451 research outputs found
Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000–2010
Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000–2010) record of summer-time energy balance components (net radiation, R n; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G) from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD) during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (β=H/LE) compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (D s) was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/R n and LE/R n and decreasing G/R n and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system
Performing the paradox: collaboration as intervention in Eis o Homem
After the economic crisis of 2008, Portugal, like other European countries, underwent a readjustment programme based on neo-liberal principles. This programme widened the gap between rich and poor and elevated the economic over the social, the political and the affective. This paper analyses the devised performance Eis o Homem (Behold Man) as both an artistic and intellectual intervention in this context of crisis. It suggests that collaboration between artists on an explicitly non-hierarchical basis functioned as a coping mechanism for both the artists involved and the audience. The material generated during rehearsals contrasted the powerful reality of life as lived by Portuguese citizens during this period with the Real, that, as Slavoj Zizek has argued, masked this reality with social discourses that emphasized that there was no alternative to the dominance of the market. It concludes that such forms of theatrical collaboration, which explicitly contemplate the right to dissensus, can lead to complex, transformative responses to social situations and to dialogically-informed performances
Lepton flavor conserving Z -> l^+ l^-$ decays in the general two Higgs doublet model
We calculate the new physics effects to the branching ratios of the lepton
flavor conserving decays Z -> l^+ l^- in the framework of the general two Higgs
Doublet model. We predict the upper limits for the couplings
|\bar{\xi}^{D}_{N,\mu\tau}| and |\bar{\xi}^{D}_{N,\tau\tau}| as 3\times 10^2
GeV and 1\times 10^2 GeV, respectively.Comment: 9 pages, 3 figure
Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland
The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt. For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during summer clouds have a cooling effect over tundra and a warming effect over ice, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled with modelling efforts are essential for assessing the impact of warming in the Arctic. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13280-016-0867-5) contains supplementary material, which is available to authorized users
Weak magnetic dipole moments in two-Higgs-doublet models
We investigate the effects of the new scalars in a two-Higgs-doublet model on
the weak magnetic dipole moments of the fermions at the peak.
Proportionality of the Yukawa couplings to the fermion masses, and to
, makes such effects more important for the third family, and
potentially relevant. For the lepton, the new diagrams are suppressed by
, or by powers of , but may still
be comparable to the SM electroweak contributions. In contrast, we find that
the new contributions for the bottom quark may be much larger than the SM
electroweak contributions. These new effects may even compete with the gluonic
contribution, if the extra scalars are light and is large. We also
comment on the problem of the gauge dependence of the vertex, arising when the
is off mass shell. We compute the contributions from the new scalars to the
magnetic dipole moments for top-quark production at the NLC, and for bottom and
production at LEP2. In the case of the top, we find that the SM
electroweak and gluonic contributions to the vertex are
comparable. The new contributions may be of the same order of magnitude as the
standard-model ones, but not much larger.Comment: 17 pages, LaTex, 8 figures available upon reques
Status of the LUX Dark Matter Search
The Large Underground Xenon (LUX) dark matter search experiment is currently
being deployed at the Homestake Laboratory in South Dakota. We will highlight
the main elements of design which make the experiment a very strong competitor
in the field of direct detection, as well as an easily scalable concept. We
will also present its potential reach for supersymmetric dark matter detection,
within various timeframes ranging from 1 year to 5 years or more.Comment: 4 pages, in proceedings of the SUSY09 conferenc
Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin Asymmetries
We present a measurement of semi-inclusive spin asymmetries for positively
and negatively charged hadrons from deep inelastic scattering of polarised
muons on polarised protons and deuterons in the range 1
GeV. Compared to our previous publication on this subject, with the new
data the statistical errors have been reduced by nearly a factor of two.
From these asymmetries and our inclusive spin asymmetries we determine the
polarised quark distributions of valence quarks and non-strange sea quarks at
=10 GeV. The polarised valence quark distribution, , is positive and the polarisation increases with . The polarised
valence quark distribution, , is negative and the non-strange
sea distribution, , is consistent with zero over the measured
range of . We find for the first moments , and
, where we assumed
. We also determine for the first time the
second moments of the valence distributions .Comment: 17 page
- …