1,690 research outputs found
Contemporary Art and Historical Archives: Collaborations and Convergences in a Digital Multicultural Age
Literature illuminating the relationship between contemporary art and historical archives around the turn of the twenty-first century and how these interactions inform the evolution of archives in a digital multicultural age is the topic of this review. The literature reveals the extent to which art has been a means for members of marginalized groups to address their representation in historical archives, and also a means for archives to connect with a broader audience. Collaborations between artists and historical archives add new dimension to the debate about the nature of the archive as a creation in and of itself, and in turn the question of whether participatory culture may be a necessary component in achieving more complete representation of all segments of the community. Types of relationships explored in this review include: the questioning of and re-imagining of the archive by artists, particularly those from marginalized groups; the blending of art and digital archives; and how such collaborations have informed the mission and practical concerns of archives. As digitization leads to increasing convergence of previously distinct cultural heritage collections and enthusiasm for participatory platforms accelerates, interactions between individual artists, people from marginalized communities, and GLAM (galleries, libraries, archives and museums) will continue to evolve and expand. From this literature review emerge observations about prior collaborations from around the world as they inform future developments
Limit on the Temporal Variation of the Fine-Structure Constant Using Atomic Dysprosium
Over a period of eight months, we have monitored transition frequencies
between nearly degenerate, opposite-parity levels in two isotopes of atomic
dysprosium (Dy). These transition frequencies are highly sensitive to temporal
variation of the fine-structure constant () due to relativistic
corrections of large and opposite sign for the opposite-parity levels. In this
unique system, in contrast to atomic-clock comparisons, the difference of the
electronic energies of the opposite-parity levels can be monitored directly
utilizing a radio-frequency (rf) electric-dipole transition between them. Our
measurements show that the frequency variation of the 3.1-MHz transition in
Dy and the 235-MHz transition in Dy are 9.06.7 Hz/yr and
-0.66.5 Hz/yr, respectively. These results provide a value for the rate of
fractional variation of of yr (1
) without any assumptions on the constancy of other fundamental
constants, indicating absence of significant variation at the present level of
sensitivity.Comment: 4 pages, 2 figure
The tholeiites of the Valaisan domain (Versoyen, western Alps): a Carboniferous magma emplaced in a small oceanic basin
International audienceThe mafic-ultramafic assemblages of the Versoyen complex exposed in the Valaisan domain is close to the boundary between the Internal and the External domains of the western Alps. Zircons extracted from the Versoyen complex suggest an emplacement during Paleozoic times, and probably during the Visean (~337 Ma). The base of the Versoyen complex is formed of laccoliths and sills associated with black shales, while pillow basalts and tuffs predominate at the uppermost levels. Locally, basaltic dikelets intruded leucocratic gneiss. Ultramafic-mafic cumulates form the bottom of the thickest intrusions while diabases are present along the chilled margins. All these rocks have been affected by a polyphased metamorphism under eclogitic to blueschist and greenschist facies conditions. Magmatic textures have been destroyed and the igneous mineralogy is seldom preserved. The mafic rocks of the Versoyen complex show tholeiitic to alkali-transitional affinities. The pillow basalts and the sill cores have flat REE patterns characteristic of N-MORB and T-MORB. Their {varepsilon}Nd (assuming an age of 337 Ma) ratios range from + 5.7 to + 9 which suggest a mixing of N-MORB and OIB sources. The sill margins show Th, U and LREE-enrichments and negative {varepsilon}Nd ratios. These features are likely related to contamination when hot mafic magmas intruded unconsolidated sediments rich in water. The high Th, U, LREE abundances and low {varepsilon}Nd ratio of the basaltic dikelet are probably related to crustal contamination occurring during magma ascent. The geochemical characteristics of the Versoyen rocks are compatible with a tholeiitic magma emplaced into a small oceanic basin in the vicinity of a continent. The importance of pre-Mesozoic crustal thinning evidenced in one segment of the boundary between the Internal and External zones of the Alps suggests that the Pennine Front is an Alpine mega-thrust inherited from a Variscan suture
Variation of the Fine-Structure Constant and Laser Cooling of Atomic Dysprosium
Radio-frequency electric-dipole transitions between nearly degenerate,
opposite parity levels of atomic dysprosium (Dy) were monitored over an
eight-month period to search for a variation in the fine-structure constant,
. The data provide a rate of fractional temporal variation of
of yr or a value of for , the variation coefficient for in a changing
gravitational potential. All results indicate the absence of significant
variation at the present level of sensitivity. We also present initial results
on laser cooling of an atomic beam of dysprosium.Comment: 10 pages, 6 figures, fixed typos in section 5, updated result
Investigation of the Gravitational Potential Dependence of the Fine-Structure Constant Using Atomic Dysprosium
Radio-frequency E1 transitions between nearly degenerate, opposite parity
levels of atomic dysprosium were monitored over an eight month period to search
for a variation in the fine-structure constant. During this time period, data
were taken at different points in the gravitational potential of the Sun. The
data are fitted to the variation in the gravitational potential yielding a
value of for the fit parameter . This
value gives the current best laboratory limit. In addition, our value of
combined with other experimental constraints is used to extract
the first limits on k_e and k_q. These coefficients characterize the variation
of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p,
and m_q are electron, proton, and quark masses. The results are and .Comment: 6 pages, 3 figure
Anisotropic Hall Effect in Single Crystal Heavy Fermion YbAgGe
Temperature- and field-dependent Hall effect measurements are reported for
YbAgGe, a heavy fermion compound exhibiting a field-induced quantum phase
transition, and for two other closely related members of the RAgGe series: a
non-magnetic analogue, LuAgGe and a representative, ''good local moment'',
magnetic material, TmAgGe. Whereas the temperature dependent Hall coefficient
of YbAgGe shows behavior similar to what has been observed in a number of heavy
fermion compounds, the low temperature, field-dependent measurements reveal
well defined, sudden changes with applied field; in specific for a
clear local maximum that sharpens as temperature is reduced below 2 K and that
approaches a value of 45 kOe - a value that has been proposed as the
quantum critical point. Similar behavior was observed for where a
clear minimum in the field-dependent Hall resistivity was observed at low
temperatures. Although at our base temperatures it is difficult to distinguish
between the field-dependent behavior predicted for (i) diffraction off a
critical spin density wave or (ii) breakdown in the composite nature of the
heavy electron, for both field directions there is a distinct temperature
dependence of a feature that can clearly be associated with a field-induced
quantum critical point at persisting up to at least 2 K.Comment: revised versio
First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
The first direct mass-measurement of He has been performed with the
TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the
mass of He was determined with improved precision over our previous
measurement. The obtained masses are (He) = 6.018 885 883(57) u and
(He) = 8.033 934 44(11) u. The He value shows a deviation from
the literature of 4. With these new mass values and the previously
measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and
1.959(16) fm for He and He respectively. We present a detailed
comparison to nuclear theory for He, including new hyperspherical harmonics
results. A correlation plot of the point-proton radius with the two-neutron
separation energy demonstrates clearly the importance of three-nucleon forces.Comment: 4 pages, 2 figure
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