On the noise reduction mechanisms of over-tip liners.

The application of acoustic liners near/directly over a sound source has gained significant interest for the excess noise reduction achieved with Over-the-Rotor (OTR) liners compared to the conventional liner installations at the intake of an aero-engine. However, the mechanism of noise reduction achieved in the OTR liners is not clearly understood. This paper aims to explain this mechanism by considering a static monopole source placed over a finite liner insert with a zero background mean flow. This has been investigated numerically using COMSOL Multiphysics in a half-space domain and compared with reference analytical solutions for infinite lined walls. One of the key findings of the paper is the underlying physics of the source modification mechanism, which has been found to be the interference between the primary noise source and a secondary noise source forming on the liner surface. It is identified through an optimal impedance study that this back-reaction mechanism is dominant when the source is located for a normalised tip gap, e/λ<0.25, where e is the distance between the source and the liner surface and λ is the acoustic wavelength. Within this region, there exists an optimum normalised liner length, L / e providing a maximum insertion loss.

Meconium pseudocyst secondary to ileum volvulus perforation without peritoneal calcification: a case report.

INTRODUCTION: A case of giant meconium pseudocyst secondary to ileum volvulus perforation is presented. Conventional radiographic features of meconium peritonitis with secondary meconium pseudocyst formation are well described. Our case is unusual in comparison to other cases reported in the literature and needs to be reported because the meconium pseudocyst presented without the typical ultrasound features (calcifications, polyhydramnios and ascites) and was initially identified as an abdominal mass. CASE PRESENTATION: We describe the case of a 29-year-old Caucasian woman in her third trimester of pregnancy, in which an abdominal mass was detected in the fetus. The newborn was diagnosed in the early neonatal period with meconium pseudocyst secondary to ileum volvulus perforation. CONCLUSIONS: The prenatal appearance of a meconium pseudocyst can be complemented by other signs of bowel obstruction (if present) such as polyhydramnios and fetal bowel dilatation. This is an original case report of interest to all clinicians in the perinatology and fetal ultrasound field. We consider that the utility of this case is the recognition that a meconium pseudocyst might appear without the typical ultrasound features and should be considered as a differential diagnosis when an echogenic intra-abdominal cyst is seen.

Polycystic ovaries in nonobese adolescents and young women with ovarian androgen excess: relation to prenatal growth.

OBJECTIVE: Reduced growth before birth is known to associate with a smaller ovarian volume in adolescents and women without androgen excess. We studied whether prenatal growth relates also to ovarian size and polycystic ovary (PCO) morphology in nonobese adolescents and young women with ovarian androgen excess. DESIGN: A cross-sectional analysis of standardized case notes over a 2-yr period was performed. PATIENTS: Nonobese adolescents and young women (age approximately 17 yr; n = 86) seen for ovarian androgen excess, as confirmed by 17-hydroxy-progesterone hyperresponse to a GnRH agonist, were included in the study. MEASUREMENTS: Endocrine-metabolic assessment in fasting state, together with a vaginal ultrasound scan to verify the presence or absence of PCO was performed. Birth weight and gestational age were derived from medical records. RESULTS: PCO prevalence by ultrasound was 38%. Absence of PCO was associated with a shift (P < 0.0005) of the birth weight distribution toward lower values. Patients with a birth weight less than 3.0 kg were 6-fold more likely to have no PCO than to have PCO. Birth weight was across a wide range (1.5-4.0 kg) associated with ovarian volume in hyperandrogenic patients with noncystic ovaries (r = 0.60; P < 0.00001) and was, in a multiple regression analysis, the prime variable linked to ovarian volume (beta = 0.57; P < 0.00001), explaining 32% of its variance. CONCLUSIONS: The ovarian size and the development of a PCO morphology in nonobese adolescents and young women with ovarian androgen excess relate to prenatal growth. These findings indicate that there are two subgroups of nonobese patients with ovarian androgen excess: one with a normal birth weight distribution and with PCO, and one with lower birth weights and without PCO.

