This work presents and discusses the antiwear behaviour of nanoparticle suspensions in a polyalphaolefin (PAO 6). CuO, ZnO and ZrO2 nanoparticles were separately dispersed at 0.5%, 1.0% and 2.0%wt. ...in PAO 6 using an ultrasonic probe for 2 min. AW properties were obtained using a TE53SLIM tribometer with a block-on-ring configuration. Tests were made under a load of 165 N, sliding speed of 2 m/s and a total distance of 3.066 m. Wear surfaces were analysed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) after wear tests. The study led to the following conclusions: all nanoparticle suspensions exhibited reductions in friction and wear compared to the base oil; the suspensions with 0.5% of ZnO and ZrO2 had the best general tribological behaviour, exhibiting high friction and wear reduction values even at low deposition levels on the wear surface; CuO suspensions showed the highest friction coefficient and lowest wear per nanoparticle content of 2%; and the antiwear mechanism of nanoparticulate additive was produced by tribo-sintering.
The application of lidar remote-sensing technology has revolutionized the practice of settlement and landscape archaeology, perhaps nowhere more so than in the Maya lowlands. This contribution ...presents a substantial lidar dataset from the Puuc region of Yucatan, Mexico, a cultural subregion of the ancient Maya and a distinct physiographic zone within the Yucatan peninsula. Despite the high density of known sites, no large site has been fully surveyed, and little is known about intersite demography. Lidar technology allows determination of settlement distribution for the first time, showing that population was elevated but nucleated, although without any evidence of defensive features. Population estimates suggest a region among the most densely settled within the Maya lowlands, though hinterland levels are modest. Lacking natural bodies of surface water, the ancient Puuc inhabitants relied upon various storage technologies, primarily chultuns (cisterns) and aguadas (natural or modified reservoirs for potable water). Both are visible in the lidar imagery, allowing calculation of aguada capacities by means of GIS software. The imagery also demonstrates an intensive and widespread stone working industry. Ovens visible in the imagery were probably used for the production of lime, used for construction purposes and perhaps also as a softening agent for maize. Quarries can also be discerned, including in some cases substantial portions of entire hills. With respect to agriculture, terrain classification permits identification of patches of prime cultivable land and calculation of their extents. Lidar imagery also provides the first unequivocal evidence for terracing in the Puuc, indeed in all northern Yucatan. Finally, several types of civic architecture and architectural complexes are visible, including four large acropolises probably dating to the Middle Formative period (700-450 B.C.). Later instances of civic architecture include numerous Early Puuc Civic Complexes, suggesting a common form of civic organization at the beginning of the Late Classic demographic surge, (A.D. 600-750).
In the present work, we describe a simple procedure to produce biomimetically coated silver nanoparticles (Ag NPs), based on the postfunctionalization and purification of colloidal silver stabilized ...by citrate. Two biological capping agents have been used (cysteine Cys and glutathione GSH). The composition of the capped colloids has been ascertained by different techniques and antibacterial tests on GSH-capped Ag NPs have been conducted under physiological conditions, obtaining values of Minimum Inhibitory Concentration (MIC) of 180 and 15 μg/mL for Staphylococcus aureus and Escherichia coli, respectively. The antibacterial activity of these GSH capped NPs can be ascribed to the direct action of metallic silver NPs, rather than to the bulk release of Ag+.
