bluuebunny/crossref_metadata_2025 huggingface dataset:
The geographic distribution and ecological preferences of theAmerican dog tick,Dermacentor variabilis(Say), in theU.S.A.
Authors: JAMES A. M. , BURDETT C. , MCCOOL M. J. , FOX A. , RIGGS P.
Published: February 2015

Equine piroplasmosis (EP), caused by two parasitic organisms,Theileria equiandBabesia caballi, is a tick‐borne disease of recent concern in horses in theU.S.A.Outbreaks ofEPhave been detected inFlorida,Missouri,Kansas andTexas. In 2009,EPtransmission inTexas occurred through the adults of two tick species,Amblyomma mixtum[formerly known asAmblyomma cajennense(Fabricius, 1787)]Koch (Ixodida:Ixodidae) andDermacentor variabilis(Say) (Ixodida:Ixodidae), theAmerican dog tick (ADT). In this study, we developed a continent‐scale map for the distribution of theEPvector speciesD. variabilis, using a presence‐only modelling approach to assess the habitat preferences of this tick. We used identification records from our tick geodatabase of locations in which the presence of theADThad been noted. The potential distribution of theADTin theU.S.A.was estimated from environmental factors using the maximum entropy approach based on localities in which there is a high probability of occurrence according to habitat suitability. Elevation and temperature were found to be biologically significant environmental variables influencing the presence of this tick species. Properly designed and constructed probability surfaces using maximum entropy offer one useful approach to the mapping of distribution ranges of tick species based on suitable habitat in theU.S.A.
Peer Effects: Evidence from Secondary School Transition in England
Authors: Gibbons Stephen , Telhaj Shqiponja
Published: February 2015

We estimate the effect of peers' prior achievement on student progress in secondary school, using administrative data on four cohorts of students in England. Students leaving primary for secondary school experience a big change in their peer group and these changes vary randomly from cohort to cohort. We exploit this variation to identify the effect of new peers on student achievement. We show that peer quality on entry to secondary school has a significant effect on students' subsequent achievement at age 14. The effect sizes are relatively small and are linked to peers' family background and early age achievements.
Carcass size shapes the structure and functioning of an African scavenging assemblage
Authors: Moleón Marcos , Sánchez‐Zapata José A. , Sebastián‐González Esther , Owen‐Smith Norman
Published: February 2015

The particle size of the food resource strongly determines the structure and dynamics of food webs. However, the ecological implications of carcass size variation for scavenging networks structure and functioning have been largely overlooked. Here we investigate differences in scavenging patterns due to carcass size in a complex vertebrate scavenger community, Hluhluwe‐iMfolozi Park, South Africa, while taking into account seasonality. We monitored the consumption of three types of experimental carcasses: ‘small’ (< 10 kg), ‘medium’ (10–100 kg) and ‘large’ (> 100 kg). We employed general lineal models to explore the influence of carcass size on 1) scavenging network structure (scavenger species richness per carcass) and 2) functioning (carcass detection time, consumption time, consumption rate and percentage of carrion consumed). We also tested whether the structure of the scavenging network of each carcass size was nested, i.e. whether the scavenging assemblage in species‐poor carcasses was a subset of the assemblage consuming species‐rich carcasses. We found strong evidence indicating that carcass size is a major factor governing the associated scavenger assemblage. Scavenger species richness per carcass and carcass consumption time and rate increased with carcass size, while carcass detection time and percentage of carrion biomass consumed were negatively related to carcass size. Strikingly, most of the carrion biomass was consumed by facultative scavengers, represented by large mammalian carnivores, rather than by obligate scavengers (i.e. vultures). Scavenging network nestedness tended to be higher at larger carcasses, and nestedness was sensitive to the removal of the most connected species in the network (spotted hyena) rather than vultures. When comparing scavenging and predation assemblages, crucial size‐dependent differences emerge. Also, we identified a traditionally ignored mechanism by which hunting large prey could be relatively less profitable for predators, namely the costs associated with competition from scavengers and decomposers.
Pre‐treatment social anxiety severity moderates the impact of mindfulness‐based stress reduction and aerobic exercise
Authors: Jazaieri Hooria , Lee Ihno A. , Goldin Philippe R. , Gross James J.
Published: February 2015

We examined whether social anxiety severity at pre‐treatment would moderate the impact of mindfulness‐based stress reduction (MBSR) or aerobic exercise (AE) for generalized social anxiety disorder. MBSR and AE produced equivalent reductions in weekly social anxiety symptoms. Improvements were moderated by pre‐treatment social anxiety severity.

Practitioner points

Mindfulness‐based stress reduction (MBSR) and aerobic exercise (AE) are effective in reducing symptoms of social anxiety.

Pre‐treatment social anxiety severity can be used to inform treatment recommendations.

Both MBSR and AE produced equivalent reductions in weekly levels of social anxiety symptoms.

MBSR appears to be most effective for patients with lower pre‐treatment social anxiety symptom severity.

AE appears to be most effective for patients with higher pre‐treatment social anxiety symptom severity.
Assessment of Food Intake, Obesity, and Health Risk among the Homeless in Rhode Island
Authors: Martins Diane C. , Gorman Kathleen S. , Miller Robin J. , Murphy Leah , Sor Sekboppa , Martins Jonah C. , Vecchiarelli Maria L.
Published: February 2015

Objective

The objective of this study was to examine the relationship between the nutritional status, incidence of food insecurity, and health risk among the homeless population in Rhode Island.

