Crystallization study of sol-gel un-doped and Pd-doped TiO2 materials

Sol-gel nanostructured titania materials have been reported to have applications in areas ranging from optics via solar energy to gas sensors. In order to enhance the photocatalytic activity, there are many studies regarding the doping of titanium dioxide (TiO₂) material with either non-metals (S, C, N, P) or metals (Ag, Pt, Nd, Fe). The present work has studied some un-doped and Pd-doped sol-gel TiO₂ materials (films and gels), with various surface morphologies and structures, obtained by simultaneous gelation of both precursors Ti(OEt)₄ and Pd(acac)₂. Their structural evaluation and crystallization behavior with thermal treatment were followed by DTA/TG analysis, infrared (IR) spectroscopy, Fourier transform infrared (FTIR), spectroellipsometry (SE), X-ray diffraction (XRD) and atomic force microscope (AFM). The influence of Pd on TiO₂ crystallization for both supported and un-supported materials was studied (lattice parameters, crystallite sizes, internal microstrains). The changes in the optical properties of the TiO₂-based vitreous materials were correlated with the changes of the structure. The hydrophilic properties of the films were also connected with their structure, composition and surface morphology.     

Induced birefringence of rubbed and stretched polyvinyl alcohol foils as alignment layers for nematic molecules

Some optical properties of poly (vinyl alcohol) (PVA) films are investigated prior and after the rubbing and stretching of the samples. Birefringence of the prepared foils is enhanced as their stretching degree and rubbing become larger. These processing factors are also affecting the values of the ordinary and extraordinary refractive indices. The induced anisotropy in PVA foils is evidenced in the morphological characteristics observed by optical microscopy. The spreading and adhesion behaviors of a nematic liquid crystal on PVA foils are analyzed by means of contact angle measurements. Preliminary testing of the nematic on the PVA films revealed significant variations in transmitted light intensity during sample rotation under crossed polarizers. The high contrast between dark and bright patterns is indicative of uniform and homogenous alignment of nematic on the rubbed and stretched PVA foils.     

A Harnack inequality for the parabolic Allen–Cahn equation

We prove a differential Harnack inequality for the solution of the parabolic Allen–Cahn equation \( \frac{\partial f}{\partial t}=\triangle f-(f^3-f)\) on a closed n-dimensional manifold. As a corollary, we find a classical Harnack inequality. We also formally compare the standing wave solution to a gradient estimate of Modica from the 1980s for the elliptic equation.     

Advancement in the Biomedical Applications of the (Nano)gel Structures Based on Particular Polysaccharides

(Nano)gels from macromolecular compounds—natural, synthetic, or a combination thereof, suitable crosslinkers—and conferred characteristics—such as degradability, size, charge, amphiphilicity, responsiveness, and softness—are capable of responding to the challenges imposed by bioengineering applications. Polysaccharide‐based gels have received particular attention in this field. This review addresses recent advancement in the use of (nano)gel structures prepared only from compounds based on gellan gum, heparin, chondroitin sulfate, carrageenan, guar gum, galactose, or agarose, which represent an important part of the special class of natural polymers, the polysaccharides. Also, future trends are taken into discussion regarding the (nano)gels' use in biomedical applications such as biomimetics, biosensors, artificial muscles, and chemical separations in relation with their ability to be used as a vehicle for various biomolecules due to their physicochemical properties, biocompatibility, and biodegradability.     

Promising Roles of Alternative Medicine and Plant-Based Nanotechnology as Remedies for Urinary Tract Infections

Urinary tract infections (UTIs) are considered to be the most common infections worldwide, having an incidence rate of 40−60% in women. Moreover, the prevalence of this disorder in adult women is 30 times more than in men. UTIs are usually found in many hospitals and clinical practice; as disorders, they are complicated and uncomplicated; in uncomplicated cases, there is no structural or functional abnormality in the urogenital tract. However, obstruction, retention of urine flow and use of catheters increase the complexity. There are several bacteria (e.g., E. coli, Klebsiella pneumoniae, Proteus vulgaris, etc.) successfully residing in the tract. The diagnosis must not only be accurate but rapid, so early detection is an important step in the control of UTIs caused by uropathogens. The treatment of UTIs includes appropriate antimicrobial therapy to control the infection and kill the causal microbes inside the body. A long-time usage of antibiotics has resulted in multidrug resistance causing an impediment in treatment. Thus, alternative, combinatorial medication approaches have given some hope. Available treatments considered Homeopathic, Ayurvedic, Unani, and other herbal-based drugs. There are new upcoming roles of nanoparticles in combating UTIs which needs further validation. The role of medicinal plant-based nanotechnology approaches has shown promising results. Therefore, there must be active research in phyto-based therapies of UTIs, such as Ayurvedic Biology.     

