Abstract:
An analog detection system for determining a ring-down rate or decay rate 1/&tgr; of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.
Abstract:
Light is coupled into a cavity ring down spectroscopy (CRDS) resonant cavity using an acousto-optic modulator. The AOM allows in-coupling efficiencies in excess of 40%, which is two to three orders of magnitude higher than in conventional systems using a cavity mirror for in-coupling. The AOM shutoff time is shorter than the roundtrip time of the cavity. The higher light intensities lead to a reduction in shot noise, and allow the use of relatively insensitive but fast-responding detectors such as photovoltaic detectors. Other deflection devices such as electro-optic modulators or elements used in conventional Q-switching may be used instead of the AOM. The method is particularly useful in the mid-infrared, far-infrared, and ultraviolet wavelength ranges, for which moderately reflecting input mirrors are not widely available.
Abstract:
In many separation techniques, such as field flow fractionation, liquid chromatography and electro-phoresis, chemical species form bands that migrate at different velocities. If the data-digitization rate and excitation intensity are both set to be optimal for the fastest migrating band, to compensate for different band velocities, both the data-digitization rate and the excitation intensity are decreased as a function of time by a factor equal to the migration time of the fastest migrating band to the separation time.
Abstract:
A capillary tube has a structure in its wall that permits ions to flow but no substantial amount of electrolyte to move therethrough. The structure therefore permits electrical contact between the electrolyte inside the tube and the outside environment without diluting the electrolyte. The structure forms only a small part of the side wall so that the tube retains its structural integrity and can be used in electrophoresis without requiring structural support. In the preferred embodiment, the structure is formed by drilling a hole in the side wall, filling the hole with glass powder and fused silica and heating the mixture to form a frit structure to plug the hole. The frit structure permits ions to flow but substantially no electrolyte to move therethrough. Electrophoretic samples exiting from the end of the tube are not diluted and can be continuously collected, such as on top of a moving plate.
Abstract:
A voltage alternating between a high value and a low value is applied across a separation capillary in an electrophoretic system and electrochemical detection is performed only during time periods when a low voltage or no voltage is applied to the tube to improve the sensitivity of detection.
Abstract:
An end-column conductivity detector is described. A sensing electrode is placed in the outlet end of a capillary that has a hole in its side wall through which electrolyte moves past the sensing electrode into a reservoir that contains the ground electrode. This structure is simple to construct, has almost no dead volume, and minimizes electrolyte contact with adhesives used to mount the sensing electrode. The end-column conductivity detector is operated in conjunction with a commercial capillary zone electrophoresis system that has a capillary cartridge and a UV absorption detector. This design thus permits sequential measurement of the absorption and conductivity characteristics of separated analyte zones. When a species can be detected by both conductivity and UV absorption, then the absorption coefficient can be determined from the relation between the conductivity signal and the concentration of the species.
Abstract:
A method and apparatus for continuously introducing samples for mass spectrometry analysis which comprises providing sample molecules in an aqueous solution containing one or more organic solvents, preferably ethylene glycol, introducing said aqueous solution into the vacuum chamber of an ion source to enable said solution to solidify into a thread of solid matrix, and exposing the solid matrix to a source of energy to desorb sample molecules to be analyzed. The desorbed molecules are then photoionized and focused into a mass spectral analysis zone. The technique is suitable for interfacing liquid chromatographic separation techniques.
Abstract:
In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, embodiments of the present disclosure, in one aspect, relate to methods of making nanostructures (e.g., nanoparticles, nanofibers), systems for making nanostructures, and the like.
Abstract:
Devices, methods, and systems related to imaging and ablation are disclosed. Devices methods, and systems are disclosed herein that include a local bypass, one or more first energy sources configured to function in, or proximal to, a lumen of the local bypass and to provide energy configured to elicit one or more image responses associated with the local bypass lumen; one or more sensors configured to capture the one or more image responses, control circuitry coupled to the one or more sensors, one or more second energy source responsive to the control circuitry, and configured to provide ablation energy to a target area in the local bypass lumen during the expected transit time of the one or more targets through the target area.