303 research outputs found
Instanton Solutions for the Universal Hypermultiplet
We expand our previous analysis on fivebrane and membrane instanton solutions
in the universal hypermultiplet, including near-extremal multi-centered
solutions and mixed fivebrane-membrane charged instantons. The results are most
conveniently described in terms of a double-tensor multiplet.Comment: Minor changes, clarification added. Contribution to the proceedings
of the 36th International Symposium Ahrenshoop, August 200
Fungicide resistance among Cladobotryum spp. â causal agents of cobweb disease of the edible mushroom Agaricus bisporus
A survey of fungicide resistance among isolates of the mushroom pathogens Cladobotryum mycophilum and C. dendroides Types I and II was undertaken, with respect to the active ingredients thiabendazole, carbendazim (benzimidazoles) and prochloraz manganese following an epidemic in Britain and Ireland in 1994/95. The majority of isolates (41/57) were strongly resistant to thiabendazole (ED50 > 200 ppm) and were exclusively C. dendroides Type II. All C. mycophilum and C. dendroides Type I isolates, and four C. dendroides Type II isolates, were weakly resistant to thiabendazole (ED50 1â10 ppm). Thiabendazole-resistant C. dendroides Type II isolates were only weakly resistant to carbendazim (ED50 2â10 ppm) and isolates which were weakly resistant to thiabendazole were carbendazim-sensitive (ED50 < 1 ppm), demonstrating a lack of complete cross resistance between these two benzimidazole fungicides. The ED50 values for all isolates with respect to prochloraz manganese ranged from 0.14 to 7.8 ppm. Benzimidazole resistance was considered to have been an important factor influencing the severity of the 1994/95 cobweb epidemic but 25% of isolates collected were benzimidazole sensitive
Hypermultiplets and Topological Strings
The c-map relates classical hypermultiplet moduli spaces in compactifications
of type II strings on a Calabi-Yau threefold to vector multiplet moduli spaces
via a further compactification on a circle. We give an off-shell description of
the c-map in N=2 superspace. The superspace Lagrangian for the hypermultiplets
is a single function directly related to the prepotential of special geometry,
and can therefore be computed using topological string theory. Similarly, a
class of higher derivative terms for hypermultiplets can be computed from the
higher genus topological string amplitudes. Our results provide a framework for
studying quantum corrections to the hypermultiplet moduli space, as well as for
understanding the black hole wave-function as a function of the hypermultiplet
moduli.Comment: 21 pages, references adde
Quantitative analysis of aortic Na[<sup>18</sup>F]F uptake in macrocalcifications and microcalcifications in PET/CT scans
Background: Currently, computed tomography (CT) is used for risk profiling of (asymptomatic) individuals by calculating coronary artery calcium scores. Although this score is a strong predictor of major adverse cardiovascular events, this method has limitations. Sodium [18F]fluoride (Na[18F]F) positron emission tomography (PET) has shown promise as an early marker for atherosclerotic progression. However, evidence on Na[18F]F as a marker for high-risk plaques is limited, particularly on its presentation in clinical PET/CT. Besides, the relationship between microcalcifications visualized by Na[18F]F PET and macrocalcifications detectable on CT is unknown. Purpose: To establish a match/mismatch score in the aorta between macrocalcified plaque content on CT and microcalcification Na[18F]F PET uptake. Methods: Na[18F]F-PET/CT scans acquired in our centre in 2019â2020 were retrospectively collected. The aorta of each low-dose CT was manually segmented. Background measurements were placed in the superior vena cava. The vertebrae were automatically segmented using an open-source convolutional neural network, dilated with 10 mm, and subtracted from the aortic mask. Per patient, calcium and Na[18F]F-hotspot masks were retrieved using an in-house developed algorithm. Three match/mismatch analyses were performed: a population analysis, a per slice analysis, and an overlap score. To generate a population image of calcium and Na[18F]F hotspot distribution, all aortic masks were aligned. Then, a heatmap of calcium HU and Na[18F]F-uptake on the surface was obtained by outward projection of HU and uptake values from the centerline. In each slice of the aortic wall of each patient, the calcium mass score and target-to-bloodpool ratios (TBR) were calculated within the calcium masks, in the aortic wall except the calcium masks, and in the aortic wall in slices without calcium. For the overlap score, three volumes were identified in the calcium and Na[18F]F masks: volume of PET (PET+/CT-), volume of CT (PET-/CT+), and overlapping volumes (PET+/CT+). A Spearman's correlation analysis with Bonferroni correction was performed on the population image, assessing the correlation between all HU and Na[18F]F vertex values. In the per slice analysis, a paired Wilcoxon signed-rank test was used to compare TBR values within each slice, while an ANOVA with post-hoc KruskalâWallis test was employed to compare TBR values between slices. p-values < 0.05 were considered significant. Results: In total, 186 Na[18F]F-PET/CT scans were included. A moderate positive exponential correlation was observed between total aortic calcium mass and total aortic TBR (r = 0.68, p < 0.001). A strong positive correlation (r = 0.77, p < 0.0001) was observed between CT values and Na[18F]F values on the population image. Significantly higher TBR values were found outside calcium masks than inside calcium masks (p < 0.0001). TBR values in slices where no calcium was present, were significantly lower compared with outside calcium and inside calcium (both p < 0.0001). On average, only 3.7% of the mask volumes were overlapping. Conclusions: Na[18F]F-uptake in the aorta behaves similarly to macrocalcification detectable on CT. Na[18F]F-uptake values are also moderately correlated to calcium mass scores (match). Higher uptake values were found just outside macrocalcification masks instead of inside the macrocalcification masks (mismatch). Also, only a small percentage of the Na[18F]F-uptake volumes overlapped with the calcium volumes (mismatch).</p
Supergravity description of spacetime instantons
We present and discuss BPS instanton solutions that appear in type II string
theory compactifications on Calabi-Yau threefolds. From an effective action
point of view these arise as finite action solutions of the Euclidean equations
of motion in four-dimensional N=2 supergravity coupled to tensor multiplets. As
a solution generating technique we make use of the c-map, which produces
instanton solutions from either Euclidean black holes or from Taub-NUT like
geometries.Comment: 35 pages, some clarifications adde
On NS5-brane instantons and volume stabilization
We study general aspects of NS5-brane instantons in relation to the
stabilization of the volume modulus in Calabi-Yau compactifications of type II
strings with fluxes, and their orientifold versions. These instantons correct
the Kahler potential and generically yield significant contributions to the
scalar potential at intermediate values of string coupling constant and volume.
Under suitable conditions they yield uplifting terms that allow for
meta--stable de Sitter vacua.Comment: 29 pages, 3 figures; statements about fields G^a made more precise,
added some clarifications, typos correcte
Five-brane Instantons vs Flux-induced Gauging of Isometries
In five-dimensional heterotic M-theory there is necessarily nonzero
background flux, which leads to gauging of an isometry of the universal
hypermultiplet moduli space. This isometry, however, is poised to be broken by
M5-brane instanton effects. We show that, similarly to string theory, the
background flux allows only brane instantons that preserve the above isometry.
The zero-mode counting for the M5 instantons is related to the number of
solutions of the Dirac equation on their worldvolume. We investigate that
equation in the presence of generic background flux and also, in a particular
case, with nonzero worldvolume flux.Comment: 27 pages; reference adde
Are There Any Significant Differences in Terms of Age and Sex in Pedestrian and Cyclist Accidents?
This study has analyzed sex-specific differences in pedestrian and cyclist accidents involving passenger cars. The most frequently injured body regions, types of injuries, which show sex-specific differences and the general accident parameters of females and males were compared. Accident data from three different European countries (Austria, Netherlands, Sweden) were analyzed. The current analysis shows that for both, females and males, pedestrian and cyclist injuries are sustained mainly to the body regions head, thorax, upper extremities and lower extremities. The results show that the odds for sustaining skeletal injuries to the lower extremities (incl. pelvis) in females are significantly higher. It was observed in all datasets, that the odds of females being involved in a rural accident or an accident at night are lower than for males. Elderly pedestrian and cyclist (â„60YO) tend to sustain more severe injuries (AIS2+ and AIS3+) than younger pedestrian and cyclists
De Sitter vacua from N=2 gauged supergravity
Typical de Sitter (dS) vacua of gauged supergravity correspond to saddle
points of the potential and often the unstable mode runs into a singularity. We
explore the possibility to obtain dS points where the unstable mode goes on
both sides into a supersymmetric smooth vacuum. Within N=2 gauged supergravity
coupled to the universal hypermultiplet, we have found a potential which has
two supersymmetric minima (one of them can be flat) and these are connected by
a de Sitter saddle point. In order to obtain this potential by an Abelian
gauging, it was important to include the recently proposed quantum corrections
to the universal hypermultiplet sector. Our results apply to four as well as
five dimensional gauged supergravity theories.Comment: 25 pages, 1 figure, add refs and corrected typo
An index for the Dirac operator on D3 branes with background fluxes
We study the problem of instanton generated superpotentials in Calabi-Yau
orientifold compactifications directly in type IIB string theory. To this end,
we derive the Dirac equation on a Euclidean D3 brane in the presence of
background fluxes. We propose an index which governs whether the generation of
a superpotential in the effective 4d theory by D3 brane instantons is possible.
Applying the formalism to various classes of examples, including the K3 x
T^2/Z_2 orientifold, in the absence and presence of fluxes, we show that our
results are consistent with conclusions attainable via duality from an M-theory
analysis.Comment: Fermion coupling to five-form restored, conclusions of the paper
unchange
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