bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Tutorial on Multilevel Survival Analysis: Methods, Models and Applications
Authors: Austin Peter C. 
Published: March 2017

SummaryData that have a multilevel structure occur frequently across a range of disciplines, including epidemiology, health services research, public health, education and sociology. We describe three families of regression models for the analysis of multilevel survival data. First, Cox proportional hazards models with mixed effects incorporate cluster‐specific random effects that modify the baseline hazard function. Second, piecewise exponential survival models partition the duration of follow‐up into mutually exclusive intervals and fit a model that assumes that the hazard function is constant within each interval. This is equivalent to a Poisson regression model that incorporates the duration of exposure within each interval. By incorporating cluster‐specific random effects, generalised linear mixed models can be used to analyse these data. Third, after partitioning the duration of follow‐up into mutually exclusive intervals, one can use discrete time survival models that use a complementary log–log generalised linear model to model the occurrence of the outcome of interest within each interval. Random effects can be incorporated to account for within‐cluster homogeneity in outcomes. We illustrate the application of these methods using data consisting of patients hospitalised with a heart attack. We illustrate the application of these methods using three statistical programming languages (R, SAS and Stata).
C–(N)–S–H and N–A–S–H gels: Compositions and solubility data at 25°C and 50°C
Authors: Gomez‐Zamorano Lauren , Balonis Magdalena , Erdemli Bartu , Neithalath Narayanan , Sant Gaurav 
Published: March 2017

AbstractCalcium silicate hydrates containing sodium [C–(N)–S–H], and sodium aluminosilicate hydrates [N–A–S–H] are the dominant reaction products that are formed following reaction between a solid aluminosilicate precursor (eg, slags, fly ash, metakaolin) and an alkaline activation agent (eg NaOH) in the presence of water. To gain insights into the thermochemical properties of such compounds, C–(N)–S–H and N–A–S–H gels were synthesized with compositions: 0.8≤Ca/Si≤1.2 for the former, and 0.25≤Al/Si≤0.50 (atomic units) for the latter. The gels were characterized using thermogravimetric analysis (TGA), scanning electron microscopy with energy‐dispersive X‐ray microanalysis (SEM‐EDS), and X‐ray diffraction (XRD). The solubility products (KS0) of the gels were established at 25°C and 50°C. Self‐consistent solubility data of this nature are key inputs required for calculation of mass and volume balances in alkali‐activated binders (AABs), and to determine the impacts of the precursor chemistry on the hydrated phase distributions; in which, C–(N)–S–H and N–A–S–H compounds dominate the hydrated phase assemblages.
The effect of glass composition on the reactivity of synthetic glasses
Authors: Schöler Axel , Winnefeld Frank , Haha Mohsen Ben , Lothenbach Barbara 
Published: March 2017

AbstractThe reactivity of synthetic glasses depends on their chemical compositions. In far from equilibrium dissolution experiments, the reactivity of Ca‐rich glasses with compositions similar to blast‐furnace slag is found to be much higher (up to ~60 wt.% after 7 days) compared to Si‐rich glasses with compositions similar to type F fly ash (up to ~20 wt.% after 7 days). Isothermal calorimetry and TGA experiments conducted on model systems containing portlandite and calcite and on glass‐blended Portland cement confirmed the higher reactivity of the Ca‐rich glasses. The degree of glass reaction after 91 days ranged from 7 to 20 wt.%. The results showed also a higher reactivity of the glasses containing more aluminum (both for Ca‐rich and Si‐rich glasses) indicating that not only calcium but also aluminum acted rather as network modifier than as network former. The results confirm a strong dependence of the glass reactivity on the degree of polymerization of the glass network.
Bottom‐up vs reactive sintering of Al2O3–YAG–YSZ composites via one or three‐phase nanoparticles (NPs). Bottom‐up processing wins this time
Authors: Taylor Nathan J. , Stangeland‐Molo Sandra , Laine Richard M. 
Published: March 2017

