374 research outputs found
Clutter Detection and Surface/Subsurface Slope Determination by Combination of Repeat-Pass Sounder Orbits Applied to SHARAD Data
Nadir-looking low-frequency radar sounders cannot easily resolve off-nadir surface returns from the subsurface nadir echoes. Cross-track surface echoes (also named "clutter ") with time delays synchronized with subsurface returns are renowned for being a major challenge for scientists, as they can affect the analysis of orbital radar sounders data. We present a method for clutter discrimination and surface/subsurface slope estimation using data acquired from radar sounders in closely spaced repeated orbits configuration. The method takes advantage of cross-track signal migration to discriminate off-nadir clutter from subsurface signal returns received at the nadir. The migration of the off-nadir signals is also used to determine the clutter direction of arrival (DOA) as well as the surface/subsurface cross-track slopes. The effectiveness of the method has been proven on the Mars Reconnaissance Orbiter (MRO)'s Shallow Radar (SHARAD) dataset and provides a proof-of-concept demonstration for the surface clutter discrimination when radar sounders repeated-passes data are available
UWB processing applied to multifrequency radar sounders. The case of MARSIS and comparison with SHARAD
We readapt ultrawideband (UWB) processing to
enhance the range resolution of the Mars Advanced Radar for
Subsurface and Ionosphere Sounding (MARSIS) up to a factor
of 6 (25 m). The technique provides for the estimation of radar
signature over a wider spectrum via the application of wellknown super-resolution (SR) techniques to adjoining subbands.
The measured spectra are first interpolated and then extrapolated
outside the original bands. The revised algorithm includes the
estimation and removal of ionospheric effects impacting the
two signals. Because the processing requires the realignment of
the echoes at different frequencies, we derived the maximum
tolerable retracking error to obtain reliable super-resolved range
profiles. This condition is fulfilled by low-roughness areas compared to MARSIS wavelength, which proves to be suitable for the
application of our processing. Examples of super-resolved experimental products over different geological scenarios show the
detection of shallow dielectric interfaces not visible from original
MARSIS products. Our results are validated by comparison with
the Shallow Radar (SHARAD) data acquired at the crossovers,
demonstrating the potential of the method to provide enhanced
imaging capabilities
Understanding the scale and nature of outcome change in area-regeneration programmes: evidence from the New Deal for Communities Programme in England
The New Deal for Communities (NDC) Programme is one of the most intensive area-based initiatives (ABIs) launched in England. Between 1998 and 2010, 39 NDC Partnerships were charged with improving conditions in relation to six outcomes within deprived neighbourhoods, each accommodating around 9,800 people. Data point to only modest change, much of which reflected improving attitudes towards the area and the environment. There are problems in identifying positive people-based outcomes because relatively few individuals benefit from relevant initiatives. Few positive benefits leak out of NDC areas. Transformational change was always unlikely bearing in mind the limited nature of additional resources, and because only a minority of individuals directly engage with NDC projects. This evidence supports perspectives of ABIs rooted in 'local-managerialism'
Stuck in the slow lane: reconceptualising the links between gender, transport and social exclusion
This article draws upon primary research undertaken with over 3,000 women in the North East of England to explore the links between women, transport and the labour market. The research, funded by the ESF, advances the idea of spatiality as a social construction and builds on seminal studies relating to women and poverty to consider the way in which a gender division of transport constrains women's mobility and restricts their employment opportunities. It is likely to contribute to important debates, concerning strategies to tackle worklessness and the most effective spatial level at which to configure public transport networks
Selective neurogenic blockades and perioperative immune reactivity in patients undergoing lung resection
Strategies for Increasing Protection Effectiveness in the Camplong Nature Park Area, Kupang Regency, East Nusa Tenggara Province
