Extrinsic factor and

In 1929, Castie (7) tied the work of Combe and Addison with that of Whipple, Miaot, and Murphy by ptoposiag that both an extrinsic factor and an intrinsic factor ate iavolved ia the coatrol of pernicious anemia. The extrinsic factor, from food, is vitamin 2- Th intrinsic factor is a specific B22-biading protein secreted by the stomach. This protein is requited for vitamin B 2 absorption. 

Cobalamine can only be resorbed in the small intestine when the gastric mucosa secretes what is known as intrinsic factor—a glycoprotein that binds cobalamine (the extrinsic factor) and thereby protects it from degradation. In the blood, the vitamin is bound to a special protein known as trans-cobalamin. The liver is able to store vitamin Bi2 in amounts suf cient to last for several months. Vitamin B12 deficiency is usually due to an absence of intrinsic factor and the resulting resorption disturbance. This leads to a disturbance in blood formation known as pernicious anemia. 

In 1925, it was demonstrated that two factors were required to cure pernicious anaemia one in the food (extrinsic factor) and one in gastric juice (intrinsic factor). 

The poor stability of some semiconducting polymers and their sensitivity to external factors often make it difficult to deduce true intrinsic properties of a certain material [101,102]. Most commonly, the off-currents in a TFT are governed by extrinsic factors and it also has an impact on subthreshold slope, threshold voltages, and bias stress. In fact, this sensitivity prompted some researchers to use OSC materials as gas and chemical sensors in TFT devices [103,104]. The observed selective sensitivity is related either to the chemical nature of the semiconductor functionalities or the interaction of the grain... 

Fig. 28.6 Dependence of the strongest size xc (m,f, T/TJiQ)) on a the extrinsic factor/and b the intrinsic bond nature indicator m. At T/T (0) < 0.15, xc depends insignificantly on the / the m influences the xc over the whole range of temperature. One critical size xc can be obtained at two temperatures with different hardness (Reprinted with permission from [15])...

Vitamin B12 is special in as far as its absorption depends on the availability of several secretory proteins, the most important being the so-called intrinsic factor (IF). IF is produced by the parietal cells of the fundic mucosa in man and is secreted simultaneously with HC1. In the small intestine, vitamin B12 (extrinsic factor) binds to the alkali-stable gastric glycoprotein IF. The molecules form a complex that resists intestinal proteolysis. In the ileum, the IF-vitamin B 12-complex attaches to specific mucosal receptors of the microvilli as soon as the chymus reaches a neutral pH. Then either cobalamin alone or the complex as a whole enters the mucosal cell. 

Mixed asthma (caused by both intrinsic and extrinsic factors)... 

Figure 51-1. The pathways of blood coagulation. The intrinsic and extrinsic pathways are indicated. The events depicted below factor Xa are designated the final common pathway, culminating in the formation of cross-linked fibrin. New observations (dotted arrow) include the finding that complexes of tissue factor and factor Vila activate not only factor X (in the classic extrinsic pathway) but also factor IX in the intrinsic pathway, in addition, thrombin and factor Xa feedback-activate at the two sites indicated (dashed arrows). (PK, prekallikrein HK, HMW kininogen PL, phospholipids.) (Reproduced, with permission, from Roberts HR, Lozier JN New perspectives on the coagulation cascade. Hosp Pract [Off Ed] 1992Jan 27 97.)...

LUDIKHUYZE L, RODRIGO L and HENDRICKSE M (2000) The activity of myrosinase from broccoli (Brassica oleracea L.cv. Italica) influence of intrinsic and extrinsic factors J Food Protect, 63 400-403. 

Major determinants of membrane fluidity may be grouped within two categories [53] (1) intrinsic determinants, i.e., those quantifying the membrane composition and phase behavior, and (2) extrinsic determinants, i.e., environmental factors (Table 1). In general, any manipulation that induces an increase in the molal volume of the lipids, e.g., increase in temperature or increase in the fraction of unsaturated acyl chains, will lead to an increase in membrane fluidity. In addition, several intrinsic and extrinsic factors presented in Table 1 determine the temperature at which the lipid molecules undergo a transition from the gel state to liquid crystalline state, a transition associated with a large increase in bilayer fluidity. 

