bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Dynamic Bond Concentration on the Viscoelastic and Mechanical Properties of Dynamic Poly(alkylurea‐co‐urethane) Networks
Authors: Chen Lifeng , Zhang Longhe , Griffin Philip J. , Rowan Stuart J. 
Published: November 2019

AbstractPolymer networks containing dynamic covalent bonds do not exhibit traditional thermoset material properties. Such dynamic covalent networks have the ability to undergo stress relaxation processes associated with dynamic covalent bond exchange, imparting these materials with adaptive/responsive properties. Reported herein is an investigation on the effect that changing the amount of dynamic hindered alkylurea bonds has on the viscoelastic behavior of a series of poly(alkylurea‐co‐urethane) networks prepared by reacting a trifunctional isocyanate crosslinker with varying ratios of an N‐isopropyl amine endcapped poly(propylene glycol) and a poly(propylene glycol). Films that contain >50% dynamic alkylurea bonds (wrt. alkylurea + urethane bonds) exhibit facile reprocessability, while those films with <50% dynamic alkylurea bonds exhibit poor reprocessability under these same conditions. Analysis of the temperature‐dependent shear rheometry and uniaxial stress relaxation measurements demonstrates that the primary stress relaxation mode in these materials is linked to the dynamic bond exchange process. Interestingly, these films exhibit an increasingly rich viscoelastic spectrum with increasing fraction of non‐dynamic urethane bonds. In addition to the primary relaxation process an order‐of‐magnitude slower relaxation emerges, which is identified as being related to the relaxation of larger, permanently crosslinked polymeric clusters in an otherwise dynamic matrix.
A putative protein–RNA complex regulates posttranscriptional processing of cytochrome P450 aromatase (CYP19A1) in bovine granulosa cells
Authors: Sahmi Fatiha , Sahmi Malha , Gévry Nicolas , Sahadevan Pramod , Allen Bruce G. , Price Christopher A. 
Published: November 2019

AbstractFollicle growth and granulosa cell health are dependent on the secretion of estradiol from granulosa cells. Estradiol is synthesized from androgen precursor by cytochrome P450 aromatase (CYP19A1), and in cattle CYP19A1 messenger RNA has a short half‐life but a long (3.5 kb) 3′‐untranslated region (3′UTR), suggesting that posttranscriptional regulation may be important for control of enzyme activity. We tested this hypothesis by inserting the CYP19A1 3′UTR and fragments thereof into a reporter vector between the end of the luciferase coding region and the polyadenylation signal. The full‐length aromatase 3′UTR suppressed luciferase activity to 10% of control levels, and smaller fragments showed that this inhibitory activity lies between +926 and +1134 of the 3′UTR. Protein–RNA cross‐linking experiments revealed that these 3′UTR fragments formed an RNA–protein complex of approximately 70 kDa that was present in granulosa cells but not in corpus luteum, lung, liver, kidney, pancreas, or bladder extracts. The RNA‐binding activity was specific to the 3′UTR, as shown by competition experiments with unlabeled RNA, and was present only in 3′UTR constructs that inhibited luciferase activity. These data suggest that posttranscriptional regulation is an important component of the control of CYP19A1 expression and involves protein binding to a specific sequence in the 3′UTR.
Simulation of Polymer Reactors Using the Compartment Modeling Approach
Authors: Cremer‐Bujara Esther , Biessey Philip , Grünewald Marcus 
Published: November 2019