Camplong Nature Tourism Park (NTP) is one of the conservation areas in Kupang Regency, East Nusa Tenggara Province. The NTP Camplong area is partially designated as a Nature Tourism Park managed by the Natural Resources Conservation Agency East Nusa Tenggara (BBKSDA NTT) based on the Decree of the Minister of Forestry Number: SK.347 / MenhutII / 2010 with an area of ​​696.60 Ha. One of the management activities carried out in Camplong NTP is protection of forest areas. Protection efforts are faced with various threats, including being located near settlements and public roads, making them vulnerable to habitat destruction. Forest fires, illegal use of area resources and waste disposal are the main problems that threaten the existence of the NTP Camplong area. Based on the Management Effectiveness Tracking Tool (METT) assessment by BBKSDA NTT, the METT score was 69%, from the minimum value of 70%. This study aims to determine the effectiveness and strategies to increase the effectiveness of efforts to protect the Camplong Nature Park area. The research was conducted in July-August 2019 at NTP Camplong. Data collection was carried out by direct observation and in-depth interviews. From the research results, it is known that the management aspects in the form of planning, organizing, implementing, and monitoring carried out in NTP Camplong have generally been implemented even though they have not run optimally. This has an impact on the less than optimal protection efforts for the NTP Camplong area. Strategies for increasing the effectiveness of the management of the NTP Camplong area, namely: strengthening management management; increasing the implementation of area protection and security; coordination with government and legal institutions; as well as increasing community participation in area protection efforts
Subsurface structure of Planum Boreum from Mars Reconnaissance Orbiter Shallow Radar soundings
We map the subsurface structure of Planum Boreum using sounding data from the Shallow Radar (SHARAD) instrument onboard the Mars Reconnaissance Orbiter. Radar coverage throughout the 1,000,000- km2 area reveals widespread reflections from basal and internal interfaces of the north polar layered deposits (NPLD). A dome-shaped zone of diffuse reflectivity up to 12 ls (1-km thick) underlies twothirds of the NPLD, predominantly in the main lobe but also extending into the Gemina Lingula lobe across Chasma Boreale. We equate this zone with a basal unit identified in image data as Amazonian sand-rich layered deposits [Byrne, S., Murray, B.C., 2002. J. Geophys. Res. 107, 5044, 12 pp. doi:10.1029/2001JE001615; Fishbaugh, K.E., Head, J.W., 2005. Icarus 174, 444–474; Tanaka, K.L., Rodriguez, J.A.P., Skinner, J.A., Bourke, M.C., Fortezzo, C.M., Herkenhoff, K.E., Kolb, E.J., Okubo, C.H., 2008. Icarus 196, 318–358]. Elsewhere, the NPLD base is remarkably flat-lying and co-planar with the exposed surface of the surrounding Vastitas Borealis materials. Within the NPLD, we delineate and map four units based on the radar-layer packets of Phillips et al. [Phillips, R.J., and 26 colleagues, 2008. Science 320, 1182– 1185] that extend throughout the deposits and a fifth unit confined to eastern Gemina Lingula. We estimate the volume of each internal unit and of the entire NPLD stack (821,000 km3), exclusive of the basal unit. Correlation of these units to models of insolation cycles and polar deposition [Laskar, J., Levrard, B., Mustard, J.F., 2002. Nature 419, 375–377; Levrard, B., Forget, F., Montmessin, F., Laskar, J., 2007. J. Geophys. Res. 112, E06012, 18 pp. doi:10.1029/2006JE002772] is consistent with the 4.2-Ma age of the oldest preserved NPLD obtained by Levrard et al. [Levrard, B., Forget, F., Montmessin, F., Laskar, J., 2007. J. Geophys. Res. 112, E06012, 18 pp. doi:10.1029/2006JE002772]. We suggest a dominant layering mechanism of dust–content variation during accumulation rather than one of lag production during periods of sublimation
‘It’s the best thing I’ve done in a long while’: teenage mothers’ experiences of educational alternatives
Pregnant and mothering schoolgirls have been identified as an educationally vulnerable group. Many are not welcomed in their mainstream schools and as a consequence, access a range of educational alternatives. This article presents the views and experiences of 14 young women in the English Midlands, who became pregnant while still of statutory school age, 12 of whom spent time in alternative educational settings. It is based on data gathered from repeat interviews over an 18-month period and shows that all who attended the educational alternatives rated them highly and benefitted from what they had to offer. Using the concept of ‘difference’ as a central analytic theme, the article examines how and why this was the case. The analysis shows that it was through recognising some differences but not others that the educational alternatives were successful in supporting young women’s learning and well-being. Importantly, those that were recognised were done so in non-stigmatising ways. The research also highlights some limitations of the alternatives, alongside the ways in which gender and class continue to impact the educational outcomes and career trajectories of this particular group of students
Shallow radar (SHARAD) sounding observations of the Medusae Fossae Formation, Mars
The SHARAD (shallow radar) sounding radar on the Mars Reconnaissance Orbiter detects subsurface reflections in the eastern and western parts of the Medusae Fossae Formation (MFF). The radar waves penetrate up to 580 m of the MFF and detect clear subsurface interfaces in two locations: west MFF between 150 and 155◦ E and east MFF between 209 and 213◦ E. Analysis of SHARAD radargrams suggests that the real part of the permittivity is ∼3.0, which falls within the range of permittivity values inferred from MARSIS data for thicker parts of the MFF. The SHARAD data cannot uniquely determine the composition of the MFF material, but the low permittivity implies that the upper few hundred meters of the MFF material has a high porosity. One possibility is that the MFF is comprised of low-density welded or interlocked pyroclastic deposits that are capable of sustaining the steep-sided yardangs and ridges seen in imagery. The SHARAD surface echo power across the MFF is low relative to typical martian plains, and completely disappears in parts of the east MFF that correspond to the radar-dark Stealth region. These areas are extremely rough at centimeter to meter scales, and the lack of echo power is most likely due to a combination of surface roughness and a low near-surface permittivity that reduces the echo strength from any locally flat regions. There is also no radar evidence for internal layering in any of the SHARAD data for the MFF, despite the fact that tens-of-meters scale layering is apparent in infrared and visible wavelength images of nearby areas. These interfaces may not be detected in SHARAD data if their permittivity contrasts are low, or if the layers are discontinuous. The lack of closely spaced internal radar reflectors suggests that the MFF is not an equatorial analog to the current martian polar deposits, which show clear evidence of multiple internal layers in SHARAD dat
Characterization of HIV drug resistance mutations among patients failing first-line antiretroviral therapy from a tertiary referral center in Lusaka, Zambia: Sequence Analysis of HIV DRMs in Lusaka, Zambia
In settings of resource constraint, an understanding of HIV drug resistance can guide antiretroviral therapy (ART) at switch to second-line therapy. To determine the prevalence of such HIV drug resistance mutations (HIV DRM), we used an in-house sequencing assay in the pol gene (protease and partial reverse transcriptase) in a cohort of patients suspected of failing a first-line regimen, which in Zambia comprises two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and one non-nucleoside reverse transcriptase inhibitor (NNRTI). Our analysis cohort (n=68) was referred to the University Teaching Hospital in Lusaka from November 2009 to October 2012. Median duration on first-line ART to suspected treatment failure was 3.2 years (IQR 1.7–4.7 years). The majority of patients (95%) harbored HIV-1 subtype C virus. Analysis of reverse transcriptase revealed M184V (88%), K103N/S (32%), and Y181C/I/V (41%) DRMs, with the latter conferring reduced susceptibility to the salvage therapy candidates etravirine and rilpivirine. Three patients (5%) had major protease inhibitor (PI) resistance mutations: all three had the V82A mutation, and one patient (Clade J virus) had a concurrent M46I, Q58E, and L76V DRM. HIV-1 genotyping revealed major and minor DRMs as well as high levels of polymorphisms in subtype C isolates from patients failing first-line antiretroviral therapy. Closer monitoring of DRM mutations at first-line failure can inform clinicians about future options for salvage therapy
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