bluuebunny/crossref_metadata_2025 huggingface dataset:
Rodent granivory strengthens relationships between seed size and plant abundance in a desert annual community
Authors: Chen Ting C. , Valone Thomas J.
Published: March 2017

Aim

The seed size/number trade‐off model explains the co‐existence of plants that produce different‐sized seeds by assuming an establishment fitness advantage for larger seeds via enhanced competition or environmental tolerance, and a colonization fitness advantage for smaller seeds. The model predicts a negative relationship between seed mass and plant abundance among co‐existing species in a community. Here, we evaluate the hypothesis that rodent granivory affects the slope of this relationship, causing it to become less negative when granivore pressure is reduced because rodents selectively harvest large seeds.

Location

Chihuahuan Desert, USA.

Methods

We analysed long‐term data from an annual plant community in southeast Arizona to characterize the relationship between seed mass and mean plant abundance in three types of plots that manipulated the rodent community. Some plots excluded all rodents, other selectively excluded only large‐bodied kangaroo rats (Dipodomys), while control plots allowed access by all rodents.

Results

We observed negative relationships between seed mass and plant abundance on 23 of the 24 experimental plots. The slopes of these relationships were significantly affected by the experimental treatments. Slopes were most negative for control plots and least negative for plots that excluded all rodents.

Conclusion

Rodent granivore exclusion caused the slope of the relationship between seed mass and plant abundance to become less negative. These results illustrate how granivory can affect seed mass–plant abundance relationships, and may provide further insight into the co‐existence of plants that vary in seed size.
Social determinants of inequalities in child undernutrition in Bangladesh: A decomposition analysis
Authors: Huda Tanvir M. , Hayes Alison , El Arifeen Shams , Dibley Michael J.
Published: March 2017

Socioeconomic inequalities in child undernutrition remain one of the main challenges in Bangladesh. The social determinants of health are mostly responsible for such inequalities across different population groups. However, no study has examined the relative contribution of different social determinants to the socioeconomic inequality in child undernutrition in Bangladesh. Our objective is to measure the extent of socioeconomic‐related inequalities in childhood stunting and identify the key social determinants that potentially explain these inequalities in Bangladesh. We used data for children younger than 5 years of age for this analysis from 2 rounds of Bangladesh Demographic and Health Surveys conducted in 2004 and 2014. We examined the socioeconomic inequality in stunting using the concentration curve and concentration index. We then decomposed the concentration index into the contributions of individual social determinants. We found significant inequality in stunting prevalence. The negative concentration index of stunting indicated that stunting was more concentrated among the poor than among the well‐off. Our results suggest that inequalities in stunting increased between 2004 and 2014. Household economic status, maternal and paternal education, health‐seeking behavior of the mothers, sanitation, fertility, and maternal stature were the major contributors to the disparity in stunting prevalence in Bangladesh. Equity is a critical component of sustainable development goals. Health policymakers should work together across sectors and develop strategies for effective intersectoral actions to adequately address the social determinants of equity and reduce inequalities in stunting and other health outcomes.
Association of cortical microinfarcts and cerebral small vessel pathology in the ageing brain
Authors: Kövari E. , Herrmann F. R. , Gold G. , Hof P. R. , Charidimou A.
Published: March 2017

Aims

Cortical microinfarcts (CMI) are frequently observed in the ageing brain independent of cognitive decline, but their aetiology is not fully elucidated. To examine the potential role of different vessel pathologies, including cerebral amyloid angiopathy (CAA), arteriolosclerosis‐hyalinosis and thromboembolism in the development of CMI, we examined 80 autopsy cases with more than one CMI on routine neuropathological examination.

Methods

Pial and intracortical vessels around CMI were assessed for their integrity with haematoxylin–eosin staining and antibodies against amyloid‐β protein and fibrinogen using a semiquantitative four‐level rating scale (absent to severe) in the hippocampus, and the frontal, temporal and occipital cortex. Four histological categories of changes were defined: CAA, vessel pathology other than CAA, thromboembolism and absence of vessel pathology near CMI.

Results

A differential distribution of microvascular pathology was observed depending on brain regions. In the occipital cortex, CAA was commonly associated with CMI. In contrast, in the hippocampus and the frontal cortex, cases without any vascular pathology in pial and intracortical vessels were significantly more frequent.

Conclusions

The aetiology of CMI differs depending on brain location. CAA may play a role principally in the occipital cortex. The large number of intact vessels around the CMI (mainly in the frontal cortex and hippocampus) raises the possibility that pathologies other than structural microangiopathy, including hypoperfusion/arterial hypotension or large vessel atherosclerosis, play a role in the development of microvascular lesions. These results are relevant in the context of aetiopathogenesis of vascular changes associated with conditions like vascular dementia.
Stimpsonia nanlingensis sp. nov. (Primulaceae) from Guangdong, China
Authors: Huang Ge‐Han , Hao Gang
Published: March 2017

A new species of Stimpsonia (Primulaceae), S. nanlingensis G.H. Huang & G. Hao, from Guangdong, China, is described and illustrated as the second species in the genus. In general morphology it resembles S. chamaedryoides but can be distinguished by its foliose bracts and a corolla with a shorter tube and shorter truncate or obtuse lobes.
Patient preferences for endpoints in fecal incontinence treatment studies
Authors: Heymen S. , Palsson O. , Simren M. , Whitehead W. E.
Published: March 2017

Background

Randomized controlled trials of treatments for fecal incontinence (FI) are difficult to compare because case definitions and study endpoints vary. Our aims were to assess patient perspectives on the case definition for FI and how treatment success should be measured.

