bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of α-Alumina Powder Obtained from Irradiated Pseudoboehmites
Authors: Munhoz Antonio H. , Peres Renato Meneghetti , Faldini Sonia B. , Andrade e Silva Leonardo Gondim , Aguiar Amanda Abati , de Miranda Leila Figueiredo
Published: October 2010

The alumina powder was obtained through a technique based on firing irradiated pseudoboehmites powder to study the radiation effects in the alumina properties. The electron beam radiation effect in a pseudoboehmite produced by sol-gel synthesis was investigated, using aluminum chloride and ammonium hydroxide as precursors. The addition of poly(vinyl alcohol) ([C2H3OH]n) solution (8 wt% in water) was also analyzed. The aluminum chloride solution was mixed with the polyvinyl alcohol and the mixture was dropped into an ammonium hydroxide solution. The work presents the effects of pseudoboehmite radiation in the structure of alumina. The alumina was obtained by pseudoboehmite calcinations. The milky-white colloidal pseudoboehmite precipitate obtained by sol-gel method was filtered, washed with distilled water, dried at 70°C, and powdered in a mortar. The sample acquired was calcined 4 hours at 1100oC, and after that X-ray powder diffraction was performed. The well defined α-alumina crystal was obtained from 1100oC treatment for some samples. The X-ray powder diffraction data shows that in some irradiated samples calcined at 1100o C for four hours presented θ-alumina and -alumina. The powder dried at 70o C was also examined by thermal analysis. The Thermo Gravimetric Analysis (TG) and Differential Thermal analysis (DTA) were used to evaluate mass loss and the pseudoboehmite endothermic and exothermic transformations. The samples were analyzed through scanning electron microscopy technique
Obtaining of Mullite by Rapid Sintering from Bentonite Clay
Authors: Gomes Josileido , Rocha Alysson Israel Oliveira , Menezes Romualdo Rodrigues , Neves Gelmires Araújo , Brasileiro Maria Isabel , de Lima Santana Lisiane Navarro
Published: October 2010

Bentonite clays are aluminium–silicates that when heated turn into mullite. The sintering of mullite obtained from these mineral clays by quick microwaves heating comes up as an alternative process for mullite powders synthesis. The use of quick heating on ceramics nano-powders synthesis is a recent technology that is being successfully used on synthesis with microwaves and synthesis process by combustion. The quick microwaves heating enable adding heat quickly and equally, accelerating the nucleation kinetics and the development of the mullite stage. Thus, the purpose of this work is to analyze the effect of the microwaves heating process variables, analyzing the influence of the applied power and of the heating rate on the mullite powders obtaining from bentonite clays. The clays have been favored and submitted to the following characterizations: chemical granulometric and mineralogically. Subsequently, the clays have been delamined aiming disagglomeration and separation of the thinner fractions and submitted to granulometric and mineralogical characterization. The synthesis has been realized on a domestic microwaves oven. The obtained powders have been characterized by X-ray diffraction. The results showed that the applied power variation and the sintering time are fundamental on the obtaining of mullite powders.
Characterization of Proton Exchange Membrane Fuel Cell Cathode Catalysts Prepared by Alcohol-Reduction Process
Authors: Santoro T.A.B. , Oliveira Neto Almir , Chiba Rubens , Seo Emília Satoshi Miyamaru , Franco E.G.
Published: October 2010

Pt/rare-earth cathode catalysts were synthesized by the alcohol-reduction process and its structure was investigated by transmission electron microscopy (TEM), energy dispersive analyses (EDS), X-ray Diffraction (XRD). The electrochemical behavior of the cathode catalyst was analyzed by cyclic voltammetry (CV) chronoamperommetry (CA).
Synthesis of Ni-Zn Ferrite Catalysts by Combustion Reaction Using Different Fuels
Authors: de Freitas Normanda Lino , Coutinho Juliana Pimentel , Silva Mirele Costa , Lira Hélio Lucena , Kiminami Ruth Herta Goldsmith Aliaga , de Melo Costa Ana Cristina Figueiredo
Published: October 2010

The aim of this work is to evaluate the effect of different fuels in the preparation of Ni-Zn ferrites by combustion reaction. The catalysts were prepared according to the propellants chemistry, in stoichiometric composition, using a vitreous silica container. Carbohydrazine, monohydrated citric acid and glycine fuels were used. During the synthesis parameters as flame combustion time and temperature were measured. The structural and morphological characteristics of the powders were evaluated by XRD, textural analysis by nitrogen adsorption and SEM. The fuel monohydrated citric acid presented the greatest time and temperature of combustion reaction. The results show that the type of fuel changed the final characteristics of the powders. The XRD results showed the formation of Ni-Zn ferrite phase for all fuels used in this study. The powders prepared with carbohydrazine resulted in largest value of surface area. All powders showed morphology constituted by soft agglomerates of nanoparticles.
Synthesis of Fine B4C Powder Using B4C Seeding in Carbothermal Reduction Process
Authors: da Rocha Rosa Maria , de Melo Francisco Cristóvão Lourenço
Published: October 2010

The focus of this work is to investigate the effect of seeding on the synthesis of B4C powder obtained by carbothermal reduction. B4C particles were added to act as seeds during reaction. Starting materials were boric acid (H3BO3) and two different carbon sources (graphite and carbon black). Mixtures of C, B2O3 (25 wt% B2O3 excess in relation to stoichiometric composition) and commercial B4C powder (0, 2.5 and 5.0 wt%) were prepared. The effect of 1.5 wt% of NaCl was also investigated. The powder mixtures were uniaxially die-pressed to form cylindrical shaped green bodies, then placed in a graphite crucible and heated at 1750°C/1h with a heating rate of 30°C/min, under argon-flowing atmosphere. Samples with seeds addition exhibited a decrease in particle size distribution. The particle morphology was uniform with a narrow size distribution and a medium particle size around 6 m regardless the initial concentration of seeds.
Obtaining Tetracalcium Pohosphate and Hydroxyapatite in Powder Form by Wet Method
Authors: de Oliveira Sara Verusca , Fook Marcus Vinícius Lia , Araújo Elaine Patrícia , Medeiros Keila Machado , Rabello Guilherme Portela , Barbosa Renata , Araújo Edcleide Maria
Published: October 2010

