943 research outputs found
Mapping traditions:historically tendencies of an urban design method
Mapping has a long tradition as a method within urban design and landscape practice and is generally used in three ways: To analyze spatial conditions, generate design interventions, and communicate design ideas or spatial knowledge. It is a tool for thinking through the activity of reformulating and interpreting the complex and three-dimensional world into often simplistic, two-dimensional visual representations. Looking at mapping in retrospect, historically positions and tendencies that reflect contemporary society and urban landscape is revealed. This paper seeks to trace the mapping positions and tendencies through time. The paper takes its historically starting point in the period of the industrialization and seeks at outlining shifting understandings and perspectives of the spatial and physical world, which has affected plans and design of urban landscapes. From this unfolding of various mapping tendencies and ways of doing thought time, the paper wishes to discuss the contemporary tendencies of urban design mapping. Here the paper discusses the implication of technological improvement in mappings. Technology has and is affecting mappings in two ways. Firstly, technology has and still is advancing the accuracy of measures of urban structure, and it increases geospatial knowledge usable in mappings as GIS (Geographical Information System) is a result of. Secondly, technology enables new ways of sensing and understanding the world, which makes it relevant to reflect on how new technologies extend the human senses and what new spatial knowledge they might enable. Hence, the paper discusses the possibilities and implications of a more technology driven urban design mapping practice
Flies and Campylobacter Infection of Broiler Flocks
A total of 8.2% of flies caught outside a broiler house in Denmark had the potential to transmit Campylobacter jejuni to chickens, and hundreds of flies per day passed through the ventilation system into the broiler house. Our study suggests that flies may be an important source of Campylobacter infection of broiler flocks in summer
HLA-A24 and survivin: possibilities in therapeutic vaccination against cancer
Recently, it was described that an HLA-A24 restricted peptide derived from the survivin splice variant survivin-2B can be recognized by CD8(+) cytotoxic T-cells. The identification of an HLA-A24 epitope is critical for survivin-based immunotherapy as HLA-24 is the most frequent HLA allele in Asia. Consequently, this survivin-2B epitope is already a target in a clinical study in patients with advanced or recurrent colorectal cancer expressing survivin. However, the splice variant survivin-2B has been described to be pro-apoptotic, and is only expressed at low levels in most malignant tissues. Furthermore, survivin-2B expression are significantly decreased in later tumor stages and inversely correlated with tumor differentiation and invasion. Consequently, survivin is a more general vaccination candidate than the splice variant survivin-2B. Here, we on the basis of spontaneous immune responses in HLA-A24+ cancer patients describes that a HLA-A24-restricted survivin epitopes does indeed exist. Consequently, this epitope is an attractive target for the ongoing survivin-based peptide immunotherapy against cancer
Cavity-enhanced sum-frequency generation of blue light with near-unity conversion efficiency
We report on double-resonant highly efficient sum-frequency generation in the
blue range. The system consists of a 10-mm-long periodically poled KTP crystal
placed in a double-resonant bow-tie cavity and pumped by a fiber laser at
1064.5 nm and a Ti:sapphire laser at 849.2 nm. An optical power of 375 mW at
472.4 nm in a TEM mode was generated with pump powers of 250 mW at 849.2
nm and 200 mW at 1064.5 nm coupled into the double-resonant ring resonator with
88 mode-matching. The resulting internal conversion efficiency of 95() of the photons mode-matched to the cavity constitutes, to the best of
our knowledge, the highest overall achieved quantum conversion efficiency using
continuous-wave pumping. Very high conversion efficiency is rendered possible
due to very low intracavity loss on the level of 0.3 and high nonlinear
conversion coefficient up to 0.045(0.015) W. Power stability
measurements performed over one hour show a stability of 0.8. The generated
blue light can be tuned within 5 nm around the center wavelength of 472.4 nm,
limited by the phase-matching of our nonlinear crystal. This can however be
expanded to cover the entire blue spectrum (420 nm to 510 nm) by proper choice
of nonlinear crystals and pump lasers. Our experimental results agree very well
with analytical and numerical simulations taking into account cavity impedance
matching and depletion of the pump fields.Comment: 9 pages, 5 figure
Polarization Squeezing of Continuous Variable Stokes Parameters
We report the first direct experimental characterization of continuous
variable quantum Stokes parameters. We generate a continuous wave light beam
with more than 3 dB of simultaneous squeezing in three of the four Stokes
