221 research outputs found
Critical geography in Germany: from exclusion to inclusion via internationalisation
Critical perspectives have become more visible in German human geography. Drawing on an analysis of the debate around the German reader âKulturgeographieâ published in 2003, we suggest that this case provides new insights into the âgeography of critical geographyâ. We briefly discuss the history of left geography in Germany, leading to a comparison of the conditions of left geography around 1980 and in recent years. The focus is on two factors in the changed role of critical perspectives in German geography: (1) the growing internationalisation of German geography, which opened new avenues and allowed new approaches to enter the discipline; and (2) the high citation indices of âcriticalâ journals, which leads to an enhanced reputation and a high significance of international critical geography in the German discipline. However, we draw an ambiguous conclusion: the increased role of critical approaches in German geography is linked to a growing neoliberalisation of academia and a decline of critical approaches in other disciplines
Critical geography in Germany: from exclusion to inclusion via internationalisation
Critical perspectives have become more visible in German human geography. Drawing on an analysis of the debate around the German reader "Kulturgeographie" published in 2003, we suggest that this case provides new insights into the "geography of critical geography". We briefly discuss the history of critical geography in Germany, leading to a comparison of the conditions of critical geography around 1980 and in recent years. The focus is on two factors in the changed role of critical perspectives in German geography: (1) the growing internationalisation of German geography, which opened new avenues and allowed new approaches to enter the discipline; and (2) the high citation indices of "critical" journals, which leads to an enhanced reputation and a high significance of international critical geography in the German discipline. However, we draw an ambiguous conclusion: the increased role of critical approaches in German geography is linked to a growing neoliberalisation of academia and a decline of critical approaches in other disciplines
Coherent Interaction of a Single Fermion with a Small Bosonic Field
We have experimentally studied few-body impurity systems consisting of a
single fermionic atom and a small bosonic field on the sites of an optical
lattice. Quantum phase revival spectroscopy has allowed us to accurately
measure the absolute strength of Bose-Fermi interactions as a function of the
interspecies scattering length. Furthermore, we observe the modification of
Bose-Bose interactions that is induced by the interacting fermion. Because of
an interference between Bose-Bose and Bose-Fermi phase dynamics, we can infer
the mean fermionic filling of the mixture and quantify its increase (decrease)
when the lattice is loaded with attractive (repulsive) interspecies
interactions.Comment: 4+ pages, 5 figures, updated to <a
href="http://dx.doi.org/10.1103/PhysRevLett.106.115305">published version</a
Relativistic Kinetic Equations for Electromagnetic, Scalar and Pseudoscalar Interactions
We derive the kinetic equations for both the covariant and equal-time Wigner
functions of Dirac particles with electromagnetic, scalar and pseudoscalar
interactions. We emphasize the constraint equations for the spinor components
in the equal-time formulation.Comment: 12 pages, no figures, revte
Techno-economic evaluation of electricity price-driven heat production of a river water heat pump in a German district heating system
Large scale heat pumps (HP) are an important technology that will link district heating (DH) systems to the electricity sector in future smart energy systems. This paper examines the feasibility of the integration of a river water HP at a combined heat and power plant in Germany. It is part of a more extensive study about the transformation of a DH system in an urban district towards a 4th generation DH system. The focus is on operational characteristics and economic efficiency of electricity price-driven heat production. A novel method for estimating the coefficient of performance (COP) of two-stage ammonia HPs based on the difference between sink and source temperature is presented. The HP achieves a seasonal COP in the range of 3.4 to 3.7. The 15-year simulation with the software energyPRO shows that electricity-price driven operation is especially relevant for lower heat loads during the non-heating season. The correlation between volatility of electricity market price change and flexible operation is analysed. Finally, the levelized cost of heat for four designs with heat outputs of the HP from 4.7 MWth to 6.1 MWth and increasing storage sizes are compared. The results indicate that electricity costs are reduced in more flexible systems, but cost parity to the minimum dimensioning is not yet reached with the underlying economic framework conditions. However, the parameters that benefit the economic efficiency of more flexible systems are discussed
The optical spectra of X-shaped radio galaxies
X-shaped radio galaxies are defined by their peculiar large-scale radio
morphology. In addition to the classical double-lobed structure they have a
pair of low-luminosity wings that straddles the nucleus at almost right angles
to the active lobes, thus giving the impression of an 'X'. In this paper we
study for the first time the optical spectral properties of this object class
using a large sample (~50 sources). We find that the X-shaped radio population
is composed roughly equally of sources with weak and strong emission line
spectra, which makes them, in combination with the well-known fact that they
preferentially have radio powers intermediate between those of Fanaroff-Riley
type I (FR I) and type II (FR II) radio galaxies, the archetypal transition
population. We do not find evidence in support of the proposition that the
X-shape is the result of a recent merger: X-shaped radio sources do not have
unusually broad emission lines, their nuclear environments are in general not
dusty, and their host galaxies do not show signs of enhanced star formation.
