Recency of Faulting and Subsurface Architecture of the San Diego Bay Pull-Apart Basin, California, USA

In Southern California, plate boundary motion between the North American and Pacific plates is distributed across several sub-parallel fault systems. The offshore faults of the California Continental Borderland (CCB) are thought to accommodate ∼10–15% of the total plate boundary motion, but the exact distribution of slip and the mechanics of slip partitioning remain uncertain. The Newport-Inglewood-Rose Canyon fault is the easternmost fault within the CCB whose southern segment splays out into a complex network of faults beneath San Diego Bay. A pull-apart basin model between the Rose Canyon and the offshore Descanso fault has been used to explain prominent fault orientations and subsidence beneath San Diego Bay; however, this model does not account for faults in the southern portion of the bay or faulting east of the bay. To investigate the characteristics of faulting and stratigraphic architecture beneath San Diego Bay, we combined a suite of reprocessed legacy airgun multi-channel seismic profiles and high-resolution Chirp data, with age and lithology controls from geotechnical boreholes and shallow sub-surface vibracores. This combined dataset is used to create gridded horizon surfaces, fault maps, and perform a kinematic fault analysis. The structure beneath San Diego Bay is dominated by down-to-the-east motion on normal faults that can be separated into two distinct groups. The strikes of these two fault groups can be explained with a double pull-apart basin model for San Diego Bay. In our conceptual model, the western portion of San Diego Bay is controlled by a right-step between the Rose Canyon and Descanso faults, which matches both observations and predictions from laboratory models. The eastern portion of San Diego Bay appears to be controlled by an inferred step-over between the Rose Canyon and San Miguel-Vallecitos faults and displays distinct fault strike orientations, which kinematic analysis indicates should have a significant component of strike-slip partitioning that is not detectable in the seismic data. The potential of a Rose Canyon-San Miguel-Vallecitos fault connection would effectively cut the stepover distance in half and have important implications for the seismic hazard of the San Diego-Tijuana metropolitan area (population ∼3 million people)

SARS-CoV-2 Omicron is an immune escape variant with an altered cell entry pathway

Vaccines based on the spike protein of SARS-CoV-2 are a cornerstone of the public health response to COVID-19. The emergence of hypermutated, increasingly transmissible variants of concern (VOCs) threaten this strategy. Omicron (B.1.1.529), the fifth VOC to be described, harbours multiple amino acid mutations in spike, half of which lie within the receptor-binding domain. Here we demonstrate substantial evasion of neutralization by Omicron BA.1 and BA.2 variants in vitro using sera from individuals vaccinated with ChAdOx1, BNT162b2 and mRNA-1273. These data were mirrored by a substantial reduction in real-world vaccine effectiveness that was partially restored by booster vaccination. The Omicron variants BA.1 and BA.2 did not induce cell syncytia in vitro and favoured a TMPRSS2-independent endosomal entry pathway, these phenotypes mapping to distinct regions of the spike protein. Impaired cell fusion was determined by the receptor-binding domain, while endosomal entry mapped to the S2 domain. Such marked changes in antigenicity and replicative biology may underlie the rapid global spread and altered pathogenicity of the Omicron variant

Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes

Background The first epidemic wave of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over one-third of care homes reported an outbreak, while there was limited testing of hospital patients discharged to care homes. Aim To investigate patients discharged from hospitals as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave. Methods A clinical review was performed for all patients discharges from hospitals to care homes from 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease 2019 (COVID-19) test history, clinical assessment at discharge, whole-genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis using Cluster Investigation and Virus Epidemiological Tool software. Patient timelines were obtained using electronic hospital records. Findings In total, 787 patients discharged from hospitals to care homes were identified. Of these, 776 (99%) were ruled out for subsequent introduction of SARS-CoV-2 into care homes. However, for 10 episodes, the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data were available. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission, leading to 10 positive cases in their care home. Conclusion The majority of patients discharged from hospitals were ruled out for introduction of SARS-CoV-2 into care homes, highlighting the importance of screening all new admissions when faced with a novel emerging virus and no available vaccine

Mississippi River subaqueous delta is entering a stage of retrogradation

© 2018 Elsevier B.V. The subaqueous delta of the Mississippi River, the largest river system in the conterminous U.S., has entered a stage of retrogradation caused by multiple natural and anthropogenic activities. Since the 1950s, the suspended sediment load of the Mississippi River has decreased by ~50% due primarily to the construction of \u3e50,000 dams in the Mississippi basin. The impact of this decreased sediment load has been observed in subaerial environments, but the impact on sedimentation and geomorphology of the subaqueous delta front has yet to be examined. To identify historic trends in sedimentation patterns, we compiled bathymetric datasets, including historical charts, industry and academic surveys, and National Oceanic and Atmospheric Administration hydrographic data, collected between 1764 and 2009. The progradation rate (measured at the 10 m depth contour) of Southwest Pass, which receives 69% of the suspended sediment load reaching Head of Passes, has decreased from ~67 m/yr between 1874 and 1940 to ~26 m/yr between 1940 and 1979, with evidence of further deceleration from 1979 to 2009. At South Pass and Pass a Loutre, the delta front has entered the destructive phase, with the 10 m contour retreating at rates \u3e20 m/yr at both passes since 1979. Advancement of the delta front also decelerated in deeper water (in some areas out to ~180 m depth). Except locally, where mudflow lobes are advancing, deeper contours show a pattern of decreasing progradation rate between 1874–1940 and 1979–2005 time periods. Furthermore, based on differences measured between available bathymetric datasets, the sediment accumulation rate across the delta front decreased by ~73% for the same period. The retention rate of Mississippi River sediment on the delta front ranged from 67 to 81% for the time periods assessed, with total sediment load stored on the delta front equal to 317 ± 54 Mt/yr from 1874 to 1940, 145 ± 25 Mt/yr from 1940 to 1979, and 87 ± 15 Mt/yr from 1979 to 2005. We document for the first time that the Mississippi River delta front has entered a phase of retrogradation, which will likely be accelerated by future upstream activities that divert a portion of the sediment load to the upper delta for coastal protection and restoration projects. The decline of the subaqueous Mississippi River Delta has critical implications for biogeochemical cycling, subaqueous mass wasting, and sediment dispersal to the coastal ocean

