bluuebunny/crossref_metadata_2025 huggingface dataset:
The Bibliotheca of Gabriel Harvey
Authors: Stern Virginia F.
Published: April 2006

The titles in an individual's library should be an excellent indicator of his interests. In the case of the extensive and remarkably varied collection of annotated volumes belonging to the Renaissance scholar Gabriel Harvey, knowledge of the contents of his library can reveal much not only about the man but about his era as well.

Harvey, eldest of a family of four brothers and two sisters, was born about 1550 in Essex at Saffron Walden, an important town of that period, situated about fifteen miles southeast of Cambridge. A person of considerable intellectual attainments he became a Cambridge don and by 1578 had published several original works in Latin prose and poetry. Although highly esteemed by his close friend the poet Edmund Spenser and by a number of eminent Cambridge scholars, Harvey was undoubtedly resented by others, perhaps because of his espousal of such antitraditional notions as Ramus’ reforms of Aristotelian logic, his awareness of his own intellectual superiority, and his fellow students' disdain for his middle-class background.
St. Thomas More and Music: The Epigrams
Authors: Carpenter Nan C.
Published: April 2006

Among the Latin epigrams of Thomas More, several are highly interesting for musical reasons. Two bear the caption ‘Poem Translated from an English Song.’ The first of these (63), beginning ‘O cor triste,’ reads in literal English translation,

Break, sad heart, pitiably engulfed in deepest woe. Let this be the end of your punishment. Show your mistress your bloody wounds. In short, it is she, only she, who will keep us two apart. Alas, how long shall I in my misery thus weep and complain? Come, dreaded death, and release me from monstrous woes.

The song on which this is based has apparently not yet been found.
Renaissance Attitudes to New Testament Apocryphal Writings: Jacques Lèfevre d'Étaples and His Epigones
Authors: Backus Irena
Published: April 2006

The standard medieval view of New Testament Apocrypha was that they were Christian writings (related to matters treated in the canonical books of the Bible), which had to be treated with caution and often dismissed as heretical. A list of the Apocrypha figured in the [Pseudo-]Gelasian Decree. In the Renaissance, for authors such as Lèfevre d'Etaples, Nicholas Gerbel and many others, the term assumed a multiplicity of meanings, both positive and negative. This article shows that although no attempts were made in the early 16th century to bring N. T. Apocrypha together into a corpus, the editors' ambivalent and complex attitude to texts such as the Laodiceans or Paul's Correspondence with Seneca led to their definitive marginalisation and encouraged their subsequent publication (by Fabricius and others) as corpora of dubious writings.
Donor cell leukemia in a patient developing 11 months after an allogeneic bone marrow transplantation for chronic myeloid leukemia
Authors: Ataergin Selmin , Arpaci Fikret , Cetin Turker , Guran Sefik , Yakicier Cengiz , Beyzadeoglu Murat , Ozet Ahmet
Published: April 2006

A 38‐year‐old female with chronic myeloid leukemia underwent an allogeneic bone marrow transplantation from her full‐matched brother. Eleven months later, she readmitted with an acute leukemia that was shown to be of donor origin. The patient never achieved a remission even after chemotherapies with cytarabine and mitoxantrone, donor lymphocyte infusion, and second allogeneic peripheral blood stem cell transplantation. Donor cell leukemia (DCL) is sometimes misdiagnosed as relapse by clinicians and the real incidence may be higher than expected. Cytogenetic and molecular techniques may be helpful to clarify the issue of the leukemia. The current case is another case of DCL reported in the literature after an allogeneic transplant for a kind of leukemia. Am. J. Hematol. 81:370–373, 2006
Modeling of Cdc25B Dual Specifity Protein Phosphatase Inhibitors: Docking of Ligands and Enzymatic Inhibition Mechanism
Authors: Lavecchia Antonio , Cosconati Sandro , Limongelli Vittorio , Novellino Ettore
Published: April 2006

The Cdc25 dual specificity phosphatases have central roles in coordinating cellular signalling processes and cell proliferation. It has been reported that an improper amplification or activation of these enzymes is a distinctive feature of a number of human cancers, including breast cancers. Thus, the inhibition of Cdc25 phosphatases might provide a novel approach for the discovery of new and selective antitumor agents. By using the crystal structure of the catalytic domain of Cdc25B, structural models for the interaction of various Cdc25B inhibitors (1–13) with the enzyme were generated by computational docking. The parallel use of two efficient and predictive docking programs, AutoDock and GOLD, allowed mutual validation of the predicted binding poses. To evaluate their quality, the models were validated with known structure–activity relationships and site‐directed mutagenesis data. The results provide an improved basis for structure‐based ligand design and suggest a possible explanation for the inhibition mechanism of the examined Cdc25B ligands. We suggest that the recurring motif of a tight interaction between the inhibitor and the two arginine residues, 482 and 544, is of prime importance for reversible enzyme inhibition. In contrast, the irreversible inhibition mechanism of 1–4 seems to be associated with the close vicinity of the quinone ring and the Cys473 catalytic thiolate. We believe that this extensive study might provide useful hints to guide the development of new potent Cdc25B inhibitors as novel anticancer drugs.
A Fluorine Scan at the Catalytic Center of Thrombin: CF, COH, and COMe Bioisosterism and Fluorine Effects on pKaand log DValues
Authors: Schweizer Eliane , Hoffmann‐Röder Anja , Schärer Kaspar , Olsen Jacob A. , Fäh Christoph , Seiler Paul , Obst‐Sander Ulrike , Wagner Björn , Kansy Manfred , Diederich François
Published: April 2006

