1,031 research outputs found
Understanding Molecular Crystal Structures at Extreme Conditions
No full textUnderstanding the structure of matter in the solid state could be considered as being
one of ‘the big questions’ in chemistry. Whereas the structural behaviour of
molecules in the gas phase is relatively well-understood, this is not the case for the
condensed phase due to the complexity of short and long-range intermolecular
interactions. The purpose of the work in this thesis is to examine the structural
response of solid molecular materials to stimuli of extreme pressure and temperature.
L-alanine crystallises as a zwitterion in the space group P212121. Neutron
powder diffraction and X-ray single crystal diffraction data show that the a and caxes
are very similar in length. The a-axis is more compressible than the c-axis, and
at ca. 2 GPa the cell becomes metrically tetragonal, however the underlying
symmetry is still orthorhombic. The structure remains in a compressed form of the
ambient phase up to 9.87 GPa. Previous Raman and energy dispersive powder
diffraction studies have interpreted changes in spectra at ca. 2 and 9 GPa as phase
transitions. The diffraction data and DFT calculations described here suggest that
these are in fact due to changes in conformation of the ammonium group.
L-alanine shows remarkable resistance to the effects of pressure but
something must happen to the structure if pressure continues to be increased.
Neutron powder diffraction has been used to obtain high-pressure data for L-alanine
up to 15.46 GPa. These are the highest-pressure diffraction data reported for any
amino acid. Above ca. 15 GPa, L-alanine undergoes a reversible transition to an
amorphous phase through volume collapse of the crystal, driven by the need to
minimise the PV term in the Gibbs free energy equation, as opposed to relieving
destabilising contacts. It is currently the only amino acid known to undergo a
transition of this type.
The co-crystal of methylpyridine and pentachlorophenol (MP-PCP) forms in
the space group P-1. When the phenolic proton is deuterated (MP-PCP-d) it exhibits
isotopic polymorphism, crystallising in the space group Cc. Structures of the two
other combinations of isotope and space group, i.e MP-PCP in Cc and MP-PCP-d in
P-1 have not yet been determined. We demonstrate that these polymorphs can be
obtained using high-pressure and low-temperature conditions predicted by
thermodynamics. The use of in-situ crystallisation at pressure has driven MP-PCP to
pack with Cc symmetry, minimising the PV term in the Gibbs free energy equation.
Low-temperature crystallisation causes MP-PCP-d to form in P-1 due to this phase
being favoured by vibrational enthalpic and entropic contributions.
Aniline is a liquid under ambient conditions but freezes at 267 K in the
monoclinic space group P21/c. It can also be frozen by pressure (ca. 0.8 GPa) in the
orthorhombic space group Pna21. Neutron powder diffraction shows that on
decompression the orthorhombic form transforms to the monoclinic phase at 0.3
GPa, owing to the monoclinic packing being less dense. PIXEL calculations provide
an insight into the intermolecular energies of the orthorhombic crystal up to 7.301
GPa. They show that dispersive forces are more dominant than the hydrogen bonds,
one of which becomes destabilising at higher pressure. Thermodynamic calculations
estimating the relative stabilities of the two polymorphs prove inconclusive owing to
improper treatment of dispersion interactions by Density Functional Theory
calculations. The structural behaviour of cyclohexane in the crystalline (P21/c) and plastic
phases (Fm3m) has been studied using neutron total scattering data and Reverse
Monte Carlo (RMC) modelling. Atomistic models show that the molecules exhibit
correlated motion as they prepare to undergo transformation on heating. Inclusion of
I(t) data in the RMC refinements is shown to be important as when it is not
accounted for, the RMC method is incapable of distinguishing the form of the
disorder in the plastic phase. Molecular motion in this phase is shown to be
correlated through the avoidance of short intermolecular D···D contacts.
