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Autopolyploids are traditionally used to demonstrate multivalent pairing and unstable inheritance. However, the autotetraploid fish (4nRR) (RRRR, 4n = 200) derived from the distant hybridization of Carassius auratus red var. (RCC) (RR, 2n = 100) (♀) × Megalobrama amblycephala (BSB) (BB, 2n = 48) (♂) exhibits chromosome number (or ploidy) stability over consecutive generations (F1–F10). Comparative analysis based on somatic and gametic chromosomal loci [centromeric, 5S rDNA, and Ag-NORs (silver-stained nucleolar organizer regions)] revealed that a substantial loss of chromosomal loci during genome doubling increases the divergence between homologous chromosomes and that diploid-like chromosome pairing was restored during meiosis in the first generation of 4nRR lineages. In addition, a comparative analysis of genomes and transcriptomes from 4nRR (F1) and its diploid progenitor (RCC) exhibited significant genomic structure and gene expression changes. From these data, we suggest that genomes and genes diverge and that expression patterns change in the first generations following autotetraploidization, which are processes that might contribute to the stable inheritance and successful establishment of autotetraploid lineages. Electronic supplementary material The online version of this article (10.1007/s10126-018-9859-8) contains supplementary material, which is available to authorized users.

Over 20 Stirling-type nonmagnetic and nonmetallic pulse tube cryocoolers (NNPTCs) intended to support the portable cryogen-free low-noise continuous operation of high-Tc SQUIDs have been constructed and tested at CL/TIPC/CAS. All cooler components in the vicinity of the SQUIDs’ pickup loops are made of nonmagnetic and nonmetallic materials to eliminate cooler-generated interference and to realize direct coupling with the SQUIDs. The system designs are described, and the positive and negative effects of the use of nonmetallic materials on the cooler performance are analyzed. A set of experiments on 24 Stirling-type NNPTCs have been carried out to optimize the cooler geometry and working parameters, and to investigate the working principles of the coolers. Preliminary results are considered satisfactory, and the analysis and evaluation of the cooling performance and interference characteristics of this new-type pulse tube cooler are presented.

We report here on a performance study and the system design of a 60 K pulse tube cryocooler driven by a linear compressor. The goal of the development was to achieve the design of a fully integrated, cryogen-free HTS RF filter subsystem for wireless telecommunication. Two different single-stage pulse tube cold finger geometries were designed and analyzed—a U-type and a coaxial. The objective was for 3.5 W of cooling capacity at 65 K with a specific power of 30 W/W. Based on quantitative optimization, the U-type cold finger is predicted to provide 3.5 W at 65 K with a P-V input power of 89 W. The corresponding COP and the specific power are about 3.8% and 25W/W, respectively. In contrast, the coaxial cold finger operated at the same conditions is predicted to require 112 W of P-V power for the same cooling capacity. The corresponding COP and the specific power are about 3.1% and 32W/W, respectively.

Along with the commercialization of HTS devices in fields such as mobile communications, and the development of far infrared devices for space and military applications, there arises a strong demand for compact and reliable cryocoolers working at 40–60K. The pulse tube cryocooler driven by a linear pressure wave generator has the potential to achieve high reliability and very long lifetime because of the absence of moving parts at low temperature. The ability of this kind of pulse tube cryocooler to achieve efficiencies comparable with Stirling cryocoolers has been theoretically and practically proven1-3. Hence, pulse tube cryocoolers appear a good choice to meet the abovementioned requirements.

For continuous low-noise cooling of a highly magnetic flux sensitive high-Tc SQUID by using a cryocooler, the cooler systems have to meet rather stringent requirements concerning mechanical vibrations and electromagnetic interference (EMI). These cooler-generated disturbances must be below the intrinsic noise level of the sensors. The pulse tube cooler (PTC) is an attractive candidate for SQUID operation due to the absence of mechanical moving parts in the cold head. But the vibration and EMI noise originating from the metallic-made cold head of a PTC are still enormous obstacles for practical applications.

An experimental system was designed and constructed to investigate the oscillating flow characteristics of a regenerator under low temperatures. Experimental data on the pressure drops of a regenerator subject to oscillating flow under low-temperature conditions have been obtained. It is found that the value of the cycle-averaged pressure drop of the oscillating flow in the regenerator under liquid nitrogen temperatures is 5~6 times higher than that of a steady flow at the same Reynolds number based on the cross-sectional mean velocity. A correlation equation for the friction factor at liquid nitrogen temperatures has been obtained, and a comparison is made with that obtained at ambient temperatures. Because the test conditions are very close to the operating conditions of practical high frequency cryocoolers, the experimental data should be useful for the prediction of performance and design of cryogenic regenerators.

For the purpose of cooling space-borne infrared devices, two types of miniature multi-bypass coaxial pulse tube refrigerators are currently under development in our laboratory. The Oxford-style compressors with flexure bearings and clearance seals made by our laboratory are used to generate the pressure waves. The first type of miniature pulse tube refrigerator is designed for a compressor with about 2 cc swept volume. It is expected to provide 1 W of cooling power at 80 K. The second type of miniature pulse tube refrigerator uses a compressor with 0.79 cc swept volume. It is designed to have a cooling capacity of 150 mW at 85 K. At present the first one, coupled with a 1.66 cc compressor, reaches 66 K with no cooling load and produces 0.6 W of cooling power at 80 K with 66 W compressor input power, while the second one reaches 82 K and produces 100 mW at 85 K with 29 W input power.

A simple introduction is given to the development of a pulse tube cooler driven by a selfadjusted air-conditioning compressor in our laboratory. Based on our previous work, with input power increased to less than 650 W, the cooling power at 80 K increased from 4 W to 6 W and the lowest temperature slowly dropped from 51 K to 38.4 K. Some results related to stability when operating for a relatively long time are also given. They include the latest three steps of experiments which show that through continuous improvement, our pulse tube refrigeration system has been developed into a very stable system that can operate for a long time. This system will soon be available for practical applications.

This paper presents an optimal design of a 1W / 80K co-axial miniature pulse tube cooler based on the aid of numerical model that incorporates both thermodynamics and hydrodynamics for the oscillating flow and the regenerator matrix. The simulation allowed clear visualization of the instantaneous parameters variations and the entire process occurring in the pulse tube cooler and gave quantitative information on the dominant influence in the cooling capacity of the co-axial miniature pulse tube cooler. The cooler should produce 1W of cooling power at 80K with a total input power of less than 30W and with a heat sink temperature of 300K. Based on the numerical analysis, a compact co-axial miniature pulse tube cooler with a rotary drive 1.66cc compressor was designed and studied. The flow channels of the pulse tube and regenerator were designed to fit the cold heat exchanger. A lowest temperature of 66.5K and cooling capacity of 0.6W at 80K with a total input power of 66W was achieved with the system pressure of 4.0MPa and the operating frequency of around 30Hz. This design was very compact and could be made into a commercially available pulse tube cooler.