7Li MR measures of blood lithium--correlation with chemical analysis data

Lithium is used in the treatment and prophylaxis of manic-depressive illness. A narrow therapeutic range of lithium (0.4-1.2 meq/l) requires constant monitoring of these levels to avoid neurotoxicity and overdose. It is general practice to measure plasma lithium levels as a guide to monitor the therapy. Efforts to predict the concentration of Li at its active sites in the brain have led to the use of red blood cells (RBCs) because they are similar to neuronal cells. Thus RBC lithium is a very relevant clinical parameter for monitoring therapy and to observe the changes at intracellular levels under varying treatment conditions. A measure of both plasma and RBC lithium may be of significant value to physicians and researchers as lithium profile for RBCs correlate more closely with the brain lithium than plasma lithium. Although methods to measure lithium in blood such as atomic absorption or flame photometry exist, a complete quantitation of both plasma and RBC lithium requires a tedious physical separation of the two components prior to chemical analysis. On the other hand, lithium MR technique, via the use of shift reagents, can provide both plasma and RBC lithium in a single study. Here we have performed a correlation study of lithium results obtained from MR with the vitros dry-slide method on blood samples from rats treated with lithium. The results show a high degree of correlation between the two methods. Additionally, the MR measurements made on dilute samples of blood indicate that small blood samples with lithium concentration in the neighborhood of 0.08 meq/l can be measured with high accuracy and reproducibility needed for clinical purposes.     

Synthesis of nanocrystalline YFeO3 and its magnetic properties

Single phase nanocrystalline YFeO₃ has been synthesized by a simple solution method. The average particle diameter is 42.2 nm. The particles exhibit ferromagnetic behaviour in the temperature range 10-300 K with a coercivity of 23 kOe. The magnetization versus temperature over the temperature range 2-300 K obeys Bloch equation with a Bloch constant value 9.98×10⁻⁶ K^−3/2. Ferromagnetic hysteresis loops have been observed up to a temperature of 300 K. At 10 K a field-cooled sample shows an exchange bias field.     

Modification of Lexan polycarbonate induced by electron irradiation

An 8 MeV electron-induced modification of Lexan polycarbonate (Lexan) films has been studied systematically using UV–visible spectroscopy, LCR meter, X-ray diffractogram (XRD) and differential scanning calorimetry (DSC) techniques. The optical properties of the Lexan films showed a decrease in the optical energy gap with an increase in the electron dose. The AC conductivity and dielectric constant were found to change significantly due to irradiation, and the dielectric constant was found to obey the universal law of dielectric constant. The XRD results show that the crystallite size and the percentage of crystallinity of films decrease after irradiation. The decrease in glass transition temperature shown by DSC studies reveals that the polymeric system has changed towards a more disordered state.     

Knowledge supply network

This paper introduces the idea of knowledge supply network (KSN). Being an extension of the conception of supply chain management familiar to operations managers, knowledge supply network provides a most natural framework for operations management to contribute to the issues of knowledge management and intellectual capital, while retaining its tradition of practicality. This paper has three parts: (i) set up the idea of KSN, and clarify the focus of the paper; (ii) through case examples, illustrate the nature and structure of KSN; and (iii) point out the connection of KSN to business strategy, operations, information systems, and knowledge management.     

Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay

Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14x10(-5) to 8.62x10(-3) M), and temperature (5-45 degrees C). The surfactant-modified clay surface was stable when exposed to extremes in pH. The optimum pH for maximum sorption of Cr(VI) species was found to be at pH 1 and was constant between pH 2 and pH 6. The sorption data obtained was well described by DKR and Langmuir sorption isotherms. Sorption energy (E) for (i) surfactant sorption by montmorillonite clay and (ii) sorption of chromium(VI) species by surfactant modified clay have been computed from the DKR equation. Sorption energy evaluated for the sorption of both surfactant and Cr(VI) species showed that an ion-exchange mechanism was operative. The mechanism of retention appears to be replacement of counterion of the surfactant by Cr(VI) anionic species. Adsorbent capacity for the sorption of Cr(VI) species has been evaluated from the Langmuir sorption isotherm data. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees ) for surfactant sorption on montmorillonite clay and Cr(VI) sorption by modified clay have been evaluated. The specific rate constant for sorption of Cr(VI) species on modified montmorillonite was rapid during the first 10 min and equilibrium was found to be attained within 30 min. The sorption of Cr(VI) species onto modified montmorillonite clay followed first-order rate kinetics. Copyright 2000 Academic Press.     

Lithium spectroscopic imaging of rat brain at therapeutic doses

Since the discovery that lithium (Li) is efficacious for the treatment of manic depressive illness, the brain Li distribution of mammals treated with lithium has been of interest. However, the spatial relationship of lithium in the brain regions to its function remains largely unknown. Knowledge of Li distribution in the brain is necessary to localize its action in the brain. Both the therapeutic and neurotoxic side effects of Li are centered mainly in the central nervous system and hence there is considerable interest in understanding the extent of lithium penetration into the central nervous system. The mechanism by which neurotoxic side effects are generated is not known and may, in part, be related to the particular distribution of lithium in the brain. The regional specificity in lithium's brain distribution could underlie important steps on its action. Li levels in various brain regions for autopsied rats and humans have been reported. However, many results are conflicting due to ion redistribution at death or during sample preparation. A direct nondestructive measurement of Li levels in the brain where the drug exerts its effects is certainly desirable. Because magnetic resonance technique can be used to observe Li, it can be an appropriate method to monitor and map the distribution in the brain. The application of MR technology to rat brain regions has provided information on lithium distribution in a non-invasive manner. The earlier development work at lower field strengths provided brain lithium information at high dose of Li administration. Here we demonstrate the feasibility of quantitative spectroscopic imaging on rat brain under therapeutic doses.     

Sorption of inorganic nanoparticles in woven cellulose fabrics

Titanium dioxide was deposited from aqueous suspension onto cellulosic surfaces.Titania was sourced from Degussa (P25TM,70:30 anatase:rutile).Dry uptake of particles was shown to be rapid and dominant with one-third of the deposition occurring in less than 30 s and over one-half in the first minute.Isotherms were recorded to compare the rate of titanium deposition on dry and pre-wetted cotton.In the dry case uptake reached a maximum in 30 min whereas in the pre-wetted case the uptake was seen to continue beyond 180 min.A broad trend of higher deposition occurring at lower pH was seen,corresponding to the region where surface charges were opposite and thus attractive.Dry pickup was less significant at high pH.The response to varying ionic strength was complex and was attributed to the combined effect of charge screening,particle aggregation and consequent particle entrapment or occlusion.Titania deposition into the interstices of woven cotton sheets resulted in the formation of inorganic,nanoparticulate skeletons which could be isolated by controlled combustion of the cellulose and thus cotton was suggested to have potential for the templated synthesis of high surface area semiconductor materials.