Mobile NMR for geophysical analysis and materials testing

Initiated by well logging NMR, portable NMR instruments are being developed for a variety of novel applications in materials testing, process analysis and control, which provides new opportunities for geophysical investigations. Small-diameter cylindrical sensors can probe short distances into the walls of slim-line logging holes, and single-sided sensors enable non-destructive testing of large objects. Both sensors are characterized by small sensitive volumes. Barrel-shaped magnets that accommodate the sample in their center have higher sensitivity due to a larger sensitive volume but can accommodate only samples like drill cores, which fit in size to the diameter of the magnet bore. Both types of magnets can be scaled down to the size of a coffee mug to arrive at sub-compact NMR equipment. Portable NMR magnets are reviewed in the context of applications related to geophysics.     

Influence of Extrusion Cooking on In Vitro Digestibility,Physical and Sensory Properties of Brazilian Pine Seeds Flour (Araucaria Angustifolia)

Brazilian pine seeds (pinhão) are gluten‐free products derived from Araucaria angustifolia. The commercialization of these seeds is essentially associated with a low level of industrialization. In this context, extrusion cooking is a potential alternative for preparing extrudates of pinhão as a food product, which can be easily digested and is ready for human consumption. Brazilian pine seeds flour was processed in a single‐screw extruder following a central composite rotatable design. Three factors (independent parameters) were considered: moisture content (14 to 22 g/100 g), screw speed (100 to 250 rpm), and temperature in the 3rd heating zone (120 to 200 °C). The structural characteristics, in vitro digestibility and sensory acceptance were also evaluated. The resistant starch contents is almost reduced to zero after extrusion cooking while the slowly digestible starch content is increased. An increase in moisture positively affected the hardness and the luminosity (L^*), although it negatively affected the volumetric expansion index, crispness, and color parameters (a^*, b^*, and ΔE). The experimental conditions of this study allowed the production of expanded extrudates from Brazilian pine seeds with good expansion, texture properties, and acceptance qualities. Thus, extrusion cooking was found to be a potential method for the industrialization of Brazilian pine seeds as a food product.     

Spray deposition and property analysis of anatase phase titania (TiO2) nanostructures

Anatase phase titanium dioxide thin films have been deposited at various substrate temperatures by chemical spray pyrolysis of an aerosol of titanyl acetylacetonate. Deposited TiO₂ films were nanocrystalline and preferentially oriented along [101] direction, uniform and adherent to the glass substrate. Best films processed at 450 °C were characterized to analyze its phase composition, texture, roughness, optical and electrical properties. X-ray photoelectron spectroscopy revealed that the surface of the film has only the Ti⁴⁺ cations to form perfect TiO₂ stoichiometry with less amount of hydration. Atomic force microscopy image demonstrated the existence of homogeneous and rough surface, suitable for electrocatalytic applications. The film has an optical transmittance more than 90% and the refractive index of 2.07 was recorded at the wavelength 633 nm. Due to nano-sized grains, obtained optical band gap (3.65 eV) of the TiO₂ thin film was larger than that of the bulk TiO₂ (3.2 eV). Calculated porosity of the films 0.44, revealed the porous nature of the films. Hall measurements indicated that these materials are p-type and yield a carrier density of the order 8.8 × 10²⁰ cm⁻³ and a carrier mobility of 0.48 × 10⁻⁶ cm²/Vs. The dc electrical conductivity was therefore very low (8.91 × 10⁻⁶ S/cm) because of lower value of mean free path of the charge carriers (4.36 × 10⁻¹¹ cm). It gives an impression that the process of spray pyrolysis provides an easy way to tailor make thin films possessing superior properties.     

Formulation of Silicone Matrix Systems for Long Term Constant Release of Peptides

Theoretically, release of drug through the water-filled pores of matrix systems is expected to show a square-root-of-time dependence, with time exponents of 0.5 and hence continuosly declining release rates. Yet there have been many research groups finding remarkable deviations.

The aim of this work was to investigate on factors which lead to deviations from the square-root-of-time law and may be helpful for the development of matrix systems with constant drug release for long time. Matrices of polydimethylsiloxane (PDMS) were prepared incorporating varying amounts of different pore-building, water soluble hydrogels. The hydrophilic model drug was Gly-Tyr.

The following essential factors influencing the long-term release profiles were found: (i) total matrix loading, (ii) its dissolution rate and (iii) the viscosity of the pore-building hydrogel. A proper choice of conditions lead to release profiles with time-exponents up to 0.8 for a time period of several weeks.     

Effects of dobutamine on myocardial blood flow, contractile function, and bioenergetic responses distal to coronary stenosis: implications with regard to dobutamine stress testing

To determine the effects of dobutamine stimulation on myocardium distal to a coronary stenosis, transmural spatially localized phosphorus 31 nuclear magnetic resonance measurements of myocardial high-energy phosphate compounds (adenosine triphosphate and phosphocreatine), inorganic phosphate, and blood flow and systolic wall thickening were made in 8 open-chested dogs. Data were collected under (1) control conditions, (2) after the application of a moderate coronary stenosis, (3) during infusion of dobutamine with continuing stenosis, and (4) after the release of the stenosis with continuing dobutamine. Stenosis was associated with concordant reductions of subendocardial blood flow, wall thickening, and high-energy phosphate, and mild elevation of inorganic phosphate; subepicardial measurements were essentially unchanged. During dobutamine infusion, blood flow increased in all myocardial layers. Wall thickening returned to control values in the subendocardium and increased nonsignificantly in the subepicardium. Additional loss of high-energy phosphate occurred only in the subepicardium. The data suggest that improved contractile function associated with dobutamine infusion resulted from the inotropic effects of dobutamine and was made possible by the improved blood flow it produced. The data indicate that measurements of blood flow and contractile function do not reliably predict the transmural myocardial metabolic responses to inotropic perturbations in the hypoperfused heart. Taken together, the present findings yield insights with regard to the interpretation of diagnostic dobutamine stimulation testing with single photon emission tomography, radionuclide angiography, and echocardiography.     

A fast software one-way hash function

One way hash functions are an important cryptographic primitive, and can be used to solve a wide variety of problems involving authentication and integrity. It would be useful to adopt a standard one-way hash function for use in a wide variety of systems throughout the world. Such a standard one-way hash function should be easy to implement, use, and understand; resistant to cryptographic attack, and should be fast when implemented in software. We present a candidate one-way hash function which appears to have these desirable properties. Further analysis of its cryptographic security is required before it can be considered for widespread use.     

MALDI-TOF-MS analysis of droplets prepared in an electrodynamic balance: "wall-less" sample preparation

Methodology enabling mass spectral analysis of the composition of droplet(s) prepared in an electrodynamic balance (EDB) by matrix-assisted laser desorption/ionization (MALDI) is described. The dc field surrounding the electrodynamic balance was manipulated to eject single droplets at a time from the EDB thereby causing their deposition onto a MALDI sample plate precoated with matrix. When the laser was directed onto the droplet(s) and held stationary, marked gains in the signal-to-noise and signal-to-background ratios were realized with each subsequent mass spectrum due to the suppression of matrix cluster ion formation. Optical microscopy of the plate, after 1024 laser shots were fired at eight droplets that had been deposited one on top of the other, revealed a residual island of droplet matter (area approximately 3.1 x 10(-9) m2) inside the region where the crystalline matrix had been ablated away within the laser spot (area approximately 1.6 x 10(-8) m2). Removing the predried crystalline matrix layer and, instead, adding matrix into the starting solution was found to be a more effective means of suppressing matrix cluster ion formation. The chemical composition of the droplet(s) prepared in the EDB is discussed with regard to sample preconcentration, the images of the laser spot after MALDI, matrix cluster ion suppression, and the possibility for improved quantitation and detection limits by MALDI-TOF-MS.     

Pale vacuolated epithelial cells in epididymis of aflatoxin-treated mice

The responses of the mouse epididymal epithelium to subchronic doses of aflatoxin B1 were investigated in a histological study. Either few and large or small and profuse vacuoles containing an amorphous to dense periodic acid-Schiff-positive material were observed in the epithelium of all the segments of the epididymis. Resin-embedded semi-thin sections and transmission electron microscopy indicated that these vacuoles were intracellular. The cells that contained these vacuoles were quite different in organization and electron density from the cell types already established in the epididymal epithelium and are designated as pale vacuolated epithelial cells. Owing to aflatoxin B1 toxicity, the apical membrane of some of the principal cells, either individually or in groups, disintegrated so that the principal cells released their contents into the lumen of the duct through development of a 'fistula'. Spermatozoa from the ductal lumen entered the principal cell fistula and reached the basal lamina. If extravasation of the spermatozoa via this route occurred, it would bring about an autoimmune response, leading to the formation of spermatic granulomas and the generation of anti-sperm antibodies. Extravasation of spermatozoa seems to be offset by the underlying basal cell, which is presumed to develop into a pale vacuolated epithelial cell to enclose the disintegrating principal cells and the spermatozoa arriving at the principal cell. Thus, the development of pale vacuolated epithelial cells may be a protective device preventing an autoimmune response to sperm antigens in the context of toxicant-induced degeneration of the principal cells of the epididymal epithelium.     

Measurement of arterial input function of <Superscript>17</Superscript>O water tracer in rat carotid artery by using a region-defined (REDE) implanted vascular RF coil

A method of determining arterial input function (AIF) by continuously detecting the ¹⁷O MR signal changes of ¹⁷O-labeled water tracer in the rat carotid artery using a region-defined (REDE) implanted vascular RF coil at 9.4 Tesla is reported. This coil has a compact physical size of 1 mm inner diameter, 3 mm outer diameter and 11 mm in length. It can be readily implanted into the rat neck and wrapped around the rat carotid artery for achieving adequate MR detection sensitivity for determining AIF with minimal surgical trauma. Water phantom and in vivo MR experiments were conducted for validating the coil's performance. A signal-to-noise ratio of ~20:1 was achieved for the ¹⁷O signal acquired from naturally abundant H₂ ¹⁷O in a small amount of blood (~7 μl) inside the rat carotid artery with an acquisition time of 11 s. The REDE RF coil design electromagnetically isolates the rat carotid artery from surrounding tissues and ensures that the MR signal detected by the RF coil is only attributable to the artery blood. It also minimizes the electromagnetic coupling between the implanted RF coil and a head surface coil tuned at the same operating frequency (two-coil configuration). This configuration allowed simultaneous measurements of dynamic changes of ¹⁷O MR signal of the H₂ ¹⁷O tracer in both rat carotid artery and brain. Compared to most contemporary MR approaches, the REDE implanted RF provides a simple, accurate, and promising solution for determination of AIF in small experimental animals.