Study of the correlation between the magnetic and electrical properties of the La0.6Sr0.4MnO3 compound.

In this work, we investigated the relationship between the electrical and magnetic properties of the superparamagnetic (SPM) La0.6Sr0.4MnO3 (S1C0) compound prepared by the sol-gel method. The (S1C0) sample displayed a ferromagnetic metallic (FMM) behavior at low temperatures and a paramagnetic semiconductor (PMSC) behavior at high temperatures. The FMM behavior was described by the Zener Double Exchange (ZDE) polynomial law containing the contributions of the electron-electron (e-e) interactions and the electron-magnon (e-m) scattering. The PMSC behavior was described by the Mott Variable Range Hopping (Mott-VRH) transport model. The semiconductor/metallic transition temperature has been approximated at the blocking temperature. The Thermal Coefficient of Resistivity (TCR), which exhibits a linear variation around ambient temperature, can be used as a calibration curve for thermometry. Thus, our sample can be considered as a good candidate for the detection of infrared radiation used in night vision bolometer technologies.

Impact of synthesis route on structural, magnetic, magnetocaloric and critical behavior of Nd0.6Sr0.4MnO3 manganite.

Nd0.6Sr0.4MnO3 polycrystalline manganite was synthesized by two different methods: the auto-combustion reaction (NSMO-AC) and the sol-gel method (NSMO-SG). The structural, magnetic, magnetocaloric and critical behavior of the samples were examined. Rietveld refinements of the XRD patterns revealed that both compounds are pure single phase indexed to the orthorhombic system adopting the Pnma space group. The nanometric size estimated using the Williamson-Hall method was confirmed by TEM micrographs. Magnetic measurements as a function of temperature indicated that both samples underwent a second order ferromagnetic (FM)-paramagnetic (PM) phase transition at Curie temperature (T C). The relative cooling power was observed to be around 95.271 J kg-1 for NSMO-AC and 202.054 J kg-1 for NSMO-SG at µ 0 H = 5 T, indicating that these materials are potential candidates for magnetic refrigeration application close to room temperature. The critical behavior was estimated using diverse techniques based on the isothermal magnetization data recorded around the critical temperature T C. The calculated values are fully satisfactory to the requirements of the scaling theory, implying their reliability. The estimated critical exponents matched well with the values anticipated for the mean-field model and the 3D Ising model for NSMO-AC and NSMO-SG, respectively, showing that the magnetic interactions depended on the process of elaboration.

Screening of biological activities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio cultivations in Tunisia.

AIMS: In this study, we aimed to explore the enzymatic diversity, the entomopathogenic and the antimicrobial potentialities of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus. METHODS AND RESULTS: A total of 40 isolates were screened for enzymatic diversity. Most of them, 92·5%, were able to produce at least two of the screened enzymes. Pathogenic assays performed on C. vestitus showed a high entomopathogenic activity of the isolates Ata_io_1 (A. tamarii), Fve_io_1 (F. verticillioides), Tpi_io_1 (T. pinophilus), Pal_io_1 (P. album), Pbi_io_2 (Penicillium bilaiae) and Pch_io_1 (P. chrysogenum), as based on mean mortality of C. vestitus. A screening of antimicrobial activity using well diffusion method showed that the isolates Tro_io_1 (T. pinophilus), Tat_io_1 (T. atroroseus) and Pch_io_1 (P. chrysogenum) presented the highest antibacterial activity. Furthermore, Mgu_io_1 (M. guilliermondii), Asc_io_1 (A. sclerotiorum), Ata_io_1 (A. tamarii), G. lavendula (Gla_io_1), Pva_io_1 (P. variotii), Pul_io_1 (P. ulaiense), Tat_io_1 (T. atroroseus) and Tro_io_1 (T. roseum) were active against at least two of the three tested fungal phytopathogens. CONCLUSIONS: Fungal isolates representing entomopathogenic activity and a broad spectrum of antimicrobial activities can be considered as promising resources for biological pistachio trees protection. SIGNIFICANCE AND IMPACT OF THE STUDY: Fungi associated with C. vestitus were investigated for detecting their potential biotechnological applications.

The effects of hyperbaric oxygen therapy on diabetic retinopathy: A preliminary study.

