Inverse

The so-called passive' participle in NENA dialects is said to function as both passive and active. This apory is resolved once it is shown that it is neither one or the other, namely that the opposition is not diathetic to begin with but aspectual. Tha so-called passive participle is perfect(ive) and the so-called active one is imperfect(ive). Transitivity, or rather valency, is narrowly linked to that, and in this language so are ergativity and case.

Systems biology is a new discipline built upon the premise that an understanding of how cells and organisms carry out their functions cannot be gained by looking at cellular components in isolation. Instead, consideration of the interplay between the parts of systems is indispensable for analyzing, modeling, and predicting systems' behavior. Studying biological processes under this premise, systems biology combines experimental techniques and computational methods in order to construct predictive models. Both in building and utilizing models of biological systems, inverse problems arise at several occasions, for example, (i) when experimental time series and steady state data are used to construct biochemical reaction networks, (ii) when model parameters are identified that capture underlying mechanisms or (iii) when desired qualitative behavior such as bistability or limit cycle oscillations is engineered by proper choices of parameter combinations. In this paper we review principles of the modeling process in systems biology and illustrate the ill-posedness and regularization of parameter identification problems in that context. Furthermore, we discuss the methodology of qualitative inverse problems and demonstrate how sparsity enforcing regularization allows the determination of key reaction mechanisms underlying the qualitative behavior.

The paper shows that Thibault's limit sets allow an iff-characterization of local Lipschitzian invertibility in finite dimension. We consider these sets as directional derivatives and extend the calculus in a way that can be used to clarify whether critical points are strongly stable in C ''1 optimization problems.

The capillary pressure in a reservoir determines the saturation distribution, and hence the total in situ volumes of fluids (oil/water/gas). The accurate knowledge of the capillary pressure distribution is one of the primary factors that may be decisive in the reliable estimation of hydrocarbon reserves.

This paper aims to design a mathematical model for determining blood pressures response to cardiac and respiratory parameters. For this purpose a three-compartmental model is investigated to provide a two-nonlinear coupled ordinary differential equations. Stability conditions are established and inverse technics are proposed for identifying model parameters. The validation of the model is achieved throughout a comparative study with an existing model.

Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and lowtemperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As 30 S 70 chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Dn $ 0.84 near k = 770 nm) and the inverse opal As-S photonic structure (Dn $ 1.26 near k = 660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Dn $ 0.434 near k = 600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated ''inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors.

Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

The surface properties of chemical vapor deposition (CVD)-grown, multiwalled carbon nanotubes (CNTs) have been studied using inverse gas chromatography (IGC). By adapting known IGC methodologies to these challenging materials, the surface character of a broad range of CNT materials can be reliably compared and quantified in terms of dispersive and specific surface energies, electron acceptor and donor numbers, and adsorption capacities. The effect of CNT surface modification by high temperature annealing, thermal oxidation, and grafting of methyl methacrylate was explored. The IGC surface characterization of these materials was consistent with results from other surface-sensitive analytical techniques, including X-ray photoelectron spectroscopy (XPS), titration, and electron microscopy, confirming the validity and sensitivity of our approaches. The same IGC methodologies were successfully applied to characterize three as-received CNT materials which differed significantly in their specific surface areas and functional surface group concentrations.

With the help of some techniques based upon certain inverse pairs of symbolic operators, the authors investigate several decomposition formulas associated with Srivastava's hypergeometric functions H A , H B and H C in three variables. Many operator identities involving these pairs of symbolic operators are first constructed for this purpose. By means of these operator identities, as many as 15 decomposition formulas are then found, which express the aforementioned triple hypergeometric functions in terms of such simpler functions as the products of the Gauss and Appell hypergeometric functions. Other closely-related results are also considered briefly.

