bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Quality and Water Intake in Traditional‐Till vs. No‐Till Paired Farms in Washington's Palouse Region
Authors: Kennedy Ann C. , Schillinger William F.
Published: April 2006

Many farmers in the steeply sloped Palouse region of eastern Washington and northern Idaho practice no‐till (NT) farming. Soil quality and water intake parameters were assessed in standing wheat (Triticum aestivum L.) stubble along summit, side, and toe‐slope positions in a 2‐yr study at three paired‐farm sites using traditional tillage (TT) vs. NT management. Paired sites had similar south‐facing aspect, slopes ranged from 29 to 45%, and NT fields had not been tilled from 2 to 20 yr. Soil aggregates >1000 μm were 5.4 to 9.8% higher in NT compared with TT. Soil organic carbon (SOC) in NT was 30% greater than in TT at the toe‐slope position. Dehydrogenase enzyme activity (DEA) was higher in TT, mainly due to the exposed CaCO3 layer at the side‐slope position and higher pH of TT. Phospholipid fatty acid methyl ester (PLFA) analysis showed that fungal biomarkers were higher and Gram positive and Gram negative biomarkers were lower in NT compared with TT. There were no differences in over‐winter soil water storage or ponded water infiltration rate in undisturbed standing wheat stubble between TT and NT, indicating soils that produce high wheat grain yield of 6 Mg ha−1 or more have similar water intake regardless of tillage history as long as the stubble is left standing over winter. Results show long‐term cumulative benefits of NT vs. TT on soil quality, but no differences in soil water intake when stubble is left standing over winter, possibly due to the high quantity of wheat root channels produced in both systems.
New Light on Marvell's ‘A Dialogue between the Soul and Body'
Authors: Datta Kitty Scoular
Published: April 2006

Marvell’ s ‘A Dialogue between the Soul and Body’ is one of those idiosyncratic poems which when read nowadays without a proper awareness of the tradition, both in prose and verse, upon which it plays tempts to an over-biographical interpretation and to an assorted variety of philosophical explanations. Indeed, quite contrary conclusions have been drawn from the inconclusiveness of the debate between soul and body—that Marvell is, at least for the space of the poem, dangerous cynic; Pyrrhonist in his suspension of a verdict; Cartesian in his dualism; Puritan idealist coming to terms with historical exigency;
Skelton's Magnyfycence
Authors: Winser Leigh
Published: April 2006

Six generations of students of Magnyfycence have accepted 1515-16 as the date of its composition. Largely as the result of William O. Harris's recent serious questioning of Robert Lee Ramsay's political interpretation of Magnyfycence there is sufficient cause for re-examining the date traditionally assigned the play. I shall review the reasons for the date and then propose, tentatively, that Magnyfycence was conceived, perhaps actually composed, before 1504 during Skelton's first experience at the Tudor court.

In Skelton's ‘Magnyfycence’ and the Cardinal Virtue Tradition Harris has demonstrated that Magnyfycence is probably not what Ramsay thought it was—a personal attack upon Cardinal Wolsey, his rise to power and his abuse of authority.
Leonardo Bruni and the Restoration of the University of Rome (1406)
Authors: Griffiths Gordon
Published: April 2006

Leonardo Bruni has been celebrated in the works of Hans Baron for his Florentine patriotism. What stimulated this in Bruni's early works (the Laudatio Florentinae Urbis and the second of the Dialogi addressed to Vergerio), according to Baron, was the Florentine victory over Giangaleazzo Visconti in 1402. Yet Bruni had hardly completed the last of these tributes to Florence before he was off for Rome to spend ten years in the papal curia.
John Minsheu: Scholar or Charlatan?
Authors: Schäfer Jürgen
Published: April 2006

John Minsheu, Shakespeare's contemporary, is primarily known as the author of id est, Ductor in Linguas, The Guide into Tongues (London, 1617). More than any other English work of the period the Ductor in Linguas reflects linguistic research and speculation at home and abroad and represents an important link in the beginnings of modern English lexicography. On the basis of this work Minsheu has been praised as a scholar, antiquarian, and etymologist of note.
The Turnip Wagon: A Boschian Motif Transformed
Authors: Gibson Walter S.
Published: April 2006

The theme of the Haywain, Hieronymus Bosch's great allegory of avarice (Fig. I), seems to have enjoyed a certain vogue in Brabant during the third quarter of the sixteenth century. Two manifestations of its influence were published and extensively analyzed some years ago by Lebeer, Grauls and Keyser. One of these is an etching by Frans Hogenberg, issued in 1559 by the Antwerp print publisher Bartholomeus de Mompere (Fig. 2). It depicts a broad plain crowded with figures whose acts of folly are epitomized by the large hay cart dominating the middle distance. The cart unmistakably shows Hogenberg's debt to Bosch, although he replaced the music-making lovers seated on Bosch's wagon with a devil triumphantly displaying two tufts of hay.
William Tyndale's Pentateuch: Its Relation to Luther's German Bible and the Hebrew Original
Authors: Hammond Gerald
Published: April 2006

