bluuebunny/crossref_metadata_2025 huggingface dataset:
Establishing a Methodology for Resolving Convective Heat Transfer From Complex Geometries
Authors: Ostanek J. , Thole K. , Prausa J. , Van Suetendael A.
Published: August 2009

Current turbine airfoils must operate at extreme temperatures, which are continuously driven higher by the demand for high output engines. Internal cooling plays a key role in the longevity of gas turbine airfoils. Ribbed channels are commonly used to increase heat transfer by generating turbulence and to provide a greater convective surface area. Because of the increasing complexity in airfoil design and manufacturing, a methodology is needed to accurately measure the convection coefficient of a rib with a complex shape. Previous studies that have measured the contribution to convective heat transfer from the rib itself have used simple rib geometries. This paper presents a new methodology to measure convective heat transfer coefficients on complex ribbed surfaces. The new method was applied to a relatively simple shape so that comparisons could be made with a commonly accepted method for heat transfer measurements. A numerical analysis was performed to reduce experimental uncertainty and to verify the lumped model approximation used in the new methodology. Experimental measurements were taken in a closed-loop channel using fully rounded, discontinuous, skewed ribs oriented 45° to the flow. The channel aspect ratio was 1.7:1 and the ratio of rib height to hydraulic diameter was 0.075. Heat transfer augmentation levels relative to a smooth channel were measured to be between 4.7 and 3 for Reynolds numbers ranging from 10,000 to 100,000.
An Integrated Approach to Gas Turbine Monitoring and Diagnostics
Authors: Loboda Igor , Yepifanov Sergey , Feldshteyn Yakov
Published: August 2009

This paper presents an investigation of a conventional gas turbine diagnostic process and its generalization. A usual sequence of diagnostic actions consists of two stages: monitoring (fault detection) and subsequent proper diagnosis (fault identification). Such an approach neither implies fault identification nor uses the information about incipient faults unless the engine is recognized as faulty. In previous investigations for engine steady state operation conditions we addressed diagnostics problems without their relation with the monitoring process. Fault classes were given by samples of patterns generated by a static gas turbine performance model. This fault simulation took into account faults of varying severity including incipient ones. A diagnostic algorithm employed artificial neural networks to identify an actual fault. In the present paper we consider the monitoring and diagnosis as joint processes extending our previous approach over both of them. It is proposed to form two classes for the monitoring using the above-mentioned classes constructed for the diagnosis. A two-shaft industrial gas turbine has been chosen to test the proposed integrated approach to monitoring and diagnosis. A general recommendation following from the presented investigation is to identify faults simultaneously with fault detection. This permits accumulating preliminary diagnoses before the engine faulty condition is detected and a rapid final diagnosis after the fault detection.
Numerical Investigation on the Originating Mechanism of Unsteadiness in Tip Leakage Flow for a Transonic Fan Rotor
Authors: Du Juan , Lin Feng , Zhang Hongwu , Chen Jingyi
Published: August 2009

Despite the fact that the importance of steady tip leakage flows in rotor efficiency and stability has been long recognized and extensively studied, the unsteadiness of tip leakage flows became an interesting research topic only about 10 years ago. Many issues, such as its onset conditions, its role in compressor instability, etc. need to be further explored. In this paper, we present a numerical investigation on the influences of two important driving “forces”, the incoming main flow and the tip leakage flow, to clarify the originating mechanism of self-induced unsteadiness in transonic compressors. NASA Rotor 67 is chosen as the computational model. It is found that among all the simulated cases, the self-induced unsteadiness exists when the size of the tip clearance equals or larger than design tip clearance of the computational model. The time-dependent flow pattern in the rotor tip region is provided to illustrate that the main unsteady regions are on the blade’s pressure side that happens to be under the alternate influence of tip leakage flow and the incoming main flow. It is found the self-induced unsteady mechanism in the transonic rotor is the same as that in previously studied low-speed rotor. The interaction between shock wave and tip leakage vortex does not initiate the self-induced unsteadiness, but might be the cause of other unsteadiness, such as turbulent unsteadiness. A correlation based on the momentum ratio of tip leakage flow over the main incoming flow at the tip region is used as an indicator for the onset of the self-induced unsteadiness in tip leakage flow.
Refinement of Physics Based Approach Used in the Prediction of Impeller Rotordynamic Forces for Centrifugal Compressors
Authors: Moore J. Jeffrey , Ransom David L.
Published: August 2009

The accurate prediction of centrifugal compressor stability continues to be an important area of interest in the oil and gas industry. Ensuring stability is critical to the cost-effective installation and operation of these machines in remote environments where field stability problems are much more expensive to diagnose and correct. Current industry standards and tools for the prediction of impeller destabilizing forces are based on empirical methods that, to date, have served fairly well for systems with reasonable stability margins. However, as stability margins are decreased, use of a modeling method that is more physics based that can better represent the observed trends in machine behavior at low stability margins is needed. Furthermore, the development of mega-class Liquefied Natural Gas (LNG) compressors and ultra-high pressure re-injection compressors provide further motivation to improve accuracy. In this paper, a new physics based expression for the prediction of impeller cross-coupling, previously introduced by Moore et al. [1] is further investigated by analyzing several classes and scale factors of impellers ranging from 2-D designs used in re-injection up to full 3-D impellers typically used in LNG. The new expression is based on both numerical simulation (CFD) and experimental test data from a known instability. Comparisons are made for overall stability prediction as well as sensitivity to system changes. Conclusions are made regarding the applicability and limits of this new approach.
Foreign Object Damage and Fatigue Strength Loss in Compressor Blades
Authors: Nikhamkin Mickhail S. , Voronov Leonid V. , Semenova Irina V.
Published: August 2009

