bluuebunny/crossref_metadata_2025 huggingface dataset:
Boundary Conditions and Sensitivities of Mass-Elastic Systems
Authors: Morrison D.
Published: December 2011

It has been noted in numerous practical applications that the sensitivities of mass elastic systems to external disturbance are closely bound up with the nonzero values of the normalized boundary and field actions, both forces and displacements. This leads in many cases to rapid analyses without, for example, the need for a separate calculation of “participation factors” in seismic applications. This short paper sets down some relationships in general terms and indicates examples of practical interest.
The Transfer Matrix Impedance Coupling Method for the Eigensolutions of Multi-Spool Rotor Systems
Authors: Taiping Huang
Published: December 2011

In this paper, the transfer matrix impedance coupling method for calculating the eigensolutions of multi-spool rotor systems with several intershaft bearings is developed. This method can also be used for the eigensolutions of the damped rotor systems. The numerical examples of dual and tri-spool rotor systems with intershaft bearings show that the results are in good agreement with the exact solutions.
Finite Element Analysis on Modal Parameters of Anisotropic Laminated Plates
Authors: Xiao C. Z. , Lin D. X. , Ju F.
Published: December 2011

This paper is concerned with the finite element technique for predicting the dynamic properties of anisotropic fiber-reinforced composite laminated plates. Considering the effect of transverse shear deformation, a higher order shear deformation theory which satisifes the zero shear stress conditions at the upper and bottom surfaces is assumed. The natural frequencies and mode shapes of a rectangular plate with all free edges are obtained by finite element method and the modal damping values by finite damped element technique. An equivalent stiffness method is introduced to reduce computation time. Four different theoretical predictions of natural frequencies and damped values of a laminated plate are compared with experimental results. Discussions on the effect of transverse shear deformation to the dynamic properties of composite plates are given.
Recent Developments in Multiple Input Modal Analysis
Authors: Breitbach E. J.
Published: December 2011

Over the last two decades in experimental modal analysis many different approaches have been developed for application to a great variety of structural engineering problems. The effectiveness of modal testing depends directly on the capability to construct optimal excitation force vectors in order to identify a complete set of normal modes in a frequency band of interest and to extract the corresponding modal parameters. These tasks can be considerably facilitated by means of so-called mode indicator functions (MIF) the most current of which will be thoroughly investigated in order to reveal their features and capabilities. Furthermore, emphasis will be placed on the problem of finding appropriate force vectors to excite either real or complex normal modes. A new concept to determine optimal force vectors for the excitation of complex normal modes will be presented. In the context with the definition of complex normal modes the problem of transforming complex normal modes into real normal modes will be treated as well.
Modelling and Control of Turbomachinery Vibrations
Authors: Firoozian R. , Stanway R.
Published: December 2011

The authors describe an integrated approach to the modelling and active control of lateral vibrations in turbomachinery. Starting with consideration of the control of multiple rotor bending modes, the generation of a state vector from available measurements using an observer is discussed together with the effect on stability of employing a controller of reduced order. The various points are illustrated in an extended case study which also compares the active schemes with one involving a simple passive damper.
Experiments on Dynamic Stiffness and Damping of Tapered Bore Seals
Authors: Fleming D. P.
Published: December 2011

Stiffness and damping were measured in tapered bore ring seals with air as the sealed fluid. Excitation was provided by a known unbalance in the shaft which rotated in the test seals. Results were obtained for various seal supply pressures, clearances, unbalance amounts, and shaft speeds. Stiffness and damping varied little with unbalance level, indicating linearity of the seal. Greater variation was observed with speed and particularly supply pressure. A one-dimensional analysis predicted stiffness fairly well, but considerably overestimated damping.
Modeling and Vibration Analysis of Friction Joints
Authors: Menq C.-H.
Published: December 2011

This paper presents a microslip model of friction joints, which may be viewed as a generalization of the simple model considered by Menq et al. (1986a). Laboratory experiments have shown that microslip of friction joints has important implications in the dynamic response of frictionally constrained structures in which the friction interface is subjected to high normal loads (Menq et al., 1986b). In the simple model, the friction interface is idealized as a bar pressed with a uniform normal pressure against a rigid support. The use of a rigid support in the model shows that a direct link between the model’s parameters and its physical counterparts is lacking. The model presented in this paper consists of two bars held together with uniform clamping normal pressure. In addition to these two bars, the third element, a shear layer, is added to account for the effects of the shear deformation of the two contact bodies. This generalization of the microslip model is to enhance the link between the model’s parameters and the physical configurations of the contacting surfaces of the friction joint. With a physical model like this, the objective is to determine the distribution of the friction force at the contact surface while quasi-steady axial loads applied to the ends of both bars increase gradually. In particular, it is of interest for the analysis of vibration problems to determine the force-displacement curve that describes the relationship, upon first loading, between the applied load and the resulting relative displacement between the two ends where the loads are applied. After the case of first loading, the cases of unloading and reloading of the joint will be examined; and then the hysteresis loop in the course of cyclic loading can be obtained.
Quenching of Self-Excited Vibrations
Authors: Asfar K. R.
Published: December 2011

