Search results for "Bases"
showing 10 items of 1240 documents
Aminosäureester als chirale Hilfsgruppen in Lewis-Säure-katalysierten Diels-Alder-Reaktionen
1990
Amino Acid Esters as Chiral Auxiliaries in Lewis Acid Catalyzed Diels-Alder Reactions Cyclopentadiene, cyclohexadiene and alkyl-substituted butadienes react with N-acryloyl-, N-crotonoyl- and N-(4-nitro-cinnamoyl)-(S)-proline benzyl and allyl ester in the presence of Lewis acids to give the cycloadducts in high yields and with stereoselectivities of up to 97:3 for the endo isomers. The sense of the asymmetric induction in these reactions can be directed by the use of differently coordinating catalysts (e.g. TiCl4: (2R):(2S) = 96:4; EtAlCl2: (2R):(2S) = 10:90 at 0°C). In the TiCl4-catalyzed reactions with the fumaric acid derivatives the ratio of the diastereomers reaches values of up to 112…
High spin polarization in Co2CrAl–Cr superlattice
2009
The electronic structure, magnetic properties and interface effects in Co2CrAl?Cr superstructures have been investigated by the use of first principle calculations. The results show that at the interface, a large magnetic moment and a high spin polarization can be induced by a strong ferromagnetic exchange interaction at the Cr?Co interface. However, at the CrAl?Cr interface, both the magnetic moment and the spin polarization of the Cr atoms are decreased due to a Cr?Cr antiferromagnetic interaction. It can also be found that the interface effect is only a short range effect. So, high spin polarization in Co2CrAl?Cr superlattice can be obtained. Based on this theoretical analysis, a large g…
Mechanism of Anionic Polymerization of (Meth)acrylates in the Presence of Aluminum Alkyls, 6. Polymerization of Primary and Tertiary Acrylates
1998
The kinetics of the polymerization of n-butyl acrylate initiated by lithiated ester enolates in the presence of aluminum alkyls was investigated in toluene and in toluene/Lewis base mixed solvents at −78 °C. In pure toluene, curved time−conversion plots, incomplete monomer conversion, and broad molecular weight distributions (Mw/Mn ≈ 2) are observedin the absence of aluminum alkyls the molecular weight distributions are significantly broader (Mw/Mn > 14). High monomer conversions and narrower molecular weight distributions (Mw/Mn ≈ 1.5) are obtained when using Lewis bases (e.g., methyl pivalate) as cosolvents. The polymerization of tert-butyl acrylate rapidly reaches full monomer conversion…
Calculations of organic-solvent dispersions of single-wall carbon nanotubes
2005
The aqueous solubility Sw and 1-octanol–(Po), cyclohexane–(Pch), and chloroform–(Pcf) water partition coefficients are calculated. The properties of single-wall carbon nanotubes (SWNT) are related to the indices (n, m) designating the chiral vector. SWNTs are classified in zigzag (n, 0), armchair (n, n), and chiral (n, m). These properties permit classifying SWNTs according to (n, m). Correlations between (n2 + nm + m2)1/2, log Sw, log Po, log Pch, and log Pcf show that (n, m) are adequate indices. The (10,10) is the most abundant SWNT, presenting consistency between great kinetic stability, small Sw, and great {Po, Pch, Pcf}. The room temperature solubility of SWNTs is investigated in a va…
La transformación de DICAT: el potencial de la visualización digital de redes para el teatro clásico español
2021
This paper analyses and proposes the steps to transform Diccionario biográfico de actores del teatro clásico español DICAT in order to be federated on ASODAT system of databases. We intend to assess whether or not the visualization of nets may be a useful and operational tool to analysing the biographical and professional information established between actors and actress of early modern Spanish theater, and to show patterns of social relation. Este artículo analiza y propone los pasos para transformar el Diccionario biográfico de actores del teatro clásico español DICAT para que pueda ser federado en el sistema de bases de datos ASODAT. Se pretende evaluar si la visualización de redes pued…
Thyroid neoplasms: surgical and cyto-histopathological connections on a six year cases study
2018
This study aims to evaluate the percentage of cyto-histologic correlation in patients with a thyroid disease documented through clinical-instrumental, cytological (FNAB), histological and surgical examinations. The purpose of this study is also to determine the percentage of disease incidence and evaluating any surgical indication in relation to biological behavior (benign, malignant or indeterminate lesions, occult carcinomas), sex, and age.Almost all of thyroid neoplasms is manifested through thyroid nodule. Therefore, clinical evidence of the thyroid nodule analysis is primarily related to the need to exclude malignant pathology or carcinoma of the thyroid, present in 4-6.5% of cases.The…
Total energy expenditure is repeatable in adults but not associated with short-term changes in body composition
2022
Low total energy expenditure (TEE, MJ/d) has been a hypothesized risk factor for weight gain, but repeatability of TEE, a critical variable in longitudinal studies of energy balance, is understudied. We examine repeated doubly labeled water (DLW) measurements of TEE in 348 adults and 47 children from the IAEA DLW Database (mean ± SD time interval: 1.9 ± 2.9 y) to assess repeatability of TEE, and to examine if TEE adjusted for age, sex, fat-free mass, and fat mass is associated with changes in weight or body composition. Here, we report that repeatability of TEE is high for adults, but not children. Bivariate Bayesian mixed models show no among or within-individual correlation between body c…
The economic impact of rectal cancer: A population-based study in Italy list of authors
2021
Costs of cancer care are increasing worldwide, and sustainability of cancer burden is critical. In this study, the economic impact of rectal cancer on the Italian healthcare system, measured as public healthcare expenditure related to investigation and treatment of rectal cancer patients is estimated. A cross-sectional cohort of 9358 rectal cancer patients is linked, on an individual basis, to claims associated to rectal cancer diagnosis and treatments. Costs refer mainly to years 2010&ndash
Priming index of the Spanish word fragments from the Dasí, Soler, and Ruiz (2004) database
2007
Word-fragment completion is a frequently used test in implicit memory research. A database of 196 Spanish fragments was recently published (Dasi, Soler, & Ruiz, 2004) in which the fragments were described for indices, such as difficulty, familiarity, frequency, number of meanings, and so on (www.psychonomic.org/archive). In this work, a new index, thepriming index, is described for the same 196 fragments. This index is calculated for each fragment by subtracting the difficulty index (the proportion of correct completion when the fragment is not studied) from the proportion of correct completion when the fragment is studied, and it means the capacity of an item to be primed. In order to dete…
Invasive meningococcal disease in Italy: from analysis of national data to an evidence-based vaccination strategy
2020
Introduction. Invasive meningococcal disease (IMD) is one of the most severe vaccine-preventable diseases not yet under control. In Italy, although different anti-meningococcal vaccines are available, their offer among regions is heterogeneous. The aim of this study is to describe the epidemiology of IMD in Italy based on analysis of national surveillance data for 2011–2017 to optimize the vaccination strategy. Methods: IMD surveillance data from the Italian National Health Institute were analysed. Microsoft Excel was used to present trend analysis, stratifying by age and serogroups. Results: In Italy, during the period 2011–2017, the incidence of IMD increased from 0.25 cases/100,000 inhab…