bluuebunny/crossref_metadata_2025 huggingface dataset:
De Novo Design of a Bolaamphiphilic Peptide with Only Natural Amino Acids
Authors: Qiu Feng , Chen Yongzhu , Tang Chengkang , Zhou Qinghan , Wang Chen , Shi Ying‐Kang , Zhao Xiaojun
Published: October 2008

A new self‐assembling bolaamphiphilic peptide has been designed and synthesized using only natural amino acids. This simple peptide is composed of two lysines connected by 4–8 alanines to maintain the characteristics of the traditional bolaamphiphiles. Based on an irregular secondary structure, it can self‐assemble into nanospheres, nanorods, or nanofibers with lengths up to micrometers. The long nanofibers can be broken into smaller fragments by sonication, however, they could reassemble into nanofibers after incubation. Furthermore, the nanostructures were shown to have considerable thermostability. This new bolaamphiphilic peptide differs from any other self‐assembling peptides or bolaamphiphiles, and possibly provides a new approach to fabricate nanomaterials.

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Effect of Ionic Species on the Structures and Properties of Salt‐Containing PEO/Montmorillonite Nanocomposites
Authors: Stefanescu Eduard A. , Stefanescu Cristina , Negulescu Ioan I. , Daly William H.
Published: October 2008

This contribution describes the preparation and characterization of PEO/montmorillonite nanocomposite gels and films containing various lithium and sodium salts. The objective is to understand how the size and diffusion abilities of different ionic species added to these systems alter the crystallinity of the polymer, and affect the mechanical properties and ionic conductivities of the solid nanocomposites. The network strength of the polymer/clay dispersions influences decisively the crystallinity of the PEO chains and the final layered texture of the solid films. The characteristics of films were investigated using a combination of techniques, such as DSC, DMA, DEA, SEM, SAXS and XRD.

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Spectral assignments and anisotropy data of cellulose Iα: 13C‐NMR chemical shift data of cellulose Iα determined by INADEQUATE and RAI techniques applied to uniformly 13C‐labeled bacterial celluloses of different Gluconacetobacter xylinus strains
Authors: Hesse‐Ertelt Stephanie , Witter Raiker , Ulrich Anne S. , Kondo Tetsuo , Heinze Thomas
Published: October 2008

Solid‐state 13C‐NMR spectroscopy was used to characterize native cellulose pellicles from two strains of Gluconacetobacter xylinus (ATCC 53582, ATCC 23769), which had been statically cultivated in Hestrin–Schramm (HS) medium containing fully 13C‐labeled β‐D‐glucose‐U‐13C6 as the sole source of carbon. For both samples, the 13C‐NMR chemical shifts were completely assigned for each 13C‐labeled site of cellulose Iα with the aid of 2D refocused INADEQUATE NMR. To determine the principal chemical shift tensor components, a pulse sequence based on the recoupling of anisotropy information (RAI) was applied at 10 kHz MAS. The detailed 13C tensors of cellulose Iα from different bacterial celluloses are thus available now for the first time, and these results have been compared with previously published data of nonenriched material and with theoretical predictions. Copyright © 2008 John Wiley & Sons, Ltd.
Distinctive clinicopathological associations of amplification of the cortactin gene at 11q13 in head and neck squamous cell carcinomas
Authors: Rodrigo JP , García‐Carracedo D , García LA , Menéndez ST , Allonca E , González MV , Fresno MF , Suárez C , García‐Pedrero JM
Published: October 2008

Amplification of the 11q13 region is a prevalent genetic alteration in head and neck squamous cell carcinoma (HNSCC). We investigated the clinical significance of cortactin (CTTN) and cyclin D1 (CCND1) amplification in both malignant transformation and tumour progression. CTTN and CCND1 amplification was analysed by differential and real‐time PCR in a prospective series of laryngeal/pharyngeal carcinomas and archival premalignant tissues. CTTN mRNA and protein expression were respectively determined by real‐time RT‐PCR and immunohistochemistry, and correlated with gene status. Molecular alterations were associated with clinicopathological parameters and disease outcome. CTTN and CCND1 amplifications were respectively found in 75 (37%) and 90 (45%) tumours. Both correlated with advanced disease; however, only CTTN amplification was associated with recurrence and reduced disease‐specific survival (p = 0.0022). Strikingly, CTTN amplification differentially influenced survival depending on tumour site (p = 0.0001 larynx versus p = 0.68 pharynx) and was an independent predictor of reduced survival in the larynx (p = 0.04). CCND1 amplification was detected in early tumourigenesis and increased with the severity of dysplasia. Importantly, CTTN amplification was only found in high‐grade dysplasias that progressed to invasive carcinoma. CTTN gene status strongly correlated with mRNA and protein expression. Furthermore, CTTN overexpression correlated significantly with reduced disease‐specific survival (p = 0.018). Taken together, these data indicate that CTTN may serve as a valuable biomarker to identify patients with laryngeal tumours at high risk of recurrence and poor outcome. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Expression patterns of microRNAs in the chorioamniotic membranes: a role for microRNAs in human pregnancy and parturition
Authors: Montenegro D , Romero R , Kim SS , Tarca AL , Draghici S , Kusanovic JP , Kim JS , Lee DC , Erez O , Gotsch F , Hassan SS , Kim CJ
Published: October 2008