AbstractThe bottom‐up approach describes the synthesis of bulk materials from the finest possible length scales to obtain the best global properties. This approach was adapted to the synthesis of multi‐phase ceramic composites produced from metal oxides produced by liquid‐feed flame spray pyrolysis (LF‐FSP). The effect of length scale of mixing was tested through two processing schemes, mixed single metal‐oxide nanopowders (NPs) and nanocomposite NPs having the desired composition within single particles. For the Al2O3–Y2O3–ZrO2 ternary system, composites prepared from nanostructured nanoparticles sinter to finer grain sizes (<410 nm) at equivalent densities of 95%TD than those prepared from mixed nanoparticle processing. These contrast with our previous studies in this area where mixed NP processing gave the best or equivalent results. The nanocomposite NPs produced in this study exhibit novel nanostructures with three phases contained within single particles <26 nm average particle size (APS). This nanostructure may directly explain the enhanced sintering of the nanocomposite NPs and may provide an impetus for future synthesis of similarly structured NPs.
High‐temperature structural stability of ceria‐based inverse opals
Authors: Casillas Danielle C. , Wilkinson Dan C. , Lai Chun‐Han , Wilke Stephen K. , Ignatowich Michael J. , Haile Sossina M. , Dunn Bruce S. 
Published: March 2017

AbstractThe use of ceria‐based inverse opals as a catalyst system for the thermochemical production of fuels from sunlight offers the potential of improved fuel production kinetics over materials with random porosity. Quantitative methods for characterizing ordered porosity are lacking, thus limiting the ability to predict the lifetime of ordered structures at elevated temperatures. In the present work, Fourier transform image analysis was used to determine the effect of composition and temperature on ordered porosity for a series of CeO2‐ZrO2 inverse opals having pore sizes ranging from 300 nm to 1 μm. An order parameter, γ, derived from the image analysis, was applied to scanning electron microscopy images and used to determine the degree of order in the inverse opal. The thermal stability studies indicate that loss of ordered porosity is highly dependent on temperature and that gas cycling effects have a minor effect on periodicity. A minimum Zr content of 20 at.% is necessary to retain periodicity for annealing up to 1000°C with pore diameters larger than 1 μm. These results show that CeO2‐ZrO2 inverse opals can be used at higher temperatures than previously thought for efficient thermochemical hydrogen production without loss of the benefits associated with ordered porosity.
Hydroxyapatite‐barium titanate piezocomposites with enhanced electrical properties
Authors: Prakasam Mythili , Albino Marjorie , Lebraud Eric , Maglione Mario , Elissalde Catherine , Largeteau Alain 
Published: March 2017

AbstractThe present work aims to obtain Hydroxyapatite (HA) ‐ Barium Titanate (BT) piezocomposites with improved electrical properties by retaining OH− ions and tuning BT grain size. Dense piezocomposites of HA‐BT were obtained, using single step Spark Plasma Sintering. The presence of OH− ions in the sintered piezocomposites of HA‐BT was confirmed by thermal characterization and Fourier transform infrared transmittance. No decomposition/interaction between HA and BT phases were observed in the complete range of temperature studied. The dielectric and pyroelectric properties were studied as a function of temperature (100 K to 450 K) and frequency (100 Hz to 2 MHz). The influence of the ferroelectric grain size (300 and 500 nm) on the electrical properties of HA‐BT has been analyzed. The dielectric permittivity of HA‐BT ceramics can be enhanced with appropriate ferroelectric grain size and volume fraction of BT (<80%).
Microwave dielectric properties of SnO‐SnF2‐P2O5 glass and its composite with alumina for ULTCC applications
Authors: Induja Indira J. , Sebastian Mailadil T. 
Published: March 2017

AbstractUltralow‐temperature sinterable alumina‐45SnF2:25SnO:30P2O5 glass (Al2O3‐SSP glass) composite has been developed for microelectronic applications. The 45SnF2:25SnO:30P2O5 glass prepared by melt quenching from 450°C has a low Tg of about 93°C. The SSP glass has εr and tanδ of 20 and 0.007, respectively, at 1 MHz. In the microwave frequency range, it has εr=16 and Qu × f=990 GHz with τf=−290 ppm/°C at 6.2 GHz with coefficient of thermal expansion (CTE) value of 17.8 ppm/°C. A 30 wt.% Al2O3‐70 wt.% SSP composite was prepared by sintering at different temperatures from 150°C to 400°C. The crystalline phases and dielectric properties vary with sintering temperature. The alumina‐SSP composite sintered at 200°C has εr=5.41 with a tanδ of 0.01 (1 MHz) and at microwave frequencies it has εr=5.20 at 11 GHz with Qu × f=5500 GHz with temperature coefficient of resonant frequency (τf)=−18 ppm/°C. The CTE and room‐temperature thermal conductivity of the composite sintered at 200°C are 8.7 ppm/°C and 0.47 W/m/K, respectively. The new composite has a low sintering temperature and is a possible candidate for ultralow‐temperature cofired ceramics applications.
Microstructure and mechanical properties of TaC ceramics with 1–7.5 mol% Si as sintering aid
Authors: Geng Guihong , Liu Limeng , Wang Yujin , Hai Wanxiu , Sun Wenzhou , Chen Yuhong , Wu Laner 
Published: March 2017

