NASA metric system study

Statistical analysis of metric and English unit usage and trends in technical documents generated by NASA Center

Efficiency in Quantum Key Distribution Protocols with Entangled Gaussian States

Quantum key distribution (QKD) refers to specific quantum strategies which permit the secure distribution of a secret key between two parties that wish to communicate secretly. Quantum cryptography has proven unconditionally secure in ideal scenarios and has been successfully implemented using quantum states with finite (discrete) as well as infinite (continuous) degrees of freedom. Here, we analyze the efficiency of QKD protocols that use as a resource entangled gaussian states and gaussian operations only. In this framework, it has already been shown that QKD is possible (M. Navascu\'es et al. Phys. Rev. Lett. 94, 010502 (2005)) but the issue of its efficiency has not been considered. We propose a figure of merit (the efficiency $E$) to quantify the number of classical correlated bits that can be used to distill a key from a sample of $N$ entangled states. We relate the efficiency of the protocol to the entanglement and purity of the states shared between the parties.Comment: 13 pages, 2 figures, OSID style, published versio

Do retailers benefit from the long tail phenomenon?

The Internet and related technologies have vastly expanded the variety of products that can be profitably promoted and sold by online retailers. As a result, while in most offline markets, a few best selling products (blockbusters) generate the bulk of demand, online demand for blockbusters is often accompanied by sales for a huge number of less-selling products (niches). In response to emerging long-tailed sales distribution patterns, Anderson (2004, 2006) coined the phrase Long Tail to describe the phenomenon that niche products can gain a significant share in total sales. Most important from a retailers' perspective is whether additionally offered niche products mainly substitute former existing ones or if consumers expand their demand. While the latter can generate additional profit, substitution is only beneficial if substitutes have higher margins than products that were purchased before. By using a unique data set of a monopolistic video-on-demand operator in Germany that covers all individual sales since its launch from December 2004 until August 2007, we disentangle demand for additional offered films into substitution and additional consumption. Our results reveal that demand of additionally offered films is driven by on average 86.10% additional consumption and only 13.90% substitution, suggesting huge profit potential for retailers by increasing their assortments. © 2010 IADIS

Quantum State Transfer in Spin-1 Chains

We study the transfer of quantum information through a Heisenberg spin-1 chain prepared in its ground state. We measure the efficiency of such a quantum channel {\em via} the fidelity of retrieving an arbitrarily prepared state and {\em via} the transfer of quantum entanglement. The Heisenberg spin-1 chain has a very rich quantum phase diagram. We show that the phase boundaries are reflected in sharp variations of the transfer efficiency. In the vicinity of the border between the dimer and the ferromagnetic phase (in the conjectured spin-nematic region), we find strong indications for a qualitative change of the excitation spectrum. Moreover, we identify two regions of the phase diagram which give rise to particularly high transfer efficiency; the channel might be non-classical even for chains of arbitrary length, in contrast to spin-1/2 chains.Comment: 4 pages, 4 figures, published versio

HPC for improved efficiency on standard machine tools by using new fluid-driven spindles

Part of: Seliger, Günther (Ed.): Innovative solutions : proceedings / 11th Global Conference on Sustainable Manufacturing, Berlin, Germany, 23rd - 25th September, 2013. - Berlin: Universitätsverlag der TU Berlin, 2013. - ISBN 978-3-7983-2609-5 (online). - http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-40276. - pp. 241-246.The use of fluid-driven spindles is well known for machining various components, but not in real metal cutting. Machining of larger precision components as prototypes, tools and dies requires the use of relatively large machine tools and high-performance spindles. Usually these are mechanical spindles with relatively high power, displaying a rather low maximum speed of approximately 15,000 rpm. However, in semi-finishing and finishing with HPC conditions and in micro machining, the required rotation speeds are higher and the required power is lower. This paper presents sustainability and efficiency using fluid-driven spindles for HPC on standard machine tools with small tool diameters and rotation speeds of up to 90,000 rpm using air and 30,000 rpm using the coolant flow. The fluid-driven spindle leads to a significant widening of the application range of larger machine tools and to an improvement of productivity by higher efficiency and faster tool- and spindle change, respectively

Thin sample alloy solidification in electromagnetic driven convection

During the directional solidification of Ga-In25%wt., density variations in the liquid cause plumes of solute to be ejected from the interface through natural convection. This can lead to the formation of chimneys during solidification and ultimately freckles. The application of external magnetic fields can be used to suppress these plumes. Two magnetic systems are considered. The first is a rotating magnetic wheel, which provides conditions analogous to forced convection at the solidification interface. The forced convection causes preferential growth of secondary branches and causes the plumes to be transported downstream and back into the bulk. The second is through the application of a static magnetic field that interacts with inherent thermoelectric currents, generating a Lorentz force that drives fluid flow within the inter-dendritic region. However, in the bulk where there are no thermoelectric currents, electromagnetic damping dominates and plumes are stunted. Using a fully coupled transient numerical model each of these systems has been analysed. Comparisons to experiments are given for the cases of natural and forced convection. The experimental setup uses a Hele-Shaw cell with an electric heater and Peltier cooler, allowing for control over the thermal gradient and cooling rate

Expressão de proteína capsídica recombinante do Apple stem pitting virus e produção de antissoro policlonal.

O objetivo deste trabalho foi a expressão do gene da proteína capsidíca do ASPV em bactérias e a produção do antissoro policlonal contra a proteína expressada.Resumo

Avaliação de longo prazo do efeito de eliminação de Apple stem grooving virus por quimioterapia em macieira cv. Royal Gala.

Neste estudo, plantas da cv. Royal Gala foram submetidas a PEV (procedimento de eliminação de vírus) por quimioterapia in vitro com ribavirina por 60 dias (tratamento 0 (controle negativo), sem ribavirina; 1, 1 pg/ml; 2, 5 pg/ml; 3, 10 pg/ml de ribavirina), com 4 repetições independentes, aclimatadas e avaliadas quanto à eficácia do PEV por RT-PCR convencional, imediatamente após o tratamento (maio-julho/2010) e após mais 1 ano (julho/2011). As plantas sobreviventes dos experimentos acima, quatro anos após o tratamento inicial, foram reavaliadas quanto à presença de ASGV (Apple stem grooving virus) por RT-PCR convencional e RT-PCR em tempo real com Sybr Green l