The Impact of Deep Fjord Water Temperatures on the Ice Flow Velocities of Helheim Glacier, Greenland

Increasing ice flow velocities of marine terminating glaciers are often linked to rising ocean temperatures. Unfortunately, direct comparisons between glacier velocity and ocean temperatures are impeded by the fact that few oceanographic datasets span multiple years or contain temperatures at depth. Here, we use an oceanographic dataset collected in Helheim Fjord over several years (described in Straneo et al., 2011, Nat. Geoscience) in both shallow and deep waters. We compare the water temperatures at different depths with ice flow velocities that have been calculated from feature-tracking of LandSAT 7 and 8 images. Our results cover the period 2009–2013 and show both seasonal and inter-annual variability. We find that the velocity of Helheim glacier is likely influenced by the deep ocean water temperatures, namely the influx of warm Atlantic water, whereas water temperature at shallower depths do not have a significant influence on glacier speed. This is in contrast with findings from, for example, Svalbard. Our study demonstrates the need for multiple–year ocean datasets at different depths, if we are to disentangle the complex interactions between glaciers and ocean

Un jurista en el nacimiento de la ciencia política moderna: los estudios de las organizaciones de partido de Moisei Ostrogorski

[ES]El trabajo de Moisei Ostrogorski sobre las organizaciones de partido en Estados Unidos e Inglaterra (1903) fue considerado por la ciencia política de la segunda mitad del siglo XX como fundacional de la disciplina. En este artículo se discute el carácter genealógico de esta lectura, exponiendo que Ostrogorski era, también, un jurista. Su biografía, su investigación sobre los derechos de las mujeres e, incluso, su trabajo más propiamente politológico sobre los partidos, nos muestran este carácter de Ostrogorski como jurista. Además, las lecturas de su obra por parte de los juristas franceses de su tiempo expresan los problemas de proyectar sobre el pasado las divisiones disciplinares del presente

Quasi elastic cross sections for the Bi-209(e, e \u27 p)Pb-208 reaction: Jefferson Lab experiment E06007

Quasi elastic cross sections were measured for the first time for both negative and positive missing momenta for the Bi-209(e, e\u27p)Pb-208 reaction leading to the ground state and hole states of Pb-208. Experimental cross sections obtained between -0.3 GeV/c to 0.3 GeV/c agree with theoretical calculations using RDWIA techniques both in shape and magnitude for the ground state. The data for the ground state production of Pb-208 are consistent with a theoretical model assuming a single proton(1.06 +/- 0.10) in the 1h9/2 orbit in Bi-209

Overview of Neutrino–Nucleus Interactions

Neutrino–nucleus reactions are surveyed. The approximations usually made are identified and a comparison to the corresponding electron–nucleus processes is presented. Impulse Approximation (IA), factorization of the cross-section and scaling approaches (SA) to lepton–nucleus scattering are examined in detail

Overview of neutrino-nucleus quasielastic scattering

A review of quasielastic neutrino-nucleus scattering will be presented, with emphasis on bringing together the knowledge (and language) of neutrino physics, electron scattering, and nuclear structure communities. Assumptions commonly made which simplify the theoretical calculations will be examined. Finally, an attempt will be made to identify places where improvement from either theoretical or experimental sides would be more significant.Dirección General de Investigación (DGI). España FPA2007-62216, FIS2008-04189 y FPA2006-13807-C02-01Spanish Consolider-Ingenio programme CPAN CSD2007-0004

Multi-modal ultrasound imaging for breast cancer detection

This work describes preliminary results of a two-modality imaging system aimed at the early detection of breast cancer. The first technique is based on compounding conventional echographic images taken at regular angular intervals around the imaged breast. The other modality obtains tomographic images of propagation velocity using the same circular geometry. For this study, a low-cost prototype has been built. It is based on a pair of opposed 128-element, 3.2 MHz array transducers that are mechanically moved around tissue mimicking phantoms. Compounded images around 360 degrees provide improved resolution, clutter reduction, artifact suppression and reinforce the visualization of internal structures. However, refraction at the skin interface must be corrected for an accurate image compounding process. This is achieved by estimation of the interface geometry followed by computing the internal ray paths. On the other hand, sound velocity tomographic images from time of flight projections have been also obtained. Two reconstruction methods, Filtered Back Projection (FBP) and 2D Ordered Subset Expectation Maximization (2D OSEM), were used as a first attempt towards tomographic reconstruction. These methods yield useable images in short computational times that can be considered as initial estimates in subsequent more complex methods of ultrasound image reconstruction. These images may be effective to differentiate malignant and benign masses and are very promising for breast cancer screening. (C) 2015 The Authors. Published by Elsevier B.V

