Studies on physicochemical characteristics of chitosan derivatives with dicarboxylic acids

Chitosan (N-deacetylated derivative of chitin) was solubilised in different aqueous dicarboxylic acid solutions, including oxalic acid, malonic acid, adipic acid, azelaic acid and also in monocarboxylic acetic acid. These dicarboxylic acid solutions were used with the objective that they not only act as solvents but also enhance material properties of chitosan gel films through chemical cross-linking. The properties including conformational changes of chitosan, chemical interaction, and mechanical, morphological and thermal characteristics of selected chitosan samples studied in this work. The circular dichroism study indicated that the intensity of the broad negative transition of chitosan helical structure in the wavelength region of 190–230 nm decreased with decreasing the chain length of the dicarboxylic acids. The infrared spectra revealed the formation of amide linkage between chitosan and carboxylic acids in solid state. The cross-sections of the films produced from malonic acid and acetic acid solutions of chitosan exhibited granular morphologies with different granule sizes and hill-valley-structures under atomic force microscope. The chitosan/malonic acid film showed improved water resistance and decreased tensile properties compared with the chitosan/acetic acid and chitosan/adipic acid films. These physical characteristics of chitosan/malonic acid film are attributed to the dual effects of malonic acid, which acts as a chemical cross-linker and also as a plasticizer. A strong glass transition (T _g) peak at 166 °C in differential scanning calorimetric analysis was observed, indicating the possible plasticizing effect with malonic acid.     

Effect of α-Fe2O3 addition on the morphological,optical and decolorization properties of ZnO nanostructures

Visible light sensitive photocatalysts of Fe₂O₃/ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe₂O₃ and sodium hydroxide at room temperature. The products were characterized by scanning electron microscopy, powder X-ray diffraction, N₂ adsorption–desorption measurement, UV–vis absorption, and photoluminescence spectroscopy and used for photodecolorization of Congo red. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe³⁺ to Zn²⁺ ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98–3.81 eV and 2.88–2.98 eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed. These nanocomposites showed high decolorization ability in visible light with wavelength up to about 400 nm. Among the samples, Fe₂O₃/ZnO nanoflower (molar ratio of Fe³⁺ to Zn²⁺ is 1:100) exhibited higher decolorization efficiency than the other nanocomposites. It could be considered as a promising photocatalyst for dyes treatment.     

Synthesis and characterization of alumina flakes/polymer composites

Alumina flakes were prepared by solution combustion method and milled to provide powder. XRD and SEM data exhibited microsized flakes with 100 nm thickness and nanosized grains. Then the powders were dispersed in polystyrene (PS) and poly methyl methacrylate (PMMA) matrixes and thin sheets of composites were produced by solution method. Mechanical properties of the composites were characterized using tensile test and their fracture surfaces, elemental composition and hydrophobic property were tested by SEM, EDX and contact angle techniques, respectively. The results exhibited better mechanical properties compared to pure polymer samples i.e. the elastic modulus in PMMA and PS composites, were increased about 107 and 109%, respectively. In addition the composite surfaces became more hydrophobic than pure polymer systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparative Analysis of Flower Volatiles from Nine Citrus at Three Blooming Stages

Volatiles from flowers at three blooming stages of nine citrus cultivars were analyzed by headspace-solid phase microextraction (HS-SPME)-GC-MS. Up to 110 volatiles were detected, with 42 tentatively identified from citrus flowers for the first time. Highest amounts of volatiles were present in fully opened flowers of most citrus, except for pomelos. All cultivars were characterized by a high percentage of either oxygenated monoterpenes or monoterpene hydrocarbons, and the presence of a high percentage of nitrogen containing compounds was also observed. Flower volatiles varied qualitatively and quantitatively among citrus types during blooming. Limonene was the most abundant flower volatile only in citrons; α-citral and β-citral ranked 2nd and 3rd only for Bergamot, and unopened flowers of Ponkan had a higher amount of linalool and β-pinene while much lower amount of γ-terpinene and p-cymene than Satsuma. Taking the average of all cultivars, linalool and limonene were the top two volatiles for all blooming stages; β-pinene ranked 3rd in unopened flowers, while indole ranked 3rd for half opened and fully opened flower volatiles. As flowers bloomed, methyl anthranilate increased while 2-hexenal and p-cymene decreased. In some cases, a volatile could be high in both unopened and fully opened flowers but low in half opened ones. Through multivariate analysis, the nine citrus cultivars were clustered into three groups, consistent with the three true citrus types. Furthermore, an influence of blooming stages on clustering was observed, especially with hybrids Satsuma and Huyou. Altogether, it was suggested that flower volatiles can be suitable markers for revealing the genetic relationships between citrus cultivars but the same blooming stage needs to be strictly controlled.     

Modified calibrated control charts for monitoring the population mean under stratified sampling

In this research paper, we discuss the use of calibration technique to propose some new estimators under stratified sampling design and its use in reliability engineering. We first proposed the estimators using the calibration technique and then modify the already existing control charts such as Shewhart, exponentially weighted moving average and hybrid exponentially weighted moving averages using these calibration estimators. We also have studied the use of the proposed control charts in detail by showing their efficiency in terms of average run length. We find out that a hybrid control chart is more effective to detect the early shifts in the mean of the process.     

