bluuebunny/crossref_metadata_2025 huggingface dataset:
Three New Dimeric Benzofuran Derivatives from the Roots of Ligularia stenocephala Matsum. et Koidz.
Authors: Toyoda Kazuki , Yaoita Yasunori , Kikuchi Masao
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Stemphones, Novel Potentiators of Imipenem Activity Against Methicillin‐Resistant Staphylococcus aureus, Produced by Aspergillus sp. FKI‐2136.
Authors: Koyama Nobuhiro , Nagahiro Tomoko , Yamaguchi Yuichi , Masuma Rokuro , Tomoda Hiroshi , Omura Satoshi
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Lichenicolins A and B, New Bisnaphthopyrones from an Unidentified Lichenicolous Fungus, Strain LL‐RB0668.
Authors: He Haiyin , Bigelis Ramunas , Yang Hui Y. , Chang Li‐Ping , Singh Maya P.
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
New Aldose Reductase Inhibitors N99‐596 A and B from Streptomyces.
Authors: Dong Yuesheng , Yang Junshan , Ren Xiao , Zhang Hua , He Jiangong
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Nanostructural Magnetoelastic Materials for Sensor Applications
Authors: Ong Keat G. , Grimes Craig A.
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Atom Probe Characterization of Microstructures of Nanocrystalline and Nanocomposite Magnetic Materials
Authors: Hono Kazuhiro
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Nanoscale Molecular Cavities for Stabilization of Highly Reactive Species
Authors: Goto Kei , Kawashima Takayuki
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Self‐Organization of Disc‐Like Molecules: Chemical Aspects
Authors: Kumar Sandeep
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Relevance of Polymer and Biopolymer Clay Nanocomposites in Electrochemical and Electroanalytical Applications
Authors: Aranda P. , Darder M. , Fernandez‐Saavedra R. , Lopez‐Blanco M. , Ruiz‐Hitzky E.
Published: April 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A Prospective Study of the Use of the [Os(tpy)2]2+ (tpy = 2,2′;6′:2″‐Terpyridine) Core as Signalling Scaffolding for the Development of Chemical Sensors
Authors: Ros‐Lis Jose V. , Martínez‐Máñez Ramón , Soto Juan , McDonagh Colette , Guckian Adrian
Published: April 2006

The heteroleptic osmium(II) complex [Os(L1)(Me‐phtpy)][PF6]2 (L1 = 1‐[4′‐p‐tolyl‐(2,2′:6′,2″‐terpyridyl)]‐1,4,8,11‐tetraazacyclotetradecane, Me‐phtpy = 4′‐p‐tolyl‐2,2′:6′,2″‐terpyridine) has been prepared, characterized and its potential use for chemical sensing purposes studied. The complex contains a polyazacycloalkane as “binding site” and a Os(tpy)22+ core that acts as a “signalling subunit”. The emission intensity of the osmium complex was quenched in acetonitrile/water (1:1 v/v) by Cu2+ and Ni2+. Potentiometric titrations of [Os(L1)(Me‐phtpy)]2+ in the presence of Cu2+ were carried out in order to determine thermodynamic binding constants in acetonitrile/water (70:30 v/v, 0.1 mol·dm–3 tetrabutylammonium perchlorate). With Cu2+ the receptor [Os(L1)(Me‐phtpy)]2+ forms the complex {Cu[Os(L1)(Me‐phtpy)]}4+ at neutral pH. Moreover it undergoes two stepwise protonation processes at acid pH related to the partial protonation of the cyclam core and forms two hydroxo complexes at basic pH. The Ni2+ complexes of the osmium receptor [Os(L1)(Me‐phtpy)]2+ are able to act as an anion fluorogenic chemosensor in acetonitrile/water mixtures. A displacement of the quenching effect to more acidic pH in the Ni2+–[Os(L1)(Me‐phtpy)]2+ system was observed for anions in the order ATP > AMP > chloride. A prospective study of the use of the [Os(L1)(Me‐phtpy)]2+ complex as a fluorogenic sensor for oxygen was also carried out by incorporation of the complex in sol‐gel silica films made with TEOS and MTEOS. Significant quenching of the osmium fluorescence by oxygen was observed. The oxygen response of the films showed good stability and repeatability. The study suggested that theOs(tpy)22+ core might act as suitable signalling scaffolding in chemical sensing systems of cations, anions and gases.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis and Characterization of MoOI2(PMe3)3 and Use of MoOX2(PMe3)3 (X = Cl, I) in Controlled Radical Polymerization
Authors: Mata José A. , Maria Sébastien , Daran Jean‐Claude , Poli Rinaldo
Published: April 2006

Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields. The geometry of the compound is mer‐cis octahedral, that is, identical to that of the dichloride precursor, as shown by NMR spectroscopy and by an X‐ray crystallographic study. Electrochemical investigations of MoOX2(PMe3)3 show irreversible oxidation waves at Ep,a = +0.18 and +0.39 V for X = Cl and I, respectively. A study of the halide exchange between MoOCl2(PMe3)3 and NaI, or between MoOI2(PMe3)3 and Bu4NCl, shows two equilibrated isomers for the mixed halide intermediate MoOICl(PMe3)3. The diiodide complex rapidly exchanges the iodo ligands with chloride upon dissolution in chloroform at room temperature, and with bromide from (1‐bromoethyl)benzene (BEB) under more forcing conditions. The equilibrium favors the softer halide (I) on C and the harder one (Cl or Br) on MoIV. Both oxido compounds catalyze the atom transfer radical polymerization (ATRP) of styrene in combination with the BEB initiator, yielding polymers with quite narrow molecular weight distributions (down to 1.11). The apparent polymerization rate constant is approximately doubled in the presence of 1 equiv. of the Al(OiPr)3 cocatalyst. On the other hand, the system is not capable of efficiently controlling the radical chain growth for methyl acrylate polymerization. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
PDT‐associated host response and its role in the therapy outcome
Authors: Korbelik Mladen
Published: April 2006

Background and Objectives

The outcome of the treatment of solid tumors by photodynamic therapy (PDT) is critically dependent on the contribution from the host. This host response is provoked by the rapidly induced massive tumor tissue injury delivered by PDT that is experienced as a local trauma threatening the integrity and homeostasis at the affected site.

Study Design/Materials and Methods

Mouse tumor models were extensively employed in pre‐clinical studies investigating various aspects of host‐tumor interaction following PDT, but important input was also derived from clinical data.

Results

The recognition of this PDT‐inflicted insult by innate immune sensors detecting danger signals from the distressed/altered tumor tissue, triggers host‐protecting responses dominantly manifested as acute inflammation that are elicited and orchestrated by the innate immune system. To secure the affected PDT‐targeted site, the inflammatory reaction attacks tumor vasculature and then neutralizes the focal source of danger signals by eliminating the injured tumor cells.

Conclusion

The provoked highly intensified phagocytosis of dead tumor cells occurring in the context of a vigorous innate immune reaction emerges as a key factor responsible for the development of tumor antigen‐specific adaptive immune response that contributes to the eradication of PDT‐treated cancers. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.
Clinical Pharmacokinetics of the PDT Photosensitizers Porfimer Sodium (Photofrin), 2‐[1‐Hexyloxyethyl]‐2‐Devinyl Pyropheophorbide‐a (Photochlor) and 5‐ALA‐Induced Protoporphyrin IX
Authors: Bellnier David A. , Greco William R. , Loewen Gregory M. , Nava Hector , Oseroff Allan R. , Dougherty Thomas J.
Published: April 2006

Background and Objectives

Photodynamic therapy (PDT) uses a photosensitizer activated by light, in an oxygen‐rich environment, to destroy malignant tumors. Clinical trials of PDT at Roswell Park Cancer Institute (RPCI) use the photosensitizers Photofrin, Photochlor, and 5‐ALA‐induced protoporphyrin IX (PpIX). In some studies the concentrations of photosensitizer in blood, and occasionally in tumor tissue, were obtained. Pharmacokinetic (PK) data from these individual studies were pooled and analyzed. This is the first published review to compare head‐to‐head the PK of Photofrin and Photochlor.

Study Design/Materials and Methods

Blood and tissue specimens were obtained from patients undergoing PDT at RPCI. Concentrations of Photofrin, Photochlor, and PpIX were measured using fluorescence analysis. A non‐linear mixed effects modeling approach was used to analyze the PK data for Photochlor (up to 4 days post‐infusion; two‐compartment model) and a simpler multipatient‐data‐pooling approach was used to model PK data for both Photofrin and Photochlor (at least 150 days post‐infusion; three‐compartment models). Physiological parameters were standardized to correspond to a standard (70 kg; 1.818 m2 surface area) man to facilitate comparisons between Photofrin and Photochlor.

Results

Serum concentration‐time profiles obtained for Photofrin and Photochlor showed long circulating half‐lives, where both sensitizers could be found more than 3 months after intravenous infusion; however, estimated plasma clearances (standard man) were markedly smaller for Photofrin (25.8 ml/hour) than for Photochlor (84.2 ml/hour). Volumes of distribution of the central compartment (standard man) for both Photofrin and Photochlor were about the size (3.14 L, 4.29 L, respectively) of plasma volume, implying that both photosensitizers are almost 100% bound to serum components. Circulating levels of PpIX were generally quite low, falling below the level of instrument sensitivity within a few days after topical application of 5‐ALA.

Conclusion

We have modeled the PK of Photochlor and Photofrin. PK parameter estimates may, in part, explain the relatively long skin photosensitivity attributed to Photofrin but not Photochlor. Due to the potential impact and limited experimental PK data in the PDT field further clinical studies of photosensitizer kinetics in tumor and normal tissues are warranted. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.
Clinical and histological healing pattern of peri‐implantitis lesions following non‐surgical treatment with an Er:YAG laser
Authors: Schwarz Frank , Bieling Katrin , Nuesry Enaas , Sculean Anton , Becker Jürgen
Published: April 2006

Background and Objectives

The aim of the present study was to assess clinical and histo‐pathological healing pattern of peri‐implantitis lesions following non‐surgical treatment with an Er:YAG laser (ERL).

