Escuchar a los objetos

This experimental section includes some parts of the performative event “The materiality of transformations: Listening to objects”, which closed the 14th SIEF conference held in Santiago de Compostela in 2019. Barbara Kirshenblatt-Gimblett, Regina Bendix, Dorothy Noyes, Sharon Roseman and Francisco Cruces conversed on stage about the cultural meanings of a selection of personal objects. By unveiling the stories contained in mezuzahs, hair, a serving platter and a shawl, they put the methodological power of the object/story couplet to the test. The benefits of articulating narrativity with materiality; the silent power of things in everyday life; the embedded character of storytelling, and some of its affective, moral and celebratory virtues were highlighted. The final event can be seen at <https://vimeo.com/362078953> from minute 00:52:50 to 01:31:00.Esta sección experimental incluye algunas partes del evento performativo “La materialidad de las transformaciones: escuchar a los objetos”, que clausuró el XIV congreso de SIEF celebrado en Santiago de Compostela en 2019. Barbara Kirshenblatt-Gimblett, Regina Bendix, Dorothy Noyes, Sharon Roseman y Francisco Cruces conversaron sobre los significados culturales de una selección de objetos personales. Al desvelar las historias contenidas en mezuzahs, cabello, una fuente o un chal, se puso a prueba el poder metodológico del par objeto / historia, los beneficios de articular la narratividad con la materialidad y el silencioso poder de las cosas en la vida cotidiana. Se destacó el carácter incorporado de la narración y algunas de sus virtudes afectivas, morales y celebratorias. Este evento performativo se puede ver en <https://vimeo.com/362078953> from minute 00:52:50 to 01:31:00

Radical cation salts of TTF donors with XF6 (X = Re,Ta) anions

Electrocrystallization of the dianionic Re(IV)F6 species with different organic π electron donors was carried out. Depending on the first oxidation potential of the TTF derivatives this crystallization technique gave rise to various radical cations salts involving Re(IV) or Re(V) anions. With tetramethyltetrathiafulvalene (TMTTF) the (TMTTF)2Re(IV)F6  salt was obtained. However, with tetramethyltetraselenafulvalene (TMTSF) we obtained very small needles of the (TMTSeF)2Re(V)F6 system, analogue to the so called “Bechgaard salts” [1]. We present some characteristics of this new metallic phase. We compare to the diamagnetic (TMTSeF)2Ta(V)F6 obtained by the same strategy using TBATaF6 prepared according to the Browstein’s method [2] and explore electrocrystallization of the tantalum based anions [3], [4]. References: [1] K. Bechgaard, C.S. Jacobsen, K. Mortensen, H.J. Pedersen, N. Thorup, Solid State Commun. 1980, 33, 1119-1125. [2] S. Brownstein, Inorg. Chem. 1973, 12, N°3, 584-589. [3] C. Lenoir, K. Boubekeur, P. Batail, E. Canadell, P. Auban, O. Traetteberg, D. Jérome, Synth. Met. 1991, 42, 1939-1942. [4] F. Iwase, K. Sugiura, K. Furukawa, T. Nakamura, J. Phys. Soc. Jpn. 2009, 78, N°10, 104717:1-104717:7

Terminal Ligand and Packing Effects on Slow Relaxation in an Isostructural Set of [Dy(H2_{2}dapp)X2_{2}]+ Single Molecule Magnets**

