iCODEHOP: a new interactive program for designing COnsensus-DEgenerate Hybrid Oligonucleotide Primers from multiply aligned protein sequences

PCR amplification using COnsensus DEgenerate Hybrid Oligonucleotide Primers (CODEHOPs) has proven to be highly effective for identifying unknown pathogens and characterizing novel genes. We describe iCODEHOP; a new interactive web application that simplifies the process of designing and selecting CODEHOPs from multiply-aligned protein sequences. iCODEHOP intelligently guides the user through the degenerate primer design process including uploading sequences, creating a multiple alignment, deriving CODEHOPs and calculating their annealing temperatures. The user can quickly scan over an entire set of degenerate primers designed by the program to assess their relative quality and select individual primers for further analysis. The program displays phylogenetic information for input sequences and allows the user to easily design new primers from selected sequence sub-clades. It also allows the user to bias primer design to favor specific clades or sequences using sequence weights. iCODEHOP is freely available to all interested researchers at https://icodehop.cphi.washington.edu/i-codehop-context/Welcome

Study of silicon solar cell at different intensities of illumination and wavelengths using impedance spectroscopy

The electrical properties of an n+–p–p+ structure-based single-crystalline silicon solar cell were studied by impedance spectroscopy, I–V and spectral response. The impedance spectrum is measured in dark, under different intensities (14, 43, 57, 71, 86, 100 mW/cm2) of illumination and wavelengths (400–1050 nm) of light. Under dark and at low intensities of illumination (<50 mW/cm2) the impedance spectra show perfect semicircles but at high intensities the semicircles are distorted at low frequencies. It is found that illumination provides an additional virtual R1C1 network parallel to the initial bulk RpCp network observed under dark conditions. The value of virtual resistance R1 depends on the illumination wavelength and shows an inverse relationship with the spectral response of the device

Generation and recombination lifetime measurement in silicon wafers using impedance spectroscopy

Minority carrier lifetime in silicon wafers has been measured by applying an impedance spectroscopy technique (IST). Induced p+–p and p–n junctions were formed on both sides of the silicon wafer by thermally evaporating semitransparent metal layers of palladium and aluminium respectively. As such, no thermal treatment was given to the device, and therefore there is no diffusion of impurities inside the semiconductor and the two junctions are induced in the form of accumulation and depletion regions of charge carriers respectively. Both generation and recombination lifetimes applicable under the reverse and forward bias conditions respectively have been measured. The generation lifetime was estimated to be around 73 µs, whereas the recombination lifetime has been found to be about 11 µs. It is shown that the effective recombination lifetime is determined mainly by surface recombination velocity at the silicon–palladium interface. The effective minority carrier lifetime as measured by the microwave-detected photoconductive decay method on the same sample is 12 µs which is close to the measured recombination value by the IST. This shows that impedance spectroscopy can be used to measure effective lifetime of the wafer using an induced junction structure prior to the formation of an actual device like the solar cell. Moreover, the series resistance (Rs), diode ideality factor (n) and barrier height (Vbi) obtained from C–V (using the IST) data as well as the I–V measurement of the device show agreement with the expected device parameters. Thus, the IST can be effectively employed as a tool in extracting many relevant characteristic parameters of the material and the device