A passive vibration control system for the quenching of undesirable self-excited vibrations in mechanical systems is presented. The system is a Lanchester damper, attached to the main self-excited system; a van der Pol oscillator. A first-order perturbation solution shows that complete quenching of self-excited vibration is possible. The result is verified by numerical integration of the governing differential equations. Furthermore, the damper is shown to be effective in suppressing forced self-excited vibrations.
Modeling and Finite Element Analysis of Drill Bit Vibrations
Authors: Tekinalp O. , Ulsoy A. G.
Published: December 2011

Drill bit vibrations are modeled using the Euler-Bernoulli beam theory. The model includes the most important properties of drill bits and of the drilling operation. These are: the drill bit cross sectional geometry, the drill helix angle, rotational speed of the drill bit, the thrust force, torque, and cutting forces generated during drilling. Equations of motion are derived in an inertial frame and then transformed to a rotating fluted frame for convenience in the solution. The transformed equations are discretized using finite element techniques. The finite element code developed is capable of solving the eigenvalue problem for various boundary conditions and drill cross sectional geometries. Finite element solutions are compared to known analytical, numerical, and experimental results from the literature and good agreement is obtained.
Anti-Swirl Arrangements Prevent Rotor/Seal Instability
Authors: Muszynska A. , Bently D. E.
Published: December 2011

Fluid involved in rotative motion (fluid “swirl”) within seals of high speed fluid handling machines is a recognized source of rotor instability. This type of instability leads to the limit cycle of rotor lateral precessional self-excited vibrations of a subsynchronous frequency. The anti-swirl concept is based on the injection of an additional flow to the seal, in the tangential direction, opposite to the direction of the shaft rotation. This flow causes a decrease of the shaft rotation-generated circumferential velocity of the fluid, and improves rotor/seal stability. In this paper the anti-swirl concept is outlined. The mathematical model of the rotor/seal system is analyzed. The analysis and experimental tests establish the physical basis of the anti-swirl concept. The fluid force model, based on the fluid circumferential average velocity of the flow, proves to be an adequate way to represent the seal fluid dynamic forces.
An Experimental Study of Induction Noise in Four-Cylinder Internal Combustion Engines
Authors: Lamancusa J. S. , Todd K. B.
Published: December 2011

Induction noise has become a major source of consumer complaints in automobiles powered by four-cylinder engines. Induction noise typically manifests itself as a low frequency booming or “mooing.” It is most noticeable and objectionable under wide open throttle, hard acceleration conditions. In an effort to understand the basic causes of this noise, so that potential remedies might be more intelligently applied, an extensive study was undertaken. Careful measurements were made on a four-cylinder, motored engine. Dynamic pressure variations within the induction system, and external to the engine were studied. Peak to peak pressure variations of over 2 psi were found in the intake runners at the valves. Evidence of nonlinear acoustic behavior was found. A detailed examination of the events that cause induction noise is presented.
A Generalized Approach to the Dynamics of Cracked Shafts
Authors: Li Changhe , Bernasconi O. , Xenophontidis N.
Published: December 2011

A new analytic-experimental method for describing crack breathing and obtaining shaft local stiffness change is presented. A generalized nonlinear formulation using the finite element method, which can be widely used for both horizontal and vertical cracked shafts, is derived. Some results previously explicited in other studies are confirmed and clarified. This advanced model can serve as a solid basis for further studies.
Convergence Properties of Modal Costs for Certain Distributed Parameter Systems
Authors: Hu A. , Skelton R. E.
Published: December 2011

A complete modal cost analysis is presented for the vibration of various kinds of simple continua with different boundary conditions. Explicit formulas for the total cost are derived for these distributed parameter systems. The convergence theorems developed are useful in the model reduction of the equivalent continuum models of large space structures as well as in the selection of finite element code for control design.
Calculation of Acoustic Transfer Properties of Closed-Loop Type Pipeline Systems Having More Than One Output
Authors: Gyo¨ri I. , Joo´ G.
Published: December 2011

Expanding the previously elaborated algorithm of tree structure pipeline systems of reciprocating compressor installations, the paper introduces an analytical description and a procedure for combined tree-ring structures having more than one output points. A comparative study of the suggested method and the four-pole representation of simple closed loops is presented including a numerical example as well.
An Evaluation of Active Noise Control in a Cylindrical Shell
Authors: Silcox R. J. , Lester H. C. , Abler S. B.
Published: December 2011

This paper examines the physical mechanisms governing the use of active noise control in an extended volume of a cylindrical shell. Measured data were compared with computed results from a previously derived analytical model based on infinite shell theory. For both the analytical model and experiment, the radiation of external monopoles is coupled to the internal acoustic field through the radial displacement of the thin, elastic, cylindrical shell. An active noise control system was implemented inside the cylinder using a fixed array of discrete monopole sources, all of which lie in the plane of the exterior noise sources. Good agreement between measurement and prediction was obtained for both internal pressure response and overall noise reduction. Attenuations in the source plane greater than 15 dB were recorded along with a uniformly quieted noise environment over an indicative length inside the experimental model. Results indicate that for forced responses with extended axial distributions, axial arrays of control sources may be required. Finally, the Nyquist criteria for the number of azimuthal control sources is shown to provide for effective control over the full cylinder cross section.
The Lower Bound of the Stability Threshold Speed of a Flexible Rotor System in Fluid-Film Bearings
Authors: Zhang Wen
Published: December 2011

