Self-adjoint symmetry operators connected with the magnetic Heisenberg ring

We consider symmetry operators a from the group ring C[S_N] which act on the Hilbert space H of the 1D spin-1/2 Heisenberg magnetic ring with N sites. We investigate such symmetry operators a which are self-adjoint (in a sence defined in the paper) and which yield consequently observables of the Heisenberg model. We prove the following results: (i) One can construct a self-adjoint idempotent symmetry operator from every irreducible character of every subgroup of S_N. This leads to a big manifold of observables. In particular every commutation symmetry yields such an idempotent. (ii) The set of all generating idempotents of a minimal right ideal R of C[S_N] contains one and only one idempotent which ist self-adjoint. (iii) Every self-adjoint idempotent e can be decomposed into primitive idempotents e = f_1 + ... + f_k which are also self-adjoint and pairwise orthogonal. We give a computer algorithm for the calculation of such decompositions. Furthermore we present 3 additional algorithms which are helpful for the calculation of self-adjoint operators by means of discrete Fourier transforms of S_N. In our investigations we use computer calculations by means of our Mathematica packages PERMS and HRing.Comment: 13 page

The structure of algebraic covariant derivative curvature tensors

We use the Nash embedding theorem to construct generators for the space of algebraic covariant derivative curvature tensors

Synchronization Properties of Network Motifs

We address the problem of understanding the variable abundance of 3-node and 4-node subgraphs (motifs) in complex networks from a dynamical point of view. As a criterion in the determination of the functional significance of a n-node subgraph, we propose an analytic method to measure the stability of the synchronous state (SSS) the subgraph displays. We show that, for undirected graphs, the SSS is correlated with the relative abundance, while in directed graphs the correlation exists only for some specific motifs.Comment: 7 pages, 3 figure

The ROCK inhibitor Fasudil prevents chronic restraint stress-induced depressive-like behaviors and dendritic spine loss in rat hippocampus

Indexación: Web of Science; Scopus.Background: Dendritic arbor simplification and dendritic spine loss in the hippocampus, a limbic structure implicated in mood disorders, are assumed to contribute to symptoms of depression. These morphological changes imply modifications in dendritic cytoskeleton. Rho GTPases are regulators of actin dynamics through their effector Rho kinase. We have reported that chronic stress promotes depressive-like behaviors in rats along with dendritic spine loss in apical dendrites of hippocampal pyramidal neurons, changes associated with Rho kinase activation. The present study proposes that the Rho kinase inhibitor Fasudil may prevent the stress-induced behavior and dendritic spine loss. Methods: Adult male Sprague-Dawley rats were injected with saline or Fasudil (i.p., 10 mg/kg) starting 4 days prior to and maintained during the restraint stress procedure (2.5 h/d for 14 days). Nonstressed control animals were injected with saline or Fasudil for 18 days. At 24 hours after treatment, forced swimming test, Golgi-staining, and immuno-western blot were performed. Results: Fasudil prevented stress-induced immobility observed in the forced swimming test. On the other hand, Fasudiltreated control animals showed behavioral patterns similar to those of saline-treated controls. Furthermore, we observed that stress induced an increase in the phosphorylation of MYPT1 in the hippocampus, an exclusive target of Rho kinase. This change was accompanied by dendritic spine loss of apical dendrites of pyramidal hippocampal neurons. Interestingly, increased pMYPT1 levels and spine loss were both prevented by Fasudil administration. Conclusion: Our findings suggest that Fasudil may prevent the development of abnormal behavior and spine loss induced by chronic stress by blocking Rho kinase activity.https://academic.oup.com/ijnp/article/20/4/336/263217

Synthetic, Spectroscopic and DFT Studies of Iron Complexes with Iminobenzo(semi)quinone Ligands: Implications for o-Aminophenol Dioxygenases

The oxidative CC bond cleavage of o-aminophenols by nonheme Fe dioxygenases is a critical step in both human metabolism (the kynurenine pathway) and the microbial degradation of nitroaromatic pollutants. The catalytic cycle of o-aminophenol dioxygenases (APDOs) has been proposed to involve formation of an FeII/O2/iminobenzosemiquinone complex, although the presence of a substrate radical has been called into question by studies of related ring-cleaving dioxygenases. Recently, we reported the first synthesis of an iron(II) complex coordinated to an iminobenzosemiquinone (ISQ) ligand, namely, [Fe(Tp)(tBuISQ)] (2 a; where Tp=hydrotris(3,5-diphenylpyrazol-1-yl)borate and tBuISQ is the radical anion derived from 2-amino-4,6-di-tert-butylphenol). In the current manuscript, density functional theory (DFT) calculations and a wide variety of spectroscopic methods (electronic absorption, Mössbauer, magnetic circular dichroism, and resonance Raman) were employed to obtain detailed electronic-structure descriptions of 2 a and its one-electron oxidized derivative [3 a]+. In addition, we describe the synthesis and characterization of a parallel series of complexes featuring the neutral supporting ligand tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (TIP). The isomer shifts of about 0.97 mm s−1 obtained through Mössbauer experiments confirm that 2 a (and its TIP-based analogue [2 b]+) contain FeII centers, and the presence of an ISQ radical was verified by analysis of the absorption spectra in light of time-dependent DFT calculations. The collective spectroscopic data indicate that one-electron oxidation of the FeII–ISQ complexes yields complexes ([3 a]+ and [3 b]2+) with electronic configurations between the FeIII–ISQ and FeII–IBQ limits (IBQ=iminobenzoquinone), highlighting the ability of o-amidophenolates to access multiple oxidation states. The implications of these results for the mechanism of APDOs and other ring-cleaving dioxygenases are discussed

Structural Examination of Au/Ge(001) by Surface X-Ray Diffraction and Scanning Tunneling Microscopy

The one-dimensional reconstruction of Au/Ge(001) was investigated by means of autocorrelation functions from surface x-ray diffraction (SXRD) and scanning tunneling microscopy (STM). Interatomic distances found in the SXRD-Patterson map are substantiated by results from STM. The Au coverage, recently determined to be 3/4 of a monolayer of gold, together with SXRD leads to three non-equivalent positions for Au within the c(8x2) unit cell. Combined with structural information from STM topography and line profiling, two building blocks are identified: Au-Ge hetero-dimers within the top wire architecture and Au homo-dimers within the trenches. The incorporation of both components is discussed using density functional theory and model based Patterson maps by substituting Germanium atoms of the reconstructed Ge(001) surface.Comment: 5 pages, 3 figure

Subtropical dust storms and downslope wind events

We performed detailed mesoscale observational analyses and Weather Research and Forecasting (WRF) model simulations to study the terrain-induced downslope winds that generated dust-emitting winds at the beginning of three strong subtropical dust storms in three distinctly different regions of North Africa and the Arabian Peninsula. We revisit the Harmattan dust storm of 2 March 2004, the Saudi dust storm of 9 March 2009, and the Bodélé Depression dust storm of 8 December 2011 and use high-resolution WRF modeling to assess the dynamical processes during the onset of the storms in more depth. Our results highlight the generation of terrain-induced downslope winds in response to the transition of the atmospheric flow from a subcritical to supercritical state in all three cases. These events precede the unbalanced adjustment processes in the lee of the mountain ranges that produced larger-scale dust aerosol mobilization and transport. We see that only the higher-resolution data sets can resolve the mesoscale processes, which are mainly responsible for creating strong low-level terrain-induced downslope winds leading to the initial dust storms. ©2017. The Authors

Past Perceptions, Present Usage: Latinx Students and Academic Libraries

Over the last two decades, the population of Latinx students enrolled in higher education has increased by 142%, but they are still underrepresented overall. According to 2015 United States census data, only 16% of Hispanic adults have a Bachelor’s degree or higher compared to 54% of Asian Americans, 36% of (non-Hispanic) white people, and 23% of Black people. The needs of Latinx students in higher education are obviously not being met. Academic libraries have long seen themselves as integral to student success, but there is little research about how they are (or are not) serving Latinx students specifically. The IFLA/UNESCO Multicultural Library Manifesto states that “as libraries serve diverse interests and communities, they function as learning, cultural, and information centers,” and called for all library types to “reflect, support and promote cultural and linguistic diversity.