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Strain rates are fundamental measures of ice flow and are used in a wide variety of glaciological applications including investigations of bed properties, calculations of basal mass balance on ice shelves, and constraints on ice rheological models. However, despite their extensive application, strain rates are calculated using a variety of methods and length scales and the details are often not specified. In this study, we compare the results of nominal and logarithmic strain-rate calculations based on a satellite-derived velocity field of the Antarctic ice sheet generated from Landsat 8 satellite data. Our comparison highlights the differences between the two common approaches in the glaciological literature. We evaluate the errors introduced by each approach and their impacts on the results. We also demonstrate the importance of choosing and specifying a length scale over which strain-rate calculations are made, which can strongly influence other derived quantities such as basal mass balance on ice shelves. Finally, we present strain-rate data products calculated using an approximate viscous length-scale with satellite observations of ice velocity for the Antarctic continent.
The time required to obtain Institutional Review Board (IRB) approval is a frequent subject of efforts to reduce unnecessary delays in initiating clinical trials. This study was conducted by and for IRB directors to better understand factors affecting approval times as a first step in developing a quality improvement framework.
807 IRB-approved clinical trials from 5 University of California campuses were analyzed to identify operational and clinical trial characteristics influencing IRB approval times.
High workloads, low staff ratios, limited training, and the number and types of ancillary reviews resulted in longer approval times. Biosafety reviews and the need for billing coverage analysis were ancillary reviews that contributed to the longest delays. Federally funded and multisite clinical trials had shorter approval times. Variability in between individual committees at each institution reviewing phase 3 multisite clinical trials also contributed to delays for some protocols. Accreditation was not associated with shorter approval times.
Reducing unnecessary delays in obtaining IRB approval will require a quality improvement framework that considers operational and study characteristics as well as the larger institutional regulatory environment.
It is by now evident that most young stars have associated disks and/or envelopes, which may be active (accreting) or passive (reprocessing stellar photons), or both. Knowing how such disks evolve is crucial to our understanding of how stars form, and may be relevant to other questions, such as the time available for the formation of planets in solar nebulae. In this poster we discuss the properties of pre-main sequence circumstellar disks in Lynds 1641 in Orion, the nearest giant molecular cloud complex.
This article explores and reconsiders the view of children's encounters with place as central to a place-based pedagogy that seeks to dismantle rather than support constructions of a nature-culture binary. I unpack the current fervour for reinserting the child in nature and nature-based education as a significant phenomenon in environmental and outdoor education. I will draw on recent literature on place-based research and theorise using new materialist and posthumanist approaches that seek to disrupt anthropocentric views and support new ways of considering our encounters with the more-than-human world. Then, using these new approaches, I will theorise a recent place-based research project with children in the city of La Paz, Bolivia, to illustrate how it is possible to challenge current assumptions that are firmly entrenched in the child in nature movement. I will conclude by considering what intra-species relations, place encounters and child-body-animal-place relations can teach us about questioning anthropocentrism and human exceptionalism. Finally, I consider how can we overcome these limitations of a narrow and nostalgic view of ‘child and nature’ and reimagine a more diverse approach to education for a sustainable future.
Mounting an antibody response capable of discriminating amongst and appropriately targeting different parasites is crucial in host defence. However, cross-reactive antibodies that recognize (bind to) multiple parasite species are well documented. We aimed to determine if a higher inoculating dose of one species, and thus exposure to larger amounts of antigen over a longer period of time, would fine-tune responses to that species and reduce cross-reactivity. Using the Plasmodium chabaudi chabaudi (Pcc)–Nippostrongylus brasiliensis (Nb) co-infection model in BALB/c mice, in which we previously documented cross-reactive antibodies, we manipulated the inoculating dose of Pcc across 4 orders of magnitude. We investigated antigen-specific and cross-reactive antibody responses against crude and defined recombinant antigens by enzyme linked immunosorbent assay, Western blot and antibody depletion assays. Contrary to our hypothesis that increasing exposure to Pcc would reduce cross-reactivity to Nb, we found evidence for increased avidity of a subpopulation of antibodies that recognized shared antigens. Western blot indicated proteins of apparent monomer molecular mass 28 and 98 kDa in both Nb and Pcc antigen preparations and also an Nb protein of similar size to recombinant Pcc antigen, merozoite surface protein-119. The implications of antibodies binding antigen from such phylogenetically distinct parasites are discussed.