MicroRNAs (miRNAs) are involved in the post‐transcriptional regulation of gene expression during development. This study was performed to determine gestational age‐dependent changes in miRNA expression in the chorioamniotic membranes and to assess the significance of miRNAs in human pregnancy and parturition. The expression profile of 455 miRNAs was compared between patients at term without labour (TNL: n = 10), in labour (TL: n = 10), and preterm labour (PTL: n = 10) using microarrays. A total of 39 miRNAs were differentially expressed between term and preterm cases, of which 31 (79.5%) were down‐regulated at term. Expression of ten miRNAs, including miR‐338, differentially expressed between PTL and TL groups was decreased at term. Computational analyses using miRBase Targets have identified PLA2G4B, a phospholipase implicated in parturition, as a putative target of miR‐338. Inhibition of endogenous miR‐338 with anti‐miR‐338 increased the mRNA and protein expression of PLA2G4B in decidual cells. Luciferase assay with reporter constructs confirmed that the suppression of PLA2G4B occurs through binding of miR‐338 to the 3′UTR of PLA2G4B. Interestingly, the expression of Dicer, a key miRNA‐processing enzyme, was markedly decreased at term, particularly with labour in the chorioamniotic membranes. Collectively, the novel findings reported herein strongly suggest that post‐transcriptional regulation of genes by miRNAs, coupled with the changes of miRNA processing machinery in the chorioamniotic membranes, plays a role in pregnancy and parturition. Furthermore, the expression level of Dicer in the chorioamniotic membranes dichotomizes pathological preterm labour and physiological spontaneous labour at term. Published in 2008 by John Wiley & Sons, Ltd.
Recurrent intrathecal methotrexate induced neurotoxicity in an adolescent with acute lymphoblastic leukemia: Serial clinical and radiologic findings
Authors: Brugnoletti Fulvia , Morris E. Brannon , Laningham Fred H. , Patay Zoltán , Pauley Jennifer L. , Pui Ching‐Hon , Jeha Sima , Inaba Hiroto
Published: October 2008

Systemic and intrathecal methotrexate (MTX) are integral components of acute lymphoblastic leukemia (ALL) therapy, but can be associated with neurotoxicity. We describe here the case of an adolescent male with T‐cell ALL who developed recurrent episodes of subacute neurotoxicity characterized by slurred speech, emotional lability, and hemiparesis after intrathecal MTX administration. Serial magnetic resonance imaging with diffusion‐weighted imaging showed recurrent areas of restricted diffusion within cerebral hemispheric white matter, which correlated chronologically with the administration of intrathecal therapy and severity of clinical symptoms. Resolution of diffusion abnormalities did not preclude further toxicity and a large lesion could cause persisting symptoms. Pediatr Blood Cancer 2009;52:293–295. © 2008 Wiley‐Liss, Inc.
Levetiracetam for seizures in children with brain tumors and other cancers
Authors: Partap Sonia , Fisher Paul Graham
Published: October 2008

Children with brain tumors and other cancers can suffer from seizures. Unfortunately, most antiepileptic therapies are metabolized by the hepatic cytochrome P450 (CYP) system. Levetiracetam, a newer anticonvulsant, does not undergo CYP metabolism and does not alter the pharmacokinetics of chemotherapy, antiemetics, and corticosteroids, which are metabolized by the liver. We studied 23 patients with cancer and seizures treated with levetiracetam. Over 95% of patients had fewer seizures, with 65.2% becoming seizure free; only one patient experienced an adverse reaction. Levetiracetam is effective and well tolerated in children with brain tumors and other cancers, who are often on multiple enzyme‐inducing drugs. Pediatr Blood Cancer 2009;52:288–289. © 2008 Wiley‐Liss, Inc.
Micro‐ and macrophase separation of thermosetting systems modified with epoxidized styrene‐block‐butadiene‐ block‐styrene linear triblock copolymers and their influence on final mechanical properties
Authors: Ocando Connie , Tercjak Agnieszka , Serrano Elena , Ramos José A , Corona‐Galván Sergio , Parellada M Dolores , Fernández‐Berridi M José , Mondragon Iñaki
Published: October 2008

BACKGROUND: The goal of this work was to establish the minimum degree of epoxidation needed to develop nanostructured epoxy systems by modification with poly(styrene‐block‐butadiene‐block‐styrene) (SBS) triblock copolymers epoxidized to several degrees, and also to investigate the effect of polystyrene (PS) content on the final morphologies. By using two SBS copolymers, the influence of the weight ratio of the two blocks on the generated morphologies and mechanical properties was also analysed.

RESULTS: Nanostructured thermosets were effectively obtained through reaction‐induced microphase separation of PS blocks from the matrix. A minimum of 27 mol% of epoxidation, which corresponds to 4.8 wt% of epoxidized polybutadiene (PB) units in the overall mixture, was needed to ensure nanostructuring of final mixtures and thus their transparency. Hexagonally ordered nanostructures were achieved for PS contents of around 16–20 wt%, which agrees with our previous results for mixtures with other SBS copolymers with different ratios between blocks. The fracture toughness of the epoxy matrix was improved or at least retained with mixing.

