Superlattice formation of the type AB in an adsorbed layer

1939 ◽  
Vol 35 (1) ◽  
pp. 70-83 ◽  
Author(s):  
T. S. Chang
Keyword(s):  
Free Energy ◽  
Interaction Potential ◽  
Adsorbed Layer ◽  
Rate Of Change ◽  
Nearest Neighbours ◽  
Adsorbed Atoms ◽  
The One ◽  
Type Ab ◽  
A Site ◽  
Detailed Balancing

The possibility, pointed out in a previous paper, of superlattice formation in an adsorbed layer when the adsorbed atoms tend to repulse each other is developed in detail. Both Bragg and Williams's approximation and Bethe's approximation are used, but restricted to superlattices of the type AB. In a range of θ, the fraction of surface covered, a superlattice is found to be possible. Bragg and Williams's approximation shows further that the state with the lowest free energy is the one with a superlattice when the latter is possible. Rough kinetic expressions are also given. The equations derived from the principle necessary to preserve equilibrium are found to reduce to those of detailed balancing, and they also agree with the formula obtained statistically. As expected, all the corresponding results obtained from the two methods become the same when the number of nearest neighbours of a site approaches infinity, provided that the product of this number and the interaction potential of two adsorbed atoms occupying two neighbouring sites remains finite.The only significant result is the large value of the slope of isotherms (the rate of change of the pressure with respect to the fraction of adsorption) when there is a nearly complete superlattice.

Historical Perspectives

2019 ◽  
pp. 70-114
Author(s):  
Anne Fuchs
Keyword(s):  
Coping Mechanisms ◽  
Rate Of Change ◽  
Urban Modernity ◽  
Historical Perspectives ◽  
Modern Subject ◽  
The One ◽  
A Site ◽  
And Coping ◽  
The City ◽  
Modern Technologies

This chapter discusses the emergence of modern speed politics. Cinema, the most innovative medium of the early twentieth century, created a captivating visual imaginary for the energizing yet frightening experience of modern speed politics. Two of the most iconic films of the Weimar period—Walter Ruttmann's Berlin: Symphony of a Great City and Fritz Lang's Metropolis—explored the city as a site of a contradictory modernity. On the one hand, these films celebrate modern technologies, the pleasure of speed, and the visual stimuli unleashed by a world that is constantly in motion; on the other hand, however, they bring into view the uncontrollable effects of a runaway world in which machines begin to transform human behavior. Released in 1927, both films created a striking visual aesthetic of urban modernity that exploited the technical opportunities of film to new effect. Meanwhile, from the 1870s, psychologists, philosophers, writers, and artists addressed the urgent question as to whether and how the modern subject would cope with the rate of change and the experience of social and technological acceleration. Attention, distraction, lateness, and slowness emerged as central tropes in a far-ranging discourse that foregrounded the precariousness of modern subjectivity, while also exploring modern reactions and coping mechanisms.

scholarly journals I. General theory

1938 ◽  
Vol 168 (932) ◽  
pp. 56-67 ◽  
Keyword(s):  
General Theory ◽  
Interaction Energy ◽  
Lattice Site ◽  
Three Dimensional ◽  
Present Theory ◽  
Nearest Neighbours ◽  
Long Range Interactions ◽  
Adsorbed Atoms ◽  
Crystal Block ◽  
The One

