9,276 research outputs found
Characteristics of Q-switched cladding-pumped ytterbium-doped fiber lasers with different high-energy fiber designs
No full textWe theoretically and experimentally analyze Q-switched cladding pumped ytterbium-doped fiber lasers designed for high pulse energies. We compare the extractable energy from two high-energy fiber designs: (1) single- or few-moded low-NA large mode area (LMA) fibers and (2) large-core multimode fibers, which may incorporate a fiber taper for brightness enhancement. Our results show that the pulse energy is proportional to the effective core area and, therefore, LMA fibers and multimode fibers of comparable core size give comparable results. However, the energy storage in multimode fibers is mostly limited by strong losses due to amplified spontaneous emission (ASE) or even spurious lasing between pulses. The ASE power increases with the number of modes in a fiber. Furthermore, spurious feedback is more difficult to suppress with a higher NA, and Rayleigh back-scattering increases with higher NA, too. These effects are smaller in low-NA LMA fibers, allowing for somewhat higher energy storage. For the LMA fibers, we found that facet damage was a more severe restriction than ASE losses or spurious lasing. With a modified laser cavity, we could avoid facet damage in the LMA fiber, and reached output pulse energies as high as 2.3 mJ, limited by ASE. Theoretical estimates suggest that output pulse energies around 10 mJ are feasible with a larger core fiber, while maintaining a good beam qualit
Multi-mJ, multi-Watt Q-switched fiber laser
No full textUsing a large mode area, ytterbium-doped cladding-pumped fiber and a novel cavity configuration we obtain 2.3 mJ Q-switched pulses, a record pulse energy for a fiber laser. Average powers in excess of 5W were achieved
SYNTHETIC CANNABINOIDS AND THE SEROTONIN SYNDROME: AN UNFORESEEN ASSOCIATION
No full textSYNTHETIC CANNABINOIDS AND THE SEROTONIN SYNDROME: AN UNFORESEEN ASSOCIATION Duccio Papanti 1, Laura Orsolini 2, Tommaso Bonavigo 1, Federico Sandri 1, Elisabetta Pascolo-Fabrici 1, Fabrizio Schifano 3 1 University of Trieste, Italia 2 University of Marche, Italia 3 University of Hertfordshire, UK Educational Objectives: Use of synthetic cannabinoids (SCs) has been increasingly associated with severe adverse effects, including deaths. SC intoxication is very different to cannabis one and shows common features with the serotonin syndrome. Purpose Synthetic cannabinoid compounds belong to a new psychoactive class of substances misused as an alternative to marijuana (MJ). These compounds have been developed for research purposes and have never been tested in clinical human studies. Currently, SCs can be easily bought on a global level, both online and in local stores. We aimed here at identifying SC pharmacodynamics, effects/symptoms of intoxication and neurobehavioral sequaelae in humans, with a focus on findings compatible/common to the serotonin syndrome. Methods: A search was carried out on PubMed/Medline for the terms “synthetic cannabimimetics”, “synthetic cannabinoids”, “synthetic cannabis” in order to identify effects/symptoms of intoxication, neurobehavioral sequaelae related to SC intake in humans. Results: SC compounds are structurally dissimilar and incorporate indole mojeties, not present in MJ. SC are full agonists on cannabinoid receptors (CB-rs) while cannabis main psychoactive, tetrahydrocannabinol (THC), exerts partial agonism on cannabinoid receptors. SCs visual hallucinations are described as fractals/trails/flashes of colour/geometric patterns [1]. Signs of intoxication are elevated heart rate; hallucinations; mydriasis; agitation; vomiting; and seizures; these signs are common in the serotonin syndrome. Indole is structurally similar to serotonin (5-HT), has activity on 5-HT receptors and is typically identified within indoleamine hallucinogens such as DMT. While 5-HT2A receptors are the primary site of action for DMT (typically producing visual geometric hallucinations in the users), the agonism of 5-HT2A receptors contributes substantially to the development of the serotonin syndrome. Conclusions: Beside the well-known cannabimimetic properties, SC drugs could have additive hallucinogenic effects due to the indole mojeties incorporated in their structures. SCs intake/intoxication can produce acute signs/symptoms/clinical findings belonging to the serotonin syndrome. Literature Reference [1] Spaderna, M., Addy, P.H., D’Souza, D.C., 2013. Spicing thin
Distribution of Y chromosomal STRs loci in Mayan and Mestizo populations from Guatemala
No full textIn this study, a sample of 225 Guatemalan males, comprising 115 Mestizo-Guatemalan and 110 Mayan-Guatemalan, was typed for 17 Y-short tandem repeats (STRs) loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, YGATA_H4.1 and DYS385a/b). The haplotype diversity (H = 1) and discrimination capacity (96.86%) were calculated. Analysis of molecular variance (AMOVA) demonstrated a low but significant interpopulation differentiation when compared with the results obtained when we confront the Mestizo and Mayanpopulations with the European populations.
