The magnitude of viscous dissipation in strongly stratified two-dimensional convection

Convection in astrophysical systems must be maintained against dissipation. Although the effects of dissipation are often assumed to be negligible, theory suggests that in strongly stratified convecting fluids, the dissipative heating rate can exceed the luminosity carried by convection. Here we explore this possibility using a series of numerical simulations. We consider two-dimensional numerical models of hydrodynamic convection in a Cartesian layer under the anelastic approximation and demonstrate that the dissipative heating rate can indeed exceed the imposed luminosity. We establish a theoretical expression for the ratio of the dissipative heating rate to the luminosity emerging at the upper boundary, in terms only of the depth of the layer and the thermal scale height. In particular, we show that this ratio is independent of the diffusivities and confirm this with a series of numerical simulations. Our results suggest that dissipative heating may significantly alter the internal dynamics of stars and planets.Comment: 8 pages, 5 figures, accepted for publication in ApJ Letter

From Colonial Port to Post-Revolution: Urban Planning for 21st Century Havana

Coffee table books are filled with them: the clichés of Havana as "frozen in time", scented with "nostalgia for a bygone era". At first sight, the city's unique combination of urban design and architectural styles suggest a tension between the island's various historical and political periods. At second glance, the tension lessens into what is a mostly complimentary relationship between patterns, designs, and vision. That is, a city made rich by its combination of continuous innovation and historic preservation. The result is an avant-garde, mostly European (compact, pedestrian, grid-based), urban planning agenda with many assets and challenges to its name. This photo essay aims to: examine how Havana’s colonial history created the city’s basic modern grid street pattern, compact block structure; identify what elements make Havana's urban character different from that of other major Latin American cities; observe current projects as outlined by the New Master Plan; and, finally identify challenges ahead. By covering these points, the essay sets out to challenge the “frozen in time” perception of Havana by replacing it with one of a unique and historically rich city on the brink of major changes

Extradition and trial delays: recent developments (and lessons?) from Canada

Extradition – the formal rendition of criminal fugitives between states – is well-known to be a time-consuming process that often has impacts, minor or major, on the ability of states to complete prosecution in a timely manner. Thus, the extradition process can sometimes be at odds with the right to trial within a reasonable time, which is part of the overall package of fair trial rights enshrined in international human rights law. In Canada, this right is implemented by paragraph 11(b) of the Canadian Charter of Rights and Freedoms. In recent years, Canadian courts have developed a series of principles to be applied to cases where extradition is involved in claims of trial delay. These range from the prosecution’s obligation to pursue timely trial in a diligent manner, to the extent to which extradition should simply be treated as procedurally neutral, to the attribution of delays when an accused has deliberately left the country to avoid prosecution. This body of case law is surveyed and analysed in this article, as a means of providing an illustrative example of state practice regarding this right. The authors conclude that, while Canadian law on this question is not entirely coherent internally, it generally complies with international standards.A extradição – a entrega formal de criminosos fugitivos entre Estados – é notória por ser um processo moroso que tem muitas vezes impacto, maior ou menor, na capacidade dos Estados concluírem a prossecução penal atempadamente. Assim, o processo de extradição pode por vezes entrar em conflito com o direito a um julgamento num prazo razoável, direito esse que faz parte no conjunto geral de direitos a um julgamento justo estabelecido no corpo internacional de Direitos Humanos. No Canadá, este direito é estatuído pelo parágrafo 11(b) do Canadian Charter of Rights and Freedoms. Em anos recentes, os tribunais canadianos desenvolveram uma série de princípios a ser aplicados a casos em que a extradição está envolvida em alegações de atraso de julgamento. Estes vão desde a obrigação da acusação promover um julgamento num prazo razoável de forma diligente, à ideia de que a extradição deve ser processualmente neutra, ou à atribuição de atrasos quando um arguido saiu deliberadamente do país de modo a evitar a prossecução penal. Este conjunto de jurisprudência é analisado neste artigo, enquanto meio de oferecer um exemplo ilustrativo das práticas públicas relativas a este direito. Os Autores concluem que enquanto a lei canadiana não é inteiramente coerente em termos internos, esta é, de uma forma geral, conforme aos padrões internacionais

Compromised cardiovascular function in aged rats corresponds with increased expression and activity of calcium/calmodulin dependent protein kinase IIδ in aortic endothelium

Ageing is the greatest risk factor for cardiovascular disease. Calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) plays a fundamental role in the pathology of heart disease yet a potential role for CaMKIIδ in cardiovascular pathology associated with ageing remains unclear. Taking a combined in vivo and in vitro approach, we have for the first time investigated whether CaMKIIδ expression and CaMKII activity may be altered following age-related cardiovascular deterioration. Both cardiac contractility and aortic blood flow are compromised in aged rats and we have shown that this occurs in parallel with increased inflammation and crucially, autonomous activation of CaMKII. Endothelial cells isolated from young and aged aortae exhibit differences in cell phenotype and physiology. In line with observations in aortic tissue, aged aortic endothelial cells also show increased basal levels of pro-inflammatory markers and oxidative stress with concurrent increased basal activation of CaMKII. These results are the first to demonstrate that elevated CaMKIIδ expression and CaMKII activation occur in parallel with the pathological progression associated with ageing of the heart and vasculature. Specifically, CaMKIIδ expression is significantly increased and activated in the endothelium of aged aorta. As such, CaMKIIδ could serve as an important marker of endothelial dysfunction that accompanies the ageing process and may be an appropriate candidate for investigating targeted therapeutic intervention

The driving of mean flows by convection

The interaction of convection with rotation and magnetic fields plays an important role in determining the dynamics of many geophysical and astrophysical phenomena. In particular, this interaction is thought to be associated with the generation of large-scale mean flows as observed, for example, in the atmospheres of the giant planets and in the interior of the Sun. This study examines the interaction of convection with rotation and magnetic fields in a simplified, two-dimensional, plane layer model. We consider the case where the fluid rotates about an axis that is oblique to gravity, and is in the presence of a horizontal magnetic field. Also considered, is the case where a horizontal temperature gradient maintains a thermal wind. The fluid is taken to be either incompressible, using the Boussinesq approximation, or compressible, using the anelastic approximation. An examination of the linear behaviour is undertaken to investigate the conditions required for the onset of convection, in a number of different regimes. The existence of an unexpected symmetry is proved in the anelastic case. A pseudospectral numerical code, developed in order to solve the nonlinear equations, is then described. The code is employed to investigate the dynamics in the nonlinear regime and determine the underlying physical interactions for mean flow maintenance. It is shown that whether convection acts to decrease or increase the thermal wind shear, depends on the Prandtl number and the angle of tilt of the rotation vector. Furthermore, the asymmetries introduced when a background stratification is present, manifest themselves in the time-dependent nature of the mean flows driven. We also show that an imposed horizontal magnetic field not only inhibits mean flow generation but also affects the vertical structure of the flows. To finish, a discussion of the applicability of the work to astrophysical phenomena is given

