1,786,457 research outputs found
Making Kr+1-free graphs r-partite
Get PDFThe Erdős–Simonovits stability theorem states that for all ε > 0 there exists α > 0 such that if G is a Kr+1-free graph on n vertices with e(G) > ex(n, Kr+1)– α n2, then one can remove εn2 edges from G to obtain an r-partite graph. Füredi gave a short proof that one can choose α = ε. We give a bound for the relationship of α and ε which is asymptotically sharp as ε → 0.This article is published as Balogh J, Clemen FC, Lavrov M, Lidický B, Pfender F. Making Kr+1-free graphs r-partite. Combinatorics, Probability and Computing. 2021;30(4):609-618. doi:10.1017/S0963548320000590
Making Kr+1-Free Graphs r-partite
Get PDFThe Erdos-Simonovits stability theorem states that for all epsilon > 0 there exists alpha > 0 such that if G is a Kr+1-free graph on n vertices with e(G) > ex(n, Kr+1)-alpha n2, then one can remove epsilon n2 edges from G to obtain an r-partite graph. Furedi gave a short proof that one can choose alpha = epsilon. We give a bound for the relationship of alpha and epsilon which is asymptotically sharp as epsilon right arrow 0.This pre-print is made available through arixiv: https://arxiv.org/abs/1910.00028.</p
Kr-h1 acts downstream of ecdysone signalling to negatively regulate the specification of α’β’ MB neurons.
No full text(A-B’) WL3 MB cell bodies from control (A,A’) and OK107>EcR-DN (B, B’) brains carrying the Kr-h110642::LacZ enhancer trap line revealed with anti-βGal antibody (magenta). Green: GAL4-OK107-driven mGFP in A-B’. (C) Quantification of Kr-h110642::LacZ signal in control and OK107>EcR-DN brains. 10 brains were analysed for control or OK107>EcR-DN conditions. Statistical comparison to the control: ***, pOK107>Kr-h1 (E) brains stained with anti-FasII antibody (magenta). Green: GMR26E01-LexA-α’β’-MB-driven mGFP in D,E. (F) Quantification of the number of adult α’β’ MB neuron cell bodies from control and OK107>Kr-h1 brains. Statistical comparison to the control: ***, pt test). (G-H’) WL3 MB cell bodies from control (G,G’) and OK107>Kr-h1 (H, H’) stained with anti-EcR-B1 antibody (magenta). Green: GAL4-OK107-driven mGFP in G-H’. (I) Quantification of EcR-B1 signal in control and OK107>Kr-h1 brains. 10 brains were analysed for both control and OK107>Kr-h1 conditions. Statistical comparison to the control: **, pOK107>babo RNAi, luciferase RNAi (J) and OK107>babo RNAi, Kr-h1 RNAi (K) brains stained with anti-FasII antibody (magenta). Green: GMR26E01-LexA-α’β’-MB-driven mGFP in J,K. (L) Quantification of number of adult α’β’ MB neuron cell bodies from OK107>babo RNAi, luciferase RNAi and OK107>babo RNAi, Kr-h1 RNAi brains. Statistical comparison to the control: ***, pt test).</p
Understanding the adsorption mechanism of noble gases Kr and Xe in CPO-27-Ni, CPO-27-Mg, and ZIF-8
No full textAn experimental study of Xe and Kr adsorption in metal-organic frameworks CPO-27-Ni, CPO-27-Mg, and ZIF-8 was carried out. In situ synchrotron X-ray powder diffraction experiments allowed precise determination of the adsorption sites and sequence of their filling with increasing of gas pressure at different temperatures. Structural investigations were used for interpretation of gas adsorption measurements.Peer reviewe
Maximizing five-cycles in Kr-free graphs
Get PDFThe Pentagon Problem of Erd˝os problem asks to find an n-vertex triangle-free graph that is maximizing the number of 5-cycles. The problem was solved using flag algebras by
Grzesik and independently by Hatami, Hladky´, Kr´al’, Norin, and Razborov. Recently, Palmer suggested a more general problem of maximizing the number of 5- cycles in Kk₊₁-free graphs. Using flag algebras, we show that every Kk₊₁-free graph of order n contains at most 1 10k4(k⁴ − 5k³ + 10k² − 10k + 4)n⁵ + o(n⁵) copies of C₅ for any k ≥ 3, with the Turán graph being the extremal graph for large enough n.This is a manuscript of an article published as Lidický, Bernard, and Kyle Murphy. "Maximizing five-cycles in Kr-free graphs." European Journal of Combinatorics 97 (2021): 103367. doi:10.1016/j.ejc.2021.103367
Analysis of molecular and physiological pathways regulating social behavior in honey bees: elucidating the role of Kr-h1 and cGMP
