172,684 research outputs found
On the cubicity of certain graphs
No full textThe boxicity of a graph G is the minimum dimension b such that G is representable as the intersection graph of axis-parallel boxes in the b-dimensional space. When the boxes are restricted to be axis-parallel b-dimensional cubes, the minimum dimension b required to represent G is called the cubicity of G. In this paper we show that cubicity(H-d) <=, 2d, where Hd is the d-dimensional hypercube. (The d-dimensional hypercube is the graph on 2d vertices which corresponds to the 2(d) d-vectors whose components are either 0 or 1, two of the vertices being adjacent when they differ in just one coordinate.) We also show that cubicity(H-d) >= (d - 1)/(log d). We also show that (1) cubicity(G) >= (log alpha)/(log(D + 1)), (2) cubicity(G) >= (log n - log omega)/(log D), where alpha, omega, D and n denote the stability number, the clique number, the diameter and the number of vertices of G. As consequences of these lower bounds we provide lower bounds for the cubicity of planar graphs, bipartite graphs, triangle-free graphs, etc., in terms of their diameter and the number of vertices. (c) 2005 Elsevier B.V. All rights reserved
The stable set problem and the thinness of a graph
No full textWe introduce a poly-time algorithm for the maximum weighted stable set problem, when a certain representation is given for a graph. The algorithm generalizes the algorithm for interval graphs and that for graphs with bounded pathwidth. By a suitable application to the frequency assignment problem, we improved several solutions to relevant benchmark instances. (c) 2006 Elsevier B.V. All rights reserved
Greenhouse gas emissions from membrane bioreactors: Analysis of a two-year survey on different MBR configurations
No full textThis study aimed at evaluating the nitrous oxide (N2O) emissions from membrane bioreactors (MBRs) for wastewater treatment. The study investigated the N2O emissions considering multiple influential factors over a two-year period: (i) different MBR based process configurations; (ii) wastewater composition (municipal or industrial); (iii) operational conditions (i.e. sludge retention time, carbon-to-nitrogen ratio, C/N, hydraulic retention time); (iv) membrane modules. Among the overall analysed configurations, the highest N2O emission occurred from the aerated reactors. The treatment of industrial wastewater, contaminated with salt and hydrocarbons, provided the highest N2O emission factor (EF): 16% of the influent nitrogen for the denitrification/nitrification-MBR plant. The lowest N2O emission (EF 1⁄4 0.5% of the influent nitrogen) was obtained in the biological phosphorus removal-moving bed-MBR plant likely due to an improvement in biological performances exerted by the co-presence of both suspended and attached biomass. The influent C/N ratio has been identified as a key factor affecting the N2O production. Indeed, a decrease of the C/N ratio (from 10 to 2) promoted the increase of N2O emissions in both gaseous and dissolved phases, mainly related to a decreased efficiency of the denitrification processes
Cubicity, Degeneracy, and Crossing Number
No full textA k-box B=(R_1,R_2,...,R_k), where each R_i is a closed interval on the real line, is defined to be the Cartesian product R_1 X R_2 X ... X R_k. If each R_i is a unit length interval, we call B a k-cube. Boxicity of a graph G, denoted as box(G), is the minimum integer k such that G is an intersection graph of k-boxes. Similarly, the cubicity of G, denoted as cub(G), is the minimum integer k such that G is an intersection graph of k-cubes.
It was shown in [L. Sunil Chandran, Mathew C. Francis, and Naveen Sivadasan. Representing graphs as the intersection of axis-parallel cubes. MCDES-2008, IISc Centenary Conference, available at CoRR, abs/cs/0607092, 2006.] that, for a graph G with maximum degree \Delta, cub(G) <= \lceil 4(\Delta +1) ln n\rceil. In this paper we show that, for a k-degenerate graph G, cub(G) <= (k+2) \lceil 2e log n \rceil. Since k is at most \Delta and can be much lower, this clearly is a stronger result. We also give an efficient deterministic algorithm that runs in O(n^2k) time to output a 8k(\lceil 2.42 log n\rceil + 1) dimensional cube representation for G.
The crossing number of a graph G, denoted as CR(G), is the minimum number of crossing pairs of edges, over all drawings of G in the plane. An important consequence of the above result is that if the crossing number of a graph G is t, then box(G) is O(t^{1/4}{\lceil log t\rceil}^{3/4}) . This bound is tight upto a factor of O((log t)^{3/4}).
