bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study of the Flow of R-407C in an Adiabatic Spiral Capillary Tube
Authors: Mittal M. K. , Kumar R. , Gupta A.
Published: June 2010

The objective of this study is to investigate the effect of coiling on the flow characteristics of R-407C in an adiabatic spiral capillary tube. The characteristic coiling parameter for a spiral capillary tube is the coil pitch; hence, the effect of the coil pitch on the mass flow rate of R-407C was studied on several capillary tube test sections. It was observed that the coiling of the capillary tube significantly reduced the mass flow rate of R-407C in the adiabatic spiral capillary tube. In order to quantify the effect of coiling, the experiments were also conducted for straight a capillary tube, and it was observed that the coiling of the capillary tube reduced the mass flow rate in the spiral tube in the range of 9–18% as compared with that in the straight capillary tube. A generalized nondimensional correlation for the prediction of the mass flow rates of various refrigerants was developed for the straight capillary tube on the basis of the experimental data of R-407C of the present study, and the data of R-134a, R-22, and R-410A measured by other researchers. Additionally, a refrigerant-specific correlation for the spiral capillary was also proposed on the basis of the experimental data of R-407C of the present study.
Effect of Phase Transformation on the Wear Behavior of NiTi Alloy
Authors: Abedini M. , Ghasemi H. M. , Nili Ahmadabadi M. , Mahmudi R.
Published: June 2010

In this paper, mechanical and tribological properties of a Ti-50.3 at % Ni alloy were investigated. The transformation temperatures of the alloy were determined using differential scanning calorimetry. Three-point bending tests were performed to characterize the pseudoelasticity and shape memory effects. Uni-axial compression tests were also performed at different testing temperatures. The wear tests were conducted using a pin-on-disk tribometer at testing temperatures ranging from 0°C to 80°C. The wear results showed that with increasing the testing temperature from 0°C to 50°C, the wear of the alloy was decreased, which could be attributed to the higher pseudoelasticity of the alloy at a testing temperature of 50°C. The pseudoelasticity of the alloy decreased at a higher testing temperature of 80°C; however, its wear resistance increased considerably due to higher ultimate strength and work hardening.
An Innovative Falling Film Evaporative Cooling With Recirculation Driven by Low-Grade Heat
Authors: He S. , Wang R. Z. , Xia Z. Z. , Tian B. , Wang L. W.
Published: June 2010

A falling film evaporator integrated with a recirculation tube driven by low-grade heat has been proposed to achieve a more compact and reliable system, which can be easily integrated into small-scale systems. An experimental study of the evaporative cooling of such an innovative falling film evaporator is presented. Water was used as the working fluid. The results are compared with published data for systems using mechanical pumps to circulate the fluid. Experimental investigation showed that the evaporative heat transfer coefficient of 6770–6870 W/m2 K can be achieved when the inlet temperature of the falling fluid is 29°C and the hot water entry temperature is 70°C. Detailed investigation on the effects of the driving heat source temperature and the inlet temperature of the hot water on the liquid film cooling mechanism was investigated. The results showed that for such a system, the effect of the falling film inlet temperature is more pronounced as compared with the other two parameters. Comparisons with traditional falling film evaporator with a mechanical pump indicated that the proposed integrated evaporator is more compact, reliable, and cost effective without impairing the heat transfer performance.
Development of Scalable Silicon Heat Spreader for High Power Electronic Devices
Authors: Cai Qingjun , Chen Bing-Chung , Tsai Chailun , Chen Chung-lung
Published: June 2010

A silicon heat spreader, called hexcell, is presented to develop thin, strong, interconnected, and scalable heat transfer devices for high power electronics cooling. Several key technical aspects, reflected characteristics of fabrication, thermomechanical, hermetic sealing, and heat transfer on wick structures, have been performed to underlie the system integration. The hexcell prototypes are developed through microelectromechanical system photolithography and dry-etch processes, associated with eutectic bonding to form a sealed silicon chamber. Hexcells are structurally optimized to minimize the stress, expanding the maximum operating pressure and temperature ranges. As a result, the developed hexcells can survive 0.32 MPa pressure difference and are able to sustain an operating temperature over 135°C. Experimental results of both helium and vapor leakage tests indicate that eutectic bonding with limited bonding surface area may not provide hermetic sealing. Vacuum sealing is achieved by introducing epoxy to fill the leak pine-holes on the bonding interface. The developed hexcell wick exhibits good heat and mass transport performance, reaching a maximum 300 W/cm2 cooling capacity with 35°C superheat as demonstrated with a prototype of a 2×2 mm2 heating area.
H
∞

Closed-Loop Control for Uncertain Discrete Input-Shaped Systems
Authors: Stergiopoulos John , Tzes Anthony
Published: June 2010

The article addresses the problem of stabilization for uncertain discrete input-shaped systems. The uncertainty affects the autoregressive portion of the transfer function of the system. A discrete input shaper compensator is designed in order to reduce the oscillations of the plant’s response. The input-shaped system’s dynamics are appropriately reformulated for robust controller synthesis, and a robust H∞-controller is used in an outer-loop, in order to guarantee stability of the uncertain input-shaped plant. Simulation results confirm the efficacy of the proposed combined scheme in comparison with open-loop input shaping and closed-loop linear quadratic control.
Stochastic Recruitment Control of Large Ensemble Systems With Limited Feedback
Authors: Odhner Lael U. , Asada Harry
Published: June 2010

