bluuebunny/crossref_metadata_2025 huggingface dataset:
Peculiar Velocity Surveys: Optimal Moments Analysis
Authors: Feldman Hume A. , Watkins Richard , Melott Adrian L. , Gorman Patrick
Published: July 2010

Abstract: A new formalism to analyze peculiar velocity surveys is presented. Results from these surveys are shown to be dominated by small‐scale noise, aliasing, and incomplete cancellations. The formalism allows us to filter out the signal from scales that are not of interest and thus provides us with a clean signal that probe large scales. We use maximum likelihood techniques to analyze the filtered data and compare it to the analysis of the full dataset. The filtered analysis gives a much better parameter estimation than the full analysis, leading us to conclude that, indeed, the large‐scale signal is obscured by small‐scale noise.
The Cosmological Mass Function in the Zel'dovich Approximation
Authors: Shandarin Sergei F.
Published: July 2010

Abstract: The Press‐Schechter theory of the cosmological mass function and its modifications allow constraint of cosmological scenarios of structure formation. Recently, a few new models that explored the influence of anisotropic collapse on the shape of the mass function have been suggested. I discuss in more detail a particular model that assumes a fluid particle becomes part of a gravitationally bound halo when the smallest eigenvalue of the deformation tensor of the filtered initial density field reaches a certain threshold (like the filtered density contrast reaches the threshold in the Press‐Schechter formalism). Choosing the smallest eigenvalue guarantees that the fluid particle in question experiences collapse along all three axes. The model shows a better agreement with the N‐body simulations than with the standard Press‐Schechter model.
Transglutaminase‐Mediated Crosslinking of Specific Core Histone Subunits and Cellular Senescence
Authors: Kim Jae Hong , Choy Hyon E. , Nam Kang Hoon , Park Sang Chul
Published: July 2010

Abstract: We observed that the transglutaminase (tTGase) level and activity increased in aged rats and senescent primary fibroblasts, suggesting that the tTGase‐mediated macromolecule crosslinking may play a mechanistic role during aging. Although preliminary, our in vitro experiment suggests that the target of tTGase is core histones: H2A:H2B and H3:H4 are specifically crosslinked by tTGase. On the basis of these data, we postulate that the changes of DNA metabolism in association with cellular aging may be ascribed primarily to the crosslinking of core histone subunits. Further speculation awaits substantive data showing increased histone crosslinking in senescent cells and also what crosslinked histones in various DNA metabolisms may imply. At the moment, present data are sufficient to propose that tTGase is a senescence marker and it may be primarily responsible for the phenotypes associated with cellular senescence.
Attenuation of EGF Signaling in Senescent Cells by Caveolin
Authors: Park Woong‐Yang , Cho Kyung‐A , Park Jeong‐Soo , Kim Deok‐In , Park Sang Chul
Published: July 2010

Abstract: One of the characteristics of senescent cells is unresponsiveness to external stimuli like EGF. Although they have a normal level of receptors and downstream signaling molecules, EGF cannot induce the activation of Erk kinases and DNA synthesis in senescent cells as much as in young cells. Caveolin proteins directly interact with signaling molecules including EGF receptor and suppress the activation of EGFR upon EGF stimulation. We found that Erk activation after EGF stimulation in senescent human diploid fibroblasts was down‐regulated. Those senescent cells showed an increased level of three isoforms of caveolin proteins. This change seems to lie in transcriptional control in senescent cells. We also demonstrated up‐regulated caveolin proteins were co‐localized with EGFR proteins in detergent‐insoluble fractions. From these results, we suggest that the up‐regulated expression of caveolin might explain the unresponsiveness of senescent fibroblasts to EGF stimulation.
Increases of Mitochondrial Mass and Mitochondrial Genome in Association with Enhanced Oxidative Stress in Human Cells Harboring 4,977 BP‐Deleted Mitochondrial DNA
Authors: Wei Yau‐Huei , Lee Cheng‐Feng , Lee Hsin‐Chen , Ma Yi‐Shing , Wang Chia‐Wen , Lu Ching‐You , Pang Cheng‐Yoong
Published: July 2010

Abstract: In order to investigate the effect of aging‐ and disease‐associated deletion of mtDNA on cellular functions, we used cytoplasm fusion to construct a series of the cybrids harboring varying proportions of mtDNA with 4,977 bp deletion from skin fibroblasts of a patient with chronic progressive external ophthalmoplegia. The cybrids were grown in the Dulbecco's modified Eagle medium supplemented with 5% fetal bovine serum, 100 μg/ml pyruvate and 50 μg/ml uridine. The population doubling time was longer for the cybrids containing higher proportions of 4,977 bp‐deleted mtDNA. In addition, we found that the respiratory function was decreased with the increase of mtDNA with 4,977 bp deletion in the cybrids. Since impairment of the respiratory system of mitochondria increases the electron leak of the respiratory chain, we further determined the oxidative stress in these cybrids. The results showed that the specific contents of 8‐hydroxy 2′‐deoxyguanosine and lipid peroxides of the cybrids harboring > 65% of the 4,977 bp‐deleted mtDNA were significantly increased as compared with those of the cybrids containing undetectable mutant mtDNA. On the other hand, we found that the mitochondrial mass and the relative content of the mitochondrial genome in the cybrids harboring 4,977 bp‐deleted mtDNA were higher than those of the cybrids containing only wild type mtDNA. The relative content of mtDNA was increased 17% and 30%, respectively, in the cybrids harboring 17% and 56% of mtDNA with 4,977 bp deletion. Moreover, both mitochondrial mass and mtDNA content were concurrently increased by treatment of the cybrids with 180 μM of hydrogen peroxide. Taken these findings together, we conclude that increase of mitochondrial mass and mtDNA are the molecular events associated with enhanced oxidative stress in human cells with impaired respiratory function caused by mtDNA deletion.
Premature Aging and Predisposition to Cancers Caused by Mutations in RecQ Family Helicases
Authors: Furuichi Yasuhiro
Published: July 2010

