bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the active feedback control of a swirling flow in a finite-length pipe
Authors: Wang Shixiao , Rusak Zvi , Taylor Steve , Gong Rui 
Published: November 2013

AbstractThe physical properties of a recently proposed feedback-stabilization method of a vortex flow in a finite-length straight pipe are studied for the case of a solid-body rotation flow. In the natural case, when the swirl ratio is beyond a certain critical level, linearly unstable modes appear in sequence as the swirl level is increased. Based on an asymptotic long-wave (long-pipe) approach, the global feedback control method is shown to enforce the decay in time of the perturbation’s kinetic energy and thereby quench all of the instability modes for a swirl range above the critical swirl level. The effectiveness of an extended version of this feedback flow control approach is further analysed through a detailed mode analysis of the full linear control problem for a solid-body rotation flow in a finite-length pipe that is not necessarily long. We first rigourously prove the asymptotic decay in time of all modes with real growth rates. We then compute the growth rate and shape of all modes according to the full linearized control problem for swirl levels up to 50 % above the critical level. We demonstrate that the flow is stabilized in the whole swirl range and can be even further stabilized for higher swirl levels. However, the control effectiveness is sensitive to the choice of the feedback control gain. A potentially best range of the gain is identified. An inadequate level of gain, either insufficient or excessive, could lead to a marginal control or failure of the control method at high swirl levels. The robustness of the proposed control law to stabilize both initial waves and continuous inlet flow perturbations and the elimination of the vortex breakdown process are demonstrated through numerical computations.
On the scaling in sink-flow turbulent boundary layers
Authors: Dixit Shivsai Ajit , Ramesh O. N. 
Published: November 2013

AbstractScaling of the streamwise velocity spectrum ${\phi }_{11} ({k}_{1} )$ in the so-called sink-flow turbulent boundary layer is investigated in this work. The present experiments show strong evidence for the ${ k}_{1}^{- 1} $ scaling i.e. ${\phi }_{11} ({k}_{1} )= {A}_{1} { U}_{\tau }^{2} { k}_{1}^{- 1} $, where ${k}_{1} $ is the streamwise wavenumber and ${U}_{\tau } $ is the friction velocity. Interestingly, this ${ k}_{1}^{- 1} $ scaling is observed much farther from the wall and at much lower flow Reynolds number (both differing by almost an order of magnitude) than what the expectations from experiments on a zero-pressure-gradient turbulent boundary layer flow would suggest. Furthermore, the coefficient ${A}_{1} $ in the present sink-flow data is seen to be non-universal, i.e. ${A}_{1} $ varies with height from the wall; the scaling exponent −1 remains universal. Logarithmic variation of the so-called longitudinal structure function, which is the physical-space counterpart of spectral ${ k}_{1}^{- 1} $ scaling, is also seen to be non-universal, consistent with the non-universality of ${A}_{1} $. These observations are to be contrasted with the universal value of ${A}_{1} $ (along with the universal scaling exponent of −1) reported in the literature on zero-pressure-gradient turbulent boundary layers. Theoretical arguments based on dimensional analysis indicate that the presence of a streamwise pressure gradient in sink-flow turbulent boundary layers makes the coefficient ${A}_{1} $ non-universal while leaving the scaling exponent −1 unaffected. This effect of the pressure gradient on the streamwise spectra, as discussed in the present study (experiments as well as theory), is consistent with other recent studies in the literature that are focused on the structural aspects of turbulent boundary layer flows in pressure gradients (Harun et al., J. Fluid Mech., vol. 715, 2013, pp. 477–498); the present paper establishes the link between these two. The variability of ${A}_{1} $ accommodated in the present framework serves to clarify the ideas of universality of the ${ k}_{1}^{- 1} $ scaling.
Linearized no-slip boundary conditions at a rough surface
Authors: Luchini Paolo 
Published: November 2013

