bluuebunny/crossref_metadata_2025 huggingface dataset:
The Unique Crystal Structure of the Triclinic Samarium(III) Oxoselenate(IV) Sm2[SeO3]3
Authors: Krügermann Ina , Wickleder Mathias S. , Wontcheu Joseph , Schleid Thomas
Published: March 2006

Pale yellow, needle‐shaped single crystals of Sm2[SeO3]3 were obtained by heating stoichiometric mixtures of Sm2O3 and SeO2 (molar ratio: 1:3) along with substantial amounts of CsCl as fluxing agent in evacuated sealed silica tubes at 830 °C for one week. According to X‐ray single‐crystal diffraction data, Sm2[SeO3]3 crystallizes triclinic (space group: $P{\bar 1}$ ) with two formula units per unit cell of the dimensions a = 698.62(7), b = 789.71(8), c = 910.34(9) pm, α = 96.693(5), β = 104.639(5), γ = 115.867(5)°. Its crystal structure contains two crystallographically distinct Sm3+ cations in eight‐ and ninefold coordination with oxygen atoms arranged as distorted uncapped or capped square antiprisms (d(Sm3+−O2−) = 232−271 pm). These [(Sm1)O8] and [(Sm2)O9] polyhedra share opposite edges and faces to form zigzag chains along [100] with discrete pyramidal [SeO3]2− anions bridging units. Further linkage by [SeO3]2− anions in [010] direction leads to a three‐dimensional network, which exhibits almost rectangular channels along [111]. These tunnels offer width enough to incorporate the free non‐bonding electron pairs („lone pairs”︁) at the Se4+ cations, since all nine different Ψ1‐tetrahedral [SeO3]2− groups (d(Se4+−O2−) = 165−173 pm, ∢(O–Se–O) = 94 – 108°) exhibit a pronounced stereochemical „lone‐pair”︁ activity. For not being isotypic with neither triclinic Er2[SeO3]3 (CN(Er3+) = 7 and 8) nor the remainder rare‐earth metal(III) oxoselenates(IV) of the composition M2[SeO3]3 (≡ M2Se3O9; M = Sc, Y, La, Ce – Lu), Sm2[SeO3]3 claims a unique crystal structure among them.
Casein kinase Iε associates with and phosphorylates the tight junction protein occludin
Authors: McKenzie Jenny A.G. , Riento Kirsi , Ridley Anne J.
Published: March 2006

Occludin is an integral‐membrane protein that contributes to tight junction function. We have identified casein kinase Iε (CKIε) as a binding partner for the C‐terminal cytoplasmic domain of occludin by yeast two‐hybrid screening. CKIε phosphorylated occludin and co‐localised and co‐immunoprecipitated with occludin from human endothelial cells. Amino acids 265–318 of occludin were sufficient for CKIε binding and phosphorylation. Deletion of the C‐terminal 48 amino acids of occludin increased CKIε binding and phosphorylation, suggesting that this region inhibits CKIε binding. These data identify CKIε as a novel occludin kinase that may be important for the regulation of occludin.
Molecular nature of methicillin‐resistant Staphylococcus aureus derived from explosive nosocomial outbreaks of the 1980s in Japan
Authors: Taneike Ikue , Otsuka Taketo , Dohmae Soshi , Saito Kohei , Ozaki Kyoko , Takano Misao , Higuchi Wataru , Takano Tomomi , Yamamoto Tatsuo
Published: March 2006

Community‐acquired methicillin‐resistant Staphylococcus aureus (CA‐MRSA) with Panton‐Valentine leukocidin (PVL) genes is increasing worldwide. Nosocomial outbreak‐derived (hospital‐acquired) MRSA (HA‐MRSA) in Japan in the 1980s was also largely PVL+. PVL+ HA‐MRSA and CA‐MRSA shared the same multi‐locus sequence type (ST30) and methicillin resistance cassette (SCCmecIV), but were divergent in oxacillin resistance, spa typing, PFGE analysis or clfA gene analysis. PVL+ HA‐MRSA, which probably originated in PVL+ S. aureus ST30, was highly adhesive (carrying cna and bbp genes), highly‐toxic (carrying luk

PV
and sea genes) and highly drug‐resistant. PVL+ HA‐MRSA was once replaced by other PVL− HA‐MRSA (e.g., ST5), and is re‐emerging as CA‐MRSA.
Evidence that low doses of Taxol enhance the functional transactivatory properties of p53 on p21 waf promoter in MCF‐7 breast cancer cells
Authors: Panno M. Luisa , Giordano Francesca , Mastroianni Fabrizia , Morelli Catia , Brunelli Elvira , Palma M. Grazia , Pellegrino Michele , Aquila Saveria , Miglietta Antonella , Mauro Loredana , Bonofiglio Daniela , Andò Sebastiano
Published: March 2006

