2,186 research outputs found
Vortices in Bose-Einstein Condensate Dark Matter
If dark matter in the galactic halo is composed of bosons that form a
Bose-Einstein condensate then it is likely that the rotation of the halo will
lead to the nucleation of vortices. After a review of the Gross-Pitaevskii
equation, the Thomas-Fermi approximation and vortices in general, we consider
vortices in detail. We find strong bounds for the boson mass, interaction
strength, the shape and quantity of vortices in the halo, the critical
rotational velocity for the nucleation of vortices and, in the Thomas-Fermi
regime, an exact solution for the mass density of a single, axisymmetric
vortex.Comment: 10 pages, 3 figures; minor corrections, references adde
Fruit Pest Events and Phenological Development According to Accumulated Heat Units
Mammals are "warm-blooded" and develop at a constant
rate regardless of the environmental temperature,
because they are able to maintain an internal temperature
that allows their biochemical reactions to progress normally.
Insects, which are "exothermic" (the same temperature as
their environment; there is no such thing as "cold-blooded"),
do not generate body heat, and are therefore limited in their
development to periods of favorable external temperature.
Below a certain temperature, which varies among species,
the insect's biochemical reactions cannot proceed, and
development stops. This temperature is known as the
insect's developmental threshold ordevelopmental base.
By charting the ambient temperature, it is possible to keep
track of insect development, which is directly proportional to
the amount of time accumulated above the developmental
threshold (up to some maximum not often reached during
the season). We arbitrarily divide this time into heat units,
or degree-days (DD)
Energy Deposition in Adjacent LHC Superconducting Magnets from Beam Loss at LHC Transfer Line Collimators
Injection intensities for the LHC are over an order of magnitude above the damage threshold. The collimation system in the two transfer lines is designed to dilute the beam sufficiently to avoid damage in case of accidental beam loss or mis-steered beam. To maximise the protection for the LHC most of the collimators are located in the last 300 m upstream of the injection point where the transfer lines approach the LHC machine. To study the issue of possible quenches following beam loss at the collimators part of the collimation section in one of the lines, TI 8, together with the adjacent part of the LHC has been modeled in FLUKA. The simulated energy deposition in the LHC for worst-case accidental losses and as well as for losses expected during a normal filling is presented
Cosmological Consequences of String Axions
Axion fluctuations generated during inflation lead to isocurvature and
non-Gaussian temperature fluctuations in the cosmic microwave background
radiation. Following a previous analysis for the model independent string axion
we consider the consequences of a measurement of these fluctuations for two
additional string axions. We do so independent of any cosmological assumptions
except for the axions being massless during inflation. The first axion has been
shown to solve the strong CP problem for most compactifications of the
heterotic string while the second axion, which does not solve the strong CP
problem, obeys a mass formula which is independent of the axion scale. We find
that if gravitational waves interpreted as arising from inflation are observed
by the PLANCK polarimetry experiment with a Hubble constant during inflation of
H_inf \apprge 10^13 GeV the existence of the first axion is ruled out and the
second axion cannot obey the scale independent mass formula. In an appendix we
quantitatively justify the often held assumption that temperature corrections
to the zero temperature QCD axion mass may be ignored for temperatures T
\apprle \Lambda_QCD.Comment: 27 pages, 4 figures; v2: References corrected; v3: Assumptions
simplified, minor corrections, conclusions unchange
Preliminary Canopy Removal Experiments in Algal Dominated Communities Low on the Shore and in the Shallow Subtidal on the Isle of Man
The algal dominated communities immediately above and below the low-water spring level on a moderately exposed Manx shore were investigated by canopy removal experiments. Fucus serratus, Laminaria digitata and L. hyperborea were removed. Competition was shown to be important in determining the zonation of L. digitata and the distribution along the wave exposure gradient of other species such as Alaria esculenta, Desmarestia aculeata and D. viridis, and L. saccharina. Many species of algal epiphytes were early colonizers of canopy removal areas suggesting that competition from canopy algae usually restricts them to an epiphytic habit. The results indicate that interactions between macrophytes are much more important than grazing in structuring these communities
Wachstum von Winterweizen bei Gärrestdüngung und unterschiedlichen Kleegrasmanagement
Wheat performance and yields were tested in field an experiment regarding pre-crop management and fertilization with biogas digestate. Digestate fertilization led to an increased nitrogen uptake, higher yield and higher protein content. The yield increases were due to denser stands related to earlier fertilization. Recycling nitrogen from the harvested and digested clover-grass increased yield 50 % compared to mulching the above-ground biomass
Evaluating and Understanding Parameterized Convective Processes and their Role in the Development of Mesoscale Precipitation Systems
Research efforts during the second year have centered on improving the manner in which convective stabilization is achieved in the Penn State/NCAR mesoscale model MM5. Ways of improving this stabilization have been investigated by (1) refining the partitioning between the Kain-Fritsch convective parameterization scheme and the grid scale by introducing a form of moist convective adjustment; (2) using radar data to define locations of subgrid-scale convection during a dynamic initialization period; and (3) parameterizing deep-convective feedbacks as subgrid-scale sources and sinks of mass. These investigations were conducted by simulating a long-lived convectively-generated mesoscale vortex that occurred during 14-18 Jul. 1982 and the 10-11 Jun. 1985 squall line that occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. The long-lived vortex tracked across the central Plains states and was responsible for multiple convective outbreaks during its lifetime
Tuning the transition temperature of superconducting Ag/Pb films via the proximity effect
We report measurements of the transition temperature (TC) of superconducting films composed of various combinations of Ag and Pb layers. For samples with good electrical contact between the layers, the measured TC values show reasonable agreement with the Cooper model of the proximity effect. In poorly coupled samples, the normal layers appear to cause little if any suppression of the TC. We present a simple predictive expression for TC as a function of Ag content
Experimental results of crystal-assisted slow extraction at the SPS
The possibility of extracting highly energetic particles from the Super
Proton Synchrotron (SPS) by means of silicon bent crystals has been explored
since the 1990's. The channelling effect of a bent crystal can be used to
strongly deflect primary protons and eject them from the synchrotron. Many
studies and experiments have been carried out to investigate crystal
channelling effects. The extraction of 120 and 270 GeV proton beams has already
been demonstrated in the SPS with dedicated experiments located in the ring.
Presently in the SPS, the UA9 experiment is performing studies to evaluate the
possibility to use bent silicon crystals to steer particle beams in high energy
accelerators. Recent studies on the feasibility of extraction from the SPS have
been made using the UA9 infrastructure with a longer-term view of using
crystals to help mitigate slow extraction induced activation of the SPS. In
this paper, the possibility to eject particles into the extraction channel in
LSS2 using the bent crystals already installed in the SPS is presented. Details
of the concept, simulations and measurements carried out with beam are
presented, before the outlook for the future is discussed.Comment: 4 pages, 7 figures, submitted to to International Particle
Accelerator Conference (IPAC) 2017 in Copenhagen, Denmar
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