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In the present study, we present our investigation on the structure and magnetocaloric effect (MCE) of La0.7Sr0.3Mn1−xCuxO3 (x = 0.08 and 0.12) compounds prepared by a conventional solid-state method. X-ray diffraction patterns indicate that the samples have a rhombohedral structure with the R 3 ¯ c space group. The Curie temperature decreases with increasing Cu concentration. Using a phenomenological model, the MCE of the two samples was predicted from the experimental magnetization data measured at magnetic fields of 3 kOe, 5 kOe, 8 kOe, and 10 kOe. The type of second-order magnetic phase transition of the samples is confirmed by the collapse of the entire master curve of magnetic entropy change in the same plot. Our investigation on the magnetocaloric behavior of the title compounds suggests that they are suitable candidates for application to near-room temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In this work, critical behavior, and magnetocaloric effect, as well as the relationship between these characteristics in polycrystalline sample La0.7Ba0.3Mn0.8Ti0.2O3 has been studied in detail. The positive value of the slope of Arrott plots exhibits that the magnetic phase transition of this sample is of a second order at Curie temperature of 96 K. The critical exponents β, γ, and δ have been determined using various ways including the modified Arrott plots, the Kouvel–Fisher plots, and the critical isotherm analysis. Interestingly, the experimental critical exponent values were β = 0.349 ± 0.002, γ = 1.350 ± 0.033, and δ = 4.868 ± 0.002, which are close to those deduced for the 3D-Heisenberg model below the Curie temperature and for the 3D-XY model above it. Additionally, the ferromagnetic interaction in La0.7Ba0.3Mn0.8Ti0.2O3 was found to be at the borderline of the long-range and short-range magnetic coupling, which was confirmed through the exchange distance decaying of J r ∼ r - 4.9 . Moreover, the magnetocaloric characteristics of La0.7Ba0.3Mn0.8Ti0.2O3 were consistent with the analysis of critical behavior. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study on the structural, magnetic, and critical behavior and magnetocaloric effect of LaSrMnCuO prepared by solid-state reaction method. X-ray diffraction patterns indicate that Cu-doped manganite crystallizes to a single phase with a rhombohedral structure. Critical components β, γ, and δ were determined by using modified Arrott plot, Kouvel-Fisher method, and critical isotherm analyses. These components are consistent with their corresponding values and were validated by Widom scaling law and scaling theory. The deduced critical exponents ( β = 0.456, γ = 0.9912, and δ = 3.206) are also close to their corresponding theoretical values predicted by mean-field model, indicating that long-range interaction dominates the critical behavior of the LSMCO system. Spontaneous magnetization was determined by two methods. One method is based on magnetic entropy change under different magnetic fields, and the other method is based on classical extrapolation from the Arrott plot. The two methods are in excellent agreement, confirming the validity of the deduction of spontaneous magnetization using the magnetic entropy change. [ABSTRACT FROM AUTHOR]

We have investigated the structure, magnetic, and electrical properties, and the resistance switching effect (RSE) of La2NiO $_{{ {4+\delta }}} compounds with different excess oxygen levels of \delta = 0.004 - 0.031 . Our results showed the structure changes from tetragonal I4/mmm to orthorhombic Fmmm when reducing \delta value from 0.011 to 0.006. The M(H) curves measured at several temperatures exhibit a coexistence of the weak ferromagnetic and antiferromagnetic interactions. Two shoulders on M(T) curves related to the spin and charge ordering have also been observed. These ordering temperatures depend strongly on \delta ) and low ( RL ) values. The resistance change ratio of the samples defined as 100% \times [RH - RL]/RL is found to be about 18%–57%, which depends on the value of $\delta $ in the samples. [ABSTRACT FROM AUTHOR]

In this paper, we report the effect of Pb doping on the magnetic and magnetocaloric properties of La0.7Ca0.3-xPbxMnO3 (0.15 ≤ x ≤ 0.3) polycrystalline samples. The samples were prepared by solid state synthesis method. X-ray diffraction patterns indicate that these samples have monoclinic structure with the Pc/2 space group. The magnetization measurements indicated that all samples exhibited a paramagnetic-ferromagnetic transition and the transition temperature increased with increasing of Pb concentration. Using phenomenological model, the magnetocaloric behavior of all the samples has been calculated based on the experimental magnetization data. Our results on the magnetocaloric properties suggest that the compound La0.7Ca0.15Pb0.15MnO3 is attractive as a possible material for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In this study, we report the electric transport of La 0.7Ca 0.3MnO 3 prepared by various methods. Based on the fact that the metallic ferromagnetic and insulating paramagnetic clusters simultaneously exist at transition temperature, we applied phase-coexistence transport model to calculate the temperature dependence of the resistivity. This model can explain quantitatively the electrical conductivity of La 0.7Ca 0.3MnO 3 for the whole temperature range studied. [ABSTRACT FROM AUTHOR]

