Li Ratio Research Articles

Lithium zincopyrophosphate, Li2Zn3(P2O7)2

The title compound, dilithium(I) trizinc(II) bis[diphosphate(4-)], is the first quaternary lithium zincopyrophosphate in the Li-Zn-P-O system. It features zigzag chains running along c, which are built up from edge-sharing [ZnO(5)] trigonal bipyramids. One of the two independent Zn sites is fully occupied, whereas the other is statistically disordered by Zn(2+) and Li(+) cations, although the two Zn sites have similar coordination environments. Li(+) cations occupy a four-coordinated independent site with an occupancy factor of 0.5, as well as being disordered on the partially occupied five-coordinated Zn site with a Zn(2+)/Li(+) ratio of 1:1.

The isotopic6Li/7Li ratio in Centaurus X-4 and the origin of Li in X-ray binaries

Context. Cool stars, companions to compact objects, are known to show Li abundances which are high compared to field stars of the same spectral type, which are heavily Li depleted. This may be due either to Li production or Li preservation in these systems. Aims. Our aim is to measure the lithium isotopic ratio in the companion star of the neutron star X-ray binary Cen X-4. Methods. We use UVES spectra obtained in years 2000 and 2004 around the orbital quadratures. The spectra are analysed with spectrum synthesis techniques and the errors estimated with Monte Carlo simulations. Results. We measure A(Li) = 2.87± 0.20 and 6 Li/ 7 Li = 0.12 +0.08 −0.05 at 68% confidence level. We also present updated system parameters „ „ „ „ „ „ „ „ „ „

Source and development of large manganese enrichments above eastern Mediterranean sapropel S1

The residual dark unit of the most recent eastern Mediterranean sapropel (S1) is usually overlain by sediments with enhanced concentrations of MnOx in two separated layers. The variability and magnitude of the Mn enrichment at different locations and water depths indicate that Mn must have been added preferentially to sediments at intermediate (1–2 km) water depths. We propose a two‐stage mechanism for the Mn enrichment that involves decreasing oxygenation with increasing water depth. This mechanism involves the loss of reduced Mn2+ from the deepest sediments (>2 km water depth) into overlying anoxic waters and a variable gain of MnOx in sediments in contact with oxygenated waters at shallower depth. In the S1 unit that receives the extra MnOx input, an upper higher Mn‐enriched zone (>3 wt %) is maintained continuously at the top of the accumulating S1 unit because the pore waters are anoxic at shallow sediment depth while bottom waters are oxic to some degree. In a reactive‐transport model, the Mn enrichment in the upper zone could not be supported by normal sediment diagenesis. Thus the MnOx in the upper Mn horizon must have formed mainly in the water column. The MnOx in the upper Mn‐enriched zone adsorbed Mo and Li from seawater in a similar manner as other Mn‐enriched oxic sediments, nodules, and crusts, with a Mn:Mo ratio of ∼600:1, a Mn:Li ratio of ∼750:1, and a δ98/95MoMOMO of −2.5 ‰.

Therapeutic Implications of Interferon Regulatory Factor (IRF)-1 and IRF-2 in Diffusely Infiltrating Astrocytomas (DIA): Response to Interferon (IFN)-β in Glioblastoma Cells and Prognostic Value for DIA

