scholarly journals Excluding Kuratowski graphs and their duals from binary matroids

2020 ◽  
Author(s):  
Dillon Mayhew ◽  
G Royle ◽  
Geoffrey Whittle
Keyword(s):  
Growth Rate ◽  
Critical Exponent ◽  
Binary Matroid ◽  
Binary Matroids ◽  
Practical Algorithm ◽  
A Minor

© 2017 Elsevier Inc. We consider some applications of our characterisation of the internally 4-connected binary matroids with no M(K3,3)-minor. We characterise the internally 4-connected binary matroids with no minor in M, where M is a subset of {M(K3,3),M⁎(K3,3),M(K5),M⁎(K5)} that contains either M(K3,3) or M⁎(K3,3). We also describe a practical algorithm for testing whether a binary matroid has a minor in M. In addition we characterise the growth-rate of binary matroids with no M(K3,3)-minor, and we show that a binary matroid with no M(K3,3)-minor has critical exponent over GF(2) at most equal to four.

scholarly journals Excluding Kuratowski graphs and their duals from binary matroids

2020 ◽  
Author(s):  
Dillon Mayhew ◽  
G Royle ◽  
Geoffrey Whittle
Keyword(s):  
Growth Rate ◽  
Critical Exponent ◽  
Binary Matroid ◽  
Binary Matroids ◽  
Practical Algorithm ◽  
A Minor

© 2017 Elsevier Inc. We consider some applications of our characterisation of the internally 4-connected binary matroids with no M(K3,3)-minor. We characterise the internally 4-connected binary matroids with no minor in M, where M is a subset of {M(K3,3),M⁎(K3,3),M(K5),M⁎(K5)} that contains either M(K3,3) or M⁎(K3,3). We also describe a practical algorithm for testing whether a binary matroid has a minor in M. In addition we characterise the growth-rate of binary matroids with no M(K3,3)-minor, and we show that a binary matroid with no M(K3,3)-minor has critical exponent over GF(2) at most equal to four.

scholarly journals On the Excluded Minors for Matroids of Branch-Width Three

10.37236/1648 ◽  
2002 ◽  
Vol 9 (1) ◽  
Author(s):  
Petr Hliněný
Keyword(s):  
Computer Assisted ◽  
Binary Matroids ◽  
Alternative Characterization ◽  
Excluded Minor ◽  
Practical Algorithm ◽  
Branch Width ◽  
A Minor ◽  
Excluded Minors

Knowing the excluded minors for a minor-closed matroid property provides a useful alternative characterization of that property. It has been shown in [R. Hall, J. Oxley, C. Semple, G. Whittle, On Matroids of Branch-Width Three, submitted 2001] that if $M$ is an excluded minor for matroids of branch-width $3$, then $ M$ has at most $14$ elements. We show that there are exactly $10$ such binary matroids $M$ (7 of which are regular), proving a conjecture formulated by Dharmatilake in 1994. We also construct numbers of such ternary and quaternary matroids $ M$, and provide a simple practical algorithm for finding a width-$3$ branch-decomposition of a matroid. The arguments in our paper are computer-assisted — we use a program $MACEK$ [P. Hliněný, The MACEK Program, http://www.mcs.vuw.ac.nz/research/macek, 2002] for structural computations with represented matroids. Unfortunately, it seems to be infeasible to search through all matroids on at most $14$ elements.

scholarly journals Limited impact of El Niño–Southern Oscillation on variability and growth rate of atmospheric methane

2018 ◽  
Vol 15 (21) ◽  
pp. 6371-6386 ◽  
Author(s):  
Hinrich Schaefer ◽  
Dan Smale ◽  
Sylvia E. Nichol ◽  
Tony M. Bromley ◽  
Gordon W. Brailsford ◽  
...  
Keyword(s):  
Climate Change ◽  
Growth Rate ◽  
Biomass Burning ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Atmospheric Methane ◽  
Ch4 Production ◽  
A Minor

Abstract. The El Niño–Southern Oscillation (ENSO) has been suggested as a strong forcing in the methane cycle and as a driver of recent trends in global atmospheric methane mole fractions [CH4]. Such a sensitivity of the global CH4 budget to climate events would have important repercussions for climate change mitigation strategies and the accuracy of projections for future greenhouse forcing. Here, we test the impact of ENSO on atmospheric CH4 in a correlation analysis. We use local and global records of [CH4], as well as stable carbon isotopic records of atmospheric CH4 (δ13CH4), which are particularly sensitive to the combined ENSO effects on CH4 production from wetlands and biomass burning. We use a variety of nominal, smoothed, and detrended time series including growth rate records. We find that at most 36 % of the variability in [CH4] and δ13CH4 is attributable to ENSO, but only for detrended records in the southern tropics. Trend-bearing records from the southern tropics, as well as all studied hemispheric and global records, show a minor impact of ENSO, i.e. < 24 % of variability explained. Additional analyses using hydrogen cyanide (HCN) records show a detectable ENSO influence on biomass burning (up to 51 %–55 %), suggesting that it is wetland CH4 production that responds less to ENSO than previously suggested. Dynamics of the removal by hydroxyl likely counteract the variation in emissions, but the expected isotope signal is not evident. It is possible that other processes obscure the ENSO signal, which itself indicates a minor influence of the latter on global CH4 emissions. Trends like the recent rise in atmospheric [CH4] can therefore not be attributed to ENSO. This leaves anthropogenic methane sources as the likely driver, which must be mitigated to reduce anthropogenic climate change.

