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1.
Eur J Appl Physiol ; 124(3): 909-924, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37768344

RESUMO

INTRODUCTION: This is a 12-weeks randomized controlled trial examining the effects of aerobic exercise (AE), computerized cognitive training (CCT) and their combination (COMB). We aim to investigate their impact on cardiovascular health and white matter (WM) integrity and how they contribute to the cognitive benefits. METHODS: 109 participants were recruited and 82 (62% female; age = 58.38 ± 5.47) finished the intervention with > 80% adherence. We report changes in cardiovascular risk factors and WM integrity (fractional anisotropy (FA); mean diffusivity (MD)), how they might be related to changes in physical activity, age and sex, and their potential role as mediators in cognitive improvements. RESULTS: A decrease in BMI (SMD = - 0.32, p = 0.039), waist circumference (SMD = - 0.42, p = 0.003) and diastolic blood pressure (DBP) (SMD = - 0.42, p = 0.006) in the AE group and a decrease in BMI (SMD = - 0.34, p = 0.031) and DBP (SMD = - 0.32, p = 0.034) in the COMB group compared to the waitlist control group was observed. We also found decreased global MD in the CCT group (SMD = - 0.34; p = 0.032) and significant intervention-related changes in FA and MD in the frontal and temporal lobes in the COMB group. CONCLUSIONS: We found changes in anthropometric measures that suggest initial benefits on cardiovascular health after only 12 weeks of AE and changes in WM microstructure in the CCT and COMB groups. These results add evidence of the clinical relevance of lifestyle interventions and the potential benefits when combining them. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT031123900.


Assuntos
Sistema Cardiovascular , Substância Branca , Pessoa de Meia-Idade , Adulto , Humanos , Feminino , Masculino , Substância Branca/diagnóstico por imagem , Exercício Físico , Cognição
2.
Pediatr Emerg Care ; 40(7): 521-526, 2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38713834

RESUMO

OBJECTIVES: The objective of this study was to measure the impact of an intervention on pain treatment in a pediatric emergency department (ED). The application of interventions to improve pain management in DE has demonstrated diverse effects so far, most of them successful. METHODS: This is a quasi-experimental before-and-after, longitudinal, prospective study.Patients were collected between January 2020 and December 2021. Principal outcome was the number of patients with moderate or severe pain who received analgesia before 30 minutes to the ED arrival. The intervention consisted of several training sessions for nursing staff, pediatricians, and trauma physicians. RESULTS: A total of 515 patients were enrolled, 230 during preintervention period and 285 during postintervention period. The percentage of patients receiving analgesia before 30 minutes increased from 24% to 29% and before 60 minutes increased from 31% to 42%. Time to analgesia administration decreased from 43 to 39 minutes.Only 254 patients (49%) received analgesia at some point during their stay in the ED, 137 (26.6%) before 30 minutes and 193 (37.5%) before 60 minutes. The probability of receiving analgesia was greater in patients seen by a pediatrician rather than an orthopedist (59%-37%). Metamizole was the most commonly used drug (48%), followed by ibuprofen and acetaminophen. CONCLUSIONS: The application strategies to enhance early pain treatment in the ED can improve analgesia administration. Training strategies aimed at healthcare personnel working in the ED can change the way they work and achieve clear benefits for the patient. The treatment of pain in the ED should begin as soon as possible, and in this objective, the involvement of the nursing staff is a priority, because they are the professional who has the best opportunity for the detection and treatment of pain from the moment of triage.


Assuntos
Dor Aguda , Serviço Hospitalar de Emergência , Manejo da Dor , Humanos , Estudos Prospectivos , Manejo da Dor/métodos , Masculino , Feminino , Criança , Dor Aguda/tratamento farmacológico , Dor Aguda/terapia , Estudos Longitudinais , Pré-Escolar , Analgésicos/uso terapêutico , Adolescente , Medição da Dor , Analgesia/métodos , Lactente
3.
Proteome Sci ; 21(1): 23, 2023 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-38049858

