The chemist’s concept of molecular structure

The concept of molecular structure is fundamental to the practice and understanding of chemistry, but the meaning of this term has evolved and is still evolving. The Born–Oppenheimer separation of electronic and nuclear motions lies at the heart of most modern quantum chemical models of molecular structure. While this separation introduces a great computational and practical simplification, it is neither essential to the conceptual formulation of molecular structure nor universally valid. Going beyond the Born–Oppenheimer approximation introduces new paradigms, bringing fresh insight into the chemistry of fluxional molecules, proteins, superconductors and macroscopic dielectrics, thus opening up new avenues for exploration. But it requires that our ideas of molecular structure need to evolve beyond simple ball-and-stick-type models.

Use of basic principle of nucleation in determining temperature–threshold neutron energy relationship in superheated emulsions

Detection of neutrons through use of superheated emulsions has been known for about two decades. The minimum neutron energy (threshold) required to nucleate drops of a given liquid has a dependence on the temperature of the liquid. The basic principle of nucleation has been utilized to find the relationship between the operating temperature and threshold neutron energy for superheated emulsions made of R-114 liquid. The threshold energy thus determined for different temperatures has been compared with accurate experimental results obtained using monoenergetic neutron sources. The agreement is found to be satisfactory and confirms the applicability of the present simple method to other liquids.     

Machine learning method for simulation of adsorption separation: Comparisons of model’s performance in predicting equilibrium concentrations

In this work, we implemented different models for predicting adsorption separation of a dye from aqueous solution using porous materials. The equilibrium data of solute concentrations were collected from resources and used in the models for training and verification purposes to develop the models. For prediction of the equilibrium solute concentrations (Ce), we used tree models: Multi-layer Perceptron (MLP), Passive aggressive regression, and Decision Tree (DT) Regressor. In the modeling, we considered the adsorbent dosage as well as solution pH as the input parameters to the model, and the model was able to generate the output values, i.e., equilibrium concentrations based on the input variables. The evaluation of the models’ performances revelated that the final R² scores are 0.99, 0.98, 0.93 for DT, MLP and Passive-Aggressive, respectively and a very low RMSE of 0.055 for decision tree that shows this model is the best among models used in this study. Indeed, decision tree model is recommended among the other three models to be employed for correlation of adsorption equilibrium data.     

Paneth’s epistemology of chemical elements in light of Kant’s Opus postumum

Friedrich Paneth’s conception of “chemical element” has functioned as the official definition adopted by the International Union of Pure and Applied Chemistry since 1923. Paneth maintains a distinction between empirical and “transcendental” concepts of element; furthermore, chemical science requires fluctuation between the two. The origin of the empirical-transcendental split is found in Immanuel Kant’s classic Critique of Pure Reason (1781/1787). The present paper examines Paneth’s foundational concept of element in light of Kant’s attempt, late in life, to revoke key distinctions made in his Critique, including that of regulative and constitutive functions of reason. In a section of his Opus postumum devoted to the “Transition from the Metaphysical Foundations of Natural Science to Physics,” Kant bends his philosophical system to address the newly emerging sciences of matter of his time. Specifically, he tried, without success, to develop the transcendental ground for microscale motions of bodies encountered in physical, electrical and chemical processes. Paneth’s discussion of chemical element does not take the Opus postumum into account, which is why it begins with a rejection of Kant’s rejection (in his earlier writings) of chemistry’s status as science. I make the case that Paneth’s definition of element effectively maintains something very like Kant’s critical separation of regulative and constitutive principles, while a advancing the concept of chemical science.     

How do molecular interactions affect fluorescence behavior of AIEgens in solution and aggregate states?

