bluuebunny/crossref_metadata_2025_split huggingface dataset:
3Y‐TZP In‐Depth Phase Transformation by Raman Spectroscopy: A Comparison of Three Methods
Authors: Wulfman Claudine , Djaker Nadia , Sadoun Michaël , Lamy de la Chapelle Marc 
Published: April 2014

Zirconia phase transformation is usually studied on surface. For in‐depth study, three methods were proposed using Raman microspectroscopy quantitative evaluation: direct measurement on sample cross section, confocal Raman spectroscopy (CRS), and progressive pinhole aperture enlargement (PPAE). The aim of this study was to compare transformation profiles obtained with these three methods on the same sample. Three 3Y‐TZP samples were aged, respectively, for 25, 72, and 90 h in artificial saliva. Transformation profiles were determined with cross‐sectional measurement, CRS and PPAE. A transformation profile simulation model based on PPAE measurements is proposed, using the convolution of the excitation intensity profile and the Beer–Lambert law (optical properties of zirconia). The simulation model was validated with the determination of 3Y‐TZP transformation factor, T = 1.15 μm−1, identical for the three aging durations. Both cross section and PPAE measured similar in‐depth transformation decrease, but with a 10 μm‐shift: transformed zirconia layer is more important in cross‐sectional protocol (36 μm with PPAE and 46 μm with cross‐sectional after 90 h aging). Complementary measurements on a 10 h aged sample, where transformation is initiated by Low‐Temperature Degradation, showed that sample preparation and polishing, necessary in the cross‐sectional method, were responsible for the higher transformation. PPAE method enables noninvasive in‐depth measurements with limited optical and mechanical biases.
Thermal Expansion, Heat Capacity, and Thermal Conductivity of Nickel Ferrite (NiFe2O4)
Authors: Nelson Andrew T. , White Joshua T. , Andersson David A. , Aguiar Jeffery A. , McClellan Kenneth J. , Byler Darrin D. , Short Michael P. , Stanek Christopher R. 
Published: April 2014

Nickel ferrite (NiFe2O4) is a major constituent of the corrosion deposits formed on the exterior of nuclear fuel cladding tubes during operation. NiFe2O4 has attracted much recent interest, mainly due to the impact of these deposits, known as CRUD, on the operation of commercial nuclear reactors. Although advances have been made in modeling CRUD nucleation and growth under a wide range of conditions, the thermophysical properties of NiFe2O4 at high temperatures have only been approximated, thereby limiting the accuracy of such models. In this study, samples of NiFe2O4 were synthesized to provide the thermal diffusivity, specific heat capacity, and thermal expansion data from room temperature to 1300 K. These results were then used to determine thermal conductivity. Numerical fits are provided to facilitate ongoing modeling efforts. The Curie temperature determined through these measurements was in slight disagreement with literature values. Transmission electron microscopy investigation of multiple NiFe2O4 samples revealed that minor nonstoichiometry was likely responsible for variations in the Curie temperature. However, these small changes in composition did not impact the thermal conductivity of NiFe2O4, and thus are not expected to play a large role in governing reactor performance.
Temperature and Frequency Dependence of Electric Field‐Induced Phase Transitions in PMN–0.32PT
Authors: Wooldridge Jenny , Stewart Mark , Vecchini Carlo , Cain Markys G. , Gutmann Matthias , Reece Mike 
Published: April 2014

Single crystal (1 − x)Pb(Mg1/3 Nb2/3)O3–xPbTiO3 [PMN–xPT] (x = 0.32) is a relaxor‐ferroelectric material known to exhibit ‘giant’ piezoelectric behavior, with achievable strains in excess of 1% for samples of certain particular crystallographic orientations and chemical compositions close to the morphotropic phase boundary. In this study, we investigate the electric field‐induced structural phase transitions in single crystal PMN–0.32PT with time‐of‐flight neutron diffraction and macroscopic electrical polarization measurements, and show that both the frequency of the applied ac field and the temperature of the sample are critical factors in determining these phase transition fields.
Computational Modeling of Die Swell of Extruded Glass Preforms at High Viscosity
Authors: Trabelssi Mohamed , Ebendorff‐Heidepriem Heike , Richardson Kathleen C. , Monro Tanya M. , Joseph Paul F. 
Published: April 2014

Computational simulations of glass extrusion are performed to quantify the effects of material behavior and slip at the die/glass interface on the die swell. Experimental data for three glass types are used to guide the computational study, which considers glass material to be viscous with and without shear thinning and viscoelastic using the Maxwell upper‐convected model. The study starts with assuming no‐slip at the glass/die interface to see if material behavior alone can explain the die swell results, and then considers slip using the Navier model where interface shear is directly proportional to the relative slip speed at the interface. Consistent with the possibility of slip and intended high viscosity applications, viscosity ranging from 107.4–108.8 Pa·s was used. Based on optimization of the various input parameters required to achieve the measured die swell and ram force values, the study concludes that interface slip occurred as only extreme values of the shear thinning parameters provided an alternative.
Preparation of a Novel Cementitious Material from Hydrothermally Synthesized C–S–H Phases
Authors: Garbev Krassimir , Beuchle Günter , Schweike Uwe , Merz Daniela , Dregert Olga , Stemmermann Peter 
Published: April 2014

New cementitious materials based on calcium hydrosilicate hydrates were recently developed as potential substitutes for ordinary portland cement, but with a reduced CO2 footprint. The materials are produced by hydrothermal processing of SiO2 and Ca(OH)2, giving rise to calcium silicate hydrates, followed by mechanical activation of the latter via cogrinding with various siliceous materials. Thus, the chemical composition in terms of C/S ratio could be adjusted over a broad range (1–3). In this study the synthesis of a previously unknown cementitious material produced via the combination of mechanical activation in a laboratory mill and thermal treatment of a mixture of quartz and hydrothermally synthesized calcium silicate hydrates: α‐Ca2[HSiO4](OH) (α‐C2SH) and Ca6[Si2O7](OH)6 (jaffeite) are reported. It forms independently of the type of mill used (eccentric vibrating mill, vibration grinding mill) after thermal treatment of the ground materials at 360°C–420°C. The new material is X‐ray amorphous and possesses a CaO/SiO2 ratio of 2. A characteristic feature in regards to the silicate anionic structure is the increased silicate polymerization (up to 27% Si2O7 dimers) as revealed by the trimethylsilylation method. Infrared (IR) spectra show a very broad absorption band centered at about 935 cm−1. Another characteristic feature is the presence of ~2.5 wt% H2O as shown by thermogravimetry (TG) coupled with IR spectroscopy. As this water is bound mostly as hydroxyl to Ca, we refer to this new cementitious material as calcium‐oxide–hydroxide–silicate (C–CH–S). Calorimetric measurements point to a very high hydraulic reactivity which is beyond that for typical C2S materials. The influence of the type of grinding on the thermal behavior of α‐C2SH upon its transformation into water‐free Ca2SiO4 modifications is discussed.
Control of Oxygen Permeability in Alumina under Oxygen Potential Gradients at High Temperature by Dopant Configurations
Authors: Kitaoka Satoshi , Matsudaira Tsuneaki , Wada Masashi , Saito Tomohiro , Tanaka Makoto , Kagawa Yutaka 
Published: April 2014

The oxygen permeability of polycrystalline α‐alumina wafers, which served as models for alumina scales on alumina‐forming alloys, under steep oxygen potential gradients () was evaluated at 1873 K. Oxygen permeation occurred by the grain‐boundary (GB) diffusion of oxygen from the higher‐oxygen‐partial‐pressure () surface to the lower‐ surface, along with the simultaneous GB diffusion of aluminum in the opposite direction. The fluxes of oxygen and aluminum at the outflow side of the wafer were significantly larger than at the inflow side. Furthermore, Lu and Hf segregation at the GBs selectively reduced the mobility of oxygen and aluminum, respectively. A wafer with a bilayer structure, in which a Lu‐doped layer was exposed to a lower and an Hf‐doped layer was exposed to a higher , decreased the oxygen permeability. When the sign of was reversed, however, the oxygen permeability of the wafer was comparable to that of a nondoped wafer. Co‐doping with both Lu and Hf markedly increased the oxygen permeation, presumably because the Lu‐stabilized HfO2 particles that were segregated at the GBs acted as extremely fast diffusion paths for oxygen through the large number of oxygen vacancies introduced by the solid solution of Lu in the particles.
Maintaining Unity – relatives in older patients' fast‐track treatment programmes. A grounded theory study
Authors: Berthelsen Connie Bøttcher , Lindhardt Tove , Frederiksen Kirsten 
Published: April 2014

