Model study of nonleading mass singularities,I

We investigate the effects of finite masses on the short distance properties in the context of the two-dimensional Federbush model. We comment in particular on the limiting procedure in deriving the equation of motion and on changes in Wilson expansions of certain operators as compared to the massless case.     

A comparison of the performance of two chromatographic and three extraction techniques for the analysis of PAHS in sources of drinking water

The aim of this work is to establish a sensitive and reliable method for the analysis of the 16 priority Environmental Protection Agency-defined polycyclic aromatic hydrocarbons (PAHs) found in water samples. Gas chromatography (GC)-mass spectrometry (MS) and high-performance liquid chromatography (HPLC)-fluorescence detection (FLD)-UV techniques are optimized to obtain an adequate resolution of all compounds. Validation of the methods is carried out, and a good performance is observed for both techniques. The HPLC-FLD-UV technique is somewhat more sensitive than the GC-MS technique for the determination of PAHs; thus, the HPLC-FLD-UV method is used to follow up both the solid-phase extraction (SPE) analysis using cartridges and discs and the liquid-liquid extraction (LLE), which are also evaluated for the extraction of the PAHs. Low recoveries between 43% and 79% are obtained using SPE cartridges, and higher values are obtained using SPE discs (56-96%) and LLE (60-105%). Better results are obtained using the LLE technique, and, thus, analysis of real water samples is carried out using this technique. LODs between 0.6 and 21 ng/L and relative standard deviations less than 15% are obtained using a spiked water sample analyzed using the full LLE HPLC-FLD-UV method.     

Iron oxide film growth under ultrathin polysiloxane networks

This study focuses on the preparation and characterization of magnetic switchable thin iron oxide–polymer films. In a series of experiments, the formation and growth of iron oxide under ultrathin polysiloxane layers was controlled by changing the concentration of iron ions in the aqueous subphase or by varying the residence time of ammonia in the gas phase above the liquid sample. The growth of the combined film structures is studied in situ by interfacial rheology, optical microscopy, and x-ray scattering experiments and ex situ by scanning electron microscopy. Different stages of iron oxide aggregation, from a very thin layer of amorphous iron oxide with thickness of a few nanometers up to micrometer thick coatings of crystalline maghemite (γ-Fe₂O₃) were investigated. The specific interactions between the inorganic iron oxide and the polymer membranes cause the creation of new composite materials which are sensitive to magnetic forces.

Demulsification of Crude Oil Emulsions Using Some New Water-Soluble Schiff Base Surfactant Blends

Six new surfactant blends were prepared by mixing one Schiff base non ionic surfactant prepared by etherification of Schiff base monomer with β, ^` β-dichlorodiethylether and PEG 400 in presence of NaOH with six water-soluble Schiff base nonionic surfactants prepared in the same way but etherified with PEG 2000. The mixing process was based on the high dehydration rates given by the PEG 400 Schiff base surfactant compared to the other PEG 2000 surfactants. The experimental results of this study indicate that the demulsification rates of these blends are higher than those of the PEG 400 surfactant. Demulsification process was carried out on an emulsion of w/o ratio 50:50 and studied at 60°C at two different concentrations of the demulsifiers (200 and 240 ppm). The dehydration rates of the six prepared blends reached 100%. The total dehydration time varied from 50 minutes up to 2 hours.     

A Convenient Synthesis of 1-Amino-4-methyl-4H-3-thia-4,5a,10-triazacyclopenta[a]fluoren-5-ones and Some New 2,3-Dihydro-1,3,4-thiadiazoles

1-amino-4-methyl-4H-3-thia-4,5a,10-triazacyclopenta-[a]fluoren-5-one and 6-methyl-6H-,9H-thia-4b,6,9,11,12-pentaazaindeno[1,2-a]-fluorene-5,8-dione derivatives were prepared from 2-methyl-1-oxo-3-thioxo-2,4,9b-trihydropyrimidino[1,6-a] benzimidazole-4-carbonitrile. Also, 2,3-dihydro-1,3,4-thidazoles were synthesized via a reaction of hydrazonoyl chlorides with 3-(methylamino)-2-substituted 3-thioxopropanenitrile. Structures of newly synthesized compounds were elucidated on the basis of elemental analyses, spectral data, and alternative methods synthesis whenever possible.     

Energy‐dependent dead‐time correction in digital pulse processors applied to silicon drift detector's X‐ray spectra

Dead‐time effects in X‐ray spectra taken with a digital pulse processor and a silicon drift detector were investigated when the number of events at the low‐energy end of the spectrum was more than half of the total, at counting rates up to 56 kHz. It was found that dead‐time losses in the spectra are energy dependent and an analytical correction for this effect, which takes into account pulse pile‐up, is proposed. This and the usual models have been applied to experimental measurements, evaluating the dead‐time fraction either from the calculations or using the value given by the detector acquisition system. The energy‐dependent dead‐time model proposed fits accurately the experimental energy spectra in the range of counting rates explored in this work. A selection chart of the simplest mathematical model able to correct the pulse‐height distribution according to counting rate and energy spectrum characteristics is included.     

Recent Trends in the Preparation of Nano-Starch Particles

Starch is affected by several limitations, e.g., retro-gradation, high viscosity even at low concentrations, handling issues, poor freeze–thaw stability, low process tolerance, and gel opacity. In this context, physical, chemical, and enzymatic methods have been investigated for addressing such limitations or adding new attributes. Thus, the creation of biomaterial-based nanoparticles has sparked curiosity. Because of that, single nucleotide polymorphisms are gaining a lot of interest in food packaging technology. This is due to their ability to increase the mechanical and water vapor resistance of the matrix, as well as hide its re-crystallization during storage in high-humidity atmospheres and enhance the mechanical properties of films when binding in paper machines and paper coating. In medicine, single nucleotide polymorphisms (SNPs) are suitable as carriers in the field of drug delivery for immobilized bioactive or therapeutic agents, as well as wastewater treatments as an alternative to expensive activated carbons. Starch nanoparticle preparations can be performed by hydrolysis via acid hydrolysis of the amorphous part of a starch molecule, the use of enzymes such as pullulanase or isoamylase, or a combination of two regeneration and mechanical treatments with the employment of extrusion, irradiation, ultrasound, or precipitation. The possibility of obtaining cheap and easy-to-use methods for starch and starch derivative nanoparticles is of fundamental importance. Nano-precipitation and ultra-sonication are rather simple and reliable methods for nanoparticle production. The process involves the addition of a diluted starch solution into a non-solvent, and ultra-sonication aims to reduce the size by breaking the covalent bonds in polymeric material due to intense shear forces or mechanical effects associated with the collapsing of micro-bubbles by sound waves. The current study focuses on starch nanoparticle manufacturing, characterization, and emerging applications.