The precise mechanisms governing the direct effect of IFN-beta, including apoptosis induction, are not yet fully understood. To gain a better insight into these mechanisms, we investigated the signaling pathways focusing particularly on interferon regulatory factor 1 (IRF-1) and IRF-2 in glioblastoma cell lines. Furthermore, we attempted to determine whether or not IRF-1 and IRF-2 act as additional prognostic indicators in diffusely infiltrating astrocytomas (DIA). We first assessed the cytotoxic effects of IFN-beta based on a cell growth study and modified MTT assay, and then quantified the apoptosis using a sandwich enzyme immunoassay following IFN-beta treatment in the cell lines, U-87MG, T98G, and A-172. Subsequently, we carried out an analysis of apoptosis-related molecules as evaluated by densitometric analysis of Western blots, focusing on IRF-1 and IRF-2, and two major initiator caspases, caspase-8 and caspase-9. Furthermore, we assessed the expression of type I IFN receptor, IRF-1, and IRF-2 using immunohistochemical techniques in 63 DIA (15 of WHO grade II, 18 of grade III, and 30 of grade IV), and analyzed their impact on prognosis. An increase in apoptosis was apparent after 48 h of IFN-beta treatment (1 x 10(4) IU/ml) in T98G but not in U-87MG or A-172. IFN-beta treatment for 6 h significantly enhanced the expression of IRF-1 in all three cell lines. However, an enhanced expression of IRF-2 was observed only in the not-most-sensitive, non-apoptosis-induced U-87MG and A-172. While minimal processing of caspase-8 was noted in the three cell lines throughout the experiment, caspase-9 activation was observed in the apoptosis-detected T98G after 48 h of treatment, as indicated by a 1.33-fold increase (P=0.037). On the other hand, the IRF-1 LI and IRF-1/IRF-2 LI ratio were greater in low-grade DAI, and were negatively correlated with the histopathological grade in DIA (P=0.017 and P=0.001, respectively). Furthermore, the IRF-1/IRF-2 LI ratio was negatively correlated with the MIB-1 LI in DIA (P=0.004), and represented an independent and most powerful determinant of overall survival compared to other conventional prognostic factors (P=0.018). However, the relation was not statistically significant when only patients with high-grade DIA were assessed. Our findings suggest that up-regulation of IRF-1 and IRF-2 might be an important determinant of susceptibility to IFN-beta mediated cytotoxicity including apoptosis. Furthermore, the IRF-1/IRF-2 LI ratio may reflect the proliferative state of DIA and constitute an important prognostic marker in DIA. Thus, IRF-1 and IRF-2 could represent one of the therapeutic target sites for the regulation of cell growth in DIA.

Perfluoroalkyl‐terminated star polymer electrolyte

AbstractA perfluoroalkyl‐terminated multiarm star polymer (perfluoroalkyl‐terminated hyperbranched polyglycerol) was synthesized and characterized on the basis of perfluorooctanoyl chloride grafting on hyperbranched polyglycerol. The conductivity of a blend of the perfluoroalkyl‐terminated star polymer and linear poly(ether urethane) was studied. The results indicated that this blend had better solvating capability in salt and higher ionic conductivity. The conductivity of the blend was 2.5 × 10−4 S cm−1 at 60°C when the concentration of the perfluoroalkyl‐terminated hyperbranched polyglycerol was 30 wt % and the ethylene oxide (EO)/Li ratio was 4 in the blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 238–242, 2005

Multivariate classification of wines from different Bohemian regions (Czech Republic)

Fifty-three samples of wines were analysed by inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. The contents of 27 parameters were determined: Al, As, Ba, Ca, Ce, Co, Cr, Cs, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Sb, Sn, Sr, Th, U, V, Y and Zn. The best results for identification of sample origin were achieved when determining the following parameters: the contents of Al, Ba, Ca, Co, K, Li, Mg, Mn, Mo, Rb, Sr, V and element ratios Sr/Ba, Sr/Ca, Sr/Mg. With these parameters, a 97.4% correct classification was achieved for white wines and a 100% correct classification for red wines.

Localized 7Li MR spectroscopy: In vivo brain and serum concentrations in the rat

The brain concentration of lithium (Li) in treated rats was measured using a recently developed method based on in vivo 7Li PRESS localized MRS. Comparison was made to the corresponding serum concentration at two treatment durations. The brain and serum Li concentrations were highly correlated with each other, more so than found previously for humans. The brain and serum Li concentrations also correlated with dose. Both the brain Li concentration and the serum concentration at 16.1 days of treatment correlated with the corresponding measure at 6.6 days. After correction of the brain Li concentrations for reduced 7Li MRS visibility, the mean brain/serum Li ratio for rats was close to unity, unlike most previous values found for humans. However, in some individual cases the ratio deviated substantially from the mean, suggesting that serum Li is not always a reliable indicator of brain Li.

Solid Polymer Electrolytes from Polyanionic Lithium Salts Based on the LiTFSI Anion Structure

Effects of anion size on ionic conductivity were studied for a series of solid polymer electrolytes prepared from lithium polyanionic salts based on a series of lithium bis[(perfluoromethyl)sulfonyl]imide (LiTFSI) units connected together by perfluoroalkane linkers to form oligomeric anionic chains of variable length. Solid polymer electrolytes were prepared from the salts using polyethylene oxide as the host and characterized using X-ray diffraction, differential scanning calorimetry, and electrochemical impedance spectroscopy. Ionic conductivities were measured over a temperature range between 120°C and ambient for electrolytes with ethylene oxide (EO)/Li ratios of 30:1 and 10:1. Solid polymer electrolytes prepared from the lithium polyanionic salts exhibited ionic conductivities that were consistently lower (by factors of between 2 and 10) relative to those of monomeric LiTFSI-based electrolytes over the entire temperature and salt concentration ranges. This finding probably reflects a diminished contribution of anions to the overall conductivity for salts with large, polymeric anions. Trends in ionic conductivity with respect to anion chain length and EO/Li ratio were studied. The existence of an optimal anion chain length that is different for solid polymer electrolytes of differing EO/Li ratio was noted and is rationalized in terms of the cumulative effects of anion mobility, ion-pairing, variations in host chain dynamics in the vicinity of ions as a function of anion structure, and salt-phase segregation on the conductivity. © 2004 The Electrochemical Society. All rights reserved.

