Uniqueness in an integral geometry problem and an inverse problem for the kinetic equation

In this paper, we discuss the uniqueness in an integral geometry problem along the straight lines in a strongly convex domain. Our problem is related with the problem of finding a Riemannian metric by the distances between all pairs of the boundary points. For the proof, the problem is reduced to an inverse source problem for a kinetic equation and then the uniqueness theorem is proved using the tools of Fourier analysis.     

Forward kinematics analysis of the 6-3 SPM by using neural networks

A feed-forward neural network has been trained using backpropagation algorithm to solve the forward kinematics problem of the 6-3 Stewart Platform Mechanism (SPM). The forward kinematics problem of the SPM does not have a unique solution since it involves solving a polynomial of order 16. Purely translational, purely rotational and general spatial data sets have been used in training and testing, and then an optimization procedure has been applied to fine-tune the solution. The method yields results fast and accurate enough such that it can be used instead of a gyro and a position sensor for real time control of the mechanism.     

A Tandem Mass Spectrometric Method for Singlet Oxygen Measurement

Singlet oxygen, a harmful reactive oxygen species, can be quantified with the substance 2,2,6,6‐tetramethylpiperidine (TEMP) that reacts with singlet oxygen, forming a stable nitroxyl radical (TEMPO). TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we designed an ultra–high‐performance liquid chromatographic—tandem mass spectrometric (UHPLC‐ESI‐MS/MS) quantification method for TEMPO and showed that the method based on multiple reaction monitoring (MRM) can be used for the measurements of singlet oxygen from both nonbiological and biological samples. Results obtained with both UHPLC‐ESI‐MS/MS and EPR methods suggest that plant thylakoid membranes produce 3.7 × 10^?7 molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000 μmol m^?2 s^?1.     

Compactifications whose remainders are zero dimensional and retract

LetX be a locally compact non compact space. Necessary and sufficient conditions forfX/X to be a retract offX are given wherefX is the Freudenthal compactification ofX. LetX be a locally compact and zero dimensional space,m be any cardinal number andJ be a set with cardinalitym. It is proved thatX has a dyadic family of powerm if and only if there exist and compactificationY ofX such thatY/X=2 ^J andY/X is a retract ofY.     

Implicit solvent coarse‐grained model of polyamidoamine dendrimers: Role of generation and pH

Highly branched polymers such as polyamidoamine (PAMAM) dendrimers are promising macromolecules in the realm of nanobiotechnology due to their high surface coverage of tunable functional groups. Modeling efforts of PAMAM can provide structural and morphological properties, but the inclusion of solvents and the exponential growth of atoms with generations make atomistic simulations computationally expensive. We apply an implicit solvent coarse‐grained model, called the Dry Martini force field, to PAMAM dendrimers. The reduced number of particles and the absence of a solvent allow the capture of longer spatiotemporal scales. This study characterizes PAMAM dendrimers of generations one through seven in acidic, neutral, and basic pH environments. Comparison with existing literature, both experimental and theoretical, is done using measurements of the radius of gyration, moment of inertia, radial distributions, and scaling exponents. Additionally, ion coordination distributions are studied to provide insight into the effects of interior and exterior protonation on counter ions. This model serves as a starting point for future designs of larger functionalized dendrimers. © 2015 Wiley Periodicals, Inc.     

Simultaneous quantification of acylated and desacylated ghrelin in biological fluids

This study reports simultaneous quantification of both acylated and desacylated forms of ghrelin in biological samples, utilizing a reverse-phase high-performance liquid chromatography (HPLC) system. The HPLC assay was also compared with RIA assays in use. Biological samples (serum, saliva, urine, milk) known for the presence of ghrelin were collected from a total of eight post-partum women and eight male volunteers. Analysis of ghrelin with HPLC was also validated for linearity, precision, detection limit and accuracy. An elution time of 6 min was observed for pure (commercial) desacylated human ghrelin and for the same form of the hormone from all body fluids studied. The elution time for acylated pure human ghrelin and that in body fluids, however, was around 16 min. The mean recovery rate was over 90% for both forms with no significant interference. The lowest detectable levels for acylated and desacylated ghrelin with the method used here were 11 (+/-2) and 14 (+/-3) pg mL(-1), respectively. Given its simplicity, accuracy, time and cost-effectiveness, the HPLC method described here for determination of two forms of ghrelin (active and inactive) might prove useful for certain diagnostic purposes.     

