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1.
Proc Natl Acad Sci U S A ; 121(18): e2318666121, 2024 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-38652747

RESUMO

In bacteria, intracellular K+ is involved in the regulation of membrane potential, cytosolic pH, and cell turgor as well as in spore germination, environmental adaptation, cell-to-cell communication in biofilms, antibiotic sensitivity, and infectivity. The second messenger cyclic-di-AMP (c-di-AMP) has a central role in modulating the intracellular K+ concentration in many bacterial species, controlling transcription and function of K+ channels and transporters. However, our understanding of how this regulatory network responds to c-di-AMP remains poor. We used the RCK (Regulator of Conductance of K+) proteins that control the activity of Ktr channels in Bacillus subtilis as a model system to analyze the regulatory function of c-di-AMP with a combination of in vivo and in vitro functional and structural characterization. We determined that the two RCK proteins (KtrA and KtrC) are neither physiologically redundant or functionally equivalent. KtrC is the physiologically dominant RCK protein in the regulation of Ktr channel activity. In explaining this hierarchical organization, we found that, unlike KtrA, KtrC is very sensitive to c-di-AMP inactivation and lack of c-di-AMP regulation results in RCK protein toxicity, most likely due to unregulated K+ flux. We also found that KtrC can assemble with KtrA, conferring c-di-AMP regulation to the functional KtrA/KtrC heteromers and potentially compensating KtrA toxicity. Altogether, we propose that the central role of c-di-AMP in the control of the K+ machinery, by modulating protein levels through gene transcription and by regulating protein activity, has determined the evolutionary selection of KtrC as the dominant RCK protein, shaping the hierarchical organization of regulatory components of the K+ machinery.


Assuntos
Bacillus subtilis , Proteínas de Bactérias , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/genética , Bacillus subtilis/metabolismo , Bacillus subtilis/genética , Potássio/metabolismo , Regulação Bacteriana da Expressão Gênica , Fosfatos de Dinucleosídeos/metabolismo , Canais de Potássio/metabolismo , Canais de Potássio/genética
2.
J Cell Sci ; 136(11)2023 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-37305997

RESUMO

Septins are cytoskeletal proteins interacting with the inner plasma membrane and other cytoskeletal partners. Being key in membrane remodeling processes, they often localize at specific micrometric curvatures. To analyze the behavior of human septins at the membrane and decouple their role from other partners, we used a combination of bottom-up in vitro methods. We assayed their ultrastructural organization, their curvature sensitivity, as well as their role in membrane reshaping. On membranes, human septins organize into a two-layered mesh of orthogonal filaments, instead of generating parallel sheets of filaments observed for budding yeast septins. This peculiar mesh organization is sensitive to micrometric curvature and drives membrane reshaping as well. The observed membrane deformations together with the filamentous organization are recapitulated in a coarse-grained computed simulation to understand their mechanisms. Our results highlight the specific organization and behavior of animal septins at the membrane as opposed to those of fungal proteins.


Assuntos
Citoesqueleto , Septinas , Animais , Humanos , Septinas/genética , Membranas , Membrana Celular , Bioensaio
3.
Biophys J ; 123(14): 2024-2037, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38219015

RESUMO

Slow deactivation is a critical property of voltage-gated K+ channels encoded by the human Ether-à-go-go-Related Gene 1 (hERG). hERG1 channel deactivation is modulated by interactions between intracellular N-terminal Per-Arnt-Sim (PAS) and C-terminal cyclic nucleotide-binding homology (CNBh) domains. The PAS domain is multipartite, comprising a globular domain (gPAS; residues 26-135) and an N-terminal PAS-cap that is further subdivided into an initial unstructured "tip" (residues 1-12) and an amphipathic α-helical region (residues 13-25). Although the PAS-cap tip has long been considered the effector of slow deactivation, how its position near the gating machinery is controlled has not been elucidated. Here, we show that a triad of hydrophobic interactions among the gPAS, PAS-cap α helix, and the CNBh domains is required to support slow deactivation in hERG1. The primary sequence of this "hydrophobic nexus" is highly conserved among mammalian ERG channels but shows key differences to fast-deactivating Ether-à-go-go 1 (EAG1) channels. Combining sequence analysis, structure-directed mutagenesis, electrophysiology, and molecular dynamics simulations, we demonstrate that polar serine substitutions uncover an intermediate deactivation mode that is also mimicked by deletion of the PAS-cap α helix. Molecular dynamics simulation analyses of the serine-substituted channels show an increase in distance among the residues of the hydrophobic nexus, a rotation of the intracellular gating ring, and a retraction of the PAS-cap tip from its receptor site near the voltage sensor domain and channel gate. These findings provide compelling evidence that the hydrophobic nexus coordinates the respective components of the intracellular gating ring and positions the PAS-cap tip to control hERG1 deactivation gating.


Assuntos
Interações Hidrofóbicas e Hidrofílicas , Humanos , Ativação do Canal Iônico , Canal de Potássio ERG1/metabolismo , Canal de Potássio ERG1/química , Canal de Potássio ERG1/genética , Domínios Proteicos , Canais de Potássio Éter-A-Go-Go/química , Canais de Potássio Éter-A-Go-Go/metabolismo , Canais de Potássio Éter-A-Go-Go/genética , Sequência de Aminoácidos , Espaço Intracelular/metabolismo , Animais , Células HEK293
4.
Langmuir ; 40(14): 7433-7443, 2024 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-38532537

RESUMO

We investigate the structure and interactions of a model anionic/amphoteric mixed surfactant micellar system, namely, sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine N-oxide (DDAO), employing SANS, FTIR, DLS, and pH measurements, in the range 0.1-100 mM total surfactant concentration and 0-100% DDAO. Increasing surfactant concentration is found to elongate the prolate ellipsoid micelles (RPolar ∼ 25-40 Å), accompanied by up to a 6-fold increase in micellar charge. The surfactant synergy, in terms of micellar charge and size, diffusion coefficient, solution pH, and headgroup interactions, was found to vary with concentration. At lower concentrations (≤50 mM), the SDS-DDAO ratio of maximum synergy is found to be asymmetric (at 65-85% DDAO), which is rationalized using regular solution theory, suggesting an equilibrium between Na+ dissociation, DDAO protonation, and counterion concentration. At higher concentrations, maximum synergy shifts toward the equimolar ratio. Overall, our study expands and unifies previous reports, providing a comprehensive understanding for this model, synergetic mixed micellar system.

5.
BMC Pediatr ; 24(1): 59, 2024 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-38243191

RESUMO

The aim of this paper is to review the topic of neonatal fractures of the upper limb, describing the different types of fractures focusing on the etiology, epidemiology, risk factors, clinical approach, diagnosis, treatment and prognosis of these injuries. We included all types of research studies, both experimental and observational, published in English, French, Portuguese and Spanish. The information was obtained using the keywords neonatal upper limb fracture, clavicle fracture or humerus fracture from the following resources: MEDLINE database, Embase® database and LILACS database. Other resources such as hand searches of the references of retrieved literature and authoritative texts, personal and hospital libraries searching for texts on upper limb neonatal fractures, discussions with experts in the field of upper limb neonatal fractures and personal experience, were also considered for the completion of the article.Neonatal fractures of the upper limb are consensually considered to have a good prognosis and no long-term sequelae. Conservative treatment is the option in the vast majority of the fractures and is associated with excellent results, with good healing, full range of motion, adequate remodeling without obvious deformity, neurologic impairment or functional implications.


Assuntos
Fraturas Ósseas , Fraturas do Úmero , Recém-Nascido , Humanos , Fraturas Ósseas/diagnóstico , Fraturas Ósseas/etiologia , Fraturas Ósseas/terapia , Extremidade Superior , Clavícula , Prognóstico , Fatores de Risco
6.
Proc Natl Acad Sci U S A ; 118(14)2021 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-33790011