The development of research in the area of advanced materials and tissue engineering has increased greatly in recent years found that bioceramics are outstanding in the replacement and regeneration of bone tissue, mainly formed by the calcium phosphate ceramics. The objective of this research is to obtain the calcium phosphate where Ca/P = 1.67 and 2.0, to observe the formation of phases after having subjected these materials to heat treatment. The calcium phosphate was produced by the wet method using a direct reaction of neutralization and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray microanalysis (EDS). The XRD results confirm the presence of hydroxyapatite phase in the sample with Ca/P = 1.67, where as the phosphates prepared with Ca/P = 2.0 ratio show a combination of hydroxyapatite and phase β- tricalcium phosphate. The micrographs obtained are characteristic of ceramic material called calcium phosphate. EDS confirmed the presence of Ca, P and O in the material.
The Effect of Hydrothermal Treatment on Samaria and Gadolinia Doped Ceria Powders Synthesized by Coprecipitation
Authors: Arakaki Alexander Rodrigo , Yoshito Walter Kenji , Ussui Valter , Lazar Dolores Ribeiro Ricci
Published: October 2010

One of the main applications of ceria-based (CeO2) ceramics is the manufacturing of Intermediate Temperature Solid Oxide Fuel Cells electrolytes. In order to improve ionic conductivity and densification of these materials various powder synthesis routes have been studied. In this work powders with composition Ce0.8(SmGd)0.2O1.9 have been synthesized by coprecipitation and hydrothermal treatment. A concentrate of rare earths containing 90wt% of CeO2 and other containing 51% of Sm2O3 and 30% of Gd2O3, both prepared from monazite processing, were used as precursor materials. The powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, agglomerate size distribution by laser scattering and specific surface area by gas adsorption. Ceramic sinterability was evaluated by dilatometry and density measurements by Archimedes method. High specific surface area powders (~100m2/g) and cubic fluorite structure were obtained after hydrothermal treatment around 200°C. Ceramic densification was improved when compared to the one prepared from powders calcined at 800°C.
Study of Crystallite Size of Yttria-Stabilized Zirconia Powders by Rietveld Method
Authors: Leite Wellington Claiton , Chinelatto Adriana Scoton Antonio , Brinatti André Maurício , Ribeiro Mauricio Aparecido , de Andrade André Vitor Chaves , Chinelatto Adilson Luiz
Published: October 2010

The yttria-stabilized zirconia (YSZ) is used in a great variety of applications, for example, electrolytes of solid oxide fuel cells and oxygen sensors. In the study of YSZ, the particle size powders and sintering processes are important to define the final properties of the zirconia products. The objectives of this work were to determine the phases and the crystalline size using X-Ray Diffraction (XRD) data and the Rietveld Method (RM) of the YSZ powders obtained by chemical synthesis based on the Pechini method. It was used ZrOCl2.8H2O and Y(NO3)3.5H2O as precursors reagents. After calcination at 550oC during 24 hours, the powder was analyzed by XRD and scanning electronic microscopy (SEM). From XRD and using Rietveld method were verified that there is only cubic phase with lattice parameter a = 5.1307(1) Å and the space group Fm3m. Due to substitution of the Zr atoms in the Y atoms sites, there were vacancies in 17.72 % of O atoms sites. However, the percentage of substitution of Zr atoms in Y atoms sites in the structure not was determinate because the curves of atomic scattering of them are very similar. Using Scherrer equation and considering anisotropy effect, the average crystalline size was determinate: 10,43 nm (c axis) and 10,39 (b axis). This spherical symmetry also observed for SEM.
Synthesis Characterization and Sintering of Cobalt-Doped Lanthanum Chromite Powders for Use in SOFCs
Authors: Yamagata Chieko , de Mello-Castanho Sonia Regina Homem
Published: October 2010

Doped lanthanum chromite is a promising as interconnect material because of its good conductivity at high temperatures and its stability in oxidizing and reducing atmospheres. Perovskite oxide powders of Co-doped lanthanum chromite were synthesized by dispersing precursor metal salt solutions in a polymer matrix followed by a thermal treatment. XRD patterns showed that a highly crystalline cobalt-doped lanthanum chromite was obtained. Fine perovskite powder with a surface area of 6.15 m2 g-1 calcined at 700oC for 1 h, were obtained. After the sample sintered at 1450oC for 3h, the powder reached high densities exceeding 97% of the theoretical density. The proposed here has proved to be a very promising technique for the synthesis of lanthanum chromite powders.
Synthesis of Nickel Oxide - Zirconia Composites by Coprecipitation Route Followed by Hydrothermal Treatment
Authors: Yoshito Walter Kenji , Ussui Valter , Lazar Dolores Ribeiro Ricci , Paschoal José Octavio Armani
Published: October 2010

