Optical properties of crystalline-amorphous core-shell silicon nanowires.

The optical absorption in a nanowire heterostructure consisting of a crystalline silicon core surrounded by a conformal shell of amorphous silicon is studied. We show that they exhibit extremely high absorption of 95% at short wavelengths (λ < 550 nm) and a concomitant very low absorption of down to less than 2% at long wavelengths (λ > 780 nm). These results indicate that our nanowires do not have optically active energy levels in the band gap. The absorption edge of silicon nanowires arrays is observed to shift to longer wavelengths as a function of the overall nanowire diameter. The near-infrared absorption of the nanowire array is significantly better than that of thin film amorphous silicon. These properties indicate potential use in large area optoelectronic and photovoltaic applications.

Prothrombin time and activated partial thromboplastin time can be performed on the first tube.

The current practice standard for coagulation studies on venous blood specifies the use of the second (or subsequent) tube for testing. Unless other tests are ordered, the first tube is discarded. This practice, derived from early experience using nondisposable materials, gained support from a report based on modern phlebotomy methods but inexperienced phlebotomists. For our study, paired blood specimens were collected by experienced phlebotomists from 175 outpatients whose physicians had ordered coagulation tests. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were performed on the first and second tubes. Similar values were obtained for PT and APTT. (PT: n = 174; mean = 15.36 seconds; mean difference = 0.10 seconds; y = 1.02x - 0.28; t = 0.24; P>.81; r = 0.995; APTT: n = 160; mean = 38.25 seconds; mean difference = 0.48 seconds; y = 1.03x - 0.71; t = 0.25; P=.80; r = 0.993.) For coagulation tests on specimens collected by experienced phlebotomists, the first tube yields accurate results and need not be discarded.

Core-shell silicon nanowire solar cells.

Silicon nanowires can enhance broadband optical absorption and reduce radial carrier collection distances in solar cell devices. Arrays of disordered nanowires grown by vapor-liquid-solid method are attractive because they can be grown on low-cost substrates such as glass, and are large area compatible. Here, we experimentally demonstrate that an array of disordered silicon nanowires surrounded by a thin transparent conductive oxide has both low diffuse and specular reflection with total values as low as < 4% over a broad wavelength range of 400 nm < λ < 650 nm. These anti-reflective properties together with enhanced infrared absorption in the core-shell nanowire facilitates enhancement in external quantum efficiency using two different active shell materials: amorphous silicon and nanocrystalline silicon. As a result, the core-shell nanowire device exhibits a short-circuit current enhancement of 15% with an amorphous Si shell and 26% with a nanocrystalline Si shell compared to their corresponding planar devices.

Carcinoma of the trachea: a hidden tumor.

Seventy-five percent or more of the tracheal lumen may be compressed before any signs or symptoms are evident. Typically, chest x-rays are normal. CT scanning is the best radiologic procedure; bronchoscopy is also valuable.