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An empirical law for the rank-order behavior of journal impact factors is found. Using an extensive data base on impact factors includ-have found extremely good fittings outperforming other rank-order models. Based in our results we propose a two-exponent Lotkaian Informetrics. Some extensions to other areas of knowledge are discussed.
Searching for generic behaviors has been one of the driving forces leading to a deep understanding and classification of diverse phenomena. Usually a starting point is the development of a phenomenology based on observations. Such is the case for power law distributions encountered in a wealth of situations coming from physics, geophysics, biology,(More)
Hammerhead ribozymes previously were found in satellite RNAs from plant viroids and in repetitive DNA from certain species of newts and schistosomes. To determine if this catalytic RNA motif has a wider distribution, we decided to scrutinize the GenBank database for RNAs that contain hammerhead or hammerhead-like motifs. The search shows a widespread(More)
Many eukaryotic nuclear genomes as well as mitochondrial plasmids contain genes displaying evident sequence similarity to those encoding the single-subunit RNA polymerase (ssRNAP) of bacteriophage T7 and its relatives. We have collected and aligned these ssRNAP sequences and have constructed unrooted phylogenetic trees that demonstrate the separation of(More)
Recent results add to the mystery of the origin of the genetic code. In spite of early doubts, RNA can discriminate between hydrophobic amino acids under certain contexts. Moreover, codon reassignment, which has taken place in several organisms and mitochondria, is not a random process. Finally, phylogenies of some aminoacyl-tRNA synthetases suggest that(More)
We propose an index of DNA homogeneity (IDH) based on a binary distribution model that quantifies structural and thermodynamic aggregates present in DNA primary structures. Extensive analysis of sequence databases with the IDH uncovers significant constraints on DNA sequence other than those derived from codon usage or protein function. This index clearly(More)
The amount of non-unique sequence (non-singletons) in a genome directly affects the difficulty of read alignment to a reference assembly for high throughput-sequencing data. Although a longer read is more likely to be uniquely mapped to the reference genome, a quantitative analysis of the influence of read lengths on mappability has been lacking. To address(More)
Recently, Trifonov's group proposed a 10-mer DNA motif YYYYYRRRRR as a solution of the long-standing problem of sequence-based nucleosome positioning. To test whether this generic decamer represents a biological meaningful signal, we compare the distribution of this motif in primates and Archaea, which are known to contain nucleosomes, and in Eubacteria,(More)
The limited range in its abscissa of ranked letter frequency distributions causes multiple functions to fit the observed distribution reasonably well. In order to critically compare various functions, we apply the statistical model selections on ten functions, using the texts of U.S. and Mexican presidential speeches in the last 1-2 centuries. Dispite minor(More)