Clinical Application and Research Progress of Remimazolam for Pediatric Patients.

Remimazolam is a novel ultrashort-acting benzodiazepine that allosterically modulates γ-aminobutyric acid type A (GABAA) receptors to exert sedative effects. Remimazolam has the properties of controllable sedation, rapid onset, and a short duration of action, along with minor depression of circulation and respiration. Remimazolam has been approved for clinical use since 2020 in Japan, and it has been applied for procedural sedation, general anesthesia induction and maintenance, and sedation in ICU patients, and has been proven to be safe and effective. Currently, no consensus has been reached on the clinical application of remimazolam in pediatric patients. This review introduces the clinical research progress and limitations of remimazolam in recent years, aiming to supply scientific guidance and a theoretical reference for the application of remimazolam in pediatric anaesthesia.

Direct structure elucidation by powder X-ray diffraction of a metal-organic framework material prepared by solvent-free grinding.

Powder X-ray diffraction (XRD) has been exploited to establish the structural properties of a porous interpenetrated mixed-ligand metal-organic framework material prepared by solid-state grinding, recognizing that product phases from mechanochemical synthesis are typically microcrystalline powders. The importance of subjecting the powder XRD data to rigorous scrutiny in such applications is emphasized.

Nitrogen and hydrogen adsorption by an organic microporous crystal.

Quick on the uptake: Following its identification during a targeted search, the intriguing crystal structure of 3,3',4,4'-tetra(trimethylsilylethynyl)biphenyl was investigated. Simple removal of the included solvent provides an organic crystal with an open microporous structure that has a striking similarity to that of zeolite A (see picture). Reversible adsorption of nitrogen and hydrogen gases at 77 K confirms that the microporosity is permanent.

In situ solid-state (1)H NMR studies of hydration of the solid acid catalyst ZSM-5 in its ammonium form.

Hydration of the ammonium form of the solid acid catalyst ZSM-5 is investigated by applying a technique that has been developed recently for carrying out in situ solid-state NMR studies of adsorption processes. From (1)H MAS NMR spectra recorded as a function of time and temperature during the hydration process, insights are established on the nature of the interaction between the adsorbed water molecules and the ammonium cations in the ZSM-5 material. The change in isotropic chemical shift for the ammonium cations is consistent with the formation of N-Hcdots, three dots, centeredO hydrogen bonding with the water molecules. Studies of the adsorption of deuterated water, and dehydration of the hydrated material, are also reported.

Mapping the evolution of adsorption of water in nanoporous silica by in situ solid-state 1H NMR spectroscopy.

A recently developed technique for carrying out in situ solid-state NMR studies of adsorption processes in nanoporous materials is applied to map the evolution of the adsorption of water on the widely used siliceous nanoporous host material MCM-41. The technique allows the very earliest stages of the adsorption process to be probed, and using solid-state 1H NMR, the time resolution is of the order of a few hundred seconds. This work reveals that different water environments are populated at different stages of the adsorption process and reveals insights regarding both the sequence in which these different environments become populated and the exchange of water molecules between these environments. The results also provide access to information on the kinetics of the adsorption process, revealing an initial regime of rapid water adsorption up to ca. 1 wt % water, followed by a regime of slower water adsorption. In both regimes, the amount of water adsorbed increases linearly with time. As demonstrated by these results, the approach employed in this work creates new opportunities for investigating, in unprecedented detail, adsorption processes in nanoporous materials.

Alteration of polymorphic selectivity through different crystallization mechanisms occurring in the same crystallization solution.

We report a case in which two different crystallization mechanisms occurring in the same crystallization experiment are found to yield different polymorphic outcomes. In particular, we focus on crystallization of glycine from neutral aqueous solution. Crystallization in the bulk solution gives only the metastable alpha-polymorph, as observed in previous studies, whereas crystallization by evaporation of a thin film of the solution on the walls of the crystallization vessel is found to give rise to the thermodynamically stable gamma-polymorph, and furthermore produces an uncharacteristic crystal morphology for this polymorph. A detailed set of control experiments are described that elucidate mechanistic details relating to the latter crystallization process. The fact that crystallization on the walls of a crystallization vessel can yield a different polymorphic outcome from crystallization in the bulk solution in the same experiment has potentially much wider significance with regard to other polymorphic systems.

Understanding the structural properties of a dendrimeric material directly from powder X-ray diffraction data.

Complete structure determination of an early-generation dendrimeric material has been carried out directly from powder X-ray diffraction data, using the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement. This work represents the first application of modern direct-space techniques for structure determination from powder X-ray diffraction data in the case of a dendrimeric material and paves the way for the future application of this approach to enable complete structure determination of other dendrimeric materials that cannot be prepared as single crystal samples suitable for single crystal X-ray diffraction studies.

Highly efficient one-step conversion of cyclohexane to adipic acid using single-site heterogeneous catalysts.

A solid source of 'active' oxygen (acetylperoxyborate, APB), when dissolved in aqueous solution in the presence of a single-site microporous catalyst containing redox centres (Fe(III)AlPO-31, Mn(III)AlPO-5, Fe(III)AlPO-5), converts cyclohexane with high efficiency (ca. 88%) and exceptionally high selectivity (ca. 81%) to adipic acid at 383 K; this procedure is also effective in converting styrene to styrene oxide and -pinene and (+)-limonene to their corresponding epoxides.

Altering the polymorphic product distribution in a solid-state dehydration process by rapid sample rotation in a solid-state NMR probe.

There is currently considerable interest in the phenomenon of polymorphism in organic molecular solids, and a key issue in this field is to understand the experimental techniques and procedures that may be employed to obtain new polymorphic forms of a given molecule. This paper demonstrates that the polymorphic form of a material (sodium acetate) obtained by a solid-state dehydration process (starting from sodium acetate trihydrate) can be altered by carrying out the dehydration process under conditions of rapid (several kilohertz) sample rotation in a solid-state magic-angle-spinning NMR probe. This observation suggests a new opportunity to influence the outcome of solid-state dehydration/desolvation processes and, in particular, to alter the polymorphic form of the product obtained.

Time-resolved observation of the decomposition process of N,N,N-Trimethylanilinium cations on zeolite H-Y by in situ stopped-flow 13C MAS NMR spectroscopy.

N,N,N-Trimethylanilinium cations were synthesized on acidic zeolite H-Y by direct reaction of N,N-dimethylaniline and methanol. Time-resolved observation of the detailed decomposition process of N,N,N-trimethylanilinium cations was achieved by in situ 13C stopped-flow (SF) MAS NMR spectroscopy at reaction temperatures of 498 K to 573 K.

Formation of acetone enol on acidic zeolite ZSM-5 evidenced by H/D exchange.

H/D exchange observed between bridging hydroxyl groups in acidic zeolite ZSM-5 and adsorbed acetone (acetone-d6/H-ZSM-5 and 13C-2-acetone/D-ZSM-5) indicates a concerted catalytic function of Brønsted acid sites and neighbouring framework oxygen atoms acting as Lewis base sites.