bluuebunny/crossref_metadata_2025 huggingface dataset:
Crime Victimisation: A Study into the Profile of Homicide Victims in Istanbul
Authors: Geleri Aytekin , Demirbilek Mesut
Published: April 2006

This study attempts to explore the characteristics of homicide victimisation and the nature of homicide victims in Istanbul between 1996 and 2000. The purpose of the study is twofold. First, to draw a profile of the victim of homicide incidents. Second, to establish a homicide data set for researchers to use. Using data provided from the Homicide Bureau of Istanbul Police Department as a major database, 578 homicide cases have been examined. The findings of this research show that males predominate as victims. Homicide victimisations are more likely to occur in ‘not visible’ locations. Firearms are the overwhelming choice as a murder weapon. The reasons for homicide incidents are mostly disputes, domestic quarrels, and disputes over money.
Prevention of Crime and Community Policing in India: An Empirical Evaluation of the Strategies and Practices of the Delhi Police
Authors: Sharma Rajvir
Published: April 2006

The police are faced with new challenges in a democratising India that is beset with corruption, and has a predominantly parochial social structure, an unequal distribution of national wealth and prevailing poverty. Policing urban areas is also becoming difficult in view of increases in the poor, the unemployed, organised crime, pressure on infrastructure and basic amenities, illegal settlements and ruralisation of the urban territories. There has been a growing perception of the decaying policing system in terms of credibility, popular image, corruption and attitudinal dimensions of policing in India (see Indian National Police Commission Report, vol. II, Delhi: Government of India, 1979).
The Dunce cAMP Phosphodiesterase PDE-4 Negatively Regulates Gαs-Dependent and Gαs-Independent cAMP Pools in the Caenorhabditis elegans Synaptic Signaling Network
Authors: Charlie Nicole K , Thomure Angela M , Schade Michael A , Miller Kenneth G
Published: April 2006

Forward genetic screens for mutations that rescue the paralysis of ric-8 (Synembryn) reduction-of-function mutations frequently reveal mutations that cause hyperactivation of one or more components of the Gαs pathway. Here, we report that one of these mutations strongly reduces the function of the Dunce cAMP phosphodiesterase PDE-4 by disrupting a conserved active site residue. Loss of function and neural overexpression of PDE-4 have profound and opposite effects on locomotion rate, but drug-response assays suggest that loss of PDE-4 function does not affect steady-state acetylcholine release or reception. Our genetic analysis suggests that PDE-4 regulates both Gαs-dependent and Gαs-independent cAMP pools in the neurons controlling locomotion rate. By immunostaining, PDE-4 is strongly expressed throughout the nervous system, where it localizes to small regions at the outside boundaries of synaptic vesicle clusters as well as intersynaptic regions. The synaptic subregions containing PDE-4 are distinct from those containing active zones, as indicated by costaining with an antibody against the long form of UNC-13. This highly focal subsynaptic localization suggests that PDE-4 may exert its effects by spatially regulating intrasynaptic cAMP pools.
Identification and Classification of Genes That Act Antagonistically to let-60 Ras Signaling in Caenorhabditis elegans Vulval Development
Authors: Ceol Craig J , Stegmeier Frank , Harrison Melissa M , Horvitz H Robert
Published: April 2006

The synthetic multivulva (synMuv) genes negatively regulate Ras-mediated vulval induction in the nematode Caenorhabditis elegans. The synMuv genes define three classes, A, B, and C, such that double mutants carrying mutations in genes of any two classes are multivulva. The class B synMuv genes include lin-35, a homolog of the retinoblastoma (Rb) tumor suppressor gene, as well as homologs of genes that function with Rb in transcriptional regulation. We screened for additional synMuv mutations using a strategy different from that of previous synMuv genetic screens. Some of the mutations we recovered affect new synMuv genes. We present criteria for assigning synMuv mutations into different genetic classes. We also describe the molecular characterization of the class B synMuv gene lin-65.
Nuclear Magnetic Resonance Based Investigations of Contaminant Interactions with Soil Organic Matter
Authors: Simpson Myrna J.
Published: April 2006

Contaminant interactions with soil organic matter (SOM) are central to understanding the fate and transport of chemicals in soil environments. Elucidation of sorption processes will facilitate the efficiency of passive remedial methods and improve the accuracy of risk assessment models. Early studies in the 1960s identified a relationship between SOM and the sorption of chemicals and laid the foundation for an area of research which is still active today. The onset of analytical instrumentation assisted the characterization of SOM chemical fractions, namely the fulvic acid (FA) and humic acid (HA) fractions. The employment of SOM chemical fractions in contaminant sorption studies has produced many empirical relationships between contaminant sorption behavior and SOM structure. More recently, molecular‐level techniques such as nuclear magnetic resonance (NMR) spectroscopy have been applied to examine specific interactions between contaminants and SOM fractions. These methods enable direct studies and are likely to further improve the fundamental understanding of contaminant interactions with SOM in the near future. For instance, NMR techniques should produce mechanistic information that will enable the accurate explanation of sorption phenomena at the macroscopic and landscape level. In addition to SOM chemical structure, researchers must consider the organic matter physical conformation at the soil–water interface because chemical methods provide structural information of the whole sample but do not provide detail about their physical architecture within the soil. This manuscript highlights studies which have examined contaminant interactions at the macroscopic‐ and molecular‐level and demonstrates the common themes stemming from different levels of investigation.
Creative Partners: The Marriage of Laura Battiferra and Bartolomeo Ammannati
Authors: Kirkham Victoria
Published: April 2006

