Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 383
Filtrar
Mais filtros

Intervalo de ano de publicação
1.
Nature ; 627(8004): 564-571, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38418889

RESUMO

Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1,2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4,5, which increases community stabilization, species coexistence and the diversity of local tree species6,7. Previous analyses supporting such a latitudinal gradient in CNDD8,9 have suffered from methodological limitations related to the use of static data10-12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14,15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests.


Assuntos
Biodiversidade , Florestas , Mapeamento Geográfico , Árvores , Modelos Biológicos , Especificidade da Espécie , Árvores/classificação , Árvores/fisiologia , Clima Tropical
2.
Small ; 20(2): e2305219, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37658514

RESUMO

Materials with negative thermal expansion (NTE) attract significant research attention owing to their unique physical properties and promising applications. Although ferroelectric phase transitions leading to NTE are widely investigated, information on antiferroelectricity-induced NTE remains limited. In this study, single-crystal and polycrystalline Pb2 CoMoO6 samples are prepared at high pressure and temperature conditions. The compound crystallizes into an antiferroelectric Pnma orthorhombic double perovskite structure at room temperature owing to the opposite displacements dominated by Pb2+ ions. With increasing temperature to 400 K, a structural phase transition to cubic Fm-3m paraelectric phase occurs, accompanied by a sharp volume contraction of 0.41%. This is the first report of an antiferroelectric-to-paraelectric transition-induced NTE in Pb2 CoMoO6 . Moreover, the compound also exhibits remarkable NTE with an average volumetric coefficient of thermal expansion αV = -1.33 × 10-5 K-1 in a wide temperature range of 30-420 K. The as-prepared Pb2 CoMoO6 thus serves as a prototype material system for studying antiferroelectricity-induced NTE.

3.
Chemphyschem ; : e202400151, 2024 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-38635959

RESUMO

Polycyclic aromatic hydrocarbons (PAHs) imply the missing link between resonantly stabilized free radicals and carbonaceous nanoparticles, commonly referred to as soot particles in combustion systems and interstellar grains in deep space. Whereas gas phase formation pathways to the simplest PAH - naphthalene (C10H8) - are beginning to emerge, reaction pathways leading to the synthesis of the 14π Hückel aromatic PAHs anthracene and phenanthrene (C14H10) are still incomplete. Here, by utilizing a chemical microreactor in conjunction with vacuum ultraviolet (VUV) photoionization (PI) of the products followed by detection of the ions in a reflectron time-of-flight mass spectrometer (ReTOF-MS), the reaction between the 1'- and 2'-methylnaphthyl radicals (C11H9⋅) with the propargyl radical (C3H3⋅) accesses anthracene (C14H10) and phenanthrene (C14H10) via the Propargyl Addition-BenzAnnulation (PABA) mechanism in conjunction with a hydrogen assisted isomerization. The preferential formation of the thermodynamically less stable anthracene isomer compared to phenanthrene suggests a kinetic, rather than a thermodynamics control of the reaction.

4.
Inorg Chem ; 63(7): 3499-3505, 2024 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-38320745

RESUMO

An AA'3B2B'2O12-type quadruple perovskite oxide of CaCu3Cr2Re2O12 was synthesized at 18 GPa and 1373 K. Both an A- and B-site ordered quadruple perovskite crystal structure was observed, with the space group Pn-3. The valence states are verified to be CaCu32+Cr23+Re25+O12 by bond valence sum calculations and synchrotron X-ray absorption spectroscopy. The spin interaction among Cu2+, Cr3+, and Re5+ generates a ferrimagnetic transition with the Curie temperature (TC) at about 360 K. Moreover, electric transport properties and specific heat data suggest the presence of a half-metallic feature for this compound. The present study provides a promising quadruple perovskite oxide with above-room-temperature ferrimagnetism and possible half-metallic properties, which shows potential in the usage of spintronic devices.

