An isocratic HPLC procedure was developed for the simultaneous determination of caffeine and six catechins in tea samples. When 31 commercial teas extracted by boiling water or 75% ethanol were analyzed by HPLC, the levels of (-)-epigallocatechin 3-gallate (EGCG), and total catechins in teas were in the order green tea (old leaves) > green tea (young leaves) and oolong tea > black tea and pu-erh tea. Tea samples extracted by 75% ethanol could yield higher levels of EGCG and total catechins. The contents of caffeine and catechins also have been measured in fresh tea leaves from the Tea Experiment Station in Wen-Shan or Taitung; the old tea leaves contain less caffeine but more EGCG and total catechins than young ones. To compare caffeine and catechins in the same tea but manufactured by different fermentation processes, the level of caffeine in different manufactured teas was in the order black tea > oolong tea > green tea > fresh tea leaf, but the levels of EGCG and total catechins were in the order green tea > oolong tea > fresh tea leaf > black tea. In addition, six commercial tea extracts were used to test the biological functions including hydroxyl radical scavenging, nitric oxide suppressing, and apoptotic effects. The pu-erh tea extracts protected the plasmid DNA from damage by the Fenton reaction as well as the control at a concentration of 100 microg/mL. The nitric oxide suppressing effect of tea extracts was in the order pu-erh tea >/= black tea > green tea > oolong tea. The induction of apoptosis by tea extract has been demonstrated by DNA fragmentation ladder and flow cytometry. It appeared that the ability of tea extracts to induce HL-60 cells apoptosis was in the order green tea > oolong > black tea > pu-erh tea. All tea extracts extracted by 75% ethanol have stronger biological functions than those extracted by boiling water.

In this paper we give new techniques for designing eficient algorithms for computational geometry problems that are too large to be solved in internal memory. W e use these techniques l o develop optimal and practical algorithms for a number of important largescale problems. W e discuss our algorithms primarily in the context of single processor/single disk machines, a domain in which they are not only the first known optimal results but also of tremendous practical value. Our methods also produce the first known optimal algorithms for a wide range of two-level and hierarchical multilevel memory models, including parallel models.The algoriihms are optimal both in terms of 1/0 cost and internal computation.

Theanine, caffeine, and catechins in fresh tea leaves and oolong tea were determined by using capillary electrophoresis (CE). CE separated these tea polyphenols from three other tea ingredients, namely, caffeine, theophylline, and theanine, within 8 min. The young leaves (apical bud and the two youngest leaves) were found to be richer in caffeine, (-)-epigallocatechin gallate (EGCg), and (-)-epicatechin gallate (ECg) than old leaves (from 5th to 7th leaves). On the other hand, the old leaves (from 8th to 10th leaves) contained higher levels of theanine, (-)-epigallocatechin (EGC), and (-)-epicatechin (EC). Results from a comparison of fresh young tea and oolong tea compositions indicated oolong tea contained more theanine and catechins than fresh young tea. Furthermore, it was found that the levels of theanine, EGC, and EGCg in young leaves rose markedly with the withering process. Caffeine did not markedly change. However, fully or partially fermented teas (oolong tea or pauchong tea) have a common initial step in the withering process. Fresh tea leaves or oolong tea extract (0.1%, w/v) markedly inhibited neurosphere adhesion, cell migration, and neurite outgrowth in rat neurospheres. Theanine (348 micrograms/mL) and caffeine at high concentration (50 micrograms/mL) did not inhibit neurosphere adhesion or migration activities, but EGCg at 20 micrograms/mL effectively inhibited neurosphere adhesion for 24 h. These results indicated that EGCg might affect neural stem cell survival or differentiation.

Combined cyclic voltammetry and in situ scanning tunneling microscopy studies were employed to gain information about the interfacial structure of a chloride modified Cu(100) electrode surface exposed to an acidic electrolyte solution that contained redox-active dibenzylviologens (DBV, 1,1‘-dibenzyl-4,4‘-bipyridinium molecules). A particular focus of this contribution lies in the structural characterization of the electrode surface under nonequilibrium reactive conditions, for example, during the occurrence of an electron-transfer reaction. Typically, two pairs of clearly distinguishable current waves denoted as P1/P1‘ and P2/P2‘ appear in the cyclic voltammogram of Cu(100) in a mixture of 10 mM HCl and 0.1 mM DBVCl2, provided the cathodic potential limit remains restricted to values of E work > −425 mV vs reversible hydrogen electrode. Systematic variations of the DBV solution concentration and the nature of the counterion strongly suggest that P1 has to be assigned to the first electron-transfer reaction reducing the dicationic DBV2+ to the radical monocationic DBV•+ species while P1‘ represents the corresponding oxidation process. Not only solution but also preadsorbed viologen species are involved in this charge-transfer reaction. Triggered by the electron transfer, the more open “cavitand” structure formed on top of the preadsorbed c(2 × 2)-Cl layer prior to the electron transfer transforms into a more compact polymeric ( ) n stacking phase upon reaching P1. Both the reactants and products of the electron-transfer reaction form condensed and laterally ordered 2D phases. In particular, the quite stable ( ) n stacking phase maintains its structural integrity during the ongoing electron-transfer reaction involving solution species. Passing P2 in the cyclic voltammogram, however, initiates an order−disorder transition within the organic film with defect lines or point defects in the ( ) n stacking phase acting as active sites for this structural transition. The driving force for this further phase transition is the starting chloride desorption through the ( ) n film. In the presence of the covering viologen film, the chloride desorption occurs at a potential that is ΔE desorp ≈ 100 mV lower than that in the pure supporting electrolyte pointing to a significant additional activation barrier for that process. Reduced monomeric and oligomeric viologen species reveal a significantly lower lateral mobility on the metallic substrate than that on the chloride lattice. In the reverse potential sweep, chloride anions are forced to readsorb on the metallic copper substrate through the disordered viologen film resulting in a full restoration of the c(2 × 2)-Cl lattice in direct contact to the metallic copper and, in addition, in the full restoration of the ordered ( ) n stacking phase on top of the chloride lattice.

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The relation between magnetic properties and microscopic structure for a metal/semiconductor system is described. Cobalt films on a CoSi interface possess an in-plane easy axis of magnetization as the result of magnetocrystalline anisotropy of the Co∕CoSi interface. On a Si(111)-7×7 surface, direct evidence for the formation of CoSi2 compounds at the interface was found by the appearance of doubled spot defects in scanning tunneling microscopic images. The interfacial effects cause the easy axis of magnetization of a Co∕Si interface to be canted out of plane.

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