Assay of ascorbic phosphates and in-vitro availability assay of ascorbic mono-and polyphosphates

A method was devised to assay ascorbic phosphate esters in biological materials by potassium bromoxide hydrolysis followed by determination of the liberated ascorbic acid. For the differential measurement of ascorbic acid and ascorbic phosphate, a spectrophotometric method was employed to screen out the interfering substances based on studies of absorbance curves of 2,4-dinitrophenyl hydrazine derivatives. A variety of vertebrate tissues were examined for phosphatase activity on ascorbic phosphate esters. The results suggest that pigeon kidney, rat liver and several tissues of fishes readily hydrolyse ascorbic monophosphate but not ascorbic polyphosphate. Hydrolysis of ascorbic monophosphate is completed by both phosphatases of intestine, kidney and liver acting at neutral pH and phosphatase of stomach acting at acid pH. Thus, ascorbic monophosphate has the potential to be a source of available vitamin C in vivo, and this explains its antiscorbutic activity in scurvy-prone animals.     

Calculating the steady-state polarizations of quantum cellular automata (QCA) circuits

We present on the use of well-known stochastic methods for computing the steady-state polarizations of quantum cellular automata (QCA) circuits. Typically, a Boltzmann distribution, which requires the exploration of the complete configuration space of an \(N\) -cell QCA circuit, is used to compute the \(2^N\) steady-states of the QCA circuit. However, the exponential growth in states as the circuit size grows makes computing the Boltzmann distribution infeasible for large circuits. Thus, we approximate the Boltzmann distribution of a QCA circuit by conducting a partial exploration of the complete configuration space by means of a Monte Carlo method, simulated annealing, and a genetic algorithm. The approximated Boltzmann distribution from each method was able to compute the steady-state polarizations with a very high degree of accuracy, with the simulated annealing algorithm producing the best results.     

Measures of overall persistence and the temporal remote state

The overall persistence, Pov, has been suggested as an indicator that integrates single media half-lives and phase partitioning. However, the application of this indicator is hindered by the fact that there are different definitions of Pov and that the most common measure of Pov, the residence time at steady state, depends heavily on the release pattern. Here, different measures are compared that can be used to compute Pov from the mass of a chemical in the environment as a function of time in a dynamic multimedia model. These measures include the equivalence width, which corresponds to the residence time at steady state, the mean value of the function of mass vs time ("mean time"), and the clearance time. The temporal remote state is defined as the state of the model system long after the stop of emissions; it is independent of the release pattern of a chemical. The mean time in the temporal remote state reflects the long-term removal rate of a chemical and is used as a persistence benchmark. Correlations of the three measures of Pov to the persistence benchmark are analyzed. The maximum equivalence width, which is obtained with release to one of the media air, water, or soil, is a good approximation of the mean time in the temporal remote state. Because the maximum equivalence width is identical to the maximum residence time at steady state, the mean time in the temporal remote state can be estimated with existing steady-state models.     

The role of state policies and programs in buffering the effects of poverty on children's immunization receipt

OBJECTIVES: This study assessed the influence of public policies on the immunization status of 2-year old children in the United States. METHODS: Up-to-dateness for the primary immunization series was assessed in a national sample of 8100 children from the 1988 National Maternal and Infant Health Survey and its 1991 Longitudinal Follow-Up. RESULTS: Documented immunization rates of this sample were 33% for poor children and 44% for others. More widespread Medicated coverage was associated with greater likelihood of up-to-dateness among poor children. Up-to-dateness was more likely for poor children with public rather than private sources of routine pediatric care, but all children living in states where most immunizations were delivered in the public sector were less likely to be up to date. Poor children in state with partial vaccine replacement programs were less likely to be up to date than those in free-market purchase states. CONCLUSIONS: While state policies can enhance immunization delivery for poor children, heavy reliance on public sector immunization does not ensure timely receipt of vaccines. Public- and private-sector collaboration is necessary to protect children from vaccine-preventable diseases.     

