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41.
A solid object can be coated by a nonwetting liquid since a receding contact line cannot exceed a critical speed. In this Letter we study the dynamical wetting transition at which a liquid film gets deposited by withdrawing a vertical plate out of a liquid reservoir. It has recently been predicted that this wetting transition is critical with diverging time scales and coincides with the disappearance of stationary menisci. We demonstrate experimentally and theoretically that the transition is due to the formation of a solitary wave, well below the critical point. As a consequence, relaxation times remain finite at threshold. The structure of the liquid deposited on the plate involves a capillary ridge that does not trivially match the Landau-Levich film. 相似文献
42.
43.
Reverse‐phase high‐performance liquid chromatography for the simultaneous determination of sildenafil and N‐desmethyl sildenafil in plasma of children
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Bianca Maria Goffredo Sara Cairoli Alessia Vitale Tiziana Corsetti Anna Pastore 《Biomedical chromatography : BMC》2016,30(12):2070-2073
Sildenafil is a selective inhibitor of cGMP‐specific type 5 phosphodiesterase used for the treatment of pulmonary arterial hypertension (PAH) in the adults. In pediatrics, PAH treatment options include the off‐label use of sildenafil. Sildenafil is metabolized in the liver by cytocrome P450 into its active metabolite, N‐desmethyl sildenafil. The determination of plasma levels of sildenafil and N‐desmethyl sildenafil could be useful for therapy optimization and pharmacokinetic studies. We have developed and validated a method for the quantification of sildenafil and its metabolite in plasma of children by rapid extraction, using high‐performance liquid chromatography with ultraviolet detection. The calibration range was fitted at least square model (r2 ≥ 0.999), with an accuracy and an intra‐ and inter‐day relative standard deviation <15% for both analytes. The mean recovery was 102.5% for sildenafil and 101.8% for N‐desmethyl sildenafil. This simple method could be successfully used in children with PAH under treatment with sildenafil. 相似文献
44.
Rosini G Borzatta V Boschi F Candido G Marotta E Righi P 《Chemical communications (Cambridge, England)》2007,(26):2717-2719
The occurrence of p(1),n(1) salt when accompanied by substrate self-association can have profound effects on enantiomer separation processes of non-racemic mixtures, impeding the complete recovery of the major enantiomer through formation of an inescapable racemate cage. 相似文献
45.
Alessio Adamiano Stefano Goffredo Zvy Dubinsky Oren Levy Simona Fermani Daniele Fabbri Giuseppe Falini 《Analytical and bioanalytical chemistry》2014,406(24):6021-6033
Off-line analytical pyrolysis combined with gas chromatography–mass spectroscopy (GC–MS), directly or after trimethylsilylation, along with infrared spectroscopy and amino acid analysis was applied for the first time to the characterization of the intra-skeletal organic matrix (OM) extracted from four Mediterranean hard corals. They were diverse in growth form and trophic strategy namely Balanophyllia europaea and Leptopsammia pruvoti—solitary corals, only the first having zooxanthelle—and Cladocora caespitosa and Astroides calycularis—colonial corals, only the first with zooxanthelle. Pyrolysis products evolved from OM could be assigned to lipid (e.g. fatty acids, fatty alcohols, monoacylglicerols), protein (e.g. 2,5-diketopiperazines, DKPs) and polysaccharide (e.g. anhydrosugars) precursors. Their quantitative distribution showed for all the species a low protein content with respect to lipids and polysaccharides. A chemometric approach using principal component analysis (PCA) and clustering analysis was applied on OM mean amino acidic compositions. The small compositional diversity across coral species was tentatively related with coral growth form. The presence of N-acetyl glucosamine markers suggested a functional link with other calcified tissues containing chitin. The protein fraction was further investigated using novel DKP markers tentatively identified from analytical pyrolysis of model polar linear dipeptides. Again, no correlation was observed in relation to coral ecology. These analytical results revealed that the bulk structure and composition of OMs among studied corals are similar, as it is the textural organization of the skeleton mineralized units. Therefore, they suggest that coral’s biomineralization is governed by similar macromolecules, and probably mechanisms, independently from their ecology. 相似文献
46.
B. Andreotti P. Claudin S. Douady 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):341-352
We present in this paper a simplification of the dune model proposed by Sauermann et al. which keeps the basic mechanisms but allows analytical and parametric studies. Two kinds of purely propagative two dimensional
solutions are exhibited: dunes and domes. The latter, by contrast to the former, do not present a slip face. Their shape and
velocity can be predicted as a function of their size. We recover that dune profiles are not scale invariant (small dunes
are flatter than the large ones), and that the inverse of the velocity grows almost linearly with the dune size. We furthermore
get the existence of a critical mass below which no dune solution exists. It rises the problem of dune nucleation: how can
dunes appear if any bump below this minimal mass gets eroded and disappears? The linear stability analysis of a flat sand
bed shows that it is unstable at large wavelengths: dune can in fact nucleate from a small sand mass if the proto-dune is
sufficiently long.
