A study of objective functions for organs with parallel and serial architecture

A hemodynamics model of cerebral Willis circulation is proposed. The model consists of the compensation of blood flow as well as the compliance, resistance and inductance of arteries. The impedances of carotid and vertebral arteries are obtained by solving the govern equations. The theoretical impedances correspond well with the experimental results. The simulating results demonstrate that the alteration of the arterial dynamic parameters influences not only the ipsilateral impedance but also the contralateral arterial system. These conclusions suggest that the carotid or vertebral impedance is not suitable for describing the behaviour of its own arterial system, because the impedance is also influenced by the other arterial system and blood pressure.     

Integral kinetics of multisubstrate enzyme reactions. Criteria of kinetic behavior and characteristic coordinates for solution of direct and reverse problems

General schemes of unbranched multisubstrate enzyme reactions associated with enzyme inactivation during catalysis are analyzed. Equations of integral kinetics at constant substrate concentrations and at depletion in one of the substrate are presented. Experimental dose-response curve characterized by additivity of some enzyme intermediates (absorption spectra, fluorescence, EPR, etc.) are theoretically analyzed. Also rapid equilibrium at certain stages of enzyme reaction is considered. The interrelationship of enzyme intermediates is a criterion of the kinetic behavior of enzyme reaction mechanism. New coordinates are suggested for the analysis of the integral kinetics of self-inactivating enzymes. Results of the analysis are used for interpretation of the data on arachidonic cascade enzymes.     

Aesthetic considerations in endodontics: internal bleaching

During endodontic treatment of any tooth, aesthetics must be considered in the same manner as during any other dental treatment. The most common aesthetic challenge associated with endodontics is the discoloration of natural tooth structure. The discoloration may be a result of pulp pathosis, especially pulpal hemorrhage prior to or during treatment, or it may be due to various endodontic and restorative materials placed in the pulp chamber. There are several simple measures that can be utilized during and following endodontic treatment to eliminate or reduce aesthetic deficiency. The learning objective of this article is to discuss internal bleaching of discolored pulpless teeth that have been endodontically treated. The discussion includes the chemical composition of bleaching agents and principles by which they function during the bleaching procedures.     

Use of formal and informal sources of mental health care among older African-American public-housing residents

BACKGROUND: Elderly residents of public housing have high rates of psychiatric disorders, but most of those in need of care do not use any mental health service. This study examines the use of formal and alternative informal sources of mental health care in a sample of elderly African-American public-housing residents. METHOD: Data from an epidemiological survey of six Baltimore public-housing developments for the elderly (weighted N = 818) were analysed to examine the utilization of mental health services by older African-American residents. Logistic regression analyses were used to determine correlates of using formal and informal sources by those needing mental health care. RESULTS: Thirty-five per cent of subjects needed mental health care. Less than half (47%) of those in need received any mental health care in the previous 6 months. Residents in need were more likely to use formal (38.5%) than informal sources (18.6%) for care. The strongest correlates of using formal providers were substance use disorder (OR = 15.62), Medicare insurance (OR = 10.31) and psychological distress (OR = 10.27). The strongest correlates of using informal sources were perceiving little or no support from religious/spiritual beliefs (OR = 21.65), cognitive disorder (OR = 19.71) and having a confidant (OR = 15.07). CONCLUSIONS: Contrary to elderly African-Americans in general, those in public housing rely more on formal than informal sources for mental health problems. Nevertheless, both sources fail to fill the gap between need and met need. Interventions to increase identification, referral and treatment of elderly public-housing residents in need should target general medical providers and clergy and include assertive outreach by mental health specialists.     

Stream biodiversity: the ghost of land use past

The influence of past land use on the present-day diversity of stream invertebrates and fish was investigated by comparing watersheds with different land-use history. Whole watershed land use in the 1950s was the best predictor of present-day diversity, whereas riparian land use and watershed land use in the 1990s were comparatively poor indicators. Our findings indicate that past land-use activity, particularly agriculture, may result in long-term modifications to and reductions in aquatic diversity, regardless of reforestation of riparian zones. Preservation of habitat fragments may not be sufficient to maintain natural diversity in streams, and maintenance of such biodiversity may require conservation of much or all of the watershed.