Search results for "CONTACT"
showing 10 items of 1003 documents
Effect of relative humidity on carvacrol release and permeation properties of chitosan based films and coating
2014
International audience; The influence of water vapour conditions on mass transport and barrier properties of chitosan based films and coatings were studied in relation to surface and structural properties. Water contact angles, material swelling, polymer degradation temperature, barrier properties (PO2, PCO2, WVP) and aroma diffusion coefficients were determined. The solvent nature and the presence of carvacrol influenced the surface and structural properties and then the barrier performance of activated chitosan films. Increasing RH from 0% to 100% led to a significant increase in material swelling. The plasticization effect of water was more pronounced at high humid environment, while at …
Dynamics of a Spreading Nanodroplet: A Molecular Dynamic Simulation
2003
The spreading of polymer nanodroplets upon a sudden change from partial to complete wetting on an ideally flat and structureless solid substrate has been studied by molecular dynamic simulations using a coarse-grained bead-spring model of flexible macromolecules. Tanner's law for the growth of the lateral droplet radius {R(f) t 0.1 } is found to hold as long as the droplet does not disintegrate into individually moving chains. The data for the contact angle θ following from Tanner's law correspond to a dependence on time {θ(t) t -0.3 }. Our analysis of the mean square displacements of the polymer centers of mass reveals several dynamic regimes during the process of spreading. PACS numbers: …
Form defect influence on the shrinkage fit characteristics
1998
Abstract Today, manufacturing products must meet more and more severe specifications. The different parts composing the product often necessitate high dimensional precision, which increases the difficulties for a large series production. Then it it necessary to optimize dimensioning of the different components in an economic context. In the case of small dimensional fits, there is an influence of the micro-geometry (form of defect, roughness) and time of the process on the geometrical characteristics of the assembly. At the time of conception, it is necessary to obtain a good specification that relates the product functionalities with the best cost. The objective study of this is to simulat…
The effects of modifying contact, duration, and teaching strategies in awareness interventions on attitudes towards inclusion in physical education
2020
This quasi-experimental study analyses the effects of an awareness intervention programme with five different branches designed to improve the attitudes of physical education (PE) students towards the inclusion of classmates with disabilities. The contact (yes/no) and its frequency (×1 vs. ×3) with para-athletes, the duration of the programme (1 vs. 6/7 sessions), and the provision of teaching strategies and materials (yes/no) were manipulated. The study involved 603 students aged 14‒19 from five public educational centres in southern Spain. Attitudes were assessed pre- and post-intervention with the Spanish version of the Children's Attitude towards Integrated Physical Education (general a…
Opportunities and threats to contact lens practice: A global survey perspective
2021
Aim: To understand the views of contact lens (CL) practitioners across the globe regarding what they perceive as opportunities and threats in CL practice. Methods: A self-administered anonymised questionnaire, constructed in English and translated in six more languages, was distributed through reputed international professional bodies and academic institutions worldwide. The questionnaire included items on demographic characteristics, type of practice, and questions designed to explore practitioners’ perspective on the future of their CL practice over the next five years. Results: A total of 2408 valid responses were analysed. Multifocal CLs for presbyopia, CLs for myopia control, use of da…
Nitrogen recovery using a membrane contactor: Modelling nitrogen and pH evolution
2020
[EN] A hollow fibre membrane contactor has been applied for nitrogen recovery from anaerobic digestion supernatant at different operating conditions obtaining nitrogen recovery efficiencies over 99 %. A mathematical model able to represent the time evolution of pH and nitrogen concentration during the recovery process is presented in this paper. The developed model accurately reproduced the results obtained in 26 experiments carried out at different pH values (from 9 to 11), temperatures (from 25 to 35 degrees C), membrane surfaces (from 1.2 to 2.4 m(2)) and feed flow rates (from 0.33 x 10(-5) to 5.83 x 10(-5) m(3)/s) predicting the variations in nitrogen recovery rates measured at the diff…
How does a transition zone affect the electric field enhanced water dissociation in bipolar membranes?
1994
The changes in the electric field in the space charge regions and the corresponding effect on the water dissociation rate when a transition zone exists between the layers of a bipolar membrane are theoretically studied. A quasi-equilibrium approach based on the Poisson-Boltzmann equation for the space charge interfacial regions is used. The transition zone acts to decrease significantly the water dissociation rate. However, for realistic values of the thickness δ of the transition zone and provided that the ohmic drop over δ be small, this decrease in the dissociation rate is not very dependent on δ. The results obtained give theoretical support to some recent experimental findings.
Influence of cell-cell contact between L. thermotolerans and S. cerevisiae on yeast interactions and the exo-metabolome
2019
International audience; Sequential fermentation of grape must inoculated with L. thermotolerans and then S. cerevisiae 24 h later (typical wine-making practice) was conducted with or without cell-cell contact between the two yeast species. We monitored cell viability of the two species throughout fermentation by flow cytometry. The cell viability of S. cerevisiae decreased under both conditions, but the decrease was greater if there was cell-cell contact. An investigation of the nature of the interactions showed competition between the two species for nitrogen compounds, oxygen, and must sterols. Volatile-compound analysis showed differences between sequential and pure fermentation and that…
[Cr(dpa)(ox)2]–: a new bis-oxalato building block for the design of heteropolymetallic systems. Crystal structures and magnetic properties of PPh4[Cr…
2001
[EN] The new complexes of formulae PPh4[Cr(dpa)(ox)(2)] (1), AsPh4[Cr(dpa)(OX)(2)] (2), Hdpa[Cr(dpa)(ox)(2)]-4H(2)O (3), Rad[Cr(dpa)(ox)(2)] . H2O (4) and Sr[Cr(dpa)(ox)(2)](2) . 8H(2)O (5) [PPh4 = tetraphenylphosphonium cation; AsPh4 = tetraphenylarsoniurn cation; dpa = 2,T-dipyridylamine; ox = oxalate dianion; Rad = 2-(4-N-methylpyridinium)4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-a-oxyl-3-N-oxide] have been prepared and characterised by single-crystal X-ray diffraction. The structures of 1-4 consist of discrete [Cr(dpa)(ox)(2)](-) anions, tetraphenylphosphonium. (1), tetraphenylarsonium (2), monoprotonated Hdpa (3) and univalent radical (4) cations and uncoordinated water molecules (2-…
Exploiting redox activity of MIL-100(Fe) carrier enables carvacrol prolonged antimicrobial activity
2021
The design of efficient food contact materials that maintain optimal levels of food safety is of paramount relevance to reduce the increasing foodborne illnesses. In this work, we develop a smart composite MOF-based material that fosters a unique prolonged antibacterial activity. The composite is obtained by entrapping a natural preserving food molecule, carvacrol, into the mesoporous MIL-100(Fe) material following a direct and biocompatible impregnation method and obtaining particularly high payloads. By exploiting the intrinsic redox nature of MIL-100(Fe) material it is possible to achieve a prolonged activity against E. coli bacteria due to a triggered two-step carvacrol release of films…