High-spin excitations of 81, 82, 83, 85Se : Competing single-particle and collective structures around N = 50

The ^{81, 82, 83, 85}Se nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple -ray coincidence data and - angular correlations have been analyzed in order to assign spin and parity values to many observed states. The lowest-spin states of the two-neutron and three-neutron configurations are strongly mixed with two-proton excitations among the fp orbits. On the other hand, the highest-spin states of these neutron configurations are found to remain almost pure. Neutron excitation across the N = 50 gap is observed both in ⁸³Se₄₉ and in ⁸⁵Se₅₁ .     

Magnetic calorimeter for registration of small energy release

A scheme of magnetic calorimeter for registration of rare events characterized by small energy release (cosmic rays, WIMPs, solitary X-ray quanta) is proposed. The calorimeter is brought to operation by adiabatic demagnetization, and its magnetic response is measured by a quantum interferometer (SQUID, A. Barone and G. Paterno, Physics and applications of Josephson Effect). Special consideration is given to the specific features of calorimeter operation in the ferromagnetic transition region. The trigger registration of ultrasmall energy release by a ferromagnetic system in the metastable state is described.     

Experimental indications for the response of the spectators to the participant blast

Precise momentum distributions of identified projectile fragments, formed in the reactions 238U+Pb and 238U+Ti at 1A GeV, are measured with a high-resolution magnetic spectrometer. With increasing mass loss, the velocities first decrease as expected from previously established systematics, then level off, and finally increase again. Light fragments are on the average even faster than the projectiles. This finding is interpreted as the response of the spectators to the participant blast. The reacceleration of projectile spectators is sensitive to the nuclear mean field and provides a new tool for investigating the equation of state of nuclear matter.     

MRI and x-ray CT study of spatial distribution of core breakdown in 'Conference' pears

Two non-destructive tomographic techniques, X-ray CT imaging and magnetic resonance imaging (MRI), were applied to study the development of core breakdown disorder in 'Conference' pears (Pyrus communis cv. Conference). This disorder, which is characterized by brown discoloration of the tissue and development of cavities, is induced by elevated CO(2) and decreased O(2) levels during controlled atmosphere storage. Tomographic images of pears stored for 10 months under disorder inducing conditions, were acquired with both techniques and compared to the actual slices. Both X-ray and MRI were able to differentiate between unaffected tissue, brown tissue and cavities. A simple image-processing program, based on threshold values, was developed to determine the area percentage of affected and unaffected tissue as well as the cavity and core area per slice. For all three imaging techniques the area percentage brown tissue per slice increased with the diameter of the pear, but was systematically underestimated by 12% and 6% for, respectively, X-ray and MRI, compared to the actual slices. The area percentage cavity corresponded very well for all techniques. It was also found that the contours of the brown tissue were parallel to the fruit boundaries, suggesting a relation between the disorder symptoms and gas diffusion properties of the fruit. It was concluded that MRI is the most appropriate technique to study the development of core breakdown disorder during postharvest storage in future experiments.     

p-type porous-silicon transducer for cation detection: effect of the porosity, pore morphology, temperature and ion valency on the sensor response and generalisation of the Nernst equation

This paper shows the possibility of using oxidised porous silicon (PS) as a transducer material for ion-sensor applications. It aims to study the over-Nernstian behaviour of the porous electrodes towards the concentration of cations in contact. The dependence of the sensitivity on the porosity of the samples prepared from highly doped substrates has been studied. Maximal values of over-Nernstian sensitivities around 240 mV/pNa and ∼92 mV/pCu, corresponding to a PS-layer porosity of about 65%, obtained respectively from p⁻ and p⁺ silicon substrates, have been registered. Furthermore, the effect of the porous nanostructure morphology has been studied, by preparing PS samples from weakly doped wafers. The porous-silicon-based sensor behaviour for different PS-layer thicknesses has also been experimentally investigated. According to these results, a physical model has been proposed to explain the mechanisms which govern the charge-carrier transfer from one side to the other of the functionalised oxide layer, and leads to the over-Nernstian adsorption of the cationic species at the electrolyte/SiO₂ interface. Afterwards, the Nernst relation has been generalised accordingly, on one hand, to the previous experimental results, and on the other hand, to the results obtained about the ion-valency and the electrolyte-temperature effects on the sensor responses. Received: 15 December 2000 / Accepted: 18 December 2000 / Published online: 23 March 2001     

New excited superdeformed bands in heavy Pb nuclei: Clue for an octupole softness near the N = 118 gap at large deformation

We report the identification of six new superdeformed (SD) bands in ^197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals and confirm indirectly a N = 118 SD gap. Received: 20 December 2000 / Accepted: 24 January 2001     

Spectroscopic analysis of a laser-induced NaCl–water plasma. The influence of self-absorption

A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have been constructed for concentrations ranging up to 1.5%.     