From the time of their courtship until death parted them forty years later, Bartolomeo Ammannati (1511-1592) and Laura Battiferra (1523-1589) nurtured a loving relationship with reciprocal support for complementary careers. Their childless union generated two bodies of art, vast and beautiful. Renaissance contemporaries esteemed the Ammannati as a rarity, creative peers in a close marriage, but history has indifferently divorced them, dropping Bartolomeo to the ranks of second best and pushing his accomplished wife into obscurity. Reunited, the couple can return as they deserve, in the entwined lives that enriched their joint corpus and enhanced the fame each won as an individual — she for her poetry, praised by the most prominent men and women of culture in Counter Reformation Italy; he in his dual activity as sculptor and architect for projects ordered by popes in Rome, leaders of the new Society of Jesus, and three generations of Medici rulers in Florence.
Sir Epicure Mammon: A Study in 'Spiritual Fornication'
Authors: Jones Myrddin
Published: April 2006

In his illuminating chapter on The Alchemist in The Broken Compass, Edward B. Partridge discusses the central role of the parody of religion. But he adds the surprising comment that Jonson ‘only sketches it in outline lest the impiety neutralize the comic tone’ (The Broken- Compass, Chatto & Windus, London, 1957). I wish to argue that the caricature of religion in the figure of Sir Epicure Mammon is strong and would have been recognized and condemned as such by the contemporary audience.

The insane hyperbole of Mammon's language is evident immediately on his arrival at Lovewit's house. To him, the den of thieves and prostitutes in which we have just seen Dapper and Drugger pettily deluded and swindled, is ‘the novo orbe,’ ‘the rich Peru.'
When Did Machiavelli Write Mandragola*
Authors: Bertelli Sergio
Published: April 2006

The dating of La Mandragola is one of the most difficult problems in Machiavelli scholarship. Roberto Ridolfi, first in his biography of Machiavelli (1954) and more recently in an essay in La Bibliofilia (1962), proposed a new and apparently definitive solution; the comedy must have been written between January and February 1518, for the marriage of Lorenzo de’ Medici the younger, in the short space of one month, and performed soon after, on February 16, 1518.

In fact, we have very few and very late records about the performance of La Mandragola and the text of the comedy has come down to us only through an anonymous edition and one manuscript.
The Hangman's Noose and the Empty Box: Kyd's Use of Dramatic and Mythological Sources in The Spanish Tragedy (III.iv-vii)
Authors: Ardolino Frank
Published: April 2006

Source study has generally been discredited as a useful critical tool because of the past simplistic conception of the relationship between the source and its adapted context. Generally, source hunters emphasized parallel passages as the major proof of similarities between texts, merely listing the parallels without investigating more important critical implications. If we are to continue to consider source study a valuable scholarly tool—and there are good reasons to do so—we need to establish its interpretational relevance through a method which compares the conventional ideas and symbols of the source with the motifs and themes of the adapted context. Thus, the contextual method of ascription, as it shall be termed for purposes of discussion, will require an understanding of the interaction between the source's original context, including subsequent intellectual history, and the themes of the new context.
The Narrative Stance in ‘The Adventures of Master F.J.’: Gascoigne as Critic of His Own Poems
Authors: Schott Penelope Scambly
Published: April 2006

Too much discussion of George Gascoigne's ‘Adventures of Master F.J.’ has bogged down in the question of whether the story is fiction or autobiography. While it is impossible now to be sure to what degree the young Master F.J. is an autobiographical portrait of the younger Gascoigne, it is not only possible but inevitable to find Gascoigne the writer in the figure of G.T.

‘The Adventures’ as it first appears in the Hundreth Sundrie Flowres of 1573 is an older man's account of the misadventures of a younger man in love. The raconteur, one G.T., reports what happened to his young friend, Master F.J. Following much negative reaction, the story is transformed in the revised Posies of 1575 into ‘The Pleasant Fable of Ferdinando Jeronimi and Leonora de Valesco, translated out of the Italian riding tales of Bartello.’ This pseudo-translation becomes an anonymous omniscient narrator's account of the misadventures of a young man in love. The loss of G.T. as narrator entails with it the loss of a multitude of subtleties of attitude and tone.
M.O.A.L "What should that alphabetical position portend?" An Answer to the Metamorphic Malvolio*
Authors: Smith Peter J.
Published: April 2006

This paper is an attempt to answer the riddle set up by Malvolio's cryptic question which occurs in the box-tree scene (2.5) of Twelfth Night. The essay surveys a number of alternative solutions proposed by critics, editors, and actors. All are found, in their own ways, to be wanting: some are exposed as literal minded, too arcane, reliant upon language games that are unavailable to a theater audience or flawed by chronology. As the first step in decoding the puzzle, the paper rehearses a Renaissance view of semantics, according to which sense arises from utterances quintessentially — not, as modern linguistics would have it, approximately. Language, that is, is shown to signify inherently rather than conventionally. This linguistic veracity is shown to condemn Malvolio as he repeats an acrostic which he doesn't perceive, even while he utters it. The paper proposes that M.O.A.I. alludes to Sir John Harington's The Metamorphosis Of A Iax.
Arteriosclerotic events are less frequent in persons with chronic anemia: Evidence from families with hereditary spherocytosis
Authors: Schilling Robert F. , Gangnon Ronald E. , Traver Myrna
Published: April 2006

Because anemic persons have lower cholesterol and whole blood viscosity than those who are not anemic, we hypothesized that subjects with hereditary spherocytosis who have not had the spleen removed should have fewer arteriosclerotic events than unaffected family members. We defined arteriosclerotic events as myocardial infarct, stroke, coronary artery surgery, and carotid artery surgery. We compared the rate of these events in affected–not splenectomized persons to the rate in unaffected family members. The relative risk of an arteriosclerotic event in hereditary spherocytosis patients with a spleen was one fifth that in unaffected family members. These data support the hypothesis that chronic anemia retards the development of arteriosclerosis. Spherocytosis is another example of an inherited condition that conveys an advantage in one system and a disadvantage in another. Am. J. Hematol. 81:315–317, 2006. © 2006 Wiley‐Liss, Inc.
Enterovirus 71 infection induces Fas ligand expression and apoptosis of Jurkat cells
Authors: Chen Lien‐Cheng , Shyu Huey‐Wen , Chen Shun‐Hua , Lei Huan‐Yao , Yu Chun‐Keung , Yeh Trai‐Ming
Published: April 2006

T‐cell depletion is found in enterovirus 71 (EV71)‐infected patients with pulmonary edema. However, the mechanism that causes T‐cell depletion is unclear. To address this question, the effects of EV71 infection on the cell viability of human Jurkat T cells were studied. Viable viruses were recovered from both the culture supernatant and the cell lysate of Jurkat cells after EV71 infection. Results from reverse‐transcription polymerase chain reaction (RT‐PCR) and immunofluorescence assay confirmed further the presence of EV71 negative‐strand RNA and antigen, respectively, in EV71‐infected Jurkat cells. The viability of the Jurkat cells decreased after 48 hr of EV71 infection. Both terminal transferase end labeling (TUNEL) and DNA fragmentation assays demonstrated that the apoptosis of EV71‐infected Jurkat cells had increased. In addition, the expression of Fas ligand (FasL) in EV71‐infected Jurkat cells increased at both mRNA and surface expression levels. Taken together, these results confirmed that EV71 infected T cells and induced FasL expression, which may contribute to T‐cell apoptosis during EV71 infection. J. Med. Virol. 78:780–786, 2006. © 2006 Wiley‐Liss, Inc.
Convection in rectangular cavities with differentially heated end walls
Authors: Simpkins P. G. , Dudderar T. D.
Published: April 2006

This paper describes an experimental study of free convection in an enclosed rectangular cavity, the end walls of which are maintained at uniform but different temperatures. The experiments are carried out for a variety of Rayleigh numbers, R = αgΔTh4/κνl, and aspect ratios, L = l/h, for fluids with Prandtl number σ ≥ 10. For R ∼ O(103) it is shown that the basic structure of the flow field is a single two-dimensional cell for 0·25 ≤ L ≤ 9. When R > O(104) the boundary layers on the vertical walls control the flow field, but the basic overall structure remains unicellular. At greater values of R secondary vortices appear for all L ≥ 0·5. As R increases the intensity and then the number of these vortices increases. Measurements of the end-wall boundary-layer profiles at different values of R and L confirm Gill's boundary-layer analysis. The effects of variations of viscosity with temperature are discussed in the context of the observed boundary-layer profiles.

Core shear profiles and mass flux measurements are also reported. For L = 1 the observed shear profiles are in good agreement with numerical solutions of the Boussinesq equations. However, when L > 1 the observations suggest that the horizontal boundary layers have a significant effect on the core flow field. The stream function is demonstrated to be L-dependent in the boundary-layer regime, where variations due to R are second order. Similarities between the results of the present work and earlier observations by Elder and by Seki, Fukusaka & Inaba for tall slender cavities (L [Lt ] 1) are discussed.
Steady, supercritical flow in collapsible tubes. Part 1. Experimental observations
Authors: Kececioglu Ifiyenia , Mcclurken Michael E. , Kamm Roger D. , Shapiro Ascher H.
Published: April 2006

Experimental results are presented for steady, supercritical flow of a liquid in a thin-walled compliant tube which is in a state of partial collapse due to a negative transmural pressure. Particular attention is paid to the effects of longitudinal tension.