The paper is devoted to the estimation of the lower bound of the stability threshold speed (STS) of a flexible rotor system supported in fluid-film bearings. It is proved theoretically that the STS of any multi-degree-of-freedom flexible rotor system is always higher than the STS of the corresponding equivalent single disk rotor. The conclusion offers us a simple approach to estimate the STS of any actual rotor system and provides a theoretical foundation for the approach.
A New Approach to the Dynamic Characteristic of Undamped Rotor-Bearing Systems
Authors: Shiau Ting Nung , Hwang Jon Li
Published: December 2011

A new approach to the dynamic characteristic of undamped rotor-bearing systems is presented. The dynamic behavior of a rotor bearing system is usually studied using finite element approach and/or transfer matrix approach. In this paper, the assumed mode method is first employed to describe the system response and the properties of Rayleigh quotient are applied to analyze the critical speeds of a rotor-bearing system. Three examples are used to illustrate the efficiency and the accuracy of the present approach. The numerical results, based on the present approach, stand with very good agreement with those using the finite element method. Moreover, the present approach will provide a significant computing time saving for a relative large order system. It may be a more effective way to analyze the dynamic characteristic for most of the rotor bearing systems.
The Elastodynamic Response of a Class of Intelligent Machinery, Part II: Computational and Experimental Results
Authors: Sunappan D. , Soong K. , Thompson B. S.
Published: December 2011

This paper, together with a companion paper [1], describes a comprehensive theoretical and experimental investigation on a methodology proposed for suppressing the elastodynamic response of flexible mechanisms. This methodology involves retrofitting the original mechanism by the introduction of a microprocessor-controlled perturbational motion at one of the normally fixed ground-link joints. The orchestration of this motion will, it is hypothesized, enable the inertial loading on the flexible members to be reduced and consequently the magnitude of the elastodynamic response will also be reduced. In Part I of two companion papers, the theoretical developments are presented. Part II presents an experimental investigation of a four-bar linkage with a flexible rocker link, which was then retrofitted to provide an additional, microprocessor-controlled input. The magnitude of the midspan deflections of the retrofitted mechanism were less than those of the original mechanism over a broad range of operating speeds thereby validating the proposed methodology for this class of mechanism system.
A Frequency Approach to Mathematical Modeling of a Nuclear Power Plant Piping System
Authors: Skormin V.
Published: December 2011

A methodology is presented for identification of a nuclear power plant piping system, which employs mathematical description in the form of transfer function matrix, frequency domain technique for estimation of system dynamic parameters, statistical technique for verification of model configuration and evaluation of parameter estimates, adaptive approach for current model updating. Model applications for estimation and monitoring of forcing functions, displacements, and stresses due to transient processes and steady state vibrations in the piping system are proposed. Methodology is illustrated by numerical examples.
A Time Domain Identification Technique: The Oversized Eigenmatrix (OEM) Method
Authors: Yang Yongxin
Published: December 2011

A method of identifying natural frequencies and associated damping ratios of a structure from its free decay response is presented. The method is based on the Prony’s algorithm with which the idea of using an oversized math model as in ITD to reduce the noise effect is incorporated. Two approaches are proposed for use in distinguishing the true poles from the extraneous poles introduced by oversizing the eigenmatrix. The simulated experiments on a cantilever beam show high efficiency of the method in reducing the noise effect on the identification results under extremely noisy conditions.
A Nonparametric Identification Technique for a Variety of Discrete Nonlinear Vibrating Systems
Authors: Yang Yongxin , Ibrahim S. R.
Published: December 2011

A relatively simple nonparametric identification technique based on the use of power series expansions for the identification of nonlinearities of a variety of discrete nonlinear vibrating systems has been developed. The input data required can be either forced or free response of the accelerations, velocities, and displacements. The individual masses of the system can also be estimated while knowing their sum and using free response data. Two examples are given to demonstrate the accuracy of the technique under noisy measurements. The method is shown to be more simple and yet versatile than other presently known techniques in this area.
Water-Heated Pool Boiling of Different Refrigerants on the Outside Surface of a Horizontal Smooth Tube
Authors: Chen Tailian
Published: December 2011

Pool boiling heat transfer has been extensively studied over decades, but the effect of boundary heating conditions on boiling received little attention. In this work, heat transfer coefficients during pool boiling of five different refrigerants (R123, R245fa, R236fa, R134a, and R22) on the outside surface of a smooth copper tube were measured at the saturation temperature of 6.7 °C; water flows inside the tube and provides heat to the refrigerants to boil (thus, water-heated boiling). Measurements showed that the refrigerant of a higher vapor pressure has a higher heat transfer coefficient, with the exception that R22 performs nearly the same as R134a. A correlation previously developed for electrically-heated pool boiling on cylindrical tubes underpredicts by 30%–46% the heat transfer coefficients during water-heated boiling of the five refrigerants. Among the pool boiling correlations reviewed in this work, the Cooper correlation (for pool boiling on cylindrical tubes) predicts the boiling heat transfer coefficients of R22 and R245fa reasonably well (within ±8.5%), but not as well those of the other three refrigerants (underpredicts by nearly 30% for R134a and R236fa and overpredicts by nearly 40% for R123). It is found that the predicted boiling heat transfer coefficients of the five refrigerants by the modified Gorenflo correlation (simply adding a constant multiplier of 1.47 to the Gorenflo correlation) are in excellent agreement with their respective measurements.
A Monolithic Approach Based on the Balancing Domain Decomposition Method for Acoustic Fluid-Structure Interaction
Authors: Minami S. , Kawai H. , Yoshimura S.
Published: December 2011

