Li Distribution Research Articles

Lithium distribution in the brain of normal mice and of "quaking" dysmyelinating mutants.

Using nuclear reaction 6Li(n, alpha)3H and dielectric detectors, we have studied the distribution of Li in the brain of adult mice, following Li treatment of the animals. Two strains of animals were used in parallel: "quaking" dysmyelinating mutants and normally myelinated controls. The distribution appeared to be sharply regionalized in the brain of the normal mice (higher Li concentration in the gray rather than in the white matter, with the area postrema being particularly Li rich). In contrast, the Li distribution was practically homogeneous in the brain of the quaking dysmyelinating mutants, with a mean Li concentration comparable to that in the gray matter of the controls. The present method of Li detection has made it possible to estimate the Li equilibrium potentials (nerve cells with regard to plasma) in the different brain substructures. The results are consistent with (a) Li being actively extruded from nerve cells in all the cases and (b) myelination decreasing the relative importance of the passive component of Li transport in the nerve cells, as compared with the active component.

Electrical behavior of lithium intercalated layered In-Se compounds

InSe and In 2 Se 3 was lithium intercalated by mean of a spontaneous intercalation reaction. The electrical conductivity was studied and was found to be altered by 3-orders of magnitude with respect to non-intercalated samples. An interesting time dependent anisotropy appeared during intercalation, associed to the initial non-uniform Li distribution and the movement of Li concentration kinks.

Distribution and behavior of lithium in the K-alkaline rocks from the Roccamonfina Volcano (Campania, southern Italy)

The Li content in whole rocks, matrix and mineral separates (biotite, sanidine, leucite, phlogopite) from 58 igneous rocks of the K-alkaline suites of the Roccamonfina Volcano has been measured by atomic absorption. Among the minerals, sanidine contains as much Li as biotite x ̄ = 41.8 ppm and x ̄ = 40.2 ppm , respectively), while phlogopite and leucite have a much smaller amount ( x ̄ = 6.0 ppm and x ̄ = 2.6 ppm , respectively). Average Li distribution coefficients between minerals and groundmass are: D biot matrix Li = 0.50 , D san matrix Li = 0.84 and D leuc matrix Li = 0.06 , respectively. The Li content increases with magmatic differentiation in the rocks of the K series, showing an enrichment factor of ∼ 3.6 in the salic relative to the mafic rocks. In the high-K series the Li content increases from primitive to intermediate rocks, but shows a levelling off in the more salic rocks. Li acts incompatibly except in the most salic rocks, whose Li content was probably mainly controlled by diffusion processes through the magmas. The Li content in the Roccamonfina primitive rocks ( x ̄ = 20 ppm ) does not discriminate between the K and high-K series, and is higher than that of the “average” basalt ( x ̄ = 10 ppm ); however, it is similar to that of basalts from continental settings. This relatively high Li content in the Roccamonfina primitive rocks can be accounted for by either crustal contamination or the existence of an enriched mantle region beneath the volcano, but in both hypotheses there is a suggestion of some involvement of the lower crust in the generation of the Roccamonfina parental magmas.

Some aspects of Li behavior in ion implanted HgCdTe

SIMS has been used on both unimplanted and B-ion implanted LPE grown HgCdTe to study the distribution of the Li impurity background. In unimplanted layers Li decorates some types of crystal defects and also reflects the p/n distribution in the layer. In implanted layers Li decorates the implantation-induced damage and also reveals the junction region. Ion-implanted junctions have been evaluated by Hall, differential Hall, EBIC, C–V, and TEM techniques and the results correlated with the features exhibited by the Li distribution. The Li distribution analysis reinforces our previous understanding that implanted junctions are several microns deep, n+/p−, graded in the p region and formed by implant-induced native donors.

Crystal chemistry and stability of petalite

New data confirm that most petalites are slightly Li-deficient, Al-excessive and (OH)-bearing with respect to the idealized formula LiAlSi4O10. Primary substitution or secondary hydrolysis involving H+⇌Li+ or 3 Li+⇌Al3++2□, or both, are responsible. No evidence was found for either significant participation of other substitutions, or incipient alteration into hydrous silicates. The Fe content seems to be restricted to less than 0.003 per 20 oxygens. The Ga contents (22–64) and Al/Ga (3577–1378) are moderate, similar to other framework aluminosilicates in parent pegmatites. Statistically identical IR absorption spectra and unit-cell dimensions indicate ordered Si−Al−Li distribution in all natural as well as synthetic samples examined. For quartz-saturated bulk compositions, the stability field of petalite is bounded by beta-spodumene at high T, by spodumene at moderate to high P and T, and by eucryptite (or bikitaite) at low P and T. Kinetic factors such as sluggish reaction rates at low T and low solubilities of aluminosilicates in CO2-rich fluids may account for the metastable preservation of petalite in some pegmatites.

