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1.
JAMA ; 332(6): 471-481, 2024 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-38824442

RESUMO

Importance: Despite the evidence for early palliative care improving outcomes, it has not been widely implemented in part due to palliative care workforce limitations. Objective: To evaluate a stepped-care model to deliver less resource-intensive and more patient-centered palliative care for patients with advanced cancer. Design, Setting, and Participants: Randomized, nonblinded, noninferiority trial of stepped vs early palliative care conducted between February 12, 2018, and December 15, 2022, at 3 academic medical centers in Boston, Massachusetts, Philadelphia, Pennsylvania, and Durham, North Carolina, among 507 patients who had been diagnosed with advanced lung cancer within the past 12 weeks. Intervention: Step 1 of the intervention was an initial palliative care visit within 4 weeks of enrollment and subsequent visits only at the time of a change in cancer treatment or after a hospitalization. During step 1, patients completed a measure of quality of life (QOL; Functional Assessment of Cancer Therapy-Lung [FACT-L]; range, 0-136, with higher scores indicating better QOL) every 6 weeks, and those with a 10-point or greater decrease from baseline were stepped up to meet with the palliative care clinician every 4 weeks (intervention step 2). Patients assigned to early palliative care had palliative care visits every 4 weeks after enrollment. Main Outcomes and Measures: Noninferiority (margin = -4.5) of the effect of stepped vs early palliative care on patient-reported QOL on the FACT-L at week 24. Results: The sample (n = 507) mostly included patients with advanced non-small cell lung cancer (78.3%; mean age, 66.5 years; 51.4% female; 84.6% White). The mean number of palliative care visits by week 24 was 2.4 for stepped palliative care and 4.7 for early palliative care (adjusted mean difference, -2.3; P < .001). FACT-L scores at week 24 for the stepped palliative care group were noninferior to scores among those receiving early palliative care (adjusted FACT-L mean score, 100.6 vs 97.8, respectively; difference, 2.9; lower 1-sided 95% confidence limit, -0.1; P < .001 for noninferiority). Although the rate of end-of-life care communication was also noninferior between groups, noninferiority was not demonstrated for days in hospice (adjusted mean, 19.5 with stepped palliative care vs 34.6 with early palliative care; P = .91). Conclusions and Relevance: A stepped-care model, with palliative care visits occurring only at key points in patients' cancer trajectories and using a decrement in QOL to trigger more intensive palliative care exposure, resulted in fewer palliative care visits without diminishing the benefits for patients' QOL. While stepped palliative care was associated with fewer days in hospice, it is a more scalable way to deliver early palliative care to enhance patient-reported outcomes. Trial Registration: ClinicalTrials.gov Identifier: NCT03337399.


Assuntos
Neoplasias Pulmonares , Cuidados Paliativos , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/psicologia , Neoplasias Pulmonares/terapia , Cuidados Paliativos/métodos , Assistência Centrada no Paciente , Qualidade de Vida , Assistência Terminal/métodos , Estadiamento de Neoplasias
2.
Am Fam Physician ; 99(12): 751-759, 2019 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-31194487

RESUMO

Globally, approximately 20% of the 400 million individuals with diabetes mellitus have diabetic kidney disease (DKD). DKD is associated with higher cardiovascular and all-cause morbidity and mortality, so timely diagnosis and treatment are critical. Screening for early DKD is best done with annual spot urine albumin/creatinine ratio testing, and diagnosis is confirmed by repeated elevation in urinary albumin excretion. Treatment includes management of hyperglycemia, hypertension, hyperlipidemia, and cessation of tobacco use. Multiple antihyperglycemic medications, including sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide-1 receptor agonists, and dipeptidyl-peptidase-4 inhibitors, may help prevent DKD by lowering blood glucose levels and through intrinsic renal protection. Blood pressure should be monitored at every clinical visit and maintained at less than 140/90 mm Hg to prevent microvascular changes. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers prevent progression of DKD and may decrease albuminuria. Statin therapy should be considered for all patients with DKD, and tobacco cessation reduces the risk of DKD. Given the complexity of the disease and the risk of poor outcomes, patients who progress to stage 3 DKD or beyond may benefit from referral to nephrology subspecialists.