Abstract: DNA helicases, because they unwind duplex DNA, have important roles in cellular DNA events such as replication, recombination, repair, and transcription. Multiple DNA helicase families with seven consensus motifs have been found, and members within each helicase family also share sequence homologies between motifs. The RecQ helicase family includes helicases that have extensive amino acid sequence homologies to the E. coli DNA helicase RecQ, which has been implicated in double‐strand break repair and suppression of illegitimate recombination. To date, five RecQ helicase species exist in humans, but their exact biological functions remain unknown. In this paper, on the basis of five years of work, I overview the updated molecular biology of five human RecQ helicases; genetic diseases such as Werner's, Bloom's, and Rothmund‐Thomson's syndromes caused by helicase mutations; the associated premature aging phenotype; and an increased risk of neoplasms. I also describe a hypothesis of “tissue‐specific genomic instability” that accounts for the pathology behind multisymptomatic RecQ helicase syndromes.
Impairment of Learning and Memory in Rats Caused by Oxidative Stress and Aging, and Changes in Antioxidative Defense Systems
Authors: Fukui Koji , Onodera Koji , Shinkai Tadashi , Suzuki Shozo , Urano Shiro
Published: July 2010

Abstract: To elucidate the influence of oxidative stress on the brain functions during aging, the cognitive performance ability of rats was assessed by using the water‐maze test as an oxidative stress before and after hyperoxia. Young rats showed significantly greater learning ability than both old rats and vitamin‐E‐deficient rats. Although the memory functions of all rats were impaired after oxidative stress, the memory retention of young rats was greater than those of other groups. After the stress, none of the rats recovered their learning ability. During aging and through hyperoxia, the release of acetylcholine from nerve terminals was remarkably decreased. Instead, thiobarbituric acid reactive substance (TBARS) contents in rat hippocampus and cebral cortex, and their synaptic membranes, were significantly increased during aging and by oxidative stress. The antioxidative defense system in rat brain was also changed by the stress. These results suggest that oxidative stress may contribute to learning and memory deficits following oxidative brain damage during aging.
Cellular and Molecular Pathogenic Mechanisms of Insulin‐Dependent Diabetes Mellitus
Authors: Yoon Ji‐Won , Jun Hee‐Sook
Published: July 2010

Abstract: Insulin‐dependent diabetes mellitus (IDDM), also known as type 1 diabetes, is an organ‐specific autoimmune disease resulting from the destruction of insulin‐producing pancreatic β cells. The hypothesis that IDDM is an autoimmune disease has been considerably strengthened by the study of animal models such as the BioBreeding (BB) rat and the nonobese diabetic (NOD) mouse, both of which spontaneously develop a diabetic syndrome similar to human IDDM. β cell autoantigens, macrophages, dendritic cells, B lymphocytes, and T cells have been shown to be involved in the pathogenesis of autoimmune diabetes. Among the β cell autoantigens identified, glutamic acid decarboxylase (GAD) has been extensively studied and is the best characterized. β cell‐specific suppression of GAD expression in NOD mice results in the prevention of IDDM. Macrophages and/or dendritic cells are the first cell types to infiltrate the pancreatic islets. Macrophages play an essential role in the development and activation of β cell‐cytotoxic T cells. B lymphocytes play a role as antigen‐presenting cells, and T cells have been shown to play a critical role as final effectors that kill β cells. Cytokines secreted by immunocytes, including macrophages and T cells, may regulate the direction of the immune response toward Th1 or Th2 as well as cytotoxic effector cell or suppressor cell dominance. β cells are destroyed by apoptosis through Fas‐Fas ligand and TNF‐TNF receptor interactions and by granzymes and perforin released from cytotoxic effector T cells. Therefore, the activated macrophages and T cells, and cytokines secreted from these immunocytes, act synergistically to destroy β cells, resulting in the development of autoimmune IDDM.
The Epistemic Paradox of Mind and Matter
Authors: MOROWITZ HAROLD J.
Published: July 2010

Abstract: The attempt to posit independent mind and matter results in an unavoidable circularity. We propose to accept this circularity and then explore the steps from the various “constructs” of matter to those biological structures associated with mind. This enables us to explore the hierarchical levels of emergence that take us from the periodic table of the elements to consciousness as it develops in the evolutionary radiation. The possibility of undiscovered principles of the same epistemological status as the Pauli exclusion principle is discussed.
Complexity and Tinkering
Authors: JACOB FRANÇOIS
Published: July 2010

