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A simple cascade process based on the hydrothermal fractionation of Ulva spp. biomass was proposed. Considering the overall extraction yields (50â¯%), ulvan recovery (23â¯%), and ulvan composition, structural, mechanical and cytotoxic properties, the selected optimal final heating temperature was 160⯰C. Ethanol precipitation provided the highest ulvan recovery yields but choline chloride precipitated ulvans showed stronger mechanical properties, G´ moduli 1.5·104â¯Pa and 3·104â¯Pa for ethanol and for choline chloride, respectively. Both products were safe on L929 mouse fibroblasts and after a cooling stage, formed films without requiring any additives. From the ulvan-free liquid fraction, one product with 43â¯% (wt, d.b.) phenolics and moderate antiradical properties and a byproduct containing nutrients and minerals were separated. The methane potential of the corresponding residual solids was influenced by the hydrothermal heating temperature and was doubled compared to than for the untreated seaweed biomass (60â¯mL/g VS). This scheme could be also applied to the wet algal biomass, in a chemical free alternative to provide ready to use ulvan biopolymers, bioactives, nutrients, salts and biogas, conforming a biorefinery approach.
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This study investigates the effect of scaffold architecture on bone regeneration, focusing on 3D-printed polylactic acid-bioceramic calcium phosphate (PLA-bioCaP) composite scaffolds in rabbit femoral condyle critical defects. We explored two distinct scaffold designs to assess their influence on bone healing and scaffold performance. Structures with alternate (0°/90°) and helical (0°/45°/90°/135°/180°) laydown patterns were manufactured with a 3D printer using a fused deposition modeling technique. The scaffolds were meticulously characterized for pore size, strut thickness, porosity, pore accessibility, and mechanical properties. The in vivo efficacy of these scaffolds was evaluated using a femoral condyle critical defect model in eight skeletally mature New Zealand White rabbits. Then, the results were analyzed micro-tomographically, histologically, and histomorphometrically. Our findings indicate that both scaffold architectures are biocompatible and support bone formation. The helical scaffolds, characterized by larger pore sizes and higher porosity, demonstrated significantly greater bone regeneration than the alternate structures. However, their lower mechanical strength presented limitations for use in load-bearing sites.
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Introduction: We examined the gut microbiota of travellers returning from tropical areas with and without traveller's diarrhoea (TD) and its association with faecal lipocalin-2 (LCN2) levels. Methods: Participants were recruited at the Hospital Clinic of Barcelona, Spain, and a single stool sample was collected from each individual to perform the diagnostic of the etiological agent causing gastrointestinal symptoms as well as to measure levels of faecal LCN2 as a biomarker of gut inflammation. We also characterised the composition of the gut microbiota by sequencing the region V3-V4 from the 16S rRNA gene, and assessed its relation with the clinical presentation of TD and LCN2 levels using a combination of conventional statistical tests and unsupervised machine learning approaches. Results: Among 61 participants, 45 had TD, with 40% having identifiable etiological agents. Surprisingly, LCN2 levels were similar across groups, suggesting gut inflammation occurs without clinical TD symptoms. Differential abundance (DA) testing highlighted a microbial profile tied to high LCN2 levels, marked by increased Proteobacteria and Escherichia-Shigella, and decreased Firmicutes, notably Oscillospiraceae. UMAP analysis confirmed this profile's association, revealing distinct clusters based on LCN2 levels. The study underscores the discriminatory power of UMAP in capturing meaningful microbial patterns related to clinical variables. No relevant differences in the gut microbiota composition were found between travellers with or without TD. Discussion: The findings suggest a correlation between gut microbiome and LCN2 levels during travel, emphasising the need for further research to discern the nature of this relationship.
