Electrical properties of lead telluride single crystals doped with Gd
Temperature dependences of electric conductivity, free carrier concentration and mobility in single-crystalline PbTe: Gd samples with a varied impurity content are investigated. The features of electron transport in PbTe: Gd may be caused by a variable gadolinium valence. The striking result from the Seebeck coefficient measurements is that the thermoelectric power factor increases dramatically. Measurements of the magnetic susceptibility at low temperatures permit us to suggest that Gd ions exist in different charge states.
Performance and spectral response of Pb1−xSnxTe(In) far-infrared photodetectors
We have compared directly the performance of a Pb1−xSnxTe(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb1−xSnxTe(In) photodetector has current responsivity SI several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with SI∼103 A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb1−xSnxTe(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions.
Assessment of fractures in endodontically treated teeth restored with and without root canal posts using high-resolution cone beam computed tomography
Background Root fractures are a diagnostic challenge for dentists in endodontic treatment. This study aimed to determine the relationship between the characteristics of tooth fractures and the presence of root canal posts in endodontically treated teeth using high-resolution cone beam computed tomography (CBCT). Material and Methods Fifty high-resolution CBCT scans of endodontically treated teeth with a diagnosis of fracture were obtained, of which 30 were from women and 20 were from men. These scans were acquired with three Veraviewepocs 3D units and one 3D Accuitomo 170 unit, with a 40 × 40-mm field of view and 125 μm voxel size. The variables assessed included the type of fracture, extent of fracture, type of retention, post length, cause of endodontic failure, location of the lesion, and time required to detect the fracture (difficulty score). For data analysis, the chi-squared test, Student’s t-test, and multiple linear regression (α <0.05) were used. Results No association was found between the type of fracture and type of retention or between the type of fracture and its extent (P>0.05). On the other hand, the type of fracture significantly influenced the time required for its detection. Additionally, the most difficult plane for detecting the fracture and the difficulty score were associated, with statistically significant results. Conclusions The type of fracture in endodontically treated teeth was not associated with the type of post used for restoration. All of the CBCT systems used to detect tooth fracture showed the same efficiency. Key words:Cone-Beam CT, Tooth Fracture, Root Canal Post.