Gravitational sedimentation effect of colloidal silica crystals in binary systems of titanium dioxide and silica particles

Colloidal crystals can be formed of silica particles while those of titania particles are not known under the normal gravitational field, because of their high specific gravity. We found by the Kikuchi--Kossel diffraction technique that, when silica particles (diameter: D?=?170?nm; density: ρ?=?2.2?g cm^?3) are mixed with titania particles (D?=?127?nm; ρ?=?3.9?g cm^?3), colloidal crystals are formed. Colloidal crystals started out with body-centred-cubic structure and changed to face-centred-cubic structures after about 60 days. Transitions began from the bottom of the container. Thus, the transitions are considered to be due to gravitational sedimentation. It is significant that the crystal growth process, which has not been observed in one-component dispersions of the silica particles, was found using titania particles with a wide range of the practical applicability.     

A Fluorine-19 Magnetic Resonance Probe,Shiga-Y5, Downregulates Thioredoxin-Interacting Protein Expression in the Brain of a Mouse Model of Alzheimer’s Disease

Thioredoxin-interacting protein (TXNIP) is involved in multiple disease-associated functions related to oxidative stress, especially by inhibiting the anti-oxidant- and thiol-reducing activity of thioredoxin (TXN). Shiga-Y5 (SY5), a fluorine-19 magnetic resonance probe for detecting amyloid-β deposition in the brain, previously showed therapeutic effects in a mouse model of Alzheimer’s disease; however, the mechanism of action of SY5 remains unclear. SY5 passes the blood–brain barrier and then undergoes hydrolysis to produce a derivative, Shiga-Y6 (SY6), which is a TXNIP-negative regulator. Therefore, this study investigates the therapeutic role of SY5 as the prodrug of SY6 in the thioredoxin system in the brain of a mouse model of Alzheimer’s disease. The intraperitoneal injection of SY5 significantly inhibited TXNIP mRNA (p = 0.0072) and protein expression (p = 0.0143) induced in the brain of APP/PS1 mice. In contrast, the levels of TXN mRNA (p = 0.0285) and protein (p = 0.0039) in the brain of APP/PS1 mice were increased after the injection of SY5. The ratio of TXN to TXNIP, which was decreased (p = 0.0131) in the brain of APP/PS1 mice, was significantly increased (p = 0.0072) after the injection of SY5. These results suggest that SY5 acts as a prodrug of SY6 in targeting the thioredoxin system and could be a potential therapeutic compound in oxidative stress-related diseases in the brain.     

Double-pulse LIBS of gadolinium oxide ablated by femto- and nano-second laser pulses

Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in the reheating mode in the double-pulse configuration.     

Phase transition and extended X-ray absorption fine structure of melt-spun amorphous Fe100−xYx alloys

The phase diagram and local structure of melt-spun amorphous (a-) Fe_100−xY_x (22?x?62) alloys were investigated using AC and DC magnetic and extended X-ray absorption fine structure (EXAFS) measurements. The a-Fe–Y system shows reentrant spin glass (RSG) behavior for 42?x?58 and spin glass (SG) behavior for 60?x. Two SG transition temperatures, T_g and T_f, were obtained in the RSG state. The T_g, T_f and Curie temperature T_C decrease with increasing x, and the T_C and T_g vanish at x=60. A new magnetic phase diagram for the melt-spun a-Fe_100−xY_x alloys was obtained from magnetic measurements for higher Y concentration. The magnetic states of the a-Fe_100−xY_x alloys change remarkably around x=60 and an EXAFS study revealed that the average atomic distance between nearest-neighboring Fe atoms changes at approximately x=60.     

Effects of Nb and Y substitution on negative thermal expansion of ZrV 2−XPXO7 (0≦X≦0.8)

Zirconium vanadates with a novel chemical composition including niobium and yttrium were synthesized by the sol-gel method. An aqueous solution of NH₄H₂PO₄ and NH₄V O₃ and an ethanol solution of ZrOCl₂,NbCl₅, and Y Cl₃ were prepared. These two solutions were stirred and mixed to prepare precursors of zirconium vanadates at 333 K, following the evaporation of the solvent at 363 K. The precursor gels obtained were heated at 373-973 K in air. A zirconium vanadate phase began to crystallize above 673 K and a single phase of zirconium vanadate was synthesized at 973 K. Although ZrV ₂O₇ generally had a positive thermal expansion in the temperature range above RT, the degree of positive thermal expansion decreased with the two types of substitution of P for V and a set of Nb and Y for Zr of ZrV ₂O₇. X-ray diffraction peaks due to a superlattice structure, causing a positive thermal expansion from RT, were not observed in the synthesized (Nb, Y)-substituted zirconium vanadates.     

A Cohen-type theorem for Artinian modules

We show that a finitely embedded module M over a commutative ring R is Artinian if the factor module M/(0 :_M P) is finitely embedded for every prime ideal P of R. Received: 10 June 2005     

Lower-frequency infrared spectra and structures of some typical aliphatic polyamides

The Polarized lower-frequency infrared spectra (800–33 cm^-1) of nylon 66 (α form), nylon 77 (γ form), and nylon 6 (both α and γ form) have been examined. The spectral changes which occur on complex formation of the polyamides with iodine-potassium iodide solution and on subsequent iodine desorption have been studied in relation to the changes in the polymer structures. On the basis of these results, most of the stronger bands have been reasonably assigned to the vibrations characteristic of the amide group and the methylene chain of the polyamides, and some new structure–frequency correlations have been established for the polymers.     

Flow-injection determination of inorganic pyrophosphate with use of an enzyme thermistor containing immobilized inorganic pyrophosphate

Inorganic pyrophosphate immobilized on controlled-pore glass is used in a simple flow enzyme thermistor system. The heat produced in hydrolysis of pyrophosphate is enhanced. by using Tris-HCl buffer, pH 7.2, containing 1 mM magnesium chloride, as carrier stream. The calibration graph is linear for 0.1–20 mM pyrophosphate; 500 assays are possible without loss of enzyme activity. For 0.5-ml injections of 10 mM pyrophosphate, the relative standard deviation was 2.0% (n=30). A single determination takes 6 min. Calcuim and strontium interfere.     

Triglyceride determination with use of an enzyme thermistor

The application of a split-flow type of enzyme thermistor for determining triglycerides is described. The device measures the protonation heat produced when a triglyceride is passed through a column containing triacyl glycerol lipase covalently bound to controlled-pore glass beads. The time required for a determination is less than 5 min, and the calibration graph for a triolein standard is linear up to 5 mM. The procedure is used for determining triglycerides in human blood sera and is compared with a conventional spectrophotometric method.