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Although several reports have been published regarding the cyclin-dependent kinases (Cdks) in developmentally competent mammalian oocytes, still little is known about their expression pattern in developmentally incompetent female gametes. Since Cdks are the main cell cycle division regulators, also described as \"checkpoints\" in the MI to MII transition, the aim of this study was to investigate the differential mRNA expression of genes encoding Cdkn1 and Cdkn5 in developmentally competent and incompetent porcine oocytes. Porcine cumulus-oocyte complexes (COCs) were collected from crossbred Landrace gilts after slaughter and partly subjected to brilliant cresyl blue (BCB) staining and in vitro maturation (IVM). Three groups of COCs were analysed: (i) oocytes soon after collection without BCB staining, (ii) oocytes which remained colourless after staining (BCB-) and (iii) COCs which stained blue (BCB+). BCB+ COCs were additionally cultured in standard porcine medium (TCM199) for 44 h. All oocytes were analysed using QT-PCR targeting CDKN1 and CDKN5 mRNA expression. The highest CDKN1 mRNA expression was found in oocytes without BCB staining and IVM (Group I) compared to BCB- and BCB+ oocytes, (P less than 0.001, P less than 0.01, respectively). An increased CDKN5 mRNA level was observed in BCB+ oocytes (Group III) compared to oocytes of Group I and Group II (P less than 0.01), respectively. The mRNA expression of both genes was always higher in BCB+ compared to BCB- oocytes. Based on this study it can be supposed that CDKN1 and CDKN5 are differentially expressed in developmentally distinct porcine oocytes and in a maturation stage-dependent manner. Moreover, CDKN1 may play a role as a molecule which regulates cell cycle arrest and the specific \"block of maturation\" from MI to MII.

This paper describes TEM characterization of bulk GaN crystals grown at 1500-1800K in the form of plates from a solution of atomic nitrogen in liquid gallium under high nitrogen pressure (up to 20 kbars). The x-ray rocking curves for these crystals were in the range of 20-30 arc-sec. The plate thickness along the c axis was about 100 times smaller than the nonpolar growth directions. A substantial difference in material quality was observed on the opposite sides of the plates normal to the c direction. On one side the surface was atomically flat, while on the other side the surface was rough, with pyramidal features up to 100 nm high. The polarity of the crystals was determined using convergent-beam electron diffraction. The results showed that, regarding the long bond between Ga and N along the c-axis, Ga atoms were found to be closer to the flat side of the crystal, while N atoms were found to be closer to the rough side. Near the rough side, within 1/10 to 1/4 of the plate thickness, there was a high density of planar defects (stacking faults and dislocation loops decorated by Ga/void precipitates). A model explaining the defect formation is proposed. [PUBLICATION ABSTRACT]

We discuss problem of Rashba field in bulk GaN and in GaN/AlGaN two-dimensional electron gas, basing on results of X-band microwave resonance experiments. We point at large difference in spin-orbit coupling between bulk material and heterostructures. We observe coupled plasmon-cyclotron resonance from the two-dimensional electron gas, but no spin resonance, being consistent with large zero-field spin splitting due to the Rashba field reported in literature. In contrast, small anisotropy of g-factor of GaN effective mass donors indicates rather weak Rashba spin-orbit coupling in bulk material, not exceed 400 Gauss, alpha_BIA < 4*10^-13 eVcm. Furthermore, we observe new kind of electron spin resonance in GaN, which we attribute to surface electron accumulation layer. We conclude that the sizable Rashba field in GaN/AlGaN heterostructures originates from properties of the interface.

We investigate properties of doping-induced metal-insulator transition in GaN:Si by means of electron spin resonance and Hall effect. While increasing the doping concentration, Si-related bands are formed below the bottom of the GaN conduction band. The D0 band of single-occupied Si donor sites is centered 27 meV below the bottom of the GaN conduction band, the D- band of double-occupied Si states at 2.7 meV below the bottom of the GaN conduction band. Strong damping of the magnetic moment occurs due to filling of the D- states at Si concentrations approaching the metal-insulator transition. Simultaneously, shortening of electron spin relaxation time due to limited electron lifetime in the single-occupied D0 band is observed. The metal-insulator transition occurs at the critical concentration of uncompensated donors equal to about 1.6 * 10^18 cm^-3. Electronic states in metallic samples beyond the metal-insulator transition demonstrate non-magnetic character of double-occupied states.