Study Design/Materials and Methods

Twelve patients suffering from peri‐implantitis (n = 12 implants) received a single episode of non‐surgical instrumentation using ERL (12.7 J/cm2). Assessment of clinical parameters (plaque index (PI), bleeding on probing (BOP), probing pocket depth, gingival recession (GR), and clinical attachment level (CAL)), surgical defect examination, and histo‐pathological examination of peri‐implant tissue biopsies was performed after 1, 3, 6, 9, 12, and 24 months.

Results

All patients exhibited improvements of all clinical parameters investigated. However, histo‐pathological examination of tissue biopsies revealed a mixed chronic inflammatory cell infiltrate (macrophages, lymphocytes, and plasma cells) which seemed to be encapsulated by deposition of irregular bundles of fibrous connective tissue showing increased proliferation of vascular structures.

Conclusion

It was concluded that a single course of non‐surgical treatment of peri‐implantitis using ERL may not be sufficient for the maintenance of failing implants. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.
Individual and collective fluid dynamics of swimming cells
Authors: Kessler John O.
Published: April 2006

Gravitational and viscous torques acting on swimming micro-organisms orient their trajectories. The horizontal component of the swimming velocity of individuals of the many algal genera having a centre of mass displaced toward the rear of the cell is therefore in the direction g × ([dtri ] × u), where g is the acceleration due to gravity. This phenomenon, called gyrotaxis, results in the cells swimming toward downward-flowing regions of their environment. Since the cells’ density is greater than that of water, regions of high (low) cell concentration sink (rise). The horizontal component of gyrotaxis reinforces this type of buoyant convection, whilst the vertical one maintains it. Gyrotactic buoyant convection results in the spontaneous generation of descending plumes containing high cell concentration, in spatially regular concentration/convection patterns, and in the perturbation of initially well-defined flow fields. This paper presents a height- and azimuth-independent steady-state solution of the Navier-Stokes and cell conservation equations. This solution, and the growth rate of a concentration fluctuation, are shown to be governed by a parameter similar to a Rayleigh number.
Space-laboratory and numerical simulations of thermal convection in a rotating hemispherical shell with radial gravity
Authors: Hart John E. , Glatzmaier Gary A. , Toomre Juri
Published: April 2006

The Sun and the giant planets rotate and possess deep shells of convection. Some basic aspects of prototypical global convection have been studied with a laboratory model operated in the microgravity environment of Spacelab 3 that flew on the space shuttle Challenger in May 1985. This experiment studied thermally driven circulations within a rotating hemispherical shell of fluid across which are imposed radial and latitudinal temperature gradients. The radial force of gravity is modelled by imposing a strong electric field across the shell, with dielectric polarization forces producing radial accelerations proportional to temperature. When the influence of rotation is large, the experiments yield north-south oriented columnar convection in equatorial and subequatorial regions. As the differential heating is increased, these roll-like cells interact with mid-latitude waves, ultimately being destroyed by turbulent, horizontally isotropic convection that moves down from the pole. When a significant equator-to-pole temperature difference is imposed on the boundaries, spiral waves develop on top of a strong meridional circulation. Intricate, non-axisymmetric, convective patterns that propagate in longitude and evolve in time are described. Schlieren visualizations of these laboratory flows are compared with three-dimensional nonlinear simulations.
Bending waves on inviscid columnar vortices
Authors: Leibovich S. , Brown S. N. , Patel Y.
Published: April 2006

Bending waves, perturbation modes leading to deflections of the vortex centreline, are considered for an infinitely long straight vortex embedded in an irrotational flow of unlimited extent. We first establish the general form of the dispersion relation for long waves on columnar vortices with arbitrary distributions of axial and azimuthal vorticity by a singular perturbation analysis of the Howard-Gupta equation. The asymptotic results are shown to compare favourably with numerical solutions of the Howard-Gupta equation for wavelengths comparable to the vortex core radius and longer. Dispersion relations are then found numerically for specific models of vortex core structures observed experimentally; here no restrictions are placed on wavelength. The linear dispersion relation has an infinite number of branches, falling into two families; one with infinite phase speed at zero wavenumber (which we call ‘fast’ waves), the other with zero phase speed (‘slow’ waves). In the long-wave limit, slow waves have zero group velocity, while the fast waves may have finite non-zero group speeds that depend on the form of the velocity profiles on the axis of rotation. Weakly nonlinear waves are described under most circumstances by the nonlinear Schrödinger equation. Solitons are possible in certain ‘windows’ of wavenumbers of the carrier waves. An example has already been presented by Leibovich & Ma (1983), who compute solitons and soliton windows on a fast-wave branch for a vortex with a particular core structure. Experimental data of Maxworthy, Hopfinger & Redekopp (1985) reveal solitons which appear to be associated with the slow branch, and these are computed for velocity profiles fitting their data. The nonlinear Schrödinger equation is shown to fail for long waves, and to be replaced by a nonlinear integro-differential equation.
Assessment of local isotropy using measurements in a turbulent plane jet
Authors: Antonia R. A. , Anselmet F. , Chambers A. J.
Published: April 2006

