Relative Configuration Research Articles

Logico-semantic relations between spoken text and slides’ visual elements in student presentations conducted online in the English as a Foreign Language context

Student presentations conducted with the help of PowerPoint represent communicative events that are inherently multimodal by incorporating visuals on slides accompanied by spoken commentary. However, despite their ubiquity in higher education, few studies have investigated the rhetorical relations between their auditory and visual modes. This study attempts to address this gap by applying theoretical frameworks for logico-semantics and image–text relations to student presentations conducted online at a private university in Japan. Analysis of over 5 hours of recorded data revealed how clauses in students’ spoken commentary related to visible entities on the screen primarily through exposition and, to a lesser extent, specification, summary, extension and enhancement. A further comparison of different stages within the presentations showed that summary and expansion played a bigger role whenever students provided background information or concluded the presentation. Further, qualitative discussion on selected excerpts sheds light on how the reading path alternated between exposition of visual text through repetition or synonymy and embellishment through specification or enhancement. However, comparing students also indicated that genre-specifics are not yet established for all students. The selection and configuration of logico-semantic relations influenced how slides compensated for verbal deficiencies, which has implications for the English as a Foreign Language context.

Relativistic configurations of Tolman stellar spheres in f(𝒢,𝒯 ) gravity

This study is devoted to investigate the formation of compact stars using Tolman–Kuchowicz space-time in [Formula: see text] gravity. By taking into account the physically reliable formulations of metric potentials, [Formula: see text] = [Formula: see text] and [Formula: see text] = [Formula: see text], we investigate the equation of motion for spherically symmetric space-time in the presence of an anisotropic matter distribution. Furthermore, matching conditions are employed to compute the unknown constants. By making use of dynamical equations, the pivotal relevant aspects, including energy density, radial and tangential pressures, dynamical equilibrium, anisotropy effect, energy conditions and stability, are physically tested in order to determine the physical acceptability of yielding celestial model, which are thoroughly compared with experimental facts and figures of ten different compact stars. Finally, we observe that obtained anisotropic outcomes are physically viable, free from geometrical and physical singularities. Moreover, these outcomes also provide circumstantial evidence for the existence of super-massive compact stars.

Antibacterial polyketides and ascochlorins from deep-sea cold-seep-derived fungus Furcasterigmium furcatum (syn. Acremonium furcatum)

Three new secondary metabolites, including a new polyketide, acrefurcatone A (1), a new ascochlorin analogue, acremochlorin N (2), and 3-phenylcyclopentane-1,2-diol (±-3), a pair of new naturally occurring enantiomers, along with nine known ascochlorins (4–12), were identified from Furcasterigmium furcatum CS-280 (syn. Acremonium furcatum CS-280), a fungus isolated from the deep-sea cold-seep sediment samples collected in the South China Sea. Their structures were determined by detailed interpretation of NMR spectroscopic and mass spectrometric data. The relative configurations of compounds 1–3 were assigned by NOESY correlations combined with gauge-independent atomic orbital (GIAO) NMR shift calculations and DP4+ probability analysis, while their absolute configurations were assigned by time-dependent density functional (TDDFT) ECD calculations and specific rotation calculations. Compound 1 exhibited potent activity against the human pathogenic bacterium Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) value of 8 μg/mL. The isolated ascochlorins also showed potent activities against aquatic bacteria, especially for Vibrio harveyi and V. alginolyticus, with MIC values comparable to chloramphenicol. Analysis of the structure-activity relationship indicated that the cinnamate derivative, such as compound 1, or the presence of chlorine atom in ascochlorin derivatives, such as compounds 4, 6, and 7, significantly enhanced the antibacterial activities. This is the first report of anti-Vibrio activities for ascochlorin derivatives.

Enigmazole Phosphomacrolides from the Marine Sponge Cinachyrella enigmatica.

