Abstract: CO2 exchange between terrestrial ecosystems and the atmosphere is key to understanding the feedbacks between climate change and the land surface. In regions with carbonaceous parent material, CO2 exchange patterns occur that cannot be explained by biological processes, such as disproportionate outgassing during the daytime or night-time CO2 uptake during periods when all vegetation is senescent. Neither of these phenomena can be attributed to carbonate weathering reactions, since their CO2 exchange rates are too small. Soil ventilation induced by high atmospheric turbulence is found to explain atypical CO2 exchange between carbonaceous systems and the atmosphere. However, by strongly altering subsurface CO2 concentrations, ventilation can be expected to influence carbonate weathering rates. By imposing ventilation-driven CO2 outgassing in a carbonate weathering model, we show here that carbonate geochemistry is accelerated and does play a surprisingly large role in the observed CO2 exchange pattern of a semi-arid ecosystem. We found that by rapidly depleting soil CO2 during the daytime, ventilation disturbs soil carbonate equilibria and therefore strongly magnifies daytime carbonate precipitation and associated CO2 production. At night, ventilation ceases and the depleted CO2 concentrations increase steadily. Dissolution of carbonate is now enhanced, which consumes CO2 and largely compensates for the enhanced daytime carbonate precipitation. This is why only a relatively small effect on global carbonate weathering rates is to be expected. On the short term, however, ventilation has a drastic effect on synoptic carbonate weathering rates, resulting in a pronounced diel pattern that exacerbates the non-biological behavior of soil-atmosphere CO2 exchanges in dry regions with carbonate soils.

Abstract: Recently, a group of MAX phases, (Mo2/3Y1/3)(2)AlC, (Mo2/3Sc1/3)(2)AlC, (W2/3Sc1/3)(2)AlC,(W2/3Y1/3)(2)AlC, and (V-2/3 Zr-1/3)(2)AlC, with in-plane ordered double transition metals, named iMAX phases, have been synthesized. Experimentally, some of these MAX phases can be chemically exfoliated into two-dimensional (2D) single- or multilayered transition metal carbides, so-called MXenes. Accordingly, the 2D nanostructures derived from iMAX phases are named iMXenes. Here we investigate the structural stabilities and electronic structures of the experimentally discovered iMAX phases and their possible iMXene derivatives. We show that the iMAX phases and their pristine, F, or OH-terminated iMXenes are metallic. However, upon 0 termination, (Mo2/3Y1/3)(2)C, (Mo2/3Sc1/3)(2)C, (W2/3Y1/3)(2)C, and (W2/3Sc1/3)(2)C iMXenes turn into semiconductors. Owing to the absence of centrosymmetry, the semiconducting iMXenes may find applications in piezoelectricity. Our calculations reveal that the semiconducting iMXenes possess giant piezoelectric coefficients as large as 45 x 10(-)(10) C/m.

Abstract: This study comprises the first application of the Passive Flux Meter (PFM) for the measurement of chlorinated aliphatic hydrocarbon (CAH) mass fluxes and Darcy water fluxes in groundwater at a European field site. The PFM was originally developed and applied to measurements near source zones. The focus of the PFM is extended from near source to plume zones. For this purpose, 48 PFMs of 1.4 m length were constructed and installed in eight different monitoring wells in the source and plume zone of a CAH-contaminated field site located in France. The PFMs were retrieved, sampled, and analyzed after 3 to 11 weeks of exposure time, depending on the expected contaminant flux. PFM evaluation criteria include analytical, technical, and practical aspects as well as conditions and applicability. PFM flux data were compared with so-called traditional soil and groundwater concentration data obtained using active sampling methods. The PFMs deliver reasonable results for source as well as plume zones. The limiting factor in the PFM applicability is the exposure time together with the groundwater flux. Measured groundwater velocities at the field site range from 2 to 41 cm/day. Measured contaminant flux data raise up to 13 g/m(2)/day for perchloroethylene in the plume zone. Calculated PFM flux averaged concentration data and traditional concentration data were of similar magnitude for most wells. However, both datasets need to be compared with reservation because of the different sampling nature and time. Two important issues are the PFM tracer loss during installation/extraction and the deviation of the groundwater flow field when passing the monitoring well and PFM. The demonstration of the PFM at a CAH-contaminated field site in Europe confirmed the efficiency of the flux measurement technique for source as well as plume zones. The PFM can be applied without concerns in monitoring wells with European standards. The acquired flux data are of great value for the purpose of site characterization and mass discharge modeling, and can be used in combination with traditional soil and groundwater sampling methods.