A scalable and efficient monolithic approach based on the Balancing Domain Decomposition (BDD) method for acoustic fluid-structure interaction problems is developed. The BDD method is a well-known domain decomposition method for non-overlapping sub-domains, which consists of Neumann-Neumann (NN) preconditioning and coarse grid correction. In this study, we derive four types of BDD method, considering two options for NN preconditioning (NN-I and NN-C) and two options for coarse grid correction (CGC-FULL and CGC-DIAG). From the results of numerical experiments, the combination of NN-I and CGC-FULL turns out to be the most efficient scheme, showing fast convergence property irrespective of the number of sub-domains, DOFs of fluid and solid domains, and the added-mass effect of fluid. The combination of NN-I and CGC-DIAG is also expected to be an efficient scheme in some situations in a parallel environment.
A Review of Full Eulerian Methods for Fluid Structure Interaction Problems
Authors: Takagi Shu , Sugiyama Kazuyasu , Ii Satoshi , Matsumoto Yoichiro
Published: December 2011

We have recently developed a novel numerical method for fluid–solid and fluid–membrane interaction problems. The method is based on a finite difference fractional step technique, corresponding to a standard numerical approach for simulating incompressible fluid flows, and applicable to treating nonlinear constitutive laws of solid/membrane and large deformations. The temporal change of the solid deformation is described in the Eulerian frame by updating the advection equations for a left Cauchy-Green deformation tensor, which is used to express the constitutive equations for materials and membranes. This method is reviewed in detail with some numerical results.
Analytical study of the horizontal ducting of sound by an oceanic front over a slope
Authors: Lin Ying-Tsong , Lynch James F.
Published: December 2011

The horizontal ducting of sound by an oceanic temperature front over a sloping bottom is studied with an idealized wedge model consisting of a lateral interface across the slope. The water outside the frontal interface has higher temperature, hence faster sound speed, and it will produce inshore reflection/refraction of the sound. Combining the offshore refraction caused by the sloping bottom, propagating sound can be ducted along the front. An analytical solution to the sound pressure field in the idealized model is derived, and an example is presented to demonstrate and discuss the ducting effect.
Spectral integration versus multiple looks in the sample discrimination of intensity
Authors: Lutfi Robert A. , Gilbertson Lynn
Published: December 2011

A fundamental property of hearing is that signals become more detectable as their bandwidth is increased. Two models have been proposed to account for this result. The integration model assumes that detection is mediated by the output of a single frequency channel matched in bandwidth to the signal. The multiple-looks model assumes that detection is based on the combination of outputs from multiple channels matched to the individual frequencies of the signal. Results are reported supporting the integration model.
Is the Regulation of Insulin Signaling Multi-Organismal?
Authors: Douglas Angela E.
Published: December 2011

Gut microbiota in
Drosophila
promote metabolic signaling pathways, resulting in increased growth and development rates.
Contrasting Effects of Physical Wear on Elution of Two Antibiotics from Orthopedic Cement
Authors: Dodds S. , Smith T. J. , Akid R. , Stephenson J. , Nichol T. , Banerjee R. D. , Stockley I. , Townsend R.
Published: December 2011

The use of antibiotics as a supplement to bone cement for the purposes of providing a local release of antibiotics is common practice in arthroplasty surgery and the kinetics of elution of the antibiotics in such systems have been investigated previously. However, in these previous studies no account was taken of the potential effects that wear may have on the elution kinetics of the antibiotic. Here, we have modified an existing wear testing rig to allow the simultaneous study of the elution kinetics of bone cement samples containing antibiotics being subjected to immersion only and immersion and conjoint wear. The results show contrasting effects with two commonly used antibiotics. Bone cement containing daptomycin showed no substantial change in antibiotic elution due to wear, while cement containing gentamicin (the most commonly used antibiotic in this application) in contrast demonstrated a substantial reduction in the rate of antibiotic elution when wear was applied. Scanning electron microscopy revealed a possible explanation for these diverse results, due to wear-induced “sealing” of the surface in conjunction with the crystal morphology of the antibiotic.
High Prevalence of Isolates with Reduced Glycopeptide Susceptibility in Persistent or Recurrent Bloodstream Infections Due to Methicillin-Resistant Staphylococcus aureus
Authors: Uçkay Ilker , Bernard Louis , Buzzi Marta , Harbarth Stephan , François Patrice , Huggler Elzbieta , Ferry Tristan , Schrenzel Jacques , Renzoni Adriana , Vaudaux Pierre , Lew Daniel P.
Published: December 2011

