Study Of Weak Interactions Research Articles

Engineering aramid nanofibers into robust macroscopic aerogel spheres for water purification

Aerogels are being developed for efficient removal of contaminants from water due to their high specific surface area and versatile surface chemistry. However, the formation of robust and chemical resistant aerogels is still challenging for practical implementation. Herein, the aramid nanofiber aerogel microspheres (ANFAMs) with dense skin and porous inner structures were fabricated on a large scale via the wet-spinning technique. The robust ANFAMs exhibit the ability to remove organic dye molecules with high efficiency in dynamic and harsh chemical environment. The visual study of weak interactions including electrostatic interactions, π-π interactions, and hydrogen bonding were revealed based on independent gradient model analysis. Moreover, one-step thermoinduced crosslinking enables the ANFAMs with superelasticity, which can maintain spherical after 500 compress-release cycles at 50% strain. The aerogel microspheres show excellent adsorption of various organic solvents with good reusability, paving the way to renewable adsorption for organic liquids from water. Therefore, this work provides a scalable and cost-effective production of robust aerogel microspheres toward the removal of the multiple water pollutants, and will guide future exploration on customizing high-performance enviromental remediation materials based on aramid nanofiber-based aerogels.

Engineering highly reversible hydrogen bonding interaction in pebax/deep eutectic solvent blended membranes for efficient separation of H2S from CO2 and CH4

Removal of H2S and CO2 is a key step for natural gas upgrading. However, further separating H2S/CO2 remains challenging as they are both acid gas with similar kinetic diameters, incurring complex processes and high cost for recovering H2S as sulfur resource. Herein we reported for the first time the introduction of highly reversible hydrogen bonding into Pebax/deep eutectic solvent (DES) blended membranes comprising 1-ethyl-3-methylimidazolium chloride ([Emim]Cl)-based DESs for selectively separating H2S from CO2 and CH4. The successful fabrication of Pebax/DES membranes was confirmed by various characterizations. Benefitting from the highly reversible DES–H2S hydrogen bonding interaction, the H2S permeability, H2S/CO2 and H2S/CH4 selectivity for single gas tests are high up to 1829 Barrer, 14.35 and 242.0, respectively. Based on solution-diffusion data, the acidic [Emim]Cl/levulinic acid (Lev) DESs are found to be the most efficient owing to the moderate DES–H2S hydrogen bonding interaction and thus fast H2S diffusion, which was also confirmed by quantum chemical calculations coupled with visual study of weak interactions. Permeation test of mixed gas shows that Pebax/DES blended membranes can steadily and efficiently separate H2S/CO2/CH4 (3/3/94 vol%) ternary gas, with 1450 Barrer of H2S permeability, 34.5 of H2S/CO2 selectivity and 160 of H2S/CH4 selectivity obtained, which may indicates the applicability of these materials in desufuration of natural gas. To summarize, this work demonstrated the vital role of DES–H2S hydrogen bonding interaction in dominating H2S permeation, which may provide an easy but effective way for fabricating high-performance H2S sepration membranes.

Exploring weak ligand-protein interactions by relaxometry of long-lived spin order.

Relaxation times of nuclear spins often serve as a valuable source of information on the dynamics of various biochemical processes. Measuring relaxation as a function of the external magnetic field turned out to be extremely useful for the studies of weak ligand-protein interactions. We demonstrate that observing the relaxation of the long-lived spin order instead of longitudinal magnetization extends the capability of this approach. We studied the field-dependent relaxation of the longitudinal magnetization and the singlet order (SO) of methylene protons in alanine-glycine dipeptide and citrate in the presence of human serum albumin (HSA). As a result, SO relaxation proved to be more sensitive to ligand-protein interaction, providing higher relaxation contrast for various HSA concentrations. To assess the parameters of the binding process in more details, we utilized a simple analytical relaxation model to fit the experimental field dependences for both SO and T1 relaxation. We also tested the validity of our approach in the experiments with trimethylsilylpropanoic acid (TSP) used as a competitor in ligand binding with HSA.

Capturing Weak Interactions in Surface Adsorbate Systems at Coupled Cluster Accuracy: A Graph-Theoretic Molecular Fragmentation Approach Improved through Machine Learning.

