bluuebunny/crossref_metadata_2025 huggingface dataset:
An Entry to Novel Platinum Complexes: Carboxylation of Dihydroxoplatinum(IV) Complexes with Succinic Anhydride and Subsequent Derivatization
Authors: Reithofer Michael , Galanski Mathea Sophia , Roller Alexander , Keppler Bernhard K.
Published: April 2006

An improved carboxylation method of (OC‐6‐33)‐dichloro(ethane‐1,2‐diamine)dihydroxyplatinum(IV) based on succinic anhydride is reported. Reaction of the uncoordinated carboxylic acid with simple amines and alcohols leads to the corresponding amides and esters in the presence of 1,1′‐carbonyldiimidazole. The resulting new complexes are characterized by IR, 1H, 13C, 15N, and 195Pt NMR spectroscopy, mass spectrometry, and elemental analysis. This reaction provides an entry to a new class of kinetically inert platinum(IV) complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Monomeric and Polymeric Amines as Dual Reductants/Stabilisers for the Synthesis of Gold Nanocrystals: A Mechanistic Study
Authors: Richardson Michael J. , Johnston James H. , Borrmann Thomas
Published: April 2006

Uniform, monodisperse gold nanocrystals have been prepared in a single‐step synthesis by the addition of secondary and tertiary alkylamines, or a cationic polymer containing these moieties, to dilute solutions of gold tetrachloraurate. The acidic pH resulted in the formation of quaternary ammonium sites, scavenging loosely bound chloride ions from the tetrachloraurate species, lowering the overall potential and reducing AuIII to nanocrystalline Au0. The secondary amino groups then served to stabilise the particles, preventing aggregation and collapse of the colloidal system. Addition of further capping groups was thus not required. The particles were characterised by UV/Visible spectroscopy, HR‐TEM, X‐ray diffraction, electrochemical potential and pH measurements (Eh‐pH) and FTIR. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Outgrowth of human liver metastases after resection of the primary colorectal tumor: A shift in the balance between apoptosis and proliferation
Authors: Peeters Charlotte F.J.M. , de Waal Robert M.W. , Wobbes Theo , Westphal Johan R. , Ruers Theo J.M.
Published: April 2006

Rapid outgrowth of metastases after removal of the primary tumor has been described in several mouse models. Loss of primary tumor‐induced inhibition of angiogenesis in the metastases has been suggested as the underlying cause. Accordingly, we recently demonstrated that vascular density in human colorectal liver metastases increases after primary tumor resection. Here, we investigate whether this increase in vascular density has, in its turn, effects on the tumor growth of the liver metastases. We analyzed tumor growth in synchronous liver metastases from patients with the primary tumor in place, in synchronous metastases from patients with the primary tumor resected and in metachronous metastases. Tumor growth was studied by assessing the percentage of cells undergoing apoptosis by activated caspase‐3 staining, and the percentage of proliferating cells by Ki‐67 staining. While the percentage of proliferating cells within the metastases showed a modest increase after primary tumor resection, a significant decrease in the percentage of apoptotic cells was observed. Taken together, an increased net tumor growth of the metastases occurred after primary tumor resection. This acceleration of tumor growth could be confirmed by studying biopsies taken from the same patient before and after tumor resection. Our data show that in human cancer patients, a primary tumor may inhibit the growth of its liver metastases. © 2006 Wiley‐Liss, Inc.
Frequent EGFR mutations in brain metastases of lung adenocarcinoma
Authors: Matsumoto Shingo , Takahashi Kenji , Iwakawa Reika , Matsuno Yoshihiro , Nakanishi Yukihiro , Kohno Takashi , Shimizu Eiji , Yokota Jun
Published: April 2006

Lung adenocarcinomas often metastasize to the brain, and the prognosis of patients with brain metastases is still very poor. The epidermal growth factor receptor (EGFR) gene is mutated in a considerable fraction of primary lung adenocarcinomas, in particular those with drastic response to EGFR tyrosine kinase inhibitors. The present study was designed to elucidate the prevalence of EGFR mutations in brain metastases and the timing of their occurrence during cancer progression. EGFR mutations were detected in 12 of 19 metastatic lung adenocarcinomas to the brain (63%). This frequency was higher than those in previous studies for EGFR mutations at various stages of lung adenocarcinoma in East Asia, including Japan (i.e., 20–55%). In 6 cases with EGFR mutations, the corresponding primary lung tumors were also examined for the mutations, and in all of them, the same types of EGFR mutations were detected also in the primary tumors. In 2 of them, second metastatic brain tumors in addition to the first ones were also available for analysis, and the same types of EGFR mutations were detected in both the first and second ones in both cases. These results indicate that EGFR mutations are present frequently in brain metastases and occur preceding brain metastasis. These findings will be highly informative for treatment of metastatic lung adenocarcinoma to the brain. © 2006 Wiley‐Liss, Inc.
Family history of breast cancer and short‐term effects of childbirths on breast cancer risk
Authors: Albrektsen Grethe , Heuch Ivar , Thoresen Steinar , Kvåle Gunnar
Published: April 2006