Methods

In Phase 1, 28 FI patients participated in anonymous on‐line focus groups, and in Phase 2, 186 people with FI, stratified by gender, race, and age completed an online survey.

Key Results

Focus group participants described frequency and urgency as the most important characteristics for defining FI. Most (80%) thought staining of underwear constitutes FI, but only 33% thought gas leakage was FI. When asked how the success of treatment should be defined, 77% said by a reduction in frequency or complete cure, but less than half thought a 50% reduction in frequency was enough. When asked how much reduction would be needed, responses averaged 80%. The Phase 2 survey confirmed that frequency, urgency, and intestinal discomfort are the most important characteristics for case definition, and that success should be defined by at least a 75% decrease in frequency. A 50% reduction was an acceptable endpoint for 58% overall but only 26% for those aged ≥65. “Adequate relief” was acceptable to 78%.

Conclusions and Inferences

Inclusion criteria for trials should specify a minimum frequency of FI. Most patients would require a ≥75% reduction in FI frequency to call a treatment successful but young adults and those with more severe FI would accept a ≥50% reduction as meaningful.
Triangular love–hate: management and control in creative crowdworking
Authors: Schörpf Philip , Flecker Jörg , Schönauer Annika , Eichmann Hubert
Published: March 2017

This article analyses the ways in which creative crowdwork is managed and controlled within social and economic power relations. It presents findings from a research project on creative crowdworkers focussing on aspects of management and control. The research shows that the design of the platforms and the strategies of their operating companies clearly structure the triangular relationship between platform, clients and workers. In addition to bureaucratic rules and surveillance exercised by the platform, rating opportunities and other control features utilised by clients strongly impact on crowdworkers’ time use, income and creativity and thus on their working and living conditions.
The (lack of) relation between straylight and visual acuity. Two domains of the point‐spread‐function
Authors: van den Berg Thomas J. T. P.
Published: March 2017

Purpose

The effect of cataract and other media opacities on functional vision is typically assessed clinically using visual acuity. In both clinical and basic research, straylight (the functional result of light scattering in the eye) is commonly measured. The purpose of the present study was to determine the link between these two measures: is visual acuity in cataract and other media opacities related to straylight?

Methods

Interdependence between acuity and straylight is addressed from three different points of view: (1) Methodological: can acuity differences affect the measurement value of straylight, and vice versa? (2) Basic optics: does the optical process of light scattering in the human eye affect both straylight and visual acuity? (3) Statistical: how strongly are acuity and straylight correlated in the practice of important clinical conditions? Experimental and theoretical aspects will be considered, with a focus on normal ageing and cataract formation.

Results

(1) Methodological: testing potential effects of acuity, artificially manipulated with positive trial lenses, showed no effect on measured straylight values. Since light scattering in the eye involves a low percentage of the light and has large angular spreading, contrast reduction due to straylight is limited, resulting in virtually absent acuity effects. (2) Basic optics: light scattering from the human donor eye lens is found to have virtually no effect in the centre of the point‐spread‐function, also for cataractous lenses, resulting in virtually absent acuity effects. (3) Statistical: literature data on straylight and visual acuity show a weak correlation for the important groups of normal ageing and cataract populations.

Conclusions

The point‐spread‐function of the normal ageing and cataractous human eye is built upon two rather independent basic parts. Aberrations control the central peak. Light scattering controls the periphery from about 1° onwards. The way acuity and straylight are measured ensures no confounding between them. Statistically within the normal ageing and cataract populations, visual acuity and straylight vary quite independently from each other. Visual acuity losses with cataract and other media opacities are not due to straylight, but caused by aberrations and micro‐aberrations. Straylight defines disability glare, and causes symptoms of glare, haloes, hazy vision etc. Overall, visual acuity and straylight are rather independent aspects of quality of vision.
Fitness of Bt‐resistant cabbage loopers on Bt cotton plants
Authors: Tetreau Guillaume , Wang Ran , Wang Ping
Published: March 2017

Development of resistance to the insecticidal toxins from Bacillus thuringiensis (Bt) in insects is the major threat to the continued success of transgenic Bt crops in agriculture. The fitness of Bt‐resistant insects on Bt and non‐Bt plants is a key parameter that determines the development of Bt resistance in insect populations. In this study, a comprehensive analysis of the fitness of Bt‐resistant Trichoplusia ni strains on Bt cotton leaves was conducted. The Bt‐resistant T. ni strains carried two genetically independent mechanisms of resistance to Bt toxins Cry1Ac and Cry2Ab. The effects of the two resistance mechanisms, individually and in combination, on the fitness of the T. ni strains on conventional non‐Bt cotton and on transgenic Bt cotton leaves expressing a single‐toxin Cry1Ac (Bollgard I) or two Bt toxins Cry1Ac and Cry2Ab (Bollgard II) were examined. The presence of Bt toxins in plants reduced the fitness of resistant insects, indicated by decreased net reproductive rate (R0) and intrinsic rate of increase (r). The reduction in fitness in resistant T. ni on Bollgard II leaves was greater than that on Bollgard I leaves. A 12.4‐day asynchrony of adult emergence between the susceptible T. ni grown on non‐Bt cotton leaves and the dual‐toxin‐resistant T. ni on Bollgard II leaves was observed. Therefore, multitoxin Bt plants not only reduce the probability for T. ni to develop resistance but also strongly reduce the fitness of resistant insects feeding on the plants.
Enhanced transport of plant‐produced rabies single‐chain antibody‐RVG peptide fusion protein across an in cellulo blood–brain barrier device
Authors: Phoolcharoen Waranyoo , Prehaud Christophe , van Dolleweerd Craig J. , Both Leonard , da Costa Anaelle , Lafon Monique , Ma Julian K‐C.
Published: March 2017