Reduced susceptibility to glycopeptides in methicillin-resistant
Staphylococcus aureus
(MRSA) clinical isolates is considered a risk factor for failure of glycopeptide therapy. We compared the prevalences of MRSA isolates with reduced glycopeptide susceptibility in patients with versus without persistent or recurrent MRSA bloodstream infections. A retrospective cohort study at the University Hospital of Geneva identified 27 patients with persistent or recurrent clonally related MRSA bacteremic episodes over an 8-year period, which included 208 consecutive nosocomial MRSA bacteremic episodes. Vancomycin and teicoplanin MICs were determined by a modified macrodilution assay allowing improved detection of glycopeptide-intermediate MRSA isolates (GISA), characterized by elevated teicoplanin or/and vancomycin MICs (≥4 μg/ml). For 16 patients (59%), their pretherapy and/or posttherapy MRSA isolates showed elevated teicoplanin MICs, among which 10 (37%) concomitantly displayed elevated vancomycin MICs. In contrast, 11 other patients (41%) were persistently or recurrently infected with non-GISA isolates. In comparison, only 39 (22%) of 181 single isolates from patients with no microbiological evidence of persistent or recurrent infections showed elevated teicoplanin MICs, among which 14 (8%) concomitantly displayed elevated vancomycin MICs. Clinical, microbiological, and pharmacokinetic variables for patients persistently or recurrently infected with GISA or non-GISA isolates were similar. Bacteremic patients with a poor response to glycopeptide therapy had a 2.8-fold- and 4.8-fold-higher rates of MRSA isolates displaying elevated teicoplanin and vancomycin MICs, respectively, than patients with single isolates (
P
< 0.0001). Detection of elevated teicoplanin MICs may help to predict a poor response to glycopeptide therapy in MRSA bacteremic patients.
Prospective Multicenter Study of the Impact of Carbapenem Resistance on Mortality in Pseudomonas aeruginosa Bloodstream Infections
Authors: Peña Carmen , Suarez Cristina , Gozalo Mónica , Murillas Javier , Almirante Benito , Pomar Virginia , Aguilar Manuela , Granados Ana , Calbo Esther , Rodríguez-Baño Jesús , Rodríguez Fernando , Tubau Fe , Martínez-Martínez Luis , Oliver Antonio ,   for the Spanish Network for Research in Infectious Diseases (REIPI)
Published: December 2011

The impact of antimicrobial resistance on clinical outcomes is the subject of ongoing investigations, although uncertainty remains about its contribution to mortality. We investigated the impact of carbapenem resistance on mortality in
Pseudomonas aeruginosa
bacteremia in a prospective multicenter (10 teaching hospitals) observational study of patients with monomicrobial bacteremia followed up for 30 days after the onset of bacteremia. The adjusted influence of carbapenem resistance on mortality was studied by using Cox regression analysis. Of 632 episodes, 487 (77%) were caused by carbapenem-susceptible
P. aeruginosa
(CSPA) isolates, and 145 (23%) were caused by carbapenem-resistant
P. aeruginosa
(CRPA) isolates. The median incidence density of nosocomial CRPA bacteremia was 2.3 episodes per 100,000 patient-days (95% confidence interval [CI], 1.9 to 2.8). The regression demonstrated a time-dependent effect of carbapenem resistance on mortality as well as a significant interaction with the Charlson index: the deleterious effect of carbapenem resistance on mortality decreased with higher Charlson index scores. The impact of resistance on mortality was statistically significant only from the fifth day after the onset of the bacteremia, reaching its peak values at day 30 (adjusted hazard ratio for a Charlson score of 0 at day 30, 9.9 [95% CI, 3.3 to 29.4]; adjusted hazard ratio for a Charlson score of 5 at day 30, 2.6 [95% CI, 0.8 to 8]). This study clarifies the relationship between carbapenem resistance and mortality in patients with
P. aeruginosa
bacteremia. Although resistance was associated with a higher risk of mortality, the study suggested that this deleterious effect may not be as great during the first days of the bacteremia or in the presence of comorbidities.
Resuscitation-Promoting Factors Are Required for β-Lactam Tolerance and the Permeability Barrier in Mycobacterium tuberculosis
Authors: Wivagg Carl N. , Hung Deborah T.
Published: December 2011

Mycobacterial resuscitation-promoting factors (RPFs) have been of great interest since the discovery that they promote the growth of nonculturable
Mycobacterium tuberculosis
cells. Yet, their precise role in mycobacterial survival and infection has remained elusive. We performed a chemical screen to identify molecules that show preferential killing of a
Mycobacterium tuberculosis
mutant lacking RPFs over wild-type bacilli and found that the mutant has enhanced sensitivity to the β-lactam class of antibiotics. By monitoring β-lactam diffusion across the mycobacterial outer membrane, we found that the RPFs are required to maintain the outer membrane integrity, as their deletion results in an increase in outer membrane permeability.
Interleukin-1β Regulates CXCL8 Release and Influences Disease Outcome in Response to Streptococcus pneumoniae, Defining Intercellular Cooperation between Pulmonary Epithelial Cells and Macrophages
Authors: Marriott Helen M. , Gascoyne Kate A. , Gowda Ravi , Geary Ian , Nicklin Martin J. H. , Iannelli Francesco , Pozzi Gianni , Mitchell Timothy J. , Whyte Moira K. B. , Sabroe Ian , Dockrell David H.
Published: December 2011