In the present study, we evidence how in breast cancer cells low doses of Taxol for 18 h determined the upregulation of p53 and p21 waf expression concomitantly with a decrease of the anti‐apoptotic Bcl‐2. P53 and its gene product, the mdm2 protein, in treated cells exhibits a prevalent nuclear compartmentalization, thus potentiating p53 transactivatory properties. Indeed, the most important finding of this study consists with the evidence that Taxol at lower concentrations is able to produce the activation of p21 promoter via p53. Prolonged exposure of MCF‐7 cells to Taxol (48 h) resulted in an increased co‐association between p21 and PCNA compared to control and this well fits with the simultaneous block of cell cycle into the G2/M phase.
Negotiation, email, and Internet reverse auctions: How sourcing mechanisms deployed by buyers affect suppliers’ trust
Authors: Gattiker Thomas F. , Huang Xiaowen , Schwarz Joshua L.
Published: March 2006

The Internet has made a wealth of new tools available to the industrial buyer. However, researchers have suggested that computer‐mediated interaction with suppliers may not be conducive to strong supplier relationships in general and to trust in particular. This paper compares two computer‐mediated sourcing tools (email negotiation and Internet reverse auctions) with face‐to‐face negotiation. Information richness theory suggests that the different media will produce different impacts relating to sellers’ trust in buyers. Data are generated with a simulation experiment using 117 subjects. We found that information richness affects seller–buyer trust: Sellers who used face‐to‐face negotiation, the richest medium in the study, always reported higher trust in their buyer counterparts than did sellers using Internet reverse auctions. There were also some trust advantages of face‐to‐face negotiation over email and limited advantages of email over reverse auctions. We also found that procurement complexity influences the relationship between information richness and trust. As hypothesized, when face‐to‐face negotiation is used, procurement complexity has no effect on seller trust. When reverse auctions are utilized, the greater the complexity of the purchase, the less the seller trust. However, when email is used, greater procurement complexity is associated with greater seller trust, and there are no differences in trust between the email and face‐to‐face channels. Finally, we found that sellers’ trust in buyers is positively associated with sellers’ desire for future dealings with the buyer.
Color Doppler Ultrasonography is a Reliable Predictor of Free Tissue Transfer Outcomes in Head and Neck Reconstruction
Authors: Khalid Ayesha N. , Quraishi Sadeq A. , Zang William A. , Chadwick Johnathan L. , Stack Brendan C.
Published: March 2006

OBJECTIVE

The purpose of our investigation was to report our experience with a color flow doppler (CFD) ultrasonography for postoperative monitoring of free tissue transfers.

METHODS

A retrospective analysis of head and neck free tissue transfers at a single institution between 2000 and 2005 (n = 84; 80 successful, 4 failures). CFD measured blood flow velocity (cm/sec) and resistance to flow in the pedicle vein and artery on postoperative days 1, 3, and 7.

RESULTS

Analysis of artery/vein ratio revealed vascular congestion by postoperative day 3 which later resolved. In flap failures, there was a significant reduction (P < 0.05) in venous blood flow by postoperative day 3. Waveform morphology representing vascular resistance and origin of donor flap did not correlate with flap outcome (r2 = 0.23 and 0.44 respectively).

CONCLUSION

Postoperative monitoring of free tissue transfers may allow for detection of poor perfusion. CFD is an objective method of studying blood flow postoperatively.
Sedimentary evolution of a Palaeozoic basin and ridge system: the Middle and Upper Devonian of the Ahnet and Mouydir (Algerian Sahara)
Authors: WENDT JOBST , KAUFMANN BERND , BELKA ZDZISLAW , KLUG CHRISTIAN , LUBESEDER STEFAN
Published: March 2006

The Ahnet and Mouydir regions of southern Algeria are part of one of the world's largest, almost undeformed exposures of Palaeozoic rocks which exemplify a hitherto poorly known early Variscan development of a Devonian basin and ridge system. This area includes a series of intracratonic basins along the northern margin of the West African Craton which consists (from W to E) of the Reggane Basin, Azel Matti Ridge, Ahnet Basin, Foum Belrem Ridge and Mouydir Basin. The depositional and palaeogeographic interpretation is based on 71 sections in this region, which for the first time were biostratigraphically calibrated by means of conodonts, goniatites and brachiopods. The structural evolution during Devonian times was probably controlled by reactivation of ancient N–S- to NW–SE-running faults in the Precambrian basement, which caused differential subsidence and uplift of a previously largely unstructured siliciclastic shelf. A hiatus during Emsian times indicates widespread emergence during this interval. The entire area was flooded during the earliest Eifelian, when the first vestiges of the Azel Matti Ridge become evident by stratigraphic condensation. The palaeogeographic differentiation is most apparent during the Givetian, when a shoal with reduced carbonate sedimentation was established on the Azel Matti Ridge passing towards the west and east into basinal environments of the Reggane and Ahnet basins, respectively. The Foum Belrem Ridge is distinguished by increased subsidence during the early Givetian and by revived uplift during the late Givetian. In the Mouydir Basin further east, up to 1000 m of shales were deposited during the Givetian. The early Frasnian is marked by the ubiquitous sedimentation of black shales and bituminous styliolinites. These lithologies occur repeatedly already during the Middle Devonian and document intermittent anoxic conditions. The basin and ridge topography is levelled by the shallowing-up sequence of up to 1400 m thick upper Frasnian and Famennian shales which grade into a deltaic sequence of uppermost Famennian/Tournaisian sandstones. The up to now only vaguely discriminated lithostratigraphic formations of the Devonian have been biostratigraphically defined in suitable type sections.
From “Landsknecht” to “Soldier”: The Low German Foot Soldiers of the Low Countries in the Second Half of the Sixteenth Century
Authors: Swart Erik
Published: March 2006

