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排序方式: 共有68条查询结果,搜索用时 93 毫秒
1.
A copper-sensitive optical chemical sensor (optrode) is described. The optrode is based on a Nafion membrane and an immobilized organic ligand coupled with a flow injection (FI) system. The FI system includes a flow-through removable measuring cell and a simple spectrophotometer. Owing to the miniature size of the system and the efficient use of optical fibers, this optrode is well suited for monitoring environmental water samples. The success of the described optrode system depends on the effectiveness of the FI reagent delivery system. Optimum contact time with the membrane (as determined by the reagent flow rates) and the injected sample volume are critical. Environmental water samples were analyzed for copper content using the optimized optrode system. To validate the optrode's performance, the same water samples were analyzed using the atomic absorption spectrophotometer. 相似文献
2.
Jennifer S. Holmgren John R. Shapley Patricia A. Belmonte 《Journal of organometallic chemistry》1985,284(1):C5-C8
The single hydride resonance observed for each of the compounds H3Os3(CO)9CX (X = OMe, Br, H) has one set of 187Os satellites which are further split into doublets by HH coupling. The implications of this observation for structural assignments based on 187Os satellites are discussed. 相似文献
3.
4.
Vidal JL Vega AB Arrebola FJ González-Rodríguez MJ Sánchez MC Frenich AG 《Rapid communications in mass spectrometry : RCM》2003,17(18):2099-2106
A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain). 相似文献
5.
Dr. Martha V. Escárcega‐Bobadilla Dr. Marta Martínez Belmonte Eddy Martin Eduardo C. Escudero‐Adán Prof. Dr. Arjan W. Kleij 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(8):2641-2648
A tetraoxo bis‐Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO2. The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent‐free conditions. 相似文献
6.
We report on a convenient synthesis of the ligand precursor, diethylethylene-1,2-bis(oxamate), (Et2H2oeo, 1), and show how a partial and preferential hydrolysis of the ester group can give rise to the dianionic ligand, (H2oeo)2−. Reaction of this ligand with Cu(II) affords the neutral dimeric species, [Cu2(H2oeo)2], which has a low aqueous solubility. We describe the crystal structure of the hydrate Cu2(H2oeo)2(H2O)4 (2) and report magnetic studies that show a weak exchange interaction in the solid. Under more basic conditions and in the presence
of Cu(II) ions, we are able to avoid amide cleavage and yet deprotonate the amide group, resulting in the formation of the
highly soluble [Cu(Hoeo)2]4− complex anion. The structure of (NBu4)4[Cu(Hoeo)2](H2O)4 (3) is described and compared with the recently reported anhydrous phase. 相似文献
7.
We present an experimental study of the motion of a viscoelastic micellar fluid around a moving cylinder, which ranges from fluidlike flow to solidlike tearing and fracture, depending on the cylinder radius and velocity. The observation of crack propagation driven by the cylinder indicates an extremely low tear strength, approximately equal to the steady state surface tension of the fluid. At the highest speeds a driven crack is observed in front of the cylinder, propagating with a fluctuating speed equal on average to the cylinder speed, here as low as 5% of the elastic wave speed. 相似文献
8.
E. A. Bernardelli T. Belmonte D. Duday G. Frache F. Poncin-Epaillard C. Noël P. Choquet H.-N. Migeon A. Maliska 《Plasma Chemistry and Plasma Processing》2011,31(1):205-215
We study the interaction of thick films (~4 mm) of stearic acid (SA), a C18 alkane skeleton with an acid function, with late Ar–O2 post-discharge. Contrary to what is observed with thin films of SA (~2–3 μm) which are efficiently etched (part I), only functionalization is observed over the first 2 h of treatment with a plasma source operated in the continuous mode, whatever the temperature. The heat released by surface reactions affects non-linearly the temperature of the substrate. Pulsing the source at a frequency ranging from 0.1 to 1 kHz slows down the functionalization process but does not allow any etching of the material. On the contrary, the SA can be etched as thick films by pulsing the oxygen flow rate at a frequency below 50 mHz. By pulsing the reactive gas, the time averaged value of the [O]/[O2] ratio is decreased, limiting the functionalization processes due to oxygen atoms, and the mean temperature is lowered, decreasing the diffusion length of O2 (and/or possibly O2*) species in the SA which are responsible for the scission of C–C bonds of radicals. 相似文献
9.
Mirco Cosottini Ilaria Pesaresi Patrizia Maritato Gina Belmonte Arianna Taddei Ferdinando Sartucci Mario Mascalchi Luigi Murri 《Magnetic resonance imaging》2010
Blood oxygenation level dependent (BOLD) response related to interictal activity was evaluated in a patient with post-traumatic focal epilepsy at repeated continuous electroencephalogram (EEG)-functional magnetic resonance imaging examinations. Lateralized interictal EEG activity induced a main cluster of activation co-localized with the anatomical lesion. Spreading of EEG interictal activity to both frontal lobes evoked bilateral clusters of activation indicating that topography of BOLD response might depend on the spatial distribution of epileptiform activity. 相似文献
10.
J. Belmonte‐Beitia 《Mathematical Methods in the Applied Sciences》2013,36(8):974-982
The dark soliton solutions corresponds to certain heteroclinic orbits for related autonomous planar differential equations. In this paper, we give a proof of the existence of upper and lower bounds of these heteroclinic orbits and find these bounds of explicit form. We put it into practice for a particular case of the derivative nonlinear Schrödinger equation. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献