Application of the principle of harmonic-disturbance model separation for structural-parametric construction of selectively invariant electromechanical systems

The problem of improving the response of harmonic disturbance of electric-motor load torque with simultaneous reduction of the degree of complexity of regulators taking into account additional quality factors of electromechanical systems, such as noise stability, sensitivity to variations in object parameters, and delay of power-converter signals are considered. A selective invariance principle assuming incorporation of the disturbance model into an electric-motor control device is used as the main principle. This paper has some distinctive features. The first one is the application of dual-circuit structures of electromechanical systems with a rapid inner control loop. The second is the application of the separation principle of disturbance model into integral and oscillatory components. The third feature is transfer of one of the disturbance model components into a rapid subsystem. Design procedures of regulator parameters are developed. Comparative investigation of the constructed electromechanical systems on the basis of a complex of main and additional quality factors is performed.     

COMPLEXATION IN ION EXCHANGER PHASE. PROPERTIES AND APPLICATION OF ION EXCHANGER COMPLEXES

ABSTRACT

This paper reviews the properties of complex forming ion exchangers (CFIE) and those of the ion exchanger complexes (IEC) with transition metal ions. It is mainly dedicated to the development of a novel approach in characterizing IEC which is based on the consideration of CFIE as three-dimensional polymeric ligands. The approach is illustrated by the results obtained by studying the specificity of complex formation with CFIE of different types, the structure, properties and possible applications of IEC as anion exchangers, as electron exchangers, as ligand exchangers and some others. A particular attention is paid to the tailored synthesis of the IEC with desired properties such as the composition of the statistically-average coordination center, the distribution of metal ions along the polymer chain, etc., and to their application as catalysts which combine the high selectivity and activity of the homogenous metal-complex catalysts with the technological convenience of the heterogeneous ones. The application of the IEC as convenient models for bio-catalysts (metalloenzymes) is also discussed.     

The reasons for tooth extractions in adults and their validation

OBJECTIVES: To investigate the primary reasons for the extraction of permanent teeth in adults and to validate the dentists' reasons for extraction. METHODS: Twenty-one dentists in the Greater Manchester area took part in the study. These dentists provided extracted teeth stored in 10% buffered formal saline together with details of the patient's age, sex, dental attendance pattern and the reason for extraction. In order to validate the reasons for extraction, teeth were examined for the presence or absence of coronal and root caries. A subgroup of 80 teeth, half of which were extracted primarily for caries and half for periodontal reasons were selected, stained and attachment loss measured at six sites per tooth to validate periodontal reasons for extraction. RESULTS: Three hundred and eighty-nine teeth were collected of which 37% were extracted primarily due to caries and 29% due to periodontal disease. Caries was the main reason for extraction in patients under 50 years, whereas periodontal disease was the commonest reason in the over-50 age group. Irregular attenders had more extractions for caries than regular attenders but attendance pattern did not affect the proportion of teeth extracted for periodontal reasons. The mean greatest loss of attachment on teeth extracted for periodontal reasons was 12 mm compared with 6.5 mm for caries. CONCLUSION: In this group of patients caries was the most common reason for extraction of teeth but periodontal disease became a more important reason for extraction after 50 years of age. The study validated the dentists' given reason for extraction.     

Comparison of radiological procedures in preoperative assessment of anchorage strength of spinal implants

PURPOSE: To compare three techniques with regards to their ability to estimate pull out strength of spinal fusion hardware. MATERIAL AND METHODS: VDS-screw fixation strength in 50 human cadaveric vertebral bodies was approximated by means of pull out force measurement. Bone quality was assessed by Dual X-ray Absorptiometry (DXA). Quantitative Computed Tomography (QCT) and T2*-relaxation time. For each of these techniques, correlation with axial pull out force strength was investigated. RESULTS: Highest correlation was found for cancellous bone density measured by QCT (r = 0.72; p < 0.001). Immediately followed by DXA (r = 0.70; p < 0.001), which involves all bone components. Inverted T2*-relaxation time (r = 0.55; p < 0.001) and cortical bone density (QCT) correlated just slightly with pull-out force strength. CONCLUSIONS: Absorptiometrical techniques like QCT and DXA are most appropriate to estimate VDS-screw fixation strength preoperatively.     

The eight-amino acid internal loop of PSI-C mediates association of low molecular mass iron-sulfur proteins with the P700-FX core in photosystem I

The PSI-C subunit of photosystem I (PS I) shows similarity to soluble 2[4Fe-4S] ferredoxins. PSI-C contains an eight residue internal loop and a 15 residue C-terminal extension which are absent in the ferredoxins. The eight-residue loop has been shown to interact with PSI-A/PSI-B (Naver, H., Scott, M. P., Golbeck, J. H., Moller, B. L., and Scheller, H. V. (1996) J. Biol. Chem. 271, 8996-9001). Four mutant proteins were constructed. Two were modified barley PSI-C proteins, one lacking the loop and the C terminus (PSI-Ccore) and one where the loop replace the C-terminal extension (PSI-CcoreLc-term). Two were modified Clostridium pasteurianum ferredoxins, one with the loop of barley PSI-C and one with both the loop and the C terminus of PSI-C. Wild-type proteins and the mutants were used to reconstitute barley P700-FX cores lacking PSI-C, -D, and-E. Western blotting showed that PSI-CcoreLc-term binds to PS I, whereas PSI-Ccore does not. Without PSI-D the PSI-CcoreLc-term mutant accepts electrons from FX in contrast to PSI-C mutants without the loop. Flash photolysis of P700-FX cores reconstituted with C. pasteurianum ferredoxin showed that only the ferredoxin mutants with the loop accepted electrons from FX. From this, it is concluded that the loop of PSI-C is necessary and sufficient for the association between PS I and PSI-C, and that the loop is functional as an interaction domain even when positioned at the C terminus of PSI-C or on a low molecular mass, soluble ferredoxin.     

Effectiveness of HIV interventions among women drug users

A prospective cohort study was conducted among chronic injecting and crack cocaine drug using women. The hypothesis tested was that participation in a standard-plus-innovative intervention was more likely to produce behavior change than participation in a standard intervention. Standardized intervention protocols and corresponding instruments were designed. Data were collected on drug and sex risk behaviors at baseline and six-month follow-up intervals. The level of behavioral change in two intervention arms--standard and a standard-plus-innovative intervention--was measured by composite sex risk and drug risk scores using the generalized estimating equation approach. The results show that on four risk measures the enhanced intervention was significantly associated with positive change in both drug use and sexual behavior: less frequent drug use, less drug use during sex, and more frequent condom use during particular frequencies for specific types of sexual activities. Public health interventions are effective when targeting specific risk behaviors through interventions tailored to prevent HIV and reduce risk behaviors among specific cultural and gender groups.