bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Shell and Perfectly Transparent Open-Boundary Condition for Unsteady Wave-Body Interactions
Authors: Hamilton J. Andrew , Yeung Ronald W.
Published: March 2003

This work, presented in the OMAE-2002 Special Symposium in honor of John V. Wehausen, is dedicated to him, an admirable teacher, colleague, and scholar. A general open boundary condition for time-dependent wave-body interaction problems is developed. The technique is based on domain decomposition and a use of the unsteady free-surface Green function in an outer region. The boundary condition results in a shell condition which may be applied to a variety of interior solution methods. When the interior solution method is a boundary-integral method, an implicit matching can be done. When a volume-discretization method is used in the interior region, a newly developed explicit matching procedure is performed. Demonstrations of the transparent properties of this shell are made for several types of unsteady problems.
A Strongly-Nonlinear Model for Water Waves in Water of Variable Depth—The Irrotational Green-Naghdi Model
Authors: Kim J. W. , Bai K. J. , Ertekin R. C. , Webster W. C.
Published: March 2003

Recently, the authors have derived a new approximate model for the nonlinear water waves, the Irrotational Green-Naghdi (IGN) model. In this paper, we first derive the IGN equations applicable to variable water depth, and then perform numerical tests to show whether and how fast the solution of the IGN model converges to the true solution as its level increases. The first example given is the steady solution of progressive waves of permanent form, which includes the small-amplitude sinusoidal wave, the solitary wave and the nonlinear Stokes wave. The second example is the run-up of a solitary wave on a vertical wall. The last example is the shoaling of a wave train over a sloping beach. In each numerical test, the self-convergence of the IGN model is shown first. Then the converged solution is compared to the known analytic solutions and/or solutions of other approximate models such as the KdV and the Boussinesq equations.
Numerical Computations for a Nonlinear Free Surface Problem in Shallow Water
Authors: Bai K. J. , Kyoung J. H. , Kim J. W.
Published: March 2003

A finite-element method is developed to simulate a numerical towing tank, in the scope of potential theory. The exact nonlinear free-surface flow problem formulated in an initial/boundary value problem is replaced by an equivalent weak formulation and then discretized by the finite-element method. Emphasis is made on the present simulation to include the dry bottom occurring at the downstream of a transom stern model stretched from the free surface to the tank bottom in supercritical speeds. The dry bottom has been observed in an earlier study of Bai et al. But it was not clear whether the phenomenon was physical or simply due to numerical instability. In the present paper, we have introduced a number of numerical schemes to improve the numerical stability and to simulate the dry bottom in more robust manner. Also made is a series of experiments to validate the numerical results and the existence of the dry bottom at the downstream. Numerical simulations and towing-tank tests are made for wedge-shaped ships with different stern shape, beam-draft ratios and the Froude numbers. For the model with transom stern, both the computed results and the experimental observations show the generation of the dry bottom behind the transom stern. We dedicate this article to our teacher, Prof. John V. Wehausen.
On the Interaction of Waves With Intake/Discharge Flows Originating From a Freely-Floating Body
Authors: Padmanabhan B. , Ertekin R. C.
Published: March 2003

A linear theory is developed to obtain the motions of a two-dimensional, freely floating body (from which steady intake/discharge flows originate) that encounters incoming waves. The boundary-value problem is formulated within the assumptions of linear potential theory by decomposing the total potential into its oscillatory and steady components. The steady potential is further decomposed into the double-model and perturbation potentials. The time-harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained by use of the quadratic boundary-element method based on the Rankine source. The effect of the steady intake/discharge flows on the diffraction loads, hydrodynamic force coefficients, as well as the motions of a two-dimensional prismatic body floating on the free surface are presented. It is shown that the exciting wave forces and the hydrodynamic coefficients other than the damping coefficients are not appreciably affected in the case of low intake/discharge Froude numbers that are estimated, for example, for a 100 MW floating OTEC plant.
Experiments on Deep-Water Waves With Two-Dimensional Surface Patterns
Authors: Hammack Joseph L. , Henderson Diane M.
Published: March 2003

Experiments are conducted in a three-dimensional wave basin with a wavemaker system comprising 32 side-by-side paddles for which there is precise control. Two types of wavemaker forcings are used to create two-dimensional surface patterns: (1) two symmetric carrier waves interacting at an oblique angle and (2) a single carrier wave propagating in the x-direction with a Jacobi elliptic, sn-function modulation in the y-direction. Data are presented from overhead photographs and from time series obtained by traversing a wave-gage through the patterns. Two parameters are systematically varied: the horizontal aspect ratio of the cells comprising the surface pattern and the measure of nonlinearity of the input wavefield. Unlike such waves in shallow water for which the surface pattern is made up of six-sided cells, the wave pattern for waves in deep water is made up of rectangular cells. Both the overhead photographs and the time series show that for most values of the two parameters, the wavefields evolve with significant modulations in both the x and y directions. In particular, when the aspect ratio of the cells is below about 0.4 for a fixed measure of nonlinearity, there is significant modulation in the y-direction that results in cells with smaller aspect ratios. For aspect ratio above about 0.4, the cells appear to be stable (except for viscous decay) for smaller values of nonlinearity. However, for larger values of nonlinearity even these cells modulate in the y-direction, further increasing the aspect ratio of the evolving cells. For the largest value of nonlinearity considered, the pattern evolves into one that comprises cells with aspect ratios of about 1.
Spectral Representation of Ship-Generated Waves in Finite-Depth Water
Authors: Scragg Carl A.
Published: March 2003

