The absorption and photoconduction spectra in the ultraviolet region for PMDA-ODA polyimide films fabricated under various curing temperatures have been measured. There are four absorption peaks located at 3.65, 4.35, 5.65, and 6.40 eV in the fully cured polyimide films. The peak at 6.40 eV is practically independent of the curing temperature, but the other three peaks increase with increasing curing temperature. These four peaks are due to intra- and intermolecular optical transitions. In the photoconduction quantum efficiency spectra, there are also four peaks in the fully cured polyimide films but they are located at 3.55, 4.05, 4.90, and 5.80 eV. Analysis of the photoconduction quantum efficiency spectra yields values of 4.17 and 4.37 eV as the potential barrier heights for photoemission from Au and Ag electrodes to polyimide, respectively. The quantum efficiency increases with increasing applied electric field, following closely the Onsager theory with a thermalization separation 30 Å in the uv region. The primary yield increases with increasing curing temperature. All experimental results are briefly discussed.

The histological characteristics and extent of mammographic density were compared between 170 post screen-detected (PSD) breast cancers and 466 screen-detected (SD) breast cancers in women attending the Screening Mammography Program of British Columbia. In addition, methods of detection and clinical presentation for the PSD cancers were examined. Invasive ductal, comedo, and medullary carcinoma were significantly more common in PSD cancer in women under age 50 years, and invasive ductal carcinoma in women over age 50 years. Mammographic density was more common in PSD cancers for all age groups under 70 years. The majority of PSD cancers were node negative with no evidence of metastases; however, they tended to be of more advanced stage than SD cancer. Most PSD cancers regardless of age were initially found by the woman herself, presenting as a palpable mass, and the likelihood of being detected within 12 months of the last screening mammogram was higher at younger ages.

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P h o t o c o n d u c t i o n i n P o l y i m i d e L. Kan and K . C . Kao M a t e r i a l s and Devices Research L a b o r a t o r y Department of E l e c t r i c a l and Computer E n g i n e e r i n g U n i v e r s i t y o f Manitoba,Winnipeg,Canada R3T 2 N 2 ABS TRACT P h o t o c u r r e n t h a s b e e n m e a s u r e d i n p o l yi m i d e under e x c i t i n g r a d i a t i o n i n t h e wavel e n g t h r a n g e o f 700A-2000A u s i n g a sandwich e l e c t r o d e c o n f i g u r a t i o n . There a r e two photoc u r r e n t p e a k s o c c u r r i n g a t 4650A and 3550A i f b o t h t h e i l l u m i n a t e d and n o n -i l l u m i n a t e d elect r o d e s are s o l i d e l e c t r o d e s .