A series of 16 tricyclic thrombin inhibitors was prepared by using the 1,3‐dipolar cycloaddition of azomethine ylides derived from 3‐ or 4‐hydroxyproline and 4‐bromobenzaldehyde, withN‐(4‐fluorobenzyl)maleimide as the key step. The terminal pyrrolidine ring of the inhibitors was systematically substituted to explore the potential bioisosteric behavior of CF, COH, and COMe residues pointing into the environment of the catalytic center of a serine protease. X‐ray crystal structure analyses revealed a distinct puckering preference of this ring. Substitution by F, HO, and MeO has a strong effect on the basicity of the adjacent pyrrolidine nitrogen center which originates from two σ‐inductive pathways between this center and the electronegative O and F atoms.gem‐Difluorination decreases the pKavalue of this tertiary amine center to <2, making the conjugated ammonium ion a moderately strong acid. Unexpectedly, F substitution next to the nitrogen center reduced the lipophilicity of the ligands, as revealed by measurements of the logarithmic partition coefficient log D. The biological assays showed that all compounds are thrombin inhibitors with activities betweenKi=0.08 and 2.17 μM. Bioisosteric behavior of F, HO, and MeO substituents was observed. Their electronegative F and O atoms undergo energetically similar polar interactions with positively polarized centers, such as the N atom of His 57 which is hydrogen bonded to the catalytic Ser 195. However, for energetically similar polar interactions of CF, COH, and COMe to occur, sufficient space is necessary for the accommodation of the Me group of the COMe residue, and a H‐bond acceptor must be present to prevent unfavorable desolvation of the COH residue.
A microphone array system with echo canceller
Authors: Kobayashi Kazunori , Furuya Ken'Ichi , Kataoka Akitoshi
Published: April 2006

This paper proposes a microphone array unified with an echo canceller that resolves the problem of deteriorated echo suppression performance due to variations of the echo path when a microphone array and an echo canceller are connected. In a teleconferencing system, high‐quality sound acquisition with noise suppression is desirable in addition to acoustic echo suppression. However, in a configuration in which a microphone array to suppress the noise and an echo canceller to suppress the echo are simply connected, the adaptation for the echo canceller cannot follow the echo path variations due to directivity control of the microphone array, so that there is a problem of deteriorated echo suppression performance. In the microphone array with an echo canceller proposed in this paper, the training of the microphone array and that of the echo canceller are performed in a unified way. In this way, the problem of deteriorated echo suppression performance due to echo path variations can be resolved. An evaluation experiment shows that the proposed method can perform stable noise suppression and echo cancellation. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 89(10): 23–32, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20090
A Series of One‐ to Three‐Dimensional Copper Coordination Polymers Based on N‐Heterocyclic Ligands
Authors: He Xiang , Lu Can‐Zhong , Wu Chuan‐De , Chen Li‐Juan
Published: April 2006

A family of copper coordination polymers containing different N‐heterocyclic ligands, namely [Cu(CN)(dmpyz)]n (1),[Cu2(CN)2(imz)]n (2), [Cu3(CN)(trz)2]n (3), [Cu6(CN)6(dmtrz)3]n(4), [Cu2(CN)(5‐metta)]n (5), [Cu2(CN)(5‐phtta)]n (6), and {[Cu6(CN)6(dmtrz)]2[Cu2(CN)2(dmtrz)2]}n (7) has been prepared and structurally characterized by X‐ray crystallography. The crystal structures of 1 and 2 are 1D chain frameworks. Compound 3 is a twofold interpenetrating 2D supramolecular framework in which the cyanide groups act as bridging ligands to link the copper centers into an unusual bilayer motif with large channels. Compounds 4–6 all possess 3D networks. Compound 4 is constructed by two parts: 2D rectangular‐grid layers and {Cu2(CN)2(dmtrz)2} building blocks. Compound 5 is built up by X‐shaped chains that connect each other in an ABAB arrangement to generate the3D network. The structure of 6 is a 3D network includingone‐dimensional square‐grid channels, with a shortest Cu2···Cu2A (A: –x + 1, –y + 1, –z) distance of about 2.347(1) Å. Compound 7 features a peculiar 3D + 1D network in which 1D guest metal‐organic polymer chains are filled in an unusual 3D architecture constructed by double helical host tubes. Compounds 1–7 show a systematic variation in dimensionality from 1D to 3D to 3D + 1D. The luminescence properties of these compounds have been also studied. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Locally acquired hepatitis E virus infection, El Paso, Texas
Authors: Amon Joseph J. , Drobeniuc Jan , Bower William A. , Magaña Jorge C. , Escobedo Miguel A. , Williams Ian T. , Bell Beth P. , Armstrong Gregory L.
Published: April 2006

