Article

1999 ◽  
Vol 77 (8) ◽  
pp. 1340-1348
Author(s):  
Alex D Bain ◽  
P Hazendonk ◽  
P Couture
Keyword(s):  
Chemical Exchange ◽  
Substituent Effects ◽  
Theoretical Work ◽  
Atoms In Molecules ◽  
Amide Bond ◽  
Resonance Spectroscopy ◽  
Carbonyl Carbon ◽  
Aim Analysis ◽  
Recent Theoretical Work

Recent theoretical work on amide systems has brought into question the application of the concept of resonance. In particular, the role of the oxygen atom was questioned, since the calculations showed little change in its properties when the amide bond was rotated. This paper investigates, both experimentally and computationally, the effect of a substituent on the carbonyl carbon on the amide barrier, in order to test this view. The barriers to the amide rotation in seven spiro-fused oxazolidines were measured by NMR, to within 1 kJ mol-1. A subset of three of them was modelled to the 6-31G** level. For all three substituents the computed and measured barriers corresponded to within 7 kJ mol-1. The electron densities were analyzed using the Atoms in Molecules (AIM) theory. The AIM analysis revealed that the oxazolidines behaved similarly to formamide. The substituent effect was described in terms of the atomic populations and energies of the amide C, O, and N. A substituent on the carbonyl carbon caused electron redistributions between N and C, changing their basin attractive energies. Neither the population nor the energy of oxygen changed significantly. When interactions outside the basin of interest were considered, the energy of C was seen to be more sensitive to changing the substituent than the energy of N. However, the atomic parameters from the AIM analysis did not fully reflect the substituent effects observed. For these molecules, the barrier includes contributions from several sources - there is no single, dominant contribution.Key words: amides, barrier, substituent, nuclear magnetic resonance spectroscopy, chemical exchange, atoms in molecules, slow exchange, NMR lineshape analysis.

scholarly journals Mixed-polarity random-dot stereograms alter GABA and Glx concentration in the early visual cortex

2019 ◽  
Author(s):  
Reuben Rideaux ◽  
Nuno Goncalves ◽  
Andrew E Welchman
Keyword(s):  
Visual Cortex ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Dimensional Structure ◽  
Resonance Spectroscopy ◽  
Gaba Concentration ◽  
Recent Theoretical Work ◽  
Random Dot Stereograms ◽  
Mixed Polarity ◽  
Early Visual Cortex

ABSTRACTThe offset between images projected onto the left and right retinae (binocular disparity) provides a powerful cue to the three-dimensional structure of the environment. It was previously shown that depth judgements are better when images comprise both light and dark features, rather than only dark or only light elements. Since Harris and Parker (1995) discovered the “mixed-polarity benefit”, there has been limited evidence supporting their hypothesis that the benefit is due to separate bright and dark channels. Goncalves and Welchman (2017) observed that single- and mixed-polarity stereograms evoke different levels of positive and negative activity in a deep neural network trained on natural images to make depth judgements, which also showed the mixed-polarity benefit. Motivated by this discovery, here we seek to test the potential for changes in the balance of excitation and inhibition that are produced by viewing these stimuli. In particular, we use magnetic resonance spectroscopy to measure Glx and GABA concentration in the early visual cortex of adult humans while viewing single- and mixed-polarity random-dot stereograms (RDS). We find that observers’ Glx concentration is significantly higher while GABA concentration is significantly lower when viewing mixed-polarity RDS than when viewing single-polarity RDS. These results indicate that excitation and inhibition facilitate processing of single- and mixed-polarity stereograms in the early visual cortex to different extents, consistent with recent theoretical work (Goncalves & Welchman, 2017).

scholarly journals Persuasion architectures: Consumer spaces, affective engineering and (criminal) harm

2019 ◽  
pp. 136248061989467
Author(s):  
Theo Kindynis
Keyword(s):  
Moral Responsibility ◽  
Urban Studies ◽  
Cultural Geography ◽  
Theoretical Work ◽  
Political Accountability ◽  
Shopping Malls ◽  
Night Time ◽  
Spatial Design ◽  
Recent Theoretical Work

Drawing together recent theoretical work from both within and beyond criminology, this article considers the role of strategically designed consumer spaces in eliciting potentially criminogenic and harmful dispositions and behaviours. First, the article introduces recent work in cultural geography and urban studies, which has drawn attention to the manipulation of affect through spatial design. Second, by way of example, the article considers how such strategies are deployed in three types of consumer environments: shopping malls and retail spaces; casinos and other gambling environments; and the so-called night time economy. Third, the article engages such developments theoretically. It is suggested we rethink the distinctions and interrelationships between human subjectivity and agency and the built environment. The implications of this proposed conceptual reorientation are explored—first, for our understandings of agency, intentionality, moral responsibility and political accountability; and second, for criminological thinking around embodied difference, power and exclusion.

