On the sigma-model of deformed special geometry

We discuss the deformed sigma-model that arises when considering four-dimensional N=2$N=2$ abelian vector multiplets in the presence of an arbitrary chiral background field. In addition, we allow for a class of deformations of special geometry by non-holomorphic terms. We analyze the geometry of the sigma-model in terms of intrinsic torsion classes. We show that, generically, the deformed geometry is non-Kähler. We illustrate our findings with an example. We also express the deformed sigma-model in terms of the Hesse potential that underlies the real formulation of special geometry.     

Advances in bonding and properties of inorganic systems from relativistic calculations in Latin America

The inclusion of relativistic effects to understand chemical structures and related properties brings to the scientific community challenging study cases, showing the rich diversity of chemical behavior of the different elements along the periodic table. The results highlighted here represent applications of relativistic methodologies to study the nature of bonding and a prediction of optical and magnetic properties of meaningful chemical entities containing heavy atoms, all made in Latin America. The good agreement between calculated and experimental observables in many molecular and cluster-like systems ratifies that relativistic methods are appropriate to describe these entities realistically. We expect to enhance our knowledge in these methodologies, currently included in doctoral programs in our region.     

Aromatic character of Oh-C24N24. A cavernous nitride fullerene bearing N4-macrocycle motifs

Spherical fullerenes offer noteworthy structures usually involving six- and five-membered faces, with application in technological issues. In this sense, cavernous spherical-like structures bearing larger holes provide interesting examples for further understanding of structure-properties relationship. Here, we explored the magnetic response of a proposed cavernous nitride fullerene, C₂₄N₂₄, which has a O_h-symmetry with six N₄-macrocyclic and eight 1,3,5-triazine faces displaying 48-π electrons. C₂₄N₂₄ exhibits a local aromatic behavior owing to the contrasting antiaromatic response of the N₄-macrocyclic faces and the aromatic character of the 1,3,5-triazine faces. Thus, the overall structure is ascribed as a local aromatic species, where the triazine faces exhibit the characteristic shielding cone for aromatic rings. Furthermore, the constructive combination of local shielding cones in C₂₄N₂₄ delivers a related shielding-cone response, as expected for a perfect aromatic cage. Hence, the local aromatic/nonaromatic/antiaromatic sections exhibit an additive or subtractive interaction, leading to a characteristic response inherent to the nature of the spherical cage. We expect that further study of the interplay between different aromatic and antiaromatic faces in fullerene-like cages can deliver interesting pseudo-aromatic or pseudo-antiaromatic spherical species.     

Modulating Polymer Dispersity with Light: Cationic Polymerization of Vinyl Ethers Using Photochromic Initiators

Deterministic methods for tuning polymer dispersity are rare, especially for nonradical polymerizations. Reported here is the first example of photomodulating dispersity in controlled cationic polymerizations of vinyl ethers using carboxy‐functionalized dithienylethene initiators. Reversible photoisomerization of these initiators induces changes in their acidities by up to an order of magnitude. Using the more acidic, ring‐closed isomers as initiators results in polymers with lower dispersities. The degree of light‐induced pK_a change in the initiators correlates with the degree of dispersity change in polymers derived from the isomeric initiators. The polymerizations are controlled, and dynamic photoswitching of dispersity during the polymerization reaction was demonstrated. This work provides a framework for photomodulating dispersity in other controlled polymerizations and developing one‐pot block copolymerization reactions in which the dispersities of component blocks can be controlled using light.     

Long‐Term Photostability in Terephthalate Metal–Organic Frameworks

Prolonged (weeks) UV/Vis irradiation under Ar of UiO‐66(Zr), UiO66 Zr‐NO₂, MIL101 Fe, MIL125 Ti‐NH₂, MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD‐containing MOFs, zeolitic imidazolate ZIF‐8 does not evolve CO₂ or any other gas upon irradiation.     

