1,800,780 research outputs found
Τη μακαρία σκιά του αοιδίμου Νικολάου Στ. Δούμπα ___ : Den Manen des unvergesslichen Nikolaus Dumba ___ / Υπό Θ. Λ.
No full textMore about Divisible Design Graphs
No full textAbstract: Divisible design graphs (DDG for short) have been recently defined by Kharaghani, Meulenberg and the second author as a generalization of (v, k, λ)-graphs. In this paper we give some new constructions of DDGs, most of them using Hadamard matrices and (v, k, λ)-graphs. For three parameter sets we give a nonexistence proof. Furthermore, we find conditions for a DDG to be walk-regular. It follows that most of the known examples are walk-regular, but some are not. In case walk-regularity of a DDG is forced by the parameters, necessary conditions for walk-regularity lead to new nonexistence results for DDGs. We examine all feasible parameter sets for DDGs on at most 27 vertices, establish existence in all but one cases, and decide on existence of a walk-regular DDG in all cases.divisible design graph;divisible design;walk-regular graph;(v;k;λ)-graph;Hadamard matrix
On λ D − R0 And λ D − R1 Spaces
No full textIn this paper we introduce the new types of separation axioms called λ D − R0 and λ D − R1 spaces, by using λ D-open set. The notion λ D − R0 and λ D − R1 spaces are introduced and some of their properties are investigated.namiq, sarhad-will be generated-orcid-0000-0001-8747-2542-600ROSAS, ENNIS-will be generated-orcid-0000-0001-8123-9344-60
Study of the kinematic dependences of Λ b 0 production in pp collisions and a measurement of the Λ b 0 → Λ c + π − branching fraction
No full textThe kinematic dependences of the relative production rates, fΛ0b/fd, of Λ b 0 baryons and B 0 mesons are measured using Λ b 0 → Λ c + π − and B¯¯0 →D+π− decays. The measurements use proton-proton collision data, corresponding to an integrated luminosity of 1 fb−1 at a centre-of-mass energy of 7 TeV, recorded in the forward region with the LHCb experiment. The relative production rates are observed to depend on the transverse momentum, p T, and pseudorapidity, η, of the beauty hadron, in the studied kinematic region 1.5 < p T < 40 GeV/c and 2 < η < 5. Using a previous LHCb measurement of fΛ0b/fd in semileptonic decays, the branching fraction ℬ(Λ b 0 → Λ c + π −) = (4.30 ± 0.03 − 0.11 + 0.12 ± 0.26 ± 0.21) × 10− 3 is obtained, where the first uncertainty is statistical, the second is systematic, the third is from the previous LHCb measurement of fΛ0b/fd and the fourth is due to the b B¯¯0 →D+π− branching fraction. This is the most precise measurement of a Λ b 0 branching fraction to date
Ratio between two Λ and Λ¯ production mechanisms in p scattering
No full textAbstractWe consider Λ and Λ¯ production in a wide range of proton scattering experiments. The produced Λ and Λ¯ may or may not contain a diquark remnant of the beam proton. The ratio of these two production mechanisms is found to be a simple universal function r=[κ/(yp−y)]i of the rapidity difference yp−y of the beam proton and the produced Λ or Λ¯, valid over four orders of magnitude, from r≈0.01 to r≈100, with κ=2.86±0.03±0.07, and i=4.39±0.06±0.15
The DNA Ejection Process in Bacteriophage λ
No full textBacteriophages have long served as model systems through which the nature of life may be explored. From a physical or mechanical point of view, phages are excellent examples of natural nanotechnology: they are nanometer-scale systems which depend critically on forces, pressures, velocities, and other fundamentally physical quantities for their biological functions. The study of the physical properties of phages has therefore provided an arena for application of physics to biology. In particular, recent studies of the motor responsible for packaging a phage gnome into a capsid showed a buildup of pressure within the capsid of tens of atmospheres. This thesis reports a combined theoretical and experimental study on various aspects of the genome ejection process, so that a comparison may be drawn with the packaging experiments. In particular, we examine various theoretical models of the forces within a phage capsid, deriving formulas both for the force driving genome ejection and for the velocity at which the genome is translocated into a host cell. We describe an experiment in which the force was measured as a function of the amount of genome within the phage capsid, and another where the genome ejection velocity was measured for single phages under the microscope. We make direct quantitative comparisons between the theory and experiments, stringently testing the extent to which we are able to model the genome ejection process
On λ-designs
No full textAbstractA λ-design is a system of subsets S1, S2,…, Sn from an n-set S, n > 3, where |Si ∩ Sj| = λ for i ≠ j, |Sj| = kj > λ > 0, and not all kj, are equal. Ryser [9] and Woodall [101 have shown that each element of S occurs either r1, or r2 times (r1 ≠ r2) among the sets S1,…, Sn and r1 +r2 = n + 1. Here we: (i) mention most of what is currently known about λ-designs; (ii) provide simpler proofs of some known results; (iii) present several new general theorems; and (iv) apply our theorems and techniques to the calculation of all λ-designs for λ ⩽ 5. In fact, this calculation has been done for all λ ≷/ 9 and is available from the author
On Automorphisms of P(λ)/[λ]<λ
No full textWe investigate the statement "all automorphisms of P(λ)=[λ]<λ are trivial". We show that MA implies the statement for regular uncountable < 2 0 ; that the statement is false for measurable λ if 2λ = λ+; and that for "densely trivial"it can be forced (together with 2λ = λ++) for inaccessible λ
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