bluuebunny/crossref_metadata_2025_split huggingface dataset:
On non-Oberbeck–Boussinesq effects in three-dimensional Rayleigh–Bénard convection in glycerol
Authors: Horn Susanne , Shishkina Olga , Wagner Claus 
Published: April 2013

AbstractRayleigh–Bénard convection in glycerol (Prandtl number $\mathit{Pr}= 2547. 9$) in a cylindrical cell with an aspect ratio of $\Gamma = 1$ was studied by means of three-dimensional direct numerical simulations (DNS). For that purpose, we implemented temperature-dependent material properties into our DNS code, by prescribing polynomial functions up to seventh order for the viscosity, the heat conductivity and the density. We performed simulations with the common Oberbeck–Boussinesq (OB) approximation and with non-Oberbeck–Boussinesq (NOB) effects within a range of Rayleigh numbers of $1{0}^{5} \leq \mathit{Ra}\leq 1{0}^{9} $. For the highest temperature differences, $\Delta = 80~\mathrm{K} $, the viscosity at the top is ${\sim }360\hspace{0.167em} \% $ times higher than at the bottom, while the differences of the other material properties are less than $15\hspace{0.167em} \% $. We analysed the temperature and velocity profiles and the thermal and viscous boundary-layer thicknesses. NOB effects generally lead to a breakdown of the top–bottom symmetry, typical for OB Rayleigh–Bénard convection. Under NOB conditions, the temperature in the centre of the cell ${T}_{c} $ increases with increasing $\Delta $ and can be up to $15~\mathrm{K} $ higher than under OB conditions. The comparison of our findings with several theoretical and empirical models showed that two-dimensional boundary-layer models overestimate the actual ${T}_{c} $, while models based on the temperature or velocity scales predict ${T}_{c} $ very well with a standard deviation of $0. 4~\mathrm{K} $. Furthermore, the obtained temperature profiles bend closer towards the cold top plate and further away from the hot bottom plate. The situation for the velocity profiles is reversed: they bend farther away from the top plate and closer towards to the bottom plate. The top boundary layers are always thicker than the bottom ones. Their ratio is up to 2.5 for the thermal and up to 4.5 for the viscous boundary layers. In addition, the Reynolds number $\mathit{Re}$ and the Nusselt number $\mathit{Nu}$ were investigated: $\mathit{Re}$ is higher and $\mathit{Nu}$ is lower under NOB conditions. The Nusselt number $\mathit{Nu}$ is influenced in a nonlinear way by NOB effects, stronger than was suggested by the two-dimensional simulations. The actual scaling of $\mathit{Nu}$ with $\mathit{Ra}$ in the NOB case is $\mathit{Nu}\propto {\mathit{Ra}}^{0. 298} $ and is in excellent agreement with the experimental data.
The dam-break problem for concentrated suspensions of neutrally buoyant particles
Authors: Ancey C. , Andreini N. , Epely-Chauvin G. 
Published: April 2013

AbstractThis paper addresses the dam-break problem for particle suspensions, that is, the flow of a finite volume of suspension released suddenly down an inclined flume. We were concerned with concentrated suspensions made up of neutrally buoyant non-colloidal particles within a Newtonian fluid. Experiments were conducted over wide ranges of slope, concentration and mass. The major contributions of our experimental study are the simultaneous measurement of local flow properties far from the sidewalls (velocity profile and, with lower accuracy, particle concentration) and macroscopic features (front position, flow depth profile). To that end, the refractive index of the fluid was adapted to closely match that of the particles, enabling data acquisition up to particle volume fractions of 60 %. Particle migration resulted in the blunting of the velocity profile, in contrast to the parabolic profile observed in homogeneous Newtonian fluids. The experimental results were compared with predictions from lubrication theory and particle migration theory. For solids fractions as large as 45 %, the flow behaviour did not differ much from that of a homogeneous Newtonian fluid. More specifically, we observed that the velocity profiles were closely approximated by a parabolic form and there was little evidence of particle migration throughout the depth. For particle concentrations in the 52–56 % range, the flow depth and front position were fairly well predicted by lubrication theory, but taking a closer look at the velocity profiles revealed that particle migration had noticeable effects on the shape of the velocity profile (blunting), but had little impact on its strength, which explained why lubrication theory performed well. Particle migration theories (such as the shear-induced diffusion model) successfully captured the slow evolution of the velocity profiles. For particle concentrations in excess of 56 %, the macroscopic flow features were grossly predicted by lubrication theory (to within 20 % for the flow depth, 50 % for the front position). The flows seemed to reach a steady state, i.e. the shape of the velocity profile showed little time dependence.
Global stability of the rotating-disc boundary layer with an axial magnetic field
Authors: Thomas Christian , Davies Christopher 
Published: April 2013