PURPOSE: The objective of this study was to prospectively assess the effect of hyperbaric oxygen therapy (HBOT) on diabetic retinopathy lesions and macular edema in patients undergoing the treatment for diabetic foot ulcers. METHODS: We compared two groups: a first group including 25 patients with non-proliferative diabetic retinopathy treated by HBOT for foot ulcers, and a second group (control group) composed of 25 patients with diabetic retinopathy who did not receive HBOT. The HBOT protocol performed for the patients in the first group was: 30 sessions of 90 minutes each at 2.5 ATA with a mean frequency of five sessions per week. All patients had an ophthalmological exam at baseline (visual acuity, intraocular pressure, fundus exam), fundus photography and an OCT exam. A follow-up exam was performed at the conclusion of the HBOT. RESULTS: Compared to the control group, patients treated with HBOT showed a regression or stabilization of diabetic retinopathy lesions and a decrease in central macular thickness (CMT). CONCLUSION: Hyperbaric oxygen therapy may improve diabetic retinopathy and diabetic macular edema. This therapy may serve as an adjunctive treatment in the management of retinal ischemia and capillary hyperpermeability in diabetic retinopathy.

Phytopathogenic and antagonistic potentialities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio (Pistacia vera) in Tunisia.

AIM: This study investigated the biodiversity of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus, in Tunisia. We evaluated the phytopathogenic activities and tested antagonistic potentialities with respect to phytopathogens. METHODS AND RESULTS: A total of 41 fungal isolates were randomly isolated from C. vestitus adults and galleries. We identified 28 species belonging to 13 genera using ITS sequences of the ribosomal RNA operons. Pathogenicity assays performed using the excised shoot method revealed that isolates Aal_io_1 (Alternaria alternata), Feq_io_1 (Fusarium equiseti), Fgra_io_1 (Fusarium graminearum), Fve_io_1 (Fusarium verticilloides), Tro_io_1 (Trichothecium roseum) and Nqu_io_1 (Nothophoma quercina) displayed a high pathogenic activity on pistachio stems. Estimation of the antagonistic potentialities of isolated fungi against several phytopathogenic isolates as tested using a dual-culture method showed that isolates Tpi_io_1 (Talaromyces pinophilus), Pbi_io_2 (Penicillium bilaiae), Asc_io_1 (Aspergillus sclerotiorum) and Gla_io_1 (Geosmithia lavendula) displayed a broad range of antagonistic activities. CONCLUSION: Fungi associated with C. vestitus had a variable range of pathogenic activity on pistachio stem. Phytopathogenic fungi were antagonized by different fungal isolates which could be promising in pistachio protection against phytopathogenic fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first that investigated the diversity of fungi associated with C. vestitus and evaluated both their phytopathogenic activity and antagonistic potential against fungal phytopathogens.

Screening of bacterial isolates related to olive orchard pests in Tunisia using 16S ribosomal RNA and evaluation of their biotechnological potential.

AIM: This study investigated the bacterial diversity of dead insects collected from olive tree orchards widely cultivated in Tunisia. We aimed to explore metabolic diversity, screen enzymatic activities for biotechnological applications and carry out preliminary bioassays for bio-insecticide development. METHODS AND RESULTS: A total of 50 bacteria strains were randomly isolated from four different biotopes situated in Sfax (Tunisia). 16S rRNA gene sequencing was used to identify 24 species, and isolates were evaluated for enzymatic activity and antimicrobial potential. Nineteen of the total number of Bacillus strains have enzymatic activity compared to strains from the other genera (14/50). Our bacterial collection was evaluated for antimicrobial potential against bacterial and fungal isolates. Isolates B8-2 (Bacillus subtilis) showed strong antibacterial activities and isolates B2-3 (Bacillus licheniformis) and B10-1 (Serratia marcescens) showed the highest antifungal activity. Seventeen of the total number of isolates caused greater than 50% mortality rate of second and fourth instar larvae of Ephestia kuehniella. CONCLUSION: The selected species from olive orchards represent a broad spectrum of antimicrobial and insecticidal activities and can be considered promising resources in biological control. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteria isolated from olive pests in olive orchards were investigated for detecting their potential biotechnological applications.

Magnetocaloric study, critical behavior and spontaneous magnetization estimation in La0.6Ca0.3Sr0.1MnO3 perovskite.

