risk control (LRC, n = 70). Risk classification was based on salivary mutans streptococcal levels (MS, </≧1.0 × 105 cfu/ml). Basic measures (oral hygiene, dietary counselling every 4 months) were given to all groups. HRT also underwent CHX gel applications for 3 consecutive days at 3-month intervals for 15 months. Eighteen months after baseline d3ft increments and proportions of children with d3ft increment ≧1 (%d3ft increment ≧1) among all groups were assessed. Anti-MS effect on high-risk children and caries-preventive effect on all children were statistically analysed by residual change analysis (MS), non-parametric tests and logistic regression analysis (caries). No differences were found between the groups in basic programme compliance. CHX significantly reduced MS levels. %d3ft increment ≧1 and mean d3ft increments were 34.3%, 0.56 (HRT), 32.4%, 0.54 (HRC) and 11.4%, 0.11 (LRC), with HRT/HRC values statistically significantly higher than LRC values and no significant difference between HRT and HRC. HRT children were not less likely to show new lesions than HRC children (OR = 1.09; 95% confidence interval 0.54–2.19), while high-risk children were 4 times more likely to show new lesions than low-risk children (OR = 3.71; 95% confidence interval 1.53–9.03). CHX gel applications showed moderate anti-MS effect but negligible caries-preventive effect.