Cyclic cooling of quantum systems at the saturation limit

The achievable bounds of cooling quantum systems, and the possibility to violate them is not well-explored experimentally. For example, among the common methods to enhance spin polarization (cooling), one utilizes the low temperature and high-magnetic field condition or employs a resonant exchange with highly polarized spins. The achievable polarization, in such cases, is bounded either by Boltzmann distribution or by energy conservation. Heat-bath algorithmic cooling schemes (HBAC), on the other hand, have shown the possibility to surpass the physical limit set by the energy conservation and achieve a higher saturation limit in spin cooling. Despite, the huge theoretical progress, and few principle demonstrations, neither the existence of the limit nor its application in cooling quantum systems towards the maximum achievable limit have been experimentally verified. Here, we show the experimental saturation of the HBAC limit for single nuclear spins, beyond any available polarization in solid-state spin system, the Nitrogen-Vacancy centers in diamond. We benchmark the performance of our experiment over a range of variable reset polarizations (bath temperatures), and discuss the role of quantum coherence in HBAC.

THE LAYER-BY-LAYER VARIATION OF WOOD DENSITY UNDER UNIAXIAL COMPRESSION

Currently, stocks of hardwoods in the Russian Federation are severely depleted and there is a shortage of raw materials on the market. One solution to this problem is the possibility of replacing hardwoods with pressed wood obtained from softwoods. As a result of the performed study, the change in the layer-by-layer density in the thickness of blanks made of pressed wood was found. The variation of density in the thickness of the workpiece depends on the moisture content of the wood at the time of pressing. At a humidity of 15 %, the wood is more compacted in the Central part than on the surface of the workpiece. When the humidity corresponds to the saturation limit of the cell walls of 30 %, the wood on the contrary is less compacted in the Central part, as well as on the surface of the samples. It was found that with the same average density of blanks made of pressed wood, the difference between the densest and less dense parts of the workpiece averaged 7.6-10.1 %. Based on these data, it is possible to obtain pressed wood with a given density distribution over the thickness of the workpieces. The results of the experiments will be useful in obtaining pressed wood with specified quality indicators, as well as in the manufacture of various structural elements and components from pressed wood.

Cell Wall Saturation Limit and Selected Properties of Thermally Modified Oak Wood and Cellulose

The interaction of water and oak wood is common in outdoor expositions and will remain a probable occurrence in the future. New insights into the recognition of a cell wall saturation limit are presented by a double-weighing method at 20 °C. The cell wall saturation limit, as the property of thermally modified oak wood, is significantly influenced by different treatment temperatures (20, 160, 180, 210 and 240 °C) on a 5% alpha level. A significantly higher equilibrium moisture content was reached by thermally modified oak wood at a temperature of 20 °C and relative humidity of 65% after its equilibrium in the water-in-reservoir. Moreover, the results are used in the treatment of woodchips to produce cellulose or decomposition of thermally modified wood to its basic chemical components. The investigated properties of cellulose revealed its relationship with water. The number of water molecules bonded to a cellulose chain was correlated with other measured compositions: average molecular weight, total crystalline index, lateral order index and polydispersity index. Analyses showed that there was a strong negative correlation between lateral order index and average molecular weight. The same was true between total crystalline index and average molecular weight. The rest of the properties were positively correlated with the number of water molecules bonded to glucopyranose. The results revealed the possible regeneration of a wood sorption ability after heat treatment and the stability of cellulose in such process.

Motorization rate in Serbia, Republic of Srpska, Federation of BiH, Montenegro and North Macedonia

Motorization rate is defined in two ways. The first definition says that the degree of motorization is the number of inhabitants per passenger car while the second definition represents motorization rate as the number of passenger cars per 1000 inhabitants. As absolute saturation limit, 500 passenger cars per 1000 inhabitants are taken. This paper analyzes motorization rate for local government units in the territory of Serbia, Republic of Srpska, Federation of BiH and Montenegro. The number of inhabitants and the number of registered passenger cars were collected. In addition, the analysis was done for countries and entities. Also, the data has been collected for Northern Macedonia as a state. A comparison of the results obtained with other European and individual world countries for 2017 was made.

A Swift view of X-ray and UV radiation in the planet-forming T Tauri system PDS 70

ABSTRACT PDS 70 is a ∼5-Myr-old star with a gas and dust disc in which several protoplanets have been discovered. We present the first ultraviolet (UV) detection of the system along with X-ray observations taken with the Neil Gehrels Swift Observatory satellite. PDS 70 has an X-ray flux of 3.4 × 10−13 erg cm−2 s−1 in the 0.3–10.0 keV range, and UV flux (U band) of 3.5 × 10−13 erg cm−2 s−1 . At the distance of 113.4 pc determined from Gaia Data Release 2, this gives luminosities of 5.2 × 1029 and 5.4 × 1029 erg s−1, respectively. The X-ray luminosity is consistent with coronal emission from a rapidly rotating star close to the log $\frac{L_{\mathrm{X}}}{L_{\mathrm{bol}}} \sim -3$ saturation limit. We find the UV luminosity is much lower than would be expected if the star were still accreting disc material and suggest that the observed UV emission is coronal in origin.