Site Disorder Research Articles

Exposure to Ti4Al4V Titanium Alloy Leads to Redox Abnormalities, Oxidative Stress, and Oxidative Damage in Patients Treated for Mandible Fractures.

Due to the high biotolerance, favourable mechanical properties, and osseointegration ability, titanium is the basic biomaterial used in maxillofacial surgery. The passive layer of titanium dioxide on the surface of the implant effectively provides anticorrosive properties, but it can be damaged, resulting in the release of titanium ions to the surrounding tissues. The aim of our work was to evaluate the influence of Ti6Al4V titanium alloy on redox balance and oxidative damage in the periosteum surrounding the titanium miniplates and screws as well as in plasma and erythrocytes of patients with mandibular fractures. The study included 31 previously implanted patients (aged 21–29) treated for mandibular fractures and 31 healthy controls. We have demonstrated increased activity/concentration of antioxidants both in the mandibular periosteum and plasma/erythrocytes of patients with titanium mandibular fixations. However, increased concentrations of the products of oxidative protein and lipid modifications were only observed in the periosteum of the study group patients. The correlation between the products of oxidative modification of the mandible and antioxidants in plasma/erythrocytes suggests a relationship between the increase of oxidative damage at the implantation site and central redox disorders in patients with titanium miniplates and screws.

Analysis of Adverse Reactions Related to Drugs and Vaccines Received at the National Centre for Pharmacovigilance from 2009 to 2016 in Togo

Objectives: To assess the received suspected adverse events occurring upon treatment with drugs and vaccines, at National Centre for Pharmacovigilance, in Togo, from 2009 to 2016. Methods: A crossover study was conducted in order to collect data about patients, drugs, suspected adverse events and notifiers. Suspected adverse events were classified using Med DRA 19.1. Notification’s circumstances were classified into Public Health Programs’ campaigns and routine practice. Data were collated into Excel spreadsheet and processed with SPSS software. Key Findings: Regional distribution is irregular. Of the 322 collected report forms, paramedics have notified 60.8% of the cases. Adult patients were the most represented (70.2%). Public Health Programs campaigns provided 72.6% versus 27.4% for routine practice including Neglected Tropical Diseases (41.4%), immunization (27.7%), tuberculosis (25.9%) and 4.5% for HIV. Skin disorders were the most prevalent suspected adverse events (147 sheets; 45.7%) followed by general disorders and administration site disorders (29.8%) and gastro-intestinal disorders (12.7%). General anti-infective drugs for systemic use, antiparasites, and insecticides were the most reported class of medications (161 sheets; 44.7%). Conclusions: A thorough follow-up of pharmacovigilance launched activities is needed to build a sustainable adverse effect’s surveillance system and routine practice has to be strengthened.

Entanglement in site diluted quantum two-dimensional antiferromagnet

The von Neumann entanglement entropy is studied for the two-dimensional Heisenberg antiferromagnet with ion single anisotropy in the square lattice and in the presence of nonmagnetic impurities, at T=0 using the SU(3) Schwinger boson theory. In particular, we discuss the influence of site disorder on the quantum entanglement of this model that is characterized by a quantum phase transition at Dc, that separates a Néel phase, D<Dc, which is gapless, from a disordered phase, gapped phase, D>Dc. We find that the quantum entanglement in D<Dc for the model is destroyed for a concentration of nonmagnetic impurities xc≈0.5.

Hidden Magnetic States Emergent Under Electric Field, In A Room Temperature Composite Magnetoelectric Multiferroic

The ability to control a magnetic phase with an electric field is of great current interest for a variety of low power electronics in which the magnetic state is used either for information storage or logic operations. Over the past several years, there has been a considerable amount of research on pathways to control the direction of magnetization with an electric field. More recently, an alternative pathway involving the change of the magnetic state (ferromagnet to antiferromagnet) has been proposed. In this paper, we demonstrate electric field control of the Anomalous Hall Transport in a metamagnetic FeRh thin film, accompanying an antiferromagnet (AFM) to ferromagnet (FM) phase transition. This approach provides us with a pathway to “hide” or “reveal” a given ferromagnetic region at zero magnetic field. By converting the AFM phase into the FM phase, the stray field, and hence sensitivity to external fields, is decreased or eliminated. Using detailed structural analyses of FeRh films of varying crystalline quality and chemical order, we relate the direct nanoscale origins of this memory effect to site disorder as well as variations of the net magnetic anisotropy of FM nuclei. Our work opens pathways toward a new generation of antiferromagnetic – ferromagnetic interactions for spintronics.

Spectroscopic properties of photosystem II reaction center revisited.

Photosystem II (PSII) is the only biological system capable of splitting water to molecular oxygen. Its reaction center (RC) is responsible for the primary charge separation that drives the water oxidation reaction. In this work, we revisit the spectroscopic properties of the PSII RC using the complex time-dependent Redfield (ctR) theory for optical lineshapes [A. Gelzinis et al., J. Chem. Phys. 142, 154107 (2015)]. We obtain the PSII RC model parameters (site energies, disorder, and reorganization energies) from the fits of several spectra and then further validate the model by calculating additional independent spectra. We obtain good to excellent agreement between theory and calculations. We find that overall our model is similar to some of the previous asymmetric exciton models of the PSII RC. On the other hand, our model displays differences from previous work based on the modified Redfield theory. We extend the ctR theory to describe the Stark spectrum and use its fit to obtain the parameters of a single charge transfer state included in our model. Our results suggest that ChlD1+PheoD1- is most likely the primary charge transfer state, but that the Stark spectrum of the PSII RC is probably also influenced by other states.

Dielectric and Ferroelectric Properties in Highly Substituted Bi2Sr(A)TiNb2O12 (A = Ca2+, Sr2+, Ba2+) Aurivillius Phases

Structure–property relationships were determined for the family of three-layer Aurivillius materials Bi2Sr(A)TiNb2O12 (A = Ca2+, Sr2+, Ba2+). X-ray and neutron diffraction along with selected area electron diffraction indicate that Bi2SrBaTiNb2O12 crystallizes in the nonpolar I4/mmm space group, whereas the polar B2cb space group best describes Bi2SrCaTiNb2O12 and Bi2Sr2TiNb2O12. Despite the different space groups, all three compositions show relaxor behavior as evidenced through P(E) and dielectric measurements. These relaxor properties are derived from the extensive amount of disorder in each composition that is found at every cationic crystallographic site and do not depend on the space group. This disorder is so extensive that it disrupts the ferroelectric properties allowed by symmetry in the B2cb space group. This work demonstrates the important role of cation substitution and site disorder in these three-layered Aurivillius materials and its significant effect on both ferroelectric and dielectric p...

Neutron scattering of advanced magnetic materials

An overview of notable contributions of neutron scattering in the advancement of magnetic materials has been presented. A brief description of static neutron scattering techniques, viz., diffraction, depolarization, small angle scattering, and reflectivity, employed in the studies of advanced magnetic materials, is given. Apart from providing the up-to-date literature, this review highlights the importance of neutron scattering techniques in achieving microscopic as well as mesoscopic understanding of static magnetic properties of the following selective classes of advanced magnetic materials: (i) magnetocaloric materials, (ii) permanent magnets, (iii) multiferroic materials, (iv) spintronic materials, and (v) molecular magnetic materials. In the area of magnetocaloric materials, neutron diffraction studies have greatly improved the understanding of magneto-structural coupling by probing (i) atomic site distribution, (ii) evolution of structural phases and lattice parameters across the TC, and (iii) microscopic details of magnetic ordering in several potential magnetocaloric materials. Such an understanding is vital to enhance the magnetocaloric effect. Structural and magnetic investigations, employing neutron diffraction and allied techniques, have helped to improve the quality of permanent magnets by tailoring (understanding) structural phases, magnetic ordering, crystallinity, microstructure (texture), and anisotropy. The neutron diffraction studies of structural distortions/instabilities and magnetic ordering in multiferroic materials have improved the microscopic understanding of magnetoelectric coupling that allows one to control magnetic order by an electric field and electric order by a magnetic field in multiferroic materials. In the field of molecular magnetic materials, neutron diffraction studies have enhanced the understanding of (i) structural and magnetic ordering, (ii) short-range structural and magnetic correlations, (iii) spin density distribution and spin delocalization at molecular levels, and (iv) role of bridging ligands in propagating magnetic exchange interactions. The neutron diffraction studies have contributed towards the development of spintronics by bringing out (i) correlations between atomic site disorder and electronic spin polarization in full Heusler and half Heusler alloys, and (ii) microscopic origin of magnetic ordering in antiferromagnetic spintronics and other potential spintronic materials. Neutron depolarization, small angle neutron scattering, and neutron reflectometry techniques, on the other hand, have probed magnetism at mesoscopic length scales in such advanced magnetic materials. The derived understanding would be useful to exploit such materials for their practical applications as well as to set directions for future research in these areas.