CONCLUSION: The degree of epoxidation of PB blocks needed to switch epoxy/SBS mixtures from a macrophase‐separated to a nanostructured state has been established. The generated morphologies in the epoxy systems are mainly dependent on the PS content in the mixture. Copyright © 2008 Society of Chemical Industry
Do built‐in fields improve solar cell performance?
Authors: Green Martin A.
Published: October 2008

Intrinsic fields can be built into solar cells by varying the doping level and/or the cell bandgap with potential benefits long recognised. A counteracting effect is that varying the doping or bandgap from the optimum for a particular material system will result in poorer material quality. New solutions are described to the standard semiconductor transport and recombination equations that allow such effects to be incorporated and the impact of these fields on device current and voltage to be assessed. Clear boundaries are found between when built‐in fields are beneficial or deleterious. For the case of doping gradients, built‐in fields decrease both cell current and voltage if carrier lifetime decrease more quickly than as the inverse square of doping; decrease current but can increase voltage if the inverse variation is between linear and square; can improve both if less than linear but only significantly if lifetime varies less than the inverse square root of doping. In the case of a graded bandgap, an optimal field exists as a trade‐off between decreased absorption and increased carrier collection. Copyright © 2008 John Wiley & Sons, Ltd.
Very high efficiency solar cell modules
Authors: Barnett Allen , Kirkpatrick Douglas , Honsberg Christiana , Moore Duncan , Wanlass Mark , Emery Keith , Schwartz Richard , Carlson Dave , Bowden Stuart , Aiken Dan , Gray Allen , Kurtz Sarah , Kazmerski Larry , Steiner Myles , Gray Jeffery , Davenport Tom , Buelow Roger , Takacs Laszlo , Shatz Narkis , Bortz John , Jani Omkar , Goossen Keith , Kiamilev Fouad , Doolittle Alan , Ferguson Ian , Unger Blair , Schmidt Greg , Christensen Eric , Salzman David
Published: October 2008

The Very High Efficiency Solar Cell (VHESC) program is developing integrated optical system–PV modules for portable applications that operate at greater than 50% efficiency. We are integrating the optical design with the solar cell design, and have entered previously unoccupied design space. Our approach is driven by proven quantitative models for the solar cell design, the optical design, and the integration of these designs. Optical systems efficiency with an optical efficiency of 93% and solar cell device results under ideal dichroic splitting optics summing to 42·7 ± 2·5% are described. Copyright © 2008 John Wiley & Sons, Ltd.
Compositional engineering of chemical bath deposited (Zn,Cd)S buffer layers for electrodeposited CuIn(S,Se)2 and coevaporated Cu(In,Ga)Se2 solar cells
Authors: Naghavi N. , Hubert C. , Etcheberry A. , Bermudez V. , Hariskos D. , Powalla M. , Lincot D.
Published: October 2008

A comparative study of chemical bath deposition (CBD) of ZnS, CdS, and a mixture of (Cd,Zn)S buffer layers has been carried out on electrodeposited CuIn(S,Se)2 (CISSe) and coevaporated Cu(In,Ga)Se2 (CIGS) absorbers. For an optimal bath composition with the ratio of [Zn]/[Cd] = 25, efficiencies higher than those obtained with CdS and ZnS recipes, both on co‐evaporated CIGS and electrodeposited CISSe, have been obtained independent of the absorber used. In order to better understand the (Cd,Zn)S system and its impact on the increased efficiency of cells, predictions from the solubility diagrams of CdS and ZnS in aqueous medium were made. This analysis was completed by in situ growth studies with varying bath composition by quartz crystal microbalance (QCM). The morphology and composition of the films were studied using scanning electron microscopy (SEM) and X‐ray photoelectron spectra (XPS) techniques. Preliminary XPS studies showed that films are composed of a mixture of CdS and Zn(O,OH) phases and not a pure ternary Cd1 − xZnxS compound. The effect of the [Zn]/[Cd] molar ratio on properties of the corresponding CISSe and CIGS solar cells was investigated by current voltage [J(V)] and capacitance voltage [C(V)] characterizations. The origin of optimal results is discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Comprehensive analysis of advanced solar cell contacts consisting of printed fine‐line seed layers thickened by silver plating
Authors: Pysch D. , Mette A. , Filipovic A. , Glunz S. W.
Published: October 2008

This work presents a detailed analysis of a new two‐layer process to contact industrial solar cells. However, most of the results seem to be transferable to standard screen print paste contacts. The seed layer was created by a pad or screen printer and thickened by light‐induced plating (LIP) of silver. These contact structures were investigated microscopically to gain a better understanding of the observed electrical parameters. A review of the present microscopic contact formation model for flat surfaces is presented. This model was extended and applied to surfaces textured with random pyramids. This analysis has revealed two new types of silver crystallites which can be described by a crystallographic model. The dependence of the silver crystallite density on the surface doping concentration was investigated. Next, the dependence of the contact resistance on the width of the seed layer was measured showing that the contact resistivity increases with a reduction of the seed layer width. These results have been further approved by an analysis of SEM images of wet‐chemically etched contacts examining the density of crystallites and the fraction of removed SiNx layer. Contact resistance RC measurements before and after LIP of silver showed surprisingly a positive influence of the plating process on RC. A detailed microscopical analysis revealed four new possible current flow paths due to the LIP of a conventional contact or a seed layer. The results led to an extension of the existing model for a screen‐printed contact. Copyright © 2008 John Wiley & Sons, Ltd.
Comparing Photovoltaic Capacity Value Metrics: A Case Study for the City of Toronto
Authors: Pelland Sophie , Abboud Ihab
Published: October 2008

