Comparative studies of chemically synthesized polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid

Polyaniline and poly(o-toluidine) doped with p-toluene sulphonic acid (p-TSA) were synthesized by in situ chemical polymerization method using ammonium per sulphate as an oxidizing agent. This is a novel polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV-Vis and FT-IR spectroscopy, SEM, elemental analyzer, TGA/DSC and conductivity measurements. Thermal analysis shows that poly(o-toluidine) is less thermally stable compared to polyaniline. The less conductivity in poly(o-toluidine) is due to the cumulative steric as well as electronic effect of the bulky methyl substituent present on the benzene ring. High temperature conductivity measurements show ‘thermal activated behavior’.     

Arzela-Ascoli theorem is stable

A quantitative version of the Arzela-Ascoli theorem is proved. This version implies that a closed and bounded subset of C(X) is nearly compact, if and only if, it is nearly equicontinuous.     

Concentration and refractive index sensor for methanol using short period grating fiber

This paper reports on the spectral (response) characteristics of fiber Bragg grating sensor to various methanol concentrations. A complete experimental analysis on the use of Ge-B co-doped fiber Bragg grating sensor for a concentration and refractive index measurement is presented. The spectral changes in the grating response due to variation of concentration have been investigated in relation to new sensing configurations. The results also highlight the possibilities of using the sensor for medical and biological applications.     

Electron spin resonance from annealed titania nanotubes

Titania nanotubes were prepared using a hydrothermal method. Hydrogen titanate nanotubes (H-TNTs) with an anatase phase changed to anatase nanocrystals at about 500 °C, and then a rutile structure at ∼800 °C. A sharp and symmetrical electron spin resonance (ESR) signal (g=2.003), attributed to a single-electron-trapped oxygen-vacancy (SETOV), was obtained at the annealed H-TNTs (T<500 °C). The SETOV signal increased and maximized remarkably at about 400–500 °C. Then, the nanotube structure appeared to be demolished. Yet, when the vacuum-heated H-TNTs were sealed in N₂ or Ar ambient, some additional ESR signals appeared besides the SETOV signal. The broad asymmetric ESR signal (g=1.98) was attributed to a surface oxygen vacancy related to the Ti³⁺ sites in a reduced TiO₂ matrix. The vacuum-heated sodium titanate nanotubes (Na-TNTs) showed only the SETOV signal (T<500 °C). PACS 61.46.Fg; 61.72.Ji; 76.30.-v     

Two-day appointment scheduling with patient preferences and geometric arrivals

We consider an appointment system where the patients have preferences about the appointment days. A patient may be scheduled on one of the days that is acceptable to her, or be denied appointment. The patient may or may not show up at the appointed time. The net cost is a convex function of the actual number of patients served on a given day. We study the optimal scheduling policy that minimizes the long-run average cost and study its structural properties. We advocate an index policy, which is easy to implement, performs well in comparison with other heuristic policies, and is close to the optimal policy.     

NHC-Pd complex heterogenized on graphene oxide for cross-coupling reactions and supercapacitor applications

N-heterocyclic carbene (NHC)-palladium(II) complex (GO@NHC-Pd) was synthesized on graphene oxide (GO) support via a simple and cost-effective multistep approach. The spectroscopic, microscopic, thermal, and surface analyses of GO@NHC-Pd confirmed the successful formation of the catalyst. The investigation of catalytic activity showed that GO@NHC-Pd was very effective in Suzuki–Miyaura as well as Hiyama cross-coupling. Being heterogeneous in nature, GO@NHC-Pd was recovered after each reaction cycle easily and reused for up to nine and six cycles in Suzuki–Miyaura and Hiyama cross-coupling, respectively, without significant loss of activity. Further exploration of the supercapacitor performance of GO@NHC-Pd catalyst assembled in a two-electrode cell configuration shown a maximum attained capacitance of 105.26 F/g at a current density of 0.1 A/g with good cycling stability of 96.89% over 2,500 cycles.     

A sharp‐interface immersed boundary framework for simulations of high‐speed inviscid compressible flows

A new finite‐volume flow solver based on the hybrid Cartesian immersed boundary (IB) framework is developed for the solution of high‐speed inviscid compressible flows. The IB method adopts a sharp‐interface approach, wherein the boundary conditions are enforced on the body geometry itself. A key component of the present solver is a novel reconstruction approach, in conjunction with inverse distance weighting, to compute the solutions in the vicinity of the solid‐fluid interface. We show that proposed reconstruction leads to second‐order spatial accuracy while also ensuring that the discrete conservation errors diminish linearly with grid refinement. Investigations of supersonic and hypersonic inviscid flows over different geometries are carried out for an extensive validation of the proposed flow solver. Studies on cylinder lift‐off and shape optimisation in supersonic flows further demonstrate the efficacy of the flow solver for computations with moving and shape‐changing geometries. These studies conclusively highlight the capability of the proposed IB methodology as a promising alternative for robust and accurate computations of compressible fluid flows on nonconformal Cartesian meshes.     

Phase transition in Na2SO4: all five polymorphic transformations in DSC

In this investigation, we have characterized the Na₂SO₄ using differential scanning calorimetry (DSC). It is well known that Na₂SO₄ exhibits five polymorphs. However, the experimental evidence for all five polymorphs has never been observed in DSC. In this investigation, the five polymorphic transformations have been observed in heating cycle. Furthermore, the transition I–II is observed, which is not reversible. In addition, phase transition temperature for V→IV and IV→III transition appears to be much closed and may get unnoticed.