We tested the hypothesis of synchronous interannual changes in forage fish dynamics around the North Pacific Rim. To do this, we sampled forage fish communities using a seabird predator, the rhinoceros auklet (Cerorhinca monocerata), at six coastal study sites from Japan to California. We investigated whether take of forage fishes was related to local marine conditions as indexed by sea surface temperature (SST). SST was concordant across sites in the eastern Pacific, but inversely correlated between east and west. Forage fish communities consisted of anchovy (Engraulis spp.), sandlance (Ammodytes spp.), capelin (Mallotus spp.), and juvenile rockfish (Sebastes spp.), among others, and take of forage fish varied in response to interannual and possibly lower-frequency oceanographic variability. Take of primary forage species were significantly related to changes in SST only at the eastern sites. We found synchrony in interannual variation of primary forage fishes across several regions in the eastern Pacific, but no significant east-west correlations. Specifically in the Japan Sea, factors other than local SST or interannual variability may more strongly influence forage fishes. Predator diet sampling offers a fishery-independent, large-scale perspective on forage fish dynamics that may be difficult to obtain using conventional means of study.

We present a contrast source inversion (CSI) algorithm using a finite-difference (FD) approach as its backbone for reconstructing the unknown material properties of inhomogeneous objects embedded in a known inhomogeneous background medium. Unlike the CSI method using the integral equation (IE) approach, the FD-CSI method can readily employ an arbitrary inhomogeneous medium as its background. The ability to use an inhomogeneous background medium has made this algorithm very suitable to be used in through-wall imaging and time-lapse inversion applications. Similar to the IE-CSI algorithm the unknown contrast sources and contrast function are updated alternately to reconstruct the unknown objects without requiring the solution of the full forward problem at each iteration step in the optimization process. The FD solver is formulated in the frequency domain and it is equipped with a perfectly matched layer (PML) absorbing boundary condition. The FD operator used in the FD-CSI method is only dependent on the background medium and the frequency of operation, thus it does not change throughout the inversion process. Therefore, at least for the two-dimensional (2D) configurations, where the size of the stiffness matrix is manageable, the FD stiffness matrix can be inverted using a non-iterative inversion matrix approach such as a Gauss elimination method for the sparse matrix. In this case, an LU decomposition needs to be done only once and can then be reused for multiple source positions and in successive iterations of the inversion. Numerical experiments show that this FD-CSI algorithm has an excellent performance for inverting inhomogeneous objects embedded in an inhomogeneous background medium.

We present a contrast source inversion (CSI) algorithm using a finite-difference (FD) approach as its backbone for reconstructing the unknown material properties of inhomogeneous objects embedded in a known inhomogeneous background medium. Unlike the CSI method using the integral equation (IE) approach, the FD-CSI method can readily employ an arbitrary inhomogeneous medium as its background. The ability to use an inhomogeneous background medium has made this algorithm very suitable to be used in through-wall imaging and time-lapse inversion applications. Similar to the IE-CSI algorithm the unknown contrast sources and contrast function are updated alternately to reconstruct the unknown objects without requiring the solution of the full forward problem at each iteration step in the optimization process. The FD solver is formulated in the frequency domain and it is equipped with a perfectly matched layer (PML) absorbing boundary condition. The FD operator used in the FD-CSI method is only dependent on the background medium and the frequency of operation, thus it does not change throughout the inversion process. Therefore, at least for the two-dimensional (2D) configurations, where the size of the stiffness matrix is manageable, the FD stiffness matrix can be inverted using a non-iterative inversion matrix approach such as a Gauss elimination method for the sparse matrix. In this case, an LU decomposition needs to be done only once and can then be reused for multiple source positions and in successive iterations of the inversion. Numerical experiments show that this FD-CSI algorithm has an excellent performance for inverting inhomogeneous objects embedded in an inhomogeneous background medium.

This work is focused on the influence of an ionic liquid (IL), i.e. ethyl-methylimidazolium hexylsulfate, on the spontaneous formation of microemulsions with ionic surfactants. The influence of the ionic liquid on structure formation in the optically clear phase region in water/toluene/pentanol mixtures in presence of the cationic surfactant CTAB was studied in more detail. The results show a significant increase of the transparent phase region by adding the ionic liquid. Conductometric investigations demonstrate that adding the ionic liquid can drastically reduce the droplet-droplet interactions in the L 2 phase. 1 H nuclear magnetic resonance ( 1 H NMR) diffusion coefficient measurements in combination with dynamic light scattering measurements clearly show that inverse microemulsion droplets still exist, but the droplet size is decreased to 2 nm. A more detailed characterisation of the isotropic phase channel by means of conductivity measurements, dynamic light scattering (DLS), 1 H NMR and cryo-scanning electron microscopy (SEM), allows the identification of a bicontinuous sponge phase between the L 1 and L 2 phase. When the poly(ethyleneimine) is added, the isotropic phase range is reduced drastically, but the inverse microemulsion range still exists.

