bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the Advanced Combustor Liner Composed of CMC/GMC Hybrid Composite Material
Authors: Igashira Ken-ichiroh , Matsubara Go , Matsuda Yoshihiro , Imamura Akira
Published: July 2014

Research Institute of Advanced Materials Gas-Generator (AMG), a joint effort by the Japan Key Technology Center and 14 companies in Japan, has, since 1993, been conducting technological studies on an innovative gas generator that will use 20% less fuel, weigh 50% less, and emit 70% less NOx than the conventional gas generator through the use of advanced materials[1].

In the course of R&D, the feasibility of applying a gradient composite material with ceramic matrix composite (CMC) and glass matrix composite (GMC), which is expected to reduce the thermal stress of actual parts with temperature distribution, was evaluated based on its mechanical and thermal properties, productivity and stress analysis for an actual part as a combustor liner with 500 mm diameter, and non-cooled combustion tests for the liner outlet temperature of 1873 K.

Through our studies we have confirmed the applicability of the selected CMC/GMC hybrid composite as a combustor liner.
EBC Protection of SiC/SiC Composites in the Gas Turbine Combustion Environment: Continuing Evaluation and Refurbishment Considerations
Authors: Eaton Harry E. , Linsey Gary D. , Sun Ellen Y. , More Karren L. , Kimmel Joshua B. , Price Jeffrey R. , Miriyala Narendernath
Published: July 2014

Silicon carbide fiber reinforced silicon carbide composites (SiC/SiC CMC’s) are attractive for use in gas turbine engines as combustor liner materials because the temperature capability allows for reduced cooling. This enables the engine to operate more efficiently and enables the design of very stringent emission goals for NOx and CO. It has been shown, however, that SiC/SiC CMC’s and other silica formers can degrade with time in the high steam environment of the gas turbine combustor due to accelerated oxidation and subsequent volatilization of the silica due to reaction with high pressure water (ref.s 1, 2, 3, & 4). As a result, an environmental barrier coating (EBC) is required in conjunction with the SiC/SiC CMC in order to meet long life goals. Under the U.S. Department of Energy (DOE) sponsored Solar Turbines Incorporated Ceramic Stationary Gas Turbine (CSGT) engine program (ref. 5), EBC systems developed under the HSCT EPM program and improved under the CSGT program have been applied to both SiC/SiC CMC coupons and SiC/SiC CMC combustion liners which have been evaluated in long term laboratory testing and in ground based turbine power generation. This paper discusses the continuing evaluation (see ref. 6) of EBC application to SiC/SiC CMC’s and the results from laboratory and engine test evaluations along with refurbishment considerations.
Development of the Hybrid Gas Turbine: 1st Year Summary — Research and Development on Practical Industrial Cogeneration Technology in Japan
Authors: Tanaka Ryozo , Tastumi Testuo , Ichikawa Yoshihiro , Sanbonsugi Koji
Published: July 2014

Based on the successful results of the Japanese national project for 300 kW ceramic gas turbine(CGT302) development (this project was finished in March 1999), the Ministry of International Trade and Industry (MITI) started “Research and Development on Practical Industrial Co-generation Technology” project in August 1999.

The objective of this project is to encourage prompt industrial applications of co-generation technology that employs hybrid gas turbines (HGT; using both metal and ceramic parts in its high-temperature section) by confirming its soundness and reliability.

The development activities are performed through material evaluation tests and long-term operation tests for the HGT of the medium size (8,000-kW class). It is expected that the development can realize low pollution and reducing the emission of CO2 with highly efficient use of energy. The HGT will be developed by applying ceramic components to an existing commercial 7,000-kW class gas turbine.

The development targets are thermal efficiency of 34% or higher, output of 8,000-kW class, inlet temperature of 1250deg-C, and 4,000hrs of operation period for confirmation of reliability. The HGT for long-term evaluation tests and the test plant are under development. This paper gives the summary of last year’s developments in the HGT project.
Development and Evaluation of Ceramic Components for 8000-kW Class Hybrid Gas Turbine
Authors: Tsuruzono Sazo , Yoshida Makoto , Kubo Toshifumi , Ono Takashi , Fukudome Takero
Published: July 2014

An 8000 kW class hybrid gas turbine (HGT) project, administered by the New Energy and Industrial Technology Development Organization (NEDO) and sponsored by the Ministry of International Trade and Industry (MITI), has been started in July 1999 in Japan[1]. The target of this project is improvement in thermal efficiency and output power by using ceramic components, and earlier commercialization of the gas turbine system. Ceramic components are used for stationary parts subjected to high temperature, such as combustor liners, transition ducts, and first stage turbine nozzles. The gas turbine development was conducted in cooperation with Kawasaki Heavy Industries, Ltd. (KHI).

