Measurement of the activity of electrolytes and the application of activity to hydrometallurgical studies

The activity of HC1 in solutions of HCl-NaCl, and the approximate values of the activities of H⁺ and Cl⁻ in solutions of HC1, HC1O₄, HCl-NaCl, HClO₄-NaClO₄ and HC1O₄-NaCl were determined at 25 ° by measuring the electromotive force of a cell consisting of a Pt-Pt black electrode and an Ag-AgCl electrode. The liquid junction potential, estimated by using Henderson’s equation as a first approximation, was subtracted from the measured electromotive force of the cell. Some hydrometallurgical problems which were difficult to understand with the concept of concentration were re-examined, using the activity values thus determined. These problems were the rate of non-oxidative leaching of galena and sphalerite, the acid dissolution rate of cupric oxide, and the rate of oxidation of Fe(II) with molecular dissolved oxygen. Although the dependence of the dissolution rates of galena, sphalerite and cupric oxide upon acid concentration appeared to be rather complicated, the dissolution rates of these minerals were found to be of first order with respect to a_H+. It was also possible to elucidate the role of Cl⁻ ions by using thea _Cl-values. A rate equation obtained experimentally for the autoxidation of Fe(II) in HC1 solutions was found to generally explain the experimental results of previous researchers, which seemed to be inconsistent with each other. On leave-of-absence to the Department of Metallurgy and Material Science, University of Toronto, Ontario, Canada.     

Oxidase activity of the acyl-CoA dehydrogenases

The medium chain acyl-CoA dehydrogenase catalyzes the flavin-dependent oxidation of a variety of acyl-CoA thioesters with the transfer of reducing equivalents to electron-transferring flavoprotein. The binding of normal substrates profoundly suppresses the reactivity of the reduced enzyme toward molecular oxygen, whereas the oxidase reaction becomes significant using thioesters such as indolepropionyl-CoA (IP-CoA) and 4-(dimethylamino)-3-phenylpropionyl-CoA (DP-CoA). Steady-state and stopped-flow studies with IP-CoA led to a kinetic model of the oxidase reaction in which only the free reduced enzyme reacts with oxygen (Johnson, J. K., Kumar, N. R., and Srivastava, D. K. (1994) Biochemistry 33, 4738-4744). We have tested their proposal with IP-CoA and DP-CoA. The dependence of the oxidase reaction on oxygen concentration is biphasic with a major low affinity phase incompatible with a model predicting a simple Km for oxygen of 3 microM. If only free reduced enzyme reacts with oxygen, increasing IP-CoA would show strong substrate inhibition because it binds tightly to the reduced enzyme. Experimentally, IP-CoA shows simple saturation kinetics. The Glu376-Gln mutant of the medium chain dehydrogenase allows the oxygen reactivity of complexes of the reduced enzyme with IP-CoA and the corresponding product indoleacryloyl-CoA (IA-CoA) to be characterized without the subsequent redox equilibration that complicates analysis of the oxidase kinetics of the native enzyme. In sum, these data suggest that when bulky, nonphysiological substrates are employed, multiple reduced enzyme species react with molecular oxygen. The relatively high oxidase activity of the short chain acyl-CoA dehydrogenase from the obligate anaerobe Megasphaera elsdenii was studied by rapid reaction kinetics of wild-type and the Glu367-Gln mutant using butyryl-, crotonyl-, and 2-aza-butyryl-CoA thioesters. In marked contrast to those of the mammalian dehydrogenase, complexes of the reduced bacterial enzyme with these ligands react with molecular oxygen at rates similar to those of the free protein. Evolutionary and mechanistic aspects of the suppression of oxygen reactivity in the acyl-CoA dehydrogenases are discussed.     

