Experimental studies and kinetics of single drop drying and their relevance in drying of sugar‐rich foods: A review

Levitation and free‐flight techniques applied to investigate the drying kinetics and morphology of single drops containing dissolved solids and suspensions are reviewed. A review of works related to receding interface model proposed to quantify the drying kinetics of single drops along with techniques to measure the kinetic parameters such as moisture diffusivity, thermal conductivity and specific heat capacity is presented. Problems associated with spray drying of sugar‐rich compounds are briefly discussed and possible links of stickiness and flavor retention with glass transition temperature (T_g), temperature history, drying rate and morphological changes including skin formation, as monitored through single drop experiments, are explored.     

Induced doping by sodium ion in poly(m-aminophenol) through the functional groups

Poly(m-aminophenol) (PmAP) was synthesized by the oxidative polymerization of m-aminophenol in sodium hydroxide medium using ammonium persulfate oxidant at room temperature. The synthesized polymer showed very good solution processability as it was well soluble in aqueous sodium hydroxide, dimethylsulfoxide (DMSO), dymethylformamide (DMF), etc. A free-standing film was cast from thermal evaporation of DMSO solution of the synthesized PmAP. The film was then doped with aqueous sodium hydroxide and methanol mixture by solution doping technique at room temperature. The doping conditions were standardized in terms of the DC-conductivity of the doped film. The doped PmAP was characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Electron dispersion spectroscopy, X-ray diffraction spectroscopy, elemental analysis by atomic absorption spectroscopy, thermogravimetric analysis and DC-electrical conductivity. The DC-electrical conductivity of PmAP film was increased to 2.34 × 10^?5 S/cm from <10^?12 S/cm due to sodium ion doping. From all the above characterizations it was confirmed that the sodium ions were not the reason for the conduction. The incorporated sodium cation in the polymer through free –OH groups of the polymer chain was induced the electron cloud of the polymer and so the polymer became conducting.     

Design and Collection Efficiency of a New Electrostatic Precipitator for Bioaerosol Collection

We have developed and tested a new bioaerosol sampler in which airborne microorganisms are collected by electrostatic means. In this sampler, 2 ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection. The organisms are then subjected to a precipitating electric field and are collected onto 2 square agar plates positioned along the flow axis. Tests with nonbiological NaCl particles versus B. subtilis var. niger (BG) spores and vegetative cells have shown that airborne microorganisms are collected more efficiently than nonbiological particles, even when the microorganisms have first passed through an electric charge neutralizer with no additional charging applied. The difference was attributed to the natural charges contained in cell membranes or spore coats of the microorganisms. Charge-neutralized BG spores and vegetative cells were collected at 4 L/min with efficiencies close to 80%, depending on the precipitation voltage, versus 50-60% for NaCl test particles. When incoming BG spores were charged with positive ions and then collected by a precipitating voltage of + 1,300 V, about 80% of the incoming spores were collected and more than 70% of incoming spores formed colonies. These experiments with BG spores have also indicated that there were no significant particle losses inside the sampler. The collection efficiency of biological and nonbiological particles increased to 90-100% when the particles were externally charged and the precipitating voltage was increased to more than - 4,000 V. It has also been shown that the aerosolized BG spores (used as anthrax simulants for bioaerosol sensors) carry a net negative electric charge. Thus the collection efficiency depends on the polarity of the electric field applied across the agar plates. These findings indicate that the collection of airborne microorganisms is possible by electrostatic precipitation without prior electric charging if the microorganisms already carry electric charges. These are usually high immediately after their release into the air.     

Stenotrophomonas,Mycobacterium, and Streptomyces in home dust and air: associations with moldiness and other home/family characteristics

Respiratory illnesses have been linked to children's exposures to water‐damaged homes. Therefore, understanding the microbiome in water‐damaged homes is critical to preventing these illnesses. Few studies have quantified bacterial contamination, especially specific species, in water‐damaged homes. We collected air and dust samples in twenty‐one low‐mold homes and twenty‐one high‐mold homes. The concentrations of three bacteria/genera, Stenotrophomonas maltophilia, Streptomyces sp., and Mycobacterium sp., were measured in air and dust samples using quantitative PCR (QPCR). The concentrations of the bacteria measured in the air samples were not associated with any specific home characteristic based on multiple regression models. However, higher concentrations of S. maltophilia in the dust samples were associated with water damage, that is, with higher floor surface moisture and higher concentrations of moisture‐related mold species. The concentrations of Streptomyces and Mycobacterium sp. had similar patterns and may be partially determined by human and animal occupants and outdoor sources of these bacteria.     

Distributed parameter model updating using the Karhunen–Loève expansion

Discrepancies between experimentally measured data and computational predictions are unavoidable for complex engineering dynamical systems. To reduce this gap, model updating methods have been developed over the past three decades. Current methods for model updating often use discrete parameters, such as thickness or joint stiffness, for model updating. However, there are many parameters in a numerical model which are spatially distributed in nature. Such parameters include, but are not limited to, thickness, Poisson's ratio, Young's modulus, density and damping. In this paper a novel approach is proposed which takes account of the distributed nature of the parameters to be updated, by expressing the parameters as spatially correlated random fields. Based on this assumption, the random fields corresponding to the parameters to be updated have been expanded in a spectral decomposition known as the Karhunen–Loève (KL) expansion. Using the KL expansion, the mass and stiffness matrices are expanded in series in terms of discrete parameters. These parameters in turn are obtained using a sensitivity based optimization approach. A numerical example involving a beam with distributed updating parameters is used to illustrate this new idea.     