On the crystalline and quasi-crystalline phase compounds in an Al–Li–Cu–Mg base alloy

The presence of the quasi-crystalline T 2 (Al 6CuLi 3) as a major equilibrium phase in as-cast and heat treated Al–(2.2–2.5) wt% Li–1.2 wt% Cu–0.8 wt% Mg–0.12 wt% Zr alloys i.e. the widely studied compositions in the AA 8090 alloy having the composition range of Al–(2.2–2.7) wt% Li–(1.0–1.6) wt% Cu–(0.7–1.3) wt% Mg–(0.04–0.20) wt% Zr, is known. This article examines an AA 8090 alloy having varying Cu, Mg and Li concentrations to demonstrate that reduced Cu:Mg and Cu:Li ratios in the alloy composition tend to destabilize the quasi-crystalline T 2 phase in favor of the Al–Li–Cu–Mg base C phase, having the tetragonal structure.

Mixed-ligand ytterbium(iii) complexes incorporating one or two bidentate (N,O) amide ligands

Examples of the ability of the donor-functionalised amide ligands N-(2-methoxyphenyl)-N-(trimethylsilyl)amide (L1) and N-(2-phenoxyphenyl)-N-(trimethylsilyl)amide (L2) to support mixed-ligand lanthanoid complexes of the type [Ln(L)2A] or [Ln(L)AB] are described. Reaction of [Yb(OAr)3] (Ar = C6H3But2-2,6) with two equivalents of [Li(L2)]n in hexane gave hexane-soluble, monomeric and five-coordinate [Yb(L2)2(OAr)] (1) in high yield. Attempted preparation of an analogous [Yb(L1)2(MeCp)] complex by reaction of [Yb(MeCp)Cl2(thf)] with [Li(L1)(OEt2)]2 (with a Yb ∶ Li ratio of 1 ∶ 2) in thf instead gave the known [Yb(L1)2(μ-Cl)]2 (2). In contrast, the stable complexes [Yb(MeCp)(L1)(μ-Cl)]2 (3) and [Yb(MeCp)(L2)(μ-Cl)]2 (4) were readily obtained from 1 ∶ 1 (Li ∶ Yb) reaction of [Yb(MeCp)Cl2(thf)] with [Li(L1)(OEt2)]2 or [Li(L2)(dme)] in thf. The complexes 1, 3 and 4 have been characterised by X-ray structure determination.

A VAPID analysis of interstellar lithium in the ζ Oph sightline

ABSTRA C T We present observations of the Li I 6708 Adoublet in the z Oph sightline, obtained at a resolution of , 10 6 and a signal-to-noise ratio of , 1200, together with supplementary observations of K I l7699 and the Na I l3302 doublet. These observations marginally resolve the main ' 2 15 km s 21 ' system into its two principal clouds; we model the data using standard physical assumptions, but in a statistically rigorous manner, taking fully into account the hyperfine, doublet and isotopic structure for each species, in each cloud, using a new code, VAPID. The average 7 Li/ 6 Li ratio determined in this sightline is 1:12 ^ 0:20 dex (68 per cent confidence interval), in excellent agreement with the solar-system (meteoritic) value. The ratios in the individual clouds are determined with less precision, but are also consistent with the solar-system value, as is the total lithium abundance (with little evidence for depletion). The thermal and 'turbulent' broadening in the two clouds is discussed on the basis of observed line widths.

Structure and conductivity in polydioxolane/LiCF 3SO 3 electrolytes

Thermal transition ( T g and T m), ionic association and ionic conductivity have been measured as a function of LiCF 3SO 3 concentration in polydioxolane (CH 2OCH 2CH 2O) n -based electrolytes. DSC and X-ray diffraction measurements were performed on samples with wt% between 2 and 58 wt% ( n=O:Li ratio between 207 and 3), as well as on the pure polymer. Ionic association in the electrolytes was investigated by micro-Raman spectroscopy at room temperature. Conductivity isotherms at 300, 323 and 345 K were obtained. It was found that: (a) T g increases from −69 to −44°C with increasing salt concentration; (b) the electrolyte is completely amorphous between 22 and 30 wt%; (c) the relative areas of the Raman peaks associated with different ionic species indicate the appearance of a new peak for a crystalline polymer/salt complex, also identified by the X-ray diffractograms; and (d) the ionic conductivity at 300 K shows a large maximum value of 7×10 −5 S cm −1 between 12 and 48 wt%.