The long‐term protective effect of a pregnancy on breast cancer risk is preceded by a short‐term adverse effect, possibly reflecting a promoting effect of pregnancy hormones. In the present study, we explore whether a family history of breast cancer modifies time‐related effects of pregnancies, with special emphasis on the transient increase in risk of breast cancer shortly after birth. Our study cohort comprises 1,067,289 Norwegian women aged 20–74 years. The mean follow‐up time was 18 years. Incidence rate ratios were estimated by Poisson regression analyses of person‐years at risk. Of the 7,377 women diagnosed with breast cancer during follow‐up, a total of 828 (11%) had a mother or a sister with breast cancer diagnosis. Women with a family history of breast cancer had a 2–3‐fold higher risk of breast cancer than did women without any affected family member, highest for those with a relative diagnosed before they were 50 years. Similar to women without a familial excess risk, increasing parity was associated with an overall protective effect among women with a familial predisposition, regardless of age at diagnosis of the relative. Whereas women with no familial excess risk experienced a transient increase in risk mainly after late age births, women with a family history of breast cancer experienced an adverse effect of pregnancies also at younger ages. The present results give further support to the hypothesis that the adverse effect of a term birth can be explained by a promoting effect of pregnancy hormones. © 2006 Wiley‐Liss, Inc.
Dietary fiber intake and subsequent risk of colorectal cancer: The Japan Public Health Center‐Based Prospective Study
Authors: Otani Tetsuya , Iwasaki Motoki , Ishihara Junko , Sasazuki Shizuka , Inoue Manami , Tsugane Shoichiro
Published: April 2006

Results on the association of dietary fiber intake with colorectal cancer risk were inconsistent among previous large prospective studies, but studies in non‐Western populations are lacking. Consequently, the authors investigated the association between dietary fiber intake and the subsequent risk of colorectal cancer in a prospective cohort study of a Japanese population. Dietary fiber intake was estimated from food‐frequency questionnaires comprising 44 or 52 items at the baseline survey and 138 food items at a 5‐year follow‐up survey. The authors identified 907 cases of colorectal adenocarcinoma diagnosed pathologically in 86,412 subjects during a 10‐year follow‐up from the baseline survey. After the 5‐year follow‐up survey, 522 cases were identified in 78,326 subjects during a 5.8‐year follow‐up. The authors estimated the multivariate‐adjusted hazard ratios of colorectal cancer for dietary fiber intake using Cox's proportional hazards model. The authors found no statistically significant association between dietary fiber intake and colorectal cancer in analyses using data either from the baseline survey or from the 5‐year follow‐up survey. However, the risk of only the lowest quintile was high, compared with the second to the fifth quintiles. Furthermore, the lowest subtertile in the lowest quintile was associated with an increased risk in women (hazard ratioSub1 vs. Q5, 2.3; 95% confidence interval, 1.0–5.2). In conclusion, although a minor effect cannot be ruled out, the results did not support a hypothesis of a dose‐dependent protective effect of dietary fiber intake against colorectal cancer. © 2006 Wiley‐Liss, Inc.
An analysis of the distribution of extremes in indices of share returns in the US, UK and Japan from 1963 to 2000
Authors: Gettinby G. D. , Sinclair C. D. , Power D. M. , Brown R. A.
Published: April 2006

This paper seeks to characterize the distribution of extreme returns for US, UK and Japanese equity indices over the years 1963–2000. In particular, the suitability of the following distributions is investigated: Normal, Frechet, Gumbel, Weibull, Generalized Extreme Value (GEV), Generalized Pareto and Generalized Logistic (GL). Daily returns were obtained for each of the countries, and the minima over a variety of selection intervals were calculated. Plots of higher moment statistics for the minima on statistical distribution maps suggested that the best fitting distribution would be either the GEV or the GL. The results from fitting each of these distributions to extremes of a series of US, UK and Japanese share returns supported the preliminary evidence that the GL distribution best fitted the data in all three countries over the period of study. The GL distribution has fatter tails than the GEV distribution; hence this finding is of importance to investors who are concerned with assessing the risk of a portfolio. The paper highlights the important finance implications and in particular the potential for underestimation of risk if distributions without fat enough tails are employed. Copyright © 2006 John Wiley & Sons, Ltd.
Nitric oxide contributes to the development of a post‐injury Th2 T‐cell phenotype and immune dysfunction
Authors: Daniel TanJanika , Alexander Michelle , Hubbard William J. , Chaudry Irshad H. , Choudhry Mashkoor A. , Schwacha Martin G.
Published: April 2006

