bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of shock motion in shockwave and turbulent boundary layer interaction using direct numerical simulation data
Authors: WU MINWEI , MARTÍN M. PINO
Published: December 2007

Direct numerical simulation data of a Mach 2.9, 24○ compression ramp configuration are used to analyse the shock motion. The motion can be observed from the animated DNS data available with the online version of the paper and from wall-pressure and mass-flux signals measured in the free stream. The characteristic low frequency is in the range of (0.007–0.013) U∞/δ, as found previously. The shock motion also exhibits high-frequency, of O(U∞/δ), small-amplitude spanwise wrinkling, which is mainly caused by the spanwise non-uniformity of turbulent structures in the incoming boundary layer. In studying the low-frequency streamwise oscillation, conditional statistics show that there is no significant difference in the properties of the incoming boundary layer when the shock location is upstream or downstream. The spanwise-mean separation point also undergoes a low-frequency motion and is found to be highly correlated with the shock motion. A small correlation is found between the low-momentum structures in the incoming boundary layer and the separation point. Correlations among the spanwise-mean separation point, reattachment point and the shock location indicate that the low-frequency shock unsteadiness is influenced by the downstream flow. Movies are available with the online version of the paper.
An experimental study and modelling of roughness effects on laminar flow in microchannels
Authors: GAMRAT G. , FAVRE-MARINET M. , LE PERSON S. , BAVIÈRE R. , AYELA F.
Published: December 2007

Three different approaches were used in the present study to predict the influence of roughness on laminar flow in microchannels. Experimental investigations were conducted with rough microchannels 100 to 300μm in height (H). The pressure drop was measured in test-sections prepared with well-controlled wall roughness (periodically distributed blocks, relative roughness k* =k/0.5H≈0.15) and in test-sections with randomly distributed particles anchored on the channel walls (k* ≈0.04–0.13). Three-dimensional numerical simulations were conducted with the same geometry as in the test-section with periodical roughness (wavelength L). A one-dimensional model (RLM model) was also developed on the basis of a discrete-element approach and the volume-averaging technique. The numerical simulations, the rough layer model and the experiments agree to show that the Poiseuille number Po increases with the relative roughness and is independent of Re in the laminar regime (Re<2000). The increase in Po observed during the experiments is predicted well both by the three-dimensional simulations and the rough layer model. The RLM model shows that the roughness effect may be interpreted by using an effective roughness height keff. keff/k depends on two dimensionless local parameters: the porosity at the bottom wall; and the roughness height normalized with the distance between the rough elements. The RLM model shows that keff/k is independent of the relative roughness k* at given k/L and may be simply approximated by the law: keff/k = 1 − (c(ϵ)/2π)(L/k) for keff/k>0.2, where c decreases with the porosity ϵ.
Wave-activity conservation laws for the three-dimensional anelastic and Boussinesq equations with a horizontally homogeneous background flow
Authors: SHAW TIFFANY A. , SHEPHERD THEODORE G.
Published: December 2007

Wave-activity conservation laws are key to understanding wave propagation in inhomogeneous environments. Their most general formulation follows from the Hamiltonian structure of geophysical fluid dynamics. For large-scale atmospheric dynamics, the Eliassen–Palm wave activity is a well-known example and is central to theoretical analysis. On the mesoscale, while such conservation laws have been worked out in two dimensions, their application to a horizontally homogeneous background flow in three dimensions fails because of a degeneracy created by the absence of a background potential vorticity gradient. Earlier three-dimensional results based on linear WKB theory considered only Doppler-shifted gravity waves, not waves in a stratified shear flow. Consideration of a background flow depending only on altitude is motivated by the parameterization of subgrid-scales in climate models where there is an imposed separation of horizontal length and time scales, but vertical coupling within each column. Here we show how this degeneracy can be overcome and wave-activity conservation laws derived for three-dimensional disturbances to a horizontally homogeneous background flow. Explicit expressions for pseudoenergy and pseudomomentum in the anelastic and Boussinesq models are derived, and it is shown how the previously derived relations for the two-dimensional problem can be treated as a limiting case of the three-dimensional problem. The results also generalize earlier three-dimensional results in that there is no slowly varying WKB-type requirement on the background flow, and the results are extendable to finite amplitude. The relationship $A^{\cal E}\,{=}\,cA^{\cal P}$ between pseudoenergy $A^{\cal E}$ and pseudomomentum $A^{\cal P}$, where c is the horizontal phase speed in the direction of symmetry associated with $A^{\cal P}$, has important applications to gravity-wave parameterization and provides a generalized statement of the first Eliassen–Palm theorem.
Vortex-induced vibrations of a circular cylinder at low Reynolds numbers
Authors: PRASANTH T. K. , MITTAL S.
Published: December 2007

