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.     

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.     

Task‐related preparatory modulations multiply with acoustic processing in monkey auditory cortex

We characterised task‐related top‐down signals in monkey auditory cortex cells by comparing single‐unit activity during passive sound exposure with neuronal activity during a predictable and unpredictable reaction‐time task for a variety of spectral‐temporally modulated broadband sounds. Although animals were not trained to attend to particular spectral or temporal sound modulations, their reaction times demonstrated clear acoustic spectral‐temporal sensitivity for unpredictable modulation onsets. Interestingly, this sensitivity was absent for predictable trials with fast manual responses, but re‐emerged for the slower reactions in these trials. Our analysis of neural activity patterns revealed a task‐related dynamic modulation of auditory cortex neurons that was locked to the animal's reaction time, but invariant to the spectral and temporal acoustic modulations. This finding suggests dissociation between acoustic and behavioral signals at the single‐unit level. We further demonstrated that single‐unit activity during task execution can be described by a multiplicative gain modulation of acoustic‐evoked activity and a task‐related top‐down signal, rather than by linear summation of these signals.     

Clinical evaluation of acetate-free biofiltration at 84 0/00 in patients with chronic renal insufficiency

We report in this study the outcome of chronically hemodialysed patients with a new technique: Acetate free biofiltration 84@1000. This study is divided into two steps: during the first period we studied the hemodynamic stability of the technique in patients hemodynamically unstable under bicarbonate hemodialysis. During the second period we compared the hemodynamic effects and the quality of dialysis in these patients with other patients under bicarbonate hemodialysis. We obtained less hypotensive episodes, a better correction of acidosis, a better tolerance of the technique and comfort of the patient with the new technique, the quality of dialysis was the same with both techniques. We recommend the use of acetate free biofiltration 84@1000 whenever the patients are hemodynamicallyunstable with bicarbonate hemodialysis.     

Suppression of the tumorigenic growth of Burkitt's lymphoma cells in immunodeficient mice by cytokine gene transfer using EBV-derived episomal expression vectors

Epstein-Barr virus (EBV)-based expression vectors were tested for cytokine gene transfer-mediated induction of an immune response against human lymphoma cells. These vectors express the EBV latent gene EBNA 1 and carry the EBV latent origin of replication (ori P) for episomal replication in transfected cells. In addition, 3 human immunoglobulin light chain enhancer elements augment expression in B-cells. The suitability of these vectors for expression of cytokine genes in human lymphoma cells in vitro has been demonstrated. In order to extend these experiments in vivo, highly tumorigenic Burkitt's lymphoma (BL) cells were transfected with different cytokine genes of human and murine origin cloned into the EBNA 1/ori P vectors. Tumorigenicity of the transfectants was measured after inoculation into nude mice. No effect on tumorigenicity was observed after hIL 6 transfection and an inconsistent effect after hTNFalpha transfection. In contrast, complete suppression of tumor outgrowth occurred in hIL 10 transfectants. This tumor suppressive effect, however, was restricted to the IL 10 transfectants themselves and not directed against non-transfected cells. By comparison, mIL 4 transfected BL cells also were non-tumorigenic. However, co-inoculation of mIL 4 transfected and non transfected cells resulted in suppression of the tumorigenicity of the non-transfected cells. Thus, highly tumorigenic BL cells in nude mice are sensitive to immune effector mechanisms triggered by cytokine expression. In this experimental model, EBNA 1/ori P expression vectors are a suitable tool for cytokine gene transfer mediated induction of an anti-lymphoma immune response of the host.     

Kaposi' s sarcoma. A series of 65 cases

Kaposi sarcoma (SK) is characterized by proliferation of vascular and spindle-shaped cells with variable clinical presentations. The association with AIDS modifies the profile of this disease. The pathophysiology seems to be based on the major role HHV-8. The goal of this work was to specify the profile of this disease in our region through a retrospective study of 65 cases of SK over a 23-year period (1981-2003). In our series, the classic form prevailed 163 cases (96.9%)]. One patient had a secondary form due to steroid therapy and another patient had a KS associated with AIDS. A male prevalence was noticed (M/F: 2.8). Cutaneous lesions were dominated by papulo-nodular lesions (90.9%) of the lower limbs (92.3% of the cases). Mucous lesions were present in 15.4% of the cases. Therapeutic abstention was decided in 38.4%. Surgical excision was indicated in 35.4% of cases, radiotherapy in 4.6% of the cases and chemotherapy in 23% of the cases. The classic form of KS is the most frequent in our area; the other forms remaining rare.     

Focus on the various techniques of anaesthesia in ophthalmologic surgery

Ophthalmologic surgery is not a vital one. It mostly concerns patients in extreme ages: children and old people. The risk of anaesthesia mainly depends on the health conditions of the patient. General anaesthesia through use of intravenous drugs alters the balance of the endocrine and sympathetic systems. Tracheal airway intubation constitutes an added constraint and stress especially for the vascular system. Retrobulbar anaesthesia is not devoid of risks: ptosis, diplopic, orbit haematoma, lesion of the optic nerve, eye perforation, vascular occlusion, intra arterial injection, neurologic and cardiovascular toxic effects of local anaesthetics, are all ever present risk Topical anaesthesia with its various variants (single topic or associated with intracameral injection, subconjunctival, circumferential perilimbal, subtenon) represents an interesting alternative for it is simple, less toxic and harless. In our experience, this method is indicated in surgery of eye's anterior segment. We find it safe, efficacisious and economical. Regional anaesthesia is preferred to general anaesthesia especially in the surgery of dacryocystitis and ptosis. General anaesthesia in stell indicated in case of children.     

Cryoglobulinemia in chronic hepatitis C virus infection. About 76 cases

Cryolobulines are immunoglobulins that persist in the serum, precipitate with cold temperature and resolubilize when rewarmed. There are 3 types of cryoglobulinemia. Type II and III define mixed cryoglobulinemia. 40% approximately of patients with chronic hepatitis C virus (HCV) infection had cryoglobulinemia. OBJECTIVE: To evaluate the frequency of cryoglobulinemia in a chronic hepatitis virus (CHV) infection group and determine the characteristics of positive cryoglobulinemia patients. RESULTS: 76 patients were included. There were 53 women an 23 men. The mean age was 59.45 years. Mixed cryoglobulinemia was detected in 65 patients (85.5 %). Cirrhosis, old age and the long duration of CHV infection were the 3 factors associated with cryoglobulinemia positivity. CONCLUSION: Mixed cryoglobulinemia is a frequent manifestation during chronic hepatitis C infection virsus especially in patients with cirrhosis.