1,478 research outputs found
Shoreline Dynamics and Environmental Change Under the Modern Marine Transgression: St. Catherines Island, Georgia
The current study has evaluated shoreline dynamics and environmental change at St. Catherines Island, Georgia, with attention to the two major controls of barrier island formation and modification processes. These major controls include the increase in accommodation space, or the rate of sea level rise for the Georgia Bight which has remained constant in 20th and 21st century tide gauge data and dynamically changing rates of sediment supply based on anthropogenic modifications to land cover (Trimble, 1974) that are reflected in sediment transport (McCarney-Castle et al., 2010). Vibracoring and radiocarbon data provided valuable insights into the stratigraphy and development of St. Catherines Island. A stratigraphic model has been developed for the sediments associated with the Late Holocene accretional terrains where multiple small scale fluctuations in sea level have resulted in the formation of a sedimentary veneer punctuated with transgressive surfaces and regressive sequences. A working model for an interpolated Late Holocene sea level curve has been constructed using direct evidence from vibracore data as constraining points and indirect evidence from other regional sea level studies to provide additional structure. The relationship between the timing of the regressions versus periods of beach ridge formation and implications from the current shoreline dynamics study regarding the role of sediment supply complement each other. The ages of beach ridge formation strongly correlate to periods that are associated with regressions in sea level based on the sedimentary record and an evaluation of Late Holocene sea level conditions. The evaluation of anthropogenic modifications to the rate of sediment supply performed under the current study indicates that in spite of significant changes in sediment flux rates of +300% (pre-dam era) and -20% (post-dam era), shoreline retreat was continuous during the study period with an acceleration noted in the rates of shoreline retreat associated with spit and berm landforms during the post-dam or modern era. The two associations indicate strongly that the rate of sediment supply plays a secondary role to the major control of the rate of sea level rise in the formation and modification processes at St. Catherines Island
Initiating technological and pedagogical shifts in low achieving urban minority classrooms
This study explored the introduction of multi-modal teaching strategies alongside technology implementation in high poverty schools. Teachers were provided with scientific tools, simulations, and teaching stations and provided with training and opportunities to practice teaching strategies developed in conjunction with special education and literacy experts. Teacher interviews, classroom observations, and student focus groups comprised the bulk of the sited data supplementing the student achievement scores and pre and post content tests administered for each unit. Findings suggested not all teachers incorporated multi-modal strategies into lessons incorporating technology and that lower achieving students interpreted lessons quite differently than their teachers in these contexts. Implications for ways technology implementations may explicate emerging literacies are discussed
Whole-Genome Sequencing to Identify Mutants and Polymorphisms in Chlamydomonas reinhardtii
Whole-genome sequencing (WGS) provides a new platform for the identification of mutations that produce a mutant phenotype. We used Illumina sequencing to identify the mutational profile of three Chlamydomonas reinhardtii mutant strains. The three strains have more than 38,000 changes from the reference genome. NG6 is aflagellate and maps to 269 kb with only one nonsynonymous change; the V12E mutation falls in the FLA8 gene. Evidence that NG6 is a fla8 allele comes from swimming revertants that are either true or pseudorevertants. NG30 is aflagellate and maps to 458 kb that has six nonsynonomous changes. Evidence that NG30 has a causative nonsense allele in IFT80 comes from rescue of the nonswimming phenotype with a fragment bearing only this gene. This gene has been implicated in Jeune asphyxiating thoracic dystrophy. Electron microscopy of ift80-1 (NG30) shows a novel basal body phenotype. A bar or cap is observed over the distal end of the transition zone, which may be an intermediate in preparing the basal body for flagellar assembly. In the acetate-requiring mutant ac17, we failed to find a nonsynonymous change in the 676 kb mapped region, which is incompletely assembled. In these strains, 43% of the changes occur on two of the 17 chromosomes. The excess on chromosome 6 surrounds the mating-type locus, which has numerous rearrangements and suppressed recombination, and the changes extend beyond the mating-type locus. Unexpectedly, chromosome 16 shows an unexplained excess of single nucleotide polymorphisms and indels. Overall, WGS in combination with limited mapping allows fast and accurate identification of point mutations in Chlamydomonas
Availability and use of therapeutic interchange policies in managing antimicrobial shortages among South African public sector hospitals; findings and implications
Background: Therapeutic interchange policies in hospitals are useful in dealing with antimicrobial shortages and minimising resistance rates. The extent of antimicrobial shortages and availability of therapeutic interchange policies is unknown among public sector hospitals in South Africa. This study aimed to ascertain the extent and rationale for dealing with antimicrobial shortages and describe policies or guidelines and the role of pharmacists in the process. Methods: A quantitative and descriptive study was conducted with a target population of 403 public sector hospitals. Data were collected from hospital pharmacists using an electronic questionnaire via SurveyMonkeyTM. Results: The response rate was 33.5% and most (83.3%) hospitals had experienced shortages in the previous six months. Antimicrobials commonly reported as out of stock included cloxacillin (54.3%), benzathine benzylpenicillin (54.2%), and erythromycin (39.6%). Reasons for shortages included pharmaceutical companies with supply constraints (85.3%) and an inefficient supply system. Only 42.4% had therapeutic interchange policies, and 88.9% contacted the prescriber when there for substitution. Conclusions: Antimicrobial shortages are prevalent in South African public sector hospitals with the most affected being penicillins and cephalosporins. Therapeutic interchange policies are not available at most hospitals. Effective strategies are required to improve communication between pharmacists and prescribers to ensure that safe, appropriate, and therapeutically equivalent alternatives are available
Soluble Receptor for Advanced Glycation End Products (sRAGE) Is a Sensitive Biomarker in Human Pulmonary Arterial Hypertension.