Results are presented for a numerical simulation of vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m* = 10) in the laminar flow regime (60 < Re < 200). The natural structural frequency of the oscillator, fN, matches the vortex shedding frequency for a stationary cylinder at Re = 100. This corresponds to fND2/ν = 16.6, where D is the diameter of the cylinder and ν the coefficient of viscosity of the fluid. A stabilized space–time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. Unlike at high Re, where the cylinder response is known to be associated with three branches, at low Re only two branches are identified: ‘initial’ and ‘lower’. For a blockage of 2.5% and less the onset of synchronization, in the lower Re range, is accompanied by an intermittent switching between two modes with vortex shedding occurring at different frequencies. With higher blockage the jump from the initial to lower branch is hysteretic. Results from free vibrations are compared to the data from experiments for forced vibrations reported earlier. Excellent agreement is observed for the critical amplitude required for the onset of synchronization. The comparison brings out the possibility of hysteresis in forced vibrations. The phase difference between the lift force and transverse displacement shows a jump of almost 180° at, approximately, the middle of the synchronization region. This jump is not hysteretic and it is not associated with any radical change in the vortex shedding pattern. Instead, it is caused by changes in the location and value of the maximum suction on the lower and upper surface of the cylinder. This is observed clearly by comparing the time-averaged flow for a vibrating cylinder for different Re. While the mean flow for Re beyond the phase jump is similar to that for a stationary cylinder, it is associated with a pair of counter-rotating vortices in the near wake for Re prior to the phase jump. The phase jump appears to be one of the mechanisms of the oscillator to self-limit its vibration amplitude.
Sound, text and identity in Korn’s ‘Hey Daddy’
Authors: PIESLAK JONATHAN
Published: December 2007

Most of the existing literature on metal approaches the subject from a sociological, anthropological or historical perspective, dedicating more attention to the surrounding musical (sub)cultures and their transformations than to the songs and music itself. This essay addresses this gap in recent metal scholarship by examining issues of sound, text and identity in one of the most influential and popular metal bands of the post-grunge era, Korn. I interpret possible meanings within ‘Hey Daddy’, a track from Issues (1999), based on the relationships among the music, both as pitch and sound/timbre, and the text. In addition, I explore different processes of identification, offering an assessment of identification in the genre of metal and challenges in respect to listener identity in ‘Hey Daddy’.
The medium and materials of popular music: ‘Hound Dog’, turntablism
and muzak as situated musical practices
Authors: FAIRCHILD CHARLES
Published: December 2007

Popular music studies has rarely exhibited the kinds of disciplinary coherence found in closely related disciplines mostly due to the field’s adoption and adaptation of methodological and theoretical innovations from a variety of disciplines, notably sociology, cultural studies, anthropology, media studies and musicology. However, many commentators continue to seek disciplinary coherence without making any critical aesthetic distinctions between the medium and materials of popular music. Distinctions and interrelationships between the literal or material aspects of popular music and the social or cultural processes of making meaning from popular music are central to the definition of a particular but not exclusive field of analysis. Through such distinctions, the very category ‘popular music’ can be understood as a more flexible and supple distinction based on an understanding of methods of construction, production and mediation in specific relation to the technical, contextual and sociological aspects of music. I use different performances of ‘Hound Dog’, the practices of ‘turntablism’, and the exigencies of Muzak as examples for analysis offering ways in which the aesthetic, material and contextual aspects of popular music can be understood in order to incorporate the actual sound of music into the analysis of its social, cultural and musical construction.
Abiding memories: the community singing movement and English social life in the 1920s
Authors: RUSSELL DAVE
Published: December 2007

The community singing movement was a distinctive feature of English popular musical life in the mid-1920s. Although initiated by individuals who saw it as essentially educational, it was rapidly appropriated by sections of the press, and especially the Daily Express, as an instrument in the circulation wars of the period. It was typified by a restricted range of music comprising ‘national’ songs, hymns (with the performance of ‘Abide with Me’ at the FA Cup Final singing particularly important), and songs of the First World War. This mixture and the concomitant neglect of modern popular song reflects the rather nostalgic thrust behind activities, with calls for community singing to recreate a ‘Merrie England’ that would heal the deep social divisions of the 1920s. Whether the singers were fully aware of these various musical and socio-political agendas is unclear, but community singing undoubtedly enjoyed a period of considerable popularity, with the music appreciated for allowing displays of individual and collective emotion.
Que viva la música popular! International Association for the Study of Popular music, 14th Biennial Conference, 25–29 June 2007, Mexico City
Authors: Till Rupert , Fairley Jan
Published: December 2007

The International Association for the Study of Popular Music’s biennial international conference took place in July this year in Mexico City. The facilities in the Universidad Iberoamericana, a modern private Jesuit University in the city’s business quarter, were excellent, with video projection and a good sound system in all the air-conditioned rooms. The plenary sessions were translated to and from Spanish and also video recorded and streamed onto the Internet, with a blog where watchers could leave comments.
Homocysteine and stroke
Authors: Zaw K , Hasan M T , Bhowmick B , Khanna P B , Freeman E A
Published: December 2007

Interest in homocysteine's role in vascular disease was stimulated by the paper of McCully (1969) in which, based on autopsy evidence of extensive arterial thrombosis in two children with elevated plasma homocysteine concentrations and homocystinuria, he proposed that elevated plasma homocysteine (hyperhomocysteinaemia) can cause atherosclerotic vascular disease. A meta-analysis of subsequent prospective observational studies concluded that elevated homocysteine is indeed a modest independent predictor of ischaemic heart disease and stroke risk in healthy populations with a 25% reduction in serum homocysteine concentration, a reduction of approximately 3 micromol per litre (μmol/l) being associated with a 19% lower risk of stroke (odds ratio, 0.81; 95% confidence interval (CI), 0.69 – 0.95). In the nationally representative sample of US adults, elevated homocysteine concentration was independently associated with an increased likelihood of non-fatal stroke in both black and white adults. In this article, the current concepts relating homocysteine to ischaemic stroke are reviewed.
Executive function, mentalizing and humor in major depression
Authors: UEKERMANN J. , CHANNON S. , LEHMKÄMPER C. , ABDEL-HAMID M. , VOLLMOELLER W. , DAUM I.
Published: December 2007

Major depression is associated with cognitive deficits including memory, executive functions, and affect perception, which have been linked to dysfunction of fronto-subcortical networks. However, little is known about social cognition on more complex socially relevant tasks, such as humor processing. In this investigation a computerized humor-processing task was administered to 27 patients with a diagnosis of major depression (Dep) and 27 healthy controls (HC). Theory of mind (mentalizing) and executive functions were also assessed. Both groups were similar in IQ, age, and gender. Depressed patients performed below the control group with respect to both affective and cognitive aspects of humor processing, and these were related to mentalizing and executive performance. Our findings suggest social cognition deficits in major depression. Ability to process humor and appreciate mentalistic perspectives may in turn influence social interactions and should be given consideration in therapeutic approaches to depression. (JINS, 2008,14, 55–62.)
Detecting the significance of changes in performance on the Stroop Color-Word Test, Rey's Verbal Learning Test, and the Letter Digit Substitution Test: The regression-based change approach
Authors: VAN DER ELST WIM , VAN BOXTEL MARTIN P.J. , VAN BREUKELEN GERARD J.P. , JOLLES JELLE
Published: December 2007

Serial neuropsychological assessment is often conducted to monitor changes in the cognitive abilities of individuals over time. Because practice effects occur and the reliability of test scores is less than perfect, it is difficult to judge whether varying test results should be attributed to chance trends or to real changes in underlying cognitive abilities. In a large sample of adults (age range, 49–81 years), we evaluated the influence of age, gender, and education on test–retest changes in performance after 3 years on Rey's Verbal Learning Test (VLT), the Stroop Color-Word Test (SCWT), and the Letter Digit Substitution Test (LDST). A new statistical method was applied to assess the significance of changes in test performance (i.e., the regression-based change method). The results showed that test–retest changes differed as a function of age for the VLT Total recall 1–3, VLT Total recall 1–5, VLT Delayed recall, and LDST measures. An age × gender interaction was found for the SCWT Interference change score, suggesting that the age-related decline in executive functioning after 3 years was more pronounced for males than for females. A normative change table with appropriate corrections for the relevant independent variables was established. (JINS, 2008,14, 71–80.)
A demonstration of endogenous modulation of unilateral spatial neglect: The impact of apparent time-pressure on spatial bias
Authors: GEORGE MELANIE S. , MERCER JACKIE S. , WALKER ROBIN , MANLY TOM
Published: December 2007

Unilateral neglect, a lack of awareness for one side of space, is a common and debilitating consequence of stroke. Previous work has identified a relationship between enduring left neglect and diminished general alertness and shown that increasing alertness can temporarily reduce the severity of the spatial bias. In that research, alertness was modulated by loud tones or with pharmacological stimulants. Here we examine whether cognitive, endogenously driven changes can produce similar short-term improvements. Time-pressure is associated with increased subjective arousal and increased activation in cortical regions associated with alertness. Here five patients completed a spatial cancellation task with and without instructions regarding a time limit. Significant reductions in neglect severity were observed when patients believed that they were acting under time-pressure, despite the conditions being equivalent in the actual (unlimited) time available. Functional imaging work has highlighted the secondary effects that damage to networks mediating alertness can have on structurally intact spatial systems. The results here suggest that activation of presumably spared function in these damaged networks can induce moment-by-moment changes in spatial function and, crucially, that this can be achieved using entirely endogenous means. (JINS, 2008,14, 33–41.)
Long-term effects of risperidoneversushaloperidol on verbal memory, attention, and symptomatology in schizophrenia
Authors: RÉMILLARD SOPHIE , POURCHER EMMANUELLE , COHEN HENRI
Published: December 2007

There is evidence in the literature that cognitive functions in schizophrenia (SC) may be improved by atypical neuroleptics (NLPs) in contrast to typical medication, but there is still controversy regarding this apparent superiority of atypical drugs. In this study, we assessed the differential effects of risperidone and haloperidol on verbal memory, attention, and psychiatric symptoms in SC. The performance of 28 SC participants, randomly assigned to risperidone (2–6 mg/day) or haloperidol (2–40 mg/day), was compared with that of healthy controls. The California Verbal Learning Test (CVLT), the d2 Cancellation Test, and the Positive and Negative Symptoms Scale were administered at baseline and 3, 6, and 12 months. Relative to controls, all SC participants showed markedly impaired verbal memory and processing speed at each assessment period. There was no differential effect between the two NLPs on CVLT and d2 performance. However, risperidone was more effective than haloperidol in reducing psychiatric symptoms. Improvement in symptom severity was not associated with improvement in neurocognitive performance on these specific tests. Neither conventional nor atypical neuroleptic medications improved neurocognitive functioning over a 12-month follow-up, suggesting that psychopathological improvement under risperidone is independent of cognitive function. (JINS, 2008,14, 110–118.)
All the Important Things You Wanted to Know About the Effects of Stroke: Location, Location, Location
Authors: Mattis Steven
Published: December 2007

