Search results for "medium"
showing 10 items of 3746 documents
Dynamic Mechanical Behavior Analysis of Flax/Jute Fiber-Reinforced Composites under Salt-Fog Spray Environment
2020
Over the last decades, natural fiber-reinforced polymer composites (NFRPs) gained great attention in several engineering fields thanks to the reduction of the environmental impact and the end-of-life cost disposal. Unfortunately, the use of NFRPs is limited, mainly due to their weak resistance against humid environments. Since limited literature is available about the evolution of the dynamic mechanical response of NFRPs under aggressive environments, this paper aims to investigate the damping properties of flax, jute and flax/jute epoxy composites exposed to salt-fog up to 60 days. Furthermore, sodium bicarbonate fiber treatment was performed to improve the composites&rsquo
Seasonal changes in some thermoregulatory variables of the house sparrow (Passer domesticus L.)
1975
Abstract 1. The body weight, plumage, insulation, oxygen consumption and body lipids were studied seasonally in the house sparrow, Passer domesticus L. 2. The weights of body and plumage were greater in autumn and winter than in summer. 3. The insulative property of the plumage was better in autumn and winter birds than in summer birds. 4. The oxygen consumption of young birds was higher than that of plucked and adult birds. 5. The amount of subcutaneous depot fat tissue and its lipid content was greatest in autumn. The C18-unsaturated fatty acids were most prominent in the subcutaneous fat. Palmitic acid was the most prevalent fatty acid in the liver. The relative amount of C18-unsaturated…
The influence of the nature of the surface oxide on the adhesive fracture energy of aluminium-bonded joints as measured by T-peel tests
2008
Abstract Modification of aluminium alloy substrates microstructure and morphology by depositing new oxide layers on top of the metal surface has been investigated, with the aim of improving adhesion. The effect of treating the metal with boiling water or immersing it in a cerate bath has been studied by means of electron microscopy, contact angle measurements and peeling tests. The formation of pseudoboehmite layers or cerium conversion coatings both led to an increase in joint's adhesive fracture energy and more durable adhesive bonds with respect to joints obtained with “mechanically grinded only” substrates. Differences in the performance of the bonded joints has been discussed in terms …
CAN HELICICULTURE ACT AS A TOOL FOR EDIBLE LAND SNAILS’ NATURAL POPULATIONS’ MANAGEMENT IN ROMANIA?
2013
ABSTRACT Edible land snails are intensively exploited and the management of natural populations is a complex issue due the variety of factors involved. Two species of the genus Helix are present in our country, Helix pomatia and Helix lucorum, both of them collected since 1956. Although current legislation regulates the exploited amount and the dimension of collected snails, the exploitable amount is not assessed using appropriate ecological studies. The farming of edible snails has evolved in Romania especially during the period 2004-2008, the first farms being financed by the SAPARD Project. The inappropriate documentation on the matter of snail farming had lead to a quick failure of this…
Impact of histidine spacing on modified polyhistidine tag – Metal ion interactions
2018
Abstract Histidine rich sequences are chosen both by nature and by molecular biologists due to their high affinity towards metal ions. In this work, we examine the affinity and binding modes of Cu 2+ , Ni 2+ and Zn 2+ towards two histidine tags, the common His 6 -tag (Ac-HHHHHH-NH 2 ) and its modified sequence, which also contains six histidines, but separated with two alanine residues (Ac-HAAHAAHAAHAAHAAHAA-NH 2 ). The spatial separation of histidines has an important impact on its coordination properties. Cu 2+ and Ni 2+ complexes with Ac-HHHHHH-NH 2 are more stable than those with Ac-HAAHAAHAAHAAHAAHAA-NH 2 ; the contrary is observed for Zn 2+ . In a narrow range of pH, Cu 2+ -Ac-HHHHHH-…
Sometimes less is more—the impact of the number of His residues on the stability of Zn(ii)–SmtB and BigR4 α-5 domain complexes
2021
The increasing number of antibiotic-resistant pathogens has become one of the major health problems of modern times, including infections caused by Mycobacterium tuberculosis. One of the possible mammalian immune system responses to mycobacterial infection is the increase of the zinc(II) concentration in phagosomes to a toxic level. The mycobacterial SmtB protein belongs to the family of ArsR/SmtB transcription regulators. In the presence of high concentrations of metals, SmtB dissociates from DNA and activates the expression of metal efflux proteins. In this work, we focus on the α5 zinc(II) binding domains of SmtB/BigR4 proteins (the latter being the SmtB homolog from non-pathogenic M. sm…
Modelling of proton and metal exchange in the alginate biopolymer.
2005
Acid-base behaviour of a commercial sodium alginate extracted from brown seaweed (Macrocystis pyrifera) has been investigated at different ionic strengths (0.1or=I/mol l(-1)or=1.0) and in different supporting electrolytes (Et4NI, NaCl, KCl, LiCl, NaCl+MgCl2), with the aim of examining the influence of ionic medium on the proton-binding capacity and of quantifying the strength of interaction with light metal ions in the perspective of speciation studies in natural aqueous systems. Potentiometric ([H+]-glass electrode) and titration calorimetric data were expressed as a function of the dissociation degree (alpha) using different models (Henderson-Hasselbalch modified, Högfeldt three parameter…
Ceramics from Samshvilde (Georgia): A pilot archaeometric study
2020
Abstract This archaeometric study deals with seven samples of prehistoric pottery and, for the first time in Georgian studies, thirteen samples of glazed medieval pottery. All specimens were collected at Samshvilde, the most remarkable archaeological complex in southern Georgia and believed to represent locally-manufactured products. Two additional samples of raw materials composed of clay, silt, and sand were collected near the site and used to compare composition. Several analytical techniques were applied: Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF). The results allowed to build a c…
The defined adsorption site of sodium on the TiO2(110)–(1×1) surface
2004
The adsorption site of sodium on the TiO2(1 1 0)–(1 × 1) surface was studied by extended X-ray absorption fine structure. For coverage ranging between 0.25 and 0.5 ML, we find that sodium is on an ‘in-between' site where it is bound to two bridging oxygen atoms at 2.25 Å and one in-plane oxygen atom at 2.40 Å, in full agreement with DFT calculations. At higher coverage the site becomes an hollow site where the sodium atom is equidistant to the three oxygen atoms at 2.30 Å, while metallic sodium clusters are also formed at the surface.
Mo–V–Nb mixed oxides as catalysts in the selective oxidation of ethane
2003
Abstract Mo–V–Nb–O mixed metal oxides, obtained by heat-treatment in N 2 at 425 °C, have been studied as catalysts in the oxidative dehydrogenation of ethane. They present higher catalytic activity, while maintaining the same selectivity to ethylene, than the corresponding metal oxides calcined under air. Both amorphous and crystalline phases are present on active and selective catalysts. The implications of the presence of these phases as well as their physicochemical characteristics on the nature of active and selective sites are discussed.