Jefferson lab free-electron laser starts operation with sustained lasing at the kilowatt level

The relationship between the Brazilian Synchrotron Light Laboratory (LNLS) and the Brazilian industry started at the very early stages of the laboratory in the mid-1980s when the project proposal was submitted to the Brazilian government. Factors such as the relatively small size of the project, and the uniqueness and level of complexity of the technological challenges raised by the LNLS developers kept the Brazilian industry involved within a few areas. As a result, LNLS was led during the 1990s to dedicate in-house resources to internally develop more components and systems than initially expected and the LNLS staff established expertise in several critical areas for the success of the synchrotron facility construction and operation. Therefore what seemed initially to be a difficulty ended up being the driving force for fruitful industrial development projects bringing together LNLS and Brazilian companies.     

Real-time instrumentation for monitoring water quality: An Australian perspective

Current research in the field of real-time monitoring of water quality is reviewed from an Australian perspective. The desirable features of continuous monitoring instruments and progress in developing multi-parameter real-time instruments are considered first. Then Australian R&D in the three main areas involved in developing a complete instrument are considered; these are sample preparation and handling, new sensors and sensing chemistry, and finally data capture, processing and display. The review identifies five areas where developments are needed: new methods for handling and processing ‘real’ (i.e. ‘dirty’ and heterogeneous) samples; the development of new sensors to provide more detailed information on particular forms (e.g. bioavailable) of contaminants; new sensors for detecting and quantifying the presence of low concentrations of toxic organic compounds in natural waters; new real-time methods for assessing the microbial quality of waters; and greater use of chemometrics in processing the signals obtained from complex sample matrices.     

Growing inhomogeneities in cosmological Goldstone modes

We examine the evolution of initial inhomogeneities in a Goldstone field in an expanding Friedmann-Robertson-Walker universe. We find subhorizon inhomogeneities grow, relative to the homogeneous state. This stems not from growing fluctuations — which simply redshift — but from rapid ( a⁻⁶) decay of the homogeneous state. We show how Goldstone modes escape assumptions — some inapplicable, some ill-founded — underpinning conventional analyses of cosmological fluctuations. Finally, we reconcile our analysis to standard cosmology, noting that the Goldstone evolution is essentially decoupled and dynamical.     

Dynamics of pulse propagation in phase-shifted fibre Bragg gratings: a numerical investigation

Fibre Bragg gratings (FBGs) are an integral component of optical fibre based communication systems for signal processing. Uniform FBGs and phase-shifted FBGs find major applications as add-drop filters in dense wavelength division multiplexing (DWDM) systems where these are used to filter out channels and to shape the signal spectrum. We investigate numerically the spatiotemporal deformation of pulses as they propagate through the gratings. In particular, the effect on the pulse dynamics of phase shift or defect present in the gratings, often introduced intentionally in a grating to generate a narrow transmission spike within the stopband, is studied in time domain. This study is of significance since the deformation in the pulse in time limits the maximum bit rate achievable, and hence the pulse duration and shape need to be analysed and controlled accurately. A time domain numerical tool based on the Transmission Line Modelling (TLM) method is developed to study the pulse dynamics. The results obtained give useful information about the signal dynamics in gratings with defects, including the signal oscillations trapped in the defect, to be considered in applications such as while designing spectral filters.     

General, high-affinity approach for the synthesis of fluorophore appended protein nanoparticle assemblies

Metallothionein fusion proteins allow for site-specific, orthogonal functionalization of proteins to a variety of nanoparticles.     

Kinetics and equilibria in the system Br + t-BuO2H ⇆ HBr + t-BuO2. OH bond dissociation energy in t-BuO2-H

The kinetics and equilibria in the system Br + t-BuO₂H ? HBr + t-BuO₂· have been measured in the range of 300–350 K using the very low pressure reactor (VLPR) technique. Using an estimated entropy change in reaction (1) ΔS₁ = 3.0 ± 0.4 cal/mol·K together with the measured ΔG₁, we find ΔH₁ = 1.9 ± 0.2 kcal/mol and DHº (t-BuO₂-H) = 89.4 ± 0.2 kcal/mol ΔH_f·(tBuO₂·) = 20.7 kcal/mol and DH^º (t-Bu-O₂) = 29.1 kcal/mol. The latter values make use of recent values of ΔH_f·(t-Bu) = 8.4 ± 0.5 kcal/mol and the known thermochemistry of the other species. The activation energy E₁ is found to be 3.3 ± 0.6 kcal/mol, about 1 kcal lower than the value found for Br attack on H₂O₂. It suggests a bond 1 kcal stronger in H₂O₂ than in tBuO₂H.     

Partial molar volumes of gases dissolved in liquids. Part II. A dilatometer for measuring infinite-dilution partial molar volumes,and results for 40 liquid-gas systems

A dilatometer with an imprecision of less than 0.4% is described for the determination of partial molar volumes of gases dissolved in liquids. Measurements at 298.15 K are reported for 40 liquid-gas systems having n-alkanes and 1-alkanols as the liquid component. The results are interpreted in terms of a number of empirical and semiempirical correlations.     

Fragmentation of metal rings by electromagnetic loading

A method is described for performing fragmentation studies on rapidly expanding metal rings. A fast-discharge capacitor system generates magnetic forces which accelerate the rings to maximum radial velocities of approximately 200 m/s corresponding to circumferential-strain rates of approximately 10⁴/s at fragmentation. Streak-camera techniques are used to record the time-resolved motion of the rings. Fracture-strain and fragmentation experiments have been performed on samples of OFHC copper and 1100-0 aluminum.     

Intramolecular isotopic effect in the pyrolysis of ethyl-2d1 chloride

The thermal decomposition of deuterated ethyl chloride CH₂DCH₂Cl was studied in a static system in the pressure range of 0.1–26 torr, and the Arrhenius expression for the overall decomposition at the high-pressure limit and in the temperature range of 670–1100 K was found to be The intramolecular isotopic effects were first examined in the pressure range of 0.1–26 torr at 837 K, and the branching ratio k_H/k_D was found to decrease with increasing pressure. The RRKM-theory calculations describe the experimental data well. The intramolecular isotopic effect was also examined in the temperature range of 728–926 K, and the branching ratio at the high pressure limit was given by the expression when k_H and k_D are the rate constants for the HCl and DCl channels of elimination. The Arrhenius A factors obtained at the high-pressure limit together with the temperature-dependent expression of the branching ratio provided additional experimental data for an assignment (fine-tuned) of the vibrational frequencies of both activated complexes involved in the thermal decomposition of CH₂DCH₂Cl. The evaluated vibrational frequencies were then used in the RRKM calculations describing the pressure dependence of the intramolecular isotopic effect. The RRKM calculations and the experimental data were in good agreement, supporting the choice of vibrational frequencies for both the activated complexes as well as the transition-state model.