In the decades after 1550 the soldiery of the Netherlands witnessed the disappearance of the Landsknecht, who had the right to participate in decision-making and shape his daily life. He gradually became a mere “soldier”, subject to stricter discipline and control. This development accelerated after 1572 because William of Orange needed to maintain the support of the inhabitants of the Netherlands for the Revolt. Better discipline and control over his soldiers were imperative in this. Meanwhile, a progressive process of proletarianization left them largely unable to resist: they simply had nowhere else to go.
“Guerrillas Don't Die Easily”: Everyday Life in Wartime and the Guerrilla Myth in the National Resistance Army in Uganda, 1981–1986
Authors: Schubert Frank
Published: March 2006

This article examines the civil war in central Uganda between guerrillas of the National Resistance Army and the government of Milton Obote between 1981 and 1986. Its central focus is the wartime experience of guerrilla fighters – men, women, and children. The material for the article has been collected through interviews with participants about their experiences. The interview partners described their motives and expectations as guerrillas as well as their perception of the reality of war “in the bush”. Their narratives differ from the victorious guerrilla's official history of the war and the guerrilla myth cultivated in that history, as they lack the subsequent certainty of victory and emphasize the fighters' disappointments and suffering. In this way, the method of oral history provides important points of departure for a social history of this war and allows us, at the same time, to differentiate and correct our current understanding of it in significant ways.
α-Tocopherol concentration and stereoisomer composition in plasma and milk from dairy cows fed natural or synthetic vitamin E around calving
Authors: Meglia Guillermo E , Jensen Søren K , Lauridsen Charlotte , Persson Waller Karin
Published: March 2006

The aim of this study was to compare the effects of supplementing dairy cows with 1000 IU/day of all-rac-α-tocopheryl acetate (SynAc), RRR-α-tocopheryl acetate (NatAc), or RRR-α-tocopherol (NatAlc), from approximately 3 weeks before estimated calving until 2 weeks after calving, on the concentration of α-tocopherol and its stereoisomers (RRR-, RSS-, RRS-, RSR- and the four 2S-forms of α-tocopherol) in blood and milk. An unsupplemented group was included as control. Blood samples were collected at 3, 2 and 1 weeks before estimated calving, at calving, and 3, 7 and 14 days after calving, while milk samples were taken twice within 24 h after calving and at 7 and 14 days in milk. Overall, time and treatment had significant effects on plasma α-tocopherol with higher concentrations in NatAc than in the other groups. In addition, SynAc had higher concentrations than Control, and NatAlc tended to be higher than Control. The lowest plasma concentrations were observed at calving and 3 days after calving. Independent of treatment, the concentration was higher in colostrum than in milk day 7 and 14 after calving. Analyses of the stereoisomer distribution in plasma and milk showed that, irrespective of dietary treatment, RRR-α-tocopherol was the most predominant form, constituting more than 86%, whereas the remaining part of α-tocopherol was made up by the three synthetic 2R isomers, while the 2S isomers only contributed less than 1% of the total α-tocopherol. In control cows and cows supplemented with natural vitamin E, the proportion of RRR-α-tocopherol in plasma and milk constituted more than 98% of the total α-tocopherol. In conclusion, the results indicate that daily oral supplementation of dairy cows with RRR-α-tocopheryl acetate gives the highest blood concentrations of α-tocopherol in the periparturient period. Analyses of the distribution of the individual stereoisomers of α-tocopherol further indicate that the bioavailability of RRR-α-tocopherol relative to synthetic stereoisomers in cattle is considerably higher than officially accepted until now.
Cyprian and Women in a Time of Persecution
Authors: DUNN GEOFFREY D.
Published: March 2006

Cyprian believed that the maintenance of ecclesial disciplina was the prime responsibility of a bishop's pastoral ministry, particularly in a time of persecution when people's loyalty was under threat. Throughout his episcopate Cyprian ministered to women as well as men who experienced persecution. Not only was he attempting to secure socio-political support through patronage for his position as bishop but he was applying the prescriptions of the Gospels. He praised women who remained faithful as role models for others, instructed and encouraged them in their perseverance and aided them in their need. Women who lapsed were dealt with according to ecclesial disciplina no differently than were the men who lapsed. While lay women and men had their own share in pastoral ministry, the issue of what to do with lapsed Christians raised the question of the extent to which a bishop's responsibilities were primary. In some letters not by Cyprian we sense not only a greater degree of familiarity with lay people but less of a concern with the importance of disciplina. In response to a recent paper in this JOURNAL by Allen Brent, it is argued here that a close reading of these non-Cyprianic letters in the corpus reveals that the male and female confessors who wanted the lapsed to be reconciled did not consider themselves to be presbyters who could reconcile but thought of themselves as confessors with the right to tell the bishop of those whom he was to reconcile.
On the rise of small air bubbles in water
Authors: Saffman P. G.
Published: March 2006

This paper is concerned with the motion in water of air bubbles whose equivalent spherical radii are in the range 0.5-4.0 mm. These bubbles are not spherical but are, approximately, oblate spheroids; and they may rise steadily in a vertical straight line, or along a zig-zag path, or in a uniform spiral. The rectilinear motion occurs when the radius is less than about 0.7 mm, and the other motions occur for larger bubbles. There is disagreement in the literature as to whether it is the zig-zag or the spiral motion that occurs. It was found experimentally that, when the bubbles are produced in the manner described in this paper, only the zig-zag motion occurs when the radius of the bubble is less than about 1 mm, but bubbles of larger radius either zig-zag or spiral depending upon various factors.