The accurate and efficient study of the interactions of organic matter with the surface of water is critical to a wide range of applications. For example, environmental studies have found that acidic polyfluorinated alkyl substances, especially perfluorooctanoic acid (PFOA), have spread throughout the environment and bioaccumulate into human populations residing near contaminated watersheds, leading to many systemic maladies. Thus, the study of the interactions of PFOA with water surfaces became important for the mitigation of their activity as pollutants and threats to public health. However, theoretical study of the interactions of such organic adsorbates on the surface of water, and their bulk concerted properties, often necessitates the use of ab initio methods to properly incorporate the long-range electronic properties that govern these extended systems. Notable theoretical treatments of "on-water" reactions thus far have employed hybrid DFT and semilocal DFT, but the interactions involved are weak interactions that may be best described using post-Hartree-Fock theory. Here, we aim to demonstrate the utility of a graph-theoretic approach to molecular fragmentation that accurately captures the critical "weak" interactions while maintaining an efficient ab initio treatment of the long-range periodic interactions that underpin the physics of extended systems. We apply this graph-theoretical treatment to study PFOA on the surface of water as a model system for the study of weak interactions seen in the wide range of surface interactions and reactions. The approach divides a system into a set of vertices, that are then connected through edges, faces, and higher order graph theoretic objects known as simplexes, to represent a collection of locally interacting subsystems. These subsystems are then used to construct ab initio molecular dynamics simulations and for computing multidimensional potential energy surfaces. To further improve the computational efficiency of our graph theoretic fragmentation method, we use a recently developed transfer learning protocol to construct the full system potential energy from a family of neural networks each designed to accurately model the behavior of individual simplexes. We use a unique multidimensional clustering algorithm, based on the k-means clustering methodology, to define our training space for each separate simplex. These models are used to extrapolate the energies for molecular dynamics trajectories at PFOA water interfaces, at less than one-tenth the cost as compared to a regular molecular fragmentation-based dynamics calculation with excellent agreement with couple cluster level of full system potential energies.

Surface Passivation Method for the Super-repellence of Aqueous Macromolecular Condensates.

Solutions of macromolecules can undergo liquid-liquid phase separation to form droplets with ultralow surface tension. Droplets with such low surface tension wet and spread over common surfaces such as test tubes and microscope slides, complicating in vitro experiments. The development of a universal super-repellent surface for macromolecular droplets has remained elusive because their ultralow surface tension requires low surface energies. Furthermore, the nonwetting of droplets containing proteins poses additional challenges because the surface must remain inert to a wide range of chemistries presented by the various amino acid side chains at the droplet surface. Here, we present a method to coat microscope slides with a thin transparent hydrogel that exhibits complete dewetting (contact angles θ ≈ 180°) and minimal pinning of phase-separated droplets in aqueous solution. The hydrogel is based on a swollen matrix of chemically cross-linked polyethylene glycol diacrylate of molecular weight 12 kDa (PEGDA), and can be prepared with basic chemistry laboratory equipment. The PEGDA hydrogel is a powerful tool for in vitro studies of weak interactions, dynamics, and the internal organization of phase-separated droplets in aqueous solutions.

Temporal resolution of birth rate analysis in zooplankton and its implications for identifying strong interactions in ecology.

Expanding on Haeckel's classical definition, ecology can be defined as the study of strong and weak interactions between the organism and the environment, hence the need for identifying strong interactions as major drivers of population and community dynamics. The solution to this problem is facilitated by the fact that the frequency distribution of interaction strengths is highly skewed, resulting in few or, according to Liebig's law of the minimum, just one strong interaction. However, a single strong interaction often remains elusive. One of the reasons may be that, due to the ever-present dynamics of ecological systems, a single strong interaction is likely to exist only on relatively short time intervals, so methods with sufficient temporal resolution are required. In this paper, we study the temporal resolution of contribution analysis of birth rate in zooplankton, a method to assess the relative strength of bottom-up (food) versus top-down (predation) effects. Birth rate is estimated by the Edmondson-Paloheimo model. Our test system is a population of the cladoceran Bosmina longirostris inhabiting a small northern lake with few planktivorous predators, and thus likely controlled by food. We find that the method's temporal resolution in detecting bottom-up effects corresponds well to the species' generation time, and the latter seems comparable to the lifetime of a single strong interaction. This enables one to capture a single strong interaction "on the fly," right during its time of existence. We suggest that this feature, the temporal resolution of about the lifetime of a single strong interaction, may be a generally desirable property for any method, not only the one studied here, intended to identify and assess strong interactions. Success in disentangling strong interactions in ecological communities, and thus solving one of the key issues in ecology, may critically depend on the temporal resolution of the methods used.

