Selection and Optimization of Dispersant in Ceramic Slurry Processing by Different Techniques: Comparison,Correlation, and Standardization

This article describes the selection and optimization of dispersant dosage in colloidal processing of ceramic slurry by techniques such as particle charge detector (PCD), capillary suction time (CST), rheological measurement, and wet point and flow point techniques. In general, experimental results are found to be in good agreement with each other with some degree of variation. PCD, CST, and rheological techniques are related by a simple linear function. The experimental and calculated values are well matching within an error limit of 10%. Attempt has been made to develop formula for correlating results of optimization from one technique to those obtained from another technique. The region where the suspension is well dispersed, CST is linearly correlated with PCD. The advantages and limitations of each technique have been described and discussed.     

Construction of universal one-way hash functions: Tree hashing revisited

We present a binary tree based parallel algorithm for extending the domain of a universal one-way hash function (UOWHF). For t?2, our algorithm extends the domain from the set of all n-bit strings to the set of all ((2^t-1)(n-m)+m)-bit strings, where m is the length of the message digest. The associated increase in key length is 2m bits for t=2; m(t+1) bits for 3?t?6 and m×(t+⌊log₂(t-1)⌋) bits for t?7.     

A new heterogeneous catalyst for epoxidation of alkenes via one-step post-functionalization of IRMOF-3 with a manganese(II) acetylacetonate complex

A manganese(II) acetylacetonate complex has been immobilized to the metal-organic framework IRMOF-3 through a one-step post-synthetic route for the first time, providing an effective and recyclable heterogeneous catalyst for epoxidation of alkenes.     

New polymorphs of curcumin

Two new crystalline polymorphs and an amorphous phase of the active curcuminoid ingredient in turmeric are reported. Curcumin polymorph 2 has higher dissolution rate and better solubility than the known polymorph 1.     

Adsorption kinetics of a fluorescent dye in a long chain fatty acid matrix

This work reports the adsorption kinetics of a highly fluorescent laser dye rhodamine B (RhB) in a preformed stearic acid (SA) Langmuir monolayer. The reaction kinetics was studied by surface pressure-time (π-t) curve at constant area and in situ fluorescence imaging microscopy (FIM). Increase in surface pressure (at constant area) with time as well as increase in surface coverage of monolayer film at air-water interface provide direct evidence for the interaction. ATR-FTIR spectra also supported the interaction and consequent complexation in the complex films. UV-vis absorption and Fluorescence spectra of the complex Langmuir-Blodgett (LB) films confirm the presence of RhB molecules in the complex films transferred onto solid substrates. The outcome of this work clearly shows successful incorporation of RhB molecules into SA matrix without changing the photophysical characteristics of the dye, thus making the dye material as LB compatible.     

Generation of cold electrons in the downstream region of a microwave plasma source with near boundary resonances for production of negative ions

A microwave driven multicusp plasma based volume negative ion source equipped with a magnetic filter is developed. Instead of employing any electrodes or current carrying filaments, microwaves of frequency 2.45 GHz is used to generate plasma by resonance heating mechanisms namely the electron cyclotron resonance (ECR) and upper hybrid resonances (UHR), occurring near the boundary plasma layers. The principal process of negative ion production in hydrogen is dissociative attachment of low energy (0.5–1.0 eV) electrons to vibrationally excited neutral molecules generated from high energy (15–20 eV) electron impact. The source therefore necessitates two distinct spatial regions (a) production and (b) attachment chambers; which would contain electrons with optimum cross section for the aforementioned processes. A biased grid after the magnetic filter further helps to lower down the electron temperature to ≤1 eV which is favorable for the dissociative attachment process.     

J-aggregates of thiacyanine dye organized in LB films: Effect of irradiation of light

In the present communication we report the preparation and characterizations of Langmuir and Langmuir-Blodgett films of a thiacyanine dye N,N′-dioctadecyl thiacyanine perchlorate (NK) mixed with Octadecyl trimethyl ammonium bromide (OTAB). The relationship between the molar ratio of OTAB and NK and the orientation of molecules at the air-water interface was investigated using surface pressure-area per molecule (π-A) isotherm. UV-vis absorption and fluorescence spectroscopic investigations reveal that prominent J-aggregation of NK molecule was observed in the LB films lifted at higher surface pressure. This J-aggregation can be controlled by diluting the NK molecules with OTAB. It was observed that the J-aggregates of NK decayed to monomer and H-aggregates when the NK-LB film was exposed to a monochromatic light of wavelength 460 nm (λ_max of J-aggregates).     

A trade-off between collision probability and key size in universal hashing using polynomials

Let \mathbbF{\mathbb{F}} be a finite field and suppose that a single element of \mathbbF{\mathbb{F}} is used as an authenticator (or tag). Further, suppose that any message consists of at most L elements of \mathbbF{\mathbb{F}}. For this setting, usual polynomial based universal hashing achieves a collision bound of (L-1)/|\mathbbF|{(L-1)/|\mathbb{F}|} using a single element of \mathbbF{\mathbb{F}} as the key. The well-known multi-linear hashing achieves a collision bound of 1/|\mathbbF|{1/|\mathbb{F}|} using L elements of \mathbbF{\mathbb{F}} as the key. In this work, we present a new universal hash function which achieves a collision bound of mélog_m Lù/|\mathbbF|, m 3 2{m\lceil\log_m L\rceil/|\mathbb{F}|, m\geq 2}, using 1+élog_m Lù{1+\lceil\log_m L\rceil} elements of \mathbbF{\mathbb{F}} as the key. This provides a new trade-off between key size and collision probability for universal hash functions.     

Electrical excitation of surface plasmons

We exploit a plasmon mediated two-step momentum down-conversion scheme to convert low-energy tunneling electrons into propagating photons. Surface plasmon polaritons (SPPs) propagating along an extended gold nanowire are excited on one end by low-energy electron tunneling and are then converted to free-propagating photons at the other end. The separation of excitation and outcoupling proves that tunneling electrons excite gap plasmons that subsequently couple to propagating plasmons. Our work shows that electron tunneling provides a nonoptical, voltage-controlled, and low-energy pathway for launching SPPs in nanostructures, such as plasmonic waveguides.     

Influence of electrostatic and chemical heterogeneity on the electric-field-induced destabilization of thin liquid films

A numerical model for thin liquid film (<100 nm) drainage in the presence of an external electric field is developed. Long-wave theory is applied to approximate and simplify the governing equations. A spatiotemporal film morphology evolution equation thus obtained is then solved using a combination of finite difference to resolve the spatial dimensions and an adaptive time step ODE solver for the temporal propagation. The effect of fluid properties, namely, viscosity and surface tension, on the film drainage time is observed for a homogeneous electric field, which leads to random dewetting spots. Electrically heterogeneous fields, achieved by modeling electrodes with various periodic patterns, are explored to identify their effect on the drainage time and behavior. Finally, the chemical heterogeneity of the substrate is coupled with the periodic electric heterogeneity to understand the implications of combined heterogeneity. It is observed that the introduction of any heterogeneity results in faster drainage of the film when compared to that of the homogeneous field. In all cases, the thin film is drained, leaving submicrometer-scale structures at the interface. Well-controlled surface patterns are found on the application of periodic heterogeneity. This study effectively demonstrates the immense potential of electrically induced thin film drainage as a means for faster de-emulsification and for the creation of ordered submicrometer-scale surface patterns on soft materials.