Abstract: All recent results in the fields of development and evolution point to a role of regulatory circuits as a major cause of evolutionary changes.
Consciousness and the Binding Problem
Authors: SINGER WOLF
Published: July 2010

Abstract: It is proposed that phenomenal awareness, the ability to be aware of one's sensations and feelings, emerges from the capacity of evolved brains to analyze their own cognitive processes by iterating and reapplying on themselves the very same cortical operations that they use for the interpretation of signals from the outer world. Search for the neuronal substrate of awareness therefore converges with the search for the cognitive mechanisms through which brains analyze their environment. The hypothesis is put forward that the mammalian brain generates continuously highly dynamic states that, when modulated by input signals, rapidly converge towards points of transient stability that correspond to the respective input constellation. It is proposed that these states are characterized by the dynamic binding of feature‐specific cells into functionally coherent cell assemblies which as a whole represent the constellation of features defining a particular perceptual object. Arguments are presented that favor the notion that the cognitive operations supporting awareness consist of an iteration of such dynamic binding processes which then lead to the formation of higher‐order assemblies that correspond to the contents of conscious awareness. Experimental data are reviewed relating to the questions of how assemblies are formed and which signatures define the relations among the responses of distributed neurons. It is argued that assemblies self‐organize through reciprocal interactions of neurons coupled by reentrant loops and that the signature of relatedness consists of the transient synchronization of the discharges of the respective neurons. Evidence is presented that these synchronization phenomena depend on the same state variables as awareness: Both require for their manifestation activated brain states characterized by desynchronized EEGs. It is concluded that phenomenal awareness is amenable to neurobiological reductionism; but it is also proposed that self‐consciousness requires a different explanatory approach because it emerges from the dialogue between different brains and hence has the quality of a cultural construct.
The Neuroanatomy of Phenomenal Vision: A Psychological Perspective
Authors: STOERIG PETRA
Published: July 2010

Abstract: Somewhere in the visual system, phenomenal vision—the seeing of colors, brightness, depths, shades, and motion—is generated not only from the distribution of light on the retina, but also when the eyes are closed, in dreams, hallucinations, phosphenes, and (possibly) imagery. Whether these different forms of phenomenal vision share a common substrate although their origins are different (optical, mechanical, electrical, endogenous) is discussed in the light of evidence from neuropsychological and functional imaging studies. Whereas extrastriate visual cortical areas appear to be involved in all types of phenomenal vision that have been studied, the necessity of a contribution from primary visual cortex is demonstrated by the loss of conscious vision that follows its destruction. If both extrastriate and primary cortical activation are needed, the latter may not just provide an indispensable input, but may also need to receive the output of the extrastriate processing via reentrant connections.
Is Music an Evolutionary Adaptation?
Authors: HURON DAVID
Published: July 2010

Abstract:In contemplating the function and origin of music, a number of scholars have considered whether music might be an evolutionary adaptation. This article reviews the basic arguments related to evolutionary claims for music. Although evolutionary theories about music remain wholly speculative, musical behaviors satisfy a number of basic conditions, which suggests that there is indeed merit in pursuing possible evolutionary accounts.
Cerebral Substrates for Musical Temporal Processes
Authors: SAMSON SÉVERINE , EHRLÉ NATHALIE , BAULAC MICHEL
Published: July 2010

Abstract: Music as well as language consists of a succession of auditory events in time, which require elaborate temporal processing. Although several lines of evidence suggest that the left dominant hemisphere is predominantly involved in the processing of rapid temporal changes of speech, very little is known about the cerebral substrates underlying such auditory temporal processes in music. To investigate this issue, we examined epileptic patients with either left (LTL) or right (RTL) temporal lobe lesions as well as normal control subjects (NC) in two different tasks involving the processing of time‐related (temporal) information. By manipulating the interonset interval (IOI) in a psychophysical task, as well as in a task of detection of rhythmic changes in real tunes, we studied the processing of temporal microvariations in music. The first task assessed anisochrony (or irregularity) discrimination of sequential information according to different presentation rates (between 80 and 1000 ms IOI). For all subjects, an effect of tempo was obtained; thresholds were lower for the 80 ms IOI than for longer IOIs. Furthermore, there was a specific impairment of rapid anisochronous discrimination (80 ms IOI) for LTL patients as compared to RTL and NC subjects, but no deficit was observed for longer IOIs. These findings suggest the specialization of left temporal lobe structures in processing rapid sequential auditory information. The second task involved the detection of IOI increments in familiar monodic tunes. Performance was measured for two increments (easy vs. difficult to detect according to cognitive expectation) to assess the effect of cognitive expectation using a forced‐choice paradigm (changed vs. unchanged melody). The results showed that LTL patients but not RTL were impaired as compared to NC subjects in the increment detection. However, all groups showed differences between the two levels of difficulty, suggesting that top‐down processing remains functional. These findings suggest that left temporal lobe structures are predominantly involved in perceiving time‐related perturbations in familiar tunes as well as in isochronous sequences, extending to the musical domain findings previously reported in speech.
The Brain of Musicians
Authors: SCHLAUG GOTTFRIED
Published: July 2010