Following a review of the difficulties associated with the measurement and interpretation of statistics of the small-scale motion, the evidence for and against local isotropy is assessed in the light of measurements in a turbulent plane jet at moderate values of the Reynolds and Péclet numbers. These measurements include spatial derivatives with respect to different spatial directions of the longitudinal velocity fluctuation and of the temperature fluctuation. Relations between mean-square values of these derivatives suggest strong departures from local isotropy for both velocity and temperature. In contrast, the locally isotropic forms of the vorticity and temperature dissipation budgets are approximately satisfied. Possible contamination of the fine-scale measurements by the anisotropic large-scale motion is assessed in the context of the measured structure functions of temperature and of the measured skewness of the streamwise derivative of temperature. Structure functions are, within the framework of local isotropy, consistent with the average frequency and amplitude of temperature signatures that characterize the quasi-organized large-scale motion. Conditional averages associated with this motion account, in an approximate way, for the skewness of the temperature derivative but make negligible contributions to the skewness of velocity derivatives. The degree of spatial organization of the fine structure is inferred from conditional statistics of temperature derivatives.
Network models for two-phase flow in porous media Part 2. Motion of oil ganglia
Authors: Dias Madalena M. , Payatakes Alkiviades C.
Published: April 2006

The behaviour of non-wetting ganglia undergoing immiscible displacement in a porous medium is studied with the help of a theoretical simulator. The porous medium is represented by a network of randomly sized unit cells of the constricted-tube type. The fluid of a non-wetting ganglion is in contact with the wetting fluid at menisci which are assumed to be spherical cups. The flow in every constricted unit cell occupied by a single fluid is modelled as flow in a sinusoidal tube. The flow in every unit cell that contains a meniscus and portions of both fluids is treated with a combination of a Washburn-type analysis and a lubrication-theory approximation. The flow problem is thus reduced to a system of linear equations the solution of which gives the instantaneous pressures on the nodes, the flowrates through the unit cells, and the velocities of the menisci. The motion of a ganglion is determined by assuming quasi-static flow, taking a small time increment, updating the positions of the menisci, and iterating. The behaviour of solitary ganglia is studied under conditions of quasi-static displacement (Ca slightly larger than critical), as well as dynamic displacement (Ca substantially larger than critical). Shape evolution, rate of flow, mode of break-up, and stranding are examined. The stranding and break-up coefficients are determined as functions of the capillary number and the ganglion size for a 100 × 200 sandpack. The dependence of the average ganglion velocity on ganglion size, capillary number, viscosity ratio and dynamic contact angle is examined for the simple case of motion between straight rows of spheres. It is found, among other things, that when μo < μw the velocity of ganglia can be substantially larger than that of the displacing fluid.
Buoyancy-driven crack propagation: a mechanism for magma migration
Authors: Spence D. A. , Sharp P. W. , Turcotte D. L.
Published: April 2006

A solution has been obtained for steady propagation of a two-dimensional fluid fracture driven by buoyancy in an elastic medium. The problem is formulated in terms of an integro-differential equation governing the elastic deformation, coupled with the differential equation of lubrication theory for viscous flow in the crack. The numerical treatment of this system is carried out in terms of an eigenfunction expansion of the cavity shape, in which the coefficients are found by use of a nonlinear constrained optimization technique. When suitably non-dimensionalized, the solution appears to be unique. It exhibits a semi-infinite crack of constant width following the propagating fracture. For each value of the stress intensity factor of the medium, the width and propagation speed are determined. The results are applied to the problem of the vertical ascent of magma through the earth's mantle and crust. Values obtained for the crack width and ascent velocity are in accord with observations. This mechanism can explain the high ascent velocities required to quench diamonds during a Kimberlite eruption. The mechanism can also explain how basaltic eruptions can carry large mantle rocks (xenoliths) to the surface.
The effect of spatial restriction on the inner-layer structure of wall turbulence
Authors: Maruyama Shigeo , Tanaka Hiroaki
Published: April 2006

Hot-film-anemometer measurements were carried out in a shear flow between a flat plate and a moving plate fitted with an array of tall fences. The effect of spatial restriction by the fences on the inner-layer structure of the boundary layer developing on the flat-plate side was investigated. It was revealed that the inner-layer structure was maintained even when the tips of the fences were passing at a distance y+ = 45 from the flat plate; the flow did not become laminar-like until the tips reached y+ = 25. These results suggested the physical view that the inner layer of wall turbulence has a tough, self-sustaining structure, which is uniquely determined under a given mean wall shear stress and is hardly influenced by outer-layer disturbances provided that its own spatial extent of about 45 ν/u* from the wall is maintained.
The effect of flow oscillations on cavity drag
Authors: Gharib M. , Roshko A.
Published: April 2006