Video Condensation by Ribbon Carving

Efficient browsing of long video sequences is a key tool in visual surveillance, e.g., for postevent video forensics, but can also be used for fast review of motion pictures and home videos. While frame skipping (fixed or adaptive) is straightforward to implement, its performance is quite limited. Although more efficient techniques have been developed, such as video summarization and video montage, they lose either the temporal or semantic context of events. A recently proposed method called video synopsis deals with some of these issues but involves multiple processing stages and is fairly complex. Video condensation, that we propose here, is novel in the way information is removed from the space-time video volume, is conceptually simple and relatively easy to implement. We introduce the concept of a video ribbon inspired by that of a seam recently proposed for image resizing. We recursively carve ribbons out by minimizing an activity-aware cost function using dynamic programming. The ribbon model we develop is flexible and permits an easy adjustment of the compromise between temporal condensation ratio and anachronism of events. We also propose sliding-window ribbon carving to handle streaming video and demonstrate the method's efficiency on motor and pedestrian traffic data.     

Approximated matrix decomposition for IMRT planning with multileaf collimators

A standard problem in intensity modulated radiation therapy is the representation of a given intensity matrix, i.e. a matrix of nonnegative integers, as a nonnegative linear combination of special 0-1-matrices, called segments. These segments can be practically realized by multileaf collimators. One important aim is the minimization of the sum of the coefficients of the linear combination, i.e. the delivery time. In this article, we study the question how much the delivery time can be reduced if some small deviation from the given intensity matrix is allowed. We characterize the optimal solutions for one-row matrices and show that the approximation can be carried out in an iterative way. The structural characterization yields a fast algorithm that minimizes the delivery time and then also the deviation. Moreover, algorithms for the general case together with numerical results are presented.     

Interplay and Competition Between Superconductivity and Charge Orderings in the Zero-Bandwidth Limit of the Extended Hubbard Model with Pair Hopping and on-Site Attraction

We present studies of an effective model which is a simple generalization of the standard model of a local pair superconductor with on-site pairing (i.e., the model of hard core bosons on a lattice) to the case of finite pair binding energy. The tight binding Hamiltonian consists of (i) the effective on-site interaction U, (ii) the intersite density-density interactions W between nearest-neighbors, and (iii) the intersite charge exchange term I, determining the hopping of electron pairs between nearest-neighbor sites. In the analysis of the phase diagrams and thermodynamic properties of this model, we treat the intersite interactions within the mean-field approximation. Our investigations of the U<0 and W>0 case show that, depending on the values of interaction parameters, the system can exhibit three homogeneous phases: superconducting (SS), charge-ordered (CO), and nonordered (NO) as well as the phase separated SS–CO state.     

Two-constraint domain decomposition with Space Filling Curves

In scientific computing, Space Filling Curves are a widely used tool for one-constraint domain decomposition. They provide a mechanism to sort multi-dimensional data in a locality preserving way, and, in this way, a (one dimensional) list of mesh elements is established which is subsequently split into 3 partitions under consideration of the constraint. This procedure has a runtime of O(NlogN) (N is the number of mesh elements) while nearly perfect load balancing can be established with reasonable partition surface sizes.In this work, we discuss the extensibility of this procedure to two-constraint settings which is desirable, since the methodology is extremely fast. Here, the splitting operation is subject to two constraints, and, unlike to the one-constraint case, obtaining near perfect balancing is often hard to establish, and is, even more as in the one-constraint case, in conflict with the induced surface sizes (or edge-cuts). We discuss multiple strategies to tackle the splitting, and we present a fast, O(NlogN) splitting heuristic algorithm which provides an integer σ that allows to trade off between balancing and surface sizes which results in a O(NlogN) two-constraint decomposition method. Results are compared to the multi-constraint domain decomposition abilities implemented in the Metis software package, and show that the method produces higher surface sizes, but is orders of magnitudes faster which makes the method superior for certain applications.