Nickel oxide-yttria stabilized zirconia (NiO-YSZ) for use as solid oxide fuel cell anode were synthesized by coprecipitation to obtain amorphous zirconia and crystallized β-nickel gels of the corresponding metal hydroxides. Hydrothermal treatment at 200°C and 220 psi from 2 up to 16 hours, under stirring, was performed to produce nanocrystalline powder. The as-synthesized powders were uniaxially pressed and sintered in air. Powders were characterized by X-ray diffraction, laser scattering, scanning and transmission electron microscopy (SEM/TEM), gas adsorption technique (BET) and TG-DTA thermal analysis. Ceramic samples were characterized by dilatometric analysis and density measurements by Archimedes method. The characteristics of hydrothermally synthesized powders and compacts were compared to those produced without temperature and pressure application. Crystalline powders were obtained after hydrothermal process, excluding the calcination step from this route. The specific surface area of powders decreases with increasing time of hydrothermal treatment while the agglomerate mean size is not affected by this parameter.
Hydrothermal Treatment of Coprecipitated YSZ Powders
Authors: Arakaki Alexander Rodrigo , Yoshito Walter Kenji , Ussui Valter , Lazar Dolores Ribeiro Ricci
Published: October 2010

Zirconia stabilized with 8.5 mol% yttria (YSZ) were synthesized by coprecipitation and resulting gels were hydrothermallly treated at 200°C and 220 PSI for 4, 8 and 16 hours. Products were oven dried at 70°C for 24 hours, isostatically pressed as pellets and sintered at 1500 °C for 1 hour. Powders were characterized for surface area with N2 gas adsorption, X-ray diffraction, laser diffraction granulometric analysis and scanning and transmission electronic microscopy. Density of ceramics was measured by an immersion method based on the Archimedes principle. Results showed that powders dried at 70°C are amorphous and after treatment has tetragonal/cubic symmetry. Surface area of powders presented a significant reduction after hydrothermal treatment. Ceramics prepared from hydrothermally treated powders have higher green density but sintered pellets are less dense when compared to that made with powders calcined at 800°C for 1 hour due to the agglomerate state of powders. Solvothermal treatment is a promising procedure to enhance density.
Quantitative Phases Determination of Zirconia Ceramics via Rietveld Method
Authors: Muñoz R.A. , Rodriguez J.E. , Santos C. , Silva Cosme Roberto Moreira
Published: October 2010

Industrial applications of partially stabilized zirconia (PSZ) has increased substantially recently, considering its excellent thermal stability, strength and ionic conductibility. Its main application includes oxygen sensors and fuel cells. In this work zirconia ceramic powder is produced by Pechini process, mixing citric acid and ethylene glycol, adding yttrium and zirconium precursors. All the process was carried out with complete agitation. The obtained powder after this procedure is heat treated at 650°C during two hours. Characterization was performed by infra-red spectroscopy, x-ray diffractometry and quantitative analysis by Rietveld Method. The results show tetragonal and monoclinic phases, with nanometric crystallite.
Effects of Dependence between Solid Solution and Surface Excess in Nanoparticles
Authors: Pereira Gilberto J. , Gouvea Douglas
Published: October 2010

In this work, samples of 10 mol% Mg-doped SnO2 were synthesized by Pechini's method and calcined at 500°C. Previous analysis suggests that the additive is preferentially located on the surface of nanoparticles as a surface excess. Since MgO is highly soluble even in weak acid medium, the samples were "washed" with concentrated nitric acid for a few hours in order to remove Mg from the surface. After the lixiviation, the sample was thermally treated again. This procedure was carried out five times using the same sample, and the dependence between macroscopic properties and surface excess was demonstrated, since it was detected a direct relationship on particle size and isoelectric point on each new washing. Also, a new method to measure surface excess in solids was applied.
Reproductive Technologies and Genomic Selection in Cattle
Authors: Humblot Patrice , Le Bourhis Daniel , Fritz Sebastien , Colleau Jean Jacques , Gonzalez Cyril , Guyader Joly Catherine , Malafosse Alain , Heyman Yvan , Amigues Yves , Tissier Michel , Ponsart Claire
Published: October 2010

The recent development of genomic selection induces dramatic changes in the way genetic selection schemes are to be conducted. This review describes the new context and corresponding needs for genomic based selection schemes and how reproductive technologies can be used to meet those needs. Information brought by reproductive physiology will provide new markers and new improved phenotypes that will increase the efficiency of selection schemes for reproductive traits. In this context, the value of the reproductive techniques including assisted embryo based reproductive technologies (Multiple Ovaluation Embryo Transfer and Ovum pick up associated toin vitroFertilization) is also revisited. The interest of embryo typing is discussed. The recent results obtained with this emerging technology which are compatible with the use of the last generation of chips for genotype analysis may lead to very promising applications for the breeding industry. The combined use of several embryo based reproductive technologies will probably be more important in the near future to satisfy the needs of genomic selection for increasing the number of candidates and to preserve at the same time genetic variability.
The effects of solar radiation on the stability of 3H‐thymidine and 3H‐leucine during bacterioplankton production measurements
Authors: Vaughan Pamela , Bullock Avery , Joux Fabien , Jeffrey Wade H.
Published: October 2010

Whereas [3H]thymidine ([3H]TdR) and [3H]leucine ([3H]leu) are commonly used to measure bacterial production, their stability during ultraviolet radiation (UVR) exposure has been questioned. Because these molecules prove invaluable in studies examining UVR effects on bacterial production, molecule integrity during and after exposure to UVR is critical. The stability of both radiolabeled and non‐radiolabeled leucine and thymidine stability was examined after UVR exposure. Solutions of [3H]TdR and [3H]leu were prepared in deionized water, 0.2 µm‐filtered estuarine and marine waters followed by sunlight exposure for 4 h centered around solar noon. Incorporation of each irradiated substrate by bacterioplankton was then determined in Pensacola Bay and Gulf of Mexico waters and compared with incorporation using nonirradiated replicate [3H]TdR and [3H]leu solutions. Differences in [3H]TdR incorporation rates for irradiated versus nonirradiated compounds were of marginal statistical difference when irradiated in seawater but not in distilled water whereas no statistical differences were observed for [3H]leu. However, nonradiolabeled samples analyzed after solar exposure using high performance liquid chromatography (HPLC) showed no significant difference for irradiated samples versus dark controls. Therefore, UVR exposure has no effect on compound integrity. Furthermore, there is no reason to discontinue use or question results obtained by employing [3H]TdR or [3H]leu during simultaneous exposure and incubation experiments measuring bacterial production. This type of incubation can lead to a more realistic view of the cumulative effect of UVR on bacterial production over the day rather than short incubations performed in the dark following exposure to sunlight.
A Systematic Review of Root Canal Filling Materials for Deciduous Teeth: Is There an Alternative for Zinc Oxide-Eugenol?
Authors: Barja-Fidalgo Fernanda , Moutinho-Ribeiro Michele , Oliveira Maria Angelina Amorim , Oliveira Branca Heloísa de
Published: October 2010

