bluuebunny/crossref_metadata_2025 huggingface dataset:
On Vibration Properties of Piping Systems and Practical Measures for Preventing Vibration Damages
Authors: Jansson Lennart G. , Zeng Lingfu
Published: November 2014

This paper addresses several key issues relevant to piping vibration: (1) vibration properties and their identification; (2) the dynamic susceptibility of a piping system; (3) standard velocity criteria for vibration damage. Practical approaches for identifying vibration properties and practical measures for preventing vibration damages are overviewed. An approach is presented for conducting vibration design reducing measures prior to installation of a piping system, and for planning post-installation vibration recording activities.

This approach is based on “theoretical predictions” of “critical” sections of a piping system, namely the sections most sensitive to vibration. The critical sections can be ranked from most vulnerable to least vulnerable. Combined with knowledge of typical vibration sources, this is a cost effective way for preventing vibration damages and for forming a base for controlling actual vibrations in operation of plant, especially for closed premises. Examples are given to exemplify vibration risk.
AREVA’s Test Facility KATHY: Robust Critical Heat Flux Measurements, a Prerequisite for Reliable CHF Prediction
Authors: Wieckhorst O. , Kronenberg J. , Gabriel H. , Opel S. , Kreuter D. , Berger T. , Harne R. , Greene K. , Filhol F.
Published: November 2014

The primary tool for assuring the heat removal from the fuel design’s rod surfaces is properly represented in the numerical simulations of a LWR fuel assembly design is the critical heat flux (CHF) or dryout correlation.

During the last decade, AREVA has compiled unique experience in correlation development that has led to an improved development process to meet increased technical challenges. This is based upon the high level of expertise in CHF measurements for PWR and BWR fuel assembly designs gained by AREVA at its KATHY facility (KArlstein Thermal HYdraulic facility). The utilization of KATHY in conjunction with this improved development process is a key factor in ensuring reliable CHF prediction for safety analysis application. This paper describes the capabilities of the KATHY loop and the process used by AREVA to attain high quality CHF measurements.
Performance of Equipment Qualification Safety Factor of Periodic Safety Review for Qinshan III CANDU NPP
Authors: Xiaoyao Shen
Published: November 2014

Qinshan phase III is the only CANDU nuclear power plant (NPP) in China, which has two 728MW units, and starts commercial operation on Dec. 31st, 2002 and July 24th, 2003 respectively. According to the Periodic Safety Review of Nuclear Power Plants (NS-G-2.10) issued by IAEA in 2003 and the corresponding Chinese edition HAD103/11 issued by NNSA in 2006, the first PSR of Qinshan III should be carried out in 2012 and 2013 after 10 years of commercial operation. Comprehensive assessment of plant safety is a complex task and is facilitated by dividing it into a number of factors. The equipment qualification (EQ) factor is an important one of them. In this paper, the equipment qualification safety factor review of PSR is carried out for Qinshan III. Firstly, the project background is described. Then objectives, scopes and main review elements of EQ factor review are summarized. Also, the EQ factor review process is emphasized. Finally, the project team and outcome of EQ factor review are given.
Optimization of Confined Laminar Natural Convection for Dry Cask Storage Systems
Authors: Clifford Corey E. , Kimber Mark L.
Published: November 2014

Although high-density pool storage provides an acceptable method for housing used fuel elements, a number of concerns have triggered a call for the reduction of current inventories by mandating a maximum permissible time in which assemblies may be placed in wet storage before transfer to passive, dry storage conditions. In anticipation of an accelerated fuel transfer program, the principal goal of this investigation is to develop a fundamental understanding of the physics associated with the buoyancy-induced flow around dry casks in an effort to improve the heat rejection capability of the overall system. The aim of this research initiative is to minimize the amount of active pool cooling necessary by maximizing the thermal capacity of dry storage casks. A simplified geometry of a heated horizontal cylinder confined between two, vertical adiabatic walls is employed to evaluate the coupled heat and mass transfer. Two different treatments of the cylinder surface are investigated: constant temperature (isothermal) and constant surface heat flux (isoflux). To quantify the effect of wall distance on the effective heat transfer from the cylinder surface, 18 different confinement ratios are selected in varying increments from 1.125 to 18.0. Each of these geometrical configurations are evaluated at seven distinct Rayleigh numbers ranging from 102 to 105. Maximum values of the surface-averaged Nusselt number are observed at an optimum confinement ratio for each analyzed Rayleigh number. Relative to the pseudo-unconfined cylinder at the largest confinement ratio, a 54.2% improvement in the heat transfer from an isothermal cylinder surface is observed at the optimum wall spacing for the highest analyzed Rayleigh number. An analogous improvement of 46.6% is determined for the same conditions with a constant heat flux surface. Several correlations are proposed to evaluate the optimal confinement ratio and the effective rate of heat transfer at that optimal confinement level for both thermal boundary conditions.
Cost Saving When Using Enhanced Conductivity Nuclear Fuel Containing BeO in WWER-1000 Reactors
Authors: Zahrádka Tomáš , Škoda Radek
Published: November 2014

