Method detection

The following methods are applied in order to detect extrasolar planets  

Hanslmeier, Water in the Universe, Astrophysics and Space Science Library 368, DOI 10.1007/978-90-481-9984-6 6, Springer Science+Business Media B.V. 2011 

Astrometry consider two bodies with masses mi, m2. Moving around their center of mass (barycenter), they will attract each other according to Newton s law of 

The more massive one of the two components, the more the center of mass will be located near to that mass (see Fig. 6.1). Let us consider the center of mass of the system Sun and Jupiter. Since the mass of the Sun is about 1000 times the mass of Jupiter, the center of mass of such a two body system must be located 1000 times nearer to the Sun than to Jupiter—in fact it is located just outside the Sun s sphere. Therefore, precise position measurements are required in order to detect the small motion of a star around the center of gravity in case of the presence of other planets. 

Radial velocity or Doppler method as we have seen above, a star will move under the gravitational attraction of a planet. This motion about the center of gravity of the system can be detected by small Doppler shifts of the star s spectral lines (see Fig. 6.2). Note that only the radial velocity component, that is the velocity that is directed toward (or away) from the observer causes a Doppler shift which varies periodically. This method has been so far the most promising one and most of the extrasolar planets detected so far were found from these Doppler shifts. The inclination / of the orbital plane with the sky is unknown, therefore, we measure the velocity 

There are some methods and techniques used by microbiologists to assess MIC cases. All these methods have their pros and cons. We will be dealing with each very briefly here without going through the microbiological details of each more details can be found in the given references. 

Considering these properties we will now discuss a number of detection methods. 

It is also possible to perform mass or energy analysis of the ions generated. This can be accomplished using a time-of-flight (TOF) spectrometer, where the ions generated are sent through an evacuated drift tube equipped with ion optics, and the arrival time at an ion detector (electron multipher tube or a channeltron) is recorded. It is also possible to accelerate low-velocity ions in a well-defined electric field before the passage of the drift tube. Since the velocity attained depends on the mass, species identification can be performed. TOF spectrometers are discussed in [9.44]. 

Collisional Ionization. Highly excited atoms have a high probability of colliding because of their considerable size. Since the thermal energy of the atom kT) may be larger than the energy required to reach the ionization limit, there is a significant probability that a collision results in the formation of an ion. A thermo-ionic detectoi can be used to detect the presence of the ions. This teclmique is extremely sensitive [9.45, 9.46]. 

Field Ionization. Highly excited atoms are very sensitive to electrical fields. Field ionization (Sect. 2.5.2) can be brought about by populating a well-defined highly excited state using stepwise, pulsed excitation in the absence of an electric field and then applying an electric field pulse [9.47]. The electrons can be detected with a suitably located electron multiplier. 

In order to obtain information about the energy distributions of reaction products, it is necessary to use a detection method that can determine either the internal state populations of the products or their recoil velocities. The methods employed to measure electronic, vibrational or rotational energy distributions are generally based on a form of emission or absorption spectroscopy, although there are other techniques that are sensitive to internal excitation. A variety of methods are used to measure recoil energy distributions these are commonly based on a mass spectrometric detection system used with some form of velocity analyser. 

Obtaining product energy distributions from the intensities of chemiluminescence spectra is relatively straightforward, requiring a knowledge of the appropriate transition probabilities and the spectral efficiency of the detector. One complication that can arise in the analysis of chemiluminescence data is the possibility of cascading an emitting state 

Whilst most measurements are of the total chemiluminescent emission from a reaction, the angular distribution of chemiluminescence has been recently studied [82, 83] in crossed-molecular beam experiments. An additional property of the chemiluminescence observed in beam experiments that may contain information about the reaction dynamics is the degree of polarisation of the emission [84, 85], There have been several recent reviews dealing with the topic of chemiluminescence [3, 77, 86-88]. 

