Echo-CGC: A Communication-Efficient Byzantine-Tolerant Distributed Machine Learning Algorithm in Single-Hop Radio Network

In the past few years, many Byzantine-tolerant distributed machine learning (DML) algorithms have been proposed in the point-to-point communication model. In this paper, we focus on a popular DML framework - the parameter server computation paradigm and iterative learning algorithms that proceed in rounds, e.g., [Gupta and Vaidya, 2020; El-Mhamdi et al., 2020; Chen et al., 2017]. One limitation of prior algorithms in this domain is the high communication complexity. All the Byzantine-tolerant DML algorithms that we are aware of need to send n d-dimensional vectors from worker nodes to the parameter server in each round, where n is the number of workers and d is the number of dimensions of the feature space (which may be in the order of millions). In a wireless network, power consumption is proportional to the number of bits transmitted. Consequently, it is extremely difficult, if not impossible, to deploy these algorithms in power-limited wireless devices. Motivated by this observation, we aim to reduce the communication complexity of Byzantine-tolerant DML algorithms in the single-hop radio network [Alistarh et al., 2010; Bhandari and Vaidya, 2005; Koo, 2004]. Inspired by the CGC filter developed by Gupta and Vaidya, PODC 2020 [Gupta and Vaidya, 2020], we propose a gradient descent-based algorithm, Echo-CGC. Our main novelty is a mechanism to utilize the broadcast properties of the radio network to avoid transmitting the raw gradients (full d-dimensional vectors). In the radio network, each worker is able to overhear previous gradients that were transmitted to the parameter server. Roughly speaking, in Echo-CGC, if a worker "agrees" with a combination of prior gradients, it will broadcast the "echo message" instead of the its raw local gradient. The echo message contains a vector of coefficients (of size at most n) and the ratio of the magnitude between two gradients (a float). In comparison, the traditional approaches need to send n local gradients in each round, where each gradient is typically a vector in a ultra-high dimensional space (d ? n). The improvement on communication complexity of our algorithm depends on multiple factors, including number of nodes, number of faulty workers in an execution, and the cost function. We numerically analyze the improvement, and show that with a large number of nodes, Echo-CGC reduces 80% of the communication under standard assumptions

Brief Announcement: Reaching Approximate Consensus When Everyone May Crash

Fault-tolerant consensus is of great importance in distributed systems. This paper studies the asynchronous approximate consensus problem in the crash-recovery model with fair-loss links. In our model, up to f nodes may crash forever, while the rest may crash intermittently. Each node is equipped with a limited-size persistent storage that does not lose data when crashed. We present an algorithm that only stores three values in persistent storage - state, phase index, and a counter

Small interference RNA targeting tissue factor inhibits human lung adenocarcinoma growth in vitro and in vivo

<p>Abstract</p> <p>Background</p> <p>The human coagulation trigger tissue factor (TF) is overexpressed in several types of cancer and involved in tumor growth, vascularization, and metastasis. To explore the role of TF in biological processes of lung adenocarcinoma, we used RNA interference (RNAi) technology to silence TF in a lung adenocarcinoma cell line A549 with high-level expression of TF and evaluate its antitumor effects in vitro and in vivo.</p> <p>Methods</p> <p>The specific small interfering RNA (siRNA) designed for targeting human TF was transfected into A549 cells. The expression of TF was detected by reverse transcription-PCR and Western blot. Cell proliferation was measured by MTT and clonogenic assays. Cell apoptosis was assessed by flow cytometry. The metastatic potential of A549 cells was determined by wound healing, the mobility and Matrigel invasion assays. Expressions of PI3K/Akt, Erk1/2, VEGF and MMP-2/-9 in transfected cells were detected by Western blot. In vivo, the effect of TF-siRNA on the growth of A549 lung adenocarcinoma xenografts in nude mice was investigated.</p> <p>Results</p> <p>TF -siRNA significantly reduced the expression of TF in the mRNA and protein levels. The down-regulation of TF in A549 cells resulted in the suppression of cell proliferation, invasion and metastasis and induced cell apoptosis in dose-dependent manner. Erk MAPK, PI3K/Akt pathways as well as VEGF and MMP-2/-9 expressions were inhibited in TF-siRNA transfected cells. Moreover, intratumoral injection of siRNA targeting TF suppressed the tumor growth of A549 cells in vivo model of lung adenocarcinoma.</p> <p>Conclusions</p> <p>Down-regulation of TF using siRNA could provide a potential approach for gene therapy against lung adenocarcinoma, and the antitumor effects may be associated with inhibition of Erk MAPK, PI3K/Akt pathways.</p

Characteristics and Influencing Factors of Size-Fractionated Chlorophyll-a in Litopenaeus vannamei Mariculture Ponds

Aquaculture in large water bodies has become an important culture mode of Litopenaeus vannamei in coastal waters. Fractionated chlorophyll-a (Chl-a) and environmental factors of the large water ponds with high salinity (54, n=3) and the control ponds (32, n=3) were investigated from May to July 2020 to explore the variations in Chl-a, phytoplankton particle size, and the response to environmental factors during the aquaculture season. Pearson correlation analysis was performed to analyze the relationship between the environmental factors and the size-fractionated Chl-a concentration. Partial redundancy analysis (RDA) was applied to assess the effects of environmental factors (including silicate, active phosphate, ammonia salt, nitrite, nitrate, water temperature, salinity, dissolved organic nitrogen, and dissolved organophosphorus) on total Chl-a, Chl-a of micro phytoplankton (micro Chl-a), Chl-a of nano phytoplankton (nano Chl-a), and Chl-a of pico phytoplankton (pico Chl-a). The following results were obtained:1) Diurnal variation of Chl-a: Total Chl-a of the high-salinity group showed no significant diurnal variation (P > 0.05). Total Chl-a of the control group showed significant diurnal change in May and June (P 0.05). Pico Chl-a, nano Chl-a, and micro Chl-a of the control group in July were significantly higher than those in May and June (P 0.05).3) Contribution of size-fractionated phytoplankton in high-salinity and control groups: The contribution of micro Chl-a, nano Chl-a, and pico Chl-a to total Chl-a in the high-salinity group were (15.64±0.16)%, (73.81±0.13)%, and (10.55±0.06)%, respectively. Nano Chl-a was dominant in May, June, and July. The contribution of pico Chl-a increased from 6.43% in May to 16.81% in July, and exceeded that of micro Chl-a. The contributions of micro Chl-a, nano Chl-a, and pico Chl-a to total Chl-a in the control group were (52.29±0.10)%, (41.82±0.10)%, and (5.59±0.01)%, respectively. Micro Chl-a concentration had a major advantage in May and June, accounting for 59.64% and 57.49%, respectively. Nano Chl-a concentration accounted for 35.46% and 36.90%, respectively. By July, nano Chl-a had a major advantage, contributing to 53.09%.4) Pearson correlation analysis showed no significant correlation between the diurnal variation of Chl-a and the environmental factors of the high-salinity group in May and June (P < 0.05). Yet, the concentrations of nano Chl-a and total Chl-a were negatively correlated with the concentration of nitrate in July (P < 0.05). The concentrations of micro Chl-a and total Chl-a were positively correlated with those of silicate (P < 0.05). For the control group, Pearson correlation analysis showed a significant positive correlation between nano Chl-a and water temperature (P < 0.05). Total Chl-a and phosphate were negatively correlated in May (P < 0.05). There was a significant negative correlation between pico Chl-a and nitrate in July (P < 0.05).5) For the high-salinity group, RDA revealed a significant positive correlation between Chl-a and water temperature, and the contribution of nano Chl-a increased with the increase in temperature. Total Chl-a was positively correlated with silicate and negatively correlated with phosphate, dissolved organic nitrogen, and dissolved organophosphorus in the high-salinity group. For the control group, RDA showed that total Chl-a was positively correlated with dissolved organic nitrogen and negatively correlated with silicate and nitrite. In general, Chl-a in high-salinity ponds has a small diurnal variation, and the phytoplankton particle size gradually decreased with cultivation, which may be caused by the increasing temperature and high organic nitrogen concentration

Refining the late-Holocene coastline and delta development of the northern Yangtze River delta : combining historical archives and OSL dating

Historical documents provide a general chronological overview of the environmental evolution of the Yangtze River delta (YRD) during the last ca. 2000 years; however, absolute dating of the region’s late Holocene sediment is relatively rare. Optically stimulated luminescence (OSL) dating has been increasingly applied to the age determination of Holocene deposits in deltaic environments. In this study, three 23–27 m long drill cores running from south to north were collected from the Qihai plain of the northern YRD in order to reconstruct the history of this region’s formation since the late Holocene. A total of 24 samples from the three cores were subjected to OSL dating using coarse silt-sized (45–63 μm) quartz. The OSL ages range from approximately 190–3490 a revealing that the age of the delta front and delta plain facies in the coring sites are younger than 500 a while the sediments in the underlying prodelta facies are older than 2000 a. On the basis of the large age gap between the two set of deposits, we suspect that the coring sites remained submerged from 2000 to 500 years ago. As the central core has older and coarser sandy deposits than the neighbouring cores, we infer that the central core was located on a sandy mouth bar, while other cores sat within distributary channels within the estuary. The OSL ages are consistent with both the chronology implied by historical documents and other stratigraphic records in the area. This study enhances the chronological framework of land formation and delta evolution in the Qihai plain area of the YRD and thereby consolidates the conclusions derived from the application of a single technique alone