259 research outputs found
First Record of Leptocybe invasa and Ophelimus maskelli Eucalyptus Gall Wasps in Tunisia
Two Australian gall wasps were detected for the first time in Tunisia on the foliage of Eucalyptus
camaldulensis trees. Leptocybe invasa was detected in 2004, while Ophelimus maskelli in 2006. L.
invasa makes galls on petioles, leaf midribs and young branches whereas O. maskelli induces galls on
limbs. Vigilance is recommended when seedlings are carried to plantation
Influence of oxygen deficiency on optical and dielectric properties of La0.75Ba0.10Sr0.15FeO2.875-δ compounds
Using the conventional sol-gel process, the series of non-stoichiometric oxygen lanthanum
ferrites with the formula 0.750.100.152.875 ― (δ=0.00, 0.125 and 0.25) were
prepared. X-ray diffraction analysis confirmed the formation of the orthorhombic structure
with Pnma space group. In the present work, we confirm the potential of 0.750.100.15
2.875 ― (δ=0.00, 0.125 and 0.25) as an efficient dielectric material. All samples show high
absorbance in the visible region with wavelength above 300 nm. The optical band gaps are
found to increase from 3.25 to 4.1 with increasing oxygen vacancy concentration. The
dielectric constant, dielectric loss and loss factor were carried out as a function of oxygen
vacancy concentration and frequency (102
-106 Hz) at room temperature. The variation of
dielectric constant with frequency indicates dispersive behavior and giant dielectric response
(more than 104
) at low frequencies for compounds deficient in oxygen. Such value of makes ′
these samples an interesting material to be used in applications namely the reduction of
electronic components size. To summarize, incorporating vacancy oxygen enhances the
dielectric properties. Thus, the interesting dielectric constant and weak loss strengthen the use
for potential applications.publishe
Ultrafast Electrochemical Self-Doping of Anodic Titanium Dioxide Nanotubes for Enhanced Electroanalytical and Photocatalytic Performance
This study explores an ultrarapid electrochemical self-doping procedure applied to anodic titanium dioxide (TiO2) nanotube arrays in an alkaline solution to boost their performance for electroanalytical and photocatalytic applications. The electrochemical self-doping process (i.e., the creation of surface Ti3+ states by applying a negative potential) is recently emerging as a simpler and cleaner way to improve the electronic properties of TiO2 compared to traditional chemical and high-temperature doping strategies. Here, self-doping was carried out through varying voltages and treatment times to identify the most performing materials without compromising their structural stability. Interestingly, cyclic voltammetry characterization revealed that undoped TiO2 shows negligible activity, whereas all self-doped materials demonstrate their suitability as electrode materials: an outstandingly short 10 s self-doping treatment leads to the highest electrochemical activity. The electrochemical detection of hydrogen peroxide was assessed as well, demonstrating a good sensitivity and a linear detection range of 3–200 µM. Additionally, the self-doped TiO2 nanotubes exhibited an enhanced photocatalytic activity compared to the untreated substrate: the degradation potential of methylene blue under UV light exposure increased by 25% in comparison to undoped materials. Overall, this study highlights the potential of ultrafast electrochemical self-doping to unleash and improve TiO2 nanotubes performances for electroanalytical and photocatalytic applications
Hopping conduction mechanism and impedance spectroscopy analyses of La0.70Sr0.25Na0.05Mn0.70Ti0.30O3 ceramic
The perovskite sample La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 (LSNM0.70T0.30) was produced via a solid-state route process. The frequency dependence of electrical conduction plot established that according to the Jonscher law. The electrical conduction process was based on both theoretical conduction models assigned to the non-overlapping small polaron tunneling model at low temperatures and correlated barrier hopping mechanism at high temperatures. Detailed investigation of impedance data revealed a non-Debye-type relaxation occurring in the polycrystalline. In addition, the dielectric response confirmed the dominance of the Maxwell–Wagner model and Koop’s phenomenological theory effect in conduction phenomenon. The values of permittivity is high for LSNM0.70T0.30 were observed. These values make this composition interesting for microelectric applications. In the thermal study, the relaxation processes observed by electrical conductivity, impedance, and modulus are associated with singly and doubly ionized oxygen vacancies for the lower and higher temperature, respectively. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Majmaah University, MU: R-2021-121The author would like to thank Deanship of Scientific Research at Majmaah University for supporting this work under Project Number No. R-2021-121
Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry
In this paper we examine the role of crystal chemistry factors in creating
conditions for formation of magnetoelectric ordering in BiFeO3. It is generally
accepted that the main reason of the ferroelectric distortion in BiFeO3 is
concerned with a stereochemical activity of the Bi lone pair. However, the lone
pair is stereochemically active in the paraelectric orthorhombic beta-phase as
well. We demonstrate that a crucial role in emerging of phase transitions of
the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order
types belongs to the change of the degree of the lone pair stereochemical
activity - its consecutive increase with the temperature decrease. Using the
structural data, we calculated the sign and strength of magnetic couplings in
BiFeO3 in the range from 945 C down to 25 C and found the couplings, which
undergo the antiferromagnetic-ferromagnetic transition with the temperature
decrease and give rise to the antiferromagnetic ordering and its delay in
regard to temperature, as compared to the ferroelectric ordering. We discuss
the reasons of emerging of the spatially modulated spin structure and its
suppression by doping with La3+.Comment: 18 pages, 5 figures, 3 table
Erratum to: Changes in patterns of uveitis at a tertiary referral center in Northern Italy: analysis of 990 consecutive cases
Erratum to: Changes in patterns of uveitis at a tertiary referral center in Northern Italy: analysis of 990 consecutive case
Synthesis and electric characterization of rare earth double perovskite Ho2CdZrO6 ceramics
Critical Behavior Near the Paramagnetic to Ferromagnetic Phase Transition Temperature in Sr1.5Nd0.5MnO4 Compound
Changes in patterns of uveitis at a tertiary referral center in Northern Italy: analysis of 990 consecutive cases
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