Design and Sample

This correlational study utilized a convenience sample of 319 homeless adults from Rhode Island's largest service agency for the homeless. Information on use of services such as access to emergency foods, shelters, and the Supplemental Nutrition Assistance Program (SNAP) was requested.

Measures

Food security was measured by the six‐item subset of the USDA Food Security Core Module. Anthropometric measures included height, weight, and waist circumference. A 24‐hr dietary recall was collected to determine the food intake for a subset of participants who agreed to supply this information (n = 197).

Conclusion

Average dietary recall data indicated insufficient intake of vegetables, fruit, dairy, and meats/beans. It also indicated excessive intake of fats. Of the 313 participants, 29.4% were overweight and 39% were obese. Over 94% of the participants were food insecure, with 64% of this subset experiencing hunger. Fifty‐five percent of the participants were currently receiving SNAP benefits. The majority of the sample was found to be food insecure with hunger.
Electronic and Vibrational Dynamics of Hollow Au Nanocages Embedded in Cu2O Shells
Authors: Szymanski Paul , Mahmoud Mahmoud A. , O'Neil Daniel , Garlyyev Batyr , El‐Sayed Mostafa A.
Published: February 2015

We have synthesized hollow Au nanocages embedded within thick porous shells of cuprous oxide (Cu2O). The shell causes a significant redshift of the localized surface plasmon resonance of Au into the near‐IR. Electron–phonon coupling in the Au nanocage is 3–6 times faster in the core–shell structure due to the higher thermal conductivity of Cu2O compared to water. Coherent phonon oscillations within the Au lattice are characterized by a breathing mode of the entire structure for both bare and core–shell nanocages, an assignment made through the use of structural mechanics simulations. The experimental frequencies are obtained through simulations by selectively applying a force to the shell of the core–shell structure. We interpret this as rapid thermal expansion of the gold leading to a mechanical force that acts on the shell.
Human Hair as a Natural Sun Protection Agent: A Quantitative Study
Authors: de Gálvez María Victoria , Aguilera José , Bernabó Jean‐Luc , Sánchez‐Roldán Cristina , Herrera‐Ceballos Enrique
Published: February 2015

The rising incidence of skin cancers attributable to excessive sun exposure has become a major health concern worldwide. While numerous studies have analyzed the sun protective effect of sunscreens, clothing and antioxidants, none to date have measured the photoprotective effect of hair, despite clinical evidence that individuals with balding or thinning hair are at greater risk of skin lesions that can progress to cancer, hence the recommendation to use hats or umbrellas. We analyzed the level of protection offered by hair according to hair density, thickness and color using the spectral transmittance and corrected for relative erythema effectiveness. Our results show that hair provides a barrier against both UVB and UVA radiation which is significantly increased with respect to the hair density, thickness and the presence of melanins. This is the first study to quantify sun protection factor offered by hair, namely hair ultraviolet protection factor (HUPF). We believe that hair should be recognized as an important natural sun barrier in the prevention of UV‐induced skin cancers.
Improved Spectral Coverage and Fluorescence Quenching in Donor–acceptor Systems Involving Indolo[3‐2‐b]carbazole and Boron‐dipyrromethene or Diketopyrrolopyrrole
Authors: Khetubol Adis , Van Snick Sven , Clark Melissa L. , Fron Eduard , Coutiño‐González Eduardo , Cloet Arvid , Kennes Koen , Firdaus Yuliar , Vlasselaer Maarten , Leen Volker , Dehaen Wim , Van der Auweraer Mark
Published: February 2015

A novel π‐conjugated triad and a polymer incorporating indolo[3,2‐b]‐carbazole (ICZ) and 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) were synthesized via a Sonogashira coupling. Compared to the parent BODIPY the absorption and fluorescence spectrum were for both compounds broader and redshifted. The redshift of the fluorescence and the decrease of the fluorescence quantum yield and decay time upon increasing solvent polarity were attributed to the formation of a partial charge‐transfer state. Upon excitation in the ICZ absorption band the ICZ fluorescence was quenched in both compounds mainly due to energy transfer to the BODIPY moiety. In a similar ICZ–π–DPP polymer (where DPP is diketopyrrolopyrrole), a smaller redshift of the absorption and fluorescence spectra compared to the parent DPP was observed. A less efficient quenching of the ICZ fluorescence in the ICZ–π–DPP polymer could be related to the unfavorable orientation of the transition dipoles of ICZ and DPP. The rate constant for energy transfer was for all compounds an order of magnitude smaller than predicted by Förster theory. While in a solid film of the triad a further redshift of the absorption maximum of nearly 100 nm was observed, no such shift was observed for the ICZ–π–BODIPY polymer.
Effects of lead contamination on the clonal propagative ability of Phragmites australis (common reed) grown in wet and dry environments
Authors: Zhang N. , Zhang J. W. , Yang Y. H. , Li X. Y. , Lin J. X. , Li Z. L. , Cheng L. Y. , Wang J. F. , Mu C. S. , Wang A. X.
Published: February 2015

