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We determined the hepatitis E virus (HEV) seroprevalence and detection rate in commercial swine herds in Italy's utmost pig-rich area, and assessed HEV seropositivity risk in humans as a function of occupational exposure to pigs, diet, foreign travel, medical history and hunting activities. During 2011–2014, 2700 sera from 300 swine herds were tested for anti-HEV IgG. HEV RNA was searched in 959 faecal pools from HEV-seropositive herds and in liver/bile/muscle samples from 179 pigs from HEV-positive herds. A cohort study of HEV seropositivity in swine workers (n = 149) was also performed using two comparison groups of people unexposed to swine: omnivores (n = 121) and vegetarians/vegans (n = 115). Herd-level seroprevalence was 75·6% and was highest in farrow-to-feeder herds (81·6%). Twenty-six out of 105 (24·8%) herds had HEV-positive faecal samples (25 HEV-3, one HEV-4). Only one bile sample tested positive. HEV seropositivity was 12·3% in swine workers, 0·9% in omnivores and 3·0% in vegetarians/vegans. Factors significantly associated with HEV seropositivity were occupational exposure to pigs, travel to Africa and increased swine workers’ age. We concluded that HEV is widespread in Italian swine herds and HEV-4 circulation is alarming given its pathogenicity, with those occupationally exposed to pigs being at increased risk of HEV seropositivity.
Multi-decade observing campaigns of the globular clusters 47 Tucanae and M15 have led to an outstanding number of discoveries. Here, we report on the latest results of the long-term observations of the pulsars in these two clusters. For most of the pulsars in 47 Tucanae we have measured, among other things, their higher-order spin period derivatives, which have in turn provided stringent constraints on the physical parameters of the cluster, such as its distance and gravitational potential. For M15, we have studied the relativistic spin precession effect in PSR B2127+11C. We have used full-Stokes observations to model the precession effect, and to constrain the system geometry. We find that the visible beam of the pulsar is swiftly moving away from our line of sight and may very soon become undetectable. On the other hand, we expect to see the opposite emission beam sometime between 2041 and 2053.
A total of 18 radio sources selected on the basis of steep low-frequency radio spectra have been searched for the presence of millisecond pulsars using the Molonglo Observatory synthesis telescope. The search covered pulsar periods down to 2 ms with a limiting sensitivity of approximately 10 mJy. No pulsars were detected.
The Parkes pulsar data archive currently provides access to 144044 data files obtained from observations carried out at the Parkes observatory since the year 1991. Around 105 files are from surveys of the sky, the remainder are observations of 775 individual pulsars and their corresponding calibration signals. Survey observations are included from the Parkes 70 cm and the Swinburne Intermediate Latitude surveys. Individual pulsar observations are included from young pulsar timing projects, the Parkes Pulsar Timing Array and from the PULSE@Parkes outreach program. The data files and access methods are compatible with Virtual Observatory protocols. This paper describes the data currently stored in the archive and presents ways in which these data can be searched and downloaded.
In-line monitoring of the electrical properties of high-k dielectrics in logic or memory fab-lines has become increasingly important in the semiconductor industry. Non-contact corona-Kelvin based metrology can be used to affectively monitor in-line key dielectric properties. Furthermore, we present an important extension of this metrology to the micro-scale that allows measurement of dielectric properties on test sites as small as 40μm × 70μm. This is achieved through miniaturization of the corona charging apparatus and of the Kelvin probe without a sacrifice in precision or repeatability. Corona-Kelvin micro-metrology allows for the monitoring of the critical dielectric properties directly on product wafers that can then be returned to the fab-line for continued processing. Application examples are given for dielectric capacitance of advanced dielectrics and for the properties of an oxide-nitride-oxide (ONO) memory structure. In the latter case we demonstrate programming and erasing of the ONO structure realized by corona charging. We also use the measured flatband voltage and total charge to identify the location of the programmed charge at the first SiO2/Si3N4 interface in the ONO structure.
In this paper, we present a non-contact C-V technique
for ultra-thin dielectrics on silicon. The technique
uses incremental corona charging of dielectric and a
measurement of the surface potential with a vibrating
capacitive electrode. A differential quasistatic C-V
curve is generated using time-resolved measurements.
The technique incorporates transconductance corrections
that enable corresponding ultra-low electrical oxide
thickness (EOT) determination down to the sub-nanometer
range. It also provides a means for monitoring the flat
band voltage, VFB, the interface trap spectrum,
DIT, and the total dielectric charge, QTOT. This
technique is seen as a replacement for not only MOS C-V
measurements but also for mercury-probe C-V. In addition, EOT
measurement by the corona C-V has a major advantage over optical
thickness methods because it is not affected by water adsorption
and molecular airborne contamination, MAC. These effects have
been a problem for optical metrology of ultra-thin dielectrics.
