Proceedings of Bhutan: Biodemocracy & Resilience Conference 2020

The Second Bhutan Biodemocracy and Resilience Conference With a focus on pathways to resilience in the face of cross-sectoral and regional effects of the coronavirus pandemic)(held on December 21-22, 2020) brought together a range of people from politics, civil society, media, business, academia, education, industry, agriculture in multiple panels to discuss the key developmental challenges in the context of the pandemic. The conference was covered in the Bhutanese media and received an overwhelmingly positive feedback from various sectors of society and on social media. The aim of the project was to bring together key stakeholders in Bhutan to produce engaged deliberations and reports that can guide policymaking. The two-day conference had panel discussions on the effects of the coronavirus crisis in relation to economic vulnerability and climate change, volunteerism and public health, local governments, agriculture, employment, hydropower and tourism. A keynote address from Lyonpo Ugyen Dorji, Minister of Labour and Human Resources of the Royal Government of Bhutan, began the two days of panel discussions on the pandemic, public policy and development. The talks were livestreamed and watched by thousands of people and were covered nationally. The BBR 2020 conference built upon the first conference titled ‘Bhutan as Biodemocracy: Building Socioeconomic and Environmental Resilience’ which was held in July 2019

Logarithmic correction to the Bekenstein-Hawking entropy of the BTZ black hole

We derive an exact expression for the partition function of the Euclidean BTZ black hole. Using this, we show that for a black hole with large horizon area, the correction to the Bekenstein-Hawking entropy is $-3/2 log(Area)$, in agreement with that for the Schwarzschild black hole obtained in the canonical gravity formalism and also in a Lorentzian computation of BTZ black hole entropy. We find that the right expression for the logarithmic correction in the context of the BTZ black hole comes from the modular invariance associated with the toral boundary of the black hole.Comment: LaTeX, 10 pages, typos corrected, clarifications adde

Semi-Supervised Learning of Lift Optimization of Multi-Element Three-Segment Variable Camber Airfoil

This chapter describes a new intelligent platform for learning optimal designs of morphing wings based on Variable Camber Continuous Trailing Edge Flaps (VCCTEF) in conjunction with a leading edge flap called the Variable Camber Krueger (VCK). The new platform consists of a Computational Fluid Dynamics (CFD) methodology coupled with a semi-supervised learning methodology. The CFD component of the intelligent platform comprises of a full Navier-Stokes solution capability (NASA OVERFLOW solver with Spalart-Allmaras turbulence model) that computes flow over a tri-element inboard NASA Generic Transport Model (GTM) wing section. Various VCCTEF/VCK settings and configurations were considered to explore optimal design for high-lift flight during take-off and landing. To determine globally optimal design of such a system, an extremely large set of CFD simulations is needed. This is not feasible to achieve in practice. To alleviate this problem, a recourse was taken to a semi-supervised learning (SSL) methodology, which is based on manifold regularization techniques. A reasonable space of CFD solutions was populated and then the SSL methodology was used to fit this manifold in its entirety, including the gaps in the manifold where there were no CFD solutions available. The SSL methodology in conjunction with an elastodynamic solver (FiDDLE) was demonstrated in an earlier study involving structural health monitoring. These CFD-SSL methodologies define the new intelligent platform that forms the basis for our search for optimal design of wings. Although the present platform can be used in various other design and operational problems in engineering, this chapter focuses on the high-lift study of the VCK-VCCTEF system. Top few candidate design configurations were identified by solving the CFD problem in a small subset of the design space. The SSL component was trained on the design space, and was then used in a predictive mode to populate a selected set of test points outside of the given design space. The new design test space thus populated was evaluated by using the CFD component by determining the error between the SSL predictions and the true (CFD) solutions, which was found to be small. This demonstrates the proposed CFD-SSL methodologies for isolating the best design of the VCK-VCCTEF system, and it holds promise for quantitatively identifying best designs of flight systems, in general

