Multiple scattering and attenuation corrections in Deep Inelastic Neutron Scattering experiments

Multiple scattering and attenuation corrections in Deep Inelastic Neutron Scattering experiments are analyzed. The theoretical basis is stated, and a Monte Carlo procedure to perform the calculation is presented. The results are compared with experimental data. The importance of the accuracy in the description of the experimental parameters is tested, and the implications of the present results on the data analysis procedures is examined.Comment: 19 pages, 8 figure

Formalism for obtaining nuclear momentum distributions by the Deep Inelastic Neutron Scattering technique

We present a new formalism to obtain momentum distributions in condensed matter from Neutron Compton Profiles measured by the Deep Inelastic Neutron Scattering technique. The formalism describes exactly the Neutron Compton Profiles as an integral in the momentum variable $y$. As a result we obtain a Volterra equation of the first kind that relates the experimentally measured magnitude with the momentum distributions of the nuclei in the sample. The integration kernel is related with the incident neutron spectrum, the total cross section of the filter analyzer and the detectors efficiency function. A comparison of the present formalism with the customarily employed approximation based on a convolution of the momentum distribution with a resolution function is presented. We describe the inaccuracies that the use of this approximation produces, and propose a new data treatment procedure based on the present formalism.Comment: 11 pages, 8 figure

Localized magnetoplasmon modes arising from broken translational symmetry in semiconductor superlattices

The electromagnetic propagator associated with the localized collective magnetoplasmon excitations in a semiconductor superlattice with broken translational symmetry, is calculated analytically within linear response theory. We discuss the properties of these collective excitations in both radiative and non-radiative regimes of the electromagnetic spectra. We find that low frequency retarded modes arise when the surface density of carriers at the symmetry breaking layer is lower than the density at the remaining layers. Otherwise a doublet of localized, high-frequency magnetoplasmon-like modes occurs.Comment: Revtex file + separate pdf figure

Measurement of the total cross section of heavy water in the 0.1 meV–1 eV energy range at 20 and 50 ◦C

Despite the importance of heavy water as a neutron moderator, there are few measurements of its total neutron cross section for cold and thermal energies, and none of them covers the range of temperature (40–70◦C) used in moderator and reflector tanks in research reactors, and in CANDU nuclear power plants. To cover this deficit, we measured the total cross section of liquid heavy water at 20◦C and 50◦C using the SANS beamline at the LENS facility at Indiana University. The time-of-flight technique was used, in a sample-in/sample-out measurement. The use of the solid methane cold neutron source at LENS allowed measuring in a broad range in energy, from 0.1meV to 1 eV. In this paper we present details of the measurement and processing of the data, and comparison with previous experimental measurements and calculation models. This work is included in the Action Plan of the IAEA Coordinated Research Project “Advanced Moderators for Intense Cold Neutron Beams in Materials Research”

Detrital zircon typology and U/Pb geochronology for the Miocene Ladrilleros-Juanchaco sedimentary sequence, Equatorial Pacific (Colombia) : new constraints on provenance and paleogeography in northwestern South America

Typology and internal texture analyses were performed on detrital zircons obtained from the Miocene sandstones of the Ladrilleros-Juanchaco sedimentary sequence (Colombia, Equatorial Pacific). This analysis was complemented with zircon U/Pb dating to identify typology-age associations as indicators of provenance of these sediments. Our results show that zircons with S and P dominant typology have internal structures/zoning that indicate mostly igneous and possibly some metamorphic origins. Morphometric results suggest little transport from source areas. Both typology and U/Pb data point to the Western Cordillera as the main source of the detrital materials of this sedimentary sequence. A paleogeographic reconstruction shows that during Late Miocene times there were significant portions of the Western Cordillera uplifted, eroding away and acting as a fluvio-topographic barrier blocking sediments from the Central Cordillera to reach the Pacific basins. Miocene plutons at the axis of the Western Cordillera were also probably exhumed and played a role as geomorphologically active massifs. This study demonstrates that typologic analysis on detrital zircon grains is a powerful tool as indicator of provenance and paleogeography in complex litho-tectonic areas where overlapping U/Pb signatures can lead to contradictory results

How Coupling Determines the Entrainment of Circadian Clocks

Autonomous circadian clocks drive daily rhythms in physiology and behaviour. A network of coupled neurons, the suprachiasmatic nucleus (SCN), serves as a robust self-sustained circadian pacemaker. Synchronization of this timer to the environmental light-dark cycle is crucial for an organism's fitness. In a recent theoretical and experimental study it was shown that coupling governs the entrainment range of circadian clocks. We apply the theory of coupled oscillators to analyse how diffusive and mean-field coupling affects the entrainment range of interacting cells. Mean-field coupling leads to amplitude expansion of weak oscillators and, as a result, reduces the entrainment range. We also show that coupling determines the rigidity of the synchronized SCN network, i.e. the relaxation rates upon perturbation. %(Floquet exponents). Our simulations and analytical calculations using generic oscillator models help to elucidate how coupling determines the entrainment of the SCN. Our theoretical framework helps to interpret experimental data

Prognostic heterogeneity of adult B-cell precursor acute lymphoblastic leukaemia patients with t(1;19)(q23;p13)/TCF3-PBX1 treated with measurable residual disease-oriented protocols

The prognosis of t(1;19)(q23;p13)/transcription factor 3-pre-B-cell leukaemia homeobox 1 (TCF3-PBX1) in adolescent and adult patients with acute lymphoblastic leukaemia (ALL) treated with measurable residual disease (MRD)-oriented trials remains controversial. In the present study, we analysed the outcome of adolescent and adult patients with t(1;19)(q23;p13) enrolled in paediatric-inspired trials. The patients with TCF3-PBX1 showed similar MRD clearance and did not have different survival compared with other B-cell precursor ALL patients. However, patients with TCF3-PBX1 had a significantly higher cumulative incidence of relapse, especially among patients aged ≥35 years carrying additional cytogenetic alterations. These patients might benefit from additional/intensified therapy (e.g. immunotherapy in first complete remission with or without subsequent haematopoietic stem cell transplantation). 40 __ $u https://creativecommons.org/licenses/by-nc-nd/4.0

Acute success and short-term follow-up of catheter ablation of isthmus-dependent atrial flutter; a comparison of 8 mm tip radiofrequency and cryothermy catheters

Objectives: To compare the acute success and short-term follow-up of ablation of atrial flutter using 8 mm tip radiofrequency (RF) and cryocatheters. Methods: Sixty-two patients with atrial flutter were randomized to RF or cryocatheter (cryo) ablation. Right atrial angiography was performed to assess the isthmus. End point was bidirectional isthmus block on multiple criteria. A pain score was used and the analgesics were recorded. Patients were followed for at least 3 months. Results: The acute success rate for RF was 83% vs 69% for cryo (NS). Procedure times were similar (mean 144±48 min for RF, vs 158±49 min for cryo). More applications were given with RF than with cryo (26±17 vs. 18±10, p<0.05). Fluoroscopy time was longer with RF (29±15 vs. 19±12 min, p<0.02). Peak CK, CK-MB and CK-MB mass were higher, also after 24 h in the cryo group. Troponin T did not differ. Repeated transient block during application (usually with cryoablation) seemed to predict failure. Cryothermy required significantly less analgesia (p<0.01), and no use of long sheaths (p<0.005). The isthmus tended to be longer in the failed procedures (p=0.117). This was similar for both groups, as was the distribution of anatomic variations. Recurrences and complaints in the successful patients were similar for both groups, with a very low recurrence of atrial flutter after initial success. Concl