Molecular interactions are crucial in diverse fields of protein folding,material science,nanotechnology,and life origins.Although mounting experimental research controls luminescent behavior by adjusting molecular interactions in light-emitting materials,it remains elusive to correlate microscopic molecular interactions with macroscopic luminescent behavior directly.Here,we synthesized three red luminogens with subtle structural variation and investigated the influence of molecular interactions on their luminescent behavior in solution and aggregate states.Our results indicate that strongπ-πand D-A interactions in both dilute solution(between luminogen and solvent molecules)and aggregate(between luminogens)states cause the redshift in emission,while weak interactions(e.g.,Van der Waals,C–H…π,and C–H…F interactions)enhance the quantum yield.This work provides a thoughtful investigation into the complicated influence of various molecular interactions on luminescent behavior.     

Between Aquinas and Eymerich: The Roman Inquisition’s Use of Dominican Thought in the Censorship of Alchemy

In the latter half of the sixteenth century the Roman Inquisition developed criteria to prosecute a series of operative arts, including various forms of divination and magic. Its officials had little interest in alchemy. During that period the Roman Inquisition tried few people for practising alchemy, and it was rarely discussed in official documents. Justifications for prosecuting alchemists did exist, however. In his influential handbook, Directorium inquisitorum, the fourteenth-century inquisitor Nicholas Eymerich had developed a clear rationale for the investigation and prosecution of alchemists as heretics. His position was endorsed in the 1570s by Francisco Peña in his commentary on Eymerich’s handbook. In this article I explore the reasons why alchemy held this ambiguous status. I argue that members of the Dominican Order developed two traditions of thinking about alchemy from Aquinas’s thought. The first, and closest to Aquinas’s own belief, held that alchemy was a natural art that posed no danger to the Christian faith. The second, developed by Eymerich from a selective reading of Aquinas’s writings, indicated specific circumstances in which alchemists could be investigated. The Roman Inquisition’s response to alchemy vacillated between the positions advocated by Aquinas and Eymerich.     

Review and construction of interatomic potentials for molecular dynamics studies of hydrogen embrittlement in Fe─C based steels

Reducing hydrogen embrittlement in the low-cost Fe─C based steels have the potential to significantly impact the development of hydrogen energy technologies. Molecular dynamics studies of hydrogen interactions with Fe─C steels provide fundamental information about the behavior of hydrogen at microstructural length scales, although such studies have not been performed due to the lack of an Fe─C─H ternary interatomic potential. In this work, the literature on interatomic potentials related to the Fe─C─H systems are reviewed with the aim of constructing an Fe─C─H potential from the published binary potentials. We found that Fe─C, Fe─H, and C─H bond order potentials exist and can be combined to construct an Fe─C─H ternary potential. Therefore, we constructed two such Fe─C─H potentials and demonstrate that these ternary potentials can reasonably capture hydrogen effects on deformation characteristics and deformation mechanisms for a variety of microstructural variations of the Fe─C steels, including martensite that results from γ to α phase transformation, and pearlite that results from the eutectic formation of the Fe₃C cementite compound.     

Borrowing titania’s photoinduced electrons for molecular switching

正When exposed to light,titanium dioxide(titania,TiO_2)can act as a powerful catalyst for degrading a variety of organic compounds.Anatase—one of the polymorphs of TiO_2—has a band gap of 3.2 e V;exposing it to ultraviolet light causes the formation of electron-hole pairs,which,in the presence of water,can generate hydroxyl radicals—strong oxidizing agents.The photocatalytic behavior of titania has enabled     

Synthesis of aromatic polyamidines in Eaton’s reagent

Aromatic polyamidines are prepared via the polycondensation of dicarboxamides and diamines in Eaton’s reagent. The polymers are investigated by elemental analysis and IR and NMR spectroscopy. Polyamidines are well soluble in concentrated sulfuric acid and concentrated formic acid and in polar organic solvents, and temperatures corresponding to their 10% weight losses are in the range 245–280°C.     