Received 22 December 2001 / Received in final form 31 May 2002 Published online 31 July 2002 相似文献
47.
Summary The dehydration mass loss of samples of montmorillonite (a layered hydrated silicate) was measured in an environment at constant
temperature and at constant undersatured water vapour content. The hydration curves were analysed by assuming the model of
thermally activated, monoenergetic and first-order process compatible with the experimental results. Two dehydration kinetics
with activation energies (0.21±0.02) eV and (0.34±0.02) eV were found that can be related to the existence of two kinds of
water (structured and nonstructured) in the hydrated silicate interlayers. The possibility of an icelike structure of a fraction
of the adsorbed molecules is briefly discussed. The experimental results show, furthermore, that in the investigated hydration
range (up to about 10% in mass) the fraction of structured water has a maximum when the hydration is about 6%.
To spped up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
Riassunto è stata misurata la perdita di massa per deidratazione di campioni di montmorillonite (un silicato idrato lamellare) in ambiente a temperatura e contenuto sottosaturo di vapore d'acqua costanti. Le curve di deidratazione sono state analizzate assumendo un modello di processo termicamente attivato, monoenergetico, del primo ordine, che è compatibile con i risultati sperimentali. Sono state individuate due cinetiche di deidratazione, con energie di attivazione di (0.21±0.02) eV e di (0.34±0.02) eV, che possono essere correlate all'esistenza di due tipi d'acqua, strutturata e non strutturata, negli spazi interlamellari del silicato idrato. La possibilità di una strutturazione tipo ghiaccio di una frazione delle molecole adsorbite è brevemente discussa. I risultati delle misure indicano inoltre che, nell'intervallo di idratazione indagato che va fino al 10% circa in massa, la frazione di acqua strutturata presenta un massimo quando l'idratazione è di circa il 6%.
Резюме Измеряется гидратация образцов монтморилонита (слоистого гидратного силиката) при постоянной температуре и постоянном содержанин ненасыщенных водяных паров. Анализируются кривые гидратации. Обнаружено два процесса дегидратции с энергиями активации (0.21±0.02) эВ и (0.34±0.02) эВ, которые могут быть связаны с существованием двух типов воды (структурной и бесструктурной) в промежуточных слоях гидратного силиката. Обсуждается возможность существования доли поглощенных молекул со структурой, подобной структуре льда. Экспериментальные результаты показывают, что в исследованной области тидратации доля структурной воды имеет максимум, когда гидратация составляет порядка 6%.
To spped up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
48.
Andreotti M Bagnasco S Baldini W Bettoni D Borreani G Buzzo A Calabrese R Cester R Cibinetto G Dalpiaz P Garzoglio G Gollwitzer KE Graham M Hu M Joffe D Kasper J Lasio G Lo Vetere M Luppi E Macrì M Mandelkern M Marchetto F Marinelli M Menichetti E Metreveli Z Mussa R Negrini M Obertino MM Pallavicini M Pastrone N Patrignani C Pedlar TK Pordes S Robutti E Roethel W Rosen JL Rumerio P Rusack R Santroni A Schultz J Seo SH Seth KK Stancari G Stancari M Tomaradze A Uman I Vidnovic T Werkema S 《Physical review letters》2003,91(9):091801
Fermilab experiment E835 has observed (-)pp annihilation production of the charmonium state chi(c0) and its subsequent decay into pi(0)pi(0). Although the resonant amplitude is an order of magnitude smaller than that of the nonresonant continuum production of pi(0)pi(0), an enhanced interference signal is evident. A partial wave expansion is used to extract physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate the expansion. Both are accessed by L=1 in the entrance (-)pp channel. The product of the input and output branching fractions is determined to be B((-)pp-->chi(c0))xB(chi(c0)-->pi(0)pi(0))=(5.09+/-0.81+/-0.25)x10(-7). 相似文献
49.
50.
The song of dunes as a wave-particle mode locking 总被引:2,自引:0,他引:2
Andreotti B 《Physical review letters》2004,93(23):238001
Singing dunes, which emit a loud sound as they avalanche, constitute a striking and poorly understood natural phenomenon. We show that, on the one hand, avalanches excite elastic waves at the surface of the dune, whose vibration produces the coherent acoustic emission in the air. The amplitude of the sound (approximately 105 dB) saturates exactly when the vibration makes the grains take off the flowing layer. On the other hand, we show that the sound frequency (approximately 100 Hz) is controlled by the shear rate inside the sand avalanche, which for granular matter is equivalent to the mean rate at which grains make collisions. This proves the existence of a feedback of elastic waves on particle motion, leading to a partial synchronization of the avalanching sand grains. It suggests that the song of dunes results from a wave-particle mode locking. 相似文献