AbstractMetallic Si as sintering aid was effective in densifying tantalum carbide ceramic (TaC) by spark plasma sintering (SPS) at 1700°C. Full density was reached at 5.0 mol% Si addition (equivalent to 1.088% Si in weight) and above. Enhanced densification of TaC ceramic with Si was associated with decrease in oxygen content from ~0.24 wt% in TaC powder to ~0.03 wt% in consolidated specimen. Rest of the oxygen species was collected at multigrain conjunctions to form SiO2‐based liquid at high temperatures. Upon cooling, Ta, Si, O, and C dissolving in the liquid precipitated minor phases of TaSix and SiC of low concentrations. Microstructure of TaC ceramics was refined by the Si addition, with average grain size decreasing from 11±8 μm at 1.0 mol% Si to 3±2 μm at 7.5 mol% Si addition. Ta solute in SiC and Si solute in TaC were evidenced. TaC ceramic containing 7.5 mol% Si had a relatively good flexural strength and fracture toughness of 646±51 MPa and 5.0 MPa·m1/2, respectively.
Enhanced magnetic and dielectric properties of Ti‐doped YFeO3 ceramics
Authors: Madolappa Shivanand , Ponraj Bharathi , Bhimireddi Rajasekhar , Varma Kalidindi B. R. 
Published: March 2017

AbstractPolycrystalline YFeO3 (YFO) and YFe1−(4/3)xTixO3(YFTO) ceramics were prepared using the powder synthesized from the sol‐gel route. X‐ray diffraction analyses of the polycrystalline ceramics revealed the crystallization of the phase in orthorhombic crystal structure associated with the space group Pnma. The magnetization versus magnetic field hysteresis loops were obtained at room temperature for YFO and YFTO ceramics. The magnetic property changes from weak ferromagnetic in YFO to ferromagnetic in YFTO ceramics. The dielectric constant recorded at room temperature for YFTO ceramics was six times higher than that of YFO, whereas the dielectric loss gets reduced to 0.06 from 0.3 for YFO at 1 kHz. Impedance spectroscopy study carried out on YFO and YFTO ceramics confirmed the existence of non‐Debye‐type relaxation. Observed single semicircle in Z′ vs −Z′′ plot established the incidence of intrinsic (bulk) effect and ruled out any grain boundary or electrode effects. The mechanism for the dielectric relaxation and electrical conduction process observed in YFO and YFTO ceramics was discussed by invoking electric modulus formalisms. Activation energy obtained by ac conductivity study suggested that the conduction process in YFO was linked up with the existence of the polaron and oxygen vacancies, whereas only oxygen vacancies contribute to the conduction process in YFTO ceramics.
Commentary: What makes a life go well? Moral functioning and quality of life measurement in neurodevelopmental disorders – reflections on Jonsson et al. (2017)
Authors: Singh Ilina 
Published: March 2017

Jonsson et al.'s excellent review of the literature on quality of life (QoL) and childhood mental and behavioural disorders (Jonsson et al., ) highlights the need for studies that utilise child self‐reported QoL, in contrast to parent or proxy QoL measures, and further challenges the field to develop QoL measures that ‘put the child's own views and priorities first’.
A simple self‐diagnosis tool to assess the prevalence of dermatoporosis in France
Authors: Saurat J.‐H. , Mengeaud V. , Georgescu V. , Coutanceau C. , Ezzedine K. , Taïeb C. 
Published: March 2017

AbstractImportanceThe term dermatoporosis has been proposed to describe clinical signs and functional consequences of age‐related extreme skin fragility.ObjectiveTo create a simple dermatoporosis self‐diagnosis tool (IDA: Index Dermatoporosis Assessment) and to use this tool to estimate the prevalence of dermatoporosis in France.Design, setting and participantsA specific dermatoporosis questionnaire was developed with the help of senior dermatologists and survey experts. This questionnaire was submitted to consecutive individuals aged ≥65 years who consulted a dermatologist. At the end of the consultation, the dermatologist was asked to assess ‘whether or not’ dermatoporosis was present. In a second step, the final questionnaire was mailed to a representative sample of the French population aged ≥65 years in order to estimate the prevalence of dermatoporosis.ResultsThe initial questionnaire, consisting of two modules (24 questions), was validated in 173 individuals aged ≥65 years) during a dermatologist consultation. Dermatologists diagnosed 46% of the individuals with dermatoporosis. The final validated questionnaire consisted of 14 items, 12 consisting in presence or absence of clinical signs and two items consisting of the self‐assessment by individuals of skin ageing on neckline and hands (none/moderate/significant/very significant). A scoring system was generated to quote quantitatively dermatoporosis (from 0 if no sign of dermatoporosis to 20 maximal dermatoporosis). The area under the receiver operator curve was 0.8535, indicating a very good ability of the questionnaire to differentiate between individuals. A cut‐off value of 11 was linked to positive and negative predictive values of 0.78 and 0.81, respectively. In a second step, using the questionnaire in a representative sample of the French population (n = 533), the estimated overall prevalence of dermatoporosis was 37.5% in French subjects aged ≥65 years [27.5% (males) vs. 43.9% (females); P < 0.05]. The estimated prevalence of dermatoporosis was twice higher in subjects with eczema or atopic dermatitis during childhood than in the population without dermatoporosis (60.6% vs. 33.4%, P < 0.001). Individuals with dermatoporosis also reported a higher prevalence of itching, long‐term corticosteroid use, anticoagulant use and prior sun exposure.Conclusions and relevanceUsing a new simple dermatoporosis self‐diagnosis tool, this study provides a previously unprecedented insight into the high prevalence of dermatoporosis in elderly individuals. IDA questionnaire is a short (14‐item) and easy to use tool for evaluating dermatoporosis in adults and may allow an easy evaluation of each subject.
Overexpression of Drosha, DiGeorge syndrome critical region gene 8 (DGCR8), and Dicer mRNAs in the pathogenesis of psoriasis
Authors: Rostami Mogaddam Majid , Safavi Ardabili Nastaran , Shafaeei Yousef , Maleki Nasrollah , Jafari Naser , Jafari Alireza 
Published: March 2017

SummaryIntroductionPsoriasis is a complex autoimmune inflammatory disease that occurs in genetically susceptible individuals and presents with the development of inflammatory plaques on the skin. Recent studies have indicated that microRNAs (miRNAs) play important roles in psoriasis.ObjectiveTo investigate whether expression of Drosha, DGCR8, and Dicer mRNAs is involved in the pathogenesis of psoriasis.MethodsBiopsies were obtained from involved psoriatic skin (PP), noninvolved psoriatic skin (PN), and healthy skin (NN). Expression of Drosha, Dicer, and DGCR8 was assessed with real‐time quantitative real‐time PCR in 25 patients with psoriasis and 25 healthy volunteers.ResultsWe observed that expression levels of Drosha, Dicer, and DGCR8 were upregulated in patients with psoriasis compared to the control group. However, the Drosha and Dicer expression levels were higher in PP tissues and PN tissues compared to NN tissues, but they were more upregulated in PP tissues compared to PN tissues (P<.001). Although the DGCR8 expression was higher in PP tissues and PN tissues compared to NN tissues, it was more upregulated in PN tissues compared to PP tissues (P<.001).ConclusionOur data demonstrate that upregulated expression of Drosha, DGCR8, and Dicer mRNAs may be involved in the pathogenesis of psoriasis.
Real‐world experience with the all‐oral, interferon‐free regimen of ombitasvir/paritaprevir/ritonavir and dasabuvir for the treatment of chronic hepatitis C virus infection in the German Hepatitis C Registry
Authors: Welzel T. M. , Hinrichsen H. , Sarrazin C. , Buggisch P. , Baumgarten A. , Christensen S. , Berg T. , Mauss S. , Teuber G. , Stein K. , Deterding K. , van Bömmel F. , Heyne R. , John C. , Zimmermann T. , Lutz T. , Schott E. , Hettinger J. , Kleine H. , König B. , Hüppe D. , Wedemeyer H. 
Published: March 2017

SummaryReal‐world studies are relevant to complement clinical trials on novel antiviral therapies against chronic hepatitis C; however, clinical practice data are currently limited. This study investigated effectiveness and safety of ombitasvir/paritaprevir/ritonavir (OBV/PTV/r)±dasabuvir (DSV)±ribavirin (RBV) for treatment of HCV genotype (GT) 1 and GT4 infection in a large real‐world cohort. The German Hepatitis C Registry is an observational cohort study prospectively collecting clinical practice data on direct‐acting antiviral therapies. Patients with GT1/4 infection treated with OBV/PTV/r±DSV±RBV were analysed. Effectiveness was assessed by sustained virologic response in 558 patients who reached post‐treatment week 12 (SVR12). Safety is reported in 1017 patients who initiated treatment. Of the patients, 892 (88%) had GT1 and 125 (12%) had GT4 infection. Prior treatment experience and cirrhosis were reported in 598 (59%) and 228 (22%) patients, respectively. Overall, SVR12 (mITT) was 96% (486/505) in GT1‐ and 100% (53/53) in GT4 patients. SVR12 rates were high across subgroups including patients with cirrhosis (95%, 123/129), patients with moderate to severe renal impairment (100%, 34/34), and subgroups excluded from registrational trials like patients ≥70 years (96%, 64/67) and failures to prior protease inhibitor treatment (96%, 46/48). Adverse events (AEs) and serious AEs were reported in 52% (525/1017) and 2% (21/1017) of patients, respectively, and led to treatment discontinuation in 1.5% (15/1017) of patients. OBV/PTV/r±DSV±RBV was effective and generally well tolerated for treatment of HCV infection in clinical practice.
On Maximum Likelihood Estimation of Dynamic Panel Data Models
Authors: Bun Maurice J.G. , Carree Martin A. , Juodis Artūras 
Published: March 2017

AbstractWe analyse the finite sample properties of maximum likelihood estimators for dynamic panel data models. In particular, we consider transformed maximum likelihood (TML) and random effects maximum likelihood (RML) estimation. We show that TML and RML estimators are solutions to a cubic first‐order condition in the autoregressive parameter. Furthermore, in finite samples both likelihood estimators might lead to a negative estimate of the variance of the individual‐specific effects. We consider different approaches taking into account the non‐negativity restriction for the variance. We show that these approaches may lead to a solution different from the unique global unconstrained maximum. In an extensive Monte Carlo study we find that this issue is non‐negligible for small values of T and that different approaches might lead to different finite sample properties. Furthermore, we find that the Likelihood Ratio statistic provides size control in small samples, albeit with low power due to the flatness of the log‐likelihood function. We illustrate these issues modelling US state level unemployment dynamics.
Cardinal and anti‐cardinal points, equalities and chromatic dependence
Authors: Evans Tanya , Harris William F. 
Published: March 2017

AbstractPurposeCardinal points are used for ray tracing through Gaussian systems. Anti‐principal and anti‐nodal points (which we shall refer to as the anti‐cardinal points), along with the six familiar cardinal points, belong to a much larger set of special points. The purpose of this paper is to obtain a set of relationships and resulting equalities among the cardinal and anti‐cardinal points and to illustrate them using Pascal's ring.MethodsThe methodology used relies on Gaussian optics and the transference T. We make use of two equations, obtained via the transference, which give the locations of the six cardinal and four anti‐cardinal points with respect to the system. We obtain equalities among the cardinal and anti‐cardinal points. We utilise Pascal's ring to illustrate which points depend on frequency and their displacement with change in frequency.ResultsPascal described a memory schema in the shape of a hexagon for remembering equalities among the points and illustrating shifts in these points when an aspect of the system changes. We modify and extend Pascal's ring to include the anti‐cardinal points. We make use of Pascal's ring extended to illustrate which points are dependent on the frequency of light and the direction of shift of the equalities with change in frequency. For the reduced eye the principal and nodal points are independent of frequency, but the focal points and the anti‐cardinal points depend on frequency. For Le Grand's four‐surface model eye all six cardinal and four anti‐cardinal points depend on frequency. This has implications for definitions, particularly of chromatic aberrations of the eye, that make use of cardinal points and that themselves depend on frequency.ConclusionsPascal's ring and Pascal's ring extended are novel memory schema for remembering the equalities among the cardinal and anti‐cardinal points. The rings are useful for illustrating changes among the equalities and direction of shift of points when an aspect of a system changes. Care should be taken when defining concepts that rely on cardinal points that depend on frequency.