A 323-year long reconstruction of drought for SW Romania based on black pine (Pinus Nigra) tree-ring widths

Increase in temperature and decrease in precipitation pose a major future challenge for sustainable ecosystem management in Romania. To understand ecosystem response and the wider social consequences of environmental change, we constructed a 396-year long (1615–2010) drought sensitive tree-ring width chronology (TRW) of Pinus nigra var. banatica (Georg. et Ion.) growing on steep slopes and shallow organic soil. We established a statistical relationship between TRW and two meteorological parameters—monthly sum of precipitation (PP) and standardised precipitation index (SPI). PP and SPI correlate significantly with TRW (r?=?0.54 and 0.58) and are stable in time. Rigorous statistical tests, which measure the accuracy and prediction ability of the model, were all significant. SPI was eventually reconstructed back to 1688, with extreme dry and wet years identified using the percentile method. By means of reconstruction, we identified two so far unknown extremely dry years in Romania—1725 and 1782. Those 2 years are almost as dry as 1946, which was known as the “year of great famine.” Since no historical documents for these 2 years were available in local archives, we compared the results with those from neighbouring countries and discovered that both years were extremely dry in the wider region (Slovakia, Hungary, Anatolia, Syria, and Turkey). While the 1800–1900 period was relatively mild, with only two moderately extreme years as far as weather is concerned, the 1900–2009 period was highly salient owing to the very high number of wet and dry extremes—five extremely wet and three extremely dry events (one of them in 1946) were identified.     

Synthesis,structure, antimycobacterial and anticancer evaluation of new pyrrolo-phenanthroline derivatives

A study concerning design, synthesis, structure and in vitro antimycobacterial and anticancer evaluation of new fused derivatives with pyrrolo[2,1-c][4,7]phenanthroline skeleton is described. The strategy adopted for synthesis involves a [3?+?2] dipolar cycloaddition of several in situ generated 4,7-phenanthrolin-4-ium ylides to different substituted alkynes and alkenes. Stereo- and regiochemistry of cycloaddition reactions were discussed. The structure of the new compounds was proven unambiguously, single-crystal X-ray diffraction studies including. The antimycobacterial and anticancer activity of a selection of new synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv under aerobic conditions and 60 human tumour cell line panel, respectively. Five of the tested compounds possess a moderate antimycobacterial activity, while two of the compounds have a significant antitumor activity against renal cancer and breast cancer.     

Regulation of PSII function in Cyanothece sp. ATCC 51142 during a light–dark cycle

Photosynthesis Research - Cyanobacteria, as well as green algae and higher plants, have highly conserved photosynthetic machinery. Cyanothece sp. ATCC 51142 is a unicellular, aerobic, diazotrophic...     

The reaction of [Os6(CO)18] with [(SPPh2)2NH]: Facile rearrangement of the metal framework

The reaction of [Os₆(CO)₁₈] 1 with [(SPPh₂)₂NH] in the presence of Me₃NO produces a purple compound characterized spectroscopically and by X-ray crystallography, as [HOs₆(CO)₁₇(SPPh₂)₂N] 2. The structure shows the hexanuclear fragment to have suffered a geometrical rearrangement to give a metal framework that can be described as an edge-bridged tetrahedron with an additional terminal osmium atom bonded to one of the bridged metal atoms. The ligand acts as a bimetallic tetraconnective unit through both sulphur atoms between two non-bonded osmium atoms.     