The spiralling bubble is treated theoretically by assuming that the flow near the front of the bubble is inviscid (the Reynolds number of the motion is several hundred) and considering the distribution of pressure over the front surface. Equations are obtained relating the geometrical parameters of the spiral, the shape of the bubble and the velocity of rise. The analysis is simplified by assuming that the pitch of the spiral is large compared with its radius, and the velocity of rise and shape of the bubble are determined as functions of the radius. The experimental and theoretical values are compared, and fair agreement found. Reasons to account for the disagreement are proposed.

A modification of the theory is proposed to take account of the presence of impurities or surface-active substances in the water, and the velocities of rise thus predicted are in agreement with the experimental observations.

The zig-zag motion is treated in a similar way, and the analysis leads to an equation which determines the stability of the rectilinear motion. The value of the Weber number at which the rectilinear motion. The value of the Weber number at which the rectilinear motion becomes unstable is deduced, and is found to be in fair agreement with experiment. The experimental evidence on the wake behind solid bodies is described briefly, and reasons are given for suggesting that the zig-zag motion is due to an interaction between the instability of the rectilinear motion and a periodic oscillation of the wake.
Measurements of heat transfer from fine wires in supersonic flows
Authors: Laufer John , Mcclellan Robert
Published: March 2006

Results of an experimental investigation of the heat loss of fine heated wires immersed in a supersonic stream at right angles to the flow direction are presented. The measurements show that the heat loss of the wire is independent of the free-stream Mach number for values of the latter between 1.3 and 4.5. Since the wire is always in the wake of a detached shock wave, the streamlines in the neighbourhood of the wire pass through a normal shock wave. The Reynolds number Re2 based on conditions behind a normal shock, thus becomes the characteristic parameter for the heat transfer. The measurements covering a Reynolds number range of 3 to 220 show the existence of two flow regimes. For Re2 > 20 the Nusselt number is a linear function of the square root of the Reynolds number, and the equilibrium temperature is nearly independent of Re2 < 20 the Nusselt number decreases more slowly, and the equilibrium temperature rises sharply with decreasing Reynolds number.
The impact of a water wedge on a wall
Authors: Cumberbatch E.
Published: March 2006

This paper is intended to give some indication of the impact forces of a water wave on a wall. The effect of gravity forces in the small time interval of impact considered will be small and is neglected. The shape of the wave before impact is considered to be a two-dimensional wedge which is assumed to strike a wall at right angles to its path. The wedge is assumed to be infinite in extent and to have uniform translational velocity V before impact. The choice of a wedge shape enables the problem to be formulated in terms of similarity variables x/Vty/Vt, where the origin of the x, y plane is at the initial point of contact of the vertex of the wedge with the wall. The solution presented here can be easily adapted to the problem of an axi-symmetric cone of water striking a wall, but this is not pursued in the present paper.
Rayleigh instability of a thermal boundary layer in flow through a porous medium
Authors: Wooding R. A.
Published: March 2006

It is supposed that a heated liquid is rising very slowly through a semi-infinite porous medium towards the permeable horizontal surface, where it mixes with a layer of cool overlying fluid. In the steady state a thermal boundary layer of exponential form exists in the medium. It is shown that the layer is stable provided that the Rayleigh number for the system does not exceed a critical positive value, and that the wave-number of the critical neutral disturbance is finite. The stability properties of the layer are explained qualitatively from physical considerations.
Steady wave patterns on a non-uniform steady fluid flow
Authors: Ursell F.
Published: March 2006

A steady slightly non-uniform flow with a free surface is subject to a concentrated surface pressure which gives rise to a pattern of surface waves. (For gravity waves on deep water this is the well-known Kelvin ship-wave pattern.) The motion is assumed inviscid, and the waves are assumed small. A theory is developed for the wave pattern, based on the following assumptions:

The stream velocity component normal to a wave crest is equal to the phase velocity based on the local wavelength;

the separation between consecutive crests is equal to the local wave-length.
These assumptions are expressed in mathematical form, and the existence of a set of characteristic curves (associated with the group velocity) is deduced from them. These characteristics are not identical with the crests. Let the additional assumption be made that

the characteristics all pass through the point disturbance; the characteristics are then completely defined and may be constructed by a step-by-step process starting at the point disturbance. The same construction gives the direction of the wave crests at all points. The wave crests can then be deduced.