Severe injury induces immune dysfunction resulting in increased susceptibility to opportunistic infections. Previous studies from our laboratory have demonstrated that post‐burn immunosuppression is mediated by nitric oxide (NO) due to the increased expression of macrophage inducible nitric oxide synthase (iNOS). In contrast, others suggest that injury causes a phenotypic imbalance in the regulation of Th1‐ and Th2 immune responses. It is unclear whether or not these apparently divergent mediators of immunosuppression are interrelated. To study this, C57BL/6 mice were subjected to major burn injury and splenocytes were isolated 7 days later and stimulated with antiCD3. Burn injury induced NO‐mediated suppression of proliferative responses that was reversed in the presence of the NOS inhibitor L‐monomethyl‐L‐arginine and subsequently mimicked by the addition of the NO donor, S‐nitroso‐N‐acetyl‐penicillamine (SNAP). SNAP also dose‐dependently suppressed IFN‐γ and IL‐2 (Th1), but not IL‐4 and IL‐10 (Th2) production. Delaying the addition of SNAP to the cultures by 24 h prevented the suppression of IFN‐γ production. The Th2 shift in immune phenotype was independent of cGMP and apoptosis. The addition of SNAP to cell cultures also induced apoptosis, attenuated mitochondrial oxidative metabolism and induced mitochondrial membrane depolarization. However, these detrimental cellular effects of NO were observed only at supra‐physiologic concentrations (>250 µM). In conclusion, these findings support the concept that NO induces suppression of cell‐mediated immune responses by selective action on Th1 T cells, thereby promoting a Th2 response. J. Cell. Physiol. 208: 418–427, 2006. © 2006 Wiley‐Liss, Inc.
Lactic acid fermentation of black beans (Phaseolus vulgaris): microbiological and chemical characterization
Authors: Granito Marisela , Álvarez Glenda
Published: April 2006

Legumes, and particularly Phaseolus vulgaris, are an important source of nutrients, especially in developing countries. In spite of being part of the staple diets of these populations, their consumption is limited by the flatulence they produce. Natural lactic acid fermentation has proved to be an effective method to decrease flatulence‐producing compounds. However, in order to use this method as a process on a large scale, it is fundamental to identify the microbial flora involved. When fermented seeds of Phaseolus vulgaris (black bean) were analysed microbiologically, it was found that the microorganisms present were Lactobacillus casei and Lactobacillus plantarum. On performing back‐slopping or induced fermentation with different inocula, a 63.35% decrease was found for the soluble fibre and 88.6% for raffinose, one of the main flatulence‐producing compounds. When cooking under atmospheric pressure was applied to the fermented samples, a significant diminution of the trypsin inhibitors and tannins was found as well as an increase in the in vitro and in vivo digestibility of the beans. All these results demonstrate that the lactic acid bacteria used for the induced fermentation can lead to a functional food with improved nutritional quality. Copyright © 2006 Society of Chemical Industry
Evaluation of pediatric oncology patients with previous multiple central catheters for vascular access: Is doppler ultrasound needed?
Authors: Gupta Himesh , Araki Yuko , Davidoff Andrew M. , Rao Bhaskar N. , Hoffer Fredric A. , Billups Catherine , Wu Jianrong , Shochat Stephen J.
Published: April 2006

Background/Purpose

Pediatric oncology patients who have undergone placement of multiple central venous catheters may have thrombosis or stenosis in the upper venous system. The purpose of this study was to identify factors that predict venous thrombosis or stenosis and to evaluate the role of Doppler ultrasonography in assessing the upper venous system of pediatric patients requiring multiple central vascular catheters.

Methods

The medical records of eligible patients were reviewed with regard to demographics, primary disease, type of catheter, duration of previous central venous access, association with infection, operative notes, and Doppler ultrasonographic findings.

Results

Our evaluation criteria were met in 50 cases (47 patients). In 10 cases, Doppler ultrasonography revealed abnormality in the upper venous system. Patient demographics, primary disease, type of catheter, duration of previous central venous access, or association with infection were not found to significantly predict the abnormality in the upper venous system. Placement of central venous access device was performed without difficulty when the site of placement was chosen on the basis of ultrasonographic findings.

Conclusion

Doppler ultrasonography is useful in diagnosing thrombosis or stenosis in asymptomatic pediatric patients requiring placement of multiple central venous catheters. Pediatr Blood Cancer 2007;48:527–531. © 2006 Wiley‐Liss, Inc.
Effect of race on outcome of white and black children with acute myeloid leukemia: The St. Jude experience
Authors: Rubnitz Jeffrey E. , Lensing Shelly , Razzouk Bassem I. , Pounds Stanley , Pui Ching‐Hon , Ribeiro Raul C.
Published: April 2006

Background

The association between race and outcome of treatment for childhood acute myeloid leukemia (AML) has not been adequately studied.

Procedure

We compared the clinical characteristics, biological features, and outcomes between white and black children with AML who were treated on five consecutive clinical protocols (1980–2002) at St. Jude Children's Research Hospital. We used proportional hazards modeling to investigate the relation between race and outcome.

Results

We observed no statistically significant differences between the 229 white and 58 black patients in clinical characteristics, FAB subtype, cytogenetic features, or outcome. There were no significant differences in event‐free survival (EFS) or overall survival (OS) between the two race groups in individual clinical trials or in all studies combined. For the study group as a whole, the 5‐year survival estimate was 39.2% ± 3.6% for white patients and 33.8% ± 6.5% for black patients. However, on our most recent trial (AML‐97), there was a trend towards inferior outcome among black patients: the 5‐year survival estimates were 55.6% ± 12.3% and 27.3% ± 13.5% for whites and blacks, respectively.

