Crystal structure of a highly hydrated tristrontium phosphate,Sr9(PO4)6·16H2O

The crystal structure of a highly hydrated tristrontium phosphate, nonastrontium hexakis(phosphate) hexadecahydrate, Sr₉(PO₄)₆·16H₂O, has been determined by single crystal X-ray diffraction. The crystals are monoclinic,a=15.203(2),b=6.488(1),c=18.984(7) Å, =98.42(2)^o, space groupP2/c (No. 13),Z=2,V=1852.3 ų,d _c =2.951 Mg·m^–3. The structure was refined by full-matrix least-squares techniques toR=0.038,R _w =0.051, for 2329 reflections with I3(I). The structure can be described in terms of a layer-type arrangement parallel to (100). One layer consists of a compact assembly of columns of Sr and PO₄ ions in a pseudohexagonal arrangement resembling an apatitic structure. A second layer containing all the water molecules and one PO₄ ion that occupies the interstitial space may be referred to as the hydrated layer. The structure has an overall similarity to that of octacalcium phosphate and can be considered as a model for amorphous calcium phosphate.Certain commercial materials and equipment are identified in this paper to specify the experimental procedure. In no instance does such identification imply recommendation or endorsement by the National Institute of Standards and Technology or the ADA Health Foundation or that the material or equipment identified is necessarily the best available for the purpose.     

Integral invariants for non-barotropic flows in a four dimensional space time manifold

Properties of non-barotropic flows are described using Lie derivatives of differential forms in a Euclidean four dimensional space-time manifold. Vanishing of the Lie derivative implies that the corresponding physical quantity remains invariant along the integral curves of the flow. Integral invariants of non-barotropic perfect and viscous flows are studied using the concepts of relative and absolute invariance of forms. The four dimensional expressions for the rate of change of the generalized circulation, generalized vorticity flux, generalized helicity and generalized parity in the case of ideal and viscous non-barotropic flows are thereby obtained.     

Structural modifications of diamond like carbon films induced by MeV nitrogen ion irradiation

Diamond-like carbon (DLC) films were deposited on Si(1 0 0) substrates using plasma deposition technique. The deposited films were irradiated using 2 MeV N⁺ ions at fluences of 1×10¹⁴, 1×10¹⁵ and 5×10¹⁵ ions/cm². Samples have been characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Analysis of Raman spectra shows a gradual shift of both D and G band peaks towards higher frequencies along with an increase of the intensity ratio, I(D)/I(G), with increasing ion fluence in irradiation. These results are consistent with an increase of sp² bonding. XPS results also show a monotonic increase of sp²/sp³ hybridization ratio with increasing ion fluence. Plan view TEM images show the formation of clusters in the irradiated DLC films. HRTEM micrographs from the samples irradiated at a fluence of 5×10¹⁵ ions/cm² show the lattice image with an average interplanar spacing of 0.34 nm, revealing that the clusters are graphite clusters. The crystallographic planes in these clusters are somewhat distorted compared to the perfect graphite structure.     

Nonlocalized modulation of periodic reaction diffusion waves: The Whitham equation

In a companion paper, we established nonlinear stability with detailed diffusive rates of decay of spectrally stable periodic traveling-wave solutions of reaction diffusion systems under small perturbations consisting of a nonlocalized modulation plus a localized (L ¹) perturbation. Here, we determine time-asymptotic behavior under such perturbations, showing that solutions consist of a leading order of a modulation whose parameter evolution is governed by an associated Whitham averaged equation.     

A Review on Characterization Techniques for Carbon Quantum Dots and Their Applications in Agrochemical Residue Detection

Journal of Fluorescence - Carbon quantum dots (CQDs) have emerged as one of the most promising nanomaterials in the carbon nanostructures family in recent years due to their low toxicity, simple...     

Impact of glucose on the electrochemical performance of nano-LiCoPO4 cathode for Li-ion batteries

LiCoPO₄ nanoparticles were synthesized by standard and glucose-assisted sol–gel methods for use as cathodes in lithium-ion batteries. The effect of glucose on the characteristics of the formed LiCoPO₄ nanoparticles was investigated by TGA, XRD, and FESEM. The TGA results indicated gradual decomposition of glucose in the temperature range 400–700 °C. The XRD results showed olivine phases in addition to small traces of Co₃O₄ for samples calcined at 400 °C while pure olivine phases were confirmed for the 700 °C calcined samples. The addition of glucose strongly suggests promotion of LiCoPO₄ crystallization, as revealed by FESEM studies. The electrochemical measurements pertaining to LiCoPO₄ samples calcined at 400 °C suggested an enhancement of initial discharge capacity from 103.3 to 144.6 mAh/g for the standard and glucose-based electrodes, respectively. Further, the effects of conductive additive and excess lithium on the electrochemical performance of LiCoPO₄ have also been investigated.     

Percolation of even sites for random sequential adsorption

Consider random sequential adsorption on a red/blue chequerboard lattice with arrivals at rate 1 on the red squares and rate λ$\lambda$ on the blue squares. We prove that the critical value of λ$\lambda$, above which we get an infinite blue component, is finite and strictly greater than 1.     

Stability of periodic Kuramoto–Sivashinsky waves

In this note, we announce a general result resolving the long-standing question of nonlinear modulational stability, or stability with respect to localized perturbations, of periodic traveling-wave solutions of the generalized Kuramoto–Sivashinsky equation, establishing that spectral modulational stability, defined in the standard way, implies nonlinear modulational stability with sharp rates of decay. The approach extends readily to other second- and higher-order parabolic equations, for example, the Cahn Hilliard equation or more general thin film models.     

Oncologic applications of biophotonics

The understanding of various intrinsic photobiophysical processes has prompted researchers to develop different types of biodevices for health care. In the recent past, because of extensive contributions from various groups in the field of biophotonics, several important biomedical applications are emerging in the fields of both diagnostics and therapy. In this brief review, we discuss a few specific applications related to early detection and characterization of premalignant and malignant lesions using optical spectroscopic techniques, namely, fluorescence and Raman, and in management of cancer, the emerging scene of photodynamic therapy.     

Numerical study of vortex effects in superconducting microstrip lines

A high transition temperature superconducting microstrip structure is modeled using the theoretical approach developed by Coffey and Clem for elucidating the vortex effects in propagation. Impedance type Green’s functions are derived for the electric field around the strip and the propagation characteristics are computed for a wide range of applied field, reduced temperature and superconducting strip thickness in a Galerkin procedure. The increase of static field and temperature result in increased vortex motion, which in turn, causes a corresponding change in the propagation characteristics of the transmission line. Numerical results are presented for propagation parameters and quality factor.