Enigmazole B (1) and four new analogues, cis-enigmazole B (2), dehydroenigmazole B (3), enigmimide B (4), and enigmimide A (5), were isolated from the marine sponge Cinachyrella enigmatica. Their planar structures were elucidated by detailed NMR and MS data analyses, which established 1-3 to be oxazole-substituted 18-membered phosphomacrolides, while 4 and 5 were oxazole ring-opened congeners. The relative and absolute configurations in 1 were determined by a combination of chemical transformations and spectroscopic analyses. Photooxidation of the oxazole moiety in 1 gave enigmimide B (4), thus establishing that 4 has the same absolute configuration of 1. Enigmazole B (1) along with analogues 2 and 3 showed cytotoxicity against murine IC-2 mast cells with IC50 values of 3.6-7.0 μM. The enigmimides (4 and 5) and dephosphoenigmazoles did not show cytotoxicity (IC50 > 10 μM), implying that both the oxazole moiety and the phosphate group are necessary for the cytotoxicity of the enigmazole class macrolides.

Enantio- and Diastereomerically Pure Titanocenes by Dynamic Conformational Locking.

The synthesis of enantiomerically pure titanocenes is limited to cases with enantiomerically pure substituents at the cyclopentadienyl ligands and to ansa-titanocenes. For the latter complexes, the use of achiral ligands requires a resolution of enantiomers and frequently also a separation of the diastereoisomers obtained after metalation. Here, we introduce a new synthetic method that relies on the use of enantiomerically pure camphorsulfonate (CSA) ligands as control elements for the absolute and relative configuration of titanocene complexes. Starting from the conformationally flexible (RC5 H4 )2 TiCl2 , the desired conformationally locked and hence enantio- and diastereomerically pure complexes (RC5 H4 )2 Ti(CSA)2 are obtained in just two steps. According to X-ray crystallography the (RC5 H4 )2 Ti fragment is essentially C2 -symmetric and nuclear magnetic resonance displays overall C2 -symmetry. We applied density functional theory methods to unravel the dynamics of the complexes and the mechanisms and selectivities of their formation.

The configuration of ethnic and religious relations towards the 2024 general election: A case study in Medan, Indonesia

After the 2014 presidential election, which Jokowi-Jusuf Kalla won, sentiments based on religion and ethnicity towards Jokowi persisted. The discourse regarding the strengthening of ethnicity and religious politics continues not only at the national level but also at the municipal level during the political transition period. Almost identical to the elections for the Governor held in 2008, 2013, and 2018, the issues that continue to develop in the election for the Governor of North Sumatra cover the same three aspects: religious issues, ethnic identity politics, and local son issues. This study aims to discover ethnic and religious relations in Medan following the 2019 general elections and the configuration of ethnic and religious connections in Medan towards the 2024 general elections. The research method used was quantitative research. The sample of this study was 100 responders chosen randomly by using simple random sampling technique. The data were collected through a close-ended questionnaire distributed offline to responders. It was found that the polarization of inter-ethnic and inter-religious relations in Medan following the 2019 elections and the 2020 Medan mayoral race altered the societal patterns of interaction. Several factors contribute to this, including ending amicable contacts, viewing other races or religions as provocateurs, and establishing political preferences based on ethnic and religious concerns.

An ECD and NMR/DP4+ Computational Pipeline for Structure Revision and Elucidation of Diphenazine-Based Natural Products.

Discovery and structure elucidation of natural products available in infinitesimally small quantities are recognized challenge. This challenge is epitomized by the diphenazine class of molecules that contain three bridged stereocenters, several conformations, ring fusions, and multiple spatially isolated phenols. Because empirical NMR and spatial analyses using ROESY/NOESY were unsuccessful in tackling these challenges, we developed a computational pipeline to determine the relative and absolute configurations and phenol positions of diphenazines as inhibitors of eukaryotic translation initiation factor 4E (eIF4E) protein-protein interactions. In this pipeline, we incorporated ECD and GIAO NMR calculations coupled with a DP4+ probability measure, enabling the structure revision of phenazinolin D (4), izumiphenazine A (5), and baraphenazine G (7) and the structure characterization of two new diphenazines, baraphenazine H (3) and izumiphenazine E (6). Importantly, through these efforts, we demonstrate the feasibility of NMR/DP4+ analysis for the determination of phenol positions in phenazine-based molecules, further expanding the limits of computational methods for the structure elucidation of complex natural products.

