The variability in measurements of complex permittivities of tumor tissues between multiple samples could be attributed to the volume fraction of cancer cells in the excised tumor tissue. By the use of a digital photomicrograph image and hematoxylin-eosin staining, it was found that the malignant tumor tissue was not fully occupied by the cancer cells, but the cells were distributed locally in the stroma cells depending on the growth of cancer. The results showed that the volume fraction of cancer cells in the tumor tissue had a correlation to the measured conductivity and dielectric constant in the frequency range from 1 GHz to 6 GHz. It introduces a method to understand and gauge variability in measurements between different tumors.
InGaN multiple quantum well (MQW) laser diodes were fabricated on (0001)Si oriented 6H–SiC substrate using low-pressure metal organic vapor phase epitaxy (LP-MOVPE). The laser oscillation was observed above the threshold current of 800 mA at a peak wavelength of 414.3 nm under pulsed current injection at room-temperature. The pulse duration was 300 ns and the repetition frequency was 1 kHz. The threshold current density and differential efficiency were estimated to be 16 kA/cm2 and 0.03 W/A, respectively. The full width at half maximum (FWHM) of the lasing emission lines was between 0.03 nm and 0.21 nm. Streak-shaped far field patterns were clearly observable. The lifetime of the laser diode was more than 5 hours.
A time-domain reflectometry breast cancer detection system was developed, which was composed of a Gaussian monocycle pulse (GMP) transmitter circuit fabricated by complementary metal oxide semiconductor (CMOS) 65 nm technology and an ultra wide-band (UWB) planar slot antenna array. The center frequency and bandwidth of the antenna were 6 and 9.2 GHz, respectively. The GMP train having the pulse width of 160 ps was generated by the 65 nm CMOS logic circuit with a core area of 0.0017 mm2 and was emitted by the 4 × 4 planar slot antenna array. The fabricated planar 4 × 4 antenna array with the matching layer could resolve the two separate 5 × 5 × 5 mm3 breast tumor phantoms, which were located at the depth of 22 mm with the spacing of 8 mm.
We demonstrated for the first time room-temperature continuous wave operation of
InGaN laser diodes with a vertical conducting structure fabricated on a SiC substrate.
The threshold current and voltage were 84 mA and 12 V, respectiely, under pulsed
operation. The threshold current corresponds to a threshold current density of 5.6 kA/cm2,
which is the lowest ever reported with InGaN laser diodes on a SiC substrate.
Under continuous wave operation, the threshold current and voltage were 115 mA and
10.5 V, respectiely. The peak lasing wavelength was 408.2 nm. Longitudinal modes
of the optical cavity were clearly obsered. The laser oscillation was obsered up to
40°C under CW operation.
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