An experimental investigation of flow over an axisymmetric cavity shows that self-sustained, periodic oscillations of the cavity shear layer are associated with low cavity drag. In this low-drag mode the flow regulates itself to fix the mean-shear-layer stagnation point at the downstream corner. Above a critical value of the cavity width-to-depth ratio there is an abrupt and large increase of drag due to the onset of the ‘wake mode’ of instability. It is also shown by measurement of the momentum balance how the drag of the cavity is related to the state of the shear layer, as defined by the mean momentum transport $\rho\overline{u}\overline{v}$ and the Reynolds stress $\rho\overline{u^{\prime}v^{\prime}}$, and how these are related to the amplifying oscillations in the shear layer. The cavity shear layer is found to be different, in several respects, from a free shear layer.
Axisymmetrization and vorticity-gradient intensification of an isolated two-dimensional vortex through filamentation
Authors: Melander M. V. , Mcwilliams J. C. , Zabusky N. J.
Published: April 2006

We consider the evolution of an isolated elliptical vortex in a weakly dissipative fluid. It is shown computationally that a spatially smooth vortex relaxes inviscidly towards axisymmetry on a circulation timescale as the result of filament generation. Heuristically, we derive a simple geometrical formula relating the rate of change of the aspect ratio of a particular vorticity contour to its orientation relative to the streamlines (where the orientation is defined through second-order moments). Computational evidence obtained with diagnostic algorithms validates the formula. By considering streamlines in a corotating frame and applying the new formula, we obtain a detailed kinematic understanding of the vortex's decay to its final state through a primary and a secondary breaking. The circulation transported into the filaments although a small fraction of the total, breaks the symmetry and is the chief cause of axisymmetrization.
Stokes flow down a wall into an infinite pool
Authors: Hansen Erik B.
Published: April 2006

The two-dimensional flow of a thin film down a vertical or tilted plane wall into an infinite pool is studied in the Stokes approximation, the principal aim being to determine the shape of the fluid surface. Results are obtained for fluids with or without surface tension. Earlier results by Ruschak, that the surface tension gives rise to thickness variation of the film, are confirmed. For small or vanishing surface tension a dip of the pool surface is found to exist close to the wall. The case of a wall moving downwards is also considered.
Characteristics of ejections in turbulent channel flow
Authors: Bogard D. G. , Tiederman W. G.
Published: April 2006

Quantitative measurements of the structure of ejections from the wall region have been made using conditional-sampling techniques. Discrete ejections from a burst event were identified using fluorescent-dye flow visualization simultaneously with streamwise, u, and normal, v, velocity measurements. These velocity measurements, at y+ = 15, were conditionally sampled based on different phases of the ejection event. Features of the ejection which were educed from the conditional sampling were found to be very sensitive to the phase alignment. Results showed that ejections were characterized by a rapid deceleration at the leading edge followed by a strong positive velocity gradient at the trailing edge. An intense second-quadrant uv spike occurred immediately following the leading edge. This uv peak was highly correlated with a positive peak in the v velocity. The first ejection which occurred in a burst was found to be significantly more intense than the following ejections. Many characteristics of bursts which have been obtained from previous conditional-sampling studies were found to correspond to different phases of the ejection event.
Growth and collapse of translating compound multiphase drops: analysis of fluid mechanics and heat transfer
Authors: O~uz H. N. , Sadhal S. S.
Published: April 2006

The time history is examined of the motion of a compound multiphase drop formed by a vapour bubble completely covered by its liquid phase in another immiscible liquid. The compound drop is growing or collapsing owing to change of phase while it is translating under buoyant forces. In the limit of large surface-tension forces the interfaces are spherical. An exact analytical solution for the fluid-mechanical part of the problem can be obtained. The heat-transfer treatment of the problem, however, requires numerical solution if we are to include convective terms along with time dependence. The drag component induced by radial velocity contributes to the total drag on the bubble in eccentric configuration. This drag force is towards the centre of the drop in the case of growth and has an effect of restoring concentricity. However, it is found that, in the case of growth, the compound drop, in general, cannot maintain its configuration of two non-intersecting eccentric spheres. On the other hand, in the case of collapse the bubble stays inside the drop if the collapse velocity is high enough. The complete analysis exhibits some interesting flow patterns relating to compound drops and bubbles. The time-dependent Nusselt number for a single bubble generally decreases with time but it may have a strong dependence on the compound-drop configuration, as well as the conductivities of the participating liquids. The radial convection opposes heat transfer but it has to compete with translatory convection, which is usually overwhelming in the case of growth.
Axisymmetric vortex breakdown with and without temperature effects in a container with a rotating lid
Authors: Lugt Hans J. , Abboud Michel
Published: April 2006