No full textKruppel homolog 1 (Kr-h1) is a zinc finger transcription factor whose brain expression levels are associated with foraging behavior and are regulated by queen mandibular pheromone (QMP) in honey bees. We used behavioral, physiological, and genomic approaches to investigate the factors which regulate expression of Kr-h1 in honey bees, and employed a comparative genomics approach to begin to characterize the molecular function of this protein. We demonstrated that brain expression of Kr-h1 is associated with permanent physiological changes that occur during behavioral maturation from nursing to foraging, rather than the acute expression of foraging behavior. Furthermore, we demonstrated that Kr-h1 expression is modulated by cGMP, a key regulator of behavior maturation, and identified a potential cGMP response element in the promoter of Kr-h1. We then characterized the interactions between cGMP and QMP. cGMP inhibited behavioral and physiological responses to QMP, and partially inhibited expression changes of QMP-responsive genes in the brain. Treatment with these factors specifically altered expression of genes associated with GTPase regulator activity, phototransduction, and positive regulation of antibacterial peptide biosynthetic process. However, cGMP did not affect the expression of AmOr11, an odorant receptor specific for a major chemical component of QMP, suggesting that cGMP might work centrally rather than peripherally to modulate the response to QMP. Finally, we elucidated changes in gene expression that resulted from the absence of Kr-h1 expression during D. melanogaster development and discovered an associated motif in the promoter of the majority of the significantly expressed genes, which may mediate the effects of Kr-h1. Further analysis, however, showed that this motif is unlikely to be biologically relevant. These studies have demonstrated the ability of physiological factors to modulate responsiveness to social cues, and provided further information about the role of Kr-h1 in regulating behavior in bees
Rapid processing of ⁸⁵5 Kr/Kr ratios using Atom Trap Trace Analysis
Get PDFWe report a methodology for measuring ⁸⁵ Kr/Kr isotopic abundances using Atom Trap Trace Analysis (ATTA) that increases sample measurement throughput by over an order of magnitude to six samples per 24 h. The noble gas isotope ⁸⁵ Kr (half-life 510.7 years) is a useful tracer for young groundwater in the age range of 5–50 years. ATTA, an efficient and selective laser-based atom counting method, has recently been applied to ⁸⁵ Kr/Kr isotopic abundance measurements, requiring 5–10 μL of krypton gas at STP extracted from 50 to 100 L of water. Previously, a single such measurement required 48 h. Our new method demonstrates that we can measure 85Kr/Kr ratios with 3–5% relative uncertainty every 4 h, on average, with the same sample requirements
Calibration of cosmogenic noble gas production based on ³⁶Cl-³⁶Ar ages. Part 2. The ⁸¹Kr-Kr dating technique
No full textWe calibrated the ⁸¹Kr-Kr dating system for ordinary chondrites of different sizes using independent shielding-corrected ³⁶Cl-³⁶Ar ages. Krypton concentrations and isotopic compositions were measured in bulk samples from 14 ordinary chondrites of high petrologic type and the cosmogenic Kr component was obtained by subtracting trapped Kr from phase Q. The thus-determined average cosmogenic ⁷⁸Kr/⁸³Kr, ⁸⁰Kr/⁸³Kr, ⁸²Kr/⁸³Kr, and ⁸4Kr/⁸³Kr ratiC(Lavielle and Marti 1988; Wieler 2002). The cosmogenic ⁷⁸Kr/⁸³Kr ratio is correlated with the cosmogenic 22Ne/21Ne ratio, confirming that ⁷⁸Kr/⁸³Kr is a reliable shielding indicator. Previously, ⁸¹Kr-Kr ages have been determined by assuming the cosmogenic production rate of ⁸¹Kr, P(⁸¹Kr)c, to be 0.95 times the average of the cosmogenic production rates of ⁸⁰Kr and ⁸²Kr; the factor Y = 0.95 therefore accounts for the unequal production of the various Kr isotopes (Marti 1967a). However, Y should be regarded as an empirical adjustment. For samples whose ⁸⁰Kr and ⁸²Kr concentrations may be affected by neutron-capture reactions, the shielding-dependent cosmogenic (⁷⁸Kr/⁸³Kr)c ratio has been used instead to calculate P(⁸¹Kr)/P(⁸³Kr), as for some lunar samples, this ratio