Conclusions

Although we detected no differences in treatment outcome between white and black children with AML over the entire study period, black children appear to have worse outcomes than white children during more recent studies. Improved treatment is needed for all children with AML. Pediatr Blood Cancer 2007;48:10–15. © 2006 Wiley‐Liss, Inc.
Comparison of treatment outcomes of childhood Hodgkin lymphoma in two US centers and a center in Recife, Brazil
Authors: Hsu Saunders C. , Metzger Monika L. , Hudson Melissa M. , Pedrosa Francisco , Lins Mecneide , Pedrosa Marcia , Barros Cynthia , Maciel Kaline , Pui Ching‐Hon , Ribeiro Raul C. , Howard Scott C.
Published: April 2006

Background

Pediatric Hodgkin lymphoma (HL) has a cure rate of more than 80% in high‐income countries (HIC). However, more than 80% of the world's children live in low‐income countries (LIC), where the cure rate is often much lower.

Procedure

We compared the outcome of HL of 371 patients treated at two pediatric oncology centers in the US to that of 62 patients treated at one center in Recife, Brazil (IMIP) to determine whether the same treatment strategy should be used in both high‐income and LIC. The logrank test was used to compare event‐free and overall survival.

Results

The percentages of patients with unfavorable disease at each center were similar (P = 0.72). Patients with favorable disease at IMIP had estimated 5‐year survival rates comparable to those of the US centers (100% and 99%, respectively). Among patients with unfavorable disease, those treated at IMIP had a 5‐year event‐free survival (EFS) rate of 60%, compared to 78% at the US centers; (P = 0.08). The 5‐year survival estimate after relapse was 25% at IMIP versus 61% at the US centers (P = 0.08). The 5‐year overall survival for patients with unfavorable disease was 72% at IMIP versus 90% at the US centers (P = 0.01).

Conclusions

Intensive frontline therapy should be considered for patients with unfavorable HL in LIC where the relapse rate is high and the salvage rate is low, provided that supportive care is adequate. Pediatr Blood Cancer 2007;49:139–144. © 2006 Wiley‐Liss, Inc.
Synthesis of poly(2‐hydroxyethyl methacrylate) in protic media through atom transfer radical polymerization using activators generated by electron transfer
Authors: Oh Jung Kwon , Matyjaszewski Krzysztof
Published: April 2006

Atom transfer radical polymerization (ATRP) using activators generated by electron transfer (AGET) was investigated for the controlled polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a protic solvent, a 3/2 (v/v) mixture of methyl ethyl ketone and methanol. The AGET process enabled ATRP to be started with an air‐stable Cu(II) complex that was reduced in situ by tin(II) 2‐ethylhexanoate. The reaction temperature, Cu catalysts with different ligands, and variation of the initial concentration ratio of HEMA to the initiator were examined for the synthesis of well‐controlled poly(2‐hydroxyethyl methacrylate) and a poly(methyl methacrylate)‐b‐poly(2‐hydroxyethyl methacrylate) block copolymer. The level of control in AGET ATRP was similar to that in normal ATRP in protic solvents, and this resulted in a linear increase in the molecular weight with the conversion and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight < 1.3). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3787–3796, 2006
High infant and child mortality rates in Orissa: an assessment of major reasons
Authors: Pradhan Jalandhar , Arokiasamy P.
Published: April 2006

Infant and child mortality rates in Orissa are the highest among the Indian states. This is surprising, given other demographic indicators, such as the relatively rapid fertility decline and the quite high levels of antenatal care coverage in this state compared with other comparatively poor states. In this article, the macro‐ and micro‐level determinants of high infant and child mortality are assessed using multivariate logistic regression analyses. The results demonstrate that the major contributors to the high infant and child mortality rates are the extremely low levels of health sector investments and the associated quality of care. Copyright © 2006 John Wiley & Sons, Ltd.
An introductory note to CHMP guidelines: choice of the non‐inferiority margin and data monitoring committees
Authors: Brown David , Volkers Peter , Day Simon
Published: April 2006

The Committee on Medical Products for Human Use (CHMP) has recently issued two new guidance documents that are of particular note to statisticians. The purpose of this short note is to give a little background to the origins of these documents and a flavour of some of their most important features. The two guidelines are reproduced as the next two papers in the journal (Stat. Med. 2006; 25:1628–1645). Copyright © 2006 John Wiley & Sons, Ltd.
Petrogenesis of Late Jurassic Qianlishan granites and mafic dykes, Southeast China: implications for a back-arc extension setting
Authors: JIANG YAO-HUI , JIANG SHAO-YONG , ZHAO KUI-DONG , LING HONG-FEI
Published: April 2006