Quantum chemical studies, spectroscopic NMR and FT-IR analysis, and molecular docking investigation of 3,3′-di-O-methyl ellagic acid (DMA) as a potent Mycobacterium tuberculosis agent

Tuberculosis which is mainly caused by Mycobacterium tuberculosis remains of public health importance due to the resistance of the causative pathogen to the present antibiotics used as treatment options. This resistance has led to the need for the discovery of new treatment options. Herein, the isolation, geometrical optimization, spectroscopic NMR and FT-IR analysis, a study of weak interactions, electronic properties, and the in-silico biological activity of 3,3′-di-O-methyl ellagic acid (DMA) were determined. In addition, the effect of solvent on the kinetic stability, reactivity, and other electronic properties of DMA was determined in three solvents; DMSO, methanol, and water. Also, the biological activity potential and the drug-likeness of DMA were determined using molecular docking protocol and ADMET studies. The studied compound was isolated using column and thin-layer chromatography techniques while characterization was done using spectroscopic techniques. Key vibrations in the compound are C = O vibrations, C = C vibrations, C-H vibrations, –CH3 vibrations, and O-H vibrations. A study of quantum descriptors revealed that DMA is more reactive in water with an energy gap of −3.162 eV and those in three solvents are −3.163, −3.944, and −4.3022 eV in methane, gas, and water respectively. The compound shows great optical potentials with dipole moments of 3.2415D, 5.221D, 5.2015D, and 4.469D in water, DMSO, methanol, and Gas-phase respectively which are greater than that of urea used in the comparison. The QTAIM analysis based on the bond ellipticity < 0.5 suggests the presence of covalent bonds within the atoms of the studied compound. The MESP result shows the presence of π- H bond interaction within the OCH3 and oxygen atom. Molecular docking studies of the studied compound were carried out employing proteins 1W2G, 1YWF, and 1F0N proteins for mycobacterial tuberculosis and the standard drug isoniazid. The result was compared with that of a standard drug. The binding affinities of −7.1, −6.9, and −7.1 kcal/mol for 1W2G, 1YWF, and 1F0N were obtained, and −5.9, −5.9 and −6.0 kcal/mol for the standard drug with 1W2G, 1YWF and 1F0N. These results show that the studied compound has greater biological activity against these proteins as compared to the standard drug. ADMET studies show that the studied compound has great drug-likeness and bioavailability since it did not violate any of Lipinski’s rule of five.

Systematic exo-endo encapsulation of hydroxyurea (HU) by Cu, Ag, and Au-doped gallium nitride nanotubes (GaNNT) for smart therapeutic delivery

Similar to the more well-known carbon nanotubes, gallium nitride nanotubes (GaNNT) are among the materials that scientists have found to be extremely helpful in transporting drugs and to provide significant potential for multi-modal medical therapies. Here, the potential of Cu, Ag, and Au-doped GaNNT for smart delivery of the anticancer medication hydroxyurea (HU) was extensively investigated employing quantum chemical analysis and density functional theory (DFT) computation at the B3LYP-GD3BJ/def2-SVP level of theory. The systematic approach used in this study entails examining the exo (outside)-and endo (inside) loading of HU utilizing the investigated nanotubes in order to understand the adsorption, sensing processes, bonding types, and thermodynamic properties. Results of the HOMO-LUMO studies show that metal-doped GaNNTs with the hydroxyurea (HU) at the endo - interaction of the drug of the nanotube produced more reduced energy gaps (0.911–2.039 eV) compared with metal-doped GaNNTs complexes at the outside – interaction of the drug on the nanotube (2.25–3.22 eV) and as such reveal their suitability for use as drug delivery materials. As observed in the endo-interaction of HU adsorptions in the tubes, HU_endo_Au@GaNNT possessed the highest adsorption energy values of −118.716 kcal/mol which shows the most chemisorption between the surfaces and the adsorbate while for HU_exo_Ag@GaNNT is −97.431 kcal/mol for the highest exo-interactions. These results suggest that HU drug interacted inside the Ag, Au, and Cu doped GaNNT will be very proficient as a carrier of the HU drug into bio systems. These results are along with visual studies of weak interactions, thermodynamics, sensor, and drug release mechanisms suggest strongly the endo-encapsulation of HU as the best mode for smart drug delivery.