Hepatitis E virus (HEV) is an enterically transmitted RNA virus that causes both epidemic and sporadic cases of acute hepatitis. Despite sero‐surveys showing antibody to HEV in up to 36% of the US population, acute hepatitis E has been reported among individuals with no history of international travel only three times in the United States. We report a case of apparently locally‐acquired hepatitis E that occurred in El Paso, Texas that was 98% similar to a previously isolated HEV found in swine in the United States. Like the three previous cases, a thorough investigation found no conclusive sources of infection. Active case surveillance found no additional cases.J. Med. Virol. 78:741–746, 2006. © 2006 Wiley‐Liss, Inc.
Correlations between synthetic peptide‐based enzyme immunoassays and immunofluorescence assay for detection of human herpesvirus 8 antibodies in different Argentine populations
Authors: Pérez Celeste , Tous Mónica , Benetucci Jorge , Gómez Jorge
Published: April 2006

Human herpesvirus 8 (HHV‐8) antibody tests vary in sensitivity and specificity, depending on the population tested and on the type of assay. In this study, we evaluated the sensitivity and specificity of two peptide enzyme immunoassays using a multiple antigenic peptide (PK8.1‐MAP) or a chimeric peptide (PK8.1‐orf65) as the antigens and determined the HHV‐8 seroprevalence in different Argentine polulations using an immunofluorescence assay (IFA) as reference. For analysis, when either or both of the peptide EIAs were positive, the specimen was considered positive (PEIA). We estimated the sensitivity and specificity of PEIA to be 97% using Kaposi's sarcoma (KS) patients and healthy individuals as positive and negative controls respectively. Then, we expanded the control groups to include IFA positive men who have sex with men (MSM) and IFA negative blood donors. The sensitivity decreased to 83% but specificity remained high at 98%. Concordance between PEIA and IFA was 77% for 1/40 IFA titers and increased to 90% for titers ≥1/160. Seroprevalences for HHV‐8 performed in the HIV positive MSM were (IFA 73.1%; PEIA55.2%); heterosexuals (52.5%, 22.2%), which includes injecting drug users (IDU) (54.0%, 32.4%) and non‐IDU (51.6%, 16.1%). The inclusion of non‐KS HHV‐8 IFA positive individuals to the positive controls may be a substantial improvement towards the realistic assessment of assay sensitivity. These peptide EIAs can be used for trends in populations with high probablity of being HHV‐8 infected and negative results should be confirmed by IFA. IFA test is still the most suitable test for populations with low probabilities of being infected. J. Med. Virol. 78:806–813, 2006. © 2006 Wiley‐Liss, Inc.
Phantom Chain Simulations of Realistically Sized Polymer‐Based Nanocomposites
Authors: Vacatello Michele
Published: April 2006

Summary: Phantom chain MC simulations have been performed for realistically sized systems of polymer chains filled with solid nanoparticles. The results of the simulations and simple theoretical considerations are used to rationalize a number of parameters relevant to the characterization of these systems. Even when the average number of nanoparticles in contact with a chain is very small (much less than unity), the nanoparticles are nodes of highly interconnected transient networks bridged by the polymer chains.

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Complete assignments of 1H and 13C NMR data for seven arylnaphthalide lignans from Justicia procumbens
Authors: Yang Meihua , Wu Jun , Cheng Fan , Zhou Yuan
Published: April 2006

Three new arylnaphthalide lignans named 6′‐hydroxy justicidin A (1), 6′‐hydroxy justicidin B (2) and 6′‐hydroxy justicidin C (3) have been isolated from the whole plant of Justicia procumbens, together with four known ones, neojusticin A (4), chinensinaphthol methyl ester (5), isodiphyllin (6) and taiwanin C (7). The complete assignments of 1H and 13C NMR chemical shifts for the new lignans and the 13C NMR chemical shifts for the known lignans were obtained for the first time by means of 2D NMR techniques, including HSQC and HMBC. Copyright © 2006 John Wiley & Sons, Ltd.
Continuously improving PSM effectiveness—A practical roadmap
Authors: Arendt Steve
Published: April 2006

PSM practices and formal management systems have been in place in many companies for more than 20 years. PSM is widely credited for perceived reductions in major accident risk and in improved chemical industry performance. Nevertheless, many companies continue to be challenged by resource pressures, inadequate management system audit results, and stagnant process safety incident performance.

While most companies claim to advocate Continuous Improvement, few have actually put substance into these words and succeeded in practice. This is partly because there is no clear vision of what PSM performance and continuous improvement are. This article defines the following function:

PSM Effectiveness = f [PSM performance + PSM efficiency]

Continuous improvement can address performance issues or efficiency issues or both. Companies are seeking new ways to improve process safety management activities. This article defines these terms and gives examples and lessons that show ways companies are improving performance, efficiency, and effectiveness. © American Institute of Chemical Engineers Process Saf Prog, 2006
Fate of the herbicides glyphosate, glufosinate‐ammonium, phenmedipham, ethofumesate and metamitron in two Finnish arable soils
Authors: Laitinen Pirkko , Siimes Katri , Eronen Liisa , Rämö Sari , Welling Leena , Oinonen Seija , Mattsoff Leona , Ruohonen‐Lehto Marja
Published: April 2006

