Gang Liang

Today’s Internet is a massive, distributed network which continues to explode in size as e-commerce and related activities grow. The heterogeneous and largely unregulated structure of the Internet renders tasks such as dynamic routing, optimized service provision, service level verification and detection of anomalous/malicious behavior extremely challenging. The problem is compounded by the fact that one cannot rely on the cooperation of individual servers and routers to aid in the collection of network traffic measurements vital for these tasks. In many ways, network monitoring and inference problems bear a strong resemblance to other “inverse problems” in which key aspects of a system are not directly observable. Familiar signal processing or statistical problems such as tomographic image reconstruction and phylogenetic tree identification have interesting connections to those arising in networking. This article introduces network tomography, a new field which we believe will benefit greatly from the wealth of statistical theory and algorithms. It focuses especially on recent developments in the field including the application of pseudo-likelihood methods and tree estimation formulations.

In recent years, microblog systems such as Twitter and Sina Weibo have averaged multimillion active users. On the other hand, the microblog system has become a new means of rumor-spreading platform. In this paper, we investigate the machine-learning-based rumor identification approaches. We observed that feature design and selection has a stronger impact on the rumor identification accuracy than the selection of machine-learning algorithms. Meanwhile, the rumor publishers' behavior may diverge from normal users', and a rumor post may have different responses from a normal post. However, mass behavior on rumor posts has not been explored adequately. Hence, we investigate rumor identification schemes by applying five new features based on users' behaviors, and combine the new features with the existing well-proved effective user behavior-based features, such as followers' comments and reposting, to predict whether a microblog post is a rumor. Experiment results on real-world data from Sina Weibo demonstrate the efficacy and efficiency of our proposed method and features. From the experiments, we conclude that the rumor detection based on mass behaviors is more effective than the detection based on microblogs' inherent features.

OBJECTIVE: Percutaneous vertebroplasty (PVP) and kyphoplasty (PKP) have been widely used to treat osteoporotic vertebral compression fractures (OVCF), but the risk of vertebral re-fracture after PVP/PKP remains controversial. This study aims to investigate the incidence and risk factors of vertebral re-fracture after PVP/PKP. METHODS: Relevant literatures published up to November 2021 were collected from PubMed, Embase and Web of Science. A meta-analysis was performed to extract data associated with risk factors of SVCF following the PRISMA guidelines. Also, pooled odds ratio (OR) or weighted mean difference (WMD) with 95% confidence interval (CI) was calculated. RESULTS: A total of 23 studies, encompassing 9372 patients with OVCF, met the inclusion criteria. 1255 patients (13.39%) suffered re-fracture after PVP/PKP surgery. A total of 22 studies were from Eastern Asia and only 1 study was from Europe. Female sex (OR = 1.34, 95%CI 1.09-1.64, P = 0.006), older age (WMD = 2.04, 95%CI 0.84-3.24, P = 0.001), lower bone mineral density (BMD, WMD = - 0.38, 95%CI - 0.49-0.26, P < 0.001) and bone cement leakages (OR = 2.05, 95% CI 1.40-3.00, P < 0.001) increased the risk of SVCF. The results of subgroup analysis showed the occurrence of re-fracture was significantly associated with gender (P = 0.002), age (P = 0.001) and BMD (P < 0.001) in Eastern Asia. Compared with the unfractured group, anterior-to-posterior vertebral body height ratio (AP ratio, WMD = 0.06, 95%CI 0.00-0.12, P = 0.037) and visual analog scale score (VAS, WMD = 0.62, 95%CI 0.09-1.15, P = 0.022) were higher in the refracture group, and kyphotic angle correction ratio (Cobb ratio, WMD = - 0.72, 95%CI - 1.26-0.18, P = 0.008) was smaller in Eastern Asia. In addition, anti-osteoporosis treatment (OR = 0.40, 95% CI 0.27-0.60, P < 0.001) could be a protective factor. CONCLUSION: The main factors associated with re-fracture after PVP/PKP are sex, age, bone mineral density, AP ratio, Cobb ratio, VAS score, bone cement leakage and anti-osteoporosis treatment, especially in Eastern Asia.

An approach to model order determination based on the minimum description length (MDL) criterion is proposed and shown to depend on the minimum eigenvalues of a covariance matrix derived from the observed data. A selection procedure for estimating the model order by means of the MDL method is proposed. Examples are given to illustrate the significantly improved accuracy of the technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Cysteine (C)-X-C motif chemokine receptor 4 (CXCR4), the primary receptor for stromal cell-derived factor-1 (SDF-1), is involved in bone morphogenic protein 2 (BMP2)-induced osteogenic differentiation of mesenchymal progenitors. To target the in vivo function of CXCR4 in bone and explore the underlying mechanisms, we conditionally inactivated CXCR4 in osteoprecursors by crossing osterix (Osx)-Cre mice with floxed CXCR4 (CXCR4(fl/fl)) mice to generate knock-outs with CXCR4 deletion driven by the Osx promoter (Osx::CXCR4(fl/fl)). The Cre-mediated excision of CXCR4 occurred exclusively in bone of Osx::CXCR4(fl/fl) mice. When compared with littermate controls, Osx::CXCR4(fl/fl) mice developed smaller osteopenic skeletons as evidenced by reduced trabecular and cortical bone mass, lower bone mineral density, and a slower mineral apposition rate. In addition, Osx::CXCR4(fl/fl) mice displayed chondrocyte disorganization in the epiphyseal growth plate associated with decreased proliferation and collagen matrix syntheses. Moreover, mature osteoblast-related expression of type I collagen α1 and osteocalcin was reduced in bone of Osx::CXCR4(fl/fl) mice versus controls, suggesting that CXCR4 deficiency results in arrested osteoblast progression. Primary cultures for osteoblastic cells derived from Osx::CXCR4(fl/fl) mice also showed decreased proliferation and impaired osteoblast differentiation in response to BMP2 or BMP6 stimulation, and suppressed activation of intracellular BMP receptor-regulated Smads (R-Smads) and Erk1/2 was identified in CXCR4-deficient cells and bone tissues. These findings provide the first in vivo evidence that CXCR4 functions in postnatal bone development by regulating osteoblast development in cooperation with BMP signaling. Thus, CXCR4 acts as an endogenous signaling component necessary for bone formation.