bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolving Innovative Reactor Design: Putting the I Into R&D
Authors: Duffey Romney B. , Khartabil Hussam
Published: February 2010

This paper traces the development path adopted for the SCWR, including the directions taken for innovative collaboration (R&D+i). In the pre-conceptual design work, instead of taking a fixed concept, the constraints and resulting design targets are defined first. By encouraging innovation, the motivation for the work is not just the size of the R&D funding for a single project, but rather the scale and opportunity of the technology challenge and the potential for attracting grass-roots support at all levels. From the beginning of the Generation IV ideas, the SCWR has taken a somewhat different path from other systems. Learning from the historical lessons of earlier unsuccessful designs of gas-cooled and liquid metal-cooled concepts, the SCWR targets the twin aims of increased efficiency and low cost by leveraging conventional thermal technology while also improving safety and avoiding open-ended development. By working with universities nationally, and other partners internationally, a wider R&D+i activity was possible that was not constrained by any early time-frame demonstration project. As a result, presently a number of unique and creative achievements stand out, where the collaborative SCWR R&D+i partnership is very different from other systems in approach, potential and scope by: a) Providing an open opportunity for some 30 countries to share their development efforts, while representing major global industrial and economic development (the 24 EU nations, plus Canada, Japan, Russia, China, India, Korea and others) without the impediments of any “national” demonstration projects; b) Allowing differing design concepts to flourish, from simple systems to more complex ideas, with process heat and hydrogen production applications emerging naturally, providing flexibility in application and design approach; c) Encouraging extensive educational research opportunities, ideas and contributions outside national laboratories, providing a unique framework for quality assurance that meets the needs of industry, universities and other partners worldwide, as well as a coordinated effort within the Generation IV International Forum and the IAEA cooperative research efforts; d) Examining many innovations (e.g., on alternate thermal cycles, fuel cycles and energy uses) without impacting any specific demonstration, so the testing and research are based largely on new capability development, without committing large funding to design teams with already fixed or unrealizable concepts. This paper describes this new R&D+i concept and its potential directions and results.
The Gasification of Graphite Matrix in Pebble Bed Reactors
Authors: Yu Xinli , Yu Suyuan
Published: February 2010

This paper mainly deals with the simulations of graphite matrix of the spherical fuel elements by steam in normal operating conditions. The fuel element matrix graphite was firstly simplified to an annular part in the simulations. Then the corrosions to the matrix graphite in 10 MW High Temperature Gas-cooled Reactor (HTR-10) and the High Temperature Gas-cooled Reactor—–Pebble-bed Module (HTR-PM) were investigated respectively. The results showed that the gasification of fuel element matrix graphite was uniform and mainly occurred at the bottom of the core in both of the reactors in the mean residence time of the spherical fuel elements. This was mainly caused by the designed high temperature at the bottom. The total mass gasified in HTR-PM was much greater than the HTR-10, while it did not mean much severer corrosion occurred there. As it is known the core volume of HTR-PM is much larger than the HTR-10, which will result in much greater consumed graphite even for the same corrosion rate. The steam only lost about 1 to 3 percent after flowing through the cores in both reactors for different steam conditions. The corrosion of graphite became worse when the steam concentrations increased in helium coolant. The results also indicated that the corrosion rate of fuel element matrix graphite tended to increase slightly with the prolonging of the service time.
Potential Ways to Modify the NRC Safety Goal Policy
Authors: Arndt Steven A. , Denning Richard
Published: February 2010

There have been significant discussions over the past few years by the U.S. Nuclear Regulatory Commission (NRC) staff and the Advisory Committee on Reactor Safeguards (ACRS), as to the adequacy of the safety goals for use with the next generation of nuclear power reactors to be built in the United States. The NRC, in its safety goals policy statement, has provided general qualitative safety goals and basic quantitative health objectives (QHOs) for nuclear reactors in the U.S. Risk metrics such as core damage frequency (CDF) and large early release frequency (LERF) have also been used as surrogates for the QHOs. This study will examine a potential approach to update the safety goals that includes the establishment of new qualitative goals associated with the comparative risk of generating electricity by viable competing technologies, and the development of preliminary tests in support of a new qualitative goal.
Human Reliability, Experience and Error Probability: A New Benchmark
Authors: Duffey Romney B. , Ha Tae Sung
Published: February 2010

In this paper, we apply a totally new approach to benchmark human reliability analysis, which is derived directly from the Universal Learning Curve (ULC) for homo-technological system (HTS) outcomes. We compare the latest second-generation predictions, based on the well-known and proven learning hypothesis, against some of the common Human Reliability Analysis (HRA) methods used to date for analyzing human reliability in transient and accident analysis. Therefore, we provide a straightforward, general and simple methodology for evaluating and predicting the Human Error Probability (HEP) in transients for accident risk prediction and reduction, as validated against all the available data, producing a completely independent assessment of the uncertainty.
MELCOR/VISOR PWR Desktop Simulator for Accident Analysis and Training
Authors: de With Anka , Wakker Pieter H. , Slootman Marcel L. F.
Published: February 2010

