Sc Site Research Articles

(45)Sc NMR spectroscopy and first-principles calculation on the symmetry of ScO6 polyhedra in BaO-Sc2O3-based oxides.

The correlation between the local structure and the electric-field gradient at the Sc site in ScO6 polyhedra in Sc2O3, Ba3Sc4O9 and BaSc2O4 was investigated by means of (45)Sc NMR spectroscopy and DFT calculations. The electric-field gradient at the nucleus as determined experimentally and by calculations is compared using the quadrupolar coupling constant, CQ, around chemically and crystallographically distinct Sc sites in Sc-containing compounds. With CQ as the NMR parameter, the results obtained from the DFT calculation were in good agreement with the NMR measurements. The increase in the CQ values with the standard deviation of the O-O bond length surrounding Sc indicates that CQ is affected by the distribution of the six nearest neighboring O atoms around Sc. This study suggests that CQ plays an important role as an indicator of the local structure around ions, and that a combined complementary approach using both NMR spectroscopy and DFT calculation can be used along with diffraction techniques to provide a detailed understanding of crystal structures.

Electronic and optical properties of ScN and (Sc,Mn)N thin films deposited by reactive DC-magnetron sputtering

Scandium nitride (ScN) is a rocksalt semiconductor that has attracted significant attention from various researchers for a diverse range of applications. Motivated by the prospect of using its interesting electronic structure for optoelectronic and dilute magnetic semiconductor applications, we present detailed studies of the electronic transport and optical properties of ScN and its alloys with manganese nitride (MnN). Our results suggest (a) dilute manganese doping in ScN compensates for the high n-type carrier concentrations arising due to oxygen impurities and (b) an n-type to p-type carrier type transition occurs at a composition between 5.8% and 11% Mn on Sc sites. In terms of its optical properties, our analysis clearly indicates direct and indirect bandgap absorption edges of ScN located at 2.04 eV and 1.18 eV, respectively. In addition to the direct gap absorption edge, (Sc,Mn)N samples also show Mn-defect induced electronic absorption. Photoluminescence measurements at room temperature from ScN films exhibit a yellowish-green emission corresponding to direct gap radiative recombination. Direct gap recombination is not expected given the smaller indirect gap. A possible role of high excitation intensities in suppressing relaxation and recombination across the indirect bandgap is suspected. Raman spectroscopic and ellipsometric characterization of the dielectric permittivities of ScN and (Sc,Mn)N are also presented to assist in understanding the potential of ScN for optoelectronic applications.

Some new [(thione)2Au(diamine)]Cl3 complexes: Synthesis, spectroscopic characterization, computational and in vitro cytotoxic studies

Recent advances in oncology are focused on developing new complexes of gold(III) with various ligands that show augmented anti-proliferative potential and reduced toxicity as compared to cis-platin. In this study, new Au(III) complexes of the type [(thione)2Au(diamine)]Cl3 are reported, where thione=1,3-imidazolidine-2-thione (Imt), 1,3-Diazinane-2-thione (Diaz) and diamine=1,2-diaminoethane (en), 1,3-diaminopropane (pn) or 1,4-diaminobutane (bn). The solid state IR as well as 13C and 15N NMR data indicate that Au(III) center is bonded via sulfur of thiocarbonyl SC site of the thiones and also chelated by the diamines from the trans side of coordinated thiones. Spectroscopic data are evaluated by comparisons with calculated data from the built and optimized structure by GAUSSIAN 09 at the RB3LYP level with LanL2DZ bases set. These new Au(III) complexes based on mixed thione and diamine ligands are very similar to the square planar structure of tetracoordinate [Au(en)2]Cl3complex. In this study, cytotoxicity data for these gold(III) complexes against C6 glioma cell lines are also reported, and the results indicate some complexes have cytotoxicity comparable to cis-platin.