AbstractAimTo generate a substantive grounded theory of relatives' pattern of behaviour in older patients' fast‐track treatment programmes during total hip or knee replacement.BackgroundFast‐track treatment programmes are designed to make total hip and knee replacements more efficient through recovery improvements. The support of relatives during older patients' trajectory is important. However, knowledge is needed on the relatives' pattern of behaviour to strengthen their involvement in fast‐track treatment programmes.DesignWe used a Glaserian grounded theory approach based on a systematic generation of theory from data to explain the latent pattern of behaviour of relatives.MethodsData were collected from 2010–2011 in orthopaedic wards at two Danish university hospitals and consisted of 14 non‐participant observations, 14 postobservational interviews and five interviews. Seven relatives of patients over 70 years of age participated. The constant comparative method was the guiding principle for simultaneous data collection, data analysis and coding, while theoretically sampling and writing memos.FindingsMaintaining Unity emerged as the relatives' pattern of behaviour through which they resolved their main concern: preventing the patients from feeling alone. The relatives resolved their main concern through three interchangeable behavioural modes: Protecting Mode, by providing loving and respectful support; Substituting Mode, with practical and cognitive support; and an Adapting Mode, by trying to fit in with the patients' and health professionals' requirements.ConclusionThe substantive theory of Maintaining Unity offers knowledge of relatives' strong desire to provide compassionate and loving support for the older patients during fast‐track treatment programmes.
Assessing model sensitivity in ancestral area reconstruction using Lagrange: a case study using the Colchicaceae family
Authors: Chacón Juliana , Renner Susanne S. 
Published: April 2014

AbstractAimLikelihood analyses of ancestral ranges require a parameterized model that consists of a time‐calibrated phylogeny, an ‘adjacency matrix’ of allowed or forbidden area connections, and an ‘area–dispersal’ matrix with probabilities for discrete periods of time. The approach is implemented in the software Lagrange. Because it can incorporate information about past continental positions, the approach has been used in historical biogeographical studies of relatively old clades. Surprisingly, no study has evaluated the interactions among these input matrices. Here we use the lily family Colchicaceae and artificial data to study the relative effect of the input matrices on final estimates.LocationAfrica, Australia, Eurasia, North America and South America.MethodsUsing eight plastid, mitochondrial and nuclear DNA regions from 85 of the c. 280 species of Colchicaceae (representing all genera and the entire geographical range) and relevant outgroups, we obtained a well‐resolved phylogeny dated with a molecular clock. We then assigned species to six geographical distributions and carried out 22 Lagrange runs in which we modified the adjacency and dispersal matrices, the latter with zero, two or four time periods and one, three or five dispersal probabilities. For a second data set, the areas at deep nodes in the empirical tree were modified by shuffling species distributions. Models were compared based on global log‐likelihoods.ResultsThe adjacency matrix strongly determined the outcome, while time slices and dispersal probability categories had minor effects. Ancestral areas reconstructed at most nodes were unaffected by the different input matrices. Colchicaceae are likely to have originated in Cretaceous East Gondwana, initially diversified in Australia (c. 67 Ma), reached southern Africa during the Palaeocene–Eocene, and from there extended their range to Southeast Asia (probably through Arabia) and then North America (through Beringia).Main conclusionsAt least in small data sets, Lagrange models should be tested with sensitivity analyses as carried out here, concentrating on constrained versus unconstrained adjacency matrices, and it should be good practice to report the set‐up of both input matrices, not just the dispersal matrix, which is the less decisive of the two.
Predictors of digital competence in 7th grade: a multilevel analysis
Authors: Hatlevik O.E. , Ottestad G. , Throndsen I. 
Published: April 2014

