Validation of Shear‐Wave Velocity Models of the Pacific Northwest

Four surface‐wave tomographic models in the Pacific Northwest and a combined CRUST2.0 and AK135 model are tested and validated systematically. Synthetic Green’s functions calculated with the models using a finite‐difference method are compared with empirical Green’s functions at periods of 7–50 s. To ensure high‐quality signals, empirical Green’s functions are extracted from the ambient noise cross correlation of vertical‐to‐vertical components between station pairs that have up to a decade of recorded data. The observed and synthetic Green’s functions are cross correlated at multiple frequency bands to determine phase delay times and cross‐correlation coefficients. The delay time predicted by the CRUST2.0 and AK135 model is predominantly positive and is linearly dependent on interstation distance, indicating that the combined model is, on average, too fast for the Pacific Northwest. Among the four shear‐wave velocity models, CUB and one model derived from regional tomography exhibit moderately and weakly negative linear trends, respectively, between the delay time and interstation distance, a result indicative of a slower‐than‐actual velocity. The delay times of the other two models are normally distributed with an approximately zero mean and without any apparent relationship with interstation distance. The cross‐correlation coefficients are more scattered at short periods, reflecting unresolved heterogeneities of the crust structure in these models. The misfit between the empirical Green’s functions and synthetic waveforms suggests the need for a better‐resolved crust and uppermost mantle velocity model, which is critical for the precise estimate of ground motion for seismic hazard evaluation and understanding of the tectonic processes of the Pacific Northwest

Upper Mantle Structure of the Cascades from Full-Wave Ambient Noise Tomography: Evidence for 3D Mantle Upwelling in the Back-Arc

Melt generation and volcanism at subduction zones may result from several possible processes: hydration of the mantle wedge by fluid released from the slab, subduction-induced mantle upwelling beneath the back-arc, and heating of downgoing sediments/oceanic crust atop the slab. Each process predicts a distinctly different spatial pattern of melt generation and can thus be distinguished with high-resolution seismic imaging. Here we construct an upper mantle model of the Pacific Northwest using a full-wave ambient noise tomographic method. Normalized vertical components of continuous seismic records at station pairs are cross-correlated to extract empirical Green\u27s functions at periods of 7–200 s. We simulate wave propagation within the 3D Earth structure using a finite-difference method and calculate sensitivity kernels of Rayleigh waves to perturbations of VpVp and VsVs based on the Strain Green\u27s Tensor database. Phase delays are extracted by cross-correlating the observed and synthetic waveforms at multiple frequency bands. Our tomographic result reveals three separate low shear-wave velocity anomalies along the back-arc in the upper mantle ∼200 km east of the Cascade volcanic arc, with the central one being the largest in size and lowest in velocity. These back-arc low-velocity anomalies are spatially correlated with the three arc-volcano clusters. The geometry of the low-velocity volumes relative to the slab and arc is consistent with the pattern of subduction-induced decompressional melting in the back-arc. Their along-strike variation suggests that the large-scale plate-motion-induced flow in the back-arc mantle wedge is modulated by small-scale convection, resulting in a highly 3D process that defines the segmentation of volcanism along the Cascade arc

A Preliminary Full‐Wave Ambient‐Noise Tomography Model Spanning from the Juan de Fuca and Gorda Spreading Centers to the Cascadia Volcanic Arc

The Cascadia Initiative (CI) Amphibious Array provides us an unprecedented opportunity to investigate seismologically the formation, alteration, and subduction of the downgoing Juan de Fuca and Gorda plates, as well as the fore‐arc and volcanic arc (Fig. 1). Formed at the spreading center, the oceanic crust undergoes normal faulting near the ridge axis. As the plate cools and moves away from the spreading center, the thermal stress and forces at the plate boundaries and the base of the plate may cause faulting and deformation in the plate interior. Near the subduction trench, the plate bends, forming cracks in the upper plate (e.g., Ranero et al., 2003). The faults and cracks provide pathways for fluid to penetrate deep into the crust and possibly mantle lithosphere (e.g., Nedimović et al., 2009), causing chemical reactions that alter the composition of the plate, including serpentinization of the mantle lithosphere (Melson and Thompson, 1971). As the plate subducts, fluid within the plate and in the entrained sediment is released progressively with increasing pressure and temperature, affecting the rheology and fault behavior at and near the plate interface and resulting in partial melting in the mantle wedge and volcanism along the arc (Ranero et al., 2003). To understand subduction zones, we must have a clear and complete picture of the fore‐arc structure and the incoming plate at the trench, which in turn requires a good understanding of the interior of the plate

Towards Deadline Guaranteed Cloud Storage Services

More and more organizations move their data and workload to commercial cloud storage systems. However, the multiplexing and sharing of the resources in a cloud storage system present unpredictable data access latency to tenants, which may make online data-intensive applications unable to satisfy their deadline requirements. Thus, it is important for cloud storage systems to provide deadline guaranteed services. In this paper, to meet a current form of service level objective (SLO) that constrains the percentage of each tenant\u27s data access requests failing to meet its required deadline below a given threshold, we build a mathematical model to derive the upper bound of acceptable request arrival rate on each server. We then propose a Deadline Guaranteed storage service (called DGCloud) that incorporates three algorithms. Its deadline-aware load balancing scheme redirects requests and creates replicas to release the excess load of each server beyond the derived upper bound. Its workload consolidation algorithm tries to maximally reduce servers while still satisfying the SLO to maximize the resource utilization. Its data placement optimization algorithm re-schedules the data placement to minimize the transmission cost of data replication. Our trace-driven experiments in simulation and Amazon EC2 show the higher performance of DGCloud compared with previous methods in terms of deadline guarantees and system resource utilization, and the effectiveness of its individual algorithms