The success ofStreptococcus pneumoniae(the pneumococcus) as a pulmonary pathogen is related to its restriction of innate immune responses by respiratory epithelial cells. The mechanisms used to overcome this restriction are incompletely elucidated. Pulmonary chemokine expression involves complex cellular and molecular networks, involving the pulmonary epithelium, but the specific cellular interactions and the cytokines that control them are incompletely defined. We show that serotype 2 or 4 pneumococci induce only modest levels of CXCL8 expression from epithelial cell lines, even in the absence of a polysaccharide capsule. In contrast, coculture of A549 cells with the macrophage-like THP-1 cell line, differentiated with vitamin D, or monocyte-derived macrophages enhanced CXCL8 release. Supernatants from the THP-1 cell line prime A549 cells to release CXCL8 at levels similar to cocultures. Interleukin-1Ra (IL-1Ra) inhibits CXCL8 release from cocultures and reduces the activity of macrophage-conditioned media, but inhibition of tumor necrosis factor alpha (TNF-α) had only a minimal effect on CXCL8 release. Release of IL-1β but not TNF-α was upregulated in cocultures. IL-1 type 1 receptor knockout C57BL/6 and BALB/c mice confirmed the importance of IL-1 signaling in CXC chemokine expression and neutrophil recruitmentin vivo. In fulminant disease, increased IL-1 signaling resulted in increased neutrophils in the airway and more invasive disease. These results demonstrate that IL-1 is an important component of the cellular network involving macrophages and epithelial cells, which facilitates CXC chemokine expression and aids neutrophil recruitment during pneumococcal pneumonia. They also highlight a potential clinical role for anti-IL-1 treatment to limit excessive neutrophilic inflammation in the lung.
In Vivo
-Induced InvA-Like Autotransporters Ifp and InvC of Yersinia pseudotuberculosis Promote Interactions with Intestinal Epithelial Cells and Contribute to Virulence
Authors: Pisano Fabio , Kochut Annika , Uliczka Frank , Geyer Rebecca , Stolz Tatjana , Thiermann Tanja , Rohde Manfred , Dersch Petra
Published: December 2011

The
Yersinia pseudotuberculosis
Ifp and InvC molecules are putative autotransporter proteins with a high homology to the invasin (InvA) protein. To characterize the function of these surface proteins, we expressed both factors in
Escherichia coli
K-12 and demonstrated the attachment of Ifp- and InvC-expressing bacteria to human-, mouse-, and pig-derived intestinal epithelial cells. Ifp also was found to mediate microcolony formation and internalization into polarized human enterocytes. The
ifp
and
invC
genes were not expressed under
in vitro
conditions but were found to be induced in the Peyer's patches of the mouse intestinal tract. In a murine coinfection model, the colonization of the Peyer's patches and the mesenteric lymph nodes of mice by the
ifp
-deficient strain was significantly reduced, and considerably fewer bacteria reached liver and spleen. The absence of InvC did not have a severe influence on bacterial colonization in the murine infection model, and it resulted in only a slightly reduced number of
invC
mutants in the Peyer's patches. The analysis of the host immune response demonstrated that the presence of Ifp and InvC reduced the recruitment of professional phagocytes, especially neutrophils, in the Peyer's patches. These findings support a role for the adhesins in modulating host-pathogen interactions that are important for immune defense.
MULTIPLE SCATTERING APPROACHES ON THE ELECTRORHEOLOGICAL FLUIDS
Authors: JIAO MINGCHUN , SUN GANG , WANG QIANG , LU KUNQUAN
Published: December 2011

The multiple scattering method is used in calculating the electric field distribution for the systems composed of spheres. According to the calculation result, we propose a new mechanism of the electrorheological effect and show that the yield stress induced by this mechanism exhibits the typical characteristics of that observed in experiments.
OPTICAL PROPERTIES OF BMN-BT FERROELECTRIC THIN FILMS PREPARED BY SPRAY PYROLYSIS DEPOSITION
Authors: GHASEMIFARD M.
Published: December 2011

By using spray pyrolysis method, 0.65 Ba ( Mg 1/3, Nb 2/3) O 3-0.35 BaTiO 3 thin films were deposited on glass/aluminum substrates. The effect of annealing temperature on perovskite phase and crystalline structure analysis of the BMN-BT films performed on an X-ray diffraction (XRD). The optical properties of the resultant materials have been characterized as a function of substrate's temperature. The absorption coefficient (α) and extinction coefficient (k) of the films are obtained by using UV-vis spectroscopy. The band gap energy values of the films using analysis of the absorption coefficient and Tauc's formula have also been determined. For films deposited at different substrate temperatures, direct transitions occur with energies varying from 4.57 eV to 4.21 eV.
Synthesis and characterization of the most distorted 16π porphyrin: 16π octaisopropyltetraphenylporphyrin (OiPTPP)
Authors: Sugawara Shun , Kodama Megumi , Hirata Yusuke , Kojima Satoshi , Yamamoto Yohsuke
Published: December 2011