The ordered and disordered solid phases of oxalyl chloride (space groups
P21/c and Pbca respectively) have been studied by neutron total scattering and
modelled using a Reverse Monte Carlo approach. Atomistic models show that on
heating, the atoms vibrate out of the plane of the molecule until 245 K where they
show approximately isotropic vibration owing to reduced steric restriction. This may
provide the molecules with the freedom they require to rotate and undergo the solidsolid
transition. The onset of disorder has also been partially predicted by molecular
dynamics simulations. RMC modelling does not provide satisfactory atomic
configurations of the disordered solid phase due to an unrealistic distribution of
intermolecular chlorine-chlorine contacts. This study presents an example of a
flexible, 3-atom-type system that may be too complex for analysis by the RMC
method
External interventions and the duration of civil wars
No full textThe authors combine an empirical model of external intervention, with a theoretical model of civil war duration. Their empirical model of intervention allows them to analyze civil war duration, using"expected"rather than"actual"external intervention as an explanatory variable in the duration model. Unlike previous studies, they find that external intervention is positively associated with the duration of civil war. They distinguish partial third-party interventions that extend the length of war, from multilateral"peace"operations, which have a mandate to restore peace without taking sides - and which typically take place at war's end, or at least when both sides have agreed to a cease-fire. In a future paper, the authors will examine whether partial third-party interventions - whatever their effect on a war's duration - increase the risk of war's recurrence. If that proves true, then even if interventions reduce the length of civil war, they may do so at the cost of further destabilizing the political system, and sowing the seeds of future rebellion.Children and Youth,Peace&Peacekeeping,Post Conflict Reconstruction,Post Conflict Reconstruction,International Affairs,Post Conflict Reconstruction,Social Conflict and Violence,Peace&Peacekeeping,Post Conflict Reconstruction,International Affairs
Students read from their original, award wining works at the 2006 Michigan State University Student Writers Awards Night
No full textAt the 2006 Michigan State University Student Writers Awards Night, students read from their original, award wining works. Readers include: double winner Nicholas Miller, Lauren Linsalata, Patrick Walchak, and Chris Goetz. The event is convened and hosted by MSU Professor of English and co-director of Film Studies Jeff Wray. A special appearance to present awards is made by noted author Paul Beatty. Part of the MSU Libraries' Michigan Writers Series. Held in the MSU Main Library
Paul, Antioch, and Jerusalem: a study in relationships and authority in earliest Christianity
No full textPaul's life and work, including his relationship with the Jerusalem church, were dynamic, rather than having been predetermined in his conversion. The Antiochene church was crucial to Paul's development, to a degree not previously appreciated. Little is known of the years following Paul's conversion, other than it was unsettled, and included travels and sojourns in Arabia, Damascus, Jerusalem, and Tarsus. The encounter with the Jerusalem church did not result in a stable relationship or social integration. It was at Antioch that Paul was first fully incorporated into a Christian community, from which he derived his dyadic identity, and later his apostolic commission. His relationship with the Jerusalem church consisted in corporate participation in the коιυυυία between the churches of Jerusalem and Antioch. In this context, Paul joined Barnabas in defending the Antiochene gospel of uncircumcision, and not his own theology or apostleship, at the Jerusalem conference. The Antioch incident resulted in Paul's separation from the Antiochene church, and exclusion from its коιυυυία with the Jerusalem church. His independent ministry followed, during which he developed his conception of apostleship independent of human authority, in which his self-identity is bound up with the gospel, in response to his isolation, and loss of dyadic identity and apostolic commission. Paul sought to end his isolation through reconciliation with the Antiochene church, and, through its коιυυυία, with the Jerusalem church. This was the object of the collection, but the crisis in Corinth delayed completion, requiring Paul to convey his offering separately. His implicit claim to коιυυυία accordingly became overt, and the collection became the basis, rather than a correlative obligation, of the relationship. This jeopardized the acceptability of Paul's overtures, and, while his reception is uncertain, the journey occasioned his arrest, and ended his missionary career
Paul Philippot, o restauro arquitetônico no Brasil e o tempo. Conversaciones con... Paul Philippot. Num. 1 Año 1 (2015) enero-diciembre
