591 research outputs found
Can Machines Think in Radio Language?
People can think in auditory, visual and tactile forms of language, so can
machines principally. But is it possible for them to think in radio language?
According to a first principle presented for general intelligence, i.e. the
principle of language's relativity, the answer may give an exceptional solution
for robot astronauts to talk with each other in space exploration.Comment: 4 pages, 1 figur
Anisotropy of the space orientation of radio sources. I: The catalog
A catalog of the extended extragalactic radio sources consisting of 10461
objects is compiled based on the list of radio sources of the FIRST survey. A
total of 1801 objects are identified with galaxies and quasars of the SDSS
survey and the Veron-Veron catalog. The distribution of the position angles of
the axes of radio sources from the catalog is determined, and the probability
that this distribution is equiprobable is shown to be less then 10^(-7). This
result implies that at Z equal to or smaller then 0.5, spatial orientation of
the axes of radio sources is anisotropic at a statistically significant level.Comment: 8 pages, 7 figure
Self-Modification of Policy and Utility Function in Rational Agents
Any agent that is part of the environment it interacts with and has versatile
actuators (such as arms and fingers), will in principle have the ability to
self-modify -- for example by changing its own source code. As we continue to
create more and more intelligent agents, chances increase that they will learn
about this ability. The question is: will they want to use it? For example,
highly intelligent systems may find ways to change their goals to something
more easily achievable, thereby `escaping' the control of their designers. In
an important paper, Omohundro (2008) argued that goal preservation is a
fundamental drive of any intelligent system, since a goal is more likely to be
achieved if future versions of the agent strive towards the same goal. In this
paper, we formalise this argument in general reinforcement learning, and
explore situations where it fails. Our conclusion is that the self-modification
possibility is harmless if and only if the value function of the agent
anticipates the consequences of self-modifications and use the current utility
function when evaluating the future.Comment: Artificial General Intelligence (AGI) 201
Superconductivity in an Einstein Solid AxV2Al20 (A = Al and Ga)
A cage compound AxV2Al20 (Al10V), that was called an Einstein solid by Caplin
and coworkers 40 years ago, is revisited to investigate the low-energy, local
vibrations of the A atoms and their influence on the electronic and
superconducting properties of the compound. Polycrystalline samples with A =
Al, Ga, Y, and La are studied through resistivity and heat capacity
measurements. Weak-coupling BCS superconductivity is observed below Tc = 1.49,
1.66, and 0.69 K for Ax = Al0.3, Ga0.2, and Y, respectively, but not above 0.4
K for Ax = La. Low-energy modes are detected only for A = Al and Ga, which are
approximately described by the Einstein model with Einstein temperatures of 24
and 8 K, respectively. A weak but significant coupling between the low-energy
modes, which are almost identical to those called rattling in recent study, and
conduction electrons manifests itself as anomalous enhancement in resistivity
at around low temperatures corresponding to the Einstein temperatures.Comment: 12 pages, 5 figures, to be published in J. Phys. Soc. Jp
Urban environmental exposures during the first 2000 days of life as a foundation for health across the life-course: a scoping review
Objectives: By 2030, 60% of the global population is expected to live in urban areas. Exposure to urban environments during the first 2000 days of life can have positive or negative health outcomes across the life course. Understanding the types of urban exposures that influence health outcomes is needed to guide research priorities for public health and urban planning. This review aims to summarise the published research examining the health outcomes of all urban environmental exposures during the first 2000 days of life, identify the quantity and characteristics of research in this area, methods used, and knowledge gaps. Methods: We conducted a scoping review using the JBI methodology for scoping reviews. Eight databases were searched for peer-reviewed primary studies. Inclusion criteria were studies that measured maternal, infant and child exposure to everyday urban environment features and conditions in cities/metropolitan areas during the first 2000 days of life and reported offspring health outcomes across the life course, including embryo, fetal/ newborn, infant, child, adolescent, and adult outcomes. We used Covidence software for data screening and extraction. Study characteristics and findings were summarised using tables and narrative synthesis. Results: We reviewed 235 articles, which included studies conducted across 41 countries, the majority in the US (n = 63). A broad range of environmental exposures were studied, spanning seven categories: air pollution; energy-based pollution; atmosphere, chemical and metal exposure; neighbourhood-built and natural environment features; neighbourhood community conditions; and residential living conditions. Air pollution was the most studied exposure type (n = 153 studies). Health outcomes were reported for all life stages except adults, with fetal/ newborn outcomes the most studied life stage (n = 137). Conclusions: We found that most research investigating urban environmental exposures in the first 2000 days and health outcomes across the life course focused on air pollution exposures and fetal/ newborn health outcomes, using correlational retrospective cohort designs. Few studies included multiple environmental exposures. There is a clear need for more longitudinal research to determine the health impacts of multiple urban environmental exposures across the life course. This will assist in developing urban design and planning strategies and population health to mitigate health risks across the life course
Transmission of High-Power Electron Beams Through Small Apertures
Tests were performed to pass a 100 MeV, 430 kWatt c.w. electron beam from the
energy-recovery linac at the Jefferson Laboratory's FEL facility through a set
of small apertures in a 127 mm long aluminum block. Beam transmission losses of
3 p.p.m. through a 2 mm diameter aperture were maintained during a 7 hour
continuous run.Comment: arXiv admin note: text overlap with arXiv:1305.019
General relativistic polarized radiative transfer: building a dynamics-observations interface
The rising amount of polarized observations of relativistic sources requires
the correct theory for proper model fitting. The equations for general
relativistic (GR) polarized radiative transfer are derived starting from the
Boltzmann equation and basic ideas of general relativity. The derivation is
aimed at providing a practical guide to reproducing the synchrotron part of
radio & sub-mm emission from low luminosity active galactic nuclei (LLAGNs), in
particular Sgr A*, and jets. The recipe for fast exact calculation of
cyclo-synchrotron emissivities, absorptivities, Faraday rotation and conversion
coefficients is given for isotropic particle distributions. The multitude of
physical effects influencing simulated spectrum is discussed. The application
of the prescribed technique is necessary to determine the black hole (BH) spin
in LLAGNs, constraining it with all observations of total flux, linear and
circular polarization fractions, and electric vector position angle as
functions of the observed frequency.Comment: 9 pages, 3 figures, accepted by MNRA
Measured Radiation and Background Levels During Transmission of Megawatt Electron Beams Through Millimeter Apertures
We report measurements of photon and neutron radiation levels observed while
transmitting a 0.43 MW electron beam through millimeter-sized apertures and
during beam-off, but accelerating gradient RF-on, operation. These measurements
were conducted at the Free-Electron Laser (FEL) facility of the Jefferson
National Accelerator Laboratory (JLab) using a 100 MeV electron beam from an
energy-recovery linear accelerator. The beam was directed successively through
6 mm, 4 mm, and 2 mm diameter apertures of length 127 mm in aluminum at a
maximum current of 4.3 mA (430 kW beam power). This study was conducted to
characterize radiation levels for experiments that need to operate in this
environment, such as the proposed DarkLight Experiment. We find that sustained
transmission of a 430 kW continuous-wave (CW) beam through a 2 mm aperture is
feasible with manageable beam-related backgrounds. We also find that during
beam-off, RF-on operation, multipactoring inside the niobium cavities of the
accelerator cryomodules is the primary source of ambient radiation when the
machine is tuned for 130 MeV operation.Comment: 9 pages, 11 figures, submitted to Nuclear Instruments and Methods in
Physics Research Section
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