Search results for "mass [baryon]"
showing 10 items of 262 documents
Isotope shifts and hyperfine structure in the transitions of gadolinium
2000
High-resolution resonance ionization mass spectrometry has been used to measure isotope shifts and hyperfine structure in all (J = 2-6) and the transitions of gadolinium (Gd I). Gadolinium atoms in an atomic beam were excited with a tunable single-frequency laser in the wavelength range of 422-429 nm. Resonant excitation was followed by photoionization with the 363.8 nm line of an argon ion laser and resulting ions were mass separated and detected with a quadrupole mass spectrometer. Isotope shifts for all stable gadolinium isotopes in these transitions have been measured for the first time. Additionally, the hyperfine structure constants of the upper states have been derived for the isotop…
Measurement of the velocity and attenuation of fourth sound in helium II
1979
The velocity and the attenuation of fourth sound have been measured in liquid helium at temperatures between 0.8 K and the λ point, along the vapor pressure curve. The measurements were made using the resonance technique and the helium was contained between small pores in packed powder specimens. From the velocity, it could be determined that the sound propagates under “adiabatic” conditions. According to theory, the attenuation of fourth sound consists of two contributions: surface losses due to heat exchange with the resonator body and volume losses due to dissipative processes associated with the viscosity coefficients η and ζ3. The results of our attenuation measurements are in agreemen…
Photocatalytic CO2 reduction in gas–solid regime in the presence of H2O by using GaP/TiO2 composite as photocatalyst under simulated solar light
2014
GaP/TiO2 composites exhibited a remarkable photocatalytic activity for CO2 reduction in the presence of water vapor producing methane. By decreasing the GaP:TiO2 mass ratio an increase in the photocatalytic activity of the composite was observed for up to a 1:10 mass ratio. The photocatalytic activity of the composite can be attributed to the band structures of the solids as well as to the efficient charge transfer between GaP and TiO2 heterojunction.
Lead speciation in rainwater samples by modified fused silica capillaries coupled to a direct injection nebulizer (DIN) for sample introduction in IC…
2001
Lead speciation using modified silica capillaries for the introduction of liquid samples to a direct injection nebulizer of an inductively coupled plasma quadrupole mass spectrometer is described and demonstrated. The fused silica capillaries were coated by covalently bonding a cation exchange active organic molecule to the activated capillary surface. The best results were obtained by introducing a bifunctional reagent in a prior step. In this case, a silane reagent was chosen which acted as a methacrylic acid group for further binding. The influence of the chemical modification of the surface of the sample capillary of the DIN on the selective retention of inorganic lead (Pb2+) and trieth…
Performance of a MBR pilot plant treating high strength wastewater subject to salinity increase: Analysis of biomass activity and fouling behaviour
2013
Membrane bioreactors produce high quality effluents that could be suitable for reuse. However, when treating high strength wastewater subject to a salinity increase, a modification of biomass characteristics may occur. This circumstance is of importance, since it can have a significant impact in terms of biokinetic as well as fouling behaviour. The aim of the study was to evaluate the performance of a pilot plant MBR, in terms of biomass activity and membrane fouling, fed with high strength synthetic wastewater, when subject to a salinity increase. With normal salinity, the pilot plant showed high removal efficiencies and high biomass respiratory activity. On the other hand, the salinity in…
The biogeochemical cycle of mercury in the Augusta Bay
2014
Mercurial, the metaphor for volatile unpredictable behavior, aptly reflects the complexities of one of the most insidiously interesting and scientifically challenging biogeochemical cycles at the Earth’s surface. At the base of this toxic metal cycle there is the conversion between the different Hg chemical species, in which the balance between the reduced and oxidized forms depends primary on redox system conditions. The potential risks of human exposure to Hg, especially in the form of monomethylmercury (MMHg), particularly prenatally, and the potential deleterious ecological consequences from localized to global scale Hg pollution, have given much impetus to mercury studies and regulator…
Evaluation of methane emissions from Palermo municipal landfill: Comparison between field measurements and models
2010
Methane (CH(4)) diffuse emissions from Municipal Solid Waste (MSW) landfills represent one of the most important anthropogenic sources of greenhouse gas. CH(4) is produced by anaerobic biodegradation of organic matter in landfilled MSW and constitutes a major component of landfill gas (LFG). Gas recovery is a suitable method to effectively control CH(4) emissions from landfill sites and the quantification of CH(4) emissions represents a good tool to evaluate the effectiveness of a gas recovery system in reducing LFG emissions. In particular, LFG emissions can indirectly be evaluated from mass balance equations between LFG production, recovery and oxidation in the landfill, as well as by a d…
Modeling of perched leachate zone formation in municipal solid waste landfills.
2010
The paper presents a 1D mathematical model for the simulation of the percolation fluxes throughout a landfill for municipal solid waste (MSW). Specifically, the model was based on mass balance equations, that enable simulation of the formation of perched leachate zones in a landfill for MSW. The model considers the landfill divided in several layers evaluating the inflow to and outflow from each layer as well as the continuous moisture distribution. The infiltration flow was evaluated by means of the Darcy’s law for an unsaturated porous medium, while the moisture distribution evaluation has been carried out on the basis of the theory of the vertically distributed unsaturated flow. The solu…
Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes
2020
Isotopes with an odd number of neutrons are usually slightly smaller in size than their even-neutron neighbours. In charge radii of short-lived copper isotopes, a reduction of this effect is observed when the neutron number approaches fifty. The mesoscopic nature of the atomic nucleus gives rise to a wide array of macroscopic and microscopic phenomena. The size of the nucleus is a window into this duality: while the charge radii globally scale as $A^{1/3}$, their evolution across isotopic chains reveals unanticipated structural phenomena [1-3]. The most ubiquitous of these is perhaps the Odd-Even Staggering (OES) [4]: isotopes with an odd number of neutrons are usually smaller in size than …
A compact apparatus for mass selective resonance ionization spectroscopy in a buffer gas cell
1997
Abstract An ultra-sensitive laser spectroscopic method for the investigation of transuranium nuclides has been developed based on resonance ionization in an argon buffer gas cell. This method has been combined with ion-guide extraction and mass selective direct detection of the resonantly ionized atoms. Using argon as a buffer gas, recoils of fusion reactions can be thermalized even at low pressure. The differential pumping system consists of only one roots pump and two turbo molecular pumps. The set-up has been tested with 243 Am evaporated from a filament located inside the optical gas cell. Resonance ionization is performed using a two-step excitation with an excimer-dye-laser combinatio…