Search Results (7,284)

The real-time measurement of the content of impurities such as iron and aluminium ions is one of the keys to quality evaluation in the production process of high-purity lithium carbonate; however, impurity detection has been a time-consuming process for many years, which limits the optimisation of the production of high-purity lithium carbonate. In this context, this work explores the possibility of using water-soluble fluorescent probes for the rapid detection of impurity ions. Salicylaldehyde was modified with the hydrophilic group dl-alanine to synthesise a water-soluble Al³⁺ fluorescent probe (Probe A). Moreover, a water-soluble Fe³⁺ fluorescent probe (Probe B) was synthesised from coumarin-3-carboxylic acid and 3-hydroxyaminomethane. Probe A and Probe B exhibited good stability in the pH range of 4–9 in aqueous solutions, high sensitivity, as well as high selectivity for Al³⁺ and Fe³⁺; the detection limits for Al³⁺ and Fe³⁺ were 1.180 and 1.683 μmol/L, whereas the response times for Al³⁺ and Fe³⁺ were as low as 10 and 30 s, respectively. Electrostatic potential (ESP) analysis and density functional theory calculations identified the binding sites and fluorescence recognition mechanism; theoretical calculations showed that the enhanced fluorescence emission of Probe A when detecting Al³⁺ was due to the excited intramolecular proton transfer (ESIPT) effect, whereas the fluorescence quenching of Probe B when detecting Fe³⁺ was due to the electrons turning off fluorescence when binding through the photoelectron transfer (PET) mechanism. Full article

Here we describe the synthesis and evaluation of a molecular corrosion sensor that can be applied in situ in aerospace coatings, then used to detect corrosion after the coating has been applied. A pH-sensitive molecule, 4-mercaptopyridin (4-MP), is attached to a gold nanoparticle to allow surface-enhanced Raman-scattering (SERS) for signal amplification. These SERS nanoparticles, when combined with an appropriate micron-sized carrier system, are incorporated directly into an MIL-SPEC coating and used to monitor the process onset and progression of corrosion using pH changes occurring at the metal–coating interface. The sensor can track corrosion spatially as it proceeds underneath the coating, due to the mobility of the proton front generated during corrosion and the homogeneous distribution of the sensor in the coating layer. To our knowledge, this report is the first time a 4-MP functionalized gold nanoparticle has been used, along with SERS spectroscopy, to monitor corrosion in an applied commercial coating in a fast, non-contact way. Full article

Stimulus-responsive luminescent materials are pivotal in the field of sensing. Fluorescent transition metal complexes with a charge transfer excited state, especially terpyridine-coordinated polymers, are of particular interest due to their tunable emission. In this paper, a novel bis-terpyridine ligand was synthesized and assembled into a coordination polymer, which showed intense visible light absorption and fluorescence emission in the solid state that could be regulated by an acidic or basic pH. After being protonated by acid, the fluorescence of the polymer P2 was quenched. The emission of the polymer split from 635 nm to two peaks of 674 and 440 nm, and then stabilized at 728 nm for 7 days, which showed a significant red-shift and good protonation stability. The fluorescence emission wavelength of the protonated polymers recovered after alkalization, and the fluorescence intensity of the polymer was greatly improved after alkalization, showing interesting acid–base-response luminescence characteristics. The sensitive response of the synthesized coordination polymers to acids and bases will contribute to expanding the application of linear coordination polymers in sensing and other fields. Full article

PEMFCs’ operation entails the presence of heterogeneities in the generation of current, heat and water along the active surface area. Indeed, PEMFCs are open systems, and as such, operating heterogeneities are inherent to their operation. A review of the literature reveals numerous attempts to achieve uniform current density distribution. These attempts are primarily focused on bipolar plate design and operating conditions, with the underlying assumption that uniform current density correlates with enhanced performance. Most studies focus on the influence of gas flow-field design and inlet hydrogen and air flow conditioning, and less attention has been paid to the coolant operating condition. However, uncontrolled temperature distribution over a large cell active surface area can lead to performance loss and localized degradations. On this latter point, we notice that studies to date have been confined to a narrow range of operating conditions. It appears that complementary durability studies are needed in order to obtain in-depth analyses of the coupled influence of temperature distribution and gas humidification in large PEMFCs. Full article