A detailed study of structural, magnetic and magnetocaloric properties of the polycrystalline manganite La0.6Ca0.3Sr0.1MnO3 is presented. The Rietveld refinement of X-ray diffraction pattern reveals that our sample is indexed in the orthorhombic structure with Pbnm space group. Magnetic measurements display a second order paramagnetic (PM)/ferromagnetic (FM) phase transition at Curie temperature T c = 304 K. The magnetic entropy change (ΔS M) is calculated using two different methods: Maxwell relations and Landau theory. An acceptable agreement between both data is noted, indicating the importance of magnetoelastic coupling and electron interaction in magnetocaloric effect (MCE) properties of La0.6Ca0.3Sr0.1MnO3. The maximum magnetic entropy change (-ΔS max M) and the relative cooling power (RCP) are found to be respectively 5.26 J kg-1 K-1 and 262.53 J kg-1 for µ 0 H = 5 T, making of this material a promising candidate for magnetic refrigeration application. The magnetic entropy curves are found to follow the universal law, confirming the existence of a second order PM/FM phase transition at T c which is in excellent agreement with that already deduced from Banerjee criterion. The critical exponents are extracted from the field dependence of the magnetic entropy change. Their values are close to the 3D-Ising class. Scaling laws are obeyed, implying their reliability. The spontaneous magnetization values determined using the magnetic entropy change (ΔS M vs. M 2) are in good agreement with those obtained from the classical extrapolation of Arrott curves (µ 0 H/M vs. M 2). The magnetic entropy change can be effectively used in studying the critical behavior and the spontaneous magnetization in manganites system.

Structural, magnetic and magnetocaloric properties of 0.75La0.6Ca0.4MnO3/0.25La0.6Sr0.4MnO3 nanocomposite manganite.

The present study involves an investigation of structural, magnetic and magnetocaloric effect (MCE) properties of 0.75La0.6Ca0.4MnO3/0.25La0.6Sr0.4MnO3 composite material. Crystal structure analysis is performed by using Rietveld refinement of the X-ray diffraction patterns. The studied composite exhibits two structural phases; the rhombohedral and the orthorhombic structures corresponding to the mother compounds; La0.6Ca0.4MnO3 and La0.6Sr0.4MnO3, respectively. The scanning electron microscopy micrographs support our findings. Magnetic measurements as a function of temperature of the composite display two successive second order magnetic phase transitions at 255 and 365 K associated to both mother compounds. Therefore, a broadening of the magnetic entropy change peak is noted. A better relative cooling power (RCP) value of 360 J kg-1 compared to those observed in mother compounds is obtained at µ 0 H = 5 T, making of this material considered as a suitable candidate for magnetic refrigeration applications near room temperature. A consistent agreement between experimental results and numerical calculations based on the rule of mixtures has been shown. The theoretical modeling of the MCE using Landau theory reveals an acceptable concordance with experimental data indicating the importance of magnetoelastic coupling and electron interaction in the MCE properties of manganite systems. The field dependence of the magnetic entropy change is applied to study the critical behavior. Our results go in tandem with the values corresponding to the mean field model. The spontaneous magnetization values determined using the magnetic entropy change (ΔS M vs. M 2) are in good agreement with those found from the classical extrapolation of Arrott curves (µ 0 H/M vs. M 2).

Development and application of an in-house reverse hybridization method for Chlamydia trachomatis genotyping.

AIM: To develop and evaluate an in-house reverse hybridization technique for Chlamydia trachomatis genotype identification. METHODS AND RESULTS: The evaluation of the developed and optimized reverse hybridization method on reference strains showed the specific detection of all genotypes. This technique showed its ability to type one inclusion-forming unit of C. trachomatis genotype E and equivalent sensitivity to the Cobas TaqMan assay. It was also able to detect mixed infections in vitro. Application of the reverse hybridization method on 38 isolated C. trachomatis strains and their respective swabs allowed the detection of six urogenital genotypes D, E, F, G, H and K and one trachoma genotype B. Genotype E was the most prevalent, detected in 73% of the swab samples. Mixed infections were detected in 26% of swab cases. CONCLUSION: The reverse hybridization technique is simple and does not require specialized instruments. It is powerful in the diagnosis of mixed infections and is suitable for use in epidemiological studies. SIGNIFICANCE AND IMPACT OF THE STUDY: This technique allowed rapid C. trachomatis genotype identification.