In April and May 1996, a geophysical study of the Cascadia continental margin off Oregon and Washington was conducted aboard the German R/V
Sonne. This cooperative experiment by GEOMAR and the USGS ...acquired wide-angle reflection and refraction seismic data, using ocean-bottom seismometers (OBS) and hydrophones (OBH), and multichannel seismic reflection (MCS) data. The main goal of this experiment was to investigate the internal structure and associated earthquake hazard of the Cascadia subduction zone and to image the downgoing plate. Coincident MCS and wide-angle profiles along two tracks are presented here. The plate boundary has been imaged precisely beneath the wide accretionary wedge close to shore at ca. 13 km depth. Thus, the downgoing plate dips more shallowly than previously assumed. The dip of the plate changes from 2° to 4° at the eastern boundary of the wedge on the northern profile, where approximately 3 km of sediment is entering the subduction zone. On the southern profile, where the incoming sedimentary section is about 2.2 km thick, the plate dips about 0.5° to 1.5° near the deformation front and increases to 3.5° further landwards. On both profiles, the deformation of the accretionary wedge has produced six ridges on the seafloor, three of which represent active faulting, as indicated by growth folding. The ridges are bordered by landward verging faults which reach as deep as the top of the oceanic basement. Thus the entire incoming sediment package is being accreted. At least two phases of accretion are evident, and the rocks of the older accretionary phase(s) forms the backstop for the younger phase, which started around 1.5 Ma ago. This documents that the 30 to 50 km wide frontal part of the accretionary wedge, which is characterized by landward vergent thrusts, is a Pleistocene feature which was formed in response to the high input of sediment building the fans during glacial periods. Velocities increase quite rapidly within the wedge, both landward and downward. At the toe of the deformation front, velocities are higher than 4.0 km/s, indicating extensive dewatering of deep, oceanic sediment. Further landward, considerable velocity variation is found, which indicates major breaks throughout the accretionary history.
Normal faults along the seaward trench slope (STS) commonly strike parallel to the trench in response to bending of the oceanic plate into the subduction zone. This is not the circumstance for the ...Aleutian Trench, where the direction of convergence gradually changes westward, from normal to transform motion. GLORIA side‐scan sonar images document that the Aleutian STS is dominated by faults striking oblique to the trench, west of 179°E and east of 172°W. These images also show a pattern of east‐west trending seafloor faults that are aligned parallel to the spreading fabric defined by magnetic anomalies. The stress‐strain field along the STS is divided into two domains west and east, respectively, of 179°E. Over the western domain, STS faults and nodal planes of earthquakes are oriented oblique (9°–46°) to the trench axis and (69°–90°) to the magnetic fabric. West of 179°E, STS fault strikes change by 36° from the E‐W trend of STS where the trench‐parallel slip gets larger than its orthogonal component of convergence. This rotation indicates that horizontal stresses along the western domain of the STS are deflected by the increasing obliquity in convergence. An analytical model supports the idea that strikes of STS faults result from a superposition of stresses associated with the dextral shear couple of the oblique convergence and stresses caused by plate bending. For the eastern domain, most nodal planes of earthquakes strike parallel to the outer rise, indicating bending as the prevailing mechanism causing normal faulting. East of 172°W, STS faults strike parallel to the magnetic fabric but oblique (10°–26°) to the axis of the trench. On the basis of a Coulomb failure criterion the trench‐oblique strikes probably result from reactivation of crustal faults generated by spreading.
Human organoids recapitulating the cell-type diversity and function of their target organ are valuable for basic and translational research. We developed light-sensitive human retinal organoids with ...multiple nuclear and synaptic layers and functional synapses. We sequenced the RNA of 285,441 single cells from these organoids at seven developmental time points and from the periphery, fovea, pigment epithelium and choroid of light-responsive adult human retinas, and performed histochemistry. Cell types in organoids matured in vitro to a stable “developed” state at a rate similar to human retina development in vivo. Transcriptomes of organoid cell types converged toward the transcriptomes of adult peripheral retinal cell types. Expression of disease-associated genes was cell-type-specific in adult retina, and cell-type specificity was retained in organoids. We implicate unexpected cell types in diseases such as macular degeneration. This resource identifies cellular targets for studying disease mechanisms in organoids and for targeted repair in human retinas.
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•Light-sensitive, multilayered human retinal organoids with functional synapses•285,441 transcriptomes from light-responsive human retinas and retinal organoids•Organoid cell types converge to adult peripheral retinal cell types•Linking retinal diseases to human retinal and retinal organoid cell types
Light-sensitive, multilayered human retinal organoids with functional synapses are developed and benchmarked against human retinas obtained under conditions that preserve retinal integrity.