Government, Anti-Reflexivity, and the Construction of Public Ignorance about Climate Change: Australia and Canada Compared

2013 ◽  
Vol 13 (2) ◽  
pp. 89-108 ◽  
Author(s):  
Nathan Young ◽  
Aline Coutinho
Keyword(s):  
Climate Change ◽  
Climate Change Policy ◽  
Theoretical Work ◽  
The Political ◽  
Political Resistance ◽  
Change Policy ◽  
Recent Theoretical Work ◽  
Public Ignorance ◽  
John Howard

This article compares the political strategies used by conservative governments in Australia (John Howard) and Canada (Stephen Harper) to manage public impressions of climate change and climate change policy. These cases are significant in part because both governments acted against the weight of domestic public opinion. While many studies of political resistance to climate change mitigation focus on the role of denial, skepticism, and counter-claims, our comparison finds a significant role for what we call “affirmation techniques,” namely the rhetorical acceptance of the consensus position on climate change followed by concerted attempts to control precisely what acceptance means. We draw on recent theoretical work on anti-reflexivity and the sociology of ignorance to explain the political effectiveness of these strategies.

scholarly journals Role of Anharmonic Interactions for Vibration Density of States in α-Cristobalite

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 617
Author(s):  
Yongda Huang ◽  
Jian Zhou ◽  
Guanjie Wang ◽  
Zhimei Sun
Keyword(s):  
Density Of States ◽  
First Principles ◽  
Low Frequency ◽  
Theoretical Work ◽  
Atomic Displacement ◽  
Main Peak ◽  
Recent Theoretical Work ◽  
Different Temperatures ◽  
Anharmonic Interactions

The vibrational density of states (VDOS) of solids in the low-energy regime controls the thermal and transport properties of materials, such as heat capacity, heat conduction, free energy and entropy. In α-Cristobalite, the low-frequency part of vibration density of states (VDOS) has many common features with the Boson peak in silica glass of matched densities. Recent theoretical work reported that anharmonic phonon–phonon interactions were critical for the low-frequency part of VDOS in α-Cristobalite. Therefore, it is urgent to identify the role of different anharmonic interactions from first principles. In this paper, we focus on the main peak of the low-frequency part of VDOS in α-Cristobalite. Calculated by our own developed codes and first principles, we find that the quartic anharmonic interaction can increase the frequency of the peak, while the cubic anharmonic can reduce the frequency and change the shape of the peak. Meanwhile, the anharmonic interactions are critical for the temperature effect. Therefore, we calculated the temperature-dependent property of the peak. We find that the frequency of the peak is directly proportional to the temperature. The atomic displacement patterns of different temperatures also confirm the above conclusion. All our calculations converged well. Moreover, our basic results agree well with other published results. Finally, we highlight that our codes offer a general and reliable way to calculate the VDOS with temperature.

scholarly journals Halogen bonding. The role of the polarizability of the electron-pair donor

2016 ◽  
Vol 18 (10) ◽  
pp. 7300-7309 ◽  
Author(s):  
Darío J. R. Duarte ◽  
Gladis L. Sosa ◽  
Nélida M. Peruchena ◽  
Ibon Alkorta
Keyword(s):  
Theoretical Calculation ◽  
Electron Pair ◽  
Decomposition Analysis ◽  
Halogen Bonding ◽  
Atoms In Molecules ◽  
Molecular Polarizability ◽  
Aim Analysis ◽  
Molecular Potential

The nature of F–Br⋯X–R interactions (with X = Cl, Br, I and R = –H, –F) has been investigated through theoretical calculation of molecular potential electrostatic (MEP), molecular polarizability, atoms in molecules (AIM) analysis and energetic decomposition analysis (EDA).