The aim of this systematic review was to determine whether there is a root canal filling for deciduous teeth equally or more effective than zinc oxide-eugenol cement (ZOE). Six clinical trials selected for inclusion were independently reviewed by two researchers. Only two showed statistically significant different success rates between the test and the control groups. One found that an iodoform paste with calcium hydroxide () performed better than ZOE, and the other found that ZOE performed similarly to . The other four studies compared ZOE with an iodoform paste (IP), a calcium hydroxide cement , or . In these trials, the success rates in the ZOE groups were slightly lower than in the other groups. There seems to be no convincing evidence to support the superiority of any material over ZOE, and both ZOE and appear to be suitable as root canal fillings for deciduous teeth.
Liquid Chromatography, 1. Fundamentals, History, Instrumentation, Materials
Authors: Jandera Pavel , Henze Günter
Published: October 2010

The article contains sections titled:1.Introduction1.1.History1.2.Definition and Theoretical Background2.Equipment2.1.Solvent Reservoir, Filters, Degasser and Connecting Tubing2.2.Pumps2.3.Sample Introduction Units2.4.Column Hardware2.5.Detectors2.5.1.Photometric Detectors2.5.2.The Fluorescence Detector2.5.3.Refractive Index (RI) Detectors2.5.4.Light‐Scattering Detectors2.5.5.Electrochemical Detectors2.6.Data Processing Systems3.Packing Materials and Stationary Phases for HPLC3.1.Types and Porosity of Column Packing Materials3.2.Particle Size, Hydrodynamic Aspects of Column Operation3.3.Superficially Porous Particles3.4.Monolithic Columns3.5.Stationary Phases for Liquid Chromatography3.5.1.Silica Gel3.5.2.Metal Oxides3.5.3.Chemically Bonded Phases3.5.4.Carbon Adsorbents3.5.5.Organic Polymer Adsorbents3.5.6.Characterization of HPLC Column Properties4.The Mobile Phase4.1.Purification and Pretreatment of LC Solvents4.2.Selection of Mobile Phase
Liquid Chromatography, 2. Methods, Programmed and Coupling Techniques
Authors: Jandera Pavel , Lembke Peter
Published: October 2010

The article contains sections titled:1.Separation Processes and HPLC Modes1.1.Normal‐Phase Liquid Chromatography (NPLC)1.1.1.Separations on Polar Adsorbents and Chemically Bonded Phases in Nonaqueous Mobile Phases1.1.1.1.Principles of Retention in NPLC1.1.1.2.Structural and Mobile Phase Effects in Nonaqueous NPLC1.1.1.3.Practical Aspects and Application Examples of Nonaqueous NPLC1.1.2.Normal‐Phase Separations of Hydrophilic and Ionic Compounds in Aqueous‐Organic Media ‐ HILIC Mode1.2.Reversed‐Phase Liquid Chromatography (RPLC)1.2.1.Separations of Nonionic Samples1.2.2.Separations of Ionizable Samples with Buffer and Salt Additives1.2.3.Ion‐Pair Chromatography1.2.4.Micellar Chromatography1.3.Ion‐Exchange Chromatography (IEX)1.4.Size‐Exclusion Chromatography (SEC)2.Optimization of Separation Selectivity and Resolution2.1.Optimization of the Column Parameters2.2.Two‐Component (Binary) Mobile Phases2.3.Selectivity Control using Ternary or more Complex Mobile Phases2.4.Computer‐Assisted HPLC Method Development and Optimization3.Programmed and Coupling Techniques3.1.Gradient‐Elution Technique3.2.High‐Temperature and Programmed Temperature HPLC Separations3.3.Column Serial Coupling and Switching3.4.Multidimensional HPLC3.4.1.Peak Capacity and 2D System Orthogonality3.4.2.Off‐Line and In‐Line Heart Cutting Techniques3.4.3.Comprehensive Two‐Dimensional LCxLC3.4.4.Applications of 2D LC‐LC3.5.HPLC– Mass Spectrometry3.5.1.Principles of the HPLC‐MS Technique3.5.2.Instrumentation for HPLC‐MS3.5.3.Applications of LC‐MS3.6.HPLC‐NMR4.Quantitative Analysis4.1External Standard Method4.2.Internal Standard Method4.3.Error Sources in HPLC5.Sample Preparation and Derivatization5.1.Sample Cleanup and Enrichment5.2.Pre‐ and Postcolumn Derivatization5.2.1.Precolumn Derivatization5.2.2.Postcolumn Derivatization
Switching of Ferroelectrics Without Domains
Authors: Scott James F.
Published: October 2010