This work is focused on the influence of an ionic liquid (IL), i.e. ethyl-methylimidazolium hexylsulfate, on the spontaneous formation of microemulsions with ionic surfactants. The influence of the ionic liquid on structure formation in the optically clear phase region in water/toluene/pentanol mixtures in presence of the cationic surfactant CTAB was studied in more detail. The results show a significant increase of the transparent phase region by adding the ionic liquid. Conductometric investigations demonstrate that adding the ionic liquid can drastically reduce the droplet-droplet interactions in the L 2 phase. 1 H nuclear magnetic resonance ( 1 H NMR) diffusion coefficient measurements in combination with dynamic light scattering measurements clearly show that inverse microemulsion droplets still exist, but the droplet size is decreased to 2 nm. A more detailed characterisation of the isotropic phase channel by means of conductivity measurements, dynamic light scattering (DLS), 1 H NMR and cryo-scanning electron microscopy (SEM), allows the identification of a bicontinuous sponge phase between the L 1 and L 2 phase. When the poly(ethyleneimine) is added, the isotropic phase range is reduced drastically, but the inverse microemulsion range still exists.

This article examines the divergent voice systems of a selection of Malay/Indonesian varieties. I will show that the voice systems of the different Malay/Indonesian varieties largely (but not completely) reflect the voice systems in the languages in which that variety is spoken. In this way Malay/Indonesian, in its different varieties, can be seen as a mirror on the development of voice systems in Austronesian languages. While many languages show a syntactically privileged 'subject', in many western Austronesian languages (including Malay/Indonesian) some subject properties accrue according to argument structure position, and some other of these properties accrue to the argument that is morphologically marked as 'special' in the clause. At the same time, those Austronesian languages belonging to the (eastern) Oceanic branch lack voice alternations, or else show a simple active/passive dichotomy. The change in the presence and nature voice systems follows the migration path of the Austronesians, moving the highly marked diathesis to a more 'normal' diathesis. The voice systems of the different Malay varieties vary greatly, encompassing almost all the variation that is found across the Austronesian languages. I propose a model in terms of the speakers' access to universal grammar in determining the grammar of the new variety of Malay/Indonesian.

Male bowerbirds collect and decorate their bowers with coloured objects that influence female choice. A recent version of the sensory drive hypothesis claims that female food colour preferences have driven the evolution of female preferences for the colour of male display traits. This hypothesis predicts a positive correlation between male display and food colour preferences. A positive correlation between food and decoration preferences could also arise because of sensory biases built into bowerbirds or the environment. Here we test hypotheses that (1) male and female satin bowerbirds show well-defined food colour preferences, (2) these preferences correlate with independently assessed preferences for bower decorations, and, in a cross-species comparison, (3) food items were used as the first bower decorations. We found that male and female satin bowerbirds, Ptilonorhynchus violaceus, preferentially use long wavelength and were colours as food items. Male decoration preferences were biased towards colours of short wavelength and were negatively correlated with food colour preferences. Our reconstruction of ancestral character states is most consistent with the hypothesis that the original bower decorations were inedible objects and were thus unlikely to have been dual-use traits that also functioned as food items. Our results do not support the hypothesis that food colour preferences have driven the evolution of bower decoration colour preferences nor that sensory drive has caused similar food and decoration preferences, but instead suggest that different factors have shaped female preferences for male display and food colour preferences in bowerbirds.

