CuII chain compound showing a ferromagnetic coupling through triple N1,N2-1,2,4-triazole bridges

[Cu(hyetrz)3](CF3SO3)2·H2O [hyetrz = 4-(2′-hydroxyethyl)-1,2,4-triazole] represents the first structurally characterised ferromagnetically coupled CuII chain compound containing triple N1,N2-1,2,4-triazole bridges. catena-[μ-Tris{4-(2′-hydroxyethyl)-1,2,4-triazole-N1,N2}copper(II)] bis(trifluoromethanesulfonate) hydrate (C14H23F6S2O10CuN9) crystallises in the triclinic space group Pl, a = 13.54(3), b = 14.37(3), c = 15.61(4) Å, α = 95.9(1), β = 104.9(1), γ = 106.5(1)°, V = 2763(11) Å3, Z = 4 (CuII units). The CuII ions are linked by triple N1,N2-1,2,4-triazole bridges yielding an alternating chain with Cu1−Cu2 = 3.8842(4) Å and Cu2−Cu3 = 3.9354(4) Å. Analysis of the magnetic data according to a high-temperature series expansion gives a J value of +1.45(3) cm−1. The nature and the magnitude of the ferromagnetic exchange have been discussed on the basis of the structural features. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Crystal structure of [{Cu(H2O)(en)2}{Cu(en)2}Re6Te8(CN)6]·3H2O

The reaction of Cs4[Re6Te8(CN)6]·2H2O with Cu(en)2Cl2 in water affords crystals of a cluster complex [{Cu(H2O)(en) 2}{Cu(en)2}Re6Te8(CN)6]·3H2O. The structure of the compound is determined by single crystal X-ray diffraction (a = 10.8082(4) Å, b = 16.5404(6) Å, c = 24.6480(7) Å, β = 92.696(1)°, V = 4401.5(3) Å3, Z = 4, space group P21/n, R 1 = 0.0331, wR 2 (all data) = 0.0652). In the complex, cluster [Re6Te8(CN)6]4- anions are linked by Cu2+ cations into zigzag chains through cyanide bridges. The coordination environment of the copper cations is complemented by ethylenediamine molecules. Each of the cluster anions is additionally coordinated by a terminal fragment {Cu(H2O)(en)2}. © 2014 Pleiades Publishing, Ltd.

Estudo sobre a relação entre a atividade geomagnética e cintilações de sinais de GPS em Natal-RN (Brasil)

To identify the relationship between GPS scintillation in Natal-RN (Brazil) and geomagnetic disturbances of any intensities and variations, this work made analysis of the ionospheric behavior and magnetic indexes (Dst , AE and Bz of the interplanetary magnetic field) concerning to different periods of the solar cycle between 2000 and 2014. Part of the data of this research originated at the UFRN observatory, from a GEC Plessey board connected to an ANP -C 114 antenna, modified by Cornell University’s Space group Plasma Physics in order to operate the ScintMon, a GPS monitoring program. This study, therefore, found several cases of inhibited scintillations after the main phase of magnetic storms, a fact that, along with others, corroborated with categorization of Aarons (1991) and models of disturbed dynamo (according to Bonelli, 2008) and over-shielding penetration, defended by Kelley et al. (1979) and Abdu (2011) [4]. In addition to these findings, different morphologies were noted in such disruptions in the GPS signal in accordance with previous magnetic activities. It also found a moderate relationship (R2 = 0.52) between the Dst rate (concerning to specific time) and the average of S4 through a polynomial function. This finding therefore, corroborating Ilma et al. (2012) [17], is an important evidence that the scintillation GPS are not directly controlled by magnetic induction of storms. Completing this work, this relation did show itself as a way of partial predicting of scintillations.

Methyl tetra-O-acetyl-α-d-glucopyranuronate: crystal structure and influence on the crystallisation of the β anomer

Methyl tetra-O-acetyl-β-d-glucopyranuronate (1) and methyl tetra-O-acetyl-α-d-glucopyranuronate (3) were isolated as crystalline solids and their crystal structures were obtained. That of the β anomer (1) was the same as that reported by Root et al., while anomer (3) was found to crystallise in the orthorhombic space group P212121 with two independent molecules in the asymmetric unit. No other crystal forms were found for either compound upon recrystallisation from a range of solvents. The α anomer (3) was found to be an impurity in initially precipitated batches of β-anomer (1) in quantities <3%; however, it was possible to remove the α impurity either by recrystallisation or by efficient washing, i.e. the α anomer is not incorporated inside the β anomer crystals. The β anomer (1) was found to grow as prisms or needles elongated in the a crystallographic direction in the absence of the α impurity, while the presence of the α anomer (3) enhanced this elongation.