AbstractA compartment modeling approach based on computational fluid dynamics (CFD) simulations is applied to a simplified static mixer geometry. Compartments are derived from velocity fields obtained from cold CFD simulations. This methodology is based on the definition of periodic flow zones (PFZ) derived from the recurrent flow profile within the static mixer. In general, PFZ can be characterized by two different compartments: flow zones with hydrodynamic behavior of a tubular reactor and dead zones exhibiting a more continuous stirred tank reactor‐like characteristic. In CFD studies the influence of changing fluid properties, for example viscosity, on flow profile due to polymerization progress is considered. In the deterministic compartment model, the continuous flow profile within the static mixer is transformed to basic reactor models interconnected via an exchange stream. To reduce model complexity and the number of model parameters, constant volumes of compartments are assumed. Changes in hydrodynamics are considered by a variable exchange flow rate as a function of Re manipulating residence time in compartments. Simulation studies show the influence of decreasing exchange flow rates with polymerization progress, as Re decreases, resulting in a greater increase of viscosity in dead zones. The reactor performance is qualitatively represented by the simulation results.
Optimizing Delivery of Breast Milk for Premature Infants: Comparison of Current Enteral Feeding Systems
Authors: Abdelrahman Khaled , Jarjour Jane , Hagan Joseph , Yang Heeju , Sutton Danielle , Hair Amy 
Published: November 2019

AbstractBackgroundIncomplete delivery of fat from expressed breast milk (EBM) during enteral feeding to premature neonates remains a significant problem. Feeding system manufacturers have introduced changes to the enteral syringe design to improve fat delivery that have not yet been evaluated in the literature.MethodsThis study compares percentage delivery of fat from EBM using 2 major enteral feeding systems in various configurations with silicone and polyurethane tubing material and ENFit and Legacy connection systems at 3 clinically relevant infusion rates.ResultsThe percent of fat delivery from EBM was significantly higher for the eccentric syringe system than the concentric system (P = 0.036) but did not vary significantly across infusion rates (P = 0.081). Silicone tubing had a significantly higher percent of fat delivery than polyurethane tubing within the eccentric syringe system (P = 0.039) but did not vary significantly across infusion rates (P = 0.105). There was no significant difference between ENFit and Legacy connectors using eccentric syringes with silicone tubing (P = 0.360).ConclusionWe demonstrate that changes to syringe design and tubing material are effective and improve fat delivery from EBM, which may result in improved growth and outcomes in premature infants. The eccentric syringe marginally improves fat delivery in comparison with the concentric syringe, and silicone tubing significantly improves fat delivery compared with polyurethane tubing.
Mechanical Microstructure Characterization of Discontinuous‐Fiber Reinforced Composites by means of Experimental‐Numerical Micro Tensile Tests
Authors: Schober Michael , Dittmann Kerstin , Gumbsch Peter , Kuboki Takashi , Hohe Jörg 
Published: November 2019

AbstractThe mechanical characteristics and especially the damage behavior of discontinuous‐fiber reinforced composites greatly depend on its constituents and also on its microstructural properties, namely the extent and distribution of fiber agglomerations, the fiber orientation distribution, and the fiber‐matrix interfaces. Several methods exist to individually analyze the different microstructural properties, such as µCT scanning to obtain the distribution of the fibers and their orientation and the Microbond test to obtain the interfacial characteristics. However, the interdependencies of the individual characteristics and the initiation of fracture with respect to the microstructure are still hard to analyze regarding a real composite structure. For this reason, the microscopic fracture behavior of a glass fiber reinforced sheet molding compound (SMC) shall be investigated by means of a micro tensile test. Therefore, a specimen with a gauge length of approx. 1 mm, 0.3 mm width and 0.1 mm thickness is extracted from a composite plaque and put to an in‐situ observed tensile test. With a finite element model of each specimen, including the position and orientation of each fiber, the fiber‐matrix‐interface characteristics are extracted with a reverse‐engineering approach. The tests show a microstructure‐specific fracture behavior, which depends on the fiber dispersion, the fiber orientation, and the fiber‐matrix interfaces. The numerical simulations well agree with the physical experiments, making the obtained parameters suitable for further simulations of the investigated structure on a larger scale.
Effects of a temperature cycle on a rotating shrink fit with FGM‐hub
Authors: Arslan Eray , Apatay Tunç , Mack Werner 
Published: November 2019

