bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Ventilation Design Using CFD
Authors: Wark Christopher
Published: February 2009

In an effort to make buildings healthier and more energy efficient, architects are increasingly incorporating natural ventilation into their design strategies in order to take advantage of free, available wind power. The extent to which natural ventilation can replace forced ventilation in a given building depends on the local climate and specific site utilization. The ASHRAE Standards 55 and 62.1 that cover natural ventilation establish minimal requirements for climate and building openings but also concede that the ultimate responsibility for proving the effectiveness of this technique lies with the design team and the specific requirements of local codes. But how does a design team prove that air is flowing according to plan without actually creating the structure and taking measurements? Only two possibilities exist — regard each room as a very large ratio conduit and apply conventional equations to those spaces, or do a 3-dimensional numerical analysis of the flow path. Numerical analysis, known as Computational Fluid Dynamics (CFD), is now being recognized as the only reliable way to predict natural airflow through a building and assure that adequate air quality and comfort is provided at all points of each room before construction begins. CFD computer programs allow designers to divide a volume into a large number of small regions and calculate the air and heat transfer between each region, minimizing the assumption-related errors that would otherwise occur. Minimizing computational error at the beginning of the design process reduces the risk of costly post-construction order changes that can occur as substandard air quality is discovered. CFD software can vary in its level of sophistication. While the most basic Navier-Stokes heat and mass transfer equations are essential and can be of great use, a proper natural ventilation analysis tool should include calculations for buoyancy, turbulent convection, and the ability to do open boundary modeling. Other features such as local solar loading and transient analysis are also desirable. A comprehensive CFD package can be particularly useful for modeling the complex airflow found in mixed-mode designs and identifying regions of stagnant air, high heat loss or gain, short-circuited airflow, and other conditions that inhibit good building performance and limit the potential for sustainability.
Design to Maximize Performance of a Thermoelectric Power Generator With a Dynamic Thermal Power Source
Authors: Crane Douglas T. , Bell Lon E.
Published: February 2009

It is a difficult technical challenge to design thermoelectric power generation systems that work optimally over a broad dynamic range of thermal input power. Conventional systems are designed to work optimally for a nominal operating condition, while maintaining the ability to operate at off nominal and extreme operating conditions without damage to the system. For systems that operate in a narrow range of thermal power conditions, thermoelectric waste heat recovery system design is simplified. However, for applications that do have a wide range of operating conditions, designs typically exhibit overall average efficiencies that are reduced by approximately 20% or more compared to that achievable for the thermoelectric material operating at peak efficiency. Both cars and trucks consume significant fuel at low mass flow rates. Since the ultimate goal of waste heat recovery systems is to minimize fuel consumption, it is critical that the recovery system be designed to operate near peak efficiency over the range of mass flow rates that make a significant contribution to overall power recovery. Such performance capability is especially important in city driving, and in hybrid vehicle applications. This paper describes a design concept that maximizes the performance for thermoelectric power generation systems in which the thermal power to be recovered is from a fluid stream (e. g. exhaust gas) subject to varying temperatures and a broad range of fuel flow rates. The device is constructed in several parts, with each part optimized for a specific range of operating conditions. The thermoelectric system characteristics, inlet mass flow rates and fluid temperatures, and load and internal electrical resistances are monitored and generator operation is controlled to maximize performance. With this design, the system operates near optimal efficiency for a much wider range of operating conditions. Application of the design concept to an automobile is used to show the benefits to overall system performance.
Aerodynamics Performance Test of a High-Speed Miniature Centrifugal Compressor
Authors: Zhou Lei , Acharya Dipjyoti , Kapat Jayanta , Chow Louis , Arakere Nagaraj
Published: February 2009

Reverse Turbo-Brayton cryocooler (RTBC) is a possible solution for NASA long term Zero-Boil-off (ZBO) hydrogen storage system for future space missions. RTBC cryocooler can have similar thermal efficiency as the current state-of-the-art LH2 cryocoolers with much less weight and size. The miniature helium compressor is the key component for this system, because it contributes the major portion in weight reduction. The present paper concentrates on the performance evaluation of an aerodynamically scaled miniature single-stage air compressor design, which is the first stage in the prototype of the future two-stage inter-cooled helium compressor. The single stage centrifugal compressor, designed by the authors, features a radial impeller, an axial diffuser driven by an integrated high speed permanent magnet synchronous motor run on ceramic ball bearings. In this paper, issues addressing performance of a miniature machine such as the present integrated single-stage centrifugal compressor and issues including thermal management, rotordynamics, effect of blade tip clearance, testing techniques are discussed. According to the test results, the design of the single stage was successful and established a solid base for the future two-stage helium compressor design.
Comparison of Multi-Tank and Large Single Tank Thermal Storages for Solar DHW Applications
Authors: Cruickshank Cynthia A. , Harrison Stephen J.
Published: February 2009