No full textAugé, Marc (2011) Où est passé l’avenir? Éditions du Seuil, ParisBrandi, Cesare (1950) Il fondamento teorico del restauro. Bollettino dell’Istituto Centrale del Restauro, numero 1, pp. 5-12.Brandi, Cesare (2004) Teoria da restauração. Ateliê Editorial, Cotia.Carbonara, Giovanni (1995) I trent’anni di una buona carta del restauro. Restauro. Volume 24, numero 131-132, pp. 57-60.Carbonara, Giovanni (2006) Brandi e a restauração arquitetônica hoje. Desígnio. Número 6, pp. 35-47.Carta de Veneza (1964)Damé, Luiza; Chico de Gois (2010) Lula volta a despachar no Palácio do Planalto após reforma que durou um ano e meio. O Globo. 24 de agosto de 2010. Disponível em: [http://oglobo.globo.com/politica/lula-volta-despachar-no-palacio-do-planalto-apos-reforma-que-durou-umano-meio-2960773] [acesso em 12 de novembro de 2014]ICCROM (2009). ICCROM Newsletter. Number 35, October 2009, p. 9.Goulart, Ghilherme (2009) Reforma do Palácio do Planalto prevê a remoção de painéis de Athos Bulcão.Correio Brasiliense [On Line] 6 de maio de 2009 [http://www.correiobraziliense.com.br/app/noticia/cidades/2009/05/06/interna_cidadesdf,105685/index.shtml] [acesso em 12 de novembro de 2014]Kühl, Beatriz M. (2009) Preservação do patrimônio arquitetônico da industrialização. Ateliê Editorial, São Paulo.Kühl, Beatriz M. (2010) “Notas sobre a Carta de Veneza” em Anais do Museu Paulista. Volume 18, número 2. Julho-dezembro 2010, pp. 287-320. Também disponível em: [http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-47142010000200008&lng=ptnrm=iso]Le Goff, Jacques (2003) História e memória. Editora Unicamp, Campinas.Mendes, Fabiana (2010) Reforma estaria com falhas. Jornal de Brasília [On Line] 13 de julho de 2010. Disponível em [http://www.jornaldebrasilia.com.br/noticias/cidades/288680/reforma-com-falhas-no-palaciodo-planalto/] [acesso em 12 de novembro de 2014]Philippot, Albert and Paul Philippot (1959) Le problème de l’intégration des lacunes dans la restauration des peintures. Bulletin de l’Institut Royal du Patrimoine Artistique. Volume 2, pp. 5-18.Philippot, Paul (1966) La notion de patine et le nettoyage des peintures. Bulletin de l’Institut Royal du Patrimoine Artistique. Volume 9, pp. 138-143.Philippot, Paul (1996) “Historic preservation: philosophy, criteria, guidelines” in Stanley Price, Nicholas, Talley,M. Kirby and Melucco Vaccaro, Alessandra (eds.) Historical and philosophical issues in the conservation of cultural heritage. Getty Conservation Institute, Los Angeles, pp. 268-274; 358-364.Philippot, Paul, Laura Mora, e Paolo Mora (1986) Il restauro degli intonaci colorati in architettura: L’esempio di Roma e la questione di metodo. Bollettino d’Arte, supplemento al numero 35-36, pp. 139-141.Quatremère de Quincy, Antoine (1815) Considérations morales sur la destination des ouvrages de l’art. Le Clere, Paris.This paper aims at reflecting on some relevant issues for present conservation by means of an analysis of some aspects of Paul Philippot’s thought, especially his considerations regarding the role of time in conservation. Therefore, the text focuses on the following aspects: subjects related to the interpretation of theoretical references in the field of restoration in Brazil; the importance of discussing those references to analyse the role of time in conservation; issues resulting from the fact of not considering the passing of time in recent interventions made in that country; finally, as a conclusion, a reflection on the traces of time in the work of art, i.e. patina.Este artigo tem por intuito refletir sobre alguns temas relevantes para a preservação hoje, por meio da análise de aspectos do pensamento de Paul Philippot, em especial no que diz respeito ao papel do tempo na restauração. Para tanto, o texto enfatiza os seguintes aspectos: questões relacionadas à interpretação dos referenciais teóricos do campo disciplinar do restauro no Brasil; a importância de discutir esses referenciais para analisar o papel do tempo na restauração; alguns problemas resultantes do fato de não considerar a passagem do tempo em intervenções recentes no país; por fim, como conclusão, uma reflexão sobre as marcas do tempo na obra, a pátina
Paul Philippot, la restauración arquitectónica en Brasil y el tiempo. Conversaciones con... Paul Philippot. Num. 1 Año 1 (2015) enero-diciembre
No full textAugé, Marc (2011) Où est passé l’avenir? Éditions du Seuil, ParisBrandi, Cesare (1950) Il fondamento teorico del restauro. Bollettino dell’Istituto Centrale del Restauro, numero 1, pp. 5-12.Brandi, Cesare (1988) Teoría de la restauración. Alianza Editorial, S.A., Madrid.Carbonara, Giovanni (1995) I trent’anni di una buona carta del restauro. Restauro. Volume 24, numero 131-132, pp. 57-60.Carbonara, Giovanni (2006) Brandi e a restauração arquitetônica hoje. Desígnio. Número 6, pp. 35-47.Carta de Venecia (1964)Damé, Luiza; Chico de Gois (2010) Lula volta a despachar no Palácio do Planalto após reforma que durou um ano e meio. O Globo. 24 de agosto de 2010. Disponível em: [http://oglobo.globo.com/politica/lula-volta-despachar-no-palacio-do-planalto-apos-reforma-que-durou-umano-meio-2960773] [acesso em 12 de novembro de 2014]ICCROM (2009) ICCROM Newsletter. Number 35, October 2009, p. 9.Goulart, Ghilherme (2009) Reforma do Palácio do Planalto prevê a remoção de painéis de Athos Bulcão.Correio Brasiliense [On Line] 6 de maio de 2009.;