With a constant external pressure, friction acts to increase the area in the down-stream direction. With the tube tilted downward, friction may be so balanced by gravity forces as to result in an asymptotic approach to an equilibrium situation in which the area and velocity remain constant. When the downstream pressure is increased sufficiently, shock-like transitions to subcritical inflated states, with positive transmural pressure, occur. The longitudinal length scale of the shock is on the order of one to several tube diameters. The pressure rise across the shock lies between that for loss-free pressure recovery and that given by the Borda-Carnot sudden-expansion theory.

The presence of longitudinal tension causes a train of standing waves of area to appear upstream of a local area disturbance, such as a shock-like transition. The standing waves are superimposed upon the more gradual area changes associated with friction and gravity. The wave amplitude grows in the downstream direction. Theoretical interpretations of the observations are presented in the companion paper (part 2).
A note on turbulence measurements with a laser velocimeter
Authors: Lau J. C. , Whiffen M. C. , Fisher M. J. , Smith D. M.
Published: April 2006

In recent comparative measurements using a burst-counter type laser velocimeter and a hot-wire anemometer to assess the capabilities of the velocimeter (e.g. Barnett & Giel 1976; Lau, Morris & Fisher 1979), it was found that the laser velocimeter held good promise as an instrument for turbulence research, especially in high speed, high temperature flows where a hot-wire cannot be used. The axial mean velocities obtained with the LV compared very well with hot-wire measurements. Similarly, the characteristic shapes of the spectra and probability density distributions of the velocity fluctuations were faithfully reproduced. The trends in the distributions of the various turbulence characteristics (e.g. turbulence intensity, velocity covariances, skewness and kurtosis) in a given flow field were identical to those obtained with hotwires. The one significant difference between LV and hot-wire results was the magnitudes of the turbulence level. Since the LV results were obtained with the help of the latest validation and discrimination techniques (Asher 1973), which have now become standard equipment (Durst, Melling & Whitelaw 1976), such a discrepancy was unexpected. The reason for the discrepancy is now fairly clear and a method has been suggested by Whiffen, Lau & Smith (1978) on how to eliminate the error. But the approach is lengthy and time-consuming. This paper describes a method which effectively accomplishes the same end with less effort.
Large-eddy simulation of a passive scalar in isotropic turbulence
Authors: Antonopoulos-Domis M.
Published: April 2006

TEMTY, a code for large-eddy simulation of a passive scalar in isotropic turbulence, is developed and proved by successful simulation of experiment. The role of each term in the scalar equation and the concept of prefiltering the scalar equation is examined. The ratio of the exponents in the decay of velocity and temperature intensities is found to parametrize with the ratio Λu/Λ0, where Λu, Λ0, are the velocity and temperature Taylor microscales respectively.
Flow beneath a stagnant film on water: the Reynolds ridge
Authors: Scott John C.
Published: April 2006

Surface-active material is present in most naturally occurring water samples, and it naturally diffuses steadily to free surfaces, where it both reduces the surface tension and gives the surface elastic properties which enable it to resist compression. When the water flows so that the surface layer is trapped and compressed against a fixed shallow-draught barrier the film material makes the surface incompressible, and flow beneath the barrier forms a viscous boundary layer under the film. The stresses associated with this boundary layer are found to distort the surface in the region of the leading edge of the film, giving rise to a phenomenon which is commonly observed in nature and which has been called the Reynolds ridge. This paper describes experimental work on the measurement of the ridge, and compares the results with a theoretical model due to Harper & Dixon. Good agreement is indicated.
The stability of quasi-geostrophic fields induced by potential vorticity sources
Authors: Merkine Lee-Or
Published: April 2006

The stability of quasi-geostrophic barotropic fields induced by localized finite-amplitude potential vorticity sources or topographies which depend only on the zonal direction is investigated both analytically and numerically. The analytical study is for weak forcing. It demonstrates that the field induced by the topography is stable whereas the field induced by the potential vorticity source can be unstable. The growth rate is exponential and is a function of both nonlinearity and friction. In the absence of friction the flow field is always unstable. The instability takes the form of a current whose meridional wavenumber is that of a stationary Rossby wave. In the zonal direction the current exhibits long-scale oscillations and exponential decay. The numerical computations which are for strong forcing verify all the indications of the asymptotic study. They show a rapid exponential growth of a non-propagating but oscillatory wave packet whose location is fixed relative to the forcing. The zonal scale of the packet is that of a stationary Rossby wave. For weak forcing the instability can be responsible for changing the flow field from one quasi-steady state to another where the energy extraction takes place in the region of the source. It is efficient for potential vorticity sources whose length scale is comparable to the length scale of stationary Rossby waves. In agreement with the asymptotic study, fields induced by strong topographic forcing are found to be stable. The asymptotic analysis is also applied to baroclinic flows where the investigation is performed in the framework of the two-layer model. It is demonstrated that the same mechanism which operates in barotropic systems can also destabilize baroclinic flows which possess subcritical shears.
The converging shock wave from a spherical or cylindrical piston
Authors: Dyke Milton Van , Guttmann A. J.
Published: April 2006

