Encapsulation of food grade antioxidant in natural biopolymer by electrospinning technique: A physicochemical study based on zein–gallic acid system

Gallic acid was successfully incorporated into zein ultra-fine fibres at different loading amount (5%, 10% and 20%) in order to develop an encapsulating technology for functional ingredient delivery using electrospinning. The produced fibres exhibit diameters ranging from 327 to 387 nm. The physical and thermal properties of encapsulated gallic acid were determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC); and the interaction between gallic acid and zein was attested by attenuated total reflection-Fourier transform infrared (ATR-FTIR). Thermogravimetric analysis (TGA) demonstrated a different thermal stability of the fabricated complex before and after the gallic acid incorporation. Lastly, the 1,1′-diphenyl-2-picrylhydrazyl (DPPH) assay showed that the gallic acid had retained its antioxidant activity after incorporation in zein electrospun fibres. Overall, electrospinning technique had shown promising results as an efficient and effective method for the preparation of sub-micron structured encapsulated functional ingredient that may find uses in food industry.     

Optimized preparation of alumina based fillers for tuning composite properties

Alumina based particles were prepared from aluminium chloride hydroxide as starting material by sol-gel technique. One series of particles was doped with ferrous oxide. Both series of particles were calcinated at three different temperatures: 700?°C, 800?°C and 900?°C. Poly(methyl methacrylate), PMMA, was used as a matrix and two different types of alumina based particles were added into the matrix to form the composites. All composites consisted of 3?wt% of alumina based particles. The aim of this study was to examine whether and how the temperature of particle calcination affects the microhardness and mechanical properties of the composite. The particles were characterized by the X-ray diffraction (XRD) and physical absorption methods. The morphology of the composites was examined using a field emission scanning electron microscope (FESEM). The microhardness of composites was measured using a traditional Vickers hardness (HV) method. The mechanical characteristics of obtained composites were determined using tensile test and impact testing.     

Processing and properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films

We have investigated the processing of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a T_m of 174 °C, a permittivity at the T_m of 21,000 and a d₃₃ of 140 pC/N.     

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating.     

Suitability of some selected maize hybrids from Serbia for the production of bioethanol and dried distillers' grains with solubles

BACKGROUND: Bioethanol is mostly produced from starchy parts of the corn grain kernel leaving significant amounts of valuable by‐products such as dried distillers' grains with solubles (DDGS) which can be used as a substitute for traditional feedstuff. The suitability of six maize hybrids from Serbia was investigated for bioethanol and DDGS production. The correlation between physical and chemical characteristics of the grain, bioethanol yield and quality of the corresponding DDGS was assessed. RESULTS: All hybrids had very different chemical composition and physical characteristics which could allow various applications. The highest bioethanol yield (94.5% of theoretical) and volumetric productivity (2.01 g l^?1 h^?1) were obtained with hybrid ZP 434 and the lowest with ZP 611k. Regarding chemical composition, all DDGS samples manifested good properties as feed components. Their protein content was higher compared to the kernel. In addition, the samples showed high digestibility and high mineral content, especially of calcium and phosphorus. CONCLUSION: A hybrid ZP 434 was selected as the most promising bioethanol producer. This property is attributed to the highest level of soft endosperm which is more susceptible to starch‐hydrolysing enzymes. A high yield potential per hectare makes it the best candidate for commercial bioethanol production. © 2012 Society of Chemical Industry     

MatLab program for precision calibration of optical tweezers

Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the (x,y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum. First, cross-talk between channels in 2D position measurements is tested for, and eliminated if detected. Then, the Lorentzian power spectrum that results from the Einstein-Ornstein-Uhlenbeck theory, is fitted to the low-frequency part of the experimental spectrum in order to obtain an initial guess for parameters to be fitted. Finally, a more complete theory is fitted, a theory that optionally accounts for the frequency dependence of the hydrodynamic drag force and hydrodynamic interaction with a nearby cover slip, for effects of finite sampling frequency (aliasing), for effects of anti-aliasing filters in the data acquisition electronics, and for unintended “virtual” filtering caused by the position detection system. Each of these effects can be left out or included as the user prefers, with user-defined parameters. Several tests are applied to the experimental data during calibration to ensure that the data comply with the theory used for their interpretation: Independence of x- and y-coordinates, Hooke's law, exponential distribution of power spectral values, uncorrelated Gaussian scatter of residual values. Results are given with statistical errors and covariance matrix.

