bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality and Inspection of Machining Operations: Review of Condition Monitoring and CMM Inspection Techniques — 2000 to Present
Authors: Roth John T. , Mears Laine , Djurdjanovic Dragan , Yang Xiaoping , Kurfess Thomas
Published: March 2009

In order to consistently produce quality parts, many aspects of the manufacturing process must be carefully monitored, controlled, and measured. The methods and techniques by which to accomplish these tasks has been the focus of numerous studies in recent years. With the rapid advances in computing technology, the complexity and overhead that can be feasibly incorporated in any developed technique has dramatically improved. Thus, techniques that would have been impractical for implementation just a few years ago can now be realistically applied. This rapid growth has resulted in a wealth of new capabilities for improving part and process quality and reliability. In this paper, overviews of recent advances that apply to machining are presented. Moreover, due to the relative significance of two particular machining aspects, this review focuses specifically on research publications pertaining to using tool condition monitoring and coordinate measurement machines to improve the machining process. Tool condition has a direct effect on part quality and is discussed first. The application of tool condition monitoring as it applies to turning, drilling, milling, and grinding is presented. The subsequent section provides recommendations for future research opportunities. The ensuing section focuses on the use of coordinate measuring machines in conjunction with machining and is subdivided with respect to integration with machining tools, inspection planning and efficiency, advanced controller feedback, machine error compensation, and on-line tool calibration, in that specific order and concludes with recommendations regarding where future needs remain.
Identification and Anomaly Detection for PLC Controlled Automatic Tool Changer Using Timed Petri Net
Authors: Liu Jianbo , Djurdjanovic Dragan , Ni Jun
Published: March 2009

In this paper, a new method is proposed for incremental identification of Programmable Logic Controller (PLC) controlled tool changing process using available binary event logs obtained from the PLC. The identified discrete event model identified takes the form of a modified Timed Petri Net (TPN). A real time anomaly detection system is then constructed by synchronizing the identified TPN model with the actual tool changing process through the event sequence. Any discrepancies between the model and actual system are recognized as anomalies. The test results show that the diagnostic system automatically constructed using the newly proposed procedure is able to detect anomalies, such as incorrect timing and illegal event sequence. The same procedure has been successfully applied to monitor other PLC controlled automation processes.
Fatigue Crack Growth Behavior of TC-128-B Steel Under Variable Amplitude Loading
Authors: Garcia Daniel B. , Feiger James H. , McKeighan Peter C. , Cardinal Joseph W. , Jeong David Y.
Published: March 2009

Railroad tank cars are exposed to a high degree of variable amplitude loading that is comprised of both tensile compressive cycles. In order to consistently and accurately predict this type of loading, material properties, usage, and load interaction models must be used in concert. The objective of this study is to present the methodology necessary to generate tank car specific spectrum crack growth life prediction models. Experimental fatigue crack growth data from this project and previous efforts provided the baseline data necessary to develop NASGRO® models and predict simplified over-load and under-load experiments. The methods were then advanced to predict spectrum crack growth experimental data representative of tank car usage. The results show that significant amounts of compressive loads in the tank car spectra essentially negate the need for a tensile stress based load interaction model. In order to provide consistently conservative prediction, the most basic model must be implemented instead of the more elaborate retardation models.
Recent Research to Improve Wheel and Axle Composition, Properties and Designs
Authors: Lonsdale Cameron , Dedmon Steven , Galbraith Jay , Pilch James
Published: March 2009

This paper describes research efforts by a North American railroad wheel and axle manufacturer to improve steel chemistry, cleanliness, and properties for improved component service performance. The authors describe extensive work to improve steel cleanliness in the melting process. Also they review attempts to correlate ultrasonic testing data with microcleanliness test results, and detail subsequent work to determine steel cleanliness using the Advanced Steel Cleanliness Assessment Technique (ASCAT), which is being developed by a university and a supplier. Emphasis is placed on determining the type, number and size of discontinuities within the steel. Additionally, efforts to improve mechanical properties of microalloyed axles are reviewed along with microstructural details relevant to the work. The role of vanadium, molybdenum, aluminum, and other elements, on axle structure and properties is discussed. A new axle design, with significantly larger body diameter, is described and finite element analysis (FEA) results for the design are presented.
Equations of Motion for Train Derailment Dynamics
Authors: Jeong D. Y. , Lyons M. L. , Orringer O. , Perlman A. B.
Published: March 2009

This paper describes a planar or two-dimensional model to examine the gross motions of rail cars in a generalized train derailment. Three coupled, second-order differential equations are derived from Newton’s Laws to calculate rigid-body car motions with time. Car motions are defined with respect to a right-handed and fixed (i.e., non-rotating) reference frame. The rail cars are translating and rotating but not deforming. Moreover, the differential equations are considered as stiff, requiring relatively small time steps in the numerical solution, which is carried out using a FORTRAN computer code. Sensitivity studies are conducted using the purpose-built model to examine the relative effect of different factors on the derailment outcome. These factors include the number of cars in the train makeup, car mass, initial translational and rotational velocities, and coefficients of friction. Derailment outcomes include the number of derailed cars, maximum closing velocities (i.e., relative velocities between impacting cars), and peak coupler forces. Results from the purpose-built model are also compared to those from a model for derailment dynamics developed using commercial software for rigid-body dynamics called Automatic Dynamic Analysis of Mechanical Systems (ADAMS). Moreover, the purpose-built and the ADAMS models produce nearly identical results, which suggest that the dynamics are being calculated correctly in both models.
A New Approach for Noise and Vibration Control in Locomotive Cabs
Authors: Harrigan Timothy P. , Samavedam Gopal , Punwani S. K.
Published: March 2009

