bluuebunny/crossref_metadata_2025 huggingface dataset:
Privacy‐preserving rental services using one‐show anonymous credentials
Authors: Yang Yanjiang , Deng Robert H. , Bao Feng
Published: March 2009

Rental services play an important part in our daily life and the trend has been towards digital transactions. Rental records contain lots of sensitive information on individuals, so if abused by rental service providers, users' privacy could be jeopardized. To mitigate this concern, we present privacy‐preserving rental services where interests of both the users and the service provider are protected. Specifically, our system enables normal users to engage in a rental service in an anonymous manner, whereas users with overdue items are subject to anonymity revocation by the rental service provider; moreover, the rental service provider enforces a rental limit which caps the number of rentals per user under a prescribed limit. We propose a novel one‐show anonymous credential scheme to realize the above design objectives. While this scheme is tailored to the scenario of online credential issuing in the proposed rental services, we believe that it is of independent interest and may find its use in other applications. Copyright © 2009 John Wiley & Sons, Ltd.
A theory of optimized resource allocation from systems perspectives
Authors: Xiong Ying , S. Chaudhry Sohail
Published: March 2009

A construction project is an example of a complex systems engineering problem. In this paper, we have characterized a construction project in the context of the theory of six forces on the factors of production. This new approach was defined by giving consideration to the characteristics of the construction project's resource allocation. An economic efficiency index was also used to assess resource allocation of a construction project. Based on this approach, a theory of optimized resource allocation of the construction project is proposed. Copyright © 2009 John Wiley & Sons, Ltd.
Downregulation of APE1/Ref-1 Is Involved in the Senescence of Mesenchymal Stem Cells
Authors: Heo Jun-Young , Jing Kaipeng , Song Kyoung-Sub , Seo Kang-Sik , Park Ji-Hoon , Kim Jong-Seok , Jung Yeon-Joo , Hur Gang-Min , Jo Deog-Yeon , Kweon Gi-Ryang , Yoon Wan-Hee , Lim Kyu , Hwang Byung-Doo , Jeon Byeong Hwa , Park Jong-Il
Published: March 2009

The senescence of human mesenchymal stem cells (hMSCs) causes disruption of tissue and organ maintenance, and is thus an obstacle to stem cell-based therapies for disease. Although some researchers have studied changes in the characteristics of hMSCs (decreases in differentiation ability and self-renewal), comparing young and old ages, the mechanisms of stem cell senescence have not yet been defined. In this study, we developed a growth curve for human bone marrow derived MSCs (hBMSCs) which changes into a hyperbolic state after passage number 7. Senescence associated β-galactosidase (SA β-gal) staining of hBMSCs showed 10% in passage 9 and 45% in passage 11. We detected an increase in endogenous superoxide levels during senescence that correlated with senescence markers (SA β-gal, hyperbolic growth curve). Interestingly, even though endogenous superoxide increased in a replicative senescence model, the expression of APE1/Ref-1, which is sensitive to intracellular redox state, decreased. These effects were confirmed in a stress-induced senescence model by exogenous treatment with H2O2. This change is related to the p53 activity that negatively regulates APE1/Ref-1. p21 expression levels, which represent p53 activity, were transiently increased in passage 9, meaning that they correlated with the expression of APE1/Ref-1. Overexpression of APE1/Ref-1 suppressed superoxide production and decreased SA β-gal in hBMSCs. In conclusion, intracellular superoxide accumulation appears to be the main cause of the senescence of hBMSCs, and overexpression of APE1/Ref-1 can rescue cells from the senescence phenotype. Maintaining characteristics of hBMSCs by regulating intracellular reactive oxygen species production can contribute to tissue regeneration and to improved cell therapy.

Disclosure of potential conflicts of interest is found at the end of this article.
cAMP Response Element Binding Protein Is Required for Mouse Neural Progenitor Cell Survival and Expansion
Authors: Dworkin Sebastian , Malaterre Jordane , Hollande Frédéric , Darcy Phillip K. , Ramsay Robert G. , Mantamadiotis Theo
Published: March 2009

Development of the mammalian brain relies on the coordinated expansion of neural cells in a relatively short time, spanning for a period of only a few days in mice. The molecular networks regulating neural cell birth and expansion, termed neurogenesis, are still unresolved, although many studies using genetically modified mice have revealed a growing number of genes that are involved in regulating these processes. The cAMP response element binding protein (CREB) lies at the hub of a diverse array of intracellular signaling pathways and is a major transcriptional regulator of numerous functions in adult neural cells, including learning and memory and neuronal survival. Recent studies have shown that activated CREB is highly expressed in immature dividing cells in adult mouse and zebrafish brains and that CREB regulates neural stem/progenitor cells (NSPCs) proliferation in embryonic zebrafish brain. Using genetically modified mice, we show that deletion of CREB, without the concomitant loss of the related compensating factor cAMP response element modifier, leads to defects in neural progenitor cell expansion and survival. Cultured primary CREB−/− NSPCs exhibited decreased expression of several target genes important for neuronal survival and growth, including brain-derived neurotrophic factor and neural growth factor and showed that the survival and growth defect can be rescued by the addition of wild-type NSPC-conditioned medium. This is the first study showing a specific role for CREB in mammalian embryonic neurogenesis. This role appears to be mediated via the expression of factors important for NSPC survival and growth and suggests that CREB is an important signaling regulator within the developing neurogenic niche.