Previously unreported octaisopropyltetraphenylporphyrin (OiPTPP) was prepared from 3,4-diisopropylpyrrole, an unstable previously unisolated heterocyclic compound. Purification of the free-base 18π porphyrin required conversion to its 18π zinc(II) complex, chromatographic separation, and acid mediated demetalation. Oxidation of the 18π porphyrin with SbCl5 furnished metal-free 16π octaisopropyltetraphenylporphyrin (OiPTPP). X-ray structural determination revealed that the novel species is the most distorted 16π porphyrin to date. The time course of decomposition of the oxidized species monitored by UV-vis spectra implied that the introduction of high steric repulsion was effective for enhancing stability of the 16π porphyrin. The reaction of metal-free 16π OiPTPP with LiBF4 followed by Pd2(dba)3 gave the corresponding 18π OiPTPP palladium(II) complex via reduction of the OiPTPP lithium(I) complex as previously reported for 16π octaisobutyltetraphenylporphyrin (OiBTPP). The new 18π porphyrin system could be characterized by the X-ray analysis of the 18π OiPTPP palladium(II) complex. The X-ray structure of the 18π metal complex also indicated that the distortion of the porphyrin ring had become larger than that of previously known 18π porphyrins
Asset Pricing with Status Risk
Authors: Krasny Yoel
Published: December 2011

This paper examines the impact of status-seeking considerations on investors' portfolio choices and asset prices in a general equilibrium setting. The economy studied in this paper consists of traditional ("Markowitz") investors as well as status-seekers who are concerned about relative wealth. The model highlights the strategic and interdependent nature of portfolio selection in such a setting: Low-status investors look for portfolio choices that maximize their chances of moving up the ladder while high-status investors look to maintain the status quo and hedge against these choices of the low-status investors. In equilibrium, asset returns obey a novel two-factor model in which one factor is the traditional market factor and the other is a particular "high volatility factor" that does not appear to have been identified so far in the theoretical or empirical literature. This two-factor model found significant support when tested with stock market data. Of particular interest is that the model and the empirical results attribute the low returns on idiosyncratic volatility stocks to their covariance with the portfolio of highly volatile stocks held by investors with relatively low status.
Do Mutual Funds Perform When It Matters Most to Investors? US Mutual Fund Performance and Risk in Recessions and Expansions
Authors: Kosowski Robert
Published: December 2011

This paper shows that the stylized fact of average mutual fund underperformance documented in the literature stems from expansion periods when funds have statistically significant negative risk-adjusted performance and not recession periods when risk-adjusted fund performance is positive. These results imply that traditional unconditional performance measures understate the value added by active mutual fund managers in recessions, when investors' marginal utility of wealth is high. The risk-adjusted performance (or alpha) difference between recession and expansion periods is statistically and economically significant at 3% to 5% per year. Our findings are based on a novel multi-variate conditional regime-switching performance methodology used to carry out one of the most comprehensive examinations of the performance of US domestic equity mutual funds in recessions and expansions from 1962 to 2005. The findings are robust to the choice of the factor model (including bond and liquidity factor extensions), the use of NBER business cycle dates, fund load, turnover, expenses and percentage of equity holdings.
The ties linking rock and fossil records and why they are important for palaeobiodiversity studies
Authors: Smith Andrew B. , McGowan Alistair J.
Published: December 2011

A correlation exists between the quality of the rock record and the diversity of fossils recorded from that rock record but what drives that correlation, and how consistent that correlation is across different environments, remain to be determined. Palaeontologists wishing to investigate past diversity patterns need to first address issues of geological bias in their data.
Uncovering the diversification history of marine tetrapods: ecology influences the effect of geological sampling biases
Authors: Benson Roger B. J. , Butler Richard J.
Published: December 2011

Mesozoic terrestrial vertebrates gave rise to sea-going forms independently among the ichthyosaurs, sauropterygians, thalattosaurs, crocodyliforms, turtles, squamates, and other lineages. Many passed through a shallow marine phase before becoming adapted for open ocean life. This allows quantitative testing of factors affecting our view of the diversity of ancient organisms inhabiting different oceanic environments. We implemented tests of correlation using generalized difference transformed data, and multiple regression models. These indicate that shallow marine diversity was driven by changes in the extent of flooded continental area and more weakly influenced by uneven fossil sampling. This is congruent with studies of shallow marine invertebrate diversity and suggests that ‘common cause’ effects are influential in the shallow marine realm. In contrast, our view of open ocean tetrapod diversity is strongly distorted by temporal heterogeneity in fossil record sampling, and has little relationship with continental flooding. Adaptation to open ocean life allowed plesiosaurs, ichthyosaurs and sea turtles to ‘escape’ from periodic extinctions driven by major marine regressions, which affected shallow marine taxa in the Late Triassic and over the Jurassic–Cretaceous boundary. Open ocean taxa declined in advance of the end-Cretaceous extinction. Shallow marine taxa continued diversifying in the terminal stages due to increasing sea-level.