RESUMO

bis-(3',5')-cyclic diadenosine monophosphate (c-di-AMP) is a second messenger with roles in virulence, cell wall and biofilm formation, and surveillance of DNA integrity in many bacterial species, including pathogens. Strikingly, it has also been proposed to coordinate the activity of the components of K+ homeostasis machinery, inhibiting K+ import, and activating K+ export. However, there is a lack of quantitative evidence supporting the direct functional impact of c-di-AMP on K+ transporters. To gain a detailed understanding of the role of c-di-AMP on the activity of a component of the K+ homeostasis machinery in B. subtilis, we have characterized the impact of c-di-AMP on the functional, biochemical, and physiological properties of KhtTU, a K+/H+ antiporter composed of the membrane protein KhtU and the cytosolic protein KhtT. We have confirmed c-di-AMP binding to KhtT and determined the crystal structure of this complex. We have characterized in vitro the functional properties of KhtTU and KhtU alone and quantified the impact of c-di-AMP and of pH on their activity, demonstrating that c-di-AMP activates KhtTU and that pH increases its sensitivity to this nucleotide. Based on our functional and structural data, we were able to propose a mechanism for the activation of KhtTU by c-di-AMP. In addition, we have analyzed the impact of KhtTU in its native bacterium, providing a physiological context for the regulatory function of c-di-AMP and pH. Overall, we provide unique information that supports the proposal that c-di-AMP is a master regulator of K+ homeostasis machinery.


Assuntos
Proteínas de Bactérias/metabolismo , AMP Cíclico/metabolismo , Antiportadores de Potássio-Hidrogênio/metabolismo , Potássio/metabolismo , Bacillus subtilis , Sítios de Ligação , AMP Cíclico/química , Homeostase , Antiportadores de Potássio-Hidrogênio/química , Ligação Proteica
7.
Proc Natl Acad Sci U S A ; 118(44)2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34716268

RESUMO

The human ERG (hERG) K+ channel has a crucial function in cardiac repolarization, and mutations or channel block can give rise to long QT syndrome and catastrophic ventricular arrhythmias. The cytosolic assembly formed by the Per-Arnt-Sim (PAS) and cyclic nucleotide binding homology (CNBh) domains is the defining structural feature of hERG and related KCNH channels. However, the molecular role of these two domains in channel gating remains unclear. We have previously shown that single-chain variable fragment (scFv) antibodies can modulate hERG function by binding to the PAS domain. Here, we mapped the scFv2.12 epitope to a site overlapping with the PAS/CNBh domain interface using NMR spectroscopy and mutagenesis and show that scFv binding in vitro and in the cell is incompatible with the PAS interaction with CNBh. By generating a fluorescently labeled scFv2.12, we demonstrate that association with the full-length hERG channel is state dependent. We detect Förster resonance energy transfer (FRET) with scFv2.12 when the channel gate is open but not when it is closed. In addition, state dependence of scFv2.12 FRET signal disappears when the R56Q mutation, known to destabilize the PAS-CNBh interaction, is introduced in the channel. Altogether, these data are consistent with an extensive structural alteration of the PAS/CNBh assembly when the cytosolic gate opens, likely favoring PAS domain dissociation from the CNBh domain.


Assuntos
Canal de Potássio ERG1/metabolismo , Canais de Cátion Regulados por Nucleotídeos Cíclicos/metabolismo , Citosol/metabolismo , Canal de Potássio ERG1/genética , Canal de Potássio ERG1/imunologia , Canais de Potássio Éter-A-Go-Go/imunologia , Canais de Potássio Éter-A-Go-Go/metabolismo , Transferência Ressonante de Energia de Fluorescência , Células HEK293 , Humanos , Ativação do Canal Iônico , Síndrome do QT Longo/genética , Conformação Molecular , Mutação , Conformação Proteica , Domínios Proteicos/genética , Domínios Proteicos/imunologia , Proteínas Serina-Treonina Quinases/metabolismo , Relação Estrutura-Atividade
8.
Cell Tissue Bank ; 25(1): 325-337, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37945942