Experimental setup for Weak Interaction Studies with Radioactive ion-beams WISArD

The article describes the commissioning and technical development of the Weak Interaction Studies with 32Ar Decay (WISArD) experiment, installed at the radioactive ion-beam facility ISOLDE/CERN. The experiment aims to extend the present limits on scalar and tensor currents in the weak interaction and hence search for physics beyond the Standard Model. The evaluation of these limits relies on measuring the proton energy in beta-delayed proton emission, sensitive to both the beta-neutrino angular correlation coefficient aβν and the Fierz interference term b. The method tries to improve previous studies by considering the positron-proton coincidences when determining the kinematic shift in the energy of the emitted protons. Using this coincidence technique, the aβν and b coefficients will be measured at the per mil level. Simulations were employed to optimize the ion beam transport efficiency and validate proof-of-principle results obtained in November 2018 (Nov2018). Upgrades are ongoing, and we are looking into improvements to the overall performance of the setup.

Computational study on nickel doped encapsulated Mg, K, Ca on pristine C24 nanocage for gas sensing applications

Intense attention have been channeled into environmental sustainability due to the high emission of greenhouse gases therefore, this investigatiom focuses on the adsorption and sensing properties of nickel doped encapsulated Mg, K, Ca on pristine C24 nanocage for CO2, NO2 and SO2 gases using density functional theory (DFT) method. Two adsorption models were designed due to the shape of the gas molecules, interacting to the doped atom, the DFT/TPSSh/Gen method was utilized to explore the adsorption properties from the perspective of geometry analysis, adsorption energy (Eads), electronic properties, visual study of weak interactions, dipole moment, and recovery time for reusability were considered. This work incorporated a comprehensive reference for the selectivity of the adsorbents’ modification towards the effective sensing of these toxic gases. Thus, the electronic properties confirms the conductivity on modification of surface with dopant. Also, the nature of interaction as reveal by the QTAIM analysis was non-covalent in nature and was further confirmed by the analysis of the non-covalent interaction (NCI). Moreso, the reusability analysis confirms surface sensing properties. Adsorption energies; −3.67, −2.48, −3.89, −2.50, −3.82, −3.67 eV, were reported for NO2–Ni@MgC, CO2–Ni@KC, NO2–Ni@KC, CO2–Ni@CaC, NO2–Ni@CaC, SO2–Ni@CaC respectively. Moreover, the aforementioned analyses demonstrate the significant impact on the adsorption models most especially NO2–Ni@KC. Hence, Ni@KC and Ni@CaC shows promising sensitivity towards the gas molecules than Ni@MgC. Based on our theoretical results, the encapsulation of K, Ca, Mg, and late transition metal dopant enhances the adsorbents, which induced the improvement in surface properties. The highest Eads was observed at M3a at −5.11 eV and the least at M1 at −2.11 eV all for SO2 adsorption.

Modeling of Mg12O11–X (X = B, N, P and S) Nanostructured Materials as Sensors for Melamine (C3H6N6)

This research is focused on the sensor properties of pure and X-decorated ([Formula: see text], N, P and S) magnesium oxide (Mg[Formula: see text]O[Formula: see text]) nanocages for melamine (C3H6N6) molecule detection using density functional theory (DFT) electronic structure approach. Comparative adsorption study was carried out on four distinct computational models of hybrid functionals: [Formula: see text]B97XD, PBE0-D3BJ, M062X-D3BJ and DSDPBEP86 with the double-hybrid (DSDPBEP86), being the superior model at the fifth rung of the Jacobi’s ladder, was used as the reference. The atoms-in-molecule (AIM), alongside with the non-covalent interactions (NCIs) as visual extension had been utilized in the study of weak interactions and to affirm the degree of interactions between the clusters and the toxin. In all cases, this study suggests that the adsorption phenomena are best described as chemisorption due to the negative adsorption enthalpy observed. The mean absolute deviation (MAD) and root mean square deviation (RMSD) statistical approaches suggest the behavior of the possible adsorptions to be ranked as follows: PBE0-D3BJ (first rank), [Formula: see text]B97XD (second rank) and finally, M062X-D3BJ (third rank) with ([Formula: see text], 0.7870 and 0.8402) and ([Formula: see text], 0.8946 and 0.9560), respectively. These results are consistent with those of the topological and the sensing parameters, hence, arriving at a conclusive scientific report that Mg[Formula: see text]O[Formula: see text] and Mg[Formula: see text]PO[Formula: see text] surfaces exhibit relatively better sensing performances for the trapping of melamine (MB).

