bluuebunny/crossref_metadata_2025 huggingface dataset:
Désengagement professionnel des enseignants canadiens : de la vocation à la désillusion. Une analyse à partir d’une modélisation par équations structurelles
Authors: Kamanzi Pierre Canisius , Barroso da Costa Carla , Ndinga Pascal
Published: August 2017

Cet article vise à cerner les facteurs en lien avec le désengagement professionnel observé auprès des enseignants canadiens. Une analyse des données tirées d’une enquête pancanadienne auprès des enseignants (N = 3 221) révèle que ce désengagement est significativement associé aux facteurs suivants : les expériences émotionnelles négatives dues aux relations difficiles avec les élèves, la perception des changements de politiques éducatives, la satisfaction vis-à-vis des conditions de travail et le sentiment de compétence. Des quatre variables étudiées, les expériences émotionnelles représentent le facteur qui explique davantage le désengagement professionnel. Des analyses révèlent qu’à quelques différences près, la situation est similaire dans les quatre provinces étudiées : Alberta, Colombie-Britannique, Ontario et Québec.
Le parcours de formation axée sur l’emploi : la parole aux jeunes
Authors: Rousseau Nadia , Bergeron Léna
Published: August 2017

Le Parcours de formation axée sur l’emploi (PFAE) constitue une offre de formation qualifiante principalement destinée aux élèves ayant des défis scolaires variés et importants. En d’autres mots, il s’agit là d’une diversification des parcours menant à l’obtention d’un certificat de formation qualifiante reconnu par le Ministère de l’Éducation et de l’Enseignement supérieur (MEES). Cela dit, que pensent les jeunes, souvent inscrits par obligation, de cette formation ? Qu’ont-ils à nous apprendre sur la cohérence entre ce qu’ils y vivent et sur les intentions premières de ce programme ? C’est à travers une recherche qualitative réalisée auprès de 149 élèves provenant de six écoles secondaires que nous avons cherché à comprendre comment se vit cette voie de formation.
Description et analyse des postures épistémologiques sous-tendues par l’épreuve unique ministérielle de quatrième secondaire en Histoire et éducation à la citoyenneté
Authors: Déry Catherine
Published: August 2017

Cet article décrit et analyse les postures épistémologiques sous-tendues par l’épreuve unique ministérielle de quatrième secondaire en Histoire et éducation à la citoyenneté et, plus précisément, les analyses de documents que les élèves doivent réaliser et les critères employés pour les évaluer, en se basant sur l’information ministérielle et les épreuves de juin 2012 à 2015. Les critères d’évaluation, le rôle de chaque document, son type et sa nature, la possibilité de le critiquer, ainsi que l’évaluation et l’utilisation du savoir historique ont été décrits et analysés. L’épreuve n’évalue pas l’exercice de la pensée historienne. Elle suggère une posture épistémologique appuyée sur un savoir fixe, transmis par une autorité détenant la vérité, ce qui diverge des finalités soutenues par le programme et la recherche.
L’identification à la nation dans les représentations sociales des enseignants d’histoire québécois
Authors: Lanoix Alexandre
Published: August 2017

L’enseignement de l’histoire fait l’objet de nombreux débats au Québec et à travers le monde et la place qu’y occupe la nation est un élément central des discussions. Notre recherche tente de mieux comprendre le rôle que joue l’identification à la nation dans l’enseignement de l’histoire et l’impact que peut avoir le programme de formation sur cet aspect de la pratique enseignante. Pour apporter des éléments de réponse à cette question, nous avons mené des entrevues avec huit enseignants d’histoire du Québec. Nous visons ainsi à cerner les représentations sociales des enseignants à propos de la place de la nation dans l’enseignement de l’histoire. Les résultats indiquent que l’identification à la nation est toujours bien présente dans les représentations sociales des enseignants, malgré le changement de programme.
Participation in Sports-Related Extracurricular Activities: A Strategy That Enhances School Engagement
Authors: St-Amand Jerome , Girard Stéphanie , Hiroux Marie-Hélène , Smith Jonathan
Published: August 2017

This article outlines a strategy that we, as high school teachers, used in the academic year 2012-2013 to improve a student’s school engagement. Extracurricular activities such as sports have proven useful (among other strategies) to counter school disengagement, specifically in enhancing positive social relations among the teachers and students involved. The authors present an approach implemented in partnership with the students, and discuss the consequences of this strategy for the students and the desired improvements. Finally, we emphasize the importance of peer involvement, teachers’ collaboration, and the teachers’ willingness to inspire and empower change.
Classes sociales et apprentissage en régime capitaliste
Authors: Loulou Miriam
Published: August 2017

Ce compte-rendu appartient à une série de trois articles de la section Forum sur le livre de Barnes (2016), Are They Rich Because They’re Smart? qu’il résume pour contextualiser le débat opposant les deux autres articles. L’ouvrage analyse les inégalités sociales causées par le capitalisme et l’intensification des conflits qu’elles produisent. Il critique les autocongratulations des élites justifiant leurs privilèges et pouvoirs par leurs diplômes. Enfin, il soutient que les travailleurs mèneront des luttes pour changer le monde qui changeront également leur image d’eux-mêmes.
Au-delà des déterminismes biologique et classiste dans l’explication des inégalités scolaires
Authors: Goyer Renaud , Borri-Anadon Corina
Published: August 2017

