Vanadium behavioral effect

Shiller AM, Boyle EA (1991) Trace elements in the Mississippi River Delta outflow region behavior at high discharge. Geochim Cosmochim Acta 55 3241-3251 Shiller AM, Mao L (2000) Dissolved vanadium in rivers Effects of silicate weathering. Chem Geol 165 13-22... 

The stress or growth pathways modulated by vanadium involve specialized effectors and often can be activated by excess ROS. Cytokines, small proteins that effect communication between cells or cell behavior, can be involved in the cellular stress response. Tumor necrosis factor a (TNFa) is a cytokine stress signal that binds to a membrane receptor (tumor necrosis factor receptor, or TNFR). This interaction stimulates kinase activity that leads to cell injury and inflammation and also to the activation of caspases, a family of cysteine-dependent aspartate-directed proteases that are involved in apoptosis. The mitogen-activated protein (MAP) kinase cascade regulates both mitosis and apoptosis signaling pathways. 

Spectral studies show that the configuration of the valence electrons of the niobium atom ( -4d4 5s) is different from that in the vanadium atom ( 3d 4s2) and in the tantalum atom ( 5dz 6s2) but this difference, in so far as is known, has no effect on the chemical behavior of the elements. 

The nature of the oxidic support plays an important role in modulating the nature of vanadium species and the catalytic behavior of the materials. In fact, changes in the electron density of the vanadyl double bond can be produced by the inductive effect through the bonds anchoring the tripodal vanadyl groups to the oxidic support [111]. These electronic effects can be clearly demonstrated using... 

In this chapter we will discuss how the behavior of the catalyst is influenced by a number of factors including the method of preparation of the precursor, the oxidation state of the catalyst, the phosphorus/vanadium raho of the catalyst and the activation conditions. A variety of techniques have been used to characterize the morphology and nature of the achve sites of the catalysts and gain insight into the mechanism. Furthermore, the effect of these preparatory techniques will be discussed, with emphasis on the partial oxidation of n-butane. We will pay particular attention to industrially relevant examples where possible and attempt to describe the current state of the art. 

Certain systems which behave reversibly in the equilibrium state exhibit considerable polarization in the course of electrolytic reduction examples are the conversion of 5-valent vanadium to the 4-valent state, and of the latter to the 3-valent condition, the reduction of 6- to 5- and of 5- to 3-valent molybdenum, and the reduction of 6-valent to 5-valent tungsten. There is reason to believe, however, that in all these cases the abnormal behavior is to be attributed to the presence of oxide films on the cathode by producing a partial blocking of the surface, these oxide films increase the effective c.d., so that the potential rises. Considerable polarization, accompanied by oxide-film formation, occurs in the reduction of chromate to chromic ions, but it is not certain how far this system is reversible. 

In the present chapter, which deals with theoretical concepts applied to vanadium and molybdenum oxide surfaces, we will restrict the discussion to binary oxide systems. So far, mixed metal oxide systems have not been studied by quantitative theory. Theoretical methods that have been used to study oxide surfaces can be classified according to the approximations made in the system geometry where two different concepts are applied at present, local cluster and repeated slab models. Local cluster models are based on the assumption that the physical/chemical behavior at selected surface sites can be described by finite sections cut out from the oxide surface. These sections (surface clusters) are treated as fictitious molecules with or without additional boundary conditions to take the effect of environmental coupling into account. Therefore, their electro-... 

A number of dissimilar surface compositions and structures develop at the NiAl ordered bulk alloy by preparation dependent effects. Completely different chemical behavior against oxygen adsorption and dissociation has been found for two CujAu surfaces, the (100) and (110) plane, consisting of the same surface composition. The (100) surface with Cu atoms surrounded by Au atoms turns up non-reactive alike Au. On the other hand, the (110) surface with Cu chains in the first layer acts similar to a Cu(l 10) surface. Intermixing or phase separation can be manipulated at CujAu too. Upon vanadium deposition on the bare alloy surface, strong intermixing and alloy formation towards a V3AU... 

We showed the vanadium-titania catalysts to be also effective for oxidation of P-picoline to nicotinic acid [6]. In the present work we studied the influence of the chemical composition of the vanadium-titania system on the phase composition, the structural arrangment and catalytic behavior in p-picoline oxidation. 

The element vanadium exhibits multiple oxidation states in its compounds, including +2. The compound VCI2 is known, whereas SCCI2 is unknown. Use electron configurations and effective nuclear charges to account for this difference in behavior. 

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