A late Mesozoic belt of volcanic-intrusive complexes occurs in Southeast China. The Qianlishan granites are distributed in the northwest of the belt. The pluton is composed of porphyritic biotite granite (153 Ma) and equigranular biotite granite (151 Ma) and was intruded by granite-porphyry dykes (144 Ma) and mafic dykes such as lamprophyre and diabase (142 Ma). The granitic rocks, consisting mainly of K-feldspar, plagioclase, quartz and Fe-rich biotite, have SiO2 contents of 72.9–76.9%, and are enriched in alkalis, rare earth elements (REE), high field strength elements (HFSE) and Ga with high Ga/Al ratios, but depleted in Ba, Sr and transition metals. Trace-element geochemistry and Sr–Nd isotope systematics further imply that the Qianlishan granitic magmas were most probably derived by partial melting of Palaeo- to Mesoproterozoic metamorphic lower-crustal rocks that had been granulitized during an earlier thermal event. These features suggest an A-type affinity. The Qianlishan lamprophyre and neighbouring coeval mafic dykes (SiO2 = 47.9–53.8 wt%) have high MgO and compatible element contents. These rocks also have high K2O contents and are enriched in alkalis, light REE, large ion lithophile elements, and depleted in HFSE. They have low initial εNd values and relatively high initial 87Sr/86Sr ratios. We suggest a subduction-modified refractory lithospheric mantle (phlogopite-bearing harzburgite or lherzolite) for these high-Mg potassic magmas. The Qianlishan diabases (SiO2 = 48.4–48.7 wt%) are alkaline and have high TiO2 and total Fe2O3 contents, together with the positive initial εNd value, suggesting derivation from fertile asthenopheric mantle (phlogopite-bearing lherzolite). A back-arc extensional setting, related to subduction of the Palaeo-Pacific plate, is favoured to explain the petrogenesis of the Qianlishan granites and associated mafic dykes. Between 180 and 160 Ma, Southeast China was a continental arc, forming the 180–160 Ma plutons of the late Mesozoic volcanic-intrusive complex belt, and the lower-crust was granulitized. Since 160 Ma the northwestern belt has been in a back-arc extensional setting as a consequence of slab roll-back, resulting in the lithosphere thinning and an influx of asthenophere. The upwelling asthenosphere, on the one hand, induced the local lithospheric mantle to melt partially, forming high-Mg potassic magmas, and on the other hand it underwent decompression melting itself to form alkaline diabase magma. Pulsatory injection of such high-temperature magmas into the granulitized crustal source region induced them to partially melt and generate the A-type magmas of the Qianlishan granitic rocks.
Numerical simulation of thermal convection in a two-dimensional finite box
Authors: Goldhirsch Isaac , Pelz Richard B. , Orszag Steven A.
Published: April 2006

The problems of dynamical onset of convection, textural transitions and chaotic dynamics in a two-dimensional, rectangular Rayleigh-Bénard system have been investigated using well-resolved, pseudo-spectral simulations. All boundary conditions are taken to be no-slip. It is shown that the process of creating the temperature gradient in the system, is responsible for roll creation at the side boundaries. These rolls either induce new rolls or move into the interior of the cell, depending on the rate of heating. Complicated flow patterns and textural transitions are observed in both non-chaotic and chaotic flow regimes. Multistability is frequently observed. Intermediate-Prandtl-number fluids (e.g. 0.71) have a quasiperiodic time dependence up to Rayleigh numbers of order 106. When the Prandtl number is raised to 6.8, one observes aperiodic (chaotic) flows of non-integer dimension. In this case roll merging and separation is observed to be an important feature of the dynamics. In some cases corner rolls are observed to migrate into the interior of the cell and to grow into regular rolls; the large rolls may shrink and retreat into corners. The basic flow patterns observed do not change qualitatively when the chaotic regime is entered.
The effect of a weak vertical magnetic field on the buoyancy-driven boundary-layer flow past a vertical heated wall
Authors: Kerr Oliver S. , Wheeler A. A.
Published: April 2006

In this paper we investigate the effect of a weak vertical magnetic field on the boundary-layer flow of an electrically conducting fluid past a vertical heated wall. We derive similarity solutions for the flow and temperature and show that the flow is composed of three regions: an inner region where the flow is a regular perturbation of the classical boundary-layer flow due to a heated semi-infinite vertical plate; an inviscid outer region where fluid is entrained from downwards towards the plate; and beyond this a quiescent region, separated from the outer region by a free shear layer. Thus the effect of the magnetic field is to inhibit the entrainment of fluid across the magnetic field lines in the whole region and confine it to an outer boundary layer.
Surface wave mode interactions: effects of symmetry and degeneracy
Authors: Simonelli F. , Gollub J. P.
Published: April 2006

Parametrically excited surface wave modes on a fluid layer driven by vertical forcing can interact with each other when more than one spatial mode is excited. We have investigated the dynamics of the interaction of two modes that are degenerate in a square layer, but non-degenerate in a rectangular one. Novel experimental techniques were developed for this purpose, including the real-time measurement of all relevant slowly varying mode amplitudes, investigation of the phase-space structure by means of transient studies starting from a variety of initial conditions, and automated determination of stability boundaries as a function of driving amplitude and frequency. These methods allowed both stable and unstable fixed points (sinks, sources, and saddles) to be determined, and the nature of the bifurcation sequences to be clearly established. In most of the dynamical regimes, multiple attractors and repellers (up to 16) were found, including both pure and mixed modes. We found that the symmetry of the fluid cell has dramatic effects on the dynamics. The fully degenerate case (square cell) yields no time-dependent patterns, and is qualitatively understood in terms of third-order amplitude equations whose basic structure follows from symmetry arguments. In a slightly rectangular cell, where the two modes are separated in frequency by a small amount (about 1%), mode competition produces both periodic and chaotic states organized around unstable pure and mixed-state fixed points.
Measurements of heat transfer in separated highenthalpy dissociated laminar hypersonic flow behind a step
Authors: Gai S. L. , Reynolds N. T. , Ross C. , Baird J. P.
Published: April 2006

