57 research outputs found
1D and 2D metal–organic frameworks functionalized with free pyridyl groups
No full textWe show that a molecule constructed from an organic solid-state synthesis, namely, rctt-1,3-bis(2-pyridyl)-2,4-bis(4-pyridyl)cyclobutane (ht-2,4 ‘-tpcb) upon reaction with Cu(II) and Zn(II) ions gives one- (1D) and two-dimensional (2D) metal-organic frameworks (MOFs) of composition [Cu(hfac)(2)(2,4 ‘-tpcb-ht)](infinity) (where: hfac=hexafluoroacetylacetonate) (1) and [Zn(2,4 ‘-tpcb-ht)(2)(H2O)(2)](infinity)(2+), (2). Each MOF possesses uncoordinated, or free, 2-pyridyl groups that decorate the walls of each extended structure. (c) 2006 Elsevier B.V. All rights reserved
Visualization of Hyperconjugation and Subsequent Structural Distortions through 3D Printing of Crystal Structures
No full textParamagnetic Ionic Liquids for Measurements of Density Using Magnetic Levitation
No full textParamagnetic ionic liquids (PILs) provide new capabilities to measurements of density using magnetic levitation (MagLev). In a typical measurement, a diamagnetic object of unknown density is placed in a container containing a PIL. The container is placed between two magnets (typically NdFeB, oriented with like poles facing). The density of the diamagnetic object can be determined by measuring its position in the magnetic field along the vertical axis (levitation height, h), either as an absolute value, or relative to internal standards of known density. For density measurements by MagLev, PILs have three advantages over solutions of paramagnetic salts in aqueous or organic solutions: (i) negligible vapor pressures; (ii) low melting points; (iii) high thermal stabilities. In addition, the densities, magnetic susceptibilities, glass transition temperatures, thermal decomposition temperatures, viscosities, and hydrophobicities of PILs can be tuned over broad ranges by choosing the cation–anion pair. The low melting points and high thermal stabilities of PILs provide large liquidus windows for density measurements. This paper demonstrates applications and advantages of PILs in density-based analyses using MagLev.Chemistry and Chemical BiologyAccepted Manuscrip
Paramagnetic Ionic Liquids for Measurements of Density Using Magnetic Levitation
No full textParamagnetic
ionic liquids (PILs) provide new capabilities to measurements
of density using magnetic levitation (MagLev). In a typical measurement,
a diamagnetic object of unknown density is placed in a container containing
a PIL. The container is placed between two magnets (typically NdFeB,
oriented with like poles facing). The density of the diamagnetic object
can be determined by measuring its position in the magnetic field
along the vertical axis (levitation height, h), either
as an absolute value or relative to internal standards of known density.
For density measurements by MagLev, PILs have three advantages over
solutions of paramagnetic salts in aqueous or organic solutions: (i)
negligible vapor pressures; (ii) low melting points; (iii) high thermal
stabilities. In addition, the densities, magnetic susceptibilities,
glass transition temperatures, thermal decomposition temperatures,
viscosities, and hydrophobicities of PILs can be tuned over broad
ranges by choosing the cation–anion pair. The low melting points
and high thermal stabilities of PILs provide large liquidus windows
for density measurements. This paper demonstrates applications and
advantages of PILs in density-based analyses using MagLev
How Can International Staff Exchange be Implemented as Part of the Execution of an Internationalisation Strategy in UK Higher Education? The Case of a Strategic Entrepreneur
No full textThis work constructs a bridge across the "knowing-doing gap" of international staff exchange: the gap between strategy formulation and its execution within the constraints of a post-1992 university business school in the UK. It goes beyond the common, well-intentioned and yet vague statements involving the "encouragement" of international staff exchange to propose a model of execution through strategic entrepreneurship.
The promotion of international staff mobility is a founding principle of the "Bologna Process", designed to create a converged system of higher education across Europe. Many UK "new" (ie post-1992) universities are engaged in the development of internationalisation strategies which include staff exchange. Meanwhile, the failure to execute strategy is increasingly acknowledged as a major problem in organisational performance.
Using a first-, second and third-person Insider Action Research (AR) approach, the author initiated, planned, organised and implemented an international staff exchange between universities in the UK and France. Data generated were subjected to a double process of analysis in order to construct the new model. A policy of "subjectivity with transparency" and transcontextual credibility throughout enables the reader to judge transferability. Duality is the nature of this "bridge" and the simplistic transplant of the expatriation policies of commercial organisations is avoided. Concepts from the theoretical literature in three domains - strategic management and entrepreneurship in higher education, internationalisation of higher education and strategy execution through strategic entrepreneurship - are combined with the research analysis to propose that "strategic entrepreneurs" can execute the riskier elements of an internationalisation strategy, such as staff exchange. Members of the creative class, strategic entrepreneurs are attracted and motivated by the foundation of a diverse environment and entrepreneurial culture promoted by a university's values-driven, holistic approach to internationalisation. Their autonomous strategic behaviour must be facilitated by an execution-focussed organisational architecture. In a university, the overall approach to staff exchange should combine central and local (school-based) functions and resource both to develop strategic initiatives and to exploit tactical opportunities.