Uterine activity in the multiparous patient

There were 149 parous patients with normal cervical dilatation patterns studied. The purpose was to quantitate and characterize uterine activity in a group of multiparous patients with normal labor using our present on-line method and to evaluate our method against pervious work done on uterine activity. A mean total of 5,299 uterine activity units (UAU) was required to progress from 4 cm. through delivery. In the patients receiving oxytocin 5,907 UAU were required and 4,498 UAU for those not receiving oxytocin. Of the total uterine work from 4 cm. to delivery, 49.4% was required to progress from 4 to 6 cm. 38.7% to progress from 6 to 10 cm., and 11.9% for the second stage. This study establishes in a quantitative way, using on-line methods, the patterns of uterine activity expended by the parous patient in normal labor and can be compared to previous off-line and manual evaluations. These data can be compared with the on-line observations previously made in a primiparous group, and will be fundamental to automated evaluations including definitions of abnormal labor.     

Cortical activity and the explanatory gap

An exploration is given of neural network features now being uncovered in cortical processing which begins to go a little way to help bridge the "Explanatory Gap" between phenomenal consciousness and correlated brain activity. A survey of properties suggested as being possessed by phenomenal consciousness leads to a set of criteria to be required of the correlated neural activity. Various neural styles of processing are reviewed and those fitting the criteria are selected for further analysis. One particular processing style, in which semiautonomous and long-lasting cortical activity "bubbles" are created by input, is selected as being the most appropriate. Further experimental criteria are used to help narrow the possible neural styles involved. This leads to a class of neural models underpinning phenomenal consciousness and to a related set of testable predictions.     

Background electrical activity of the claustrum

The dynamics of the spontaneous electrical activity of the rostral, dorsal, ventral and caudal claustrum was studied chronically in 12 dogs with biologically significant distinctions in the physiological state of the animals: extinction of orientative reflexes, replacement of the feeding conditions for the acid and defensive situation and elaboration of internal inhibition. The obtained data correlated with the hypothesis on an intermediate position of the claustrum between the cortex and subcortex and permit expressing a suggestion on availability in this nucleus of special representations for different physiological activities, in particular--orientative, feeding, rejecting and defensive. The ventral claustrum seems to take a maximal part in the orientative behaviour, the rostral and caudal claustrum--in the feeding behaviour, and the dorsal and ventral parts of the nucleus--in the rejecting and the defensive behaviour.     

On the antioxidant activity of melatonin

Melatonin has been widely reported to be an effective antioxidant. Studies of its ability to inhibit the autoxidation of lipids in homogeneous solution and in model heterogeneous systems show that melatonin is not a peroxyl radical trapping antioxidant. In contrast, melatonin can inhibit metal ion-catalyzed oxidation processes.     

The cognitive activity of the clinician.

Functions performed by the psychodiagnostician can be trichotomized: formal diagnosis, prognosis, and personality assessment. "Quite apart from the validity of current techniques for performing these various cognitive functions, their pragmatic value is open to question." If there is anything that justifies the existence of the clinical psychologist "it is that we think scientifically about human behavior and that we come from a long tradition, going way back to the very origins of experimental psychology in the study of human error, of being critical of ourselves as cognizing organisms and of applying quantitative methods to the outcomes of our cognitive activity." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reentrainment of motor activity and spontaneous neuronal activity in the suprachiasmatic nucleus of Djungarian hamsters

Neurons in the suprachiasmatic nucleus (SCN) of the hypothalamus exhibit a daily rhythm in spontaneous electrical activity. Essentially two methods have been employed to record this circadian rhythm: (1) an in vitro brain slice technique and (2) in vivo multiunit recordings. Reentrainment of a circadian output to a shifted light:dark cycle commonly takes several cycles (depending on the amount of shift) until completed. Such a resetting kinetic has also been shown to be valid for SCN electrical activity if recorded in vivo. In an in vitro slice preparation, however, pharmacologically induced resetting is much faster and lacks transients; that is, a shift is completed within one cycle. This study was designed to probe for the presence of transients in the neuronal activity of the SCN in a brain slice preparation. The authors exposed Djungarian hamsters to an 8-h advanced or delayed light:dark cycle and monitored wheel-running activity during reentrainment. Additional groups of identically treated hamsters were used to record the pattern of spontaneous neuronal activity within the SCN using the brain slice preparation. Neuronal activity exhibited the usual rhythm with high firing rates during the projected day and low firing rates during the projected night. However, following 1 day of exposure to the 8-h advanced light:dark cycle, this rhythm disappeared in 6 of 7 slices. Rhythmicity was still absent following 3 days of exposure to the advanced light:dark cycle (n = 4). By contrast, 3 of 7 slices prepared from hamsters exposed to a delayed light:dark cycle for 3 days exhibited a daily rhythm in electrical activity. Although pharmacological agents reset the in vitro SCN neuronal activity almost instantaneously and in in vivo studies a stable phase relationship to a shifted light:dark cycle occurs gradually over several cycles, the authors did not detect either of these patterns. Such differences in resetting kinetics (e.g., rapid resetting, gradual reentrainment, temporary lack of measurable rhythmicity) may be due to (a) application of a resetting stimulus in vivo versus in vitro, (b) duration of the resetting stimulus, (c) the nature of the resetting stimulus, or (d) the recording technique employed.     