Effective flocculation and dewatering of mineral processing streams containing colloidal clays has become increasingly urgent. Release of water from slurries in tailings streams and dam beds for recycle water consumption, is usually slow and incomplete. To achieve fast settling and minimization of retained water, individual particles need to be bound, in the initial stages of thickening, into large, high-density aggregates, which may sediment more rapidly with lower intra-aggregate water content. Quantitative cryo-SEM image analysis shows that the structure of aggregates formed before flocculant addition has a determinative effect on these outcomes. Without flocculant addition, 3 stages occur in the mechanism of primary dewatering of kaolinite at pH 8: initially, the dispersed structures already show edgeedge (EE) and edge-face (EF) inter-particle associations but these are open, loose and easily disrupted; in the hindered settling region, aggregates are in adherent, chain-like structures of EE and stairstep face-face (FF) associations; this network structure slowly partially rearranges from EE chains to more compact face-face (FF) contacts densifying the aggregates with increased settling rates. During settling, the sponge-like network structure with EE and FF string-like aggregates, limits dewatering because the steric effects in the resulting partially-gelled aggregate structures are dominant. With flocculant addition, the internal structure and networking of the pre-aggregates is largely preserved but they are rapidly and effectively bound together by the aggregate-bridging action of the flocculant. The effects of initial pH and Ca ion addition on these structures are also analyzed. Statistical analysis from cryo-SEM imaging shows that there is an inverse correlation of intra-aggregate porosity with Darcian inter-aggregate permeability whereas there is a strong positive correlation of Darcian permeability with settling and primary dewatering rate as a function of pH in suspension. Graphs of partial void contributions also suggest that it is not total porosity that dominates permeability in these systems but the abundance of larger intra-aggregate voids.

This paper proposes the analysis and application of the Preisach inverse, which is implemented in a very simple fashion, and allows applying them easily into electromagnetic codes formulated in terms of a vector potential. Such an algorithm has been proposed in realtime control of hysteretic systems but never in the numerical analysis of devices employing ferromagnetic materials. Such a model has also been compared to other Preisach-based models. Their properties are briefly discussed and accurate analyses of their performances are reported, both in terms of accuracy and computational efficiency.

A comprehensive investigation is performed on highly monodisperse silica-based inverse ferrofluids under smallamplitude oscillatory shear in the presence of external magnetic fields up to 1 T. The effect of particle volume fraction and continuous medium Newtonian viscosity is thoroughly investigated. Experimental results for storage modulus are used to validate existing micromechanical magnetorheological models assuming different particle-level field-induced structures.

We consider the problem of detecting elastic inclusions in elastic bodies by means of mechanical boundary data only, that is measurements of boundary displacement and traction. In previous work of some of the present authors, upper and lower bounds on the size (area or volume) of the inclusions were proven analytically. Following the guidelines drawn up in such previous theoretical study, an extended numerical investigation has been performed in order to prove the effectiveness of this approach. The sensitivity with respect to various relevant parameters is also analysed.

This work is focused on the influence of an ionic liquid (IL), i.e. ethyl-methylimidazolium hexylsulfate, on the spontaneous formation of microemulsions with ionic surfactants. The influence of the ionic liquid on structure formation in the optically clear phase region in water/toluene/pentanol mixtures in presence of the cationic surfactant CTAB was studied in more detail. The results show a significant increase of the transparent phase region by adding the ionic liquid. Conductometric investigations demonstrate that adding the ionic liquid can drastically reduce the droplet-droplet interactions in the L 2 phase. 1 H nuclear magnetic resonance ( 1 H NMR) diffusion coefficient measurements in combination with dynamic light scattering measurements clearly show that inverse microemulsion droplets still exist, but the droplet size is decreased to 2 nm. A more detailed characterisation of the isotropic phase channel by means of conductivity measurements, dynamic light scattering (DLS), 1 H NMR and cryo-scanning electron microscopy (SEM), allows the identification of a bicontinuous sponge phase between the L 1 and L 2 phase. When the poly(ethyleneimine) is added, the isotropic phase range is reduced drastically, but the inverse microemulsion range still exists.

Models for deep bed filtration in the injection of sea water with solid inclusions depend on an empirical filtration function that represents the rate of particle retention. This function must be calculated indirectly from experimental measurements of other quantities. The practical petroleum engineering purpose is to predict injectivity loss in the porous rock around wells. In this work, we determine the filtration function from the effluent particle concentration history measured in laboratory tests knowing the inlet particle concentration.

First the principles of mapping spatial points to surfaces is introduced in the context of the inverse kinematics of a general six revolute serial wrist partitioned robot. Then the advantage of choosing ideal frames is illustrated by showing that in the case of some architectures an image space formulation, though possible, may be an impediment to clear geometric insight and a satisfactory and much simpler solution. After showing how the general point mapping transformation is reduced to classical Blaschke-Grünwald planar mapping a novel three legged planar robot's direct kinematics is solved in image space and then using conventional "distance" constraints. The purpose is to show why the latter approach yields spurious solutions and how the displacement pole rotation performed with kinematic mapping reliably avoids this problem. In conclusion certain other new and/or interesting reduced mobility parallel robots are discussed briefly to point out some advantages and insights gained with an image space approach. Particular effort is made to expose in detail how mapping simplifies and extends the solution of direct kinematics pertaining to Calvel's "Delta" 3D translational robot.

