Anaesthetic management of endoscopic resection of juvenile nasopharyngeal angiofibroma: our experience and a review of the literature

Background: Juvenile nasopharyngeal angiofibroma (JNA) is a rare, benign, vascular tumour in adolescent males with potential life-threatening complications. Advances in endoscopic surgery, invasive monitoring and hypotensive anaesthesia have made JNAs amenable to endoscopic surgical resection. We present the anaesthetic management of endoscopic resection of 14 JNAs, together with a review.Method: The medical records of patients who underwent endoscopic excision of JNAs within the last seven years were reviewed retrospectively. Information was collected and analysed with regard to demographics, preoperative evaluation, intraoperative management, complications and postoperative course. Fourteen patients were included in the study. If the surgery needed to be converted to open surgery, the patients were excluded from the study.Results: The age of the patients ranged from 10-18 years. Two patients had preoperative embolisation of the feeding vessel. Standard anaesthesia induction technique, together with invasive monitoring, was used. Controlled hypotension (mean arterial pressure of 60 ± 5 mmHg) was achieved with the help of inhalational anaesthetics, vasodilators and beta blockers. Mean duration of surgery was 197.14 ± 77 minutes, and median blood loss was 500 ml (100- 4 300 ml). Seven patients were extubated in the operating room. The other seven patients remained intubated for 24 hours owing to extensive surgery with a risk of postoperative bleeding, and were monitored either in the postoperative care unit (five patients) or the intensive care unit (two patients). There was no significant morbidity or mortality in any of the patients.Conclusion: JNAs remain a challenge for anaesthesiologists because of excessive intraoperative bleeding. Anaesthetists should be aware of recent techniques to reduce tumour vascularity, such as embolisation of the feeding vessel and controlled hypotension. Invasive monitoring, together with multimodal blood conservation strategies, decreases blood loss and provides a clear field of vision for endoscopic surgery.Keywords: anaesthetic management, JNA, endoscopic resection, controlled hypotensio

Persistence at the onset of spatiotemporal intermittency in coupled map lattices

We study persistence in coupled circle map lattices at the onset of spatiotemporal intermittency, an onset which marks a continuous transition, in the universality class of directed percolation, to a unique absorbing state. We obtain a local persistence exponent of theta_l = 1.49 +- 0.02 at this transition, a value which closely matches values for theta_l obtained in stochastic models of directed percolation. This result constitutes suggestive evidence for the universality of persistence exponents at the directed percolation transition. Given that many experimental systems are modelled accurately by coupled map lattices, experimental measurements of this persistence exponent may be feasible.Comment: 7 pages, Latex, 6 Postscript figures, Europhysics Letters (to appear

Electronic Structure of Ordered Double Perovskite Ba2CoWO6

Ba2CoWO6 (BCoW) has been synthesized in polycrystalline form by solid state reaction at 1200C. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The crystal structure is cubic, space group Fm-3m (No 225) with the lattice parameter, a=8.210A. Optical band-gap of the present system has been calculated using the UV-Vis Spectroscopy and Kubelka-Munk function, its value being 2.45 eV. A detailed study of the electronic properties has also been carried out using the density functional theory (DFT) techniques implemented on WIEN2k. Importance of electron-electron interaction between the Co ions leading to half-metallic behavior, crystal and exchange splitting together with the hybridization between O and Co, W has been investigated using the total and partial density of states.Comment: 3 pages, 3 figures, submitted to 58th DAE-SSPS 201

The self-organized critical forest-fire model on large scales

We discuss the scaling behavior of the self-organized critical forest-fire model on large length scales. As indicated in earlier publications, the forest-fire model does not show conventional critical scaling, but has two qualitatively different types of fires that superimpose to give the effective exponents typically measured in simulations. We show that this explains not only why the exponent characterizing the fire-size distribution changes with increasing correlation length, but allows also to predict its asymptotic value. We support our arguments by computer simulations of a coarse-grained model, by scaling arguments and by analyzing states that are created artificially by superimposing the two types of fires.Comment: 26 pages, 7 figure

Astrophysical S_{17}(0) factor from a measurement of d(7Be,8B)n reaction at E_{c.m.} = 4.5 MeV

Angular distribution measurements of $^2$H($^7$Be,$^7$Be)$^2$H and $^2$H($^7$Be,$^8$B)$n$ reactions at $E_{c.m.}\sim$~4.5 MeV were performed to extract the astrophysical $S_{17}(0)$ factor using the asymptotic normalization coefficient (ANC) method. For this purpose a pure, low emittance $^7$Be beam was separated from the primary $^7$Li beam by a recoil mass spectrometer operated in a novel mode. A beam stopper at 0$^{\circ}$ allowed the use of a higher $^7$Be beam intensity. Measurement of the elastic scattering in the entrance channel using kinematic coincidence, facilitated the determination of the optical model parameters needed for the analysis of the transfer data. The present measurement significantly reduces errors in the extracted $^7$Be(p,$\gamma$) cross section using the ANC method. We get $S_{17}$~(0)~=~20.7~$\pm$~2.4 eV~b.Comment: 15 pages including 3 eps figures, one figure removed and discussions updated. Version to appear in Physical Review