Circulant type matrices with heavy tailed entries

We study the limiting spectral distribution for a class of circulant type random matrices with heavy tailed input sequence. Unlike the light tailed case where the limit is nonrandom, here the limit is a random probability distribution. We provide an explicit representation of the limit.     

Simultaneous parallel and antiparallel self-assembly in a triazole/amide macrocycle conformationally homologous to D-,L-α-amino acid based cyclic peptides: NMR and molecular modeling study

A 1,4-linked triazole/amide based peptidomimetic macrocycle, synthesized from a triazole amide oligomer of cis-furanoid sugar triazole amino acids, possesses a conformation resembling the D-,L-α-amino acid based cyclic peptides despite having uniform backbone chirality. It undergoes a unique mode of self-assembly through an antiparallel backbone to backbone intermolecular H-bonding involving amide NH and triazole N2/N3 as well as parallel stacking via amide NH and carbonyl oxygen H-bonding, leading to the formation of a tubular nanostructure.     

Chemical investigation of carrageenan from the red alga Sarconema filiforme (Gigartinales, Rhodophyta) of Indian waters

Sulphated galactan (SF(A)) containing alpha (alpha), iota (i) and pyruvated alpha-carrageenans (17.6:18.8:25.3 mol %) was extracted and characterized from Sarconema filiforme of Indian waters. The SF(A) and its alkali modified derivative (SF(AM)) were composed of D-galactose, 3, 6-anhydro-D-galactose, 6-O-methylated-D-galactose (64.5:23.0:9.8 and 59.6:29.8:7.6 mol %) respectively. The linkage analysis, physicochemical analysis, infra red and 13C nuclear magnetic resonance spectra of SFA along with linkage analysis of the desulphated derivative (SF(D)) of SFA, reveals that it was a hybrid/combination of alpha/iota carrageenan as well as 3-linked 4',6'-O-(1-carboxyethylidene)-galactose (pyruvated alpha carrageenan) and 6-O-methylated alpha-carrageenan. The flow behavior of SF(A) obtained from rheological measurements suggested strong network formation in presence of 1% aqueous KCl and CaCl2 solutions.     

Structure and photoelectron spectral properties of I(-)·nCO2 clusters: an ab initio study

Structures and photoelectron spectral properties of I^??nCO₂ (n=1–7) clusters are presented at the level of second‐order Møller–Plesset perturbation theory with relativistic corrections. Triple split‐valence 6‐311++G(d,p) basis set functions are employed herein. It is observed that the CO₂ molecules approach the I^? anion from one side in all the clusters and that I^??nCO₂ clusters prefer the surface structure. The calculated vertical detachment energy of these clusters is in excellent agreement with the reported experimentally measured values (within 4 %). Efforts are also made to extract vertical detachment energy of large size of clusters, including the bulk. The extracted vertical detachment energy values for larger clusters (n=8–13) by employing the microscopic theory‐based expression are also close (within 4 %) to that of the experimentally measured values.     

Addition of halide to π-bond directly from aqueous NaX solution: a general strategy for installation of two different functional groups

Activation of π-bond with organic Lewis acid and cationic surfactant mediated direct transfer of halides to alkyne and alkene are demonstrated to afford α,α-dihaloketones and other valuable synthons with outstanding selectivities.     

Use of Some Organic Acids and Amines as Photoinitiators of Vinyl Polymerization in the Absence and in the Presence of Benzophenone Photosensitizer

Preliminary studies on the suitability of some organic acids and amines, separately and in combination with each other, as photo-initiators for the polymerization of methyl methacrylate were made. Combinations of maleic acid or phthalic acid with any of the tertiary amines–triethyl amine, demethyl aniline, and diethylaniline-proved to be interesting photoinitiator systems in view of the fact that the initiator components in each combination were ineffective as initiators when used separately. The rate of photopolymerization in each of the above acid-amine combination system was much enhanced and the respective inhibition period largely reduced when benzophenone was used as the photoinitiator. Aliphatic diamine or polyamines such as ethylene diamine, diethylene triamine, and tri-ethylene tetramine, were ineffective as photoinitiators when used alone or in combination with maleic acid, but became effective     

Synthesis of Substituted Pyrimidinones Catalyzed by Boric Acid and Glycerol in Aqueous Medium

An expeditious one-pot synthesis of substituted pyrimidinone derivatives with aromatic aldehydes, cyclopentanone, and urea (or thiourea) was developed with boric acid (10 mol%) and glycerol (0.1 mL) in aqueous medium at 45–50 °C. The methodology is simple, highly efficient, and high yielding. The idea behind this methodology is that boric acid, being a weak acid, behaves as a strong acid in presence of glycerol in aqueous medium.     

A Ru-N-heterocyclic carbene (NHC) complex from metal-metal singly bonded diruthenium(I) precursor: Synthesis, structure and catalytic evaluation

A mononuclear Ru(II)-N-heterocyclic carbene (NHC) complex [Ru^II(CO)₂(κ²C,N-BIN)(H₂O)Br][OTf] (OTf = trifluoromethane sulphonate) (1) has been synthesized in high-yield by the oxidative cleavage of the metal-metal singly-bonded diruthenium(I) precursor [Ru₂(CO)₄(CH₃CN)₆(OTf)₂] with 1,8-naphthyridine functionalized NHC precursor 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (BIN·HBr) at room temperature. Compound 1 catalyzes transfer hydrogenation of ketones to alcohols, and carbene-transfer from ethyl diazoacetate to a variety of substrates. It is shown to be an excellent catalyst for the insertion of carbene into the O-H and N-H bonds of alcohols and amines.     

Exploring naphthyl derivatives as SARS-CoV papain-like protease (PLpro) inhibitors and its implications in COVID-19 drug discovery

Molecular Diversity - Novel coronavirus disease 2019 (COVID-19) emerges as a serious threat to public health globally. The rapid spreading of COVID-19, caused by severe acute respiratory syndrome...