A characterization of the squares in a Fibonacci string

A (finite) Fibonacci stringFn is defined as follows: F0 = b, F1 = a; for every integer n ⩾ 2, Fn = Fn − 1Fn − 2. For n ⩾ 1, the length of Fn is denoted by . The infinite Fibonacci stringF is the string which contains every Fn, n ⩾ 1, as a prefix. Apart from their general theoretical importance, Fibonacci strings are often cited as worst-case examples for algorithms which compute all the repetitions or all the “Abelian squares” in a given string. In this paper we provide a characterization of all the squares in F, hence in every prefix Fn; this characterization naturally gives rise to a algorithm which specifies all the squares of Fn in an appropriate encoding. This encoding is made possible by the fact that the squares of Fn occur consecutively, in “runs”, the number of which is . By contrast, the known general algorithms for the computation of the repetitions in an arbitrary string require time (and produce outputs) when applied to a Fibonacci string Fn

A linear algorithm for computing all the squares of a Fibonacci string

A (finite) Fibonacci string $F_n$ is defined as follows: $F_0 = b$, $F_1 = a$; for every integer $n \ge 2$, $F_n = F_{n-1}F_{n- 2}$. For $n \ge 1$, the length of $F_n$ is denoted by $f_n = |F_n|$, while it is convenient to define $f_0 \equiv 0$. The infinite Fibonacci string $F$ is the string which contains every $F_n$, $n \ge 1$, as a prefix. Apart from their general theoretical importance, Fibonacci strings are often cited as worst case examples for algorithms which compute all the repetitions or all the ``Abelian squares'' in a given string. In this paper we provide a characterization of all the squares in $F$, hence in every prefix $F_n$; this characterization naturally gives rise to a $\Theta(f_n)$ algorithm which specifies all the squares of $F_n$ in an appropriate encoding. This encoding is made possible by the fact that the squares of $F_n$ occur consecutively, in ``runs'', the number of which is $\Theta(f_n)$. By contrast, the known general algorithms for the computation of the repetitions in an arbitrary string require $\Theta(f_n\log f_n)$ time (and produce $\Theta(f_n\log f_n)$ outputs) when applied to a Fibonacci string $F_n$

The covers of a circular Fibonacci string

Fibonacci strings turn out to constitute worst cases for a number of computer algorithms which find generic patterns in strings. Examples of such patterns are repetitions, Abelian squares, and "covers". In particular, we characterize in this paper the covers of a circular Fibonacci string C(F k ) and show that they are \Theta(jF k j 2 ) in number. We show also that, by making use of an appropriate encoding, these covers can be reported in \Theta(jF k j) time. By contrast, the fastest known algorithm for computing the covers of an arbitrary circular string of length n requires time O(n log n)

Coronary heart disease risk factors in a rural and urban Orange Free State black population

Objective. To determine and compare the prevalence of ischaemic heart disease (IHD) risk factors in a rural and an urban black population.Design. A survey to determine the prevalence of hypertension, diabetes mellitus, smoking, obesity, central obesity and dyslipidaemia in black subjects 25 years and older.Setting. The indigenous black populations of QwaQwa and Mangaung.Participants. A random sample of 950 households was selected from each area. From each household an unrelated male and/or female subject was selected in a standardised way. From QwaQwa 853 subjects (279 men and 574 women) and from Mangaung 758 subjects (290 men and 468 women) participated in the study. The response rate was 68% and 62% respectively for QwaQwa and Mangaung.Main outcome measures. Few urban-rural differences in the prevalence of IHD risk factors were found in this study. A low prevalence of clustering of major IHD risk factors was noted.Results. The age- and sex-adjusted prevalences of hypertension were 29% in QwaQwa and 30,3% in Mangaung. Oiabetes was present in 4,8% of the QwaQwa sample and 6% of the Mangaung sample. The prevalence of heavy smoking in the Mangaung sample was almost double that of the QwaQwa sample and mostly confined to men. High-risk hypercholesterolaemia was present in 12,5% of QwaQwa and 6% of Mangaung men in the  25 - 34-year age group. The corresponding figures for moderate-risk hypercholesterolaemia were 34% and 44,8% and both levels of risk declined with increasing age. The mean body mass index of women in both samples exceeded 25 kg/m2.Conclusion. All the elements for a potential epidemic of atherosclerotic cardiovascular disease are present in the study populations. The similarity of findings in the two samples may be indicative of the advanced stage of urbanisation and westernisation of the rural group. It is alarming that subjects in the younger age groups tendeo to have the highest prevalences of moderate and even high-risk hypercholesterolaemia

Gauss Law Constraints in Chern-Simons Theory From BRST Quantization

The physical state condition in the BRST quantization of Chern-Simons field theory is used to derive Gauss law constraints in the presence of Wilson loops, which play an important role in explicitly establishing the connection of Chern-Simons field theory with 2-dimensional conformal field theory.Comment: Some typetwritten errors have been corrected. A few formulas have been modified to make the arguments clear. A little English have been re-edite

Occupational Communication as Boundary Mechanism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69000/2/10.1177_073088847400100404.pd

Variation with mass of B(E3;01+→31-) transition rates in A=124-134 even-mass xenon nuclei

B(E3;01+→31-) transition matrix elements have been measured for even-mass Xe124-134 nuclei using subbarrier Coulomb excitation in inverse kinematics. The trends in energy E(3-) and B(E3;01+→31-) excitation strengths are well reproduced using phenomenological models based on a strong coupling picture with a soft quadrupole mode and an increasing occupation of the intruder h11/2 orbital

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio