Search results for " density"

Modeling the Interaction of Carbon Monoxide with Flexible Graphene: From Coupled Cluster Calculations to Molecular-Dynamics Simulations

2018

The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite graphene models with the use of coronene for coupled cluster calculations and circumcoronene for B97D calculations showed that there was no preferential site for adsorption and that the most important factor was the orientation of CO relative to graphene. The parallel orientation was preferred, with binding energies around 9 kJ mol-1 at the CCSD(T) and B97D levels, which was in good agreement with experimental findings. From a large number of CO-circumcoronene and CO-CO interactions, computed at different distances and randomly generated orientations, parameters were fi…

Two-terminal nanoelectromechanical devices based on germanium nanowires.

2009

A two-terminal bistable device, having both ON and OFF regimes, has been demonstrated with Ge nanowires using an in situ TEM-STM technique. The function of the device is based on delicately balancing electrostatic, elastic, and adhesion forces between the nanowires and the contacts, which can be controlled by the applied voltage. The operation and failure conditions of the bistable device were investigated, i.e. the influence of nanowire diameter, the surface oxide layer on the nanowires and the current density. During ON/OFF cycles the Ge nanowires were observed to be more stable than carbon nanotubes, working at similar conditions, due to the higher mechanical stability of the nanowires. …

Elastic wave propagation in bone in vivo: methodology.

1995

The purpose of this study was to investigate the usefulness of elastic wave propagation (EWP) in estimating the mechanical properties (elasticity) of human tibia. The test group was composed of 78-yr-old women assigned to high (n = 19) and low (n = 17) bone mineral density (BMD) groups as measured at the calcaneus by the 125I-photon absorption method. The EWP apparatus consisted of an impact-producing hammer with a force strain gauge and two accelerometers positioned on the bone. Results for nylon and acrylic were used to calibrate the apparatus. Polyvinyl chloride (PVC) solid rods and tubes of various diameters were used to evaluate the relationship between the elastic wave velocity and cr…

Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

2015

Background This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant s…

Photothermal excitation setup for a modified commercial atomic force microscope

2014

High-resolution imaging in liquids using frequency modulation atomic force microscopy is known to suffer from additional peaks in the resonance spectrum that are unrelated to the cantilever resonance. These unwanted peaks are caused by acoustic modes of the liquid and the setup arising from the indirect oscillation excitation by a piezoelectric transducer. Photothermal excitation has been identified as a suitable method for exciting the cantilever in a direct manner. Here, we present a simple design for implementing photothermal excitation in a modified Multimode scan head from Bruker. Our approach is based on adding a few components only to keep the modifications as simple as possible and …

Millisecond radiative recombination in poly(phenylene vinylene)-based light-emitting diodes from transient electroluminescence

2007

The current and electroluminescence transient responses of standard poly phenylene vinylene -based light-emitting devices have been investigated. The electroluminescence time response is longer milliseconds scale than the current switch-off time by more than one order of magnitude, in the case of small area devices 0.1 cm2 . For large area devices 6 cm2 the electroluminescence decay time decreases from 1.45 ms to 100 s with increasing bias voltage. The fast current decay limits the electroluminescence decay at higher voltages. Several approaches are discussed to interpret the observed slow decrease of electroluminescence after turning off the bias. One relies upon the Langevin-type bimolecu…

Publisher's Note: “Low intrinsic carrier density LSMO/Alq3/AlOx/Co organic spintronic devices” [Appl. Phys. Lett. 112, 142401 (2018)]

2018

Nitrogen Hydrate Cage Occupancy and Bulk Modulus Inferred from Density Functional Theory-Derived Cell Parameters

2021

International audience; Gas clathrate hydrate solid materials, ubiquitous in nature as found either on the ocean floor, permafrost on the Earth, or in extraterrestrial planets and comets, are also technologically relevant, for example, in energy storage or carbon dioxide sequestration. Nitrogen hydrate, in particular, is of great interest as a promoter of the kinetics of the methane replacement reaction by carbon dioxide in natural gas hydrates. This hydrate may also appear in the chemistry of planets wherever nitrogen constitutes the majority of the atmosphere. A fine understanding of the stability of this hydrate under various thermodynamic conditions is thus of utmost importance to asses…

Polymerization and Damage of C60 Single Crystals under Low Fluency Laser Irradiation

2001

Photo-induced hardening, substructure formation and damage of C 60 single crystals under the 632.8 nm He-Ne laser irradiation in air at a power density of 1.47 mW/mm 2 was investigated by microhardness and AFM methods. Photo-induced formation of the dislocation substructure and crystallographically oriented crack patterns on the (111) face due to lattice contraction on polymerization were observed. Two phototransformed states: soft (400-450 MPa) and hard (650-1000 MPa) are found to appear under laser-irradiation. Hard fullerite is created in the subsurface layer < 1 μm at the saturation stage of phototransformation. It softens to 400-450 MPa at 340 K and reverts to non-polymerized state at …

Investigation of Critical Points of Pore Formation Voltage on the Surface of Semiconductors of A3B5 Group

2021

In this work, critical values of pore-formation in electrochemical machining of semiconductors of A 3 B 5 group are studied. On the example of indium phosphide, the indicators of the series of dependence of current density on the voltage of anodization are studied. The rates of current density increase in the regime of gradual rise of anodization voltage are determined. According to these indicators, the intervals are established, within which the active pore-formation occurs on the surface of semiconductor.