Hourly electric power demand data in Toronto from 2000 to 2006 was analyzed along with coincident, simulated hourly photovoltaic (PV) power generation to quantify PV capacity value on a year‐round basis. Three different methods commonly employed by electric utilities were used to assess PV capacity value, and their results were compared. The first method is the Garver approximation to effective load carrying capability (ELCC), which served as a benchmark for capacity value. The other two methods equate PV capacity value with the capacity factor during “peak demand intervals”: for method 2 the interval includes all hours with loads within a given per cent deviation from the peak load; for method 3, a fixed “on‐peak” interval of 11–17 h in June–August is used. Methods 2 and 3 yielded PV capacity values of about 40%, in agreement with the results of the Garver approximation at low grid penetration. This is considerably higher than the yearly PV capacity factor of about 12%, and is in good agreement with previous studies. Capacity value varies significantly from year to year: for instance, values from method 1 at low grid penetration levels range from 30% (year 2000) to 44% (year 2006). Yearly variations in capacity value appear correlated with variations in the demand summer to winter peak ratio, reflecting the fact that PV capacity value is strongly linked to its capacity to reduce peak demand (“peak shaving”) during the summer. Copyright © 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
Analysis of the human immune response to vaccinia by use of a novel protein microarray suggests that antibodies recognize less than 10% of the total viral proteome
Authors: Schmid Kara , Keasey Sarah L. , Pittman Phillip , Emerson Ginny L. , Meegan James , Tikhonov Alexander P. , Chen Gengxin , Schweitzer Barry , Ulrich Robert G.
Published: October 2008

Control of smallpox by mass vaccination was one of the most effective public health measures ever employed for eradicating a devastating infectious disease. However, new methods are needed for monitoring smallpox immunity within current vulnerable populations, and for the development of replacement vaccines for use by immunocompromized or low‐responding individuals. As a measure for achieving this goal, we developed a protein microarray of the vaccinia virus proteome by using high‐throughput baculovirus expression and purification of individual elements. The array was validated with therapeutic‐grade, human hyperimmune sera, and these data were compared to results obtained from individuals vaccinated against smallpox using Dryvax. A high level of reproducibility with a very low background were apparent in repetitive assays that confirmed previously reported antigens and identified new proteins that may be important for neutralizing viral infection. Our results suggest that proteins recognized by antibodies from all vaccinees constituted <10% of the total vaccinia proteome.
Preface: phys. stat. sol. (c) 5/11
Authors: Lincot Daniel , Hodes Gary , Schmuki Patrik , Symposium Organizers
Published: October 2008

The formation of thin films and nanostructures with unique properties on solid surfaces can be achieved from solutions by chemical or electrochemical routes. These processes named chemical bath deposition, chemical solution deposition, liquid phase impregnation, hydrothermal growth, electrodeposition, and anodic oxidation are based on a common conceptual ground of interfacial reactions at the solid–solution interface. The materials can be semiconductors, oxides, metals, hybrids or nanocomposites in the form of thin films, porous networks, nanorods or nanotubes arrays, grown directly by self‐organization mechanisms or inside templates like porous membranes. In recent years we have followed a remarkable development of these synthesis approaches seeking for advanced applications in electronics, photovoltaics, lasing, sensors, photocatalysis, magnetism, batteries etc.

The general objective of the symposium was “Chemical and Electrochemical Synthesis of Advanced Materials and Nanostructures on Solid Surfaces: Growth Mechanisms, Characterizations and Applications”. It was held at the E‐MRS Fall Meeting in Warsaw from 17 to 21 September 2007. The aim of the symposium was to promote exchange between researchers in this field for:

(i) improving a common understanding of the growth mechanisms involved in the formation pro‐ cesses, from the molecular to the final structure level, involving interfacial chemical or electrochemical reactions, the influence of solution composition including additives, and the effect of external parameters like illumination,

(ii) the advanced characterization and optimization of the properties of the films or nanostructures in relation to the formation conditions,

(iii) advanced applications in forefront technologies,

(iv) theory and modelling.

The present issue assembles papers which were presented during the symposium reflecting such developments, in particular in the field of chalcogenide materials, oxide nanostructures based on electrodeposited ZnO, porous semiconductors prepared by anodic oxidation, metal electrodeposition, and hybrid organic–inorganic materials. They give a general view of some of these recent advances and we hope that they will benefit the readers interested to enter this domain of increasing importance. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Antiobesity effects of wild ginseng (Panax ginseng C.A. Meyer) mediated by PPAR‐γ, GLUT4 and LPL in ob/ob mice
Authors: Mollah Mohammad Lalmoddin , Kim Gi‐Sang , Moon Hye‐Kyung , Chung Shin‐Kyo , Cheon Yong‐Pil , Kim Jong‐Kuk , Kim Kil‐Soo
Published: October 2008