Novel analgesic interventions in cancer-induced bone pain

Cancer-induced bone pain (CIBP), due to bony metastases, is a major clinical problem, significantly reducing quality of life in cancer patients. Current therapies often provide inadequate analgesia or unacceptable side effects. The aim of this thesis was to characterise behaviours of a preclinical model of CIBP and test novel analgesic interventions in this model. A secondary aim was to investigate the involvement of the N-methyl-D-Aspartate (NMDA) receptors and TRP channels (TRPM8, TRPV1 and TRPV4) in CIBP. Investigation of CIBP in a preclinical model may lead to better pain management in CIBP patients. The results presented here demonstrate that this model of CIBP develops behaviours that may be indicative of mechanical allodynia, thermal sensitivity, movement-evoked pain, ongoing pain and spontaneous pain. This suggests that this model reflects the clinical condition of CIBP, where patients suffer from constant background pain with spontaneous and movement-related breakthrough pain. In this study it was found that radiotherapy significantly attenuated movement-evoked pain and thermal sensitivity to 20°C and 40°C. XRT also significantly reduced anxiety and risk assessment behaviours (grooming behaviour and number of protected stretch attends) compared to untreated CIBP. Duloxetine attenuated CIBP-induced mechanical allodynia, thermal sensitivity to 40°C and movement-evoked pain, whereas S,S-reboxetine attenuated thermal sensitivity to 40°C but did not effect CIBP-induced mechanical allodynia or movement-evoked pain. In addition, CB 65 attenuated movement-evoked pain and thermal sensitivity to 40°C. A single dose of gabapentin did not attenuate CIBP-induced mechanical allodynia, thermal sensitivity to 40°C or movement-evoked pain. These studies confirm that the CIBP model shows characteristics and pharmacological sensitivities consistent with known and predicted mechanisms and validate it as a useful model for assessing potential new treatments proposed for use in patients. Behavioural results suggest that NMDA receptors containing the NR2A subunit are involved in CIBP-induced movement-evoked pain. This suggests that NR2A antagonists may be useful for treating CIBP-induced movement-evoked pain. Additionally, results show that there is increased expression of NR2A in the laminae I, II and III in the dorsal horn of the spinal cord. XRT treated animals also showed increased expression of NR2A in laminae I and II. The selective involvement of NR2A in CIBP is different to other chronic pain states, for example, neuropathic pain states that appear to involve the NR2B subunit. The TRPV1 antagonist AMG 9810 did not attenuate mechanical allodynia, thermal sensitivity to 40°C or movement-evoked pain. Interestingly, the TRPM8 agonist icilin attenuated movement-evoked pain, which suggests that icilin might be useful in the treatment of movement-evoked pain. The TRPV4 antagonist RN 1734 attenuated mechanical allodynia, thermal sensitivity to 40°C and movement-evoked pain in CIBP. This suggests RN 1734 may be useful in the treatment of mechanical allodynia, thermal sensitivity to 40°C and movement-evoked pain in CIBP. Results show that the expression of TRPV4 is increased in DRG ipsilateral to the cancerbearing tibia. In conclusion, these results show that the preclinical model of CIBP investigated in this thesis is suitable for testing novel analgesic interventions. This thesis identified some useful targets for the analgesic treatment of CIBP and results suggest that many different mechanisms contribute to CIBP. A point to consider is that any robust effective treatment may need to target all (or at least several) of these mechanisms

La implementación de la virtualidad obligatoria en el ámbito universitario en un contexto extraordinario. De la teoría a la práctica

En el siguiente artículo se expondrán propuestas pedagógicas realizadas por las autoras para la cátedra Arquitectura I. Dichas ideas surgen de la tentativa de aplicar el bagaje teórico suministrado por la Diplomatura Universitaria en Educación Mediada por TIC de la UNNE en un contexto excepcional de pandemia, donde la virtualidad se presenta como la única alternativa didáctica posible. Asimismo, se extraerán conclusiones sobre su aplicación

Magnetic field generation in finite beam plasma system

For finite systems boundaries can introduce remarkable novel features. A well known example is the Casimir effect [1, 2] that is observed in quantum electrodynamic systems. In classical systems too novel effects associated with finite boundaries have been observed, for example the surface plasmon mode [3] that appears when the plasma has a finite extension. In this work a novel instability associated with the finite transverse size of a beam owing through a plasma system has been shown to exist. This instability leads to distinct characteristic features of the associated magnetic field that gets generated. For example, in contrast to the well known unstable Weibel mode of a beam plasma system which generates magnetic field at the skin depth scale, this instability generates magnetic field at the scales length of the transverse beam dimension [4]. The existence of this new instability is demonstrated by analytical arguments and by simulations conducted with the help of a variety of Particle - In - Cell (PIC) codes (e.g. OSIRIS, EPOCH, PICPSI). Two fluid simulations have also been conducted which confirm the observations. Furthermore, laboratory experiments on laser plasma system also provides evidence of such an instability mechanism at work