Spontaneous formation of grains has been observed for the MnAs layer grown by means of MBE on the GaN(0001)-(1x1) surface. Electronic structure of the system was investigated in situ by resonant photoemission spectroscopy. Density of the valence band states of MnAs and its changes due to increase of the layer thickness were revealed.

The surface and electronic structure of MOCVD-grown layers of Ga(0.92)In(0.08)N have been investigated by means of photoemission. An additional feature at the valence band edge, which can be ascribed to the presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface was prepared by argon ion sputtering and annealing. Stability of chemical composition of the investigated surface subjected to similar ion etching was proven by means of X-ray photoemission spectroscopy.

This paper details an experimental investigation into flame propagation of a stoichiometric hydrogen mixture within a fixed 40 cm 3 volume channel, utilizing ANSYS Fluent for simulation. The geometry was delineated as a 200x20 mm plane, with ignition positioned at the center. Certain input parameters were determined using MATLAB’s Cantera. The study explored different configurations of ANSYS Fluent’s channel combustion models, specifically examining both laminar and turbulent scenarios. Overpressure within the chamber was gauged at points 50 mm from the channel’s center to assess the impact of the relaxation factor on these measurements. These models underwent comparative analysis with actual experimental results, focusing on the highest achieved pressures and the flame’s shape at 1.9 ms, 2.9 ms, and 4.8 ms post-ignition. The findings underscore the complexity of modelling hydrogen mixture combustion in enclosed channels, highlighting the necessity for a specialized approach. Standard modules struggled to accurately replicate pressure variations over time, leading to significant discrepancies between the resulting models.

This article presents approximating relations defining energy-optimal structures of the HVAC (Heating, Ventilation, Air Conditioning) system for cleanrooms as a function of key constant parameters and energy-optimal control algorithms for various options of heat recovery and external climates. The annual unit primary energy demand of the HVAC system for thermodynamic air treatment was adopted as the objective function. Research was performed for wide representative variability ranges of key constant parameters: cleanliness class—Cs (ISO5÷ISO8), unit cooling loads—q˙j (100 ÷ 500) W/m2 and percentage of outdoor air—αo (5 ÷ 100)%. HVAC systems are described with vectors x¯ with coordinates defined by constant parameters and decision variables, and the results are presented in the form of approximating functions illustrating zones of energy-optimal structures of the HVAC system x¯* = f (Cs, q˙j, αo). In the optimization procedure, the type of heat recovery as an element of optimal structures of the HVAC system and algorithms of energy-optimal control were defined based on an objective function and simulation models. It was proven that using heat recovery is profitable only for HVAC systems without recirculation and with internal recirculation (savings of 5 ÷ 66%, depending on the type of heat recovery and the climate), while it is not profitable (or generates losses) for HVAC systems with external recirculation or external and internal recirculation at the same time.

This study presents a detailed analysis of the combustion dynamics of stoichiometric H2–air and CH4–air mixtures in a 20 L closed vessel over an initial temperature range of 298–423 K. We integrate experimental pressure–time P(t) measurements with numerical analysis to extract laminar burning velocity (LBV) and deflagration index (KG) values, and we assess three independent kinetic mechanisms (KiBo_MU, University of San Diego, Lund University) via simulations. For H2–air, LBV increases from 0.50 m/s at 298 K to 0.94 m/s at 423 K (temperature exponent α ≈ 1.79), while for CH4–air, LBV rises from 0.36 m/s to 0.96 m/s (α ≈ 2.82). In contrast, the deflagration index KG decreases by ca. 20% for H2–air and ca. 30% for CH4–air over the same temperature span. The maximum explosion pressure (Pmax) and peak pressure rise rate ((dP/dt)max) also exhibit systematic increases with temperature. A comparison with model predictions shows agreement within experiments, providing data for safety modeling and kinetic mechanism validation in H2- and CH4-based energy systems.