[http://www.correiobraziliense.com.br/app/noticia/cidades/2009/05/06/interna_cidadesdf,105685/index.shtml] [acesso em 12 de novembro de 2014]Kühl, Beatriz M. (2009) Preservação do patrimônio arquitetônico da industrialização. Ateliê Editorial, São Paulo.Kühl, Beatriz M. (2010) “Notas sobre a Carta de Veneza” em Anais do Museu Paulista. Volume 18, número 2.Julho-dezembro 2010, pp. 287-320. Também disponível em: [http://www.scielo.br/scielo.php?script=sci_arttextpid=S010147142010000200008ng=ptnrm=iso]Le Goff, Jacques (2003) História e memória. Editora Unicamp, Campinas.Mendes, Fabiana (2010) Reforma estaria com falhas. Jornal de Brasília [On Line] 13 de julho de 2010. Disponível em [http://www.jornaldebrasilia.com.br/noticias/cidades/288680/reforma-com-falhas-no-palaciodo-planalto/] [acesso em 12 de novembro de 2014]Philippot, Albert and Paul Philippot (1959) Le problème de l’intégration des lacunes dans la restauration des peintures. Bulletin de l’Institut Royal du Patrimoine Artistique. Volume 2, pp. 5-18.Philippot, Paul (1966) La notion de patine et le nettoyage des peintures. Bulletin de l’Institut Royal du Patrimoine Artistique. Volume 9, pp. 138-143.Philippot, Paul (1996) “Historic preservation: philosophy, criteria, guidelines” in Stanley Price, Nicholas, Talley, M. Kirby and Melucco Vaccaro, Alessandra (eds.) Historical and philosophical issues in the conservation of cultural heritage. Getty Conservation Institute, Los Angeles, pp. 268-274; 358-364.Philippot, Paul, Laura Mora, e Paolo Mora, (1986) Il restauro degli intonaci colorati in architettura: L’esempio di Roma e la questione di metodo. Bollettino d’Arte, supplemento del numero 35-36, pp. 139-141.Quatremère de Quincy, Antoine (1815) Considérations morales sur la destination des ouvrages de l’art. Le Clere, Paris.Este artículo tiene por objetivo reflexionar sobre algunos temas relevantes para la conservación actual, por medio del análisis de aspectos del pensamiento de Paul Philippot, en especial lo que dice respecto al papel del tiempo en la restauración. Por tanto, el texto enfatiza los siguientes aspectos: cuestiones relacionadas con la interpretación de referencias teóricas del campo de la restauración en Brasil; la importancia de discutir esas referencias para analizar el papel del tiempo en la restauración; algunos problemas resultantes del hecho de no considerar el paso del tiempo en intervenciones recientes en ese país; por último, como conclusión, una reflexión sobre las marcas del tiempo en la obra, la pátina
Competition Policy in Network Industries: An Introduction
No full textThe author discusses issues of the application of antitrust law and regulatory rules to network industries. In assessing the application of antitrust in network industries, we analyze a number of relevant features of network industries and the way in which antitrust law and regulatory rules can affect them. These relevant features include (among others) network effects, market structure, market share and profits inequality, choice of technical standards, relationship between the number of active firms and social benefits, existence of market power, leveraging of market power in complementary markets, and innovation races. The author finds that there are often significant differences on the effects of application of antitrust law in network and non-network industries.
Open access self-archiving: An author study
No full textThis, our second author international, cross-disciplinary study on open access had 1296 respondents. Its focus was on self-archiving. Almost half (49%) of the respondent population have self-archived at least one article during the last three years. Use of institutional repositories for this purpose has doubled and usage has increased by almost 60% for subject-based repositories. Self-archiving activity is greatest amongst those who publish the largest number of papers. There is still a substantial proportion of authors unaware of the possibility of providing open access to their work by self-archiving. Of the authors who have not yet self-archived any articles, 71% remain unaware of the option. With 49% of the author population having self-archived in some way, this means that 36% of the total author population (71% of the remaining 51%), has not yet been appraised of this way of providing open access. Authors have frequently expressed reluctance to self-archive because of the perceived time required and possible technical difficulties in carrying out this activity, yet findings here show that only 20% of authors found some degree of difficulty with the first act of depositing an article in a repository, and that this dropped to 9% for subsequent deposits. Another author worry is about infringing agreed copyright agreements with publishers, yet only 10% of authors currently know of the SHERPA/RoMEO list of publisher permissions policies with respect to self-archiving, where clear guidance as to what a publisher permits is provided. Where it is not known if permission is required, however, authors are not seeking it and are self-archiving without it. Communicating their results to peers remains the primary reason for scholars publishing their work; in other words,
researchers publish to have an impact on their field. The vast majority of authors (81%) would willingly comply with a mandate from their employer or research funder to deposit copies of their articles in an institutional or subject-based repository. A further 13% would comply reluctantly; 5% would not comply with such a mandate
Iowa\u27s Notable Dead …
No full textObituaries for notable Iowans including author Paul Anton Olson, Federal official Nicholas F. Reed, and author Mary Eleanor Fahnestock
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