Comparison of structural magnetic resonance imaging findings between neuropsychiatric systemic lupus erythematosus and systemic lupus erythematosus patients: A systematic review and meta-analysis

Introduction: Neuropsychiatric systemic lupus erythematosus is often clinically challenging to diagnose, treat and monitor. Although brain magnetic resonance imaging is frequently performed before lumbar puncture in neuropsychiatric systemic lupus erythematosus, it is not clear from the literature whether specific brain magnetic resonance imaging findings are associated with distinct clinical features of neuropsychiatric systemic lupus erythematosus. Methods: We conducted a systematic review and meta-analysis on published studies of neuropsychiatric systemic lupus erythematosus including brain magnetic resonance imaging and the 1999 American College of Rheumatology-defined clinical neuropsychiatric systemic lupus erythematosus syndromes to determine their relationship. Pooled prevalence and risk ratio for distinct neuropsychiatric systemic lupus erythematosus associations were determined with 95% confidence intervals. Results: Of 821 studies screened, 21 fulfilled inclusion criteria. A total of 818 participants were evaluated (91% female) with 1064 neuropsychiatric systemic lupus erythematosus episodes assessed. Neuropsychiatric systemic lupus erythematosus features included headache (24%), seizures (19%), cerebrovascular disease (18%), cognitive dysfunction (15%) and acute confusional state (14%). Normal magnetic resonance imaging was significant for anxiety disorder (risk ratio: 9.00; 95% confidence interval: 2.40, 33.79), autonomic disorder (risk ratio: 7.00; 95% confidence interval: 0.51, 96.06) and plexopathy (risk ratio: 5.00; 95% confidence interval: 0.81, 31.00). Highest risk ratio of neuropsychiatric systemic lupus erythematosus syndrome with abnormal magnetic resonance imaging was observed for cerebrovascular disease (risk ratio: 0.15; 95% confidence interval: 0.10, 0.24) and demyelination (risk ratio: 0.11; 95% confidence interval: 0.02, 0.72). Conclusion: Normal magnetic resonance imaging in neuropsychiatric systemic lupus erythematosus was the most significant correlate from our meta-analysis for psychological symptoms including anxiety and peripheral nerve features of autonomic disorder and plexopathy. The main abnormal brain magnetic resonance imaging correlates included cerebrovascular disease and demyelination. Brain magnetic resonance imaging correlates poorly with neuropsychiatric systemic lupus erythematosus features, and specific clinical symptoms should be the main determinants of performing magnetic resonance imaging rather than presence of neuropsychiatric systemic lupus erythematosus per se

Spin wave dispersion based on the quasiparticle self-consistent GWGW method: NiO, MnO and α\alpha-MnAs

We present spin wave dispersions in MnO, NiO, and $\alpha$-MnAs based on the quasiparticle self-consistent $GW$ method (\qsgw), which determines an optimum quasiparticle picture. For MnO and NiO, \qsgw results are in rather good agreement with experiments, in contrast to the LDA and LDA+U description. For $\alpha$-MnAs, we find a collinear ferromagnetic ground state in \qsgw, while this phase is unstable in the LDA.Comment: V2: add another figure for SW life time. Formalism is detaile

Finite-size effects in amorphous Fe90Zr10/Al75Zr25 multilayers

The thickness dependence of the magnetic properties of amorphous Fe90Zr10 layers has been explored using Fe90Zr10/Al75Zr25 multilayers. The Al75Zr25 layer thickness is kept at 40 \AA, while the thickness of the Fe90Zr10 layers is varied between 5 and 20 \AA. The thickness of the Al75Zr25 layers is sufficiently large to suppress any significant interlayer coupling. Both the Curie temperature and the spontaneous magnetization decrease non-linearly with decreasing thickness of the Fe90Zr10 layers. No ferromagnetic order is observed in the multilayer with 5 {\AA} Fe90Zr10 layers. The variation of the Curie temperature $T_c$ with the Fe90Zr10 layer thickness $t$ is fitted with a finite-size scaling formula [1-\Tc(t)/\Tc(\infty)]=[(t-t')/t_0]^{-\lambda}, yielding $\lambda=1.2$, and a critical thickness $t'=6.5$ \AA, below which the Curie temperature is zero.Comment: 8 pages, 8 figure

