Charge Transport Asymmetry in Cryogenic High Purity Germanium

The SuperCDMS experiment relies on detection of free charges generated in high purity germanium (HPGe) crystals by particle interactions. To better understand long-term trapping effects which make carriers unavailable for such rapid ionization measurements, we used infrared LEDs ( \(\lambda \) = 940 nm) to create electron-hole pairs near each face of a HPGe SuperCDMS detector operated under applied electric field at 400 mK. By alternating the polarity of an applied electric field, we were able to study propagation of each carrier through the crystal separately. Asymmetry in the resulting current transients revealed differences in trapping characteristics between electrons and holes at these low temperatures.     

Femtosecond optical pulses

Recent advances in generation, amplification, compression, and frequency broadening of femtosecond optical pulses are reviewed. We describe use of colliding pulse mode locking to generate pulses of 65 fs duration and pulse compression to reduce those pulse durations to 30 fs. Amplification of femtosecond pulses to gigawatt powers and frequency broadening to obtain white light continuum pulses while retaining femtosecond pulse durations are also examined.     

Personal work ethic and effort training affect cheating.

Assessed in 357 undergraduates the personal work ethic, an individual's general interest and satisfaction in performing tasks industriously, using a survey of work values (SWV). On the basis of the median SWV score, the high work-ethic Ss were separated from the low work-ethic Ss. Some Ss first were tested for cheating; others, before being tested for cheating, underwent low-effort training or high-effort training in mathematics and perceptual identifications. Ss could cheat by falsely stating that they had solved what was really an unsolvable anagram task. The Ss with a high work ethic persisted on the anagram task almost twice as long before cheating as did the Ss with a low work ethic. High-effort training did not affect the resistance of high work-ethic Ss to cheating, but it more than doubled the duration of the low work-ethic Ss. Strong resistance to cheating among high work-ethic Ss is consistent with their ideology that reward should be commensurate with achievement. The similar effects of effort training and work ethic on resistance to cheating support the view that long-term effort training contributes to the development of the work ethic. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Breast cancer and family history: a multivariate analysis of levels of tumor HER2 protein and family history of cancer in women who have breast cancer

BACKGROUND: The HER2 gene, located on the long arm of chromosome 17, codes for a protein with the characteristics of a growth factor receptor. In a preliminary study, we reported that high levels of tumor HER2 (erbB-2/neu) protein are associated with a family history of breast cancer (that is, one or more female blood relatives with breast cancer). METHODS: We have now collected a larger number of subjects (94) and performed a multivariate analysis of the independent variables family history of breast cancer, tumor estrogen receptor, age, and tumor DNA index. Family history of breast cancer was assessed by questioning the patient, in many cases by telephone. RESULTS: HER2 levels were significantly higher in women with a family history of breast cancer (p = 0.015, two-tailed t-test). The 27 women with family history were predominantly postmenopausal, mean age 61 +/- 2.3 (mean +/- SEM), versus a mean age of 56 +/- 1.7 for the 67 women with no family history. Of the 27 women with a family history of breast cancer, 13 had a first-degree relative (mother or sister) with the disease. The remaining 14 women had other relatives (grandmothers, aunts, cousins, or a niece) with breast cancer. The results of multiple linear regression analysis, with HER2 as the dependent variable, showed that family history of breast cancer was significantly associated with elevated HER2 levels in the tumors (p = 0.0038), after controlling for the effects of age, tumor estrogen receptor, and DNA index. CONCLUSIONS: The association of family history of breast cancer and elevated tumor HER2 protein suggests that postmenopausal familial breast cancer may be associated with altered HER2 expression.     

Dynamics of spectral hole burning

A model calculation is presented that describes the features of spectral-hole burning measurements performed under conditions of femtosecond transient excitation and probing. Pump-induced changes in the spectrum of probe transmittance arise not only from changes in level population (hole burning), but also from the presence of pump polarization during the probe, and from perturbations of the decay of the probe polarization. These latter effects give rise to oscillating differential transmittance spectra when the (shorter) probe pulse arrives prior to the peak of the pump noise. Only when the probe pulse follows the bulk of the pump pulse does the level population effect dominate the spectrum, so that one can observe dynamic hole-burning effects without distortion