A pulsed Sagnac source of narrowband polarization-entangled photons

We demonstrate pulsed operation of a bidirectionally pumped polarization Sagnac interferometric down-conversion source and its generation of narrowband, high-visibility polarization-entangled photons. Driven by a narrowband, mode-locked pump at 390.35 nm, the phase-stable Sagnac source with a type-II phase-matched periodically poled KTiOPO$_4$ crystal is capable of producing 0.01 entangled pair per pulse in a 0.15-nm bandwidth centered at 780.7 nm with 1 mW of average pump power at a repetition rate of 31.1 MHz. We have achieved a mean photon-pair generation rate of as high as 0.7 pair per pulse, at which multi-pair events dominate and significantly reduce the two-photon quantum-interference visibility. For low generation probability $\alpha$, the reduced visibility $V=1-\alpha$ is independent of the throughput efficiency and of the polarization analysis basis, which can be utilized to yield an accurate estimate of the generation rate $\alpha$. At low $\alpha$ we have characterized the source entanglement quality in three different ways: average quantum-interference visibility of 99%, the Clauser-Horne-Shimony-Holt $S$ parameter of $2.739 \pm 0.119$, and quantum state tomography with 98.85% singlet-state fidelity. The narrowband pulsed Sagnac source of entangled photons is suitable for use in quantum information processing applications such as free-space quantum key distribution.Comment: 10 pages, 6 figures, accepted for publication in Phys. Rev.

Baryon deceleration by strong chromofields in ultrarelativistic nuclear collisions

It is assumed that strong chromofields are generated at early stages of ultrarelativistic heavy-ion collisions which give rise to a collective deceleration of net baryons from colliding nuclei. We have solved classical equations of motion for baryonic slabs under the action of a time-dependent longitudinal chromoelectric field. It is demonstrated that the slab final rapidities are rather sensitive to the strength and decay time of the chromofield as well as to the back reaction of the produced partonic plasma. The net-baryon rapidity loss of about 2 units, found for most central Au-Au collisions at RHIC, can be explained by the action of chromofields with the initial energy density of about 50 GeV/fm^3. Predictions for the baryon stopping at the LHC are made.Comment: 10 pages in revtex, 3 eps figure

Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig

Odontoameloblastomas (previously incorporated within ameloblastic odontomas) are matrix-producing odontogenic mixed tumors and are closely related in histologic appearance to the 2 other types of matrix-producing odontogenic mixed tumors: odontomas and ameloblastic fibro-odontomas. The presence or absence of intralesional, induced non-neoplastic tissue must be accounted for in the diagnosis. Herein we describe a naturally occurring odontoameloblastoma with extensive chondroid cementum deposition in a guinea pig (Cavia porcellus). Microscopically, the mass featured palisading neoplastic odontogenic epithelium closely apposed to ribbons and rings of a pink dental matrix (dentinoid), alongside extensive sheets and aggregates of chondroid cementum. The final diagnosis was an odontoameloblastoma given the abundance of odontogenic epithelium in association with dentinoid but a paucity of pulp ectomesenchyme. Chondroid cementum is an expected anatomical feature of cavies, and its presence within the odontoameloblastoma was interpreted as a response of the ectomesenchyme of the dental follicle to the described neoplasm. Our case illustrates the inductive capabilities of odontoameloblastomas while highlighting species-specific anatomy that has resulted in a histologic appearance unique to cavies and provides imaging and histologic data to aid diagnosis of these challenging lesions

Efficient and spectrally bright source of polarization-entangled photons

We demonstrate an efficient fiber-coupled source of nondegenerate polarization entangled photons at 795 and 1609 nm using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of 50 GHz and a spectral brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits.Comment: 8 pages, 7 figures, submitted to Phys. Rev.