Utilisation of the OliveNet™ Library to investigate phenolic compounds using molecular modelling studies in the context of Alzheimer’s disease

Alzheimer’s disease (AD) is a debilitating neurodegenerative disease that affects over 47 million people worldwide, and is the most common form of dementia. There is a vast body of literature demonstrating that the disease is caused by an accumulation of toxic extracellular amyloid-β (Aβ) peptides and intracellular neurofibrillary tangles that consist of hyperphosphorylated tau. Adherence to the Mediterranean diet has been shown to reduce the incidence of AD and the phenolic compounds in extra virgin olive oil, including oleocanthal, have gained a significant amount of attention. A large number of these ligands have been described in the pre-existing literature and 222 of these compounds have been characterised in the OliveNet™ database. In this study, molecular docking was used to screen the 222 phenolic compounds from the OliveNet™ database and assess their ability to bind to various forms of the Aβ and tau proteins. The phenolic ligands were found to be binding strongly to the hairpin-turn of the Aβ₁₋₄₀ and Aβ₁₋₄₂ monomers, and binding sites were also identified in the tau fibril protein structures. Luteolin-4′-O-rutinoside, oleuricine A, isorhoifolin, luteolin-7-O-rutinoside, cyanidin-3-O-rutinoside and luteolin-7,4-O-diglucoside were predicted to be novel lead compounds. Molecular dynamics (MD) simulations performed using well-known olive ligands bound to Aβ₁₋₄₂ oligomers highlighted that future work may examine potential anti-aggregating properties of novel compounds in the OliveNet™ database. This may lead to the development and evaluation of new compounds that may have efficacy against Alzheimer’s disease.     

Controlled polymerization of styrene in the presence of Blatter’s radicals

Russian Chemical Bulletin - Controlled polymerization of styrene (both self-initiated and initiated with azobisisobutyronitrile) in the presence of Blatter’s radical at 125 °C was...     

Applications of Danishefsky’s dienes in asymmetric Oxo-Diels-Alder reactions

Applications of Danishefsky’s dienes in catalytic asymmetric hetero-Diels-Alder (AHDA) reactions or specifically, their asymmetric Oxo-Diels-Alder (AOxo-DA) reactions with appropriate dienophiles are highlighted in detail, including the preparation of catalysts with discussion from a mechanistic points of view. Danishefsky’s dienes are effective and useful compounds for the synthesis of optically active six-membered rings such as dihydropyrones, dihydropyridones and dihydropyrans. Due to the broad range of the overall subject, we have limited ourselves, to the recent developments in the utility of Danishefsky’s dienes in the reaction with carbonyl compounds (aldehydes, ketones and 1,2-dicarbonyl compounds) in asymmetric Oxo-Diels-Alder (AOxo-DA) reactions.     

A molecular insight into deoiled asphalt’s slurry-phase hydrocracking process

Qilu vacuum residue with Ni + V content of 120 ppm and Ca content of 40 ppm, is hard to process for fixed bed hydrocracking technology. In this work, solvent deasphalting process was used as a pretreatment for processing Qilu vacuum residue, and the yield of deasphalted oil could be up to 48.3 %, with less metal (Ni + V + Ca < 15 ppm) and asphaltene (<0.1 %) in deasphalted oil. The n-butane solvent in solvent deasphalting (SDA) process had higher selectivity for HC class, and correspondingly the relative abundance of HC class of deasphalted oil (DAO) was much higher than that of deasphalted oil (DAO). The abundance of DAO was higher than that of DOA when double bond equivalent (DBE) < 14 or carbon number (CN) < 46, and the relative abundance of SDA1-DOA was higher than that of SDA2-DOA when DBE < 20 or CN < 46. Deoiled asphalt was taken as the feed of slurry-phase hydrocracking (SHC) process, and the conversion ratio of deoiled asphalt in slurry-phase hydrocracking process could be more than 80 % for 240 min reaction. The conversion ratios of SDA1-DOA for SHC1-120 min and SHC1-240 min reactions were 66.92 % and 81.64 % respectively, and the conversion ratios of SDA2-DOA for SHC2-120 min and SHC2-240 min reactions were 70.19 % and 85.71 % respectively. Sulfur species and asphaltene changing rules at molecular level were determined to evaluate DOA’s slurry-phase hydrocracking process.     