Assumptions of the same type as (1) and (2) have long been familiar in various applications of ray tracing. For uniform flows the present theory gives the same pattern as the method of stationary phase.
One-dimensional magnetogasdynamics in oblique fields
Authors: Shercliff J. A.
Published: March 2006

Earlier work on the dynamics of a perfectly conductive gas in situations where all variables depend on one space co-ordinate only is extended to the case where the magnetic field has a component in the direction of variation. The theory is developed for an arbitrary gas in equilibrium, subject only to certain reasonable restrictions.

The first main section studies the variation of the transverse field component in slow and fast simple waves and the tendency of compressive waves in which the transverse field does not change sign to steepen into shocks.

The next section develops a symmetrical treatment of the Rayleigh, Fanno and other processes of ordinary steady one-dimensional gasdynamics, generalized to allow for electromagnetic effects. The slow, fast and Alfvén wave speeds are critical. A particular case of this analysis is a generalization of ordinary gasdynamics which allows for the effect of transverse forces such as occur in turbo-machinery.

The final section is an exhaustive study of shocks in the presence of a field component normal to the shock front. From the generalized Rayleigh line it is established that there are up to six different types of shocks, all compressive and distinguishable by the relative magnitudes of the upstream and downstream normal velocities in comparison with the local slow, fast and Alfvén wave speeds.

Some aspects of shock structure are discussed briefly.
Diffraction of strong shocks by cones, cylinders, and spheres
Authors: Bryson A. E. , Gross R. W. F.
Published: March 2006

This paper presents experimental investigations of the diffraction of plane strong shocks by several cones, a cylinder, and a sphere. The diffraction pattern, in particular the loci of Mach triple points and the shape of the diffracted shocks are compared with theoretical results obtained from a diffraction theory proposed by Whitham (1957, 1958, 1959). The agreement between theory and experiment is shown to be good. Also given are extensive numerical results supplementing Whitham's papers, and theortical considerations applying Whitham's theory to very blunt bodies.
The motion of a thin oil sheet under the steady boundary layer on a body
Authors: Squire L. C.
Published: March 2006

A solution is obtained for the motion of a thin oil sheet, of non-uniform thickness, under a boundary layer. The following points are deduced: (a) The oil flows in the direction of the boundary-layer skin-friction, except near separation, where the oil tends to indicate separation too early. These conclusions are independent of oil viscosity. (b) The effect of the oil flow on the boundary-layer motion is very small.

The application of the results to the interpretation of oil-flow patterns is briefly considered.
An experimental investigation of the oscillating lift and drag of a circular cylinder shedding turbulent vortices
Authors: Gerrard J. H.
Published: March 2006

The oscillating lift and drag on circular cylinders are determined from measurements of the fluctuating pressure on the cylinder surface in the range of Reynolds number from 4 × 103 to just above 105.

The magnitude of the r.m.s. lift coefficient has a maximum of about 0.8 at a Reynolds number of 7 × 104 and falls to about 0.01 at a Reynolds number of 4 × 103. The fluctuating component of the drag was determined for Reynolds numbers greater than 2 × 104 and was found to be an order of magnitude smaller than the lift.
Effect of finite boundaries on the Stokes resistance of an arbitrary particle
Authors: Brenner Howard
Published: March 2006

A general theory is put forward for the effect of wall proximity on the Stokes resistance of an arbitrary particle. The theory is developed completely for the case where the motion of the particle is parallel to a principal axis of resistance. In this case, the wall-effect correction can be calculated entirely from a knowledge of the force experienced by the particle in anunboundedfluid, providing (i) that the wall correction is already known for a spherical particle and (ii) that the particle is small in comparison to its distance from the boundary. Experimental data are cited which confirm the theory. The theory is extended to the wall effect on a particlerotatingnear a boundary.
A note on vortex-tube flows
Authors: Reynolds A. J.
Published: March 2006

Vortex-tube flows have been examined which lack the relatively quiescent, nearly isothermal, core common to those studied by other authors.
Transverse plasma waves and their instability
Authors: Kahn F. D.
Published: March 2006

Linearized equations are derived for disturbances in an infinite plasma without an imposed magnetic field. It is shown that besides the electrostatic, or longitudinal, waves which are usually considered, there can also exist electromagnetic, or transverse, waves. The two sets of waves are generally coupled, but one can nevertheless classify the waves as either mainly longitudinal or mainly transverse. It turns out that a plasma which is stable to longitudinal waves will be unstable to transverse waves unless the velocity distribution of its particles satisfies some rather stringent conditions. In a practical case these conditions would require the distribution to be isotropic.
Physical interpretation of the mathematical theory of wave generation by wind
Authors: Lighthill M. J.
Published: March 2006