Temperature Dependence of 1H Paramagnetic Chemical Shifts in Actinide Complexes,Beyond Bleaney's Theory: The AnVIO22+–Dipicolinic Acid Complexes (An=Np,Pu) as an Example

Actinide +VI complexes ( = , and ) with dipicolinic acid derivatives were synthesized and characterized by powder XRD, SQUID magnetometry and NMR spectroscopy. In addition, and complexes were described by first principles CAS based and two-component spin-restricted DFT methods. The analysis of the ¹H paramagnetic NMR chemical shifts for all protons of the ligands according to the X-rays structures shows that the Fermi contact contribution is negligible in agreement with spin density determined by unrestricted DFT. The magnetic susceptibility tensor is determined by combining SQUID, pNMR shifts and Evans’ method. The SO-RASPT2 results fit well the experimental magnetic susceptibility and pNMR chemical shifts. The role of the counterions in the solid phase is pointed out; their presence impacts the magnetic properties of the complex. The temperature dependence of the pNMR chemical shifts has a strong contribution, contrarily to Bleaney's theory for lanthanide complexes. The fitting of the temperature dependence of the pNMR chemical shifts and SQUID magnetic susceptibility by a two-Kramers-doublet model for the complex and a non-Kramers-doublet model for the complex allows for the experimental evaluation of energy gaps and magnetic moments of the paramagnetic center.     

Derivation of Lanthanide Series Crystal Field Parameters From First Principles

Two series of lanthanide complexes have been chosen to analyze trends in the magnetic properties and crystal field parameters (CFPs) along the two series: The highly symmetric LnZn₁₆(picHA)₁₆ series (Ln=Tb, Dy, Ho, Er, Yb; picHA=picolinohydroxamic acid) and the [Ln(dpa)₃](C₃H₅N₂)₃ ⋅ 3H₂O series (Ln=Ce–Yb; dpa=2,6-dipicolinic acid) with approximate three-fold symmetry. The first series presents a compressed coordination sphere of eight oxygen atoms whereas in the second series, the coordination sphere consists of an elongated coordination sphere formed of six oxygen atoms. The CFPs have been deduced from ab initio calculations using two methods: The AILFT (ab initio ligand field theory) method, in which the parameters are determined at the orbital level, and the ITO (irreducible tensor operator) decomposition, in which the problems are treated at the many-electron level. It has been found that the CFPs are transferable from one derivative to another, within a given series, as a first approximation. The sign of the second-order parameter differs in the two series, reflecting the different environments. It has been found that the use of the strength parameter S allows for an easy comparison between complexes. Furthermore, in both series, the parameters have been found to decrease in magnitude along the series, and this decrease is attributed to covalent effects.     

A Bis-Chelating / Ligand for the Synthesis of Heterobimetallic Platinum(II)/Rhenium(I) Complexes: Tools for the Optimization of a New Class of Platinum(II) Anticancer Agents

The two independent and coordination sites of a newly synthesized bis[2-(hydroxyphenyl)-1,2,4-triazole] platform have been exploited to prepare four monometallic neutral ()Pt^II complexes carrying DMSO, pyridine, triphenylphosphine, or N-heterocyclic carbene as the fourth ligand. Then, the second coordination site was used to introduce an IR-active rhenium tricarbonyl entity, affording the four corresponding heterobimetallic neutral Pt^II/Re^I complexes, as well as a cationic Pt^II/Re^I derivative. X-ray crystallographic studies showed that distortion of the organic platform occurred to accommodate the coordination geometry of both metal centers. No ligand exchange or transchelation occurred upon incubation of the Pt^II complexes in aqueous environment or in the presence of Fe^III, respectively. The antiproliferative activity of the ligand and complexes was first screened on the triple-negative breast cancer cell line MDA-MB-231. Then, the IC₅₀ values of the most active candidates were determined on a wider panel of human cancer cells (MDA-MB-231, MCF-7, and A2780), as well as on a nontumorigenic cell line (MCF-10A). Low micromolar activities were reached for the complexes carrying a DMSO ligand, making them the first examples of highly active, but hydrolytically stable, Pt^II complexes. Finally, the characteristic mid-IR signature of the {Re(CO)₃} fragment in the Pt/Re heterobimetallic complexes was used to quantify their uptake in breast cancer cells.