Noise and vibrations in locomotive cabs can significantly affect crew performance and cause long-term ailments, such as hearing loss, fatigue, and low back pain. Methods to reduce noise and vibrations have been implemented for the high frequency range but resulted in low frequency resonances. These resonances can exacerbate low frequency vibrations (<0.5 Hz), which can cause motion sickness. In addition, a tonal noise exists in the 50 to 200 Hz frequency range, which is more annoying than broadband noise, and which is not addressed in current noise reduction methods based on A-weighted noise metrics. To reduce vibration, the innovative approach proposed here will consider isolating only the floor of the cab rather than the whole cab as was previously reported in the literature. The isolation is achieved using nonlinear springs and dampers that provide isolation at high frequencies while avoiding resonances at low frequencies. The smaller inertia of the floor, controls, and crew, as compared to the entire cab, makes the necessary components much less expensive. To reduce the tonal noise in the range 50 to 200 Hz, active noise control is used in the vicinity of the crew seats. Analyses have shown that this new approach is very promising, and demonstrations are planned for mockups of locomotive cabs.
Analysis of Impact Energy to Fracture Unnotched Charpy Specimens Made From Railroad Tank Car Steel
Authors: Yu H. , Jeong D. Y. , Gordon J. E. , Tang Y. H.
Published: March 2009

This paper describes a nonlinear finite element analysis (FEA) framework that examines the impact energy to fracture unnotched Charpy specimens by an oversized, nonstandard pendulum impactor called the Bulk Fracture Charpy Machine (BFCM). The specimens are made from railroad tank car steel, have different thicknesses and interact with impact tups with different sharpness. The FEA employs a Ramberg-Osgood equation for plastic deformations. Progressive damage and failure modeling is applied to predict initiation and evolution of fracture and ultimate material failure. Two types of fracture initiation criterion, i.e., the constant equivalent strain criterion and the stress triaxiality dependent equivalent strain criterion, are compared in material modeling. The impact energy needed to fracture a BFCM specimen is calculated from the FEA. Comparisons with the test data show that the FEA results obtained using the stress triaxiality dependent fracture criterion are in excellent agreement with the BFCM test data.
Changes in Temperature Preferences and Energy Homeostasis in Dystroglycan Mutants
Authors: Takeuchi Ken-ichi , Nakano Yoshiro , Kato Utako , Kaneda Mizuho , Aizu Masako , Awano Wakae , Yonemura Shigenobu , Kiyonaka Shigeki , Mori Yasuo , Yamamoto Daisuke , Umeda Masato
Published: March 2009

Temperature affects the physiology, behavior, and evolution of organisms. We conducted mutagenesis and screens for mutants with altered temperature preference inDrosophila melanogasterand identified a cryophilic (cold-seeking) mutant, namedatsugari(atu). Reduced expression of theDrosophilaortholog of dystroglycan (DmDG) induced tolerance to cold as well as preference for the low temperature. A sustained increase in mitochondrial oxidative metabolism caused by the reduced expression of DmDG accounted for the cryophilic phenotype of theatumutant. Although most ectothermic animals do not use metabolically produced heat to regulate body temperature, our results indicate that their thermoregulatory behavior is closely linked to rates of mitochondrial oxidative metabolism and that a mutation in a single gene can induce a sustained change in energy homeostasis and the thermal responses.
Controlled Formation of Sharp Zigzag and Armchair Edges in Graphitic Nanoribbons
Authors: Jia Xiaoting , Hofmann Mario , Meunier Vincent , Sumpter Bobby G. , Campos-Delgado Jessica , Romo-Herrera José Manuel , Son Hyungbin , Hsieh Ya-Ping , Reina Alfonso , Kong Jing , Terrones Mauricio , Dresselhaus Mildred S.
Published: March 2009

Graphene nanoribbons can exhibit either quasi-metallic or semiconducting behavior, depending on the atomic structure of their edges. Thus, it is important to control the morphology and crystallinity of these edges for practical purposes. We demonstrated an efficient edge-reconstruction process, at the atomic scale, for graphitic nanoribbons by Joule heating. During Joule heating and electron beam irradiation, carbon atoms are vaporized, and subsequently sharp edges and step-edge arrays are stabilized, mostly with either zigzag- or armchair-edge configurations. Model calculations show that the dominant annealing mechanisms involve point defect annealing and edge reconstruction.
Increasing Hyperpolarized Spin Lifetimes Through True Singlet Eigenstates
Authors: Warren Warren S. , Jenista Elizabeth , Branca Rosa Tamara , Chen Xin
Published: March 2009

