Stability and Generalization for Minibatch SGD and Local SGD

The increasing scale of data propels the popularity of leveraging parallelism to speed up the optimization. Minibatch stochastic gradient descent (minibatch SGD) and local SGD are two popular methods for parallel optimization. The existing theoretical studies show a linear speedup of these methods with respect to the number of machines, which, however, is measured by optimization errors. As a comparison, the stability and generalization of these methods are much less studied. In this paper, we study the stability and generalization analysis of minibatch and local SGD to understand their learnability by introducing a novel expectation-variance decomposition. We incorporate training errors into the stability analysis, which shows how small training errors help generalization for overparameterized models. We show both minibatch and local SGD achieve a linear speedup to attain the optimal risk bounds

Precision Higgs physics at the CEPC

The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider~(CEPC) is one of such proposed Higgs factories. The CEPC is an $e^+e^-$ circular collider proposed by and to be hosted in China. Located in a tunnel of approximately 100~km in circumference, it will operate at a center-of-mass energy of 240~GeV as the Higgs factory. In this paper, we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements.Comment: 46 pages, 37 figure

A Non-Interactive Attribute-Based Access Control Scheme by Blockchain for IoT

As an important method of protecting data confidentiality in the Internet of Things (IoT), access control has been widely concerned. Because attribute-based access control mechanisms are dynamic, it is not only suitable to solve the dynamic access problem in IoT, but also to deal with the dynamic caused by node movement and access data change. The traditional centralized attribute-based access control mechanism has some problems: due to the large number of devices in IoT, the central trusted entity may become the bottleneck of the whole system. Moreover, when a central trusted entity is under distributed denial-of-service (DDoS) attack, the entire system may crash. Blockchain is a good way to solve the above problems. Therefore, we developed a non-interactive, attribute-based access control scheme that applies blockchain technology in IoT scenarios by using PSI technology. In addition, the attributes of data user and data holder are hidden, which protects the privacy of both parties’ attributes and access policy. Furthermore, the experimental results indicate that our scheme has high efficiency

Surface-induced gas-phase redistribution effects in plasma-catalytic dry reforming of methane : numerical investigation by fluid modeling

Plasma catalysis is an emerging process electrification technology for industry decarbonization. Plasma-catalytic dry reforming of methane relies on the mutual effects of the plasma and the catalyst leading to the higher chemical conversion efficiency. The effects of catalyst surfaces on the plasma are predicted to play a major role, yet they remain unexplored. Here, a 1D plasma fluid model combined with 0D surface kinetics is developed to reveal how the surface reactions on platinum (Pt) catalyst affect the redistribution of the gas-phase particles. Two contrasting models with and without the surface kinetics as well as the Spearman rank correlation coefficients are used to quantify the effect of the key species (H, CH, CH2) on the CO generation. Advancing the common knowledge that Pt catalyst can influence the plasma chemistry directly by changing the surface loss/production of particles, this study reveals that the catalyst can also affect the spatial distributions of active species, thereby influencing the plasma chemistry in an indirect way. This result goes beyond the existing state-of-the-art which commonly relies on over-simplified 0D models which cannot resolve the spatial distribution. Further analysis indicates that the species spatial redistribution is driven by the dynamic catalyst surface adsorption-desorption processes. This work enables the previously elusive account of active species redistribution and may open new opportunities for plasma-catalytic sustainable chemical processes.</p

Synthesis of core-shell Au-Pt nanodendrites with high catalytic performance via overgrowth of platinum on in situ gold nanoparticles

We present a simple and effective strategy for high yield synthesis of well-dispersed, core-shell Au-Pt nanodendrites (CS Au-Pt NDs) via overgrowth of platinum on in situ 5.5 nm gold nanoparticles in water at room temperature. The sizes of the resulting CS Au-Pt NDs are 14 nm, which should be the smallest so far to the best of our knowledge. The average dimensions of the small Pt branches on the Au nanoparticle surfaces are about 2.6 nm × 4.2 nm, which lead to a significantly increased electrochemically active surface area (up to 35.2 m2 g-1). It is found that the morphology of CS Au-Pt NDs is dependent on the reaction conditions such as the incubation time of citrate-HAuCl4 solution, the mixing time of citrate-HAuCl4-K2PtCl4 solution before AA addition, and Pt-to-Au and AA-to-Pt molar ratios. In comparison with commercial Pt black (0.12 A mgPd-1), the resulting Au-Pt5 NDs show a superior catalytic activity towards methanol oxidation (0.45 A mgPd-1) due to the electronic interaction between the Au cores and Pt branches in bimetallic Au-Pt NDs and the high fraction of atomic steps, kinks, and corner atoms on the surfaces of the Pt branches

