Unsaturated media

Yeh G. T., Carpenter S. L., Hopkins P. L., and Siegel M. D. (1995) Users Manual for LEHGC A Lagrangian-Eulerian Finite-element Model of HydroGeoChemical Transport through Saturated-unsaturated Media-version 1.1. Sandia National Laboratories. 

For stationary flow conditions, D and v are independent parameters describing the transport process. In transient conditions, however, the relationship between D and v must be taken into account. Experimental evidences show that for transport in homogeneous saturated porous media, D is a monotoneous function of v. In unsaturated media, this relation becomes extremely complicated since the transport volume 6<,u changes with the water flux. Therefore, the structure of the water fdled pore-space and, hence, the flow field depends on the saturation degree (Flury, M. et al. (1995)) so that the variance of local velocities and the mixing time cannot be simply related to the mean advection velocity. As a consequence, no validated theoretical models exist to calculate the relationship between D and v for unsaturated soils and the dispersivity X cannot be considered to be a material constant, i.e. independent of 0. 

The first term of the equation results from a generalization of Darcy s law of water flow in variably saturated porous media. In this term, k/j is the saturated permeability tensor (m ) K, ( non-dimensional) is the relative permeability of unsaturated media and is a function of the degree of saturation S (For S=l, K,= l) p (kg/m/s) is the viscosity of water p is the density of water, which are both functions of temperature. 

In this paper, only constitutive equations in unsaturated bentonite are explained because the other constrains are almost general. Assuming elasticity of bentonite, increment of total stress in unsaturated media can be written as follows. 

Evaluation of process of swelling pressure in unsaturated media... 

This paper explains only constitutive equations in the unsaturated bentonite because the other consU ains are almost general. Assuming the elasticity of bentonite, the increment of the total stress in unsaturated media is written as follows. 

Yeh GT (1990) HYDROGEOCHEM a coupled model of hydrologic transport and geochemical reactions in saturated-unsaturated media. Technical Report, Department of Civil Engineering, Pennsylvania State University, University Park... 

Equations 15.5a through 15.5c have been shown to accurately model dispersion in saturated porous media and for a stationary flow in unsaturated media. In transient conditions, however, the relationship between hydrodynamic dispersion coefficients and velocity becomes more complicated. In unsaturated media, the water content of the soil changes with the water flux. Hence, the structure of the water-filled pore space also changes with the water flux. The flow field, and therefore the distribution of pore velocities, depends on the saturation of the medium (Flury et al., 1994). As a consequence, dispersivity coefficients are strongly impacted by the volumetric water content. Usually, dispersivity is found to increase when the water content decreases as a result of the larger tortuosity of solute trajectories and a disconnection of continuous flow paths (Vanclooster et al., 2006). In some cases, especially when the activation of macropores significantly enhances pore-water variability, dispersivity is found to increase with volumetric water content. Currently, there is no unique validated theoretical model available for dispersivity in transient unsaturated flow. 

Dicyano-substituted triafulvenes react with enamines to produce exclusively the cross-conjugated dicyanomethylene compounds 519, whose formation can be rationalized by a methylene bicyclo(2,l,0)pentane intermediate 51879 296 Since cyclanone enamines 520 and other cyclic enamines 522 react analogously, this C-C-insertion 237) of the triafulvene ring skeleton into the enamine C=C bond represents a versatile ring expansion mode (C + C3), which makes accessible a series of unsaturated medium-ring compounds (521/523) that are otherwise difficult to synthesize. 

In 1993, we reported that various unsaturated heterocycles can be alkylated with Et-, wPr- and nBuMgCl in the presence of optically pure (EBTHI)ZrCl2 (3a) or (EBTHI)Zr-binol (3b) to afford the derived unsaturated products in >90% ee (cf. 5 6, Scheme 2) [4a]. Many of the simpler five- and six-membered starting materials are available commercially or can be prepared by established procedures. In contrast, catalytic enantioselective reactions involving unsaturated medium ring hetero cycles were not a trivial undertaking the synthesis of these olefinic substrates, by the extant methods, was prohibitively cumbersome. 

It is important to note that the Ru-catalyzed RCM and the Zr-catalyzed resolution can be carried out in a single vessel, without recourse to intermediate isolation. The unsaturated medium-ring amides 5 and 8 can be subjected to 10 mol% of the chiral Zr catalyst and EtMgCl, in the same flask, to afford unsaturated 6 and 9 in 81% and 54% isolated yield, respectively. As depicted in Eq. 1, a similar tandem diene metathesis/ethylmagnesation can be carried out on ether 10, leading to the formation of unsaturated chiral alcohol 11 in 73% yield and >99% ee. 

C. W. Johannes, M. S. Visser, G. S. Weatherhead, A H. Hoveyda Zr-Catalyzed Kinetic Resolution of Allylic Ethers and Mo-Catalyzed Chromene Formation in Synthesis. Enantioselective Total Synthesis of the Antihypertensive Agent (SJUUD-Nebivolol J. Am Chem Soc 1998, 120, 8340-8347. For development of the enantioselective methodology, see M. S. Visser, J. P. A. Harrity, A. H. Hoveyda Zirconium-Catalyzed Kinetic Resolution of Cyclic Allylic Ethers. An Enantioselective Route to Unsaturated Medium Ring Systems , J. Am Chem Soc 1996,118, 3779-3780. 

