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>

Planar graphs with girth at least 5 are (3,5)-colorable

Choi, I.,Raspaud, A. North-Holland Pub. Co ; Elsevier Science Ltd 2015 Discrete mathematics Vol.338 No.4

A graph is (d<SUB>1</SUB>,...,d<SUB>r</SUB>)-colorable if its vertex set can be partitioned into r sets V<SUB>1</SUB>,...,V<SUB>r</SUB> where the maximum degree of the graph induced by V<SUB>i</SUB> is at most d<SUB>i</SUB> for each i@?{1,...,r}. Let G<SUB>g</SUB> denote the class of planar graphs with minimum cycle length at least g. We focus on graphs in G<SUB>5</SUB> since for any d<SUB>1</SUB> and d<SUB>2</SUB>, Montassier and Ochem constructed graphs in G<SUB>4</SUB> that are not (d<SUB>1</SUB>,d<SUB>2</SUB>)-colorable. It is known that graphs in G<SUB>5</SUB> are (2,6)-colorable and (4,4)-colorable, but not all of them are (3,1)-colorable. We prove that graphs in G<SUB>5</SUB> are (3,5)-colorable, leaving two interesting questions open: (1) are graphs in G<SUB>5</SUB> also (3,d<SUB>2</SUB>)-colorable for some d<SUB>2</SUB>@?{2,3,4}? (2) are graphs in G<SUB>5</SUB> indeed (d<SUB>1</SUB>,d<SUB>2</SUB>)-colorable for all d<SUB>1</SUB>+d<SUB>2</SUB>≥8 where d<SUB>2</SUB>≥d<SUB>1</SUB>≥1?

Advances in seeded dimension reduction: Bootstrap criteria and extensions

North-Holland Pub. Co ; Elsevier Science Ltd 2013 Computational statistics & data analysis Vol.60 No.-

A seeded dimension reduction approach recently developed provides a paradigm to enable existing dimension reduction methods for the central subspace to be adapted to regressions with n<p. The approach is based on successive projection of a seed matrix on a subspace to contain the central subspace. In the article, we will suggest a bootstrap determination procedure to select a proper value for terminating the projections. Also, extensions of seeded dimension reduction are proposed to cover more various types of regressions with n<p such as a categorical predictor regression and survival regression. Then we apply the new development to analyze diffuse large-B-cell lymphoma data and leukemia data. Numerical studies are also presented.

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.

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.

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.

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.

Non-overlapping inversion on strings and languages

Kim, H.,Han, Y.S. North-Holland Pub. Co ; Elsevier Science Ltd 2015 Theoretical computer science Vol.592 No.-

Given a string, a non-overlapping inversion is to reverse some non-overlapping fragments of the string simultaneously. We define a non-overlapping inversion operation to be the computation of all possible non-overlapping inversions. We apply the operation on a string, which gives rise to a set of strings, and construct an NFA recognizing the set. Then, we design an efficient DFA reduction algorithm from the resulting NFA. We also consider the non-overlapping inversion operation on a language and show the closure properties for regular, context-free and context-sensitive languages. We furthermore examine iterative non-overlapping inversions and establish the closure properties. Finally, we introduce non-overlapping inversion-free languages and present the decidability results for regular and context-free languages.