Valve, normally closed, titanium Pyronetics model 1426

Performance tests of the explosive actuated, normally closed titanium valve 1426, are outlined. The valves are used to control hydrazine flow in a monopropellant thruster. Data cover pressure tests, internal and external leakage tests, flow control tests, and actuator tests. No failures were noted in any of the tests

Commercially-and-socially-oriented postal services

The main goal of this paper is show how postal communication service, which has been strengthened with the technology development in the last century, is nowadays commercially-and-socially-oriented very important for human life. Furthermore, I will prove how postal service becomes overwhelming for some not communicated, far and isolated geographic areas in developing countries, to get in touch with people and businesses from around the world. Over one hundred of Postal Operators were interviewed in Peru between 2004 and 2006, around 25% of total, which said that distance and security are not longer considered as a challenge for postal services thanks to new Information and Communication Technologies (ICT) and Internet; which in turn has facilitated (i) social communication, (ii) financial services, (iii) e-commerce and (iv) international business, bolstered by postal services. This last issue can be proved with high correlation statistics between the international postal (and courier) shipments and the exportation of non traditional goods, as well as importation of goods in Peru; moreover, some international remittances from around the world are making through the postal transferences. Consequently, Peruvian authorities, especially from the Ministry of Transport and Communications, must consider the importance of postal and/or courier services in the elaboration of public policies to pursuit the socioeconomic development.Postal services; financial postal; international business; communication; e-commerce;

On the CkC^k-embedding of Lorentzian manifolds in Ricci-flat spaces

In this paper we investigate the problem of non-analytic embeddings of Lorentzian manifolds in Ricci-flat semi-Riemannian spaces. In order to do this, we first review some relevant results in the area, and then motivate both the mathematical and physical interest in this problem. We show that any $n$-dimensional compact Lorentzian manifold $(M^{n},g)$, with $g$ in the Sobolev space $H_{s+3}$, $s>\frac{n}{2}$, admits an isometric embedding in an $(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold. The sharpest result available for this type of embeddings, in the general setting, comes as a corollary of Greene's remarkable embedding theorems [R. Greene, Mem. Am. Math. Soc. 97, 1 (1970)], which guarantee the embedding of a compact $n$-dimensional semi-Riemannian manifold into an $n(n+5)$-dimensional semi-Euclidean space, thereby guaranteeing the embedding into a Ricci-flat space with the same dimension. The theorem presented here improves this corollary in $n^{2}+3n-2$ codimensions by replacing the Riemann-flat condition with the Ricci-flat one from the beginning. Finally, we will present a corollary of this theorem, which shows that a compact strip in an $n$-dimensional globally hyperbolic space-time can be embedded in a $(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold