Hollow probe

The pitot tube is a device for measuring v(r), the local velocity at a given position in the conduit, as illustrated in Fig. 10-1. The measured velocity is then used in Eq. (10-2) to determine the flow rate. It consists of a differential pressure measuring device (e.g., a manometer, transducer, or DP cell) that measures the pressure difference between two tubes. One tube is attached to a hollow probe that can be positioned at any radial location in the conduit, and the other is attached to the wall of the conduit in the same axial plane as the end of the probe. The local velocity of the streamline that impinges on the end of the probe is v(r). The fluid element that impacts the open end of the probe must come to rest at that point, because there is no flow through the probe or the DP cell this is known as the stagnation point. The Bernoulli equation can be applied to the fluid streamline that impacts the probe tip ... 

For photodissociation experiments, a special probe was constructed to replace the 12.7 mm diameter direct insertion probe normally employed. It consists of a hollow stainless steel tube which has a 38 mm focal length quartz lens vacuum sealed at one end and an extended hollow probe tip at the other. The beam of a Lambda Physik excimer laser operating at 308 nm was passed through the probe and lens into the FTMS cell through a small hole in the center of the trap plate as shown in Figure 1. 

One type of probe is a hand-held stainless-steel hollow auger, which has soil-air vent holes drilled into the shaft near the bottom and is fitted with a gas sample port near the top (Lovell, 1979). Another type of hollow probe has a straight shaft with a gas sample port at the top and soil-air vent holes at the bottom this probe is pounded into the soil by means of a captive hammer that slides up and down the shaft to either drive the probe into or remove it from the soil (Dyck, 1972 Chemical Projects Limited, Toronto, Ontario, Canada, written common., 1972 Lovell, 1979). Both the hollow auger and hollow hammer-probe are efficient dynamic soil-gas samplers in light soils. Neither sampler works well in stony or hard, compacted soils, or in soils containing layers of caliche attempts to use probes in these soils may either bend the probe or disturb the soil to the extent that the soil-gas sample is diluted by atmospheric air. Soil gas can not be sampled in wet soils with these probes. 

A soil-gas sample collected by hollow probe needs no further preparation for injection into a GC system. However, the results obtained from sulphur analysis of a soil gas may be inaccurate representatives of their original state in the field. The time elapsed between collection of the sample in the field and analysis in the laboratory permits many changes in the sample. Some sulphur components may adsorb on the walls of the glass, plastic, or stainless-steel syringes or sample carriers used for sample transportation. Non-adsorbed components may interact with each other. The most reliable soil-gas analyses are those made almost immediately after collection. Even these analyses may not be completely accurate. 

Ball et al. (1983a, 1990) pumped soil air from a hollow probe into a modified Orstat gas analysis apparatus. A known volume of soil air is first pumped into the gas burette of the apparatus, and subsequently transferred to integral absorption vessels (Fig. 14-4). The absorbent for CO2 is 40% aqueous KOH. The volume of gas absorbed is recorded from the gas burette. The remaining gas is exposed to a mixture of saturated aqueous ammonium chloride and ammonia in contact with copper coils for absorption of O2. Again the gas volume reduction is recorded from the gas burette. Practical limits of detection under field conditions are 0.01-0.1% for each gas. 

Fig. 2.6.6 Remotely reconstructed high field NMR images of laser-polarized 129Xe gas in the hollow CAL pores. Owing to the flow pattern where the spins have to flow around two corners [see the probe design in...

Modification of the apparatus to accomplish automation is allowed by <711>. One example is hollow shaft sampling as illustrated in Figure 10 (15). This method is theoretically within the stated sampling location of the text of <711>, although there may be question about the concentration of sample surrounding the shaft. This and other sampling techniques, for example in-residence probes, are convenient sampling tools but should be properly validated. 

The technique consists of a microdialysis probe, a thin hollow tube made of a semi-permeable membrane usually around 200-500 /xm in diameter, which is implanted into the skin and perfused with a receiver solution that recovers the unbound permeant from the local area. In principle, the driving force of dialysis is the concentration gradient existing between two compartments separated by a semi-permeable membrane. For skin under in vivo conditions, these compartments represent the dermal or subcutaneous extracellular fluid (depending on the probe position) and an artificial physiological solution inside the probe [36-38],... 

Down shaft Probe positioned down the hollow shaft of the stirring blade in each vessel Eliminates the problem of flow disturbance at the sampling point Sampling depth not as USP-prescribed flow effectiveness through shaft ill-determined... 

Stettbacher(Ref 2 Ref 8,p 361) proposed a test which was claimed to det simultaneously brisance and energy. In this method, known as Strahlungs probe (Radiation Test), a finely powdered expl (ca 50g), packed lightly in a thick Fe or Ni crucible, was placed in the center of a square plate of soft Fe, 6.8mm thick, supported on the op of a hollow cylinder. After initiating the expl Dy means of l-2g MF-LA mixt, the detonating effect was measured by the depth of impression... 

Abstract This chapter reviews the development of optical fiber probe Raman systems and their applications in life science and pharmaceutical studies. Especially, it is focused on miniaturized Raman probes which open new era in the spectroscopy of the life forms. The chapter also introduces the important optical properties of conventional optical fibers to use for Raman probes, as well as new types of optical fiber and devices, such as hollow optical fibers and photonic crystai fibers. 

Several modifications of the ESI technique have been introduced, principally micro-electrospray14 and nano-electrospray15 that have the advantage of using much lower flow rates, reducing the amount of analyte needed for a mass-spectrometric analysis this is performed using adapted probed tips. When performing nanospray, the sample is loaded into a fine hollow needle with a... 

Crystalline nanorings, literally closed circular nanoparticles with a hollow centre, were first prepared from zinc oxide in 2004 by a spontaneous self-coiling process from polar nanobelts.44 Semiconductor nanorings and indeed interestingly shaped nanoobjects in general, promise much in the way of applications as tools to probe fundamental physical phenomena and as nanoscale sensors, transducers, and resonators. 

A straightforward way to collect solutes from the interstitial fluid (ISF) space would be to have a semipermeable, hollow fiber, membrane-based device as originally described by Bito et al.1 Two semipermeable membrane-based devices that have been used to collect different types of analytes from various mammalian tissues include microdialysis sampling probes (catheters) and ultrafiltration probes. The heart of each of these devices is the semipermeable polymeric membrane shown in Figure 6.1. The membranes allow for collection of analytes from the ISF that are below the membrane molecular weight cutoff (MWCO). Each of these devices provides a sample that has a significantly reduced amount of protein when compared to either blood or tissue... 

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