3,734 research outputs found
Absorbing Phase Transition in a Four State Predator Prey Model in One Dimension
The model of competition between densities of two different species, called
predator and prey, is studied on a one dimensional periodic lattice, where each
site can be in one of the four states say, empty, or occupied by a single
predator, or occupied by a single prey, or by both. Along with the pairwise
death of predators and growth of preys, we introduce an interaction where the
predators can eat one of the neighboring prey and reproduce a new predator
there instantly. The model shows a non-equilibrium phase transition into a
unusual absorbing state where predators are absent and the lattice is fully
occupied by preys. The critical exponents of the system are found to be
different from that of the Directed Percolation universality class and they are
robust against addition of explicit diffusion.Comment: 10 pages, 6 figures, to appear in JSTA
Location, function, and nucleotide sequence of a promoter for bacteriophage T3 RNA polymerase
The major promoters for bacteriophage T3 RNA polymerase on the T3 genome have been mapped by DNA.RNA filter hybridization. One promoter is located in a 300-base-pair Hpa I restriction fragment near the genetic "left" end of T3 DNA. The sequence in the vicinity of the major initiation site of transcription in this region has been determined. A part of the (-)strand sequence is 5' T-A-T-T-T-A-C-C-C-T-C-A-C-T-A-A-A-G-+1 G-G-A-A-U 3'. Comparison of this sequence with the prototype 23-base-pair promoter sequence for bacteriophage T7 RNA polymerase shows a striking pattern of homology and divergence. Between positions -9 and +4, the sequences are virtually identical, whereas between positions -17 and -10, the sequences are quite different. It is postulated that these sequence subsets may perform different functions in transcription initiation by the phage RNA polymerases
Revisiting Absorbing Phase Transition in Energy Exchange Models
A recent study of conserved Manna model, with both discrete and continuous
variable, indicates that absorbing phase transitions therein belong to the
directed percolation (DP) universality class. In this context we revisit
critical behaviour in energy exchange models with a threshold. Contrary to the
previous claims [PRE 83, 061130 (2011), arXiv:1102.1631], our results indicate
that both the maximal and minimal versions of this model belong to the DP
class.Comment: 8 pages, 7 eps figure
Active-to-absorbing state phase transition in the presence of fluctuating environments: Weak and strong dynamic scaling
We investigate the scaling properties of phase transitions between survival
and extinction (active-to-absorbing state phase transition, AAPT) in a model,
that by itself belongs to the directed percolation (DP) universality class,
interacting with a spatio-temporally fluctuating environment having its own
non-trivial dynamics. We model the environment by (i) a randomly stirred fluid,
governed by the Navier-Stokes (NS) equation, and (ii) a fluctuating surface,
described either by the Kardar-Parisi-Zhang (KPZ) or the Edward-Wilkinson (EW)
equations. We show, by using a one-loop perturbative field theoretic set up,
that depending upon the spatial scaling of the variance of the external forces
that drive the environment (i.e., the NS, KPZ or EW equations), the system may
show {\em weak} or {\em strong dynamic scaling} at the critical point of active
to absorbing state phase transitions. In the former case AAPT displays scaling
belonging to the DP universality class, whereas in the latter case the
universal behavior is different.Comment: 17 pages, 2 figures, accepted in PR
Synthetic Turbulence, Fractal Interpolation and Large-Eddy Simulation
Fractal Interpolation has been proposed in the literature as an efficient way
to construct closure models for the numerical solution of coarse-grained
Navier-Stokes equations. It is based on synthetically generating a
scale-invariant subgrid-scale field and analytically evaluating its effects on
large resolved scales. In this paper, we propose an extension of previous work
by developing a multiaffine fractal interpolation scheme and demonstrate that
it preserves not only the fractal dimension but also the higher-order structure
functions and the non-Gaussian probability density function of the velocity
increments. Extensive a-priori analyses of atmospheric boundary layer
measurements further reveal that this Multiaffine closure model has the
potential for satisfactory performance in large-eddy simulations. The
pertinence of this newly proposed methodology in the case of passive scalars is
also discussed
The effect of lockdown regulations on SARS-CoV-2 infectivity in Gauteng Province, South Africa
