1,721,124 research outputs found
EXTENSION OF TWO-PHOTON SPECTROSCOPY TO THE VACUUM ULTRAVIOLET USING SYNCHROTRON RADIATION
No full textSynchrotron radiation has been used for the first time in two-photon spectroscopy. The experimental apparatus, built at the ADONE storage ring in Frascati, and using a Q-switched Nd:YAG laser as a powerful source is presented. Space and time superposition of the beams is discussed extensively. Testing of the apparatus has been performed by measuring the two-photon absorption spectra of KCl and NaCl
Synthesis and characterization of new ferrocene, porphyrin and C<inf>60</inf> triads, connected by triple bonds
No full textThe 2,12 pyrrole positions of meso-tetraphenylporphyrinwere functionalized through triple carbonecarbon
bonds by ferrocene and C60 giving new electron donor-acceptor triads which have been characterized and
studied by photophysical methods
Optical investigation on dye-doped sol-gel glasses
No full textWe have investigated the optical properties of the 3,3'-diethyloxadicarbocyanine iodide (DODCI) dye incorporated in a number of sol-gel glasses in order to study the interaction between the trapped molecule and the host matrix. The differences found in both the absorption and the photoemission spectra demonstrate that the excitation processes of the dye molecule are influenced by the chemical reactivity and the degree of porosity of the surrounding network. We have found that while the molecular photoisomerization is quenched in all the matrices, for the modifications of the electronic excited states the high rigidity of the purely inorganic silica matrix is required. Conversely, the possibility of chemical attacks to the molecular conjugate chain seems to increase in the hybrid organic/inorganic ormosil matrices. © Societò Italiana di Fisica
Thermophysical Parameters Evaluation by Pyroelectric Detection
No full textThe different configurations of the photopyroelectric calorimetry which can be adopted for the evaluations of the thermophysical parameters in liquids and in solids, and the advantages, with respect to other calorimetric techniques, are briefly described. A review of the recent results obtained by the photopyroelectric back-detection configuration for the determination of the different thermophysical properties in various materials is presented with particular attention to the cases where the temperature dependence of such parameters is studied. The results concerning the studies carried out by performing simultaneous calorimetric and imaging evaluations are also described. Finally, the possibility of performing “absolute” measurements of the thermal parameters, eliminating the influence of eventual coupling fluid, is discussed
Study of the refractive index of microscopic glass beads by light-refraction analysis
No full textThe refractive index of submillimeter glass beads has been measured by means of a novel, to our knowledge, procedure with reference liquids that does not require close index matching and therefore avoids the use of toxic compounds for high-index glasses (i.e., n ≥ 1.8). The method is based on the analysis of the light refracted by a monolayer of beads in comparison with ray-tracing simulations. For the three different types of glass beads investigated a satisfactory fit is achieved by the assumption of a radial variation of the refractive index inside the beads. This is ascribed to the tensile and compressive stresses originating inside the beads during rapid solidification of the glass. © 1997 Optical Society of America
Proving the preclusion of data manipulation using parallel data acquisition in chromatography
No full textTraceability has an enormous value for companies, but especially for those working in the regulated environment. It plays a special role in the field of pharmacy with respect to manufacturing, controlling and distributing batches of drugs. Through the guidance of Good Manufacturing Practice (GMP) traceability should be ensured. An increasing number of pharmaceutical companies are member of one of the global pharmacopoeias (United States Pharmacopeia, European Pharmacopeia and Japanese Pharmacopeia). The specifications of these pharmacopoeias describe the best practice in documentation, control, qualification and risk management. But however, the pharmacopoeias are written very generally and do not distinguish between the vendors of the analytical instruments. Here, we analyze how chromatographic analyses and data acquisition rely on a specific vendor of the device and the chromatography data system (CDS), the controlling software. We present a way to compare the data acquisition of different CDSs communicating with HPLC instruments. A newly developed software called Data Collector allows the acquisition of data from a HPLC detector parallel to the controlling CDS in the same run. Two HPLC systems and two different CDSs using a well defined sample standard have been tested. The direct comparison of the acquired data precludes unexpected data manipulations of both tested CDSs and shows that there are primarily deviations between the CDSs due to time variations only which depend on the sampling rate. All in all the Data Collector can be used for the traceability of data acquisition
Double entry method for the verification of data a chromatography data system receives
No full textThe importance of software validation increases since the need for a high usability and suitability of software applications grows. In order to reduce costs and manage risk factors more and more recommendations up to rules have been established. In the field of pharmacy the vendors of so called chromatography data systems (CDS) had to implement the guidelines of the Code of Federal Regulations Title 21 (CFR 21) during the last years in order to fulfill the increasing requirements. The CFR 21 part 11 deals with electronic records and signatures. This part is binding for each company in the regulated environment that will create, edit and sign electronic information instead of printing them on paper. The subsection CFR 21 part 11.10(h) explains how to perform an input check but it is very focused on the manual entry of data by the user. In this article we like to present a method in order to extend the input check to the data that will be provided by the hardware instrument and received by the CDS. A software tool has been written which allowes to communicate with a HPLC detector and acquire data from it. The communication is completely independent from a CDS which is started separately and connected to the same system. Using this configuration we made a parallel data acquisition of two instances at the same time possible. Two CDSs have been tested and for at least one of them it has been shown that a comparison of the acquired data can be done as like as the double entry method for the data verification. Same would be applicable for the second CDS after a few modifications. The given approach could be either used for a live data verification of produced raw data or as a single test during a software operational qualification to verify the data acquisition functionality of the software
Detection of heavy metals in water using graphene oxide quantum dots: an experimental and theoretical study
Full text linkIn this work, we investigate by ab initio calculations and optical experiments the sensitivity
of graphene quantum dots in their use as devices to measure the presence, and concentration, of
heavy metals in water. We demonstrate that the quenching or enhancement in the optical response
(absorption, emission) depends on the metallic ion considered. In particular, two cases of opposite
behaviour are considered in detail: Cd2+, where we observe an increase in the emission optical
response for increasing concentration, and Pb2+ whose emission spectra, vice versa, are quenched
along the concentration rise. The experimental trends reported comply nicely with the different
hydration patterns suggested by the models that are also capable of reproducing the minor quenching/
enhancing effects observed in other ions. We envisage that quantum dots of graphene may be
routinely used as cheap detectors to measure the degree of poisoning ions in water
Laser pulse effects on plasma-sprayed and bulk tungsten
Full text linkTungsten (W) is considered a promising plasma-facing material for protecting the divertor of the ITER (International Thermonuclear Experimental Reactor). The effects on W of transient thermal loads of high energy occurring in a tokamak under operative conditions have been simulated through a single laser pulse delivered by an Nd:YAG laser. Bulk and plasma-sprayed (PS) samples have been submitted to tests and successively examined via SEM (scanning electron microscopy) observations. In both types of materials, the laser pulse induces similar effects: (i) a crater forms in the spot central area; (ii) all around the area, the ejection and the movement of molten metal give rise to a ridge; (iii) in a more external area, the surface shows plates with jagged boundaries and cracks induced by thermal stresses; (iv) the pores present in the original material become preferred ablation sites. However, the affected surface area in PS samples is larger and asymmetric if compared to that of bulk material. Such a difference has been explained by considering how microstructural characteristics influence heat propagation from the irradiated spot, and it was found that grain size and shape play a decisive role
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