179 research outputs found
Mechanisms of Auger-induced chemistry derived from wave packet dynamics
To understand how core ionization and subsequent Auger decay lead to bond breaking in large systems, we simulate the wave packet dynamics of electrons in the hydrogenated diamond nanoparticle C_(197)H_(112). We find that surface core ionizations cause emission of carbon fragments and protons through a direct Auger mechanism, whereas deeper core ionizations cause hydrides to be emitted from the surface via remote heating, consistent with results from photon-stimulated desorption experiments [Hoffman A, Laikhtman A, (2006) J Phys Condens Mater 18:S1517–S1546]. This demonstrates that it is feasible to study the chemistry of highly excited large-scale systems using simulation and analysis tools comparable in simplicity to those used for classical molecular dynamics
seIPp 93/24 1 a The Case for e-e-Linear Colliders at High Energy
Abstract I review the physics motivation for colliding electrons with electrons at very high energies for QED studies, Standard-Model-predicted processes in the WW sector, and for the investigation of Standard Model extensions. Intensity, luminosity, and polarization parameters for collider operation and interaction region requirements are briefly considered. Opening statement for the e-e-session, presented at the Workshop on Physics and Experiments at Linear e+e-Colliders Waikoloa, Hawaii, April 26-30, 1993 -
The association of the original OSHA chemical hazard communication standard with reductions in acute work injuries/illnesses in private industry and the industrial releases of chemical carcinogens
Background OSHA predicted the original chemical Hazard Communication Standard (HCS) would cumulatively reduce the lost workday acute injury/illness rate for exposure events by 20% over 20 years and reduce exposure to chemical carcinogens. Methods JoinPoint trend software identified changes in the rate of change of BLS rates for days away from work for acute injuries/illnesses during 1992–2009 for manufacturing and nonmanufacturing industries for both chemical, noxious or allergenic injury exposure events and All other exposure events. The annual percent change in the rates was used to adjust observed numbers of cases to estimate their association with the standard. A case‐control study of EPA's Toxic Release Inventory 1988–2009 data compared carcinogen and non‐carcinogens' releases. Results The study estimates that the HCS was associated with a reduction in the number of acute injuries/illnesses due to chemical injury exposure events over the background rate in the range 107,569–459,395 (Hudson method/modified BIC model) depending on whether the HCS is treated as a marginal or sole factor in the decrease. Carcinogen releases have declined at a substantially faster rate than control non‐carcinogens. Discussion The previous HCS standard was associated with significant reductions in chemical event acute injuries/illnesses and chemical carcinogen exposures. Am. J. Ind. Med. 57:138–152, 2014. © 2013 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102719/1/ajim22269.pd
Prodigious submarine landslides during the inception and early growth of volcanic islands
Volcanic island inception applies large stresses as the ocean crust domes in response to magma ascension and is loaded by eruption of lavas. There is currently limited information on when volcanic islands are initiated on the seafloor, and no information regarding the seafloor instabilities island inception may cause. The deep sea Madeira Abyssal Plain contains a 43 million year history of turbidites among which many originate from mass movements in the Canary Islands. Here, we investigate the composition and timing of a distinctive group of
turbidites that we suggest represent a new unique record of large-volume submarine landslides triggered during the inception, submarine shield growth, and final subaerial emergence of the Canary Islands. These slides are predominantly multi-stage and yet represent among the largest mass movements on the Earth’s surface up to three or more-times larger than subaerial Canary Islands flank collapses. Thus whilst these deposits provide invaluable information on ocean island geodynamics they also represent a significant, and as yet unaccounted, marine geohazard
Personal protective equipment use by health-care workers in intensive care units during the COVID-19 pandemic in Japan: comparative analysis with the PPE-SAFE survey
AimWe investigated personal protective equipment (PPE) use and supply shortage, training, and adverse events among health-care workers (HCWs) in the intensive care unit (ICU) during the coronavirus disease (COVID-19) pandemic in Japan and compared the results with an international survey that used the same methodology.MethodsThis Web-based survey was carried out from 14 April to 6 May, 2020, in Japan and included HCWs directly involved in ICU management of COVID-19 patients. A survey invitation was emailed using the Japanese Society of Intensive Care Medicine’s mailing list.ResultsWe analyzed 460 valid responses from among 976 responses. The N95/FFP2 mask (77%) was the most frequently used, although half of our respondents reported reuse of single-use N95/FFP2 masks. The median duration (1 h) of uninterrupted PPE use per shift was less than that in the international study. The most common PPE-related adverse event was experiencing intense heat (75%). Logistic regression analysis revealed that being a nurse was independently associated with experiencing intense heat.ConclusionShortage of PPE and frequent mask reuse were prevalent during the COVID-19 pandemic in Japan. Intense heat is the most significant symptom, especially for nurses, even with short-duration PPE use. Strategies to protect HCWs from dehydration and intense heatstroke are needed
TGFβR signalling determines CD103<sup>+</sup>CD11b<sup>+</sup> dendritic cell development in the intestine
CD103+CD11b+ dendritic cells (DCs) are unique to the intestine, but the factors governing their differentiation are unclear. Here we show that transforming growth factor receptor 1 (TGFβR1) has an indispensable, cell intrinsic role in the development of these cells. Deletion of Tgfbr1 results in markedly fewer intestinal CD103+CD11b+ DCs and a reciprocal increase in the CD103−CD11b+ dendritic cell subset. Transcriptional profiling identifies markers that define the CD103+CD11b+ DC lineage, including CD101, TREM1 and Siglec-F, and shows that the absence of CD103+CD11b+ DCs in CD11c-Cre.Tgfbr1fl/fl mice reflects defective differentiation from CD103−CD11b+ intermediaries, rather than an isolated loss of CD103 expression. The defect in CD103+CD11b+ DCs is accompanied by reduced generation of antigen-specific, inducible FoxP3+ regulatory T cells in vitro and in vivo, and by reduced numbers of endogenous Th17 cells in the intestinal mucosa. Thus, TGFβR1-mediated signalling may explain the tissue-specific development of these unique DCs
A new macrofaunal limit in the deep biosphere revealed by extreme burrow depths in ancient sediments
Macrofauna is known to inhabit the top few 10s cm of marine sediments, with rare burrows up to two metres below the seabed. Here, we provide evidence from deep-water Permian strata for a previously unrecognised habitat up to at least 8 metres below the sediment-water interface. Infaunal organisms exploited networks of forcibly injected sand below the seabed, forming living traces and reworking sediment. This is the first record that shows sediment injections are responsible for hosting macrofaunal life metres below the contemporaneous seabed. In addition, given the widespread occurrence of thick sandy successions that accumulate in deep-water settings, macrofauna living in the deep biosphere are likely much more prevalent than considered previously. These findings should influence future sampling strategies to better constrain the depth range of infaunal animals living in modern deep-sea sands. One Sentence Summary: The living depth of infaunal macrofauna is shown to reach at least 8 metres in new habitats associated with sand injections
Axiomatic Choice Theory Traveling between Mathematical Formalism, Normative Choice Rules and Psychological Measurement, 1944-1956
The following analysis is meant to contribute to a history of rational choice theory. More specifically, I provide a multi-layered account of rational choice theory in terms of its biography as a scientific object. I argue that its axiomatic version, choice theory traveled between different research sites, specified within the context of different mathematical formalisms and occupying different epistemic functions; it was being applied to prescribe rules of proper behavior, as representation of behavioral hypotheses, and as measurement device to capture individual values. New modifications of what I call 'axiomatic choice theory' did not fully replace old versions of it, which prevents the reconstruction of its 'travels' as a continuous process and acknowledges the different versions of axiomatic choice theory that are currently used in the social sciences, particularly in economics. Furthermore, by revealing the diversity of its manifestations within the context of social networks and within particular research sites, the account of axiomatic choice theory developed here will ultimately contributes to an explanation of the disunity and confusion surrounding current debates about rational choice theory and allows for providing a more nuanced picture of its nature and scope. Jacob Marschak's professional development is used as a guide through this history of axiomatic choice theory to illustrate its journey
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