Electroform replication used for multiple x-ray mirror production

Work done to produce x-ray mirrors via electroform replication is reported. Several advances have been made over previous work. We have produced lower grazing incidence angle (30 min) mirrors, obtained quantitative measurements up to higher energies (6.40 keV), produced about four times as many replicas from one mandrel, and obtained angular resolutions better than other work done with replicated metal mirrors.     

The impact of Mpact 2

Mpact media processors enable powerful, flexible and cost-effective multimedia in a PC. A single chip replaces today's multiboard, multichip solutions for graphics, video, audio, and communications. The architecture combines a high-bandwidth RAMBUS memory, VLIW/SIMD (single instruction, multiple data) processing, standard buses, and software programmability for the cost of a modern graphics chip. Mpact architecture uses a modified VLIW style with two RISC-like instructions per VLIW. The instructions are either executed sequentially or concurrently based on a tag in the VLIW. Classical VLIW suffers from low code density due to unused instruction fields, but the Mpact modified VLIW has the same code density as RISC instructions. Additionally, the SIMD instructions improve code density by increasing the work done by each instruction. An 8 byte word size was chosen to balance vector and scalar performance and also to balance data and instruction bandwidth. A 9 bit byte was chosen to represent color-component differences in one byte and to represent 18 bit color or 18 bit audio samples in two bytes. Hardware-dithered rounding of quantization noise allows most audio to be processed in two byte precision. The maximal multiplier precision of 24×24 was chosen for audio requirements. The article reviews the first-generation Mpact media processor and then describes the multimedia performance goals and architecture of Chromatic's second-generation media processor architecture. It then presents newer modules of the architecture in more detail     

Describing head shape with surface harmonic expansions

Surface harmonic expansions are used to represent boundaries between regions of different conductivity in the human head. This facilitates calculation of the electric potential and magnetic field generated by neural current sources using discretized integral equations.     

Compact High Gain CMOS Op Amp Design using Comparators

This paper discusses the design of high gain, general purpose op amps. The op amp is based on a novel cascaded design using comparators and with structural simplicity approaching that of digital circuits. Ideally, the design tool presented here can be used to optimize gain and CMRR independent of the other op amp performance parameters. The designed op amp has 140 dB open-loop gain and 43 MHz unity gain frequency (GBW) in Berkeley Spice3f Level-2 simulation. The circuit is implemented using a 2.0 m nwell CMOS process through MOSIS. The op amp is self-biased and requires only power supplies of ±2.5 V. It occupies an area of 113 m×474 m.     

Primary beneficiation of tantalite using magnetic separation and acid leaching

Primary beneficiation was successfully performed prior to dissolution of manganotantalite （sample A） and ferrotantalite （sample C） samples obtained from two different mines in the Naquissupa area, Mozambique. Magnetic separation removed the majority of iron and titanium, whereas H2SO4 leaching removed a large portion of thorium and uranium in these samples. Analytical results indicated that 64.14wt% and 72.04wt% of the total Fe and Ti, respectively, and -2wt% each of Nb205 and Ta205 were removed from sample C （ferrotantalite） using the magnetic separation method, whereas only 9.64wt% and 8.66wt% of total Fe203 and TiO2, respectively, and -2wt% each of NbEOs and Ta2O5 were removed from sample A （manganotantalite）. A temperature of 50℃ and a leaching time of 3 h in the presence of concentrated HESOa were observed to be the most appropriate leaching conditions for removal of radioactive elements from the tantalite ores. The results obtained for sample A under these conditions indicated that 64.14wt% U3O8 and 60.77wt% ThO2 were leached into the acidic solution, along with 4.45wt% and 0.99wt% of Nb2O5 and Ta2O5, respectively.     

Impact on the photothermal emission from single wall nanotubes by some alkali halide salts

We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS).     

Identification and synthesis of altered peptides modulating T cell recognition of a synthetic peptide antigen

In studies of T cell responses to synthetic peptides we have observed agonist and antagonist activities associated with contaminants identified within the parent synthesis. The synthesis of two candidate analogues implied by a peptide contaminant formed during the synthesis of La 51-58 (IMIKFNRL) has been carried out. The peptide contaminant was 17-18 Da smaller than the parent peptide consistent with a modified asparagine residue at position 6 and so we synthesised both an aspartimide and a nitrile analogue, representing cyclisation or dehydration of the asparagine residue. The candidate aspartimide and nitrile analogues both bound empty MHC class I molecules to form allo determinants recognised by monoclonal antibodies. These results demonstrate that altered synthetic peptides can bind class I MHC molecules and prompt caution in the use of synthetic peptides as a source of immunising antigen.