Measurements of heat transfer in the separated region behind a rearward-facing step in a hypersonic high-enthalpy stream, are described. The range of enthalpies considered was much greater than those reported previously in the literature. High-response surface thermocouples were used to measure the heat-transfer rates. Flow visualization by way of interferograms, with a Mach-Zehnder interferometer, were obtained and improved visualization was further facilitated by digitizing the interferograms and using Fourier analysis to determine fringe positions. This then provided a phase map of the flow region in which the phase was colour coded to emphasize flow characteristics.
The dynamics of the near field of strong jets in crossflows
Authors: Coelho Sergio L. V. , Hunt J. C. R.
Published: April 2006

An inviscid three-dimensional vortex-sheet model for the near field of a strong jet issuing from a pipe into a crossflow is derived. The solution for this model shows that the essential mechanisms governing this idealized flow are the distortion of the main transverse vorticity by the generation of additional axial and transverse vorticity within the pipe owing to the pressure gradients induced by the external flow, and the convection of both components of vorticity from the upwind side of the jet to its downwind side.

The deformation of the cross-section of the jet which is predicted by this model is compared with the deformation predicted by the commonly used time-dependent two-dimensional vortex-sheet model. Differences arise because the latter model does not take into account the effects of the transport of the transverse component of vorticity. The complete three-dimensional vortex-sheet model leads to a symmetrical deformation of the jet cross-section and no overall deflection of the jet in the direction of the stream.

To account for viscous effects, the initial region of a strong jet issuing into a uniform crossflow is modelled as an entraining three-dimensional vortex sheet, which acts like a sheet of vortices and sinks, redistributing the vorticity in the bounding shear layer and inducing non-symmetrical deformations of the cross-section of the jet. This leads to a deflection of the jet in the direction of the stream, and the loci of the centroids of the cross-sections of the jet describe a quadratic curve.

Deformations predicted by each of the three models are compared with measurements obtained from photographs of the cross-sections of a jet of air emerging into a uniform crossflow in a wind tunnel. Mean velocity measurements around the jet made with a hot-wire anemometer agree with the theory; they clearly invalidate models of jets based on ‘pressure drag’.
Slot suction from inviscid channel flow
Authors: Dewynne J. N. , Howison S. D. , Ockendon J. R. , Morland L. C. , Watson E. J.
Published: April 2006

Motivated by a problem in turbine blade cooling, we consider suction from an inviscid channel flow into a slot in the channel wall. The flow is assumed to separate smoothly from the leading edge of the slot and the pressure in the stagnant separated region controls the suction. The mass flux into the slot is found in terms of the pressure; for small values of this flux the predicted flow pattern is found to be quite different from that which would result if there were no separated region. In particular, the stagnation point never penetrates more than approximately 0.05 slot widths into the slot.
The effect of interaction on the boundary layer induced by a convected rectilinear vortex
Authors: Chuang Fu-Sheng , Conlisk A. T.
Published: April 2006

The effect of interaction on the boundary layer induced by a convected rectilinear vortex is considered. Two schemes are employed in the numerical discretization of the edge interaction condition; the first, developed by Veldman (1981) is useful at larger Reynolds numbers but fails to capture the interactive phase of the motion for Reynolds numbers less than 8 × 104. A scheme devised by Napolitano, Werlé & Davis (1978) is employed at smaller Reynolds numbers and yields similar results to Veldman's scheme at higher Reynolds numbers, while exhibiting greater numerical stability during the interactive phase of the motion. The effect of interaction is found to be negligible during much of the motion, even for a strong vortex, but during the latter stages of the calculations, interaction appears to round off the top of the eddy and delays breakdown for all Reynolds numbers studied when compared with the non-interactive results of Doligalski & Walker (1984). In addition, in the latter stages of the calculations, and during the early stages of the interactive phase, a third eddy is formed with vorticity of the same sign as the main eddy spawned deep within the boundary layer. Such a tertiary eddy has been observed in the experimental work of Walkeret al.(1987) in their study of the boundary layer induced by a vortex ring. During the interactive phase of the motion a streamwise lengthscale emerges whose length is approximately$O(Re^{-\frac{3}{11}})$, broadly in line with the analytical predictions of Elliott, Cowley & Smith (1983). A novel feature of the computations is the use of a pseudospectral method (Burggraf & Duck 1982) in the streamwise direction which requires no special coding in reversed-flow regions.
Frontogenesis in a fluid with horizontal density gradients
Authors: Simpson J. E. , Linden P. F.
Published: April 2006