Réponse des Larves de Perla burmeisteriana Claassen (Plecoptera) aux variations de la pression hydrostatique

In order to explain the reactions of larvae of P. burmeisteriana to an ecological change following the impoundment of a Man-made lake on River Bistritza (Roumania), we made some experiments on the responses of this species to variations of hydrostatic pressure. Experiments were carried out in the lake of Bicaz. Observations were direct, either by diving or by monitoring the situation visually from a submerged laboratory. Sets of 40 specimens were exposed to pressure of 1, 1.5 or 2 atmospheres. It was found that survival time of the larvae decreased as pressure increased. A temperature dependance of this phenomenon was stated. Pressure influences gaseous exchanges, by altering the rate of elimination of CO₂. This finally leads to hypercapnia. Je tiens à exprimer ici toute ma gratitude aux PROF. Dr. P. Jitariu, Membre Correspondant de l'Académie RSR, pour le privilège de me diriger vers l'étude écologo-physiologique et le Prof. Dr. L. De Conincl et le Dr. H. Dumont de l'Instituut voor Dierkunde de l'Université de Gand, où j'ai trouvé toute l'aide désirable pour pouvoir rendre définitif ce travail.      

Dimeric thiophosphorus complexes of sodium and zinc: Structural characterization of [(THF)2NaO(S)PPh2]2 and [Zn{S2P(OMe)C6H4OEt-p}2]2

Sodium P,P-diphenylphosphinothioate (2) was prepared by treatment of the free acid, Ph₂P(S)OH (1), with sodium bis(trimethylsilyl)amide and isolated as its THF adduct. The zinc phosphonodithioate complex [Zn{S₂P(OMe)C₆H₄OEt-p}₂]₂ (3) was obtained from ZnCl₂ and the readily accessible sodium salt of the ligand. According to X-ray diffraction studies, both compounds form dimers in the solid state.     

Direct Quantification of the Attempt Frequency Determining the Mechanical Unfolding of Ubiquitin Protein

Understanding protein dynamics requires a comprehensive knowledge of the underlying potential energy surface that governs the motion of each individual protein molecule. Single molecule mechanical studies have provided the unprecedented opportunity to study the individual unfolding pathways along a well defined coordinate, the end-to-end length of the protein. In these experiments, unfolding requires surmounting an energy barrier that separates the native from the extended state. The calculation of the absolute value of the barrier height has traditionally relied on the assumption of an attempt frequency, υ^‡. Here we used single molecule force-clamp spectroscopy to directly determine the value of υ^‡ for mechanical unfolding by measuring the unfolding rate of the small protein ubiquitin at varying temperatures. Our experiments demonstrate a significant effect of the temperature on the mechanical rate of unfolding. By extrapolating the unfolding rate in the absence of force for different temperatures, varying within the range spanning from 5 to 45 °C, we measured a value for the activation barrier of ΔG^‡ = 71 ± 5 kJ/mol and an exponential prefactor υ^‡ ∼4 × 10⁹ s⁻¹. Although the measured prefactor value is 3 orders of magnitude smaller than the value predicted by the transition state theory (∼6 × 10¹² s⁻¹), it is 400-fold higher than that encountered in analogous experiments studying the effect of temperature on the reactivity of a protein-embedded disulfide bond (∼10⁷ m⁻¹ s⁻¹). This approach will allow quantitative characterization of the complete energy landscape of a folding polypeptide from highly extended states, of capital importance for proteins with elastic function.     

Climate–growth relationship of tree species from a mixed stand of Apuseni Mts., Romania

We present the first results of a dendroecological investigation on three prevailing species growing in the Apuseni Mountains. In this study we succeeded in building up about 200-year long local master chronologies for spruce, fir and beech. These chronologies will serve as a reference for crossdating of (sub-fossil) logs that were preserved in ice caves at the Apuseni Mts.

The analysis of climate–growth relationship provided interesting and different results for the three studied species: we found significant correlations between the beech chronology and the mean temperature of the prior July, autumn and January of the actual year as well as the weather conditions at the beginning of the vegetation period. Conifers yielded coherent results for the mean temperature of prior July and sum of precipitation in April. In addition, fir seems to be favouring above-average temperatures in January and February. The coherent and significant correlations with the April precipitation suggest a common coniferous phenomenon. Finally, beech index showed negative correlation with April temperature.