Search Results (3,216)

This study aims to investigate the oxidative pyrolysis of biomass volatiles with a particular focus on the formation of liquid products. Furfural, hydroxyacetone, and 3,4-dimethoxybenzaldehyde were chosen as volatile model compounds. The impacts of the oxygen equivalence ratio (ER, 0–15%) and temperature (400–500 °C) on the product composition and distribution were examined using a two-stage quartz-tube reactor. The results showed that volatile pyrolysis was limited at the lower temperature of 400 °C even with oxygen introduction, while it could be significantly promoted at 500 °C as illustrated by the observed great decrease in the GC-MS peak areas of the volatile compounds especially under an oxidative atmosphere. For instance, the peak area of 3,4-dimethoxybenzaldehyde at 500 °C under an ER of 4% was only ~9% of that at 400 °C. Oxygen introduction enhanced the volatile decomposition with the formation of mainly permanent gases (although not given in the study) rather than liquid products, but distinct impacts were obtained for varied volatile compounds possibly due to their different chemical structures and autoignition temperatures. From the perspective of liquid product formation, furfural would undergo the cleavage of C-C/C-O bonds to form linear intermediates and subsequent aromatization to generate aromatics (benzene and benzofuran). The presence of oxygen could enhance the oxidative destruction of the C-C/C-O bonds and the removal of O from the molecules to form simple aromatics such as benzene, phenol, and toluene. Hydroxyacetone mainly underwent C-C/C-O cleavage that was further enhanced in the presence of oxygen; the resultant intermediates would recombine to generate acetoin and 2,3-pentanedione. A higher ER would directly oxidize the alcoholic hydroxyl group (-OH) into an aldehyde group (-CHO) to form methyl glyoxal, while 3,4-dimethoxybenzaldehyde mainly underwent cleavage and recombination of bonds connected with the benzene ring including aldehyde group (-CHO), C_Ar-O, C_Methoxy-O bonds, thus forming 1,2-dimethoxybenzene, toluene, and 3-hydroxybenzadehyde. This study provides more fundamental insights into the homogeneous oxidation of volatiles during the oxidative fast pyrolysis of biomass, facilitating the deployment of this technology. Full article

Various forms of alumina have attracted considerable attention for their ability to remove anionic dyes from wastewater, attributed to their high specific surface area, and environmental safety. In this study, a series of modified alumina materials were synthesized for the first time using the reverse precipitation method with dual aluminum sources and without template agent to explore their applicability in various scenarios, including adsorption processes and regeneration cycles. The results revealed that non-modified alumina exhibited superior adsorption properties, while silicon-modified alumina demonstrated exceptional thermal stability during high temperature calcination. For silicon-modified alumina, the replacement of some Al–OH groups with silicon resulted in the formation of a protective silicon layer on the alumina surface, which delayed the sintering process. The pseudo-second-order kinetic model and Langmuir model were utilized to fit the experimental data. Furthermore, the adsorption and regeneration properties of silicon-modified alumina were investigated, revealing a maximum equilibrium adsorption capacity of 822.6 mg/g for Congo Red using non-modified alumina. Notably, the non-modified alumina demonstrated a 40.6% increase in its adsorption capacity compared to its initial capacity after six regeneration cycles at 1000 °C. Full article

During the thermal treatment of kaolinite, the main mineral phase in kaolin rock, dehydroxylation occurs, forming metakaolin through a process that has significant industrial applications. This study experimentally analyzed dehydroxylation in two kaolinite samples: a well-crystallized reference sample from the Clay Mineral Society and a locally sourced, industrial kaolin sample. The mechanism and kinetic parameters were evaluated from a series of thermogravimetric measurements. Non-isothermal kinetic analysis revealed that dehydroxylation followed a third-order (F3) reaction mechanism, with activation energies ($E_a$) ranging from 35 to 60 kcal/mol. Additionally, theoretical calculations based on Density Functional Theory were performed on four systems in which a water molecule was removed by combining OH group and H atom vacancies in the kaolinite unit cell. These models represented the onset of dehydroxylation and provided values for the reaction energy Q from first-principles calculations, which served as reference values for $E_a$. The results confirm that water molecule formation involving both OH at the kaolinite outer surface and inner surface are energetically competitive and highlight the crucial role of structural relaxations following water removal to determine Q values in the range of 30–50 kcal/mol, in very good agreement with the experiments. Full article

n-Octanol and related ether alcohols are studied via molecular dynamics (MD) simulations using the two classical all-atom force fields OPLS-AA and CHARMM. The ether alcohols studied possess one ether functionality separated by varying n carbon atoms from the hydroxy group to elucidate how the positioning of the ether functionality affects intra- and intermolecular hydrogen bonding and, in turn, the physical properties of the studied alcohols. Important general trends observed from simulations with both force fields include the following: Intramolecular hydrogen bonding is majorly present in 3-butoxypropanol and 4-propoxybutanol (n = 3 and 4) while being only marginally present for 5-ethoxypentanol and 6-methoxyhexanol (n = 5 and 6) and absent in 1-hexyloxymethanol and 2-pentyloxyethanol (n = 1 and 2). The intramolecular hydrogen bonds formed by 3-butoxypropanol and 4-propoxybutanol are among the most stable ones of all present hydrogen bonds. Intermolecular hydrogen bonding is stronger between hydroxy groups (OH-OH) than between hydroxy and ether groups (OH-OE). An increased temperature causes a reduction in intermolecular OH-OH and OH-OE hydrogen bonding but a slight increase in intramolecular hydrogen bonding. A reduction in end-to-end distances at a higher temperature is also observed for all studied alcohols, which is likely a reflection of increased dihedral bond rotations. Hydrogen bonding extends mostly between just two molecules while hydrogen bonding networks are rare but do exist, involving, in some instances, up to 30 hydrogen bonds. Regardless of force field and temperature, the obtained radial distribution functions (RDFs) mostly show the same features at same distances that only vary in their intensity. 1-hexyloxymethanol forms a very specific and stable intermolecular double OH-OE hydrogen-bonded dimer. Similar double-hydrogen-bonded dimers can be found for the ether alcohols but are only significantly present for 2-pentyloxyethanol. Overall, the main difference between OPLS-AA and CHARMM is their quantitative prediction of the present hydrogen bonding speciation largely due to the stiffer dihedral potentials in OPLS-AA compared to the CHARMM force field. The simulations indicate that (a) the variations in densities are correlated to the reduced packing efficiency caused by intramolecular hydrogen bonding, (b) self-diffusion correlates with the stability of the intermolecular hydrogen bonds, and (c) the presence of hydrogen-bonded networks, although small in numbers, affect the viscosity. Full article

Background and Aims: Preterm newborns are particularly susceptible to hypovitaminosis D, potentially impairing bone mineralization. In Thailand, data on its prevalence and standardized supplementation protocols remain limited. This study aimed to compare the efficacy of two vitamin D3 dosages (400 IU/day vs. 800 IU/day) in improving serum vitamin D concentrations and metabolic bone parameters in preterm newborns. Methods: A randomized controlled trial was conducted in preterm newborns born at ≤32 weeks’ gestation or with birth weight ≤1500 g. Preterm newborns were randomized to receive either 400 IU or 800 IU/day of vitamin D3. Serum 25-hydroxyvitamin D (25(OH)D) was measured using electrochemiluminescence immunoassay (ECLIA). Metabolic bone parameters—including calcium, phosphorus, alkaline phosphatase, and albumin—were assessed at baseline and again at six weeks of age. Results: Of the 38 enrolled infants, baseline 25(OH)D levels were comparable between groups (14.8 ± 4.8 ng/mL in the 800 IU/day group vs. 14.7 ± 6.9 ng/mL in the 400 IU/day group). At six weeks, the 800 IU group demonstrated significantly higher 25(OH)D levels (47.3 ± 21.0 ng/mL vs. 32.0 ± 14.2 ng/mL; p = 0.013), with a large effect size (Cohen’s d = 0.85) and the difference-in-differences of +15.7 ng/mL. The prevalence of hypovitaminosis D declined from 89% to 5% in the 800 IU/day group and from 74% to 32% in the 400 IU/day group (p = 0.036). No significant differences in metabolic bone parameters or signs of toxicity were observed. Conclusions: Vitamin D3 supplementation at 800 IU/day significantly improved vitamin D status and reduced hypovitaminosis D in preterm newborns, without observed toxicity. Full article

