2,890 research outputs found
Electrostatic Characterization of Lunar Dust Simulants
Lunar dust can jeopardize exploration activities due to its ability to cling to most surfaces. In this paper, we report on our measurements of the electrostatic properties of the lunar soil simulants. Methods have been developed to measure the volume resistivity, dielectric constant, chargeability, and charge decay of lunar soil. While the first two parameters have been measured in the past [Olhoeft 1974], the last two have never been measured directly on the lunar regolith or on any of the Apollo samples. Measurements of the electrical properties of the lunar samples are being performed in an attempt to answer important problems that must be solved for the development of an effective dust mitigation technology, namely, how much charge can accumulate on the dust and how long does the charge remain on surfaces. The measurements will help develop coatings that are compatible with the intrinsic electrostatic properties of the lunar regolith
Multi-lepton Signatures of a Hidden Sector in Rare B Decays
We explore the sensitivity of flavour changing b -> s transitions to a
(sub-)GeV hidden sector with generic couplings to the Standard Model through
the Higgs, vector and axion portals. The underlying two-body decays of B
mesons, B -> X_s S and B0 -> SS, where S denotes a generic new GeV-scale
particle, may significantly enhance the yield of monochromatic lepton pairs in
the final state via prompt decays of S to a dilepton pair. Existing
measurements of the charged lepton spectrum in neutral-current semileptonic B
decays provide bounds on the parameters of the light sector that are
significantly more stringent than the requirements of naturalness. New search
modes, such as B -> X_s + n(l+l-) and B0 -> n(l+l-) with n > 1 can provide
additional sensitivity to scenarios in which both the Higgs and vector portals
are active, and are accessible to (super-)B factories and hadron colliders.Comment: 12 pages, 2 figures; v2: reference added, minor correction
Indirect Detection of a Light Higgsino Motivated by Collider Data
Kane and Wells recently argued that collider data point to a Higgsino-like
lightest supersymmetric partner which would explain the dark matter in our
Galactic halo. They discuss direct detection of such dark-matter particles in
laboratory detectors. Here, we argue that such a particle, if it is indeed the
dark matter, might alternatively be accessible in experiments which search for
energetic neutrinos from dark-matter annihilation in the Sun. We provide
accurate analytic estimates for the rates which take into account all relevant
physical effects. Currently, the predicted signal falls roughly one to three
orders of magnitude below experimental bounds, depending on the mass and
coupling of the particle; however, detectors such as MACRO, super-Kamiokande,
and AMANDA will continue to take data and should be able to rule out or confirm
an interesting portion of the possible mass range for such a dark-matter
particle within the next five years.Comment: 10 pages, RevTe
Dissemination of Microprocessor Courses Through Classroom and Interactive Cyber-Enabled Technologies
The project is in the middle stages of the implementation. There seems to be a positive attitude of learning and using of the training system and curriculum package by all project staffs. Microchip, Inc. and microEngineering Labs, Inc. have donated supplies to support the hardware and software development for this project. The next objectives are team training, recruitment of interested trainees/teachers to participate in training for summers 2014, and assess the effectiveness of the implementations with teachers and students. Photo 2 is the project logo that describes all the concepts of this project
Time Asymmetric Quantum Physics
Mathematical and phenomenological arguments in favor of asymmetric time
evolution of micro-physical states are presented.Comment: Tex file with 2 figure
Paper Session II-A - Results of a Wheel Electrometer for Measuring the Triboelectric Properties of Martian Regolith
The preliminary results of a prototype Wheel Electrometer System (WES) are presented that show that it is indeed possible to use the static electricity generated between polymers and soils after contact (triboelectricity) as a means of detecting property changes. Changes in the triboelectric signals offer information as to the mechanical properties of the soil such as grain size differences, texture, hardness and even moisture content. Initially, four polymers are chosen that span the triboelectric series such as Teflon, Lucite, Fiberglass and Lexan. It is shown that the average charge on Teflon is much higher when rolled over beach sand as compared to Martian simulant and limestone. Lucite was the most susceptible to particle size differences, while Lexan was able to detect underlying materials in the case of a soil lightly covered with a different soil type. All polymers responded differently when rolled over dry soil compared with moist soil. This information can be used as a type of triboelectric spectroscopy when a library of data is used to categorize the unique charging characteristics of individual polymers. This system is of great interest to planetary scientists and such measurements may be included in future Mars rover missions
