1,922 research outputs found
Author response: India and China in Africa: a comparative perspective of the oil industry by Raj Verma
No full textEarlier this month Ian Taylor reviewed India and China in Africa, a new book about Asian engagement in the West African oil industry. Here, the book’s author Raj Verma responds to Taylor’s comments, outlining the rationale and evidence for the framework used in the study. India and China in Africa: A comparative perspective of the oil industry. Raj Verma. London: Routledge. 2017
Management of Feeding Problems in Infants with Cleft Palate and Review on Pierre-Robin Syndrome
No full textPierre Robin syndrome is a congenital disorder with triad of features micrognathia, glossoptosis which result in airway obstruction and feeding difficulties and cleft palate. Cleft palate is the most common congenital anomalies of craniofacial region seen in Pierre-Robin syndrome. Infants with cleft palate have to face various problems. Difficulty in feeding is the most common problem faced by cleft palate neonates that made them difficult to maintain adequate nutrition, result in failure to thrive. There are many methods given in literature to overcome this problem including special type of nursing bottles. In this case report, fabrication of feeding plate to obturate the defect in palate and its use in managing feeding problem is described. Keywords: Cleft palate, Feeding plate, PierreRobin Syndrom
Sparse nested Markov models with log-linear parameters
No full textHidden variables are ubiquitous in practical data analysis, and therefore modeling marginal densities and doing inference with the resulting models is an important problem in statistics, machine learning, and causal inference. Recently, a new type of graphical model, called the nested Markov model, was developed which captures equality constraints found in marginals of directed acyclic graph (DAG) models. Some of these constraints, such as the so called `Verma constraint', strictly generalize conditional independence. To make modeling and inference with nested Markov models practical, it is necessary to limit the number of parameters in the model, while still correctly capturing the constraints in the marginal of a DAG model. Placing such limits is similar in spirit to sparsity methods for undirected graphical models, and regression models. In this paper, we give a log-linear parameterization which allows sparse modeling with nested Markov models. We illustrate the advantages of this parameterization with a simulation study
A Study Of The Metric Induced By The Robin Function
No full textLet D be a smoothly bounded domain in Cn , n> 1. For each point p _ D, we have the Green function G(z, p) associated to the standard sum-of-squares Laplacian Δ with pole at p and the Robin constant __
Λ(p) = lim G(z, p) −|z − p−2n+2
z→p |
at p. The function p _→ Λ(p) is called the Robin function for D.
Levenberg and Yamaguchi had proved that if D is a C∞-smoothly bounded pseudoconvex domain, then the function log(−Λ) is a real analytic, strictly plurisubharmonic exhaustion function for D and thus induces a metric
ds2 = n∂2 log(−Λ)(z) dzα ⊗ dzβ
z
∂zα∂zβ
α,β=1
on D, called the Λ-metric. For an arbitrary C∞-smoothly bounded domain, they computed the boundary asymptotics of Λ and its derivatives up to order 3, in terms of a defining function for the domain. As a consequence it was shown that the Λ-metric is complete on a C∞-smoothly bounded strongly pseudoconvex domain or a C∞-smoothly bounded convex domain.
In this thesis, we study the boundary behaviour of the function Λ and its derivatives of all orders near a C2-smooth boundary point of an arbitrary domain. We compute the boundary asymptotics of the Λ-metric on a C∞-smoothly bounded pseudoconvex domain and as a consequence obtain that on a C∞-smoothly bounded strongly pseudoconvex domain, the Λ-metric is comparable to the Kobayashi metric (and hence to the Carath´eodory and the Bergman metrics). Using the boundary asymptotics of Λ and its derivatives, we calculate the holomorphic sectional curvature of the Λ-metric on a C∞-smoothly bounded strongly pseudoconvex domain at points on the inner normals and along the normal directions. The unit ball in Cn is also characterised among all C∞-smoothly bounded strongly convex domains on which the Λ-metric has constant negative holomorphic sectional curvature. Finally we study the stability of the Λ-metric under a C2 perturbation of a C∞-smoothly bounded pseudoconvex domain.