Disclosure of potential conflicts of interest is found at the end of this article.
Results of a second survey to assess the reproductive status of female Asian and African elephants in North America
Authors: Proctor Christine M. , Freeman Elizabeth W. , Brown Janine L.
Published: March 2009

Surveys are being conducted to monitor the reproductive health of elephants managed by the TAG/SSP. This study summarizes results of a 2005 survey and compares data to one conducted in 2002. Surveys were returned for 100% and 79.0% of Asian and African elephants, respectively. Of those, 79.3% of Asian and 92.1% of African elephants had weekly progestagen data to assess ovarian cyclicity. For Asian elephants, acyclicity rates were similar between the 2002 and 2005 surveys (13.3% versus 10.9%), whereas irregular cycling increased in 2005 (2.6% versus 7.6%), respectively. For African elephants, the percentages of both acyclicity (22.0% versus 31.2%) and irregular cycling females (5.2% versus 11.8%) increased. In both species, ovarian inactivity was more prevalent in the older age categories (>30 years of age), but for African elephants also occurred in the reproductive aged groups. Reproductive tract pathologies did not account for the majority of acyclicity problems. Several females changed cyclicity status between the two surveys, including from noncycling to cycling, suggesting this is not an irreversible condition. However, seven African females went from cycling to abnormal or no cyclic activity. In summary, the incidence of ovarian acyclicity in Asian elephants is low and stable, but appears to be increasing in African females. These findings reinforce the need for long‐term reproductive monitoring programs and continuous reproductive surveys, even for females not being considered for breeding. With more data we hope to determine what factors are related to changes in ovarian status and how to reverse the trend towards acyclicity. Zoo Biol 29:127–139, 2010. © 2009 Wiley‐Liss, Inc.
A rigorous methodology for specification and verification of business processes
Authors: Masalagiu Cristian , Chin Wei-Ngan , Andrei Ştefan , Alaiba Vasile
Published: March 2009

Both specification and verification of business processes are gaining more and more attention in the field. Most of the existing works in the last years are dealing with important, yet very specialized, issues. Among these, we can enumerate compensation constructs to cope with exceptions generated by long running business transactions, fully programmable fault and compensation handling mechanism, web service area, scope-based compensation and shared-labels for synchronization, and so on. The main purpose of this paper is to present a semi-automatized framework to describe and analysebusiness processes. Business analysts can now use a simple specification language (e.g.,BPMN[Obj06]) to describe any type of activity in a company, in aconcurrentandmodularfashion. The associated programs (e.g.,BPDs [Obj06]) have to be executed in an appropriate language (e.g.,BPEL4WS[ACD+03]). Much more, they have to beconfirmed to be sound, via some prescribed (a priori) conditions. We suggest how all the issues can be embedded in aunifying computer tool. We link our work with similar approaches and we justify our particular choices (besidesBPMNandBPD): theTLA+ language for expressing the imposed behavioural conditions andPetri Nets([EB87], [EB88]) to describe an intermediate semantics. In fact, we want to manage in an appropriate way the general relationship diagram (Fig. 1). Examples and case studies are provided.
Type II Gaucher disease manifesting as haemophagocytic lymphohistiocytosis
Authors: Sharpe L.‐R. , Ancliff P. , Amrolia P. , Gilmour K. C. , Vellodi A.
Published: March 2009

Haemophagocytic lymphohistiocytosis (HLH) is a rare and rapidly progressive disease which, untreated, invariably leads to death. Gaucher disease is a rare lysosomal storage disorder. The acute neuronopathic variant; type II, is also rapidly progressive. We report an infant with Gaucher disease type II manifesting as HLH. Immunoblot revealed a deficiency of Munc 13‐4, an intracellular protein responsible for docking of secretory lysosomes. This, and other possible pathogenetic mechanisms to explain the link are discussed.
Comprehensive description of the phenotype of the first case of congenital disorder of glycosylation due to RFT1 deficiency (CDG In)
Authors: Clayton P. T. , Grunewald S.
Published: March 2009

Very recently, Haeuptle and colleagues described a new glycosylation defect due to RFT1 deficiency (CDG In). Accumulation of intracellular DolPP‐GlcNAc2Man5 with absence of cytosolic GlcNAc2Man5 resembled the profile of a yeast mutant deficient in RFT1, a protein that is thought to have a role as a flippase. This is the first detailed description of the clinical phenotype of this patient. It was a severe disorder affecting intrauterine development and movement, and leading to intrauterine growth retardation. The child was born with several musculoskeletal abnormalities including arthrogryposis. Postnatally, severe reflux and irregular bowl movements contributed to failure to thrive. The patient showed very little development and no vision and suffered from drug‐resistant epilepsy. Abnormal coagulation resulted in thrombosis and the patient died at the age of 4 years from a pulmonary embolus.
Synthesis of Novel Porphyrin and its Complexes Covalently Linked to Multi-Walled Carbon Nanotubes and Study of their Spectroscopy
Authors: Jin Jun , Dong Zhengping , He Jianguo , Li Rong , Ma Jiantai
Published: March 2009

