Acoustic quantification of ATP using a quartz crystal microbalance with dissipation

A quartz crystal microbalance with a dissipation monitoring (QCM-D) sensor was developed for highly sensitive and specific detection of adenosine-5'-triphosphate (ATP) by using an aptamer. The binding of ATP molecules on the aptamer films could be calculated as accurate mass changes using multiple frequency and dissipation measurements. The detection is achieved by calculating the mass changes from conformational rearrangements of the sensor surface upon interaction with the target. The sensor was demonstrated to respond to changes in ATP concentrations in real time suitable for continuous monitoring applications. This sensor showed excellent selectivity toward ATP compared with other chemically similar nucleotide GTP. The feasibility of the sensor was demonstrated by analyzing ATP concentrations in cell culture media with serum. The maximum frequency change was about -2 Hz after injection of 500 μM ATP. The affinity constant of the aptamer was determined to be 49 ± 7.59 μM. The proposed sensor can extend the application of the QCM-D system in medical diagnosis, and could be adopted for the detection of other small molecules with the use of specific aptamers.     

Mechanical and thermal properties of perfluoroalkyl ethyl methacrylate-methyl methacrylate statistical copolymers synthesized in supercritical carbon dioxide

Poly(methyl methacrylate-ran-perfluoroalkyl ethyl methacrylate) copolymers having varying perfluoroalkyl ethyl methacrylate ester (Zonyl-TM) contents were synthesized in supercritical CO₂. Complete amorphous structures of the copolymers were verified by XRD. Young's modulus (Y_mod) of the copolymers was decreased linearly from 1.57 to 1.08 GPa and T_g values from 102 to 77 °C with the increase of Zonyl-TM content. A linear relationship between the Y_mod and the T_g values of the copolymer was also found. The increase of the large branched pendant groups resulted in the increase of the free volume and a corresponding decrease in Y_mod and T_g of the copolymers. A good fit was found when the Schneider equation was used. Negative deviation from the Gordon-Taylor equation was observed when Zonyl-TM content was lower than 14% due to rapid increase in free volume and then a positive deviation was found due to the dipole-dipole interactions between the methyl ester and fluoroalkyl ester groups.     

Rapid detection of sucrose adulteration in honey using Fourier transform infrared spectroscopy

Abstract

Honey authenticity is of great importance for commercial and health reasons. The most common adulteration methods are overfeeding of bees with sugar or by adding sucrose. In the study, a Fourier transform infrared spectroscopy based on chemometric method, a partial least squares, for determination of sucrose sirup adulteration of Turkish honeys was improved. For this purpose, honey samples were adulterated with known amounts of sucrose sirup in concentrations ranging between 5.94 and 27.80%. A calibration curve was constructed within 992–923?cm^?1 with the regression coefficient of 0.999. Obtained results from the spectra were confirmed by high performance liquid chromatography-refractive index detector and a good correlation was found between the results of the spectroscopic and chromatographic methods. Additionally, some method validation parameters (linearity, repeatability, limit of detection, and quantification) of the spectroscopic method were studied and obtained results were compared with chromatographic method. To prove the usefulness of the method, twenty different honey samples were collected from markets in Turkey and analyzed for sucrose contents. The results indicated that predicted sucrose concentration of honey samples by the spectroscopic method ranged between 4.52 and 15.16% and results were confirmed by the chromatographic method with high correlation (correlation coefficient = 92%). The results of the present indicated showed that adulteration ratio of honey samples by sugar addition can be detected using Fourier transform infrared spectroscopy technique in a short time with high accuracy. In conclusion, this method could be regarded as a new alternative technique for routine analysis in quality control of honey samples.     

Delayed myelination in a rhizomelic chondrodysplasia punctata case: MR spectroscopy findings

Rhizomelic chondrodysplasia punctata is a member of genetic peroxisomal disorders. Delayed myelination, which is probably related to the inadequacy of plasmalogens biosynthesis, is an important feature of this disorder. Direct assessment of neuropathologic aspects of RCDP syndrome such as neuronal degeneration and delayed myelination is possible with MR spectroscopy.In this report, MR spectroscopy findings (decreased Cho/Cr and increased Ins-Gly/Cr ratios and increased levels of mobile lipids) of a rhizomelic chondrodysplasia punctata case supporting delayed myelination are presented. This is the second report of MR spectroscopy examination of the specific brain metabolic changes associated with rhizomelic chondrodysplasia punctata.     

Proton MR spectroscopy features of normal appearing white matter in neurofibromatosis type 1

To determine whether differences exist between neurofibromatosis type 1 (NF1) patients with or without focal lesions and healthy normal volunteers in the metabolite ratios of normal appearing white matter, 27 patients with NF1 (with parenchymal lesion, MR positive, n: 17; without parenchymal lesions, MR negative, n: 10) and 20 healthy volunteers underwent MRI and short TE (31 ms) proton MR spectroscopy (MRS). In 17 patients with parenchymal lesions, 61 focal lesions were detected by MRI. MRS was performed from normal appearing frontal and posterior parietal white matter (FWM and PWM) in NF1 and from control groups. NAA/Cr, Cho/Cr and MI/Cr ratios were calculated. Significant increase in Cho/Cr and MI/Cr ratios were found in FWM and PWM in MR negative and positive groups when compared to control group. NAA/Cr ratio in MR positive group was significantly decreased in FWM compared to control group. There were no significant differences between FWM and PWM in all metabolite ratios of MR negative group. MI/Cr ratio in MR positive group was significantly elevated in PWM compared to FWM. Metabolite changes detected by MRS could indicate demyelination and gliosis in normal appearing white matter in all NF1 patients, and additionally neuroaxonal damage in the FWM of NF1 patients with focal lesions. For that reason, in the clinical evaluation and follow-up of these patients MRS features of normal appearing white matter should be considered in addition to focal lesions.     