History of the stellar birthrate from lithium abundances in red giants

The lithium abundance at the end of main-sequence evolution should increase strongly with mass for masses less than 1.4 M/sub sun/. It is shown that because of this dependence the frequency distribution of Li abundances in red giants is a sensitive probe of the history of the stellar birthrate in the solar neighborhood since the Li distribution directly reflects the stellar age distribution. A birthrate which decreases with time gives a smaller mean red giant Li abundance than an increasing birthrate because a larger fraction of red giants are older and hence less massive. Theoretical Li abundance frequency distributions are calculated for exponentially increasing, constant, and exponentially decreasing birthrates using a semiempirical prescription for main-sequence Li destruction, theoretical main-sequence lifetimes and red giant dilution factors, and self-consistent initial mass functions. The results are compared with the observed abundance distribution for 35 giants studied by Lambert and his colleagues. Allowing for uncertainties, we find that the ratio of present birthrate to average past birthrate has a value between 0.5 and 2. These limits are consistent with results of most other methods of determining the birthrate history, but the present method provides a considerably more stringent lower limit. It is also shownmore » that, with more observational data, fluctuations in the birthrate with a time scale of about one billion years during the period between two and six billion years ago could be resolved.« less

Applications of (n, p) and (n, α) reactions and a backscattering technique to fusion reactor materials, archeometry, and nuclear spectroscopy

Depth profiles of He, Li and B are determined by 3He(n, p)T, 6Li(n, α)T and 10B(n, α) 7Li reactions with thermal neutrons at the high flux reactor of the ILL, Grenoble. The behaviour of Li in Be is examined with respect to future fusion reactors. Range profiles of 70–300 keV Li + are measured and found to agree with theory based on Lindhard-Scharff electronic stopping and Molière potential. Li becomes mobile in Be above 100°C. Further, B and Li distributions in glaze of ancient pottery are examined for studying ancient production techniques. It is found that all examined samples (of Islamic, Thai and North American provenience) show Li and B concentrations which are enriched relative to the original material. Li is mostly depleted in a surface layer of 0.1–1.6 μm half-width due to various burning conditions. In experimental nuclear physics, gas cells are now often replaced by thin foils with implanted gas. In many cases the knowledge of the concentration profile is required, and is presently evaluated for the case of 3He in Ni and Au with the (n, p) reaction. This is compared to results obtained by a special Rutherford backscattering technique yielding good agreement.

Differential fragmentation cross sections for 7.3 GeV nitrogen ions incident on protons

Differential cross sections $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}$ for the inclusive reaction $^{14}\mathrm{N}$ + $p\ensuremath{\rightarrow}Z$ + anything (for $3\ensuremath{\le}Z\ensuremath{\le}6$) have been measured at six laboratory production angles ($\ensuremath{\theta}<5\ifmmode^\circ\else\textdegree\fi{}$) for 7.3 GeV nitrogen ions interacting in liquid hydrogen. The angular distributions for C, B, and Be fragments decrease sharply with increasing angle, as expected for this type of peripheral reaction. The corresponding transverse momentum (${p}_{t}$) distributions for these fragments can be represented by Gaussian functions of ${p}_{t}$. The Li distribution appears to be non-Gaussian, suggesting one (or more) different production mechanisms. The dependence of the widths of the momentum distributions on fragment mass is not consistent with theoretical predictions, and shows some evidence for an "effective" number of nucleons which determine the fragmentation spectrum of the nitrogen nucleus. Integration of the angular distributions gives partial production cross sections which are consistent with results at higher energy. This energy-independent behavior implies that limiting fragmentation is applicable down to energies of 0.5 GeV/nucleon.NUCLEAR REACTIONS Relativistic heavy ions; fragmentation of 7.3 GeV nitrogen on protons.

