RESUMO
Panicle development is an important determinant of the grain number in rice. A thorough characterization of the molecular mechanism underlying panicle development will lead to improved breeding of high-yielding rice varieties. Frizzy Panicle (FZP), a critical gene for panicle development, is regulated by OsBZR1 and OsARFs at the transcriptional stage. However, the translational modulation of FZP has not been reported. We reveal that the CU-rich elements (CUREs) in the 3' UTR of the FZP mRNA are crucial for efficient FZP translation. The knockout of CUREs in the FZP 3' UTR or the over-expression of the FZP 3' UTR fragment containing CUREs resulted in an increase in FZP mRNA translation efficiency. Moreover, the number of secondary branches (NSB) and the grain number per panicle (GNP) decreased in the transformed rice plants. The CUREs in the 3' UTR of FZP mRNA were verified as the targets of the polypyrimidine tract-binding proteins OsPTB1 and OsPTB2 in rice. Both OsPTB1 and OsPTB2 were highly expressed in young panicles. The knockout of OsPTB1/2 resulted in an increase in the FZP translational efficiency and a decrease in the NSB and GNP. Furthermore, the over-expression of OsPTB1/2 decreased the translation of the reporter gene fused to FZP 3' UTR in vivo and in vitro. These results suggest that OsPTB1/2 can mediate FZP translational repression by interacting with CUREs in the 3' UTR of FZP mRNA, leading to changes in the NSB and GNP. Accordingly, in addition to transcriptional regulation, FZP expression is also fine-tuned at the translational stage during rice panicle development.
Assuntos
Oryza , Regiões 3' não Traduzidas , Grão Comestível/metabolismo , Oryza/metabolismo , Melhoramento Vegetal , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMO
OBJECTIVE: To carry out genetic analysis for a family with a fetus manifesting micrognathia and a previous history for fetal micromandibular deformity. METHODS: Systematic ultrasound examination was carried out for the fetus, and the prenatal and postnatal phenotype of the first fetus were retrospectively analyzed. The fetus and his parents were subjected to whole exome sequencing (WES) to identify potential pathogenic variants. Candidate variants were verified by Sanger sequencing. RESULTS: Fetal ultrasound has indicated micrognathia. The first fetus was found to have micrognathia by prenatal ultrasonography and have featured macrosomia and dyspnea due to with tongue retraction, high palatal arch and small mandibular deformity. WES revealed that the fetus has a harbored a c.3G>C (p.Met1?) variant of the COL2A1 gene, which was inherited from the father who had myopia and retinal detachment. CONCLUSION: Stickler syndrome is mainly characterized prenatally by micrognathia, in addition with a variety of postnatal anomalies. The c.3G>C (p.Met1?) variant probably underlay the Stickler syndrome in this pedigree.
Assuntos
Oftalmopatias Hereditárias , Micrognatismo , Osteocondrodisplasias , Descolamento Retiniano , Artrite , Doenças do Tecido Conjuntivo , Feminino , Feto/anormalidades , Feto/diagnóstico por imagem , Perda Auditiva Neurossensorial , Humanos , Mutação , Linhagem , Gravidez , Descolamento Retiniano/diagnóstico por imagem , Descolamento Retiniano/genética , Estudos RetrospectivosRESUMO
The objective of this White Paper, submitted to ESA's Voyage 2050 call, is to get a more holistic knowledge of the dynamics of the Martian plasma system, from its surface up to the undisturbed solar wind outside of the induced magnetosphere. This can only be achieved with coordinated multi-point observations with high temporal resolution as they have the scientific potential to track the whole dynamics of the system (from small to large scales), and they constitute the next generation of the exploration of Mars analogous to what happened at Earth a few decades ago. This White Paper discusses the key science questions that are still open at Mars and how they could be addressed with coordinated multipoint missions. The main science questions are: (i) How does solar wind driving impact the dynamics of the magnetosphere and ionosphere? (ii) What is the structure and nature of the tail of Mars' magnetosphere at all scales? (iii) How does the lower atmosphere couple to the upper atmosphere? (iv) Why should we have a permanent in-situ Space Weather monitor at Mars? Each science question is devoted to a specific plasma region, and includes several specific scientific objectives to study in the coming decades. In addition, two mission concepts are also proposed based on coordinated multi-point science from a constellation of orbiting and ground-based platforms, which focus on understanding and solving the current science gaps.
