Hawking radiation of massive modes and undulations

We compute the analogue Hawking radiation for modes which posses a small wave vector perpendicular to the horizon. For low frequencies, the resulting mass term induces a total reflection. This generates an extra mode mixing that occurs in the supersonic region, which cancels out the infrared divergence of the near horizon spectrum. As a result, the amplitude of the undulation (0-frequency wave with macroscopic amplitude) emitted in white hole flows now saturates at the linear level, unlike what was recently found in the massless case. In addition, we point out that the mass introduces a new type of undulation which is produced in black hole flows, and which is well described in the hydrodynamical regime.Comment: 37 pages, 8 figures, published versio

Direct reconstruction of the effective atomic number of materials by the method of multi-energy radiography

A direct method is proposed for reconstruction of the effective atomic number by means of multi-energy radiography of the material. The accuracy of the method is up to 95% . Advantages over conventional radiographic methods, which ensure accuracy of just about 50%, are discussed. A physical model has been constructed, and general expressions have been obtained for description of the effective atomic number in a two-energy monitoring scheme. A universal dependence has been predicted for the effective atomic number as a function of relative (two-energy) radiographic reflex. The established theoretical law is confirmed by the experimental data presented. The proposed development can find multiple applications in non-destructive testing and related fields, including those in the civil sphere as well as anti-terrorist activities.Comment: 15 pages LaTeX, 4 figures, the paper accepted in Nuclear Methods and Instruments in Physics Research, Section

Impaired aerobic exercise adaptation in children and adolescents with craniopharyngioma is associated with hypothalamic involvement

OBJECTIVE: Many patients treated for craniopharyngioma (CP) complain of a relative incapacity for physical activity. Whether this is due to an objective decrease in adaptation to exercise is unclear. We assessed exercise tolerance in children with surgically treated CP and appropriate pituitary hormone replacement therapy compared with healthy controls and we examined the potential relationships with hypothalamic involvement, GH replacement, and the catecholamine deficiency frequently observed in these subjects. DESIGN AND METHODS: Seventeen subjects (12 males and five females) with CP and 22 healthy controls (14 males and eight females) aged 15.3+/-2.5 years (7.3-18 years) underwent a standardized cycle ergometer test. Maximum aerobic capacity was expressed as the ratio of VO(2max) to fat-free mass (VO(2max)/FFM), a measure independent of age and fat mass in children. RESULTS: VO(2max)/FFM was 20% lower in children with CP compared with controls (P<0.05), even after adjustment for gender. Children with hypothalamic involvement (n=10) had a higher percentage of fat mass (P<0.05) than those without hypothalamic involvement (n=7) and lower VO(2max)/FFM (P<0.05), whereas children without hypothalamic involvement had VO(2max)/FFM close to that of controls (P>0.05). GH treatment was associated with a significant positive effect on aerobic capacity (P<0.05) only in the absence of hypothalamic involvement. No relationship was found between exercise capacity parameters and daily urine epinephrine excretion or epinephrine peak response to insulin-induced hypoglycemia. CONCLUSIONS: Children with CP have a decrease in aerobic capacity mainly related to hypothalamic involvement. The hypothalamic factors altering aerobic capacity remain to be determined

Laparoscopic adjustable gastric banding in adolescents: Results at two years including psychosocial aspects

BACKGROUND/PURPOSE: Obesity now affects 3%-4% of the pediatric population and contributes to the increase in cardiac mortality in adulthood. Bariatric surgery is the best treatment for weight loss and the obesity-associated comorbidities in adults. We report here our experience of laparoscopic adjustable gastric banding (LAGB) in adolescents. METHODS: The medical charts of the first 16 patients operated on in our center were reviewed. Data were compiled concerning weight loss, physical and biological comorbidities, health-related quality of life (QOL) and surgical complications before surgery and during 24months of follow-up. RESULTS: The maximal pre-operative median body mass index was 43.0kg·m(-2), decreasing to 33.0kg·m(-2) at 2years post-LAGB, which corresponded to a 49.2% excess body weight loss (p<0.001). Most comorbidities (glucose intolerance, hypertension and sleep apnea) resolved within the first year post-LAGB and QOL was improved on the PedsQL™ scales. No severe surgical complications were noted, with only three re-interventions for device failure (2) or band removal (1). CONCLUSION: LAGB is well tolerated in adolescents and shows a beneficial impact on weight loss and obesity-related comorbidities. Associated with global management, it may have a positive impact on patients\u27 QOL and social and psychological status

M004 In aortic stenosis, 2D speckle tracking differentiates left ventricular dysfunction load- to remodelling-dependant

BackgroundIn aortic stenosis, it is not known which between longitudinal, radial and circumferential contraction is influenced by loading conditions or remodelling. To test our hypothesis and to understand left ventricular function recovery, we investigated patients at early, i.e. 7 days (contractility enhancement load-dependant) and at late follow-up, i.e. 3 months (contractility enhancement remodelling-dependant) after transcutaneous aortic valve implantation (TAVI).Methods and ResultsTwenty-three subjects (AS: valve orifice < or =0.7cm2; 14 female; mean age, 84+/-6 years) were studied. All subjects of the study had conventional 2D-Doppler echocardiography and speckle tracking analysis (GE HealthCare). Speckle tracking was sampled in short-axis view for radial and circumferential strain and in apical 4, 3 and 2-chamber view for averaged longitudinal strain. Measurements were performed before, 7 days and 3 months after TAVI. Mean pressure gradient decreased from 41±20mmHg to 10±3mmHg (p<0.001) while aortic valve area increased from 0.6±0.1 to 1.7±0.2cm2 (p<0.001) after implantation. Biplane Simpson EF was 50±10 %, 51±13 and 58±11 % at baseline, 7-day and 3-month follow-up (p=0.01), respectively. Improvement of circumferential strain found 7 days after TAVI is sustained at 3 months. Radial strain increased shortly after TAVI, then decreased at 3 months and was compensated by improvement of longitudinal strain (see figure).ConclusionIn patients with aortic stenosis, radial contraction is load dependant, circumferential contraction is both load- and remodelling-dependant, whereas longitudinal contraction is remodeling-dependant

The imprint of the analogue Hawking effect in subcritical flows

We study the propagation of low-frequency shallow water waves on a one-dimensional flow of varying depth. When taking into account dispersive effects, the linear propagation of long-wavelength modes on uneven bottoms excites new solutions of the dispersion relation which possess a much shorter wavelength. The peculiarity is that one of these new solutions has a negative energy. When the flow becomes supercritical, this mode has been shown to be responsible for the (classical) analog of the Hawking effect. For subcritical flows, the production of this mode has been observed numerically and experimentally, but the precise physics governing the scattering remained unclear. In this work, we provide an analytic treatment of this effect in subcritical flows. We analyze the scattering of low-frequency waves using a new perturbative series, derived from a generalization of the Bremmer series. We show that the production of short-wavelength modes is governed by a complex value of the position: a complex turning point. Using this method, we investigate various flow profiles and derive the main characteristics of the induced spectrum