Thermodynamic properties and structural stability of thorium dioxide

Using density functional theory (DFT) calculations, we have systematically investigated the thermodynamic properties and structural stabilities of thorium dioxide (ThO$_2$). Based on the calculated phonon dispersion curves, we calculate the thermal expansion coefficient, bulk modulus, and heat capacities at different temperatures for ThO$_2$ under the quasi-harmonic approximation. All the results are in good agreement with corresponding experiments proving the validity of our methods. Our theoretical studies can help people more clearly understand the thermodynamic behaviors of ThO$_2$ at different temperatures. In addition, we have also studied possible defect formations and diffusion behaviors of helium in ThO$_2$, to discuss its structural stability. It is found that in intrinsic ThO$_2$ without any Fermi energy shifts, the interstitial Th$_i^{4+}$ defect other than oxygen or thorium vacancies, interstitial oxygen, and any kinds of Frenkel pairs, is most probable to form with an energy release of 1.74 eV. However, after upshifting the Fermi energy, the formation of the other defects also becomes possible. For helium diffusion, we find that only through the thorium vacancy can it happen with the small energy barrier of 0.52 eV. Otherwise, helium atoms can hardly incorporate or diffuse in ThO$_2$. Our results indicate that people should prevent upshifts of the Fermi energy of ThO$_2$ to avoid the formation of thorium vacancies and so as to prevent helium caused damages.Comment: 11 pages, 11 figure

From lean production to Industrie 4.0: More autonomy for employees?

The article examines the relationship between lean production and Industrie 4.0 focusing on the question of autonomy in the work process. In contrast to the claim made by official Industrie 4.0 concepts that the autonomy of the employees would increase, we see in the current implementation projects a tendency towards greater standardization and control of work. This is in continuity with concepts of lean production, but neglects the participation-oriented elements of lean production such as teamwork and shop-floor-based improvement activities. Our argument is developed by analyzing practical examples from three relevant fields (digital assistance systems, data-based process management, modular assembly). The conclusions of this article also discuss the extent to which the concept of individual autonomy is suitable for the assessment of Industrie 4.0 concepts, given the high levels of interdependence already achieved in production processes

Irreversible impacts of heat on the emissions of monoterpenes, sesquiterpenes, phenolic BVOC and green leaf volatiles from several tree species

Climate change will induce extended heat waves to parts of the vegetation more frequently. High temperatures may act as stress (thermal stress) on plants changing emissions of biogenic volatile organic compounds (BVOCs). As BVOCs impact the atmospheric oxidation cycle and aerosol formation, it is important to explore possible alterations of BVOC emissions under high temperature conditions. Applying heat to European beech, Palestine oak, Scots pine, and Norway spruce in a laboratory setup either caused the well-known exponential increases of BVOC emissions or induced irreversible changes of BVOC emissions. Considering only irreversible changes of BVOC emissions as stress impacts, we found that high temperatures decreased the <i>de novo</i> emissions of monoterpenes, sesquiterpenes and phenolic BVOC. This behaviour was independent of the tree species and whether the <i>de novo</i> emissions were constitutive or induced by biotic stress. <br><br> In contrast, application of thermal stress to conifers amplified the release of monoterpenes stored in resin ducts of conifers and induced emissions of green leaf volatiles. In particular during insect attack on conifers, the plants showed <i>de novo</i> emissions of sesquiterpenes and phenolic BVOCs, which exceeded constitutive monoterpene emissions from pools. The heat-induced decrease of <i>de novo</i> emissions was larger than the increased monoterpene release caused by damage of resin ducts. For insect-infested conifers the net effect of thermal stress on BVOC emissions could be an overall decrease. <br><br> Global change-induced heat waves may put hard thermal stress on plants. If so, we project that BVOC emissions increase is more than predicted by models only in areas predominantly covered with conifers that do not emit high amounts of sesquiterpenes and phenolic BVOCs. Otherwise overall effects of high temperature stress will be lower increases of BVOC emissions than predicted by algorithms that do not consider stress impacts

An elementary stringy estimate of transport coefficients of large temperature QCD

Modeling QCD at large temperature with a simple holographic five dimensional theory encoding minimal breaking of conformality, allows for the calculation of all the transport coefficients, up to second order, in terms of a single parameter. In particular, the shear and bulk relaxation times are provided. The result follows by deforming the AdS background with a scalar dual to a marginally relevant operator, at leading order in the deformation parameter.Comment: 11 pages; v2: comments and references adde

Aharonov-Bohm cages in two-dimensional structures

We present an extreme localization mechanism induced by a magnetic field for tight-binding electrons in two-dimensional structures. This spectacular phenomenon is investigated for a large class of tilings (periodic, quasiperiodic, or random). We are led to introduce the Aharonov-Bohm cages defined as the set of sites eventually visited by a wavepacket that can, for particular values of the magnetic flux, be bounded. We finally discuss the quantum dynamics which exhibits an original pulsating behaviour.Comment: 4 pages Latex, 3 eps figures, 1 ps figur

Mothers behaving badly: chaotic hedonism and the crisis of neoliberal social reproduction

This article focuses on the significance of the plethora of representations of mothers ‘behaving badly’ in contemporary anglophone media texts, including the films Bad Moms, Fun Mom Dinner and Bad Mom’s Christmas, the book and online cartoons Hurrah for Gin and the recent TV comedy dramas Motherland, The Let Down and Catastrophe. All these media texts include representations of, first, mothers in the midst of highly chaotic everyday spaces where any smooth routine of domesticity is conspicuous by its absence; and second, mothers behaving hedonistically, usually through drinking and partying, behaviour that is more conventionally associated with men or women without children. After identifying the social type of the mother behaving badly (MBB), the article locates and analyses it in relation to several different social and cultural contexts. These contexts are: a neoliberal crisis in social reproduction marked by inequality and overwork; the continual if contested role of women as ‘foundation parents’; and the negotiation of longer-term discourses of female hedonism. The title gestures towards a popular British sitcom of the 1990s, Men Behaving Badly, which popularized the idea of the ‘new lad’; and this article suggests that the new lad’s counterpart, the ladette, is mutating into the mother behaving badly, or the ‘lad mom’. Asking what work this figure does now, in a later neoliberal context, it argues that the mother behaving badly is simultaneously indicative of a widening and liberating range of maternal subject positions and symptomatic of a profound contemporary crisis in social reproduction. By focusing on the classed and racialised dynamics of the MBB – by examining who exactly is permitted to be hedonistic, and how – and by considering the MBB’s limited and partial imagining of progressive social change, the article concludes by emphasizing the urgency of creating more connections between such discourses and ‘parents behaving politically’

Expansion in perfect groups

Let Ga be a subgroup of GL_d(Q) generated by a finite symmetric set S. For an integer q, denote by Ga_q the subgroup of Ga consisting of the elements that project to the unit element mod q. We prove that the Cayley graphs of Ga/Ga_q with respect to the generating set S form a family of expanders when q ranges over square-free integers with large prime divisors if and only if the connected component of the Zariski-closure of Ga is perfect.Comment: 62 pages, no figures, revision based on referee's comments: new ideas are explained in more details in the introduction, typos corrected, results and proofs unchange