Resonance Techniques Research Articles

Magnetite in the abdomen and antennae of Apis mellifera honeybees.

The detection of magnetic fields by animals is known as magnetoreception. The ferromagnetic hypothesis explains magnetoreception assuming that magnetic nanoparticles are used as magnetic field transducers. Magnetite nanoparticles in the abdomen of Apis mellifera honeybees have been proposed in the literature as the magnetic field transducer. However, studies with ants and stingless bees have shown that the whole body of the insect contain magnetic material, and that the largest magnetization is in the antennae. The aim of the present study is to investigate the magnetization of all the body parts of honeybees as has been done with ants and stingless bees. To do that, the head without antennae, antennae, thorax, and abdomen obtained from Apis mellifera honeybees were analyzed using magnetometry and Ferromagnetic Resonance (FMR) techniques. The magnetometry and FMR measurements show the presence of magnetic material in all honeybee body parts. Our results present evidence of the presence of biomineralized magnetite nanoparticles in the honeybee abdomen and, for the first time, magnetite in the antennae. FMR measurements permit to identify the magnetite in the abdomen as biomineralized. As behavioral experiments reported in the literature have shown that the abdomen is involved in magnetoreception, new experimental approaches must be done to confirm or discard the involvement of the antennae in magnetoreception.

Electrochemical detection of glutamate and histamine using redox-labeled stimuli-responsive polymer as a synthetic target receptor.

Glutamate (Glu) and histamine (His) are two major neurotransmitters that play many critical roles in brain physiological functions and neurological disorders. Therefore, specific and sensitive monitoring of Glu and His is essential in the diagnosis and treatment of various mental health and neurodegenerative disorders. Both being non-electroactive species, direct electrochemical detection of Glu and His has been challenging. Herein, we report a stimuli-responsive polymer-based biosensor for the electrochemical detection of Glu and His. The polymer-based target receptors consist of a linear chain stimuli-responsive templated polymer hybrid that is labeled with an osmium-based redox-active reporter molecules to elicit conformation-dependent electrochemical responses. The polymers are then attached to a gold electrode to implement an electrochemical sensor. The cyclic voltammetry (CV) and square-wave voltammetry (SWV) results confirmed the polymers' conformational changes due to the specific target (i.e., Glu and His) recognition and the corresponding electrochemical detection capabilities. The voltammetry results indicate that this biosensor can be used as a 'signal-on' and 'signal-off' sensors for the detection of Glu and His concentrations, respectively. The developed biosensor also showed excellent regeneration capability by fully recovering the initial current signal after rinsing with deionized water. To further validate the polymer's utility as a target bioreceptor, the surface plasmon resonance (SPR) technique was used to characterize the binding affinity between the designed polymers and the target chemical. The SPR results exhibited the equilibrium dissociation constants (KD) of 2.40 μM and 1.54 μM for the polymer-Glu and polymer-His interactions, respectively. The results obtained this work strongly suggest that the proposed sensing technology could potentially be used as a platform for monitoring non-electroactive neurochemicals from animal models.

Assessment of the strength of grignard reagent for the synthesis of secondary and tertiary alcohols of terpenes using metal plate flow reactor

The secondary and tertiary alcohols of terpenes were synthesized from aldehydes, and ketones using allyl magnesium chloride by the continuous metal flow reactor method. The flow process was conducted using metal plate reactors of 10 ml capacity in the presence of solvent mixtures, instead of large amounts of pure solvent like tetrahydrofuran. The products were isolated, and confirmed using gas chromatography and Nuclear magnetic resonance techniques respectively. Subsequently, the optimization studies were conducted to obtain mild, and economical reaction conditions, by varying the amount of allyl magnesium chloride, temperature, pressure, retention time, and flow rates. A comparison between batch processes and flow processes proved the advantages of the flow process in terms of reproducibility and product yield without the requirement of excess reagents compared to the batch process. The product yield was found to be excellent (60–97 %) and reproducible at (1–50) gram scale through flow process. The scope of the reaction was studied by synthesizing terpene alcohols using different carbonyl compounds at optimized reaction conditions, which resulted in high product yield. This research addresses a crucial gap in terpene alcohol synthesis, offering a scalable and environmentally friendly approach with broad applicability.