A desktop simulator of the Pressurized Water Reactor (PWR) for training of the accident response has been created under the contract of the Dutch nuclear regulatory body (KFD). The desktop simulator is a software package that provides a simulation of the two-loop PWR. It uses the nuclear accident analysis code MELCOR as a computational tool and the visualization tool VISOR as a graphical user interface. The simulator is a realistic model of the plant, mimicking the behaviour of the plant including control and safety systems, and response to user’s actions. Its graphical user interface is user friendly and it displays the coloured mimic of the primary system, containment and the secondary system. The status of important parameters and colour-coded values are displayed on the screen as a part of the plant mimic. Furthermore, parameters of interest can also be shown as a function of time. It can simulate a steady-state run of the power plant and also a variety of accident conditions in auto or interactive mode allowing the user to interfere with the transient, change conditions and analyse the response of the simulator to the interference. The simulator will be used for training of the KFD staff in order to increase the insight in accident progressions. The training will include the use of measures and strategies applied in the Emergency Operating Procedures (EOPs) and the Severe Accident Management Guidelines (SAMGs).
Non-Proliferative, Thorium-Based, Core and Fuel Cycle for Pressurized Water Reactors
Authors: Raitses Gilad , Todosow Michael , Galperin Alex
Published: February 2010

Two of the major barriers to the expansion of worldwide adoption of nuclear power are related to proliferation potential of the nuclear fuel cycle and issues associated with the final disposal of spent fuel. The Radkowsky Thorium Fuel (RTF) concept proposed by Professor A. Radkowsky offers a partial solution to these problems. The main idea of the concept is the utilization of the seed-blanket unit (SBU) fuel assembly geometry which is a direct replacement for a “conventional” assembly in either a Russian pressurized water reactor (VVER-1000) or a Western pressurized water reactor (PWR). The seed-blanket fuel assembly consists of a fissile (U) zone, known as seed, and a fertile (Th) zone known as blanket. The separation of fissile and fertile allows separate fuel management schemes for the thorium part of the fuel (a subcritical “blanket”) and the “driving” part of the core (a supercritical “seed”). The design objective for the blanket is an efficient generation and in-situ fissioning of the U233 isotope, while the design objective for the seed is to supply neutrons to the blanket in a most economic way, i.e. with minimal investment of natural uranium. The introduction of thorium as a fertile component in the nuclear fuel cycle significantly reduces the quantity of plutonium production and modifies its isotopic composition, reducing the overall proliferation potential of the fuel cycle. Thorium based spent fuel also contains fewer higher actinides, hence reducing the long-term radioactivity of the spent fuel. The analyses show that the RTF core can satisfy the requirements of fuel cycle length, and the safety margins of conventional pressurized water reactors. The coefficients of reactivity are comparable to currently operating VVER’s/PWR’s. The major feature of the RTF cycle is related to the total amount of spent fuel discharged for each cycle from the reactor core. The fuel management scheme adopted for RTF core designs allows a significant decrease in the amount of discharged spent fuel, for a given energy production, compared with standard VVER/PWR. The total Pu production rate of RTF cycles is only 30% of standard reactor. In addition, the isotopic compositions of the RTF’s and standard reactor grade Pu are markedly different due to the very high burnup accumulated by the RTF spent fuel.
Assessment of Reliability of Emergency Core Cooling System (ECCS) of Bushehr Nuclear Power Plant
Authors: Sotoudeh Mohammad , Sepanloo Kamran
Published: February 2010

Bushehr Nuclear Power Plant (BNPP) originally designed by German KWU and then modified by Russian companies is approaching commissioning. In this paper, the reliability of Emergency Core Cooling System (ECCS) of the new design is compared with the older one using both deterministic and probabilistic methods. The reliability of both systems is calculated in case of occurrence of Large Loss of Coolant Accident (Large LOCA). The new Russian design is based on the original KWU Convoy design and the applied modifications have improved its reliability. To perform the reliability analysis the event tree/fault tree method is used and the calculations are done by IAEA computer code PSAPACK. The results show that the applied modifications such as, increase of redundancy from 4 × 50% to 4 × 100%, change of cool down route, fuel storage pool cooling in all four trains have reduced the ECCS unavailability from 5.9 E−4 to 1.7 E−4. Furthermore, based on the results it is shown that both designs comply well with the IAEA recommendations on Probabilistic Safety Criteria (PSC) and INSAG-3 requirements.
Why Massive Nuclear Deployment is Essential
Authors: Miller Alistair I. , Duffey Romney B.
Published: February 2010

