Phase decorrelation, streamwise vortices and acoustic radiation in mixing layers

Several direct numerical simulations were performed and analyzed to study various aspects of the early development of mixing layers. Included are the phase jitter of the large-scale eddies, which was studied using a 2-D spatially-evolving mixing layer simulation; the response of a time developing mixing layer to various spanwise disturbances; and the sound radiation from a 2-D compressible time developing mixing layer

The Nature of the UV/X-Ray Absorber in PG 2302+029

We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029. This quasar has a rare system of ultra-high velocity (-56,000 km/s) UV absorption lines that form in an outflow from the active nucleus (Jannuzi et al. 2003). The Chandra data indicate that soft X-ray absorption is also present. We perform a joint UV and X-ray analysis, using photoionization calculations, to detemine the nature of the absorbing gas. The UV and X-ray datasets were not obtained simultaneously. Nonetheless, our analysis suggests that the X-ray absorption occurs at high velocities in the same general region as the UV absorber. There are not enough constraints to rule out multi-zone models. In fact, the distinct broad and narrow UV line profiles clearly indicate that multiple zones are present. Our preferred estimates of the ionization and total column density in the X-ray absorber (log U=1.6, N_H=10^22.4 cm^-2) over predict the O VI 1032, 1038 absorption unless the X-ray absorber is also outflowing at ~56,000 km/s, but they over predict the Ne VIII 770, 780 absorption at all velocities. If we assume that the X-ray absorbing gas is outflowing at the same velocity of the UV-absorbing wind and that the wind is radiatively accelerated, then the outflow must be launched at a radius of < 10^15 cm from the central continuum source. The smallness of this radius casts doubts on the assumption of radiative acceleration.Comment: Accepted for Publication in Ap

A Novel Classification System to Address Financial Impact and Referral Decisions for Bile Duct Injury in Laparoscopic Cholecystectomy

Purpose. The study was undertaken to evaluate a novel classification system developed to estimate financial cost of bile duct injury (BDI) and to aid in decision making for referral. Study Design. A retrospective review of patients referred for BDI was performed. Grade I injuries involve the duct of Luschka or accessory right hepatic ducts, grade II includes all other biliary injuries, and grade III includes all vasculobiliary injuries. Groups were compared using standard statistical methods. Results. There were 14 grade I, 74 grade II, and 20 grade III injuries. There was a significant difference in the cost and mortality of grade I ($12,457, 0$46,481, 1.4%), and grade III ($69,368, 15%, P = 0.002 and P = 0.030, resp.) injuries. Grade II and III injuries were significantly more likely to require surgical repair (OR 27.7, P < 0.001). Conclusion. We have presented a simple classification system that is able to accurately predict cost and need for surgical repair

Surgical resection for hilar cholangiocarcinoma: experience improves resectability

AbstractObjectivesIn hilar cholangiocarcinoma, resection provides the only opportunity for longterm survival. A US experience of hilar cholangiocarcinoma was examined to determine the effect of clinical experience on negative margin (R0) resection rates.MethodsWe conducted a retrospective analysis of 110 consecutive hilar cholangiocarcinoma patients presenting over an 18-year period. Analyses were performed using chi-squared, Wilcoxon rank sum and Kaplan–Meier methods, and multivariable Cox and logistic regression modelling.ResultsOf the 110 patients in the cohort, 59.1% were male and 90.9% were White. The median patient age was 64 years. A total of 59 (53.6%) patients underwent resection; 37 of these demonstrated R0. The 30-day mortality rate was 5.1%; the complication rate was 39.0%. The rate of resectability increased over time (36.4% vs. 70.9%; P= 0.001), as did the percentage of R0 resections (10.9% vs. 56.5%; P < 0.001). Of the 59 patients who underwent resection, 23 (39.0%) experienced recurrence. Multivariable Cox regression analysis identified resection margins [hazard ratio (HR) = 4.124 for positive vs. negative; P= 0.002] and type of operation (HR = 5.075 for exploration vs. resection; P= 0.001) as significant to survival.ConclusionsAlthough R0 resection can be achieved in only a minority of patients, these patients have a reasonable chance of longterm survival. The last decade has seen a significant rise in rates of resectability of Klatskin's tumour at specialty centres

Mapping the Polarization of the Radio-Loud Lyα\alpha Nebula B3 J2330+3927

Lya nebulae, or "Lya blobs", are extended (up to ~100 kpc), bright (L[Lya] > 10^43 erg/s) clouds of Lya emitting gas that tend to lie in overdense regions at z ~ 2--5. The origin of the Lya emission remains unknown, but recent theoretical work suggests that measuring the polarization might discriminate among powering mechanisms. Here we present the first narrowband, imaging polarimetry of a radio-loud Lya nebula, B3 J2330+3927 at z=3.09, with an embedded active galactic nucleus (AGN). The AGN lies near the blob's Lya emission peak and its radio lobes align roughly with the blob's major axis. With the SPOL polarimeter on the 6.5m MMT telescope, we map the total (Lya + continuum) polarization in a grid of circular apertures of radius 0.6" (4.4kpc), detecting a significant (>2sigma) polarization fraction P in nine apertures and achieving strong upper-limits (as low as 2%) elsewhere. P increases from <2% at ~5kpc from the blob center to ~17% at ~15-25kpc. The detections are distributed asymmetrically, roughly along the nebula's major axis. The polarization angles theta are mostly perpendicular to this axis. Comparing the Lya flux to that of the continuum, and conservatively assuming that the continuum is highly polarized (20-100%) and aligned with the total polarization, we place lower limits on the polarization of the Lya emission P(Lya) ranging from no significant polarization at ~5 kpc from the blob center to ~ 3--17% at 10--25kpc. Like the total polarization, the Lya polarization detections occur more often along the blob's major axis.Comment: 9 pages, 7 figures, accepted for publication in Ap

The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei

We reinvestigate the relationship between the characteristic broad-line region size (R_blr) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of R_blr for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of R_blr for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data sub-sample and regression technique. Though small systematic differences were found depending on the method of analysis, our results are generally consistent. Assuming a power-law relation R_blr \propto L^\alpha, we find the mean best-fitting \alpha is about 0.67+/-0.05 for the optical continuum and the broad H\beta luminosity, about 0.56+/-0.05 for the UV continuum luminosity, and about 0.70+/-0.14 for the X-ray luminosity. We also find an intrinsic scatter of about 40% in these relations. The disagreement of our results with the theoretical expected slope of 0.5 indicates that the simple assumption of all AGNs having on average same ionization parameter, BLR density, column density, and ionizing spectral energy distribution, is not valid and there is likely some evolution of a few of these characteristics along the luminosity scale.Comment: 11 pages, 2 figures, emulateapj, accepted for publication in The Astrophysical Journa