scholarly journals The kinetics of the reaction between hydrogen and nitrous oxide. Part II

1934 ◽  
Vol 146 (859) ◽  
pp. 737-759 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Wave Length ◽  
Kinetic Method ◽  
Strong Support ◽  
Chain Process ◽  
Absorption Region ◽  
Chain Character ◽  
A Chain ◽  
The Individual ◽  
Low Pressures

An analysis of the mechanism of the thermal hydrogen-nitrous oxide reaction in silica vessels by the kinetic method has shown that it is a chain process. The experiments were confined to a comparatively narrow pressure range and the evidence for chain propagation, although quite definite, required confirmation. The present paper is therefore concerned with the kinetics under a much wider variety of conditions. First, the experiments have been extended to pressures below 30 mm; second, photochemical methods have been employed to she more light on the individual steps of the reaction and to demonstrate unequivocally its chain character; third, in view of the close similarity of the hydrogen-nitrous oxide and hydrogen-oxygen reactions, a detailed study has been made of the effect of small amounts of oxygen on the former reaction. The results of these experiments all lend additional strong support to the chain hypothesis. Small alterations to the apparatus were made. A glass spring gauge was employed for measuring low pressures. One end of the furnace was provided with quartz lens in order to focus the light from the mercury lamp on the reaction bulb; the cathode of the lamp was water cooled. Arrangements were also made for inserting a hollow silica cell between the lamp and the lens so that filters could be used for controlling the intensity and wave-length of the light reaching the bulb. Direct photo dissociation of the nitrous oxide molecule was not attempted since ( a ) absorption of photochemically active light at low pressures in small bulbs is not complete, ( b ) the intensity of the lines of the mercury arc in the absorption region of nitrous oxide is weak. Recourse was therefore made to mercury sensitization in spite of a little additional complication.

scholarly journals The kinetics of the reaction between hydrogen and nitrous oxide.─I

1933 ◽  
Vol 142 (847) ◽  
pp. 524-545 ◽  
Keyword(s):  
Nitrous Oxide ◽  
Kinetic Method ◽  
Gaseous Mixture ◽  
Theoretical Treatment ◽  
Chain Process ◽  
Combustion Chemistry ◽  
Chain Reactions ◽  
Simple Molecules ◽  
A Chain ◽  
Kinetics Of

Until about five years ago, the theoretical treatment of the mechanism of the oxidation of simple molecules had been comparatively neglected. Prior to this, however, considerable progress had been made in the study of the kinetics of thermal and photochemical gas reactions. That knowledge has now been successfully applied and extended to solve some of the major problems in combustion chemistry, and thereby has given rise to the development of the theory of thermal chain reactions. Hitherto, the investigation of these reactions has been confined almost entirely to oxidations by molecular oxygen. It is known, however, that many gases ignite in:nitrous oxide at about the same temperature as they do in oxygen, and it might be anticipated that here, too, a chain process is in operation. The object of studying the interaction of hydrogen and nitrous oxide was to determine whether it is a chain reaction, and if so, to make a detailed analysis of its mechanism by the kinetic method. One of the first criteria in looking for the possibility of the propagation of chains in a gaseous mixture is that the reaction must be exothermic. This condition is amply fulfilled in the present instance, for 75 k. cal. are liberated per mole of water formed. Indeed, the reaction is even more exothermic than the formation of one mole of water from hydrogen and oxygen, when only 50 k. cal. are evolved. This greater exothermicity is due to the fact that 45 k. cal. required to dissociate 1 mole of N 2 O N 2 and O, whereas the production of 1 mole of O atoms from O 2 required about 60 k. cal.

