Eruption dynamics of CO₂-driven cold-water geysers: Crystal, Tenmile geysers in Utah and Chimayo geyser in New Mexico

Watson, Z.T.,Han, W.S.,Keating, E.H.,Jung, N.H.,Lu, M. North-Holland Pub. Co ; Elsevier Science Ltd 2014 Earth and planetary science letters Vol.408 No.-

The CO<SUB>2</SUB> bubble volume fraction, eruption velocity, flash depth and mass emission of CO<SUB>2</SUB> were determined from multiple wellbore CO<SUB>2</SUB>-driven cold-water geysers (Crystal and Tenmile geysers, in Utah and Chimayo geyser in New Mexico). At shallow depths the bubble volume fraction ranges from 0 to 0.8, eruption velocities range from 2 to 20 m/s and flash depths are predominately shallow ranging from 5 to 40 m below the surface. Annual emission of CO<SUB>2</SUB> is estimated to be (4.77+/-1.92)x10<SUP>3</SUP>, (6.17+/-1.73)x10<SUP>1</SUP>, (6.54+/-0.57)x10<SUP>1</SUP>t/yr for Crystal, Tenmile and Chimayo geysers, respectively. These estimates are coherent with Burnside et al. (2013) showing that the rate of CO<SUB>2</SUB> leakage from wellbores is greater than fault-parallel or diffuse CO<SUB>2</SUB> leakage. The geyser plumbing geometry consists of a vertical wellbore which allows for the upward migration of CO<SUB>2</SUB>-rich fluids due to artesian conditions. The positive feedback system of a CO<SUB>2</SUB>-driven eruption occurs within the well. Active inflow of CO<SUB>2</SUB> into the regional aquifers through faulted bedrock allows geysering to persist for decades. Crystal geyser erupts for over 24 h at a time, highlighting the potential for a wellbore in a natural environment to reach relatively steady-state high velocity discharge. Mitigating high velocity CO<SUB>2</SUB>-driven discharge from wellbores will, however, be easier than mitigating diffuse leakage from faults or into groundwater systems.

Synthesis and optimization of ceftriaxone-loaded solid lipid nanocarriers

Kumar, S.,Bhanjana, G.,Kumar, A.,Taneja, K.,Dilbaghi, N.,Kim, K.H. North-Holland Pub. Co ; Elsevier Science Ltd 2016 Chemistry and physics of lipids Vol.200 No.-

<P>The use of nanocarriers to enhance drug delivery efficacy has been increasing in the healthcare field due to their tunable surface properties. In this study, ceftriaxone-loaded solid lipid nanoparticles (CL-SLNPs) were synthesized using a water-in-oil-in-water (w/o/w) type double emulsification method. The formulation was optimized using response surface methodology (RSM) and was characterized using transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), and UV vis and Fourier transform infrared (FTIR) spectroscopy. The CL-SLNPs were of spherical shape, 15-20 nm in size, and retained the properties of the drug or other constituents/ingredients after loading. The prepared nanoformulation offered sustained drug release after 24 h, while ceftriaxone sodium followed a burst release. Antibacterial activity of the nanoformulation was evaluated against different gram-positive and gram-negative bacterial strains. The minimum inhibitory concentration of CL-SLNPs against Pseudomonas aeruginosa was determined as 31 mu g/mL. (C) 2016 Elsevier Ireland Ltd. All rights reserved.</P>

Potential theory of subordinate Brownian motions with Gaussian components

Kim, P.,Song, R.,Vondracek, Z. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Stochastic processes and their applications Vol.123 No.3

In this paper we study a subordinate Brownian motion with a Gaussian component and a rather general discontinuous part. The assumption on the subordinator is that its Laplace exponent is a complete Bernstein function with a Levy density satisfying a certain growth condition near zero. The main result is a boundary Harnack principle with explicit boundary decay rate for non-negative harmonic functions of the process in C<SUP>1,1</SUP> open sets. As a consequence of the boundary Harnack principle, we establish sharp two-sided estimates on the Green function of the subordinate Brownian motion in any bounded C<SUP>1,1</SUP> open set D and identify the Martin boundary of D with respect to the subordinate Brownian motion with the Euclidean boundary.

Statistical inference and visualization in scale-space using local likelihood

Park, C.,Huh, J. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.57 No.-

SiZer (SIgnificant ZERo crossing of the derivatives) is a graphical scale-space visualization tool that allows for exploratory data analysis with statistical inference. Various SiZer tools have been developed in the last decade, but most of them are not appropriate when the response variable takes discrete values. In this paper, we develop a SiZer for finding significant features using a local likelihood approach with local polynomial estimators. This tool improves the existing one (Li and Marron, 2005) by proposing a theoretically justified quantile in a confidence interval using advanced distribution theory. In addition, we investigate the asymptotic properties of the proposed tool. We conduct a numerical study to demonstrate the sample performance of SiZer using Bernoulli and Poisson models using simulated and real examples.