Valence band offset of MgO/TiO2 (rutile) heterojunction measured by X-ray photoelectron spectroscopy

The valence band offset (VBO) of MgO/TiO₂ (rutile) heterojunction has been directly measured by X-ray photoelectron spectroscopy. The VBO of the heterojunction is determined to be 1.6 ± 0.3 eV and the conduction band offset (CBO) is deduced to be 3.2 ± 0.3 eV, indicating that the heterojunction exhibits a type-I band alignment. These large values are sufficient for MgO to act as tunneling barriers in TiO₂ based devices. The accurate determination of the valence and conduction band offsets is important for use of MgO as a buffer layer in TiO₂ based field-effect transistors and dye-sensitized solar cells.     

An attempt of improving polyester inkjet printing performance by surface modification using β‐cyclodextrin

To improve the sharpness and the color yield of polyester fabrics with water‐based pigment inkjet printing, surface modification was proceeded using β‐cyclodextrin and citric acid. Fabrics were modified in the solution of β‐cyclodextrin with the concentration 100g/L and citric acid 100g/L. The line width and image area of printed patterns, which could evaluate the printing performances, on the modified polyester fabric were decreased by 77% and 62% in comparison with that of the control, respectively. The color yield characterized by the K/S value was enhanced by 47%. Scanning electron microscope and atomic force microscope images confirmed that the capillary effect was decreased and the surface roughness was increased after the surface modification. The microscope images of the printed patterns clearly showed that the sharpness and the color yield were improved. Thereby, β‐cyclodextrin modification offered a potential way to polyester pretreatment for pigment inkjet printing. Copyright © 2012 John Wiley & Sons, Ltd.     

An analytic and numerical solution with spectral Green's function method for transport equation in spherical geometry

Since in many cases curvilinear geometry is more appropriate than cartesian geometry for precise modeling of the complex systems for reactor calculation, we have developed the spectral Green's function (SGF) method which is employed to obtain angular and scalar flux distributions in heterogeneous sphere geometry with isotropic scattering. In this study, we showed that the neutron transport problems of homogeneous spheres could be reduced to the solution of plane geometry equation.Finally, some results are discussed and compared with those already obtained by diamond difference scheme to test the accuracy of the results. The agreement is satisfactory. SGF method is very suitable for the numerical solution of the neutron transport equation with isotropic scattering.     

Some applications of perturbed angular correlation and positron annihilation to materials science

The perturbed angular correlation (PAC) and positron annihilation spectroscopy (PAS) that use nuclear probes to characterize the micro-structure of materials are briefly described. Three examples are given to show their partial applications. The first example is the study of radiation damage in Si irradiated by fast neutrons of 1.45·10²⁰ cm⁻² and ¹⁷⁸W heavy ions of 5·10¹¹ cm⁻², respectively. The PAC and PAS measurements all show that the monovacancy-oxygen complexes and divacancies and divacancy-oxygen complexes were produced by the irradiations, and quadrivacancies and quadrivacancy-oxygen complexes were formed during thermal annealing. The second one illustrates the investigation of high T _c superconductivity for YBaCuO. The PAS experiment found the charge transfer during the superconducting trasition. The PAC measurement suggested a transition of two-to one-dimensional Cu-O-Cu chain structure at the superconducting trasition temperature T _c , which favors the charge transfer from the CuO layer to the CuO chain in YBaCuO. The third one is for investigating the hydrogen behavior in Pd_0.75Ag_0.25-H _x as functions of temperature from 77 K to RT and hydrogen concentration (x) from 0 to 35 at.%. The PAC and PAS results exhibit that hydrogen atoms are congregated into the hydrogen bubbles and the hydrogen bubbles grow with the increasing of the hydrogen concentration in Pd_0.75Ag_0.25-H _x . These examples demonstrate that the PAC and PAS techniques are very sensitive and powerful tools in materials science, which can well investigate phenomena in materials on atomic scale.