Metal–organic frameworks (MOFs), formed by the self-assembly of metal ions/clusters and organic linkers, have attracted considerable attention due to their well-exposed active sites, exceptionally high porosity, and diversified pore architectures. MOF-derived materials obtained through high-temperature pyrolysis or composite structural design not only inherit the porous framework advantages of their precursors but also demonstrate significantly enhanced electrical conductivity and structural stability via the formation of carbon-based frameworks and in situ transformation of metallic species. However, conventional MOF-derived materials struggle to address persistent technical challenges in contemporary energy storage systems, particularly those requiring ultralong cycling stability and ultrahigh-rate capability under practical operating conditions. The integration of MXene, characterized by its abundant surface functional groups (-O, -OH, -F) and exceptional electrical conductivity, with MOF-derived materials presents a viable strategy to address these challenges. Multidimensional nanocomposites constructed through in situ growth and self-assembly techniques synergistically integrate MXene’s conductive network scaffolding effect with the structural tunability of MOF-derived frameworks. This unique architecture enables the following: (i) enhanced exposure of electroactive sites, (ii) optimized ion diffusion kinetics, (iii) mechanical integrity maintenance, collectively boosting the applicability of MXene/MOF hybrids in advanced energy storage systems. This review summarizes the synthesis methods, energy storage performance, and applications of multidimensional nanostructured MXene/MOF-derived composites. Finally, it discusses the opportunities and challenges for MXene/MOF-derived composites in future energy storage applications. Full article

For the interaction of angiotensin II (AngII) with AngII type 1 receptors (AT₁R), two potential proton hopping pathways have been identified, each associated with distinct physiological outcomes. The octapeptide AngII (Asp¹-Arg²-Val³-Tyr⁴-Ile⁵-His⁶-Pro⁷-Phe⁸) appears to form a charge relay system (CRS) in solution in which the C-terminal carboxylate abstracts a proton from the His⁶ imidazole group, which, in turn, abstracts a proton from the Tyr⁴ hydroxyl (OH) group, creating a tyrosinate anion. When AngII binds to the AT₁R, the CRS can be reconstituted with D281 of the receptor taking up the role of the Phe⁸ carboxylate in the tripartite interaction, whilst the Phe⁸ carboxylate forms a salt bridge with K199 of the receptor. As a consequence, the Tyr⁴ OH of AngII is positioned with accessibility to either the Phe⁸ carboxylate (bound to K199) or the His⁶ imidazole (activated by D281), thereby creating a potential gating mechanism for AT₁R receptor signaling. This study summarizes evidence based on structure activity data for various analogs wherein Tyr⁴ OH interaction with His⁶ imidazole (CRS formation) leads to G protein sequestration and vasoconstriction, whereas Tyr⁴ OH interaction with Phe⁸ carboxylate (bound to K199) engenders arrestin-mediated vasodilation and receptor desensitization. These findings, combined with quantum mechanical (semiempirical) calculations of CRS proton transfer presented herein, provide insights for the therapeutic targeting of angiotensin receptor blockers (sartans) and the development of second-generation drugs (bisartans). Full article

The development of earth-abundant nickel-based catalysts is currently one of the greatest challenges for the straightforward synthesis of functionalized polyolefins. With environmental protection concerns, controllable copolymerizations of ethylene with biosourced comonomers derived from castor oil, such as methyl 10-undecenoate (U-COOMe), 10-undecen-1-ol (U-OH), or 10-undecenyl bromide (U-Br), were realized using α-diimine nickel catalyst (Ni-DBB) with dibenzobarrelene backbone. Catalyst Ni-DBB was highly tolerant toward polar comonomers, and functional polyethylenes were successfully prepared. The influences of the polar group, temperature, and comonomer concentration were studied in detail. Catalyst Ni-DBB was able to catalyze the copolymerization of ethylene with U-OH to afford high-molecular-weight (~180 kg/mol) functional polyethylene in a controlled fashion. NMR analysis showed that the produced functional polyethylenes were highly branched and had broad melting peaks ranging from 0 to 30 °C. Water contact angle (WCA) measurements showed that the surface of the obtained hydroxyl-functionalized polyethylene changed from hydrophobic to hydrophilic with the introduction of the comonomer U-OH. Full article

