bluuebunny/crossref_metadata_2025 huggingface dataset:
Social marketing with challenging target groups: smoking cessation in prisons in England and Wales
Authors: MacAskill Susan , Lindridge Andrew , Stead Martine , Eadie Douglas , Hayton Paul , Braham Mark
Published: October 2007

Smoking levels among prisoners are much higher than amongst the UK population as a whole. Our research focuses on the development and implementation of a pilot smoking cessation project:

Using a social marketing process combined with the Health Behaviour Model, 159 participants, drawn from four prisons, undertook a smoking cessation programme.

Data was collected using a case study approach, with a variety of research methods: primarily depth individual and mini‐group qualitative interviews, but also document analysis and observation.

The findings draw on prisoners' perspectives in the context of the marketing mix in elements of the strategy design, implementation and evaluation.

The discussion identifies the need to maintain a consumer perspective, feeding into the marketing mix, and to identify and promote aspects of mutually beneficial exchange over and above basic health and monetary costs.

The positive outcomes and insights gained show that using a social marketing strategy, as part of a smoking cessation programme, has important policy and practice implications. Lessons could be applied to other health issues and in similar settings such as forensic mental health.

Copyright © 2007 John Wiley & Sons, Ltd.
How UK universities engage with their local communities: a study of employer supported volunteering
Authors: Bussell Helen , Forbes Deborah
Published: October 2007

In 2000, the UK Prime Minister pledged that employers should be encouraged to release staff for 1 day a year to undertake volunteering activity. Many and varied programmes are being set up to assist employees to volunteer, whether during work hours or in their own time. This is called employer supported volunteering (ESV). This paper discusses the increasing use of ESV and aims to provide an understanding of the key concepts of this phenomenon. An E‐mail survey was completed of all 122 universities in England, Scotland, Wales and Northern Ireland. University websites linked to volunteering for staff and students were also examined. Responses were received from 65 institutions (a response rate of 53%). This initial research reveals that university commitment to ESV varies across the sector. Many universities support staff volunteering and informally encourage links with the local community through voluntary activity but only seven institutions had developed a formal policy allowing staff time off work to volunteer. From this initial research, three best practice universities have emerged and their activities are discussed. The next stage in this project is to research the areas identified and to explore the extent of volunteering by university staff and staff attitudes to volunteering with a view to provide a full picture of ESV in the UK university sector.

Copyright © 2007 John Wiley & Sons, Ltd.
Interfacial polymerization of morphologically modified polyaniline: from hollow microspheres to nanowires
Authors: Li Jinbo , Jia Qingming , Zhu Jiewu , Zheng Maosheng
Published: October 2007

BACKGROUND: Polyaniline (PANI) has attracted much attention in many fields due to its chemical and physical properties, and different nanostructures of PANI changing from one‐dimensional to three‐dimensional have been obtained. By changing the concentration of cetyltrimethylammonium bromide (CTAB), the morphology of hydrochloric acid‐doped polyaniline could be changed from one‐dimensional nanoneedles or nanowires with a network structure (50–100 nm in diameter) to three‐dimensional hollow microspheres (ca 400 nm in outer diameter) via combining interfacial polymerization and self‐assembly process.

RESULTS These different nanostructures of PANI were proved using scanning electron and transmission electron microscopies. A plausible mechanism of the formation of the changeable nanostructures of PANI may be different from that of interfacial polymerization without surfactant or a traditional homogenous reaction system using CTAB as surfactant.

CONCLUSION The results obtained from Fourier transform infrared spectrometry, X‐ray diffraction and the four‐probe method showed that the molecular structure of PANI does not change with increasing CTAB concentration, but crystallinity and conductivity of PANI increase with surfactant concentration. Copyright © 2007 Society of Chemical Industry
The graviton propagator with a non‐conserved external generating source
Authors: Manoukian E.B. , Sukkhasena S.
Published: October 2007

A novel general expression is obtained for the graviton propagator from Lagrangian field theory by taking into account the necessary fact that in the functional differential approach of quantum field theory, in order to generate non‐linearities in gravitation and interactions with matter, the external source Tμν, coupled to the gravitational field, should a priori not be conserved ∂μ Tμν≠ 0, so variations with respect to its ten components may be varied independently. The resulting propagator is the one which arises in the functional approach and does not coincide with the corresponding time‐ordered product of two fields and it includes so‐called Schwinger terms. The quantization is carried out in a gauge corresponding to physical states with two polarization states to ensure positivity in quantum applications.
Some aspects of c = ‐2 theory
Authors: Rajabpour M.A. , Rouhani S. , Saberi A.A.
Published: October 2007

