10,060 research outputs found
Reverse engineering small 4-manifolds
We introduce a general procedure called `reverse engineering' that can be
used to construct infinite families of smooth 4-manifolds in a given
homeomorphism type. As one of the applications of this technique, we produce an
infinite family of pairwise nondiffeomorphic 4-manifolds homeomorphic to
CP^2#3(-CP^2).Comment: 13 pages, 2 figures. This is the final version published in AGT,
volume 7 (2007), pp. 2103-2116
Comprehending environmental and economic sustainability: Comparative analysis of stability principles in the biosphere and free market economy
Using the formalism of Lyapunov potential function it is shown that the
stability principles for biomass in the ecosystem and for employment in
economics are mathematically similar. The ecosystem is found to have a stable
and an unstable stationary state with high (forest) and low (grasslands)
biomass, respectively. In economics, there is a stable stationary state with
high employment, which corresponds to mass production of conventional goods
sold at low cost price, and an unstable stationary state with lower employment,
which corresponds to production of novel goods appearing in the course of
technological progress. An additional stable stationary state is described for
economics, the one corresponding to very low employment in production of life
essentials such as energy and raw materials. In this state the civilization
currently pays 10% of global GDP for energy produced by a negligible minority
of the working population (currently ~0.2%) and sold at prices greatly
exceeding the cost price by 40 times. It is shown that economic ownership over
energy sources is equivalent to equating measurable variables of different
dimensions (stores and fluxes), which leads to effective violation of the laws
of energy and matter conservation.Comment: 51 pages, 6 figure
Time Scales in Long GRBs
We analyze a sample of bright long bursts and find that the pulses duration
have a lognormal distribution while the intervals between pulses have an excess
of long intervals (relative to lognormal distribution). This excess can be
explained by the existence of quiescent times, long periods with no signal
above the background. The lognormal distribution of the intervals (excluding
the quiescent times) is similar to the distribution of the pulses width. This
result suggests that the quiescent times are made by a different mechanism than
the rest of the intervals. It also suggests that the intervals (excluding the
quiescent times) and the pulse width are connected to the same parameters of
the source. We find that there is a correlation between a pulse width and the
duration of the interval preceding it. There is a weaker, but still a
significant, correlation between a pulse width and the interval following it.
The significance of the correlation drops substantially when the intervals
considered are not adjacent to the pulse.Comment: 5 pages, 8 figures, accepted for publication by MNRA
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Cats with thermal burn injuries from California wildfires show echocardiographic evidence of myocardial thickening and intracardiac thrombi.
Recent increases in the prevalence and severity of wildfires in some regions have resulted in an increased frequency of veterinary burn patients. Few studies exist regarding diagnostics and management of burn wounds in veterinary patients and current knowledge is extrapolated from human literature and research models. Post-burn cardiac injury is a common finding and predictor of mortality in human patients and echocardiography is an important tool in monitoring response to therapy and predicting outcome. We describe the notable findings from cats naturally exposed to California wildfires in 2017 and 2018. Domestic cats (n = 51) sustaining burn injuries from the Tubbs (2017) and Camp (2018) wildfires were prospectively enrolled and serial echocardiograms and cardiac troponin I evaluations were performed. Echocardiograms of affected cats revealed a high prevalence of myocardial thickening (18/51) and spontaneous echocardiographic contrast and thrombi formation (16/51). Forty-two cats survived to discharge and 6 died or were euthanized due to a possible cardiac cause. For the first time, we describe cardiovascular and coagulation effects of thermal burn and smoke inhalation in cats. Further studies in veterinary burn victims are warranted and serve as a translational research opportunity for uncovering novel disease mechanisms and therapies
The Power Spectra of Two Classes of Long-duration Gamma-ray Bursts
