A 'snip' in time: what is the best age to circumcise?

<p>Abstract</p> <p>Background</p> <p>Circumcision is a common procedure, but regional and societal attitudes differ on whether there is a need for a male to be circumcised and, if so, at what age. This is an important issue for many parents, but also pediatricians, other doctors, policy makers, public health authorities, medical bodies, and males themselves.</p> <p>Discussion</p> <p>We show here that infancy is an optimal time for clinical circumcision because an infant's low mobility facilitates the use of local anesthesia, sutures are not required, healing is quick, cosmetic outcome is usually excellent, costs are minimal, and complications are uncommon. The benefits of infant circumcision include prevention of urinary tract infections (a cause of renal scarring), reduction in risk of inflammatory foreskin conditions such as balanoposthitis, foreskin injuries, phimosis and paraphimosis. When the boy later becomes sexually active he has substantial protection against risk of HIV and other viral sexually transmitted infections such as genital herpes and oncogenic human papillomavirus, as well as penile cancer. The risk of cervical cancer in his female partner(s) is also reduced. Circumcision in adolescence or adulthood may evoke a fear of pain, penile damage or reduced sexual pleasure, even though unfounded. Time off work or school will be needed, cost is much greater, as are risks of complications, healing is slower, and stitches or tissue glue must be used.</p> <p>Summary</p> <p>Infant circumcision is safe, simple, convenient and cost-effective. The available evidence strongly supports infancy as the optimal time for circumcision.</p

Scaling infrared femtosecond optical parametric oscillators to high average powers

Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2017A demand for ultrafast, highly energetic laser sources in the infrared exists for various applications such as high-harmonic generation, waveguide inscription, and remote sensing. These applications require high repetition rates for faster processing speed and better signal-to-noise ratios. Until recently, laser pulses used in these systems were usually provided by optical parametric oscillators and amplifiers pumped by Ti:sapphire laser systems. The output power and spectral bandwidth of this pump source are fundamentally restricted due to unavoidable limitations caused by the quantum-defect heating and restricted emission spectrum of the gain medium. Advancements to Yb-based sources have provided a significant increase in average power and pulse energy available from ultrafast pumps, thereby increasing the capabilities of parametric devices. In this thesis, an ultrafast optical parametric oscillator was constructed as a test bed for investigating the scaling potential of these devices. The main goals of this study were to utilize recent technological advancements to ultrafast pump sources and test the limits for obtaining high-energy pulses with high average powers from an optical parametric oscillator. Various nonlinear crystals and parametric pumping geometries were investigated to determine how best to use the available power of a home-built pump laser and the general potential for scalability. To utilize recent developments of similar pump sources, a long cavity was designed to take advantage of the high-average-powers with scalable pulse energies. While the designing the cavity, it became apparent that the cavity length could be done easily without notable change to critical cavity parameters by using telescopic imaging relays. It was discovered that limitations to the power scalability of this system were directly linked to problems with the thermal management of the nonlinear crystal. While minor changes could have been implemented to reduce the impact of these boundaries, understanding thermal effects in parametric devices will be critical to fully utilizing the state-of-the-art pump sources. Simple and cost-effective methods were developed for characterizing the impact of the thermal gradient on the available gain. This analysis could easily be extended to other systems for predicting and mitigating thermally induced power scaling limitations

Petawatt and exawatt class lasers worldwide

In the 2015 review paper ‘Petawatt Class Lasers Worldwide’ a comprehensive overview of the current status of highpower facilities of >200 TW was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multi-disciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development

Petawatt and exawatt class lasers worldwide

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