The biomedical applications of antibody engineering are developing rapidly and have been expanded to plant expression platforms. In this study, we have generated a novel antibody molecule in planta for targeted delivery across the blood–brain barrier (BBB). Rabies virus (RABV) is a neurotropic virus for which there is no effective treatment after entry into the central nervous system. This study investigated the use of a RABV glycoprotein peptide sequence to assist delivery of a rabies neutralizing single‐chain antibody (ScFv) across an in cellulo model of human BBB. The 29 amino acid rabies virus peptide (RVG) recognizes the nicotinic acetylcholine receptor (nAchR) at neuromuscular junctions and the BBB. ScFv and ScFv‐RVG fusion proteins were produced in Nicotiana benthamiana by transient expression. Both molecules were successfully expressed and purified, but the ScFv expression level was significantly higher than that of ScFv‐RVG fusion. Both ScFv and ScFv‐RVG fusion molecules had potent neutralization activity against RABVin cellulo. The ScFv‐RVG fusion demonstrated increased binding to nAchR and entry into neuronal cells, compared to ScFv alone. Additionally, a human brain endothelial cell line BBB model was used to demonstrate that plant‐produced ScFv‐RVGP fusion could translocate across the cells. This study indicates that the plant‐produced ScFv‐RVGP fusion protein was able to cross the in celluloBBB and neutralize RABV.
Pheomelanogenesis is promoted at a weakly acidic pH
Authors: Wakamatsu Kazumasa , Nagao Ayano , Watanabe Miu , Nakao Kenta , Ito Shosuke
Published: March 2017

The diversity of pigmentation in the skin, hair, and eyes of humans has been largely attributed to the diversity of pH in melanosomes with an acidic pH being proposed to suppress melanin production, especially eumelanogenesis. We previously showed that an acidic pH greatly suppresses the late stage of eumelanogenesis after the dopachrome stage. The oxidation of tyrosine by tyrosinase in the presence of cysteine forms cysteinyldopa isomers, which are further oxidized to give rise to pheomelanin via benzothiazine intermediates. However, how those steps are controlled by pH has not been characterized. We therefore examined whether pheomelanin synthesis is chemically promoted at an acidic pH. We found that pheomelanin production either from dopa or tyrosine in the presence of cysteine by tyrosinase was greatest at pH values of 5.8–6.3, while eumelanin production was suppressed at pH 5.8. This suggests that mixed melanogenesis is chemically shifted to more pheomelanic states at a weakly acidic pH.
Understanding the human side of openness: the fit between open innovation modes and CEO characteristics
Authors: Ahn Joon Mo , Minshall Tim , Mortara Letizia
Published: March 2017

In small‐ and medium‐sized enterprises (SMEs), where typically the decision‐making process is highly centralised, important decisions, such as open innovation (OI) adoption, will be strongly influenced by the characteristics of their Chief Executive Officers (CEOs). Pointing the attention to the strategic leadership and human elements, this paper sheds light on the micro‐foundation of OI by emphasising the role that the personal traits of key individuals in innovation. OI adoption could result in the enactment of several OI modes – each representing an opportunity of potential change (of market, of technology or/and of the organisation) – and this paper attempts to examine the relationships between the CEO characteristics and each of the OI modes. Our analysis, using Korean SME data, shows that CEOs’ positive attitude, entrepreneurial orientation (EO), patience and education can play important roles in facilitating OI in SMEs. However, this paper also observed that the effects of CEO characteristics on OI adoption were differently configured according to the nature of each OI mode, for example, CEOs’ patience and EO had different impacts depending on the degree of uncertainty in the OI mode. This suggest that OI must be understood as a wide innovation spectrum, and, to increase opportunities for successful OI adoption, CEOs have to attempt to compensate for characteristics they may lack by recruiting appropriate complementary top managements. The research has practical implications for CEOs and policy makers who are interested in enhancing competitiveness of SMEs.
Sectoral determinants of foreign affiliate sales employing European data
Authors: Bekkers Eddy , Macskasi Indre
Published: March 2017