Mass wasting on the Mississippi River subaqueous delta

© 2019 Elsevier B.V. The Mississippi River delta front (MRDF) is an excellent natural laboratory for studying seafloor instability and evaluating the preconditioning factors and triggering mechanisms that lead to seafloor failures. The occurrence of seafloor landslides on the MRDF has been recognized since the 1950s, but the bulk of research on the topic was conducted in the 1970s-80s after seafloor landslides triggered by Hurricane Camille damaged offshore infrastructure. Through these efforts, it was recognized that seafloor instability features are present across the entire delta front, that rapid sediment delivery from the Mississippi River is a primary preconditioning factor for failures, and that cyclic loading from hurricane waves is the main triggering mechanism for deep-seated catastrophic events. However, mounting evidence shows that MRDF seafloor motion occurs even during periods of no hurricane activity, which could be attributed to creep-like motion of underconsolidated sediment, or smaller episodic flows triggered by winter storms or Mississippi River floods. Given the extensive spatial distribution of instabilities on the MRDF, the multiple mechanisms of failure and variety of resulting morphology, and the range of potential triggering mechanisms with short recurrence, the MRDF is an exceptional location to assess the complex problem of seafloor landslides. An improved understanding of seafloor landslides is crucial for understanding global sediment budgets and associated biogeochemical cycling, as they can evacuate large volumes of sediment into deep water over short time periods. Additionally, seafloor landslides pose a hazard to offshore infrastructure and to coastal communities through possible tsunami inundation, and advancing research on preconditioning factors and triggering mechanisms would improve hazard assessments. This paper presents a review and synthesis of geological and geotechnical research on the MRDF, particularly with respect to seafloor landslides: their occurrence, geological and geotechnical controls, triggering mechanisms, and knowledge gaps related thereto. This synthesis is conducted at times of rapidly developing technologies for studying seafloor instability, and as the MRDF enters a stage of degradation characterized by reduced sediment delivery and accumulation

Spray coated high-conductivity PEDOT:PSS transparent electrodes for stretchable and mechanically-robust organic solar cells

High conductivity poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was spray cast to form highly flexible transparent electrodes for forward- and inverted-mode organic solar cells (OSCs). A multiple solvent ink containing ethylene glycol was developed, and a post-deposition annealing step contributed to a high conductivity of 1070\ub150 S cm-\ub9. Sheet resistance and transmission at a wavelength of 550 nm were controlled within 24-259 \u3a9 \u25a1-\ub9 and 71-95%, respectively, which are amongst the best-reported combined characteristics. Forward-mode OSCs with spray coated PEDOT:PSS anodes yielded a power conversion efficiency of 3.2%. Mechanical bending and stretching tests demonstrated that the flexibility of these PEDOT:PSS layers were far superior to that of ITO: elastic moduli were reduced by more than an order of magnitude, and the resistance increased far more slowly under both uniaxial stretching and bending to progressively smaller radii of curvature. With these experiments, the minimum radii of curvature and maximum uniaxial strains at which acceptable performance is maintained were investigated. Collectively, our results illustrate a promising future for the scalable printing of low-cost PEDOT:PSS-based flexible transparent electrodes. \ua9 2012 Crown All rights reserved.Peer reviewed: YesNRC publication: Ye

Genomic epidemiology of SARS-CoV-2 in a university outbreak setting and implications for public health planning

AbstractWhole genome sequencing of SARS-CoV-2 has occurred at an unprecedented scale, and can be exploited for characterising outbreak risks at the fine-scale needed to inform control strategies. One setting at continued risk of COVID-19 outbreaks are higher education institutions, associated with student movements at the start of term, close living conditions within residential halls, and high social contact rates. Here we analysed SARS-CoV-2 whole genome sequences in combination with epidemiological data to investigate a large cluster of student cases associated with University of Glasgow accommodation in autumn 2020, Scotland. We identified 519 student cases of SARS-CoV-2 infection associated with this large cluster through contact tracing data, with 30% sequencing coverage for further analysis. We estimated at least 11 independent introductions of SARS-CoV-2 into the student population, with four comprising the majority of detected cases and consistent with separate outbreaks. These four outbreaks were curtailed within a week following implementation of control measures. The impact of student infections on the local community was short-term despite an underlying increase in community infections. Our study highlights the need for context-specific information in the formation of public health policy for higher educational settings.</jats:p