We study the boundedness on L p of the Riesz transform ∇L −1/2 , where L is one of several operators defined on R or R + , endowed with the measure r d−1 dr, d > 1, where dr is Lebesgue measure. For integer d, this mimics the measure on Euclidean d-dimensional space, and in this case our setup is equivalent to looking at the Laplacian acting on radial functions on Euclidean space or variations of Euclidean space such as the exterior of a sphere (with either Dirichlet or Neumann boundary conditions), or the connected sum of two copies of R d . In this way we illuminate some recent results on the Riesz transform on asymptotically Euclidean manifolds.

An RD-spaceX is a space of homogeneous type in the sense of Coifman and Weiss with the additional property that a reverse doubling property holds. The authors prove that for a space of homogeneous typeX having \dimension" n, there exists a p02 (n=(n + 1); 1) such that for certain classes of distributions, the Lp(X ) quasi-norms of their radial

The present research study focuses on the analysis and characterization of certain aspects of the dynamic behavior displayed by persistent chemicals in a multimedia environment (chemodynamics), which is jointly determined by the inherent physicochemical properties of the chemical substance under consideration, as well as underlying environmental processes such as degradation in different phases/media (soil, water and air) coupled with intermedia transport (interphase mass transfer). In particular, dynamic multimedia environmental models are considered with constant source terms describing steady chemical release/discharge rates into various environmental media of interest, and key risk-related aspects of the dynamic behavior of persistent chemicals are analyzed using perturbation theory techniques under conditions where degradation rates in different media are considerably slower than intermedia transport rates. Under the above conditions, the problem of defining physically meaningful and practical quantitative measures of overall persistence of chemicals in a multimedia environment is revisited, given its role as a key exposure-based indicator within all major chemical risk assessment frameworks, and a proof is provided N. Kazantzis (B) J Math Chem (2010) 48:290-304 291 that rigorously establishes equivalence between two important and popular persistence measures, namely the characteristic time at steady state and the inverse of the associated chemodynamics overall decay rate (slowest chemodynamic mode).

Models for deep bed filtration in the injection of sea water with solid inclusions depend on an empirical filtration function that represents the rate of particle retention. This function must be calculated indirectly from experimental measurements of other quantities. The practical petroleum engineering purpose is to predict injectivity loss in the porous rock around wells. In this work, we determine the filtration function from the effluent particle concentration history measured in laboratory tests knowing the inlet particle concentration.

We define in the space of n × m matrices of rank n, n ≤ m, the condition Riemannian structure as follows: For a given matrix A the tangent space at A is equipped with the Hermitian inner product obtained by multiplying the usual Frobenius inner product by the inverse of the square of the smallest singular value of A denoted σ n (A). When this smallest singular value has multiplicity 1, the function A → log(σ n (A) −2 ) is a convex function with respect to the condition Riemannian structure that is t → log(σ n (A(t)) −2 ) is convex, in the usual sense for any geodesic A(t). In a more abstract setting, a function α defined on a Riemannian manifold (M, , ) is said to be * Mathematics Subject Classification (MSC2000): 65F35 (Primary), 15A12 (Secondary).

A new matroid is introduced: this matroid is deÿned starting from any matroid and one of its bases, hence we call it base-matroid. Besides some properties of the base-matroid, a non-trivial algorithm for the solution of the related matroid optimization problem is presented. The new matroid has application in the ÿeld of inverse combinatorial optimization problems. We discuss in detail the LP formulation of the inverse matroid optimization problem and we propose an e cient algorithm for computing its primal and dual solutions. ?

An RD-space X is a space of homogeneous type in the sense of Coifman and Weiss with the additional property that a reverse doubling property holds. The authors prove that for a space of homogeneous type X having "dimension" n, there exists a p 0 ∈ (n/(n + 1), 1) such that for certain classes of distributions, the L p (X ) quasi-norms of their radial maximal functions and grand maximal functions are equivalent when p ∈ (p 0 , ∞]. This result yields a radial maximal function characterization for Hardy spaces on X .