Cette critique appartient à une série de trois articles de la section Forum sur le livre de Barnes (2016), Are They Rich Because They’re Smart? Elle analyse les arguments dont Barnes se sert pour déconstruire le point de vue défendu par Herrstein et Murray (1994) dans The Bell Curve. Pour Barnes, le discours de Herrstein et Murray remplit une fonction politique, et non scientifique : il sert à justifier, avec des arguments biologiques faux, les inégalités économiques dont la soi-disant méritocratie profite, alors que l’explication des inégalités socioéconomiques et culturelles est sociopolitique. La réponse de Barnes, centrée sur la lutte des classes sociales, minimise toutefois le rôle des pratiques et des interactions des agents dans l’analyse des rapports sociaux inégalitaires.
Shifting communities after­­ typhoon damage on an upper mesophotic reef in Okinawa, Japan
Authors: White Kristine N. , Weinstein David K. , Ohara Taku , Denis Vianney , Montenegro Javier , Reimer James D.
Published: August 2017

Very few studies have been conducted on the long-term effects of typhoon damage on mesophotic coral reefs. This study investigates the long-term community dynamics of damage from Typhoon 17 (Jelawat) in 2012 on the coral community of the upper mesophotic Ryugu Reef in Okinawa, Japan. A shift from foliose to bushy coral morphologies between December 2012 and August 2015 was documented, especially on the area of the reef that was previously recorded to be poor in scleractinian genera diversity and dominated by foliose corals. Comparatively, an area with higher diversity of scleractinian coral genera was observed to be less affected by typhoon damage with more stable community structure due to less change in dominant coral morphologies. Despite some changes in the composition of dominant genera, the generally high coverage of the mesophotic coral community is facilitating the recovery of Ryugu Reef after typhoon damage.
Population structure ofBathymodiolus manusensis, a deep-sea hydrothermal vent-dependent mussel from Manus Basin, Papua New Guinea
Authors: Thaler Andrew D. , Saleu William , Carlsson Jens , Schultz Thomas F. , Van Dover Cindy L.
Published: August 2017

Deep-sea hydrothermal vents in the western Pacific are increasingly being assessed for their potential mineral wealth. To anticipate the potential impacts on biodiversity and connectivity among populations at these vents, environmental baselines need to be established.Bathymodiolus manusensisis a deep-sea mussel found in close association with hydrothermal vents in Manus Basin, Papua New Guinea. Using multiple genetic markers (cytochrome C-oxidase subunit-1sequencing and eight microsatellite markers), we examined population structure at two sites in Manus Basin separated by 40 km and near a potential mining prospect, where the species has not been observed. No population structure was detected in mussels sampled from these two sites. We also compared a subset of samples withB. manusensisfrom previous studies to infer broader population trends. The genetic diversity observed can be used as a baseline against which changes in genetic diversity within the population may be assessed following the proposed mining event.
Inadequate thermal refuge constrains landscape habitability for a grassland bird species
Authors: Tomecek John M. , Pierce Brian L. , Reyna Kelly S. , Peterson Markus J.
Published: August 2017

Ecologists have long recognized the influence that environmental conditions have on abundance and range extent of animal species. We used the northern bobwhite (Colinus virginianus; hereafter bobwhite) as a model species for studying how microclimates serve as refuge against severe weather conditions. This species serves as an indicator or umbrella species for other sensitive ground-nesting, grassland obligate species. We conducted a mensurative field experiment in the rolling plains of Texas, USA, a semi-arid ecosystem on the southwestern periphery of bobwhite range, to determine whether native bunch grasses, apparently suitable for bobwhite nesting, could reduce ambient temperature below levels harmful for eggs. During the nesting season, we compared temperature and relative humidity readings at daily heat maxima (i.e., the 3 h during each day with highest temperatures) during the nesting season over the course of two years at 63 suitable nest sites paired with 63 random locations (n= 126) using two sensors at ∼10 and ∼60 cm above ground level. Mean temperature at nest height was 2.3% cooler at nest sites (35.99 °C ± 0.07 SE) compared to random locations (36.81 °C ± 0.07 SE); at ambient height, nest sites were slightly cooler (32.78 °C ± 0.06 SE) than random location (32.99 °C ± 0.06 SE). Mean relative humidity at nest sites was greater at nest height (34.53% ± 0.112 SE) and ambient height (36.22% ± 0.10 SE) compared to random locations at nest (33.35% ± 0.12 SE) and ambient height (35.75% ± 0.10 SE). Based on these results, cover at sites that appear visually suitable for nesting by bobwhites and other ground nesting birds provided adequate thermal refuge in the rolling plains by maintaining cooler, moister microclimates than surrounding non-nesting locations. Post-hoc analyses of data revealed that habitat conditions surrounding suitable nest sites strongly influenced thermal suitability of the substrate. Given that eggs of bobwhites and probably other species would experience lethal temperatures without these thermal refuges in the context of proper habitat condition, nesting vegetation is a critical component of niche space for bobwhites and other ground nesting birds in semi-arid regions. Many contemporary land uses, however, degrade or destroy bunch grasses and grassland systems, and thus decrease landscape inhabitability. Conservationists working with obligate grassland species that require bunch grasses in semi-arid regions should develop land management strategies that maximize the availability of these thermal refuges across space and time.
Spatial patterns of the epipelagic species caught incidentally in the tuna fishery on floating objects, in the eastern Pacific Ocean
Authors: Solana-Sansores R
Published: August 2017