Background. On 26 March 2020, the South African (SA) government initiated a 21-day national level 5 lockdown which was subsequently eased off and downgraded to level 4 on 1 May and to level 3 on 1 June. The effect of lockdown measures on SARS-CoV-2 infectivity is currently uncertain. In this article, we analyse the effects of the lockdown measures on the SARS-CoV-2 epidemic in one of the epicentres in SA.Objectives. To measure the effects of lockdown measures introduced in SA on SARS-CoV-2 attack rates (ARs, the percentage of individuals who tested positive in a specified time period) in Gauteng Province during a 4-month period (March - June 2020).Methods. In this retrospective cohort study, we used a comprehensive database from an independent pathology laboratory in Gauteng. We analysed trends of positivity rates of reverse transcription polymerase chain reaction tests done during the 4-month period. The ARs are reported over time (unweighted and age-weighted 14-day moving averages) by age groups, gender, and different regions/districts in Gauteng.Results. A total of 162 528 tests were performed at a private laboratory between 5 March and 30 June 2020, of which 20 574 were positive (overall AR 12.7%). These positive tests constituted 44.8% of all positive cases in the province (20 574/45 944). Sixty-two percent of all tests were done in June during lockdown level 3. There was an exponential increase in the AR in June (18.3%) when lockdown was eased to level 3, in comparison with 4.2% (March), 2.2% (April) and 3.3% (May). The increase in June was seen in all the age groups, although it was more pronounced in the 21 - 60 years age groups than the younger (0 - 20 years) and older (>60 years) age groups. The AR was significantly higher in males (13.2%) compared with females (12.1%) (χ2 test, p<0.0001).Conclusions. The findings of this study testify to the rapid increase in ARs resulting from easing of the lockdown regulations, especially to level 3 in June. Of concern is the upward trend in the AR across all age groups, especially <20 years (15.9%), which was not reported in other parts of the world. Population age dynamics should therefore be considered when taking future decisions about lockdown regulations
Modular Cosmology
An exploratory study of the cosmology of moduli in string theory. Moduli are
argued to be natural inflaton fields and lead to a robust inflationary
cosmology in which inflation takes place at the top of domain walls. The
amplitude of microwave background fluctuations constrains the dynamics
responsible for inflation to take place at a higher scale than supersymmetry
breaking. Models explaining this difference in scales and also preventing the
dilaton from running to infinity are proposed. The problem of dilaton
domination of the energy density of the universe is not resolved.Comment: harvmac, 37 pages, 3 figures as a separate uuencoded tar fil
CCAT-prime: Science with an Ultra-widefield Submillimeter Observatory at Cerro Chajnantor
We present the detailed science case, and brief descriptions of the telescope
design, site, and first light instrument plans for a new ultra-wide field
submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m
elevation site on Cerro Chajnantor in northern Chile. Our science goals are to
study star and galaxy formation from the epoch of reionization to the present,
investigate the growth of structure in the Universe, improve the precision of
B-mode CMB measurements, and investigate the interstellar medium and star
formation in the Galaxy and nearby galaxies through spectroscopic,
polarimetric, and broadband surveys at wavelengths from 200 um to 2 mm. These
goals are realized with our two first light instruments, a large field-of-view
(FoV) bolometer-based imager called Prime-Cam (that has both camera and an
imaging spectrometer modules), and a multi-beam submillimeter heterodyne
spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very
low system emissivity, so that combined with its wide FoV at the unsurpassed
CCAT site our telescope/instrumentation combination is ideally suited to pursue
this science. The CCAT-prime telescope is being designed and built by Vertex
Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.Comment: Presented at SPIE Millimeter, Submillimeter, and Far-Infrared
Detectors and Instrumentation for Astronomy IX, June 14th, 201
Meso-Level Database Coverage and Insights Village Dynamics in South Asia
Background: The meso-level dataset for India and
Bangladesh contains data pertaining to the performance,
structure and dynamics of agricultural economy at
country level and its disaggregation at state/region,
district, and sub-district level.
The dataset maintained by ICRISAT and updated under
the Village Dynamics in South Asia (VDSA) Project
provides a comprehensive one-stop shop for data related
to key agricultural and socioeconomic variables that are
relevant for hypotheses testing, identification of regions/
districts for priority setting, and targeted poverty alleviation
development initiatives. The meso-data thus acts as a link
between the country/state/district level macro/meso-data
and household-level micro data (see Figure 1)
A scalar field instability of rotating and charged black holes in (4+1)-dimensional Anti-de Sitter space-time
We study the stability of static as well as of rotating and charged black
holes in (4+1)-dimensional Anti-de Sitter space-time which possess spherical
horizon topology. We observe a non-linear instability related to the
condensation of a charged, tachyonic scalar field and construct "hairy" black
hole solutions of the full system of coupled Einstein, Maxwell and scalar field
equations. We observe that the limiting solution for small horizon radius is
either a hairy soliton solution or a singular solution that is not a regular
extremal solution. Within the context of the gauge/gravity duality the
condensation of the scalar field describes a holographic
conductor/superconductor phase transition on the surface of a sphere.Comment: 16 pages including 8 figures, v2: discussion on soliton solutions
extended; v3: matches version accepted for publication in JHE
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