Novel covalent porphyrin and its complexes (Co2+, Zn2+) functionalized multi-walled carbon nanotubes (MWNTs) have been successfully synthesized by the reaction of the carboxyl on the surface of MWNTs which was synthesized to use carbon radicals generated by the thermal decomposition of azodiisobutyronitrile (AIBN) with 5-p-hydroxyphenyl-10,15,20-triphenyl-porphyrin and its complexes (Co2+, Zn2+). Three resulting nanohybrids were characterized by spectroscopy (FT-IR, Raman, and UV-vis), TGA, and TEM. The quality of porphyrin attached to the MWNTs was determined from thermogravimeric analysis (TGA) of the MWNTs, which showed a weight loss of about 60%. The Raman and absorption spectroscopy data showed that the electronic properties of modified MWNTs were mostly retained, without damaging their one-dimensional electronic properties. From fluorescence measurements, it was observed that the porphyrin and its complexes (Co2+, Zn2+) were nearly quenched by MWNTs, indicating that this covalently modified mode facilitated the effective energy or electron transfer between the excited porphyrin moiety and the extended π-system of MWNTs.
Long‐term follow‐up of tailored behavioural treatment and exercise based physical therapy in persistent musculoskeletal pain: A randomized controlled trial in primary care
Authors: Åsenlöf Pernilla , Denison Eva , Lindberg Per
Published: March 2009

This study examined long‐term effects of a tailored behavioural treatment protocol (TBT), as compared with an exercise based physical therapy protocol (EBT). One‐hundred and twenty‐two patients who, due to persistent musculoskeletal pain, consulted physical therapists in primary care were originally randomized to either of the two conditions. Follow‐up assessments two‐year post‐treatment were completed by 65 participants. According to per‐protocol analyses, short‐term effects were maintained in both groups for the primary outcome, pain‐related disability. The TT‐group reported lower disability levels compared with the EBT‐group. Intention‐to‐treat analyses (ITT) conveyed similar results. Secondary outcomes of pain intensity, pain control, and functional self‐efficacy were maintained over the 2‐year post‐treatment, but previous group differences were levelled out according to the most conservative method of ITT. Fear of movement/(re)injury increased in the EBT‐group, and EBT participants reported higher fear of movement/(re)injury two years post‐treatment compared to TT.

The study supports tailoring of treatments in concordance with patients’ needs and preferences of activity goals and functional behavioural analyses including predictors of pain‐related disability, for successful immediate outcomes and their maintenance in the long run. Exercise‐based treatments resulted in somewhat smaller immediate treatment effects but had similar maintenance of effects over the 2‐year follow‐up period.
Anti‐apoptotic role of omega‐3‐fatty acids in developing brain: perinatal hypothyroid rat cerebellum as apoptotic model
Authors: Sinha Rohit A. , Khare Priyanka , Rai Asit , Maurya Shailendra Kumar , Pathak Amrita , Mohan Vishwa , Nagar Geet Kumar , Mudiam Mohana Krishna Reddy , Godbole Madan M. , Bandyopadhyay Sanghamitra
Published: March 2009

Inadequate maternal intake of omega‐3‐fatty acids (ω3 FAs) causes adverse neurodevelopmental outcome in the progeny; however, their molecular mechanism of action is obscure. Since ω3 FAs are known to inhibit neuronal apoptosis during neuro‐degeneration, we investigated their possible contribution in regulating neuronal apoptosis during brain development. Using rat model of hypothyroidism‐induced neuronal apoptosis, we provide evidence for anti‐apoptotic role of ω3 FAs during cerebellar development. ω3 FAs were supplemented as a mixture of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) to pregnant and lactating rats, and primary hypothyroidism was induced by administering methimazole. The cerebella from postnatal day 16 (d16) pups were isolated, and studies on apoptosis were conducted. We observed that ω3 FA‐supplementation significantly reduced DNA fragmentation and caspase‐3 activation in developing cerebellum of hypothyroid pups. The protection provided by ω3 FAs was associated with their ability to prevent increases in the level of pro‐apoptotic basal cell lymphoma protein‐2 (Bcl‐2)‐associated X protein (Bax) in the cerebellum during thyroid hormone (TH) deficiency. ω3 FAs increased the levels of anti‐apoptotic proteins like Bcl‐2 and Bcl‐extra large (Bcl‐xL), known to be repressed in hypothyroidism. ω3 FAs also restored levels of cerebellar phospho (p)‐AKT, phospho‐extracellular regulated kinase (p‐ERK) and phospho‐c‐Jun N‐terminal kinase (p‐JNK), which were altered by hypothyroid insults, without interfering with the expression of TH responsive gene, myelin basic protein (mbp). Taken together, these results supplement an insight into the molecular mechanism of action of ω3 FAs in developing brain that involves regulation of apoptotic signaling pathways under stress.
Incorporation of Core Competency Questions Into an Annual National Self‐Assessment Examination for Residents in Physical Medicine and Rehabilitation: Results and Implications
Authors: Webster Joseph B.
Published: March 2009

