76,824 research outputs found
Bell-CHSH function approach to quantum phase transitions in matrix product systems
Recently, nonlocality and Bell inequalities have been used to investigate
quantum phase transitions (QPTs) in low-dimensional quantum systems.
Nonlocality can be detected by the Bell-CHSH function (BCF). In this work, we
extend the study of BCF to the QPTs in matrix product systems (MPSs). In this
kind of QPTs, the ground-state energy keeps analytical in the vicinity of the
QPT points, and is usually called the MPS-QPTs. For several typical models, our
results show that BCF can signal the MPS-QPTs very well. In addition, we find
BCF can capture signal of QPTs in unentangled states and classical states, for
which other measures of quantum correlation (quantum entanglement and quantum
discord) fail. Furthermore, we find that in these MPSs, there exists some kind
of quantum correlation which cannot be characterized by entanglement, or by
nonlocality.Comment: 12 pages, 4 figure
Dimensionality Reduction for Stationary Time Series via Stochastic Nonconvex Optimization
Stochastic optimization naturally arises in machine learning. Efficient
algorithms with provable guarantees, however, are still largely missing, when
the objective function is nonconvex and the data points are dependent. This
paper studies this fundamental challenge through a streaming PCA problem for
stationary time series data. Specifically, our goal is to estimate the
principle component of time series data with respect to the covariance matrix
of the stationary distribution. Computationally, we propose a variant of Oja's
algorithm combined with downsampling to control the bias of the stochastic
gradient caused by the data dependency. Theoretically, we quantify the
uncertainty of our proposed stochastic algorithm based on diffusion
approximations. This allows us to prove the asymptotic rate of convergence and
further implies near optimal asymptotic sample complexity. Numerical
experiments are provided to support our analysis
Clinical Features and Genetic Analysis of 20 Chinese Patients with X-Linked Hyper-IgM Syndrome
X-linked hyper-IgM syndrome (XHIGM) is one type of primary immunodeficiency diseases, resulting from defects in the CD40 ligand/CD40 signaling pathways. We retrospectively analyzed the clinical and molecular features of 20 Chinese patients diagnosed and followed up in hospitals affiliated to Shanghai Jiao Tong University School of Medicine from 1999 to 2013. The median onset age of these patients was 8.5 months (range: 20 days–21 months). Half of them had positive family histories, with a shorter diagnosis lag. The most common symptoms were recurrent sinopulmonary infections (18 patients, 90%), neutropenia (14 patients, 70%), oral ulcer (13 patients, 65%), and protracted diarrhea (13 patients, 65%). Six patients had BCGitis. Six patients received hematopoietic stem cell transplantations and four of them had immune reconstructions and clinical remissions. Eighteen unique mutations in CD40L gene were identified in these 20 patients from 19 unrelated families, with 12 novel mutations. We compared with reported mutation results and used bioinformatics software to predict the effects of mutations on the target protein. These mutations reflected the heterogeneity of CD40L gene and expanded our understanding of XHIGM
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