The influence of Sr and Fe on the conductance of magnetoresistant compounds

Single-phase giant magnetoresistance (GMR) compounds were prepared by doping the parent compound, NdMnO₃, with Sr at Nd sites. The resistivity of the doped samples showed two prominent regions (Δρ/ΔT < 0, insulating and Δρ/ΔT > 0, metallic). The doped samples exhibited an enhancement in double exchange (DE) interactions causing an increase in T _c (transition temperature). Magnetic field decreased the resistance of all the samples because of the suppression of spin fluctuations and an increase in disorder in the system. The polaron and variable range hopping (VRH) models were good for studying the transport mechanism of electrons and understand their behavior at T > T _c.     

Solutions globales de certaines équations de Fuchs non linéaires dans les espaces de Gevrey

We consider nonlinear partial differential equations with several Fuchsian variables of type , where is a Fuchsian principal part of weight zero. We prove existence and uniqueness of a global solution to this problem in the space of holomorphic functions with respect to the Fuchsian variable and in Gevrey spaces with respect to the other variable . The method of proof is based on the application of the fixed point theorem in some Banach algebras defined by majorant functions that are suitable to this kind of equation.

     

Development of Antibacterial,Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R² = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.     

Platinum electrode modified with polyterthiophene doped with metallic nanoparticles,as sensitive sensor for the electroanalysis of ascorbic acid (AA)

A novel electrochemical sensor for ascorbic acid (AA) detection based on platinum electrode modified with polyterthiophene (P3T) and doped with metallic particles (Cu, Co, Ag, Au, Pd) was constructed. The electrocatalytic performances of the modified electrode with polyterthiophene-metallic particles related to the detection of AA, showed a better catalytic activity compared to the modified electrode with polyterthiophene film. The obtained results demonstrate also that the use of P3T–Ag nanocomposite allows a good sensitivity; which gives a high response in oxidation peak of AA. In order to have a good performance using this sensor, several parameters such as polymerization time of the film and immersion time of the film in AgNO₃ solution were optimized.     

Scarlet Flax Linum grandiflorum (L.) In Vitro Cultures as a New Source of Antioxidant and Anti-Inflammatory Lignans

In vitro cultures of scarlet flax (Linum grandiflorum L.), an important ornamental flax, have been established as a new possible valuable resource of lignans and neolignans for antioxidant and anti-inflammatory applications. The callogenic potential at different concentrations of α-naphthalene acetic acid (NAA) and thidiazuron (TDZ), alone or in combinations, was evaluated using both L. grandiflorum hypocotyl and cotyledon explants. A higher callus induction frequency was observed on NAA than TDZ, especially for hypocotyl explants, with a maximum frequency (i.e., 95.2%) on 1.0 mg/L of NAA. The presence of NAA (1.0 mg/L) in conjunction with TDZ tended to increase the frequency of callogenesis relative to TDZ alone, but never reached the values observed with NAA alone, thereby indicating the lack of synergy between these two plant growth regulators (PGRs). Similarly, in terms of biomass, NAA was more effective than TDZ, with a maximum accumulation of biomass registered for medium supplemented with 1.0 mg/L of NAA using hypocotyls as initial explants (DW: 13.1 g). However, for biomass, a synergy between the two PGRs was observed, particularly for cotyledon-derived explants and for the lowest concentrations of TDZ. The influence of these two PGRs on callogenesis and biomass is discussed. The HPLC analysis confirmed the presence of lignans (secoisolariciresinol (SECO) and lariciresinol (LARI) and neolignan (dehydrodiconiferyl alcohol [DCA]) naturally accumulated in their glycoside forms. Furthermore, the antioxidant activities performed for both hypocotyl- and cotyledon-derived cultures were also found maximal (DPPH: 89.5%, FRAP 866: µM TEAC, ABTS: 456 µM TEAC) in hypocotyl-derived callus cultures as compared with callus obtained from cotyledon explants. Moreover, the anti-inflammatory activities revealed high inhibition (COX-1: 47.4% and COX-2: 51.1%) for extract of hypocotyl-derived callus cultures at 2.5 mg/L TDZ. The anti-inflammatory action against COX-1 and COX-2 was supported by the IC₅₀ values. This report provides a viable approach for enhanced biomass accumulation and efficient production of (neo)lignans in L. grandiflorum callus cultures.     

