Static non-reciprocity in mechanical metamaterials

Reciprocity is a fundamental principle governing various physical systems, which ensures that the transfer function between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity have been mostly considered in dynamic systems, for electromagnetic, acoustic and mechanical wave propagation associated with spatio-temporal variations. Here we show that it is possible to strongly break reciprocity in static systems, realizing mechanical metamaterials that, by combining large nonlinearities with suitable geometrical asymmetries, and possibly topological features, exhibit vastly different output displacements under excitation from different sides, as well as one-way displacement amplification. In addition to extending non-reciprocity and isolation to statics, our work sheds new light on the understanding of energy propagation in non-linear materials with asymmetric crystalline structures and topological properties, opening avenues for energy absorption, conversion and harvesting, soft robotics, prosthetics and optomechanics.Comment: 19 pages, 3 figures, Supplementary information (11 pages and 5 figures

Soft Coral Sarcophyton (Cnidaria: Anthozoa: Octocorallia) Species Diversity and Chemotypes

Research on the soft coral genus Sarcophyton extends over a wide range of fields, including marine natural products and the isolation of a number of cembranoid diterpenes. However, it is still unknown how soft corals produce this diverse array of metabolites, and the relationship between soft coral diversity and cembranoid diterpene production is not clear. In order to understand this relationship, we examined Sarcophyton specimens from Okinawa, Japan, by utilizing three methods: morphological examination of sclerites, chemotype identification, and phylogenetic examination of both Sarcophyton (utilizing mitochondrial protein-coding genes MutS homolog: msh1) and their endosymbiotic Symbiodinium spp. (utilizing nuclear internal transcribed spacer of ribosomal DNA: ITS- rDNA). Chemotypes, molecular phylogenetic clades, and sclerites of Sarcophyton trocheliophorum specimens formed a clear and distinct group, but the relationships between chemotypes, molecular phylogenetic clade types and sclerites of the most common species, Sarcophyton glaucum, was not clear. S. glaucum was divided into four clades. A characteristic chemotype was observed within one phylogenetic clade of S. glaucum. Identities of symbiotic algae Symbiodinium spp. had no apparent relation to chemotypes of Sarcophyton spp. This study demonstrates that the complex results observed for S. glaucum are due to the incomplete and complex taxonomy of this species group. Our novel method of identification should help contribute to classification and taxonomic reassessment of this diverse soft coral genus

K65R in Subtype C HIV-1 Isolates from Patients Failing on a First-Line Regimen Including d4T or AZT: Comparison of Sanger and UDP Sequencing Data

BACKGROUND: We and others have shown that subtype C HIV-1 isolates from patients failing on a regimen containing stavudine (d4T) or zidovudine (AZT) exhibit thymidine-associated mutations (TAMs) and K65R which can impair the efficacy of Tenofovir (TDF) at second line. Depending on the various studies, the prevalence of K65R substitution as determined by the Sanger method ranges from 4 to 30%. Our aim was to determine whether ultra-deep pyrosequencing (UDPS) could provide more information than the Sanger method about selection of K65R in this population of patients. METHODS: 27 subtype C HIV-1 isolates from treated patients failing on a regimen with d4T or AZT plus lamivudine (3TC) plus nevirapine (NVP) or efavirenz (EFV) and who had been sequenced by Sanger were investigated by UDPS at codon 65 of the reverse transcriptase (RT). 18 isolates from naïve patients and dilutions of a control K65R plasmid were analysed by Sanger plus UDPS. RESULTS: Analysis of Sanger sequences of subtype C HIV-1 isolates from naïve patients exhibited expected polymorphic substitutions compared to subtype B but no drug resistance mutations (DRMs). Quantitation of K65R variants by UDPS ranged from <0.4% to 3.08%. Sanger sequences of viral isolates from patients at failure of d4T or AZT plus 3TC plus NVP or EFV showed numerous DRMs to nucleoside reverse transcriptase inhibitors (NRTIs) including M184V, thymidine-associated mutations (TAMs) plus DRMs to non- nucleoside reverse transcriptase inhibitors (NNRTIs). Two K65R were observed by Sanger in this series of 27 samples with UDPS percentages of 27 and 87%. Other samples without K65R by Sanger exhibited quantities of K65R variants ranging from <0.4% to 0.80%, which were below the values observed in isolates from naïve patients. CONCLUSIONS: While Sanger sequencing of subtype C isolates from treated patients at failure of d4T or AZT plus 3TC plus NVP or EFV exhibited numerous mutations including TAMs and 8% K65R, UDPS quantitation of K65R variants in the same series did not provide any more information than Sanger

Three Essential Ribonucleases—RNase Y, J1, and III—Control the Abundance of a Majority of Bacillus subtilis mRNAs

Bacillus subtilis possesses three essential enzymes thought to be involved in mRNA decay to varying degrees, namely RNase Y, RNase J1, and RNase III. Using recently developed high-resolution tiling arrays, we examined the effect of depletion of each of these enzymes on RNA abundance over the whole genome. The data are consistent with a model in which the degradation of a significant number of transcripts is dependent on endonucleolytic cleavage by RNase Y, followed by degradation of the downstream fragment by the 5′–3′ exoribonuclease RNase J1. However, many full-size transcripts also accumulate under conditions of RNase J1 insufficiency, compatible with a model whereby RNase J1 degrades transcripts either directly from the 5′ end or very close to it. Although the abundance of a large number of transcripts was altered by depletion of RNase III, this appears to result primarily from indirect transcriptional effects. Lastly, RNase depletion led to the stabilization of many low-abundance potential regulatory RNAs, both in intergenic regions and in the antisense orientation to known transcripts

Cell cycle checkpoint status in human malignant mesothelioma cell lines: response to gamma radiation

Knowledge of the function of the cell cycle checkpoints in tumour cells may be important to develop treatment strategies for human cancers. The protein p53 is an important factor that regulates cell cycle progression and apoptosis in response to drugs. In human malignant mesothelioma, p53 is generally not mutated, but may be inactivated by SV40 early region T antigen (SV40 Tag). However, the function of p53 has not been investigated in mesothelioma cells. Here, we investigated the function of the cell cycle checkpoints in six human mesothelioma cell lines (HMCLs) by studying the cell distribution in the different phases of the cell cycle by flow cytometry, and expression of cell cycle proteins, p53, p21WAF1/CIP1 and p27KIP1. In addition, we studied p53 gene mutations and expression of SV40 Tag. After exposure to γ-radiation, HMCLs were arrested either in one or both phases of the cell cycle, demonstrating a heterogeneity in cell cycle control. G1 arrest was p21WAF1/CIP1- and p53-dependent. Lack of arrest in G1 was not related to p53 mutation or binding to SV40 Tag, except in one HMCL presenting a missense mutation at codon 248. These results may help us to understand mesothelioma and develop new treatments

Phylogenomics of non-model ciliates based on transcriptomic analyses

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