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Iodide as a Nucleophilic Trigger in Aryne Three-Component Coupling for the Synthesis of 2-lodobenzyl Alcohols
No full textThe synthetic potential of KI as the iodide source in aryne three-component coupling has been demonstrated using aldehydes as the third component. This mild and transition-metal free coupling reaction allowed the straightforward synthesis of 2-iodobenzyl alcohols in moderate to good yields with good functional group compatibility. Moreover, KBr and KCl could be used as the nucleophilic trigger in this aryne multicomponent coupling (MCC) and N-methylisatin and CO2 could be used as the electrophilic third components
Mycobacterium tuberculosis UvrD1 and UvrD2 helicases unwind G-quadruplex DNA
No full textUnresolved G-quadruplex (G4) DNA secondary structures impede DNA replication and can lead to DNA breaks and to genome instability. Helicases are known to unwind G4 structures and thereby facilitate genome duplication. Escherichia coli UvrD is a multifunctional helicase that participates in DNA repair, recombination and replication. Previously, we had demonstrated a novel role of E. coli UvrD helicase in resolving G4 structures. Mycobacterium tuberculosis genome encodes two orthologs of E. coli UvrD helicase, UvrD1 and UvrD2. It is unclear whether UvrD1 or UvrD2 or both helicases unwind G4 DNA structures. Here, we demonstrate that M. tuberculosis UvrD1 and UvrD2 unwind G4 tetraplexes. Both helicases were proficient in resolving previously characterized tetramolecular G4 structures in an ATP hydrolysis and single-stranded 3 `-tail-dependent manner. Notably, M. tuberculosis UvrD1 and UvrD2 were efficient in unwinding G4 structures derived from the potential G4 forming sequences present in the M. tuberculosis genome. These data suggest an extended role for M. tuberculosis UvrD1 and UvrD2 helicases in resolving G4 DNA structures and provide insights into the maintenance of genome integrity via G4 DNA resolution
Physical Layer Security in Wireless Sensor Networks Using Distributed Co-Phasing
No full textIn this paper, we consider physical layer security in wireless sensor networks (WSNs) using distributed co-phasing (DCP)-based transmissions. For this protocol, we first analyze the achievable ergodic secrecy rate of a single stream DCP system in the presence of one or more eavesdroppers. We show that the coherent combining gain offered by DCP leads to the signal-to-interference-plus-noise-ratio (SINR) over the main channel increasing as the square of the number of SNs N and that over the eavesdropper channel increasing linearly with N. This results in a strictly positive ergodic secrecy rate that increases as log N. We then analyze the performance of multi-stream DCP and show that using K data streams in DCP leads to a K-fold increase in the achievable secrecy rate at high SNRs. We also discuss an alternative power allocation scheme for multi-stream DCP, such as distributed maximal ratio transmission with a per-user power constraint and show that this improves the achievable secrecy rates as compared to standard multi-stream DCP. Finally, we analyze the role of artificial noise in improving the achievable secrecy rates. We validate the accuracy of these derived results and illustrate the efficacy of DCP in ensuring secure data fusion in WSNs using Monte Carlo simulations
All-Male Groups in Asian Elephants: A Novel, Adaptive Social Strategy in Increasingly Anthropogenic Landscapes of Southern India
No full textMale Asian elephants are known to adopt a high-risk high-gain foraging strategy by venturing into agricultural areas and feeding on nutritious crops in order to improve their reproductive fitness. We hypothesised that the high risks to survival posed by increasingly urbanising and often unpredictable production landscapes may necessitate the emergence of behavioural strategies that allow male elephants to persist in such landscapes. Using 1445 photographic records of 248 uniquely identified male Asian elephants over a 23-month period, we show that male Asian elephants display striking emergent behaviour, particularly the formation of stable, long-term all-male groups, typically in non-forested or human-modified and highly fragmented areas. They remained solitary or associated in mixed-sex groups, however, within forested habitats. These novel, large all-male associations, may constitute a unique life history strategy for male elephants in the high-risk but resource-rich production landscapes of southern India. This may be especially true for the adolescent males, which seemed to effectively improve their body condition by increasingly exploiting anthropogenic resources when in all-male groups. This observation further supports our hypothesis that such emergent behaviours are likely to constitute an adaptive strategy for male Asian elephants that may be forced to increasingly confront anthropogenically intrusive environments
