Losses in GaInAs(P)/InP and GaAlSb(As)/GaSb lasers--The influence of the split-off valence band

GaInAs(P)/InP and GaAlSb(As)/GaSb are interesting material systems for long wavelength optical fiber communication. However lasers fabricated from these materials exhibit a substantially higher temperature dependence of the threshold current than GaAs/ GaAlAs lasers ("T0-problem"). lntervalence band absorption and CHSH-Auger-recombination have been suggested as two possible causes for the strong temperature dependent losses in long wavelength lasers. Both mechanisms, if present, should lead to a population of the split-off valence band. In GaInAsP/InP lasers, we have studied this population by directly observing the radiative high-energy recombination of electrons with holes in the split-off valence band. In the case of the band structure of GaAlSb(As), the band gap energy E0is close or equal to the spin-orbit splitting energy Δ0, which favors hole-Auger recombination and intervalence band absorption, as confirmed by our experimental results.     

Hop maturation and resin formation: Field trials

The resin and essential oil contents of hops (Humulus lupulus L., var., Pride of Ringwood) together with cone weight were studied over a period of 4 weeks prior to and 1 week subsequent to the estimated time of normal harvesting. The petrol ether- and methanol-soluble fractions of the hop cone showed no significant change during this period. Essential oil and α-acid contents increased gradually over the sampling period, whilst cone weight increased up to the estimated time of normal harvesting and decreased thereafter. The results indicate that, with the particular variety studied, harvesting could have been conducted over a 4-week period without significantly affecting α-acid or hop cone yield. The advantages of harvesting high-yielding hops over a 4-week period rather than planting an earlier maturing but lower-yielding variety are discussed.     

NUCLEOTIDES IN BEER

Nucleotidic material was isolated by anion exchange chromatography of beer on a Dowex 1 × 8 (formate) column. Ultraviolet spectroscopy and retention volume data suggested the presence of cytidine monophosphate (CMP) [max. 5 mg/litre], in one of the fractions. No other mononucleotides were detected. Chromatography of charcoal extracts of beer on DEAE Sephadex A25 failed to yield a fraction containing mononucleotides. Triangular taste tests indicated that addition of adenosine-5′-monophosphate (AMP) and guanosine-5′-monophosphate (GMP) to beer (30 mg/litre and 25 mg/litre respectively) did not cause significant flavour changes.     

The eddy current probe as a holographic transducer

Experimental work with the application of holography to eddy current imaging has previously been performed. This paper presents a theoretical analysis of the holographic imaging characteristics of the eddy current probe. A specially shaped probe design has been developed during this analysis for enhanced imaging performance. The phase multiplied holographic imaging process is explained and demonstrated. Experimental data are presented confirming the theoretical analysis and thus the eddy current probe as a viable holographic transducer.     

Approaches for functional characterization of diatom silicic acid transporters

A major component of the diatom cell wall is silica, derived from silicon taken up from the environment. Due to limiting environmental concentrations of silicon, and a substantial requirement during cell wall synthesis, diatoms must transport silicon into the cell against a steep concentration gradient. This is accomplished through the silicic acid transporters (SITs). The SITs were first identified in the marine pennate diatom Cylindrotheca fusiformis. Five distinct SITs were found and have been classified as a novel family of transporters. This review covers our current understanding of silicon transport in diatoms with a focus on the SITs. Approaches for in-depth functional characterization of the SITs are discussed, including (1) isolating SITs from evolutionarily distant diatom species to identify conserved amino acids that may be important for function, (2) developing expression systems to assay the function of selected SITs, and (3) determining the cellular location and membrane topology of the C. fusiformis SITs to further clarify their roles in diatom silicon metabolism. Because of the specificity of interaction between the SITs and silicon, and the ability of the SITs to transport silicic acid across lipid bilayers, the SITs may have applications in nanotechnology.     

What does Halobacterium tell us about photoreception?

At the inception of this study, 6-hydroxydopamine (6-HD) was administered to 137 eyes of 100 glaucoma patients by subconjunctival injection (27 applications) and later by iontophoresis (202 applications). Eighty-four patients were receiving maximum medical therapy, and 24 had had previous glaucoma surgery. Seventy-seven had primary open-angle glaucoma. In 49 patients with data adequate for analysis, 6-HD therapy was effective in 41%, questionable in 31%, and not effective in 28%. The median peak-pressure drop was 13 mm Hg from a baseline of 26 by subconjunctival injection and 6 mm Hg from a baseline of 24 by iontophoresis. The median effective period before return to baseline pressure was 2.5 months. There was a direct correlation between the effectiveness of epinephrine therapy with and without 6-HD. Iontophoresis is a much more practical method for the administration of 6-HD.     

Investigation of the Sintering of Heterogeneous Powder Systems by Synchrotron Microtomography and Discrete Element Simulation

Collective particle behavior such as interparticle coordination and particle rearrangement plays a significant role in the sintering of heterogeneous powder systems. Those phenomena have been investigated by in situ X-ray microtomography and discrete element simulation (DEM). In situ 3D images of sintering copper-based systems have been obtained at the European Synchrotron Research Facilities. The sintered systems comprise a dense packing of atomized copper powder with a size range of 0–63 μm and the same powder including artificial pores. Quantitative analysis of these images provided valuable data on local strain, coordination number, and particle movement. The sintering of the same systems has been simulated with the discrete element code dp3D. From this set of information, the importance of collective behavior on densification and microstructural evolution is assessed and the relevance of DEM to describe it is discussed.