Avoiding CO2 emissions while meeting global energy needs is a far greater challenge than most commentators and governments appreciate. Even the Intergovernmental Panel on Climate Change has offered no scenario that would stabilize atmospheric levels. The capacity of the oceans to absorb CO2 is limited to about 40% of the level of emissions in 1990. Shared equitably among the present-day world population, per capita emissions of 35% of the current European average would only return the world to 100% of 1990 emission levels. Yet world population will probably grow by 25% by 2050 and, between 1990 and 2007, global emissions increased by 29%. Our current global trajectory is hurtling us toward ever-higher levels, perhaps even disaster. Consequently, near-zero-emitting sources are the only approaches to energy generation that should be deployed. Nuclear power, with its immense energy density, is the only available source that qualifies for widespread deployment. Existing alternative options are not and cannot effectively contribute (see e.g. MacKay, 2008). The weakness in wind is the need for back-up and supplementation, not so much from its short-term fickleness but its seasonal variability. Carbon capture and storage would have to achieve far higher levels of capture than currently seem feasible. Hydroelectricity has limited remaining potential as well as needing careful deployment to avoid collateral emissions. Aggressive conservation and efficiency measures reduce but do not solve the growth in energy demand and usage. Global economic downturns provide temporary relief but huge social political pain, and energy supply security concerns remain unresolved issue for many countries, even today. Of course nuclear alone would face an overwhelming challenge. We shall need to deploy massive improvements in the efficiency with which energy is used. Solar power in various forms has promise and could have a substantial role at lower latitudes in consistently sunny areas though photovoltaic electricity is still a high-cost option. Geothermal and various forms of ocean-derived energy have development potential. However, we argue that worldwide deployment of 5000 to 10 000 nuclear reactors by 2050 is the only clearly accessible pathway to CO2 stabilization that exists today. This will require extension of the resource beyond once-through cycles and so the deployment of advanced reactor types. But it is doable, it is affordable, and our planet must plan to accomplish this deployment.
A Study for the Practicality of the 3D Full Model in the SSI Analysis on the Nuclear Power Plant
Authors: Jang Youngsun , Kim Taeyoung , Lee Jongbo , Kim Jonghak
Published: February 2010

This study is a part of research project ‘the practicality of the 3-D Full Model in the SSI (Soil-Structure Interaction) Analysis on the Nuclear Power Plant’ from June 2006 to May 2009. The purpose of the project is getting advanced and more accurate results with the practicality of Full Model SSI analysis. The SSI analyses of the NPP were being performed for the APR1400 (Advanced Power Reactor 1400MWe) design because the APR1400 was developed as a Standard NPP concept enveloping suitable soil conditions. The soil properties of SSI analyses were from lower bound characteristics to firm condition. The Standard NPP that was developed in early 1990 had the rigid foundation assumption because rigid mat had many advantages, simple modeling and quick calculation. But this assumption may create licensing issue because the rigid mat could include uncertainties in the modeling and analysis procedure. Now, the advanced computing capacities can offer the calculating environment using Full Model in the SSI analysis, and through this study the Full Model SSI analysis may be applied to the NI (Nuclear Island) of APR1400. The full modeling concept can be distinguished into two methods. First one is the Full Model about excavated soil part below the ground surface only, the super structures can be beam sticks. Another modeling is the Full Model about excavated soil part below ground surface together with the super structure. Finally, the Full Model of excavated soil part with the super structure was built, each structure of the Full Model was verified.
Study on Pipe Wastage Mechanism by Liquid Droplet Impingement Erosion
Authors: Higashi Yuma , Narabayashi Tadashi , Shimazu Yoichiro , Tsuji Masashi , Ohmori Syuichi , Mori Michitsugu , Tezuka Kenichi
Published: February 2010

Evaluation of wastage speed for nuclear power plant maintains plant reliability and power up rating is important. There are two main cause of wastage flow accelerated corrosion (FAC) and mechanical erosion. This study is to develop evaluating the wastage speed by liquid droplet impingement erosion (LDIE). LDIE often occurs at downstream of corner of pipe or orifice. In this study, the liquid drop impinging tests were conducted with the test pieces mounted on a high speed rotating disk that cross thin water down jet and produced LDIE phenomena. The amount of the wastage by LDIE was evaluated by changing the rotational speed, the impingement frequency, and test piece materials. In addition, the generation mechanism of erosion was investigated by observing the surface of the test piece with a microscope. There is a method of evaluating by the mass difference before and after experiments. But this method is not correct because error becomes larger for mass measurement in the experiment, for the lost mass by LDIE is very little amount. Therefore, the method was developed to measure the volume in the erosion part. In this method, depth of LDIE was measured by the accuracy of ±0.01μm; therefore accurate measurement of the wastage can be improved.
Experimental and Research Study of Novel Nuclear Concepts (Survey of Current Results of ISTC Programs)
Authors: Tocheny L. V.
Published: February 2010

The International Science and Technology Center (ISTC) is a unique international organization created in Moscow fifteen years ago by Russia, USA, EU and Japan. Later Korea and Canada, and several CIS countries as well acceded to ISTC. The basic idea behind establishing the ISTC was to support non-proliferation of the mass destruction weapons technologies by re-directing former Soviet weapons scientists to peaceful research thus preventing the drain of dangerous knowledge and expertise from Russia and other CIS countries. Numerous science and technology projects are realized with the ISTC support in different areas, from biotechnologies and environmental problems to all aspects of nuclear studies, including those focused on the development of effective innovative concepts and technologies in the nuclear field, in general, and for improvement of nuclear safety, in particular. Presently, the ISTC now has 40 member countries (27 from EU), representing the CIS, Europe, Asia, and North America. The Partner list includes over 180 organizations and leading industrial companies from all ISTC parties. ISTC Activities to the beginning of 2009: above 2500 projects approved for funding. More than 350 institutions and 35,000 specialists received grants from ISTC. The presentation addresses some consequences of the ISTC projects and programs, related to nuclear science and technologies, as well as methods and approaches employed by the ISTC to foster close international collaboration and joint manage projects towards fruitful results.
Best Estimate Simulation and Uncertainty Analysis of LB LOCA for KudanKulam VVER-1000 NPP
Authors: Sabotinov Luben , Srivastava Abhishek , Probst Pierre
Published: February 2010