Supplementary material:

The data series and full analytical results are available at
http://www.geolsoc.org.uk/SUP18486
Geological and anthropogenic controls on the sampling of the terrestrial fossil record: a case study from the Dinosauria
Authors: Upchurch P. , Mannion P. D. , Benson R. B. J. , Butler R. J. , Carrano M. T.
Published: December 2011

Dinosaurs provide excellent opportunities to examine the impact of sampling biases on the palaeodiversity of terrestrial organisms. The stratigraphical and geographical ranges of 847 dinosaurian species are analysed for palaeodiversity patterns and compared to several sampling metrics. The observed diversity of dinosaurs, Theropoda, Sauropodomorpha and Ornithischia, are positively correlated with sampling at global and regional scales. Sampling metrics for the same region correlate with each other, suggesting that different metrics often capture the same signal. Regional sampling metrics perform well as explanations for regional diversity patterns, but correlations with global diversity are weaker. Residual diversity estimates indicate that sauropodomorphs diversified during the Late Triassic, but major increases in the diversity of theropods and ornithischians did not occur until the Early Jurassic. Diversity increased during the Jurassic, but many groups underwent extinction during the Late Jurassic or at the Jurassic/Cretaceous boundary. Although a recovery occurred during the Cretaceous, only sauropodomorphs display a long-term upward trend. The Campanian–Maastrichtian diversity ‘peak’ is largely a sampling artefact. There is little evidence for a gradualistic decrease in diversity prior to the end-Cretaceous mass extinction (except for ornithischians), and when such decreases do occur they are small relative to those experienced earlier in dinosaur evolution.

Supplementary material:

The full data set and details of analyses are available at
www.geolsoc.org.uk/SUP18487
The same materials (in the form of an Excel workbook) are also available from the first author on request.
Assessing the quality of the fossil record: insights from vertebrates
Authors: Benton Michael J. , Dunhill Alexander M. , Lloyd Graeme T. , Marx Felix G.
Published: December 2011

Assessing the quality of the fossil record is notoriously hard, and many recent attempts have used sampling proxies that can be questioned. For example, counts of geological formations and estimated outcrop areas might not be defensible as reliable sampling proxies: geological formations are units of enormously variable dimensions that depend on rock heterogeneity and fossil content (and so are not independent of the fossil record), and outcrop areas are not always proportional to rock exposure, probably a closer indicator of rock availability. It is shown that in many cases formation counts will always correlate with fossil counts, whatever the degree of sampling. It is not clear, in any case, that these proxies provide a good estimate of what is missing in the gap between the known fossil record and reality; rather they largely explore the gap between known and potential fossil records. Further, using simple, single numerical metrics to correct global-scale raw data, or to model sampling-driven patterns may be premature. There are perhaps four approaches to exploring the incompleteness of the fossil record, (1) regional-scale studies of geological completeness; (2) regional- or clade-scale studies of sampling completeness using comprehensive measures of sampling, such as numbers of localities or specimens or fossil quality; (3) phylogenetic and gap-counting methods; and (4) model-based approaches that compare sampling as one of several explanatory variables with measures of environmental change, singly and in combination. We suggest that palaeontologists, like other scientists, should accept that their data are patchy and incomplete, and use appropriate methods to deal with this issue in each analysis. All that matters is whether the data are
adequate
for a designated study or not. A single answer to the question of whether the fossil record is driven by macroevolution or megabias is unlikely ever to emerge because of temporal, geographical, and taxonomic variance in the data.
ACCENT
Authors: Park Ki-Woong , Park Kyu Ho
Published: December 2011

Emerging cloud services, including mobile offices, Web-based storage services, and content delivery services, run diverse workloads under various device platforms, networks, and cloud service providers. They have been realized on top of SSL/TLS, which is the de facto protocol for end-to-end secure communication over the Internet. In an attempt to achieve a cognitive SSL/TLS with heterogeneous environments (device, network, and cloud) and workload awareness, we thoroughly analyze SSL/TLS-based data communication and identify three critical mismatches in a conventional SSL/TLS-based data transmission. The first mismatch is the performance of loosely coupled encryption-compression and communication routines that lead to underutilized computation and communication resources. The second mismatch is that the conventional SSL/TLS only provides a static compression mode, irrespective of the dynamically changing status of each SSL/TLS connection and the computing power gap between the cloud service provider and diverse device platforms. The third is the memory allocation overhead due to frequent compression switching in the SSL/TLS. As a remedy to these rudimentary operations, we present a system called an Adaptive Cryptography Plugged Compression Network (ACCENT) for SSL/TLS-based cloud services. It is comprised of the following three novel mechanisms, each of which aims to provide an optimal SSL/TLS communication and maximize the network transfer performance of an SSL/TLS protocol stack: tightly-coupled threaded SSL/TLS coding, floating scale-based adaptive compression negotiation, and unified memory allocation for seamless compression switching. We implemented and tested the mechanisms in OpenSSL-1.0.0. ACCENT is integrated into the Web-interface layer and SSL/TLS-based secure storage service within a real cloud computing service, called
iCubeCloud
, as the key primitive for SSL/TLS-based data delivery over the Internet.