Dynamic model of methane–water diffusion

This paper presents a mathematical model to describe the time evolution of the diffusion process of methane exchange between liquid and gaseous phases. In order to reach the equilibrium, the distribution of gas in the liquid phase decreases to a constant value over time. Generalized model is analyzed under the assumption that both, reversible and irreversible form of absorption and desorption, occur at the same time. For the application in case of the real system of methane–water, model is developed under the assumption that the processes of absorption and desorption are irreversible. From the experimental data are determined the coefficients of model and their dependence on initial conditions, with constant end conditions. This paper tests the introduced theoretical model on the existing experimental data.     

Preparation and characterization of PLA composites with modified magnesium hydroxide obtained from seawater

Journal of Thermal Analysis and Calorimetry - Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification...     

Sorbent-excluding sample preparation method for GC–MS pesticide analysis in apple peel

Apple peel is frequently exposed to pesticides, especially in the last stages of the pesticide treatment practice. For a certain period, peel retains most of the applied pesticides, which precisely indicates the presence of pesticide residues. This study was conducted to establish and evaluate the method for the residue analysis of pyrimethanil, cyprodinil, trifloxystrobin, bifenthrin and boscalid by GC–MS in peel of Granny Smith, Golden Delicious and Idared varieties. The method consisted of few steps, without the routine usage of sorbents, and resulted in efficient removal of waxes, targeted as main interferences in GC–MS analysis. The matrix effect, boscalid selectivity issue, trend of lower trueness for bifenthrin in all matrices and for all analytes in Granny Smith matrix were in some way associated with the waxes. Finally, the method was applied to the analysis of three varieties of apple orchard samples, after 9 and 5 months of treatment with commercial formulations that contain pyrimethanil, cyprodinil and boscalid as active ingredients. Since the developed method consisted of few steps and used nontoxic and economic reagents, it could be implemented as a fast, economic and reliable screening method.     

Vesicle formation from temperature jumps in a nonionic surfactant system

When heating a dilute sample of the binary system of tetraethyleneglycol dodecyl ether (C12E4) and water from the micellar phase (L1) into the two-phase region of a lamellar phase (L(alpha)), and excess water (W) vesicles are formed. During heating, one passes a region of phase separation in the micellar phase (L1' + L1') where the initial micelles rapidly fuse into larger aggregates forming the concentrated L1 phase (L1') with a structure of branched cylindrical micelles, a so-called "living network". The static correlation length of the micelles are increasing with increasing concentration, from ca. 10 nm to 80 nm in the concentration range of 0.0001 g/cm3-0.0035 g/cm3. The overlap concentration was determined to 0.0035 g/cm3. When the temperature reaches the L1' + L(alpha) region the network particles transform into bilayer vesicles with a z-average apparent hydrodynamic radius in the order of 200 nm depending on the composition. The size of the final vesicles depends on the extent of aggregation/fusion in the L1' + L1' region and hence on the rate of heating. The aggregation/fusion in the L1' + L1' is slower than diffusion-limited aggregation, and it is shown that 1/100 of the collisions are sticky results in the fusion event.     

Recognition of homo-polynucleotides containing adenine by a phenanthridinium bis-uracil conjugate in aqueous media

Among novel bis-nucleobase-phenanthridinium conjugates bis-uracil analogue stabilized significantly more effective poly-dA-poly-dT and poly-AH(+)-poly-AH(+) than adenine analogue and reference compound . For the alternating poly-dAdT-poly-dAdT however, the binding preference is lost, pointing to the importance of specific interactions of uracils of with homopolynucleotides containing consecutive adenines.     

Laser-tweezer-controlled solid immersion microscopy in microfluidic systems

We describe the creation and implementation of a near-field scanning solid immersion microscope that is specifically tailored for use in microfluidic systems. The microscope comprises a newly fabricated Weierstrass solid immersion lens (SIL), which is detached from its substrate and is free floating in the fluid, and a laser optical tweezer, which serves both as a trapping beam for alignment and positioning of the SIL and as a near-field scanning beam that images the sample through the SIL. A discussion of the SIL's fabrication method is presented along with experimental results that demonstrate the effectiveness of our microscope design.     

