A clock network for geodesy and fundamental science.

Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10(-17) via a newly established phase-coherent frequency link connecting Paris and Braunschweig using 1,415 km of telecom fibre. The remote comparison is limited only by the instability and uncertainty of the strontium lattice clocks themselves, with negligible contributions from the optical frequency transfer. A fractional precision of 3 × 10(-17) is reached after only 1,000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than any previous long-distance clock comparison. 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.

Optical frequency transfer via a 660 km underground fiber link using a remote Brillouin amplifier.

In long-distance, optical continuous-wave frequency transfer via fiber, remote bidirectional Er³ ⁺ -doped fiber amplifiers are commonly used to mitigate signal attenuation. We demonstrate for the first time the ultrastable transfer of an optical frequency using a remote fiber Brillouin amplifier, placed in a server room along the link. Using it as the only means of remote amplification, on a 660 km loop of installed underground fiber we bridge distances of 250 km and 160 km between amplifications. Over several days of uninterrupted measurement, we find an instability of the frequency transfer (Allan deviation of Λ-weighted data with 1 s gate time) of around 1 × 10(-19) and less for averaging times longer than 3000 s. The modified Allan deviation reaches 3 × 10(-19) at an averaging time of 100 s. Beyond 100 s it follows the interferometer noise floor, and for averaging times longer than 1000 s the modified Allan deviation is in the 10(-20) range. A conservative value of the overall accuracy is 1 × 10(-19)

[Long-term oxygen therapy of chronic pulmonary heart disease]. / Dlugotrwala tlenoterapia w przewleklym sercu plucnym.

Pulmonary artery pressure was measured in 70 patients with chronic bronchitis. Those with pulmonary hypertension underwent two hours oxygen therapy (flow 10-12 l/min). Those in whom a decrease of pulmonary artery pressure was observed were qualified for long term oxygen therapy (LTOT). In 32 patients which were qualified for LTOT, after a two week period of 18 hour per day oxygen therapy a decrease of systolic pulmonary arterial pressure from 336.1 mm Hg to 30.9 mm Hg and a decrease of mean pulmonary artery pressure from 25.9 to 23.2 mm Hg was observed.

[Effect of mechanical vibrations and noise on creatine kinase activity in workers]. / Wplyw drgan mechanicznych i halasu na aktywnosc kinazy kreatynowej u pracowników narazonych.

In two groups of workers exposed to vibration and noise exceeding allowable standards within 3 to 30 years for over 4 hrs daily, the activity of creatine kinase-test enzyme for the diagnosis of muscular diseases and traumata was evaluated. Both in group I, composed of 74 workers aged 21-51 (38 on average) topically exposed to mechanical vibrations and noise, and in group II, composed of 45 workers aged 25-51 (37 on average), with topical or whole-body exposure to mechanical vibrations CPK was found to be significantly increased as compared to controls--26 workers carrying on medium (i.e. not very hard) work. In the group of 30 workers exposed to noise only, CPK values were comparable with the control group. CPK was increased irrespective of evident angioneurosis and duration of exposure. The obtained results indicate the advisability of applying the CPK activity investigation as an exposure test.

[Electrocardiographic examination of the heart and the study of catecholamine secretion in workers subjected to mechanical vibration and occupational noise]. / Badanie elektrokardiograficzne serca i wydzielanie katecholamin u pracowników narazonych na drgania mechaniczne i halas przemyslowy.

Electrocardiographic tests in 281 workers of metallurgical industry, exposed for 3-20 years to mechanical and acoustic vibrations exceeding allowable standards, were carried out. The control group consisted of 120 subjects unexposed to physical or chemical hazards. In 82 subjects exposed to vibration and noise, 43 workers exposed to isolated noise and 30 subjects of the control group, the amount of 3 methoxy--4 hydroxymandelic (3M4HM) acid before and after work was determined. Significantly more frequent repolarization disturbances of neurovegetative nature (V-3), particularly in those simultaneously exposed to general and local vibration, were evidenced. In those exposed exclusively to noise no ECG changes were found. In addition, increased 3M4HM secretion, due to both local and whole--body transmitted vibration, was found. Isolated noise does not induce an increase in 3M4HM secretion.