| 1. |
- Dagan, G., et al.
(author)
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Tailing of the breakthrough curve in aquifer contaminant transport : The impact of permeability spatial variability
- 2008
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Conference paper (peer-reviewed)abstract
- A contaminant plume of mass Mo is inserted at time t = 0 at an injection plane at × = 0 in an aquifer of spatially variable conductivity K. The log-conductivity Y = InK is modelled as stationary and isotropic, of univariate distribution f(Y), and of finite integral scale I. The flow of water is uniform in the mean (natural gradient) and the plume is of large transverse extent relative to the integral scale. Advective transport and longitudinal spread are quantified by the solute mass arrival ("breakthrough curve", BTC) M(t,x) at a control plane at × > I. For a large plume (ergodic conditions) the relative mass flux μ(t,x) = (l/Mo)M/t is approximately equal to the probability density function of travel times of solute particles f(τx) and the latter is used to analyse transport. f(τx) is derived by adopting a structural model of the aquifer that contains spherical or cubic inclusions of uniform size and of independent Y that fill the space. Such a structure can represent any formation of given f(Y) and I. The flow and transport solutions are obtained by a simple semianalytical model and by accurate numerical simulations. The travel time distribution at few control planes is determined for a log-normal f(K) first. Under the assumption of weak heterogeneity, i.e. for small variance σy 2 and for x»I, the travel time distribution is symmetrical and Gaussian. Subsequently, by using the semi-analytical model and numerical simulations we derive f(τx) for a highly heterogeneous formation of σ y 2 = 2. The main finding is f(τx) is highly skewed due to the presence of a thin, but long tail, for large travel times. The tail is of significance to applications that deal with aquifer pollution and remediation. The tail is related to the large residence time of solute particles in blocks of low conductivity. A simple relationship is established between the tail of f(Y) for low K and that f(τx) for large τ. To further examine the impact of the log-conductivity distribution on BTC tailing, a non-Gaussian model, the subordinate model, is adopted for f(Y). This distribution depends on an additional parameter Is; travel time distribution tends to normal for Is→0, whereas the tails of the two distributions are different for Is > 0. This choice reflects the difficulty of identification of the tail of f(Y) based on field data. The relevance of results to applications is examined in terms of impact of conductivity spatial distribution, as well as influence of plume size (non-ergodic behaviour) and diffusion.
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| 2. |
- Fiori, A., et al.
(author)
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Tailing of the breakthrough curve in aquifer contaminant transport : Equivalent longitudinal macrodispersivity and occurrence of anomalous transport
- 2008
-
Conference paper (peer-reviewed)abstract
- We analyse the mass arrival (breakthrough curve) at control planes at × of a plume of conservative solute injected at time t = 0 in the plane × = 0. The formation is of random three-dimensional stationary and isotropic conductivity K, characterized by the univariate normal distribution f(Y), Y = lnK, and the integral scale I. The flow is uniform in the mean, of velocity U, and longitudinal transport is quantified by f(z,x), the probability density function (pdf) of travel time r at x. We characterize transport by an equivalent longitudinal macrodispersivity αL(x), which is proportional to the variance of the travel time. If αL is constant, transport is coined as Fickian, while it is anomalous if αL increases indefinitely with x. If f(z,x) is normal (for × I), transport is coined as Gaussian and the mean concentration satisfies an ADE with constant coefficients. For the subordinate structural model transport is anomalous, in spite of the closeness of the conductivity distribution to the lognormal one. To further analyse anomalous behaviour, a relationship is established between the shape of f(K) for K→0 and the behaviour of αL, arriving at criteria for normal or anomalous transport. The model is used in order to compare results with the recent ones presented in the literature, which are based on the Continuous Time Random Walk (CTRW) approach. It is found that a class of anomalous transport cases proposed by CTRW methodology cannot be supported by a conductivity structure of finite integral scale.
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| 3. |
- Rajic, Zoran A, et al.
(author)
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Size of the protein-coding genome and rate of molecular evolution.
- 2005
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In: Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1434-5161 .- 1435-232X. ; 50:5, s. 217-29
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Journal article (peer-reviewed)abstract
- In diploid populations of size N, there will be 2 Nmu mutations per nucleotide (nt) site (or per locus) per generation (mu stands for mutation rate). If either the population or the coding genome double in size, one expects 4 Nmu mutations. What is important is not the population size per se but the number of genes (coding sites), the two being often interconverted. Here we compared the total physical length of protein-coding genomes (n) with the corresponding absolute rates of synonymous substitution (K(S)), an empirical neutral reference. In the classical occupancy problem and in the coupons collector (CC) problem, n was expressed as the mean rate of change (K(CC)). Despite inherently very low power of the approaches involving averaging of rates, the mode of molecular evolution of the total size phenotype of the coding genome could be evidenced through differences between the genomic estimates of K(CC) [K(CC)=1/(ln n + 0.57721) n] and rate of molecular evolution, K(S). We found that (1) the estimates of n and K(S) are reciprocally correlated across taxa (r=0.812; p<< 0.001); (2) the gamete-cell division hypothesis (Chang et al. Proc Natl Acad Sci USA 91:827-831, 1994) can be confirmed independently in terms of K(CC)/K(S) ratios; (3) the time scale of molecular evolution changes with change in mutation rate, as previously shown by Takahata (Proc Natl Acad Sci USA 87:2419-2423, 1990), Takahata et al. (Genetics 130:925-938, 1992), and Vekemans and Slatkin (Genetics 137:1157-1165, 1994); (4) the generation time and population size (Lynch and Conery, Science 302:1401-1404, 2003) effects left their "signatures" at the level of the size phenotype of the protein-coding genome.
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| 4. |
- von Mackensen, S., et al.
(author)
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Development of a disease-specific quality of life questionnaire for children & adolescents with idiopathic thrombocytopenic purpura (ITP-QoL)
- 2006
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In: Pediatric Blood & Cancer. - : Wiley. - 1545-5017 .- 1545-5009. ; 47:Suppl.5, s. 688-691
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Journal article (peer-reviewed)abstract
- Quality of life (QoL) assessment in children with coagulation disorders is a relatively unstudied area. While hemophilia-specific questionnaires (such as Haemo-QoL) are available, no instrument for children with idiopathic thrombocytopenic purpura (ITP) has been validated yet. A disease-specific questionnaire for children with ITP was therefore developed (ITP-QoL) in three phases: (a) a preparatory phase; (b) a developmental phase; (c) a pilot testing phase. Since dimensions of Haemo-QoL were considered important for children with ITP, items were adapted, reformulated and additional dimensions were included. Two age-group versions were designed for children (aged 3-7, 8-18 years) and parents in Italian, German, and Swedish languages and were pilot tested. Pediatr Blood Cancer 2006;47:688-691. (c) 2006 Wiley-Liss, Inc.
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