The adjustment under gravity of a fluid containing a horizontal density gradient is described.’ The fluid is initially at rest and the resulting motion is calculated as the flow accelerates, driven by the baroclinic density field. Two forms of the initial density distribution are considered. In the first the initial horizontal gradient is constant. A purely horizontal motion develops as the isopycnals rotate towards the horizontal. The vertical density gradient increases continually with time but the horizontal density gradient remains unchanged. The horizontal velocity has a uniform vertical shear, and the gradient Richardson number is constant in space and decreases monotonically with time to ½. The second density distribution consists of a piecewise constant gradient with a jump in the gradient along a vertical isopycnal. The density is continuous. In this case frontogenesis is predicted to occur on the isopycnal between the two constant-density-gradient regions, and the timescale for the formation of a front is determined. Laboratory experiments are reported which confirm the results of these calculations. In addition, lock exchange experiments have been carried out in which the horizontal mean gradient is represented by a series of step density differences separated by vertical gates.
Spectral evolution of wind-generated surface gravity waves in a dispersed ice field
Authors: Masson D. , Leblond P. H.
Published: April 2006

The Marginal Ice Zone includes wide areas covered by dispersed ice floes in which wave conditions are significantly affected by the ice. When the wind blows from the solid ice pack, towards the open sea, growing waves are scattered by the floes, and their spectral characteristics modified. To further understand this problem, a model for the evolution of wind waves in a sparse field of ice floes has been developed. The sea state is described by a two-dimensional discrete spectrum. Time-limited wave growth is obtained by numerical integration of the energy balance equation using the exact nonlinear transfer integral. Wave scattering by a single floe is represented in terms of far-field expressions of the diffracted and forced potentials obtained numerically by the Green function method. The combined effect of a homogeneous field of floes on the wave spectrum is expressed in terms of the Foldy–Twersky integral equations under the assumption of single scattering. The results show a strong dependence of the spectrum amplitude and directional properties on the ratio of the ice floe diameter to the wavelength. For a certain range of this parameter, the ice cover appears to be very effective in dispersing the energy; the wave spectrum rapidly tends to isotropy, a tendency which prevents the normal growth of wave energy and the decrease in peak frequency. Therefore, in the Marginal Ice Zone, the ability of an offshore wind to generate a significant wave field is severely limited.
Numerical simulations of freely evolving turbulence in stably stratified fluids
Authors: Métais Olivier , Herring Jackson R.
Published: April 2006

Results of direct numerical simulations of stably stratified, freely evolving, homogeneous turbulence are presented. An examination of initial data designed to give insight into laboratory flows suggests that the numerical simulations have a satisfactory degree of realism, insofar as statistical parameters such as total energy and length scales are concerned. The motion is decomposed into a stratified turbulence (vortical) component and a wave component. For initial-value problems similar to laboratory studies of stratified flows, the vortical component decays at a rate virtually identical to that of the non-buoyant case up to t = 6N−1 (N is the Brunt-Väisälä frequency). The decay rate decreases after this time, suggesting a kind of turbulence ‘collapse’. The temperature structure that emerges clearly shows the development of the collapse stage of the flow, which is also diagnosed by the behaviour of parameters such as the Thorpe scale.

We next examine the very small-Froude-number regime in order to understand possible universal aspects of the flow. An examination of various initial conditions with different proportions of stratified and wave components indicates a lack of universality. For initial data containing only vortical motion (motions derived from the vertical vorticity field), the vortical field tends to dominate, in subsequent evolution, at strong stratification. However, contrary to two-dimensional turbulence, the flow is more strongly dissipative than two-dimensional flows due to the frictional effect associated with layering. Other quantities examined are frequency spectra, and the probability distribution for vertical shear. The frequency spectra exhibit some features in common with spectra extracted from oceanographic data.
Hydrodynamic and morphological stability of the unidirectional solidification of a freezing binary alloy: a simple model
Authors: Forth S. A. , Wheeler A. A.
Published: April 2006

In this paper we consider the effect of a model boundary-layer flow on the hydrodynamic and morphological stability of a simple model of the solidification of a binary alloy. We conduct a linear analysis and develop asymptotic solutions for large Schmidt number and large Reynolds number. We also present numerical solutions for data appropriate to a lead–tin alloy. We show that for modes parallel to the free-stream velocity the flow is responsible for the appearance of travelling waves and, for common values of the material parameters, may stabilize the morphological stability of the interface. However the morphological stability of modes perpendicular to the free-stream velocity is unaffected by the presence of the flow. The hydrodynamic stability of the boundary layer is very weakly affected by the presence of the interface, which we attribute to the large Schmidt numbers associated with real crystal growth situations.
Droplet pair interactions in a shock-wave flow field
Authors: Temkin S. , Ecker G. Z.
Published: April 2006

Binary interactions between water droplets of nearly equal size in the flow field behind a weak shock wave were studied experimentally. The droplets had diameters of about 270 mm, and the Reynolds numbers, based on this diameter and on the relative velocity between the droplets and the free stream, ranged from about 130 to about 600. In this paper we report only data for Re < 150, corresponding to non-deforming droplets. The droplets in a given pair were aligned so that each pair fell on a plane parallel to the direction of the incoming flow. In this manner, the second droplet in the pair was ‘behind’ the first, at horizontal distances ranging from 1.5 to 11 diameters, and at vertical distances from the dividing streamline ranging from −3 to 6 diameters. We have quantified the interaction in terms of drag force changes on the droplets, and show that the first, or upstream, droplet is not affected by the second, but that the second experiences significant reductions for vertical distances of about one droplet diameter or less. At the smallest horizontal distances, the maximum decrease observed was about 50%, relative to its isolated value. We also show that the drag changes clearly demarcate a wake behind the first droplet. Further, on the basis of these changes, we define a region of influence attached to the first droplet, where the free-stream velocity is significantly reduced. For the droplets used in this study, this region is a slender paraboloid of revolution, having a length of about 15 diameters and a radius of about one diameter.
An algebraic model for the turbulent flux of a passive scalar
Authors: Rogers Michael M. , Mansour Nagi N. , Reynolds William C.
Published: April 2006