Background: Cervical dysplasia is a pre-malignant condition of the uterine cervix and is highly prevalent in Sub-Saharan Africa; especially affecting HIV-infected Black women. The anti-dysplastic effect of vitamin D hormones in cervical dysplasia is poorly understood. Therefore, we conducted a cross-sectional case–control observational study to assess the relationship between serum 25-hydroxycholecalciferol (25(OH)D) and cervical dysplasia, amongst Black women with and without HIV infection. Methods: The study participants attended a gynaecologic oncology clinic at an academic hospital in Pretoria, South Africa (n = 109). Patient clinical data were obtained during consultation. Cervical dysplasia was identified by cytology (PAP smear) which classified the case group as high-grade squamous epithelial lesions (HSILs), and the control group as <HSIL. Serum biochemistry measured 25(OH)D and its covariate biochemical variables. The data were statistically modelled to adjust for clinical and biochemical covariates, identify a significant relationship (p ≤ 0.05) between 25(OH)D and cervical dysplasia, and analyse subgroup interaction between HIV status and cervical dysplasia. Results: The data showed high levels of vitamin D insufficiency and deficiency in Black women with and without HIV infection. After covariate adjustment, 25(OH)D demonstrated an inverse relationship with HSIL in HIV-uninfected Black women. Furthermore, an interaction effect between women with and without HIV infection was observed. Conclusions: The role of 25(OH)D in the primary prevention of cervical dysplasia in Black women without HIV infection is promising, and dosing strategies require investigation. Also, future studies exploring the immunomodulatory role of 25(OH)D in cervical dysplasia in HIV-infected women is warranted. Full article

To address the underutilization of Schizochytrium limacinum meal, polysaccharides from Schizochytrium limacinum meal (SLMPs) were prepared via ultrasonic-assisted eutectic-solvent-based extraction. Although polysaccharides exhibit promising application potential, the structural ambiguity of SLMPs necessitates systematic investigation to elucidate their structure–activity relationships, thereby providing a scientific foundation for their subsequent development and utilization. Using response-surface methodology (RSM), the optimized extraction conditions were determined as follows: ultrasonic temperature of 52 °C, ultrasonic duration of 31 min, ultrasonic power of 57 W, water content of 29%, and a material-to-liquid ratio of 1:36 g/mL. Under these conditions, the maximum polysaccharide yield reached 9.25%, demonstrating a significant advantage over the conventional water extraction method (4.18% yield). Following purification, the antioxidant activity and structural characteristics of SLMPs were analyzed. The molecular weight, monosaccharide composition, reducing groups, and higher-order conformation were systematically correlated with antioxidant activity. Fourier-transform infrared spectroscopy (FTIR), monosaccharide composition analysis, and ¹H nuclear magnetic resonance (NMR) spectroscopy revealed characteristic polysaccharide functional groups (C–O, O–H, and C=O). Monosaccharides such as glucose (Glc), galactose (Gal), and arabinose (Ara) were found to enhance antioxidant activity. High-performance gel permeation chromatography (HPGPC) indicated a molecular weight of 20.7 kDa for SLMPs, with low-molecular-weight fractions exhibiting superior antioxidant activity. Scanning electron microscopy (SEM) further demonstrated that ultrasonically extracted polysaccharides possess porous structures capable of chelating redox-active functional groups. These findings suggest that ultrasonic-assisted eutectic-solvent-based extraction is an efficient method for polysaccharide extraction while preserving antioxidant properties. Full article