The subject of this study is William Tyndale's 1530 translation of the Pentateuch. The historical and literary importance of Tyndale's Bible translation has been well established. In an England moving towards the Reformation he gave the greatest impulse to the use of the vernacular, and he laid the foundation for the "Biblical style" of the 1611 Authorized Version. What remains in dispute is the degree of Tyndale's independence: how far did he rely on his own resources, and how far was he dependent upon his predecessors, in particular Jerome's Vulgate, Luther's German Bible, the Latin translation of Pagninus, and the earlier English translation, the Wyclif Bible?
Hemoglobinopathies mimicking Hb S/β‐thalassemia: Hb S/S with α‐thalassemia and Hb S/Volga
Authors: Luo Hong‐Yuan , Heeney Matthew , Wang Winfred C. , Eung Shawn H. , Ware Russell E. , Steinberg Martin H. , Chui David H.K.
Published: April 2006

There are approximately 1200 known natural mutations of the human globin genes. In most clinical laboratories, the diagnosis of hemoglobin disorders is based on blood counts, hemoglobin electrophoresis, or column chromatography, which can identify common variant hemoglobins such as Hb S, C, and E, but are unable to definitively diagnose most other hemoglobin variants and thalassemia mutations. We report two unrelated cases, both thought initially to have Hb S/β‐thalassemia. Subsequent mutational analyses revealed that one is Hb S/S with compound heterozygosity for nondeletional α‐thalassemia mutations. The other is the first reported case of compound heterozygosity for Hb S and an unstable hemoglobin, Hb Volga. Correct diagnoses of these hereditary disorders are needed for prognosis and proper management and also for genetic counseling. These studies underscore the importance to correlate clinical course with laboratory diagnosis and to make DNA‐based diagnostics more widely available for patients with unusual or complicated hemoglobin disorders. Am. J. Hematol. 81:361–365, 2006. © 2006 Wiley‐Liss, Inc.
UGT1A1 polymorphism outweighs the modest effect of deletional (−3.7 kb) α‐thalassemia on cholelithogenesis in sickle cell anemia
Authors: Chaar Vicky , Kéclard Lysiane , Etienne‐Julan Maryse , Diara Jean Pierre , Elion Jacques , Krishnamoorthy Rajagopal , Romana Marc
Published: April 2006

Enhanced erythrocyte destruction in sickle cell anemia results in chronic hyperbilirubinemia. Only a subset of patients develop cholelithiasis. UGT1A1 promoter polymorphism is associated both with unconjugated bilirubin level and elevated risk for cholelithiasis in such subset. Here, we investigated the role of α‐thalassemia, yet another genetic factor that modulates hemolysis, in conferring protection from cholelithiasis. We show that, although α‐thalassemia is associated with modest reduction in hemolysis and unconjugated bilirubin level, UGT1A1 polymorphism outweighs its effect on cholethiogenesis in sickle cell anemia patients. Am. J. Hematol. 81:377–379, 2006. © 2006 Wiley‐Liss, Inc.
Novel valproic acid derivatives with hemoglobin F inducing activity
Authors: Rönndahl G. , Mönkemeyer S. , Schulze S. , Pekrun A. , Eikel D. , Nau H. , Witt O.
Published: April 2006

Pharmacological induction of hemoglobin F expression may be a promising approach for the treatment of β‐thalassemia and sickle cell disease. Valproic acid, a drug frequently used for the treatment of seizure disorders, has been shown to enhance fetal hemoglobin synthesis in erythroid cells. However, this effect is only modest and requires relative high concentrations. Therefore, the drug appears not to be applicable for the treatment of β‐globin chain disorders. Here, we describe the identification of novel valproic acid derivatives with potent hemoglobin F inducing activities at concentrations that presumably can be obtained in vivo. Am. J. Hematol. 81:374–376, 2006. © 2006 Wiley‐Liss, Inc.
Polymers or Supramolecules Generated From a New V‐Shaped Bis‐monodentate Ligand and the Effect of Steric Hindrance on Coordination Modes of the Ligand
Authors: Zhou Caihua , Wang Yaoyu , Li Dongsheng , Zhou Lijun , Liu Ping , Shi Qizhen
Published: April 2006

A new V‐shaped bis‐monodentate ligand L (L = 2,3′‐dipyridylamine) (1) has been designed and synthesized by alkylation reaction of pyridylamine. An investigation of the charge distributions of the coordination atoms and single‐point energy calculations of four conformers of ligand L based on the geometry of conformers optimized by the DFT (density functional theory) method was carried out. The results show that the four conformers of ligand L take on two stable and two less stable configurations. Theory forecasts that two relatively stable configurations present in complexes as probable coordination motifs of the ligand, and that steric hindrance of pyridine nitrogen atoms in isomers will affect its coordination ability together with the electronic factor. This forecast has been demonstrated by the coordination chemistry of ligand L, that is, configuration (a) and (b) of the ligand occur in the following reported complexes, which combines with AgI or CuII through two coordination modes (bidentate bridging or a monodentate mode) resulting in coordination polymers {[Ag (L)2]NO3}n (2), [Cu2(L)2(maa)4]n (maa = methacrylic acid) (3), and the mononuclear molecule [Cu(L)4](ClO4)2·2CH3CH2OH (4). The ligand assumes different coordination modes in the three complexes because of different levels of steric hindrance of the pyridine nitrogen atoms in the conformers. Interestingly, polymers 2 and 3 assume a 1D helical structure and a linear framework, respectively, and 4 has a 2D supramolecular architecture induced from hydrogen bond interactions. In addition, the magnetic properties of 3 have been explored, which shows a strong antiferromagnetic interaction.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Elimination of spurious trends in marine wind data using pressure observations
Authors: Lindau Ralf
Published: April 2006