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Diarreia , Fezes , Microbioma Gastrointestinal , Lipocalina-2 , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Biomarcadores , Diarreia/microbiologia , Fezes/microbiologia , Fezes/química , Inflamação/microbiologia , Lipocalina-2/metabolismo , RNA Ribossômico 16S/genética , Espanha , ViagemRESUMO
OBJECTIVE: Nationwide, obstetric clinics modified prenatal care to include telehealth visits in response to the coronavirus disease 2019 (COVID-19) pandemic, enabling the opportunity to investigate its impact on patient outcomes. We hypothesized that use of prenatal telehealth visits would increase the number of prenatal visits, decrease the frequency of urgent triage/emergency department (ED) visits, and improve perinatal outcomes. This study aimed to determine the impact of telehealth on number of obstetric prenatal visits and urgent triage/ED visits amidst the COVID-19 pandemic. STUDY DESIGN: This is a retrospective cohort of patients from a federally qualified health center in central Texas. Patients with a singleton gestation who delivered after 32 weeks were included. Comparison groups were made between those patients who delivered between May 2020 and December 2020 (presumed modified prenatal visit schedule with in-person and telehealth) and those patients delivering between June 2019 and February 2020 (the traditional care model with in-person visits only). Multivariable linear and logistic regression models were used to estimate differences in the number of prenatal visits and unscheduled triage/ED visits. RESULTS: A total of 1,654 patients were identified with 801 (48.4%) patients undergoing modified prenatal care and 853 (51.6%) patients receiving traditional care during the study period. No significant differences were seen in overall prenatal attendance or triage/ED presentations. However, when stratified by parity, multiparous patients undergoing modified prenatal care were less likely to experience an urgent triage/ED presentation (8.7 vs. 12.7%; odds ratio, 1.69; 95% confidence interval, 1.10-2.61). CONCLUSION: When compared with a traditional prenatal visitation cohort prepandemic, patients who received modified telehealth prenatal care during the COVID-19 pandemic had similar prenatal attendance and unscheduled emergency presentations. However, multiparous patients experienced a decreased rate of unscheduled emergency presentations. Supplementing prenatal care with telehealth may provide overall comparable prenatal care delivery. KEY POINTS: · Use of telehealth has the potential to improve prenatal care.. · The COVID-19 pandemic allowed for comparison to traditional prenatal care.. · Multiparous patients had a decreased frequency of ED visits.. · Similar prenatal attendance was seen between both prenatal models..
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Introduction: The health crisis of the last 3 years has revealed the weaknesses of the child and family support system based on the professional use of digital resources in social agencies. This study addresses three aims: to examine the level of professional digital competence; to analyze the user profiles in a variety of digital resources; and to test the impact of level of competences and user profiles on four aspects: professional practice, family satisfaction with the services, child and family wellbeing, and family autonomy in the exercise of the parenting role. Methods: Participants were 148 practitioners from social agencies who voluntarily responded to an online survey with 47 questions. Results and discussion: Results showed that professionals perceive themselves as more competent in areas of information / data management and communication / collaboration than in the creation of digital content, security measures, and technical problem solving. Websites, email, and instant messaging were the sources more frequently used and with higher satisfaction, than structured programs, social networks and multimedia content. Variability in the user profiles showed three clusters: Cluster 1 Social network user (n = 13), Cluster 2 Diversified user (n = 75) and Cluster 3 Communicative instant user (n = 60). Participants in Cluster 2 compared to those in the other clusters were the most proficient on their digital competences and acknowledge the positive impact of digital resources on their professional practice and the psychological and social wellbeing of families. This study points the need for improvement in professionals' digital competences in some of the measured areas and the user profile of digital resources since both provide benefits on professional practice and family autonomy and wellbeing.
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BACKGROUND: Cross-sectional and short-term cohort studies have demonstrated an association between urinary incontinence and dementia, as well as lower performance on cognitive testing. The Health and Retirement Study, a longitudinal study of community-dwelling older adults, offers an opportunity to assess the temporal association between these conditions because it included an assessment of incontinence symptoms and biennial assessments of cognitive function. OBJECTIVE: This study aimed to evaluate if urinary incontinence before the age of 70 years had an effect on changes in cognitive function among women participating in the Health and Retirement Study. STUDY DESIGN: This secondary analysis included data from female respondents in the Health and Retirement Study aged 58 to 67 years with ≥2 cognitive assessments. Urinary incontinence was defined as any involuntary loss of any urine in the preceding 12 months. A control group without incontinence was reweighted for better comparability using coarsened exact matching for age and comorbidities. Validated methods, including neuropsychological test data, estimated a memory score and dementia probability for each participant biennially. Coprimary outcomes were the changes in memory score and dementia probability. Linear regression models were used to estimate the association of urinary incontinence with change in memory score and dementia probability, adjusting for baseline demographics and comorbidities. A subgroup analysis was performed to assess the effects of urinary incontinence frequency on these outcomes. The infrequent subgroup reported <15 days of leakage per month and the frequent subgroup reported ≥15 days of leakage per month. RESULTS: Among eligible female respondents, 40.6% reported urinary incontinence between the ages of 58 and 69 years. Baseline memory scores and dementia probability were similar between those with urinary incontinence (n=1706) and controls (n=2507). Memory score declined significantly in both cohorts, indicating poorer memory over time (-0.222 among those with incontinence [95% confidence interval, -0.245 to -0.199] vs -0.207 in controls [95% confidence interval, -0.227 to -0.188]). The decline of memory score was not statistically significantly different between cases and controls (mean difference, -0.015; 95% confidence interval, -0.045 to 0.015). Dementia probability increased significantly in both groups, indicating a greater probability of developing dementia by 0.018 among those with incontinence (95% confidence interval, 0.015-0.020) and by 0.020 among controls (95% confidence interval, 0.017-0.022). The change in dementia probability was not significantly different between groups (mean difference, -0.002; 95% confidence interval, -0.006 to 0.002). Frequent urinary incontinence was reported in 105 of 1706 (6%) of those with urinary incontinence. Memory score declined and dementia probability increased with time (P<.001) in frequent and infrequent urinary incontinence subgroups. There was no dose-response relationship. CONCLUSION: Measures of cognitive performance declined during approximately 10 years of observation. The changes in performance were not associated with the presence of urinary incontinence in the participants' younger years.