A spherical or cylindrical cavity containing quiescent gas begins to contract at high constant radial speed, driving an axisymmetric shock wave inward to collapse at the centre. We analyse the flow field by expanding the solution in powers of time, and calculate 40 terms by delegating the arithmetic to a computer. Analysis of the series for the radius of the shock wave confirms Guderley's local self-similar solution for the focusing, including recent refined values for his similarity exponent, and yields higher terms in his local expansion. In the range of adiabatic exponent where the Guderley solution has been shown not to be unique we find, in accord with a conjecture of Gel'fand, that the smallest admissible similarity exponent is realized.
On characteristics of the water-particle velocity in a plunging breaker
Authors: Nakagawa Takeo
Published: April 2006

Three velocity components of water particles in a plunging breaker over a horizontal step on the bed of a two-dimensional laboratory wave tank have been determined simultaneously by means of an elaborate flowmeter that measures the flow drag on three ‘tension threads’, with each recording a separate flow component.

It is found that all three of the r.m.s. values in the plunging breaker become maximum at x/L ≈ 0·7, where x is the distance from the breaking point to the shore and L is the wavelength. It is found that both the velocity and r.m.s. values of the transverse flow component generated by the shoaling and wave breaking become comparable to those of the other two flow components.

On the basis of spectral analyses it is found that major wave frequencies in both the longitudinal and vertical flow components of the original two-dimensional wave survive even after experiencing relatively strong shoaling and wave breaking, and part of the original wave energy is transferred to the transverse flow component and is located at these major frequencies. It is found that the majority of the higher-harmonic-frequency components (or turbulent fluctuations) are generated in the shoaling process and that the wave breaking provides a relatively minor contribution to the generation. Finally, it is found that, through the shoaling and wave breaking, the original wave energy is transported to a frequency range lower than the primary wave frequency (negative cascade), as well as to the higher frequency range (positive cascade) in each flow component.
Azimuthal rotation in the axisymmetric meridional flow due to an electric-current source
Authors: Bojarevičs V. , Shcherbinin E. V.
Published: April 2006

The steady laminar flow driven by the meridional electromagnetic force due to an electric-current point source on a plane is considered. The previous studies of the problem (Shercliff 1970; Shilova & Shcherbinin 1971) lead to a self-similar solution of the full Navier–Stokes equations analogous to the classic Landau jet. The solution breaks down when a critical electric-current magnitude is exceeded (Sozou 1971). In the present paper the converging meridional flow is shown to be unstable to an axisymmetric azimuthal perturbation when the corresponding critical Reynolds number is exceeded. The flow solution breakdown is eliminated for the coupled converging and rotating flow. The physical process is suggested by the draining-vortex formation. The fluid-flow equations are solved by the Galerkin method, using expansions in Gegenbauer functions. The mechanism sustaining the rotation is examined; the increased angular momentum in the fluid region is maintained by the balance of viscous diffusion upstream and convection to the axis of symmetry. The experimental evidence for vortex formation is considered.
The deformation of a viscous particle surrounded by an elastic shell in a general time-dependent linear flow field
Authors: Brunn P. O.
Published: April 2006

The dynamics of a viscous particle surrounded by an elastic shell of arbitrary thickness freely suspended in a general linear flow field is investigated. Assuming the unstressed shell to be spherical, an analysis is presented for the case in which the flow-induced deformation leads to small departures from sphericity. The general time-dependent evolution of shape is derived and various special cases (purely elastic sphere, rigid and gaseous interior, elastic membranes) are discussed in detail. It is found that for steady-state flows the equilibrium deformations are absolutely stable and depend only upon the shell thickness, although the rates at which they are attained show the effect of the inside viscosity, too.
Transition of Taylor–Görtler vortex flow in spherical Couette flow
Authors: Nakabayashi Koichi
Published: April 2006

The critical Taylor number, phenomena accompanying the transition to turbulence, and the cellular structure of Taylor–Görtler vortex in the flow between two concentric spheres, of which the inner one is rotating and the outer is stationary, are investigated using three kinds of flow-visualization technique. The critical Taylor number generally increases with the ratio β of clearance to inner-sphere radius. For β [les ] 0.08, the critical Taylor number in spherical Couette flow is smaller than in circular Couette flow, but vice versa for β > 0.08. A pair of toroidal Taylor–Görtler vortices occurs first around the equator at the critical Reynolds number Rec (or critical Taylor number Tc). More Taylor–Görtler vortices are added with increasing Reynolds number Re. After reaching the maximum number of vortex cells, as Re is increased, the number of vortex cells decreases along with the various transition phenomena of Taylor–Görtler vortex flow, and the vortex finally disappears for very large Re, where the turbulent basic flow is developed. The instability mode of Taylor–Görtler vortex flow depends on both β and Re. The vortex flows encountered as Re is increased are toroidal, spiral, wavy, oscillating (quasiperiodic), chaotic and turbulent Taylor–Görtler vortex flows. Fourteen different flow regimes can be observed through the transition from the laminar basic flow to the turbulent basic flow. The number of toroidal and/or spiral cells and the location of toroidal and spiral cells are discussed as a means to clarify the spatial organization of the vortex. Toroidal cells are stationary. However, spiral cells move in relation to the rotating inner sphere, but in the reverse direction of its rotation and at about half its speed. The spiral vortices number about six, and the spiral angle is 2–10°.
Sedimentation in a dispersion with vertical inhomogeneities
Authors: Feuillebois Fran¸ois
Published: April 2006