In the light of accumulated evidence in favour of Miles's mathematical theory of wave generation by wind, the author has thought it desirable to translate the theory into the form of a physical argument, which goes as follows. Travelling water waves in a wind produce, to a first approximation, airflow undulations with pressures least over crests and greatest over troughs. Hence, just above the ‘critical height’ where the airflow component in the direction of propagation equals the wave velocity, air after slowly overtaking a crest is turned back by the higher pressure near the trough, moves down to a lower level and back towards the crest. Similarly, behind crests, an upward movement at the critical height occurs. Quantitatively, the vertical velocity v is such that the ‘vortex force’ − ρων (where ρ is density and ω vorticity) balances the sinusoidal pressure gradient. Furthermore, since in turbulent boundary layers vorticity decreases with height, any downflow produces a local vorticity defect, and upflow a local vorticity excess, and hence the vortex force varies about a negative mean at the critical height (although at other levels, where air moves sinusoidally, with vertical displacement and velocity 90° out of phase, the mean vortex force is zero). The negative total mean force extracts wind energy, and transfers it to the wave, enabling it to grow exponentially. For pressure gradients adequate to initiate substantial energy transfer, the critical height must be fairly small compared with the wavelength, and waves can grow whenever their velocity and direction satisfies this condition, a conclusion supported by measurements (Longuet-Higgins 1962) of the directional spectrum of wind-generated waves.
The characteristics of the turbulence in the mixing region of a round jet
Authors: Davies P. O. A. L. , Fisher M. J. , Barratt M. J.
Published: March 2006

Measurements in the mixing region of a 1 in. diameter cold air jet are described for Mach numbers ranging from 0.2 to 0.55. The statistical characteristics of the turbulence in the first few diameters of the flow may be expressed in terms of simple kinematic similarity relationships. These are based on the jet diameter and the distance downstream from the jet orifice as length-scales, and the inverse of the local shear as a time-scale. The experiments show that the integral time scale of the turbulence in a frame convected with the maximum energy of the turbulent motion is inversely proportional to the local shear.

The most interesting result obtained is that the local intensity of the turbulence is equal to 0.2 times the shear velocity. This velocity is defined as the product of the local integral length-scale of the turbulence with the local shear. The local intensity is defined as the R.M.S. value of the local velocity fluctuations divided by the jet efflux velocity. It was found that the length-scale is proportional to the distance from the jet orifice, while the maximum shear is also related to this distance as well as to the jet efflux velocity. These two similarity relations break down close to the jet orifice and change beyond the first six or so diameters downstream. The convection velocity is not equal to the local mean velocity but varies slowly over the region of maximum shear when it is just over half the jet efflux velocity. The measurements of other observers fit the relationships obtained quite well. From these relationships it is possible to calculate the noise generated by the mixing region of a given jet directly, using expressions derived by Lilley (1958).
The mechanics of dunes and antidunes in erodible-bed channels
Authors: Kennedy John F.
Published: March 2006

An analytic model of free-surface flow over an erodible bed is developed and used to investigate the stability of the fluid-bed interface and the characteristics of the bed features. The model is based on the potential flow over a two-dimensional, moving, wavy bed with a sinusoidal profile of varying amplitude, and a sediment transport relation in which the transport rate is proportional to a power of the fluid velocity at the level of the bed. By assuming that the dominant wavelength is that for which the rate of amplitude growth is the greatest, expressions are obtained for the wavelength and velocity of the bed features. In addition, conditions for the occurrence of the different configurations, dunes, flat bed, and antidunes, are found from the model. The predicted wavelengths of antidunes and ranges of wavelengths of dunes, and the predicted conditions for change of bed configuration are found to be in good agreement with experimental data. Finally, brief consideration is given to the factors involved in determining the maximum heights of the bed features and surface waves.
Heat and mass transfer from rotating cones
Authors: Tien C. L. , Campbell D. T.
Published: March 2006

Heat transfer by convection from isothermal rotating cones is investigated experimentally by measuring the sublimation rate from naphthalene-coated cones and using the analogy between heat and mass transfer. Measurements are made for a range of conditions from entirely laminar flow to conditions when the outer 70% of the surface area is covered by turbulent flow. Mass-transfer measurements for laminar flow over cones of vertex angles 180°, 150°, 120° and 90° are in good agreement with the theoretical prediction. For turbulent flow, experimental results for cones of the above vertex angles also agree very well with the semi-empirical analogy calculations for the disk case. A different heat- and mass-transfer relationship with the rotational Reynolds number is observed in the measurements on the 60° cone, and is believed to be due to a change of flow characteristics. The instability and the transition of flows over different cone models are also discussed.
Some general theorems concerning the finite motion of a shallow rotating liquid lying on a paraboloid
Authors: Ball F. K.
Published: March 2006

The motion of a bounded shallow liquid, initially of arbitrary shape, in an arbitrary state of motion and lying on a paraboloid of revolution (including a level surface as a special case) can always be separated into three parts:

the motion of the centre of gravity, which is entirely independent of the other motions and is governed by a pair of simple ordinary linear differential equations;

an isotropic two-dimensional dilatation and rotation which are also governed by a simple linear differential equation;

the motions that remain after removal of the velocity fields associated with the preceding motions; these will be called additional motions.

The additional motions exert a ‘pressure’, determined by their total energy, which tends to increase the spread of the liquid. If the spread does increase then the additional motions lose energy which then appears as energy associated with the dilatation.

