Search results for "FAST"
showing 10 items of 821 documents
Small bowel motility: relationship between smooth muscle contraction and electroenterogram signal.
2000
A study is made to correlate the electrical and mechanical activity of the smooth muscle of the small bowel. Bioelectrical signal recording from the intestinal serosa (electroenterogram) comprises a slow wave (SW) and spike burst (SB), though only the latter reflects intestinal pressure. The electroenterogram and smooth muscle pressure are simultaneously recorded in the canine small bowel. Spectral and time series analysis of the electroenterogram are performed to establish those electrical parameters that best reflect intestinal pressure. The results reveal an underlying correlation between the estimated parameters of electrical activity and smooth muscle pressure. In addition, parameters …
Computational Fluid Dynamics Simulation of Hydrodynamics and Stresses in the PhEur/USP Disintegration Tester Under Fed and Fasted Fluid Characteristi…
2015
ABSTRACT: Disintegration of oral solid dosage forms is a prerequisite for drug dissolution and absorption and is to a large extent dependent on the pressures and hydrodynamic conditions in the solution that the dosage form is exposed to. In this work, the hydrodynamics in the PhEur/USP disintegration tester were investigated using computational fluid dynamics (CFD). Particle image velocimetry was used to validate the CFD predictions. The CFD simulations were performed with different Newtonian and non-Newtonian fluids, representing fasted and fed states. The results indicate that the current design and operating conditions of the disintegration test device, given by the pharmacopoeias, are n…
Phase transitions in Ag-based solid electrolytes as detected by thermosonimetry
2001
Abstract Observations of the acoustic emission accompanying the solid–solid (polymorphic) phase changes in silver iodide and silver chalcogenides were performed. It has been found that the temperature dependencies of both the number of acoustic events and their counting rate, registered when heating the investigated materials, display distinct anomalies at the temperature corresponding to the polymorphic phase transition occurring in a given substance. The phase transition temperatures determined from the position of these anomalies agree well with the results of control DSC measurements, as well as with the literature data on the temperatures of the transition of investigated materials to …
Giant barocaloric effects over a wide temperature range in superionic conductor AgI
2017
Current interest in barocaloric effects has been stimulated by the discovery that these pressure-driven thermal changes can be giant near ferroic phase transitions in materials that display magnetic or electrical order. Here we demonstrate giant inverse barocaloric effects in the solid electrolyte AgI, near its superionic phase transition at ~420 K. Over a wide range of temperatures, hydrostatic pressure changes of 2.5 kbar yield large and reversible barocaloric effects, resulting in large values of refrigerant capacity. Moreover, the peak values of isothermal entropy change (60 J K−1 kg−1 or 0.34 J K−1 cm−3) and adiabatic temperature changes (18 K), which we identify for a starting tempera…
Experimental and theoretical studies of polaron optical properties in KNbO3 perovskite
2004
Time-resolved absorption and luminescence spectra have been measured in KNbO3 perovskite crystals after pulsed band-gap excitation by 200 fs laser pulses and 10 ns electron pulses. Quantum chemical calculations using the large unit cell periodic model support the interpretation of the observed transient absorption bands at 0.8 and 1.1 eV as the self-trapped electron polarons and bound hole polarons, respectively. The activation energy for the 2.2 eV green luminescence quenching is 0.05 eV. We suggest that the short lifetime (,15 ns) of the luminescence at RT is caused by the radiative recombination of nearest electron and hole polarons. q 2003 Elsevier Ltd. All rights reserved.
X‐ray and pulsed electron beam excited luminescence and optical absorption in KTaO 3 crystals
2005
Pulsed electron beam excited time-resolved transient absorption and luminescence have been studied in nominally pure and Li-doped KTaO3 single crystals. It is found that under electron beam excitation in nominally pure KTaO3 the absorption bands peaks at ∼0.8 eV, ∼1.1 eV and 1.7 eV whereas in KTaO3:Li at ∼1.1 eV and ∼1.7 eV. The transient absorption decay varies over the spectrum thus revealing several short-lived centers. The main luminescence peak is centred at ∼2.7 eV in all KTaO3 specimens. Luminescence decay kinetics observed for the two bands slightly differ indicating different kinds of excited states are involved. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast Relaxation Dynamics of Osmium−Polypyridine Complexes in Solution
2013
We present steady-state absorption and emission spectroscopy and femtosecond broadband photoluminescence up-conversion spectroscopy studies of the electronic relaxation of Os(dmbp)(3) (Os1) and Os(bpy)(2)(dpp) (Os2) in ethanol, where dmbp is 4,4'-dimethyl-2,2'-biypridine, bpy is 2,2'-biypridine, and dpp is 2,3-dipyridyl pyrazine. In both cases, the steady-state phosphorescence is due to the lowest (MLCT)-M-3 state, whose quantum yield we estimate to be <= 5.0 x 10(-3). For Os1, the steady-state phosphorescence lifetime is 25 ns. In both complexes, the photoluminescence excitation spectra map the absorption spectrum, pointing to an excitation wavelength-independent quantum yield. The ultrafa…
Carbon Nanodots: A Review—From the Current Understanding of the Fundamental Photophysics to the Full Control of the Optical Response
2018
Carbon dots (CDs) are an emerging family of nanosystems displaying a range of fascinating properties. Broadly speaking, they can be described as small, surface-functionalized carbonaceous nanoparticles characterized by an intense and tunable fluorescence, a marked sensitivity to the environment and a range of interesting photochemical properties. CDs are currently the subject of very intense research, motivated by their possible applications in many fields, including bioimaging, solar energy harvesting, nanosensing, light-emitting devices and photocatalyis. This review covers the latest advancements in the field of CDs, with a focus on the fundamental understanding of their key photophysica…
Effect of Halogen Ions on the Photocycle of Fluorescent Carbon Nanodots
2019
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, especially in view of their possible sensing applications, the existing works have mostly focused on the quenching of C-dot fluorescence induced by metal cations. In fact, these latter easily bind to C-dots surfaces, which are negatively charged in most cases, promoting an electron transfer from the surface to them. Much less is known from the literature on the effect induced on C-dots by prototypi…
The fast photon detection system of COMPASS RICH-1
2007
Abstract A fast photon detection system has been built for the upgrade of COMPASS RICH-1, the large size gaseous RICH detector in use at the COMPASS Experiment at the CERN SPS since 2001. The photon detectors of the central region have been replaced by a new system based on multi-anode photomultipliers coupled to individual fused silica lens telescopes and a fast readout electronics system, while in the outer region the existing MWPCs with CsI photocathodes have been equipped with a new readout system, based on the APV chip. RICH-1 has been successfully operated in its upgraded version during the 2006 run. We report on the upgrade design and construction, and on the preliminary characteriza…