Reflection of Reflections: Scientist’s Activity in the Mirror of Bibliometrics

Using data form Chemical Abstracts Plus, Web of Science, Scopus, and Russian Science Citation Index, a bibliometric and thematic analysis of scientific publications by V.A. Parmon, full member of the Russian Academy of Sciences, is made.     

Metal-amyloid-β peptide interactions: a preliminary investigation of molecular mechanisms for Alzheimer’s disease

Although humans have spent exactly 100 years combating Alzheimer’s disease (AD), the molecular mechanisms of AD remain unclear. Owing to the rapid growth of the oldest age groups of the popula-tion and the continuous increase of the incidence of AD, it has become one of the crucial problems to modern sciences. It would be impossible to prevent or reverse AD at the root without elucidating its molecular mechanisms. From the point of view of metal-amyloid-β peptide (Aβ) interactions, we review the molecular mechanisms of AD, mainly including Cu2 and Zn2 inducing the aggregation of Aβ, cata-lysing the production of active oxygen species from Aβ, as well as interacting with the ion-channel-like structures of Aβ. Moreover, the development of therapeutic drugs on the basis of metal-Aβ interactions is also briefly introduced. With the increasingly rapid progress of the molecular mechanisms of AD, we are now entering a new dawn that promises the delivery of revolutionary developments for the control of dementias.     

Extension of Fermat’s last theorem in Minkowski natural spaces

Journal of Mathematical Chemistry - Minkowski natural (N?+?1)-dimensional spaces constitute the framework where the extension of Fermat’s last theorem is discussed. Based on...     

Radiometric dating of sediment records in Kuwait’s marine area

Six sediment cores collected from the Northwestern Arabian/Persian Gulf have been radiometrically dated by ²¹⁰Pb. Three cores were collected from stations within the Kuwait Bay, and three others were collected from stations outside the bay. Two models have been used for ²¹⁰Pb dating of sediment cores, i.e. Constant Flux: Constant Sedimentation (CF:CS) Model and the Constant Rate of Supply (CRS) Model. The average rates were found to vary significantly between 0.16 and 1.00 cm y^?1 for stations outside and within the bay respectively. The variability of the sedimentation rate was essentially physiographic characteristics and variable hydrodynamic condition. In this study, ¹³⁷Cs fallout radiotracer was also used to construct a realistic chronology. It was observed that the ¹³⁷Cs in the entire vertical profile has been continuously contributed by fluvial and atmospheric deposition.     

Calorimetric examination of palmar connective tissue in Dupuytren’s disease

Dupuytren’s disease is a hand deformity in which the connective tissue of the subcutaneous palmar fascia contracts and toughens over time, eventually forming a thick cord that pulls one or more fingers into a bent position. The reason why this tissue becomes thickened is not precisely described yet. The aim of this study was to characterize the altered metabolism in palmar connective tissue that promotes disease progression. Normal and diseased palmar fascial complexes were acquired during live surgery and the investigation was performed in a relatively short period of time compared to the earlier reports. Similar sample environment was provided for the normal and degenerative samples. The thermal properties of samples were determined by differential scanning calorimetry. Before the examination all water from the surface was removed. Samples were heated from 0 to 80 °C. The heating rate was 0.3 K min^?1. Conventional aluminum alloy vessels were used with 40 μL sample volume. All samples showed a clear denaturation peak on the calorimetric curve. Change in the enthalpy was observed in normal palmar aponeurosis at ?1431.85 kJ kg^?1 (SD = 371.58). In the affected sample ?1508.70 kJ kg^?1 (SD = 245.66) was measured. Our results showed clear evidence that complex deviations from the normal matrix composition during the late stage of degeneration correlated significantly with changes in thermal properties.