Arctic haze is a seasonal phenomenon with high concentrations of accumulation-mode aerosols occurring in the Arctic in winter and early spring. Chemistry transport models and climate chemistry models ...struggle to reproduce this phenomenon, and this has recently prompted changes in aerosol removal schemes to remedy the modeling problems. In this paper, we show that shortcomings in current emission data sets are at least as important. We perform a 3 yr model simulation of black carbon (BC) with the Lagrangian particle dispersion model FLEXPART. The model is driven with a new emission data set ("ECLIPSE emissions") which includes emissions from gas flaring. While gas flaring is estimated to contribute less than 3% of global BC emissions in this data set, flaring dominates the estimated BC emissions in the Arctic (north of 66° N). Putting these emissions into our model, we find that flaring contributes 42% to the annual mean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface. Most of the flaring BC remains close to the surface in the Arctic, so that the flaring contribution to BC in the middle and upper troposphere is small. Another important factor determining simulated BC concentrations is the seasonal variation of BC emissions from residential combustion (often also called domestic combustion, which is used synonymously in this paper). We have calculated daily residential combustion emissions using the heating degree day (HDD) concept based on ambient air temperature and compare results from model simulations using emissions with daily, monthly and annual time resolution. In January, the Arctic-mean surface concentrations of BC due to residential combustion emissions are 150% higher when using daily emissions than when using annually constant emissions. While there are concentration reductions in summer, they are smaller than the winter increases, leading to a systematic increase of annual mean Arctic BC surface concentrations due to residential combustion by 68% when using daily emissions. A large part (93%) of this systematic increase can be captured also when using monthly emissions; the increase is compensated by a decreased BC burden at lower latitudes. In a comparison with BC measurements at six Arctic stations, we find that using daily-varying residential combustion emissions and introducing gas flaring emissions leads to large improvements of the simulated Arctic BC, both in terms of mean concentration levels and simulated seasonality. Case studies based on BC and carbon monoxide (CO) measurements from the Zeppelin observatory appear to confirm flaring as an important BC source that can produce pollution plumes in the Arctic with a high BC / CO enhancement ratio, as expected for this source type. BC measurements taken during a research ship cruise in the White, Barents and Kara seas north of the region with strong flaring emissions reveal very high concentrations of the order of 200–400 ng m−3. The model underestimates these concentrations substantially, which indicates that the flaring emissions (and probably also other emissions in northern Siberia) are rather under- than overestimated in our emission data set. Our results suggest that it may not be "vertical transport that is too strong or scavenging rates that are too low" and "opposite biases in these processes" in the Arctic and elsewhere in current aerosol models, as suggested in a recent review article (Bond et al., Bounding the role of black carbon in the climate system: a scientific assessment, J. Geophys. Res., 2013), but missing emission sources and lacking time resolution of the emission data that are causing opposite model biases in simulated BC concentrations in the Arctic and in the mid-latitudes.
The discovery of quasicrystals in 1984 changed our view of ordered solids as periodic structures and introduced new long-range-ordered phases lacking any translational symmetry. Quasicrystals permit ...symmetry operations forbidden in classical crystallography, for example five-, eight-, ten- and 12-fold rotations, yet have sharp diffraction peaks. Intermetallic compounds have been observed to form both metastable and energetically stabilized quasicrystals; quasicrystalline order has also been reported for the tantalum telluride phase with an approximate Ta1.6Te composition. Later, quasicrystals were discovered in soft matter, namely supramolecular structures of organic dendrimers and tri-block copolymers, and micrometre-sized colloidal spheres have been arranged into quasicrystalline arrays by using intense laser beams that create quasi-periodic optical standing-wave patterns. Here we show that colloidal inorganic nanoparticles can self-assemble into binary aperiodic superlattices. We observe formation of assemblies with dodecagonal quasicrystalline order in different binary nanoparticle systems: 13.4-nm Fe2O3 and 5-nm Au nanocrystals, 12.6-nm Fe3O4 and 4.7-nm Au nanocrystals, and 9-nm PbS and 3-nm Pd nanocrystals. Such compositional flexibility indicates that the formation of quasicrystalline nanoparticle assemblies does not require a unique combination of interparticle interactions, but is a general sphere-packing phenomenon governed by the entropy and simple interparticle potentials. We also find that dodecagonal quasicrystalline superlattices can form low-defect interfaces with ordinary crystalline binary superlattices, using fragments of (33.42) Archimedean tiling as the 'wetting layer' between the periodic and aperiodic phases.