By using either a continuous or pulsed source of radiation and by measuring the amount of radiation absorbed by the reaction products, it is possible to determine product state distributions. The source of radiation can either be monochromatic (resonance lamp or laser) or broad-band (flash lamp or arc lamp) used in conjunction with a form of monochromator at the detector. The amount of absorption is monitored by an appropriate photosensitive or energy-sensitive detector. Particular care must be taken in the case of resonance lamps to avoid self-reversal of the output of the source, as this will complicate the quantitative analysis of product densities [17]. Similarly, laser sources must not be operated at such high output powers that the transitions involved become saturated, as this also complicates the analysis. Absorption measurements can be used for a wide range of reaction products, both ground and excited states of atoms, radicals and molecules [9,17, 22]. 

Fluorescence detection of species is analogous to the pure absorption measurements discussed above, except that the emission from the excited-state species produced by the absorption is monitored rather than the amount of absorbed radiation. This is inherently a more sensitive method 

There are several reagents that can be used for qualitative and quantitative assay of the separated lipids. Apart from these there are specific spray reagents available to characterize individual lipid groups. Detection methods can be classified mainly into two categories, the nondestructive methods and the destructive methods, and these can be further classified into specific and non-specific detection methods. It is 

Iodine. The most convenient and commonly used technique is exposure to iodine vapours. Iodine crystals are put in one of the covered tanks and placed under the fume hood, vapours of iodine being toxic. After it is freed from the solvent, the TLC plate is placed in the iodine tank and the spots are visualized. This is a qualitative technique, although some researchers use it for quantitation by densitometry. The theory behind iodine exposure is that the iodine is physically absorbed into the lipid spot. The disadvantage with this technique is that the saturated lipid samples do not take up iodine easily and, moreover, when unsaturated molecules are left in iodine for a sufficiently long time they tend to react with it chemically. Iodine is added at the double bonds and produces artifacts, and this has been proved by GC analysis of material extracted from plates after exposure to iodine (Vioque and Holman, 1962). 

Rhodamine 6G. This is similar to 2 7 -dichlorofluorescein except that the lipids appear pink under a UV lamp. With the use of these dyes fluorimetry can be used for quantitation. 

Occasionally we have sprayed our plates with water when purifying large amounts of lipids, for example triglycerides, from oil samples. The hydrophobicity of triglycerides makes them appear as white spots against a translucent background when held up to the light. 

Lipids containing chromophores. Some lipids contain chromophores and can be visualized directly under UV or visible light without any staining. We have separated triglycerides containing conjugated trienoic acid, as well as their methyl esters, by visualization under UV light. 

We will show several examples of the use of 2DLC for nonionic surfactants. The resulting resolution can be dramatically different depending on the two separation modes in the 2DLC system. As discussed previously, the separation of the hydrophobic groups can be accomplished with a reversed-phase column, and the separation of the 

Absorption is the simplest method for measuring an X-ray spectrum. The incoming radiation, lo is measured and related it to the transmitted radiation (/,). 

This method makes use of all the photons that are incident on the sample. 

Sometimes it is of advantage to measure absorption not directly, but by associated processes. This is mainly used when the X-ray absorption is only a small fraction of the total absorption process. Problems with absorption are often observed with highly diluted samples and also for low-energy EXAFS. In these cases the transmission results from the difference of either two nearly identical signals or two vastly different signals, both needing very accurate data. 

In addition to the removal of one core electron by the incident X-rays (photoelectron process), the Auger process is taking place approximately 10 seconds after the photoelectron event. In this process an outer electron falls into the inner orbital vacancy from the photoelectron process and a second electron is emitted 

Modern solid-state detectors have windowing functions that can filter the fluorescence radiation. 

