Density functional investigation on the structures and properties of Li atom doped Au20 cluster

Structures and properties of an Au₂₀ cluster doped with two Li atoms, Au₁₈Li₂, have been investigated using relativistic density functional theory within the framework of the zeroth-order regular approximation. Various initial structures have been generated and employed for geometry optimization followed by vibration analysis to check the stability of the final optimized structures. We have calculated various properties like binding energy, ionization potential, electron affinity and the HOMO–LUMO gap of these structures. It has been found that two dopant Li atoms favour occupying two different surface positions of the pyramidal Au₂₀ cluster. The binding energy of the surface-doped Au₁₈Li₂ cluster is 1.017?eV higher than that of the pure Au₂₀ cluster and the HOMO–LUMO gap (1.742?eV) is as high as a pure Au₂₀ cluster (1.786?eV). Interestingly, we observe that the HOMO–LUMO gap as well as the binding energy can be increased beyond those of the Au₁₈Li₂ cluster with the help of further Li atom doping. In fact, a doped tetrahedral Au₁₆Li₄ cluster, where all the dopants are at the surface sites, possesses a very high HOMO–LUMO gap of 2.117?eV. Geometric and energetic parameters indicate that the Au₁₆Li₄ cluster might be considered as a possible ‘superatom’ in the design of novel cluster-assembled materials.     

Ontological Models,Preparation Contextuality and Nonlocality

The ontological model framework for an operational theory has generated much interest in recent years. The debate concerning reality of quantum states has been made more precise in this framework. With the introduction of generalized notion of contextuality in this framework, it has been shown that completely mixed state of a qubit is preparation contextual. Interestingly, this new idea of preparation contextuality has been used to demonstrate nonlocality of some \(\psi \) -epistemic models without any use of Bell’s inequality. In particular, nonlocality of a non maximally \(\psi \) -epistemic model has been demonstrated from preparation contextuality of a maximally mixed qubit and Schrödinger’s steerability of the maximally entangled state of two qubits (Leifer and Maroney, Phys Rev Lett 110:120401, 2013). In this paper, we, show that any mixed state is preparation contextual. We, then, show that nonlocality of any bipartite pure entangled state, with Schmidt rank two, follows from preparation contextuality and steerability provided we impose certain condition on the epistemicity of the underlying ontological model. More interestingly, if the pure entangled state is of Schmidt rank greater than two, its nonlocality follows without any further condition on the epistemicity. Thus our result establishes a stronger connection between nonlocality and preparation contextuality by revealing nonlocality of any bipartite pure entangled states without any use of Bell-type inequality.     

Balancing life with glycoconjugates: monitoring unfolded protein response-mediated anti-angiogenic action of tunicamycin by Raman Spectroscopy

Asparagine-linked protein glycosylation is a hallmark for glycoprotein structure and function. Its impairment by tunicamycin [a competitive inhibitor of N-acetylglucosaminyl 1-phosphate transferase (GPT)] has been known to inhibit neo-vascularization (i.e., angiogenesis) in humanized breast tumor due to an induction of ER stress-mediated unfolded protein response (UPR). The studies presented here demonstrate that (i) tunicamycin (i) inhibits capillary endothelial cell proliferation in a dose dependent manner; (ii) treated cells are incapable of forming colonies upon its withdrawal; and (iii) tunicamycin treatment causes nuclear fragmentation. Tunicamycin-induced ER stress-mediated UPR event in these cells was studied with the aid of Raman spectroscopy, in particular, the interpretation of bands at 1672, 1684 and 1694 cm(-1), which are characteristics of proteins and originate from C=O stretching vibrations of mono-substituted amides. In tunicamycin-treated cells these bands decreased in area as follows: at 1672 cm(-1) by 41.85% at 3 h and 55.39% at 12 h; at 1684 cm(-1) by 20.63% at 3 h and 40.08% at 12 h; and also at 1994 cm(-1) by 33.33% at 3 h and 32.92% at 12 h, respectively. Thus, in the presence of tunicamycin, newly synthesized protein chains fail to arrange properly into their final secondary and/or tertiary structures, and the random coils they form had undergone further degradation.     

Convergence of tail sum for records

Suppose is the sequence of lower records from a distribution F, where F is continuous with . We derive conditions under which logarithm of the tail sum of records, ∑ _j=n ^∞ R _n ^(L) (F), properly centered and scaled, converge weakly. We also prove two results on Π-varying and regularly varying functions, which are of independent interest.     

Role of Ab Initio Calculations in the Design and Development of Organometallic Lanthanide‐Based Single‐Molecule Magnets

Single‐molecule magnets based on lanthanides are very attractive due to their potential applications proposed in the area of microelectronic devices. Very recent advances in this area are due to the blend of conventional lanthanide chemistry with organometallic ligands, and several breakthrough achievements are attained with this combination. Ab initio methods based on multi‐reference CASSCF calculations are playing a vital role in the design and development of such molecules. In this minireview, we aim to appraise various contributions in the area of organometallic lanthanide complexes (those containing lanthanide‐carbon bonds) and describe how these robust wavefunction‐based methods have played a constructive role not only in rationalizing the observed magnetic properties but also proven to be a potential predictive tool with some selected examples.     

Flavonolignan silibinin abrogates SDS induced fibrillation of human serum albumin

Misfolding, aggregation and fibrillation of amyloidogenic proteins have been established as hallmark events in pathophysiology of various degenerative diseases. Inhibition of protein fibrillation through use of plant derived molecular scaffolds is currently considered as one solution to it. Further, rational design of therapeutic originating with the specific plant molecular scaffolds appeared passable to aid in mitigating amyloidogenic diseases. Silibinin (SB) is a flavonolignan obtained from milk thistle plant. SB is well acclaimed as a potent hepatoprotective, cardioprotective and an attenuator of receptor signaling in case of type 2 diabetes. This work reports the inhibitory capacity of SB against protein fibrillation under experimental conditions. Human serum albumin (HSA), an ubiquitous serum protein was used and various platform studies were carried out for indepth understanding of similar effects. Biophysical studies and electron microscopy confirmed that SB inhibited HSA fibrils formations by 36% at optimal molar ratio. In silico studies further demonstrated that intermolecular hydrogen bonds and hydrophobic interactions hindered progressive aggregation and protein fibrillation.     

Matrix polynomial generalizations of the sample variance-covariance matrix when <Emphasis Type="Italic">pn</Emphasis><Superscript>−1</Superscript> → <Emphasis Type="Italic">y</Emphasis> ∈ (0, ∞)

Let {Z _u = ((ε_{u, i, j}))_p×n} be random matrices where {ε_{u, i, j}} are independently distributed. Suppose {A _i }, {B _i } are non-random matrices of order p × p and n × n respectively. Consider all p × p random matrix polynomials \(P = \prod\nolimits_{i = 1}^{k_l } {\left( {n^{ - 1} A_{t_i } Z_{j_i } B_{s_i } Z_{j_i }^* } \right)A_{t_{k_l + 1} } }\). We show that under appropriate conditions on the above matrices, the elements of the non-commutative *-probability space Span {P} with state p^?1ETr converge. As a by-product, we also show that the limiting spectral distribution of any self-adjoint polynomial in Span{P} exists almost surely.     

Microwave‐induced perchloric acid catalyzed novel solvent‐free synthesis of 4‐aryl‐3,4‐dihydropyrimidones via biginelli condensation

We report here domestic microwave‐induced perchloric acid‐catalyzed solvent‐free synthesis of various 4‐aryl‐3,4‐dihydropyrimidones for the first time. In all the cases the yields are excellent and the mechanism follows a simple Biginelli condensation to produce the dihydropyrimidones in a few seconds. This procedure has been successfully employed to synthesize the mitotic kinesin EG5 inhibitor Monastrol (Figure I).     

Ligand-Induced Chirality in ClMBA2SnI4 2D Perovskite**

Chiral perovskites possess a huge applicative potential in several areas of optoelectronics and spintronics. The development of novel lead-free perovskites with tunable properties is a key topic of current research. Herein, we report a novel lead-free chiral perovskite, namely (R/S−)ClMBA₂SnI₄ (ClMBA=1-(4-chlorophenyl)ethanamine) and the corresponding racemic system. ClMBA₂SnI₄ samples exhibit a low band gap (2.12 eV) together with broad emission extending in the red region of the spectrum (∼1.7 eV). Chirality transfer from the organic ligand induces chiroptical activity in the 465–530 nm range. Density functional theory calculations show a Rashba type band splitting for the chiral samples and no band splitting for the racemic isomer. Self-trapped exciton formation is at the origin of the large Stokes shift in the emission. Careful correlation with analogous lead and lead-free 2D chiral perovskites confirms the role of the symmetry-breaking distortions in the inorganic layers associated with the ligands as the source of the observed chiroptical properties providing also preliminary structure-property correlation in 2D chiral perovskites.     

The Strong Law of Large Numbers for Kaplan–Meier U-Statistics

We introduce a Kaplan–Meier U-statistic of degree two for randomly censored data and prove a strong law for it. We use the technique of Stute and Wang⁽³⁾ by identifying appropriate reverse-time supermartingale processes. This approach avoids the stringent assumptions of Gijbels and Veraverbeke⁽¹⁾ who consider similar functionals.