RESUMO

BACKGROUND: Major depressive disorder (MDD) affects more than 350 million people worldwide, and there is currently no laboratory test to diagnose it. This pilot study aimed to identify potential biomarkers in peripheral blood mononuclear cells (PBMCs) from MDD patients. METHODS: We used tandem mass tagging coupled to synchronous precursor selection (mass spectrometry) to obtain the differential proteomic profile from a pool of PBMCs from MDD patients and healthy subjects, and quantitative PCR to assess gene expression of differentially expressed proteins (DEPs) of our interest. RESULTS: We identified 247 proteins, of which 133 had a fold change ≥ 2.0 compared to healthy volunteers. Using pathway enrichment analysis, we found that some processes, such as platelet degranulation, coagulation, and the inflammatory response, are perturbed in MDD patients. The gene-disease association analysis showed that molecular alterations in PBMCs from MDD patients are associated with cerebral ischemia, vascular disease, thrombosis, acute coronary syndrome, and myocardial ischemia, in addition to other conditions such as inflammation and diabetic retinopathy. CONCLUSIONS: We confirmed by qRT-PCR that S100A8 is upregulated in PBMCs from MDD patients and thus could be an emerging biomarker of this disorder. This report lays the groundwork for future studies in a broader and more diverse population and contributes to a deeper characterization of MDD.

4.
Arch Microbiol ; 205(5): 201, 2023 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-37081186

RESUMO

The production of alcoholic and non-alcoholic rosé wines using Saccharomyces cerevisiae var. boulardii probiotic yeast is described in this study for the first time. Before and after fermentation and distillation, the volatile acidity, lactic, and malic acid levels were evaluated for S. cerevisiae var. boulardii. These contents were compared to those obtained with a standard S. cerevisiae EC-1118 yeast. We measured the levels of gluconic acid and free amino nitrogen in the musts. After fermentation and distillation, yeast viability was assessed as a function of time (0, 15 days, 3 months, and 6 months), both at ambient temperature (25 ± 0.5 °C) and refrigerator temperature (4 ± 0.5 °C). The outcomes revealed that the rosé wine made with S. cerevisiae var. boulardii had the same values and preliminary sensory characteristics as other commercial wines made with S. cerevisiae EC-1118. The S. cerevisiae var. boulardii yeast successfully survived the high alcohol level produced during fermentation and vacuum distillation. The study also revealed that this unique rosé wine retains its probiotic viability for at least 6 months when stored at room temperature or in the refrigerator, making it a suitable candidate for large-scale production where long storage intervals are required by both producers and consumers.


Assuntos
Probióticos , Saccharomyces boulardii , Vinho , Saccharomyces cerevisiae , Vinho/análise , Temperatura , Fermentação
5.
J Chem Phys ; 159(1)2023 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-37403855

RESUMO

In this work, we study how electrostatic forces slow down the diffusion of solute in flexible gels through coarse-grained simulations. The model used explicitly considers the movement of solute particles and polyelectrolyte chains. These movements are performed by following a Brownian dynamics algorithm. The effect of three electrostatic parameters characterizing the system (solute charge, polyelectrolyte chain charge, and ionic strength) is analyzed. Our results show that the behavior of both the diffusion coefficient and the anomalous diffusion exponent changes upon the reversal of the electric charge of one of the species. In addition, the diffusion coefficient in flexible gels differs significantly from that in rigid gels if the ionic strength is low enough. However, the effect of chain flexibility on the exponent of anomalous diffusion is significant even at high ionic strength (100 mM). Our simulations also prove that varying the polyelectrolyte chain charge does not have exactly the same effect as varying the solute particle charge.

6.
Int J Mol Sci ; 24(15)2023 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-37569397

RESUMO

The global COVID-19 pandemic has warned scientists of the requirement to look for new antimicrobial compounds to prevent infection by this type of viral pathogen. Natural compounds are becoming a promising avenue of research thanks to their renewable, biodegradable, and non-toxic properties. In this work, tiger nut milk's (TNM) antiviral properties, with and without sugar, were studied against enveloped and non-enveloped viruses. The antiviral properties of TNM were evaluated at different concentrations. The antiviral tests showed that TNM is antiviral against the enveloped bacteriophage phi 6, which is commonly used as a surrogate for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), although it did not have any antiviral effect against the non-enveloped bacteriophage MS2. We also found that adding sugar to this natural drink can improve its antiviral properties against enveloped viruses and render it antiviral against non-enveloped viruses like bacteriophage MS2. The antiviral activity of TNM depends on the TNM concentration. TNM is a natural bioproduct that could help to fight against viral infections and protect against a wide range of viral illnesses. These results confirm that the typical sweetened drink made from tiger nut extract and sugar (known as horchata in Spain) possesses broad-spectrum antiviral properties.


