High accuracy 235 U(n,f) data in the resonance energy region

The 235U neutron-induced cross section is widely used as reference cross section for measuring other fission cross sections, but in the resonance region it is not considered as an IAEA standard because of the scarce experimental data covering the full region. In this work, we deal with a new analysis of the experimental data obtained with a detection setup based on parallel plate ionization chambers (PPACs) at the CERN n_TOF facility in the range from 1 eV to 10 keV. The relative cross section has been normalised to the IAEA value in the region between 7.8 and 11 eV, which is claimed as well-known. Comparison with the ENDF/B-VII evaluation and the IAEA reference file from 100 eV to 10 keV are provide

Controlling Water Exchange Rates in Potential Mn²⁺-Based MRI Agents Derived From NO2A²⁻

[Abstract] We report a series of pentadentate ligands based on a 1,4,7-triazacyclononane-1,4-diacetic acid (H2NO2A) containing different substituents attached to the third nitrogen atom of the macrocyclic unit. Detailed 1H Nuclear Magnetic Relaxation Dispersion (NMRD) characterisation of the corresponding Mn2+ complexes suggests the formation of six-coordinate species in solution containing an inner-sphere water molecule. This was confirmed by recording the transverse 17O relaxation time and chemical shift measurements. The water exchange rate of the coordinated water molecule was found to be strongly influenced by the nature of the substituent R at position 7 of the triazacyclononane unit (R = Me, k298ex = 62.6 × 107 s−1; R = Bz, k298ex = 4.4 × 107 s−1; R = 1-phenylethyl, k298ex = 2.6 × 107 s−1). The decreasing exchange rates are explained by the increasing bulkiness of the substituent, which hinders the approach of the entering water molecule in an associatively activated water exchange mechanism. This is supported by DFT calculations (M062X/TZVP), which confirm the associative nature of the water exchange reaction. A potentially decadentate ligand containing two NO2A units linked by a xylenyl spacer in the meta position was also synthesised. The corresponding binuclear Mn2+ complex contains two metal ions with different hydration numbers, as evidenced by 1H NMRD and 17O NMR measurements. DFT calculations show that this is related to the presence of a bridging bidentate μ–η1-carboxylate group connecting the two metal centers. The results reported in this work provide a straightforward strategy to control the exchange rate of the coordinated water molecule in this family of MRI contrast agent candidates.Authors R. P.-P., I. B., E. I., C. P.-I. and D. E.-G. thank Ministerio de Economía y Competitividad (CTQ2016-76756-P) and Xunta de Galicia (ED431B 2017/59 and ED431D 2017/01) for generous financial support and Centro de Supercomputación of Galicia (CESGA) for providing the computer facilities. R. P.-P. thanks Ministerio de Economía y Competitividad for a PhD FPI grant (BES-2014-068399) and a fellowship for a short term stay in Alessandria (EEBB-I-18-13075). M. B. and F. C. are grateful to Università del Piemonte Orientale for financial support (Ricerca locale 2016). This work was carried out within the framework of the COST CA15209 Action "European Network on NMR Relaxometry"Xunta de Galicia; ED431B 2017/59Xunta de Galicia; ED431D 2017/0

Results of time-of-flight transmission measurements for natW at 25 m and 50 m stations of GELINA

Transmission measurements have been performed at the time-of-flight facility GELINA using metallic discs of natural tungsten. The measurements have been carried out at 25 m and 50 m stations using Li-glass scintillators with the accelerator operating at 800 Hz. This report describes the experimental details required to deliver the data to the EXFOR data library, which is maintained by the Nuclear Data Section of the International Atomic Energy Agency (NDS/IAEA) and the Nuclear Energy Agency of the Organisation for Economic Co-operation and Development (NEA/OECD). The experimental conditions and data reduction procedures are described. In addition, full covariance information based on the AGS concept is given such that nuclear reaction model parameters together with their covariances can be derived in a least squares adjustment to the data or the data can be used to validate resonance parameters recommended in evaluated data libraries.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Results of transmission measurements for 40Ca at GELINA