Text Encryption Using Pell Sequence and Elliptic Curves with Provable Security

The demand for data security schemes has increased with the significant advancement in the field of computation and communication networks. We propose a novel three-step text encryption scheme that has provable security against computation attacks such as key attack and statistical attack. The proposed scheme is based on the Pell sequence and elliptic curves, where at the first step the plain text is diffused to get a meaningless plain text by applying a cyclic shift on the symbol set. In the second step, we hide the elements of the diffused plain text from the attackers. For this purpose, we use the Pell sequence, a weight function, and a binary sequence to encode each element of the diffused plain text into real numbers. The encoded diffused plain text is then confused by generating permutations over elliptic curves in the third step. We show that the proposed scheme has provable security against key sensitivity attack and statistical attacks. Furthermore, the proposed scheme is secure against key spacing attack, ciphertext only attack, and known-plaintext attack. Compared to some of the existing text encryption schemes, the proposed scheme is highly secure against modern cryptanalysis.     

Multimodal Medical Image Registration and Fusion for Quality Enhancement

For the last two decades, physicians and clinical experts have used a single imaging modality to identify the normal and abnormal structure of the human body. However, most of the time, medical experts are unable to accurately analyze and examine the information from a single imaging modality due to the limited information. To overcome this problem, a multimodal approach is adopted to increase the qualitative and quantitative medical information which helps the doctors to easily diagnose diseases in their early stages. In the proposed method, a Multi-resolution Rigid Registration (MRR) technique is used for multimodal image registration while Discrete Wavelet Transform (DWT) along with Principal Component Averaging (PCAv) is utilized for image fusion. The proposed MRR method provides more accurate results as compared with Single Rigid Registration (SRR), while the proposed DWT-PCAv fusion process adds-on more constructive information with less computational time. The proposed method is tested on CT and MRI brain imaging modalities of the HARVARD dataset. The fusion results of the proposed method are compared with the existing fusion techniques. The quality assessment metrics such as Mutual Information (MI), Normalize Cross-correlation (NCC) and Feature Mutual Information (FMI) are computed for statistical comparison of the proposed method. The proposed methodology provides more accurate results, better image quality and valuable information for medical diagnoses.     

A control chart for monitoring the lognormal process variation using repetitive sampling

Control charts are developed to make the specific quality measures for a successful production process and follow normal distribution behaviors. But some real-life practices do not match such practices and exhibit some positively skewed behavior like lognormal distribution. The present study has considered this situation and proposed a monitoring control chart based on lognormal process variation using a repetitive sampling scheme. This concept proved better for detecting shifts as quickly as possible, and compared with the existing concept, results are elaborated through extensive tables. The average run lengths and standard deviations of the run lengths are being used as a performance evaluation measures and computed by using Monte Carlo simulations performed in R language. A real-life situation has been discussed in the example section to strengthen the proposed control chart concept in a real-life situation.     

The effect of silk fibroin nanoparticles on the morphology,rheology, dynamic mechanical properties,and toughness of poly(lactic acid)/poly(ε-caprolactone) nanocomposite

The silk fibroin nanoparticles (SFNPs) were extracted from silkworm cocoons and used as a nanofiller in poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blend. The nanoparticle localization was studied theoretically and experimentally and the effects of SFNP on the morphology, rheology, toughness, and dynamic mechanical properties of the blend were investigated. According to the calculated wetting coefficient, SFNP should be thermodynamically located in the PLA matrix during the melting process. The results of SEM illustrated a common sea-island structure for the PLA/PCL blend and the incorporation of SFNP reduced the PCL domain sizes from 1.170 ± 92 μm to 794 ± 46 nm. The atomic force microscopy results showed that the nanoparticles are mainly located in the PLA matrix and also, partially at the phase interface with a thickness of layers around 80 nm. The rheological tests displayed the network formation of SFNP in the prepared nanocomposites. The dynamic mechanical analysis revealed that by the addition of SFNP, the storage modulus of neat PLA and PLA/PCL blend were increased by around 57 and 50%, respectively and the glass transition temperatures (Tg) values of PLA and PCL shifted toward each other. Additionally, using SFNP caused a lower water uptake and higher impact strength (~64%) of the blend.     

Application of fluorescence spectroscopy for rapid and noninvasive quality determination of yoghurt ice cream using chemometrics

The aim of this study was to explore the potential of fluorescence spectroscopy to determine the quality of yoghurt ice cream, prepared by adding different concentrations of yoghurt (10, 20, 30, 40, 50%). The addition of 50% of yoghurt showed the lowest pH and meltdown values, whereas the highest acidity and overrun rates were observed at the same concentration. Additionally, fluorescence spectra taken at varied emission and excitation ranges were preprocessed for baseline correction. The partial least square regression analysis on proposed excitation wavelengths (270 nm, 280 nm, 290 nm and 315 nm) showed effective prediction of various quality parameters of yoghurt ice cream.