In the last few years, we have witnessed an increasing use of mobile devices in several areas, such as e-commerce, e-learning and e-government. At present, there are several kinds of mobile devices, ...each one already equipped with the most current wireless technologies, e.g., Bluetooth, WiFi (the standard 802.11x) and GPRS (general packet radio system). Such a technological basis allows to build ad-hoc networks (MANETs - mobile ad-hoc networks) among mobile devices, but the mere fact that it is technically possible is not sufficient to allow for effective usage of the resources (in particular software applications) contained within these networks. Up to now, research on MANETs concentrates on routing protocols, but more issues need to be taken into account when designing and realizing information systems for MANETs, such as how to exploit mobility and adaptivity at the application layer. This position paper analyzes ad-hoc network routing protocols in order to determine the minimal services that a MANET network layer should provide for the upper layers. Starting from such an analysis, a service interface is defined, on top of which to build application layer software, and specifically, an orchestration platform to support cooperative workflows on mobile ad-hoc networks. A scenario is presented showing the opportunity of having cooperative workflow on MANETs. Such a service interface might be a common factor between researchers on MANET routing protocols and researchers on information systems for ad-hoc networks.
The surprising discovery of superconductivity in layered iron-based materials, with transition temperatures climbing as high as 55 K, has led to thousands of publications on this subject over the ...past two years. Although there is general consensus on the unconventional nature of the Cooper pairing state of these systems, several central questions remain--including the role of magnetism, the nature of chemical and structural tuning, and the resultant pairing symmetry--and the search for universal properties and principles continues. Here we review the progress of research on iron-based superconducting materials, highlighting the main experimental benchmarks that have been reached so far and the important questions that remain to be conclusively answered. PUBLICATION ABSTRACT
Although it is generally accepted that superconductivity is unconventional in the high-transition-temperature copper oxides, the relative importance of phenomena such as spin and charge (stripe) ...order, superconductivity fluctuations, proximity to a Mott insulator, a pseudogap phase and quantum criticality are still a matter of debate. In electron-doped copper oxides, the absence of an anomalous pseudogap phase in the underdoped region of the phase diagram and weaker electron correlations suggest that Mott physics and other unidentified competing orders are less relevant and that antiferromagnetic spin fluctuations are the dominant feature. Here we report a study of magnetotransport in thin films of the electron-doped copper oxide La(2 - x)Ce(x)CuO(4). We show that a scattering rate that is linearly dependent on temperature--a key feature of the anomalous normal state properties of the copper oxides--is correlated with the electron pairing. We also show that an envelope of such scattering surrounds the superconducting phase, surviving to zero temperature when superconductivity is suppressed by magnetic fields. Comparison with similar behaviour found in organic superconductors strongly suggests that the linear dependence on temperature of the resistivity in the electron-doped copper oxides is caused by spin-fluctuation scattering.
To study the influence of regional biomass burning emissions and secondary processes, ambient samples of fog and aerosol were collected in the Po Valley (Italy) during the 2013 Supersito field ...campaign. After the extent of fresh vs. aged biomass burning influence was estimated from proton nuclear magnetic resonance (1H NMR) and high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS), two samples of fog water and two samples of PM1 aerosol were selected for ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Molecular compositions indicated that the water-soluble organic matter was largely non-polymeric without clearly repeating units. The selected samples had an atypically large frequency of molecular formulas containing nitrogen and sulfur (not evident in the NMR composition) attributed to multifunctional organonitrates and organosulfates. Higher numbers of organonitrates were observed in aerosol, and higher numbers of organosulfates were observed in fog water. Consistent with the observation of an enhanced aromatic proton signature in the 1H-NMR analysis, the average molecular formula double-bond equivalents and carbon numbers were higher in the fresh biomass-burning-influenced samples. The average O : C and H : C values from FT-ICR MS were higher in the samples with an aged influence (O : C = 0.50–0.58, and H : C = 1.31–1.37) compared to those with fresh influence (O : C = 0.43–0.48, and H : C = 1.13–1.30). The aged fog had a large set of unique highly oxygenated CHO fragments in the HR-ToF-AMS, which reflects an enrichment of carboxylic acids and other compounds carrying acyl groups, highlighted by the NMR analysis. Fog compositions were more oxidized and SOA (secondary organic aerosol)-like than aerosols as indicated by their NMR measured acyl-to-alkoxyl ratios and the observed molecular formula similarity between the aged aerosol and fresh fog, implying that fog nuclei must be somewhat aged. Overall, functionalization with nitrate and sulfate moieties, in addition to aqueous oxidation, triggers an increase in the molecular complexity in this environment, which is apparent in the FT-ICR MS results. This study demonstrates the significance of the aqueous phase in transforming the molecular chemistry of atmospheric organic matter and contributing to secondary organic aerosol.
We investigate optical–microphysical–chemical properties of brown carbon (BrC) in the urban ambient atmosphere of the Po Valley. In situ ground measurements of aerosol spectral optical properties, ...PM1 chemical composition (HR-ToF-AMS), and particle size distributions were carried out in Bologna. BrC was identified through its wavelength dependence of light absorption at visible wavelengths, as indicated by the absorption Ångström exponent (AAE). We found that BrC occurs in particles with a narrow monomodal size distribution peaking in the droplet mode, enriched in ammonium nitrate and poor in black carbon (BC), with a strong dependance on OA-to-BC ratios, and SSA530 of 0.98 ± 0.01. We demonstrate that specific complex refractive index values (k530 = 0.017 ± 0.001) are necessary in addition to a proper particle size range to match the large AAEs measured for this BrC (AAE467 − 660 = 3.2 ± 0.9 with values up to 5.3). In terms of consistency of these findings with literature, this study i. provides experimental evidence of the size distribution of BrC associated with the formation of secondary aerosol;ii. shows that in the lower troposphere AAE increases with increasing OA-to-BC ratios rather than with increasing OA – contributing to sky radiometer retrieval techniques (e.g., AERONET);iii. extends the dependence of AAE on BC-to-OA ratios previously observed in chamber experiments to ambient aerosol dominated by wood-burning emissions. These findings are expected to bear important implications for atmospheric modeling studies and remote sensing observations as regards the parametrization and identification of BrC in the atmosphere.