A computational study of X-H···Y binary hydrogen-bonded complexes was undertaken to examine the red- and blue-shifting behavior of three model X-H proton donors interacting with a series of Lewis bases: Y = NH₃, NCLi, NCH, NCF, C₂H₂, BF, CO, N₂ and Ne. Two of these proton donors, FArH and F₃CH, have blue-shifting tendencies, while the third, FH, has red-shifting tendencies. A perturbation theory model for frequency shifts that was derived many years ago was employed to partition the predicted frequency shift into the sum of two components, one dependent on the second derivative of the interaction energy with respect to X-H displacement and the other dependent on the X-H bond length change in the binary complex. The predicted shifts were found to be in good agreement with standard ab initio computations, but they were obtained at much lower computational cost. The change in the infrared intensity of the X-H stretching frequency, expressed as a ratio of complex to monomer intensities, was also investigated, along with its relation to the X-H permanent dipole moment derivative and total induced dipole moment derivative with respect to X-H displacement, and used to rationalize the observed infrared intensity changes in the red- and blue-shifted X-H···Y complexes. Full article

The role of pre-plasma in the efficient generation of protons by intense laser-matter interaction from structured targets is investigated. Optimal energy coupling between laser and plasma is found by varying the fluence and arrival time of an independently controllable ultrashort pre-pulse with respect to the main interaction pulse. The coupling is evaluated based on the energy of the accelerated protons. The accelerated proton energy is maximized at optimal pre-pulse delay and fluence conditions. Plasma emission spectrum and Particle-in-Cell simulations provide a possible explanation of the obtained experiment results. Full article

Catalyzing hydrogen evolution reaction (HER) is a key process in high-efficiency proton exchange membrane water electrolysis (PEMWE) devices. To replace the use of Pt-based HER catalyst, tungsten carbide (W₂C) is one of the most promising non-noble-metal-based catalysts with low cost, replicable catalytic performance, and durability. However, the preparation access to scalable production of W₂C catalysts is inevitable. Herein, we introduced a facile protocol to achieve the tungsten carbide species by plasma treatment under a CH₄ atmosphere from the WO₃ precursor. Moreover, the heterogeneous structure of the tungsten carbide/tungsten oxide nanosheets further enhances the catalytic activity for HER with the enlarged specific surface area and the synergism on the interfaces. The prepared tungsten carbide/tungsten oxide heterostructure nanosheets (WO_3-x-850-P) exhibit exceptional HER catalytic activity and stable longevity in acid electrolytes. This work provides a facile and effective method to construct high-performance and non-precious-metal-based electrocatalysts for industrial-scale water electrolysis. Full article

Background/Objectives: This study investigated the potential chemopreventive role of proton pump inhibitor (PPI) use in relation to the occurrence of head and neck cancer (HNC) within a national cohort amid concerns of PPI overprescription. Methods: From a cohort of 1,137,861 individuals and 219,673,817 medical claim records collected between 2005 and 2019, 1677 HNC patients were identified and matched 1:4 with 6708 controls after adjusting for covariates. Odds ratios (ORs) for PPI use and its duration in relation to HNC and its subsites were estimated using propensity score overlap-weighted multivariable logistic regression. Additional subgroup analyses were performed based on age, sex, income level, and geographic region. Results: In the crude model, both current (OR 7.85 [95% CI 6.52–9.44]) and past PPI (OR 1.44 [95% CI 1.23–1.70]) use were associated with increased odds for HNC. However, after overlap weighting, this association reversed for both current (aOR 0.14 [95% CI 0.11–0.17]) and past PPI (aOR 0.69 [95% CI 0.60–0.79]). Subsite analysis showed reduced odds for hypopharyngeal (aOR 0.33, [95% CI 0.25–0.43]) and laryngeal cancer (aOR 0.19 [95% CI 0.16–0.22]) in current PPI users and similar results for past users. Conclusions: This study suggests a potential chemopreventive effect of PPIs, particularly in hypopharyngeal and laryngeal cancers. Additional studies are required to investigate the mechanisms underlying the association of the development of HNC with PPI use. Full article

