Relationship between Crystal Shape, Photoluminescence, and Local Structure in SrTiO3 Synthesized by Microwave-Assisted Hydrothermal Method

This paper describes the effect of using different titanium precursors on the synthesis and physical properties of SrTiO3 powders obtained by microwave-assisted hydrothermal method. X-ray diffraction measurements, X-ray absorption near-edge structure (XANES) spectroscopy, field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HRTEM) were carried out to investigate the structural and optical properties of the SrTiO3 spherical and cubelike-shaped particles. The appropriate choice of the titanium precursor allowed the control of morphological and photoluminescence (PL) properties of SrTiO3 compound. The PL emission was more intense in SrTiO3 samples composed of spherelike particles. This behavior was attributed to the existence of a lower amount of defects due to the uniformity of the spherical particles.

Does Lithium Prevent Alzheimer's Disease?

Lithium salts have a well-established role in the treatment of major affective disorders. More recently, experimental and clinical studies have provided evidence that lithium may also exert neuroprotective effects. In animal and cell culture models, lithium has been shown to increase neuronal viability through a combination of mechanisms that includes the inhibition of apoptosis, regulation of autophagy, increased mitochondrial function, and synthesis of neurotrophic factors. In humans, lithium treatment has been associated with humoral and structural evidence of neuroprotection, such as increased expression of anti-apoptotic genes, inhibition of cellular oxidative stress, synthesis of brain-derived neurotrophic factor (BDNF), cortical thickening, increased grey matter density, and hippocampal enlargement. Recent studies addressing the inhibition of glycogen synthase kinase-3 beta (GSK3B) by lithium have further suggested the modification of biological cascades that pertain to the pathophysiology of Alzheimer's disease (AD). A recent placebo-controlled clinical trial in patients with amnestic mild cognitive impairment (MCI) showed that long-term lithium treatment may actually slow the progression of cognitive and functional deficits, and also attenuate Tau hyperphosphorylation in the MCI-AD continuum. Therefore, lithium treatment may yield disease-modifying effects in AD, both by the specific modification of its pathophysiology via inhibition of overactive GSK3B, and by the unspecific provision of neurotrophic and neuroprotective support. Although the clinical evidence available so far is promising, further experimentation and replication of the evidence in large scale clinical trials is still required to assess the benefit of lithium in the treatment or prevention of cognitive decline in the elderly.

Synthesis, crystal structure and magnetic properties of the helical oxalate-bridged copper(II) chain {[(CH3)(4)N](2)[Cu(C2O4)(2)] center dot H2O}(n)

The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH3)(4)N](2)]Cu(C2O4)(2)] center dot H2O}(n) (1) [(CH3)(4)N+ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(H) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1)cm(-1), the Hamiltonian being defined as H = -J Sigma nm S-i . S-j]. This value is analyzed and discussed in the light of available magnetostructural data for oxalate-bridged copper(H) complexes with the same out-of-plane exchange pathway. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Enhancement of the Nonlinear Optical Absorption of the E7 Liquid Crystal at the Nematic-Isotropic Transition

We present an experimental study of the nonlinear optical absorption of the eutectic mixture E7 at the nematic-isotropic phase transition by the Z-scan technique, under continuous-wave excitation at 532 nm. In the nematic region, the effective nonlinear optical coefficient beta, which vanishes in the isotropic phase, is negative for the extraordinary beam and positive for an ordinary beam. The parameter , whose definition in terms of the nonlinear absorption coefficient follows the definition of the optical-order parameter in terms of the linear dichroic ratio, behaves like an order parameter with critical exponent 0.22 +/- 0.05, in good agreement with the tricritical hypothesis for the nematic-isotropic transition.

Terbium(III) and dysprosium(III) 8-connected 3D networks containing 2,5-thiophenedicarboxylate anion: Crystal structures and photoluminescence studies

Two novel coordination polymers with the formula {[Ln(2)(2,5-tdc)(3)(dmso)(2)].H2O}(n) (Ln = Tb(III) for (1) and Dy(III) for (2)), (2,5-tdc(2-) = 2,5-thiophenedicarboxylate and dmso = dimethylsulfoxide) have been synthesized by the diffusion method and characterized by thermal analysis, vibrational spectroscopy and single crystal X-ray diffraction analysis. Structure analysis reveals that 2,5-tdc(2-) play a versatile role toward different lanthanide ions to form three-dimensional metal-organic frameworks (MOFs) in which the lanthanides ions are heptacoordinated. Photophysical properties were studied using excitation and emission spectra, where the photoluminescence data show the high emission intensity of the characteristic transitions D-5(4 ->) F-7(J) (J= 6, 5, 4 and 3) for (1) and (F9/2 -> HJ)-F-4-H-6 (J = 15/2, 13/2 and 11/2) for (2), indicating that 2,5-tdc(2-) is a good sensitizer. (C) 2012 Elsevier Ltd. All rights reserved.