Flutamide-metformin plus ethinylestradiol-drospirenone for lipolysis and antiatherogenesis in young women with ovarian hyperandrogenism: the key role of early, low-dose flutamide.

A low-dose combination of flutamide-metformin and ethinylestradiol-drospirenone was recently found to reduce the excess of total and abdominal fat, to diminish the deficit in lean mass, and to attenuate the dysadipocytokinemia of young women with ovarian hyperandrogenism, a variant of polycystic ovary syndrome. We questioned the need to give flutamide, an androgen receptor blocker, together with an oral contraceptive that contains drospirenone, a progestin claimed to have antiandrogen properties. The additive effects of low-dose flutamide (62.5 mg/d) were assessed over 3 months in young patients with hyperinsulinemic ovarian hyperandrogenism (n = 40; age, approximately 17 yr; body mass index, approximately 22 kg/m(2)); all participants started on metformin (850 mg/d) and a fourth-generation contraceptive (ethinylestradiol 30 microg plus drospirenone 3 mg, 21 d/month), and they were randomized to receive flutamide in addition (n = 20) or not (n = 20). Fasting blood glucose, serum insulin, lipid profile, testosterone, adiponectin, and IL-6 were determined at baseline and after 3 months, together with body composition (by dual x-ray absorptiometry) and with Doppler assessment of ovarian arterial resistance. At start, the pulsatility and resistance indices of ovarian arteries were elevated. By comparison of 3-month changes between randomized subgroups, the addition of low-dose flutamide was found to have consistently (more) normalizing effects on low-density lipoprotein cholesterol, IL-6, and adiponectin, lean body mass, total and abdominal fat mass, and arterial flow in the ovaries. In conclusion, low-dose flutamide is herewith identified as a pivotal component within a first contraceptive combination therapy that has been shown to attenuate the hypoadiponectinemia, ovarian vascular hyperresistance, lean mass deficit, and central adiposity of young women with polycystic ovary syndrome. Finally, these data challenge any claim that drospirenone, as currently used in a contraceptive, is a clinically significant antiandrogen.

Heterotopic ovarian transplantation without vascular pedicle in syngeneic Lewis rats: long-term evaluation of effects on ovarian structure and function.

OBJECTIVE: To assess the long-term efficacy of intraperitoneal (IP) and subcutaneous (SC) ovarian autotransplantation in rats. DESIGN: Experimental animal study. SETTING: Unit of Experimental Research, Barcelona University School of Medicine. ANIMAL(S): Female syngeneic Lewis rats aged 14 weeks. INTERVENTION(S): Group A, control group undergoing ovariectomy (n = 15); group B, undergoing ovariectomy and IP autologous heterotopic transplant (n = 15); and group C, ovariectomized with SC autologous heterotopic transplant (n = 15). In groups B and C, five animals were killed and their ovaries removed for morphometric analysis at 30 days after transplantation; five additional animals were killed at 180 days, and the remaining five animals were killed at 360 days. MAIN OUTCOME MEASURE(S): Ovarian morphometric analysis and serial measurement of E(2) and FSH serum levels. RESULT(S); The mean number of antral follicles in the control group A was significantly higher than that observed in the ovarian grafts collected and examined 30 days after grafting in rats from groups B and C, but the mean granulosa cell area was significantly higher in both transplantation groups than in controls because of ovarian follicular hyperplasia. Histological examination of ovaries removed at 6 and 12 months after grafting in groups B and C showed increasing degrees of fibrosis, loss of primordial follicles, and the presence of epithelial cysts. In groups B and C, from day 30 after surgery onward, serum E(2) was significantly higher and FSH significantly lower, respectively, than in group A. E(2) and FSH patterns in groups B and C were similar throughout the study period. CONCLUSION(S): Heterotopic ovarian transplantation without vascular pedicle in rats is characterized by follicular hyperplasia endocrinologically functional, followed by progressive loss of follicles in heterotopic ovarian autografts.