SYNTHESIS OF Ag-MODIFIED TiO2 SOL-GEL FILMS AND ITS APPLICATION AS PHOTOCATALYSTS FOR METHYLENE BLUE DEGRADATION

In the study, the photocatalytic activity of TiO2 films that are created by dip-coating from a sol that contained titanium (IV) isopropoxide, monoethanolamine, and 2-methoxyethanol is demonstrated. Through photo-fixation of Ag (I) ions with varied concentration (10-2 - 10-4 M) in the water phase under UV illumination, the films are subsequently surface-modified with Ag co-catalyst layers. Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Ultraviolet-Visible (UV) Spectroscopy, and Electron Paramagnetic Resonance (EPR) techniques are used to physically characterize the samples. Results reveal that the modification of the co-catalyst had no impact on the thickness and porosity of the films. In addition, the study show that the modified TiO2 films had increased photocatalytic activity. All the characterization methods used have shown the formationof surface - bound Ag (I) species and metallic silver nanoclusters. By measuring the Methylene Blue (MB) dye degradation under UV light illumination, as - prepared and Ag -modified TiO2 films are evaluated for their photocatalytic activity, and the impact of the silver precursor concentration during photo-fixation is investigated.The highest catalytic activity is seen for films that have been modified at a concentration of Ag (I) of 10-2 M. Ordered from highest to lowest, the MB photodegradation rate constants are TiO2 < TiO2 /Ag, 10-4 < TiO2 /Ag, 10-3 < TiO2 / Ag, 10-2.

2D MoS2 nanosheets supported CoFe2O4 nanoparticles mediated persulfate activation for antibiotic removal

Advanced oxidation technology based on persulfate activation has caused extensive concern in the field of wastewater treatment. Nevertheless, this new technology is limited to the low catalytic efficiency and poor recovery of powder catalysts. Herein, we successfully synthesized MoS2 surface-supported CoFe2O4 nanoparticles composite catalyst employing a simple hydrothermal method. Compared with other systems, the performance of TC degradation was significantly improved by CoFe2O4/MoS2/PS system. Additionally, the influence of solution pH, catalyst dosage, PS dosage, and co-existing ions on the degradation process were studied. Both free radical (O2•−, •OH, SO4•−) and non-free radical (1O2) pathways coexisted in the catalytic degradation of TC on the account of radicals quenching experiments and electron spin resonance (ESR) technique. Additionally, the degradation pollutants were confirmed to display obvious decrease in toxicity based on microbial toxicology tests. Besides, CoFe2O4/MoS2 nanocomposite displays good magnetic recovery performance due to the introduction of CoFe2O4. In summary, this research provides a solid foundation for the application of magnetic CoFe2O4/MoS2 nanocomposite in the treatment of antibiotic wastewater.

Effects of polyols at low concentration on the release of sweet aroma compounds in model soda beverages

This study investigated the effect of polyols erythritol, d-mannitol, and maltitol on the volatility of aroma compounds γ-butyrolactone, 3-methyl-1-butanol, and 2-phenylethanol in aqueous solution. Headspace solid-phase microextraction/gas chromatography and diffusion-ordered nuclear magnetic resonance techniques were used to obtain information on aroma–food matrix interaction. Results demonstrated that adding polyols at final low concentrations of 5% or 10% (w/w) to an aqueous solution of 2-phenylethanol reduced the release of vapor-phase aromas, except in the case of 3-methyl-1-butanol, which was not affected by the presence of polyols in the liquid matrix. Polyols also reduced the diffusion coefficients of all three aroma compounds, probably due to friction between the molecules. At low polyol concentrations, aroma compound volatility and diffusion coefficient values were altered compared to those of aromas released from pure water. This observation is related to the physicochemical properties of the aroma compounds. These insights may help guide the use of the combination of aroma compounds and polyols in the formulation of sugar-free and reduced-sugar beverages. Chemical compoundsγ-butyrolactone (PubChem CID: 7302), 3-methyl-1-butanol (PubChem CID: 31260), 2-phenylethanol (PubChem CID: 6054), erythritol (PubChem CID: 222285), d-mannitol (PubChem CID: 6251), maltitol (PubChem CID: 493591).

