252 research outputs found
The SYZ conjecture via homological mirror symmetry
These are expository notes based on a talk given at the Superschool on
derived categories and D-branes at University of Alberta in July of 2016. The
goal of these notes is to give a motivated introduction to the
Strominger-Yau-Zaslow (SYZ) conjecture from the point of view of homological
mirror symmetry.Comment: Contribution to the proceedings of the Superschool on derived
categories and D-brane
Exploring the band structure of Wurtzite InAs nanowires using photocurrent spectroscopy
We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs. Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory. The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate. From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs. This information is vital to the development of crystal phase engineering of this important III-V semiconductor.ER
Balance Performance in Irradiated Survivors of Nasopharyngeal Cancer with and without Tai Chi Qigong Training
G2 Hitchin functionals at one loop
We consider the quantization of the effective target space description of
topological M-theory in terms of the Hitchin functional whose critical points
describe seven-manifolds with G2 structure. The one-loop partition function for
this theory is calculated and an extended version of it, that is related to
generalized G2 geometry, is compared with the topological G2 string. We relate
the reduction of the effective action for the extended G2 theory to the Hitchin
functional description of the topological string in six dimensions. The
dependence of the partition functions on the choice of background G2 metric is
also determined.Comment: 58 pages, LaTeX; v2: Acknowledgments adde
Deformations of calibrated D-branes in flux generalized complex manifolds
We study massless deformations of generalized calibrated cycles, which
describe, in the language of generalized complex geometry, supersymmetric
D-branes in N=1 supersymmetric compactifications with fluxes. We find that the
deformations are classified by the first cohomology group of a Lie algebroid
canonically associated to the generalized calibrated cycle, seen as a
generalized complex submanifold with respect to the integrable generalized
complex structure of the bulk. We provide examples in the SU(3) structure case
and in a `genuine' generalized complex structure case. We discuss cases of
lifting of massless modes due to world-volume fluxes, background fluxes and a
generalized complex structure that changes type.Comment: 52 pages, added references, added comment on ellipticity in appendix
B, made minor changes according to instructions referee JHE
Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast
Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs). The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM) pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR) pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI) whereas no significant reduction was found in smaller chromosomes (III and VI). On the other hand, the absence of Rad17 (a critical component of the ATR pathway) lead to an increase in DSB formation (chromosomes VII and II were tested). We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation
Total Synthesis of (±)-Phomoidride D
Described herein is a synthetic strategy for the total synthesis of (±)‐phomoidride D. This highly efficient and stereoselective approach provides rapid assembly of the carbocyclic core by way of a tandem phenolic oxidation/intramolecular Diels–Alder cycloaddition. A subsequent SmI2‐mediated cyclization cascade delivers an isotwistane intermediate poised for a Wharton fragmentation that unveils the requisite bicyclo[4.3.1]decene skeleton and sets the stage for synthesis completion
Ward-Takahashi Identity with External Field in Ladder QED
We derive the Ward-Takahashi identity obeyed by the fermion-antifermion-gauge
boson vertex in ladder QED in the presence of a constant magnetic field. The
general structure in momentum space of the fermion mass operator with external
electromagnetic field is discussed. Using it we find the solutions of the
ladder WT identity with magnetic field. The consistency of our results with the
solutions of the corresponding Schwinger-Dyson equation ensures the gauge
invariance of the magnetic field induced chiral symmetry breaking recently
found in ladder QED.Comment: new references(refs.10,11) added, 18 pages, Late
Paediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2: a case report
Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector
We report the measurement of electron neutrino elastic scattering from 8B
solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran
Sasso (Italy). The rate of solar neutrino-induced electron scattering events
above this energy in Borexino is 0.217 +- 0.038 (stat) +- 0.008 (syst) cpd/100
t, which corresponds to the equivalent unoscillated flux of (2.4 +- 0.4 (stat)
+- 0.1 (syst))x10^6 cm^-2 s^-1, in good agreement with measurements from SNO
and SuperKamiokaNDE. Assuming the 8B neutrino flux predicted by the high
metallicity Standard Solar Model, the average 8B neutrino survival probability
above 3 MeV is measured to be 0.29+-0.10. The survival probabilities for 7Be
and 8B neutrinos as measured by Borexino differ by 1.9 sigma. These results are
consistent with the prediction of the MSW-LMA solution of a transition in the
solar electron neutrino survival probability between the low energy
vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation
regimes.Comment: 10 pages, 8 figures, 6 table
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