Assessment of Vegetation Establishment on Tailings Dam at an Iron Ore Mining Site of Suburban Beijing, China, 7 Years After Reclamation with Contrasting Site Treatment Methods

Strip-mining operations greatly disturb soil, vegetation and landscape elements, causing many ecological and environmental problems. Establishment of vegetation is a critical step in achieving the goal of ecosystem restoration in mining areas. At the Shouyun Iron Ore Mine in suburban Beijing, China, we investigated selective vegetation and soil traits on a tailings dam 7years after site treatments with three contrasting approaches: (1) soil covering (designated as SC), (2) application of a straw mat, known as "vegetation carpet", which contains prescribed plant seed mix and water retaining agent (designated as VC), on top of sand piles, and (3) combination of soil covering and application of vegetation carpet (designated as SC+VC). We found that after 7 years of reclamation, the SC+VC site had twice the number of plant species and greater biomass than the SC and VC sites, and that the VC site had a comparable plant abundance with the SC+VC site but much less biodiversity and plant coverage. The VC site did not differ with the SC site in the vegetation traits, albeit low soil fertility. It is suggested that application of vegetation carpet can be an alternative to introduction of topsoil for treatment of tailings dam with fine-structured substrate of ore sands. However, combination of topsoil treatment and application of vegetation carpet greatly increases vegetation coverage and plant biodiversity, and is therefore a much better approach for assisting vegetation establishment on the tailings dam of strip-mining operations. While application of vegetation carpet helps to stabilize the loose surface of fine-structured mine wastes and to introduce seed bank, introduction of fertile soil is necessary for supplying nutrients to plant growth in the efforts of ecosystem restoration of mining areas.

Tunable Color of Ce3+/Tb3+/Mn2+-Coactivated CaScAlSiO6 via Energy Transfer: A Single-Component Red/White-Emitting Phosphor

A series of single-component red/white-emitting CaScAlSiO6:Ce(3+),Tb(3+),Mn(2+) phosphors have been synthesized by a solid-state reaction. It is observed that CaScAlSiO6:Ce(3+),Tb(3+) phosphors exhibit two dominating bands situated at 380 and 542 nm, originating from the allowed 5d → 4f transition of the Ce(3+) ion and the (5)D4 → (7)F(J) = (J = 6, 5, 4, 3) transition of the Tb(3+) ion, respectively. As for CaScAlSiO6:Ce(3+),Mn(2+), our results indicate that Mn(2+) may occupy not only a Ca(2+) site to generate an orange emission [Mn(2+)(I)] at 590 nm but also a Sc(3+) site to generate a red emission [Mn(2+)(II)] at 670 nm. Both energy transfers from Ce(3+) to Tb(3+) and from Ce(3+) to Mn(2+) in the CaScAlSiO6 host are investigated and have been demonstrated to be of the resonant type via a dipole-dipole mechanism. By proper tuning of the relative composition of Tb(3+)/Mn(2+), white light can also be achieved upon excitation of UV light, indicating that the developed phosphor may potentially be used as a single-component red/white-emitting phosphor for UV-light-emitting diodes.

Lanthanide-doped NaScF4 nanoprobes: crystal structure, optical spectroscopy and biodetection

Trivalent lanthanide ions (Ln(3+))-doped inorganic nanoparticles (NPs) as potential luminescent bioprobes have been attracting tremendous interest because of their unique upconversion (UC) and downconversion (DC) luminescence properties. NaScF4, as an important host material, has been rarely reported and its crystal structure remains unclear. Herein, based on the single crystal X-ray diffraction, the space group of NaScF4 crystals was determined to be P31 containing multiple sites of Sc(3+) with crystallographic site symmetry of C1, which was verified by high-resolution photoluminescence spectroscopy of Eu(3+) at low temperature (10 K). Furthermore, monodisperse and size-controllable NaScF4:Ln(3+) NPs were synthesized via a facile thermal decomposition method. The biotinylated NaScF4:Er(3+)/Yb(3+) NPs were demonstrated for their applications as a heterogeneous UC luminescence bioprobe to detect avidin with a detection limit of 180 pM. After bioconjugation with amino-terminal fragment (ATF) of urokinase plasminogen activator (uPA), NaScF4:Ln(3+) NPs also exhibited specific recognition of cancer cells overexpressed with uPA receptor (uPAR, an important marker of tumor biology and metastasis), showing great potentials in tumor-targeted bioimaging.