The effect of the dilatation and rotation on the additional motions can be described by transformation into a co-ordinate system that rotates and dilates with the liquid. In these co-ordinates, with a properly adjusted time scale, the additional motions satisfy equations that are isomorphic with the original equations of motion; however, the liquid now appears to be lying on a parabola that is always concave upwards.
Hamel flow of certain anisotropic fluids
Authors: Leslie F. M.
Published: March 2006

An exact solution is given for the flow in a convergent or divergent channel of a class of anisotropic fluids in which the fluid has a preferred direction.
The travelling-wave plasma converter
Authors: Messerle H. K.
Published: March 2006

The travelling-wave plasma converter is analyzed allowing for the compressible nature of the fluid. The study is restricted to conditions for which the magnetic Reynolds number is small. Steady and time-varying flow conditions are investigated using small perturbation theory. Relations for optimum conversion effectiveness are established and the effects of variable electrical conductivity are investigated. Conditions for electromechanical resonance are derived and it is shown that the conversion process introduces a damping effect.
Magnetohydrodynamic flow in rectangular ducts
Authors: Hunt J. C. R.
Published: March 2006

The paper presents an analysis of laminar motion of a conducting liquid in a rectangular duct under a uniform transverse magnetic field. The effects of the duct having conducting walls are investigated. Exact solutions are obtained for two cases, (i) perfectly conducting walls perpendicular to the field and thin walls of arbitrary conductivity parallel to the field, and (ii) non-conducting walls parallel to the field and thin walls of arbitrary conductivity perpendicular to the field.

The boundary layers on the walls parallel to the field are studied in case (i) and it is found that at high Hartmann number (M), large positive and negative velocities of order MVc are induced, where Vc is the velocity of the core. It is suggested that contrary to previous assumptions the magnetic field may in some cases have a destabilizing effect on flow in ducts.
Numerical solutions for the time-dependent viscous flow between two rotating coaxial disks
Authors: Pearson Carl E.
Published: March 2006

The nature of the steady-state viscous flow between two large rotating disks has often been discussed, usually qualitatively, in the literature. Using a version of the numerical method described in the preceding paper (Pearson 1965), digital computer solutions for the time-dependent case are obtained (steady-state solutions are then obtainable as limiting cases for large times). Solutions are given for impulsively started disks, and for counter-rotating disks. Of interest is the fact that, at high Reynolds numbers, the solution for the latter problem is unsymmetrical; moreover, the main body of the fluid rotates at a higher angular velocity than that of either disk.
Similarity laws for turbulent boundary layers with suction or injection
Authors: Tennekes H.
Published: March 2006

The concept of a law of the wall and a velocity defect law which are related to each other through a common velocity scale and a semilogarithmic velocity profile in the region where they overlap, can be applied successfully to turbulent boundary layers with suction or injection. For turbulent boundary layers at moderate suction rates the velocity scale is proportional to u2r/v0. For layers at arbitrary suction or blowing rates the velocity scale, which has been determined empirically, is proportional to (ur + 9v0).
On the generation of spatially growing waves in a boundary layer
Authors: Gaster M.
Published: March 2006

The solution is obtained in general terms for the velocity fluctuations generated in a laminar boundary layer by an oscillating disturbance on the boundry wall. The form of excitation is chosen to represent a vibrating ribbon of the type used by Schubauer to force disturbance in boundary layers. The forced wave system generated by the ribbon is shown to be a spatially growing one, which is described far downstream by an eigenmode of the system which has a complex wave-number.
Gravitational instability of a viscous fluid in a magnetic field
Authors: Yih Chia-Shun
Published: March 2006

The instability of a viscous fluid between two infinite vertical plates and heated from below in the presence of a magnetic field perpendicular to the plates is investigated, and the most critical stability boundary in the space of the Rayleigh number R, Hartmann number M, and the horizontal wave number a is determined. It is found that the most unstable mode is a symmetric mode with zero wave-number, and that for any M the fluid is unstable for any non-zero R, however small.
On some aspects of fully-developed turbulent flow in rectangular channels
Authors: Gessner F. B. , Jones J. B.
Published: March 2006

For fully-developed turbulent flow in straight channels of non-circular cross-section, there exists a transverse mean flow superimposed upon the axial mean flow. This transverse flow, commonly known as secondary flow, interacts with the axial mean flow and turbulence structure in a complex manner. In this paper several heretofore unexplored aspects of this type of secondary flow are discussed on the basis of results of an extensive experimental programme which was conducted for steady, incompressible, fully-developed turbulent air flow in both square and rectangular channels. Specifically, the following aspects are examined: (a) the Reynolds-number effect on secondary flow, (b) the directional characteristics of local wall shear stress, (c) the orientation of Reynolds-stress principal planes in a plane normal to the axial flow direction, and (d) the Reynolds equation along a secondary-flow streamline.

Within the Reynolds-number range of the investigation, the results indicate that secondary-flow velocities, when non-dimensionalized with either the bulk velocity or the axial mean-flow velocity at the channel centreline, decrease for an increase in Reynolds number. Also, the greatest skewness of local wall shear-stress vectors is shown to occur in the near vicinity of corners where secondary flow is maximum. In addition, it is shown that in planes normal to the axial flow direction, traces of Reynolds stress principal planes are not tangent and normal to lines of constant axial mean-flow velocity. This behaviour is in contrast to that for less complicated turbulent flows, for example, two-dimensional channel flow or circular-pipe flow where such traces are always tangent and normal to lines of constant axial mean-flow velocity in accordance with symmetry considerations. Finally, through experimental evaluation of terms in a momentum balance along a typical secondary-flow streamline, it is shown that secondary flow is the result of small differences in magnitude of opposing forces exerted by the Reynolds stresses and static pressure gradients in planes normal to the axial flow direction.
Experiments on turbulent-flow phenomena in eccentric annular ducts
Authors: Jonsson V. K. , Sparrow E. M.
Published: March 2006