A flow circulation in a closed circular-cylindrical container is produced by a rotating lid. After a transient phase from an initial state at rest a steady-flow situation is reached for a certain parameter range. In a subspace of this parameter range an undulating meridional flow occurs that may exhibit at the axis of rotation one or several separation bubbles which are interpreted as vortex breakdown. Numerical calculations on the basis of the Navier-Stokes equations for incompressible homogeneous and Boussinesq fluids enable the study of the influence of various flow parameters on the properties of these separation bubbles. The parameters varied are the Reynolds, Prandtl, Rayleigh, and Eckert numbers together with the ratio of height to radius of the container. The numerical results are in good agreement with experiments performed by Vogel, Ronnenberg, and Escudier. The stability of the fluid motions in these experiments with respect to non-axisymmetric disturbances strongly suggests that the corresponding axisymmetric solutions of the Navier-Stokes equations are stable configurations.
A second-moment closure study of rotating channel flow
Authors: Launder B. E. , Tselepidakis D. P. , Younis B. A.
Published: April 2006

The second-moment closure applied by Gibson & Launder (1978) to buoyant turbulent flows is here employed without modification to compute the effects of Coriolis forces on fully-developed flow in a rotating channel. The augmentation of turbulent transport on the pressure surface of the channel and its damping on the suction surface seem to be well captured by the computations, provided the flow near the suction surface remains turbulent. The rather striking alteration in shape of the mean velocity profile that occurs as the Rossby number is increased from 0.06 to 0.2 is shown to be explicable in terms of the modification to the intensity of the turbulent velocity fluctuations normal to the plate; for the larger value of Rossby number these fluctuations become larger than those in the flow direction causing what at low spin rates is a source of shear stress to become a sink.
Experiments on the trajectory and circulation of the starting vortex
Authors: Auerbach David
Published: April 2006

Various reasons have been given as to why the trajectories and circulations of vortices generated at sharp edges do not follow classical similarity-theory predictions for at least an initial short time. Amongst these are the effect of the particular flow geometry (e.g. duct with wedge, nozzle) distant from the salient edge (for rectilinear vortices); axisymmetry (for ring vortices); end effects (for rectilinear vortices); viscous diffusion; finite thickness of the detaching shear layer, as well as secondary vorticity caused by the interaction of the primary vortex with the edge at which it was generated. A further process that may be active is that of viscous entrainment. Experiments, in which essentially straight-line vortices were generated, indicate that of the seven possibilities mentioned, the first five do not play a significant part. All models consist of a basic flow onto which the modelled vortex is superposed. Thus either the basic flow or the vortex model are at fault. The basic flow onto which the vortex is superposed may well not be a pure edge flow, but one that is already taking on the character of an entraining jet flow. On the other hand, the vortex model fails to incorporate secondary vorticity which, particularly when rolled up, might be expected to be dynamically important.
The effects of surface tension and tube inclination on a two-dimensional rising bubble
Authors: Couët Benoit , Strumolo Gary S.
Published: April 2006

The effects of surface tension σ and tube inclination β on the Froude number Fr of a large bubble rising in a two-dimensional duct is considered. It is found that there exists either one (for small σ and β > 0°) or a set (for any σ and β = 0°) of Fr-values for which the bubble has a continuous derivative at the nose. By selecting either this single Fr (or the maximum of the set), we obtain solutions in excellent agreement with both theoretical predictions and experimental results.
Calculations of edgetone flow with forced longitudinal oscillations
Authors: Ohring Samuel
Published: April 2006

Numerical calculations were carried out to study the effect of forced, symmetric, longitudinal flow oscillations on the inherent, strongly antisymmetrical oscillations of a previously studied edgetone flow at a Reynolds number of 450. The flow consists of a two-dimensional jet issuing from a nozzle and impinging on a body with a wedge-shaped leading edge. The flow is assumed to be incompressible, laminar and two-dimensional, and a finite-difference vorticity/stream-function formulation of the Navier-Stokes equations is employed. Three cases were considered with various combinations of forcing frequency and amplitude. It was found that for the two cases with large forcing amplitudes, the naturally dominant flow frequencies lock-in to the forcing frequency and its harmonics. In the third case the forcing amplitude was smaller and lock-in was not observed but the forced oscillations still had a significant impact on the flow. Mode competition between symmetric and antisymmetric modes is discussed for the three cases along with the manner in which the jet vortical structure is altered as a function of time and space. Results for all three cases are presented in the form of computer drawn equivorticity lines and plots of frequency spectra for the jet oscillations and for the pressure on the wedge.
The initial evolution of gravity-capillary waves
Authors: Janssen Peter A. E. M.
Published: April 2006