Objective

To determine the performance and change over time when incorporating questions in the core competency domains of practice‐based learning and improvement (PBLI), systems‐based practice (SBP), and professionalism (PROF) into the national PM&R Self‐Assessment Examination for Residents (SAER).

Design

Prospective, longitudinal analysis.

Setting

The national Self‐Assessment Examination for Residents (SAER) in Physical Medicine and Rehabilitation, which is administered annually.

Participants

Approximately 1100 PM&R residents who take the examination annually.

Interventions

Inclusion of progressively more challenging questions in the core competency domains of PBLI, SBP, and PROF.

Main Outcome Measurements

Individual test item level of difficulty (P value) and discrimination (point biserial index).

Results

Compared with the overall test, questions in the subtopic areas of PBLI, SBP, and PROF were relatively easier and less discriminating (correlation of resident performance on these domains compared with that on the total test). These differences became smaller during the 3‐year time period. The difficulty level of the questions in each of the subtopic domains was raised during the 3 year period to a level close to the overall exam. Discrimination of the test items improved or remained stable.

Conclusions

This study demonstrates that, with careful item writing and review, multiple‐choice items in the PBLI, SBP, and PROF domains can be successfully incorporated into an annual, national self‐assessment examination for residents. The addition of these questions had value in assessing competency while not compromising the overall validity and reliability of the exam. It is yet to be determined if resident performance on these questions corresponds to performance on other measures of competency in the areas of PBLI, SBP, and PROF.
Enhanced External Counterpulsation: An Innovative Physical Therapy for Refractory Angina
Authors: Braverman Debra L.
Published: March 2009

The prevalence of refractory angina in the United States is 600,000 to 1.8 million. Improved pharmacological, invasive, and surgical therapies for cardiovascular diseases during the last few decades have led to an increase in life expectancy of such individuals. Despite treatment with multiple medications and invasive procedures, these patients remain symptomatic and functionally limited. Enhanced external counterpulsation (EECP) is a safe, noninvasive, well‐tolerated, and clinically effective outpatient physical therapy for many patients with refractory angina. Numerous trials demonstrate positive clinical responses among at least 80% of patients undergoing EECP, including reductions in angina and nitrate use, increases in exercise tolerance, and enhanced quality of life. Several mechanisms, including the promotion of collateral blood flow, improvement in endothelial function, reduction in inflammation, and the production of peripheral training effects similar to exercise, are thought to be responsible for the clinical benefits of this therapy. Despite the marked success rates EECP achieves with appropriately selected patients who have end‐stage coronary artery disease, the treatment remains largely unknown, particularly among physiatrists. This review will summarize the current evidence for the use of EECP and spark a better understanding of the potential role of this treatment in cardiac rehabilitation.
A Review of Osteoporosis: Part I. Impact, Pathophysiology, Diagnosis and Unique Role of the Physiatrist
Authors: Kasturi Gopi C. , Cifu David X. , Adler Robert A.
Published: March 2009

Osteoporosis is characterized by decreased bone quantity and quality, leading to increased fracture risk. Despite important strides in understanding and treating this disorder, there is a large gap between knowledge and practice. In this first section of a 3‐part review, the impact, pathophysiology, and diagnosis of osteoporosis are discussed. In addition, the role of the physiatrist is highlighted in closing the gap between science and clinical performance.
The Slovak Greens: A complex story of a small party
Authors: Kopeček Lubomír
Published: March 2009

This article is a case study of the Green Party in Slovakia. The line of explanation of the party’s trajectory is chronological, from foundation to its present marginal status. The two main causes of repeated internal party splits identified by the article are the influence of nationalism and the party’s relationship to the most important formation in Slovak politics during the 1990s, Vladimír Mečiar’s Movement for a Democratic Slovakia. It, furthermore, points to the barrier of a relatively high clause in the electoral system to national parliament which determined the Greens’ tendency to enter wider coalition partnerships. These partnerships, however, had a negative impact on the long-term perspective on the distinctiveness of the Greens from the point of view of voters. Other important factors in the party’s lack of political success have been their isolation from the environmental movement and the public’s low level of interest in ecological and other post-material issues.
REGULATING TRANSATLANTIC STOCK EXCHANGES
Authors: Schammo Pierre
Published: March 2009

