bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanical behavior of polylactic acid (PLA) films: fabrication, experiments and modelling
Authors: Mirkhalaf S. M. , Fagerström M. 
Published: September 2019

AbstractPolylactic acid (PLA) is one of the highly applicable bio-polymers in a wide variety of applications including medical fields and packaging. In order to quantitatively model the mechanical behavior of PLA and PLA based bio-composite materials, and also tailor new bio-composites, it is required to characterize the mechanical behavior of PLA. In this study, thin films of PLA are fabricated via hot-pressing, and tensile experiments are performed under different strain rates. To model the mechanical behavior, an elasto-viscoplastic constitutive model, developed in a finite strain setting, is adopted and calibrated. Using the physically-based constitutive model, all regimes of deformation under uniaxial stress state, including post-yield softening, were adequately captured in the simulations. Also, the rate dependency of the stress–strain behavior was properly modelled.
Field scale row unit vibration affecting planting quality
Authors: Zhai Changyuan , Long John , Taylor Randal , Weckler Paul , Wang Ning 
Published: September 2019

Abstract
With recent developments allowing increased planter speeds, improving spatial uniformity of crop emergence will continue to be an important focus of research. Vertical vibration during planting usually interferes with the seed metering and delivery process, and thereby affects seeding quality. Two different row crop planters were instrumented with accelerometers to monitor vertical vibration of planter row units in five fields with a total area of 220 ha in both no-till and strip-tilled conditions. The test results showed that the row unit vibration linearly increased with planting speeds. The R2 of each fitting equation was more than 0.90. The main frequencies of the vibration were concentrated in a low-frequency band of 3 Hz to 10 Hz. These frequencies did not show an increasing trend with the planter speed. However, the amplitude clearly increased when the planter speed increased. For the John Deere MaxEmerge™ 5 planter, the manually measured average plant spacing was close to the target plant spacing with a maximum error of 21 mm, and a max coefficient of variation (CV) of 24.3%; the standard deviation (SD) increased with travel speed and row unit vibration. For the John Deere ExactEmerge™ planter, the plant spacing was closer to the target plant spacing with a maximum error of only 5 mm and a max CV of 14.3%; the SD remained almost constant, at lower values than that of the MaxEmerge™ 5, at different speeds. For both planters, overall, the row unit vibration increased planting spatial variability. The quality of feed index decreased with increased vertical acceleration on the row unit while the miss index increased. However, the multiples index was generally unaffected by row unit vibration.
Magnetron-Sputtered Ni-Cr and Ti-Si Layers to Protect Ti-46Al-8Nb (at.%) Substrates Against Gas Absorption
Authors: Mitoraj-Królikowska Marzena , Godlewska Elzbieta 
Published: September 2019

Abstract
Ni-Cr and Ti-Si layers were deposited by magnetron sputtering on Ti-46Al-8Nb (at.%) substrates to suppress penetration of gases, which brings about undesirable changes in mechanical properties. Alloy samples with and without surface protection were subjected to interrupted oxidation at elevated temperature (700 and 800 °C) for up to 300 h. Selected mechanical properties as well as adhesion of surface layers were examined in the as-received and oxidized state. Analytical techniques used to characterize surfaces and cross sections of the samples included scanning electron microscopy and light microscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and x-ray diffraction. Both investigated layers were sufficiently adherent and effective in hindering gas absorption at 700 °C; however, only Ni-Cr showed promising properties for higher-temperature applications.
Highly dispersed cobalt Fischer–Tropsch synthesis catalysts supported on γ-Al2O3, CNTs, and graphene nanosheet using chemical vapor deposition
Authors: Kazemnejad Iraj , Feizbakhsh Alireza , Niazi Ali , Tavasoli Ahmad 
Published: September 2019

