Anomalous X-ray Pulsar 1E 1048.1-5937: Pulsed Flux Flares and Large Torque Variations

We report on continued monitoring of the Anomalous X-ray pulsar (AXP) 1E 1048.1-5937 using the Rossi X-ray Timing Explorer. We confirm that this pulsar has exhibited significant pulsed flux variability. The principal features of this variability are two pulsed X-ray flares. Both flares lasted several months and had well-resolved few-week-long rises. The long rise times of the flares are a phenomenon not previously reported for this class of object. The epochs of the flare peaks were MJD 52,218.8+/-4.5 and 52,444.4+/-7.0. Both flares had shorter rise than fall times. The flares had peak fluxes of 2.21+/-0.16 and 3.00+/-0.13 times the quiescent value. We estimate a total 2-10 keV energy release of ~2.7x10^40 ergs and ~2.8x10^41 ergs for the flares, assuming a distance of 5 kpc. We also report large (factor of ~12) changes to the pulsar's spin-down rate on time scales of weeks to months, shorter than has been reported previously. We find marginal evidence for correlation between the flux and spin-down rate variability, with probability of nonrandom correlation 6%. We discuss the implications of our findings for AXP models.Comment: 11 pages, 2 figures, ApJ Letters accepted. Modifications to the text, calculations and figures. We corrected a problem which resulted in reducing the scatter in the earlier flux points in Figure 1. Conclusions unchange

Forest structure, diversity, and primary production in relation to disturbance severity

Differential disturbance severity effects on forest vegetation structure, species diversity, and net primary production (NPP) have been long theorized and observed. Here, we examined these factors concurrently to explore the potential for a mechanistic pathway linking disturbance severity, changes in light environment, leaf functional response, and wood NPP in a temperate hardwood forest.Using a suite of measurements spanning an experimental gradient of tree mortality, we evaluated the direction and magnitude of change in vegetation structural and diversity indexes in relation to wood NPP. Informed by prior observations, we hypothesized that forest structural and species diversity changes and wood NPP would exhibit either a linear, unimodal, or threshold response in relation to disturbance severity. We expected increasing disturbance severity would progressively shift subcanopy light availability and leaf traits, thereby coupling structural and species diversity changes with primary production.Linear or unimodal changes in three of four vegetation structural indexes were observed across the gradient in disturbance severity. However, disturbance‐related changes in vegetation structure were not consistently correlated with shifts in light environment, leaf traits, and wood NPP. Species diversity indexes did not change in response to rising disturbance severity.We conclude that, in our study system, the sensitivity of wood NPP to rising disturbance severity is generally tied to changing vegetation structure but not species diversity. Changes in vegetation structure are inconsistently coupled with light environment and leaf traits, resulting in mixed support for our hypothesized cascade linking disturbance severity to wood NPP.We examined multiple metrics of vegetation structural and biological diversity concurrently to explore the potential for a mechanistic pathway linking disturbance severity, changes in light environment, leaf functional response, and wood NPP in a temperate hardwood forest. Significant linear or unimodal changes in three of four vegetation structural indexes were observed across the gradient in disturbance severity, although disturbance‐related changes in vegetation structure were not consistently correlated with shifts in light environment, leaf traits, and wood NPP. We conclude that, in our study system, the sensitivity of wood NPP to rising disturbance severity is generally tied to changing vegetation structure but not species diversity.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155474/1/ece36209.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155474/2/ece36209_am.pd

Magnetic resonance imaging with pathological correlation in a case of mantle cell lymphoma of the parotid gland: a case report

<p>Abstract</p> <p>Introduction</p> <p>Mantle cell lymphoma is a rare non-Hodgkin's lymphoma. It is a subtype of B-cell lymphoma with frequent involvement of the bone marrow and the gastrointestinal tract. Isolated parotid gland involvement seldom occurs. Here we report an unusual case of isolated infiltration of the parotid gland by mantle cell lymphoma. The aim of our study is to correlate magnetic resonance imaging findings with the histological features of the disease. To the best of our knowledge, no similar radiological findings of mantle cell lymphoma have been published before.</p> <p>Case presentation</p> <p>A 72-year-old Caucasian woman presented with a painful left parotid enlargement. She was diagnosed with mantle cell lymphoma involving the left submandibular gland seven years prior to presentation. Her whole body CT scan showed the absence of pathologically enlarged lymph nodes. However, a magnetic resonance imaging showed enlargement of her left parotid gland and an abnormal parenchyma with mixed-type solid and cystic lesions. A biopsy of her left parotid gland and subsequent histological examination confirmed a mantle cell lymphoma (common variant) relapse.</p> <p>Conclusion</p> <p>Although rare, the involvement of parotid gland with mantle cell lymphoma must be considered in the differential diagnosis of parotid tumors.</p