The spatial pattern of the fauna associated with floating objects in the eastern tropical Pacific (ETP) was analyzed. Different presence indexes for the groups of species caught incidentally in log sets were estimated, using information from the Inter-American Tropical Tuna Commission database (1993–1997). These indexes allowed a preliminary grouping of species in relation to the percentage of presence in the log sets on floating objects and to school type (solitary or schooling fish). They were then classified using quadratic discriminant functions, with diverse classification criteria: zone, annual period, groups of species and type of floating object. The models were based on several variance and covariance matrices. Three models were selected to classify the associated fauna, using the likelihood ratio test and the reduction observed in the error rates. The results show two zones in the ETP with different composition of groups of species and floating objects of different origin. The Equatorial Countercurrent, located around 4ºN, is the border between these zones. The northern zone presents an associated fauna dominated by adults and recruits of the silky shark (Carcharhinus falciformis) and of the blacktip shark (C. limbatus); by recruits of yellowfin tuna (Thunnus albacares); and, to a lesser extent, by yellowtail (Seriola lalandi). In the southern zone, the recruits of bigeye tuna (T. obesus) predominate. Both zones share fauna that is only found far from the coast, such as the whitetip shark (C. longimanus).
Floating objects of the eastern pacific: types, spatial distribution and temporal changes
Authors: Solana-Soares R
Published: August 2017

The spatial pattern was analyzed of different types of floating objects associated with the tuna fishery in the eastern tropical Pacific (ETP). Of the 34 types of floating objects, four classes were defined: floating objects of terrestrial origin (FOTE), floating objects of marine origin (FOMA), artificial floating objects (FOA), and fish aggregating devices (FAD). The information source was the observer database of the Inter-American Tropical Tuna Commission, for 1987 to 1997. The records of floating objects and fishery effort directed at them were analyzed, spatially and seasonally. The encounter rate and proportion per class were estimated, by one-degree quadrants. Spatial models were obtained for these variables using non-parametric regression. Before 1993, the encounter rates and proportion of FOTE were the most important, located close to the Central American coast. After that year, the region to the west of the Galapagos Islands was the most important. Since 1994, a spatial expansion of the floating objects fishery is observed to the southwest of the ETP, with the use of FAD. FOMA were found to concentrate in two zones: one off the coasts of Ecuador and Peru, and the other off Baja California, Mexico. The spatial patterns of the types of floating objects indicate a seasonal variation. It was concluded that the ETP can be divided into three zones: one coastal and two offshore zones. FOTE dominate in the coastal zone and to the north of the Equator, whereas FAD are the most important in the zone south of the Equator.
Comparative feeding behaviour of Penaeus kerathurus (Forskål, 1775) (Crustacea, Penaeidae) and Palaemon Serratus (Pennant, 1777) (Crustacea, Palaemonidae) during larval development
Authors: Narciso L , Morais S
Published: August 2017

Aspects of larval feeding of two autochthonous species of shrimp, Penaeus kerathurus (Forskål, 1775) and Palaemon serratus (Pennant, 1777), were studied. For P. kerathurus, feeding rates on Chlorella sp. and Isochrysis galbana Parke were determined at 3 different concentrations, during the protozoeal stage, and on Artemia franciscana Kellog at 4 different densities, during the mysis stage. The selectivity between Brachionus plicatilis Müller and Artemia franciscana nauplii was tested experimentally and the Ivlev selectivity index was calculated at the mysis stage. For Palaemon serratus Zoea III, V and VII, feeding rates on newly hatched A. franciscana nauplii, on metanauplii enriched during 24 hours in Protein Selco– and on starved metanauplii were determined. The Ivlev selectivity index was also calculated. The results revealed that Penaeus kerathurus and Palaemon serratus larvae have a negative selectivity for B. plicatilis. It is also suggested that the optimal density of A. franciscana for the mysis stage of P. kerathurus is around 10 nauplii mL–1. Finally, it was shown that the use of enrichment products leading to a very high lipid content of the prey may reduce their consumption rate.
Least squares data fitting
Authors: Ripa P
Published: August 2017

It is desired to represent, as good as possible, a series of data by means of certain functions with free parameters. "As good as possible" means that these parameters ara chosen so that the residuals, the difference between data and fitting functions, be as small as it is feasible. Our objective is not limited to finding the parameters of the best fit, but we also wish to know something about their uncertainties, this is, how well they are determined, given the errors of the original data as well as the imperfection of the fitting. Finally, supposing that we use the parameters of the fit in the calculation of other variables, we also want to have an estimation of the uncertainties of the latter. In order to do that, we imagine basic properties, wich we call "hypothesis", and then proceed from there with mathematical rigor. It is not superfluous to remember that the conclusions at wich we arrive depende on the hyphotheses done throughout the way, including the idea that useful information can be extracted from a least squares fit, of those data by these functions.
Time series prediction using artificial neural networks
Authors: Pérez-Chavarría MA , Hidalgo-Silva HH , Ocampo-Torres FJ
Published: August 2017

