Several mixtures obtained by ultrasonic agitation of colloidal silica with a sol solution containing tetraethoxysilane (TEOS) were used to form crack-free monoliths. The dry gels that were submitted to mercury porosimetry showed differences in behavior according to the proportion of silica colloid in the gel. For low proportions, the mercury isostatic pressure exclusively induced an irreversible compaction of material, but intrusion occurred in gels with a high proportion of colloid. This permitted the evaluation of the textural properties of intruded gels, whereas the pressurization-depressurization paths, where intrusion was prevented, provided information about their compression behavior. Specimens exhibited elastic strain, followed by yield and plastic hardening. Bulk modulus was significantly reduced as the content of silica particles in the gel was increased. This was related to the increase in free volume of the network. The yield point, which characterizes the limit of the elastic region, was taken as a reference for estimating the maximum capillary pressure of drying; the inclusion of colloidal silica progressively reduced the maximum capillary pressure occurring during the drying for all samples except those containing the highest proportion of colloid (82%). This anomalous behavior was associated with low TEOS content, which complicates the formation of siloxane bonds. Textural properties determined by nitrogen adsorption confirmed the results obtained by porosimetry. Both porous volume and pore size were gradually increased in line with the colloid content. Therefore, we offer an effective means of tailoring the derived sol-gel porosity by increasing the proportion of colloidal silica, starting from a dense microporous material to achieve a mesoporous gel with a high pore volume and reduced capillary pressure.
Crack-free monolithic gels were prepared from different mixtures of colloidal silica with a sol solution containing tetraethoxysilane, under powerful ultrasonic agitation (sonosol). Recently, information on the structure of these gels, inferred from N2 adsorption and mercury intrusion porosimetry, was presented. In the present paper, these data were used to construct structural models of the gels using Monte Carlo calculations on the basis of random close packing (RPC) premises. In addition, the structure of gels under study was investigated by transmission and scanning electron microscopy. The material can be described as a composite in which the sonogel is the matrix and the colloid particles the reinforcing phase. For low colloid content, the colloid forms discrete clusters, and the main structural characteristic of sonogels, i.e., a network of uniformly sized particles of ∼3-4-nm radius, remains unmodified. However, for high colloid silica content, a multimode distribution appears, the structure is discontinuous, and only colloid aggregates larger than 100 nm are observed. For medium colloid content, aggregates of ∼50-100 nm can be seen, but the sonogel structure extends throughout the whole material. By the processing method and election of a suitable precursor concentration, it is possible to design the composite for specific purposes.
Neurosurgery is a therapeutic option for patients with refractory obsessive–compulsive disorder who do not respond to previous treatments. Although its efficacy in reducing clinical symptomatology has been proven, few studies have analyzed its effects at the cognitive level. The aim of this systematic review was to describe the cognitive outcomes of functional neurosurgery in patients that went through capsulotomies or cingulotomies. PubMed, Medline, Scopus, PsycInfo, PsyArticles, and Web of Knowledge were searched for studies reporting cognitive outcomes in refractory obsessive–compulsive patients after capsulotomies and cingulotomies. The risk of bias was assessed with the Assessment Tool for Before-After (Pre-Post) Studies With No Control Group tool; 13 studies met inclusion criteria, including 205 refractory obsessive–compulsive disorder patients for both surgical procedures. Results showed a substantial number of studies that did report significant cognitive improvement after surgery, being this improvement specially related to memory and executive functions. The second-most frequent finding is the maintenance of cognitive performance (nor improvement or worsening). From a neuropsychological point of view, this outcome might be considered a success, given that it is accompanied by amelioration of obsessive–compulsive symptoms. Subtle cognitive adverse effects have also been reported. Neurosurgery procedures appear to be safe from a cognitive point of view. Methodological issues must be improved to draw clearer conclusions, but capsulotomies and cingulotomies constitute an effective alternative treatment for refractory obsessive–compulsive disorder patients.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.