Synchronization Transition of Identical Phase Oscillators in a Directed Small-World Network

We numerically study a directed small-world network consisting of attractively coupled, identical phase oscillators. While complete synchronization is always stable, it is not always reachable from random initial conditions. Depending on the shortcut density and on the asymmetry of the phase coupling function, there exists a regime of persistent chaotic dynamics. By increasing the density of shortcuts or decreasing the asymmetry of the phase coupling function, we observe a discontinuous transition in the ability of the system to synchronize. Using a control technique, we identify the bifurcation scenario of the order parameter. We also discuss the relation between dynamics and topology and remark on the similarity of the synchronization transition to directed percolation.Comment: This article has been accepted in AIP, Chaos. After it is published, it will be found at http://chaos.aip.org/, 12 pages, 9 figures, 1 tabl

Spectral properties of fractional Fokker-Plank operator for the L\'evy flight in a harmonic potential

We present a detailed analysis of the eigenfunctions of the Fokker-Planck operator for the L\'evy-Ornstein-Uhlenbeck process, their asymptotic behavior and recurrence relations, explicit expressions in coordinate space for the special cases of the Ornstein-Uhlenbeck process with Gaussian and with Cauchy white noise and for the transformation kernel, which maps the fractional Fokker-Planck operator of the Cauchy-Ornstein-Uhlenbeck process to the non-fractional Fokker-Planck operator of the usual Gaussian Ornstein-Uhlenbeck process. We also describe how non-spectral relaxation can be observed in bounded random variables of the L\'evy-Ornstein-Uhlenbeck process and their correlation functions.Comment: 10 pages, 5 figures, submitted to Euro. Phys. J.

Tuning the Clock: Uranium and Thorium Chronometers Applied to CS 31082-001

We obtain age estimates for the progenitor(s) of the extremely metal-poor ([Fe/H = -2.9) halo star CS 31082-001, based on the recently reported first observation of a Uranium abundance in this (or any other) star. Age estimates are derived by application of the classical r-process model with updated nuclear physics inputs. The [U/Th] ratio yields an age of 13+-4 Gyr or 8+-4 Gyr, based on the use of the ETFSI-Q or the new HFBCS-1 nuclear mass models, respectively. Implications for Thorium chronometers are discussed.Comment: 5 pages incl. 1 figure, a shorter 3 page version will be published in the proceedings of the "Astrophysical Ages and Timescales" conference held in Hilo, Hawaii, Feb 5-9, 200

Xenotransplantation of decellularized pig heart valves-Regulatory aspects in Europe

BACKGROUND: The lack of human donors for allotransplantation forces the development of other strategies to circumvent the existing organ shortage documented on the waiting lists. Here, xenotransplantation offers a suitable option since the genetic modification of animals has become an established method that allows the generation of animals as donors of cells, tissues, and organs with reduced antigenicity. METHODS: Focus is given on the generation of decellularized matrix scaffolds, for example, for valve transplantation and/or repair, that have the potential being fully assimilated by the recipient as they are no longer a mechanical implant with risk of calcification and related failure. RESULTS: This new class of products is transplants that will be regulated either as medical devices or as cell-based medicinal products, that is, advanced therapy medicinal products, according to the regulations in the European Union. CONCLUSIONS: In this review, we compile relevant regulatory aspects and point out the possibilities of how these products for human use may be regulated in the future

Limited environmental stability of infectious porcine endogenous retrovirus type C; Usage of reverse transcriptase in combination with viral RNA as markers for infectious virus

INTRODUCTION: Porcine endogenous retroviruses (PERVs) are an integral part of the pig genome with infectious potential, as shown in vitro. HYPOTHESIS/GAP STATEMENT: In view of nonclinical and clinical xenotransplantation, data are essential that give an insight into viral pathogenicity. This includes PERV's environmental stability and environmental risk.AIM: We analyzed two ecotropic PERV-C (PERV-C[1312] and -[5683]), monitoring cell-free culture supernatants of infected ST-IOWA cells at various time intervals at room temperature (22°C +/−1°C). The virus was stored in the presence or absence of sterile wood litter, as used for large animal husbandry. This approach was set to determine the environmental stability of exogenous PERV-C at defined conditions for the first time. METHODOLOGY: Reverse transcriptase (RT) activity and viral RNA were monitored for up to 57 days and remaining infectivity of supernatant without wood litter was tested from day 7 onwards on naïve ST-IOWA cells. RESULTS: Results show that viral RNA decreases but remains detectable over the whole observation period, whereas RT activity showed 83%–96% reduction from day 7 on. This effect was stronger in the presence of wood litter and fresh harvested virus was more stable than frozen virus stocks. Even under these optimal conditions, no infectivity was shown for viral RNA-positive and RT-reduced supernatant harvested at day 7. CONCLUSION: The results confirm that PERV-C is less stable and the reduction of RT activity is accompanied by reduced infectivity, independently of existing viral RNA. The combination of both RT and viral RNA measurement is a suitable method to differentiate infectious PERV-C

Decellularized pig pulmonary heart valves-Depletion of nucleic acids measured by proviral PERV pol

BACKGROUND: Decellularized human pulmonary heart valve (dhHV) scaffolds have been shown to be the gold standard especially for younger, adolescent patients. However, human heart valves are limited in availability. Xenogeneic decellularized pig heart valves (dpHV) may serve as alternative. METHODS: The efficacy of DNA reduction processes upon decellularization of heart valves from German Landrace pigs was analyzed by measurements of remaining nucleic acids including proviral porcine endogenous retrovirus (PERV) sequences. Porcine pulmonary heart valves (pPHV) were decellularized by three different protocols and further treated with DNaseI or Benzonase, at varying incubation times. DNA isolated from valve associated muscle (m), valve cusp (c), and pulmonary artery (pa) was monitored by PCR and qRT-PCR using GAPDH and the PERV polymerase (pol) for read-out. RESULTS: Decellularization of pPHV led to a significant reduction of DNA (>99%) which could be further significantly increased for (m) and (pa) by nuclease treatment, reducing proviral PERV pol from approximately 5 × 107 to 5 × 103 copies/mg in nuclease treated tissues. CONCLUSIONS: Both nucleases demonstrated comparable activities. But DNaseI revealed to be less consistent for PERV, especially at muscular tissue. Noteworthy, remaining proviral sequences are still detectable by PCR; however, due to the absence of the cellular replication machinery the production of infectious particles is not expected. Decellularization and nuclease treatment of pPHV is an efficient procedure to reduce the DNA content including PERV, thus represents a valuable option to increase virus safety independently from the source animal background