Recent efforts to compare the waves generated by different vessels traveling in finite-depth water have struggled with difficulties presented by various data sets of wave elevations (either measurements or predictions) corresponding to different lateral distances from the ship. Some of the attempts to shift the data to a common reference location have relied upon crude and potentially misleading approximations. The use of free-wave spectral-methods not only overcomes such difficulties, but is also provides us the means to accurately extend CFD results into the far field. As in the deep-water case, one can define a free-wave spectrum that is valid for all lateral positions and distances astern of the vessel. The free-wave spectrum contains a complete description of the Kelvin wake, and wave elevations at any far-field position can be readily calculated once the spectrum is known. For the case of infinitely deep water, Eggers, Sharma, and Ward [1] presented a method by which free-wave spectra can be determined from appropriate measurements of the far-field wave elevations. The current paper discusses the use of free-wave spectra for finite-depth problems and presents a method for the determination of free-wave spectra based upon fitting predicted wave elevations to a corresponding data set. The predicted wave elevations can be calculated from an unknown distribution of finite-depth Havelock singularities. The unknown singularities are determined by minimizing the mean-square-difference between predicted and measured wave fields. The method appears to be quite general and can be used to calculate either finite or infinite-depth free-wave spectra from experimental data or from local CFD predictions.
Nonlinear Interaction of Submerged Cylinder With Free Surface
Authors: Makarenko Nikolai I.
Published: March 2003

The fully nonlinear problem on the unsteady water waves generated by submerged moving cylinder is considered. Using the analytic majorant method we prove local in time unique solvability of this problem. For the case when the dimensionless cylinder radius is small, the solution estimate obtained predicts rigorously dipole-like structure for the lowest order far field flow. The strength of dipole concentrated at the cylinder axis depends on the instantaneous wave form and fluid velocity at the free surface. A special case of the lifting accelerated cylinder starting from the rest is studied analytically in more detail.
Heat Transfer in Friction Stir Welding—Experimental and Numerical Studies
Authors: Chao Yuh J. , Qi X. , Tang W.
Published: March 2003

In the friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. This heat flows into the workpiece as well as the tool. The amount of heat conducted into the workpiece determines the quality of the weld, residual stress and distortion of the workpiece. The amount of the heat that flows to the tool dictates the life of the tool and the capability of the tool for the joining process. In this paper, we formulate the heat transfer of the FSW process into two boundary value problems (BVP)—a steady state BVP for the tool and a transient BVP for the workpiece. To quantify the physical values of the process the temperatures in the workpiece and the tool are measured during FSW. Using the measured transient temperature fields finite element numerical analyses were performed to determine the heat flux generated from the friction to the workpiece and the tool. Detailed temperature distributions in the workpiece and the tool are presented. Discussions relative to the FSW process are then given. In particular, the results show that (1) the majority of the heat generated from the friction, i.e., about 95%, is transferred into the workpiece and only 5% flows into the tool and (2) the fraction of the rate of plastic work dissipated as heat is about 80%.
Nanomechanics of carbon nanotubes and composites
Authors: Srivastava and Deepak , Wei Chenyu , Cho Kyeongjae
Published: March 2003

Computer simulation and modeling results for the nanomechanics of carbon nanotubes and carbon nanotube-polyethylene composite materials are described and compared with experimental observations. Young’s modulus of individual single-wall nanotubes is found to be in the range of 1 TPa within the elastic limit. At room temperature and experimentally realizable strain rates, the tubes typically yield at about 5–10% axial strain; bending and torsional stiffness and different mechanisms of plastic yielding of individual single-wall nanotubes are discussed in detail. For nanotube-polyethylene composites, we find that thermal expansion and diffusion coefficients increase significantly, over their bulk polyethylene values, above glass transition temperature, and Young’s modulus of the composite is found to increase through van der Waals interaction. This review article cites 54 references.
Modeling and Control of an Electro-hydraulic Injection Molding Machine With Smoothed Fill-to-Pack Transition*
Authors: Zheng Danian , Alleyne Andrew
Published: March 2003

In this paper the modeling of a typical injection cycle for an injection-molding machine (IMM) is examined. Both the mold filling and mold packing phases of the cycle are examined along with a critical fill-to-pack transition. The novelty in this modeling work is that the nonlinear model considers both the machine hydraulic actuator and polymer flow characteristics in extensive detail. The simulation model is validated against experimental data and demonstrates the availability of a relatively accurate system model for full cycle control design of this electro-hydraulic system. The accurate process model is used in the design of a controller for the injection cycle including the fill-to-pack transition. The overall algorithm includes two Iterative Learning Controllers connected by a bumpless transfer scheme between them. The algorithm is successfully tested through model simulations and machine experiments. The simulation and experimental results presented demonstrate a significantly smoother control signal and pressure transient between the two learning controlled phases as well as overall tracking convergence for each phase.
Measurement and Analysis of Laboratory Generated Steep Waves
Authors: Chakrabarti Subrata K.
Published: March 2003

