Search results for "r process"
showing 10 items of 665 documents
Elastic Properties and Line Tension of Self-Assembled Bilayer Membranes
2013
The elastic properties of a self-assembled bilayer membrane are studied using the self-consistent field theory, applied to a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents. Examining the free energy of bilayer membranes with different geometries allows us to calculate their bending modulus, Gaussian modulus, two fourth-order membrane moduli, and the line tension. The dependence of these parameters on the microscopic characteristics of the amphiphilic chain, characterized by the volume fraction of the hydrophilic component, is systematically studied. The theoretical predictions are compared with the results from a simple monolayer model, whic…
Raman Spectra of ZrS2 and ZrSe2 from Bulk to Atomically Thin Layers
2016
In the race towards two-dimensional electronic and optoelectronic devices, semiconducting transition metal dichalcogenides (TMDCs) from group VIB have been intensively studied in recent years due to the indirect to direct band-gap transition from bulk to the monolayer. However, new materials still need to be explored. For example, semiconducting TMDCs from group IVB have been predicted to have larger mobilities than their counterparts from group VIB in the monolayer limit. In this work we report the mechanical exfoliation of ZrX2 (X = S, Se) from bulk down to the monolayer and we study the dimensionality dependence of the Raman spectra in ambient conditions. We observe Raman signal from bul…
Development of a three-dimensional cell culture system based on microfluidics for nuclear magnetic resonance and optical monitoring
2014
A new microfluidic cell culture device compatible with real-time nuclear magnetic resonance (NMR) is presented here. The intended application is the long-term monitoring of 3D cell cultures by several techniques. The system has been designed to fit inside commercially available NMR equipment to obtain maximum readout resolution when working with small samples. Moreover, the microfluidic device integrates a fibre-optic-based sensor to monitor parameters such as oxygen, pH, or temperature during NMR monitoring, and it also allows the use of optical microscopy techniques such as confocal fluorescence microscopy. This manuscript reports the initial trials culturing neurospheres inside the micro…
Low Conductive Electrodeposited Poly(2,5-dimethoxyaniline) as a Key Material in a Double Lateral Heterojunction, for Sub-ppm Ammonia Sensing in Humid…
2019
We present a new device called a double lateral heterojunction (DLH) as an ammonia sensor in humid atmosphere. It combines polyaniline derivatives in their poor conducting state with a highly conductive molecular material, lutetium bisphthalocyanine, LuPc2. Polyaniline and poly(2,5-dimethoxyaniline) are electrodeposited on ITO interdigitated electrodes, leading to an original device that can be obtained only by electrochemistry and not by other solution processing techniques. Both polymers lead to highly conducting materials that require a neutralization step before their coverage by LuPc2. While the device based on polyaniline shows ohmic behavior, the nonlinear I- V characteristics of the…
Monte Carlo analysis of polymer translocation with deterministic and noisy electric fields
2012
AbstractPolymer translocation through the nanochannel is studied by means of a Monte Carlo approach, in the presence of a static or oscillating external electric voltage. The polymer is described as a chain molecule according to the two-dimensional “bond fluctuation model”. It moves through a piecewise linear channel, which mimics a nanopore in a biological membrane. The monomers of the chain interact with the walls of the channel, modelled as a reflecting barrier. We analyze the polymer dynamics, concentrating on the translocation time through the channel, when an external electric field is applied. By introducing a source of coloured noise, we analyze the effect of correlated random fluct…
Effect of Fiber-Reinforced Composite and Elastic Post on the Fracture Resistance of Premolars with Root Canal Treatment—An In Vitro Pilot Study
2020
(1) Background: To analyze the fracture resistance of endodontically upper premolar teeth restored with glass fiber reinforced posts, glass fiber elastic posts, conventional composite resin (CR) and glass fiber reinforced composite (FRC) resins as restorations. (2) Methods: Seventy premolars were submitted to root canal treatment and restored with the following restorative materials (n = 10): A. FRC posts restored with resin
Glassy PEEK‐WC vs Rubbery Pebax®1657 Polymers: Effect on the Gas Transport in CuNi‐MOF Based Mixed Matrix Membranes
2020
Mixed matrix membranes (MMMs) are seen as promising candidates to overcome the fundamental limit of polymeric membranes, known as the so-called Robeson upper bound, which defines the best compromise between permeability and selectivity of neat polymeric membranes. To overcome this limit, the permeability of the filler particles in the MMM must be carefully matched with that of the polymer matrix. The present work shows that it is not sufficient to match only the permeability of the polymer and the dispersed phase, but that one should consider also the individual contributions of the diffusivity and the solubility of the gas in both components. Here we compare the gas transport performance o…
Ab Initio Simulation of Attosecond Transient Absorption Spectroscopy in Two-Dimensional Materials
2018
We extend the first-principles analysis of attosecond transient absorption spectroscopy to two-dimensional materials. As an example of two-dimensional materials, we apply the analysis to monolayer hexagonal boron nitride (h-BN) and compute its transient optical properties under intense few-cycle infrared laser pulses. Nonadiabatic features are observed in the computed transient absorption spectra. To elucidate the microscopic origin of these features, we analyze the electronic structure of h-BN with density functional theory and investigate the dynamics of specific energy bands with a simple two-band model. Finally, we find that laser-induced intraband transitions play a significant role in…
Stability of Halloysite, Imogolite, and Boron Nitride Nanotubes in Solvent Media
2018
Inorganic nanotubes are attracting the interest of many scientists and researchers, due to their excellent application potential in different fields. Among them, halloysite and imogolite, two naturally-occurring aluminosilicate mineral clays, as well as boron nitride nanotubes have gained attention for their proper shapes and features. Above all, it is important to reach highly stable dispersion in water or organic media, in order to exploit the features of this kind of nanoparticles and to expand their applications. This review is focused on the structural and morphological features, performances, and ratios of inorganic nanotubes, considering the main strategies to prepare homogeneous col…
Designing voltage multipliers with nanofluidic diodes immersed in aqueous salt solutions.
2016
[EN] Membranes with nanofluidic diodes allow the selective control of molecules in physiological salt solutions at ambient temperature. The electrical coupling of the membranes with conventional electronic elements such as capacitors suggests opportunities for the external monitoring of sensors and actuators. We demonstrate experimentally and theoretically the voltage multiplier functionality of simple electrical networks composed of membranes with conical nanopores coupled to load capacitors. The robust operation of half and full wave voltage multipliers is achieved in a broad range of experimental conditions (single pore and multipore membranes, electrolyte concentrations, voltage amplitu…