Three-dimensional vector beam-propagation method for secondharmonic generation analysis

A full vectorial three-dimensional beam-propagation method (BPM) based on the finite-element method is described for the analysis of second harmonic generation (SHG). Quasi-phase-matched SHG devices with periodically domain-inverted GaAlAs- and LiTaO₃-based waveguides are analyzed. The influences of the shape of domain-inverted regions and of the inversion width on the conversion efficiencies are investigated in detail. The results of full-wave analysis are compared to those of approximate scalar analysis     

Combination of beam propagation method and mode expansionpropagation method for bidirectional optical beam propagation analysis

A combined method of the beam propagation method (BPM) and the mode expansion propagation method (MEPM) is proposed for the analysis of reflections of both transverse electric (TE) and transverse magnetic (TM) polarized waves in waveguiding structures containing longitudinal discontinuities. BPM based on the finite-element method (FEM) is applied to slowly varying regions and MEPM is applied only to regions including abrupt discontinuities. FEM is also utilized for evaluating the eigenmodes necessary for the MEPM analysis. To show the validity and usefulness of the present approach, numerical examples for a semiconductor laser facet with antireflection coating and an optical directional coupler are presented     

Results of transrectal ultrasound-guided biopsies and clinical significance of Japanese prostate cancer

BACKGROUND: We review the outcomes of ultrasound-guided biopsy in consecutive patients and assess clinical significance of Japanese prostate cancer. METHODS: Examination was made of 1469 patients subsequent to transrectal ultrasound-guided biopsy of the prostate gland. For 84 patients, two or more sets of ultrasound-guided biopsies were conducted following the initial negative results during this period. Two hundred and thirty-two patients with benign histology at the initial biopsy underwent transurethral resection of the prostate (TURP). The clinical significance of the cancers was assessed based on patient age and calculated tumor volume at diagnosis, assumed cancer volume doubling time and life-expectancy in the Japanese male population. RESULTS: Overall, 327 of the 1469 patients (22.3%) had prostate carcinoma. Positive biopsy rates in patients with PSA 2.0 ng/ml or lower, 2.1-4.0 ng/ml, 4.1-10.0 ng/ml and 10.1 ng/ml or greater were 4.6%, 8.6%, 15.8% and 59.5%, respectively. Of the 232 patients who underwent TURP, 15 (6.5%) had cancer. Of the 84 patients subjected to the multiple sets of biopsies, 19 (22.6%) cancers were detected. Of the 203 cancers without distant metastasis at initial biopsy, 13.3%, 25.1%, 32.5% and 40.4% of tumors for 2-, 3-, 4- and 6-year tumor doubling times gave no indication of clinical significance. Nearly half these patients (43-52%) had clinical stage T1c disease. The estimated proportion of clinically insignificant tumors in repeat biopsy was virtually the same as first set biopsies. CONCLUSIONS: Low PSA was not necessarily an indication of indolent cancer and repeat biopsy did not often demonstrate clinically unimportant cancers. Many patients with stage T1c disease may eventually prove to require no treatment.     

Expression of Msx genes in regenerating and developing limbs of axolotl

Msx genes, homeobox-containing genes, have been isolated as homologues of the Drosophila msh gene and are thought to play important roles in the development of chick or mouse limb buds. We isolated two Msx genes, Msx1 and Msx2, from regenerating blastemas of axolotl limbs and examined their expression patterns using Northern blot and whole mount in situ hybridization during regeneration and development. Northern blot analysis revealed that the expression level of both Msx genes increased during limb regeneration. The Msx2 expression level increased in the blastema at the early bud stage, and Msx1 expression level increased at the late bud stage. Whole mount in situ hybridization revealed that Msx2 was expressed in the distal mesenchyme and Msx1 in the entire mesenchyme of the blastema at the late bud stage. In the developing limb bud, Msx1 was expressed in the entire mesenchyme, while Msx2 was expressed in the distal and peripheral mesenchyme. The expression patterns of Msx genes in the blastemas and limb buds of the axolotl were different from those reported for chick or mouse limb buds. These expression patterns of axolotl Msx genes are discussed in relation to the blastema or limb bud morphology and their possible roles in limb patterning.     

