579 research outputs found
Observation of shot-noise-induced asymmetry in the Coulomb blockaded Josephson junction
We have investigated the influence of shot noise on the IV-curves of a single
mesoscopic Josephson junction. We observe a linear enhancement of zero-bias
conductance of the Josephson junction with increasing shot noise power.
Moreover, the IV-curves become increasingly asymmetric. Our analysis on the
asymmetry shows that the Coulomb blockade of Cooper pairs is strongly
influenced by the non-Gaussian character of the shot noise.Comment: 4 pages, 5 figures, RevTE
Reachability in Parametric Interval Markov Chains using Constraints
Parametric Interval Markov Chains (pIMCs) are a specification formalism that
extend Markov Chains (MCs) and Interval Markov Chains (IMCs) by taking into
account imprecision in the transition probability values: transitions in pIMCs
are labeled with parametric intervals of probabilities. In this work, we study
the difference between pIMCs and other Markov Chain abstractions models and
investigate the two usual semantics for IMCs: once-and-for-all and
at-every-step. In particular, we prove that both semantics agree on the
maximal/minimal reachability probabilities of a given IMC. We then investigate
solutions to several parameter synthesis problems in the context of pIMCs --
consistency, qualitative reachability and quantitative reachability -- that
rely on constraint encodings. Finally, we propose a prototype implementation of
our constraint encodings with promising results
Characterization of BIS20x3, a bi-specific antibody activating and retargeting T-cells to CD20-positive B-cells
This paper describes a bi-specific antibody, which was called BIS20x3. It retargets CD3É-positive cells (T-cells) to CD20-positive cells and was obtained by hybridâhybridoma fusion. BIS20x3 could be isolated readily from quadroma culture supernatant and retained all the signalling characteristics associated with both of its chains. Cross-linking of BIS20x3 on Ramos cells leads to DNA fragmentation percentages similar to those obtained after Rituximab-cross-linking. Cross-linking of BIS20x3 on T-cells using cross-linking F(abâČ)2-fragments induced T-cell activation. Indirect cross-linking of T-cell-bound BIS20x3 via Ramos cells hyper-activated the T-cells. Furthermore, it was demonstrated that BIS20x3 effectively re-targets T-cells to B-cells, leading to high B-cell cytotoxicity. The results presented in this paper show that BIS20x3 is fully functional in retargeting T-cells to B-cells and suggest that B-cell lymphomas may represent ideal targets for T-cell retargeting bi-specific antibodies, because the retargeted T-cell is maximally stimulated in the presence of B-cells. Additionally, since B-cells may up-regulate CD95/ Fas expression upon binding of CD20-directed antibodies, B-cells will become even more sensitive for T-cell mediated killing via CD95L/ Fas L, and therefore supports the intention to use T-cell retargeting bi-specific antibodies recognizing CD20 on B-cell malignancies as a treatment modality for these diseases. © 2001 Cancer Research Campaign http://www.bjcancer.co
Absolute electron and positron fluxes from PAMELA/Fermi and Dark Matter
We extract the positron and electron fluxes in the energy range 10 - 100 GeV
by combining the recent data from PAMELA and Fermi LAT. The {\it absolute
positron and electron} fluxes thus obtained are found to obey the power laws:
and respectively, which can be confirmed by the
upcoming data from PAMELA. The positron flux appears to indicate an excess at
energies E\gsim 50 GeV even if the uncertainty in the secondary positron flux
is added to the Galactic positron background. This leaves enough motivation for
considering new physics, such as annihilation or decay of dark matter, as the
origin of positron excess in the cosmic rays.Comment: Accepted by JCA
Cosmic Ray Anomalies from the MSSM?