Situations where normal autografts cannot be used to replace damaged skin often lead to a greater risk of mortality, prolonged hospital stay and increased expenditure for the National Health Service. ...There is a substantial need for tissue-engineered skin bioconstructs and research is active in this field. Significant progress has been made over the years in the development and clinical use of bioengineered components of the various skin layers. Off-the-shelf availability of such constructs, or production of sufficient quantities of biological materials to aid rapid wound closure, are often the only means to help patients with major skin loss. The aim of this review is to describe those materials already commercially available for clinical use as well as to give a short insight to those under development. It seeks to provide skin scientists/tissue engineers with the information required to not only develop in vitro models of skin, but to move closer to achieving the ultimate goal of an off-the-shelf, complete full-thickness skin replacement.
Assembly of small building blocks such as atoms, molecules and nanoparticles into macroscopic structures—that is, ‘bottom up’ assembly—is a theme that runs through chemistry, biology and material ...science. Bacteria, macromolecules and nanoparticles can self-assemble, generating ordered structures with a precision that challenges current lithographic techniques. The assembly of nanoparticles of two different materials into a binary nanoparticle superlattice (BNSL) can provide a general and inexpensive path to a large variety of materials (metamaterials) with precisely controlled chemical composition and tight placement of the components. Maximization of the nanoparticle packing density has been proposed as the driving force for BNSL formation, and only a few BNSL structures have been predicted to be thermodynamically stable. Recently, colloidal crystals with micrometre-scale lattice spacings have been grown from oppositely charged polymethyl methacrylate spheres. Here we demonstrate formation of more than 15 different BNSL structures, using combinations of semiconducting, metallic and magnetic nanoparticle building blocks. At least ten of these colloidal crystalline structures have not been reported previously. We demonstrate that electrical charges on sterically stabilized nanoparticles determine BNSL stoichiometry; additional contributions from entropic, van der Waals, steric and dipolar forces stabilize the variety of BNSL structures.
We investigate insurance purchases when bequest motives are age-varying and life insurance and life annuities both carry loads. The existing life cycle literature assumes bequests are normal goods ...without being either necessities or luxuries. Much of the literature also assumes implicitly that life annuity loads are negative. A key finding of the literature is that the demand for life insurance and the demand for life annuities are symmetrical. It is optimal to buy life-contingent insurance throughout life, even under loads. A life annuity phase backs directly onto a life insurance phase. We find that realistic examples with positive loads on both products reveal up to two distinct periods of non-participation, one in midlife and the other adjoining the maximum age. We highlight examples with necessity bequests during child-rearing years and luxury bequests thereafter. This set of assumptions explains why a substantial demand for life insurance during child-rearing years can co-exist with negligible demand for life annuities later on. A realistic 18% load on both products generates this outcome.
Abstract
The basalts of the 2021 Fagradalsfjall eruption were the first erupted on the Reykjanes Peninsula in 781 years and offer a unique opportunity to determine the composition of the mantle ...underlying Iceland, in particular its oxygen isotope composition (δ
18
O values). The basalts show compositional variations in Zr/Y, Nb/Zr and Nb/Y values that span roughly half of the previously described range for Icelandic basaltic magmas and signal involvement of Icelandic plume (OIB) and Enriched Mid-Ocean Ridge Basalt (EMORB) in magma genesis. Here we show that Fagradalsfjall δ
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O values are invariable (mean δ
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O = 5.4 ± 0.3‰ 2 SD,
N
= 47) and indistinguishable from “normal” upper mantle, in contrast to significantly lower δ
18
O values reported for erupted materials elsewhere in Iceland (e.g., the 2014–2015 eruption at Holuhraun, Central Iceland). Thus, despite differing trace element characteristics, the melts that supplied the Fagradalsfjall eruption show no evidence for
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O-depleted mantle or interaction with low-δ
18
O crust and may therefore represent a useful mantle reference value in this part of the Icelandic plume system.