Expression of hypoxia-inducing factor-1α and matrix metalloproteinase-9 in the recipient parasylvian cortical arteries with different hemodynamic sources in adult moyamoya disease

ObjectiveIn our latest research, we have demonstrated that the recipient parasylvian cortical arteries (PSCAs) with hemodynamic sources from the middle cerebral artery (M-PSCAs) has a higher risk of postoperative cerebral hyperperfusion (CHP) syndrome than those from non-M-PSCAs in adult moyamoya disease (MMD) patient. However, whether there are differences between M-PSCAs and non-M-PSCAs in vascular specimens characteristics has not been studied. In this study, we further investigate the vascular specimen of recipient PSCAs by histological and immunohistochemical methods.Methods50 vascular specimens of recipient PSCAs were obtained from 50 adult MMD patients during the combined bypass surgeries in our departments of Zhongnan hospital. 4 recipient PSCAs samples were also obtained in the same way from the middle cerebral artery occlusion patients. The samples were received the pathological sectioning, hematoxylin and eosin staining, and immunohistochemistry, then the vascular wall thickness, matrix metalloproteinase-9 (MMP-9) and hypoxia-inducing factor-1α (HIF-1α) were analyzed.ResultsM-PSCAs adult MMD patients had a thinner intima than non-M-PSCAs in the recipient PSCAs specimens. In recipient non-M-PSCAs vascular specimens, the immunoreactivity indicating HIF-1α and matrix metalloproteinase-9 (MMP-9) was significantly higher than M-PSCAs groups. The logistic regression analyses showed that the M-PSCAs was an independent risk factor of postoperative cerebral hyperperfusion (CHP) syndrome (OR 6.235, 95% CI1.018-38.170, P = 0.048) in MMD.ConclusionOur results indicate that M-PSCAs adult MMD patients had thinner intima than non-MCAs adult MMD patients in the PSCAs. More importantly, HIF-1α and MMP-9 were overexpressed in non-M-PSCAs vascular specimens

Effect of subsequent bladder cancer on survival in upper tract urothelial carcinoma patients post-radical nephroureterectomy: a systematic review and meta-analysis

Abstract Background Radical nephroureterectomy (RNU) is the primary treatment strategy for upper tract urothelial carcinoma (UTUC). However, the intravesical recurrence occurs in 20–50% of all patients. The specific effect of subsequent bladder cancer (SBCa) on survival remains unclear. Therefore, we investigated the effect of SBCa following RNU in patients with UTUC. Methods PubMed, EMBASE, and Cochrane Library were exhaustively searched for studies comparing oncological outcomes between SBCa and without SBCa. Standard cumulative analyses using hazard ratios (HR) with 95% confidence intervals (CI) were performed using Review Manager (version 5.3). Results Five studies involving 2057 patients were selected according to the predefined eligibility criteria. Meta-analysis of cancer-specific survival (CSS) and overall survival (OS) revealed no significant differences between the SBCa and non-SBCa groups. However, subgroup analysis of pT0-3N0M0 patients suggested that people with SBCa had worse CSS (HR = 5.13, 95%CI 2.39–10.98, p < 0.0001) and OS (HR = 4.00, 95%CI 2.19–7.31, p < 0.00001). Conclusions SBCa appears to be associated with worse OS in patients with early stage UTUC. However, caution must be taken before recommendations are made because this interpretation is based on very few clinical studies and a small sample size. Research sharing more detailed surgical site descriptions, as well as enhanced outcome data collection and improved reporting, is required to further investigate these nuances