The antiobesity effect of wild ginseng (WG; Panax ginseng C.A. Meyer) in male obese leptin‐deficient (B6.V‐Lepob, ‘ob/ob’) mice was evaluated. WG was administered orally to mice at doses of 100 mg/kg and 200 mg/kg daily for 4 weeks. The WG‐treated ob/ob mice showed a loss of body weight and a decrease in blood glucose levels compared with control mice. WG regulated the mRNA expression level especially, it increased peroxisome proliferators‐activated receptors‐γ (PPAR‐γ) and lipoprotein lipase (LPL) in adipose tissue, as well as glucose transporter 4 (GLUT4) and insulin receptor (IR) in the skeletal muscle and liver. Taken together, these results suggest that WG may play a vital role in the antiobesity effect in ob/ob mice; this has importance in insulin sensitivity. This may prove to be of clinical importance in improving the management of obesity and related metabolic syndromes. Copyright © 2008 John Wiley & Sons, Ltd.
New method for aroma barrier testing
Authors: Vähä‐Nissi M. , Hjelt T. , Jokio M. , Kokkonen R. , Kukkonen J. , Mikkelson A.
Published: October 2008

In the above article (DOI: 10.1002/pts.791), reference to work published by Drs. Lindner‐Steinert, Piringer and Franz1–3 in which they had developed the method using polyethylene glycol (PEG 400) as a diluting agent in the source cell both for the single aromas and an aroma blend with seven compounds, and where the receiving cell is continuously flushed with nitrogen to transport the permeated aroma compounds to an adsorption trap was accidentally omitted.
Towards norms for accreditation of biobanks for human health and medical research: compilation of existing guidelines into an ISO certification/accreditation norm‐compatible format
Authors: Betsou F. , Luzergues A. , Carter A. , Geary P. , Riegman P. , Clark B. , Morente M. , Vaught J. , Dhirr R. , Druez‐Vérité C.
Published: October 2008

In recent years, biobanks have evolved into professional infrastructures that acquire, validate, process, store, manage and distribute biological material of human origin to public or private end‐users/researchers. This article (a) highlights the importance of quality assurance for both the biobank basic processes and sample annotation in order to ensure reliable results of research based on these samples, (b) suggests that certification according to international standards can contribute to the organization of the biobanking processes while accreditation can contribute to the organization of sample characterization/validation, and (c) provides a compilation of all existing guidelines against an International Organization for Standardization (ISO) format. Copyright © 2008 John Wiley & Sons, Ltd.
GLP SOPs for equipment calibration and maintenance. Part 6: implementation of SOPs
Authors: Colligon Irina , Rosa Michelle
Published: October 2008

No one will argue that writing good Standard Operating Procedures (SOPs) is a major undertaking, but success at this task does not guarantee their use and compliance with what they say. In this installment we will look at the critical next step in the life of an SOP: its implementation. Copyright © 2008 John Wiley & Sons, Ltd.
What's New?
Authors: Bens Catherine M. , Clemons Stephanie K. , Bosau Anita , Schroeder Robert
Published: October 2008

The What's New? section in the Quality Assurance Journal aims to draw attention to items of importance to QA professionals. There is usually a three‐month interval between final submission of manuscripts and distribution of the journal. For this issue, the entries in the What's New? section arise from the period of 1 March 2007 to 31 August 2007. If you feel that there is any other new information that should be brought to the attention of readers, please let us know by e‐mailing rha@verdandi.ch. Copyright © 2008 John Wiley & Sons, Ltd.
Study of Foaming Properties and Effect of the Isomeric Distribution of Some Anionic Surfactants
Authors: Azira Hakima , Tazerouti Amel , Canselier Jean Paul
Published: October 2008

Using different reaction conditions of photosulfochlorination of n‐dodecane, two samples of anionic surfactants of sulfonate type are obtained. Their micellar behavior has been already reported and the relationship between their isomeric distribution and their chemical structures and micellar behaviors have been more thoroughly explored. In this investigation, we screened the foaming properties (foaming power and foam stability) by a standardized method very similar to the Ross–Miles foaming tests to identify which surfactants are suitable for applications requiring high foaming, or, alternatively, low foaming. The results obtained for the synthesized surfactants are compared to those obtained for an industrial sample of secondary alkanesulfonate (Hostapur 60) and to those of a commercial sample of sodium dodecylsulfate used as reference for anionic surfactants. The foam formation and foam stability of aqueous solutions of the two samples of dodecanesulfonate are compared as a function of their isomeric distribution. These compounds show good foaming power characterized in most cases by metastable or dry foams. The highest foaming power is obtained for the sample rich in primary isomers which also produces foam with a relatively high stability. For the sample rich in secondary isomers we observe under fixed conditions a comparable initial foam height but the foam stability turns out to be low. This property is interesting for applications requiring low foaming properties such as dishwashing liquid for machines. The best results are observed near and above the critical micellar concentrations and at 25 °C for both the samples.
LysoPtdOH Enhances CXCL16 Production Stimulated by LPS from Macrophages and Regulates T cell Migration
Authors: Kang Shijun , Yang Chunlan , Luo Rongcheng
Published: October 2008