It is known that ultrashort echo time (UTE) magnetic resonance imaging (MRI) sequences can detect signals from water protons but not collagen protons in short T2 species such as cortical bone and tendons. However, whether collagen protons are visible with the zero echo time (ZTE) MRI sequence is still unclear. In this study, we investigated the potential of the ZTE MRI sequence on a clinical 3T scanner to directly image collagen protons via D₂O exchange and freeze-drying experiments. ZTE and UTE MRI sequences were employed to image fully hydrated bovine cortical bone (n = 10) and human patellar tendon (n = 1) specimens. Then, each specimen was kept in a 30 mL syringe filled with D₂O solution for two days. Fresh D₂O was flushed every 2 h to reach a more complete D₂O–H₂O exchange. Later, the samples were lyophilized for over 40 h and then sealed in tubes. Finally, the samples were brought to room temperature and visualized using the identical 3D ZTE and UTE sequences. All hydrated bone and tendon specimens showed high signals with ZTE and UTE sequences. However, all specimens showed zero signal after the D₂O exchange and freeze-drying procedures. Therefore, similar to UTE imaging, the signal source in ZTE imaging is water. The ZTE sequence cannot directly detect signals from collagen protons in bone and tendons. Full article

Ab initio calculations of cross sections for electron capture by protons in collisions with CO₂ are carried out at energies between 100 eV/u and 50 keV/u, employing a semiclassical method within the Franck–Condon framework. The scattering wave function is expanded in a set of ab initio electronic wave functions of the HCO₂⁺ supermolecule. The calculation is performed on several trajectory orientations to obtain orientation-averaged total cross sections. A two-state model with an exponential interaction between the entrance and the lowest charge transfer channel is proposed to describe the main aspects of the charge transfer process and to estimate the precision of the molecular expansion. The symmetry of the HOMO ${\pi }_g$ of CO₂ is relevant to choose the signs of the molecular functions and to set up the orientation average of the cross sections. Very good agreement is found with the experimental charge transfer cross sections. Full article

Highly active antiretroviral therapy has led to a significant increase in the life expectancy of people living with HIV. The trade-off is that HIV-infected patients often suffer from comorbidities that require additional treatment, increasing the risk of Drug-Drug Interactions (DDIs), the clinical relevance of which has often not been determined during registration trials of the drugs involved. Therefore, it is important to identify potential clinically relevant DDIs in order to establish the most appropriate therapeutic approaches. This review aims to summarize and analyze data from studies published over the last two decades on DDI-related adverse clinical outcomes involving anti-HIV drugs and those used to treat comorbidities. Several studies have examined the pharmacokinetics and tolerability of different drug combinations. Protease inhibitors, followed by nonnucleoside reverse transcriptase inhibitors and integrase inhibitors have been recognized as the main players in DDIs with antivirals used to control co-infection, such as Hepatitis C virus, or with drugs commonly used to treat HIV comorbidities, such as lipid-lowering agents, proton pump inhibitors and anticancer drugs. However, the studies do not seem to be consistent with regard to sample size and follow-up, the drugs involved, or the results obtained. It should be noted that most of the available studies were conducted in healthy volunteers without being replicated in patients. This hampered the assessment of the clinical burden of DDIs and, consequently, the optimal pharmacological management of people living with HIV. Full article

