A theoretical analysis of acoustic microscopy with converging acoustic beams

A theoretical analysis is carried out to synthesize acoustic material signatures (AMS) of solid plates immersed in water. The distinctive feature of this analysis is that it avoids three major simplifying assumptions of the presently available techniques, which are, paraxial approximation, assumption of perfect reflection and Gaussian summation of the incident field. Presently available techniques can avoid some but not all of these simplifying assumptions for computing the AMS. In this paper the analysis is carried out for lowfrequency acoustic waves generated by a cylindrical transducer without a lens rod. Reasons for these changes in the conventional acoustic microscope geometry is given. The AMS is synthesized for an aluminium plate in presence as well as in absence of water on its one side. As expected a significant difference is observed between the signatures generated under these two situations.     

A factorization theorem for a certain class of graphs

In this note we give a necessary and sufficient condition for factorization of graphs satisfying the “odd cycle property”. We show that a graph G with the odd cycle property contains a [k_i] factor if and only if the sequence [H]+[k_i] is graphical for all subgraphs H of the complement of G.A similar theorem is shown to be true for all digraphs.     

Bounds on the number of disjoint spanning trees

It is shown that an n-edge connected graph has at least ?$\text{(n ? 1)}\text{2}$? pairwise edge-disjoint spanning trees. This bound is best possible in general. A maximal planar graph with four or more vertices contains two edge-disjoint spanning trees. For a maximal toroidal graph, this number is three.     

Detection of kissing bonds by Lamb waves

Closed cracks under compressive normal stresses are difficult to detect by the conventional ultrasonic techniques. When the crack surfaces stay in very close contact with each other then the bond between the two surfaces of the crack is called a ‘kissing bond’. This is a very dangerous bond. Catastrophic failures can result if the system is subjected to crack opening normal stresses or shear stresses. When the crack surfaces are smooth then kissing bonds cannot transmit shear stress very well but can carry compressive normal stress, these bonds are called ‘slip bonds’. Conventional P-wave scans (C-scan or A-scan) are based on the assumptions that P-waves are reflected by the defective interface. However, an interface subjected to a large compressive stress cannot reflect P-waves effectively, hence these bonds remain invisible to the conventional P-wave based C-scan or A-scan techniques. In this paper it is shown that the kissing bonds can be effectively detected by some leaky Lamb mode. Theoretical and experimental results are presented to show that using the Lamb waves is an effective way of detecting kissing bonds.     

Orientational order in liquid crystals exhibited by some binary mixtures of rod-like and bent-core molecules

We report measurements of the temperature variations of the optical birefringence in the nematic (N) and partial bilayer SmA (SmA_d) phases in 4-n-octyloxy 4^′ -cyanobiphenyl made of rod-like (R) molecules and five mixtures of this compound with 1,3-phenylene bis[4-(3-methylbenzoyloxy)] 4^′ -n- dodecylbiphenyl 4^′ -carboxylate, made of bent-core (BC) molecules. The birefringence decreases with the concentration x of the BC molecules but the macroscopic order parameter initially decreases upto 11mol% of BC molecules and subsequently increases with x . This is attributed to the possible formation of polar clusters of BC molecules. Orientation of BC molecules changes between the N and SmA_d phases and the birefringence data in the two phases imply that the kink angle of the BC molecules is ∼ 90^° rather than ∼ 110^° as obtained from calculations which minimize the energy of the molecule. IR spectroscopic measurements on the mixture with 11mol% of BC molecules have been used to estimate the molecular order parameter S of the R molecules, and to provide additional support for a relatively small kink angle of BC molecules.     

Numerical simulation of electromagnetic acoustic transducers using distributed point source method

In spite of many advances in analytical and numerical modeling techniques for solving different engineering problems, an efficient solution technique for wave propagation modeling of an electromagnetic acoustic transducer (EMAT) system is still missing. Distributed point source method (DPSM) is a newly developed semi-analytical technique developed since 2000 by Placko and Kundu (2007) [12] that is very powerful and straightforward for solving various engineering problems, including acoustic and electromagnetic modeling problems. In this study DPSM has been employed to model the Lorentz type EMAT with a meander line and flat spiral type coil. The problem of wave propagation has been solved and eddy currents and Lorentz forces have been calculated. The displacement field has been obtained as well. While modeling the Lorentz force the effect of dynamic magnetic field has been considered that most current analyses ignore. Results from this analysis have been compared with the finite element method (FEM) based predictions. It should be noted that with the current state of knowledge this problem can be solved only by FEM.     

