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Environmental catastrophes, climate change, and attribution
In our discussion of environmental and ecological catastrophes or disasters resulting from extreme weather events, we unite disparate literatures, the biological and the physical. Our ultimate goal is to tie together biological understandings of extreme environmental events with physical understandings of extreme weather events into joint causal accounts. This requires fine-grained descriptions, in both space and time, of the ecological, evolutionary, and biological moving parts of a system together with fine-grained descriptions, also in both space and time, of the extreme weather events. We find that both the âstorylineâ approach to extreme event attribution and the probabilistic ârisk-basedâ approach have uses in such descriptions. However, the storyline approach is more readily aligned with the forensic approach to evidence that is prevalent in the ecological literature, which cultivates expert-based rules of thumb, i.e., heuristics, and detailed methods for analyzing causes and mechanisms. We introduce below a number of preliminary examples of such studies, as instances of what could be pursued in the future in much more detail
Bottom-up thermalization in heavy ion collisions
We describe how thermalization occurs in heavy ion collisions in the
framework of perturbative QCD. When the saturation scale is large
compared to , thermalization takes place during a time of order
and the maximal temperature achieved is
.Comment: 11 pages; acknowledgement added; section IIIB slightly extended,
version accepted for publication in Phys. Lett.
The fitness costs of antibiotic resistance mutations
Antibiotic resistance is increasing in pathogenic microbial populations and is thus a major threat to public health. The fate of a resistance mutation in pathogen populations is determined in part by its fitness. Mutations that suffer little or no fitness cost are more likely to persist in the absence of antibiotic treatment. In this review, we performed a meta-analysis to investigate the fitness costs associated with single mutational events that confer resistance. Generally, these mutations were costly, although several drug classes and species of bacteria on average did not show a cost. Further investigations into the rate and fitness values of compensatory mutations that alleviate the costs of resistance will help us to better understand both the emergence and management of antibiotic resistance in clinical settings
Thermal and Chemical Equilibration in Relativistic Heavy Ion Collisions
We investigate the thermalization and the chemical equilibration of a parton
plasma created from Au+Au collision at LHC and RHIC energies starting from the
early moment when the particle momentum distributions in the central region
become for the first time isotropic due to longitudinal cooling. Using the
relaxation time approximation for the collision terms in the Boltzmann
equations for gluons and for quarks and the real collision terms constructed
from the simplest QCD interactions, we show that the collision times have the
right behaviour for equilibration. The magnitude of the quark (antiquark)
collision time remains bigger than the gluon collision time throughout the
lifetime of the plasma so that gluons are equilibrating faster than quarks both
chemically and kinetically. That is we have a two-stage equilibration scenario
as has been pointed out already by Shuryak sometimes ago. Full kinetic
equilibration is however slow and chemical equilibration cannot be completed
before the onset of the deconfinement phase transition assumed to be at
MeV. By comparing the collision entropy density rates of the
different processes, we show explicitly that inelastic processes, and
\emph{not} elastic processes as is commonly assumed, are dominant in the
equilibration of the plasma and that gluon branching leads the other processes
in entropy generation. We also show that, within perturbative QCD, processes
with higher power in \alpha_s need not be less important for the purpose of
equilibration than those with lower power. The state of equilibration of the
system has also a role to play. We compare our results with those of the parton
cascade model.Comment: 17 pages, revtex+psfig style with 14 embedded postscript figures, to
appear in Phys. Rev.
New exact solution of Dirac-Coulomb equation with exact boundary condition
It usually writes the boundary condition of the wave equation in the Coulomb
field as a rough form without considering the size of the atomic nucleus. The
rough expression brings on that the solutions of the Klein-Gordon equation and
the Dirac equation with the Coulomb potential are divergent at the origin of
the coordinates, also the virtual energies, when the nuclear charges number Z >
137, meaning the original solutions do not satisfy the conditions for
determining solution. Any divergences of the wave functions also imply that the
probability density of the meson or the electron would rapidly increase when
they are closing to the atomic nucleus. What it predicts is not a truth that
the atom in ground state would rapidly collapse to the neutron-like. We
consider that the atomic nucleus has definite radius and write the exact
boundary condition for the hydrogen and hydrogen-like atom, then newly solve
the radial Dirac-Coulomb equation and obtain a new exact solution without any
mathematical and physical difficulties. Unexpectedly, the K value constructed
by Dirac is naturally written in the barrier width or the equivalent radius of
the atomic nucleus in solving the Dirac equation with the exact boundary
condition, and it is independent of the quantum energy. Without any divergent
wave function and the virtual energies, we obtain a new formula of the energy
levels that is different from the Dirac formula of the energy levels in the
Coulomb field.Comment: 12 pages,no figure
Public Sentiment Analysis and Topic Modeling Regarding COVID-19âs Three Waves of Total Lockdown: A Case Study on Movement Control Order in Malaysia
[Abstract] The COVID-19 pandemic has affected many aspects of human life. The pandemic not only caused millions of fatalities and problems but also changed public sentiment and behavior. Owing to the magnitude of this pandemic, governments worldwide adopted full lockdown measures that attracted much discussion on social media platforms. To investigate the effects of these lockdown measures, this study performed sentiment analysis and latent Dirichlet allocation topic modeling on textual data from Twitter published during the three lockdown waves in Malaysia between 2020 and 2021. Three lockdown measures were identified, the related data for the first two weeks of each lockdown were collected and analysed to understand the public sentiment. The changes between these lockdowns were identified, and the latent topics were highlighted. Most of the public sentiment focused on the first lockdown as reflected in the large number of latent topics generated during this period. The overall sentiment for each lockdown was mostly positive, followed by neutral and then negative. Topic modelling results identified staying at home, quarantine and lockdown as the main aspects of discussion for the first lockdown, whilst importance of health measures and government efforts were the main aspects for the second and third lockdowns. Governments may utilise these findings to understand public sentiment and to formulate precautionary measures that can assure the safety of their citizens and tend to their most pressing problems. These results also highlight the importance of positive messaging during difficult times, establishing digital interventions and formulating new policies to improve the reaction of the public to emergency situations.Taiwan. Ministry of Science and Technology; 108-2511-H-224-007-MY
Where am I in virtual reality?
It is currently not well understood whether people experience themselves to be located in one or more specific part(s) of their body. Virtual reality (VR) is increasingly used as a tool to study aspects of bodily perception and self-consciousness, due to its strong experimental control and ease in manipulating multi-sensory aspects of bodily experience. To investigate where people self-locate in their body within virtual reality, we asked participants to point directly at themselves with a virtual pointer, in a VR headset. In previous work employing a physical pointer, participants mainly located themselves in the upper face and upper torso. In this study, using a VR headset, participants mainly located themselves in the upper face. In an additional body template task where participants pointed at themselves on a picture of a simple body outline, participants pointed most often to the upper torso, followed by the (upper) face. These results raise the question as to whether head-mounted virtual reality might alter where people locate themselves making them more âhead-centredâ
Closed-Time Path Integral Formalism and Medium Effects of Non-Equilibrium QCD Matter
We apply the closed-time path integral formalism to study the medium effects
of non-equilibrium gluon matter. We derive the medium modified resummed gluon
propagator to the one loop level in non-equilibrium in the covariant gauge. The
gluon propagator we derive can be used to remove the infrared divergences in
the secondary parton collisions to study thermalization of minijet parton
plasma at RHIC and LHC.Comment: Final version, To appear in Physical Review D, Minor modification,
reference adde
Extension of the JIMWLK Equation in the Low Gluon Density Region
It has recently been realized that the Balitsky-JIMWLK equations have serious
shortcomings as equations to be used in small-x evolution near the unitarity
limit. A recent generalization of the Balitsky equations has been given which
corrects these shortcomings. In this paper we present an equivalent discussion,
but in terms of the JIMWLK equation where we show that a new (fourth order
functional derivative) term should be included. We also present a stochastic
version of the new equation which, however, has some unusual mathematical
aspects which are not as yet well understood.Comment: 23 pages, 1 figure, corrected typos, corrected references, published
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