FTA: Stealthy and Robust Backdoor Attack with Flexible Trigger on Federated Learning

Current backdoor attacks against federated learning (FL) strongly rely on universal triggers or semantic patterns, which can be easily detected and filtered by certain defense mechanisms such as norm clipping, comparing parameter divergences among local updates. In this work, we propose a new stealthy and robust backdoor attack with flexible triggers against FL defenses. To achieve this, we build a generative trigger function that can learn to manipulate the benign samples with an imperceptible flexible trigger pattern and simultaneously make the trigger pattern include the most significant hidden features of the attacker-chosen label. Moreover, our trigger generator can keep learning and adapt across different rounds, allowing it to adjust to changes in the global model. By filling the distinguishable difference (the mapping between the trigger pattern and target label), we make our attack naturally stealthy. Extensive experiments on real-world datasets verify the effectiveness and stealthiness of our attack compared to prior attacks on decentralized learning framework with eight well-studied defenses

Robust backdoor attack against federated learning

Current backdoor attacks against federated learning (FL) strongly rely on universal triggers or semantic patterns, which can be easily detected and filtered by certain defense mechanisms such as norm clipping, comparing parameter divergences among local updates. In this work, we propose a new stealthy and robust backdoor attack with flexible triggers against FL defenses. To achieve this, we build a generative trigger function that can learn to manipulate the benign samples with an imperceptible flexible trigger pattern and simultaneously make the trigger pattern include the most significant hidden features of the attacker-chosen label. Moreover, our trigger generator can keep learning and adapt across different rounds, allowing it to adjust to changes in the global model. By filling the distinguishable difference (the mapping between the trigger pattern and target label), we make our attack naturally stealthy. Extensive experiments on real-world datasets verify the effectiveness and stealthiness of our attack compared to prior attacks on decentralized learning framework with eight well-studied defenses.Computer Science | Cyber Securit

Remote linkage of record-breaking U.S. Tornado outbreaks to the tropical cyclone in western North Pacific in December 2021

The frequency of tornadoes usually peaks during spring to summer rather than winter in climatology. However, the United States (U.S.) experienced more than 200 tornadoes in December 2021, which broke the historical record and caused 87 fatalities. Historically, the frequency of tornadoes in December tends to increase under El Niño conditions. Our results show that the monthly large-scale weather regime conducive to these record-breaking tornado outbreaks under a La Niña condition is closely associated with Typhoon Nyatoh in the western North Pacific. As the tropical cyclone (TC) recurved into the mid-latitudes, its interaction with the extratropical flows has caused distortions in the Asian jet stream and the dramatic development of anomalous anticyclone west of the dateline, which in turn strongly regulated the response of the monthly atmospheric teleconnection to La Niña forcing. Accurate forecasts of the monthly mean circulation for December 2021 first appeared in the European Center for Medium-Range Weather Forecasts sub-seasonal to seasonal forecasts from 29 November, with a forecast skill closely related to that of Typhoon Nyatoh. Given most studies on the warm seasons with frequent tornadoes, the present results advance our understanding of the TC effect on the monthly atmospheric response to El Niño-Southern Oscillation forcing and its linkage to the tornado occurrence during boreal winter

Droughts near the northern fringe of the East Asian summer monsoon in China during 1470–2003

Historical annual dry-wet index for 1470-2003 combined with instrumental precipitation since 1951 were used to identify extremely dry years and events near the northern fringe of the East Asian summer monsoon in China-the Great Bend of the Yellow River (GBYR) region. In total, 49 drought years, of which 26 were severe, were identified. Composites of the dry-wet index under the drought years show an opposite wet pattern over the Southeast China. The longest drought event lasted for 6 years (1528-1533), the second longest one 4 years (1637-1640). The most severe 2-year-long drought occurred in 1928-1929, and the two driest single years were 1900 and 1965. These persistent and extreme drought events caused severe famines and huge losses of human lives. Wavelet transform applied to the dry-wet index indicates that the severe drought years are nested in several significant dry-wet variations across multiple timescales, i.e., the 65-85 year timescale during 1600- 1800, 40-55 year timescale before 1640 and 20-35 year timescale mainly from 1550 to 1640. These timescales of dry-wet variations are discussed in relation to those forcing such as cycles of solar radiation, oscillation in the thermohaline circulation and the Pacific Decadal Oscillation (PDO). Comparing 850 hPa winds in Asia in extremely dry and wet years, it was concluded that dry-wet variability in the GBYR region strongly depends upon whether the southerly monsoon flow can reach northern China.Environmental SciencesMeteorology & Atmospheric SciencesSCI(E)EI10ARTICLE1-2373-38311

Niclosamide alleviates pathological angiogenesis in hepatopulmonary syndrome by inhibiting