Postoperative Critical Care: Resource Availability, Patient Risk and Other Factors Influencing Referral and Admission

Although intended for benefit, surgery exposes patients to potential complications. Critical care is thought to protect against the development of these complications, and is recommended for patients at higher risk. However, previous literature suggests that high-risk patients do not consistently receive postoperative critical care. In this PhD thesis, I investigate the supposed misallocation of critical care resources, and seek to answer the following research questions: 1. What is the availability of postoperative critical care? 2. How do clinicians estimate perioperative risk? 3. How accurate are current available risk prediction tools? 4. How do clinicians decide which patients to admit for postoperative critical care? 5. What factors influence their admission? A survey of postoperative critical care availability was conducted in 309 hospitals across the United Kingdom, Australia and New Zealand (NZ). Then, in a subset of 274 of these hospitals, a cohort study enrolling 26,502 patients undergoing inpatient surgery was undertaken. Postoperative critical care availability was found to differ between countries. UK hospitals reported fewer critical care beds per 100 hospital beds (median = 2.7) compared with Australia (median = 3.7) and NZ (median = 3.5). Enhanced care/high-acuity beds used to manage some high-risk patients were identified in around 31% of hospitals. The estimated numbers of critical care beds per 100,000 population were 9.3, 14.1, and 9.1 in the UK, Australia, and NZ, respectively. The estimated per capita high-acuity bed capacities per 100,000 population were 1.2, 3.8, and 6.4 in the UK, Australia, and NZ, respectively. The risk profile of inpatients undergoing inpatient surgery and the incidence of short-term mortality and morbidity outcomes were described. Less than 40% of predicted high-risk patients (defined as having a 5% or higher predicted 30-day mortality) in the cohort were admitted to critical care directly after surgery, regardless of risk model used. Compared with objective risk tools, subjective clinical assessment performed similarly in terms of discrimination, but consistently overpredicted risk. The Area Under the Receiver Operating Characteristic curve (AUROC) for subjective clinical assessment was 0.89, compared to 0.91 for the Surgical Outcome Risk Tool (SORT), the best-performing objective risk tool. However, a model combining information from both objective tools and subjective assessment improved the accuracy and clinical applicability of risk predictions (combined model AUROC = 0.93; continuous Net Reclassification Index [NRI] = 0.347, p <0.001). Associations were identified between patient risk factors (e.g. increased comorbidities, more complex surgery, higher surgical urgency) and the likelihood of being recommended postoperative critical care admission. Increased critical care bed availability had a small but significant association with critical care recommendation (adjusted odds ratio [OR] = 1.05 per empty critical care bed at the time of surgery), suggesting a subtle effect of exogenous influences on clinical decision-making. These results will have value in informing policy around the delivery of postoperative care for high-risk patients undergoing surgery, both at a macroscopic level in planning services, and at a microscopic level in making clinical decisions for individual patients

The Supershell-Molecular Cloud Connection in the Milky Way and Beyond

The role of large-scale stellar feedback in the formation of molecular clouds has been investigated observationally by examining the relationship between HI and 12CO(J=1-0) in supershells. Detailed parsec-resolution case studies of two Milky Way supershells demonstrate an enhanced level of molecularisation over both objects, and hence provide the first quantitative observational evidence of increased molecular cloud production in volumes of space affected by supershell activity. Recent results on supergiant shells in the LMC suggest that while they do indeed help to organise the ISM into over-dense structures, their global contribution to molecular cloud formation is of the order of only ~10%.Comment: Proceedings of IAUS 292 - Molecular Gas, Dust, and Star Formation in Galaxies, eds. T. Wong & J. Ott. 4 pages, 3 figure

The molecular environment of massive star forming cores associated with Class II methanol maser emission

Methanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7 GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.Comment: 5 pages, 1 figure, IAU Symposium 242 Conference Proceeding

Pion Interferometry for Hydrodynamical Expanding Source with a Finite Baryon Density

We calculate the two-pion correlation function for an expanding hadron source with a finite baryon density. The space-time evolution of the source is described by relativistic hydrodynamics and the Hanbury-Brown-Twiss (HBT) radius is extracted after effects of collective expansion and multiple scattering on the HBT interferometry have been taken into account, using quantum probability amplitudes in a path-integral formalism. We find that this radius is substantially smaller than the HBT radius extracted from the freeze-out configuration.Comment: 4 pages, 2 figure