Volcanism and subduction Eichelberger, John; Gordeev, Evgenii; Izbekov, Pavel ...
Geophysical monograph,
♭2007., Letnik:
172
eBook
Recenzirano
Odprti dostop
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 172.The Kamchatka Peninsula and contiguous North Pacific Rim is among the most active regions in the ...world. Kamchatka itself contains 29 active volcanoes, 4 now in a state of semi-continuous eruption, and I has experienced 14 magnitude 7 or greater earthquakes since accurate recording began in 1962. At its heart is the uniquely acute subduction cusp where the Kamchatka and Aleutian Arcs and Emperor Seamount Chain meet. Volcanism and Subduction covers coupled magmatism and tectonics in this spectacular region, where the torn North Pacific slab dives into hot mantle. Senior Russian and American authors grapple with the dynamics of the cusp with perspectives from the west and east of it, respectively, while careful tephrostratigraphy yields a remarkably precise record of behavior of storied volcanoes such as Kliuchevskoi and Shiveluch. Towards the south, Japanese researchers elucidate subduction earthquake processes with unprecedented geodetic resolution. Looking eastward, new insights on caldera formation, monitoring, and magma ascent are presented for the Aleutians. This is one of the first books of its kind printed in the English language. Students and scientists beginning research in the region will find in this book a useful context and introduction to the region's scientific leaders. Others who wish to apply lessons learned in the North Pacific to their areas of interest will find the volume a valuable reference.
IMPORTANCE: Sensitive outcome measures for disease progression are needed for treatment trials of Stargardt disease. OBJECTIVE: To describe the yearly progression rate of atrophic lesions in the ...retrospective Progression of Stargardt Disease study. DESIGN, SETTING, AND PARTICIPANTS: A multicenter retrospective cohort study was conducted at tertiary referral centers in the United States and Europe. A total of 251 patients aged 6 years or older at baseline, harboring disease-causing variants in ABCA4 (OMIM 601691), enrolled in the study from 9 centers between August 2, 2013, and December 12, 2014; of these patients, 215 had at least 2 gradable fundus autofluorescence images with atrophic lesion(s) present in at least 1 eye. EXPOSURES: Areas of definitely decreased autofluorescence (DDAF) and questionably decreased autofluorescence were quantified by a reading center. Progression rates were estimated from linear mixed models with time as the independent variable. MAIN OUTCOMES AND MEASURES: Yearly rate of progression using the growth of atrophic lesions measured by fundus autofluorescence. RESULTS: A total of 251 participants (458 study eyes) were enrolled. Images from 386 eyes of 215 participants (126 females and 89 males; mean SD age, 29.9 14.7 years; mean SD age of onset of symptoms, 21.9 13.3 years) showed atrophic lesions present on at least 2 visits and were graded for 2 (156 eyes), 3 (174 eyes), or 4 (57 eyes) visits. A subset of 224 eyes (123 female participants and 101 male participants; mean SD age, 33.0 15.1 years) had areas of DDAF present on at least 2 visits; these eyes were included in the estimation of the progression of the area of DDAF. At the first visit, DDAF was present in 224 eyes (58.0%), with a mean (SD) lesion size of 2.2 (2.7) mm2. The total mean (SD) area of decreased autofluorescence (DDAF and questionably decreased autofluorescence) at first visit was 2.6 (2.8) mm2. Mean progression of DDAF was 0.51 mm2/y (95% CI, 0.42-0.61 mm2/y), and of total decreased fundus autofluorescence was 0.35 mm2/y (95% CI, 0.28-0.43 mm2/y). Rates of progression depended on the initial size of the lesion. CONCLUSIONS AND RELEVANCE: In Stargardt disease with DDAF lesions, fundus autofluorescence may serve as a monitoring tool for interventional clinical trials that aim to slow disease progression. Rates of progression depended mainly on initial lesion size.