Assuntos
Albuminúria/diagnóstico , Albuminúria/tratamento farmacológico , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/tratamento farmacológico , Nefropatias Diabéticas/diagnóstico , Nefropatias Diabéticas/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Guias de Prática Clínica como Assunto , Adulto , Idoso , Idoso de 80 Anos ou mais , Currículo , Complicações do Diabetes/tratamento farmacológico , Diabetes Mellitus Tipo 2/fisiopatologia , Nefropatias Diabéticas/etiologia , Educação Médica Continuada , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
3.
J Fam Pract ; 68(1): 10;14;16;24, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30724899

RESUMO

Beyond tried-and-true therapies are new therapeutic targets on the horizon-giving you a bigger toolbox to help patients abort and prevent migraine episodes.


Assuntos
Transtornos de Enxaqueca/diagnóstico , Transtornos de Enxaqueca/terapia , Fatores Etários , Terapia Combinada , Diagnóstico Diferencial , Predisposição Genética para Doença , Humanos , Transtornos de Enxaqueca/etiologia , Transtornos de Enxaqueca/fisiopatologia , Fatores de Risco , Prevenção Secundária/métodos
4.
J Funct Biomater ; 10(1)2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30791603

RESUMO

A synthetic technique inspired by the biomineralisation process in nacre has been previously reported to be effective in replicating the nanostructural elements of nacre in 2D chitosan hydrogel films. Here we evaluate the applicability of this synthetic biomineralisation technique, herein called the McGrath method, in replicating the flat tabular morphology of calcium carbonate and other nanostructural elements obtained when 2D chitosan hydrogel films were used, on a 3D porous chitosan hydrogel-based scaffold, hence developing 3D chitosan-calcium carbonate composites. Nozzle extrusion-based 3D printing technology was used to develop 3D porous scaffolds using chitosan hydrogel as the printing ink in a custom-designed 3D printer. The rheology of the printing ink and print parameters were optimised in order to fabricate 3D cylindrical structures with a cubic lattice-based internal structure. The effects of various dehydration techniques, including air-drying, critical point-drying and freeze-drying, on the structural integrity of the as-printed scaffolds from the nano to macroscale, were evaluated. The final 3D composite materials were characterised using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. The study has shown that McGrath method can be used to develop chitosan-calcium carbonate composites wherein the mineral and matrix are in intimate association with each other at the nanoscale. This process can be successfully integrated with 3D printing technology to develop 3D compartmentalised polymer-mineral composites.

6.
Fam Med ; 48(10): 801-804, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27875603

RESUMO

BACKGROUND AND OBJECTIVES: Elevated blood lead levels have well-described detrimental effects to growth and development in children, yet screening rates remain low. We sought to determine if a reminder within the electronic health record (EHR) could change provider behavior and improve blood lead level (BLL) screening test ordering rates in an urban academic family medicine practice. METHODS: Baseline BLL test ordering rates were calculated for children ages 9-72 months. An update adding reminders to screen was made to the electronic note template used during pediatric well and sick visits at the practice. Data from the 10-week periods both before and after the change was made were compared through a retrospective chart review. RESULTS: A total of 210 children were seen during the pre-intervention period. Forty-eight percent (n=101) had already been screened. Of the 109 eligible for screening, 23 had tests ordered, and 18 of those had tests completed. Eighty-four children were eligible for screening in the post-intervention period. Forty-one of those children had tests ordered, and 15 had tests completed. Provider ordering rates increased from 21% of eligible patients to 49%. Test completion rates only increased from 17% to 18%. CONCLUSIONS: An electronic note-based reminder system significantly improves provider ordering rates of BLL tests. Researchers are currently investigating how the use of point-of-care BLL sample collection can improve test completion rates and therefore increase the frequency of successful screening.


Assuntos
Registros Eletrônicos de Saúde/estatística & dados numéricos , Medicina de Família e Comunidade , Chumbo/toxicidade , Programas de Rastreamento , População Urbana , Criança , Pré-Escolar , Humanos , Lactente , Atenção Primária à Saúde , Estudos Retrospectivos
7.
Biomacromolecules ; 17(5): 1572-81, 2016 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-27075297

