Synthesis of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene,isosteres of benzofluoranthenes

The total syntheses of fluorantheno[1,2-b]thiophene and fluorantheno[3,2-b]thiophene are reported. The common cyclobutanone intermediate which was obtained by [2 + 2] addition of fluorenylidene ketene with 2,3-dihydrothiophene underwent regioselectively α or β ring opening to lead to linear or angular PAC skeleton molecules under desired conditions. 2,3-Dichloro-5,6-dicyanobenzoquinone was applied for aromatization to achieve the formation of PAC's. These two isosteres exhibit very similar uv/visible spectra to benzo[a] and [b]fluoranthenes respectively. Spectroscopic data used for their structural assignments is also discussed.     

GC-MS determination of steroids related to androgen biosynthesis in human hair with pentafluorophenyldimethylsilyl-trimethylsilyl derivatisation

An efficient method for the simultaneous determination of eight steroids, androstenedione, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), testosterone, androsterone, etiocholanolone, progesterone and pregnenolone, in human hair by gas chromatography-mass spectrometry (GC-MS) using d3-testosterone as internal standard is described. The method involves alkaline digestion, liquid-liquid extraction and subsequent conversion to mixed pentafluorophenyldimethylsilyl-trimethylsilyl (flophemesyl-TMS) derivatives for sensitive analysis in the selected ion monitoring (SIM) mode. This method showed good overall repeatability and reproducibility of 4.88-11.24 and 3.19-9.58%, respectively. For the first time, the quantification of DHT, DHEA and pregnenolone in human hair has been achieved by GC-MS, testosterone was also quantified. The detection of four steroids in hair samples was possible in the concentration range 0.12-8.45 ng g-1. The other four steroids, androstenedione, androsterone, etiocholanolone and progesterone, were not detected. The detection limits for SIM of the steroids varied in the range 0.02-0.5 ng g-1, and the SIM responses were linear with correlation coefficients varying from 0.991 to 0.996 for most of the steroids studied. The concentrations of the four steroids detected were different in male and female hair samples.     

Kinetic fluorometric FIA determination of total ascorbic acid, based on use of two serial injection valves

The kinetic determination of total ascorbic acid with a flow-injection analysis system is described. The sample is loaded into two serial sample injection valves and injected into a carrier system containing mercuric chloride and o-phenylenediamine. The formation of a fluorescent product is monitored. The single-point and double-point kinetic methods are compared by using both peak height and peak area as the analytical signal. A detection limit of 0.1 mu/ml for vitamin C was achieved with a sample throughput rate of 30 per hour.     

Application of BGO detector to monitor in situ16N concentration in a reactor pool

A high efficiency BGO detecting system coupled to a coolant pumping device was used to monitor on-line the 6.13 MeV high energy gamma-ray, which is emitted from the 7.1 s half-life of¹⁶N activated by¹⁶O(n, p) reaction in a nuclear reactor. The system has been demonstrated effectively to monitor the real-time reactor power level as well as the space-time neutron flux distribution in reactor coolant.     

Generalized fundamental equations on the submanifolds of a manifoldESX n

A connection which is both Einstein and semisymmetric is called anES connection, and a generalizedn-dimensional Riemannian manifold on which the differential geometric structure is imposed by a unified field tensorg through anES connection is called ann-dimensionalES manifold and denoted byESX _n . We investigate some necessary and sufficient conditions for submanifolds ofESX _n to be also Einstein and derive the generalized fundamental equations on various submanifolds ofESX _n , such as generalized Gauss formulas, generalized Weingarten equations, and generalized Gauss-Codazzi equations. We employ the useful and powerful concept ofC-nonholonomic frame of reference, introduced in earlier work.     

PDMS-based microfluidic device with multi-height structures fabricated by single-step photolithography using printed circuit board as masters

We have developed a method for fabricating microfluidic devices with multi-height structures using single step photolithography. The whole fabrication process is executed by conventional printed circuit board (PCB) technology without the need of having access to clean room facilities. Specifically designed "windows" and "rims" architectures were printed on films that were used as photomasks. Different levels of protruding features on the PCB master were produced by exposing a photomask followed by chemical wet etching. Poly(dimethylsiloxane) (PDMS) was then moulded against the positive relief master to generate microfluidic structures. In this report, we described the fabrication of a microfluidic device featured with a multi-height "sandbag" structure for particle entrapment and peripheral microchannels. Controlled immobilization of biological cells and immunocytochemcial staining assays were performed to demonstrate the applicability of the microfluidic device for cellular analysis. The integrity of the microdevice remained stable under applied pressure, indicating the robustness of the elastic PDMS structures for analytical operation. The simple microfabrication process requires only low-cost materials and minimal specialized equipment and can reproducibly produce mask lines of about 20 microm in width, which is sufficient for most microfluidic applications.     

A polymer-based microfluidic device for immunosensing biochips

This paper describes the design, fabrication, and test of a PDMS/PMMA-laminated microfluidic device for an immunosensing biochip. A poly(dimethyl siloxane)(PDMS) top substrate molded by polymer casting and a poly(methyl methacrylate)(PMMA) bottom substrate fabricated by hot embossing are bonded with pressure and hermetically sealed. Two inlet ports and an air vent are opened through the PDMS top substrate, while gold electrodes for electrochemical biosensing are patterned onto the PMMA bottom substrate. The analyte sample is loaded from the sample inlet port to the detection chamber by capillary force, without any external intervening forces. For this and to control the time duration of sample fluid in each compartment of the device, including the inlet port, diffusion barrier, reaction chamber, flow-delay neck, and detection chamber, the fluid conduit has been designed with various geometries of channel width, depth, and shape. Especially, the fluid path has been designed so that the sample flow naturally stops after filling the detection chamber to allow sufficient time for biochemical reaction and subsequent washing steps. As model immunosensing tests for the microfluidic device, functionalizations of ferritin and biotin to the sensing surfaces on gold electrodes and their biospecific interactions with antiferritin antiserum and streptavidin have been investigated. An electrochemical detection method for immunosensing by biocatalyzed precipitation has been developed and applied for signal registration. With the biochip, the whole immunosensing processes could be completed within 30 min.     

Capillary electrophoresis of trace metals in highly saline physiological sample matrices

Trace metal ions in highly saline samples such as urine were determined with capillary electrophoresis (CE) without desalting or off-line preconcentration. By mixing with a dye, 4-(2-pyridylazo) resorcinol (PAR), the metal ions were converted into anionic complexes having strong absorbance near 500 nm. A large volume of the metal-PAR complex sample solution injected into a coated capillary was stacked isotachophoretically and separated under a reverse potential. The salt anion (chloride) and PAR in the sample matrix acted as the leading and terminating electrolytes, respectively. In a sample containing a 250 mM NaCl matrix, more than 400-fold enhancement in the absorbance detector response was realized compared to the normal CE injection mode. Combination of the dye complexation and isotachophoretic stacking provided excellent detection limits (S/N = 3) for three trace metal ions in the low ppb range (Fe(2+), 0.7 ppb, Ni(2+), 0.4 ppb; Zn(2+), 1.2 ppb) with absorbance detection. The migration time reproducibility was excellent (relative standard deviations: standard samples < 1%, urine samples approximately 1%). The proposed method is convenient and fast, and the sample analysis can be completed within 20 min.     

Chemical Constituents of Brown Rice Grain (<Emphasis Type="Italic">Oryza sativa</Emphasis>)

One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (¹H-¹HCOSY, ¹H-¹³C HETCOR) aided by EI-MS, and IR spectra. __________ Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005.