Abstract
Highly dispersed 15.0 wt% cobalt catalysts were prepared on γ-Al2O3, carbon nanotubes (CNTs), and graphene nanosheet (GNS) using chemical vapor deposition (CVD) procedure. The physico-chemical properties of the catalysts were studied by inductively coupled plasma (ICP), Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), and temperature-programmed reduction (TPR) techniques, and the Fischer–Tropsch synthesis (FTS) performance of the catalysts was assessed at 220 °C, 18 bar, H2/CO = 2 and feed flow rate of 45 ml/min g cat. Based on BET results, Co/GNS catalyst provided highest surface area in comparison to the other catalysts. XRD and FESEM results revealed that CVD method prepared smaller particles on GNS compared to the other supports and resulted in the most dispersed metal particles on GNS according to H2-chemisorption results. The performance of Co/Al2O3 catalyst prepared by CVD method was compared with conventional 15 wt% Co/Al2O3 catalyst prepared by impregnation method. The Co/Al2O3 catalyst prepared with CVD method showed 5.3% higher %CO conversion and 2.1% lower C5+ selectivity as compared with the Co/Al2O3 catalysts prepared by impregnation method. Among three catalysts prepared by CVD, Co/GNS showed higher %CO conversion of 78.4% and C5+ selectivity of 70.3%. Co/γ-Al2O3 catalyst showed higher stability.
Exponential Jacobi spectral method for hyperbolic partial differential equations
Authors: Youssri Y. H. , Hafez R. M. 
Published: September 2019

Abstract
Herein, we have proposed a scheme for numerically solving hyperbolic partial differential equations (HPDEs) with given initial conditions. The operational matrix of differentiation for exponential Jacobi functions was derived, and then a collocation method was used to transform the given HPDE into a linear system of equations. The preferences of using the exponential Jacobi spectral collocation method over other techniques were discussed. The convergence and error analyses were discussed in detail. The validity and accuracy of the proposed method are investigated and checked through numerical experiments.
Leaching improvement of ceramic cores for hollow turbine blades based on additive manufacturing
Authors: Zhu Wei-Jun , Tian Guo-Qiang , Lu Yang , Miao Kai , Li Di-Chen 
Published: September 2019

Abstract
The precision casting method based on alumina-based ceramic cores is one of the main techniques used to manufacture hollow turbine blades. Additive manufacturing (AM) technology provides an alternate solution to fabricating ceramic cores quickly and precisely. As the complexity of the structure increases and the strength of the material improves, the leaching process of the cores becomes more complicated. This study proposes a compound pore-forming method to increase the porosity of ceramic cores by adding a preformed-pore agent and materials that convert to easy-to-corrode phases. The preformed-pore agents (e.g., carbon fibers) can be burned off during sintering to form pores before the leaching, and the easy-to-corrode phases (e.g., CaCO3, SiO2, β-Al2O3) can be leached firstly to form pores during the leaching process. The pores formed in the aforementioned two stages increase the contact area of the cores and leaching solution, thus improving the leaching rate. In the current study, the additive amount of the preformed-pore agent was optimized, and the effect of the easy-to-corrode phases on the comprehensive properties of the cores was then compared. Based on this, the corresponding model was established.
Brief report: Problematic social media use and sleep disturbances are longitudinally associated with depressive symptoms in adolescents
Authors: Raudsepp Lennart 
Published: September 2019

ABSTRACTIntroductionProblematic social media use and sleep disturbances are independently related with mental health. However, evidence of combined effects of changes in problematic social media use and sleep disturbances on changes in depressive symptoms in adolescents is limited. The aim of this study was to examine complex longitudinal associations between problematic social media use, sleep disturbances and depressive symptoms during middle adolescence.MethodsA 2‐year longitudinal study was conducted consisting of three waves, each separated by 1 year. The participants were 249 Estonian adolescents (46,6% female) aged 15.3 ± 0.3 years (M ± SD) who completed self‐report measures of problematic social media use, sleep disturbances and depressive symptoms.ResultsThe findings revealed that initial level in both problematic social media use and sleep disturbances both significantly predicted change in depressive symptoms. Moreover, the increases in problematic social media use and sleep disturbances were both associated with an increase in depressive symptoms, irrespective of gender.ConclusionsOur findings add strength to the evidence supporting longitudinal associations between problematic social media use and depressive symptoms and sleep disturbances and depressive symptoms in middle adolescence.
Quantitative MRI study of infant regional brain size following surgery for long‐gap esophageal atresia requiring prolonged critical care
Authors: Lee Mongerson Chandler Rebecca , Jennings Russell William , Zurakowski David , Bajic Dusica 
Published: September 2019