We test theories on sectoral determinants of foreign affiliate sales employing European foreign affiliate sales statistics (FATS). On the one hand, we test hypotheses that foreign affiliate sales are less likely in sectors with complex tasks and more likely in sectors where communication with customers is important. On the other hand, we test the hypothesis that the force of gravity is stronger in more complex sectors. Employing Poisson and negative binomial estimators, we find support for the first hypotheses and contradict the second hypothesis. We show that the interaction effect between distance and complexity changes sign from negative to positive when complexity is included as a separate regressor. We propose an explanation to reconcile our findings with the basic assertion in the second hypothesis that the force of gravity is stronger in more complex sectors, based on a composition effect between horizontal and vertical affiliate sales.
Siglec‐9 is upregulated in rheumatoid arthritis and suppresses collagen‐induced arthritis through reciprocal regulation of Th17‐/Treg‐cell differentiation
Authors: Wang X. , Liu D. , Ning Y. , Liu J. , Wang X. , Tu R. , Shen H. , Chen Q. , Xiong Y.
Published: March 2017

Sialic acid‐binding Ig‐like lectin‐9 (Siglec‐9) is a novel sialic acid‐binding member of the immunoglobulin superfamily and is broadly expressed on immune cells, which can inhibit both innate and adaptive immune responses through immunoreceptor tyrosine‐based inhibitory motifs. However, the exact role of Siglec‐9 in the pathogenesis of rheumatoid arthritis (RA) remains unknown. In this study, we determined soluble Siglec‐9 (sSiglec‐9) levels in the serum and synovial fluid of patients with RA and evaluated the relation between sSiglec‐9 levels and clinical factors. In addition, we investigated whether Siglec‐9 could alleviate collagen‐induced arthritis (CIA) development in mice and explored the molecular mechanisms involved. The results showed that, in the serum and synovial fluid of patients with RA, sSiglec‐9 levels were elevated. Thus, high sSiglec‐9 serum levels associated with disease severity in patients with RA. Furthermore, administration of recombinant human Siglec‐9 Fc chimera protein significantly attenuated collagen‐induced arthritis development in vivo and in vitro by reciprocal regulation of the differentiation of Th17 and Treg cells. Our findings collectively indicate that Siglec‐9 plays a potent immunosuppressive role in the pathogenesis of RA by reciprocal regulation of Th17‐/Treg‐cell differentiation. In conclusion, Siglec‐9 may serve as a potential diagnostic and therapeutic target for RA.
Computational Prediction of Usutu Virus E Protein B Cell and T Cell Epitopes for Potential Vaccine Development
Authors: Palanisamy N. , Lennerstrand J.
Published: March 2017

Usutu virus (family Flaviviridae), once confined to Africa, has emerged in Europe a decade ago. The virus has been spreading throughout Europe at a greater pace mostly affecting avian species. While most bird species remain asymptomatic carriers of this virus, few bird species are highly susceptible. Lately, Usutu virus (USUV) infections in humans were reported sporadically with severe neuroinvasive symptoms like meningoencephalitis. As so much is unknown about this virus, which potentially may cause severe diseases in humans, there is a need for more studies of this virus. In this study, we have used computational tools to predict potential B cell and T cell epitopes of USUV envelope (E) protein. We found that amino acids between positions 68 and 84 could be a potential B cell epitope, while amino acids between positions 53 and 69 could be a potential major histocompatibility complex (MHC) class I‐ and class II‐restricted T cell epitope. By homology 3D modeling of USUV E protein, we found that the predicted B cell epitope was predominantly located in the coil region, while T cell epitope was located in the beta‐strand region of the E protein. Additionally, the potential MHC class I T cell epitope (LAEVRSYCYL) was predicted to bind to nearly 24 human leucocyte antigens (HLAs) (IC50 ≤5000 nm) covering nearly 86.44% of the Black population and 96.90% of the Caucasoid population. Further in vivo studies are needed to validate the predicted epitopes.
PTEN/PI3k/AKT Regulates Macrophage Polarization in Emphysematous mice
Authors: Lu J. , Xie L. , Liu C. , Zhang Q. , Sun S.
Published: March 2017

Macrophages play an important role in the pathogenesis of COPD. Macrophage polarization towards the M2 phenotype has been observed in the lung tissues of COPD patients and cigarette smokers. The molecular basis of this process remains unclear, and it has not been completely illuminated in animal models of emphysema. In our study, we combined cigarette smoke (CS) exposure with intraperitoneal injection of cigarette smoke extract (CSE) to build an emphysema model. We found by immunohistochemical staining and flow cytometry that the expression level of CD206 and the ratio of M2 to M1 macrophages was increased in emphysematous mice. We also demonstrated that decreased protein level for phosphatase and tensin homology deleted on chromosome ten (PTEN) and increased total protein levels for phosphorylation ‐protein kinase B (p‐AKT) in the lung tissue of emphysematous mice and in CSE‐treated RAW264.7 cells. In both bone marrow‐derived macrophages (BMDMs) from emphysematous mice and CSE‐treated RAW264.7 cells, we observed by RT‐PCR that the mRNA levels of M2 macrophage‐related markers and cytokines were increased. Furthermore, M1 macrophage‐related markers and cytokines were decreased. Meanwhile we treated BMDMs from emphysematous mice and CSE‐treated RAW264.7 cells with the phosphoinositide 3‐kinase (PI3K)/Akt inhibitor (LY294002), we observed a reduction in RNA levels of M2 macrophage‐related markers and cytokines. In conclusion, we confirmed that macrophage M2 polarization was induced in emphysematous mice generated by CS exposure combined with intraperitoneal injection of CSE. We also showed that M2 polarization was mediated through PTEN/PI3k/AKT pathway activation.
Weed growth and crop yield responses to tillage and mulching under different crop rotation sequences in semi‐arid conditions
Authors: Mashingaidze N. , Twomlow S. , Madakadze I.C. , Mupangwa W. , Mavunganidze Z.
Published: March 2017