The performance of a multi-tank water storage was studied by experiment and computer simulation. The unit investigated consisted of three 270 L storage tanks connected in series and was charged through individual side-arm, natural convection heat exchangers. Laboratory tests were conducted on a specially instrumented prototype to characterize its performance in terms of temperature stratification, heat transfer and energy storage rates. Based on these tests, a computer model of a complete multi-tank solar thermal system was created. With this model, the performance of a multi-unit storage was compared to a single-tank system of equal total storage volume for a multi-family solar domestic hot water (SDHW) system application. Data were produced for two U.S. locations representative of differing climatic locations. Results show that a reasonably insulated multi-tank system can be used in place of a large single tank with only a small reduction in delivered solar energy.
Measurement Techniques for the Optical Quality Assessment of Parabolic Trough Collector Fields in Commercial Solar Power Plants
Authors: Ulmer Steffen , Pottler Klaus , Lu¨pfert Eckhard , Ro¨ger Marc
Published: February 2009

The optical quality of the collector field of concentrating solar power plants is an essential factor for their profitability. High optical quality can be achieved and guaranteed when the manufacturing process is continuously monitored and adjusted in its essential steps. A stationary, automatic photogrammetry system has been developed for the shape accuracy control of concentrator structures. It uses a digital camera, automatically moved around the object, computer controlled automatic image evaluation and continuous calibration checks. It is robust and fast enough to be integrated in a solar collector production line. For on-site measurements of mirror slope in parabolic trough collector fields, a new method is presented. It uses a set of pictures of the reflections of the absorber tube in the concentrator. The slope errors of the mirror surface are calculated with high spatial resolution and accuracy. The effects of the reflector slope deviations on the optical performance are evaluated with ray-tracing. The results give detailed information about the optical quality of the concentrator, inaccuracies in the manufacturing process, and their optical performance penalty.
A Simplified Method to Estimate Cooling Energy Savings From Night Ventilation for Office Buildings
Authors: Liu Xiang , Krarti Moncef
Published: February 2009

This paper provides a simplified analysis method and to evaluate the potential of night ventilation to save cooling energy for office buildings. Specifically, impacts on cooling energy performance are investigated for various combinations of night ventilation flow rates and duration periods. The analysis results indicate that an increase of ventilation duration period and volume rate leads to greater night ventilation benefits for dwellings located in Denver, CO. However, an increase of the ventilation volume rate above 5 air changes per hour has a little impact on cooling energy savings. When the ventilation period is short (less than 10 hours), and the flow rate is high (more than 3 ACH), the cooling energy savings from night ventilation increase linearly with the ventilation duration period length. A simplified calculation method has been developed based on the results of a series of parametric simulation analyses. Commercial building designers and operators can use the proposed simplified calculation tool to assess the effectiveness of night ventilation in reducing cooling energy use.
Comprehensive Evaluation of Impacts From Potential, Future Automotive Fuel Replacements
Authors: Kreider Jan F. , Curtiss Peter S.
Published: February 2009

In modern society, everything from transportation to commerce to food supply is heavily dependent on the availability of cheap and plentiful energy supplies. In the past few years many have realized that the traditional sources of energy — oil and gas — are in limited supply and that we need to prepare for the approaching production maxima. It is in the interest of national economic security to investigate alternative sources of transportation energy before the extraction of existing supplies becomes prohibitively expensive. This meta-study investigates a number of potential fuels and their sources, including: • agricultural solutions - ethanol (corn and cellulosic), • agricultural solutions - biodiesel, • unconventional refining techniques such as coal-to-liquid, • oil shale retorting and tar sand processing, • traditional petroleum sources. The concentration in the current study is on transportation needs, although it is recognized that building space conditioning and electricity consumption are also significant demands for energy. The results are reported for land use, water use, input-to-output energy ratio, and carbon emissions for each fuel cycle and source. Data are given for the cases of 10, 25, and 50 percent displacements of the 2012 predicted transportation energy needs (i.e., the equivalent of 430 million gallons of gasoline per day). Cradle to grave findings indicate that some novel fuels cannot substitute for conventional fuels without consuming more water or land and emitting more greenhouse gases than fuels in use today. The most sustainable direction for the US transportation fuels sector is suggested.
Modeling of a Multi-Tube Solar Reactor for Hydrogen Production at High Temperatures
Authors: Haussener Sophia , Hirsch David , Perkins Christopher , Weimer Alan , Lewandowski Allan , Steinfeld Aldo
Published: February 2009