The Behavioral and Cognitive Neurology of Stroke. 2007. Olivier Godefroy and Julien Bogousslavsky (Eds.). Cambridge, UK: Cambridge University Press, 664 pp., $160.00 (HB)

The Behavioral and Cognitive Neurology of Stroke is a very handy reference book for the bedside or brief office examination of the stroke patient. The initial chapter highlights the need for serial mental status exams during the critical initial post stroke period. The book is then organized by functional sections, each containing several chapters. The sections are organized by neuropsychological processes in the usual “walk around the brain” format. Thus, the reader is offered sections on motor and gestural disorders, aphasia and arthric disorders, hemineglect and right hemisphere syndromes, agnosia and Balint's syndrome, and executive and memory disorders. Of great significance is the inclusion of a section on behavioral and mood disorders, which reviews the clinical domains where the disciplines of psychiatry and neurology overlap. The final section, dementia and anatomical left/right syndromes, extends and integrates the previous sections.
What's New With the Frontal Lobes?
Authors: Anderson Vicki
Published: December 2007

The Human Frontal Lobes: Functions and Disorders (Second Edition). 2007. Bruce L. Miller & Jeffrey L. Cummings (Eds.). New York: The Guilford Press, 666 pp., $95.00 (HB)

Miller and Cummings published their original text, The Human Frontal Lobes: Functions and Disorders, in 1999. At that time, their work was quite unique and provided a valuable reference for both health professionals and researchers in the emerging field of the frontal lobes. The years since then have seen an increasing focus on these fascinating brain structures across a range of disciplines including neurosciences, neurology, neuropsychology and psychiatry. The importance of the frontal structures for both cognition and emotion is firmly established and the complexity of these associations continues to challenge those working in these fields. As Miller and Cummings note, due to the major advances that have occurred since they first published their work, their second edition represents not only an update but also an introduction to a range of new issues. In particular, this second edition emphasizes advances in neurosciences and neuroimaging with a substantial amount of new material presented in these areas. In addition, the increasing interest in the role of the frontal lobes in social and emotional function is also acknowledged and discussed.
Localized ductile shear below the seismogenic zone: Structural analysis of an exhumed strike‐slip fault, Austrian Alps
Authors: Cole Joshua , Hacker Bradley , Ratschbacher Lothar , Dolan James , Seward Gareth , Frost Erik , Frank Wolfgang
Published: December 2007

The Miocene Salzachtal‐Ennstal‐Mariazell‐Puchberg (SEMP) strike‐slip fault in Austria allows study of the internal structure of a fault zone from the near surface to ∼30 km depth. As it enters the Tauern Window along the Rinderkarsee shear zone, the SEMP fault passes from a dominantly brittle to a dominantly ductile structure. The shear zone consists of three 1‐ to 100‐m‐wide zones of brittle‐ductile and ductile deformation separated by 500‐m‐wide zones of less deformed rocks. The southern shear zone is mylonitic, with ductile amphibole and plagioclase; weak crystal preferred orientations imply that the main deformation mechanism was dislocation‐accommodated grain boundary sliding. The northern and central shear zones are characterized by discrete millimeter‐wide shear zones with ductile quartz, muscovite, and biotite and brittle feldspar. Shear zone nucleation at the grain scale involved dislocation creep and the transformation of plagioclase to muscovite; strain then localized in muscovite‐rich grain boundary shear zones that linked to form throughgoing shear zones.
Different glycoforms of prostate-specific membrane antigen are intracellularly transported through their association with distinct detergent-resistant membranes
Authors: Castelletti Deborah , Alfalah Marwan , Heine Martin , Hein Zeynep , Schmitte Ruth , Fracasso Giulio , Colombatti Marco , Naim Hassan Y.
Published: December 2007

Hormone-refractory prostate carcinomas as well as the neovasculature of different tumours express high levels of PSMA (prostate-specific membrane antigen). PSMA is a type II-transmembrane glycoprotein and a potential tumour marker for both diagnosis and passive immunotherapy. Here, we report on the association of PSMA with DRMs (detergent-resistant membranes) at different stages of the protein maturation pathway in human prostate carcinoma LNCaP cells. At least three PSMA glycoforms were biochemically identified based on their extractability behaviour in different non-ionic detergents. In particular, one precursor glycoform of PSMA is associated with Tween 20-insoluble DRMs, whereas the complex glycosylated protein segregates into membrane structures that are insoluble in Lubrol WX and display a different lipid composition. Association of PSMA with these membranes occurs in the Golgi compartment together with the acquisition of a native conformation. PSMA homodimers reach the plasma membrane of LNCaP cells in Lubrol WX-insoluble lipid/protein complexes. At the steady state, the majority of PSMA remains within these membrane microdomains at the cell surface. We conclude that the intracellular transport of PSMA occurs through populations of DRMs distinct for each biosynthetic form and cellular compartment.
Human ornithine decarboxylase paralogue (ODCp) is an antizyme inhibitor but not an arginine decarboxylase
Authors: Kanerva Kristiina , Mäkitie Laura T. , Pelander Anna , Heiskala Marja , Andersson Leif C.
Published: December 2007

