BAGEL: Backdoor Attacks against Federated Contrastive Learning

Federated Contrastive Learning (FCL) is an emerging privacy-preserving paradigm in distributed learning for unlabeled data. In FCL, distributed parties collaboratively learn a global encoder with unlabeled data, and the global encoder could be widely used as a feature extractor to build models for many downstream tasks. However, FCL is also vulnerable to many security threats (e.g., backdoor attacks) due to its distributed nature, which are seldom investigated in existing solutions. In this paper, we study the backdoor attack against FCL as a pioneer research, to illustrate how backdoor attacks on distributed local clients act on downstream tasks. Specifically, in our system, malicious clients can successfully inject a backdoor into the global encoder by uploading poisoned local updates, thus downstream models built with this global encoder will also inherit the backdoor. We also investigate how to inject backdoors into multiple downstream models, in terms of two different backdoor attacks, namely the \textit{centralized attack} and the \textit{decentralized attack}. Experiment results show that both the centralized and the decentralized attacks can inject backdoors into downstream models effectively with high attack success rates. Finally, we evaluate two defense methods against our proposed backdoor attacks in FCL, which indicates that the decentralized backdoor attack is more stealthy and harder to defend

Selection of Surgical Modality for Massive Splenomegaly in Children

BACKGROUND: Laparoscopic splenectomy (LS), a treatment for both benign and malignant splenic diseases, can prove technically challenging in patients with massive splenomegaly. In particular, the optimal surgical modality for treating massive splenomegaly in children remains controversial. METHODS: The clinicopathologic data of 289 pediatric patients undergoing splenectomy for massive splenomegaly were studied in a retrospective analysis. Accordingly, the patients were classified into the LS surgery group and open splenectomy (OS) surgery group. In the laparoscopy cohort, they were separated into two subgroups according to the method of surgery: the multi-incision laparoscopic splenectomy (MILS) and the single-incision laparoscopic splenectomy (SILS) surgery groups, respectively. Patient demographics, clinical data, surgery, complications, and postoperative recovery underwent analysis. Concurrently, we compared the risk of adverse laparoscopic splenectomy outcomes utilizing univariable and multivariable logistic regression. RESULTS: The total operation time proved remarkably shorter in the OS group in contrast to the LS group (149.87 ± 61.44 versus 188.20 ± 52.51 min, P \u3c 0.001). Relative to the OS group, the LS group exhibited lowered postoperative pain scores, bowel recovery time, and postoperative hospitalization time (P \u3c 0.001). No remarkable difference existed in post-operation complications or mortality (P \u3e 0.05). Nevertheless, the operation duration was remarkably longer in the SILS surgery group than in the MILS surgery group (200 ± 46.11 versus 171.39 ± 40.30 min, P = 0.02). Meanwhile, the operative duration of MILS and SILS displayed a remarkable positive association with splenic length. Moreover, the operative duration of SILS displayed a remarkable positive association with the age, weight, and height of the sick children. Splenic length proved an independent risk factor of adverse outcomes (P \u3c 0.001, OR 1.378). CONCLUSIONS: For pediatric patients with massive splenomegaly who can tolerate prolonged anesthesia and operative procedures, LS surgery proves the optimal treatment regimen. SILS remains a novel surgery therapy which may be deemed a substitutional surgery approach for treating massive splenomegaly

Spatiotemporal heterogeneity and impact factors of hepatitis B and C in China from 2010 to 2018: Bayesian space–time hierarchy model

IntroductionViral hepatitis is a global public health problem, and China still faces great challenges to achieve the WHO goal of eliminating hepatitis.MethodsThis study focused on hepatitis B and C, aiming to explore the long-term spatiotemporal heterogeneity of hepatitis B and C incidence in China from 2010 to 2018 and quantify the impact of socioeconomic factors on their risk through Bayesian spatiotemporal hierarchical model.ResultsThe results showed that the risk of hepatitis B and C had significant spatial and temporal heterogeneity. The risk of hepatitis B showed a slow downward trend, and the high-risk provinces were mainly distributed in the southeast and northwest regions, while the risk of hepatitis C had a clear growth trend, and the high-risk provinces were mainly distributed in the northern region. In addition, for hepatitis B, illiteracy and hepatitis C prevalence were the main contributing factors, while GDP per capita, illiteracy rate and hepatitis B prevalence were the main contributing factors to hepatitis C.DisussionThis study analyzed the spatial and temporal heterogeneity of hepatitis B and C and their contributing factors, which can serve as a basis for monitoring efforts. Meanwhile, the data provided by this study will contribute to the effective allocation of resources to eliminate viral hepatitis and the design of interventions at the provincial level

Virulence Determinants Are Required for Brain Abscess Formation Through Staphylococcus aureus Infection and Are Potential Targets of Antivirulence Factor Therapy

Bacterial brain abscesses (BAs) are difficult to treat with conventional antibiotics. Thus, the development of alternative therapeutic strategies for BAs is of high priority. Identifying the virulence determinants that contribute to BA formation induced by Staphylococcus aureus would improve the effectiveness of interventions for this disease. In this study, RT-qPCR was performed to compare the expression levels of 42 putative virulence determinants of S. aureus strains Newman and XQ during murine BA formation, ear colonization, and bacteremia. The alterations in the expression levels of 23 genes were further confirmed through specific TaqMan RT-qPCR. Eleven S. aureus genes that persistently upregulated expression levels during BA infection were identified, and their functions in BA formation were confirmed through isogenic mutant experiments. Bacterial loads and BA volumes in mice infected with isdA, isdC, lgt, hla, or spa deletion mutants and the hla/spa double mutant strain were lower than those in mice infected with the wild-type Newman strain. The therapeutic application of monoclonal antibodies against Hla and SpA decreased bacterial loads and BA volume in mice infected with Newman. This study provides insights into the virulence determinants that contribute to staphylococcal BA formation and a paradigm for antivirulence factor therapy against S. aureus infections

The Gender Gap in Household Bargaining Power: A Revealed-Preference Approach

When members of the same household have different risk preferences, whose preference matters more for investment decisions and why? We propose an intrahousehold model that aggregates individual preferences at the household level as a result of bargaining. We structurally estimate the model, analyze the determinants of bargaining power, and find a significant gender gap. The gap is partially explained by gender differences in individual characteristics, but it is also driven by gender effects. These patterns hold broadly across Australia, Germany, and the US. We further link the distribution of bargaining power to perceived gender norms in the cross-section of households.the British Academy (Grant SRG1920\101488) and the Keynes Fund at Cambridge for financial support. Also support from Cambridge Endowment for Research in Finance (CERF)

Insight into the C8 light hydrocarbon compositional differences between coal-derived and oil-associated gases

To analyze the C8 light hydrocarbon of absorbed gas in the source rock and natural gas, both the PY-GC and GC were applied. This is done in order to develop the discrimination parameters of different genetic gases. Eight samples, including six mudstones with type II1 and type I organic matter and two coals, were analyzed by PY-GC. On the other hand, the sixteen typical coal-derived gases and sixteen oil-associated gases were analyzed by GC. The results show that there exists a great difference in the ratio of 2-methylheptane and 1-cis-3-dimethylcyclohexane in coal-derived gases, oil-associated gases, and source rock absorbed gases. The ratio in coal-derived gases is less than 0.5, whereas it is higher than 0.5 in oil-associated gases. In addition, there are also differences in the relative composition of C8 normal alkanes, isoparaffin, and cycloparaffin in coal-derived and oil-associated gases. Coal-derived gas is characterized by high cycloparaffin content that is generally higher than 40%, while the oil-associated gas exhibits low cycloparaffin content that generally less than 40%, as well as high isoparaffin content. Therefore, these parameters can be used to identify a coal-derived gas from an oil-associated gas. Keywords: C8 light hydrocarbons, Coal-derived gas, Oil-associated ga