9,347 research outputs found
Gravity duals of supersymmetric gauge theories on three-manifolds
We study gravity duals to a broad class of N=2 supersymmetric gauge theories
defined on a general class of three-manifold geometries. The gravity
backgrounds are based on Euclidean self-dual solutions to four-dimensional
gauged supergravity. As well as constructing new examples, we prove in general
that for solutions defined on the four-ball the gravitational free energy
depends only on the supersymmetric Killing vector, finding a simple closed
formula when the solution has U(1) x U(1) symmetry. Our result agrees with the
large N limit of the free energy of the dual gauge theory, computed using
localization. This constitutes an exact check of the gauge/gravity
correspondence for a very broad class of gauge theories with a large N limit,
defined on a general class of background three-manifold geometries.Comment: 74 pages, 2 figures; v2: minor change
Viroids of grapevines in Italy
Rebviroide in ItalienEs wird über das Vorkommen niedermolekularer RNAs bei 48 Vitis-vinifera-Stämmen und 15 amerikanischen Vitis-Arten und Kreuzungen aus Italien, Osteuropa, Mittelmeer- und Nahost-Ländern berichtet. In den Sämlingen zweier Sorten wurden keine derartigen RNAs gefunden. Aufgrund ihres elektrophoretischen Verhaltens wurden diese RNAs vorläufig identifiziert als Grapevine yellow speckle-Viroid (GYSVd), Grapeivine-Viroid 2 (GVd2) und Hop stunt-Viroid (HSVd). Das letztere Viroid löste bei künstlich infizierten Pflanzen von Tomate cv. Rutgers und Gurke cv. Suyo Befallssymptome aus. HSVd, GYSVd und GVd2 wurden in 97, 92 bzw. 11 % der untersuchten Proben wiedergefunden. In der Regel lagen Mischinfektionen vor, wobei die Kombination von HSVd mit GYSVd überwog. Diese beiden Viroide kamen regelmäßig in Reben mit den Symptomen von Yellow speckle oder Vein banding vor. Es wurde keine eindeutige Beziehung zwischen dem Vorkommen eines der Viroide und Rebkrankheiten mit unklarer Ätiologie, wie Vein necrosis oder Fleck, gefunden
Virus-like particles and ultrastructural modifications in the phloem of leafroll-affected grapevines
Ultrastructural studies were carried out on thin-sectioned phloem and mesophyll tissues of 42 grapevine accessions with leafroll symptoms, coming from 12 different countries (Italy, Portugal, Spain, France, Yugoslavia, Hungary, Soviet Union, Bulgaria, Greece, Cyprus, Malta and Nigeria). A total of 47 specimens were observed with the electron microscope. About half (48 %) the samples examined contained isometric virus-like particles in one or more phloem elements (sieve tubes, companion and parenchyma cells), whereas only 15 % of the samples contained filamentous virus-like particles in the same type of cells. None of these viruses could be transmitted by sap inoculation. Ultrastructural features of major importance were double-membraned vesiculated bodies possibly representing profoundly modified cell organelles (mitochondria and/or plastids) and bundles of tubular structures 40-45 nm or 60-100 nm in diameter, the !arger of which exhibited a central core seemingly made up of one or more filaments of tubular P-protein. The present results are discussed in the light of the findings reported in the literature on leafroll-infected grapevine tissues.Virusartige Partikeln und Veränderungen der Ultrastruktur im Phloem blattrollkranker RebenBei 42 Rebenstämmen mit Blattrollsymptomen wurde die Ultrastruktur des Blattphloems und Mesophylls untersucht. Die Reben stammten aus 12 verschiedenen Ländern (Italien, Portugal, Spanien, Frankreich, Jugoslawien, Ungarn, Sowjetunion, Bulgarien, Griechenland, Cypern, Malta und Nigeria). Insgesamt wurden 47 Exemplare elektronenmikroskopisch untersucht. Etwa die Hälfte der Proben (48 %) enthielt isometrische virusartige Partikeln in einem oder mehreren Phloemelementen (Siebröhren, Geleit- und Parenchymzellen); bei 15 % der Proben waren in denselben Zelltypen filamentöse virusartige Partikeln enthalten. Eine Saftübertragung der Viren war in keinem Falle möglich. Wichtige ultrastrukturelle Bildungen waren doppelwandige vesiculäre Körper, die möglicherweise stark abgewandelte Zellorganellen (Mitochondrien und/oder Plastiden) darstellen, sowie Bündel tubulärer Strukturen vom Durchmesser 40-45 nm oder 60-100 nm; die größeren Tubuli zeigten einen zentralen Kern, der anscheinend von einem oder mehreren Filamenten tubulären P-Proteins gebildet wurde. Die vorliegenden Ergebnisse werden im Zusammenhang mit den Literaturbefunden über blattrollinfiziertes Rebengewebe diskutiert
Intellectual property rights and the international transfer of climate change mitigating technologies
Our study is a quasi-replication of Dechezleprêtre et al. (2013), which was among the first studies to find a strong role for IPRs in explaining the international transfer of climate change and mitigation technologies (CCMTs). Their result is at odds with the received wisdom on the ambiguous role of IPRs in determining technology transfer to developing countries as strong IPRs can enable a market expansion effect and result in technology transfer but they may also strengthen monopoly power, increase value and reduce the incentive to transfer a large volume of technology. We extend the Dechezleprêtre et al. (2013) study by distinguishing between OECD and non-OECD groups of countries, including the effect of both de jure and de facto IPRs, and extending the period of study to include the years 2008–2018, when global trade and investment slowed down. Our exercise reveals that technology transfer to non-OECD countries is associated with a different set of policies compared to OECD countries. We also find that strong IP policies have not had the same beneficial CCMTs transfer outcomes in 2008–2018 as they did in the earlier period and in fact strong de facto IPR reduced the volume of CCMTs transfer to all countries
The Mn site in Mn-doped Ga-As nanowires: an EXAFS study
We present an EXAFS study of the Mn atomic environment in Mn-doped GaAs
nanowires. Mn doping has been obtained either via the diffusion of the Mn used
as seed for the nanowire growth or by providing Mn during the growth of
Au-induced wires. As a general finding, we observe that Mn forms chemical bonds
with As but is not incorporated in a substitutional site. In Mn-induced GaAs
wires, Mn is mostly found bonded to As in a rather disordered environment and
with a stretched bond length, reminiscent of that exhibited by MnAs phases. In
Au-seeded nanowires, along with stretched Mn-As coordination we have found the
presence of Mn in a Mn-Au intermetallic compound.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Semiconductor Science and Technology. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
doi:10.1088/0268-1242/27/8/08500
Operator Counting and Eigenvalue Distributions for 3D Supersymmetric Gauge Theories
We give further support for our conjecture relating eigenvalue distributions
of the Kapustin-Willett-Yaakov matrix model in the large N limit to numbers of
operators in the chiral ring of the corresponding supersymmetric
three-dimensional gauge theory. We show that the relation holds for
non-critical R-charges and for examples with {\mathcal N}=2 instead of
{\mathcal N}=3 supersymmetry where the bifundamental matter fields are
nonchiral. We prove that, for non-critical R-charges, the conjecture is
equivalent to a relation between the free energy of the gauge theory on a three
sphere and the volume of a Sasaki manifold that is part of the moduli space of
the gauge theory. We also investigate the consequences of our conjecture for
chiral theories where the matrix model is not well understood.Comment: 27 pages + appendices, 5 figure
Holographic renormalization and supersymmetry
Holographic renormalization is a systematic procedure for regulating
divergences in observables in asymptotically locally AdS spacetimes. For dual
boundary field theories which are supersymmetric it is natural to ask whether
this defines a supersymmetric renormalization scheme. Recent results in
localization have brought this question into sharp focus: rigid supersymmetry
on a curved boundary requires specific geometric structures, and general
arguments imply that BPS observables, such as the partition function, are
invariant under certain deformations of these structures. One can then ask if
the dual holographic observables are similarly invariant. We study this
question in minimal N = 2 gauged supergravity in four and five dimensions. In
four dimensions we show that holographic renormalization precisely reproduces
the expected field theory results. In five dimensions we find that no choice of
standard holographic counterterms is compatible with supersymmetry, which leads
us to introduce novel finite boundary terms. For a class of solutions
satisfying certain topological assumptions we provide some independent tests of
these new boundary terms, in particular showing that they reproduce the
expected VEVs of conserved charges.Comment: 70 pages; corrected typo
Identification of the agent of grapevine fleck disease
An antiserum against an Italian isolate of grapevine phloem-limited isometric virus (GPLIV) was used in an ELISA survey carried out for assessing the natural distribution of the virus and its association with fleck disease. A total of 591 vines of Vitis rupestris were checked for the presence of GPLIV. Of 150 plants with fleck symptoms, 138 (92 %) were ELISA-positive and 12 (8 %) negative. Of 441 symptomless V. rupestris, 435 (98,6 %) were ELISA-negative and 6 (1,4 %) positive for GPLIV. The virus was detected in about 30 % of 694 vines of different origin grown in Apulia (Southern Italy). The highest infection (53 %) was in a commercial vineyard of cv. Italia and the lowest (8 %) in a plot of certified and visually selected rootstocks. Fleck-infected, but not fleck-free V. rupestris contained virus particles and vesiculated inclusion bodies in phloem tissues. LN 33 plantlets derived from in vitro culture of meristem tips from ELISA-positive fleck-infected mother plants were found to be free from GPLIV, as ascertained by ELISA and thin-sectioning. These vines failed to induce fleck symptoms when grafted on V. rupestris. It is concluded that GPLIV is the agent of fleck and, therefore, it should be renamed grapevine fleck virus (GFKV)
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