RESUMO

A case series of the use of amniotic membrane (AM) for treating chronic nonhealing wounds. It presents five cases of polymorbid patients with a total of nine chronic nonhealing wounds. The patient group consisted of four men and one woman with various comorbidities, aged 45-72 years. The mean initial wound size was 15.8 cm2, and the mean time from the onset of the wound to the first application of AM was 122 weeks. The wounds were caused by chronic venous insufficiency and/or peripheral arterial disease. Wounds were treated in a standardized protocol. AM was applied weekly in the first month and then every two weeks. Photo documentation of the wound and microbiological colonization was carried out at each visit. In three out of five patients, the AM treatment effectively promoted healing up to complete wound closure. In two cases, the wounds stayed unhealed despite numerous AM applications. Pain relief was noted in all patients. The success of the treatment was closely tied to patient factors, such as adherence to the prescribed treatment regimen and individual patient characteristics. In some cases, treatment failure was observed, possibly due to underlying comorbidities, wound parameters, or poor patient compliance. AM treatment has the potential to become a viable treatment option for these nonhealing wounds. However, the effectiveness of the treatment may be influenced by various patient factors and the underlying cause of the wound. Therefore, it is crucial to have an individualized treatment plan that considers these particular factors.


Assuntos
Âmnio , Cicatrização , Masculino , Feminino , Humanos , Resultado do Tratamento , Criopreservação/métodos , Estudos Retrospectivos
9.
Phys Rev Lett ; 131(21): 218101, 2023 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-38072592

RESUMO

We investigate the drying of isolated polymer solution droplets, employing acoustic levitation, and demonstrate the spontaneous generation of breath figures (BF) on the resulting polymer particles and capsules (∼5-1000 µm) with controlled surface pore arrays (<1-20 µm). By contrast with supported polymer thin films, the evaporative cooling experienced by suspended droplets suffices to yield ubiquitous BF formation, owing to their thermal insulation and the synchronous condensation and self-assembly of water microdroplets, accompanied by capsule skin formation and kinetic arrest. A simple model describes simultaneously the radius and temperature evolution along the droplet-to-particle transformation, and the scaling of surface pore dimensions, with environmental parameters. The generality of the approach is demonstrated with a range of model polymers, and the coupled roles of solution thermodynamics and droplet environment are shown to permit the facile design of capsules with tunable transport and dissolution kinetics.

10.
World J Urol ; 41(10): 2671-2677, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37668717

RESUMO

PURPOSE: The Hugo™ RAS system is a novel robotic platform with innovative features. However, there are currently no available data on extraperitoneal robot-assisted radical prostatectomy (RARP) performed using this system. The objective of this study is to describe the surgical setup and assess the safety and feasibility of the extraperitoneal approach in robotic radical prostatectomy with the Hugo™ RAS system. METHODS: Sixteen consecutive patients diagnosed with localized prostate cancer underwent extraperitoneal RARP ± lymph node dissection at our institution, between March and May 2023. All RARP procedures were performed extraperitoneal with a modular four-arm configuration. The focus was to describe the operative room setup, trocar placement, tilt and docking angles and evaluate the safety and feasibility of this approach with this robotic platform. Secondary outcomes recorded included, total operative time, console time, estimated bleeding, intra- and postoperative complications, and length of stay after surgery. A descriptive analysis was conducted. RESULTS: We report on the first sixteen cases of extraperitoneal robot-assisted radical prostatectomy performed with the new Hugo™ RAS system. All procedures were completed, without the need for conversion or placement of additional ports. No intraoperative complications or major technical failures that would prevent the completion of surgery were recorded. The median operative time was 211 min (IQR 180-277), and the median console time was 152 min (IQR 119-196). The mean docking time was 4.6 min (IQR 4.1-5.2). The median estimated blood loss and the median time to remove the vesical catheter were 200 mL (IQR 150-400) and 8 days (IQR 7-8), respectively. The median length of stay was 2 days (IQR 2-2). Only one minor complication was registered in the first 30 days. CONCLUSION: This study provides evidence of the safety and feasibility of the extraperitoneal approach in RARP with the Hugo™ RAS system. The description of the surgical setup in terms of trocar placement, arm-cart disposition, tilt and docking angles offers valuable information for surgeons interested in adopting this surgical approach with the Hugo™ RAS platform.