The behaviour of passive-scalar fields resulting from mean scalar gradients in each of three orthogonal directions in homogeneous turbulent shear flow has been studied using direct numerical simulations of the unsteady incompressible Navier-Stokes equations with 128 × 128 × 128 grid points. It is found that, for all orientations of the mean scalar gradient, the sum of the pressure-scalar gradient and velocity gradient-scalar gradient terms in the turbulent scalar flux balance equation are approximately aligned with the scalar flux vector itself. In addition, the time derivative of the scalar flux is also approximately aligned with the flux vector for the developed fields (corresponding to roughly constant correlation coefficients). These alignments lead directly to a gradient transport model with a tensor turbulent diffusivity. The simulation results are used to fit a dimensionless model coefficient as a function of the turbulence Reynolds and Péclet numbers. The model is tested against two different passive-scalar fields in fully developed turbulent channel flow (also generated by direct numerical simulation) and is found to predict the scalar flux quite well throughout the entire channel.
Numerical analysis of gas-particle two-phase flows
Authors: Ishii R. , Umeda Y. , Yuhi M.
Published: April 2006

This paper is concerned with a numerical analysis of axisymmetric gas-particle two-phase flows. Underexpanded supersonic free-jet flows and supersonic flows around a truncated cylinder of gas-particle mixtures are solved numerically on the super computer Fujitsu VP-400. The gas phase is treated as a continuum medium, and the particle phase is treated partly as a discrete one. The particle cloud is divided into a large number of small clouds. In each cloud, the particles are approximated to have the same velocity and temperature. The particle flow field is obtained by following these individual clouds separately in the whole computational domain. In estimating the momentum and heat transfer rates from the particle phase to the gas phase, the contributions from these clouds are averaged over some volume whose characteristic length is small compared with the characteristic length of the flow field but large compared with that of the clouds. The results so obtained reveal that the flow characteristics of the gas-particle mixtures are widely different from those of the dust-free gas at many points.
A canonical statistical theory of oceanic internal waves
Authors: Allen Kenneth R. , Joseph Richard I.
Published: April 2006

We use the methods of statistical mechanics to develop a theoretical relationship between the observed oceanic spectra and the probability distributions usually studied in statistical mechanics. We also find that the assumption that in terms of Lagrangian variables the oceanic internal wave field is near canonical equilibrium (i.e. the internal wave modes are populated in accordance with a Maxwell–Boltzmann-type distribution) yields expressions for the various marginal or reduced Eulerian spectra associated with both moored and towed measurements which are in striking qualitative agreement with experiment. In developing this theory it is important to distinguish carefully between Lagrangian and Eulerian variables. The important difference between the two sets of variables is due to the advective nonlinearity (i.e. (v∇) v where v is the Eulerian velocity) which is present only in the Eulerian frame. Our method treats the dynamics within the Lagrangian frame, where because of the absence of the advective nonlinearity it is fundamentally simpler, and then transforms to the Eulerian or measurement frame. We find that at small wavenumbers the four-dimensional Eulerian frequency wavenumber spectrum is approximately equal to the corresponding Lagrangian frequency wavenumber spectrum. At large wavenumbers, however, advective contributions become important and the two types of spectra are significantly different. While from a Lagrangian frame point of view the system is entirely wavelike, at large wavenumbers the Eulerian spectrum is not confined to the dispersion surface and the system, from an Eulerian frame point of view, is not wavelike. Further, the three-dimensional Eulerian wavenumber spectrum exhibits a large-wavenumber advective tail which decays as a power law and results in one-dimensional marginal spectra which are in excellent qualitative agreement with experiment. The above features are exhibited independent of the detailed nature of the underlying Lagrangian frequency wavenumber spectrum.
On the onset of three-dimensionality and time-dependence in Görtler vortices
Authors: Hall Philip , Seddougui Sharon
Published: April 2006

The secondary instability of large-amplitude Görtler vortices in a growing boundary layer is discussed in the fully nonlinear regime. It is shown that the three-dimensional breakdown to a flow with wavy vortex boundaries, similar to that which occurs in the Taylor vortex problem takes place. However, the instability is confined to the thin shear layers which were shown by Hall & Lakin (1988) to trap the region of vortex activity. The disturbance eigenfunctions decay exponentially away from the centre of these layers, so that the upper and lower shear layers can support independent modes of instability. The structure of the instability, in particular its location and speed of downstream propagation, is found to be entirely consistent with recent experimental results. Furthermore, it is shown that the upper and lower layers support wavy vortex instabilities with quite different frequencies. This result is again consistent with the available experimental observations.