43 research outputs found
Investigating an unusually large 28-day oscillation in mesospheric temperature over Antarctica using ground-based and satellite measurements
The Utah State University (USU) Advanced Mesospheric Temperature Mapper (AMTM) was deployed at the AmundsenâScott South Pole Station in 2010 to measure OH temperature at ~87 km as part of an international network to study the mesospheric dynamics over Antarctica. During the austral winter of 2014, an unusually large amplitude ~28âday oscillation in mesospheric temperature was observed for ~100 days from the South Pole Station. This study investigates the characteristics and global structure of this exceptional planetaryâscale wave event utilizing groundâbased mesospheric OH temperature measurements from two Antarctic stations (South Pole and Rothera) together with satellite temperature measurements from the Microwave Limb Sounder (MLS) on the Aura satellite, and the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite. Our analyses have revealed that this large oscillation is a winter time, high latitude phenomenon, exhibiting a coherent zonal wave #1 structure below 80 km altitude. At higher altitudes, the wave was confined in longitude between 180â360°E. The amplitude of this oscillation reached ~15 K at 85 km and it was observed to grow with altitude as it extended from the stratosphere into the lower thermosphere in the southern hemisphere. The satellite data further established the existence of this oscillation in the northern hemisphere during the boreal winter time. The main characteristics and global structure of this event as observed in temperature are consistent with the predicted 28âday Rossby Wave (1,4) mode
Salerno's model of DNA reanalysed: could solitons have biological significance?
We investigate the sequence-dependent behaviour of localised excitations in a
toy, nonlinear model of DNA base-pair opening originally proposed by Salerno.
Specifically we ask whether ``breather'' solitons could play a role in the
facilitated location of promoters by RNA polymerase. In an effective potential
formalism, we find excellent correlation between potential minima and {\em
Escherichia coli} promoter recognition sites in the T7 bacteriophage genome.
Evidence for a similar relationship between phage promoters and downstream
coding regions is found and alternative reasons for links between AT richness
and transcriptionally-significant sites are discussed. Consideration of the
soliton energy of translocation provides a novel dynamical picture of sliding:
steep potential gradients correspond to deterministic motion, while ``flat''
regions, corresponding to homogeneous AT or GC content, are governed by random,
thermal motion. Finally we demonstrate an interesting equivalence between
planar, breather solitons and the helical motion of a sliding protein
``particle'' about a bent DNA axis.Comment: Latex file 20 pages, 5 figures. Manuscript of paper to appear in J.
Biol. Phys., accepted 02/09/0
About Bianchi I with VSL
In this paper we study how to attack, through different techniques, a perfect
fluid Bianchi I model with variable G,c and Lambda, but taking into account the
effects of a -variable into the curvature tensor. We study the model under
the assumption,div(T)=0. These tactics are: Lie groups method (LM), imposing a
particular symmetry, self-similarity (SS), matter collineations (MC) and
kinematical self-similarity (KSS). We compare both tactics since they are quite
similar (symmetry principles). We arrive to the conclusion that the LM is too
restrictive and brings us to get only the flat FRW solution. The SS, MC and KSS
approaches bring us to obtain all the quantities depending on \int c(t)dt.
Therefore, in order to study their behavior we impose some physical
restrictions like for example the condition q<0 (accelerating universe). In
this way we find that is a growing time function and Lambda is a decreasing
time function whose sing depends on the equation of state, w, while the
exponents of the scale factor must satisfy the conditions
and
, i.e. for all equation of state relaxing in this way the
Kasner conditions. The behavior of depends on two parameters, the equation
of state and a parameter that controls the behavior of
therefore may be growing or decreasing.We also show that through
the Lie method, there is no difference between to study the field equations
under the assumption of a var affecting to the curvature tensor which the
other one where it is not considered such effects.Nevertheless, it is essential
to consider such effects in the cases studied under the SS, MC, and KSS
hypotheses.Comment: 29 pages, Revtex4, Accepted for publication in Astrophysics & Space
Scienc
The Anatomic Variations of the Circle of Willis in Preterm-at-Term and Term-Born Infants: An MR Angiography Study at 3T
âItâs Kinda Punishmentâ: Tandem Logics and Penultimate Power in the Penal Voluntary Sector for Canadian Youth
This paper draws on original empirical research in Ontario, Canada which analyses penal voluntary sector practice with youth in conflict with the law. I illustrate how youth penal voluntary sector practice (YPVS) operates alongside, or in tandem with the statutory criminal justice system. I argue that examining the PVS and the statutory criminal justice system simultaneously, or in tandem, provides fuller understandings of PVS inclusionary (and exclusionary) control practices (Tomczak and Thompson 2017). I introduce the concept of penultimate power, which demonstrates the ability of PVS workers to trigger criminal justice system response toward a young person in conflict with the law. My novel concepts of tandem logics and penultimate power are useful for understanding PVS practice, explaining how seemingly contradictory approaches across state and âcommunityâ organizations not only co-exist, but depend upon the tandem relationship between the PVS and the statutory criminal justice system
Bianchi II with time varying constants. Self-similar approach
We study a perfect fluid Bianchi II models with time varying constants under
the self-similarity approach. In the first of the studied model, we consider
that only vary and The obtained solution is more general that
the obtained one for the classical solution since it is valid for an equation
of state while in the classical solution
Taking into account the current observations, we conclude
that must be a growing time function while is a positive
decreasing function. In the second of the studied models we consider a variable
speed of light (VSL). We obtain a similar solution as in the first model
arriving to the conclusions that must be a growing time function if
is a positive decreasing function.Comment: 10 pages. RevTeX
Surveying the effects of aging a high C-containing co-based superalloy from the As-cast and solution heat-treated conditions
The microstructure of the high carbon-containing cobalt-based superalloy, Co-101, has been studied in the as-cast state and following a variety of heat treatments. In the as-cast state both M7C3 and Mo-rich M23C6 carbides were observed in the interdendritic regions. After thermal exposure at temperatures between 1000 °C and 1250 °C for 1, 10, and 100 hours, the M7C3 interdendritic carbide network was observed to transform into a Mo-lean M23C6 carbide. These changes were rationalized with thermodynamic calculations. The carbide transformation liberated carbide-forming elements that resulted in the precipitation of intragranular carbides in the dendritic regions at temperatures below 1150 °C. These carbides in the cast-aged material preferentially formed at the dendrite peripheries early during exposure, leading to wide particle size distributions. Peak hardness in the cast-aged material was attained within the first 10 hours of exposure and softening was observed thereafter. After solution heat treating at 1250 °C for 10 hours, the microstructure of Co-101 comprised an M23C6 interdendritic carbide network and solid solution dendrites supersaturated with carbide-forming elements. Subsequent aging of this microstructure for 100 hours at 900 °C led to a high number density and narrow particle size distribution of intragranular carbides. The characteristics of these carbides in the solution-aged material resulted in greater hardness, which was retained for longer durations of exposure, than the cast-aged specimens