Assuntos
Laparoscopia , Neoplasias da Próstata , Procedimentos Cirúrgicos Robóticos , Robótica , Masculino , Humanos , Procedimentos Cirúrgicos Robóticos/métodos , Próstata/cirurgia , Prostatectomia/métodos , Neoplasias da Próstata/cirurgia , Laparoscopia/métodos
11.
Soft Matter ; 19(44): 8542-8551, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37899739

RESUMO

We investigate the solution structures of model sodium dodecyl sulfate/octanol/brine ternary mixtures across the lamellar (Lα), vesicle (L4) and micellar (L1) phases employing small angle neutron scattering (SANS), optical microscopy and nuclear magnetic resonance (NMR). Specifically, we examine the effect of co-surfactant octanol (0.2-9.48 w/v%) and temperature (25-65 °C) along dilution lines at fixed octanol : SDS ratios (0.08-1.21). A transition from Lα to sponge phase (L3) above 35 °C is found along the octanol : SDS = 1.21 isopleth, with phase coexistence above ϕ ≈ 0.14 weight fraction of surfactant and co-surfactant. The lamellar bilayers swell upon dilution, with an approximately linear increase of d-spacing, accompanied by a decrease of the Caillé parameter, indicative of greater membrane rigidity. At a lower octanol : SDS ratio of 0.62, coexistence of oblate micelles and vesicles is observed with preferential formation of vesicles at low concentrations. Dilution of the L1 phase, along octanol : SDS = 0.08, results in elongated micelles, as the NaCl : SDS ratio increases, while higher temperatures favour the formation of less elongated micelles. Our results provide a detailed map of the equilibrium structures found in the Lα vicinity of this extensively investigated flow-responsive surfactant system.

12.
Soft Matter ; 19(37): 7070-7083, 2023 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-37492886

RESUMO

Coupling microfluidics and small-angle neutron scattering (SANS), we investigate the influence of shear flow on a model bicontinuous microemulsion of D2O/n-octane/C10E4, examining the role of membrane volume fraction in the transformation towards a lamellar structure. We employ a contraction-expansion geometry with flow velocities in excess of 10 m s-1 and spatially map the microfluidic field using a small SANS beam, illuminating down to 10 nL sample volumes. The shear-induced, progressive, bicontinuous-to-lamellar transition is found to be promoted by additional extensional flow (>103 s-1), while fast relaxation kinetics (<2 ms) return the scattering pattern to isotropic shortly after the constriction. Further, increasing the domain size of the bicontinuous structure (determined by the membrane volume fraction) appears to amplify its response to shear. Hence, the structural changes within the dilute bicontinuous microemulsions simply scale with the volume fraction of the membrane. By contrast, the stronger response of the microemulsion with the smallest domain size, located near the bicontinuous/lamellar coexistence, indicates an influence of an already more ordered structure with fewer passages. Our findings provide insight into the high shear behaviour of microemulsions of both academic and industrial relevance.

13.
Mol Biol Rep ; 50(11): 9019-9027, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37716919

RESUMO

BACKGROUND: Biochemical markers and imaging tests have been used with the aim of stratifying the risk and detecting atrial fibrosis. Speckle-tracking echocardiography (STE) is used for the detection of atrial fibrosis and Gal-3 provides an important prognostic value. The objective of the study was to assess the association between atrial fibrosis markers and serum levels, genetic polymorphisms and genic expression of galectin-3. METHODS: 206 patients with permanent AF and 70 patients with paroxysmal AF were included in the study. Real time PCR (TaqMan) system was used to study SNPs rs4652 and 4644 of the gene LGALS3. Serum levels of Gal-3 were determined by ELISA and STE was performed to assess fibrosis. RESULTS: Mean age of individuals with permanent AF was 66.56 ± 12 years. As for the echocardiography results, those patients showed an decrease in the following parameters peak atrial longitudinal strain (PALS) (p = 0.002) when compared to the same parameters from the paroxysmal AF group of patients. There was a correlation between serum levels of Gal-3 and PALS in the group of patients with permanent AF; the lower the levels of gal-3, the lower the LA strain (r = 0.24; p = 0.01). CONCLUSIONS: Echocardiographic findings showed association with the groups, and with serum levels of Gal-3 in patients with permanent AF. The distribution of allelic and genotypic frequencies, and of the haplotypes of polymorphism LGALS3 rs4652 and rs4644 did not present statistical variation, which suggests that those SNPs are not associated with the AF clinical forms (permanent and paroxysmal).