parameters. The polarization squeezed beam is produced by mixing two quadrature
squeezed beams on a polarizing beam splitter. Depending on the squeezed
quadrature of these two beams the quantum uncertainty volume on the
Poincar\'{e} sphere became a `cigar' or `pancake'-like ellipsoid.Comment: 4 pages, 5 figure
Entanglement and spin squeezing in the two-atom Dicke model
We analyze the relation between the entanglement and spin-squeezing parameter
in the two-atom Dicke model and identify the source of the discrepancy recently
reported by Banerjee and Zhou et al that one can observe entanglement without
spin squeezing. Our calculations demonstrate that there are two criteria for
entanglement, one associated with the two-photon coherences that create
two-photon entangled states, and the other associated with populations of the
collective states. We find that the spin-squeezing parameter correctly predicts
entanglement in the two-atom Dicke system only if it is associated with
two-photon entangled states, but fails to predict entanglement when it is
associated with the entangled symmetric state. This explicitly identifies the
source of the discrepancy and explains why the system can be entangled without
spin-squeezing. We illustrate these findings in three examples of the
interaction of the system with thermal, classical squeezed vacuum and quantum
squeezed vacuum fields.Comment: 7 pages, 1 figur
Three-dimensional theory for interaction between atomic ensembles and free-space light
Atomic ensembles have shown to be a promising candidate for implementations
of quantum information processing by many recently-discovered schemes. All
these schemes are based on the interaction between optical beams and atomic
ensembles. For description of these interactions, one assumed either a
cavity-QED model or a one-dimensional light propagation model, which is still
inadequate for a full prediction and understanding of most of the current
experimental efforts which are actually taken in the three-dimensional free
space. Here, we propose a perturbative theory to describe the three-dimensional
effects in interaction between atomic ensembles and free-space light with a
level configuration important for several applications. The calculations reveal
some significant effects which are not known before from the other approaches,
such as the inherent mode-mismatching noise and the optimal mode-matching
conditions. The three-dimensional theory confirms the collective enhancement of
the signal-to-noise ratio which is believed to be one of the main advantage of
the ensemble-based quantum information processing schemes, however, it also
shows that this enhancement need to be understood in a more subtle way with an
appropriate mode matching method.Comment: 16 pages, 9 figure
Assessing and mitigating the radar–radar interference in the German C-band weather radar network
The national German weather radar network operates in C-band between 5.6 and 5.65 GHz. In a radar network, individual transmit frequencies
have to be chosen such that radar–radar-induced interferences are avoided. In a unique experiment the Hohenpeißenberg research radar and five operational systems from the radar network were used to characterize radar–radar-induced interferences as a function of the radar frequency. The results allow assessment of the possibility of adding additional C-band radars with magnetron transmitters into the existing network. Based on the experiment, at least a 15 MHz separation of the nominal radar frequency is needed to avoid a radar–radar interference. The most efficient mitigation of radar–radar interference is achieved by the “Radar Tango”, which refers to the synchronized scanning of all radar systems in the network. Based on those results, additional C-band radar systems can be added to the German weather radar network if a further improvement of the radar coverage is needed.</p
Experimental demonstration of quantum memory for light
The information carrier of today's communications, a weak pulse of light, is
an intrinsically quantum object. As a consequence, complete information about
the pulse cannot, even in principle, be perfectly recorded in a classical
memory. In the field of quantum information this has led to a long standing
challenge: how to achieve a high-fidelity transfer of an independently prepared
quantum state of light onto the atomic quantum state? Here we propose and
experimentally demonstrate a protocol for such quantum memory based on atomic
ensembles. We demonstrate for the first time a recording of an externally
provided quantum state of light onto the atomic quantum memory with a fidelity
up to 70%, significantly higher than that for the classical recording. Quantum
storage of light is achieved in three steps: an interaction of light with
atoms, the subsequent measurement on the transmitted light, and the feedback
onto the atoms conditioned on the measurement result. Density of recorded
states 33% higher than that for the best classical recording of light on atoms
is achieved. A quantum memory lifetime of up to 4 msec is demonstrated.Comment: 22 pages (double line spacing) incl. supplementary information, 4
figures, accepted for publication in Natur
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