has been shown to linearly increase with (⁷⁸Kr/⁸³Kr)c (Marti and Lugmair 1971). However, the ⁸¹Kr-Kr ages of our samples calculated with these methods are on average ~30% higher than their ³⁶Cl-³⁶Ar ages, indicating that most if not all the ⁸¹Kr-Kr ages determined so far are significantly too high. We therefore re-evaluated both methods to determine P(⁸¹Kr)c/P(⁸³Kr)c. Our new Y value of 0.70 ± 0.04 is more than 25% lower than the value of 0.95 used so far. Furthermore, together with literature data, our data indicate that for chondrites, P(⁸¹Kr)c/P(⁸³Kr)c is rather constant at 0.43 ± 0.02, at least for the shielding range covered by our samples ([⁷⁸Kr/⁸³Kr]c = 0.119–0.185; [22Ne/21Ne]c = 1.083–1.144), in contrast to the observations on lunar samples. As expected considering the method used, ⁸¹Kr-Kr ages calculated either directly with this new P(⁸¹Kr)c/P(⁸³Kr)c value or with our new Y value both agree with the corresponding ³⁶Cl-³⁶Ar ages. However, the average deviation of 2% indicates the accuracy of both new ⁸¹Kr-Kr dating methods and the precision of the new dating systems of ~10% is demonstrated by the low scatter in the data. Consequently, this study indicates that the ⁸¹Kr-Kr ages published so far are up to 30% too high
Organizzazione del 13th International Conference on Principles of Knowledge Representation and Reasoning (KR 2012)
No full textKnowledge Representation and Reasoning (KR&R) is a well-established and vibrant field of research. KR&R techniques are key drivers of innovation in computer science, and they have led to significant advances in practical applications in a wide range of areas from Artificial Intelligence to Software Engineering. The underlying approach of explicitly representing knowledge in a tangible form, suitable for processing by dedicated reasoning engines, is a fundamental component of many modern intelligent systems. Foundational and applied research in KR&R contributes to the principles of artificial intelligence. It also contributes to the foundations of longstanding fields including automated planning, databases, and software engineering. In recent years KR&R has also derived challenges from new and emerging fields including the semantic web, computational biology, and the development of software agents.
The KR conference series is a leading forum for timely in-depth presentation of progress in the theory and principles underlying the representation and computational management of knowledge. KR 2012 will be a forum for the exchange and discussion of new ideas, issues, and results on the principles and practice of KR&R
Formation of solid Kr nanoclusters in MgO
Get PDFThe phenomenon of positron confinement enables us to investigate the electronic structure of nanoclusters embedded in host matrices. Solid Kr nanoclusters are a very interesting subject of investigation because of the very low predicted value of the positron affinity of bulk Kr. In this work, positron trapping in solid Kr nanoclusters embedded in MgO is investigated. The Kr nanoclusters were created by means of 280 keV Kr ion implantation in single crystals of MgO(100) and subsequent thermal annealing at a temperature of 1100 K. The nanoclusters were observed by cross-sectional transmission electron microscopy in high-resolution mode. The fcc Kr nanoclusters are rectangularly shaped with sizes of 2 to 5 nm and are in a cube-on-cube orientation relationship with the MgO host matrix. From the Moiré fringes in high-resolution recordings, the lattice parameter of the solid Kr was deduced and found to vary from 5.3 to 5.8 Å. The corresponding pressures are 0.6–2.5 GPa as found using the Ronchi equation of state. The relationship between lattice parameter and cluster size was investigated and it was found that the lattice parameter increases linearly with increasing nanocluster size. The defect evolution during annealing was monitored by means optical absorption spectroscopy and positron beam analysis. No evidence of positron trapping was found despite the very low positron affinity of solid Kr. Alternative definitions of the positron affinity are proposed for application to insulator materials.
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