The pyrochlore-type molybdate Pr2Mo1.73Sc0.27O7

Dipraseodymium molybdenum scandium hepta­oxide, Pr2Mo1.73Sc0.27O7, crystallizes in the cubic pyrochlore-type structure. In the crystal, (Mo,Sc)O6 octa­hedra are linked together by common corners, forming a three-dimensional [(Mo,Sc)2O6] framework. The Pr atom and another O atom atom are located in the voids of this framework. The Mo and the Sc atom are distributed statistically over the same 16d crystallographic position, with site-occupancy factors of 0.867 (3) and 0.133 (3), respectively. The Pr3+ ions are surrounded by six O atoms from the MoO6 octa­hedra and by two other O atoms, forming a ditrigonal scalenohedron. All atoms lie on special positions. The Pr and the statistically distributed (Mo,Sc) sites are in the 16c and 16d positions with .-3m symmetry, and two O atoms are in 48f and 8a positions with 2.mm and -43m site symmetry, respectively.

A first-principles study of hydrogen interaction and saturation on ScAl3

Complex metal hydrides are promising hydrogen storage material for mobile applications. The presence of scandium catalysts in complex metal hydrides is found to improve significantly the kinetics of H2 adsorption and desorption. The exact role of these additives is not completely understood. NMR studies suggests the presence of distorted ScAl3 phase which is attributed to the enhancement of reversible uptake and release rates of H2. In this study, we have investigated the hydrogen interaction and saturation on stable ScAl3 cluster at various sites using the density functional theory by employing unrestricted B3LYP/6-311++G(d,p) and the GGA-PW91/DNP methods. From natural bond orbital charge analysis and electrostatic potential superimposed on electron density plots, ScAl3 is found to be more polarized and Sc atom in ScAl3 cluster has higher negative charge and electron density over Al atoms. H2 undergoes dissociative chemisorption on the Sc atop site in ScAl3 resulting in Sc–H–Al bridge structure. The hydrogen saturation is studied by sequential H2 adsorption on ScAl3 cluster. In the Sc site, the first H2 molecule undergoes dissociative chemisorption and further addition results in H2 physisorption with the maximum loading of 6 H2 molecules resulting in stable ScAl3H12 structure. To obtain mechanistic insights into the hydrogenation process, the transition state and activation energy of H2 dissociation on the ScAl3 system has been determined.

Inhibition of the binding of MSG-intermolt-specific complex, MIC, to the sericin-1 gene promoter and sericin-1 gene expression by POU-M1/SGF-3

The sericin-1 gene encoding a glue protein is expressed in the middle silk gland (MSG) of the silkworm, Bombyx mori. A member of the class III POU domain transcription factors, POU-M1, was cloned as the factor bound to the SC site of the sericin-1 promoter and has been proposed to be a positive transcription factor. In this study, we analyzed the expression pattern of the POU-M1 gene in fourth and fifth instars in comparison with the pattern of the sericin-1 gene. The POU-M1 gene was expressed strongly in the region anterior to the sericin-1-expressing portion of the silk gland at both feeding stages. As the sericin-1-expressing region expands from the posterior to middle portions of the MSG in the fifth instar, the POU-M1-expressing region retreated from the middle to anterior portion. Introduction of the expression vector of POU-M1 into the silk glands by gene gun technology repressed promoter activity of the sericin-1 gene, suggesting that POU-M1 regulates the sericin-1 gene negatively. An in vitro binding assay showed that POU-M1 bound not only to the SC site but also to other promoter elements newly detected in vivo. Another spatiotemporal specific factor MIC binds to these elements, and POU-M1 competed with MIC to bind at the -70 site essential for promoter activity. These results suggest that POU-M1 is involved in restricting the anterior boundary of the sericin-1-expressing region in the silk gland by inhibiting the binding of the transcriptional activator to the promoter elements.

Sc0.43(2)Rb2Mo15S19, a partially Sc-filled variant of Rb2Mo15S19

The structure of scandium dirubidium pentadecamolybdenum nonadecasulfide, Sc(0.43(2))Rb(2)Mo(15)S(19), constitutes a partially Sc-filled variant of Rb(2)Mo(15)S(19) [Picard, Saillard, Gougeon, Noel & Potel (2000), J. Solid State Chem. 155, 417-426]. In the two compounds, which both crystallize in the R ̅3c space group, the structural motif is characterized by a mixture of Mo(6)S(i)(8)S(a)(6) and Mo(9)S(i)(11)S(a)(6) cluster units (`i' is inner and `a' is apical) in a 1:1 ratio. The two components are interconnected through interunit Mo-S bonds. The cluster units are centred at Wyckoff positions 6b and 6a (point-group symmetries ̅3. and 32, respectively). The Rb(+) cations occupy large voids between the different cluster units. The Rb and the two inner S atoms lie on sites with 3. symmetry (Wyckoff site 12c), and the Mo and S atoms of the median plane of the Mo(9)S(11)S(6) cluster unit lie on sites with .2 symmetry (Wyckoff site 18e). A unique feature of the structure is a partially filled octahedral Sc site with ̅1 symmetry. Extended Hückel tight-binding calculations provide an understanding of the variation in the Mo-Mo distances within the Mo clusters induced by the increase in the cationic charge transfer due to the insertion of Sc.

Study on the Luminescence and Energy Level of Lanthanide Ions in Lu0.8Sc0.2BO3 Host

Emission and excitation spectra of undoped and Ln(3+) (Ln = Ce, Pr, Nd, Yb)-doped Lu(0.8)Sc(0.2)BO(3) were studied by vacuum ultraviolet spectroscopy, and the X-ray excited luminescence spectra were measured as well at room temperature. The undoped specimen presented two different emissions upon excitation at energies in the vicinity of the band gap or with X-ray. The emission at the highest energy side, located at 4.77 eV, was ascribed to self-trapped exciton, which is anchored by electron capture around the Sc site. We also observed three broad emission bands at 4.43, 3.02, and 2.10 eV, which might be attributed to the trapped exciton, defect -related emissions, or both. Energy transfer processes to the doped lanthanide ions in Lu(0.8)Sc(0.2)BO(3) via exciton state or sequential electron-hole capture are discussed. Finally, the energy level diagram for divalent and trivalent lanthanides in Lu(0.8)Sc(0.2)BO(3) was constructed using the obtained spectroscopic parameters and the three parameters method (Dorenbos, P. J. Phys.: Condens. Matter 2003, 15, 8417).

Interpretation of the Magnetic Order, Neutron Diffraction and <sup>111</sup>Cd PAC Studies of NdScGe

NdScGe is a ferromagnet with TC = 194(2) K. The magnetic moments of the Nd substructure order along the tetragonal c-axis just below TC and undergo a gradual canting away from the c-axis upon cooling, commencing at around 165 K. We used neutron powder diffraction to show that the Nd magnetic moments lie 70(3)o off the c-axis at 4 K [1]. The apparent discrepancy between our neutron diffraction results and those obtained using PAC [2] (a canting angle of around 32o just below TC , increasing to 45o at 25 K) can be reconciled by placing the principal axis of the electric field gradient tensor in the tetragonal basal plane, rather than along the c-axis, as assumed in the PAC analysis. The unusual temperature dependence of the 111Cd PAC quadrupole frequency at the Sc site, which was interpreted in terms of a lattice softening occurring near the Curie temperature, is shown to be a consequence of the fact that one cannot determine the sign of the quadrupole frequency from a PAC experiment. Finally, we show that the Nd magnetic moments in the canted regime have a [110] basal component rather than [100].