PSRs J1847–0130 and J1718–37184 have inferred surface dipole magnetic fields greater than those of any other known pulsars and well above the “quantum critical field” above which some models predict radio emission should not occur. These fields are similar to those of the anomalous X-ray pulsars (AXPs), which growing evidence suggests are “magnetars”. The lack of AXP-like X-ray emission from these radio pulsars (and the non-detection of radio emission from the AXPs) creates new challenges for understanding pulsar emission physics and the relationship between these classes of apparently young neutron stars.
Measurement of accurate positions, pulse periods and period derivatives is an essential follow-up to any pulsar survey. The procedures being used to obtain timing parameters for the pulsars discovered in the Parkes multibeam pulsar survey are described. Completed solutions have been obtained so far for about 80 pulsars. They show that the survey is preferentially finding pulsars with higher than average surface dipole magnetic fields. Eight pulsars have been shown to be members of binary systems and some of the more interesting results relating to these are presented.
The Parkes multibeam pulsar survey which began in 1997 and is now about 50% complete. It has discovered more than 400 new pulsars so far, including a number of young, high magnetic field, and relativistic binary pulsars. Early results, descriptions of the survey and follow up timing programs can be found in papers by Lyne et al. (1999 MNRAS in press), Camilo et al. (this volume), and Manchester et al. (this volume). This paper describes the data release policy and how you can gain access to the raw data and details on the pulsars discovered.
The Parkes multibeam pulsar survey uses a 13-element receiver operating at a wavelength of 20 cm to survey the inner Galactic plane with remarkable sensitivity. To date we have collected and analyzed data from 45% of the survey region (|b| < 5°; 260° < l < 50°), and have discovered 440 pulsars, in addition to re-detecting 190 previously known ones. Most of the newly discovered pulsars are at great distances, as inferred from a median dispersion measure (DM) of 400 cm−3 pc.
Hydroxylated alumina films have been synthesized by water oxidation of single crystal Al(110) surfaces. Thermal dehydroxylation results in anion vacancies which produce an Al(3s) defect state 3.5 eV below the conduction band edge. The defect-DOS exhibits a maximum for oxides heated to 648±25 K, which is just where the materials exhibit maximum Lewis acidity with respect to C2H4 Adsorbed C2H4 produces thermally reactive C2 species which interact covalently with the defect-DOS and nonbonding O(2p) states from the top of the valence band. C(1s) binding energies suggest significant charge transfer which is consistent with a carbenium ion. Ni deposits behave similarly but transfer charge directly to Al species and do not interact with O atoms at the defect site. The defect-DOS is regenerated when the C2 species decomposes or when Ni migrates thermally through the oxide layer.
We have utilized Ginzberg-Landau mean field theory to analyze the branching ratio and soft X-ray magnetic circular dichroism measurements of the L3 and L2 adsorption edges of thin Mn overlayers on ferromagnetic fcc Co(001) at room temperature. We have determined a short range magnetic correlation of 4.25Å and that the long range magnetic magnetic order has a decay length of 1.29Å. These results indicate that the first monolayer of Mn ferromagnetically couple with the Co substrate. The paramagnetic Mn layer exhibits short range magnetic order, but lacks long range magnetic order. Due to the exponential decrease of both the branching ratio and dichroism signals, we have concluded that the magnetization of the Mn overlayer is substrate induced.
Thin amorphous films (t=200Å) of Fe80B20 were annealed at temperatures ranging from 473K–823K and studied using extended X-ray absorption fine structure to investigate the evolution of local structure around the Fe atoms during crystallization. Modeling of the local environment around Fe using empirical standards was employed to determine the relative fraction of the crystalline phases present in annealed samples. Results illustrate the sensitivity of EXAFS in detecting the onset of crystallization in thin amorphous films and its ability to quantitatively measure the relative fraction of crystalline phases present in partially crystallized thin film samples.
Diffraction anomalous fine structure (DAFS) is the fine structure in the intensity of an X-ray diffraction peak in the vicinity of an absorption edge. DAFS is measured by monitoring the intensity of a diffraction peak as a function of the incident X-ray energy as it is scanned through an absorption edge. It combines the short range structural sensitivity of X-ray absorption spectroscopy with the long range periodicity of X-ray diffraction, and can provide structural information which is not available from these techniques alone, or in combination. We present a methodology which allows extraction of a specific X-ray absorbance spectrum from the DAFS spectrum, and illustrate it for KMnO4. We also demonstrate the ability of DAFS to separate the contributions to the X-ray absorption spectrum of the tetrahedral and octahedral cobalt sites in the spinel Co3O4.
