83 W, 3.1 MHz, square-shaped, 1 ns-pulsed all-fiber-integrated laser for micromachining

Cataloged from PDF version of article.We demonstrate an all-fiber-integrated laser based on off-the-shelf components producing square-shaped, 1 ns-long pulses at 1.03 mu m wavelength with 3.1 MHz repetition rate and 83 W of average power. The master-oscillator power-amplifier system is seeded by a fiber oscillator utilizing a nonlinear optical loop mirror and producing incompressible pulses. A simple technique is employed to demonstrate that the pulses indeed have a random chirp. We propose that the long pulse duration should result in more efficient material removal relative to picosecond pulses, while being short enough to minimize heat effects, relative to nanosecond pulses commonly used in micromachining. Micromachining of Ti surfaces using 0.1 ns, 1 ns and 100 ns pulses supports these expectations. (C) 2011 Optical Society of Americ

Three-dimensional modelling of the femur and humerus in adult male guinea pigs (guinea pig) with computed tomography and some biometric measurement values

Background: Guinea pig is a species belonging to the Caviidae family of the Rodentia order and is frequently used in experimental studies. Biomedical imaging methods are used in the diagnosis and treatment of many diseases in medicine. Among these methods, computed tomography (CT) is one of the most important imaging methods. In this study, it was aimed to perform the three-dimensional (3D) modelling of the CT images, obtained from the humerus and femur in the guinea pigs, via the MIMICS programme, and to make some biometric measurements regarding the bones over these models. Materials and methods: In the present study, 12 male adult guinea pigs were used. The soft tissue on the humerus and femur bones of the guinea pigs was removed. After this procedure, CT images at a 0.5 mm-thickness were obtained from the animals. The images were recorded in DICOM format. Then, the reconstruction process was performed from the images by using the 3D modeling programme MIMICS® 13.1. On the 3D model of the humerus and femur (right-left), volumes, surface areas and lengths as well as other biometric parameters were measured separately, and the values were recorded. In addition, measurements of the bones were made with the help of a digital calliper. Results: Among the parameters obtained from 3D models, a statistical difference was observed between the right and left cortical thicknesses of the femur from the measurements of calliper and the right and left humerus volumes (p < 0.05); whereas, no statistical difference was found in other parameters of both measurements (p > 0.05). Conclusions: It can be stated that CT and 3D modelling can be used for the measurement of some parameters in the long bones of the guinea pigs

Phylogenetic analysis of some fungi species in West Kazakhstan based on nuclear ribosomal DNA ITS sequences

In this study, phylogenetic analysis of some fungal species distributed in West Kazakhstan was performed based on ITS sequences. All of the mushroom samples were collected from different regions of West Kazakhstan and brought to the laboratory. Total genomic DNA was extracted using a GeneMark commercial kit. ITS1 and ITS4 primers were used for the amplification of the ITS region in PCR analyses. The resulting DNA sequences were then edited using BioEdit and FinchTV. For phylogenetic analysis used MEGA 6.0 program. As a result of the study, ITS sequences ranged from 532 to 715 nucleotides, while the divergence values of the sequences differed between 0.000 and 0.468. The maximum likelihood tree constructed using ITS sequences consists of two clades. According to the phylogenetic analysis results obtained using other fungal species, ITS results were found to be a good indicator for the differentiation of fungal genera

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

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

The effect of bovine serum albumin and fetal calf serum on sperm quality, DNA fragmentation and lipid peroxidation of the liquid stored rabbit semen

The aim of the present study was to determine the effects of the bovine serum albumin (BSA) and fetal calf serum (FCS) on sperm quality, DNA fragmentation and lipid peroxidation of liquid stored rabbit semen stored up to 72 h at 5 C. Ejaculates were collected from five New Zealand male rabbits by artificial vagina and pooled at 37 C following evaluation. Each pooled ejaculate was split into three equal experimental groups and diluted to a final concentration of approximately 40 106 sperm/ml (single step dilution), in an Eppendorf tube, with the Tris based extender containing BSA (5 mg/ml), FCS (10%) or no additive (control) at 37 C, cooled to 5 C and stored for up to 72 h. The extender supplemented with BSA and FCS did not improve the percentages of motility and acrosomal abnormality during 48 h compared to the control. The additives BSA and FCS had a significant effect in the maintaining of plasma membrane integrity between 48 and 72 h storage period, compared to the control (P < 0.01). The supplementation of BSA and FCS had a protective effect on motility (P < 0.05), plasma membrane integrity (P < 0.01) and acrosomal integrity (P < 0.01) at 72 h compared to the control. The supplementations with BSA and FCS led to a reduction in DNA damage of rabbit sperm at 48 and 72 h during storage period, compared to the control (P < 0.001). Although supplementation of BSA and FCS caused significant (P < 0.01) decreases in malondialdehyde (MDA) level at 48 h and 72 h, they significantly (P < 0.01) increased the glutathione peroxidase (GPx) antioxidant activity up to 72 h when compared to the control group. In conclusion, BSA and FCS supplementation to liquid stored rabbit semen provide a protection for spermatozoa against cool storage-induced DNA damage and plasma membrane integrity by their antioxidative properties