Efficient synthesis of dihydropyranochromene derivatives via nanocopper immobilized on Zn/Cr-LDH functionalized with poly(p-phenylenediamine)

A new catalyst, poly(p-phenylenediamine) functionalized with copper nanoparticles stabilized on layered double hydroxide (LDH@poly(p-phenylenediamine)@CuI), was prepared. The structure of the new catalyst was identified and confirmed using different analyzes such as FESEM, EDX, XRD, TGA and elemental mapping. The efficiency of the mentioned catalyst was confirmed in the three-component one-pot synthesis of various derivatives of dihydropyrano[3,2-c]chromene in aqueous ethanol solvent. The structure of the synthesized products was confirmed using infrared spectrometry (FT-IR), nuclear magnetic resonance (1H NMR and 13C NMR) and Mass techniques. High yield of products, short reaction time, easy purification, reuse of catalyst, and the use of a soft reaction method can be considered as the main advantages of this method. Additionally, this catalyst was recycled four times without a significant loss of catalytic power.

Improved optical contrast of plasmonic phase change memory using a Fabry-Perot cavity

As a promising technology to realize multilevel, non-volatile data storage and information processing, optical phase change technologies have attracted extensive attention in recent years. However, existing phase-change photonic devices face significant challenges such as limited switching contrast and high switching energy. This study introduces an innovative approach to tackle these issues by leveraging Fabry-Perot (F-P) cavity resonance and plasmon resonance techniques to enhance the modulation effect of phase change materials (PCMs) on the light. To the best of our knowledge, a novel device structure is proposed, featuring an elliptic nano-antenna placed on an F-P cavity waveguide composed of symmetric Bragg grating. This design exploits the enhanced electric field to achieve low power consumption and high contrast. The device enables crucial functions, including read, write, and erase operations, under all light conditions. Through the synergistic utilization of plasma and F-P cavity effects, an ultra-high switching contrast of around 70.6% is achieved. By varying the pulse power or duration, the proportion between the crystalline and amorphous states of the PCMs is altered, consequently modifying its refractive index. With its wide range of applications in optical storage and computing, the device holds significant potential for advancing these fields.

Effect of initial water saturation and water film on imbibition behavior in tight reservoirs using nuclear magnetic resonance technique

Initial water saturation has a significant influence on spontaneous imbibition, and it impacts the imbibition rate and imbibed liquid dynamic distribution among pore networks. At present, the effect of initial water saturation on spontaneous imbibition is still unclear, especially the water film effect caused by initial water saturation varies during imbibition. To address these issues, we prepared the samples with varied initial water saturation through vapor adsorption and then conducted spontaneous imbibitions on these samples, which were monitored by nuclear magnetic resonance (NMR). Samples were selected from tight sandstone reservoirs in the eastern Ordos Basin. From the NMR spectrum corresponding to different imbibition duration, the left wing of the left peak at the initial water saturation is usually higher than the ones after imbibition, mainly caused by the water film effect. When the water film on the surface of large pores is too thin, it is prone to be interpreted as water in small pores because the water film has a quick relaxation time than the water in the center part of pores. The water film effect disappears when the whole pores are filled with water, and the inversed small pores decrease. The relaxation time of the water film is shorter than 0.51 ms in the tested samples. This study is conducive to understanding the effect of initial water saturation on liquid dynamic distribution during imbibition, especially the water film effect variation during imbibition and the T2 value of the water film.

