17,509 research outputs found
Superconductivity and Dirac Fermions in 112-phase Pnictides
This article reviews the status of current research on the 112-phase of
pnictides. The 112-phase has gained augmented attention due to the recent
discovery of high-temperature superconductivity in \cl with a maximum
critical temperature \tc\sim 47\,K upon Sb substitution. The structural,
magnetic, and electronic properties of \cl bear some similarities with other
superconducting pnictide phases, however, the different valence states of the
pnictogen and the presence of a metallic spacer layer are unique features of
the 112-system. Low-temperature superconductivity which coexists with
antiferromagnetic order was observed in transition metal (Ni, Pd) deficient
112-compounds like \cn, \lpb, \lps, \lns. Besides superconductivity,
the presence of naturally occurring anisotropic Dirac Fermionic states were
observed in the layered 112-compounds \smb, \cmb, \lab which are of
significant interest for future nanoelectronics as an alternative to graphene.
In these compounds, the linear energy dispersion resulted in a high
magnetoresistance that stayed unsaturated even at the highest applied magnetic
fields. Here, we describe various 112-type materials systems combining
experimental results and theoretical predictions to stimulate further research
on this less well-known member of the pnictide family.Comment: 18 pages, 20 figure
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Field efficacy evaluation and post-treatment contamination risk assessment of an ultraviolet disinfection and safe storage system.
Inconsistent use of household water treatment and safe storage (HWTS) systems reduces their potential health benefits. Ultraviolet (UV) disinfection is more convenient than some existing HWTS systems, but it does not provide post-treatment residual disinfectant, which could leave drinking water vulnerable to recontamination. In this paper, using as-treated analyses, we report on the field efficacy of a UV disinfection system at improving household drinking water quality in rural Mexico. We further assess the risk of post-treatment contamination from the UV system, and develop a process-based model to better understand household risk factors for recontamination. This study was part of a larger cluster-randomized stepped wedge trial, and the results complement previously published population-level results of the intervention on diarrheal prevalence and water quality. Based on the presence of Escherichia coli (proportion of households with ≥ 1 E. coli/100 mL), we estimated a risk difference of -28.0% (95% confidence interval (CI): -33.9%, -22.1%) when comparing intervention to control households; -38.6% (CI: -48.9%, -28.2%) when comparing post- and pre-intervention results; and -37.1% (CI: -45.2%, -28.9%) when comparing UV disinfected water to alternatives within the household. We found substantial increases in post-treatment E. coli contamination when comparing samples from the UV system effluent (5.0%) to samples taken from the storage container (21.1%) and drinking glasses (26.0%). We found that improved household infrastructure, additional extractions from the storage container, additional time from when the storage container was filled, and increased experience of the UV system operator were associated with reductions in post-treatment contamination. Our results suggest that the UV system is efficacious at improving household water quality when used as intended. Promoting safe storage habits is essential for an effective UV system dissemination. The drinking glass appears to represent a small but significant source of recontamination that is likely to impact all HWTS systems
Classical T Tauri-like Outflow Activity in the Brown Dwarf Mass Regime
Over the last number of years spectroscopic studies have strongly supported
the assertion that protostellar accretion and outflow activity persists to the
lowest masses. In this paper we present the results of our latest investigation
of brown dwarf (BD) outflow activity and report on the discovery of two new
outflows. Here ISO-Oph 32 is shown to drive a blue-shifted outflow with a
radial velocity of 10-20 km/s and spectro-astrometric analysis constrains the
position angle of this outflow to 240 +/- 7 degrees. The BD candidate ISO-Cha1
217 is found to have a bipolar outflow bright in several key forbidden lines
(radial velocity = -20 km/s, +40 km/s) and with a PA of 190-210 degrees. A
striking feature of the ISO-Cha1 217 outflow is the strong asymmetry between
the red and blue-shifted lobes. This asymmetry is revealed in the relative
brightness of the two lobes (red-shifted lobe is brighter), the factor of two
difference in radial velocity (the red-shifted lobe is faster) and the
difference in the electron density (again higher in the red lobe). Such
asymmetries are common in jets from low mass protostars and the observation of
a marked asymmetry at such a low mass supports the idea that BD outflow
activity is scaled down from low mass protostellar activity.
In addition to presenting these new results, a comprehensive comparison is
made between BD outflow activity and jets launched by CTTSs. In particular, the
application of current methods for investigating the excitation conditions and
mass loss rates in CTT jets to BD spectra is explored.Comment: Accepted by Astrophysical Journa
Muon-spin rotation measurements of the vortex state in SrRuO: type-1.5 superconductivity, vortex clustering and a crossover from a triangular to a square vortex lattice
Muon-spin rotation has been used to probe vortex state in SrRuO. At
moderate fields and temperatures a lattice of triangular symmetry is observed,
crossing over to a lattice of square symmetry with increasing field and
temperature. At lower fields it is found that there are large regions of the
sample that are completely free from vortices which grow in volume as the
temperature falls. Importantly this is accompanied by {\it increasing} vortex
density and increasing disorder within the vortex-cluster containing regions.
Both effects are expected to result from the strongly temperature-dependent
long-range vortex attractive forces arising from the multi-band chiral-order
superconductivity.Comment: 13 pages, 4 figure
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