Our understanding of subsurface processes suffers from a profound observation bias: seismometers are sparse and clustered on continents. A new seismic recording approach, distributed acoustic sensing ...(DAS), transforms telecommunication fiber‐optic cables into sensor arrays enabling meter‐scale recording over tens of kilometers of linear fiber length. We analyze cataloged earthquake observations from three DAS arrays with different horizontal geometries to demonstrate some possibilities using this technology. In Fairbanks, Alaska, we find that stacking ground motion records along 20 m of fiber yield a waveform that shows a high degree of correlation in amplitude and phase with a colocated inertial seismometer record at 0.8–1.6 Hz. Using an L‐shaped DAS array in Northern California, we record the nearly vertically incident arrival of an earthquake from The Geysers Geothermal Field and estimate its backazimuth and slowness via beamforming for different phases of the seismic wavefield. Lastly, we install a fiber in existing telecommunications conduits below Stanford University and show that little cable‐to‐soil coupling is required for teleseismic P and S phase arrival detection.
Plain Language Summary
A new seismic recording technology, called distributed acoustic sensing (DAS), turns common telecommunications fiber‐optic cables into a very long (tens of kilometers) array of single‐component seismometers. We catalog and analyze earthquake observations from three different DAS experiments and demonstrate some of the possibilities of using this technology for earthquake seismology. We compare DAS records with a conventional seismometer and then show how the array style response of DAS enables recording of additional information such as the direction of the seismic energy. We also install a fiber in a typical telecommunications conduit below Stanford University, as opposed to directly burying the fiber in soil, and show that main seismic waves are still detected despite the hypothesized decrease in coupling between the fiber and the ground.
Key Points
Distributed acoustic sensing (DAS) transforms fiber optics into dense seismic arrays (1 sensor/meter) using laser scattering
Earthquake observations indicate that DAS and seismometer sensitivity is similar at 0.8‐1.6 Hz
Fiber installed in telecommunication conduit shows sensitivity to propagating seismic waves
Ambient-noise-based seismic monitoring of the near surface often has limited spatiotemporal resolutions because dense seismic arrays are rarely sufficiently affordable for such applications. In ...recent years, however, distributed acoustic sensing (DAS) techniques have emerged to transform telecommunication fiber-optic cables into dense seismic arrays that are cost effective. With DAS enabling both high sensor counts ("large N") and long-term operations ("large T"), time-lapse imaging of shear-wave velocity (V
) structures is now possible by combining ambient noise interferometry and multichannel analysis of surface waves (MASW). Here we report the first end-to-end study of time-lapse V
imaging that uses traffic noise continuously recorded on linear DAS arrays over a three-week period. Our results illustrate that for the top 20 meters the V
models that is well constrained by the data, we obtain time-lapse repeatability of about 2% in the model domain-a threshold that is low enough for observing subtle near-surface changes such as water content variations and permafrost alteration. This study demonstrates the efficacy of near-surface seismic monitoring using DAS-recorded ambient noise.
Apple bitter rot caused by Colletotrichum species is a growing problem worldwide. Colletotrichum spp. are economically important but taxonomically un-resolved. Identification of Colletotrichum spp. ...is critical due to potential species-level differences in pathogenicity-related characteristics. A 400-isolate collection from New York apple orchards were morphologically assorted to two groups, C. acutatum species complex (CASC) and C. gloeosporioides species complex (CGSC). A sub-sample of 44 representative isolates, spanning the geographical distribution and apple varieties, were assigned to species based on multi-locus phylogenetic analyses of nrITS, GAPDH and TUB2 for CASC, and ITS, GAPDH, CAL, ACT, TUB2, APN2, ApMat and GS genes for CGSC. The dominant species was C. fioriniae, followed by C. chrysophilum and a novel species, C. noveboracense, described in this study. This study represents the first report of C. chrysophilum and C. noveboracense as pathogens of apple. We assessed the enzyme activity and fungicide sensitivity for isolates identified in New York. All isolates showed amylolytic, cellulolytic and lipolytic, but not proteolytic activity. C. chrysophilum showed the highest cellulase and the lowest lipase activity, while C. noveboracense had the highest amylase activity. Fungicide assays showed that C. fioriniae was sensitive to benzovindiflupyr and thiabendazole, while C. chrysophilum and C. noveboracense were sensitive to fludioxonil, pyraclostrobin and difenoconazole. All species were pathogenic on apple fruit with varying lesion sizes. Our findings of differing pathogenicity-related characteristics among the three species demonstrate the importance of accurate species identification for any downstream investigations of Colletotrichum spp. in major apple growing regions.
