The traditional method for electron lifetime measurements of CdZnTe (CZT) detectors relies on using the Hecht equation. The procedure involves measuring the dependence of the detector response on the applied bias to evaluate the μτ product, which in turn can be converted into the carrier lifetime. Despite general acceptance of this technique, which is very convenient for comparative testing of different CZT materials, the assumption of a constant electric field inside a detector is unjustified. In the Hecht equation, this assumption means that the drift time would be a linear function of the distance. This condition is not fulfilled in practice at low applied biases, where the Hecht equation is most sensitive to the μτ product. As a result, researchers usually take measurements at relatively high biases, which work well in the case of the low μτ-product material, <10−3 cm2/V, but give significantly underestimated values for the case of high μτ-product crystals. In this work, we applied the drift-time method to measure the electron lifetimes in long-drift-length (4 cm) standard-grade CZT detectors produced by the Redlen Technologies. We found that the electron μτ product of tested crystals is in the range 0.1–0.2 cm2/V, which is an order of the magnitude higher than any value previously reported for a CZT material. In comparison, using the Hecht equation fitting, we obtained μτ = 2.3 × 10−2 cm2/V for a 2-mm thin planar detector fabricated from the same CZT material.

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We have developed a compact dual-view endoscopic probe without field obscuration to address the need of simultaneously observing forward and backward fields of view (FOVs) in the colon. The objective is compact with the forward-view and rear-view optical paths sharing the same optical elements. The compact objective is new in that no FOV is blocked. The illumination for forward-view imaging is provided by the cylindrical light guide and backward illumination is achieved with a reflector. We have designed, prototyped, and tested the endoscope by comparing it to a standard clinical colonoscope. We will discuss the system concept, objective design, fabrication of the freeform lens, and test results.

Chronic infection with the hepatitis B virus (HBV) is a major risk factor for the development of end-stage liver disease, including cirrhosis, liver failure, and primary liver cancer. There are now 7 antiviral agents approved by the US Food and Drug Administration for the management of chronic HBV infection. Despite the fact that there are between 1.4 and 2 million chronic HBV infections in the United States, fewer than 50,000 people per year receive prescriptions for HBV antiviral medications. This report discusses possible explanations for the disparity between the number of people who are chronically infected and the number of people who receive treatment. Explanations for this incongruence include the potentially large number of infected persons who are unscreened and thus remain undiagnosed, and lack of access, including insurance, education, and referral to appropriate medical care, particularly for disproportionately infected populations. CommentThe incidence of acute hepatitis B (HBV) infection has decreased since the implementation of universal screening of pregnant women and vaccination of newborns.1 However, there still exists a substantial number of Asian Americans, Africans, and other groups immigrating from areas of high prevalence, men who have sex with men (MSM), and IV injection drug users (IVDU) who are already infected or are at risk of infection. Once chronic, HBV increases the risk of cirrhosis, as well as hepatocellular carcinoma (HCC). Unfortunately, even with the success of preventative strategies there still exist 730,000 to 2 million people in the United States who are already chronically infected with HBV, 2 with the largest proportion being MSM, IVDU, and Asian Americans. Of the chronically infected, Cohen et al. suggest only 50,000 patients are receiving antiviral treatment. 3 Although not all infected persons require therapy, understanding why this large disparity exists requires understanding the individual, specific community, health care provider-related, and health care systems-based barriers that may exist.One group affected by HBV infection is the Asian American/Pacific Islanders (AAPI), who comprise approximately 4% of the US population and are expected to be 9.2% of the population by 2050.1 This group is disproportionately affected by chronic HBV compared to the rest of the US population as an estimated 1 in 10 AAPIs have chronic HBV. Of new cases of chronic HBV diagnosed in the United States, approximately 24% of those cases are found in AAPIs.4 This is in contrast to the prevalence of chronic HBV among whites, which is estimated at 0.2%. 5 Many of these chronically infected AAPIs are immigrants from countries where the prevalence of hepatitis B surface antigen positivity may be as high as 10% to 20% of the population, which is seen in many parts of Southeast Asia. 5 Contributing to the issue is that two-thirds of immigrants from high-prevalence areas such as Southeast Asia do not know they are infected.1 Many of the countries with the highest prevalence of HBV w...