1,942 research outputs found
The formation of thallium chloride complexes and their extraction into ether
Thallium is one of a large group of elements which can be extracted into ethers from halogen acid solutions. The general lack of knowledge of the extraction process for these salts has given strong impetus to the study of all aspects of it
Category 5
Follow Elizabeth and her family through this family oriented video series which highlights topics such as preparing for a hurricane, how to help those affected by a storm and raises awareness for mental health after a natural disaster.
Nexus Maximus IV
The Challenge: Innovation for Refugees and Displaced Populations
One of the great challenges of our time is how to help refugees and displaced populations, and how to prevent the causes in the first place. Every minute, 24 people around the world are forced to flee their homes. That’s 34,000 people a day who leave everything behind in the hope of finding safety and a better tomorrow. The impact of war, political, racial and religious conflict, and environmental crises of famine and climate change, have caused great suffering and there is a great opportunity to do better.
The issues these populations and the countries who receive them face are diverse and complex. They include public health, housing/built environment, cultural integration, public safety, employment/economic and more.
How can innovation address these challenges? How do we create the social systems and products to support a healthy, safe and integrated program for refugees? How do we address the physical, emotional, and social needs of refugees to restore hope and opportunity? The solutions may be as far ranging as the challenges, exploring the acute needs during a crisis, as well as the chronic needs of the permanently displaced; looking at immigration and adjustments to new cultures. We encourage participants to draw upon all disciplines, from health professions to architecture, engineering to design, ethics, communication and every way of thinking we have, to find better ways to innovate on physical solutions, processes, policies, systems, and more.
Recap of poster presentationshttps://jdc.jefferson.edu/nexusmaximus/1015/thumbnail.jp
Tsunamis Generated by Subaquatic Volcanic Explosions: Unique Data from 1996 Eruption in Karymskoye Lake, Kamchatka, Russia
Slider-Block Friction Model for Landslides: Application to Vaiont and La Clapiere Landslides
Accelerating displacements preceding some catastrophic landslides have been
found empirically to follow a time-to-failure power law, corresponding to a
finite-time singularity of the velocity [{\it Voight},
1988]. Here, we provide a physical basis for this phenomenological law based on
a slider-block model using a state and velocity dependent friction law
established in the laboratory and used to model earthquake friction. This
physical model accounts for and generalizes Voight's observation: depending on
the ratio of two parameters of the rate and state friction law and on the
initial frictional state of the sliding surfaces characterized by a reduced
parameter , four possible regimes are found. Two regimes can account for
an acceleration of the displacement. We use the slider-block friction model to
analyze quantitatively the displacement and velocity data preceding two
landslides, Vaiont and La Clapi\`ere. The Vaiont landslide was the catastrophic
culmination of an accelerated slope velocity. La Clapi\`ere landslide was
characterized by a peak of slope acceleration that followed decades of ongoing
accelerating displacements, succeeded by a restabilizing phase. Our inversion
of the slider-block model on these data sets shows good fits and suggest to
classify the Vaiont (respectively La Clapi\`ere) landslide as belonging to the
velocity weakening unstable (respectively strengthening stable) sliding regime.Comment: shortened by focusing of the frictional model, Latex document with
AGU style file of 14 pages + 11 figures (1 jpeg photo of figure 6 given
separately) + 1 tabl
Transcriptome analysis of chemically-induced sensory neuron ablation in zebrafish
Peripheral glia are known to have a critical role in the initial response to axon damage and degeneration. However, little is known about the cellular responses of non-myelinating glia to nerve injury. In this study, we analyzed the transcriptomes of wild-type and mutant (lacking peripheral glia) zebrafish larvae that were treated with metronidazole. This treatment allowed us to conditionally and selectively ablate cranial sensory neurons whose axons are ensheathed only by non-myelinating glia. While transcripts representing over 27,000 genes were detected by RNAseq, only a small fraction (~1% of genes) were found to be differentially expressed in response to neuronal degeneration in either line at either 2 hrs or 5 hrs of metronidazole treatment. Analysis revealed that most expression changes (332 out of the total of 458 differentially expressed genes) occurred over a continuous period (from 2 to 5 hrs of metronidazole exposure), with a small number of genes showing changes limited to only the 2 hr (55 genes) or 5 hr (71 genes) time points. For genes with continuous alterations in expression, some of the most meaningful sets of enriched categories in the wild-type line were those involving the inflammatory TNF-alpha and IL6 signaling pathways, oxidoreductase activities and response to stress. Intriguingly, these changes were not observed in the mutant line. Indeed, cluster analysis indicated that the effects of metronidazole treatment on gene expression was heavily influenced by the presence or absence of glia, indicating that the peripheral non-myelinating glia play a significant role in the transcriptional response to sensory neuron degeneration. This is the first transcriptome study of metronidazole-induced neuronal death in zebrafish and the response of non-myelinating glia to sensory neuron degeneration. We believe this study provides important insight into the mechanisms by which non-myelinating glia react to neuronal death and degeneration in sensory circuits
Fluid-dynamics of the 1997 Boxing Day volcanic blast on Montserrat, W.I.
Directed volcanic blasts are powerful explosions with a significant laterally¬directed component, which can generate devastating, high-energy pyroclastic density currents (PDCs). Such blasts are an important class of eruptive phenomena, but quantified understanding of their dynamics and effects is still incomplete. Here we use 2D and 3D multiparticle thermofluid dynamic flow codes to examine a powerful volcanic blast that occurred on Montserrat in December 1997. Based on the simulations, we divide the blast into three phases; an initial burst phase lasts roughly 5 s and involves rapid expansion of the gas-pyroclast mixture, a gravitational collapse phase which occurs when the erupted material fails to mix with sufficient air to form a buoyant column and thus collapses asymmetrically, and a PDC phase which is dominated by motion parallel to the ground surface and is influenced by topography. We vary key input parameters such as total gas energy and total solid mass to understand their influence on simulations, and compare the simulations with independent field observations of damage and deposits, demonstrating that the models generally capture important large-scale features of the natural phenomenon. We also examine the 2D and 3D model results to estimate the flow Mach number and conclude that the range of damage sustained at villages on Montserrat can be reasonably explained by the spatial and temporal distribution of the dynamic pressure associated with subsonic PDCs
Subtle changes in strain prior to sub-Plinian eruptions recorded by vault-housed extensometers during the 2011 activity at Shinmoe-dake, Kirishima volcano, Japan
Towards Landslide Predictions: Two Case Studies
In a previous work [Helmstetter, 2003], we have proposed a simple physical
model to explain the accelerating displacements preceding some catastrophic
landslides, based on a slider-block model with a state and velocity dependent
friction law. This model predicts two regimes of sliding, stable and unstable
leading to a critical finite-time singularity. This model was calibrated
quantitatively to the displacement and velocity data preceding two landslides,
Vaiont (Italian Alps) and La Clapi\`ere (French Alps), showing that the former
(resp. later) landslide is in the unstable (resp. stable) sliding regime. Here,
we test the predictive skills of the state-and-velocity-dependent model on
these two landslides, using a variety of techniques. For the Vaiont landslide,
our model provides good predictions of the critical time of failure up to 20
days before the collapse. Tests are also presented on the predictability of the
time of the change of regime for la Clapi\`ere landslide.Comment: 30 pages with 12 eps figure
Tri-critical behavior in rupture induced by disorder
We discover a qualitatively new behavior for systems where the load transfer
has limiting stress amplification as in real fiber composites. We find that the
disorder is a relevant field leading to tri--criticality, separating a
first-order regime where rupture occurs without significant precursors from a
second-order regime where the macroscopic elastic coefficient exhibit power law
behavior. Our results are based on analytical analysis of fiber bundle models
and numerical simulations of a two-dimensional tensorial spring-block system in
which stick-slip motion and fracture compete.Comment: Revtex, 10 pages, 4 figures available upon reques
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