In this paper we discuss the initial evolution of wind-generated, gravity-capillary waves by means of a dynamical model that includes the effects of wind input, viscous dissipation and three-wave interactions. In particular, we study the generation of the initial wavelets by wind and the subsequent migration of the peak of the spectrum to lower wavenumbers. Under certain conditions a sudden migration of the peak wavenumber is found. It is argued that this sudden migration is related to the phenomenon of second-harmonic resonance. We also observe that during the generation of the initial wavelets by wind, nonlinear three-wave interactions may be important. Therefore, the experimental determination of the growth rate of the waves by wind by just analysing the time series of the surface elevation (as is done by e.g. Kawai 1979 and Plant & Wright 1977) might be in error.
Simulation of flow between concentric rotating spheres. Part 2. Transitions
Authors: Marcus Philip S. , Tuckerman Laurette S.
Published: April 2006

We examine the transitions among the steady-state axisymmetric spherical Couette flows with zero, one, and two vortices per hemisphere. The steady flows are reflection symmetric with respect to the equator, but some of the transitions that we find break this symmetry. This is the first study to reproduce numerically the transitions to the one-vortex flow from the zero- and two-vortex flows. In our study, we use a numerical initial-value code to: (i) compute the bifurcation diagrams of the steady (stable and unstable) states, (ii) solve for the most unstable or least stable linear eigenmode and eigenvalue of a steady state, (iii) calculate the velocity field as a function of time during both the linear and nonlinear stages of the transitions, and (iv) determine the energy transfer mechanism into and out of the antireflection-symmetric components of the flow during the transitions.

Our study provides the explanation of the laboratory observation that some transitions occur only when the inner sphere of the Couette-flow apparatus is accelerated or decelerated quickly, whereas other transitions occur only when the acceleration is slow.
Experimental studies of wakes behind circularly capped bubbles
Authors: Bessler W. F. , Littman H.
Published: April 2006

The wake behind a circularly capped bubble rising in fluids of different viscosity has been experimentally investigated using aspirin powder for flow visualization and high-speed photography synchronized with pressure-time measurements to measure the pressure field. The bubble plus its primary wake with a cusped tail is observed to contain symmetric pressure minima within the primary wake. Adjacent to the boundary wake is a free shear layer which contains large-scale vortices generated near the bubble rim that remain essentially stationary to an observer in the laboratory reference frame. The change in wake geometry and the transition to an ellipsoidal bubble shape as fluid viscosity increases is documented.

The airfoil shape of the boundary of the circularly capped bubble and its closed primary wake is modelled using a Joukowski transformation in which the Joukowski constant is adjusted to match the experimental and potential-flow pressures along the bubble cap. The model successfully predicts the frontal pressure field, and the wake size and shape. The Davies & Taylor bubble-cap boundary condition is also verified.
A model for the dynamics of polymers in laminar shear flows
Authors: Keyes D. E. , Abernathy F. H.
Published: April 2006

A novel primitive model is proposed for the hydrodynamic behaviour of an isolated dissolved polymer molecule in a laminar shear flow. The model, in which inertial effects are neglected, allows for rotation and partial stretching of the molcule, but not for bending. Dilute solutions of flexible long-chain polymers have been experimentally observed to exhibit periodic velocity fluctuations distinct from turbulence over a broad frequency range when flowed in high-shear-rate water-table and pipe configurations. In these experiments, the frequency of the fluctuations does not increase with increasing shear rate; rather, it is lowest in the regions of the flow where the shear is the highest. A manifestation of viscous shear thickening has also been observed in these laminar flows. The proposed polymer representation appears capable of accounting for the salient features of these flows with adjustment of a single dimensionless parameter, a ratio of polymer-spring and solvent-viscosity forces.
Stability bounds on turbulent Poiseuille flow
Authors: Ierley G. R. , Malkus W. V. R.
Published: April 2006

For steady-state turbulent flows with unique mean properties, we determine a sense in which the mean velocity is linearly supercritical. The shear-turbulence literature on this point is ambiguous. As an example, we reassess the stability of mean profiles in turbulent Poiseuille flow. The Reynolds & Tiederman (1967) numerical study is used as a starting point. They had constructed a class of one-dimensional flows which included, within experimental error, the observed profile. Their numerical solutions of the resulting Orr-Sommerfeld problems led them to conclude that the Reynolds number for neutral infinitesimal disturbances was twenty-five times the Reynolds number characterizing the observed mean flow. They found also that the first nonlinear corrections were stabilizing. In the realized flow, this latter conclusion appears incompatible with the former. Hence, we have sought a more complete set of velocity profiles which could exhibit linear instability, retaining the requirement that the observed velocity profile is included in the set. We have added two dynamically generated modifications of the mean. The first addition is a fluctuation in the curvature of the mean flow generated by a Reynolds stress whose form is determined by the neutrally stable Orr-Sommerfeld solution. We find that this can reduce the stability of the observed flow by as much as a factor of two. The second addition is the zero-average downstream wave associated with the above Reynolds stress. The three-dimensional linear instability of this modification can even render the observed flow unstable. Those wave amplitudes that just barely will ensure instability of the observed flow are determined. The relation of these particular amplitudes to the limiting conditions admitted by an absolute stability criterion for disturbances on the mean flow is found. These quantitative results from stability theory lie in the observationally determined Reynolds-Tiederman similarity scheme, and hence are insensitive to changes in Reynolds number.
Melting the roof of a chamber containing a hot, turbulently convecting fluid
Authors: Huppert Herbert E. , Sparks R. Stephen J.
Published: April 2006