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 4: Cosmic Frontier
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 4, on the Cosmic Frontier, discusses the
program of research relevant to cosmology and the early universe. This area
includes the study of dark matter and the search for its particle nature, the
study of dark energy and inflation, and cosmic probes of fundamental
symmetries.Comment: 61 page
The Concordance Cosmic Star Formation Rate: Implications from and for the Supernova Neutrino and Gamma Ray Backgrounds
We constrain the Cosmic Star Formation Rate (CSFR) by requiring that massive
stars produce the observed UV, optical, and IR light while at the same time not
overproduce the Diffuse Supernova Neutrino Background as bounded by
Super-Kamiokande. With the massive star component so constrained we then show
that a reasonable choice of stellar Initial Mass Function and other parameters
results in SNIa rates and iron yields in good agreement with data. In this way
we define a `concordance' CSFR that predicts the optical SNII rate and the SNIa
contribution to the MeV Cosmic Gamma-Ray Background. The CSFR constrained to
reproduce these and other proxies of intermediate and massive star formation is
more clearly delineated than if it were measured by any one technique and has
the following testable consequences: (1) SNIa contribute only a small fraction
of the MeV Cosmic Gamma-Ray Background, (2) massive star core-collapse is
nearly always accompanied by a successful optical SNII, and (3) the Diffuse
Supernova Neutrino Background is tantalizingly close to detectability.Comment: Improved discussion. Version accepted for publication in JCA
Oscillator neural network model with distributed native frequencies
We study associative memory of an oscillator neural network with distributed
native frequencies. The model is based on the use of the Hebb learning rule
with random patterns (), and the distribution function of
native frequencies is assumed to be symmetric with respect to its average.
Although the system with an extensive number of stored patterns is not allowed
to get entirely synchronized, long time behaviors of the macroscopic order
parameters describing partial synchronization phenomena can be obtained by
discarding the contribution from the desynchronized part of the system. The
oscillator network is shown to work as associative memory accompanied by
synchronized oscillations. A phase diagram representing properties of memory
retrieval is presented in terms of the parameters characterizing the native
frequency distribution. Our analytical calculations based on the
self-consistent signal-to-noise analysis are shown to be in excellent agreement
with numerical simulations, confirming the validity of our theoretical
treatment.Comment: 9 pages, revtex, 6 postscript figures, to be published in J. Phys.
Comprehensive framework for human health risk assessment of nanopesticides
Nanopesticides are not only in an advanced state of research and development but have started to appear on the market. Industry and regulatory agencies need a consolidated and comprehensive framework and guidance for human health risk assessments. In this perspective we develop such a comprehensive framework by exploring two case studies from relevant product types: an active ingredient delivered with a nanocarrier system, and a nanoparticle as an active ingredient. For a nanocarrier system, three entities are tracked during the assessment: the nanocarrier–active ingredient complex, the empty nanocarrier remaining after the complete release of the active ingredient, and the released active ingredient. For the nanoparticle of pure active ingredient, only two entities are relevant: the nanoparticle and the released ions. We suggest important adaptations of the existing pesticide framework to determine the relevant nanopesticide entities and their concentrations for toxicity testing. Depending on the nature of the nanopesticides, additional data requirements, such as those pertaining to durability in biological media and potential for crossing biological barriers, have also been identified. Overall, our framework suggests a tiered approach for human health risk assessment, which is applicable for a range of nanopesticide products to support regulators and industry in making informed decisions on nanopesticide submissions. Brief summaries of suitable methods including references to existing standards (if available) have been included together with an analysis of current knowledge gaps. Our study is an important step towards a harmonized approach accepted by regulatory agencies for assessing nanopesticides
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