Statistical studies of hydrodynamic interactions between many particles in a dilute dispersion raise a problem of divergent integrals. This problem arises in particular when calculating the average velocity of sedimentation of solid spheres in a viscous fluid. The solution to this problem was given by Batchelor (1972) for monodisperse suspensions of spheres, on the basis of an assumption of homogeneity. This assumption is removed here. The problem of divergent integrals is reconsidered. The solution treats as successive steps:

the average flow due to random statistically independent point forces;

the average flow due to random statistically independent solid spheres, without hydrodynamic interactions;

the average sedimentation velocity of random, pairwise-dependent solid spheres with hydrodynamic interactions, in a dilute suspension.

Considering the case of identical spheres, and assuming homogeneity in any horizontal plane, an expression is obtained for the average sedimentation velocity of a sphere in an otherwise inhomogeneous dispersion. The formula is written in terms of integrals involving probability distributions. It reduces, when the suspension is homogeneous, to a formula obtained by Batchelor.

The probability distributions are not calculated in this paper. In order to evaluate numerically the average velocity of sedimentation, a simple expression for the pair distribution function is assumed, and two different concentration profiles are considered, viz. a sinusoidal variation and a step function. In the case of sinusoidal concentration wave, it is found that the contribution of the inhomogeneity is, for small wavelengths, comparable in magnitude to that calculated for a homogeneous dispersion by Batchelor (1972), i.e. –6.55c.

The difference in velocity between the crest and trough of the wave is an increasing function of the wavelength. For a step function in concentration, particles at the top of the cloud start to fall faster, this effect being limited to a top layer about 10 radii thick.

For future study of the long-term behaviour of a sedimenting cloud, the evolution of the pair distribution function should be added to the present theory.
Unsteady natural convection in a cavity with internal heating and cooling
Authors: Patterson John C.
Published: April 2006

The problem of transient natural convection in a cavity of aspect ratio A < 1 driven by internal buoyancy sources and sinks distributed linearly in the horizontal and uniformly in the vertical is considered. Scaling analysis is used to show that a number of possible transient flow regions are possible, collapsing ultimately onto one of conductive, transitional, or convective steady-state flow regimes. A number of numerical solutions are obtained, and their relationships to the scaling analysis are discussed.
Viscous-inviscid interactions on axisymmetric bodies of revolution in supersonic flow
Authors: Kluwick A. , Gittler P. , Bodonyi R. J.
Published: April 2006

Using the method of matched asymptotic expansions, the interaction between axisymmetric laminar boundary layers and inviscid supersonic external flows is investigated in the limit of large Reynolds numbers. The resulting triple-deck equations are solved numerically for two different cases of body shapes: a cylinder-cone configuration and a configuration consisting of two concentric cylinders which are connected by a smooth curve. Solutions to the linearized as well as the fully nonlinear equations are presented.
Refraction-diffraction model for weakly nonlinear water waves
Authors: Liu Philip L.-F. , Tsay Ting-Kuei
Published: April 2006

A model equation is derived for calculating transformation and propagation of Stokes waves. With the assumption that the water depth is slowly varying, the model equation, which is a nonlinear Schrödinger equation with variable coefficients, describes the forward-scattering wavefield. The model equation is used to investigate the wave convergence over a semicircular shoal. Numerical results are compared with experimental data (Whalin 1971). Nonlinear effects, which generate higher-harmonic wave components, are definitely important in the focusing zone. Mean free-surface set-downs over the shoal are also computed.
Two-layer spin-up and frontogenesis
Authors: Linden P. F. , Heijst G. J. F. Van
Published: April 2006

The spin-up of a two-layer fluid in a cylinder with a free surface and with a thin lower layer is examined in the laboratory. It is found that when the increase in rotation rate of the cylinder is large enough the radial outflow in the viscous boundary layer on the tank bottom is sufficient to cause the interface to descend near the centre of the tank and to intersect the bottom. The intersection between the interface and the bottom produces a front between stratified (two-layer) fluid and a central region (called the bare spot) in which the upper layer is in direct contact with the bottom. It is observed that the radius of the circular bare spot increases until the lower layer is spun up. Observations of the maximum size of the bare spot are compared with a theoretical calculation in which it is assumed that the lower layer acquires the new angular velocity of the container and where viscous coupling between the layers is neglected. An expansion in F, the upper-layer Froude number, gives good agreement with the observations.

