Onset of cavitation in the quark-gluon plasma

We study the onset of bubble formation (cavitation) in the quark-gluon plasma as a result of the reduction of the effective pressure from bulk-viscous corrections. By calculating velocity gradients in typical models for quark-gluon plasma evolution in heavy-ion collisions, we obtain results for the critical bulk viscosity above which cavitation occurs. Since present experimental data for heavy-ion collisions seems inconsistent with the presence of bubbles above the phase transition temperature of QCD, our results may be interpreted as an upper limit of the bulk viscosity in nature. Our results indicate that bubble formation is consistent with the expectation of hadronisation in low-temperature QCD.Comment: 12 pages, 2 figure

FGF receptor signalling is required to maintain neural progenitors during Hensen's node progression

Previous analyses of labelled clones of cells within the developing nervous system of the mouse have indicated that descendants are initially dispersed rostrocaudally followed by more local proliferation, which is consistent with the progressing node's contributing descendants from a resident population of progenitor cells as it advances caudally. Here we electroporated an expression vector encoding green fluorescent protein into the chicken embryo near Hensen's node to test and confirm the pattern inferred in the mouse. This provides a model in which a proliferative stem zone is maintained in the node by a localized signal; those cells that are displaced out of the stem zone go on to contribute to the growing axis. To test whether fibroblast growth factor (FGF) signalling could be involved in the maintenance of the stem zone, we co-electroporated a dominant-negative FGF receptor with a lineage marker, and found that it markedly alters the elongation of the spinal cord primordium. The results indicate that FGF receptor signalling promotes the continuous development of the posterior nervous system by maintaining presumptive neural progenitors in the region near Hensen's node. This offers a potential explanation for the mixed findings on FGF in the growth and patterning of the embryonic axis

The equilibrium tide in viscoelastic parts of planets

International audienceEarth-like planets have viscoelastic mantles, whereas giant planets may have viscoelastic cores. As for the fluid parts of a body, the tidal dissipation of such solid regions, gravitationally perturbed by a companion body, highly depends on the tidal frequency, as well as on the rheology. Therefore, modelling tidal interactions presents a high interest to provide constraints on planet properties, and to understand their history and their evolution. Here, we examine the equilibrium tide in the solid core of a planet, taking into account the presence of a fluid envelope. We explain how to obtain the different Love numbers that describe its deformation. Next, we discuss how the quality factor Q depends on the chosen viscoelastic model. Finally, we show how the results may be implemented to describe the dynamical evolution of planetary systems

Spin alignment of stars in old open clusters

Stellar clusters form by gravitational collapse of turbulent molecular clouds, with up to several thousand stars per cluster. They are thought to be the birthplace of most stars and therefore play an important role in our understanding of star formation, a fundamental problem in astrophysics. The initial conditions of the molecular cloud establish its dynamical history until the stellar cluster is born. However, the evolution of the cloud's angular momentum during cluster formation is not well understood. Current observations have suggested that turbulence scrambles the angular momentum of the cluster-forming cloud, preventing spin alignment amongst stars within a cluster. Here we use asteroseismology to measure the inclination angles of spin axes in 48 stars from the two old open clusters NGC~6791 and NGC~6819. The stars within each cluster show strong alignment. Three-dimensional hydrodynamical simulations of proto-cluster formation show that at least 50 % of the initial proto-cluster kinetic energy has to be rotational in order to obtain strong stellar-spin alignment within a cluster. Our result indicates that the global angular momentum of the cluster-forming clouds was efficiently transferred to each star and that its imprint has survived after several gigayears since the clusters formed.Comment: 14 pages, 3 figures, 1 table. Published in Nature Astronom

Evaluation of Methods for Semantic Segmentation of Endoscopic Images

We examined multiple semantic segmentation methods, which consider the information contained in endoscopic images at different levels of abstraction in order to predict semantic segmentation masks. These segmentations can be used to obtain position information of surgical instruments in endoscopic images, which is the foundation for many computer assisted systems, such as automatic instrument tracking systems. The methods in this paper were examined and compared in regard to their accuracy, effort to create the data set, and inference time. Of all the investigated approaches, the LinkNet34 encoder-decoder network scored best, achieving an Intersection over Union score of 0.838 with an inference time of 30.25 ms on a 640 x 480 pixel input image with a NVIDIA GTX 1070Ti GPU

Polymerase chain reaction for detection of patent infections of Echinococcus granulosus ("sheep strain”) in naturally infected dogs

Polymerase chain reaction (PCR) for the identification of eggs of the tapeworm Echinococcus granulosus ("sheep strain”) was evaluated with primers derived from mitochondrial sequences. Specificity of these primers was confirmed by investigating DNA of other strains of E. granulosus and of 14 helminth species which inhabit the intestines of dogs. This PCR assay was used to investigate 131 purged dogs from Kazakhstan. Eighteen dogs harboured Echinococcus worms, ten of them in mixed infections with Taenia spp. Coproantigen detection was positive in 15 and taeniid eggs could be recovered from 13 of these specimens. Eight of the egg-containing samples were positive in the PCR for E. granulosus and four in a Echinococcus multilocularis -specific PCR revealing one mixed infection. Egg-containing faeces from two dogs harbouring both Taenia spp. and Echinococcus spp. were negative in both PCRs. The combination of egg isolation and PCR will also be of value in epidemiological studies when investigating environmental sample

Lumbar Facet Joint Radiofrequency Denervation Therapy for Chronic Low Back Pain: Enhanced Outcome Compared With Chemical Neurolysis (Ethyl Alcohol 95% or Glycerol 20%)

BACKGROUND It was hypothesized that radiofrequency denervation (RFD) of lumbar facet joints is associated with superior pain abolishment and less complications than chemical neurolysis (with ethyl alcohol or glycerol) in patients with chronic facet joint arthropathy. METHODS For this prospective cohort study, adult patients with chronic lumbar facet joint arthropathy were prospectively enrolled between 2017 and 2019. The following groups were compared before the intervention and 6 weeks, 6 months, and 12 months after the intervention: RFD, chemical neurolysis with ethyl alcohol 95% (EA-95), or glycerol 20% (Gly-20). Outcome parameters included the Core Outcome Measures Index for the back (COMI-back), World Health Organization (WHO) pain ladder level, and visual analog scale (VAS). P values <0.05 were considered statistically significant. RESULTS A total of 95 patients with a mean age of 63.7 years were included. Among them, 30 patients underwent RFD, 30 patients were treated with EA-95, and 35 individuals were treated with Gly-20. After 6 weeks, RFD patients had significantly lower VAS scores compared with the EA-95 group. After 6 months, both VAS and COMI were significantly lower in RFD patients than in the Gly-20 group. Twelve months after intervention, VAS scores were significantly lower in the RFD group compared with the Gly-20 group. CONCLUSIONS This study reveals that RFD is associated with improved pain relief and quality of life compared with chemical neurolysis for facet joint-related chronic lower back pain and should be considered as the treatment of choice in patients with chronic low back pain due to facet joint arthropathy. CLINICAL RELEVANCE The current study provides information that may improve clinical decision making in the treatment of chronic lumbar facet joint arthropathy and to appropriately counsel such patients about expected outcomes