Clonal propagation is important for the survival and maintenance of the common reed Phragmites australis. Pot culture experiments were conducted to investigate the effects of lead (Pb) concentration (0, 500, 1500, 3000, 4500 mg·kg−1) and water stress on the clonal reproductive ability of this species. The Pb concentration found in plant organs, in decreasing order, was roots >shoots >rhizomes. There was a negative relationship between the growth of clonal propagative modules (excluding axillary shoot buds) and Pb concentrations, which caused a decrease in biomass, rhizome growth and number of axillary and apical rhizome buds. Daughter axillary shoots exhibited a tolerance strategy, with no significant change in their number; the axillary and apical rhizome buds, daughter apical rhizome shoots and rhizomes exhibited compensatory growth during the late stage of Pb (excluding 4500 mg·kg−1) treatment in a wet environment. Pb applications above 500 mg·kg−1 reduced these parameters significantly in the drought treatment, except for the number of axillary shoot buds, which did not change. Our results indicate that clonal propagative resistance to Pb contamination can occur via tolerance strategies, compensatory growth and a Pb allocation strategy, enabling these reeds to maintain population stability in wet environments. However, clonal modular growth and reproductive ability were inhibited significantly by the interaction between drought and Pb, which would cause a decline in P. australis populations in a dry environment. Lead concentrations of 4500 and 500 mg·kg−1 in soils might meet or exceed the Pb tolerance threshold of clonally propagated reeds in wet and dry environments, respectively.
From dusk till dawn: nocturnal and diurnal pollination in the epiphyteTillandsia heterophylla(Bromeliaceae)
Authors: Aguilar‐Rodríguez P. A. , Krömer T. , García‐Franco J. G. , MacSwiney G. M. C.
Published: February 2015

In order to compare the effectiveness of diurnal and nocturnal pollinators, we studied the reproductive biology and pollinators ofTillandsia heterophyllaE. Morren, an epiphytic tank bromeliad endemic to southeastern Mexico. Since anthesis inT. heterophyllais predominantly nocturnal but lasts until the following day, we hypothesised that this bromeliad would receive visits from both diurnal and nocturnal visitors, but that nocturnal visitors would be the most effective pollinators, since they arrive first to the receptive flower, and that bats would be the most frequent nocturnal visitors, given the characteristics of the nectar. Flowering ofT. heterophyllabegan in May and lasted until July. The species is fully self‐compatible, with an anthesis that lasts forca. 15–16 h. Mean volume of nectar produced per flower was 82.21 μl, with a mean sugar concentration of 6.33%. The highest volume and concentration of nectar were found at 20:00 h, with a subsequent decline in both to almost zero over the following 12‐h period.T. heterophyllahas a generalist pollination system, since at least four different morphospecies of visitors pollinate its flowers: bats, moths, hummingbirds and bees. Most of the pollinating visits corresponded to bats and took place in the early evening, when stigma receptivity had already begun; making bats the probable pollinator on most occasions. However, diurnal pollinators may be important as a ‘fail‐safe’ system by which to guarantee the pollination ofT. heterophylla.
Policy Entrepreneurs and the Reorientation of National Security Policy under the G. W. Bush Administration (2001‐04)
Authors: David Charles‐Philippe
Published: February 2015

How are we to explain U.S. foreign policy—particularly policy making on national security—during the transformative years of the G. W. Bush administration? Who were the actors and what were the factors that produced what were some of the most controversial policies? This article argues that security choices and decisions have been the results of the work and methods of “policy entrepreneurs.” It looks first at theoretical approaches to entrepreneurs and their influence over the formulation of national security policy, and secondly at who those entrepreneurs were and how they achieved their goal of transforming U.S. security policy. Two decisions are discussed: the invasion of Iraq and the legal redefinition of torture by the G. W. Bush administration.

Related Articles

Dolan, Chris J. 2008. “.” Politics & Policy 36 (): 542‐585. http://onlinelibrary.wiley.com/doi/10.1111/j.1747‐1346.2007.00121.x/abstract

Haar, Roberta. 2010. “.” Politics & Policy 38 (): 965‐990. http://onlinelibrary.wiley.com/doi/10.1111/j.1747‐1346.2010.00265.x/abstract

Clark, John F. 1995. “.” Southeastern Political Review 23 (): 559‐579. http://onlinelibrary.wiley.com/doi/10.1111/j.1747‐1346.1995.tb00076.x/abstract

Related Media

Films and Documentaries

Brolin, Josh. 2009. Lionsgate. http://www.imdb.com/title/tt1175491/

Kirk, Michael. 2006. “.” Frontline Documentary. http://www.pbs.org/wgbh/pages/frontline/darkside/

Kirk, Michael. 2005. “.” Frontline Documentary. http://www.pbs.org/wgbh/pages/frontline/torture/

Jones, Sherry. 2008. “.” Washington Media Associates. http://www2.gwu.edu/~nsarchiv/torturingdemocracy/info/
Distribution of Subcutaneous Fat and the Relationship with Blood Pressure in Obese Children and Adolescents in Shandong, China
Authors: Zhang Ying‐xiu , Wang Shu‐rong
Published: February 2015

Background

The association between elevated blood pressure (BP) and childhood obesity has been documented in several studies. However, the association between BP and body fat distribution in obese children remains poorly understood. We examined the distribution of subcutaneous fat and its association with BP in obese children and adolescents.

