4,749 research outputs found

    Twist-2 Generalized TMDs and the Spin/Orbital Structure of the Nucleon

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    Generalized transverse-momentum dependent parton distributions (GTMDs) encode the most general parton structure of hadrons. Here we focus on two twist-2 GTMDs which are denoted by F1,4F_{1,4} and G1,1G_{1,1} in parts of the literature. As already shown previously, both GTMDs have a close relation to orbital angular momentum of partons inside a hadron. However, recently even the mere existence of F1,4F_{1,4} and G1,1G_{1,1} has been doubted. We explain why this claim does not hold. We support our model-independent considerations by calculating the two GTMDs in the scalar diquark model and in the quark-target model, where we also explicitly check the relation to orbital angular momentum. In addition, we compute F1,4F_{1,4} and G1,1G_{1,1} at large transverse momentum in perturbative Quantum Chromodynamics and show that they are nonzero.Comment: 29 pages, 6 figures; two clarifications and a reference added; version to appear in Phys. Rev.

    Determination of the lowest energy structure of Ag8_8 from first-principles calculations

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    The ground-state electronic and structural properties, and the electronic excitations of the lowest energy isomers of the Ag8_8 cluster are calculated using density functional theory (DFT) and time-dependent DFT (TDDFT) in real time and real space scheme, respectively. The optical spectra provided by TDDFT predict that the D2d_{2d} dodecahedron isomer is the structural minimum of Ag8_8 cluster. Indeed, it is borne out by the experimental findings.Comment: 4 pages, 2 figures. Accepted in Physical Review A as a brief repor

    A simple method for isolation of PCR fragments from silver-stained polyacrylamide gels by scratching with a fine needle

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    This project investigated how NoSQL databases can be used together with a logical layer, instead of a relational database with separated backend logic, to search for products with customer specific constraints in an e-commerce scenario. The motivation behind moving from a relational database was the scalability issues and increased read latencies experienced as the data increased. The work resulted in a framework called Cauldron that uses pipelines a sequence of execution steps to expose its data stored in an in-memory key-value store and a document database. Cauldron uses write replication between distributed instances to increase read throughput at the cost of write latency. A product database with customer specific constraints was implemented using Cauldron to compare it against an existing solution based on a relational database. The new product database can serve search queries 10 times faster in the general case and up to 25 times faster in extreme cases compared to the existing solution.Projektet undersökte hur NoSQL databaser tillsammans med ett logiskt lager, istället för en relationsdatabas med separat backend logik, kan användas för att söka på produkter med kundunika restriktioner. Motivationen till att byta ut relationsdatabasen berodde på skalbarhetsproblem och långsammare svarstider när datamängden ökade. Arbetet resulterade i ett ramverk vid namn Cauldron som använder pipelines sammankopplade logiska steg för att exponera sin data från en minnesbunden nyckel-värde-databas och en dokumentdatabas. Cauldron använder replikering mellan distribuerade instanser för att öka läsgenomstömmningen på bekostnad av högre skrivlatenser. En produktdatabas med kundunika restriktioner implementerades med hjälp av Cauldron för att jämföra den mot en befintlig lösning baserad på en relationsdatabas. Den nya databasen kan besvara sökförfrågningar 10 gånger snabbare i normalfallen och upp till 25 gånger snabbare i extremfallen jämfört med den befintliga lösningen

    The Ultimate Light Curve of SN 1998bw/GRB 980425

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    We present multicolor light curves of SN 1998bw which appeared in ESO184-G82 in close temporal and spacial association with GRB 980425. They are based on observations done at Cerro Tololo Inter-American Observatory and data from the literature. The CTIO photometry reaches ~86 days after the GRB in UU and ~160 days after the GRB in BV(RI)_C. The observations in U extend by about 30 days the previously known coverage, and determine the slope of the early exponential tail. We calibrate a large set of local standards in common with those of previous studies and use them to transform published observations of the SN to our realization of the standard photometric system. We show that the photometry from different sources merges smoothly and provide a unified set of 300 observations of the SN in five bands. Using the extensive set of spectra in public domain we compute extinction and K corrections, and build quasi-bolometric unreddened rest frame light curves. We provide low degree piecewise spline fits to these light curves with daily sampling. They reach ~86 rest frame days after the GRB with U band coverage, and ~498 rest frame days after the GRB without U.Comment: 38 pages, 5 figures, 3 table

    Pfleiderer2: identification of a new globular cluster in the Galaxy

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    We provide evidence that indicate the star cluster Pfleiderer 2, which is projected in a rich field, as a newly identified Galactic globular cluster. Since it is located in a crowded field, core extraction and decontamination tools were applied to reveal the cluster sequences in B, V and I Color-Magnitude Diagrams (CMDs). The main CMD features of Pfleiderer 2 are a tilted Red Giant Branch, and a red Horizontal Branch, indicating a high metallicity around solar. The reddening is E(B-V)=1.01. The globular cluster is located at a distance from the Sun d_{\odot} = 16±\pm2 kpc. The cluster is located at 2.7 kpc above the Galactic plane and at a distance from the Galactic center of RGC_{\rm GC}=9.7 kpc, which is unusual for a metal-rich globular cluster.Comment: Accepted by The Astronomical Journa

    Device and Method for Digital-To-Analog Transformations and Reconstructions of Multi-Channel Electrocardiograms

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    The present invention includes a method and apparatus for digital to analog conversion and reconstruction of multichannel electrocardiograms. The method may include receiving digital information representative of a plurality of independent signals, producing a plurality of analog outputs from said digital information wherein a first analog output is designated as a common reference, and imposing a predetermined voltage on a second analog output with respect to said common reference, which provides for a substantial recreation of the original independent signals. The apparatus may comprise a processor operable for receiving digital information representative of independent lead signals from a first ECG machine and digital to analog circuitry for substantially reproducing the original lead signals for analysis on a second ECG machine for convenient and efficient second opinions of cardiac data
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