Sildenafil reduces polyuria in rats with lithium-induced NDI

Sanches TR, Volpini RA, Massola Shimizu MH, de Bragan a AC, Oshiro-Monreal F, Seguro AC, Andrade L. Sildenafil reduces polyuria in rats with lithium-induced NDI. Am J Physiol Renal Physiol 302: F216-F225, 2012. First published October 12, 2011; doi:10.1152/ajprenal.00439.2010.-Lithium (Li)-treated patients often develop urinary concentrating defect and polyuria, a condition known as nephrogenic diabetes insipidus (NDI). In a rat model of Li-induced NDI, we studied the effect that sildenafil (Sil), a phosphodiesterase 5 (PDE5) inhibitor, has on renal expression of aquaporin-2 (AQP2), urea transporter UT-A1, Na(+)/H(+) exchanger 3 (NHE3), Na(+)-K(+)-2Cl(-) cotransporter (NKCC2), epithelial Na channel (ENaC; alpha-, beta-, and gamma-subunits), endothelial nitric oxide synthase (eNOS), and inducible nitric oxide synthase. We also evaluated cGMP levels in medullary collecting duct cells in suspension. For 4 wk, Wistar rats received Li (40 mmol/kg food) or no treatment (control), some receiving, in weeks 2-4, Sil (200 mg/kg food) or Li and Sil (Li+Sil). In Li+Sil rats, urine output and free water clearance were markedly lower, whereas urinary osmolality was higher, than in Li rats. The cGMP levels in the suspensions of medullary collecting duct cells were markedly higher in the Li+Sil and Sil groups than in the control and Li groups. Semiquantitative immunoblotting revealed the following: in Li+Sil rats, AQP2 expression was partially normalized, whereas that of UT-A1, gamma-ENaC, and eNOS was completely normalized; and expression of NKCC2 and NHE3 was significantly higher in Li rats than in controls. Inulin clearance was normal in all groups. Mean arterial pressure and plasma arginine vasopressin did not differ among the groups. Sil completely reversed the Li-induced increase in renal vascular resistance. We conclude that, in experimental Li-induced NDI, Sil reduces polyuria, increases urinary osmolality, and decreases free water clearance via upregulation of renal AQP2 and UT-A1.

Color Dependence on Thickness in Topaz Crystal from Brazil

It is well known that crystals of topaz from the Eastern Brazilian Pegmatite Province may turn blue by the irradiation with Co-60 gamma rays followed by heat treatment. Also, it is known that the sensation of color changes with the thickness of these crystals. The dependence of the color, given by 1931 CIE chromaticity coordinates, with the thickness of the crystal was analyzed. The absorbance used in the calculation of these coordinates was given by the sum of Gaussian lines. The parameters of these lines were determined through the decomposition of the optical absorption spectra in the ultraviolet and visible regions. The decomposition revealed several lines, whose assignment was made considering studies in spodumene and beryl crystals and highly accurate quantum mechanical calculations. The transmittance becomes very narrow with increasing thickness, and the CIE chromaticity coordinates converge to the borderline of the CIE Chromaticity Diagram at the wavelength of maximum transmittance. Furthermore, the purity of color increases with increasing thickness, and the dominant wavelength reaches the wavelength of maximum transmittance.