Performance evaluation of SiPM photodetectors for PET imaging in the presence of magnetic fields

The multi pixel photon counter (MPPC) or silicon photomultiplier (SiPM), recently introduced as a solid state photodetector, consists of an array of Geiger mode photodiodes (microcells). It is a promising device for PET due to its potential for high photon detection efficiency (PDE) and its foreseeable immunity to magnetic fields. It is also easy to use with simple read outs, has a high gain and a small size. In this work we evaluate the in field performance of three 1x1mm2 (with 100, 400 and 1600 microcells, respectively) and one 6x6mm2 (arranged as a 2x2 array) Hamamatsu MPPCs for their use in PET imaging. We examine the dependence of the energy resolution and the gain of these devices on the temperature and reverse bias voltage, when coupled to LYSO scintillator crystals under conditions that one would find in a PET system. We find that the 400 and 1600 microcells models and the 2x2 array are suitable for small size crystals, like those employed in high resolution small animal scanners. We have confirmed the good performance of these devices up to magnetic fields of 7 T as well as their suitability for performing PET acquisitions in the presence of fast switching gradients and high duty radiofrequency MRI sequencesThis work was supported in part by the CDTEAM project of the CENIT program, and by Ministerio de Ciencia e Innovacio´n under projects FPA2007 62216TEC2008 06715 C02 01, UCM (Grupos UCM; 910059), CPAN (Consolider Ingenio 2010) CSPD 2007 00042 projects, and project SENSORCZT S 0505/MAT/000279, Comunidad de Madrid. Part of the computations of this work were done at the ‘‘High Capacity Cluster for Physical Techniques’’ of UCM, funded in part by the UE under the FEDER program and in part by UCMPublicad

Statistical reconstruction methods in PET: resolution limit, noise, edge artifacts and considerations for the design of better scanners

Proceeding of: 2005 IEEE Nuclear Science Symposium Conference Record, Puerto Rico, 23-29 Oct. 2005Small animal positron emission tomography (PET) scanners are being increasingly used as a basic measurement tool in modern biomedical research. The new designs and technologies of these scanners and the modern reconstruction methods have allowed to reach high spatial resolution and sensitivity. Despite their successes, some important issues remain to be addressed in high resolution PET imaging. First, iterative reconstruction methods like maximum likelihood-expectation maximization (MLEM) are known to recover resolution, but also to create noisy images and edge artifacts if some kind of regularization is not imposed. Second, the limit of resolution achievable by iterative methods on high resolution scanners is not quantitatively understood. Third, the use of regularization methods like Sieves or maximum a posteriori (MAP) requires them determination of the optimal values of several adjustable parameter that may be object-dependent. In this work we review these problems in high resolution PET and establish that the origin of them is more related with the physical effects involved in the emission and detection of the radiation during the acquisition than with the kind of iterative reconstruction method chosen. These physical effects (positron range, non-collinearity, scatter inside the object and inside the detector materials) cause that the tube of response (TOR) that connects the voxels with a line of response (LOR) is rather thick. This implies that the higher frequencies of the patient organ structures are not recorded by the scanner and therefore cannot be recovered during the reconstruction. As iterations grow, MLEM algorithms try to recover higher frequencies in the image. Once that a certain critic frequency is reached, this only maximizes high frequency noise. Using frequency response analyses techniques, we determine the maximum achievable resolution, before edge artifacts spoil the quality of the image, for a particular scanner as a function of the thickness of the TOR, and independently of the reconstruction method employed. With the same techniques, we can deduce well defined stopping criteria for reconstructions methods. Also, criteria for the highest number of subsets which should be used and how the design of the scanners can be optimized when statistical reconstruction methods are employed, is established.This work was supported in part by the UCM, Fundación para la investigación biomédica del Hospital Gregorio Marañon”, support from MEC project (BFM2003 04147 C02 01)

Performance evaluation of SIPM Photosensors for PET imaging in the presence of magnetic fields

[Poster] 4th European Molecular Imaging Meeting, Barcelona, Spain, May 27 - 30, 2009This work has been supported in part by MEC (FPA2007-62216), CDTEAM (Programa CENIT, Ministerio de Industria), UCM (Grupos UCM; 910059), CPAN (Consolider-Ingenio 2010) CSPD-2007-00042, and the RECAVA-RETIC networkPublicad