RESUMO
We report on experimental investigations of proton acceleration from solid foils irradiated with PW-class laser-pulses, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses. The paper further proves the robustness and applicability of this enhancement effect for the use of different target materials and thicknesses as well as laser energy and temporal intensity contrast settings. We demonstrate that application relevant proton beam quality was reliably achieved over many months of operation with appropriate control of spectral phase and temporal contrast conditions using a state-of-the-art high-repetition rate PW laser system.
RESUMO
We present light induced refractive index changes in iron doped lithium niobate detected with a novel microscopy technique called ptychography. This method determines the change of the refractive index together with the intensity distribution of the writing beam from a single scan with a reconstructed spatial resolution of 3 µm and a sensitivity of the refractive index change of 10-5. We show that the light induced refractive index change is strongly connected to the intensity shape of the writing beam and that it shows the expected nonlocal behaviour. Applying the novel method to the investigation of the photorefractive effect offers an excellent opportunity to study this nonlocal response to the spatial distribution of the writing beam.
RESUMO
More than 200,000 people underwent obesity surgery in France. Most of them are women. Pregnancy after bariatric surgery is becoming a common situation. This surgery results in major nutritional and gastro-intestinal tract modifications that may influence or be influenced by pregnancy, and yields benefits as well as complications. A multidisciplinary management including a nutritionist, an obstetrician, an anesthesiologist, and a bariatric surgeon is required. The aim of this review is to analyze the impact of bariatric surgery on pregnancy and vice versa, and to identify the key points of this management.
Assuntos
Cirurgia Bariátrica/efeitos adversos , Complicações na Gravidez/prevenção & controle , Adulto , Feminino , Humanos , GravidezRESUMO
In recent years, the recourse to obesity surgery to treat morbid obesities has grown. The number of "malabsorptive" interventions, such as the gastric bypass (RYGB: Roux-en-Y gastric bypass) increases each year. The RYGB, which combines two mechanisms promoting weight loss, restriction and malabsorption, has proven its effectiveness in term of weight loss and improvement of obesity-associated co-morbidities. However this intervention involves a profound change in digestive physiology and is the source of nutritional and metabolic complications. The deficits observed most frequently concern proteins, iron, calcium, vitamin B12 and vitamin D. The deficiencies in vitamin B1 are rare but potentially serious. Multidisciplinary follow-up is essential to ensure prevention, diagnosis and treatment of these complications. Based on an analysis of the literature, this article summarizes the various nutritional complications observed after RYGB and the means to diagnose it. It proposes practical recommendations for follow-up, preventive supplementation and treatment of these deficiencies, both generally and in the more specific case of a pregnancy after RYGB.