Program summary

Title of program: tweezercalibCatalogue identifier: ADTVProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland.Program Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTVComputer for which the program is designed and others on which it has been tested: General computer running MatLab (MathWorks Inc.).Programming language used: MatLab (MathWorks Inc.). Uses “Optimization Toolbox” and “Statistics Toolbox”.Memory required to execute with typical data: Of order 4 times the size of the data file.High speed storage required: NoneNo. of lines in distributed program, including test data, etc.: 133 183No. of bytes in distributed program, including test data, etc.: 1 043 674Distribution format: tar gzip fileNature of physical problem: Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system.Method of solution: Elimination of cross-talk between quadrant photo-diode's output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects: Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for “virtual filtering” caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting. Statistical support for fit is given, with several plots suitable for inspection of consistency and quality of data and fit.Restrictions on the complexity of the problem: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate: The sampling rate should be well above the characteristic frequency of the trap, the so-called corner frequency. Thus, the sampling frequency should typically be larger than 10 kHz. The Fast Fourier Transform applied requires the time series to contain 2ⁿ data points, and long measurement time is obtained with n>12-15. Finally, the optics should be set to ensure a harmonic trapping potential in the range of positions visited by the bead. The fitting procedure checks for harmonic potential.Typical running time: (Tens of) minutesUnusual features of the program: NoneReferences: The theoretical underpinnings for the procedure are found in [K. Berg-Sørensen, H. Flyvbjerg, Rev. Sci. Instrum. 75 (3) (2004) 594].     

Electrical properties and chemical compatibility of PZT thick film on Ni substrates

The characteristics of Pb(Zr,Ti)O₃(PZT) thick films that were printed and fired on Ni substrates were studied. The dielectric characteristics of samples sintered at 850°C on Ni substrates could not be measured due to the formation of a NiO layer at the Ni/PZT interface. The scanning electron microscope and energy dispersive X-ray analysis of cross-sections of the PZT thick films on Ni substrates, and of a mixture of PZT and NiO powders, fired at 850°C, did not indicate the formation of secondary phases. However, the transmission electron microscopy showed around 8% solid solubility of NiO in the PZT. A new structure with a prefired, Au thick-film layer was designed in order to prevent the diffusion of the NiO to the PZT layer during sintering. The dielectric properties of the PZT layers printed and fired on the Ni substrates with the prefired Au electrode were significantly better than those of the layers on the uncoated substrate, the dielectric losses decreased from 0.23 to 0.05.     

Comparison of linear and rotationally shearing interferometric layouts for extrasolar planet detection from space

We use the point spread function and the modulation transfer function (MTF) as two figures-of-merit to evaluate the performance of the multiaperture interferometric configurations for the detection of a faint planet in the vicinity of its bright star. We design nonredundant interferometric layouts that provide satisfactory coverage of the spatial frequencies of interest. We propose a design incorporating a rotating, rotationally shearing interferometer in a gravity-free environment and compare its performance with the Earth-based, fixed, linear configurations. The side peak of its MTF may be centered on the coordinate associated with a likely planet spatial frequency, resulting in planet signal enhancement and isolation.     

A Conjoint-based approach to student evaluations of teaching performance

In recent years, the need for greater accountability and improvement in teaching’s quality has become a major issue in higher education. The results of student evaluation of teaching are increasingly used to make judgments about teaching quality, career advancement, and the funding of teaching itself. An important component of any such student evaluation is the communication of rating results in a manner that allows for fair and meaningful interpretations and comparisons of results by a wide range of evaluation users. In this paper, an approach for a more objective evaluation of university teachers is proposed, one which is based on previously obtained conjoint analysis data concerning criteria importance from a student’s point of view. Therein, an illustrative example is given to demonstrate the efficiency and practical usage of such a proposed approach.     

Overview of HVAC system simulation

The paper gives an overview of heating, ventilation and air-conditioning (HVAC) system modeling and simulation. The categorization of tools for HVAC system design and analysis with respect to which problems they are meant to deal with is introduced. Each categorization is explained and example tools are given. Further, the paper summarizes current approaches used for modeling (i) HVAC components, (ii) HVAC control and (iii) HVAC systems in general. After giving an overview of solution techniques for HVAC system simulation, the paper provides suggestions on how one should select an HVAC modeling approach relative to the simulation objective at hand.