Scalar variational analysis of single mode,graded-core,W-type fibres

A scalar variational analysis for the fundamental mode of a graded-core, W-type fibre based on single and two parameter trial fields has been presented. Comparison with the exact numerical results shows that the two parameter trial field estimates the propagation characteristics accurately.On study leave from Physics Department, G.M. College, Sambalpur-768004, India.     

The radial force on a charged particle in superimposed magnetic fields on Schwarzschild spacetime

Following the approach of optical reference geometry we derive the expression for the total force in the radial direction acting on a charged particle in magnetic fields superimposed on the static Schwarzschild background and show the possible existence of bound orbits for particles in the field of ultra compact objects at distancesr?3m wherein the Lorentz force counterbalances both the gravitational and centrifugal forces.     

Leptogenesis from spin-gravity coupling following inflation

The energy levels of the left- and the right-handed neutrinos are split in the background of gravitational waves generated during inflation, which, in presence of lepton-number-violating interactions, gives rise to a net lepton asymmetry at equilibrium. Lepton number violation is achieved by the same dimension five operator which gives rise to neutrino masses after electroweak symmetry breaking. A net baryon asymmetry of the same magnitude can be generated from this lepton asymmetry by electroweak sphaleron processes.     

Bright molecules with sense, logic, numeracy and utility

Using cartoons as an organizational aid, we illustrate how the 'fluorophore-spacer-receptor' format of fluorescent PET (photoinduced electron transfer) sensors and switches can be logically extended in many different directions. These include emissive sensors for various chemical species and properties, and exploit various kinds of emission. Common sensing issues such as dynamic range, internal referencing, selectivity, mapping and space resolution are addressed. The sensory output function is also developed into more complex forms, molecular logic/computation being one such example. Molecular logic leads to molecular arithmetic. Real-life applications to physiological monitoring, medical diagnostics and molecular computational identification of small objects are included.     

Crystal structure and magnetic properties of hydrogen bonded charge-transfer compound – TMPD:TCNB

1,2,4,5-Tetracyanobenzene (TCNB), a moderate electron acceptor, reacts readily with N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), a strong electron donor, to form black colored TMPD:TCNB complex when treated in 1:1 molar ratio. Single crystal X-ray diffraction studies on this complex showed that molecule of TMPD and TCNB are alternately stacked with an interplanar distance of 3.4 Å between them. The structure of the complex does not seem to show usual π–π interaction between the two aromatic rings, but indicates the presence of n–π interaction localized between the nitrogen atoms of TMPD and the cyano groups of TCNB. Along with this a prominent presence of CN···HAr hydrogen bonded ribbon network between nitrogen of cyanide moiety and hydrogen of neighboring aromatic carbon is observed with distance of 2.610 Å and angle of 147.19°. Magnetic measurements on the powdered compound using SQUID magnetometer (5–20 K) showed that the complex is weakly antiferromagnetic (θ = ?0.85 K). To my best knowledge CN···HAr interaction amongst electron acceptor molecules, to form a ribbon-like network, has not been observed before for a magnetic complex.     

Validation of capillary electrophoresis method for determination of N-methylpyrrolidine in cefepime for injection

The present study relates to a new capillary electrophoresis method for the determination of N-methylpyrrolidine, an impurity considered to be toxic and also potential degradation impurity in cefepime hydrochloride drug substance. The newly developed capillary electrophoresis method for determining the content of N-methylpyrrolidine in cefepime for injection has been validated as per International Conference on Harmonization (ICH) guidelines to prove the selectivity, sensitivity, suitability, robustness, and ruggedness of the method. This simple, efficient, and rapid methodology may be used by pharmaceutical industry for routine analysis as well as during stability studies. The newly developed capillary electrophoresis method to determine the content of N-methylpyrrolidine in cefepime for injection requires 10 min for data acquisition, and uses an indirect UV photometry method to detect the analyte signal at 240 nm against the reference signal at 210 nm. The electrophoretic system is optimized to get stable base line, higher signal to noise ratio and peaks with narrow peak width. The method employs bare fused silica capillary with extended light path, effective length of capillary is 56 cm and inner diameter of capillary is 50 μm, 5 mmole of imidazole buffer adjusted to pH 5.1 with 3 molar acetic acid solution is used as background electrolyte. The sample is introduced in hydrodynamic mode employing pressure of 50 mbar for 5 s, and the desired separation is achieved with constant applied voltage of 25 kV at ambient temperature (~25°C).     

Consolidating molecular AND logic with two chemical inputs

A novel molecular AND logic gate 1 is demonstrated based on the competition between fluorescence and photoinduced electron transfer (PET). It is constructed according to a 'receptor2-spacer-fluorophore-spacer-receptor1-spacer-fluorophore-spacer-receptor2' format where receptor1 is a tertiary amine, receptor2 is a benzo-15-crown-5 ether and the fluorophore is an anthracene moiety, which are separated from each other by methylene spacers. The fluorescence response in methanol is significantly enhanced only when both H+ and Na+ are the inputs at high enough concentrations in accordance with AND logic. Cs+ behaves similarly to Na+, but with a lower fluorescence enhancement, whereas the other alkali metal cations are not effective. Electrospray ionization mass spectrometry provides evidence for formation of 1:1 and 1:2 (1:metal) complexes with alkali cations, and formation of a 1:2:1 (1:metal:proton) complex in the additional presence of acid.