X-ray generation in inverse capillary discharges forpumping

An inexpensive, tunable, filamentary X-ray generator, based on the bremsstrahlung of a pulsed, high-power-density electron beam cruising along a dielectric fiber is presented. At small scale, it encodes some of the features of an X-ray machine for triggering the energy stored in the long-lived ¹⁷⁸Hf^m2 nuclear isomer, in particular an optimum coupling to the active medium This revised version was published online in August 2006 with corrections to the Cover Date.     

Finite filtrations of modules and shellable multicomplexes

We introduce pretty clean modules, extending the notion of clean modules by Dress, and show that pretty clean modules are sequentially Cohen–Macaulay. We also extend a theorem of Dress on shellable simplicial complexes to multicomplexes.     

Integrable structure of the field theory of open superstrings

We find asymptotic expansions in the “string mass” μ for μ-deformed Γ-functions and Neumann coefficients characterizing the three-string vertex in the light-cone gauge of the field theory of open superstrings on a maximally supersymmetric pp-wave background. Dedicated to the 80th birthday of Academician Anatolii Alekseevich Logunov __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 149, No. 3, pp. 381–385, December, 2006.     

Thermal properties of quantum electrodynamics in 2 + 1 dimensions and confinement

Conclusions Thus, we have shown that in QED₃ systematic allowance for screening makes it possible to eliminate infrared divergences and in this respect advance further than in QCD₄, in which the question of the mechanism of their elimination remains open. The comparative simplicity of the model also makes it possible to study systematically the more important question of the general structure of the series of skeleton perturbation theory and the excitation spectrum. We are currently working on this question.All-Union Scientific-Research Center for the Study of Surface and Vacuum Properties. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 69, No. 1, pp. 25–39, October, 1986.     

Sodium‐Naphthalenide‐Driven Synthesis of Base‐Metal Nanoparticles and Follow‐up Reactions

Mo⁰, W⁰, Fe⁰, Ru⁰, Re⁰, and Zn⁰ nanoparticles—essentially base metals—are prepared as a general strategy by a sodium naphthalenide ([NaNaph])‐driven reduction of simple metal chlorides in ethers (1,2‐dimethoxyethane (DME), tetrahydrofuran (THF)). All the nanoparticles have diameters ≤10 nm, and they can be obtained either as powder samples or long‐term stable suspensions. Direct follow‐up reactions (e.g., Mo⁰+S₈, FeCl₃+AsCl₃, ReCl₅+MoCl₅), moreover, allow the preparation of MoS₂, FeAs₂, or Re₄Mo nanoparticles of similar size as the pristine metals (≤10 nm).     

Gravitational Field Equations on Fefferman Space–Times

The total space \({\mathfrak M} \approx {\mathbb H}_1 \times S^1\) of the canonical circle bundle over the 3-dimensional Heisenberg group \({\mathbb H}_1\) is a space–time with the Lorentzian metric \(F_{\theta _0}\) (Fefferman’s metric) associated to the canonical Tanaka–Webster flat contact form \(\theta _0\) on \({\mathbb H}_1\). The matter and energy content of \(\mathfrak M\) is described by the energy-momentum tensor \({T}_{\mu \nu }\) (the trace-less Ricci tensor of \(F_{\theta _0}\)) as an effect of the non flat nature of Feferman’s metric \(F_{\theta _0}\). We study the gravitational field equations \(R_{\mu \nu } - (1/2) \, R \, g_{\mu \nu } = {T}_{\mu \nu }\) on \({\mathfrak M}\). We consider the first order perturbation \(g = F_{\theta _0} + \epsilon \, h\), \(\epsilon<< 1\), and linearize the field equations about \(F_{\theta _0}\). We determine a Lorentzian metric g on \({\mathfrak M}\) which solves the linearized field equations corresponding to a diagonal perturbation h.     

Recovery of Immersions from Their Metric Tensors and Nonlinear Korn Inequalities: A Brief Survey

The authors discuss the existence and uniqueness up to isometries of Enof immersions φ : Ω  R~n→ E~n with prescribed metric tensor field(g ij) : Ω→ S~n, and discuss the continuity of the mapping(gij) →φ defined in this fashion with respect to various topologies. In particular, the case where the function spaces have little regularity is considered. How, in some cases, the continuity of the mapping(gij) →φ can be obtained by means of nonlinear Korn inequalities is shown.     

Deteriorated Geometrical Stiffness for Higher Order Finite Elements with Application to Panel Flutter

Higher order elements were first design for linear problems where, in certain situations, they present advantages over the lower order elements. A method to efficiently extend their use to geometrical nonlinear problems as panel flutter and postbuckling behavior is presented. The chaotic and limit-cycle oscillations of an isotropic plate are obtained based on direct integration of the discretized equation of motion. The plate is modeled using the von Karman theory and the geometrical nonlinearities are separated in a nonlinear term of the first kind which manifests especially in the prebuckling and buckling regimes, and a nonlinear term of the second kind which is responsible for the postbuckling behavior. A fifth order, fully compatible element has been used to model thin plates while the inplane loads where introduced through a membrane element. The aerodynamics was modeled using the first order 'piston theory. The method introduces the concept of a deteriorated form of the second geometric matrix which is equivalent to neglecting higher order terms in the strain energy of the plate. This allows for a drastic reduction in the computational effort with no observable loss of accuracy. Well established results in the literature are used to validate the method.