The sensitivity limitations for magnetic resonance imaging of organic molecules have recently been addressed by hyperpolarization methods, which prepare excess nuclear spin polarization. This approach can increase sensitivity by orders of magnitude, but the enhanced signal relaxes away in tens of seconds, even in favorable cases. Here we show theoretically that singlet states between strongly coupled spins in molecules can be used to store and retrieve population in very-long-lived disconnected eigenstates, as long as the coupling between the spins substantially exceeds both the couplings to other spins and the resonance frequency difference between them. Experimentally, 2,3-carbon-13–labeled diacetyl has a disconnected eigenstate that can store population for minutes and is read out by hydration to make the two spins inequivalent.
Reversible Interactions with para-Hydrogen Enhance NMR Sensitivity by Polarization Transfer
Authors: Adams Ralph W. , Aguilar Juan A. , Atkinson Kevin D. , Cowley Michael J. , Elliott Paul I. P. , Duckett Simon B. , Green Gary G. R. , Khazal Iman G. , López-Serrano Joaquín , Williamson David C.
Published: March 2009

The sensitivity of both nuclear magnetic resonance spectroscopy and magnetic resonance imaging is very low because the detected signal strength depends on the small population difference between spin states even in high magnetic fields. Hyperpolarization methods can be used to increase this difference and thereby enhance signal strength. This has been achieved previously by incorporating the molecular spin singlet para-hydrogen into hydrogenation reaction products. We show here that a metal complex can facilitate the reversible interaction of para-hydrogen with a suitable organic substrate such that up to an 800-fold increase in proton, carbon, and nitrogen signal strengths are seen for the substrate without its hydrogenation. These polarized signals can be selectively detected when combined with methods that suppress background signals.
Lubrication at Physiological Pressures by Polyzwitterionic Brushes
Authors: Chen Meng , Briscoe Wuge H. , Armes Steven P. , Klein Jacob
Published: March 2009

The very low sliding friction at natural synovial joints, which have friction coefficients of μ < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have μ values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.
Queen Succession Through Asexual Reproduction in Termites
Authors: Matsuura Kenji , Vargo Edward L. , Kawatsu Kazutaka , Labadie Paul E. , Nakano Hiroko , Yashiro Toshihisa , Tsuji Kazuki
Published: March 2009

The evolution and maintenance of sexual reproduction may involve important tradeoffs because asexual reproduction can double an individual's contribution to the gene pool but reduces diversity. Moreover, in social insects the maintenance of genetic diversity among workers may be important for colony growth and survival. We identified a previously unknown termite breeding system in which both parthenogenesis and sexual reproduction are conditionally used. Queens produce their replacements asexually but use normal sexual reproduction to produce other colony members. These findings show how eusociality can lead to extraordinary reproductive systems and provide important insights into the advantages and disadvantages of sex.
Identification of Domains of the Hag/MID Surface Protein Recognized by Systemic and Mucosal Antibodies in Adults with Chronic Obstructive Pulmonary Disease following Clearance of
Moraxella catarrhalis
Authors: LaFontaine Eric R. , Snipes Lauren E. , Bullard Brian , Brauer Aimee L. , Sethi Sanjay , Murphy Timothy F.
Published: March 2009

Moraxella catarrhalis
is a common cause of respiratory tract infection in the setting of chronic obstructive pulmonary disease (COPD). Adults with COPD acquire and clear strains of
M. catarrhalis
from the respiratory tract continuously and develop strain-specific protection following clearance of a strain. In previous work, we identified Hag/MID (
Moraxella
immunoglobulin D-binding protein), a large multifunctional surface protein that acts as an adhesin and hemagglutinin, as a target of antibody responses in adults with COPD after clearance of
M. catarrhalis
. The goal of the present study was to characterize the domains of Hag/MID to which humans make antibodies, including both systemic and mucosal antibody responses. Analysis of recombinant peptide constructs, which spanned the
M. catarrhalis
strain O35E Hag/MID protein, with well-characterized serum and sputum samples revealed that most adults with COPD made antibodies directed toward a region of the molecule bounded by amino acids 706 to 863. Serum immunoglobulin G (IgG) and IgA purified from sputum both recognized the same domain. Some flanking sequence of this fragment was necessary for the epitope(s) in this region to maintain its conformation to bind human antibodies. These results reveal that humans consistently generate both systemic and mucosal antibody responses to an immunodominant region of the Hag/MID molecule, which was previously shown to overlap with several biologically relevant domains, including epithelial cell adherence, IgD binding, collagen binding, and hemagglutination.
Development of Loop-Mediated Isothermal Amplification Assay for Detection of
Entamoeba histolytica
Authors: Liang Shih-Yu , Chan Yun-Hsien , Hsia Kan-Tai , Lee Jing-Lun , Kuo Ming-Chu , Hwa Kuo-Yuan , Chan Chi-Wen , Chiang Ting-Yi , Chen Jung-Sheng , Wu Fang-Tzy , Ji Dar-Der
Published: March 2009

A novel one-step, closed-tube, loop-mediated isothermal amplification (LAMP) assay for detecting
Entamoeba histolytica
, one of the leading causes of morbidity in developing countries, was developed. The sensitivity of the LAMP assay is 1 parasite per reaction. A total of 130 clinical samples were analyzed, and the results compared with those of conventional nested PCR to validate the practicability of this assay. No DNA was amplified from other diarrheal pathogens, such as other
Entamoeba
species, bacteria, and viruses. These results indicate that LAMP is a rapid, simple, and valuable diagnostic tool for epidemiological studies of amebiasis.
Ezrin-Radixin-Moesin Family Proteins Are Involved in Parvovirus Replication and Spreading
Authors: Nüesch Jürg P. F. , Bär Séverine , Lachmann Sylvie , Rommelaere Jean
Published: March 2009

The propagation of autonomous parvoviruses is strongly dependent on the phosphorylation of the major nonstructural protein NS1 by members of the protein kinase C (PKC) family. Minute virus of mice (MVM) replication is accompanied by changes in the overall phosphorylation pattern of NS1, which is newly modified at consensus PKC sites. These changes result, at least in part, from the ability of MVM to modulate the PDK-1/PKC pathway, leading to activation and redistribution of both PDK-1 and PKCη. We show that proteins of the ezrin-radixin-moesin (ERM) family are essential for virus propagation and spreading through their functions as adaptors for PKCη. MVM infection led to redistribution of radixin and moesin in the cell, resulting in increased colocalization of these proteins with PKCη. Radixin was found to control the PKCη-driven phosphorylation of NS1 and newly synthesized capsids in vivo. Conversely, radixin phosphorylation and activation were driven by the NS1/CKIIα complex. Altogether, these data argue for ERM proteins being both targets and modulators of parvovirus infection.
Role of Untranslated Regions of the Hemagglutinin-Neuraminidase Gene in Replication and Pathogenicity of Newcastle Disease Virus
Authors: Yan Yongqi , Rout Subrat N. , Kim Shin-Hee , Samal Siba K.
Published: March 2009

To determine the role of untranslated regions (UTRs) in replication and pathogenesis of Newcastle disease virus (NDV), we generated recombinant viruses with deletions in 5′ and 3′ UTRs of the HN mRNA. Deletion of any HN UTR did not noticeably affect in vitro replication of these viruses. However, complete deletion of the 5′ UTR of the HN gene decreased the HN mRNA levels and HN protein contents in virus particles, resulting in attenuation of the virus in chickens. This indicates that the 5′ UTR of HN mRNA plays an important role in replication and pathogenicity of NDV in vivo.
Intranasal Vaccination with 1918 Influenza Virus-Like Particles Protects Mice and Ferrets from Lethal 1918 and H5N1 Influenza Virus Challenge
Authors: Perrone Lucy A. , Ahmad Attiya , Veguilla Vic , Lu Xiuhua , Smith Gale , Katz Jacqueline M. , Pushko Peter , Tumpey Terrence M.
Published: March 2009

Influenza vaccines capable of inducing cross-reactive or heterotypic immunity could be an important first line of prevention against a novel subtype virus. Influenza virus-like particles (VLPs) displaying functional viral proteins are effective vaccines against replication-competent homologous virus, but their ability to induce heterotypic immunity has not been adequately tested. To measure VLP vaccine efficacy against a known influenza pandemic virus, recombinant VLPs were generated from structural proteins of the 1918 H1N1 virus. Mucosal and traditional parenteral administrations of H1N1 VLPs were compared for the ability to protect against the reconstructed 1918 virus and a highly pathogenic avian H5N1 virus isolated from a fatal human case. Mice that received two intranasal immunizations of H1N1 VLPs were largely protected against a lethal challenge with both the 1918 virus and the H5N1 virus. In contrast, mice that received two intramuscular immunizations of 1918 VLPs were only protected against a homologous virus challenge. Mucosal vaccination of mice with 1918 VLPs induced higher levels of cross-reactive immunoglobulin G (IgG) and IgA antibodies than did parenteral vaccination. Similarly, ferrets mucosally vaccinated with 1918 VLPs completely survived a lethal challenge with the H5N1 virus, while only a 50% survival rate was observed in parenterally vaccinated animals. These results suggest a strategy of VLP vaccination against a pandemic virus and one that stimulates heterotypic immunity against an influenza virus strain with threatening pandemic potential.
Regulation of Histone Deposition on the Herpes Simplex Virus Type 1 Genome during Lytic Infection
Authors: Kutluay Sebla B. , Triezenberg Steven J.
Published: March 2009

During lytic infection by herpes simplex virus type 1 (HSV-1), histones are present at relatively low levels on the viral genome. However, the mechanisms that account for such low levels—how histone deposition on the viral genome is blocked or how histones are removed from the genome—are not yet defined. In this study, we show that histone occupancy on the viral genome gradually increased with time when transcription of the viral immediate-early (IE) genes was inhibited either by deletion of the VP16 activation domain or by chemical inhibition of RNA polymerase II (RNAP II). Inhibition of IE protein synthesis by cycloheximide did not affect histone occupancy on most IE promoters and coding regions but did cause an increase at delayed-early and late gene promoters. IE gene transcription from HSV-1 genomes associated with high levels of histones was stimulated by superinfection with HSV-2 without altering histone occupancy or covalent histone modifications at IE gene promoters. Moreover, RNAP II and histones cooccupied the viral genome in this context, indicating that RNAP II does not preferentially associate with viral genomes that are devoid of histones. These results suggest that during lytic infection, VP16, RNAP II, and IE proteins may all contribute to the low levels of histones on the viral genome, and yet the dearth of histones is neither a prerequisite for nor a necessary result of VP16-dependent transcription of nucleosomal viral genomes.
Protein Kinase PKR-Dependent Activation of Mitogen-Activated Protein Kinases Occurs through Mitochondrial Adapter IPS-1 and Is Antagonized by Vaccinia Virus E3L
Authors: Zhang Ping , Langland Jeffrey O. , Jacobs Bertram L. , Samuel Charles E.
Published: March 2009

The p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) play important roles in the host innate immune response. The protein kinase regulated by RNA (PKR) is implicated in p38 MAPK activation in response to proinflammatory signals in mouse embryonic fibroblasts. To test the role of PKR in the activation of p38 and JNK MAPKs in human cells following viral infection, HeLa cells made stably deficient in PKR by using an RNA interference strategy were compared to cells with sufficient PKR. The phosphorylation of both p38 and JNK in cells with sufficient PKR was activated following either infection with an E3L deletion (ΔE3L) mutant of vaccinia virus or transfection with double-stranded RNA (dsRNA) in the absence of infection with wild-type vaccinia virus. The depletion of PKR by stable knockdown impaired the phosphorylation of both p38 and JNK induced by either the ΔE3L mutant virus or dsRNA but not that induced by tumor necrosis factor alpha. The PKR-dependent activation of MAPKs in ΔE3L mutant-infected cells was abolished by treatment with cytosine β-
d
-arabinoside. The complementation of PKR-deficient cells with the human PKR wild-type protein, but not with the PKR catalytic mutant (K296R) protein, restored p38 and JNK phosphorylation following ΔE3L mutant virus infection. Transient small interfering RNA knockdown established that the p38 and JNK kinase activation following ΔE3L infection was dependent upon RIG-I-like receptor signal transduction pathway components, including the mitochondrial adapter IPS-1 protein.
Dimerization and a Novel Tax Speckled Structure Localization Signal Are Required for Tax Nuclear Localization
Authors: Fryrear Kimberly A. , Durkin Sarah S. , Gupta Saurabh K. , Tiedebohl Jessica B. , Semmes O. John
Published: March 2009

The human T-cell leukemia virus type 1 oncoprotein Tax has pleiotropic activities, a subset of which likely leads to immortalization of T cells. Tax is expressed and known to function in both the cell nucleus and the cytoplasm. Tax has defined nuclear localization (NLS) and nuclear export signals that enable shuttling between the two compartments. In this study, we identified a novel region in Tax that targets the protein to discrete nuclear foci that we have previously termed Tax speckled structures (TSS). We demonstrated that the identified region is both necessary and sufficient for directing proteins to TSS. This novel TSS localization signal (TSLS), spanning amino acids 50 to 75, is separable from and adjacent to the NLS of Tax. Coexpression of a Tax NLS mutant and a Tax TSLS mutant rescued the nuclear entry and subnuclear TSS targeting of both proteins, demonstrating that these signals are independent domains. Our analysis also revealed that Tax proteins deficient for dimerization fail to localize to the nucleus. Consequently, when we restored dimerization via induction of a heterologous “dimerizer” domain, nuclear localization was rescued. Thus, we defined additional domains in Tax specific for nuclear localization and subnuclear targeting. Our results reveal a more complex network for regulation of Tax subcellular localization and subsequent function.
Plant Virus Cell-to-Cell Movement Is Not Dependent on the Transmembrane Disposition of Its Movement Protein
Authors: Martínez-Gil Luis , Sánchez-Navarro Jesús A. , Cruz Antonio , Pallás Vicente , Pérez-Gil Jesús , Mingarro Ismael
Published: March 2009

The cell-to-cell transport of plant viruses depends on one or more virus-encoded movement proteins (MPs). Some MPs are integral membrane proteins that interact with the membrane of the endoplasmic reticulum, but a detailed understanding of the interaction between MPs and biological membranes has been lacking. The cell-to-cell movement of the
Prunus necrotic ringspot virus
(PNRSV) is facilitated by a single MP of the 30K superfamily. Here, using a myriad of biochemical and biophysical approaches, we show that the PNRSV MP contains only one hydrophobic region (HR) that interacts with the membrane interface, as opposed to being a transmembrane protein. We also show that a proline residue located in the middle of the HR constrains the structural conformation of this region at the membrane interface, and its replacement precludes virus movement.
Virion Stability Is Important for the Circulative Transmission of
Tomato Yellow Leaf Curl Sardinia Virus
by
Bemisia tabaci
, but Virion Access to Salivary Glands Does Not Guarantee Transmissibility
Authors: Caciagli Piero , Medina Piles Vicente , Marian Daniele , Vecchiati Manuela , Masenga Vera , Mason Giovanna , Falcioni Tania , Noris Emanuela
Published: March 2009

The capsid protein (CP) of the monopartite begomovirus
Tomato yellow leaf curl Sardinia virus
(TYLCSV), family
Geminiviridae
, is indispensable for plant infection and vector transmission. A region between amino acids 129 and 152 is critical for virion assembly and insect transmissibility. Two previously described mutants, one with a double Q129P Q134H mutation (PNHD) and another with a further D152E change (PNHE), were found nontransmissible (NT). Another NT mutant with a single N130D change (QDQD) was retrieved from a new mutational analysis. In this study, these three NT mutants and the wild-type (wt) virus were compared in their relationships with the whitefly vector
Bemisia tabaci
and the nonvector
Trialeurodes vaporariorum
. Retention kinetics of NT mutants were analyzed by quantitative dot blot hybridization in whiteflies fed on infected plants. The QDQD mutant, whose virions appeared nongeminate following purification, was hardly detectable in either whitefly species at any sampling time. The PNHD mutant was acquired and circulated in both whitefly species for up to 10 days, like the wt virus, while PNHE circulated in
B. tabaci
only. Using immunogold labeling, both PNHD and PNHE CPs were detected in
B. tabaci
salivary glands (SGs) like the wt virus, while no labeling was found in any whitefly tissue with the QDQD mutant. Significant inhibition of transmission of the wt virus was observed after prior feeding of the insects on plants infected with the PNHE mutant, but not on plants infected with the other mutants. Virion stability and ability to cross the SG barrier are necessary for TYLCSV transmission, but interactions with molecular components inside the SGs are also critical for transmissibility.
Single-Amino-Acid Alterations in a Highly Conserved Central Region of Vesicular Stomatitis Virus N Protein Differentially Affect the Viral Nucleocapsid Template Functions
Authors: Nayak Debasis , Panda Debasis , Das Subash C. , Luo Ming , Pattnaik Asit K.
Published: March 2009

The nucleocapsid protein (N) of vesicular stomatitis virus and other rhabdoviruses plays a central role in the assembly and template functions of the viral N-RNA complex. The crystal structure of the viral N-RNA complex suggests that the central region of the N protein interacts with the viral RNA. Sequence alignment of rhabdovirus N proteins revealed several highly conserved regions, one of which spanned residues 282 to 291 (GLSSKSPYSS) in the central region of the molecule. Alanine-scanning mutagenesis of this region suggested that replacement of the tyrosine residue at position 289 (Y289) with alanine resulted in an N-RNA template that is nonfunctional in viral genome replication and transcription. To establish the molecular basis of this defect, our further studies revealed that the Y289A mutant maintained its interaction with other N protein molecules but that its interactions with the P protein or with the viral RNA were defective. Replacement of Y289 with other aromatic, polar, or large amino acids indicated that the hydrophobic and aromatic nature of this position in the N protein is functionally important and that a larger aromatic residue is less favorable. Interestingly, we have observed that several single-amino-acid substitutions in this highly conserved region of the molecule rendered the nucleocapsid template nonfunctional in transcription without adversely affecting the replication functions. These results suggest that the structure of the N protein and the resulting N-RNA complex, in part, regulate the viral template functions in transcription and replication.
Fas-Mediated Apoptotic Signaling in the Mouse Brain following Reovirus Infection
Authors: Clarke Penny , Beckham J. David , Leser J. Smith , Hoyt Cristen C. , Tyler Kenneth L.
Published: March 2009

Type 3 (T3) reovirus strains induce apoptotic neuronal cell death and lethal encephalitis in infected mice. T3 strain Dearing (T3D)-induced apoptosis in primary neuronal cultures occurs by a Fas-mediated mechanism and requires the activation of caspase 8. We now show that Fas mRNA is upregulated in the brains of mice infected with encephalitic reovirus T3D and T3 strain Abney (T3A) but not following infection with nonencephalitic reovirus type 1 strain Lang. Fas is upregulated in regions of the brain that are injured during infection with T3 reovirus strains and colocalizes with virus antigen in individual neurons. In contrast, levels of FasL mRNA induced by encephalitic and nonencephalitic reovirus strains do not differ significantly. Caspase 8, the initiator caspase associated with Fas-mediated apoptosis, is activated in the cortex and hippocampal regions of both T3D- and T3A-infected mice. Furthermore, Bid cleavage and the activation of caspase 9 in the brains of T3D-infected mice suggest that the caspase 8-dependent activation of mitochondrial apoptotic signaling contributes to virus-induced apoptosis. We have previously shown that the inhibition of c-Jun N-terminal kinase (JNK) signaling blocks T3D-induced apoptosis and improves the outcome of virus-induced encephalitis. We now show that the reovirus-induced upregulation of Fas requires JNK signaling, thereby providing a link between reovirus-induced death receptor signaling and mitogen-activated protein kinase pathways and a potential mechanism for the therapeutic action of JNK inhibition.
Tissue-Specific Sequence Alterations in the Human Immunodeficiency Virus Type 1 Envelope Favoring CCR5 Usage Contribute to Persistence of Dual-Tropic Virus in the Brain
Authors: Gray Lachlan , Roche Michael , Churchill Melissa J. , Sterjovski Jasminka , Ellett Anne , Poumbourios Pantelis , Sheffief Shameem , Wang Bin , Saksena Nitin , Purcell Damian F. J. , Wesselingh Steven , Cunningham Anthony L. , Brew Bruce J. , Gabuzda Dana , Gorry Paul R.
Published: March 2009

Most human immunodeficiency virus type 1 (HIV-1) strains isolated from the brain use CCR5 for entry into macrophages and microglia. Strains that use both CCR5 and CXCR4 for entry (R5X4 strains) have been identified in the brains of some individuals, but mechanisms underlying the persistence of R5X4 viruses compartmentalized between the brain and other tissue reservoirs are unknown. Here, we characterized changes in the HIV-1 envelope (Env) that enhance the tropism of R5X4 variants for brain or lymphoid tissue. R5X4 Envs derived from the brains of two individuals had enhanced CCR5 usage in fusion assays compared to R5X4 Envs derived from matched spleen or blood, which was associated with reduced dependence on specific residues in the CCR5 N terminus and extracellular loop 1 (ECL1) and ECL3 regions. In contrast, spleen/blood-derived Envs had enhanced CXCR4 usage compared to brain-derived Envs, which was associated with reduced dependence on residues in the CXCR4 N terminus and ECL2 region. Consequently, brain-derived Envs had preferential CCR5 usage for HIV-1 entry into the JC53 cell line, could use either CCR5 or CXCR4 for entry into monocyte-derived macrophages (MDM), and could use CCR5 (albeit inefficiently) for entry into peripheral blood mononuclear cells (PBMC), whereas the entry of spleen-derived Envs was CXCR4 dependent in all three cell types. Mutagenesis studies of Env amino acid variants influencing coreceptor usage showed that S306 in the gp120 V3 region of brain-derived Envs reduces dependence on the CCR5 N terminus and enhances CCR5 usage for HIV-1 entry into PBMC and MDM, whereas R306 in spleen-derived Envs reduces dependence on the CXCR4 N terminus and confers the CXCR4 restricted phenotype. These results identify mechanisms underlying R5X4 HIV-1 persistence in different tissue reservoirs. Tissue-specific changes in the gp120 V3 region that increase the efficiency of CCR5 or CXCR4 usage, and thereby influence coreceptor preference, may enhance the tropism of R5X4 strains for CCR5-expressing macrophage lineage cells in the brain and CXCR4-expressing T cells in lymphoid tissues, respectively.
NUMEROV-TYPE METHODS FOR OSCILLATORY LINEAR INITIAL VALUE PROBLEMS
Authors: TH. FAMELIS I.
Published: March 2009

We present a new explicit Numerov-type method for the solution of second-order linear initial value problems with oscillating solutions. The new method attains algebraic order seven at a cost of six function evaluations per step. The method has the characteristic of zero dissipation and high phase-lag order making it suitable for the solution of problems with oscillatory solutions. The numerical tests in a variety of problems justify our effort.
TRAFFIC CELLULAR AUTOMATA SIMULATION OF A CONGESTED ROUND-ABOUT IN MAURITIUS
Authors: FOWDUR S. C. , RUGHOOPUTH S. D. D. V.
Published: March 2009

In this paper a Traffic Cellular Automata (TCA) simulation of a highly congested round-about in Mauritius is performed. The simulations are performed using a multi-cell model that includes anticipation and probability randomization. The simulation model is first calibrated to match actual traffic count statistics taken at the round-about. The topology of the round-about is then modified and the TCA model is used to predict the impact on the congestion level of different changes made. The simulation results enable the assessment of the impact on the traffic density and travel time of the different modifications made. It has been found that the construction of a flyover bridge at the round-about will be the most convenient solution to alleviate congestion and improve the flux significantly.
Collecting duct-specific Rh C glycoprotein deletion alters basal and acidosis-stimulated renal ammonia excretion
Authors: Lee Hyun-Wook , Verlander Jill W. , Bishop Jesse M. , Igarashi Peter , Handlogten Mary E. , Weiner I. David
Published: March 2009

NH3movement across plasma membranes has traditionally been ascribed to passive, lipid-phase diffusion. However, ammonia-specific transporters, Mep/Amt proteins, are present in primitive organisms and mammals express orthologs of Mep/Amt proteins, the Rh glycoproteins. These findings suggest that the mechanisms of NH3movement in mammalian tissues should be reexamined. Rh C glycoprotein (Rhcg) is expressed in the collecting duct, where NH3secretion is necessary for both basal and acidosis-stimulated ammonia transport. To determine whether the collecting duct secretes NH3via Rhcg or via lipid-phase diffusion, we generated mice with collecting duct-specific Rhcg deletion (CD-KO). CD-KO mice had loxP sites flanking exons 5 and 9 of the Rhcg gene (Rhcgfl/fl) and expressed Cre-recombinase under control of the Ksp-cadherin promoter (Ksp-Cre). Control (C) mice were Rhcgfl/flbut Ksp-Cre negative. We confirmed kidney-specific genomic recombination using PCR analysis and collecting duct-specific Rhcg deletion using immunohistochemistry. Under basal conditions, urinary ammonia excretion was less in KO vs. C mice; urine pH was unchanged. After acid-loading for 7 days, CD-KO mice developed more severe metabolic acidosis than did C mice. Urinary ammonia excretion did not increase significantly on the first day of acidosis in CD-KO mice, despite an intact ability to increase urine acidification, whereas it increased significantly in C mice. On subsequent days, urinary ammonia excretion slowly increased in CD-KO mice, but was always significantly less than in C mice. We conclude that collecting duct Rhcg expression contributes to both basal and acidosis-stimulated renal ammonia excretion, indicating that collecting duct ammonia secretion is, at least in part, mediated by Rhcg and not solely by lipid diffusion.
Anticipatory Changes in Regional Cerebral Hemodynamics: A New Role for Dopamine?
Authors: Tan Can Ozan
Published: March 2009

Recently, adaptively timed, anticipatory changes in hemodynamic responses, independent of neural activity, were described in primate primary visual cortex. Task-related properties of these responses point to a possible link between regional cerebral microcirculation and dopaminergic signaling. In this report, this link is elaborated on the basis of known physiological data and further experiments are proposed to test the possible role of dopamine in task-dependent, “on-demand” allocation of metabolic resources.
Contributions of Primate Prefrontal and Posterior Parietal Cortices to Length and Numerosity Representation
Authors: Tudusciuc Oana , Nieder Andreas
Published: March 2009

The ability to understand and manipulate quantities ensures the survival of animals and humans alike. The frontoparietal network in primates has been implicated in representing, along with other cognitive abilities, abstract quantity. The respective roles of the prefrontal and parietal areas and the way continuous quantities, as opposed to discrete ones, are represented in this network, however, are unknown. We investigated this issue by simultaneously analyzing recorded single-unit activity in the prefrontal cortex (PFC) and the fundus of the intraparietal sulcus (IPS) of two macaque monkeys while they were engaged in delayed match-to-sample tasks discriminating line length and numerosity. In both areas, we found anatomically intermingled neurons encoding either length, numerosity, or both types of quantities. Even though different sets of neurons coded these quantities, the representation of length and numerosity was similar within the IPS and PFC. Both length and numerosity were coded by tuning functions peaking at the preferred quantity, thus supporting a labeled-line code for continuous and discrete quantity. A comparison of the response characteristics between parietal and frontal areas revealed a larger proportion of IPS neurons representing each quantity type in the early sample phase, in addition to shorter response latencies to quantity for IPS neurons. Moreover, IPS neurons discriminated quantities during the sample phase better than PFC neurons, as quantified by the receiver operating characteristic area. In the memory period, the discharge properties of PFC and IPS neurons were comparable. These single-cell results are in good agreement with functional imaging data from humans and support the notion that representations of continuous and discrete quantities share a frontoparietal substrate, with IPS neurons constituting the putative entry stage of the processing hierarchy.
Excitatory Actions of Ventral Root Stimulation During Network Activity Generated by the Disinhibited Neonatal Mouse Spinal Cord
Authors: Bonnot Agnes , Chub Nikolai , Pujala Avinash , O'Donovan Michael J.
Published: March 2009

To further understand the excitatory effects of motoneurons on spinal network function, we investigated the entrainment of disinhibited rhythms by ventral root (VR) stimulation in the neonatal mouse spinal cord. A brief train of stimuli applied to a VR triggered bursting reliably in 31/32 experiments. The same roots that entrained disinhibited bursting could also produce locomotor-like activity with a similar probability when the network was not disinhibited. The ability of VR stimulation to entrain the rhythm persisted in nicotinic and muscarinic cholinergic antagonists but was blocked by the AMPAR antagonist NBQX. Bath application of the type I mGluR1 receptor antagonist CPCCOEt reduced the ability of both dorsal root and VR stimulation to entrain the disinhibited rhythm and abolished the ability of either type of stimulation to evoke locomotor-like activity. Calcium imaging through the lateral aspect of the cord revealed that VR stimulation and spontaneously occurring bursts were accompanied by a wave of activity that originated ventrally and propagated dorsally. Imaging the cut transverse face of L5 revealed that the earliest VR-evoked optical activity began ventrolaterally. The optical activity accompanying spontaneous bursts could originate ventrolaterally, ventromedially, or throughout the mediolateral extent of the ventral horn or very occasionally dorsally. Collectively, our data indicate that VR stimulation can entrain disinhibited spinal network activity and trigger locomotor-like activity through a mechanism dependent on activation of both ionotropic and metabotropic glutamate receptors. The effects of entrainment appear to be mediated by a ventrolaterally located network that is also active during spontaneously occurring bursts.
GABAC Receptor-Mediated Inhibition Is Altered But Not Eliminated in the Superior Colliculus of GABAC ρ1 Knockout Mice
Authors: Schlicker Katja , McCall Maureen A. , Schmidt Matthias
Published: March 2009

GABAC receptors (GABACRs) are widely expressed in the mammalian subcortical visual system, particularly in the retina and superior colliculus (SC). GABACRs are composed of specific ρ1–3 subunits the expression of which varies among visual structures. Thus ρ1 subunits are most abundant in retina, and their loss eliminates GABACR expression and function. In the SC, ρ2 subunit expression may be equal to or stronger than ρ1 subunit expression; however, results across studies vary considerably. To more directly assess the expression of GABACR subunits, we characterized inhibition in the SC of wild-type (WT) and GABAC ρ1 Null mice that lack expression of GABAC ρ1 subunits. We used whole cell patch-clamp recordings and evaluated GABACR-mediated modulation of electrically evoked post synaptic currents using either agonists or antagonists in WT mice. In GABAC ρ1 Null stratum griseum superficiale (SGS) cells, inhibitory postsynaptic currents were shorter in duration and their excitatory postsynaptic currents (EPSCs) were longer, indicating that a slow GABACR-mediated inhibitory component was reduced in each case. In contrast to retina, GABACR-mediated currents in the SC were altered but not eliminated in GABAC ρ1 Null mice. In the majority of SC cells in GABAC ρ1 Null mice, GABACR activation could still be induced to alter EPSC peak amplitudes in putative interneurons and in many projection neurons. These results, compared with previously published data, indicate a fundamental difference between retina and SC in the control of GABACR expression and subunit composition.