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941.
942.
943.
Stanley Alama Gabriella Tarantello 《Calculus of Variations and Partial Differential Equations》1993,1(4):439-475
This paper concerns semilinear elliptic equations whose nonlinear term has the formW(x)f(u) whereW changes sign. We study the existence of positive solutions and their multiplicity. The important role played by the negative part ofW is contained in a condition which is shown to be necessary for homogeneousf. More general existence questions are also discussed.Supported in part by NSF grant DMS9003149. 相似文献
944.
Stanley Gudder 《Foundations of Physics》1989,19(8):949-970
We first present a realistic framework for quantum probability theory based on the path integral formalism of quantum mechanics and illustrate this framework by constructing a model that describes a quantum particle evolving in a discrete space-time lattice. We then present a finite model for describing the internal dynamics of elementary particles and show that this model gives the standard particle classification scheme and successfully predicts particle masses. 相似文献
945.
Stanley Alama Percy A. Deift Rainer Hempel 《Communications in Mathematical Physics》1989,121(2):291-321
The authors study the eigenvalue branches of the Schrödinger operatorH — W in a gap of (H). In particular, they consider questions of asymptotic distribution of eigenvalues and bounds on the number of branches. They also address the completeness problem. 相似文献
946.
Stanley E. Payne 《Geometriae Dedicata》1989,32(1):93-118
Astract We study a class of generalized quadrangles satisfying a local Moufang condition that is more restrictive than the usual concept of skew translation GQ. A new infinite family is constructed whose point-line duals are translation generalized quadrangles with very small kernel. They have parameters (q
2, q), q=3
r
, for r>2.This paper was written while the author was supported by the CNR as a visiting professor at the University of Rome La Sapienza. 相似文献
947.
A molecularly imprinted solid phase extraction (MISPE) method was developed for the rapid screening of cephalexin in human plasma and serum. The method employed a micro-column packed with molecularly imprinted polymer (MIP) particles for the selective solid phase extraction (SPE) of cephalexin. Since the MIP interacted indiscriminately with two other α-aminocephalosporins, cefradine and cefadroxil, their removal was ultimately achieved using differential pulsed elution (DPE) with acetonitrile+12% acetic acid. Cephalexin was then determined in a final pulsed elution (FPE) with methanol+1% trifluoroacetic (CF3COOH, TFA) acid. This excellent selectivity represents a significant advance in analytical separation, demonstrating how a MIP can differentiate between molecules that are structurally dissimilar only in their non-hydrogen-bonding moieties, even if their hydrogen-bonding moieties are identical to each other. With UV detection, a concentration detection limit of 0.1 μg/ml (or 2 ng in 20 μl) was afforded for cephalexin. By increasing the CHCl3 flow rate to 1.25 ml/min, each MISPE-DPE-FPE analysis required only 2 min to complete. Rapid screening was demonstrated in a modified MISPE-PE method, which used 14% CH3COOH+CH3CN as the mobile phase, followed by direct PE with 1% TFA+CH3OH. 相似文献
948.
H. Umesha Shetty Eileen M. Daly Nigel H. Greig Stanley I. Rapoport Timothy T. Soncrant 《Journal of the American Society for Mass Spectrometry》1991,2(2):168-173
An automatic reaction control chemical ionization technique in an ion trap detector (lTD) was used to quantitate the levels of the cholinergic drug, arecoline, in plasma of treated patients with Alzheimer’s disease. The chemical ionization reaction was carried out with acetonitrile. The protonated molecules of arecoline (m I z 156) and the internal standard, homoarecoline (m / z 170), were monitored. Human plasma samples were extracted with a readily evaporable solvent mixture, the residues reconstituted and injected along with a tertiary amine-carrier into a capillary gas chromatograph interfaced with the ITD. Standard curves for plasma-extracted arecoline between 20-ng/mL and 156-pg/mL levels were linear (r> 0.9980). Satisfactory precision (relative standard deviation < 20%) and accuracy (relative error < 15%) at the limit of quantitation, 156 pg/mL arecoline, were achieved. Optimal conditions for handling of blood samples obtained by venipuncture were determined. The assay was successfully applied for the therapeutic monitoring of Alzheimer patients treated intravenously with arecoline. 相似文献
949.
Dieter H. Klaubert Stanley C. Bell Thomas W. Pattison 《Journal of heterocyclic chemistry》1985,22(2):333-336
A three step synthesis of 5H-tetrazolo[5,1-c][1,4]benzodiazepin-11-ones 8a-d via the reaction of a substituted benzyl azide and ethyl cyanoformate is described. The derived lactams are converted to the corresponding 11-thiones 9a-d and, through the S-methylated derivatives, to the 11-amino analogs 11a-f. All of the described compounds are representatives of a novel ring system. 相似文献
950.
Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins
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María Rosa Flores‐Molina Ralf Rautenberger Pamela Muñoz Pirjo Huovinen Iván Gómez 《Photochemistry and photobiology》2016,92(3):455-466
The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade‐adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore, this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM‐fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field grown were analyzed in response to different conditions of radiation (PAR and PAR + UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (Fv/Fm) decreased with increasing doses of UV radiation, but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of Fv/Fm in all experimental treatments, highlighting the UV‐protective role of these compounds in D. anceps. 相似文献