Synthesis, X-ray crystallography, molecular electronic property investigation, and leukopoiesis activity of novel 4,6-dimethyl-1,6-dihydropyridin-2-amino nitrate hybrid material

Herein, a new hybrid organic-inorganic material: 4,6-dimethyl-1,6-dihydropyridin-2-amino nitrate (I) has been synthesized and characterized by X-ray diffraction technique and Fourier transform infrared (FT-IR) spectroscopy. The structural, electronic and topological properties were investigated by a theoretical approach along with a validation of vibrational properties using the dispersion-corrected density functional theory (DFT-D3) method (PWPB95 D3(BJ)) along with the meta-generalized gradient approximation (Meta-GGA) functional of the Minnesota family (M06–2x). All computations were conducted with the 6–311++G(2df,2pd) and def2-TZVP basis set. A visual study of weak interactions was achieved via Bader's Quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) using the promolecular electron density approach, Electron localization function and molecular electrostatic potential. Natural orbital analysis and charge delocalization were equally considered to comprehend and appraise the various intermolecular stabilization mechanisms in the studied system. Molecular electronic properties (quantum descriptors) were also investigated to assess the reactive nature and stability index of the synthesized structure. Due to the ionic nature and structural similarity of the studied compound with methyluracil, molecular docking investigations of the Leukopoiesis stimulating activity of (I) were assessed and compared with a series of Krebs ’regulating enzymes. These studies divulged that the synthesized compound has the potential to stimulate the synthesis of nucleic acids, proteins, cell division, and leukopoiesis.

Qualitative and quantitative study of intermolecular weak interactions for aminosalicylic acid isomers by terahertz spectroscopy

AbstractIn the field of chemical science, the development of new drugs, the formation of crystals and molecular clusters, and the optimization of drug safety and efficacy are all closely related to weak molecular interactions. In this paper, the salicylic drugs 4‐aminosalicylic acid (4‐ASA) and 5‐aminosalicylic acid (5‐ASA) are used as the research objects. First, the terahertz (THz) absorption spectra of the two isomers were measured in the range of .4–2.0 THz by terahertz time‐domain spectroscopy (THz‐TDS). Then the unit cells were calculated by using density functional theory (DFT). We found that the characteristic absorption peaks of the experimental spectra were basically consistent with the theoretical calculation. In addition, under the solvent model, the free energy of dissolution and the free energy of the systems were considered and calculated, and the results showed that solvation had a certain influence on the position and intensity of spectral absorption peaks. In order to further explore the origin of the characteristic absorption peaks, the vibrational properties of the unit cell model were analyzed using the potential energy distribution (PED) method. At the same time, the weak interactions of the system were qualitatively and quantitatively analyzed by interaction region indicator (IRI) and energy decomposition analysis based on forcefield (EDA‐FF) methods, respectively. The results show that the absorption peaks of 4‐ASA and 5‐ASA are mainly derived from the vibration mode of dihedral angle torsion. The weak interactions in the 4‐ASA are dominated by dispersion, while they are dominated by electrostatic and dispersion in the 5‐ASA. Therefore, it is an effective way to identify isomers and study intermolecular weak interactions by using THz‐TDS combined with PED, IRI, and EDA‐FF.

The Relevance of Experimental Charge Density Analysis in Unraveling Noncovalent Interactions in Molecular Crystals.

