Comparative electrical behavior at low and high current of SnO(2)- and ZnO-based varistors

The complete I-V characteristics of SnO(2)-based varistors, particularly of the Pianaro system SCNCr consisting in 98.9%SnO(2)+1%CoO+0.05%Nb(2)O(5)+0.05%Cr(2)O(3), all in mol%, have been seldom reported in the literature. A comparative study at low and high currents of the nonohmic behavior of SCNCr- and ZnO-based varistors (modified Matsuoka system) is proposed in this work. The SCNCr system showed higher nonlinearity coefficients in the whole range of measured current. The electrical breakdown field (E(b)) was twice as high for the SCNCr system (5400 V/cm) than for the ZnO varistor (2600 V/cm) due to a smaller average grain size of the former (4.5 mu m) with respect to the latter (8.5 mu m). Nevertheless, we consider that another important factor responsible for the high E(b) in the SCNCr system is the great number of electrically active interfaces (85%) as determined with electrostatic force microscopy (EFM). It was also established that the SCNCr system might be produced in disks of smaller dimensions than that of commercial ZnO-based product, with a 5.0 cm(-1) minimal area-volume (A/V) ratio. The SCNCr reached the saturation current in a short time because of the high resistivity of the grains, which is five times higher than that of the grains in ZnO-based varistors.

The influence of "C-factor" and light activation technique on polymerization contraction forces of resin composite

Objectives: This study evaluated the influence of the cavity configuration factor ("C-Factor") and light activation technique on polymerization contraction forces of a Bis-GMA-based composite resin (Charisma, Heraeus Kulzer). Material and Methods: Three different pairs of steel moving bases were connected to a universal testing machine (Emic DL 500): groups A and B - 2x2 mm (CF=0.33), groups C and D - 3x2 mm (CF=0.66), groups E and F - 6x2 mm (CF=1.5). After adjustment of the height between the pair of bases so that the resin had a volume of 12 mm(3) in all groups, the material was inserted and polymerized by two different methods: pulse delay (100 mW/cm(2) for 5 s, 40 s interval, 600 mW/cm(2) for 20 s) and continuous pulse (600 mW/cm(2) for 20 s). Each configuration was light cured with both techniques. Tensions generated during polymerization were recorded by 120 s. The values were expressed in curves (Force(N) x Time(s)) and averages compared by statistical analysis (ANOVA and Tukey's test, p<0.05). Results: For the 2x2 and 3x2 bases, with a reduced C-Factor, significant differences were found between the light curing methods. For 6x2 base, with high C-Factor, the light curing method did not influence the contraction forces of the composite resin. Conclusions: Pulse delay technique can determine less stress on tooth/restoration interface of adhesive restorations only when a reduced C-Factor is present.

Minimally invasive mastectomy: minimal incisions for better aesthetic quality of breast reconstruction

Background: Women with a family history of breast cancer who develop this disease are confronted with important situations regarding the increased risk for development of a second cancer in the contralateral breast. Prophylactic contralateral mastectomy (PCM) reduces by approximately 95% the risk for contralateral breast cancer. In spite of an increase in indications for PCM, the technical difficulties are many regarding the accomplishment of these procedures. The aim of this study is to describe the technique of mastectomy with preservation of the nipple-areola complex and a small incision, reducing surgical difficulties and complications attributed to this technique, thus allowing better aesthetic results in breast reconstruction. Methods: Forty-six patients with indications for PCM (28 bilateral) were submitted to minimally invasive mastectomy from March 2005 to November 2007. A small incision in the superior pole of the areola, sufficient to pass a liposuction 4 mm cannula is made. With the help of this cannula, detachment of the skin from the gland tissue is performed. Then a 3.5 to 4.5-cm long incision in the inframammary fold is made. Glandular detachment is completed using cautery in the sub,glandular portion and scissors in the upper breast portion cutting the restraints left by the cannula. The mammary gland tissue is removed through this incision. Results: Seventy-four breasts were operated on. The resected breast mass ranged from 285 g to 475 g. All 43 patients were reconstructed with prostheses. There was no necrosis of the nipple-areola complex or of the skin. Conclusions: This technique is an option for cases of patients with indications for PCM.