Foreign object damage (FOD) is always an all-important problem of gas turbine engines safety, reliability and operating costs. This paper describes experimental and numerical prediction investigations of FOD to compressor blades of gas turbine engine. Experimental modeling of FOD processes was done using a special plant on the base of a pneumatic gun. Real steel blades of a high-pressure compressor were impacted with spherical steel projectiles at the velocity about 200 m/s. Typical in-service damages as well as round dents, tears and bends were reproduced in the experiment. Numerical prediction analyses of the damage process were fulfilled by finite element method (FEM). Material behavior is described with elastic-plastic strain rate dependent model. We find the form and sizes of the calculated damages to be in good agreement with the experimental findings. Furthermore, the experimental and computational procedure for estimation of fatigue strength loss of damaged blades is proposed. It is based on study of stress concentration in damages. Stress concentration factor for different concentrator shapes was calculated using 3-D finite element analyses and refined via a stress concentration sensitivity factor. Stress concentration sensitivity factor was experimentally defined through fatigue tests of real blades with V-shape notches at leading edge. This technique supposes minimum laborious fatigue tests. Experimentally confirmed numerical methodology and model may be used for prediction study of FOD and fatigue strength loss of gas turbine engine blades.
A Systematic Comparison and Multi-Objective Optimisation of Humid Power Cycles: Part II—Economics
Authors: Kavanagh Ronan M. , Parks Geoffrey T.
Published: August 2009

The STIG, HAT and TOPHAT cycles lie at the centre of the debate on which humid power cycle will deliver optimal performance when applied to an aero-derivative gas turbine and, indeed, when such cycles will be implemented. Of these humid cycles, it has been claimed that the TOPHAT cycle has the highest efficiency and specific work, followed closely by the HAT (Humid Air Turbine) and then the STIG (STeam Injected Gas turbine) cycle. In this study, the systems have been simulated using consistent thermodynamic and economic models for the components and working fluid properties, allowing a consistent and non-biased appraisal of these systems. Part 1 of these two papers focussed on the thermodynamic performance and the impact of the system parameters on the performance, part 2 studies the economic performance of these cycles. The three humid power systems and up to ten system parameters are optimised using a multi-objective Tabu Search algorithm, developed in the Cambridge Engineering Design Centre.
Improving Component Life Prediction Accuracy and Reliability Through Physics Based Prognosis: A Probabilistic Turbine Blade Case Study
Authors: Koul Ashok K. , Bhanot Saurabh , Tiku Ajay , Junkin Brent
Published: August 2009

The paper presents the results of a probabilistic creep life study on RRA 501 KB turbine blades and demonstrates the importance of using physics based probabilistic damage modeling techniques to deal with life prediction uncertainty in cast equiaxed components. It is shown that physics based damage analysis yields accurate results and considerably less mechanical properties data is needed for life prediction of cast components. In physics based damage analysis, it is also easy to quickly assess the life limiting damage modes and to establish fracture critical locations in components. In physics based modeling, the influence of individual microstructural or thermal-mechanical loading factors on metallurgical crack nucleation can also be studied with relative ease. Residual life of service exposed parts and effectiveness of life extension techniques can also be predicted because the state of microstructure due to prior service and repair can be taken into account. In this study, Life Prediction Technologies Inc.’s (LPTi’s) prognosis tool known as XactLIFE™ was successfully used to establish the fracture critical location of RRA 501KB first stage gas turbine blades under steady state loads. Deterministic analysis was first used to compute the lower bound airfoil nodal creep life of the various finite element nodes and this was followed by probabilistic creep life analysis to take into account the variability of microstructure from one blade to another. The analysis used typical engine operating data from the field in terms of engine speed and average turbine inlet temperature (TIT). The primary objectives of the case study are to show how prognosis can allow a user to predict component fracture critical locations, establish inspection intervals to avoid failures and establish fleet reliability for engine specific operating conditions.
Aerodynamics of Compressor Casing Treatment: Part I—Experiment and Time-Accurate Numerical Simulation
Authors: Lin Fan , Ning Fangfei , Liu Huoxing
Published: August 2009

This paper presents both experimental and unsteady RANS investigations of a slot-type casing treatment at a transonic axial flow compressor rotor. Experimental results show that at 60% and 98% of rotor design wheel speeds, approximately 100% and 200% extra extensions of the rotor operation ranges are achieved, respectively. On the other hand, there are about 3.6% and 2.0% drops of efficiencies at 60% and 98% speeds respectively if comparisons are made at the same peak-efficiency mass flow rates of the solid casing case. If comparing the respective peak efficiencies for the solid casing case with those for the treated casing case, there are still about 3.4% and 0.7% drops at 60% and 98% speeds, respectively. As for the unsteady RANS study, an in-house unsteady RANS code has been used to study the casing treatment flow at several operating points, i.e., the peak efficiency and the near stall with regard to the solid casing case at 60% speed and 98% speed, respectively. It is shown that the interactions between the blade passage flow and the casing treatment flow exhibit different manner at two rotating speeds. The flow condition in which the rotor operates, i.e., either the subsonic condition at the 60% speed or the transonic condition with passage shock presented at the 98% speed, is one of the determinate factors that are responsible for the manner the casing treatment works. The loss production due to casing treatment is also particularly discussed.
Mitochondrial DNA Variation Reveals Genetically Distinct Sympatric Populations of Anadromous and Nonanadromous Atlantic Salmon,Salmo salar
Authors: Birt Tim P. , Green John M. , Davidson William S.
Published: August 2009

Mitochondrial DNA variation was surveyed among wild anadromous and nonanadromous Atlantic salmon, Salmo salar, which occur in sympatry in Gambo River, Newfoundland. Seventy-one salmon were screened with 18 restriction enzymes, 5 of which revealed nucleotide sequence variation. Nucleotide sequence divergence estimates among the four distinct genotypes detected ranged from 0.2 to 1.0%. Significant heterogeneity in mtDNA genotype frequencies supports the view that exchange of breeding females between groups is infrequent or does not occur, an inference consistent with the observation that the forms use separate spawning sites within the system. Mitochondrial DNA diversity was somewhat greater among the nonanadromous salmon than the anadromous salmon (nucleon diversity (h) = 0.37 and 0.52, respectively). Potential mechanisms for maintaining reproductive isolation include selection of different spawning habitats, different spawning times, and sexual selection based upon the size difference between the two forms.
Composition and Mechanics of Routine Swimming of Rainbow Trout,Oncorhynchus mykiss
Authors: Webb Paul W.
Published: August 2009

Routine swimming encompasses all volitional motions of fish. It is usually assumed to be quasi-steady, i.e. routine swimming is mechanically equivalent to steady swimming. Routine swimming of rainbow trout, Oncorhynchus mykiss, was dominated by unsteady motions of linear and centripetal (angular) acceleration. Constant-speed swimming was rare. Mean speeds and acceleration rates were small. Tail-beat frequencies were nevertheless strongly correlated with mean swimming speed, but increased more rapidly with increasing speed in routine swimming than in steady swimming. Tail-beat amplitudes and propulsive wavelengths were similar to values seen in steady swimming. The composition of routine swimming and analysis of the force balance showed that routine swimming was not quasi-steady. Therefore, forces and rates of working should be estimated from a complete description of whole-body deformation. This is impractical. Drag dominated resistance in routine swimming, such that average thrust (= resistance) may be computed from mean speed and/or averaged kinematic variables for the trailing edge with a correction factor of approximately 3. Analysis of routine swimming may permit comparisons among a wider range of vertebrates than possible with commonly used methods.
Behaviour, Energetics, and Associated Mortality of Young-of-the-Year White Perch (Morone americana) and Yellow Perch (Perca flavescens) under Simulated Winter Conditions
Authors: Johnson Timothy B. , Evans David O.
Published: August 2009

After 150 d of simulated winter conditions, 71.2% of the white perch (Morone americana) had died at 2.5 °C, while only 11.1% had died at 4.0 °C. For yellow perch (Perca flavescens), 0.8% had died at 2.5 °C, while 17.7% had died at 4.0 °C. For both species, small fish died first. Multiple regression models relating overwinter mortality versus fall total length and winter duration predict 3.3 times greater mortality for white perch versus similar sized yellow perch at winter temperature regimes typical of the Great Lakes region. In laboratory tanks, white perch remained active throughout the winter period, while yellow perch sought cover and rested on or near the bottom of the experimental tanks. As a direct consequence, yellow perch had a lower routine metabolic rate and consumed body energy more gradually than white perch. During their inactive wintering period at 4.0 °C, yellow perch consumed 25.8% less oxygen than white perch. Actual measurements of dry weight loss indicated that yellow perch in the experimental tanks at 2.5 °C consumed 24.6% less dry weight than similar sized white perch. These differences in overwinter behaviour, metabolism, and survival appear to be adequate to account for observed differences in survival of these species in the wild.
Replacement of herbivore zooplankton species along gradients of ecosystem productivity and fish predation pressure
Authors: Hessen Dag O. , Andersen Tom , Faafeng Bjørn A.
Published: August 2009

In general the pooling of major taxa did not provide a basis for classifying zooplankton communities in 342 large Norwegian lakes, as neither cladocerans nor calanoids varied systematically with lake productivity or fish predation pressure. At the species level, most herbivorous cladocerans and calanoids, which constituted three quarters of the metazoan zooplankton biomass, differed in their preference for lake productivity and fish community and could be distinctly grouped according to these variables by canonical correspondance analysis. The analysis pointed out one oligotrophic and one eutrophic specialist among the herbivorous cladocerans, while two of the calanoids were oligotrophic specialists. The biomasses of cladocerans, calanoids, or daphnids were poorly correlated with both lake productivity and fish predation, whereas shifts in average size and species distribution could be attributed to these variables. At low lake productivity, chemical variables such as pH and Ca, as well as the species' physiological adaptations, appear as the main determinants for the competitive advantage and relative success of herbivorous species. Fish community composition changes with increasing lake productivity, but only at very high fish predation intensity (cyprinid communities) did the effects of predation become the main determinant of the zooplankton community, superimposed on the lake productivity.
Size-specific fish avoidance of the spined crustacean Bythotrephes: field support for laboratory predictions
Authors: Barnhisel D. Rae , Harvey Heather A.
Published: August 2009

Stomach contents of juvenile fish and zooplankton samples taken simultaneously with fish were analyzed to determine whether young fish in Lake Superior utilize Bythotrephes (cederstroemi form), a spined crustacean present in the Great Lakes since the 1980s. Bythotrephes made up approximately 11% of the zooplankton samples on our sampling date; however, it comprised approximately 0.3% of the fish diet (N = 358 fish, 2.8–23.9 cm in total length). No fish < 7.0 cm in length (N = 208) contained Bythotrephes. According to the Manly–Chesson selectivity index, fish negatively selected or avoided the spined zooplankter. A Spearman rank correlation analysis indicated that although the number of Bythotrephes in the gut significantly increased with fish length, preference did not. These field results support predictions derived from laboratory experiments that (1) Bythotrephes is not a preferred prey item for young fish, (2) there is a threshold size of fish that can utilize Bythotrephes as a food source, and (3) as fish increase in size, they are more likely to consume Bythotrephes.
Temporal variability in the chemical characteristics along the Rivière de l'Achigan: How many samples are necessary to describe stream chemistry?
Authors: Cattaneo Antonella , Prairie Yves T.
Published: August 2009

We examined the temporal variability of several chemical characteristics at 12 different sites in a river system of the Laurentian region of Quebec. Mean–variance relationships (log–log) differed considerably among chemical variables with slopes ranging from about 1.3 to over 5. Guidelines and equations are given to help decide how many samples should be taken to obtain a mean value with an error of 20% or less for the different chemical variables. Relative temporal variabilities (coefficients of variation) were highest for nutrients and lowest for pH, alkalinity, and conductivity. Data from the same sites but for different years showed no systematic differences and similarly mean–variance relationships for TP and TDP obtained from a different region were not significantly different suggesting a wider applicability to our results. We also show that although the temporal variability of chlorophyll in streams is similar to that found in lakes, the same does not apply to phosphorus, which is about two to three times more variable in streams.
Estimating the influence of temperature on the survival of chinook salmon smolts (Oncorhynchus tshawytscha) migrating through the Sacramento – San Joaquin River Delta of California
Authors: Baker Peter Fritz , Ligon Franklin K. , Speed Terence P.
Published: August 2009

Data from the U.S. Fish and Wildlife Service are used to investigate the relationship between water temperature and survival of hatchery-raised fall-run chinook salmon (Oncorhynchus tshawytscha) smolts migrating through the Sacramento – San Joaquin Delta of California. A formal statistical model is presented for the release of smolts marked with coded-wire tags (CWTs) in the lower Sacramento River and the subsequent recovery of marked smolts in midwater trawls in the Delta. This model treats survival as a logistic function of water temperature, and the release and recovery of different CWT groups as independent mark–recapture experiments. Iteratively reweighted least squares is used to fit the model to the data, and simulation is used to establish confidence intervals for the fitted parameters. A 95% confidence interval for the upper incipient lethal temperature, inferred from the trawl data by this method, is 23.01 ± 1.08 °C This is in good agreement with published experimental results obtained under controlled conditions (24.3 ± 0.1 and 25.1 ± 0.1 °C for chinook salmon acclimatized to 10 and 20 °C, respectively): this agreement has implications for the applicability of laboratory findings to natural systems.
Alterations in the ultrastructure of Chlamydia psittaci 6BC harvested from the allantoic fluid of chick embryos
Authors: Costerton J. W. , Poffenroth Linda , Wilt J. C. , Kordová Nonna
Published: August 2009

The allantoic fluid of chick embryos infected with Chlamydia psittaci is routinely used as a source of material for the study of the chemical and biological properties of the chlamydiae. We have examined pellets recovered from this allantoic fluid by low- and high-speed centrifugation, as well as high-speed pellets which had been stored at −70 °C, and we find that all of the pleomorphic forms of the chlamydiae are present in these materials. The reticulate bodies and large intermediate bodies are always seen to be morphologically damaged in that their cell envelopes are modified and in that they are distended and occasionally 'leaky.' No morphological evidence of damage was seen in small intermediate bodies or in elementary bodies in any of the materials which were examined. Thus the chlamydial population recovered from the allantoic fluid of infected chick embryos has been modified by selective damage to the least-condensed particles. We propose that the release of lysosomal enzymes from the host cell may coincide with the release of the chlamydia and that these enzymes may be responsible for this selective damage.
Ultrastructural studies of the nucleoids of the pleomorphic forms of Chlamydia psittaci 6BC: a comparison with bacteria
Authors: Costerton J. W. , Poffenroth Linda , Wilt J. C. , Kordová Nonna
Published: August 2009

The nucleoids of the various pleomorphic forms of Chlamydia psittaci have been examined by direct observation of infected cells and by observations on isolated particles. The fixation and staining methods used were the same as those routinely used for the examination of bacteria to facilitate the comparison of chlamydial fine structure with that of bacteria.The nucleoids of reticulate bodies were composed of fine fibrils which extended throughout these particles. The nucleoids of intermediate bodies are characterized by an electron-dense mass with which the fibrous elements are associated in a structurally coherent manner. As condensation of the intermediate bodies proceeds, the electron-dense mass becomes eccentrically located and the fibers form a distinct radiating structure. Large elementary bodies have a few fibers associated with their condensed electron-dense nucleoids but the more condensed mature elementary bodies have a very discrete and homogeneous electron-dense nucleoid which is separated from the cytoplasmic elements of these particles by a very distinct electron-transparent space. These highly condensed elementary body nucleoids are usually ovoid, but may be elongated or irregular, and a small number of these structures react very strongly with ruthenium red.While the nucleoid structure of reticulate bodies resembles that of the bacterial cell, both the condensation process and the nucleoid morphologies which result from it in intermediate and elementary bodies have no parallels among the bacteria. Thus we conclude that major differences in nucleoid organization exist between the chlamydia and the bacteria.
Electron microscopy of vesicular-arbuscular mycorrhizae of yellow poplar. IV. Host–endophyte interactions during arbuscular deterioration
Authors: Kinden Darrell A. , Brown Merton F.
Published: August 2009

Scanning electron stereoscopy and transmission electron microscopy were used to correlate morphological alterations and cytological phenomena associated with deterioration of arbuscules in yellow poplar mycorrhizae. Arbuscular degradation was initiated at the tips of the finest branches and progressed basipetally. Cytoplasm in arbuscular hyphae progressively deteriorated and was followed by collapse of the fungal walls. Degraded portions of the arbuscules aggregated into clumps comprised of host wall material and the distorted fungal walls. Host nuclei, abundant mitochondria, and proplastids were closely associated with arbuscular branches undergoing cytoplasmic deterioration and with clumped portions of the arbuscule which contained degraded hyphal branches. Most of the arbuscules observed had deteriorated to the clumped stage. Some cortical cells contained several clumped arbuscules and nearly mature, intact arbuscules which indicated that reinfection occurs even as degradative phenomena are in progress. It is suggested that substantial quantities of mineral nutrients may be made available to the host via degradation of fungal cytoplasm in the arbuscular hyphae preceding aggregation of degraded hyphae into discrete clumps.
Ultrastructure and lipid identification during conidium germination of Stemphylium sarcinaeforme
Authors: Murray Gordon M. , Maxwell Douglas P.
Published: August 2009

Multicelled conidia of Stemphylium sarcinaeforme germinate in water forming several germ tubes. Individual cells within conidia are connected by pores which are plugged in ungerminated conidia and open in germinated ones. During germination, vacuoles enlarge, endoplasmic reticulum profiles increase in number, and mitochondria change from spherical to elongate. The germ tube wall is laid down at the site of emergence from the conidium. Shortly after germination, a septum with a central pore forms where the germ tube emerged. The germ tube wall is surrounded by a fibrillar sheath. Lipid bodies are closely associated with vacuoles during germination. The ultrastructural location of lipid was found by extraction of conidia with lipid solvents. Total lipid decreases from 14.4% of the dry weight of ungerminated conidia to 13.4% of the dry weight of conidia germinated for 10 h. No qualitative changes occurred in the major lipid classes of conidia during germination. The activities of lipase and acid phosphatase were detected in ungerminated and germinated conidia.
CREATION OF RESEARCH-ORIENTED COMPETENCE-CELL-BASED PRODUCTION NETWORKS
Authors: MEJIA ALEJANDRO , WEIDLICH DIETER
Published: August 2009

With the basis that research is one of the most important internal sources for innovation, a new approach to create competence-cell-based production networks focused on research activities is presented. Thus, a research process, specific for competence-cell-based networks, is also described. In this process, which is subdivided in different phases, the competence-cells, as the smallest performance units, are temporarily linked in a production network. They cooperate to carry out industry-oriented applied research to generate new ideas or technologies to be used in innovative products. For this process, an approach for the non-hierarchical selection of the necessary competence cells is also introduced. This selection is accomplished by means of the innovation potential, which is based on parameters that evaluate nearly objectively the innovative capabilities of the competence cells.
A SENSOR OF ACETONE BASED ON ION-SENSITIVE FIELD-EFFECT TRANSISTOR
Authors: TONG MIN-MING , NIU MU , LIU TAO
Published: August 2009

With ion-sensitive field-effect transistor (ISFET) studied in this paper, nano- TiO 2- Al 2 O 3 insulation film was used as the gate electrode of ISFET. By this means, acetone was analyzed indirectly by detecting hydrogen ion dissociated from acetone solution. Under electric field function, the improvement of decomposition efficiency of acetone and the catalysis of nano- TiO 2 improved the sensitivity of sensor greatly. Based on experiments, the paper verified the effect of electric field and catalysis of nano- TiO 2.
RELIABLE PROBABILISTIC CLASSIFICATION OF INTERNET TRAFFIC
Authors: DASHEVSKIY MIKHAIL , LUO ZHIYUAN
Published: August 2009

Classification of Internet traffic is very important to many applications such as network resource management, network security enforcement and intrusion detection. Many machine-learning algorithms have been successfully used to classify network traffic flows with good performance, but without information about the reliability in classifications. In this paper, we present a recently developed algorithmic framework, namely the Venn Probability Machine, for making reliable decisions under uncertainty. Experiments on publicly available real Internet traffic datasets show the algorithmic framework works well. Comparison is also made to the published results.
SCREW MOTION OF DNA DUPLEX DURING TRANSLOCATION THROUGH PORE I: INTRODUCTION OF THE COARSE-GRAINED MODEL
Authors: STARIKOV E. B. , HENNIG D. , YAMADA H. , GUTIERREZ R. , NORDÉN B. , CUNIBERTI G.
Published: August 2009

Based upon the structural properties of DNA duplexes and their counterion-water surrounding in solution, we have introduced here a screw model which may describe translocation of DNA duplexes through artificial nanopores of the proper diameter (where the DNA counterion–hydration shell can be intact) in a qualitatively correct way. This model represents DNA as a kind of "screw," whereas the counterion-hydration shell is a kind of "nut." Mathematical conditions for stable dynamics of the DNA screw model are investigated in detail. When an electrical potential is applied across an artificial membrane with a nanopore, the "screw" and "nut" begin to move with respect to each other, so that their mutual rotation is coupled with their mutual translation. As a result, there are peaks of electrical current connected with the mutual translocation of DNA and its counterion–hydration shell, if DNA is possessed of some non-regular base-pair sequence. The calculated peaks of current strongly resemble those observed in the pertinent experiments. An analogous model could in principle be applied to DNA translocation in natural DNA–protein complexes of biological interest, where the role of "nut" would be played by protein-tailored "channels." In such cases, the DNA screw model is capable of qualitatively explaining chemical-to-mechanical energy conversion in DNA–protein molecular machines via symmetry breaking in DNA–protein friction.
Relation between extent of myostatin depletion and muscle growth in mature mice
Authors: Welle Stephen , Burgess Kerri , Thornton Charles A. , Tawil Rabi
Published: August 2009

Myostatin is a negative regulator of muscle growth and fiber size. Changes in myostatin expression might contribute to changes in muscle mass associated with various conditions, and reducing the amount of active myostatin is a potential strategy for preventing or reversing muscle atrophy. The present study was done to determine the extent to which myostatin levels must decline to induce growth of mature muscles. Myostatin expression was reduced by activating Cre recombinase in adult mice with floxed myostatin genes. The duration of Cre activation varied from 1 to 6 wk, and the residual myostatin mRNA expression after Cre activation varied from 3 to 63% of the normal level. Promyostatin levels declined in parallel with myostatin mRNA. There was no increase in muscle mass over the 3 mo following Cre activation if residual myostatin expression was ≥40% of normal. In mice with <40% of normal myostatin expression, muscle mass increased in proportion to the extent of myostatin depletion. In mice with ≤10% of normal myostatin expression, muscle mass increased ∼25%. Myostatin depletion increased myonuclear domain volumes and the ratio of RNA to myonuclei probably by enhancing DNA transcription rather than by inhibiting RNA decay. There was no evidence that maintenance of the hypertrophy during chronic myostatin deficiency requires altered activity of Akt/mTOR or p38 MAPK signaling pathways. These data suggest that anabolic therapies based on reducing the concentration of active myostatin will be effective only if a very large proportion of the myostatin is removed or inactivated.
Maternal and postweaning diet interaction alters hypothalamic gene expression and modulates response to a high-fat diet in male offspring
Authors: Page Kathleen C. , Malik Raleigh E. , Ripple Joshua A. , Anday Endla K.
Published: August 2009

Epidemiological data and results from animal studies indicate that imbalances in maternal nutrition impact the expression of metabolic disorders in the offspring. We tested the hypothesis that consumption of excess saturated fats during pregnancy and lactation contributes to adult metabolic dysfunction and that these disturbances can be further influenced by the postweaning diet. Adult male offspring from chow-fed dams were compared with males from dams fed a diet high in saturated fat (45 kcal/100 kcal) before mating, pregnancy, and lactation. Offspring were weaned to a standard chow diet or high fat diet. Animals were killed at 120 days after a 24-h fast. Body weight, energy intake, fat deposition, serum leptin, and insulin were significantly higher in offspring from control or high-fat dams if fed a high-fat diet from weaning to adulthood. Only fat-fed offspring from fat-fed dams were hyperglycemic. Leptin receptor, proopiomelanocortin, and neuropeptide Y (NPY) were also significantly increased in offspring exposed to excess saturated fat during gestation and into adulthood, whereas NPY1 receptor was downregulated. Signal transducer and activator of transcription 3 mRNA level was significantly higher in offspring from high-fat-fed dams compared with controls; however, no change was detected in cocaine and amphetamine-regulated transcript or suppressor of cytokine signaling 3. An increase in agouti-related protein expression did not reach significance. A significant reduction in phosphatidylinositol 3-kinase regulatory subunit (p85α) coupled to an upregulation of protein kinase B was observed in offspring from high-fat-fed dams transitioned to chow food, whereas p85α expression was significantly increased in high-fat offspring weaned to the high-fat diet. These data support the hypothesis that early life exposure to excess fat is associated with changes in hypothalamic regulation of body weight and energy homeostasis and that postweaning diet influences development of metabolic dysfunction and obesity.
Comparison of Spatial Summation Properties of Neurons in Macaque V1 and V2
Authors: Shushruth S. , Ichida Jennifer M. , Levitt Jonathan B. , Angelucci Alessandra
Published: August 2009

In visual cortex, responses to stimulation of the receptive field (RF) are modulated by simultaneous stimulation of the RF surround. The mechanisms for surround modulation remain unidentified. We previously proposed that in the primary visual cortex (V1), near surround modulation is mediated by geniculocortical and horizontal connections and far surround modulation by interareal feedback connections. To understand spatial integration in the secondary visual cortex (V2) and its underlying circuitry, we have characterized spatial summation in different V2 layers and stripe compartments and compared it to that in V1. We used grating stimuli in circular and annular apertures of different sizes to estimate the extent and sensitivity of RF and surround components in V1 and V2. V2 RFs and surrounds were twice as large as those in V1. As in V1, V2 RFs doubled in size when measured at low contrast. In both V1 and V2, surrounds were about fivefold the size of the RF and the far surround could exceed 12.5° in radius, averaging 5.5° in V1 and 9.2° in V2. The strength of surround suppression was similar in both areas. Thus although differing in spatial scale, the interactions among RF components are similar in V1 and V2, suggesting similar underlying mechanisms. As in V1, the extent of V2 horizontal connections matches that of the RF center, but is much smaller than the largest far surrounds, which likely derive from interareal feedback. In V2, we found no laminar or stripe differences in size and magnitude of surround suppression, suggesting conservation across stripes of the basic circuit for surround modulation.
Characterization of Multidrug Resistant ESBL‐Producing Escherichia coli Isolates from Hospitals in Malaysia
Authors: Lim King-Ting , Yasin Rohani , Yeo Chew-Chieng , Puthucheary Savithri , Thong Kwai-Lin
Published: August 2009

The emergence of Escherichia coli that produce extended spectrum β‐lactamases (ESBLs) and are multidrug resistant (MDR) poses antibiotic management problems. Forty‐seven E. coli isolates from various public hospitals in Malaysia were studied. All isolates were sensitive to imipenem whereas 36 were MDR (resistant to 2 or more classes of antibiotics). PCR detection using gene‐specific primers showed that 87.5% of the ESBL‐producing E. coli harbored the blaTEM gene. Other ESBL‐encoding genes detected were blaOXA, blaSHV, and blaCTX-M. Integron‐encoded integrases were detected in 55.3% of isolates, with class 1 integron‐encoded
intI1 integrase being the majority. Amplification and sequence analysis of the 5′CS region of the integrons showed known antibiotic resistance‐encoding gene cassettes of various sizes
that were inserted within the respective integrons. Conjugation and transformation experiments indicated that some of the
antibiotic resistance genes were likely plasmid‐encoded and transmissible. All 47 isolates were subtyped by PFGE and PCR‐based fingerprinting using random amplified polymorphic DNA (RAPD), repetitive extragenic palindromes (REPs), and
enterobacterial repetitive intergenic consensus (ERIC). These isolates were very diverse and heterogeneous. PFGE, ERIC, and
REP‐PCR methods were more discriminative than RAPD in subtyping the E. coli isolates.
Endothelial Cell Migration and Vascular Endothelial Growth Factor Expression Are the Result of Loss of Breast Tissue Polarity
Authors: Chen Amy , Cuevas Ileana , Kenny Paraic A. , Miyake Hiroshi , Mace Kimberley , Ghajar Cyrus , Boudreau Aaron , Bissell Mina , Boudreau Nancy
Published: August 2009

Recruiting a new blood supply is a rate-limiting step in tumor progression. In a three-dimensional model of breast carcinogenesis, disorganized, proliferative transformed breast epithelial cells express significantly higher expression of angiogenic genes compared with their polarized, growth-arrested nonmalignant counterparts. Elevated vascular endothelial growth factor (VEGF) secretion by malignant cells enhanced recruitment of endothelial cells (EC) in heterotypic cocultures. Significantly, phenotypic reversion of malignant cells via reexpression of HoxD10, which is lost in malignant progression, significantly attenuated VEGF expression in a hypoxia-inducible factor 1α–independent fashion and reduced EC migration. This was due primarily to restoring polarity: forced proliferation of polarized, nonmalignant cells did not induce VEGF expression and EC recruitment, whereas disrupting the architecture of growth-arrested, reverted cells did. These data show that disrupting cytostructure activates the angiogenic switch even in the absence of proliferation and/or hypoxia and restoring organization of malignant clusters reduces VEGF expression and EC activation to levels found in quiescent nonmalignant epithelium. These data confirm the importance of tissue architecture and polarity in malignant progression. [Cancer Res 2009;69(16):6721–9]
Down-regulation of CXCR4 and CD62L in Chronic Lymphocytic Leukemia Cells Is Triggered by B-Cell Receptor Ligation and Associated with Progressive Disease
Authors: Vlad Amalia , Deglesne Pierre-Antoine , Letestu Rémi , Saint-Georges Stéphane , Chevallier Nathalie , Baran-Marszak Fanny , Varin-Blank Nadine , Ajchenbaum-Cymbalista Florence , Ledoux Dominique
Published: August 2009

Progressive cases of B-cell chronic lymphocytic leukemia (CLL) are frequently associated with lymphadenopathy, highlighting a critical role for signals emanating from the tumor environment in the accumulation of malignant B cells. We investigated on CLL cells from 30 untreated patients the consequence of B-cell receptor (BCR) triggering on the membrane expression of CXCR4 and CD62L, two surface molecules involved in trafficking and exit of B-lymphocytes from lymph nodes. BCR stimulation promoted a strictly simultaneous down-regulation of CXCR4 and CD62L membrane expression to a variable extent. The variable BCR-dependent decrease of the two proteins was strikingly representative of the heterogeneous capacity of the CLL cells to respond to BCR engagement in a given patient. Functionally, cells down-regulating CXCR4 and CD62L in response to BCR engagement displayed a reduction in both migration toward CXCL12 and adhesion to lymphatic endothelial cells. Remarkably, the ability of CLL cells to respond to BCR ligation was correlated with unfavorable prognostic markers and short progression-free survival. In conclusion, BCR signaling promotes decrease of CXCR4 and CD62L membrane expression in progressive cases only. These results are consistent with the hypothesis that BCR-mediated signaling pathways favor accumulation of a proliferative pool within the lymph nodes of progressive CLL cases. [Cancer Res 2009;69(16):6387–95]
Antigen Presented by TumorsIn vivoDetermines the Nature of CD8+ T-Cell Cytotoxicity
Authors: Shanker Anil , Brooks Alan D. , Jacobsen Kristen M. , Wine John W. , Wiltrout Robert H. , Yagita Hideo , Sayers Thomas J.
Published: August 2009

The biological relevance of the perforin and Fas ligand (FasL) cytolytic pathways of CD8+ T lymphocytes (CTL) for cancer immunotherapy is controversial. We investigated the importance of these pathways in a murine renal cell carcinoma expressing influenza viral hemagglutinin as a defined surrogate antigen (Renca-HA). Following Renca-HA injection, all FasL-dysfunctional FasLgld/gld mice (n = 54) died from Renca-HA tumors by day 62. By contrast, perforin−/− (51%; n = 45) and Faslpr/lpr (55%; n = 51) mice remained tumor-free at day 360. Blocking FasL in vivo inhibited tumor rejection in these mice. Moreover, established Renca-HA tumors were cleared more efficiently by adoptively transferred HA518-526–specific T-cell receptor–transgenic CTL using FasL rather than perforin. Strikingly, a range of mouse tumor cells presenting low concentrations of immunogenic peptide were all preferentially lysed by the FasL but not the Pfp-mediated effector pathway of CTL, whereas at higher peptide concentrations, the preference in effector pathway usage by CTL was lost. Interestingly, a number of human renal cancer lines were also susceptible to FasL-mediated cytotoxicity. Therefore, the FasL cytolytic pathway may be particularly important for eradicating Fas-sensitive tumors presenting low levels of MHC class I–associated antigens following adoptive T-cell therapy. [Cancer Res 2009;69(16):6615–23]
Nicotine Stimulates PPARβ/δ Expression in Human Lung Carcinoma Cells through Activation of PI3K/mTOR and Suppression of AP-2α
Authors: Sun XiaoJuan , Ritzenthaler Jeffrey D. , Zhong XiaoRong , Zheng Ying , Roman Jesse , Han ShouWei
Published: August 2009

We previously showed that nicotine stimulates non–small cell lung carcinoma (NSCLC) cell proliferation through nicotinic acetylcholine receptor (nAChR)–mediated signals. Activation of peroxisome proliferator–activated receptor β/δ (PPARβ/δ) has also been shown to induce NSCLC cell growth. Here, we explore the potential link between nicotine and PPARβ/δ and report that nicotine increases the expression of PPARβ/δ protein; this effect was blocked by an α7 nAChR antagonist (α-bungarotoxin), by α7 nAChR short interfering RNA, and by inhibitors of phosphatidylinositol 3-kinase (PI3K; wortmannin and LY294002) and mammalian target of rapamycin (mTOR; rapamycin). In contrast, this effect was enhanced by PUN282987, an α7 nAChR agonist. Silencing of PPARβ/δ attenuated the stimulatory effect of nicotine on cell growth, which was overcome by transfection of an exogenous PPARβ/δ expression vector. Of note, nicotine induced complex formation between α7 nAChR and PPARβ/δ protein and increased PPARβ/δ gene promoter activity through inhibition of AP-2α as shown by reduced AP-2α binding using electrophoretic gel mobility shift and chromatin immunoprecipitation assays. In addition, silencing of Sp1 attenuated the effect of nicotine on PPARβ/δ. Collectively, our results show that nicotine increases PPARβ/δ gene expression through α7 nAChR–mediated activation of PI3K/mTOR signals that inhibit AP-2α protein expression and DNA binding activity to the PPARβ/δ gene promoter. Sp1 seems to modulate this process. This study unveils a novel mechanism by which nicotine promotes human lung carcinoma cell growth. [Cancer Res 2009;69(16):6445–53]