Peptoids are peptidomimetics in which the side chain is attached to the nitrogen of the amide group rather than the α-carbon. This alteration in the backbone structure is highly valued because it endows beneficial properties, including enhanced resistance to proteolysis, greater immunogenicity, improved biostability, and superior bioavailability. In this current study, we focused on the Ugi-4CR-based one-pot synthesis of peptoids using 1,4-dithiane-2,5-diol as the carbonyl component together with amine, carboxylic acid, and isocyanides. Four new peptoids—5a, 5b, 5c, and 5d—were designed and efficiently prepared in good chemical yields and were subjected to DFT investigations for their electronic behavior. These compounds have free OH, SH, and terminal triple bonds for further chemistry. In a computational analysis, the spectral data of compounds 5a–5d were juxtaposed with calculated spectral values derived from the B3LYP/6-311G(d,p) level. The electronic excitation and orbital contributions of 5a–5d were predicted using TD-DFT calculations. A natural bond order (NBO) analysis was utilized to investigate the electronic transition of newly synthesized peptoids, focusing on their charge distribution patterns. Furthermore, MEP and NPA analyses were conducted to predict charge distribution in these compounds. The reactivity and stability of the targeted peptoids were evaluated by global reactivity descriptors, which were determined with frontier molecular orbital analysis. The DFT results revealed that compound 5c displayed marginally higher reactivity compared to 5a, 5b, and 5d, possibly due to its extended conjugation. Full article

The treatment of trans-dihydroxo[5,10,15,20-tetrakis(3-pyridyl)porphyrinato]Sn(IV) or [Sn(OH)₂(TPyP)] with 1% nitric acid in a mixture of water and acetone resulted in the formation of an ionic complex 1 [Sn(OH)₂(TPy^HP)](NO₃)₄. Complex 1 was fully characterized by ¹H NMR spectroscopy, elemental analysis, UV-vis spectroscopy, powder X-ray diffraction, fluorescence spectroscopy, FT-IR spectroscopy, and single-crystal X-ray crystallography. X-ray crystallographic analysis confirmed that each peripheral pyridyl N atom is protonated to form tetra-cationic species {Sn(OH)₂(TPy^HP)}⁴⁺ stabilized by four NO₃⁻ counter anions. Intermolecular hydrogen bonding interaction between axial hydroxo ligands leads to the formation of a 1D porphyrin array. Nitrate anions also involve hydrogen bonding interactions with axial hydroxo ligands and the peripheral pyridinium groups. Full article

Objective: The aim of this study was to investigate the relationship between primary monosymptomatic enuresis nocturna (PMNE) and vitamin D deficiency in children. Patients and Methods: This retrospective case–control study included 307 PMNE patients aged 5–18 years and 254 age- and sex-matched healthy control subjects. Demographic data and biochemical parameters of the participants were obtained from hospital records. Serum 25(OH)D3 levels were measured using the chemiluminescence immunoassay method. The Mann–Whitney U test, Chi-square test, Pearson correlation and multivariate logistic regression analysis were used for statistical analyses. Results: Serum 25(OH)D3 levels were significantly lower in the PMNE group compared to the control group (p < 0.001). The rate of vitamin D deficiency was higher in the PMNE group. Vitamin D deficiency (OR: 3.164, 95% CI: 1.195–8.378, p = 0.02) and family history of enuresis (OR: 2.790, 95% CI: 1.01–5.8, p = 0.04) were found to be independent associated factors for PMNE. A significant negative correlation was found between serum vitamin D level and weekly bedwetting frequency (r = −0.377, p < 0.001). Conclusions: Serum 25(OH)D3 levels were significantly lower in the PMNE group (p < 0.001, Cohen’s d = 0.89). It is recommended that vitamin D levels should be routinely evaluated in children with PMNE and the potential benefits of vitamin D supplementation should be investigated in prospective studies. Full article