A discussion of switching in polyvinyl difluoride copolymers is given (see L. Zhang, EPL 2010, 91, 47001) in terms of the general history of ferroelectric switching with and without domain wall participation.
The dystonia gene DYT1 is repressed by the transcription factor THAP1 (DYT6)
Authors: Kaiser Frank J. , Osmanoric Alma , Rakovic Aleksandar , Erogullari Alev , Uflacker Nils , Braunholz Diana , Lohnau Thora , Orolicki Slobodanka , Albrecht Melanie , Gillessen‐Kaesbach Gabriele , Klein Christine , Lohmann Katja
Published: October 2010

Mutations in THAP1 have been associated with dystonia 6. THAP1 encodes a transcription factor with mostly unknown targets. We tested the hypothesis that THAP1 regulates the expression of DYT1 (TOR1A), another dystonia‐causing gene. After characterization of the TOR1A promoter, we demonstrate that THAP1 binds to the core promoter of TOR1A. Further, we report that wild type THAP1 represses the expression of TOR1A, whereas dystonia 6‐associated mutant THAP1 results in decreased repression of TOR1A. Our data demonstrate that THAP1 regulates the transcription of TOR1A, suggesting transcriptional dysregulation as a cause of dystonia. Ann Neurol 2010;68:554–559
Adaptive dose‐finding: Proof of concept with type I error control
Authors: Miller Frank
Published: October 2010

We consider an adaptive dose‐finding study with two stages. The doses for the second stage will be chosen based on the first stage results. Instead of considering pairwise comparisons with placebo, we apply one test to show an upward trend across doses. This is a possibility according to the ICH‐guideline for dose‐finding studies (ICH‐E4). In this article, we are interested in trend tests based on a single contrast or on the maximum of multiple contrasts. We are interested in flexibly choosing the Stage 2 doses including the possibility to add doses. If certain requirements for the interim decision rules are fulfilled, the final trend test that ignores the adaptive nature of the trial (naïve test) can control the type I error. However, for the more common case that these requirements are not fulfilled, we need to take the adaptivity into account and discuss a method for type I error control. We apply the general conditional error approach to adaptive dose‐finding and discuss special issues appearing in this application. We call the test based on this approach Adaptive Multiple Contrast Test. For an example, we illustrate the theory discussed before and compare the performance of several tests for the adaptive design in a simulation study.
Multiple imputation for estimating the risk of developing dementia and its impact on survival
Authors: Yu Binbing , Saczynski Jane S. , Launer Lenore
Published: October 2010

Dementia, Alzheimer's disease in particular, is one of the major causes of disability and decreased quality of life among the elderly and a leading obstacle to successful aging. Given the profound impact on public health, much research has focused on the age‐specific risk of developing dementia and the impact on survival. Early work has discussed various methods of estimating age‐specific incidence of dementia, among which the illness‐death model is popular for modeling disease progression. In this article we use multiple imputation to fit multi‐state models for survival data with interval censoring and left truncation. This approach allows semi‐Markov models in which survival after dementia depends on onset age. Such models can be used to estimate the cumulative risk of developing dementia in the presence of the competing risk of dementia‐free death. Simulations are carried out to examine the performance of the proposed method. Data from the Honolulu Asia Aging Study are analyzed to estimate the age‐specific and cumulative risks of dementia and to examine the effect of major risk factors on dementia onset and death.
Modelling animal growth in random environments: An application using nonparametric estimation
Authors: Filipe Patrícia A. , Braumann Carlos A. , Brites Nuno M. , Roquete Carlos J.
Published: October 2010

We study a stochastic differential equation growth model to describe individual growth in random environments. In particular, in this paper, we discuss the estimation of the drift and the diffusion coefficients using nonparametric methods for the case of nonequidistant data for several trajectories. We illustrate the methodology by using bovine growth data. Our goal is to assess: (i) if the parametric models (with specific functional forms for the drift and the diffusion coefficients) previously used by us to describe the evolution of bovine weight were adequate choices; (ii) whether some alternative specific parameterized functional forms of these coefficients might be suggested for further parametric analysis of this data.
Simulation‐based power calculations for large cohort studies
Authors: Brown Patrick , Jiang Hedy
Published: October 2010

A large number of factors can affect the statistical power and bias of analyses of data from large cohort studies, including misclassification, correlated data, follow‐up time, prevalence of the risk factor of interest, and prevalence of the outcome. This paper presents a method for simulating cohorts where individual's risk is correlated within communities, recruitment is staggered over time, and outcomes are observed after different follow‐up periods. Covariates and outcomes are misclassified, and Cox proportional hazards models are fit with a community‐level frailty term. The effect on study power of varying effect sizes, prevalences, correlation, and misclassification are explored, as well as varying the proportion of controls in nested case–control studies.
Estimation of the diagnostic threshold accounting for decision costs and sampling uncertainty
Authors: Skaltsa Konstantina , Jover Lluís , Carrasco Josep Lluís
Published: October 2010

Medical diagnostic tests are used to classify subjects as non‐diseased or diseased. The classification rule usually consists of classifying subjects using the values of a continuous marker that is dichotomised by means of a threshold. Here, the optimum threshold estimate is found by minimising a cost function that accounts for both decision costs and sampling uncertainty. The cost function is optimised either analytically in a normal distribution setting or empirically in a free‐distribution setting when the underlying probability distributions of diseased and non‐diseased subjects are unknown. Inference of the threshold estimates is based on approximate analytically standard errors and bootstrap‐based approaches. The performance of the proposed methodology is assessed by means of a simulation study, and the sample size required for a given confidence interval precision and sample size ratio is also calculated. Finally, a case example based on previously published data concerning the diagnosis of Alzheimer's patients is provided in order to illustrate the procedure.
A novel definition of the multivariate coefficient of variation
Authors: Albert Adelin , Zhang Lixin
Published: October 2010