Among the hybrid organic–inorganic perovskites MAPbX3 (MA: methyl-ammonium CH3–NH3+, X = halogen), the triiodide specimen (MAPbI3) is still the material of choice for solar energy applications. ...Although it is able to absorb light above its 1.6 eV bandgap, its poor stability in humid air atmosphere has been a major drawback for its use in solar cells. However, we discovered that this perovskite can be prepared by ball milling in a straightforward way, yielding specimens with a superior stability. This fact allowed us to take atomic-resolution STEM images for the first time, with sufficient quality to unveil microscopic aspects of this material. We demonstrated full Iodine content, which might be related to the enhanced stability, in a more compact PbI6 framework with reduced unit-cell volume. A structural investigation from neutron powder diffraction (NPD) data of an undeuterated specimen was essential to determine the configuration of the organic MA unit in the 100–298 K temperature range. A phase transition is identified, from the tetragonal structure observed at RT (space group I4/mcm) to an orthorhombic (space group Pnma) phase where the methyl-ammonium organic units are fully localized. Our NPD data reveal that the MA changes are gradual and start before reaching the phase transition. Optoelectronic measurements yield a photocurrent peak at an illumination wavelength of 820 nm, which is redshifted by 30 nm with respect to previously reported measurements on MAPbI3 perovskites synthesized by crystallization from organic solvents.
Autochthonous Crimean-Congo Hemorrhagic Fever in Spain Negredo, Anabel; de la Calle-Prieto, Fernando; Palencia-Herrejón, Eduardo ...
New England journal of medicine/The New England journal of medicine,
07/2017, Letnik:
377, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Crimean-Congo hemorrhagic fever (CCHF) is a widely distributed, viral, tickborne disease. In Europe, cases have been reported only in the southeastern part of the continent. We report two ...autochthonous cases in Spain. The index patient acquired the disease through a tick bite in the province of Ávila - 300 km away from the province of Cáceres, where viral RNA from ticks was amplified in 2010. The second patient was a nurse who became infected while caring for the index patient. Both were infected with the African 3 lineage of this virus. (Funded by Red de Investigación Cooperativa en Enfermedades Tropicales RICET and Efficient Response to Highly Dangerous and Emerging Pathogens at EU European Union Level EMERGE.).
The mechanisms that determine the inhibition of calcite growth by magnesium have remained unclear and subject to controversy over decades. Although it has been long apparent that the inhibition ...mechanisms take place at the crystal-solution interface, the molecular phenomena occurring at calcite surfaces in contact with Mg-bearing solutions are still not completely understood. The main goal of this work is to contribute to further clarify those phenomena. With this aim, we carried out
in situ atomic force microscopy (AFM) observations of the growth behaviour of calcite
{
10
1
¯
4
}
surfaces in contact with supersaturated aqueous solutions (
β
=
5) bearing different amounts of Mg (ranging from 0.05 to 4.00
mmol
dm
−
3
). Under the conditions considered, growth occurred by monolayer spreading. Our observations revealed that only the first elementary growth layer advancing on the original calcite surfaces grow normally, showing characteristics nearly identical to the growth of pure calcite. However, subsequent monolayers behave differently. Thus, as soon as one of these monolayers reaches areas of the surface that have grown incorporating Mg and whose composition can consequently be described as Mg
xCa
1-xCO
3, the rate at which this step advances significantly decreases. Moreover, the step becomes progressively rougher. A clear relationship between the extent of the inhibition effect and the concentration of Mg in the aqueous solution exists. Furthermore, our observations allow us to conclude that each newly formed monolayer exerts a certain control on the development of the growth of subsequent monolayers. Such a control causes the reproduction of the nanotopographic features of the original surface, producing the so called “template effect”. This behaviour cannot be easily incorporated within the general framework of the currently accepted impurity crystal growth models, which are based on either the pinning of elementary step motion by impurities or changes in the solubility of the newly formed layers as a result of the incorporation of the impurity into the lattice of the growing crystal. We discuss our results on the basis of the solid solution–aqueous solution model and provide a complementary explanation for the development of “dead zones” in the case of the growth of calcite
{
10
1
¯
4
}
surfaces from divalent cation-bearing aqueous solutions.
SmFeO3 has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well ...as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown SmFeO3 single crystals in order to determine its magnetic structure. We found a k=0 G-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the Néel-temperature of ∼675 K, the dielectric measurements remain silent as far as ferroelectricity is concerned.
