4,235 research outputs found
Annual Variation in Northern Bobwhite Survival and Raptor Migration
We estimated survival of radio-marked northern bobwhite (Colinus virginianus) on a managed prairie site in northeast Mississippi during 2 disparate winters (15 Sep-14 Apr 2000–2002). We retrospectively examined factors that may influence bobwhite survival. Pooled survival rates differed substantially between years (S 1⁄4 0.03 6 0.02 in 2000–2001 and S 1⁄4 0.36 6 0.16 in 2001–2002). Regional relative abundance of 3 species of raptors thought to be important predators of bobwhite was greater during 2000 compared to 2001 based on kriging of Christmas Bird Count (CBC) data. We demonstrate an approach for characterizing annual variation in spatial distribution of migratory raptors and suggest that annual variation in local winter predator context may be useful for explaining annual variation in winter survival of local bobwhite populations
GNSS Spoofing Detection via Opportunistic IRIDIUM Signals
In this paper, we study the privately-own IRIDIUM satellite constellation, to
provide a location service that is independent of the GNSS. In particular, we
apply our findings to propose a new GNSS spoofing detection solution,
exploiting unencrypted IRIDIUM Ring Alert (IRA) messages that are broadcast by
IRIDIUM satellites. We firstly reverse-engineer many parameters of the IRIDIUM
satellite constellation, such as the satellites speed, packet interarrival
times, maximum satellite coverage, satellite pass duration, and the satellite
beam constellation, to name a few. Later, we adopt the aforementioned
statistics to create a detailed model of the satellite network. Subsequently,
we propose a solution to detect unintended deviations of a target user from his
path, due to GNSS spoofing attacks. We show that our solution can be used
efficiently and effectively to verify the position estimated from standard GNSS
satellite constellation, and we provide constraints and parameters to fit
several application scenarios. All the results reported in this paper, while
showing the quality and viability of our proposal, are supported by real data.
In particular, we have collected and analyzed hundreds of thousands of IRA
messages, thanks to a measurement campaign lasting several days. All the
collected data ( hours) have been made available to the research
community. Our solution is particularly suitable for unattended scenarios such
as deserts, rural areas, or open seas, where standard spoofing detection
techniques resorting to crowd-sourcing cannot be used due to deployment
limitations. Moreover, contrary to competing solutions, our approach does not
resort to physical-layer information, dedicated hardware, or multiple receiving
stations, while exploiting only a single receiving antenna and
publicly-available IRIDIUM transmissions. Finally, novel research directions
are also highlighted.Comment: Accepted for the 13th Conference on Security and Privacy in Wireless
and Mobile Networks (WISEC), 202
Collinear helium under periodic driving: stabilization of the asymmetric stretch orbit
The collinear eZe configuration of helium, with the electrons on opposite
sides of the nucleus, is studied in the presence of an external electromagnetic
(laser or microwave) field. We show that the classically unstable "asymmetric
stretch" orbit, on which doubly excited intrashell states of helium with
maximum interelectronic angle are anchored, can be stabilized by means of a
resonant driving where the frequency of the electromagnetic field equals the
frequency of Kepler-like oscillations along the orbit. A static magnetic field,
oriented parallel to the oscillating electric field of the driving, can be used
to enforce the stability of the configuration with respect to deviations from
collinearity. Quantum Floquet calculations within a collinear model of the
driven two-electron atom reveal the existence of nondispersive wave packets
localized on the stabilized asymmetric stretch orbit, for double excitations
corresponding to principal quantum numbers of the order of N > 10.Comment: 13 pages, 12 figure
The effect of parallel static and microwave electric fields on excited hydrogen atoms
Motivated by recent experiments we analyse the classical dynamics of a
hydrogen atom in parallel static and microwave electric fields. Using an
appropriate representation and averaging approximations we show that resonant
ionisation is controlled by a separatrix, and provide necessary conditions for
a dynamical resonance to affect the ionisation probability.
The position of the dynamical resonance is computed using a high-order
perturbation series, and estimate its radius of convergence. We show that the
position of the dynamical resonance does not coincide precisely with the
ionisation maxima, and that the field switch-on time can dramatically affect
the ionisation signal which, for long switch times, reflects the shape of an
incipient homoclinic. Similarly, the resonance ionisation time can reflect the
time-scale of the separatrix motion, which is therefore longer than
conventional static field Stark ionisation. We explain why these effects should
be observed in the quantum dynamics.