Paramagnetic Effects in NMR Spectroscopy of Transition-Metal Complexes: Principles and Chemical Concepts.

ConspectusMagnetic resonance techniques represent a fundamental class of spectroscopic methods used in physics, chemistry, biology, and medicine. Electron paramagnetic resonance (EPR) is an extremely powerful technique for characterizing systems with an open-shell electronic nature, whereas nuclear magnetic resonance (NMR) has traditionally been used to investigate diamagnetic (closed-shell) systems. However, these two techniques are tightly connected by the electron-nucleus hyperfine interaction operating in paramagnetic (open-shell) systems. Hyperfine interaction of the nuclear spin with unpaired electron(s) induces large temperature-dependent shifts of nuclear resonance frequencies that are designated as hyperfine NMR shifts (δHF).Three fundamental physical mechanisms shape the total hyperfine interaction: Fermi-contact, paramagnetic spin-orbit, and spin-dipolar. The corresponding hyperfine NMR contributions can be interpreted in terms of through-bond and through-space effects. In this Account, we provide an elemental theory behind the hyperfine interaction and NMR shifts and describe recent progress in understanding the structural and electronic principles underlying individual hyperfine terms.The Fermi-contact (FC) mechanism reflects the propagation of electron-spin density throughout the molecule and is proportional to the spin density at the nuclear position. As the imbalance in spin density can be thought of as originating at the paramagnetic metal center and being propagated to the observed nucleus via chemical bonds, FC is an excellent indicator of the bond character. The paramagnetic spin-orbit (PSO) mechanism originates in the orbital current density generated by the spin-orbit coupling interaction at the metal center. The PSO mechanism of the ligand NMR shift then reflects the transmission of the spin polarization through bonds, similar to the FC mechanism, but it also makes a substantial through-space contribution in long-range situations. In contrast, the spin-dipolar (SD) mechanism is relatively unimportant at short-range with significant spin polarization on the spectator atom. The PSO and SD mechanisms combine at long-range to form the so-called pseudocontact shift, traditionally used as a structural and dynamics probe in paramagnetic NMR (pNMR). Note that the PSO and SD terms both contribute to the isotropic NMR shift only at the relativistic spin-orbit level of theory.We demonstrate the advantages of calculating and analyzing the NMR shifts at relativistic two- and four-component levels of theory and present analytical tools and approaches based on perturbation theory. We show that paramagnetic NMR effects can be interpreted by spin-delocalization and spin-polarization mechanisms related to chemical bond concepts of electron conjugation in π-space and hyperconjugation in σ-space in the framework of the molecular orbital (MO) theory. Further, we discuss the effects of environment (supramolecular interactions, solvent, and crystal packing) and demonstrate applications of hyperfine shifts in determining the structure of paramagnetic Ru(III) compounds and their supramolecular host-guest complexes with macrocycles.In conclusion, we provide a short overview of possible pNMR applications in the analysis of spectra and electronic structure and perspectives in this field for a general chemical audience.

Flow Characterization in Fractured Shale Oil Matrices Using Advanced Nuclear Magnetic Resonance Techniques

The evaluation of flow dynamics in fractured shale oil reservoirs presents significant challenges due to the complex pore configurations and high organic material concentration. Conventional methods for petrophysical and fluid dynamic evaluations are insufficient in addressing these complexities. However, nuclear magnetic resonance (NMR) technology is an effective technique for quantitatively delineating fluid micro-transport properties across the reservoir core. This study presents an experimental methodology rooted in NMR technology to quantify the flow capabilities within the shale oil matrix. This approach incorporates high-pressure saturation flow experiments across seven distinct core samples to gauge the micro-transport phenomena of fluids across various pore dimensions. The results revealed that under high-pressure saturation, shale cores devoid of fractures demonstrated an average crude oil saturation rate of merely 19.44%. Cores with evident stratification exhibited a 16.18% increase in flow capacity compared to their non-stratified counterparts. The flow dynamics within these shale reservoirs exhibited a range of behaviors, from non-linear to linear. In lower-permeability zones, non-linear patterns became increasingly apparent. An NMR T2 spectrum analysis was used to identify the minimum effective pore size conducive to shale oil flow within the matrix, which was between 8 and 10 nanometers. These insights provide a foundation for a deeper understanding of the mechanisms behind oil and gas migration in fractured shale oil matrices, offering valuable insight into their extractive potential.