Detectors such as those based on on-line light-scattering, UV absorbance, or refractive index measurements are employed to characterize the molecular weights of polypeptides, simple proteins, and glycoproteins or to determine the stoichiometry of protein complexes [22], 

Poor resolution 1. Unsuitable column material 2. Column dimensions not optimal 3. Non-optimal flow rate 4. Sample size 1. Choose a support with a narrower fractionation range or a smaller particle size 2. Use longer columns or couple two columns 3. Reduce the flow rate 4. Reduce the sample concentration and/or the sample volume 

High back- Precipitation of proteins during the Filter the eluent and add a 

Loss of protein activity 1. Adsorption of protein on the column 2. Separation of subunits 1. Add salt 2. Change the mobile phase 

200 mM NaCl at pH 6.5). Many proteins were successfully analyzed, including thyroglobulin, catalase, collagen, transferin, albumin, carbonic anhydrase, lysozyme, and insulin. For most SEC columns, a volatile buffer solution containing the salt ammonium acetate proved to be suitable for the analysis of polysaccharides (dextrans, heparin) or nucleic acid polymers (RNA, oligonucleotides) [24]. 

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At the column outlet, either of two detection methods are employed ... 

Because these pipes are key components used for airplanes, their ultrasonic testing quality must be guranteed. Therefore, the author has conducted studies about the flaw detection methods for coarse-grained TC4P extrusion pipes. 

Luminescence has been used in conjunction with flow cells to detect electro-generated intennediates downstream of the electrode. The teclmique lends itself especially to the investigation of photoelectrochemical processes, since it can yield mfonnation about excited states of reactive species and their lifetimes. It has become an attractive detection method for various organic and inorganic compounds, and highly sensitive assays for several clinically important analytes such as oxalate, NADH, amino acids and various aliphatic and cyclic amines have been developed. It has also found use in microelectrode fundamental studies in low-dielectric-constant organic solvents. 

The pump-probe concept can be extended, of course, to other methods for detection. Zewail and co-workers [16,18, 19 and 2Q, 93] have used the probe pulse to drive population from a reactive state to a state that emits fluorescence [94, 95, 96, 97 and 98] or photodissociates, the latter situation allowing the use of mass spectrometry as a sensitive and selective detection method [99, 100]. 

Hefter U and Bergmann K 1988 Spectroscopic detection methods Atomic and Moiecuiar Beam Methods vol 1, ed G Scoles et a/(New York Oxford University Press) pp 193-253... 

Many experimental methods may be distinguished by whether and how they achieve time resolution—directly or indirectly. Indirect methods avoid the requirement for fast detection methods, either by detemiining relative rates from product yields or by transfonuing from the time axis to another coordinate, for example the distance or flow rate in flow tubes. Direct methods include (laser-) flash photolysis [27], pulse radiolysis [28]... 

A second use of arrays arises in the detection of trace components of material introduced into a mass spectrometer. For such very small quantities, it may well be that, by the time a scan has been carried out by a mass spectrometer with a point ion collector, the tiny amount of substance may have disappeared before the scan has been completed. An array collector overcomes this problem. Often, the problem of detecting trace amounts of a substance using a point ion collector is overcome by measuring not the whole mass spectrum but only one characteristic m/z value (single ion monitoring or single ion detection). However, unlike array detection, this single-ion detection method does not provide the whole spectrum, and an identification based on only one m/z value may well be open to misinterpretation and error. 

Further, peak overlap results in nonlinear detector response vs concentration. Therefore, some other detection method must be used in conjunction with either of these types of detection. Nevertheless, as can be seen from Figure Ilf, chiroptical detection can be advantageous if there is considerable overlap of the two peaks. In this case, chiroptical detection may reveal that the lea ding and tailing edges of the peak are enantiomerically enriched which may not be apparent from the chromatogram obtained with nonchiroptical detection (Fig. He). 

Superfluid helium can pass easily through openings so small that they caimot be detected by conventional leak detection methods. Such leaks, permeable only to helium II, are called supedeaks. They can be a source of fmstrating difficulties in the constmction of apparatus for use with helium II. 

Biosensors (qv) and DNA probes ate relatively new to the field of diagnostic reagents. Additionally, a neat-infrared (nit) monitoring method (see Infrared TECHNOLOGY AND RAMAN SPECTROSCOPY), a teagenfless, noninvasive system, is under investigation. However, prospects for a nit detection method for glucose and other analytes ate uncertain. 

