Fiber amplification of pulse bursts up to 20 mu J pulse energy at 1 kHz repetition rate

Cataloged from PDF version of article.We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of similar to 20 mu J and total burst energy of 0.25 mJ. The pulses are externally compressed to similar to 400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length. (C) 2011 Optical Society of Americ

The reliability of national videos related to the kidney stones on YouTube

Objective: Kidney stones are one of the most common disorders of the urinary tract. With increasing awareness, a larger proportion of patients are seeking medical knowledge from the Internet. In present study, the features, reliability and efficacy of videos on YouTube related to the treatment of kidney stones were evaluated. Material and methods: In December 2014, YouTube was searched using keywords “nephrolithiasis”; “renal calculi”; “renal stones”; and “kidney stones” for videos uploaded containing relevant information about the disease. Only videos in Turkish were included in the study. Two physician viewers watched each video and classified them as useful, partially useful and useless according to European Association of Urology (EAU) Guidelines. The source, length, number of views, number of favourable opinions, and days since uploaded date of the all videos were evaluated. Results: A total of 600 videos were analysed The median length of videos was 6.7±10.4 (median: 3, IQR: 0.03-58) minutes . Each video was viewed at an average of 2368 (min: 11, max: 97133) times. Most of the videos (32.8%) were created by academicians and physicians. Nearly half (47.4%) of the videos were uploaded in 2014. The majority of the videos (62.5%) contained information for treatment. Percutaneous nephrolithotomy and ureterorenoscopy were the most common treatment modalities (32.8% and 28.0%, respectively) in these videos. A statistically significant difference was not detected between view numbers and source of videos (p=0.87). However, there was a statistically significant difference between usefulness to the viewers and source of videos. Hospital -based videos were detected to be more useful (p=0.000). Conclusion: As a result, videos that would be prepared in internet environment by professional individuals or organizations in a way which would attract attention and be easily comprehended by the public could contribute to the knowledge and education of our society about the stone disease which is commonly seen in our country. © 2016 by Turkish Association of Urology

Fiber amplification of pulse bursts up to 20 μj pulse energy at 1 kHz repetition rate

We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of ∼20 μJ and total burst energy of 0:25 mJ. The pulses are externally compressed to ∼400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length. © 2011 Optical Society of America

The Risk Factors Associated with Grip Lock Injuries in Artistic Gymnasts: A Systematic Review

Artistic gymnastics (AG) is a sport that demands grace, strength, and flexibility, leading to a broad spectrum of injuries. The dowel grip (DG) is widely used by gymnasts to securely hold onto the high bar or uneven bars. However, incorrect usage of the DG can result in grip lock (GL) injuries. This systematic review aims to (1) identify studies that have investigated the risk factors related to GL injuries among gymnasts and (2) synthesize the key evidence. A comprehensive electronic search was conducted in the following databases: PubMed, ScienceDirect, Elsevier, SportDiscus, and Google Scholar, covering the period from their inception until November 2022. The data extraction and analysis were independently completed by two investigators. A total of 90 relevant studies were initially identified, out of which seven clinical trials met the eligibility criteria. For the quantitative synthesis, five studies were included. The details extracted from each article include: the sample characteristics (number, gender, age, and health status), the study design, the instrumentation or intervention used, and the final results. Our results revealed that the underlying causes of the risk factors of GL injuries were the irregular checking of the dowel grip and the mating surface of the bar, the tearing of the dowel of the leather strap, and the use of the dowel grip in different competition apparatuses. In addition, GL injuries may occur either as severe forearm fractures or mild injuries. Excessive flexion of the forearm and overpronation of the wrist during rotational movements, such as the swing or backward/forward giant circle, may increase the possibility of GL injury on the high bar. Future studies should focus on GL injury prevention strategy and rehabilitation protocol for GL injuries. Further high-quality research is required to establish the validity of these findings. © 2023 by the authors.European Commission, EC: .02.2.69/0.0/0.0/18_054/0014627Published with the financial support of the European Union, as part of the project entitled Development of capacities and environment for boosting the international, intersectoral, and interdisciplinary cooperation At UWB, project reg. no.CZ.02.2.69/0.0/0.0/18_054/0014627

Doping management for high-power fiber lasers: 100 W, few-picosecond pulse generation from an all-fiber-integrated amplifier

Cataloged from PDF version of article.Thermal effects, which limit the average power, can be minimized by using low-doped, longer gain fibers, whereas the presence of nonlinear effects requires use of high-doped, shorter fibers to maximize the peak power. We propose the use of varying doping levels along the gain fiber to circumvent these opposing requirements. By analogy to dispersion management and nonlinearity management, we refer to this scheme as doping management. As a practical first implementation, we report on the development of a fiber laser-amplifier system, the last stage of which has a hybrid gain fiber composed of high-doped and low-doped Yb fibers. The amplifier generates 100 W at 100 MHz with pulse energy of 1 mu J. The seed source is a passively mode-locked fiber oscillator operating in the all-normal-dispersion regime. The amplifier comprises three stages, which are all-fiber-integrated, delivering 13 ps pulses at full power. By optionally placing a grating compressor after the first stage amplifier, chirp of the seed pulses can be controlled, which allows an extra degree of freedom in the interplay between dispersion and self-phase modulation. This way, the laser delivers 4.5 ps pulses with similar to 200 kW peak power directly from fiber, without using external pulse compression. (C) 2012 Optical Society of Americ

Fiber amplification of pulse bursts at low repetition rates via synchronous pulsed pumping

We report, for the first time, amplification of pulse-bursts in Yb-doped fiber at repetition rates as low as 200 Hz for applications to accelerators and material processing. Synchronous pulsed pumping allows suppression of ASE generation. © 2011 Optical Society of America

Burst-mode Yb fiber amplifier producing 30 μJ individual pulse energy

We report 30-μJ individual pulse energy for 150-ns long amplified bursts of 0.4 mJ total energy from a 1-kHz Yb-fiber amplifier. Non-uniformity of pulse energy distribution inside amplified bursts is significantly reduced. ©2012 Optical Society of America

Development of a rapid-scan fiber-integrated terahertz spectrometer

Scientists in terahertz (THz) wave technologies have benefited from the recent developments in ultrafast laser technologies and RF technologies and applied these new gained techniques into characterizing a wide variety of phenomena. Undoubtedly, the most successful of these applications has been in the development of time-domain terahertz spectroscopic and imaging systems which has been utilized in the characterization of dielectrics and semiconductors. This pulsed technique has allowed users to characterize dynamical behavior inside materials under illumination with picosecond resolution. Typically pump/probe or similar dynamical measurements require the use of amplified pulses derived from free-space solid state lasers in the μJ-mJ range and since interferometric techniques are typically used in pulsed measurements the measurement time of a THz spectrum can last at least tens of minutes. Better systems can be realized based on fiber laser technologies. Here we discuss the advantages of a THz spectrometer driven by an ultrafast Ytterbium doped fiber laser whose repetition rate can be tuned rapidly allowing for rapid dynamical measurements. The efficient gain medium, robust operation and compact design of the system opens up the possibility of exploring rapid detection of various materials as well as studying dynamical behavior using the high brightness source. © 2013 Springer Science+Business Media New York

Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers

Cataloged from PDF version of article.We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. (C) 2011 Optical Society of Americ

Maximizing team synergy in AI-related interdisciplinary groups: an interdisciplinary-by-design iterative methodology

In this paper, we propose a methodology to maximize the benefits of interdisciplinary cooperation in AI research groups. Firstly, we build the case for the importance of interdisciplinarity in research groups as the best means to tackle the social implications brought about by AI systems, against the backdrop of the EU Commission proposal for an Artificial Intelligence Act. As we are an interdisciplinary group, we address the multi-faceted implications of the mass-scale diffusion of AI-driven technologies. The result of our exercise lead us to postulate the necessity of a behavioural theory that standardizes the interaction process of interdisciplinary groups. In light of this, we conduct a review of the existing approaches to interdisciplinary research on AI appliances, leading to the development of methodologies like ethics-by-design and value-sensitive design, evaluating their strengths and weaknesses. We then put forth an iterative process theory hinging on a narrative approach consisting of four phases: (i) definition of the hypothesis space, (ii) building-up of a common lexicon, (iii) scenario-building, (iv) interdisciplinary self-assessment. Finally, we identify the most relevant fields of application for such a methodology and discuss possible case studies