Non-reciprocal phase transitions.

Out of equilibrium, a lack of reciprocity is the rule rather than the exception. Non-reciprocity occurs, for instance, in active matter1-6, non-equilibrium systems7-9, networks of neurons10,11, social groups with conformist and contrarian members12, directional interface growth phenomena13-15 and metamaterials16-20. Although wave propagation in non-reciprocal media has recently been closely studied1,16-20, less is known about the consequences of non-reciprocity on the collective behaviour of many-body systems. Here we show that non-reciprocity leads to time-dependent phases in which spontaneously broken continuous symmetries are dynamically restored. We illustrate this mechanism with simple robotic demonstrations. The resulting phase transitions are controlled by spectral singularities called exceptional points21. We describe the emergence of these phases using insights from bifurcation theory22,23 and non-Hermitian quantum mechanics24,25. Our approach captures non-reciprocal generalizations of three archetypal classes of self-organization out of equilibrium: synchronization, flocking and pattern formation. Collective phenomena in these systems range from active time-(quasi)crystals to exceptional-point-enforced pattern formation and hysteresis. Our work lays the foundation for a general theory of critical phenomena in systems whose dynamics is not governed by an optimization principle.

Quantum Criticality in Open Quantum Spin Chains with Nonreciprocity.

We investigate the impact of nonreciprocity on universality and critical phenomena in open quantum interacting many-body systems. Nonreciprocal open quantum systems often have an exotic spectral sensitivity to boundary conditions, known as the Liouvillian skin effect (LSE). By considering an open quantum XXZ spin chain that exhibits LSE, we demonstrate the existence of a universal scaling regime that is not affected by the presence of the LSE. We resolve the critical exponents, which differ from those of free fermions, via tensor network methods and demonstrate that observables exhibit a universal scaling collapse, irrespective of the reciprocity. We find that the LSE only becomes relevant when a healing length scale ξ_{heal} at the system's edge (which is different from the localization length of the eigenstate of the Liouvillian) exceeds the system size, allowing edge properties to dominate the physics. We expect this result to be a generic feature of nonreciprocal models in the vicinity of a critical point. The driven-dissipative quantum criticality we observe has no classical analog and stems from the existence of multiple dark states.

Chemical and Genetic Diversity of Ligularia kanaitzensis in the Hengduan Mountains Area. Chemical Relationship with L. subspicata.

Root chemicals and the sequences of the internal transcribed spacers (ITSs) were analyzed for 9 Ligularia kanaitzensis and 3 L. subspicata samples collected in northwestern Yunnan and southwestern Sichuan, China. Subspicatins A and C were isolated from two L. kanaitzensis samples. Introgression of genes responsible for these compounds from L. subspicata was suggested by their strong connection with L. subspicata/L. lamarum and the geographical proximity of the samples to L. subspicata. DNA analysis of a set of 27 L. kanaitzensis samples including those analyzed previously showed that they belong to two clades, designated A and B. Together with the presence/absence of furanoeremophilane, the 27 samples were sorted into three groups: clade A/furan, clade B/furan, and clade B/non-furan. The ancestral plant presumably belonged to clade B/non-furan, because furanoeremophilanes are biosynthesized from eremophilan-8-ones. 1ß-Angeloyloxyfukinone, a likely intermediate between fukinone and subspicatin C, was isolated for the first time. This finding allowed us to propose plausible biosynthetic pathways of subspicatins A and C.

Non-Hermitian Phase Transition from a Polariton Bose-Einstein Condensate to a Photon Laser.

We propose a novel mechanism for a nonequilibrium phase transition in a U(1)-broken phase of an electron-hole-photon system, from a Bose-Einstein condensate of polaritons to a photon laser, induced by the non-Hermitian nature of the condensate. We show that a (uniform) steady state of the condensate can always be classified into two types, namely, arising either from lower or upper-branch polaritons. We prove (for a general model) and demonstrate (for a particular model of polaritons) that an exceptional point where the two types coalesce marks the end point of a first-order-like phase boundary between the two types, similar to a critical point in a liquid-gas phase transition. Since the phase transition found in this paper is not in general triggered by population inversion, our result implies that the second threshold observed in experiments is not necessarily a strong-to-weak-coupling transition, contrary to the widely believed understanding. Although our calculation mainly aims to clarify polariton physics, our discussion is applicable to general driven-dissipative condensates composed of two complex fields.