Abstract: Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.

Abstract: The chemical composition of the plumes of seagoing ships was measured during a two week long measurement campaign in the port of Rotterdam, Hoek van Holland The Netherlands, in September 2009. Altogether, 497 ships were monitored and a statistical evaluation of emission factors (g kg−1 fuel) was provided. The concerned main atmospheric components were SO2, NO2, NOx and the aerosol particle number. In addition, the elemental and water-soluble ionic composition of the emitted particulate matter was determined. Emission factors were expressed as a function of ship type, power and crankshaft rotational speed. The average SO2 emission factor was found to be roughly half of what is allowed in sulphur emission control areas (16 vs. 30 g kg−1 fuel), and exceedances of this limit were rarely registered. A significant linear relationship was observed between the SO2 and particle number emission factors. The intercept of the regression line, 4.8 × 1015 (kg fuel)−1, gives the average number of particles formed during the burning of 1 kg zero sulphur content fuel, while the slope, 2 × 1018, provides the average number of particles formed with 1 kg sulphur burnt with the fuel. Water-soluble ionic composition analysis of the aerosol samples from the plumes showed that ~144 g of particulate sulphate was emitted from 1 kg sulphur burnt with the fuel. The mass median diameter of sulphate particles estimated from the measurements was ~42 nm.

Abstract: The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra-high-pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3ngmL(-1) were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25ngmL(-1). A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost-effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright (c) 2014 John Wiley & Sons, Ltd.

Abstract: Atmospheric nitrogen dioxide (NO2) and sulfur dioxide (SO2) levels were monitored simultaneously by means of Radiello passive samplers at six sites of Santa Clara city, Cuba, in the cold and the warm seasons in 2010. The dissolved ionic forms of NO2 and SO2 as nitrate and sulfite plus sulfate, respectively, were determined by means of ion chromatography. Analysis of NO2 as nitrite was also performed by UVVis spectrophotometry. For NO2, significant t tests show good agreement between the results of IC and UVVis methods. The NO2 and SO2 concentrations peaked in the cold season, while their minimum levels were experienced in the warm season. The pollutant levels do not exceed the maximum allowable limit of the Cuban Standard 39:1999, i.e., 40 μg/m3 and 50 μg/m3 for NO2 and SO2, respectively. The lowest pollutant concentrations obtained in the warm season can be attributed to an increase in their removal via precipitation (scavenging) while to the decreased traffic density and industrial emission during the summer holidays (e.g., July and August).

Abstract: Studies of materials' properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (similar to 460 GPa at a confining pressure of similar to 70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications.

Abstract: The potential of cold atmospheric plasma (CAP) in biomedical applications has received significant interest, due to its ability to generate reactive oxygen and nitrogen species (RONS). Upon exposure to living cells, CAP triggers alterations in various cellular components, such as the cell membrane. However, the permeation of RONS across nitrated and oxidized membranes remains understudied. To address this gap, we conducted molecular dynamics simulations, to investigate the permeation capabilities of RONS across modified cell membranes. This computational study investigated the translocation processes of less hydrophilic and hydrophilic RONS across the phospholipid bilayer (PLB), with various degrees of oxidation and nitration, and elucidated the impact of RONS on PLB permeability. The simulation results showed that less hydrophilic species, i.e., NO, NO2, N2O4, and O3, have a higher penetration ability through nitro-oxidized PLB compared to hydrophilic RONS, i.e., HNO3, s-cis-HONO, s-trans-HONO, H2O2, HO2, and OH. In particular, nitro-oxidation of PLB, induced by, e.g., cold atmospheric plasma, has minimal impact on the penetration of free energy barriers of less hydrophilic species, while it lowers these barriers for hydrophilic RONS, thereby enhancing their translocation across nitro-oxidized PLB. This research contributes to a better understanding of the translocation abilities of RONS in the field of plasma biomedical applications and highlights the need for further analysis of their role in intracellular signaling pathways.

