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•Strong Lewis acid sites on alumina inhibit metal sintering during PDH.•Excess Lewis acid sites increased coke deposition during PDH.•Strong but less residual Lewis acid sites are ...important for control the deactivation.
The surface properties of catalyst supports are important in regulating the catalytic properties of heterogeneous catalysts. Herein, we studied the effect of acid-base properties of alumina on metal-support interaction and coke deposition, and investigated the stability of catalysts in propane dehydrogenation (PDH) using PtSn/Al2O3. We prepared γ-Al2O3 (A750) from ammonium aluminum carbonate hydroxide (AACH) and compared it with a commercial sample (Sasol Puralox SBA-200; P200). We loaded 0.5 wt% Pt and 0.9 wt% Sn on alumina then conducted propane dehydrogenation at 590 °C (WHSV = 5.2 h−1). PtSn/A750 and PtSn/P200 showed compatible initial activity (conversion = ˜50%) and selectivity (> 95%). After 20 h of reaction, PtSn/A750 showed a slight decrease in activity (39.9%) while the activity of PtSn/P200 dropped significantly (28.4%). Spent catalysts showed different metal sintering behavior and coke deposition which are well known causes for catalyst deactivation. A high strength of Lewis acid sites in A750 (higher Td in ethanol TPD) prevented the sintering of metal by strong metal-support interaction. Also, the lower number of Lewis acid sites in A750 than that of P200 reduced deposited coke on the catalysts (PtSn/A750: 1.8 wt% and PtSn/P200: 8.6 wt%). Furthermore, diffuse reflectance infrared Fourier-transform spectroscopy after CO adsorption at -150 °C clearly demonstrated that coke deposition was initiated from Lewis acid sites on the alumina surface, but then aromatization occurs at these sites. These results suggested that strong metal-support interactions to hold metal particles and less residual Lewis acid sites after metal loading to reduce coke deposition are important factors for designing stable and coke-resistant PtSn on alumina catalysts. Furthermore, precise characterization and understanding of the acid-base properties of alumina will contribute in developing catalysts with high stability.
The purpose of this study was to identify personality factor-associated predictors of smartphone addiction predisposition (SAP). Participants were 2,573 men and 2,281 women (n = 4,854) aged 20-49 ...years (Mean ± SD: 33.47 ± 7.52); participants completed the following questionnaires: the Korean Smartphone Addiction Proneness Scale (K-SAPS) for adults, the Behavioral Inhibition System/Behavioral Activation System questionnaire (BIS/BAS), the Dickman Dysfunctional Impulsivity Instrument (DDII), and the Brief Self-Control Scale (BSCS). In addition, participants reported their demographic information and smartphone usage pattern (weekday or weekend average usage hours and main use). We analyzed the data in three steps: (1) identifying predictors with logistic regression, (2) deriving causal relationships between SAP and its predictors using a Bayesian belief network (BN), and (3) computing optimal cut-off points for the identified predictors using the Youden index. Identified predictors of SAP were as follows: gender (female), weekend average usage hours, and scores on BAS-Drive, BAS-Reward Responsiveness, DDII, and BSCS. Female gender and scores on BAS-Drive and BSCS directly increased SAP. BAS-Reward Responsiveness and DDII indirectly increased SAP. We found that SAP was defined with maximal sensitivity as follows: weekend average usage hours > 4.45, BAS-Drive > 10.0, BAS-Reward Responsiveness > 13.8, DDII > 4.5, and BSCS > 37.4. This study raises the possibility that personality factors contribute to SAP. And, we calculated cut-off points for key predictors. These findings may assist clinicians screening for SAP using cut-off points, and further the understanding of SA risk factors.
Caulerpa is a marine green macroalga distinguished by a large single cell with multiple nuclei. It also exhibits remarkable morphological intraspecies variations, in response to diverse environmental ...types. However, the molecular mechanisms underlying this phenotypic plasticity remain poorly understood. In this work, we compare the transcriptomes of Caulerpa okamurae Weber Bosse, 1897 displaying altered phenotypes of cultivation and natural phenotypes and investigate significantly regulated genes and their biological functions using differential expression analyses. We observe light‐harvesting complex upregulation and cellular framework stability downregulation in altered phenotypes compared to the natural phenotypes. Intertidal macrophytes reduce light capture to avoid photodamage and regulate their morphology to protect against wave damage. In contrast, the lower light conditions and the cultivation environment augment light capture and increase a morphology prioritizing light trapping. Moreover, the addition of simulated wave‐sweeping stimuli induces a return to the natural morphology under high‐light conditions, showing how mechanical stress affects morphological organization in C. okamurae. We provide detailed gene expression patterns in C. okamurae under varying light intensities and water conditions, suggesting a distinct influence on its morphological traits.
