Schiff bases obtained by the condensation of 2-amino-5-mercapto-1,3,4-thiadiazole with 2,4-pentandione or 1-phenyl-1,3-butandione
were synthesized and characterized in order to obtain polydentate ligands HL1 and HL2, respectively. The complexes with these ligands of the type M(L)Cl·nH2O [(1) M:Ni, L:L1, n = 0.5; (3) M:Ni, L:L2, n = 0.5]; [(2) M:Cu, L:L1, n = 1; (4) M:Cu, L:L2, n = 0] were also synthesized and characterized. The modifications evidenced in IR spectra of complexes were correlated with
the presence of monodeprotonate Schiff bases. The electronic spectra display the characteristic pattern of square-planar stereochemistry.
The in vitro qualitative and quantitative antimicrobial activity assays showed that the new complexes exhibited variable antimicrobial
activity. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany
them. Schiff bases and complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion
removal as well as oxidative degradation of the organic ligands were observed. 相似文献
In this work we report on the properties of the ablation plume and the characteristics of the films produced by ultra-fast
pulsed laser deposition (PLD) of TiO2 in vacuum. Ablation was induced by using pulses with a duration of ≈300 fs at 527 nm. We discuss both the composition and
the expansion dynamics of the TiO2 plasma plume, measured by exploiting time- and space-resolved emission spectroscopy and gated imaging. The properties of
the TiO2 nanoparticles and nanoparticle-assembled films were characterized using different techniques, i.e. environmental scanning
electron microscopy (ESEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). It is suggested that
most of the material decomposes in the form of nanoparticles. 相似文献
Promising applications of TiO2 nanostructures include the development of optical devices, sensors, photocatalysts and self-cleaning coatings. In view of
their importance, research on the synthesis of nanosized TiO2 is a particularly active field. In this work we report on the investigation of the effect of laser irradiation wavelength
(Q-switched Nd:YAG laser at 532, 355 and 266 nm), the temperature of the substrate and the atmosphere of deposition (vacuum,
Ar and O2) that are suitable for obtaining nanostructured deposits from TiO2 sintered targets. The ablation plume emission is characterized with spectral and temporal resolution by optical emission
spectroscopy (OES), while the surface morphology and chemical states of the material deposited on a Si (100) substrate are
examined by environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) and by X-ray photoelectron
spectroscopy (XPS), respectively. Deposits with nanostructured morphology with grain size down to 40 nm and keeping the stoichiometry
of the targets were obtained at high temperature, while the highest concentration of particulates was observed at the longest
laser wavelength of 532 nm on a substrate heated up to 650°C. In situ characterization of the ablation plume, carried out
by OES, indicated the presence of emissions assigned to Ti I, Ti II and O I. 相似文献
A variety of linear dienynes can deliver complex tetracyclic frameworks in the presence of an IrIII complex and visible light. Product formation involves the generation of four new C?C bonds and six contiguous stereocenters, which decorate two [3.1.0] bicyclic units tethered through their bridging quaternary carbon atoms. The internal alkyne acts as a formal dicarbenoid for the generation of two cyclopropanes in these radical cation cascades. This behavior has not been previously observed for organic reactive intermediates and can be extended to intermolecular reactions and diendiynes. 相似文献
The paper concerns a class of n-dimensional non-autonomous delay differential equations obtained by adding a non-monotone delayed perturbation to a linear homogeneous cooperative system of ordinary differential equations. This family covers a wide set of models used in structured population dynamics. By exploiting the stability and the monotone character of the linear ODE, we establish sufficient conditions for both the extinction of all the populations and the permanence of the system. In the case of DDEs with autonomous coefficients (but possible time-varying delays), sharp results are obtained, even in the case of a reducible community matrix. As a sub-product, our results improve some criteria for autonomous systems published in recent literature. As an important illustration, the extinction, persistence and permanence of a non-autonomous Nicholson system with patch structure and multiple time-dependent delays are analysed. 相似文献
Simple inorganic salts are used to tune N‐containing conjugated microporous polymers (CMPs) synthesized by Buchwald–Hartwig (BH) cross‐coupling reactions. Poly(triphenylamine), PTPA, initially shows a broad distribution of micropores, mesopores, and macropores. However, the addition of inorganic salts affects all porous network properties significantly: the pore size distribution is narrowed to the microporous range only, mimicking COFs and MOFs; the BET surface area is radically improved from 58 m2 g?1 to 1152 m2 g?1; and variations of the anion and cation sizes are used to fine‐tune the surface area of PTPA, with the surface area showing a gradual decrease with an increase in the ionic radius of salts. The effect of the salt on the physical properties of the polymer is attributed to adjusting and optimizing the Hansen solubility parameters (HSPs) of solvents for the growing polymer, and named the Beijing–Xi'an Jiaotong (BXJ) method. 相似文献
Early diagnosis of acute myocardial infarction (AMI) is of outmost importance to reduce the mortality rate, and cardiac troponins are considered the gold standard biomarkers of myocardial necrosis. In this scenario, the characterization of two troponin T (TnT)-binding aptamers as viable alternative to antibodies employed on clinical immunoassays is here reported for the first time. Their recognition ability was first investigated through surface plasmon resonance (SPR). Subsequently, an enzyme-linked oligonucleotide assay (ELONA) was developed on common 96-well polystyrene plates, both by direct and sandwich detection strategies for comparison. In both cases, the assay exhibits a detection ability of TnT in the range of low nanomolar but a great advantage on serum interference was obtained by using both aptamers in a sandwich format, with excellent reproducibility and recovery values. Despite the sensitivity needing to be enhanced to the low picomolar range, these results are encouraging for the development of new, low-cost, and rapid antibody-free colorimetric assays for AMI studies based on aptamer–Troponin T recognition.
