Multivariate optimization of hydrodistillation-headspace solvent microextraction of thymol and carvacrol from Thymus transcaspicus

In this paper multivariate response surface methodology (RSM) has been used for the optimization of hydrodistillation-headspace solvent microextraction (HD-HSME) of thymol and carvacrol in Thymus transcaspicus. Quantitative determination of compounds of interest was performed simultaneously using gas chromatography coupled with flame ionization detector (GC-FID). Parameters affecting the extraction efficiency were assessed and the optimized values were 5 min, 2 μL and 3 min for the extraction time, micro-drop volume and cooling time after extraction, respectively. The amounts of analyte extracted increased with plant weight. The calibration curves were linear in the ranges of 6.25-81.25 and 1.25-87.50 mg L⁻¹ for thymol and carvacrol, respectively. Limit of detection (LOD) for thymol and carvacrol was 1.87 and 0.23 mg L⁻¹, respectively. Within-day and between-day precisions for both analytes were calculated in three different concentrations and recoveries obtained were in the range of 89-101% and 95-116% for thymol and carvacrol, respectively.     

Synthesis,Characterization, and Crystal Structure of a Chromium(III)‐Complex Containing 2,6‐Pyridinedicarboxylic Acid and 1,10‐Phenanthroline

The reaction of solution 2,6‐pyridinedicarboxylic acid and 1,10‐phenanthroline ( 1 ) with CrCl₃·6H₂O led to the complex [Cr(phen)(pydc)(H₂O)][Cr(pydc)₂]·4H₂O ( 2 ) (phen is 1,10‐phenanthroline and pydcH₂ is 2,6‐pyridinedicarboxylic acid). 2 was characterized by elemental analysis, IR spectroscopy and single‐crystal structure determination. Crystal data for 2 at ?80 °C: triclinic, space group , a = 818.5(1), b = 1492.2(1), c = 1533.6(2) pm, α = 76.45(1)°, β = 84.22(1)°, γ = 77.99(1)°, Z = 2, R₁ = 0.0416.     

A novel robust proportional-integral （PI） adaptive observer design for chaos synchronization

In this paper, chaos synchronization in the presence of parameter uncertainty, observer gain perturbation and exogenous input disturbance is considered. A nonlinear non-fragile proportional-integral (PI) adaptive observer is designed for the synchronization of chaotic systems; its stability conditions based on the Lyapunov technique are derived. The observer proportional and integral gains, by converting the conditions into linear matrix inequality (LMI), are optimally selected from solutions that satisfy the observer stability conditions such that the effect of disturbance on the synchronization error becomes minimized. To show the effectiveness of the proposed method, simulation results for the synchronization of a Lorenz chaotic system with unknown parameters in the presence of an exogenous input disturbance and abrupt gain perturbation are reported.     

A green non-acid-catalyzed process for direct N=N–C group formation: comprehensive study,modeling, and optimization

The aim of this work is to introduce, model, and optimize a new non-acid-catalyzed system for a direct N\(=\)N–C bond formation. By reacting naphthols or phenol with anilines in the presence of the sodium nitrite as nitrosonium (\(\hbox {NO}^{+})\) source and triethylammonium acetate (TEAA), a N\(=\)N–C group can be formed in non-acid media. Modeling and optimization of the reaction conditions were investigated by response surface method. Sodium nitrite, TEAA, and water were chosen as variables, and reaction yield was also monitored. Analysis of variance indicates that a second-order polynomial model with F value of 35.7, a P value of 0.0001, and regression coefficient of 0.93 is able to predict the response. Based on the model, the optimum process conditions were introduced as 2.2 mmol sodium nitrite, 2.2 mL of TEAA, and 0.5 mL \(\hbox {H}_{2}\hbox {O}\) at room temperature. A quadratic (second-order) polynomial model, by analysis of variance, was able to predict the response for a direct N=N–C group formation. Predicted response values were in good agreement with the experimental values. Electrochemistry studies were done to introduce new Michael acceptor moieties. Broad scope, high yields, short reaction time, and mild conditions are some advantages of the presented method.     

