ABSTRACT
PURPOSE: This study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability. MATERIALS AND METHODS: Regular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (α=0.05). RESULTS: THE POSTLOAD REMOVAL TORQUE VALUE WAS HIGH IN THE FOLLOWING ORDER WITH REGARD TO MAGNITUDE: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05). CONCLUSION: The results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate.
ABSTRACT
Using a ray matrix method, we analyze theoretically how the r and theta polarizations affect the resonator stability condition of two laser heads with or without thermal birefringence compensation. The resonator stability condition is analyzed graphically for a plane-parallel and a concave-concave resonator. The maximum range of stable region is found for both the short and the long cavity. The characteristics of the laser output power are confirmed experimentally in association with the resonator stability condition. The laser output power of 776 W is obtained with the optical-to-optical efficiency of 45% for a plane-parallel resonator with a short crystal separation.
ABSTRACT
Until recently, vascular endothelial growth factor (VEGF) was the only growth factor proven to be specific and critical for blood vessel formation. Other long-known factors, such as the fibroblast growth factors (FGFs), platelet-derived growth factor, or transforming growth factor-beta, had profound effects in endothelial cells. But such factors were nonspecific, in that they could act on many other cells, and it seemed unlikely that these growth factors would be effective targets for treatment of endothelial cell diseases. A recently discovered endothelial cell specific growth factor, angiopoietin, has greatly contributed to our understanding of the development, physiology, and pathology of endothelial cells (Davis et al., 1996; Yancopoulos et al., 2000). The recent studies that identified and characterized the physiological and pathological roles of angiopoietin have allowed us to widen and deepen our knowledge about blood vessel formation and vascular endothelial function. Therefore, in this review, we describe the biomedical significance of these endothelial cell growth factors, the angiopoietins, in the vascular system under normal and pathological states.
Subject(s)
Angiogenesis Inducing Agents/metabolism , Endothelium, Vascular/physiology , Membrane Glycoproteins/metabolism , Proto-Oncogene Proteins , Alternative Splicing , Angiogenesis Inducing Agents/genetics , Angiopoietin-1 , Angiopoietin-2 , Animals , Cell Survival , Endothelial Growth Factors/metabolism , Endothelium, Vascular/cytology , Hematopoiesis/physiology , Humans , Intercellular Signaling Peptides and Proteins/metabolism , Lymphokines/metabolism , Membrane Glycoproteins/genetics , Neoplasm Proteins/metabolism , Neovascularization, Pathologic , Neovascularization, Physiologic , Signal Transduction/physiology , Urogenital System/physiology , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsABSTRACT
We fabricated and analyzed the output power and polarization characteristics of an efficient diode-side-pumped Nd:YAG rod laser with a diffusive optical cavity. The resonator stability conditions are analyzed graphically in the symmetric and asymmetric configurations for a plane-parallel resonator. On the basis of an analysis of the stability condition and mode size for the r and theta polarizations, we clarify how the stable laser operation is possible for various resonator configurations. In particular, we show that the critical stability region of around g1*g2* = 0 provides a stable resonator in the symmetric resonator, even with a slight asymmetry. Experimentally, the output power and polarization characteristics are confirmed in association with the resonator stability condition.
ABSTRACT
A ray-tracing code has been developed, and the design parameters of the laser pump head were analyzed in terms of crystal diameter, doping concentration, and optical cavity diameter. According to the numerical analysis, we fabricated an efficient diode-pumped Nd:YAG laser and experimentally obtained 500-W output power. The output power is close to the numerically calculated output power of approximately 450 W and corresponds to an optical-to-optical conversion efficiency of 46.7% and an optical slope efficiency of 49%.