The thermo chemical dissociation of zinc oxide is the first step in a two-step water splitting cycle to produce hydrogen. In previous work, the dissociation of zinc oxide has been investigated in a single-tube solar reactor that was enclosed in a sealed quartz tube and irradiated by concentrated sunlight. That reactor concept allowed the successful demonstration of the zinc oxide dissociation in the temperature range 1500–2100 K at the High-Flux Solar Furnace (HFSF) at NREL in Golden, CO. The current modeling work focuses on the further development and optimization of the previously tested reactor design. The commercial software FLUENT is used to run simulations in 2 and in 3 dimensions. The new design consists of a multitube configuration in a closed cavity with a small aperture. The inner cavity wall has a layer of a highly reflective material. Parametric simulation studies have been conducted in order to investigate the influence of parameters such as solar flux concentration, number of tubes, tube size, zinc oxide mass flow and particle size (0.06 and 1 micrometer) on the overall efficiency. Solar average flux concentrations of 3000 and 6000 suns have been chosen. The secondary concentrator currently used at NREL (∼2000 suns average flux) will have to be redesigned in order to achieve about 3000 suns average flux. Between 3 and 10 tubes that are circularly positioned in the cavity have been simulated. The zinc oxide mass flow ranges from 2–20 g/min per tube. In 2D, an energy sink equation is incorporated that accounts for the heating-up of the inert gas and the zinc oxide particles and for the heat of reaction. The heat of reaction is calculated using a set of Arrhenius-type kinetic parameters that were determined experimentally. The simulation results show that the flux concentration, the zinc oxide mass flow and the number of tubes have the most significant effect on the thermal efficiency of the reactor. Conclusions are: 1) A reaction efficiency (energy solely used by the chemical reaction divided by the solar input) of about 29% with a total efficiency of about 36% is achievable. 2) Complete conversion can be obtained at temperatures in the order of 2000 K. 3) In a design for NREL’s HFSF (∼8 kW solar input power) a total zinc oxide mass flow of about 30 g/min is optimal. 4) More and smaller tubes lead to higher efficiencies. In the coming months, a new reactor will be constructed and tested at NREL’s HFSF.
Computational Fluid Dynamics Simulation of a Tubular Aerosol Reactor for Solar Thermal ZnO Decomposition
Authors: Perkins Christopher , Weimer Alan W.
Published: February 2009

Computational fluid dynamics simulations were performed to model solar ZnO dissociation in a tubular aerosol reactor at ultra-high temperatures (1900 K–2300 K). Reactor aspect ratios ranged between 0.15 and 0.45, with the smallest ratio base case corresponding to a reactor diameter of .02286 m. Gas flowrates were set such that the Ar:ZnO ratio was greater than 3:1 and the system residence time was below 2 s. The system was found to exhibit highly laminar flow in all cases (Re ∼ 10), but gas velocity profiles did not seriously affect temperature profiles. Particle heating was nearly instantaneous, a result of the high radiation heat flux from the wall. There was essentially no difference between gas and particle temperatures due to the high surface area for conductive heat exchange between the phases. Calculation of ZnO conversion showed that significant conversions (>90%) could be attained for residence times typical of rapid aerosol processing. Particle sizes larger than 1 μm negatively affected conversion, but sizes of 10 μm still gave acceptable conversion levels. Simulation of reaction of product oxygen with the reactor wall showed that a reactor constructed of an oxidation-sensitive material would not be a viable choice for a high temperature solar reactor.
Performance Simulation of a Combined Cycle Power Generation System With Steam Injection in the Gas Turbine Combustion Chamber
Authors: Law B. , Reddy B. V.
Published: February 2009

In the present work the effect of steam injection in the gas turbine combustion chamber is investigated on gas turbine and steam turbine work output and on thermal efficiency of the combined cycle power plant. The operating conditions investigated include gas turbine pressure ratio and gas turbine inlet temperature. The steam injection decreases the steam cycle output and boosts the gas cycle output and the net combined cycle work output and thermal efficiency significantly.
Effects of Intake Air Cooling Performance Improvement on a Two-Shaft Laboratory-Scale Gas Turbine Unit
Authors: Al-Madani Hussain , Ayhan Teoman , Al-Abbasi Omar
Published: February 2009

The present study deals with the thermodynamically modelled two-shaft gas turbine system consisting of a cooling unit at the compressor inlet. The system is used to investigate the generated power, thermal efficiency and second law efficiency. The parametric study using this model shows effect of ambient conditions, compressor inlet temperature, and pressure ratios on power output, thermal efficiency and second law efficiency. Theoretical results using the proposed model show that when the compressor inlet temperature is decreased by some kind of cooling systems, the net power output and thermal efficiency increases up to 30% and 23%, respectively. Also, the second law efficiency of the proposed system increases in compression to the specified reference state. It shows that the proposed model is thermodynamically viable. A comparison of the performance test results of the model and the experimental results are in good agreement. The results provide valuable information regarding the gas turbine system and will be useful for designers.
Exergetic Assessment of a Turbocharged Stationary Diesel Engine
Authors: Kanoglu Mehmet , Dincer Ibrahim , Rosen Marc A.
Published: February 2009

An exergetic analysis is presented of a turbocharged stationary diesel engine with a power output of about 19 MW. The system studied consists of a diesel engine, a turbine, a compressor, an intercooler and a radiator. The sites of exergy destructions are identified and quantified and the exergy efficiencies of various components determined. The exergy efficiency of the engine is found to be 40.5% at the specified reference state. The greatest exergy destruction occurs in the engine itself, which account for 84% of total exergy destruction in the system. A parametric investigation shows that the exergy losses of all system components increase with increasing reference-environment temperature. The results provide valuable information regarding the exergetic characteristics of turbocharged stationary diesel engines and appear to be useful for designers. The use of turbocharged stationary diesel engines has increased considerably in recent years as potential small-scale power generating solutions and in vehicle applications, due to their good power output, which helps overcome problems associated with some extreme operating conditions.
Optimization of a Mesoscale Combustor Using Heat Recirculation and Porous Inert Media
Authors: Deal Benjamin , Marbach Timothy L.
Published: February 2009

