Search results for "Elements"
showing 10 items of 799 documents
Elements with square roots in compact groups
2010
The probability that a randomly chosen element has a square root is studied in [1, 2, 8] in the finite case. Here we deal with the infinite case.
The symmetric boundary element method for unilateral contact problems
2008
Abstract On the basis of the boundary integral equation method, in its symmetric formulation, the frictionless unilateral contact between two elastic bodies has been studied. A boundary discretization by boundary elements leads to an algebraic formulation in the form of a linear complementarity problem. In this paper the process of contact or detachment is obtained through a step by step analysis by using generalized (weighted) quantities as the check elements: the detachment or the contact phenomenon may happen when the weighted traction or the weighted displacement is greater than the weighted cohesion or weighted minimum reference gap, respectively. The applications are performed by usin…
Numerical and experimental analysis of a pegs-wing ventilated disk brake rotor, with pads and cylinders
2005
Hexafluoro complex of rutherfordium in mixed HF/HNO3 solutions
2008
Formation of anionic fluoride-complexes of element 104, rutherfordium, produced in the 248 Cm( 18 O, 5n) 261 Rf reaction was studied by anion-exchange on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF 6 ] 2- , was formed in the studied fluoride ion concentrations of 0.0005-0.013 M. Formation of [RfF 6 ] 2- was significantly different from that of the homologues Zr and Hf, [ZrF 6 ] 2- and [HfF 6 ] 2- ; the evaluated formation constant of [RfF 6 ] 2- is at least one-order of magnitude smaller than those of [ZrF 6 ] 2- and [HfF 6 ] 2- .
Liquid-Phase Chemistry of Superheavy Elements
2013
An overview over the chemical separation and characterization experiments of the four transactinide elements so far studied in liquid phases, rutherfordium (Rf), dubnium (Db), seaborgium (Sg), and hassium (Hs), is presented. Results are discussed in view of the position of these elements in the Periodic Table and of their relation to theoretical predictions. Short introductions on experimental techniques in liquid-phase chemistry, specifically automated rapid chemical separation systems, are also given. Studies of nuclear properties of transactinide nuclei by chemical isolation will be mentioned. Some perspectives for further liquid-phase chemistry on heavier elements are briefly discussed.
Elementsastāva un minerālvielu izmaiņas atkarībā no augu biomasas veida un apstrādes metodes
2016
Elementsastāva un minerālvielu izmaiņas atkarībā no augu biomasas veida un apstrādes metodes. Fridrihsons R., zinātniskie vadītāji prof. Dr. chem. Vīksna A. un M.Sc. Lauberts M. Bakalaura darbs, 70 lappuses, 38 attēli, 28 tabulas, 42 literatūras avoti, 4 pielikumi. Latviešu valodā. Darbā veikta neapstrādātas un ar ultraskaņas ekstrakcijas, torrifikācijas metodēm apstrādātas biomasas elementsastāva un minerālvielu analīze. Kopumā apskatīti 70 paraugi, 67 noteikts elementsastāvs, 11 paraugiem noteikts pelnu saturs un minerālvielu sastāvs. Veikta minerālvielu sastāva analīze, izmantojot četras metodes – FES, FAAS, ICP-MS un WD-XRF, rezultāti salīdzināti savā starpā. Elementsastāvs noteikts izm…
Precision Measurement of the First Ionization Potential of Nobelium
2018
One of the most important atomic properties governing an element's chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626 21±0.000 05 eV. This work provides a stringent benchmark for st…
First Ionization Potentials of Fm, Md, No, and Lr
2018
We report the first ionization potentials (IP1) of the heavy actinides, fermium (Fm, atomic number Z = 100), mendelevium (Md, Z = 101), nobelium (No, Z = 102), and lawrencium (Lr, Z = 103), determined using a method based on a surface ionization process coupled to an online mass separation technique in an atom-at-a-time regime. The measured IP1 values agree well with those predicted by state-of-the-art relativistic calculations performed alongside the present measurements. Similar to the well-established behavior for the lanthanides, the IP1 values of the heavy actinides up to No increase with filling up the 5f orbital, while that of Lr is the lowest among the actinides. These results clear…
Mosses as a biomonitor to identify elements released into the air as a result of car workshop activities
2022
Human activity as a result of civilization development contributes to creating new sources of environmental pollution. Air pollution is one of the major problems because it affects the fauna and flora, and people themselves. There is a lack of public awareness of the level of atmospheric analytes pollution emitted from people's occupational and recreational (leisure) activities. A quick, cheap and easy way to investigate the state of the environment is to use organisms-biomonitors that indicate the level of environmental pollution. The study aimed to assess air pollution in an urban area using three moss species: Sphagnum fallax, Pleurozium schreberi and Dicranum polysetum. Mosses were expo…
Starptautisko privāttiesību attīstība Latvijā
2016
Maģistra darbā “Starptautisko privāttiesību attīstība Latvijā”, izmantojot vairākas zinātniskās pētniecības metodes, analizēta starptautisko privāttiesību, galvenokārt kolīziju normu, attīstība Latvijā, vērtējot nacionālā regulējuma mijiedarbību ar starptautisko un Eiropas Savienības regulējumu. Maģistra darba gaitā secināts, ka, lai gan ir notikusi starptautisko privāttiesību attīstību, tomēr Civillikumā ietverto kolīziju normu attīstība Latvijā gandrīz nav notikusi, pamatojoties uz arvien pieaugošo Eiropas Savienības regulējuma ietekmi. Tomēr, neskatoties uz Eiropas Savienības regulējumu, būtu nepieciešams atkārtoti aktualizēt jautājumu par starptautisko privāttiesību likuma izstrādi Latv…