The use of pressure reports from merchant ships provides a reasonable way to correct the trends in marine wind data. However, the appropriate method to derive pressure gradients from the ship data is controversial. Three principal proceedings are analysed: The method of using three simultaneous pressure observations, the method of deriving monthly mean pressure gradients, and the method presented by Lindau (1995). For the first two, it is shown that they are unable to provide reliable reference values for wind speed; if observation triples are used, random errors in the raw data cause systematic errors in the derived pressure gradients. The problem concerning monthly mean pressure gradients is that they are only proportional to the vector wind, but not to the scalar wind. Therefore, these methods are inapplicable for calibration purposes. The method of Lindau (1995) is recommended for a proper elimination of spurious trends in marine wind observations. Copyright © 2006 Royal Meteorological Society
An Error in Variables Method for Determining the Implicit Penultimate Copolymerization Ratios by On‐Line Monitoring of Reactions
Authors: Sünbül Didem , Giz Ahmet T.
Published: April 2006

Summary: In copolymerization systems with implicit penultimate effect, there are two radical reactivity ratios, sa and sb, which influence the reaction kinetics in addition to the monomer reactivity ratios, ra and rb, which govern the copolymer composition. Here, an error in variables method has been developed to determine sa and sb. It is based on continuous on‐line monitoring of the polymerization process, where monomer and polymer concentrations are measured through the monitoring of two independent properties of the system. The ratios and the corresponding χ2 values were found by taking into account errors emanating from measurements and from calibration of the instruments. It is shown that the kinetic data allows both ratios to be found if both monomer reactivity ratios are less than one. If the system is near ideality (rarb ≅ 1) or if both reactivities are greater than one, only an average radical reactivity ratio, $\overline s$, can be reliably determined.

The 2σ confidence contours for the 3 individual experiments. The reactivity ratios are ra = 0.5, rb = 0.2, sa = 0.3, sb = 0.4. For clarity the contours are plotted as functions of 1/sa and 1/sb.

magnified image

The 2σ confidence contours for the 3 individual experiments. The reactivity ratios are ra = 0.5, rb = 0.2, sa = 0.3, sb = 0.4. For clarity the contours are plotted as functions of 1/sa and 1/sb.
Repair of the main nerve trunk of the upper limb with end‐to‐side neurorrhaphy: An experimental study in rabbits
Authors: Zhang Zijie , Johnson Elizabeth O. , Vekris Marios D. , Zoubos Aristides B. , Bo Jinyan , Beris Alexandros E. , Soucacos Panayotis N.
Published: April 2006

The aim of this study was to assess the effectiveness of reinnervation using end‐to‐side neurorrhaphy in the upper extremity of the rabbit. The cut right ulnar nerve was repaired and sutured to the side of the median nerve about 3 cm above the elbow joint. The extent of reinnervation was quantitatively evaluated, as well as the integrity of the intact donor nerve in 36 rabbits randomly treated with fresh or delayed nerve repair with or without perineurotomy. Evaluations included nerve conduction velocity (NCV) of both the ulnar and medial nerves, dry muscle weight, and histologic examination (neurofilament stain and morphometric assessment) at 3 and 6 months postoperatively. NCV recovery rates were 79% and 87% for the ulnar nerve, and 89% and 94% for the median nerve compared to contralateral intact nerves, at 3 and 6 months, respectively. Flexor carpi ulnaris muscle mass measurements revealed a recovery in dry muscle weight of about 81% and 88% at 3 and 6 months, respectively, compared to the intact contralateral flexor carpi ulnaris. Histologic studies with neurofilament staining reveal numerous axonal sprouts at the distal end of the median nerve, indicative of myelinated axonal regeneration. Morphometric analysis demonstrated no difference between fresh and delayed repairs. These results indicate that in the upper extremity of rabbits, end‐to‐side neurorrhaphy permits axonal regeneration from the intact donor nerve, and is associated with satisfactory recovery. The effect of the procedure on the donor nerve was negligible. © 2006 Wiley‐Liss, Inc. Microsurgery, 2006
Secondary reanimation procedures in late obstetrical brachial plexus palsy patients
Authors: Soucacos Panayotis N. , Vekris Marios D. , Zoubos Aristides B. , Johnson Elizabeth O.
Published: April 2006