Three undescribed compounds from Diaporthe biguttusis T-24, an endophytic fungus isolated from Ligularia fischeri

Diaporthpyran A (1), diaporthester E (2) and diaporthester F (3), three new compounds along with four known compounds (4-7) were isolated from the crude extract of Diaporthe biguttusis T-24, an endophytic fungus isolated from Ligularia fischeri. The planar structures of compounds 1-3 including the relative and absolute configurations were elucidated on the basis of HRMS, NMR, J-based coupling constant analysis, CD, and calculated ECD analysis. In addition, compounds 1 and 3 were evaluated for their cytotoxic activities against four human cancer cell lines.

From Pyridine to (−)‐Agelastatin A

Abstract(−)‐Agelastatin A was synthetized employing a flow photorearrangement of a pyridinium salt, constructing in one step the cyclopentene core possessing the desired functionalities and relative configurations. A flow enzymatic kinetic resolution of the resulting bicyclic vinyl aziridine delivered the enantiopure precursor to the natural product. This total synthesis required the use of a single protective group. Two novel agelastatin N3‐derivatives were synthesized and their cytotoxicity evaluated against a series of cancer cell lines, which corroborated the importance of unsubstituted N3 in the biological activity of (−)‐agelastatin A.

Experimental Study on Uplift Behavior of Two-Plate Horizontal Anchors in Sand

Abstract An experimental study on sand deformation around two-plate anchors connected to one shaft was conducted by using the digital image correlation technique to investigate load–displacement response and deformation fields in various embedment depth, plate spacing, and relative density configurations. A test setup comprising a camera, loading frame, and computer was developed to measure the uplifting load and displacement and to capture pictures during anchor uplifting. The uplift load of the top and bottom plates was observed to be characterized by asynchrony and a “relay” phenomenon. The deformation fields between the top and bottom plates also illustrated the “relay” phenomenon. Based on the experimental results, three failure models (shallow, deep, and composite failure) are proposed to describe the degree and the extent of soil shear mobilization around the two-plate anchors.

Evaporation and information puzzle for 2D nonsingular asymptotically flat black holes

We investigate the thermodynamics and the classical and semiclassical dynamics of two-dimensional (2D), asymptotically flat, nonsingular dilatonic black holes. They are characterized by a de Sitter core, allowing for the smearing of the classical singularity, and by the presence of two horizons with a related extremal configuration. For concreteness, we focus on a 2D version of the Hayward black hole. We find a second order thermodynamic phase transition, separating large unstable black holes from stable configurations close to extremality. We first describe the black-hole evaporation process using a quasistatic approximation and we show that it ends in the extremal configuration in an infinite amount of time. We go beyond the quasistatic approximation by numerically integrating the field equations for 2D dilaton gravity coupled to N massless scalar fields, describing the radiation. We find that the inclusion of large backreaction effects (N ≫ 1) allows for an end-point extremal configuration after a finite evaporation time. Finally, we evaluate the entanglement entropy (EE) of the radiation in the quasistatic approximation and construct the relative Page curve. We find that the EE initially grows, reaches a maximum and then goes down towards zero, in agreement with previous results in the literature. Despite the breakdown of the semiclassical approximation prevents the description of the evaporation process near extremality, we have a clear indication that the end point of the evaporation is a regular, extremal state with vanishing EE of the radiation. This suggests that the nonunitary evolution, which commonly characterizes the evaporation of singular black holes, could be traced back to the presence of the singularity.