We have studied both the atomic and electronic structures of nitrogenase Mo-Fe proteins using EXAFS and L-edge spectroscopy. The Mo and Fe K-edge EXAFS data show not only 2.37, 2.70, 2.29, and 2.63 Å first shell Mo-S, Mo-Fe, Fe-S, and Fe-Fe distances, but also 3.8, 4.3 and 5.1 Å second shell Fe-Fe, Fe-S, and Mo-Fe interactions. These observed distances are consistent with recent crystallographic models for the M-center. The average Mcenter distances have been defined with unprecedented accuracy. The nitrogenase Fe L-edge spectra have been obtained for the first time, and the result suggests that the Fe exists in both Fe2+ and Fe3+ states.
A new experimental technique for the characterisation of the thermal-morphological properties of materials has been developed at Daresbury. Many thermal events, for example melting endotherms, are signals of changes in morphology covering size scales from the atomic to the microscopic, that is Å to μm. There are obvious advantages in collecting both the wide angle (1-20Å) and small angle (20-1000Å) patterns simultaneously to unambiguously characterise such thermal events. The new apparatus comprises a Linkam hot-stage capable of controlled heating and cooling mounted in a combined SAXS/WAXS camera. The camera is equipped with a multiwire quadrant detector (SAXS) located 3.5 m from the sample position and a curved knifeedge detector (WAXS) that covers 120° of arc at a radius of 0.4 m. SAXSIWAXS is possible with a time resolution of 0.1 seconds and heating/cooling rates up to 120 °C min-1.
Cr2O3 is a common nucleating agent useful for forming ceramics from oxide glasses. In this study we have used a variety of synchrotron radiation techniques to examine the atomic structure, crystallinity and microstructure of a magnesium alumino-silicate glass ceramic whose composition is close to that of the mineral cordierite, Mg2Al4Si5O13. X-ray Absorption spectra on the Cr K-edge have been performed with samples that were heat treated at different temperatures and times to examine the metamorphosis of the nucleating site. This study reveals that Cr3+ is always octahedrally coordinated with oxygen. In addition, the second nearest neighbour environment changes from an amorphous, single shell of Al/Si, but upon crystallisation, develops into a well ordered Al/Mg shell indicative of the formation of a dilute Cr spinel phase. Powder X-ray Diffraction (XRD) patterns, however, reveal that the major phase initially precipitated (˜900°C) is a stuffed quartz and from the lattice parameters that the composition is SiO2 -rich. With prolonged heat treatment a small quantity of a spinel phase emerges whose composition from its lattice parameter is close to MgAl2O4. Combined Small Angle X-ray Scattering (SAXS) and XRD establish that devitrification at these temperatures is associated with particles about 250 Å in size, on average. Energy dispersive powder diffraction patterns were collected in situ to observe changes in crystallinity with temperature and time. From these measurements the stuffed quartz phase identified at 900°C is found to be intermediate, being eventually replaced at higher temperatures by cordierite with a small quantity of spinel.
We have synthesized dilute magnetic semiconductor (DMS) thin films of CdMnTe and ZnMnSe using the ion beam technique. High doses of Mn ions (∼2–5×1016/cm 2) were implanted into single crystal CdTe and into ZnSe epilayers on GaAs, forming subsurface layers of Cdl.xMnxTe and Znl-xMnxSe alloys, respectively, with x∼0.15–0.22. Fluorescence extended x-ray absorption fine structure (EXAFS) measurements on these materials reveal that the Mn atoms in the CdMnTe and ZnMnSe layers, both as-implanted and annealed, have local environments similar to their corresponding bulk-grown DMS alloys. While the anion-cation distances (Ra-c) in the annealed samples are equivalent to those in the corresponding bulk-grown DMS, the Ra-c in the asimplanted samples are slightly larger (∼0.01Å) than those in the bulk-grown DMS. This is most likely due to the implantation damage in the as-implanted materials. Our results on the Ra-c of the ion beam synthesized layers deviate significantly from Vegard's law, but are consistent with the bimodal distribution model. The EXAFS results are corroborated with results from ion beam analysis and Raman spectroscopy.
X-ray fluorescence spectra from magnetized iron excited by circularly polarized synchrotron radiation are reported. The Fe L2.3 emission band gives rise to a distinct dichroic signal in confirmation of a recent theoretical prediction. These preliminary experiments carried out with “white” and only partially circularly-polarized synchrotron radiation nevertheless reveal an asymmetry which reflects the spin polarization of the Fe 3d valence electrons. The usefulness of developing specialized high flux circularly-polarized sources is clearly established.
We present structural characterizations of a series of sputtered Fe/Nb and V/Nb superlattices by high-angle x-ray diffraction. Diffraction scans were performed with the scattering vector at various angles (χ) with respect to the layers. χ=0° diffraction spectra (normal to the layers) were fitted to a general structural model to determine the (110) lattice strains, interfacial disorder and interdiffusion. χ>0° spectra probe the lattice strain of the individual layers and the in-plane interfacial coherence. Both systems form incoherent interfaces above a critical modulation wavelength (ΛC). At ΛC, the Fe/Nb system undergoes a crystalline-to-amorphous transition while the V/Nb forms in-plane coherent interfaces.