Assuntos
Fibrilação Atrial , Humanos , Pessoa de Meia-Idade , Idoso , Fibrilação Atrial/diagnóstico por imagem , Fibrilação Atrial/genética , Galectina 3/genética , Átrios do Coração/diagnóstico por imagem , Átrios do Coração/patologia , Ecocardiografia/métodos , Fibrose
14.
Cell Tissue Bank ; 24(4): 779-788, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37227562

RESUMO

This study aimed to evaluate the efficacy of cryopreserved amniotic membrane (AM) grafts in chronic wound healing, including the mean percentage of wound closure per one AM application, and to determine whether the healing efficiency differs between AM grafts obtained from different placentas. A retrospective study analyzing inter-placental differences in healing capacity and mean wound closure after the application of 96 AM grafts prepared from nine placentas. Only the placentas from which the AM grafts were applied to patients suffering from long-lasting non-healing wounds successfully healed by AM treatment were included. The data from the rapidly progressing wound-closure phase (p-phase) were analyzed. The mean efficiency for each placenta, expressed as an average of wound area reduction (%) seven days after the AM application (baseline, 100%), was calculated from at least 10 applications. No statistical difference between the nine placentas' efficiency was found in the progressive phase of wound healing. The 7-day average wound reduction in particular placentas varied from 5.70 to 20.99% (median from 1.07 to 17.75) of the baseline. The mean percentage of wound surface reduction of all analyzed defects one week after the application of cryopreserved AM graft was 12.17 ± 20.12% (average ± SD). No significant difference in healing capacity was observed between the nine placentas. The data suggest that if there are intra- and inter-placental differences in AM sheets' healing efficacy, they are overridden by the actual health status of the subject or even the status of its individual wounds.


Assuntos
Âmnio , Placenta , Humanos , Feminino , Gravidez , Estudos Retrospectivos , Âmnio/transplante , Cicatrização , Criopreservação
15.
Molecules ; 28(4)2023 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-36838698

RESUMO

We investigate the combined effects of surface diffraction and total internal reflection (TIR) in the design of 3-dimensional materials exhibiting distinct structural colour on various facets. We employ mechanical wrinkling to introduce surface diffraction gratings (from the nano to the micron scales) on one face of an elastomeric rectangular parallelepiped-shaped slab and explore the roles, in the perceived colours, of wrinkling pattern, wavelength, the directionality of incident light and observation angles. We propose a simple model that satisfactorily accounts for all experimental observations. Employing polydimethylsiloxane (PDMS), which readily swells in the presence of various liquids and gases, we demonstrate that such multifaceted colours can respond to their environment. By coupling a right angle triangular prism with a surface grating, we demonstrate the straightforward fabrication of a so-called GRISM (GRating + prISM). Finally, using a range of examples, we outline possibilities for a predictive material design using multi-axial wrinkling patterns and more complex polyhedra.


Assuntos
Gases , Elasticidade
16.
Behav Res Methods ; 55(7): 3645-3657, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-36220950

RESUMO

Online experiments are an alternative for researchers interested in conducting behavioral research outside the laboratory. However, an online assessment might become a challenge when long and complex experiments need to be conducted in a specific order or with supervision from a researcher. The aim of this study was to test the computational validity and the feasibility of a remote and synchronous reinforcement learning (RL) experiment conducted during the social-distancing measures imposed by the pandemic. An additional feature of this study was to describe how a behavioral experiment originally created to be conducted in-person was transformed into an online supervised remote experiment. Open-source software was used to collect data, conduct statistical analysis, and do computational modeling. Python codes were created to replicate computational models that simulate the effect of working memory (WM) load over RL performance. Our behavioral results indicated that we were able to replicate remotely and with a modified behavioral task the effects of working memory (WM) load over RL performance observed in previous studies with in-person assessments. Our computational analyses using Python code also captured the effects of WM load over RL as expected, which suggests that the algorithms and optimization methods were reliable in their ability to reproduce behavior. The behavioral and computational validation shown in this study and the detailed description of the supervised remote testing may be useful for researchers interested in conducting long and complex experiments online.