Thermal stratification and mixing are important to the physicochemical composition of reservoirs and lakes and impact their water quality and biogeochemical cycles. However, it remains unclear how ...thermal stratification and mixing process control the exchange of CO2 between surface water and the Earth’s atmosphere. To address this issue, we examine the temporal characteristics of some physicochemical parameters, partial pressure of CO2 (pCO2), the δ13CDIC, and CO2 emission from a typical karst groundwater-fed reservoir (Dalongdong reservoir). During the 23 month study (2016–2018) thermal stratification limited CO2 emission, in part from photosynthetic uptake of CO2, from early April to late October, while mixing processes stimulated CO2 emission of CO2 generated from organic matter remineralization in bottom water from October to April. The Dalongdong reservoir is an atmospheric source of CO2 for most of the study period; however, during periods of stratification, approximately 0.37 ± 0.44 Gg CO2 (1 Gg = 109g) dissolved into the water from the atmosphere, while approximately 6.24 ± 3.73 Gg CO2 was lost to the atmosphere during periods lacking stratification. Limited emissions during stratified period may thus represent a negative feedback to CO2 contributions to global warming, which has increased lengths of stratified periods. These study results are important to optimize sampling monitoring strategies to reduce errors of regional CO2 emission estimation.
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•Varying thermal structure control temporal variations of CO2 emissions.•Thermal stratification limits CO2 emission during summer.•Mixing processes stimulate CO2 emissions during early winter.
By in‐situ measuring the scattered light during microstructure formation, the polymerization kinetics of three‐dimensional direct laser writing are investigated in detail. Oxygen quenching, oxygen ...diffusion, and inhibitor depletion are shown to have substantial impact on the kinetic behavior. For typical photoresists based on multifunctional acrylates, the polymerization occurs in less than a millisecond.
Giving the early fossil record of sponges a squeeze Antcliffe, Jonathan B.; Callow, Richard H. T.; Brasier, Martin D.
Biological reviews of the Cambridge Philosophical Society,
November 2014, Letnik:
89, Številka:
4
Journal Article
Recenzirano
ABSTRACT
Twenty candidate fossils with claim to be the oldest representative of the Phylum Porifera have been re‐analysed. Three criteria are used to assess each candidate: (i) the diagnostic ...criteria needed to categorize sponges in the fossil record; (ii) the presence, or absence, of such diagnostic features in the putative poriferan fossils; and (iii) the age constraints for the candidate fossils. All three criteria are critical to the correct interpretation of any fossil and its placement within an evolutionary context. Our analysis shows that no Precambrian fossil candidate yet satisfies all three of these criteria to be a reliable sponge fossil. The oldest widely accepted candidate, Mongolian silica hexacts from c. 545 million years ago (Ma), are here shown to be cruciform arsenopyrite crystals. The oldest reliable sponge remains are siliceous spicules from the basal Cambrian (Protohertzina anabarica Zone) Soltanieh Formation, Iran, which are described and analysed here in detail for the first time. Extensive archaeocyathan sponge reefs emerge and radiate as late as the middle of the Fortunian Stage of the Cambrian and demonstrate a gradual assembly of their skeletal structure through this time coincident with the evolution of other metazoan groups. Since the Porifera are basal in the Metazoa, their presence within the late Proterozoic has been widely anticipated. Molecular clock calibration for the earliest Porifera and Metazoa should now be based on the Iranian hexactinellid material dated to c. 535 Ma. The earliest convincing fossil sponge remains appeared at around the time of the Precambrian‐Cambrian boundary, associated with the great radiation events of that interval.
Redox flow batteries (RFBs) are one of the most promising scalable electricity-storage systems to address the intermittency issues of renewable energy sources such as wind and solar. The prerequisite ...for RFBs to be economically viable and widely employed is their low cost. Here we present a new zinc-iron (Zn-Fe) RFB based on double-membrane triple-electrolyte design that is estimated to have under $100 per kW h system capital cost. Such a low cost is achieved by a combination of inexpensive redox materials (i.e., zinc and iron) and high cell performance (e.g., 676 mW cm super(-2) power density). Engineering of the cell structure is found to be critical to enable the high power density. Our cost model shows that a Zn-Fe RFB demonstrates the lowest cost among some notable RFBs and could reach the 2023 cost target set by the U.S. Department of Energy ($150 per kW h).
