Long term stability of atomic time scales

AbstractWe review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are in the low 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.

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Atomic time scales TAI and TT(BIPM): present performances and prospects

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310008896 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 220-221

Author(s):

Gérard Petit

Keyword(s):

Time Scales ◽

Time Scale ◽

Time Transfer ◽

Relative Value ◽

The Stability ◽

Primary Standards ◽

Stability And Accuracy ◽

Atomic Time

AbstractWe review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are at the level of a few 10−16 in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16 value could be reached or superseded and which are the present limitations to attain this goal.

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Current and future realizations of coordinate time scales

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309990214 ◽

2009 ◽

Vol 5 (S261) ◽

pp. 95-101

Author(s):

E. Felicitas Arias

Keyword(s):

Time Scales ◽

Time Scale ◽

Proper Time ◽

Frequency Stability ◽

Reference Time ◽

Weights And Measures ◽

Coordinate Time ◽

Future Improvement ◽

Stability And Accuracy ◽

Atomic Time

AbstractTwo atomic time scales maintained at the International Bureau of Weights and Measures (BIPM) are realizations of terrestrial time: International Atomic Time (TAI) and TT(BIPM). They are calculated from atomic clocks realizing proper time in national laboratories. The algorithm for the calculation of TAI has been designed to optimize the frequency stability and accuracy of the time scale. Plans for the future improvement of the reference time scales are presented.

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The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657008 ◽

1979 ◽

Vol 42 (04) ◽

pp. 1135-1140 ◽

Cited By ~ 9

Author(s):

G I C Ingram

Keyword(s):

Human Brain ◽

Collaborative Study ◽

Calibration Constant ◽

Long Term Stability ◽

Freeze Dried ◽

Show Evidence ◽

Human Material ◽

Reference Preparation ◽

The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

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The long-term instability of the new generation hydrogen masers

Izmeritel`naya Tekhnika ◽

10.32446/0368-1025it.2020-1-35-38 ◽

2020 ◽

pp. 35-38

Author(s):

S.I. Donchenko ◽

I.Y. Blinov ◽

I.B. Norets ◽

Y.F. Smirnov ◽

A.A. Belyaev ◽

...

Keyword(s):

Time Scale ◽

Frequency Difference ◽

Clock Frequency ◽

Quantum Frequency ◽

Frequency Standards ◽

Quantum Frequency Standards ◽

New Generation ◽

Atomic Time

The latest changes in the algorithm for the formation of the international atomic time scale TAI are reported in terms of estimating the weights of the clocks involved in the formation of TAI. Studies of the characteristics of the long-term instability of new-generation hydrogen masers based on processing the results of the clock frequency difference with respect to TAI are performed. It has been confirmed that at present, new-generation hydrogen masers show significantly less long-term instability in comparison with quantum frequency standards ofsimilar and other types.

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The Stability of Mars’s Annular Polar Vortex

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0293.1 ◽

2017 ◽

Vol 74 (5) ◽

pp. 1533-1547 ◽

Cited By ~ 10

Author(s):

William J. M. Seviour ◽

Darryn W. Waugh ◽

Richard K. Scott

Keyword(s):

Relaxation Time ◽

Time Scales ◽

Time Scale ◽

Thermal Relaxation ◽

Polar Vortex ◽

Radiative Relaxation ◽

Equilibrium Profile ◽

Rotating Shallow Water ◽

The Stability ◽

Topographic Forcing

Abstract The Martian polar atmosphere is known to have a persistent local minimum in potential vorticity (PV) near the winter pole, with a region of high PV encircling it. This finding is surprising, since an isolated band of PV is barotropically unstable, a result going back to Rayleigh. Here the stability of a Mars-like annular vortex is investigated using numerical integrations of the rotating shallow-water equations. The mode of instability and its growth rate is shown to depend upon the latitude and width of the annulus. By introducing thermal relaxation toward an annular equilibrium profile with a time scale similar to that of the instability, a persistent annular vortex with similar characteristics as that observed in the Martian atmosphere can be simulated. This time scale, typically 0.5–2 sols, is similar to radiative relaxation time scales for Mars’s polar atmosphere. The persistence of an annular vortex is also shown to be robust to topographic forcing, as long as it is below a certain amplitude. It is therefore proposed that the persistence of this barotropically unstable annular vortex is permitted owing to the combination of short radiative relaxation time scales and relatively weak topographic forcing in the Martian polar atmosphere.

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Limitations and Challenges in the Stability of Cysteamine Eye Drop Compounded Formulations

Pharmaceuticals ◽

10.3390/ph15010002 ◽

2021 ◽

Vol 15 (1) ◽

pp. 2

Author(s):

Cristina Martín-Sabroso ◽

Mario Alonso-González ◽

Ana Fernández-Carballido ◽

Juan Aparicio-Blanco ◽

Damián Córdoba-Díaz ◽

...