In this work, artificial neural network (ANN) algorithms were used to predict time series of the oceanographic variables Southern Oscilation Index (SOI) and sea surface temperature anomaly (SSTA). The finite impulse response neural network (FIRNN) was applied to data obtained from the NOAA. In order to determine the most efficient FIRNN architecture, several experiments were made varying different parameters. The best predictions were obtained for a network with one input neuron and 10th-order filters in the input layer, two 8-neuron 5th-order filter hidden layers and one output neuron. All the networks were trained with the temporal backpropagation learning algorithm, using the sigmoid transfer function at the hidden layers and a linear output. The learning rate was 0.001. In most experiments a normalized mean square error of 0.4 ± 0.1 and a correlation coefficient between the original and the predicted series greater than 0.8 were found. From a comparison with other SSTA prediction methods, the results obtained with the neural network were the best ones for the short term forecasting case.
Age and growth of the annular seabream, Diplodus annularis (Pisces: Sparidae), from the Canarian archipelago (central-east Atlantic)
Authors: Pajuelo JG , Lorenzo JM
Published: August 2017

Age and growth of the annular seabream Diplodus annularis off the Canary Islands (Central-east Atlantic) were studied. The length range of fish was between 82 and 209 mm in total length. Otoliths showed clear growth rings. Two rings, one opaque and one translucent, were laid down each year on the otoliths. Seasonal growth cycles were related to physiological changes produced by the influence of temperature and reproductive cycle.The opaque ring was deposited during the summer months and the translucent one during the winter months. Individuals aged 0 to 6 years were found. After the first year, the annual growth rate droped rapidly as a consequence of the sexual maturity. The difference in size between males and females was not considered as evidence of an intersexual difference in growth rates since they are the same specimens at different stages of sexual succession. The parameters of the von Bertalanffy growth equation for all individuals were: L∞ = 248.5 mm, k = 0.259 year–1, and t0 = –0.871 year. The backcalculation method demonstrated the validity of using otoliths for estimating age and growth.
Effect of dark and salinity treatment in the yield and quality of agar from Gracilaria cornea (Rhodophyceae)
Authors: Freile-Pelegrín Y , Robledo D , Pedersén M , Bruno E , Rönnqvist J
Published: August 2017

The alkali treatment used previous to agar extractions from the Gracilaria genus reduces, among other reactions, the sulphate content and improves the gel strength; however, at an industrial level it requires expensive effluent processing to reduce its polluting charge. The red alga Gracilaria cornea was cultivated under dark and salinity treatments to replace this alkali treatment. The different treatments tested were: (a) darkness and 33‰ salinity for 8 days, [dark treatment]; (b) darkness and 50‰ salinity for 4 days, followed by darkness and 25‰ salinity for 4 days, [4+4]; and (c) darkness and 50‰ salinity for 8 days, followed by darkness and 25‰ salinity for 4 days, [8+4]. The treatment [4+4] increased the agar yield in 26% (from 36.6 to 46.1%). All treatments reduced the sulphate content of the agar in approximately 24% when compared with agar obtained without any treatment. For G. cornea the [4+4] treatment might become in the future an additional treatment to a mild alkali treatment using less alkaline reagents for agar extraction.
Effect of photon fluence rates of white and blue-green light on growth efficiency and Pigment Content Of Three Diatom Species In Batch Cultures
Authors: Sánchez-Saavedra MP , Voltolina D
Published: August 2017

This study provides information on the combined effect of light quality and photon fluence rates (light intensity) on growth efficiency and pigment content of the coastal plankton diatoms Chaetoceros sp., Skeletonema costatum and Thalassiosira pseudonana. The relative growth efficiencies of the three species were significantly higher at 210 µE m-2s-1, under mixed bluegreen light for Chaetoceros sp. and S. costatum, and with white light for T. pseudonana. The chlorophyll a contents of the three species grown under blue-green light, alone or mixed with white light, were significantly higher (P < 0.001) than those with white light and, in all cases, contents were lower at high photon fluence rates, while carotenoids showed inverse trends. The relative growth efficiencies of the three species were significantly different (P < 0.001). There were also changes in the relative pigment concentrations associated with the growth phase, probably due to autoshading.
Zinc and its transporter ZIP6 are key mediators of breast cancer cell survival under high glucose conditions
Authors: Matsui Chihiro , Takatani‐Nakase Tomoka , Hatano Yuki , Kawahara Satomi , Nakase Ikuhiko , Takahashi Koichi
Published: August 2017

Recent studies have shown that hyperglycaemia is related to breast cancer progression; however, the mechanisms underlying the relationship between hyperglycaemia and breast cancer cell survival remain unknown. Here, we demonstrate that as compared to physiological glucose conditions, high glucose conditions promote a significant increase in MCF‐7 cell survival under hypoxia. High glucose levels inhibit apoptosis and induce epithelial‐to‐mesenchymal transition, resulting in increased cell viability under hypoxic conditions. Moreover, high glucose‐treated cells display significant increases in intracellular Zn2+ levels and reduction in mRNA expression of the zinc (Zn) transporter Zrt‐ and Irt‐like protein 6 (ZIP6) in hypoxia. ZIP6 deficiency disturbs intracellular Zn2+ homeostasis, leading to increased cell survival in hypoxia and reduced E‐cadherin expression, indicating that decreased ZIP6 expression is strongly associated with resistance to hypoxia.
Spatiotemporal changes of seismic attenuation caused by injected CO2 at the Frio‐II pilot site, Dayton, TX, USA
Authors: Zhu Tieyuan , Ajo‐Franklin Jonathan B. , Daley Thomas M.
Published: August 2017

A continuous active source seismic monitoring data set was collected with crosswell geometry during CO2 injection at the Frio‐II brine pilot, near Liberty, TX. Previous studies have shown that spatiotemporal changes in the P wave first arrival time reveal the movement of the injected CO2 plume in the storage zone. To further constrain the CO2 saturation, particularly at higher saturation levels, we investigate spatial‐temporal changes in the seismic attenuation of the first arrivals. The attenuation changes over the injection period are estimated by the amount of the centroid frequency shift computed by local time‐frequency analysis. We observe that (1) at receivers above the injection zone seismic attenuation does not change in a physical trend; (2) at receivers in the injection zone attenuation sharply increases following injection and peaks at specific points varying with distributed receivers, which is consistent with observations from time delays of first arrivals; then, (3) attenuation decreases over the injection time. The attenuation change exhibits a bell‐shaped pattern during CO2 injection. Under Frio‐II field reservoir conditions, White's patchy saturation model can quantitatively explain both the P wave velocity and attenuation response observed. We have combined the velocity and attenuation change data in a crossplot format that is useful for model‐data comparison and determining patch size. Our analysis suggests that spatial‐temporal attenuation change is not only an indicator of the movement and saturation of CO2 plumes, even at large saturations, but also can quantitatively constrain CO2 plume saturation when used jointly with seismic velocity.
Sensitivity analysis of multiport S‐parameter measurements due to nonideal TRL calibration standards
Authors: Wang M. , Zhao Y. J. , Jin Y. M. , Zhou Y. G.
Published: August 2017

In this paper, a detailed analysis of n‐port vector network analyzer measurement uncertainties due to nonideal standards for multiport through‐reflect‐line calibration is presented. By using the concept of general node equations, the error correction equation is simplified by the matrix operation; thus, a generalized formula for the deviations of the measured S parameters with respect to the error terms is derived, which can be implemented in further analysis of multiport measurement uncertainties applying arbitrary calibration method based on 4n‐term error model. The final expressions for the sensitivity coefficients of S parameters with simple and clear form provide a deeper understanding of error propagation mechanisms.
Implementation of respiratory‐gated VMAT on a Versa HD linear accelerator
Authors: Snyder Jeffrey E. , Flynn Ryan T. , Hyer Daniel E.
Published: August 2017

The accurate delivery of respiratory‐gated volumetric modulated arc therapy (VMAT) treatment plans presents a challenge since the gantry rotation and collimator leaves must be repeatedly stopped and set into motion during each breathing cycle. In this study, we present the commissioning process for an Anzai gating system (AZ‐733VI) on an Elekta Versa HD linear accelerator and make recommendations for successful clinical implementation. The commissioning tests include central axis dose consistency, profile consistency, gating beam‐on/off delay, and comparison of gated versus nongated gamma pass rates for patient‐specific quality assurance using four clinically commissioned photon energies: 6 MV, 6 FFF, 10 MV, and 10 FFF. The central axis dose constancy between gated and nongated deliveries was within 0.6% for all energies and the analysis of open field profiles for gated and nongated deliveries showed an agreement of 97.8% or greater when evaluated with a percent difference criteria of 1%. The measurement of the beam‐on/off delay was done by evaluating images of a moving ball‐bearing phantom triggered by the gating system and average beam‐on delays of 0.22–0.29 s were observed. No measurable beam‐off delay was present. Measurements of gated VMAT dose distributions resulted in decrements as high as 9% in the gamma passing rate as compared to nongated deliveries when evaluated against the planned dose distribution at 3%/3 mm. By decreasing the dose rate, which decreases the gantry speed during gated delivery, the gamma passing rates of gated and nongated treatments can be made equivalent. We present an empirically derived formula to limit the maximum dose rate during VMAT deliveries and show that by implementing a reduced dose rate, a gamma passing rate of greater than 95% (3%/3 mm) was obtained for all plan measurements.
Wearable Microfluidic Diaphragm Pressure Sensor for Health and Tactile Touch Monitoring
Authors: Gao Yuji , Ota Hiroki , Schaler Ethan W. , Chen Kevin , Zhao Allan , Gao Wei , Fahad Hossain M. , Leng Yonggang , Zheng Anzong , Xiong Furui , Zhang Chuchu , Tai Li‐Chia , Zhao Peida , Fearing Ronald S. , Javey Ali
Published: August 2017

Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, and more. In particular, liquid‐metal‐based sensors are especially promising as they can undergo strains of over 200% without failure. However, current liquid‐metal‐based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart‐rate monitoring, which require a much lower pressure detection resolution. In this paper, a microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width × 70 µm height) capable of resolving sub‐50 Pa changes in pressure with sub‐100 Pa detection limits and a response time of 90 ms is demonstrated. An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of a 0.0835 kPa−1 change in output voltage. The Wheatstone bridge also provides temperature self‐compensation, allowing for operation in the range of 20–50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real‐time pulse monitoring and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated.
Conjugated Microporous Polymer Nanosheets for Overall Water Splitting Using Visible Light
Authors: Wang Lei , Wan Yangyang , Ding Yanjun , Wu Sikai , Zhang Ying , Zhang Xinlei , Zhang Guoqing , Xiong Yujie , Wu Xiaojun , Yang Jinlong , Xu Hangxun
Published: August 2017

