Dielectric properties of PVDF thin films doped with 3 wt.% of RCl3 (R = Gd or Er)

The dielectric permittivity (ɛ′), electric modulus (M″), and ac conductivity (σac) of pure polyvinylidene fluoride (PVDF) and PVDF containing 3 wt.% RCl3 (R = Er or Gd) were measured. The incorporation of 3 wt.% of ErCl3 or GdCl3 within the PVDF matrix is found significantly to increase its ɛ′ and σac. All investigated samples show different relaxation processes within the studied temperature and frequency ranges. The first process is αa-relaxation, which occurs around the glass transition temperature, Tg. The second process is αc-relaxation, which is associated with the molecular motions in the crystalline region of the main polymer chain. Third is the ρ-relaxation which observed for pure PVDF at low temperatures and high frequencies. The frequency dependence of σac shows that the conduction mechanism for pure PVDF and PVDF containing 3 wt.% of RCl3 is correlated barrier hopping (CBH). The binding energy of the carriers was calculated based on the CBH model. Finally, the results obtained in this work are discussed and compared with those for 3 wt.% LaCl3-doped PVDF and similar materials

Ultrasonographic evaluation of lower uterine segment thickness in pregnant women with previous cesarean section

Objective: To evaluate the accuracy of prenatal sonography (U/S) in determining the lower uterine segment (LUS) thickness in women with previous cesarean section (CS) and to assess its usefulness in predicting the risk of uterine rupture during a trial of vaginal birth. Design: Prospective controlled study. Setting: Suzan Mubarak University Hospital. Subjects: One hundred and fifty pregnant women with singleton pregnancies, with the gestational age between 37 and 40weeks were recruited for the study during the period from October 2007 to June 2008. The recruited patients were allocated into three equal groups. Group I included those with previous one low transverse CS and with the history of successful VBAC. Group II included those without the history of successful VBAC. Group III included those without the previous history of CS (control group). Interventions: The recruited patients were subjected to clinical and U/S evaluations. The LUS thickness was evaluated by both transabdominal (TA) and transvaginal (TV) U/S. Women were categorized for the mode of delivery into either trial of VBAC or elective repeated CS (ERCS). All the intraoperative findings were correlated with U/S findings. Main outcome measures: Accuracy of US in predicting uterine dehiscence. Results: Mean LUS thickness was lower among the study groups than in the control group. The present study reported 14 (28%) cases of dehiscent scar. Mean LUS thickness was significantly lower among the dehiscence groups (1.7±0.7mm) than in the non-dehiscence groups (2.6±0.8mm) (P⩽0.01). At a cutoff value of 2.5mm, the sensitivity, specificity, and positive and negative predictive values were 90.9%, 84%, 71.4%, and 95.5%, respectively, using (TA) U/S and 81.8%, 84%, 69.2%, and 91.3%, respectively, using (TV) U/S. At LUS thickness ⩽2.5mm, there was a higher risk for dehiscence than those with a thickness of more than 2.5mm. Conclusions: If the thickness of the LUS is more than 2.5mm, the possibility of dehiscence during the subsequent trials of labor is very small and a safe vaginal delivery can be achieved. Further large studies are recommended

Three-dimensional power Doppler indices of ovarian stromal blood flow and serum vascular endothelial growth factor after laparoscopic ovarian drilling in women with polycystic ovary syndrome

Objective: To evaluate the effects of laparoscopic ovarian drilling (LOD) on three-dimensional (3D) power Doppler indices of ovarian stromal blood flow and serum vascular endothelial growth factor (VEGF) levels in women with polycystic ovary syndrome (PCOS). Design: Prospective controlled study. Setting: Minia University Hospital, Minia, Egypt. Material and methods: 30 clomiphene citrate resistant women with PCOS undergoing LOD and 30 fertile women with normal ovaries were recruited in this study. Hormonal profile, Doppler indices of ovarian stromal blood flow and serum VEGF assays before and after LOD were evaluated and compared between the two groups. Evaluation was done at the beginning of the study, 1 week after LOD and at 3 and 6 month follow up periods. Main outcome measures: 3-D power Doppler indices of both ovaries and serum VEGF concentration. Results: Before LOD, serum levels of VEGF, total testosterone (T), free androgen index (FAI), LH, LH:FSH ratio, total antral follicle count (AFC), total ovarian volume (OV) and the 3D power Doppler blood flow indices were significantly higher in the PCOS group than in the control group. After LOD, there was a significant reduction in the serum levels of VEGF, T, sex-hormone binding globulin (SHBG), FAI, LH, LH:FSH ratio, AFC, OV and the 3D power Doppler indices and remained all low at 3 and 6 month follow up. There were significant positive correlations between power Doppler flow indices (VI, FI, and VFI) with serum VEGF, total T, and LH before and after LOD. Conclusions: Serum VEGF and ovarian blood flow indices were higher in women with PCOS than in normal women. LOD reduced serum levels of VEGF, in addition to ovarian blood flow indices, in women with PCOS