Gamma phase

Half-life is the time taken to decrease the concentration of a drug to one-half its original value. There may be several phases in the elimination, and the most common is the so-called beta-phase. Alpha-phase is a distribution phase and gamma-phase is the terminal phase when the drug is finally leaving the tissues. 

Perhaps even more noteworthy is the effect of crystallographic phase. While one phase of a specific composition may readily incorporate from a particular bath composition, another phase of the same composition may incorporate to a much lower extent or not at all. For instance, in the alumina particle system, the alpha phase has been found to readily incorporate from an acidic copper bath while the gamma phase incorporates at less than one tenth the amount of alpha, if at all, as shown in Table 1 [2, 11, 27, 31, 33],... 

X-ray diffraction of the Buehler-supplied gamma alumina powder used in a RCE study showed the powder to be actually a combination of alpha and gamma phase alumina [28], However, the relatively high particle incorporation obtained with this alpha-gamma alumina cannot be attributed to the partial alpha crystallographic character of the powder, since the pure alpha alumina codeposited to a lesser extent. 

If the alloy is quenched so as to preserve some of the high temperature gamma phase which is not ferromagnetic, one observes a single peak at the center in addition to the six-line pattern from the disordered solid... 

The gamma modification at ordinary temperatures can exist in sohd or liquid form. In sohd form it is a colloidal ice-hke mass melting at 16.8°C. In the hquid form it has a density of 1.9224 g/mL, boiling at 44.8°C. It has a vapor pressure of 433 torr at 25°C. The gamma phase consists of both cychc trimer and monomer molecules. When solid sulfur trioxide melts, it converts to its gamma phase which on sohdification changes to alpha modification. 

Fig. 11 Fish and gamma phase behavior diagrams exhibiting a severe twisting at low surfactant concentration...

URANIUM. [CAS 7440-61-1], Chemical element symbol. U, at. no. 92, at. wt, 238,03, periodic table group (Actinides), mp 1,131 to i. 33°C, bp 3,818°C, density 18.9 g/cm3 (20UC). Uranium metal is found in three allotropic forms (1) alpha phase, stable below 668°C, orthorhombic (2) beta phase, existing between 668 and 774°C. tetragonal and (3) gamma phase, above 774°C, body-centered cubic crystal structure. The gamma phase behaves most nearly that of a true metal. The alpha phase has several nonmetallic features in its crystallography. The beta phase is brittle. See also Chemical Elements. 

Pharmacokinetic data were available for 97 patients. The tasidotin plasma concentrations declined rapidly, and were less than 1% of maximal concentrations within about 8 h after dosing (Fig. 13.2). With such a short effective half-life, accumulation with daily tasidotin administration was not likely - once-daily multiple doses resemble a series of single doses. Concentrations appeared to decline in a biphasic manner (Fig. 13.2). The presence of a third, gamma phase was observed in some patients, but was not consistently detected, and for this reason the effective half-life was calculated instead of the terminal elimination phase half-life. 

Gamma phase. Face-centered cubic hydride, presumably fluorite-type... 

S = strong, M = medium, F 6 Duplex gamma phase observed. c Unknown B. = faint, V = very, O = absent. 

Schmidt, M. U. and Metz, H. J. (1998a). Novel crystal modification of C.I. Pigment Red 53 2 (gamma-phase) German Patent DE 19827272.3. [260t]... 

Alumina membranes. It has been established that several phases of alumina exist and a particular phase of alumina is determined not only by the temperature it has experienced but also by the chemical path it has taken. For commercial membrane applications, the alpha- and gamma-phases of alumina are the most common. Alpha-alumina membranes are well known for their thermal and hydrothermal stabilities beyond 1,000 C. In fact, other transitional forms of alumina will undergo transformation towards the thermodynamically stable alpha-alumina at elevated tcmjxratures beyond 900 C. On the contrary, commercial gamma-alumina membranes are typically calcined at 400-600 C during production and are, therefore, subject to potential structural changes beyond 600°C. Moreover, alumina chemistry reveals that phase transition also occurs beyond that temperature [Wefers and Misra, 1987]. 

Chen JH, Weidner DJ (1997) X-ray diffraction study of iron partitioiting between alpha and gamma phases of the (Mg,Fe)2Si04 system. Physica A 239 78-86... 

Fig. 1.12 Serum concentration-time profile of gentamicin in an animal after intravenous administration, illustrating three phases of disposition. Alpha and beta phases, relevant for therapeutic monitoring, are the only phases evident when drug concentrations are monitored over a short time after dosing (inset). When a sensitive assay is employed to monitor drug concentrations for prolonged periods, the third (gamma) phase becomes evident. It is this last phase that is responsible for predicting tissue withdrawal times. (Reproduced with permission from Riviere (1988).)...

The gamma (y) phase of uranium is formed at temperatures above those required for beta phase stability. In the gamma phase, the lattice structure is BCC and expands equally in all directions when heated. 

Ash] Ashby, J.A., Flower, H.M., Rawlings, R.D., Gamma Phase in an Fe-Co-2% V Alloy , Metal Sci, 11, 91-96 (1977) (Crys. Structure, Experimental, Morphology, Phase Diagram, Phase Relations, 20)... 

A nylon 66 clay nanocomposite was produced using the dry-compound method [26]. Co-intercalation organophihc clay was used as the clay base. Na-montmorillonite was first processed using hexadecyl trimethyl ammonium ions and epoxy resin. It was then kneaded using a twin screw extruder to make a clay nano composite. As the amount of clay that was added increased, the amount of y (gamma) phases increased. This is thought to be due to the strong interactions between the nylon 66 chains and the sinface of the clay layers. 

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