This work broadens AR from education into strategic management, specifically linking the areas of strategic execution and strategic entrepreneurship
Predicting adherence to antiretroviral therapy and retention to HIV care : effects of baseline biopsychosocial status and neuropsychological functioning
No full textThese drugs have demonstrated efficacy in improving immune function and reducing HIV-related morbidity and mortality, and while a cure is not available, patients on treatment may live longer, healthier lives. However, early optimism has been tempered by the growing recognition that meticulous adherence is a prerequisite for optimal clinical response and prevention of drug resistance
Seasonal, diurnal and nocturnal behaviors of lower carbonyl compounds in the urban environment of Beirut, Lebanon
No full textLower carbonyl concentrations were measured for the first time in two different sampling sites (American University of Beirut (AUB) and Abdel-Aziz (AA)) in Beirut, Lebanon. Formaldehyde (C1) and acetaldehyde (C2) were the most abundant carbonyls with respective maximum concentrations of 12.2 and 5.2 ppbv at AUB and 8.6 and 5.1 ppbv at AA. Diurnal variations of carbonyls exhibited similar behaviors, suggesting related formation and decomposition routes. Morning levels of carbonyls were either equal or higher than the ones in the afternoon at the coastal site (AUB) due to atmospheric dilution. However, morning levels were mostly lower than noon levels at a three-busy street intersection (AA) due to the enhancement of photochemical activities. Vehicle emissions constituted the dominant source of carbonyls measured as confirmed by the good correlation between C1, C2 and propanal (C3) and the C1-CO and C2-CO ratios in the mornings. Seasonal variation showed the predominance of summertime photolysis and photo-oxidation reactions of aldehydes. Based on the measured formaldehyde levels, ozone and nitrous acid concentrations, morning and afternoon OH radical fluxes are computed and consequently their contribution to photochemical smog processes are assessed. © 2006 Elsevier Ltd. All rights reserved.ATKINSON R, 2003, SUMMARY EVALUATED KI, P1; Atkinson R, 2000, ATMOS ENVIRON, V34, P2063, DOI 10.1016-S1352-2310(99)00460-4; Atkinson R, 1997, J PHYS CHEM REF DATA, V26, P521; Baez AP, 2001, ATMOS ENVIRON, V35, P1813, DOI 10.1016-S1352-2310(00)00475-1; Bakeas EB, 2003, CHEMOSPHERE, V52, P805, DOI 10.1016-S0045-6535(03)00257-1; Cecinato A, 2002, J ENVIRON MONITOR, V4, P223, DOI 10.1039-b110616n; Christensen CS, 2000, ATMOS ENVIRON, V34, P287, DOI 10.1016-S1352-2310(99)00297-6; Correa SM, 2003, ATMOS ENVIRON, V37, P23, DOI 10.1016-S1352-2310(02)00805-1; Finlayson-Pitts B.J., 2000, CHEM UPPER LOWER ATM; Granby K, 1997, ATMOS ENVIRON, V31, P1403, DOI 10.1016-S1352-2310(96)00347-0; GROSJEAN D, 2002, RES REPORT HLTH EFFE, V107, P57; Grosjean E, 1996, ENVIRON SCI TECHNOL, V30, P2687, DOI 10.1021-es950758w; Ho KF, 2002, ATMOS ENVIRON, V36, P1259, DOI 10.1016-S1352-2310(01)00570-2; Kalabokas P, 1997, ATMOS ENVIRON, V31, P67, DOI 10.1016-S1352-2310(97)00075-7; Leong ST, 2002, ATMOS ENVIRON, V36, P3495, DOI 10.1016-S1352-2310(02)00288-1; Macdonald AM, 2001, J GEOPHYS RES-ATMOS, V106, P32361, DOI 10.1029-2001JD000513; Mohamed MF, 2002, CHEMOSPHERE, V47, P863, DOI 10.1016-S0045-6535(02)00107-8; Montero L, 2001, ENVIRON SCI TECHNOL, V35, P3071, DOI 10.1021-es001875g; Muller K, 1997, CHEMOSPHERE, V35, P2093, DOI 10.1016-S0045-6535(97)00267-1; Nguyen HTH, 2001, ATMOS ENVIRON, V35, P3075, DOI 10.1016-S1352-2310(01)00136-4; Possanzini M, 2003, ATMOS ENVIRON, V37, P1309, DOI 10.1016-S1352-2310(02)01010-5; Possanzini M, 1996, ATMOS ENVIRON, V30, P3757, DOI 10.1016-1352-2310(96)00110-0; Possanzini M, 2002, ATMOS ENVIRON, V36, P3195, DOI 10.1016-S1352-2310(02)00192-9; Seinfeld J.H., 1998, ATMOPSHERIC CHEM PHY; SIN D, 2001, ATMOS ENVIRON, V32, P5961; Slemr J, 1996, ATMOS ENVIRON, V30, P3667, DOI 10.1016-1352-2310(96)00025-8; Solberg S, 2001, ATMOS ENVIRON, V35, P195, DOI 10.1016-S1352-2310(00)00256-9; Viskari EL, 2000, ATMOS ENVIRON, V34, P917, DOI 10.1016-S1352-2310(99)00307-6; Wagner V, 2001, J GEOPHYS RES-ATMOS, V106, P28529, DOI 10.1029-2000JD900825; WINER AM, 1994, RES CHEM INTERMEDIAT, V20, P423, DOI 10.1163-156856794X00405; ZHOU X, 1997, MAR CHEM, V59, P201; ZHOU XL, 1990, ENVIRON SCI TECHNOL, V24, P1864, DOI 10.1021-es00082a013; Zou SC, 2003, CHEMOSPHERE, V51, P1015, DOI 10.1016-S0045-6535(03)00004-341463