In this work, the sign distribution for all inverse elements of general tridiagonal H-matrices is presented. In addition, some computable upper and lower bounds for the entries of the inverses of diagonally dominant tridiagonal matrices are obtained. Based on the sign distribution, these bounds greatly improve some well-known results due to [23], [26], Nabben (1999) and recently given by [24], Peluso and Popolizio [25] and so forth. It is also stated that the inverse of a general tridiagonal matrix may be described by 2n − 2 parameters ({θ k } n k=2 and {ϕ k } n−1 k=1 ) instead of 2n + 2 ones as given by [3], El-Mikkawy and Karawia (2006) [4] and [10]. According to these results, a new symbolic algorithm for finding the inverse of a tridiagonal matrix without imposing any restrictive conditions is presented, which improves some recent results. Finally, several applications to the preconditioning technology, the numerical solution of differential equations and the birth-death processes together with numerical tests are given.

We analyze the effective potential for nanoparticles trapped at a fluid interface within a simple model which incorporates surface and line tensions as well as a thermal average over interface fluctuations (capillary waves). For a single colloid, a reduced steepness of the potential well hindering movements out of the interface plane compared to rigid interface models is observed, and an instability of the capillary wave partition sum in case of negative line tensions is pointed out. For two colloids, averaging over the capillary waves leads to an effective Casimir-type interaction which is long-ranged, power-like in the inverse distance but whose power sensitively depends on possible restrictions of the colloid degress of freedom. A nonzero line tension leads to changes in the magnitude but not in the functional form of the effective potential asymptotics.

The inversion of the one-dimensional Radon transform on the rotation group SO(3) is an ill posed inverse problem which applies to X-ray tomography with polycrystalline materials. This communication presents a novel approach to the numerical inversion of the one-dimensional Radon transform on SO(3). Based on a Fourier slice theorem the discrete inverse Radon transform of a function sampled on the product space S 2 × S 2 of two two-dimensional spheres is determined as the solution of a minimization problem, which is iteratively solved using fast Fourier techniques for S 2 and SO(3). The favorable complexity and stability of the algorithm based on these techniques has been confirmed with numerical tests.

Surveillance data from an oncology hospital unit on Vancomycin-resistant Enterococcus (VRE), one of the most prevalent and dangerous pathogens involved in hospital infections, is used to motivate possibilities of modeling nosocomial infection dynamics. This is done in the context of hospital monitoring and isolation procedures as a prelude to the evaluation and improved design of control measures. A discrete event delay differential equation model in conjunction with statistical computational methods is formulated to estimate key population-level nosocomial transmission parameters and isolation procedures. This framework is used to test the surveillance data's usefulness in model validation. In the process of model calibration we discovered significant irregularities in the available surveillance data; these irregularities are most likely the result of the data observational recordingprocess as well as those in the isolation procedures. Efforts to fit data within our highly flexible dynamic-modeling framework suggest that clinical-trial level surveillance data is needed if one is to successfully develop quantitative models for disease transmission and intervention. It is concluded that typical "cold" data sets typically encountered in biological/sociological quantitative modeling efforts may be inadequate for support of serious model development.

We present a general method for estimating the location of small, well-separated scatterers in a randomly inhomogeneous environment using an active sensor array. The main features of this method are (i) an arrival time analysis of the echo received from the scatterers, (ii) a singular value decomposition of the array response matrix in the frequency domain, and (iii) the construction of an objective function in the time domain that is statistically stable and peaks on the scatterers. By statistically stable we mean here that the objective function is self-averaging over individual realizations of the medium. This is a new approach to array imaging that is motivated by time reversal in random media, analyzed in detail previously. It combines features from seismic imaging like arrival time analysis with frequency-domain signal subspace methodology like MUltiple SIgnal Classification (MUSIC). We illustrate the theory with numerical simulations for ultrasound.

A schema mapping is a specification that describes how data from a source schema is to be mapped to a target schema. Once the data has been transferred from the source to the target, a natural question is whether one can undo the process and recover the initial data, or at least part of it. In fact, it would be desirable to find a reverse schema mapping from target to source that specifies how to bring the exchanged data back.