The varying degrees of spontaneous reinnervation that occur in untreated obstetrical brachial plexus palsy leave characteristic deformities of the shoulder, elbow, forearm, wrist, and hand. Common sequelae are internal rotation and adduction deformity of the shoulder, elbow flexion contractures, forearm supination deformity, and lack of wrist extension and finger flexion. Early microsurgical reconstruction of the affected plexus leads to a more rewarding overall function of the upper arm, but residual deformities might appear later which are similar, although less serious, than those observed in untreated cases. Secondary procedures of the shoulder, elbow, forearm, and hand will improve the appearance and function of the upper extremity in late cases of obstetrical brachial plexus. Careful preoperative planning is mandatory and a multistage approach should be applied, depending on the type of palsy and the age of the patient. © 2006 Wiley‐Liss, Inc. Microsurgery, 2006
Crystallization and melting behavior of biodegradable poly(butylene succinate‐co‐butylene carbonate)
Authors: Qiu Zhaobin , Miao Laiquan , Yang Wantai
Published: April 2006

As a new biodegradable poly(ester carbonate), poly(butylene succinate‐co‐butylene carbonate) (PEC) is a random copolymer, which is composed of butylene succinate unit and butylene carbonate unit. The crystal structure, melting behavior, and morphology of PEC have been investigated by means of wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC), and optical microscopy (OM) in this manuscript. The crystal structure of PEC was found to be the same as that of poly(butylene succinate) (PBSU) through WAXD study, indicating that the butylene carbonate unit did not crystallize in the copolymer. Double melting behavior or one major melting endotherm with a shoulder was found on crystallizing PEC at various temperatures based on DSC study, which was explained by the melt‐recrystallization mechanism. The TMDSC experiment gave a direct proof for the melt‐recrystallization mechanism. The spherulitic growth of PEC was studied with OM at various crystallization temperatures. The spherulitic growth rates of PEC were analyzed by the Lauritzen‐Hoffman equation. The thermal parameters of PEC were compared with those of PBSU. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1556–1561, 2006
Study on nonlinear phase‐separation for PMMA/α‐MSAN blends by dynamic rheological and small angle light scattering measurements
Authors: Zuo Min , Peng Mao , Zheng Qiang
Published: April 2006

The phase‐separation behavior of poly(methyl methacrylate)/poly(α‐methyl styrene‐co‐acrylonitrile) (PMMA/α‐MSAN) blends upon heating was studied through dynamic rheological measurements and time‐resolved small angle light scattering, as a function of temperatures and heating rates. The spinodal temperatures could be obtained by an examination of the anomalous critical viscoelastic properties in the vicinity of phase‐separation induced by the enhanced concentration fluctuation on the basis of the mean field theory. It is found that the dependence of the critical temperatures determined by dynamic rheological measurements and small angle light scattering on heating rates both deviates obviously from the linearity, even at the very low heating rates. Furthermore, the cloud‐point curves decrease gradually with the decrease of heating rates and present the trend of approaching Tgs of the blends. The nonlinear dependence is in consistence with that extracted from the isothermal phase‐separation behavior as reported in our previous paper. It is suggested that the equilibrium phase‐separation temperature could be hardly established by the linear extrapolating to zero in the plotting of cloud points versus heating rates. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1547–1555, 2006
Analysis of the stochastic variation in LTQ single scan mass spectra
Authors: Li Qunhua , Xia Qiangwei , Wang Tiansong , Meila Marina , Hackett Murray
Published: April 2006

A better understanding of the scan‐to‐scan signal intensity variation can lead to more sophisticated algorithms for database searching and de novo peptide sequencing using single scan mass spectra. In this study, we systematically studied the variation in relative intensity of m/z values in the single scan product ion mass spectra (MS2) derived from five representative precursor ions (MS1) collected using an LTQ linear ion trap under constant flow direct infusion conditions with peptide concentrations held constant. We applied a matching algorithm based on a pair hidden Markov model to align the peaks from each scan belonging to the same m/z value prior to assessing the signal intensity variation. The most significant single contributor to scan‐to‐scan signal intensity variation for high abundance ions was centroider error. Our study also showed that the variation in signal intensity is higher than what would be expected if the ion statistics derived from the dual geometry electron multiplier detector followed a Poisson distribution. Copyright © 2006 John Wiley & Sons, Ltd.
The effects of surface topography on momentum and mass transfer in a turbulent boundary layer
Authors: Dawkins R. A. , Davies D. R.
Published: April 2006

An approximate, conveniently applied theory with corresponding experimental data is presented concerning the changes in momentum and mass transfer produced by a ridge of small slopes in a flat-surface quasi-stationary turbulent boundary layer. A first-order mean velocity perturbation solution is found to be in good agreement with measured velocities on the up-slope side of a two-dimensional ridge, of length 20 cm and height 1 cm, fixed on the floor of the working section of an open-circuit wind tunnel. A vapour-transfer eddy-diffusivity distribution is then calculated for the inner boundary-layer region and solutions of the consequent vapour-transfer equation give the variation of rate of evaporation from surfaces of varying lengths placed at different positions on the up-slope region of the ridge. Corresponding measurements are found to be in good agreement with the theoretical calculations, and show that, even over small slopes (of 1 in 10), the evaporation rate varied with position by 25% from maximum to minimum. This method of calculation is extended to examine the effect of surface curvature on diffusion of gas from an upstream line source in a turbulent boundary layer over the ridge; experimental and theoretical concentration profiles compare extremely well over the leading slope.
Nonlinear Taylor vortices and their stability
Authors: Jones C. A.
Published: April 2006

