154 research outputs found
Linear spaces with a line-transitive point-imprimitive automorphism group and Fang-Li parameter gcd(k,r) at most eight
In 1991, Weidong Fang and Huiling Li proved that there are only finitely many
non-trivial linear spaces that admit a line-transitive, point-imprimitive group
action, for a given value of gcd(k,r), where k is the line size and r is the
number of lines on a point. The aim of this paper is to make that result
effective. We obtain a classification of all linear spaces with this property
having gcd(k,r) at most 8. To achieve this we collect together existing theory,
and prove additional theoretical restrictions of both a combinatorial and group
theoretic nature. These are organised into a series of algorithms that, for
gcd(k,r) up to a given maximum value, return a list of candidate parameter
values and candidate groups. We examine in detail each of the possibilities
returned by these algorithms for gcd(k,r) at most 8, and complete the
classification in this case.Comment: 47 pages Version 1 had bbl file omitted. Apologie
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EBR-II inherent shutdown and heat removal tests: a survey of test results
An experimental study of inherently safe characteristics of LMFBR systems is being conducted in EBR-II. Experiments have been conducted which show (1) capabilities of heat removal without the aid of active safety systems and (2) capabilities to mitigate a reduction in-core cooling flow or heat rejection to the balance of plant (BOP) without aid of active control or protection systems. Experiments involving loss of forced reactor cooling flow and loss of all heat rejection to the BOP are planned to be conducted. Purpose of this paper is to summarize the result of the test program by presenting representative test data
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Convective transport of formaldehyde to the upper troposphere and lower stratosphere and associated scavenging in thunderstorms over the central United States during the 2012DC3 study
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Decay heat removal and dynamic plant testing at EBR-II
The complete testing program at EBR-II directed towards transient thermal-hydraulic performance is described. The program, which was initially directed towards an understanding of the dynamics of natural convective flow and the validation of related computer codes, has evolved into studies of unprotected transients. These later tests are intended to provide experimental data as well as to directly demonstrate the inherently safe response of an LMR to transients which in the recent past were thought to lead to core disruption. Tpical results and conclusions from the series of protected natural circulation tests are also presented
Families of twisted tensor product codes
Using geometric properties of the variety \cV_{r,t}, the image under the
Grassmannian map of a Desarguesian -spread of \PG(rt-1,q), we
introduce error correcting codes related to the twisted tensor product
construction, producing several families of constacyclic codes. We exactly
determine the parameters of these codes and characterise the words of minimum
weight.Comment: Keywords: Segre Product, Veronesean, Grassmannian, Desarguesian
spread, Subgeometry, Twisted Product, Constacyclic error correcting code,
Minimum weigh
Effects of Scavenging, Entrainment, and Aqueous Chemistry on Peroxides and Formaldehyde in Deep Convective Outflow over the Central and Southeast U.S.
Deep convective transport of gaseous precursors to ozone (O3) and aerosols to the upper troposphere is affected by liquid- and mixed-phase scavenging, entrainment of free tropospheric air, and aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high resolution (dx <= 3 km) WRF-Chem simulations of a severe storm, an airmass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH2O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF-Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH2O, methyl hydroperoxide (CH3OOH), and hydrogen peroxide (H2O2) are quantified. Liquid-phase microphysical scavenging was the dominant process reducing CH2O and H2O2 outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH3OOH mixing ratios in the storm cores were primarily due to entrainment of low background CH3OOH. In the airmass storm, lower CH3OOH and H2O2 scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH3OOH and H2O2. Overestimated rain and hail production in WRF-Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH2O
The Hardness of Code Equivalence over and its Application to Code-based Cryptography
International audienceThe code equivalence problem is to decide whether two linear codes over F_q are equivalent, that is identical up to a linear isometry of the Hamming space. In this paper, we review the hardness of code equivalence over F_q due to some recent negative results and argue on the possible implications in code-based cryptography. In particular, we present an improved version of the three-pass identification scheme of Girault and discuss on a connection between code equivalence and the hidden subgroup problem
Serotonin and Dopamine Protect from Hypothermia/Rewarming Damage through the CBS/ H2S Pathway
Biogenic amines have been demonstrated to protect cells from apoptotic cell death. Herein we show for the first time that serotonin and dopamine increase H2S production by the endogenous enzyme cystathionine-β-synthase (CBS) and protect cells against hypothermia/rewarming induced reactive oxygen species (ROS) formation and apoptosis. Treatment with both compounds doubled CBS expression through mammalian target of rapamycin (mTOR) and increased H2S production in cultured rat smooth muscle cells. In addition, serotonin and dopamine treatment significantly reduced ROS formation. The beneficial effect of both compounds was minimized by inhibition of their re-uptake and by pharmacological inhibition of CBS or its down-regulation by siRNA. Exogenous administration of H2S and activation of CBS by Prydoxal 5′-phosphate also protected cells from hypothermic damage. Finally, serotonin and dopamine pretreatment of rat lung, kidney, liver and heart prior to 24 h of hypothermia at 3°C followed by 30 min of rewarming at 37°C upregulated the expression of CBS, strongly reduced caspase activity and maintained the physiological pH compared to untreated tissues. Thus, dopamine and serotonin protect cells against hypothermia/rewarming induced damage by increasing H2S production mediated through CBS. Our data identify a novel molecular link between biogenic amines and the H2S pathway, which may profoundly affect our understanding of the biological effects of monoamine neurotransmitters
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