Mechanical performance of original; yellowish and blueish ProFile instruments: isolating heat-treatment as a variable

The present study aimed to perform two different heat-treatments in an austenitic NiTi ProFile instrument and to compare the mechanical performance of original and heat-treated instruments. Heat treatment of ProFile (tip size 25 and 0.06 taper) instruments were carried out in a furnace in argon atmosphere using a heating rate of 10° C/min. After reaching the programmed temperatures of 450 ºC or 500 ºC the system remained at a constant temperature for 10 minutes; followed by cooling in water at room temperature. Afterwards; the three groups (n=30 per group) of instruments were compared regarding their cyclic fatigue (n=10 per group); bending (n=10 per group); and buckling resistance (n=10 per group). After cyclic fatigue tests; a scanning electron microscope was used to analyze the fracture surfaces and observe the fracture mode. Statistical analysis was performed using One-way ANOVA and Student-Newman-Keuls test; with an alpha type error set at 0.05. Yellowish and blueish coloration was observed in the ProFile instruments after 450 ºC or 500 ºC heat treatments; respectively. Conventional ProFile instruments showed the lower cyclic fatigue; and the higher bending and buckling resistance (P<0.05). In contrast; yellowish ProFile instruments (heat treated at 500° C) showed the higher cyclic fatigue; and the lower bending and buckling resistance (P>0.05). It can be concluded that the different heat treatments performed on ProFile instruments increased its cyclic fatigue resistance and improved the flexibility and buckling resistance.

Longitudinal photocurrent spectroscopy of a single GaAs/AlGaAs v-groove quantum wire

Modulation-doped GaAs v-groove quantum wires (QWRs) have been fabricated with novel electrical contacts made to two-dimensional electron-gas (2DEG) reservoirs. Here, we present longitudinal photocurrent (photoconductivity/PC) spectroscopy measurements of a single QWR. We clearly observe conductance in the ground-state one-dimensional subbands; in addition, a highly temperature-dependent response is seen from other structures within the v-groove. The latter phenomenon is attributed to the effects of structural topography and localization on carrier relaxation. The results of power-dependent PC measurements suggest that the QWR behaves as a series of weakly interacting localized states, at low temperatures.

[Experience in patients with suspected chronic liver disease and contraindication for percutaneous biopsy using modified Ross needle]

PURPOSE

This work aimed at introducing the transjugular liver biopsy technique oriented by radiologic methods in our hospitals. This technique is indicated for obtaining histopathologic diagnosis in patients clinically and laboratory suspected of having chronic liver disease with contraindications to percutaneous liver biopsy.

METHODS

Liver biopsy was obtained with a modified Ross needle through the right jugular vein and right hepatic vein under fluoroscopic control.

RESULTS

Transjugular liver biopsy was attempted for 39 patients, liver tissue obtained en 32 and histopathologic diagnosis in 25 (64.1%). In 11 patients (28.2%) there was agreement between the diagnoses established before and after biopsy, however, in 14 patients (35.9%), there was disagreement. The yield of diagnosis was low when patients were suspected for cirrhosis. The procedure was well tolerated by the majority of patients. Nonetheless, 1 presented intra-abdominal bleeding and required immediate surgery to control retroperitoneal hemorrhage.

CONCLUSIONS

Transjugular liver biopsy is useful for the histopathologic diagnosis of patients with chronic liver diseases whenever the percutaneous route is contraindicated. In this series we obtained histopathologic diagnosis for 64.1% of the subjects studied. Patients suspected of having cirrhosis had a low yield of histopathologic diagnosis (50%) when compared to subjects without clinical evidence for cirrhosis (78.9%). The technique is rather complex, and can cause serious complications. This, it should be performed in reference centers in radiology and hepatology.