Observation of unusual ferromagnetic cluster glass behavior in CrAlGe

We report on an experimental study on the structural and magnetic properties of the intermetallic compound CrAlGe. The material has been investigated in detail by x-ray diffraction, dc magnetization, ac susceptibility, and electrical resistivity measurements. X-ray diffraction and associated Rietveld analysis show that the compound crystallizes in the orthorhombic $\mathrm{TiS}{\mathrm{i}}_{2}\text{\ensuremath{-}}\mathrm{type}$ structure, with lattice parameters $a=4.7531(1)\phantom{\rule{0.16em}{0ex}}\AA{},\phantom{\rule{0.16em}{0ex}}b=8.2182(1)\phantom{\rule{0.16em}{0ex}}\AA{}$, and $c=8.6951(1)\phantom{\rule{0.16em}{0ex}}\AA{}$. The magnetization measurements demonstrate that the alloy is ferromagnetic with a Curie temperature of ${T}_{\mathrm{C}}\ensuremath{\approx}80\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At 5 K the magnetization saturates at 50 kOe with a saturation moment of ${M}_{\mathrm{S}}=19\phantom{\rule{0.16em}{0ex}}\mathrm{emu}/\mathrm{g}$. Below ${T}_{\mathrm{C}}$, the ac susceptibility data exhibit two distinct frequency dependent peaks, which are also strongly dependent on ac field amplitude and dc magnetic fields. The experimental results strongly suggest the coexistence of ferromagnetic and reentrant spin glass type states in CrAlGe, which is due to the effect of the structural disorder in the $16f$ site (mixed Al/Ge occupation) on the crystallographically ordered $8a$ site of Cr. To our knowledge, CrAlGe is the first example where such unusual magnetic behavior is brought about not by structural disorder on the site occupied by the magnetic atom, but is due to the disorder in the atomic sites of the neighboring atoms.

High-resolution crystal structures and STD NMR mapping of human ABO(H) blood group glycosyltransferases in complex with trisaccharide reaction products suggest a molecular basis for product release.

The human ABO(H) blood group A- and B-synthesizing glycosyltransferases GTA and GTB have been structurally characterized to high resolution in complex with their respective trisaccharide antigen products. These findings are particularly timely and relevant given the dearth of glycosyltransferase structures collected in complex with their saccharide reaction products. GTA and GTB utilize the same acceptor substrates, oligosaccharides terminating with α-l-Fucp-(1→2)-β-d-Galp-OR (where R is a glycolipid or glycoprotein), but use distinct UDP donor sugars, UDP-N-acetylgalactosamine and UDP-galactose, to generate the blood group A (α-l-Fucp-(1→2)[α-d-GalNAcp-(1→3)]-β-d-Galp-OR) and blood group B (α-l-Fucp-(1→2)[α-d-Galp-(1→3)]-β-d-Galp-OR) determinant structures, respectively. Structures of GTA and GTB in complex with their respective trisaccharide products reveal a conflict between the transferred sugar monosaccharide and the β-phosphate of the UDP donor. Mapping of the binding epitopes by saturation transfer difference NMR measurements yielded data consistent with the X-ray structural results. Taken together these data suggest a mechanism of product release where monosaccharide transfer to the H-antigen acceptor induces active site disorder and ejection of the UDP leaving group prior to trisaccharide egress.

Adherence to NICE guidance on lifestyle advice for people with schizophrenia: a survey.