Assuntos
Aprendizagem , Reforço Psicológico , Humanos , Memória de Curto Prazo , Simulação por Computador , Software
17.
Phys Rev Lett ; 128(5): 058001, 2022 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-35179945

RESUMO

We report the formation of "ripple" patterns by the sequential superposition of nonorthogonal surface waves excited by the spontaneous buckling of polymeric bilayers. Albeit of a different nature and micron scale compared to the familiar sedimentary ripples caused by gentle wave oscillations, we find commonalities in their topography, defects, and bifurcations. The patterns are rationalized in terms of a defect density that depends on the relative angle between generations, and a constant in-plane bending angle that depends on skin thickness. A minimal wave summation model enables the design of ripple and checkerboard surfaces by tuning material properties and fabrication process.

18.
Langmuir ; 38(23): 7198-7207, 2022 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-35658451

RESUMO

We examine the solution structures in a mixed surfactant system of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine N-oxide (DDAO) in water, on both sides of the two-phase boundary, employing dynamic light scattering, small-angle neutron scattering, and Fourier transform infrared spectroscopy. The precipitate phase boundary was accessed by lowering pH to 8, from its floating pH 9.5 value, and was experimentally approached from the monomeric and micellar regions in three ways: at fixed DDAO or SDS concentrations and at a fixed (70:30) SDS:DDAO molar ratio. We characterize the size, shape, and interactions of micelles, which elongate approaching the boundary, leading to the formation of disk-like aggregates within the biphasic region, coexisting with micelles and monomers. Our data, from both monomeric and micellar solutions, indicate that the two phase structures formed are largely pathway-independent, with dimensions influenced by both pH and mixed surfactant composition. Precipitation occurs at intermediate stoichiometries with a similar SDS:DDAO ratio, whereas asymmetric stoichiometries form a re-entrant transition, returning to the mixed micelle phase. Overall, our findings demonstrate the effect of stoichiometry and solution pH on the synergistic interaction of mixed surfactants and their impact on phase equilibrium and associated micellar and two-phase structures.

19.
Soft Matter ; 18(37): 7010-7019, 2022 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-35912998

RESUMO

We investigate the effect of added (NaCl) salt and varying flow rate on the phase behaviour and flow response of a model surfactant Lα phase, sodium dodecyl sulfate (SDS)/octanol/water, using small angle neutron scattering (SANS) and polarised optical microscopy in microfluidics, supported by NMR, viscosity, conductivity and zeta potential measurements. A long (∼3 m) tubular microchannel device is employed to quantify the spatiotemporal structural evolution of the system towards multilamellar vesicles (MLV). The effect of salt is rationalised in terms of changes in membrane bending rigidity and phase stability. It is shown that ∼1.8 w/w% NaCl addition results in MLV formation within the shortest time (or equivalent lengthscale) and yields near-centrosymmetric scattering profiles characteristic of MLVs (at a reference 1 mL h-1 flow rate and ≃90 s-1 shear rate). Further salt addition yields biphasic systems that remain strongly aligned under flow, while lower salt content also increases scattering anisotropy, accompanied by higher membrane rigidity and solution viscosity. Increasing flow rate causes greater initial Lα alignment, and thus flow anisotropy, but also faster evolution towards isotropy and MLV formation.

20.
Phys Chem Chem Phys ; 24(48): 29413-29422, 2022 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-36448993

RESUMO

We investigate the phase behavior of model ternary triacylglycerol blends, comprising triolein (C57H104O6, OOO), tripalmitin (C51H98O6, PPP) and tristearin (C57H110O6, SSS), building upon extensive characterisation of single and binary mixtures, in order to rigorously map the thermal transitions of model natural 'fats'. A combination of calorimetry, X-ray diffraction, and FTIR spectroscopy is employed to determine crystallisation and melting temperatures and identify the corresponding phases in the complex ternary system. We recover the eutectic behaviour of SSS-PPP blends and the invariability of OOO neat transitions, and resolve the complex ß' + ß ternary surface, reflecting the roles of unsaturation and polymorphism of its constituents. Our results provide a representation of the OOO:PPP:SSS:temperature phase behaviour into a triangular prism, consistent with binary pair-wise data, which can inform a range of food science, cosmetic, pharmaceutical and cleaning applications that depend strongly on the physical-chemistry of such multicomponent 'triglycerides'.


Assuntos
Trioleína , Trioleína/química , Triglicerídeos/química , Cristalização , Difração de Raios X
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