The work carried out by our research group over the last couple of decades in the context of quantitative crystal engineering involves the analysis of intermolecular interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding using experimental charge density methodology is reviewed. The focus is to extract electron density distribution in the intermolecular space and to obtain guidelines to evaluate the strength and directionality of such interactions towards the design of molecular crystals with desired properties. Following the early studies on halogen bonding interactions, several “sigma-hole” interaction types with similar electrostatic origins have been explored in recent times for their strength, origin, and structural consequences. These include interactions such as carbon (tetrel) bonding, pnicogen bonding, chalcogen bonding, and halogen bonding. Experimental X-ray charge density analysis has proved to be a powerful tool in unraveling the strength and electronic origin of such interactions, providing insights beyond the theoretical estimates from gas-phase molecular dimer calculations. In this mini-review, we outline some selected contributions from the X-ray charge density studies to the field of non-covalent interactions (NCIs) involving elements of the groups 14–17 of the periodic table. Quantitative insights into the nature of these interactions obtained from the experimental electron density distribution and subsequent topological analysis by the quantum theory of atoms in molecules (QTAIM) have been discussed. A few notable examples of weak interactions have been presented in terms of their experimental charge density features. These examples reveal not only the strength and beauty of X-ray charge density multipole modeling as an advanced structural chemistry tool but also its utility in providing experimental benchmarks for the theoretical studies of weak interactions in crystals.

Suppressing Nonspecific Binding in Biolayer Interferometry Experiments for Weak Ligand-Analyte Interactions.

Quantitative analysis of protein–protein interactions (PPIs) using biolayer interferometry (BLI) requires effective suppression of nonspecific binding (NSB) between analytes and biosensors. In particular, the study of weak interactions (i.e., KD > 1 μM) requires high concentrations of analytes, which substantially increases NSB. However, there are only a few so-called NSB blockers compatible with biomolecules, which limits the use of BLI in the accurate analysis of weak interactions. The present study aims to identify a new NSB blocker for the quantitative analysis of weak PPIs using BLI. We find that saccharides, especially sucrose, are potent NSB blockers and demonstrate their compatibility with other blocking additives. We also demonstrate the effects of the new NSB blocker by characterizing the binding between nonstructural protein 1 of the influenza A virus and human phosphoinositide 3-kinase. We anticipate that the new NSB-blocking admixture will find broad applications in studying weak interactions using BLI.

Investigation of the efficient adsorption performance and adsorption mechanism of 3D composite structure La nanosphere-coated Mn/Fe layered double hydrotalcite on phosphate

Severe water eutrophication due to large releases of phosphorus has become a worldwide environmental problem. Adsorption active sites is less of traditional adsorbents in the phosphorus removal process resulting in low removal efficiency, so the new high-efficiency phosphorus removal adsorbents become an effective way to solve the problem. In this work, quercetin modified MnFe layered double hydrotalcite three-dimensional composites structures encapsulated by lanthanum (La(III)) nanoparticles (QLa@MnFe-LDH) were successfully prepared by a classical hydrothermal method. The results of the adsorption experiments show that La(III) nanosphere-encapsulated MnFe-LDH provides a more adequate binding site for phosphate adsorption. The adsorption performance of QLa@MnFe-LDH for phosphate was outstanding, the maximum adsorption capacity was 346.5 mg/g at 298.15 K, which was 300 % higher than that of MnFe-LDH. Moreover, QLa@MnFe-LDH retained its high adsorption capacity (>315.5 mg/g) over a wide range of pH (4.0 ∼ 7.0). The active sites of the reactions were predicted by Multiwfn and Visual Molecular Dynamics (VMD), and novel visualization studies of weak interactions were applied to theoretical studies. The modified MnFe-LDH encapsulated by La nanospheres has a strong adsorption capacity for phosphate adsorption. Therefore, the modified QLa@MnFe-LDH was expected to become an effective adsorption material for phosphorus removal.

Study of weak intermolecular interactions and vibrational modes in hydroxybenzoic acid isomers using terahertz spectroscopy and density functional theory techniques

