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Recoil imaging entails the detection of spatially resolved ionization tracks generated by particle interactions. This is a highly sought-after capability in many classes of detector, with broad applications across particle and astroparticle physics. However, at low energies, where ionization signatures are small in size, recoil imaging only seems to be a practical goal for micro-pattern gas detectors. This white paper outlines the physics case for recoil imaging, and puts forward a decadal plan to advance towards the directional detection of low-energy recoils with sensitivity and resolution close to fundamental performance limits. The science case covered includes: the discovery of dark matter into the neutrino fog, directional detection of sub-MeV solar neutrinos, the precision study of coherent-elastic neutrino-nucleus scattering, the detection of solar axions, the measurement of the Migdal effect, X-ray polarimetry, and several other applied physics goals. We also outline the R&D programs necessary to test concepts that are crucial to advance detector performance towards their fundamental limit: single primary electron sensitivity with full 3D spatial resolution at the $\sim$100 micron-scale. These advancements include: the use of negative ion drift, electron counting with high-definition electronic readout, time projection chambers with optical readout, and the possibility for nuclear recoil tracking in high-density gases such as argon. We also discuss the readout and electronics systems needed to scale-up such detectors to the ton-scale and beyond.

A number of regulatory initiatives on the national, international and EU levels both foster and fortify the principle of Maximizing Shareholder Value (MSV) in corporate governance. This tendency can be clearly seen in such areas as financial accounting standards and various soft and hard law initiatives pertaining to corporate governance that have flourished in recent decades. These have created a new type of accountability for managers of listed corporations as will be exemplified below. One of the most important regulatory changes over this period was when the EU opted for International Financial Reporting Standards (IFRS) as a basis for financial reporting for the accounts of all listed, EU-based corporations in 2005. These accounting standards, amounting to quasi legislation, are issued by a private sector body – the International Accounting Standards Board (IASB). Other important regulatory changes include the various national ‘corporate governance codes’ that have mushroomed since the early 1990s. Although such codes pertain to member states, the EU remains the main body prescribing most new hard-law corporate governance regulation within the union, for example, by means of the 13 company law directives issued so far.

International audience

We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M-14(L)(6)O-6(OMe)(18)Cl-6] (M = Fe-III, Cr-III) and [V-14(L)(6)O-6(OMe)(18)Cl6-xOx] (L = anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M-14} complexes [Fe-14(C2H2N3)(6)O-6(OMe)(18)Cl-6], [Cr-14(bta)(6)O-6(OMe)(18)Cl-6] (btaH = benzotriazole), [V14O6(Me(2)bta)(6)(OMe)(18)Cl6-xOx] [Me(2)btaH = 5,6-Me-2-benzotriazole; eight metal sites are V-III, the remainder are disordered between {V-III-Cl}(2+) and {(VO)-O-IV}(2+)] and for the distorted [(Fe14O9)-O-III(OH)(OMe)(8)(bta)(7)(MeOH)(5)(H2O)Cl-8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe-14} complexes to have ground state electronic spins of S

Udgivelsesdato: JUN

Four highly crystalline, cobalt-containing microporous aluminophosphates (CoAPO-5, CoAPO-11, CoAPO-44, and CoAPO-46) have been investigated by using liquid He X- and/or Q-band electron spin resonance(ESR) spectroscopy in order to investigate the coordination of high-spin cobalt before and after calcination. The ESR spectra of the four zeolite structures are characterized by an axial signal with an effective g^ ≈ 5.80-5.44 and gII ≈ 2.00. Quantitative temperature dependence measurements of this axial signal in the temperature range 4-30 K reveal a Curie-Weiss behavior for both as-synthesized and calcined samples confirming (a) the ms ) ( 1/2 ground state of magnetically isolated high-spin cobalt and (b) a zero field splitting ¢ > 0 cm-1. Quantitation of the ESR signals indicated that most of the Co2+ is ESR active and that only about 30% of this Co2+ can be oxidized to the ESR-inactive Co3+ after calcination. The spin Hamiltonian parameters of as-synthesized and calcined CoAPO-5 material, as determined by spectrum simulation and the microwave power saturation technique, support the presence of framework Co2+ in a flattened or elongated Four highly crystalline, cobalt-containing microporous aluminophosphates (CoAPO-5, CoAPO-11, CoAPO- 44, and CoAPO-46) have been investigated by using liquid He X- and/or Q-band electron spin resonance (ESR) spectroscopy in order to investigate the coordination of high-spin cobalt before and after calcination. The ESR spectra of the four zeolite structures are characterized by an axial signal with an effective g^ ≈ 5.80-5.44 and gII ≈ 2.00. Quantitative temperature dependence measurements of this axial signal in the temperature range 4-30 K reveal a Curie-Weiss behavior for both as-synthesized and calcined samples confirming (a) the ms ) ( 1/2 ground state of magnetically isolated high-spin cobalt and (b) a zero field splitting ¢ > 0 cm-1. Quantitation of the ESR signals indicated that most of the Co2+ is ESR active and that only about 30% of this Co2+ can be oxidized to the ESR-inactive Co3+ after calcination. The spin Hamiltonian parameters of as-synthesized and calcined CoAPO-5 material, as determined by spectrum simulation and the microwave power saturation technique, support the presence of framework Co2+ in a flattened or elongated tetrahedron (D2d).

The X- and Q-band EPR spectra of Cr5+ and Cr3+ ions in heterogeneous Cr catalysts have been investigated as a function of the support type and composition (silica, silica–alumina, alumina, mordenite and AlPO-5). A spin-Hamiltonian operator for each of the observed types of resonances is proposed and discussed, while the extensive use of computer-simulated spectra provides detailed information on the nature of supported Cr ions. Mononuclear Cr5+ ions (-signal), with g-values ca. 2, are axial on alumina and silica–alumina, and rhombic on silica and mordenite. Two different X-band EPR signals of Cr3+ ions are present on amorphous and crystalline oxidic surfaces: a broad signal with g around 2 and zero field parameters D and E equal to 0, due to clustered Cr3+(-signal) or isolated octahedral Cr3+ complexes, and a signal with a positive lobe in the region g= 3.5–5.5 (-signal). The latter signal is characterized by high values of D and E and due to the presence of a highly distorted Cr3+ octahedron. The data so obtained allow us to develop a general model of supported Cr5+ and Cr3+ ions on oxidic surfaces.