Carbon dots with strong excitation-dependent fluorescence changes towards pH. Application as nanosensors for a broad range of pH

In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation–Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability.     

Designing of an efficient multi-aperture,edge pumped thin-disk laser

In this article the operation of a composite Yb:YAG/YAG asymmetric hexagonal thin disk laser is optimized. This structure consists an Yb:YAG thin sheet as laser material and a diffusion bonded undoped material on top of thin sheet. Three diodes are placed outside the asymmetric hexagonal shape disk, and the emitting light is coupled via three lens ducts through its three edges and propagates through the disk along the zigzag path and repeatedly passes the gain medium, thus pump uniformity and absorption efficiency are improved. A Monte Carlo ray tracing code and Finite Element Analysis is utilized for calculation of absorbed pump density and volume temperature distribution and also thermal and mechanical stresses, respectively. Finally the output power is calculated. The triplet designing parameters, namely absorbed power efficiency, absorption uniformity and temperature distribution are optimized. Results show this edge-facet pumped geometry is a high efficient configuration for thin gain lasers.     

The Effect of Space Dimensions on a Generalized Hydrogen-Atom Specific Heat in the Generalized Boltzmann-Gibbs Statistics

In this article, the effect of the space dimensions on the generalized hydrogen-atom specific heat in the generalized Boltzmann-Gibbs statistics is studied. The temperature dependence of the specific heat for a few different values of q and for different low space dimensions using Tsallis statistics is numerically calculated. The results indicate that for a fixed value of q, as the space dimension increases the temperature range where the specific heat has a nonzero value, decreases, while the general behavior of the specific heat does not show any change. Also, there exits a q-independent quantity related to two specific temperatures of the system which is almost linearly dependent on the space dimensions.     

Measuring Dirac CP-violating phase with intermediate energy beta beam facility

We find that spontaneously broken parity ( $P$ ) or left–right symmetry stabilizes dark matter in a beautiful way. If dark matter has a non-real intrinsic parity $\pm i$ (e.g. if it entails Majorana fermions), parity can ensure that it cannot decay to all normal particles with real intrinsic parities. However, if Majorana couplings are absent either in the lepton or the dark sector, $P$ symmetry can be redefined to remove relative non-real intrinsic phases. It is therefore predicted that neutrinos and dark matter fermions must have Majorana masses if dark matter is stable due to parity. The strong CP problem is solved by additionally imposing CP and including vectorlike fermions that help generate CP violation. If leptonlike heavy fermions are provided purely imaginary intrinsic parity phase, they do not couple to the usual leptons, and leptonic CP phases are not generated, which is a testable prediction. Experimentally if leptonic CP phases are not found (if they are consistent with $0$ or $\pi $ ) it can be evidence for the type of models in this work where CP is spontaneously or softly broken and there is also a second hidden or softly broken symmetry such as $P$ , $Z_2$ or $Z_4$ . However, leptonic CP violation can be present in closely related or some non-minimal versions of these models, such as by also including vectorlike leptons with real intrinsic parities.     

Mechanical buckling of a functionally graded cylindrical shell with axial and circumferential stiffeners using the third-order shear deformation theory

This paper deals with an analytical approach of the buckling behavior of a functionally graded circular cylindrical shell under axial pressure with external axial and circumferential stiffeners. The shell properties are assumed to vary continuously through the thickness direction. Fundamental relations and equilibrium and stability equations are derived using the third-order shear deformation theory. The resulting equations are employed to obtain the closed-form solution for the critical buckling loads. A simply supported boundary condition is considered for both edges of the shell. The comparison of the results of this study with those in the literature validates the present analysis. The effects of material composition (volume fraction exponent), of the number of stiffeners and of shell geometry parameters on the characteristics of the critical buckling load are described. The analytical results are compared and validated using the finite-element method. The results show that the inhomogeneity parameter, the geometry of the shell and the number of stiffeners considerably affect the critical buckling loads.     

Tensor Green Function for the System of Maxwell's Equations in a Layered Medium

A general method is considered for the construction of the tensor Green function for Maxwell's equations in a layered medium. An efficient algorithm for the evaluation of the tensor Green function is proposed. The properties of various components of the Green tensor are investigated.