5.
J Phys Chem A ; 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38967960

RESUMO

To understand the reactivity of resonantly stabilized radicals, often found in relevant concentrations in gaseous environments, it is important to determine their main reaction pathways. Here, it is investigated whether the fulvenallenyl radical (C7H5·) reacts preferentially with closed-shell molecules or radicals. Electronic structure calculations on the C10H9 potential energy surface accessed by the reactions of C7H5· with methylacetylene (CH3CCH) and allene (H2CCCH2) were combined with RRKM-ME calculations of temperature- and pressure-dependent rate constants using the automated EStokTP software suite and kinetic modeling to assess the reactivity of C7H5· with closed-shell unsaturated hydrocarbons. Experimentally, the reactions were attempted in a chemical microreactor heated to 998 ± 10 K by preparing fulvenallenyl radicals via pyrolysis of trichloromethylbenzene (C7H5Cl3) and seeding the radicals in methylacetylene or allene carrier gas, with product identification by means of photoionization mass spectrometry. The measured photoionization efficiency curve of m/z = 128 was assigned to a linear combination of the reference curves of two C10H8 isomers, azulene (minor) and naphthalene (major), presumably resulting from the C7H5· plus C3H4 reactions. However, the calculations demonstrated that these reactions are too slow, and kinetic modeling of processes in the reactor allowed us to conclude that the observation of naphthalene and azulene is due to the C7H5· plus C3H3· reaction, where propargyl is produced by direct hydrogen atom abstraction by chlorine (Cl) atoms from allene or methylacetylene and Cl stem from the pyrolysis of C7H5Cl3. Modeling results under the copyrolysis conditions of toluene and methylacetylene in high-temperature shock tube experiments confirmed the prevalence of the fulvenallenyl reaction with propargyl over its reactions with C3H4 even when the concentrations of allene and methylacetylene largely exceed that of propargyl. Overall, the reactions of fulvenallenyl with both allene and methylacetylene were found to be noncompetitive in the formation of naphthalene and azulene thus attesting the inefficiency of the fulvenallenyl radical reactions with the prototype closed-shell hydrocarbon species. In the meantime, the new reaction pathways revealed, including H-assisted isomerizations between C10H8 isomers and decomposition reactions of various C10H9 isomers, emerge as relevant and are recommended for inclusion in combustion kinetic models for naphthalene formation.

6.
J Environ Sci (China) ; 144: 87-99, 2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-38802241

RESUMO

There is a lack of understanding about the bacterial, fungal and archaeal communities' composition of solid-phase denitrification (SPD) systems. We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit (OTU) and amplicon sequence variant (ASV). The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone (CPSP, 0.86±0.04 mg NO3--N/(g·day)) and corncob (0.85±0.06 mg NO3--N/(g·day)) had better denitrification efficiency than polycaprolactone (PCL, 0.29±0.11 mg NO3--N/(g·day)) and polyvinyl alcohol-sodium alginate (PVA-SA, 0.24±0.07 mg NO3--N/(g·day)). The bacterial, fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL (OTU: 83.72%, ASV: 82.49%) and Rozellomycota in PVA-SA (OTU: 71.99%, ASV: 81.30%). ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum, unclassified_ f_ Xanthobacteraceae genus, etc., indicating ASV may be more conducive to understand SPD microbial communities. The co-occurring network showed some correlation between the bacteria fungi and archaea species, indicating different species may collaborate in SPD systems. Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems. These results may be beneficial for understanding microbial communities in SPD systems.


Assuntos
Bactérias , Carbono , Desnitrificação , Microbiota , Bactérias/metabolismo , Bactérias/classificação , Bactérias/genética , Carbono/metabolismo , Archaea/genética , Archaea/metabolismo , Fungos/metabolismo
7.
Small ; 19(46): e2302726, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37480195

RESUMO

The rational design of novel high-performance cathode materials for sodium-ion batteries is a challenge for the development of the renewable energy sector. Here, a new sodium-deficient NASICON phosphate, namely Na3.40 □0.60 Co0.5 Fe0.5 V(PO4 )3 , demonstrating the excellent electrochemical performance is reported. The presence of Co allows a third Na+ to participate in the reaction thus exhibiting a high reversible capacity of ≈155 mAh g-1 in the voltage range of 2.0-4.0 V versus Na+ /Na with a reversible single-phase mechanism and a small volume shrinkage of ≈5.97% at 4.0 V. 23 Na solid-state nuclear magnetic resonance (NMR) combined with ex situ X-ray diffraction (XRD) refinements provide evidence for a preferential Na+ insertion within the Na2 site. Furthermore, the enhanced sodium kinetics ascribed to Co-substitution is also confirmed in combination with electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and theoretical calculation.