Dependence of brittle-to-ductile transition on crystallographic direction in diamond turning of single-crystal silicon

The objective of this paper is to show the dependence relationship between the crystallographic orientations upon brittle-to-ductile transition during diamond turning of monocrystalline silicon. Cutting tests were performed using a -5 degrees rake angle round nose diamond tool at different machining scales. At the micrometre level, the feedrate was kept constant at 2.5 micrometres per revolution (mu m/r), and the depth of cut was varied from 1 to 5 mu m. At the submicrometre level, the depth of cut was kept constant at 500 nm and the feedrate varied from 5 to 10 mu m/r. At the micrometre level, the uncut shoulder generated with an interrupted cutting test procedure provided a quantitative measurement of the ductile-to-brittle transition. Results show that the critical chip thickness in silicon for ductile material removal reaches a maximum of 285 nm in the [100] direction and a minimum of 115 nm in the [110] direction, when the depth of cut was 5 mu m. It was found that when a submicrometre depth of cut was applied, microcracks were revealed in the [110] direction, which is the softer direction in silicon. Micro Raman spectroscopy was used to estimate surface residual stress after machining. Compressive residual stress in the range 142 MPa and smooth damage free surface finish was probed in the [100] direction for a depth of cut of 5 mu m, whereas residual stresses in the range 350 MPa and brittle damage was probed in the [110] direction for a depth of cut of 500 nm.

Spectroscopic characterization and crystal structure of cis-Bis(N-(2-benzoyl)-N ',N '-diphenylthioureato-k O-2,S)nickel(II)

The title compound [Ni(C20H15N2OS)(2)] is prepared by the reaction of metal acetate with the corresponding acylthiourea derivative. The complex is characterized by elemental analysis, IR, H-1 and C-13 NMR, and its structure is determined by single crystal X-ray diffraction. The Ni(II) ion is coordinated by the S and O atoms of two N-benzoyl-N',N'-diphenylthiourea ligands in a slightly distorted square-planar coordination geometry. The two O and two S atoms are mutually cis to each other. The substance crystallizes triclinic (P-1 space group) with cell dimensions a = 10.7262(9) , b = 12.938(3) , c = 14.2085(12) , alpha = 74.650(4)A degrees, beta = 78.398(4)A degrees, gamma = 68.200(5)A degrees, and two formula units in the unit cell. The structure is very close to the related N-(2-furoyl) Ni complex reported previously.

Effects of lithium on oxidative stress parameters in healthy subjects

Increased neuronal oxidative stress (OxS) induces deleterious effects on signal transduction, structural plasticity and cellular resilience, mainly by inducing lipid peroxidation in membranes, proteins and genes. Major markers of OxS levels include the thiobarbituric acid reactive substances (TBARS) and the enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase. Lithium has been shown to prevent and/or reverse DNA damage, free-radical formation and lipid peroxidation in diverse models. This study evaluates OxS parameters in healthy volunteers prior to and following lithium treatment. Healthy volunteers were treated with lithium in therapeutic doses for 2-4 weeks. Treatment with lithium in healthy volunteers selectively altered SOD levels in all subjects. Furthermore, a significant decrease in the SOD/CAT ratio was observed following lithium treatment, wich was associated with decreased OxS by lowering hydrogen peroxide levels. This reduction in the SOD/CAT ratio may lead to lower OxS, indicated primarily by a decrease in the concentration of cell hydrogen peroxide. Overall, the present findings indicate a potential role for the antioxidant effects of lithium in healthy subjects, supporting its neuroprotective profile in bipolar disorder (BD) and, possibly, in neurodegenerative processes.

Lithium in M 67: From the main sequence to the red giant branch

Context. Lithium abundances in open clusters are a very effective probe of mixing processes, and their study can help us to understand the large depletion of lithium that occurs in the Sun. Owing to its age and metallicity, the open cluster M 67 is especially interesting on this respect. Many studies of lithium abundances in M 67 have been performed, but a homogeneous global analysis of lithium in stars from subsolar masses and extending to the most massive members, has yet to be accomplished for a large sample based on high-quality spectra. Aims. We test our non-standard models, which were calibrated using the Sun with observational data. Methods. We collect literature data to analyze, for the first time in a homogeneous way, the non-local thermal equilibrium lithium abundances of all observed single stars in M 67 more massive than similar to 0.9 M-circle dot. Our grid of evolutionary models is computed assuming a non-standard mixing at metallicity [Fe/H] = 0.01, using the Toulouse-Geneva evolution code. Our analysis starts from the entrance into the zero-age main-sequence. Results. Lithium in M 67 is a tight function of mass for stars more massive than the Sun, apart from a few outliers. A plateau in lithium abundances is observed for turn-off stars. Both less massive (M >= 1.10 M-circle dot) and more massive (M >= 1.28 M-circle dot) stars are more depleted than those in the plateau. There is a significant scatter in lithium abundances for any given mass M <= 1.1 M-circle dot. Conclusions. Our models qualitatively reproduce most of the features described above, although the predicted depletion of lithium is 0.45 dex smaller than observed for masses in the plateau region, i.e. between 1.1 and 1.28 solar masses. More work is clearly needed to accurately reproduce the observations. Despite hints that chromospheric activity and rotation play a role in lithium depletion, no firm conclusion can be drawn with the presently available data.