The Essentiality of the Epididymal Fat Pad for Spermatogenesis

In 1935, two landmark publications by Cornell University scientists established the dogma that longevity and reproductive performance in rodents are primarily controlled by energy intake. McCay, Crowell, and Maynard (1) reported that the lifespans of rats maintained on calorie-restricted diets that retarded growth were prolonged, especially in males. In the same year, Asdell and Crowell (2) showed that sexual development in these growth-retarded rats was also retarded; vaginal opening and age at first estrus were delayed, and in contrast to ad libitum-fed rats, the two events became completely dissociated. After World War II, these findings were extended to domestic animals, where it was shown, for example, that calves fed from birth to sexual maturity at 130% of the recommended total digestible nutrient (TDN) allowances first came into estrus at 37.4 wk of age, compared with 49.1 wk for calves fed 100% of recommended TDN allowances and 72.0 wk for calves fed 70% of recommended TDN allowances (3). Similar data were obtained for age at the onset of spermatogenesis in male calves. Greater longevity of dairy cattle fed the 70% recommended TDN allowance was demonstrated by 1964 (4), and later the ability of caloric restriction to increase longevity was demonstrated in species as diverse as flies (5), worms (6), yeast (7), rodents (8), and monkeys (9). Because the calorie-restricted and control diets used in these early studies contained equal amounts of fat, most workers assumed that any influence of fat on reproduction was through its contributions to energy metabolism. However, by 1963, evidence that fat plays an important role in reproductive performance was obtained by Kennedy and Mitra (10) and by Frisch and McArthur in 1974 (11). These studies were the first to indicate that adipose tissue plays a direct role in female reproduction and suggested the need for a minimal amountof fat fornormal reproductivedevelopment.Finally, the discovery of leptin, a peptide hormone produced only in fat cells, removed any doubt as to the ability of fat cells to act as an endocrine organ and firmly established the role of adipose tissue in reproductive performance (12). Now, in what may become another landmark paper, Chu et al. (13) have extended these early results by establishing, for the first time, that a specific fat depot, the epididymal fat pad, produces a locally acting factor responsible for maintaining spermatogenesis in the hamster. Removal of the epididymal fat pad interrupts spermatogenesis and increases FSH concentration but does not affect testosterone, LH concentration, or mating behavior. However, it increases serum FSH concentrations. Transplantation of the excised epididymal fat pad to a sc site did not restore spermatogenesis. Removal of comparable amounts of white adipose tissue from other sites (inguinal) was also without effect, disproving the idea that the effect is due to a decreased energy supply and/or the need for some minimal amount of fat. The authors do point out the possibility that altered testicular blood flow, resulting in increased testicular temperature, might be an alternative explanation for the inhibition of spermatogenesis that occurs after removal of the epididymal fat pad. However, they do not think this is the case, because of the histological normality of the testicular interstitial cells and the normal testosterone production. They also point out that denervation of the testes at both poles, including the pampiniform plexus, which is more likely to produce damage to the venous drainage than epididymal fat pad removal, did not affect spermatogenesis. If the authors are correct in these conclusions, the race is on to identify any compounds of epididymal fat pad

Electronic and structural properties, and hyperfine interactions at Sc sites in the semiconductorSc2O3: TDPAC andab initiostudy

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Magnetic interactions in equi-atomic rare-earth intermetallic alloys RScGe(R = Ce,Pr, Nd and Gd) studied by time differential perturbed angular correlation spectroscopy andab initio calculations

Applying the time differential perturbed angular correlation (TDPAC)technique we have measured electric and magnetic hyperfine fields of the111Cd impurity in equi-atomic rare-earth intermetallic alloys RScGe(R = Ce,Pr and Gd) showing antiferro- and ferromagnetism with unusually high ordering temperatures.The Cd nuclei occupying the Sc site show high magnetic hyperfine fields with saturation valuesBhf(0) = 21 kG, 45 kG and 189 kG in CeScGe, PrScGe and GdScGe, respectively. By comparing the resultswith the hyperfine field data of Cd in rare-earth metals and estimations from the RKKY model,we find evidence for the presence of additional spin density at the probe nucleus, possibly dueto spin polarization of Sc d band electrons. The principal electric field gradient componentVzz in CeScGe, PrScGe and GdScGe has been determined to be5.3 × 1021 V m−2,5.5 × 1021 V m−2 and 5.6 × 1021 V m−2, respectively. Supplementing the experimental measurements, we have carriedout ab initio calculations for pure and Cd-doped RScGe compounds withR = Ce, Pr, Nd and Gd using the full potential linearized augmented plane wave(FLAPW) method based on density functional theory (DFT). From the totalenergies calculated with and without spin polarization we find ferrimagnetic groundstates for CeScGe and PrScGe while NdScGe and GdScGe are ferromagnetic.In addition, we find a sizable magnetic moment at the Sc site, increasing from≈0.10 μB inCeScGe to ≈0.3 μB in GdScGe, confirming the spin polarization of Sc d band electrons. The calculated electricfield gradient and magnetic hyperfine fields of the Cd impurity closely agree with theexperimental values. We believe spin polarization of Sc 3d band electrons, stronglyhybridized with spin polarized 5d band electrons of the rare-earth, enables a long rangeRuderman–Kittel–Kasuya–Yosida (RKKY) interaction between RE 4f momentswhich in turn leads to high magnetic ordering temperatures in RScGe compounds.

