Dissociative multi-photon ionization of isolated uracil and uracil-adenine complexes

Recent multi-photon ionization (MPI) experiments on uracil revealed a fragment ion at m/z 84 that was proposed as a potential marker for ring opening in the electronically excited neutral molecule. The present MPI measurements on deuterated uracil identify the fragment as C3H4N2O+ (uracil+ less CO), a plausible dissociative ionization product from the theoretically predicted open-ring isomer. Equivalent measurements on thymine do not reveal an analogous CO loss channel, suggesting greater stability of the excited DNA base. MPI and electron impact ionization experiments have been carried out on uracil-adenine clusters in order to better understand the radiation response of uracil within RNA. Evidence for C3H4N2O+ production from multi-photon-ionized uracil-adenine clusters is tentatively attributed to a significant population of π-stacked configurations in the neutral beam

Earth resources evaluation for New Mexico by LANDSAT-2

The author has identified the following significant results. The Middle Rio Grande project has not yet progressed to the point where mineral exploration sites can be chosen; however, there does appear to be some correlation between the known structure and mineral deposits and the LANDSAT lineament map. A circular feature identified in the southern Magdalena Mountains on LANDSAT-1 imagery agrees well with the location of a newly proposed caldron complex. Several recognized and unrecognized circular features were identified on imagery of the Mogollon-Datil volcanic field. A check of aeromagnetic maps for New Mexico found that the circular features on the LANDSAT imagery showed up as areas of generally high magnetic intensity

The Effect of a Blast Load from Propane Gas Leakage on an RC Structure

The knowledge of the way a gas explosion affects a structure is still in its development. In this study, structural analysis software was used to construct a simplified approach to predict the impact of a Dynamic Blast Load (DBL) from gas leakage. During the explosion process, the overpressure distribution in a room is decomposed to maximum dynamic pressure point (DPPmax), where the explosion damages the most the structure. The simulation of the DBL was compared with the real consequences of gas explosion with the phenomenological data of a case study in Batna, Algeria. The results show that the simulation reproduced by our modeling of the DBL at structural scale is in good agreement with a real explosion. The distribution of stresses and strains over time indicates that the gas explosion inside residential buildings affected the entire surrounding of the area of the blast

Histological classification of mammary tumors of the domestic animals

молочная железа, домашние животные, опухоли, онкология, гистология, классификация, гистологическая классификаци

Long-term high-effort endurance exercise in older adults: diminishing returns for cognitive and brain aging

While there is evidence that age-related changes in cognitive performance and brain structure can be offset by increased exercise, little is known about the impact on these of long-term high-effort endurance exercise. In a cross-sectional design with 12-month follow-up, we recruited older adults engaging in high-effort endurance exercise over at least twenty years, and compared their cognitive performance and brain structure with a non-sedentary control group similar in age, sex, education, IQ, and lifestyle factors. Our findings showed no differences on measures of speed of processing, executive function, incidental memory, episodic memory, working memory, or visual search for older adults participating in long-term high-effort endurance exercise, when compared without confounds to non-sedentary peers. On tasks that engaged significant attentional control, subtle differences emerged. On indices of brain structure, long-term exercisers displayed higher white matter axial diffusivity than their age-matched peers, but this did not correlate with indices of cognitive performance

Cognitive and neural signatures of the APOE E4 allele in mid-aged adults

The apolipoprotein E (APOE) e4 allele is strongly associated with increased risk of cognitive impairments in older adulthood. There is also a possible link to enhanced cognitive performance in younger adults, and the APOE e4 allele may constitute an example of antagonistic pleiotropy. The aim of this work was to investigate the cognitive and neural (functional) effects of the APOE e4 allele during mid-age (45-55 years), where a transition toward cognitive deficit might be expected. APOE e4 carriers (e4+) were compared with non-e4 carriers (e4-) on tasks of sustained and covert attention and prospective memory, and functional magnetic resonance imaging data acquired. Performance by e4+ was equivalent or better than e4- on all 3 tasks, although performance benefits were less pronounced than in youth. Neurally, e4+ showed less task-related recruitment of extrastriate and parietal areas. This became more evident when neural activation data were compared with that of young adults acquired in a parallel study. As expected, mid-age participants showed more diffuse neural activation. Notable was the fact that e4+ showed a relative inability to recruit parietal regions as they aged. This was coupled with a tendency to show greater recruitment of frontal regions, and underactivation of extrastriate visual regions. Thus, mid-age e4+ show a pattern of neural recruitment usually seen later in life, possibly reflecting the source of an accelerated aging profile that describes the e4 genotype

Mid age APOE ε4 carriers show memory-related functional differences and disrupted structure-function relationships in hippocampal regions

Carriers of the APOE e4 allele are at higher risk of age-related cognitive decline and Alzheimer's disease (AD). The underlying neural mechanisms are uncertain, but genotype differences in medial temporal lobe (MTL) functional activity and structure at mid-age might contribute. We tested 16 non-e4 and 16 e4 carriers (aged 45-55) on a subsequent memory task in conjunction with MRI to assess how hippocampal volume (from T1 structural) and microstructure (neurite orientation-dispersion, from NODDI) differs by genotype and in relation to memory encoding. No previous study has investigated APOE effects on hippocampal microstructure using NODDI. Recall performance did not differ by genotype. A genotype by condition interaction in left parahippocampus indicated that in e4 carriers activity did not differentiate subsequently remembered from forgotten words. Hippocampal volumes and microstructure also did not differ by genotype but hippocampal volumes correlated positively with recognition performance in non-e4 carriers only. Similarly, greater hippocampal neurite orientation-dispersion was linked to better recall but only in non-e4s. Thus, we suggest that mid-age e4 carriers show a breakdown of normal MTL activation and structure-performance relationships. This could reflect an inability to utilise compensatory mechanisms, and contribute to higher risk of cognitive decline and AD in later life

CONTRIBUTION A L’ETUDE DE LA FORMATION DU SILICIURE DE TITANE Ti/Si(B), TiN/Ti/Si(B) MISE EN EVIDENCE D’UN MODELE THERMODYNAMIQUE

Dans les nouvelles technologies des circuits intégrés, il est nécessaire que la résistivité des interconnexions soit très faibles, laconcentration des dopants aux contacts siliciure/silicium détermine directement cette résistance. Parmi ces dopants il y al’arsenic et le bore qui se caractérisent par des comportements variés d’un siliciure à un autre.Dans ce travail nous allons suivre le comportement du bore implanté dans un substrat de silicium avant le dépôt de la couchemétallique. Le titane est un métal très réactif avec l’oxygène pour cela nous avons utilisé l’encapsulation. Nous faisons le pointquant à l’effet de l’encapsulation par rapport à des échantillon non encapsulés.Cette étude a été menée en recuit thermique rapide. L’analyse des échantillons se fait par le rétro diffusion des particules(RBS). Les résultats seront traité par un modèle basé sur la chaleur effective de formation ce modèle qui s’appliquer bien pourles siliciures pures (sans présence des dopants ou autres impuretés). Nous avons élaboré un modèle général qui tient comptedes impureté