The coefficient of variation CV (%) is widely used to measure the relative variation of a random variable to its mean or to assess and compare the performance of analytical techniques/equipments. A review is made of the existing multivariate extensions of the univariate CV where, instead of a random variable, a random vector is considered, and a novel definition is proposed. The multivariate CV obtained only requires the calculation of the mean vector, the covariance matrix and simple quadratic forms. No matrix inversion is needed which makes the new approach equally attractive in high dimensional as in very small sample size problems. As an illustration, the method is applied to electrophoresis data from external quality assessment in laboratory medicine, to phenotypic characteristics of pocket gophers and to a microarray data set.
A note on the tests for clustered matched‐pair binary data
Authors: Yang Zhao , Sun Xuezheng , Hardin James W.
Published: October 2010

McNemar's test is used to assess the difference between two different procedures (treatments) using independent matched‐pair data. For matched‐pair data collected in clusters, the tests proposed by Durkalski et al. and Obuchowski are popular and commonly used in practice since these tests do not require distributional assumptions or assumptions on the structure of the within‐cluster correlation of the data. Motivated by these tests, this note proposes a modified Obuchowski test and illustrates comparisons of the proposed test with the extant methods. An extensive Monte Carlo simulation study suggests that the proposed test performs well with respect to the nominal size, and has higher power; Obuchowski's test is most conservative, and the performance of the Durkalski's test varies between the modified Obuchowski test and the original Obuchowski's test. These results form the basis for our recommendation that (i) for equal cluster size, the modified Obuchowski test is always preferred; (ii) for varying cluster size Durkalski's test can be used for a small number of clusters (e.g. K < 50), whereas for a large number of clusters (e.g. K ≥ 50) the modified Obuchowski test is preferred. Finally, to illustrate practical application of the competing tests, two real collections of clustered matched‐pair data are analyzed.
Comparison of positive lymph node ratio with an inflammation-based prognostic score in colorectal cancer
Authors: Moug S J , McColl G , Lloyd S M , Wilson G , Saldanha J D , Diament R H
Published: October 2010

Background

Two prognostic scoring systems have been proposed in colorectal cancer: the pathologically based positive lymph node ratio (pLNR) and the inflammation-based modified Glasgow Prognostic Score (mGPS). This study compared these two scores with the tumour node metastasis (TNM) staging system in terms of cancer survival.

Methods

Between 2003 and 2005, 206 patients, of mean(s.d.) age 69·9(10·6) (range 40–95) years, underwent curative resection for colorectal cancer in two centres. Age, sex, primary tumour site and whether radio/chemotherapy was given were recorded in addition to the three scores (TNM stage, pLNR and mGPS). Univariable and multivariable analyses of overall survival were performed.

Results

Age, rectal cancer, TNM stage, pLNR and mGPS were significant factors in univariable analysis. On multivariable analysis, N category and tumour stage (I–III) were removed from the model, leaving pLNR and mGPS as independent predictors of overall survival: hazard ratio 1·51 (95 per cent confidence interval 1·24 to 1·84; P < 0·001) and 1·56 (1·18 to 2·08; P = 0·020) respectively. C-statistic analysis, used to compare pLNR and mGPS directly, found only pLNR to be significant (P < 0·001)

Conclusion

This study found pLNR to be the superior prognostic scoring system in determining long-term survival in patients undergoing resection for colorectal cancer.
Macroporous Poly(N‐isopropylamide‐co‐acrylamide) Hydrogels Prepared by Two‐Step Polymerization for Drug Delivery Applications
Authors: Huo D. , Yang J. , Hou C. , Yang M.
Published: October 2010

Macroporous poly(N‐isopropylamide‐co‐acrylamide) [P(NIPAAm‐co‐AAm)] hydrogels were successfully prepared by a two‐step polymerization method. The initial polymerization was carried out at 18 °C with different duration, followed by freezing polymerization at –18 °C for 24 h. The results showed that the immediate performance of freezing polymerization played a dominant role in the final properties of the P(NIPAAm‐co‐AAm) hydrogels. The thermoresponsive rate and mechanical strength of the hydrogels were drastically changed by freezing the reaction mixture after 3 min of the first polymerization (PNA‐3). Scanning electron microscopy (SEM) studies revealed that the hydrogel frozen after 3 min exhibited the most highly interconnected porous structures and the largest pore size. These open pore structures were very useful to accelerate the responsive rate of the hydrogels. In vitro BSA (bovine serum albumin) release from the hydrogel PNA‐3 exhibited relatively small initial burst release followed by a steady release. Such results demonstrated that the P(NIPAAm‐co‐AAm) hydrogels frozen before gelation have the potential to be applicated for delivering proteins.
Suspension Polymerization Processes
Authors: Brooks B.
Published: October 2010

Industrial suspension polymerization usually proceeds by a free‐radical mechanism to produce polymer beads. The size distribution of the polymer beads is often similar to that of the polymerizing drops in the reactor. That distribution is determined by the operating mechanisms of drop breakage and drop coalescence. Consequently, the value of the Reynolds number is significant and a potential change in flow regime must be considered in reactor scale‐up. The choice of suspending agent, which can be a water‐miscible polymer or a finely divided particulate solid, can affect both the drop size and the properties of the final product. High monomer conversions are attainable but reaction kinetics can be affected by increases in drop viscosity during the polymerization. Drop mixing, which sometimes takes place, can be slow, so that non‐uniformity occurs in the final product. With copolymerization, complications can arise if the initiator, or one of the monomers, is partially soluble in the continuous phase. Adverse environmental impact of suspension polymerization can be avoided by cleaning and/or recycling the continuous phase when it leaves the reactor.
Melt Index Prediction Based on Adaptive Particle Swarm Optimization Algorithm‐Optimized Radial Basis Function Neural Networks
Authors: Zhao C. , Liu X. , Ding F.
Published: October 2010