PREPARING PUBLIC SERVANTS IN EUROPEAN COUNTRIES: ARCHETYPAL APPROACH

2018 ◽  
Vol 1 (14) ◽  
pp. 255-263
Author(s):  
Oleh Ivanovich Rohulskyi
Keyword(s):  
Public Administration ◽  
Public Service ◽  
Professional Training ◽  
European Countries ◽  
Anglo Saxon ◽  
Public Servants ◽  
German Model ◽  
Managerial Positions ◽  
A Chain ◽  
The Individual

The article describes the main components of the institutional framework of an archetypical approach to public administration. It is determined that the system of preparation of public servants is based on a chain of universal foundations of archetype, in particular, it is influenced by the principle of formation of personnel in the public service, formed on the basis of public opinion. Based on two basic principles relating to admission to public service, three basic models of training civil servants in the European country are defined: German. French and Anglo-Saxon. We analyze each of the models and define the archetypes that influenced their formation and development. The advantages of each model are determined, in particular, the benefits are: the German model of training managers is the balancing between the theoretical knowledge and practical skills that a public servant receives during training, but as a disadvantage one can distinguish the orientation of preparation for legal orientation, which limits the ability to hold managerial positions for many employees The French model of professional training of public servants should include a well-balanced understanding of tasks, namely: decentralization and territorial organization of public services, communication, support of territorial communities, in-depth knowledge and understanding of the need for cooperation with institutions of the European Commonwealth, high-quality human resource management and orientation towards environmentally friendly innovations, such a model of training of public servants is holistic, costly and effective; The Anglo-Saxon model of training of public servants is its orientation towards the implementation of the concept of public administration and the individual approach to employee training, taking into account all the specifics of its activities, providing for the formation of personnel capable of solving specific problems. It is concluded that today in most European countries dominated by mixed models that include elements of different models.

scholarly journals Social and biological issues in infant survivorship among Danish cohorts born between 1982 and 1990

1996 ◽  
pp. 82-100
Author(s):  
Hans O. Hansen
Keyword(s):  
Birth Weight ◽  
Strong Support ◽  
General Question ◽  
Birth Cohorts ◽  
Principal Characteristics ◽  
Individual Level ◽  
Infant Deaths ◽  
Intermediate Variable ◽  
The Individual ◽  
Official Records

The purpose of this project is to identify possible differentials in the infant survivorship of the Danish cohorts bom between 1982 and 1990. The principal characteristics to be considered are gender and birth weight. Our data consist of official records of live births and infant deaths linked at the individual level. We report some rather detailed measurements of the survivorship impact of sex and birth weight in the framework of logistic regression and loglinear modeling. This paper gives strong support to sex and birth weight as major determinants of infant survivorship. Falling infant mortality is closely associated with increasing expected birth weight over the birth cohorts considered. The present paper should be seen as an appetizer for addressing the more general question of birth weight as an intermediate variable for survivorship impacts of biosocial factors related to the parents and to intrauterine gestation.

scholarly journals An MEG Study of Picture Naming

1998 ◽  
Vol 10 (5) ◽  
pp. 553-567 ◽  
Author(s):  
Willem J. M. Levelt ◽  
Peter Praamstra ◽  
Antje S. Meyer ◽  
Päivi Helenius ◽  
Riitta Salmelin
Keyword(s):  
Picture Naming ◽  
Time Windows ◽  
Naming Latency ◽  
Cortical Activation ◽  
Response Patterns ◽  
Phonological Encoding ◽  
A Chain ◽  
Wernicke’S Area ◽  
The Individual ◽  
The Right

The purpose of this study was to relate a psycholinguistic processing model of picture naming to the dynamics of cortical activation during picture naming. The activation was recorded from eight Dutch subjects with a whole-head neuromagnetometer. The processing model, based on extensive naming latency studies, is a stage model. In preparing a picture's name, the speaker performs a chain of specific operations. They are, in this order, computing the visual percept, activating an appropriate lexical concept, selecting the target word from the mental lexicon, phonological encoding, phonetic encoding, and initiation of articulation. The time windows for each of these operations are reasonably well known and could be related to the peak activity of dipole sources in the individual magnetic response patterns. The analyses showed a clear progression over these time windows from early occipital activation, via parietal and temporal to frontal activation. The major specific findings were that (1) a region in the left posterior temporal lobe, agreeing with the location of Wernicke's area, showed prominent activation starting about 200 msec after picture onset and peaking at about 350 msec, (i.e., within the stage of phonological encoding), and (2) a consistent activation was found in the right parietal cortex, peaking at about 230 msec after picture onset, thus preceding and partly overlapping with the left temporal response. An interpretation in terms of the management of visual attention is proposed.