REGENERATIVE PROLIFERATION OF MOUSE EPIDERMAL CELLS FOLLOWING ADHESIVE TAPE STRIPPING

The proliferating cells of mouse epidermis (basal cells) can be separated from the non-proliferating cells (differentiating cells) Laerum, 1969) and brought into a monodisperse suspension. This makes it possible to determine the cell cycle distributions (e.g. the relative number of cells in the G1, S and (G1 + M) phases of the cell cycle) of the basal cell population by means of micro-flow fluorometry. To study the regenerative cell proliferation in epidermis in more detail, changes in cell cycle distributions were observed by means of micro-flow fluorometry during the first 48 hr following adhesive tape stripping. 3H-TdR uptake (LI and grain count distribution) and mitotic rate (colcemid method) were also observed. An initial accumulation of G2 cells was observed 2 hr after stripping, followed by a subsequent decrease to less than half the control level. This was followed by an increase of cells entering mitosis from an initial depression to a first peak between 5 and 9 hr which could be satisfactorily explained by the changes in the G2 pool. After an initial depression of the S phase parameters, three peaks with intervals of about 12 hr followed. The cells in these peaks could be followed as cohorts through the G2 phase and mitosis, indicating a partial synchrony of cell cycle passage, with a shortening of the mean generation time of basal cells from 83-3 hr to about 12 hr. The oscillations of the proportion of cells in G2 phase indicated a rapid passage through this cell cycle phase. The S phase duration was within the normal range but showed a moderate decrease and the G1 phase duration was decreased to a minimum. In rapidly proliferating epidermis there was a good correlation between change in the number of labelled cells and cells with S phase DNA content. This shows that micro-flow fluorometry is a rapid method for the study of cell kinetics in a perturbed cell system in vivo.

Lithium protection against oxygen toxicity in rats: ammonia and amino acid metabolism.

1. The use of Li pre-treatment in rats before high pressure oxygen exposure has been reported effective in controlling convulsions. This is an effect which is better demonstrated if exposure to oxygen follows shortly after Li injection than exposure following several hours later. 2. This study has investigated the hypothesis that the protective action of Li may be exerted, in the short term, by its removing ammonia from the blood and alleviating the latter's known toxic action. 3. A normal Li distribution time profile in unstressed rat brain and blood following intraperitoneal injection has been established. Brain and blood ammonia, amino acids and Li concentrations were also measured in Li-treated animals exposed and convulsed by oxygen. These measurements were made both shortly (15 min) and also several hours after (24 hr) Li treatment. Ammonia and amino acid values in Li-protected groups were compared to normal unstressed animal values and also to values in animals convulsed by oxygen unprotected by Li pre-treatment. 4. In rat brain abd blood significant (P less than 0-001) elevation of ammonia and glutamine and depression of gamma-amino butyric acid (brain only) and glutamate was noted following oxygen treatment in unprotected animals. Prior injection of Li 15 min before high pressure oxygen exposure delayed convulsions twice as long. Additionally if these animals were only exposed to oxygen for a period of time equal to that which would normally produce convulsions in unprotected animals, brain and blood ammonia and amino acids were maintained near to unstressed animal levels. Concomitantly, blood Li concentrations were considerably depressed below the values one would expect from the previously determined Li distribution time profile. 5. In rats exposed to high pressure oxygen 24 hr after Li treatment there was no protective action against high pressure oxygen convulsion, rather a potentiating effect for convulsion was seen. 6. These data present compelling evidence for the controlling effect of Li in rats, on rising blood ammonia concentration which occurs in high pressure oxygen exposure. The effect might well be due to the known chelating properties of Li with ammonia.

Lithium transport by the colon of normal and sodium‐depleted rats.

1. The transport of Li by colonic epithelium has been examined in normal and Na-depleted rats. 2. Substitution of Li for Na with lumen of the conon causes the transepithelial electrical potential difference (p.d.) and short-circuit current to fall to low levels and the electrical resistance of fall moderately. Recovery occurs by fairly slowly after removal of Li. 3. Li absorption increases linearly with increasing concentration in the lumen and is significantly faster in Na-depleted rats. Increasing the luminal Na concentration reduces Li absorption from solutions of low Li concentration. 4. Comparison of absorption rates with secretion rates in rats given Li systemically, together with measurements of Li distribution across the epithelium in relationship to the transepithelial p.d. indicate that Li transport is predominatly or entirely passive. Interference with Li absorption by Na suggests, however a mucosal membrane carrier which, since Li absorption rises after Na depletion, may be increased in the Na-depleted state.

The geochemistry of sediments from the northern Reykjanes Ridge and the Iceland—Faroes Ridge

Samples from the active Reykjanes Ridge and the inactive Iceland—Faroes Ridge have been investigated sedimentologically, mineralogically, and geochemically. The sediments display polymodal grain-size distributions and are poorly sorted, indicating deposition by various mechanisms and contributions from numerous sources. The mineralogy is fairly typical for the region and strongly reflects the large input of volcanic ash and ice-rafted material. Bulk chemical analyses indicate that the Reykjanes Ridge sediments appear to be enriched in Fe, Mn, Cu, Cr, and Zn as has been reported for other active ridges while the inactive Iceland—Faroes Ridge does not display such enrichments. The enriched metals in the ridge sediments do not show a particular affinity for any one size class. Partition studies indicate that the enriched Fe and Mn are held in separate phases while the other metals are present in all phases. Adsorption is not a major concentrating mechanism for the enhanced elements. Li distributions are apparently unaffected by active ridges and Pb seems to be partially concentrated biologically. There are indications that other criteria must be used in conjunction with bulk chemical analyses, in order to establish the presence of active ridge metal contributions.