We investigate some aspects of the c = ‐2 logarithmic conformal field theory (LCFT). At first, we calculate some correlators of logarithmic conformal fields which have third order singular OPE with the energy‐momentum tensor. Then, we argue about the fields in the c = ‐2 model which are associated with this kind of more general logarithmic primary fields. We go on to find fermionic representations for all the fields in the extended Kac table, in particular the untwisted sector. Moreover, we calculate the various OPEs of the fields, especially for the logarithmic energy‐momentum tensor and by using these OPEs we find the exact finite transformation of this field. We briefly discuss about the important role of the zero modes in the c = ‐2 model. Finally we consider the perturbation of this theory and its relationship with integrable models, and generalization of Zamalodchikov's c‐theorem.
Isolation of nucleotide binding site‐leucine rich repeat and kinase resistance gene analogues from sugarcane (Saccharum spp.)
Authors: Glynn Neil C , Comstock Jack C , Sood Sushma G , Dang Phat M , Chaparro Jose X
Published: October 2007

BACKGROUND: Resistance gene analogues (RGAs) have been isolated from many crops and offer potential in breeding for disease resistance through marker‐assisted selection, either as closely linked or as perfect markers. Many R‐gene sequences contain kinase domains, and indeed kinase genes have been reported as being proximal to R‐genes, making kinase analogues an additionally promising target. The first step towards utilizing RGAs as markers for disease resistance is isolation and characterization of the sequences.

RESULTS: Sugarcane clone US01‐1158 was identified as resistant to yellow leaf caused by the sugarcane yellow leaf virus (SCYLV) and moderately resistant to rust caused by Puccinia melanocephala Sydow & Sydow. Degenerate primers that had previously proved useful for isolating RGAs and kinase analogues in wheat and soybean were used to amplify DNA from sugarcane (Saccharum spp.) clone US‐01‐1158. Sequences generated from 1512 positive clones were assembled into 134 contigs of between two and 105 sequences. Comparison of the contig consensuses with the NCBI sequence database using BLASTx showed that 20 had sequence homology to nuclear binding site and leucine rich repeat (NBS‐LRR) RGAs, and eight to kinase genes. Alignment of the deduced amino acid sequences with similar sequences from the NCBI database allowed the identification of several conserved domains. The alignment and resulting phenetic tree showed that many of the sequences had greater similarity to sequences from other species than to one another.

CONCLUSION: The use of degenerate primers is a useful method for isolating novel sugarcane RGA and kinase gene analogues. Further studies are needed to evaluate the role of these genes in disease resistance. Published in 2007 by John Wiley & Sons, Ltd.
Preference of birds for zinc phosphide bait formulations
Authors: Jacob Jens , Leukers Angela
Published: October 2007

BACKGROUND: Zinc phosphide baits are used for controlling pest rodents but are also highly toxic to other vertebrates. The base for rodent baits containing zinc phosphide is usually wheat kernels which are highly attractive to birds. In this study, wheat‐based pellets of different shapes and colours without zinc phosphide were tested for their attractiveness for pigeons (Columba livia Gmelin) and Japanese quails (Coturnix japonica Temm. & Schleg.) in aviaries and for pigeons and corvids (Corvus monedula L., Corvus corone L., Pica pica L.) in the field.

RESULTS: In aviaries, wheat was clearly preferred over other bait. In the field, some bait formulations were avoided by birds in certain conditions. However, no formulation was avoided consistently across species to lower the potential uptake of zinc phosphide below the LD50 for highly susceptible bird species (8 mg kg−1 body weight). The formulations that were not rapidly eaten by birds (blue granules, red lentil‐shaped pellets) were not avoided consistently at low and high vegetative cover.

CONCLUSIONS: The bait formulations tested may not considerably enhance the safety of birds when using zinc phosphide for rodent control. Field testing other combinations of bait colour and shape to minimise background contrast may result in bait with higher potential for bird protection. Copyright Jens Jacob and Angela Leukers, employees of the Federal Biological Research Centre for Agriculture and Forestry, Germany. Printed with permission
Synthesis and thermoelectric properties of YbSb2Te4
Authors: Guloy Amado S. , Gascoin Franck , Chamoire Audrey , Tedenac Jean Claude , Snyder G. Jeffrey
Published: October 2007

The study of the ternary phase diagram Yb–Sb–Te has led to the synthesis of YbSb2Te4 as a pure phase by way of high energy ball milling followed by annealing, whereas typical high temperature powder metallurgy leads to multiphase sample with impurities of the very stable YbTe. The Hall mobility, Seebeck coefficient, electrical resistivity and thermal conductivity of the layered compound YbSb2Te4 were measured in the range of 20–550 °C. The thermoelectric figure of merit peaks at 525 K and reaches 0.5. Of particular interest is the very low lattice thermal conductivity (as low as a glass) which makes YbSb2Te4 and related compounds promising thermoelectric materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on [(4‐substituted benzoylamino)phenylmethyl]phosphonic acid diisopropyl esters under electrospray ionization tandem mass spectrometric conditions
Authors: Fang Hua , Fang Mei‐juan , Zhu Chang‐jin , Liu Lin‐na , Zhao Yu‐Fen
Published: October 2007

Phosphonate esters were synthesized and investigated by positive ion electrospray ionization mass spectrometry (ESI‐MS) in conjunction with tandem mass spectrometry (MS/MS). It was found that for the sodiated adduct there were two novel rearrangement reactions, in which the phosphoryl oxygen atom migrated to the carbonyl carbon and a cleavage occurred at the amide bond, or a benzylamine fragment was lost and the phosphorus was reduced. However, when the methyl group substituted for the isopropyl group, these migrations were inhibited. A possible mechanism was proposed, and high‐resolution mass spectrometry was applied to identify the formula of these novel ions. These results showed that ESI‐MS is a useful tool for the structural determination of phosphonate esters. Copyright © 2007 John Wiley & Sons, Ltd.
Mass spectral studies of perfluorooctane sulfonate derivatives separated by high‐resolution gas chromatography
Authors: Langlois Ingrid , Berger Urs , Zencak Zdenek , Oehme Michael
Published: October 2007

The mass spectral characteristics of perfluorooctane sulfonate (PFOS, C8F17SO) isomers present in technical PFOS were obtained using high‐resolution gas chromatography (HRGC) combined with mass spectrometry (MS). To make PFOS amenable to HRGC separation, a simple derivatization procedure was developed. The method involved the conversion of PFOS into the iso‐propyl ester using iso‐propanol as the derivatization reagent under acidic conditions. Mass spectra were generated employing electron ionization (EI) and negative chemical ionization (NCI). Interpretation of fragment ions was possible due to the use of deuterium‐labeled iso‐propanol as derivatization reagent, which induced mass shifts in the electron ionization (EI) and negative chemical ionization (NCI) mass spectra. HRMS allowed the accurate mass measurement of important EI fragments and confirmed the derivatization reaction as well as the proposed fragmentation pathway involving rearrangement. Moreover, the high resolution provided by HRGC enabled the separation of eleven PFOS isomers present in the technical product. This is an improvement over the previously reported high‐performance liquid chromatography (HPLC) separation. A complete identification of all isomers was not possible due to lack of pure reference materials. Finally, the developed derivatization procedure was successfully applied to perfluoroalkyl carboxylates (PFCA) and corresponding fragmentation involving rearrangement of the derivatized PFCA was observed. The described qualitative derivatization offers a promising alternative technique for the separation and identification of isomers of perfluoroalkyl sulfonates and carboxylates by HRGC/MS. Copyright © 2007 John Wiley & Sons, Ltd.
Capillary hydrophilic interaction chromatography/mass spectrometry for simultaneous determination of multiple neurotransmitters in primate cerebral cortex
Authors: Zhang Xiaozhe , Rauch Alexander , Lee Han , Xiao Hongbin , Rainer Gregor , Logothetis Nikos K.
Published: October 2007

A diverse array of neurotransmitters and neuromodulators control and affect brain function. A profound understanding of the signaling pathways and the neural circuits underlying behavior is therefore likely to require the tracking of concentration changes of active neurochemicals. In the present study, we demonstrate the feasibility of a method allowing the simultaneous determination of the concentrations of six neurotransmitters: acetylcholine, serotonin, dopamine, γ‐aminobutyric acid (GABA), glutamate and aspartate, in the extracellular brain fluid (EBF). We used hydrophilic interaction chromatography (HILIC) coupled to tandem mass spectrometry (MS/MS) to analyze the EBF from the monkey brain. A push‐pull sampling method was used to collect EBF from the prefrontal cortex (PFC) of conscious monkeys at flow rates in the range of low nL/min. The detection limits of acetylcholine, serotonin, dopamine, GABA, glutamate and aspartate were 0.015, 0.15, 0.3, 1.2, 6 and 15 femtomoles, respectively, allowing us to quantitatively determine the concentrations of these six neurotransmitters simultaneously from 500 nL in vivo samples. We conclude that HILIC/MS/MS combined with the push‐pull sampling method represents a sensitive technique for simultaneous monitoring of neurotransmitters from EBF samples. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of the impact of some experimental procedures on different phosphopeptide enrichment techniques
Authors: Jensen Søren S. , Larsen Martin R.
Published: October 2007

The complete characterization of phosphorylated proteins requires an efficient procedure for the enrichment of phosphopeptides from amongst a complicated peptide mixture. The sensitivity of the traditional immobilized metal affinity chromatography (IMAC) approach is severely affected by various buffers, detergents and other reagents normally utilized in biochemical and cell biological procedures, and thus pre‐purification steps such as reversed‐phase chromatography is required prior to phosphopeptide enrichment. Here we evaluate the use of different ‘non‐phosphopeptide‐excluding compounds’ in the loading buffer for titanium dioxide (TiO2) chromatography and show that TiO2 is more robust and tolerant towards many reagents, including salts, detergents and other low molecular mass molecules, than conventional IMAC. In addition, we show that the inclusion of various detergents can enhance the efficiency of this enrichment method, as phosphopeptides that otherwise adhere to plastic surfaces can be efficiently solubilized and subsequently purified. The TiO2 chromatography technique is also compared to zirconium dioxide chromatography for phosphopeptide enrichment. Copyright © 2007 John Wiley & Sons, Ltd.
The combined use of thermal desorption and selected ion flow tube mass spectrometry for the quantification of xylene and toluene in air
Authors: Ross Brian M. , Vermeulen Natasha
Published: October 2007