Conservation agriculture (CA) is thought to reduce weed pressure from the third year of adoption, when recommended practices are followed. Weed growth and crop yield were assessed during the third and fourth year of maize–cowpea–sorghum rotation, second and third year of maize–cowpea rotation and first and second year of maize monocropping on a clay loam soil at Matopos Research Station (annual rainfall, 573 mm) following recommended CA management practices. Each experiment had a split‐plot randomized complete block design with mouldboard plough (CONV), minimum tillage (MT) with ripper tine and planting basins as main‐plot factor and maize residue mulch rate (0, 2 and 4 t/ha) as a subplot factor, with threefold replication. All subplots were surface mulched and weeded by hoe at the same time. We hypothesized that under MT weed growth would be considerable with maize monocropping but from year 3 of CA, weed growth would decrease and crop yield increase relative to values from unmulched CONV. Minimum tillage increased weed growth in 2nd year of maize monocropping. Under the maize–cowpea rotation, the considerable weed growth in planting basins was likely due to the large intrarow spacing and poor light competiveness of the cowpea variety. Mulch contributed to weed growth being suppressed by up to 36% under CA in the maize–cowpea–sorghum rotation relative to unmulched CONV. When planted on the same date, crop yield did not differ between CA and unmulched CONV. Maize–cowpea–sorghum rotation grain yield (3143 kg/ha) was double that under monocropping, probably due to improvements in soil physical and chemical conditions.
Purpureocillium lilacinum tattoo‐related skin infection in a kidney transplant recipient
Authors: Trinh Sonya A. , Angarone Michael P.
Published: March 2017

Purpureocillium lilacinum is an emerging pathogenic mold among immunocompromised hosts that causes cutaneous infections related to skin breakdown. We present the first reported case of P. lilacinum tattoo‐related skin infection, to our knowledge. A kidney transplant recipient recently treated for acute cellular rejection presented with skin papules overlying a tattoo. Diagnosis was confirmed on culture, histology, and 18S ribosomal RNA polymerase chain reaction. The morphological features on culture characteristic of P. lilacinum included violet colonies on malt extract agar, long tapering brush‐like phialides, and elliptical conidia attached in chains. P. lilacinum has intrinsic resistance to many antifungal agents including amphotericin B, but voriconazole and posaconazole have good in vitro activity. The patient was treated with voriconazole with subsequent resolution of the papules after 3 months of therapy.
The K3 category of a cubic fourfold
Authors: Huybrechts Daniel
Published: March 2017

Smooth cubic hypersurfaces $X\subset \mathbb{P}^{5}$ (over $\mathbb{C}$) are linked to K3 surfaces via their Hodge structures, due to the work of Hassett, and via a subcategory ${\mathcal{A}}_{X}\subset \text{D}^{\text{b}}(X)$, due to the work of Kuznetsov. The relation between these two viewpoints has recently been elucidated by Addington and Thomas. In this paper, both aspects are studied further and extended to twisted K3 surfaces, which in particular allows us to determine the group of autoequivalences of ${\mathcal{A}}_{X}$ for the general cubic fourfold. Furthermore, we prove finiteness results for cubics with equivalent K3 categories and study periods of cubics in terms of generalized K3 surfaces.
Modeling and Experimental Investigation of Bubble Formation in Shear-Thinning Liquids
Authors: Taghi Esfidani Mohamad , Reza Oshaghi Mohammad , Afshin Hossein , Firoozabadi Bahar
Published: March 2017

This investigation presents both theoretical and experimental studies on the size of a growing bubble in power-law non-Newtonian liquids. At first, some previous works on the prediction of bubble size in Newtonian liquids have been extended by considering the balance of forces acting on the bubble at the moment of separation. Predicted bubble sizes were validated against the experimental results for a wide range of operating conditions, including different gas flow rates and needle diameters as well as a wide range of physical properties of the Newtonian liquids. Furthermore, in order to determine the size of the bubbles formed in power-law non-Newtonian liquids with a similar analysis, the effective shear rate of bubble growth was calculated in which the rheological properties of fluid were taken into account and subsequently the viscosity of the fluid was modified. Theoretically obtained bubble sizes for non-Newtonian liquids are in a good agreement with our experimental high-speed video observations of three carboxyl methyl cellulose (CMC) solutions.
Numerical Investigation of Vortex Ring Ground Plane Interactions
Authors: Bourne K. , Wahono S. , Ooi A.
Published: March 2017