The fate of five herbicides (glyphosate, glufosinate‐ammonium, phenmedipham, ethofumesate and metamitron) was studied in two Finnish sugar beet fields for 26 months. Soil types were sandy loam and clay. Two different herbicide‐tolerant sugar beet cultivars and three different herbicide application schedules were used. Meteorological data were collected throughout the study and soil properties were thoroughly analysed. An extensive data set of herbicide residue concentrations in soil was collected. Five different soil depths were sampled. The study was carried out using common Finnish agricultural practices and represents typical sugar beet cultivation conditions in Finland. The overall observed order of persistence was ethofumesate > glyphosate > phenmedipham > metamitron > glufosinate‐ammonium. Only ethofumesate and glyphosate persisted until the subsequent spring. Seasonal variation in herbicide dissipation was very high and dissipation ceased almost completely during winter. During the 2 year experiment no indication of potential groundwater pollution risk was obtained, but herbicides may cause surface water pollution. Copyright © 2006 Society of Chemical Industry
Rapid bidirectional allele‐specific PCR identification for triazine resistance in higher plants
Authors: Tian Xin , Darmency Henri
Published: April 2006

Triazine resistance is reported to be due to chloroplast herbicide target insensitivity in most species, and this is most often caused by a Ser264–Gly mutation at the D1 protein. In order to ascertain whether this mutation is really predominant amongst resistant plants, and also for gene flow studies, a rapid test is needed that allows the testing of large quantities of plants. Here a bidirectional allele‐specific PCR (polymerase chain reaction) identification is proposed. The designed primers were shown to be universal in the three grass and three broadleaf species examined. Copyright © 2006 Society of Chemical Industry
Binding of antibiotic amphotericin B to lipid membranes: A 1H NMR study
Authors: Gabrielska Janina , Gagoś Mariusz , Gubernator Jerzy , Gruszecki Wiesław I.
Published: April 2006

The 1H NMR technique was applied to study binding of AmB, an antifungal drug, to lipid membranes formed with egg yolk phosphatidylcholine. The analysis of 1H NMR spectra of liposomes, containing also cholesterol and ergosterol (at 40 mol%), shows that AmB binds preferentially to the polar headgroups. Such a binding restricts molecular motion of the choline fragment in the hydrophilic region at the surface of liposomes but increases the segmental motional freedom in the hydrophobic core. The same effects are also observed in the sterol‐containing membranes, except that the effect on the hydrophobic core was exclusively observed in the membranes containing ergosterol.
Stability of developing flow in a pipe: non-axisymmetric disturbances
Authors: Garg Vijay K.
Published: April 2006

Spatial stability results for the developing flow in a rigid circular pipe are presented for the velocity profile obtained by the Hornbeck (1963) method and compared with the available temporal stability results for the velocity profile obtained by Sparrow, Lin & Lundgren (1964). The disturbance is taken to be non-axisymmetric, and Gram–Schmidt orthonormalization is used to remove the parasitic errors during numerical integration.

It is found that the stability characteristics are very sensitive to the velocity field in the inlet region. At all axial locations investigated the critical frequency and critical wavenumber for the Hornbeck profile are larger than the corresponding values for the Sparrow profile while the critical Reynolds number is smaller. The minimum critical Reynolds number for the Hornbeck profile is only 13250 and occurs at $\overline{X} = 0.0032$ compared with 19780 at $\overline{X} = 0.0049$ for the Sparrow profile. The maximum difference between the two velocity profiles occurs near the boundary-layer edge but is within 5%. Results for the Hornbeck profile are found to be closer to the experimental data of Sarpkaya (1975).
Electrohydrodynamics in an electrostatic precipitator
Authors: Yamamoto T. , Velkoff H. R.
Published: April 2006

Experimental and theoretical studies were undertaken to investigate the particulatefree secondary flow interaction in the wire-type electrostatic precipitator. The secondary flow generated by the corona discharge is not negligible, and strong flow interactions take place owing to the induced circulatory cells. The calculated numerical results demonstrate close agreement with experiment.
An experimental investigation of the initial force of impact on a sphere striking a liquid surface
Authors: Moghisi M. , Squire P. T.
Published: April 2006

Detailed experimental results are presented for the initial impact force on a sphere striking a horizontal liquid surface vertically at speeds in the range 1-3 m s−1. Results are discussed in terms of an impact drag coefficient. Liquids having viscosities in the range 10−3−102 Pa s have been studied. For low viscosities the results have been compared with the theoretical calculations of Shiffman & Spencer. Good agreement has been found in most respects; in particular the impact force varies as the square root of the depth for depths less than a tenth of the radius. The impact drag coefficient has also been studied through the transition from inertia to viscosity-dominated conditions. The variation of the impact drag coefficient is presented as a function of Reynolds number, and its variation in the range 5 × 10−2 < Re < 5 × 103 is shown to resemble that of a fully immersed sphere moving steadily in a homogeneous fluid.
On the low-Reynolds-number flow in a helical pipe
Authors: Wang C. Y.
Published: April 2006

A non-orthogonal helical co-ordinate system is introduced to study the effect of curvature and torsion on the flow in a helical pipe. It is found that both curvature and torsion induce non-negligible effects when the Reynolds number is less than about 40. When the Reynolds number is of order unity, torsion induces a secondary flow consisting of one single recirculating cell while curvature causes an increased flow rate. These effects are quite different from the two recirculating cells and decreased flow rate at high Reynolds numbers.
Steady-state two-dimensional detonation
Authors: Bdzil J. B.
Published: April 2006

