A statistical analysis of the nulling pulsar population

ABSTRACT Approximately 8 per cent of the ∼2800 known pulsars exhibit ‘nulling,’ a temporary broad-band cessation of normal pulsar emission. Nulling behaviour can be coarsely quantified by the nulling fraction, which describes the percentage of time a given pulsar will be found in a null state. In this paper, we perform the most thorough statistical analysis thus far of the properties of 141 known nulling pulsars. We find weak, non-linear correlations between nulling fraction and pulse width, as well as nulling fraction and spin period which could be attributed to selection effects. We also further investigate a recently hypothesized gap at 40 per cent nulling fraction. While a local minimum does exist in the distribution, we cannot confirm a consistent and unique break in the distribution when we investigate with univariate and multivariate clustering methods, nor can we prove the existence of two statistically distinct populations about this minimum. Using the same methods, we find that nulling pulsars are a statistically different population from normal, radio, non-nulling pulsars, which has never been quantitatively verified. In addition, we summarize the findings of the prior nulling pulsar statistics literature, which are notoriously contradictory. This study, in context, furthers the idea that nulling fraction alone does not contain enough information to describe the behaviour of a nulling pulsar and that other parameters such as null lengths and null randomness, in addition to a better understanding of selection effects, are required to fully understand this phenomenon.

Non-cooperative Fisher–KPP systems: Asymptotic behavior of traveling waves

This paper is concerned with non-cooperative parabolic reaction–diffusion systems which share structural similarities with the scalar Fisher–KPP equation. In a previous paper, we established that these systems admit traveling wave solutions whose profiles connect the null state to a compact subset of the positive cone. The main object of this paper is the investigation of a more precise description of these profiles. Non-cooperative KPP systems can model various phenomena where the following three mechanisms occur: local diffusion in space, linear cooperation and superlinear competition.

Design and Electronic Characterization of Bio-Molecular QCA: A First Principle Approach

Molecular Quantum-dot Cellular Automata is the most promising and challenging technology nowadays for its high operating frequency, extremely high device density and non-cryogenic working temperature. In this paper, we report a First Principle approach based on analytical model of 3-dot Bio Molecular Quantum-dot Cellular Automata. The device is 19.62Å long and this bio molecular Quantum dot Cell has been made with two Adenine Nucleotide bio-molecules along with one Carbazole and one Thiol group. This whole molecular structure is supported onto Gold substrate. In this paper, two Adenine Nucleotides act as two quantum dots and Carbazole acts as another dot. These 3-Quantum-dots are mounted in a tree like structure supported with Thiol group. This model has been demonstrated with Extended Hückel Theory based semi-empirical method. The quantum ballistic transmission and HOMO-LUMO plot support the polarization state change. This state changing ability has been observed for this molecular device. Therefore, this property has been investigated and reported in this paper. HOMO-LUMO plot shows the two logic states along with null state for this 3-dots system. This phenomenon illustrates how the charge transfers take place. Two polarization states along with one additional null state have been obtained for this bio molecular nano device. This molecular device has been operated with 1000THz frequency. This nanoscale design approach will initiate one step towards the modeling of high frequency bio molecular Quantum dot Cell at room temperature.

Thermodynamic properties of rod-like chains: Entropic sampling simulations

In this work, we apply entropic sampling simulations to a three-state model which has exact solutions in the microcanonical and grand-canonical ensembles. We consider N chains placed on an unidimensional lattice, such that each site may assume one of the three states: empty (state 1), with a single molecule energetically null (state 2), and with a single molecule with energy [Formula: see text] (state 3). Each molecule, which we will treat here as dimers, consists of two monomers connected one to each other by a rod. The thermodynamic properties such as internal energy, densities of dimers and specific heat were obtained as functions of temperature, where the analytic results in the microcanonical and grand-canonical ensembles were successfully confirmed by the entropic sampling simulations.

Effects of age, nursing, and oral IGF1 supplementation on neonatal porcine cervical development

Nursing supports neonatal porcine uterine and testicular development, however, lactocrine effects on cervical development are undefined. Studies were conducted to determine the effects of i) age and the imposition of the lactocrine-null state from birth (postnatal day 0 (PND0)) by milk replacer feeding on cervical histology; ii) imposition of the lactocrine-null state for 2 days from birth on cervical cell proliferation, as reflected by proliferating cell nuclear antigen immunostaining; and iii) a single feeding of colostrum or milk replacer, administered at birth, with or without oral IGF1, on cervical cell proliferation and phosphorylated AKT (pAKT) and B-cell lymphoma 2 (BCL2) protein levels at 12 h postnatal. Cervical crypt depth and height of luminal epithelium (LE) increased with age by PND14, when both responses were reduced in replacer-fed gilts. Cell proliferation was reduced in LE at PND2, and in crypt epithelium and stroma by PND14 in replacer-fed gilts. Returning replacer-fed gilts to nursing on PND2 did not rescue the cervical phenotype by PND14. A single feeding of colostrum, but not milk replacer, was sufficient to support cervical cell proliferation at 12 h postnatal. IGF1 supplementation induced cell proliferation in replacer-fed gilts, and increased cervical pAKT and BCL2 levels in colostrum-fed gilts and replacer-fed gilts at 12 h postnatal. Results indicate that age and nursing support porcine cervical development, support is initiated at first ingestion of colostrum, IGF1 may be lactocrine-active, and identification of lactocrine-active factors can be accomplished by 12 h postnatal using this bioassay system.