Preparative three-dimensional GC and nuclear magnetic resonance for the isolation and identification of two sesquiterpene ethers from Dictyota Dichotoma.

Separation science plays a crucial role in the isolation of novel compounds contained in complex matrices. Yet their rationale employment needs preliminary structure elucidation, which usually requires sufficient aliquots of grade substances to characterize the molecule by nuclear magnetic resonance experiments. In this study, two peculiar oxa-tricycloundecane ethers were isolated by means of preparative multidimensional gas chromatography from the brown alga species Dictyota dichotoma (Huds.) Lam., aiming to assign their 3D structures. Density functional theory simulations were carried out to select the correct configurational species matching the experimental NMR data (in terms of enantiomeric couples). In this case, the theoretical approach was crucial as the protonic signal overlap and spectral overcrowding were preventing any other unambiguous structural information. Just after the identification through the density functional theory data matching of the correct relative configuration it was possible to verify an enhanced self-consistency with the experimental data, confirming the stereochemistry. The results obtained further pave the way toward structure elucidation of highly asymmetric molecules, whose configuration cannot be inferred by other means or strategies.

Pseudo-Enantiomeric Paraphaeolactones and Their Biosynthetic Derivatives from Paraphaeosphaeria sp. KT4192: A Proposition of a Favorskii Rearrangement for Their Biosynthesis.

Paraphaeolactones A1, A2, B1, and B2 (1-4, respectively), known arthropsadiol D (5), massariphenone (6) and its positional isomer 7, and massarilactones E (8) and G (9) were isolated from the culture broth of Paraphaeosphaeria sp. KT4192. Although the structural resemblance between 1 and 2 implies that these comprised a diastereomeric pair at the C-2 stereogenic center, electronic circular dichroism (ECD) spectral analyses revealed that they were pseudo-enantiomers possessing the common (2R)-configuration. Paraphaeolactones B1 and B2 (3 and 4) were the derivatives of 2, which equipped the 3-(1-hydroxy-2-oxopropyl)-4-methylcatechol moiety via an acetal bond at C-10. The relative configurations of their acetal carbons were elucidated by NOE experiments, and those of C-8' were deduced independently by ECD spectral analysis. The present study disclosed that 1-5, 8, and 9 contain a methylcyclohexene substructure with the same absolute configuration. This prompted us to reinvestigate the absolute configurations of known structurally related fungal metabolites, allowing us to conclude that the methylcyclohexene moieties of these natural products have the same absolute configuration despite the variety of configurations of other stereogenic centers. The plausible biosynthetic routes for 1-9 are discussed on the basis of the above conclusion. We propose a Favorskii rearrangement as the key transformation for biosyntheses of 1-4.

Unraveling the Effect of Stacking Configurations on Charge Transfer in WS2 and Organic Semiconductor Heterojunctions.

Photoinduced interfacial charge transfer plays a critical role in energy conversion involving van der Waals (vdW) heterostructures constructed of inorganic nanostructures and organic materials. However, the effect of molecular stacking configurations on charge transfer dynamics is less understood. In this study, we demonstrated the tunability of interfacial charge separation in a type-II heterojunction between monolayer (ML) WS2 and an organic semiconducting molecule [2-(3″',4'-dimethyl-[2,2':5',2':5″,2″'-quaterthiophen]-5-yl)ethan-1-ammonium halide (4Tm)] by rational design of relative stacking configurations. The assembly between ML-WS2 and the 4Tm molecule forms a face-to-face stacking when 4Tm molecules are in a self-aggregation state. In contrast, a face-to-edge stacking is observed when 4Tm molecule is incorporated into a 2D organic-inorganic hybrid perovskite lattice. The face-to-face stacking was proved to be more favorable for hole transfer from WS2 to 4Tm and led to interlayer excitons (IEs) emission. Transient absorption measurements show that the hole transfer occurs on a time scale of 150 fs. On the other hand, the face-to-edge stacking resulted in much slower hole transfer without formation of IEs. This inefficient hole transfer occurs on a similar time scale as A exciton recombination in WS2, leading to the formation of negative trions. These investigations offer important fundamental insights into the charge transfer processes at organic-inorganic interfaces.