Reliable estimation of the melt index (MI) is crucial in the quality control of practical propylene polymerization (PP) processes. In this paper, a novel predictive neural network system, combining the particle swarm optimization (PSO) algorithm and radial‐basis function neural networks (RBFN), is presented to infer MI from real PP process variables, where the PSO algorithm dynamically constructs the RBFN structure and parameters and a new adaptive PSO (APSO) algorithm, which adjusts the algorithm behavior based on evolution information of swarms, further accelerates the convergence speed. Principle component analysis is applied to select the most relevant process features and to reduce the number of input variables in the model. A detailed comparison between PSO, APSO and the gradient descent algorithm is carried out using historical data from a real plant.
Simulation of Polymerization Kinetics and Molecular Weight Development in the Microwave‐Activated Emulsion Polymerization of Styrene using EMULPOLY®
Authors: Jaramillo‐Soto G. , Ramírez‐Cupido M. , Tenorio‐López J. A. , Vivaldo‐Lima E. , Penlidis A.
Published: October 2010

The emulsion polymerization of styrene, activated by microwave irradiation and conductive heating, was modeled using the EMULPOLY® simulation package of the University of Waterloo. Microwave‐activated initiation was modeled as adding a hypothetical second initiator. The kinetic rate constants and model parameters used in the simulation were taken from the simulator database, with the exception of the microwave activation constant, kir, and the efficiency, fr, of the hypothetical initiator. Model predictions of conversion, number‐ and weight‐average molecular weights, for microwave‐ and thermally activated systems agreed well with the experimental data reported in the literature. The effects of microwave power supplied to the system on monomer conversion, molecular weight values and particle number were analyzed.
Copolymerization Kinetics of Styrene and Divinylbenzene in the Presence of S‐Thiobenzoyl Thioglycolic Acid as RAFT Agent
Authors: Roa‐Luna M. , Jaramillo‐Soto G. , Castañeda‐Flores P. V. , Vivaldo‐Lima E.
Published: October 2010

An experimental study on the kinetics of the reversible addition‐fragmentation chain transfer (RAFT) copolymerization of styrene (STY) and divinylbenzene (DVB) is presented. The experiments were carried out in bulk from a mixture of monomers, S‐thiobenzoyl thioglycolic acid as RAFT agent, and the initiator dibenzoyl peroxide (BPO) at 80 °C. The effect of RAFT agent concentration, including the case without RAFT controller, on polymerization rate, molecular weight development, gel fraction, and swelling index was analyzed.
Polymerization Online Monitoring
Authors: Frauendorfer E. , Wolf A. , Hergeth W.‐D.
Published: October 2010

Online monitoring of polymerization reactions is not only important due to the high exothermic nature of most polymerization systems; the data gained also provides information on product composition and quality and control possibilities thereof. Many inline and online methods are still in development and are better suited for application on the laboratory or pilot‐plant scale. Industrial polymerization plant environments pose additional technical and financial challenges and constraints for the use of such systems. Available methods and current developments are reviewed with regard to their practicability and usefulness under these aspects.
From Molecular to Plant‐Scale Modeling of Polymerization Processes: A Digital High‐Pressure Low‐Density Polyethylene Production Paradigm
Authors: Kiparissides C. , Krallis A. , Meimaroglou D. , Pladis P. , Baltsas A.
Published: October 2010

A generalized multiscale modeling framework is described for the digital simulation of a high‐pressure low‐density polyethylene (LDPE) tubular reactor. According to the proposed modeling approach, various models describing the complex physical and chemical phenomena at different length and time scales are linked together to assess the effects of reactor operating conditions on the molecular and rheological behavior of LDPE. The molecular properties of LDPE are determined by employing a comprehensive kinetic scheme. On the basis of the postulated kinetic mechanism, detailed population balance equations (PBEs) are derived describing the conservation of the various macromolecular polymer chains. A review of the potential methods for solving the governing PBEs is presented. In addition, a novel kinetic/topology Monte Carlo method to calculate the molecular and topological properties of the highly branched polymer chains and an advanced rheological model for the calculation of the viscoelastic properties of branched polymers in terms of their respective molecular and topological properties are described.
ChemInform Abstract: Optimization of Thermoelectric Properties of Type‐VIII Clathrate Ba8Ga16Sn30 by Carrier Tuning.
Authors: Saiga Y. , Suekuni K. , Deng S. K. , Yamamoto T. , Kono Y. , Ohya N. , Takabatake T.
Published: October 2010

Single crystals of the title material are prepared by the self‐flux method tuning the charge carrier type to either p‐ or n‐type by using Ga or Sn as flux, respectively.
ChemInform Abstract: Peculiarity of Component Interaction in Er—Fe—Sn Ternary System at 670 K and 770 K.
Authors: Romaka L. , Romaka V. V. , Demchenko P. , Serkiz R.
Published: October 2010

The 670 and 770 K isothermal sections of the phase diagram of the title system are determined over the whole composition range.
ChemInform Abstract: Improved Synthesis of Bis(borano)hypophosphite Salts.
Authors: Anstey Mitchell R. , Corbett Michael T. , Majzoub Eric H. , Cordaro Joseph G.
Published: October 2010

The new one‐step process for the synthesis of the [PH2(BH3)2]‐ anion with various counterions uses commercially available and relatively safe starting materials in stead of a multistep procedure with gaseous or explosive reagents such as ammonia, phosphine, and diborane.
ChemInform Abstract: A Simple and Efficient Way to Synthesize Unsolvated Sodium Octahydrotriborate.
Authors: Huang Zhenguo , King Graham , Chen Xuenian , Hoy Jason , Yisgedu Teshome , Lingam Hima K. , Shore Sheldon G. , Woodward Patrick M. , Zhao Ji‐Cheng
Published: October 2010