Direct water splitting into H2 and O2 using photocatalysts by harnessing sunlight is very appealing to produce storable chemical fuels. Conjugated polymers, which have tunable molecular structures and optoelectronic properties, are promising alternatives to inorganic semiconductors for water splitting. Unfortunately, conjugated polymers that are able to efficiently split pure water under visible light (400 nm) via a four‐electron pathway have not been previously reported. This study demonstrates that 1,3‐diyne‐linked conjugated microporous polymer nanosheets (CMPNs) prepared by oxidative coupling of terminal alkynes such as 1,3,5‐tris‐(4‐ethynylphenyl)‐benzene (TEPB) and 1,3,5‐triethynylbenzene (TEB) can act as highly efficient photocatalysts for splitting pure water (pH ≈ 7) into stoichiometric amounts of H2 and O2 under visible light. The apparent quantum efficiencies at 420 nm are 10.3% and 7.6% for CMPNs synthesized from TEPB and TEB, respectively; the measured solar‐to‐hydrogen conversion efficiency using the full solar spectrum can reach 0.6%, surpassing photosynthetic plants in converting solar energy to biomass (globally average ≈0.10%). First‐principles calculations reveal that photocatalytic H2 and O2 evolution reactions are energetically feasible for CMPNs under visible light irradiation. The findings suggest that organic polymers hold great potential for stable and scalable solar‐fuel generation.
Launching Phonon Polaritons by Natural Boron Nitride Wrinkles with Modifiable Dispersion by Dielectric Environments
Authors: Duan Jiahua , Chen Runkun , Li Jingcheng , Jin Kuijuan , Sun Zhigang , Chen Jianing
Published: August 2017

Interference‐free hyperbolic phonon polaritons (HPPs) excited by natural wrinkles in a hexagonal boron nitride (hBN) microcrystal are reported both experimentally and theoretically. Although their geometries are off‐resonant with the excitation wavelength, the wrinkles compensate for the large momentum mismatch between photon and phonon polariton, and launch the HPPs without interference. The spatial feature of wrinkles is about 200 nm, which is an order of magnitude smaller than resonant metal antennas at the same excitation wavelength. Compared with phonon polaritons launched by an atomic force microscopy tip, the phonon polaritons launched by wrinkles are interference‐free, independent of the launcher geometry, and exhibit a smaller damping rate (γ ≈ 0.028). On the same hBN microcrystal, in situ nanoinfrared imaging of HPPs launched by different mechanisms is performed. In addition, the dispersion of HPPs is modified by changing the dielectric environments of hBN crystals. The wavelength of HPPs is compressed twofold when the substrate is changed from SiO2 to gold. The findings provide insights into the intrinsic properties of hBN‐HPPs and demonstrate a new way to launch and control polaritons in van der Waals materials.
Hierarchical Graphene Foam for Efficient Omnidirectional Solar–Thermal Energy Conversion
Authors: Ren Huaying , Tang Miao , Guan Baolu , Wang Kexin , Yang Jiawei , Wang Feifan , Wang Mingzhan , Shan Jingyuan , Chen Zhaolong , Wei Di , Peng Hailin , Liu Zhongfan
Published: August 2017

Efficient solar–thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar–thermal materials. Carbon‐based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar–thermal energy conversion. However, to date, graphene‐based solar–thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h‐G foam) with continuous porosity grown via plasma‐enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar–thermal energy conversion efficiency of the h‐G foam impressively reaches up to ≈93.4%, and the solar–vapor conversion efficiency exceeds 90% for seawater desalination with high endurance.
Entropy as a Gene‐Like Performance Indicator Promoting Thermoelectric Materials
Authors: Liu Ruiheng , Chen Hongyi , Zhao Kunpeng , Qin Yuting , Jiang Binbin , Zhang Tiansong , Sha Gang , Shi Xun , Uher Ctirad , Zhang Wenqing , Chen Lidong
Published: August 2017

High‐throughput explorations of novel thermoelectric materials based on the Materials Genome Initiative paradigm only focus on digging into the structure‐property space using nonglobal indicators to design materials with tunable electrical and thermal transport properties. As the genomic units, following the biogene tradition, such indicators include localized crystal structural blocks in real space or band degeneracy at certain points in reciprocal space. However, this nonglobal approach does not consider how real materials differentiate from others. Here, this study successfully develops a strategy of using entropy as the global gene‐like performance indicator that shows how multicomponent thermoelectric materials with high entropy can be designed via a high‐throughput screening method. Optimizing entropy works as an effective guide to greatly improve the thermoelectric performance through either a significantly depressed lattice thermal conductivity down to its theoretical minimum value and/or via enhancing the crystal structure symmetry to yield large Seebeck coefficients. The entropy engineering using multicomponent crystal structures or other possible techniques provides a new avenue for an improvement of the thermoelectric performance beyond the current methods and approaches.
Ultrafine Silver Nanoparticles for Seeded Lithium Deposition toward Stable Lithium Metal Anode
Authors: Yang Chunpeng , Yao Yonggang , He Shuaiming , Xie Hua , Hitz Emily , Hu Liangbing
Published: August 2017

To exploit the high energy density of the lithium (Li) metal battery, it is imperative to address the dendrite growth and interface instability of the anode. 3D hosts for Li metal are expected to suppress the growth of Li dendrites. Heterogeneous seeds are effective in guiding Li deposition and realizing spatial control over Li nucleation. Herein, this study shows that ultrafine silver (Ag) nanoparticles, which are synthesized via a novel rapid Joule heating method, can serve as nanoseeds to direct the deposition of Li within the 3D host materials, resolving the problems of the Li metal anode. By optimizing the Joule heating method, ultrafine Ag nanoparticles (≈40 nm) are homogeneously anchored on carbon nanofibers. The Ag nanoseeds effectively reduce the nucleation overpotential of Li and guide the Li deposition in the 3D carbon matrix uniformly, free from the dendrites. A stable and reversible Li metal anode is achieved in virtue of the Ag nanoseeds in the 3D substrate, showing a low overpotential (≈0.025 V) for a long cycle life. The ultrafine nanoseeds achieved by rapid Joule heating render uniform deposition of Li metal anode in 3D hosts, promising a safe and long‐life Li metal battery for high‐energy applications.
A New Electron Acceptor with meta‐Alkoxyphenyl Side Chain for Fullerene‐Free Polymer Solar Cells with 9.3% Efficiency
Authors: Zhang Zhenzhen , Feng Liuliu , Xu Shutao , Liu Ye , Peng Hongjian , Zhang Zhi‐Guo , Li Yongfang , Zou Yingping
Published: August 2017

A new small molecule acceptor, m‐ITIC‐OR, based on indacenodithieno[3,2‐b]thiophene core with meta‐alkoxyphenyl side chains, is designed and synthesized. The m‐ITIC‐OR film shows broader and redshift absorption compared to its solution and matched energy levels with a hexafluoroquinoxaline‐based polymer donor‐HFQx‐T. Here, polymer solar cells (PSCs) by blending an HFQx‐T donor and an m‐ITIC‐OR acceptor as an active layer deliver the power conversion efficiency (PCE) of 6.36% without any posttreatment. The investigations demonstrate that the HFQx‐T:m‐ITIC‐OR blend films possess higher and more balanced charge mobility, negligible bimolecular recombination, and nanoscale interpenetrating morphology after thermal annealing (TA) treatment. Through a simple TA treatment at 150 °C for 5 min, an impressive PCE of 9.3% is obtained. This efficiency is among one of the highest PCEs for additive free PSCs. This is the first time alkoxyphenyl side chain is introduced into nonfullerene electron acceptor; more interestingly, the new electron acceptor (m‐ITIC‐OR) in this work shows a great potential for highly efficient photovoltaic properties.
Correlates of androgens in wild male Barbary macaques: Testing the challenge hypothesis
Authors: Rincon Alan V. , Maréchal Laëtitia , Semple Stuart , Majolo Bonaventura , MacLarnon Ann
Published: August 2017

Investigating causes and consequences of variation in hormonal expression is a key focus in behavioral ecology. Many studies have explored patterns of secretion of the androgen testosterone in male vertebrates, using the challenge hypothesis (Wingfield, Hegner, Dufty, & Ball, 1990; The American Naturalist, 136(6), 829–846) as a theoretical framework. Rather than the classic association of testosterone with male sexual behavior, this hypothesis predicts that high levels of testosterone are associated with male–male reproductive competition but also inhibit paternal care. The hypothesis was originally developed for birds, and subsequently tested in other vertebrate taxa, including primates. Such studies have explored the link between testosterone and reproductive aggression as well as other measures of mating competition, or between testosterone and aspects of male behavior related to the presence of infants. Very few studies have simultaneously investigated the links between testosterone and male aggression, other aspects of mating competition and infant‐related behavior. We tested predictions derived from the challenge hypothesis in wild male Barbary macaques (Macaca sylvanus), a species with marked breeding seasonality and high levels of male‐infant affiliation, providing a powerful test of this theoretical framework. Over 11 months, 251 hr of behavioral observations and 296 fecal samples were collected from seven adult males in the Middle Atlas Mountains, Morocco. Fecal androgen levels rose before the onset of the mating season, during a period of rank instability, and were positively related to group mating activity across the mating season. Androgen levels were unrelated to rates of male–male aggression in any period, but higher ranked males had higher levels in both the mating season and in the period of rank instability. Lower androgen levels were associated with increased rates of male‐infant grooming during the mating and unstable periods. Our results generally support the challenge hypothesis and highlight the importance of considering individual species’ behavioral ecology when testing this framework.
Inhibiting persistent inward sodium currents prevents myotonia
Authors: Hawash Ahmed A. , Voss Andrew A. , Rich Mark M.
Published: August 2017

Objective

Patients with myotonia congenita have muscle hyperexcitability due to loss‐of‐function mutations in the ClC‐1 chloride channel in skeletal muscle, which causes involuntary firing of muscle action potentials (myotonia), producing muscle stiffness. The excitatory events that trigger myotonic action potentials in the absence of stabilizing ClC‐1 current are not fully understood. Our goal was to identify currents that trigger spontaneous firing of muscle in the setting of reduced ClC‐1 current.