Methods

Data for this study were obtained from a large cross‐sectional survey of school children. A total of 38 873 students (19 485 boys and 19 388 girls) aged 7–17 years participated in this study. Height, weight, BP, subscapular and triceps skinfold thicknesses (SFT) of all subjects were measured. Obesity was defined by using body mass index (BMI) criteria recommended by the Working Group on Obesity in China. A total of 3 579 obese children and adolescents (2 367 boys and 1 212 girls) were examined.

Results

Most of the obese children and adolescents had high subcutaneous fat. However, a small number of the obese individuals had a lower SFT levels. Obese children and adolescents with high SFT and central distribution had higher BP levels than those with low SFT and peripheral distribution.

Conclusion

Obese children and adolescents assessed by BMI might not necessarily have a high SFT level. The BP level of obese individuals is associated with the level and distribution pattern of SFT. Additional measurement of SFT is better than BMI alone to help identify high BP risks.
Patient perceptions and expectations of an anticoagulation service: a quantitative comparison study of clinic‐based testers and patient self‐testers
Authors: Money Arthur G. , Barnett Julie , Kuljis Jasna , Duffin Debbie
Published: February 2015

Background

Government initiatives see the provision of technology‐assisted self‐care as one of the key areas in which there is capacity for improving quality of care whilst reducing costs. However, levels of patient engagement in self‐testing and management (STM) remain low. Little emphasis has been placed on understanding the patients' perspectives of the reasons for this limited engagement. Typically, patient engagement in STM is achieved via the provision of patient education programmes, which aim to enable patients to make the changes necessary to become competent self‐carers. However, placing the onus to change on the individual patient is unrealistic. If levels of patient engagement are to be improved, patient needs and expectations of clinical services must be better understood and service provision must be adapted accordingly.

Objective

Explore patient perceptions and expectations of clinical service provision and their views of having and making choices about care.

Methods

Participants [N = 191, 103 patient self‐tester managers (PSTMs) and 87 clinic‐based testers (CBTs)] completed the SERVQUAL and ChQ instruments to capture perspectives on service quality and choice, respectively. A comparative statistical analysis explored the similarities and differences between PSTMs' and CBTs' responses.

Results

Clinic‐based testers' perceptions of service quality were significantly more positive than PSTMs', as were their expectations of the ‘tangible’ aspects of service delivery. PSTMs' expectations of service quality were significantly higher than their perceptions. PSTMs attributed significantly more value to making choices compared with CBTs.

Conclusions and recommendations

To close the gap between PSTMs expectations and perceptions of service quality and better cater for their choice preferences, service providers may benefit from taking into account the following practice considerations: maintain frequent, timely, personalised and direct interactions with PSTMs; prioritise investment in resources to facilitate patient/practitioner interaction over tangible facilities; ensure that PSTMs are given the opportunity to make choices about their care.
The role of executive functions in bilingual children with reading difficulties
Authors: Jalali‐Moghadam Niloufar , Kormi‐Nouri Reza
Published: February 2015

To explore the joint effect of reading difficulties (RD) and bilingualism on executive functions, 190 children of four groups of 9–12 year‐olds (41 bilinguals with RD, 45 monolinguals with RD, 45 bilinguals without RD, and 59 monolinguals without RD) were examined on the Concentration game, Tower of Hanoi, and Stroop as measures of executive functioning tapping into inhibitory/attentional control, working memory and planning ability. The most prominent finding was that in terms of RD, the speed of performances decreased dramatically. This general decrease was more pronounced for bilingual children with RD than for their monolingual counterparts. In conclusion, the findings suggest that while bilinguals gain more from executive functions in normal reading, they lose in terms of RD. Such an outcome confirms that executive functions are essential components of both reading and bilingualism, which depending on whether reading conditions are normal or difficult will produce cognitive advantages or disadvantages. Further, it is argued that dissimilarity between the Farsi and Swedish languages may complicate handling of such a situation.
Examining the relationship between use of sexually explicit media and sexual risk behavior in a sample of men who have sex with men in Norway
Authors: Træen Bente , Noor Syed W. , Hald Gert Martin , Rosser B. R. Simon , Brady Sonya S. , Erickson Darin , Galos Dylan L. , Grey Jeremy A. , Horvath Keith J. , Iantaffi Alex , Kilian Gudruna , Wilkerson J. Michael
Published: February 2015

The purpose of this study was to investigate consumption patterns of gay‐oriented sexually explicit media (SEM) among men who have sex with men (MSM) in Norway, with a particular emphasis on a possible relationship between gay SEM consumption and HIV risk behavior. Participants included 529 MSM living in Norway recruited online to complete a SEM consumption and sexual risk survey. Of the 507 participants who responded to the all items measuring exposure to SEM, 19% reported unprotected anal intercourse with a casual partner (UAI) in last 90 days, and 14% reported having had sero‐discordant UAI. Among those with UAI experience, 23% reported receptive anal intercourse (R‐UAI) and 37% reported insertive anal intercourse (I‐UAI). SEM consumption was found to be significantly associated with sexual risk behaviors. Participants with increased consumption of bareback SEM reported higher odds of UAI and I‐UAI after adjusting for other factors using multivariable statistics. MSM who started using SEM at a later age reported lower odds of UAI and I‐UAI than MSM who started earlier. Future research should aim at understanding how MSM develop and maintain SEM preferences and the relationship between developmental and maintenance factors and HIV sexual risk behavior.
Relationship between strength qualities and short track speed skating performance in young athletes
Authors: Felser S. , Behrens M. , Fischer S. , Heise S. , Bäumler M. , Salomon R. , Bruhn S.
Published: February 2015