Continuous improvement of integrated circuitry has allowed for the development of small, sophisticated portable electronics and microelectromechanical systems (MEMS) for a wide range of applications. Compared to the electronics and other system components, the batteries powering small electronics and MEMS are large and heavy. Thus, smaller and lighter power systems are required to advance future products. Electricity for small systems may be supplied by miniature heat engines, which transform chemical energy of fuel into thermal energy, kinetic energy and electricity with the use of combustors, turbines and generators. Combustion at small scales is challenging because system heat losses to the surroundings are large and flow residence times are short. Heat recirculation can be used to improve combustion performance by reducing these heat losses and preheating reactants prior to ignition. Practical heat recirculation systems must be small to keep the overall system volume and mass small. The objectives of this study were: (a) to investigate heat transfer in miniature combustors, and (b) to identify effective means of reducing heat loss from small combustors. The analyses indicated that axial conduction through the combustor wall and radiation across the preheating annulus were the most significant pathways for heat loss from the system. Several design improvements, including extended surfaces and porous inert media (PIM) were analyzed. A design featuring PIM in the annulus with a gap between the PIM and outer wall was the most effective method of reducing system heat loss.
RNA Polymerase IV Functions in Paramutation in
Zea mays
Authors: Erhard Karl F. , Stonaker Jennifer L. , Parkinson Susan E. , Lim Jana P. , Hale Christopher J. , Hollick Jay B.
Published: February 2009

Plants have distinct RNA polymerase complexes (Pol IV and Pol V) with largely unknown roles in maintaining small RNA–associated gene silencing. Curiously, the eudicot
Arabidopsis thaliana
is not affected when either function is lost. By use of mutation selection and positional cloning, we showed that the largest subunit of the presumed maize Pol IV is involved in paramutation, an inherited epigenetic change facilitated by an interaction between two alleles, as well as normal maize development. Bioinformatics analyses and nuclear run-on transcription assays indicate that Pol IV does not engage in the efficient RNA synthesis typical of the three major eukaryotic DNA-dependent RNA polymerases. These results indicate that Pol IV employs abnormal RNA polymerase activities to achieve genome-wide silencing and that its absence affects both maize development and heritable epigenetic changes.
Global Cooling During the Eocene-Oligocene Climate Transition
Authors: Liu Zhonghui , Pagani Mark , Zinniker David , DeConto Robert , Huber Matthew , Brinkhuis Henk , Shah Sunita R. , Leckie R. Mark , Pearson Ann
Published: February 2009

About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature changed during this climate transition remains poorly understood, and evidence for Northern Hemisphere polar ice is controversial. Here, we report proxy records of sea surface temperatures from multiple ocean localities and show that the high-latitude temperature decrease was substantial and heterogeneous. High-latitude (45 degrees to 70 degrees in both hemispheres) temperatures before the climate transition were ∼20°C and cooled an average of ∼5°C. Our results, combined with ocean and ice-sheet model simulations and benthic oxygen isotope records, indicate that Northern Hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time.
Conductance of a Single Conjugated Polymer as a Continuous Function of Its Length
Authors: Lafferentz Leif , Ample Francisco , Yu Hao , Hecht Stefan , Joachim Christian , Grill Leonhard
Published: February 2009

The development of electronic devices at the single-molecule scale requires detailed understanding of charge transport through individual molecular wires. To characterize the electrical conductance, it is necessary to vary the length of a single molecular wire, contacted to two electrodes, in a controlled way. Such studies usually determine the conductance of a certain molecular species with one specific length. We measure the conductance and mechanical characteristics of a single polyfluorene wire by pulling it up from a Au(111) surface with the tip of a scanning tunneling microscope, thus continuously changing its length up to more than 20 nanometers. The conductance curves show not only an exponential decay but also characteristic oscillations as one molecular unit after another is detached from the surface during stretching.
Synchronous Hyperactivity and Intercellular Calcium Waves in Astrocytes in Alzheimer Mice
Authors: Kuchibhotla Kishore V. , Lattarulo Carli R. , Hyman Bradley T. , Bacskai Brian J.
Published: February 2009

Although senile plaques focally disrupt neuronal health, the functional response of astrocytes to Alzheimer's disease pathology is unknown. Using multiphoton fluorescence lifetime imaging microscopy in vivo, we quantitatively imaged astrocytic calcium homeostasis in a mouse model of Alzheimer's disease. Resting calcium was globally elevated in the astrocytic network, but was independent of proximity to individual plaques. Time-lapse imaging revealed that calcium transients in astrocytes were more frequent, synchronously coordinated across long distances, and uncoupled from neuronal activity. Furthermore, rare intercellular calcium waves were observed, but only in mice with amyloid-β plaques, originating near plaques and spreading radially at least 200 micrometers. Thus, although neurotoxicity is observed near amyloid-β deposits, there exists a more general astrocyte-based network response to focal pathology.
Prospective Nationwide Study of
Aeromonas
Infections in France
Authors: Lamy Brigitte , Kodjo Angeli , Laurent Frédéric
Published: February 2009