Instead, we observe that the nuclear regions of X-shaped radio sources have
relatively high temperatures. This finding favours models, which propose that
the X-shape is the result of an overpressured environment.Comment: 12 pages, 8 figures, accepted by MNRA
Evaluating the Efficacy of Point-of-Use Water Filtration Units in Fiji
Background: To develop and evaluate a strategy for reducing the prevalence and impact of waterborne disease, a water quality intervention was developed for Fiji by Give Clean Water, Inc. in partnership with the Fiji Ministry of Health. Residents were provided and trained on how to use a SawyerŽ PointONE⢠filter, while also being taught proper handwashing techniques. At the time of the filter installation, all households were surveyed inquiring about the prior 2- to 4-week period. Households were measured a second time between 19 and 225 days later (mean = 66 days).
Results: To date, five economic and health outcomes have been tracked on 503 households to evaluate the efficacy of the intervention. When comparing baseline to follow-up among the 503 households, the 2-week diarrhea prevalence decreased in households from 17.5% at baseline to 1.8% at follow-up. Also, the 2-week prevalence of severe diarrhea decreased per household from 9.7% at baseline to 0.6% at follow-up. Finally, monthly diarrhea-related medical costs reduced by an average of Fijian (FJ) 0.63 per person. All estimated values are obtained from general linear and logistic mixed-effect models, which adjusted for location, season, time to follow-up, household size, water source, and respondent changing. Changes in economic and health outcomes from installation to follow-up were statistically significant (p \u3c 0.05) in all cases, in both unadjusted and adjusted models.
Conclusions: The installation of water filters shows promise for the reduction of diarrhea prevalence in Fiji, as well as the reduction of diarrhea-related medical costs and water expenses. Future work entails evaluation in other countries and contexts, long-term health monitoring, and comparison to alternative water quality interventions
Shocks and dust survival in nearby active galaxies: implications for the alignment effect
One of the most popular explanations for the so-called alignment effect in
high redshift (z>0.7) radio galaxies is the scattering by dust of the hidden
quasar light. As shown by De Young (1998) a problem with the dust scattering
model is that the short destruction time-scale for dust grains means that they
will not survive the passage of the radio jet.
We investigate the survival of dust in the extended ionised gas of nearby
active galaxies with jet/gas interactions. We discuss the implications on the
alignment effect of high redshift (>0.7) radio galaxies. We conclude that
although shocks are likely to destroy dust grains in regions of interaction,
dust might survive in enough quantities to scatter light from the active
nucleus and produce alignment between scattered light and the radio structures.
We propose an observational test to investigate the existence of dust in
shocked regions based on the sensitivity of calcium to depletion onto dust
grains.Comment: 8 pages, 1 Figure, 3 tables, accepted for publication in MNRA
Equal-Time Hierarchies in Quantum Transport Theory
We investigate in the equal-time formalism the derivation and truncation of
infinite hierarchies of equations of motion for the energy moments of the
covariant Wigner function. From these hierarchies we then extract kinetic
equations for the physical distribution functions which are related to
low-order energy moments, and show how to determine the higher order moments in
terms of these lowest order ones. We apply the general formalism to scalar and
spinor QED with classical background fields and compare with the results
derived from the three-dimensional Wigner transformation method.Comment: 44 pages, no figure
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