A new approach to controlling the ensemble behavior of many identical agents is presented in this paper, inspired by motor recruitment in skeletal muscles. A group of finite state agents responds randomly to broadcast commands, each producing a state-dependent output that is measured in aggregate. Despite the lack of feedback signal and initial state information, this control architecture allows a single central controller to direct the aggregate output of the ensemble toward a desired value. First, the system is modeled as an ensemble of statistically independent, identically distributed, binary-state Markov processes with state transition probabilities designated by a central controller. Second, steady-state behavior, convergence rate, and variance of the aggregate output, i.e., the total number of recruited agents, are analyzed, and design trade-offs in terms of accuracy, convergence speed, and the number of spurious transitions are made. Third, a limited feedback signal, only detecting if the output has reached a goal, is added to the system, and the recruitment controller is designed as a stochastic shortest path problem. Optimal convergence rate and associated transition probabilities are obtained. Finally, the theoretical results are verified and demonstrated with both numerical simulation and control of an artificial muscle actuator made up of 60 binary shape memory alloy motor units.
Dahl Model-Based Hysteresis Compensation and Precise Positioning Control of an XY Parallel Micromanipulator With Piezoelectric Actuation
Authors: Xu Qingsong , Li Yangmin
Published: June 2010

This paper presents a new control scheme for the hysteresis compensation and precise positioning of a piezoelectrically actuated micromanipulator. The scheme employs an inverse Dahl model-based feedforward in combination with a repetitive proportional-integral-derivative feedback control algorithm along with an antiwindup strategy. The dynamic model of the system with Dahl hysteresis is established and identified through particle swarm optimization approach. The necessity of using global optimization and how to choose the model parameters to be optimized are addressed as well. The effectiveness of the proposed controller is demonstrated by several experimental studies on an XY parallel micromanipulator. Experimental results reveal that both antiwindup and repetitive control strategies can improve the positioning accuracy of the system, and a well performance of the proposed scheme for both one-dimensional tracking and two-dimensional contouring tasks of the micromanipulator is achieved. Moreover, due to a simple structure, the proposed methodology can be easily generalized to other micro- or nanomanipulators with piezoelectric actuation as well.
Enabling Automation of Friction Stir Welding: The Modulation of Weld Seam Input Energy by Traverse Speed Force Control
Authors: Longhurst William R. , Strauss Alvin M. , Cook George E.
Published: June 2010

Friction stir welding (FSW) joins materials by plunging a rotating tool into the work piece. The tool consists of a shoulder and a pin that plastically deforms the parent materials and then forges them together under the applied pressure. To create the pressure needed for forging, a rather large axial force must be maintained on the tool. Maintaining this axial force is challenging for robots due to their limited load capacity and compliant nature. To address this problem, force control has been used, and historically, the force has been controlled by adjusting the plunge depth of the tool into the work piece. This paper develops the use of tool traverse speed as the controlling variable instead of plunge depth. To perform this investigation, a FSW force controller was designed and implemented on a retrofitted Milwaukee Model K milling machine. The closed loop proportional, integral plus derivative (PID) control architecture was tuned using the Ziegler–Nichols method. Results show that the control of axial force via traverse speed is feasible and predictable. The resulting system is more robust and stable when compared with a force controller that uses plunge depth as the controlling variable. A standard deviation of 41.5 N was obtained. This variation is much less when compared with a standard deviation of 129.4 N obtained when using plunge depth. Using various combinations of PID control, the system’s response to step inputs was analyzed. From this analysis, a feed forward transfer function was modeled that describes the machinery and welding environment. From these results, a technique is presented regarding weld seam input energy modulation as a by product of force control via traverse speed. A relative indication of thermal energy in the welding environment is obtained with the feedback of axial force. It is hypothesized that, while under force control, the controller modulates weld seam input energy according to the control signal. The result is constant thermomechanical conditions in the welding environment. It is concluded that the key enablers for force control are the unidirectional behavior and load dynamics of the traverse motor. Larger bandwidths and more stable weld conditions emerge when using traverse speed instead of plunge depth to control the force. Force control of FSW via traverse speed has importance in creating efficient automatic manufacturing operations. The intelligence of the controller naturally selects the most efficient traverse speed.
Enhanced Performance and Stability in Pneumatic Servosystems With Supplemental Mechanical Damping
Authors: Wait Keith W. , Goldfarb Michael
Published: June 2010

The authors present a model-based analysis of a position-velocity-acceleration-controlled pneumatic actuator that indicates that supplementing the pneumatic actuator with mechanical damping can significantly increase the gain margin, tracking accuracy, and disturbance rejection of a closed-loop-controlled pneumatic servoactuator. In order to validate the model-based analysis and purported performance and stability benefits provided by supplemental damping, experiments were performed on a single-degree-of-freedom pneumatic servosystem. Measurements conducted on the experimental setup, which validate the respective improvements in stability margin, tracking accuracy, and disturbance rejection, are described.
Options for Biomass Utilization in Coal Fired Power Stations
Authors: Tadros Amir , Boyd Rodney , Benyon Peter , Grima Charles
Published: June 2010

This paper summarizes the results of engineering investigations conducted using a variety of computational modeling tools to evaluate different options for cofiring up to 10% (input energy) biomass in an existing large tangentially coal fired boiler. Options investigated included the direct combustion of solid biomass via both existing and auxiliary burners, the external gasification of the solid biomass, and the external combustion of the biomass in an auxiliary boiler. The methodology used, key results, and discussion of the relative features of the options studied are described in this paper.
Tube Hydroforming of Magnesium Alloys at Elevated Temperatures
Authors: Hwang Yeong-Maw , Su Yan-Huang , Chen Bing-Jian
Published: June 2010

