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PubMed1966

Physiological basis of differential strontium accumulation in two barley genotypes.

Studies of rates of Sr transport from nutrient solutions containing 8 concentrations of Sr indicate a definite trend towards higher rates of Sr transport by roots of intact 12-day-old Regal barley (Hordeum vulgare, L.) seedlings as compared with Tregal. Differences in rates of Sr transport between the 2 varieties were also indicated by higher concentrations of Sr in fluids exuding from decapitated Regal roots as compared to fluids exuding from decapitated Tregal roots.No differences between Regal and Tregal were found in the physical factors of distance from epidermis to endodermis, number of cortical cell layers, or transpiration rate. Furthermore, no relationship was observed between transpiration rate and rate of Sr accumulation.Dependence of Sr transport on metabolic processes was indicated by marked effects of temperature, cyanide, and dinitrophenol on rates of Sr transport. Q(10) values for Sr transport by Regal and Tregal approached 2, thereby indicating that metabolic reactions were associated with this process. Strontium transport by both Regal and Tregal was markedly depressed in the presence of either cyanide or dinitrophenol. These results led to the conclusion that the Sr transport process is dependent on metabolic energy derived from respiration.

Journal Article↗
PubMed2002

K(2)SrNb(6)Cl(18), dipotassium strontium hexaniobium octadecachloride.

The structure of dipotassium strontium hexaniobium octadecachloride is based on [Nb(6)Cl(i)(12)Cl(a)(6)](4-) units (i and a denote 'inner' and 'outer' ligands, respectively), which have crystallographically imposed -3 symmetry, linked together by K(+) and Sr(2+) cations. The K(+) cation occupies a tetrahedral site in the face-centered cubic lattice of cluster units, and is bonded to 12 Cl ligands. The Sr atom is located in an octahedral site and is bonded to six outer Cl ligands.

Journal Article↗
PubMed2003

Magnesium iodide-4,4'-bipyridine-water (1/3/4) and strontium iodide-4,4'-bipyridine-propan-1-ol (1/2.5/2).

Both of the title compounds, catena-poly[[[tetraaquamagnesium(I)]-micro-4,4'-bipyridine-kappa(2)N:N'] diiodide bis(4,4'-bipyridine) solvate], [[Mg(C(10)H(8)N(2))(H(2)O)(4)]I(2).2C(10)H(8)N(2)](n), (I), and catena-poly[[[micro-4,4'-bipyridine-bis[diiodobis(propan-1-ol)strontium(I)]]-di-micro-4,4'-bipyridine-kappa(4)N:N'] bis(4,4'-bipyridine) solvate], [[Sr(2)I(4)(C(10)H(8)N(2))(3)(C(3)H(8)O)(4)].2C(10)H(8)N(2)](n), (II), are one-dimensional polymers which are single- and double-stranded, respectively, the metal atoms being linked by the 4,4'-bipyridine moieties. The Mg complex, (I), is [cis-[(H(2)O)(4)Mg(N-4,4'-bipyridine-N')((2/2))]](( infinity | infinity ))I(2).4,4'-bipyridine and Mg has a six-coordinate quasi-octahedral coordination environment. The Sr complex, (II), is isomorphous with its previously defined Ba counterpart [Kepert, Waters & White (1996). Aust. J. Chem. 49, 117-135], being [(propan-1-ol)(2)I(2)Sr(N-4,4'-bipyridine-N')((3/2))](( infinity | infinity )).4,4'-bipyridine, with the I atoms trans-axial in a seven-coordinate pentagonal-bipyramidal Sr environment.

Journal Article↗
PubMed2004

Oxygen-deficient strontium cobaltate, SrCoO2.64.

Single crystals of strontium cobaltate, SrCoO(3-x), have been grown by the floating-zone method in an oxygen flow. The compound crystallizes with the cubic perovskite structure, with Pm-3m symmetry, as determined by X-ray diffraction. Refinement of the O-atom site occupancy yields the chemical composition SrCoO(2.64) [x = 0.36 (3)]. The anisotropic displacement ellipsoids of the O atoms suggest that their positional disorder occurs in a direction perpendicular to that of the Co-O bonds.

Journal Article↗
PubMed2005

A new strontium borophosphate, Sr6BP5O20, from synchrotron powder data.

Strontium borophosphate, Sr6BP5O20, was prepared by a solution synthesis method. The crystal structure was solved ab initio from synchrotron powder data without preliminary knowledge of the chemical formula. The compound crystallizes in space group -4c2. Sr atoms occupy sites coordinated by eight or nine O atoms, and the anionic layer consists of BO4 and PO4 tetrahedra. The eightfold-coordinated Sr atom lies at a site with twofold symmetry, while one P atom and the B atom are located on special positions of site symmetry -4.

Journal Article↗
PubMed2006

Supramolecular structure and second harmonic generation in strontium bis(hydrogen L-malate) hexahydrate.

The title compound, tetraaquabis(hydrogen L-malato)strontium(II) dihydrate, [Sr(C4H5O5)2(H2O)4].2H2O, is a new non-linear optical semi-organic material with a second harmonic generation efficiency approximately 3.5 times greater than that of potassium dihydrogen phosphate. The malate anions are interconnected through directional O-H...O hydrogen bonding, in a head-to-tail arrangement, creating extended anionic chains along [001]. Neighbouring parallel chains are crosslinked by water molecules, resulting in a three-dimensional architecture. The Sr2+ ion is coordinated by eight O atoms. This material is a new candidate for non-linear optical applications since the crystals are stable and easy to grow.