As an alternative to the lead tetraacetate oxidation, (diacetoxyiodo)benzene can be used to initiate a fragmentation reaction which leads to unsaturated medium-sized lactones [110]. The structures of the starting materials are similar to those of compounds VII/157, VII/160, and VII/163. The same stereochemical consequences are observed as mentioned above. 

This iodine(in) oxidative fragmentation has been exploited to generate unsaturated medium ring lactones in good yields and with complete control of double bond stereochemistiy as shown in Scheme... 

We have developed and improved the numerical code THAMES to predict and assess the coupled THM behaviour in and around the EBS of the geological disposal of high-level radioactive waste. THAMES is a finite element code for analysis of coupled thermal, hydraulic and mechanical behaviour of a saturated-unsaturated medium. Then, we applied THAMES to calculate this task of the DECOVALEX III. In this task, the evolutions and the distributions of stress, relative humidity and temperature at the specified points in bentonite buffer material are required. 

Ohnishi, Y., Shibata, H. and Kobayashi, A. 1987. Development of finite element code for the analysis of coupled thermo-hydro-mechanical behavior of a saturated-unsaturated medium. In Tsang, C.-F. editor. Coupled processes associated with nuclear waste repositories. Academic lYess, Orlando, pp.551-557. 

Ohnishi, Y., Shibata, H. Kobayashi, A. 1985. Development of Finite Element Code for the Analysis of Coupled Thermo-Hydro-Mechanical Behaviors of a Saturated-Unsaturated Medium. Proc. Int. Symp. on Coupled Process Affecting the Preformance of a Nuclear Waste Repository. Berkeley pp.263-268. 

Fragmentation of Lactols to Unsaturated Medium-ring Lactones. Ring cleavage to form a medium-sized ring lactone with a transannular double bond has been observed (eq 21). ... 

Imbs, A.B., and N. A. Latyshev, New A4 and A5 Unsaturated Medium- and Long-Chain Fatty Acids in the Freshwater Sponge Baicalospogia bacilifera, Chem. Phys. Lipids, 92 117-125 (1998). 

Mesityl oxide is on unsaturated, medium-boiling ketone mode by the dehydrotion of diacetone alcohol. 

Sun Z, Ramsay J, Guay M, Ramsay B (2009) Fed-batch production of unsaturated medium-chain-length polyhydroxyalkanoates with controlled composition by Pseudomonas putida KT2440. Appl Microbiol Biotechnol (in press)... 

Unsaturated medium Absence of resources of Good mechanical and thermal... 

More than thirteen carbonate samples are studied to measure classic electric parameters in saturated and unsaturated geological carbonate porous systems. The values of the cementation factor m range finm 1.55 to 2.49. The dolomitic crystal texture shows the highest value. The electrical behaviour of the carbonate porous system in a unsaturated medium is studied from the saturation exponent n. The highest values of n are obtained for a dolomite crystal carbonate (n = 3.5) while the lowest values of n are obtained for a mudstone-wackestone texture (n = 1.2). The values of the chargeability factor M range between 0.19 and 0.5, and they depend on the brine/gas saturation of the carbonate porous system, carbonate textures and the salinity of brine in a porous medium. 

Other unsaturated, medium-side-chain (msc) PHAs from pseudomonads have been lately reported. Lee and colleagues [97] used Pseudomonas sp. A33 and other related organisms isolated by Schirmer et al. [98] to produce various copolyesters. Pseudomonas sp. A33 in the presence of 1, 3-butanediol stored a PHA of 3HB units and nine other different constituents, including the saturated, 16-carbon 3-... 

With Unsaturated Compounds. The reaction of unsaturated organic compounds with carbon monoxide and molecules containing an active hydrogen atom leads to a variety of interesting organic products. The hydroformylation reaction is the most important member of this class of reactions. When the hydroformylation reaction of ethylene takes place in an aqueous medium, diethyl ketone [96-22-0] is obtained as the principal product instead of propionaldehyde [123-38-6] (59). Ethylene, carbon monoxide, and water also yield propionic acid [79-09-4] under mild conditions (448—468 K and 3—7 MPa or 30—70 atm) using cobalt or rhodium catalysts containing bromide or iodide (60,61). 

Dibromo-3-ketones may also be used as substrates for the preparation of A -3-ketones by Joly s method. " Hexamethylphosphoramide has been recommended as a medium suitable for the dehydrobromination of a-bromo ketones to give a, -unsaturated ketones in high yield without rearrange-... 

Unsaturated sulfoncs (314,315) and nitroolcfins (303,315-317) also give alkylation products with enamines. In the latter reactions the formation of nitroethyl or cyclobutane derivatives has been found (316) to depend on the reaction medium as well as steric and electronic parameters which determine the fate of zwitterionic intermediates. Thus no enamine products could... 

A mixture of unsaturated ethers 119 and 120 obtained from methoxybu-tenyne and diethylcarbonate, when reacted with hydroxylamine in an acidic medium, quantitatively forms the ethyl esters of isoxazolecarboxylic acids 129 (81H146). 

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