Investigating the Nature of Late-Time High-Energy GRB Emission Through Joint Fermi /Swift Observations.

We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveal that LAT non-detections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the non-detected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.

Modulation of chemosensitivity by alpha interferon in multiple myeloma and non-Hodgkin's lymphoma.

Low-grade non-Hodgkin's lymphoma and multiple myeloma are chemosensitive malignancies, but are rarely curable because of primary or acquired drug resistance. Interferon has been shown to modulate the multidrug resistance phenotype and to reinduce chemosensitivity in patients with chemoresistant tumors. Fifteen patients with multiple myeloma and 64 patients with low/intermediate grade non-Hodgkin's lymphoma unresponsive to initial chemotherapy were treated with alpha 2b interferon for 2 months. In case of an objective response, treatment was continued until disease progression; non-responding patients received the same chemotherapy to which they were resistant, preceded by a 5 day course of interferon. Interferon salvage monotherapy induced an objective response in 1/15 patients with multiple myeloma and in 7/64 patients with non-Hodgkin's lymphoma. An objective response was achieved after retreatment with first-line chemotherapy preceded by interferon in 4/14 patients (28.6%) with multiple myeloma and in 20/56 evaluable patients (35.7%) with non-Hodgkin's lymphoma. Toxicity was moderate, predictable, manageable, and never caused interruption of the treatment. Interferon appears to be able to modulate chemosensitivity of tumors refractory to chemotherapy with several potential mechanisms, including an effect on drug accumulation; its utilization in this setting warrants further evaluation.

The electrocardiographic T wave changes in highly trained athletes during training. An old problem revisited.

OBJECTIVE: To evaluate the T-wave pattern alterations during vigorous training in elite athletes. SETTING: Institute of Sport Science in Rome and National Rowing Center in Piediluco, Italy. STUDY POPULATION: Nine male and 7 female rowers of the national team were examined prospectively at different times of their conditioning period. METHODS: All athletes underwent electrocardiography and echocardiography; the ecg was analyzed for QRS voltages and axis, T-wave pattern and QTc interval; from echocardiography the left ventricular (LV) cavity dimension, wall thickness and mass were calculated. From Doppler-echocardiography the transmitral diastolic LV filling pattern was evaluated. RESULTS: Variation of T-wave voltages was seen in all the athletes. Specifically, during the low-intensity training period the T-wave pattern was positive and increased in voltage (T-wave max amplitude in V6 increased to 130% in male and 100% in female than pretraining values). During the peak training a variety of patterns was observed, and a transient flattening was present in 50% of subjects. No concomitant alteration of heart rate, QRS and T-wave axis and QTc duration were observed. No significant changes of cavity dimension, wall thickness, LV mass index and Doppler-derived diastolic peak flow velocities were detected during the study period. CONCLUSIONS: Transient changes of T-wave pattern may occur in athletes as an effect of athletic conditioning, without changes of cardiac dimension or alteration of indexes of LV function. This finding supports the role of ecg monitoring to follow-up the individual athletes response to training exercise load.

[Characterization of the difference between filtered back projection and ordered subsets expectation maximization in spect images using the Wavelet Transform]. / Caracterización de la diferencia entre retroproyección filtrada y Ordered Subsets Expectation Maximization, en imágenes SPECT, utilizando la transformada Wavelet.

Efficiency of reconstruction algorithms is important to guarantee quality of Nuclear Medicine tomographic images. The algorithms belong to one of two types: analytical or statistical. The Filtered Back Projection (BP) algorithm belongs to the first group and the Ordered Subsets Expectation Maximization (OSEM) algorithm belongs to the second group. The aim of the present paper was to compare both algorithms by means of the Wavelet Transform (WT). This tool was selected because of its capability to divide the image into different frequency levels without losing information about their spatial position. The WT was applied on the Haar basis without decimation in order to compare matrixes of the same size. Attention was drawn to the relative presence of three typical perturbations: Poisson noise, annular artifacts that express a deficient correction to the planar uniformity and attenuation phenomenon. With these purposes, we studied homologue transversal slices of images of homogeneous distribution of activity. The OSEM algorithm not only greatly improves the filtering of the Poisson noise, but also diminishes the annular artifacts, mainly at the image zone that coincides with the rotation center. The intensity of the attenuation phenomenon was the same with both algorithms, except in the peripheral zone where OSEM showed a slightly higher activity than BP. These observations encourage our interest to continue applying the WT not only to identify the artifacts, but also to try to decrease their deleterious influence on Nuclear Medicine images.

