Establishing the Range of Applicability of Hydrodynamics in High-Energy Collisions.

We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description in the conformal relaxation time approximation, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse Reynolds number Re^{-1} is sufficiently small and the early preequilibrium stage is properly accounted for. We further discuss the implications of our findings for the (in)applicability of hydrodynamics in proton-proton, proton-nucleus, and light nucleus collisions.

Universal Self-Similar Scaling of Spatial Wilson Loops Out of Equilibrium.

We investigate strongly correlated non-Abelian plasmas out of equilibrium. Based on numerical simulations, we establish a self-similar scaling property for the time evolution of spatial Wilson loops that characterizes a universal state of matter far from equilibrium. Most remarkably, it exhibits a generalized area law which holds for a sufficiently large ratio of spatial area and fractional power of time. Performing calculations also for the perturbative regime at higher momenta, we are able to characterize the full nonthermal scaling properties of SU(2) and SU(3) symmetric plasmas from short to large distance scales in terms of two independent universal exponents and associated scaling functions.

Universality far from equilibrium: from superfluid Bose gases to heavy-ion collisions.

Isolated quantum systems in extreme conditions can exhibit unusually large occupancies per mode. This overpopulation gives rise to new universality classes of many-body systems far from equilibrium. We present theoretical evidence that important aspects of non-Abelian plasmas in the ultrarelativistic limit admit a dual description in terms of a Bose condensed scalar field theory.

Prototype of an online navigation system for laparoscopic radiofrequency ablation.

BACKGROUND/AIMS: Laparoscopic Radiofrequency-ablation is a safe and effective method for tumor destruction in patients with unresectable liver tumors. However, accurate probe placement using laparoscopic ultrasound guidance is required to achieve complete tumor ablation. After development and evaluation of laparoscopic navigation tools for radiofrequency ablation, we are now presenting a prototype of a navigation- and documentation-system for laparoscopic RFA. METHODOLOGY: An image-guided surgery system for laparoscopic liver treatments (LapAssistent) based on a 3D-navigation scene was developed. A laparoscopic ultrasound probe and a RFA needle could be navigated using an electromagnetic tracking system. The system was studied using a perfused tumour-mimic-model of a porcine liver. RESULTS: The study showed that laparoscopic ultrasound-guided navigation is technically feasible. The system enables the surgeon to intraoperatively update the three-dimensional planning data in case of new findings. The RFA needle could be placed accurately in a targeted tumour with a targeting error ranging from 5 - 7 mm, even out of the ultrasound plane. In case of multiple tumours lying in close spatial relationship, the documentation module helps to keep track of the already ablated tumours and those that still need to be treated. DISCUSSION: Laparoscopic radiofrequency ablation requires advanced laparoscopic ultrasound skills for accurate placement of the RFA probe. The system adds benefit to laparoscopic RFA enabling the surgeon to place the needle accurately inside the targeted tumours using the navigation scene. The possibility to update the three-dimensional model with new intraoperative findings enables the surgeon to adapt to a new intraoperative situation.

Effects of dexpanthenol with or without Aloe vera extract on radiation-induced oral mucositis: preclinical studies.

PURPOSE: To define the effect of dexpanthenol with or without Aloe vera extract on radiation-induced oral mucositis. MATERIALS AND METHODS: Mouse tongue mucosal ulceration was analysed as the clinically relevant endpoint. Graded single or fractionated dose irradiation (10 x 3 Gy/2 weeks, graded test doses on day 14) were combined with topical administration of dexpanthenol or a base, with or without Aloe vera extract. The formulations were applied for 14 days (single dose) or 24 days after the first fraction. RESULTS: Single dose irradiation resulted in an ED50 (dose at which a positive mucosal response was expected in 50% of the animals irradiated) of 11.9+/-1.2 Gy. None of the formulations yielded a significant change in incidence or time course of ulceration. Test irradiation after 10 x 3 Gy gave an ED50 of 9.0+/-0.1 Gy. Base treatment increased the ED50-values to 10.5+/-0.8 Gy (p = 0.0095) and 9.9+/-0.7 Gy (p = 0.0445) without or with Aloe vera. Dexpanthenol resulted in ED50 values of 9.5+/-0.1 Gy without Aloe vera (p > 0.05), and of 10.9+/-0.9 Gy (p = 0.0035) with Aloe vera. The latent time to ulceration was prolonged, compared to the control (6.3 days) without Aloe vera (8.0-8.2 days, p < 0.001) and with dexpanthenol and Aloe vera (7.3 days, p = 0.0239). CONCLUSIONS: With single dose irradiation, neither dexpanthenol nor Aloe vera extract significantly changed the oral mucosal radiation response. With fractionated irradiation, drug administration significantly increased the isoeffective radiation doses, independent of dexpanthenol or Aloe vera content. Neither dexpanthenol nor Aloe vera display a prophylactic potential.

Prototype of an intraoperative navigation and documentation system for laparoscopic radiofrequency ablation: first experiences.

AIMS: Laparoscopic radiofrequency ablation (RFA) is an accepted approach to treat unresectable liver tumours, distinguishing itself from other techniques by combining minimal invasiveness and the advantages of a surgical approach. The major task of laparoscopic RFA is the accurate needle placement according to preoperative planning to achieve complete tumour ablation. This study investigates the value of an image-guided surgery system to accomplish this task. METHODS: An image-guided surgery system for laparoscopic liver treatments (LapAssistent) based on a 3D-navigation scene was developed. A laparoscopic ultrasound probe and a RFA needle could be navigated using an electromagnetic tracking system. The system was studied using a perfused tumour-mimic-model of a porcine liver. Navigating the RFA needle, the tumours were ablated. RESULTS: The system enables the surgeon to intraoperatively update the three-dimensional planning data in case of new findings. The RFA needle could be placed accurately in a targeted tumour, even out of the ultrasound plane. In case of multiple tumours lying in close spatial relationship, the documentation module helps to keep track of the already ablated tumours and those that still need to be treated. CONCLUSION: The system adds benefit to laparoscopic RFA enabling the surgeon to place the needle accurately inside the targeted tumours using the navigation scene. A manual alignment of the preoperative data to the physical space produces a feasible result for a restricted region. A precise measurement of the accuracy of this process has to be done. The possibility to update the three-dimensional model with new intraoperative findings enables the surgeon to adapt to a new intraoperative situation. Furthermore the possibility to mark ablated tumours helps to keep track of the operation plan.