Current pressurized water reactors utilize sintered UO2 that has a number of advantages and disadvantages. Uranium Dioxide’s low thermal conductivity results in a large thermal gradient within the fuel pellet corresponding to higher centerline temperatures compared to other potential fuel forms. These gradients result in non-uniform thermal expansion leading to large internal stresses resulting in cracking of the pellet and fuel-clad interaction, which can lead to loss of the integrity of the fuel pin. Higher fuel temperatures also increase the release of fission gases. Fuels with higher thermal conductivity may alleviate or reduce the severity of these adverse conditions. It is shown that higher thermal conductivity can be obtained by adding BeO to the basic UO2 matrix. This paper focuses on WWER1000 hexagonal fuel geometry. Improvements when using 10% of BeO, as proposed in this paper, reduce the centerline nuclear fuel temperature by 234°C and improve the fuel economy while reducing its cost by 7%. The study was done for NPP Temelín which has two units WWER1000/320.
MELCOR Study of VVER-1000 Behavior in Case of Overheated Reactor Core Quenching
Authors: Groudev Pavlin P. , Stefanova Antoaneta E. , Vryashkova Petya I.
Published: November 2014

This paper presents the results obtained with the MELCOR computer code from a simulation of fuel behavior in case of severe accident for the VVER-1000 reactor core. The examination is focused on investigation the influence of some important parameters, such as porosity, on fuel behavior starting from oxidation of the fuel cladding, fusion product release in the primary circuit after rupture of the fuel cladding, melting of the fuel and reactor core internals and its further relocation to the bottom of the reactor vessel.

In the first analyses are modeled options for investigation of melt blockage and debris during the relocation. In the performed analyses are investigated the uncertainty margin of reactor vessel failure based on modeling of the reactor core and an investigation of its behavior. For this purposes it have been performed sensitivity analyses for VVER-1000 reactor core with gadolinium fuel type for parametric study the influence of porosity debris bed.

The second analyses is focused on investigation of influence of cold water injection on overheated reactor core at different core exit temperatures, based on severe accident management guidance operator actions. For this purpose was simulated the same SBO scenario with injection of cold water by a high pressure pump in cold leg (quenching from the bottom of reactor core) at different core exit temperatures from 1200 °C to 1500 °C. The aim of the analysis is to track the evolution of the main parameters of the simulated accident.

The work was performed at the Institute for Nuclear Research and Nuclear Energy (INRNE) in the frame of severe accident research.

The performed analyses continue the effort in the modeling of fuel behavior during severe accidents such as Station Blackout sequence for VVER-1000 reactors based on parametric study. The work is oriented towards the investigation of fuel behavior during severe accident conditions starting from the initial phase of fuel damaging through melting and relocation of fuel elements and reactor internals until the late in-vessel phase, when melt and debris are relocated almost entirely on the bottom head of the reactor vessel. The received results can be used in support of PSA2 as well as in support of analytical validation of Sever Accident Management Guidance for VVER-1000 reactors. The main objectives of this work area better understanding of fuel behavior during severe accident conditions as well as plant response in such situations.
Development of REFT Code System for the Analysis of Highly Heterogeneous Research Reactors
Authors: Zhang Tengfei , Wu Hongchun , Zheng Youqi , Cao Liangzhi , Li Yunzhao
Published: November 2014

As an effort to enhance the accuracy in simulating the operations of research reactors, a fuel management code system REFT was developed. Because of the possible complex assembly geometry and the core configuration of research reactors, the code system employed HELIOS in the lattice calculation to describe arbitrary 2D geometry, and used the 3D triangular nodal SN method transport solver, DNTR, to model unstructured geometry in the core analysis. Flux reconstruction with the least square method and micro depletion model for specific isotopes were incorporated in the code. At the same time, to make it more user friendly, a graphical user interface was also developed for REFT.

In the analysis of the research reactors, the calculations involving the control rod movement are encountered frequently. The modeling of the control rods differential worth behavior is important in that the movement of the control rod may introduce variations on the reactivity. To handle the problem two effective ways of alleviating the control rod cusping effect are recently proposed, based on the established code system. The methodologies along with their application and validation will be discussed.
The In Vessel Retention (IVR) Strategy for VVER 1000 Units Based on Existing Level of Research and Development Work
Authors: Zdarek Jiri , Krhounek Vladimir , Batek David , Brabec Petr , Misak Josef
Published: November 2014

The Fukushima severe accident needs very intensive and detailed response from all involved, to develop relevant mitigation strategies. For VVER type units this strategy is already developed and proved for smaller output units type VVER 440 MW. For higher output units type VVER 1000 MW this strategy is under development. In presented paper recent development based on analytical and experimental research work is presented. The research work is not yet finished, however, analytical and experimental work is building strong arguments that the IVR strategy is possible even for higher power existing units in operation, with application of proved measures which will be described.
Structural Supportive Software Tool for Fire PSA
Authors: Šimurka Peter , Procháska Ján
Published: November 2014