8.
Glob Chang Biol ; 29(12): 3409-3420, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36938951

RESUMO

Accurate estimates of forest biomass stocks and fluxes are needed to quantify global carbon budgets and assess the response of forests to climate change. However, most forest inventories consider tree mortality as the only aboveground biomass (AGB) loss without accounting for losses via damage to living trees: branchfall, trunk breakage, and wood decay. Here, we use ~151,000 annual records of tree survival and structural completeness to compare AGB loss via damage to living trees to total AGB loss (mortality + damage) in seven tropical forests widely distributed across environmental conditions. We find that 42% (3.62 Mg ha-1 year-1 ; 95% confidence interval [CI] 2.36-5.25) of total AGB loss (8.72 Mg ha-1 year-1 ; CI 5.57-12.86) is due to damage to living trees. Total AGB loss was highly variable among forests, but these differences were mainly caused by site variability in damage-related AGB losses rather than by mortality-related AGB losses. We show that conventional forest inventories overestimate stand-level AGB stocks by 4% (1%-17% range across forests) because assume structurally complete trees, underestimate total AGB loss by 29% (6%-57% range across forests) due to overlooked damage-related AGB losses, and overestimate AGB loss via mortality by 22% (7%-80% range across forests) because of the assumption that trees are undamaged before dying. Our results indicate that forest carbon fluxes are higher than previously thought. Damage on living trees is an underappreciated component of the forest carbon cycle that is likely to become even more important as the frequency and severity of forest disturbances increase.


Assuntos
Árvores , Clima Tropical , Biomassa , Florestas , Carbono
9.
Chem Rec ; 23(5): e202300020, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36995073

RESUMO

Carbon-heteroatom bond formation under transition-metal free conditions provides a powerful synthetic alternative for the efficient synthesis of valuable molecules. In particular, C-N and C-O bonds are two important types of carbon-heteroatom bonds. Thus, continuous efforts have been deployed to develop novel C-N/C-O bond formation methodologies involving various catalysts or promoters under TM-free conditions, which enables the synthesis of various functional molecules comprising C-N/C-O bonds in a facile and sustainable manner. Considering the significance of C-N/C-O bond construction in organic synthesis and materials science, this review aims to comprehensively present selected examples on the construction of C-N (including amination and amidation) and C-O (including etherification and hydroxylation) bonds without transition metals. Besides, the involved promoters/catalysts, substrate scope, potential application and possible reaction mechanisms are also systematically discussed.

10.
Oecologia ; 201(3): 733-747, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36929223

RESUMO

The variation in niche breadth can affect how species respond to environmental and resource changes. However, there is still no clear understanding of how seasonal variability in food resources impacts the variation of individual dietary diversity, thereby affecting the dynamics of a population's dietary niche breadth. Optimal foraging theory (OFT) and the niche variation hypothesis (NVH) predict that when food resources are limited, the population niche breadth will widen or narrow due to increased within-individual dietary diversity and individual specialization or reduced within-individual dietary diversity, respectively. Here, we used DNA metabarcoding to examine the composition and seasonality of diets of the avivorous bat Ia io. Furthermore, we investigated how the dietary niches changed among seasons and how the population niche breadth changed when the availability of insect resources was reduced in autumn. We found that there was differentiation in dietary niches among seasons and a low degree of overlap, and the decrease of insect resource availability and the emergence of ecological opportunities of nocturnal migratory birds might drive dietary niche shifts toward birds in I. io. However, the population's dietary niche breadth did not broaden by increasing the within-individual dietary diversity or individual specialization, but rather became narrower by reducing dietary diversity via predation on bird resources that served as an ecological opportunity when insect resources were scarce in autumn. Our findings were consistent with the predictions of OFT, because birds as prey for bats provided extremely different resources from those of insects in size and nutritional value. Our work highlights the importance of size and quality of prey resources along with other factors (i.e., physiological, behavioral, and life-history traits) in dietary niche variation.


