2,610 research outputs found
Group 14 Metallocene Catalysts for Carbonyl Hydroboration and Cyanosilylation
A series of six Group 14 metallocene compounds (M = Ge, Sn, Pb) were studied as catalysts for carbonyl hydroboration and cyanosilylation reactions at room temperature. Both bis(pentamethylcyclopentadienyl) and tetramethyldisiloxa[3]metallocenophane compounds were compared. The tin and lead metallocenophanes exhibited the highest reactivity in hydroboration and cyanosilylation reactions. Hammett analysis of aldehyde hydroboration provided a ρ value of 0.73, suggesting a buildup of negative charge during the turnover-limiting step, consistent with the transition state for hydride transfer to the carbonyl center. NMR studies of Lewis acidity indicate that the Ge, Sn, and Pb tetramethyldisiloxa[3]metallocenophane compounds are weak Lewis acids
History as a frame of a dialogue within the logic of postmodernity
This work is devoted to historical consideration of postmodern, or consideration of postmodern as the specifically historical phenomena. Claiming that the postmodern can be considered as a specific historical phenomenon, we state: a) certain uniqueness of this phenomenon, existence of special "logic" of postmodern; b) some limitation, situation nature of this logic, and, possibility of a certain bigger historical context. At the same time we also can't do without mentioning special "situation of postmodern". As an example of special postmodern logic (thesis "a") it is possible to name the thought form described by Gilles Deleuze and Felix Guattari in work "Capitalism and schizophrenia", most accurately formulated in introduction to the second volume which is called "Rhizome" [10]. Also the logic named by Vladimir Bibler in "Dialogique" [8] and Anatoly Akhutin "Archeo-logics" [6][7] will be an example. (The thesis) the society described in Jean Bodrillara (Baudrillard J.,1983) and Siegmund Bauman's works [2][3][4] can be an example of "a postmodern situation". It is obvious that it is not the same because, according to Derrida, "the same isn't the same". "Situation" of a real is also and theoretical one. We should return to this in-identity forming a gap. The postmodern, in both allocated measurements has, therefore, a) its specifics as a unique event; b) it is built-in and implanted in historical process and can be considered as one of the uniform logical chain links
A Brain-Machine Interface for Control of Medically-Induced Coma
Medically-induced coma is a drug-induced state of profound brain inactivation and unconsciousness used to treat refractory intracranial hypertension and to manage treatment-resistant epilepsy. The state of coma is achieved by continually monitoring the patient's brain activity with an electroencephalogram (EEG) and manually titrating the anesthetic infusion rate to maintain a specified level of burst suppression, an EEG marker of profound brain inactivation in which bursts of electrical activity alternate with periods of quiescence or suppression. The medical coma is often required for several days. A more rational approach would be to implement a brain-machine interface (BMI) that monitors the EEG and adjusts the anesthetic infusion rate in real time to maintain the specified target level of burst suppression. We used a stochastic control framework to develop a BMI to control medically-induced coma in a rodent model. The BMI controlled an EEG-guided closed-loop infusion of the anesthetic propofol to maintain precisely specified dynamic target levels of burst suppression. We used as the control signal the burst suppression probability (BSP), the brain's instantaneous probability of being in the suppressed state. We characterized the EEG response to propofol using a two-dimensional linear compartment model and estimated the model parameters specific to each animal prior to initiating control. We derived a recursive Bayesian binary filter algorithm to compute the BSP from the EEG and controllers using a linear-quadratic-regulator and a model-predictive control strategy. Both controllers used the estimated BSP as feedback. The BMI accurately controlled burst suppression in individual rodents across dynamic target trajectories, and enabled prompt transitions between target levels while avoiding both undershoot and overshoot. The median performance error for the BMI was 3.6%, the median bias was -1.4% and the overall posterior probability of reliable control was 1 (95% Bayesian credibility interval of [0.87, 1.0]). A BMI can maintain reliable and accurate real-time control of medically-induced coma in a rodent model suggesting this strategy could be applied in patient care.National Institutes of Health (U.S.) (Director's Transformative Award R01 GM104948)National Institutes of Health (U.S.) (Pioneer Award DP1-OD003646)National Institutes of Health (U.S.) (NIH K08-GM094394)Massachusetts General Hospital. Dept. of Anesthesia and Critical Car
Sensor Arrays Based on Polycyclic Aromatic Hydrocarbons: Chemiresistors versus Quartz-Crystal Microbalance
Speech rhythm and language acquisition: an amplitude modulation phase hierarchy perspective.
Language lies at the heart of our experience as humans and disorders of language acquisition carry severe developmental costs. Rhythmic processing lies at the heart of language acquisition. Here, I review our understanding of the perceptual and neural mechanisms that support language acquisition, from a novel amplitude modulation perspective. Amplitude modulation patterns in infant- and child-directed speech support the perceptual experience of rhythm, and the brain encodes these rhythm patterns in part via neuroelectric oscillations. When brain rhythms align themselves with (entrain to) acoustic rhythms, speech intelligibility improves. Recent advances in the auditory neuroscience of speech processing enable studies of neuronal oscillatory entrainment in children and infants. The "amplitude modulation phase hierarchy" theoretical perspective on language acquisition is applicable across languages, and cross-language investigations adopting this novel perspective would be valuable for the field
ИСТОРИЯ СТАНОВЛЕНИЯ И РАЗВИТИЯ ПРОМЫШЛЕННОЙ РАДИАЦИОННОЙ ГИГИЕНЫ В САНКТ-ПЕТЕРБУРГСКОМ НАУЧНО-ИССЛЕДОВАТЕЛЬСКОМ ИНСТИТУТЕ РАДИАЦИОННОЙ ГИГИЕНЫ ИМЕНИ ПРОФЕССОРА П.В. РАМЗАЕВА
In the articcle are described in detail tge history of organization and main results of tge 40 years scientific and scientific-practical activity of tge first in the system of Public Health Ministry od Russian Federation specialized scienific department - the department of industrial radiation hygiene of the Saint-Petersburg Research Institute of Radiation Hygiene after professor P.V. Ramzaev.В статье подробно изложены истирия организации и основные итоги 40-летней научной и научно-практической деятельности первого в системе Минздрава России специализированного научного подразделения - отдела промышленной радиационной гигиены Санкт-Петербургского научно-исследовательского института радиационной гигиены имени профессора П.В. Рамзаева
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