Improved theoretical prediction for the 2s hyperfine interval in helium ion

We consider the uncertainty of theoretical calculations for a specific difference of the hyperfine intervals in the 1s and 2s states in a light hydrogen-like atom. For a number of crucial radiative corrections the result for hydrogen atom and helium ion appears as an extrapolation of the numerical data from medium to low Z. An approach to a plausible estimation of the uncertainty is suggested using the example of the difference $D_{21}= 8E_{hfs}(2s)-E_{hfs}(1s)$

Amplitude to phase conversion of InGaAs pin photo-diodes for femtosecond lasers microwave signal generation

When a photo-diode is illuminated by a pulse train from a femtosecond laser, it generates microwaves components at the harmonics of the repetition rate within its bandwidth. The phase of these components (relative to the optical pulse train) is known to be dependent on the optical energy per pulse. We present an experimental study of this dependence in InGaAs pin photo-diodes illuminated with ultra-short pulses generated by an Erbium-doped fiber based femtosecond laser. The energy to phase dependence is measured over a large range of impinging pulse energies near and above saturation for two typical detectors, commonly used in optical frequency metrology with femtosecond laser based optical frequency combs. When scanning the optical pulse energy, the coefficient which relates phase variations to energy variations is found to alternate between positive and negative values, with many (for high harmonics of the repetition rate) vanishing points. By operating the system near one of these vanishing points, the typical amplitude noise level of commercial-core fiber-based femtosecond lasers is sufficiently low to generate state-of-the-art ultra-low phase noise microwave signals, virtually immune to amplitude to phase conversion related noise.Comment: 7 pages, 6 figures, submitted to Applied Physics

Hamiltonian approach to the ac Josephson effect in superconducting-normal hybrid systems

The ac Josephson effect in hybrid systems of a normal mesoscopic conductor coupled to two superconducting (S) leads is investigated theoretically. A general formula of the ac components of time-dependent current is derived which is valid for arbitrary interactions in the normal region. We apply this formula to analyze a S-normal-S system where the normal region is a noninteracting single level quantum dot. We report the physical behavior of time-averaged nonequilibrium distribution of electrons in the quantum dot, the formation of Andreev bound states, and ac components of the time-dependent current. The distribution is found to exhibit a population inversion; and all Andreev bound states between the superconducting gap $\Delta$ carry the same amount of current and in the same flow direction. The ac components of time-dependent current show strong oscillatory behavior in marked contrast to the subharmonic gap structure of the average current.Comment: 23 pages, 10 figures, LaTe

Ассоциация полиморфизма гена IL12Bс предрасположенностью к псориазу в популяцииСеверо-Западного региона России

The IL12B gene encodes protein р40 being a common subunit of interleukin-12 and interleukin-23 playing an important part in the pathogenesis of psoriasis. The IL12B gene has polymorphism rs12188300, which can be associated with the risk of psoriasis development. The goal of the study was to assess the distribution of alleles of polymorphism rs12188300 in psoriatic patients in the Northwestern region of Russia. Genotyping was carried out using the real-time allele-specific polymerase chain reaction. An increased occurrence of a rare allele T in psoriatic patients as compared to healthy people was observed (OR = 1.96, р = 0.0007). The occurrence of the rare allele T in patients with psoriatic arthritis was higher than in the control group (OR = 3.49, р = 0.005). These results suggest that rs12188300 polymorphism of the IL12B gene is a new genetic marker of psoriasis and psoriatic arthritis.Ген IL12B кодирует белок р40, являющийся общей субъединицей интерлейкина-12 и интерлейкина-23, играющих важную роль в патогенезе псориаза. Ген IL12B содержит полиморфизм rs12188300, который может быть ассоциирован с риском развития псориаза. Целью работы явилось изучение распределения аллелей полиморфизма rs12188300 у больных псориазом Северо-Западного региона России. Генотипирование проводилось методом аллельспецифической полимеразной цепной реакции в режиме реального времени. Выявлено повышение встречаемости редкого аллеля Т среди больных псориазом по сравнению со здоровыми лицами (OR = 1,96, р = 0,0007). Частота редкого аллеля Т среди больных псориатическим артритом была выше, чем в группе контроля (OR = 3,49, р = 0,005). Полученные результаты позволяют предположить, что полиморфизм rs12188300 гена IL12B является новым генетическим маркером псориаза и псориатического артрита

Collapsing shear-free perfect fluid spheres with heat flow

A global view is given upon the study of collapsing shear-free perfect fluid spheres with heat flow. We apply a compact formalism, which simplifies the isotropy condition and the condition for conformal flatness. This formalism also presents the simplest possible version of the main junction condition, demonstrated explicitly for conformally flat and geodesic solutions. It gives the right functions to disentangle this condition into well known differential equations like those of Abel, Riccati, Bernoulli and the linear one. It yields an alternative derivation of the general solution with functionally dependent metric components. We bring together the results for static and time- dependent models to describe six generating functions of the general solution to the isotropy equation. Their common features and relations between them are elucidated. A general formula for separable solutions is given, incorporating collapse to a black hole or to a naked singularity.Comment: 26 page

Air temperature variations and gradients along the coast and fjords of western Spitsbergen

Daily temperature measurements from six meteorological stations along the coast and fjords of western Spitsbergen have been digitized and quality controlled in a Norwegian, Russian and Polish collaboration. Complete daily data series have been reconstructed back to 1948 for all of the stations. One of the station’s monthly temperature series has previously been extended back to 1898 and is included in this study. The long-term series show large temperature variability on western Spitsbergen with colder periods in the 1910s and 1960s and warmer periods in the 1930s, 1950s and in the 21st century. The most recent years are the warmest ones in the instrumental records. There is a positive and statistically significant trend in the annual times series for all of the stations; however, the strongest warming is seen in winter and spring. For the period 1979-2015, the linear trends range from 1.0 to 1.38°C/decade for the annual series and from 2.0 to 2.38°C/decade in winter. Threshold statistics demonstrate a decrease in the number of cold days per year and an increase in the number of warm days. A decreasing inter-annual variability is observed. In winter, spring and autumn, the stations in the northernmost areas of west Spitsbergen and in the innermost parts of Isfjorden are the coldest ones. In summer, however, the southernmost station is the coldest one

The upgrade of the ALICE TPC with GEMs and continuous readout

The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020.publishedVersio

Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV

Peer reviewe