AbstractSubject of the investigation is a rotating shrink fit with hollow cylindrical inclusion and functionally graded hub in a state of generalized plane strain. Elevated temperature during operation may have both a transient and – in case of partial plastification – a permanent influence on the interface pressure. These effects are exemplified by means of a shrink fit with steel/aluminum FGM‐hub.
Improving outcomes of infections in cystic fibrosis in the era of CFTR modulator therapy
Authors: Saiman Lisa 
Published: November 2019

AbstractCurrently, available single and dual‐combination cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapies have favorably altered the life course of individuals with cystic fibrosis (CF) by decreasing morbidities and increasing survival. However, even with CFTR modulator use, questions and challenges remain to optimize the management of lung infections. This review (a) identifies these ongoing challenges and discusses the current understanding of the potential impact of CFTR modulator therapy on infections; (b) describes ongoing research to optimize detection, diagnosis, and treatment of CF microorganisms; and (c) discusses strategies to develop new anti‐infective therapies. The CF Foundation has launched the Infection Research Initiative to fund research that will improve our understanding of the complex microbial ecology within the CF lung, improve detection of CF pathogens, optimize current treatment, including long‐term chronic therapies, and develop new anti‐infective therapies. Ongoing clinical trials to determine the optimal duration of treatment of pulmonary exacerbations and to diagnose and treat nontuberculous mycobacteria represent clinical research paradigms that could be used to answer other complex treatment questions. The anti‐infective pipeline includes both existing anti‐infective and non‐anti‐infective agents, many of which are proposed to have unique mechanisms of action in CF. Future studies plan to evaluate short‐ and long‐term clinical effectiveness and impact on infections, of the next generation of CFTR modulator therapy, the highly effective triple‐combination therapy, for individuals with CF, homozygous or heterozygous for F508del.
Equipment‐based route index of inherent safety
Authors: Athar Muhammad , Shariff Azmi M. , Buang Azizul , Hermansyah Heri 
Published: November 2019

AbstractProcess safety concept is used to deal with accident scenarios occurring as a result of loss containment. There are four tactics of process safety, and due to superior characteristics, the inherent theme is given priority at the preliminary design stage. In open literature, various methods have been proposed to identify the inherent safety level, and among these indexing methods are typically used. The reported indices have a shortcoming that these have not considered equipment characteristics for inherent safety assessment. Therefore, a new indexing method is proposed in this article to improve the quantification of inherent safety level. This index incorporates process, chemical, and equipment aspects to define the safety level of various process routes via the relative ranking. The proposed index has been tested on process routes to produce methyl methacrylate, which confirms the applicability of this index. The index would enable the practitioners to thoroughly analyze and compare the process routes to identify the inherently safer route.
Does moving in childhood and adolescence affect residential mobility in adulthood? An analysis of long‐term individual residential trajectories in 11 European countries
Authors: Bernard Aude , Vidal Sergi 
Published: November 2019

AbstractThe impact of childhood mobility on a range of life outcomes has been examined, but its influence on the likelihood to move in adulthood remains largely unknown. This paper examines the impact of changing residence in childhood on mobility levels in early and mid‐adulthood in 11 European countries. Drawing on nationally representative retrospective residential histories from the Study of Health, Ageing and Retirement in Europe (SHARE), the paper uses negative binomial regression to assess how the number and timing of moves from birth to age 17 affect the likelihood to move between the ages of 18 to 50 for individuals born between 1918 and 1957. While the level and timing of childhood moves vary between countries, childhood moves significantly increase the likelihood to move in adulthood in all our sample countries but Austria. The effect is particularly pronounced in low mobility countries in the south, east and centre of Europe where moving as a child is less common. While changing residence in adolescence is particularly influential, in some countries pre‐school relocations also have a long‐lasting effect on subsequent mobility. Conceptually, these results demonstrate the importance of viewing mobility as a cumulative process that takes place over the entire life‐course of individuals. Drawing on key migration and mobility concepts, we formulate a schematic decision‐making framework that traces the relationship between past and future moves. We conclude that the impact of changing residence in childhood on mobility behaviour later in life could contribute to reinforcing diverging trends in mobility levels across Europe.
Statistical inference on progressive‐stress accelerated life testing for the logistic exponential distribution under progressive type‐II censoring
Authors: Kumar Mahto Amulya , Dey Sanku , Mani Tripathi Yogesh 
Published: November 2019