Síntese e caracterização de ligantes oximas e tiossemicarbazonas e seus complexos

Este trabalho apresenta a síntese e caracterização de cinco ligantes e quatro complexos derivados de oximas e tiossemicarbazonas. Entre essas, discutem-se as estruturas cristalinas/moleculares determinadas por difração de raios-X em monocristais: do ligante 4-feniltiossemicarbazida-isatina (Ligante 5), do complexo piridina-salicilaldeído-4- feniltiossemicarbazona de niquel (II) (Complexo 1), e do bis-4-feniltiossemicarbazonaisatina de chumbo(II) (Complexo 2). A estrutura do Ligante 5 cristaliza no sistema monoclínico, grupo espacial P21/c, com parâmetros de cela a = 6,3227(2) Å, b = 15,7973(7) Å, c = 14,4572(6) Å, β = 93,9330(10)°, V = 1440,61(10) Å3 , Z = 4. O refinamento da estrutura convergiu aos índices de discordância finais R1 = 0,0520, wR2 = 0,1471. Observa-se ainda a ocorrência de interações intermoleculares do tipo ligações de hidrogênio clássicas [N18−H3---O1′ 2,907(2)Å], com a formação de estruturas dímeras inter-relacionadas por simetria dentro da cela cristalina. Para a estrutura cristalina do Complexo 1, observa-se NC=4, e geometria de coordenação quadrada plana, onde o ligante saliciladeído-4-feniltiossemicarbazida comporta-se como quelante tridentado, e completando a esfera de coordenação do centro metálico temos uma molécula de piridina. A estrutura cristaliza no sistema monoclínico, grupo espacial P21/m, parâmetros de cela a = 12,8211(2) Å, b = 5,73370(10) Å, c = 23,9950(4) Å, β = 101,0910(10)°, V = 1730,98(5) Å3 , índices de discordância finais R1= 0,0320, wR2 = 0,0888, Z=3. O Complexo 1 apresenta ainda interações intermoleculares do tipo [N(3)-H(3)---S(1) = 3,5838(17)º, N(3)–H(3A)---S(1) = 160,91(19)º], formando estruturas dímeras e ligação de hidrogênio intramolecular não-clássica do tipo [C(10)-H(10)---N(2) = 2,838(2)º e C(10) – H(10)---N(2) = 122º]. A estrutura cristalina do complexo 2, apresenta duas formas independentes (uma com centro representado por Pb1 e outra por Pb2). Para a unidade com Pb1 temos o complexo composto por duas unidades do Ligante 5, que comportam-se como quelantes tridentados, e a esfera de coordenação é completada por interações intermoleculares do tipo η 2 areno π e através da ligação polarizada com o O1 da moléculas vizinha, o que confere ao íon Pb1 NC=9. A unidade Pb2 apresenta apenas as duas unidades do Ligante 5 coordenadas conferindo-lhe NC=6. A estrutura cristaliza no sistema monoclínico, grupo espacial C2/c, parâmetros de cela a = 37,9747(6) Å, b= 9,51280(10) Å, c = 31,4378(5) Å, β = 125,951(2)°, V= 9193,5(2) Å3 , Z = 4, índices de discordância finais= R1 = 0,0643, wR2 = 0,1227.

Symmetry reduction due to gallium substitution in the garnet Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12

Single-crystal structure refinements on lithium lanthanum zirconate (LLZO; Li7La3Zr2O12) substituted with gallium were successfully carried out in the cubic symmetry space group I [Formula: see text]3d. Gallium was found on two lithium sites as well as on the lanthanum position. Due to the structural distortion of the resulting Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12 (Ga-LLZO) single crystals, a reduction of the LLZO cubic garnet symmetry from Ia[Formula: see text] d to I [Formula: see text]3d was necessary, which could hardly be analysed from X-ray powder diffraction data.