Assuntos
Antivirais , COVID-19 , Humanos , Animais , Antivirais/farmacologia , Leite , Açúcares , Pandemias , SARS-CoV-2
7.
Int J Mol Sci ; 24(15)2023 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-37569404

RESUMO

Chitosan films were prepared by solvent casting using an acetic acid-based solution. The films that were developed contained 15.49% of acetic acid solution (10% v/v) and showed biocompatibility in vitro in human keratinocyte HaCaT cells and potent antiviral activity against both enveloped and non-enveloped viruses. The results showed up to 99.98% and 99.92% viral inactivation against the phi 6 enveloped bacteriophage and MS2 non-enveloped bacteriophage, respectively, suggesting that this chitosan/acetic acid film is a promising material for biomedical applications that require biodegradable broad-spectrum antiviral materials.


Assuntos
Quitosana , Vírus , Humanos , Antivirais/farmacologia , Quitosana/farmacologia , Ácido Acético/farmacologia , Inativação de Vírus , Materiais Biocompatíveis/farmacologia
8.
Brain Inj ; 36(12-14): 1349-1356, 2022 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-36331895

RESUMO

BACKGROUND: Computerized Cognitive Training (CCT) is an effective treatment for cognitive impairment in the post-acute stage of stroke. However, it is still not clear if it is suitable for chronic stage. OBJECTIVES: To explore if patients with cognitive deficit following stroke may benefit from CCT. METHODS: Thirty patients post-stroke between 24 and 62 years old were randomized into two groups (A and B) to receive two different types of CCT. All patients were tested with a neuropsychological battery and functional questionnaires, before and after each CCT and also 6 months after the end of the study. In phase I, Group A received a customized CCT and Group B received a non-customized CCT, over 6 weeks. Three months after, each group received the other intervention (phase II). RESULTS: After phase I, between-group analyses revealed that Group A showed a relative decrease in subjective complaints. In contrast, Group B showed improvement in performance-based measures. After phase II, the decrease in subjective complaints continued in Group A, and both groups showed improvement in performance-based measures. CONCLUSIONS: Patients with chronic stroke improved cognitive functioning after performing supervised home-based multi-domain computerized cognitive training.


Assuntos
Transtornos Cognitivos , Disfunção Cognitiva , Acidente Vascular Cerebral , Humanos , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Treino Cognitivo , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/psicologia , Cognição , Disfunção Cognitiva/etiologia , Disfunção Cognitiva/terapia , Dano Encefálico Crônico
9.
Neurologia ; 2022 Aug 03.
Artigo em Espanhol | MEDLINE | ID: mdl-35936979

RESUMO

INTRODUCTION: Patients with post-COVID-19 syndrome may present cognitive and emotional symptomatology. This study aims to analyse the results of an outpatient neuropsychological intervention program for post-COVID-19 syndrome. METHOD: In June 2020 Institut Guttmann started an outpatient post-COVID-19 neurorehabilitation program, including respiratory therapy, physiotherapy, and neuropsychological rehabilitation. Before and after the program, the cognitive-emotional state of all participants is assessed. Six months after treatment, a follow-up assessment is administered (which includes a collection of information on various aspects of daily life). RESULTS: The sample analysed consisted of 123 patients (mean age: 51 years, SD: 12.41). Seventy-four per cent (n=91) had cognitive impairment and underwent cognitive treatment (experimental group); the remaining 26% (n=32) constituted the control group. After the intervention, the experimental group improved in working memory, verbal memory (learning, recall and recognition), verbal fluency and anxious-depressive symptomatology. The control group showed changes in immediate memory, verbal memory (learning and recognition) and depressive symptomatology, although the effect size in the latter two was smaller than in the experimental group. Six months after treatment, 44.9% of the patients were unable to perform their pre-COVID-19 work activity, and 81.2% reported difficulties in their activities of daily living. CONCLUSIONS: Neuropsychological rehabilitation is an effective tool to treat the cognitive-emotional deficits present in post-COVID-19 syndrome. However, months after the end of treatment, not all patients recover their pre-COVID-19 functional level.