We have studied the averaged power density spectra (PDSs) of two classes of
long-duration gamma-ray bursts in the recent classification by Balastegui et
al.(2001) based on neural network analysis. Both PDSs follow a power law over a
wide frequency range with approximately the same slope, which indicates that a
process with a self-similar temporal property may underlie the emission
mechanisms of both. The two classes of bursts are divided into groups according
to their brightness and spectral hardness respectively and each group's PDS was
calculated; For both classes, the PDS is found to flatten both with increasing
burst brightness and with increasing hardness.Comment: 6 pages, 3 figures, a translated version from published in the Acta
Astronomica Sinica, to appear in the Chinese Astronomy & Astrophysics Vol.27,
Issue
Product Formulae for Ozsvath-Szabo 4-manifold Invariants
We give formulae for the Ozsvath-Szabo invariants of 4-manifolds X obtained
by fiber sum of two manifolds M_1, M_2 along surfaces S_1, S_2 having trivial
normal bundle and genus g>0. The formulae follow from a general theorem on the
Ozsvath-Szabo invariants of the result of gluing two 4-manifolds along a common
boundary, which is phrased in terms of relative invariants of the pieces. These
relative invariants take values in a version of Heegaard Floer homology with
coefficients in modules over certain Novikov rings; the fiber sum formula
follows from the theorem that this "perturbed" version of Heegaard Floer theory
recovers the usual Ozsvath-Szabo invariants, when the 4-manifold in question
has b^+>1. The construction allows an extension of the definition of the
Ozsvath-Szabo invariants to 4-manifolds having b^+ = 1 depending on certain
choices, in close analogy with Seiberg-Witten theory. The product formulae lead
quickly to calculations of the Ozsvath-Szabo invariants of various 4-manifolds;
in all cases the results are in accord with the conjectured equivalence between
the Ozsvath-Szabo and Seiberg-Witten invariants.Comment: 70 pages, 2 figure
A Disc-Corona Model for a Rotating Black Hole
We propose a disc-corona model in which a geometrically thin, optically thick
disc surrounds a Kerr black hole, and magnetic fields exert a time-steady
torque on the inner edge of the accretion disc. The analytical expression of
the total gravitational power is derived from the thin-disc dynamics equations
by using this new boundary condition. It is shown that the magnetic torque can
considerably enhance the amount of energy released in the disc-corona system.
Furthermore, the global solutions of this disc-corona system are obtained
numerically. We find that the fraction of the power dissipated into the corona
in the total for such disc-corona system increases with the increasing
dimensionless black hole spin parameter , but is insensitive on the
which is the additional radiative efficiency parameter
relevant to magnetic torque, for . In addition, the
emerged spectra from this disc-corona system are simulated by using Monte-Carlo
method, and the effect of the different parameters on the output spectra is
discussed
Detecting stealthy cyberattacks on adaptive cruise control vehicles: A machine learning approach
With the advent of vehicles equipped with advanced driver-assistance systems,
such as adaptive cruise control (ACC) and other automated driving features, the
potential for cyberattacks on these automated vehicles (AVs) has emerged. While
overt attacks that force vehicles to collide may be easily identified, more
insidious attacks, which only slightly alter driving behavior, can result in
network-wide increases in congestion, fuel consumption, and even crash risk
without being easily detected. To address the detection of such attacks, we
first present a traffic model framework for three types of potential
cyberattacks: malicious manipulation of vehicle control commands, false data
injection attacks on sensor measurements, and denial-of-service (DoS) attacks.
We then investigate the impacts of these attacks at both the individual vehicle
(micro) and traffic flow (macro) levels. A novel generative adversarial network
(GAN)-based anomaly detection model is proposed for real-time identification of
such attacks using vehicle trajectory data. We provide numerical evidence {to
demonstrate} the efficacy of our machine learning approach in detecting
cyberattacks on ACC-equipped vehicles. The proposed method is compared against
some recently proposed neural network models and observed to have higher
accuracy in identifying anomalous driving behaviors of ACC vehicles
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