Abstract: Musicians form an ideal subject pool in which one can investigate possible cerebral adaptations to unique requirements of skilled performance as well as cerebral correlates of unique musical abilities such as absolute pitch and others. There are several reasons for this. First, the commencement of musical training usually occurs when the brain and its components may still be able to adapt. Second, musicians undergo long‐term motor training and continued practice of complicated bimanual motor activity. Third, imaging studies from our group as well as other groups have shown that motor learning and the acquisition of skills can lead to changes in the representation of motor maps and possibly also to microstructural changes. Whether the unique musical abilities and structural differences that musicians' brains show are due to learning, perhaps during critical periods of brain development and maturation, or whether they reflect innate abilities and capacities that might be fostered by early exposure to music is largely unknown. We will report studies that indicate that certain regions in the brain (corpus callosum, motor cortex, cerebellum) may show some form of adaptation to extraordinary challenges and requirements of performance. These challenges may eventually lead to functional and structural cerebral changes to accommodate the requirements for musical performance. Furthermore, we will also show the neural correlates of one unique musical ability, absolute pitch. This ability may be linked to one structure in the human brain (planum temporale), which is preferentially activated in musicians who have absolute pitch during tone tasks. This structure may undergo some form of functional plasticity that is possible only during a critical period of brain development.
The Diagnosis and Neuropsychological Assessment of Adult Attention Deficit/Hyperactivity Disorder
Authors: GALLAGHER RICHARD , BLADER JOSEPH
Published: July 2010

Abstract:The recognition of attention deficit/hyperactivity disorder (ADHD) in adults is a well documented, but relatively new development. Investigations of the disorder have indicated that disturbances in behavior and adjustment are common. These disturbances may be linked to poorly developed executive functions. This paper reviews the neuropsychological studies that have compared persons with ADHD to normal controls and to psychiatric controls. The review indicates that persons with ADHD share many neuropsychological characteristics with other persons with serious psychiatric conditions, although those with ADHD may have a particular profile of slowed performance in tasks of sustained attention and set shifting, and their use of working memory may be particularly impaired. The implications of research for clinical assessment are discussed. We contend that a neuropsychological orientation is necessary for making the diagnosis and gaining a full understanding of adult ADHD. A model for clinical assessment is proposed which utilizes a neuropsychological orientation and the targeted administration of neuropsychological instruments. The careful use of neuropsychological measures is warranted in providing an elaborate picture of a person's functioning, although the use of neuropsychological tests is not necessary to make the diagnosis.
Neurocognitive Problems in Attention Deficit Disorder
Authors: ARMSTRONG CAROL L. , HAYES KAIRA M. , MARTIN ROBERT
Published: July 2010

Abstract: The critical neurocognitive components of Attention‐Deficit/Hyperactivity Disorder (ADHD) remain controversial, despite extensive research to disclose the essential cognitive components of this disorder. We propose to organize this research into three types of cognitive mechanisms while demonstrating the consistencies and inconsistencies in each: studies of response inhibition, of executive function, and of attentional inhibition. We also present the results of cluster analyses of a group (n= 25) of narrowly selected adult patients with childhood onset of ADHD, reveal three subtypes of ADHD, and argue that the only evidence of a general cognitive deficit is found in tests of selective attention. Finally, we provide the results of exploratory studies of selective attention for perception and for semantic memories. The data suggest that the cognitive disinhibition of ADHD is found in semantic recognition, but not in visuoperceptual recognition.
Treating the Suicidal Patient with Bipolar Disorder
Authors: Baldessarini Ross J. , Tondo Leonardo , Hennen John
Published: July 2010

Abstract: Bipolar disorder is associated with increased mortality because of complications of commonly comorbid substance use and stress‐sensitive medical disorders as well as accidents and very high rates of suicide. Long‐term lithium treatment may be associated with reduced suicidal risk. We review and summarize findings that help to quantify relationships between the presence versus the absence of lithium maintenance and suicides or attempts in patients with bipolar or other major affective disorders. Results from 33 studies (1970‐2000) yielded 13‐fold lower rates of suicide and reported attempts during long‐term lithium treatment than without it or after it was discontinued. Although greatly reduced, these rates remain above those estimated for the general population. Evidence for substantial, if incomplete, protection against suicide with lithium is supported by more compelling evidence than that for any other treatment provided for patients with mood disorders. Studies of commonly used, but incompletely evaluated, alternative treatments are required, and further protection against premature mortality can be anticipated with better protection against bipolar depression.
The Compelling Anomaly of Chemical Intolerance
Authors: Miller Claudia S.
Published: July 2010