Transmission measurements have been performed at a 50 transmission station of the neutron time-of-flight facility GELINA to determine the total cross section for neutron induced reactions on 40Ca. These measurements are part of a collaboration of the Joint Research Centre and the Oak Ridge National Laboratory (US) to improve nuclear data for nuclear criticality safety applications. They have been supported by the EUFRAT project. This report provides the experimental details required to submit the data to the EXFOR data library which is maintained by the Nuclear Data Section of the IAEA and the Nuclear Energy Agency of the OECD. The experimental details, i.e. measurement conditions, sample characteristics, measurement procedures and experimental uncertainty components, together with the data reduction procedures are described. The experimental results including the full covariance information, based on the AGS-formalism, are reported following the latest recommendations of the International Nuclear Data Committee. This includes the information that is required to derive nuclear reaction model parameters together with their covariances by a least squares adjustment to experimental data.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Measurements of high-energy neutron-induced fission of natPb and 209Bi

EFNUDAT – Measurements and Models of Nuclear ReactionsThe CERN Neutron Time-Of-Flight (n_TOF) facility is well suited to measure low cross sections as those of neutron-induced fission in subactinides. The cross section ratios of natPb and 209Bi relative to 235U and 238U were measured using PPAC detectors and a fragment coincidence method that allows us to identify the fission events. The present experiment provides first results for neutron-induced fission up to 1 GeV. Good agreement is found with previous experimental data below 200 MeV. The comparison with proton-induced fission indicates that the limiting regime where neutron-induced and proton-induced fission reach equal cross sections is close to 1 Ge

Water exchange rates and mechanisms in tetrahedral [Be(H2O)4]2+ and [Li(H2O)4]+ complexes using DFT methods and cluster‐continuum models

[Abstract] The water exchange reactions in aquated Li+ and Be2+ ions were investigated with density functional theory calculations performed using the [Li(H2O)4]+·14H2O and [Be(H2O)4]2+·8H2O systems and a cluster‐continuum approach. A range of commonly used functionals predict water exchange rates several orders of magnitude lower than the experimental ones. This effect is attributed to the overstabilization of coordination number four by these functionals with respect to the five‐coordinated transition states responsible for the associative (A) or associative interchange (Ia) water exchange mechanisms. However, the M06 and M062X functionals provide results in good agreement with the experimental data: M062X/TZVP calculations yield a concerted Iamechanism for the water exchange in [Be(H2O)4]2+·8H2O that gives an average residence time of water molecules in the first coordination sphere of 260 μs. For [Li(H2O)4]+·14H2O the water exchange reaction is predicted to follow an A mechanism with a residence time of inner‐sphere water molecules of 25 ps.Ministerio de Economía y Competitividad; CTQ2013‐43243‐PMinisterio de Economía y Competitividad; CTQ2015‐71211‐RED

Developing the family of picolinate ligands for Mn2+ complexation

[Abstract] We have reported here a series of ligands containing pentadentate 6,6′-(azanediylbis(methylene))dipicolinic acid units that differ in the substituent present at the amine nitrogen atom (acetate: H3DPAAA; phenyl: H2DPAPhA; dodecyl: H2DPAC12A; 4-hexylphenyl: H2DPAC6PhA). The protonation constants of the hexadentate DPAAA3− and pentadentate DPAPhA2−ligands and the stability constants of their Mn2+ complexes were determined using pH-potentiometry (25 °C, 0.15 M NaCl). The mono-hydrated [Mn(DPAAA)]− complex (logKMnL = 13.19(5)) was found to be considerably more stable than the bis-hydrated [Mn(DPAPhA)] analogue (logKMnL = 9.55(1)). A detailed 1H and 17O NMR relaxometric study was carried out to determine the parameters that govern the proton relaxivities of these complexes. The [Mn(DPAC12A)] complex, which contains a dodecyl lipophilic chain, forms micelles in solution characterized by a critical micellar concentration (cmc) of 96(9) μM. The lipophilic [Mn(DPAC6PhA)] and [Mn(DPAC12A)] derivatives form rather strong adducts with Human Serum Albumin (HSA) with association constants of 7.1 ± 0.1 × 103 and 1.3 ± 0.4 × 105 M−1, respectively. The X-ray structure of the complex {K(H2O)4}{[Mn(DPAAA)(H2O)]}2 shows that the Mn2+ ion in [Mn(DPAAA)]− is coordinated to the six donor atoms of the ligand, a coordinated water molecule completing the pentagonal bipyramidal coordination environment.Ministerio de Economía y Competitividad; CTQ2015-71211-REDTMinisterio de Economía y Competitividad; CTQ2016-76756-