The interaction between multiple laminar thin vortex rings and solid surfaces was studied numerically so as to investigate flow patterns associated with near-wall flow structures. In this study, the vortex–wall interaction was used to investigate the tendency of the flow toward recirculatory behavior and to assess the near-wall flow conditions. The numerical model shows very good agreement with previous studies of single vortex rings for the case of orthogonal impact (angle of incidence, θ = 0 deg) and oblique impact (θ = 20 deg). The study was conducted at Reynolds numbers 585 and 1170, based on the vortex ring radius and convection velocity. The case of two vortex rings was also investigated, with particular focus on the interaction of vortex structures postimpact. Compared to the impact of a single ring with the wall, the interaction between two vortex rings and a solid surface resulted in a more highly energized boundary layer at the wall and merging of vortex structures. The azimuthal variation in the vortical structures yielded flow conditions at the wall likely to promote agitation of ground based particles.
Evaporation Effects in Shock-Driven Multiphase Instabilities
Authors: Black Wolfgang J. , Denissen Nicholas A. , McFarland Jacob A.
Published: March 2017

This paper considers the effects of multiphase parameters on a shock-driven particle-laden hydrodynamic instability using simulations performed with the hydrocode FLAG, developed at Los Alamos National Laboratory. The classic sinusoidal interface common in instability literature is created using water particles seeded in a nitrogen–water vapor mixture. The simulations model a shock tube environment as the computational domain, to guide future experimentation. Multiphase physics in FLAG include momentum and energy coupling, with this paper discussing the addition of mass coupling through evaporation. The multiphase effects are compared to a dusty gas approximation, which ignores multiphase components, as well as to a multiphase case which ignores evaporation. Evaporation is then further explored by artificially changing parameters which effect the rate of evaporation as well as the amount of total evaporation. Among all these experiments, the driving force of the hydrodynamic instability is a shock wave with a Mach number of 1.5 and a system Atwood number of 0.11 across the interface. The analysis is continued into late time for select cases to highlight the effects of evaporation during complex accelerations, presented here as a reshock phenomenon. It was found that evaporation increases the circulation over nonevaporating particles postshock. Evaporation was also shown to change the postshock Atwood number. Reshock showed that the multiphase instabilities exhibited additional circulation deposition over the dusty gas approximation. Mixing measures were found to be affected by evaporation, with the most significant effects occurring after reshock.
Lubricant Selection for Minimum Traction in Elastohydrodynamic Lubrication Line Contacts During Accelerated Motion—A Numerical Approach
Authors: Kumar Niraj , Kumar Punit
Published: March 2017

Transient thermal elastohydrodynamic lubrication (EHL) line contact simulations are carried out to study the traction behavior during accelerated motion considering realistic shear-thinning behavior. Using three lubricants with different inlet viscosity and shear-thinning parameters, the application of present analysis for lubricant selection is demonstrated. Owing to squeeze film action, the film evolution is delayed, and EHL traction during acceleration is found to increase much above the designed value. This effect decreases with increasing starting speed. The most shear-thinning test oil considered here yields the lowest traction coefficient with minimum variation in its value desirable for smooth and vibration-free operation.
Tribological Characterization of Electroless Ni–B Coatings Formed on Commercial Purity Magnesium
Authors: Correa E. , Mejía J. F. , Castaño J. G. , Echeverría F. , Gómez M. A.
Published: March 2017

Ni–B coatings have been deposited directly on commercial purity magnesium and evaluated by means of sliding wear and friction testing. The nickel and boron are distributed throughout the whole thickness of the coating. Parametric optimization has been carried out using the design of experiment based on Taguchi analysis. The friction coefficients of the coatings vary between 0.01 and 0.3, depending on the evaluated conditions. The lowest wear rate of the coating was 0.19 × 10−5 mm3 N−1 m−1. Wear and friction coefficient maps of Ni–B electroless coatings formed on magnesium surfaces are reported. Nanoparticles present in the lubricating fluid act as a third wear body increasing the wear of the electroless coating
Study on Tribological Properties of Antimony Nanoparticles as Liquid Paraffin Additive
Authors: Xu Jianlin , Yang Shuhua , Niu Lei , Liu Xiaoqi , Zhao Jinqiang
Published: March 2017

Antimony nanoparticles, whose surfaces were modified by alkyl phenol polyoxyethylene ether (OP-10), were used as one of the types of lubricating additives in liquid paraffin (LP). The tribological properties of antimony nanoparticles as lubricating additives were evaluated and compared with those of pure LP on a four-ball test machine. The morphology and chemical composition of the worn surface were investigated and analyzed by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the additives can obviously improve the anti-wear and friction reducing properties of LP, which are better under high friction load. The double-layer crystal structure of antimony can be separated and glided along the cleavage plane by a friction-shear force and a normal load, respectively. The separating and gliding of antimony can form a physical adsorption film, which can separate the friction surface to avoid direct contact of the friction surface and play an important role in improving the anti-wear and friction reducing properties.
Preparation and Structure of W/Mo Films and Their Tribological Properties in the Lubrication of MoDTC
Authors: Li Xingliang , Yue Wen , Wang Chengbiao , Liu Jiajun , Li Guolong
Published: March 2017

W, Mo, and W–Mo alloy films are prepared on 316L stainless steel by means of ion beam assisted deposition (IBAD). Tribological behaviors of the treated surfaces are investigated under lubrication with molybdenum dialkyldithiocarbamate (MoDTC) on a MS-T3000 friction and wear tester. The micromorphologies and chemical characteristics of the tribofilms generated on the worn surfaces are analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. The results showed that the obvious synergistic effects of better friction reduction and wear resistance between W–Mo film and MoDTC are attributed to the hard surface and the high decomposition rate of additives on the worn W–Mo surface.
Computational Fluid Dynamics Study for Improvement of Prediction of Various Thermally Stratified Turbulent Boundary Layers
Authors: Hattori Hirofumi , Houra Tomoya , Kono Amane , Yoshikawa Shota
Published: March 2017