In many offshore locations, storm generated steep waves are common and the survival of offshore structures in their presence is an important design condition. The design environment in depth-limited waters often includes waves of breaking and near-breaking conditions, in which currents may be present. Experiments were carried out in a wave tank with simulated steep waves with and without steady in-line current in which the wave profiles and the corresponding kinematics were simultaneously measured. The waves included both regular and random waves and often approached the breaking wave height for the water depth. These waves were analyzed by higher-order wave theory. In particular, the regular waves were simulated by the regular and irregular stream function theory. Especially steep wave profiles within the random waves were computed using the irregular stream function theory. The theory allows inclusion of steady current in its formulation for computation of wave kinematics. The correlation of the measured wave kinematics with the higher-order stream function wave theory showed that the wave theory could predict the kinematics of these steep waves (with and without the presence of current) well. However, in breaking waves, the vertical water particle velocity was not predicted well, especially near the trough. The effect of breaking and near-breaking steep waves on a fixed vertical caisson was also studied. The forces measured on the vertical caisson from the wave tank testing were analyzed to determine the effect of these waves and currents on the forces. It was found that the measured forces (and overturning moments) on the caisson model matched fairly well by the proper choice of force coefficients from the design guideline and the nonlinear stream function theory of appropriate order.
Antigenic Classification ofRickettsia felisby Using Monoclonal and Polyclonal Antibodies
Authors: Fang Rong , Raoult Didier
Published: March 2003

Rickettsia felisis a flea-transmitted rickettsia. There is a discrepancy between its reported phylogenic and phenotypic identifications. Following the first report ofR. felis, it was considered by tests with serologic reagents to be closely related to another recognized flea-transmitted rickettia,R. typhi. Subsequently, it appeared to be more closely related to spotted fever group (SFG) rickettsiae by genetic analysis. In the present work,R. feliswas studied by microimmunofluorescence (MIF) serologic typing and with monoclonal antibodies (MAbs). Mouse polyclonal antisera toR. feliscross-reacted only with SFG rickettsiae. A neighbor-joining analysis based on MIF indicated thatR. felisis actually related to SFG rickettsiae antigenically, clustering withR. australis,R. akari, andR. montanensis.A panel of 21 MAbs was raised against a 120-kDa protein antigen or a 17-kDa polypeptide ofR. felis. They cross-reacted with most members of the SFG rickettsiae but not withR. prowazekii,R. typhi, orR. canadensisof the typhus group (TG) rickettsiae. Sixty-four MAbs previously generated to seven other ricketttsial species were tested withR. felis.Three MAbs reacted with the 120-kDa antigen and were generated byR. africae,R. conorii, andR. akari, respectively. They exhibited cross-reactivities withR. felis. All our data show thatR. felisharbors the antigenic profile of an SFG rickettsia.
Contribution of Epitope Specificity to the Binding of Monoclonal Antibodies to the Capsule of
Cryptococcus neoformans
and the Soluble Form of Its Major Polysaccharide, Glucuronoxylomannan
Authors: Duro Raymond M. , Netski Dale , Thorkildson Peter , Kozel Thomas R.
Published: March 2003

Incubation of encapsulated cryptococci with monoclonal antibodies (MAbs) specific for glucuronoxylomannan (GXM), the major capsular polysaccharide of
Cryptococcus neoformans
, produces two distinct capsular quellung-type reactions termed rim and puffy. The type of capsular reaction that occurs is determined by the epitope specificity of the MAb and the serotype of the yeast cell. Several biological activities, including opsonic activity, complement activation, and protective efficacy, are associated with the type of capsular reaction produced by a MAb. The goal of this study was to examine the reactivities of two families of anti-GXM MAbs with serotype A and D capsular polysaccharides in several immunochemical assays, including agglutination, immunofluorescence, quantitative precipitation, and enzyme-linked immunosorbent assay, in an effort to identify serological assays that are predictive of the capsular quellung reaction. The results showed that the type of capsular reaction (rim versus puffy) is a qualitative assessment of antibody-capsule interaction that cannot be predicted on the basis of a serological assay. The results further showed that antibody reactivity demonstrated in one serological assay is not necessarily predictive of results in another assay, particularly in cases where one assay examines antibody-capsule interactions, e.g., agglutination, and another assay examines interaction of antibody with soluble GXM. Taken together, the results suggest caution in interpretation of immunochemical assays for anti-GXM antibodies and recommend the use of multiple assays formats when studying anticryptococcal antibodies.
Competitive-Inhibition Enzyme-Linked Immunosorbent Assay for Detection of Serum Antibodies to Caprine Arthritis-Encephalitis Virus: Diagnostic Tool for Successful Eradication
Authors: Herrmann Lynn M. , Cheevers William P. , McGuire Travis C. , Adams D. Scott , Hutton Melinda M. , Gavin William G. , Knowles Donald P.
Published: March 2003

