Ionic strontium fluorescence as a method for flow tagging velocimetry

A flow tagging technique based upon ionic fluorescence in strontium is investigated for applications to velocity measurements in gas flows. The method is based upon a combination of two laser based spectroscopic techniques, i.e. resonantly-enhanced ionisation and laser-induced ionic fluorescence. Strontium is first ionised and then planar laser-induced fluorescence is utilised to give 2D `bright images' of the ionised region of the flow at a given time delay. The results show that this method can be used for velocity measurements. The velocities were measured in two types of air–acetylene flames – a slot burner and a circular burner yielding velocities of 5.1 ± 0.1 m/s and 9.3 ± 0.2 m/s, respectively. The feasibility of the method for the determination of velocities in faster flows than those investigated here is discussed. Received: 5 November 1998/Accepted: 19 January 2000     

Flow tagging velocimetry in a superorbital expansion tube

Abstract. A non-intrusive laser-based method for direct velocity measurements has been demonstrated in a superorbital flow facility. The method is based upon laser enhanced ionisation velocimetry in which a tagged region is created by two step excitation of sodium and subsequent collisional ionisation. The achieved depletion of neutral atoms is then interrogated by planar laser induced fluorescence. The velocities were measured in the freestream at a superorbital condition yielding km/s. These results compare favourably with the measured shock speeds in the facility. Received 15 March 1999 / Accepted 2 March 2000     

Microfluidic capillary zone electrophoresis mass spectrometry analysis of alkaloids in Lobelia cardinalis transgenic and mutant plant cell cultures

Application of a microfluidic CE^* device for CZE‐MS allows for fast, rapid, and in‐depth analysis of large sample sets. This microfluidic CZE‐MS device, the 908 Devices ZipChip, involves minimal sample preparation and is ideal for small cation analytes, such as alkaloids. Here, we evaluated the microfluidic device for the analysis of alkaloids from Lobelia cardinalis hairy root cultures. Extracts from wild‐type, transgenic, and selected mutant plant cultures were analyzed and data batch processed using the mass spectral processing software MZmine2 and the statistical software Prism 8. In total 139 features were detected as baseline resolved peaks via the MZmine2 software optimized for the electrophoretic separations. Statistically significant differences in the relative abundance of the primary alkaloid lobinaline (C₂₇H₃₄N₂), along with several putative “lobinaline‐like” molecules were observed utilizing this approach. Additionally, a method for performing both targeted and untargeted MS/MS experiments using the microfluidic device was developed and evaluated. Coupling data‐processing software with CZE‐MS data acquisition has enabled comprehensive metabolomic profiles from plant cell cultures to be constructed within a single working day.     

Anomalous power laws of spectral diffusion in quantum dots: a connection to luminescence intermittency

We show that the wandering of transition frequencies in colloidal quantum dots does not follow the statistics expected for ordinary diffusive processes. The trajectory of this anomalous spectral diffusion is characterized by a sqrt[t] dependence of the squared deviation. The behavior is reproduced when the electronic states of quantum dots are assumed to interact with environments such as, for example, an ensemble of two-level systems, where the correlation times are distributed according to a power law similar to the one generally attributed to the dot's luminescence intermittency.     

Fluorescent organosilica micro- and nanoparticles with controllable size

This paper reports on the synthesis of uniformly dye-doped organosilica particles with narrow size distribution. The particle size can be controlled from tenths of nanometers up to several micrometers, whilst still maintaining monodispersity. Microparticles were observed to swell in various solvents up to approximately 2.5 times their original volume, suggesting the presence of a gel-like internal structure. As shown by confocal microscopy, this morphological control of particle swelling has important implications for the encoding of the nano/micro particles with organic dyes, such as rhodamine B isothiocyanate. Swelling allows the dye to penetrate the organosilica matrix and produce uniformly dye-doped nano- and microparticles. Finally, we suggest a coagulation model for the particle formation which significantly differs from conventional St?ber synthesis.     

An experimental study of the adhesion between clay and steel

Many practical problems in Soil Mechanics require a detail knowledge of the shearing resistance to relative sliding at the interface between soils and structural materials. This study presents a complete set of parameters for the shearing resistance between two different clays and a smooth steel surface. Results are given for the behaviour of clay samples tested in the shear box under quick undrained, consolidated undrained and consolidated drained conditions. These parameters are compared with those obtained for the internal shear strength.The drained and undrained results for both clays show that clay to steel initially has a higher shear strength than clay.to clay. Its subsequent behaviour depends upon whether the clay is over or normally consolidated. Some adhesion factors are suggested.     

The rolling resistance of towed, rigid wheels in sand

A simple relationship is developed which expresses the rolling resistance of a wheel in terms of its geometry, load and accepted soil constants. Experimental results are given which support the validity of the expression.     

Observation of a two level thermal conductivity in the low-dimensional materials

The recent theoretical one-dimensional models display invariably anomalous thermal conductivity. Thermal conductivity of several low-dimensional crystalline systems has been investigated using our new techniques. The results show that for most of the measured materials in the high temperature range the thermal conductivity is composed of two extremes: a low- and a high-conductive state. The effective thermal conductivity jumps abruptly between these two states giving rise to apparent discontinuities or “spikes”.