Single breath-hold multi-slab and cine cardiac-synchronized gadolinium-enhanced three-dimensional angiography

The rest period of the coronary arteries has been shown to be on the order of 120–160 msec. Restriction of the acquisition window in breath-hold cardiac-synchronized gadolinium-enhanced imaging to this duration limits the amount of sampled k-space data and hence the information when compared with conventional gadolinium-enhanced imaging. Two techniques for gadolinium-enhanced cardiac-synchronized angiography were implemented that acquire additional data during the unused portions of the cardiac cycle. Data acquisition is synchronized with the heart cycle and is restricted to a short period of each heart cycle. In a single breath-hold, a multi-slab acquisition (n = 5) allowed ECG-synchronized imaging of the entire heart or a CINE acquisition (n = 5) provided multiple stacks of images at different phases in the cardiac cycle over a smaller area. Preliminary results acquired in healthy volunteers and patients with aortic disease indicate that additional information can be acquired without an increase in breath-hold duration or a reduction in image quality.     

Chemical Degradation in Thermally Treated Ferrite/Superconductor Multiphase Materials: Modeling Parameters

Solid state chemical evolutions are studied in the case of superconductor/ferrite composites as a function of time and temperature. Pellets have been fabricated from ferrite NiFe₂O₄ and superconducting cuprate Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+X (noted as Bi-2223). Two types of experimental approaches are presented: high-temperature electrical complex impedance spectroscopy, and EDAX analyses performed from scanning electron microscopy. From the in situ electrical analyses, two steps in the solid state chemical evolutions have been evidenced for the first time. They can be associated with two types of solid state reactions: (i) direct reactions between the ferrite phase and the superconducting matrix and (ii) a self-degradation of the superconducting phase probably associated with a homogenization of elements. The electrical analyses are modeled using two types of kinetics parameters. From the EDAX analyses, the local distribution of each element is determined. The concentration profiles found for the various elements (Ni, Fe, Bi, Sr, Ca, Cu) are interpreted in terms of a virtual diffusion law involving virtual D^* coefficients. These coefficients are found to be of about 10⁻¹¹ (cm²/s) in the range 800–830°C.     

Accelerating the development of phase-change random access memory with in-fab plasma profiling time-of-flight mass spectrometry

We demonstrate the potential of using plasma profiling time-of-flight mass spectrometry (PP-TOFMS) to accelerate process developments for phase-change random access memory (PCRAM) applications, which require advanced materials with composition-driven properties. We assess the performances of PP-TOFMS for the chemical depth-profiling of GeSbTe phase change materials, first after deposition steps to investigate the top surface layer and the incorporation of silicon into the amorphous matrix, then after the thermal annealing step to refine in situ capping strategies, and finally in close loop with etching process steps. Comparison of reference-free semiquantitative PP-TOFMS analysis based on ion beam ratio with Rutherford backscattering spectrometry shows remarkable agreement (~10% relative). PP-TOFMS proves to be a fast screening tool, which allows process monitoring and selection of samples that indeed need more complex analysis.     

Sweeping total reflection X-ray fluorescence optimisation to monitor the metallic contamination into IC manufacturing

Among the methods available on the market today to control as metallic contamination in integrated circuit manufacturing, Sweeping Total reflection X-ray Fluorescence mode appears a very good method, providing fast and entire wafer mapping. With the goal of a pertinent use of Sweeping Total reflection X-ray Fluorescence in advanced Integrated Circuit manufacturing this work discusses how acceptable levels of contamination specified by the production (low levels to be detected) can be taken into account.     

Antiplasmodial prenylated flavanonols from Tephrosia subtriflora

The CH₂Cl₂/MeOH (1:1) extract of the aerial parts of Tephrosia subtriflora afforded a new flavanonol, named subtriflavanonol (1), along with the known flavanone spinoflavanone B, and the known flavanonols MS-II (2) and mundulinol. The structures were elucidated by the use of NMR spectroscopy and mass spectrometry. The absolute configuration of the flavanonols was determined based on quantum chemical ECD calculations. In the antiplasmodial assay, compound 2 showed the highest activity against chloroquine-sensitive Plasmodium falciparum reference clones (D6 and 3D7), artemisinin-sensitive isolate (F32-TEM) as well as field isolate (KSM 009) with IC₅₀ values 1.4–4.6 μM without significant cytotoxicity against Vero and HEp2 cell lines (IC₅₀ > 100 μM). The new compound (1) showed weak antiplasmodial activity, IC₅₀ 12.5–24.2 μM, but also showed selective anticancer activity against HEp2 cell line (CC₅₀ 16.9 μM).     