Although the incidence of severe fever with thrombocytopenia syndrome virus (SFTSV) infection has increased from its discovery with a mortality rate of 10-20%, no effective vaccines are currently ...available. Here we describe the development of a SFTSV DNA vaccine, its immunogenicity, and its protective efficacy. Vaccine candidates induce both a neutralizing antibody response and multifunctional SFTSV-specific T cell response in mice and ferrets. When the vaccine efficacy is investigated in aged-ferrets that recapitulate fatal clinical symptoms, vaccinated ferrets are completely protected from lethal SFTSV challenge without developing any clinical signs. A serum transfer study reveals that anti-envelope antibodies play an important role in protective immunity. Our results suggest that Gn/Gc may be the most effective antigens for inducing protective immunity and non-envelope-specific T cell responses also can contribute to protection against SFTSV infection. This study provides important insights into the development of an effective vaccine, as well as corresponding immune parameters, to control SFTSV infection.
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•The number and property of sites on alumina are important for Pt-Al2O3 interaction.•Pt dispersion increases with increasing number of sites on alumina.•Pt dispersion increases with ...ethanol desorption temperature (Td) increase on alumina.•Pt dispersion changes under bimodal distribution on Pt/Al2O3.
In this work, how the number and properties of specific sites on alumina surfaces affect the specific interaction between Pt and alumina was investigated by using X-ray diffraction, ethanol temperature programmed desorption, diffuse reflectance infrared Fourier transform spectroscopy, H2 chemisorption, scanning transmission electron microscopy and benzene hydrogenation reaction. Here, we chose two sets of model aluminas having different number of sites with the identical properties and different properties of sites with the same number based on ethanol TPD. The H2 chemisorption results for the model aluminas show that H/Pt are all similar for low Pt loadings, but significantly different for high Pt loadings. For 1 wt% Pt/Al2O3, the number of specific sites on all the aluminas was sufficient to disperse all the Pt, leading to only highly dispersed Pt clusters (∼1 nm). However, at 10 wt% Pt/Al2O3, the number of Pt atoms is greater than that of the specific sites on the alumina surface, resulting in a bimodal distribution of large agglomerated Pt (>10 nm) and highly dispersed Pt clusters (<3 nm) revealed by XRD and TEM. Overall, the results clearly demonstrated that Pt shows higher dispersion with increasing number of sites and interaction strength, because the Pt atoms can interact with specific sites on alumina in greater numbers and more strongly. However, these Pt dispersion changes do not represent the gradual change in Pt cluster sizes, but the relative population change of small (<3 nm) and large agglomerated Pt clusters (>10 nm) under bimodal distribution. The number of large agglomerated Pt clusters decreased with increasing number of sites and interaction strength. This fundamental understanding provides an important perspective for designing Al2O3-based supported catalysts.
Reduction of oxidized Pt (3D PtO2, 2D PtO2 raft, and atomically dispersed Pt) on Al2O3.
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•3D PtO2 particles are easily reduced than 2D PtO2 rafts and atomically dispersed ...Pt.•Metal-support interaction decides reduction and auto-reduction of supported Pt oxides.•Reduction behavior of oxidized Pt affects the CO oxidation rates.
The catalytic performance of supported heterogeneous catalysts is significantly affected by the particle size and morphologies of the active phase. In this work, we studied how metal-support interaction affected the morphology and size of Pt clusters on Al2O3. Under oxidizing atmosphere, when the specific interaction between oxidized Pt and Al2O3 is dominant, highly dispersed 2D PtO2 rafts (1 nm) and atomically dispersed Pt atoms formed. At high Pt loadings, when only a fraction of the metal atoms can interact with the alumina support, or on weakly interacting supports (e.g., SiO2), 3D PtO2 particles (>2 nm) and large Pt crystallites (>10 nm) formed. Due to the weak interaction with the support, these 3D PtO2 particles can be reduced at a lower temperature (−40 °C) than 2D PtO2 rafts (~110 °C) and atomically dispersed Pt (>300 °C). The catalytic behavior for CO oxidation is also affected by the reduction properties of supported Pt catalysts. The activity of Pt/Al2O3 stepwise increases with the reduction temperature, which is closely related with the reduction of these three types of oxidized Pt species. In contrast, Pt/SiO2 didn’t show drastic activity change with the subsequent reduction treatments up to 500 °C because it contains mainly 3D PtO2 particles. All these results demonstrate that specific metal-support interactions guide the geometric and chemical properties and the corresponding catalytic performances of oxidized Pt in Pt/Al2O3 catalysts, underlining the importance of careful catalyst activation for the efficient utilization of metallic Pt in real-world catalytic applications.