AbstractThe accelerated life testing (ALT) is an efficient approach and has been used in several fields to obtain failure time data of test units in a much shorter time than testing at normal operating conditions. In this article, a progressive‐stress ALT under progressive type‐II censoring is considered when the lifetime of test units follows logistic exponential distribution. We assume that the scale parameter of the distribution satisfying the inverse power law. First, the maximum likelihood estimates of the model parameters and their approximate confidence intervals are obtained. Next, we obtain Bayes estimators under squared error loss function with the help of Metropolis‐Hasting (MH) algorithm. We also derive highest posterior density (HPD) credible intervals of the model parameters. Monte Carlo simulations are performed to compare the performances of the proposed methods of estimation. Finally, one data set has been analyzed for illustrative purposes.
Multi‐instance multi‐label learning for surgical image annotation
Authors: Loukas Constantinos , Sgouros Nicholas P. 
Published: November 2019

AbstractBackgroundVarious techniques have been proposed in the literature for phase and tool recognition from laparoscopic videos. In comparison, research in multilabel annotation of still frames is limited.MethodsWe describe a framework for multilabel annotation of images extracted from laparoscopic cholecystectomy (LC) videos based on multi‐instance multiple‐label learning. The image is considered as a bag of features extracted from local regions after coarse segmentation. A method based on variational Bayesian gaussian mixture models (VBGMM) is proposed for bag representation. Three techniques based on different feature extraction and bag representation models are employed for comparison.ResultsFour anatomical structures (abdominal wall, gallbladder, fat, and liver bed) and a tool‐like object (specimen bag) were annotated in 482 images. Our method achieved the best performance on single label accuracy: 0.87 (highest) and 0.69 (lowest). Moreover, the performance was >20% higher in terms of four multilabel classification error metrics (one‐error, ranking‐loss, hamming‐loss, and coverage).ConclusionsOur approach provides an accurate and efficient image representation for multilabel classification of still images captured in LC.
Frequency‐dependent fault detection for networked systems under uniform quantization and try‐once‐discard protocol
Authors: Long Yue , Park Ju H. , Ye Dan 
Published: November 2019

SummaryThis paper is concerned with the frequency‐dependent fault detection scheme for networked systems under uniform quantization and try‐once‐discard protocol scheduling. By considering the communication constraint and the data node scheduling, a switched system is firstly modeled to characterize the dynamic features of the whole system. The switching function of the derived system is determined by the try‐once‐discard protocol. For this class of system, a sufficient condition to ensure the exponentially ultimately boundedness is established. With the aid of some novel analysis processes, sufficient conditions to characterize the desired finite frequency performances, which transform the frequency‐domain restrictions into time‐domain conditions, are subsequently developed. Then, the fault detection filters corresponding to the transmission nodes are synthesized by solving an optimization problem. Finally, an application to VTOL aircraft is presented to illustrate the effectiveness of the proposed fault detection strategy.
A trajectory‐based method for constructing null controllable regions
Authors: Homer Tyler , Mahmood Maaz , Mhaskar Prashant 
Published: November 2019