AbstractLinearized boundary conditions are a commonplace numerical tool in any flow problems where the solid wall is nominally flat but the effects of small waviness or roughness are being investigated. Typical examples are stability problems in the presence of undulated walls or interfaces, and receptivity problems in aerodynamic transition prediction or turbulent flow control. However, to pose such problems properly, solutions in two mathematical distinguished limits have to be considered: a shallow-roughness limit, where not only roughness height but also its aspect ratio becomes smaller and smaller, and a small-roughness limit, where the size of the roughness tends to zero but its aspect ratio need not. Here a connection between the two solutions is established through an analysis of their far-field behaviour. As a result, the effect of the surface in the small-roughness limit, obtained from a numerical solution of the Stokes problem, can be recast as an equivalent shallow-roughness linearized boundary condition corrected by a suitable protrusion coefficient (related to the protrusion height used years ago in the study of riblets) and a proximity coefficient, accounting for the interference between multiple protrusions in a periodic array. Numerically computed plots and interpolation formulas of such correction coefficients are provided.
Effects of dark chocolate and cocoa consumption on endothelial function and arterial stiffness in overweight adults
Authors: West Sheila G. , McIntyre Molly D. , Piotrowski Matthew J. , Poupin Nathalie , Miller Debra L. , Preston Amy G. , Wagner Paul , Groves Lisa F. , Skulas-Ray Ann C. 
Published: November 2013

The consumption of cocoa and dark chocolate is associated with a lower risk of CVD, and improvements in endothelial function may mediate this relationship. Less is known about the effects of cocoa/chocolate on the augmentation index (AI), a measure of vascular stiffness and vascular tone in the peripheral arterioles. We enrolled thirty middle-aged, overweight adults in a randomised, placebo-controlled, 4-week, cross-over study. During the active treatment (cocoa) period, the participants consumed 37 g/d of dark chocolate and a sugar-free cocoa beverage (total cocoa = 22 g/d, total flavanols (TF) = 814 mg/d). Colour-matched controls included a low-flavanol chocolate bar and a cocoa-free beverage with no added sugar (TF = 3 mg/d). Treatments were matched for total fat, saturated fat, carbohydrates and protein. The cocoa treatment significantly increased the basal diameter and peak diameter of the brachial artery by 6 % (+2 mm) and basal blood flow volume by 22 %. Substantial decreases in the AI, a measure of arterial stiffness, were observed in only women. Flow-mediated dilation and the reactive hyperaemia index remained unchanged. The consumption of cocoa had no effect on fasting blood measures, while the control treatment increased fasting insulin concentration and insulin resistance (P= 0·01). Fasting blood pressure (BP) remained unchanged, although the acute consumption of cocoa increased resting BP by 4 mmHg. In summary, the high-flavanol cocoa and dark chocolate treatment was associated with enhanced vasodilation in both conduit and resistance arteries and was accompanied by significant reductions in arterial stiffness in women.
Gradient Confinement Induced Uniform Tensile Ductility in Metallic Glass
Authors: Lu X. L. , Lu Q. H. , Li Y. , Lu L. 
Published: November 2013

AbstractMetallic glass (MG) generally fails in a brittle manner under uniaxial tension loading at room temperature. The lack of plastic strain of MG is due to the severe plastic instability via the easily formed one dominate shear band. There have been several approaches to improve the ductility in MG, but achieving uniform tensile ductility for monolithic MG in bulk size remains a challenge. Here we demonstrate a uniform tensile ductility of 12% achieved in a micrometer scale Ni-P amorphous film coated on a Ni substrate with gradient structure. Instead of a single run-away shear band, such a gradient structure generates massive extensive multiple shear bands in the film, leading to a record high tensile ductility in MG. The present finding highlights a novel route for achieving uniform tensile ductility in monolithic metallic glass with bulk size.
Atmospheric mercury inputs in montane soils increase with elevation: evidence from mercury isotope signatures
Authors: Zhang Hua , Yin Run-sheng , Feng Xin-bin , Sommar Jonas , Anderson Christopher W. N. , Sapkota Atindra , Fu Xue-wu , Larssen Thorjørn 
Published: November 2013

AbstractThe influence of topography on the biogeochemical cycle of mercury (Hg) has received relatively little attention. Here, we report the measurement of Hg species and their corresponding isotope composition in soil sampled along an elevational gradient transect on Mt. Leigong in subtropical southwestern China. The data are used to explain orography-related effects on the fate and behaviour of Hg species in montane environments. The total- and methyl-Hg concentrations in topsoil samples show a positive correlation with elevation. However, a negative elevation dependence was observed in the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) signatures of Hg isotopes. Both a MIF (Δ199Hg) binary mixing approach and the traditional inert element method indicate that the content of Hg derived from the atmosphere distinctly increases with altitude.
Novel Erythrocyte-like Graphene Microspheres with High Quality and Mass Production Capability via Electrospray Assisted Self-Assembly
Authors: Tian Yayang , Wu Guan , Tian Xike , Tao Xiaoming , Chen Wei 
Published: November 2013

AbstractWe report for the first time a novel erythrocyte-like graphene microsphere (ELGMs) which can be produced with high quality and mass production capability via electrospray assisted self-assembly. Through simple electrospray treatment of GO suspension into coagulation bath followed by chemical reduction, large quantity of ELGMs with uniform morphology and size can be obtained with production rate of around 2.4 mg/h. Compared with other 3D structures, the ELGMs have a very interesting structural characteristic of perfect exterior doughnut shape and interior porous network. Accordingly, the as-prepared porous ELGMs exhibit excellent capability for fast and recyclable removal of oil and toxic organic solvents from water, reaching up to 216 times of its weight in absorption efficiency, which is tens of times higher than that of conventional sorbent materials. It is strongly believed that the novel hierarchical graphene structures and synergy among different techniques will lead to more future advances in graphene applications.
HKUST‐1 coated piezoresistive microcantilever array for volatile organic compound sensing
Authors: Ellern Ilya , Venkatasubramanian Anandram , Lee Jin‐Hwan , Hesketh Peter , Stavila Vitalie , Robinson Alex , Allendorf Mark 
Published: November 2013

The HKUST‐1 metal‐organic framework (MOF) was selected because of the large internal surface area, excellent stability and known properties. Mechanical strain is generated upon the adsorption of analytes into the MOF; it is proportional to concentration and is a function of adsorbed species. Piezoresistive microcantilevers serve as a transduction mechanism to convert surface strain into electrical signals. N‐doped piezoresistive cantilever arrays were fabricated with ten structures per die. Thin films of HKUST‐1 were grown at room temperature using layer‐by‐layer techniques. Dry nitrogen was used as a carrier gas to expose devices to varying concentrations of 12 different volatile organic compounds (VOCs). Results show that stress‐induced piezoresistive microcantilever array sensors with MOF coatings can provide a highly sensitive and reversible sensing mechanism for water vapour and methanol. Characteristic response features allow discrimination based on shape, response time constants and magnitude of response for other VOCs. Devices provided reliable data and proved durable over 18 months of testing. The key advantages of this type of sensor are higher sensitivity with a microporous MOFs, reversible response, α single chip sensing system and low power operation.
Knowledge structures of a health ecosystem
Authors: Laihonen Harri 
Published: November 2013

PurposeThis paper aims to hypothesize that modern health systems are transforming towards what has been called a health ecosystem in complexity‐based health care literature. It has been argued that complexity arises from the interconnectedness, which in this paper is equated with knowledge flows between actors. The paper seeks to discuss the possible implications of a health ecosystem approach to health system management.Design/methodology/approachThe paper is conceptual in nature but the transition towards a health ecosystem is illustrated with an example of a regional health care system in Finland. The case description and related analysis presented are based on qualitative data gathered by interviewing leading office‐holders, by process modeling and by observing management group meetings.FindingsConceptually, a health ecosystem seems to have potential for the system‐level analysis of the health care system. The discussion concludes that management of knowledge flows should be a strategic management function for individual health organizations as well as for the wider health system.Research limitations/implicationsThis study focuses on a Finnish health care system. The operations and structures of health care services and systems vary in different areas and countries.Practical implicationsThe practical illustration of the health ecosystem provides a reminder that health care systems are dynamic and largely based on interaction between different actors. The approach provides new strategic insights for the development of health care systems by concentrating on interrelationships and knowledge flows.Originality/valueThe literature has suggested that the ecosystem metaphor offers useful insights for the development of health care systems. Nevertheless, this approach has not been thoroughly studied so far. This paper makes a contribution by presenting a practical illustration of the framework and in light of this discusses the possible implications for health care management.
Goal orientation, academic competences and early career success
Authors: van Dierendonck Dirk , van der Gaast Eline 
Published: November 2013