Journal Article↗
PubMed1997

Giant Piezoelectric Effect in Strontium Titanate at Cryogenic Temperatures

Piezoelectric materials have many applications at cryogenic temperatures. However, the piezoelectric response below 10 kelvin is diminished, making the use of these materials somewhat marginal. Results are presented on strontium titanate (SrTiO3), which exhibits a rapidly increasing piezoelectric response with decreasing temperature below 50 kelvin; the magnitude of its response around 1 kelvin is comparable to that of the best materials at room temperature. This "giant" piezoelectric response may open the way for a broad class of applications including use in ultralow-temperature scanning microscopies and in a magnetic field-insensitive thermometer. These observations, and the possible divergence of the mechanical response to electric fields at even lower temperatures, may arise from an apparent quantum critical point at absolute zero.

Journal Article↗
PubMed1990

Binding of Dissolved Strontium by Micrococcus luteus.

Resting cells of Micrococcus luteus have been shown to remove strontium (Sr) from dilute aqueous solutions of SrCl(2) at pH 7. Loadings of 25 mg of Sr per g of cell dry weight were achieved by cells exposed to a solution containing 50 ppm (mg/liter) of Sr. Sr binding occurred in the absence of nutrients and did not require metabolic activity. Initial binding was quite rapid (<0.5 h), although a slow, spontaneous release of Sr was observed over time. Sr binding was inhibited in the presence of polyvalent cations but not monovalent cations. Ca and Sr were bound preferentially over all other cations tested. Sr-binding activity was localized on the cell envelope and was sensitive to various chemical and physical pretreatments. Bound Sr was displaced by divalent ions or by H. Other monovalent ions were less effective. Bound Sr was also removed by various chelating agents. It was concluded that Sr binding by M. luteus is a reversible equilibrium process. Both ion exchange mediated by acidic cell surface components and intracellular uptake may be involved in this activity.

Journal Article↗
PubMed2005

Nanocrystallization of ferroelectric strontium bismuth vanadium niobate in lithium tetraborate glasses.

Transparent glass samples in (100-3x) (Li2O-2B2O3)-x(SrO-Bi2O3-0.7Nb2O5-0.3V2O5) (10 < or = x < or = 60, in molar ratio) system have been fabricated via conventional melt-quenching technique. The as-quenched samples, of all the compositions under study have been confirmed to be amorphous, by X-ray powder diffraction (XRD) studies. Differential thermal analysis (DTA) was employed to confirm the glassy nature of the as-quenched glasses. Glass composites comprising vanadium doped strontium bismuth niobate nanocrystallites were obtained by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. Perovskite SrBi2(Nb0.7VO3)2O9-delta phase formation was found to be preceded by an intermediate fluorite phase which was established via XRD and transmission electron microscopy (TEM). The dielectric constants (epsilonr) of the as-quenched glasses as well as the glass nanocrystal composites decreased with increase in frequency (100 Hz-10 kHz) at 300 K. Interestingly, the dielectric constant of the glass nanocrystal composite (heat-treated at 783 K/6 h) undergoes a maximum in the vicinity of the crystallization temperature of the host glass (Li2B4O7) reaching an anomalously high value (approximately 10(6)) at 800 K. Different dielectric mixture formulae were employed to rationalize the dielectric properties of the glass nanocrystal composite. The optical transmission properties of these glass nanocrystal composites were found to have strong compositional dependence.

Bismuth↗
PubMed2003

Efficient cooling and trapping of strontium atoms.

We report the capture of cold strontium atoms in a magneto-optical trap (MOT) at a rate of 4 x 10(10) atoms/s. The MOT is loaded from an atomic beam decelerated by a Zeeman slower operating with a focused laser beam. The 461-nm laser, used for both cooling and trapping, was generated by sum-frequency mixing in a KTP crystal with diode lasers at 813 nm and a Nd:YAG laser at 1064 nm. As much as 115 mW of blue light was obtained.

Journal Article↗
PubMed2006

Highly efficient, 0.84 slope efficiency, 901 nm, quasi-two-level laser emission of Nd in strontium lanthanum aluminate.

The possibility of using direct pumping into the emitting level of the Nd3+ ion in magnesium-compensated strontium lanthanum aluminate (Sr(1-x)La(x-y)Nd(y)Mg(x)Al(12-x)O19) to improve 900 nm 4F(3/2) --> 4I(9/2) laser emission is discussed. Selection of the composition parameters x and y for optimization of laser emission and reduction of heat generation is based on the spectroscopic and crystal growth characteristics. Pumping in the 865.5 nm absorption band 4I(9/2)(Z1) --> 4F(3/2)(R1) transforms the laser process into a quasi-two-level scheme of very low (below 4%) quantum defects. A very high slope efficiency (over 84%) for 901 nm continuous-wave laser emission is demonstrated with Ti:sapphire laser pumping in this band for a crystal with x = 0.4 and y = 0.05.

Journal Article↗
PubMed2005

[Strontium Ranelate as a new therapeutic agent for osteoporosis].

Strontium ranelate is a new chemical entity, which was recently demonstrated to reduce the fracture risk in osteoporosis patients. This unique compound has both stimulatory effect of osteoblast-mediated bone formation and inhibitory effect of osteoclast-mediated bone resorption, leading to increased bone mass.

Bone Density↗
PubMed2006

[Strontium ranelate].

Strontium ranelate, which has dual effects of decreasing bone resorption and increasing bone formation, is a new orally active drug to treat osteoporosis. Although the clinical values are scientifically proved and the governments admit as one of the treatment for osteoporosis in many countries, the clinical trial is still undergoing in Japan.

Aged↗