PACs: 32.80.Rm, 33.40.+f, 34.10.+x, 05.45.Ac, 05.45.MtComment: 47 pages, 20 figure
Magmatically folded and faulted schlieren zones formed by magma avalanching in the Sonora Pass Intrusive Suite, Sierra Nevada, California
The southwestern margin of the Late Cretaceous Sonora Pass Intrusive Suite, northern Sierra Nevada, California (USA), preserves a densely populated zone of magmatic structures that record dynamic magmatic layer formation and deformation (faulting and folding) within a solidifying upper-crustal magma mush. This zone consists largely of coupled melanocratic (or schlieren) and leucocratic bands hosted within the 95.6 ± 1.5 Ma Kinney Lakes granodiorite (Leopold, 2016), with orientations approximately parallel to the intrusive margin and with inward younging directions. Schlieren consist of a high modal abundance of medium-grained ferromagnesian minerals (hornblende + biotite), zircon, sphene, apatite, opaque minerals, and minor plagioclase and interstitial quartz. Leucocratic bands are dominated by coarse-grained feldspar + quartz with minor ferromagnesian and accessory minerals. Whole-rock geochemical and Sr and Nd isotopic data indicate that the schlieren are derived from the Kinney Lakes granodiorite by effective mechanical separation of mafic minerals and accessory phases.
We interpret that the schlieren zone at the margin of the Kinney Lakes granodiorite formed by large-scale collapse of crystal mush by “magma avalanching,” facilitated by gravity, local convection, and possibly by host-rock stoping at the margin. This process eroded a significant portion of the solidifying margin of the chamber and resulted in the formation of magmatically deformed layered structures, which experienced further mingling, re-intrusion, magmatic erosion, and recycling processes. We envisage that magma avalanching of magma mushes in plutons can be achieved by any unstable process (e.g., tectonic, fluid-assisted, stoping, or gravity-driven) in large, long-lived magma-mush chambers
Reply to Comment on "Criterion that Determines the Foldability of Proteins"
We point out that the correlation between folding times and in protein-like heteropolymer models where
and are the collapse and folding transition temperatures
was already established in 1993 before the other presumed equivalent criterion
(folding times correlating with alone) was suggested. We argue that the
folding times for these models show no useful correlation with the energy gap
even if restricted to the ensemble of compact structures as suggested by
Karplus and Shakhnovich (cond-mat/9606037).Comment: 6 pages, Latex, 2 Postscript figures. Plots explicitly showing the
lack of correlation between folding time and energy gap are adde
New Tetrahedral Global Minimum for the 98-atom Lennard-Jones Cluster
A new atomic cluster structure corresponding to the global minimum of the
98-atom Lennard-Jones cluster has been found using a variant of the
basin-hopping global optimization algorithm. The new structure has an unusual
tetrahedral symmetry with an energy of -543.665361, which is 0.022404 lower
than the previous putative global minimum. The new LJ_98 structure is of
particular interest because its tetrahedral symmetry establishes it as one of
only three types of exceptions to the general pattern of icosahedral structural
motifs for optimal LJ microclusters. Similar to the other exceptions the global
minimum is difficult to find because it is at the bottom of a narrow funnel
which only becomes thermodynamically most stable at low temperature.Comment: 3 pages, 2 figures, revte
Structural Transitions and Global Minima of Sodium Chloride Clusters
In recent experiments on sodium chloride clusters structural transitions
between nanocrystals with different cuboidal shapes were detected. Here we
determine reaction pathways between the low energy isomers of one of these
clusters, (NaCl)35Cl-. The key process in these structural transitions is a
highly cooperative rearrangement in which two parts of the nanocrystal slip
past one another on a {110} plane in a direction. In this way the
nanocrystals can plastically deform, in contrast to the brittle behaviour of
bulk sodium chloride crystals at the same temperatures; the nanocrystals have
mechanical properties which are a unique feature of their finite size. We also
report and compare the global potential energy minima for (NaCl)NCl- using two