In this paper, a hydraulic forming machine with the functions of axial feeding, counter punch, and internal pressurization is designed and developed. This self-designed forming machine has a capacity of 50 tons for axial feeding and counter punch, 70 MPa for internal pressurization, and 300°C for forming temperature. Using this testing machine, experiments of T-shape protrusion of magnesium alloy AZ61 tubes at elevated temperatures are carried out. A commercial finite element code DEFORM 3D is used to simulate the plastic deformation of the tube within the die during the T-shape protrusion process. Different kinds of loading paths for the pressurization profile and the strokes of the axial feeding and the counterpunch are scheduled for analyses and experiments of protrusion processes at 150°C and 250°C. The numerical thickness distributions and the flow line configurations of the formed product are compared with the experimental results to validate this finite element modeling. The thickness distribution of the formed product or the flowability of AZ61 tubes at 150°C and 250°C is discussed. The effects of the forming rate on tube flowability at 250°C are also investigated. Through the observation of the flow line configurations of the tube material, adequate backward speeds of the counter punch relative to the axial feeding for preventing the material from accumulating at the die entrance region are verified. Finally, a sound product with a protrusion height of 49 mm is obtained.
Simple flash evaporator for making thin films of compounds
Authors: Hemanadhan M. , Bapanayya Ch. , Agarwal S. C.
Published: June 2010

A simple and compact arrangement for flash evaporation is described. It uses a cell phone vibrator for powder dispensing that can be incorporated into a vacuum deposition chamber without any major alterations. The performance of the flash evaporation system is checked by making thin films of the optical memory chalcogenide glass Ge2Sb2Te5 (GST). Energy dispersive x-ray analysis shows that the flash evaporation preserves the stoichiometry in thin films.
The Last Glacial Termination
Authors: Denton G. H. , Anderson R. F. , Toggweiler J. R. , Edwards R. L. , Schaefer J. M. , Putnam A. E.
Published: June 2010

Warming Up

For the past half-million years, our planet has passed through a cycle of glaciation and deglaciation every 100,000 years or so. Each of these cycles consists of a long and irregular period of cooling and ice sheet growth, followed by a termination—a period of rapid warming and ice sheet decay—that precedes a relatively short warm interval. But what causes glacial terminations?

Denton
et al.

(p.
1652
) review the field and propose a chain of events that may explain the hows and whys of Earth's emergence from the last glacial period. Pulling together many threads from both hemispheres suggests a unified causal chain involving ice sheet volume, solar radiation energy, atmospheric carbon dioxide concentrations, sea ice, and prevailing wind patterns.
Resources for Anyone Interested in the Brain
Authors: Chudler Eric H.
Published: June 2010

Games, information, and discussions with scientists bring neuroscience knowledge to all hands.
Hydrogen Isotopes Preclude Marine Hydrate CH
4
Emissions at the Onset of Dansgaard-Oeschger Events
Authors: Bock Michael , Schmitt Jochen , Möller Lars , Spahni Renato , Blunier Thomas , Fischer Hubertus
Published: June 2010

Glacial Gas

Intracellular bacterial pathogens, such as a series of sudden and large warming episodes, called Dansgaard-Oeschger events, interrupted the cold conditions of the last glacial period. Large increases in the concentration of atmospheric methane accompanied the events, whose causes have remained the object of much speculation.

Bock
et al.

(p.
1686
) report measurements of the hydrogen isotopic composition of methane recovered in the North Greenland Ice Core Project. The excess atmospheric methane accompanying two Dansgaard-Oeschger events did not come from marine clathrates; instead, the methane probably came from increased fluxes from boreal wetlands, another major source of methane.
Reconstituting Organ-Level Lung Functions on a Chip
Authors: Huh Dongeun , Matthews Benjamin D. , Mammoto Akiko , Montoya-Zavala Martín , Hsin Hong Yuan , Ingber Donald E.
Published: June 2010

Just Breathe

Design of artificial systems that mimic in vivo organs could provide a better alternative for understanding mechanisms underlying physiological responses than current cell-based models or animal tests.Huhet al.(p.1662) have created a tissue-tissue interface of human-cultured epithelial cells and endothelial cells together, with extracellular matrix in a device that models the alveolar-capillary interface of the human lung. The device mimicked physiological organ-level functions, including pathogen-induced inflammatory responses and responses to cytokine exposure. Breathing-type movements affected acute pulmonary cell toxicity and proinflammatory activity of widely used nanoparticulates.
Plants Integrate Information About Nutrients and Neighbors
Authors: Cahill James F. , McNickle Gordon G. , Haag Joshua J. , Lamb Eric G. , Nyanumba Samson M. , St. Clair Colleen Cassady
Published: June 2010

Plant root growth is modified in the presence of within-species competition and uneven local resource distributions.
Incidental Haptic Sensations Influence Social Judgments and Decisions
Authors: Ackerman Joshua M. , Nocera Christopher C. , Bargh John A.
Published: June 2010

Between a Rock and a Hard Judgment

In general terms, our sensory and motor pathways mature sooner than the so-called higher cognitive centers, which become fully operational later in life. Might these early somatic communication channels with the outside world influence and become buried within the higher levels of processing involved in forming impressions of other people and deciding how to behave toward them?

Ackerman
et al.

