Laser locking to the 199Hg clock transition with 5.4x10^(-15)/sqrt(tau) fractional frequency instability

With Hg atoms confined in an optical lattice trap in the Lamb-Dicke regime, we obtain a spectral line at 265.6 nm in which the full-width at half-maximum is <15Hz. Here we lock an ultrastable laser to this ultranarrow clock transition and achieve a fractional frequency stability of 5.4x10^(-15)/sqrt(tau) for tau<=400s. The highly stable laser light used for the atom probing is derived from a 1062.6 nm fiber laser locked to an ultrastable optical cavity that exhibits a mean drift rate of -6.0x10^(-17) s^(-1) (or -16.9 mHz.s^(-1) at 282 THz) over a five month period. A comparison between two such lasers locked to independent optical cavities shows a flicker noise limited fractional frequency instability of 4x10^(-16) per cavity

Relative Calibration of the Time Transfer Link Between CERN and LNGS for Precise Neutrino Time of Flight Measurements

International audienc

Application of Population Pharmacokinetic Modeling for Individualized Infliximab Dosing Strategies in Crohn Disease

Objectives:The pharmacokinetics of infliximab (IFX) is highly variable in children with Crohn disease (CD), and a one-size-fits-all approach to dosing is inadequate. Model-based drug dosing can help individualize dosing strategies. We evaluated the predictive performance and clinical utility of a published population pharmacokinetic model of IFX in children with CD.Methods:Within a cohort of 34 children with CD who had IFX trough concentrations measured, the pharmacokinetics of each patient was estimated in NONMEM using a published population pharmacokinetic model. Infliximab concentrations were then predicted based on each patient's dosing history and compared with actual measured concentrations (n = 59). In addition, doses 5 to 10 mg/kg and dosing intervals every 4 to 8 weeks were simulated in each patient to examine dose-trough relationships.Results:Predicted concentrations were within ±1.0 μg/mL of actual measured concentrations for 88% of measurements. The median prediction error (ie, measure of bias) was -0.15 μg/mL (95% confidence interval -0.37 to -0.05 μg/mL) and absolute prediction error (ie, measure of precision) was 0.26 μg/mL (95% confidence interval 0.15 to 0.40 μg/mL). At standard maintenance dosing of 5 mg/kg every 8 weeks, a trough >3 μg/mL was predicted to be achieved in 32% of patients. To achieve a trough >3 μg/mL, a dosing interval ≤every 6 weeks was predicted to be required in 29% of patients.Conclusions:A published IFX population pharmacokinetic model demonstrated accurate predictive performance in a pediatric CD population. Individualized IFX dosing strategies in children with CD will be critical to consistently achieve trough concentrations associated with optimal outcomes

Broadband Two-Way Satellite Link Performance for Optical Clock Comparison

International audienceEnhancements of the commonly used time and frequency transfer techniques are required to prepare for steeringtimescales with optical clocks having relative frequency instabilities of less than 10-17. To explore the potential oftwo-way satellite time and frequency transfer (TWSTFT), we performed a 1-week test of simultaneous broadband(20 Mchip/s) TWSTFT satellite links between the four European national metrology institutes (NMIs) PTB, LNESYRTE,INRIM and NPL through ASTRA 3B in the Ku-band. This test prepared for a 3-week optical clock comparison campaign in June 2015.The 1 Mchip/s TWSTFT employed for regular international clock comparisons is limited to an instability ofroughly 10-15 at 1 day [1]. To deploy the potential of optical clocks, at least an order of magnitude lower instabilityat 1 day is required, which in principle is feasible by increasing the TWSTFT chip rate to the maximum of theemployed SATRE modems of 20 Mchip/s. However, technical and environmental effects in a real satellite linkmay obstruct this theoretical limit. In addition to TWSTFT link data, GPS data were recorded. Cs fountains wererun at all four NMIs and optical clocks at NPL, OP and PTB. In each institute, a hydrogen maser signal was usedas a reliable common reference for the SATRE modems and GPS receivers, as well as for the Cs fountain andoptical clock (via an optical frequency comb) frequency measurements.Here, we present the performance of the broadbandTWSTFT satellite links. We observe short-term instabilitiesof the level of 2 x 10-11 (&amp;#964; = 1 s). Even though severaldisturbances can be observed, which at lower chip ratesare usually hidden below the link noise, we reach instabilitiesof 3 x 10-16 at one day (MDEV), limited by thehydrogen masers used. We discuss the origins of thetechnical disturbances, such as multipath effects andtemperature influence. As an independent method, GPSfrequency comparisons have been carried out using theprecise point positioning (PPP) concept; the performanceof these two techniques is compared and discussed.This work was supported by the European MetrologyResearch Programme EMRP. The EMRP is jointly fundedby the EMRP participating countries within EURAMET and the European Union

Comparison between frequency standards in Europe and the USA at the 1e-15 uncertainty level