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of liver-related morbidity and mortality. Although the invasive liver biopsy remains the golden standard for MASLD diagnosis, Magnetic Resonance Imaging-derived Proton Density Fat Fraction (MRI-PDFF) is an accurate, non-invasive method for the assessment of treatment response. This study aimed at developing a Polygenic Risk Score (PRS) to improve MRI-PDFF prediction using UK Biobank data to assess an individual’s genetic liability to MASLD. Methods: We iteratively sequestered 10% of MRI-PDFF samples as a validation set and split the rest of each dataset into base and target partitions, containing GWAS summary statistics and raw genotype data, respectively. PRSice2 was deployed to derive PRS candidates. Based on the frequency of SNP appearances along the PRS candidates, we generated different SNP sets according to variable frequency cutoffs. By applying the PRSs to the validation set, we identified the optimal SNP set, which was then applied to a Greek nonalcoholic fatty liver disease (NAFLD) study. Results: Data from 3553 UK Biobank participants yielded 49 different SNP sets. After calculating the PRS on the validation set for every SNP set, an optimal PRS with 75 SNPs was selected (incremental R² = 0.025, p-value = 0.00145). Interestingly, 43 SNPs were successfully mapped to MASLD-related known genes. The selected PRS could predict traits, like LDL cholesterol and diastolic blood pressure in the UK Biobank, as also disease outcome in the Greek NAFLD study. Conclusions: Our findings provide strong evidence that PRS is a powerful prediction model for MASLD, while it can also be applied on populations of different ethnicity. Full article

Using the framework of an investigation of the stimuli-responsive behavior of peptide assembly on a solid surface, this study on the behavior of a chemisorbed peptide on a gold surface was performed. The studied peptide is a dimeric form of the antimicrobial peptide Trichogin GAIV, which was also modified by substituting the glycine with lysine residues, while the N-terminus octanoyl group was replaced by a lipoic one that was able to bind to the gold surface. In this way, a chemically linked peptide assembly that is pH-responsive was obtained because of the protonation/deprotonation of the sidechains of the Lys residues. Information about the effect of protonation/deprotonation equilibria switching the pH from acid (pH = 3) to basic (pH = 11) conditions was obtained macroscopically by performing Quartz crystal microbalance with dissipation monitoring (QCM-D), Surface Plasmon Resonance (SPR), Nanoplasmonic Sensing (NPS), and FTIR techniques. Using molecular dynamics (MD) simulations, it is possible to explain, at the molecular level, our main experimental results: (1) pH changes induce a squeezing behavior in the system, consisting in thickness and mass variations in the peptide layer, which are mainly due to the pH-driven hydrophilic/hydrophobic character of the lysine residues, and (2) the observed hysteresis is due to small conformational rearrangements from helix to beta sheets occurring mainly on the first half of the peptide, closer to the surface, while the second half remains almost unaffected. The latter result, together with the evidence that the layer thickness is not simply double the assembly of the monomeric analog, indicates that the dimeric peptide does not behave as a double monomer, but assumes very peculiar features. Full article

Hydrogen-bonded organic framework (HOF) materials are typically formed by the self-assembly of small organic units (synthons) with specific functional groups through hydrogen bonding or other interactions. HOF is commonly used as an electrolyte for batteries. Well-designed HOF materials can enhance the proton exchange rate, thereby boosting battery performance. This paper reviews recent advancements in the continuous synthesis of HOF synthons, in the continuous synthesis of HOF’s unit small molecules enabling the multi-step, rapid, and in situ synthesis of synthons, such as carboxylic acid, diaminotriazine (DAT), urea, guanidine, imidazole, pyrazole, pyridine, thiazole, triazole, and tetrazole, with online monitoring. Continuous flow reactors facilitate fast chemical reactions and precise microfluidic control, offering superior reaction speed, product yield, and selectivity compared to batch processes. Integrating the continuous synthesis of synthons with the construction of HOF materials on a single platform is essential for achieving low-cost, safe, and efficient processing, especially for reactions involving toxic, flammable, or explosive substances. Full article

Microbubbles have been applied in various fields. In the mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, which results in reducing the damage. Recently, when the proton beam power was increased and the number of injected gas bubbles was increased, unique damage morphologies were observed on the solid–liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage, i.e., the directions of streak-like defects which are formed by connecting the pit damage coincides with the direction of the gas bubble trajectories, and the distances between the pits was understandable when taking the natural period of gas bubble vibration into account. This indicates that gas microbubbles, used to reduce macroscopic pressure waves, have the potential to be inceptions of cavitation damage due to the microscopic pressure emitted from these gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles: reducing macroscopic pressure waves and reducing the microscopic pressure due to bubble dynamics. Full article