This study analyzed the relationships between isometric as well as concentric maximum voluntary contraction (MVC) strength of the leg muscles and the times as well as speeds over different distances in 17 young short track speed skaters. Isometric as well as concentric single‐joint MVC strength and multi‐joint MVC strength in a stable (without skates) and unstable (with skates) condition were tested. Furthermore, time during maximum skating performances on ice was measured. Results indicate that maximum torques during eversion and dorsal flexion have a significant influence on skating speed. Concentric MVC strength of the knee extensors was higher correlated with times as well as speeds over the different distances than isometric MVC strength. Multi‐joint MVC testing revealed that the force loss between measurements without and with skates amounts to 25%, while biceps femoris and soleus showed decreased muscle activity and peroneus longus, tibialis anterior, as well as rectus femoris exhibited increased muscle activity. The results of this study depict evidence that the skating times and speeds are primarily influenced by concentric MVC strength of the leg extensors. To be able to transfer the strength onto ice in an optimal way, it is necessary to stabilize the knee and ankle joints.
Challenges to delivery of isoniazid preventive therapy in a cohort of children exposed to tuberculosis in Timor‐Leste
Authors: Hall Charlotte , Sukijthamapan P. , dos Santos R. , Nourse C. , Murphy D. , Gibbons M. , Francis J. R.
Published: February 2015

Objectives

To evaluate the number and geographic location of children aged <5 years exposed to sputum smear‐positive tuberculosis (TB) in Timor‐Leste, to determine the proportion evaluated for isoniazid preventive therapy (IPT) and to review the programmatic challenges present in delivering IPT to this cohort.

Methods

A total of 256 consecutive sputum smear‐positive TB index cases diagnosed at Bairo Pite Clinic between August 2013 and July 2014 were interviewed about places of residence and household contacts <5 years of age in the 3 months preceding diagnosis. Attendance of these contacts for screening and the outcome of screening were recorded prospectively.

Results

The majority (225 of 256, 88%) of index cases resided in Dili, but 73 of 225 (32%) of these also had a second address outside the capital. A total of 255 contacts were identified; 172 of 255 (67%) of whom lived in Dili district and 83 of 255 (33%) of whom resided in remote districts. Only 66 of 255 (26%) contacts attended for evaluation for IPT, of whom 46 of 255 (18%) started IPT and nine of 255 (3.5%) were diagnosed with TB. Attendance was significantly less likely when the index case was not the parent of the child contact.

Conclusions

Sputum smear‐positive pulmonary TB cases frequently result in household exposure of children <5 years in Timor‐Leste, and provision of IPT is suboptimal. Contacts are located in diverse and distant locations. Further studies to delineate access barriers to IPT and review programmatic models that will facilitate IPT scale up in Timor‐Leste are needed.
Effect of substance P on recovery from laser‐induced retinal degeneration
Authors: Hong Hyun Sook , Kim Suna , Nam Seungwoo , Um Jihyun , Kim Yeong Hoon , Son Youngsook
Published: February 2015

Retinal degeneration is caused by neovascularization and persistent inflammation in the retinal pigment epithelium (RPE) and choroid, and causes serious eye disease including age‐related macular degeneration (AMD). Thus, inhibiting inflammation and neovascularization may be a primary approach to protect the retina from degeneration. The purpose of this study was to determine whether substance P (SP), which can suppress inflammation and mobilize stem cells, can protect the RPE from degeneration. The effect of SP was evaluated by analyzing systemic inflammation, cell survival, and neovascularization within the argon laser‐injured retina of mice. At 1 week postinjury, the SP‐treated group had lower tumor necrosis factor‐alpha and higher interleukin‐10 serum concentrations, and a more intact retinal structure compared to the vehicle‐treated group. In mice administered SP repeatedly for 4 weeks, the retinal structure appeared normal and showed sparse neovascularization, whereas the vehicle‐treated group showed severe retinal destruction and dense neovascularization. Moreover, the efficacy of SP was identical to that of mesenchymal stem cells that were transplanted into the vitreous after retinal injury. This study highlights the potential for the endogenous neuropeptide SP as a treatment for retinal damage to prevent conditions such as AMD.
Description and Computer Modeling of a Ball-and-Socket Hub That Enables Teetering for Three-Bladed Wind Turbines
Authors: Ramsland Arnold
Published: February 2015

