A clock network for geodesy and fundamental science

Leveraging the unrivaled performance of optical clocks in applications in fundamental physics beyond the standard model, in geo-sciences, and in astronomy requires comparing the frequency of distant optical clocks truthfully. Meeting this requirement, we report on the first comparison and agreement of fully independent optical clocks separated by 700 km being only limited by the uncertainties of the clocks themselves. This is achieved by a phase-coherent optical frequency transfer via a 1415 km long telecom fiber link that enables substantially better precision than classical means of frequency transfer. The fractional precision in comparing the optical clocks of three parts in $10^{17}$ was reached after only 1000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than with any other existing frequency transfer method. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second.Comment: 14 pages, 3 figures, 1 tabl

First international comparison of fountain primary frequency standards via a long distance optical fiber link

International audienceWe report on the first comparison of distant caesium fountain primary frequency standards (PFSs) via an optical fiber link. The 1415 km long optical link connects two PFSs at LNE-SYRTE (Laboratoire National de métrologie et d'Essais-SYstème de Références Temps-Espace) in Paris (France) with two at PTB (Physikalisch-Technische Bundesanstalt) in Braunschweig (Germany). For a long time, these PFSs have been major contributors to accuracy of the International Atomic Time (TAI), with stated accuracies of around 3 × 10 −16. They have also been the references for a number of absolute measurements of clock transition frequencies in various optical frequency standards in view of a future redefinition of the second. The phase coherent optical frequency transfer via a stabilized telecom fiber link enables far better resolution than any other means of frequency transfer based on satellite links. The agreement for each pair of distant fountains compared is well within the combined uncertainty of a few 10 −16 for all the comparisons, which fully supports the stated PFSs' uncertainties. The comparison also includes a rubidium fountain frequency standard participating in the steering of TAI and enables a new absolute determination of the 87 Rb ground state hyperfine transition frequency with an uncertainty of 3.1 × 10 −16. This paper is dedicated to the memory of André Clairon, who passed away on the 24 th of December 2015, for his pioneering and long-lasting efforts in atomic fountains. He also pioneered optical links from as early as 1997

Integrative model of the response of yeast to osmotic shock

Integration of experimental studies with mathematical modeling allows insight into systems properties, prediction of perturbation effects and generation of hypotheses for further research. We present a comprehensive mathematical description of the cellular response of yeast to hyperosmotic shock. The model integrates a biochemical reaction network comprising receptor stimulation, mitogen-activated protein kinase cascade dynamics, activation of gene expression and adaptation of cellular metabolism with a thermodynamic description of volume regulation and osmotic pressure. Simulations agree well with experimental results obtained under different stress conditions or with specific mutants. The model is predictive since it suggests previously unrecognized features of the system with respect to osmolyte accumulation and feedback control, as confirmed with experiments. The mathematical description presented is a valuable tool for future studies on osmoregulation in yeast and—with appropriate modifications—other organisms. It also serves as a starting point for a comprehensive description of cellular signaling

Blood transfusion after lung transplantation: Impact on early function and survival

Objectives: Blood transfusion is associated with higher morbidity and mortality after general cardiothoracic surgery but little is known of the impact on the transplant population. We investigated the profile of blood product transfusion in the bilateral lung transplant (BLT) population and the impact on function and survival outcomes. Methods: A total of 311 adult patients who underwent BLT between 2003 and 2013 were retrospectively reviewed. Patients were stratified according to pretransplant diagnosis and amount of blood products transfused within 24 h of surgery. Results: Patients, 174 male, 137 female (mean age 41.4 ± 14.0 years) underwent BLT, using cardiopulmonary bypass for cystic fibrosis (48.87%), fibrotic lung disease (12.21%), emphysema (27.01%), bronchiectasis (5.79%), pulmonary hypertension (1.29%) and others (4.50%). Median number of red blood cells (RBC) in the first 24 h was 3 (0–40) units, fresh frozen plasma (FFP) was 2 (0–26) units, platelets = 1 (0–7) units. There were no differences in transfusion rates according to pretransplant diagnosis. Patients were divided according to the number of units transfused in the first 24 h. Survival was not influenced by whether patients were transfused with more or less than the median number of units of RBC (P = 0.162) or FFP (P = 0.298) (Fig. 1). However, survival was adversely affected by platelet transfusion (P = 0.032). Mean FEV1 at 6 months was significantly better for patients transfused with more than the median number of units of RBC (2.66 vs 2.83, P < 0.0001), FFP (2.61 vs 2.89, P < 0.0001) and platelets (2.73 vs 2.82, P < 0.0001). Conclusion: Unlike general cardiothoracic surgery, blood transfusion has no effect on survival, but administration of platelets has an adverse effect. Blood product administration does not differ significantly with pretransplant diagnosis. Interestingly, lung function at 6 months is significantly better for patients with transfusion with more blood products