Exploring the role of the spacers and acceptors on the triphenylamine-based dyes for dye-sensitized solar cells

Six triphenylamine-based dyes were explored for their application in dye-sensitized solar cells (DSSCs). Dyes 1–3 and dyes 4–6 possess cyanoacrylic acid (C-acceptor) and rhodanine-3-acetic acid (R-acceptor), respectively. Stilbene (in dyes 2 and 5) and bis(styryl)benzene (in dyes 3 and 6) were used as π-spacers. There is no π-spacer in the dye 1 and 4. To elucidate the role of π-spacers, optical, electrochemical, and photovoltaic properties of the dyes were studied. Among C-acceptor dyes, dye 2 exhibits the highest light-to-electricity conversion efficiency of 4.45%, followed by dye 3 (4.16%). Similarly, among R-acceptor dyes, dye 5 is the best. These results indicate that stilbene is a better π-spacer over bis(styryl)benzene. Although bis(styryl)benzene could extend the light absorption range (in dye-adsorbed TiO₂ film), its tendency to promote intermolecular π-π stacking is possibly the reason for its poor performance in DSSCs. Furthermore, the conjugation break in the R-acceptor moiety attached to the TiO₂ surface limits the electron injection of R-acceptor dyes poorer than C-acceptor dyes. Density functional theory calculations were performed for the dye-(TiO₂)₈ cluster, assuming a bidentate chelation of a carboxylic acid group with Ti⁴⁺ of TiO₂ anatase. The natural bond orbital (NBO) analysis indicated relatively more electron-accepting ability of cyanoacrylic acid over rhodanine-3-acetic acid.     

Water flow through helical coils in turbulent condition

Experimental data on pressure drop across six helical coils made of rough transparent PVC pipes for flow of water in turbulent condition are presented. A correlation for predicting the friction factor has been developed.     

Stability of Interesterified Fats

The stability characteristics of a number of interesterified fat products made from vegetable oil-mixtures were studied and compared to those of a commercial hydrogenated stuff, vanaspati. It was found that the interesterified products, after addition of antioxidants had comparable stability to vanaspati in most cases, and, hence would not offer any storage problem.     

Glyceride Composition in Interesterified Fats

The positional distribution of acyl groups in interesterified fats obtained from a number of vegetable oil-mixtures was studied by the selective deacylation reaction of Pancreatic Lipase. In the case of randomised fats, there was almost equal distribution of fatty acids in the three positions, which indicated completeness of randomisation and destruction of the selective orientation of acyl groups present in natural fats. On the other hand, there was little or no change in positional distribution during directed interesterification. It was found that for natural and randomised fats, the glyceride compositions calculated from the Lipase hydrolysis data agreed quite well with those obtained by argentation thin-layer chromatography (TLC) followed by gas-liquid chromatography (GLC) with an internal standard. The glyceride compositions of directed interesterified fats, found by argentation TLC followed by GLC, indicated that the proportions of GS₃ and GU₃ increase to a considerable extent with simultaneous decrease in GSU₂, while that of GS₂U increases to a comparatively small extent, or remains unchanged.     

Reverse Micelle-Mediated Synthesis and Characterization of Tricalcium Phosphate Nanopowder for Bone Graft Applications

Nanocrystalline β-tricalcium phosphate (β-TCP) powder was synthesized using reverse micelle as a template system. Cyclohexane was used as the oil phase, aqueous solutions of calcium nitrate and phosphoric acid as the aqueous phase, and poly(oxyethylene)₅ nonylphenol ether (NP-5) and/or poly(oxyethylene)₁₂ nonylphenol ether (NP-12) as the surfactants. The powder were synthesized at a fixed Ca/P molar ratio of 1.5 at a pH of 10. The synthesized powder were calcined at 800°C to obtain monophasic β-TCP. Particle size, morphology, and surface area of the synthesized powder were dependent on the chemistry of the surfactant and composition of the microemulsion. The powder were characterized using a BET surface area analyzer, powder X-ray diffraction, dynamic light scattering technique, and transmission electron microscopy. TCP nanoparticles had a particle size between 32 and 135 nm, and a BET-specific average surface area between 57 and 103 m²/g with controlled morphology. The powder were consolidated and sintered at 1250°C in a 3 kW microwave furnace in the form of a compact disk. Human osteoprecursor cells (osteoblastic precursor cell line 1 [OPC1]) were used to assess the biocompatibility of TCP disks after 1, 5, and 11 days in culture using scanning electron microscopy, MTT assay, and alkaline phosphatase expressions. Disk samples were biocompatible and showed excellent OPC1 cell adhesion, growth, and proliferation. Biocompatible β-TCP nanopowder were synthesized with controlled particle size, morphology, and surface area using a reverse micelle-mediated template system.