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Sen D.,Bhabha Atomic Research Center | Melo J.S.,Bhabha Atomic Research Center | Bahadur J.,Bhabha Atomic Research Center | Mazumder S.,Bhabha Atomic Research Center | And 5 more authors.
Soft Matter | Year: 2011

Self-assembled grains of mixed colloids have been synthesized using evaporation induced self-assembly (EISA) by spray drying. We demonstrate using electron microscopy and small-angle neutron scattering experiments that buckling driven sphere to deformed-doughnut like morphological transformation in such a process can be arrested by proper tuning of the surface charge on the colloidal components. The buckling amplitude diminishes with a reduction in stabilization force between the colloidal particles. It is established that such arrest of morphological transformation is related to an effective exposure of the surface of softer component at gas-liquid interface. Scattering experiments confirm relatively more compact structure of the non-buckled grains compared to that of the buckled grains. A plausible mechanism regarding the arrest of morphological transformation by surface charge tuning is illustrated. © 2011 The Royal Society of Chemistry.


Sen D.,Bhabha Atomic Research Center | Bahadur J.,Bhabha Atomic Research Center | Das A.,Bhabha Atomic Research Center | Mazumder S.,Bhabha Atomic Research Center | And 3 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2015

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. © 2015 Elsevier B.V.


PubMed | Atominstitut der Osterreichischen Universitaten and University Mainz
Type: Journal Article | Journal: Journal of research of the National Institute of Standards and Technology | Year: 2016

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 experiments 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 12 (12 standard uncertainties) deviation, the reason for which is not clear yet.


PubMed | Jülich Research Center, Atominstitut der Osterreichischen Universitaten and Bhabha Atomic Research Center
Type: | Journal: Colloids and surfaces. B, Biointerfaces | Year: 2015

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 200C to 400C removes the cells without significant alteration of the nano-structured silica network. However, beyond 500C, calcination results significant coalescence between the silica particles. Calcination at 600C eventually collapses the meso-pore network of silica interstices.


Mazumder S.,Bhabha Atomic Research Center | Sen D.,Bhabha Atomic Research Center | Bahadur J.,Bhabha Atomic Research Center | Klepp J.,Atominstitut der Osterreichischen Universitaten | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Though cement is a ubiquitous material with global production exceeding that of any other material of technological importance, the mechanism of its hydration and evolution of cement-water mixtures into gels of high compressive strength is poorly understood, despite extensive research over the past century. The present investigation, based on neutron-scattering measurements, aims at unraveling this enigma and outlines the evolution of the mesoscopic structure of the cement paste which exhibits temporal oscillations, strongly dependent on the scale of observation and on the medium of hydration (light or heavy water). While the formation of hydration products is synchronous for hydration with H 2O, the process is nonsynchronous for hydration with D 2O. The reason why morphological patterns of domains at different times look dissimilar, as seen before, for different hydration media emerges as a natural consequence of this finding. The present investigation also provides an explanation for disagreement with the hypothesis of dynamical scaling for hydration of cement with heavy water and is a step forward toward general understanding of hydration process. © 2010 The American Physical Society.


Abbas S.,Bhabha Atomic Research Center | Wagh A.G.,Bhabha Atomic Research Center | Loidl R.,Atominstitut der Osterreichischen Universitaten | Lemmel H.,Atominstitut der Osterreichischen Universitaten | Rauch H.,Atominstitut der Osterreichischen Universitaten
AIP Conference Proceedings | Year: 2011

We report here a preliminary interferometric determination of neutron coherent scattering length b C for silicon using a dual non-dispersive sample. A large and exactly non-dispersive phase measured by this method can afford an order of magnitude improvement in the precision of b C determination to within a few parts in 10 6. © 2011 American Institute of Physics.


Mazumder S.,Bhabha Atomic Research Center | Sen D.,Bhabha Atomic Research Center | Loidl R.,Atominstitut der Osterreichischen Universitaten | Loidl R.,Laue Langevin Institute | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The evolution of mesoscopic structure for cement-water mixtures turning into colloidal gels remains far from being understood. Recent neutron scattering investigations reveal the role of the hydrogen bond in the temporal evolution of the mesoscopic structure during hydration of cement, which is the most consumed synthetic material. The present neutron scattering investigation on hydration of cement with a mixture of light and heavy water points to incomprehensibility of the temporal evolution of the mesoscopic structure in terms of earlier observations on hydration with pure light or heavy water. Unlike the case of hydration with light water, disagreement has been observed with the hypothesis of dynamical scaling for hydration of cement with a mixture of the two types of water. The dynamics of evolution of the mesoscopic structure has been observed to be nonlinear in regard to the composition of hydration medium. © 2011 American Physical Society.


Hasegawa Y.,Atominstitut der Osterreichischen Universitaten | Hasegawa Y.,Japan Science and Technology Agency | Loidl R.,Atominstitut der Osterreichischen Universitaten | Loidl R.,Laue Langevin Institute | And 5 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Entanglement between degrees of freedom, namely between the spin, path, and (total) energy degrees of freedom, in a single-neutron system is exploited. We implemented a triply entangled Greenberger-Horne-Zeilinger (GHZ)-like state and coherently manipulated relative phases of two-level quantum subsystems. An equality derived by Mermin was applied to analyze the generated GHZ-like state: We determined the four expectation values and finally obtained M=2.558±0.004≤2. This demonstrates a violation of Mermin-like inequality for triply entangled GHZ-like state in a single-particle system, which, in turn, clearly contradicts the noncontextual assumption and confirms quantum contextuality. © 2010 The American Physical Society.


Kohnen M.,Imperial College London | Succo M.,Imperial College London | Petrov P.G.,Imperial College London | Nyman R.A.,Imperial College London | And 3 more authors.
Nature Photonics | Year: 2011

Photonic chips that integrate optical elements on a single device can process vast amounts of information rapidly. A new branch of this technology involves coupling light to cold atoms or Bose-Einstein condensates, the quantum nature of which provides a basis for new information-processing methods. The use of optical waveguides gives the light a small cross-section, making coupling to atoms efficient. In this Letter, we present the first waveguide chip designed to address a Bose-Einstein condensate along a row of independent junctions, which are separated by only 10 μm and have large atom-photon coupling. We describe a fully integrated, scalable design, and demonstrate 11 junctions working as intended, using a low-density cold atom cloud with as little as one atom on average in any one junction. The device suggests new possibilities for engineering quantum states of matter and light on a microscopic scale. © 2011 Macmillan Publishers Limited. All rights reserved.


Laliotis A.,Imperial College London | Laliotis A.,University of Paris 13 | Trupke M.,Imperial College London | Trupke M.,Atominstitut der Osterreichischen Universitaten | And 4 more authors.
Journal of Micromechanics and Microengineering | Year: 2012

Miniature concave hollows, made by wet etching silicon through a circular mask, can be used as mirror substrates for building optical micro-cavities on a chip. In this paper, we investigate how inductively coupled plasma (ICP) polishing improves both shape and roughness of the mirror substrates. We characterize the evolution of the surfaces during the ICP polishing using white-light optical profilometry and atomic force microscopy. A surface roughness of 1 nm is reached, which reduces to 0.5 nm after coating with a high reflectivity dielectric. With such smooth mirrors, the optical cavity finesse is now limited by the shape of the underlying mirror. © 2012 IOP Publishing Ltd.

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