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•The morphology and phase changes in γ-Al2O3 during wet impregnation.•The morphology and phase changes are related with defect (AlV) sites on alumina.•Controlling the catalyst ...preparation is important to understand catalyst properties.
The surface properties of support have a large influence on the catalyst properties and the catalyst properties are usually interpreted based on the characterization results of the support surface. However, in many cases, especially when γ-Al2O3 is used as the support, the alumina surface can be changed during catalyst preparation. Here, the significant changes in the physical and chemical properties of γ-Al2O3 were observed during catalyst preparation by using incipient wetness impregnation, which follows the general protocols of catalyst production. These changes were confirmed with transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. To investigate the origin of such changes from hydrolysis, low-crystalline γ-Al2O3 (A600) was prepared, which has abundant defect sites (AlV) on its surface and bulk. Through 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) and XRD studies, it could be demonstrated that defect sites (AlV) play a crucial role in the hydrolysis of alumina. Further, the hydrolysis of the alumina surface could be controlled by altering the solvent properties like changing the volume ratio of ethanol. These results suggest that the change in the support's surface during the catalyst preparation should be considered carefully when correlating the characteristics of the alumina surface with the characteristics of an alumina-based catalyst.
Sarcopenia is defined as the involuntary loss of skeletal muscle mass and function with aging and is associated with several adverse health outcomes. Recently, the disruption of regular circadian ...rhythms, due to shift work or nocturnal lifestyle, is emerging as a novel deleterious factor for the development of sarcopenia. The underlying mechanisms responsible for circadian disruption-induced sarcopenia include molecular circadian clock and mitochondrial function associated with the regulation of circadian rhythms. Exercise is a potent modulator of skeletal muscle metabolism and is considered to be a crucial preventative and therapeutic intervention strategy for sarcopenia. Moreover, emerging evidence shows that exercise, acting as a zeitgeber (time cue) of the skeletal muscle clock, can be an efficacious tool for re-setting the clock in sarcopenia. In this review, we provide the evidence of the impact of circadian disruption on skeletal muscle loss resulting in sarcopenia. Furthermore, we highlight the importance of exercise timing (i.e., scheduled physical activity) as a novel therapeutic strategy to target circadian disruption in skeletal muscle.
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•Ethylene formation on Al2O3 shows inverse correlation with ethanol desorption temperature.•Activation barrier of ethylene changes with modification but ether does not ...change.•Ethoxide is the key intermediate for ethanol dehydration on Al2O3.
The acid-base properties of Al2O3 with various surface characteristics were studied by XRD, HR-TEM, ethanol TPD, and ethanol dehydration reaction rate measurements. Ethanol TPD showed that the desorption temperature (at maximum rate of ethylene desorption, Td) of dissociative ethanol was significantly dependent on morphology, crystalline phase, and additives. Ethylene formation rates, normalized with respect to the amount of dissociative ethanol (quantified by ethanol TPD), exhibited an inverse correlation with Td on Al2O3 with various morphologies, crystalline phases, and additives, which suggests that Td can be used as a descriptor for acid-base properties of Al2O3, irrespective of modification origins. This also indicates that the dissociative ethanol (ethoxide) is the key intermediate of ethylene formation during ethanol dehydration on Al2O3. The activities and activation barriers of commercial Al2O3 were consistent with our empirical model. This fundamental understanding of the acid-base properties of alumina is helpful for the further development of new catalysts with better activity and selectivity.
Sarcopenic obesity (SO) is characterized by atrophic skeletal muscle impairment (sarcopenia) and obesity, which is associated with adverse outcomes of morbidity and mortality in elderly people. We ...investigated the effects of melatonin and exercise training on SO in 32-week-old senescence-accelerated mouse-prone-8 (SAMP8) mice fed a normal diet or a high-fat diet for 16 weeks. Melatonin, exercise, or melatonin and exercise for 8 weeks displayed reductions in the SO-induced impairment of skeletal muscle function and atrophy. Specifically, a decrease in mitochondrial calcium retention capacity in skeletal muscles observed in the HFD-con group was attenuated in melatonin and/or exercise intervention groups. More importantly, HFD-con mice displayed a lower number of Pax7+ satellite cells (SCs) and higher expression of p16
than P8ND mice, which were attenuated by melatonin and/or exercise interventions. The cellular senescence in SC-derived primary myoblasts from HFD-con mice was significantly attenuated in myoblasts from the melatonin and/or exercise groups, which was reproduced in a senescence model of H
O
-treated C2C12 myoblasts. Our results suggest that melatonin and exercise training attenuate SO-induced skeletal muscle dysfunction, at least in part, through preserving the SC pool by inhibiting cellular senescence and attenuating mitochondrial dysfunction.
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