RESUMO
Two branching strategies are exhibited in crops: enhanced apical dominance, as in maize; or weak apical dominance, as in rice. However, the underlying mechanism of weak apical dominance remains elusive. OsWUS, an ortholog of Arabidopsis WUSCHEL (WUS) in rice, is required for tiller development. In this study, we identified and functionally characterized a low-tillering mutant decreased culm number 1 (dc1) that resulted from loss-of-function of OsWUS. The dc1 tiller buds are viable but repressed by the main culm apex, leading to stronger apical dominance than that of the wild-type (WT). Auxin response is enhanced in the dc1 mutant, and knocking out the auxin action-associated gene ABERRANT SPIKELET AND PANICLE 1 (ASP1) de-repressed growth of the tiller buds in the dc1 mutant, suggesting that OsWUS and ASP1 are both involved in outgrowth of the rice tiller bud. Decapitation triggers higher contents of cytokinins in the shoot base of the dc1 mutant compared with those in the WT, and exogenous application of cytokinin is not sufficient for sustained growth of the dc1 tiller bud. Transcriptome analysis indicated that expression levels of transcription factors putatively bound by ORYZA SATIVA HOMEOBOX 1 (OSH1) are changed in response to decapitation and display a greater fold change in the dc1 mutant than that in the WT. Collectively, these findings reveal an important role of OsWUS in tiller bud growth by influencing apical dominance, and provide the basis for an improved understanding of tiller bud development in rice.
Assuntos
Oryza/crescimento & desenvolvimento , Proteínas de Plantas/fisiologia , Caules de Planta/crescimento & desenvolvimento , Técnicas de Silenciamento de GenesRESUMO
KEY MESSAGE: CHR721 functions as a chromatin remodeler and interacts with a known single-stranded binding protein, OsRPA1a, to regulate both male and female reproductive development in rice. Reproductive development and fertility are important for seed production in rice. Here, we identified a sterile rice mutant, chr721, that exhibited defects in both male and female reproductive development. Approximately 5% of the observed defects in chr721, such as asynchronous dyad division, occurred during anaphase II of meiosis. During the mitotic stage, approximately 80% of uninucleate microspores failed to develop into tricellular pollen, leading to abnormal development. In addition, defects in megaspore development were detected after functional megaspore formation. CHR721, which encodes a nuclear protein belonging to the SNF2 subfamily SMARCAL1, was identified by map-based cloning. CHR721 was expressed in various tissues, especially in spikelets. CHR721 was found to interact with replication protein A (OsRPA1a), which is involved in DNA repair. The expressions of genes involved in DNA repair and cell-cycle checkpoints were consistently upregulated in chr721. Although numerous genes involved in male and female development have been identified, the mode of participation of chromatin-remodeling factors in reproductive development is still not well understood. Our results suggest that CHR721, a novel gene cloned from rice, plays a vital role in both male and female reproductive development.
Assuntos
Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica de Plantas , Oryza/genética , Proteínas de Plantas/genética , Reprodução/genética , Sementes/genética , Ciclo Celular/genética , Ciclo Celular/fisiologia , Cromossomos de Plantas , Clonagem Molecular , Reparo do DNA , Genes de Plantas/genética , Meiose , Oryza/embriologia , Oryza/crescimento & desenvolvimento , Óvulo Vegetal/citologia , Óvulo Vegetal/genética , Desenvolvimento Vegetal/genética , Desenvolvimento Vegetal/fisiologia , Plantas Geneticamente Modificadas , Pólen/genética , Sementes/citologia , Sementes/crescimento & desenvolvimentoRESUMO
We report the first global, time-dependent simulation of the Mars upper atmospheric responses to a realistic solar flare event, an X8.2 eruption on 10 September 2017. The Mars Global Ionosphere-Thermosphere Model runs with realistically specified flare irradiance, giving results in reasonably good agreement with the Mars Atmosphere and Volatile EvolutioN spacecraft measurements. It is found that the ionized and neutral regimes of the upper atmosphere are significantly disturbed by the flare but react differently. The ionospheric electron density enhancement is concentrated below ~110-km altitude due to enhanced solar X-rays, closely following the time evolution of the flare. The neutral atmospheric perturbation increases with altitude and is important above ~150-km altitude, in association with atmospheric upwelling driven by solar extreme ultraviolet heating. It takes ~2.5 hr past the flare peak to reach the maximum disturbance and then additional ~10 hr to generally settle down to preflare levels.