Phase Transition Behavior of a New Monotropic Liquid Crystal by Inverse GC

A new monotropic liquid crystal with crown ether substituent called Substance M was synthetized and characterized by several methods: ¹H NMR, hot stage polarizing microscopy, differential scanning calorimetry and inverse gas chromatography. Annealing experiments with inverse gas chromatography confirmed the monotropic behavior of the compound. Isothermally in the nematic state, solute probes chosen were chromatographed after different heating times. The changes of the corresponding retention times were studied.     

FTIR analysis of natural and synthetic collagen

Collagen is the most abundant protein in humans and animals, comprising of one third of the total proteins that accounts for three quarters of the dry weight skin in humans. Collagen containing a range of proteins has been reported for tissue engineering applications, but, only a small number of studies related to chemical structure evaluation of collagen are found in the literature. Collagen can be obtained from both the natural and synthetic sources and offers a wide range of biomedical applications due to its excellent biocompatibility and low immunogenicity. Hence, it is important to identify chemical structural properties of collagen and Fourier transform infrared (FTIR) appears to be a technique of choice to study their chemical structure. This review aims to highlight the use of FTIR to study collagen-based biomaterials, using it for characterization of collagen extracted from various sources. Characterization of collagen-based materials used in wound healing, skin substitutes, derma fillers, and aging of skin, collagen containing drug delivery agents, collagen-based materials used in tissue engineering, bone regeneration, and osteogenic differentiation is discussed in detail. FTIR analysis of collagen-containing materials used for dental applications, cleft-palate, and in alveolar-ridge preservation has also been highlighted.     

Influence of rare earth Ce on structural, electrical and magnetic properties of Sr based W-type hexagonal ferrites

A series of single phase W-type Sr_3−xCe_xFe₁₆O₂₇ (x=0, 0.02, 0.04, 0.06, 0.08, 0.10) hexagonal ferrites prepared by the Sol-Gel method was sintered at 1050 °C for 5 h. The X-ray diffraction analysis reveals that all the samples belong to the family of W-type hexagonal ferrites. The c/a ratio falls in the range of W-type hexagonal ferrites. The grain size was measured by SEM varies from 0.7684 to 0.4366 μm which shows that the Ce³⁺ substituted samples have smaller grain size than pure ferrite Sr₃Fe₁₆O₂₇ which results from the difference in ionic radii of Ce³⁺ (1.034 Å) and Sr²⁺ (1.12 Å). The room temperature resistivity of the present samples varies from 6.5×10⁸ to 272×10⁸ Ω-cm. The coercivity increases from 1370 to 1993 Oe which is consistent with the decrease in grain size. The coercivity values indicate that the present samples fall in the range of hard ferrites. The large value of H_c may be due to domain wall pinning at the grain boundaries.     

Synthesis and antiviral screening of some novel pyridazine and triazolopyridazine nucleosides

Some novel cyclic and acyclic pyridazine and triazolopyridazine nucleoside derivatives were prepared. Some of the prepared products were selected and tested for antiviral activity against herpes simplex virus type‐1 (HSV‐1) and hepatitis‐A virus (HAV, MBB‐cell culture adapted strain). Plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with test compounds. Compound 15 showed the highest effect on the HAV than the other tested compounds. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:274–282, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20296     

Novel functionalized cellulose derivatives fabricated with Cu nanoparticles: synthesis,characterization and degradation of organic pollutants

Cellulose - In this study, microcrystalline cellulose (MCC) was modified to oxidized cellulose (OC), 6-deoxycellulose hydrazide and 6-deoxycellulose (N,N-diethyl)amine (MCC-Hyd and MCC-DEM)...