Preliminary investigation of electrodynamic charged droplet processing to couple capillary liquid chromatography with matrix-assisted laser desorption/ionization mass spectrometry

Charged droplet processing methodology, that utilizes electrodynamic levitation technology to control the trajectories of picoliter volume charged droplets and deliver them to a target plate at atmospheric pressure, has been developed. Termed wall-less sample preparation (WaSP), this methodology offers several features that could prove beneficial to the preparation of sample spots from separation column effluents for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. These features include solute pre-concentration factors of 10(1) to 10(3) due to volatile solvent evaporation prior to droplet deposition onto the target plate, high spatial accuracy of the deposition position of each processed droplet (+/-5 microm), and the ability to prepare sample spots as small as 20 microm in diameter from a single droplet. Here a new mode of operation of this methodology is described and used as an offline post-column pre-concentrating interface between capillary liquid chromatography (capLC) and a target plate for offline MALDI-MS. Using a fraction from the capLC separation of peptides produced by the proteolytic digestion of the protein cytidine 5'-triphosphate:phosphocholine cytidylyltransferase, MALDI sample spots were prepared using the dried-droplet method, direct piezoelectric droplet dispensing, and the processing of piezo-dispensed droplets by WaSP. The sample spot morphology was investigated using light microscopy, and peptide ion abundances produced by MALDI were measured using time-of-flight (TOF) MS. The advantages of developing an online capLC/WaSP interface with MALDI-MS in the future are discussed along with some of the challenges that may be encountered in such an endeavor.     

Computer simulation investigation of the water-benzene interface in a broad range of thermodynamic States from ambient to supercritical conditions

The dependence of the properties of the water-benzene system on the thermodynamic conditions in a broad range of temperatures and pressures has been investigated by computer simulation methods. For this purpose, Monte Carlo simulations have been performed at 23 different thermodynamic states, ranging from ambient to supercritical conditions. The density profiles of the water and benzene molecules have been determined at each of the thermodynamic states investigated. Information on the dependence of the mutual solubility of the two components in each other as well as of the width of the interface on the temperature and pressure has been extracted from these profiles. The width of the interface has been found to increase with increasing temperature up to a certain point, where it diverges. The temperature of this divergence corresponds to the mixing of the two phases. The determination of the critical mixing temperature at various pressures allowed us to estimate the upper critical curve, separating the two-phase and one-phase liquid systems, of the phase diagram of the simulated water-benzene system. In analyzing the preferential orientation of the interfacial molecules relative to the interface, it has been found that the main orientational preference of the benzene molecules is to lie parallel with the plane of the interface, and the water molecules penetrated deepest into the benzene phase prefer to stay perpendicular to the interface, pointing by one of their O-H bonds almost straight toward the benzene phase, whereas the waters located at the aqueous side of the interface are preferentially aligned parallel with the interfacial plane. Although the strength of the observed orientational preferences decreases rapidly with increasing temperature, the preferred orientations themselves are found to be independent of the thermodynamic conditions. Remains of the orientational preferences of the molecules are found to be present up to temperatures as high as 650 K. The analysis of the relative orientation of the neighboring water-benzene pairs has revealed that the radius of the first hydration shell of the benzene molecules is independent of the thermodynamic conditions, even if the system consists of one single phase. It has been found that the nearest water neighbors of the benzene molecules are preferentially located above and below the benzene ring, whereas more distant water neighbors, belonging still to the first hydration shell, prefer to stay within the plane of the benzene molecule. In the two-phase systems the dipole vector of the nearest waters has been found to be preferentially perpendicular to the vector pointing from the center of the benzene molecule to the water O atom.     

The use of a highly sulfated cyclodextrin for the simultaneous chiral separation of amphetamine-type stimulants by capillary electrophoresis

We investigated the simultaneous chiral separation of nine amphetamine type stimulants (dl-norephedrine, dl-norpseudoephedrine, dl-ephedrine, dl-pseudoephedrine, dl-amphetamine, dl-methamphetamine, dl-methylenedioxyamphetamine (MDA), dl-methylenedioxymethamphetamine (MDMA), and dl-methylenedioxyethylamphetamine (MDEA)) by capillary electrophoresis using highly sulfated gamma-cyclodextrin (SU(XIII)-gamma-CD) as a chiral selector. Three different approaches using SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte were designed; (I) high CD concentration (10 mM SU(XIII)-gamma-CD) at neutral pH (pH 7.0) in the normal polarity mode, (II) low CD concentration (1.0 mM) at low pH (pH 2.6) in the normal polarity mode and (III) high CD concentration at low pH (pH 2.6) in the reversed-polarity mode. In mode (II), the effects of adding three neutral CDs (beta-CD, dimethyl-beta-CD and hydroxypropyl-beta-CD) were also investigated. The best separation was obtained after optimizing mode (III) as follows: run buffer of 10 mM SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte at pH 2.6, applied voltage of -12 kV and capillary temperature of 15 degrees C.     

Polarographic analysis of the reduction waves of Pt(II)-SATSC complex

A polarographic study of the Pt(II)-salicylaldehyde thiosemicarbazone complex in sodium perchlorate as supporting electrolyte is described. In addition to the reduction wave of the complex, a catalytic hydrogen wave is also recorded. The characteristics of this catalytic hydrogen wave are studied under different experimental conditions such as varying acid/complex/supporting electrolyte/surfactant concentrations and also with mercury droptime. Based on these, a probable mechanism for the electrode process has been postulated. Presented at the 12th Annual Symposium in Chemistry held at the Indian Institute of Technology, Madras in March 1987.