Pulmonary arterial hypertension (PAH) is a progressive condition with an unmet need for early diagnosis, better monitoring, and risk stratification. The receptor for advanced glycation end products (RAGE) is activated in response to hypoxia and vascular injury, and is associated with inflammation, cell proliferation and migration in PAH. For the adult cohort, we recruited 120 patients with PAH, 83 with idiopathic PAH (IPAH) and 37 with connective tissue disease-associated PAH (CTD-PAH), and 48 controls, and determined potential plasma biomarkers by enzyme-linked immunoassay. The established heart failure marker NTproBNP and IL-6 plasma levels were several-fold higher in both adult IPAH and CTD-PAH patients versus controls. Plasma soluble RAGE (sRAGE) was elevated in IPAH patients (3044 Ā± 215.2 pg/mL) and was even higher in CTD-PAH patients (3332 Ā± 321.6 pg/mL) versus controls (1766 Ā± 121.9 pg/mL; p < 0.01). All three markers were increased in WHO functional class II+III PAH versus controls (p < 0.001). Receiver-operating characteristic analysis revealed that sRAGE has diagnostic accuracy comparable to prognostic NTproBNP, and even outperforms NTproBNP in the distinction of PAH FC I from controls. Lung tissue RAGE expression was increased in IPAH versus controls (mRNA) and was located predominantly in the PA intima, media, and inflammatory cells in the perivascular space (immunohistochemistry). In the pediatric cohort, plasma sRAGE concentrations were higher than in adults, but were similar in PH (n = 10) and non-PH controls (n = 10). Taken together, in the largest adult sRAGE PAH study to date, we identify plasma sRAGE as a sensitive and accurate PAH biomarker with better performance than NTproBNP in the distinction of mild PAH from controls
Machine-learned climate model corrections from a global storm-resolving model
Due to computational constraints, running global climate models (GCMs) for
many years requires a lower spatial grid resolution ( km) than is
optimal for accurately resolving important physical processes. Such processes
are approximated in GCMs via subgrid parameterizations, which contribute
significantly to the uncertainty in GCM predictions. One approach to improving
the accuracy of a coarse-grid global climate model is to add machine-learned
state-dependent corrections at each simulation timestep, such that the climate
model evolves more like a high-resolution global storm-resolving model (GSRM).
We train neural networks to learn the state-dependent temperature, humidity,
and radiative flux corrections needed to nudge a 200 km coarse-grid climate
model to the evolution of a 3~km fine-grid GSRM. When these corrective ML
models are coupled to a year-long coarse-grid climate simulation, the time-mean
spatial pattern errors are reduced by 6-25% for land surface temperature and
9-25% for land surface precipitation with respect to a no-ML baseline
simulation. The ML-corrected simulations develop other biases in climate and
circulation that differ from, but have comparable amplitude to, the baseline
simulation
Emulating Fast Processes in Climate Models
Cloud microphysical parameterizations in atmospheric models describe the
formation and evolution of clouds and precipitation, a central weather and
climate process. Cloud-associated latent heating is a primary driver of large
and small-scale circulations throughout the global atmosphere, and clouds have
important interactions with atmospheric radiation. Clouds are ubiquitous,
diverse, and can change rapidly. In this work, we build the first emulator of
an entire cloud microphysical parameterization, including fast phase changes.
The emulator performs well in offline and online (i.e. when coupled to the rest
of the atmospheric model) tests, but shows some developing biases in
Antarctica. Sensitivity tests demonstrate that these successes require careful
modeling of the mixed discrete-continuous output as well as the input-output
structure of the underlying code and physical process.Comment: Accepted at the Machine Learning and the Physical Sciences Workshop
at the 36th conference on Neural Information Processing Systems (NeurIPS)
December 3, 202
Systemic NK cell ablation attenuates intraāabdominal adipose tissue macrophage infiltration in murine obesity
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108606/1/oby20823.pd
STM Spectroscopy of ultra-flat graphene on hexagonal boron nitride
Graphene has demonstrated great promise for future electronics technology as
well as fundamental physics applications because of its linear energy-momentum
dispersion relations which cross at the Dirac point. However, accessing the
physics of the low density region at the Dirac point has been difficult because
of the presence of disorder which leaves the graphene with local microscopic
electron and hole puddles, resulting in a finite density of carriers even at
the charge neutrality point. Efforts have been made to reduce the disorder by
suspending graphene, leading to fabrication challenges and delicate devices
which make local spectroscopic measurements difficult. Recently, it has been
shown that placing graphene on hexagonal boron nitride (hBN) yields improved
device performance. In this letter, we use scanning tunneling microscopy to
show that graphene conforms to hBN, as evidenced by the presence of Moire
patterns in the topographic images. However, contrary to recent predictions,
this conformation does not lead to a sizable band gap due to the misalignment
of the lattices. Moreover, local spectroscopy measurements demonstrate that the
electron-hole charge fluctuations are reduced by two orders of magnitude as
compared to those on silicon oxide. This leads to charge fluctuations which are
as small as in suspended graphene, opening up Dirac point physics to more
diverse experiments than are possible on freestanding devices.Comment: Nature Materials advance online publication 13/02/201
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