We report a systematic prospective multicenter nationwide study of clinical
Aeromonas
infections in France. During 6 months (May to October 2006), 78 cases of aeromonosis were reviewed for risk factors and clinical, microbiological, and antimicrobial susceptibility data. They included wound infections (44%), bacteremia (26%), enteritis (19%), respiratory tract infections (6%), and miscellaneous (5%) infections.
Staphylococcus lugdunensis
, a Common Cause of Skin and Soft Tissue Infections in the Community
Authors: Böcher Sidsel , Tønning Birgitte , Skov Robert L. , Prag Jørgen
Published: February 2009

Staphylococcus lugdunensis
, a rare cause of severe infections such as native valve endocarditis, often causes superficial skin infections similar to
Staphylococcus aureus
infections. We initiated a study to optimize the identification methods in the routine laboratory, followed by a population-based epidemiologic analysis of patients infected with
S. lugdunensis
in Viborg County, Denmark. Recognition of a characteristic
Eikenella corrodens
-like odor on Columbia sheep blood agar combined with colony pleomorphism and prominent β-hemolysis after 2 days of incubation, confirmed by API-ID-32 Staph, led to an 11-fold increase in the detection of
S. lugdunensis
. By these methods we found 491
S. lugdunensis
infections in 4 years, corresponding to an incidence of 53 per 100,000 per year, an increase from 5 infections per 100,000 inhabitants in the preceding years. Seventy-five percent of the cases were found in general practice; these were dominated by skin abscesses (36%), wound infections (25%), and paronychias (13%). Fifty-six percent of the infections occurred below the waist, and toes were the most frequently infected site (21%). Only 3% of the patients suffered from severe invasive infections. The median age was 52 years, and the male/female ratio was 0.69. Our study shows that
S. lugdunensis
is a common cause of skin and soft-tissue infections (SSTI) and is probably underrated by many laboratories.
S. lugdunensis
should be accepted as a significant pathogen in SSTI and should be looked for in all routine bacteriological examinations, and clinicians should be acquainted with the name and the pathology of the bacterium.
Multiplexed Real-Time PCR Assay for Discrimination of
Plasmodium
Species with Improved Sensitivity for Mixed Infections
Authors: Shokoples Sandra E. , Ndao Momar , Kowalewska-Grochowska Kinga , Yanow Stephanie K.
Published: February 2009

The implementation of real-time PCR for the diagnosis of malaria has been hampered by poor sensitivity for the detection of mixed infections. We have optimized a method that enhances the sensitivity of detection of minor species in mixed infections within a single multiplex reaction. Our assay uses species-specific forward primers in combination with a conserved reverse primer and largely overcomes primer competition for the minor species DNA. With a blind panel of clinical samples, we successfully identified the species in 13/16 mixed infections. This assay was further validated with 91 blood samples and demonstrated a specificity and sensitivity for single infections of 100% compared with nested PCR as the “gold standard.” This test has been implemented for routine confirmation of malaria species in Alberta, Canada. In comparison with species identification by microscopy, the real-time PCR test demonstrated greater sensitivity for the identification of species causing low-level and mixed infections and for the discrimination of
Plasmodium
species other than
Plasmodium falciparum
. Our experience supports a role for real-time PCR in the identification of malarial species in conjunction with microscopy.
Molecular Diagnosis of Disseminated Adiaspiromycosis Due toEmmonsia crescens
Authors: Dot J.-M. , Debourgogne A. , Champigneulle J. , Salles Y. , Brizion M. , Puyhardy J. M. , Collomb J. , Plénat F. , Machouart M.
Published: February 2009

Emmonsia crescensis a saprophytic fungus that is distributed worldwide, causing diseases mostly in rodents. It has also been described, though rarely, as an etiologic agent of pulmonary pathology in humans, potentially leading to death. A case of pulmonary adiaspiromycosis is reported in a 30-year-old immunocompetent man. The patient presented with a history of several weeks of weakness, cough, fever, and weight loss of 10 kg. Clinical and radiographic findings showed pulmonary lesions consistent with tuberculosis or histoplasmosis, but no pathogen was found with classical microbiological procedures. The diagnosis of adiaspiromycosis due toEmmonsia crescenswas initially made using molecular biology techniques. Histological observations subsequently confirmed the presence of adiaspores in granulomas. To our knowledge, this is the first case of adiaspiromycosis diagnosed by PCR and sequencing. The patient was treated with itraconazole and was seen at 1 month with symptomatic improvement. Here we will discuss this rare fungal infection and its difficult treatment and diagnosis. As represented in this case, molecular biology is a powerful method to optimize diagnostic tests and therefore improve the care of the infected patient.
Rotavirus Antagonizes Cellular Antiviral Responses by Inhibiting the Nuclear Accumulation of STAT1, STAT2, and NF-κB
Authors: Holloway Gavan , Truong Thanhmai T. , Coulson Barbara S.
Published: February 2009