An experimental setup has been built and instrumented with non intrusive measurement methods aiming at measuring temperature fields and deformations of a soda-lime-silica glass piece during thermoforming process. A real scale furnace has been used and a realistic thermal load case applied. Infrared measurements based on the Christiansen effect have been performed on the present glass sample, providing the temperature distribution on the sample surface through IR images at 7.8 μm. Piece deformation has been registered simultaneously, using a DIC (Digital Image Correlation) technique combined with a fringe projection method. Results have been analysed in a combined manner, showing a non symmetrical deformation despite a quite homogeneous thermal field, which could be explained by mould/glass contact problems. The non intrusive measurement technique has been proven to be relevant for a possible control of the thermal environment of the piece during the thermoforming process. Further tests should be carried out on a wide range of shapes and glass types. [ABSTRACT FROM AUTHOR]

Background and objective: The HLA-DRB1*15 allele is consistently associated with multiple sclerosis (MS) susceptibility in most studied populations. This study investigated the association between HLA-DRB1 alleles and the presence of oligoclonal immunoglobulin G bands (OCB) in the cerebrospinal fluid (CSF) in a Spanish population with MS. Methods: The HLA-DRB1 typing was performed in 268 patients with sporadic MS and the detection of OCB in CSF. HLA-DRB1 allelic frequencies were compared between OCB-positive and OCB-negative patients, and both groups were also compared with 1088 unrelated healthy controls. Moreover, we correlated the various HLA-DRB1 genotypes, considering all the combinations of both parental alleles found with the presence or absence of OCB. Results: We found 206 OCB-positive and 62 OCB-negative patients. The HLA-DRB1*15 allele in OCB-positive patients had a higher frequency when compared with OCB-negative patients (39.3% in OCB-positive vs. 16.1% in OCB-negative, OR = 1.38 95% CI = 1.18-1.61, P < 0.001). The other alleles did not show differences. When we compared with controls, the HLA-DRB1*15 allele was associated with the disease only in the OCB-positive patients group. None of the 55 genotypes found showed any association with the presence or absence of OCB. Conclusions: HLA-DRB1*15 allele is associated with OCB-positive patients with MS when studying a Spanish MS population. [ABSTRACT FROM AUTHOR]

The association of HLA-DRB1*15 with susceptibility to multiple sclerosis (MS) has been consistently reported although its effect on the clinical phenotype is still controversial. The objectives of this study are to investigate the influence of the HLA-DRB1 alleles on the genetic susceptibility to MS and to study their impact on disability progression in a Spanish population. HLA-DRB1 typing was performed by PCR-SSP in 380 patients with sporadic MS and 1088 unrelated healthy controls. Allelic frequencies were compared between groups. We studied the correlation between the different alleles and the progression of MS. The HLA-DRB1*15 allele in patients with MS had a statistically significant higher frequency when compared with controls (18.9% in patients vs. 10.1% in controls, Odds ratio (OR) = 2.07, 95% CI = 1.64-2.60, P < 0.001). In the univariate analysis, the DRB1*01 and DRB1*04 alleles were associated with a worse prognosis when considering the time to reach an EDSS of 6, whereas the DRB1*03 was correlated with a better outcome. In the multivariate analysis, the alleles*01 and *04 were demonstrated to be independent factors to have a worse prognosis. HLA-DRB1*15 is associated with MS when comparing patients with unrelated healthy controls in a Spanish population. The HLA-DRB1*01 and HLA-DRB1*04 alleles are related to a worse prognosis when considering the time taken to reach severe disability. [ABSTRACT FROM AUTHOR]

Background and objective: Anticipation of age at onset in the younger generations is a widely known characteristic of many diseases with genetic inheritance. This study was performed to assess whether there is anticipation of age at onset in younger generations of familial multiple sclerosis (MS) in a Spanish population and to compare clinical characteristics of familial and sporadic MS. Methods: We studied a cohort of 1110 patients diagnosed with MS and followed-up in our MS Unit. Patients were considered as familial MS if they had in their family at least one relative of first or second degree diagnosed with MS. Otherwise, patients were considered to have sporadic MS. We compared the age at onset between relatives from different generations, and we also compared the age at onset of familial and sporadic MS. Results: A lower age at onset in the younger generations was found (median 22 years vs. 30 years, P < 0.001) and a significant lower age at onset of the disease in familial MS comparing to sporadic MS (median 25 years vs. 29 years, P = 0.042). Conclusions: There is an anticipation of the age at onset of MS in the younger generations of patients with familial MS. There is also a lower age at onset in familial versus sporadic MS. [ABSTRACT FROM AUTHOR]