Resonant Mass Detectors

Burst signals (supemovae) have been the primary target for the resonant mass detectors. The minimum detectable perturbation of the metric sensor caused by a burst of GW of duration r is ... 

Resonant-mass detector A massive cylinder of aluminium, or nobium crystal, suspended in vacuum and mechanically isolated from its surroundings. When a gravitational wave impinges on the cylinder, the relative accelerations excite the cylinder s natural modes of oscillation. 

Ground-based interferometers and resonant-mass detectors operate in this band. The most promising sources of gravitational waves are inspiral and coalescence of compact stellar-mass black holes and... 

Gravitational waves deposit energy into resonant mass detectors when they excite their normal modes. The ab-... 

Efforts to directly observe gravitational waves have a history spanning at least 40 years Joseph Weber constructed the first resonant mass detectors in the early 1960s. At the start of the 21st century, a new generation of interferometric detectors will have sufficient sensitivity to detect many anticipated astrophysical sources. The commissioning and scientific operation of these instruments marks the birth of gravitational wave astronomy. 

Figure Bl.7.18. (a) Schematic diagram of the trapping cell in an ion cyclotron resonance mass spectrometer excitation plates (E) detector plates (D) trapping plates (T). (b) The magnetron motion due to tire crossing of the magnetic and electric trapping fields is superimposed on the circular cyclotron motion aj taken up by the ions in the magnetic field. Excitation of the cyclotron frequency results in an image current being detected by the detector electrodes which can be Fourier transfonned into a secular frequency related to the m/z ratio of the trapped ion(s).

Rapid scanning mass spectrometers providing unit resolution are routinely used as chroaatographic detectors. Ion separation is accomplished using either a magnetic sector, quadrupole filter or ion trap device. Ions can also be separated by time-of-flight or ion cyclotron resonance mass analyzers but these devices are not widely used with chromatograidiic inlets and will not be discussed here [20]. 

LC-MS (liquid chromatography-mass detector) and LC-NMR (liquid chromatography-nuclear magnetic resonance spectroscopy). 

Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) instrumentation offers excellent sensitivity, accuracy (<1 ppm), and high mass resolution (>1,000,000) (Table 10.2). However, because of being too expensive, difficult to use, and not compatible with conventional HPLC columns and flow rates, FTMS has not been frequently used in pharmaceutical research. This changed with an introduction of a hybrid instrument consisting of a linear ion-trap mass spectrometer compatible with LC and an ion-cyclotron-resonance (ICR) detector. Such a hybrid instrument is compatible with conventional HPLC and allows for acquisition of accurate mass data-dependent MS" spectra. Sanders et al. [128] recently reviewed the utility of hybrid LTQ-FTMS for drug metabolism and metabonomics applications while Brown et al. [129] reviewed the metabolomics applications of FT-ICR-MS. 

Liquid chromatography (LC) has already been described and is an excellent separation technique for compounds that are nonvolatile, thermally unstable and relatively polar in nature. The usual detectors for LC are based on refractive index, conductivity, amperometry, light scattering, UV and fluorescence, all of which have been discussed in Section 3.2. However, sometimes it is desirable to have a more powerful detector attached to an LC instrument and, as such, the following combinations are possible LC-infrared spectrometry, LC-atomic spectrometry, LC-inductively coupled plasma-mass spectrometry, LC-mass spectrometry, LC-UV-mass spectrometry, LC-nuclear magnetic resonance and even LC-nuclear magnetic resonance-mass spectrometry. 

Section I covers the more conventional equipment available for analytical scientists. I have used a unified means of illustrating the composition of instruments over the five chapters in this section. This system describes each piece of equipment in terms of five modules - source, sample, discriminator, detector and output device. I believe this system allows for easily comparing and contrasting of instruments across the various categories, as opposed to other texts where different instrument types are represented by different schematic styles. Chapter 2 in this section describes the spectroscopic techniques of visible and ultraviolet spectrophotometry, near infrared, mid-infrared and Raman spectrometry, fluorescence and phosphorescence, nuclear magnetic resonance, mass spectrometry and, finally, a section on atomic spectrometric techniques. I have used the aspirin molecule as an example all the way through this section so that the spectral data obtained from each... 

Various forms of tandem mass spectroscopy (MS/MS) have also been used in the analysis of biomolecules. Such instruments consist of an ionisation source (ESI or MALDI or other) attached to a first mass analyser followed by a gas-phase collision cell. This collison cell further fragments the selected ions and feeds these ions to a second mass detector. The final mass spectrum represents a ladder of fragment ions. In the case of peptides the collision cell usually cleaves the peptides at the amide bond. The ladder of resulting peptides reveals the sequence directly [496]. Thus, tandem MS instruments, such as the triple quadrupole and ion-trap instruments have been routinely applied in LC-MS/MS or ESI-MS/MS for peptide sequencing and protein identification via database searching. New configurations, which have been moving into this area include the hybrid Q-TOF [498], the MALDI-TOF-TOF [499] and the Fourier transform ion cyclotron resonance instruments [500]. 

In the early stages of development, this is used firstly as a separation tool to establish what degradation products are produced. In conjunction with a mass detector, this will often enable the identity of the impurity to be proposed. Confirmation of structure is often achieved by the use of nuclear magnetic resonance spectroscopy and mass spectroscopy or by synthesis. 

Luminescence molecular detectors have also been used for online monitoring of dissolution tests and the characterization of toxic residues using bioluminescence assays. Atomic (atomic absorption spectroscopy, inductively coupled plasma-atomic emission spectroscopy (ICP-AES)) detectors have been coupled to robotic stations either through a continuous system acting as interface or by direct aspiration into an instrument from a sample vial following treatment by the robot. Mass spectrometric and nuclear magnetic resonance (NMR) detectors... 

Several detectors used in high-performance liquid chromatography (HPLC) and in supercritical fluid chromatography (SEC) can be connected to the CCC column to detect solutes and thus follow separation. They can be, for instance, fluorimeters (very sensitive and used without modifications in CCC), UV-Visible spectroscopes, evaporative fight scattering detectors, atomic emission spectroscopes, etc. Some detectors give more information than the detection of the solute, such as stmctural information of separated components, as in infrared spectroscopy, " mass spectrometry,or nuclear magnetic resonance. These detectors are... 

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