A horizontal axis wind turbine with a ball-and-socket hub is disclosed. The hub enables horizontal axis turbines with two or more blades to teeter in response to wind shear gradients. Computer modeling was done using existing and modified fast code in order to compare the new hub design with existing designs. Results show that a three-bladed turbine with the ball-and-socket hub provides very significant reductions in out-of-plane bending loads applied to the main shaft in comparison to a three-bladed turbine with a rigid hub. Results also show that the new hub design provides significant reductions in the out-of-plane loads applied to the blades. A blade fatigue study using a rainflow counting of multi-axial torque contributions at the blade root was performed in order to assess the impact of these reductions, and results show that the three-bladed turbine equipped with a ball-and-socket, teetering hub provides for very significant reductions in lifetime blade damage in comparison to existing wind turbine designs due to a combination of factors. The first factor is that teetering largely eliminates the cyclic variations in out-of-plane torque on the blades that are observed with rigid hubs. Here, the fatigue study shows that the three-bladed wind turbine with a teetering hub provides for an approximate sixfold reduction in lifetime blade damage in comparison to a three-bladed turbine with a rigid hub. The second factor is that the addition of a third blade reduces the load on each blade by one-third. Here, the fatigue study shows that a three-bladed turbine with a teetering hub provides for an approximate fourfold reduction in lifetime blade damage in comparison to a two-bladed turbine with a teetering hub.
Effect of Evaporation and Condensation at Menisci on Apparent Thermal Slip
Authors: Hodes Marc , Steigerwalt Lam Lisa , Cowley Adam , Enright Ryan , MacLachlan Scott
Published: February 2015

We semi-analytically capture the effects of evaporation and condensation at menisci on apparent thermal slip lengths for liquids suspended in the Cassie state on ridge-type structured surfaces using a conformal map and convolution. An isoflux boundary condition is prescribed at solid–liquid interfaces and a constant heat transfer coefficient or isothermal one at menisci. We assume that the gaps between ridges, where the vapor phase resides, are closed systems; therefore, the net rates of heat and mass transfer across menisci are zero. The reduction in apparent thermal slip length due to evaporation and condensation relative to the limiting case of an adiabatic meniscus as a function of solid fraction and interfacial heat transfer coefficient is quantified in a single plot. The semi-analytical solution method is verified by numerical simulation. Results suggest that interfacial evaporation and condensation need to be considered in the design of microchannels lined with structured surfaces for direct liquid cooling of electronics applications and a quantitative means to do so is elucidated. The result is a decrease in thermal resistance relative to the predictions of existing analyses which neglect them.
Online Real-Time Quality Monitoring in Additive Manufacturing Processes Using Heterogeneous Sensors
Authors: Rao Prahalad K. , Liu Jia (Peter) , Roberson David , Kong Zhenyu (James) , Williams Christopher
Published: February 2015

The objective of this work is to identify failure modes and detect the onset of process anomalies in additive manufacturing (AM) processes, specifically focusing on fused filament fabrication (FFF). We accomplish this objective using advanced Bayesian nonparametric analysis of in situ heterogeneous sensor data. Experiments are conducted on a desktop FFF machine instrumented with a heterogeneous sensor array including thermocouples, accelerometers, an infrared (IR) temperature sensor, and a real-time miniature video borescope. FFF process failures are detected online using the nonparametric Bayesian Dirichlet process (DP) mixture model and evidence theory (ET) based on the experimentally acquired sensor data. This sensor data-driven defect detection approach facilitates real-time identification and correction of FFF process drifts with an accuracy and precision approaching 85% (average F-score). In comparison, the F-score from existing approaches, such as probabilistic neural networks (PNN), naïve Bayesian clustering, support vector machines (SVM), and quadratic discriminant analysis (QDA), was in the range of 55–75%.
Turning Functions in Optimal Synthesis of Mechanisms
Authors: Nadal Fernando , Cabrera Juan A. , Bataller Alex , Castillo Juan J. , Ortiz Antonio
Published: February 2015

In this paper, we describe the use of turning functions to compare errors between the coupler and the target paths. The main reason to use turning functions is that the measured error does not depend on the mechanism scale or the position and rotation of the fixed link. Therefore, the searching space for the optimization algorithm is reduced. To carry out mechanism synthesis, we use an evolutionary algorithm. The effectiveness of the proposed method has been demonstrated in five synthesis examples.
Failure Mechanics—Part III: A Call to Service With Solid Mechanics
Authors: Christensen Richard M.
Published: February 2015

The case is made for the present and future revitalization of the discipline of materials failure, including needed educational reforms.
Clamp Load Decay Due to Material Creep of Lightweight-Material Joints Under Cyclic Temperature
Authors: Nassar Sayed A. , Kazemi Amir
Published: February 2015

Experimental and finite element techniques are used for investigating the effect of cyclic thermal loading on the clamp load decay in preloaded single-lap bolted joints that are made of multimaterial lightweight alloys. Substrate material combinations include aluminum, magnesium, and steel, with various coupon thicknesses. The range of cyclic temperature profile varies between −20 °C and +150 °C in a computer-controlled environmental chamber for generating the desired cyclic temperature profile and durations. Real time clamp load data are recorded using strain gage-based, high-temperature, load cells. Clamp load decay is investigated for various combinations of joint materials, initial preload level, and substrate thickness. Thermal and material creep finite element analysis (FEA) is performed using temperature-dependent mechanical properties. The FEA model and results provided a valuable insight into the experimental results regarding the vulnerability of some lightweight materials to significant material creep at higher temperatures.
Design and Analysis of 3R2T and 3R3T Parallel Mechanisms With High Rotational Capability
Authors: Wang Congzhe , Fang Yuefa , Guo Sheng
Published: February 2015

