1,895 research outputs found
D-branes in Topological Minimal Models: the Landau-Ginzburg Approach
We study D-branes in topologically twisted N=2 minimal models using the
Landau-Ginzburg realization. In the cases of A and D-type minimal models we
provide what we believe is an exhaustive list of topological branes and compute
the corresponding boundary OPE algebras as well as all disk correlators. We
also construct examples of topological branes in E-type minimal models. We
compare our results with the boundary state formalism, where possible, and find
agreement.Comment: 29 pages, late
An investigation of the thermal stability of an Mg-Dy alloy after processing by high-pressure torsion
An Mg-0.41Dy (wt%) alloy was successfully processed by high-pressure tension (HPT) through 5 turns at room temperature. The evolution of the recrystallization microstructure and the texture and mechanical properties of the deformed alloy were investigated after annealing at 200 and 400 °C for 1 h using Electron Backscatter Diffraction (EBSD) and Vickers measurements. The recrystallization temperature and activation energy were evaluated using Differential Scanning Calorimetry (DSC). Processing by HPT led to significant grain refinement with an average grain size of ~0.5 ± 0.1 μm which increased to ~1.2 ± 0.8 μm after annealing at 400 °C. This slow increase in grain size at a high temperature demonstrates a good thermal stability of the microstructure. The alloy exhibited two main fiber textures after HPT processing: firstly a typical basal fiber (φ1 = 0–360°, Φ = 0° and φ2 = 0–60°) and secondly a fiber localized at φ1 = 180°, Φ = 60° and φ2 = 0–90°. These textures were retained after annealing at 400 °C. There was no change in the microhardness value after annealing at 200 °C (41 ± 1 Hv) and only a minor decrease after annealing at 400 °C (38.4 ± 0.5 Hv). The DSC results showed that the temperature associated with the recrystallization process increased with increasing heating rate and the activation energy for recrystallization was measured as ~25 kJ mol−1
A Holographic View on Matrix Model of Black Hole
We investigate a deformed matrix model proposed by Kazakov et.al. in relation
to Witten's two-dimensional black hole. The existing conjectures assert the
equivalence of the two by mapping each to a deformed c=1 theory called the
sine-Liouville theory. We point out that the matrix theory in question may be
naturally interpreted as a gauged quantum mechanics deformed by insertion of an
exponentiated Wilson loop operator, which gives us more direct and holographic
map between the two sides. The matrix model in the usual scaling limit must
correspond to the bosonic SL(2,R)/U(1) theory in genus expansion but exact in
\alpha'. We successfully test this by computing the Wilson loop expectation
value and comparing it against the bulk computation. For the latter, we employ
the \alpha'-exact geometry proposed by Dijkgraaf, Verlinde, and Verlinde, which
was further advocated by Tseytlin. We close with comments on open problems.Comment: LaTeX, 19 page
Paclitaxel-octreotide conjugates inhibit growth of human non-small cell lung cancer cells in vitro
Aim: To evaluate the effects of paclitaxel-octreotide conjugates on the growth of cultured non-small cell lung cancer cells. Methods: RT-PCR was performed to detect mRNA for the subtypes of the human somatostatin receptor (SSTR) using specific primers. MTT-based cytotoxicity assay was used to evaluate the cell viability after treatment with paclitaxel and the conjugates. Cell cycle perturbations were determined using a Fluorescence-Activated Cell Sorter. Results: Non-small cell lung cancer A549 and Calu-6 cells expressed mRNA for SSTR2 and SSTR5. Paclitaxel and the conjugates effectively inhibited the growth of A549 and Calu-6 cells in a concentration- and time-dependent manner. In SSTR-negative fibroblasts, the conjugates were less cytotoxic than paclitaxel. The conjugates and paclitaxel could induce the increase of G2/M phase ratio in A549 cells. Conclusion: The paclitaxel-octreotide conjugates can be used as selective-targeted chemotherapeutic agents for treating non-small cell lung cancer.Цель: оценить эффект конъюгатов паклитаксела-октреотида на рост культивированных клеток немелкоклеточного рака
легкого человека. Методы: для определения мРНК подтипов рецептора соматостатина человека (SSTR) применяли ОT-ПЦР.
Анализ цитотоксичности в МТТ-тесте применяли для оценки выживаемости клеток после их инкубации с паклитакселом
и конъюгатами. Нарушения клеточного цикла определяли с применением FACS — клеточного сортера. Результаты:
установлено, что клеточные линии немелкоклеточного рака легкого A549 и Calu-6 экспрессируют SSTR2 и SSTR5 мРНК.
Отмечено эффективное дозо- и времязависимое угнетение роста клеток A549 и Calu-6 паклитакселом и конъюгатами.
