bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Deformation Speed and Type of Alloy on Friction and Lubrication by Tip Test
Authors: Ajiboye Joseph S.
Published: April 2011

The tribological conditions in cold forging operations are extremely severe, especially with high ram speed, due to large surface expansion and normal pressure at the tool/workpiece interface. The effects of deformation velocity and type of alloy were determined in the two sets of experiments carried out in the present study. In the first set, two different deformation speeds of 0.1 and 1mm/s were used for the aluminum alloys of 6061-O, 1050-O and copper alloys tests. The results were further confirmed with the second sets of experiments using AA2024 and AA6061 and three deformation speeds of 0.1, 1 and 5mm/s to evaluate the performance of each lubricant under increasing ram speed. Four lubricants such as grease, corn oil, VG100 and VG32 were used. While all the lubricants show a reduction in maximum load with increasing deformation speed, grease shows a rise in the maximum load from zero to a maximum at a deformation speed of 1mm/s and then descends gradually to a minimum load at a speed of 5mm/s for AA2024-O and AA6061-O. Since the load reduction seen, with grease as lubricant, is probably due to thermal softening, it will not be considered a desirable lubricant under increasing deformation speed because of the adverse effects on the tooling. It is found that in choosing lubricant for cold forging operations the type of workpiece material and deformation speed should be properly considered. Of the liquid lubricants (corn oil, VG100 and VG32) considered, corn oil shows the best lubricant for cold forging operations of copper, aluminum 6061-O, 1050-O and 2024-0 under increasing speed magnitude.
A Dislocation Dynamics Based Constitutive Model and Experimental Validations by 3D Microscale Laser Dynamic Forming of Metallic Thin Films
Authors: Gao Huang , Cheng Gary J.
Published: April 2011

Microscale Laser Dynamic Forming (μLDF) shows great potential in fabricating the robust and high-aspect-ratio metallic microcomponents by the high speed plasma shockwave. Experiments revealed that strain rate and sample size play important roles in determining the final results of μLDF. To further understand the deformation behavior, we develop a constitutive model integrating size effects and ultrahigh strain rate effects to predict the ultimate plastic deformations. To derive this model, 3-D Discrete Dislocation Dynamics (DDD) simulations are first set up to investigate the dislocation evolutions and the dynamic responses during shockwave propagation. It is observed that there exist three dynamic stages during deformation process, and the initial strain hardening rate in Stage II increases with strain rate. The simulation also reveals that stain softening occurs only for the smaller cell size due to two competing mechanisms. In addition, the simulation predicts that the flow stress and yield strength increase with the strain rate and decrease with cell size. The modified mechanical threshold stress (MTS) model integrating these effects is implemented in Abaqus/Explicit and predicts the deformation depth and thickness variations in good agreement with the experimental results.
Fatigue Performance Improvement by Dynamic Strain Aging and Dynamic Precipitation in Warm Laser Shock Peening of AISI 4140 Steel
Authors: Ye Chang , Cheng Gary J.
Published: April 2011

Warm laser shock peening (WLSP) integrates the advantages of laser shock peening and thermal-mechanical treatment (TMT) to improve material fatigue performance. Compared to traditional laser shock peening (LSP), warm laser shock peening, i.e. LSP at elevated temperature, leads to better performance in many aspects. WLSP can induce nanoscale precipitations by dynamic precipitation and high density dislocation by dynamic strain aging (DSA), resulting in higher surface strength, which is beneficial for fatigue life improvement. Due to pinning of dislocation structure by nanoscale precipitates, and the pinning of dislocation structure by Cottrell atmosphere, or the DSA effect, stability of the dislocation arrangement is significantly increased and the residual stress stability improved. In this study, AISI 4140 steel is used to evaluate WLSP process. It is concluded that the higher residual stress stability and higher surface strength caused by dynamic precipitation and DSA in WLSP leads to fatigue life improvement.
Analysis on Filament Winding Sphere Surface Component With Multiple Polar-Holes
Authors: Min Rong , Wang Yongjun , Wu Weichao , Wang Junbiao
Published: April 2011

This paper presents a new filament winding process for multi-polar holes componet. Some kinds of filament winding components work as connecting piece which has many holes. Traditionally, the hole is usually machined after the fabrication of composite components. This will lead to the fibers around the holes are cut off. In addition, it would also increase the risk of composites delamination and crack around the area of the holes. In order to eliminate these defects, the multi-polar holes filament winding process was proposed. The winding trajectories of a sphere with two non-axial polar holes were designed and tested. Then, by calculating the area of fiber sparse zone and fiber volume fraction of this winding component, it was found that the radiuses of polar holes can significantly influence the area of fiber sparse zone and fiber volume fraction.
Experimental Setup for Multi-Sensor Fusion and Data Correlation Analysis During CNC Steel Turning Process
Authors: Joslin Andrew , Hernandez Manuel , Deane Erick , Collins Schadrick , Xu Chengying , Wilson Don F.
Published: April 2011