An analytical steady-state theory of the detonation ‘diameter effect’ is presented. This theory, which includes the off-axis flow, is a generalization of the Wood-Kirkwood analysis. When the state dependence of the reaction rate is stronger than that of the product of the sound speed squared and the flow divergence, detonation failure can occur. The leading term in the extrapolation of the detonation velocity to infinite charge size is quadratic in the inverse charge size and not linear as popularly believed. When calibrated to the detonation velocityvs.charge-size data, the theory reproduces the limited amount of experimental shock loci to a high degree of accuracy.
Conditional statistics of Reynolds stress in rough-wall and smooth-wall turbulent boundary layers
Authors: Raupach M. R.
Published: April 2006

Quadrant analysis has been used to investigate the events contributing to the Reynolds shear stress in zero-pressure-gradient turbulent boundary layers over regularly arrayed rough surfaces of several different densities, and over a smooth surface. By partitioning the stress into ejections, sweeps, and inward and outward interactions, it is shown that sweeps account for most of the stress close to rough surfaces, and that the relative magnitude of the sweep component increases both with surface roughness and with proximity to the surface. The sweep-dominated region delineates a ‘roughness sublayer’ with a depth of up to several roughness element heights, in which the turbulence characteristics depend explicitly on the roughness. In the remainder of the inner (or constant-stress) layer, and in the outer layer, the flow obeys familiar similarity laws with respect to surface roughness.

The difference ΔS0between the fractional contributions of sweeps and ejections to the stress is shown to be well related everywhere to the third moments of the streamwise and normal velocity fluctuations. Experimental proportionalities are established between the third moments and δS0, and are shown to agree with predictions made from cumulant-discard theory.

The time scale for the passage of large coherent structures past a fixed point,T, is assumed proportional to the mean time between occurrences in a specified quadrant of an instantaneous stressu'w’at leastHtimes the local mean stressu'w’, whereHis a threshold level. For both the ejection and sweep quadrants and for any choice ofH, it is found thatTscales with the friction velocityu*and the boundary-layer thickness δ, such thatTu*/δ is invariant with change of surface roughness.
Oscillatory flow around disks and through orifices
Authors: de Bernardinis B. , Graham J. M. R. , Parker K. H.
Published: April 2006

Two examples of unsteady, axisymmetric, separated flows are studied: unbounded oscillatory flow around a disk and bounded oscillatory flow through a sharp-edged orifice. Calculations are made assuming that the flow is inviscid and that the shed vortex sheets can be represented by sequences of discrete vortex rings. The solid bodies (i.e. the disk or the orifice and bounding tube) are also represented by a distribution of bound discrete vortex rings whose strengths are chosen to satisfy the Neumann or zero normal velocity boundary condition.

The results of flow visualization experiments and, for the orifice, pressure drop measurements are also reported. In general, the gross properties of the flows are predicted accurately.
Analytical and numerical aspects of the electromagnetic stirring induced by alternating magnetic fields
Authors: Fautrelle Y. R.
Published: April 2006

The dynamic effects of an alternating magnetic field on containers of conducting fluid are investigated in two special cases: (i) an infinitely long circular cylinder in a uniform magnetic field normal to the generators; (ii) a truncated circular cylinder in a uniform magnetic field parallel to the axis. Neglecting the motion effects in Maxwell's equations, the problem is conveniently decoupled into electromagnetic and dynamic parts. Using either analytical or numerical solutions of the electromagnetic equations, the electromagnetic forces are calculated and introduced in the motion equations. In the first case, asymptotic solutions of the Navier–Stokes equations valid for high frequencies are calculated and compared with numerical solutions obtained for the same geometry. The second case has been studied numerically, and the solutions are presented and interpreted.
Stability of a viscous liquid curtain
Authors: Lin S. P.
Published: April 2006

The stability of a viscous liquid curtain falling down steadily under the influence of gravity is investigated. Both spatially and temporally changing disturbances are considered in the linear analysis. Only the spatially growing sinuous disturbances whose group velocity points toward upstream are unstable. The group velocity is in the upstream direction only when the Weber number of the curtain flow exceeds ½. The predicted critical Weber number agrees completely with that found experimentally by Brown (1961). The viscosity is shown to have the dual roles of increasing the amplification rate as well as the damping rate of the disturbances.
Nonlinear Helmholtz oscillations in harbours and coupled basins
Authors: Miles John W.
Published: April 2006

Free and forced oscillations in a basin that is connected through a narrow canal to either the open sea or a second basin are considered on the assumption that the spatial variation of the free-surface displacement is negligible. The free-surface displacement in the canal is allowed to be finite, subject only to the restriction (in addition to that implicit in the approximation of spatial uniformity) that the canal does not run dry. The resulting model yields a Hamiltonian pair of phase-plane equations for the free oscillations, which are integrated in terms of elliptic functions on the additional assumption that the kinetic energy of the motion in the basin(s) is negligible compared with that in the canal or otherwise through an expansion in an amplitude parameter. The corresponding model for forced oscillations that are limited by radiation damping yields a generalization of Duffing's equation for an oscillator with a soft spring, the solution of which is obtained as an expansion in the amplitude of the fundamental term in a Fourier expansion. Equivalent circuits are developed for the various models.
A mathematical model of the dynamics of the inner ear
Authors: Holmes Mark H.
Published: April 2006