Background and Objectives: Vitamin D deficiency is linked to adverse outcomes in chronic obstructive pulmonary disease (COPD). Limited data exist on how vitamin D levels vary by disease severity during acute exacerbations of COPD (AECOPDs). This study aimed to determine whether the vitamin D status during AECOPDs—alongside inflammatory and hematological biomarkers—is associated with COPD severity. Materials and Methods: This observational study included 105 AECOPD hospitalized patients, stratified according to GOLD stages 1–2, 3, and 4. Blood samples were collected to measure serum vitamin D—as 25-hydroxyvitamin D [25(OH)D], acute phase reactants, serum calcium, and selected hematological parameters. Inter-group differences were evaluated using Kruskal–Wallis tests, with Spearman correlations applied for intra-strata associations. ROC analysis and logistic regression assessed the discriminatory power of significant biomarkers. Results: C-reactive protein (CRP) and fibrinogen concentrations were elevated across all COPD stages, whereas calcium and vitamin D remained consistently below normal. Interleukin (IL)-6 and 25(OH)D levels varied significantly with COPD stage (p = 0.033 and p = 0.047, respectively), with a marked drop from GOLD stage 3 to stage 4. High-IL-6 patients revealed significantly elevated CRP (p = 0.045), erythrocyte sedimentation rate (ESR) (p = 0.032), fibrinogen (p = 0.011), and procalcitonin (p = 0.044). The strongest correlations were seen between CRP, ESR, and fibrinogen (r_s ≥ 0.58, p ≤ 0.05), indicating a coordinated acute-phase response that weakened with advancing disease. Serum 25(OH)D was a significant independent predictor of COPD severity (AUC = 0.631, p = 0.048), while IL-6 had a weaker predictive value, losing significance in the combined regression model. Conclusions: Vitamin D deficiency is more pronounced in very severe COPD, serving as a potential clinical indicator of disease severity during exacerbation episodes. Full article

Background: Recently, vitamin D deficiency (VDD) has been described as a pandemic, affecting all groups of the population. Pregnant women and preterm infants are particularly vulnerable to vitamin D deficiency. Objectives: We aimed to evaluate the maternal and neonatal vitamin D status in relation with maternal vitamin D supplementations during pregnancy and to identify demographic, social, and healthcare risk factors for maternal VDD and vitamin D insufficiency in women delivering at ≤32 weeks of gestation. Methods: This prospective observational study was developed in the regional level III maternity unit of the Clinical County Emergency Hospital Sibiu. It included all admitted mothers who delivered at ≤32 weeks of gestation and their infants between 1 March 2022 and 28 February 2025. Infant deaths in the first 24 h of life, major congenital defects, chromosomal abnormalities, the admission of outborn infants without their mothers, or the transfer of the mother more than 48 h after birth were used as exclusion criteria. Maternal and neonatal data were collected from medical records. Data on maternal vitamin D supplementation were collected through interviews. Univariate and multivariate logistic regressions, linear regression, and predictive models were performed for data analysis. Results: A total of 146 mothers (median (IQR) age 30 (24–35) years) and their 164 preterm infants born at ≤32 weeks of gestation (median gestational age of 30 (27–31) weeks and birth weight of 1200 (900–1527) g) were included in this study. Only 43.15% of the mothers used multivitamins containing vitamin D during pregnancy, and 10.96% used specific vitamin D supplements. Vitamin D supplementation was used for a median of 4 (3–5) months at a median dose of 800 (250–1500) IU/day. Severe VDD (25(OH)D < 10 ng/mL), VDD (25(OH)D < 20 ng/mL), VDI (25(OH)D 20–29 ng/mL) were found in 19.86%, 55.48%, and 23.97% of the mothers and 16.46%, 58.53%, and 25.61% of their infants, respectively. A significant correlation was found between the maternal and neonatal status (r = 0.684, r² = 0.468, p < 0.001, B = 0.62). Both the maternal and neonatal vitamin D status were correlated with the vitamin D duration and dose used for supplementation during pregnancy. The logistic regression analysis showed that birth during a cold season and increased parity are independently associated with severe maternal VDD, while birth during the cold season and a lower educational status were independently associated with maternal VDD. Only an absent vitamin D supplementation (in the form of a multivitamin or specific vitamin D supplements) has been proven as an independent risk factor for VDI. Conclusions: Our findings revealed a worrisome prevalence of severe VDD, VDD, and VDI in mothers delivering very prematurely and in their infants. Additionally, less than half of the mothers in this study used vitamin D supplements during pregnancy despite the national recommendations. The professionals involved in advising pregnant women and policymakers should find solutions to improve the vitamin D status in these vulnerable groups of the population. Full article