In this study, the terahertz (THz) absorption spectra of 2-, 3-, and 4-hydroxybenzoic acid molecules were recorded in the frequency range of 0.6–2.0 THz using the terahertz time-domain spectroscopy (THz-TDS) technique. The characteristic absorption peaks of these three hydroxybenzoic acid isomers were identified. The peak frequencies of the 2-, 3-, and 4-hydroxybenzoic acid molecules were significantly different from each other. Apart from experimental studies, theoretical studies using the density functional theory (DFT) technique were also conducted on the unit cells of the hydroxybenzoic acid molecules for simulating the experimental THz spectral features. The results were in good agreement with the experimentally obtained results. The vibrational characteristics and the weak intermolecular interactions of the three hydroxybenzoic acid isomers were analyzed by studying the potential energy distribution (PED) and using the energy decomposition analysis (EDA) technique based on the molecular force-field (FF; EDA-FF) methods to better understand the THz absorption spectra on a molecular level. The studies helped to systematically and comprehensively interpret the origin of the characteristic absorption peaks. The data obtained by studying the PED were used to explain the absorption peak mechanism in the theoretical spectra of the three isomers. The theoretical spectra were predicted using the DFT technique. The results obtained using the EDA-FF method revealed that the vibrational modes of the 2-hydroxybenzoic acid system are primarily the angle between the vector and the plane, while the vibrational modes of the 3-hydroxybenzoic acid and 4-hydroxybenzoic acid systems were primarily the dihedral angle (torsion). Results obtained using the EDA-FF analysis and the visual molecular dynamics (VMD) visualization methods revealed that the weak interactions exhibited by the 2-, 3-, and 4-hydroxybenzoic acid systems were primarily dispersive in nature. The results presented in this study revealed that the intermolecular hydrogen bonds (HBs) exhibited an obvious resonance response and played key roles in generating the low frequency vibrations in the THz region.

High(est) energy lepton colliders

We discuss the physics opportunities and challenges presented by high energy lepton colliders in the range of center-of-mass energy between few and several tens of TeV. The focus is on the progress attainable on the study of weak and Higgs interactions in connection with new physics scenarios motivated by the shortcomings of the Standard Model.

The TAMUTRAP facility: A Penning trap facility at Texas A&M University for weak interaction studies

The Texas A&M University Penning Trap (TAMUTRAP) facility aims to test the standard model of the electroweak interaction by measuring the β-ν correlation parameter, aβν, for β-delayed proton emitters in the atomic mass range 20 < A < 40. Precision measurements of this correlation parameter and, inextricably, the Fierz interference parameter, are a sensitive probe of physics beyond the standard model. Using off-line ion sources, the TAMUTRAP facility has been commissioned by demonstrating the ability to manipulate the trapped-ion motions as well as to perform precision mass measurements. Our novel cylindrical Penning trap – the world's largest – differs from typical designs in two key aspects: the electrode structure has an 180-mm inner diameter and an overall length of 334.89 mm leading to a uniquely small length/radius ratio l/r = 3.72; and we do not use the long end cap approximation, instead our short endcap electrodes are closed and capable of being placed at an arbitrary potential. This geometry is optimized for observing β-delayed proton decays, but is also well suited for other in-trap and post-trap precision decay experiments. In addition to presenting an overview of the TAMUTRAP facility, we demonstrate that our unique Penning trap is able to measure masses with a precision similar to typical trap designs.

Solid-State NMR Spectroscopy Study of Molecular Dynamics of Pyridine 1-Oxide Encapsulated in p-tert-Butylcalix[4]arene.

The mixture of guests 25% pyridine 1-oxide (PNO) and 75% nitrobenzene (NB) encapsulated in a host cavity of p-tert-butylcalix[4]arene (p-tBC) is a suitable system for the study of intermolecular weak interactions, and the preferred orientation of the guest molecules within the host was derived. Variable temperature deuterium nuclear magnetic resonance line shape and spin-lattice relaxation studies were performed on three samples of 25% PNO as a guest (selectively and entirely deuterated) with 75% NB encapsulated in p-tBC as a host system. It is found that the PNO molecular motion supports the two-site jump model and is highly mobile throughout the temperature range from -130 to 20 °C. PNO reorients about its C2 molecular symmetry axis followed by reorientation around the compound's C4 axis of symmetry of a host. Calculation showed that besides precise molecular jumping, the guest also experiences the vibrational motion with a variation angle dispute about 15°. The correlation times for the molecular guest motion and two-dimensional exchange spectroscopy confirmed a fast exchange limit inside the cavity. These molecular dynamics follow an Arrhenius behavior motion from which the small activation energy is delivered that strongly suggests a relatively weak intermolecular interaction between the host and guest species. PNO has definite dipole orientational motion in the cavity where its aromatic covalent bond structure minimizes contact with the host p-tert-butyl groups. Experimentally found, PNO-d5 deuterons in the single crystal collapse at 55 and 125° at ambient temperature. The first splitting of 124 kHz belongs to D3(D5), the second splitting of 100 kHz belongs to D2(D6), and the last splitting of 52 kHz belongs to D4 of the ring of PNO inside the p-tBC.