Thermal desorption (TD) is commonly employed for volatile chemical analysis, it being the method of choice for occupational health and safety monitoring. TD allows for offline capture of volatiles onto a solid sorbent followed by desorption and analysis at a later time. Although TD is routinely used in conjunction with gas chromatography (TD‐GC), the assay throughput is low and requires the use of gas standards for quantification. Another technique increasingly employed for volatile chemical analysis, selected ion flow tube mass spectrometry (SIFT‐MS), is capable of real‐time absolute (i.e. without calibration standards) quantification of volatile chemicals present at single digit parts per billion or higher concentrations. SIFT‐MS is, however, normally used for online direct analysis of gas samples rather than offline collection and analysis. The goal of this study was to determine whether a combination of TD and SIFT‐MS could be used to quantify volatile compounds, specifically xylene and toluene, more rapidly than TD‐GC and without the need for calibration standards. SIFT‐MS was able to quantify xylene and toluene levels within 45 s of desorption. Due to the robustness of the SIFT‐MS analysis in the presence of water vapour and other major components of air, the purging of tubes usually required to remove these constituents during the TD cycle was not required, therefore reducing the TD cycle time. Comparing the quantity of xylene and toluene applied to the TD tube with the absolute levels quantified by SIFT‐MS subsequent to desorption suggested a recovery of over 95% of the applied compound. We conclude that the combination of TD and SIFT‐MS allows more rapid and accurate quantification of xylene and toluene (compared with TD‐GC) to be achieved without the need for calibration standards, features which may be advantageous in applications requiring rapid analysis and high throughput. Copyright © 2007 John Wiley & Sons, Ltd.
High‐field asymmetric waveform ion mobility spectrometry coupled with liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐FAIMS‐MS/MS) multi‐component bioanalytical method development, performance evaluation and demonstration of the constancy of the compensation voltage with change of mobile phase composition or flow rate
Authors: Wu Steven T. , Xia Yuan‐Qing , Jemal Mohammed
Published: October 2007

The feasibility of developing a multi‐component bioanalytical method using high‐field asymmetric waveform ion mobility spectrometry coupled with liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐FAIMS‐MS/MS) is demonstrated using nefazodone and its two metabolites as model compounds. The performance of the bioanalytical method for the three analytes, with three different compensation voltage (CV) values, is assessed using standard curves and quality control samples, which exhibited good accuracy, precision and ruggedness. The number of analytes with different CV values that can be quantitated simultaneously depends on the acquisition cycle time, which is a function of the FAIMS residence time (fixed), chromatographic peak width and selected reaction monitoring (SRM) dwell time. It is established that CV, the FAIMS selectivity parameter, is reproducible for at least 16 h, thus ensuring the constancy of the CV during a large‐batch sample analysis. It is also established that change in mobile phase composition or of flow rate does not cause a shift in CV. Thus, CV values determined from a CV scan via infusion of a sample can be used for an LC/ESI‐FAIMS‐M/MS method based on isocratic or gradient elution. Copyright © 2007 John Wiley & Sons, Ltd.
Multimarket contact and sales growth: evidence from insurance
Authors: Greve Henrich R.
Published: October 2007

Research on pricing, profits, and firm survival has shown that multimarket contact causes mutual forbearance against competition, but has not considered the consequences of imperfect observability of competitive moves. Here, predictions are developed to explain how mutual forbearance occurs—but sometimes fails—in markets with imperfect observability. Mutual forbearance means that firms do not seek to take market share from each other through price cuts or nonprice competition, and thus that sales grow at uniform rates. Firms defect from mutual forbearance, and hence have higher sales growth, if the potential rewards are high and the likelihood of being discovered is low. This theory is tested on a panel of firms operating in the Norwegian general insurance industry. The evidence suggests that sales growth is most rapid in firms that do not meet many multimarket competitors in a given market and firms that are economically troubled. Growing or highly concentrated markets have higher heterogeneity of growth rates. Copyright © 2007 John Wiley & Sons, Ltd.
Empirical‐based recovery and maintenance of input error‐correction features
Authors: Ngo Minh Ngoc , Tan Hee Beng Kuan
Published: October 2007

Most information systems deal with inputs submitted from their external environments. In such systems, input validation is often incorporated to reject erroneous inputs. Unfortunately, many input errors cannot be detected automatically and therefore result in errors in the effects raised by the system. Therefore, the provision of input error‐correction features (IECFs) to correct these erroneous effects is critical. However, recovery and maintenance of these features are complicated, tedious and error prone because there are many possible input errors during user interaction with the system; each input error, in turn, might result in several erroneous effects. Through empirical study, we have discovered some interesting control flow graph patterns with regard to the implementation of IECFs in information systems. Motivated by these initial findings, in this paper, we propose an approach to the automated recovery of IECFs by realizing these patterns from the source code. On the basis of the recovered information, we further propose a decomposition‐slicing technique to aid the maintenance of these features without interfering with other parts of the system. A case study has been conducted to show the usefulness of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.
Earthquake and wind damage repair to return a building to its pre‐event condition
Authors: Hart Gary C. , Jain Anurag , King Stephanie
Published: October 2007

This paper presents an answer to the statement ‘Please recommend the damage repair to the building that is required to restore the building to its pre‐hurricane or earthquake condition.’ Copyright © 2007 John Wiley & Sons, Ltd.
Fetal ductus venosus, middle cerebral artery and umbilical artery flow responses to uterine contractions in growth‐restricted human pregnancies
Authors: Fu J. , Olofsson P.
Published: October 2007

Objective

To explore fetal ductus venosus (DV) flow velocity changes relative to umbilical artery (UA) blood flow and brain‐sparing flow (BSF) during uterine contractions.