Living ring-opening polymerization of ɛ-caprolactone with combinations of tert-butyllithium and bilky aluminium phenoxides

The polymerization ofe-caprolactone (e-CL) with a combination of tert-butyllithium ( t-BuLi ) and bis(2,6-di-t-butylphenoxy)methylaluminum [MeAl(ODBP) 2 ] in toluene at 0°C proceeded in a living manner to give polymers with narrow molecular weight distributions ( MWD ) within a few minutes, while the polymerization with t-BuLi alone gave a polymer with much broader MWD. The yield of the polymer did not reach 100 % at the Al / Li ratio of 5, because the excess MeAl(ODBP) 2 coordinates with e-CL to protect it from the attack by the propagating species. The polymerization with t-BuLi / EtAl(ODBP) 2 gave polymers in quantitative yields regardless of Al / Li ratio, and also narrower MWD even for higher molecular weight polymers.

The synthesis and properties of triethyleneoxy-methylether and crown-ether functionalized metathesis polymers

The synthesis and characterization of metathesis polymers functionalized with triethyleneoxy-methylether and crown-ether side groups is reported. The triethyleneoxy-methylether substituted norbornene and acetylene derivatives and the 14-crown-4 functionalized norbornene were synthesized and metathesis polymerization with carbene complexes of molybdenum or ruthenium provided the substituted polynorbornene or polyacetylene backbone. The polymers were characterized with NMR, GPC, FT-IR and DSC. Addition of lithium ions to these amorphous polymers results in increasing of the glass transition temperature, T g, because the oxygen–metal coordination leads to an enhanced order. The triethyleneoxy-methylether-bearing polymers show a low T g even at high O:Li ratios. This is in contrast to the crown-ether-modified polynorbornene where the crown-ether ring stiffens the main chain and leads to higher T g.

12C/13C Ratios and Li Abundances in Low-Mass C Stars

High-resolution and high signal-to-noise-ratio spectroscopy is used to derive 12C/13C ratios from the Red System of the CN molecule at 8000 Å in several galactic low-mass C stars previously analyzed for lithium. It is found that Li-rich C stars usually have low isotopic ratios (< 15). This suggests that the Li and 13C enrichments in C stars might be produced by a similar mechanism. However, due to the large uncertainties in the abundance derivations for both Li and carbon isotope ratios, this result must be confirmed with further studies.

Lithium-6: evolution from Big Bang to present

The primordial abundances of deuterium, 4 He , and 7 Li are crucial to the determination of the baryon density of the Universe in the framework of standard Big Bang nucleosynthesis (BBN). 6 Li is only produced in tiny quantities and it is generally not considered to be a cosmological probe. However, recent major observational advances have produced an estimate of the 6 Li/ 7 Li ratio in a few very old stars in the galactic halo which impacts the question whether or not the lithium isotopes are depleted in the outer layers of halo stars, through proton induced reactions at the base of (or below) the convective zone. Here, we use (i) an empirical relation, independent of any evolutionary model, to set an upper limit on the 6 Li rise compatible with the very existence of the Spite's plateau (i.e. the flat lithium abundance measured in very old stars of the halo of our Galaxy of different iron content) and (ii) a well founded evolutionary model of light elements based on spallation production ( Vangioni-Flam et al., 1997; Vangioni-Flam et al., 1998). Indeed, 6 Li is a pure product of spallation through the major production reactions, fast oxygen and alphas interacting on interstellar H, He (especially in the early Galaxy). The rapid nuclei are both synthesized and accelerated by SN II. In this context, the 6 Li evolution should go in step with that of beryllium and boron, recently observed by the Keck and HST telescopes. 6 Li adds a new constraint on the early spallation in the Galaxy. In particular, if confirmed, the 6 Li/ 9 Be ratio observed in two halo stars (HD 84937, BD +26°3578 = HD 338529) gives strong boundary conditions on the composition and the spectrum of the rapid particles involved. Both methods converge to show that 6 Li is essentially intact in halo stars, and a fortiori 7 Li , which is more tightly bound. Moreover, extrapolating empirical and theoretical evolutionary curves to the very low metallicities, we can define a range of the 6 Li abundance in the very early Galaxy consistent with Big Bang nucleosynthesis (5.6×10 −14 to 3×10 −13). Following the evolution at increasing metallicity, we explain the abundance in the solar system within a factor of about 2. The whole evolution from Big Bang to present is reasonably reproduced, which demonstrates the general consistency of the present analysis of 6 Li . The baryonic density derived from both lithium isotopes is between 1.5 to 3.5% of the critical one, in good agreement with the determination based on independent analyses. Consequently, thanks to these new data and theoretical developments, we show that 6 Li can be used to establish stellar 7 Li abundances as a valid tracer due to the fact that it allows to reinforce the Spite's plateau as a primordial test of BBN; on the other hand, its early evolution can be used to corroborate the calculated BBN abundances. In the framework of this work, a pregalactic α+ α process producing 6 Li is not necessary. Finally, thanks to 6 Li , the physics of spallative production of light elements should be more easily mastered when more data will become available.