Crystal engineering rescues a solution organic synthesis in a cocrystallization that confirms the configuration of a molecular ladder
No full text
Treatment of an achiral molecular ladder of C
2
h
symmetry composed of five edge-sharing cyclobutane rings, or a [5]-ladderane, with acid results in
cis
- to
trans
-isomerization of end pyridyl groups. Solution NMR spectroscopy and quantum chemical calculations support the isomerization to generate two diastereomers. The NMR data, however, could not lead to unambiguous configurational assignments of the two isomers. Single-crystal X-ray diffraction was employed to determine each configuration. One isomer readily crystallized as a pure form and X-ray diffraction revealed the molecule as being achiral based on C
i
symmetry. The second isomer resisted crystallization under a variety of conditions. Consequently, a strategy based on a cocrystallization was developed to generate single crystals of the second isomer. Cocrystallization of the isomer with a carboxylic acid readily afforded single crystals that confirmed a chiral ladderane based on C
2
symmetry. The chiral ladderane and acid self-assembled to generate a five-component hydrogen-bonded complex that packs to form large solvent-filled homochiral channels of nanometer-scale dimensions. Whereas cocrystallizations are frequently applied to structure determinations of proteins, our study represents the first application of a cocrystallization to confirm the relative configuration of a small-molecule diastereomer generated in a solution-phase organic synthesis.
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Characterisation of two alcohol acyltransferases from kiwifruit (Actinidia spp.) reveals distinct substrate preferences.
No full textVolatile esters are key compounds of kiwifruit flavour and are formed by alcohol acyltransferases that belong to the BAHD acyltransferase superfamily. Quantitative RT-PCR was used to screen kiwifruitderived expressed sequence tags with proposed acyltransferase function in order to select ripeningspecific sequences and test their involvement in alcohol acylation. The screening criterion was for at least 10-fold increased transcript accumulation in ripe compared with unripe kiwifruit and in response to ethylene. Recombinant expression in yeast revealed alcohol acyltransferase activity for Actinidia-derived AT1, AT16 and the phylogenetically distinct AT9, using various alcohol and acyl-CoA substrates. Functional characterisation of AT16 and AT9 demonstrated striking differences in their substrate preferences and apparent catalytic efficiencies ðV0 max K�1 m Þ. Thus revealing benzoyl-CoA:alcohol O-acyltransferase activity for AT16 and acetyl-CoA:alcohol O-acyltransferase activity for AT9. Both kiwifruit-derived enzymes displayed higher reaction rates with butanol compared with ethanol, even though ethanol is the main alcohol in ripe fruit. Since ethyl acetate and ethyl benzoate are major esters in ripe kiwifruit, we suggest that fruit characteristic volatile profiles result from a combination of substrate availability and specificity of individual alcohol acyltransferases
Author Correction: A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
No full textIn the version of this article initially published, the ATLAS Collaboration
author names, affiliations and acknowledgements were omitted and
have now been included in the HTML and PDF versions of the article
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