Comparing ultrastable lasers at 7 × 10-17 fractional frequency instability through a 2220 km optical fibre network.

Ultrastable lasers are essential tools in optical frequency metrology enabling unprecedented measurement precision that impacts on fields such as atomic timekeeping, tests of fundamental physics, and geodesy. To characterise an ultrastable laser it needs to be compared with a laser of similar performance, but a suitable system may not be available locally. Here, we report a comparison of two geographically separated lasers, over the longest ever reported metrological optical fibre link network, measuring 2220 km in length, at a state-of-the-art fractional-frequency instability of 7 × 10-17 for averaging times between 30 s and 200 s. The measurements also allow the short-term instability of the complete optical fibre link network to be directly observed without using a loop-back fibre. Based on the characterisation of the noise in the lasers and optical fibre link network over different timescales, we investigate the potential for disseminating ultrastable light to improve the performance of remote optical clocks.

ΔK=0 M1 Excitation Strength of the Well-Deformed Nucleus

The size of a ΔK=0 M1 excitation strength has been determined for the first time in a predominantly axially deformed even-even nucleus. It has been obtained from the observation of a rare K-mixing situation between two close-lying J^{π}=1^{+} states of the nucleus ^{164}Dy with components characterized by intrinsic projection quantum numbers K=0 and K=1. Nuclear resonance fluorescence induced by quasimonochromatic linearly polarized γ-ray beams provided evidence for K mixing of the 1^{+} states at 3159.1(3) and 3173.6(3) keV in excitation energy from their γ-decay branching ratios into the ground-state band. The ΔK=0 transition strength of B(M1;0_{1}^{+}→1_{K=0}^{+})=0.008(1)µ_{N}^{2} was inferred from a mixing analysis of their M1 transition rates into the ground-state band. It is in agreement with predictions from the quasiparticle phonon nuclear model. This determination represents first experimental information on the M1 excitation strength of a nuclear quantum state with a negative R-symmetry quantum number.

[Psychrotrophic microorganisms in raw and pasteurized milk]. / Prouchvaniia vurkhu psikhrotrofnite mikroorganizmi v surovo i past'orizirano mliako.

The studied were carried out in 360 samples of unboiled milk and 1080 samples of pasteurized milk taken from three processing and distributing dairies having a different capacity and equipment. It was proved that the content of psychrotrophic microorganisms in unboiled milk from the three dairies varied from 120000 up to 200000 in 1 cm3 and was in close connection with the seasons of the year. The conditions applied for pasteurization in the three dairies killed (with the exception of those forming spores) nearly all psychrotrophic bacteria. The secondary seeding of the pasteurized milk by means of psychotrophics was carried out after the pasteurization along the whole technological route till its packing. The pasteurized milk packed in bottles showed a contamination with psychrotrophic microorganisms 4-6 times higher than that of milk packed in plastic bags. In the unboiled and in the pasteurized milk we found the psychrotrophic microorganisms of the species: Pseudomonas--respectively 64% and 53.8%, Micrococcus--8.2% and 30.7%, Enterobacter--9.8% and 2.6%, Bacillus--6.6% and 2.6%, Flavobacter--1.6% and 1.3% and Torula--2.6%. A comparatively high percentage (37.7%) of the isolated strains the psychrotrophic bacteria were lipolytic in the unboiled milk, 24.6%--proteolytic and 9.8% were simultaneously proteolytic and lipolytic. In the pasteurized milk 11.5% of the strains were lipolytic and 5.13% were proteolytic.

[Hygienic studies of frozen ocean fish]. / Khigienni prouchvaniia vurkhu zamrazena okeanska riba

Studied were batches of frozen ocean mackerel (Scomber scombrus L.) and silver hake (Merluccius bilinearis, Mitchill) during storage in a central base and in shops. The evaluation of the fish was made on the basis of organoleptic data, pH values, volatile bases, trimethylamin, volatile fatty acids, the amount of tissue fluids after Kietzmann, luminescence of musculature after Wittfogel, and through microbiologic study of the skin and musculature. It was found that the fish had been frozen in the fishing boats in a very good status. Great variations in the storage temperature are admitted in the central base, no correlation being established between the term of storage and the quantity of the product. The conditions for the preservation of the frozen fish in the shops where fish is especially sold are unappropriate--they contribute to the fast deterioration of the quality and the microbial status of the product.

[Thiobarbiturate and peroxide numbers as an index of the state of frozen ocean mackerel]. / Tiobarbiturovoto i perokisnoto chislo kato pokazateli za s'stoianieto na zamrazenata okeanska skumriia

Studied were the changes taking place in the fats of frozen mackerel according to its quality. The organoleptic evaluation performed by a standard method served as a basis of comparison. It was found that the fats of standard frozen ocean mackerel show a thiobarbiturate number after Kopecky (E/n X 10) ranging up to 10, and a peroxide number of up to 0.20% J2, resp. the index after Lea (ml 0.01n Na2S2O3 per gram of fat) being up to 1.60. The fats are extracted in a way that is based on Bligh and Dyer's method.