Single electron charging of impurity sites visualized by scanning gate experiments on a quantum point contact

A quantum point contact (QPC) patterned on a two-dimensional electron gas is investigated with a scanning gate setup operated at a temperature of 300 mK. The conductance of the point contact is recorded while the local potential is modified by scanning the tip. Single electron charging of impurities induced by the local potential is observed as a stepwise conductance change of the constriction. By selectively changing the state of some of these impurities, it is possible to observe changes in transmission resonances of the QPC. The location of such impurities is determined, and their density is estimated to be below 50 per \mu m^2, corresponding to less than 1 % of the doping concentration

Schmidt hammer and terrestrial laser scanning (TLS) used to detect single‐event displacements on the Pleasant Valley fault (Nevada, USA)

Changes in surface roughness on carbonate fault scarps often reflect varying durations of subaerial weathering. On the Pleasant Valley fault in central Nevada, the documentation of a surface rupture in 1915, a long recurrence interval of faulting, slow weathering rate, and a relatively high (2–3 m) single‐event displacement make the discrimination of the historical and penultimate slip patches unambiguous. Following from a 2018 study, we used a Schmidt hammer and terrestrial laser scanning (TLS) to further test whether these weathering patterns delineate exposed slip patches on a fault scarp. Results show that Schmidt hammer rebound value ranges (termed ΔR – the difference between minimum and maximum R‐values in repeat impacts at a point), increase by ~8–10 points across the historical–penultimate event transition zone in two separate scarp transects. TLS‐derived surface roughness also indicates a clear difference between the most recent and penultimate events. The average single‐event displacement (SED) estimated using the Schmidt hammer and TLS is 2.85 m at two transect sites and is roughly equivalent to the visually estimated 3 m. While this fault is an ideal case where we know some of the slip history, the results demonstrate that these techniques show promise for discriminating slip patches on larger carbonate fault scarps with longer paleoearthquake histories, and could be used alongside 36Cl cosmogenic exposure‐age dating to improve paleoseismic records on normal faults. © 2019 John Wiley & Sons, Ltd.The Schmidt hammer and terrestrial laser scanning (TLS) can detect hardness and mm‐ to cm‐scale surface roughness changes on bedrock fault scarps. Here, we demonstrate that these changes occur between the ‘slip patches’ of a 1915 and pre‐1915 event on the Pleasant Valley fault, yielding single event displacements of ~2‐3 m. These techniques can now be combined to estimate SEDs on larger fault scarps with longer records of paleoearthquakes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154454/1/esp4748.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154454/2/esp4748_am.pd

Dynamically-Coupled Oscillators -- Cooperative Behavior via Dynamical Interaction --

We propose a theoretical framework to study the cooperative behavior of dynamically coupled oscillators (DCOs) that possess dynamical interactions. Then, to understand synchronization phenomena in networks of interneurons which possess inhibitory interactions, we propose a DCO model with dynamics of interactions that tend to cause 180-degree phase lags. Employing an approach developed here, we demonstrate that although our model displays synchronization at high frequencies, it does not exhibit synchronization at low frequencies because this dynamical interaction does not cause a phase lag sufficiently large to cancel the effect of the inhibition. We interpret the disappearance of synchronization in our model with decreasing frequency as describing the breakdown of synchronization in the interneuron network of the CA1 area below the critical frequency of 20 Hz.Comment: 10 pages, 3 figure

Quaternary Geology and Seismic Hazard of the Sierra Madre and Associated Faults, Western San Gabriel Mountains

This detailed study of a 40-km-long section of the Sierra Madre and associated fault zones in the central transverse Ranges, along the south side of the San Gabriel Mountains, is aimed at providing information for evaluating the seismic hazard that these faults pose to the heavily populated area immediately to the south. Evidence on the location of fault strands and the style and timing of fault movements during the Quaternary was obtained from detailed geologic mapping, aerial-photograph interpretation, alluvial stratigraphy, structural and stratigraphic relations in some 33 trench excavations at critical localities, and subsurface data. We present a time-stratigraphic classification for the Quaternary deposits in the study area, based on soil development, geomorphology, and contact relations among the alluvial units. We distinguish four units, with approximate ages, as follows: unit 4, about 200,000 yr to middle Quaternary; unit 3: about 11,000 to 200,000 yr; unit 2; about 1,000 to 11,000 yr; and unit 1; younger than about 1,000 yr. We use this classification to evaluate on a semi-quantitative basis the evidence for fault activity in the study area and to infer the relative seismicity of different segments of the Sierra Madre fault zone during the Quaternary. Alluvial-fan development (particularly fanhead incision and the ages of alluvial-fan deposits) also gives clues as to relative seismicity. The most active segment of the Sierra Madre fault zone within the study area is the westernmost section, adjacent to the faults that broke during the 1971 San Fernando, Calif., earthquake. The age of activity, as indicated by the occurrence of Holocene faulting, decreases toward the east. Along the Sierra Madre fault, through La Canada, Altadena, Sierra Madre, and Duarte, is abundant evidence of late Pleistocene faulting. Total vertical displacement is more than 600 m, but there is no evidence for Holocene fault movement. These observations suggest that the presently applicable recurrence interval between major earthquakes in the central and eastern sections of the Sierra Madre fault zone is longer than about 5,000 yr. The local magnitude (M_L) of the largest credible earthquake that could occur on the Sierra Madre fault zone in the study area is estimated at 7, on the grounds that the fault zone is probably limited mechanically by subdivision into separate arcuate segments about 15 km long. The Raymond fault, which branches southwestward from the Sierra Madre fault in the eastern part of the study area, shows well-defined evidence of a late Quaternary history of repeated fault movements. Displacements of alluvial strata observed in trench excavations across the fault give evidence of five major seismic events, whose times of occurrence can be estimated from radiometric dating at approximately 36,000, 25,000, 10,000-2,200 (two events), and 2,200-1,500 yr B.P. Further evidence suggests at least three more faulting events in the past 29,000 yr, for which specific dates cannot be determined. Because some additional events probably remain undetected, we infer that an average recurrence interval of about 3,000 yr, with an average vertical displacement of 0.4 m per event, is applicable to the Raymond fault in its present state, as indicated by its history of movement over the past 36,000 yr. This level of activity is distinctly higher than that found for the Sierra Madre fault zone in the central and eastern parts of the study area. If the entire 15-km length of the Raymond fault would rupture in a single event, as seems likely, a maximum credible earthquake of M_L 6 3/4 can reasonably be assumed