(p.
1712
) provide evidence for just such a process by focusing on touch. By manipulating the weight, hardness, or roughness of objects that subjects were exposed to, they were able to bias the social judgments and behaviors of the subjects in unrelated realms, such as assessing the rigidness or seriousness of employees and job applicants.
4D Electron Tomography
Authors: Kwon Oh-Hoon , Zewail Ahmed H.
Published: June 2010

Temporal Tomography

Tomography is a widely used technique for visualizing three-dimensional objects by algorithmic reconstruction from multiple two-dimensional images from distinct vantage points. However, its application has largely been restricted to static imaging.
Kwon and Zewail
(p.
1668
) have now adapted an ultrafast electron microscope to perform tomography with subpicosecond resolution. The method relies on systematically varying the tilt angle of the sample with respect to the incoming electron beam, and enabled assembly of a detailed frame-by-frame record of the response of a curled carbon nanotube to sudden heating.
Molecular Identification ofEntamoebaspp. in Captive Nonhuman Primates
Authors: Levecke B. , Dreesen Leentje , Dorny Pierre , Verweij Jaco J. , Vercammen Francis , Casaert Stijn , Vercruysse Jozef , Geldhof Peter
Published: June 2010

This study describes the molecular identification of 520Entamoeba-positive fecal samples from a large and diverse population of captive nonhuman primates (NHP). The results revealed the presence ofEntamoeba histolytica(NHP variant only),E. dispar,E. moshkovskii,E. hartmanni,E. coli, andE. polecki-like organisms.
Emergence and Characterization of
Salmonella enterica
Serovar Typhimurium Phage Type DT191a
Authors: Peters Tansy , Hopkins Katie L. , Lane Chris , Nair Satheesh , Wain John , de Pinna Elizabeth
Published: June 2010

The emergence of a previously undefined phage type of
Salmonella enterica
serovar Typhimurium, designated DT191a, occurred in England and Wales in July 2008. The new strain exhibits a number of distinctive phenotypic and genotypic features. This report provides the tools necessary to track
S
. Typhimurium DT191a globally.
Improving HIV-2 Detection by a Combination of Serological and Nucleic Acid Amplification Test Assays
Authors: Ciccaglione Anna Rita , Miceli Michela , Pisani Giulio , Bruni Roberto , Iudicone Paola , Costantino Angela , Equestre Michele , Tritarelli Elena , Marcantonio Cinzia , Tataseo Paola , Marazzi Maria Cristina , Ceffa Susanna , Paturzo Giovanna , Doro Altan Anna Maria , Magnano San Lio Massimo , Mancinelli Sandro , Ciccozzi Massimo , Lo Presti Alessandra , Rezza Giovanni , Palombi Leonardo
Published: June 2010

The ability to detect HIV-2 and to discriminate between HIV-1 and HIV-2 infections was evaluated in 46 serum samples from Guinea-Bissau (GB) and Guinea-Conakry (GC) using serological tests and commercial (HIV-1) and in-house (HIV-2) real-time PCR assays. Samples were first identified as HIV-2 positive by Genie I/II assay in GB and GC. HIV positivity was detected in 44 of 46 samples by all screening and confirmatory assays. A diagnostic strategy based on Inno-LIA and HIV-1/2 RNA detection assays allowed accurate discrimination between HIV-1 and HIV-2 in 84% of single infections and confirmed 32% of double infections. In samples with double reactivity in the Inno-LIA test and no detection of both genomes, cross-reactivity likely hampered the identification of true double infections. In conclusion, the implementation of a diagnostic strategy, based on multiple specific serological tests and highly sensitive quantitative PCR assays, is recommended to ensure accurate HIV-2 diagnosis and appropriate therapy for individuals from areas in which the virus is endemic.
Evaluation of the MTBDRsl Test for Detection of Second-Line-Drug Resistance in
Mycobacterium tuberculosis
Authors: Kiet Vo Sy , Lan Nguyen Thi Ngoc , An Duong Duy , Dung Nguyen Huy , Hoa Dai Viet , van Vinh Chau Nguyen , Chinh Nguyen Tran , Farrar Jeremy , Caws Maxine
Published: June 2010

The MTBDRsl assay (Hain Lifescience GmbH, Germany) is a new line probe assay for the detection of extensively drug-resistant tuberculosis (XDR TB). The test simultaneously detects resistance to ethambutol, aminoglycosides/cyclic peptides, and fluoroquinolones through detection of mutations in the relevant genes. The assay format is identical to the MTBDR Hain assay. The assay was evaluated for the detection of second-line-drug resistance in Vietnamese isolates using two sample sets from the microbiology department of Pham Ngoc Thach Hospital, Ho Chi Minh City, Viet Nam, with existing conventional phenotypic drug susceptibility results for second-line drugs: 41 consecutive fluoroquinolone-resistant isolates and 21 consecutive multidrug-resistant but fluoroquinolone-sensitive isolates. The sensitivity for detection of fluoroquinolone resistance was 75.6% (31/41) (95% confidence interval [95% CI], 59.7% to 87.6%), and for kanamycin resistance, the sensitivity was 100% (5/5) (95% CI, 47.8% to 100%). The sensitivity of the test for detection of ethambutol resistance was low, consistent with previous reports, at 64.2% (34/53) (95% CI, 49.8% to 76.9%). The specificity of the test was 100% for all three drugs. These data suggest that the MTBDRsl assay is a rapid, specific test for the detection of XDR TB but should not be used exclusively to “rule out” second-line-drug resistance. Further operational evaluation is required and should be integrated with evaluations of the MTBDR test.
Systematic Internal Transcribed Spacer Sequence Analysis for Identification of Clinical Mold Isolates in Diagnostic Mycology: a 5-Year Study
Authors: Ciardo Diana E. , Lucke Katja , Imhof Alex , Bloemberg Guido V. , Böttger Erik C.
Published: June 2010