scholarly journals Initial steps of aerosol growth

2004 ◽  
Vol 4 (11/12) ◽  
pp. 2553-2560 ◽  
Author(s):  
M. Kulmala ◽  
L. Laakso ◽  
K. E. J. Lehtinen ◽  
I. Riipinen ◽  
M. Dal Maso ◽  
...  
Keyword(s):  
Growth Rate ◽  
Atmospheric Aerosols ◽  
Minor Role ◽  
Forest Site ◽  
Atmospheric Conditions ◽  
Curvature Effects ◽  
Atmospheric Nucleation ◽  
Condensational Growth ◽  
A Minor ◽  
20 Nm

Abstract. The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent – mainly condensational – growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm (diameter) in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhanced growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors.

scholarly journals The effect of shell secretion rate on Mg / Ca and Sr / Ca ratios in biogenic calcite as observed in a belemnite rostrum

2017 ◽  
Vol 14 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Clemens Vinzenz Ullmann ◽  
Philip A. E. Pogge von Strandmann
Keyword(s):  
Growth Rate ◽  
Rate Increase ◽  
Environmental Parameters ◽  
Secretion Rate ◽  
Relative Growth ◽  
Rate Effects ◽  
Minor Part ◽  
Biasing Effects ◽  
Temperature Proxy ◽  
A Minor

Abstract. Isotopic ratios and concentrations of the alkaline earth metals Mg and Sr in biogenic calcite are of great importance as proxies for environmental parameters. In particular, the Mg / Ca ratio as a temperature proxy has had considerable success. It is often hard to determine, however, which parameter ultimately controls the concentration of these elements in calcite. Here, multiple Mg / Ca and Sr / Ca transects through a belemnite rostrum of Passaloteuthis bisulcata (Blainville, 1827) are used to isolate the effect of calcite secretion rate on incorporation of Mg and Sr into the calcite. With increasing calcite secretion rate Mg / Ca ratios decrease and Sr / Ca ratios in the rostrum increase. In the studied specimen this effect is found to be linear for both element ratios over a calcite secretion rate increase of ca. 150 %. Mg / Ca ratios and Sr / Ca ratios show a linear co-variation with increasing relative growth rate, where a 100 % increase in growth rate leads to a (8.1 ± 0.9) % depletion in Mg and a (5.9 ± 0.7) % enrichment in Sr. The magnitude of the calcite secretion rate effect on Mg is (37 ± 4) % greater than that on Sr. These findings are qualitatively confirmed by a geochemical transect through a second rostrum of Passaloteuthis sp. Growth rate effects are well defined in rostra of Passaloteuthis, but only account for a minor part of chemical heterogeneity. Biasing effects on palaeoenvironmental studies can be minimized by informed sampling, whereby the apex and apical line of the rostrum are avoided.

A characterization of n-connected splitting matroids

2014 ◽  
Vol 07 (04) ◽  
pp. 1450060
Author(s):  
P. P. Malavadkar ◽  
M. M. Shikare ◽  
S. B. Dhotre
Keyword(s):  
Binary Matroid ◽  
Binary Matroids ◽  
Splitting Operation

The splitting operation on an n-connected binary matroid may not yield an n-connected binary matroid. In this paper, we characterize n-connected binary matroids which yield n-connected binary matroids by the generalized splitting operation.

Effects of glucocorticoid on body growth and serum levels of somatomedin A in the rat

1982 ◽  
Vol 100 (2) ◽  
pp. 206-210 ◽  
Author(s):  
Kumiko Asakawa ◽  
Kazue Takano ◽  
Megumi Kogawa ◽  
Yoko Hasumi ◽  
Kazuo Shizume
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Weight Gain ◽  
Body Weight Gain ◽  
Serum Levels ◽  
Radioreceptor Assay ◽  
Body Growth ◽  
Cortisone Acetate ◽  
Combined Administration ◽  
A Minor

Abstract. Serum levels of somatomedin A, as measured by radioreceptor assay, and body weight gain were 86.5 ± 9.2% and 166.9 ± 7.8% (N = 5) of the initial values, respectively, after 18 days administration of 2.5 mg cortisone acetate (CA). These values were significantly lower than those for saline treated rats (P < 0.005). Reduced serum somatomedin A and body growth rate were partially restored after halting the injection of CA. Combined administration of daily doses of 100 μg hGH with CA did not prevent the decrease in somatomedin activity in treated rats. This observation suggests that GH plays a minor (or no) role in the fall of serum somatomedin A in CA-treated rats. From these data we conclude that glucocorticoids reduce serum somatomedin by inhibiting the effect of GH on the generation of somatomedin.