Methods

Forty‐five term fetuses suspected of having growth restriction were exposed to an oxytocin challenge test (OCT) with simultaneous Doppler velocimetry in the UA, middle cerebral artery (MCA) and DV. Basal BSF was defined as a MCA‐to‐UA pulsatility index (PI) ratio of < 1.08, and de novo BSF as a decrease in MCA‐PI of ≥ 1 SD (equivalent to a value of 0.24 units) during the OCT.

Results

Basal DV flow velocities were lower in the BSF group (n = 7) than they were in the non‐BSF group (n = 38). During the OCT, DV flow velocity parameters changed in neither group but MCA‐PI decreased in the non‐BSF group. A crude de novo BSF was not associated with DV flow velocity changes, but when UA‐PI changes were considered, a serial relationship was found between decreased UA‐PI, increased DV flow velocity, and decreased MCA‐PI. When UA‐PI increased, the MCA‐PI still decreased (though not significantly) but DV flow velocity parameters remained unchanged.

Conclusions

Established fetal BSF is associated with low DV flow velocities, but in an acute sequence there might be two contrasting courses along which BSF develops: one with an increase and one with a decrease in the UA vascular flow resistance. In the former situation the DV flow velocity increases, while in the latter situation the role of the DV in the acute redistribution of fetal blood flow is unclear. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Numerical optimization of the Voith‐Schneider® Propeller
Authors: Jürgens D. , Palm M. , Singer S. , Urban K.
Published: October 2007

The Voith‐Schneider® Propeller (VSP) is an efficient ship propeller that was invented by Ernst Leo Schneider (1894–1975) in 1927. It is a complex propeller having several parameters determining the behavior of the VSP. One of them is the Blade Steering Curve (BSC) which describes the angle of a propeller blade for a time instant. We investigate the choice of this BSC in order to optimize the efficiency of the VSP. We use numerical optimization and Computational Fluid Dynamics (CFD), in particular the Vortex‐Lattice Method for the optimization and Finite Volume Method for validation. We obtain a significant improvement of 4.8%.
Mathematical and physical interpretation of the solution to the initial–boundary value problem in linear hyperbolic thermoelasticity theory
Authors: Gawinecki J.A. , Sikorska B. , Nakamura G. , Rafa J.
Published: October 2007

A new system of equations describing a thermoelastic medium in three‐dimensional space is considered. Such a system also describes the propagation of heat with finite speed.

We consider the initial‐boundary value problem (with the boundary condition of Lamb's type) for this system of equations. Using the modified Cagniard‐de Hoop method we construct an explicit solution of this problem.

Based on the constructed solution of the above mentioned problem, we describe the type of waves which propagate in the thermoelastic medium and the domain of their propagation.

The main role in our considerations is played by the physical interpetation of the singular and branch points of the integrands in the corresponding Fourier integrals.

The values of the singular and branch points and their localization on the complex plane are responsible for the velocities of the thermoelastic waves and for the type of such waves.

The analysis of these singularities has allowed for the physical intepretation of the solution.

Namely, new kind of waves in a thermoelastic medium have been discovered:

frontal waves of the Schmidt's type

surface waves of the Rayleigh's type

We have determined the exact geometric description of the wave surfaces and the character of their origin. We provided the quantitative characterization of the field of temperature, as well.
On Riemann problems and front tracking for a model of sedimentation of polydisperse suspensions
Authors: Berres S. , Bürger R.
Published: October 2007

This paper analyses a continuum model of the sedimentation of polydisperse suspensions, where the volume concentrations of the solids species are the sought unknowns. This leads to systems of conservation laws which are non‐genuinely nonlinear (“non‐convex”) in the sense that they are only piecewise genuinely nonlinear. The solution of a Riemann problem is represented as a concatenation of elementary waves, where the linear degeneracy requires using the Liu entropy condition. After a general description of the composition of elementary waves, an algorithm for the computational construction is given. The solution of the Riemann problem is then utilized as a problem‐adapted building block of a front tracking method. For the model of bidisperse suspensions, Riemann problems are classified by the location of the left and right state in the phase space of unknown variables. The front tracking method is applied to solve the initial value problem of a first‐order hyperbolic 2 × 2 system of conservation laws describing the settling of a bidisperse suspension. The solution obtained by front tracking is compared with results obtained by an experiment and a finite difference scheme.
Appell‐Hamel dynamical system: a nonlinear test of the Chetaev and the vakonomic model
Authors: Xu S.‐S. , Li S.‐M. , Berakdar J.
Published: October 2007