The recent positron excess in cosmic rays (CR) observed by the PAMELA
satellite may be a signal for dark matter (DM) annihilation. When these
measurements are combined with those from FERMI on the total () flux
and from PAMELA itself on the ratio, these and other results are
difficult to reconcile with traditional models of DM, including the
conventional mSUGRA version of Supersymmetry even if boosts as large as
are allowed. In this paper, we combine the results of a previously
obtained scan over a more general 19-parameter subspace of the MSSM with a
corresponding scan over astrophysical parameters that describe the propagation
of CR. We then ascertain whether or not a good fit to this CR data can be
obtained with relatively small boost factors while simultaneously satisfying
the additional constraints arising from gamma ray data. We find that a specific
subclass of MSSM models where the LSP is mostly pure bino and annihilates
almost exclusively into pairs comes very close to satisfying these
requirements. The lightest in this set of models is found to be
relatively close in mass to the LSP and is in some cases the nLSP. These models
lead to a significant improvement in the overall fit to the data by an amount
dof in comparison to the best fit without Supersymmetry
while employing boosts . The implications of these models for future
experiments are discussed.Comment: 57 pages, 31 figures, references adde
A Proof System for Compositional Verification of Probabilistic Concurrent Processes
Abstract. We present a formal proof system for compositional verification of probabilistic concurrent processes. Processes are specified using an SOS-style process algebra with probabilistic operators. Properties are expressed using a probabilistic modal ”-calculus. And the proof system is formulated as a sequent calculus in which sequents are given a quantitative interpretation. A key feature is that the probabilistic scenario is handled by introducing the notion of Markov proof, according to which proof trees contain probabilistic branches and are required to satisfy a condition formulated byinterpretingthemas Markov Decision Processes. We present simple but illustrative examples demonstrating the applicability of the approach to the compositional verification of infinite state processes. Our main result is the soundness of the proof system, which is proved by applying the coupling method from probability theory to the game semantics of the probabilistic modal ”-calculus.
The HERMIT in the machine: a plugin for the interactive transformation of GHC core language programs
The importance of reasoning about and refactoring programs is a central tenet of functional programming. Yet our compilers and development toolchains only provide rudimentary support for these tasks. This paper introduces a programmatic and compiler-centric interface that facilitates refactoring and equational reasoning. To develop our ideas, we have implemented HERMIT, a toolkit enabling informal but systematic transformation of Haskell programs from inside the Glasgow Haskell Compilerâs optimization pipeline. With HERMIT, users can experiment with optimizations and equational reasoning, while the tedious heavy lifting of performing the actual transformations is done for them. HERMIT provides a transformation API that can be used to build higher-level rewrite tools. One use-case is prototyping new optimizations as clients of this API before being committed to the GHC toolchain. We describe a HERMIT application - a read-eval-print shell for performing transformations using HERMIT. We also demonstrate using this shell to prototype an optimization on a specific example, and report our initial experiences and remaining challenges
Coulomb excitation of Ni at safe energies
The value in Ni has been measured using Coulomb
excitation at safe energies. The Ni radioactive beam was
post-accelerated at the ISOLDE facility (CERN) to 2.9 MeV/u. The emitted
rays were detected by the MINIBALL detector array. A kinematic
particle reconstruction was performed in order to increase the measured c.m.
angular range of the excitation cross section. The obtained value of
2.8 10 efm is in good agreement with the value
measured at intermediate energy Coulomb excitation, confirming the low
transition probability.Comment: 4 pages, 5 figure
Scalar Bilepton Dark Matter
In this work we show that 3-3-1 model with right-handed neutrinos has a
natural weakly interacting massive particle (WIMP) dark mater candidate. It is
a complex scalar with mass of order of some hundreds of GeV which carries two
units of lepton number, a scalar bilepton. This makes it a very peculiar WIMP,
very distinct from Supersymmetric or Extra-dimension candidates. Besides,
although we have to make some reasonable assumptions concerning the several
parameters in the model, no fine tunning is required in order to get the
correct dark matter abundance. We also analyze the prospects for WIMP direct
detection by considering recent and projected sensitivities for WIMP-nucleon
elastic cross section from CDMS and XENON Collaborations.Comment: 21 pages, 8 figures, uses iopart.cls, same text as published version
with a small different arrangement of figure
Results from the CLIC Test Facility
In order to study the principle of the Compact Linear Collider (CLIC) based on the Two Beam Acceleration (TBA) scheme at high frequency, a CLIC Test Facility (CTF) has been set-up at CERN. After four years of successful running, the experimental programme is now fully completed and all its objectives reached, particularly the generation of a high intensity drive beam with short bunches by a photo-injector, the production of 30 GHz RF power and the acceleration of a probe beam by 30 GHz structures. A summary of the CTF results and their impact on linear collider design is given. This covers 30 GHz high power testing, study of intense, short single bunches; as well as RF-Gun, photocathode and beam diagnostic developments. A second phase of the test facility (CTF2) is presently being installed to demonstrate the feasibility of the TBA scheme by constructing a fully engineered, 10 m long, test section very similar to the CLIC drive and main linacs, producing up to 480 MW of peak RF power at 30 GHz and accelerating the beam up to 320 MeV. The present status of CTF2 is reported
- âŠ