Direct plating method

Brichta-Harhay, D. M., Arthur, T. M., Bosilevac, J. M., Guerini, M. N., Kalchayanand, N., and Koohmaraie, M. (2007). Enumeration of Salmonella and Escherichia coli 0157 H7 in ground beef, cattle carcass, hide and faecal samples using direct plating methods. /. Appl. Microbiol. 103,1657-1668. 

Splittstoesser (1992) described a method using fluorescent dye (acridine orange) known as direct epifluorescence filter technique (DEFT), a method also applied by Divol and Lonvaud-Funel (2005). Divol and Lonvaud-Funel (2005) used a different substrate, fluoresceine diacetate, which is hydrolyzed by viable cells to form a fluorescent product, fluoresceine. However, Atlas and Bartha (1981) observed that cell population values can differ substantially between (epifluorescence and direct plating) methods (10 vs. 10 CFU), possibly due to the presence of viable-but-non-culturable cells. In addition, Meidell (1987) reported interference... 

The direct-solution method of Akers and Wade [1] is among several which attempt to reduce the amount of trial-and-error solutions. This has been accomplished and has proven quite versatile in application. The adaptation outlined modifies the symbols and rearranges some terms for convenient use by the designer [3]. Dew point and bubble point compositions and the plate temperatures can be determined directly. Constant molal overflow is assumed, and relative volatility is held constant over sections of the column. 

The Wilhelmy hanging plate method (13) has been used for many years to measure interfacial and surface tensions, but with the advent of computer data collection and computer control of dynamic test conditions, its utility has been greatly increased. The dynamic version of the Wilhelmy plate device, in which the liquid phases are in motion relative to a solid phase, has been used in several surface chemistry studies not directly related to the oil industry (14- 16). Fleureau and Dupeyrat (17) have used this technique to study the effects of an electric field on the formation of surfactants at oil/water/rock interfaces. The work presented here is concerned with reservoir wettability. 

In addition to the direct absorbance methods, colorimetric methods are suited for relatively pure proteins as purification progresses. They are accurate if calibrated from a standard curve of the test protein reference sample and fast if automated. However, they are not as simple to perform as direct absorbance methods. Hence they are not as suitable for production as direct absorbance methods. The relative simplicity of colorimetric methods makes them more suited to automated formulation and stability studies and total-protein assays of complex mixtures. Microtiter plate versions of colorimetric assays allow for automation and consumption of relatively small sample sizes while requiring little specialized equipment or training. 

Any study of colloidal crystals requires the preparation of monodisperse colloidal particles that are uniform in size, shape, composition, and surface properties. Monodisperse spherical colloids of various sizes, composition, and surface properties have been prepared via numerous synthetic strategies [67]. However, the direct preparation of crystal phases from spherical particles usually leads to a rather limited set of close-packed structures (hexagonal close packed, face-centered cubic, or body-centered cubic structures). Relatively few studies exist on the preparation of monodisperse nonspherical colloids. In general, direct synthetic methods are restricted to particles with simple shapes such as rods, spheroids, or plates [68]. An alternative route for the preparation of uniform particles with a more complex structure might consist of the formation of discrete uniform aggregates of self-organized spherical particles. The use of colloidal clusters with a given number of particles, with controlled shape and dimension, could lead to colloidal crystals with unusual symmetries [69]. 

The film pressure is usually measured by the Wilhelmy plate method. Usually the Wilhelmy plate is a piece of absorbent paper hanging into the water subphase. The force acting on it is proportional to the surface tension. More rarely, the force on the barrier is determined directly. 

If a moderately large area of flat solid surface is available, contact angles are usually measured directly from a projection of a sessile drop of the liquid. Alternatively, the tilting-plate method illustrated... 

A direct detection method was recently developed for these adducts in stratum comeum of human skin based on immunofluorescence microscopy (30). Three partial sequences of keratins containing glutamine or asparagine, adducted with a 2-hydroxyethyl-thioethyl group at the omega-amide function, were synthesized and used as antigens for raising antibodies. After immunization, monoclonal antibodies were obtained with affinity for keratin isolated from human callus exposed to 50 xM sulfur mustard (see Plate 1). In contrast to the immunochemical... 

For the Wilhelmy plate method, a thin plate with a perimeter of about 4 cm is lowered to the surface of a liquid and the downward force directed on the plate is measured. Surface tension is the force divided by the perimeter of the plate. For this method to be valid, the liquid should completely wet the plate before the measurement, which means that the contact angle between the plate and the liquid is zero. Furthermore, the position of the plate should be correct, which means that the lower end of the plate is exactly on the same level as the surface of the liquid. Otherwise the buoyancy effect must be calculated separately. 

Water Determine as directed for Method la in the Karl Fischer Titrimetric Method under Water Determination, Appendix IIB, using a 100-g sample melted on a hot plate at 60°. Use a syringe to apply the oil to the Karl Fisher titrimetric apparatus (usually 1.0 mL is sufficient, but this may vary depending on the water content of the sample). 

The sample must be introduced into the ionization source so that vacuum inside the instrument remains unchanged. Samples are often introduced without compromising the vacuum using direct infusion or direct insertion methods. For direct infusion, a capillary is employed to introduce the sample as a gas or a solution. For direct insertion, the sample is placed on a probe, a plate or a target that is then inserted into the source through a vacuum interlock. For the sources that work at atmospheric pressure and are known as atmospheric pressure ionization (API) sources, introduction of the sample is easy because the complicated procedure for sample introduction into the high vacuum of the mass spectrometer is removed. 

In the direct UV method, compounds are dissolved in DMSO stock solution at 10 mg/mL. A small volume is added to an aqueous buffer and mixed. If the target concentration exceeds the solubility of the compound, the insoluble material will precipitate. The solution is allowed to settle for certain period of time (e.g. overnight) and is then filtered to remove the precipitate. The concentration of the supernatant is determined by using a UV plate reader and the solubility is derived against a single point standard (Avdeef, 2001). 

Liquid samples can be analysed directly by the spread plate (A) or the pour plate method (B) but they can also be filtered to retain the micro-organism on a filter which is than placed on the culture medium (C). Suspensions need to be filtrated or centrifuged afterwards the filtrate or the filter can be analysed. Solids (e.g. food) must be minced before filtration. Incubation at a given temperature can be aerobic or anaerobic. The result of the counting will depend on the ability to isolate the target organisms with the best recovery rate. 

The angle of internal friction can be measured indirectly, in shear cells for example, or directly, by the grooved plate method. There... 

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