IMPORTANCE: Functional end points for clinical trials investigating the efficacy of emerging treatments for Stargardt disease type 1 (STGD1) are needed. OBJECTIVE: To assess the yearly rate of change ...of macular function in patients with STGD1 using microperimetry. DESIGN, SETTING, AND PARTICIPANTS: This multicenter prospective cohort study was conducted in an international selection of tertiary referral centers from October 21, 2013, to February 15, 2017. The study included participants with ABCA4-related STGD1 who were enrolled in the Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study at baseline. Data were analyzed from February 16, 2017, to December 1, 2019. EXPOSURE: ABCA4-related STGD1 with a minimum lesion size on fundus autofluorescence and a minimum visual acuity. MAIN OUTCOMES AND MEASURES: Changes in overall macular sensitivity (MS), deep scotoma count, number of points that tested normal, and location-specific sensitivity changes. RESULTS: Among the 359 eyes from 200 patients (87 43.5% men; mean SD age, 33.3 15.2 years) who underwent microperimetry examination graded at baseline and month 12, the mean (SD) yearly change in MS was −0.68 (2.04) dB (95% CI, −0.89 to −0.47 dB; P < .001), and deep scotoma points increased by a mean (SD) of 1.56 (5.74) points per year. The points with sensitivity of 12 dB or higher decreased in sensitivity by a mean (SD) of −3.01 (9.84) dB (95% CI, −4.03 to −1.99 dB; P < .001). The mean (SD) yearly change in MS was not significantly different between the eyes with a grading of good or fair pattern placement at both visits (−0.67 2.1 dB) and the eyes with a poor pattern placement during at least 1 visit (−0.64 2.2 dB) (P = .91). CONCLUSIONS AND RELEVANCE: This study showed that MS and the number of deep scotoma points had measurably changed after follow-up of approximately 1 year. Microperimetry may serve as a useful functional outcome parameter for clinical trials aimed at slowing the progression of STGD1.
In the paper 'Basin-centered asperities in great subduction zone earthquakes: A link between slip, subsidence, and subduction erosion?' by Ray E. Wells, Richard J. Blakely, Yuichi Sugiyama, David W. ...Scholl, and Philip A. Dinterman (Journal of Geophysical Research, 108(B10),
Published areas of high coseismic slip, or asperities, for 29 of the largest Circum‐Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free‐air gravity, ...bathymetry, and seismic profiling. On average, 71% of an earthquake's seismic moment and 79% of its asperity area occur beneath the prominent gravity low outlining the deep‐sea terrace; 57% of an earthquake's asperity area, on average, occurs beneath the forearc basins that lie within the deep‐sea terrace. In SW Japan, slip in the 1923, 1944, 1946, and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350°C isotherm on the plate boundary, the inferred downdip limit of the locked zone. Basin‐centered coseismic slip also occurred along the Aleutian, Mexico, Peru, and Chile subduction zones but was ambiguous for the great 1964 Alaska earthquake. Beneath intrabasin structural highs, seismic slip tends to be lower, possibly due to higher temperatures and fluid pressures. Kilometers of late Cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion. The deep‐sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes. Basin‐centered asperities could indicate a link between subsidence, subduction erosion, and seismogenesis. Whatever the cause, forearc basins may be useful indicators of long‐term seismic moment release. The source zone for Cascadia's 1700 A.D. earthquake contains five large, basin‐centered gravity lows that may indicate potential asperities at depth. The gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore, except in northwestern Washington, where the low extends landward beneath the coast. Transverse gravity highs between the basins suggest that the margin is seismically segmented and could produce a variety of large earthquakes.
Organoids generated from human pluripotent stem cells provide experimental systems to study development and disease, but quantitative measurements across different spatial scales and molecular ...modalities are lacking. In this study, we generated multiplexed protein maps over a retinal organoid time course and primary adult human retinal tissue. We developed a toolkit to visualize progenitor and neuron location, the spatial arrangements of extracellular and subcellular components and global patterning in each organoid and primary tissue. In addition, we generated a single-cell transcriptome and chromatin accessibility timecourse dataset and inferred a gene regulatory network underlying organoid development. We integrated genomic data with spatially segmented nuclei into a multimodal atlas to explore organoid patterning and retinal ganglion cell (RGC) spatial neighborhoods, highlighting pathways involved in RGC cell death and showing that mosaic genetic perturbations in retinal organoids provide insight into cell fate regulation.
Single-wavelength fluorescent reporters allow visualization of specific neurotransmitters with high spatial and temporal resolution. We report variants of intensity-based glutamate-sensing ...fluorescent reporter (iGluSnFR) that are functionally brighter; detect submicromolar to millimolar amounts of glutamate; and have blue, cyan, green, or yellow emission profiles. These variants could be imaged in vivo in cases where original iGluSnFR was too dim, resolved glutamate transients in dendritic spines and axonal boutons, and allowed imaging at kilohertz rates.
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