E. coli imprinted nano-structured silica micro-granules by spray drying: optimization of calcination temperature.

We have synthesized nano-structured silica-Escherichia coli composite micro-granules by spray drying of mixed suspension of silica and E. coli through evaporation-induced assembly. Synthesized micro-granules were subjected to calcination in order to form shape-matched macro-pores by removing the bacterial cells. The optimization of calcination temperature is crucial because calcination process leads to two contrasting effects, namely, (i) removal of E. coli from the granules and (ii) alteration of mesoscopic structure in the silica network. We have used small-angle neutron scattering and thermo-gravimetric analysis to determine the optimum temperature for calcination of these granules. It was found that calcination in the temperature range of 200°C to 400°C removes the cells without significant alteration of the nano-structured silica network. However, beyond 500°C, calcination results significant coalescence between the silica particles. Calcination at 600°C eventually collapses the meso-pore network of silica interstices.

Measurement of the Coherent Neutron Scattering Length of (3) He.

By means of neutron interferometry the s-wave neutron scattering length of the (3)He nucleus was re-measured at the Institut Laue-Langevin (ILL). Using a skew symmetrical perfect crystal Si-interferometer and a linear twin chamber cell, false phase shifts due to sample misalignment were reduced to a negligible level. Simulation calculations suggest an asymmetrically alternating measuring sequence in order to compensate for systematic errors caused by thermal phase drifts. There is evidence in the experiment's data that this procedure is indeed effective. The neutron refractive index in terms of Sears' exact expression for the scattering amplitude has been analyzed in order to evaluate the measured phase shifts. The result of our measurement, b' c = (6.000 ± 0.009) fm, shows a deviation towards a greater value compared to the presently accepted value of b' c = (5.74 ± 0.07) fm, confirming the observation of the partner experiment at NIST. On the other hand, the results of both precision measurements at NIST and ILL exhibit a serious 12σ (12 standard uncertainties) deviation, the reason for which is not clear yet.

Dynamical scaling of the structure factor of some non-Euclidean systems.

Predictions of nonlinear theories on dynamics of new phase formation have been examined for the hydration of calcium silicates with light water and heavy water. In the case of hydration with light water, reasonable agreement has been observed with dynamical scaling hypothesis with a new measure of the characteristic length. The characteristic length does not follow a power law relation with time. Hydrating mass is found to be mass fractal throughout hydration, with mass fractal dimension increasing with time. But, in the case of hydration with heavy water, no agreement has been observed with the scaling hypothesis. Hydrating mass undergoes transition from mass fractal to surface fractal and finally again to mass fractal. The qualitative features of the kinetics of hydration, as measured in small-angle scattering experiments, are strikingly different for hydration with light water and heavy water.

Measurement of a confinement induced neutron phase.

Particle physicists see neutrons as tiny massive particles with a confinement radius of about 0.7 fm and a distinct internal quark gluon structure. In quantum mechanics, neutrons are described by wave packets whose spatial extent may become ten orders of magnitude larger than the confinement radius, and can even reach macroscopic dimensions, depending on the degree of monochromaticity. For neutrons passing through narrow slits, it has been predicted that quantization of the transverse momentum component changes the longitudinal momentum component, resulting in a phase shift that should be measurable using interferometric methods. Here we use neutron interferometry to measure the phase shift arising from lateral confinement of a neutron beam passing through a narrow slit system. The phase shift arises mainly from neutrons whose classical trajectories do not touch the walls of the slits. In this respect, the non-locality of quantum physics is apparent.

Off-diagonal geometric phase in a neutron interferometer experiment.

Off-diagonal geometric phases acquired by an evolution of a 1/2-spin system have been observed by means of a polarized neutron interferometer. We have successfully measured the off-diagonal phase for noncyclic evolutions even when the diagonal geometric phase is undefined. Our data confirm theoretical predictions and the results illustrate the significance of the off-diagonal phase.