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Disfunção Cognitiva , Demência , Incontinência Urinária , Humanos , Feminino , Pessoa de Meia-Idade , Estudos Longitudinais , Idoso , Incontinência Urinária/epidemiologia , Incontinência Urinária/psicologia , Disfunção Cognitiva/epidemiologia , Demência/epidemiologia , Testes Neuropsicológicos , Estudos de Casos e ControlesRESUMO
BACKGROUND: Patients with obesity experience an increased duration of labor with an increased risk for perinatal morbidity. When compared with parturients without obesity, they also experience fewer uterine contractions after administration of misoprostol. It is unclear if the same dose of misoprostol should be used for induction of labor in patients with obesity compared to non-obese patients. Therefore, we sought to investigate if a higher dose of misoprostol for patients with obesity is more effective. OBJECTIVE: This study aimed to determine if 50 µg compared with 25 µg of vaginal misoprostol reduced the time from induction start to delivery among patients with obesity. STUDY DESIGN: We performed a double-blinded, pragmatic randomized controlled trial, between June 1, 2022, and July 17, 2023. Patients with a body mass index ≥30 kg/m2 who underwent labor induction at ≥ 36 weeks' gestation, had a singleton gestation, and a cervical dilation ≤3 cm at admission were included. Patients were excluded if they had a contraindication to vaginal delivery or misoprostol administration. Patients were randomized to 25 or 50 µg of vaginal misoprostol, stratified by parity, body mass index <40 kg/m2 or ≥40 kg/m2, and provider intent to use mechanical dilation at the onset of labor induction. Usual labor management was followed at the discretion of the provider. The primary outcome was time from induction to delivery. A priori, we estimated that 90 subjects per group (N=180) were needed for an 85% power to detect a 3-hour difference between groups with a type I error of 5%. Analysis was by intention-to-treat. A 2-sample t test was used for the primary outcome, Cohen's d was used as a measure of effect, and P values were reported. RESULTS: Of the 180 patients randomized, 88 were assigned to the 25 µg group and 92 were assigned to the 50 µg group. Of those, 96.1% of patients received the designated intervention. The baseline characteristics were similar between groups. No difference was found in the primary outcome of time to delivery (21.6 hours vs 18.6 hours; d=.28; 95% confidence interval, -0.02 to 0.57). In a planned subgroup analysis, multiparous patients delivered faster in the 50 µg group (15.2 hours vs 12.0 hours; d=.51; 95% confidence interval, 0.04-0.97). The risk for tachysystole associated with fetal heart tracing changes was rare overall (2.2%) and not significantly different between groups. No differences in maternal or neonatal adverse effects were observed. CONCLUSION: Patients with obesity who underwent cervical ripening with 50 µg of vaginal misoprostol experienced a similar time to delivery when compared with those who received 25 µg of misoprostol. However, multiparous patients had a significantly reduced time to delivery when 50 µg was used. A higher dose of misoprostol may be a promising intervention for reducing time in labor, which warrants further study.