Initial experience with Pomerantzeff's technique for reduction of the size of giant left atrium

Introduction: The most common indication for surgical correction of giant left atrium is associated with mitral valve insufficiency with or without atrial fibrillation. Several techniques for this purpose are already described with varying results. Objective: To present the initial experience with the tangential triangular resection technique (Pomerantzeff). Methods: From 2002 to 2010, four patients underwent mitral valve operation with reduction of left atrial volume by the technique of triangular resection tangential in our service. Three patients were female. The age ranged from 21 to 51 years old. The four patients presented with atrial fibrillation. Ejection fraction of left ventricle preoperatively ranged from 38% to 62%. The left atrial diameter ranged from 78mm to 140mm. After treatment of mitral dysfunction, the left atrium was reduced by resecting triangular tangential posterior wall between the pulmonary veins to avoid anatomic distortion of the mitral valve or pulmonary veins, reducing tension in the suture line. Results: Average hospital stay was 21.5 +/- 6.5 days. The mean cardiopulmonary bypass time was 130 +/- 30 minutes. There was no surgical bleeding or mortality in the postoperative period. All patients had sinus rhythm restored in the output of cardiopulmonary bypass, maintaining this rate postoperatively. The average diameter of the left atrium was reduced by 50.5% +/- 19.5%. The left ventricular ejection fraction improved in all patients. Conclusion: Initial results with this technique have shown effective reduction of the left atrium.

Vascular dysfunction by myofibroblast activation in patients with idiopathic pulmonary fibrosis and prognostic significance

In this study, we demonstrated the importance of telomerase protein expression and determined the relationships among telomerase, endothelin-1 (ET-1) and myofibroblasts during early and late remodeling of parenchymal and vascular areas in usual interstitial pneumonia (UIP) using 27 surgical lung biopsies from patients with idiopathic pulmonary fibrosis (IPF). Telomerase+, myofibroblasts alpha-SMA+, smooth muscle cells caldesmon+, endothelium ET-1+ cellularity, and fibrosis severity were evaluated in 30 fields covering normal lung parenchyma, minimal fibrosis (fibroblastic foci), severe ( mural) fibrosis, and vascular areas of UIP by the point-counting technique and a semiquantitative score. The impact of these markers was determined in pulmonary functional tests and follow-up until death from IPF. Telomerase and ET-1 expression was significantly increased in normal and vascular areas compared to areas of fibroblast foci. Telomerase and ET-1 expression was inversely correlated with minimal fibrosis in areas of fibroblast foci and directly associated with severe fibrosis in vascular areas. Telomerase activity in minimal fibrosis areas was directly associated with diffusing capacity of the lung for oxygen/alveolar volume and ET-1 expression and indirectly associated with diffusing capacity of the lungs for carbon monoxide and severe fibrosis in vascular areas. Cox proportional hazards regression revealed a low risk of death for females with minimal fibrosis displaying high telomerase and ET-1 expression in normal areas. Vascular dysfunction by telomerase/ET-1 expression was found earlier than vascular remodeling by myofibroblast activation in UIP with impact on IPF evolution, suggesting that strategies aimed at preventing the effect of these mediators may have a greater impact on patient outcome.

Standard surgical treatment for benign prostatic hyperplasia is safe for patients over 75 years: Analysis of 100 cases from a high-volume urologic center

OBJECTIVES: In this study, we aimed to determine the complications of standard surgical treatments among patients over 75 years in a high-volume urologic center. METHODS: We analyzed 100 consecutive patients older than 75 years who had undergone transurethral prostatic resection of the prostate or open prostatectomy for treatment of benign prostatic hyperplasia from January 2008 to March 2010. We analyzed patient age, prostate volume, prostate-specific antigen level, international prostatic symptom score, quality of life score, urinary retention, co-morbidities, surgical technique and satisfaction with treatment. RESULTS: Median age was 79 years. Forty-eight patients had undergone transurethral prostatic resection of the prostate, and 52 had undergone open prostatectomy. The median International Prostatic Symptom Score was 20, the median prostate volume was 83 g, 51% were using an indwelling bladder catheter, and the median prostate-specific antigen level was 5.0 ng/ml. The most common comorbidities were hypertension, diabetes and coronary disease. After a median follow-up period of 17 months, most patients were satisfied. Complications were present in 20% of cases. The most common urological complication was urethral stenosis, followed by bladder neck sclerosis, urinary fistula, late macroscopic hematuria and persistent urinary incontinence. The most common clinical complication was myocardial infarction, followed by acute renal failure requiring dialysis. Incidental carcinoma of the prostate was present in 6% of cases. One case had urothelial bladder cancer. CONCLUSIONS: Standard surgical treatments for benign prostatic hyperplasia are safe and satisfactory among the elderly. Complications are infrequent, and urethral stenosis is the most common. No clinical variable is associated with the occurrence of complications.