In the accident analysis of the Nuclear Power Plants (NPP) nowadays the international licensing practice considers several acceptable options for demonstrating the safety i.e. use of conservative computer codes with conservative assumptions, best estimate codes combined with conservative assumptions and conservative input data and application of best estimate codes with assumptions and realistic input data but associated with uncertainty evaluation of the results. The last option is particularly attractive because it allows for more precise prediction of safety margins with respect to safety criteria and their future use for power up-rating. The best estimate simulation with uncertainty analysis constitutes the framework of the present study which is to apply the last version of the French best estimate computer code CATHARE 2 in order to predict the thermal-hydraulic phenomena in the Indian KudanKulam Nuclear Power Plant (KK NPP) with VVER-1000 reactors during LB LOCA and to evaluate uncertainty along with sensitivity studies using the IRSN methodology. The paper first describes the modeling aspects of LB LOCA with CATHARE and then it presents the basic results. It highlights the use of SUNSET statistical tool developed by IRSN for sampling, management of several runs using CATHARE and further post treatment for uncertainty and sensitivity evaluation. The paper also deals with the difficulties associated with the selection of input uncertainties, code applicability and discusses the challenges in uncertainty evaluation.
Mechanisms Underlying Lineage Commitment and Plasticity of Helper CD4
+
T Cells
Authors: O’Shea John J. , Paul William E.
Published: February 2010

Critical Mediators

Helper T cells are the immune system's ringmasters, having a multiplicity of functions that mediate the body's immune responses to infections. Depending on the type of infection, CD4
+
helper T cells respond by secreting specific patterns of cytokines, which provide important cues to other subsets of immune cells. CD4
+
T cells with distinct cytokine profiles have been viewed classically as separate lineages; however, there is mounting evidence that these cells may not be terminally differentiated but are in fact quite plastic.
O'Shea and Paul
(p.
1098
) review the current understanding of CD4
+
T cell subset differentiation and the underlying mechanisms that drive cell-lineage commitment.
Inhibition of NF-κB Signaling by A20 Through Disruption of Ubiquitin Enzyme Complexes
Authors: Shembade Noula , Ma Averil , Harhaj Edward W.
Published: February 2010

Limiting Inflammatory Signaling

Dysregulation of the transcription factor NF-κB causes chronic inflammation, autoimmunity, and malignancy. The zinc-finger protein, A20, is vital for regulating NF-κB signaling, so much so that mice lacking A20 die young of multiorgan failure and cachexia. Similar deficiencies have been seen in Crohn's disease, rheumatoid arthritis, and other inflammatory diseases of humans. But how A20 works has remained unknown.

Shembade
et al.

(p.
1135
; see the Perspective by

S

riskantharajah and Ley
)

have discovered that the A20 protein acts through the ubiquitin labeling system of the cell required for normal protein turnover, and its lack prevents NF-κB recycling, resulting in chronic inflammation. A human T cell lymphotropic virus possesses an oncoprotein that subverts this pathway to the virus' benefit by inhibiting A20 interactions with the ubiquitin pathway to promote NF-κB signaling and cell immortalization.
On the Cutting Edge: Teaching Help for Geoscience Faculty
Authors: Manduca Cathryn A. , Mogk David W. , Tewksbury Barbara , Macdonald R. Heather , Fox Sean P. , Iverson Ellen R. , Kirk Karin , McDaris John , Ormand Carol , Bruckner Monica
Published: February 2010

A place is described for faculty to share their teaching expertise and to remain current with advances in geoscience.
Cortical Plasticity Induced by Inhibitory Neuron Transplantation
Authors: Southwell Derek G. , Froemke Robert C. , Alvarez-Buylla Arturo , Stryker Michael P. , Gandhi Sunil P.
Published: February 2010

Inflexible Timing for Flexibility

During critical periods in early life, sensory experience molds circuits in the brain. In the visual cortex, blurring or occluding vision in one eye triggers a rapid reorganization of neuronal responses known as ocular dominance plasticity. The critical period for this plasticity depends on inhibitory neurotransmission.

Southwell
et al.

(p.
1145
) show that by transplanting embryonic precursors of inhibitory neurons into mice, a period of ocular dominance plasticity can be induced after the end of the normal critical period. These observations suggest that transplantation of inhibitory neurons has therapeutic potential for brain repair and for treating neurological disorders and inducing periods of brain plasticity.
Ferroelectric Control of Spin Polarization
Authors: Garcia V. , Bibes M. , Bocher L. , Valencia S. , Kronast F. , Crassous A. , Moya X. , Enouz-Vedrenne S. , Gloter A. , Imhoff D. , Deranlot C. , Mathur N. D. , Fusil S. , Bouzehouane K. , Barthélémy A.
Published: February 2010

Spin into Control

Spintronics—the use of the spin direction of subatomic particles to control on and off states, instead of electric charge—has the potential to create low-power electronics, because less energy is needed to flip spin states than to flip switches to create voltage barriers. Theoretical work hints that spin-polarized electrons from a ferromagnetic electrode can be controlled by a change in polarization created in a ferroelectric thin film.

Garcia
et al.

