RESUMEN
Orthoferrites have occupied important place in the material science and condensed matter physics investigations due to their unique features such as electrical, magnetic and optical. The present investigation illuminates light on the electrical properties of osmium (Os) doped YbFeO3 (YbFO) rare-earth orthoferrite. The undoped YbFO and YbFe1-x Os x O3 (YbFOO) (x = 0.01 and 0.05) powders were synthesized via solid-state. X-ray diffractometer (XRD) has been utilized to examine the crystal structure of the YbFO and YbFOO powders. The cross sectional morphology of the obtained pellets was inspected via scanning electron microscope (SEM). Moreover, x-ray photoelectron spectroscopy was exploited to determine the oxidation states of the constituted elements. The electrical features for instance electrical modulus, dielectric constant and conductivity of the synthesized pellets were detailed at different frequencies and temperatures by dielectric/impedance spectroscopy studies. The x = 0.01 Os doped sample exhibits higher dielectric constant and conductivity compared to other samples. Moreover, in order to explain conductivity mechanism of the studied samples, multiple conduction models are needed to employ.
RESUMEN
To meet a required STEM resolution, the mechanical precision of the pole pieces of a magnetic lens needs to be determined. A tolerancing plugin in the EOD software is used to determine a configuration which both meets the optical specifications and is cost effective under the constraints of current manufacturing technologies together with a suitable combination of correction elements.
RESUMEN
Genes for the chemokine receptors CCR5 and CCR2 are characterized by polymorphisms resulting in a nonfunctional receptor expression. Ligands for CCR2 and CCR5 (chemokines monocyte chemotactic protein-1 [MCP-1] and RANTES) are implicated in the pathogenesis of sarcoidosis. We have, therefore, analyzed polymorphisms of CCR5 (32-bp deletion in CCR5 gene [Delta32]) and of CCR2 (replacement of valine by isoleucine in CCR2 gene [64I]) in 66 Czech patients with sarcoidosis in comparison with a representative sample of Czech normal population. The frequencies of CCR5Delta32 and CCR2-64I polymorphisms in patients with sarcoidosis were different from that in control subjects. CCR5Delta32 allelic frequency was significantly increased in patients. By contrast, the CCR2-64I allele was more frequent in control subjects; however, the difference did not attain significance. Interestingly, the CCR5Delta32 allele was associated with clinically more apparent disease: it was present in 39.1% of patients requiring corticosteroids but only in 16.7% patients who did not need therapeutic intervention (odds ratio [OR] = 2.9). When patients requiring corticosteroids were compared with control subjects, the differences in the CCR5Delta32 frequencies were enhanced (p < 0.01). In conclusion, the observed association of CCR5Delta32 and CCR2-64I with sarcoidosis implicates a role for these polymorphisms in disease susceptibility and protection.