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Índice de Massa Corporal , Trabalho de Parto Induzido , Misoprostol , Ocitócicos , Adulto , Feminino , Humanos , Gravidez , Administração Intravaginal , Relação Dose-Resposta a Droga , Método Duplo-Cego , Trabalho de Parto Induzido/métodos , Misoprostol/administração & dosagem , Obesidade , Ocitócicos/administração & dosagem , Fatores de TempoRESUMO
Using optical spectroscopy, X-ray diffraction, and electrical transport measurements, we have studied the pressure-induced metallization in BaH2 and Ba8H46. Our combined measurements suggest a structural phase transition from BaH2-II to BaH2-III accompanied by band gap closure and transformation to a metallic state at 57 GPa. The metallization is confirmed by resistance measurements as a function of the pressure and temperature. We also confirm that, with further hydrogenation, BaH2 forms the previously observed Weaire-Phelan Ba8H46, synthesized at 45 GPa and 1200 K. In this compound, metallization pressure is shifted to 85 GPa. Through a comparison of the properties of these two compounds, a question is raised about the importance of the hydrogen content in the electronic properties of hydride systems.
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The regeneration of bone remains one of the main challenges in the biomedical field, with the need to provide more personalized and multifunctional solutions. The other persistent challenge is related to the local prevention of infections after implantation surgery. To fulfill the first one and provide customized scaffolds with complex geometries, 3D printing is being investigated, with polylactic acid (PLA) as the biomaterial mostly used, given its thermoplastic properties. The 3D printing of PLA in combination with hydroxyapatite (HA) is also under research, to mimic the native mechanical and biological properties, providing more functional scaffolds. Finally, to fulfill the second one, antibacterial drugs locally incorporated into biodegradable scaffolds are also under investigation. This work aims to develop vancomycin-loaded 3D-printed PLA-HA scaffolds offering a dual functionality: local prevention of infections and personalized biodegradable scaffolds with osseointegrative properties. For this, the antibacterial drug vancomycin was incorporated into 3D-printed PLA-HA scaffolds using three loading methodologies: (1) dip coating, (2) drop coating, and (3) direct incorporation in the 3D printing with PLA and HA. A systematic characterization was performed, including release kinetics, Staphylococcus aureus antibacterial/antibiofilm activities and cytocompatibility. The results demonstrated the feasibility of the vancomycin-loaded 3D-printed PLA-HA scaffolds as drug-releasing vehicles with significant antibacterial effects for the three methodologies. In relation to the drug release kinetics, the (1) dip- and (2) drop-coating methodologies achieved burst release (first 60 min) of around 80-90% of the loaded vancomycin, followed by a slower release of the remaining drug for up to 48 h, while the (3) 3D printing presented an extended release beyond 7 days as the polymer degraded. The cytocompatibility of the vancomycin-loaded scaffolds was also confirmed.
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The binary Xe-Ar system has been studied in a series of high pressure diamond anvil cell experiments up to 60 GPa at 300 K. In-situ x-ray powder diffraction and Raman spectroscopy indicate the formation of a van der Waals compound, XeAr2, at above 3.5 GPa. Powder x-ray diffraction analysis demonstrates that XeAr2 adopts a Laves MgZn2-type structure with space group P63/mmc and cell parameters a = 6.595 Å and c = 10.716 Å at 4 GPa. Density functional theory calculations support the structure determination, with agreement between experimental and calculated Raman spectra. Our DFT calculations suggest that XeAr2 would remain stable without a structural transformation or decomposition into elemental Xe and Ar up to at least 80 GPa.
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We show that the hydrogen in metal superhydride compounds can adopt two distinct states-atomic and molecular. At low pressures, the maximum number of atomic hydrogens is typically equal to the valency of the cation; additional hydrogens pair to form molecules with electronic states far below the Fermi energy causing low-symmetry structures with large unit cells. At high pressures, molecules become unstable, and all hydrogens become atomic. This study uses density functional theory, adopting BaH4 as a reference compound, which is compared with other stoichiometries and other cations. Increased temperature and zero-point motion also favor high-symmetry atomic states, and picosecond-timescale breaking and remaking of the bond permutations via intermediate H3- units.