We contrast the results of the Chetaev and vakonomic models of nonholonomic mechanics when applied to the nonholonomically constrainted Appell‐Hamel dynamical system with a nonvanishing constant force parallel to the tangent direction of the wheel. We find that the Chetaev result is compatible with Newton‐Euler solution while the vakonomic model yields results inconsistent with the predictions of the Newton‐Euler mechanics.
Von Kármán equations with uncertain input data and the worst scenario method
Authors: Hlaváček I.
Published: October 2007

A general coercive boundary value problem for the von Kármán system is considered. Both the perpendicular and in‐plane loading of the plate is uncertain, being contained in some compact set of admissible input data. Then the worst scenario problem is defined, taking the possible nonuniqueness of the solution of the von Kármán system into consideration. A proof is presented for the existence of the worst scenario.
Calculation of eigenfrequencies for rectangular free orthotropic plates – An overview
Authors: Hurlebaus S.
Published: October 2007

In this paper, the free transverse vibrations of rectangular orthotropic plates with completely free boundary conditions are considered. Some methodologies for calculating the eigenfrequencies and eigenmodes, based on the classical thin plate theory are presented in a comparative overview. The advantages and disadvantages of these methodologies are discussed for an orthotropic plate application with specific material and geometric properties.
Uniform Test Assembly
Authors: Belov Dmitry I.
Published: October 2007

In educational practice, a test assembly problem is formulated as a system of inequalities induced by test specifications. Each solution to the system is a test, represented by a 0–1 vector, where each element corresponds to an item included (1) or not included (0) into the test. Therefore, the size of a 0–1 vector equals the number of items n in a given item pool. All solutions form a feasible set—a subset of 2n vertices of the unit cube in an n-dimensional vector space. Test assembly is uniform if each test from the feasible set has an equal probability of being assembled. This paper demonstrates several important applications of uniform test assembly for educational practice. Based on Slepian’s inequality, a binary program was analytically studied as a candidate for uniform test assembly. The results of this study establish a connection between combinatorial optimization and probability inequalities. They identify combinatorial properties of the feasible set that control the uniformity of the binary programming test assembly. Computer experiments illustrating the concepts of this paper are presented.
Transcritical rotating flow over topography
Authors: ESLER J. G. , RUMP O. J. , JOHNSON E. R.
Published: October 2007

The flow of a one-and-a-half layer fluid over a three-dimensional obstacle of non-dimensional height M, relative to the lower layer depth, is investigated in the presence of rotation, the magnitude of which is measured by a non-dimensional parameter B (inverse Burger number). The transcritical regime in which the Froude number F, the ratio of the flow speed to the interfacial gravity wave speed, is close to unity is considered in the shallow-water (small-aspect-ratio) limit. For weakly rotating flow over a small isolated obstacle (M → 0) a similarity theory is developed in which the behaviour is shown to depend on the parameters Γ = (F−1)M−2/3 and ν = B1/2M−1/3. The flow pattern in this regime is determined by a nonlinear equation in which Γ and ν appear explicitly, termed here the ‘rotating transcritical small-disturbance equation’ (rTSD equation, following the analogy with compressible gasdynamics). The rTSD equation is forced by ‘equivalent aerofoil’ boundary conditions specific to each obstacle. Several qualitatively new flow behaviours are exhibited, and the parameter reduction afforded by the theory allows a (Γ, ν) regime diagram describing these behaviours to be constructed numerically. One important result is that, in a supercritical oncoming flow in the presence of sufficient rotation (ν ≳ 2), hydraulic jumps can appear downstream of the obstacle even in the absence of an upstream jump. Rotation is found to have the general effect of increasing the amplitude of any existing downstream hydraulic jumps and reducing the lateral extent and amplitude of upstream jumps. Numerical results are compared with results from a shock-capturing shallow-water model, and the (Γ, ν) regime diagram is found to give good qualitative and quantitative predictions of flow patterns at finite obstacle height (at least for M ≲ 0.4). Results are compared and contrasted with those for a two-dimensional obstacle or ridge, for which rotation also causes hydraulic jumps to form downstream of the obstacle and acts to attenuate upstream jumps.
Exact analytical solutions for steady three-dimensional inviscid vortical flows
Authors: BHATTACHARYA S.
Published: October 2007

Vortical flows with an axial (z-axis) swirl and a toroidal circulation (in the (rho,z)-plane) can be observed in a wide range of fluid mechanical phenomena such as flow around rotary machines or natural vortices like tornadoes and hurricanes. In this paper, we obtain exact analytical solutions for a general class of steady systems with such three-dimensional circulating structures. Assuming incompressible ideal fluid, a general single-variable equation, known as the Squire–Long equation, can be constructed which can uniquely describe the velocity fields with steady axial and toroidal circulations. In this paper, we consider the case where this type of flow can be analysed by solving a linear homogeneous partial differential equation. The derived equation resembles the governing equation of the hydrogen problem. As a result, we obtain a quantization relation which is similar to the expression for the quantized energy states in a hydrogen atom.