Purpose
– This paper aims to focus on early career success as determined by a combination of what young professionals learned at school (in terms of their grades and academic competences) and how this, together with their self-regulatory focus, influenced their early objective career success in terms of salary growth and subjective career success, in terms of career satisfaction.

Design/methodology/approach
– Using an online survey, 247 alumni from a major business school in The Netherlands participated.

Findings
– The results showed that, within this sample, a person's goal orientation was an important determinant of subjective and objective career success. A master orientation was more beneficial than a performance orientation. In addition, a high mastery or a high performance orientation buffered the potential negative influence of low levels of academic competence and grades on career satisfaction.

Originality/value
– The study showed the limited predictive value of grades and academic competences to predict early career success.
Spreading the word through likes on Facebook
Authors: Swani Kunal , Milne George , P. Brown Brian 
Published: November 2013

Purpose
– This research aims to investigate the message strategies most likely to promote online “word-of-mouth” (WOM) activity for business-to-business (B2B)/business-to-consumer as well as product/service Facebook accounts.

Design/methodology/approach
– Using content analysis and HLM, the authors measure the relationship between three types of message strategies and Facebook message “Likes” by analyzing 1,143 wall post messages of 193 Fortune 500 Facebook accounts.

Findings
– Research findings suggest that B2B Facebook account posts are more effective if they include corporate brand names and avoid “hard sell” or explicitly commercial statements. Furthermore, results suggest that including emotional sentiments in Facebook posts is a particularly effective social media strategy for B2B and service marketers.

Originality/value
– This study advances the knowledge of social media and online WOM behavior, as well as B2B and service advertising/communication literature, by relating message content to message popularity. In terms of managerial implications, this research provides explanations and support for the implementation of effective social media message strategies that are likely to promote WOM activity.
Working through setbacks
Authors: Williams Alex 
Published: November 2013

Purpose
– The paper is a follow-up to a personal account published in this journal 12 months ago. The purpose of this paper is to highlight job retention through support measures during a period of crisis, contrasted with factors which undermine a quicker return to good mental health.

Design/methodology/approach
– The paper is a personal account of difficulties experienced within and outside the workplace for someone who has been through long-term mental distress and is in her first, proper, paid job. The author reflects on becoming unwell while in full-time work with fears of dismissal by the employer as well as rejection by mental health services. Due to a supportive employer the author is still employed but is more aware of distress triggers.

Findings
– Helpful approaches which make job sustainment possible include the use of independent occupational health services, supported employment advice, phased returns, income maximisation through Disability Living Allowance and employer flexibility. The factors which inhibited this were miscommunications with statutory services and a widespread inability to recognise and understand distress expressed through self-harm.

Research limitations/implications
– Further research is needed into the practical responses from employers once an employee who has ongoing mental health issues discloses deterioration in symptoms. The context of a person's home life and treatment available means that work may not be the main stress.