PINK: a tender X-ray beamline for X-ray emission spectroscopy.

A high-flux beamline optimized for non-resonant X-ray emission spectroscopy (XES) in the tender X-ray energy range has been constructed at the BESSY II synchrotron source. The beamline utilizes a cryogenically cooled undulator that provides X-rays over the energy range 2.1 keV to 9.5 keV. This energy range provides access to XES [and in the future X-ray absorption spectroscopy (XAS)] studies of transition metals ranging from Ti to Cu (Kα, Kβ lines) and Zr to Ag (Lα, Lβ), as well as light elements including P, S, Cl, K and Ca (Kα, Kβ). The beamline can be operated in two modes. In PINK mode, a multilayer monochromator (E/ΔE ≃ 30-80) provides a high photon flux (1014 photons s-1 at 6 keV and 300 mA ring current), allowing non-resonant XES measurements of dilute substances. This mode is currently available for general user operation. X-ray absorption near-edge structure and resonant XAS techniques will be available after the second stage of the PINK commissioning, when a high monochromatic mode (E/ΔE ≃ 10000-40000) will be facilitated by a double-crystal monochromator. At present, the beamline incorporates two von Hamos spectrometers, enabling time-resolved XES experiments with time scales down to 0.1 s and the possibility of two-color XES experiments. This paper describes the optical scheme of the PINK beamline and the endstation. The design of the two von Hamos dispersive spectrometers and sample environment are discussed here in detail. To illustrate, XES spectra of phosphorus complexes, KCl, TiO2 and Co3O4 measured using the PINK setup are presented.

NMR-based pore water distribution characteristics of silty clay during the soil compaction, saturation, and drying processes

The pore water distribution (PWD) of soil provides key information about soil shear strength, hydraulic conductivity, and water-retention ability. The PWD characteristics of the soil depend on the specimen preparation conditions (i.e., the variations in initial water content or compaction degree) and drying-wetting processes, which were investigated by using the nuclear magnetic resonance (NMR) technique. The NMR T2 spectrum is mathematically transformed into the PWD curve to more accurately quantify the variations in pore water content stored with pores of different radii. The pore water in silty clay can be categorized into strongly bound water, intra-aggregate pore water, and inter-aggregate pore water, which are identified by the pore radius of <0.05 μm, 0.05-1.0 μm and >1.0 μm, respectively. The effects of compaction degree and initial water content on the PWD of the soil exhibit distinctions. For unsaturated compacted specimens, the PWDs remain unaffected by changes in compaction degree, while an increase in initial water content promotes the formation of clay aggregates, thereby increasing the maximum water-holding pore radius and the intra-aggregate pore water content. For saturated compacted specimens, the inter-aggregate and intra-aggregate pore water content increases with a decrease in the compaction degree, while the changes in the PWD shape from unimodal to bimodal with an increase in the initial water content. During the soil drying process, inter-aggregate pore water is rapidly drained, the intra-aggregate dominant pore water content increases first and then decreases, and the strongly bound water content remains constant. The relationship between the cumulative pore water distribution curve and the soil-water characteristic curve (SWCC) can be established through the Young-Laplace theory. The SWCC can be well predicted by using the envelope of the cumulative pore water distribution curves during soil drying.

High spatial resolution surface plasmon resonance imaging using a plasmonic chip.