Let (P,\leq) be a partially ordered set and let G_{P} denote its underlying comparability graph. Let dim(P) denote the poset dimension of P. Another interesting consequence of our result is to show that dim(P) \leq 2(k+2) \lceil 2e \log n \rceil, where k denotes the degeneracy of G_{P}. Also, we get a deterministic algorithm that runs in O(n^2k) time to construct a 16k(\lceil 2.42 log n\rceil + 1) sized realizer for P. As far as we know, though very good upper bounds exist for poset dimension in terms of maximum degree of its underlying comparability graph, no upper bounds in terms of the degeneracy of the underlying comparability graph is seen in the literature
The cubicity of hypercube graphs
No full textFor a graph G, its cubicity View the MathML source is the minimum dimension k such that Gis representable as the intersection graph of (axis-parallel) cubes in k-dimensional space. (A k-dimensional cube is a Cartesian product R1×R2×cdots, three dots, centered×Rk, where Ri is a closed interval of the form [ai,ai+1] on the real line.) Chandran et al. [L.S. Chandran, C. Mannino, G. Oriolo, On the cubicity of certain graphs, Information Processing Letters 94 (2005) 113–118] showed that for a d-dimensional hypercube Hd, View the MathML source. In this paper, we use the probabilistic method to show that View the MathML source. The parameter boxicity generalizes cubicity: the boxicity View the MathML source of a graph G is defined as the minimum dimension k such that G is representable as the intersection graph of axis-parallel boxes in k-dimensional space. Since View the MathML source for any graph G, our result implies that View the MathML source. The problem of determining a non-trivial lower bound for View the MathML source is left open
Qualifying unmet needs and improving standards of care in psoriatic arthritis
No full textCelgeneHelliwell, P., Coates, L., Chandran, V., Gladman, D., Wit, M.D., Fitzgerald, O., Kavanaugh, A., Strand, V., Mease, P.J., Boehncke, W.H., Langley, R.G., Lubrano, E., Maccarone, M., Schulze-Koops, H., Miceli-Richard, C., Queiro, R
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sol-gel fabrication of thin-film electrolyte in an oxygen generator, U.S. Patent 7,790,221
No full textAn electrochemical cell that receives an inlet stream of air and produces an outlet stream of a high oxygen concentration of gas. The cell is made up of a plurality of layers and preferably a porous electrolyte comprised of yttria stabilized zirconia (YSZ) that allows only oxygen ions to pass therethrough and which is covered on its sides with electrodes comprised of lanthanum strontium manganate (LSM) which in turn are coated with a layer of platinum to aid in the even distribution of the electrical current. An electrical current is passed through the electrodes to produce a voltage difference therebetween. The layers of YSZ and LSM are formed by a sol-gel process
NFAT and CREB Regulate Kaposi's Sarcoma-Associated Herpesvirus-Induced Cyclooxygenase 2 (COX-2)
No full textABSTRACT
COX-2 has been implicated in Kaposi's sarcoma-associated herpesvirus (KSHV) latency and pathogenesis (A. George Paul, N. Sharma-Walia, N. Kerur, C. White, and B. Chandran, Cancer Res. 70:3697-3708, 2010; P. P. Naranatt, H. H. Krishnan, S. R. Svojanovsky, C. Bloomer, S. Mathur, and B. Chandran, Cancer Res. 64:72-84, 2004; N. Sharma-Walia, A. G. Paul, V. Bottero, S. Sadagopan, M. V. Veettil, N. Kerur, and B. Chandran, PLoS Pathog. 6:e1000777, 2010; N. Sharma-Walia, H. Raghu, S. Sadagopan, R. Sivakumar, M. V. Veettil, P. P. Naranatt, M. M. Smith, and B. Chandran, J. Virol. 80:6534-6552, 2006). However, the precise regulatory mechanisms involved in COX-2 induction during KSHV infection have never been explored. Here, we identified
cis
-acting elements involved in the transcriptional regulation of COX-2 upon KSHV
de
novo
infection. Promoter analysis using human COX-2 promoter deletion and mutation reporter constructs revealed that nuclear factor of activated T cells (NFAT) and the cyclic AMP (cAMP) response element (CRE) modulate KSHV-mediated transcriptional regulation of COX-2. Along with multiple KSHV-induced signaling pathways, infection-induced prostaglandin E
2
(PGE
2
) also augmented COX-2 transcription. Infection of endothelial cells markedly induced COX-2 expression via a cyclosporine A-sensitive, calcineurin/NFAT-dependent pathway. KSHV infection increased intracellular cAMP levels and activated protein kinase A (PKA), which phosphorylated the CRE-binding protein (CREB) at serine 133, which probably led to interaction with CRE in the COX-2 promoter, thereby enhancing COX-2 transcription. PKA selective inhibitor H-89 pretreatment strongly inhibited CREB serine 133, indicating the involvement of a cAMP-PKA-CREB-CRE loop in COX-2 transcriptional regulation. In contrast to phosphatidylinositol 3-kinase and protein kinase C, inhibition of FAK and Src effectively reduced KSHV infection-induced COX-2 transcription and protein levels. Collectively, our study indicates that mediation of COX-2 transcription upon KSHV infection is a paradigm of a complex regulatory milieu involving the interplay of multiple signal cascades and transcription factors. Intervention at each step of COX-2/PGE
2
induction can be used as a potential therapeutic target to treat KSHV-associated neoplasm and control inflammatory sequels of KSHV infection.
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Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
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