Keyword(s):

Shelf Life ◽

Stability Study ◽

Eye Drops ◽

Microbiological Analysis ◽

Nitrogen Gas ◽

Long Term Stability ◽

Main Degradation Product ◽

The Stability ◽

Unstable Molecule

Accumulation of cystine crystals in the cornea of patients suffering from cystinosis is considered pathognomonic and can lead to severe ocular complications. Cysteamine eye drop compounded formulations, commonly prepared by hospital pharmacy services, are meant to diminish the build-up of corneal cystine crystals. The objective of this work was to analyze whether the shelf life proposed for six formulations prepared following different protocols used in hospital pharmacies is adequate to guarantee the quality and efficacy of cysteamine eye drops. The long-term and in-use stabilities of these preparations were studied using different parameters: content of cysteamine and its main degradation product cystamine; appearance, color and odor; pH and viscosity; and microbiological analysis. The results obtained show that degradation of cysteamine was between 20% and 50% after one month of storage in the long-term stability study and between 35% and 60% in the in-use study. These data confirm that cysteamine is a very unstable molecule in aqueous solution, the presence of oxygen being the main degradation factor. Saturation with nitrogen gas of the solutions offers a means of reducing cysteamine degradation. Overall, all the formulae studied presented high instability at the end of their shelf life, suggesting that their clinical efficacy might be dramatically compromised.

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LONG-TERM STABILITY ANALYSIS OF ACOUSTIC ABSORBING BOUNDARY CONDITIONS

Mathematical Models and Methods in Applied Sciences ◽

10.1142/s0218202513500280 ◽

2013 ◽

Vol 23 (11) ◽

pp. 2129-2154 ◽

Cited By ~ 1

Author(s):

HÉLÈNE BARUCQ ◽

JULIEN DIAZ ◽

VÉRONIQUE DUPRAT

Keyword(s):

Stability Analysis ◽

Boundary Conditions ◽

Absorbing Boundary Conditions ◽

Computational Domain ◽

Acoustic Wave Equation ◽

Absorbing Boundary ◽

Term Stability ◽

Long Term Stability ◽

The Stability

This work deals with the stability analysis of a one-parameter family of Absorbing Boundary Conditions (ABC) that have been derived for the acoustic wave equation. We tackle the problem of long-term stability of the wave field both at the continuous and the numerical levels. We first define a function of energy and show that it is decreasing in time. Its discrete form is also decreasing under a Courant–Friedrichs–Lewy (CFL) condition that does not depend on the ABC. Moreover, the decay rate of the continuous energy can be determined: it is exponential if the computational domain is star-shaped and this property can be illustrated numerically.

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The Long-Term Stability of Becquerelite

MRS Proceedings ◽

10.1557/proc-353-647 ◽

1994 ◽

Vol 353 ◽

Cited By ~ 3

Author(s):

R.J. Finch ◽

J. Suksi ◽

K. Rasilainen ◽

R.C. Ewing

Keyword(s):

Ground Water ◽

Time Scale ◽

Solubility Product ◽

Term Stability ◽

Long Term Stability ◽

Uranium Series ◽

Lower Solubility ◽

Geologic Disposal ◽

Petrographic Analyses

AbstractUranium-series disequilibria data, in conjunction with petrographic analyses, indicate that the uranyl oxide hydrate becquerelite can persist for hundreds of thousands of years, possibly longer. Becquerelite probably forms continuously as ground water compositions permit and is resistant to U leaching by ground water. On the time scale of interest for the geologic disposal of spent UO2 nuclear fuel, becquerelite is a long-lived sink for uranium in oxidizing, U and Ca-bearing ground waters. Such long-term stability also supports recent solubility experiments that indicate natural becquerelite has a lower solubility product than that determined for synthetic becquerelites.

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Remote atomic clock synchronization via satellites and optical fibers

Advances in Radio Science ◽

10.5194/ars-9-1-2011 ◽

2011 ◽

Vol 9 ◽

pp. 1-7 ◽

Cited By ~ 32

Author(s):

D. Piester ◽

M. Rost ◽

M. Fujieda ◽

T. Feldmann ◽

A. Bauch

Keyword(s):

Time Scales ◽

Optical Fibers ◽

Time Scale ◽

Distribution Systems ◽

Clock Synchronization ◽

Atomic Clock ◽

Global Network ◽

Current Status ◽

Time Transfer ◽

Uncertainty Level

Abstract. In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10−15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps. To ensure that the ACES ground instrument will be synchronized to the local time scale at the Physikalisch-Technische Bundesanstalt (PTB) without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An uncertainty below 40 ps over a distance of 2 km has been demonstrated on the campus of PTB. This technology is thus in general a promising candidate for synchronization of enhanced time transfer equipment with the local realizations of Coordinated Universal Time UTC. Based on these experiments we estimate the uncertainty level for calibrated time transfer through optical fibers over longer distances. These findings are compared with the current status and developments of satellite based time transfer systems, with a focus on the calibration techniques for operational systems.

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