The investigation to be described here is a wide-ranging experimental study aimed at determining both the details of the flow field and the pressure drop and friction factor characteristics for turbulent flow in eccentric annular ducts. The experiments were performed utilizing three annular ducts of different diameter ratios; in each case the eccentricity was varied from zero (concentric annulus) to unity (walls in contact). To provide the broadest possible perspective, the measurements of the velocity field are presented in three different ways. First, contour maps showing lines of constant velocity are constructed. From these are deduced circumferential distributions of the local shear stress on the bounding walls. Velocity profiles along lines normal to the walls are represented in terms of both law-of-the-wall variables and defect-law variables. Neither of these representations affords complete agreement with the universal circular-tube distributions. In general, the defect law provides a somewhat closer correlation of the results for the eccentric annulus with those for the tube. The experimental findings do not substantiate a prior analytical model which assumes that the universal law of the wall applies on all lines normal to the bounding walls of the annulus. Friction factors, based on static pressure measurements, are shown to decrease with increasing eccentricity. The measured friction factors are in fair agreement with those of analysis. Hydrodynamic development lengths, deduced from entrance-region pressure data, are found to increase with increasing eccentricity. Circumferential pressure variations also increase with eccentricity.
Verification of the proposed equation for calculation of the forces on a sphere accelerating in a viscous fluid
Authors: Odar Fuat
Published: March 2006

The equation which was proposed for the calculation of forces on a sphere accelerating in a viscous fluid is verified by comparing the velocities of spheres falling under gravity in a viscous fluid with those calculated from the equation.
Condensation of water vapour during supersonic expansion in nozzles
Authors: Hill Philip G.
Published: March 2006

Existing data on the condensation of steam and moist air in supersonic nozzles are compared with predictions based on nucleation and drop-growth theory. It is concluded that, if the surface tension is assumed independent of curvature, and the classical liquid-drop theory (based on a stationary liquid drop) is used, the theory is in general agreement with the data. The effects of uncertainties in cluster surface energy and also of the large corrections to nucleation theory due to the ‘gasification’ concept are examined. The gasification correction is in accord with experimental data only if the surface tension is considered to rise significantly with curvature. In neither case can the Tolman or Kirkwood–Buff equations be supported. A review of existing data shows that there is some question as to the appropriate value of the condensation coefficient but this is of little consequence as long as the accommodation coefficient for the liquid–vapour surface is taken to be unity. The usefulness of the nozzle experiments for testing the validity of nucleation theory is demonstrated.
Equilibrium turbulent boundary layers
Authors: Mellor G. L. , Gibson D. M.
Published: March 2006

Empirical information is extracted from constant-pressure flows and, on this basis alone, the equations of motion are solved for flows where the pressure gradient parameter, β = δ*(dp/dx)/τ0 is held constant. The experimental defect profiles of Clauser and the near-separating profile of Stratford are predicted quite well.

The present work is an extension of the work of Clauser and Townsend in that a particular form for an effective or eddy viscosity is hypothesized. Here, however, a continuous, and analytically precise family of defect profiles are calculated for the entire range, −0·5 ≤ β ≤ ∞. The solutions span the whole profile with the exception of the viscous sublayer.

A detailed consideration of the viscous sublayer and a comparative examination of various eddy viscosity hypotheses are included in a companion paper.
Dynamics of flexible slender cylinders in axial flow Part 2. Experiments
Authors: Paidoussis M. P.
Published: March 2006

The experiments described here were designed to illustrate the dynamical behaviour of flexible cylinders in axial flow theoretically examined in Part 1. Rubber cylinders, either clamped or pinned at the upstream end and free at the other, or pinned at both ends, displayed both buckling and oscillatory instabilities when immersed in flowing water of sufficiently high velocity. The conditions of neutral stability were determined in a number of cases and compared with theory. The observations were in substantial agreement with the theory.
Subcritical convective instability Part 1. Fluid layers
Authors: Joseph Daniel D. , Shir C. C.
Published: March 2006

This paper elaborates on the assertion that energy methods provide an always mathematically rigorous and a sometimes physically precise theory of sub-critical convective instability. The general theory, without explicit solutions, is used to deduce that the critical Rayleigh number is a monotonically increasing function of the Nusselt number, that this increase is very slow if the Nusselt number is large, and that a fluid layer heated from below and internally is definitely stable when $RA < \widetilde{RA}(N_s) > 1708/(N_s + 1)$ where Ns is a heat source parameter and $\widetilde{RA}$ is a critical Rayleigh number. This last problem is also solved numerically and the result compared with linear theory. The critical Rayleigh numbers given by energy theory are slightly less than those given by linear theory, this difference increasing from zero with the magnitude of the heat-source intensity. To previous results proving the non-existence of subcritical instabilities in the absence of heat sources is appended this result giving a narrow band of Rayleigh numbers as possibilities for subcritical instabilities.