Multisensor biomimetic systems with fully artificial recognition strategies in food analysis

Abstract  Food materials and their products are directly connected with the life of all living beings and thus present themselves as most important candidates for quality analysis. A wide variety of method-development strategies are being applied for this purpose, but direct online systems are highly desirable, with demand ever increasing. This article reviews recent literature on the topic stressing mainly two points: the first is the development of artificial multisensor systems and the second is the design of robust materials for these devices. Although most of the progress in the area has focused on metal oxide semiconductors, novel approaches using electrochemical and mass-sensitive systems are also emerging rapidly. As far as sensing materials are concerned, tailor-made interaction layers, where interaction sites are, e.g., created in polymeric substances, are replacing biomaterials. Among these, molecular imprinting is the most prominent. In this technique selectivity is achieved by making direct imprints of templates in a polymer matrix, thus generating a material homologous with its biological counterparts. Graphical Abstract        

Wavelet based correlation coefficient of time series of Saudi Meteorological Data

In this paper, wavelet concepts are used to study a correlation between pairs of time series of meteorological parameters such as pressure, temperature, rainfall, relative humidity and wind speed. The study utilized the daily average values of meteorological parameters of nine meteorological stations of Saudi Arabia located at different strategic locations. The data used in this study cover a period of 16 years between 1990 and 2005. Besides obtaining wavelet spectra, we also computed the wavelet correlation coefficients between two same parameters from two different locations and show that strong correlation or strong anti-correlation depends on scale. The cross-correlation coefficients of meteorological parameters between two stations were also calculated using statistical function. For coastal to costal pair of stations, pressure time series was found to be strongly correlated. In general, the temperature data were found to be strongly correlated for all pairs of stations and the rainfall data the least.     

Test of a new tip material for Langmuir probe diagnostic

The objective of the work is to test a nickel–chrome alloy as a probe tip material for characterization of discharge plasmas. In order to meet the objective, a symmetric triple Langmuir probe diagnostic system and an associated driving circuit are designed and tested in an inductively coupled plasma generated by a 13.56-MHz radio frequency source coupled with an automated impedance match network. This probe is used to measure the electron temperature, electron number density, and ion saturation current as functions of the input power of the radio frequency source and the filling gas pressure. An increasing trend is noticed in the electron temperature and electron number density with an increase in the input power, whilst a decreasing trend is evident in these parameters with an increase in the nitrogen gas pressure. The overall inaccuracies in electron temperature and electron number density measurements are 5–12% and 3–13%, respectively.     

Lyciumaside and Lyciumate: A New Diacylglycoside and Sesquiterpene Lactone from Lycium shawii

One new diacylglycoside named lyciumaside ( 1 ) and a new sesquiterpene lactone named lyciumate ( 2 ) were isolated from Lycium shawii Roem . & Schult . The structures of the two new compounds were elucidated based on 1D‐ (¹H‐ and ¹³C‐NMR and NOE) and 2D‐NMR (COSY, HSQC, and HMBC) spectroscopic techniques, and mass spectrometry (ESI‐MS). Preliminary evaluations demonstrated lyciumaside ( 1 ) possesses strong antioxidant activity with an IC₅₀ = 30 μg/ml (80% inhibition) while it was inactive in α‐glucosidase and urease enzymes assays.     

Tailoring the optical and magnetic properties of La-BaM hexaferrites by Ni substitution

We investigate the impact of Ni insertion on the structural,optical,and magnetic properties of Ba_0.8La_0.2Fe_12-xNi_xO₁₉hexaferrites(Ni substituted La-BaM hexaferrites).Samples were prepared using the conventional co-precipitation method and sintered at 1000℃for 4 hours to assist the crystallization process.An analysis of the structure of the samples was carried out using an x-ray diffraction(XRD)spectrometer.The M-type hexagonal structure of all the samples was confirmed using XRD spectra.The lattice parameters a and c were found to be in the ranges of 5.8925±0.001 nm–5.8952±0.001 nm and 23.2123±0.001 nm–23.2219±0.001 nm,respectively.The M-type hexagonal nature of the prepared samples was also indicated by the presence of corresponding FT-IR bands and Raman modes in the FT-IR and Raman spectra,respectively.EDX results confirmed the successful synthesis of the samples according to the required stoichiometric ratio.A UV-vis spectrometer was used to record the absorption spectra of the prepared samples in the wavelength range of 200 nm–1100 nm.The optical energy bandgap of the samples was found to be in the range of 1.21 eV–3.39 eV.The M–H loops of the samples were measured at room temperature at an applied magnetic field range of 0 kOe–60 kOe.A high saturation magnetization of 99.92 emu/g was recorded in the sample with x=0 at a microwave operating frequency of 22.2 GHz.This high value of saturation magnetization is due to the substitution of La3+ions at the spin-up(12k,2a,and 2b)sites.The Ni substitution is proven to be a potential candidate for the tuning of the optical and magnetic parameters of M-type hexaferrites.Therefore,we suggest that the prepared samples are suitable for use in magneto-optic applications.     