Eremophilanes from Ligularia hookeri Collected in China and Structural Revision of 3ß-Acyloxyfuranoeremophilan-15,6-olide.

Chemical constituents of Ligularia hookeri (Asteraceae) collected in Yunnan and Sichuan Provinces in China were examined for the first time. Seven furanoeremophilanes, five of which were new, as well as known bisabolane- and eudesmane-type sesquiterpenoids, were isolated. Spectroscopic evidence indicates that the previously reported 3ß-(2'-methylpropenoyloxy)furanoeremophilan-15,6ß-olide should be revised to 3ß-(2'-methylpropenoyloxy)furanoeremophilan-15,6α-olide.

Terpenoids and Phenylpropanoids in Ligularia duciformis, L. kongkalingensis, L. nelumbifolia, and L. limprichtii.

The diversity in root chemicals and evolutionally neutral DNA regions in the complex of Ligularia duciformis, L. kongkalingensis, and L. nelumbifolia (the d/k/n complex) was studied using eight samples collected in central and northern Sichuan Province of China. Cacalol (14) and epicacalone (15), rearranged eremophilanes, were isolated from the complex for the first time. Two new phenylpropanoids were also obtained. Seven of the eight samples produced phenylpropanoids and the other produced lupeol alone. Two of the seven samples also produced furanoeremophilanes or their derivatives and one produced oplopanes. The geographical distribution of the sesquiterpene-producing populations suggests that the production of sesquiterpenes evolved independently in separate regions. L. limprichtii collected in northern Sichuan was also analyzed and its chemical composition and the sequence of internal transcribed spacers (ITSs) in the ribosomal RNA gene cluster were found to be similar to that in the d/k/n complex and L. yunnanensis, which are morphologically similar.

Ribosome dimerization is essential for the efficient regrowth of Bacillus subtilis.

Ribosome dimers are a translationally inactive form of ribosomes found in Escherichia coli and many other bacterial cells. In this study, we found that the 70S ribosomes of Bacillus subtilis dimerized during the early stationary phase and these dimers remained in the cytoplasm until regrowth was initiated. Ribosome dimerization during the stationary phase required the hpf gene, which encodes a homologue of the E. coli hibernation-promoting factor (Hpf). The expression of hpf was induced at an early stationary phase and its expression was observed throughout the rest of the experimental period, including the entire 6 h of the stationary phase. Ribosome dimerization followed the induction of hpf in WT cells, but the dimerization was impaired in cells harbouring a deletion in the hpf gene. Although the absence of ribosome dimerization in these Hpf-deficient cells did not affect their viability in the stationary phase, their ability to regrow from the stationary phase decreased. Thus, following the transfer of stationary-phase cells to fresh LB medium, Δhpf mutant cells grew slower than WT cells. This observed lag in growth of Δhpf cells was probably due to a delay in restoring their translational activity. During regrowth, the abundance of ribosome dimers in WT cells decreased with a concomitant increase in the abundance of 70S ribosomes and growth rate. These results suggest that the ribosome dimers, by providing 70S ribosomes to the cells, play an important role in facilitating rapid and efficient regrowth of cells under nutrient-rich conditions.

Chemical Constituents in Hybrids of Ligularia tongolensis and L. cymbulifera: Chemical Introgression in L. tongolensis.

Two samples with morphologies intermediate between Ligularia tongolensis and L. cymbulifera were collected in Desha, Sichuan Province, and one, in Pachahai, Yunnan Province, P. R. China. The DNA sequencing confirmed that the samples were hybrids of the two species. Tetradymol (1), the major compound of L. cymbulifera not found in L. tongolensis, was isolated from the hybrid samples collected at both locations, while furanoeremophilan-15-oic acid derivative 4, a compound characteristic to L. tongolensis, was found in the Pachahai hybrid but not in the Desha hybrids. Thus, the chemical consequence of hybridization can be variable. In addition, analysis of L. tongolensis samples at Pachahai indicated that introgression has been a mechanism of generating chemical diversity in the plant. Eleven compounds including three new ones were isolated.