A competitive-inhibition enzyme-linked immunosorbent assay (cELISA) was evaluated for the detection of serum antibodies to the surface envelope (SU) of caprine arthritis-encephalitis virus (CAEV) in goats. This assay utilized 96-well microtiter plates containing CAEV-63 SU captured by monoclonal antibody (MAb) F7-299 and measured the competitive displacement of horseradish peroxidase-conjugated MAb GPB 74A binding by undiluted goat sera (F. Özyörük, W. P. Cheevers, G. A. Hullinger, T. C. McGuire, M. Hutton, and D. P. Knowles, Clin. Diagn. Lab. Immunol. 8:44-51, 2001). Two hundred serum samples from goats in the United States were used to determine the sensitivity and specificity of cELISA based on the immunoprecipitation (IP) of [
35
S]methionine-labeled viral antigens as a standard of comparison. A positive cELISA was defined as >33.2% inhibition of MAb 74A binding based on 2 standard deviations above the mean percent inhibition of 140 IP-negative serum samples. At this cutoff value, there were 0 of 60 false-negative sera (100% sensitivity) and 5 of 140 false-positive sera (96.4% specificity). Additional studies utilized IP-monitored cELISA to establish a CAEV-free herd of 1,640 dairy goats.
Leucotoxic Activities of
Staphylococcus aureus
Strains Isolated from Cows, Ewes, and Goats with Mastitis: Importance of LukM/LukF′-PV Leukotoxin
Authors: Rainard Pascal , Corrales Juan-Carlos , Barrio M. Belén , Cochard Thierry , Poutrel Bernard
Published: March 2003

Among the toxins that
Staphylococcus aureus
is able to secrete, bi-component toxins named leukotoxins target specifically leukocytes, mainly phagocytic cells. Isolates from cows, goats and ewes with mastitis were selected on the basis of the presence or not of the genes encoding the recently described LukM/LukF′-PV leukotoxin. Of the 128 isolates tested, 126 had moderate to high leukotoxic activity to bovine polymorphonuclear cells (PMN). The supernatants of
lukM
-positive isolates were much more leukotoxic than the supernatants of
lukM
-negative isolates: mean leukotoxic titers were 122 versus 20 and 581 versus 26 for isolates of bovine and caprine origin, respectively. Among
lukM
/
lukF
′-
PV
positive isolates, those of caprine and ovine origins were more leukotoxic than were isolates of bovine origin (
P
< 0.01). The two most abundant proteins in the culture supernatant of a highly toxic isolate were purified and identified as the two components of LukM (LukM and LukF′-PV) on the basis of their molecular mass, N-terminal amino acid sequence, and high synergistic activity. LukM/LukF′-PV induced the flattening of bovine PMN at a concentration as low as 3.6 ng/ml (0.1 nM). A higher concentration (18 ng/ml) was necessary to produce the same effect on caprine or ovine PMN. Affinity-purified antibodies to LukM or to LukF′-PV neutralized the leukotoxic effect of all the culture supernatants. They neutralized with the same efficiency the toxic activity of supernatants from
lukM
/
lukF
′-PV positive or negative isolates. These results establish that LukM/LukF′-PV is very active on PMN of ruminants and suggest that this leukotoxin could be the most active leukotoxin produced by mastitis isolates. They prompt further studies to delineate the contribution of LukM/LukF′-PV to the pathogenesis of mastitis in ruminants and the protective effect of antibodies to this leukotoxin.
Serological Cross-Reactivities between Antibodies to Simian Virus 40, BK Virus, and JC Virus Assessed by Virus-Like-Particle-Based Enzyme Immunoassays
Authors: Viscidi Raphael P. , Rollison Dana E. M. , Viscidi Emma , Clayman Barbara , Rubalcaba Elizabeth , Daniel Richard , Major Eugene O. , Shah Keerti V.
Published: March 2003

Enzyme immunoassays (EIAs) for detection of serum antibodies to simian virus 40 (SV40), BK virus (BKV), and JC virus (JCV) were developed by using virus-like-particles (VLPs) produced in insect cells from recombinant baculoviruses expressing the VP1 protein of the respective virus. Rhesus macaque sera with neutralizing antibodies to SV40 showed a high level of reactivity in the SV40 VLP-based EIA, and these sera also showed lower levels of reactivity in the BKV and JCV VLP-based EIAs. Rhesus macaque sera negative for neutralizing antibodies to SV40 were negative in all three EIAs. Competitive binding assays showed that SV40 VLPs inhibited BKV reactivity. In rhesus macaque sera, high optical density (OD) values for antibodies to SV40 VLPs were correlated with high OD values for antibodies to BKV but not with high OD values for antibodies to JCV VLPs. Human sera with neutralizing antibodies to SV40 were more reactive to SV40 VLPs than human sera without neutralizing antibodies to SV40. The greater SV40 reactivities of human sera were correlated with greater reactivities to BKV VLPs but not JCV VLPs. These data suggest that cross-reactivity with BKV antibodies may account for part of the low-level SV40 reactivity seen in human sera. With their greater versatility and their suitability for large-scale testing, the VLP-based EIAs for SV40, BKV, and JCV are likely to contribute to a better understanding of the biology of these viruses.
Correlation of Organism Burden and Alveolar Macrophage Counts during Infection withPneumocystis cariniiand Recovery
Authors: Lasbury Mark E. , Durant Pamela J. , Bartlett Marilyn S. , Smith James W. , Lee Chao-Hung
Published: March 2003