10.
Phys Chem Chem Phys ; 23(28): 14997-15002, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34231600

RESUMO

In this work, the long-time diffusion of a solute in a chemically crosslinked and flexible hydrogel is computed from a bead-spring model of a polymeric network to assess the effect of steric obstruction. The relative diffusivities obtained for a wide variety of systems can be described by an exponential decay depending on a parameter that differs from that employed for rigid gels. The mathematical expression derived here can approximately predict the diffusivity in flexible gels if steric hindrance is the mechanism ruling diffusion.

11.
Int J Mol Sci ; 22(17)2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34502431

RESUMO

Transparent materials used for facial protection equipment provide protection against microbial infections caused by viruses and bacteria, including multidrug-resistant strains. However, transparent materials used for this type of application are made of materials that do not possess antimicrobial activity. They just avoid direct contact between the person and the biological agent. Therefore, healthy people can become infected through contact of the contaminated material surfaces and this equipment constitute an increasing source of infectious biological waste. Furthermore, infected people can transmit microbial infections easily because the protective equipment do not inactivate the microbial load generated while breathing, sneezing or coughing. In this regard, the goal of this work consisted of fabricating a transparent face shield with intrinsic antimicrobial activity that could provide extra-protection against infectious agents and reduce the generation of infectious waste. Thus, a single-use transparent antimicrobial face shield composed of polyethylene terephthalate and an antimicrobial coating of benzalkonium chloride has been developed for the next generation of facial protective equipment. The antimicrobial coating was analyzed by atomic force microscopy and field emission scanning electron microscopy with elemental analysis. This is the first facial transparent protective material capable of inactivating enveloped viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in less than one minute of contact, and the methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis. Bacterial infections contribute to severe pneumonia associated with the SARS-CoV-2 infection, and their resistance to antibiotics is increasing. Our extra protective broad-spectrum antimicrobial composite material could also be applied for the fabrication of other facial protective tools such as such as goggles, helmets, plastic masks and space separation screens used for counters or vehicles. This low-cost technology would be very useful to combat the current pandemic and protect health care workers from multidrug-resistant infections in developed and underdeveloped countries.


Assuntos
Anti-Infecciosos/farmacologia , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Equipamento de Proteção Individual , Anti-Infecciosos/química , Bacteriófago phi 6/efeitos dos fármacos , Compostos de Benzalcônio/química , Compostos de Benzalcônio/farmacologia , COVID-19/patologia , COVID-19/virologia , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Humanos , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Polietilenotereftalatos/química , SARS-CoV-2/efeitos dos fármacos , SARS-CoV-2/isolamento & purificação , Staphylococcus epidermidis/efeitos dos fármacos
12.
Int J Mol Sci ; 22(23)2021 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-34884526

RESUMO

COVID-19 pandemic and associated supply-chain disruptions emphasise the requirement for antimicrobial materials for on-demand manufacturing. Besides aerosol transmission, SARS-CoV-2 is also propagated through contact with virus-contaminated surfaces. As such, the development of effective biofunctional materials that can inactivate SARS-CoV-2 is critical for pandemic preparedness. Such materials will enable the rational development of antiviral devices with prolonged serviceability, reducing the environmental burden of disposable alternatives. This research reveals the novel use of Laser Powder Bed Fusion (LPBF) to 3D print porous Cobalt-Chromium-Molybdenum (Co-Cr-Mo) superalloy with potent antiviral activity (100% viral inactivation in 30 min). The porous material was rationally conceived using a multi-objective surrogate model featuring track thickness (tt) and pore diameter (ϕd) as responses. The regression analysis found the most significant parameters for Co-Cr-Mo track formation to be the interaction effects of scanning rate (Vs) and laser power (Pl) in the order PlVs>Vs>Pl. Contrastively, the pore diameter was found to be primarily driven by the hatch spacing (Sh). The study is the first to demonstrate the superior antiviral properties of 3D printed Co-Cr-Mo superalloy against an enveloped virus used as biosafe viral model of SARS-CoV-2. The material significantly outperforms the viral inactivation time of other broadly used antiviral metals such as copper and silver, as the material's viral inactivation time was from 5 h to 30 min. As such, the study goes beyond the current state-of-the-art in antiviral alloys to provide extra protection to combat the SARS-CoV-2 viral spread. The evolving nature of the COVID-19 pandemic brings new and unpredictable challenges where on-demand 3D printing of antiviral materials can achieve rapid solutions while reducing the environmental impact of disposable devices.


