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At least 685 records · Page 38Linked to original sources
PubMed2003

Have brain dynamics evolved? Should we look for unique dynamics in the sapient species?

Ongoing "spontaneous" electrical field potentials of assemblies of neurons in the brains of diverse animal groups differ widely in character and amplitude without obvious explanation. There may be correlates with other measures of brain complexity, such as histological differentiation, but so far there are no known differences between the EEGs of humans and other mammals or between mammals and reptiles, amphibians or fish, apart from amplitude. The proposition is defended that further search for descriptors or statistical, probably nonlinear features of the time series will reveal consistent differences, meaning that we have so far missed major features of the natural history of EEGs, just as we have thus far relatively neglected the identification of features of the physiology of the brain relevant to its evolution of complexity through major grades of phyla, classes, and orders.

Animals↗
PubMed2001

Dynamic study of metal-ion incorporation into porphyrins based on the dynamic characterization of metal ions and on sitting-atop complex formation.

We succeeded in the detection of the sitting-atop (SAT) copper(II) complex of TPP (5,10,15,20-tetraphenylporphyrin) in acetonitrile (AN) as a solvent with a very low Brønsted basicity, where two pyrrolenine nitrogens in the Cu(II)-SAT complex coordinate to the metal ion and two protons still remain on the pyrrole nitrogens. The structure parameters around the copper(II) ion in the Cu(II)-SAT complex, as determined by a fluorescent EXAFS method, suggest an axially elongated and equatorially distorted six-coordinate geometry. We measured the rates of the formation reaction of the SAT complexes for a series of transition metal(II) ions in AN using the stopped-flow technique. We propose the mechanism where there is a rapid deformation equilibrium of the porphyrin ring prior to the rate-determining step of the bond rupture of a coordinated solvent molecule on the metal(II) ion. Furthermore, we measured the rates of the deprotonation reaction of the Cu(II)-SAT complex by some Brønsted bases and indicated that the rate-determining step is the attack of the base on the proton of the pyrrole nitrogen in the SAT complex. Finally, a unified mechanism relevant to the porphyrin metalation mechanism has been proposed.

Kinetics↗
PubMed2000

[Dynamics and structure of neonatal mortality in Bulgaria - Part II. Dynamics and structure of neonatal deaths in the university maternity hospital "Maichin Dom"].

AIM OF THE STUDY: To analyse the state and the structure of the neonatal lethality in the largest perinatal center of Bulgaria 'Maichin dom' during the last five years, and to compare them with the national data on neonatal mortality. MATERIAL AND METHODS: A retrospective study on the evolution of neonatal lethality in the recent 5 years and on its structure during the last 2 years was fulfilled using the data of the Department of Neonatology of the University hospital 'Maichin dom' concerning the infants' lethality. The results were compared to the national data on infants' mortality (in 28 days of life) and presented graphically. RESULTS: The level of neonatal lethality in the University hospital increased invariably until 1997, when it reached the highest peak (12.7@1000), after that it decreased to 10.3@1000 in 1998. This tendency is predominantly due to the early neonatal mortality, which raised from 6.7@1000 in 1994 to 8.5@1000 in 1998, and remained at the same level in the last two years. The leading causes of neonatal lethality in the perinatal center are the congenital malformations--40.6@1000, which is higher than in the country. The congenital anomalies of central nervous system account to 75@1000 of all lethal malformations. The perinatal asphyxia is the second cause of death--34.7@1000, which is considerably less than in the country--41.3@1000. The neonatal respiratory distress syndrome is the third main cause of death in the neonatal period--9.4@1000 in the hospital; 10.9@1000--in the country. The neonatal lethality is mainly due to the premature infants--82.5@1000 in 1997 and 90.6@1000 in 1998. The relative portion of the term infants considerably decreased in these two years--from 17.5@1000 to 9.4@1000. These numbers are 100 times less than the data of the whole country. CONCLUSIONS: The evolution of the neonatal lethality in the University hospital 'Maichin dom' has a similar tendency of the neonatal mortality in Bulgaria, the increase being mostly due to the early neonatal mortality. The leading causes of death are the congenital malformations and predominantly the central nervous system defects. The perinatal asphyxia is the second most frequent lethal cause with a relative portion which is less than that in the country. The lethality of the premature infants in the hospital is 6 times less than that in the country and the neonatal lethality of term infants is practically discriminated.

Bulgaria↗
PubMed2000

[Dynamics of soil P pool in a long-term fertilizing experiment of wheat-maize rotation. I. Crop yield effect of fertilizer P and dynamics of soil total P and inorganic P].

The effects of long-term applying fertilizer P and manure on the pools of soil total P and inorganic P and the crop yield in rotation of winter wheat-summer maize-->spring maize were studied. The results showed that the pool of soil total P and inorganic P were increased by applying fertilizer P and manure, and the phosphorus mostly accumulated in soil was inorganic P. The critical amounts of fertilizer P (P2O5) for balancing soil P were 94.7 kg.hm-2 to winter wheat-summer maize and 51.5 kg.hm-2 to spring maize. Based on regression equations, the application rates of fertilizer P (P2O5) for economic optimum and highest yields were 135.8 and 149.8 kg.hm-2 to winter wheat-summer maize, and 88.6 and 95.9 kg.hm-2 to spring maize, respectively.

China↗