For alloys in which the numbers ot two kinds of atoms A and B are equal the statistical theory of superlattices was first developed by Bethe (1935), assuming interaction only between atoms which are nearest neighbours to one another. The theory was then extended by Peierls (1936) to the case of unequal concentrations of components still retaining the assumption of interaction between nearest neighbours, and by Chang (1937) to include the interaction between next nearest pairs of atoms in the case of equal concentartions of components. It is desirable to have a more general theory which includes long-range interactions of a general type and is applicable both to equal and unequal concentrations of components, but the interaction energy must fall off sufficiently rapidly with increasing distance to make the contribution of very distant atoms negligible so that the shape and the dimensions of the crystal block do not influence the state of the superlattice. For example, if the interaction energy is of the form V ( r ) = Ar - n , then n should be greater than 3 in order that the integral ∫ ∞ 0 V ( r ) r 2 dr may be finite. A general theory of this kind has already been developed for a similar problem in adsorption (Wang 1938). The problem of adsorption is simpler than that of superlattices for two reasons, First, the former is a twodimensional problem while the latter is a three-dimensional one. Second, there is only one kind of atom in the adsorption case and therefore every lattice site is equivalent to every other, whereas in the superlattice case there are two kinds of atoms and hence two different kinds of lattice sites, usually called α sites and β sites respectively. This second difference between the problem of adsorption and that of superlattices is the one which makes the direct application of the adsorption theory impossible, because the device of replacing the contribution of distant adsorbed atoms by that of a continuous uniform distribution no longer works for the superlattice, since it would lead to a sort of amalgamation of the two kinds of lattice sites. This difficulty is overcome in the present theory as is explained in 2.

Haemorheological Effects on Thrombocyte Adhesion and Aggregation Found Under Controlled Flow Conditions

1979 ◽  
Author(s):  
P.D. Richardson
Keyword(s):  
Rate Of Change ◽  
Continuous Observation ◽  
Flow Conditions ◽  
Wide Range ◽  
Stream Migration ◽  
Local Shear ◽  
Videotape Recording ◽  
Controlled Flow ◽  
A Site

Thrombocyte adhesion and aggregation in a vessel or on a chamber wall can be measured most readily if the flow is controlled and steady, and continuous observation is used. Videotape recording is very helpful for subsequent quantification of the dynamics. The adhesion of each thrombocyte can occur for a finite time interval:this interval has been observed to have a wide range. Platelets which escape often leave open a site which attracts other platelets preferentially. The rate of change of adhesion density (platelets/mm2) is affected by the local shear rate and the shear history upstream. Aggregation is affected similarly, and also proceeds with some platelet turnover. The role of erythrocytes in facilitating cross-stream migration of thrombocytes (which can enhance the growth rate of large thrombi) appears due in part to convective flow fields induced by the motion of erythrocytes in a shear flow, which can be demonstrated theoretically and experimentally. Observations of the phenomenlogy of adhesion and aggregation under controlled flow conditions and comparison with fLu id-dynamically based theory allows representation in terras of a small number of parameters with prospects of prediction of behaviour over a wide range of haemodynamic conditions; biochemical changes lead to changes in values of the parameters, so that activating agents and inhibiting agents modify values in different directions.

scholarly journals The One‐Dimensional Log‐Gas Free Energy Has a Unique Minimizer

2021 ◽  
Vol 74 (3) ◽  
pp. 615-675
Author(s):  
Matthias Erbar ◽  
Martin Huesmann ◽  
Thomas Leblé
Keyword(s):  
Free Energy ◽  
Unique Minimizer ◽  
One Dimensional ◽  
The One

Revisiting the valuable locales in our cities? Visualizing social interaction potential around metro station areas in Wuhan, China

2021 ◽  
pp. 0308518X2110622
Author(s):  
Jiangyue Wu ◽  
Jiangping Zhou ◽  
Hanxi Ma
Keyword(s):  
Social Interaction ◽  
Interaction Potential ◽  
Urban Spaces ◽  
Metro Station ◽  
The One

A complete tour of metro users consists of their journeys inside the carriage and various activities outside the carriage, in particular, those in or around metro station areas (MSAs). To fathom out the spatiality and magnitude of those activities, which involve substantial interactions among people or with urban spaces, we assume that (a) metro users who spent 30 min or more together in or around the same MSA would physically interact with at least another person there; (b) the more an MSA sees metro riders co-presenting there the higher social interaction potential (SIP) there is; (c) SIP of an MSA is positively correlated with the number of distinct riders co-presenting in that MSA. By exploiting two-day metro smartcard data of Wuhan, China, we use the number of distinct riders co-presenting in that MSA to measure and visualize the MSA-level SIP in that city. Our visuals show the SIP varies across MSA and time of the day. Some MSAs have higher SIP in the daytime whereas other MSAs have higher SIP at the nighttime. Few MSAs continuously have high SIP. These results inform us where and when SIP would be the highest and the lowest across MSAs, which can facilitate metro operators’ monitoring and management of MSAs on the one hand and help businessmen and officials decide where and when to provide services and/or sell products across MSAs.