Production of nitric oxide by a fragmenting bolide: An exploratory numerical study

A meteoroid's hypersonic passage through the Earth's atmosphere results in ablational and fragmentational mass loss. Potential shock waves associated with a parent object as well as its fragments can modify the surrounding atmosphere and produce a range of physico-chemical effects. Some of the thermally driven chemical and physical processes induced by meteoroid-fragment-generated shock waves, such as nitric oxide (NO) production, are less understood. Any estimates of meteoric NO production depend not only on a quantifiable meteoroid population and a rate of fragmentation, with a size capable of producing high temperature flows, but also on understanding the physical properties of the meteor flows along with their thermal history. We performed an exploratory pilot numerical study using ANSYS Fluent, the computational fluid dynamics (CFD) code, to investigate the production of NO in the upper atmosphere by small meteoroids (or fragments of meteoroids after they undergo a disruption episode) in the size range from 10⁻² to 1 m. Our model uses the simulation of a spherical body in the continuum flow at 70- and 80-km altitude to approximate the behaviour of a small meteoroid capable of producing NO. The results presented in this exploratory study are in good agreement with previous studies.     

Complete Integrability of Geodesics in Sasaki–Einstein Space T1,1 and Its Resolved Conifold

Physics of Atomic Nuclei - In this paper we are concernedwith integrability of geodesic motions in Sasaki–Einstein space T1,1 and its Calabi–Yau metric cone. There are enough...     

Minimization of vectors of curvilinear functionals on the second order jet bundle: sufficient efficiency conditions

Strongly motivated by its possible applications in Mechanics, in our previous work (Pitea and Postolache (Optim. Lett. doi:10.1007/s11590-010-0272-0, 2011)), we initiated an optimization theory for the second order jet bundle. We considered the problem of minimization of vectors of curvilinear functionals (well known as mechanical work), thought as multi-time multi-objective variational problems, subject to PDE and/or PDI constraints. Within this framework, we introduced necessary conditions. As natural continuation of our results in Pitea and Postolache (Optim. Lett. doi:10.1007/s11590-010-0272-0, 2011), the present work introduces a study of sufficient efficiency conditions. While the background in Sect. 2 is introductory, the theory in Sect. 3 is new as a whole, containing our results.     

Catalytic determination of Pb(II) in the presence of Cu(II)

A kinetic method is presented to determine micro-molar amounts of Pb(II) from various river and wastewater samples, in the presence of trace copper. The procedure is based on the catalytic effect of both species on the oxidation of mercaptosuccinic acid by chromate in acidic media. The extent of the reaction is followed spectrophotometrically at 420 nm and pseudo-first-order rate coefficients of the rate-determining step are determined as a function of catalyst concentrations. The optimum operating conditions (ionic strength, temperature, and concentration of reagents) regarding sensitivity towards lead were established. Interference by several ionic species has been studied. The effect of Fe(III), the only severe interferent, is suppressed by complexation with 1,10-phenantroline. The bi-component calibration model employs an artificial neural network to compute the Pb(II) concentration from a k(obsd) value and the a priori-known Cu(II) concentration of the sample. Working concentration ranges are 20-2160 micro g L(-1) for Pb(II) and 80-650 micro g L(-1) for Cu(II), respectively. Detection limits are 20 micro g L(-1) Pb(II) and 80 micro g L(-1) Cu(II), respectively. The relative standard deviations (3 measurements) for four different testing points are lower than 2.5%. The method was applied to samples of river and wastewater of the mining region of Baia-Mare, Northern Romania. The results were compared to those obtained by an officially standardized AAS method. Good agreement was achieved. The method is inexpensive, fairly rapid, and sensitive. Its working range covers the exact range of concentrations usually encountered in the mentioned geographic area.     

Electrochemistry and electrogenerated chemiluminescence of a thin solid film of a hydrophobic tris(bipyridine) Ru(II) derivative in contact with an aqueous solution

The present study shows the electrochemistry, electrogenerated chemiluminescence and solid-state electroluminescence of [Ru(bpy)₂(4,4-(CH₃(CH₂)₁₂COO)bpy)](ClO₄)₂ as thin film deposited onto ITO. Cyclic voltammetry in aqueous solution of the Ru-LC film shows two reversible waves with peak potentials at about 1.27 V and –0.97 V. The apparent diffusion coefficient of the slowest species was found to be 4–6×10^–10 cm²/s, with a concentration of active sites of about 0.4–0.5 M.Relatively strong ECL was observed during both oxidation and reduction, in both potential scans and potential step experiments. The reduced species appears to be much less stable than the oxidized one, as already known for other tris(bipyridine) Ru(II) derivatives in aqueous media.Two-electrode solid-state devices prepared by Ga-In printing on the tops of Ru-LC films are similar to the Ru(bpy)₃ ones. The currents that flow through these devices are however about three orders of magnitude smaller than those for Ru(bpy)₃ devices as a result of their low electron and hole mobilities.Dedicated to Zbigniew Galus on the occasion of his 70th birthday.