Assuntos
Antivirais/farmacologia , Cromo/farmacologia , Cobalto/farmacologia , Molibdênio/farmacologia , Impressão Tridimensional , Ligas , COVID-19 , Humanos , Porosidade , SARS-CoV-2/efeitos dos fármacos , Propriedades de Superfície , Inativação de Vírus/efeitos dos fármacos
13.
Int J Mol Sci ; 22(23)2021 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-34884521

RESUMO

The Coronavirus Disease (COVID-19) pandemic is demanding the rapid action of the authorities and scientific community in order to find new antimicrobial solutions that could inactivate the pathogen SARS-CoV-2 that causes this disease. Gram-positive bacteria contribute to severe pneumonia associated with COVID-19, and their resistance to antibiotics is exponentially increasing. In this regard, non-woven fabrics are currently used for the fabrication of infection prevention clothing such as face masks, caps, scrubs, shirts, trousers, disposable gowns, overalls, hoods, aprons and shoe covers as protective tools against viral and bacterial infections. However, these non-woven fabrics are made of materials that do not exhibit intrinsic antimicrobial activity. Thus, we have here developed non-woven fabrics with antimicrobial coatings of cranberry extracts capable of inactivating enveloped viruses such as SARS-CoV-2 and the bacteriophage phi 6 (about 99% of viral inactivation in 1 min of viral contact), and two multidrug-resistant bacteria: the methicillin-resistant Staphylococcus aureus and the methicillin-resistant Staphylococcus epidermidis. The morphology, thermal and mechanical properties of the produced filters were characterized by optical and electron microscopy, differential scanning calorimetry, thermogravimetry and dynamic mechanical thermal analysis. The non-toxicity of these advanced technologies was ensured using a Caenorhabditis elegans in vivo model. These results open up a new prevention path using natural and biodegradable compounds for the fabrication of infection prevention clothing in the current COVID-19 pandemic and microbial resistant era.


Assuntos
Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Extratos Vegetais/farmacologia , SARS-CoV-2/efeitos dos fármacos , Têxteis , Vaccinium macrocarpon/química , Animais , Antibacterianos , Anti-Infecciosos , Bacteriófago phi 6/efeitos dos fármacos , COVID-19/prevenção & controle , Caenorhabditis elegans/efeitos dos fármacos , Humanos , Staphylococcus aureus Resistente à Meticilina , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacos
14.
Soft Matter ; 16(12): 3022-3028, 2020 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-32129421

RESUMO

Coarse-grained Monte-Carlo simulations of nanogel-polyelectrolyte complexes have been carried out. The results presented here capture two phenomena reported in experiments with real complexes: (i) the reduction in size after absorbing just a few chains and (ii) the charge inversion detected through electrophoretic mobility data. Our simulations reveal that charge inversion occurs if the polyelectrolyte charge is large enough. In addition, the distribution of chains inside the nanogel strongly depends on whether charge inversion takes place. It should also be stressed that the chain topology has little influence on most of the properties studied here.

15.
J Int Neuropsychol Soc ; 25(9): 910-921, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31317861

RESUMO

OBJECTIVES: How brain damage after stroke is related to specific clinical manifestation and recovery is incompletely understood. We studied cognitive reserve (CR) in stroke patients by two types of measurements: (i) objectively verifiable static proxies (i.e., education, occupational attainment), and (ii) subjective, dynamic proxies based on patient testimony in response to a questionnaire. We hypothesized that one or both of these types of CR measurements might correlate positively with patient cognitive performance during the post-acute and chronic phases of recovery. METHOD: Thirty-four stroke patients underwent neuropsychological assessment at 2, 6 and 24 months after stroke onset. In chronic stage at 24+ months, self-rating assessments of cognitive performance in daily life and social integration were obtained. CR before and after stroke was estimated using static proxies and dynamic proxies were obtained using the Cognitive Reserve Scale (CRS-Pre-stroke, CRS-Post-stroke). RESULTS: CRS-Pre-stroke and CRS-Post-stroke showed significant mean differences. Dynamic proxies showed positive correlation with self-assessment of attention, metacognition, and functional ability in chronic stage. In contrast, significant correlations between static proxies and cognitive recovery were not found. CONCLUSIONS: Dynamic proxies of CR were positively correlated with patients' perception of their functional abilities in daily life. To best guide cognitive prognosis and treatment, we propose that dynamic proxies of CR should be included in neuropsychological assessments of patients with brain damage.