Experiences with two detached eddy simulation approaches through use of a high-order finite volume solver

In the present study, two advanced detached eddy simulation (DES) approaches, shear-layer-adapted delayed DES and zonal DES in mode II, which are known to help transition from RANS to LES mode, are employed in various flow problems in conjunction with a high-order finite volume solver. The numerical scheme, being only applicable on structured grids, has low-dissipation and low-dispersion features. Such features benefit mostly in the LES mode, minimizing the interference of numerical diffusion with subgrid eddy viscosity. First, corresponding subgrid models are validated via decaying homogeneous turbulence benchmark case. Then, a channel flow problem is chosen to examine these models in attached flow situations. Finally, flow around an airfoil at low Reynolds number is solved using the shear-layer-adapted delayed DES approach only, in an aim to obtain trailing-edge noise spectrum at an observer location. Despite some log-layer mismatch over turbulent boundary layers, which is typical of most DES methods, the combined application of high-resolution numerical method and advanced DES approaches, which are implemented on a stabilized Spalart-Allmaras turbulence model, shows merit in resolution of turbulence in regions of interest.     

Solid phase extraction of Pd(II) on a newly synthesized chelating resin prior to determination by flame atomic absorption spectrometry

A new solid phase extraction method for the separation and preconcentration of Pd(II) was developed. As solid phase material, a new chelating polymer, poly [N-(4-bromophenyl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid - co-divinylbenzene] was synthesized. The parameters such as the effect of pH, eluent type, volume and concentration, flow rate of sample solution, sample volume and effect of interfering ions for the preconcentration of Pd(II) were investigated. The optimum pH was found to be 9. Eluent for quantitative elution was 10 mL of 1 mol L^?1 HCl. The preconcentration factor of the method was 75. At optimum conditions, the recovery for Pd(II) was found to be 101?±?4%. The limit of detection (3σ) was 1.1?µg L^?1. The method was applied to the determination of palladium in tap water and converter samples with satisfactory results.     

On the fundamental equations of electromagnetoelastic media in variational form with an application to shell/laminae equations

The fundamental equations of elasticity with extensions to electromagnetic effects are expressed in differential form for a regular region of materials, and the uniqueness of solutions is examined. Alternatively, the fundamental equations are stated as the Euler–Lagrange equations of a unified variational principle, which operates on all the field variables. The variational principle is deduced from a general principle of physics by modifying it through an involutory transformation. Then, a system of two-dimensional shear deformation equations is derived in differential and fully variational forms for the high frequency waves and vibrations of a functionally graded shell. Also, a theorem is given, which states the conditions sufficient for the uniqueness in solutions of the shell equations. On the basis of a discrete layer modeling, the governing equations are obtained for the motions of a curved laminae made of any numbers of functionally graded distinct layers, whenever the displacements and the electric and magnetic potentials of a layer are taken to vary linearly across its thickness. The resulting equations in differential and fully variational, invariant forms account for various types of waves and coupled vibrations of one and two dimensional structural elements as well. The invariant form makes it possible to express the equations in a particular coordinate system most suitable to the geometry of shell (plate) or laminae. The results are shown to be compatible with and to recover some of earlier equations of plane and curved elements for special material, geometry and/or effects.     

EPR study of radiation damage in gamma-irradiated 3-nitroacetophenone single crystal

This paper presents the results of the electron paramagnetic resonance (EPR) study of the anion radical formed from 3-nitroacetophenone (C₈H₇NO₃) (3NAP) single crystal, by gamma irradiation. The EPR spectra of gamma-irradiated single crystals of 3NAP have been recorded at 10-degree intervals for different orientations of crystals in a magnetic field, at room temperature. The EPR analysis of gamma-irradiated crystals of 3NAP has shown that the radiation damage center produced by gamma irradiation is the carbon-centered 3NAP anion radical. One-electron reduction of 3NAP results in general bond loosening. The single crystals have been investigated between 120 and 450?K. The spectra have been found to be temperature-dependent. The EPR parameters of the 3NAP anion radical have been evaluated.     

The investigations on K and L X-ray fluorescence parameters of gold compounds

The study aimed to determine the chemical effects on the K and L X-ray intensity ratios and the K and L X-ray production cross sections for gold compounds. The K shell fluorescence yields and L shell average yields were also investigated. The samples were excited by 59.5 keV γ-rays from an ²⁴¹Am annular radioactive source and 123.6 keV γ-rays from a ⁵⁷Co annular radioactive source. K and L X-rays emitted from samples were counted by an Ultra-LEGe detector with a resolution of 0.150 keV at 5.9 keV. The experimental values were compared with theoretical, the semi-empirical and other experimental values.