A three-dimensional hydroelastic model of the dynamical motion in the cochlea is analysed. The fluid is Newtonian and incompressible, and the basilar membrane is modelled as an orthotropic elastic plate. Asymptotic expansions are introduced, based on slender-body theory and the relative high frequencies in the hearing range, which reduce the problem to an eigenvalue problem in the transverse cross-section. After this, an example is worked out and a comparison is made with experiment and the earlier low-frequency theory.
Double-diffusive convection in an inclined fluid layer
Authors: Thangam Sivagnanam , Zebib Abdelfattah , Chen C. F.
Published: April 2006

The nonlinear double-diffusive convection in a Boussinesq fluid with stable constant vertical solute gradient, and bound by two differentially heated rigid inclined parallel plates is considered. The analysis was carried out by a Galerkin method for the cases when the angle of inclination was 0°, −45° and +45° (positive angle denotes heating from below, and negative angle denotes heating from above). The counter-rotating cells predicted by the linear theory merge into single cells with the same sense of rotation within a very short period of time even under slightly supercritical conditions. This is consistent with the experimental observations. Furthermore, as observed in the experiments, the evolution of instability is more rapid when heating is from above than when heating is from below. Our results for a salt-heat system are in excellent agreement with those based on the limiting case of Lewis number → 0 and Schmidt number → ∞.
A numerical study of vortex shedding from rectangles
Authors: Davis R. W. , Moore E. F.
Published: April 2006

The purpose of this paper is to present numerical solutions for two-dimensional time-dependent flow about rectangles in infinite domains. The numerical method utilizes third-order upwind differencing for convection and a Leith type of temporal differencing. An attempted use of a lower-order scheme and its inadequacies are also described. The Reynolds-number regime investigated is from 100 to 2800. Other parameters that are varied are upstream velocity profile, angle of attack, and rectangle dimensions. The initiation and subsequent development of the vortex-shedding phenomenon is investigated. Passive marker particles provide an exceptional visualization of the evolution of the vortices both during and after they are shed. The properties of these vortices are found to be strongly dependent on Reynolds number, as are lift, drag, and Strouhal number. Computed Strouhal numbers compare well with those obtained from a wind-tunnel test for Reynolds numbers below 1000.
Taylor vortices between two concentric rotating spheres
Authors: Bartels Fritz
Published: April 2006

The laminar viscous flow in the gap between two concentric spheres is investigated for a rotating inner sphere. The solution is obtained by solving the Navier-Stokes equations by means of finite-difference techniques, where the equations are restricted to axially symmetric flows. The flow field is hydrodynamically unstable above a critical Reynolds number. This investigation indicates that the critical Reynolds number beyond which Taylor vortices appear is slightly higher in a spherical gap than for the flow between concentric cylinders. The formation of Taylor vortices could be observed only for small gap widthss≤ 0·17. The final state of the flow field depends on the initial conditions and the acceleration of the inner sphere. Steady and unsteady flow modes are predicted for various Reynolds numbers and gap widths. The results are in agreement with experiment if certain accuracy conditions of the finite-difference methods are satisfied. It is seen that the equatorial symmetry is of great importance for the development of the Taylor vortices in the gap.
Hamiltonian dynamics of internal waves
Authors: Milder D. Michael
Published: April 2006

The isopycnal elevation ζ of a stratified incompressible fluid constitutes a generalized co-ordinate in terms of which the dynamics can be described in Hamiltonian form. The description is complete, and no additional variables are necessary, when the isopycnal circulation vanishes and when there are no remote sources of flow. The Hamiltonian, constructed in a co-ordinate system that coincides with the isopycnal surfaces, generates nonlinear equations of motion for ζ and its conjugate variable π which are formally exact for arbitrary displacements of the fluid and which are equivalent at lowest order to the usual linearized equations of internal waves. The appropriate scaling parameters for the nonlinearity are the isopycnal slope [dtri ]ζ and vertical strain ∂zζ, which emerge as the expansion parameters of an explicit powerseries representation of the Hamiltonian.
Stationary waves in a laboratory flume
Authors: McIver P.
Published: April 2006

The formation of stationary waves in a laboratory flume is described, and possible mechanisms for their production discussed. In particular, an investigation is made of waves on supercritical streams. The mechanism for creating such waves involves frictional action through the boundary layers and an approximate equation describing this process is presented and shown to give qualitative agreement with observation.
Viscous frictional torque in the flow between two concentric rotating rough cylinders
Authors: Nakabayashi Koichi , Yamada Yutaka , Kishimoto Toshinori
Published: April 2006

This paper describes an experimental study of the effects of surface roughness on the flow between two concentric cylinders, one of which rotates. The surface roughness has some effects on the coefficient of viscous frictional torque CM in the transient and in the fully developed turbulent region. In the fully developed rough turbulent flow, the value of CM depends on both the Reynolds number Rω and the relative roughness rm/k in the case where the outer cylinder rotates, but CM depends only on rm/k in the case where the inner cylinder rotates. The effect of the surface roughness of the inner cylinder is greater than that of the outer one for both cases.
Transport near a vertical ice surface melting in saline water: experiments at low salinities
Authors: Carey Van P. , Gebhart Benjamin
Published: April 2006

Time-exposure photographs of the buoyancy-driven flow adjacent to a submerged vertical ice surface melting in 10‰ saline water are presented for ambient water temperatures between 1 and 15°C. For ambient temperatures greater than 1·9°C, the thermal and saline components of the buoyancy force are at least partially opposed to each other. Since most past studies of ice melting in saline water have concentrated on oceanic salinities, little is known about the complicated flow behaviour which results from these opposed buoyancy effects at ambient water salinities between fresh water and oceanic salinities (35‰).