Furthermore, the genetic variability and differences among the American, African, Asian, and European populations were analyzed with the software Statistica 9.1. In addition, the genetic distances were also calculated using other published data. Reynolds and Slatkińs genetic distance was visualized using the multidimensional scaling (MDS) analysis. All the analysis performed locates the Mayanpopulation next to the Native American population, while Guatemalan-Mestizopopulation was found to be between these populations and the European population, similar to other Mestizo one.
The implementation of the estimation of individual ancestry proportions of the whole population sample showed the presence of two well-differentiated population groups
Mobility of toxic elements in carbonate sediments from a mining area in Poland
No full textOspina-Alvarez, N., Głaz, L., Dmowski, K., & Krasnodębska-Ostręga, B. (2014). Mobility of toxic elements in carbonate sediments from a mining area in Poland. Environmental Chemistry Letters, 12, 435–441. doi:10.1007/s10311-014-0468-
Self-compression of 4.9 µm pulses to sub-40 fs with 2 mJ energy in Zinc Sulfide
No full textNonlinear self-compression of few-cycle multi-mJ pulses at 4.9 µm in ZnS is presented. 80 fs input pulses are compressed to 37 fs with 2.1 mJ energy at a 1 kHz repetition rate. © 2024 The Author(s
Genotype data for 38 INDELs of 143 unrelated adults from the SouthEast Spanish population
No full textData from the paper:Population genetic data of 38 insertion-deletion markers in South East Spanish population. M Saiz, MJ Alvarez-Cubero, LJ Martinez-Gonzalez, JC Alvarez, JA Lorente.Forensic Science International: Genetics (2014), 13; 236-
Correction to: Chamoun et al., Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection
No full textChamoun MN, Blumenthal A, Sullivan MJ, Schembri MA, Ulett GC. 2018. Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection. Critical Reviews in Microbiology. https://doi.org/10.1080/1040841X.2018.1426556.
When the above article was first published online, the below three corrections were missed.
The author ‘Antje Blumenthal’ was wrongly affiliated to the affiliation “cSchool of Chemistry and Molecular Biosciences, and Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Australia”. Now this affiliation has been removed for this author.
The affiliation ‘bTranslational Research Institute, The University of Queensland Diamantina Institute, Woolloongabba, Australia’ of the author ‘Antje Blumenthal’ should read ‘bThe University of Queensland Diamantina Institute, Translational Research Institute, Brisbane, Australia’.