The implementation of internal transcribed spacer (ITS) sequencing for routine identification of molds in the diagnostic mycology laboratory was analyzed in a 5-year study. All mold isolates (
n
= 6,900) recovered in our laboratory from 2005 to 2009 were included in this study. According to a defined work flow, which in addition to troublesome phenotypic identification takes clinical relevance into account, 233 isolates were subjected to ITS sequence analysis. Sequencing resulted in successful identification for 78.6% of the analyzed isolates (57.1% at species level, 21.5% at genus level). In comparison, extended in-depth phenotypic characterization of the isolates subjected to sequencing achieved taxonomic assignment for 47.6% of these, with a mere 13.3% at species level. Optimization of DNA extraction further improved the efficacy of molecular identification. This study is the first of its kind to testify to the systematic implementation of sequence-based identification procedures in the routine workup of mold isolates in the diagnostic mycology laboratory.
Clinical Performance of the PreTect HPV-Proofer E6/E7 mRNA Assay in Comparison with That of the Hybrid Capture 2 Test for Identification of Women at Risk of Cervical Cancer
Authors: Ratnam Samuel , Coutlee Francois , Fontaine Dan , Bentley James , Escott Nicholas , Ghatage Prafull , Gadag Veeresh , Holloway Glen , Bartellas Elias , Kum Nick , Giede Christopher , Lear Adrian
Published: June 2010

Human papillomavirus (HPV) DNA testing has a higher clinical sensitivity than cytology for the detection of high-grade cervical intraepithelial neoplasia or worse (CIN 2+). However, an improvement in specificity would be desirable. As malignant transformation is induced by HPV E6/E7 oncogenes, detection of E6/E7 oncogene activity may improve specificity and be more predictive of cervical cancer risk. The PreTect HPV-Proofer assay (Proofer; Norchip) detects E6/E7 mRNA transcripts from HPV types 16, 18, 31, 33, and 45 with simultaneous genotype-specific identification. The clinical performance of this assay was assessed in a cross-sectional study of women referred for colposcopy in comparison with the Hybrid Capture 2 (HC2; Qiagen) test, which detects DNA of 13 high-risk oncogenic HPV types collectively. Cervical specimens were collected in PreservCyt, and cytology was performed using the ThinPrep method (Hologic). The samples were processed for HPV detection with Proofer and HC2 and genotyping with the Linear Array method (Roche Molecular Systems). Histology-confirmed CIN 2+ served as the disease endpoint to assess the clinical performance of the tests. A total of 1,551 women were studied, and of these, 402 (25.9%) were diagnosed with CIN 2+ on histology. The Proofer assay showed a sensitivity of 78.1% (95% confidence interval [CI], 74.1 to 82.1) versus 95.8% (95% CI, 93.8 to 97.8) for HC2 (
P
< 0.05) and a specificity of 75.5% (95% CI, 73.0 to 78.0) versus 39.6% (95% CI, 36.8 to 42.4), respectively (
P
< 0.05). The lower sensitivity and higher specificity of Proofer for detection of CIN 2+ can be attributed to the fact that this test detects the expression of E6/E7 genes beyond a threshold from a limited number of oncogenic HPV types. In conclusion, Proofer is more specific than HC2 in identifying women with CIN 2+ but has a lower sensitivity.
Pseudomonas aeruginosa
Outbreak Linked to Mineral Water Bottles in a Neonatal Intensive Care Unit: Fast Typing by Use of High-Resolution Melting Analysis of a Variable-Number Tandem-Repeat Locus
Authors: Naze F. , Jouen E. , Randriamahazo R. T. , Simac C. , Laurent P. , Blériot A. , Chiroleu F. , Gagnevin L. , Pruvost O. , Michault A.
Published: June 2010

Pseudomonas aeruginosa
is an opportunistic pathogen that causes nosocomial infections in intensive care units. Determining a system of typing that is discriminatory is essential for epidemiological surveillance of
P. aeruginosa
. We developed a method for the typing of
Pseudomonas aeruginosa
, namely, multiple-locus variable-number tandem-repeat (VNTR) typing with high-resolution melting analysis (HRMA). The technology was used to genotype a collection of 43 environmental and clinical strains isolated during an outbreak in a neonatal intensive care unit (NICU) that we report. Nineteen strains isolated in other departments or outside the hospital were also tested. The genetic diversity of this collection was determined using VNTR-HRMA, with amplified fragment length polymorphism (AFLP) analysis as a reference. Twenty-five and 28 genotypes were identified, respectively, and both techniques produced congruent data. VNTR-HRMA established clonal relationships between the strains of
P. aeruginosa
isolated during the outbreak in the NICU and proved, for the first time, the role of mineral water as the inoculum source. VNTR typing with one primer pair in association with HRMA is highly reproducible and discriminative, easily portable among laboratories, fast, and inexpensive, and it demonstrated excellent typeability in this study. VNTR-HRMA represents a promising tool for the molecular surveillance of
P. aeruginosa
and perhaps for molecular epidemiologic analysis of other hospital infections.
Distribution of
emm
Types and Genetic Characterization of the
mgc
Locus in Group G
Streptococcus dysgalactiae
subsp.
equisimilis
from a Hospital in Northern Taiwan
Authors: Tseng Sung-Pin , Lin Yu-Yin , Tsai Jui-Chang , Hsueh Po-Ren , Chen Hsiao-Jan , Hung Wei-Chun , Teng Lee-Jene
Published: June 2010