Diaryl-Pyrano-Chromenes Atropisomers: Stereodynamics and Conformational Studies.

The dynamic scenario of di-aryls-pyrano-chromenes was investigated using DFT calculations. The symmetry of the chromene scaffold and the presence of two ortho-substituted aryls substituents can generate two syn/anti diastereoisomers and conformational enantiomers with different rotational barriers. The relative conformations and configurations were derived using NOESY-1D experiments. Depending on the energies related to the conformational exchange, the experimental energy barriers were determined through Dynamic NMR, Dynamic HPLC or kinetic studies. The atropisomeric pairs were resolved in the latter scenario, and their absolute configuration was assigned using the ECD/TD-DFT method.

Exploring the Anticancer Potential of Premna resinosa (Hochst.) Leaf Surface Extract: Discovering New Diterpenes as Heat Shock Protein 70 (Hsp70) Binding Agents.

Premna, a genus consisting of approximately 200 species, predominantly thrives in tropical and subtropical areas. Many of these species have been utilized in ethnopharmacology for diverse medicinal applications. In Saudi Arabia, Premna resinosa (Hochst.) Schauer (Lamiaceae) grows wildly, and its slightly viscid leaves are attributed to the production of leaf accession. In this study, we aimed to extract the surface accession from fresh leaves using dichloromethane to evaluate the anticancer potential. The plant exudate yielded two previously unknown labdane diterpenes, Premnaresone A and B, in addition to three already described congeners and four known flavonoids. The isolation process was accomplished using a combination of silica gel column chromatography and semi-preparative HPLC, the structures of which were identified by NMR and HRESIMS analyses and a comparison with the literature data of associated compounds. Furthermore, we employed a density functional theory (DFT)/NMR approach to suggest the relative configuration of different compounds. Consequently, we investigated the possibility of developing new chaperone inhibitors by subjecting diterpenes 1-5 to a Surface Plasmon Resonance-screening, based on the knowledge that oridonin, a diterpene, interacts with Heat Shock Protein 70 (Hsp70) 1A in cancer cells. Additionally, we studied the anti-proliferative activity of compounds 1-5 on human Jurkat (human T-cell lymphoma) and HeLa (epithelial carcinoma) cell lines, where diterpene 3 exhibited activity in Jurkat cell lines after 48 h, with an IC50 of 15.21 ± 1.0 µM. Molecular docking and dynamic simulations revealed a robust interaction between compound 3 and Hsp70 key residues.

Expanding the Utility of Bioinformatic Data for the Full Stereostructural Assignments of Marinolides A and B, 24- and 26-Membered Macrolactones Produced by a Chemically Exceptional Marine-Derived Bacterium.

Marinolides A and B, two new 24- and 26-membered bacterial macrolactones, were isolated from the marine-derived actinobacterium AJS-327 and their stereostructures initially assigned by bioinformatic data analysis. Macrolactones typically possess complex stereochemistry, the assignments of which have been one of the most difficult undertakings in natural products chemistry, and in most cases, the use of X-ray diffraction methods and total synthesis have been the major methods of assigning their absolute configurations. More recently, however, it has become apparent that the integration of bioinformatic data is growing in utility to assign absolute configurations. Genome mining and bioinformatic analysis identified the 97 kb mld biosynthetic cluster harboring seven type I polyketide synthases. A detailed bioinformatic investigation of the ketoreductase and enoylreductase domains within the multimodular polyketide synthases, coupled with NMR and X-ray diffraction data, allowed for the absolute configurations of marinolides A and B to be determined. While using bioinformatics to assign the relative and absolute configurations of natural products has high potential, this method must be coupled with full NMR-based analysis to both confirm bioinformatic assignments as well as any additional modifications that occur during biosynthesis.