ODC (ornithine decarboxylase), the rate-limiting enzyme in polyamine biosynthesis, is regulated by specific inhibitors, AZs (antizymes), which in turn are inhibited by AZI (AZ inhibitor). We originally identified and cloned the cDNA for a novel human ODC-like protein called ODCp (ODC paralogue). Since ODCp was devoid of ODC catalytic activity, we proposed that ODCp is a novel form of AZI. ODCp has subsequently been suggested to function either as mammalian ADC (arginine decarboxylase) or as AZI in mice. Here, we report that human ODCp is a novel AZI (AZIN2). By using yeast two-hybrid screening and in vitro binding assay, we show that ODCp binds AZ1–3. Measurements of the ODC activity and ODC degradation assay reveal that ODCp inhibits AZ1 function as efficiently as AZI both in vitro and in vivo. We further demonstrate that the degradation of ODCp is ubiquitin-dependent and AZ1-independent similar to the degradation of AZI. We also show that human ODCp has no intrinsic ADC activity.
Mutational analysis of the FXNPXY motif within LDL receptor-related protein 1 (LRP1) reveals the functional importance of the tyrosine residues in cell growth regulation and signal transduction
Authors: Zhang Hongyu , Lee Jonathan M. , Wang Yuwei , Dong Li , Ko Kerry W. S. , Pelletier Louise , Yao Zemin
Published: December 2007

LRP1 [LDL (low-density lipoprotein) receptor-related protein 1]-null CHO cells (Chinese-hamster ovary cells) (13-5-1 cells) exhibited accelerated cell growth and severe tumour progression after they were xenografted into nude mice. Reconstitution of LRP1 expression in these cells, either with the full-length protein or with a minireceptor, reduced growth rate as well as suppressed tumour development. We tested the role of the tyrosine residue in the FXNPXY63 motif within the LRP1 cytoplasmic domain in signal transduction and cell growth inhibition by site-specific mutagenesis. The LRP1 minireceptors harbouring Tyr63 to alanine or Tyr63 to phenylalanine substitution had diametrically opposite effects on cell growth, cell morphology and tumour development in mice. The Y63F-expressing cells showed suppressed cell growth and tumour development, which were associated with decreased β-catenin and cadherin concentrations in the cells. On the other hand, the Y63A-expressing cells lacked inhibition on cell growth and tumour development, which were associated with hyperactivation of ERKs (extracellular-signal-regulated kinases), FAK (focal adhesion kinase) and cyclin D1 in the cells. The mutant Y63A minireceptor also exhibited reduced capacity in binding to the Dab2 (disabled 2) adaptor protein. In addition, the Y63A mutant showed increased caveolar localization, and cells expressing Y63A had altered caveolae architecture. However, tyrosine to alanine substitution at the other NPXY29 motif had no effect on cell growth or tumorigenesis. These results suggest that the FXNPXY63 motif of LRP1 not only governs cellular localization of the receptor but also exerts multiple functional effects on signalling pathways involved in cell growth regulation.
The IRAK-catalysed activation of the E3 ligase function of Pellino isoforms induces the Lys63-linked polyubiquitination of IRAK1
Authors: Ordureau Alban , Smith Hilary , Windheim Mark , Peggie Mark , Carrick Emma , Morrice Nick , Cohen Philip
Published: December 2007

The protein kinases IRAK [IL-1 (interleukin 1) receptor-associated kinase] 1 and 4 play key roles in a signalling pathway by which bacterial infection or IL-1 trigger the production of inflammatory mediators. In the present study, we demonstrate that IRAK1 and IRAK4 phosphorylate Pellino isoforms in vitro and that phosphorylation greatly enhances Pellino's E3 ubiquitin ligase activity. We show that, in vitro, Pellino 1 can combine with the E2 conjugating complex Ubc13 (ubiquitin-conjugating enzyme 13)–Uev1a (ubiquitin E2 variant 1a) to catalyse the formation of K63-pUb (Lys63-linked polyubiquitin) chains, with UbcH3 to catalyse the formation of K48-pUb chains and with UbcH4, UbcH5a or UbcH5b to catalyse the formation of pUb-chains linked mainly via Lys11 and Lys48 of ubiquitin. In IRAK1−/− cells, the co-transfection of DNA encoding wild-type IRAK1 and Pellino 2, but not inactive mutants of these proteins, induces the formation of K63-pUb–IRAK1 and its interaction with the NEMO [NF-κB (nuclear factor κB) essential modifier] regulatory subunit of the IKK (inhibitor of NF-κB kinase) complex, a K63-pUb-binding protein. These studies suggest that Pellino isoforms may be the E3 ubiquitin ligases that mediate the IL-1-stimulated formation of K63-pUb–IRAK1 in cells, which may contribute to the activation of IKKβ and the transcription factor NF-κB, as well as other signalling pathways dependent on IRAK1/4.
Molecular dynamics simulation of nanocolloidal amorphous silica particles: Part I
Authors: Jenkins S. , Kirk S. R. , Persson M. , Carlen J. , Abbas Z.
Published: December 2007