AbstractA numerical study is conducted to investigate the influence of a uniform axial magnetic field on the global linear stability of the rotating-disc boundary layer. Simulation results obtained using a radially homogenized base flow were found to be in excellent agreement with an earlier linear stability analysis, which indicated that an axial magnetic field can locally suppress both convective and absolute instabilities. However, the numerical results obtained for the genuine, radially inhomogeneous, flow indicate that a global form of instability develops for sufficiently large magnetic fields. The qualitative nature of the global instability is similar to that which was observed in a previous study, where mass suction was applied at the rotating disc surface. It is shown that, just as for the case with mass suction, it is possible to explain the promotion of global instability by considering a model that includes detuning effects, which are associated with the radial variation of locally defined absolute temporal frequencies. The recurrence of the same type of instability behaviour when two distinct flow control strategies are implemented, one using suction and the other an axial magnetic field, indicates that the phenomena described by the model may be considered generic.
Advection and buoyancy-induced turbulent mixing in a narrow vertical tank
Authors: van Sommeren Daan D. J. A. , Caulfield C. P. , Woods Andrew W. 
Published: April 2013

AbstractWe describe new experiments to examine the buoyancy-induced turbulent mixing which results from the injection of a small constant volume flux of dense fluid at the top of a long narrow vertical tank with square cross-section, in which a steady laminar upward flow of less dense fluid is present. To conserve volume of fluid in the tank, fluid leaves the tank through two small openings near the top of the tank. Dense source fluid vigorously mixes with the less dense fluid of the upward flow, such that a dense mixing region of turbulent fluid propagates downwards during the transient mixing phase of the experiment. Eventually, the transport of dense fluid associated with the buoyancy-induced turbulent flow is balanced by the transport of less-dense fluid associated with the steady upward flow, such that the mixing region evolves into a layer of finite extent which stays approximately constant in height during a statistically steady mixing phase of the experiment. With an ideal source of downward constant buoyancy flux ${B}_{s} $ at the top of the tank, tank width $d$, and speed of the upward flow ${u}_{u} $, we perform experiments with Froude numbers $\mathit{Fr}= {u}_{u} {d}^{1/ 3} / { B}_{s}^{1/ 3} $ ranging between $O(0. 01)$ and $O(1)$. The steady-state height of the mixing region and the maximum reduced gravity as found near the source of buoyancy flux at the top of the tank increase with decreasing Froude number. For the experiments with intermediate values of the Froude number, we find that the steady-state mixing region is small enough to be contained in the experimental tank, but large enough not to be dominated by developing turbulence near the source of buoyancy flux. For these experiments, we show that the key buoyancy-induced turbulent mixing properties are not significantly affected by the upward flow. We use a dye-attenuation technique to obtain vertical profiles of the time- and horizontally averaged reduced gravity to show a good agreement between the experimental profiles and the solution of a nonlinear turbulent advection–diffusion equation during the steady mixing phase. Furthermore, we discuss the characteristic time scale of the transient mixing phase. We compare our experimental results with the numerical solution of a time-dependent nonlinear turbulent advection–diffusion equation during the transient mixing phase. We also describe three reduced models for the evolution of the reduced gravity distribution in the mixing region, and we demonstrate these models’ usefulness by comparison with our experimental results and the numerical solution of the time-dependent nonlinear turbulent advection–diffusion equation.
Experimental investigation of dissipation-element statistics in scalar fields of a jet flow
Authors: Gampert Markus , Schaefer Philip , Peters Norbert 
Published: April 2013