Changes in the number of alveolar macrophages were correlated with organism burden duringPneumocystis cariniiinfection. The lungs of healthy, dexamethasone-treated, and dexamethasone-treated andP. carinii-infected rats were lavaged with phosphate-buffered saline. Counting of alveolar macrophages in the lavage fluids revealed thatP. cariniiinfection caused a 58% decrease in the number of alveolar macrophages and that higherP. cariniiorganism burdens caused a more rapid decrease in alveolar macrophage number. As a control, healthy rats were challenged with the same number of organisms as that normally used to generateP. cariniiinfections in dexamethasone-treated rats. Thirteen days after challenge, these rats had a profound (54%) increase in alveolar macrophage number in response to the challenge, while the number of alveolar macrophages in immunosuppressed andP. carinii-infected rats had decreased significantly by this time point. These experiments created the first animal model to mimic human pneumocystis pneumonia in alveolar macrophage number alterations. Reduction ofP. cariniiorganism numbers by treatment of rats with trimethoprim and sulfamethoxazole brought a slow rebound in alveolar macrophage number, while recovery fromP. cariniiinfection by cessation of immunosuppression brought a rapid rebound in alveolar macrophage number. These results suggest that both the immune state of the host andP. cariniiburden affect alveolar macrophage number.
Diagnosis of Dengue Virus Infection by Detection of Specific Immunoglobulin M (IgM) and IgA Antibodies in Serum and Saliva
Authors: Balmaseda Angel , Guzmán María G. , Hammond Samantha , Robleto Guillermo , Flores Carolina , Téllez Yolanda , Videa Elsa , Saborio Saira , Pérez Leonel , Sandoval Erick , Rodriguez Yoryelin , Harris Eva
Published: March 2003

To evaluate alternative approaches to the serological diagnosis of dengue virus (DEN) infection, the detection of DEN-specific immunoglobulin M (IgM) and IgA antibodies in serum and saliva specimens was assessed in 147 patients with symptoms of DEN infection seen at the Ministry of Health in Nicaragua. Seventy-two serum samples were determined to be positive for anti-DEN antibodies by IgM capture enzyme-linked immunosorbent assay, the routine diagnostic procedure. Serum and saliva specimens were obtained from 50 healthy adults as additional controls. IgM was detected in the saliva of 65 of the 72 serum IgM-positive cases, 6 of the 75 serum IgM-negative cases, and none of the control group, resulting in a sensitivity of 90.3% and a specificity of 92.0% and demonstrating that salivary IgM is a useful diagnostic marker for DEN infection. Detection of IgA in serum may be another feasible alternative for the diagnosis of DEN infection, with serum IgA found in 68 (94.4%) of the IgM-positive cases. In contrast, detection of IgA in saliva was not found to be a useful tool for DEN diagnosis in the present study. Further studies of the kinetics of antibody detection in another set of 151 paired acute- and convalescent-phase serum samples showed that DEN-specific IgA antibodies were detected in more acute-phase samples than were IgM antibodies. Thus, we conclude that DEN-specific IgA in serum is a potential diagnostic target. Furthermore, given that saliva is a readily obtainable, noninvasive specimen, detection of DEN-specific salivary IgM should be considered a useful, cheaper diagnostic modality with similar sensitivity and specificity to IgM detection in serum.
Assessment of Thymic Activity in Human Immunodeficiency Virus-Negative and -Positive Adolescents by Real-Time PCR Quantitation of T-Cell Receptor Rearrangement Excision Circles
Authors: Pham Thao , Belzer Marvin , Church Joseph A. , Kitchen Christina , Wilson Craig M. , Douglas Steven D. , Geng Yongzhi , Silva Monica , Mitchell Richard M. , Krogstad Paul
Published: March 2003

Circular DNA molecules known as T-cell receptor rearrangement excision circles (TREC) arise during T-cell development and are present in cells that have recently emigrated from the thymus. In cross-sectional studies, the number of peripheral blood lymphocytes bearing TREC decreases with age, consistent with an anatomically demonstrated loss of thymic epithelial tissue. TREC numbers increase following hematopoietic stem cell transplantation and during therapy for human immunodeficiency virus (HIV) infection. Quantitation of TREC has therefore been proposed as a parameter of thymic activity. In this study, we used real-time PCR to quantify TREC in peripheral blood samples obtained longitudinally from HIV-seronegative adolescents. TREC values in peripheral blood T cells were very stable throughout adolescence, once thought to be a time of rapid involution of the thymus. In addition, in a cross-sectional analysis, we examined TREC values in a cohort of HIV-positive adolescents and found evidence of ongoing thymopoiesis in perinatally infected individuals, despite lifelong infection. These data demonstrate the utility of TREC assessment in adolescents and that HIV infection does not uniformly result in accelerated thymic involution in childhood.
Separation, Identification, and Characterization of Microorganisms by Capillary Electrophoresis
Authors: Desai Meera J. , Armstrong Daniel W.
Published: March 2003

