Viscosity of multicomponent gas mixtures of polar gases

Summary The rigorous binary viscosity expression _mix as transformed to the form originally suggested by Sutherland is studied for mixtures involving polar gases. Any attempt to simplify the _ij of the Sutherland viscosity expression turns out to be only approximately successful. A relation for _ij / _ji is however derived, and the procedure suggested for computing _mix on this basis appears to be very successful. The _ij to a large extent are temperature and composition independent and it has been shown that this fact can be utilised with success for predicting _mix values at high temperatures.     

A Novel Electroanalytical Biosensor Based on ZIF-8/Acetylcholinesterase Bio-nanohybrids for Early Management of Hirschsprung Disease

Hirschsprung's disease (HD) is characterised by missing nerve cells in the colon of infants and children which results in strained bowel movement. Under such situations, undiagnosed and untreated cases often lead to a cascade of gastrointestinal infections eventually resulting in Hirschsprung-assisted enterocolitis which has significantly high mortality rate. This is further exacerbated by the absence of suitable, sensitive and efficient technologies to detect the pathological segment of the intestine, which could significantly reduce surgery duration in the operation theatre, as well as associated risks to patients. It therefore becomes a matter of extreme importance to develop a point-of-care platform for early and efficient management/identification of the occurrence of HD in neonates and older children during its onset, before it proves fatal with life-threatening outcomes. The present work reports an electrochemical enzymatic biosensor using Zeolitic Imidazolate Framework-8 (ZIF-8) modified with acetylcholinesterase enzyme (AchE), for detection of HD as a function of the key biomarker – acetylcholine. The developed sensor was initially characterized using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), while the analytical performance and insights onto interfacial redox kinetics were assessed using Differential Pulse Voltammetry (DPV) and EIS respectively. The sensor exhibited limit of detection and sensitivity of 0.19 μM and sensitivity of 0.42 μA/μM/mm² with a shelf life of 1 month, while remaining unperturbed in the presence of common interferants. The performance of developed sensor was also examined in spiked serum samples and was observed to yield a high degree of linearity.     

Characterization of the drag-reducing nature of long-chain polymer–water solutions through atomization

Inclusion of minute concentrations of elongated long chain polymers is known to exhibit drastic reduction in frictional losses for turbulent fluid flows. The polymer chains interact with solvent molecules to act as eddy stress absorbers causing reduction in drag and inducing the viscoelastic nature in the fluid layer. In this work, we propose a characterization method for viscoelastic behavior of polymer-water solutions using a spray atomization experiment. The methodology is demonstrated for polyacrylamide and polyethylene oxide-based aqueous solutions. The experimental technique assesses the nature of the fluid using a predefined parameter, impact ratio (R). Computational fluid dynamics simulations of spray atomization are performed to validate the experimental values of the impact ratio. The simulation results indicate coherence with the experimental data, and are concordant with the reported behavior of such solutions in the literature.     

Novel approach to 3,3-dimethyl-4-morpholino-3,4-dihydrocoumarins via hetero-Diels–Alder reaction

A new four-step synthetic procedure has been developed to prepare 3,3-dimethyl-4-morpholino-3,4-dihydrocoumarins from substituted salicylaldehydes, morpholine, and isobutyraldehyde. It involves aminal formation, deamination, enamine formation, hetero-Diels–Alder reaction, hydrolysis, and oxidation. The aminal formation, subsequent one-pot domino deamination, enamine formation, and hetero-Diels–Alder reaction were achieved in microwave-assisted catalyst-free conditions. The following hydrolysis and oxidation steps, performed conventionally, gave quantitative yields.     

Measurement of the concentration diffusion coefficient for He-Ar and Ne-Kr by a two bulb method

Summary A two bulb glass apparatus was used to measure the concentration diffusion coefficient of the binary gas systems He-Ar and Ne-Kr. The coefficients were determined for equimolar mixtures at temperatures between 0°C and 70°C. The diffusion was followed as a function of time by withdrawing samples and analyzing them in a specially designed thermal conductivity analyzer with high accuracy. The diffusion coefficients agree with earlier reported experimental values and with those obtained on the basis of the Chapman-Enskog theory in conjunction with the modified Buckingham exp-six and Lennard-Jones (12-6) intermolecular potentials. The smoothed values were used to predict viscosity and thermal conductivity of these mixtures as a function of composition and temperature.     

On the microstructure of the charge density wave observed in La1− x Ca x MnO3

We have used low temperature (90?K) transmission electron microscopy to investigate the ‘charge ordering’ modulation in the mixed valent manganite, La_{1? x} Ca _x MnO₃. It has been stated that Mn³⁺ and Mn⁴⁺ ions order at low temperature to produce a structural modulation composed of supercells whose size is an integer multiple of the unmodulated unit cell. Here, we use convergent beam electron diffraction to show that the periodicity of the modulation need not be an integer multiple of the undistorted cell, even on the smallest scales. We therefore suggest that this modulation is a charge density wave with a uniform periodicity. We show that the modulation wavevector lies close to the a* axis of the crystal but need not be exactly collinear. A typical grain of size 0.5?µm in La_0.48Ca_0.52MnO₃ had a wavevector which varied on a scale of tens of nanometres with an average of ?q??=?0.450a * and a standard deviation Δq?=?0.004?a* in its magnitude and Δθ?=?0.56° in its direction at 90?K. The magnitude of the wavevector in this composition fell by 20% as the temperature was increased from 90?K to room temperature. This change occurred by nucleation and growth. Although weak, the modulation was still present at room temperature, some 30?K above the ‘charge ordering temperature’.     

Adding momentum to supersymmetric geometries

We consider general supersymmetric solutions to minimal supergravity in six dimensions, trivially lifted to IIB supergravity. To any such solution we add a traveling wave deformation involving the additional directions. The deformed solution is given in terms of a function which is harmonic in the background geometry. We also present a family of explicit examples describing microstates of the D1–D5 system on T⁴$T^4$. In the case where the background contains a large AdS region, the deformation is identified as corresponding to an action of a U(1)$\mathrm{U}(1)$ current of the D1–D5 orbifold CFT on a given state.