Search results for "laser"
showing 10 items of 3161 documents
Experiments and predictions of the transition of the flow pattern with impeller clearance in stirred tanks
2001
In the present work, the double- to single-loop flow pattern transition in a stirred vessel equipped with a Rushton turbine is investigated by Laser Doppler anemometry (LDA). In particular, the clearance at which such transition occurs is assessed by comparing axial velocity profiles underneath the impeller. Computational fluid dynamics (CFD) simulations of the same system are carried out, by employing the 'inner-outer' fully predictive computation strategy. The comparison of predicted results with the experimental data collected shows that the transition is well reproduced by simulations. A good agreement on the mean velocities is also observed but for the impeller discharge stream angle t…
Effect of gaseous impurities and the laser optics
2004
The impurities into the volume of a material appear while the elaboration process of the considered material. If a material is non-homogenous, even if we machine this material by means of a classical technology we could remark some differences in the machining process like cutting, drilling a.s.o. even in the process of welding. The impurities may be gaseous or solid. Each kind of impurity has another effect for the classical tool, or for a non-traditional tool i.e. a kind of concentrated energy. Each kind of medium has another reaction versus laser beam, because each medium has other physical characteristics. The modifications of characteristics require modifications of photon beam paramet…
Collinear laser spectroscopy of ZrII
2003
A new technique involving collinear laser spectroscopy of ion bunches has been used to study the radio-isotopes 87,87m,88,89,89m Zr.
First on-line laser spectroscopy of radioisotopes of a refractory element
1999
The first fully on-line isotope shift measurement of a radioactive refractory element is reported. Collinear laser-induced fluorescence measurements were made on the radioactive isotopes ${}^{170,172,173,174}\mathrm{Hf}$ produced with a flux of $2--3\ifmmode\times\else\texttimes\fi{}{10}^{3}$ ions per second from an ion-guide fed isotope separator. The method may be applied to all elements and isomers with lifetimes as short as 1 ms. The systematics of the new charge radii measurements are well reproduced by theory, with the maximum deformation in the chain occurring significantly below the midshell.
Collinear fast-beam laser spectroscopy
1987
The progress in atomic and molecular spectroscopy has gone hand in hand with improvements of the resolution. Before the tunable narrow-band lasers led to the invention of Doppler-free techniques, spectral lines from cooled hollow-cathode discharges(1) had typical widths larger than 300 MHz, and high resolution was achieved only in rf spectroscopy, e.g., within hyperfine structure multiplets, by the classical techniques like atomic beam magnetic resonance,(2) optical pumρing,(3) or double resonance.(4) While the Doppler broadening $$\delta {v_D} = {v_0}{\left( {{{8kT{\rm{ }}\ln {\rm{ 2}}} \over {m{c^2}}}} \right)^{1/2}}$$ (1) is negligible for resonance frequencies v 0 in the rf regime, the …
Author response: The primary structural photoresponse of phytochrome proteins captured by a femtosecond X-ray laser
2020
Energy transfer to xanthene dyes in dansylated POPAM dendrimers
2011
Abstract Excitation energy transfer (EET) in host–guest complexes of dansylated POPAM dendrimers and xanthene dyes have been studied by transient absorption spectroscopy. EET from dansyl periphery to guests: rose bengal, eosin, or fluorescein, showed non-exponential behaviour as a result of distribution of donor–acceptor distances. Time constants range from 100 fs to 8 ps, independent of the dye and the dendrimer generation. Experiments suggested that in dendrimers binding more than one guest, EET among the guests becomes effective. Guest–host and guest–guest interactions induce non-radiative relaxation channels making excitation decays of the guests clearly faster in complexes than in solu…
Erbium Family Laser and Nd:YAG Laser Impact on Bacteriology and Fungi in Dentistry
2021
Lai gan zobārstniecībā pielietojamie lāzeri tiek izmantoti salīdzinoši nesen ir veikts liels daudzums klīnisko pētījumu ,kuros novērtēta gan to efektivitāte ,baktericīdā iedarbība, gan klīniskais sniegums. Er:YAG, Er,Cr:YSGG un Nd:YAG ir visdaudzsološākie zobārstniecībā izmantojamie lāzeri, ko nosaka to multifunkcionālais pielietojums un pretmikrobā efektivitāte. Galvenais uzsvars šajā darbā vērsts uz Er:YAG, Er,Cr:YSGG un Nd:YAG, analizējot to bakterioloģisko un pretmikrobo darbību.
Treatment of post-surgical scars of cheek’s mucosa with Er, Cr: YSGG laser
2013
Background. Bulkiness and unsightly scarring are very common complaints after oral cancer surgical treatment. The scar of cheek can give complications such as: reduced mouth opening or interference with mastication. Both of these complications are particularly sources of discomfort for patient and may cause additional trauma to the treated mucosa.There are several ways to reduce these complications: the most widely used is surgical excision of the scar but this treatment often requires more invasive surgery. Case report. A 58-year-old male patient, treated surgically for a carcinoma in situ in the right cheek, reported to our oral medicine sector after this excision. The patient manifested …
Minimally invasive approach to eliminate pyogenic granuloma using Er, Cr: YSGG laser
2013
Backgroung. PG or granuloma pyogenicum is a common tumor like growth of the oral cavity that is considered to be of non-neoplastic nature, arising commonly as a result of constant low grade trauma and poor oral hygiene and in few instances because of hormonal disturbances. Since it is a benign lesion, choice of treatment is surgical excision with removal of underlying cause if any. A newer treatment modality using laser has been reported. Case report. A 16-year-old male patient reported to our sector of oral medicine with the chief complaint of intra-oral painless growth since four months. Past history and medical history did not reveal any relevant information. He was taking no medication …