As a transmembrane chemokine, CXCL16 has been detected in various tissues and organs under normal and pathological conditions, it also plays an important role in macrophages/dendritic cells (DC) and T cell interactions and trafficking during inflammation and immune responses. LysoPtdOH, a bioactive lipid mediator has been indicated to regulate DC and epithelial functions during wound healing and inflammation responses. However, the direct link of CXCL16 expression with lysoPtdOH has not been established. Using monocyte‐derived macrophages/DC (MoDC), we investigated the roles of lysoPtdOH in CXCL16 production and cell surface presentation. We found that macrophages/MoDC constitutively express and secrete CXCL16, lysoPtdOH significantly enhanced CXCL16 protein production stimulated with lipopolysaccharide (LPS) by more than twofold, which was reflected by increased mRNA transcription by 64‐fold. Production of CXCL16 increased by lysoPtdOH and LPS from macrophages was inhibited around 70% by Pertussis toxin (Gi/o specific inhibitor), exoC3 (Rho specific inhibitor), and pyrrolidine dithiocarbamate (the NF‐κB‐dependent pathway inhibitor) separately. LysoPtdOH treatment increased macrophages’ chemotactic activity to activated T cells. The soluble form of CXCL16 produced by macrophages/MoDC was functionally chemoattractive to T cells.
Liquid interfaces in viscous straining flows: numerical studies of the selective withdrawal transition
Authors: BERKENBUSCH MARKO KLEINE , COHEN ITAI , ZHANG WENDY W.
Published: October 2008

This paper presents a numerical analysis of the transition from selective withdrawal to viscous entrainment. In our model problem, an interface between two immiscible layers of equal viscosity is deformed by an axisymmetric withdrawal flow, which is driven by a point sink located some distance above the interface in the upper layer. We find that steady-state hump solutions, corresponding to selective withdrawal of liquid from the upper layer, cease to exist above a threshold withdrawal flux, and that this transition corresponds to a saddle-node bifurcation for the hump solutions. Numerical results on the shape evolution of the steady-state interface are compared against previous experimental measurements. We find good agreement where the data overlap. However, the larger dynamic range of the numerical results allows us to show that the large increase in the curvature of the hump tip near transition is not consistent with an approach towards a power-law cusp shape, an interpretation previously suggested from inspection of the experimental measurements alone. Instead, the large increase in the curvature at the hump tip reflects a robust trend in the steady-state interface evolution. For large deflections, the hump height is proportional to the logarithm of the curvature at the hump tip; thus small changes in hump height correspond to large changes in the value of the hump curvature.
Characterization of coherent vortical structures in a supersonic turbulent boundary layer
Authors: PIROZZOLI SERGIO , BERNARDINI MATTEO , GRASSO FRANCESCO
Published: October 2008

A spatially developing supersonic boundary layer at Mach 2 is analysed by means of direct numerical simulation of the compressible Navier--Stokes equations, with the objective of quantitatively characterizing the coherent vortical structures. The study shows structural similarities with the incompressible case. In particular, the inner layer is mainly populated by quasi-streamwise vortices, while in the outer layer we observe a large variety of structures, including hairpin vortices and hairpin packets. The characteristic properties of the educed structures are found to be nearly uniform throughout the outer layer, and to be weakly affected by the local vortex orientation. In the outer layer, typical core radii vary in the range of 5–6 dissipative length scales, and the associated circulation is approximately constant, and of the order of 180 wall units. The statistical properties of the vortical structures in the outer layer are similar to those of an ensemble of non-interacting closed-loop vortices with a nearly planar head inclined at an angle of approximately 20° with respect to the wall, and with an overall size of approximately 30 dissipative length scales.
Numerical simulations of boundary-layer bypass transition due to high-amplitude free-stream turbulence
Authors: OVCHINNIKOV VICTOR , CHOUDHARI MEELAN M. , PIOMELLI UGO
Published: October 2008

Direct numerical simulations (DNS) of bypass transition due to high-amplitude free-stream turbulence (FST) are carried out for a flat-plate boundary layer. The computational domain begins upstream of the plate leading edge and extends into the fully turbulent region. Thus, there is noad hoctreatment to account for the initial ingestion of FST into the laminar boundary layer. We study the effects of both the FST length scale and the disturbance behaviour near the plate leading edge on the details of bypass transition farther downstream. In one set of simulations, the FST parameters are chosen to match the ERCOFTAC benchmark case T3B. The inferred FST integral length scaleL11is significantly larger (RL=UL11/ν = 6580) than that employed in previous simulations of bypass transition (RL≃ 1000). An additional set of simulations was performed atRL= 1081 to compare the transition behaviour in the T3B case with that of a smaller value of FST length scale. The FST length scale is found to have a profound impact on the mechanism of transition. While streamwise streaks (Klebanoff modes) are observed at both values of the FST length scale, they appear to have clear dynamical significance only at the smaller value ofRL, where transition is concomitant with streak breakdown. For the T3B case, turbulent spots form upstream of the region where streaks could be detected. Spot precursors are traced to quasi-periodic spanwise structures, first observed as short wavepackets in the wall-normal velocity component inside the boundary layer. These structures are reoriented to become horseshoe vortices, which break down into young turbulent spots. Two of the four spots examined for this case had a downstream-pointing shape, similar to those found in experimental studies of transitional boundary layers. Additionally, our simulations indicate the importance of leading-edge receptivity for the onset of transition. Specifically, higher fluctuations of the vertical velocity at the leading edge of the plate result in higher levels of streamwise Reynolds stress inside the developing boundary layer, facilitating breakdown to turbulence.
Boundary-layer transition at high free-stream disturbance levels – beyond Klebanoff modes
Authors: GOLDSTEIN M. E. , SESCU ADRIAN
Published: October 2008

