Guest Dynamics Research Articles

Complementary and competitive dynamics of CO2 and N2 in CH4 – Flue gas replacement within natural gas hydrates

To mitigate global warming, the paramount imperative lies in curbing the emission of CO2. The guest replacement method is a prominent carbon-neutral technological advancement that involves injecting CO2 into natural gas hydrate layers to accomplish the dual objectives of energy production and carbon storage. In this study, the guest dynamics in the CH4 – flue gas replacement process were examined, and the impacts of the N2 concentration of the injected gas were systematically analyzed. A powder X-ray diffraction analysis of the cage-specific guest distributions after CH4 − CO2 (20 %) + N2 (80 %) replacement revealed that CH4 production increased in both the large and small cages compared to the CH4 – CO2 replacement. This enhancement was attributed to the N2 molecules participating in both cages. However, this simultaneously led to a decrease in CO2 storage potential, indicating a ‘complementary’ relationship for CH4 production and a ‘competitive’ one for CO2 storage with respect to CO2 and N2. In situ Raman spectroscopy revealed that the introduction of N2 resulted in a deceleration of CO2 storage kinetics. Guest composition measurements after replacement showed an upward trend in CH4 production and a simultaneous decline in CO2 storage as the N2 composition increased. Notably, an intriguing correlation was established between the CO2/N2 ratios for the injected gas and the replaced hydrates, exhibiting a strong alignment with a simple first-order equation. The findings not only contribute to a deeper understanding of the CH4 − CO2 + N2 replacement technique but provide practical insights for its application in real-world scenarios.

Irresistible Invitations: Relational Possibilities in Collaborative Tea Experience

Abstract This arts-based research study investigates the relational possibilities afforded by shared experience when participants are invited to collaborate in a tea gathering. Inspired by Japanese tea ceremony tradition and the relations of host and guests, who demonstrate mutual respect and appreciation through prescribed gestures, the author aims to translate and make more accessible the relational possibilities of this practice by inviting guests to collaborate and co-create the experience. Through these gatherings, participant-collaborators explore the interplay of relational potential, sensory experience, and collaboration. This article considers how the relational dynamics of host and guest can have implications for art education when the teacher is understood as a host to student-guests in interdependent roles.

Compatibility as a pivotal design factor for digital concierge apps: exploring hotel guests’ socio-psychological dynamics

PurposeThis paper addresses a crucial research need by examining the influence of compatibility, a pivotal design element for hotel concierge apps, on the socio-psychological dynamics of digital hotel guests. While prior research has examined the constructs, their application to digital concierge apps introduces a unique context. We posit that compatibility significantly influences central variables rooted in theory of planned behaviors (TPBs) and technology acceptance model (TAM), fostering positive usage intentions.Design/methodology/approachAnalyzing data from 668 four-star hotel guests through PLS-SEM substantiates compatibility’s role, endorsing the theoretical amalgamation of affordance, TPB, and TAM frameworks.FindingsCompatibility positively affected perceived ease of use, perceived usefulness, and attitude toward behavior. Besides, usage intention positively affected willingness to pay a price premium and revisit intention.Originality/valueThis paper adopts compatibility as a unifying force for integrating TPB and TAM; the predictive ability of digital concierges' usage intentions on revisit intentions to upscale hotels. Further, this paper is the first attempt to highlight employing compatibility as a pivotal design factor for digital concierge apps in the hospitality setting.

Temperature-tunable multiple dielectric switch in hybrid rare-earth perovskites regulated by hierarchical guest dynamics, lanthanide contraction and doping

Here we report a unique class of cage-like hybrid rare-earth perovskites, (i-PrNHMe2)2[RbLn(NO3)6] (Ln = La, Ce, Nd or Sm), capable of functioning as temperature-responsive multiple dielectric switches.

Cold, Hot, Dry, and Wet: Locations and Dynamics of CO2 and H2O Co-Adsorbed in an Ultramicroporous MOF.

Climate change from anthropogenic carbon dioxide (CO2) emissions poses a severe threat to society. A variety of mitigation strategies currently include some form of CO2 capture. Metal-organic frameworks (MOFs) have shown great promise for carbon capture and storage, but several issues must be solved before feasible widespread adoption is possible. MOFs often exhibit reduced chemical stabilities and CO2 adsorption capacities in the presence of water, which is ubiquitous in nature and many practical settings. A comprehensive understanding of water influence on CO2 adsorption in MOFs is necessary. We have used multinuclear nuclear magnetic resonance (NMR) experiments at temperatures ranging from 173 to 373 K, along with complementary computational techniques, to investigate the co-adsorption of CO2 and water across various loading levels in the ultra-microporous ZnAtzOx MOF. This approach yields detailed information regarding the number of CO2 and water adsorption sites along with their locations, guest dynamics, and host-guest interactions. Guest adsorption and motional models proposed from NMR data are supported by computational results, including visualizations of adsorption locations and the spatial distribution of guests in different loading scenarios. The wide variety and depth of information presented demonstrates how this experimental methodology can be used to investigate humid carbon capture and storage applications in other MOFs.

Dielectric Relaxation Behavior of Halobenzene Confined in the δ‐Phase of Syndiotactic Polystyrene

AbstractSyndiotactic polystyrene (sPS) incorporates low‐mass guest molecules to form a co‐crystalline structure, the δ‐phase, in which the guest molecules are confined within a nanosized space. Under such spatial constraints, what factors determine the dynamics of the guest molecules? This is an interesting question and needs to be clarified toward the functionalization of sPS/functional guest systems. In this study, the size effect of the guest molecules and use monosubstituted halobenzenes (fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene) to systematically change the molecular size is focussed. Since halobenzene has a large electric dipole moment, dielectric relaxation measurements can effectively detect its molecular motion. This study aims to identify the guest dynamics in the δ‐phase by dielectric relaxation measurement and examines the molecular length dependence of the rotational relaxation times and their activation energies.

Multicultural hospitality and immigration in Winnipeg, Manitoba: Host–guest dynamics

Relying on qualitative data obtained from newcomers in Winnipeg, Manitoba, this article critically examines hospitality, specifically host–guest dynamics, with special attention to cultural discontinuities and contentious policies on foreign credentials. In particular, this article sheds light on the contested nature of hospitality practices, thereby moving beyond the notion of vertical power relations between the nation state as host and immigrants as guests to acknowledge the existence of everyday reciprocal practices of welcoming and supporting one another, such as those occurring in ethnocultural communities. In order to highlight the challenges related to the implementation of the principles of hospitality, we begin by making a brief presentation of the dimensions of this concept and by problematizing multicultural hospitality with special attention to critical multiculturalism. Based on qualitative data, we then problematize hospitality with special attention to social relations and cultural discontinuities. Finally, we conclude with a discussion on guest and host factors in the concretization of multicultural hospitality with and for immigrants.

Events at the Interface: How Do Interfaces Modulate the Dynamics and Functionalities of Guest Molecules?

Chemical and biological interfaces are of various types, which could be between two materials of the same and/or different states, two phases of the same material, biological substrates and the outer environment, surfactant or polymeric membranes and the bulk, and so forth. Small-molecule guests frequently interact with such interfaces that decide their functionalities. The structural and behavioral properties undergo considerable characteristic changes, which control their final course of action in the targeted application. This Perspective will discuss mainly the chemical interfaces constituted by the surfactants, polymers, lipids, and nucleic acids and their impacts on the dynamics of small-molecule guests. Some specific and interesting phenomena and future prospects will be elucidated in this Perspective.

More complex than originally thought: revisiting the origins of the relaxation processes in dimethylammonium zinc formate

Metal formates are a subclass of coordination polymers that is renowned for the rich phase transition behavior arising from the complex interplay of molecular dynamics of organic guests and the surrounding coordination net.

Tuning the affinity of amphiphilic guest molecules in a supramolecular polymer transient network.