The use of capillary electrophoresis (CE) for the analysis, identification, and characterization of microorganisms has been gaining in popularity. The advantages of CE, such as small sample requirements, minimal sample preparation, rapid and simultaneous analysis, ease of quantitation and identification, and viability assessment, make it an attractive technique for the analysis of microbial analytes. As this instrumental method has evolved, higher peak efficiencies have been achieved by optimizing CE conditions, such as pH, ionic strength, and polymer additive concentration. Experimental improvements have allowed better quantitation and more accurate results. Many practical applications of this technique have been investigated. Viability and identification of microbes can be accomplished in a single analysis. This is useful for evaluation of microbial analytes in consumer products. Diagnosis of microbe-based diseases is now possible, in some cases, without the need for culture methods. Microbe-molecule, virus-antibody, or bacteria-antibiotic interactions can be monitored using CE, allowing for the screening of possible drug candidates. Fermentation can be monitored using this system. This instrumental approach can be adapted to many different applications, including assessing the viability of sperm cells. Progress has been made in the development of microelectrophoresis instrumentation. These advances will eventually allow the development of small, dedicated devices for the rapid, repetitive analyses of specific microbial samples. Although these methods may never fully replace traditional approaches, they are proving to be a valuable addition to the collection of techniques used to analyze, quantitate, and characterize microbes. This review outlines the recent developments in this rapidly growing field.
Two Families of Mechanosensitive Channel Proteins
Authors: Pivetti Christopher D. , Yen Ming-Ren , Miller Samantha , Busch Wolfgang , Tseng Yi-Hsiung , Booth Ian R. , Saier, Milton H.
Published: March 2003

Mechanosensitive (MS) channels that provide protection against hypoosmotic shock are found in the membranes of organisms from the three domains of life: bacteria, archaea, and eucarya. Two families of ubiquitous MS channels are recognized, and these have been designated the MscL and MscS families. A high-resolution X-ray crystallographic structure is available for a member of the MscL family, and extensive molecular genetic, biophysical, and biochemical studies conducted in many laboratories have allowed postulation of a gating mechanism allowing the interconversion of a tightly closed state and an open state that controls transmembrane ion and metabolite fluxes. In contrast to the MscL channel proteins, which are of uniform topology, the much larger MscS family includes protein members with topologies that are predicted to vary from 3 to 11 α-helical transmembrane segments (TMSs) per polypeptide chain. Sequence analyses reveal that the three C-terminal TMSs of MscS channel proteins are conserved among family members and that the third of these three TMSs exhibits a 20-residue motif that is shared by the channel-forming TMS (TMS 1) of the MscL proteins. We propose that this C-terminal TMS in MscS family homologues serves as the channel-forming helix in a homooligomeric structure. The presence of a conserved residue pattern for the putative channel-forming TMSs in the MscL and MscS family proteins suggests a common structural organization, gating mechanism, and evolutionary origin.
OPTICAL NONLINEARITIES OF METAL-DIELECTRIC COMPOSITES
Authors: LEPESHKIN N. N. , KIM W. , SAFONOV V. P. , ZHU J. G. , ARMSTRONG R. L. , WHITE C. W. , ZUHR R. A. , SHALAEV V. M.
Published: March 2003

Nonlinear optical properties of metal-dielectric composites, such as fractal colloid aggregates and clusters created by ion implantation, are studied. Strong fluctuations of local fields result in huge enhancements of optical nonlinearities in fractal colloid aggregates. The real and imaginary parts of the cubic susceptibility of silver colloid aggregates are measured. It is found that the coefficient of nonlinear absorption strongly depends on the laser wavelength and intensity. Optical limiting effect in fractal silver colloids is observed. Nondegenerate forward four-wave mixing technique is used to investigate the third-order nonlinear susceptibility for nanocomposite material with Au nanocrystals formed inside a SiO 2 glass matrix. The Au nanocrystals are formed by the ion implantation and annealing method that produces very high volume fraction of nanoparticles. The large value |χ(3)|=1.3×10-7 esu is measured. Two characteristic relaxation times, 5.3 ps and 0.66 ps, are estimated from the detuning curve of |χ(3)|, as the probe beam wavelength changes. A novel class of optical materials, microcavities doped with nanostructured fractal aggregates, is also studied. In our experiments, lasing at extremely low pump intensities, below 1 mW, and dramatically enhanced Raman scattering was observed in microcavity/fractal composites.
OPTICAL LIMITING CAPABILITY OF THICK NONLINEAR ABSORBERS
Authors: HERMANN J. A. , BUBNER T. , MCKAY T. J. , WILSON P. J. , STAROMLYNSKA J. , ERIKSSON A. , LINDGREN M. , SVENSSON S.
Published: March 2003

A theoretical model describing the fluence-dependent absorption of Gaussian shaped laser beams by optically thick nonlinear media is applied to the interpretation of Z-scan measurements with thick samples of chloro-aluminium-phthalocyanine. The results obtained from the measurements and the modeling have produced an enhanced understanding of the nonlinear processes operating within this type of material, as well as the role of the relaxation mechanisms and saturation effects in shaping the nonlinear absorption, and the optical limiting capability of this type of absorber. An exact first-order analysis of a five-level molecular model has been developed and explored for the case where the incident beam possesses a flat temporal profile. The predictions of the model are in excellent agreement with experimental observations and with results produced from a numerical modeling technique, previously developed, where a simple "relaxation-free" and "population-saturation-free" three-level model is used to predict the transmission properties of a thick five-level system.
OPTICAL SOLITON PERTURBATION WITH BANDWIDTH LIMITED AMPLIFICATION AND SATURABLE AMPLIFIERS
Authors: BISWAS ANJAN
Published: March 2003

The propagation of solitons through an optical fiber, described by the perturbed Nonlinear Schrödinger's equation, is studied in this paper by the method of Multiple Scale Perturbation Expansion. Here, it is shown for the first time that, by introducing a new definition of the phase of soliton, one can obtain corrections to the pulse, in presence of the perturbation terms, where the standard soliton perturbation theory fails. This dynamically stable soliton is a very useful physical model in the optical soliton communication world. A comparison is made with results obtained by other methods along with numerical simulations.
A REVIEW OF NONLINEAR OPTICAL PROPERTIES OF NEMATIC LIQUID CRYSTALS
Authors: KHOO I. C.
Published: March 2003

