Vinen's latest thoughts on the "bump'' puzzle in decaying He II counterflow turbulence

The pioneering work of William F. Vinen (also known as Joe Vinen) on thermal counterflow turbulence in superfluid helium-4 largely inaugurated the research on quantum turbulence. But despite decades of research on this topic, there are still open questions remaining to be solved. One such question is related to the anomalous increase of the vortex-line density $L(t)$ during the decay of counterflow turbulence, which is often termed as the ``bump'' on the $L(t)$ curve. In 2016, Vinen and colleagues developed a theoretical model to explain this puzzling phenomenon (JETP Letters, \textbf{103}, 648-652 (2016)). However, he realized in the last a few years of his life that this theory must be at least inadequate. In remembrance of Joe, we discuss in this paper his latest thoughts on counterflow turbulence and its decay. We also briefly outline our recent experimental and numerical work on this topic.Comment: 15 pages, 3 figure

Imaging the decay of quantized vortex rings to decipher quantum dissipation

Like many quantum fluids, superfluid helium-4 (He II) can be considered as a mixture of two miscible fluid components: an inviscid superfluid and a viscous normal fluid consisting of thermal quasiparticles [1]. A mutual friction between the two fluids can emerge due to quasiparticles scattering off quantized vortex lines in the superfluid [2]. This quantum dissipation mechanism is the key for understanding various fascinating behaviors of the two-fluid system [3,4]. However, due to the lack of experimental data for guidance, modeling the mutual friction between individual vortices and the normal fluid remains an unsettled topic despite decades of research [5-10]. Here we report an experiment where we visualize the motion of quantized vortex rings in He II by decorating them with solidified deuterium tracer particles. By examining how the rings spontaneously shrink and accelerate, we provide unequivocal evidences showing that only a recent theory [9] which accounts for the coupled motion of the two fluids with a self-consistent local friction can reproduce the observed ring dynamics. Our work eliminates long-standing ambiguities in our theoretical description of the vortex dynamics in He II, which will have a far-reaching impact since similar mutual friction concept has been adopted for a wide variety of quantum two-fluid systems, including atomic Bose-Einstein condensates (BECs) [11,12], superfluid neutron stars [13-15], and gravity-mapped holographic superfluid [16,17].Comment: 10 pages, 6 figure

Effect of Cys168 substitutions on the Thermostability and the Thermal Aggregation of Thermus thermophilus Inorganic Pyrophosphatase.

Thermus thermophilus Inorganic pyrophosphatase (Tth PPase) is comprised of homohexamer，and exhibits high thermostability. However，the thermal aggregation containing the cross-linked dimer was observed after heating above 85℃. Therefore，we focused on the sole cysteine (Cys168) in C-terminalregion，and evaluated the effects of substitutions at this position on thermostability and thermal aggregation of Tth PPase. Firstly，we prepared the four Cys168-substituted variants (C168A，L ，1，and F) by site-directed mutagenesis. Although all variants formed hexamer in native state，C168A variant exhibited the highest thermostabilities for the enzyme activity and quatemary structure in wild type and all variants，while the other variants decreased them drastically as the side chain at the 168 position was much more bulky and hydrophobic in Tth PPase. Moreover， suppression of thermal aggregation for C168A variant was observed in the ANS fluorescence experiments. Therefore，we suggest that the small volume and less hydrophobicity of side chain at 168 position may contribute to the conformational thermostability, and substitution with Ala is the most suitable for thermostabilization and suppression ofthermal aggregation of Tth PPase

The Japanese Society of Pathology Guidelines on the handling of pathological tissue samples for genomic research: Standard operating procedures based on empirical analyses

Genome research using appropriately collected pathological tissue samples is expected to yield breakthroughs in the development of biomarkers and identification of therapeutic targets for diseases such as cancers. In this connection, the Japanese Society of Pathology (JSP) has developed “The JSP Guidelines on the Handling of Pathological Tissue Samples for Genomic Research” based on an abundance of data from empirical analyses of tissue samples collected and stored under various conditions. Tissue samples should be collected from appropriate sites within surgically resected specimens, without disturbing the features on which pathological diagnosis is based, while avoiding bleeding or necrotic foci. They should be collected as soon as possible after resection: at the latest within about 3 h of storage at 4°C. Preferably, snap‐frozen samples should be stored in liquid nitrogen (about −180°C) until use. When intending to use genomic DNA extracted from formalin‐fixed paraffin‐embedded tissue, 10% neutral buffered formalin should be used. Insufficient fixation and overfixation must both be avoided. We hope that pathologists, clinicians, clinical laboratory technicians and biobank operators will come to master the handling of pathological tissue samples based on the standard operating procedures in these Guidelines to yield results that will assist in the realization of genomic medicine