[Nb@Ge13/14]3−: New Family Members of Ge-Based Intermetalloid Clusters

During the past two decades, single-atom-centered medium-sized germanium clusters [M@Ge_n] (M=transition metals, n>12) have been extensively explored, both from theoretical perspectives and experimental gas-phase syntheses. However, the actual structural arrangements of the Ge₁₃ and Ge₁₄ endohedral cages are still ambiguous and have long remained an unresolved problem for experimental implementation. In this work, we successfully synthesize 13-/14-vertex Ge clusters [Nb@Ge₁₃]³⁻ ( 1 ) and [Nb@Ge₁₄]³⁻ ( 2 ), which are structurally characterized and exhibit unprecedented topologies, neither classical deltahedra nor 3-connected polyhedral structures. Theoretical analysis indicates that the major stabilization of the Ge backbones arises due to the substantial interaction of Ge 4p-AOs with the endohedral Nb 4d-AOs through three/four-center two-electron bonds with an enhanced electron density accumulated over the shortest Nb−Ge13 contact in 1 . Low occupancies of the direct two-center two-electron (2c–2e) Nb−Ge and Ge−Ge σ bonds point to a considerable degree of electron delocalization over the Ge cages revealing their electron deficiency.     

Comparative bioavailability of two zolpidem hemitartrate formulations in healthy human Brazilian volunteers using high-performance liquid chromatography coupled to tandem mass spectrometry

To assess the bioequivalence of two zolpidem hemitartrate formulations in 30 healthy volunteers. Plasma samples were obtained over a 24 h period. Plasma concentrations of zolpidem were analyzed by liquid chromatography coupled to tandem mass spectrometry with positive ion electrospray ionization using multiple reaction monitoring. Values of peak concentration (C_max), area under curve (AUC), half-life, elimination constant, volume of distribution and clearance showed statistically significant differences when comparing women (604.34 ng h/ml, 127.36 ng/ml, 4.4 h, 0.18 1/h, 50.56 L and 8.55 L/h, respectively) and men (276.1 ng h/ml, 70.9 ng/ml, 3.3 h, 0.26 1/h, 91.42 L and 24.34 L/h, respectively), receiving the same dose (5 mg), respectively. The geometric means with corresponding 90% confidence interval for Test/Reference percentage ratios were 99.73% (CI 93.69–106.16) for C_max, 97.44% (90% CI = 91.85–103.37%) for area under curve of plasma concentration until the last concentration observed (AUC_last) and 98.30% (90% CI = 92.48–104.49) for the area under curve between the first sample (pre-dosage) and infinity (AUC_0–inf). Since the 90% CI for AUC_last, AUC_0–inf and C_max ratios were within the 80–125% interval proposed by the US Food and Drug Administration, it was concluded that zolpidem hemitartrate formulation (5 mg orodispersible tablet) is bioequivalent to the zolpidem hemitartrate formulation (Patz SL 5 mg sublingual tablet) with regard to both the rate and the extent of absorption. A new formulation of zolpidem 2.5 mg may be useful in women for the same clinical benefits as the 5 mg formulation in men.     

Monotonic models and cycles

A partitional model of knowledge is monotonic if there exists a linear order on the state space such that, for every player, each element of her partition contains only a sequence of consecutive states. In monotonic models, the absence of alternating cycles is equivalent to the property that, for every pair of players, the join of their partitions contains only singletons. Under these equivalent conditions any set of posteriors for the players is consistent (i.e., there is a common prior). When checking for consistency in a monotonic model, it is not necessary to evaluate all cycle equations; if the cycle equations corresponding to cycles of length two hold, then there is a common prior.     

Impact of tetrahedralization on parallel conforming octree mesh generation

This work discusses the performance impact from the tetrahedralization of non‐conforming meshes generated by a parallel octree method capable of handling arbitrary immersed geometries. First, we review conforming techniques for meshes created from octrees. Then we implement a tetrahedralization scheme based on templates in a parallel meshing algorithm that uses a linear octree with 2:1 balancing constraint. Besides, we also propose a change on the partitioning strategy for the same meshing algorithm to improve the octree refinement load balancing. Scalability analyses show that the chosen tetrahedralization technique preserves algorithm performance. Copyright © 2014 John Wiley & Sons, Ltd.