Thermal analysis of Romanian ancient ceramics

The present work is focused on thermoanalytical investigations as thermogravimetric analysis (TG) and derivative thermal analysis (DTG), applied for the characterization of some samples collected from archaeological sites (Brasov and Trofeum Traiani) located in different regions of Romania. New informations derived about ceramic technologies concerning raw materials and binding materials (mineralogical components) have been obtained. All these experimental results have been correlated with related techniques as X-ray diffraction (XRD), energy-dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma—atomic emission spectrometry (ICP-AES). By progressive heating in static air atmosphere and in the temperature range of 20–800 °C, all investigated materials exhibit three main successive processes, associated with the dehydration and thermo-oxidative degradations. The rate of the first thermooxidative process, temperatures corresponding to the maximum rate of the second thermooxidative process and shrinkage temperature were associated with the damage of the investigated materials due to environmental impact. Heating also affects the contact between the fine-sized clay matrix and mineral clast fragments, appearing in reaction rims, sometimes showing newly formed phases. The temperature at which ancient ceramics and pottery were fired varies over a wide range (600–800 °C) depending on the type of clay used, although firing temperatures not above 30–400 °C have also been suggested. Clay minerals, as the main material for production of ceramics and pottery, show some characteristic reactions (dehydroxylation, decomposition, transformation) in the course of firing (heating effects) and several thermoanalytical criteria can be used for reconstruction of former production conditions.     

Graduated adaptive image denoising: local compromise between total variation and isotropic diffusion

We introduce variants of the variational image denoising method proposed by Blomgren et al. (In: Numerical Analysis 1999 (Dundee), pp. 43–67. Chapman & Hall, Boca Raton, FL, 2000), which interpolates between total-variation denoising and isotropic diffusion denoising. We study how parameter choices affect results and allow tuning between TV denoising and isotropic diffusion for respecting texture on one spatial scale while denoising features assumed to be noise on finer spatial scales. Furthermore, we prove existence and (where appropriate) uniqueness of minimizers. We consider both L ² and L ¹ data fidelity terms.     

Photochemistry of 1,2-dihydronaphthalene oxide: concurrent triplet and singlet processes via singlet excitation

The photochemistry of 1,2-dihydronaphthalene oxide (254 nm) was reexamined and indan was found to be a primary photoproduct, as well as the traditionally assumed secondary photoproduct. Quenching studies demonstrated that indan, as a primary photoproduct, is derived from a triplet pathway, competing with a singlet route, back to the ground state surface. CASSCF calculations strongly suggest that the triplet pathway consists of a dissociation of the oxirane moiety to give a triplet carbene and aldehyde, which via hydrogen abstraction-decarbonylation-ISC recloses to give indan. Conical intersections corresponding to the presumed 1,2-hydrogen shift and 1,2-alkyl shift to give 2-tetralone and 1-indancarbaldehyde, respectively, were located computationally.     

Surface-mediated growth of transparent, oriented, and well-defined nanocrystalline anatase titania films

A new, surface-mediated method to grow transparent, oriented, and well-defined nanocrystalline anatase TiO2 films has been developed. The morphology of crystals is tunable from octahedral pyramids to truncate octahedral pyramids. These novel nanocrystalline films could have implications not only for practical applications but also for understanding the structure and orientation dependent properties of the important anatase material.     

A polarizable,charge transfer model of water using the drude oscillator

The transfer of small amounts of charge between neighboring particles can be a significant part of interactions among particles. A model is developed for treating charge transfer (CT) combined with the Drude model for polarizability to create an efficient model for liquid water which includes both CT and polarizability. The model is shown to be accurate for a variety of liquid properties, including the density as a function of temperature and the dielectric constant. A new model for water with CT and polarization is developed and applied to the liquid. The inclusion of CT increases the accuracy of many properties, like the density as a function of temperature, indicating the importance of charge redistribution as induced by other particles. © 2016 Wiley Periodicals, Inc.     

Verifying the presence of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy

This paper examines the problems associated with analysis of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy (EELS) on the transmission electron microscope (TEM). The detection of neptunium in a matrix of uranium can be impeded by the occurrence of a plural scattering event from uranium (U-M₅ + U-O_4,5) that results in severe overlap on the Np-M₅ edge at 3665 eV. Low levels of Np (1600–6300 ppm) can be detected in a uranium solid, uranophane [Ca(UO₂)₂(SiO₃OH)₂(H₂O)₅], by confirming that the energy gap between the Np-M₅ and Np-M₄ edges is at 184 eV and showing that the M₄/M₅ ratio for the neptunium is smaller than that for uranium. The Richardson–Lucy deconvolution method was applied to energy-loss spectral images and was shown to increase the signal to noise ratio.     

