Accurate estimates of asymptotic indices via fractional calculus

We devise a three-parameter random search strategy to obtain accurate estimates of the large-coupling amplitude and exponent of an observable from its divergent Taylor expansion, known to some desired order. The endeavor exploits the power of fractional calculus, aided by an auxiliary series and subsequent construction of Padé approximants. Pilot calculations on the ground-state energy perturbation series of the octic anharmonic oscillator reveal the spectacular performance.     

Small‐Angle Neutron Scattering Studies of Hemoglobin Confined Inside Silica Tubes of Varying Sizes

In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20–200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small‐angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si‐tube pore diameter. The high radius of gyration (R_g) and polydispersity of Hb in the 20 nm diameter Si‐tube indicates that Hb undergoes a significant amount of aggregation. However, for Si‐tube diameters greater or equal to 100 nm, the R_g of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (R_g of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native‐like non‐aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si‐tube size is a key parameter for protein stability and structure.     

Incorporation of Cell-Adhesive Proteins in 3D-Printed Lipoic Acid-Maleic Acid-Poly(Propylene Glycol)-Based Tough Gel Ink for Cell-Supportive Microenvironment

In extrusion-based 3D printing, the use of synthetic polymeric hydrogels can facilitate fabrication of cellularized and implanted scaffolds with sufficient mechanical properties to maintain the structural integrity and physical stress within the in vivo conditions. However, synthetic hydrogels face challenges due to their poor properties of cellular adhesion, bioactivity, and biofunctionality. New compositions of hydrogel inks have been designed to address this limitation. A viscous poly(maleate-propylene oxide)-lipoate-poly(ethylene oxide) (MPLE) hydrogel is recently developed that shows high-resolution printability, drug-controlled release, excellent mechanical properties with adhesiveness, and biocompatibility. In this study, the authors demonstrate that the incorporation of cell-adhesive proteins like gelatin and albumin within the MPLE gel allows printing of biologically functional 3D scaffolds with rapid cell spreading (within 7 days) and high cell proliferation (twofold increase) as compared with MPLE gel only. Addition of proteins (10% w/v) supports the formation of interconnected cell clusters (≈1.6-fold increase in cell areas after 7-day) and spreading of cells in the printed scaffolds without additional growth factors. In in vivo studies, the protein-loaded scaffolds showed excellent biocompatibility and increased angiogenesis without inflammatory response after 4-week implantation in mice, thus demonstrating the promise to contribute to the printable tough hydrogel inks for tissue engineering.     

Improved lithium cyclability and storage in mesoporous SnO2 electronically wired with very low concentrations (≤1 %) of reduced graphene oxide

On the wire: Mesoporous tin dioxide (SnO(2)) wired with very low amounts (≤1?%) of reduced graphene oxide (rGO) exhibits a remarkable improvement in lithium-ion battery performance over bare mesoporous or solid nanoparticles of SnO(2). Reversible lithium intercalation into SnO(2)/SnO over several cycles was demonstrated in addition to conventional reversible lithium storage by an alloying reaction.     

Synthesis of 3,4-dihydropyridin-2-one derivatives in convergent mode applying bio catalyst vitamin B1 and polymer supported catalyst PEG-SO3H from two different sets of building blocks

Two highly efficient, green protocols have been developed for the synthesis of 3,4-dihydropyridin-2-one derivatives from different starting materials exploring two reaction specific catalysts, vitamin B₁ (VB₁), and PEG-SO₃H. VB₁ catalyzed simple and convenient protocol has been developed for the synthesis of 3,4-dihydropyridin-2-one derivatives by the installation of aldehyde, cyanoacetamide, and 1,3-dicarbonyl compounds. In addition, 3,4-dihydropyridin-2-one derivatives have also been synthesized by simply combining aldehyde, malononitrile, and 1,3-dicarbonyl compounds via the formation of 4H-pyran nucleus and PEG-SO₃H catalyzed one-pot rearrangement.     

Conformational specificity of non-canonical base pairs and higher order structures in nucleic acids: crystal structure database analysis

Non-canonical base pairs contribute immensely to the structural and functional variability of RNA, which calls for a detailed characterization of their spatial conformation. Intra-base pair parameters, namely propeller, buckle, open-angle, stagger, shear and stretch describe structure of base pairs indicating planarity and proximity of association between the two bases. In order to study the conformational specificities of non-canonical base pairs occurring in RNA crystal structures, we have upgraded NUPARM software to calculate these intra-base pair parameters using a new base pairing edge specific axis system. Analysis of base pairs and base triples with the new edge specific axis system indicate the presence of specific structural signatures for different classes of non-canonical pairs and triples. Differentiating features could be identified for pairs in cis or trans orientation, as well as those involving sugar edges or C-H-mediated hydrogen bonds. It was seen that propeller for all types of base pairs in cis orientation are generally negative, while those for trans base pairs do not have any preference. Formation of a base triple is seen to reduce propeller of the associated base pair along with reduction of overall flexibility of the pairs. We noticed that base pairs involving sugar edge are generally more non-planar, with large propeller or buckle values, presumably to avoid steric clash between the bulky sugar moieties. These specific conformational signatures often provide an insight into their role in the structural and functional context of RNA.     

Small amplitude, free longitudinal vibrations of a load on a finitely deformed stress-softening spring with limiting extensibility

A constitutive theory for a general class of incompressible, isotropic stress-softening, limited elastic rubberlike materials is introduced. The model is applied to study the small amplitude, free longitudinal vibrational frequency of a load about a suspended static equilibrium stretch of a finitely deformed, stress-softening spring with limiting extensibility. A number of physical results, including bounds on the frequency, are reported. It is proved, for example, that the normalized vibrational frequency for the ideally elastic neo-Hookean oscillator is a lower bound for the normalized frequency of every incompressible, isotropic stress-softening, limited elastic oscillator within the general class. All results are illustrated for the special limited elastic Gent and the purely elastic Demiray biomaterial models, both with stress-softening characterized by a Zú?iga–Beatty front factor damage function. The results for both stress-softening models are compared with experimental data for several gum rubbers and thoracic aortic tissue provided by others; and, overall, it is found that the stress-softening, limited elastic Gent model best characterizes the data.     

Stability of an internally damped non-ideal flexible spinning shaft

The stability domain of an internally damped flexible spinning shaft, which is driven by a non-ideal source, is studied in this paper. It is found that the higher transverse modes may become unstable before the lower ones under certain conditions. In particular, we find the entrainment of the shaft spinning speed at specific values corresponding to the lowest stability threshold among all transverse modes. Moreover, the steady state amplitude of the transverse vibrations when the shaft spinning speed is stuck at the stability threshold is determined analytically. The analytical results thus obtained are validated with numerical simulations.