(For equation pl refer the abstract pdf file
Sweeping has no effect on renormalized turbulent viscosity
No full textWe perform renormalization group analysis (RG) of the Navier-Stokes equation in the presence of constant mean velocity field , and show that the renormalized viscosity is unaffected by , thus negating the ``sweeping effect", proposed by Kraichnan [Phys. Fluids {\bf 7}, 1723 (1964)] using random Galilean invariance. Using direct numerical simulation, we show that the correlation functions for and differ from each other, but the renormalized viscosity for the two cases are the same. Our numerical results are consistent with the RG calculations
A Unified Shell model for Buoyancy-Driven Turbulence
No full textWe construct a unified shell model for stably stratified and convective turbulence. Shell model simulation of stably stratified flow in turbulent regime exhibit Bolgiano-Obukhbov (BO) scaling in which the kinetic energy spectrum varies as . However, simulation of convective turbulence shows Kolmogorov's spectrum. These results are consistent with the direct numerical simulations of Kumar {\em et al.} [Phys. Rev. E {\bf 90}, 023016 (2014)]. We also observe a dual scaling ( and ) for a limited range of parameters in stably stratified flow
Energy transfers in small-scale and large-scale dynamos
No full textWe study energy transfers during magnetic energy growth in small-scale and large-scale dynamos. We perform direct numerical simulations for magnetic Prandtl number Pm =20 and 0.2 in a periodic box on 1024^3 grid. Energy fluxes and shell-to-shell energy transfers indicate that in small-scale dynamo for Pm =20, the magnetic energy growth takes place due to a non-local energy transfer from large-scale velocity field to small-scale magnetic field. On the other hand, in large-scale dynamo for Pm =0.2, local energy transfers from large-scale velocity field to large-scale magnetic field takes place
Role of the strain-rate tensor in turbulent scalar-transport modeling
No full textWe examine the geometric orientation of the subfilter-scale scalar-flux vector in homogeneous isotropic turbulence. Vector orientation is determined using the eigenframe of the resolved strain-rate tensor. The Schmidt number is kept sufficiently large so as to leave the velocity field, and hence, the strain-rate tensor, unaltered by filtering in the viscous-convective subrange. Strong preferential alignment is observed for the case of Gaussian and box filters, whereas the sharp-spectral filter leads to close to a random orientation. The orientation angle obtained with the Gaussian and box filters is largely independent of the filter-width and the Schmidt number. It is shown that the alignment direction observed numerically using these two filters is predicted very well by the tensor-diffusivity model. Further a-priori tests indicate poor alignment of the Smagorinsky and stretched vortex model predictions with the exact subfilter flux
Systems of Differential Operators and Generalized Verma Modules
No full textIn this paper we close the cases that were left open in our earlier works on the study of conformally invariant systems of second-order differential operators for degenerate principal series. More precisely, for these cases, we find the special values of the systems of differential operators, and determine the standardness of the homomorphisms between the generalized Verma modules, that come from the conformally invariant systems.The author was supported by the Global COE program at the Graduate School of Mathematical
Sciences, the University of Tokyo, Japan. He would like to be thankful for the referees for their
careful reading and invaluable comments
Twisted de Rham Complex on Line and Singular Vectors in sl₂ˆ Verma Modules
No full textWe consider two complexes. The first complex is the twisted de Rham complex of scalar meromorphic differential forms on the projective line, holomorphic on the complement to a finite set of points. The second complex is the chain complex of the Lie algebra of sl₂-valued algebraic functions on the same complement, with coefficients in a tensor product of contragradient Verma modules over the affine Lie algebra sl₂ˆ. In [Schechtman V., Varchenko A., Mosc. Math. J. 17 (2017), 787-802] a construction of a monomorphism of the first complex to the second was suggested, and it was indicated that under this monomorphism, the existence of singular vectors in the Verma modules (the Malikov-Feigin-Fuchs singular vectors) is reflected in the relations between the cohomology classes of the de Rham complex. In this paper, we prove these results.The authors thank V. Schechtman for useful discussions. The second author was supported in part by NSF grant DMS-1665239
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