Defect in the formation of 70S ribosomes caused by lack of ribosomal protein L34 can be suppressed by magnesium.

To elucidate the biological functions of the ribosomal protein L34, which is encoded by the rpmH gene, the rpmH deletion mutant of Bacillus subtilis and two suppressor mutants were characterized. Although the ΔrpmH mutant exhibited a severe slow-growth phenotype, additional mutations in the yhdP or mgtE gene restored the growth rate of the ΔrpmH strain. Either the disruption of yhdP, which is thought to be involved in the efflux of Mg(2+), or overexpression of mgtE, which plays a major role in the import of Mg(2+), could suppress defects in both the formation of the 70S ribosome and growth caused by the absence of L34. Interestingly, the Mg(2+) content was lower in the ΔrpmH cells than in the wild type, and the Mg(2+) content in the ΔrpmH cells was restored by either the disruption of yhdP or overexpression of mgtE. In vitro experiments on subunit association demonstrated that 50S subunits that lacked L34 could form 70S ribosomes only at a high concentration of Mg(2+). These results showed that L34 is required for efficient 70S ribosome formation and that L34 function can be restored partially by Mg(2+). In addition, the Mg(2+) content was consistently lower in mutants that contained significantly reduced amounts of the 70S ribosome, such as the ΔrplA (L1) and ΔrplW (L23) strains and mutant strains with a reduced number of copies of the rrn operon. Thus, the results indicated that the cellular Mg(2+) content is influenced by the amount of 70S ribosomes.

Chemical and genetic studies on hybrid of Ligularia subspicata and Ligularia cyathiceps collected in Yunnan Province of China.

Two morphologically ambiguous Ligularia samples (samples A and B), and samples with morphology of Ligularia subspicata (sample C), Ligularia lamarum (sample D), or Ligularia cyathiceps (sample E), were collected at Tianchi Pond, Shangrila County, Yunnan Province, China. Analysis of the nucleotide sequence of the internal transcribed spacers (ITSs) in the nuclear ribosomal RNA gene cluster indicated that not only sample B but also sample D was a hybrid of L. cyathiceps and L. lamarum/L. subspicata. Although the morphology of sample A suggested that it was also a hybrid, the ITS sequence of sample A was that of L. cyathiceps. Twenty compounds were isolated from the five samples, and the structures of two new compounds 7 and 14 were determined. Furanoeremophilanes typical of L. lamarum/L. subspicata were detected not only in samples C and D, but also in samples A and B. These results indicate that the ability to produce root chemicals can spread through introgression.

Screening for termination sequences of a rolling-circle plasmid: a novel scheme using genomic DNA.

The Escherichia coli genome was searched for potential terminators of the rolling-circle replication of staphylococcal plasmid pC194. The replication origin of pC194 was randomly inserted into the E. coli chromosome and rolling-circle replication was initiated by producing pC194's replication protein from a plasmid. Circular DNA resulting from termination in the chromosome was recovered from 42 of the 100 insertion clones screened. The nucleotide sequences at the ends of the chromosomal segment in the recovered DNA were determined and used to identify the locus of integration and the point of termination. The sequence beyond the termination point was retrieved from the database. This information would have been unrecoverable if synthetic random sequences had been used for screening. The consensus sequence based on the discovered potential terminators was consistent with the results of previous and new experiments. The recovered circular DNAs contain a hybrid origin consisting of a 5' part derived from the chromosomal DNA and a 3' part of the integrated origin. Two such hybrid origins were examined for initiation function and shown to be as effective as the authentic pC194 origin. These results suggest a possible evolutionary mechanism in which a rolling-circle plasmid may acquire genes from the host organism.

[Questionnaire Survey of Hands-on Seminar Using a Web Conferencing System in the COVID-19 Pandemic].