SummaryThe problem of determining a system's set of stabilizable states, the null controllable region (NCR), is intricately related to the problem of determining control Lyapunov functions. In this paper, we address the problem of construction of the NCR for control‐affine nonlinear systems with input constraints. To this end, we explain how the boundary of the NCR is covered by time‐optimal trajectories. To construct the NCR, we employ an algorithm based on Pontryagin's minimum principle, which integrates optimal trajectories of a special smooth system in reverse time from the boundary of an initial NCR estimate. We illustrate this algorithm with linear and nonlinear system examples.
Camera trapping reveals trends in forest duiker populations in African National Parks
Authors: O'Brien Timothy G. , Ahumada Jorge , Akampurila Emmanuel , Beaudrot Lydia , Boekee Kelly , Brncic Terry , Hickey Jena , Jansen Patrick A. , Kayijamahe Charles , Moore Jennifer , Mugerwa Badru , Mulindahabi Felix , Ndoundou‐Hockemba Mireille , Niyigaba Protais , Nyiratuza Madeleine , Opepa Cisquet K. , Rovero Francesco , Uzabaho Eustrate , Strindberg Samantha 
Published: November 2019

AbstractBushmeat hunting is widely cited as cause for declines of wildlife populations throughout Africa. Forest duikers (Bovidae, Cephalophinae) are among the most exploited species. Whether current harvest rates imperil duikers is debated because of the difficulty of accurately assessing population trends. To assess population trends, we first reviewed literature for historical duiker population estimates. Second, we used systematic camera‐trap monitoring to assess population trends for 15 populations of nine duiker species in six national parks in Central and East Africa. We analysed annual monitoring data using Royle‐Nichols heterogeneity‐induced occupancy models to estimate abundance/sample point and derive occupancy estimates. Published density estimates indicate that duiker populations declined significantly throughout Africa between 1973 and 2013. There was a wide range of densities depending on species ( range: 0.26–20.6 km−1) and whether populations were hunted ( =6.3 km−1) or unhunted ( = 16.3 km−1). More recent analysis of camera‐trap monitoring produced different results. Estimated mean point abundance over time was between 0 and 0.99 individuals/point for four populations, between 1.0 and 1.99 for six populations, and greater than 2.0 for five populations. We observed five populations of duikers with negative trends in point abundances, although only one trend was significant and point abundance estimates for three populations were above 2.0 in the final survey year. Six populations showed positive trends in point abundance (three significant), and the remaining populations displayed no trends. Average occupancy was high (Ψ > 0.60) except for three populations. While literature indicates that historical population declines have occurred, most duiker populations appear relatively healthy in monitored parks. Our results indicate that these parks are effective in protecting most duikers despite hunting pressure. We recommend that systematic, standardized camera‐trap monitoring be initiated in other African parks in combination with point‐abundance models to objectively assess forest ungulate population trends.
Impact of mobile technology‐based physics curriculum on preservice elementary teachers' technology self‐efficacy
Authors: Menon Deepika , Chandrasekhar Meera , Kosztin Dorina , Steinhoff Douglas C. 
Published: November 2019

AbstractThe growing popularity of mobile technologies in educational settings, from grade schools through college, has prompted science educators to prepare preservice teachers to successfully integrate technology into science teaching. This mixed‐methods study explores the effectiveness of a mobile technology‐based physics curriculum, Exploring Physics, on preservice elementary teachers' technology self‐efficacy. Participants included 67 preservice elementary teachers enrolled in a specialized physics content course at a large public university in the United States. The experimental group (N = 34) used the Exploring Physics curriculum on iPads, and the comparison group (N = 33) used a hard‐copy version of a similar curriculum. Data sources included a technology self‐efficacy survey administered as pre‐ and posttests, focus group and individual interviews with 24 participants at two time points, weekly classroom observations, and artifacts. Data analyses included repeated measures analysis of variance and posthoc t tests with Bonferroni adjustments and grounded theory techniques. The results showed significant positive changes in the experimental group participants' technology self‐efficacy. In contrast, there was a significant decrease in the comparison group participants' technology self‐efficacy. Several affordances of the curriculum assisted the experimental group participants in developing an appreciation for using mobile technologies in science teaching. Implications for preservice teacher preparation for technology integration in science teaching are discussed.