This paper discusses a preliminary setup for an ongoing research project with goals of off-line modeling and optimization for a CNC turning process of AISI 4137 steel alloy; followed by online monitoring, optimization, and control of the machining process. A full factorial Design Of Experiment (DOE) of three machining parameter factors was created in Minitab™ and Analysis of Variance was performed, in order to determine which parameters influenced the machining process the most. Accelerometers, acoustic emission sensors and force sensors have given researchers insights into the relationships between mechanical vibration and tool condition during the turning process. Similarly, correlations have been recognized between electrical power consumption, machining forces, tool temperature, and tool condition. While monitoring the machining process with sophisticated force and acceleration sensors is effective, implementation in a large scale factory environment may not be an economical solution to online monitoring and control. Finding an ideal combination of sensors capable of monitoring significant factors that affect the CNC steel turning process will allow process optimization and reduce the cost of machining.
A 3D Finite Element Study on Material Flow Under the Cutting Edge in Hard Milling
Authors: Singh H. M. , Guo Y. B.
Published: April 2011

A 3D finite element model of hard milling has been created to have a deeper insight into some key issues. The model illustrates the effects of milling insert geometry on ploughed depth, material flow, transition from ploughing to cutting, and stresses and temperatures in the subsurface. Different ploughing depths from 0.6 μm – 3.0 μm are used to study the effects. The Johnson-Cook constitutive equation is used to model the plastic behavior of workpiece material AISI H13 steel (50±1 HRC). Surface and subsurface transient stresses and temperatures during ploughing show similar characteristics except the magnitudes. Ploughing depth of 1.8 μm corresponding to stagnation angle 35° is observed to be the threshold minimum uncut chip thickness at which transition from ploughing to cutting takes place. The material flow pattern with pile-up characteristics in front of the tool rake face is presented.
The Development of a Novel On-Line Optical Inspection System for Tool Conditions in Machining Processes
Authors: Li W. , Singh H. M. , Salahshoor M. , Guo Y. B.
Published: April 2011

Tool abrasion and material adhesion lead to tool flank wear and flank build-up respectively in machining magnesium alloys, which adversely affect surface integrity due to higher cutting forces and temperatures. In this paper, a novel on-line optical tool monitoring system integrated with CNC machining center is designed and applied to examining these two phenomena. Flank wear evolution on PVD coated inserts in end milling of AISI H13 tool steel and material adhesion on flank face of PCD inserts in face milling of lightweight magnesium alloys were on-line inspected to assess the function of the designed optical measurement system. Tool wear failure criterion for the PVD milling inserts is set to be VBmax = 250 μm and flank wear evolution with cutting time is presented. Tool/work adhesion between the PCD inserts and magnesium alloy were observed under different combinations of cutting parameters including speed, feed, and depth-of-cut. The advantages of the on-line optical tool inspection system are discussed.
Cutting Force Modeling When Milling Nickel-Base Superalloys
Authors: Henderson Andrew J. , Bunget Cristina , Kurfess Thomas R.
Published: April 2011

Superalloys are a relatively new class of materials that exhibit high mechanical strength, ductility, creep resistance at high operating temperatures, high fatigue strength, and typically superior resistance to corrosion and oxidation even at elevated temperatures. These properties make superalloys ideal for applications in aircraft, cryogenic tanks, submarines, nuclear reactors, and petrochemical equipment. In the aerospace industry, the most commonly used superalloy is the nickel-base alloy and it accounts for 30–50% of the total material required in the manufacturing of the aircraft engine. It is used for rotating parts of gas turbines such as blades and disks, engine mounts, turbine casings and components for rocket motors and pumps. To make full use of nickel-base superalloys, a machining process must be developed that is capable of controlling and identifying tool wear, and identifying the onset of subsurface damage and controlling its formation during processing. To accomplish this, a model relating process characteristics and cutting parameters need to be developed. Due to high tool wear, the cutting forces increase drastically during machining, thus making impossible to estimate the forces with existing models. This research proposes an update to the specific cutting forces model taking into consideration rapid tool wear. As milling is the most common machining processes used to cut superalloys (e.g., turbine blades), it is specifically targeted by this research. Experiments were conducted under different cutting conditions to observe the cutting characteristics of nickel-base superalloys. Empirical observations were used to formulate updated coefficients. Later this model will be applied for real-time control of the process results, such as geometry, tool wear and subsurface damage, and also for estimation and control of other quantities such as force, deflection, surface quality and energy consumed. This will provide new insights into machining these advanced alloys.
A Perfused Two-Chamber System for Anticancer Drug Screening
Authors: Ma Liang , Barker Jeremy , Zhou Changchun , Lin Biaoyang , Li Wei
Published: April 2011

A cell culture microfluidic device has been developed to test the cytotoxicity of anticancer drugs while reproducing multi-organ interactions in vitro. Cells were cultured in separate chambers representing the liver and tumor. The two chambers were connected through a channel to mimick the blood flow. Glioblastoma (GBM) cancer cells (M059K) and hepatoma cells (HepG2) were cultured in the tumor and the liver chambers, respectively. The cytotoxic effect of cancer treatment drug Temolozomide (TMZ) was tested using this two chamber system. The experimental results showed that with the liver cells, the cancer cells showed much higher viability than those without the liver cells. This indicates that the liver metabolism has strong effect on the toxicity of the anticancer drug. The results demonstrated that the perfused two chamber cell culture system has the potential to be used as a platform for drug screening in a more physiologically realistic environment.
Emergent Structure Detection for Multi-Axis Machining
Authors: Petrzelka Joseph E. , Frank Matthew C.
Published: April 2011