Abstract: In science, anomalies expose the limitations of existing paradigms and drive the search for new ones. In the late 1800s, physicians observed that certain illnesses spread from sick, feverish individuals to those contacting them, paving the way for the germ theory of disease. The germ theory served as a crude, but elegant formulation that explained dozens of seemingly unrelated illnesses affecting literally every organ system. Today, we are witnessing another medical anomaly—a unique pattern of illness involving chemically exposed groups in more than a dozen countries, who subsequently report multisystem symptoms and new‐onset chemical, food, and drug intolerances. These intolerances may be the hallmark for a new disease process or paradigm, just as fever is a hallmark for infection. The fact that diverse demographic groups, sharing little in common except some initial chemical exposure event, develop these intolerances is a compelling anomaly pointing to a possible new theory of disease, one that has been referred to as “Toxicant‐Induced Loss of Tolerance” (“TILT”). TILT has the potential to explain certain cases of asthma, migraine headaches, and depression, as well as chronic fatigue, fibromyalgia, and “Gulf War syndrome”. It appears to evolve in two stages: (1) initiation, characterized by a profound breakdown in prior, natural tolerance resulting from either acute or chronic exposure to chemicals (pesticides, solvents, indoor air contaminants, etc.), followed by (2) triggering of symptoms by small quantities of previously tolerated chemicals (traffic exhaust, fragrances, gasoline), foods, drugs, and food/drug combinations (alcohol, caffeine). While the underlying dynamic remains an enigma, observations indicating that affected individuals respond to structurally unrelated drugs and experience cravings and withdrawal‐like symptoms, paralleling drug addiction, suggest that multiple neurotransmitter pathways may be involved.
Repeated Formaldehyde Effects in an Animal Model for Multiple Chemical Sensitivity
Authors: Sorg Barbara A. , Tschirgi Matthew L. , Swindell Samantha , Chen Lichao , Fang Jidong
Published: July 2010

Abstract: Chemical intolerance is a phenomenon observed in multiple chemical sensitivity (MCS) syndrome, an ill‐defined disorder in humans attributed to exposure to volatile organic compounds. Amplification of symptoms in individuals with MCS resembles the phenomenon of psychostimulant‐ and stress‐induced sensitization in rodents. We have recently tested in rats the hypothesis that repeated chemical exposure produces sensitization of central nervous system (CNS) circuitry. A rat model of MCS in our laboratory has employed several endpoints of CNS function after repeated formaldehyde (Form) exposure (1 h/day × 5 days/week × 4 weeks). Repeated Form exposure produced behavioral sensitization to later cocaine injection, suggesting altered dopaminergic sensitivity in mesolimbic pathways. Rats given repeated Form also demonstrated increased fear conditioning to odor paired with footshock, implicating amplification of neural circuitry guiding fear responding to a conditioned odor cue. Recent studies examining the effects of repeated Form on locomotor activity during each daily exposure showed a decrease in rearing activity after 12‐15 days of Form exposure compared to air‐exposed controls. EEG recordings taken 1 week after withdrawal from daily Form revealed altered sleep architecture. Some of the differences in sleep disappeared after subsequent brief (15 min) challenge with Form the next day. Overall, the findings indicate that repeated low‐level chemical exposure produces behavioral changes that may be akin to those observed in individuals with MCS, such as greater sensitivity to chemicals manifest as increased anxiety upon chemical exposure and altered sleep and/or fatigue. Study of the underlying CNS changes will provide a basis for mechanistically based animal models for MCS.
Cooling Systems for Ultra‐High Temperature Turbines
Authors: YOSHIDA TOYOAKI
Published: July 2010

Abstract: This paper describes an introduction of research and development activities on steam cooling in gas turbines at elevated temperature of 1500 C and 1700 C level, partially including those on water cooling. Descriptions of a new cooling system that employs heat pipes are also made. From the view point of heat transfer, its promising applicability is shown with experimental data and engine performance numerical evaluation.
Selection of a Turbine Cooling System Applying Multi‐Disciplinary Design Considerations
Authors: GLEZER BORIS
Published: July 2010

Abstract: The presented paper describes a multi‐disciplinary cooling selection approach applied to major gas turbine engine hot section components, including turbine nozzles, blades, discs, combustors and support structures, which maintain blade tip clearances. The paper demonstrates benefits of close interaction between participating disciplines starting from early phases of the hot section development. The approach targets advancements in engine performance and cost by optimizing the design process, often requiring compromises within individual disciplines.
Analysis of Particle Laden Flow and Heat Transfer in Cascade and Rocket Nozzle
Authors: CHO H. H. , KIM W. S. , YU M. S. , BAE J. C.
Published: July 2010

Abstract: This paper presents results for the calculation of particle trajectories in a cascade and a rocket nozzle using a Lagrangian method. When the floating particles collide to the components, the component surface is damaged severely. The surface erosion rate is strongly dependent on a particle size, a particle impact angle and a surface material. For a compressor cascade, the particle impact rate increases proportionally with the flow inlet angle and the erosion rate on the pressure side surface of blade are related to the surface or coating materials. For a solid rocket nozzle, the particle free zone in the nozzle divergent section increases quickly with increasing particle size and the maximum heat transfer density occurs at the starting region of nozzle convergent section. The Al2O3 droplet breaks up around the nozzle throat due to the high velocity difference between the droplet and gas stream, resulting in the big change of particle free zone.
Convective Heat Transfer on An Inlet Guide Vane
Authors: HOLMER M.‐L. , ERIKSSON L.‐E. , SUNDEN B.
Published: July 2010

Abstract: The flow and temperature fields around an inlet guide vane are determined numerically by a CFD method. Outer surface temperatures, heat transfer coefficient distributions, and static pressure distributions are presented. Three different thermal boundary conditions on the vane are analysed. The computed results are compared with experimental data. The governing equations are solved by a finite‐volume method with the low Reynolds number version of the k‐ω turbulence model by Wilcox implemented. It is found that the calculated results agree best with measurements if a conjugate heat transfer approach is applied and thus this wall condition is recommended for future investigations of film cooling of guide vanes and turbine blades.
Heat Transfer and Flow Characteristics on a Gas Turbine Shroud
Authors: OBATA Masakazu , KUMADA Masaya , IJICHI Nobuaki
Published: July 2010

Abstract: The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo‐charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on‐ and off‐design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.
Effects of Entrance Crossflow Directions to Film Cooling Holes
Authors: SAUMWEBER CHRISTIAN , SCHULZ ACHMED , WITTIG SIGMAR , GRITSCH MICHAEL
Published: July 2010

Abstract: Two‐dimensional distributions of local adiabatic film cooling effectiveness as well as discharge coefficients have been measured to investigate the effect of different entrance crossflow orientations and magnitudes on film‐cooling performance. Operating conditions have been varied in terms of hot gas Mach number (up to 0.6), coolant crossflow Mach number (up to 0.6), coolant crossflow orientation (perpendicular or parallel with respect to the mainflow), and blowing ratio (0.5 ‐ 1.5). The temperature ratio of coolant and hot gas was kept constant at 0.56 for the effectiveness tests, leading to an enginelike density ratio of 1.8. Infrared thermography was applied to perform local measurements of the surface temperatures with high resolution. The results indicate that the impact of hot gas crossflow Mach number is not very pronounced within the range of Mach numbers investigated. In contrast to this finding, the effect of internal coolant crossflow is very pronounced and strongly depends on coolant crossflow orientation and the ejected mass flow rate.
Numerical Investigation of Combined Impingement and Convection Heat Transfer
Authors: ABDON A. , SUNDéN B.
Published: July 2010

Abstract: This paper concerns development of a prediction method for combined turbulent impingement and convection heat transfer. Firstly, a prediction of a single round unconfined impinging air jet without crossflow is investigated to assess the performance of linear and non‐linear two‐equation turbulence models. The results show that realizable and/or non‐linear two‐equation models may successfully be used for impinging jet heat transfer predictions but there are significant differences between the formulations. Among the models tested, a non‐linear k‐omega showed superior performance. Secondly, the influence of crossflow is considered and a plane confined air jet is investigated. For this case the models based on a frequency‐equation (omega) show quite different and more reasonable predictions compared to the dissipation‐equation (epsilon) based models.
Detailed Heat/Mass Transfer Distributions in a Rotating Two Pass Coolant Channel With Engine‐Near Cross Section and Smooth Walls
Authors: RATHJEN L. , HENNECKE D. K. , BOCK S. , KLEINSTÜCK R.
Published: July 2010

Abstract: This paper shows results obtained by experimental and numerical investigations concerning flow structure and heat/mass transfer in a rotating two‐pass coolant channel with engine‐near geometry. The smooth two passes are connected by a 180° U‐bend in which a 90° turning vane is mounted. The influence of rotation number, Reynolds number and geometry is investigated. The results show a detailed picture of the flow field and distributions of Sherwood number ratios determined experimentally by the use of the naphthalene sublimation technique as well as Nusselt number ratios obtained from the numerical work. Especially the heat/mass transfer distributions in the bend and in the region after the bend show strong gradients, where several separation zones exist and the flow is forced to follow the turbine airfoil shape. Comparisons of numerical and experimental results show only partly good agreement.
Contribution of Heat Transfer to Turbine Blades and Vanes for High Temperature Industrial Gas Turbines Part 2: Heat Transfer on Serpentine Flow Passage
Authors: TAKEISHI KEN‐ICHIRO , AOKI SUNAO
Published: July 2010

Abstract: The improvement of the heat transfer coefficient of the 1st row blades in high temperature industrial gas turbines is one of the most important issues to ensure reliable performance of these components and to attain high thermal efficiency of the facility. This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of such gas turbines in order to attain efficient and environmentally benign engines. Following the experiments described in Part 1, a set of trials was conducted to clarify the influence of the blade's rotating motion on the heat transfer coefficient for internal serpentine flow passages with turbulence promoters. Test results are shown and discussed in this second part of the contribution.
SECONDARY FLOW EFFECT TO HEAT TRANSFER OF A DUCT WITH DISCRETE RIB TURBULATORS
Authors: TATSUMI K. , IWAI H. , INAOKA K. , SUZUKI K.
Published: July 2010

Abstract: In the present study, three‐dimensional numerical simulation is carried out for discrete rib arrays to investigate the local fluid and heat transfer characteristics. Rib pitch and gap width were varied in several steps. Furthermore, two kinds of rib arrays were studied, i.e. an array of ribs having the gaps at both spanwise ends and a staggered array of ribs with gaps at both spanwise ends and with gaps in the middle. Eventually, the staggered arrayed ribs is suggested to be best in performance of heat transfer.
Numerical Modelling of Flow and Heat Transfer in the Rotating Disc Cavities of a Turboprop Engine
Authors: FARAGHER JOHN , OOI ANDREW
Published: July 2010

Abstract: A numerical analysis of the flow and heat transfer in the cavity between two co‐rotating discs with axial inlet and radial outflow of fluid, a configuration common in gas turbine engines, is described. The results are compared with the experimental data of Northrop and Owen1. The effectiveness of the k ‐ ε turbulence model with the two‐layer zonal model for near‐wall treatment of Chen and Patel2 is tested for this type of flow. Using three‐dimension models it is shown that modelling discrete holes at the outlet as opposed to a continuous slot, which is the approximation inherent in the two‐dimensional axisymmetric model, has little effect on the predicted Nusselt number distribution along the disc surface. Results of a conjugate heat transfer analysis of a spacer in the turbine section of a turboprop engine are then presented.
Toward Mechanism‐based Antioxidant Interventions
Authors: KAGAN VALERIAN E. , KISIN ELENA R. , KAWAI KAZUAKI , SERINKAN BEHICE F. , OSIPOV ANATOLY N. , SERBINOVA ELENA A. , WOLINSKY IRA , SHVEDOVA ANNA A.
Published: July 2010

It is generally accepted that one of the major and important contributions to skin aging, skin disorders, and skin diseases results from reactive oxygen species. More than other tissues, the skin is exposed to numerous environmental chemical and physical agents, such as ultraviolet light, causing oxidative stress. Accelerated cutaneous UV‐induced aging, photo aging, is only one of the harmful effects of continual oxygen radical production in the skin. Interestingly, our ELISA assays of 8‐oxo‐2′‐deoxyguanosine in skin of young and old Balb/c mice showed that cumene hydroperoxide‐induced accumulation of the biomarker of oxidative DNA damage in skin of 32‐week‐old mice occurred independently of their vitamin E status, while no accumultaion of oxo8‐dG was detectable in the skin of young animals. This suggests that vitamin E is not the major protector of skin against cumene hydroperoxide‐induced oxidative stress. Production and accumulation of apoptotic cells is one of the characteristic features of skin damage by oxidative stress that, in the absence of effective scavenging by macrophages, dramatically enhances oxidative damage and inflammatory response. In our model experiments, we demonstrated that Cu‐OOH induces significant oxidative stress in phospholipids of normal human epidermal keratinocytes (NHEK) whose characteristic feature is an early and profound oxidation of phosphatidylserine (PS), likely related to PS externalization. Since externalized PS is a signal for recognition of apoptotic cells by macrophage scavenger receptors, PS oxidation may be translatable into elimination of thus damaged NHEKs. Experiments are now underway to determine whether inhibition of PS oxidation by antioxidants may interfere with improtant signaling functions of oxidative stress in eliminating apoptotic cells.
Cognitive Impairment of Rats Caused by Oxidative Stress and Aging, and Its Prevention by Vitamin E
Authors: FUKUI KOJI , OMOI NAO‐OMI , HAYASAKA TAKAHIRO , SHINNKAI TADASHI , SUZUKI SHOZO , ABE KOUICHI , URANO SHIRO
Published: July 2010

In order to verify whether brain damage caused by chronic oxidative stress induces the impairment of cognitive function, the ability of learning and memory was assessed using the water maze and the eight‐arm radial maze tasks. Young rats showed significantly greater learning ability before the stress than the old and vitamin E‐deficient rats. At five days after subjection to oxidative stress, the memory function of the young declined toward the level of that in the aged rats maintained under normal condition. This phenomenon is supported by the findings that the delayed‐type apoptosis appeared in the CA1 region of the hippocampus of the young at five to seven days after the stress. Vitamin E supplementation to the young accelerated significantly their learning functions before the stress and prevented the deficit of memory caused by the stress. When rats were subjected to stress, thiobarbituric acid‐reactive substance (TBARS), lipid hydroperoxides, and protein carbonyls were significantly increased in synaptic plasma membranes. It was found that ζ‐potential of the synaptic membrane surface was remarkably decreased. These phenomena were also observed in the aged and vitamin E‐deficient rats maintained under normal condition. These results suggest that oxidative damage to the rat synapse in the cerebral cortex and hippocampus during aging may contribute to the deficit of cognitive functions.
A Unified Mechanism in the Initiation of Cancer
Authors: CAVALIERI ERCOLE L. , ROGAN ELEANOR G.
Published: July 2010