Aims and method The STEPWISE trial (STructured lifestyle Education for People WIth SchizophrEnia, schizoaffective disorder and first episode psychosis) is currently evaluating a lifestyle education programme in addition to usual care. However, it is difficult to define what constitutes ‘usual care’. We aimed to define ‘usual care’ for lifestyle management in people with schizophrenia, schizoaffective disorder and first-episode psychosis in STEPWISE study sites. Ten National Health Service (NHS) mental health trusts participated in a bespoke survey based on the National Institute for Health and Care Excellence (NICE) guidance.Results Eight trusts reported offering lifestyle education programmes and nine offered smoking cessation support. Reported recording of biomedical measures varied.Clinical implications Although recommended by NICE, lifestyle education programmes are not consistently offered across UK NHS mental health trusts. This highlights missed opportunities to improve the physical health of people with psychotic illness. Our survey benchmarks ‘usual care’ for the STEPWISE study, against which changes can be measured. Furthermore, future studies will be able to identify whether any progress in clinical practice has been made towards achieving the NICE recommendations.

Dependence of magnetisation and magnetocrystalline anisotropy on site distribution of alloying elements in RE-TM phases with ThMn12 structure

The effect of site disorder (originating from the presence of substitutional atoms) on intrinsic magnetic properties of intermetallic phases derived from the ThMn12-type crystal structure has been studied using the tight-binding linear-muffin-tin-orbital atomic-sphere approximation (TB-LMTO-ASA) method of density functional theory (DFT). The focus was put on the analysis of magnetisation and magnetocrystalline anisotropy in 42 inequivalent configurations that differed in their arrangements of the substitutional atoms. The first-order anisotropy constant K1 turns out to be far more sensitive to the site occupancy than the magnetisation M. Addition of light interstitial atoms B, C or N gives rise to much higher K1 values but the same range of scattering is retained. As the anisotropy constant K1 is strongly increased by interstitial atoms, the influence of the atomic disorder is less pronounced for these systems.

Observation of relaxor like dielectric and magnetodielectric behaviour in nanoparticles of half doped LaSrCoMnO6

We report the dielectric characteristics of sol-gel derived nanoparticles of half doped ferromagnetic double perovskite LaSrCoMnO6 (LSCMO) over broad temperature and frequency ranges. The diffuse dielectric peak with strong frequency dispersion, Vogel-Fulcher functional relation like relaxation behaviour etc. confirm the relaxor type dielectric nature of these magnetic nanoparticles. The chemical and compositional disorder in the LSCMO nanoparticles, the Co/Mn site disorder, and the surface disorder are attributed to the relaxor like behaviour by the formation of local polar nano-regions. The observed magnetodielectric effect is attributed to the phenomena of magnetic field controlled electric relaxation and magnetoresistance.

Thermodynamic stability of SFCA (silico‐ferrite of calcium and aluminum) and SFCA‐I phases

AbstractSilico‐ferrite of calcium and aluminum (SFCA) and SFCA‐I phases form in iron ore sintering operations. Their behavior in blast furnaces, with sinter being a significant component of blast furnace burden, is of critical importance to the ironmaking process. They have complex disordered crystal structures and form over a range of composition. In the present work, enthalpies of formation from oxides for five different SFCA compounds and one SFCA‐I phase were measured by oxide melt solution calorimetry in molten lead borate solvent at 800°C. The enthalpies of formation from binary oxides are zero within experimental error for SFCA phases and slightly endothermic for SFCA‐I, confirming that SFCA phases are stabilized, not by energetics, but by their configurational entropies resulting from atomic site disorder. In addition, enthalpies of drop solution into a molten slag at 1450°C were measured for SFCA phases and show good agreement with values predicted using the heats of formation and previously measured drop solution enthalpies for the binary oxides. This agreement confirms data consistency and shows that the presence of variable amounts of SFCA relative to binary oxides in a sinter will have negligible effect on the heat balance in the blast furnace.