Perfect quantum excitation energy transport via single edge perturbation in a complete network

We consider quantum excitation energy transport (EET) in a network of two-state nodes in the Markovian approximation by employing the Lindblad formulation. We find that EET from an initial site, where the excitation is inserted to the sink, is generally inefficient due to the inhibition of transport by localization of the excitation wave packet in a symmetric, fully-connected network. We demonstrate that the EET efficiency can be significantly increased up to ≈100% by perturbing hopping transport between the initial node and the one connected directly to the sink, while the rate of energy transport is highest at a finite value of the hopping parameter. We also show that prohibiting hopping between the other nodes which are not directly linked to the sink does not improve the efficiency. We show that external dephasing noise in the network plays a constructive role for EET in the presence of localization in the network, while in the absence of localization it reduces the efficiency of EET. We also consider the influence of off-diagonal disorder in the hopping parameters of the network.     

Gelatin methacrylate as a promising hydrogel for 3D microscale organization and proliferation of dielectrophoretically patterned cells

Establishing the 3D microscale organization of cells has numerous practical applications, such as in determining cell fate (e.g., proliferation, migration, differentiation, and apoptosis) and in making functional tissue constructs. One approach to spatially pattern cells is by dielectrophoresis (DEP). DEP has characteristics that are important for cell manipulation, such as high accuracy, speed, scalability, and the ability to handle both adherent and non-adherent cells. However, widespread application of this method is largely restricted because there is a limited number of suitable hydrogels for cell encapsulation. To date, polyethylene glycol-diacrylate (PEG-DA) and agarose have been used extensively for dielectric patterning of cells. In this study, we propose gelatin methacrylate (GelMA) as a promising hydrogel for use in cell dielectropatterning because of its biocompatibility and low viscosity. Compared to PEG hydrogels, GelMA hydrogels showed superior performance when making cell patterns for myoblast (C2C12) and endothelial (HUVEC) cells as well as in maintaining cell viability and growth. We also developed a simple and robust protocol for co-culture of these cells. Combined application of the GelMA hydrogels and the DEP technique is suitable for creating highly complex microscale tissues with important applications in fundamental cell biology and regenerative medicine in a rapid, accurate, and scalable manner.     

A miniature gas analyzer made by integrating a chemoresistor with a microchannel

A microfluidic channel is integrated with a tin oxide-based generic gas sensor on a PMMA (polymethyl methacrylate) substrate to fabricate a miniature gas analyzer. The analyte gas diffuses along the air-filled channel to affect the sensor installed in a microcavity positioned at the end of the channel. Analyte diffusion rates, experimentally estimated based on the temporal responses received from the sensor, are connected to the analyte's interactions with the channel walls as well as its diffusivity in air. The analyte-related information is extracted from the recorded responses and used for analyte recognition. A single PMMA channel of 80 μm × 3 mm × 50 mm dimensions facilitates the correct classification of single component contaminants each introduced in a wide concentration range in air. The device is also shown to identify 15 ppm of 2-butanol in air contaminated with 1500 ppm of 1-butanol. The gas analyzer fabricated based on this concept is durable, inexpensive, handheld and suitable for a variety of applications.     

Effect of second monomer and initiator type, mixing method, and stabilizer content on the shape of the particles produced by seeded dispersion polymerization in the presence of saturated hydrocarbon droplets

In this work, the preparation of micron-sized polymer particles with nonspherical shapes via seeded dispersion polymerization of 2-ethylhexyl methacrylate with polystyrene seed particles in the presence of hydrocarbon droplets and evaporation of hydrocarbon after the polymerization under various polymerization conditions was discussed. The effect of second monomer and initiator type, mixing method, and stabilizer content on the shape of the obtained particles was investigated. It was observed that particles with more nonspherical shapes were obtained with increasing the alkyl chain length of ester group of the methacrylate of the second monomer which is because of increasing the absorption amounts of hydrocarbon by second polymer domains. Moreover, the experimental results showed that shape of the particles which was produced by shaking is more nonspherical than the shape of the particles which was obtained from tumbling. Furthermore, particles with different nonspherical shapes were prepared by changing the initiator type and stabilizer content.     

Sonochemical syntheses of a nano-sized copper(II) supramolecule as a precursor for the synthesis of copper(II) oxide nanoparticles

Nanoparticles of a three-dimensional supramolecular, [Cu(L)₂(H₂O)₂] (1), (L⁻ = 1H-1,2,4-triazole-3-carboxylate), have been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The thermal stability of compound 1 both its bulk and nano-size has been studied by thermal gravimetric (TG) and differential thermal analyses (DTA) and compared each other. Concentration of initial reagents effects on size and morphology of nano-structured compound 1, have been studied. Calcination of the nano-sized compound 1 at 600 °C under air atmosphere yields CuO nanoparticles.