A total of 274
Streptococcus dysgalactiae
subsp.
equisimilis
isolates was analyzed by
emm
typing and by determining the organization of their
mgrC
loci. Three of the most frequent
emm
types were
stG485.0
(45/274, 16.4%),
stG6.1
(43/274, 15.7%), and
stC839.0
(32/274, 11.7%), in decreasing order. The
cpdB
-positive
mgrC
locus appears to be predominant in some
emm
types.
Low Specificities of HIV Diagnostic Tests Caused by
Trypanosoma brucei gambiense
Sleeping Sickness
Authors: Lejon V. , Ngoyi D. Mumba , Ilunga M. , Beelaert G. , Maes I. , Büscher P. , Fransen K.
Published: June 2010

The accuracy of diagnostic tests for HIV in patients with tropical infections is poorly documented. Human African trypanosomiasis (HAT) is characterized by a polyclonal B-cell activation, constituting a risk for false-positive reactions to diagnostic tests, including HIV tests. A retrospective study of the accuracy of HIV diagnostic tests was performed with 360 human African HAT patients infected with
Trypanosoma brucei gambiense
before treatment and 163
T. b. gambiense
-infected patients 2 years after successful treatment in Mbuji Mayi, East Kasai, Democratic Republic of the Congo. The sensitivities, specificities, and positive predictive values (PPVs) of individual tests and algorithms consisting of 3 rapid tests were determined. The sensitivity of all tests was 100% (11/11). The low specificity (96.3%, 335/348) and PPV (45.8%, 11/24) of a classical seroconfirmation strategy (Vironostika enzyme-linked immunosorbent assay [ELISA] followed by line immunoassay) complicated the determination of HIV status, which had to be determined by PCR. The specificities of the rapid diagnostic tests were 39.1% for Determine (136/348); 85.3 to 92.8% (297/348 to 323/348) for Vikia, ImmunoFlow, DoubleCheck, and Bioline; and 96.6 to 98.3% (336/348 to 342/348) for Uni-Gold, OraQuick, and Stat-Pak. The specificity of Vironostika was 67.5% (235/348). PPVs ranged between 4.9 and 64.7%. Combining 3 different rapid tests resulted in specificities of 98.3 to 100% (342/348 to 348/348) and PPVs of 64.7 to 100% (11/17 to 11/11). For cured HAT patients, specificities were significantly higher for Vironostika, Determine, Uni-Gold, and ImmunoFlow.
T. b. gambiense
infection decreases the specificities of antibody detection tests for HIV diagnosis. Unless tests have been validated for interference with HAT, HIV diagnosis using classical algorithms in untreated HAT patients should be avoided. Specific, validated combinations of 3 HIV rapid tests can increase specificity.
Peptide Nucleic Acid Array for Detection of Point Mutations in Hepatitis B Virus Associated with Antiviral Resistance
Authors: Jang Hyunjung , Kim Jihyun , Choi Jae-jin , Son Yeojin , Park Heekyung
Published: June 2010

The detection of antiviral-resistant hepatitis B virus (HBV) mutations is important for monitoring the response to treatment and for effective treatment decisions. We have developed an array using peptide nucleic acid (PNA) probes to detect point mutations in HBV associated with antiviral resistance. PNA probes were designed to detect mutations associated with resistance to lamivudine, adefovir, and entecavir. The PNA array assay was sensitive enough to detect 10
2
copies/ml. The PNA array assay was able to detect mutants present in more than 5% of the virus population when the total HBV DNA concentration was greater than 10
4
copies/ml. We analyzed a total of 68 clinical samples by this assay and validated its usefulness by comparing results to those of the sequencing method. The PNA array correctly identified viral mutants and has high concordance (98.3%) with direct sequencing in detecting antiviral-resistant mutations. Our results showed that the PNA array is a rapid, sensitive, and easily applicable assay for the detection of antiviral-resistant mutation in HBV. Thus, the PNA array is a useful and powerful diagnostic tool for the detection of point mutations or polymorphisms.
The Herpes Simplex Virus Type 1 UL20 Protein and the Amino Terminus of Glycoprotein K (gK) Physically Interact with gB
Authors: Chouljenko Vladimir N. , Iyer Arun V. , Chowdhury Sona , Kim Joohyun , Kousoulas Konstantin G.
Published: June 2010

Herpes simplex virus type 1 (HSV-1) glycoprotein K (gK) and the UL20 protein (UL20p) are strictly required for virus-induced cell fusion, and mutations within either the gK or UL20 gene cause extensive cell fusion (syncytium formation). We have shown that gK forms a functional protein complex with UL20p, which is required for all gK and UL20p-associated functions in the HSV-1 life cycle. Recently, we showed that the amino-terminal 82 amino acids (aa) of gK (gKa) were required for the expression of the syncytial phenotype of the mutant virus gBΔ28 lacking the carboxyl-terminal 28 amino acids of gB (V. N. Chouljenko, A. V. Iyer, S. Chowdhury, D. V. Chouljenko, and K. G. Kousoulas, J. Virol. 83:12301-12313, 2009). This work suggested that the amino terminus of gK may directly or indirectly interact with gB and/or other viral glycoproteins. Two-way coimmunoprecipitation experiments revealed that UL20p interacted with gB in infected cells. Furthermore, the gKa peptide was coimmunoprecipitated with gB but not gD. Three recombinant baculoviruses were constructed, expressing the amino-terminal 82 aa of gKa together with either the extracellular portion of gB (30 to 748 aa), gD (1 to 340 aa), or gH (1 to 792 aa), respectively. Coimmunoprecipitation experiments revealed that gKa physically interacted with the extracellular portions of gB and gH but not gD. Three additional recombinant baculoviruses expressing gKa and truncated gBs encompassing aa 30 to 154, 30 to 364, and 30 to 500 were constructed. Coimmunoprecipitation experiments showed that gKa physically interacted with all three truncated gBs. Computer-assisted prediction of possible gKa binding sites on gB suggested that gKa may interact predominantly with gB domain I (E. E. Heldwein, H. Lou, F. C. Bender, G. H. Cohen, R. J. Eisenberg, and S. C. Harrison, Science 313:217-220, 2006). These results imply that the gK/UL20p protein complex modulates the fusogenic properties of gB and gH via direct physical interactions.
Temporal and Spatial Resolution of Type I and III Interferon ResponsesIn Vivo
Authors: Pulverer Julia Elisabeth , Rand Ulfert , Lienenklaus Stefan , Kugel Daniela , Ziętara Natalia , Kochs Georg , Naumann Ronald , Weiss Siegfried , Staeheli Peter , Hauser Hansjörg , Köster Mario
Published: June 2010

