Naupliolide, a sesquiterpene lactone with a novel tetracyclic skeleton from Nauplius graveolens subsp. odorus

The aerial parts of Nauplius graveolens subsp. odorus (Schousb) Wikl. afforded a novel sesquiterpene lactone (1) named naupliolide together with the known 6,7,9,10-tetradehydroasteriscanolide 2 and asteriscunolides A-D 3a-d. The structure of compound 1 corresponds to a novel skeleton of 14,15-dimethyl-7,13-dioxotricyclic[6.4.0.0^9,11]dodeca-12,13-olide, and was established on the basis of spectroscopic methods including 2D-NMR. The coexistence of naupliolide 1 together with the structurally related sesquiterpene lactones asterisculolides A-D (3a-d) and 6,7,9,10-tetradehydroasteriscanolide 2, seems to indicate their biosynthetic relationship.     

Formation of silicon nanocrystals by thermal annealing of low-pressure chemical-vapor deposited amorphous SiNx (x=0.16) thin films

Silicon nanocrystals have been produced by thermal annealing of SiN_x thin film obtained by low pressure chemical vapor deposition using a mixture between disilane and ammonia. Morphological, structural, and photoluminescence properties of the thin film were investigated using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and photoluminescence spectroscopy. The results revealed a high crystallinity of film with a crystalline volume fraction exceeded 70%, and a dominance of silicon nanocrystallites having the sizes within the range 2.5–5 nm and density ~1.98.10¹²/cm². The PL peaks consist of nanocrystalline silicon and amorphous silicon. The luminescence from the silicon nanocrystals was dominant.     

Measurement of temperature of a dusty plasma from its configuration

A new concept called “configurational temperature” is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two-dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three-dimensional case is also presented, which can be employed for the temperature measurement of a three-dimensional dust crystal in laboratory devices.     

EDTA and mixed-ligand complexes of tetravalent and trivalent plutonium

EDTA forms stable complexes with plutonium that are integral to nuclear material processing, radionuclide decontamination, and the potentially enhanced transport of environmental contamination. To characterize the aqueous Pu(4+/3+)EDTA species formed under the wide range of conditions of these processes, potentiometry, spectrophotometry, and cyclic voltammetry were used to measure solution equilibria. The results reveal new EDTA and mixed-ligand complexes and provide more accurate stability constants for previously identified species. In acidic solution (pH < 4) and at 1:1 ligand to metal ratio, PuY (where Y4- is the tetra-anion of EDTA) is the predominant species, with an overall formation constant of log beta110 = 26.44. At higher pH, the hydrolysis species, PuY(OH)- and PuY(OH)(2)2-, form with the corresponding overall stability constants log beta(11 - 1) = 21.95 and log beta(11 - 2) = 15.29. The redox potential of the complex PuY at pH = 2.3 was determined to be E(1/2) = 342 mV. The correlation between redox potential, pH, and the protonation state of PuY- was derived to estimate the redox potential of the Pu(4+/3+)Y complex as a function of pH. Under conditions of neutral pH and excess EDTA relative to Pu4+, PuY(2)4- forms with an overall formation constant of log beta120 = 35.39. In the presence of ancillary ligands, mixed-ligand complexes form, as exemplified by the citrate and carbonate complexes PuY(citrate)3- (log beta1101 = 33.45) and PuY(carbonate)2- (log beta1101 = 35.51). Cyclic voltammetry shows irreversible electrochemical behavior for these coordinatively saturated Pu4+ complexes: The reduction wave is shifted approximately -400 mV from the reduction wave of the complex PuY, while the oxidation wave is invariant.     

Solubilization and purification of galactosyltransferase from golgi membranes of rat ventral prostate

UDP-galactose ovomucoid galactosyltransferase, a membrane-bound enzyme involved in the biosynthetic pathways for formation of the nonreducing terminal oligosaccharide sequences on glycoproteins, has been solubilized and purified from rat ventral prostate Golgi membranes. Solubilization was effected by treatment of the particulate fraction with Triton X-100 (0.5% v/v) and MnCl₂ (25 mM). The solubilized enzyme was purified by affinity chromatography on hen ovomucoid-sepharose column. The purified galactosyltransferase showed three protein bands of approx. 74,000, 60,000, and 54,000 daltons on sodium dodecyl sulfate gel electrophoresis. On gel filtration, enzyme activity eluted at approx. 70,000 daltons with a broad shoulder between 60,000 and 50,000 daltons. Isoelectric focusing of the purified enzyme resolved at least five active bands with pHi of 9, 7.4, 6.75, 6.1, and 4.8.     

Molecular interaction of N-formylmorpholine with alkanols,a spectroscopic study

The interactions of N-formylmorpholine (NFM) with different alkanols were monitored using proton nuclear magnetic resonance and IR spectroscopy. It was found that the NFM interaction with alkanols decreases with increasing length and branching of the alkanols. A good correlation was obtained between the proton chemical shift and the volume of mixing of alkanols with NFM.     

High-performance liquid chromatographic assay of cefotaxime, desacetylcefotaxime and ceftriaxone in rat plasma

A simple and selective high-performance liquid chromatographic method is described for the analysis of the cephalosporins cefotaxime (CXM), desacetylcefotaxime (DACXM) and ceftriaxone (CFX) in rat plasma. Plasma was deproteinized with methanol, and the supernatant was directly injected into the chromatograph and monitored at 254 nm. For determination of the unbound drugs, a centrifugal ultrafiltration method was employed. The calibration curves were linear (r = 0.999) from 2.5 to 500 micrograms/ml; the detection limits were 100 ng/ml for DACXM and 250 ng/ml for CXM and CFX. The method was not interfered with by other plasma components, nor by barbital sodium or caffeine, and has been applied to study the pharmacokinetics of the cephalosporins in rats.     

Laser desorption/ablation combined with nuclear analytical methods for materials characterization

Ubiquitous elements like carbon and oxygen always contaminate surfaces and, therefore, are the soucre of important analytical errors at trace level. Even in the case of radioactivation (with charged particles), where the sample can be etched after irradiation, analytical problems exist. In this work, we show that laser desorption/ablation can efficiently clean surfacaes, in the case of GaAs samples, resulting in better analytical conditions. Under ultra high vacuum, these surfaces remain clean long enough, so that the analysis of carbon and oxygen can be carried out using various nuclear methods, according to the needs of the analyst.