12,617 research outputs found

    Principles of Pituitary Surgery

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    Key Points 1. Understand the principles of pituitary surgery including the key-elements of surgical planning and decision-making 2. Identify the technical nuances distinguishing the endoscopic from the microscopic transsphenoidal approach 3. Understand the strategies utilized during the nasal, sphenoidal, and sellar stages of surgery that maximize tumor resection while minimizing complications and preserving sino- nasal anatomy/functio

    Locating the minimum : Approach to equilibrium in a disordered, symmetric zero range process

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    We consider the dynamics of the disordered, one-dimensional, symmetric zero range process in which a particle from an occupied site kk hops to its nearest neighbour with a quenched rate w(k)w(k). These rates are chosen randomly from the probability distribution f(w)∼(w−c)nf(w) \sim (w-c)^{n}, where cc is the lower cutoff. For n>0n > 0, this model is known to exhibit a phase transition in the steady state from a low density phase with a finite number of particles at each site to a high density aggregate phase in which the site with the lowest hopping rate supports an infinite number of particles. In the latter case, it is interesting to ask how the system locates the site with globally minimum rate. We use an argument based on local equilibrium, supported by Monte Carlo simulations, to describe the approach to the steady state. We find that at large enough time, the mass transport in the regions with a smooth density profile is described by a diffusion equation with site-dependent rates, while the isolated points where the mass distribution is singular act as the boundaries of these regions. Our argument implies that the relaxation time scales with the system size LL as LzL^{z} with z=2+1/(n+1)z=2+1/(n+1) for n>1n > 1 and suggests a different behaviour for n<1n < 1.Comment: Revtex, 7 pages including 3 figures. Submitted to Pramana -- special issue on mesoscopic and disordered system

    A general construction of strictly Neumaier graphs and related switching

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    In this paper we propose a construction of Neumaier graphs with nexus 1, which generalises two known constructions. We then discuss small strictly Neumaier graphs obtained from the general construction and give a geometric description for some of them. Finally, we apply a variation of the Godsil-McKay switching to the general construction

    early nutritional programming and progeny performance is reproductive success already set at birth

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    Compelling evidence indicates that the environment encountered dur-ing fetal life exerts a profound influence on development, physiological function, and risk of disease in adult mammals (Barker, 2007; Langley-Evans and McMullen, 2010). Development is a plastic process, wherein a range of different phenotypes can be expressed from a given genotype. The developing conceptuses respond to conditions in the environment during sensitive periods of cellular proliferation, differentiation, and maturation, resulting in structural and functional changes in cells, tissues, and organ systems. These changes may have short- and/or long-term consequences for health and disease susceptibility. Hence, the term "programming" has been adopted to describe the process whereby a stimulus or an insult at a critical and sensitive period of fetal or perinatal life has permanent effects on the structure, physiology, and metabolism of different organs and sys-tems. Despite many studies investigating the associations between mater-nal environment during fetal development and the onset of cardiovascular disease, obesity, and diabetes in offspring as adults (McMillen and Robin-son, 2005), few studies have investigated the impact of maternal environ-ment on the reproductive potential of offspring. This paper reviews the existing literature on the effects of prenatal and perinatal nutrition on the development and function of the reproductive system in female and male domestic mammals, with particular emphasis on cattle and sheep

    Planetary radio astronomy observations from Voyager-2 near Saturn

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    Voyager-2 planetry radio astronomy measurements obtained near Saturn are discussed. They indicate that Saturnian kilometric radiation is emitted by a strong, dayside source at auroral latitudes in the northern hemisphere and by a weaker (by more than an order of magnitude) source at complementary latitudes in the southern hemisphere. These emissions are variable both due to Saturn's rotation and, on longer time scales, probably due to influences of the solar wind and the satellite Dione. The Saturn electrostatic discharge bursts first discovered by Voyager-1 and attributed to emissions from the B-ring were again observed with the same broadband spectral properties and a 10(h)11(m) + or - 5(m) episodic recurrence period but with an occurrence frequency of only of about 30 percent of that detected with Voyager-1. During the crossing of the ring plane at a distance of 2.88 R sub S, an intense noise event is interpreted to be consequence of the impact/vaporization/ionization of charged micron-size G-ring particles distributed over a total vertical thickness of about 1500 km

    Lattice Boltzmann Simulation of Non-Ideal Fluids

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    A lattice Boltzmann scheme able to model the hydrodynamics of phase separation and two-phase flow is described. Thermodynamic consistency is ensured by introducing a non-ideal pressure tensor directly into the collision operator. We also show how an external chemical potential can be used to supplement standard boundary conditions in order to investigate the effect of wetting on phase separation and fluid flow in confined geometries. The approach has the additional advantage of reducing many of the unphysical discretisation problems common to previous lattice Boltzmann methods.Comment: 11 pages, revtex, 4 Postscript figures, uuencode

    Quadriceps Tendon Repair Using Double-Row Suture Anchor Fixation

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    Quadriceps tendon ruptures compromise the knee extensor mechanism and cause an inability to ambulate and significant functional limitations. Therefore, the vast majority of quadriceps tendon ruptures are indicated for operative intervention to restore patient mobility and function. Although these injuries were traditionally repaired using a transosseous repair technique, recent literature has shown that suture anchor repair may offer biomechanical advantages. Additionally, research in other areas of orthopaedics has found that a double-row suture anchor construct can offer additional biomechanical strength to tendinous repair. This technical note describes a safe and effective quadriceps tendon repair using a double-row suture anchor construct

    Surface diffusion in mixed overlayers with superlattice ordering: Percolative transport around obstacles and along domain boundaries

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    To elucidate surface diffusion in the presence of a coadsorbate with superlattice ordering, we consider particle hopping on a square lattice with some fraction, u B , of quenched blocking sites arranged with checkerboard or c(232) ordering. Behavior for low u B corresponds to diffusion around isolated obstacles, and can be described by exact density expansions. Behavior for high u B corresponds to percolative diffusion along ~or sometimes away from! domain boundaries. The connectivity of these domain boundaries is closely related to the existence of symmetry breaking @i.e., long-range c(232) order# in the distribution of blocking sites. In some cases, symmetry breaking induces critical behavior for diffusive transport which is fundamentally different from that for the conventional ‘‘ant in the labyrinth’’ problem. Our results apply to recently developed models for CO oxidation, where CO~ads! diffuses rapidly through coadsorbed relatively immobile c(2 32)-O~ads!. The characterization of CO diffusion in these systems is key to describing spatial pattern formation
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