CREATING A MODERN ENVIRONMENTALLY FRIENDLY NON-FREEZING LIQUID

Проведено исследование составов и свойств стеклоомывющих жидкостей для пониженных температур, представленных на рынке. А также осуществлен подбор поверхностно-активных веществ и хладагента, для их дальнейшего использования в качестве основных компонентов при создании экологически безопасных не спиртовых стеклоомывающих жидкостей. In this article, a study of the composition and properties of winter glass-washing fluids on the market is carried out. Also, the selection of surfactants and refrigerants for their further use as the main components in the creation of environmentally friendly non-alcoholic glass-washing liquids was carried out.

Pressure increase in a flat fracture filled with freezing liquid

The paper considers the problem of pressure variations in circular and rectangular flat fractures filled with liquid as the liquid crystallises, taking into account rigidity of the solid phase forming. We suppose that as a liquid crystallises, the volume it occupies inside the fracture changes due to the difference in density of the solid and liquid phases, and the fracture walls deform due to the pressure difference between the environment and the internal zone. Assuming that the solid and liquid phases are incompressible, we may equate the change in the internal fracture volume caused by the deformation of the surrounding walls to that in the volume of the liquid undergoing a state transition. We presume that crystallisation occurs at the top of the fracture, the temperature of the liquid is constant and equals its crystallisation temperature, and the phase boundary between the liquid and solid phases is flat. We consider the side walls and the bottom to be thermally insulated and perfectly rigid. We derived analytical expressions for determining the pressure

Low-temperature ground freezing methods for underground construction in urban areas

Artificial ground freezing (AGF) is a commonly used ground improvement technique. It can be applied in diverse construction projects in dense populated urban areas where other methods are inapplicable. In this article are discussed several methods of ground freezing, such as: “brine” freezing, liquid nitrogen freezing, solid carbon dioxide freezing. Their advantages and disadvantages are indicated. For solid carbon dioxide freezing, several approaches are presented. One of them is a brine “aftercooling” freezing method. They can significantly increase efficiency of ground freezing and reduce its cost.

Determination of the heating pile numerical model parameters based on the laboratory strength tests of clay at low temperatures

Heating piles combine the function of the foundation and the heat source. They acquire heat from the ground through in built the installation. Inside the installation is non-freezing liquid at low temperature. In connection with the above, piles and the surrounding soil are exposed to significant temperature changes. As a result of these changes, the mechanical parameters of the soil and the behavior of the pile and soil contact surface were changed. This affects directly the load capacity of the heating piles. To describe this effect, laboratory tests were carried out to determine the thermal and mechanical parameters of the soil at low temperatures. The results from laboratory tests were applied as material parameters in the Z_Soil program. Based on the analysis using the finite element method, it was found that there is an negative effect on the friction on the surface of pile associated with the heat transfer between the soil and the pile.

POST-HARVEST QUALITY OF PEQUI (Caryocar brasiliense CAMB.) COLLECTED FROM THE PLANT OR AFTER NATURALLY FALLING OFF AND SUBJECTED TO SLOW AND QUICK FREEZING

ABSTRACT Soluble solids (SS), titratable acidity (TA), SS/TA ratio, pH, moisture, soluble sugars (SSU), total reducing sugars (RSU), and non-reducing sugars (NRS) were assessed in the pulp of pequi fruits collected at three ripening stages: from the plant, from the ground after naturally falling off, and collected from the ground three days after naturally falling off. The evaluation was performed after six months of freezer storage both for fruits subjected to quick freezing (liquid nitrogen followed by freezer) and slow freezing (straight into the freezer). The variables assessed were not influenced by the freezing method. The SS, TA, and RSU contents increased with the ripening stage, suggesting that the fruits collected from the plant are still immature and have lower quality than those collected after naturally falling off. Although considered mature when they fall off, fruits consumed three days after naturally falling off have better quality.