The input of a hot, turbulently convecting fluid to fill a chamber can result in the roof of the chamber melting. The rate of melting of the roof is here analysed experimentally and theoretically. Three separate cases are considered. The melt may be heavier than the fluid and initially sink through it. The intense motion in the fluid then mixes the falling melt in with it. Alternatively, the melt may be less dense than the fluid and form a separate layer between the roof and the fluid. This melt layer can itself be in quite vigorous convective motion. An intermediate case is shown to be possible, wherein the melt is initially denser than the fluid, and sinks. As its temperature increases and its density decreases, it becomes less dense than the surrounding fluid and rises. Experimental simulations of each of these three cases are described. The experiments employ a roof of either wax or ice which is melted by the aqueous salt solution beneath it. The second case, that of a light melt, has important geological applications. It describes the melting of the continental crust by the emplacement of a hot, relatively dense input of fluid basaltic rock. Both the basaltic layer and the resultant granitic melt layer crystallize and increase their viscosities as they cool. These effects are incorporated into the analysis and the rate of melting and the temperatures of the two layers are calculated as functions of time. The process is exemplified by the formation of the Cerro Galan volcanic system in Northwestern Argentina over the last 5 million years. An Appendix analyses the thermal history of the fluid in a chamber that does not melt and compares the results obtained with those derived previously.
The surface velocity field in steep and breaking waves
Authors: Melville W. K. , Rapp Ronald J.
Published: April 2006

Coincident simultaneous measurements of the surface displacement and the horizontal velocity at the surface of steep and breaking waves are presented. The measurements involve a novel use of laser anemometry at the fluctuating air-water interface and clearly show the limitations of surface displacement measurements in characterizing steep and breaking wave fields. The measurements are used to examine the evolution of the surface drift velocity, spectra, wave envelopes, and forced long waves in unstable deep-water waves. Preliminary results of this work were reported by Melville & Rapp (1983).
Deep-water plunging breakers: a comparison between potential theory and experiments
Authors: Dommermuth Douglas G. , Yue Dick K. P. , Lin W. M. , Rapp R. J. , Chan E. S. , Melville W. K.
Published: April 2006

The primary objective of this paper is to provide a detailed confirmation of the validity of potential-flow theory for describing steep gravity waves produced in an experimental tank. Very high-resolution computations are carried out which use a refined mixed Eulerian-Lagrangian solution scheme under the assumptions of potential flow. The numerical results for a plunging breaker produced by a programmed piston-type wavemaker are found to be in excellent agreement with tank measurements up to and including overturning. The calculated free-surface elevations are almost indistinguishable from measured profiles, even close to where the wave plunges. The horizontal and vertical water-particle velocities measured with a laser anemometer throughout the water depth at two longitudinal stations are also well predicted by the theory. In contrast to the fully nonlinear theory, predictions based on linearized theory become poorer as the wave packet moves down the tank. To allow other investigators to evaluate the computations and experiments, the Fourier amplitudes and phases which completely specify the time history of the wavemaker's velocity are given in Appendix B.
Incoherent turbulence structure in the near wake of a normal plate
Authors: Kiya M. , Matsumura M.
Published: April 2006

In this paper experimentally studied characteristics of various frequency components of incoherent velocity fluctuations in the near wake behind a thin normal plate immersed in a uniform flow are described. Measurements were made at a position 8 plate heights downstream of the plate where the wake had a marked periodicity, so that coherent vortices shed from the plate are expected to have a small dispersion in streamwise spacing, transverse location, strength and shape. Shearing stress associated with the incoherent fluctuations is mainly contributed by components with frequencies around half of the vortex-shedding frequency fs on one side of the wake. The ½fs frequency component appears to be caused by the spanwise locations of ribs, which are connected to the coherent vortices, being different from vortex to vortex. A probable spanwise arrangement of the ribs is suggested.
Excitation of long internal waves by groups of short surface waves incident on a barrier
Authors: Agnon Yehuda , Mei Chiang C.
Published: April 2006

The effects of diffraction by a long barrier on second-order long waves forced by sinusoidally modulated short incident waves are examined for a two-layered model ocean. When the group velocity of the short waves lies between the phase velocities of the longest baroclinic and barotropic modes, long internal waves of the frequency equal to twice the modulational frequency of the short waves are found to radiate away from the edge ray which divides the geometrical shadow and the illuminated region. In particular the baroclinic wave can penetrate the shadow. This penetration occurs when the internal long wave is not resonated by short surface waves.