Transport Properties of a High Molecular Weight Poly(propylene oxide)‐ LiCF3 SO 3 System

Conductivities (σ), salt diffusion coefficients , and cationic transference numbers are reported for a high molecular weight polypropylene oxide polymer electrolyte system at 85°C. Transference numbers were determined as a function of salt concentration using a recently described electrochemical method based on concentrated solution theory. For the Parel‐ system, is slightly positive for electrolytes with O:Li ratios of 15 or 12:1 but decreases to negative values for more concentrated solutions. This implies that negatively charged ionic aggregates such as triplets are more mobile than free cations in this concentration range. Such behavior is commonly seen in binary salt/polymer electrolytes, which typically exhibit a high degree of nonideality. The nonunity transference numbers and microphase separation in the Parel‐ system strongly suggest that salt precipitation or phase separation in operating cells containing these electrolytes due to the development of large concentration gradients during passage of current. © 1999 The Electrochemical Society. All rights reserved.

Dynamical emission and isotope thermometry

Ratios of the populations of ground and excited states of He, Li, and Be and double ratios constructed from the yields He, Li, C isotopes were measured for central Kr1Nb collisions at E/A 535, 70, 100, and 120 MeV. These ratios were analyzed to estimate an apparent temperature for emission. Consistent and approximately constant apparent temperatures were obtained from the excited states of He, Li, and Be nuclei and from thermometers based upon the yields of carbon isotopes. In contrast, apparent temperatures obtained from thermometers based upon the ratios using helium isotopes increase monotonically with incident energy. @S0556-2813~98!50511-0#

New lipophilic cyclo- and poly-phosphazenes containing surfactant substituents

The reaction of the sodium salt of the commercially available surfactant Igepal CA 210™ with hexachlorocyclotriphosphazene, N3P3Cl6 (1) and poly(dichlorophosphazene), [—P(Cl2)=N—]n (Publisher's note: for graphical representation please see printed journal or the Acrobat PDF version on this website.) affords lipophilic cyclo- and poly-phosphazenes SSCP (2) and SSPP (4), respectively. These materials, containing a short chain oligo etheroxy side group while being completely insoluble in water, are soluble in a wide range of solvents ranging from hexane to chloroform. The polymer, SSPP (4) forms polymer–metal salt complexes with lithium salts. DC conductivity measurements by a complex impedance method have been carried out. The maximum conductivity observed for SSPP–LiClO4 (O: Li ratio, 6:1) is 1·0×10-6Scm-1 at 348K. © 1998 SCI.

Electrical, thermal and NMR investigation of composite solid electrolytes based on PEO, LiI and high surface area inorganic oxides

High salt concentration polymer composite electrolytes, containing poly(ethylene oxide) (PEO), LiI and nanoscale Al 2O 3 or MgO and, in some cases, ethylene carbonate (EC) and poly(methyl methacrylate) (PMMA), were investigate by electrical conductivity, differential scanning calorimetry (DSC) and both wide-line and high resolution solid state 7Li NMR. The high resolution NMR spectrum of a sample with a PEO:Li ratio of 3:2 is consistent with at least two Li environments, one solvated by the polymer and one in small ionic clusters. A correlation between the observed change in Li environment at elevated temperature and a sudden increase in conductivity is suggested. All results demonstrate that the conduction mechanism in concentrated composite electrolytes is significantly different than in more dilute polymer electrolytes, in which the ion transport process is associated with polymer segmental motion.