Weak Coordinating Carboxylate Directed Rhodium(III)-Catalyzed C-H Activation: Switchable Decarboxylative Heck-Type and 4+1] Annulation Reactions with Maleimides
No full textA weakly coordinating carboxylate directing group assisted C-H activation with maleimides leading to novel and switchable decarboxylative Heck-type and 4 + 1] annulation products catalyzed by Rh(III) has been reported. In these reactions, solvents play a vital role in switching the selectivity. An aprotic solvent, THF, leads to the decarboxylative Heck-type product while the protic solvent, TFE, results in the 4 + 1] annulation product. The methodology shows high functional group tolerance
Coupling the High-Throughput Property Map to Machine Learning for Predicting Lattice Thermal Conductivity
No full textLow thermal conductivity materials are crucial for applications such as thermoelectric conversion of waste heat to useful energy and thermal barrier coatings. On the other hand, high thermal conductivity materials are necessary for cooling electronic devices. However, search for such materials via explicit evaluation of thermal conductivity either experimentally or computationally is very challenging. Here, we carried out high-throughput ab initio calculations, on a dataset containing 195 binary, ternary, and quaternary. compounds. The lattice thermal conductivity kappa(l) values of 120 dynamically stable and nonmetallic compounds are calculated, which span over 3 orders of magnitude. Among these, 11 ultrahigh and 15 ultralow kappa(l) materials are identified. An analysis of generated property map of this dataset reveals a strong dependence of kappa(l) on simple descriptors, namely, maximum phonon frequency, integrated Griineisen parameter up to 3 THz, average atomic mass, and volume of the unit cell. Using these descriptors, a Gaussian process regression-based machine learning (ML) model is developed. The model predicts log-scaled xi with a very small root mean square error of similar to 0.21. Comparatively, the Slack model, which uses more involved parameters, severely overestimates kappa(l). The superior performance of our ML model can ensure a reliable and accelerated search for multitude of low and high thermal conductivity materials
Naphthalene-triazolopyrimidine hybrid compounds as potential multifunctional anti-Alzheimer's agents
No full textIn an attempt to construct potential anti-Alzheimer's agents Naphthalene-triazolopyrimidine hybrids were synthesized and screened in vitro against the two cholinesterases (ChE) s, amyloid beta aggregation and for antioxidation activity. Single-crystal X-ray crystallography was utilized for crystal structure determination of one of the compounds. In vitro study of compounds revealed that most of the compounds are capable of inhibiting acetylcholinesterase and Butyrylcholinesterase activity. Particularly, the compounds 4e and 4d exhibited IC50 values ranging from 8.6 to 14 nM against AChE lower than the standard drug Donepezil (IC50 49 nM). Best result was found for compound 4e with IC50 of 8.6 nM (for AChE) and 150 nM (for BuChE). Selectivity upto that of Donepezil and even more was observed for 4a, 4c and 4h. Investigation by electron microscopy, transmission electron microscopy and ThT fluorescence assay unveils the fact that synthesized hybrids exhibit amyloid beta self-aggregation inhibition. The compounds 4i and 4j revealed highest inhibitory potential, 85.46% and 72.77% at 50 mu M respectively; above the standard A beta disaggregating agent, Curcumin. Their antioxidation profile was also analyzed. Studies from DPPH free radical scavenging assay and ORAC assay depicts molecules to possess low antioxidation profile. Results suggest that triazolopyrimidines are potential candidate for Acetylcholinesterase (AChE), Butyrylcholinesterase (BuChE), and amyloid beta aggregation inhibition. In silico ADMET profiling indicates drug-like properties with a very low toxic influence. Such synthesized compounds provide a strong vision for further development of potential anti-Alzheimer's agents
Recent results on vector bundles, principal bundles and related topics
No full textThis is a short survey of the interesting work in the theory of vector bundles (with various augmenting structures), principal bundles and related topics by Indian mathematicians in the last decade. The focus is on topics in which Indian mathematicians have made major contributions
Differential geometry in India
No full textThis is a brief survey of work done in India in differential geometry during the period 2000 to 2015. The survey is not exhaustive and highlights aspects that the author is familiar with