Expression of two angiogenic factors, vascular endothelial growth factor and platelet-derived endothelial cell growth factor in human pancreatic cancer, and its relationship to angiogenesis

Twenty-three cases of ductal carcinoma in situ (DCIS), ten of which had an associated invasive component, were studied for loss of heterozygosity (LOH) of microsatellite markers on chromosome 9p and the results compared with a panel of 20 invasive breast carcinomas. In addition to the gene encoding p16, chromosome 9p is also thought to contain other putative tumour-suppressor genes. If the three panels of breast tumours showed LOH of markers in this region this would suggest that such putative genes were important in breast carcinogenesis. By studying both preinvasive and invasive breast tumours, it should also be possible to gain further information about the relationship between lesions of a different stage and to determine whether DCIS is indeed a precursor of invasive ductal carcinoma. Levels of LOH were low in the invasive-only set of tumours. Surprisingly, considerably higher levels of loss were observed in the tumours with an in situ component. Also, much heterogeneity was observed between different DCIS ducts or invasive tumour and DCIS from the same case.     

Impact of life expectancy and tumor doubling time on the clinical significance of prostate cancer in Japan

Theoretical projected prostate cancer volume at the time of expected death was determined based on patient age and index cancer volume at diagnosis, assumed cancer volume doubling time and life expectancy of the Japanese male population. Based on the data obtained, evaluation was made of the results for 104 consecutive radical prostatectomy cases with no prior treatment. Clinically insignificant cancer in 104 prostatectomy specimens was found to occur at 4.8, 10.6, 15.4 and 26.9% for tumor doubling times of 2, 3, 4 and 6 years, respectively. Assuming a 2-year doubling time with clinically insignificant cancer excluded, only 36.4% of significant cancers could be considered potentially curable and with a 3-year doubling time, 32.3%. For 4- and 6-year doubling times, only 30.7 and 25.0% of the clinically insignificant cancers were potentially curable, respectively. Approximately half of these insignificant cancers were clinically stage T1c disease. In all stage T1c cases, 8.8-47.1% was considered insignificant, depending on tumor doubling time. Patient life expectancy and tumor doubling time significantly determine the outcome of treatment for prostate cancer, especially in elderly males with higher risk of mortality. The outcome of radical prostatectomy is less satisfactory with these factors taken into consideration. Many patients with stage T1c disease may eventually prove to require no treatment.     

Numerical verification of degeneracy in hexagonal photonic crystalfibers

Modal birefringences in photonic crystal fibers with six air holes symmetrically arranged around the core region and with multiple air holes in a hexagonal lattice are numerically investigated in detail. It is confirmed from the computed results obtained by a full-vector finite element method that both the hexagonal holey fibers are not birefringent, namely, the two fundamental modes are degenerate     

Fluidic Sensors Based on Photonic Crystal Fiber Gratings: Impact of the Ambient Temperature

The spectral and thermooptical responses of photonic crystal fiber gratings (PCFGs) infiltrated with gaseous solutions, are investigated theoretically using an accurate semivectorial modal solver combined with exact equations for the reflection response of fiber Bragg gratings. We demonstrate numerically perhaps for the first time, that by an appropriate selection of the design parameters, it is possible to obtain compact sensing platforms based on the shift of the calculated reflectance spectra of the PCFG. Thus, our investigation adds evidence to the potential use of PCFGs as gas/liquid sensors. In addition, we show through a thermooptical sensitivity analysis that this type of sensors can easily meet the requirements for channel allocation in wavelength-division-multiplexing systems with relatively low temperature sensitivity     

Hybrid-mode analysis of multilayered and multiconductortransmission lines

Hybrid-mode propagation properties of multilayered and multiconductor transmission lines are studied by using an efficient vector finite element method (FEM) with high-order hybrid edge/nodal triangular elements, which can give frequency-dependent propagation constants directly. Characteristic impedances are also calculated from the FEM field solutions employing a reciprocity-related definition and taking the modal orthogonality into account. The numerical results of a coupled microstrip line are compared with those of the boundary integral equation technique, and good agreement is obtained. Also, a dual-plane triple microstrip line is analyzed. The approach is found to be very general and able to simultaneously handle different thicknesses and widths of strip conductors. The flexibility of the approach is also shown by including anisotropy in the dielectric substrates of such lines