This paper describes the design, kinematics, and workspace analysis of 3R2T and 3R3T parallel mechanisms (PMs) with large rotational angles about three axes. Since the design of PMs with high rotational capability is still a challenge, we propose the use of a new nonrigid (or articulated) moving platform with passive joints in order to reduce the interference between limbs and the moving platform. According to the proposed nonrigid platform and Lie subgroup of displacement theory, several 3R2T and 3R3T PMs are presented. Subsequently, the inverse kinematics and velocity analysis of one of the proposed mechanisms are detailed. Based on the derived inverse kinematic model, the constant-orientation workspace is computed numerically. Then, the analysis of rotational capability about the three axes is performed. The result shows that even if interference and singularity are taken into account, the proposed mechanisms still reveal the high continuously rotational capability about the three axes, by means of actuation redundancy.
The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 2 — Fluctuation Quantities
Authors: Mislevy Scott P. , Wang Ting
Published: February 2015

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6%. Boundary layer measurements were conducted for two constant K cases, K1=−0.51 × 10−6 and K2=−1.05 × 10−6.

The fluctuation quantities, u′, v′, t′, the Reynolds shear stress (uv¯), and the Reynolds heat fluxes (vt¯ and ut¯) were measured. In general, u′/U∞, v′/U∞, and vt¯ have higher values across the boundary layer for the adverse pressure-gradient cases than they do for the baseline case (K=0). The development of v′ for the adverse pressure gradients was more actively involved than that of the baseline. In the early transition region, the Reynolds shear stress distribution for the K2 case showed a near-wall region of high-turbulent shear generated at Y+=7. At stations farther downstream, this near-wall shear reduced in magnitude, while a second region of high-turbulent shear developed at Y+=70. For the baseline case, however, the maximum turbulent shear in the transition region was generated at Y+=70, and no near-wall high-shear region was seen. Stronger adverse pressure gradients appear to produce more uniform and higher t′ in the near-wall region (Y,+<20) in both transitional and turbulent boundary layers.

The instantaneous velocity signals did not show any clear turbulent/non-turbulent demarcations in the transition region. Increasingly stronger adverse pressure gradients seemed to produce large non-turbulent unsteadiness (or instability waves) at a similar magnitude as the turbulent fluctuations such that the production of turbulent spots was obscured. The turbulent spots could not be identified visually or through conventional conditional-sampling schemes. In addition, the streamwise evolution of eddy viscosity, turbulent thermal diffusivity, and Prt are also presented.
Flow Visualization in a Linear Turbine Cascade of High Performance Turbine Blades
Authors: Wang Hai-Ping , Olson Steven J. , Goldstein Richard J. , Eckert Ernst R. G.
Published: February 2015

Multiple smoke wires are used to investigate the secondary flow near the endwall of a plane cascade with blade shapes as used in high performance turbine stages. The wires are positioned parallel to the endwall and ahead of the cascade, within and outside the endwall boundary layer. The traces of the smoke generated by the wires are visualized within a laser light sheet arranged at various cross-sections around the cascade. During the experiment, a periodically fluctuating horseshoe vortex system of varying number of vortices is observed near the leading edge of the cascade. A series of photographs and video tapes was taken in the cascade to trace these vortices. The development and evolution of the horseshoe vortex and the passage vortex are clearly resolved in the photographs. The interaction between the suction side leg of the horseshoe vortex and the passage vortex is also observed in the experiment. A vortex induced by the passage vortex, starting about 1/4 of the curvilinear distance along the blade on the suction surface, is clearly shown in the photographs. This vortex stays close to the suction surface and above the passage vortex in the laminar flow region on the blade. From this flow visualization, a model describing the secondary flows in a cascade is proposed and compared with previous published models. Some naphthalene mass transfer results from a blade near an endwall are cited and compared with the current model. The flows inferred from both techniques agree well with each other.
Heat Transfer Coefficients Over a Flat Surface With Air and CO2 Injection Through Compound Angle Holes Using a Transient Liquid Crystal Image Method
Authors: Ekkad Srinath V. , Zapata Dyrk , Han Je-Chin
Published: February 2015

This paper presents the detailed heat transfer coefficients over a flat surface with one row of injection holes inclined streamwise at 35° for three blowing ratios (M=0.5–2.0). Three compound angles of 0°, 45°, and 90° with air (D.R.=0.98) and CO2 (D.R.=1.46) as coolants were tested at an elevated free-stream turbulence condition (Tu≈8.5%). The experimental technique involves a liquid crystal coating on the test surface. Two related transient tests obtained detailed heat transfer coefficients and film effectiveness distributions. Heat transfer coefficients increase with increasing blowing ratio for a constant density ratio but decrease with increasing density ratio for a constant blowing ratio. Heat transfer coefficients increase for both coolants over the test surface as the compound angle increases from 0° to 90°. The detailed heat transfer coefficients obtained using the transient liquid crystal technique, particularly in the near hole region, will provide a better understanding of the film cooling process in gas turbine components.
A New Analogy Function for the Naphthalene Sublimation Technique to Measure Heat Transfer Coefficients on Turbine Airfoils
Authors: Häring M. , Weigand B.
Published: February 2015

The naphthalene sublimation technique is based on the analogy between mass and heat transfer. This analogy is only fully valid for incompressible flow and if the Prandtl and Schmidt number are equal. In the present investigation the energy- and mass transfer equations were solved simultaneously to establish an analogy function which allows the calculation of the Nusselt number from the Sherwood number in function of the Mach, the Prandtl and the Schmidt number.