(p.
1106
, published online 14 January) fabricated an iron-barium titanate junction on a lanthanum strontium manganate substrate that acts as a spin detector. Local control of spin polarization was observed in the ferroelectric layer, which retained its polarization without any applied power.
A Nodule-Specific Protein Secretory Pathway Required for Nitrogen-Fixing Symbiosis
Authors: Wang Dong , Griffitts Joel , Starker Colby , Fedorova Elena , Limpens Erik , Ivanov Sergey , Bisseling Ton , Long Sharon
Published: February 2010

Legume Symbiosome

Leguminous plants (peas and beans) are major players in global nitrogen cycling by virtue of their symbioses with nitrogen-fixing bacteria that are harbored in specialized structures, called nodules, on the plant's roots.

Van de Velde
et al.

(p.
1122
) show that the host plant,
Medicago truncatula
produces nodule-specific cysteine-rich peptides, resembling natural plant defense peptides. The peptides enter the bacterial cells and promote its development into the mature symbiont. In a complementary study,

D. Wang
et al.

(p.
1126
), have identified the signal peptidase, also encoded by the plant, that is required for processing these specialized peptides into their active form.
Integrated Catalytic Conversion of γ-Valerolactone to Liquid Alkenes for Transportation Fuels
Authors: Bond Jesse Q. , Alonso David Martin , Wang Dong , West Ryan M. , Dumesic James A.
Published: February 2010

Lactic Fuels

In the quest to find sustainable alternatives to petrochemicals, a small cyclic ester, γ-valerolactone, derived from cellulose offers promising raw material.

Bond
et al.

(p.
1110
) show that carbon dioxide can be catalytically excised from the lactone efficiently at high pressure, leaving a mixture of butanes. In a second-stage reactor, the butanes can be strung together to form heavier hydrocarbons similar to those found in automotive and jet fuels. The method simultaneously yields fuel and a relatively pure stream of pressurized carbon dioxide amenable to sequestration or further chemical modification.
Photorhabdus luminescens
Toxins ADP-Ribosylate Actin and RhoA to Force Actin Clustering
Authors: Lang Alexander E. , Schmidt Gudula , Schlosser Andreas , Hey Timothy D. , Larrinua Ignacio M. , Sheets Joel J. , Mannherz Hans G. , Aktories Klaus
Published: February 2010

Tripartite Toxin

Luminescent bacterial symbionts of nematode worms that attack insects have long stirred interest in their possibilities for biological control. The bacteria produce a family of toxins composed of at least three subunits that resemble a widely occurring class of bacterial toxins also produced by human pathogens.

Lang
et al.

(p.
1139
) have elucidated the mode of action and structural interactions of some of these tripartite protein toxins and found that they poison the cell's actin cytoskeleton by catalyzing unusual reactions. One toxin mediated adenosine diphosphate (ADP)–ribosylation at threonine-148 to cause actin polymerization, another ADP-ribosylated Rho protein at glutamine-63, and both synergized to cause actin clustering and cell paralysis.
What Makes a Prion Infectious?
Authors: Supattapone Surachai
Published: February 2010

Nonproteinaceous cofactors may be essential to generate infectious prions.
Keeping Tabs on Tumor DNA
Authors: Kaiser Jocelyn
Published: February 2010

A group at Johns Hopkins University has been monitoring free-floating tumor DNA in blood to track cancer. A new study being published in
Science Translational Medicine
this week suggests that advances in DNA sequencing may make this approach more viable.
Iceball Mars Proving a Tough Place to Find Liquid Water
Authors: Kerr Richard A.
Published: February 2010

Although Mars was once awash in flowing water, all the water found by orbiting radars has long been tied up in recurring ice ages.
Assessment of Imprecision in Gamma Interferon Release Assays for the Detection of Exposure to
Mycobacterium tuberculosis
Authors: Tuuminen Tamara , Tavast Esko , Väisänen Riitta , Himberg Jaakko-Juhani , Seppälä Ilkka
Published: February 2010

New gamma interferon (IFN-γ) release assays (IGRAs) to detect an exposure to
Mycobacterium tuberculosis
have recently been launched. The majority of the studies in temperate-climate countries agree that these methods have superior specificity and equal or even superior sensitivity over tuberculin skin tests (TSTs) in the diagnosis of latent tuberculosis (TB) infection (LTBI). However, reproducibility data of IGRAs are virtually missing. We assessed within-run, between-run, and total imprecision of two commercial IGRAs by testing samples from subjects with a stable state of TB infection or treated pulmonary TB, a sample from a healthy volunteer, and internal quality control samples. We calculated coefficients of variance (CV%s) to describe assays variability and compared the obtained results to the reported CV%s for other commercial immunodiagnostic methods. We illustrate an example of assay variability near the cutoff zone to demonstrate the necessity of a gray zone. Due to the strict adherence to the standard operation procedures (SOP) adopted in our laboratory, the total imprecision of enzyme-linked immunospot (ELISPOT)- and enzyme immunoassay (EIA)-based IGRAs was at a maximum CV% of 37.8% for the samples with moderate and high reactivities. Imprecision of testing samples with very low reactivity levels or nonreactive samples may, however, exceed 100%. In conclusion, despite multiple steps of the method performance, the analytical imprecision of IGRAs, which in our study design included also between-lot variability and had a component of normal biological variation, was well in accordance with the reported imprecisions of other manual immunodiagnostic tests. The recognition of the variability around the cutoff point advocates the use of a gray zone to avoid ambiguous result interpretations.
Naturally Competent
Acinetobacter baumannii
Clinical Isolate as a Convenient Model for Genetic Studies
Authors: Ramirez Maria Soledad , Don Michelle , Merkier Andrea K. , Bistué Alfonso J. Soler , Zorreguieta Angeles , Centrón Daniela , Tolmasky Marcelo E.
Published: February 2010

Acinetobacter baumannii
A118 was isolated from a patient's blood culture. It is susceptible to several antibiotics, is naturally competent, and supports replication and stable maintenance of four plasmid replicons
. A. baumannii
A118 took up a fluorophore-labeled oligonucleotide analog. These characteristics make this isolate a convenient model for genetic studies.
Significantly Larger Numbers of Methicillin-Resistant
Staphylococcus aureus
Bacteria Are Recovered from Polymicrobial Respiratory and Wound Sites by Use of Chromogenic Primary Media than by Use of Conventional Culture
Authors: Harrington Amanda T. , Mahlen Steven D. , Clarridge Jill E.
Published: February 2010

Previous studies have validated the properties and documented the utility of chromogenic agar for surveillance of methicillin-resistant
Staphylococcus aureus
(MRSA). In this study, we used one of the chromagars, MRSA
Select
(Bio-Rad), as one of the primary isolation media for selected wound and respiratory clinical specimens which, in our institution, were typically polymicrobial. We examined a total of 638 specimens; 142 (22%) MRSA isolates were recovered. Twenty-six of these isolates were recovered only on the MRSA
Select
plate, representing a 28% (15/54) increase for endotracheal aspirates/sputa and a 15% increase for superficial wounds/ulcers (11/73) compared to the results with conventional culture. One isolate (1 CFU) was recovered by conventional medium alone. MRSA
Select
has generally been used for surveillance cultures; however, we document that an additional 21% of MRSA isolates would have gone unreported in these selected clinical specimens using only standard culture media. For 40% (6/15) of inpatients, MRSA isolated from the MRSA
Select
plate was the sole indicator of MRSA. Although these isolates can represent either colonization or infection, they are a potential reservoir of infection and nosocomial transmission. Our data support the focused use of chromogenic selective media for the increased detection of MRSA in polymicrobial wound and respiratory specimens, which could have an impact on both clinical treatment and infection control.
Molecular Characterization of
Acinetobacter
Isolates Collected in Intensive Care Units of Six Hospitals in Florence, Italy, during a 3-Year Surveillance Program: a Population Structure Analysis
Authors: Donnarumma Francesca , Sergi Simona , Indorato Cristina , Mastromei Giorgio , Monnanni Roberto , Nicoletti Pieluigi , Pecile Patrizia , Cecconi Daniela , Mannino Roberta , Bencini Sara , Fanci Rosa , Bosi Alberto , Casalone Enrico
Published: February 2010

The strain diversity and the population structure of nosocomial
Acinetobacter
isolated from patients admitted to different hospitals in Florence, Italy, during a 3-year surveillance program, were investigated by amplified fragment length polymorphism (AFLP). The majority of isolates (84.5%) were identified as
A. baumannii
, confirming this species as the most common hospital
Acinetobacter
. Three very distinct
A. baumannii
clonal groups (A1, A2, and A3) were defined. The A1 isolates appeared to be genetically related to the well-characterized European EU II clone. A2 was responsible for three outbreaks which occurred in two intensive care units. Space/time population dynamic analysis showed that A1 and A2 were successful nosocomial clones. Most of the
A. baumannnii
isolates were imipenem resistant. The genetic determinants of carbapenem resistance were investigated by multiplex PCR, showing that resistance, independently of hospital origin, period of isolation, or clonal group, was associated with the presence of a
bla
OXA-58-like
gene and with IS
Aba2
and IS
Aba3
elements flanking this gene.
bla
OXA-58
appeared to be horizontally transferred. This study showed that the high discriminatory power of AFLP is useful for identification and typing of nosocomial
Acinetobacter
isolates. Moreover the use of AFLP in a real-time surveillance program allowed us the recognition of clinically relevant and widespread clones and their monitoring in hospital settings. The correlation between clone diffusion, imipenem resistance, and the presence of the
bla
OXA-58-like
gene is discussed.
Coamplification of HIV-1 Proviral DNA and Viral RNA in Assays Used for Quantification of HIV-1 RNA
Authors: Wan H. , Seth A. , Rainen L. , Fernandes H.
Published: February 2010