Understanding the physical mechanisms of thiolated molecules adsorption on metal surfaces has required copious research, particularly on Au–cysteine systems due to the affinity of sulfur molecules to ...gold surfaces, as well as the interesting structural modifications that this strong interaction induces and the peculiar optical, chiroptical, and electronic properties of Au(SR) systems. Here, we present vibrational experimental data on the adsorption of L‐ and D‐cysteine on small gold nanoparticles (<2 nm) by means of Raman spectroscopy. L‐ and D‐cysteine molecules adopt the same strained conformation upon adsorption on colloidal gold nanoparticles, regaining structure due to the stabilization that the gold nanoparticle induces on the cysteine, reflected in the recuperation of vibrational bands from their polymorphically distinctive crystalline forms. Through the analysis of Raman vibrational modifications after adsorption, we found experimental evidence that confirms a stabilized cysteine conformation locating the carboxyl group in the antiposition (PC isomeric rotamer) for both molecules. This result is supported by extensive density functional theory (DFT) calculations and simulated Raman spectra, considering zwitterionic cysteine adsorbed on a Au34 cluster, emulating experimental nanoparticle sizes. Our Raman spectroscopy experimental and DFT results determine one of the oxygen atoms of the carboxyl group as a second adsorption site after the sulfur atom, confirming that independent of its polymorphism and enantiomerism, zwitterionic cysteine interacts with gold nanoparticles through the thiol group and the carboxyl group as adsorption sites.
Experimental vibrational data of small (>2 nm) synthesized L‐ and D‐cysteine capped gold nanoparticles are obtained by means of Raman spectroscopy, confirming a stable conformation for cysteine that locates the carboxyl group in the antiposition for both L‐ and D‐cysteines. Au34 Cys configurations are obtained using DFT‐D3 global optimization random searches in order to explore the preferred cysteine adsorption sites and calculate the Raman spectra. General analysis confirms the cysteine interaction with gold through the carboxyl and thiol groups.
Aim
To determine the plasma and saliva levels of IL‐6 in patients with bisphosphonate‐related osteonecrosis of the jaws (BRONJ) and to investigate whether there is a correlation between more advanced ...stages of BRONJ and levels of IL‐6.
Material and Methods
We studied three groups: group 1 consisted of 30 patients with BRONJ due to intravenous bisphosphonates (ivBP), group 2 consisted of 25 patients treated with ivBP but without BRONJ, and group 3 consisted of 15 healthy controls. In each case, we assayed plasma and saliva IL‐6 samples using an ELISA test.
Results
Significantly, higher IL‐6 values were found in both saliva and plasma in group 1 vs groups 2 and 3 (P < 0.01). Group 1 showed no differences in plasma or saliva IL‐6 according to patient gender (P > 0.05), type of tumor, BRONJ location, etiology of BRONJ, or disease stage (P > 0.05). We found higher plasma and saliva IL‐6 values in the more advances stages of BRONJ, although the differences were not statistically significant.
Conclusions
Plasma and saliva IL‐6 values were higher in our patients with BRONJ than in controls and therefore might be a useful tool for monitoring the severity of BRONJ.
This paper examines the degree of interdependence between three agricultural commodity prices, crude oil price returns, macroeconomic variables and the S&P GSCI commodity returns index. We apply the ...Aielli (2013) cDCC model using monthly data from 1982 to 2012 to estimate the dynamic correlations of the returns series and endogenously detect structural instability of the correlations. Our results indicate that crude oil price returns present statistically significant dynamic correlations with all the macroeconomic variables and the GSCI index. Additionally, we detect structural changes in these dynamic correlations mainly associated with the financial crisis of 2008. We find evidence of volatility spillover between crude oil and maize, but not among oil with soybean and sugar markets. This can be explained by an increasing interdependence between crude oil and maize price returns induced by the introduction of biofuel policies. Our results also show a significance degree of interdependence between soybeans with the US exchange rate and sugar with global economic activity. Nevertheless, only the GSCI index has significant dynamic correlations with crude oil price returns and we find no significant correlation between the GSCI with any of the agricultural price returns.
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