Assuntos
Quirópteros , Animais , Estações do Ano , Dieta , Insetos , Comportamento Predatório , Aves , Ecossistema
11.
Nature ; 550(7674): 105-108, 2017 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-28953870

RESUMO

The tropical forests of Borneo and Amazonia may each contain more tree species diversity in half a square kilometre than do all the temperate forests of Europe, North America, and Asia combined. Biologists have long been fascinated by this disparity, using it to investigate potential drivers of biodiversity. Latitudinal variation in many of these drivers is expected to create geographic differences in ecological and evolutionary processes, and evidence increasingly shows that tropical ecosystems have higher rates of diversification, clade origination, and clade dispersal. However, there is currently no evidence to link gradients in ecological processes within communities at a local scale directly to the geographic gradient in biodiversity. Here, we show geographic variation in the storage effect, an ecological mechanism that reduces the potential for competitive exclusion more strongly in the tropics than it does in temperate and boreal zones, decreasing the ratio of interspecific-to-intraspecific competition by 0.25% for each degree of latitude that an ecosystem is located closer to the Equator. Additionally, we find evidence that latitudinal variation in climate underpins these differences; longer growing seasons in the tropics reduce constraints on the seasonal timing of reproduction, permitting lower recruitment synchrony between species and thereby enhancing niche partitioning through the storage effect. Our results demonstrate that the strength of the storage effect, and therefore its impact on diversity within communities, varies latitudinally in association with climate. This finding highlights the importance of biotic interactions in shaping geographic diversity patterns, and emphasizes the need to understand the mechanisms underpinning ecological processes in greater detail than has previously been appreciated.


Assuntos
Biodiversidade , Florestas , Análise Espaço-Temporal , Árvores/fisiologia , Clima Tropical , Mapeamento Geográfico , Reprodução , Estações do Ano , Fatores de Tempo , Árvores/crescimento & desenvolvimento
12.
Environ Res ; 236(Pt 1): 116644, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37454797

RESUMO

MFC anodic denitrification is more suitable for the coexistence of organic matter and nitrate in actual sewage, but the traditional carbon source has some problems such as high cost and difficulty of dosage control in MFC. Herein, corncob and polycaprolactone (PCL) were mechanically pulverized and mixed in the system of polyvinyl alcohol and sodium alginate, and cross-linked to prepare slow-release carbon source fillers (CPSP), which were added to the MFC anolyte to realize the coupling of solid-phase denitrification and anodic denitrification. Results showed the start-up period of MFC experimental group (MFC-C) with CPSP was slightly longer than the control group (MFC-0), but MFC-C's maximum output voltage (648.4 mV) and power density (2738 mW/m3) could be increased by 5% and 15% higher than that of MFC-0 (P < 0.05). The degradation process of MFC substrate in unit cycle was mainly divided into nitrogen removal stage (0-8 h) and electricity generation stage (8-48 h). The NO3--N and COD degradation and power generation kinetic processes of MFC conformed to the Han-Levenspiel model. Kinetics experiments showed CPSP can improve the affinity and tolerance of MFC to NO3--N, also it can alleviate the pressure of electron competition in anolyte and improve coulombic efficiency. In addition, microbial communities were significantly changed under the effect of CPSP (P < 0.001). Meanwhile, CPSP can promote the synthesis of denitrification functional genes. This study provides a new strategy to improve the performance of MFC by the addition of novel denitrification carbon source.