Purification and preliminary crystallographic analysis of a new Lys49-PLA2 from B-jararacussu

BjVIII is a new myotoxic Lys49-PLA2 isolated from Bothrops jararacussu venom that exhibits atypical effects on human platelet aggregation. To better understand the mode of action of BjVIII, crystallographic studies were initiated. Two crystal forms were obtained, both containing two molecules in the asymmetric unit (ASU). Synchrotron radiation diffraction data were collected to 2.0 angstrom resolution and 1.9 angstrom resolution for crystals belonging to the space group P2(1)2(1)2(1) (a = 48.4 angstrom, b = 65.3 angstrom, c = 84.3 angstrom) and space group P3(1)21 (a = b = 55.7 angstrom, c = 127.9 angstrom), respectively. Refinement is currently in progress and the refined structures are expected to shed light on the unusual platelet aggregation activity observed for BjVIII.

Crystal structure of Bn IV in complex with myristic acid: A Lys49 myotoxic phospholipase A(2) from Bothrops neuwiedi venom

The LY549-PLA(2)s myotoxins have attracted attention as models for the induction of myonecrosis by a catalytically independent mechanism of action. Structural studies and biological activities have demonstrated that the myotoxic activity of LYS49-PLA(2) is independent of the catalytic activity site. The myotoxic effect is conventionally thought to be to due to the C-terminal region 111-121, which plays an effective role in membrane damage. In the present study, Bn IV LYS49-PLA(2) was isolated from Bothrops neuwiedi snake venom in complex with myristic acid (CH3(CH2)(12)COOH) and its overall structure was refined at 2.2 angstrom resolution. The Bn IV crystals belong to monoclinic space group P2(1) and contain a dimer in the asymmetric unit. The unit cell parameters are a = 38.8, b = 70.4, c = 44.0 angstrom. The biological assembly is a "conventional dimer" and the results confirm that dimer formation is not relevant to the myotoxic activity. Electron density map analysis of the Bn IV structure shows clearly the presence of myristic acid in catalytic site. The relevant structural features for myotoxic activity are located in the C-terminal region and the Bn IV C-terminal residues NKKYRY are a probable heparin binding domain. These findings indicate that the mechanism of interaction between Bn IV and muscle cell membranes is through some kind of cell signal transduction mediated by heparin complexes. (C) 2010 Elsevier Masson SAS. All rights reserved.

Crystallization, preliminary X-ray analysis and molecular-replacement solution of haemoglobin-II from the fish matrinxa (Brycon cephalus)

Haemoglobins constitute a set of proteins with interesting structural and functional properties, especially when the two large animal groups reptiles and fishes are focused on. Here, the crystallization and preliminary X-ray analysis of haemoglobin-II from the South American fish matrinxa (Brycon cephalus) is reported. X-ray diffraction data have been collected to 3.0 Angstrom resolution using synchrotron radiation (LNLS). Crystals were determined to belong to space group P2(1) and preliminary structural analysis revealed the presence of two tetramers in the asymmetric unit. The structure was determined using the standard molecular-replacement technique.

Crystallization and preliminary X-ray diffraction analysis of a eumenine mastoparan toxin: a new class of mast-cell degranulating peptide in the wasp venom

Mastoparans are tetradecapeptides found to be the major component of vespid venoms. A mastoparan toxin isolated from the venom of Anterhynchium flavomarginatum micado has been crystallized and X-ray diffraction data collected to 2.7 Angstrom resolution using a synchrotron-radiation source. Crystals were determined to belong to the space group P6(2)22 (P6(4)22). This is the first mastoparan to be crystallized and will provide further insights into the conformational significance of mastoparan toxins with respect to their potency and activity in G-protein regulation.

Preliminary cryocrystallography analysis of an eumenine mastoparan toxin isolated from the venom of the wasp Anterhynchium flavomarginatum micado

Mastoparans are tetradecapeptides found to be the major component of vespid venoms. These peptides present a wide spectrum of biological activities, such as mast cell degranulation, hemolytic activity and also reveals antimicrobial activity. A mastoparan toxin isolated from the venom of Anterhynchium flavomarginatum micado has been crystallized. At room temperature these crystals diffracted to 2.8 Angstrom resolution. However, upon cooling to cryogenic temperature around 85 K, the original resolution limit could be improved to 2.0 Angstrom. Crystals were determined to belong to the space group P3(1) (P3(2)). This is the first mastoparan to be crystallized and it will provide further insights in the conformational significance of mastoparan toxins, with respect to their potency and activity in G protein regulation. (C) 3001 Elsevier B.V. B.V. All rights reserved.

Time, place and space – student group collaboration using Google Drive

Virtual working environments are intrinsic to the contemporary workplace and collaborative skills are a vital graduate capability. To develop students’ collaborative skills, first year medical laboratory science students undertake a group poster project, based on a blended learning model. Learning is scaffolded in lectures, workshops in collaborative learning spaces, practitioner mentoring sessions, and online resources. Google Drive provides an online collaborative space for students to realise tangible outcomes from this learning. A Google Drive document is created for each group and shared with members. In this space, students assign tasks and plan workflow, share research, progressively develop poster content, reflect and comment on peer contributions and use the messaging functions to ‘talk’ to group members. This provides a readily accessible, transparent record of group work, crucial in peer assessment, and a communication channel for group members and the lecturer, who can support groups if required. This knowledge creation space also augments productivity and effectiveness of face-to-face collaboration. As members are randomly allocated to groups and are often of diverse backgrounds and unknown to each other, resilience is built as students navigate the uncertainties and complexities of group dynamics, learning to focus on the goal of the team task as they constructively and professionally engage in team dialogue. Students are responsible and accountable for individual and group work. The use of Google Drive was evaluated in a survey including Likert scale and open ended qualitative questions. Statistical analysis was carried out. Results show students (79%) valued the inclusion of online space in collaborative work and highly appreciated (78%) the flexibility provided by Google Drive, while recognising the need for improved notification functionality. Teaching staff recognised the advantages in monitoring and moderating collaborative group work, and the transformational progression in student collaborative as well as technological skill acquisition, including professional dialogue.

Some remarks on the symplectic pairing on the moduli space of representations of the fundamental group of surfaces

This work grew out of an attempt to understand a conjectural remark made by Professor Kyoji Saito to the author about a possible link between the Fox-calculus description of the symplectic structure on the moduli space of representations of the fundamental group of surfaces into a Lie group and pairs of mutually dual sets of generators of the fundamental group. In fact in his paper [3] , Prof. Kyoji Saito gives an explicit description of the system of dual generators of the fundamental group.

Four group decodable differential scaled unitary linear space-time codes

Differential Unitary Space-Time Block codes (STBCs) offer a means to communicate on the Multiple Input Multiple Output (MIMO) channel without the need for channel knowledge at both the transmitter and the receiver. Recently Yuen-Guan-Tjhung have proposed Single-Symbol-Decodable Differential Space-Time Modulation based on Quasi-Orthogonal Designs (QODs) by replacing the original unitary criterion by a scaled unitary criterion. These codes were also shown to perform better than differential unitary STBCs from Orthogonal Designs (ODs). However the rate (as measured in complex symbols per channel use) of the codes of Yuen-Guan-Tjhung decay as the number of transmit antennas increase. In this paper, a new class of differential scaled unitary STBCs for all even number of transmit antennas is proposed. These codes have a rate of 1 complex symbols per channel use, achieve full diversity and moreover they are four-group decodable, i.e., the set of real symbols can be partitioned into four groups and decoding can be done for the symbols in each group separately. Explicit construction of multidimensional signal sets that yield full diversity for this new class of codes is also given.

On four-group ML decodable distributed space time codes for cooperative communication

A construction of a new family of distributed space time codes (DSTCs) having full diversity and low Maximum Likelihood (ML) decoding complexity is provided for the two phase based cooperative diversity protocols of Jing-Hassibi and the recently proposed Generalized Non-orthogonal Amplify and Forward (GNAF) protocol of Rajan et al. The salient feature of the proposed DSTCs is that they satisfy the extra constraints imposed by the protocols and are also four-group ML decodable which leads to significant reduction in ML decoding complexity compared to all existing DSTC constructions. Moreover these codes have uniform distribution of power among the relays as well as in time. Also, simulations results indicate that these codes perform better in comparison with the only known DSTC with the same rate and decoding complexity, namely the Coordinate Interleaved Orthogonal Design (CIOD). Furthermore, they perform very close to DSTCs from field extensions which have same rate but higher decoding complexity.