Cooccurrence of Multiple AmpC β-Lactamases in Escherichia coli,Klebsiella pneumoniae,and Proteus mirabilis in Tunisia

Over a period of 40 months, plasmid-mediated AmpC β-lactamases were detected in Tunis, Tunisia, in 78 isolates (0.59%) of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. In 67 isolates, only one ampC gene was detected, i.e., bla_CMY-2-type (n = 33), bla_ACC (n = 23), bla_DHA (n = 6) or bla_EBC (n = 5). Multiple ampC genes were detected in 11 isolates, with the following distribution: bla_MOX-2, bla_FOX-3, and bla_CMY-4/16 (n = 6), bla_FOX-3 and bla_MOX-2 (n = 3), and bla_CMY-4 and bla_MOX-2 (n = 2). A great variety of plasmids carrying these genes was found, independently of the species and the bla gene. If the genetic context of bla_CMY-2-type is variable, that of bla_MOX-2, reported in part previously, is unique and that of bla_FOX-3 is unique and new.     

Magnetic and spectroscopic properties of Ni–Zn–Al ferrite spinel: from the nanoscale to microscale

This article presents the annealing effect on the structural, elastic, thermodynamic, optical, magnetic, and electric properties of Ni_0.6Zn_0.4Fe_1.5Al_0.5O₄ (NZFAO) nanoparticles (NPs). The samples were successfully synthesized by the sol–gel method followed by annealing of the as-synthesized at 600, 800, 900, 1050, and 1200 °C. This approach yielded the formation of a highly crystalline structure with crystallite size ranging from 17 nm to 40 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques, as well as energy disperse spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman spectroscopy, were used in order to determine the structural and morphological properties of the prepared samples. Rietveld XRD refinement reveals that Ni–Zn–Al ferrite nanoparticles crystallize in inverse cubic (Fd$\bar{3}$m) spinel structure. Using FTIR spectra, the elastic and thermodynamic properties were estimated. It was observed that the particle size had a pronounced effect on elastic and thermodynamic properties. Magnetic measurements were performed up to 700 K. The prepared ferrite samples present the highest Curie temperature, which decreases with increasing particle size and which is consistent with finite-size scaling. The thickness of the surface shell of about 1 nm was estimated from size-dependent magnetization measurements using the core–shell model. Besides, spin resonance, magnetostriction, temperature coefficient of resistance (TCR), and electrical resistivity properties have been scientifically studied and appear to be different according to their size. The optical properties of synthesized NZFAO nanoparticles were investigated, and the differences caused by the particle sizes are discussed on the basis of the phonon confinement effect. This effect was also inspected by the Raman analysis. Tuning of the physical properties suggests that the Ni–Zn–Al ferrite samples may be promising for multifunctional diverse applications.

This article presents the annealing effect on the structural, elastic, thermodynamic, optical, magnetic, and electric properties of Ni_0.6Zn_0.4Fe_1.5Al_0.5O₄ (NZFAO) nanoparticles (NPs).     

Structural,optical and dielectric properties of Cu1.5Mn1.5O4 spinel nanoparticles

In this study, a Cu_1.5Mn_1.5O₄ spinel was successfully synthesized by a sol–gel method at 500 °C for 5 h and characterized by different techniques. X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectroscopy and Raman spectroscopic analyses confirmed the formation of a spinel cubic structure with the Fd$\bar{3}$m space group. The SEM proves that the grain size of our compound is of the order of 48 nm. Crystallite sizes determined from three estimates are closer to the grain size obtained from the SEM, indicating the single domain nature of the sample. The optical properties of UV-visible spectroscopy for our sample showed that the gap value is equal to 3.82 eV, making our compound a good candidate for optoelectronic applications. For electrical properties, impedance spectroscopy was performed at a frequency range of 40 ≤ frequency ≤ 10⁶ Hz. This suggested hoping conduction due to three theoretical models. The latter can be attributed to the correlated barrier hopping (CBH) model in region I, overlapping large polaron tunneling (OLPT) in region II and non-overlapping small polaron tunneling (NSPT) mechanism in region III. One dielectric relaxation is detected from the dielectric impedance and modulus, attributed to grain contributions. This behavior was confirmed by both Nyquist and Argand''s plots of dielectric impedance at different measuring temperatures.

In this study, a Cu_1.5Mn_1.5O₄ spinel was successfully synthesized by a sol–gel method at 500 °C for 5 h and characterized by different techniques.     

Protein kinase Czeta (PKCzeta) regulates ocular inflammation and apoptosis in endotoxin-induced uveitis (EIU): signaling molecules involved in EIU resolution by PKCzeta inhibitor and interleukin-13

We show that inhibitory effect of interleukin-13 on endotoxin-induced uveitis in the Lewis rat is dependent on signaling activity of protein kinase Czeta (PKCzeta). To understand the effect of interleukin-13 or PKCzeta inhibitor treatment, the activation status of rat bone marrow-derived macrophages was studied in vitro. At 6 hours, lipopolysaccharide-stimulated macrophages produced tumor necrosis factor-alpha (TNF-alpha) with nuclear factor kappaB (NF-kappaB)/p65 expression. Treatment led to absence of NF-kappaB/p65 expression and low levels of TNF-alpha, suggesting accelerated inactivation of macrophages. At 24 hours after lipopolysaccharide stimulation, nuclear NF-kappaB/p65 decreased and nuclear NF-kappaB/p50 increased, associated with nuclear BCL-3 and a low level of TNF-alpha, indicating onset of spontaneous resolution. Treatment limited PKCzeta cleavage, with expression of nuclear NF-kappaB/p50 and BCL-3 and low nuclear NF-kappaB/p65 promoting macrophage survival, as evidenced by Bcl-2 expression. At 24 hours, intraocular treatment decreased membranous expression of PKCzeta by ocular cells, reduced vascular leakage with low nitric-oxide synthase-2 expression in vascular endothelial cells, and limited inflammatory cell infiltration with decreased intraocular TNF-alpha, interleukin-6, and nitric-oxide synthase-2 mRNA. Importantly, treatment decreased nuclear NF-kappaB/p65, increased transforming growth factor-beta2, and reduced caspase 3 expression in infiltrating macrophages, implying a change of their phenotype within ocular microenvironment. Treatment accelerated endotoxin-induced uveitis resolution through premature apoptosis of neutrophils related to high expression of toll-like receptor 4 and caspase 3.     

Study of physical properties of a ferrimagnetic spinel Cu1.5Mn1.5O4: spin dynamics,magnetocaloric effect and critical behavior

The present work reports a detailed study of the spin dynamics, magnetocaloric effect and critical behaviour near the magnetic phase transition temperature, of a ferrimagnetic spinel Cu_1.5Mn_1.5O₄. The dynamic magnetic properties investigated using frequency-dependent ac magnetic susceptibility fitted using different phenomenological models such as Neel–Arrhenius, Vogel–Fulcher and power law, strongly indicate the presence of a cluster-glass-like behavior of Cu_1.5Mn_1.5O₄ at 40 K. The magnetization data have revealed that our compound displays an occurrence of second-order paramagnetic (PM) to ferrimagnetic (FIM) phase transition at the Curie temperature T_C = 80 K as the temperature decrease. In addition, the magnetic entropy change (ΔS_M) was calculated using two different methods: Maxwell relations and Landau theory. An acceptable agreement was found between both sets of data, which proves the importance of both electron interaction and magnetoelastic coupling in the magnetocaloric effect (MCE) properties of Cu_1.5Mn_1.5O₄. The relative cooling power (RCP) reaches 180.13 (J kg⁻¹) for an applied field at 5 T, making our compound an effective candidate for magnetic refrigeration applications. The critical exponents β, γ and δ as well as transition temperature T_C were extracted from various techniques indicating that the magnetic interaction in our sample follows the 3D-Ising model. The validity of the critical exponents is confirmed by applying the Windom scaling hypothesis.

The present work reports a detailed study of the spin dynamics, magnetocaloric effect and critical behaviour near the magnetic phase transition temperature, of a ferrimagnetic spinel Cu_1.5Mn_1.5O₄.