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The reconstruction or regeneration of damaged bone tissue is one of the challenges of orthopedic surgery and tissue engineering. Among all strategies investigated, additive manufacturing by fused deposition modeling (3D-FDM printing) opens the possibility to obtain patient-specific scaffolds with controlled architectures. The present work evaluates in depth 3D direct printing, avoiding the need for a pre-fabricated filament, to obtain bone-related scaffolds from direct mixtures of polylactic acid (PLA) and hydroxyapatite (HA). For it, a systematic physicochemical characterization (SEM-EDS, FT-Raman, XRD, micro-CT and nanoindentation) was performed, using different PLA/HA ratios and percentages of infill. Results prove the versatility of this methodology with an efficient HA incorporation in the 3D-printed scaffolds up to 13 wt.% of the total mass and a uniform distribution of the HA particles in the scaffold at the macro level, both longitudinal and cross sections. Moreover, an exponential distribution of the HA particles from the surface toward the interior of the biocomposite cord (micro level), within the first 80 µm (10% of the entire cord diameter), is also confirmed, providing the scaffold with surface roughness and higher bioavailability. In relation to the pores, they can range in size from 250 to 850 µm and can represent a percentage, in relation to the total volume of the scaffold, from 24% up to 76%. The mechanical properties indicate an increase in Young's modulus with the HA content of up to ~50%, compared to the scaffolds without HA. Finally, the in vitro evaluation confirms MG63 cell proliferation on the 3D-printed PLA/HA scaffolds after up to 21 days of incubation.
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BACKGROUND: Hyperthermia-based therapies have shown great potential for clinical applications such as for the antitumor and antipathogenic activities. Within all strategies, the so-called photothermal therapy proposes to induce the hyperthermia by the remote laser radiation on a photothermal conversion agent, in contact with the target tissue. METHODS: This paper reviews the most relevant in vitro and in vivo studies focused on NIR laser-induced hyperthermia due to photoexcitation of graphene oxide (GO) and reduced graphene oxide (rGO). Relevant parameters such as the amount of GO/rGO, the influence of the laser wavelength and power density are considered. Moreover, the required temperature and exposure time for each antitumor/antipathogenic case are collected and unified in a thermal dose parameter: the CEM43. RESULTS: The calculated CEM43 thermal doses revealed a great variability for the same type of tumor/strain. In order to detect potential tendencies, the values were classified into four ranges, varying from CEM43 < 60 min to CEM43 ≥ 1 year. Thus, a preference for moderate thermal doses of CEM43 < 1 year was detected in antitumor activity, with temperatures ≤ 50 °C and exposure time ≤ 15 min. In case of the antipathogenic studies, the most used thermal dose was higher, CEM43 ≥ 1 year, with ablative hyperthermia (> 60ºC). CONCLUSIONS: The ability of GO/rGO as effective photothermal conversion agents to promote a controlled hyperthermia is proven. The variability found for the CEM43 thermal doses on the reviewed studies reveals the potentiality to evaluate, for each application, the use of lower temperatures, by modulating time and/or repetitions in the doses.
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Grafite , Hipertermia Induzida , Neoplasias , Humanos , Grafite/farmacologia , Neoplasias/terapia , LuzRESUMO
The present work evaluates the thermal behavior of graphene oxide (GO) when deposited on 3D-printed polylactic acid (PLA), in order to develop a medical device for photothermal therapy applications. An experimental-numerical analysis was performed to assess the photothermal conversion capacity, based on the power emitted by a NIR (785 nm) laser, and the subsequent temperature distribution on the GO-PLA material. The influence of the deposited mass of GO and the PLA thickness was studied through 40 different scenarios. The results estimated a value of photothermal conversion efficiency of up to 32.6%, achieved for the lower laser power density that was tested (0.335 mW/mm²), and a high mass value of deposited GO (1.024 × 10-3 mg/mm²). In fact, an optimal mass of GO in the range of 1.024-2.048 × 10-3 mg/mm2 is proposed, in terms of absorption capacity, since a higher mass of GO would not increase the conversion efficiency. Moreover, the study allowed for an estimation of the thermal conductivity of this specific biomaterial (0.064 W/m·K), and proved that a proper combination of GO mass, PLA thickness, and laser power can induce ablative (>60 °C, in a concentrated area), moderate (50 °C), and mild (43 °C) hyperthermia on the bottom face of the biomaterial.
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Cultural change is theorized to generate intergroup hostility. Three experiments apply the Cultural Inertia Model to test the effects of change on intergroup relations. Two predictions of cultural inertia were tested: (a) cultures at rest tend to stay at rest and (b) individual difference variables function as psychological anchors. In static societies, perceived change leads to greater threat (Experiment 1), endorsement of anti-immigration legislation (Experiment 1), and collective angst (Experiments 1 and 2). Perceptions of change in static societies lead to more fear-related emotional reactions (Experiment 3). Framing cultural change as continuous rather than abrupt may be a solution for reducing negative reactions caused by cultural change (Experiments 2 and 3). Individual difference factors function as anchors that cement individuals in a state of uniformity (Experiment 2). The findings demonstrate that social interactions rely on perceptions toward change and individual difference factors that anchor one's willingness to accept change.
