Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

Characterization of Stress Responses of Heavy Metal and Metalloid Inducible Promoters in Synechocystis PCC6803

Abstract: In several biotechnological applications of living bacterial cells with inducible gene expression systems, the extent of overexpression and the specificity to the inducer are key elements. In the present study, we established the concentration ranges of Zn(2+), Ni(2+), Co(2+), AsO(2)(-), and Cd(2+) ions that caused significant activation of the respective promoters of Synechocystis sp. without concomitant unspecific stress responses. The low expression levels can be increased up to 10-100-fold upon treatments with Cd(2+), AsO(2)(-), Zn(2+), and Co(2+) ions and up to 800-fold upon Ni(2+) treatment. These results facilitate the development of conditional gene expression systems in cyanobacteria.

NO reduction by CH4 over well-structured Pt nanocrystals supported on γ-Al2O3

Abstract: Platinum nanocrystals, with an average diameter of 12 nm, were prepared by reduction of K 2 PtCl 4 with H 2 in the presence of a structure-directing agent (polymer of N -isopropylacrylamide). The Pt nanocrystals, having mainly (1 0 0) structure (≈64%), were supported on γ-Al 2 O 3 and then tested for the reduction of NO (1%) with CH 4 (0.6%) in the temperature range 300–500 °C. The NO was completely converted to N 2 and N 2 O starting from 400 °C. The formation of NH 3 as side product could not be evidenced below 600 °C. In the temperature range investigated, the only product of methane oxidation was CO 2 . The highest selectivity to N 2 (≈73%) was observed at 500 °C. In contrast to Pt(1 0 0)/Al 2 O 3 catalyst, substantial amounts of CO and NH 3 are formed over the conventionally prepared Pt/γ-Al 2 O 3 catalyst (NH 3 starts to be formed at temperatures as low as 400 °C). The remarkable differences observed between Pt(1 0 0)/Al 2 O 3 and Pt/Al 2 O 3 (conventional) catalysts reveal the importance of the morphology of the supported Pt particles for NO/CH 4 reaction. Both, the size and dominant crystallographic orientation of the supported Pt particles have been found to be determining factors for the catalyst activity and selectivity. The formation of NH 3 and CO can be suppressed by using as catalyst the large, well-defined Pt nanocrystals supported on alumina.

Effect of temperature on the electrochemical synthesis and properties of polyaniline films

Abstract: The effect of temperature on the electrochemical oxidative polymerization of aniline and on the electrochemical properties of the resulting polyaniline (PANI) film was studied. The electrochemical deposition of PANI has been carried out on platinum at different temperatures. Three different films (PANI-25, PANI-40 and PANI-60) have been prepared at 25, 40 and 60 °C by electrochemical polymerization and characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Increasing the synthesis temperature leads to an increase of the polyaniline films thickness from 0.4 to 0.9 μm and, respectively, 1.1 μm, associated with an increase of the films capacitances from 3 × 10−2 F cm−2 to 7 × 10−2 F cm−2 and 10 × 10−2 F cm−2. The impedance measurements showed that only PANI-25 and PANI-40 exist in the conductive state over a large potential window, while PANI-60 has an intermediate behavior at low and high electrode potentials.

Dynamic cubic instability in a 2D Q-tensor model for liquid crystals

Abstract: We consider a four-elastic-constant Landau–de Gennes energy characterizing nematic liquid crystal configurations described using the Q-tensor formalism. The energy contains a cubic term and is unbounded from below. We study dynamical effects produced by the presence of this cubic term by considering an L2 gradient flow generated by this energy. We work in two dimensions and concentrate on understanding the relations between the physicality of the initial data and the global well-posedness of the system.

Spatial assessment of land degradation sensitive areas in southwestern Romania using modified MEDALUS method

Abstract: Land degradation, a current environmental threat of global proportions, is a complex issue which needs an interdisciplinary approach in order to tackle a given territory's sensitivity to the process. This study aims to spatially analyse the land degradation sensitivity in south-western Romania, a region currently known for this type of environmental deterioration. The analysis is based on mapping and assessing land susceptibility to degradation by means of a multifactorial approach using GIS techniques, such as the well-established MEDALUS (Mediterranean Desertification and Land Use) method. Widely used in the Mediterranean region and other areas worldwide due to advantageous features such as simplicity, flexibility and rapid implementation, the method was used in this study for the analysis of the main indicators identified to be driving forces of land degradation, i.e. Climate Quality Index, Soil Quality Index, Vegetation Quality Index and Management Quality Index. The paper aims to adjust the method in relation to local conditions by considering certain additional variables (sub-indicators) for computing the main indicators, as well as by integrating a new regionally relevant indicator for this environmental issue – Water Quality Index. The final results, assessed with the proposed Land Degradation Sensitivity Index (based on 21 sub-indicators, of which 15 are included in the original MEDALUS method, and 6 are additional), showed that approximately 70% of the total study area is critically sensitive to degradation, mainly due to high agricultural pressures and very low vegetation cover. Surprisingly, in terms of administration, it was found that > 80% of the region's territorial administrative units include sectors which are critically exposed to degradation that exceed half their area. The results can constitute a basic support for regional-level decision makers who can implement the appropriate measures in order to attenuate the restrictive environmental conditions.