DEHIDRASI DAN PEMBEKUAN JARINGAN APEKS TEBU UNTUK PENYIMPANAN JANGKA PANJANG

<p>ABSTRAK<br />Tebu (Saccharum officinarum L.) merupakan tanaman yang<br />diperbanyak secara vegetatif. Kriopreservasi merupakan metode yang<br />paling sesuai untuk penyimpanan jangka panjang bagi tanaman yang<br />diperbanyak secara vegetatif. Dehidrasi dan pembekuan jaringan merupa-<br />kan tahapan paling kritis yang menentukan keberhasilan kriopreservasi.<br />Tujuan penelitian adalah untuk memperoleh durasi dehidrasi yang optimal<br />dan metode pembekuan jaringan apeks tebu. Penelitian dilakukan di<br />Laboratorium Kultur Jaringan, Kelompok Peneliti Biologi Sel dan<br />Jaringan, Balai Penelitian dan Pengembangan Bioteknologi dan Sumber-<br />daya Genetik Pertanian, Bogor pada Mei 2013 sampai Februari 2014.<br />Untuk optimasi metode dehidrasi, apeks direndam dalam larutan PVS2<br />(MS + gliserol 30% + etilen glikol 15% + dimetil sulfoksida 15% +<br />sukrosa 0,4 M) selama 10, 20, 30, dan 40 menit. Untuk optimasi metode<br />pembekuan, diujikan kombinasi perlakuan prakultur (dengan sukrosa 0;<br />0,1; dan 0,3 M selama 5 hari) dan pemuatan dalam larutan LS (MS +<br />gliserol 2 M + sukrosa 0,4 M) selama 0, 10, 20, dan 30 menit sebelum<br />tahapan dehidrasi dan pembekuan jaringan di dalam nitrogen cair (-<br />196 o C). Hasil penelitian menunjukkan durasi dehidrasi jaringan yang<br />terbaik adalah 30 menit dalam larutan PVS2. Kombinasi perlakuan<br />prakultur dengan sukrosa 0,3 M dan pemuatan dengan larutan LS selama<br />10 menit merupakan metode terbaik untuk pembekuan jaringan. Persentase<br />tumbuh sebelum dan setelah pembekuan dalam nitrogen cair berturut-turut<br />adalah 100 dan 40%. Setelah kriopreservasi, biakan mampu tumbuh<br />dengan tingkat multiplikasi tunas sekitar 10 tunas/eksplan. Metode yang<br />diperoleh pada penelitian ini berpeluang diterapkan untuk penyimpanan<br />plasma nutfah tebu dalam jangka panjang secara kriopreservasi dan<br />eliminasi patogen obligat secara krioterapi.<br />Kata kunci: Saccharum officinarum L., apeks, dehidrasi, pembekuan,<br />nitrogen cair</p><p>ABSTRACT<br />Sugarcane (Saccharum officinarum L.) is vegetatively propagated<br />plant. Cryopreservation is the most suitable method for long-term<br />preservation of vegetatively propagated plant. Dehydration and freezing<br />are critical steps of successful cryopreservation so that it should be<br />optimized. The research aimed to obtain the optimal duration of<br />dehydration and freezing method of sugarcane apex tissues. The<br />experiments were conducted at Tissue Culture Laboratory, Plant Cell<br />Tissue Biology Group, Indonesian Center for Agricultural Biotechnology<br />and Genetic Resources Research and Development on May<br />2013−February 2014. To optimize dehydration method, the tissues were<br />exposured in PVS2 solution (MS + 30% glycerol + 15% ethylene glycol +<br />15% dimethyl sulphoxide + 0.4 M sucrose) for 10, 20, 30, and 40 minutes.<br />To optimize freezing method, the combined treatment of preculture with<br />sucrose (0, 0.1, dan 0.3 M) for 5 days and loading in LS solution (MS + 2<br />M glycerol + 0.4 M sucrose) for 0, 10, 20, dan 30 minutes) were tested<br />before dehydration for 30 minutes and freezing in liquid nitrogen (-196 o C).<br />The best duration of dehydration was 30 minutes. The combined treatment<br />of preculture on 0.3 M sucrose and loading for 10 minutes was the best<br />method for tissues freezing. Percentage of regrowth before and after<br />freezing in liquid nitrogen was 100 and 40% respectively. After<br />cryopreservation, the cultures could grow with high shoot multiplication<br />rate about 10 shoots/explant. The method resulted in this study can be<br />applied for long-term storage of sugarcane germplasms by cryopreser-<br />vation and (elimination of obligate pathogens by cryotherapy.<br />Keywords: Saccharum officinarum L., apex, dehydration, freezing, liquid<br />nitrogen.</p>

High accuracy computational methods for behavioral modeling of thick-film resistors at cryogenic temperatures

The aim of this work was to elaborate two-dimensional behavioral modeling method of thick-film resistors working in low-temperature conditions. The investigated resistors (made from 5 various resistive inks: 10 resistor coupons, each with 36 resistors with various dimensions), were measured automatically in a cryostat system. The low temperature was achieved in a nitrogen-helium continuous-flow cryostat. For nitrogen used as a freezing liquid the minimal temperature possible to achieve was equal to −195.85 °C (77.3 K). Mathematical model in the form of a multiplication of two polynomials was elaborated based on the above mentioned measurements. The first polynomial approximated temperature behavior of the normalized resistance, while the second one described the dependence of resistance on planar resistors dimensions. Special computational procedures for multidimensional approximation purpose were elaborated. It was shown that proper approximation polynomials and sufficiently exact methods of calculations ensure acceptable modeling errors.