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231.
Ramon S. Vilela Thiago L. Oliveira Felipe T. Martins Javier A. Ellena Francesc Lloret Miguel Julve Danielle Cangussu 《Comptes Rendus Chimie》2012,15(10):856-865
The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH3)4N]2[Cu(C2O4)2] · H2O}n (1) [(CH3)4N+ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm−1, the Hamiltonian being defined as H = –J ∑nmSi · Sj]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway. 相似文献
232.
Martins PT Velazquez-Campoy A Vaz WL Cardoso RM Valério J Moreno MJ 《Journal of the American Chemical Society》2012,134(9):4184-4195
Passive transport across cell membranes is the major route for the permeation of xenobiotics through tight endothelia such as the blood–brain barrier. The rate of passive permeation through lipid bilayers for a given drug is therefore a critical step in the prediction of its pharmacodynamics. We describe a detailed study on the kinetics and thermodynamics for the interaction of chlorpromazine (CPZ), an antipsychotic drug used in the treatment of schizophrenia, with neutral and negatively charged lipid bilayers. Isothermal titration calorimetry was used to study the partition and translocation of CPZ in lipid membranes composed of pure POPC, POPC:POPS (9:1), and POPC:Chol:POPS (6:3:1). The membrane charge due to the presence of POPS as well as the additional charge resulting from the introduction of CPZ in the membrane were taken into account, allowing the calculation of the intrinsic partition coefficients (K(P)) and the enthalpy change (ΔH) associated with the process. The enthalpy change upon partition to all lipid bilayers studied is negative, but a significant entropy contribution was also observed for partition to the neutral membrane. Because of the positive charge of CPZ, the presence of negatively charged lipids in the bilayer increases both the observed amount of CPZ that partitions to the membrane (KP(obs)) and the magnitude of ΔH. However, when the electrostatic effects are discounted, the intrinsic partition coefficient was smaller, indicating that the hydrophobic contribution was less significant for the negatively charged membrane. The presence of cholesterol strongly decreases the affinity of CPZ for the bilayer in terms of both the amount of CPZ that associates with the membrane and the interaction enthalpy. A quantitative characterization of the rate of CPZ translocation through membranes composed of pure POPC and POPC:POPS (9:1) was also performed using an innovative methodology developed in this work based on the kinetics of the heat evolved due to the interaction of CPZ with the membranes. 相似文献
233.
This paper proposes an individual-based model that takes into account the evolutionary effects of selective fishing on exploited populations. The model is an adaptation of the Penna model based on the biology of exploited species and characteristics of fishing. Given the importance of the Pintado Pseudoplatystoma corruscans, a native species of great economic value in the Brazilian fishery, the model was applied to study the effects of selective fishing on the growth characteristics of this species. 相似文献
234.
L.L. Tezani R.S. Pessoa R.S. Moraes H.S. Medeiros C.A. Martins H.S. Maciel G. Petraconi Filho M. Massi A. S. da Silva Sobrinho 《等离子体物理论文集》2012,52(9):735-743
In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF6/CH4 radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high‐aspect‐ratio of mask pattern transfer to substrate surface. In other words, this control allows the attainment of deep Si etching process. Here, the automation of the gas injection system was realized through the interface between a computer and a data acquisition board. The automation software developed allows controlling the gas flow rate switching it on and off during whole process through the use of a square waveform routine, intermittent flow, beyond the conventional condition of a fixed value for gas flow rate, continuous flow. In order to investigate the time‐multiplex SF6/CH4 plasma etching of Si, the residual gas analysis was performed. The investigations were made keeping the following process parameters: flow of SF6: 10 sccm, flow of CH4: 6 sccm, 100 W rf power, wave period: 20 sec. It were monitored the partial pressure of SF+ 5 (parent neutral specie: SF6), CH+4 (CH4) and SiF+ 3 (SiF4) species as a function of time for different gas flow switching and duty cycle. The results showed that with the generation of plasma occurs a drastic change in behavior of partial pressures of SF+ 5 and CH+4 species. Moreover, it is evidenced that the interactions between the SF6 and CH4 fragments promotes a high production rate of HF molecule and consequently a decrease of atomic fluorine, mainly when plasma is on. Finally, the behavior of partial pressure of SiF+ 3 specie for alternatively intermittent SF6 and CH4 flow operation shows us that both the etching processes and the deposition of a polymer passivation layer are occurring alternatively, a desirable feature for multi‐step etching process (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
235.
Isabel Martins Filipe Alvelos Miguel Constantino 《Computational Optimization and Applications》2012,51(1):363-385
Recently, research on exact methods has been undertaken to solve forest management problems subject to constraints on the
maximum clearcut area by using the area restriction model approach. Three main basic integer programming models for these
problems have been discussed in the literature: the so-called cluster, path and bucket formulations. Solving these models
via branch-and-bound, where all variables and constraints are used a priori, is adequately suited for real problems of a small
to medium size, but is not appropriate for larger problems. In this paper, we describe a branch-and-price approach for the
cluster model, and we show that this formulation dominates the bucket model, by completing the results of the dominance relationships
between the bounds of the three models. Branch-and-price was tested on real and hypothetical forests ranging from 45 to 2945
stands and temporal horizons ranging from three to twelve periods were employed. Results show that the solutions obtained
by the proposed approach stood within 1% of the optimal solution and were achieved in a short computation time. It was found
that branch-and-bound was unable to produce solutions for most forests from 850 stands with either eleven or an average number
of stands per clearcut greater or equal than eight. 相似文献
236.