13.
Ann Plast Surg ; 90(5S Suppl 2): S172-S176, 2023 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-37192418

RESUMO

BACKGROUND: How to evaluate blepharoptosis concomitantly presented with refractory and uncontrollable blepharospasm? To date, there is a paucity of publications on the ideal evaluation methods. An innovative method-video recordings, idiosyncratic facial expressions, sensory tricks, and ancillary procedures (VISA)-is developed for preoperative evaluation, and the surgical outcomes are demonstrated. METHODS: A retrospective study using VISA for blepharoptosis evaluation was conducted on 51 patients with refractory blepharospasm. Based on the evaluation, patients underwent blepharoptosis correction simultaneously besides the selective myectomy and myotomy in situ of the eyelid protractors for blepharospasm. Preoperative and postoperative palpebral fissure height, margin reflex distance 1, ptosis severity, and levator function were assessed to identify the effectiveness of VISA. All the procedures were performed by the senior author C.-S.L. RESULTS: There were 42 patients diagnosed with essential blepharospasm and 9 patients with Meige syndrome. Forty-one patients (82/102 eyelids [80.4%]) had concomitant blepharoptosis and blepharospasm. Ptosis severity was mild in 21 eyelids (25.6%), moderate in 12 eyelids (14.6%), and severe in 49 eyelids (59.8%). Preoperative/postoperative (6 months) values of palpebral fissure height, margin reflex distance 1, and levator function were 4.70 ± 2.45 mm/8.35 ± 1.33 mm (P < 0.05), -0.30 ± 3.19 mm/3.73 ± 1.05 mm (P < 0.05), and 13.07 ± 2.56 mm/13.68 ± 2.34 mm (P < 0.05), respectively. Undercorrection and revision rate reported 9.8% and 3.7%, individually. CONCLUSIONS: VISA approach overcomes the difficulty of blepharoptosis assessment in patients with refractory blepharospasm. It provides useful preoperative information required for adequate blepharoptosis correction in blepharospasm surgery and yielded desirable outcomes.


Assuntos
Blefaroplastia , Blefaroptose , Blefarospasmo , Humanos , Blefaroptose/diagnóstico , Blefaroptose/cirurgia , Blefarospasmo/complicações , Blefarospasmo/cirurgia , Estudos Retrospectivos , Músculos Oculomotores/cirurgia , Pálpebras/cirurgia , Blefaroplastia/métodos , Resultado do Tratamento
14.
Ann Plast Surg ; 90(1 Suppl 1): S84-S88, 2023 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-36752539

RESUMO

BACKGROUND: Meige syndrome is characterized by involuntary blepharospasm and varied subphenotypes of oromandibular tonic-clonic muscle contraction. Despite botulinum toxin (BTx) being the mainstay of treatment for Meige syndrome, a small subset of patients remain refractory to its effects because the disease is a form of functional blindness. An integrative surgical procedure combining selective myectomy and myotomy in situ of eyelid protractors, blepharoptosis correction, and tightening of the lower eyelid laxity was first applied to treat refractory blepharospasm in patients with Meige syndrome. MATERIALS AND METHODS: This study is a retrospective review conducted on 24 patients with refractory Meige syndrome between 2013 and 2020. Besides selective myectomy and myotomy in situ of eyelid protractors, levator plication and lateral tarsoplasty or canthopexy was performed for blepharoptosis correction and lower eyelid tightening, respectively. Patient demographics, associated diseases, medical treatment history, associated surgical procedures, final aesthetic outcomes, and therapeutic effects as reflected by changes in function disability score and Botox (BTx) treatment were thoroughly recorded and analyzed. RESULTS: The mean age of the patients was 65.2 ± 8.9 years. Twenty-one patients (87.5%) received blepharoptosis correction by levator plication with an average of 11.2 ± 2.9 mm in length. Lateral tarsoplasty was performed in 16 patients (66.7%) by pentagonal tarsal resection with an average of 3.9 ± 0.8 mm in width. Five patients (20.8%) received lateral canthopexy. Among the total of 96 operated eyelids, scar revision with fat graft was performed in 3 eyelids (3.1%). The average amount of BTx treatment decreased from 49.2 ± 12.8 U once every 2.7 ± 0.8 months before surgery to 35.4 ± 7.8 U once every 3.8 ± 0.7 months after surgery. Function disability score improved from 76.7 ± 17.5% preoperatively to 15.6 ± 9.9% postoperatively ( P < 0.001). Only 3 upper eyelids (3.1%) received scar revision and fat grafting due to minor postoperative contour depression. All patients expressed high satisfaction with both functional and aesthetic outcomes (Likert scale 4.5 ± 0.5). CONCLUSIONS: Selective myectomy and myotomy in situ of eyelid protractors combining blepharoplasty correction and lower eyelid tightening can produce long-lasting functional and aesthetic results with minimal complication in patients with refractory Meige syndrome.