The surface plasmon resonance (SPR) technique has been widely applied to biosensing technologies for the rapid quantification of biomolecules without enzyme and fluorescent labeling. However, the conventional prism-coupling SPR method generally has a detection area of a few mm2, and the large contribution of the background signal forms a barrier to highly sensitive detection. Based on a highly spatially resolved SPR method, the present study constructed a scanning GC-SPR imaging instrument using an objective lens with a high numerical aperture and a plasmonic chip that could be used for grating-coupled SPR. Focusing light on the diffraction limit can suppress background signals and improve detection sensitivity. SPR imaging can also be performed by scanning a focal spot. Using this method, the refractive index of a mixture of water and dimethyl sulfoxide was measured with a detection accuracy of 2.43 × 10-3 RIU. Polydopamine films prepared with a thickness of <5nm were also measured, and each film thickness was evaluated with high sensitivity from the effective refractive index detected in a small area of <1 µm2.

Carbon capture in polymer-based electrolytes.

Nanoparticle organic hybrid materials (NOHMs) have been proposed as excellent electrolytes for combined CO2 capture and electrochemical conversion due to their conductive nature and chemical tunability. However, CO2 capture behavior and transport properties of these electrolytes after CO2 capture have not yet been studied. Here, we use a variety of nuclear magnetic resonance (NMR) techniques to explore the carbon speciation and transport properties of branched polyethylenimine (PEI) and PEI-grafted silica nanoparticles (denoted as NOHM-I-PEI) after CO2 capture. Quantitative 13C NMR spectra collected at variable temperatures reveal that absorbed CO2 exists as carbamates (RHNCOO- or RR'NCOO-) and carbonate/bicarbonate (CO32-/HCO3-). The transport properties of PEI and NOHM-I-PEI studied using 1H pulsed-field-gradient NMR, combined with molecular dynamics simulations, demonstrate that coulombic interactions between negatively and positively charged chains dominate in PEI, while the self-diffusion in NOHM-I-PEI is dominated by silica nanoparticles. These results provide strategies for selecting adsorbed forms of carbon for electrochemical reduction.

Magnetic Resonance Study of Bulky CVD Diamond Disc.

Diamonds produced using chemical vapor deposition (CVD) have found many applications in various fields of science and technology. Many applications involve polycrystalline CVD diamond films of micron thicknesses. However, a variety of optical, thermal, mechanical, and radiation sensing applications require more bulky CVD diamond samples. We report the results of a magnetic resonance and structural study of a thick, sizable polycrystalline CVD diamond disc, both as-prepared and treated with e-beam irradiation/high-temperature annealing, as well as gamma irradiation. The combination of various magnetic resonance techniques reveals and enables the attribution of a plentiful collection of paramagnetic defects of doublet and triplet spin origin. Analysis of spectra, electron, and nuclear spin relaxation, as well as nuclear spin diffusion, supports the conclusion of significant macro- and micro-inhomogeneities in the distribution of nitrogen-related defects.

Periodate activation by MnFe2O4 spinel for sulfamethoxazole degradation: Iodate radical dominance, degradation pathway, DFT calculation and toxicity assessment

