Search results for "medium"
showing 10 items of 3746 documents
Method of Discrimination of Surface Fractality
1993
Abstract A simple method for the discrimination of surface fractality is proposed. This method is based on the comparison of the nitrogen adsorption isotherm on a given sample with the "standard" isotherm on a smooth surface. The proposed comparative method makes it possible to determine the lower limit of the scale range of surface fractality. A thermodynamic method is recommended as a complement to fractal analysis in the scale range of about 10-1000 A. The results of the investigation of surface roughness are presented with examples of typical samples of silica gels, porous glasses, apatite, and coal.
Electric-field-controlled reversible order-disorder switching of a metal tip surface
2018
While it is well established that elevated temperatures can induce surface roughening of metal surfaces, the effect of a high electric field on the atomic structure at ambient temperature has not been investigated in detail. Here we show with atomic resolution using in situ transmission electron microscopy how intense electric fields induce reversible switching between perfect crystalline and disordered phases of gold surfaces at room temperature. Ab initio molecular dynamics simulations reveal that the mechanism behind the structural change can be attributed to a vanishing energy cost in forming surface defects in high electric fields. Our results demonstrate how surface processes can be d…
Surface Reflectance: An Optical Method for Multiscale Curvature Characterization of Wear on Ceramic–Metal Composites
2020
Surface gradient characterization by light reflectance (SGCLR) is used for the first time for multiscale curvature calculations and discrimination of worn surfaces on six damaged ceramic&ndash
α-d-Glucopyranose Adsorption on a Pd30 Cluster Supported on Boron Nitride Nanotube
2016
Boron nitride nanotube (BNNT) as an innovative support for carbohydrate transformation processes was evaluated, using density functional theory. The α-d-glucopyranose adsorption on a Pd30 cluster, supported on BNNT, was used to check both the local activity of topologically different metallic sites and the effects of the proximity of the BNNT surface to the same metallic sites. Detailed geometrical and electronic analyses performed on Pd30/BNNT and α-d-glucopyranose/Pd30/BNNT systems were discussed. It was observed that the deposition of the Pd30 cluster onto the BNNT support gives rise to an electronic rearrangement, determining a charge transfer from the support to the adsorbed metal clus…
Diagnostic tools for female urethral diverticulum: Current perspectives
2019
Although once considered quite a rare condition in the past, female urethral diverticulum (UD) would now appear to have a higher frequency, perhaps due to greater attention from physicians. To date, there is no agreement on which is the best method for diagnosis of female UD. Traditionally, the approach was based on quite invasive techniques, such as voiding cystourethrography, and double-balloon urethrography, with satisfactory results but relevant limitations. More recent high-resolution imaging techniques, such as 2D-3D ultrasonography (US) and magnetic resonance imaging (MRI) have also been applied in the study of the abnormalities of the female urethra. US had the advantage of the outp…
Policies to enhance social development through the promotion of SME and social entrepreneurship: a study in the Colombian construction industry
2016
[EN] The intent of this research is to propose and analyse a set of policies in the construction industry to enhance social development. First, the paper shows the connections between the development of small and medium enterprises (SMEs) and social entrepreneurship (SE), the reduction of the leakage, and then the generation of social value (SV) for sustainable regional development. For that, the article analyses briefly the literatures on SE and leakage, and focuses on the relevance of SME and social entrepreneurs as promoters of SV creation and development. Second, the paper proposes a framework and proposes a set of 20 policies aimed to reduce leakage, reinforce SMEs and entrepreneurship…
Adoption of Green Environmental Practices in Small and Medium-Sized Enterprises: Entrepreneur and Business Policies Patterns in Romania
2021
Current research shows that SMEs’ social and environmental actions are fragmented and informal, and few have formal policies and intentions. At the same time, many SMEs are engaged with environmental policies, often not knowing it. Concurrently, there is a gap between the pro-environmental attitudes of the SMEs managers, who are often seen as the main drivers for the firm’s behavior, and the policies implemented in reality in their firms. To this end, our research’s objective is to explore pro-environmental behavior, both at the individual and firm level, to identify connections between these levels and measures but also with firm’s and managers’ demographics, based on a study of Romanian S…
Evidences of release and catch mechanism in the Heck reaction catalyzed by palladium immobilized on highly cross-linked-supported imidazolium salts
2014
Abstract Palladium (10 wt%) on a highly cross-linked imidazolium-based material was used as catalyst in 0.1 mol% in the Heck reaction between several alkenes and aryl iodides. Products were obtained from good to high yields. Deeper investigations showed a release of Pd species in solution and their capture by the imidazolium-based support. When a sixfold amount of support was employed the re-captured Pd species (0.5–0.6 wt%) were not anymore catalytically active. This result represents a new interesting aspect of this work since the highly cross-linked imidazolium-based material can act also as Pd scavenger avoiding the release of the metal in solution. Important differences between Heck an…
Triiodothyronine accelerates the synthesis of synapsin I in developing neurons from fetal rat brain cultured in a synthetic medium.
1990
The effect of Triiodothyronine (T3) on Synapsin I appearance in rat cortical neurons has been investigated in vitro. Neuronal cultures from 16-day-old fetal rat brain grown in the absence of T3, express immunohystochemically detectable Synapsin I at the 14th day in vitro. The addition of the hormone to the culture medium determines an early (at the 7th day in vitro) appearance of fluorescent dots specific for Synapsin I. © 1990 Plenum Publishing Corporation.
Use of linear discriminant analysis applied to vibrational spectroscopy data to characterize commercial varnishes employed for art purposes.
2007
An improvement of methodologies for characterising synthetic resins used in varnishes employed for art purposes has been suggested. Several kinds of standard of the most common polymeric resins (acrylic, vinyl, poly(vinyl alcohol), alkyd, cellulose nitrate, latex, polyester, polyurethane, epoxy, organosilicic, and ketonic) were analyzed by Fourier transform infrared (FTIR) spectroscopy. Synthetic resins characterization is based on the mathematical treatment of their whole spectrum, dividing it in 13 sections, avoiding the one-by-one interpretation of the absorption bands. The mathematical model takes as variables the maximal absorbance of each section, and each synthetic standard resin as …