scholarly journals The T788G Mutation in thecyp51CGene Confers Voriconazole Resistance in Aspergillus flavus Causing Aspergillosis

2012 ◽  
Vol 56 (5) ◽  
pp. 2598-2603 ◽  
Author(s):  
Wei Liu ◽  
Yi Sun ◽  
Wei Chen ◽  
Weixia Liu ◽  
Zhe Wan ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Resistant Strain ◽  
Antifungal Susceptibility ◽  
Gene Replacement ◽  
Content Type ◽  
Replacement Method ◽  
First Choice ◽  
The One ◽  
A Site ◽  
First Time

ABSTRACTWith voriconazole (VRC) being approved as the first choice in treating invasive aspergillosis (IA) and its increasing use in treatment, a VRC-resistant strain ofAspergillus flavus, the second leading cause of IA afterAspergillus fumigatus, has emerged. The VRC-resistant strain ofA. flavuswas isolated for the first time from the surgical lung specimen of an IA patient with no response to VRC therapy. In order to ascertain the mechanism of VRC resistance, the azole target enzyme genes in this strain ofA. flavuswere cloned and sequenced, and 4 mutations generating amino acid residue substitutions were found in thecyp51Cgene. To further determine the role of this mutated gene for VRC resistance inA. flavus, anAgrobacterium tumefaciens-mediated gene replacement approach was applied. Consequently, the mutatedcyp51Cgene from thisA. flavusstrain was proven to confer the VRC resistance. Finally, to discern the one out of the four mutations in thecyp51Cgene that is responsible for contributing to VRC resistance, a site-directed gene mutagenesis procedure combined with a gene replacement method was performed. As a result, the T788G missense mutation in thecyp51Cgene was identified as responsible for VRC resistance inA. flavus. These findings indicated that the detection of this mutation inA. flavuscould serve as an indicator for physicians to avoid the use of VRC during IA treatment. Further comprehensive surveillance for antifungal susceptibility, as well as intensive study on the mechanism of azole resistance inA. flavuscausing IA, would be required to fully understand this mechanism.

scholarly journals Re-Assembling Anti-Oppressive Practice (1): The Personal, the Political, the Professional

2021 ◽  
Vol 11 (10) ◽  
pp. 645
Author(s):  
Janet Batsleer
Keyword(s):  
Theory And Practice ◽  
Academic Disciplines ◽  
Memory Work ◽  
Work Spaces ◽  
Informal Educators ◽  
Paolo Freire ◽  
The One ◽  
The Uk ◽  
A Site ◽  
Uk Higher Education

This essay offers a broken narrative concerning the early history of anti-oppressive practice as an approach in the U.K. to youth and community work and the struggles over this in the context of UK higher education between the 1960′s and the early 2000’s. Educating informal educators as youth and community workers in the UK has been a site of contestation. Aspects of a genealogy of that struggle are presented in ways which link publicly available histories with personal memories and narratives, through the use of a personal archive developed through collective memory work. These are chosen to illuminate the links between theory and practice: on the one hand, the conceptual field which has framed the education of youth and community workers, whose sources lie in the academic disciplines of education and sociology, and, on the other hand, the social movements which have formed the practice of informal educators. Six have been chosen: (1) The long 1968: challenging approaches to authority; (2) the group as a source of learning; (3) The personal and political: experiential learning from discontent; (4) Paolo Freire and Critical Praxis; (5) A critical break in social education and the reality of youth work spaces as defensive spaces; (6) New managerialism: ethics vs. paper trails. The approach taken, of linking memory work with present struggles, is argued to be a generative form for current critical and enlivening practice.

scholarly journals Branding Stratford: Social Representation and the Re-making of Place

2013 ◽  
Author(s):  
Antonio Desiderio
Keyword(s):  
Critical Discourse Analysis ◽  
Urban Space ◽  
Urban Regeneration ◽  
Social Representation ◽  
London 2012 ◽  
Dialectical Process ◽  
The Media ◽  
The One ◽  
A Site ◽  
The Way