Kyocera started a study on fabricating the ceramic HGT components after evaluating their shape, placement, and fabrication methods. For these ceramic components, we are using the SN282 silicon nitride material developed and used for ceramic gas turbine components in the previous ceramic gas turbine project (300kW CGT)[2-4]. We have started to accumulate the strength evaluation data, using test bars cut from the aforementioned components, and begun long term tensile creep testing to confirm the reliability of the ceramic components.
Transient Modeling for Assessing Catalytic Combustor Performance in Small Gas Turbine Applications
Authors: Zhu Huayang , Jackson Greg S.
Published: July 2014

The development of lean-premixed catalytic reactors for ultra-low emissions combustors in gas turbines presents many design and operability challenges that are not addressed with conventional steady-state reactor models with one-step chemistry mechanisms. These challenges include transient light-off from low temperatures, catalyst deactivation, and hysteresis in catalytic activity. To address these issues, a transient 1-D reactor model with a validated multi-step surface chemistry mechanism has been developed to explore such behavior in catalytic combustors. The surface chemistry sub-model has been incorporated for investigating lean catalytic combustion of CH4 on Pd-based catalysts. The current study investigated the effects of operating conditions — such as pressure, inlet temperature, and velocity — on catalytic reactor ignition and deactivation. The transient modeling provides curves for reactor light-off for a range of inlet pressures and velocities and reveals conditions wherein Pd-catalyst undergoes reduction/deactivation. Model results are compared with some experimental measurements and implications for catalytic combustor design and operation for gas turbine applications are discussed.
Analysis of a 115MW, 3-Shaft, Helium Brayton Cycle Using Nuclear Heat Source
Authors: Kumar K. Pradeep , Tourlidakis A. , Pilidis P.
Published: July 2014

This paper describes the steady state performance analysis of a 3-shaft closed cycle helium turbine using nuclear heat source. The analysis is carried out using a computer program, which is specifically made for this cycle. The computer model was tested for various Turbine Entry Temperatures (TET) and absolute pressures. The analysis of the change was focused on the compressors, as these are relatively more critical than the rest of the equipments.

The change in TET triggered changes in shaft speed, mass flow rate, power output, absolute pressure etc. Adjustable guide vanes were used to study the operation with constant surge margin. The closed cycle was tested for various absolute pressures and it was established that the efficiency will not be affected in using the inventory control for the load variation.
Demand Based Reliability: A Proposed Measurement Approach
Authors: Steele Robert F. , DellaVilla Sal
Published: July 2014

Significant change is taking place in the power generation market. We are witnessing structural change as we move to a deregulated and competitive global market. And we can also see significant technological change, as new products are driven towards improved efficiencies, greater output and environmental friendliness. Measuring the impact of these changes in terms of efficiency, output and reduced emissions is a straightforward exercise, and the ability to judge if the change has been positive is relatively objective.

However, these structural and technological changes have created challenges in terms of reliability and availability measurements.

• First, our measurement approach is obsolete and has no consideration for duty cycle… The demand, the mission profile, which must be achieved for the unit to meet its economic contribution value, is the single most important issue for power producers today.

• Second, if the measurements have no consideration for the demand that the unit must meet, then the measure is not tied to the profitability of the plant, and therefore the operators are forced to use non-standard measures to accommodate management reporting.

• And third, the strong relationship between effective plant operations and profitability demands “real time” data gathering from the unit control or plant DCS, and transformation of the data points into meaningful information for effective decision support, specifically related to the availability and reliability of systems, components, and the full plant, with a specific focus on measuring “demand” based availability and reliability.

This paper addresses the issue and the opportunities associated with developing both new standard for measuring demand related reliability and availability, as well as the focus on “real time” data capture.
Bleed Airflow CFD Modeling in Aerodynamics Simulations of Jet Engine Compressors
Authors: Conan Franck , Savarese Stephan
Published: July 2014

Several types of bleed airflow in jet engine compressors are required for both aircraft and engine operations. Since accessory, discharge or ventilation bleeds divert a significant percentage of the total input flow rate, it is compulsory to take these variations into account both in through-flow and in 3D Navier-Stokes compressor computations. While the former is straightforward to implement, which has been done for some time, several options are available for the three-dimensional case. The details of such models are most likely to have a local effect on the pressure and velocity fields distribution near the bleed section. Nevertheless, for the purpose of modeling the global effect of bleed flow magnitude on stage matching and overall aerodynamic stage performance, it is thought that a simple geometrical model of the bleed section combined with a simple outlet boundary condition will be accurate enough to provide a realistic representation of the actual compressor characteristics under various bleed flow rate conditions. Thus, our purpose in this study was to develop, implement and validate a simple model based upon both analytical geometry descriptions and outlet flow boundary conditions without any mesh modification or refinement with respect to the standard no-bleed calculations. The analytical description of bleed section is restricted to the intersection of the hub or casing with a set of radial cylinders or axisymetric slots, covering within manufacturing tolerance the known range of bleed section shapes. The physical boundary condition is applied at the intersection of the main flow path with the bleed duct or cavity outlet, ideally imposing a predefined exit flow rate. However, without access to an experimental database of engine bleed flow section measurements, only a qualitative comparison of the models with academic bleed flow experiments has been achieved. In order to assess the modeling scatter due to the details of the methods, two different models have been tested and validated against meridional flow computations, based upon compressor test results.
Low CO2 Emission Combined Cycles With Natural Gas Reforming, Including NOx Suppression
Authors: Lozza Giovanni , Chiesa Paolo
Published: July 2014

