16,901 research outputs found
Erosional development of bedrock spur and gully topography in the Valles Marineris, Mars
Gully networks separated by resistant bedrock spurs are a common erosional feature along the escarpments that border the Valles Marineris. The resistant spur topography is best developed where the base of the slope is truncated by linear scarps interpreted as fault scarps. Regional variations in slope morphology imply that spur and gully topography undergoes a systematic progressive degradation through time associated with the erosional destruction of the basal fault scarps. The comparative morphometry of the divide networks indicates that the density of the spur networks and the number of first-order unbranched spurs decreases as the basal slope break becomes more sinuous. Abstraction of the spurs occurs through regolith storage in adjacent gullies at the slope base and the most degraded slope forms are entirely buried in talus. The basal fault scarps apparently control regolith transport by allowing debris to drain from the slope. As these basal scarps decay the slope base becomes increasingly sinuous and the slopes become transport limited. Dry mass-wasting may be the most important process acting on these slopes where a continually lowered base level is required to maintain the spur topography. In contrast to the Martian slopes, range front fault escarpments in the western U.S. show no systematic trend in spur network geometry as they are eroded. These weathering limited slopes are controlled by the more efficient removal of regolith through fluvial processes which rapidly create quasi-equilibrium drainage networks
Galaxy pairs in the Sloan Digital Sky Survey - XII: The fuelling mechanism of low excitation radio-loud AGN
We investigate whether the fuelling of low excitation radio galaxies (LERGs)
is linked to major galaxy interactions. Our study utilizes a sample of 10,800
spectroscopic galaxy pairs and 97 post-mergers selected from the Sloan Digital
Sky Survey with matches to multi-wavelength datasets. The LERG fraction amongst
interacting galaxies is a factor of 3.5 higher than that of a control sample
matched in local galaxy density, redshift and stellar mass. However, the LERG
excess in pairs does not depend on projected separation and remains elevated
out to at least 500 kpc, suggesting that major mergers are not their main
fuelling channel. In order to identify the primary fuelling mechanism of LERGs,
we compile samples of control galaxies that are matched in various host galaxy
and environmental properties. The LERG excess is reduced, but not completely
removed, when halo mass or D4000 are included in the matching parameters.
However, when BOTH M_halo and D4000 are matched, there is no LERG excess and
the 1.4 GHz luminosities (which trace jet mechanical power) are consistent
between the pairs and control. In contrast, the excess of optical and mid-IR
selected AGN in galaxy pairs is unchanged when the additional matching
parameters are implemented. Our results suggest that whilst major interactions
may trigger optically and mid-IR selected AGN, the gas which fuels the LERGs
has two secular origins: one associated with the large scale environment, such
as accretion from the surrounding medium or minor mergers, plus an internal
stellar mechanism, such as winds from evolved stars.Comment: Accepted for publication in MNRAS Letters; 5 page
Shear Flows of Rapidly Flowing Granular Materials
Shear flows of granular materials are studied in an open channel. The wall shear is calculated from an open channel momentum equation which includes the density variations in the flow. An experimental technique was developed that allowed the measurement of the average density of the flow at different longitudinal locations in the channel. Two sizes of glass beads are examined and results show the variations in the wall shear as a function of various dimensionless parameters
Neutrino-nucleus coherent scattering as a probe of neutron density distributions
Neutrino-nucleus coherent elastic scattering provides a theoretically
appealing way to measure the neutron part of nuclear form factors. Using an
expansion of form factors into moments, we show that neutrinos from stopped
pions can probe not only the second moment of the form factor (the neutron
radius) but also the fourth moment. Using simple Monte Carlo techniques for
argon, germanium, and xenon detectors of 3.5 tonnes, 1.5 tonnes, and 300 kg,
respectively, we show that the neutron radii can be found with an uncertainty
of a few percent when near a neutrino flux of
neutrinos/cm/s. If the normalization of the neutrino flux is known
independently, one can determine the moments accurately enough to discriminate
among the predictions of various nuclear energy functionals.Comment: 10 pages, 5 figure
Recommended from our members
Revision of the Chiapan deer mouse, Peromyscus zarhynchus, with the description of a new species
We analyzed morphometric and molecular variation among 8 populations of Peromyscus zarhynchus grouped into 5 pooled samples representing separate physiographic regions across the range of this species in Chiapas, Mexico, and western Guatemala. Mitochondrial sequence data identify 2 well-supported and reciprocally monophyletic clades, separating all Chiapas specimens from those in Guatemala. These 2 clades group as a strongly supported monophyletic lineage aligned with other members of the Peromyscus mexicanus species group. The Chiapas clade is further subdivided into 4 subclades: 1) samples from the western part of the state, 2) specimens from a single locality in Northern Chiapas, 3) all central localities, and 4) those from a single locality in Eastern Chiapas. The molecular distance in the mitochondrial cytochrome-b gene (Cytb) between the 2 major clades is relatively low (mean p-distance = 3.66%); those between the 4 Chiapas subclades are even less (mean p-distance 2.73%). Multivariate analyses of external and craniodental morphometric variables also distinguish 2 major groups, separating Guatemalan from Chiapas samples but with the latter also divided into 2 subgroups, one that segregates the Northern Chiapas sample from those distributed elsewhere in that state. The Guatemalan and Chiapas samples differ in both cranial size and shape variables. The second-level separation of samples from within Chiapas (northern versus all others) is interpreted to result from the combination of local adaptation to distinct physiographic regions and geographic isolation generated by patches of suitable habitat. We describe the Guatemalan samples as a distinct species based on their molecular and morphological uniqueness, and argue that P. zarhynchus itself is divided into definable subspecies, with the nominotypical form P. z. zarhynchus, restricted to the vicinity of its type locality (Tumbalá) in Northern Chiapas, and P. z. cristobalensis with type locality of San Cristobal, over the remainder of the species range in the state
