Remarks about uniform boundedness of rational points over function fields

We prove certain uniform versions of the Mordell Conjecture and of the Shafarevich Conjecture for curves over function fields and their rational points.

     

Nanoreactors based on amphiphilic uracilophanes: self-organization and reactivity study

New amphiphilic pyrimidinic macrocycles (APMs) with two (APM-1) and three (APM-2) decyl tails have been synthesized by quaternization of the bridged N. Complex examination of the APM-based systems with the help of tensiometry, conductometry, dynamic light scattering, and UV and NMR spectroscopy provides evidence for their aggregation. Calculations based on surface tension isotherms and on packing parameter considerations make it possible to assume a lamellar packing of macrocycles when aggregating. Marked differences in the aggregation behavior of APM-1 and APM-2 have been found. The additives of polyethylenimine (PEI) exert little influence on the critical micelle concentration (cmc) of APM-1, while in the APM-2/PEI systems there occurs a pronounced decrease in the cmc and also a ca. 2-fold decrease in the surface area per molecule. The APM-based assemblies are explored as nanoreactors for the hydrolysis of O-alkyl O-p-nitrophenyl (chloromethyl)phosphonates (alkyl = ethyl, hexyl). The kinetic study reveals a minor rate effect of the APM-1-based systems. In the APM-2-based systems an acceleration of the hydrolysis of both phosphonates occurs as compared to the uncatalyzed process. Within the APM-2 --> APM-2/PEI --> APM-2/PEI/La(III) series, due to the cooperative contributions of the supramolecular, polymer, and homogeneous catalysis, an increase in the catalytic effect is observed from 30 times to 3 orders of magnitude as compared to that of the basic hydrolysis of the substrates.     

Development and validation of an LC-MS/MS analysis for simultaneous determination of delphinidin-3-glucoside, cyanidin-3-glucoside and cyanidin-3-(6-malonylglucoside) in human plasma and urine after blood orange juice administration

Blood orange juice has a high content in anthocyanins, especially represented by delphinidin-3-glucoside (D3G), cyanidin-3-glucoside (C3G) and cyanidin-3-(6-malonylglucoside) (CMG). An LC-MS/MS method for the simultaneous determination of D3G and C3G in human plasma and urine was developed and validated. After sample preparation by SPE, chromatographic separation was performed with an RP-C(18) column, using a water/methanol linear gradient. The quantitation of target compounds was determined by multiple reaction monitoring (MRM) mode, using ESI. The method showed good selectivity, sensitivity (LOD = 0.05 and 0.10 ng/mL for C3G in plasma and urine, respectively; LOD = 0.10 ng/mL for D3G in plasma and urine), linearity (0.20-200 ng/mL; r >or= 0.998), intra- and interday precision and accuracy (相似文献   

Gold(III)-dithiocarbamato complexes induce cancer cell death triggered by thioredoxin redox system inhibition and activation of ERK pathway

Although gold compounds are now recognized as promising anticancer agents, so far only gold(I) derivatives have been investigated for this purpose, whereas the use of gold(III) complexes has been hampered by their poor stability under physiological conditions. We have therefore carried out studies on selected gold(III) anticancer agents, showing enhanced stability due to the presence of chelating dithiocarbamato ligands. We found that they induce cancer cell death through both apoptotic and nonapoptotic mechanisms. They also inhibit thioredoxin reductase activity, generate free radicals, modify some mitochondrial functions, and increase ERK1/2 phosphorylation. Based on our results, we propose and discuss a working model suggesting that deregulation of the thioredoxin reductase/thioredoxin redox system is a major mechanism involved in the anticancer activity of the investigated gold(III)-dithiocarbamato complexes.     

