Spin-lattice coupling in the ferrimagnetic semiconductor FeCr2S4 probed by surface acoustic waves

Using surface acoustic waves, the elastomagnetic coupling could be studied in thin single crystalline plates of the ferrimagnetic semiconductor FeCr2S4 by measuring the attenuation and the frequency tracking in the temperature range 4.2 K to 200 K. The data clearly display the anomalies found in low-field magnetization measurements.Comment: 15 pages, 3 figures. To appear in J. Appl. Phys., 99 (2006

Microwave imaging techniques for biomedical applications

Microwaves have been considered for medical applications involving the detection of organ movements and changes in tissue water content. More particularly cardiopulmonary interrogation via microwaves has resulted in various sensors monitoring ventricular volume change or movement, arterial wall motion, respiratory movements, pulmonary oedema, etc. In all these applications, microwave sensors perform local measurements and need to be displaced for obtaining an image reproducing the spatial variations of a given quantity. Recently, advances in the area of inverse scattering theory and microwave technology have made possible the development of microwave imaging and tomographic instruments. This paper provides a review of such equipment developed at Suplec and UPC Barcelona, within the frame of successive French-Spanish PICASSO cooperation programs. It reports the most significant results and gives some perspectives for future developments. Firstly, a brief historical survey is given. Then, both technological and numerical aspects are considered. The results of preliminary pre-clinical assessments and in-lab experiments allow to illustrate the capabilities of the existing equipment, as well as its difficulty in dealing with clinical situations. Finally, some remarks on the expected development of microwave imaging techniques for biomedical applications are given.Peer ReviewedPostprint (published version

Indoor experiments on polarimetric SAR interferometry

A coherence optimization method, which makes use of polarimetry to enhance the quality of SAR interferograms, has been experimentally tested under laboratory conditions in an anechoic chamber. By carefully selecting the polarization in both images, the resulting interferogram exhibits an improved coherence above the standard HH or VV channel. This higher coherence produces a lower phase variance, thus estimating the underlying topography more accurately. The potential improvement that this technique provides in the generation of digital elevation models (DEM) of non-vegetated natural surfaces has been observed for the first time on some artificial surfaces created with gravel. An experiment on a true outdoor DEM has not been accomplished yet, but the first laboratory results show that the height error for an almost planar surface can be drastically reduced within a wide range of baselines by using the optimization algorithm. This algorithm leads to three possible interferograms associated with statistically independent scattering mechanisms. The phase difference between those interferograms has been employed for extracting the height of vegetation samples. This retrieval technique has been tested on three different samples: maize, rice, and young fir trees. The inverted heights are compared with ground truth for different frequency bands. The estimates are quite variable with frequency, but their complete physical justification is still in progress. Finally, an alternative simplified scheme for the optimization is proposed. The new approach (called polarization subspace method) yields suboptimum results but is more intuitive and has been used for illustrating the working principle of the original optimization algorithm.Peer Reviewe

Fusing Landsat and SAR Data for Mapping Tropical Deforestation through Machine Learning Classification and the PVts-β Non-Seasonal Detection Approach

Altres ajuts: The work of Yonatan Tarazona Coronel has been partially funded by American Program in GIS and Remote Sensing and National Program of Scholarships and Educational Credit (PRONABEC-Peru) through RJ: Nº 4276-2018-MINEDU/VMGI-PRONABEC-OBE and RJ: Nº 942-2019-MINEDU/VMGI-PRONABEC-OBE.This article focuses on mapping tropical deforestation using time series and machine learning algorithms. Before detecting changes in the time series, we reduced seasonality using Photosynthetic Vegetation (PV) index fractions obtained from Landsat images. Single and multi-temporal filters were used to reduce speckle noise from Synthetic Aperture Radar (SAR) images (i.e., ALOS PALSAR and Sentinel-1B) before fusing them with optical images through Principal Component Analysis (PCA). We detected only one change in the two PV series using a non-seasonal detection approach, as well as in the fused images through five machine learning algorithms that were calibrated with Cross-Validation (CV) and Monte Carlo Cross-Validation (MCCV). In total, four categories were obtained: forest, cropland, bare soil, and water. We then compared the change map obtained with time series and that obtained with the classification algorithms with the best calibration performance, revealing an overall accuracy of 92.91% and 91.82%, respectively. For statistical comparisons, we used deforestation reference data. Finally, we conclude with some discussions and reflections on the advantages and disadvantages of the detections made with time series and machine learning algorithms, as well as the contribution of SAR images to the classifications, among other aspects

Aplastic anemia and severe pancytopenia during treatment with peg-interferon, ribavirin and telaprevir for chronic hepatitis C

Telaprevir and Boceprevir are the first direct acting antivirals approved for chronic hepatitis C in combination with peg-interferon alfa and ribavirin. Pancytopenia due to myelotoxicity caused by these drugs may occur, but severe hematological abnormalities or aplastic anemia (AA) have not been described. We collected all cases of severe pancytopenia observed during triple therapy with telaprevir in four Spanish centers since approval of the drug in 2011. Among 142 cirrhotic patients receiving treatment, 7 cases of severe pancytopenia (5%) were identified and three were consistent with the diagnosis of AA. Mean age was 59 years, five patients had compensated cirrhosis and two patients had severe hepatitis C recurrence after liver transplantation. Severe pancytopenia was diagnosed a median of 10 wk after the initiation of therapy. Three patients had pre-treatment hematological abnormalities related to splenomegaly. In six patients, antiviral treatment was interrupted at the onset of hematological abnormalities. Two patients died due to septic complications and one patient due to acute alveolar hemorrhage. The remaining patients recovered. Severe pancytopenia and especially AA, are not rare during triple therapy with telaprevir in patients with advanced liver disease. Close monitoring is imperative in this setting to promptly detect serious hematological disorders and to prevent further complications

PARSAR: A SAR processor implemented in a cluster of workstations

A parallel SAR processor is presented in this paper. The target configuration is a cluster of UNIX workstations, available in most user sites. This fact allows to obtain an increased computing performance without the need of dedicated hardware investment.Peer ReviewedPostprint (published version

PARSAR: Parallelisation of a chirp scaling algorithm SAR processor

A parallel SAR processor is presented in this paper. The target configuration is a cluster of UNIX workstations, available in most user sites. This fact allows to obtain an increased computing performance without the need of dedicated hardware investment.Peer ReviewedPostprint (published version

High frequency of acute decompensation and cancer in patients with compensated cirrhosis due to nonalcoholic fatty liver disease : A retrospective cohort study

The natural history of compensated cirrhosis due to nonalcoholic fatty liver disease (NAFLD) has not been completely characterized. The aim of the present study was to assess the incidence and risk factors of acute decompensation of cirrhosis, hepatocellular carcinoma, and extrahepatic cancers. This was a multicenter, retrospective, cohort study including 449 patients with compensated cirrhosis due to NAFLD. We calculated cumulative incidences and used competitive risk analysis to determine the risk factors associated with decompensation and cancer development. Over a median of 39 months of follow-up, 124 patients (28%) presented acute decompensation. The most frequent decompensation was ascites (21%) followed by hepatic encephalopathy (15%), variceal bleeding (9%), and spontaneous bacterial peritonitis (3%). Acute-on-chronic liver failure was diagnosed in 6% of patients during follow-up. Liver function parameters and specifically an albumin level below 40 g/L were independently associated with an increased risk of decompensation. The presence of ischemic heart disease was independently associated with acute decompensation. Seventy-eight patients (18%) developed hepatocellular carcinoma or extrahepatic cancers during follow-up (51 and 27, respectively). Conclusion : Patients with compensated cirrhosis due to NAFLD are at high risk of severe liver complications, such as the development of acute decompensation, in a relative short follow-up time. This population is at high risk of hepatic and extrahepatic cancers. The analysis of a large contemporary cohort of 449 patients with compensated cirrhosis due to non-alcoholic fatty liver disease shows a high frequency of acute decompensations (AD) and development of cancer during 39 months of follow-up. Almost 28% of the cohort developed acute decompensation and 18% developed hepatocellular carcinoma (HCC) or extrahepatic cancer. Predictors of decompensation are mainly related to liver function and portal hypertension

Linfogamagrafía cervical

[spa] Desde la época de los grandes anatomistas, la distribución y localización de las estructuras linfáticas (vías y ganglios) del cuello ha sido estudiada detenidamente. Todos los especialistas que han abordado del tema se han basado, fundamentalmente, en los estudios post-mortem, mediante la inyección de colorantes, lo que unido a la disección cuidadosa de los frágiles vasos linfáticos, ha arrojado resultados insuperables que las observaciones posteriores no han hecho más que confirmar. Por el contrario, a la hora de analizar en detalle la bibliografía sobre el sistema linfático del cuello, vemos que los medios utilizados para el estudio “in vivo” de dicha región no son todo lo completos que cabría desear, ya que las peculiares características de los vasos linfáticos de la zona, su gran fragilidad y su pequeño calibre hacen difícil la aplicación de los métodos utilizados en los vasos linfáticos de otras zonas. Dado que la patología que puede incidir sobre el sistema linfático es amplísima, a la hora de escoger el objeto de trabajo de la presente tesis hemos centrado nuestra atención fundamentalmente en los procesos tumorales secundarios, en particular las neoplasias de cabeza y de cuello, y dentro de ellos a los procesos de origen laríngeo, ya que dentro de nuestra especialidad es la forma de neoplasia que detectamos con más frecuencia. Al iniciar este trabajo no albergamos la pretensión de realizar un descubrimiento inédito; creemos seria pecar de presunción pensar que vamos a poner en marcha una técnica revolucionaria. Sin embargo, con la presente investigación querríamos contribuir a un mayor conocimiento y un mejor estudio de los grupos ganglionares del cuello, de sus zonas aferentes y de las características que poseen estas estructuras en condicionas normales y en enfermos afectos de una patología que pueda incidir sobra la morfología normal y el funcionalismo de estos elementos