Tricritical-like behavior of the nonlinear optical refraction at the nematic-isotropic transition in the E7 thermotropic liquid crystal

We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with an effective critical exponent of the order parameter, beta = 0.28 +/- 0.03, which is close to the classical value, beta = 0.25, for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase.

Early improvement of psychotic symptoms with lithium monotherapy as a predictor of later response in mania

Although lithium has been the first line agent in the treatment of bipolar disorder (BD), few studies have evaluated lithium's efficacy in mania with psychosis and its association with later response. Furthermore, given the widespread concern about antipsychotic side effects, answering a question about whether lithium alone can manage to treat both psychotic and non-psychotic mania seems a very relevant one. The present study addresses the antipsychotic efficacy of lithium monotherapy in acute mania and early improvement of psychotic symptoms as a predictor of later response of manic symptoms. Forty-six patients presenting a manic episode (32 with psychotic features and 14 subjects without psychotic features) were treated for 4 weeks with lithium monotherapy and evaluated weekly using the Young Mania Rating Scale (YMRS). Subjects with rapid cycling, substance abuse/dependence, or mixed episodes were excluded. The overall antimanic efficacy of lithium in psychosis vs. non-psychosis groups was evaluated. In addition, early improvement of psychotic symptoms and its prediction of subsequent response (>50% decrease in total YMRS scores) or remission were evaluated. Lithium showed a similar efficacy in both psychosis and non-psychosis mania. Early improvement of psychotic symptoms was associated with clinical response and remission at endpoint. (C) 2012 Elsevier Ltd. All rights reserved.

Crystal structure of isotibolone: a major degradation product of tibolone

Isotibolone is frequently found as an impurity in tibolone, a drug used for hormone reposition of post-menopause women, due to some inadequate tibolone synthesis or as a result of degradation during drug storage. The presence of isotibolone impurities should be detected and quantified in active pharmaceutical ingredient products of tibolone before its use in the manufacturing of medicaments. The X-ray powder diffraction technique offers the possibility of quantifying isotibolone amounts at different stages of drug production and storage, from the chemical synthesis to the final formulation. In the course of a study involving the quantitative analysis of isotibolone by X-ray powder diffraction, the authors determined the structure of the title compound using a recently developed approach (A. Gomez and S. Kycia, J. Appl. Crystallogr. 2011, 44, 708-713). The structure is monoclinic, space group P2(1) (4), with unit cell parameters a = 6.80704(7) angstrom, b = 20.73858(18) angstrom, c = 6.44900(6) angstrom, beta = 76.4302(5)degrees, V = 884.980(15) angstrom(3) and two molecules per unit cell (Z = 2). The molecules are hydrogen bonded in the ab plane forming layers that are held together in the crystal by van der Waals interactions along the c-axis.

The 2:1 cycloadducts from [3+2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a-d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2: 1 bisadducts, which were obtained from a double [3+2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a-d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a-d). In the second step, the addition of a second equivalent of 4 to 6 yielded the 2: 1 bisadducts 7a-d without any traces of 6. All compounds 7a-d were unstable during the transition from the mesophase to the isotropic state upon first heating as evidenced by the large peaks in the differential scanning calorimetry traces. Due to the chemical instability of the compounds upon heating, the transition temperature related to the smectic C to smectic A transitions was acquired by means of an image processing method. X-Ray diffraction experiments were also used to analyse the liquid-crystalline phases. A theoretical calculation was performed using density functional theory (DFT) methods at the PBE1PBE/6-311+G(2d,p) level (with solvent effect) in order to get information about the energetic profile of the 2: 1 cycloaddition. DFT studies revealed that the cycloaddition process is controlled by the HOMO(dipolarophile) - LUMO(1,3-dipole), and that the double [3+2] 1,3-dipolar cycloaddition reaction is quite possible.