Estrogens are involved in the initiation of breast, prostate, and other kinds of human cancer. In this process, the endogenous estrogens, estrone and estradiol, are metabolized to 2‐catechol estrogens (2‐CE, major) and 4‐CE (minor). If the 4‐CEs are further oxidized to CE‐3,4‐quinones, they may react with DNA to form depurinating adducts at N‐7 of guanine and N‐3 of adenine, and generate apurinic sites. Similarly, the carcinogenic synthetic estrogen hexestrol, a hydrogenated derivative of diethylstilbestrol, is metabolized to its quinone, which reacts with DNA to form analogous depurinating adducts. This could be the primary critical event leading to oncogenic mutations and then initiation of cancer. Evidence supporting this hypothesis has been obtained from the human breast and animal models susceptible to estrogen‐induced tumors, including the Syrian golden hamster kidney, ACI rat mammary gland, and Noble rat prostate. The oxidation of phenols to catechols and then to quinones is not only a mechanism of tumor initiation for natural and synthetic estrogens, but also for the leukemogen benzene. In fact, catechol, one of the metabolites of benzene, when oxidized to its quinone, reacts with DNA to form N7guanine and N3adenine depurinating adducts. Thus, a unifying mechanism, namely formation of catechol quinones and reaction with DNA, could initiate not only cancer by oxidation of specific endogenous estrogen metabolites, but also leukemia by oxidation of benzene.
The Maillard Hypothesis on Aging: Time to Focus on DNA
Authors: BAYNES JOHN W.
Published: July 2010

Aging is the outcome of the contest between chemistry and biology in living systems. Chronic, cumulative chemical modifications compromise the structure and function of biomolecules throughout the body. Proteins with long life spans serve as cumulators of exposure to chemical damage, which is detectable in the form of advanced glycation and lipoxidation end products (AGEs, ALEs); amino acids modified by reactive oxygen, chlorine, and nitrogen species; and deamidated and racemized amino acids. Not all of these modifications are oxidative in nature, although oxidative reactions are an important source of age‐related damage. Measurements of AGEs and ALEs in proteins are useful for assessing the rate and extent of Maillard reaction damage, but it is the damage to the genome that undoubtedly has the greatest effect on the viability of the organism. The extent of genomic damage represents a balance between the rate of modification and the rate and fidelity of repair. Damage to DNA accumulates not in the form of modified nucleic acids, but as chemically “silent” errors in repair—insertions, deletions, substitutions, transpositions, and inversions in DNA sequences—that affect the expression and structure of proteins. These mutations are random, vary from cell to cell, and are passed forward from one cell generation to another. Although they are not detectable in DNA by conventional analytical techniques, purines and pyrimidines modified by Maillard reaction intermediates may be detectable in urine, and studies on these compounds should provide insight into the role of Maillard reactions of DNA in aging and disease.
Alzheimer's Disease: Role of Aging in Pathogenesis
Authors: HARMAN DENHAM
Published: July 2010

Alzheimer's disease (AD) is characterized by intraneuronal fibrillary tangles, plaques, and cell loss. Brain lesions in both sporadic AD (SAD) and familial AD (FAD) are the same, and in the same distribution pattern, as those in individuals with Down syndrome (DS) and in smaller numbers in nondemented older individuals. Dementia onset is around 40 years for DS, 40‐60 years for FAD, and usually over 60 years for SAD. The different categories of AD may be due to processes that augment to different degrees the innate cellular aging rate, that is, mitochondrial superoxide radical (SO) formation. Thus, they increase the rate of accumulation of AD lesions. This lowers the age of onset into the dementia ranges associated with DS, FAD, and SAD, and concomitantly shortens life spans. Faster aging lowers AD onset age by decreasing the onset age for neurofibrillary tangle formation and neuronal loss, and the age when brain intercellular H2O2can activate microglial cells. The early AD onset in DS is attributed to a defective mitochondrial complex 1. The proteins associated with FAD and their normal counterparts undergo proteolytic processing in the endoplasmic reticulum (ER). The mutated compounds increase the ratio of βA42to βA40and likely also down‐regulate the ER calcium (Ca2+) buffering activity. Decreases in ER Ca2+content should increase the mitochondrial Ca2+pool, thus enhancing SO formation. SAD may be due to increased SO formation caused by mutations in the approximately 1000 genes involved in mitochondrial biogenesis and function. The hypothesis suggests measures to prevent and treat.
Time to Talk SENS: Critiquing the Immutability of Human Aging
Authors: DE GREY AUBREY D. N. J. , AMES BRUCE N. , ANDERSEN JULIE K. , BARTKE ANDRZEJ , CAMPISI JUDITH , HEWARD CHRISTOPHER B. , McCARTER ROGER J. M. , STOCK GREGORY
Published: July 2010

Aging is a three‐stage process: metabolism, damage, and pathology. The biochemical processes that sustain life generate toxins as an intrinsic side effect. These toxins cause damage, of which a small proportion cannot be removed by any endogenous repair process and thus accumulates. This accumulating damage ultimately drives age‐related degeneration. Interventions can be designed at all three stages. However, intervention in metabolism can only modestly postpone pathology, because production of toxins is so intrinsic a property of metabolic processes that greatly reducing that production would entail fundamental redesign of those processes. Similarly, intervention in pathology is a “losing battle” if the damage that drives it is accumulating unabated. By contrast, intervention to remove the accumulating damage would sever the link between metabolism and pathology, and so has the potential to postpone aging indefinitely. We survey the major categories of such damage and the ways in which, with current or foreseeable biotechnology, they could be reversed. Such ways exist in all cases, implying that indefinite postponement of aging—which we term “engineered negligible senescence”—may be within sight. Given the major demographic consequences if it came about, this possibility merits urgent debate.