IntroductionLittle is known regarding the impact of concurrent critical illness and thoracic noncardiac perioperative critical care on postnatal brain development. Previously, we reported smaller total brain volumes in both critically ill full‐term and premature patients following complex perioperative critical care for long‐gap esophageal atresia (LGEA). Our current report assessed trends in regional brain sizes during infancy, and probed for any group differences.MethodsFull‐term (n = 13) and preterm (n = 13) patients without any previously known neurological concerns, and control infants (n = 16), underwent non‐sedated 3 T MRI in infancy (<1 year old). T2‐weighted images underwent semi‐automated brain segmentation using Morphologically Adaptive Neonatal Tissue Segmentation (MANTiS). Regional tissue volumes of the forebrain, deep gray matter (DGM), cerebellum, and brainstem are presented as absolute (cm3) and normalized (% total brain volume (%TBV)) values. Group differences were assessed using a general linear model univariate analysis with corrected age at scan as a covariate.ResultsAbsolute volumes of regions analyzed increased with advancing age, paralleling total brain size, but were significantly smaller in both full‐term and premature patients compared to controls. Normalized volumes (%TBV) of forebrain, DGM, and cerebellum were not different between subject groups analyzed. Normalized brainstem volumes showed group differences that warrant future studies to confirm the same finding.DiscussionBoth full‐term and premature critically ill infants undergoing life‐saving surgery for LGEA are at risk of smaller total and regional brain sizes. Normalized volumes support globally delayed or diminished brain growth in patients. Future research should look into neurodevelopmental outcomes of infants born with LGEA.
Role of JAK2 in the Pathogenesis of Diabetic Erectile Dysfunction and an Intervention With Berberine
Authors: Song Jingyu , Tang Zhe , Li Hao , Jiang Hongyang , Sun Taotao , Lan Ruzhu , Wang Tao , Wang Shaogang , Ye Zhangqun , Liu Jihong 
Published: September 2019

AbstractBackgroundOxidative stress is a significant contributor to the poor treatment efficacy on erectile dysfunction induced by diabetes mellitus (DMED). Thus, understanding the mechanism underlying oxidative stress will aid in the identification of novel therapeutic targets.AimTo define the role of Janus kinase 2 (JAK2) in mediating oxidative stress in the corpus cavernosum smooth muscle cells (CCSMCs) and to investigate the therapeutic effect of monomeric berberine (BB), which inhibits JAK2, in the pathogenesis of DMED.MethodsStreptozotocin was used to establish type I diabetic rat models and apomorphine tests were conducted to determine DMED rats. Eighteen DMED rats were divided into the DMED group and the DMED+BB group, whereas another 10 age-matched rats formed the control group. CCSMCs were isolated from the corpus cavernosum of rats and were treated with the JAK2 inhibitor alpha cyanano-(3,4-hydroxyl)N-benzophenylamine (AG490) and/or BB.OutcomesMetabolic parameters; erectile function; histologic and molecular alterations.ResultsErectile function was impaired and excessive oxidative stress was found in the DMED group. Excessive oxidative stress led to decreased expression level of phosphorylated endothelial nitric oxide synthase at serine 1177/endothelial nitric oxide synthase and increased expression level of Ras homolog gene family and Rho kinase 1/2. Meanwhile, the relative expression ratio of phosphorylated JAK2/JAK2 was significantly greater in the DMED group than that in the other groups. In vitro, oxidative stress was significantly reduced along with reduced intracellular calcium upon treatment with the JAK2 inhibitor, AG490. Moreover, the CCSMCs treated with BB showed changes similar to those upon treatment with AG490. In vivo experiments also confirmed that the erectile function of the DMED+BB group was improved, accompanied by decreased phosphorylated JAK2/JAK2 and decreased oxidative stress.Clinical TranslationJAK2 can be used as a therapeutic target and BB can be used as a potential drug for the clinical treatment of DMED.Strengths and LimitationsThis study examines the promoting effect of JAK2 on oxidative stress occurrence in the corpus cavernosum and on the development of DMED in both animal experiments and cell experiments, as well evaluates the inhibitory effect of BB on JAK2 and its therapeutic effect on DMED. The main limitation of our current study is the lack of an appropriate means for activating JAK2.ConclusionsJAK2 can induce DMED by enhancing oxidative stress and BB can play a role in treating DMED by inhibiting JAK2 and reducing oxidative stress. Our study provides an option and an idea for further studies on the pathogenesis and treatment of DMED.
Mitochondrial calcium uniporter as a potential therapeutic strategy for Alzheimer’s disease
Authors: Venugopal Anila , Iyer Mahalaxmi , Balasubramanian Venkatesh , Vellingiri Balachandar 
Published: September 2019

AbstractAlzheimer’s disease (AD), a neurodegenerative disorder, is the leading cause of dementia in the world whose aetiology is still unclear. AD was always related to ageing though there have been instances where people at an early age also succumb to this disease. With medical advancements, the mortality rate has significantly reduced which also makes people more prone to AD. AD is rare, yet the prominent disease has been widely studied with several hypotheses trying to understand the workings of its onset. The most recent and popular hypothesis in AD is the involvement of mitochondrial dysfunction and calcium homeostasis in the development of the disease though their exact roles are not known. With the sudden advent of the mitochondrial calcium uniporter (MCU), many previously known pathological hallmarks of AD may be better understood. Several studies have shown the effect of excess calcium in mitochondria and the influence of MCU complex in mitochondrial function. In this article, we discuss the possible involvement of MCU in AD by linking the uniporter to mitochondrial dysfunction, calcium homeostasis, reactive oxygen species, neurotransmitters and the hallmarks of AD – amyloid plaque formation and tau tangle formation.
Military Aid, Regime Vulnerability and the Escalation of Political Violence
Authors: Boutton Andrew 
Published: September 2019

AbstractThis article offers an explanation for the failures of US military assistance programs in some countries. The author argues that the effects of military aid are conditional upon the vulnerability of the recipient regime. Power consolidation by an insecure leader often provokes violent opposition. However, because military aid strengthens the security forces of the recipient state, it generates a moral hazard that encourages exclusionary power consolidation, with the expectation that continued military aid will help manage violent blowback. Using proxies for regime vulnerability and an instrument for US military aid, the study shows that military aid increases anti-regime violence in new regimes (particularly new democracies) and in all personalist regimes. In contrast, military assistance has no effect on violence in established, non-personalist regimes. The article develops a novel theory of how regime characteristics condition responses to external military support, and identifies a distinct mechanism through which military aid increases domestic political violence.
Debt Renegotiation and Debt Overhang: Evidence from Lender Mergers
Authors: Chu Yongqiang 
Published: September 2019

AbstractThis article studies whether debt renegotiation mitigates debt overhang and increases corporate investment. Using mergers between lenders participating in the same syndicated loans as natural experiments that reduce the number of lenders and thus make renegotiation easier, I find that the firms affected by the mergers become more likely to renegotiate the loans and increase capital investment. The effect is stronger for firms with higher Q and firms in financial distress, supporting the hypothesis that the lender mergers mitigate the debt-overhang problem.
Transboundary conservation of the last remaining population of the cao vit gibbon Nomascus nasutus
Authors: Ma Chang-yong , Trinh-Dinh Hoang , Nguyen Van-Truong , Le Trong-Dat , Le Van-Dung , Le Huu-Oanh , Yang Jiang , Zhang Zi-Jie , Fan Peng-Fei 
Published: September 2019

AbstractThe cao vit gibbon Nomascus nasutus, also known as eastern black crested gibbon, is categorized as Critically Endangered on the IUCN Red List and was considered one of the world's 25 most threatened primates. The only known population occurs along the border between China and Viet Nam. Accurate information on population size and dynamics is critical for the species’ conservation, but population surveys conducted in only one country may over- or underestimate total population size because the home ranges of cao vit gibbon groups often cross the international border. In 2007 and 2016 we conducted two collaborative transboundary censuses of the cao vit gibbon populations in the Trung Khanh Cao Vit Gibbon Species and Habitat Conservation Area in Viet Nam and the Bangliang Gibbon National Nature Reserve in China. The results showed a population size of 102–110 in 2007, which increased to 107–136 in 2016. Our results indicate that previous surveys conducted separately in Viet Nam and China underestimated the global population size of this species. According to our more comprehensive surveys, the gibbon population is increasing slowly. The gibbons and their habitat are legally protected in both countries. Hunting and charcoal making have not been reported in this area since 2007. As habitat carrying capacity is a limiting factor, habitat restoration is required. However, lack of funding to protect the cao vit gibbon remains a challenge.
Black rhinoceros avoidance of tourist infrastructure and activity: planning and managing for coexistence
Authors: Muntifering Jeff R. , Linklater Wayne L. , Naidoo Robin , !Uri-≠Khob Simson , du Preez Pierre , Beytell Petrus , Jacobs Shayne , Knight Andrew T. 
Published: September 2019

AbstractWildlife-based tourism poses opportunities and challenges for species conservation. Minimizing potential negative impacts of tourism is critical to ensure business and conservation enterprises can coexist. In north-western Namibia tourism is used as a conservation tool for the Critically Endangered black rhinocerosDiceros bicornis. However, black rhinoceroses are susceptible to human disturbance and may become displaced by tourist activities, which threatens not only the security and health of the rhinoceros population but also the sustainability of the business. We examined areas avoided by black rhinoceroses to understand how they respond to the type and extent of tourism development, and to evaluate management alternatives. We used spatial data on use of water sources by rhinoceroses to create a series of a priori candidate models that described the negative influences of tourist activities on rhinoceros habitat use. A model selection approach strongly supported a cumulative zones of influence model comprised of a 6 km buffer around the airstrip combined with a 1 km buffer around roads used daily. We compared alternative management scenarios using the best-performing model and found that an optimal road-use policy combined with airstrip relocation could minimize the total area avoided by the black rhinoceros to 7.1% and loss of high quality habitat to 20.7%. Under the worst-case scenario the area avoided and loss of high quality habitat were 153 and 85% greater, respectively, than under the scenario with optimal management. Our findings provide a novel framework and a practical, policy-relevant decision support tool to improve the contribution of tourism to wildlife conservation.
A review of toxoplasmosis in humans and animals in Turkey
Authors: Kolören Z. , Dubey J. P. 
Published: September 2019

AbstractInfections by the protozoan parasiteToxoplasma gondiiare widely prevalent in humans and animals in Turkey but little is known of the burden of their clinical toxoplasmosis. Many early papers on toxoplasmosis in Turkey were published in Turkish and often not available widely. Here, we review prevalence, clinical spectrum, epidemiology and diagnosis ofT. gondiiin humans and animals in Turkey. This knowledge should be useful to biologists, public health workers, veterinarians and physicians. Although one-third of the human population in Turkey is seropositive, the rate of congenital toxoplasmosis is unknown and no information is available in children 12 years old or younger. One large outbreak of acute toxoplasmosis has been reported in 14–18-year old school children in Turkey. An alarming rate (36%) ofT. gondiitissue cysts were reported in tissues of sheep and water buffalo meats destined for human consumption; these reports require verification. Genetically,T. gondiistrains from domestic cats and wild birds in Turkey were generally classical type II and III, like those prevalent in Europe. A separate genotype, Type 1 Africa, was isolated from two congenitally infected children and a domestic cat in Turkey.