Explicit molecular dynamics simulations were applied to a pair of amorphous silica nanoparticles in aqueous solution, with diameter of 4.4nm and with four different background electrolyte concentrations, to extract the mean force acting between the two silica nanoparticles. Dependences of the interparticle forces on the separation and the background electrolyte concentration were demonstrated. The nature of the interaction of the counterions with charged silica surface sites (deprotonated silanols) was investigated. A “patchy” double layer of adsorbed sodium counterions was observed. Dependences of the interparticle potential of mean force on the separation and the background electrolyte concentration were demonstrated. Direct evidence of the solvation forces is presented in terms of changes of the water ordering at the surfaces of the isolated and double nanoparticles. The nature of the interaction of the counterions with charged silica surface sites (deprotonated silanols) was investigated in terms of quantifying the effects of the number of water molecules separately inside each pair of nanoparticles by defining an impermeability measure. A direct correlation was found between the impermeability (related to the silica surface “hairiness”) and the disruption of water ordering. Differences in the impermeability between the two nanoparticles are attributed to differences in the calculated electric dipole moment.
Micromagnetic analysis of L1 ordered FePt perpendicular recording media prepared by magnetron sputtering
Authors: Li Zhenghua , Cao Jiangwei , Wei Fulin , Piao Kun , She Shenxian , Wei Dan
Published: December 2007

A three-dimensional micromagnetic model is built up to analyze the relationship between the magnetic property and the microstructure of FePt thin films, with careful discussions of the tetragonal symmetry and the magnetostriction. It is found that the in-plane magnetoelastic effect with a residual tensile stress on the order of 1Gpa would enlarge the perpendicular coercivity and the saturation field of the longitudinal loop; the tetragonal anisotropy, such as tetragonal anisotropy with 5:1 in-plane∕out-of-plane anisotropy ratio, tends to enlarge the longitudinal coercivity and conduce the open up between the tails of the longitudinal and perpendicular loops. The high perpendicular squareness is caused by the perfect orientation of the c axis and large exchange interactions. The simulated M-H loops agree well with experiments.
A simple and efficient CCSD(T)-F12 approximation
Authors: Adler Thomas B. , Knizia Gerald , Werner Hans-Joachim
Published: December 2007

A new explicitly correlated CCSD(T)-F12 approximation is presented and tested for 23molecules and 15 chemical reactions. The F12 correction strongly improves the basis set convergence of correlation and reaction energies. Errors of the Hartree-Fock contributions are effectively removed by including MP2 single excitations into the auxiliary basis set. Using aug-cc-pVTZ basis sets the CCSD(T)-F12 calculations are more accurate and two orders of magnitude faster than standard CCSD(T)/aug-cc-pV5Z calculations.
New explicit solutions of Einstein equations in the framework of GAP Theory
Authors: Starkl Reinhard
Published: December 2007

The presented paper develops a new method for solving Einstein equations explicitly. Not only the solutions are new but also the mathematical framework of their construction which is given by a nonstandard function theory built over nonstandard algebras (in the following denoted as GAPs) and will be called here as “GAP Theory.” It is shown that the GAP theory succeeds in regions, where group theory fails: the group structure is too small to solve Einstein equations explicitly.
Statistics of passive tracers in three-dimensional magnetohydrodynamic turbulence
Authors: Busse Angela , Müller Wolf-Christian , Homann Holger , Grauer Rainer
Published: December 2007

Magnetohydrodynamic (MHD) turbulence is studied from the Lagrangian viewpoint by following fluid particle tracers in high resolution direct numerical simulations. Results regarding turbulent diffusion and dispersion as well as Lagrangian structure functions are presented. Whereas turbulent single-particle diffusion exhibits essentially the same behavior in Navier-Stokes and MHD turbulence, two-particle relative dispersion in the MHD case differs significantly from the Navier-Stokes behavior. This observation is linked to the local anisotropy of MHD turbulence which is clearly reflected by quantities measured in a Lagrangian frame of reference. In the MHD case the Lagrangian structure functions display a lower level of intermittency as compared to the Navier-Stokes case contrasting Eulerian results. This is not only true for short time increments [H. Homann, R. Grauer, A. Busse, and W.-C. Müller, J. Plasma Phys. 73, 821 (2007)] but also holds for increments up to the order of the integral time scale. The apparent discrepancy can be explained by the difference in the characteristic shapes of fluid particle trajectories in the vicinity of most singular dissipative structures.
A massive Feynman integral and some reduction relations for Appell functions
Authors: Shpot M. A.
Published: December 2007

New explicit expressions are derived for the one-loop two-point Feynman integral with arbitrary external momentum and masses m12 and m22 in D dimensions. The results are given in terms of Appell functions, manifestly symmetric with respect to the masses mi2. Equating our expressions with previously known results in terms of Gauss hypergeometric functions yields reduction relations for the involved Appell functions that are apparently new mathematical results.
Percolative effects on noise in pentacene transistors
Authors: Conrad B. R. , Cullen W. G. , Yan W. , Williams E. D.
Published: December 2007

Noise in pentacene thin film transistors has been measured as a function of device thickness from well above the effective conduction channel thickness to only two conducting layers. Over the entire thickness range, the spectral noise form is 1∕f, and the noise parameter varies inversely with gate voltage, confirming that the noise is due to mobility fluctuations, even in the thinnest films. Hooge’s parameter varies as an inverse power law with conductivity for all film thicknesses. The magnitude and transport characteristics of the spectral noise are well explained in terms of percolative effects arising from the grain boundary structure.
Theory of the dielectric nonlinearity in ferroelectric relaxors in the vicinity of the Vogel-Fulcher temperature under dc bias fields
Authors: Prosandeev S. , Panchelyuga M. , Raevskaya S. , Raevski I.
Published: December 2007

Usually, dipole glass phase transitions are associated with the divergence of the third harmonic of the dielectric response. We show that, in reality, (i) random fields diffuse this singularity; (ii) even if the random field is absent, the divergence is one sided (it exists only at the temperatures, which are lower than the Vogel-Fulcher temeprature}; (iii) in the latter case, the divergence is followed by a jump of the first and third harmonics; and (iv) if the bias field exceeds the random field, all dielectric anomalies must be seen well.
Coupling of surface plasmons between two silver films in a plasmonic thermal emitter
Authors: Chen Chia-Yi , Tsai Ming-Wei , Jiang Yu-Wei , Ye Yi-Han , Chang Yi-Tsung , Lee Si-Chen
Published: December 2007

The emission spectra of Ag∕SiO2∕Ag trilayer plasmonic thermal emitters with various SiO2 thicknesses were investigated. By analyzing the relationship between emission peaks and thicknesses of SiO2, the coupling of surface plasmons between two silver films in a plasmonic thermal emitter is demonstrated and the coupling length is determined as well. Furthermore, the dispersion relation of plasmonic thermal emitter is detected by measuring the reflection spectra with various incident angles. This confirms that the main mechanism involved in the emission of a plasmonic thermal emitter is due to the excitation of surface plasmons.
Temperature-mediated saturation and current-induced recovery of the Vf drift in 4H-SiC p-i-n diodes
Authors: Caldwell Joshua D. , Glembocki Orest J. , Stahlbush Robert E. , Hobart Karl D.
Published: December 2007

4 H - Si C is desirable for high power and temperature electronic applications. However, for bipolar devices, device operation induces Shockley stacking fault (SSF) expansion and a drift in the forward voltage drop (Vf). Here, we present results showing that the electrically induced SSF expansion and Vf drift saturate. The saturation voltage is strongly temperature dependent and decreases tenfold at 247°C from 30°C. In heavily faulted diodes, the injection of relatively high currents (<35A∕cm2) at elevated temperatures (∼245°C) actually induced a partial recovery of the drift. A possible driving force mechanism for SSF expansion based on these results is then presented.
Particle concentration and tube size dependence of viscosities of Al2O3-water nanofluids flowing through micro- and minitubes
Authors: Jang Seok Pil , Lee Ji-Hwan , Hwang Kyo Sik , Choi Stephen U. S.
Published: December 2007

An experimental and theoretical investigation has been performed on the effective viscosity of Al2O3-water nanofluids flowing through micrometer- and millimeter-sized circular tubes in the fully developed laminar flow regime. We have discovered that the effective viscosity of Al2O3-water nanofluids increases nonlinearly with the volume concentration of nanoparticles even in the very low range of 0.02–0.3vol% and strongly depends on the ratio of the nanoparticle diameter to the tube diameter. We have developed a modified Einstein model that accounts for the slip mechanism in nanofluids. The new model captures these new rheological features of nanofluids.
Dynamics of random laser and coherent backscattering of light from ZnO amplifying random medium
Authors: Sun T. , Qiu Z. R. , Su H. M. , Zhang X. D. , Zhang Z. Q. , Wong G. K. L. , Wong K. S.
Published: December 2007

We investigated the dynamics of coherent backscattering cone and random laser in a disordered gain medium of ZnO powder. Theoretical fit to the coherent backscattering cone yields a transport mean free path l approximately equal to the probe wavelength λ, indicating that the scattering process is in the strong scattering regime. Supernarrow emissions from the laser are accompanied by enhancement and sharpening of the coherent backscattering cone. This enhanced and sharpened backscattering cone returns to a normal profile within 10–20ps, indicating an ultrafast gain lifetime in the medium, which is in good agreement with the time-resolved measurement of the random laser emissions.
Temperature stability of ZnO:Al film properties for poly-Si thin-film devices
Authors: Lee K. Y. , Becker C. , Muske M. , Ruske F. , Gall S. , Rech B. , Berginski M. , Hüpkes J.
Published: December 2007