Micellar parameters of diblock copolymers and their interactions with ionic surfactants

The interactions of non-ionic amphiphilic diblock copolymer poly（oxyethylene/oxybutylene）(E₃₉B₁₈) with anionic surfactant sodium dodecyl sulphate（SDS） and cationic surfactant hexadecyltrimethylammonium bromide（CTAB） were studied by using various techniques such as surface tension,conductivity,steady-state fluorescence and dynamic light scattering.Surface tension measurements were used to determine the critical micelle concentration（CMC） and thereby the free energy of micellization(△G_mic),free energy of adsorption(△G_ads),surface excess concentration（Γ） and minimum area per molecule（A）.Conductivity measurements were used to determine the critical micelle concentration（CMC）,critical aggregation concentration（CAC）,polymer saturation point（PSP）,degree of ionization（α） and counter ion binding（β）. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles taken place due to the interactions of diblock copolymers with ionic surfactants.The ratio of the first and third vibronic peaks（I₁/I₃） indicated the polarity of the pyrene micro environment and was used for the detection of micelle as well as polymer-surfactant interactions.Aggregation number（N）,number of binding sites（n） and free energy of binding （△G_b） for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by the fluorescence quenching method.     

Genotypic Variability Among Soybean Genotypes Under NaCl Stress and Proteome Analysis of Salt-Tolerant Genotype

The present investigation was conducted to evaluate salt tolerance in ten genotypes of soybean (Glycine max L.). Twelve-day-old seedlings, grown hydroponically, were treated with 0, 25, 50, 75, 100, 125 and 150?mM NaCl for 10?days. Growth, lipid peroxidation and antioxidant enzyme activities were evaluated. Growth, measured in terms of length, fresh weight and dry weight of plants, was drastically reduced in Pusa-24 while there was little effect of NaCl treatment on Pusa-37 genotype of soybean. High level of lipid peroxidation was observed in Pusa-24 as indicated by increased level of malondialdehyde. Activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were maximum in Pusa-37 where 9-, 1-, 5- and 6-fold increase over control were observed, respectively. The results suggested that Pusa-24 and Pusa-37 are salt-sensitive and salt-tolerant genotype of soybean, respectively, and antioxidant defence system is involved in conferring the sensitiveness and tolerance in these genotypes. Salt-tolerant genotype Pusa-37, was further analysed by 2-dimensional gel electrophoresis to analyse the differential expression of proteins at high salt stress. In the present study, 173 protein spots were identified. Of these, 40 proteins were responsive to salinity in that they were either up- or downregulated. This study could help us in identifying the possible regulatory switches (gene/s) controlling novel proteins of the salt-tolerant genotype of the crop plants and their possible role in defence mechanism.     

Effects of divalent alkaline earth ions on the magnetic and transport features of La0.65A0.35Mn0.95Fe0.05O3 (A = Ca, Sr, Pb, Ba) compounds

We have studied the magnetic and transport properties of Fe doped La_0.65A_0.35Mn_0.95Fe_0.05O₃ (A = Ca, Sr, Pb, Ba) manganites. All the compositions show ferromagnetic/metal to paramagnetic/insulator transition (T_C) except the Pb doped sample which is insulating and ferromagnetic (FM) in the entire temperature range. The magnetization and T_C are decreased by decreasing the cation size on La site. The transition temperature and magnetic moment at 77 K is a maximum for Sr doped sample and is decreasing if we increase or decrease the cation size from Sr size. The maximum value of T_C and magnetic moment for Sr based sample is most likely due to the closer ionic sizes of La and Sr as compared to the other dopants (Ca, Pb, and Ba). We observed a spin freezing type effect in the Pb doped sample below 120 K in resistivity, ac susceptibility and in magnetization. This suggests that the AFM interactions introduced by the Fe are most effective in the Pb doped composition leading to increased competition between the FM and AFM interactions. This FM and AFM interaction generates some degree of frustration leading to the appearance of spin glass like phase whose typical magnetic behavior is studied for small ion when the metallic like behavior is lost.