Calof A.L. (1995). Intrinsic and extrinsic factors regulating vertebrate neurogenesis. Curr Opin Neurobiol 5, 19-27. 

Steels and other structural transition-metal alloys are hardened by various extrinsic factors. The compositions and internal micro-structures of these materials are very complex. Therefore, simple descriptions and/or interpretations of their behaviors cannot be given, so they will not be discussed here. 

The most important of the extrinsic factors that affect the hardnesses of the transition metals are covalent chemical bonds scattered throughout their microstructures. These bonds are found between solute atoms and solvent atoms in alloys. Also, they lie within precipitates both internally and at precipitate interfaces with the matrix metal. In steel, for example, there are both carbon solutes and carbide precipitates. These effects are ubiquitous, but there... 

The crystal structure of NiAl is the CsCl, or (B2) structure. This is bcc cubic with Ni, or A1 in the center of the unit cell and Al, or Ni at the eight comers. The lattice parameter is 2.88 A, and this is also the Burgers displacement. The unit cell volume is 23.9 A3 and the heat of formation is AHf = -71.6kJ/mole. When a kink on a dislocation line moves forward one-half burgers displacement, = b/2 = 1.44 A, the compound must dissociate locally, so AHf might be the barrier to motion. To overcome this barrier, the applied stress must do an amount of work equal to the barrier energy. If x is the applied stress, the work it does is approximately xb3 so x = 8.2 GPa. Then, if the conventional ratio of hardness to yield stress is used (i.e., 2x3 = 6) the hardness should be about 50 GPa. But according to Weaver, Stevenson and Bradt (2003) it is 2.2 GPa. Therefore, it is concluded that the hardness of NiAl is not intrinsic. Rather it is determined by an extrinsic factor namely, deformation hardening. 

Clearly, the hardnesses of thermoplastic polymers are not intrinsic. They depend on various extrinsic factors. Only trends can be cited. For example, as the molecular weight in polyethylene materials increases, they become harder. And, as the molecular aromaticity increases, a polymeric material becomes harder. Thus, higher molecular weight anthracene is harder than napthalene and more aromatic Kevlar is harder than polymethacrylate. 

Therefore, other factors that have not yet been studied and are not easily quantifiable, such as the absorption properties of the C.-T. adduct at the surface of the metal powder and the solubility of the formed species should be important in determining the oxidation properties of C.-T. adducts towards metal powders. Furthermore, some extrinsic factors inherent to the experimental conditions, such as reaction temperature, reagent concentration, and nature of the solvent have been reported to affect the overall yield or the course of the reaction, and led to separation of different products in some cases.55 59 In any case, it appears that the simultaneous presence of the donor molecule and the di-/inter-halogen lowers the oxidation potentials of the metals, allowing their oxidation, dissolution, and complexation. 

Two coagulation factors function uniquely in the extrinsic pathway factor III (tissue factor) and factor VII. Tissue factor is an integral membrane protein present in a wide variety of tissue types (particularly lung and brain). This protein is exposed to blood constituents only upon rupture of... 

Direct and indirect costs are compared public and private costs are estimated at 3.5-4 times those for EPA in 1981. Among the former is loss of innovation. While several studies of this factor have been made for the industry, their reliability is questioned, due in part to lack of sound data prior to 1976. No mention was made of economic trends affecting corporate expenditures for research and development, or of trends in the maturation of industrial chemistry itself. Other indirect costs, such as concentration of manufacture within the industry, may result from costs of compliance, especially for smaller manufacturers. These factors were not compared with extrinsic factors, such as shifts in feedstock supply and commodity manufacture from the United States to other countries. 

The forward and backward activation free energies and the corresponding rate constants thus depend on an extrinsic factor, the standard free energy of the reaction, AG° = E — E°, and an intrinsic factor, the standard activation free energy, that reflects the solvent and internal reorganization energy, Aq and A [equation (1.31)]. 

Whether or not chemical reactivity hazards are present is a function not only of each chemical s reactivity (by itself and in combination), but also of various extrinsic factors i.e., factors that are not intrinsic properties of the chemicals being handled. As the design for a facility progresses, decisions will be made regarding these factors that will affect the magnitude of the chemical reactivity hazards and the potential consequences if their control is lost. A partial list of extrinsic factors includes ... 

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