The objectives of this study are to reconstruct a turbulence model of both the large Eddy simulation (LES) and the Reynolds-averaged Navier–Stokes simulation (RANS) which can predict wind synopsis in various thermally stratified turbulent boundary layers over any obstacles. Hence, the direct numerical simulation (DNS) of various thermally stratified turbulent boundary layers with/without forward-step, two-dimensional block, or two-dimensional hill is carried out in order to obtain detailed turbulent statistics for the construction of a database for the evaluation of a turbulence model. Also, DNS clearly reveals the characteristics of various thermally stratified turbulent boundary layers with/without forward-step, two-dimensional block, or two-dimensional hill. The turbulence models employed in LES and RANS are evaluated using the DNS database we obtained. In the LES, an evaluated turbulence model gives proper predictions, but the quantitative agreement of Reynolds shear stress with DNS results is difficult to predict. On the other hand, the nonlinear eddy diffusivity turbulence models for Reynolds stress and turbulent heat flux are also evaluated using DNS results of various thermally stratified turbulent boundary layers over a forward-step in which the turbulence models are evaluated using an a priori method. Although the evaluated models do not make it easy to properly predict the Reynolds shear stresses in all cases, the turbulent heat fluxes can be qualitatively predicted by the nonlinear eddy diffusivity for a heat turbulence model. Therefore, the turbulence models of LES and RANS should be improved in order to adequately predict various thermally stratified turbulent boundary layers over an obstacle.
Optimal V-Reflector Design With Maximum Solar Concentration
Authors: Ibrahim Rabady Rabi
Published: March 2017

For low-concentration solar applications, v-reflectors are attractive choice to collect sunlight since they are simple to build with reduced manufacturing cost and technical requirements. In this paper, with the account for the power evolution of all possible reflection modes, careful modeling for the concentration ratio of such collectors was achieved and optimized by numerical methods in order to determine the optimal apex-angle that facilitates maximum utilization of the solar energy. The outcome of this research is interesting since it provides a useful recipe for an optimal design of v-reflectors that can be found in various solar applications.
Effect of Crack Patterns on the Stress Distribution of Hard Chromium Coatings Under Sliding Contact: Stochastic Modeling Approach
Authors: Fochesatto Nicolas S. , Buezas Fernando S. , Rosales Marta B. , Tuckart Walter R.
Published: March 2017

In this work, the influence of different crack arrangements in the stress distribution of hard chromium (HC) coatings was determined. Three parameters for position and length of the cracks for two different types of coatings were probabilistically modeled based on measured scanning electron microscopy (SEM) images. Probability density functions (PDF) for those parameters were obtained to characterize each kind of coating. A two-dimensional finite element (FE) model of the coating in contact with a rigid disk was developed, modeling cracks with elliptical shapes. A Monte Carlo method was used to simulate different crack distributions for each kind of coating, and values of stress and strains in the domain were obtained. Both the J-integral and the stress intensity factors (SIFs) were taken as comparative parameters of the results. Coatings which statistically present larger quantities of shorter cracks have lower values of J-integral and SIFs, and, therefore, distribute stresses better than those with low density of longer cracks.
Vertical line array measurements of ambient noise in the North Pacific
Authors: Farrokhrooz Mehdi , Wage Kathleen E. , Dzieciuch Matthew A. , Worcester Peter F.
Published: March 2017

Shipping noise and wind are the dominant sources of ocean noise in the frequency band between 20 and 500 Hz. This paper analyzes noise in that band using data from the SPICEX experiment, which took place in the North Pacific in 2004–2005, and compares the results with other North Pacific experiments. SPICEX included vertical arrays with sensors above and below the surface conjugate depth, facilitating an analysis of the depth dependence of ambient noise. The paper includes several key results. First, the 2004–05 noise levels at 50 Hz measured in SPICEX had not increased relative to levels measured by Morris [(1978). J. Acoust. Soc. Am. 64, 581–590] at a nearby North Pacific site three decades earlier, but rather were comparable to those levels. Second, at 50 Hz the noise below the conjugate depth decreases at a rate of −9.9 dB/km, which is similar to the rate measured by Morris and much less than the rate measured by Gaul, Knobles, Shooter, and Wittenborn [(2007). IEEE J. Ocean. Eng. 32, 497–512] for the CHURCH OPAL experiment. Finally, the paper describes the seasonal trends in noise over the year-long time series of the measurements.
The Association Between Spanish Physical Education Teachers’ Self-Efficacy Expectations and Their Attitudes Toward Overweight and Obese Students
Authors: Martínez-López Emilio J. , Zamora-Aguilera Nestor , Grao-Cruces Alberto , De la Torre-Cruz Manuel J.
Published: March 2017

Purpose:

The aim of this study was to investigate the association between Spanish physical education teachers’ perceived self-efficacy toward including overweight and obese students and their attitudes toward overweight and obese students.