Three new dysprosium complexes with a pentadentate ligand occupying five equatorial sites differ only in the nature of the axial ligands. These help tune the relaxation properties as judged by an analysis of the AC susceptibility data. More in depth analysis by using two recently suggested fitting equations lead to similar outcomes for all three systems. As a further contribution to the relaxation pathway involving the phonon bath it is concluded that a short nitrate-nitrate interaction between molecules helps dampen the spin phonon coupling. We report three structurally related single ion Dy compounds using the pentadentate ligand 2,6-bis((E)-1-(2-(pyridin-2-yl)-hydrazineylidene)ethyl)pyridine (H$_{2}$dapp) [Dy(H$_{2}$dapp)(NO$_{3}$)$_{2}$]NO$_{3}$ (1), [Dy(H$_{2}$dapp)(OAc)$_{2}$]Cl (2) and [Dy(H$_{2}$dapp)(NO$_{3}$)$_{2}$]Cl$_{0.92}$(NO$_{3}$)$_{0.08}$ (3). The (H$_{2}$dapp) occupies a helical twisted pentagonal equatorial arrangement with two anionic ligands in the axial positions. Further influence on the electronic and magnetic structure is provided by a closely associated counterion interacting with the central N−H group of the (H$_{2}$dapp). The slow relaxation of the magnetisation shows that the anionic acetates give the greatest slowing down of the magnetisation reversal. Further influence on the relaxation properties of compounds1 and 2 is the presence of short nitrate-nitrate intermolecular ligand contact opening further lattice relaxation pathways

Structure formation in active networks

Structure formation and constant reorganization of the actin cytoskeleton are key requirements for the function of living cells. Here we show that a minimal reconstituted system consisting of actin filaments, crosslinking molecules and molecular-motor filaments exhibits a generic mechanism of structure formation, characterized by a broad distribution of cluster sizes. We demonstrate that the growth of the structures depends on the intricate balance between crosslinker-induced stabilization and simultaneous destabilization by molecular motors, a mechanism analogous to nucleation and growth in passive systems. We also show that the intricate interplay between force generation, coarsening and connectivity is responsible for the highly dynamic process of structure formation in this heterogeneous active gel, and that these competing mechanisms result in anomalous transport, reminiscent of intracellular dynamics

Ferromagnetism in Co7(TeO3)4Br6: A byproduct of complex antiferromagnetic order and single-ion anisotropy

Pronounced anisotropy of magnetic properties and complex magnetic order of a new oxi-halide compound Co7(TeO3)4Br6 has been investigated by powder and single crystal neutron diffraction, magnetization and ac susceptibility techniques. Anisotropy of susceptibility extends far into the paramagnetic temperature range. A principal source of anisotropy are anisotropic properties of the involved octahedrally coordinated single Co(2+) ions, as confirmed by angular-overlap-model calculations presented in this work. Incommensurate antiferromagnetic order sets in at TN=34 K. Propagation vector is strongly temperature dependent reaching k1=(0.9458(6), 0, 0.6026(5)) at 30 K. A transition to a ferrimagnetic structure with k2=0 takes place at TC=27 K. Magnetically ordered phase is characterized by very unusual anisotropy as well: while M-H scans along b-axis reveals spectacularly rectangular but otherwise standard ferromagnetic hysteresis loops, M-H studies along other two principal axes are perfectly reversible, revealing very sharp spin flop (or spin flip) transitions, like in a standard antiferromagnet (or metamagnet). Altogether, the observed magnetic phenomenology is interpreted as an evidence of competing magnetic interactions permeating the system, first of all of the single ion anisotropy energy and the exchange interactions. Different coordinations of the Co(2+)-ions involved in the low-symmetry C2/c structure of Co7(TeO3)4Br6 render the exchange-interaction network very complex by itself. Temperature dependent changes in the magnetic structure, together with an abrupt emergence of a ferromagnetic component, are ascribed to continual spin reorientations described by a multi-component, but yet unknown, spin Hamiltonian.Comment: 12 pages, 13 figures; submitted to PR

Model parameterization to simulate and compare the PAR absorption potential of two competing plant species

Mountain pastures dominated by the pasture grass Setaria sphacelata in the Andes of southern Ecuador are heavily infested by southern bracken (Pteridium arachnoideum), a major problem for pasture management. Field observations suggest that bracken might outcompete the grass due to its competitive strength with regard to the absorption of photosynthetically active radiation (PAR). To understand the PAR absorption potential of both species, the aims of the current paper are to (1) parameterize a radiation scheme of a two-big-leaf model by deriving structural (LAI, leaf angle parameter) and optical (leaf albedo, transmittance) plant traits for average individuals from field surveys, (2) to initialize the properly parameterized radiation scheme with realistic global irradiation conditions of the Rio San Francisco Valley in the Andes of southern Ecuador, and (3) to compare the PAR absorption capabilities of both species under typical local weather conditions. Field data show that bracken reveals a slightly higher average leaf area index (LAI) and more horizontally oriented leaves in comparison to Setaria. Spectrometer measurements reveal that bracken and Setaria are characterized by a similar average leaf absorptance. Simulations with the average diurnal course of incoming solar radiation (1998–2005) and the mean leaf–sun geometry reveal that PAR absorption is fairly equal for both species. However, the comparison of typical clear and overcast days show that two parameters, (1) the relation of incoming diffuse and direct irradiance, and (2) the leaf–sun geometry play a major role for PAR absorption in the two-big-leaf approach: Under cloudy sky conditions (mainly diffuse irradiance), PAR absorption is slightly higher for Setaria while under clear sky conditions (mainly direct irradiance), the average bracken individual is characterized by a higher PAR absorption potential. (∼74 MJ m−2 year−1). The latter situation which occurs if the maximum daily irradiance exceeds 615 W m−2 is mainly due to the nearly orthogonal incidence of the direct solar beam onto the horizontally oriented frond area which implies a high amount of direct PAR absorption during the noon maximum of direct irradiance. Such situations of solar irradiance favoring a higher PAR absorptance of bracken occur in ∼36% of the observation period (1998–2005). By considering the annual course of PAR irradiance in the San Francisco Valley, the clear advantage of bracken on clear days (36% of all days) is completely compensated by the slight but more frequent advantage of Setaria under overcast conditions (64% of all days). This means that neither bracken nor Setaria show a distinct advantage in PAR absorption capability under the current climatic conditions of the study area

Regulatory T cells ameliorate intrauterine growth retardation in a transgenic rat model for preeclampsia

Preeclampsia is a multisystemic syndrome during pregnancy that is often associated with intrauterine growth retardation. Immunologic dysregulation, involving T cells, is implicated in the pathogenesis. The aim of this study was to evaluate the effect of upregulating regulatory T cells in an established transgenic rat model for preeclampsia. Application of superagonistic monoclonal antibody for CD28 has been shown to effectively upregulate regulatory T cells. In the first protocol (treatment protocol), we applied 1 mg of CD28 superagonist or control antibody on days 11 and 15 of pregnancy. In the second protocol (prevention protocol), the superagonist or control antibody was applied on days 1, 5, and 9. Superagonist increased regulatory T cells in circulation and placenta from 8.49+/-2.09% of CD4-positive T cells to 23.50+/-3.05% and from 3.85+/-1.45% to 23.27+/-7.64%, respectively. Blood pressure and albuminuria (30.6+/-15.1 versus 14.6+/-5.5 mg/d) were similar in the superagonist or control antibody-treated preeclamptic group for both protocols. Rats treated with CD28 superagonist showed increased pup weights in the prevention protocol (2.66+/-0.03 versus 2.37+/-0.05 g) and in the treatment protocol (3.04+/-0.04 versus 2.54+/-0.1 g). Intrauterine growth retardation, calculated by brain:liver weight ratio, was also decreased by the superagonist in both protocols. Further analysis of brain development revealed a 20% increase in brain volume by the superagonist. Induction of regulatory T cells in the circulation and the uteroplacental unit in an established preeclamptic rat model had no influence on maternal hypertension and proteinuria. However, it substantially improved fetal outcome by ameliorating intrauterine growth retardation

Security sector reform in Africa: donor approaches versus local needs

Many African states have security sector reform (SSR) programs. These are often internationally funded. But how do such programs account for previously existing security institutions and the security needs of local communities? This article examines SSR all over Africa to assess local ownership and path dependency from a New Institutionalist perspective. It finds that SSR, particularly in post-conflict countries, tends to be driven by ideas and perceptions of international donors promoting generalized blueprints. Often, such programs only account in a very limited way for path-dependent aspects of security institutions or the local context. Hence the reforms often lack local participation and are thus not accepted by the local community eventually