We have investigated the complexation of Zn(2+) with 1,4,8,11-tetrakis(naphthylmethyl) cyclam (1; cyclam=1,4,8,11-tetraazacyclotetradecane) and with two dendrimers consisting of a cyclam core with four dimethoxybenzene and eight naphthyl appendages (2), and twelve dimethoxybenzene and sixteen naphthyl appendages (3). An important, common feature of model compound 1 and dendrimers 2 and 3 is that their potentially fluorescent naphthyl units are quenched by exciplex formation with the cyclam nitrogen atoms. Complexation with Zn(2+), however, prevents exciplex formation and results in the appearance of an intense naphthyl fluorescence signal that can be used for monitoring the complexation process. Luminescence titration, together with competition experiments and (1)H NMR titration, have shown that 1:1 and 1:2 (metal/ligand) complexes are formed in the cases of 2 and 3, whereas model compound 1 gives only a 1:1 complex. We have also investigated the 1:1 complexation kinetics by the stopped-flow technique. In the case of 1, a second-order process (k(1)=44x10(5) M(-1) s(-1)) is followed by two consecutive first-order steps (k(2)=0.53 s(-1) and k(3)=0.10 s(-1)). For 2, a slower second-order process (k(1)=4.9x10(5) M(-1) s(-1)) is followed by a slow first-order step (k(2)=0.40 s(-1)). In the case of 3, only a very slow second-order process was observed (k(1)=1.2x10(5) M(-1) s(-1)). The different metal-ion incorporation rates for model compound 1 and dendrimers 2 and 3 have been discussed in terms of conformational changes of the dendron subunits affecting the chelating properties of the cyclam core. This work reports the first kinetic study on metal-ion coordination by dendrimers with a well-defined coordination site. 相似文献
Dichotic pitch perception reflects the auditory system's use of binaural cues to perceptually separate different sound sources and to determine the spatial location of sounds. Several studies were conducted to identify factors that influence children's dichotic pitch perception thresholds. An initial study of school children revealed an age-related improvement in thresholds for lateralizing dichotic pitch tones. In subsequent studies potential sensory and nonsensory limitations on young children's performance of dichotic pitch lateralization tasks were examined. A training study showed that with sufficient practice, young children lateralize dichotic pitch stimuli as well as adults, indicating an age difference in perceptual learning of the lateralization task. Changing the task requirements so that young children made a judgment about the pitch of dichotic pitch tones, rather than the spatial location of the tones, also resulted in significantly better thresholds. These findings indicate that nonsensory factors limit young children's performance of dichotic pitch tasks. 相似文献
The essential oil extracted from the different parts of Eryngium bourgatii Gouan: stems + leaves (E.b.SL), inflorescences (E.b.I) and roots (E.b.R), have been extracted by steam distillation and analysed by gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). Quantitative but not qualitative differences have been found between the analysed parts. The principal compounds from the inflorescences oil were found to be phyllocladene (37.6%) and bicyclogermacrene (15.1%), while the oil from stems and leaves showed phyllocladene (20.4%), gamma-muurolene (11.8%) and (E)-caryophyllene (10.1%) as main ones. The oil from the roots presented gamma-muurolene (15.4%) and phyllocladene (15.0%) as major constituents. It is worth mentioning the presence of a diterpene, phyllocladene, as main compound of the essential oil. This is the first report on the essential oil of this species. 相似文献