Prospective data on the efficacy of a watch-and-wait strategy to achieve organ preservation in patients with locally advanced rectal cancer treated with total neoadjuvant therapy are limited.
In this ...prospective, randomized phase II trial, we assessed the outcomes of 324 patients with stage II or III rectal adenocarcinoma treated with induction chemotherapy followed by chemoradiotherapy (INCT-CRT) or chemoradiotherapy followed by consolidation chemotherapy (CRT-CNCT) and either total mesorectal excision (TME) or watch-and-wait on the basis of tumor response. Patients in both groups received 4 months of infusional fluorouracil-leucovorin-oxaliplatin or capecitabine-oxaliplatin and 5,000 to 5,600 cGy of radiation combined with either continuous infusion fluorouracil or capecitabine during radiotherapy. The trial was designed as two stand-alone studies with disease-free survival (DFS) as the primary end point for both groups, with a comparison to a null hypothesis on the basis of historical data. The secondary end point was TME-free survival.
Median follow-up was 3 years. Three-year DFS was 76% (95% CI, 69 to 84) for the INCT-CRT group and 76% (95% CI, 69 to 83) for the CRT-CNCT group, in line with the 3-year DFS rate (75%) observed historically. Three-year TME-free survival was 41% (95% CI, 33 to 50) in the INCT-CRT group and 53% (95% CI, 45 to 62) in the CRT-CNCT group. No differences were found between groups in local recurrence-free survival, distant metastasis-free survival, or overall survival. Patients who underwent TME after restaging and patients who underwent TME after regrowth had similar DFS rates.
Organ preservation is achievable in half of the patients with rectal cancer treated with total neoadjuvant therapy, without an apparent detriment in survival, compared with historical controls treated with chemoradiotherapy, TME, and postoperative chemotherapy.
Influenza vaccine effectiveness (VE) is generally interpreted in the context of vaccine match/mismatch to circulating strains with evolutionary drift in the latter invoked to explain reduced ...protection. During the 2012-13 season, however, detailed genotypic and phenotypic characterization shows that low VE was instead related to mutations in the egg-adapted H3N2 vaccine strain rather than antigenic drift in circulating viruses.
Component-specific VE against medically-attended, PCR-confirmed influenza was estimated in Canada by test-negative case-control design. Influenza A viruses were characterized genotypically by amino acid (AA) sequencing of established haemagglutinin (HA) antigenic sites and phenotypically through haemagglutination inhibition (HI) assay. H3N2 viruses were characterized in relation to the WHO-recommended, cell-passaged vaccine prototype (A/Victoria/361/2011) as well as the egg-adapted strain as per actually used in vaccine production. Among the total of 1501 participants, influenza virus was detected in 652 (43%). Nearly two-thirds of viruses typed/subtyped were A(H3N2) (394/626; 63%); the remainder were A(H1N1)pdm09 (79/626; 13%), B/Yamagata (98/626; 16%) or B/Victoria (54/626; 9%). Suboptimal VE of 50% (95%CI: 33-63%) overall was driven by predominant H3N2 activity for which VE was 41% (95%CI: 17-59%). All H3N2 field isolates were HI-characterized as well-matched to the WHO-recommended A/Victoria/361/2011 prototype whereas all but one were antigenically distinct from the egg-adapted strain as per actually used in vaccine production. The egg-adapted strain was itself antigenically distinct from the WHO-recommended prototype, and bore three AA mutations at antigenic sites B H156Q, G186V and D S219Y. Conversely, circulating viruses were identical to the WHO-recommended prototype at these positions with other genetic variation that did not affect antigenicity. VE was 59% (95%CI:16-80%) against A(H1N1)pdm09, 67% (95%CI: 30-85%) against B/Yamagata (vaccine-lineage) and 75% (95%CI: 29-91%) against B/Victoria (non-vaccine-lineage) viruses.
These findings underscore the need to monitor vaccine viruses as well as circulating strains to explain vaccine performance. Evolutionary drift in circulating viruses cannot be regulated, but influential mutations introduced as part of egg-based vaccine production may be amenable to improvements.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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