RESUMO
Grain size is an important agronomic trait in determining grain yield. However, the molecular mechanisms that determine the final grain size are not well understood. Here, we report the functional analysis of a rice (Oryza sativa L.) mutant, dwarf and small grain1 (dsg1), which displays pleiotropic phenotypes, including small grains, dwarfism and erect leaves. Cytological observations revealed that the small grain and dwarfism of dsg1 were mainly caused by the inhibition of cell proliferation. Map-based cloning revealed that DSG1 encoded a mitogen-activated protein kinase (MAPK), OsMAPK6. OsMAPK6 was mainly located in the nucleus and cytoplasm, and was ubiquitously distributed in various organs, predominately in spikelets and spikelet hulls, consistent with its role in grain size and biomass production. As a functional kinase, OsMAPK6 interacts strongly with OsMKK4, indicating that OsMKK4 is likely to be the upstream MAPK kinase of OsMAPK6 in rice. In addition, hormone sensitivity tests indicated that the dsg1 mutant was less sensitive to brassinosteroids (BRs). The endogenous BR levels were reduced in dsg1, and the expression of several BR signaling pathway genes and feedback-inhibited genes was altered in the dsg1 mutant, with or without exogenous BRs, indicating that OsMAPK6 may contribute to influence BR homeostasis and signaling. Thus, OsMAPK6, a MAPK, plays a pivotal role in grain size in rice, via cell proliferation, and BR signaling and homeostasis.
Assuntos
Biomassa , Grão Comestível/metabolismo , Proteína Quinase 6 Ativada por Mitógeno/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Brassinosteroides/farmacologia , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Grão Comestível/genética , Grão Comestível/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Proteína Quinase 6 Ativada por Mitógeno/genética , Quinases de Proteína Quinase Ativadas por Mitógeno/genética , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Dados de Sequência Molecular , Mutação , Oryza/genética , Oryza/crescimento & desenvolvimento , Reguladores de Crescimento de Plantas/farmacologia , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Ligação Proteica , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de AminoácidosRESUMO
The family Euphorbiaceae includes some of the most efficient biomass accumulators. Whole genome sequencing and the development of genetic maps of these species are important components in molecular breeding and genetic improvement. Here we report the draft genome of physic nut (Jatropha curcas L.), a biodiesel plant. The assembled genome has a total length of 320.5 Mbp and contains 27,172 putative protein-coding genes. We established a linkage map containing 1208 markers and anchored the genome assembly (81.7%) to this map to produce 11 pseudochromosomes. After gene family clustering, 15,268 families were identified, of which 13,887 existed in the castor bean genome. Analysis of the genome highlighted specific expansion and contraction of a number of gene families during the evolution of this species, including the ribosome-inactivating proteins and oil biosynthesis pathway enzymes. The genomic sequence and linkage map provide a valuable resource not only for fundamental and applied research on physic nut but also for evolutionary and comparative genomics analysis, particularly in the Euphorbiaceae.
Assuntos
Genoma de Planta/genética , Jatropha/genética , Ricinus communis/genética , Sequência de Bases , Biocombustíveis , Mapeamento Cromossômico , DNA Complementar/química , DNA Complementar/genética , DNA de Plantas/química , DNA de Plantas/genética , Evolução Molecular , Genótipo , Anotação de Sequência Molecular , Dados de Sequência Molecular , Família Multigênica , Análise de Sequência de DNA , TranscriptomaRESUMO
Aerial architecture in higher plants is dependent on the activity of the shoot apical meristem (SAM) and axillary meristems (AMs). The SAM produces a main shoot and leaf primordia, while AMs are generated at the axils of leaf primordia and give rise to branches and flowers. Therefore, the formation of AMs is a critical step in the construction of plant architecture. Here, we characterized the rice (Oryza sativa) lax panicle2 (lax2) mutant, which has altered AM formation. LAX2 regulates the branching of the aboveground parts of a rice plant throughout plant development, except for the primary branch in the panicle. The lax2 mutant is similar to lax panicle1 (lax1) in that it lacks an AM in most of the lateral branching of the panicle and has a reduced number of AMs at the vegetative stage. The lax1 lax2 double mutant synergistically enhances the reduced-branching phenotype, indicating the presence of multiple pathways for branching. LAX2 encodes a nuclear protein that contains a plant-specific conserved domain and physically interacts with LAX1. We propose that LAX2 is a novel factor that acts together with LAX1 in rice to regulate the process of AM formation.
Assuntos
Meristema/crescimento & desenvolvimento , Proteínas Nucleares/metabolismo , Oryza/genética , Proteínas de Plantas/metabolismo , Clonagem Molecular , Dados de Sequência Molecular , Mutação , Proteínas Nucleares/genética , Oryza/crescimento & desenvolvimento , Filogenia , Proteínas de Plantas/genéticaRESUMO
In the rapidly evolving landscape of Internet of Things (IoT), Zigbee networks have emerged as a critical component for enabling wireless communication in a variety of applications. Despite their widespread adoption, Zigbee networks face significant security challenges, particularly in key management and network resilience against cyber attacks like distributed denial of service (DDoS). Traditional key rotation strategies often fall short in dynamically adapting to the ever-changing network conditions, leading to vulnerabilities in network security and efficiency. To address these challenges, this paper proposes a novel approach by implementing a reinforcement learning (RL) model for adaptive key rotation in Zigbee networks. We developed and tested this model against traditional periodic, anomaly detection-based, heuristic-based, and static key rotation methods in a simulated Zigbee network environment. Our comprehensive evaluation over a 30-day period focused on key performance metrics such as network efficiency, response to DDoS attacks, network resilience under various simulated attacks, latency, and packet loss in fluctuating traffic conditions. The results indicate that the RL model significantly outperforms traditional methods, demonstrating improved network efficiency, higher intrusion detection rates, faster response times, and superior resource management. The study underscores the potential of using artificial intelligence (AI)-driven, adaptive strategies for enhancing network security in IoT environments, paving the way for more robust and intelligent Zigbee network security solutions.
RESUMO
Separating plasma or serum from blood is essential for precise testing. However, extracting precise plasma quantities outside the laboratory poses challenges. A recent study has introduced a capillary force-driven membrane filtration technique to accurately separate small plasma volumes. This method efficiently isolates 100-200 µL of pure human whole blood with a 48% hematocrit, resulting in 5-30 µL of plasma with less than a 10% margin of error. The entire process is completed within 20 min, offering a simple and cost-effective approach to blood separation. This study has successfully addressed the bottleneck in self-service POCT, ensuring testing accuracy. This innovative method shows promise for clinical diagnostics and point-of-care testing.
RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: The Sang Yu granule (SY), a traditional Chinese medicine prescription of Xijing Hospital, was developed based on the Guanyin powder in the classical prescription "Hong's Collection of Proven Prescriptions" and the new theory of modern Chinese medicine. It has been proved to have a certain therapeutic effect on drug-induced liver injury (DILI), but the specific mechanism of action is still unclear. AIM OF STUDY: Aim of the study was to explore the effect of SangYu granule on treating drug-induced liver injury induced by acetaminophen in mice. MATERIALS AND METHODS: The chemical composition of SY, serum, and liver tissue was analyzed using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry. To assess hepatic function, measurements were taken using kits for total bile acids, as well as serum AST, ALT, and ALP activity. Concentrations of IL-1ß and TNF-α in serum were quantified using ELISA kits. Transcriptome Sequencing Analysis and 2bRAD-M microbial diversity analysis were employed to evaluate gene expression variance in liver tissue and fecal microbiota diversity among different groups, respectively. Western blotting was performed to observe differences in the activation levels of FXR, SHP, CYP7A1 and PPARα in the liver, and the levels of FXR and FGF-15 genes and proteins in the ileum of mice. Additionally, fecal microbiota transplantation (FMT) experiments were conducted to investigate the potential therapeutic effect of administering the intestinal microbial suspension from mice treated with SY on drug-induced liver injury. RESULTS: SY treatment exhibited significant hepatoprotective effects in mice, effectively ameliorating drug-induced liver injury while concurrently restoring intestinal microbial dysbiosis. Furthermore, SY administration demonstrated a reduction in the concentration of total bile acids, the expression of FXR and SHP proteins in the liver was up-regulated, CYP7A1 protein was down-regulated, and the expressions of FXR and FGF-15 proteins in the ileum were up-regulated. However, no notable impact on PPARα was observed. Furthermore, results from FMT experiments indicated that the administration of fecal suspensions derived from mice treated with SY did not yield any therapeutic benefits in the context of drug-induced liver injury. CONCLUSION: The aforementioned findings strongly suggest that SY exerts a pronounced ameliorative effect on drug-induced liver injury through its ability to modulate the expression of key proteins involved in bile acid secretion, thereby preserving hepato-enteric circulation homeostasis.
Assuntos
Acetaminofen , Doença Hepática Induzida por Substâncias e Drogas , Medicamentos de Ervas Chinesas , Microbioma Gastrointestinal , Fígado , PPAR alfa , Animais , Acetaminofen/toxicidade , Doença Hepática Induzida por Substâncias e Drogas/prevenção & controle , Doença Hepática Induzida por Substâncias e Drogas/tratamento farmacológico , Medicamentos de Ervas Chinesas/farmacologia , Masculino , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Camundongos , PPAR alfa/metabolismo , Microbioma Gastrointestinal/efeitos dos fármacos , Fatores de Crescimento de Fibroblastos , Colesterol 7-alfa-Hidroxilase/metabolismo , Colesterol 7-alfa-Hidroxilase/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Fator de Necrose Tumoral alfa/sangue , Ácidos e Sais Biliares/metabolismo , Interleucina-1beta/metabolismo , Interleucina-1beta/genéticaRESUMO
BACKGROUND: Mucopolysaccharidosis (MPS) refers to a group of lysosomal storage disorders for which seven types and 11 subtypes are currently recognized. Targeted next-generation sequencing (NGS) offers an important method of disease typing, diagnosis, prenatal diagnosis, and treatment. METHODS: Gene variations in 48 Chinese MPS patients were evaluated using NGS, and the pathogenicity of the DNA alterations was evaluated using PolyPhen2, SIFT, and Mutation Taster. The effect of amino acid substitution on protein structure was also assessed. RESULTS: Four pedigrees with MPS I (8.3%), 28 with MPS II (58.3%), two with MPS IIIA (4.2%), two with MPS IIIB (4.2%), six with MPS IVA (12.5%), one with MPS IVB (2.1%), and five with MPS VI (10.4%) were identified. Of the 69 variations identified, 11 were novel variants (three in IDUA, five in IDS, and three in GALNS), all of which were predicted to be disease-causing except for one, and were associated with impaired protein structure and function. CONCLUSIONS: Targeted NGS technology is effective for the gene-based testing of MPS disorders, which show high allelic heterogeneity. MPS II was the predominant form in Chinese. Our study expands the existing variation spectrum of MPS, which is important for disease management and genetic counseling.
