5,797 research outputs found
Surface transport coefficients for three-dimensional topological superconductors
We argue that surface spin and thermal conductivities of three-dimensional
topological superconductors are universal and topologically quantized at low
temperature. For a bulk winding number , there are "colors" of
surface Majorana fermions. Localization corrections to surface transport
coefficients vanish due to time-reversal symmetry (TRS). We argue that
Altshuler-Aronov interaction corrections vanish because TRS forbids color or
spin Friedel oscillations. We confirm this within a perturbative expansion in
the interactions, and to lowest order in a large- expansion. In both
cases, we employ an asymptotically exact treatment of quenched disorder effects
that exploits the chiral character unique to two-dimensional,
time-reversal-invariant Majorana surface states.Comment: 24 pages, 15 figures. v3: published versio
Topological protection, disorder, and interactions: Survival at the surface of 3D topological superconductors
We consider the interplay of disorder and interactions upon the gapless
surface states of 3D topological superconductors. The combination of topology
and superconducting order inverts the action of time-reversal symmetry, so that
extrinsic time-reversal invariant surface perturbations appear only as
"pseudomagnetic" fields (abelian and non-abelian vector potentials, which
couple to spin and valley currents). The main effect of disorder is to induce
multifractal scaling in surface state wavefunctions. These critically
delocalized, yet strongly inhomogeneous states renormalize interaction matrix
elements relative to the clean system. We compute the enhancement or
suppression of interaction scaling dimensions due to the disorder exactly,
using conformal field theory. We determine the conditions under which
interactions remain irrelevant in the presence of disorder for symmetry classes
AIII and DIII. In the limit of large topological winding numbers (many surface
valleys), we show that the effective field theory takes the form of a
Finkel'stein non-linear sigma model, augmented by the
Wess-Zumino-Novikov-Witten term. The sigma model incorporates interaction
effects to all orders, and provides a framework for a controlled perturbative
expansion; the inverse spin or thermal conductance is the small parameter. For
class DIII we show that interactions are always irrelevant, while in class AIII
there is a finite window of stability, controlled by the disorder. Outside of
this window we identify new interaction-stabilized fixed points.Comment: 27 pages, 10 figures. v2: published versio
Unifying and Merging Well-trained Deep Neural Networks for Inference Stage
We propose a novel method to merge convolutional neural-nets for the
inference stage. Given two well-trained networks that may have different
architectures that handle different tasks, our method aligns the layers of the
original networks and merges them into a unified model by sharing the
representative codes of weights. The shared weights are further re-trained to
fine-tune the performance of the merged model. The proposed method effectively
produces a compact model that may run original tasks simultaneously on
resource-limited devices. As it preserves the general architectures and
leverages the co-used weights of well-trained networks, a substantial training
overhead can be reduced to shorten the system development time. Experimental
results demonstrate a satisfactory performance and validate the effectiveness
of the method.Comment: To appear in the 27th International Joint Conference on Artificial
Intelligence and the 23rd European Conference on Artificial Intelligence,
2018. (IJCAI-ECAI 2018
Topological Protection from Random Rashba Spin-Orbit Backscattering: Ballistic Transport in a Helical Luttinger Liquid
The combination of Rashba spin-orbit coupling and potential disorder induces
a random current operator for the edge states of a 2D topological insulator. We
prove that charge transport through such an edge is ballistic at any
temperature, with or without Luttinger liquid interactions. The solution
exploits a mapping to a spin 1/2 in a time-dependent field that preserves the
projection along one randomly undulating component (integrable dynamics). Our
result is exact and rules out random Rashba backscattering as a source of
temperature-dependent transport, absent integrability-breaking terms.Comment: 6+3 pages, 2+1 figure
High-resolution Ultrasonography in Superficial Soft Tissue Tumors
Surgical removal and clinical follow-up of soft tissue masses are easily managed in clinical practice but are dependent on the experience of the clinician. Occasionally, however, a patient is referred from a local clinician to our clinic with an inoperable mass following a surgical procedure. We consider it important to fully understand the nature of the mass prior to surgery, thus avoiding unnecessary surgery in some cases. High-resolution ultrasonography has been widely applied in the musculoskeletal system over the past two decades and is very useful in evaluating the nature of superficial soft tissue masses. It enables the differentiation of benign and malignant masses and the detection of many different types of histology in superficial soft tissue masses. The purpose of this review is to demonstrate the characteristic findings of high-resolution ultrasonography and color Doppler ultrasonography in superficial soft tissue tumors
Ultrasonography-guided Percutaneous Interventional Procedures of the Spleen
Since the introduction of real-time ultrasonography (US) to the medicine in late 1970s, the unique benefit of the real-time cross-sectional imaging has made US one of the most widely used imaging modalities to guide interventional procedures. Among the intra-abdominal solid organs, the spleen is the least common solid organ considered for interventional procedures. Although splenic puncture for splenoportography was performed as early as the 1950s and has had a low complication rate, traditionally a direct splenic puncture is still avoided due to the risk of hemorrhage or laceration. US-guided percutaneous drainage of splenic abscesses has been used as a safe alternative procedure for more than 20 years, however, only a few series reporting such an interventional procedure have been published. This review describes briefly the usefulness, technique, safety, and the outcome of US-guided interventional procedures of the spleen
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