empirical potentials, and comment on the effect of polarization.Comment: extended version, 13 pages, 8 figures, revte
KESESUAIAN DAN DAYA DUKUNG KAWASAN EKOWISATA KEBUN KIMA NEGERI MORELLA, KABUPATEN MALUKU TENGAH
Tihlepuai Bay in Morella Village has a protected area called Kebun Kima, which has been developed to become a location for marine ecotourism. An increase in visitor numbers is thought to disrupt conservation activities due to the lack of understanding of local people and tourists regarding the importance of developing marine conservation and tourism. This study aims to analyze the suitability and carrying capacity of the Kebun Kima ecotourism area. The research was conducted in Kebun Kima ecotourism area in Tihlepuai Bay from April to June 2020. Data collection on the suitability of the location designated for the snorkeling and diving categories was obtained from the results of measuring the suitability parameters of the area. Carrying capacity data is intended to determine the number of tourists who can occupy the area. Community social data collection in the form of support for the development of marine ecotourism in the Kebun Kima and tourists' assessment of the coral reef's beauty was obtained from interview results, field observation, and questionnaires. The data obtained were then analyzed descriptively. Based on the study's results, diving and snorkeling activities are suitable for development with a carrying capacity of 4 people per day, both snorkeling and diving. The proportion of people who do not know about the impact of coral reef damage is about 55%, while the proportion of tourists evaluating the coral reef's attractiveness is 60% for the 'very good' category.
ABSTRAK
Pantai Teluk Tihlepuai di Negeri Morella memiliki sebuah kawasan yang dilindungi bernama Kebun Kima yang dikembangkan menjadi lokasi ekowisata bahari. Peningkatan jumlah pengunjung di kawasan konservasi Kebun Kima diduga dapat mengganggu kegiatan konservasi. Hal ini disebabkan kurangnya pemahaman masyarakat lokal maupun wisatawan tentang pentingnya pengembangan konservasi dan wisata bahari. Penelitian ini bertujuan untuk menganalisis kesesuaian dan daya dukung kawasan ekowisata kebun kima. Penelitian dilakukan di kawasan ekowisata Kebun Kima di Pantai Teluk Tihlepuai, Negeri Morella, Kabupaten Maluku Tengah pada April-Juni 2020. Pengambilan data kesesuaian lokasi yang diperuntukkan untuk kategori snorkeling dan selam diperoleh dari hasil pengukuran parameter kesesuaian kawasan. Pengambilan data daya dukung diperuntukkan untuk mengetahui jumlah wisatawan yang dapat menempati kawasan tersebut. Pengambilan data sosial masyarakat berupa dukungan terhadap pengembangan ekowisata bahari kebun kima dan penilaian wisatawan terhadap keindahan terumbu karang diperoleh dari hasil wawancara, pengamatan lapangan, dan penyebaran kuesioner. Data yang diperoleh kemudian dianalisis secara deskriptif. Berdasarkan hasil penelitian, kegiatan selam dan snorkeling sesuai untuk dikembangkan serta snorkeling dengan daya dukung mampu melayani 4 orang/hari, dan kategori selam dengan tingkat pelayanan 4 orang wisatawan/hari. Persepsi masyarakat kategori tidak tahu tentang dampak kerusakan terumbu karang sebesar 55%, sedangkan penialian wisatawan terhadap keindangan terumbu karang di kebun kima kategori sangat bagus sebesar 60%.
Kata kunci: Ekowisata, kebun kima, kesesuaian, daya dukung, Negeri Morell
Coarse grained description of the protein folding
We consider two- and three-dimensional lattice models of proteins which were
characterized previously. We coarse grain their folding dynamics by reducing it
to transitions between effective states. We consider two methods of selection
of the effective states. The first method is based on the steepest descent
mapping of states to underlying local energy minima and the other involves an
additional projection to maximally compact conformations. Both methods generate
connectivity patterns that allow to distinguish between the good and bad
folders. Connectivity graphs corresponding to the folding funnel have few loops
and are thus tree-like. The Arrhenius law for the median folding time of a
16-monomer sequence is established and the corresponding barrier is related to
easily identifiable kinetic trap states.Comment: REVTeX, 9 pages, 15 EPS figures, to appear in Phys. Rev.
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