We present a review of the electronic and non-electronic optical nonlinearities of nematic liquid crystals (NLC), and recently observed nonlinear optical processes. In both the ordered and isotropic phases, NLCs exhibit large optical nonlinearities with response times ranging from picoseconds to milliseconds. The fundamental principles underlying these nonlinearities, their dynamics and practical application potential are discussed. Comparisons are made with other nonlinear optical materials currently being investigated.
EXPERIMENTAL OBSERVATION OF NONLINEAR BEAM SPLITTING IN DYE-DOPED LIQUID CRYSTAL WAVEGUIDES
Authors: ABBATE G. , DE STEFANO L. , SANTAMATO E. , SCALIA G. , MORMILE P.
Published: March 2003

Liquid crystals have effective nonlinear optical coefficients that are orders of magnitude larger than other materials exploited in integrated optics. The addition of some organic dyes in small amounts may further enhance the nonlinear optical response and even change its sign. We used a dye-nematic liquid crystal mixture exhibiting a negative optical nonlinearity. We observed the nonlinear spatial splitting of the guided modes in a symmetric planar waveguide whose core was the liquid crystal mixture. This non-linear effect has been observed with very low laser power input and the power threshold dependence on dye concentration and core thickness was investigated.
FROM BULK JANOSSY EFFECT TO NONLINEAR SELF WAVE-GUIDING OR SPATIAL SOLUTION IN DYE-DOPED LIQUID CRYSTALS
Authors: WARENGHEM M. , HENNINOT J. F. , ABBATE G.
Published: March 2003

The pure liquid crystalline state of matter is known for its large optical nonlinearity. The effect has been widely studied in thin film as the beam crosses it. Few studies have been done for a geometry in which the light interacts with the matter on a large volume. In this paper, we report the results we have obtained in this configuration (Bulk Optical Freederisckz Effect) and for dye-doped liquid crystals. In such mixtures, the nonlinear effect occurs at low input powers and is called the Janossy effect. Besides similar behaviors which occur in the Bulk Freederisckz Effect, it is reported in this paper a beam behavior, namely a self wave-guiding or "spatial soliton," which is probably more specific to the bulk Janossy Effect. This self created wave-guide is assigned to be a consequence of the dye absorption: the optically induced refractive index gradient is finely tuned by the additional anisotropic thermal contribution, allowing a quasi perfect optical coupling of the fiber source with the optically induced liquid crystal wave-guide.
THE PHOTOELECTRICAL REORIENTATION EFFECT IN NEMATIC LIQUID CRYSTALS
Authors: MACDONALD R. , MEINDL P. , BUSCH S.
Published: March 2003

A new photoelectrical reorientation effect in nematic liquid crystals has been investigated. The effect occurs under the combined application of DC electrical fields and low power illumination. It leads to very sensitive Kerr-like optical nonlinearties which can be characterized by rather large coefficients up to 6 cm2/W. So far, it was observed in nematic liquid crystals of discotic molecules but recently also with certain calamitic, i.e., rod-like molecules. A comparison of results obtained with discotic and calamitic mesogens will be given and a first model of the effect is discussed.
INVESTIGATION OF THIRD-ORDER NONLINEARITY OF POLYBENZONITRILES BY HETERODYNED FEMTOSECOND OPTICAL KERR GATE
Authors: LIN L. , QIAN W. , WANG C. F. , ZOU Y. H. , WANG Q. , CHEN H. Y.
Published: March 2003

The femtosecond optical heterodyne detected optical Kerr effect is described in detail. The real and the imaginary parts of complex third-order optical nonlinearity can be effectively separated and their values and signs can be determined. Using this method, we thoroughly investigated the substitution effect by adding different side-groups on the –(–C=N–)– conjugated system, a new class of nonlinear optical material. We discussed the improvement in their third-order susceptibilities. And we found the value of second-order hyperpolarizability depends on the polymerization degree, but the relationship is different for different substituted polymers.
PUMP-PROBE SPECTROSCOPIC ANALYSIS OF FREE INDUCTION DECAY IN GaAs/AlxGa1-xAs QUANTUM WELL STRUCTURES
Authors: MAJUMDAR INDRANI , SEM PRATIMA
Published: March 2003

The theoretical formulation for pump-probe spectroscopic analysis of free induction decay has been made using semiclassical time dependent perturbation technique in GaAs/AlxGa1-xAs quantum well structure. The pump pulse is considered to be tuned below the band edge and the excitation intensity is assumed to be in the moderate power regime so that the only many-body effect that dominates is the excitonic effect. The probe transmission spectrum features the characteristic resonance frequencies of the system concerned. The temporal nature of the transmitted probe signal is also found to characterize the ultrafast free induction decay of the pump induced polarization, which is recorded by the low intensity probe transmission in the system.
MODELING PROPAGATION OF CHIRPED SOLITONS IN AN ELLIPTICALLY LOW BIREFRINGENT SINGLE-MODE OPTICAL FIBER
Authors: MAHMOOD M. F. , QADRI S. B.
Published: March 2003