The results presented here provide new insight concerning the subtle mechanisms which arise in such flows. Photographs of the entire flow field document the many different and complicated flow configurations that arise. At 10‰, as the ambient temperature is increased from 1 to 15°C, regimes of upward, bi-directional and split flow are observed. In the latter circumstance, the flow is laminar and bi-directional over part of the ice surface and turbulent over the rest of the surface. Bi-directional flow results from reversal of part of the upward wake above the top of the ice surface. Split flow appears to be a consequence of the transition to turbulence of either the inner or outer portion of the laminar bi-directional flow. Measured velocity profiles, surface heat-transfer rates and interface temperatures agree well with the analytical results reported in a previous study for conditions that result in conventional boundary-layer flow. These experimental results, together with those of previous studies, indicate the approximate extent of the different flow regimes that arise for a vertical ice surface melting in cold, low-salinity water.
Self-generation of organized waves in an impinging turbulent jet at low Mach number
Authors: Rockwell Donald , Schachenmann Andreas
Published: April 2006

Self-generation of highly organized waves in a nominally turbulent jet at very low Mach number can arise from its impingement upon the downstream orifice of an axisymmetric cavity, having an impingement length much shorter than the corresponding acoustic wavelength. The oscillation frequencies are compatible with the resonant modes of a long pipe located upstream of the cavity and with jet-instability frequencies based on the column mode (0·3 [siml ] SD [siml ] 0·6), as well as the near-field shear layer mode (0·016 [siml ] Sθ0 [siml ] 0·03). Moreover, the frequency of the organized wave is constant from separation to impingement; consequently vortex pairing does not occur.

Within the cavity, the pressure amplitude associated with the organized wave is directly related to the phase difference between the organized velocity fluctuations at separation and impingement. Maximum pressure amplitude occurs when this phase difference, measured along the cavity (i.e. jet) centre-line, is 2nπ. Streamwise amplitude and phase distributions of the organized wave cannot be explained from purely hydrodynamic considerations; however, they can be effectively modelled by superposing contributions from hydrodynamic and acoustic waves. This aspect has important consequences for externally excited jets as well.
The viscous spreading of plane and axisymmetric gravity currents
Authors: Didden N. , Maxworthy T.
Published: April 2006

Measurements of the spreading rates of gravity-driven currents at both the surface and the bottom of a fluid layer of different density are reported. For the case of a constant inflow rate the spreading relations are derived by estimating the order of magnitude of the forces involved. After an initial balance between gravity and inertia forces the final spreading phase is governed by the balance between gravity and viscous forces. For the latter flow regime, measurements in plane and axisymmetric flow geometries agree well with the spreading relations for gravity currents with a no-slip boundary. The proportionality factor, which is not predicted from this model, is then determined from the measurements and a good agreement is found with the theoretical value derived in the accompanying paper by Huppert (1982).
Onset of convection in a variable-viscosity fluid
Authors: Stengel Karl C. , Oliver Dean S. , Booker John R.
Published: April 2006

The Rayleigh number R, in a horizontal layer with temperature-dependent viscosity can be based on the viscosity at T0, the mean of the boundary temperatures. The critical Rayleigh number Roc for fluids with exponential and super-exponential viscosity variation is nearly constant at low values of the ratio of the viscosities at the top and bottom boundaries; increases at moderate values of the viscosity ratio, reaching a maximum at a ratio of about 3000, and then decreases. This behaviour is explained by a simple physical argument based on the idea that convection begins first in the sublayer with maximum Rayleigh number. The prediction of Palm (1960) that certain types of temperature-dependent viscosity always decrease Roc is confirmed by numerical results but is not relevant to the viscosity variations typical of real liquids. The infinitesimal-amplitude state assumed by linear theory in calculating Roc does not exist because the convection jumps immediately to a finite amplitude at R0c. We observe a heat-flux jump at R0c exceeding 10% when the viscosity ratio exceeds 150. However, experimental measurements of R0c for glycerol up to a viscosity ratio of 3400 are in good agreement with the numerical predictions when the effects of a temperature-dependent expansion coefficient and thermal diffusivity are included.
Stability of circular Couette flow with variable inner cylinder speed
Authors: Neitzel G. P.
Published: April 2006

Energy & ability theory is employed to study the finite-amplitude stability of a viscous incompressible fluid occupying the space between a pair of concentric cylinders when the inner-cylinder angular velocity varies linearly with time. For the case with a fixed outer cylinder and increasing inner-cylinder speed, we find an enhancement of stability, consistent with a linear-theory result due to Eagles. When the inner-cylinder speed decreases, we find an initially decreased stability bound, indicating the possibility of hysteresis, while, if the inner cylinder is allowed to reverse direction and linearly increase in speed, we find significant stability enhancement.
Transition from regular to Mach reflection of shock waves Part 2. The steady-flow criterion
Authors: Hornung H. G. , Robinson M. L.
Published: April 2006