This paper examines the regulatory questions surrounding transatlantic stock exchange consolidation. Underlying these questions is, in essence, a problem of fit between, on the one hand, the market space and, on the other hand, the regulatory space. Legislation which has predominantly a domestic focus is outdated in view of the increasingly global focus of financial market actors. High-profile mergers such as NYSE Euronext have brought the problem of the regulation of transatlantic or indeed global stock exchanges to the fore. Which national securities laws apply? What consequences does technological integration have for the regulatory position of exchanges and financial market actors? What are the extraterritorial implications? This article takes these questions as a starting point for investigating the problems of, and solutions to, transatlantic stock exchange consolidation.
TRANSITIONAL JUSTICE: A FUTURE TRUTH COMMISSION FOR ZIMBABWE?
Authors: du Plessis Max , Ford Jolyon
Published: March 2009

An eventual sustained democratic transition process in Zimbabwe may include a ‘truth and reconciliation’ commission. The need for—and possible form of—any such institution is situated in a number of discussions: the balance of principle and pragmatism that peace deals sometimes require; comparative experiences in other societies and the promise and limits of institutional modelling; the dynamic between global expectations or prescriptions and ground-level exigencies; the interface of international criminal law and institutions with national-level justice processes; the content of the State's international legal duty to afford a remedy. In considering the extent of an international normative framework limiting the justice options of transitional States, a certain margin of appreciation may be appropriate or necessary to enable a society to reconcile with its violent past on its own terms.
THE BRITISH BANK NATIONALIZATIONS: AN INTERNATIONAL LAW PERSPECTIVE
Authors: Calamita N Jansen
Published: March 2009

The British Government's nationalization of the shares of Northern Rock plc and Bradford & Bingley plc in 2008 raises important issues about the standard of protection owed to the banks' non-UK investors and the manner in which compensation should be calculated. The United Kingdom is party to numerous bilateral investment treaties as well as the European Convention on Human Rights, which adopt an international standard of protection for foreign investors and require the payment of ‘market value’ compensation for the property taken. As the analysis in this article shows, the compensation scheme established by the British Government appears to fall short of these obligations.
Equilibrium turbulent boundary layers with lateral streamline convergence or divergence
Authors: NICKELS T. B.
Published: March 2009

The constraints necessary for equilibrium solutions of the boundary layer equations are explored for turbulent boundary layers subject to lateral convergence and divergence and with longitudinal pressure gradients. It is shown that in addition to the well-known equilibrium solutions for two-dimensional boundary layers there are additionalpossibleequilibrium states for boundary layers with these extra rates-of-strain acting. The necessary constraints for equilibrium are derived and discussed.
Revisiting the aerodynamics of hovering flight using simple models
Authors: HSIEH CHENG-TA , CHANG CHIEN C. , CHU CHIN-CHOU
Published: March 2009

In this study, we revisit two simplified models of hovering motion for fruit fly and dragonfly from the perspective of force decomposition. The unsteady aerodynamics are analysed by examining the lift force and its four constituent components, each of which is directly related to a physical effect. These force components include one from the vorticity within the flow, one from the surface vorticity and two contributions credited to the motion of the insect wing. According to the phase difference in the models, a hovering motion can be classified into one of three types: symmetric, advanced and delayed rotations. The relative importance of the force components under various flow conditions are carefully analysed. It is shown that the symmetric rotation has the maximum vorticity lift (from volume and surface vorticity), but the optimal average lift is attained for an advanced rotation, which, compared to the symmetric rotation, increases the force contribution due to the unsteady surface motion at the expense of sacrificing contribution from the vorticity. By identifying the variations of the vorticity lift with flow characteristics, we may further explore the detailed mechanisms associated with the unsteady aerodynamics at different phases of hovering motion. For the different types of rotation, the insect wing shares the same mechanism of gaining lift when in the phase of driving with a fuller speed but exhibits different mechanisms at turning from one phase of motion to another. Moreover, we also examine the effects of the Reynolds number in an appropriate range and evaluate the performance of different wing profiles from symmetric to largely cambered.
Characterising line fountains
Authors: HUNT G. R. , COFFEY C. J.
Published: March 2009

We present analytical solutions for the initial rise heightzmof two-dimensional turbulent fountains issuing from a horizontal linear source of width 2b0into a quiescent environment of uniform density. Using the initial rise height prediction as a measure we classify line fountains into three types depending on their source conditions. For source Froude numbersFr0≫ 1, the near-source flow of the ‘forced’ fountain is dominated by source momentum flux and behaves like a jet; the asymptotic solution to the fountain equations yields, in agreement with previous studies,zm/b0~Fr04/3. ForFr0=O(1) the fountain is ‘weak’ and fluid is projected vertically to a height that is consistent with an energy-conserving flow – the sensitivity of the rise height withFr0increases aszm/b0~Fr02. ForFr0≪ 1, the fountain is ‘very weak’ and we find thatzm/b0~Fr02/3. As the local value of the Froude number decreases with height, all three forms of fountain behaviour identified are expected above a highly forced source and we provide scalings for the three lengths that contribute to the total rise height. Comparisons between our predicted rise heights and the previous experimental results show good agreement across a wide range ofFr0. The collated data highlights that experiments have focused in the majority on fountains above sources with intermediateFr0. Notably there is a lack of measurements on very weak line fountains and of independent experimental confirmation of the initial rise heights across the range ofFr0.
Three-dimensional instabilities of oscillatory equatorial zonal shear flows
Authors: NATAROV ANDREI , RICHARDS KELVIN J.
Published: March 2009

