Energy efficiency analysis of double suction centrifugal pumps with new impeller geometry

The development of energy saving determines the importance of improving the efficiency of equipment that uses most of the energy consumed. Pumping equipment is one of the most significant consumers of electrical energy. Thus, the drive of pumps (mainly centrifugal pumps) at some CHPPs consumes up to 10 % of the total energy produced at the plant [1]. In general, the total share of consumption of pumping equipment operated in industry, according to various estimates, is from 15 to 25 % of all generated electricity. In this paper, a new impeller configuration (with variable blade curvature) for double suction centrifugal pumps with higher efficiency was proposed. The head and efficiency of centrifugal pump with different vane grids were compared. The main conclusions are that the static pressure and relative velocity have increased in the modernised impeller, leading to an increase in hydraulic and overall efficiency, the kinetic energy of turbulence has less pulsation. the operating point of the pump has shifted. In spite of the fact that the average integral efficiency has increased in the modified pump, the operating point of the pump is shifted to the side of decreasing flow by 1.5%. The theory of the variable curvature vane system was verified by computational methods

Selective binding of looped oligonucleotides to a single-stranded DNA and its influence on replication in vitro.

Complexing of looped and circular oligonucleotides, composed of either 2'-deoxyribo- or 2'-O-methylribonucleoside units, with completely matching or partially mismatching complementary DNA sequences was studied. Melting experiments revealed considerable differences among the stabilities of these hybrid complexes. Maximum stability and selectivity was displayed by oligomers 2 and 5. It was concluded that a linear stretch, attached to 1'-O- of 3'-deoxypsicothymidine unit (Z) increases the selectivity of hybridisation and stability of the complex as a whole. This allows one to aim the target DNA very precisely at its polyadenine part as well as at adjacent sequence simultaneously. Experiments on termination of primer extension catalysed by different DNA-polymerases--Sequenase, Klenow fragment and Tth--have demonstrated that looped oligomer 5, composed of 2'-O-methylribonucleosides appears to be a highly selective and potent inhibitor of replication in vitro. Features of looped oligonucleotides, composed of 2'-O-methylribonucleosides seem to be useful for design of highly specific antigene oligonucleotides

Looped oligonucleotides form stable hybrid complexes with a single-stranded DNA.

Several new branched (1, 2), circular (9) and looped oligonucleotides (14-17) were synthesized. 3'-Deoxypsicothymidine was employed to create the site of branching when required. The circular and looped structures were obtained by oxidative disulfide bond formation between mercaptoalkyl tether groups. All the oligonucleotides prepared contained two T11 sequences, and the branched and looped oligomers an additional alternating CT sequence. The melting experiments revealed that the branched oligonucleotides form relatively weak hybrid (double/triple helix) complexes with the single-stranded oligodeoxyribonucleotide, showing a considerable destabilizing effect produced by the structure at the point of branching. The data obtained with looped oligonucleotides demonstrated considerable stabilization of the hybrid (double/triple helix) complexes with the complement. The data reported may be useful in attempting to design new antisense or antigene oligonucleotides capable of forming selective and stable bimolecular hybrid complexes with nucleic acids