Search results for "RADIATION"
showing 10 items of 5298 documents
(Me3Sn)2SbSb(SnMe3)2, 1∞-verknüpfte SbSb-Hanteln in einem thermochromen Distiban mit Schweratomgerüst
1987
Abstract Single crystals of the thermochromic distibane (Me 3 Sn) 4 Sb 2 ( 1 ) are obtained by irradiation of (Me 3 Sn) 3 Sb with sunlight. The crystal structure of 1 is reported as linear chains of distibane molecules in trans conformation with Sb ⋯ Sb contacts of 389 ppm. Diffuse reflexion spectra of 1 in the solid state and in solution demonstrate thermochromic effect. The Raman spectrum of solid 1 exhibits strong absorption at 162 cm −1 for ν(Sb 2 ).
Thermochromic Fluorescence from B18H20(NC5H5)2: An Inorganic–Organic Composite Luminescent Compound with an Unusual Molecular Geometry
2017
BH(NCH) is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of BH(NCH) emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a thermochromicity to the fluorescence of BH(NCH). Cooling to 8 K engenders a further shift in the emission wavelength to 585 nm and a twofold increase in intensity. Immobilization in a polystyrene thin-film matrix results in an efficient absorption of pumping excitation energy at 414 nm and a 609 nm photostable fluorescence. Such fluorescence from polystyrene t…
Numerical study of the accuracy of temperature measurement by thermocouples in small-scale reactors
2018
Proper temperature measurement is imperative in any laboratory study if reliable data are to be obtained, particularly in the field of chemical kinetics. In this paper we analyze in silico some typical thermowell configurations used in small-scale reactors by coupling computational fluid dynamics (CFD) with conjugated heat transfer phenomena. This allows us to identify deviations in measurements arising from thermal radiation and self-conductivity in mid and high temperature ranges, in addition to radial temperature gradients. A novel design is proposed and optimized by additional simulation, showing potential for faster and more accurate temperature measurements.
Influence of crystallinity and OH surface density on the photocatalytic activity of TiO2 powders
2014
Abstract The aim of the work was to study the influence of crystallinity and OH surface density on the photocatalytic activity of two commercial and two home-prepared TiO 2 powders. The samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG) and electron paramagnetic resonance (EPR) measurements. The photoactivity of the powders was tested employing the photodegradation of 4-nitrophenol (4-NP) and the selective oxidation of 4-methoxybenzyl alcohol (4-MBA) to 4-methoxybenzaldehyde ( p -anisaldehyde) under UV irradiation. An anti-correlation between oxidant power and selectivity of the various samples was found. A higher rate of 4-NP degradation was exhibited by…
An Approach on the Hydrogen Absorption in Carbon Black after Gamma Irradiation
2013
In this work, different samples of an industrial carbon black are used to study the hydrogen intake from an over pres-surized atmosphere and its changes due to alteration of its level of crystallinity produced by ¿-irradiation. The monitor-ing of the hydrogen adsorption was made by means of thermogravimetric analysis and by measurements of some elec-trical parameters as the Seebeck coefficient. X-ray diffraction shows that the irradiation diminishes the level of crystal-line perfection. These results show interesting possibilities to use carbon black as cheap hydrogen absorbers.
Radiation curing of diacrylate glycerolate of bisphenol-A in the presence of an organically modified montmorillonite for the production of flame-resi…
2006
Polymerization of an acrylate derivative of bisphenol-A by ionizing radiation in the presence of an organically modified montmorillonite was carried out in order to produce a flame-retardant composite. The measurement of the thermal effect during irradiation indicates that radiation curing of pure resin and resin-clay mixtures occurred in both cases. Moreover, differential scanning calorimetry and dynamic mechanical thermal analysis showed that a curing completion can be obtained by thermal curing after irradiation with a significant increase of the glass transition temperature. The morphology was investigated by X-ray diffraction and transmission electron microscopy. These have indicated t…
Computer simulation of ferroelectric property changes in PLZT ceramics under neutron irradiation
2001
The response of ferroelectric materials to high energy irradiation is of great interest because of their possible application in radiation environments such as thermonuclear reactors. In the present work a physical model for the defect evolution in PLZT ceramics under neutron irradiation and annealing is proposed. The influence of the defect system on the ferroelectric properties of these materials has been investigated. Satisfactory agreement between the theoretical estimated oxygen defect concentration after irradiation and annealing and the experimentally determined polarization has been obtained.
Therapy response evaluation of malignant lymphoma in a multicenter study: comparison of manual and semiautomatic measurements in CT.
2014
Purpose: Comparison of manual one-/bi-dimensional measurements versus semi-automatically derived one-/bi-dimensional and volumetric measurements for therapy response evaluation of malignant lymphoma during CT follow-up examinations in a multicenter setting. Materials and Methods: MSCT data sets of patients with malignant lymphoma were evaluated before (baseline) and after two cycles of chemotherapy (follow-up) at radiological centers of five university hospitals. The long axis diameter (LAD), the short axis diameter (SAD) and the bi-dimensional WHO of 307 target lymph nodes were measured manually and semi-automatically using dedicated software. Lymph node volumetry was performed semi-automa…
Available evidence on re-irradiation with stereotactic ablative radiotherapy following high-dose previous thoracic radiotherapy for lung malignancies
2015
Patients affected with intra-thoracic recurrences of primary or secondary lung malignancies after a first course of definitive radiotherapy have limited therapeutic options, and they are often treated with a palliative intent. Re-irradiation with stereotactic ablative radiotherapy (SABR) represents an appealing approach, due to the optimized dose distribution that allows for high-dose delivery with better sparing of organs at risk. This strategy has the goal of long-term control and even cure. Aim of this review is to report and discuss published data on re-irradiation with SABR in terms of efficacy and toxicity. Results indicate that thoracic re-irradiation may offer satisfactory disease c…
Findings and Utility of Chest Computed Tomography in Pediatric Tuberculosis
2017
AbstractThe objectives of this study are to describe the radiologic abnormalities detected on chest computed tomography (CT) of children suffering from tuberculosis and identify in which asymptomatic children, with positive tuberculin skin test and normal chest radiography, CT has the highest diagnostic yield using a low radiation dose protocol. The most common finding on CT in cases of tuberculosis is lymphadenopathy with necrotic appearance. In asymptomatic children with positive tuberculin skin test and normal chest radiography, CT had higher diagnostic yield in children younger than 5 years, modifying the therapeutic approach in a high percentage of cases. Reduction kilovoltage (kV) and…