Groups of Galaxies in the Two Micron All-Sky Redshift Survey

We present the results of applying a percolation algorithm to the initial release of the Two Micron All-Sky Survey Extended Source Catalog, using subsequently measured redshifts for almost all of the galaxies with K < 11.25 mag. This group catalog is based on the first near-IR all-sky flux-limited survey that is complete to |b| = 5 deg. We explore the dependence of the clustering on the length and velocity scales involved. The paper describes a group catalog, complete to a limiting redshift of 10,000 km/s, created by maximizing the number of groups containing 3 or more members. A second catalog is also presented, created by requiring a minimum density contrast of 80 to identify groups. We identify known nearby clusters in the catalogs and contrast the groups identified in the two catalogs. We examine and compare the properties of the determined groups and verify that the results are consistent with the UZC-SSRS2 and northern CfA redshift survey group catalogs. The all-sky nature of the catalog will allow the development of a flow-field model based on the density field inferred from the estimated cluster masses.Comment: Accepted for publication in ApJ (29 pages including 13 figures). A version with high-resolution figures is available at http://www.cfa.harvard.edu/~acrook/preprints

Genetic counseling and testing practices for late-onset neurodegenerative disease: a systematic review

ObjectiveTo understand contemporary genetic counseling and testing practices for late-onset neurodegenerative diseases (LONDs), and identify whether practices address the internationally accepted goals of genetic counseling: interpretation, counseling, education, and support.MethodsFour databases were systematically searched for articles published from 2009 to 2020. Peer-reviewed research articles in English that reported research and clinical genetic counseling and testing practices for LONDs were included. A narrative synthesis was conducted to describe different practices and map genetic counseling activities to the goals. Risk of bias was assessed using the Qualsyst tool. The protocol was registered with PROSPERO (CRD42019121421).ResultsSixty-one studies from 68 papers were included. Most papers focused on predictive testing (58/68) and Huntington's disease (41/68). There was variation between papers in study design, study population, outcomes, interventions, and settings. Although there were commonalities, novel and inconsistent genetic counseling practices were identified. Eighteen papers addressed all four goals of genetic counseling.ConclusionContemporary genetic counseling and testing practices for LONDs are varied and informed by regional differences and the presence of different health providers. A flexible, multidisciplinary, client- and family-centered care continues to emerge. As genetic testing becomes a routine part of care for patients (and their relatives), health providers must balance their limited time and resources with ensuring clients are safely and effectively counseled, and all four genetic counseling goals are addressed. Areas of further research include diagnostic and reproductive genetic counseling/testing practices, evaluations of novel approaches to care, and the role and use of different health providers in practice

Health system interventions to integrate genetic testing in routine oncology services: A systematic review

Background Integration of genetic testing into routine oncology care could improve access to testing. This systematic review investigated interventions and the tailored implementation strategies aimed at increasing access to genetic counselling and testing and identifying hereditary cancer in oncology. Methods The search strategy results were reported using the PRISMA statement and four electronic databases were searched. Eligible studies included routine genetic testing for breast and ovarian cancer or uptake after universal tumour screening for colorectal or endometrial cancer. The titles and abstracts were reviewed and the full text articles screened for eligibility. Data extraction was preformed using a designed template and study appraisal was assessed using an adapted Newcastle Ottawa Scale. Extracted data were mapped to Proctor’s et al outcomes and the Consolidated Framework for Implementation Research and qualitatively synthesised. Results Twenty-seven studies, published up to May 2020, met the inclusion criteria. Twenty-five studies ranged from poor (72%), fair to good (28%) quality. Most interventions identified were complex (multiple components) such as; patient or health professional education, interdisciplinary practice and a documentation or system change. Forty-eight percent of studies with complex interventions demonstrated on average a 35% increase in access to genetic counselling and a 15% increase in testing completion. Mapping of study outcomes showed that 70% and 32% of the studies aligned with either the service and client or the implementation level outcome and 96% to the process or inner setting domains of the Consolidated Framework for Implementation Research. Conclusion Existing evidence suggests that complex interventions have a potentially positive effect towards genetic counselling and testing completion rates in oncology services. Studies of sound methodological quality that explore a greater breadth of pre and post implementation outcomes and informed by theory are needed. Such research could inform future service delivery models for the integration of genetics into oncology services