A vital arm of the innate immune response to viral infection is the induction and subsequent antiviral effects of interferon (IFN). Rotavirus reduces type I IFN induction in infected cells by the degradation of IFN regulatory factors. Here, we show that the monkey rotavirus RRV and human rotavirus Wa also block gene expression induced by type I and II IFNs through a mechanism allowing signal transducer and activator of transcription 1 (STAT1) and STAT2 activation but preventing their nuclear accumulation. In infected cells, this may allow rotavirus to block the antiviral actions of IFN produced early in infection or by activated immune cells. As the intracellular expression of rotavirus nonstructural proteins NSP1, NSP3, and NSP4 individually did not inhibit IFN-stimulated gene expression, their involvement in this process is unlikely. RRV and Wa rotaviruses also prevented the tumor necrosis factor alpha-stimulated nuclear accumulation of NF-κB and NF-κB-driven gene expression. In addition, NF-κB was activated by rotavirus infection, confirming earlier findings by others. As NF-κB is important for the induction of IFN and other cytokines during viral infection, this suggests that rotavirus prevents cellular transcription as a means to evade host responses. To our knowledge, this is the first report of the use of this strategy by a double-stranded RNA virus.
The Signal Peptide of a Simple Retrovirus Envelope Functions as a Posttranscriptional Regulator of Viral Gene Expression
Authors: Caporale Marco , Arnaud Frederick , Mura Manuela , Golder Matthew , Murgia Claudio , Palmarini Massimo
Published: February 2009

Retroviruses use different strategies to regulate transcription and translation and exploit the cellular machinery involved in these processes. This study shows that the signal peptide of the envelope glycoprotein (Env) of Jaagsiekte sheep retrovirus (JSRV) plays a major role in posttranscriptional viral gene expression. Expression of the JSRV Env in
trans
increases viral particle production by mechanisms dependent on (i) its leader sequence, (ii) an intact signal peptide cleavage site, (iii) a
cis
-acting RNA-responsive element located in the viral genome, (iv) Crm1, and (v) B23. The signal peptide of the JSRV Env (JSE-SP) is 80 amino acid residues in length and contains putative nuclear localization and export signals, in addition to an arginine-rich RNA binding motif. JSE-SP localizes both in the endoplasmic reticulum and in the nucleus, where it colocalizes with nucleolar markers. JSE-SP is a multifunctional protein, as it moderately enhances nuclear export of unspliced viral mRNA and considerably increases viral particle release by favoring a posttranslational step of the replication cycle.
Receptor-Dependent and -Independent Axonal Retrograde Transport of Poliovirus in Motor Neurons
Authors: Ohka Seii , Sakai Mai , Bohnert Stephanie , Igarashi Hiroko , Deinhardt Katrin , Schiavo Giampietro , Nomoto Akio
Published: February 2009

Poliovirus (PV), when injected intramuscularly into the calf, is incorporated into the sciatic nerve and causes an initial paralysis of the inoculated limb in transgenic (Tg) mice carrying the human PV receptor (hPVR/CD155) gene. We have previously demonstrated that a fast retrograde axonal transport process is required for PV dissemination through the sciatic nerves of hPVR-Tg mice and that intramuscularly inoculated PV causes paralytic disease in an hPVR-dependent manner. Here we showed that hPVR-independent axonal transport of PV was observed in hPVR-Tg and non-Tg mice, indicating that several different pathways for PV axonal transport exist in these mice. Using primary motor neurons (MNs) isolated from these mice or rats, we demonstrated that the axonal transport of PV requires several kinetically different motor machineries and that fast transport relies on a system involving cytoplasmic dynein. Unexpectedly, the hPVR-independent axonal transport of PV was not observed in cultured MNs. Thus, PV transport machineries in cultured MNs and in vivo differ in their hPVR requirements. These results suggest that the axonal trafficking of PV is carried out by several distinct pathways and that MNs in culture and in the sciatic nerve in situ are intrinsically different in the uptake and axonal transport of PV.
The
Autographa californica
Multicapsid Nucleopolyhedrovirus GP64 Protein: Analysis of Transmembrane Domain Length and Sequence Requirements
Authors: Li Zhaofei , Blissard Gary W.
Published: February 2009

GP64, the major envelope glycoprotein of the
Autographa californica
multicapsid nucleopolyhedrovirus budded virion, is important for host cell receptor binding and mediates low-pH-triggered membrane fusion during entry by endocytosis. Previous transmembrane (TM) domain replacement studies showed that the TM domain serves a critical role in GP64 function. To extend the prior studies and examine specific sequence requirements of the TM domain, we generated a variety of GP64 TM domain mutations. The mutations included 4- to 8-amino-acid deletions, as well as single and multiple point mutations. While most TM domain deletion constructs remained fusion competent, those containing deletions of eight amino acids from the C terminus did not mediate detectable fusion. The addition of a hydrophobic amino acid (A, L, or V) to the C terminus of construct C8 (a construct that contains a TM domain deletion of eight amino acids from the C terminus) restored fusion activity. These data suggest that the membrane fusion function of GP64 is dependent on a critical length of the hydrophobic TM domain. All GP64 proteins with a truncated TM domain mediated detectable virion budding with dramatically lower levels of efficiency than wild-type GP64. The effects of deletions of various lengths and positions in the TM domain were also examined for their effects on viral infectivity. Further analysis of the TM domain by single amino acid substitutions and 3-alanine scanning mutations identified important but not essential amino acid positions. These studies showed that amino acids at positions 485 to 487 and 503 to 505 are important for cell surface expression of GP64, while amino acids at positions 483 to 484 and 494 to 496 are important for virus budding. Overall, our results show that specific features and amino acid sequences, particularly the length of the hydrophobic TM domain, play critical roles in membrane anchoring, membrane fusion, virus budding, and infectivity.
The Interaction of the Gammaherpesvirus 68 orf73 Protein with Cellular BET Proteins Affects the Activation of Cell Cycle Promoters
Authors: Ottinger Matthias , Pliquet Daniel , Christalla Thomas , Frank Ronald , Stewart James P. , Schulz Thomas F.
Published: February 2009