Although the action of interferons (IFNs) has been extensively studiedin vitro, limited information is available on the spatial and temporal activation pattern of IFN-induced genesin vivo. We created BAC transgenic mice expressing firefly luciferase under transcriptional control of the Mx2 gene promoter. Expression of the reporter with regard to onset and kinetics of induction parallels that of Mx2 and is thus a hallmark for the host response. Substantial constitutive expression of the reporter gene was observed in the liver and most other tissues of transgenic mice, whereas this expression was strongly reduced in animals lacking functional type I IFN receptors. As expected, the reporter gene was induced not only in response to type I (α and β) and type III (λ) IFNs but also in response to a variety of IFN inducers such as double-stranded RNA, lipopolysaccharide (LPS), and viruses.In vivoIFN subtypes show clear differences with respect to their kinetics of action and to their spatial activation pattern: while the type I IFN response was strong in liver, spleen, and kidney, type III IFN reactivity was most prominent in organs with mucosal surfaces. Infection of reporter mice with virus strains that differ in their pathogenicity shows that the IFN response is significantly altered in the strength of IFN action at sites which are not primarily infected as well as by the onset and duration of gene induction.
Delaying the Expression of Herpes Simplex Virus Type 1 Glycoprotein B (gB) to a True Late Gene Alters Neurovirulence and Inhibits the gB-CD8
+
T-Cell Response in the Trigeminal Ganglion
Authors: Ramachandran Srividya , Davoli Katherine A. , Yee Michael B. , Hendricks Robert L. , Kinchington Paul R.
Published: June 2010

Following herpes simplex virus type 1 (HSV-1) ocular infection of C57BL/6 mice, activated CD8
+
T cells specific for an immunodominant epitope on HSV-1 glycoprotein B (gB-CD8 cells) establish a stable memory population in HSV-1 latently infected trigeminal ganglia (TG), whereas non-HSV-specific CD8
+
T cells are lost over time. The retention and activation of gB-CD8 cells appear to be influenced by persistent viral antigenic exposure within the latently infected TG. We hypothesized that the low-level expression of gB from its native promoter before viral DNA synthesis is critical for the retention and activation of gB-CD8 cells in the TG during HSV-1 latency and for their ability to block HSV-1 reactivation from latency. To test this, we created a recombinant HSV-1 in which gB is expressed only after viral DNA synthesis from the true late gC promoter (gCp-gB). Despite minor growth differences compared to its rescuant in infected corneas, gCp-gB was significantly growth impaired in the TG and produced a reduced latent genome load. The gCp-gB- and rescuant-infected mice mounted similar gB-CD8 effector responses, but the size and activation phenotypes of the memory gB-CD8 cells were diminished in gCp-gB latently infected TG, suggesting that the stimulation of gB-CD8 cells requires gB expression before viral DNA synthesis. Surprisingly, late gB expression did not compromise the capacity of gB-CD8 cells to inhibit HSV-1 reactivation from latency in
ex vivo
TG cultures, suggesting that gB-CD8 cells can block HSV-1 reactivation at a very late stage in the viral life cycle. These data have implications for designing better immunogens for vaccines to prevent HSV-1 reactivation.
A Single Asparagine-Linked Glycosylation Site of the Severe Acute Respiratory Syndrome Coronavirus Spike Glycoprotein Facilitates Inhibition by Mannose-Binding Lectin through Multiple Mechanisms
Authors: Zhou Yanchen , Lu Kai , Pfefferle Susanne , Bertram Stephanie , Glowacka Ilona , Drosten Christian , Pöhlmann Stefan , Simmons Graham
Published: June 2010

Mannose-binding lectin (MBL) is a serum protein that plays an important role in host defenses as an opsonin and through activation of the complement system. The objective of this study was to assess the interactions between MBL and severe acute respiratory syndrome-coronavirus (SARS-CoV) spike (S) glycoprotein (SARS-S). MBL was found to selectively bind to retroviral particles pseudotyped with SARS-S. Unlike several other viral envelopes to which MBL can bind, both recombinant and plasma-derived human MBL directly inhibited SARS-S-mediated viral infection. Moreover, the interaction between MBL and SARS-S blocked viral binding to the C-type lectin, DC-SIGN. Mutagenesis indicated that a single N-linked glycosylation site, N330, was critical for the specific interactions between MBL and SARS-S. Despite the proximity of N330 to the receptor-binding motif of SARS-S, MBL did not affect interactions with the ACE2 receptor or cathepsin L-mediated activation of SARS-S-driven membrane fusion. Thus, binding of MBL to SARS-S may interfere with other early pre- or postreceptor-binding events necessary for efficient viral entry.
Vα14iNKT Cells Promote Liver Pathology during Adenovirus Infection by Inducing CCL5 Production: Implications for Gene Therapy
Authors: Ajuebor Maureen N. , Chen Qingling , Strieter Robert M. , Adegboyega Patrick A. , Aw Tak Yee
Published: June 2010