Platform of Citizen Interaction: the contribution to the governability of New TIC´s and Citizen Relational Management

Understanding "governability" as an interaction process among government and society, the New Technologies of Information and Communications (NTICs) can contribute as a strategy of improvement and conversion in the type of communication between both actors. This article introduces concepts referred to Customer Relationship Management applications turned into Citizen Relationship Management tools. The plus of a modeling of the multiplatforms functionalities that this solution offers and a protocol of implementation and system migration is a step forward in the achievement of obtaining an electronic government with civil democratic interaction and transparency in the management. The idea of a Platform of Citizen Interaction that auspice as a repository of the communication between public and civil entities allows having a unique and centralized database capable of being segmented of different ways to attend to a great diversity of subject matters.VIII Workshop Innovación en Sistemas de Software (WISS).Red de Universidades con Carreras en Informática (RedUNCI

Platform of Citizen Interaction: the contribution to the governability of New TIC´s and Citizen Relational Management

Understanding "governability" as an interaction process among government and society, the New Technologies of Information and Communications (NTICs) can contribute as a strategy of improvement and conversion in the type of communication between both actors. This article introduces concepts referred to Customer Relationship Management applications turned into Citizen Relationship Management tools. The plus of a modeling of the multiplatforms functionalities that this solution offers and a protocol of implementation and system migration is a step forward in the achievement of obtaining an electronic government with civil democratic interaction and transparency in the management. The idea of a Platform of Citizen Interaction that auspice as a repository of the communication between public and civil entities allows having a unique and centralized database capable of being segmented of different ways to attend to a great diversity of subject matters.VIII Workshop Innovación en Sistemas de Software (WISS).Red de Universidades con Carreras en Informática (RedUNCI

Reinforced Ni(ɪɪ)-Cyclam Derivatives as Dual ¹H/¹⁹F MRI Probes

[Abstract] Reinforced cross-bridged Ni²⁺-cyclam complexes were functionalised with pendant arms containing both amide protons and CF₃ groups that lead to a dual ¹H/¹⁹F response. The resulting complexes possess very high inertness favourable for MRI applications. The paramagnetism of the Ni²⁺ ion shifts the amide resonance 56 ppm away from bulk water favouring the chemical exchange saturation transfer (CEST) effect and shortening the acquisition times in ¹⁹F magnetic resonance imaging (MRI) experiments, thus enhancing the signal-to-noise ratios compared to the fluorinated diamagnetic reference.Authors R. P.-P., D. E.-G. and C. P.-I. thank Ministerio de Economía y Competitividad (CTQ2016-76756-P) and Xunta de Galicia (ED431B 2017/59 and ED431D 2017/01) for generous financial support. R. P.-P. thanks Ministerio de Economía y Competitividad for a PhD FPI grant (BES-2014-068399) and a fellowship for a short term stay in Tuebingen (EEBB-I-17-12213). T. S. thanks the German Academic Exchange Service (DAAD) for the PhD fellowshipXunta de Galicia; ED431B 2017/59Xunta de Galicia; ED431D 2017/0