Ground-state phase diagram and magnetic properties of a tetramerized spin-1/2 J_1-J_2 model: BEC of bound magnons and absence of the transverse magnetization

We study the ground state and the magnetization process of a spin-1/2 $J_1$-$J_2$ model with a plaquette structure by using various methods. For small inter-plaquette interaction, this model is expected to have a spin-gap and we computed the first- and the second excitation energies. If the gap of the lowest excitation closes, the corresponding particle condenses to form magnetic orders. By analyzing the quintet gap and magnetic interactions among the quintet excitations, we find a spin-nematic phase around $J_1/J_2\sim -2$ due to the strong frustration and the quantum effect. When high magnetic moment is applied, not the spin-1 excitations but the spin-2 ones soften and dictate the magnetization process. We apply a mean-field approximation to the effective Hamiltonian to find three different types of phases (a conventional BEC phase, ``striped'' supersolid phases and a 1/2-plateau). Unlike the BEC in spin-dimer systems, this BEC phase is not accompanied by transverse magnetization. Possible connection to the recently discovered spin-gap compound (CuCl)LaNb2O7 is discussed.Comment: 18pages, 17figures; title changed, typos correcte

Influence of ion implantation on the magnetic and transport properties of manganite films

We have used oxygen ions irradiation to generate controlled structural disorder in thin manganite films. Conductive atomic force microscopy CAFM), transport and magnetic measurements were performed to analyze the influence of the implantation process in the physical properties of the films. CAFM images show regions with different conductivity values, probably due to the random distribution of point defect or inhomogeneous changes of the local Mn3+/4+ ratio to reduce lattice strains of the irradiated areas. The transport and magnetic properties of these systems are interpreted in this context. Metal-insulator transition can be described in the frame of a percolative model. Disorder increases the distance between conducting regions, lowering the observed TMI. Point defect disorder increases localization of the carriers due to increased disorder and locally enhanced strain field. Remarkably, even with the inhomogeneous nature of the samples, no sign of low field magnetoresistance was found. Point defect disorder decreases the system magnetization but doesn t seem to change the magnetic transition temperature. As a consequence, an important decoupling between the magnetic and the metal-insulator transition is found for ion irradiated films as opposed to the classical double exchange model scenario.Comment: 27 pages, 11 Figure

Phase diagram and isotope effect in (PrEu)_0.7Ca_0.3CoO_3 cobaltites exhibiting spin-state transitions

We present the study of magnetization, thermal expansion, specific heat, resistivity, and a.c. susceptibility of (Pr$_{1-y}$Eu$_y$)$_{0.7}$Ca$_{0.3}$CoO$_3$ cobaltites. The measurements were performed on ceramic samples with $y = 0.12 - 0.26$ and $y = 1$. Based on these results, we construct the phase diagram, including magnetic and spin-state transitions. The transition from the low- to intermediate-spin state is observed for the samples with $y > 0.18$, whereas for a lower Eu-doping level, there are no spin-state transitions, but a crossover between the ferromagnetic and paramagnetic states occurs. The effect of oxygen isotope substitution along with Eu doping on the magnetic/spin state is discussed. The oxygen-isotope substitution ($^{16}$O by $^{18}$O) is found to shift both the magnetic and spin-state phase boundaries to lower Eu concentrations. The isotope effect on the spin-state transition temperature ($y > 0.18$) is rather strong, but it is much weaker for the transition to a ferromagnetic state ($y < 0.18$). The ferromagnetic ordering in the low-Eu doped samples is shown to be promoted by the Co$^{4+}$ ions, which favor the formation of the intermediate-spin state of neighboring Co$^{3+}$ ions.Comment: 13 pages, including 11 figures, to be published in Phys. Rev.