Synthetic Study of Natural Metabolites Containing a Benzo[c]oxepine Skeleton: Heterocornol C and D.

A versatile strategy for the enantioselective synthesis of a benzo[c]oxepine structural core containing natural secondary metabolites was developed. The key steps of the synthetic approach include ring-closing alkene metathesis for seven-member ring construction, the Suzuki-Miyaura cross-coupling reaction for the installation of the double bond and Katsuki-Sharpless asymmetric epoxidation for the introduction of chiral centers. The first total synthesis and absolute configuration assignment of heterocornol D (3a) were achieved. Four stereoisomers, 3a, ent-3a, 3b and ent-3b, of this natural polyketide were prepared, starting with 2,6-dihydroxy benzoic acid and divinyl carbinol. The absolute and relative configuration of heterocornol D was assigned via single-crystal X-ray analysis. The extension of the described synthetic approach is further presented with the synthesis of heterocornol C by applying the ether group reduction method to the lactone.

The investigation of the neutronic responses of components in the K-DEMO

The neutronic response of consisting materials of the Korean fusion DEMOnstration reactor (K-DEMO) in its fusion neutron environment is a crucial consideration factor from the conceptual design stage of the K-DEMO. Especially in the design of in-vessel components (IVCs) of the K-DEMO that are placed in the most extreme neutron irradiation field, neutronic damage of constituent components is a major limiting factor that determines the lifetime of IVCs. From the analysis of the neutronic response of IVCs of the K-DEMO, the neutron wall loading (NWL) related to the tritium breeding ratio and nuclear heating of IVCs can be quantified to assess the self-sufficient supply of tritium, and thermal energy transferred from fusion neutrons, respectively. The calculated NWL shows that the harmonizing design of the cooling configuration of each blanket segment with the corresponding NWL is critical thermos-hydraulic design issue for the efficient utilization of thermal energy in the blanket. Another finding is that the double null magnetic field configuration and related blanket configuration with a water-cooled pebble bed of the K-DEMO make a self-sufficient tritium supply challenging. The implicated lifetime of the first plasma-facing tungsten wall of the K-DEMO is around 2 full power years (FPY) in the severely neutron-irradiated region. For the reduced activation ferritic/martensitic steel layers in the blanket, the lifetime of it is estimated around 4 FPY in the inboard region. Based on the response analysis results of this study, optimization of the design of the K-DEMO will continue iteratively in the future.

Oxygenated Cembrane Diterpenes from the South China Sea Soft Coral Sinularia tumulosa.

The chemical investigation of the rarely studied soft coral Sinularia tumulosa resulted in the discovery of five oxygenated cembrane diterpenes 1-5, including two new compounds situmulins A (1) and B (2). The structures of 1 and 2 were established through the extensive analyses of 1D and 2D NMR spectral data together with the comparisons with the known compounds. Furthermore, the absolute configuration of 1 was determined by the time-dependent density functional theory (TDDFT) ECD approach, while the relative configuration of 2 was assigned via the quantum mechanical-NMR (QM-NMR) calculations. It might be worth to point out it is the first time to disclose the presence of cembrane diterpenes in the title species. In the bioassays, compound 2 not only showed strong antibacterial activities against fish pathogenic bacteria Streptococcus parauberis FP KSP28 and Phoyobacterium damselae FP2244 with both minimum inhibitory concentration for 90 % (MIC90 ) values of 25 μM, but also demonstrated substantial inhibitory efficacy against vancomycin-resistant Enterococcus faecium bacteria G1, G4, G7, G8 and G13 from several individuals, with MIC90 values of 25, 50, 100, 50 and 25 μM, respectively.