The Po Valley (Italy) is a well-known air quality hotspot characterized by
particulate matter (PM) levels well above the limit set by the European Air
Quality Directive and by the World Health ...Organization, especially during
the colder season. In the framework of Emilia-Romagna regional project
“Supersito”, the southern Po Valley submicron aerosol chemical composition
was characterized by means of high-resolution aerosol mass spectroscopy
(HR-AMS) with the specific aim of organic aerosol (OA) characterization and
source apportionment. Eight intensive observation periods (IOPs) were
carried out over 4 years (from 2011 to 2014) at two different sites
(Bologna, BO, urban background, and San Pietro Capofiume, SPC, rural
background), to characterize the spatial variability and seasonality of the
OA sources, with a special focus on the cold season. On the multi-year basis of the study, the AMS observations show that OA
accounts for averages of 45±8 % (ranging from 33 % to 58 %) and 46±7 % (ranging from 36 % to 50 %) of the total non-refractory submicron particle
mass (PM1-NR) at the urban and rural sites, respectively. Primary
organic aerosol (POA) comprises biomass burning (23±13 % of OA) and fossil fuel (12±7 %) contributions with a marked seasonality in concentration. As expected, the biomass burning contribution to POA is more
significant at the rural site (urban / rural concentration ratio of 0.67),
but it is also an important source of POA at the urban site during the cold
season, with contributions ranging from 14 % to 38 % of the total OA mass. Secondary organic aerosol (SOA) contributes to OA mass to a much larger
extent than POA at both sites throughout the year (69±16 % and
83±16 % at the urban and rural sites, respectively), with important
implications for public health. Within the secondary fraction of OA, the
measurements highlight the importance of biomass burning aging products
during the cold season, even at the urban background site. This biomass
burning SOA fraction represents 14 %–44 % of the total OA mass in the cold
season, indicating that in this region a major contribution of combustion
sources to PM mass is mediated by environmental conditions and atmospheric
reactivity. Among the environmental factors controlling the formation of SOA in the Po
Valley, the availability of liquid water in the aerosol was shown to play a
key role in the cold season. We estimate that the organic fraction originating
from aqueous reactions of biomass burning products (“bb-aqSOA”) represents
21 % (14 %–28 %) and 25 % (14 %–35 %) of the total OA mass and 44 %
(32 %–56 %) and 61 % (21 %–100 %) of the SOA mass at the urban and rural
sites, respectively.
ABSTRACT
The Open Researcher & Contributor ID (ORCID) registry presents a unique opportunity to solve the problem of author name ambiguity. At its core the value of the ORCID registry is that it ...crosses disciplines, organizations, and countries, linking ORCID with both existing identifier schemes as well as publications and other research activities. By supporting linkages across multiple datasets – clinical trials, publications, patents, datasets – such a registry becomes a switchboard for researchers and publishers alike in managing the dissemination of research findings. We describe use cases for embedding ORCID identifiers in manuscript submission workflows, prior work searches, manuscript citations, and repository deposition. We make recommendations for storing and displaying ORCID identifiers in publication metadata to include ORCID identifiers, with CrossRef integration as a specific example. Finally, we provide an overview of ORCID membership and integration tools and resources.
Abstract
The helimagnet FeP is part of a family of binary pnictide materials with the MnP-type structure, which share a nonsymmorphic crystal symmetry that preserves generic band structure ...characteristics through changes in elemental composition. It shows many similarities, including in its magnetic order, to isostructural CrAs and MnP, two compounds that are driven to superconductivity under applied pressure. Here we present a series of high magnetic field experiments on high-quality single crystals of FeP, showing that the resistance not only increases without saturation by up to several hundred times its zero-field value by 35 T, but that it also exhibits an anomalously linear field dependence over the entire range when the field is aligned precisely along the crystallographic
c
-axis. A close comparison of quantum oscillation frequencies to electronic structure calculations links this orientation to a semi-Dirac point in the band structure, which disperses linearly in a single direction in the plane perpendicular to field, a symmetry-protected feature of this entire material family. We show that the two striking features of magnetoresistance—large amplitude and linear field dependence—arise separately in this system, with the latter likely due to a combination of ordered magnetism and topological band structure.
The compound UTe2 has recently been shown to realize spin triplet superconductivity from a nonmagnetic normal state. This has sparked intense research activity, including theoretical analyses that ...suggest the superconducting order parameter to be topologically nontrivial. However, the underlying electronic band structure is a critical factor for these analyses, and remains poorly understood. Here, we present high resolution angle-resolved photoemission measurements covering multiple planes in the 3D Brillouin zone of UTe2, revealing distinct Fermi-level features from two orthogonal quasi-one-dimensional light electron bands and one heavy band. The electronic symmetries are evaluated in comparison with numerical simulations, and the resulting picture is discussed as a platform for unconventional many-body order.
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