Originality/value
– Published testimonies from service users and survivors on successes in sustaining employment remain few in number.
Antimicrobial susceptibility profile of Acinetobacter species isolated from blood cultures in two Japanese university hospitals
Authors: Kishii Kozue , Kikuchi Ken , Yoshida Atsushi , Okuzumi Katsuko , Uetera Yushi , Yasuhara Hiroshi , Moriya Kyoji 
Published: November 2013

ABSTRACTCarbapenem‐resistant Acinetobacter baumannii has rapidly spread worldwide. This study investigated antibiotic susceptibility and genotypic resistance of 123 consecutive blood culture isolates of Acinetobacter species collected between 2003 and 2011 in two Japanese hospitals. The isolates were assigned to 13 species. Carbapenem resistance was detected in four isolates. Only one A. baumannii isolate had blaOXA‐23 together with ISAba1; the remaining three isolates had IMP‐1 metallo‐β‐lactamase. Quinolone resistance was detected in five isolates that had point mutations in the quinolone resistance‐determining region. The predominance of various non‐A. baumannii species and low prevalence of carbapenem resistance among blood culture isolates of Acinetobacter species in two Japanese hospitals were confirmed.
Stimulation of boreal tree seedling growth by wood‐derived charcoal: effects of charcoal properties, seedling species and soil fertility
Authors: Pluchon Nathalie , Gundale Michael J. , Nilsson Marie‐Charlotte , Kardol Paul , Wardle David A. 
Published: November 2013

Summary

Fire is a major disturbance in many ecosystems world‐wide including the boreal forest, and significant quantities of charcoal can be input to the soil from fire. Some recent studies have provided evidence that wood‐derived charcoal produced by fire can significantly stimulate plant growth. However, the mechanisms by which charcoal affects plant growth are poorly understood, and little is known about how charcoal effects on plant growth are influenced by charcoal type, soil type and plant species.

Seedlings from four common boreal tree species, two evergreen gymnosperms and two deciduous angiosperms, were grown in each of two soils of contrasting nutrient availability amended with charcoal with each of nine charcoal types (each produced from wood from a different plant species) in a greenhouse experiment. We also measured several functional traits for each of the charcoal types, as well as of the wood used to prepare the charcoal.

Charcoal addition had either positive or neutral effects on seedling growth, with great variability among charcoal types. The charcoal types that had the strongest positive effect were those that had the greatest concentrations of phosphate and total phosphorus and, in some cases, were derived from woods that had the highest total phosphorus concentration. Addition of charcoal on average had a stronger positive effect on plant growth on soil with the lowest levels of phosphate and total phosphorus.

Generally, charcoal derived from angiosperms stimulated seedling growth more than charcoal from gymnosperms. Further, angiosperm seedlings were on average stimulated more by charcoal addition than were gymnosperm seedlings. These results indicate that charcoal produced by fire could contribute to the initial dominance of angiosperm trees in post‐fire succession and suggest a possible feedback whereby charcoal from angiosperm tree species favours growth of angiosperm seedlings.

This study highlights a new means by which functional trait variation among tree species could potentially exert ‘after‐life’ effects in forested ecosystems through influencing traits (and notably phosphate concentrations) of the charcoal that they produce following wildfire, with potentially important consequences for plant growth and community and ecosystem properties during post‐fire succession.
Swimming with a sword: tail beat kinematics in relation to sword length in Xiphophorus
Authors: Oufiero Christopher E. , Jugo Kristine , Garland Theodore 
Published: November 2013

Summary

Exaggerated morphological structures that evolve under sexual selection have the potential to alter functional relationships and hence affect aspects of movement. These effects may be more pronounced when the exaggerated morphological trait is coupled to the propulsive system.

Many studies have examined the effects of sexually selected traits on whole‐organism performance, but few have documented their effects on the kinematics of locomotion.

Using four swordtail (Xiphophorus) species that vary naturally in their expression of the sexually selected sword, and an experimental manipulation for the species in our sample with the longest sword (X. alvarezi), we examined how variation in sword length affects the kinematics of swimming.

Among the four species, we found few differences in tail beat kinematics, despite the large variation in sword length among species. In particular, the two species with long swords did not differ from the species lacking a sword, suggesting no locomotor ‘cost’ of having long swords.

Using experimental manipulation, sword removal significantly increased tail beat amplitude, but not frequency, suggesting a potential increase in thrust production.

Our comparative results suggest that swimming kinematics do not vary much with sword length, despite the variation in this sexually selected trait among the four species. This result suggests that other physiological mechanisms may be compensating for sword length, or as has been suggested recently, the sword may not impose a significant swimming cost.