Seasonal variation and activity size distribution of <Superscript>7</Superscript>Be in ambient air

The seasonal variation of the ⁷Be activities in air and the size distribution of the ⁷Be aerosols were studied by using a continuous air sampler and a five stage cascade impactor. The mean monthly activity level of ⁷Be at the Korea Atomic Energy Research Institute (KAERI) site varied from 0.5 to 4.8 Bq·m⁻³ and revealed a seasonal variation, in which the ⁷Be activity levels were high in winter and low in summer. The mass size distribution showed a bi-modal distribution with a higher peak around 0.49 μm and a smaller peak between 3 μm and 7.2 μm. The activity median aerodynamic diameter (AMAD) decreased with increasing ambient ⁷Be concentrations. The mean residence times by using a mean growth rate of 0.004 μm·h⁻¹ were estimated to be 2.5–6.4 days. The AMAD has an increasing tendency with higher relative humidity. It seemed that the high humidity condition facilitated the growth of the aerosol, resulting in increased deposition rates of the aerosols and the low ⁷Be content in the surface air. The AMAD of the ⁷Be aerosols increased with an increasing temperature, but the temperature dependency of AMAD should be explained with geological and meteorological conditions.     

Facile syntheses of all possible diastereomers of conduritol and various derivatives of inositol stereoisomers in high enantiopurity from myo-inositol

Phosphoinositide-based signaling processes are crucially important in intracellular signal transduction events. Inositol phosphate analogues have been useful in probing the structure-activity relationships between inositol phosphates and biomacromolecules, and in studying biological functions of newly found inositol phosphates. Thus, a systematic and ready access to inositol stereoisomers is highly desirable. And practical and convenient syntheses of conduritols and related compounds are also important because of their biological activities and their synthetic utilities in the preparation of other bioactive molecules. We herein report the first syntheses of all possible diastereomers of conduritol and various derivatives of eight inositol stereoisomers in high enantiopurity from myo-inositol, which involve efficient enzymatic resolution of the intermediates conduritol B and C derivatives, followed by oxidation-reduction or the Mitsunobu reaction, and cis-dihydroxylation in stereo- and regioselective manners.     

Self-assemblies of new rigid angular ligands and metal centers toward the rational construction and modification of novel coordination polymer networks

Self-assemblies of rigid angular ligands with 120 degrees molecular angle and metal centers have been investigated with the aim of achieving the rational construction and modification of coordination polymer structures. The reactions of Co(NCS)(2) with 1,3-bis(trans-4-styrylpyridyl)benzene (L(1)()), 2,6-bis(trans-4-styrylpyridyl)pyridine (L(2)()), 1,3-bis(trans-4-styrylpyrimidyl)benzene (L(3)()), and 1,3-bis(trans-4-styrylquinoly)benzene (L(4)()) afford complexes [Co(L(1)())(2)(NCS)(2)]( infinity ) (1), [Co(L(2)())(2)(NCS)(2)]( infinity ) (2), Co(L(3)())(2)(NCS)(2)(CH(3)OH)(2) (3), and [Co(L(4)())(NCS)(2)]( infinity ) (4), respectively. The resulting complexes exhibit open framework, stairlike hydrogen-bonded chain and single-stranded helical coil structures, which are controlled by the variation of the geometry around the coordination site in ligands. Moreover, the coordination of L(1)() and L(2)() to Mn(hfac)(2) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) yields single-stranded helical coordination polymers of [Mn(L(1)())(hfac)(2)]( infinity ) (5) and [Mn(L(2)())(hfac)(2)]( infinity ) (6), respectively.     

Soluble factor from tumor cells induces heme oxygenase-1 by a nitric oxide-independent mechanism in murine peritoneal macrophages

Tumor target-derived soluble secretary factor has been known to influence macrophage activation to induce nitric oxide (NO) production. Since heme oxygenase-1 (HO-1) is induced by a variety of conditions associated with oxidative stress, we questioned whether soluble factor from tumor cells induces HO-1 through NO-dependent mechanism in macrophages. We designated this factor as a tumor-derived macrophage-activating factor (TMAF), because of its ability to activate macrophages to induce iNOS. Although TMAF alone showed modest activity, TMAF in combination with IFN-gamma significantly induced iNOS expression and NO synthesis. Simultaneously, TMAF induced HO-1 and this induction was slightly augmented by IFN-gamma. Surprisingly, however, induction of HO-1 by TMAF was not inhibited by the treatment with the highly selective iNOS inhibitor, 1400 W, indicating that TMAF induces the HO-1 enzyme by a NO-independent mechanism. While rIFN-gamma alone induced iNOS, it had no effect on HO-1 induction by itself. Collectively, the current study reveals that soluble factor from tumor target cells induces HO-1 enzyme in macrophages. However, overall biological significance of this phenomenon remains to be determined.     

Spin—rotational relaxation study of molecular reorientation in the presence of internal extended rotational diffusion

Molecular reorientation in the presence of internal rotation is investigated and an analytical expression for the spin—rotational rate of a nucleus attached to the internal rotor is obtained in terms of the internal angular-momentum correlation time. A model of a symmetric-top molecule undergoing anisotropic rotational diffusion is extended to include a modified extended diffusion of internal rotation. The result is applied to liquid toluene and the internal angular-momentum correlation time is evaluated from the ¹³C nuclear spin—rotational relaxation rate of the methyl carbon. A comparison with the previous result on the dipole—dipole relaxation data is made and the consistency of the present theory is discussed.     

Surface-grafted polystyrene beads with comb-like poly(ethylene glycol) chains: preparation and biological application

We prepared surface-grafted polystyrene (PS) beads with comb-like poly(ethylene glycol) (PEG) chains. To accomplish this, conventional gel-type PS beads (35-75 microm) were treated with ozone gas to introduce hydroperoxide groups onto the surface. Using these hydroperoxide groups, poly(methyl methacrylate) (PMMA, Mn= 22,000-25,000) was grafted onto the surface of the PS beads. The ester groups of the grafted PMMA were reduced to hydroxyl groups with lithium aluminum hydride (LAH). After adding ethylene oxide (EO) to the hydroxyl groups, we obtained the PS-sg-PEG beads, which had a rugged surface and a diameter of 80-150 microm. We could obtain several kinds of the PS-sg-PEG beads by controlling the chain lengths of the grafted PMMA and the molecular weights of the PEG chains. The grafted PEG layer was about 30-50 microm thick, which was verified from the cross-sectioned views of the fluorescamine-labeled beads. These fluorescence images proved that the beads possessed a pellicular structure. Furthermore, we found that the surface-grafted PEG chains had the characteristic property of reducing non-specific protein adsorption on the beads.     

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.