Axisymmetric numerical solutions of the Navier–Stokes equations for flow between rotating cylinders are obtained. The stability of these solutions to non-axisymmetric perturbations is considered and the results of these calculations are compared with recent experiments.
Turbulence in two-phase dispersed flows
Authors: Theofanous T. G. , Sullivan J.
Published: April 2006

Turbulence measurements in dispersed-bubble two-phase pipe flow, using laser velocimetry techniques, are presented. The turbulence-intensity measurements show a strong dependence on the quality of the flow. A theoretical basis for the prediction of turbulence levels in two-phase flows is proposed. The approach is applied to dispersed-gas/liquid (bubbly) and solid/gas (particulate) two-phase flows, for which experimental data are available, with excellent results.
Interferometric study of stable salinity gradients heated from below or cooled from above
Authors: Lewis W. T. , Incropera F. P. , Viskanta R.
Published: April 2006

Mixing-layer development is investigated in laboratory experiments of salt-stratified solutions which are cooled from above or heated from below through the imposition of isothermal boundaries. A Mach-Zehnder interferometer is used to infer salt and density distributions within stable regions of the solution and to determine the extent of mixing-layer development. In both heating from below and cooling from above, this development differs significantly from that which has been observed for constant heating from below. Although the formation of a secondary mixed layer is observed, it does not lead to the development of additional mixed layers. Instead, the secondary layer eventually recedes, and the existence of a single mixed layer is restored. This behaviour is due to the isothermal boundary and the effect which it has no decreasing the heat transfer to or from the solution with increasing time. Once the condition of a single mixed layer is restored, extremely large (stable) density gradients develop in the boundary layer separating the mixed and stable regions, and subsequent growth of the mixed layer is slow. In cooling from above, mixing-layer development depends strongly on whether the isothermal boundary is in direct contact with the solution or separated by an air space.
on the accuracy of turbulence measurements with inclined hot wires
Authors: Müller Udo R.
Published: April 2006

Since the accuracy of mean velocities and Reynolds stresses measured with inclined hot wires depends on the accurate knowledge of the hot-wire cooling law, each hot wire used in the boundary-layer experiment of Müller (1982, hereinafter referred to as I) had to be calibrated individually with respect to the magnitude and direction of the flow vector. In the present paper details of the calibration procedure and an example of calibrated data are reported. The directional hot-wire response was described by an effective cooling velocity, which was then used for the data reduction. The errors in the measured Reynolds stresses evaluated with an empirical cooling law as opposed to the actual one were estimated analytically from the governing equations and were confirmed by corresponding recalculations from the same set of measurements. Additionally, the validity of the conventional linearized method for evaluating the Reynolds stress tensor from the root-expanded equation for the cooling velocity was checked for increasing turbulence levels. In the test measurements all triple velocity correlations, which are usually neglected compared with second-order ones, were measured and taken into account in the data reduction.
Flow in alluvial-river curves
Authors: Ascanio Marco Falcón , Kennedy John F.
Published: April 2006

Uniform flow in curved, wide, erodible-bed channels is formulated on the basis of the conservation of flux of moment-of-momentum, to obtain relations for the vertical distributions of radial-plane velocity and radial shear stress. The expression for the radial stress exerted on the bed is utilized in a force-equilibrium analysis of the moving bed layer to obtain relations for the average transverse slope of the bed and for the radial bed profile. The reduction of primary bed shear stress due to the net radial transport of streamwise momentum toward the outer (concave) bank is then calculated, by introducing the derived expressions for the velocity components into the momentum equation for the primary-flow direction. It is found that the stress reductions in deep, narrow channels can exceed 50%. Bed profiles and velocity distributions measured in natural and laboratory streams are found to be in good conformity with those calculated from this moment-based theory.
On the stability of plane Poiseuille flow to finite-amplitude disturbances, considering the higher-order Landau coefficients
Authors: Sen P. K. , Venkateswarlu D.
Published: April 2006

In this work a study has been made of the Stuart (1960)–Watson (1960) formalism as applied to plane Poiseuille flow. In particular, the higher-order Landau coefficients have been calculated for the Reynolds & Potter (1967) method and for the Watson (1960) method. The results have been used to study the convergence of the Stuart–Landau series. A convergence curve in the (α, R)-plane has been obtained by using suitable Domb–Sykes plots. In the region of poor convergence of the series, and also in a part of the divergent region of the series, it has been found that the Shanks (1955) method, using the em1 transformation, serves as a very effective way of finding the proper sum of the series, or of finding the proper antilimit of the series. The results for the velocity calculations at R = 5000 are in very good agreement with Herbert's (1977) Fourier-truncation method using N = 4. The Watson method and the Reynolds & Potter method have also been compared inthe subcritical and supercritical regions. It is found in the supercritical region that there is not much difference in the results by the ‘true problem’ of Watson and the ‘false problem’ of Reynolds & Potter when the respective series in both methods are summed by the Shanks method. This fact could possibly be capitalized upon in the subcritical region, where the Watson method is difficult to apply.
Particle-sampling statistics in laser anemometers: sample-and-hold systems and saturable systems
Authors: Edwards Robert V. , Jensen Arne Skov
Published: April 2006

The output statistics of a laser anemometer operating in a low particle density are discussed. A rigorous derivation is given for the influence of two popular data-handling algorithms on these statistics. In particular it is shown that the measured statistics can differ from those of the flow statistics and from the particle-arrival statistics. The variables that control the statistical regime are derived and quantitative estimates are given for their ranges of influence.

The first system discussed is a sample-and-hold system where the output is a piecewise-continuous signal obtained by holding the last processor measurement until a new one is obtained. The second system is one where an attempt is made to store all the measurements for processing, but which contains a rate-limiting device. Because of this device, some measurements may be lost when the particle rate is high. This system is referred to as a saturable system.

In both cases it is found that the statistics of the output depend on the product of the mean particle rate and the flow correlation time as well as the flow statistics. The statistics of the saturable system also depend on the ratio of the mean particle rate to the maximum rate at which measurements can be accepted by the system. Because of this, the statistics of both systems depend on the particle density.

Attainable conditions are demonstrated, where the output velocity measurement statistics are essentially identical with the flow statistics.
The effects of turbulence on the mean flow past square rods
Authors: Nakamura Y. , Ohya Y.
Published: April 2006

There are two main effects of turbulence on the mean flow past rods of square cross-section aligned with the approaching flow. Small-scale turbulence increases the growth rate of the shear layer, while large-scale turbulence enhances the roll-up of the shear layer. The consequences of these depend on the length of a square rod. The mean base pressure of a square rod varies considerably with turbulence intensity and scale as well as with its length.
Three-dimensional baroclinic instability of a Hadley cell for small Richardson number
Authors: Antar Basil N. , Fowlis William W.
Published: April 2006

A three-dimensional linear stability analysis of a baroclinic flow for Richardson number Ri of order unity is presented. The model considered is a thin, horizontal, rotating fluid layer which is subjected to horizontal and vertical temperature gradients. The basic state is a Hadley cell which is a solution of the Navier–Stokes and energy equations and contains both Ekman and thermal boundary layers adjacent to the rigid boundaries; it is given in closed form. The stability analysis is also based on the Navier–Stokes and energy equations; and perturbations possessing zonal, meridional and vertical structures were considered. Numerical methods were developed for the solution of the stability problem, which results in an ordinary differential eigenvalue problem. The objectives of this work were to extend the previous theoretical work on three-dimensional baroclinic instability for small Ri to a more realistic model involving the Prandtl number σ and the Ekman number E, and to finite growth rates and a wider range of the zonal wavenumber. The study covers ranges of 0.135 [les ] Ri [les ] 1.1, 0.2 [les ] σ [les ] 5.0, and 2 × 10−4 [les ] E [les ] 2 σ 10−3. For the cases computed for E = 10−3 and σ ≠ 1, we found that conventional baroclinic instability dominates for Ri > 0.825 and symmetric baroclinic instability dominates for Ri < 0.675. However, for E [ges ] 5 × 10−4 and σ = 1 in the range 0.3 [les ] Ri [les ] 0.8, conventional baroclinic instability always dominates. Further, we found in general that the symmetric modes of maximum growth are not purely symmetric but have weak zonal structure. This means that the wavefronts are inclined at a small angle to the zonal direction. The results also show that as E decreases the zonal structure of the symmetric modes of maximum growth rate also decreases. We found that when zonal structure is permitted the critical Richardson number for marginal stability is increased, but by only a small amount above the value for pure symmetric instability. Because these modes do not substantially alter the results for pure symmetric baroclinic instability and because their zonal structure is weak, it is unlikely that they represent a new type of instability.
On the stability of the decelerating laminar boundary layer
Authors: Gad-El-Hak Mohamed , Davis Stephen H. , Mcmurray J. Thomas , Orszag Steven A.
Published: April 2006

The stability of a decelerating boundary-layer flow is investigated experimentally and numerically. Experimentally, a flat plate having a Blasius boundary layer is decelerated in an 18 m towing tank. The boundary layer becomes unstable to two-dimensional waves, which break down into three-dimensional patterns, hairpin vortices, and finally turbulent bursts when the vortices lift off the wall. The unsteady boundary-layer equations are solved numerically to generate instantaneous velocity profiles for a range of boundary and initial conditions. A quasi-steady approximation is invoked and the stability of local velocity profiles is determined by solving the Orr–Sommerfeld equation using Chebyshev matrix methods. Comparisons are made between the numerical predictions and the experimentally observed instabilities.
Nonlinear gravity–capillary standing waves in water of arbitrary uniform depth
Authors: Vanden-Broeck Jean-Marc
Published: April 2006

Gravity–capillary standing waves in water of arbitrary uniform depth are considered. The classical perturbation calculation yields unbounded coefficients for some critical values of the depth. In the present paper solutions valid near the first critical value of the depth are derived. A problem of non-uniqueness is discovered and discussed. It is shown that two solutions exist, one with higher frequency and one with lower frequency than the zeroth-order solution. They are found analytically at the critical value of the depth and numerically in an interval around it. Graphs of the results are included.
Temporal moments at large distances downstream of contaminant releases in rivers
Authors: Smith Ronald
Published: April 2006

