We focus on the state-of-the-art theory of electromigration under single and multiple complexation equilibrium. Only 1:1 complexation stoichiometry is discussed because of its unique status in the ...field of affinity capillary electrophoresis (ACE). First, we summarize the formulas for the effective mobility in various ACE systems as they appeared since the pioneering days in 1992 up to the most recent theories till 2015. Disturbing phenomena that do not alter the mobility of the analyte directly but cause an unexpected peak broadening have been studied only recently and are also discussed in this paper. Second, we turn our attention to the viscosity effects in ACE. Change in the background electrolyte viscosity is unavoidable in ACE but numerous observations scattered throughout the literature have not been reviewed previously. This leads to an uncritical employment of correction factors that may or may not be appropriate in practice. Finally, we consider the ionic strength effects in ACE, too. Limitations of the current theories are also discussed and the tasks identified where open problems still prevail.
Graphical Abstract
A weak base (
A
) undergoes an acidic-basic equilibria (
in blue
) and migrates with an electrophoretic mobility of
μ
A
0
. Simultaneously, it interacts with a selector (
sel
) while the analyte-selector complex migrates with an electrophoretic mobility of
μ
A
sel
. The strength of the interaction (
in orange
) is governed by the binding constant,
K
A
, and the concentration of the selector,
c
sel
. This all gives the analyte an effective mobility of
μ
A
eff
and moves it out of the zero position (EOF; right top insert). The interaction of the positively charged analyte with the neutral selector slows down the analyte with increasing selector concentration (right bottom insert).
A new detection device for the measurements of light ions (p, d, t, α) emitted as the products of the nuclear reactions induced by fast neutrons (5-33 MeV) was recently developed at the Nuclear ...Physics Institute of the Czech Academy of Sciences. The main objective of the Chamber-for-Light-Ion-Detection (CLID) is to produce new differential nuclear data of high interest for the material applications related to fusion and aerospace technologies and to potentially test and validate models of nuclear reactions. Hereby the experimental set-up for the measurements with the CLID is described in detail. The experimental characterization of the collimated fast neutron beams produced by the cyclotron-driven converter (p(35 MeV)+Be(2.5 mm)) is presented. In particular, the implementation of the Proton-Recoil-Telescope technique used for neutron energy spectra determination with the CLID is described.
Beta-blockers are chiral compounds with enantiomers that have different bioactivity, which means that while one is active, the other can be inactive or even harmful. Due to their high consumption and ...incomplete degradation in waste water, they may reach surface waters and affect aquatic organisms. To address this issue we developed a chromatographic method suitable for determining beta-blocker enantiomers in surface waters. It was tested on five beta-blockers (acebutolol, atenolol, bisoprolol, labetalol and metoprolol) and validated on bisoprolol enantiomers. Good enantioseparation of all analysed beta-blockers was achieved on the Chirobiotic V column with the mobile phase composed of methanol/acetic acid/triethylamine (100/0.20/0.15 v/v/v) at a flow rate of 0.5 mL/min and column temperature of 45 °C. Method proved to be linear in the concentration range from 0.075 µg/mL to 5 µg/mL, and showed good recovery. The limits of bisoprolol enantiomer detection were 0.025 µg/mL and 0.026 µg/mL and of quantification 0.075 µg/mL and 0.075 µg/mL. Despite its limitations, it seems to be a promising method for bisoprolol enantiomer analysis in surface water samples. Further research could focus on waste water analysis, where enantiomer concentrations may be high. Furthermore, transferring the method to a more sensitive one such as liquid chromatography coupled with tandem mass spectrometry and using ammonium acetate as the mobile phase additive instead of acetic acid and triethylamine would perhaps yield much lower limits of detection and quantification.
•Ordinary Concrete (OC) and Heavy Concrete (HC) have been optimized and designed for IFMIF-DONES based on ITER reference.•Technical properties (density, compressive and flexural strength) are ...superior in comparison to ITER reference.•Neutron shielding efficiency of HC is higher – thermal neutron absorption for HC is more than 8 times higher than for OC.•Neutron shielding efficiency of optimized concrete is better than for ITER reference concrete – both in case of OC and HC.•Calculation methods of neutron shielding efficiency are effective for comparison – experimental verification ongoing.
The aim of this study was to optimize and evaluate structural and shielding concrete for the IFMIF-DONES building. An ordinary concrete of lime-dolomite aggregate from local sources has been chosen for structural concrete and magnetite aggregate was chosen for heavy-weight radiation shielding. The reference for concrete materials design was the one used in the ITER project. After investigations of raw materials, a group of prebatches were prepared and technical properties – density of compressive strength, were measured. Finally, two compositions have been elaborated – one for structural concrete of density 2.5 g/cm3 and the second for radiation shielding concrete of density 3.9 g/cm3. Then a set of 50 × 50 × 5 cm3 slabs were prepared and sent to the Nuclear Physics Institute of the CAS in the Czech Republic for shielding mock-up experiments. Also the other technical properties like E-modulus, bending strength etc. have been determined. Additionally, radiation shielding efficiency has been calculated based on atomic composition.
The Nuclear Energy Agency’s High Priority Nuclear Data Request List is a compilation of the highest priority nuclear data requirements. The U-120M cyclotron of the Nuclear Physics Institute of the ...Czech Academy of Sciences is a suitable tool for studies of several reactions from this list. In this paper, we present the measurements of the 7Be and 3H production in the lithium-7 after the irradiation with deuterons and the validation measurement for the 39Ar production in 39K after irradiation with neutrons .
Good knowledge of cross section neutron induced reactions on Zr becomes of importance due to the use of zirconium as structural material in reactors, its applicability in neutron dosimetry and the ...theoretical model testing. Thin Zr foils (0.05 mm thickness, 99.2% purity) were irradiated in the quasi-monoenergetic p-Li neutron fields, the proton beams from NPI CAS variable-energy cyclotron U120M at proton energies 20.33, 22.44, 24.69, 27.64, 29.85, 32.31 and 35.11 MeV. Li target with carbon stopper was used for the generation of neutron flux. The reaction 7Li (p,n) produces the high-energy quasi-monoenergetic neutrons with a tail to lower energies. The flux density and neutron spectra were evaluated by MCNPX code and validated with set of measurements including Time-Of-Flight and Proton recoil Telescope and additional activation monitors. The pneumatic tranfer system enables the investigation of short living isotopes. The foil activity determination was performed by the nuclear spectrometry method employing two calibrated HPGe detectors. The reaction rates for natZr(n,*)89m,89g,89Zr, 87m,87,88,89m,90m,91m,92,93,94,95Y and 87m,91,92Sr were obtained and cross sections were extracted. The preliminary results are discussed.
New detection systems at U-120M cyclotron Novák, Jan; Ansorge, Martin; Bém, Pavel ...
EPJ Web of Conferences,
2020, Letnik:
239
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Intensive neutron beams with energies up to 33 MeV are produced using cyclotron driven broad-spectrum and quasi-monoenergetic neutron generators at the NPI CAS. The neutron beams are well ...characterized with the TOF and PRT measurements. The segmented Fe-CH2 collimator is used to collimate the neutron beam and two detection systems are being developed for the studies of the reactions with neutrons. The first one is the detection system of the charged particles at different angles from the (neutron, charged particle) reactions in a vacuum chamber, the second is an array of four HPGe detectors for the detection of direct and delayed gamma photons produced in reactions of the studied material with neutrons. The advanced bunching system is also being developed at the U120M cyclotron. It will allow to direct a short (few ns long) pulse of accelerated particles to the neutron converter with the 1
µ
s delay between bunches. Together with 7 m long flight path this extension will open new possibilities in the cross section measurements.
At the NPI in Rez, the p
+
Be source reaction was investigated for 30 MeV proton beam and thick beryllium target. For neutron field determination of the p(30)+Be source reaction in close ...source-to-sample distance, the multi-foil activation technique with a set of 10 activation materials (Au, Co, Lu, Ti, In, Al, Y, Fe, Ni, Nb) was utilized. From resulting reaction rates, the neutron spectrum was reconstructed using the SAND-II unfolding code. New neutron field of white spectrum up to 28 MeV has an intensity of 8.6 × 10
10
cm
−2
s
−1
close to target. The obtained neutron field extends the utilization of cyclotron-based fast neutron sources at the NPI and provides new experimental opportunities for future irradiation experiments such as fast neutron activation analysis, nuclear data validation, and radiation damage study of electronics and materials for nuclear energetics.
Fast neutron generators driven by isochronous cyclotron U-120M developed at Nuclear Physics Institute were used for neutron cross-section measurements. The target station with 2 mm thin lithium was ...used to produce pulsed beams of fast quasi-monoenergetic neutrons in the
7
Li
(p,n) reaction. The Time-of-Flight technique was used to determine the exact neutron energy spectra. The transmission measurements on liquid oxygen were conducted for several neutron peak energies between 18 and 27 MeV and the cross-sections for reaction
nat
O(n,tot) were derived.
New experimental data on the peak neutron production in the 7Li(p,n) reaction were collected during several irradiation campaigns at the NPI CAS. Time-of-flight method was used to measure the number ...of the peak neutrons in the forward direction, and the number of produced 7Be nuclei was determined using γ-spectrometry. The new measurement results are compared with experimental data from the literature and used for the validation of several different systematics and nuclear data libraries developed over the years.
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