Search results for "SCAD"

Many Body Modes of Excitation in Heavy Ion Collisions

1989

The one step excitation of two particle holes in heavy ion collisions is shown to be an important channel in the reaction. Pion production has to compete against this new channel, not present in the NN free reaction, and is reduced sensibly. The effective NN cross section is increased leading to a more effective stopping of the nucleons.

A spin rotator for producing a longitudinally polarized electron beam with MAMI

1993

Abstract The design and performance characteristics of a full 4 π-space spin rotator for 100 keV electrons are described. The spin rotator was developed as part of the acceleration scheme for polarized electrons in the MAINZ race track microtron cascade MAMI [1]. It allows to orientate the polarization vector in any direction before injection. Thus it is possible to optimize the longitudinal polarization component, required for experiments with polarized high energy electrons, at target position. With this scheme various experimental halls can be supplied with longitudinally polarized electrons in the full energy range of MAMI between 180 and 855 MeV.

Positron-Electron Angular Correlations in Heavy Ion Collisions

1987

Recent measurements of positrons in coincidence with electrons emitted in U+Th collisions near the Coulomb barrier show sharp line structures in the sum and difference energy spectra of the two leptons (ref. 1). A possible method to clarify the origin of these lines is to study the angular correlation of the leptons. In this short contribution we want to report on a positron-electron coincidence test measurement performed with the TORI spectrometer. This apparatus offers the possibility to measure positrons in coincidence with electrons emitted into the same and opposite hemisphere as well.

Soil animals and ecosystem processes: How much does nutrient cycling explain?

2008

Summary Trophic-dynamic hypotheses have been extensively tested by manipulating the presence of soil animals in experimental laboratory microcosms. Soil animals typically have pronounced effects on microbial populations, nutrient cycling and plant growth. However, because often only the total effect has been reported, the relative importance of feeding interactions versus non-trophic effects remains obscure. Using simple calculations based on mass conservation I argue that the observed faunal effect on microbes and system functioning is often larger than can be explained by trophic dynamics and nutrient cycling. Non-trophic effects may help to explain why microcosm experiments have failed t…

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

2015

A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.

Role of the gem-Difluoro Moiety in the Tandem Ring-Closing Metathesis−Olefin Isomerization:  Regioselective Preparation of Unsaturated Lactams

2006

Careful selection of the metathesis catalyst, solvent, and reaction conditions allows for the efficient and regioselective synthesis of isomeric fluorinated and nonfluorinated lactam derivatives II and III from precursor amides I through a ring-closing metathesis (RCM) reaction or a tandem RCM-isomerization protocol, respectively. The presence of the gem-difluoro moiety in the starting materials exerts a pivotal effect by directing the isomerization step, making the overall tandem transformation a regioselective process. The scope, limitations, and synthetic usefulness of this protocol are also discussed.

Adaptive P-splines via L1-type penalty in generalized additive models

2022

Inclusive semileptonic branching ratios of b hadrons produced in Z decays

2001

A measurement of the inclusive semileptonic branching ratios of b hadrons produced in Z decay is presented, using four million hadronic events collected by the ALEPH detector from 1991 to 1995. Electrons and muons are selected opposite to b-tagged hemispheres. Two different methods are explored to distinguish the contributions from direct $\bl$ and cascade $\bcl$ decays to the total lepton yield. One is based on the lepton transverse momentum spectrum, the other makes use of the correlation between the charge of the lepton and charge estimators built from tracks in the opposite hemisphere of the event. The latter method reduces the dependence on the modelling of semileptonic b decays. The r…

Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in root s=7 TeV proton-proton collis…

2011

Results are presented of a search for supersymmetric particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e or mu) of opposite charge in sqrt{s}=7 TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corres…

BVS: A Lightweight Forward and Backward Secure Scheme for PMU Communications in Smart Grid

2011

In smart grid, phaser measurement units (PMUs) can upload readings to utility centers via supervisory control and data acquisition (SCADA) or energy management system (EMS) to enable intelligent controlling and scheduling. It is critical to maintain the secrecy of readings so as to protect customers' privacy, together with integrity and source authentication for the reliability and stability of power scheduling. In particular, appealing security scheme needs to perform well in PMUs that usually have computational resource constraints, thus designed security protocols have to remain lightweight in terms of computation and storage. In this paper, we propose a family of schemes to solve this p…