AbstractWe present a detailed experimental investigation of conditional statistics obtained from dissipation elements based on the passive scalar field$\theta $and its instantaneous scalar dissipation rate$\chi $. Using high-frequency planar Rayleigh scattering measurements of propane discharging as a round turbulent jet into coflowing carbon dioxide, we acquire with Taylor’s hypothesis a highly resolved three-dimensional field of the propane mass fraction$\theta $. The Reynolds number (based on nozzle diameter and jet exit velocity) varies between 3000 and 8600. The experimental results for the joint probability density of the scalar difference$ \mathrm{\Delta} \theta $and the length$l$of dissipation elements resembles those previously obtained from direct numerical simulations of Wang & Peters (J. Fluid Mech., vol. 554, 2006, pp. 457–475). In addition, the normalized marginal probability density function$\tilde {P} (\tilde {l} )$of the length of dissipation elements follows closely the theoretical model derived by Wang & Peters (J. Fluid Mech., vol. 608, 2008, pp. 113–138). We also find that the mean linear distance${l}_{m} $between two extreme points of an element is of the order of the scalar Taylor microscale${\lambda }_{u} $. Furthermore, the conditional mean$\langle \mathrm{\Delta} \theta \vert l\rangle $scales with Kolmogorov’s$1/ 3$power law. The investigation of the orientation of long dissipation elements in the jet flow reveals a preferential alignment, perpendicular to the streamwise direction for long elements, while the orientation of short elements is close to isotropic. Following an approach proposed by Kholmyansky & Tsinober (Phys. Lett. A, vol. 373, 2009, pp. 2364–2367), we finally investigate the probability density function of the scalar increment$\delta \theta $in the streamwise direction, when strong dissipative events are either retained in or excluded from the measurement volume. In the present study, however, these events are related to maximum points of the scalar dissipation rate$\chi $together with their local extent. When these regions are excluded from the scalar field, we observe a tendency of the probability density function$P(\delta \theta (r))$towards a Gaussian bell-shaped curve.
OPTIMAL PLANNING OF COCOA CLONAL SELECTION PROGRAMMES
Authors: OWUSU-ANSAH F. , CURNOW R. N. , ADU-AMPOMAH Y. 
Published: April 2013

SUMMARYData from three cocoa (Theobroma cacao) clonal selection trials are used to investigate the genetic and environmental components of variation in yield and the percentage of total pods affected by black pod disease (Phytophtorapod rot). Simulations based on these estimated components of variation are then used to discuss the best choice in future of numbers of clones, replicates and years of harvest to maximise selection advances in the traits measured. The three main conclusions are the need to increase the number of clones at the expense of the number of replicates of each clone, the diminishing returns from additional years of harvesting and the importance of widening the genetic base of the clones chosen to be tested.
Communicative focus on second language phonetic form: Teaching Japanese learners to perceive and produce English /ɹ/ without explicit instruction
Authors: SAITO KAZUYA 
Published: April 2013

ABSTRACTThe current study examines in depth how two types of form-focused instruction (FFI), which are FFI with and without corrective feedback (CF), can facilitate second language speech perception and production of /ɹ/ by 49 Japanese learners in English as a Foreign Langage settings. FFI effectiveness was assessed via three outcome measures (perception, controlled production, and spontaneous production) and also according to two lexical contexts (trained and untrained items). Two experimental groups received 4 hr of FFI treatment to notice and practice the target feature of /ɹ/ (but without any explicit instruction) in meaningful discourse. A control group (n= 14) received comparable instruction in the absence of FFI. During FFI, the instructors provided CF only to students in the FFI + CF group (n= 18) by recasting their mispronunciations of /ɹ/, while no CF was provided to those in the FFI-only group (n= 17). Analyses of pre- and posttests showed that FFI itself can sufficiently promote the development of speech perception and production of /ɹ/ and the acquisitional value of CF in second language speech learning remains unclear. The results suggest that the beginner learners without much phonetic knowledge on how to repair their mispronunciation of /ɹ/ should be encouraged to learn the target sound only through FFI in a receptive mode without much pressure for modified output.
Legal Pluralism in the Pacific: Solomon Island's World War II Heritage
Authors: Forrest Craig , Corrin Jennifer 
Published: April 2013

AbstractThe country of Solomon Islands, like most Pacific island nations, has a legally pluralistic regime. That is, customary law operates in parallel with the common law, a legacy of Solomon Islands' colonial past. Legal pluralism raises significant difficulties, including in the way cultural heritage is protected and managed. To date, the courts have rarely been called on to deal with such issues, but in 2010 the High Court had to examine legislation designed to regulate the recovery and export of World War II relics. This seemingly innocuous case raised a number of issues concerning the rights of different stakeholders to this material. Moreover, it raised a foundational question as to whether these relics might be considered cultural heritage, and if so, just whose heritage it was. A consideration of this case and the legislation that applies to this heritage serves to illustrate some of the difficulties that arise in protecting cultural heritage within pluralistic legal systems.
Respiratory syncytial virus prophylaxis in children with cardiac disease: a retrospective single-centre study
Authors: Butt Michelle , Symington Amanda , Janes Marianne , Steele Susan , Elliott LouAnn , Chant-Gambacort Catherine , Mondal Tapas , Paes Bosco 
Published: April 2013

AbstractObjectivesTo examine the characteristics of congenital heart disease patients hospitalised with respiratory syncytial virus infection after prophylaxis and determine the associated comorbidities and the incidence of breakthrough respiratory syncytial virus infections.Study designThis is a retrospective, single-centre study that was conducted over a period of 7 years. Respiratory syncytial virus infection was identified by classification codes and confirmed by virological tests. Data on baseline demographics, cardiac anomalies, other underlying disease, criteria for hospitalisation, type of respiratory illness and management, complications, and palivizumab prophylaxis were analysed by standard descriptive methods and comparative statistics.ResultsA total of 30 patients were enrolled. The majority were ≤2 years (n = 24). The mean admission age was 15.1 months (standard deviation = 18.3). In all, 90% were acyanotic, 40% had haemodynamically significant disease, and 60% had ≥1 underlying medical illness. Patients were admitted with: respiratory distress (86.7%), hypoxaemia (66.7%), fever (60%), inability to maintain oral intake (36.7%), and apnoea (16.7%). More than 50% required mechanical ventilation and intensive care with a median stay of 11 days (range: 1–43); the length of hospital stay for all children was 10 days (range: 1–65). Complications included: concurrent bacterial sepsis (20%), electrolyte abnormalities (16.7%), and worsening pulmonary hypertension (13.3%). Of 10 infants ≤2 years with haemodynamically significant heart disease, four had received prophylaxis. There was one death, which was attributed to respiratory syncytial virus infection.ConclusionsOverall, 185 infants ≤2 years with haemodynamically significant cardiac disease received prophylaxis. In all, six qualifying infants missed immunisation and were hospitalised. Breakthrough respiratory syncytial virus infections occurred in 2.2%, demonstrating good efficacy of palivizumab in this population compared with the original, multi-centre, randomised trial.
Adaptation can help mitigation: an integrated approach to post-2012 climate policy
Authors: Bosello Francesco , Carraro Carlo , De Cian Enrica 
Published: April 2013

AbstractThis paper analyzes the optimal mix of adaptation and mitigation expenditures in a cost-effective setting, in which countries cooperate to achieve a long-term stabilization target (550 CO2-eq). It uses an Integrated Assessment Model (AD-WITCH) that describes the relationships between different adaptation modes (reactive and anticipatory), mitigation and capacity building to analyze the optimal portfolio of adaptation measures. Results show that the optimal intertemporal distribution of climate policy measures is characterized by early investments in mitigation followed by large adaptation expenditures a few decades later. Hence, the possibility of adapting does not justify postponing mitigation. Moreover, a climate change policy combining mitigation and adaptation is less costly than mitigation alone. In this sense mitigation and adaptation are shown to be strategic complements rather than mutually exclusive.
In Situ Thickness Assessment During Ion Milling of a Free-Standing Membrane Using Transmission Helium Ion Microscopy
Authors: Hall Adam R. 
Published: April 2013

AbstractWe describe a novel method for in situ measurement of the local thickness of a freely suspended solid-state membrane after thinning with a focused helium ion beam. The technique utilizes a custom stage for the helium ion microscope that allows the secondary electron detector used for normal imaging to collect information from ions transmitted through the sample. We find that relative brightness in the transmission image scales directly with the membrane thickness as determined by atomic force microscopy measurements.
Effects of Ghrelin on the Structural Complexity of Exocrine Pancreas Tissue Architecture
Authors: Pantic Igor , Nesic Dejan , Stevanovic Darko , Starcevic Vesna , Pantic Senka , Trajkovic Vladimir 
Published: April 2013

AbstractRecent studies have shown that ghrelin increases pancreatic exocrine secretion. However, the potential effects of ghrelin on the morphology of exocrine pancreas (EP) remain unknown. In this work, using fractal analysis, we demonstrate that centrally administered ghrelin increases structural complexity and tissue disorder in rat EP. The study was carried out on a total of 40 male Wistar rats divided into four groups (n = 10): ghrelin-treated animals (average age, 1.5 months), ghrelin-treated animals (8.5 months), and controls (1.5 and 8.5 months). The pancreas tissue sections were stained with hematoxylin/eosin and visualized by light microscopy. For each animal, the average values of tissue fractal dimension, lacunarity, as well as parameters of co-occurrence matrix texture, were determined using tissue digital micrographs. The results indicate that ghrelin administration increases EP fractal dimension and textural entropy, and decreases lacunarity, regardless of the age. To our knowledge, this is the first study to investigate the effects of ghrelin on the morphological properties of pancreatic tissue, and also the first to apply fractal and textural analysis methods in quantification of EP tissue architecture.
“IT'S NOT WHAT YOU KNOW . . .”: ENCOUNTERS, GO-BETWEENS AND THE GEOGRAPHY OF KNOWLEDGE
Authors: OGBORN MILES 
Published: April 2013

Sometime in the 1760s, a Constantinople-born, French-educated Muslim arrived at the port of Balassor in north-east India. Known variously as Mustapha or Monsieur Raymond, he had, he later wrote, “with a mediocre dictionary and a bad grammar”, and by conversing with the ship's captain en route from Bombay, “learned enough of English . . . as I might delight in Bolingbroke's Philosophical works”. This student of contemporary intellectual history soon put his knowledge to work, securing a position translating for Robert Clive, the conquering hero of the English East India Company's new imperial administration in India. Subsequently falling from favour, Mustapha crossed over to seek employment with the English company's French rivals, earning himself a spell in prison as a spy. He also travelled to Mecca, where he gained the honorific “Haji” but lost his fortune, his cabinet of curiosities and his collection of books and manuscripts. He then became the keeper of a zenana (to the Europeans, a harem or seraglio), and he entered the world of publishing. In 1789, in Calcutta, Mustapha had printed for himself a pamphlet-length diatribe on the iniquitous administration of the law in British Bengal entitled Some Idea of the Civil and Criminal Courts of Justice at Moorshoodabad. In the same year he was also involved, as the pseudonymous editor “Nota Manus”, in the publication of a three-volume English translation of a Persian work of Indian history—Ghulam Hussain Khan Tabatabai's Seir Mutaqherin, or View of Modern Times (written in 1781–2)—which dealt with the British conquest and administration of Bengal, and offered a stern critique of the new rulers who seemed to have “an aversion to the Society of Indians, and a disdain against conversing with them”. Finally, Mustapha (who called himself a “Semi-Englishman” who had the interests of his “adopted countrymen” at heart) claimed to have published in London a work of futurology entitled State of Europe in 1800. In his encounters with Europeans, his travels within and beyond India (although he never made it to England as he had planned), and his involvement in the production of historical and geographical knowledge, Mustapha was deeply interested in that which shaped his own fortunes: the relationships of knowledge and power between Europe and other parts of the world.