Residual stress relaxation in cleaved fibers

The relaxation of intrinsic stress, in particular, the frozen-in stress in the vicinity of the cleaved end of optical fibers is studied. Stress distribution is measured at many cross sections along the fiber using a conventional polariscopic stress measurement technique. Fibers drawn with different tensions are used to study the dependence of stress release on the draw tension. From the measured frozen-in stress, the frozen-in viscoelastic stress is studied through the calculation of mean axial stress. The dependence of the release of viscoelastic stress on the draw tension is established. Though the presence of residual stress shows a sudden decline as a consequence of cleaving, it is not completely released at the cleaved end and is explained by the frozen-in viscoelastic stress in the optical fiber. The study shows that the relaxation of frozen-in viscoelastic stress near the cleaved fiber end is only a fraction of the amount of total residual stress in the optical fiber.     

Traceless polymer-supported divergent synthesis of quinoxalinones by microwave irradiation

A novel protocol for rapid assemble of quinoxalinones framework has been demonstrated. This method incorporated with soluble polymer support provides a convenient approach for diversification of heterocyclic compounds and for easy purification via facile precipitation from reaction matrix. The key transformation of this study involves in situ reduction of aromatic nitro compound, tandem lactamization concomitant with traceless cleavage of the polymer support under microwave irradiation in a one-pot fashion. Moreover, forward synthetic routes were introduced to maximize complexity of the master intermediate on which further chemical elaboration was applied. The strategy is envisaged to apply for establishment of drug-like small-molecule libraries for high-throughput screening.     

Novel saccharinate-bridged palladium complexes for efficient C-O bond activation displaying promising luminescence properties

The synthesis of mono- and dinuclear cyclometallated palladium(II) complexes with deprotonated saccharinate ligands displaying different coordination modes is described. The new compounds were prepared by direct reaction between saccharine and the corresponding hydroxo-complexes [{Pd(μ-OH)(C^N)}(2)] (C^N = 2-(2-pyridyl)phenyl (Phpy) I; = 7,8-benzoquinolyl (Bzq) II), showing a general formula [{Pd(μ-sac)(C^N)}(2)] with saccharinate 1 displaying a bridging -NCO-coordination mode. Bridge splitting with neutral ligands (L = pyridine (py) 2, quinoline (quinol) 3 or acridine (acrid) 4) yielded new mononuclear derivatives with saccharinate acting as an N-monodentated ligand. Structural characterization by X-ray diffraction of complexes I1, I2 and II2 confirmed the proposed formulae. All complexes emit in the solution and solid state at room temperature. Emission features between 640-680 nm in the solid state for complexes I1 and II1 are significantly red-shifted if compared to the emission in solution. These broad emissions are consistent with the simultaneous presence of (3)ππ* and (3)MMLCT transitions indicating the existence of a strong intramolecular Pd-Pd ground state interaction. The dimeric complexes have also shown to catalyze Suzuki-Miyaura cross-coupling of coumaryl tosylate and aryl boronic acids under phosphine-free conditions. Initial studies suggest the involvement of palladium nanoparticles, which has been further investigated using mercury-drop test and poisoning experiments.     

Mutually immiscible ionic liquids

This work presents the novel discovery of room-temperature ionic liquids that are mutually immiscible, some of which are also immiscible with solvents as diverse as water and alkanes; an archetypal biphasic system is trihexyltetradecylphosphonium chloride with 1-alkyl-3-methylimidazolium chloride (where the alkyl group is shorter than hexyl).     

Synthesis and antibacterial activity of a series of 2-trifluoromethylbenzimidazole-thiazolidinone derivatives

A series of 2-phenyl-3-(2-(trifluoromethyl)-1H-benzoimidazol-6-yl)thiazolidin-4-one derivatives were synthesized from p-nitro-o-phenylenediamine in a three-step reaction. Their structures were elucidated by NMR and mass spectral data. The synthesized compounds showed excellent antibacterial activity ranging from 3-fold, to greater than 100-fold higher than the standard antibiotics, ciprofloxacin and levofloxacin. Compounds 3d (2′-Br), 3j (4′-Br), and 3l (4′-NO₂) displayed a broad spectrum of activity against the strains tested (0.14–38.33 μM). The brominated derivatives 3d and 3j showed excellent activity against the Gram-positive bacterial strains (MBC between 0.12 and 35.46 μM), while the nitro derivative 3l showed excellent activity against all four Gram-negative strains tested (MBC between 0.15 and 9.58 μM).     

Hierarchical routing over dynamic wireless networks

The topology of a mobile wireless network changes over time. Maintaining routes between all nodes requires the continuous transmission of control information, which consumes precious power and bandwidth resources. Many routing protocols have been developed, trading off control overhead and route quality. In this paper, we ask whether there exist low‐overhead schemes that produce low‐stretch routes, even in large networks where all the nodes are mobile. We present a scheme that maintains a hierarchical structure within which constant‐stretch routes can be efficiently computed between every pair of nodes. The scheme rebuilds each level of the hierarchy periodically, at a rate that decreases exponentially with the level of the hierarchy. We prove that this scheme achieves constant stretch under a mild smoothness condition on the nodal mobility processes. Furthermore, we prove tight bounds for the network‐wide control overhead under the additional assumption of the connectivity graph forming a doubling metric space. Specifically, we show that for a connectivity model combining the random geometric graph with obstacles, constant‐stretch routes can be maintained with a total overhead of bits of control information per time unit. © 2015 Wiley Periodicals, Inc. Random Struct. Alg., 47, 669–709, 2015     

Cu–Cl Thermochemical Water Splitting Cycle: Probing Temperature-Dependent CuCl2 Hydrolysis and Thermolysis Reaction Using In Situ XAS

Journal of Thermal Analysis and Calorimetry - Recently, we reported detailed investigations on a hydrolysis step of Cu–Cl thermochemical cycle (Singh et al. in Int J Energy Res...     

Correction to: Brönsted acid hydrotrope combined catalysis in water: a green approach for the synthesis of indoloquinoxalines and bis-tetronic acids

Research on Chemical Intermediates - A correction to this paper has been published: https://doi.org/10.1007/s11164-021-04495-7     

Introduction of Octadecyl-Bonded Porous Particles in 3D-Printed Transparent Housings with Multiple Outlets

Chromatographia - Microfluidic devices for comprehensive three-dimensional spatial liquid chromatography will ultimately require a body of stationary phase with multiple in- and outlets. In the...     

Algebraic and geometric intersection numbers for free groups

We show that the algebraic intersection number of Scott and Swarup for splittings of free groups coincides with the geometric intersection number for the sphere complex of the connected sum of copies of S²×S¹.