Abstract: Biomethane is a renewable natural gas substitute produced from biogas. Storage of this sustainable energy vector in confined clathrate hydrates, encapsulated in the pores of a host material, is a highly promising avenue to improve storage capacity and energy efficiency. Herein, a new type of periodic mesoporous organosilica (PMO) nanotubes, referred to as hollow ring PMO (HR-PMO), capable of promoting methane clathrate hydrate formation under mild working conditions (273 K, 3.5 MPa) and at high water loading (5.1 g water/g HR-PMO) is reported. Gravimetric uptake measurements reveal a steep single-stepped isotherm and a noticeably high methane storage capacity (0.55 g methane/g HR-PMO; 0.11 g methane/g water at 3.5 MPa). The large working capacity throughout consecutive pressure-induced clathrate hydrate formationdissociation cycles demonstrates the material's excellent recyclability (97% preservation of capacity). Supported by ex situ cryo-electron tomography and x-ray diffraction, HR-PMO nanotubes are hypothesized to promote clathrate hydrate nucleation and growth by distribution and confinement of water in the mesopores of their outer wall, along the central channels of the nanotubes and on the external nanotube surface. These findings showcase the potential for application of organosilica materials with hierarchical and interconnected pore systems for pressure-based storage of biomethane in confined clathrate hydrates.

Abstract: Formation and aggregation of metal carboxylates (metal soaps) can degrade the appearance and integrity of oil paints, challenging efforts to conserve painted works of art. Endeavors to understand the root cause of metal soap formation have been hampered by the limited spatial resolution of Fourier transform infrared microscopy (mu-FTIR). We overcome this limitation using optical photothermal infrared spectroscopy (O-PTIR) and photothermal-induced resonance (PTIR), two novel methods that provide IR spectra with approximate to 500 and approximate to 10 nm spatial resolutions, respectively. The distribution of chemical phases in thin sections from the top layer of a 19th-century painting is investigated at multiple scales (mu-FTIR approximate to 10(2) mu m(3), O-PTIR approximate to 10(-1) mu m(3), PTIR approximate to 10(-5) mu m(3)). The paint samples analyzed here are found to be mixtures of pigments (cobalt green, lead white), cured oil, and a rich array of intermixed, small (often << 0.1 mu m(3)) zinc soap domains. We identify Zn stearate and Zn oleate crystalline soaps with characteristic narrow IR peaks (approximate to 1530-1558 cm(-1)) and a heterogeneous, disordered, water-permeable, tetrahedral zinc soap phase, with a characteristic broad peak centered at approximate to 1596 cm(-1). We show that the high signal-to-noise ratio and spatial resolution afforded by O-PTIR are ideal for identifying phase-separated (or locally concentrated) species with low average concentration, while PTIR provides an unprecedented nanoscale view of distributions and associations of species in paint. This newly accessible nanocompositional information will advance our knowledge of chemical processes in oil paint and will stimulate new art conservation practices.

Abstract: Quantum anomalous Hall, high-Chern number, and axion phases in topological insulators are characterized by its Chern invariant C (respectively, C = 1, integer C > 1, and C = 0 with half-quantized Hall conductance of opposite signs on top and bottom surfaces). They are of recent interest because of novel fundamental physics and prospective applications, but identifying and controlling these phases has been challenging in practice. Here we show that these states can be created and switched between in thin films of Bi2Se3 by Floquet engineering, using irradiation by circularly polarized light. We present the calculated phase diagrams of encountered topological phases in Bi2Se3, as a function of wavelength and amplitude of light, as well as sample thickness, after properly taking into account the penetration depth of light and the variation of the gap in the surface states. These findings open pathways towards energy-efficient optoelectronics, advanced sensing, quantum information processing and metrology.

Abstract: SmFe8.75 Si-0.25 C/alpha-Fe nanocomposites have been successfully synthesized using high energy milling, followed by annealing at 750 degrees C. The crystal structure of these compounds was characterized by the Rietveld method using powder X-ray diffraction data. By increasing the concentration of Sm, we observed a decrease in the amount of alpha-Fe phase. The morphology of the samples was determined by scanning and transmission electron microscopy. The average grain size is about 20 nm. The magnetic properties were investigated at room temperature and at 10 K. A ferromagnetic behavior was observed in all samples at both temperatures. An increase of the soft magnetic phase alpha-Fe induced an increase in the magnetization and a decrease in coercivity. (C) 2016 Elsevier B.V. All rights reserved.