Infection of mice with murine gammaherpesvirus 68 (MHV-68) provides a valuable animal model for gamma-2 herpesvirus (rhadinovirus) infection and pathogenesis. The MHV-68 orf73 protein has been shown to be required for the establishment of viral latency in vivo. This study describes a novel transcriptional activation function of the MHV-68 orf73 protein and identifies the cellular bromodomain containing BET proteins Brd2/RING3, Brd3/ORFX, and BRD4 as interaction partners for the MHV-68 orf73 protein. BET protein members are known to interact with acetylated histones, and Brd2 and Brd4 have been implicated in fundamental cellular processes, including cell cycle regulation and transcriptional regulation. Using MHV-68 orf73 peptide array assays, we identified Brd2 and Brd4 interaction sites in the orf73 protein. Mutation of one binding site led to a loss of the interaction with Brd2/4 but not the retinoblastoma protein Rb, to impaired chromatin association, and to a decreased ability to activate the BET-responsive cyclin D1, D2, and E promoters. The results therefore pinpoint the binding site for Brd2/4 in a rhadinoviral orf73 protein and suggest that the recruitment of a member of the BET protein family allows the MHV-68 orf73 protein to activate the promoters of G
1
/S cyclins. These findings point to parallels between the transcriptional activator functions of rhadinoviral orf73 proteins and papillomavirus E2 proteins.
Crystal Structure of a Novel Dimeric Form of NS5A Domain I Protein from Hepatitis C Virus
Authors: Love Robert A. , Brodsky Oleg , Hickey Michael J. , Wells Peter A. , Cronin Ciarán N.
Published: February 2009

A new protein expression vector design utilizing an N-terminal six-histidine tag and tobacco etch virus protease cleavage site upstream of the hepatitis C virus NS5A sequence has resulted in a more straightforward purification method and improved yields of purified NS5A domain I protein. High-resolution diffracting crystals of NS5A domain I (amino acids 33 to 202) [NS5A(33-202)] were obtained by using detergent additive crystallization screens, leading to the structure of a homodimer which is organized differently from that published previously (T. L. Tellinghuisen, J. Marcotrigiano, and C. M. Rice, Nature 435:374-379, 2005) yet is consistent with a membrane association model for NS5A. The monomer-monomer interface of NS5A(33-202) features an extensive buried surface area involving the most-highly conserved face of each monomer. The two alternate structural forms of domain I now available may be indicative of the multiple roles emerging for NS5A in viral RNA replication and viral particle assembly.
Hepatitis Delta Antigen Requires a Minimum Length of the Hepatitis Delta Virus Unbranched Rod RNA Structure for Binding
Authors: Defenbaugh Dawn A. , Johnson Matthew , Chen Renxiang , Zheng Ying Yi , Casey John L.
Published: February 2009

Hepatitis delta virus (HDV) is a subviral pathogen that increases the severity of liver disease caused by hepatitis B virus. Both the small circular RNA genome and its complement, the antigenome, form a characteristic unbranched rod structure in which approximately 70% of the nucleotides are base paired. These RNAs are associated with the sole virally encoded protein, hepatitis delta antigen (HDAg), in infected cells; however, the nature of the ribonucleoprotein complexes (RNPs) is not well understood. Previous analyses of binding in vitro using native, bacterially expressed HDAg have been hampered by a lack of specificity for HDV RNA. Here, we show that removal of the C-terminal 35 amino acids of HDAg yields a native, bacterially expressed protein, HDAg-160, that specifically binds HDV unbranched rod RNA with high affinity. In an electrophoretic mobility shift assay, this protein produced a discrete, micrococcal nuclease-resistant complex with an ∼400-nucleotide (nt) segment of HDV unbranched rod RNA. Binding occurred with several segments of HDV RNA, although with various affinities and efficiencies. Analysis of the effects of deleting segments of the unbranched rod indicated that binding did not require one or two specific binding sites within these RNA segments. Rather, a minimum-length HDV RNA unbranched rod approximately 311 nt was essential for RNP formation. The results are consistent with a model in which HDAg binds HDV unbranched rod RNA as multimers of fixed size rather than as individual subunits.
Entry of Herpes Simplex Virus 1 and Other Alphaherpesviruses via the Paired Immunoglobulin-Like Type 2 Receptor α
Authors: Arii Jun , Uema Masashi , Morimoto Tomomi , Sagara Hiroshi , Akashi Hiroomi , Ono Etsuro , Arase Hisashi , Kawaguchi Yasushi
Published: February 2009