scholarly journals Quasiregular Matroids

10.37236/6911 ◽  
2018 ◽  
Vol 25 (3) ◽  
Author(s):  
S. R. Kingan
Keyword(s):  
The Self ◽  
Binary Matroid ◽  
Binary Matroids

Regular matroids are binary matroids with no minors isomorphic to the Fano matroid $F_7$ or its dual $F_7^*$. Seymour proved that 3-connected regular matroids are either graphs, cographs, or $R_{10}$, or else can be decomposed along a non-minimal exact 3-separation induced by $R_{12}$. Quasiregular matroids are binary matroids with no minor isomorphic to the self-dual binary matroid $E_4$. The class of quasiregular matroids properly contains the class of regular matroids. We prove that 3-connected quasiregular matroids are either graphs, cographs, or deletion-minors of $PG(3,2)$, $R_{17}$ or $M_{12}$ or else can be decomposed along a non-minimal exact 3-separation induced by $R_{12}$, $P_9$, or $P_9^*$.

scholarly journals SOME ASPECTS OF THE CULTURE OF EUCHEMA

1970 ◽  
Vol 17 ◽  
pp. 145-146
Author(s):  
U. Horstman ◽  
A. Colina ◽  
W. Schramm
Keyword(s):  
Growth Rate ◽  
The Philippines ◽  
Minor Role ◽  
Bacterial Disease ◽  
Surrounding Water ◽  
Low Salinity ◽  
In Situ Experiments ◽  
Spraying Plants ◽  
A Minor

Eucheuma striatum and Eucheuma spinosum, are red algae of commercial value because of their carrageenin content, to an increasing extent are cultivated in the Philippines. The influence of environmental factors on growth rate and photosynthesis of these seaweeds were studied through observations in their natural biotope in seaweed farms, from in-situ experiments, and photosynthesis experiments in an incubator. While difference in light intensity and temperature play only a minor role, the algae were found out to be sensitive to low salinity and to the amount of dissolved gases and nutrients in the surrounding seawater. The algae can only be cultured in areas where there is sufficient current but to a cer-tain extent lack of current can be compensated by exposing the plants to wave action. This leads to certain conclusions regarding the most suitable method of commercial Eucheuma culture. Eucheuma can be successfully cultured in small rafts or in floating baskets in areas where there is insufficient current for the use of fixed nets or strings. There is evidence that-the CO2 -02 metabolism in the surrounding water plays an important role in Eucheuma growth. Eucheuma harvest can be further increased by introducing more nutrients. Fertilizing with phosphate caused a bigger increase in growth rate than with nitrogen. The method of spraying plants after temporarily removing them from the water, found to be more effective than fertilizing solutions by the use of clay pots. The presence of a bacterial disease, locally referred to as "ice-ice", was recognized as a clear indication that certain environment conditions were unfavourable for Eucheuma culture. Low salinity, in the first place, but also lack of current favors the attack of "ice-ice". Finally, it was found that Eucheuma adapts itself to its culture site in such a way that after maintaining seedlings in an area for a sufficient length of time, the cultured plants showed better growth rates and were resistent to unfavorable conditions than plants recently transferred to the area.

scholarly journals Kazantsev dynamo in turbulent compressible flows

2019 ◽  
Vol 475 (2223) ◽  
pp. 20180591 ◽  
Author(s):  
Marco Martins Afonso ◽  
Dhrubaditya Mitra ◽  
Dario Vincenzi
Keyword(s):  
Growth Rate ◽  
Reynolds Number ◽  
Critical Exponent ◽  
Compressible Flows ◽  
Critical Value ◽  
Magnetic Reynolds Number ◽  
Scaling Exponent ◽  
Scaling Exponents ◽  
Potential Part

We consider the kinematic fluctuation dynamo problem in a flow that is random, white-in-time, with both solenoidal and potential components. This model is a generalization of the well-studied Kazantsev model. If both the solenoidal and potential parts have the same scaling exponent, then, as the compressibility of the flow increases, the growth rate decreases but remains positive. If the scaling exponents for the solenoidal and potential parts differ, in particular if they correspond to typical Kolmogorov and Burgers values, we again find that an increase in compressibility slows down the growth rate but does not turn it off. The slow down is, however, weaker and the critical magnetic Reynolds number is lower than when both the solenoidal and potential components display the Kolmogorov scaling. Intriguingly, we find that there exist cases, when the potential part is smoother than the solenoidal part, for which an increase in compressibility increases the growth rate. We also find that the critical value of the scaling exponent above which a dynamo is seen is unity irrespective of the compressibility. Finally, we realize that the dimension d  = 3 is special, as for all other values of d the critical exponent is higher and depends on the compressibility.

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