The Effect of Organizational Communication Media on Organizational Culture and Performance: An Agent-Based Simulation Model

This paper examines the mutual relationship between the communication richness of media used for conducting organizational communication and organizational culture. The richness of the media influences how well the organization might maintain its culture. On the other hand, a strong organizational culture allows a more effective use of the media by providing members with some of the necessary common ground to better understand the information exchanged. These relationships are investigated using an agent-based simulation model (ABM). Our ABM incorporates many partial theories into a coherent and fully defined model, which helps formalize and integrate those theories. Our model allows us to analyze non-linearities and interaction effects, which are difficult to investigate using other techniques. Additionally, the ABM allows us to investigate the dynamics of the phenomenon and generate hypotheses that could then be tested using empirical studies. Given the substantial resources necessary to conduct empirical studies, we think that the present ABM is valuable in helping guide data collection efforts. In this paper, we present results that show that organizational culture can influence the effectiveness of the media used for organizational communication and that a high media richness can help maintain and stabilize a culture. The effect of media richness on organizational culture depends on the initial strength of the culture. In general, for a given richness of the media, an initially strong culture stabilizes faster and becomes stronger through time than an initially weak culture. Additionally, the model suggests that a stable network of contacts among agents fosters a high achievement of organizational tasks. Conversely, when agents are forced to establish contacts with agents outside the usual network for doing their work, the accomplishment of tasks decreases.     

Coordination number of zinc ions in the phosphotriesterase active site by molecular dynamics and quantum mechanics

We have run several molecular dynamics (MD) simulations on zinc-containing phosphotriesterase (PTE) with two bound substrates, sarin and paraoxon, and with the substrate analog diethyl 4-methylbenzylphosphonate. A standard nonbonded model was employed to treat the zinc ions with the commonly used charge of +2. In all the trajectories, we observed a tightly bound water (TBW) molecule in the active site that was coordinated to the less buried zinc ion. The phosphoryl oxygen of the substrate/inhibitor was found to be coordinated to the same zinc ion so that, considering all ligands, the less buried zinc was hexa-coordinated. The hexa-coordination of this zinc ion was not seen in the deposited X-ray pdb files for PTE. Several additional MD simulations were then performed using different charges (+1, +1.5) on the zinc ions, along with ab initio and density functional theory (DFT) calculations, to evaluate the following possibilities: the crystal diffraction data were not correctly interpreted; the hexa-coordinated zinc ion in PTE is only present in solution and not in the crystal; and the hexa-coordinated zinc ion in PTE is an artifact of the force field used. A charge of +1.5 leads to a coordination number (CN) of 5 on both zinc ions, which is consistent with the results from ab initio and DFT calculations and with the latest high resolution X-ray crystal structure. The commonly used charge of +2 produces a CN of 6 on the less buried zinc. The CN on the more buried zinc ion is 5 when the substrate/inhibitor is present in the simulation, and increases to 6 when the substrate/inhibitor is removed prior to the simulation. The results of both of the MD and quantum mechanical calculations lead to the conclusion that the zinc ions in the PTE active site are both penta-coordinated, and that the MD simulations performed with the charge of +2 overestimate the CN of the zinc ions in the PTE active site. The overall protein structures in the simulations remain unaffected by the change in zinc charge from +2 to +1.5. The results also suggest that the charge +1.5 is the most appropriate for the molecular dynamics simulations on zinc-containing PTE when a nonbonded model is used and no global thermodynamic conclusion is sought. We also show that the standard nonbonded model is not able to properly treat the CN and energy at the same time. A preliminary, promising charge-transfer model is discussed with the use of the zinc charge of +1.5.     

Copper-mediated N-alkynylation of carbamates, ureas, and sulfonamides. A general method for the synthesis of ynamides

[reaction: see text] A general amination strategy for the N-alkynylation of carbamates, sulfonamides, and chiral oxazolidinones and imidazolidinones is described. A variety of substituted ynamides are available by deprotonation of amides with KHMDS followed by reaction with CuI and an alkynyl bromide.     

Determination of plutonium in sediments by solvent extraction and α-spectrometry

A simple technique for the determination of environmental levels of plutonium in a highly complex matrix (sediments containing very high amounts of iron and other metals) is reported. The sediments, collected from the Hudson River Estuary with an Emory dredge, were hand-homogenized before a sample aliquot was taken. Samples were airdried, weighed, spiked with ²⁴²Pu tracer, and heated at 400°C for 24 h. Plutonium was leached from the sediment with an acid mixture. The leachate was filtered, and plutonium coprecipitated with iron by adding ammonia solution. After dissolution, plutonium was extracted with 20% trilaurylamine in xylene, the extracts were thoroughly acid-washed to remove uranium and thorium traces, and plutonium was then back-extracted with 2 M sulfuric acid prior to electrodeposition onto a platinum planchet. The isotopic composition of plutonium was determined by α-spectrometry. Tracer yield and plutonium concentrations determined on aliquots of the same samples by this method and by an ion-exchange technique were not significantly different.