Mutual replacement reactions in alkali feldspars II: trace element partitioning and geothermometry

Perthitic alkali feldspar primocrysts in layered syenites in the Klokken intrusion in South Greenland, underwent dissolution–reprecipitation reactions in a circulating post-magmatic aqueous fluid at ~450°C, and are to a large degree pseudomorphs. These ‘mutual replacement’ reactions provide a perfect natural experiment with which to study trace element partitioning between sodium and potassium feldspars growing simultaneously. The reactant ‘phase’ was a cryptoperthitic feldspar consisting of low albite and low microcline in a coherent sub-μm ‘braid’ intergrowth and the product phases were ‘strain-free’ incoherent subgrains of low albite and low microcline forming microporous patch perthites on scales up to 200 μm. The driving force for the reaction was reduction of coherency strain energy. The mechanisms of this process are described in Part I. Five mixed braid perthite–patch perthite crystals were analysed for major and trace elements using laser ablation-inductively coupled plasma mass spectrometry with a 19 μm beam diameter. This gave bulk analyses of the braid texture, which were in the range Ab73–54Or45–27An4.3–0.8, but could resolve Ab- and Or-rich patches in patch perthite. The major element bulk compositions of the crystals were retained during the replacement reactions. Major components in patches plot on tielines in the Ab–Or–An ternary system that pass through or very close to the parent braid perthite composition and indicate local equilibrium on the scale of a few tens of mm. Many trace elements, including REE, were lost to the fluid during the deuteric reactions, but the effect is large only for Fe and Ti. Cs, Pb and Sr were added to some crystals. Plots of log distribution coefficient D for Rb, Ba, Pb, Eu2+, La and Ce between Or- and Ab-rich patches against ionic radius are straight lines, assuming eightfold coordination, and to a first approximation are independent of ionic charge. K also lies on these lines, and the smaller ions Na and Ca lie close to them. The best linear fits were obtained using ionic radii for [8]K and [8]Ca, but there is ambiguity as to whether [7]Na or [5]Na is most appropriate. The linear relationship shows that the listed trace elements are in the feldspar M-site rather than in inclusions. Tl is in M although an exact D could not be obtained. The very large Cs ion partitions strongly into the Or-rich phase but its D value appears to be less than predicted by extrapolation. The near-linearity arises because partitioning is occurring between two solids into sites which have similar Young’s moduli, so that the parabolas that normally represent trace element partitioning between crystals and liquids (which have negligible shear strength) approximately cancel out. Ga and Be are in T-sites, as well as some of the Fe and Ti present, although part is in oxide inclusions. The site of Sc is unclear, but if structural it is likely to be T. Partitioning on M-sites is a potential geothermometer but because the effective size of the irregular M-site is defined by its K and (Na + Ca) contents, which are controlled by ternary solvus relationships, its calibration is not independent of conventional two-feldspar geothermometers. Trace elements may however provide a useful means of confirming that feldspar pairs are in equilibrium, and of recognising feldspar intergrowths produced by non-isochemical replacement rather than exsolution. Two-feldspar geothermometry for the ternary phases in the low-albite microcline patch perthites gives temperatures above the stability range of microcline, markedly so if a correction is made for Si–Al ordering. This is probably because current geothermometers are too sensitive to low concentrations of An in ordered Or-rich feldspars. This interpretation is supported by two-feldspar assemblages growing at known temperatures in geothermal systems and sedimentary basins.

Solid state NMR spectroscopy as a probe of structure and bonding in the carbides Sc 3TC 4 (T = Co, Ni, Ru, Rh, Os, Ir)

Scandium transition metal carbides having the formula Sc 3TC 4 (T = Co, Ni, Ru, Rh, Os, Ir) have been structurally characterized by solid state 13C and 45Sc nuclear magnetic resonance spectroscopy. In all the compounds investigated, well-resolved signals are observed for crystallographically distinct carbon and scandium sites, confirming the formation of superstructures in the Rh and Ir compounds at ambient temperature. 45Sc NMR spectra are dominated by anisotropic broadening due to second-order quadrupolar perturbations. The nuclear electric quadrupolar coupling parameters (the coupling constant C Q and the asymmetry parameter η) are generally found in good agreement with values calculated theoretically from the crystal structure using the WIEN2k program. Furthermore, the spectra reveal large isotropic resonance shift differences between inequivalent Sc sites in a given compound and between sites of the same type for different compounds. Altogether the results illustrate that 45Sc NMR is a sensitive method for detecting isotropic and anisotropic local electron density variations in the Sc 3TC 4 family.

Pharmacokinetic study with N-Ile1-Thr2-63-desulfato-r-hirudin in rabbits by means of bioassay

To study the pharmacokinetic (PK) properties in rabbits treated with N-Ile(1)-Thr(2)-63-desulfato-r-hirudin (rH) newly developed in China by means of bioassay in order to provide preclinical experiment basis for its development as a novel anticoagulant agent. rH plasma concentration was determined using bioassay based on ex vivo antithrombin activity of rH. Normal rabbits received iv rH 4.0, 2.0 and 1.0 mg/kg or sc rH 2.0 mg/kg, respectively. The rabbits with acute severe renal failure were given iv rH 2.0 mg/kg. The bioassay described in this paper met requirements for study of PK in rabbits. The major PK parameters after iv dosing were as follows: t(1/2beta) 58.4-59 min. V(d) 0.09-0.12 L/kg, CL 0.0035-0.0040 L/(kg.min); AUC were proportional to the doses, t(1/2) and CL did not change significantly with the doses. The sc bioavailability reached 94%. The rabbits suffering from acute severe renal failure presented 11-fold longer t(1/2beta) and 13-fold greater AUC than normal healthy rabbits. rH exhibited rapid elimination, distribution was only limited to extracellular space and good absorption from sc site. The excretion of rH by kidneys played a very important role in the elimination of rH. The PK of rH could be described by the two- and one-compartment model after iv and sc dosing, respectively, and followed linear kinetics.

Ectopic bone formation using an injectable biphasic calcium phosphate/Si-HPMC hydrogel composite loaded with undifferentiated bone marrow stromal cells

We have used a new synthetic injectable composite constituted of hydroxyapatite/tricalcium phosphate (HA/TCP) particles in suspension in a self-hardening Si–hydroxypropylmethylcellulose (HPMC) hydrogel. The aim of this study was to evaluate in vivo the biocompatibility and the new bone formation efficacy of this scaffold loaded with undifferentiated bone marrow stromal cells (BMSCs). This biomaterial was mixed extemporaneously with BMSCs prepared from C57BL/6 mice, injected in subcutaneous and intramuscular sites and retrieved 4 and 8 weeks after implantation. Dissection of the implants revealed a hard consistency and the absence of a fibrous capsule reflecting a good integration into the host tissues. Histological analysis showed mineralized woven bone in the granule inter-space with numerous active osteoclasts attached to the particles as assessed by the presence of multinucleated cells positively stained for TRAP activity and for the a3 subunit of the V-ATPase. Small vessels were homogenously distributed in the whole implants. Similar results were obtained in SC and IM sites and no bone formation was observed in the control groups when cell-free and particle-free transplants were injected. These results indicate that this injectable biphasic calcium phosphate–hydrogel composite mixed with undifferentiated BMSCs is a new promising osteoinductive bone substitute. It also provides with an original in vivo model of osteoclast differentiation and function.

Classical antiferromagnetism inMnSc2S4: ASc45NMR study

$^{45}\mathrm{Sc}$ NMR has been measured for the spinel compound $\mathrm{Mn}{\mathrm{Sc}}_{2}{\mathrm{S}}_{4}$. The Knight shift and the spin-lattice relaxation rate show typical behaviors expected for conventional localized moment systems. The Sc site separates into two different magnetic sites in the antiferromagnetic state below ${T}_{N}\ensuremath{\simeq}2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, pointing to a simple spin structure. These results suggest that $\mathrm{Mn}{\mathrm{Sc}}_{2}{\mathrm{S}}_{4}$ is a rather conventional antiferromagnet.