In this paper, we investigate the linear stability of oscillating zonal flows on the equatorial β-plane in the presence of fully three-dimensional disturbances. To exclude inflection point effects, we focus on the simplest case of a linear meridional shear with time-mean and oscillating components. For purely oscillatory background flows we find that in addition to resonant excitation of ‘additive’ type that occurs in the zonally invariant case, resonant excitation of ‘difference’ type is also possible. For flows with an oscillatory shear superimposed on an unstable time-mean shear it is shown that while the oscillatory shear has a stabilizing influence on disturbances with a small zonal wave number k, at higher k the effect of the oscillating shear diminishes and can even be destabilizing. Overall, a small oscillatory shear tends to reduce the fastest growth rate in the system and pushes the dominant k to higher values. Calculation of dominant zonal and vertical modes shows that the zonally asymmetric modes dominate a large portion of the parameter space, especially at high time-mean background shear and low oscillatory shear. As a result, the dominant vertical mode can have a somewhat larger vertical scale than in the zonally invariant case. At intermediate values of the time-mean shear the growth rate is relatively flat with respect to the zonal mode number, with maximum growth rate occurring in bands of high and low k. We have uncovered a rich assortment of vertical and zonal modes which are likely to play a role in the nonlinear evolution of equatorial flows.
The dynamics of the transitional flow over a backward-facing step
Authors: SCHÄFER F. , BREUER M. , DURST F.
Published: March 2009

The internal flow over a backward-facing step in the transitional regime (ReD = 6000) was studied based on direct numerical simulations. The predictions were carried out with the help of a finite-volume Navier–Stokes solver equipped with a co-visualization facility which allows one to investigate the flow dynamics at high temporal resolution. First, grid-induced oscillations were precluded by a careful grid design. Second, the strong influence of the velocity profile approaching the step was studied and outlined. The main objective, however, was to provide a comprehensive insight into the dynamic flow behaviour, especially oscillations of the reattachment length of the primary recirculation region. The origin of this well-known flapping behaviour of the reattachment line is not yet completely understood. In the present work, the mechanisms leading to the oscillations of the reattachment length were extensively investigated by analysing the time-dependent flow. Besides the oscillations of the primary recirculation region, oscillations of the separation and the reattachment line of the secondary recirculation bubble at the upper channel wall were also observed. The results clearly show that in the present flow case the flapping of the primary reattachment and the secondary separation line is due to vortical structures in the unstable shear layers between the main flow and the recirculation bubbles. Vortices emerging in the shear layers and sweeping downstream convectively induce small zones of backward-flowing fluid at the channel walls while passing the recirculation regions. In the case of the primary recirculation region, the rotational movement of the shear-layer vortices impinging on the lower channel wall was found to cause zones of negative fluid velocity at the end of the recirculation bubble and thus flapping of the reattachment line. In contrast, in the case of the secondary recirculation region, the shear-layer vortices moved away from the upper channel wall so that their rotational movement did not reach the boundary. In this case, the pressure gradients originating from local pressure minima located in the shear-layer vortices were identified as being responsible for the oscillations of the separation line at the upper channel wall. While moving downstream with the shear-layer vortices, the pressure gradients were found to influence the top boundary of the channel and create alternating zones of forward- and backward-flowing fluid along the wall. All of these unsteady processes can best be seen from animations which are provided on the Journal of Fluid Mechanics website: journals.cambridge.org/FLM.
Destabilizing effects of confinement on homogeneous mixing layers
Authors: HEALEY J. J.
Published: March 2009

The absolute and convective instability properties of plane mixing layers are investigated for linearized inviscid disturbances. It is shown that confinement by plates parallel to the flow can enhance the absolute instability so much that even a co-flow plane mixing layer becomes absolutely unstable when the ratio of distances of the plates from the mixing layer lies in a certain range. Even when the plates are placed equidistantly from the mixing layer, a co-flow mixing layer can become absolutely unstable if the velocity profile has an asymmetry about its mid-plane. ‘Semiconfinement’, where a plate is only added to one side of the mixing layer, is also investigated. A substantial destabilization is possible when the plate is added on the side of the faster stream. Previous investigations seem only to have found absolute instability when the streams flow in opposite directions.
Three-dimensional flows around low-aspect-ratio flat-plate wings at low Reynolds numbers
Authors: TAIRA KUNIHIKO , COLONIUS TIM
Published: March 2009