scholarly journals Research on the Construction of a Student Model of an Adaptive Learning System Based on Cognitive Diagnosis Theory

2020 ◽  
Vol 12 (4) ◽  
pp. 20-31
Author(s):  
Yang Zhao ◽  
Yaqin Fan ◽  
Mingrui Yin ◽  
Cheng Fang
Keyword(s):  
Online Education ◽  
Adaptive Learning ◽  
Strong Support ◽  
Individual Characteristics ◽  
Learning System ◽  
Cognitive Diagnosis ◽  
Selection Strategy ◽  
Student Model ◽  
Adaptive Learning System ◽  
The Individual

With the promotion of online education, the adaptive learning system has attracted attention due to its good curriculum recommendation function. The student model is an important interface between the adaptive learning system and the user, reflecting the individual characteristics, knowledge status, and cognitive ability of the student. The accuracy of the information in the student model directly affects the quality of the system recommendation service. The traditional student model only judges students based on the basic information and simple test scores. This paper introduces the self-adaptive item bank and adaptive item selection strategy based on the cognitive diagnosis theory that dynamically detects the students' knowledge and analyzes the state according to the answering habits and knowledge mastering status of different students. This paper analyzes and contrasts a variety of traditional cognitive diagnosis theories and proposes a mixed cognitive diagnosis question bank and a selection strategy model to provide strong support for the construction of student models.

scholarly journals The oxidation of phosphine at low pressures

1929 ◽  
Vol 125 (797) ◽  
pp. 294-308 ◽  
Keyword(s):  
Energy Content ◽  
Stable Condition ◽  
High Energy ◽  
Gaseous Reaction ◽  
Molecular Collision ◽  
Active Chemical ◽  
Recent Developments ◽  
Collision Processes ◽  
A Chain ◽  
Low Pressures

In the recent developments of chemical kinetics there have been many indications of a type of reaction known as a chain reaction, in which each act of transformation gives rise to a product which, on account of its active chemical nature or high energy content, causes further molecules to be transformed without special activation. Under certain conditions the chain may "branch," and the number of centers from which reaction proceeds increases indefinitely unless the chains are broken. In a gaseous reaction there may be a definite concentration at which the rate of initiation of chains just begins to exceed the rate at which they are broken. At this point a stable condition ceases to be possible. However slow the reaction may be on one side of the limiting concentration, on the other side its rate increases continuously with time till explosion results. The acceleration may require an imperceptible fraction of a second only, since the time scale on which molecular collision processes occur is a very minute one. The remarkable phenomenon to which this gives rise, namely an abrupt transition from negligibly slow reaction to explosion, is exemplified in the union of oxygen with phosphorus vapour and with sulphur vapour at low pressure, and in the combination of hydrogen and oxygen under certain conditions. The present paper deals with a similar phenomenon in the oxidation of phosphine.

scholarly journals Reduction of disulfide bonds during antigen processing: evidence from a thiol-dependent insulin determinant.

1991 ◽  
Vol 174 (5) ◽  
pp. 1121-1130 ◽  
Author(s):  
P E Jensen
Keyword(s):  
T Cells ◽  
Disulfide Bonds ◽  
Antigen Processing ◽  
Strong Support ◽  
Class Ii ◽  
Protein Antigens ◽  
Competition Binding ◽  
Peptide Binding Site ◽  
A Chain ◽  
Necessary And Sufficient