Dynamicity plays a central role in biological systems such as in the cellular microenvironment. Here, the affinity and dynamics of different guest molecules in a transient supramolecular polymer hydrogel system, i.e. the host network, are investigated. The hydrogel system consists of bifunctional ureido-pyrimidinone (UPy) poly(ethylene glycol) polymers. A monofunctional complementary UPy guest is introduced, designed to interact with the host network based on UPy–UPy interactions. Furthermore, two other guest molecules are synthesized, being cholesterol and dodecyl (c12) guests; both designed to interact with the host network via hydrophobic interactions. At the nanoscale in solution, differences in morphology of the guest molecules were observed. The UPy–guest molecule formed fibers, and the cholesterol and c12 guests formed aggregates. Furthermore, cellular internalization of fluorescent guest molecules was studied. No cellular uptake of the UPy–cy5 guest was observed, whereas the cholesterol–cy5 guest showed membrane binding and cellular uptake. Also the c12–cy5 guest showed cellular uptake. Formulation of the guest molecules into the UPy hydrogel system was done to study the guest–host affinity. No changes in mechanical properties as measured with rheology were found upon guest–hydrogel formulation. Fluorescence recovery after photobleaching showed the diffusive properties of the cy5-functionalized guests throughout the host network. The c12 guest displayed a relatively fast mobility, the UPy guest displayed a decrease in mobility, and the cholesterol–guest remained relatively stable in the host network with little mobility. This demonstrates the tunable dynamic differences of affinity-based interaction between guest molecules and the host network. Interestingly, the cholesterol guest is internalized in cells and is robustly incorporated in the hydrogel network, while the UPy guest is not taken up by cells but shows an affinity to the hydrogel network. These results show the importance of guest–hydrogel affinity for future drug release. However, if modified with cholesterol these guests, or future drugs, will be taken up by cells; if modified with a UPy unit this does not occur. In this way both the drug–hydrogel interaction and the cell internalization behavior can be tuned. Regulating the host–guest dynamics in transient hydrogels opens the door to various drug delivery purposes and tissue engineering.

The role of mandible morphology in termite inquilinism

AbstractIn heterospecific termite–termite (Blattodea, Isoptera) cohabitation, defensive morphologies are more evident in inquiline soldiers than in the workers. Nevertheless, these latter are prone to present defensive adaptations as well. After all, by living and feeding inside the nest of other species, such workers would suffer less pressure from building and foraging, but more demand for defensive adaptations. Interestingly, these three functions – building, foraging, and defense – can be exerted by a single structure, the mandibles. Providing that, in inquilines, defensive needs may prevail over building and foraging, it seems adaptive for inquiline termite workers to have mandibles modified for defense. Here we report on a significant correlation between mandibular modifications in termite workers and their propensity to inquilinism. Using behavioral assays, we show these adaptations to play relevant roles in the defense/attack dynamics of guests and hosts. We show that, in termite workers, the size and position of the apical tooth relative to the marginal teeth may arm termite hosts and termite inquilines with an effective defensive weapon. Hosts may also use it as a weapon to attack inquilines. The latter, however, are unable to do so, confirming previous reports on peaceful behavior as a typical strategy for termite inquilines. We argue that mandibular patterns in termites (as measured by the left mandible index, LMI), more than a product of feeding habit selective pressure, may also serve to mediate nest heterospecific cohabitation.

A curved host and second guest cooperatively inhibit the dynamic motion of corannulene

Biomolecular systems show how host–guest binding can induce changes in molecular behavior, which in turn impact the functions of the system. Here we report an artificial host–guest system where dynamic adaptation during guest binding alters both host conformation and guest dynamics. The self-assembled cage host employed here possesses concave walls and a chirotopic cavity. Complementarity between the curved surfaces of fullerenes and the inner surface of the host cavity leads the host to reconfigure stereochemically in order to bind these guests optimally. The curved molecule corannulene undergoes rapid bowl-to-bowl inversion at room temperature. Its inversion barrier is increased upon binding, however, and increased further upon formation of a ternary complex, where corannulene and a cycloalkane are both bound together. The chiral nature of the host also leads to clear differences in the NMR spectra of ternary complexes involving corannulene and one or the other enantiomer of a chiral guest, which enables the determination of enantiomeric excess by NMR.

Structure and properties of KNi–hexacyanoferrate Prussian Blue Analogues for efficient CO2 capture: Host–guest interaction chemistry and dynamics of CO2 adsorption

Potassium Nickel hexacyanoferrate Prussian Blue Analogues (K-NiFe-PBAs) offer an excellent platform for efficient CO2 capture due to their porous nature and accessible channels. Herein, the effect of Ni:K atomic ratio on the structure and the CO2 storage capacity was studied by employing K-NiFe-PBAs with Ni:K ratio of ca. 2.5 and 12. The porosity and the isosteric heat of CO2 adsorption can be modulated and optimized by varying the Ni:K atomic ratio in the PB framework and thus, covering the thermodynamic criterion for easy CO2capture and release with acceptable energy costs. The synthesized K-NiFe-PBAs containing only trace amounts of K+ ions (with Ni:K = 12) shows an adsorption capacity (∼3.0 mmol g–1 CO2 at 273 K and 100 kPa) comparable to other well established CO2 adsorbents. In situ FTIR spectroscopy was further employed to elucidate the host–guest interaction chemistry and the dynamics of K-NiFe-PBAs within CO2 and H2O. The analysis enabled, to the best of our knowledge, is the first FTIR spectroscopic observation of the high sensitivity of the material to structural distortions induced by small changes under water vapor pressure. It was found that H2O hardly affects CO2 adsorption and the materials are perspective for CO2 capture in the presence of water.

Managing crowded museums: Visitors flow measurement, analysis, modeling, and optimization

We present an all-around study of the visitors flow in crowded museums: a combination of Lagrangian field measurements and statistical analyses enable us to create stochastic digital-twins of the guest dynamics, unlocking comfort- and safety-driven optimizations. Our case study is the Galleria Borghese museum in Rome (Italy), in which we performed a real-life data acquisition campaign.We specifically employ a Lagrangian IoT-based visitor tracking system based on Raspberry Pi receivers, displaced in fixed positions throughout the museum rooms, and on portable Bluetooth Low Energy beacons handed over to the visitors. Thanks to two algorithms: a sliding window-based statistical analysis and an MLP neural network, we filter the beacons RSSI and accurately reconstruct visitor trajectories at room-scale. Via a clustering analysis, hinged on an original Wasserstein-like trajectory-space metric, we analyze the visitors paths to get behavioral insights, including the most common flow patterns. On these bases, we build the transition matrix describing, in probability, the room-scale visitor flows. Such a matrix is the cornerstone of a stochastic model capable of generating visitor trajectories in silico. We conclude by employing the simulator to enhance the museum fruition while respecting numerous logistic and safety constraints. This is possible thanks to optimized ticketing and new entrance/exit management.

The mechanism of the selective binding ability between opiate metabolites and acyclic cucurbit[4]uril: an MD/DFT study.

Subtle changes in molecular structure often lead to significant differences in host-guest interactions, which result in different host-guest recognition capabilities and dynamics behaviours in complex formation. Herein, we reveal the influence of the guest substituents on host-guest molecular recognition by molecular dynamics (MD) simulation and density functional theory (DFT) approaches. The results suggest that the binding energy barrier of acyclic cucurbit[4]uril (ACB[4]) with opiate metabolites gradually decreases. The methyl group in morphine (MOR) and morphine-3-glucuronide (M3G) strengthens the hydrophobicity of the guest, while depressing the energy loss of the desolvation of polar groups (e.g. hydroxyl) inside the ACB[4] cavity. However, in M3G, the 3-glucuronide group located outside the ACB[4] host cavity effectively alleviates the unfavourable desolvation effect of the hydroxyl and increases the binding constant by two orders of magnitude (compared with normorphine (NMOR)). Our findings stressed the essentiality of the binding mode and intermolecular noncovalent interactions in the host-guest selective binding ability.

Characterization of the Clathrate Hydrate Formed with Fluoromethane and Pinacolone: The Thermodynamic Stability and Volumetric Behavior of the Structure H Binary Hydrate.

To reveal the relation of guest dynamics within the structure H clathrate hydrate and its macroscopic physical properties, experimental and computational works have been conducted on the system of fluoromethane (HFC-41) and pinacolone coexisting with water. The phase boundaries of the hydrate formed from HFC-41 and pinacolone within the pressure range of (0.25-2.48) MPa and the temperature range of (277-293) K were measured. The equilibrium hydrate formation pressure incorporating HFC-41 was lowered by adding the pinacolone as a large guest molecule compound to form a sH phase compared to the HFC-41 single hydrate. Powder X-ray diffraction measurements confirmed the formation of the structure H hydrate with the HFC-41 and pinacolone binary hydrate. The lattice constants of the sH hydrate were also measured to see the effect of the help guest molecular size, which showed a different trend from that of the previous studies of sH pinacolone hydrates. Molecular dynamics simulations of the binary sH phase indicate weak hydrogen bonding of the pinacolone molecules with the water in the cages in the phase with HFC-41. The oblate HFC-41 molecules showed strong orientational preference to the equatorial planes of the D' cages, which may explain some of the trends in the behavior of this phase.