It is shown experimentally that, in steady flow, transition to Mach reflection occurs at the von Neumann condition in the strong shock range (Mach numbers from 2.8 to 5). This criterion applies with both increasing and decreasing shock angle, so that the hysteresis effect predicted by Hornung, Oertel & Sandeman (1979) could not be observed. However, evidence of the effect is shown to be displayed in an unsteady experiment of Henderson & Lozzi (1979).
Strouhal numbers of rectangular cylinders
Authors: Okajima Atsushi
Published: April 2006

Experiments on the vortex-shedding frequencies of various rectangular cylinders were conducted in a wind tunnel and in a water tank. The results show how Strouhal number varies with a width-to-height ratio of the cylinders in the range of Reynolds number between 70 and 2 × l04. There is found to exist a certain range of Reynolds number for the cylinders with the width-to-height ratios of 2 and 3 where flow pattern abruptly changes with a sudden discontinuity in Strouhal number. The changes in flow pattern corresponding to the discontinuity of Strouhal number have been confirmed by means of measurements of velocity distribution and flow visualization. These data are compared with those of other investigators. The experimental results have been found to show a good agreement with those of numerical calculations.
Transonic shear flow in a three-dimensional channel
Authors: Adamson T. C. , Sichel M.
Published: April 2006

Inviscid transonic shear flow in a rectangular channel is considered; opposite walls are parallel except in the region of interest, where one pair of opposing walls form a nozzle-like constriction. The flow exhibits the essential features found in an axial-flow rotor of zero stagger angle, where the relative velocity is transonic, the constricted passage being similar to the channel formed between two adjacent blades. Analytical solutions, valid to second order, are presented for the case where the ratio of the order of the change in velocity caused by the variation in flow area to the order of the change in velocity across the channel due to the shear is unity. The case where this ratio is small compared with one is discussed, as is the problem formulation for a flow with a shock wave in the passage
Homeotropic nematics heated from above under magnetic fields: convective thresholds and geometry
Authors: Salan J. , Guyon E.
Published: April 2006

The thermal convective instability of a nematic layer aligned perpendicular to horizontal plates displays original characteristics, due to the coupling of the nematic distortion with the temperature gradient; in particular the adverse temperature gradient threshold ΔTc can be modified by the application of a vertical (stabilizing) or horizontal (destabilizing) magnetic field. In addition, the application of a magnetic field H controls both the threshold of this instability and the geometric form of the instabilities above ΔTc.
A sufficient condition for the instability of columnar vortices
Authors: Leibovich S. , Stewartson K.
Published: April 2006

The inviscid instability of columnar vortex flows in unbounded domains to three-dimensional perturbations is considered. The undisturbed flows may have axial and swirl velocity components with a general dependence on distance from the swirl axis. The equation governing the disturbance is found to simplify when the azimuthal wavenumber n is large. This permits us to develop the solution in an asymptotic expansion and reveals a class of unstable modes. The asymptotic results are confirmed by comparisons with numerical solutions of the full problem for a specific flow modelling the trailing vortex. It is found that the asymptotic theory predicts the most-unstable wave with reasonable accuracy for values of n as low as 3, and improves rapidly in accuracy as n increases. This study enables us to formulate a sufficient condition for the instability of columnar vortices as follows. Let the vortex have axial velocity W(r), azimuthal velocity V(r), where r is distance from the axis, let Ω be the angular velocity V/r, and let Γ be the circulation rV. Then the flow is unstable if
$
V\frac{d\Omega}{dr}\left[ \frac{d\Omega}{dr}\frac{d\Gamma}{dr} + \left(\frac{dW}{dr}\right)^2\right] < 0.$
Instabilities of dynamic thermocapillary liquid layers. Part 2. Surface-wave instabilities
Authors: Smith Marc K. , Davis Stephen H.
Published: April 2006

A planar liquid layer is bounded below by a rigid plate and above by an interface with a passive gas. A steady shear flow is set up by imposing a temperature gradient along the layer and driving the motion by thermocapillarity. This dynamic state is susceptible to surface-wave instabilities that couple the interfacial deflection to the underlying shear flow. These instabilities are found to be directly related to the two-dimensional waves on an isothermal layer subject to wind shear as described by Miles and by Smith & Davis. Hence the surface-tension gradients are important only in that they drive the basic shear flow. The surface-wave stability characteristics for liquid layers with and without return-flow profiles are presented, and special attention is paid to long-wave instabilities. Comparisons are made with available experimental observations.
Temperature-gradient-driven electrohydrodynamic instability with unipolar injection in air
Authors: Hoburg James F.
Published: April 2006

Electrohydrodynamic instability is described in a planar region of gas, with unipolar injection through a linear temperature gradient, with corresponding mobility, viscosity, and density gradients. The role of charge-relaxation instability, which is incipient at a critical value of electric Rayleigh number in a uniform mobility layer, is distinguished from the mobility-gradient-driven mechanism, which can produce instability at much smaller voltage thresholds. Relative values of electroviscous time, viscous diffusion time and ion transit time determine the nature of the instability process. The instability is stationary or dynamic for wavenumbers respectively below or above a critical value. The fastest-growing wavenumber and corresponding growth rate are determined as functions of time constants and temperature gradient.