At larger times the circular front is observed to be unstable to frontal waves which appear to gain energy via baroclinic instability from the sloping density interface. At large amplitude these waves ‘break’, producing regions of closed streamlines in the upper layer. The shape of the bare spot is severely distorted by these waves and the associated motions. The effect of the bottom stress on the spin-up of the upper layer is found to be limited to the bare spot where it is in direct contact with the bottom. Some comments are made on the formation and decay of fronts in the benthic boundary layer of the ocean.
Axisymmetric Couette flow at large Taylor numbers
Authors: Townsend A. A.
Published: April 2006

Measurements have been made in flow between concentric cylinders with only the inner one rotating, for Reynolds numbers (based on flow gap) from 17 000 to 120 000, corresponding to Taylor numbers from 8 × 107 to 4 × 109. At the lower speeds (Reynolds numbers less than 30 000), the large-scale motion consists of toroidal eddies, highly uniform in spacing and intensity and convected by a slow axial flow past fixed sensors. By synchronizing an external oscillator with the passage frequency, flow velocity and small-scale turbulent intensity may be sampled at defined stages of the passage cycle and averaged to provide maps of the velocity fields and the associated distributions of small-scale intensity and Reynolds stress.

At higher speeds, the passage of toroidal eddies becomes too irregular to establish the passage cycle, but, by comparing the velocity fluctuations from four inclined hot wires placed near the outer cylinder, the current location of large-scale flow separation from the outer cylinder can be approximately determined. Statistics of the temporal variations of the location show that the large-scale motion still approximates to the toroidal form, but that there are azimuthal variations of separation position and velocity that indicate a change from toroidal to helical eddies. Conditional averages of flow velocity and small-scale turbulent intensity, based on relative distance from the position of flow separation, are very similar in form and magnitude to phase-selected averages obtained at lower speeds.

The considerable changes in the large-scale motion that occur as the Reynolds number increases from 300 to 1200 times the critical value are believed to arise from increase in the ‘turbulent Taylor number’ of the central flow, based on variation of angular momentum and on the eddy diffusion coefficients for linear and angular momentum. Effects on the motion of the slow axial flow, always less than 1% of the peripheral flow velocity, are also discussed.
Laminar flow through a slowly rotating straight pipe
Authors: Mansour Kamyar
Published: April 2006

We consider fully developed steady laminar flow through a pipe that is rotating slowly about a line perpendicular to its own axis. The solution is expanded for low Reynolds numbers in powers of a single combined similarity parameter and the series extended to 34 terms by computer. Analysis shows that convergence is limited by a square-root singularity on the negative real axis of the similarity parameter. An Euler transformation and extraction of the leading, secondary and tertiary singularities at infinity render the series accurate for all values of the similarity parameter. The major conclusion of this investigation is that the friction ratio in a slowly rotating pipe grows asymptotically as the ⅛ power of the similarity parameter and not as the ¼ power as previously deduced from boundary-layer analysis. This discrepancy between the present computer-extended method and boundary-layer analysis has also occurred in the similar problem of flow through a loosely coiled pipe (Van Dyke 1978).
Turbulence suppression in free turbulent shear flows under controlled excitation. Part 2. Jet-noise reduction
Authors: Hussain A. K. M. F. , Hasan M. A. Z.
Published: April 2006

It is shown that reduction of broadband (even total) far-field jet noise can be achieved via controlled excitation of a jet at a frequency in the range 0.01 < Stθ < 0.02, where Stθ is the Strouhal number based on the exit momentum thickness of the shear layer. Hot-wire measurements in the noise-producing region of the jet reveal that the noise suppression is a direct consequence of turbulence suppression, produced by early saturation and breakdown of maximally growing instability modes.
A perspective view of the plane mixing layer
Authors: Jimenez Javier , Cogollos Marta , Bernal Luis P.
Published: April 2006

A three-dimensional model of the plane mixing layer is constructed by applying digital image processing to laser fluorescence motion pictures of the layer, and displayed using computer graphic techniques. A system of streamwise counterrotating vortices is shown to exist on top of the classical spanwise eddies, and its influence in mixing is discussed briefly. Some quantitative information on their strength is also given.
The structure of strongly stratified flow over hills: dividing-streamline concept
Authors: Snyder William H. , Thompson Roger S. , Eskridge Robert E. , Lawson Robert E. , Castro Ian P. , Lee J. T. , Hunt Julian C. R. , Ogawa Yasushi
Published: April 2006

