1,531 research outputs found
Crossover of Microscopic Dynamics in Metallic Supercooled Liquid Observed by NMR
Nuclear magnetic resonance is used to characterize local atomic motions in the glassy and supercooled liquid states of the bulk metallic glass system Pd43Ni10Cu27P20. The temperature dependence of the Knight shift reveals that certain local atomic motion decreases rapidly below a crossover temperature Tc down to the glass transition temperature Tg. Above Tc as well as below Tg the mean-squared amplitude of local motions depends linearly on the temperature. The observed gradual transition below Tc is inconsistent with heterogeneity effects. It reveals that qualitative changes of microscopic properties in the supercooled liquid take place at temperatures significantly above Tg
A Study of Anyon Statistics by Breit Hamiltonian Formalism
We study the anyon statistics of a dimensional Maxwell-Chern-Simons
(MCS) gauge theory by using a systemmetic metheod, the Breit Hamiltonian
formalism.Comment: 25 pages, LATE
Occupational hand dermatitis among cement workers in Taiwan
Background/PurposeOccupational dermatitis among cement workers is a major occupational health concern. The two most important occupational hazards for cement workers are irritant and allergic cement contact dermatitis. The objective of this study was to investigate the severity of occupational cement contact dermatitis and the common allergens among cement workers in Taiwan.MethodsA total of 97 cement workers from the Cement Workersâ Association of Tainan City and County participated in this study. A structured questionnaire was used to evaluate the demographic data and work-related activities of these cement workers. A complete skin examination was conducted, and skin manifestations were assessed by a dermatologist. Allergens from European Standard Tray (Chemotechnique Diagnostic AB, Sweden) with a total of 25 substances were used for patch testing.ResultsOur results showed that 65 out of 97 cement workers were suffering from occupational cement hand contact dermatitis. The most affected skin area was the hand. Thickening of the dorsal surface of the hand, especially around the metacarpophalangeal joint area, and hyperkeratosis of the palm were the major skin manifestations. The results of the patch test showed that 24 out of 97 were allergic to potassium dichromate, nine were allergic to thiuram mix, nine were allergic to fragrance mix and seven were allergic to cobalt chloride. The final diagnosis, based on the results of the skin examination and the patch test, showed that 43 of 97 cement workers had irritant cement contact dermatitis and 22 had allergic cement contact dermatitis.ConclusionWe conclude that occupational cement hand dermatitis among cement workers is an important and severe issue in Taiwan, and the most common allergens among cement workers are potassium dichromate, thiuram mix, fragrance mix and cobalt chloride. The high positive rate of chromium hypersensitivity among cement workers reflects the urgency to regulate the addition of ferrous sulfate to cement in Taiwan
The Discovery of A Luminous Broad Absorption Line Quasar at A Redshift of 7.02
Despite extensive efforts, only two quasars have been found at to date
due to a combination of low spatial density and high contamination from more
ubiquitous Galactic cool dwarfs in quasar selection. This limits our current
knowledge of the super-massive black hole (SMBH) growth mechanism and
reionization history. In this letter, we report the discovery of a luminous
quasar at , DELS J003836.10152723.6 (hereafter J00381527),
selected using photometric data from DESI Legacy imaging Survey (DELS),
Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore
() mid-infrared all-sky survey. With an absolute magnitude of
=27.1 and bolometric luminosity of =5.610 , J00381527 is the most luminous quasar
known at . Deep optical to near infrared spectroscopic observations
suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the
Eddington limit, with an Eddington ratio of 1.250.19. The CIV broad
emission line of J00381527 is blue-shifted by more than 3000 km s to
the systemic redshift. More detailed investigations of the high quality spectra
reveal three extremely high velocity CIV broad absorption lines (BALs) with
velocity from 0.08 to 0.14 times the speed of light and total balnicity index
of more than 5000 km s, suggesting the presence of relativistic
outflows. J00381527 is the first quasar found at the epoch of reionization
(EoR) with such strong outflows and provides a unique laboratory to investigate
AGN feedback on the formation and growth of the most massive galaxies in the
early universe.Comment: ApJL in pres
Thermodynamically favorable reactions shape the archaeal community affecting bacterial community assembly in oil reservoirs
Microbial community assembly mechanisms are pivotal for understanding the ecological functions of microorganisms in biogeochemical cycling in Earthâs ecosystems, yet rarely investigated in the context of deep terrestrial ecology. Here, the microbial communities in the production waters collected from water injection wells and oil production wells across eight oil reservoirs throughout northern China were determined and analyzed by proportional distribution analysis and null model analysis. A âcoreâ microbiota consisting of three bacterial genera, including Arcobacter, Pseudomonas and Acinetobacter, and eight archaeal genera, including Archaeoglobus, Methanobacterium, Methanothermobacter, unclassified Methanobacteriaceae, Methanomethylovorans, Methanoculleus, Methanosaeta and Methanolinea, was found to be present in all production water samples. Canonical correlation analysis reflected that the core archaea were significantly influenced by temperature and reservoir depth, while the core bacteria were affected by the combined impact of the core archaea and environmental factors. Thermodynamic calculations indicate that bioenergetic constraints are the driving force that governs the enrichment of two core archaeal guilds, aceticlastic methanogens versus hydrogenotrophic methanogens, in low- and high-temperature oil reservoirs, respectively. Collectively, our study indicates that microbial community structures in wells of oil reservoirs are structured by the thermodynamic window of opportunity, through which the core archaeal communities are accommodated directly followed by the deterministic recruiting of core bacterial genera, and then the stochastic selection of some other microbial members from local environments. Our study enhances the understanding of the microbial assembly mechanism in deep terrestrial habitats. Meanwhile, our findings will support the development of functional microbiota used for bioremediation and bioaugmentation in microbial enhanced oil recovery
High-throughput discovery of genetic determinants of circadian misalignment.
Circadian systems provide a fitness advantage to organisms by allowing them to adapt to daily changes of environmental cues, such as light/dark cycles. The molecular mechanism underlying the circadian clock has been well characterized. However, how internal circadian clocks are entrained with regular daily light/dark cycles remains unclear. By collecting and analyzing indirect calorimetry (IC) data from more than 2000 wild-type mice available from the International Mouse Phenotyping Consortium (IMPC), we show that the onset time and peak phase of activity and food intake rhythms are reliable parameters for screening defects of circadian misalignment. We developed a machine learning algorithm to quantify these two parameters in our misalignment screen (SyncScreener) with existing datasets and used it to screen 750 mutant mouse lines from five IMPC phenotyping centres. Mutants of five genes (Slc7a11, Rhbdl1, Spop, Ctc1 and Oxtr) were found to be associated with altered patterns of activity or food intake. By further studying the Slc7a11tm1a/tm1a mice, we confirmed its advanced activity phase phenotype in response to a simulated jetlag and skeleton photoperiod stimuli. Disruption of Slc7a11 affected the intercellular communication in the suprachiasmatic nucleus, suggesting a defect in synchronization of clock neurons. Our study has established a systematic phenotype analysis approach that can be used to uncover the mechanism of circadian entrainment in mice
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A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): A First Look at the Rest-frame Optical Spectra of z > 6.5 Quasars Using JWST
© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/Studies of rest-frame optical emission in quasars at z > 6 have historically been limited by the wavelengths accessible by ground-based telescopes. The James Webb Space Telescope (JWST) now offers the opportunity to probe this emission deep into the reionization epoch. We report the observations of eight quasars at z > 6.5 using the JWST/NIRCam Wide Field Slitless Spectroscopy as a part of the âA SPectroscopic survey of biased halos In the Reionization Era (ASPIRE)â program. Our JWST spectra cover the quasarsâ emission between rest frame âŒ4100 and 5100 Ă
. The profiles of these quasarsâ broad HÎČ emission lines span a full width at half maximum from 3000 to 6000 km sâ1. The HÎČ-based virial black hole (BH) masses, ranging from 0.6 to 2.1 billion solar masses, are generally consistent with their Mg ii-based BH masses. The new measurements based on the more reliable HÎČ tracer thus confirm the existence of a billion solar-mass BHs in the reionization epoch. In the observed [O iii] λ λ 4960,5008 doublets of these luminous quasars, broad components are more common than narrow core components (†1200 km sâ1), and only one quasar shows stronger narrow components than broad. Two quasars exhibit significantly broad and blueshifted [O iii] emission, thought to trace galactic-scale outflows, with median velocities of â610 and â1430 km sâ1 relative to the [C ii] 158 ÎŒm line. All eight quasars show strong optical Fe ii emission and follow the eigenvector 1 relations defined by low-redshift quasars. The entire ASPIRE program will eventually cover 25 quasars and provide a statistical sample for the studies of the BHs and quasar spectral properties.Peer reviewe
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