Standard surgical treatment for benign prostatic hyperplasia is safe for patients over 75 years: analysis of 100 cases from a high-volume urologic center

OBJECTIVES: In this study, we aimed to determine the complications of standard surgical treatments among patients over 75 years in a high-volume urologic center. METHODS: We analyzed 100 consecutive patients older than 75 years who had undergone transurethral prostatic resection of the prostate or open prostatectomy for treatment of benign prostatic hyperplasia from January 2008 to March 2010. We analyzed patient age, prostate volume, prostate-specific antigen level, international prostatic symptom score, quality of life score, urinary retention, co-morbidities, surgical technique and satisfaction with treatment. RESULTS: Median age was 79 years. Forty-eight patients had undergone transurethral prostatic resection of the prostate, and 52 had undergone open prostatectomy. The median International Prostatic Symptom Score was 20, the median prostate volume was 83 g, 51% were using an indwelling bladder catheter, and the median prostatespecific antigen level was 5.0 ng/ml. The most common comorbidities were hypertension, diabetes and coronary disease. After a median follow-up period of 17 months, most patients were satisfied. Complications were present in 20% of cases. The most common urological complication was urethral stenosis, followed by bladder neck sclerosis, urinary fistula, late macroscopic hematuria and persistent urinary incontinence. The most common clinical complication was myocardial infarction, followed by acute renal failure requiring dialysis. Incidental carcinoma of the prostate was present in 6% of cases. One case had urothelial bladder cancer. CONCLUSIONS: Standard surgical treatments for benign prostatic hyperplasia are safe and satisfactory among the elderly. Complications are infrequent, and urethral stenosis is the most common. No clinical variable is associated with the occurrence of complications.

Doppler-guided hemorrhoidal artery ligation with rectal mucopexy technique: initial evaluation of 42 cases

The treatment of hemorrhoidal disease (HD) by conventional hemorrhoidectomy is associated with significant morbidity, mainly represented by the postoperative pain and the late return to daily activities. Doppler-guided hemorrhoid artery ligation (DGHAL) is a minimal-invasive surgical treatment for HD that has been used as an alternative method in order to reduce these inconveniences. OBJECTIVE: To analyze the initial results of the DGHAL technique associated with rectal mucopexy in the treatment of HD. METHODS:Forty-two patients with stage I, III and IV hemorrhoids who were submitted to DGHAL were analyzed from December 2010 to August 2011. Eleven patients (26%) were stage II; 21 (50%), stage III; and 10 (24%), stage IV HD. All patients were operated by the same surgeon under spinal anesthesia and using the same equipment and technique to perform the procedure. The 42 patients underwent ligation of six arterial branches followed by rectal mucopexia by uninterrupted suture. Nine patients needed concomitant removal of perianal skin tag. In the postoperative, the following parameters were evaluated: pain, tenesmus, bleeding, itching, prolapse, mucus discharge and recurrence. The mean postoperative follow-up lasted four months (one to nine months). RESULTS: Tenesmus was the most common postoperative complaint for 85.7% of patients followed by pain, in 28.6%, perianal burning, in 12.3%, mucus discharge and perianal hematoma in 4.7%. Two patients had severe postoperative bleeding and required surgical haemostasis, one of which needed blood transfusion. Ninety-five percent of the patients declared to be satisfied with the method. CONCLUSION: Even though DGHAL has complications similar to those of other surgical methods, its results present less postoperative pain, allowing faster recovery and return to work. Studies with more cases and a longer follow-up are still necessary to assess the late recurrence.