We consider a nominally uniform flow over a semi-infinite flat plate and show how a small slowly modulated (predominantly streamwise) disturbance of the upstream flow is amplified by leading-edge bluntness effects and eventually develops into a small-amplitude but nonlinear spanwise motion far downstream from the edge. This motion is then imposed on the viscous boundary layer at the surface of the plate – causing an order-one change in its profile shape, which can reduce the wall shear to zero and thereby causes the boundary layer to separate. The present study is similar to an earlier steady flow analysis, but the unsteady effects now cause the upstream boundary layer to develop inflectional profiles which can support rapidly growing inviscid instabilities that give rise to transition before the separation can occur.
Experimental study of physical mechanisms in the control of supersonic impinging jets using microjets
Authors: ALVI FARRUKH S. , LOU HUADONG , SHIH CHIANG , KUMAR RAJAN
Published: October 2008

Supersonic impinging jet(s) inherently produce a highly unsteady flow field. The occurrence of such flows leads to many adverse effects for short take-off and vertical landing (STOVL) aircraft such as: a significant increase in the noise level, very high unsteady loads on nearby structures and an appreciable loss in lift during hover. In prior studies, we have demonstrated that arrays of microjets, appropriately placed near the nozzle exit, effectively disrupt the feedback loop inherent in impinging jet flows. In these studies, the effectiveness of the control was found to be strongly dependent on a number of geometric and flow parameters, such as the impingement plane distance, microjet orientation and jet operating conditions. In this paper, the effects of some of these parameters that appear to determine control efficiency are examined and some of the fundamental mechanisms behind this control approach are explored. Through comprehensive two- and three-component velocity (and vorticity) field measurements it has been clearly demonstrated that the activation of microjets leads to a local thickening of the jet shear layer, near the nozzle exit, making it more stable and less receptive to disturbances. Furthermore, microjets generate strong streamwise vorticity in the form of well-organized, counter-rotating vortex pairs. This increase in streamwise vorticity is concomitant with a reduction in the azimuthal vorticity of the primary jet. Based on these results and a simplified analysis of vorticity transport, it is suggested that the generation of these streamwise vortices is mainly a result of the redirection of the azimuthal vorticity by vorticity tilting and stretching mechanisms. The emergence of these longitudinal structures weakens the large-scale axisymmetric structures in the jet shear layer while introducing substantial three-dimensionality into the flow. Together, these factors lead to the attenuation of the feedback loop and a significant reduction of flow unsteadiness.
Instability of coupled geostrophic density fronts and its nonlinear evolution
Authors: SCHERER EMILIE , ZEITLIN VLADIMIR
Published: October 2008

Instability of coupled density fronts, and its fully nonlinear evolution are studied within the idealized reduced-gravity rotating shallow-water model. By using the collocation method, we benchmark the classical stability results on zero potential vorticity (PV) fronts and generalize them to non-zero PV fronts. In both cases, we find a series of instability zones intertwined with the stability regions along the along-front wavenumber axis, the most unstable modes being long wave. We then study the nonlinear evolution of the unstable modes with the help of a high-resolution well-balanced finite-volume numerical scheme by initializing it with the unstable modes found from the linear stability analysis. The most unstable long-wave mode evolves as follows: after a couple of inertial periods, the coupled fronts are pinched at some location and a series of weakly connected co-rotating elliptic anticyclonic vortices is formed, thus totally changing the character of the flow. The characteristics of these vortices are close to known rodon lens solutions. The shorter-wave unstable modes from the next instability zones are strongly concentrated in the frontal regions, have sharp gradients, and are saturated owing to dissipation without qualitatively changing the flow pattern.
Acoustic propagation and scattering in the exhaust flow from coaxial cylinders
Authors: VEITCH B. , PEAKE N.
Published: October 2008

In this paper we present an analytical solution to the problem of sound radiation from semi-infinite coaxial cylinders, as a model for rearward noise emission by aeroengines. The cylinders carry uniform subsonic flows, whose Mach numbers may differ from each other and from that of the external flow. The incident field takes the form of a downstream-going acoustic mode in either the outer cylinder (the bypass flow) or the inner cylinder (the jet). The key geometrical ingredient of our problem is that the two open ends are staggered by a finite axial distance, so that the inner cylinder can be either buried upstream inside the outer cylinder, or can protrude downstream beyond the end of the outer cylinder (sometimes called the ‘half-cowl’ configuration). The solution is found by solving a matrix Wiener–Hopf equation, which involves the factorization of a certain matrix in the form − = +, with ± analytic, invertible and with algebraic behaviour at infinity in the upper and lower halves of the complex Fourier plane respectively. It turns out that the method of solution is different for the buried and protruding cases. In the buried case the well-known pole removal technique can be applied to a certain meromorphic function (denoted k11), but in the protruding case the corresponding function k22 is no longer meromorphic. Progress is made, however, by using a Padé representation of k22 to yield a meromorphic problem which can then be solved using the pole removal technique as before. A range of results is presented, for both buried and protruding systems and with and without mean flow, and it becomes clear that the stagger of the two open ends can have a very significant effect on the far-field noise. We also obtain reasonable agreement between our predictions and some experimental results. One particular noise mechanism we identify in the presence of mean shear is the way in which a Kelvin–Helmholtz instability mode launched from the upstream trailing edge can be scattered into sound by its interaction with the downstream edge, provided that the separation between the edges is sufficiently large in a way which we identify.
Transition in pipe flow: the saddle structure on the boundary of turbulence
Authors: DUGUET Y. , WILLIS A. P. , KERSWELL R. R.
Published: October 2008