Для SSTR-негативных фибробластов конъюгаты менее цитотоксичны, чем паклитаксел. Конъюгаты и паклитаксел могут
индуцировать повышение соотношения фаз G2
/M в клетках A549. Выводы: конъюгаты паклитаксел-октреотида могут быть
использованы как селективные химиотерапевтические агенты для воздействия на немелкоклеточный рак легкого
Dynamical electron transport through a nanoelectromechanical wire in a magnetic field
We investigate dynamical transport properties of interacting electrons moving
in a vibrating nanoelectromechanical wire in a magnetic field. We have built an
exactly solvable model in which electric current and mechanical oscillation are
treated fully quantum mechanically on an equal footing. Quantum mechanically
fluctuating Aharonov-Bohm phases obtained by the electrons cause nontrivial
contribution to mechanical vibration and electrical conduction of the wire. We
demonstrate our theory by calculating the admittance of the wire which are
influenced by the multiple interplay between the mechanical and the electrical
energy scales, magnetic field strength, and the electron-electron interaction
Scaling law of Wolff cluster surface energy
We study the scaling properties of the clusters grown by the Wolff algorithm
on seven different Sierpinski-type fractals of Hausdorff dimension in the framework of the Ising model. The mean absolute value of the surface
energy of Wolff cluster follows a power law with respect to the lattice size.
Moreover, we investigate the probability density distribution of the surface
energy of Wolff cluster and are able to establish a new scaling relation. It
enables us to introduce a new exponent associated to the surface energy of
Wolff cluster. Finally, this new exponent is linked to a dynamical exponent via
an inequality.Comment: 12 pages, 3 figures. To appear in PR
Submergence of the Sidebands in the Photon-assisted Tunneling through a Quantum Dot Weakly Coupled to Luttinger Liquid Leads
We study theoretically the photon-assisted tunneling through a quantum dot
weakly coupled to Luttinger liquids (LL) leads, and find that the zero bias dc
conductance is strongly affected by the interactions in the LL leads. In
comparison with the system with Fermi liquid (FL) leads, the sideband peaks of
the dc conductance become blurring for 1/2<g<1, and finally merge into the
central peak for g<1/2, (g is the interaction parameter in the LL leads). The
sidebands are suppressed for LL leads with Coulomb interactions strong enough,
and the conductance always appears as a single peak for any strength and
frequency of the external time-dependent field. Furthermore, the quenching
effect of the central peak for the FL case does not exist for g<1/2.Comment: 9 pages, 4 figure
Operadic formulation of topological vertex algebras and Gerstenhaber or Batalin-Vilkovisky algebras
We give the operadic formulation of (weak, strong) topological vertex
algebras, which are variants of topological vertex operator algebras studied
recently by Lian and Zuckerman. As an application, we obtain a conceptual and
geometric construction of the Batalin-Vilkovisky algebraic structure (or the
Gerstenhaber algebra structure) on the cohomology of a topological vertex
algebra (or of a weak topological vertex algebra) by combining this operadic
formulation with a theorem of Getzler (or of Cohen) which formulates
Batalin-Vilkovisky algebras (or Gerstenhaber algebras) in terms of the homology
of the framed little disk operad (or of the little disk operad).Comment: 42 page
Isotropic atomic layer etching of GaN using SF<sub>6</sub> plasma and Al(CH<sub>3</sub>)<sub>3</sub>
GaN is an enabling material for light emitting diodes, advanced radio frequency, and power semiconductor devices. However, fabrication of GaN devices often relies on harsh etch processes, which can leave an etch damage layer, limiting final device performance. In this work, an isotropic atomic layer etching (ALE) process involving SF6 plasma and trimethylaluminium [Al(CH3)3] is presented for the controlled etching of GaN, which reduces oxygen and carbon contamination while smoothing the surface. The ALE chemistry was first examined with density functional theory. A comparison between proposed thermal and plasma-driven reactions is made by implementing Natarajan-Elliott analysis, highlighting that the plasma process is a good candidate for GaN ALE. Saturation was experimentally confirmed for both ALE half-cycles at 150 and 300 °C, with etch rates of 0.31 ± 0.01 and 0.40 ± 0.02 nm/cycle, respectively. Analysis of the films post-ALE shows that the RMS roughness of the films decreases from 2.6 ± 0.1 to 1.9 ± 0.1 nm after 25 nm of etching at 300 °C, in agreement with a previously developed curvature-dependent smoothing model. Taken together, this ALE process enables accurate GaN thickness tuning, surface cleaning, and surface smoothing, allowing for further development of GaN devices.</p
Tunnel splitting and quantum phase interference in biaxial ferrimagnetic particles at excited states
The tunneling splitting in biaxial ferrimagnetic particles at excited states
with an explicit calculation of the prefactor of exponent is obtained in terms
of periodic instantons which are responsible for tunneling at excited states
and is shown as a function of magnetic field applied along an arbitrary
direction in the plane of hard and medium axes. Using complex time
path-integral we demonstrate the oscillation of tunnel splitting with respect
to the magnitude and the direction of the magnetic field due to the quantum
phase interference of two tunneling paths of opposite windings . The
oscillation is gradually smeared and in the end the tunnel splitting
monotonously increases with the magnitude of the magnetic field when the
direction of the magnetic field tends to the medium axis. The oscillation
behavior is similar to the recent experimental observation with Fe
molecular clusters. A candidate of possible experiments to observe the effect
of quantum phase interference in the ferrimagnetic particles is proposed.Comment: 15 pages, 5 figures, acceptted to be pubblished in Physical Review
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