A detailed experimental and computational study of Cd complexes with pyridyl-based thiazolyl hydrazones

Interest in Cd complexes has been growing in recent years. Cd complexes are considered a potential solution in the search for novel antibiotics that can fight antimicrobial resistance. In addition, Cd complexes draw attention to material chemistry. The main objective of this work was to prepare the first Cd(II) complexes with anionic forms of pyridine-based thiazolyl hydrazone (THs) ligands HLS² [(E)-4-(4-methoxyphenyl)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)thiazole] and HLS³ [(E)-2-(2-[pyridine-2-ylmethylene]hydrazinyl)-4-(p-tolyl)thiazole] and perform their structural and spectroscopic characterization, as well as stability in solution and upon heating. Studies related to their biological activities and possible electrochromic applications are also being conducted. Complexes [Cd(HLS²)₂] ( 1 ) and [Cd(HLS³)₂] ( 2 ) have been characterized by a single-crystal X-ray diffraction and computational analysis of intermolecular interactions responsible for their solid-state structures was performed. Thermal stability of 1 and 2 in the solid-state was analyzed by TGA/MS, where as their solution stability was determined by the spectrophotometric titration method. Electrochemical and in situ UV–Vis spectroelectrochemical analyses of 1 and 2 were carried out to determine redox mechanisms and the influence of the substituents and electrolytes on their redox responses. The antioxidant capacity of both complexes was tested in antioxidant assays, while their antimicrobial activity was tested against five Gram-positive and four Gram-negative bacteria, as well as against three fungi. The obtained results indicate their potent antioxidant capacity. The antimicrobial activity of investigated compounds on almost all tested bacterial strains was stronger than that of the standard antibiotic erythromycin. The results of docking studies indicate that the minor groove DNA is the possible biological target of 1 and 2 .     

Synthesis and biological evaluation of 99mTc tricarbonyl complex of O,O′‐diethylethylenediamine‐N,N′‐di‐3‐propanoate as potential tumour diagnostic agent

The extensive development of radiopharmaceuticals towards early tumour detection and treatment has increased the demand for new ligands with higher tumour selectivity. Research has been done on the potential of the novel O,O′‐diethylethylenediamine‐N,N′‐di‐3‐propanoate ( L ) ligand as a radionuclide vehicle for tumour targeting. Under alkaline conditions, L hydrolyses and produces half ester ligand ( L' ) and diacid ligand ( L'' ), with characteristic donor atom array N,N,O. Ligand L was successfully labelled with ^99mTc at pH = 9 by coordination with the octahedral fac‐[^99mTc(CO)₃(H₂O)₃]⁺ intermediate, forming the main radioproduct fac‐[^99mTcL′(CO)₃] (Tc1). The ^99mTc complex showed a low lipophilic character (log P = 0.48) and low binding affinity to human serum albumin (2.51 ± 0.48%). In vitro stability studies in saline and human plasma, as well as challenge studies with cysteine and histidine, revealed high stability of the complex during 24 h. Biodistribution studies of Tc1 in female C57BL/6 mice bearing B16/F1 melanoma metastases showed significant tumour uptake: 9.81 ± 1.19%ID g^?1 in the liver, 5.87 ± 0.54%ID g^?1 in the lungs and 3.17 ± 0.33%ID g^?1 in the ovary at 30 min post‐injection. Favourable physicochemical properties, satisfactory in vitro/in vivo stability and biodistribution profile in the experimental metastatic melanoma model indicate the possible application of the radiolabelled ligand in tumour diagnosis. Copyright © 2015 John Wiley & Sons, Ltd.     

Conditions of matrices in discrete tension spline approximations of DMBVP

Some splines can be defined as solutions of differential multi-point boundary value problems (DMBVP). In the numerical treatment of DMBVP, the differential operator is discretized by finite differences. We consider one dimensional discrete hyperbolic tension spline introduced in (Costantini et al. in Adv Comput Math 11:331–354, 1999), and the associated specially structured pentadiagonal linear system. Error in direct methods for the solution of this linear system depends on condition numbers of corresponding matrices. If the chosen mesh is uniform, the system matrix is symmetric and positive definite, and it is easy to compute both, lower and upper bound, for its condition. In the more interesting non-uniform case, matrix is not symmetric, but in some circumstances we can nevertheless find an upper bound on its condition number. This research was supported by Grant 0037114, by the Ministry of Science, Education and Sports of the Republic of Croatia.