In Table 3, the sentence ‘Benefit of manipulating IL-17 levels to improve immunization strategies M. tuberculosis’ should read “Benefit of manipulating IL-17 levels to improve immunization strategies against M. tuberculosis”.No Full Tex
High-power fibre lasers
No full textThis thesis reports on the experimental study of high-power, high-energy, cladding-pumped, rare-earth (Yb3+, Er3+/Yb3+)-doped fibre lasers. Some of the main capabilities of fibre lasers such as: High brightness and thermal properties were exploited for the development of a variety of continuous wave (CW) and Q-switched devices, whose characteristics also includes compactness. Our devices could already be considered an option for several applications. The 25-year long scientific and commercial evolution that fibre lasers have experienced is discussed in the first two chapters. The invention of Erbium-doped fibre amplifiers (EDFA's) and Internet were two major breakthroughs, which launched the need of WDM systems and laser sources. Fibre lasers, are now considered a flexible and powerful device whose technology has finally reached its maturity. Cladding pumping is the technique employed in these experiments in order to pump double clad fibre lasers using high power, broad stripes and bars. In this work, several inner cladding shapes have been used to overcome the normally high mismatch between diode laser beams and inner cladding areas of fibre lasers. Chapter Three consists of a review of cladding-pumped fibre lasers. It describes how inner cladding geometry and pump absorption limits the output power scalability of these devices. Nonlinear effects and amplified spontaneous emission are also studied due to their implication they have over fibre lasers performance. Results on conventional, continuous wave (CW) fibre lasers including fibre characterization and employed launching techniques are described in Chapter Four. A new method to obtain high intensity laser beam output from an Yb3+-doped, cladding-pumped, highly multimode fibre laser has been proposed. In this experiment, we propose the use of fibre tapers to increase intensity and improve beam quality. In CW regime, our results show an intensity increase of ~3.5 times with a low power penalty of ~1 dB. Also, without tapering, a maximum output power of 21-W was reached with a slope efficiency of >80%. Using a simple set of optic elements such as a l/2 waveplate, a polarizing beam-splitter and a bulk grating, we investigated the polarization characteristics of an Yb3+ fibre laser, from which we obtained 6.5 W of single polarization tunable output in the range of 1070 to 1106 nm. As a free running laser, the system produced 18 W at 1090 nm and showed a threshold of 1.8 Watts. The experiment is our first approach for developing a reliable high-power Yb3+-doped fibre source, that could be used in conjunction with optical parametric oscillators (OPO) and amplifiers (OPA) to frequency convert to a broad band of wavelengths. Using a new design of ytterbium-doped fibre made in-house with the conventional modified chemical vapor deposition (MCVD) process, we explored the possibilities of energy storage with such a large mode area (LMA) fibre. The fibre system was capable of delivering energetic pulses of >2 mJ, which could suggest the feasibility of a pulsed fibre laser in the region of tens of milli-Joules. The experiment is described in Chapter Six, on which the experiment that uses the tapered fibre laser in Q-Switched regime is also described and compared to LMA fibre laser. Gaussian-type pulses were obtained which reached pulse energies of 0.6 mJ at 4 kHz using a tapered fibre laser and 1.3 mJ at 500 Hz using conventional laser, corresponding to average powers of 2.1 Watts for the tapered laser and 0.8 watts for the conventional laser. Er3+/Yb3+-doped fibre lasers were part of our experimental work. This co-doping technique allows pumping of Yb3+ ions using broad-stripe high-power pump sources to reach much higher output power levels. Efficient energy transfer from excited Ytterbium ions into Erbium is achieved. From a preliminary study, the fibre laser showed a threshold of 160 mW and a slope efficiency of 49% with respect to absorbed pump power. The maximum output power was 6.2 watts at 1535 nm and a linewidth of 1 nm. One of our co-doped fibre devices produced 16.8 W of continuous wave, multimode laser power at the interesting wavelength of operation of 1550 nm. Finally, conclusions and future work are included in Chapter Eight. <br/
Generation of 22-mJ, 2.0-ps Pulses from a 1-kHz Ho:YLF Regenerative Chirped Pulse Amplifier
No full textWe report a CW-pumped Ho:YLF regenerative amplifier (RA) delivering pulses with 22.5-mJ energy and 2.0-ps duration at 1 kHz. The RA emitting at 2051 nm is broadband-seeded and implemented in a chirped pulse amplification system. © 2024 The Author(s
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