AbstractSince 2006, the ability to use information and communication technology (ICT) has been included as a key competence in the curriculum inNorway, and specific competence aims are developed for most grades. The aim of this study was to identify students' ability to useICTaccording to the competence aims, and to examine factors that can predict students' digital competence. A sample of 1793 students and 125 school leaders from 125 schools was used. The findings show variation in digital competence both between students and between schools. Results from a multilevel analysis showed that higher levels of mastery orientation and self‐efficacy (i.e., motivation) and the students' family background (i.e., language integration and the number of books at home) were predictors of students' levels of digital competence. Additionally, when school leaders reported higher levels of culture for professional development among the teachers at school, increased levels of digital competence were found among students. Challenges for schools and teachers to support students' motivation and to emphasize digital inclusion still prevail.
Challenges to human uniqueness: bipedalism, birth and brains
Authors: Roberts A. M. , Thorpe S. K. S. 
Published: April 2014

AbstractHistorically, paleoanthropology has focused on explaining human uniqueness. This review paper highlights several recent challenges to key features that have been considered to be exclusive to hominins, testing three long‐standing theories in evolutionary anthropology. The knuckle‐walking quadrupedalism model describes the evolution of modern gorillines, panins and hominins from a common, knuckle‐walking ancestor. But the homology of knuckle‐walking in African apes has been questioned. Although habitual bipedalism is unique to humans, it may have developed from occasional bipedalism in ancestors, without a quadrupedal stage. The obstetric dilemma seeks to explain the helplessness of human infants. The timing of human birth is seen as uniquely constrained by fetal head size and maternal pelvic width. An alternative hypothesis suggests that birth occurs when fetal demand for energy threatens to exceed maternal supply; this mechanism also appears to operate in other mammals. The expensive tissue hypothesis suggests that the expansion of energy‐hungry brain tissue in hominins was offset by a reduction in gut tissue. But although large brains are correlated with both good quality diets and relatively short guts in primates, the causes of this correlation are not clear. An alternative suggestion is that the large human brain is paid for by savings in other functions, such as locomotion and reproduction, and that a concurrent expansion of low‐cost adipose tissue in humans keeps metabolic rate low. In the past, paleoanthropology may have focused on defining a boundary between humans and animals, but recent research has seen a shift of focus to exploring humans as animals. Aspects of bipedalism, birth and brains have been considered to be exclusively human, but in the last few years even these have been eroded. It is the package of features that characterizes Homo sapiens that is unique.
An overview of the utility of population simulation software in molecular ecology
Authors: Hoban Sean 
Published: April 2014

AbstractStochastic simulation software that simultaneously model genetic, population and environmental processes can inform many topics in molecular ecology. These include forecasting species and community response to environmental change, inferring dispersal ecology, revealing cryptic mating, quantifying past population dynamics, assessing in situ management options and monitoring neutral and adaptive biodiversity change. Advances in population demographic–genetic simulation software, especially with respect to individual life history, landscapes and genetic processes, are transforming and expanding the ways that molecular data can be used. The aim of this review is to explain the roles that such software can play in molecular ecology studies (whether as a principal component or a supporting function) so that researchers can decide whether, when and precisely how simulations can be incorporated into their work. First, I use seven case studies to demonstrate how simulations are employed, their specific advantage/necessity and what alternative or complementary (nonsimulation) approaches are available. I also explain how simulations can be integrated with existing spatial, environmental, historical and genetic data sets. I next describe simulation features that may be of interest to molecular ecologists, such as spatial and behavioural considerations and species' interactions, to provide guidance on how particular simulation capabilities can serve particular needs. Lastly, I discuss the prospect of simulation software in emerging challenges (climate change, biodiversity monitoring, population exploitation) and opportunities (genomics, ancient DNA), in order to emphasize that the scope of simulation‐based work is expanding. I also suggest practical considerations, priorities and elements of best practice. This should accelerate the uptake of simulation approaches and firmly embed them as a versatile tool in the molecular ecologist's toolbox.
Can frequent precipitation moderate the impact of drought on peatmoss carbon uptake in northern peatlands?
Authors: Nijp Jelmer J. , Limpens Juul , Metselaar Klaas , van der Zee Sjoerd E. A. T. M. , Berendse Frank , Robroek Bjorn J. M. 
Published: April 2014

Summary

Northern peatlands represent a large global carbon store that can potentially be destabilized by summer water table drawdown. Precipitation can moderate the negative impacts of water table drawdown by rewetting peatmoss (Sphagnum spp.), the ecosystem's key species. Yet, the frequency of such rewetting required for it to be effective remains unknown. We experimentally assessed the importance of precipitation frequency for Sphagnum water supply and carbon uptake during a stepwise decrease in water tables in a growth chamber.

CO2 exchange and the water balance were measured for intact cores of three peatmoss species (Sphagnum majus, Sphagnum balticum and Sphagnum fuscum) representative of three hydrologically distinct peatland microhabitats (hollow, lawn and hummock) and expected to differ in their water table–precipitation relationships.

Precipitation contributed significantly to peatmoss water supply when the water table was deep, demonstrating the importance of precipitation during drought. The ability to exploit transient resources was species‐specific; S. fuscum carbon uptake increased linearly with precipitation frequency for deep water tables, whereas carbon uptake by S. balticum and S. majus was depressed at intermediate precipitation frequencies.

Our results highlight an important role for precipitation in carbon uptake by peatmosses. Yet, the potential to moderate the impact of drought is species‐specific and dependent on the temporal distribution of precipitation.
A consistent occupancy–climate relationship across birds and mammals of the Americas
Authors: Boucher‐Lalonde Véronique , Morin Antoine , Currie David J. 
Published: April 2014

At broad spatial scales, species richness is strongly related to climate. Yet, few ecological studies attempt to identify regularities in the individual species distributions that make up this pattern. Models used to describe species distributions typically model very complex responses to climate. Here, we test whether the variability in the distributions of birds and mammals of the Americas relates to mean annual temperature and precipitation in a simple, consistent way. Specifically, we test if simple mathematical models can predict, as a first approximation, the geographical variation in individual species’ probability of occupancy for 3277 non‐migratory bird and 1659 mammal species. We find a Gaussian model, where the probability of occupancy of a 104 km2 quadrat decreases symmetrically and gradually around a species ‘optimal’ temperature and precipitation, was generally the best model, explaining an average of 35% of the deviance in probability of occupancy. The inclusion of additional terms had very small and idiosyncratic effects across species. The Gaussian occupancy–climate relationship appears general among species and taxa and explains nearly as much deviance as complex models including many more parameters. Therefore, we propose that hypotheses aiming to explain the broad‐scale distribution of species or species richness must also predict generally Gaussian occupancy–climate relationships.SynthesisScience aims to identify regularities in a complex natural world. General patterns should be identified before one searches for potential mechanisms and contingencies. However, species geographic distributions are often modelled as complex (sometimes black box), species‐specific, functions of their environment. We asked whether a simple model could account for as much of the geographic variation in a species' probability of occupancy, and be widely applicable across thousands of species. As a first approximation, we found that a simple Gaussian occupancy‐climate relationship is very common in Nature, whether it be causal or not.
Ectopic wisdom tooth at the mandibular ascending ramus
Authors: Kansy K. , Gander E. , Staff C. , Hoffmann J. , Freier K. 
Published: April 2014

AbstractTwenty to thirty per cent of wisdom teeth are partially or completely retained. A displacement of such teeth into the ascending ramus of the mandible is far less frequent with few reported cases in the literature. The case of a young lady and a review of the literature are presented. A 27‐year‐old woman was referred to the specialist department by her dentist. At the age of 22, a panoramic radiograph had been taken for an agenesis of the patient's lower left second molar. At this time, the lower left third molar was situated slightly submucosally at the angle of the mandible. In the present radiograph, the tooth had migrated into the ascending ramus of the mandible. Clinically, there was no pain, sensation disorder, disturbed occlusion, limited mouth opening or any other complaint. Due to significant tooth migration within the last 6 years, operative removal of the displaced tooth was recommended. Computed tomography showed that the distal root was in direct relation with the inferior alveolar nerve. Treatment was performed via a transoral approach. Post‐operative follow‐up was uneventful. This case stresses the importance of long‐time follow‐up of retained teeth and their immense potential for migration.