This paper concerns the effects of topographic changes upon the dispersion of contaminants in rivers. Exact analytical results are derived for the time-of-arrival, temporal variance and skewness far downstream of a sudden contaminant release. It is demonstrated that there can exist optimal discharge sites, such that at all positions far downstream the maximum concentrations are minimized.
Topographically generated cyclonic disturbance and lee waves in a stratified rotating fluid
Authors: Cheng H. K. , Hefazi H. , Brown S. N.
Published: April 2006

The flow about an obstacle in horizontal motion relative to a stratified Boussinesq fluid in a deep, rapidly rotating container is studied. Numerical and asymptotic analyses of the linearized boundary-value problems for a shallow topography are made to delineate the influence of stratification and ground topography on wave and flow structure, and to ascertain the presence of a solitary anticyclonic, or cyclonic, disturbance in the far field at high as well as low stratification. Although the analyses are restricted to the rapidly rotating case corresponding to a vanishingly small Rossby number, it is pointed out that the cyclonic feature remains a valid inviscid description in the far field except for an infinite Rossby number corresponding to no rotation.
Edge waves over a shelf: full linear theory
Authors: Evans D. V. , Mciver P.
Published: April 2006

Edge-wave solutions to the linearized shallow-water equations for water waves are well known for a variety of bottom topographies. The only explicit solution using the full linearized theory describes edge waves over a uniformly sloping beach, although the existence of such waves has been established for a wide class of bottom geometries. In this paper the full linearized theory is used to derive the properties of edge waves over a shelf. In particular, curves are presented showing the variation of frequency with wavenumber along the shelf, together with some mode shapes for a particular shelf geometry.
On the stability of an axisymmetric plume in a uniform stream
Authors: Riley D. S. , Tveitereid M.
Published: April 2006

The linear stability equations for a round laminar thermal plume in a coflowing vertical stream have been solved numerically. Both symmetric and asymmetric disturbances have been considered for strengths of the forced flow varying between very weak and very strong. The parallel flow analysis confirms that the forced flow has a stabilizing effect. The upper branch of the neutral curve for sinuous disturbances is qualitatively like that of a round momentum jet. However, neither a critical Reynolds number nor a lower branch of the neutral curve was found. Non-parallel effects are discussed.
Internal waves in a horizontally inhomogeneous flow
Authors: Basovich A. Ya. , Tsimring L. Sh.
Published: April 2006

The effect of horizontally inhomogeneous flows on internal wave propagation in a stratified ocean with a constant Brunt-Väisälä frequency is analysed. Dispersion characteristics of internal waves in a moving fluid and kinematics of wave packets in smoothly inhomogeneous flows are considered using wave-normal surfaces. It is shown that internal-wave blocking and short-wave transformation may occur in longitudinally inhomogeneous flows. For parallel flows internal-wave trapping is possible in the vicinity of the limiting layer where the wave frequency in the locally comoving frame of reference coincides with the Brunt-Väisälä frequency. Internal-wave trapping also takes place in jet-type flows in the vicinity of the flow-velocity maximum. WKB solutions of the equation describing internal-wave propagation in a parallel horizontally inhomogeneous flow in the linear approximation are obtained. Singular points of this equation and the related effect of internal-wave amplification (overreflection) under the action of the flow are investigated. The spectrum and the growth rate of internal-wave localized modes in a jet-type flow are obtained.
The pressure-hole problem
Authors: Ducruet C. , Dyment A.
Published: April 2006

The static pressure-hole problem is investigated both theoretically and experimentally. The influence of all significant dimensionless parameters is brought to light. These parameters represent the effects of the boundary layer, of the velocity gradient and of the wall curvature. A partial linearization makes it possible to propose a formula of correction containing three influence functions which cannot be determined by the theory. A limited number of experiments on appropriate models leads to the determination of these functions in case of practical requirements. So, a method of correction is obtained, but only in incompressible flow. The previous formula has been verified in two complex flows. The importance of the correction on the pressure drag of a slender body is brought to light and the difficulties in the application on the method are emphasized.
The dynamics of stretched vortices
Authors: Neu John C.
Published: April 2006

The dynamics of vortices subject to stretching by a uniform plane straining flow is studied asymptotically and by means of a new class of exact solutions. The asymptotic analysis treats the stretched Burger's vortex sheet for strain rates much greater than the gradient of the sheet strength. It is found that portions of the sheet where the strength density is sufficiently large compared to (viscosity x strain rate)½ will collapse to form concentrated vortices. The exact solutions describe uniform vortices of elliptical cross-section in inviscid fluid subject to stretching parallel to their axes. These solutions complement the description of vortex collapse found by asymptotic methods. The relevance of these results stems from the prevalence of vortex structures subject to strain in turbulent flows.
Secondary current and river-meander formation
Authors: Kitanidis Peter K. , Kennedy John F.
Published: April 2006