[Cardiac changes induced by deconditioning in athletes: an echocardiographic and electrocardiographic study]. / Modificazioni cardiache indotte dal decondizionamento nell'atleta: studio ecocardiografico ed elettrocardiografico.

The relationships between echocardiographic and electrocardiographic variations and the sensibility of three different electrocardiographic criteria of left ventricular (LV) hypertrophy were assessed during deconditioning in 18 top-level oarsmen (mean age 23 +/- 4 years). After seven months of training and on the 7th and 21st deconditioning days the oarsmen underwent clinical examination, electrocardiogram (ECG) and echocardiogram with Doppler evaluation. The following ECG measurements were obtained: heart rate (HR), QTc, QRS and T waves axes, QRS and T wave angular gradients, R, S and T wave amplitude and T wave area. Moreover, the sums of S wave in lead V1 plus R wave in lead V5 or V6, of S wave in lead V1 or V2 plus R wave in lead V5 or V6, and of R wave in lead aVL plus S wave in lead V3 were calculated as indices of left ventricular hypertrophy. The following echocardiographic parameters were also analyzed: intraventricular septal (IVST) and posterior wall thickness (PWT), LV internal diameter (LVID), left ventricular mass (LVM) and volumes, LV endocardial/epicardial diastolic surface area ratio, peak systolic meridional wall stress (PSS), end-systolic stress (ESS) and mean systolic wall stress (MWSI), LV ejection fraction (EF) and total peripheral resistances (TPR); early (E) and late (A) transmitral peak flow velocity, E/A ratio. Systolic blood pressure was reduced after 3 deconditioning weeks, while diastolic blood pressure and HR were unchanged. Left ventricular mass and end-systolic volume were reduced after 1 week, while LV end-diastolic volume only after 3 weeks; therefore, EF improved at the end of the first week when TPR were lower. End-systolic stress always remained unchanged; PSS increased at 1 week and then returned to previous values. In addition, the endocardial-epicardial area ratio increased after 1 week and then returned to starting values after 3 weeks. Doppler parameters were in the normal range and remained unchanged during the study. Amplitudes of R wave in aVL, V5, V6 and of S wave in V2 did not change, while S wave amplitude in V1 and V3 decreased after three weeks and one week, respectively. The most sensible criterion for LV hypertrophy was the sum of S wave in V1 or V2 plus R wave in V5 or V6 (range from 33.3% to 22.2%); the sum of S in V1 plus R in V5 or V6 performed better than the sum of R in aVL plus S in V3.(ABSTRACT TRUNCATED AT 400 WORDS)

Caracterización de la diferencia entre retroproyección filtrada y Ordered Subsets Expectation Maximization, en imágenes SPECT, utilizando la transformada Wavelet / Characterization of the difference between filtered back projection and ordered subsets expectation maximization in spect images using the wavelet transform

La eficacia de los algoritmos de reconstrucción es un factor importante a fin de garantizar la calidad de imágenes tomográficas de Medicina Nuclear. Existen dos grupos de algoritmos, los analíticos y los de carácter estadístico. El algoritmo de Retroproyección Filtrada (RPF) pertenece al primer grupo mientras que Ordered Subsets Expectation Maximization (OSEM) es uno de los algoritmos del segundo grupo.El objetivo del presente trabajo fue comparar ambos algoritmos utilizando la Transformada Wavelet (TW). Se eligió este instrumento dada su capacidad de separar la imagen en distintos niveles de frecuencia sin perder información posicional de los mismos. La misma se aplicó con base Haar y sin decimación por niveles, a fin de poder comparar matrices de igual tamaño. Se prestó atención a la presencia relativa de tres perturbaciones típicas: el ruido de Poisson, los artificios anulares que expresan una deficiente corrección de la uniformidad planar y el fenómeno de la atenuación.Con este propósito se estudiaron cortes transversales homólogos de distribuciones homogéneas de actividad. Se comprobó, que el algoritmo OSEM no solamente introduce importantes mejoras, en cuanto a filtrar el ruido de Poisson, sino que también disminuye los artificios anulares, en particular en la zona de la imagen coincidente con el centro de rotación. El fenómeno de la atenuación, para el caso de estas imágenes, mostró igual intensidad con ambos algoritmos a excepción de la zona periférica donde OSEM produjo un aumento aparente de la concentración de actividad ligeramente más importante que RPF.Estas observaciones alientan el interés de continuar en la idea de utilizar la TW no sólo para identificar, sino también para tratar de disminuir la presencia de artificios característicos de éstas imágenes (AU)