The present paper addresses the plant configuration, the thermodynamic performance and the economics of combined cycle power plants, having the following characteristics: (i) CO2 emissions reduced by at least one order of magnitude, (ii) utilization of hydrogen produced by natural gas as the fuel for the gas turbine, (iii) acceptable NOx emissions. Two plant configurations are discussed, based on high pressure reformers heated up by: (i) gas turbine exhausts with hydrogen firing, (ii) oxygen combustion of carbonated purge gases from a pressure-swing-absorber. In the first case CO2 is separated by a chemical absorption plant, in the second from the reformer exhausts after water condensation. The fuel dilution by water/steam or nitrogen was properly kept into account, to achieve NOx emission of about 30-45 ppmvd with a flame temperature of 2300 K. The two plant schemes show a net efficiency of about 48% (including CO2 liquefaction) vs. 56% of the reference combined cycle having the same gas turbine and cycle technology, with a remarkable increase of the net power output (based on the same gas turbine unit). The ability of removing CO2 from the exhausts yields to a 25-30% increase of the cost of electricity, i.e. 40-45 $/ton of CO2 sequestrated.
Pressure Field and Main-Stream Gas Ingestion in a Rotor-Stator Disk Cavity
Authors: Roy R. P. , Xu G. , Feng J. , Kang S.
Published: July 2014

The time-average and unsteady static pressure fields, and the velocity field were measured in a rotor-stator disk cavity and its main-stream gas path. Ingestion of main gas into the disk cavity was also measured. Some CFD simulations were performed. The time-average static pressure was circumferentially periodic (following the vane pitch) in the main-stream gas path and circumferentially uniform in the cavity. The unsteady pressure in the stationary frame of reference was periodic, following the passing of rotor blades, both in the main gas path and in the disk cavity. In the main gas path, the circumferential asymmetry amplitude of the time-average static pressure and the pressure unsteadiness amplitude were of the same order of magnitude. Steady CFD simulations were unable to predict ingestion in the cases where ingestion was detected by tracer gas measurement. It appears that simulations will need to be unsteady as well as three-dimensional to be able to predict ingestion correctly.
Dynamic Modeling and Validation of a Lorentz, Self Bearing Motor Test Rig
Authors: Stephens Lyndon S.
Published: July 2014

A new type of self bearing motor that uses Lorentz type forces to generate both bearing force and motoring torque has been developed. The motor stator is of slotless construction with four, three phase windings. The motor rotor is constructed of 16 surface mounted permanent magnets (PM’s). The main advantage of the design is that it eliminates the tradeoff between motoring torque and bearing force with PM thickness as found in previous designs. This paper presents the dynamic model for the self bearing motor and illustrates how the model is integrated into the overall system model of the motor test rig. The dynamic model is validated against experimentally measured transfer functions with good agreement between the two.
Alternative Multi-Nutating-Disk Engine Configurations for Diverse Applications
Authors: Korakianitis T. , Meyer L. , Boruta M. , McCormick H. E.
Published: July 2014

The nutating engine is a new type of internal combustion engine with distinct advantages over conventional piston engines and gas turbines in small power ranges. The engine’s unique arrangement flexibility allows several alternative disk and shaft configurations, each selected for a different application. Variations in cycle temperature ratio and compression ratio during normal operation enable the engine to effectively become a variable-cycle engine, allowing significant flexibility for maximum efficiency or power or other optimizing function for on-ground stationary or for airborne applications. In its basic configuration the core of the engine is a nutating non-rotating disk, with the center of its hub mounted in the middle of a Z-shaped shaft. The two ends of the shaft rotate, while the disk “nutates”, performs a wobbling motion without rotating around its axis. The motion of the disk circumference prescribes a portion of a sphere. A portion of the area of the disk is used for intake and compression, a portion is used to seal against a center casing, and the remaining portion is used for expansion and exhaust. The compressed air is admitted to an external accumulator, and then into an external combustion chamber before it is admitted to the power side of the disk. A companion paper examines the performance potential of the one-disk engine. This paper examines alternative engine configurations. The external combustion chamber enables the engine to operate on a variable compression ratio cycle. In addition, separate disks of unequal size are used for intake and expansion, resulting in distinct and significant power, efficiency, fuel flexibility, and arrangement advantages over conventional piston engines, over gas turbines, and over the basic nutating-engine configuration. The performance of these arrangements is examined for: on-ground power, on ground efficiency, (auxiliary power, automotive); and for small and light airframe applications for flight Mach numbers from 0 to 1 and altitudes from 0 to 20 km. This publication is the original presentation of the performance potential of several alternative configurations of the basic engine, such as multi-disk arrangements, combustion and exhaust disks of different size, and variable-compression ratio (variable cycle) configurations.
Simulation of Temperature Field Redistribution Through Multistage Cooled Turbines
Authors: Granovski A. V. , Kostege M. K. , Ivanov M. Ja. , Nigmatullin R. Z.
Published: July 2014

The paper presents the detail investigation of temperature field evolution through multistage cooled turbines. An investigation bases on simple enough numerical simulation and allows for transient, heat transfer, viscous and some other important effects on temperature field transformation. Herewith the special test data for a number of cooled turbines are used.

The developed numerical code has the following peculiarities:

- a time-marching method for the unsteady Euler equation system;

- a special algorithm of flow parameters averaging in mixing planes in the middle of axial gaps;

- a monotone implicit scheme of second or third order accuracy in space and time.

The code has been used for a numerical study of the flow pattern in a number of multistage aviation and industrial turbines. The described simulation demonstrates satisfactory correlation between the numerical and experimental data for temperature gradient attenuation in the flowpath of investigated cooled turbines.
Application of a High Resolution Turbine Pyrometer to Heavy Duty Gas Turbines
Authors: Frank Stefan L. F. , Holt Tim O. , Eisenlohr Holger , Raake Dieter
Published: July 2014

This paper describes the application of high resolution pyrometry for surface temperature measurements of the blading in heavy duty gas turbines. First of all, it is essential to know the actual loading, since the cylindrical pyrometer probes are traversed into the hot gas path. Therefore, analytical methods for the calculation of the heat transfer, equivalent stresses and natural frequencies of the probes are described here. The second part presents results of measurements from the latest model V84.3A 60Hz 180 MW gas turbine in the Berlin full load test bed. Emphasis is put on the effect of combustor radiation, limited resolution of the pyrometer and 3D presentations of the data.
Gas Path Blade Tip Seals: Abradable Seal Material Testing at Utility Gas and Steam Turbine Operating Conditions
Authors: Chappel Douglas E. , Vo Ly , Howe Harold W.
Published: July 2014

Abradable seals have long been used to enhance turbomachinery performance by limiting blade tip leakage losses. Most of the literature regarding this subject has focused on aerospace gas turbine materials and conditions. Furthermore, testing and evaluation described in this literature has been conducted on disparate rigs, making direct comparison among the abradable materials investigated difficult.

This study broadens the scope of available data by evaluating fibermetal, thermal-sprayed and honeycomb abradable materials at conditions found in utility gas turbine compressors and steam turbines. High speed rub interaction, low speed rub interaction and erosion data were collected and are discussed in detail.
High-Temperature Fatigue Properties of Single Crystal Superalloys in Air and Hydrogen
Authors: Arakere Nagaraj K.
Published: July 2014

Hot section components in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys such as PWA1480, PWA1484, CMSX-4 and Rene N-4 as these materials provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over their polycrystalline counterparts. Fatigue failures in PWA1480 single crystal nickel-base superalloy turbine blades used in the Space Shuttle Main Engine (SSME) fuel turbopump are discussed. During testing many turbine blades experienced Stage II non-crystallographic fatigue cracks with multiple origins at the core leading edge radius and extending down the airfoil span along the core surface. The longer cracks transitioned from stage II fatigue to crystallographic stage I fatigue propagation, on octahedral planes. An investigation of crack depths on the population of blades as a function of secondary crystallographic orientation (β) revealed that for β = 45+/- 15 degrees tip cracks arrested after some growth or did not initiate at all. Finite element analysis of stress response at the blade tip, as a function of primary and secondary crystal orientation, revealed that there are preferential β orientations for which crack growth is minimized at the blade tip.

To assess blade fatigue life and durability extensive testing of uniaxial single crystal specimens with different orientations has been tested over a wide temperature range in air and hydrogen. A detailed analysis of the experimentally determined Low Cycle Fatigue (LCF) properties for PWA1480 and SC 7-14-6 single crystal materials as a function of specimen crystallographic orientation is presented at high temperature (75 F – 1800 F) in high-pressure hydrogen and air. Fatigue failure parameters are investigated for LCF data of single crystal material based on the shear stress amplitudes on the 24 octahedral and 6 cube slip systems for FCC single crystals. The max shear stress amplitude [Δτmax] on the slip planes reduces the scatter in the LCF data and is found to be a good fatigue damage parameter, especially at elevated temperatures. The parameter Δτmax did not characterize the room temperature LCF data in high-pressure hydrogen well because of the noncrystallographic eutectic failure mechanism activated by hydrogen at room temperature. Fatigue life equations are developed for various temperature ranges and environmental conditions based on power-law curve fits of the failure parameter with LCF test data. These curve fits can be used for assessing blade fatigue life.
Hybrid Fuel Cell Heat Engines: Recent Efforts
Authors: Layne Abbie , Samuelsen Scott , Williams Mark , Holcombe Norman
Published: July 2014

A hybrid heat engine results from the fusion of a heat engine with a non-heat-engine based cycle (unlike systems). The term combined cycle, which refers to similar arrangements, is reserved for the combination of two or more heat engines (like systems). The resulting product of the integration of a gas turbine and a fuel cell is referred to here as a hybrid heat engine or “Hybrid” for short. The intent of this paper is to provide, to the gas turbine community, a review of the present status of hybrid heat engine technologies. Current and projected activities associated with this emerging concept are also presented. The National Energy Technology Laboratory (NETL) is collaborating with other sponsors and the private sector to develop a Hybrid Program. This program will address the issues of technology development, integration, and ultimately the demonstration of what may be the most efficient of power plants in the world—the Hybrid System. In the Hybrid, the synergism between the gas turbine and fuel cell provides higher efficiencies and lower costs than either system can alone. Testing of the first hybrid concept has been initiated at the National Fuel Cell Research Center (NFCRC). FuelCell Energy (FCE) will be testing its first hybrid in 2002. Honeywell’s hybrid program has just begun under the Solid State Energy Conversion Alliance (SECA). SECA fuel cells will ultimately be hybridized with turbines. A competitive SECA solicitation is planned for conceptual studies in 2003. Industry teams will be selected in 2004 to further develop hybrid fuel cell systems.
The Advanced Cycle Low-Power (ACL) Gas Turbine Alternator Project
Authors: Fielder James
Published: July 2014

The latest gas turbine development being undertaken by the Royal Navy is the ACL technology demonstrator programme. The aim of the project is to design and demonstrate a GTA of around 2MW that will have reduced whole life costs when compared to a conventional diesel generator. The project is being managed for the MoD by the Marine Propulsion Systems IPT and being procured through the prime contractor - Turbomeca. The prime contract was awarded in December 2000 and is scheduled to run for five years. This paper describes the main aims and objectives of the project. The paper also gives a detailed overview of the GTA system, describes the key technologies and discusses the outline development programme.
Shape Optimization of High-Speed Axial Compressor Blades Using 3D Navier-Stokes Flow Physics
Authors: Chung June , Shim Jeonghwan , Lee Ki D.
Published: July 2014

A CFD-based design method for transonic axial compressor blades was developed based on three-dimensional Navier-Stokes flow physics. The method starts with a three-dimensional flow analysis of an initial blade, followed by the sectional design optimization performed on a grid plane at a span station with spanwise flux components held fixed. This approach allows the sectional design to include the three-dimensional effects in compressor flows and thus overcome the difficulties associated with the use of quasi-three-dimensional flow physics in sectional designs. The “sectional three-dimensional” analysis at a span station, regardless of the initial flow condition, produced a flow solution nearly identical to the three-dimensional flow solution at the span station. After the validation of the sectional three-dimensional analysis, the developed design method was successfully applied to multiple span stations of NASA Rotor 37 blade in the inverse mode of finding a target geometry corresponding to a specified target pressure distribution. The method was also applied to optimize the adiabatic efficiencies of the blade section of Rotor 37 at 70 percent span station. The design results from two design attempts with different initial geometry indicate that there is not a lot of room for improvement for the blade section of Rotor 37 at 70 percent span station, but the present design method is capable of producing a large performance gain for a blade with lower efficiency.
Effect of nitrogen upon structural and magnetic properties of FePt in FePt/AlN multilayer structures
Authors: Gao Tenghua , Zhang Cong , Sannomiya Takumi , Muraishi Shinji , Nakamura Yoshio , Shi Ji
Published: July 2014

This paper investigates the effect of the addition of nitrogen in FePt layers for ultrathin FePt/AlN multilayer structures. X-ray diffraction results reveal that a compressive stress relaxation occurs after annealing owing to the release of interstitial nitrogen atoms in the FePt layers. The introduction of nitrogen also induces a large in-plane compressive strain during grain growth not seen in FePt deposited without nitrogen. This strain is considered to decrease the driving force for (111) grain growth and FePt ordering.
Long Noncoding RNAs in Myocardial Infarction
Authors: Drum Chester L.
Published: July 2014

Peripheral blood samples can identify lncRNA changes in patients with heart attack.
Brain Cancer Spreads
Authors: Perryman Lara , Erler Janine T.
Published: July 2014

The discovery that 20% of patients with brain cancer have circulating tumor cells breaks the dogma that these cells are confined to the brain.
Fighting Terror with Nanotechnology
Authors: White Nathan J.
Published: July 2014

Intravenous nanoparticles with platelet-like activity improve survival after blast injury.
Antivirulence Activity of the Human Gut Metabolome
Authors: Antunes L. Caetano M. , McDonald Julie A. K. , Schroeter Kathleen , Carlucci Christian , Ferreira Rosana B. R. , Wang Melody , Yurist-Doutsch Sophie , Hira Gill , Jacobson Kevan , Davies Julian , Allen-Vercoe Emma , Finlay B. Brett
Published: July 2014

The mammalian gut contains a complex assembly of commensal microbes termed microbiota. Although much has been learned about the role of these microbes in health, the mechanisms underlying these functions are ill defined. We have recently shown that the mammalian gut contains thousands of small molecules, most of which are currently unidentified. Therefore, we hypothesized that these molecules function as chemical cues used by hosts and microbes during their interactions in health and disease. Thus, a search was initiated to identify molecules produced by the microbiota that are sensed by pathogens. We found that a secreted molecule produced by clostridia acts as a strong repressor of
Salmonella
virulence, obliterating expression of the
Salmonella
pathogenicity island 1 as well as host cell invasion. It has been known for decades that the microbiota protects its hosts from invading pathogens, and these data suggest that chemical sensing may be involved in this phenomenon. Further investigations should reveal the exact biological role of this molecule as well as its therapeutic potential.

IMPORTANCE
Microbes can communicate through the production and sensing of small molecules. Within the complex ecosystem formed by commensal microbes living in and on the human body, it is likely that these molecular messages are used extensively during the interactions between different microbial species as well as with host cells. Deciphering such a molecular dialect will be fundamental to our understanding of host-microbe interactions in health and disease and may prove useful for the design of new therapeutic strategies that target these mechanisms of communication.
Inactivation of
thyA
in Staphylococcus aureus Attenuates Virulence and Has a Strong Impact on Metabolism and Virulence Gene Expression
Authors: Kriegeskorte Andre , Block Desiree , Drescher Mike , Windmüller Nadine , Mellmann Alexander , Baum Cathrin , Neumann Claudia , Lorè Nicola Ivan , Bragonzi Alessandra , Liebau Eva , Hertel Patrick , Seggewiss Jochen , Becker Karsten , Proctor Richard A. , Peters Georg , Kahl Barbara C.
Published: July 2014

Staphylococcus aureus
thymidine-dependent small-colony variants (TD-SCVs) are frequently isolated from patients with chronic
S. aureus
infections after long-term treatment with trimethoprim-sulfamethoxazole (TMP-SMX). While it has been shown that TD-SCVs were associated with mutations in thymidylate synthase (TS;
thyA
), the impact of such mutations on protein function is lacking. In this study, we showed that mutations in
thyA
were leading to inactivity of TS proteins, and TS inactivity led to tremendous impact on
S. aureus
physiology and virulence. Whole DNA microarray analysis of the constructed Δ
thyA
mutant identified severe alterations compared to the wild type. Important virulence regulators (
agr
,
arlRS
,
sarA
) and major virulence determinants (
hla
,
hlb
,
sspAB
, and
geh
) were downregulated, while genes important for colonization (
fnbA
,
fnbB
,
spa
,
clfB
,
sdrC
, and
sdrD
) were upregulated. The expression of genes involved in pyrimidine and purine metabolism and nucleotide interconversion changed significantly. NupC was identified as a major nucleoside transporter, which supported growth of the mutant during TMP-SMX exposure by uptake of extracellular thymidine. The Δ
thyA
mutant was strongly attenuated in virulence models, including a
Caenorhabditis elegans
killing model and an acute pneumonia mouse model. This study identified inactivation of TS as the molecular basis of clinical TD-SCV and showed that
thyA
activity has a major role for
S. aureus
virulence and physiology.

IMPORTANCE
Thymidine-dependent small-colony variants (TD-SCVs) of
Staphylococcus aureus
carry mutations in the thymidylate synthase (TS) gene (
thyA
) responsible for
de novo
synthesis of thymidylate, which is essential for DNA synthesis. TD-SCVs have been isolated from patients treated for long periods with trimethoprim-sulfamethoxazole (TMP-SMX) and are associated with chronic and recurrent infections. In the era of community-associated methicillin-resistant
S. aureus
, the therapeutic use of TMP-SMX is increasing. Today, the emergence of TD-SCVs is still underestimated due to misidentification in the diagnostic laboratory. This study showed for the first time that mutational inactivation of TS is the molecular basis for the TD-SCV phenotype and that TS inactivation has a strong impact on
S. aureus
virulence and physiology. Our study helps to understand the clinical nature of TD-SCVs, which emerge frequently once patients are treated with TMP-SMX.
Effect of tree nuts on metabolic syndrome criteria: a systematic review and meta-analysis of randomised controlled trials
Authors: Blanco Mejia Sonia , Kendall Cyril W C , Viguiliouk Effie , Augustin Livia S , Ha Vanessa , Cozma Adrian I , Mirrahimi Arash , Maroleanu Adriana , Chiavaroli Laura , Leiter Lawrence A , de Souza Russell J , Jenkins David J A , Sievenpiper John L
Published: July 2014

Objective

To provide a broader evidence summary to inform dietary guidelines of the effect of tree nuts on criteria of the metabolic syndrome (MetS).

Design

We conducted a systematic review and meta-analysis of the effect of tree nuts on criteria of the MetS.

Data sources

We searched MEDLINE, EMBASE, CINAHL and the Cochrane Library (through 4 April 2014).

Eligibility criteria for selecting studies

We included relevant randomised controlled trials (RCTs) of ≥3 weeks reporting at least one criterion of the MetS.

Data extraction

Two or more independent reviewers extracted all relevant data. Data were pooled using the generic inverse variance method using random effects models and expressed as mean differences (MD) with 95% CIs. Heterogeneity was assessed by the Cochran Q statistic and quantified by the I2statistic. Study quality and risk of bias were assessed.

Results

Eligibility criteria were met by 49 RCTs including 2226 participants who were otherwise healthy or had dyslipidaemia, MetS or type 2 diabetes mellitus. Tree nut interventions lowered triglycerides (MD=−0.06 mmol/L (95% CI −0.09 to −0.03 mmol/L)) and fasting blood glucose (MD=−0.08 mmol/L (95% CI −0.16 to −0.01 mmol/L)) compared with control diet interventions. There was no effect on waist circumference, high-density lipoprotein cholesterol or blood pressure with the direction of effect favouring tree nuts for waist circumference. There was evidence of significant unexplained heterogeneity in all analyses (p<0.05).

Conclusions

Pooled analyses show a MetS benefit of tree nuts through modest decreases in triglycerides and fasting blood glucose with no adverse effects on other criteria across nut types. As our conclusions are limited by the short duration and poor quality of the majority of trials, as well as significant unexplained between-study heterogeneity, there remains a need for larger, longer, high-quality trials.

Trial registration number

NCT01630980.
Regional differences in the incidence of self-reported type 2 diabetes in Germany: results from five population-based studies in Germany (DIAB-CORE Consortium)
Authors: Schipf Sabine , Ittermann Till , Tamayo Teresa , Holle Rolf , Schunk Michaela , Maier Werner , Meisinger Christine , Thorand Barbara , Kluttig Alexander , Greiser Karin Halina , Berger Klaus , Müller Grit , Moebus Susanne , Slomiany Uta , Icks Andrea , Rathmann Wolfgang , Völzke Henry
Published: July 2014

Background

Population-based data are paramount to investigate the long-term course of diabetes, for planning in healthcare and to evaluate the cost-effectiveness of primary prevention. We analysed regional differences in the incidence of self-reported type 2 diabetes mellitus in Germany.

Methods

Data of participants (baseline age 45–74 years) from five regional population-based studies conducted between 1997 and 2010 were included (mean follow-up 2.2–7.1 years). The incidence of self-reported type 2 diabetes mellitus at follow-up was compared. The incidence rates per 1000 person-years (95% CI) and the cumulative incidence (95% CI) from regional studies were directly standardised to the German population (31 December 2007) and weighted by inverse probability weights for losses to follow-up.

Results

Of 8787 participants, 521 (5.9%) developed type 2 diabetes mellitus corresponding to an incidence rate of 11.8/1000 person-years (95% CI 10.8 to 12.9). The regional incidence was highest in the East and lowest in the South of Germany with 16.9 (95% CI 13.3 to 21.8) vs 9.3 (95% CI 7.4 to 11.1)/1000 person-years, respectively. The incidence increased with age and was higher in men than in women.

Conclusions

The incidence of self-reported type 2 diabetes mellitus shows regional differences within Germany. Prevention measures need to consider sex-specific differences and probably can be more efficiently introduced toward those regions in need.
Cleaning the Periodicity in Discrete- and Continuous-Time Nonlinear Dynamical Systems
Authors: Rech Paulo C.
Published: July 2014

We investigate periodicity suppression in two-dimensional parameter-spaces of discrete- and continuous-time nonlinear dynamical systems, modeled respectively by a two-dimensional map and a set of three first-order ordinary differential equations. We show for both cases that, by varying the amplitude of an external periodic forcing with a fixed angular frequency, windows of periodicity embedded in a chaotic region may be totally suppressed.
Low-Dimensional Homoclinic Bifurcations of Repellers
Authors: Artigue Alfonso
Published: July 2014

We study the relationship between homoclinic orbits associated with repellers, usually called snap-back repellers, and expanding sets of smooth endomorphisms. We also consider critical homoclinic orbits and prove that the bifurcations they create constitute a codimension one phenomenon. This and other possible routes to the creation of homoclinic orbits are considered in low dimensions.
A Memristor-Based Scroll Chaotic System — Design, Analysis and Circuit Implementation
Authors: Li Huifang , Wang Lidan , Duan Shukai
Published: July 2014

A scroll chaotic system containing a HP memristor model and triangular wave sequence is proposed in this article. Because the memristor is both a nonlinear element and a memory element intrinsically, it is considered a potential candidate to reduce system power consumption and circuit size. A reasonable mathematical structure of triangular wave sequence and the selection of appropriate amplitude, balance point and turning point reduce the dynamic range of signal input caused by the integrator. The proposed system produces a wealth of chaos, just by changing one parameter. Circuit simulations are conducted and the chaotic attractors can be observed. Theoretical analysis, computer simulation and calculation of maximum Lyapunov exponent have been used to research the basic dynamics of this system. The consistency of circuit implementation and computer simulations verifies the effectiveness of the system design.
Powers of quantum white noise derivatives
Authors: Ettaieb Aymen , Ouerdiane Habib , Rguigui Hafedh
Published: July 2014

We introduce a new operator obtained from the quantum white noise (QWN) derivatives which satisfies new important commutation relations generalizing those of the renormalized power white noise Lie algebra introduced by Accardi, Boukas and Franz (see Ref. 5) without using renormalization conditions.
Age relationships of the Rembrandt basin and Enterprise Rupes, Mercury
Authors: Ferrari Sabrina , Massironi Matteo , Marchi Simone , Byrne Paul K. , Klimczak Christian , Martellato Elena , Cremonese Gabriele
Published: July 2014

The Rembrandt basin is the largest well-preserved impact feature in the southern hemisphere of Mercury. Its smooth volcanic infill hosts wrinkle ridges and graben, and the entire basin is cross-cut by the Enterprise Rupes scarp system. On the basis of the Model Production Function crater chronology, our analysis shows that the formation of the Rembrandt basin occurred at 3.8±0.1 Ga during the Late Heavy Bombardment, consistent with previous studies. We also find that the smooth plains interior to the basin were emplaced between 3.7 and 3.6±0.1 Ga, indicative of a resurfacing event within the Rembrandt basin that is consistent with the presence of partially buried craters. These youngest plains appear temporally unrelated to basin formation, and so we regard their origin as likely to be due to volcanism. We identify the same chronological relationship for the terrain cross-cut by Enterprise Rupes to the west of the basin. Therefore, volcanic activity affected both the basin and its surroundings, but ended prior to the majority of basin- and regional-scale tectonic deformation. If Enterprise Rupes formed prior to the Rembrandt basin, then regional-scale tectonic activity along this structure might have lasted at least 200 myr.
Transitions to Adulthood in Developing Countries
Authors: Juárez Fatima , Gayet Cecilia
Published: July 2014

The study of transitions to adulthood in developing countries merits a review that considers new developments affecting specific spheres of life. High unemployment rates in certain job markets, new health vulnerabilities, and modified preferences regarding marriage types, all within a framework of poverty, manifest in a world in which fewer certainties result in new ways of experiencing the transition to adulthood. The objective of this article is to review recent literature on interactions among the spheres of school, work, sexuality, family formation, health, political expression, and citizenship of adolescents and young adults in developing countries. Scholars are identifying diverse life paths and observing transitions to adulthood at different ages and modalities within the same society.
Taxes and Fiscal Sociology
Authors: William Martin Isaac , Prasad Monica
Published: July 2014

This article reviews recent research in fiscal sociology. We specifically examine contributions to the study of taxation that illuminate core issues in the sociology of contemporary capitalism, including the causes of poverty and inequality in rich countries and of inequality between rich and poor countries. Research on developed countries suggests that tax policy changes are important for explaining rising income inequality, tax policies may structure durable inequalities of race and gender, and earnings-conditional tax subsidies may alleviate poverty more effectively and with less stigma than means-tested social spending. Scholars also find the most generous welfare states rely the most heavily on regressive taxes, although there is disagreement over how this association arises. Comparative research on developing countries shows consumption taxes are more conducive to growth than taxes on income, tax-financed spending benefits growth if it is spent on productive investments, and taxation strengthened democracy and state building in medieval and early modern Europe. However, there is disagreement as to whether taxation contributes to state building in contemporary developing countries and whether foreign aid undermines democracy by undermining taxation. These questions are the focus of considerable current research.
Effects of mtDNA in SHR-mtF344 versus SHR conplastic strains on reduced OXPHOS enzyme levels, insulin resistance, cardiac hypertrophy, and systolic dysfunction
Authors: Houštěk Josef , Vrbacký Marek , Hejzlarová Kateřina , Zídek Václav , Landa Vladimír , Šilhavý Jan , Šimáková Miroslava , Mlejnek Petr , Kazdová Ludmila , Mikšík Ivan , Neckář Jan , Papoušek František , Kolář František , Kurtz Theodore W. , Pravenec Michal
Published: July 2014

Common inbred strains of the laboratory rat can be divided into four major mitochondrial DNA (mtDNA) haplotype groups represented by the BN, F344, LEW, and SHR strains. In the current study, we investigated the metabolic and hemodynamic effects of the SHR vs. F344 mtDNA by comparing the SHR vs. SHR-mtF344 conplastic strains that are genetically identical except for their mitochondrial genomes. Altogether 13 amino acid substitutions in protein coding genes, seven single nucleotide polymorphisms in tRNA genes, and 12 single nucleotide changes in rRNA genes were detected in F344 mtDNA compared with SHR mtDNA. Analysis of oxidative phosphorylation system (OXPHOS) in heart left ventricles (LV), muscle, and liver revealed reduced activity and content of several respiratory chain complexes in SHR-mtF344 conplastic rats compared with the SHR strain. Lower function of OXPHOS in LV of conplastic rats was associated with significantly increased relative ventricular mass and reduced fractional shortening that was independent of blood pressure. In addition, conplastic rats exhibited reduced sensitivity of skeletal muscles to insulin action and impaired glucose tolerance. These results provide evidence that inherited alterations in mitochondrial genome, in the absence of variation in the nuclear genome and other confounding factors, predispose to insulin resistance, cardiac hypertrophy and systolic dysfunction.
Structural changes in the gut microbiome of constipated patients
Authors: Zhu Lixin , Liu Wensheng , Alkhouri Razan , Baker Robert D. , Bard Jonathan E. , Quigley Eamonn M. , Baker Susan S.
Published: July 2014

Previous studies using culture-based methods suggested an association between constipation and altered abundance of certain taxa of the colonic microbiome. We aim to examine the global changes in gut microbial composition of constipated patients. A cross-sectional pilot study using 16S rRNA gene pyrosequencing was performed to compare stool microbial composition of eight constipated patients and 14 nonconstipated controls. Only obese children were enrolled so that the microbiome features associated with constipation would not be obscured by those associated with obesity. The sequencing reads were processed by QIIME for quantitative analysis of the microbial composition at genus and above levels. Dietary intake for all the individuals was assessed by dietary recalls and a food frequency questionnaire. The ecological diversities of fecal microbiome of the constipated patients differed from those of the controls. Significantly decreased abundance in Prevotella and increased representation in several genera of Firmicutes were observed in constipated patients compared with controls. The conventional probiotic genera Lactobacillus and Bifidobacteria were not decreased in the microbiomes of the constipated patients. These alterations in the fecal microbiome of constipated patients suggested that a novel probiotic treatment including certain Prevotella strains may be more effective than conventional probiotic products incorporating Lactobacillus or Bifidobacterium species. While it is possible that the observed changes in the microbiome in constipated subjects are a consequence of a low-fiber diet, these changes also predict a different pattern of bacterial fermentation end-products, such as increased butyrate production, which may contribute to pathogenesis of constipation.