Three-dimensional flows over impulsively translated low-aspect-ratio flat plates are investigated for Reynolds numbers of 300 and 500, with a focus on the unsteady vortex dynamics at post-stall angles of attack. Numerical simulations, validated by an oil tow-tank experiment, are performed to study the influence of aspect ratio, angle of attack and planform geometry on the wake vortices and the resulting forces on the plate. Immediately following the impulsive start, the separated flows create wake vortices that share the same topology for all aspect ratios. At large time, the tip vortices significantly influence the vortex dynamics and the corresponding forces on the wings. Depending on the aspect ratio, angle of attack and Reynolds number, the flow at large time reaches a stable steady state, a periodic cycle or aperiodic shedding. For cases of high angles of attack, an asymmetric wake develops in the spanwise direction at large time. The present results are compared to higher Reynolds number flows. Some non-rectangular planforms are also considered to examine the difference in the wakes and forces. After the impulsive start, the time at which maximum lift occurs is fairly constant for a wide range of flow conditions during the initial transient. Due to the influence of the tip vortices, the three-dimensional dynamics of the wake vortices are found to be quite different from the two-dimensional von Kármán vortex street in terms of stability and shedding frequency.
Stratorotational instability in Taylor–Couette flow heated from above
Authors: GELLERT M. , RÜDIGER G.
Published: March 2009

We investigate the instability and nonlinear saturation of temperature-stratified Taylor–Couette flows in a finite height cylindrical gap and calculate angular momentum transport in the nonlinear regime. The model is based on an incompressible fluid in Boussinesq approximation with a positive axial temperature gradient applied. While both ingredients, the differential rotation as well as the stratification due to the temperature gradient, are stable themselves, together the system becomes subject of the stratorotational instability and a non-axisymmetric flow pattern evolves. This flow configuration transports angular momentum outwards and will therefore be relevant for astrophysical applications. The belonging coefficient of β viscosity is of the order of unity if the results are adapted to the size of an accretion disk. The strength of the stratification, the fluid's Prandtl number and the boundary conditions applied in the simulations are well suited too for a laboratory experiment using water and a small temperature gradient around 5 K. With such a set-up the stratorotational instability and its angular momentum transport could be measured in an experiment.
Migration and motility of spermatozoa in the female reproductive tract of the soft tick Ornithodoros moubata (Acari, Argasidae)
Authors: RESLER J. H. , FRAZIER J. L. , SHEPHERD J. G. , MODAFFERI J. D.
Published: March 2009

The spermatozoa of ticks are anomalous in many respects: they are very large, cytoplasm-rich cells which lack a flagellum but move with a peculiar gliding motility. Their metamorphosis after deposition in the female has been well documented, but many of the subsequent events in the career of the spermatozoa are controversial or poorly documented. Our observations of motility imply that the many types of motility that have been reported (up to 5 different types in several reports) can be reduced to 2 apparently independent types of active motility: (1) gliding motility generated along the whole spermatozoon and (2) contortions of the anterior tip of the head. These types of motility appear as a consequence of sperm maturation after transfer to the female, but only become pronounced if the female has taken a recent bloodmeal. A consequence of this enhanced gliding motility after feeding is the movement of the spermatozoa out of the naturally ruptured neck of the spermatophore and up the female genital tract. This occurs without any apparent assistance from the female's musculature and likely is the prime mechanism of movement of the spermatozoa to the site of fertilization.
Infestation of the cupped oysters Crassostrea angulata, C. gigas and their first-generation hybrids by the copepod Myicola ostreae: differences in susceptibility and host response
Authors: BATISTA F. M. , BOUDRY P. , DOS SANTOS A. , RENAULT T. , RUANO F.
Published: March 2009

We studied the prevalence and intensity of the parasitic copepod Myicola ostreae in 2 closely related oysters Crassostrea angulata and C. gigas and their F1 hybrids. The effects on host and host reaction were also analysed to better understand host-parasite relationships between copepods and bivalve molluscs. Full reciprocal crosses were carried out between C. angulata and C. gigas and the progenies were reared in the wild in Ria Formosa Lagoon (Portugal), allowing natural infestation by M. ostreae. Prevalence and intensity were significantly higher in C. angulata than in C. gigas. The parasite level of F1 hybrids was similar to C. angulata and significantly higher than in C. gigas. The results of our study support a hypothesis of dominantly inherited susceptibility to M. ostreae infestation. Moreover, copepods were observed on the gill surface of C. gigas engulfed by a capsule-like structure. Histological analyses revealed that the copepods were surrounded by a massive agglomerate of haemocyte-like cells encircled by a thin layer of fibroblast-like cells. This encapsulation response was not observed in C. angulata or in F1 hybrids. These results suggest that the differential susceptibility to M. ostreae between C. angulata and C. gigas may be ascribed to host defence factors.
Sharing or commoditising? A discussion of some of the socio-economic implications of Nunavik's Hunter Support Program
Authors: Gombay Nicole
Published: March 2009