Replication-defective recombinant adenoviruses are the most widely studied replication-defective vectors for the potential treatment of inherited human diseases. However, broad clinical application of replication-defective adenoviruses in gene therapy is being hindered by the induction of vigorous innate and adaptive immune responses against the vector that cause deleterious effects in the liver. Vα14 invariant natural killer T cells (Vα14iNKT cells) are thymus-derived innate T cells at the interface between the two arms of the immune response and provide full engagement of host defense. The pathophysiological role of intrahepatic Vα14iNKT cells during replication-defective adenovirus infection is not known and is the main focus of our study. Our data showed that intrahepatic Vα14iNKT cells were activated in response to adenovirus infection to induce significant levels of hepatic chemokine (C-C motif) ligand 5 (CCL5) and subsequent liver toxicity. Moreover, intrahepatic CCL5 production was selectively reduced by Vα14iNKT cell deficiency.In vivostudies utilizing CCL5-deficient mice or Vα14iNKT cell-deficient mice demonstrated that CCL5 deficiency or Vα14iNKT cell deficiency was associated with reduced liver pathology. Similar results were seen after blocking the biological effects of the CCL5 receptors. In conclusion, we have identified an important proinflammatory role for activated intrahepatic Vα14iNKT cells in positively influencing hepatic CCL5 production to promote acute liver inflammation and injury. Therefore, our findings highlight the blockade of CCL5 interaction with a cognate receptor(s) as an important potential strategy to alleviate liver pathology associated with replication-defective adenovirus infection.
Poly(A)-Binding Protein 1 Partially Relocalizes to the Nucleus during Herpes Simplex Virus Type 1 Infection in an ICP27-Independent Manner and Does Not Inhibit Virus Replication
Authors: Salaun C. , MacDonald A. I. , Larralde O. , Howard L. , Lochtie K. , Burgess H. M. , Brook M. , Malik P. , Gray N. K. , Graham S. V.
Published: June 2010

Infection of cells by herpes simplex virus type 1 (HSV-1) triggers host cell shutoff whereby mRNAs are degraded and cellular protein synthesis is diminished. However, virus protein translation continues because the translational apparatus in HSV-infected cells is maintained in an active state. Surprisingly, poly(A)-binding protein 1 (PABP1), a predominantly cytoplasmic protein that is required for efficient translation initiation, is partially relocated to the nucleus during HSV-1 infection. This relocalization occurred in a time-dependent manner with respect to virus infection. Since HSV-1 infection causes cell stress, we examined other cell stress inducers and found that oxidative stress similarly relocated PABP1. An examination of stress-induced kinases revealed similarities in HSV-1 infection and oxidative stress activation of JNK and p38 mitogen-activated protein (MAP) kinases. Importantly, PABP relocalization in infection was found to be independent of the viral protein ICP27. The depletion of PABP1 by small interfering RNA (siRNA) knockdown had no significant effect on viral replication or the expression of selected virus late proteins, suggesting that reduced levels of cytoplasmic PABP1 are tolerated during infection.
Association of the Influenza Virus RNA Polymerase Subunit PB2 with the Host Chaperonin CCT
Authors: Fislová Tatiana , Thomas Benjamin , Graef Katy M. , Fodor Ervin
Published: June 2010

The RNA polymerase of influenza A virus is a host range determinant and virulence factor. In particular, the PB2 subunit of the RNA polymerase has been implicated as a crucial factor that affects cell tropism as well as virulence in animal models. These findings suggest that host factors associating with the PB2 protein may play an important role during viral replication. In order to identify host factors that associate with the PB2 protein, we purified recombinant PB2 from transiently transfected mammalian cells and identified copurifying host proteins by mass spectrometry. We found that the PB2 protein associates with the cytosolic chaperonin containing TCP-1 (CCT), stress-induced phosphoprotein 1 (STIP1), FK506 binding protein 5 (FKBP5), α- and β-tubulin, Hsp60, and mitochondrial protein p32. Some of these binding partners associate with each other, suggesting that PB2 might interact with these proteins in multimeric complexes. More detailed analysis of the interaction of the PB2 protein with CCT revealed that PB2 associates with CCT as a monomer and that the CCT binding site is located in a central region of the PB2 protein. PB2 proteins from various influenza virus subtypes and origins can associate with CCT. Silencing of CCT resulted in reduced viral replication and reduced PB2 protein and viral RNA accumulation in a ribonucleoprotein reconstitution assay, suggesting an important function for CCT during the influenza virus life cycle. We propose that CCT might be acting as a chaperone for PB2 to aid its folding and possibly its incorporation into the trimeric RNA polymerase complex.
PDZD8 Is a Novel Gag-Interacting Factor That Promotes Retroviral Infection
Authors: Henning Matthew S. , Morham Scott G. , Goff Stephen P. , Naghavi Mojgan H.
Published: June 2010

In a yeast two-hybrid screen for cellular factors that could interact with human immunodeficiency virus type 1 (HIV-1) Gag protein, we identified PDZD8 and confirmed the interaction by coimmunoprecipitation (co-IP). PDZD8 overexpression promoted the initiation of reverse transcription and increased infection by pseudotyped retroviruses independent of the route of viral entry, while transient knockdown of endogenous levels decreased HIV-1 infection. A mutant of PDZD8 lacking a predicted coiled-coil domain in its Gag-interacting region failed to bind Gag and promote HIV-1 infection, identifying the domain of PDZD8 required for mediating these effects. As such, we identify PDZD8 as a novel positive mediator of retroviral infection.