摘要:

The transmission of ions through an RF-only quadrupole collision cell is affected by both the frequency and voltage applied to the quadrupole. With a change in the RF-only quadrupole collision cell voltage (viz, the collision energy) ion intensities for both parent and product ions determined by a final mass-analyzing quadrupole vary in a modulated fashion. This pattern of ion intensities has been described as quadrupole “nodes”. Ion transmission through the RF-only quadrupole has been carefully investigated here using energy-resolved mass spectrometry with variations in the collision cell pressure and the mass of the ions. A theory is developed to explain the presence of product ion nodes that focuses on ion velocity as the critical parameter in their production.

ISSN:1073-9149    

DOI:10.1080/10739149408001190

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

When the passband of a bandpass filter is small with respect to the sample rate the filter may become unstable due to the proximity of the poles to the unit circle. Cascading a lowpass filter and a highpass filter can produce a stable bandpass filter under most circumstances. However, this technique produces poor results when the center frequency of the passband is 2 or 3 Hertz. Such cases occur, for example, when electrocardiogram signals are filtered to extract respiration rates. We present a technique that produces stable bandpass filters for such cases by cascading two filters, designed with different sampling rates. Experimental results show that the resultant filter is less susceptible to finite word effects because of a better placement of the poles.

ISSN:1073-9149    

DOI:10.1080/10739149408001191

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The development of a near-infrared fiber optic biomolecular probe (FOBP) for the detection of biological molecules will be discussed. The utility of the system is demonstrated using an immunochemical samples. The FOBP consists of a semiconductor laser diode (γmax= 780 nm), a modified fiber tip binding site, an NIR dye and a detector. The common distal end of two optical plastic fibers, connected with poly(methyl methacrylate), serves as the binding site (about < 2mmXin diameter). Activation of the binding site with different inorganic acids is discussed. Preparation of the FOBP involved in the immobilization anti-IgG antibody followed by coating with IgG for a sandwich type probe. Immobilization of anti-IgG antibody was achieved by reacting the Fc fragment of the antibody molecule to the activated binding site of the fiber. The instrument was tested by labeling the antibody with a commercially available near infrared (NIR) dye IR-144). Excitation of the antigen-antibody sandwich complex was induced with a semiconductor laser diode at 780 nm. The emission intensity signal was collected at 820 nm by using small bandwidth filters. The response time for 95% of the signal was less than 5 seconds. The low background signal of the detector allowed the detection of 2.72 ng/mL IgG in a probe coated with 10 ng/mL antibody. The general procedure used for the attachment of the biological molecule to the distal end of the probe can be used to construct more specific antigen-antibody systems. Use of smaller components shown here will allow for the manufacturing of portable instruments for applications in medicine and clinical analysis.

ISSN:1073-9149    

DOI:10.1080/10739149408001192

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The application of the microwave-induced acoustic technique, developed in this laboratory, as an indirect sensor of depolymerization of paper via online measurements of water sorption and desorption kinetics in both lignin containing and lignin-free paper samples is described. Exposure of paper samples to gaseous NO2greatly accelerated the aging of paper and is shown by this technique to have significant effects on the water sorption characteristics. Implications of these observations, related to damages effected by exposure to free radical environments and the resulting embrittlement and depolymerization of paper samples, is discussed.

ISSN:1073-9149    

DOI:10.1080/10739149408001193

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A method for catalytic determination of copper (II) is presented. The method is based on the catalytic effect of copper(II) on the rate of oxidation of indigo carmine by potassium bromate. The method is satisfactory for the determination of copper(II) in the range 1.2 to 38 ng/mL. Effect of acidity, indigo carmine, potassium bromate, temperature and tolerance limits of foreign ions are reported. The method was applied to the determination of copper in synthetic and in various milk samples.

ISSN:1073-9149    

DOI:10.1080/10739149408001194

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A software program and computer interface to a Varian ESR spectrometer, Model E-9, have been developed for scanning of magnetic field and for data acquisition digitization. The software program provides features for data manipulation, standard arithmetic functions, integral calculation, smoothing, multiscan averaging, recordings of experimental parameters with the data file, in addition to graphical data presentation on screen, plotter or laser printer.

ISSN:1073-9149    

DOI:10.1080/10739149408001195

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A qualitative investigation into the viscoelastic-surface properties of pendant drops has been conducted using a new instrumental technique, the fibre drop analyser (FDA), by means of measurement of the damped vibrations in mechanically excited pendant drop for a series of pure liquids. The study reveals a range of processes in the damped vibrations of pendant drops and could open up a new approach to measurement of physical properties for the micro-volume analysis of liquid properties.

ISSN:1073-9149    

DOI:10.1080/10739149408001196

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149408001197

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149408001198

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:1073-9149    

DOI:10.1080/10739149408001199

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor