Intravenous conscious sedation in patients under 16 years of age. Fact or fiction?

Recently published guidelines on the use of conscious sedation in dentistry have published varying recommendations on the lower age limit for the use of intravenous conscious sedation. There are a large number of dentists currently providing dental treatment for paediatric patients under intravenous conscious sedation. The 18 cases reported here (age range 11-15 years), were successfully managed with intravenous conscious sedation. The experience in this paper is not sufficient evidence to recommend the wholesale use of intravenous conscious sedation in patients who are under 16 years. The fact that a range of operators can use these techniques on paediatric patients would suggest that further study should be carried out in this population. The guidance should be modified to say there is insufficient evidence to support the use of intravenous conscious sedation in children, rather than arbitrarily selecting a cut off point at age 16 years

The dual role of Amazonian rivers in the generation and maintenance of avian diversity

Copyright © 2018 The Authors. The Amazon River and its major tributaries delimit the distributions of hundreds of terrestrial taxa. It remains unclear whether river-bounded distributions and taxon replacements reflect the historical role of rivers in generating species diversity as vicariant forces, or are the result of their role as secondary barriers, maintaining current levels of species diversity by inhibiting gene flow and population introgression. We use a community-wide comparative phylogeographic and phylogenetic approach to address the roles that the Rio Negro and the Rio Branco play in the avian speciation process in the Guiana Shield. Examining 74 pairs of ecologically similar geographic replacements that turn over across the lower Negro, we found substantial variation in the levels of genetic divergence and the inferred timing of diversification among pairs, ranging from ~0.24 to over 8 million years (Ma ago). The breadth of this variation is inconsistent with a single, shared speciation event. Coalescent simulations also rejected a simultaneous divergence scenario for pairs divided by the Rio Branco but could not reject a single diversification pulse for a subset of 12 pairs of taxa divided by the upper Negro. These results are consistent with recent geomorphological hypotheses regarding the origins of these rivers. Phylogenetically, taxon pairs represent a blend of sister (~40%) and nonsister taxa (~60%), consistent with river-associated allopatric or peripatric speciation and secondary contact, respectively. Our data provide compelling evidence that species turnover across the Rio Negro basin encompasses a mixture of histories, supporting a dual role for Amazonian rivers in the generation and maintenance of biological diversity

Two-stream instability in quasi-one-dimensional Bose-Einstein condensates

We apply a kinetic model to predict the existence of an instability mechanism in elongated Bose-Einstein condensates. Our kinetic description, based on the Wigner formalism, is employed to highlight the existence of unstable Bogoliubov waves that may be excited in the counterpropagation configuration. We identify a dimensionless parameter, the Mach number at T=0, that tunes different regimes of stability. We also estimate the magnitude of the main parameters at which two-stream instability is expected to be observed under typical experimental conditions

Multimode collective scattering of light in free space by a cold atomic gas

We have studied collective recoil lasing by a cold atomic gas, scattering photons from an incident laser into many radiation modes in free space. The model consists of a system of classical equations for the atomic motion of N atoms where the radiation field has been adiabatically eliminated. We performed numerical simulations using a molecular dynamics code pepc (Pretty Efficient Parallel Coulomb Solver) to track the trajectories of the atoms. These simulations show the formation of an atomic density grating and collective enhancement of scattered light, both of which are sensitive to the shape and orientation of the atomic cloud. In the case of an initially circular cloud, the dynamical evolution of the cloud shape plays an important role in the development of the density grating and collective scattering. The ability to use efficient molecular dynamics codes will be a useful tool for the study of the multimode interaction between light and cold gases

Substituição da torta de algodão por feno de leguminosas em rações baseadas em restolho da cultura do milho para ovinos em confinamento.

Resumo: Dois experimentos usando ovinos deslanados testaram a substituiçao da torta de algodao por feno de Ieguminosas em rações corn restolho da cultura do milho. No primeiro experimento, foi usada uma raçao-base de 51% restolho do milho, 28% torta de algodao, 20% milho e 1% sal, na quaI a torta de algodao foi substituîda por 5%, 10%, e 15% de feno de mata-pasto (Cassia sericea), enquanto um Iote-testemunha era mantido em pastoreio. Os animais confinados ganharam 95, 106, 103 e 93 gramas/cabeça/dia (P > 0,05), para as rações com 0%, 5%, 10% e 15% de mata-pasto, respectivamente. Os animais em pastoreio perderam 11 gramas/cabeça/dia (P 0.05) for tho rations with 0%, 5%, 10% and 15% of "mata-pasto", respective-ly. The grazing animais iost 11 grams/head/day , (P <0.05). in the second experiment, the cottonseed calce was either partiaiiy (50%) or totaily repiacod by "mata-pasto" or "cunha" (ditaria terl7atee) hays, whiie the grazing sheep received a suppiementation of 200 grams of corn grain/headldayWith the exception of the treatment In which the eottonseed cake was totaily repiaced by "mata-pasto" hay, the other treatments with coniined animais showed gains above 100 grams/head/day, which were hi -,er than (P <0.01) the 42 grams/head/day for the grazing animais. The resuits indicate that it is possibie to substituto "mata-pasto" hay for cottonseed calce ar leveis up to 50%, while the total substitution Lan be made "cunhâ" Is used

Determination of the freeze-out temperature by the isospin thermometer

The high-resolution spectrometer FRS at GSI Darmstadt provides the full isotopic and kinematical identification of fragmentation residues in relativistic heavy-ion collisions. Recent measurements of the isotopic distribution of heavy projectile fragments led to a very surprising new physical finding: the residue production does not lose the memory of the N/Z of the projectile ending up in a universal de-excitation corridor; an ordering of the residues in relation to the neutron excess of the projectile has been observed. These unexpected features can be interpreted as a new manifestation of multifragmentation. We have found that at the last stage of the reaction the temperature of the big clusters subjected to evaporation is limited to a universal value. The thermometer to measure this limiting temperature is the neutron excess of the residues.Comment: 8 pages, 6 figures, corrected some misprints in the abstract, to be published in "Yadernaya Fizika" as a proceeding of the "VII International School Seminar on Heavy-Ion Phyics", Dubna (Russia), May 27 - June 1, 200

Superradiant atomic recoil lasing with orbital-angular-momentum light

We analyze the collective light scattering by cold atoms in free space of a pump-laser beam possessing orbital angular momentum. We derive a set of coupled multiparticle equations for the atomic motion in which the vacuum-mode field is adiabatically eliminated. The resulting equations describe collective recoil as due to either transfer of linear momentum or orbital angular momentum. For a transverse annular atomic distribution the initial equilibrium with uniform atomic phases and no scattered field is unstable. The atoms are set in rotation and bunched in phase at different harmonics depending on the pump azimuthal index Formula Presented and on the ring radius

Classical and quantum chaos in a circular billiard with a straight cut

We study classical and quantum dynamics of a particle in a circular billiard with a straight cut. This system can be integrable, nonintegrable with soft chaos, or nonintegrable with hard chaos, as we vary the size of the cut. We use a quantum web to show differences in the quantum manifestations of classical chaos for these three different regimes.Comment: LaTeX2e, 8 pages including 3 Postscript figures and 4 GIF figures, submitted to Phys. Rev.