Method:

Four hundred and seventy-one physical education teachers filled out questionnaires to assess their self-efficacy expectations to meet overweight and obese students’ educational needs, and to identify physical education teachers’ beliefs and attitudes toward these students.

Results:

The physical education teachers with a higher perceived self-efficacy in fostering participation and in assessing and promoting overweight and obese students’ learning were more sensitive toward these students’ fitness and healthcare and showed less pejorative attitudes toward overweight and obesity.

Conclusions:

These results highlight the need for teaching education programs capable of increasing the physical education teachers’ perceived self-efficacy in this area. The results also show that there is a need for training for teachers and students in strategies aimed at reducing the cases of victimization of overweight and obese students.
Robin’s Story: Life History of an Exemplary American Female Physical Education Teacher
Authors: Cazers Gunars , Curtner-Smith Matthew D.
Published: March 2017

Purpose:

The purpose was to construct the life history of Robin, an exemplary female physical educator, to hear her voice, and to explore ways in which she experienced marginalization. Few life histories of exemplary physical educators have been recounted.

Method:

Robin’s life history was investigated in light of the theory of occupational socialization (Lawson, 1983 a, b). Three semistructured interviews were conducted, and data were analyzed deductively according to categories in the occupational socialization literature.

Results:

The study found that Robin experienced marginalization based on gender, lack of support, and being unaccepted. Occupational socialization explained how Robin’s induction into teaching helped her both teach as she had been trained and to be innovative.

Discussion/Conclusion:

The study suggests ways in which Robin persevered in her career and gives suggestions based upon her story. The sharing of this story may serve to empower other teachers not just to survive, but to challenge the status quo in their professional life.
Extracurricular School-Based Sports as a Stepping Stone Toward an Active Lifestyle? Differences in Physical Activity and Sports-Motivation Between Extracurricular School-Based Sports Participants and Non-Participants
Authors: De Meester An , Cardon Greet , De Bourdeaudhuij Ilse , Haerens Leen
Published: March 2017

Purpose:

The goals were to investigate whether extracurricular school-based sports reach students not engaging in community sports and whether extracurricular school-based sports participants are more physically active and/or autonomously motivated toward sports than nonparticipants.

Method:

1526 students (48.0% boys; 85.9% Belgian natives; age = 15.34 ± 1.83y) completed validated questionnaires to assess sports participation, physical activity (PA) and sports-motivation. Multilevel regression analyses were conducted.

Results:

Only 28.7% of all students (n = 438), and 19.7% of students not engaging in community sports (n = 123), participated in extracurricular school-based sports. Participants were significantly more physically active [β=44.19, S.E.=17.34, χ2(1)=6.50, p = .01] and autonomously motivated [β=.18, S.E.=.04, χ2(1)=25.62, p < .001] than nonparticipants, even after controlling for community sports participation. Boys were more physically active and autonomously motivated than girls (p < .001).

Conclusion:

As participation is linked to higher PA-levels and autonomous motivation, increasing overall participation rates may contribute to children developing a more physically active lifestyle and achieving the PA guidelines.
Research on Preservice Physical Education Teachers’ and Preservice Elementary Teachers’ Physical Education Identities: A Systematic Review
Authors: Keating Xiaofen D. , Zhou Ke , Liu Jingwen , Shangguan Rulan , Fan Yao , Harrison Louis
Published: March 2017

The purposes of this project were to conduct an overall review of research on preservice physical education (PE) teacher (referred to preservice PE teachers as preservice specialist) and/or preservice elementary teacher (referred to preservice elementary teachers as preservice generalist) PE identities and to identify any new trends in research on the topic. Studies were selected for analysis through searches of databases in English without time limits. In total, 27 articles were identified including 14 data-based studies. The majority of the selected studies (85.7%) employed qualitative methods. Research on the topic was not dominated by any single country. The focus of previous research was centered on determinants of preservice specialists’ PE identity construction such as PE coursework and student teaching. Information about the development and measurement of PE identity among preservice specialists and generalists is still sparse. More research on examining the complexity, nurturing, and reshaping of PE identities is needed.
To Move More and Sit Less: Does Physical Activity/Fitness Knowledge Matter in Youth?
Authors: Chen Senlin , Liu Yang , Schaben Jodee
Published: March 2017

Purpose:

The purpose of this study was to examine physical activity (PA)/fitness knowledge and its association with PA and sedentary behavior in youth.

Method:

Eighth grade students from five schools (N = 660) in a midwestern state completed a PE Metrics written test and the Youth Activity Profile to assess PA/fitness knowledge, PA (at school and after school) and sedentary behavior, respectively.

Results:

Participants were clustered into high, medium, and low knowledge groups. Students in the high knowledge group reported higher level of PA after school (p < .05, d = .28) but lower level of sedentary behavior than the low knowledge group (p = .001, d = -.45). The low knowledge group also reported higher PA at school (p < .05, d = .25). PA/Fitness knowledge significantly predicted sedentary behavior, particularly in the low knowledge group (β = -.32, t = -2.46, p < .05, R2 = .105), after controlling for gender and race/ethnicity.

Conclusion:

Physical education focused on conveying PA/fitness knowledge is warranted to educate youth to move more and sit less.