Assuntos
Blefaroplastia , Blefaroptose , Blefarospasmo , Toxinas Botulínicas Tipo A , Síndrome de Meige , Miotomia , Humanos , Pessoa de Meia-Idade , Idoso , Blefarospasmo/cirurgia , Blefarospasmo/tratamento farmacológico , Blefaroptose/cirurgia , Síndrome de Meige/tratamento farmacológico , Síndrome de Meige/cirurgia , Cicatriz/cirurgia , Toxinas Botulínicas Tipo A/uso terapêutico , Blefaroplastia/métodos , Músculos Oculomotores/cirurgia , Complicações Pós-Operatórias/cirurgia , Estudos Retrospectivos
15.
Sensors (Basel) ; 23(6)2023 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-36992065

RESUMO

Mobile health (mHealth) utilizes mobile devices, mobile communication techniques, and the Internet of Things (IoT) to improve not only traditional telemedicine and monitoring and alerting systems, but also fitness and medical information awareness in daily life. In the last decade, human activity recognition (HAR) has been extensively studied because of the strong correlation between people's activities and their physical and mental health. HAR can also be used to care for elderly people in their daily lives. This study proposes an HAR system for classifying 18 types of physical activity using data from sensors embedded in smartphones and smartwatches. The recognition process consists of two parts: feature extraction and HAR. To extract features, a hybrid structure consisting of a convolutional neural network (CNN) and a bidirectional gated recurrent unit GRU (BiGRU) was used. For activity recognition, a single-hidden-layer feedforward neural network (SLFN) with a regularized extreme machine learning (RELM) algorithm was used. The experimental results show an average precision of 98.3%, recall of 98.4%, an F1-score of 98.4%, and accuracy of 98.3%, which results are superior to those of existing schemes.


Assuntos
Redes Neurais de Computação , Smartphone , Humanos , Idoso , Algoritmos , Aprendizado de Máquina , Atividades Humanas
16.
Nano Lett ; 22(4): 1580-1586, 2022 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-35073104

RESUMO

Strontium titanate (STO), with a wide spectrum of emergent properties such as ferroelectricity and superconductivity, has received significant attention in the community of strongly correlated materials. In the strain-free STO film grown on the SrRuO3 buffer layer, the existing polar nanoregions can facilitate room-temperature ferroelectricity when the STO film thickness approaches 10 nm. Here we show that around this thickness scale, the freestanding STO films without the influence of a substrate show the tetragonal structure at room temperature, contrasting with the cubic structure seen in bulk form. The spectroscopic measurements reveal the modified Ti-O orbital hybridization that causes the Ti ion to deviate from its nominal 4+ valency (3d0 configuration) with excess delocalized 3d electrons. Additionally, the Ti ion in TiO6 octahedron exhibits an off-center displacement. The inherent symmetry lowering in ultrathin freestanding films offers an alternative way to achieve tunable electronic structures that are of paramount importance for future technological applications.

17.
Int J Mol Sci ; 24(4)2023 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-36835359

RESUMO

Body size is an important biological phenotypic trait that has attracted substantial attention. Small domestic pigs can serve as excellent animal models for biomedicine and also help meet sacrificial culture needs in human societies. Although the mechanisms underlying vertebral development regulating body size variation in domestic pigs during the embryonic period have been well described, few studies have examined the genetic basis of body size variation in post embryonic developmental stages. In this study, seven candidate genes-PLIN1, LIPE, PNPLA1, SCD, FABP5, KRT10 and IVL-significantly associated with body size were identified in Min pigs, on the basis of weighted gene co-expression network analysis (WGCNA), and most of their functions were found to be associated with lipid deposition. Six candidate genes except for IVL were found to have been subjected to purifying selection. PLIN1 had the lowest ω value (0.139) and showed heterogeneous selective pressure among domestic pig lineages with different body sizes (p < 0.05). These results suggested that PLIN1 is an important genetic factor regulating lipid deposition and consequently affecting body size variation in pigs. The culture of whole pig sacrifice in Manchu during the Qing Dynasty in China might have contributed to the strong artificial domestication and selection of Hebao pigs.