This paper examines the phenomenon of emergent structures that occur in the transient stock material during multi-axis rough machining from a plurality of fixed orientations. Taking the form of thin webs and strings, emergent structures are stock material conditions that can lead to catastrophic failure during machining, even when tool path verification is successful. We begin by discussing the motivation for use of fixed orientations in multi-axis machining using multiple automated setups via rotary axes, which enables fast processing and ‘first part correct’ machining. Next, we demonstrate how unintended emergent structures occur in this paradigm of machining and can lead to catastrophic failure of the tool or work piece. Our original work focuses on the problem of geometric detection of these structures during process planning and prior to tool path planning, to the end of altogether avoiding emergent structure formation. To quickly simulate the machining process, we present an object-space method for determining the transient state of stock material based on the inverse tool offset. To identify emergent structures within this transient stock state, we propose a metric based on the medial axis transformation. Finally, we present our implementation of these methods and demonstrate realtime computation appropriate for an optimization scheme to eliminate emergent structures. Our methods provide consistent and logical results, as demonstrated with several freeform component examples. This work enables the development of robust algorithms for autonomous tool path planning and machining in multi-axis environments.
Manufacturing Ultra Fine Filaments by Cold Air Attenuation
Authors: Jia Jun , Yao Donggang , Wang Youjiang
Published: April 2011

Ultra fine fibers, with a linear density below 1 denier, are high value products for textile, industrial and biomedical applications. Traditionally ultrafine fibers are produced by extrusion followed by mechanical drawing. In this study a customized fiber extrusion line was designed and set up with the inclusion of a jet nozzle in the spinneret pack. With only cold air attenuation, we were able to obtain drawing ratios exceeding 2500 and produce subdenier continuous filaments. We have conducted parametric studies to investigate the fiber attenuation mechanism and determine the optimal process window for making continuous microfibers. Different characterization methods were carried out to examine the resulting fiber properties, including microstructures, thermal properties, mechanical properties, orientation and crystallinity. Theoretical analysis of cold air drawing is discussed in this paper.
Hippo Pathway Inhibits Wnt Signaling to Restrain Cardiomyocyte Proliferation and Heart Size
Authors: Heallen Todd , Zhang Min , Wang Jun , Bonilla-Claudio Margarita , Klysik Ela , Johnson Randy L. , Martin James F.
Published: April 2011

Heart size is controlled through an antagonistic interaction between Hippo and Wnt signaling pathways.
Latitudinal Gradients in Greenhouse Seawater δ
18
O: Evidence from Eocene Sirenian Tooth Enamel
Authors: Clementz Mark T. , Sewall Jacob O.
Published: April 2011

Tooth enamel from fossil marine mammals shows that the middle latitudes were wetter in the past than they are today.
Restoration Seed Banks—A Matter of Scale
Authors: Merritt David J. , Dixon Kingsley W.
Published: April 2011

Seed banks must shift from being “stamp-collections” of species to collections that can provide tons of seeds and the expertise to improve restoration efforts.
Massive CO
2
Ice Deposits Sequestered in the South Polar Layered Deposits of Mars
Authors: Phillips Roger J. , Davis Brian J. , Tanaka Kenneth L. , Byrne Shane , Mellon Michael T. , Putzig Nathaniel E. , Haberle Robert M. , Kahre Melinda A. , Campbell Bruce A. , Carter Lynn M. , Smith Isaac B. , Holt John W. , Smrekar Suzanne E. , Nunes Daniel C. , Plaut Jeffrey J. , Egan Anthony F. , Titus Timothy N. , Seu Roberto
Published: April 2011

Radar measurements reveal a substantial buried deposit of carbon dioxide in the south pole of Mars.
Cold-Trapping Mars' Atmosphere
Authors: Thomas Peter C.
Published: April 2011

The Mars Reconnaissance Orbiter has observed large deposits of frozen CO
2
at Mars' southern polar region.
Spatial Coupling of mTOR and Autophagy Augments Secretory Phenotypes
Authors: Narita Masako , Young Andrew R. J. , Arakawa Satoko , Samarajiwa Shamith A. , Nakashima Takayuki , Yoshida Sei , Hong Sungki , Berry Lorraine S. , Reichelt Stefanie , Ferreira Manuela , Tavaré Simon , Inoki Ken , Shimizu Shigeomi , Narita Masashi
Published: April 2011

A cellular compartment allows simultaneous protein synthesis and degradation.
The Toll-Like Receptor 2 Pathway Establishes Colonization by a Commensal of the Human Microbiota
Authors: Round June L. , Lee S. Melanie , Li Jennifer , Tran Gloria , Jabri Bana , Chatila Talal A. , Mazmanian Sarkis K.
Published: April 2011

Signaling through innate immune receptors promotes commensal bacteria colonization of the gut.
Increased CXC Ligand 10 Levels and Gene Expression in Type 1 Leprosy Reactions
Authors: Scollard David M. , Chaduvula Meher V. , Martinez Alejandra , Fowlkes Natalie , Nath Indira , Stryjewska Barbara M. , Kearney Michael T. , Williams Diana L.
Published: April 2011

Type 1 reaction (T1R) is a systemic inflammatory syndrome causing substantial morbidity in leprosy. T1R results from spontaneously enhanced cellular immunity in borderline types of leprosy, but there are no established laboratory markers for the reaction. Preliminary studies have identified elevated circulating CXC ligand 10 (CXCL10) during T1R. Correlation of CXCL10 with clinical T1R was studied in repeated serum specimens obtained before, during, and after T1R. CXCL10 gene expression was assessed in biopsy specimens taken before and during T1R, and sections were stained for the cytokine using monoclonal antibodies. Sequential serum specimens revealed elevation of circulating CXCL10 associated with episodes of T1R (P= 0.0001) but no evidence of an earlier, predictive change in the level of the chemokine. Reverse transcriptase (RT)-PCR revealed elevated expression of CXCL10 transcripts during T1R, but not in patients who did not have T1R. No significant correlation between CXCL10 and gamma interferon (IFN-γ) mRNA levels was observed. Immunohistochemical staining of the skin biopsy specimens suggested an overall increase in CXCL10 but did not identify a particular strongly staining population of leukocytes. Increased CXCL10 in lesions and serum is characteristic of T1R. CXCL10 measurement offers new possibilities for laboratory diagnosis and monitoring of T1R. Studies of the regulation of CXCL10 may provide insight into the mechanisms of T1R and identify potential new drug targets for treatment.
Evaluation of a Novel Chimeric B Cell Epitope-Based Vaccine against Mastitis Induced by Either Streptococcus agalactiae or Staphylococcus aureus in Mice
Authors: Xu Haiyang , Hu Changmin , Gong Rui , Chen Yingyu , Ren Ningning , Xiao Ganwen , Xie Qian , Zhang Minmin , Liu Qin , Guo Aizhen , Chen Huanchun
Published: April 2011

To construct a universal vaccine against mastitis induced by eitherStreptococcus agalactiaeorStaphylococcus aureus, the B cell epitopes of the surface immunogenic protein (Sip) fromS. agalactiaeand clumping factor A (ClfA) fromS. aureuswere analyzed and predicted.sip-clfA, a novel chimeric B cell epitope-based gene, was obtained by overlap PCR, and then the recombinant Sip-ClfA (rSip-ClfA) was expressed and purified. rSip-ClfA and inactivatedS. agalactiaeandS. aureuswere formulated into different vaccines with mineral oil as the adjuvant and evaluated in mouse models. The rSip-ClfA vaccination induced immunoglobulin G (IgG) titers higher than those seen in groups immunized with inactivated bacteria. Furthermore, the response to rSip-ClfA immunization was characterized as having a dominant IgG1 subtype, whereas both bacterial immunizations produced similar levels of IgG1 and IgG2a. The antiserum capacities for opsonizing adhesion and phagocytosis were significantly greater in the rSip-ClfA immunization group than in the killed-bacterium immunization groups (P< 0.05). The immunized lactating mice were challenged with eitherS. agalactiaeorS. aureusvia the intramammary route. At 24 h postinfection, the numbers of bacteria recovered from the mammary glands in the rSip-ClfA group were >5-fold lower than those in both inactivated-bacterium groups (P< 0.01). Histopathological examination of the mammary glands showed that rSip-ClfA immunization provided better protection of mammary gland tissue integrity against bothS. agalactiaeandS. aureuschallenges. Thus, the recombinant protein rSip-ClfA would be a promising vaccine candidate against mastitis induced by eitherS. agalactiaeorS. aureus.
Aspergillus Species and Other Molds in Respiratory Samples from Patients with Cystic Fibrosis: a Laboratory-Based Study with Focus on Aspergillus fumigatus Azole Resistance
Authors: Mortensen Klaus Leth , Jensen Rasmus Hare , Johansen Helle Krogh , Skov Marianne , Pressler Tacjana , Howard Susan Julie , Leatherbarrow Howard , Mellado Emilia , Arendrup Maiken Cavling
Published: April 2011

Respiratory tract colonization by molds in patients with cystic fibrosis (CF) were analyzed, with particular focus on the frequency, genotype, and underlying mechanism of azole resistance among
Aspergillus fumigatus
isolates. Clinical and demographic data were also analyzed. A total of 3,336 respiratory samples from 287 CF patients were collected during two 6-month periods in 2007 and 2009. Azole resistance was detected using an itraconazole screening agar (4 mg/liter) and the EUCAST method.
cyp51A
gene sequencing and microsatellite genotyping were performed for isolates from patients harboring azole-resistant
A. fumigatus. Aspergillus
spp. were present in 145 patients (51%), of whom 63 (22%) were persistently colonized. Twelve patients (4%) harbored other molds. Persistently colonized patients were older, provided more samples, and more often had a chronic bacterial infection. Six of 133 patients (4.5%) harbored azole-nonsusceptible or -resistant
A. fumigatus
isolates, and five of those six patients had isolates with Cyp51A alterations (M220K, tandem repeat [TR]/L98H, TR/L98H-S297T-F495I, M220I-V101F, and Y431C). All six patients were previously exposed to azoles. Genotyping revealed (i) microevolution for
A. fumigatus
isolates received consecutively over the 2-year period, (ii) susceptible and resistant isolates (not involving TR/L98H isolates) with identical or very closely related genotypes (two patients), and (iii) two related susceptible isolates and a third unrelated resistant isolate with a unique genotype and the TR/L98H resistance combination (one patient). Aspergilli were frequently found in Danish CF patients, with 4.5% of the
A. fumigatus
isolates being azole nonsusceptible or resistant. Genotyping suggested selection of resistance in the patient as well as resistance being achieved in the environment.
RNA Elements Directing Translation of the Duck Hepatitis B Virus Polymerase via Ribosomal Shunting
Authors: Cao Feng , Tavis John E.
Published: April 2011

The duck hepatitis B virus (DHBV) reverse transcriptase (P) is translated from the downstream position on a bicistronic mRNA, called the pregenomic RNA, through a poorly characterized ribosomal shunt. Here, the positions of the discontinuous ribosomal transfer during shunting were mapped, and RNA elements important for shunting were identified as a prelude to dissecting the shunting mechanism. Mutations were introduced into the DHBV genome, genomic expression vectors were transfected into cells which support reverse transcription, and P translation efficiency was defined as the ratio of P/mRNA. Five observations were made. First, ribosomes departed from sequences that comprise the RNA stem-loop called ε that is key to viral replication, but the known elements of ε were not needed for shunting. Second, at least two landing sites for ribosomes were found on the mRNA. Third, all sequences upstream of ε, most sequences between the cap and the P AUG, and sequences within the P-coding region were dispensable for shunting. Fourth, elements on the mRNA involved in reverse transcription or predicted to be involved in shunting on the basis of mechanisms documented in other viruses, including short open reading frames near the departure site, were not essential for shunting. Finally, two RNA elements in the 5′ portion of the mRNA were found to assist shunting. These observations are most consistent with shunting being directed by signals that act through an uncharacterized RNA secondary structure. Together, these data indicate that DHBV employs either a novel shunting mechanism or a major variation on one of the characterized mechanisms.
A5-Positive Primary Sensory Neurons Are Nonpermissive for Productive Infection with Herpes Simplex Virus 1 In Vitro
Authors: Bertke Andrea S. , Swanson Sophia M. , Chen Jenny , Imai Yumi , Kinchington Paul R. , Margolis Todd P.
Published: April 2011

Herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) establish latency and express the latency-associated transcript (LAT) preferentially in different murine sensory neuron populations, with most HSV-1 LAT expression in A5
+
neurons and most HSV-2 LAT expression in KH10
+
neurons. To study the mechanisms regulating the establishment of HSV latency in specific subtypes of neurons, cultured dissociated adult murine trigeminal ganglion (TG) neurons were assessed for relative permissiveness for productive infection. In contrast to that for neonatal TG, the relative distribution of A5
+
and KH10
+
neurons in cultured adult TG was similar to that seen
in vivo
. Productive infection with HSV was restricted, and only 45% of cultured neurons could be productively infected with either HSV-1 or HSV-2. A5
+
neurons supported productive infection with HSV-2 but were selectively nonpermissive for productive infection with HSV-1, a phenomenon that was not due to restricted viral entry or DNA uncoating, since HSV-1 expressing β-galactosidase under the control of the neurofilament promoter was detected in ∼90% of cultured neurons, with no preference for any neuronal subtype. Infection with HSV-1 reporter viruses expressing enhanced green fluorescent protein (EGFP) from immediate early (IE), early, and late gene promoters indicated that the block to productive infection occurred before IE gene expression. Trichostatin A treatment of quiescently infected neurons induced productive infection preferentially from non-A5
+
neurons, demonstrating that the nonpermissive neuronal subtype is also nonpermissive for reactivation. Thus, HSV-1 is capable of entering the majority of sensory neurons
in vitro
; productive infection occurs within a subset of these neurons; and this differential distribution of productive infection is determined at or before the expression of the viral IE genes.
Human Immunodeficiency Virus Type 1 Modified To Package Simian Immunodeficiency Virus Vpx Efficiently Infects Macrophages and Dendritic Cells
Authors: Sunseri Nicole , O'Brien Meagan , Bhardwaj Nina , Landau Nathaniel R.
Published: April 2011

The lentiviral accessory protein Vpx is thought to facilitate the infection of macrophages and dendritic cells by counteracting an unidentified host restriction factor. Although human immunodeficiency virus type 1 (HIV-1) does not encode Vpx, the accessory protein can be provided to monocyte-derived macrophages (MDM) and monocyte-derived dendritic cells (MDDC) in virus-like particles, dramatically enhancing their susceptibility to HIV-1. Vpx and the related accessory protein Vpr are packaged into virions through a virus-specific interaction with the p6 carboxy-terminal domain of Gag. We localized the minimal Vpx packaging motif of simian immunodeficiency virus SIVmac
239
p6 to a 10-amino-acid motif and introduced this sequence into an infectious HIV-1 provirus. The chimeric virus packaged Vpx that was provided in
trans
and was substantially more infectious on MDDC and MDM than the wild-type virus. We further modified the virus by introducing the Vpx coding sequence in place of
nef
. The resulting virus produced Vpx and replicated efficiently in MDDC and MDM. The virus also induced a potent type I interferon response in MDDC. In a coculture system, the Vpx-containing HIV-1 was more efficiently transmitted from MDDC to T cells. These findings suggest that
in vivo
, Vpx may facilitate transmission of the virus from dendritic cells to T cells. In addition, the chimeric virus could be used to design dendritic cell vaccines that induce an enhanced innate immune response. This approach could also be useful in the design of lentiviral vectors that transduce these relatively resistant cells.
The Human Cytomegalovirus Gene Products Essential for Late Viral Gene Expression Assemble into Prereplication Complexes before Viral DNA Replication
Authors: Isomura Hiroki , Stinski Mark F. , Murata Takayuki , Yamashita Yoriko , Kanda Teru , Toyokuni Shinya , Tsurumi Tatsuya
Published: April 2011

The regulation of human cytomegalovirus (HCMV) late gene expression by viral proteins is poorly understood, and these viral proteins could be targets for novel antivirals. HCMV open reading frames (ORFs) UL79, -87, and -95 encode proteins with homology to late gene transcription factors of murine gammaherpesvirus 68 ORFs 18, 24, and 34, respectively. To determine whether these HCMV proteins are also essential for late gene transcription of a betaherpesvirus, we mutated HCMV ORFs UL79, -87, and -95. Cells were infected with the recombinant viruses at high and low multiplicities of infection (MOIs). While viral DNA was detected with the recombinant viruses, infectious virus was not detected unless the wild-type viral proteins were expressed in
trans
. At a high MOI, mutation of ORF UL79, -87, or -95 had no effect on the level of major immediate-early (MIE) gene expression or viral DNA replication, but late viral gene expression from the UL44, -75, and -99 ORFs was not detected. At a low MOI, preexpression of UL79 or -87, but not UL95, in human fibroblast cells negatively affected the level of MIE viral gene expression and viral DNA replication. The products of ORFs UL79, -87, and -95 were expressed as early viral proteins and recruited to prereplication complexes (pre-RCs), along with UL44, before the initiation of viral DNA replication. All three HCMV ORFs are indispensable for late viral gene expression and viral growth. The roles of UL79, -87, and -95 in pre-RCs for late viral gene expression are discussed.
Conserved GXXXG- and S/T-Like Motifs in the Transmembrane Domains of NS4B Protein Are Required for Hepatitis C Virus Replication
Authors: Han Qingxia , Aligo Jason , Manna David , Belton Kerry , Chintapalli Sree V. , Hong Yoojin , Patterson Randen L. , van Rossum Damian B. , Konan Kouacou V.
Published: April 2011

Hepatitis C virus (HCV) nonstructural protein 4B (NS4B) is an integral membrane protein, which plays an important role in the organization and function of the HCV replication complex (RC). Although much is understood about its amphipathic N-terminal and C-terminal domains, we know very little about the role of the transmembrane domains (TMDs) in NS4B function. We hypothesized that in addition to anchoring NS4B into host membranes, the TMDs are engaged in intra- and intermolecular interactions required for NS4B structure/function. To test this hypothesis, we have engineered a chimeric JFH1 genome containing the Con1 NS4B TMD region. The resulting virus titers were greatly reduced from those of JFH1, and further analysis indicated a defect in genome replication. We have mapped this incompatibility to NS4B TMD1 and TMD2 sequences, and we have defined putative TMD dimerization motifs (GXXXG in TMD2 and TMD3; the S/T cluster in TMD1) as key structural/functional determinants. Mutations in each of the putative motifs led to significant decreases in JFH1 replication. Like most of the NS4B chimeras, mutant proteins had no negative impact on NS4B membrane association. However, some mutations led to disruption of NS4B foci, implying that the TMDs play a role in HCV RC formation. Further examination indicated that the loss of NS4B foci correlates with the destabilization of NS4B protein. Finally, we have identified an adaptive mutation in the NS4B TMD2 sequence that has compensatory effects on JFH1 chimera replication. Taken together, these data underscore the functional importance of NS4B TMDs in the HCV life cycle.
The SUMOylation of Matrix Protein M1 Modulates the Assembly and Morphogenesis of Influenza A Virus
Authors: Wu Chung-Yi , Jeng King-Song , Lai Michael M.-C.
Published: April 2011

SUMOylation is an important posttranslational modification for regulation of cellular functions and viral replication. Here, we report that protein SUMOylation regulates the replication of influenza A virus at the steps of viral maturation and assembly. Knocking down the SUMO-conjugating enzyme Ubc9 resulted in the reduction of virus production. Dissection of the virus life cycle revealed that SUMOylation is involved in the processes of virus maturation and assembly. The viral matrix protein M1 is SUMOylated at K242. A virus carrying the SUMO-defective M1 produced a lower titer of virus, while its viral proteins and viral RNA (vRNA) accumulated in the cells. Furthermore, the mechanistic studies showed that the SUMOylation of M1 is required for the interaction between M1 and viral RNP (vRNP) to form the M1-vRNP complex. The lack of M1 SUMOylation prevented the nuclear export of vRNP and subsequent viral morphogenesis. Taken together, our findings elucidate that the maturation and assembly of influenza A virus is controlled by the SUMO modification of M1 protein. Therefore, we suggest that M1 can serve as a target for developing a new generation of drugs for flu therapy.
NF-κB-Mediated Modulation of Inducible Nitric Oxide Synthase Activity Controls Induction of the Epstein-Barr Virus Productive Cycle by Transforming Growth Factor Beta 1
Authors: Oussaief Lassad , Ramírez Vanessa , Hippocrate Aurélie , Arbach Hratch , Cochet Chantal , Proust Alexis , Raphaël Martine , Khelifa Ridha , Joab Irène
Published: April 2011

Transforming growth factor beta 1 (TGF-β1) signal transduction has been implicated in many second-messenger pathways, including the NF-κB pathway. We provide evidence of a novel TGF-β1-mediated pathway that leads to extracellular signal-regulated kinase (ERK) 1/2 phosphorylation, which in turn induces expression of an Epstein-Barr virus (EBV) protein, ZEBRA, that is responsible for the induction of the viral lytic cycle. This pathway includes two unexpected steps, both of which are required to control ERK 1/2 phosphorylation: first, a quick and transient activation of NF-κB, and second, downregulation of inducible nitric oxide synthase (iNOS) activity that requires the participation of NF-κB activity. Although necessary, NF-κB alone is not sufficient to produce downregulation of iNOS, suggesting that another uncharacterized event(s) is involved in this pathway. Dissection of the steps involved in the switch from the EBV latent cycle to the lytic cycle will be important to understand how virus-host relationships modulate the innate immune system.
The Single RBP-Jκ Site within the LANA Promoter Is Crucial for Establishing Kaposi's Sarcoma-Associated Herpesvirus Latency during Primary Infection
Authors: Lu Jie , Verma Subhash C. , Cai Qiliang , Robertson Erle S.
Published: April 2011

Kaposi's sarcoma-associated herpesvirus (KSHV; or human herpesvirus 8 [HHV8]) is implicated in the pathogenesis of many human malignancies including Kaposi's sarcoma (KS), multicentric Castleman's disease (MCD), and primary effusion lymphoma (PEL). KSHV infection displays two alternative life cycles, referred to as the latent and lytic or productive cycle. Previously, we have reported that the replication and transcription activator (RTA), a major lytic cycle transactivator, contributes to the development of KSHV latency by inducing latency-associated nuclear antigen (LANA) expression during early stages of infection by targeting RBP-Jκ, the master regulator of the Notch signaling pathway. Here, we generated a bacterial artificial chromosome (BAC) KSHV recombinant virus with a deletion of the RBP-Jκ site within the LANA promoter to evaluate the function of the RBP-Jκ cognate site in establishing primary latent infection. The results showed that genetic disruption of the RBP-Jκ binding site within the KSHV LANA promoter led to enhanced expression of the KSHV-encoded immediate early RTA, resulting in an increase in lytic replication during primary infection of human peripheral blood mononuclear cells (PBMCs). This system provides a powerful tool for use in indentifying additional cellular and viral molecules involved in LANA-mediated latency maintenance during the early stages of KSHV infection.
Prevention of sports injury I: a systematic review of applied biomechanics and physiology outcomes research
Authors: McBain Kellen , Shrier Ian , Shultz Rebecca , Meeuwisse Willem H , Klügl Martin , Garza Daniel , Matheson Gordon O
Published: April 2011

Objective

To analyse published articles that used interventions aimed at investigating biomechanical/physiological outcomes (ie, intermediate risk factors) for sport injury prevention in order to characterise the state of the field and identify important areas not covered in the literature.

Data sources

PubMed, Cinahl, Web of Science and Embase were searched using a broad search strategy.

Main results

Only 144 of 2525 articles retrieved by the search strategy met the inclusion criteria. Crossover study designs increased by 175% in the late 1980s until 2005 but have declined 32% since then. Randomised controlled trial (RCT) study designs increased by 650% since the early 1980s. Protective equipment studies (61.8% of all studies) declined by 35% since 2000, and training studies (35.4% of all studies) increased by 213%. Equipment research studied stability devices (83.1%) and attenuating devices (13.5%) whereas training research studied balance and coordination (54.9%), strength and power (43.1%) and stretching (15.7%). Almost all (92.1%) studies investigated the lower extremity and 78.1% were of the joint (non-bone)-ligament type. Finally, 57.5% of the reports studied contact sports, 24.2% collision and 25.8% non-contact sports.

Conclusion

The decrease in crossover study design and increase in RCTs over time suggest a shift in study design for injury prevention articles. Another notable finding was the change in research focus from equipment interventions, which have been decreasing since 2000 (35% decline), to training interventions, which have been increasing (213% increase). Finally, there is very little research on overuse or upper extremity injuries.
A new VO2maxprotocol allowing self-pacing in maximal incremental exercise
Authors: Mauger Alexis R , Sculthorpe Nick
Published: April 2011

Introduction The traditional maximal oxygen uptake (VO2max) protocol has received criticism for being an unnatural form of exercise, lacking ecological validity and producing different VO2maxresponses depending on protocol duration and work rate increments.

Purpose The purpose of this investigation was to design and test a new VO2maxprotocol allowing subjects to self-pace their work rate while maintaining an incremental test structure.

Methods

16 untrained subjects completed a self-paced VO2maxprotocol (SPV) and a traditional VO2maxtest in a counter-balanced, crossover design. The SPV used incremental ‘clamps’ of ratings of perceived exertion (RPE) over 5 × 2-min stages (10-min duration) while allowing subjects to vary their power output (PO) according to the required RPE.

Results

Subjects achieved significantly higher (p < 0.05) VO2maxvalues (40 ± 10 ml/kg/min vs 37 ± 8 ml/kg/min) and peak POs (273 ± 58 W vs 238 ± 55 W) in the SPV. Higher VO2maxvalues were observed in the SPV even when a plateau (VO2–time slope <0.05 l/min) occurred in the traditional test. No differences were found between any other measured physiological variable (minute ventilation, heart rate and respiratory exchange ratio).