Herpes simplex virus 1 (HSV-1) enters cells either via fusion of the virion envelope and host cell plasma membrane or via endocytosis, depending on the cell type. In the study reported here, we investigated a viral entry pathway dependent on the paired immunoglobulin-like type 2 receptor α (PILRα), a recently identified entry coreceptor for HSV-1 that associates with viral envelope glycoprotein B (gB). Experiments using inhibitors of endocytic pathways and ultrastructural analyses of Chinese hamster ovary (CHO) cells transduced with PILRα showed that HSV-1 entry into these cells was via virus-cell fusion at the cell surface. Together with earlier observations that HSV-1 uptake into normal CHO cells and those transduced with a receptor for HSV-1 envelope gD is mediated by endocytosis, these results indicated that expression of PILRα produced an alternative HSV-1 entry pathway in CHO cells. We also showed that human and murine PILRα were able to mediate entry of pseudorabies virus, a porcine alphaherpesvirus, but not of HSV-2. These results indicated that viral entry via PILRα appears to be conserved but that there is a PILRα preference among alphaherpesviruses.
The 30-Amino-Acid Deletion in the Nsp2 of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Emerging in China Is Not Related to Its Virulence
Authors: Zhou Lei , Zhang Jialong , Zeng Jingwen , Yin Shuoyan , Li Yanhua , Zheng Linying , Guo Xin , Ge Xinna , Yang Hanchun
Published: February 2009

During the past 2 years, an atypical clinical outbreak, caused by a highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) with a unique 30-amino-acid deletion in its Nsp2-coding region, was pandemic in China. In this study, we generated four full-length infectious cDNA clones: a clone of the highly virulent PRRSV strain JXwn06 (pWSK-JXwn), a clone of the low-virulence PRRSV strain HB-1/3.9 (pWSK-HB-1/3.9), a chimeric clone in which the Nsp2 region containing the 30-amino-acid deletion was replaced by the corresponding region of the low-virulence PRRSV strain HB-1/3.9 (pWSK-JXwn-HB1nsp2), and a mutated HB-1/3.9 clone with the same deletion in Nsp2 as JXwn06 (pWSK-HB1-ND30). We also investigated the pathogenicities of the rescued viruses (designated RvJXwn, RvJXwn-HB1nsp2, RvHB-1/3.9, and RvHB1-ND30, respectively) in specific-pathogen-free piglets in order to determine the role of the 30-amino-acid deletion in the virulence of the highly pathogenic PRRSV. All the rescued viruses could replicate stably in MARC-145 cells. Our findings indicated that RvJXwn-HB1nsp2 retained high virulence for piglets, like RvJXwn and the parental virus JXwn06, although the survival time of piglets infected with RvJXwn-HB1nsp2 was obviously prolonged. RvHB1-ND30 exhibited low virulence for piglets, like RvHB-1/3.9 and the parental virus HB-1/3.9. Therefore, we conclude that the 30-amino-acid deletion is not related to the virulence of the highly pathogenic PRRSV emerging in China.
Limitations of the Driving Formulas for Predicting the Bearing Capacities of Piles in Sand
Authors: Tavenas F. , Audy R.
Published: February 2009

It has often been shown by previous investigators that the existing pile driving formulas yield bearing capacities which usually do not stand in good correlation to the actual bearing capacities of piles in sand. These poor correlations have always been attributed to the formulation of the equations.Based on the observations made on a very large foundation built in an homogeneous sand deposit it is shown in the present paper, that the poor quality of the usual pile driving formulas originates essentially in the estimate of the driving energy; while it is assumed that each blow delivers a constant energy equal to W × H for drop hammers, it appears actually that the energy delivered by a given equipment varies systematically from blow to blow. This conclusion, drawn from a statistical analysis of 478 driving records, is confirmed by the driving tests made on four instrumented piles.The results of 45 load tests also confirm this conclusion in showing no correlation between the actual bearing capacities and the estimated driving energy or the bearing capacities computed from five different formulas. The observations also show a possible time effect on the bearing capacities of concrete piles in sand.
An Engineering Theory of Creep of Frozen Soils
Authors: Ladanyi Branko
Published: February 2009

Most of the existing theories of creep have been developed from two different viewpoints: micromechanistic and macroanalytical. The former deal with events occurring at the atomic level and provide knowledge of the processes that control creep. The latter are based on certain macroscopic experimental findings and represent, in fact, an extension of the theory of plasticity to include time and ltemperature effects. Both the micromechanistic and macroanalytical approaches lead to fruitful resuts and each can benefit from the other. However, although the former has the advantage of being derived from physical concepts, the use of the latter is often preferred in practice if it provides basic relations that are broad in scope and can lead to improved procedures for designing structures.In this paper, a macroanalytical view of the problem of creep of frozen soils is presented. The proposed theory of creep has been developed mainly with the purpose of being used as a basis for solving a specific soil engineering problem, i.e., the bearing capacity of buried footings and anchors.Since the problem is itself rather complex, it was endeavoured to present the creep information in a relatively simple mathematical form. The theory, while using certain concepts and data from the frozen soils literature, follows more closely, nevertheless, the methods usual in certain engineering theories of creep of metals.
Bentonite Seals for Piezometers in Frozen Soil
Authors: Guther Harvey H.
Published: February 2009

A seal of bentonite, water, and methanol is shown to possess suitable properties for sealing piezometers in frozen soil. The methanol additive depresses the freezing temperature of the bentonite seal without significantly altering its swelling characteristics.