Credibility theory based on trimming

Kim, J.H.T.,Jeon, Y. North-Holland, Pub. Co ; Elsevier Science Ltd 2013 Insurance, mathematics & economics Vol.53 No.1

The classical credibility theory proposed by Buhlmann has been widely used in general insurance applications. In this paper we propose a credibility theory via truncation of the loss data, or the trimmed mean. The proposed framework contains the classical credibility theory as a special case and is based on the idea of varying the trimming threshold level to investigate the sensitivity of the credibility premium. After showing that the trimmed mean is not a coherent risk measure, we investigate some related asymptotic properties of the structural parameters in credibility. Later a numerical illustration shows that the proposed credibility models can successfully capture the tail risk of the underlying loss model, thus providing a better landscape of the overall risk that insurers assume.

Robust inference using hierarchical likelihood approach for heavy-tailed longitudinal outcomes with missing data: An alternative to inverse probability weighted generalized estimating equations

Lee, D.,Lee, Y.,Paik, M.C.,Kenward, M.G. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.59 No.-

We examine methods appropriate for heavy-tailed longitudinal outcomes with possibly missing data. Generalized estimating equations (GEEs) have been widely used in longitudinal studies when data are not heavy-tailed and, in general, are valid only when data are missing completely at random. Robins et al. (1995) showed how inverse probability weighting in such settings (IPW-GEE) can extend validity to data that are missing at random. When data are completely observed, Preisser and Qaqish (1999) proposed the use of robust GEE methods to handle outliers. A natural extension of this to the setting with missing data is to combine these two methods. One alternative for the same setting is to use hierarchical (h-) likelihood (Lee et al., 2006). Here we compare this approach with that of IPW-GEE for heavy-tailed data in the missing data context.

The algorithmic complexity of bondage and reinforcement problems in bipartite graphs

Hu, F.T.,Sohn, M.Y. North-Holland Pub. Co ; Elsevier Science Ltd 2014 Theoretical computer science Vol.535 No.-

Let G=(V,E) be a graph. A subset D@?V is a dominating set if every vertex not in D is adjacent to a vertex in D. The domination number of G, denoted by γ(G), is the smallest cardinality of a dominating set of G. The bondage number of a nonempty graph G is the smallest number of edges whose removal from G results in a graph with domination number larger than γ(G). The reinforcement number of G is the smallest number of edges whose addition to G results in a graph with smaller domination number than γ(G). In 2012, Hu and Xu proved that the decision problems for the bondage, the total bondage, the reinforcement and the total reinforcement numbers are all NP-hard in general graphs. In this paper, we improve these results to bipartite graphs.

Oscillation of harmonic functions for subordinate Brownian motion and its applications

Kim, P.,Lee, Y. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Stochastic processes and their applications Vol.123 No.2

In this paper, we establish an oscillation estimate of nonnegative harmonic functions for a pure-jump subordinate Brownian motion. The infinitesimal generator of such subordinate Brownian motion is an integro-differential operator. As an application, we give a probabilistic proof of the following form of relative Fatou theorem for such subordinate Brownian motion X in a bounded κ-fat open set; if u is a positive harmonic function with respect to X in a bounded κ-fat open set D and h is a positive harmonic function in D vanishing on D<SUP>c</SUP>, then the non-tangential limit of u/h exists almost everywhere with respect to the Martin-representing measure of h.

M-type smoothing spline estimators for principal functions

Lee, S.,Shin, H.,Billor, N. North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.66 No.-

We propose a robust method for estimating principal functions based on MM estimation. Specifically, we formulate functional principal component analysis into alternating penalized M-regression with a bounded loss function. The resulting principal functions are given as M-type smoothing spline estimators. Using the properties of a natural cubic spline, we develop a fast computation algorithm even for long and dense functional data. The proposed method is efficient in that the maximal information from whole observed curve is retained since it partly downweighs abnormally observed individual measurements in a single curve rather than removing or downweighing a whole curve. We demonstrate the performance of the proposed method on simulated and real data and compare it with the conventional functional principal component analysis and other robust functional principal component analysis techniques.

Non-linear molecular pattern classification using molecular beacons with multiple targets

Lee, I.H.,Lee, S.H.,Park, T.H.,Zhang, B.T. North-Holland Pub. Co ; Elsevier Science Ltd ; Els 2013 Bio systems Vol.114 No.3

In vitro pattern classification has been highlighted as an important future application of DNA computing. Previous work has demonstrated the feasibility of linear classifiers using DNA-based molecular computing. However, complex tasks require non-linear classification capability. Here we design a molecular beacon that can interact with multiple targets and experimentally shows that its fluorescent signals form a complex radial-basis function, enabling it to be used as a building block for non-linear molecular classification in vitro. The proposed method was successfully applied to solving artificial and real-world classification problems: XOR and microRNA expression patterns.