Fig. 5. Detection methods for glucose enzyme electrode based on (a) oxygen, (b) hydrogen peroxide, and (c) a mediator. See text.

Concerns over safe handling of radioactive materials and issues around the cost and disposal of low level radioactive waste has stimulated the development of nonradiometric products and technologies with the aim of replacing radioactive tracers in research and medical diagnosis (25). However, for many of the appHcations described, radioactive tracer technology is expected to continue to be widely used because of its sensitivity and specificity when compared with colorimetric, fluorescent, or chemiluminescent detection methods. 

Knowledge about the radiations from each isotope is important because as the uses of the radioisotopes have iacreased, it has become necessary to develop sensitive and accurate detection methods designed to determine both the presence of these materials and the amount present. These measurements determine the amount of radiation exposure of the human body or how much of the isotope is present ia various places ia the environment. For a discussion of detection methods used see References 1 and 2. 

A considerable body of Hterature has been pubHshed on the distribution and detection methods of mbidium ia geological formations, the oceans, soils, iadustrial particulate emissions, and steUar/iatersteUar formations (2). 

Le kDetection. Leak detection methods may be subclassified according to whether or not they are on the tank. On-tank leak detection systems operate immediately upon leakage. 

More specific methods involve chromatographic separation of the retinoids and carotenoids followed by an appropriate detection method. This subject has been reviewed (57). Typically, hplc techniques are used and are coupled with detection by uv. For the retinoids, fluorescent detection is possible and picogram quantities of retinol in plasma have been measured (58—62). These techniques are particularly powerful for the separation of isomers. Owing to the thermal lability of these compounds, gc methods have also been used but to a lesser extent. Recently, the utiUty of cool-on-column injection methods for these materials has been demonstrated (63). 

Chromatographic methods including thin-layer, hplc, and gc methods have been developed. In addition to developments ia the types of columns and eluents for hplc appHcations, a significant amount of work has been done ia the kiads of detectioa methods for the vitamin. These detectioa methods iaclude direct detectioa by uv, fluoresceace after post-column reduction of the quiaone to the hydroquinone, and electrochemical detection. Quantitative gc methods have been developed for the vitamin but have found limited appHcations. However, gc methods coupled with highly sensitive detection methods such as gc/ms do represent a powerful analytical tool (20). 

Table 1 Hsts several of the chemical deterrninations and the corresponding reactions uti1i2ed, which are available on automated clinical analy2ers. With the exception of assays for various electrolytes, eg, Na", K", Cl , and CO2, deterrnination is normally done by photometric means at wavelengths in the ultraviolet and visible regions. Other means of assay include fluorescence, radioisotopic assay, electrochemistry, etc. However, such detection methods are normally required only for the more difficult assays, particularly those of semm or urine constituents at concentrations below )Tg/L. These latter assays are discussed more fully in the Hterature (3,4).

Fig. 3. Schematic of optical detection methods, (a) absorbance or colorimetric (b) turbidimetric and (c) nephelometric.

Plasma atomic emission spectrometry is also employed as a detection method for gc (see Plasma technology). By monitoring selected emission lines a kind of selective detection based on elemental composition can be achieved (see Spectroscopy). 

Shape of vessel (ciihic or elongated vessel) Detection method for triggering a shutdown... 

Rosenberg, J., R.S.H. Mah, and C. lordache, Evaluation of Schemes for Detecting and Identifying Gross Errors in Process Data, Indushial and Engineeiing Chemistiy, Reseaieh, 26(.3), 1987, 555-564. (Simulation studies of various detection methods)... 

Gro.s.s-error-detection methods detect errors when they are not pre.sent and fail to detect the gro.s.s errors when they are. Couphng the aforementioned difficulties of reconciliation with the hmitations of gross-error-detection methods, it is hkely that the adjusted measurements contain unrecognized gross error, further weakening the foundation of the parameter estimation. 

G. A. Codd, T. M. Jefferies, C. W. Keevil and E. Potter, Detection Methods for Cyanobacterial... 

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