Elevated HIV-1 viral load (VL) observed in specimens frozen
in situ
in plasma preparation tubes (PPTs) compared to EDTA plasma specimens may affect therapeutic monitoring of HIV-infected patients. The increase in viral load is cell associated and minimized when plasma from the PPT is aspirated or recentrifuged prior to freezing. This study investigates the contribution of integrated HIV-1 proviral DNA to elevated VL in the quantification of HIV-1 RNA in plasma. Fifty paired specimens collected in EDTA tubes and PPTs frozen
in situ
were used for analysis. HIV-1 VL was measured using the COBAS Amplicor Monitor ultrasensitive test version 1.5. Contaminating proviral DNA was detected using a nested PCR targeting the
Alu
repeat in human genomic DNA and HIV
pol
gene simultaneously. Treatment of the specimen with DNase resulted in significantly lower quantifiable HIV-1 RNA in specimens from PPTs compared to the corresponding EDTA tubes (
P
= 0.004). After the RNA was destroyed by heat treatment, the mean HIV-1 RNA VL decreased by 79% in the EDTA tube compared to 65% in the PPT. The nested PCR amplified integrated proviral DNA in nucleic acid extracted from plasma in PPT and EDTA specimens with high viral load values. Likewise, a semiquantitative densitometric analysis revealed that the total amount of genomic DNA in the PPT was higher than that in the EDTA tube. Our investigation clearly shows that both proviral DNA and intracellular RNA are amplified simultaneously in the COBAS Amplicor HIV-1 Monitor assay and that proviral DNA contributes to the elevated VL in plasma frozen in PPTs.
Molecular Epidemiology of Multidrug-Resistant
Acinetobacter baumannii
in a Tertiary Care Hospital in Naples, Italy, Shows the Emergence of a Novel Epidemic Clone
Authors: Giannouli Maria , Cuccurullo Susanna , Crivaro Valeria , Di Popolo Anna , Bernardo Mariano , Tomasone Federica , Amato Gerardino , Brisse Sylvain , Triassi Maria , Utili Riccardo , Zarrilli Raffaele
Published: February 2010

The molecular epidemiology of multidrug-resistant
Acinetobacter baumannii
was investigated in two intensive care units of the V. Monaldi university hospital in Naples, Italy, from May 2006 to December 2007. Genotype analysis by pulsed-field gel electrophoresis (PFGE), trilocus sequence-based typing (3LST), and multilocus sequence typing (MLST) of
A. baumannii
isolates from 71 patients identified two distinct genotypes, one assigned to PFGE group A, 3LST group 1, and ST2 in 14 patients and the other to PFGE group B, 3LST group 6, and ST78 in 71 patients, that we named ST2/A and ST78/B, respectively. Of these, ST2/A corresponded to European clone II identified in the same hospital during 2003 and 2004; ST78/B was a novel genotype that was isolated for the first time in May 2006 but became prevalent during 2007. The ST78/B profile was also identified in five patients from two additional hospitals in Naples during 2007. The ST2/A and ST78/B isolates were resistant to all antimicrobials tested, including carbapenems, but were susceptible to colistin. Both ST2/A and ST78/B isolates possessed a plasmid-borne carbapenem-hydrolyzing oxacillinase gene,
bla
OXA-58
, flanked by IS
Aba2
and IS
Aba3
elements at the 5′ and 3′ ends, respectively. The selection of the novel ST78/B
A. baumannii
clone might have been favored by the acquisition of the
bla
OXA-58
gene.
Risk Factors and Prognosis of Nosocomial Bloodstream Infections Caused by Extended-Spectrum-β-Lactamase-Producing
Escherichia coli
Authors: Rodríguez-Baño Jesús , Picón Encarnación , Gijón Paloma , Hernández José Ramón , Cisneros Jose M. , Peña Carmen , Almela Manuel , Almirante Benito , Grill Fabio , Colomina Javier , Molinos Sonia , Oliver Antonio , Fernández-Mazarrasa Carlos , Navarro Gemma , Coloma Ana , López-Cerero Lorena , Pascual Alvaro
Published: February 2010

Extended-spectrum-β-lactamase (ESBL)-producing
Escherichia coli
(ESBLEC) is an increasing cause of community and nosocomial infections worldwide. However, there is scarce clinical information about nosocomial bloodstream infections (BSIs) caused by these pathogens. We performed a study to investigate the risk factors for and prognosis of nosocomial BSIs due to ESBLEC in 13 Spanish hospitals. Risk factors were assessed by using a case-control-control study; 96 cases (2 to 16% of all nosocomial BSIs due to
E. coli
in the participating centers) were included; the most frequent ESBL was CTX-M-14 (48% of the isolates). We found CTX-M-15 in 10% of the isolates, which means that this enzyme is emerging as a cause of invasive infections in Spain. By repetitive extragenic palindromic sequence-PCR, most isolates were found to be clonally unrelated. By multivariate analysis, the risk factors for nosocomial BSIs due to ESBLEC were found to be organ transplant (odds ratio [OR] = 4.8; 95% confidence interval [CI] = 1.4 to 15.7), the previous use of oxyimino-β-lactams (OR = 6.0; 95% CI = 3.0 to 11.8), and unknown BSI source (protective; OR = 0.4; 95% CI = 0.2 to 0.9), and duration of hospital stay (OR = 1.02; 95% CI = 1.00 to 1.03). The variables independently associated with mortality were a Pitt score of >1 (OR = 3.9; 95% CI = 1.2 to 12.9), a high-risk source (OR = 5.5; 95% CI = 1.4 to 21.9), and resistance to more than three antibiotics, apart from penicillins and cephalosporins (OR = 6.5; 95% CI = 1.4 to 30.0). Inappropriate empirical therapy was not associated with mortality. We conclude that ESBLEC is an important cause of nosocomial BSIs. The previous use of oxyimino-β-lactams was the only modifiable risk factor found. Resistance to drugs other than penicillins and cephalosporins was associated with increased mortality.
Interplay between Ovine Bone Marrow Stromal Cell Antigen 2/Tetherin and Endogenous Retroviruses
Authors: Arnaud Frederick , Black Sarah G. , Murphy Lita , Griffiths David J. , Neil Stuart J. , Spencer Thomas E. , Palmarini Massimo
Published: February 2010