This study synthesized spinel MnFe2O4 at different temperatures, which was applied to activate periodate (PI) for sulfamethoxazole (SMX) degradation. It was found that the 500-MFO (MnFe2O4 calcined at 500 ℃) demonstrated superior activity in PI activation, with notable sustainability but strong substrate selectivity. Furthermore, a comprehensive analysis, including quenching experiment, electron paramagnetic resonance (EPR) technique, X-ray photoelectron spectroscopy (XPS) analysis, metal ions leaching detection, homogeneous PI activation, and methyl phenyl sulfoxide (PMSO) probe test, revealed that homo- and heterogeneous pathways as well as free and non-free radical routes coexisted in the 500-MFO/PI system. Multiple active species, including iodate radical (IO3•), hydroxyl radical (•OH), superoxide radical (O2•-), singlet oxygen (1O2), and Mn(IV) were identified, with IO3• from heterogeneous activation being the primary species. When PMSO and SMX coexisted, PMSO could react with Mn(IV), promoting the regeneration of Mn reaction sites and the production of IO3•, thereby being beneficial for the degradation of SMX. The degradation pathways of SMX were elucidated through high-performance liquid chromatography-mass spectrometry (HPLC-MS) and density functional theory (DFT) calculation. The acute and chronic toxicity of thirteen by-products to aquatic organisms were predicted using the Ecological Structure Activity Relationships (ECOSAR) software, with the corresponding results revealing that although the toxicity of intermediates fluctuated, the final products were environmentally benign. Therefore, this investigation provides a viable method for SMX degradation in wastewater treatment.

Grey modeling study on mechanical properties and pore structure of concrete with different basalt fiber contents based on NMR

This paper investigates the correlation between strength and pore characteristics of basalt fiber-reinforced concrete (BFRC) with different fiber contents and establishes a link between meso- and macro-properties. The research focuses on BFRC with differing fiber contents, analyzing compressive strength, flexural strength, and splitting tensile strength across eight admixture levels (ranging from 0 % to 0.35 %). Using the nuclear magnetic resonance (NMR) technique, T2 spectra of BFRC with varying fiber contents are obtained, deriving curves of the pore distribution. Additionally, considering the parameters of different pore size proportions, the paper delves into analyzing the impact of pore structure on BFRC's distinct mechanical properties using grey correlation. Utilizing the optimal pore structure parameters derived from GCA to forecast different strengths, this study establishes GM(1,3) prediction models for three strengths, respectively. The results showed that basalt fibers can enhance concrete strength. And, 0.25 % basalt fibers optimize concrete's the inner structure of BFRC by decreasing harmful pores. The comprehensive correlation between pore parameters and BFRC strength ranges significantly indicating a notable relationship between strength and pore alterations. The compressive strength was most related to the total porosity and the proportion of non-harmful pores, and the splitting tensile and flexural strengths were related to the fractal dimension and porosity of the harmful pores as well as to the total and non-harmful porosity, respectively. A BFRC strength prediction model formula was developed based on the most relevant pore structure parameters derived from GCA. This calculation formula showcases a high accuracy in predicting BFRC strength, establishing a mesoscopic-to-macroscopic quantitative relationship that effectively informs the production and application of BFRC.

Whole‐brain deuterium metabolic imaging via concentric ring trajectory readout enables assessment of regional variations in neuronal glucose metabolism

Whole‐brain deuterium metabolic imaging via concentric ring trajectory readout enables assessment of regional variations in neuronal glucose metabolism

Cell wall water induced dimensional changes of beech and pine wood

Hygroexpansion in timber construction is a phenomenon that occurs as a result of changes in the cell wall structure of wood caused by water. In this study, beech (Fagus sylvatica) and pine (Pinus taeda L.) wood were conditioned at different relative humidities with saturated salt solutions and saturated through vacuum pressure impregnation. The moisture content and dimensions of the samples were evaluated under various adsorption equilibrium states, as well as during drying from water saturation to an air-dried state. The results obtained using the two-dimensional time-domain nuclear magnetic resonance technique revealed two distinct types of cell wall water in both wood species, designated as B-water and C-water, as they displayed different mobilities. With increasing moisture content, the mobility of cell wall water increased; however, B-water maintained a constant level of mobility and formed water clusters when it accumulated in the high humidity region and at slightly above the fiber saturation point (FSP), which is evidence of the occurrence of free-bound water. The B-water, located in the amorphous region of microfibrils and their surrounding hemicellulose, exerted a predominant influence on the dimensional changes of the wood both under equilibrium and nonequilibrium conditions, in comparison to the C-water which located in the matrix of hemicellulose and lignin.