Nature of Nonlocality in Triangle Network based on Elegant Joint Measurement

Defining nonlocality in a no-input closed quantum network scenario is a new area of interest nowadays. Gisin, in [Entropy 21, 325 (2019)], proposed a possible condition for non-tri-locality of the trivial no-input closed network scenario, triangle network, by introducing a new kind of joint measurement bases and a probability bound. In [npj Quantum Information (2020) 6:70] they found a shred of numerical evidence in support of Gisin's probability bound. Now based on that probability bound, it finds the nature of the correlation in a triangle network scenario. This study observes how far the probability lies from that Gisin's bound with every possible combination of entangled and local pure states distributed from three independent quantum sources. Here, it uses the generalized Elegant Joint Measurements bases for each party and find that there is a dependency of non-locality on the entanglement of these joint measurement bases. It also checks the probability bound for the polygon structure.     

Chinese Oak Tasar Silkworm Antheraea pernyi Silk Proteins: Current Strategies and Future Perspectives for Biomedical Applications

Chinese nonmulberry temperate oak tasar/tussah, Antheraea pernyi (Ap) silk is a natural biopolymer that has attracted considerable attention as a biomaterial. The proteinaceous components of Ap silk proteins, namely fibroin and sericin may represent an alternative over mulberry Bombyx mori silk proteins. In fact, the silk fibroin (SF) of Ap is rich in Arginyl‐Glycyl‐Aspartic acid (RGD) peptides, which facilitate the adhesion and proliferation of various cell types. The possibility of processing Ap silk proteins into different distinct 2D‐ and 3D‐based matrices is described in earlier studies, such as membranes, nanofibers, scaffolds, and micro/nanoparticles, contributing to a different rate of degradation, mechanical properties, and biological performance useful for various biomedical applications. This review summarizes the current advances and developments on nonmulberry Chinese oak tasar silk protein (fibroin and sericin)‐based biomaterials and their potential uses in tissue engineering, regenerative medicine, and therapeutic delivery strategies.     

A metabolically engineered spin-labeling approach for studying glycans on cells

Metabolic glycan engineering (MGE) coupled with nitroxide spin-labeling (SL) was utilized to investigate the heterogeneous environment of cell surface glycans in select cancer and normal cells. This approach exploited the incorporation of azides into cell surface glycans followed by a click reaction with a new nitroxide spin label. Both sialic acid and N-acetylglucosamine (GlcNAc) were targeted for spin labelling. Although each of these moieties experiences a diverse and heterogeneous glycan environment, their EPR spectra and hence mobility are both characterized as a linear combination of two distinct spectra where one component reflects a highly mobile or uncrowded micro-environment with the second component reflecting more restricted motion, reflective of increased crowding and packing within the glycocalyx. What differs among the spectra of the targeted glycans is the relative percentage of each component, with sialic acid moieties experiencing on average an ∼80% less crowded environment, where conversely GlcNAc/GalNAz labeled sites reported on average a ∼50% more crowded environment. These distinct environments are consistent with the organization of sugar moieties within cellular glycans where some residues occur close to the cell membrane/protein backbone (i.e. more restricted) and others are more terminal in the glycan (i.e. more mobile). Strikingly, different cell lines displayed varied relative populations of these two components, suggesting distinctive glycan packing, organization, and composition of different cells. This work demonstrates the capability of SDSL EPR to be a broadly useful tool for studying glycans on cells, and interpretation of the results provides insights for distinguishing the differences and changes in the local organization and heterogeneity of the cellular glycocalyx.

Metabolic glycan engineering (MGE) coupled with nitroxide spin-labeling (SL) was utilized to investigate the heterogeneous environment of cell surface glycans in select cancer and normal cells.     

Birnbaum‐Saunders distribution: A review of models,analysis, and applications

Birnbaum and Saunders introduced a two‐parameter lifetime distribution to model the fatigue life of a metal, subject to cyclic stress. Since then, extensive work has been done on this model providing different interpretations, constructions, generalizations, inferential methods, and extensions to bivariate, multivariate, and matrix‐variate cases. More than 200 papers and one research monograph have already appeared describing all these aspects and developments. In this paper, we provide a detailed review of all these developments and, at the same time, indicate several open problems that could be considered for further research.