Evaluation of an uncalibrated agricultural land model at the sub-field scale
An uncalibrated agricultural land surface model, Agro-IBIS, was validated at the sub-field scale using data collected at a local agricultural field site planted with maize in 2009, with a focus on capturing the spatial variability and accumulation rates of soil moisture and leaf area index. Capturing the variability was deemed important for evaluating the model\u27s potential for inclusion as the land surface model in atmospheric models. An ensemble method of forcing the model with different combinations of input data was used in an attempt to produce the variability seen in measurements across the field. The model was able to produce a range of soil moisture similar to the range observed at the field site, though rates of soil water accumulation and drainage were much higher than observed. The spread in leaf area index measurements was not captured by the model, though the rate of leaf area accumulation was similar in both the field and the model. The model emerged the crop too early due to the lack of calibration, which led to a positive bias in leaf area. The bias in leaf area led to biases in a number of other variables, including sensible heat flux and in-canopy temperature. Despite the biases, which were expected due to the lack of calibration, the ability of Agro-IBIS to capture spatial variability in soil moisture at the sub-field scale make it a good candidate for coupling to other models
Estimation of forest stand structure attributes from aerial photographs| An accuracy assessment
A pilot study of the S-MAP (Solutions for Medications Adherence Problems) intervention for older adults prescribed polypharmacy in primary care: Study protocol
Background: Adhering to multiple medications as prescribed is challenging for older patients (aged ≥ 65 years) and a difficult behaviour to improve. Previous interventions designed to address this have been largely complex in nature but have shown limited effectiveness and have rarely used theory in their design. It has been recognised that theory ('a systematic way of understanding events or situations') can guide intervention development and help researchers better understand how complex adherence interventions work. This pilot study aims to test a novel community pharmacy-based intervention that has been systematically developed using the Theoretical Domains Framework (12-domain version) of behaviour change. Methods: As part of a non-randomised pilot study, pharmacists in 12 community pharmacies across Northern Ireland (n = 6) and London, England (n = 6), will be trained to deliver the intervention to older patients who are prescribed ≥ 4 regular medicines and are non-adherent (self-reported). Ten patients will be recruited per pharmacy (n = 120) and offered up to four tailored one-to-one sessions, in the pharmacy or via telephone depending on their adherence, over a 3-4-month period. Guided by an electronic application (app) on iPads, the intervention content will be tailored to each patient's underlying reasons for non-adherence and mapped to the most appropriate solutions using established behaviour change techniques. This study will assess the feasibility of collecting data on the primary outcome of medication adherence (self-report and dispensing data) and secondary outcomes (health-related quality of life and unplanned hospitalisations). An embedded process evaluation will assess training fidelity for pharmacy staff, intervention fidelity, acceptability to patients and pharmacists and the intervention's mechanism of action. Process evaluation data will include audio-recordings of training workshops, intervention sessions, feedback interviews and patient surveys. Analysis will be largely descriptive. Discussion: Using pre-defined progression criteria, the findings from this pilot study will guide the decision whether to proceed to a cluster randomised controlled trial to test the effectiveness of the S-MAP intervention in comparison to usual care in community pharmacies. The study will also explore how the intervention components may work to bring about change in older patients' adherence behaviour and guide further refinement of the intervention and study procedures. Trial registration: This study is registered at ISRCTN: https://doi.org/10.1186/ISRCTN7383153
Low frequency ultrasonic nondestructive inspection of aluminum/adhesive fuselage lap splice
The Federal Aviation Administration\u27s (FAA) Center for Aviation Systems Reliability (CASR), located at Iowa State University (ISU), was established in 1990 in response to the Aviation Safety Act (Public Law 100-591) of 1988. The Aviation Safety Act, created primarily as the result of an in-flight mishap involving an Aloha Airlines\u27 Boeing 737, mandated that the FAA develop research technologies to aid the aviation industry to (1) better predict the effects of design, maintenance, testing, wear, and fatigue life of an aircraft; (2) develop methods for improving aircraft maintenance technology and practices; and (3) expand general long-range research activities applicable to aviation systems
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