For circulating flows, this formalism provides a complete set of orthogonal basis functions which are regular and localized. Hence, each of the basis solutions can be used as a simplified model for a realistic phenomenon. Moreover, an arbitrary circulating field can be expanded in terms of these orthogonal functions. Such an expansion can be potentially useful in the study of more general vortices. As illustrations, we present a few examples where we solve the linear homogeneous equation to analyse fluid mechanical systems which can be models for circulating flow in confined geometry. First, we consider three-dimensional vortices confined between two parallel planar walls. Our examples include flows between two infinite planar walls, inside and outside a vertical cylinder bounded at the ends by horizontal plates, and in an axially confined annular region. Then we describe the special way in which the basis functions should be superposed so that a complicated steady velocity-field with three-dimensional vortical structures can be constructed. Two such cases are discussed to indicate that the derived solutions can be used for complicated fluid mechanical modelling.
The full impulse response of two-dimensional jet/wake flows and implications for confinement
Authors: JUNIPER MATTHEW P.
Published: October 2007

In this theoretical study, a linear spatio-temporal analysis is performed on unconfined and confined inviscid jet/wake flows in order to determine whether they are absolutely or convectively unstable. The impulse response is evaluated in the entire outer fluid, rather than just at the point of impulse, over a wide range of density ratios. This confirms that the dominant saddle point can validly migrate into the plane of diverging eigenfunctions. This reveals that, at certain density ratios and shear numbers, the response can grow upstream in some directions with a cross-stream component, even though it decays directly upstream of, and at, the point of impulse. This type of flow is convectively unstable when unconfined, but becomes absolutely unstable when confined. Other effects of confinement are described in a previous paper. Together, these articles have important implications for the design of fuel injectors, which often employ confined shear flows at high Reynolds number and large density ratios to generate strong mixing in combustion chambers.
Proximal bodies in hypersonic flow
Authors: LAURENCE STUART J. , DEITERDING R. , HORNUNG G.
Published: October 2007

Hypersonic flows involving two or more bodies travelling in close proximity to one another are encountered in several important situations. The present work seeks to explore one aspect of the resulting flow problem by investigating the forces experienced by a secondary body when it is within the domain of influence of a primary body travelling at hypersonic speeds.

An analytical methodology based on the blast wave analogy is developed and used to predict the secondary force coefficients for simple geometries in both two and three dimensions. When the secondary body is entirely inside the primary shocked region, the nature of the lateral force coefficient is found to depend strongly on the relative size of the two bodies. For two spheres, the methodology predicts that the secondary body will experience an exclusively attractive lateral force if the secondary diameter is larger than one-sixth of the primary diameter. The analytical results are compared with those from numerical simulations and reasonable agreement is observed if an appropriate normalization for the relative lateral displacement of the two bodies is used.

Results from a series of experiments in the T5 hypervelocity shock tunnel are also presented and compared with perfect-gas numerical simulations, with good agreement. A new force-measurement technique for short-duration hypersonic facilities, enabling the experimental simulation of the proximal bodies problem, is described. This technique provides two independent means of measurement, and the agreement observed between the two gives a further degree of confidence in the results obtained.
Axisymmetric deformation and stability of a viscous drop in a steady electric field
Authors: LAC ETIENNE , HOMSY G. M.
Published: October 2007

We consider a neutrally buoyant and initially uncharged drop in a second liquid subjected to a uniform electric field. Both liquids are taken to be leaky dielectrics. The jump in electrical properties creates an electric stress balanced by hydrodynamic and capillary stresses. Assuming creeping flow conditions and axisymmetry of the problem, the electric and flow fields are solved numerically withboundary integral techniques. The system is characterized by the physical property ratios R (resistivities), Q (permitivities) and λ (dynamic viscosities). Depending on these parameters, the drop deforms into a prolate or an oblate spheroid. The relative importance of the electric stress and of the drop/medium interfacial tension is measured by the dimensionless electric capillary number, Cae. For λ = 1, we present a survey of the various behaviours obtained for a wide range of R and Q. We delineate regions in the (R,Q)-plane in which the drop either attains a steady shape under any field strength or reaches a fold-point instability past a critical Cae. We identify the latter with linear instability of the steady shape to axisymmetric disturbances. Various break-up modes are identified, as well as more complex behaviours such as bifurcations and transition from unstable to stable solution branches. We also show how the viscosity contrast can stabilize the drop or advance break-up in the different situations encountered for λ = 1.
Viscosity of a dense suspension in Couette flow
Authors: HUANG NICOLAS , BONN DANIEL
Published: October 2007

