19,392 research outputs found
Study of the cytological features of bone marrow mesenchymal stem cells from patients with neuromyelitis optica.
Neuromyelitis optica (NMO) is a refractory autoimmune inflammatory disease of the central nervous system without an effective cure. Autologous bone marrowâderived mesenchymal stem cells (BMâMSCs) are considered to be promising therapeutic agents for this disease due to their potential regenerative, immune regulatory and neurotrophic effects. However, little is known about the cytological features of BMâMSCs from patients with NMO, which may influence any therapeutic effects. The present study aimed to compare the proliferation, differentiation and senescence of BMâMSCs from patients with NMO with that of ageâ and sexâmatched healthy subjects. It was revealed that there were no significant differences in terms of cell morphology or differentiation capacities in the BMâMSCs from the patients with NMO. However, in comparison with healthy controls, BMâMSCs derived from the Patients with NMO exhibited a decreased proliferation rate, in addition to a decreased expression of several cell cycleâpromoting and proliferationâassociated genes. Furthermore, the cell death rate increased in BMâMSCs from patients under normal culture conditions and an assessment of the gene expression profile further confirmed that the BMâMSCs from patients with NMO were more vulnerable to senescence. Plateletâderived growth factor (PDGF), as a major mitotic stimulatory factor for MSCs and a potent therapeutic cytokine in demyelinating disease, was able to overcome the decreased proliferation rate and increased senescence defects in BMâMSCs from the patients with NMO. Taken together, the results from the present study have enabled the proposition of the possibility of combining the application of autologous BMâMSCs and PDGF for refractory and severe patients with NMO in order to elicit improved therapeutic effects, or, at the least, to include PDGF as a necessary and standard growth factor in the current in vitro formula for the culture of NMO patientâderived BMâMSCs
Artificial Gauge Field and Quantum Spin Hall States in a Conventional Two-dimensional Electron Gas
Based on the Born-Oppemheimer approximation, we divide total electron
Hamiltonian in a spinorbit coupled system into slow orbital motion and fast
interband transition process. We find that the fast motion induces a gauge
field on slow orbital motion, perpendicular to electron momentum, inducing a
topological phase. From this general designing principle, we present a theory
for generating artificial gauge field and topological phase in a conventional
two-dimensional electron gas embedded in parabolically graded
GaAs/InGaAs/GaAs quantum wells with antidot lattices. By tuning
the etching depth and period of antidot lattices, the band folding caused by
superimposed potential leads to formation of minibands and band inversions
between the neighboring subbands. The intersubband spin-orbit interaction opens
considerably large nontrivial minigaps and leads to many pairs of helical edge
states in these gaps.Comment: 9 pages and 4 figure
Does share pledging promote or impede corporate social responsibility? An examination of Chinese listed firms
By employing the Chinese listed firmâs data from 2010 to 2017,
this study explores the impact of share pledging on firmsâ corporate social responsibility (CSR) performance. Empirical results indicate a negative relationship between share pledging and CSR
performance. This effect is robust after using alternative measures
and different regression methods, and also consistent after tackling the endogenous issues. Furthermore, we find that risk-taking
and agency cost are two possible underlying mechanisms
through which share pledging reduces CSR. In addition, CSR
reduction caused by share pledging leads to poorer economic
performance and lower market value of firms
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An effective method of accelerating Bose gases using magnetic coils
This is the accepted manuscript. The final published version is available from IOP at http://iopscience.iop.org/1674-1056/23/9/093701.Based on the experimental device which is a non-uniform magnetic field to trap an atom, we show
how to obtain a certain velocity of a Bose gas by controlling the magnetic coils. By comparing the
relationship of different current supply and delay time versus the ultimate velocity of the atom,we
theoretically predict the method of accelerating the gases to an expected velocity. This method
is of great convenience and significance for the applications in cold atom physics and precision
measurements.This work is supported by the National Fundamental Research Program
of China under Grant No. 2011CB921501
On the Optimal Batch Size for Byzantine-Robust Distributed Learning
Byzantine-robust distributed learning (BRDL), in which computing devices are
likely to behave abnormally due to accidental failures or malicious attacks,
has recently become a hot research topic. However, even in the independent and
identically distributed (i.i.d.) case, existing BRDL methods will suffer from a
significant drop on model accuracy due to the large variance of stochastic
gradients. Increasing batch sizes is a simple yet effective way to reduce the
variance. However, when the total number of gradient computation is fixed, a
too-large batch size will lead to a too-small iteration number (update number),
which may also degrade the model accuracy. In view of this challenge, we mainly
study the optimal batch size when the total number of gradient computation is
fixed in this work. In particular, we theoretically and empirically show that
when the total number of gradient computation is fixed, the optimal batch size
in BRDL increases with the fraction of Byzantine workers. Therefore, compared
to the case without attacks, the batch size should be set larger when under
Byzantine attacks. However, for existing BRDL methods, large batch sizes will
lead to a drop on model accuracy, even if there is no Byzantine attack. To deal
with this problem, we propose a novel BRDL method, called Byzantine-robust
stochastic gradient descent with normalized momentum (ByzSGDnm), which can
alleviate the drop on model accuracy in large-batch cases. Moreover, we
theoretically prove the convergence of ByzSGDnm for general non-convex cases
under Byzantine attacks. Empirical results show that ByzSGDnm has a comparable
performance to existing BRDL methods under bit-flipping failure, but can
outperform existing BRDL methods under deliberately crafted attacks
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