Methods

In vitro intracellular current clamp and voltage clamp recordings were performed in muscle from a mouse model of myotonia congenita.

Results

Intracellular recordings revealed a slow afterdepolarization (AfD) that triggers myotonic action potentials. The AfD is well explained by a tetrodotoxin‐sensitive and voltage‐dependent Na+ persistent inward current (NaPIC). Notably, this NaPIC undergoes slow inactivation over seconds, suggesting this may contribute to the end of myotonic runs. Highlighting the significance of this mechanism, we found that ranolazine and elevated serum divalent cations eliminate myotonia by inhibiting AfD and NaPIC.

Interpretation

This work significantly changes our understanding of the mechanisms triggering myotonia. Our work suggests that the current focus of treating myotonia, blocking the transient Na+ current underlying action potentials, is an inefficient approach. We show that inhibiting NaPIC is paralleled by elimination of myotonia. We suggest the ideal myotonia therapy would selectively block NaPIC and spare the transient Na+ current. Ann Neurol 2017;82:385–395
Persistent seizure control in epileptic mice transplanted with gamma‐aminobutyric acid progenitors
Authors: Casalia Mariana L. , Howard MacKenzie A. , Baraban Scott C.
Published: August 2017

Objective

A significant proportion of the more than 50 million people worldwide currently suffering with epilepsy are resistant to antiepileptic drugs (AEDs). As an alternative to AEDs, novel therapies based on cell transplantation offer an opportunity for long‐lasting modification of epileptic circuits. To develop such a treatment requires careful preclinical studies in a chronic epilepsy model featuring unprovoked seizures, hippocampal histopathology, and behavioral comorbidities.

Methods

Transplantation of progenitor cells from embryonic medial or caudal ganglionic eminence (MGE, CGE) were made in a well‐characterized mouse model of status epilepticus‐induced epilepsy (systemic pilocarpine). Behavioral testing (handling and open field), continuous video‐electroencephalographic (vEEG) monitoring, and slice electrophysiology outcomes were obtained up to 270 days after transplantation (DAT). Post‐hoc immunohistochemistry was used to confirm cell identity.

Results

MGE progenitors transplanted into the hippocampus of epileptic mice rescued handling and open field deficits starting at 60 DAT. In these same mice, an 84% to 88% reduction in seizure activity was observed between 180 and 210 DAT. Inhibitory postsynaptic current frequency, measured on pyramidal neurons in acute hippocampal slices at 270 DAT, was reduced in epileptic mice but restored to naïve levels in epileptic mice receiving MGE transplants. No reduction in seizure activity was observed in epileptic mice receiving intrahippocampal CGE progenitors.

Interpretation

Our findings demonstrate that transplanted MGE progenitors enhance functional GABA‐mediated inhibition, reduce spontaneous seizure frequency, and rescue behavioral deficits in a chronic epileptic animal model more than 6 months after treatment. Ann Neurol 2017;82:530–542
Intramolecular π–π Interactions in Flexibly Linked Partially Fluorinated Bisarenes in the Gas Phase
Authors: Blomeyer Sebastian , Linnemannstöns Marvin , Nissen Jan Hendrick , Paulus Jannik , Neumann Beate , Stammler Hans‐Georg , Mitzel Norbert W.
Published: August 2017

Three compounds with phenyl and pentafluorophenyl rings bridged by (CH2)3 and (CH2)2SiMe2 units were synthesized by hydrosilylation and C−C coupling reactions. Their solid‐state structures are dominated by intermolecular π stacking interactions, primarily leading to dimeric or chain‐type aggregates. Analysis of free molecules in the gas phase by electron diffraction revealed the most abundant conformer to be significantly stabilized by intramolecular π–π interactions. For the silicon compounds, structures characterized by σ–π interactions between methyl and pentafluorophenyl groups are second lowest in energy and cannot be excluded completely by the gas electron diffraction experiments. C6H5(CH2)3C6F5, in contrast, is present as a single conformer. The gas‐phase structures served as a reference for the evaluation of a series of (dispersion‐corrected) quantum‐chemical calculations.
Influence of the pretreatment and curing of alkoxysilanes on the protection of the titanium–aluminum–vanadium alloy
Authors: Salvador D. G. , Marcolin P. , Beltrami L. V. R. , Brandalise R. N. , Kunst S. R.
Published: August 2017

The use of coatings based on alkoxysilanes is one of the most effective ways to control the release of cytotoxic ions by metal implants. To improve the success rate of titanium–aluminum–vanadium implants, in this study, we evaluated the physicochemical, morphological, mechanical, and electrochemical behavior of hybrid coatings based on alkoxysilanes applied on the alloy. The coatings were prepared with the precursors 3‐(trimethoxysilyl propyl)methacrylate and tetraethoxysilane alkoxides by the sol–gel method. The curing of the coatings was evaluated at different temperatures (90, 180, and 300 °C) for 1 h. We carried out the pretreatment of the alloy by polishing and attacking it with sodium hydroxide. The results indicate that the temperature of 90 °C was effective for solvent evaporation and complete crosslinking of the film, and the alkaline pretreatment allowed the formation of a film with better anticorrosive performance; this indicated that the presence of hydroxyl groups on the surface improved the coating adhesion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45470.