Continually increasing requirements on nowadays full scope PSA L1 and L2 as whole, which is multiplied by importance of specific data for all modes of operation of nuclear power plant, highlight role of input data used in PSA quantification process. This fact also emphasizes the role of capability to process all necessary information to analyze all nuclear plant modes by appropriate way. Even if abovementioned aspects are relevant for all parts of nowadays PSAs, their importance is critical for internal hazards including specific fire analysis. Because internal fire analysis forms one of the most challenging PSA tasks, requiring interdisciplinary work including processing and integration of extensive amount of data in such a way that fire analysis results are fully consistent with internal PSA events and can be directly incorporated into PSA project. Application of tailored information system forms one of the ways to speed up analyzing process, enhances manageability and maintainability of particular PSA projects and provides effective reporting mean to document process of work as well as traceable and human readable documentation for customers. Such information system also allows implementing rapid changes in processing input data and reduces the risk of human error. Usage of information systems for modification of input data for Living PSA is invaluable. Transparent highly automatized processing of input data allows the analyst to obtain more accurate and better insight to evaluate aspects of particular fire and its consequences. This paper provides brief overview of VUJE approach and experience in this area. The paper introduces general purpose of database developed for PSA needs containing data for relevant PSA structure system and components as well as information relevant for flood and fire analyses. Paper explains as this basic data source is enhanced by adding several relatively independent tiers to employ all common data for fire PSA purpose. Paper also briefly introduces capability of such system to generate integrated documentation covering all stages of fire analyses, covering all screening stages of fire analysis as well as future plans to enhance this part of work in such a way to be capable to build automatic interface between PSA model and fire database to enable PSA model parameters automatic updating and expansion of fires in combinations of initiating events (for example Fire and seismic event).
Testing of Statistical Procedures for Use in Optimization of Reactor Performance Under Aged Conditions
Authors: Serghiuta Dumitru , Tholammakkil John , Hammouda Naj , O’Hagan Anthony
Published: November 2014

This paper discusses a framework for designing artificial test problems, evaluation criteria, and two of the benchmark tests developed under a research project initiated by the Canadian Nuclear Safety Commission to investigate the approaches for qualification of tolerance limit methods and algorithms proposed for application in optimization of CANDU reactor protection trip setpoints for aged conditions. A significant component of this investigation has been the development of a series of benchmark problems of gradually increased complexity, from simple “theoretical” problems up to complex problems closer to the real application.

The first benchmark problem discussed in this paper is a simplified scalar problem which does not involve extremal, maximum or minimum, operations, typically encountered in the real applications. The second benchmark is a high dimensional, but still simple, problem for statistical inference of maximum channel power during normal operation.

Bayesian algorithms have been developed for each benchmark problem to provide an independent way of constructing tolerance limits from the same data and allow assessing how well different methods make use of those data and, depending on the type of application, evaluating what the level of “conservatism” is. The Bayesian method is not, however, used as a reference method, or “gold” standard, but simply as an independent review method.

The approach and the tests developed can be used as a starting point for developing a generic suite (generic in the sense of potentially applying whatever the proposed statistical method) of empirical studies, with clear criteria for passing those tests. Some lessons learned, in particular concerning the need to assure the completeness of the description of the application and the role of completeness of input information, are also discussed.

It is concluded that a formal process, which should include extended and detailed benchmark tests, but targeted to the context of the particular application and aimed at identifying the domain of validity of the proposed tolerance limit method and algorithm, is needed and might provide the necessary confidence in the proposed statistical procedure.
Re-Establishment of the Nuclear Engineering Program at Virginia Tech
Authors: Brown Eugene F. , Haghighat Alireza , Pierson Mark
Published: November 2014

One of the first nuclear engineering programs in the United States was established at Virginia Tech in the mid-1950’s and continued until the mid-1980’s when it was abandoned due to a drop both in student interest and government support. In 2006, as a result of interest shown by the nuclear industry in Virginia, discussions were undertaken that led to the approval to offer Master’s and Doctorate Degrees in nuclear engineering in 2013. In parallel with these efforts, we began teaching undergraduate courses in anticipation of offering a minor in nuclear engineering to all Virginia Tech engineering and science students. Currently we have 140 undergraduate students taking nuclear engineering classes, nuclear engineering undergraduate research hours, and participating in nuclear-engineering-related senior design activities.

Our program has been conceived and designed with the objective of providing the nuclear engineering workforce required to address the most important nuclear-related issues of our time including: enhancing the safe and productive use of nuclear energy; contributing to the development of advanced technologies for national and international nuclear security and safeguards; developing advanced medical devices for nuclear diagnostics and therapy; and the establishment of effective policies for the utilization of nuclear energy and its regulation.

The Master’s degree program involves 7 courses and the equivalent of two semesters of thesis research for a total of 30 credit hours. The PhD program, which builds on the Master’s degree program, requires 5 additional courses, and the equivalent of 4 semesters of dissertation research for a total of 60 credit hours beyond the Master’s degree. The curriculum is supported by a rigorous, benchmarked assessment and evaluation process to assure that the goals of the program are attained.

Currently five faculty members support the nuclear engineering program, and typical total enrollment in our graduate programs runs between 35 and 50 students. When we reach full strength, with the addition of two more nuclear engineering faculty members, we expect to be graduating 12 Master’s students and 7 PhD students per year.
A Research Reactor Source Term and Dose Results in the Event of a LOCA
Authors: Pappas Charalampos , Ikonomopoulos Andreas , Sfetsos Athanasios , Andronopoulos Spyros , Varvayanni Melpomeni , Catsaros Nicolas
Published: November 2014

The present study discusses the source term derivation and dose result calculation for a hypothetical accident sequence in the Greek Research Reactor – 1 (GRR-1). A loss-of-coolant accident (LOCA) has been selected as a credible accident sequence. The source term derivation has been based on the GRR-1 confinement performance where the inventory has been computed assuming continuous reactor operation. A core damage fraction of 30% has been considered for the calculations while conservative core release fractions have been employed. The radionuclides released from the reactor core to the confinement atmosphere have been subjected to natural decay, deposition on and resuspension from various internal surfaces before being led to the release pathway. It has been assumed that an emergency shutdown is initiated immediately after the beginning of the accident sequence and the emergency ventilation system is also activated. Subsequently, the source term has been derived comprising of noble gases, iodine and aerosol. The JRODOS computational software for off-site nuclear emergency management has been utilized to estimate the dose results from the LOCA-initiated source term that is released in its entirety from the reactor stack at ambient temperature. The Local Scale Model Chain in conjunction with the DIPCOT atmospheric dispersion model that is embedded in JRODOS have been used with proper parameterization of the calculation settings. Five weather scenarios have been selected as representative of typical meteorological conditions at the reactor site. The scenarios have been assessed with the use of the Weather Research and Forecast model. Total effective, skin, thyroid, lung and inhalation doses downwind of the reactor building and up to a distance of 10 km have been calculated for each weather scenario and are presented. The total effective gamma dose rate at a fixed distance from the reactor building has been assessed. The radiological consequences of the dose results are discussed.
Analysis of Heat Transfer and Flow Characteristics of AP1000 Passive Residual Heat Removal Heat Exchanger
Authors: Xie Xu , Nie Changhua , Zhan Li , Zheng Hua , Li Pengzhou , Tian Wenxi , Yu Pei
Published: November 2014

In this paper, the computational fluid dynamics (CFD) method is applied to the thermal-hydraulic analysis, while the porous media model is used to simplify AP1000 passive residual heat removal heat exchanger tube. The temperature as well as flow distribution in the secondary side of the heat exchanger are obtained, aiming at analysis of natural circulation ability. It can be noted that the fluid in the secondary side of heat exchanger moves driven by the effect of thermal buoyancy, forming the natural cycle, which takes away heat in tube bundle region. The heat transfer in water tank is mainly enhanced by vortex and turbulent flow, caused by the large resistance of tube bundle region as well as large temperature difference. This phenomenon is obvious especially for the recirculation of flow near the tube bundle. The enduring change of flow rate and direction enhance the heat transfer. Besides, the big temperature difference helps to increase the driving effect of natural circulation. Consequently, the heat transfer of the tank is enhanced by above mechanism. The results of this study contribute to the capacity analysis of passive residual heat removal of natural circulation system, providing valuable information for safe operation of AP1000.
What is the Relationship Between Quality, Quality Assurance and the Section III Design Specification
Authors: Barnes Richard W.
Published: November 2014

This paper explores the relationship between the Design Specification required for each Section III component and the terms Quality, Quality Assurance, Quality Product, and Management System (Quality Management System). The author’s experience indicates that the relationship between Quality and Quality Assurance is poorly understood and that the resistance experienced to the implementation of a Quality Assurance Program is often due to the person’s lack of understanding that a Quality Assurance Program really does help people do their work “right the first time”.

This lack of understanding often results in poorly defined requirements in the purchasing documents, inadequate definition of scope and a product that does not meet requirements. Even more importantly it can lead to the development of poor relationships between the purchaser and the supplier and particularly in the nuclear field, poor relationships with Regulators. The economic impact is also significant, delays in schedule, delays in product acceptance and payment results in costs that are eventually passed on to the consumer.

Once the above relationships are properly understood and appreciated resistance can turn into positive acceptance. The Section III concept of providing a Design Specification as a complete basis for construction also takes on new meaning.
Mathematical Modeling for Contingency Determination for Nuclear Power Plant Construction Projects
Authors: Zhao Wei , Xu Shenjun
Published: November 2014

This paper uses the China AP1000 project as an example to exhibit the application of quantitative risk management in nuclear power plant construction projects. For those lump sum contracts, one of the most significant purposes of quantitative risk management is to determine the contingency, i.e. the reserved money and time for projects. This paper studies the application of Monte Carlo simulation in determining the contingency, taking into account the distinctive features of nuclear power projects.

Most nuclear power projects, especially advanced ones such as Generation III and above, meet one common obstacle in estimating key economic indicators — the absence of historical data due to its avant-garde design. As cost estimators of the coal power plant contractors may collect their data from thousands of previous cases, nuclear power plant contractors, especially in many developing countries, do not have a shared database of financial data. Some first-of-a-kind nuclear power plants have absolutely no historical data to look up.

This paper aims to provide a resolution to this problem. First, the feasibility and representativeness of different probability distributions are compared based on their respective skewness and kurtosis to determine the best-suited distribution in nuclear power projects. This paper also analyzes the use of second-order Monte Carlo simulation in reducing the error caused by the biased estimation of inexperienced risk assessment engineers.
Non-Linear Analysis of AP1000 Auxiliary and Shield Building Subjected to Combined Accident Thermal and Seismic Loadings
Authors: Zhang J. Jennifer , Tunon-Sanjur Lee J.
Published: November 2014

Under the combined accident thermal and seismic loadings, the structural response of the AP1000 Auxiliary and Shield Building (ASB) is numerically investigated. A nonlinear Finite Element Model (FEM) of the AP1000 ASB is developed, in which the rebar in the reinforced concrete is explicitly described and the nonlinear behavior of the concrete is considered. The numerical modeling method and material models used by the reinforced concrete are validated by the testing results published in the literature. The propagation of the thermal loading-induced concrete cracks along the wall thickness is studied. Furthermore, the effects of thermal cracks on the wall stiffness, the development of the thermal stress and the axial forces acting on the reinforcement are fully discussed. The impact of thermal concrete cracks on the design demand of the rebar is also investigated. It is worthy of being further studied how to incorporate the appropriate reduction factor caused by concrete cracks into the linear structural design.
Development of a 6DOF robotic motion phantom for radiation therapy
Authors: Belcher Andrew H. , Liu Xinmin , Grelewicz Zachary , Pearson Erik , Wiersma Rodney D.
Published: November 2014

Purpose:

The use of medical technology capable of tracking patient motion or positioning patients along 6 degree‐of‐freedom (6DOF) has steadily increased in the field of radiation therapy. However, due to the complex nature of tracking and performing 6DOF motion, it is critical that such technology is properly verified to be operating within specifications in order to ensure patient safety. In this study, a robotic motion phantom is presented that can be programmed to perform highly accurate motion along any X (left–right), Y (superior–inferior), Z (anterior–posterior), pitch (around X), roll (around Y), and yaw (around Z) axes. In addition, highly synchronized motion along all axes can be performed in order to simulate the dynamic motion of a tumor in 6D. The accuracy and reproducibility of this 6D motion were characterized.

Methods:

An in‐house designed and built 6D robotic motion phantom was constructed following the Stewart–Gough parallel kinematics platform archetype. The device was controlled using an inverse kinematics formulation, and precise movements in all 6 degrees‐of‐freedom (X, Y, Z, pitch, roll, and yaw) were performed, both simultaneously and separately for each degree‐of‐freedom. Additionally, previously recorded 6D cranial and prostate motions were effectively executed. The robotic phantom movements were verified using a 15 fps 6D infrared marker tracking system and the measured trajectories were compared quantitatively to the intended input trajectories. The workspace, maximum 6D velocity, backlash, and weight load capabilities of the system were also established.

Results:

Evaluation of the 6D platform demonstrated translational root mean square error (RMSE) values of 0.14, 0.22, and 0.08 mm over 20 mm in X and Y and 10 mm in Z, respectively, and rotational RMSE values of 0.16°, 0.06°, and 0.08° over 10° of pitch, roll, and yaw, respectively. The robotic stage also effectively performed controlled 6D motions, as well as reproduced cranial trajectories over 15 min, with a maximal RMSE of 0.04 mm translationally and 0.04° rotationally, and a prostate trajectory over 2 min, with a maximal RMSE of 0.06 mm translationally and 0.04° rotationally.

Conclusions:

This 6D robotic phantom has proven to be accurate under clinical standards and capable of reproducing tumor motion in 6D. Such functionality makes the robotic phantom usable for either quality assurance or research purposes.
Few‐view cone‐beam CT reconstruction with deformed prior image
Authors: Zhang Hua , Ouyang Luo , Huang Jing , Ma Jianhua , Chen Wufan , Wang Jing
Published: November 2014

Purpose:

Prior images can be incorporated into the image reconstruction process to improve the quality of subsequent cone‐beam CT (CBCT) images from sparse‐view or low‐dose projections. The purpose of this work is to develop a deformed prior image‐based reconstruction (DPIR) strategy to mitigate the deformation between the prior image and the target image.

Methods:

The deformed prior image is obtained by a projection‐based registration approach. Specifically, the deformation vector fields used to deform the prior image are estimated through iteratively matching the forward projection of the deformed prior image and the measured on‐treatment projections. The deformed prior image is then used as the prior image in the standard prior image constrained compressed sensing (PICCS) algorithm. A simulation study on an XCAT phantom and a clinical study on a head‐and‐neck cancer patient were conducted to evaluate the performance of the proposed DPIR strategy.

Results:

The deformed prior image matches the geometry of the on‐treatment CBCT more closely as compared to the original prior image. Consequently, the performance of the DPIR strategy from few‐view projections is improved in comparison to the standard PICCS algorithm, based on both visual inspection and quantitative measures. In the XCAT phantom study using 20 projections, the average root mean squared error is reduced from 14% in PICCS to 10% in DPIR, and the average universal quality index increases from 0.88 in PICCS to 0.92 in DPIR.

Conclusions:

The present DPIR approach provides a practical solution to the mismatch problem between the prior image and target image, which improves the performance of the original PICCS algorithm for CBCT reconstruction from few‐view or low‐dose projections.
Nonlinearity from FT-rheology for liquid crystal 8CB under large amplitude oscillatory shear (LAOS) flow
Authors: Lee Seung Hak , Yong Song Hyeong , Hyun Kyu , Hyup Lee Jun
Published: November 2014

This study systematically investigated the nonlinear stress behavior of liquid crystal (8CB, 4-4′-n-octyl-cyanobiphenyl) in lamellar smectic A phase under large amplitude oscillatory shear (LAOS) flow. To investigate the nonlinear stress response under LAOS flow, the nonlinearity (I3/1) from Fourier transform-rheology as a function of applied shear time (3600 s) was calculated according to changes in both strain amplitude γ0 and frequency ω. The storage modulus G′(t) and loss modulus G″(t) from the conventional rheometer program under various LAOS flow conditions decreased and reached equilibrium as a function of time. This could be attributed to shear alignment of the lamellar smectic A structure. On the contrary, with G′(t) and G″(t), the nonlinearity I3/1(t) showed three different behaviors depending on the magnitude of strain amplitude: (1) Region I: Increased (increased and reached equilibrium), (2) region II: Increased and decreased (showed maximum value; decreased and reached equilibrium), and (3) region III: Decreased (decreased and reached equilibrium) as a function of time. These three different time-dependent behaviors of nonlinearity (I3/1) were shown to be related with the alignment behavior of the lamellar structure. With stress decomposition method, the viscous and elastic stresses of 3600 s were calculated. Viscous and elastic stresses showed different behavior at region I and region III. With an equilibrium value of 3600 s, the G′, G″, and nonlinearity (I3/1) were plotted as a function of strain amplitude, γ0. Interestingly, I3/1(γ0) increased and then decreased (maximum) even though G′(γ0) and G″(γ0) only decreased with increasing strain amplitude. From these results, it can be concluded that LAOS analysis of nonlinear stress, especially I3/1 from FT-rheology, is more sensitive to microstructure than storage modulus G′ and loss modulus G″.
Role of Secondary Metabolites in Establishment of the Mutualistic Partnership between Xenorhabdus nematophila and the Entomopathogenic Nematode Steinernema carpocapsae
Authors: Singh Swati , Orr David , Divinagracia Emmanuel , McGraw Joseph , Dorff Kellen , Forst Steven
Published: November 2014

Xenorhabdus nematophila
engages in a mutualistic partnership with the nematode
Steinernema carpocapsae
, which invades insects, migrates through the gut, and penetrates into the hemocoel (body cavity). We showed previously that during invasion of
Manduca sexta
, the gut microbe
Staphylococcus saprophyticus
appeared transiently in the hemocoel, while
Enterococcus faecalis
proliferated as
X. nematophila
became dominant.
X. nematophila
produces diverse secondary metabolites, including the major water-soluble antimicrobial xenocoumacin. Here, we study the role of
X. nematophila
antimicrobials in interspecies competition under biologically relevant conditions using strains lacking either xenocoumacin (Δ
xcnKL
strain), xenocoumacin and the newly discovered antibiotic F (Δ
xcnKL
:F strain), or all
ngrA
-derived secondary metabolites (
ngrA
strain). Competition experiments were performed in Grace's insect medium, which is based on lepidopteran hemolymph.
S. saprophyticus
was eliminated when inoculated into growing cultures of either the Δ
xcnKL
strain or Δ
xcnKL
:F strain but grew in the presence of the
ngrA
strain, indicating that
ngrA
-derived antimicrobials, excluding xenocoumacin or antibiotic F, were required to eliminate the competitor. In contrast,
S. saprophyticus
was eliminated when coinjected into
M. sexta
with either the Δ
xcnKL
or
ngrA
strain, indicating that
ngrA
-derived antimicrobials were not required to eliminate the competitor
in vivo
.
E. faecalis
growth was facilitated when coinjected with either of the mutant strains. Furthermore, nematode reproduction in
M. sexta
naturally infected with infective juveniles colonized with the
ngrA
strain was markedly reduced relative to the level of reproduction when infective juveniles were colonized with the wild-type strain. These findings provide new insights into interspecies competition in a host environment and suggest that
ngrA
-derived compounds serve as signals for
in vivo
nematode reproduction.
A Previously Uncharacterized, Nonphotosynthetic Member of the Chromatiaceae Is the Primary CO
2
-Fixing Constituent in a Self-Regenerating Biocathode
Authors: Wang Zheng , Leary Dagmar H. , Malanoski Anthony P. , Li Robert W. , Hervey W. Judson , Eddie Brian J. , Tender Gabrielle S. , Yanosky Shelley G. , Vora Gary J. , Tender Leonard M. , Lin Baochuan , Strycharz-Glaven Sarah M.
Published: November 2014

Biocathode extracellular electron transfer (EET) may be exploited for biotechnology applications, including microbially mediated O
2
reduction in microbial fuel cells and microbial electrosynthesis. However, biocathode mechanistic studies needed to improve or engineer functionality have been limited to a few select species that form sparse, homogeneous biofilms characterized by little or no growth. Attempts to cultivate isolates from biocathode environmental enrichments often fail due to a lack of some advantage provided by life in a consortium, highlighting the need to study and understand biocathode consortia
in situ
. Here, we present metagenomic and metaproteomic characterization of a previously described biocathode biofilm (+310 mV versus a standard hydrogen electrode [SHE]) enriched from seawater, reducing O
2
, and presumably fixing CO
2
for biomass generation. Metagenomics identified 16 distinct cluster genomes, 15 of which could be assigned at the family or genus level and whose abundance was roughly divided between
Alpha
- and
Gammaproteobacteria
. A total of 644 proteins were identified from shotgun metaproteomics and have been deposited in the the ProteomeXchange with identifier PXD001045. Cluster genomes were used to assign the taxonomic identities of 599 proteins, with
Marinobacter
,
Chromatiaceae
, and
Labrenzia
the most represented. RubisCO and phosphoribulokinase, along with 9 other Calvin-Benson-Bassham cycle proteins, were identified from
Chromatiaceae
. In addition, proteins similar to those predicted for iron oxidation pathways of known iron-oxidizing bacteria were observed for
Chromatiaceae
. These findings represent the first description of putative EET and CO
2
fixation mechanisms for a self-regenerating, self-sustaining multispecies biocathode, providing potential targets for functional engineering, as well as new insights into biocathode EET pathways using proteomics.
Up against the Wall: Is Yeast Cell Wall Integrity Ensured by Mechanosensing in Plasma Membrane Microdomains?
Authors: Kock Christian , Dufrêne Yves F. , Heinisch Jürgen J.
Published: November 2014

Yeast cell wall integrity (CWI) signaling serves as a model of the regulation of fungal cell wall synthesis and provides the basis for the development of antifungal drugs. A set of five membrane-spanning sensors (Wsc1 to Wsc3, Mid2, and Mtl1) detect cell surface stress and commence the signaling pathway upon perturbations of either the cell wall structure or the plasma membrane. We here summarize the latest advances in the structure/function relationship primarily of the Wsc1 sensor and critically review the evidence that it acts as a mechanosensor. The relevance and physiological significance of the information obtained for the function of the other CWI sensors, as well as expected future developments, are discussed.
Draft Genome Sequence of Lactobacillus plantarum CMPG5300, a Human Vaginal Isolate
Authors: Malik Shweta , Siezen Roland J. , Renckens Bernadet , Vaneechoutte Mario , Vanderleyden Jos , Lebeer Sarah
Published: November 2014

The draft genome of a highly auto-aggregating
Lactobacillus plantarum
strain isolated from a human vagina is reported. The peculiar phenotype also provides an adhesive and co-aggregative potential with various pathogens, which could be of significance in the vaginal niche. Detailed genome analysis could aid in identifying the adhesins of the strain.
Obsessive-compulsive disorder in children and adolescents
Authors: Krebs Georgina , Heyman Isobel
Published: November 2014

Obsessive-compulsive disorder (OCD) in childhood and adolescence is an impairing condition, associated with a specific set of distressing symptoms incorporating repetitive, intrusive thoughts (obsessions) and distressing, time-consuming rituals (compulsions). This review considers current knowledge of causes and mechanisms underlying OCD, as well as assessment and treatment. Issues relating to differential diagnosis are summarised, including the challenges of distinguishing OCD from autism spectrum disorders and tic disorders in youth. The recommended treatments, namely cognitive behaviour therapy and serotonin reuptake inhibiting/selective serotonin reuptake inhibitor medications, are outlined along with the existing evidence-based and factors associated with treatment resistance. Finally, novel clinical developments that are emerging in the field and future directions for research are discussed.
A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999–2008
Authors: Abouzeid Marian , Versace Vincent L , Janus Edward D , Davey Mary-Ann , Philpot Benjamin , Oats Jeremy , Dunbar James A
Published: November 2014

Objectives

This paper reports secular trends in diabetes in pregnancy in Victoria, Australia and examines the effect of including or excluding women with pre-existing diabetes on gestational diabetes (GDM) prevalence estimates.

Design

Population-based observational study.

Setting

All births in Victoria, Australia between 1999 and 2008

Participants

634 932 pregnancies resulting in a birth registered with the Victorian Perinatal Data Collection

Outcome measures

Crude and age-standardised secular trends in pre-existing diabetes and GDM prevalence; secular GDM trends by maternal birthplace; effects on GDM prevalence of including and excluding pre-existing diabetes from the denominator.

Results

Of the 634 932 pregnancies, 2954 (0.5%) occurred in women with pre-existing diabetes and 29 147 (4.6%) were complicated by GDM. Mean maternal age increased from 29.7 years in 1999 to 30.8 years in 2008. GDM prevalence increased in most maternal age groups. In 2008, age-standardised GDM prevalence was 31% higher than in 1999; secular increases were greater for Australian-born non-Indigenous (29% increase) than immigrant women (12.3% increase). The annual number of pregnancies in women with pre-existing diabetes almost doubled from 1999 to 2008 and prevalence increased from 0.4% to 0.6%. However, including or excluding pre-existing diabetes had little effect on GDM prevalence estimates.

Conclusions

Pre-existing diabetes and GDM prevalence increased in Victoria between 1999 and 2008 and rising maternal age does not fully explain these trends. These findings have important implications for preventive initiatives. Including or excluding small numbers of women with pre-existing diabetes resulted in minimal changes in GDM estimates. As pre-existing diabetes in young women increases, this methodological issue will likely become important.
Multicentre study of investigation and management of inpatient hyponatraemia in the UK
Authors: Tzoulis Ploutarchos , Evans Rhys , Falinska Agnieszka , Barnard Maria , Tan Tricia , Woolman Emma , Leyland Rebecca , Martin Nick , Edwards Rebecca , Scott Rebecca , Gurazada Kalyan , Parsons Marie , Nair Devaki , Khoo Bernard , Bouloux Pierre Marc
Published: November 2014

Purpose

Hyponatraemia is associated with significant morbidity and mortality. The objectives of this study were to evaluate the investigation and management of hyponatraemia and to assess the use of different therapeutic modalities and their effectiveness in routine practice.

Study design

This multicentre, retrospective, observational study was conducted at three acute NHS Trusts in March 2013. A retrospective chart review was performed on the first 100 inpatients with serum sodium (sNa) ≤128 mmol/L during hospitalisation.

Results

One hundred patients (47 male, 53 female) with a mean±SD age of 71.3±15.4 years and nadir sNa of 123.4±4.3 mmol/L were included. Only 23/100 (23%) had measurements of paired serum and urine osmolality and sodium, while 31% had an assessment of adrenal reserve. The aetiology of hyponatraemia was unrecorded in 58% of cases. The mean length of hospital stay was 17.5 days with an inpatient mortality rate of 16%. At hospital discharge, 53/84 (63.1%) patients had persistent hyponatraemia, including 20/84 (23.8%) with sNa <130 mmol/L. Overall 37/100 (37%) patients did not have any treatment for hyponatraemia. Among 76 therapeutic episodes, the most commonly used treatment modalities were isotonic saline in 38/76 cases (50%) and fluid restriction in 16/76 (21.1%). Fluid restriction failed to increase sNa by >1 mmol/L/day in 8/10 (80%) cases compared with 4/26 (15.4%) for isotonic saline.

Conclusions

Underinvestigation and undertreatment of hyponatraemia is a common occurrence in UK clinical practice. Therefore, development of UK guidelines and introduction of electronic alerts for hyponatraemia should be considered to improve clinical practice.
Hydromechanical properties of bentonite–sand block assemblies with interfaces in engineered barrier systems
Authors: Popp Till , Rölke Christopher , Salzer Klaus
Published: November 2014

Deep underground repositories for radioactive waste generally rely on a multibarrier system to isolate the waste from the biosphere. It consists of the natural geological barrier provided by the repository host rock and its surroundings, the waste container and an engineered barrier system (EBS): that is, the backfilling and sealing of shafts and galleries to block any preferential path for radioactive contaminants. Bentonite emplaced in compacted block form is the preferred option for the clay buffer for most waste management organizations. In assessing the performance of bentonite block masonries, conductive discrete interfaces inside the sealing elements (i.e. contacts between blocks) and to the host rock may act not only as mechanical weakness planes but also as preferential fluid pathways. We performed hydraulic tests on prefabricated bentonite–sand block assemblies (60:40). The results document that despite existing interfaces, the investigated bentonite block assembly behaves no different to that of the homogenous matrix during the saturation of the buffer. This has been confirmed by gas-injection tests on the former interface, as well by shear tests. The outstanding observation is that our results convincingly demonstrate that interfaces between bentonite bricks may ‘heal’ (not only seal), as was physically verified by confirmation of cohesion after presaturation.
Investigation of gas migration in damaged and resealed claystone
Authors: Zhang Chun-Liang
Published: November 2014

The excavation damaged zone (EDZ) around a radioactive waste repository will act as a potential escape route for gases produced from anoxic corrosion of waste containers and other metallic components within the underground facility. For assessment of the impact of the gases on the repository safety, the gas-flow behaviour of the EDZ has to be characterized, understood and predicted. This issue has been recently investigated for the Callovo-Oxfordian and Opalinus claystones at the GRS laboratory. Various kinds of gas-flow experiments were carried out by flushing nitrogen gas through cracked and resealed claystone samples under different hydromechanical conditions. Extensive results obtained include: (a) gas permeability of fractured claystones in relation to fracture closure under loads; (b) effects of gas humidity on the sealing and gas permeability of fractures; (c) gas-flow behaviour in water-saturated and resealed fractures characterized by three key parameters, namely gas-breakthrough pressure, permeability and shut-in pressure; (d) relationships of the gas parameters to the intrinsic permeability of the resealed claystone and the applied confining stress, as well as relationships between the gas parameters; and (e) the impact of gas-pressure rise on the reopening of the closed pathways and/or creation of new ones in resealed claystone.