Temperature induced phase transformations on the Li2MoO4 system studied by Raman spectroscopy

The present research reports results of lattice dynamics calculations and temperature-dependent Raman scattering study of the dilithium molybdate system, Li2MoO4, in the 25–600 °C temperature range. The effects of the temperature duly produced gradual changes, associated with the disorder and anharmonic effects followed by thermodynamic instability, leading the structure to a phase transformation. Calorimetric measurements up to 1000 °C corroborated that the crystal structure experienced gradual modifications, characterized by changes in the DSC base line. These stated thermal events as well as the changes in the profile of the Raman spectra, suggested that a phase transformation is connected with tilting and/or rotations of the MoO4 tetrahedron leading to a disorder in the MoO4 sites. The observation of one exothermic peak on the DSC curve at about 702 °C is related with the melting in the sample. The experimental results were discussed based on the mode assignments performed by using lattice dynamics calculations from where we predicted both wavenumbers and atomic displacements.

Linear magnetoelectric effect as a signature of long-range collinear antiferromagnetic ordering in the frustrated spinel CoAl2O4

The ground state of the frustrated $A$-site magnetic spinel $\mathrm{CoA}{\mathrm{l}}_{2}{\mathrm{O}}_{4}$ has been a controversial issue whether it is a collinear antiferromagnetic ordering or a spiral spin-liquid state, as the ratio of the two competing interactions ${J}_{2}/{J}_{1}$ lies close to the boundary between these two ground states. Here we address the magnetic ground state in $\mathrm{CoA}{\mathrm{l}}_{2}{\mathrm{O}}_{4}$ with different amounts of $\mathrm{C}{\mathrm{o}}^{2+}/\mathrm{A}{\mathrm{l}}^{3+}$ site disorder from the study of magnetoelectric effect and Monte Carlo simulations. $\mathrm{CoA}{\mathrm{l}}_{2}{\mathrm{O}}_{4}$ with low site disorder exhibits a linear magnetoelectric effect below the magnetic ordering temperature. With increasing disorder, the magnetoelectric effect is suppressed and the sample with $14%$ disorder exhibits a spin glass behavior without the magnetoelectric effect. Monte Carlo simulations support the experimental findings and suggest that the site disorder suppresses long-range antiferromagnetic order and induces a spin glass state. Since the linear magnetoelectric effect requires a long-range magnetic ordering, we suggest that the ground state of $\mathrm{CoA}{\mathrm{l}}_{2}{\mathrm{O}}_{4}$ with low site disorder is a collinear antiferromagnet.

Solid-state NMR and computational insights into the crystal structure of silicocarnotite-based bioceramic materials synthesized mechanochemically

In this work, we report the results of a detailed structural study of a promising bioceramic material silicocarnotite Ca5(PO4)2SiO4 (SC) synthesized from mechanochemically treated nanosized silicon-substituted hydroxyapatite by annealing at 1000°C. This novel synthetic approach represents an attractive and efficient route towards large-scale manufacturing of the silicocarnotite-based bioceramics. A combination of solid-state nuclear magnetic resonance (NMR), powder X-ray crystallography and density function theory (DFT) calculations has been implemented to characterize the phase composition of the prepared composite materials and to gain insight into the crystal structure of silicocarnotite. The phase composition analysis based on the multinuclear solid-state NMR has been found in agreement with X-ray powder diffraction indicating the minority phases of CaO (5–6wt%) and residual silicon-apatite (7–8wt%), while the rest of the material being a fairly crystalline silicocarnotite phase (86–88wt%). A combination of computational (CASTEP) and experimental methods was used to address the anionic site disorder in the silicocarnotite crystal structure. Distorted [OPO3] pyramids have appeared as an important structural motif in the SC crystal structure. The ratio between regular [PO4] and distorted [OPO3] tetrahedra is found between 2:1 and 3:1 based on XRD experiments and CASTEP calculations. The natural abundance 43Ca magic angle spinning NMR spectra of silicocarnotite are reported for the first time.

Head-to-head pharmacokinetic and pharmacodynamic comparison of subcutaneous versus intramuscular leuprorelin acetate formulations in male patients.

e589 Background: Leuprolide acetate (LA) is the standard-of-care luteinizing hormone-releasing hormone (LHRH) agonist used to suppress serum testosterone (T) in the treatment of advanced prostate cancer. There are currently two LA formulations available: a controlled-release implant injected subcutaneously (SC) or a microsphere intra-muscular (IM) injection. The study compared the pharmacokinetics/pharmacodynamics of both formulations at the same one-month dose. Methods: Thirty-two healthy men were randomized to receive a single 7.5 mg injection of SC-LA (n = 16) or IM-LA (n = 16) in this phase 1, open-label, parallel-group study. Serum LA, T, and luteinizing hormone (LH) were assessed. Results: The initial surge of LA was higher for IM-LA than SC-LA (Cmax 27±4.9 vs. 19±8.0 ng/mL, respectively), with a shorter tmax (1.0±0.4 vs. 2.1±0.8 hrs). Mean serum LA remained above the level of quantification (LOQ, 50 pg/mL) through Day 49 for SC-LA, whereas for IM-LA, mean serum LA dropped below the LOQ after Day 28. Median LH concentration remained low at Day 56 in the SC-LA group, whereas LH levels began to rise after Day 35 in the IM-LA group. Consequently, serum T began to increase by Day 42 in the IM-LA group. By Day 56, 13 SC-LA subjects maintained serum T levels ≤ 50 ng/dL vs. 0 in the IM-LA group. Both SC-LA and IM-LA were well tolerated, however SC-LA subjects experienced more mild injection site disorders compared to IM-LA. Conclusions: The initial surge of LA was higher for IM-LA than SC-LA (Cmax 27±4.9 vs. 19±8.0 ng/mL, respectively), with a shorter tmax (1.0±0.4 vs. 2.1±0.8 hrs). Mean serum LA remained above the level of quantification (LOQ, 50 pg/mL) through Day 49 for SC-LA, whereas for IM-LA, mean serum LA dropped below the LOQ after Day 28. Median LH concentration remained low at Day 56 in the SC-LA group, whereas LH levels began to rise after Day 35 in the IM-LA group. Consequently, serum T began to increase by Day 42 in the IM-LA group. By Day 56, 13 SC-LA subjects maintained serum T levels ≤ 50 ng/dL vs. 0 in the IM-LA group. Both SC-LA and IM-LA were well tolerated, however SC-LA subjects experienced more mild injection site disorders compared to IM-LA.

Experimental and first-principles determination of the magnetocrystalline anisotropy in MnxGa

Singular point detection (SPD) for the determination of the anisotropy field (BA) using a conventional magnetometer is demonstrated. We then follow the composition dependence of BA in MnxGa using a combination of SPD measurements complemented by first-principles density functional theory (DFT) calculations. We find excellent quantitative agreement for 1.2≤x≤ 1.8, but observe a marked departure for x≤1.2. We suggest that the deviation from ideal behaviour might be associated with site disorder at low excess Mn.

Defect Engineering in Multinary Earth‐Abundant Chalcogenide Photovoltaic Materials

Application of zinc‐blende‐related chalcogenide absorbers such as CdTe and Cu(In,Ga)Se2 (CIGSe) has enabled remarkable advancement in laboratory‐ and commercial‐scale thin‐film photovoltaic performance; however concerns remain regarding the toxicity (CdTe) and scarcity (CIGSe/CdTe) of the constituent elements. Recently, kesterite‐based Cu2ZnSn(S,Se)4 (CZTSSe) materials have emerged as attractive non‐toxic and earth‐abundant absorber candidates. Despite the similarities between CZTSSe and CIGSe/CdTe, the record power conversion efficiency of CZTSSe solar cells (12.6%) remains significantly lower than that of CIGSe (22.6%) and CdTe (22.1%) devices, with the performance gap primarily being attributed to cationic disordering and associated band tailing. To capture the promise of kesterite‐like materials as prospective “drop‐in” earth‐abundant replacements for closely‐related CIGSe, current research has focused on several key directions to control disorder, including: (i) examination of the interaction between processing conditions and atomic site disorder, (ii) isoelectronic cation substitution to introduce ionic size mismatch, and (iii) structural diversification beyond the zinc‐blende‐type coordination environment. In this review, recent efforts targeting accurate identification and engineering of anti‐site disorder in kesterite‐based CZTSSe are considered. Lessons learned from CZTSSe are applied to other complex chalcogenide semiconductors, in an effort to develop promising pathways to avoid anti‐site disordering and associated band tailing in future high‐performance earth‐abundant photovoltaic technologies.

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

Phonon-glass electron-crystal (PGEC) behaviour is realised in La0.5Na0.5Ti1–xNbxO3 thermoelectric oxides.