Photoinduced electron transfer across oligo-p-phenylene bridges. Distance and conformational effects in Ru(II)-Rh(III) dyads

A series of rodlike ruthenium(II)-rhodium(III) polypyridine dyads based on modular oligo-p-phenylene bridges, of the general formula [(Me2phen)2Ru-bpy-(ph)n-bpy-Rh(Me2bpy)]5+ (Me2phen=4,7-dimethyl-1,10-phenanthroline; bpy=2,2'-bipyridine; ph=1,4-phenylene; n=1-3), have been synthesized and their photophysical properties investigated. The dyad [(Me2bpy)2Ru-bpy-(ph)3'-bpy-Rh(Me2bpy)]5+ with the central phenylene unit bearing two hexyl chains has also been studied. The metal-to-metal distance reaches 24 A for the longest (n=3) spacer in the series. For all of the dyads in a room-temperature CH3CN solution, quenching of the typical metal-to-ligand charge-transfer luminescence of the Ru-based chromophoric unit is observed, indicating that an efficient intramolecular photoinduced electron transfer from the excited Ru moiety to the Rh-based unit takes place. The rate constants for the electron-transfer process have been determined by time-resolved emission and absorption spectroscopy in the nanosecond and picosecond time scale. An exponential dependence of experimental transfer rates on the bridge length is observed, consistent with a superexchange mechanism. An attenuation factor beta of 0.65 A(-1) is determined, in line with the behavior of other systems containing oligo-p-phenylene spacers. Interestingly, for n=3, the presence/absence of hexyl substituents in the central p-phenylene ring causes a 10-fold difference in the rates between otherwise identical dyads. This comparison highlights the importance of the twist angle between adjacent spacers on the overall through-bond donor-acceptor coupling.     

The (1 X 1) --> hexagonal structural transition on Pt(100) studied by high-energy resolution core level photoemission

The (1 X 1) --> quasihexagonal (HEX) phase transition on a clean Pt(100) surface was investigated by monitoring the time evolution of the Pt4f(72) core level photoemission spectra. The spectral component originating from the atoms forming the (1x1) metastable unreconstructed surface was found at -570+/-20 meV with respect to the bulk peak. Ab initio calculations based on density functional theory confirmed the experimental assignment. At temperatures above 370 K, the (1 X 1) phase irreversibly reverts to the more stable HEX phase, characterized by a surface core level shifted component at -185 +/ -40 meV. By analyzing the intensity evolution of the core level components, measured at different temperatures in the range of 393 - 475 K, we determined the activation energy of the phase transformation, E = 0.76 +/- 0.04 eV. This value is considerably lower than the one previously determined by means of low energy electron diffraction. Possible reasons for this discrepancy are discussed.     

Synthesis and antimalarial activity of 7‐benzylamino‐1‐isoquinolinamines

Computer modelling suggests that 7‐benzylamino‐1‐isoquinolinamines should mediate antimalarial effects by a mechanism distinct from that employed by existing antimalarial drugs. A series of these compounds was prepared in seven synthetic steps, via reductive amination of 1,7‐isoquinolinediamine. In vitro efficacy testing of the novel compounds against Plasmodium falciparum revealed them to be potent antimalarial agents.     

Diastereoselective synthesis of 4,5'-bis-proline compounds via reductive dimerization of N-acyloxyiminium ions

A short, practical synthesis of novel, unsymmetrical 4,5'-bis-proline compounds has been achieved, highlighted by the application of an unprecedented samarium diiodide-driven regio- and diastereocontrolled reductive dimerization of N-acyloxyiminium ions generated from readily available 2-methoxy-5-silyloxymethyl-N-Boc pyrrolidines. The title proline dimers proved to be pertinent metal-free catalysts in aldol and Mannich reactions.     

Liquid–liquid extraction and transport through membrane of amino acid methylesters by calix[n]arene derivatives

The extractability together with the transport through liquid membrane of some amino acid methylesters by using p-tert-butylcalix[4]arene as extractant or carrier was studied. In this context, p-tert-butylcalix[n]arenes (n = 6, 8) were found to act as useful carriers or extractant reagents for l-tryptophan methylester and l-tyrosine methylester. The calix[n]arene derivatives used in experiments extracted amino acids methylesters from the aqueous phase into chloroformic phase in the presence of tropaeolin 00 ([4(4′-anilinophenylazo)benzenesulphonic acid]) as counterion at . The extraction and the transport depend on the structure of calixarenes, the structure of amino acids, the pH, and the nature of anion used as ion pair for cation-receptor complexes. The properties of solvent involved in liquid membrane play an important role in membrane stability and also in selecting membrane systems. The results demonstrated that the inclusion properties of the investigated hosts are correlated with their structural properties and also they suggest further possibilities for optimal separation of amino acids derivatives.