Endogenous betaretroviruses (enJSRVs) of sheep are expressed abundantly in the female reproductive tract and play a crucial role in conceptus development and placental morphogenesis. Interestingly, the colonization of the sheep genome by enJSRVs is likely still ongoing. During early pregnancy, enJSRV expression correlates with the production of tau interferon (IFNT), a type I IFN, by the developing conceptus. IFNT is the pregnancy recognition signal in ruminants and possesses potent antiviral activity. In this study, we show that IFNT induces the expression of bone marrow stromal cell antigen 2 (BST2) (also termed CD317/tetherin) both
in vitro
and
in vivo
. The
BST2
gene is duplicated in ruminants. Transfection assays found that ovine BST2 proteins (oBST2A and oBST2B) block release of viral particles produced by intact enJSRV loci and of related exogenous and pathogenic jaagsiekte sheep retrovirus (JSRV). Ovine BST2A appears to restrict enJSRVs more efficiently than oBST2B.
In vivo
, the expression of BST2A/B and enJSRVs in the endometrium increases after day 12 and remains high between days 14 and 20 of pregnancy.
In situ
hybridization analyses found that oBST2A is expressed mainly in the endometrial stromal cells but not in the luminal and glandular epithelial cells, in which enJSRVs are highly expressed. In conclusion, enJSRVs may have coevolved in the presence of oBST2A/B by being expressed in different cellular compartments of the same organ. Viral expression in cells unable to express BST2 may be one of the mechanisms used by retroviruses to escape restriction.
Genomic Evolution of Vesicular Stomatitis Virus Strains with Differences in Adaptability
Authors: Novella Isabel S. , Presloid John B. , Zhou Tong , Smith-Tsurkan Sarah D. , Ebendick-Corpus Bonnie E. , Dutta Ranendra N. , Lust Kim L. , Wilke Claus O.
Published: February 2010

Virus strains with a history of repeated genetic bottlenecks frequently show a diminished ability to adapt compared to strains that do not have such a history. These differences in adaptability suggest differences in either the rate at which beneficial mutations are produced, the effects of beneficial mutations, or both. We tested these possibilities by subjecting four populations (two controls and two mutants with lower adaptabilities) to multiple replicas of a regimen of positive selection and then determining the fitnesses of the progeny through time and the changes in the consensus, full-length sequences of 56 genomes. We observed that at a given number of passages, the overall fitness gains observed for control populations were larger than fitness gains in mutant populations. However, these changes did not correlate with differences in the numbers of mutations accumulated in the two types of genomes. This result is consistent with beneficial mutations having a lower beneficial effect on mutant strains. Despite the overall fitness differences, some replicas of one mutant strain at passage 50 showed fitness increases similar to those observed for the wild type. We hypothesized that these evolved, high-fitness mutants may have a lower robustness than evolved, high-fitness controls. Robustness is the ability of a virus to avoid phenotypic changes in the face of mutation. We confirmed our hypothesis in mutation-accumulation experiments that showed a normalized fitness loss that was significantly larger in mutant bottlenecked populations than in control populations.
The Lack of an Inherent Membrane Targeting Signal Is Responsible for the Failure of the Matrix (M1) Protein of Influenza A Virus To Bud into Virus-Like Particles
Authors: Wang Dan , Harmon Aaron , Jin Jing , Francis David H. , Christopher-Hennings Jane , Nelson Eric , Montelaro Ronald C. , Li Feng
Published: February 2010

The matrix protein (M1) of influenza A virus is generally viewed as a key orchestrator in the release of influenza virions from the plasma membrane during infection. In contrast to this model, recent studies have indicated that influenza virus requires expression of the envelope proteins for budding of intracellular M1 into virus particles. Here we explored the mechanisms that control M1 budding. Similarly to previous studies, we found that M1 by itself fails to form virus-like-particles (VLPs). We further demonstrated that M1, in the absence of other viral proteins, was preferentially targeted to the nucleus/perinuclear region rather than to the plasma membrane, where influenza virions bud. Remarkably, we showed that a 10-residue membrane targeting peptide from either the Fyn or Lck oncoprotein appended to M1 at the N terminus redirected M1 to the plasma membrane and allowed M1 particle budding without additional viral envelope proteins. To further identify a functional link between plasma membrane targeting and VLP formation, we took advantage of the fact that M1 can interact with M2, unless the cytoplasmic tail is absent. Notably, native M2 but not mutant M2 effectively targeted M1 to the plasma membrane and produced extracellular M1 VLPs. Our results suggest that influenza virus M1 may not possess an inherent membrane targeting signal. Thus, the lack of efficient plasma membrane targeting is responsible for the failure of M1 in budding. This study highlights the fact that interactions of M1 with viral envelope proteins are essential to direct M1 to the plasma membrane for influenza virus particle release.