The laminar–turbulent boundary Σ is the set separating initial conditions which relaminarize uneventfully from those which become turbulent. Phase space trajectories on this hypersurface in cylindrical pipe flow appear to be chaotic and show recurring evidence of coherent structures. A general numerical technique is developed for recognizing approaches to these structures and then for identifying the exact coherent solutions themselves. Numerical evidence is presented which suggests that trajectories on Σ are organized around only a few travelling waves and their heteroclinic connections. If the flow is suitably constrained to a subspace with a discrete rotational symmetry, it is possible to find locally attracting travelling waves embedded within Σ. Four new types of travelling waves were found using this approach.
Slender-body approximations for electro-phoresis and electro-rotation of polarizable particles
Authors: YARIV EHUD
Published: October 2008

Slender-body asymptotic theory is used to evaluate the translational and rotational electrophoretic velocities of initially uncharged polarizable bodies of revolution. These velocities are obtained as asymptotic expansions in the small particle slenderness. Conducting particles which lack fore–aft symmetry translate parallel to the applied field direction, regardless of their orientation relative to it. Both conducting and dielectric particles tend to align with the field. The translational and rotational velocities of dielectric particles are asymptotically smaller than those of comparable conducting particles.
Bursting dynamics due to a homoclinic cascade in Taylor–Couette flow
Authors: ABSHAGEN J. , LOPEZ J. M. , MARQUES F. , PFISTER G.
Published: October 2008

Transitions between regular oscillations and bursting oscillations that involve a bifurcational process which culminates in the creation of a relative periodic orbit of infinite period and infinite length are investigated both experimentally and numerically in a short-aspect-ratio Taylor–Couette flow. This bifurcational process is novel in that it is the accumulation point of a period-adding cascade at which the mid-height reflection symmetry is broken. It is very rich and complex, involving very-low-frequency states arising via homoclinic and heteroclinic dynamics, providing the required patching between states with very different dynamics in neighbouring regions of parameter space. The use of nonlinear dynamical systems theory together with symmetry considerations has been crucial in interpreting the laboratory experimental data as well as the results from the direct numerical simulations. The phenomenon corresponds to dynamics well beyond the first few bifurcations from the basic state and so is beyond the reach of traditional hydrodynamic stability analysis, but it is not fully developed turbulence where a statistical or asymptotic approach could be employed. It is a transitional phenomenon, where the phase dynamics of the large-scale structures (jets of angular momentum emanating from the boundary layer on the rotating inner cylinder) becomes complicated. Yet the complicated phase dynamics remains accessible to an analysis of its space–time characteristics and a comprehensive mechanical characterization emerges. The excellent agreement between the experiments and the numerical simulations demonstrates the robustness of this complex bifurcation phenomenon in a physically realized system with its inherent imperfections and noise. Movies are available with the online version of the paper.
Spread of a non-Newtonian liquid jet over a horizontal plate
Authors: ZHAO JIANGANG , KHAYAT ROGER E.
Published: October 2008

The flow of an impinging non-Newtonian jet onto a solid flat plate is examined theoretically in this study. Similarity solutions are sought for both shear-thinning and shear-thickening fluids of the power-law type. The jet is assumed to spread out in a thin layer bounded by a hydraulic jump. In addition to the stagnation-flow region, the flow domain is divided into three main regions: a developing boundary layer, fully viscous boundary layer and hydraulic jump. The anomalous behaviour of power-law fluids at small shear rate is remedied by seeking a two-layer solution in each domain. Such anomalies include the singularity of viscosity for shear-thinning fluids, and the vanishing of viscosity as well the overshoot in velocity for shear-thickening fluids. Although the rate of shear-thinning appears to affect significantly the film profile and velocity, only the overall viscosity influences the position of the hydraulic jump.
A new approach to understanding and modelling the influence of wall roughness on friction factors for pipe and channel flows
Authors: HERWIG H. , GLOSS D. , WENTERODT T.
Published: October 2008

In this study, it is shown how the equivalent sand roughness required in the Moody chart can be calculated for arbitrarily shaped wall roughnesses. After a discussion of how to define the wall location and roughness height in the most reasonable way, a numerical approach based on the determination of entropy production in rough pipes and channels is presented. As test cases, three different two-dimensional roughness types have been chosen which are representative of regular roughnesses on machined surfaces. In the turbulent range, skin friction results with these test roughnesses can be linked to Nikuradse's sand roughness results by a constant factor. For laminar flows, a significant effect of wall roughness is identified which in most other studies is neglected completely. The dissipation model of this study is validated with experimental data for laminar and turbulent flows.