Fibrinolytic activity of carcinoma of the colorectum

During an islandwide outbreak of human influenza in June and July 1971, throat swabs were taken from dogs and cats in 3 urban communities of Taiwan. Eight influenza isolates were obtained from dogs in July 1971: two were identified as influenza A closely related to the human Hong Kong/68 virus, and one was a strain of influenza type B closely resembling human influenza B virus. The latter is the first such reported isolation from dogs under natural conditions.     

The fusion promotion activity of the NDV HN protein does not correlate with neuraminidase activity

Three activities, attachment, neuraminidase, and fusion promotion, have been associated with the hemagglutinin-neuraminidase (HN) protein encoded by paramyxoviruses such as Newcastle disease virus. The fusion promotion activity of the HN protein can be separated from its attachment activity by mutation (Sergel et al., 1993, Virology 193, 717-726). To determine if neuraminidase activity of the HN protein has any role in fusion promotion, two sets of mutants were characterized. First, a change of amino acid 193 from a serine to a proline and a change of amino acid 175 from isoleucine to a methionine diminished neuraminidase activity as previously reported. However, these mutant proteins retained fusion promotion activity. In addition, mutation of amino acid 200 from a histidine to a proline resulted in nearly twice the neuraminidase activity of wild-type as previously reported. This mutant also had wild-type levels of fusion promotion activity. Second, substitution of three leucine residues at amino acids 94, 96, and 97 with three alanines resulted in a mutant protein with full neuraminidase as well as full attachment activity but no fusion promotion activity. Thus, two sets of HN protein mutants demonstrate that the fusion promotion activity does not correlate with the level of neuraminidase activity.     

发挥高校环境保护社团的能动性

环境方面“公众参与,环保NGO(非政府组织)与政府、企业及媒体的交流合作关系”的发展的程度,直接体现着一个国家环境意识的发育程度,同时也体现着一个国家民主进程和政治文明发育的程度。公众参与公共环保事业已经成为了不可阻挡的社会发展趋向,在发展的进程当中,大学生环保社团已渐渐成为群众性环保公益活动的生力军。     

Food and the circadian activity of the hypothalamic-pituitary-adrenal axis

Temporal organization is an important feature of biological systems and its main function is to facilitate adaptation of the organism to the environment. The daily variation of biological variables arises from an internal time-keeping system. The major action of the environment is to synchronize the internal clock to a period of exactly 24 h. The light-dark cycle, food ingestion, barometric pressure, acoustic stimuli, scents and social cues have been mentioned as synchronizers or "zeitgebers". The circadian rhythmicity of plasma corticosteroids has been well characterized in man and in rats and evidence has been accumulated showing daily rhythmicity at every level of the hypothalamic-pituitary-adrenal (HPA) axis. Studies of restricted feeding in rats are of considerable importance because they reveal feeding as a major synchronizer of rhythms in HPA axis activity. The daily variation of the HPA axis stress response appears to be closely related to food intake as well as to basal activity. In humans, the association of feeding and HPA axis activity has been studied under physiological and pathological conditions such as anorexia nervosa, bulimia, malnutrition, obesity, diabetes mellitus and Cushing's syndrome. Complex neuroanatomical pathways and neurochemical circuitry are involved in feeding-associated HPA axis modulation. In the present review we focus on the interaction among HPA axis rhythmicity, food ingestion, and different nutritional and endocrine states.