Conclusions

As SPV is a closed-loop test (10-min duration) that allows subjects to self-pace their work rate, it disregards the need for experimenters to estimate starting work rates, stage lengths and increments in order to bring about volitional exhaustion in 8–10 min. The observation that the SPV may also elicit higher VO2maxvalues than a traditional test warrants further research in this area and its consideration as standard measure to elicit VO2max.
Reflecting on senior medical students' ethics reports at the University of Auckland
Authors: Malpas Phillipa J
Published: April 2011

In January 2010, fifth year medical students in the medical programme at the University of Auckland were asked to write a 1200-word report as part of their ethics assessment. The purpose of the report was to get students to reflect critically on the ethical dimension of a clinical case or situation they had been involved in during the past 2 years. Students were required to identify and discuss the salient ethical issues that arose as they saw them, and consider what they had personally learnt from the situation. The purpose of the following discussion is twofold: first, to outline some of the ethical issues raised by year five medical students in their ethics reports; and second, to reflect on what we, as educators and health professionals can learn from their experiences and insights.
Creutzfeldt–Jacob disease mimics, or how to sort out the subacute encephalopathy patient
Authors: Murray Katherine
Published: April 2011

Sporadic Creutzfeldt–Jacob disease (CJD) is a rare untreatable neurodegenerative disease which every neurologist will occasionally encounter during their career. However, it is likely to appear on their differential diagnosis list significantly more frequently. Numerous conditions can present with subacute encephalopathy which might be sporadic CJD and this article explores these diagnoses. It includes the commonest sporadic CJD mimics which are neurodegenerative, and highlights the relatively rare treatable mimics which must not be missed. It discusses relevant investigations, including serum antibodies, CSF, electroencephalography and MR brain imaging, and strategies when preliminary investigations fail to support sporadic CJD but no alternative diagnosis is readily apparent.
Effect of induction dose, lactation stage and body condition on tiletamine‐zolazepam anaesthesia in adult female grey seals (Halichoerus grypus) under field conditions
Authors: Langton S. D. , Moss S. E. , Pomeroy P. P. , Borer K. E.
Published: April 2011

Tiletamine‐zolazepam (TZ) was used at a mean (sd) dose of 1.18 (0.15) mg/kg administered intramuscularly to anaesthetise adult female grey seals (Halichoerus grypus) under field conditions at three different stages during their lactation period. A significant correlation was observed between the induction dose and time to induction (r=–0.582, P=0.011). Stage of lactation had a significant effect on condition index (CI), calculated as axial girth divided by length (P<0.001), and time to induction (P=0.009). No effect of CI on induction or recovery time was demonstrated. Respiratory rate decreased during induction and increased significantly (P<0.001) during surgical biopsy of blubber. Recovery occurred after 32.5 (11.9) minutes. Minor complications (tremor, vocalisation and mild dyspnoea) were observed in a small number of cases, none of which required treatment.
Thyroid Hormone Concentrations and Muscle Metabolism in Amenorrheic and Eumenorrheic Athletes
Authors: Harber Vicki J. , Petersen Stewart R. , Chilibeck Philip D.
Published: April 2011

The relationship between resting thyroid hormone concentrations and exercise muscle metabolism was examined among eumenorrheic endurance-trained (n = 11), amenorrheic endurance-trained (n = 8), and eumenorrheic nonathletic (n = 13) subjects. Muscle metabolism was assessed with 31Phosphorous magnetic resonance spectroscopy by measuring changes in phosphocreatine (PCr), inorganic phosphate (Pi), and pH during plantar flexion exercise and recovery. All groups had similar Pi/PCr ratios and pH changes during exercise. Eumenorrheic endurance-trained subjects had faster recovery rates for PCr and Pi/PCr following exercise compared to the nonathletes (p < .05) and faster recovery rates for PCr compared to amenorrheic subjects (p < .05). Thyroxine (T4) and triiodothyronine (T3) levels were significantly lower in amenorrheic subjects compared to both eumenorrheic groups (p < .05). It was concluded that routine training enhances muscle metabolism, as measured by phosphate recovery kinetics. This enhancement was not evident in amenorrheic athletes with reduced T3 and T4 concentrations. Key words:31Phosphorous magnetic resonance spectroscopy, phosphocreatine, inorganic phosphate, T3, T4, females
Linker DNA destabilizes condensed chromatin
Authors: Green G R , Ferlita R R , Walkenhorst W F , Poccia D L
Published: April 2011

The contribution of the linker region to maintenance of condensed chromatin was examined in two model systems, namely sea urchin sperm nuclei and chicken red blood cell nuclei. Linkerless nuclei, prepared by extensive digestion with micrococcal nuclease, were compared with Native nuclei using several assays, including microscopic appearance, nuclear turbidity, salt stability, and trypsin resistance. Chromatin in the Linkerless nuclei was highly condensed, resembling pyknotic chromatin in apoptotic cells. Linkerless nuclei were more stable in low ionic strength buffers and more resistant to trypsin than Native nuclei. Analysis of histones from the trypsinized nuclei by polyacrylamide gel electrophoresis showed that specific histone H1, H2B, and H3 tail regions stabilized linker DNA in condensed nuclei. Thermal denaturation of soluble chromatin preparations from differentially trypsinized sperm nuclei demonstrated that the N-terminal regions of histones Sp H1, Sp H2B, and H3 bind tightly to linker DNA, causing it to denature at a high temperature. We conclude that linker DNA exerts a disruptive force on condensed chromatin structure which is counteracted by binding of specific histone tail regions to the linker DNA. The inherent instability of the linker region may be significant in all eukaryotic chromatins and may promote gene activation in living cells.Key words: chromatin condensation, sea urchin sperm, chicken red blood cell, nuclei, linker DNA, histone variants, micrococcal nuclease, nucleosome, trypsin, gel electrophoresis.