International audienceIstituto Elettrotecnico Nazionale Galileo Ferraris (IEN), National Institute of Standards and Technology (NIST), National Physical Laboratory (NPL), Laboratoire National de Métrologie et d'Essais---Observatoire de Paris/Systèmes de Référence Temps Espace (OP) and Physikalisch-Technische Bundesanstalt (PTB) operate cold-atom based primary frequency standards which are capable of realizing the SI second with a relative uncertainty of 1 × 10-15 or even below. These institutes performed an intense comparison campaign of selected frequency references maintained in their laboratories during about 25 days in October/November 2004. Active hydrogen maser reference standards served as frequency references for the institutes' fountain frequency standards. Three techniques of frequency (and time) comparisons were employed. Two-way satellite time and frequency transfer (TWSTFT) was performed in an intensified measurement schedule of 12 equally spaced measurements per day. The data of dual-frequency geodetic Global Positioning System (GPS) receivers were processed to yield an ionosphere-free linear combination of the code observations from both GPS frequencies, typically referred to as GPS TAI P3 analysis. Last but not least, the same GPS raw data were separately processed, allowing GPS carrier-phase (GPS CP) based frequency comparisons to be made. These showed the lowest relative frequency instability at short averaging times of all the methods. The instability was at the level of 1 part in 1015 at one-day averaging time using TWSTFT and GPS CP. The GPS TAI P3 analysis is capable of giving a similar quality of data after averaging over two days or longer. All techniques provided the same mean frequency difference between the standards involved within the 1sigma measurement uncertainty of a few parts in 1016. The frequency differences between the three fountains of IEN (IEN-CsF1), NPL (NPL-CsF1) and OP (OP-FO2) were evaluated. Differences lower than the 1sigma measurement uncertainty were observed between NPL and OP, whereas the IEN fountain deviated by about 2sigma from the other two fountains

Calibration of six European TWSTFT earth stations using a portable station

none12D. PIESTER; J. ACHKAR; J. BECKER; B. BLANZANO; K. JALDEHAG; G. DE JONG; O. KOUDELKA; LORINI L; H. RESSLER; M. ROST; I. SESIA; P. WHIBBERLEYD., Piester; J., Achkar; J., Becker; B., Blanzano; K., Jaldehag; G., DE JONG; O., Koudelka; Lorini, Luca; H., Ressler; M., Rost; Sesia, Ilaria; P., Whibberle

Broadband Two-Way Satellite LinkPerformance for Optical Clock Comparison

International audienceEnhancements of the commonly used time and frequency transfer techniques are required to prepare for steeringtimescales with optical clocks having relative frequency instabilities of less than 10-17. To explore the potential oftwo-way satellite time and frequency transfer (TWSTFT), we performed a 1-week test of simultaneous broadband(20 Mchip/s) TWSTFT satellite links between the four European national metrology institutes (NMIs) PTB, LNESYRTE,INRIM and NPL through ASTRA 3B in the Ku-band. This test prepared for a 3-week optical clock comparison campaign in June 2015.The 1 Mchip/s TWSTFT employed for regular international clock comparisons is limited to an instability ofroughly 10-15 at 1 day [1]. To deploy the potential of optical clocks, at least an order of magnitude lower instabilityat 1 day is required, which in principle is feasible by increasing the TWSTFT chip rate to the maximum of theemployed SATRE modems of 20 Mchip/s. However, technical and environmental effects in a real satellite linkmay obstruct this theoretical limit. In addition to TWSTFT link data, GPS data were recorded. Cs fountains wererun at all four NMIs and optical clocks at NPL, OP and PTB. In each institute, a hydrogen maser signal was usedas a reliable common reference for the SATRE modems and GPS receivers, as well as for the Cs fountain andoptical clock (via an optical frequency comb) frequency measurements.Here, we present the performance of the broadbandTWSTFT satellite links. We observe short-term instabilitiesof the level of 2 x 10-11 (&amp;#964; = 1 s). Even though severaldisturbances can be observed, which at lower chip ratesare usually hidden below the link noise, we reach instabilitiesof 3 x 10-16 at one day (MDEV), limited by thehydrogen masers used. We discuss the origins of thetechnical disturbances, such as multipath effects andtemperature influence. As an independent method, GPSfrequency comparisons have been carried out using theprecise point positioning (PPP) concept; the performanceof these two techniques is compared and discussed.This work was supported by the European MetrologyResearch Programme EMRP. The EMRP is jointly fundedby the EMRP participating countries within EURAMET and the European Union

Broadband Two-Way Satellite LinkPerformance for Optical Clock Comparison

International audienceEnhancements of the commonly used time and frequency transfer techniques are required to prepare for steeringtimescales with optical clocks having relative frequency instabilities of less than 10-17. To explore the potential oftwo-way satellite time and frequency transfer (TWSTFT), we performed a 1-week test of simultaneous broadband(20 Mchip/s) TWSTFT satellite links between the four European national metrology institutes (NMIs) PTB, LNESYRTE,INRIM and NPL through ASTRA 3B in the Ku-band. This test prepared for a 3-week optical clock comparison campaign in June 2015.The 1 Mchip/s TWSTFT employed for regular international clock comparisons is limited to an instability ofroughly 10-15 at 1 day [1]. To deploy the potential of optical clocks, at least an order of magnitude lower instabilityat 1 day is required, which in principle is feasible by increasing the TWSTFT chip rate to the maximum of theemployed SATRE modems of 20 Mchip/s. However, technical and environmental effects in a real satellite linkmay obstruct this theoretical limit. In addition to TWSTFT link data, GPS data were recorded. Cs fountains wererun at all four NMIs and optical clocks at NPL, OP and PTB. In each institute, a hydrogen maser signal was usedas a reliable common reference for the SATRE modems and GPS receivers, as well as for the Cs fountain andoptical clock (via an optical frequency comb) frequency measurements.Here, we present the performance of the broadbandTWSTFT satellite links. We observe short-term instabilitiesof the level of 2 x 10-11 (&amp;#964; = 1 s). Even though severaldisturbances can be observed, which at lower chip ratesare usually hidden below the link noise, we reach instabilitiesof 3 x 10-16 at one day (MDEV), limited by thehydrogen masers used. We discuss the origins of thetechnical disturbances, such as multipath effects andtemperature influence. As an independent method, GPSfrequency comparisons have been carried out using theprecise point positioning (PPP) concept; the performanceof these two techniques is compared and discussed.This work was supported by the European MetrologyResearch Programme EMRP. The EMRP is jointly fundedby the EMRP participating countries within EURAMET and the European Union