César IC Byrro RM de Santana E Silva Cardoso FF Mundim IM de Souza Teixeira L Rezende KR da Silva EP Gomes SA de Sousa VA Bonfim RR Pianetti GA 《Biomedical chromatography : BMC》2012,26(7):851-856
A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐13C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
237.
dos Santos AM 《Journal of fluorescence》2012,22(1):151-154
The emission behaviour of Aequorea green fluorescent protein (A-GFP) chromophore, in both neutral (N) and anionic (A) form, was studied in the temperature range
from 20 °C to 75 °C and at pH = 7. Excitation wavelengths of 399 nm and 476 nm were applied to probe the N and A forms environment,
respectively. Both forms exhibit distinct fluorescence patterns at high temperature values. The emission quenching rate, following
a temperature increase, is higher for the chromophore N form as a result of the hydrogen bond network weakening. The chromophore
anionic form emission maximum is red shifted, upon temperature increase, due to a charge transfer process occurring after
A form excitation. 相似文献
238.
Martins MA Rossatto M Prola LD Pizzuti L Moreira DN Campos PT Frizzo CP Zanatta N Bonacorso HG 《Ultrasonics sonochemistry》2012,19(2):227-231
The synthesis of 14 novel N-propargylic β-enaminones from the reaction of β-alkoxy vinyltrihalomethyl[carboxyethyl] ketones [R3C(O)CHC(R1)OMe, where R3 = CF3, CCl3, CO2Et and R1 = Me, Et, Pr, Bu, i-Pent, CH2CH2CO2Me] with propargyl amines [R2NHCH2CCH, where R2 = Pr, PhCH2] is reported. Yields, solvents and reaction times needed for reaction completion, by microwave irradiation (MW), conventional thermal heating (TH) and under ultrasound irradiation (US) are compared. The best results were obtained under US irradiation in good to excellent yields (70-93%). 相似文献
239.
Pala MG Baltazar S Liu P Sellier H Hackens B Martins F Bayot V Wallart X Desplanque L Huant S 《Physical review letters》2012,108(7):076802
We present evidence for a counterintuitive behavior of semiconductor mesoscopic networks that is the analog of the Braess paradox encountered in classical networks. A numerical simulation of quantum transport in a two-branch mesoscopic network reveals that adding a third branch can paradoxically induce transport inefficiency that manifests itself in a sizable conductance drop of the network. A scanning-probe experiment using a biased tip to modulate the transmission of one branch in the network reveals the occurrence of this paradox by mapping the conductance variation as a function of the tip voltage and position. 相似文献
240.
Dr. Natalia Busto Jesús Valladolid Cristina Aliende Prof. Félix A. Jalón Prof. Blanca R. Manzano Dr. Ana M. Rodríguez Prof. Jorge F. Gaspar Celia Martins Dr. Tarita Biver Dr. Gustavo Espino Prof. José María Leal Prof. Begoña García 《化学:亚洲杂志》2012,7(4):788-801
The reactions of two diaminotriazine ligands 2,4‐diamino‐6‐(2‐pyridyl)‐1,3,5‐triazine (2‐pydaT) and 6‐phenyl‐2,4‐diamino‐1,3,5‐triazine (PhdaT) with ruthenium–arene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(η6‐arene)Ru(κ2‐N,N‐2‐pydaT)Cl]X (X=BF4, TsO; arene=p‐cymene: 1.BF4 , 1.TsO arene=benzene: 2.BF4 , 2.TsO ). The neutral cyclometalated complex [(η6‐p‐cymene)Ru(κ2‐C,N‐PhdaT*)Cl] ( 3 ) was also isolated. The structures of complexes 2.BF4 and 3.H2O were determined by X‐ray diffraction. Complex 1.BF4 underwent a partial reversible‐aquation process in water. UV/Vis and NMR spectroscopic measurements showed that the reaction was hindered by the addition of NaCl and was pH‐controlled in acidic solution. At pH 7.0 (sodium cacodylate) Ru–Cl complex 1.BF4 was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1.BF4 underwent basic hydrolysis to afford a Ru–OH complex ( 5 ). Fluorimetric studies revealed that the interaction of complex 1.BF4 with DNA was not straightforward; instead, its main features were closely linked to ionic strength and to the [DNA]/complex ratio. The bifunctional complex 1.BF4 was capable of interacting concurrently through both its p‐cymene and 2‐pydaT groups. Cytotoxicity and genotoxicity studies showed that, contrary to the expected behavior, the complex species was biologically inactive; the formation of a Ru–OH complex could be responsible for such behavior. 相似文献