636 research outputs found
VR/Urban: spread.gun - design process and challenges in developing a shared encounter for media façades
Designing novel interaction concepts for urban environments is not only a technical challenge in terms of scale, safety, portability and deployment, but also a challenge of designing for social configurations and spatial settings. To outline what it takes to create a consistent and interactive experience in urban space, we describe the concept and multidisciplinary design process of VR/Urban's media intervention tool called Spread.gun, which was created for the Media Façade Festival 2008 in Berlin. Main design aims were the anticipation of urban space, situational system configuration and embodied interaction. This case study also reflects on the specific technical, organizational and infrastructural challenges encountered when developing media façade installations
VR/Urban: SMSlingshot
In this paper we describe the concept and design objectives of VR/Urban's media intervention tool SMSlingshot, which was presented at the Riga White Night Arts Festival 2009 for the first time
Three strongly correlated charged bosons in a one-dimensional harmonic trap: natural orbital occupancies
We study a one-dimensional system composed of three charged bosons confined
in an external harmonic potential. More precisely, we investigate the
ground-state correlation properties of the system, paying particular attention
to the strong-interaction limit. We explain for the first time the nature of
the degeneracies appearing in this limit in the spectrum of the reduced density
matrix. An explicit representation of the asymptotic natural orbitals and their
occupancies is given in terms of some integral equations.Comment: 6 pages, 4 figures, To appear in European Physical Journal
Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields
Multi-electron giant dipole resonances of atoms in crossed electric and
magnetic fields are investigated. Stationary configurations corresponding to a
highly symmetric arrangement of the electrons on a decentered circle are
derived, and a normal-mode stability analysis is performed. A classification of
the various modes, which are dominated either by the magnetic or Coulomb
interactions, is provided. A six-dimensional wave-packet dynamical study, based
on the MCTDH approach, is accomplished for the two-electron resonances,
yielding in particular lifetimes of more than 0.1 s for strong electric
fields.Comment: 7 pages, 3 figure
An open source software for analysis of dynamic contrast enhanced magnetic resonance images: UMMPerfusion revisited
Background: Perfusion imaging has become an important image based tool to derive the physiological information in various applications, like tumor diagnostics and therapy, stroke, (cardio-) vascular diseases, or functional assessment of organs. However, even after 20Â years of intense research in this field, perfusion imaging still remains a research tool without a broad clinical usage. One problem is the lack of standardization in technical aspects which have to be considered for successful quantitative evaluation; the second problem is a lack of tools that allow a direct integration into the diagnostic workflow in radiology. Results: Five compartment models, namely, a one compartment model (1CP), a two compartment exchange (2CXM), a two compartment uptake model (2CUM), a two compartment filtration model (2FM) and eventually the extended Toftâs model (ETM) were implemented as plugin for the DICOM workstation OsiriX. Moreover, the plugin has a clean graphical user interface and provides means for quality management during the perfusion data analysis. Based on reference test data, the implementation was validated against a reference implementation. No differences were found in the calculated parameters. Conclusion: We developed open source software to analyse DCE-MRI perfusion data. The software is designed as plugin for the DICOM Workstation OsiriX. It features a clean GUI and provides a simple workflow for data analysis while it could also be seen as a toolbox providing an implementation of several recent compartment models to be applied in research tasks. Integration into the infrastructure of a radiology department is given via OsiriX. Results can be saved automatically and reports generated automatically during data analysis ensure certain quality control
Bose-Hubbard model with occupation dependent parameters
We study the ground-state properties of ultracold bosons in an optical
lattice in the regime of strong interactions. The system is described by a
non-standard Bose-Hubbard model with both occupation-dependent tunneling and
on-site interaction. We find that for sufficiently strong coupling the system
features a phase-transition from a Mott insulator with one particle per site to
a superfluid of spatially extended particle pairs living on top of the Mott
background -- instead of the usual transition to a superfluid of single
particles/holes. Increasing the interaction further, a superfluid of particle
pairs localized on a single site (rather than being extended) on top of the
Mott background appears. This happens at the same interaction strength where
the Mott-insulator phase with 2 particles per site is destroyed completely by