We present a comparative study of optical and electronic properties for PbS nanocrystals and Au−PbS core−shell nanostructures. In Au−PbS nanostructures, we observed two nontrivial synergistic ...effects: (i) extinction enhancement due to coupling of surface plasmon resonance in the Au core to the excitonic states in the semiconducting PbS shell, and (ii) strong p-type electronic doping of Au−PbS nanocrystal solids that we explained by the intraparticle charge transfer between the PbS shell and the Au core.
Material design in terms of their morphologies other than solid nanoparticles can lead to more advanced properties. At the example of iron oxide, we explored the electrochemical properties of hollow ...nanoparticles with an application as a cathode and anode. Such nanoparticles contain very high concentration of cation vacancies that can be efficiently utilized for reversible Li ion intercalation without structural change. Cycling in high voltage range results in high capacity (∼132 mAh/g at 2.5 V), 99.7% Coulombic efficiency, superior rate performance (133 mAh/g at 3000 mA/g) and excellent stability (no fading at fast rate during more than 500 cycles). Cation vacancies in hollow iron oxide nanoparticles are also found to be responsible for the enhanced capacity in the conversion reactions. We monitored in situ structural transformation of hollow iron oxide nanoparticles by synchrotron X-ray absorption and diffraction techniques that provided us clear understanding of the lithium intercalation processes during electrochemical cycling.
Summary Background Multidrug-resistant and extensively-drug-resistant Pseudomonas aeruginosa are increasing therapeutic challenges worldwide. We did a longitudinal epidemiological and clinical study ...of extensively-drug-resistant P aeruginosa in Belarus, Kazakhstan, and Russia. Methods The study was done in three prospectively defined phases: Jan 1, 2002–Dec 31, 2004; Jan 1, 2006–Dec 31, 2007; and Jan 1, 2008–Dec 31, 2010. The first two phases were in Russia only. All consecutive, non-duplicate, nosocomial isolates and case report forms were sent to the coordinating centre (Institute of Antimicrobial Chemotherapy, Smolensk, Russia), where species reidentification, susceptibility testing, and molecular typing of isolates were done. We did susceptibility testing by agar dilution. The presence of metallo-β-lactamase (MBL) genes was established by PCR and sequencing, and class 1 integrons containing MBL gene cassettes were analysed by the PCR restriction fragment length polymorphism approach. Strain relatedness was analysed by multiple loci variable-number tandem-repeat (VNTR) analysis (at six VNTR loci) and multilocus sequence typing. Results In 2002–04, 628 of 1053 P aeruginosa isolates were insusceptible to carbapenems and 47 (4·5%) possessed MBLs. In 2006–07, 584 of 787 isolates were insusceptible to carbapenems and 160 (20·3%) possessed MBLs. In 2008–10, 1238 of 1643 Russian P aeruginosa isolates were insusceptible to carbapenems and 471 (28·7%) possessed MBLs. Additionally, the 32 P aeruginosa isolates from Belarus and Kazakhstan were all carbapenem insusceptible and all possessed MBLs. More than 96% of MBL-positive P aeruginosa isolates were resistant to all antibiotics except colistin (ie, extensively drug resistant), and, in 2010, 5·9% were resistant to colistin. 685 (96·5%) of 710 MBL-positive P aeruginosa belonged to ST235. blaVIM-2 genes were detected in 707 (99·6%) of 710 MBL-positive isolates. Interpretation Extensively-drug-resistant ST235 P aeruginosa has rapidly spread throughout Russia and into Belarus and Kazakhstan via clonal dissemination. Increases in the use of colistin will probably result in further spread of ST235 P aeruginosa resistant to all drugs. Funding HEFC, Ministry of Health of the Russian Federation, Government of the Republic of Belarus, Government of the Republic of Kazakhstan, European Union, Medical Research Council UK–Canada partnership.
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