This Summary for Policymakers presents key findings from the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). The SREX approaches the topic by assessing the scientific literature on issues that range from the relationship between climate change and extreme weather and climate events (‘climate extremes’) to the implications of these events for society and sustainable development. The assessment concerns the interaction of climatic, environmental, and human factors that can lead to impacts and disasters, options for managing the risks posed by impacts and disasters, and the important role that non-climatic factors play in determining impacts. Box SPM.1 defines concepts central to the SREX.
The character and severity of impacts from climate extremes depend not only on the extremes themselves but also on exposure and vulnerability. In this report, adverse impacts are considered disasters when they produce widespread damage and cause severe alterations in the normal functioning of communities or societies. Climate extremes, exposure, and vulnerability are influenced by a wide range of factors, including anthropogenic climate change, natural climate variability, and socioeconomic development (Figure SPM.1). Disaster risk management and adaptation to climate change focus on reducing exposure and vulnerability and increasing resilience to the potential adverse impacts of climate extremes, even though risks cannot fully be eliminated (Figure SPM.2). Although mitigation of climate change is not the focus of this report, adaptation and mitigation can complement each other and together can significantly reduce the risks of climate change. [SYR AR4, 5.3]
An anomalous effect of electron irradiation on thermal grain growth in Ni has been observed using in situ TEM. Grain growth during thermal annealing was suppressed in areas irradiated with electrons. Grain growth suppression required a minimum electron energy between 100 and 200 keV. This alteration of thermal grain growth is attributed to electron beam injection of a surface contaminant such as carbon. This work points out that care must be exercised in the execution and evaluation of in situ TEM or ion beam experiments that deal with microstructural changes which are highly compositionally sensitive.
To improve Ti SALICIDE process, Si preamorphization by arsenic before Ti sputtering has been studied in two parts: process characterization and fundamental studies. Sheet resistance (Rs) reduction by the preamorphization is more pronounced on thinner and narrower-line silicide formation. At 60keV implantation energy, there is an optimum arsenic dose for the improvement. Through the treatment, more uniform silicide layer can be formed, indicated by the improved Rs uniformity. In the fundamental study, preamorphization appears to have little effect on promoting C49-to-C54 phase transformation. It is suggested that the treatment is able to enhance the reaction rate between Ti and amorphous Si, and results in C54-TiSi2 with larger grains and consequently slightly lower resistivity.
CVD Diamond films with resistivites comparable to that measured in natural type IIA diamond can be fabricated using a microwave-plasma assisted growth environment. Modification of the resistivity of these films is typically accomplished through the introduction of impurities, or dopants such as boron. Some applications, however, require that the purity of the carbon lattice be maintained, while still altering the resistivity of the film. This is the case for many applications of diamond in space. Here, varying the resistivity of CVD diamond is investigated by controlling the introduction of sp2coordinated bonds, yet maintaining the overall diamond structure and carbon purity. Experimental results will be presented, and the use of these materials in NASA's Genesis Discovery Mission will be discussed
This report evaluated (a) the temporal stability of hemodynamic
responses to three tasks using impedance cardiography, and (b)
the influence of aging on stress responses in a multi-ethnic
pediatric sample. One hundred children 8 to 10 years old and
49 adolescents 15 to 17 years old were tested at study entry
and on average 3 years later. Results showed that the composite
task-induced changes in stroke volume (SV), cardiac output (CO),
total peripheral resistance (TPR), and pre-ejection period (PEP)
were moderately stable across 3 years (rs = .36 to
.51), with children showing greater stability in task-induced
CO change than did adolescents. However, the magnitude of the
participant's stress responses changed over time, varied
by task, age group, and gender. These results suggest that
hemodynamic responses to stress change with aging during childhood
and adolescence and that they can be measured reliably.
Long-term memory (LTM) is one of the diverse cognitive functions
adversely affected by multiple sclerosis (MS). The LTM deficits
have often been attributed to failure of retrieval, whereas
encoding processes are presumed intact. However, support for
this view comes primarily from studies in which encoding and
retrieval operations were not investigated systematically. In
the current study, we used an encoding specificity paradigm
to examine the robustness of encoding in MS and to specifically
evaluate the impact of the disease on contextual memory. We
hypothesized that persons with MS would exhibit a selective
impairment in retrieving items from LTM when required to generate
new cue-target associations at encoding, but not when cues held
a strong preexisting relationship to the targets. The findings
supported the hypotheses. We conclude that the mnemonic deficits
associated with MS affect both encoding and retrieval.
Specifically, problems with binding of contextual information
at encoding impair effective retrieval of memories. Nonetheless,
access to these memories can be gained through preexisting
associations organized in the semantic network. (JINS,
2002, 8, 395–409.)