447 research outputs found
A low-temperature dynamic mode scanning force microscope operating in high magnetic fields
A scanning force microscope was implemented operating at temperatures below
4.2K and in magnetic fields up to 8T. Piezoelectric quartz tuning forks were
employed for non optical tip-sample distance control in the dynamic operation
mode. Fast response was achieved by using a phase-locked loop for driving the
mechanical oscillator. Possible applications of this setup for various scanning
probe techniques are discussed.Comment: 5 pages, 5 figures, submitted to "Review of Scientific Instruments
Two-Loop Corrections to Top-Antitop Production at Hadron Colliders
The status of the theoretical predictions for the top-anti top production in
hadronic collisions is shortly reviewed, paying a articular attention to the
analytic calculation of the two-loop QCD corrections to the parton-level matrix
elements.Comment: Talk presented at the 35th International Conference of High Energy
Physics - ICHEP2010, July 22-28, 2010, Paris Franc
Two-Loop QCD Corrections to the Heavy-to-Light Quark Decay
We present an analytic expression for the two-loop QCD corrections to the
decay process b -> u W^*, where b and u are a massive and massless quark,
respectively, while W^* is an off-shell charged weak boson. Since the W-boson
can subsequently decay in a lepton anti-neutrino pair, the results of this
paper are a first step towards a fully analytic computation of differential
distributions for the semileptonic decay of a b-quark. The latter partonic
process plays a crucial role in the study of inclusive semileptonic charmless
decays of B-mesons. The three independent form factors characterizing the b W u
vertex are provided in form of a Laurent series in (d-4), where d is the
space-time dimension. The coefficients in the series are expressed in terms of
Harmonic Polylogarithms of maximal weight 4, and are functions of the invariant
mass of the leptonic decay products of the W-boson.Comment: 27 pages, 3 figures, References added, version published on JHE
Flow field computations for blunt bodies in planetary environments /equilibrium/ Final report
Radiative and convective heat transfer about two blunt bodies traveling at hypersonic speeds at zero angle of attack in assumed Mars atmosphere of nitrogen and carbon dioxid
Reduze 2 - Distributed Feynman Integral Reduction
Reduze is a computer program for reducing Feynman integrals to master
integrals employing a variant of Laporta's reduction algorithm. This article
describes version 2 of the program. New features include the distributed
reduction of single topologies on multiple processor cores. The parallel
reduction of different topologies is supported via a modular, load balancing
job system. Fast graph and matroid based algorithms allow for the
identification of equivalent topologies and integrals.Comment: 16 pages, 5 figure
Quantum capacitance and density of states of graphene
We report on measurements of the quantum capacitance in graphene as a
function of charge carrier density. A resonant LC-circuit giving high
sensitivity to small capacitance changes is employed. The density of states,
which is directly proportional to the quantum capacitance, is found to be
significantly larger than zero at and around the charge neutrality point. This
finding is interpreted to be a result of potential fluctuations with amplitudes
of the order of 100 meV in good agreement with scanning single-electron
transistor measurements on bulk graphene and transport studies on nanoribbons
Bestäubungsleistung der Honigbiene (Apis mellifera) in einer Feldobstanlage
Für eine ausreichende Bestäubung von Apfelbäumen braucht es eine ausreichende Anzahl geeigneter Bestäuberorganismen an einem Standort. Vor diesem Hintergrund stellen sich mehrere Fragen:
- Verdrängen Honigbienen andere Bestäuber und verringern sie damit die Bestäubungsleistung?
- Ist der Rückgang von Bestäubern wie Wildbienen auch auf die Präsenz von Honigbienen zurückzuführen?
- Reicht für die Bestäubung von Nahrungspflanzen ein einzelner Bestäuber aus, oder kann eine Kombination von verschiedenen Bestäubern die Bestäubungsleistung und damit den Ertrag steigern
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