Assuntos
Condroitina Sulfatases , Mucopolissacaridose II , Povo Asiático/genética , China , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Mucopolissacaridose II/diagnóstico , Mucopolissacaridose II/genética , LinhagemRESUMO
MicroRNAs (miRNAs) are a type of small non-coding RNA found in eukaryotes. They play a key role in gene expression by down-regulating gene expression and are involved in the environment stress response in plants. Although a large number of miRNAs have been identified from Arabidopsis, few studies have focused on Oryza sativa miRNAs, especially on stress-related miRNAs. Five cDNA libraries of small RNAs from rice seedlings treated with cold, dehydration, salinity, and abscisic acid (ABA), as well as wild-type seedlings, were constructed. Seven rice novel miRNAs were identified by Northern analysis, and their expression patterns under different stress treatments were determined. Results showed that the expression of several novel miRNAs was regulated by one or more stress treatments. Our identification of novel stress-related miRNAs in rice suggests that these miRNAs might be involved in rice stress response pathways.
Assuntos
MicroRNAs/biossíntese , MicroRNAs/genética , Oryza/genética , Estresse Fisiológico , Ácido Abscísico/química , Adaptação Fisiológica/genética , Sequência de Bases , Northern Blotting , Temperatura Baixa , Regulação da Expressão Gênica de Plantas , Biblioteca Gênica , Concentração de Íons de Hidrogênio , MicroRNAs/isolamento & purificação , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Oryza/metabolismo , RNA de Plantas/análise , RNA de Plantas/biossíntese , RNA de Plantas/genética , Salinidade , Plântula/genética , Plântula/metabolismo , ÁguaRESUMO
Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder that affects the degradation of branched chain amino acids (BCAAs). Only a few cases of MSUD have been documented in Mainland China. In this report, 8 patients (4 females and 4 males) with MSUD from 8 unrelated Chinese Han families were diagnosed at the age of 6 days to 4 months. All the coding regions and exon/intron boundaries of BCKDHA, BCDKHB, DBT and DLD genes were analyzed by targeted NGS in the 8 MSUD pedigrees. Targeted NGS revealed 2 pedigrees with MSUD Ia, 5 pedigrees with Ib, 1 pedigree with MSUD II. Totally, 13 variants were detected, including 2 variants (p.Ala216Val and p.Gly281Arg) in BCKDHA gene, 10 variants (p.Gly95Ala, p.Ser171Pro, p.Phe175Leu, p.Arg183Trp, p.Lys222Thr, p.Arg285Ter, p.Arg111Ter, p.S184Pfs*46, p.Arg170Cys, p.I160Ffs*25) in BCKDHB gene, 1 variant (p.Arg431Ter) in DBT gene. In addition, 4 previously unidentified variants (p.Gly281Arg in BCKDHA gene, p.Ser171Pro, p.Gly95Ala and p.Lys222Thr in BCKDHB gene) were identified. NGS plus Sanger sequencing detection is effective and accurate for gene diagnosis. Computational structural modeling indicated that these novel variations probably affect structural stability and considered as likely pathogenic variants.
Assuntos
3-Metil-2-Oxobutanoato Desidrogenase (Lipoamida)/genética , Doença da Urina de Xarope de Bordo/genética , 3-Metil-2-Oxobutanoato Desidrogenase (Lipoamida)/metabolismo , Aminoácidos de Cadeia Ramificada/metabolismo , Povo Asiático/genética , Simulação por Computador , Análise Mutacional de DNA , Feminino , Testes Genéticos , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Lactente , Recém-Nascido , Masculino , Doença da Urina de Xarope de Bordo/diagnóstico , Modelos Moleculares , Mutação de Sentido Incorreto , Linhagem , Estrutura Terciária de Proteína/genética , Estudos RetrospectivosRESUMO
Liquid adsorption on a substrate has great applications in inkjet printing as well as micro/nano fabrication. In this letter, we focus on obtaining a better understanding of the pinning-dewetting phenomenon through solubility measurements during droplet evaporation. The physical adsorption/penetration of liquid on the substrate material is considered to be responsible for the pinning of the three-phase contact line. Once the adsorption surrounding the contact line reaches equilibrium, dewetting occurs and the droplet shrinks. The absorption kinetics of water molecules on different substrates was monitored. An analytical technique was developed to measure the threshold adsorption density of trace solvents on these substrates including different polymers, silicon, and gold.
RESUMO
The shape of deposits obtained from drying drops containing colloidal particles matters for technologies such as inkjet printing, microelectronics, and bioassay manufacturing. In this work, the formation of deposits during the drying of nanoliter drops containing colloidal particles is investigated experimentally with microscopy and profilometry, and theoretically with an in-house finite-element code. The system studied involves aqueous drops containing titania nanoparticles evaporating on a glass substrate. Deposit shapes from spotted drops at different pH values are measured using a laser profilometer. Our results show that the pH of the solution influences the dried deposit pattern, which can be ring-like or more uniform. The transition between these patterns is explained by considering how DLVO interactions such as the electrostatic and van der Waals forces modify the particle deposition process. Also, a phase diagram is proposed to describe how the shape of a colloidal deposit results from the competition among three flow patterns: a radial flow driven by evaporation at the wetting line, a Marangoni recirculating flow driven by surface tension gradients, and the transport of particles toward the substrate driven by DLVO interactions. This phase diagram explains three types of deposits commonly observed experimentally, such as a peripheral ring, a small central bump, or a uniform layer. Simulations and experiments are found in very good agreement.
Assuntos
Coloides/química , Análise de Elementos Finitos , Concentração de Íons de Hidrogênio , Modelos TeóricosRESUMO
In order to further evaluate the behavior of ionospheric variations at Mars, we investigate the Martian ionosphere-thermosphere (IT) perturbations associated with non-migrating thermal tides using over four years of Mars Atmosphere and Volatile Evolution (MAVEN) in situ measurements of the IT electron and neutral densities. The results are consistent with those of previous studies, namely strong correlation between the tidal perturbations in electron and neutral densities on the dayside at altitudes ~150-185 km, as expected from photochemical theory. In addition, there are intervals during which this correlation extends to higher altitudes, up to ~270 km, where diffusive transport of plasma plays a dominant role over photochemical processes. This is significant because at these altitudes the thermosphere and ionosphere are only weakly coupled through collisions. The identified non-migrating tidal wave variations in the neutral thermosphere are predominantly wave-1, wave-2, and wave-3. Wave-1 is often the dominant wavenumber for electron density tidal variations, particularly at high altitudes over crustal fields. The Mars Climate Database (MCD) neutral densities (below 300 km along the MAVEN orbit) shows clear tidal variations which are predominantly wave-2 and wave-3, and have similar wave amplitudes to those observed.
RESUMO
Longitudinal structures in the Martian thermosphere and topside ionosphere between 150 and 200 km altitudes are studied using in situ electron and neutral measurements from the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Four time intervals are selected for comparison, during which MAVEN sampled similar local time (9.3-10.3 h) and latitude (near 20°S) regions but at different solar longitude positions (two near northern summer solstice, one each at northern vernal and autumnal equinoxes). Persistent and pronounced tidal oscillations characterize the ionosphere and thermosphere, whose longitudinal variations in density are generally in-phase with each other. Our analysis of simultaneous and collocated neutral and electron data provides direct observational evidence for thermosphere-ionosphere coupling through atmospheric tides. We conclude that the ionosphere is subject to modulation by upward-propagating thermal tides, via both tide-induced vertical displacement and photochemical reactions. Atmospheric tides constitute a ubiquitous and significant perturbation source to the ionospheric electron density, up to ~15% near 200 km.
RESUMO
Cosolvents have numerous applications in many industries as well as scientific research. The shortage in the knowledge of the structures in a cosolvent system is significant. In this work, we display the spatial as well as the kinetic distribution of the cosolvents using droplets as paradigms. When an alcohol/water-containing sessile droplet evaporates on a substrate, it phase segregates into a water-enriched core and a thin alcohol prevailing shell. This is considered to be due to the different escaping rate of solvents out of the liquid-vapor (l-v) interfaces. In between the core and shell phases, there exists a rough and solid-like liquid-liquid (l-l) wall interface as marked by the fluorescent polystyrene spheres and imaged by a confocal microscope. Holes and patches of beads are observed to form on this phase boundary. The water-dispersed beads prefer to partition within the core. The shell prevails in the droplet during most of the drying and shrinks with the l-v boundary. By monitoring the morphological progression of the droplet, the composition of the cosolvent at the liquid-vapor interface is obtained.