Management of Acute Spinal Fractures in Ankylosing Spondylitis

Ankylosing Spondylitis (AS) is a multifactorial and polygenic rheumatic condition without a well-understood pathophysiology (Braun and Sieper (2007)). It results in chronic pain, deformity, and fracture of the axial skeleton. AS alters the biomechanical properties of the spine through a chronic inflammatory process, yielding a brittle, minimally compliant spinal column. Consequently, this patient population is highly susceptible to unstable spine fractures and associated neurologic devastation even with minimal trauma. Delay in diagnosis is not uncommon, resulting in inappropriate immobilization and treatment. Clinicians must maintain a high index of suspicion for fracture when evaluating this group to avoid morbidity and mortality. Advanced imaging studies in the form of multidetector CT and/or MRI should be employed to confirm the diagnosis. Initial immobilization in the patient's preinjury alignment is mandatory to prevent iatrogenic neurologic injury. Both nonoperative and operative treatments can be employed depending on the patient's age, comorbidities, and fracture stability. Operative techniques must be individually tailored for this patient population. A multidisciplinary team approach is best with preoperative nutritional assessment and pulmonary evaluation

Incomplete Urethral Duplication Associated with a Dermoid Cyst within a Vascular Hamartoma in a Female Dog

A seven-year-old spayed female Labrador retriever presented for necropsy following an acute history of thrombocytopenia, anemia, leukocytosis and abdominal effusion. A 2 × 3 × 10 cm, cylindrical to tubular, mottled red-to-tan mass extended from the caudal pelvic cavity caudally and ventrally under the dermis along the caudal aspect of the left pelvic limb adjacent to the semimembranosus and semitendinosus musculature. Histologic examination of the mass revealed a singular central lumen lined by urothelium that multifocally transitioned into non-keratinizing, stratified squamous epithelium associated with few hair follicles and sweat glands. The lumen was surrounded by a dense collagenous stroma containing numerous, variably sized blood vessels. The combination of lesions was consistent with a diagnosis of incomplete urethral duplication associated with a dermoid cyst and vascular hamartoma. To the authors’ knowledge, this is the first report of an incomplete urethral duplication associated with a dermoid cyst within a vascular hamartoma

Ferromagnetic redshift of the optical gap in GdN

We report measurements of the optical gap in a GdN film at temperatures from 300 to 6K, covering both the paramagnetic and ferromagnetic phases. The gap is 1.31eV in the paramagnetic phase and red-shifts to 0.9eV in the spin-split bands below the Curie temperature. The paramagnetic gap is larger than was suggested by very early experiments, and has permitted us to refine a (LSDA+U)-computed band structure. The band structure was computed in the full translation symmetry of the ferromagnetic ground state, assigning the paramagnetic-state gap as the average of the majority- and minority-spin gaps in the ferromagnetic state. That procedure has been further tested by a band structure in a 32-atom supercell with randomly-oriented spins. After fitting only the paramagnetic gap the refined band structure then reproduces our measured gaps in both phases by direct transitions at the X point.Comment: 5 pages, 4 figure

On the Early Time X-ray Spectra of Swift Afterglows I: Evidence for Anomalous Soft X-ray Emission

We have conducted a thorough and blind search for emission lines in >70 Swift X-ray afterglows of total exposure ~10^7s. We find that most afterglows are consistent with pure power-laws plus extinction. Significant outliers to the population exist at the 5-10% level and have anomalously soft, possibly thermal spectra. Four bursts are singled out via possible detections of 2-5 lines: GRBs 060218, 060202, 050822, and 050714B. Alternatively, a blackbody model with kT~0.1-0.5 keV can describe the soft emission in each afterglow. The most significant soft component detections in the full data set of ~2000 spectra correspond to GRB060218/SN2006aj, with line significances ranging up to \~20-sigma. A thermal plasma model fit to the data indicates that the flux is primarily due to L-shell transitions of Fe at ~ solar abundance. We associate (>4-sigma significant) line triggers in the 3 other events with K-shell transitions in light metals. We favor a model where the possible line emission in these afterglows arises from the mildly relativistic cocoon of matter surrounding the GRB jet as it penetrates and exits the surface of the progenitor star. The emitting material in each burst is at a similar distance \~10^12--10^13 cm, a similar density ~10^17 cm^-3, and subject to a similar flux of ionizing radiation. The lines may correlate with the X-ray flaring. For the blackbody interpretation, the soft flux may arise from break out of the GRB shock or plasma cocoon from the progenitor stellar wind, as recently suggested for GRB060218 (Campana et al. 2006). Due to the low z of GRB060218, bursts faint in Gamma-rays with fluxes dominated by this soft X-ray component could outnumber classical GRBs 100-1.Comment: 32 pages, 10 tables, 17 figures, To Appear in ApJ v656, February 20, 200

Confirmation of the \eps -- \eiso (Amati) relation from the X-ray flash XRF 050416A observed by Swift/BAT

We report Swift Burst Alert Telescope (BAT) observations of the X-ray Flash (XRF) XRF 050416A. The fluence ratio between the 15-25 keV and 25-50 keV energy bands of this event is 1.5, thus making it the softest gamma-ray burst (GRB) observed by BAT so far. The spectrum is well fitted by the Band function with E^{\rm obs}_{\rm peak} of 15.0_{-2.7}^{+2.3} keV. Assuming the redshift of the host galaxy (z = 0.6535), the isotropic-equivalent radiated energy E_{\rm iso} and the peak energy at the GRB rest frame (E^{\rm src}_{\rm peak}) of XRF 050416A are not only consistent with the correlation found by Amati et al. and extended to XRFs by Sakamoto et al., but also fill-in the gap of this relation around the 30 - 80 keV range of E^{\rm src}_{\rm peak}. This result tightens the validity of the E^{\rm src}_{\rm peak} - E_{\rm iso} relation from XRFs to GRBs. We also find that the jet break time estimated using the empirical relation between E^{\rm src}_{\rm peak} and the collimation corrected energy E_{\gamma} is inconsistent with the afterglow observation by Swift X-ray Telescope. This could be due to the extra external shock emission overlaid around the jet break time or to the non existence of a jet break feature for XRF, which might be a further challenging for GRB jet emission, models and XRF/GRB unification scenarios.Comment: 16 pages, 4 figures; accepted for publication in ApJ

The First Swift BAT Gamma-Ray Burst Catalog

We present the first Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains bursts detected by the BAT between 2004 December 19 and 2007 June 16. This catalog (hereafter BAT1 catalog) contains burst trigger time, location, 90% error radius, duration, fluence, peak flux, and time averaged spectral parameters for each of 237 GRBs, as measured by the BAT. The BAT-determined position reported here is within 1.75' of the Swift X-ray Telescope (XRT)-determined position for 90% of these GRBs. The BAT T_90 and T_50 durations peak at 80 and 20 seconds, respectively. From the fluence-fluence correlation, we conclude that about 60% of the observed peak energies, Epeak, of BAT GRBs could be less than 100 keV. We confirm that GRB fluence to hardness and GRB peak flux to hardness are correlated for BAT bursts in analogous ways to previous missions' results. The correlation between the photon index in a simple power-law model and Epeak is also confirmed. We also report the current status for the on-orbit BAT calibrations based on observations of the Crab Nebula.Comment: 63 pages, 23 figures, Accepted in ApJS, Corrected for the BAT ground position, the image significance, and the error radius of GRB 051105, Five machine-readable tables are available at http://swift.gsfc.nasa.gov/docs/swift/results/bat1_catalog

The BAT-Swift Science Software

The BAT instrument tells the Swift satellite where to point to make immediate follow-up observations of GRBs. The science software on board must efficiently process gamma-ray events coming in at up to 34 kHz, identify rate increases that could be due to GRBs while disregarding those from known sources, and produce images to accurately and rapidly locate new Gamma-ray sources.Comment: 4 pages, no figures, to appear in Santa Fe proceedings "Gamma-Ray Bursts: 30 Years of Discovery", Fenimore and Galassi (eds), AIP, 200

In search of progenitors for supernova-less GRBs 060505 and 060614: re-examination of their afterglows

GRB060505 and GRB060614 are nearby long-duration gamma-ray bursts (LGRBs) without accompanying supernovae (SNe) down to very strict limits. They thereby challenge the conventional LGRB-SN connection and naturally give rise to the question: are there other peculiar features in their afterglows which would help shed light on their progenitors? To answer this question, we combine new observational data with published data and investigate the multi-band temporal and spectral properties of the two afterglows. We find that both afterglows can be well interpreted within the framework of the jetted standard external shock wave model, and that the afterglow parameters for both bursts fall well within the range observed for other LGRBs. Hence, from the properties of the afterglows there is nothing to suggest that these bursts should have another progenitor than other LGRBs. Recently, Swift-discovered GRB080503 also has the spike + tail structure during its prompt gamma-ray emission seemingly similar to GRB060614. We analyse the prompt emission of this burst and find that this GRB is actually a hard-spike + hard-tail burst with a spectral lag of 0.8$\pm$0.4 s during its tail emission. Thus, the properties of the prompt emission of GRB060614 and GRB080503 are clearly different, motivating further thinking of GRB classification. Finally we note that, whereas the progenitor of the two SN-less bursts remains uncertain, the core-collapse origin for the SN-less bursts would be quite certain if a wind-like environment can be observationally established, e.g, from an optical decay faster than the X-ray decay in the afterglow's slow cooling phase.Comment: 15 pages, 7 figures, 4 tables, ApJ in press; added Fig. 7 of the lag-luminosity relatio