A small-perturbation stability analysis is developed for investigation of the role of the secondary current accompanying channel curvature in the initiation and early development of meanders of alluvial and ice- or rock-incised streams. A small sinusoidal perturbation in the channel alignment of an initially straight prismatic channel is introduced. The velocity of the secondary flow is calculated for uniform quasi-steady flow conditions by application of the equation of the conservation of moment of momentum. The formulation is then closed by introducing the assumption that the differential, between the outer and inner banks, rate of boundary erosion, dissolution or melting (for incised channels) or sediment discharge (for alluvial channels) is proportional to the strength of the secondary flow. This formulation leads to a linear differential equation which is solved for its orthogonal components, which give the rates of meander growth and downstream migration. It is shown that the amplitude of the meanders tends to increase and that the meanders migrate downstream. The dominant wavelength and the corresponding phase shift between channel meandering and the velocity of the spiral motion are calculated as those corresponding to the fastest growth rate. The results are found to be in good agreement with data reported by others.
Tip streaming from slender drops in a nonlinear extensional flow
Authors: Sherwood J. D.
Published: April 2006

The deformation of inviscid and slightly viscous drops is studied using slender-body theory. The imposed axisymmetric flow is a combination of a linear extensional flow, with velocity uz = G1 z along the axis of symmetry, together with a cubic flow uz = G3z3. When G3/G1 is sufficiently small the viscous drop breaks in a manner similar to that described by Acrivos & Lo (1978). For larger G3 > 0 the drop breaks by a rapid growth at its end. Steady-state experiments in a 4-roll mill show the ejection of a column of liquid from the tip of the drop, though this is probably caused by a change in the pressure gradient rather than the mechanism described above. The ejected column then breaks into droplets via the Rayleigh instability. It is hypothesized that one or other of these mechanisms corresponds to tip streaming as observed by Taylor (1934).
A note on the mechanism of the instability at the interface between two shearing fluids
Authors: Hinch E. J.
Published: April 2006

In a recent paper Hooper & Boyd (1983) have shown that the unbounded stratified Couette flow of two viscous fluids of equal density and with no interfacial tension is always unstable. They found that the instability arises at the interface between the two fluids and occurs at short wavelengths where viscosity is more important than inertia. The purpose of this note is to provide a simple physical explanation of the mechanics of the instability.
Computation of flow around wings based on the Euler equations
Authors: Rizzi Arthur , Eriksson Lars-Erik
Published: April 2006

Inviscid transonic flows containing either strong shock waves or complex vortex structure call for the Euler equations as a realistic model. We present here a computational procedure, termed WINGA2, for solving the Euler equations for transonic flow around aircraft upon a 0–0 mesh generated by transfinite interpolation. An explicit time-marching finite-volume technique solves the flow equations and features a non-reflecting far-field boundary condition and an internal mechanism for temporal damping together with a model for artificial viscosity. The method's convergence to a steady state is studied, and results computed on the CYBER 205 vector processor are presented. The Euler equation model is found to predict the existence of a tip vortex created by flow separating from the downstream region of the tip of the ONERA M6 wing where the radius of curvature approaches zero.
Lee waves in three-dimensional stratified flow
Authors: Janowitz G. S.
Published: April 2006

The effect of a shallow isolated topography on a linearly stratified, three-dimensional, initially uniform flow in the x-direction is considered. The Green-function solution for the velocity disturbance due to this topography, which is equivalent to that due to a dipole at the origin, is shown to be without swirl, i.e. the velocity disturbance lies strictly in planes passing through the x-axis. Thus this disturbance can be described in terms of a stream function. The asymptotic forms of the wavelike portion of the stream function and the vertical displacement field are obtained. The latter is in agreement with the limited versions due to Crapper (1959). The Gaussian curvature of the zero-frequency dispersion surface is obtained analytically as a step in the stationary-phase calculation. The model is extended to determine the vertical displacement field for an arbitrary shallow topography far downstream. For topographies that are even functions of x and y it is shown that the details of the topography affect the displacement field only in the vicinity of the x-axis. Elsewhere, the amplitude of the displacement is proportional to the net volume of the topography.
Couette flow of two fluids between concentric cylinders
Authors: Renardy Yuriko , Joseph Daniel D.
Published: April 2006

We consider the flow of two immiscible fluids lying between concentric cylinders when the outer cylinder is fixed and the inner one rotates. The interface is assumed to be concentric with the cylinders, and gravitational effects are neglected. We present a numerical study of the effect of different viscosities, different densities and surface tension on the linear stability of the Couette flow. Our results indicate that, with surface tension, a thin layer of the less-viscous fluid next to either cylinder is linearly stable and that it is possible to have stability with the less dense fluid lying outside. The stable configuration with the less-viscous fluid next to the inner cylinder is more stable than the one with the less-viscous fluid next to the outer cylinder. The onset of Taylor instability for one-fluid flow may be delayed by the addition of a thin layer of less-viscous fluid on the inner wall and promoted by a thin layer of more-viscous fluid on the inner wall.
The transition to wavy Taylor vortices
Authors: Jones C. A.
Published: April 2006

The transition from steady axisymmetric Taylor vortices to time-dependent wavy vortices is examined. The critical Taylor number and frequency at the transition point are determined in the infinite-cylinder approximation for a wide range of parameters. The results are compared with long-aspect-ratio experiments. The variation with axial wavelength is examined, and is found to be important when the radius ratio η < 0.75. A new spatially subharmonic mode is found to be the most unstable mode in some parameter regimes. This mode is identified with the jet mode recently discovered experimentally by Lorenzen, Pfister & Mullin and by Cole.