EXPRESS: STRUGGLING TO MAKE SENSE OF IT ALL: THE EMOTIONAL PROCESS OF SENSEMAKING FOLLOWING AN EXTREME INCIDENT

2021 ◽  
pp. 001872672110594
Author(s):  
Graham Dwyer ◽  
Cynthia Hardy ◽  
Haridimos Tsoukas
Keyword(s):  
Emergency Management ◽  
Theoretical Work ◽  
Life And Death ◽  
Emotional Process ◽  
Recent Theoretical Work ◽  
Public Inquiry ◽  
Extreme Contexts ◽  
The Difference ◽  
Empirical Contribution

Organizations operating in extreme contexts regularly face dangerous incidents they can neither prevent nor easily control. In such circumstances, successful sensemaking can mean the difference between life and death. But what happens afterwards? Our study of emergency management practitioners following a major bushfire reveals a process of post-incident sensemaking during which practitioners continue to make sense of the incident after it ends, during the subsequent public inquiry, and as they try to implement the inquiry’s recommendations. Different varieties of sensemaking arise during this process as practitioners rely on different forms of coping to develop and share new understandings, which not only make sense of the original incident, but also enable changes to help the organization deal with future incidents. Our study also shows that practitioners experience a range of emotions during this process, some of which inhibit sensemaking while others – particularly different forms of anxiety – can facilitate it. Our study makes an important empirical contribution to recent theoretical work on varieties of sensemaking and provides new insights into the complex role of emotions in sensemaking in extreme contexts.

scholarly journals The Role of Gravitational Radiation in the Evolution of Dwarf Novae

1974 ◽  
Vol 64 ◽  
pp. 97-97 ◽  
Author(s):  
John Faulkner
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Mass Loss ◽  
Gravitational Radiation ◽  
Theoretical Work ◽  
Observational Evidence ◽  
Recent Theoretical Work ◽  
Term Response

Mechanisms promoting mass transfer include (i) envelope instability or (ii) nuclear evolution of the red star and (iii) gravitational radiation of orbital angular momentum. Growing observational evidence against (i) is supported by recent theoretical work on the medium and long-term response of stellar radii to mass-loss (Eggleton, Faulkner and Webbink, in progress). Since (ii) is in most cases too slow a process, (iii) is left as the best surviving explanation.

The light-scattering Mueller matrices for Rayleigh and Rayleigh-Gans-Debye approximation

1990 ◽  
Vol 55 (12) ◽  
pp. 2889-2897
Author(s):  
Jaroslav Holoubek
Keyword(s):  
Light Scattering ◽  
Theoretical Work ◽  
Matrix Elements ◽  
Elastic Light Scattering ◽  
Yield Information ◽  
Recent Theoretical Work ◽  
Particle Parameters ◽  
Complete Set ◽  
Single Matrix ◽  
Scattering Matrix Elements

Recent theoretical work has shown that the complete set of polarized elastic light-scattering studies should yield information about scatterer structure that has so far hardly been utilized. We present here calculations of angular dependences of light-scattering matrix elements for spheres near the Rayleigh and Rayleigh-Gans-Debye limits. The significance of single matrix elements is documented on examples that show how different matrix elements respond to changes in particle parameters. It appears that in the small-particle limit (Rg/λ < 0.1) we do not loose much information by ignoring "large particle" observables.

scholarly journals Magnetospheric Structure of Rotation-Powered Neutron Stars

1992 ◽  
Vol 128 ◽  
pp. 56-77 ◽  
Author(s):  
Jonathan Arons
Keyword(s):  
Radio Emission ◽  
Gamma Radiation ◽  
Heavy Ions ◽  
Theoretical Work ◽  
Future Research ◽  
Observational Constraints ◽  
Polar Caps ◽  
Recent Theoretical Work ◽  
Density Flow ◽  
Promising Avenue

AbstractI survey recent theoretical work on the structure of the magnetospheres of rotation-powered pulsars, within the observational constraints set by their observed spindown, their ability to power synchrotron nebulae and their ability to produce beamed collective radio emission, while putting only a small fraction of their energy into incoherent X- and gamma radiation. I find no single theory has yet given a consistent description of the magnetosphere, but I conclude that models based on a dense outflow of pairs from the polar caps, permeated by a lower density flow of heavy ions, are the most promising avenue for future research.

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