The article considers the perceptions of Inuit in one settlement in Nunavik regarding the dynamic relations between market and subsistence economies. The socio-economic role of country foods in Inuit society are described followed by a discussion about the impacts of the Hunter Support Program (HSP) on Inuit society. A hybrid institution, the HSP buys country foods in order to give them away. Based on interviews that included Inuit purveyors to, and administrators of, the programme, the article discusses some socio-economic effects of commoditisation of country foods on subsistence economies and explores the ways in which this food moves in and out of commodity status. It is argued that these shifts are linked to conflicting notions of value. Some Inuit justify the existence of the HSP because they perceive it to be an essentially non-Inuit institution which lies outside the realm of customary socio-economic organization and thereby frees them from the need to observe those rules strictly while providing them with the income to be able to respect the requirement to share food amongst Inuit. Others express reservations about the programme because it elicits behaviours amongst Inuit that they perceive as threatening their socio-economic reproduction. It is argued that the HSP, an institution that both mimics and breaks with tradition, one which is designed to help Inuit to promote the subsistence way of life yet does so in the context of at least some components of the market, is an example of Wenzel's (2001) contention that the analytical distinction between acculturation and adaptation is not a matter of oppositions, but rather, part of a whole.
Tourist images of Greenland and the Arctic: a perception analysis
Authors: Hübner Anna
Published: March 2009

Within the scope of climate change and the worldwide shift in travel patterns, the Arctic has become a highly favoured tourist destination. However, the literature on studying destination images of the northern polar regions lacks analysis of prevailing perceptions and of corresponding images held by tourists without previous travel experience. Therefore, this research, recently carried out in Germany, attempts to delineate tourists' perceptions of Greenland on the one hand and the Arctic as a whole on the other as destinations. Similarities, positive and negative differences of the cognitive and affective stages are generated and an overview of perceived dimensions and factors influencing the images are given. Although the results strongly coincide with each other, there are minor differences found in favour of Greenland. With the findings it is hoped to provide a better insight into the images held by potential visitors to the Arctic and to help those engaged in marketing Greenland as a tourist destination to identify an efficient strategy.
Norway's rule on Svalbard: tightening the grip on the Arctic islands
Authors: Pedersen Torbjørn
Published: March 2009

Over the last four decades, Norwegian rule on the Svalbard islands has developed gradually, from being virtually non-existent to firm. This study explains these developments in Norwegian jurisdiction both from a perspective of international relations and within a paradigm of domestic politics. It finds that external forces have been the permissive causes of change, while internal forces represent the efficient causes. Norway's incremental strengthening of jurisdiction, notably from the mid-1970s onward, has resulted in an unprecedented Norwegian grip on the Arctic islands in which the other parties to the 1920 Svalbard Treaty seemingly acquiesce.
A new method to solve robot inverse kinematics using Assur virtual chains
Authors: Simas H. , Guenther R. , da Cruz D. F. M. , Martins D.
Published: March 2009

This paper describes a numerical algorithm to solve the inverse kinematics of parallel robots based on numerical integration. Inverse kinematics algorithms based on numerical integration involve the drift phenomena of the solution; as a consequence, errors are generated when the end-effector location differs from that desired. The proposed algorithm associates a novel method to describe the differential kinematics with a simple numerical integration method. The methodology is presented in this paper and its exponential stability is proved. A numerical example and a real application are presented to outline its advantages.
A review of computational fluid dynamics analysis of blood pumps
Authors: BEHBAHANI M. , BEHR M. , HORMES M. , STEINSEIFER U. , ARORA D. , CORONADO O. , PASQUALI M.
Published: March 2009

Ventricular assist devices (VADs) provide long- and short-term support to chronically ill heart disease patients; these devices are expected to match the remarkable functionality of the natural heart, which makes their design a very challenging task. Blood pumps, the principal component of the VADs, must operate over a wide range of flow rates and pressure heads and minimise the damage to blood cells in the process. They should also be small to allow easy implantation in both children and adults. Mathematical methods and computational fluid dynamics (CFD) have recently emerged as powerful design tools in this context; a review of the recent advances in the field is presented here. This review focusses on the CFD-based design strategies applied to blood flow in blood pumps and other blood-handling devices. Both simulation methods for blood flow and blood damage models are reviewed. The literature is put into context with a discussion of the chronological development in the field. The review is illustrated with specific examples drawn from our group's Galerkin/least squares (GLS) finite-element simulations of the basic Newtonian flow problem for the continuous-flow centrifugal GYRO blood pump. The GLS formulation is outlined, and modifications to include models that better represent blood rheology are shown. Haemocompatibility analysis of the pump is reviewed in the context of haemolysis estimations based on different blood damage models. Our strain-based blood damage model that accounts for the viscoleasticity associated with the red blood cells is reviewed in detail. The viability of design improvement based on trial and error and complete simulation-based design optimisation schemes are also discussed.
Editorial
Authors: Leroy Xavier
Published: March 2009

This issue of the Journal of Functional Programming (JFP) marks a point of transition. After serving since 1991 as Editor, then since 2004 as co-Editor in Chief (along with Greg Morrisett from 2004 to 2006 and Xavier Leroy since 2007), Paul Hudak is stepping down.