Beacons of Peace and Tolerance: The Politics of Memory in Judeo-Moroccan Cultural and Historical Institutions

Bayt Dakira, a historical, religious, cultural, and academic institution located in the heart of Essaouira’s old medina, seeks to conserve Jewish-Moroccan memory and promote values of peace and tolerance as exemplified by the city’s history of Jewish-Muslim coexistence. As an institution dedicated to conserving the culture of a people that have all but virtually emigrated from Morocco, Bayt Dakira’s purpose is initially unclear. This study uncovers the ways in which Bayt Dakira is an example of a seemingly apolitical institution being wielded to advance national and international political agendas. As an officially apolitical place of cultural and academic exchange, Bayt Dakira is ideal for developing ties with other nations, building trust with them, and laying the groundwork for the formation of joint economic and political initiatives. As an apolitical-presenting institution advancing values of global peace, Bayt Dakira is also a non-threatening stage from which Moroccan diplomats can criticize, from a seemingly high moral ground, conflict abroad. Bayt Dakira’s celebration of Morocco’s diversity also constructs a national identity—one that unites all Moroccans under the Constitution and the King

Critical Temperature Tc and Charging Energy Ec between B-B layers of Superconducting diboride materials MgB2 in 3D JJA model

The diboride materials MB2 (M = Mg, Be, Pb, etc.) are discussed on the basis of the 3D Josephson junction array (JJA) model due to Kawabata-Shenoy-Bishop, in terms of the B-B layers in the diborides analogous to the Cu-O ones in the cuprates. We propose a possibility of superconducting materials with the MgB2-type structure which exhibit higher critical temperature Tc over 39K of MgB2. We point out a role of interstitial ionic atoms (e.g., Mg in MgB2) as capacitors between the B-B layers, which reduce the charging coupling energy in JJA.Comment: 3 pages, 1 figure included; to be published in J. Phys. Soc. Jpn. 70, No.10 (2001

Strongly interacting σ\sigma-electrons and MgB2_2 superconductivity

MgB$(p^{n_{\sigma}}p^{n_{\pi}})_{2}$ is classified as a system with strongly interacting $\sigma$-electrons and non-correlated $\pi$-electrons of boron ions. The kinematic and Coulomb interaction V between the orbitally degenerated $\sigma$-electrons provide the superconducting state with an anisotropic gap of s*-wave symmetry. The critical temperature $T_c$ has a non-monotonic dependence on the distance r between the centers of gravity of $\sigma$- and $\pi$-bands. MgB$_2$ corresponds to r=0.085 eV and V=0.45 eV in our model with flat bands. The derived superconducting density of electronic states is in good agreement with available experimental and theoretical data. The possibilities for increasing $T_c$ are discussed.Comment: 8 pages, 4 figure

Critical Temperature T_c versus Charging Energy E_c in MgB2 and C60/CHBr3

The boride compounds MB_x related to the magnesium-boron stacking layered material MgB2 are discussed in terms of the B-B layers in the borides analogous to the Cu-O ones in the cuprates. We propose a possibility of superconducting materials which exhibit higher critical temperature T_c than 39 K of MgB2. We point out a role of interstitial ionic atoms M (e.g., Mg in MgB2) as capacitors, which reduce the condensation-energy loss due to the charging energy E_c between the B-B layers. In the viewpoint of the present model, the recently discovered 117-Kelvin superconductor C60/CHBr3 is also discussed in terms of the intercalation molecules CHBr3 as possible capacitors among the superconducting grains of C60 molecules.Comment: 9 pages, 1 fugure included; prepared for Proceedings of the symposium ISS2001, Kobe, Sep. 200

The complex superstructure in Mg1-xAlxB2 at x~0.5

Electron diffraction and high resolution microscopy have been performed on Mg1-xAlxB2 with x~0.5. This composition displays a superstructure with a repeat period of exactly 2c along the c axis and about 10 nm in the a-b plane. The superstructure results in ring-shaped superreflections in the diffraction pattern. Irradiation by a strong electron beam results in a loss of the superstructure and a decrease of about 1% in the c lattice parameter. In-situ heating and cooling on the other hand showed that the superstructure is stable from 100 K to 700 K. Possible origins for the superstructure are proposed