The crystallization of thin silicon films at temperatures between 425 and 600°C was investigated on glass substrates coated with Al-doped zinc oxide (ZnO:Al). Bare ZnO:Al layers degrade at the crystallization temperatures used. A silicon layer on top, however, efficiently prevents deterioration. The resistivity was even found to drop from 4.3×10−4Ωcm for the as deposited ZnO:Al to 2.2×10−4Ωcm in the case of aluminium induced crystallization and to 3.4×10−4Ωcm for solid phase crystallization. The temperature-stable conductivity of ZnO:Al films coated with Si opens up appealing options for the production of polycrystalline silicon thin-film solar cells with transparent front contacts.
External electroluminescence measurements of InGaAs∕InAlAs avalanche photodiodes
Authors: Finkelstein Hod , Zlatanovic Sanja , Lo Yu-Hwa , Esener Sadik C. , Zhao Kai
Published: December 2007

The external efficiency of electroluminescence resulting from hot-carrier recombination has been studied in an InGaAs∕InAlAs avalanche photodiode. An analytical model that quantifies this emission is presented. Experimental data suggest that the emission originates from an intrinsic layer above the multiplication region. This electroluminescence mechanism offers a novel way for frequency upconversion, where the upconverted frequency can be controlled with proper choice of device layers. Lastly, we report for the first time the optical absorption properties of In0.52Al0.48As.
On incompressibility of a matrix in naturally occurring composites
Authors: Gorbatikh Larissa , Pingle Pawan
Published: December 2007

The work illustrates that a soft matrix, which has the Poisson ratio close to 0.5 and is reinforced with a rigid-line inclusion, possesses an interesting behavior at the inclusion/matrix interface. It experiences a hydrostatic stress state and behaves as an incompressible fluid under longitudinal and transverse loads. The stress singularities are eliminated ahead of the inclusion tips, and when interface defects are formed, their effect on the composite compliance is minimal. These observations have far reaching applications when one is interested in mechanisms of multifunctional property improvement of composites (such as toughness and stiffness) learned from naturally occurring composites.
Direct patterning of carbon nanotube network devices by selective vacuum filtration
Authors: Lim Chaehyun , Min Dong-Hun , Lee Seung-Beck
Published: December 2007

We report on a method which allows direct patterning of density controlled carbon nanotube network (NTN) devices during network formation. By lithographically patterning photoresist on the filter membrane, the nanotubes in suspension were guided to the exposed pattern areas of the filter surface during vacuum filtration allowing in situ device formation. The NTNs were transferred to an elastomer substrate by directly curing polydimethylsiloxane on its surface. We compared electrical characteristics of NTN patterns fabricated simultaneously using this method and found that the different NTNs with equal nanotube density showed reproducible characteristics.
Effect of optical lithography patterning on the crystalline structure of tunnel junctions
Authors: Mocuta C. , Barbier A. , Ramos A. V. , Guittet M.-J. , Moussy J.-B. , Stanescu S. , Mattana R. , Deranlot C. , Petroff F.
Published: December 2007

The crystalline structure of metal-oxide-based magnetic tunnel junctions patterned by optical lithography was resolved locally using a microfocused x-ray spot. We evidence several micron-sized lithography-induced distortion effects on the crystalline structure of the layers near the edges of the junction. The distortions translate into tilts (up to 1°) of the crystalline planes in the vicinity of the edges and propagate toward the center of the junction. They are attributed to the release of the elastic strain in the layers during the lithographical process. For the smallest junctions, size effects limiting the amplitude of the tilt are also evidenced.
Strain influence on valence-band ordering and excitons in ZnO: An ab initio study
Authors: Schleife A. , Rödl C. , Fuchs F. , Furthmüller J. , Bechstedt F.
Published: December 2007

Modern parameter-free methods to treat single- and two-particle electronic excitations are applied to compute the band structure and the lowest optical transitions of wurtzite ZnO under biaxial strain. The calculations are based on density functional theory with a spatially nonlocal exchange and correlation functional and include spin-orbit interaction. Quasiparticle shifts and excitonic effects are computed. In addition to the band parameters, also their dependence on biaxial strain and the ordering of the A, B, and C excitons are investigated. While the crystal-field splitting is very sensitive to strain, the spin-orbit splittings and the exciton binding energies remain unaffected.
Seasonal and diel comparisons of the diets of four dominant fish species within the main channel and flood-zone of a small intermittently open estuary in south-eastern Australia
Authors: Becker Alistair , Laurenson Laurie J. B.
Published: December 2007

The diets of four highly-abundant, dominant fish species within the Surrey River, a small intermittently open estuary in south-east Australia, were examined from specimens collected between July 2004 and June 2005. These four, similar-sized species (Atherinosoma microstoma, Galaxias maculatus, Philypnodon grandiceps and Pseudogobius olorum) have limited ability to spatially segregate along the length of the estuary owing to its small size relative to other estuarine habitats. All four species fed on a variety of prey items including crustaceans, insects and detritus. Despite this parity, the four species were demonstrated to occupy differing dietary niches that were concluded to be responsible for reducing interspecific feeding competition. Seasonal variations in the diets were observed for A. microstoma and Philypnodon grandiceps, with these species also exhibiting contrasting diel feeding behaviours. The closure of the estuary mouth led to the flooding of its margins, resulting in an increase in the size of the estuary and providing alternative food resources for the fish to exploit. It appears the inundation of the flood-zone facilitated further significant divergence in the diets of the fish and is likely to be of high ecological value to the estuary.