As part of the societal world, architecture and urban space do not have any ‘objective’ quality. They are representations. Their meaning is produced through the negotiation and interaction of individuals, groups and classes. Yet, such ‘subjective’ meanings do have a ‘material’ relevance, as they reflect a dialectical process between the functions, forms, ownership and practices of space. They reveal construal and construction: the way in which architectural spaces are represented on the one hand, and the way in which they are physically constructed and used on the other. Nowhere does this become more evident in our current society than in the arguments around urban renewal and regeneration. The Westfield Stratford City is a typical example. Part of the vast process of the urban regeneration of East London prompted by London 2012 Olympic Games, Westfield is a massive complex of luxury shops, restaurants, bars and five star hotels. It is seen by investors and local and national political authorities as capable of transforming Stratford into a site for shopping, tourism and leisure. It does this in numerous ways, one of which involves reconfiguring the image of the region through the press and media - through visual imagery and linguistic manipulations that promote a neoliberal agenda of gentrification that simultaneously devalue the existent societal structures and communities in the area. This paper offers a Critical Discourse Analysis of the manipulation of Stratford’s image by government, business and the media and suggests that the purely financially motivated misrepresentation it reveals, is typical of the urban regeneration ethos at work across the developed world today.

A multifactorial analysis of contact-induced change in speech reporting in written White South African English (WSAfE)

2019 ◽  
Vol 24 (1) ◽  
pp. 179-209 ◽  
Author(s):  
HAIDEE KRUGER ◽  
BERTUS VAN ROOY
Keyword(s):  
South African ◽  
Rate Of Change ◽  
Conditional Inference ◽  
Similar Frequency ◽  
Frequency Distributions ◽  
Slowing Down ◽  
Conditional Inference Tree ◽  
Contact Language ◽  
Trajectories Of Change ◽  
A Site

This article presents a corpus analysis of changes over a period of two centuries in speech-reporting constructions in written White South African English (WSAfE), a native variety of English that has been in contact with Afrikaans throughout its history. The analysis is based on register-differentiated comparable diachronic corpora of WSAfE, its parent variety, British English (BrE), and the contact language, Afrikaans. Three related reported-speech constructions are analysed, focusing on changes in the relative frequencies of variants of each construction. These constructions show ongoing change, with similar trajectories of change for WSAfE and BrE in some cases, but divergent trajectories in others. In the latter case, WSAfE and Afrikaans converge on similar frequency distributions, which follow from an accelerated rate of change or a slowing down of the rate of change for particular features in WSAfE in comparison to BrE. Descriptive findings are supported by conditional inference tree modelling. The effect of frequency on reinforcing similar patterns of change in WSAfE and Afrikaans, as well as simplification through the levelling of register differences in WSAfE and Afrikaans are proposed as explanations. The study highlights the importance of converging norms in a multilingual publication industry as a site of contact.

Thermodynamic studies in solution. Part IV. Solvent effect on the solvolysis of tert-butyl chloride. A new treatment of the experimental data

1979 ◽  
Vol 57 (5) ◽  
pp. 500-502 ◽  
Author(s):  
Joaquim Jose Moura Ramos ◽  
Jacques Reisse ◽  
M. H. Abraham
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Free Energies ◽  
Butyl Chloride ◽  
Activation Free Energy ◽  
Tert Butyl ◽  
New Treatment ◽  
The One ◽  
Activated Complex ◽  
Tert Butyl Chloride

A new treatment of the solvent effect on the solvolysis of tert-butyl chloride is proposed. This treatment is based on activation free energy measurements and on transfer free energy measurements of the reactant (R) on the one hand and of a model (M) of the activated complex (AC) on the other hand. Solute–solvent interaction free energies for the reactant, the activated complex and the model compound are estimated. This estimation involves the calculation of the free energy of cavity formation of these various solutes (R, AC, and M) in all the solvents. These cavity terms, which are a function of the cohesive properties of the solvent and of the surface of the cavity do not reflect the electronic structure of the solute whereas the interaction free energy term does. The method we propose can be described as a new 'experimental' approach for the study of the charge separation in an activated complex.

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