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1.
This article presents for the first time Scots pine tree-ring chronology created from historical timber (XVII–XIX cc.) from central Belarus. The chronology includes 59 tree-ring series which were collected from the different wood structures in the Nesvizh castle. This samples show different stages of the castle renovations. The chronology presented in this paper embraces 222 years covering the period between 1608 and 1829.  相似文献   
2.
A device and the results of a 3-year performance of cellular grids for mammography were described. An increase in the informative value and a decrease in radiation exposure of patients were shown during mammography with a cellular grid.  相似文献   
3.
Discrimination of colours by macaque rhesus was studied by the method of elaboration of differentiation inhibition of instrumental conditioned responses to colour stimuli. Matrix of probabilities of instrumental reactions to presentation of colour stimuli, the columns of which corresponded to the colours applied, and the lines--to series of experiments with definite reinforced colour--was processed by the method of factor analysis. Four factors describing the used colours in four-dimensional Euclidean space were singled out. Spatial structure of the seven used colours satisfies the equation of four-dimensional sphere. Two first factors are interpreted as colour-opponent red-green and yellow-blue and the third and fourth ones as achromatic light and dark neuronal channels. Perceptive space of colour stimuli based on the data of instrumental behaviour of the monkey corresponds to analogous results obtained by the method of multidimensional scaling of subjective evaluations of super-threshold colour differences for the man.  相似文献   
4.
The influence of X-radiation on activity of lysosomal enzymes (D, L, H cathepsins) in rat spleen tissue and in inoculated rat sarcoma 45 has been investigated. Intact rats and rats with tumors were subjected to whole-body and sarcoma 45 to local irradiation with doses of 0.155 C/kg and 0.31 C/kg in conditions of breathing gas hypoxic mixture containing 90% of nitrogen and 10% of oxygen (GHM-10). The combined exposure to radiation and GHM-10 was shown to produce a certain protective action (e.g. normalized cathepsin activity) in the spleen. In the tumor tissue the protective effect of GHM-10 was absent.  相似文献   
5.
The content of total protein, glycoproteins, and N-acetylneuraminic acid in different membrane fractions of rat brain tissues was studied 60 min and 24 h following X-irradiation with a dose of 0.31 C/kg. A slight increase in the amount of glycoproteins was noted upon electrophoresis due to the occurrence of low molecular weight carbohydrate-containing proteins. The derangement of the membrane glycoprotein structure is supposed to be one on the causes of radiation destruction of membranes.  相似文献   
6.
Recent studies have discovered strong differences between the dynamics of nucleic acids (RNA and DNA) and proteins, especially at low hydration and low temperatures. This difference is caused primarily by dynamics of methyl groups that are abundant in proteins, but are absent or very rare in RNA and DNA. In this paper, we present a hypothesis regarding the role of methyl groups as intrinsic plasticizers in proteins and their evolutionary selection to facilitate protein dynamics and activity. We demonstrate the profound effect methyl groups have on protein dynamics relative to nucleic acid dynamics, and note the apparent correlation of methyl group content in protein classes and their need for molecular flexibility. Moreover, we note the fastest methyl groups of some enzymes appear around dynamical centers such as hinges or active sites. Methyl groups are also of tremendous importance from a hydrophobicity/folding/entropy perspective. These significant roles, however, complement our hypothesis rather than preclude the recognition of methyl groups in the dynamics and evolution of biomolecules.  相似文献   
7.
The extent and nature of cyclic electron delocalization in free and coordinated cyclopropenylidene carbenes has been analyzed by combined experimental and theoretical charge-density studies. The significant asymmetry of the C-C bond lengths in substituted cyclopropenylidene carbenes was identified as cooperative effect which depends on contributions of both σ- and π-bonding. We show that analyses of (i) the topology of the Laplacian of the electron density distribution and (ii) the out-of-plane atomic quadrupole moments - the charge-density analogues of pπ occupation - allow to distinguish between the influence of σ- and π-electrons on cyclic electron delocalization. These studies hint for pronounced electron localization in the carbene lone pair region which dominates the electronic structure of free cyclopropenylidene carbenes and hinders the establishment of true aromaticity. We further investigated the electron donating/withdrawing ability of cyclopropenylidene ligands relative to N-heterocyclic carbenes. The experimental benchmark systems LCr(CO)5 (L = 2,3-diphenylcyclopropenylidene and 1,2-dimethylimidazol-2-ylidene) show that the cyclopropenylidene ligand clearly displays the higher π-acceptor capability relative to N-heterocyclic carbenes.  相似文献   
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