particle-hole fluctuations for arbitrarily small tunneling. In another regime,
characterized by weak interaction, but high occupation numbers, we observe a
dynamical instability in the superfluid excitation spectrum. The new ground
state is a superfluid, forming a 2D slab, localized along one spatial direction
that is spontaneously chosen.Comment: 16 pages, 4 figure
Cyclotron resonance of the quasi-two-dimensional electron gas at Hg1-xCdxTe grain boundaries
The magnetotransmission of a p-type Hg0.766Cd0.234Te bicrystal containing a single grain boundary with an inversion layer has been investigated in the submillimetre wavelength range. For the first time the cyclotron resonance lines belonging to the various electric subbands of a quasi-two-dimensional carrier system at a grain boundary could be detected. The measured cyclotron masses and the subband densities determined from Shubnikov-de Haas experiments are compared with theoretical predictions and it is found that the data can be explained very well within the framework of a triangular well approximation model which allows for non-parabolic effects
Availability of phosphate for phytoplankton and bacteria and of labile organic carbon for bacteria at different pCO2 levels in a mesocosm study
Availability of phosphate for phytoplankton and bacteria and of glucose for bacteria at different pCO2 levels were studied in a mesocosm experiment (PeECE III). Using nutrient-depleted SW Norwegian fjord waters, three different levels of pCO2 (350 ÎŒatm: 1ĂCO2; 700 ÎŒatm: 2ĂCO2; 1050 ÎŒatm: 3ĂCO2) were set up, and nitrate and phosphate were added at the start of the experiment in order to induce a phytoplankton bloom. Despite similar responses of total particulate P concentration and phosphate turnover time at the three different pCO2 levels, the size distribution of particulate P and 33PO4 uptake suggested that phosphate transferred to the >10 ÎŒm fraction was greater in the 3ĂCO2 mesocosm during the first 6â10 days when phosphate concentration was high. During the period of phosphate depletion (after Day 12), specific phosphate affinity and specific alkaline phosphatase activity (APA) suggested a P-deficiency (i.e. suboptimal phosphate supply) rather than a P-limitation for the phytoplankton and bacterial community at the three different pCO2 levels. Specific phosphate affinity and specific APA tended to be higher in the 3ĂCO2 than in the 2ĂCO2 and 1ĂCO2 mesocosms during the phosphate depletion period, although no statistical differences were found. Glucose turnover time was correlated significantly and negatively with bacterial abundance and production but not with the bulk DOC concentration. This suggests that even though constituting a small fraction of the bulk DOC, glucose was an important component of labile DOC for bacteria. Specific glucose affinity of bacteria behaved similarly at the three different pCO2 levels with measured specific glucose affinities being consistently much lower than the theoretical maximum predicted from the diffusion-limited model. This suggests that bacterial growth was not severely limited by the glucose availability. Hence, it seems that the lower availability of inorganic nutrients after the phytoplankton bloom reduced the bacterial capacity to consume labile DOC in the upper mixed layer of the stratified mesocosms
Generation of annotated multimodal ground truth datasets for abdominal medical image registration
Sparsity of annotated data is a major limitation in medical image processing
tasks such as registration. Registered multimodal image data are essential for
the diagnosis of medical conditions and the success of interventional medical
procedures. To overcome the shortage of data, we present a method that allows
the generation of annotated multimodal 4D datasets. We use a CycleGAN network
architecture to generate multimodal synthetic data from the 4D extended
cardiac-torso (XCAT) phantom and real patient data. Organ masks are provided by
the XCAT phantom, therefore the generated dataset can serve as ground truth for
image segmentation and registration. Realistic simulation of respiration and
heartbeat is possible within the XCAT framework. To underline the usability as
a registration ground truth, a proof of principle registration is performed.
Compared to real patient data, the synthetic data showed good agreement
regarding the image voxel intensity distribution and the noise characteristics.
The generated T1-weighted magnetic resonance imaging (MRI), computed tomography
(CT), and cone beam CT (CBCT) images are inherently co-registered. Thus, the
synthetic dataset allowed us to optimize registration parameters of a
multimodal non-rigid registration, utilizing liver organ masks for evaluation.
Our proposed framework provides not only annotated but also multimodal
synthetic data which can serve as a ground truth for various tasks in medical
imaging processing. We demonstrated the applicability of synthetic data for the
development of multimodal medical image registration algorithms.Comment: 12 pages, 5 figures. This work has been published in the
International Journal of Computer Assisted Radiology and Surgery volum
Pharmacological Activation of Soluble Guanylate Cyclase Protects the Heart Against Ischemic Injury
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