Objective To investigate the effects of niclosamide on S100A4 expression and pathological angiogenesis of hepatopulmonary syndrome (HPS) in rats. Methods Thirty male SD rats were randomly divided into control group (Sham group, n=6), common bile duct ligation (CBDL) group (n=18) and niclosamide treatment group (NIC group, n=6). The rats of the NIC group were gavaged with niclosamide suspension for 1 week since the first day of the third week after modelling, and the rats were dissected at the end of the fifth week to assess the pathological changes and disease progression of liver and lung tissues by HE and Masson staining. Immunofluorescence assay was used to detect the location and intensity of S100A4 and CD31 expression in the lung of rats. The expression of S100A4 at mRNA and protein levels was detected using qPCR and Western blotting. Pulmonary microvascular endothelial cells (PMVECs) were treated with small interfering RNA (siRNA) serum of HPS rats and nichosamide, respectively, and their effects on cell migration and tube-forming abilities were observed. Results Both mRNA and protein expression of S100A4 in lung tissue of the CBDL group rats were increased with disease progression, and the expression levels were higher than those in the Sham group (P < 0.000 1); The lung mRNA and protein levels of S100A4 were lower in the NIC group than the CBDL group at the 5th week, but still higher than those in the Sham group. After knockdown of S100A4 using siRNA in PMVECs, the migration and tube-forming abilities were reduced when compared with the NC group (P < 0.000 1). HE staining displayed that pulmonary pathological changes were milder in the NIC group than the CBDL group at the 5th week, while no such effect was found in the liver tissues. Masson staining showed that hepatic fibrosis was not obviously ameliorated in the NIC group. The migration and tube-forming abilities of the cells was significantly increased in the CBDL group after the 5 weeks of serum stimulation compared to the Sham rats, while niclosamide treatment reversed this phenomenon (P < 0.000 1). Conclusion S100A4 can accelerate the progression of HPS by promoting pulmonary micro-angiogenesis in HPS rats, and niclosamide inhibits the expression of S100A4 in the lung and thus delays the progression of HPS

Roles of tropical SST patterns during two types of ENSO in modulating wintertime rainfall over southern China

The impacts of the eastern-Pacific (EP) and central-Pacific (CP) El Nino-Southern Oscillation (ENSO) on the southern China wintertime rainfall (SCWR) have been investigated. Results show that wintertime rainfall over most stations in southern China is enhanced (suppressed) during the EP (CP) El Nino, which are attributed to different atmospheric responses in the western North Pacific (WNP) and South China Sea (SCS) during two types of ENSO. When EP El Nino occurs, an anomalous low-level anticyclone is present over WNP/the Philippines region, resulting in stronger-than-normal southwesterlies over SCS. Such a wind branch acts to suppress East Asian winter monsoon (EAWM) and enhance moisture supply, implying surplus SCWR. During CP El Nino, however, anomalous sinking and low-level anticyclonic flow are found to cover a broad region in SCS. These circulation features are associated with moisture divergence over the northern part of SCS and suppressed SCWR. General circulation model experiments have also been conducted to study influence of various tropical sea surface temperature (SST) patterns on the EAWM atmospheric circulation. For EP El Nino, formation of anomalous low-level WNP anticyclone is jointly attributed to positive/negative SST anomalies (SSTA) over the central-to-eastern/ western equatorial Pacific. However, both positive and negative CP Nino-related-SSTA, located respectively over the central Pacific and WNP/SCS, offset each other and contribute a weak but broad-scale anticyclone centered at SCS. These results suggest that, besides the vital role of SST warming, SST cooling over SCS/WNP during two types of El Nino should be considered carefully for understanding the El Nino-EAWM relationship

Phase Transitions in Amorphous Germanium under Non-Hydrostatic Compression

As the pioneer semiconductor in transistor, germanium (Ge) has been widely applied in information technology for over half a century. Although many phase transitions in Ge have been reported, the complicated phenomena of the phase structures in amorphous Ge under extreme conditions are still not fully investigated. Here, we report the different routes of phase transition in amorphous Ge under different compression conditions utilizing diamond anvil cell (DAC) combined with synchrotron-based X-ray diffraction (XRD) and Raman spectroscopy techniques. Upon non-hydrostatic compression of amorphous Ge, we observed that shear stress facilitates a reversible pressure-induced phase transformation, in contrast to the pressure-quenchable structure under a hydrostatic compression. These findings afford better understanding of the structural behaviors of Ge under extreme conditions, which contributes to more potential applications in the semiconductor field

Cholangiocyte-derived exosomal long noncoding RNA PICALM-AU1 promotes pulmonary endothelial cell endothelial-mesenchymal transition in hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a severe lung injury caused by chronic liver disease, with limited understanding of the disease pathology. Exosomes are important mediators of intercellular communication that modulates various cellular functions by transferring a variety of intracellular components to target cells. Our recent studies have indicated that a new long noncoding RNA (lncRNA), PICALM-AU1, is mainly expressed in cholangiocytes, and is dramatically induced in the liver during HPS. However, the mechanism by which cholangiocyte-derived PICALM-AU1 regulates Endothelial-mesenchymal transition (EndMT) in HPS remains unclear. Here, we observed that PICALM-AU1 was synthesized in the cholangiocytes of the liver and then, secreted as exosomes into the serum; serum exosomal PICALM-AU1 levels were positively correlated with the severity of HPS in a rat model and in human patients. PICALM-AU1 carrying serum exosomes induced the EndMT of pulmonary microvascular endothelial cells (PMVECs) and promoted lung injury in vivo and in vitro. Furthermore, PICALM-AU1 acted as a molecular sponge for microRNA 144-3p (miR144-3p), resulting in the up-regulation of Zinc Finger E-Box Binding Homeobox 1 (ZEB1), a known target of EndMT and enhancement of EndMT, proliferation and migration of PMVECs. Taken together, our findings indicate that the cholangiocyte-derived exosomal lncRNA PICALM-AU1 plays a critical role in the EndMT in HPS lungs. Thus, it represents a potential therapeutic target for the treatment of HPS