A temperature-dependent model for the complex dielectric function of GaAs

In this work, we discuss a temperature-dependent model for the complex dielectric function for GaAs valid for the temperature range 31°C ≤ T ≤ 634°C. We describe our model, which is an extension of the critical point parabolic band method. This is a phenomenological method which is based on the physical processes occurring in the semiconductor, and has been previously demonstrated for composition-dependent models of the dielectric function for lattice-matched materials systems. We demonstrate the quality of the model in fitting optical data for individual temperatures, and compare our results to other established models. The data used for each fitting ranges from 1.25 to 4.5 eV. Using results obtained from the individual fits, we generate a temperature-dependent model that is valid for the range of temperatures given above. Also, we show how this model can be used to accurately determine the temperature (±2.3°C) of a material whose dielectric response has been obtained but was not included when generating the model.     

Differential dyeing cotton. Part 2-stoichiometry of interaction with acid and direct dyes

The stoichiometry of interaction of both acid and direct dyes with cotton modified with a reactive cationic reagent has been examined. In the case of the acid dyes adsorption is principally by a specific site mechanism and gives a 1:1 ratio between cationic sites on the cotton and sulphonate groups on the dyes, although some diffuse adsorption occurs with the more hydrophobic dyes. The direct dyes show a much greater amount of diffuse adsorption in addition to specific site adsorption. The results show that the presence of the cationic sites enhance the amount of dye taken up by diffuse adsorption and a mechanism for this is proposed.     

Arc minimization in finite-state decoding graphs with cross-word acoustic context

Recent approaches to large vocabulary decoding with weighted finite-state transducers have focused on the use of determinization and minimization algorithms to produce compact decoding graphs. This paper addresses the problem of compiling decoding graphs with long span cross-word context dependency between acoustic models. To this end, we extend the finite-state approach by developing complementary arc factorization techniques that operate on non-deterministic graphs. The use of these techniques allows us to statically compile decoding graphs in which the acoustic models utilize a full word of cross-word context. This is in significant contrast to typical systems which use only a single phone. We show that the particular arc-minimization problem that arises is in fact an NP-complete combinatorial optimization problem. Heuristics for this problem are then presented, and are used in experiments on a Switchboard task, illustrating the moderate sizes and runtimes of the graphs we build.     

Real-time pitch extraction of voiced speech

This paper describes a novel speech analysis application which was implemented using a Motorola M68HC11 microcontroller system. This microcontroller-based platform was designed to function as a pitch extractor for voiced speech in real time. In this context, pitch extraction is the identification of individual pitch periods, or glottal cycles, from a raw speech waveform. The system implements a new pitch determination algorithm (PDA) that is based on a progressing wave model of speech generation. The PDA was developed specifically to operate in real-time and to maintain phase characteristics with the raw speech signal. As one possible application, the pitch extractor was incorporated into a dual processor system designed to function as a Musical Instrument Digital Interface (MIDI)-compatible controller.     

Oxidative Instability of Fuels: Nickel Catalyzed Reactions

The reactions that lead to long-term storage instability of fuels are not fully understood. Various reports in the literature link particular fuels with specific reactions, usually oxidation or free radical processes. Trace quantities of metals are present in all processed fuels. The metal source can be naturally occurring or present from fuel handling. The usual case is to look at the reaction of the metal or metal ion with molecular oxygen or other active oxygen species such as hydroperoxides. This article reports on the reaction of a nitrogen heterocycle, indole. We propose a mechanism that shows that catalytic amounts of nickel can produce compounds of higher molecular weight and increased polarity.     

Finding flaws in composites

From ultrasonics, through infrared and thermographic techniques, to more exotic, developmental methods, non-destructive testing (NDT) of composites can take many forms. George Marsh reports on some of the principles and equipment involved in this vital area.     

Permuteins of interleukin 1{beta}--a simplified approach for the construction of permutated proteins having new termini

A technique for the rapid and simple generation of permutatedversions of the interleukin-1ß (IL-1ß) geneis described. In this method, the human IL-1ß cDNAis twice amplified by the polymerase chain reaction (PCR) andthe resulting DNA fragments are ligated in tandem. Between thetwo genes, the DNA sequence encodes a short four amino acidloop to link the native N- and C-terminal ends of the IL-1ßprotein. By using PCR amplification from this starting template,a new version of the IL-1ß cDNA was obtained thatencodes a permutated form of the IL-1ß protein wherethe new N- and C-terminal amino acids correspond to residues65 and 64 of the native IL-1ß sequence, respectively.The name ‘permutein’ is proposed to describe proteinsgenerated by this technology. The molecular profile (IL-1 receptorbinding, biologic activity and solution properties) of the IL-1permutein produced by this technology, permutein 65/64, is shownto be identical to that of native IL-1ß The approachshould be useful to define further the structural features ofthis protein that are important for its function.     

Rheology of polybenzyl ether dendrimers their copolymer and blends

The dynamic rheological behavior of pure polybenzyl ether dendrimers and their copolymers have been studied in the molten state. The pure polybenzyl ether dendrimer generation 4 and generation 5 show Newtonian behavior whilst the generation 3 appears to be a very slightly shear-thinning within the deformation rates investigated, the behavior also being a function of thermal pretreatment. When the dendrimer component was included as a dendritic polystyrene copolymer (covalently attached), the viscosity was much lower compared to corresponding polystyrene of similar molecular weight. The same concentration of dendrimer could be physically blended into the polystyrene forming an immiscible mixture, which also reduced viscosity. However, if the dendritic component was covalently attached, it had a lower viscosity than if physically blended at the same concentration. Electronic Publication     

A phase II trial of interleukin-2 and interferon-alpha in the treatment of metastatic colorectal carcinoma

A total of 29 patients with stage IV colorectal cancer were entered into a phase II trial of bolus interleukin-2 (IL-2) and interferon-alpha (IFN alpha) (3 x 10(6) U/m2 of each cytokine given i.v. q8h x 15 doses and repeated in 2 weeks). Immunologic parameters measured on isolated peripheral blood lymphocytes revealed increased activated T cells with upregulated natural killer and lymphokine-activated killer activity. Among 24 evaluable patients, there were 4 partial responses (17%) of short duration ( < or = 6 months). Three of the responding patients had been refractory to prior chemotherapy. Overall median survival in the 24 evaluable patients was 18.5 months. Therapy necessitated an inpatient setting, with the most common toxicities being hypotension, hepatic insufficiency, fever, hypocalcemia, nausea/vomiting, and renal insufficiency. There were two treatment-related deaths. Because neither IL-2 nor IFN alpha alone has significant activity against colorectal cancer, the responses observed in this study suggest a potential synergistic effect between the two cytokines. However, the toxicity and short duration of response without survival benefit do not support the routine use of this regimen as a therapeutic modality for this tumor histology.