We study the rheology of a granular paste, i.e. a dense suspension of non-Brownian particles, quantitatively at steady state, in a cylindrical Couette cell. Previous studies have shown a discrepancy between local and global measurements of the viscosity for these materials, making it impossible to predict their resistance to flow. Using both MRI investigation techniques and classical rheology studies, we show that agreement between local and global measurements can be obtained, provided the migration of particles inside the gap is taken into account. As found by Leighton & Acrivos (J. Fluid Mech. vol. 181, 1987, p. 415), the migration leads to a particle density gradient in the flow, the highly sheared regions being less dense in particles. Here, by comparing the local viscosity and particle density measurements from MRI with the macroscopic relation between viscosity and the volume fraction, it is shown that global and local measurements agree with each other. This consequently allows us to define a viscosity for dense suspensions.
On the catalytic role of the phase-locked interaction of Tollmien–Schlichting waves in boundary-layer transition
Authors: WU XUESONG , STEWART P. A. , COWLEY S. J.
Published: October 2007

This paper is concerned with the nonlinear interaction between a planar and a pair of oblique Tollmien–Schlichting (T-S) waves which are phase-locked in that they travel with (nearly) the same phase speed. The evolution of such a disturbance is described using a high-Reynolds-number asymptotic approach in the so-called ‘upper--branch’ scaling regime. It follows that there exists a well-defined common critical layer (i.e. a thin region surrounding the level at which the basic flow velocity equals the phase speed of the waves to leading order) and the dominant interactions take place there. The disturbance is shown to evolve through several distinctive stages. In the first of these, the critical layer is in equilibrium and viscosity dominated. If a small mismatching exists in the phase speeds, the interaction between the planar and oblique waves leads directly to super-exponential growth/decay of the oblique modes. However, if the modes are perfectly phase-locked, the interaction in the first instance affects only the phase of the amplitude function of the oblique modes (so causing rapid wavelength shortening), while the modulus of the amplitude still evolves exponentially until the wavelength shortening produces a back reaction on the modulus (which then induces a super-exponential growth). Whether or not there is a small mismatch or a perfect match in the phase speeds, once the growth rate of the oblique modes becomes sufficiently large, the disturbance enters a second stage, in which the critical layer becomes both non-equilibrium and viscous in nature. The oblique modes continue to experience super-exponential growth, albeit of a different form from that in the previous stages, until the self-interaction between them, as well as their back effect on the planar mode, becomes important. At that point, the disturbance enters a third, fully interactive stage, during which the development of the disturbance is governed by the amplitude equations with the same nonlinear terms as previously derived for the phase-locked interaction of Rayleigh instability waves. The solution develops a singularity, leading to the final stage where the flow is governed by fully nonlinear three-dimensional inviscid triple-deck equations. The present work indicates that seeding a planar T-S wave can enhance the amplification of all oblique modes which share approximately its phase speed.
Dissipative descent: rocking and rolling down an incline
Authors: BALMFORTH N. J. , BUSH J. W. M. , VENER D. , YOUNG W. R.
Published: October 2007

We consider the dynamics of a hollow cylindrical shell that is filled with viscous fluid and another, nested solid cylinder, and allowed to roll down an inclined plane. A mathematical model is compared to simple experiments. Two types of behaviour are observed experimentally: on steeper slopes, the device accelerates; on shallower inclines, the cylinders rock and roll unsteadily downhill, with a speed that is constant on average. The theory also predicts runaway and unsteady rolling motions. For the rolling solutions, however, the inner cylinder cannot be suspended in the fluid by the motion of the outer cylinder, and instead falls inexorably toward the outer cylinder. Whilst ‘contact’ only occurs after an infinite time, the system slows progressively as the gap between the cylinders narrows, owing to heightened viscous dissipation. Such a deceleration is not observed in the experiments, suggesting that some mechanism limits the approach to contact. Coating the surface of the inner cylinder with sandpaper of different grades changes the rolling speed, consistent with the notion that surface roughness is responsible for limiting the acceleration.
An experimental investigation on the interaction of hydraulic jumps formed by two normal impinging circular liquid jets
Authors: KATE R. P. , DAS P. K. , CHAKRABORTY SUMAN
Published: October 2007

The flow field due to two normal impinging liquid jets is different from the flow field associated with a single normal impinging liquid jet, and even from the flow field around two normal impinging compressible fluid jets. Depending on the spacing between the two jets and their relative strengths, different kinds of hydraulic jump interactions are possible, resulting in a variety of flow patterns. The present study experimentally elucidates the jump--jump interactions formed in such cases, for different values of inter-jet spacings and for different strengths of the individual jets. Analogous flow fields associated with the interactions between a single impinging jet and a fence are also studied to allow convenient experimental flow vizualizations.
Stability control and catastrophic transition in a forced Taylor–Couette system
Authors: AVILA M. , MARQUES F. , LOPEZ J. M. , MESEGUER A.
Published: October 2007

Harmonic axial motion of the inner cylinder in the Taylor–Couette system can efficiently shift the onset of instability to larger inner cylinder rotation rates. However, once instability has set in, a rapid sequence of symmetry-breaking bifurcations results in complex spatio-temporal dynamics even for very low post-critical values of the rotation rate. Using spectral computations, we present a detailed study of this sudden transition, shedding light on the nature of the complex flows observed in recent laboratory experiments. In particular, it is shown that these bifurcations are responsible for some of the experimentally observed frequencies which had been attributed to background noise. Movies are available with the online version of the paper.