Structural barriers to HIV prevention among men who have sex with men (MSM) in Vietnam: Diversity, stigma, and healthcare access

Men who have sex with men (MSM) in Vietnam experience disproportionate rates of HIV infection. To advance understanding of how structural barriers may shape their engagement with HIV prevention services, we draw on 32 in-depth interviews and four focus groups (n = 31) conducted with MSM in Hanoi between October 2015- March 2016. Three primary factors emerged: (1) Diversity, both in relation to identity and income; Vietnamese MSM described themselves as segregated into Bóng kín (hidden, often heterosexually-identified MSM) and Bóng lộ (‘out,’ transgender, or effeminate MSM). Lower-income, ‘hidden’ MSM from rural areas were reluctant to access MSM-targeted services; (2) Stigma: MSM reported being stigmatized by the healthcare system, family, and other MSM; and (3) Healthcare access: this was limited due to economic barriers and lack of MSM-friendly services. Our research suggests the need for multiple strategies to reach diverse types of MSM as well as to address barriers in access to health services such as stigma and costs. While a great deal has been written about the diversity of MSM in relation to gender performance and sexual identities, our research points to the substantial structural-level barriers that must be addressed in order to achieve meaningful and effective HIV prevention for MSM worldwide

Implications of reflectance measurements on the mechanism for superconductivity in MgB2_2

Recent optical studies in c-axis oriented superconducting MgB$_2$ films indicate that the electron-phonon coupling is weak [tu01]. We reinforce this conclusion by examining the raw reflectance data; its frequency dependence is incompatible with strong electron-phonon scattering. This is further strengthened by analysis of the real part of the conductivity, and by the temperature dependence of the effective Drude scattering rate. Using a realistic electron-phonon spectral shape [kong01], we find $\lambda_{\rm tr} \approx 0.15$, in agreement with Tu et al. [tu01]. To the extent that $\lambda_{\rm tr} \approx \lambda$, this disagrees sharply with model calculations [kong01,kortus01,an01], and is far too low to provide the means for $T_c = 39$ K. A simple model is constructed with coupling to a high frequency excitation, which is consistent with both the low frequency optical data and the high $T_c$.Comment: 4 pages, 4 figure

Representation of Markov chains by random maps: existence and regularity conditions

We systematically investigate the problem of representing Markov chains by families of random maps, and which regularity of these maps can be achieved depending on the properties of the probability measures. Our key idea is to use techniques from optimal transport to select optimal such maps. Optimal transport theory also tells us how convexity properties of the supports of the measures translate into regularity properties of the maps via Legendre transforms. Thus, from this scheme, we cannot only deduce the representation by measurable random maps, but we can also obtain conditions for the representation by continuous random maps. Finally, we present conditions for the representation of Markov chain by random diffeomorphisms.Comment: 22 pages, several changes from the previous version including extended discussion of many detail

Surface effects in multiband superconductors. Application to MgB2_2

Metals with many bands at the Fermi level can have different band dependent gaps in the superconducting state. The absence of translational symmetry at an interface can induce interband scattering and modify the superconducting properties. We dicuss the relevance of these effects to recent experiments in MgB$_2$

Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB_2 and the isostructural AlB_2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions \alpha^2F are calculated for both systems. We also report on Raman measurements, which support the theoretical findings. The calculated generalized density-of-states for MgB_2 is in excellent agreement with recent neutron-scattering experiments. The main differences in the calculated phonon spectra and \alpha^2F are related to high frequency in-plane boron vibrations. As compared to AlB_2, they are strongly softened in MgB_2 and exhibit an exceptionally strong coupling to electronic states at the Fermi energy. The total coupling constants are \lambda_{MgB_2}=0.73 and \lambda_{AlB_2}=0.43. Implications for the superconducting transition temperature are briefly discussed.Comment: 10 pages, 4 figures, to appear in Phys. Rev. Let