Unsolvated NaB3H8 is prepared by reaction of Na/Hg amalgam with THF·BH3 at room temperature for 3 d (<70% yield).
ChemInform Abstract: New Hydrides LnScSiH and LnScGeH (Ln: La, Ce): Structure, Magnetism, and Chemical Bonding.
Authors: Chevalier Bernard , Hermes Wilfried , Heying Birgit , Rodewald Ute Ch. , Hammerschmidt Adrienne , Matar Samir F. , Gaudin Etienne , Poettgen Rainer
Published: October 2010

LnScSi and LnScGe (Ln: La, Ce) are synthesized by arc‐melting of the elements and subsequent annealing at 1170 K (21 d).
ChemInform Abstract: Construction of a Hybrid Family Based on Lanthanide—Organic Framework Hosts and Polyoxometalate Guests.
Authors: Liu Xiaoyu , Jia Yanyan , Zhang Yongfeng , Huang Rudan
Published: October 2010

The new compounds (IIIa—e) and (VIa—e) are found to be isostructural.
ChemInform Abstract: Synthesis and Structure of Pillared Molybdates and Tungstates with Framework Layers.
Authors: Nicholls Jennifer L. , Hulse Sarah E. , Callear Samantha K. , Tizzard Graham J. , Stephenson Richard A. , Hursthouse Michael B. , Clegg William , Harrington Ross W. , Fogg Andrew M.
Published: October 2010

The new compounds (III), (VI), and (VIII) are hydrothermally prepared (35—60% yield) and characterized by single crystal XRD.
ChemInform Abstract: New Three‐Dimensional Thiostannates Composed of Linked Cu8S12 Clusters and the First Example of a Mixed‐Metal Cu7SnS12 Cluster.
Authors: Behrens Malte , Ordolff Marie‐Eve , Naether Christian , Bensch Wolfgang , Becker Klaus‐Dieter , Guillot‐Deudon Catherine , Lafond Alain , Cody Jason A.
Published: October 2010

The structures of (III), (IV), and (VI) are determined by single crystal XRD.
ChemInform Abstract: New and General Nitrogen Heterocycle Synthesis: Use of Heteropoly Acids as a Heterogeneous Recyclable Catalyst.
Authors: Hekmatshoar Rahim , Sadjadi Sodeh , Sadjadi Samaheh , Heravi Majid M. , Beheshtiha Yahya S. , Bamoharram Fatemeh F.
Published: October 2010

Five‐ (pyrrole, tetrahydroindole) and six‐membered (pyridine, tetrahydroquinoline) hetrocycles are accessible via Keggin‐type heteropoly‐acid‐catalyzed condensation of β‐dicarbonyl compounds with β‐ or γ‐amino alcohols.
ChemInform Abstract: Imidazolium and Pyridinium Salts — Solvents Influencing the Rate and Direction of the Fries, Beckmann, and Claisen Rearrangements.
Authors: Katkevica S. , Zicmanis A. , Mekss P.
Published: October 2010

The effects of the structural elements of the ionic liquid media on the direction of these rearrangements and the product yields are studied.
ChemInform Abstract: Carbon—Carbon Cleavage of Aryl Diamines and Quinone Formation Using Sodium Periodate: A Novel Application.
Authors: Telvekar Vikas N. , Takale Balaram S.
Published: October 2010

Treatment of 1,2‐diaminobenzenes with sodium periodate gives ring‐cleaved dinitriles whereas 1,4‐diamines yield the corresponding p‐quinones.
ChemInform Abstract: Cu(I)‐Catalyzed Asymmetric α‐Hydroxylation of β‐Keto Esters in the Presence of Chiral Phosphine—Schiff Base‐Type Ligands.
Authors: Jiang Jia‐Jun , Huang Jian , Wang De , Zhao Mei‐Xin , Wang Fei‐Jun , Shi Min
Published: October 2010

A novel BINAP‐derived imine ligand is presented for the asymmetric Cu(I)‐catalyzed hydroxylation of cyclic β‐keto esters (I) and (III).
ChemInform Abstract: 1‐tert‐Butyl‐1H‐tetrazol‐5‐yl Fluoromethyl Sulfone (TBTSO2CH2F): A Versatile Fluoromethylidene Synthon and Its Use in the Synthesis of Monofluorinated Alkenes via Julia—Kocienski Olefination.
Authors: Zhu Lingui , Ni Chuanfa , Zhao Yanchuan , Hu Jinbo
Published: October 2010

The base‐mediated reaction between aldehydes or ketones with fluoromethyl sulfone (II) or its α‐alkylated, acylated and phenylsulfonated derivatives provides monofluoroalkenes in good yields with moderate (E)/(Z)‐selectivity.
ChemInform Abstract: Copper‐Catalyzed Asymmetric 1,4‐Conjugate Addition of Dialkylzinc to Enones.
Authors: Gou Shaohua , Ye Zhongbin , Shi Leiting , Qing Dayong , Zhang Wen , Wang Yuliang
Published: October 2010

A new bifunctional copper catalytic system containing no phosphorus atom at the BINOL‐derived ligand is shown to form a Lewis acid—Lewis base centre in the 1,4‐conjugate addition reaction of dialkyl zinc to enones, thus inducing enantioselectivities of up to 84% e.e.
ChemInform Abstract: Synthesis of a Bioxazoline‐Derived Ru Metathesis Catalyst.
Authors: Vehlow Kati , Porta Marta , Blechert Siegfried
Published: October 2010

A new class of ruthenium catalyst based on an IBox‐NHC ligand is synthesized.
ChemInform Abstract: Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts: A General Approach to the Synthesis of Enamides.
Authors: Bolshan Yuri , Batey Robert A.
Published: October 2010

Two sets of reaction conditions are developed depending on the pKa of the amide.