For a laminar flow this new analogy function is based on similarity solutions of the conservation equations for high Mach number flows. Also a numerical investigation was conducted to study the influence of the pressure gradient and the Soret effect as well as varying fluid properties. For a turbulent flow, a flat plate solution was established for Pr=1. Energy and mass transfer equations were additionally solved for a two dimensional duct flow to study the influence of the Prandtl number on the analogy function independently.

The resulting analytical and numerical solutions are shown for various pressure gradients, Prandtl and Mach numbers. In addition, approximations for the analogy function are derived. The influence of the present theory on heat transfer measurements on a turbine airfoil is shown. The theory is validated against experimental results in Häring et. al. (1995) showing a good agreement between the heat transfer coefficients calculated with the new analogy function and measurements of actual heat transfer.
Design and Evaluation of a Single Passage Test Model to Obtain Turbine Airfoil Film Cooling Effectiveness Data
Authors: Buck Frederick A. , Prakash Chander
Published: February 2015

A single passage test model has been designed to simulate the mainstream aerodynamics between two adjacent turbine airfoils and to measure the film cooling effectiveness from coolant injection on the pressure and suction sides of the airfoils. Film cooling tests were run on the model using a gas concentration/mass transfer technique with a foreign gas as the coolant to match density ratio. Aspects of the design and test are discussed including the use of a two-dimensional inviscid flow analysis to design boundary layer bleeds upstream of the pressure- and suction-side airfoil surfaces. Results of two- and three-dimensional viscous flow analyses that were used to evaluate various design features including inlet bellmouth, boundary layer bleeds, adjustable tailboards and model backpressure are presented. Aerodynamic and film cooling effectiveness test measurements made with the model will show that the model flow field can be controlled to match results from a previous thermal cascade test.
Computations of Film Cooling for the Leading Edge Region of a Turbine Blade Model
Authors: He Pingfan , Salcudean Martha , Gartshore Ian S.
Published: February 2015

Computations of film cooling are presented based on the geometry of a UBC experimental turbine blade model. This model has a semi-circlar leading edge with four rows of laterally-inclined film cooling orifices positioned symmetrically about the stagnation line. The computational domain follows the physical domain and includes the curved blade surface as well as the coolant regions in the circular coolant orifices. The injection orifices are inclined spanwise at 30° to the blade surface. A multi-zone curvilinear grid is used to simulate the complex configuration. Grids are generated by a block-structured elliptic grid generation method which represents exactly the curved blade surface as well as the circular injection orifices. Computations over the cooled turbine blade model are carried out for overall mass flow ratios of 0.52 and 0.97. The relative mass flow ratios from each orifice are specified to match experimental values. Density ratios of coolant to free stream were taken to be unity (constant density). Comparison of predicted film cooling effectiveness with experimental data showed reasonable agreement.
Cooling Flow Prediction for Fully Impingement Cooled Gas Turbine Blades
Authors: Consonni Stefano
Published: February 2015

This paper presents a one-dimensional model to calculate the cooling flow of fully impingement cooled blades. The coolant is assumed to be ejected through a jet array running along the whole blade chord, with crossflow in the blade-to-blade plane from the leading edge toward the trailing edge. The simplicity of this cooling scheme translates to analytic formulations highlighting the peculiarities of impingement and the influence of geometric and fluid-dynamic parameters.

Results show that the coolant flow required to maintain the blade surface under a given maximum temperature varies strongly with the jet-to-jet spacing, while the jet-to-wall gap mainly affects pressure losses. Compared to other types of convection, impingement does not afford reductions of cooling flow nor pressure losses: the basic benefits are the capability to achieve high local heat transfer coefficients and more uniform temperature distributions.

Since the cooling schemes of actual gas turbine blades are substantially more complex — an elaborate combination of convection, impingement and film cooling — the present model cannot be used to predict the cooling flow required by actual engines. Nonetheless, it can give quantitative indications on the potential of impingement and help the selection of impingement array geometry.
Computation of Spatially Periodic Turbulent Fluid Flow and Heat Transfer in a Channel With Various Rib Shapes
Authors: Liou Tong-Miin , Chen Shih-Hui
Published: February 2015

Periodic fully developed turbulent fluid flow and heat transfer in a channel with four shapes, namely, triangular, semicircular, semielliptic, and square cross sections, of rib pairs periodically mounted on two opposite walls has been investigated computationally with a curvilinear nonorthogonal body-fitted coordinate system. The Reynolds number based on the channel hydraulic diameter and bulk mean velocity, the rib pitch-to-height ratio, and the rib height-to-channel hydraulic diameter ratio are 1.3×104, 10, and 0.08, respectively. The standard k-ε turbulence model together with the two-layer wall region treatment was applied to solve the accelerating, decelerating, separating, recirculating, reattaching and redeveloping flows. The predicted fluid flow and heat transfer results were tested by previous laser-Doppler and holographic interferometry data, and reasonable agreement was achieved. The two layer treatment shows a superiority to the conventional wall function in predicting near wall mean velocity and peak turbulent kinetic energy. Triangular-shaped rib is favorable for a compromise between the thermal performance and possible presence of hot spots.