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Medo , Hostilidade , Humanos , Ansiedade , Interação Social , Relações InterpessoaisRESUMO
The reactivity between NaH and H2 has been investigated through a series of high-temperature experiments up to pressures of 78 GPa in diamond anvil cells combined with first principles calculations. Powder X-ray diffraction measurements show that heating NaH in an excess of H2 to temperatures around 2000 K above 27 GPa yields sodium trihydride (NaH3), which adopts an orthorhombic structure (space group Cmcm). Raman spectroscopy measurements indicate that NaH3 hosts quasi-molecular hydrogen (H2δ-) within a NaH lattice, with the H2δ- stretching mode downshifted compared to pure H2 (Δν â¼-120 cm-1 at 50 GPa). NaH3 is stable under room temperature compression to at least 78 GPa, and exhibits remarkable P-T stability, decomposing at pressures below 18 GPa. Contrary to previous experimental and theoretical studies, heating NaH (or NaH3) in excess H2 between 27 and 75 GPa does not promote further hydrogenation to form sodium polyhydrides other than NaH3.
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Polylactic acid (PLA) has become one of the most commonly used polymers in medical devices given its biocompatible, biodegradable and bioabsorbable properties. In addition, due to PLA's thermoplastic behaviour, these medical devices are now obtained using 3D printing technologies. Once obtained, the 3D-printed PLA devices undergo different sterilisation procedures, which are essential to prevent infections. This work was an in-depth study of the physicochemical changes caused by novel and conventional sterilisation techniques on 3D-printed PLA and their impact on the biological response in terms of toxicity. The 3D-printed PLA physicochemical (XPS, FTIR, DSC, XRD) and mechanical properties as well as the hydrophilic degree were evaluated after sterilisation using saturated steam (SS), low temperature steam with formaldehyde (LTSF), gamma irradiation (GR), hydrogen peroxide gas plasma (HPGP) and CO2 under critical conditions (SCCO). The biological response was tested in vitro (fibroblasts NCTC-929) and in vivo (embryos and larvae wild-type zebrafish Danio rerio). The results indicated that after GR sterilisation, PLA preserved the O:C ratio and the semi-crystalline structure. Significant changes in the polymer surface were found after HPGP, LTSF and SS sterilisations, with a decrease in the O:C ratio. Moreover, the FTIR, DSC and XRD analysis revealed PLA crystallisation after SS sterilisation, with a 52.9% increase in the crystallinity index. This structural change was also reflected in the mechanical properties and wettability. An increase in crystallinity was also observed after SCCO and LTSF sterilisations, although to a lesser extent. Despite these changes, the biological evaluation revealed that none of the techniques were shown to promote the release of toxic compounds or PLA modifications with toxicity effects. GR sterilisation was concluded as the least reactive technique with good perspectives in the biological response, not only at the level of toxicity but at all levels, since the 3D-printed PLA remained almost unaltered.
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Through a series of high pressure diamond anvil experiments, we report the synthesis of alkaline earth (Ca, Sr, Ba) tetrahydrides, and investigate their properties through Raman spectroscopy, X-ray diffraction, and density functional theory calculations. The tetrahydrides incorporate both atomic and quasi-molecular hydrogen, and we find that the frequency of the intramolecular stretching mode of the H2δ- units downshifts from Ca to Sr and to Ba upon compression. The experimental results indicate that the larger the host cation, the longer the H2δ- bond. Analysis of the electron localization function (ELF) demonstrates that the lengthening of the H-H bond is caused by the charge transfer from the metal to H2δ- and by the steric effect of the metal host on the H-H bond. This effect is most prominent for BaH4, where the precompression of H2δ- units at 50 GPa results in bond lengths comparable to that of pure H2 above 275 GPa.
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Through a series of x-ray diffraction, optical spectroscopy diamond anvil cell experiments, combined with density functional theory calculations, we explore the dense CH_{4}-H_{2} system. We find that pressures as low as 4.8 GPa can stabilize CH_{4}(H_{2})_{2} and (CH_{4})_{2}H_{2}, with the latter exhibiting extreme hardening of the intramolecular vibrational mode of H_{2} units within the structure. On further compression, a unique structural composition, (CH_{4})_{3}(H_{2})_{25}, emerges. This novel structure holds a vast amount of molecular hydrogen and represents the first compound to surpass 50 wt % H_{2}. These compounds, stabilized by nuclear quantum effects, persist over a broad pressure regime, exceeding 160 GPa.