Assuntos
Atividades Cotidianas , Atenção/fisiologia , Disfunção Cognitiva/diagnóstico , Disfunção Cognitiva/fisiopatologia , Reserva Cognitiva/fisiologia , Metacognição/fisiologia , Acidente Vascular Cerebral/fisiopatologia , Idoso , Autoavaliação Diagnóstica , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade
16.
Phys Chem Chem Phys ; 20(4): 2814-2825, 2018 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-29323684

RESUMO

In this work the equilibrium absorption of nanometric cosolutes (which could represent drugs, reactants, small globular proteins and other kind of biomacromolecules) inside neutral hydrogels is studied. We specially focus on exploring, for different swelling states, the competition between the steric exclusion induced by the cross-linked polymer network constituting the hydrogel, and the solvent-induced short-range hydrophobic attraction between the polymer chains and the cosolute particle. For this purpose, the cosolute partition coefficient is calculated by means of coarse-grained grand canonical Monte Carlo simulations, and the results are compared to theoretical predictions based on the calculation of the excluded and binding volume around the polymer chains. For small hydrophobic attractions or large cosolute sizes, the steric repulsion dominates, and the partition coefficient decreases monotonically with the polymer volume fraction, ϕm. However, for large enough hydrophobic attraction strength, the interplay between hydrophobic adhesion and the steric exclusion leads to a maximum in the partition coefficient at certain intermediate polymer density. Good qualitative and quantitative agreement is achieved between simulation results and theoretical predictions in the limit of small ϕm, pointing out the importance of geometrical aspects of the cross-linked polymer network, even for hydrogels in the swollen state. In addition, the theory is able to predict analytically the onset of the maximum formation in terms of the details of the cosolute-monomer pair interaction, in good agreement with simulations too. Finally, the effect of the many-body attractions between the cosolute and multiple polymer chains is quantified. The results clearly show that these many-body attractions play a very relevant role determining the cosolute binding, enhancing its absorption in more than one order of magnitude.


Assuntos
Hidrogéis/química , Interações Hidrofóbicas e Hidrofílicas , Método de Monte Carlo , Polímeros/química , Solventes/química
17.
Phys Chem Chem Phys ; 19(9): 6838-6848, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-28218325

RESUMO

In this work the equilibrium distribution of ions around a thermo-responsive charged nanogel particle in an electrolyte aqueous suspension is explored using coarse-grained Monte Carlo computer simulations and the Ornstein-Zernike integral equation theory. We explicitly consider the ionic size in both methods and study the interplay between electrostatic and excluded-volume effects for swollen and shrunken nanogels, monovalent and trivalent counterions, and for two different nanogel charges. We find good quantitative agreement between the ionic density profiles obtained using both methods when the excluded repulsive force exerted by the cross-linked polymer network is taken into account. For the shrunken conformation, the electrostatic repulsion between the charged groups provokes a heterogeneous polymer density profile, leading to a nanogel structure with an internal low density hole surrounded by a dense corona. The results show that the excluded-volume repulsion strongly hinders the ion permeation for shrunken nanogels, where volume exclusion is able to significantly reduce the concentration of counterions in the more dense regions of the nanogel. In general, we demonstrate that the thermosensitive behaviour of nanogels, as well as their internal structure, is strongly influenced by the valence of the counterions and also by the charge of the particles. On the one hand, an increase of the counterion valence moves the swelling transition to lower temperatures, and induces a major structuring of the charged monomers into internal and external layers around the crown for shrunken nanogels. On the other hand, increasing the particle charge shifts the swelling curve to larger values of the effective radius of the nanogel.

18.
Phys Chem Chem Phys ; 18(31): 21852-64, 2016 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-27435382

RESUMO

The asymptotic convergence of the thermodynamic and structural properties of unequally-sized charge-symmetric ions in strong electric fields was postulated more than thirty years ago by Valleau and Torrie as the dominance of counterions via the non-linear Poisson-Boltzmann theory [Valleau and Torrie, J. Chem. Phys., 1982, 76, 4623]. According to this mean field prescription, the properties of the electrical double layer near a highly charged electrode immersed in a size-asymmetric binary electrolyte converge to those of a size-symmetric electrolyte if the properties of counterions are the same in both instances. On the other hand, some of the present authors have shown that, in fact, counterions do not dominate the electrical properties of a spherical macroion in the presence of unequally-sized ions, symmetric in valence, if ion correlations and ionic excluded volume effects are taken into account consistently. These ingredients are neglected in the classical Poisson-Boltzmann picture. In the present work, we show the occurrence of the non-dominance of counterions in the opposite scenario, that is, when ions are equally-sized but asymmetric in valence. This is performed in the presence of highly charged colloidal surfaces of spherical and planar geometries for different ionic volume fractions. In addition to the phenomenon of non-dominance of counterions, our simulations and theoretical data also exhibit a non-monotonic order or precedence in the mean electrostatic potential, or electrostatic screening, at the Helmholtz plane of a charged colloid. This interesting behaviour is analyzed as a function of the coion's valence, the ionic volume fraction, and the charge and size of the colloidal particle. All these phenomena are explained in terms of the decay of the electric field near the colloidal surface, and by the appearance of a local inversion of both the electric field and the integrated surface charge density of the colloidal particle in the presence of monovalent counterions and multivalent coions.

19.
Phys Chem Chem Phys ; 17(26): 17069-78, 2015 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-26067087

RESUMO

We report experimental and simulation studies on ion specificity in aqueous colloidal suspensions of positively charged, bare magnetite nanoparticles. Magnetite has the largest saturation magnetization among iron oxides and relatively low toxicity, which explain why it has been used in multiple biomedical applications. Bare magnetite is hydrophilic and the sign of the surface charge can be changed by adjusting the pH, its isoelectric point being in the vicinity of pH = 7. Electrophoretic mobility of our nanoparticles in the presence of increasing concentrations of different anions showed that anions regarded as kosmotropic are more efficient in decreasing, and even reversing, the mobility of the particles. If the anions were ordered according to the extent to which they reduced the particle mobility, a classical Hofmeister series was obtained with the exception of thiocyanate, whose position was altered. Monte Carlo simulations were used to predict the diffuse potential of magnetite in the presence of the same anions. The simulations took into account the ion volume, and the electrostatic and dispersion forces among the ions and between the ions and the solid surface. Even though no fitting parameters were introduced and all input data were estimated using Lifshitz theory of van der Waals forces or obtained from the literature, the predicted diffusion potentials of different anions followed the same order as the mobility curves. The results suggest that ionic polarizabilities and ion sizes are to a great extent responsible for the specific ion effects on the electrokinetic potential of iron oxide particles.


Assuntos
Nanopartículas de Magnetita/química , Método de Monte Carlo , Algoritmos , Eletrólitos/química , Concentração de Íons de Hidrogênio , Íons/química , Cinética , Tamanho da Partícula , Eletricidade Estática , Propriedades de Superfície
20.
Biomed Eng Online ; 14: 48, 2015 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-26025444

RESUMO

BACKGROUND: Eye movements have been used in control interfaces and as indicators of somnolence, workload and concentration. Different techniques can be used to detect them: we focus on the electrooculogram (EOG) in which two kinds of interference occur: blinks and overshoots. While they both draw bell-shaped waveforms, blinks are caused by the eyelid, whereas overshoots occur due to target localization error and are placed on saccade. They need to be extracted from the EOG to increase processing effectiveness. METHODS: This paper describes off- and online processing implementations based on lower envelope for removing bell-shaped noise; they are compared with a 300-ms-median filter. Techniques were analyzed using two kinds of EOG data: those modeled from our own design, and real signals. Using a model signal allowed to compare filtered outputs with ideal data, so that it was possible to quantify processing precision to remove noise caused by blinks, overshoots, and general interferences. We analyzed the ability to delete blinks and overshoots, and waveform preservation. RESULTS: Our technique had a high capacity for reducing interference amplitudes (>97%), even exceeding median filter (MF) results. However, the MF obtained better waveform preservation, with a smaller dependence on fixation width. CONCLUSIONS: The proposed technique is better at deleting blinks and overshoots than the MF in model and real EOG signals.


Assuntos
Artefatos , Piscadela , Eletroculografia/métodos , Processamento de Sinais Assistido por Computador , Movimentos Sacádicos , Razão Sinal-Ruído
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