Previous studies have demonstrated that insulin, like other protein antigens, requires processing in metabolically active antigen-presenting cells (APC) before it can be recognized by class II-restricted T lymphocytes. Unlike many other proteins, insulin peptides of minimal size retain the requirement for antigen processing. We demonstrate that this requirement can be bypassed by incubation of insulin with reducing agents in the presence of aldehyde-fixed APC. Fixed APC treated in this way were able to stimulate I-Ab- and I-Ad-restricted T cell hybridomas. Data are presented that demonstrate that cloned and polyclonal T cells recognize a determinant within the NH2-terminal 14 residues of the beef insulin A chain with no requirement for B chain residues. The common feature among peptides capable of stimulating these cells in the presence of live APC is the chemical form of the cysteine thiol groups. Those forms that produce free thiols upon reduction are active, whereas those with irreversibly protected sulfhydryls are not. Functional experiments with fixed APC and competition binding experiments with purified I-Ad indicate that only A chain peptides with free thiols are able to stably associate with the peptide-binding site on class II in a form that is recognized by specific T cells. Our findings indicate that reduction of disulfide bonds is both necessary and sufficient for presentation of insulin to a major population of class II-restricted T cells. The results provide strong support for the hypothesis that protein disulfides can be reduced during physiologic antigen processing.

Un exemple d'isomérisation radicalaire en chaînes: la photoinduction de l'isomérisation cis–trans de la pentène-3 one-2

1977 ◽  
Vol 55 (22) ◽  
pp. 3915-3926 ◽  
Author(s):  
Armel Rioual ◽  
André Deflandre ◽  
Jacques Lemaire
Keyword(s):  
Energy Transfer ◽  
Quantum Yields ◽  
Unsaturated Ketone ◽  
Chain Process ◽  
Triplet Energy ◽  
Low Concentrations ◽  
Energy Transfers ◽  
Donor And Acceptor ◽  
A Chain ◽  
Triplet Energy Transfer

Mechanisms of the photosensitized cis–trans photoisomerization of 3-penten-2-one which do not imply only classical triplet–triplet energy transfer are proposed; they are based upon measurements of the variations of initial quantum yields of isomerization with the initial donor and acceptor concentrations, the wavelength of excitation, and the nature of the donor and of the solvent. Carbonyl donors (acetophenone, benzophenone, acetone) induce a radical isomerization by a chain process in reducing solvents; the example of acetophenone is specially interesting. In solvents in which the donor is not photoreduced (as benzene or CCl4) classical triplet–triplet energy transfers occur. Sensitization with aromatic donors (benzene, mesitylene) proceeds through triplet–triplet energy transfer at low concentrations of the acceptor. At higher concentrations of acceptor, an exciplex is formed between the ketone and the aromatic in its singlet excited state; this exciplex is deactivated by dissociation and by causing the isomerization of the α,β-unsaturated ketone.

The ultrastructure of Methanothrix concilii, a mesophilic aceticlastic methanogen

1986 ◽  
Vol 32 (9) ◽  
pp. 703-710 ◽  
Author(s):  
Terry J. Beveridge ◽  
Girish B. Patel ◽  
Bob J. Harris ◽  
G. Dennis Sprott
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Circular Plates ◽  
A Cell ◽  
Granular Matrix ◽  
A Chain ◽  
The Individual

Methanothrix concilii strain GP6 consists of a chain of rod-shaped cells, ca. 2.5 μm in length and 0.8 μm in width, which are encased in a tubular proteinaceous sheath. The sheath is composed of annular hoops, ca. 8.0 nm wide and 9.0 nm thick, which are stacked together to form the tube. The ends of the sheath, and therefore the cell filament, are blocked by single, multilayered, 13.5 nm thick, circular plates, designated as "spacer plugs," which contain a series of concentric rings; these also separate the individual cells within each filament. Each cell is therefore bounded by a tubular section of sheath and two spacer plugs. Completely encapsulating each cell, and lying between the sheath and cell, is an amorphous granular matrix. Overlying the plasma membrane and surrounding each protoplast is a thin veil of material which resembles a cell wall, but which is unable to maintain the rod shape when cells are extruded from the sheath.

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