The purpose of this study was to evaluate the effectiveness of a hands-on seminar using a Web conferencing system, based on the post-event questionnaires of the face-to-face and online seminars of the hands-on seminar. For participants to feel realistic training in the online seminars, four educational videos explaining the procedure of the practical skill were created. We compared results of questionnaires acquired from participants after the face-to-face and online seminars. The questions about expectation, comprehension, satisfaction level, and lecture time for the seminars were graded on a 5-point scale. The higher the scores, the higher the rating, except for lecture time. A score of 3 was appropriate for the lecture time, with a higher score indicating that the seminar felt longer and a lower score indicating that the seminar felt shorter. In the evaluation of classroom lectures, such as expectation, comprehension, and satisfaction level for the seminars, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more. There was a significant difference in the evaluation of lecture time for classroom lectures, with participants feeling that it was too short in the face-to-face but just right in the online. In all evaluations for hands-on training and discussion, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more and time was short. It was concluded that our proposed online seminar approach could achieve a high level of evaluation as face-to-face seminars.

Chemical and genetic study of Ligularia duciformis and related species in Sichuan and Yunnan Provinces of China.

The chemical constituents of the root extracts and the evolutionarily neutral DNA base sequences were studied for 28 samples of Ligularia duciformis, L. kongkalingensis, and L. nelumbifolia collected in Sichuan and Yunnan Provinces of China. The samples could be classified into four chemotypes (1-4). Sesquiterpenoids having eremophilane and oplopane skeletons were isolated from two (Chemotype 1) and three (Chemotype 2) samples, respectively. Two new oplopane derivatives were isolated and their structures were determined. In 18 samples, phenylpropenoids were the major components (Chemotype 3). In five samples, neither phenylpropenoids nor sesquiterpenoids were found (Chemotype 4). Despite this large chemical variety, no correlation was found between the chemotype and the morphological criteria of species identification. The analysis of the evolutionarily neutral DNA regions also indicated that the samples were not separated into distinct clades and that introgression was extensive.

Biochemical analysis of the replication initiator protein of staphylococcal plasmid pC194.

The staphylococcal plasmid pC194 is replicated through the rolling-circle mechanism. Its replication protein RepA has been proposed to initiate replication by making a bond between Y214 and DNA phosphate via transesterification and to terminate it by hydrolyzing DNA with E210 and carrying out strand transfer. We tested this model by examining the catalytic functions of the protein with purified RepA proteins and single-stranded DNA oligomers. The wild-type RepA formed a covalent bond with the DNA phosphate at the predicted initiation site. It hydrolyzed the phosphodiester bond at the site, which activity was found to depend on the presence of a large pseudopalindrome contained in the replication origin. The protein carried out a strand-transfer reaction which mimicked the termination step of replication. A Y214F and an E210A mutant respectively lacked the transesterification and the hydrolytic activity. These results are consistent with the previously proposed model, which was based solely on molecular genetics results. In addition, an E142A mutant was found to lack both activities, suggesting that the residue may coordinate the divalent cation necessary for them. A possible role of the pseudopalindrome in controlling the two activities of RepA during a replication cycle is also discussed.

Direct MS measurement of the extract of Ligularia virgaurea collected in Yunnan and Sichuan provinces of China.

INTRODUCTION: There are numerous Ligularia species in the eastern Qinghai-Tibet Plateau and adjacent areas. L. virgaurea has been used as a traditional folk medicine for the treatment of stomachache and nausea. Objective - To analyse chemical constituents of L. virgaurea, grown in Yunnan and Sichuan provinces of China. METHODOLOGY: The direct MS measurement of the crude extract of plant samples was used for grouping of this species. As the main compounds were available in pure form, the main peaks were analysed by LCMS. RESULTS: An easy and speedy method of analysis using MS spectra was developed. On the basis of the findings, L. virgaurea could be divided into two groups. The genetic studies also supported this grouping. Type 1 mainly includes virgaurenones and virgaurenolides. The MS of type 2 is quite different because it includes mainly ligularol and its congeners. Both MS were easily distinguished. CONCLUSION: The crude extracts of 11 L. virgaurea samples already collected in recent years were analysed and it was possible to identify them as type 1 or 2. This method was applied to three samples collected in 2009 to successfully classify them as either type 1 or 2.

Chemical and genetic differentiation of Ligularia hodgsonii in Japan and China.

The chemical composition of the root extract and neutral base sequences of L. hodgsonii samples collected in Japan and China were examined. From the Japanese and the Chinese samples, 6beta-(angeloyloxy)furanoeremophilan-15-oic acid and 3beta-acetoxy-6beta-[(2-methylbutanoyl)oxy]furanoeremophilan-10beta-ol were isolated as the major component, respectively. The sequence of the internal transcribed spacers (ITSs) of the ribosomal RNA gene was different in the Japanese and the Chinese samples. In contrast to the significant genetic difference, chemical diversity was limited to the positions of O-functionalities on the furanoeremophilane skeleton, supporting our hypothesis that the production of furanoeremophilanes is ecologically advantageous.

Chemical and genetic diversity of Ligularia vellerea in Yunnan, China.

Intra-specific diversity in Liularia vellerea growing in the northwestern to central Yunnan province of China was studied by chemical and genetic approaches. Samples collected in the Jianchuan, Lijiang, and Zhongdian areas contained 6,15-dioxygenated furanoeremophilanes as their major components (type A); whereas samples from the Luguhu area accumulated 1,6-dioxygenated furanoeremophilanes (type B); a sample from near Kunming, however, contained 6,15-dioxygenated eremophilanolides (type C). 11 beta H- and 11 alpha H-6 beta-angeloyloxy-15-carboxyeremophil-7-en-12,8-olides (eremofarfugins D and E) were also isolated and their structures were determined. A correlation between the composition and the DNA sequence was observed in the ITSs.

Chemical and genetic differentiation of Ligularia tsangchanensis in Yunnan and Sichuan provinces of China.

The intraspecific diversity in L. tsangchanensis collected in the Chinese Provinces Yunnan and southwestern Sichuan was studied by chemical and genetic approaches. The samples collected in Yunnan were found to contain cacalol (1) as the sole major component, while samples from Sichuan contained 7alpha- and 7beta-eremophila-9,11-dien-8-one (5 and 6) as well as the 3alpha-angeloyloxy derivative 7 as major components. In addition, the sequences of the internal transcribed spacers (ITSs) of the ribosomal RNA gene indicated that the Yunnan and the Sichuan samples constitute separate clades. These results demonstrate that L. tsangchanensis in Yunnan and Sichuan are distinct.

High diversity of Ligularia dictyoneura in chemical composition and DNA sequence.

The chemical composition of root extracts of the title species collected at 20 different places in the Hengduan Mountains of China was examined. From these samples, a total of 17 eremophilane derivatives were isolated, three of which were new franoeremophilane derivatives: 3beta-acetoxy-6beta-(angeloyloxy)furanoeremophilan-10beta-ol, 1alpha-acetoxyfuranoeremophilan-15,6alpha-olide, and 6beta-[2-(hydroxymethyl)prop-2-enoyloxy]furanoeremophil-1(10)-ene. Based on the chemical composition, the samples could be classified into as many as seven types: one type containing non-furanoeremophilane derivatives and the other six containing furanoeremophilane derivatives with different oxidation levels. Results of DNA sequencing of the atpB-rbcL region and the internal transcribed spacers of the ribosomal RNA gene also indicated a high diversity in the species.

Chemical and genetic diversity of Ligularia latihastata and Ligularia villosa in Yunnan Province of China.

The chemical constituents of the root extracts and the nucleotide sequences of the atpB-rbcL intergenic region of Ligularia latihastata and L. villosa, collected in northwestern Yunnan Province, were studied. In the twelve collected samples of L. latihastata, two major benzofurans, 5,6-dimethoxy-2-(1-methylethenyl)-1-benzofuran (1) and euparin (2) were detected as major components. The minor compound (2R*,3S*)-5-acetyl-2,3-dihydro-6-hydroxy-2-(1-methylethenyl)-1-benzofuran-3-yl (2Z)-2-[(acetoxy)methyl]but-2-enoate (4) was found to be susceptible to artifact formation upon extraction with EtOH. The intra-specific diversity in chemical composition of the samples was small, but the diversity in the atpB-rbcL sequence was fairly large. Compounds 1 and 2 were also found in the three collected samples of L. villosa, indicating that the two species are chemically close to each other, in agreement with morphological taxonomy.