Physical chemistry and technological applications of gas hydrates: topical aspects

The review considers the research and engineering works in selected fields of the physical chemistry of gas hydrates and gas hydrate technologies, mainly performed over the last 10–15 years. Data on the hydrate structures are given, including the structures formed during phase transitions at low temperatures, and on new hydrate structures that are formed under ultrahigh pressures. The dynamics of guest and host subsystems is considered in brief. Phase diagrams of systems involving hydrate formation (in particular, in some porous media) and methods for calculating phase equilibria and compositions of hydrates in these systems are analyzed. Data on the hydrates formed by ‘non-classical’ hydrate formers (alcohols, amines, ammonia, etc.) studied in the last decade and on some of their properties are presented. The Section devoted to hydrate formation kinetics addresses the effect of compounds dissolved in water (surfactants, low-dosage inhibitors) and catalysts on this process. The hydrate growth dynamics on the water surface and hydrate decomposition-formation processes in disperse systems are discussed. Among technological applications, the attention is focused on gas storage and transportation in the hydrate form. Methods for the preparation of hydrates are considered.The bibliography includes 618 references.

Ibuprofen incorporated into unmodified and modified mesoporous silica: From matrix synthesis to drug release

Abstract Aiming to rationalize the release profile of an incorporated pharmaceutical drug in terms of its mobility, driven by guest-host interactions, the poorly water-soluble Ibuprofen drug was loaded in a mesoporous inorganic silica matrix with unmodified (MCM-41) and modified surface (MCM-41sil) by post-synthesis silylation, both having pore sizes ∼ 3 nm. The single calorimetric detection of a broad glass transition step for both ibuprofen composites indicates full drug amorphization, confirmed by the only appearance of an amorphous halo in the powder XRD patterns. Moreover, a gradient profile is disclosed by the heat flux derivative plot in the glass transition, in coherence with the thermogravimetric profile that shows a multi-step decomposition trace for confined ibuprofen in these matrixes. While identical guest dynamics, as probed by dielectric relaxation spectroscopy, were found in both dehydrated composites, a significant molecular population with faster relaxation exists in the hydrated state for the drug inside the unmodified matrix. This was rationalized as the concurrence of true confinement effects, which manifest under nanometer dimensions, and greater water affinity of the unmodified matrix, forcing the drug molecules to be placed mostly in the pore core. Finite size effects are also felt in both dehydrated composites, however guest-host interactions give origin to a dominant population with slowed down mobility that governs the overall guest dynamics. In spite of an inferior number of active sites for drug adsorption in the silylated matrix, a faster Ibuprofen delivery in phosphate buffer (pH = 6.8) was observed when the drug is released from unmodified MCM-41 in the hydrated state. Therefore, our results suggest that a relevant role is played by water molecules, which impair a strong guest adsorption in the host surface more efficiently than the limited surface modification, influence the higher ratio of a faster population in the pore core and facilitate the diffusion of the aqueous releasing media inside pores.

Ineffective OH Pinning of the Flipping Dynamics of a Spherical Guest within a Tight‐Fitting Tube

AbstractA supramolecular/synthetic method has been devised to affix a sterically hindered substituent onto a fullerene guest encapsulated in a tubular host. A two‐wheeled complex of (C59N)‐(C59N) with a tubular host was oxidatively bisected to afford a C59N+ cation captured in the tube. The C59N+ cation in the tube was then trapped by ethanol or water, which led to an oxy substituent pinned on the guest. The guest motions within the tube were modulated by the pinned substituent, and up‐and‐down flipping motions were halted by an ethoxy substituent. A hydroxy substituent, however, was ineffective in halting the flipping motions, despite the tight‐fitting relationship between the tubular host and the spherical guest. Theoretical calculations of the dynamics revealed that the flipping motions were assisted by OH‐π hydrogen bonds between the guest and the carbon‐rich wall and that sliding motions of the OH group were also facilitated by deformations of the tube.

Ineffective OH Pinning of the Flipping Dynamics of a Spherical Guest within a Tight-Fitting Tube.

A supramolecular/synthetic method has been devised to affix a sterically hindered substituent onto a fullerene guest encapsulated in a tubular host. A two-wheeled complex of (C59 N)-(C59 N) with a tubular host was oxidatively bisected to afford a C59 N+ cation captured in the tube. The C59 N+ cation in the tube was then trapped by ethanol or water, which led to an oxy substituent pinned on the guest. The guest motions within the tube were modulated by the pinned substituent, and up-and-down flipping motions were halted by an ethoxy substituent. A hydroxy substituent, however, was ineffective in halting the flipping motions, despite the tight-fitting relationship between the tubular host and the spherical guest. Theoretical calculations of the dynamics revealed that the flipping motions were assisted by OH-π hydrogen bonds between the guest and the carbon-rich wall and that sliding motions of the OH group were also facilitated by deformations of the tube.