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We report both cracking and self-healing in crystals occurring during a thermal phase transition, followed by a topochemical polymerization. A squaramide-based monomer was designed where the azide and alkyne units of adjacent molecules are positioned favorably for a topochemical click reaction. The monomer undergoes spontaneous single-crystal-to-single-crystal (SCSC) polymerization at room temperature via regiospecific 1,3-dipolar cycloaddition, yielding the corresponding triazole-linked polymer in a few days. When heated at 60 °C, the polymerization completes in a SCSC manner in 24 h. Upon continuous heating from room temperature to 110 °C, the monomer crystals develop multiple cracks, and they self-heal immediately. The cracking occurs due to a thermal phase transition, as evidenced by differential scanning calorimetry (DSC). The cracks heal either upon further heating or upon cooling of the crystals due to the topochemical polymerization or reversal of the phase transition, respectively. Increasing the heating rate leads to the formation of longer and wider cracks, which also heal instantaneously. The self-healed crystals retained their integrity and the crystal structure of the self-healed crystals was analyzed by single-crystal X-ray diffraction. The quality of the self-healed crystals and their diffraction ability conform to those of the completely reacted crystals at room temperature or at 60 °C without developing cracks. This work demonstrates a novel mechanism for self-healing of molecular crystals that could expand the horizon of these materials for a plethora of applications.

Table of Contents Abstract Introduction Case report Discussion Conclusions References Abstract We report a case of an adult woman admitted with nausea and vomiting secondary to cytomegalovirus gastritis and then [...]

We designed and synthesized a malonamide-derived monomer, containing azide and alkyne units, for topochemical polymerization to yield nylon (n,3). This monomer on crystallization gave two concomitant polymorphs M1and M2. Both the polymorphs show crystal packings that are suitable for topochemical azide–alkyne cycloaddition polymerization. On heating, polymorph M1reacts regiospecifically to give 1,4-disubstituted-1,2,3-triazolyl-linked polymer, whereas polymorph M2yields 1,5-disubstituted-1,2,3-triazolyl-linked polymer regiospecifically. In the case of polymorph M1, polymerization proceeds perpendicular to the hydrogen bonding direction, whereas in M2, the reaction occurs along the hydrogen bonding direction. This results in the two structurally different polymers having distinct topologies. These single-crystal-to-single-crystal polymerizations allowed us to study their structure at atomic resolution by single-crystal X-ray diffraction. This is the first report of the synthesis of two chemically different polymers from a single monomer.

The spread of COVID-19 and the lockdowns that followed led to an increase in activity on online social networks. This has resulted in users sharing unfiltered and unreliable information on social networks like WhatsApp, Twitter, Facebook, etc. In this work, we give an extended overview of how Pakistan’s population used public WhatsApp groups for sharing information related to the pandemic. Our work is based on a major effort to annotate thousands of text and image-based messages. We explore how information propagates across WhatsApp and the user behavior around it. Specifically, we look at political polarization and its impact on how users from different political parties shared COVID-19-related content. We also try to understand information dissemination across different social networks—Twitter and WhatsApp—in Pakistan and find that there is no significant bot involvement in spreading misinformation about the pandemic.

miRNAs are a class of short, non-coding RNA molecules that reportedly play a central role in regulating post-transcriptional gene expression during embryonic stem cell development, myogenesis, adipogenesis, fat metabolism, and glucose homeostasis. For assessment of the effect of loss of myostatin signaling on gene expression in skeletal muscle, RNA from post-developmental myostatin transgenic and wild-type littermate mice were analyzed with Solexa deep sequencing. Sequencing data were analyzed using miRDeep software V. 2.1.2. Four hundred sixty-one mature known miRNAs were identified, out of which 57 miRNAs were found to be differentially expressed. Expression pattern demonstrated that Mmu-miR-22 was most abundant; miRNA, mmu-miR-133a, and mmu-miR-378a were abundant and significantly differentially expressed miRNAs. Sixty-nine novel miRNAs were also identified, out of which 3 NMu-1, NMu-14, and NMu-36 accounted higher read count. For these 3 novel miRNAs and 5 known miRNAs, the expression profiling was done for using Q-PCR analysis. Out of 57 differentially expressed miRNAs, the 20 most abundant miRNAs were selected for target prediction and pathway analysis. Four thousand five hundred eighty-three targets were identified, out of which FST, SMAD3, TGFBR1, ACVR1a, and MEF2c genes, which plays vital role in MSTN signaling, were found to be targeted by miR-101, miR-425, miR-199a, and miR-582 in TGFb-signaling pathway, which activates MSTN signaling. Hence, these miRNAs could prove crucial candidate miRNAs in skeletal muscle development. In conclusion, the present study proffers an initial miRNA transcriptome profile in skeletal muscle development of transgenic and control mice. Findings aided identification of miRNA and their targets, which can possibly contribute to skeletal muscle development. Information generated in this study can be further used to investigate the role of identified miRNAs and their targets in regulation of skeletal muscle development.