In stably stratified flow over a three-dimensional hill, we can define a dividing streamline that separates those streamlines that pass around the hill from those that pass over the hill. The height Hs of this dividing streamline can be estimated by Sheppard's simple energy argument; fluid parcels originating far upstream of a hill at an elevation above Hs have sufficient kinetic energy to rise over the top, whereas those below Hs must pass around the sides. This prediction provides the basis for analysing an extensive range of laboratory observations and measurements of stably stratified flow over a variety of shapes and orientations of hills and with different upwind density and velocity profiles. For symmetric hills and small upwind shear, Sheppard's expression provides a good estimate for Hs. For highly asymmetric flow and/or in the presence of strong upwind shear, the expression provides a lower limit for Hs. As the hills become more nearly two-dimensional, these experiments become less well defined because steady-state conditions take progressively longer to be established. The results of new studies are presented here of the development of the unsteady flow upwind of two-dimensional hills in a finite-length towing tank. These measurements suggest that a very long tank would be required for steady-state conditions to be established upstream of long ridges with or without small gaps and cast doubt upon the validity of previous laboratory studies.
The flow at a rear stagnation point is eventually determined by exponentially small values of the velocity
Authors: van Dommelen Leon L. , Shen Shan Fu
Published: April 2006

It is suggested that current conceptions about unsteady rear-stagnation-point flow do not fully describe the physics, since they show discrepancies from recent numerical results. The previously neglected exponentially small rotational perturbation velocity above the boundary-layer proves to have a dominating influence on the final boundary-layer development. An asymptotic analysis reveals possible difficulties for common computational schemes for viscous flows. Failure of the usual asymptotic matching rule in the analysis is in accordance with Fraenkel's warning on logarithmic expansions.
A note on the steady high-Reynolds-number flow about a circular cylinder
Authors: Peregrine D. H.
Published: April 2006

The most detailed theoretical description of the steady flow at high Reynolds number about a circular cylinder is given by Smith (1979). It appears to give a satisfactory description of much of the flow field. Numerical solutions for this flow computed by Fornberg (1985) are in conflict with some aspects of Smith's model.

An acknowledged weak point in Smith's argument is the lack of a detailed flow for the interior of the eddies, particularly with respect to their rear closure. This paper discusses this aspect of the flow with particular emphasis on the vorticity distribution and with the aid of a solution of the Navier–Stokes equations which is valid at the rear of the eddies. As a result an interpretation of Fornberg's results is possible. The self-induced velocity of translation of the vorticity distribution is considered and discussed with reference to the flow as Re → ∞.
Time-dependent viscous flow past an impulsively started rotating and translating circular cylinder
Authors: Badr H. M. , Dennis S. C. R.
Published: April 2006

A numerical study is made of the development with time of the two-dimensional flow of a viscous, incompressible fluid around a circular cylinder which suddenly starts rotating about its axis with constant angular velocity and translating at right angles to this axis with constant speed. The governing partial differential equations in two space variables and time are reduced to sets of time-dependent equations in one space variable by means of Fourier analysis. By truncating the Fourier series to a finite number of terms, a finite set of differential equations is solved to give an approximation to the theoretical flow. The solutions are obtained by numerical methods. Results are given for the initial development with time of the asymmetrical wake at the rear of the cylinder at Reynolds numbers R [ges ] 200, based on the diameter of cylinder, and at small rotation rates. The detailed results show the formation of a Kármán vortex street. The time development of this separated flow is compared in detail at R = 200 with recent experimental results. The details of the formation and movement of the vortices behind the cylinder and the velocity profiles in several locations are virtually identical in the experimental and theoretical studies. The variations with time of the lift, drag and moment exerted by the fluid on the cylinder are determined both by calculations and by means of approximate analytical expressions. The agreement between these results at small times is excellent.
Aerodynamics of slot-film cooling: theory and experiment
Authors: Fitt A. D. , Ockendon J. R. , Jones T. V.
Published: April 2006

A simple model is proposed for the two-dimensional injection of irrotational inviscid fluid from a slot into a free stream. In a certain range of values of the ratio of free-stream to injection total heads, the film thickness satisfies a nonlinear integral equation whose solution enables the mass flow in the film to be found. Some experiments are described which both agree with this theory when it is relevant and indicate its deficiencies at other values of the total head ratio.
On the interaction between fundamental and subharmonic instability waves in a turbulent round jet
Authors: Mankbadi Reda R.
Published: April 2006

The spatial interactions between a fundamental instability wave and its subharmonics in a turbulent round jet are studied for ‘natural’ or forced exit conditions. Time-averaging and conditional-averaging techniques are used to split each flow component into a mean one, a random turbulence one and several wave-like coherent-structure components at fundamental and subharmonic frequencies. The energy equations for the flow components are derived and integrated across the jet. Shape assumptions regarding the radial distributions of each flow component are used to obtain a set of nonlinear ordinary differential equations representing the energy interactions between the coherent components, while interacting with the mean flow and with the background turbulence. Vortex pairing is viewed here as occurring when the subharmonic absorbs energy from the fundamental and from the mean flow and exceeds the fundamental's level to become the dominant instability component. At the proper initial phase difference between the subharmonic and fundamental only the first subharmonic was found to amplify if the fundamental Strouhal number based on diameter is in the range of 0.6–1.0. For higher Strouhal numbers, several subharmonics can amplify. The pairing location moves closer to the nozzle exit with increasing excitation Strouhal number. The time-averaged coherent Reynolds stresses exhibit regions of sign change, indicating a reversal in the direction of energy transfer between the mean flow and the coherent components.