An analytical description is presented, for the first time, to describe propagation dynamics of chirped solitons in an elliptically low birefringent optical fiber within the framework of a model described by coupled nonlinear Schroedinger equations. Using nonlinear Schroedinger solitons as trial functions in an averaged Lagrangian formulation, a set of ordinary differential equations (ODEs) are derived for various soliton parameters. These ODEs describe chirped soliton dynamics and give a criterion for nonlinear coupling of polarized pulses to form a bound state corresponding to a phase mismatch.
SECRETION OF A BONE-INDUCING AGENT (BIA) BY CULTURED SAOS-2 HUMAN OSTEOSARCOMA CELLS
Authors: Anderson H. C. , Gurley D. J. , Hsu H. H. T. , Aguilera X. M. , Davis L. S. , Moylan P. E.
Published: March 2003

An extractable bone-inducing agent has recently been identified in freeze-dried preparations of Saos-2 cultured human osteosarcoma cells. Although not all osteoinductive components of Saos-2 cell extracts have been identified, we have shown that Saos-2 cells express high levels of mRNA for bone morphogenetic proteins (BMPs)-1,2,3,4 and 6. Any or all of these BMPs (plus possible unknown factors) may be involved in ectopic bone induction, and may act as paracrine agents, conveying morphogenetic information to juxtaposed osteoprogenitor cells. Our objectives in this study were: 1) to determine whether Saos-2 cells secrete BIA into their culture medium; and 2) if secreted, to determine whether released bone-inducing agent is soluble and/or particulate and contains BMPs. Saos-2 cells were grown to confluence, and then overlaid with serum-free DMEM culture medium for 48 hours. The serum-free conditioned medium was then decanted and filtered through 0.45μ pore-size filters to retain any vesicles or other particulates released by the cells. Particulate protein retained on the 0.45μ filter (designated "retentate") was extracted into 6M urea and bioassayed for bone-inducing activity in Nu/Nu mice, along with soluble media protein that had passed through the 0.45μ filter (designated "filtrate") plus freeze-dried Saos-2 cells from which conditioned the culture medium was obtained. Results indicate that the bone-inducing agent of Saos-2 cells is not only retained by the cells, but is also secreted in both soluble and particulate forms into serum-free conditioned medium. Bone-inducing activity (per mg protein) is more concentrated in the particulate fraction, which is shown by electron microscopy to contain a mixture of vesicles (similar to matrix vesicles) plus electron dense granules (resembling ribosomes) and 10 mM microfilaments (of possible collagenous or cytoskeletal origin). BMP-1,2,3,4,6 and 7 were detected by western blots in both the soluble and particulate fractions of conditioned medium. Thus, it is indicated that Saos-2 cells secrete an osteoinductive factor which may function in vivo as a paracrine morphogenetic agent.
DENSITY-BASED LOAD ESTIMATION PREDICTS ALTERED FEMORAL LOAD DIRECTIONS FOR COXA VARA AND COXA VALGA
Authors: Fischer Kenneth J. , Eckstein Felix , Becker Christoph
Published: March 2003

Quantifying differences in joint loading for coxa vara and coxa valga is important for understanding what constitutes a pathological deformity. Prior free-body analyses for varus and valgus femora suggest that the loading direction in single-leg stance becomes more vertical for coxa valga and more horizontal for coxa vara. The objectives of this study were: 1) to apply a density-based load estimation technique to varus and valgus femora; 2) to infer potential differences in femoral loading for varus and valgus femora from the density; and 3) to compare the results with previous studies of femoral loading for single-leg stance. Representative valgus, normal, and varus femora from male cadavers were scanned in the plane of the femoral neck using computed tomography. A two-dimensional finite element model, including the density data from the CT scans, was constructed for each femur. A density-based bone load estimation method was used to determine the dominant loading pattern, and an average load direction was calculated. The average load direction varied consistently from more vertical for coxa valga to more horizontal for coxa vara. The results indicate that the differences in loading directions reduce the risk of epiphyseal slip or neck fracture in coxa vara and increase the tendency for subluxation or dislocation in coxa valga. Agreement between relative load angles from the density-based load estimation and free-body analyses confirms that internal femoral density is adapted to applied loads regardless of external femoral geometry.
MOLECULAR DETECTION OF INFECTION IN TOTAL KNEE ARTHROPLASTY: A CLINICAL CORRELATION
Authors: Mariani Brian D. , Booth Robert E. , Levine Marc J. , Gardner Tanya A. , Tuan Rocky S.
Published: March 2003

Total knee arthroplasty patients displaying symptoms consistent with either implant biomechanical failure or periprosthetic infection, and requiring revision surgery, had synovial fluid aspirated from the affected joint and subjected to standard microbiological culture testing for bacterial infection. In this study, an aliquot of each synovial fluid specimen was analyzed for infection using the rapid, sensitive molecular assay of polymerase chain reaction (PCR), designed to selectively amplify bacterial deoxyribonucleic acid. Decisions concerning surgical procedures performed during revision surgery were based entirely on clinical criteria, including standard preoperative evaluation for infection, independent of PCR results. In total, on the basis of pre- and/or intraoperative clinical data in conjunction with postoperative information, septic failure was determined in 31 of 50 patients, all of whom tested positive using the PCR assay. This correlative study validates the application of the PCR assay for clinical evaluation of arthroplasty infections.