2,620 research outputs found
Redefining the performing arts archive
This paper investigates representations of performance and the role of the archive. Notions of record and archive are critically investigated, raising questions about applying traditional archival definitions to the performing arts. Defining the nature of performances is at the root of all difficulties regarding their representation. Performances are live events, so for many people the idea of recording them for posterity is inappropriate. The challenge of creating and curating representations of an ephemeral art form are explored and performance-specific concepts of record and archive are posited. An open model of archives, encouraging multiple representations and allowing for creative reuse and reinterpretation to keep the spirit of the performance alive, is envisaged as the future of the performing arts archive
Self-Pulsating Semiconductor Lasers: Theory and Experiment
We report detailed measurements of the pump-current dependency of the
self-pulsating frequency of semiconductor CD lasers. A distinct kink in this
dependence is found and explained using rate-equation model. The kink denotes a
transition between a region where the self-pulsations are weakly sustained
relaxation oscillations and a region where Q-switching takes place. Simulations
show that spontaneous emission noise plays a crucial role for the cross-over.Comment: Revtex, 16 pages, 7 figure
High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age
Following a severe outbreak of clinical scrapie in 2006–2007, a
large dairy goat herd was culled
and 200 animals were selected for post-mortem examinations in order to
ascertain the prevalence of infection,
the effect of age, breed and PRNP genotype on the susceptibility to scrapie,
the tissue distribution of diseaseassociated
PrP (PrP), and the comparative efficiency of different diagnostic methods.
As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the
prevalence of preclinical infection
was very high (72/200; 36.0%), with most infected animals being positive
for PrP in lymphoreticular system
(LRS) tissues (68/72; 94.4%) compared to those that were positive in
brain samples (38/72; 52.8%). The
retropharyngeal lymph node and the palatine tonsil showed the highest
frequency of PrP accumulation (87.3%
and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid
tissue (RAMALT) was positive in
only 30 (41.7%) of the infected goats. However, the efficiency of rectal
and palatine tonsil biopsies taken
shortly before necropsy was similar. The probability of brain and RAMALT
being positive directly
correlated with the spread of PrP within the LRS. The prevalence of
infection was influenced by PRNP
genetics at codon 142 and by the age of the goats: methionine carriers older
than 60 months showed a much
lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last
showed prevalence values similar to isoleucine homozygotes of any age
(40/80; 50.0%). Two of seven goats
with definite signs of scrapie were negative for PrP in brain but positive
in LRS tissues, and one goat showed
biochemical and IHC features of PrP different from all other infected
goats. The results of this study have
implications for surveillance and control policies for scrapie in goats
Vapor Generation in a Nanoparticle Liquid Suspension Using a Focused, Continuous Laser
This letter discusses experimentation with optically induced phase change in nanoparticle liquid suspensions-commonly termed nanofluids. Four different types of nanofluids at five concentrations were exposed to a similar to 120 mW, 532 nm laser beam to determine the minimum laser flux needed to create vapor. Laser irradiance was varied between 0-770 W cm(-2). While the experiments were simple, they involved many complex, interrelated physical phenomena, including: subcooled boiling, thermal driven particle/bubble motion, nanoparticle radiative absorption/scattering, and nanoparticle clumping. Such phenomena could enable novel solar collectors in which the working fluid directly absorbs energy and undergoes phase change in a single step. c 2009 American Institute of Physics. [doi: 10.1063/1.3250174
Thermoelectric Properties of Intermetallic Semiconducting RuIn3 and Metallic IrIn3
Low temperature (<400 K) thermoelectric properties of semiconducting RuIn3
and metallic IrIn3 are reported. RuIn3 is a narrow band gap semiconductor with
a large n-type Seebeck coefficient at room temperature (S(290K)~400 {\mu}V/K),
but the thermoelectric Figure of merit (ZT(290K) = 0.007) is small because of
high electrical resistivity and thermal conductivity ({\kappa}(290 K) ~ 2.0 W/m
K). IrIn3 is a metal with low thermopower at room temperature (S(290K)~20
{\mu}V/K) . Iridium substitution on the ruthenium site has a dramatic effect on
transport properties, which leads to a large improvement in the power factor
and corresponding Figure of merit (ZT(380 K) = 0.053), improving the efficiency
of the material by an over of magnitude.Comment: Submitted to JA
Neutron Scattering Study of Fluctuating and Static Spin Correlations in the Anisotropic Spin Glass FeTiO
The anisotropic spin glass transition, in which spin freezing is observed
only along the c-axis in pseudobrookite FeTiO, has long been perplexing
because the Fe moments (d) are expected to be isotropic. Recently,
neutron diffraction demonstrated that surfboard-shaped antiferromagnetic
nanoregions coalesce above the glass transition temperature, T 55
K, and a model was proposed in which the freezing of the fluctuations of the
surfboards' magnetization leads to the anisotropic spin glass state. Given this
new model, we have carried out high resolution inelastic neutron scattering
measurements of the spin-spin correlations to understand the temperature
dependence of the intra-surfboard spin dynamics on neutron (picosecond)
time-scales. Here, we report on the temperature-dependence of the spin
fluctuations measured from single crystal FeTiO. Strong quasi-elastic
magnetic scattering, arising from intra-surfboard correlations, is observed
well above T. The spin fluctuations possess a steep energy-wave vector
relation and are indicative of strong exchange interactions, consistent with
the large Curie-Weiss temperature. As the temperature approaches T from
above, a shift in spectral weight from inelastic to elastic scattering is
observed. At various temperatures between 4 K and 300 K, a characteristic
relaxation rate of the fluctuations is determined. Despite the freezing of the
majority of the spin correlations, an inelastic contribution remains even at
base temperature, signifying the presence of fluctuating intra-surfboard spin
correlations to at least T/T 0.1 consistent with a description of
FeTiO as a hybrid between conventional and geometrically frustrated
spin glasses.Comment: 6 figure
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