Search results for "structural"
showing 10 items of 5047 documents
Oxalate-based 2D magnets: the series [NBu4][MIIMnIII(ox)3] (MII= Fe, Co, Ni, Zn; ox = oxalate dianion)
2006
The synthesis, structure and physical properties of the bimetallic oxalate-based molecular magnets containing MnIII of formula [NBu4][MIIMn(ox)3] (MII = Fe, Co, Ni, Zn; ox = oxalate dianion) are presented here. All compounds are isostructural, containing two-dimensional honeycomb bimetallic networks formed by alternating MII and MIII ions connected by oxalate anions. These compounds exhibit antiferromagnetic interactions that give rise to ferrimagnets or weak ferromagnets ordering at critical temperatures up to 21 K.
δ18O values of coexisting brachiopods and fish: Temperature differences and estimates of paleo–water depths
1998
To estimate vertical thermal gradients and paleo–water depths to marine platforms we present a new method based on the difference between δ 18 O values of contemporaneous brachiopod carbonate and fish phosphate. Present-day marine fauna of well-known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures. We predict distributions of isotopic data that result from sampling strategy, basin morphology, and fauna ecology and discuss limitations. Application of the method to the Jurassic Paris-London basin gives vertical thermal variations of up to 14 °C associated with depths varying from a few meters to 170 ± 30 m. The estimated depths are …
Ab Initio Study of Stereo- and Regioselectivity in the Diels−Alder Reaction between 2-Phenylcyclopentadiene and α-(Methylthio)acrylonitrile
1997
Ab initio molecular orbital calculations have been used to investigate the Diels−Alder reaction between 2-phenylcyclopentadiene and α-(methylthio)acrylonitrile. Geometry optimizations were performed with the RHF/3-21G, RHF/3-21G*, and RHF/6-31G* calculations while the correlation energy has been calculated at MP2 and MP3 levels. Four asynchronous transition structures corresponding to the formation of different stereoisomers and regioisomers associated with the four reaction channels have been located. The observed endo/exo stereoselectivity and para/meta regioselectivity are correctly described at all levels of calculation, and the calculated activation energies reflect accurately the rela…
Generation of hexahydroazulenes
2009
(Z)-Cyclodec-1-en-6-yne (3) generates three conjugated hexahydroazulenes 3→1k→1c, 1l under FVP conditions, whereas flash vacuum pyrolysis (FVP) of cyclodecyne (2) leads to 1,2,9-decatriene (9). We attribute the different thermal behavior of 2 (ring opening) and 3 (ring closure) to different transannular interactions. Altogether 22 constitutional isomers of hexahydroazulene should exist; three new isomers (1k, 1l, and 1m) are presented here, ten were described earlier, but the reinvestigation of the dehydration route of bicyclic alcohol 11 showed that one of the ten structures has to be revised.
Orchestin, a calcium-binding phosphoprotein, is a matrix component of two successive transitory calcified biomineralizations cyclically elaborated by…
2003
Orchestia cavimana is a crustacean that cyclically replaces its calcified cuticle during molting cycles in order to grow. Its terrestrial way of life requires storage of calcium during each premolt period, as calcareous concretions, in tubular diverticula of the midgut. During the postmolt period the stored calcium is reabsorbed and is translocated through the storage organ epithelium as calcified small spherules. In a previous study, we sequenced and characterized a remarkable component of the organic matrix of the premolt storage structures, Orchestin, which is a calcium-binding phosphoprotein. In this paper, we analyzed the spatiotemporal expression of the orchestin gene by Northern blot…
Computational cluster validation for microarray data analysis: experimental assessment of Clest, Consensus Clustering, Figure of Merit, Gap Statistic…
2008
Abstract Background Inferring cluster structure in microarray datasets is a fundamental task for the so-called -omic sciences. It is also a fundamental question in Statistics, Data Analysis and Classification, in particular with regard to the prediction of the number of clusters in a dataset, usually established via internal validation measures. Despite the wealth of internal measures available in the literature, new ones have been recently proposed, some of them specifically for microarray data. Results We consider five such measures: Clest, Consensus (Consensus Clustering), FOM (Figure of Merit), Gap (Gap Statistics) and ME (Model Explorer), in addition to the classic WCSS (Within Cluster…
Estudio de imanes moleculares de Co(ii): desde sistemas aislados hasta sistemas organizados y multifuncionales
2016
Dentro de la disciplina conocida como Magnetismo Molecular, y a raíz del descubrimiento del Mn12 en 1993, ha surgido un gran interés por las moléculas que presentan una lenta relajación de la magnetización por debajo de una temperatura de bloqueo. A estas moléculas se les conoce como Imanes Unimoleculares (Single Molecule Magnets, SMMs). En la última década, la utilización de compuestos con un único centro metálico paramagnético (Single Ion Magnets, SIMs) se ha postulado como una de las nuevas estrategias utilizadas para la obtención de compuestos que presentan lenta relajación de la magnetización con barreras efectivas más elevadas. Además, desde un punto de vista experimental y teórico, l…
Structure of self-rated health among the oldest old: Analyses in the total population and those living with dementia
2020
No previous study has explored the structure of self-rated health (SRH), a measure holding strong predictive value for future health events, in the oldest old or in individuals with dementia. The aim was to construct a structural equation model of SRH for oldest old in general and for oldest old with dementia, and to explore direct and indirect associations between health-related factors and SRH. Cross-sectional data from the Vitality 90+, a population-based study in the city of Tampere, Finland, was used. Data were gathered by a mailed questionnaire in 2014. Altogether 1299 nonagenarians, of which 408 had self-reported dementia or cognitive decline, were included. Structural equation model…
Twin studies on the association of physical activity with cognitive and cerebral outcomes
2020
Regular physical activity (PA) offers positive effects on the human body. However, the effects of PA on cognition and in the brain are less clear. In this paper, we narratively review the relationship of PA with cognition and dementia, first from general perspective and then through genetically informed studies on the topic. Then we move on to imaging studies on exercise and brain anatomy first by presenting an overall picture of the topic and then discussing brain imaging studies addressing PA and brain structure in twins in more detailed way. Regarding PA and cognition or dementia, genetically informed studies are uncommon, even though the relationship between PA and cognitive ageing has …
Perceived motivational climate influences athletes’ emotion regulation strategies, emotions, and psychobiosocial experiences
2022
The purpose of the study was to investigate whether athletes’ perceptions about the motivational climate created by their coach influence emotion regulation strategies (i.e., cognitive reappraisal and expressive suppression), emotions, and psychobiosocial experiences of athletes. A sample of 459 competitive athletes (201 women, 258 men), aged 16–35 years, drawn from individual and team sports, completed self-assessment measures of perceived motivational climate, emotion regulation, sport emotions, and psychobiosocial experiences. Main results from structural equation modeling showed that perceived mastery climate was positively related to cognitive reappraisal, pleasant emotions, and psycho…