Preparation and Photocatalytic Properties of SnO 2

SnO2 nanoparticles coated on nitrogen-doped carbon nanotubes were prepared successfully via a simple wet-chemical route. The as-obtained SnO2/CNx composites were characterized using X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The photocatalytic activity of as-prepared SnO2/CNx for degradation Rhodamine B under UV light irradiation was investigated. The results show that SnO2/CNx nanocomposites have a higher photocatalytic activity than pure SnO2 and SnO2/CNTs nanocomposites. This enhanced photoresponse indicates that the photoinduced electrons in the SnO2 prefer separately transferring to the CNx, which has a high degree of defects. As a consequence, the radiative recombination of the electron-hole pairs is hampered and the photocatalytic activity is significantly enhanced for the SnO2/CNx photocatalysts

Molecular cloning and function of two tumor necrosis factor receptor-associated factors genes (TRAF2 and TRAF4) from Pinctada fucata martensii

Tumor necrosis factor receptor-associated factors (TRAFs) have been studied in a few mollusks and participate in various biological processes, like apoptosis, immune response, stress, and inflammatory response. However, TRAFs’ function and mechanism of pearl oysters (Pinctada fucata martensii) are still unclear. In this study, the novel PmTRAF2 and PmTRAF4 from P. f. martensii were cloned by rapid amplification of complementary DNA ends and their mRNA expression were analyzed by quantitative real-time PCR (qPCR). The interacting protein of PmTRAF2 was verified by the yeast two-hybrid assay. The result shows that full-length of PmTRAF2 and PmTRAF4 cDNA were 2055 bp and 2365 bp, respectively. The deduced PmTRAF2 and PmTRAF4 proteins contain TRAF-type zinc finger domain and MATH domain, while PmTRAF4 lacks a RING finger domain. Multiple sequence alignment revealed that PmTRAF2 and PmTRAF4 had high homology with the ortholog of other species. Phylogenic analysis indicated that PmTRAF4 clustered with the homolog protein of Mytilus edulis and Mytilus galloprovincialis, and PmTRAF2 has the closest genetic relationship to Crassostrea gigas TRAF2. The qPCR analysis revealed that PmTRAF2 and PmTRAF4 were expressed in all six tissues, and both of them were significantly expressed in hepatopancreas and gill (p < 0.01). Under lipopolysaccharide (LPS) stimulation, polyinosinic acid (PolyI:C) stimulation, and nucleus insertion surgery, the transcripts of PmTRAF2, PmTRAF3, PmTRAF4 and PmTRAF6 in hepatopancreas were markedly changed at corresponding time points. These results have indicated that these genes may play a role in P. f. martensii innate immunity. Yeast two-hybrid assays show that PmTRAF2 interacts with PmTRAF6 but not PmTRAF3, potentially affecting downstream immune signaling pathways. Our findings provide new perspectives for further investigation of TRAFs’ immune mechanisms in bivalves

Reduced expression of Toll-like receptor 4 inhibits human breast cancer cells proliferation and inflammatory cytokines secretion

<p>Abstract</p> <p>Background</p> <p>Tumor cell expression of Toll-like receptors (TLRs) can promote inflammation and cell survival in the tumor microenvironment. Toll-like receptor 4 (TLR4) signaling in tumor cells can mediate tumor cell immune escape and tumor progression, and it is regarded as one of the mechanisms for chronic inflammation in tumorigenesis and progression. The expression of TLR4 in human breast cancer cell line MDA-MB-231 and its biological function in the development and progression of breast cancer have not been investigated. We sought to characterize the expression of TLR1-TLR10 in the established human breast cancer cell line MDA-MB-231, and to investigate the biological roles of TLR4 in breast cancer cells growth, survival, and its potential as a target for breast cancer therapy.</p> <p>Methods</p> <p>TLRs mRNA and protein expressions were detected in human breast cancer cell line MDA-MB-231 by RT-PCR, real-time PCR and flow cytometry (FCM). RNA interference was used to knockdown the expression of TLR4 in MDA-MB-231. MDA-MB-231 transfected with the vector pGenesil-1 and the vector containing a scrambled siRNA were as controls. Recombinant plasmids named TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA specific to TLR4 were transfected into human breast cancer cell line MDA-MB-231 with Lipfectamine™2000 reagent. TLR4 mRNA and protein expressions were investigated by RT-PCR, real-time PCR, FCM and immunofluorescence after silence. MTT analysis was performed to detect cell proliferation and FCM was used to detect the secretion of inflammatory cytokines in supernatant of transfected cells.</p> <p>Results</p> <p>The human breast cancer cell line MDA-MB-231 was found to express TLR1-TLR10 at both the mRNA and protein levels. TLR4 was found to be the highest expressed TLR in MDA-MB-231. TLR4AsiRNA, TLR4BsiRNA and TLR4CsiRNA were found to significantly inhibit TLR4 expression in MDA-MB-231 at both mRNA and protein levels as compared to vector control(vector transfected cells). TLR4AsiRNA mediated the strongest effect. Knockdown of TLR4 gene in MDA-MB-231 resulted in a dramatic reduction of breast cancer cell viability. The cytokines which were secreted by the TLR4 silenced cells, such as IL-6 and IL-8, also decreased significantly as compared with vector control. No significant difference was observed in siRNA control (Recombinant plasmid named ScrambledsiRNA transfected cells) compared to vector control.</p> <p>Conclusions</p> <p>These studies identified the expression levels of multiple TLRs in human breast cancer cell line MDA-MB-231 and demonstrated that knockdown of TLR4 could actively inhibit proliferation and survival of breast cancer cells. Taken together, our results suggest RNAi-directed targeting of TLR4 may be a beneficial strategy for breast cancer therapy.</p