10,589 research outputs found
Field-Effect Transistors on Tetracene Single Crystals
We report on the fabrication and electrical characterization of field-effect
transistors at the surface of tetracene single crystals. We find that the
mobility of these transistors reaches the room-temperature value of $0.4 \
cm^2/Vs$. The non-monotonous temperature dependence of the mobility, its weak
gate voltage dependence, as well as the sharpness of the subthreshold slope
confirm the high quality of single-crystal devices. This is due to the
fabrication process that does not substantially affect the crystal quality.Comment: Accepted by Appl. Phys. Lett, tentatively scheduled for publication
in the November 24, 2003 issu
Global interlaboratory assessments of perfluoroalkyl substances under the Stockholm Convention on persistent organic pollutants
The Global Monitoring Plan (GMP) according to article 16 of the Stockholm Convention on Persistent Organic Pollutants (POPs) requires that POP laboratories must be capable – at any time – to analyse samples for POPs within a variation of ±25%. Based on this target error of 25%, a statistical model using z-scores was applied to assess the performance of analytical laboratories for POPs and a number of matrices. Since the second round of these ‘Bi-ennial Global Interlaboratory Assessment on Persistent Organic Pollutants (POPs)’, carried out in 2012/2013, perfluoroalkyl substances (PFASs) have been included into the proficiency tests. The third round was carried out in 2016/2017. The test materials included test solutions of PFASs analytical standards, the abiotic matrices sediment, air (extract) and water and the biotic matrices fish, human milk and human plasma. The number of laboratories submitting results for PFASs remained quite stable (IL2 = 27 laboratories; IL3 = 29), but there was broader geographic distribution observed in IL3: in addition to the laboratories from Asia and the Western Europe/other groups, two laboratories from Africa participated, two from Central-Eastern Europe and one from the Latin American/Caribbean region. Considering that PFASs were introduced for the first time in round 2, the results were good to reasonable compared to those of a number of other POPs included in the same study. However, it shall also be mentioned that for some matrices and PFASs, the number of laboratories submitting results was too small and the results too scattered to derive a consensus value. This was especially true for the PFOS precursor compounds and the air matrix. Also, laboratories struggle with the analysis of the branched PFOS isomers. These interlaboratory assessments on PFASs gave promising results and demonstrated the importance of proficiency tests in an international environment to generate trust in laboratory results. The need to participate regularly in such intercomparison assessments is highlighted. The results show the current level of PFAS analysis, which varies by laboratory and by matrix rather than per geographic region
Infrared Quasi Fixed Points and Mass Predictions in the MSSM II: Large tan(beta) Scenario
We consider the infrared quasi fixed point solutions of the renormalization
group equations for the Yukawa couplings and soft supersymmetry breaking
parameters in the MSSM in the \underline{large } regime. The
existence of IR quasi fixed points together with the values of gauge couplings,
third generation quarks, lepton and Z-boson masses allows one to predict masses
of the Higgs bosons and SUSY particles as functions of the only free parameter,
, or the gluino mass. The lightest Higgs boson mass for TeV is found to be GeV for and
GeV for .Comment: 15 pages, LateX file with 4 eps figures, corrected numbers, new
column in table, last versio
An Infinite-Dimensional Family of Black-Hole Microstate Geometries
We construct the first explicit, smooth, horizonless black-hole microstate
geometry whose moduli space is described by an arbitrary function of one
variable and is thus infinite-dimensional. This is achieved by constructing the
scalar Green function on a simple D6 anti-D6 background, and using this Green
function to obtain the fully back-reacted solution for a supertube with varying
charge density in this background. We show that this supertube can store
parametrically more entropy than in flat space, confirming the entropy
enhancement mechanism that was predicted using brane probes. We also show that
all the local properties of the fully back-reacted solution can, in fact, be
obtained using the DBI action of an appropriate brane probe. In particular, the
supergravity and the DBI analysis yield identical functional bubble equations
that govern the relative locations of the centers. This indicates that there is
a non-renormalization theorem that protects these functional equations as one
moves in moduli space. Our construction creates configurations that are beyond
the scope of recent arguments that appear to put strong limits on the entropy
that can be found in smooth supergravity solutions.Comment: 46 pages, 1 figure, LaTe
AdS vacua and RG flows in three dimensional gauged supergravities
We study supersymmetric vacua in N=4 and N=8, three dimensional
gauged supergravities, with scalar manifolds and , non-semisimple Chern-Simons
gaugings and ,
respectively. These are in turn equivalent to SO(4) and
Yang-Mills theories coupled to supergravity. For the N=4 case, we study
renormalization group flows between UV and IR vacua with the same
amount of supersymmetry: in one case, with (3,1) supersymmetry, we can find an
analytic solution whereas in another, with (2,0) supersymmetry, we give a
numerical solution. In both cases, the flows turn out to be v.e.v. flows, i.e.
they are driven by the expectation value of a relevant operator in the dual
. These provide examples of v.e.v. flows between two vacua
within a gauged supergravity framework.Comment: 35 pages in JHEP form, 3 figures, typos corrected, references adde
The Elliptic curves in gauge theory, string theory, and cohomology
Elliptic curves play a natural and important role in elliptic cohomology. In
earlier work with I. Kriz, thes elliptic curves were interpreted physically in
two ways: as corresponding to the intersection of M2 and M5 in the context of
(the reduction of M-theory to) type IIA and as the elliptic fiber leading to
F-theory for type IIB. In this paper we elaborate on the physical setting for
various generalized cohomology theories, including elliptic cohomology, and we
note that the above two seemingly unrelated descriptions can be unified using
Sen's picture of the orientifold limit of F-theory compactification on K3,
which unifies the Seiberg-Witten curve with the F-theory curve, and through
which we naturally explain the constancy of the modulus that emerges from
elliptic cohomology. This also clarifies the orbifolding performed in the
previous work and justifies the appearance of the w_4 condition in the elliptic
refinement of the mod 2 part of the partition function. We comment on the
cohomology theory needed for the case when the modular parameter varies in the
base of the elliptic fibration.Comment: 23 pages, typos corrected, minor clarification
Extended matrix Gelfand-Dickey hierarchies: reduction to classical Lie algebras
The Drinfeld-Sokolov reduction method has been used to associate with
extensions of the matrix r-KdV system. Reductions of these systems to the fixed
point sets of involutive Poisson maps, implementing reduction of to
classical Lie algebras of type , are here presented. Modifications
corresponding, in the first place to factorisation of the Lax operator, and
then to Wakimoto realisations of the current algebra components of the
factorisation, are also described.Comment: plain TeX, 12 page
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