In situ Raman spectroscopy at the Voroneţ Monastery (16th century,Romania): New results for green and blue pigments

The Voroneţ Monastery is one of the greatest cultural treasures of Romania, dating from the 15th century. In the present study, the green and blue pigments of its exterior frescoes (16th century) were analyzed through fibre-coupled Raman spectroscopy. A wide range of typical pigments, including malachite, basic Cu sulphates, azurite, lazurite, smalt, gypsum, anhydrite and calcite were found, together with other “rare pigments,” such as conichalcite and dolerophanite. The green pigment is either a mixture of malachite and conichalcite or Cu sulphates while the blue pigment contains either lazurite, or a mixture of azurite and a minor quantity of smalt, gypsum and anhydrite. The identification of these pigments is very important for the restoration work, the monastery being a UNESCO World Heritage Site.     

Idempotent Convexity and Algebras for the Capacity Monad and its Submonads

Idempotent analogues of convexity are introduced. It is proved that the category of algebras for the capacity monad in the category of compacta is isomorphic to the category of (max, min)-idempotent biconvex compacta and their biaffine maps. It is also shown that the category of algebras for the monad of sup-measures ((max, min)-idempotent measures) is isomorphic to the category of (max, min)-idempotent convex compacta and their affine maps.     

Impact of Mercury(II) on proteinase K catalytic center: investigations via classical and Born-Oppenheimer molecular dynamics

Mercury(II) has a strong affinity for the thiol groups in proteins often resulting in the disruption of their biological functions. In this study we present classical and first-principles, DFT-based molecular dynamics (MD) simulations of a complex of Hg(II) and proteinase K, a well-known serine protease with a very broad and diverse enzymatic activity. It contains a catalytic triad formed by Asp39, His69, and Ser224, which is responsible for its biological activity. It was found previously by X-ray diffraction experiments that the presence of Hg(II) inhibits the enzymatic action of proteinase K by affecting the stereochemistry of the triad. Our simulations predict that (i) the overall structure as well as the protein backbone dynamics are only slightly affected by the mercury cation, (ii) depending on the occupied mercury site, the hydrogen bonds of the catalytic triad are either severely disrupted (both bonds for mercury at site 1, and the His69–Ser224 contact for mercury at site 2) or slightly strengthened (the Asp39–His69 bond when mercury is at site 2), (iii) the network of hydrogen bonds of the catalytic triad is not static but undergoes constant fluctuations, which are significantly modified by the presence of the Hg(II) cation, influencing in turn the triad’s ability to carry out the enzymatic function—these facts explain the experimental findings on the inhibition of proteinase K by Hg(II).     

Structural–acoustic model of a rectangular plate–cavity system with an attached distributed mass and internal sound source: Theory and experiment

In this paper three approaches are combined to develop a structural–acoustic model of a rectangular plate–cavity system with an attached distributed mass and internal sound source. The first approach results from a recently presented analysis based on the Rayleigh–Ritz method and is used to circumvent the difficulties in obtaining the natural frequencies and mode shapes of a plate with an attached, distributed mass. Furthermore, different plate boundary conditions can be accommodated. The resulting mode shapes are defined as continuous functions; this is advantageous as they can be directly used in the second approach, i.e., the classic modal-interaction approach in order to obtain the coupled equations of the system. Finally, in the third approach a group of point sources emitting a pressure pulse in the time domain is used to model an internal sound source. For the validation of the developed model an experiment was conducted in two configurations using a simply supported aluminium plate and a clamped plate coupled with a plexiglas box containing a loudspeaker. Good agreement was found between the analytical and experimental data.     

Functionalization of Polyurethane/Urea Copolymers with Amide Groups by Polymer Treatment with Ammonia Plasma

Samples of porous foam from polyurethane/urea copolymers based on polyethylene glycol (PURPEG) were prepared in the form of 1-mm-thick discs of diameter 10 cm and exposed to ammonia plasma created by inductively coupled radiofrequency discharge in either low density (E mode) or high density (H mode). The evolution of surface composition and structure upon plasma treatment was characterized by X-ray photoelectron spectroscopy. Treatment in the H mode caused depletion of oxygen even after 2 s of treatment, whereas treatment in the E mode caused gentle functionalization with amide groups. The concentration of functional groups depended on the discharge power, and the best results were obtained at moderately high power just before the transition from E to H modes.     

Acceptable consistency of aggregated comparison matrices in analytic hierarchy process

The analytic hierarchy process is a method for solving multiple criteria decision problems, as well as group decision making. The weighted geometric mean method is appropriate when aggregation of individual judgements is used. This paper presents a new proof which confirms the property that if the comparison matrices of all decision makers are of acceptable consistency, then the weighted geometric mean complex judgement matrix (WGMCJM) also is of acceptable consistency. This property was presented and first proved by Xu (2000), but Lin et al. (2008) rejected the proof. We also discuss under what conditions the WGMCJM is of acceptable consistency when not all comparison matrices of decision makers are of acceptable consistency. For this case we determine the sufficient condition for the WGMCJM to be of acceptable consistency and provide numerical examples. For a special case of two decision makers with 3 × 3 comparison matrices we find out some additional conditions for the WGMCJM to be of acceptable consistency.     

Electron screening in the 1H(7Li,$ \alpha$)4He reaction

We have measured the cross-section for the ¹H(⁷Li,a \alpha)⁴He reaction at lithium beam energies from 0.34 to 1.05MeV. Hydrogen was forced by diffusion into Pd and PdAg alloy foils. A large electron screening effect was observed only when foils were under tensile stress. A dependence of the screening potential on hydrogen concentration or Hall coefficient of the metallic host could not be established.