Assuntos
Tamanho Corporal , Perilipina-1 , Seleção Genética , Porco Miniatura , Transcriptoma , Animais , Humanos , Aciltransferases/genética , Perilipina-1/genética , Perilipina-1/fisiologia , Fosfolipases , Tamanho Corporal/genética , Metabolismo dos Lipídeos/genética , Porco Miniatura/genética , Porco Miniatura/crescimento & desenvolvimento
18.
J Environ Sci (China) ; 130: 24-36, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37032040

RESUMO

Solid-phase denitrification (SPD) has been used in wastewater treatment plant effluent to enhance nitrate removal, and antibiotics co-existing in the effluent is a common environmental problem. In this study, it was systematically investigated the effect of single trace sulfamethoxazole (SMX)/trimethoprim (TMP) and their mixture on microbial denitrification performance, the antibiotics removal, and antibiotics resistance genes (ARGs) in corncob supported SPD system. The average denitrification rate was improved by 46.90% or 61.09% with single 50 µg/L SMX or TMP, while there was no significant inhibition with mixed SMX and TMP. The abundance of dominant denitrifiers (Comamonadaceae family and Azospia) and fermentation bacteria (Ancalomicrobium) were consistent with the denitrification performance of different antibiotics groups. Single SMX and TMP achieved relatively higher denitrification gene and enzyme abundance. Mixed SMX and TMP improved the denitrification gene copies, but they reduced the key denitrification enzymes except for EC 1.7.7.2. Additionally, the removal efficiency of TMP (56.70% ± 3.18%) was higher than that of SMX (25.44% ± 2.62%) in single antibiotic group, and the existence of other antibiotics (i.e. SMX or TMP) had no significant impact on the TMP or SMX removal performance. Biodegradation was the main removal mechanism of SMX and TMP, while sludge and corncob adsorption contributed a little to their removal. SMX had the risk of sulfanilamide resistance genes (SRGs) dissemination. Furthermore, network analysis indicated that Niveibacterium and Bradyrhizobium were the potential hosts of SRGs, which promoted the horizontal transmission of ARGs.


Assuntos
Antibacterianos , Zea mays , Antibacterianos/farmacologia , Desnitrificação , Combinação Trimetoprima e Sulfametoxazol , Resistência Microbiana a Medicamentos/genética , Sulfametoxazol
19.
Angew Chem Int Ed Engl ; 62(34): e202302664, 2023 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-37349889

RESUMO

Lithium difluoro(oxalato) borate (LiDFOB) has been widely investigated in lithium-ion batteries (LIBs) owing to its advantageous thermal stability and excellent aluminum passivation property. However, LiDFOB tends to suffer from severe decomposition and generate a lot of gas species (e.g., CO2 ). Herein, a novel cyano-functionalized lithium borate salt, namely lithium difluoro(1,2-dihydroxyethane-1,1,2,2-tetracarbonitrile) borate (LiDFTCB), is innovatively synthesized as a highly oxidative-resistant salt to alleviate above dilemma. It is revealed that the LiDFTCB-based electrolyte enables LiCoO2 /graphite cells with superior capacity retention at both room and elevated temperatures (e.g., 80 % after 600 cycles) with barely any CO2 gas evolution. Systematic studies reveal that LiDFTCB tends to form thin and robust interfacial layers at both electrodes. This work emphasizes the crucial role of cyano-functionalized anions in improving cycle lifespan and safety of practical LIBs.

20.
Ecol Lett ; 25(6): 1471-1482, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35460530

RESUMO

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250-fold increase in seed abundance from cold-dry to warm-wet climates, driven primarily by a 100-fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics.


Assuntos
Florestas , Árvores , Biodiversidade , Clima , Fertilidade , Sementes
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA