Bead probes

Nitrogen specihc detector- TSD (Varian, Darmstadt, Germany) TSD bead probe modihed by applying rubidium dotted glass bead Detector temp 320°C... 

Despite the limitations of the Pennes bioheat equation, reasonable agreement between theory and experiment has been obtained for the measured temperature profiles in perfused tissue subject to various heating protocols. This equation is relatively easy to use, and it allows the manipulation of two blood-related parameters, the volumetric perfusion rate and the local arterial temperature, to modify the results. Pennes performed a series of experimental studies to validate his model. Over the years, the validity of the Pennes bioheat equation has been largely based on macroscopic thermal clearance measurements in which the adjustable free parameter in the theory, the blood perfusion rate [Xu and Anderson, 1999] was chosen to provide reasonable agreement with experiments for the temperature decay in the vicinity of the thermistor bead probe. Indeed, if the limitation of Pennes bioheat equation is an inaccurate estimation of the strength of the perfusion source term, an adjustable blood perfusion rate will overcome its limitations and provide reasonable agreement between experiment and theory. 

This technique employs a single thermistor serving as both a temperature sensor and a heater. Typically in this technique, either a thermistor is inserted through the lumen of a hypodermic needle, which is in turn inserted into the tissue, or the thermistor is embedded in a glass-fiber-reinforced epoxy shaft. Figure 2.4 shows the structure of a thermistor bead probe embedded in an epoxy shaft. Each probe can consist of one or two small thermistor beads situated at the end or near the middle of the epoxy shaft. The diameter of the finished probe is typically 0.3 mm, and the length can vary as desired. Because the end can be sharpened to a point, it is capable of piercing most tissues with very minimal trauma. 

FIGURE 2.4 Sketch of a thermistor bead probe. [From Xu et al. (1998), with permission.]... 

Temperature Pulse Decay Technique. As described in Sec. 2.4 under Temperature Pulse Decay (TPD) Technique, local blood perfusion rate can be derived from the comparison between the dieoretically predicted and experimentally measured temperature decay of a thermistor bead probe. The details of the measurement mechanism have been described in that section. The temperature pulse decay technique has been used to measure the in vivo blood perfusion rates of different physical or physiological conditions in varimis tissues (Xu et al., 1991 1998). The advantages of this technique are that it is fast and induces little trauma. Using the Pennes bioheat transfer equation, the intrinsic thermal conductivity and blood perfusion rate can be simultaneously measured. In some of the applications, a two-parameter least-square residual fit was first performed to obtain the intrinsic therm conductivity of the tissue. This calculated value of thermal conductivity was then used to perform a one-parameter curve fit for the TPD measurements to obtain the local blood perfusion... 

Overviews of recent developments in beads, including fluorescent ones, have been provided by The Latex Course, recently sponsored by Bangs Laboratories. Also, the most recent edition of the nuts-and-bolts book of flow cytometry provides an update on literature in the area of bead probes. Furthermore, the International Federation of Clinical Chemistry (IFCC) Working Group on Nanotechnology, chaired by Larry J. Kricka (University of Pennsylvania Medical Center), has recently compiled literature on microarrays and microchips, the fourth part of which will cover literature on protein, peptide, and antibody microarrays and microchips to the middle of 2003, and will be made available via the IFCC web page. The latter literature includes that of bead suspension arrays. 

Surface Plasmon Resonance Light Scatter Nanoparticle-Bead Probes... 

The bead probes to be described in next two sections will require additional fluores-cence/luminescence emission detector(s). The number of these detectors depends on the number of different colors or wavelength regions of emission to be detected. A typical maximum that has currently been feasible with organic dye emitters has been about six. This may be augmented due to the observed narrow bandwidths (typically, 30-50 nm, and as low as 26 nm, reproducibly produced) of emission from semiconductor nanoparticles, which have been recently shown to allow 10 colors. ... 

Thus, for years now wheels have been tested with eddy-currents with a special emphasis on finding superficial defects on the wheel s running surface. At the beginning, hand-guided probes were used which the tester slid across the surface that was to be tested. To do so, the wheel was placed on a turn table which the operator had to move manually. A higher test reliability in the transitional radius between the body and the bead wheel was achieved by using special form-fitted probes. Nonetheless, it was not possible to rule out completely that the wheel was not scanned 100 %. This test method did not allow for documentation and a subsequent reconstruction of the test. 

Then, the weld depths penetration are controlled in a pulse-echo configuration because the weld bead (of width 2 mm) disturbs the detection when the pump and the probe beams are shifted of 2.2 mm. The results are presented in figure 8 (identical experimental parameters as in figure 7). The slow propagation velocities for gold-nickel alloy involve that the thermal component does not overlap the ultrasonic components, in particular for the echo due to the interaction with a lack of weld penetration. The acoustic response (V shape) is still well observed both for the slot of height 1.7 mm and for a weld depth penetration of 0.8 mm (lack of weld penetration of 1.7 mm), even with the weld bead. This is hopeful with regard to the difficulties encountered by conventional ultrasound in the case of the weld depths penetration. 

Perlen-glanz, m. pearly (or nacreous) luster, -probe, /. bead test, -schnur, /. string of beads or pearls. 

Fig. 6.5 Schematic representation of a bioelectronic protocol for detection of DNA hybridization (A) binding of the target to magnetic beads (B) hybridization with CdS-labeled probe (C) dissolution of CdS tag (D) potentiometric stripping detection at a mercury-film electrode. (Reprinted from [136], Copyright 2009, with permission from Elsevier)...

In order to probe the influence of Au and KOAc on the vinyl acetate synthesis chemistry, four different catalysts were synthesized. All of these catalysts were prepared in a manner exemplified in prior patent technology [Bissot, 1977], and each contained the same palladium loading in an egg-shell layer on the surface of a spherical silica support. The palladium content in the catalyst was easily controlled by adjusting the solution strength of palladium chloride (PdClj) added to the porous silica beads prior to its precipitation onto the support by reaction with sodium metasilicate (Na SiOj). The other two catalyst components (Au and KOAc) were either present or absent in order to complete the independent evaluation of their effect on the process chemistry, e.g., (1) Pd-i-Au-hKOAc, (2) Pd-i-KOAc, (3) Pd-hAu, and (4) Pd only. 

An important factor in all these experiments is the choice of bead used to immobilize the probe. Biochemists have considered cross-linked agarose beads to be exceptionally hydrophilic with a low tendency to bind proteins nonspecifically, and these beads have the further attraction of being commercially available in activated forms (succinimidyl esters, epoxides, and maleimides, for example). However, early trials of bead-based chemical proteomics have shown that many proteins in mammalian cell lysates bind tenaciously to agarose beads. This was unimportant in many studies in which protein-protein interactions were detected by coimmunoprecipitation with immunochemical... 

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