ABSTRACT
An efficient 2 µm in-band pumped Ho:YAG laser was demonstrated. The resonator involves two Ho:YAG crystals, each of which was dual-end-pumped by two orthogonally polarized diode-pumped Tm:YLF lasers. The maximum continuous wave output power of 103 W was achieved, corresponding to a slope efficiency of 67.8% with respect to the incident pump power and an optical-to-optical conversion efficiency of 63.5%. Under Q-switched mode, we obtained 101 W laser output at 30 kHz, corresponding to a slope efficiency of 66.2%. The beam quality or M2 factor was found to be less than 2.
Subject(s)
Lasers, Solid-State , Spectrum AnalysisABSTRACT
An intensity modulated method by scanning for the focusing therapy machine is introduced in this paper. At first, the 3-D model of the focus is delaminated through the treatment planning system, and the dose distributing of each lay is calculated by an inverse design method. Then, the exposure time of the focus at each position is determined and converted to a scanning parameter, such as position, speed and so on. Afterward, the focus continuously scans the tumor at different speeds along the planned track under the control of the computer. Consequently the point-by- point intensity modulation is achieved through the diversification of the scanning speed of the focus.
Subject(s)
Radiotherapy Planning, Computer-Assisted/methods , Radiotherapy, Conformal/instrumentation , Radiotherapy, Conformal/methods , Humans , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted/instrumentationABSTRACT
A first order system model is proposed for simulating the influence of stress stimulation on fracture strength during fracture healing. To validate the model, the diaphyses of bilateral tibiae in 70 New Zealand rabbits were osteotomized and fixed with rigid plates and stress-relaxation plates, respectively. Stress shielding rate and ultimate bending strength of the healing bone were measured at 2 to 48 weeks postoperatively. Ratios of stress stimulation and fracture strength of the healing bone to those of intact bone were taken as the system input and output. The assumed first order system model can approximate the experimental data on fracture strength from the input of stress stimulation over time, both for the rigid plate group and the stress-relaxation plate group, with different system parameters of time constant and gain. The fitting curve indicates that the effect of mechanical stimulus occurs mainly in late stages of healing. First order system can model the stress adaptation process of fracture healing. This approach presents a simple bio-mathematical model of the relationship between stress stimulation and fracture strength, and has the potential to optimize planning of functional exercises and conduct parametric studies.
Subject(s)
Animals , Rabbits , Biomechanical Phenomena , Fracture Healing , Physiology , Mathematics , Models, Animal , Models, BiologicalABSTRACT
The relationship between cell elongation and microtubules (MTs) was investigated in characean internodal cells (Nitellops obtusa). First, we examined the immunofluorescent localization of MTs in different living stages under confocal laser scanning microscope. In young, rapidly elongating cells, MTs were predominantly transverse to the long axis of the cell. As the relative growth rate fell, transverse MTs gradually decreased, and in non-growing cells, longitudinally oriented cortical MTs became most pronounced. Moreover, cells in different living stages responded to the treatment of oryzalin (microtubule-disrupting agent) differently, young active internodal cells seemed to be more sensitive. After 40 min incubation of 10 micromol/L oryzalin, nearly all cortical MTs in the elongating cells depolymerized. However, in the old, non-growing cells, some MT fragments still remained after 3 h treatment of oryzalin. Second, we measured the cell growth rates with and without the treatment of oryzalin. In young growing cells treated with 10 micromol/L oryzalin, the elongation rates were inhibited obviously. When the oryzalin was removed, the elongation rates could be recovered to some extent. Interestingly, a time-gap existed between microtubule disassembly (40 min) and cessation of cell elongation (100 min). Our data confirmed the evidence that MTs are involved in cell elongation.