RESUMO

Controlling and manipulating protein behavior at an interface is of immense relevance to a broad range of physicochemical and biological phenomena and technological processes. Although many experimental studies have contributed to rapid progress in the fundamental knowledge of protein behavior at interfaces, detailed molecular-level understanding of the mechanism of protein adsorption at an interface is still remarkably lacking. In this study, atomistic molecular dynamics simulations were used to characterize the adsorption of ß-lactoglobulin at two different oil/water (O/W) interfaces, where the oil was either the marginally hydrophilic octanol or the more hydrophilic triolein, and the results were compared to those of a previous study utilizing the hydrophobic oil decane. Both the approach to the surface and the mechanism of adsorption depend upon the hydrophilicity of the oil and the interfacial tension of the O/W interface, with the nature of the adsorption, the accompanying structural changes, and the energetic driving force differing markedly between the different oils. Intriguingly, the behavior of the protein resembles that predicted for a soft spherical particle at an O/W interface. The results are also in agreement with key experimental findings, particularly the observation that proteins undergo more conformational change upon adsorption to hydrophobic surfaces, flattening out to expose hydrophobic interior residues to the surface, and that a thicker layer of native-like adsorbed protein forms at hydrophilic surfaces, and reveal structural and mechanistic detail behind each mechanism of adsorption.


Assuntos
Lactoglobulinas/química , Óleos/química , Água/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Simulação de Dinâmica Molecular , Conformação Proteica , Propriedades de Superfície , Tensão Superficial
8.
Biomacromolecules ; 16(6): 1855-61, 2015 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-25989152

RESUMO

Protein adsorption at liquid-liquid interfaces is of immense relevance to many biological processes and dairy-based functional foods. Due to experimental limitations, however, there is still a remarkable lack of understanding of the adsorption mechanism, particularly at a molecular level. In this study, atomistic molecular dynamics simulations were used to elucidate the approach and adsorption mechanism of ß-lactoglobulin (ß-LG) at a decane-water interface. Through multiple independent simulations starting from three representative initial orientations of ß-LG relative to the decane surface the rate at which ß-LG approaches the oil/water interface is found to be independent of its initial orientation, and largely stochastic in nature. While the residues that first make contact with the decane and the final orientation of ß-LG upon adsorption are similar in all cases, the adsorption process is driven predominantly by structural rearrangements that preserve the secondary structure but expose hydrophobic residues to the decane surface. This detailed characterization of the adsorption of ß-LG at an oil/water interface should inform the design and development of novel encapsulation and delivery systems in the food and pharmaceutical sciences.


Assuntos
Lactoglobulinas/química , Simulação de Dinâmica Molecular , Óleos/química , Alcanos/química , Sequência de Aminoácidos , Interações Hidrofóbicas e Hidrofílicas , Dados de Sequência Molecular , Água/química
9.
J Colloid Interface Sci ; 403: 7-15, 2013 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-23683496

RESUMO

Macroscopic properties and ensemble average diffusion of concentrated (dispersed phase 50-60 wt%) Na-caseinate-stabilised emulsions for three different oils (soybean oil, palm olein and tetradecane) were explored. On a volume fraction basis, pulsed gradient stimulated echo (PGSTE)-NMR data show that droplet dynamics for all three systems are similar within a region of the emulsion morphology diagram. The exact limits of the emulsion space depend however on which oil is considered. The reduced solubility of tetradecane in water, and Na-caseinate in tetradecane, result in the stabilisation of flocs during formulation. Floc formation is not observed when soybean oil or palm olein is used under identical emulsion formulation conditions. Linear rheology experiments provide indirect evidence that the local structure and the properties of the thin film interfacial domain of tetradecane emulsions vary from those of soybean oil and palm olein emulsions. Collectively these data indicate that protein/oil interactions within a system dominate over specific oil droplet structure and size distribution, which are similar in the three systems.


Assuntos
Caseínas/química , Óleos/química , Emulsões , Espectroscopia de Ressonância Magnética
10.
Dalton Trans ; 42(23): 8259-69, 2013 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-23595573

RESUMO

Understanding the formation of biominerals like nacre can lead to the fabrication of more advanced biomimetic materials. Several factors are known to influence the final form of both native nacre and biomimetic synthetic variants. Two important components in calcium carbonate biominerals such as nacre are the organic scaffold and the acidic proteins. Interactions between these two components may also influence final composite characteristics. In this investigation chitosan hydrogels were prepared from acidic aqueous solution using four alcohols as cosolvents. The addition of alcohol enables direct modification of the network of the chitosan hydrogel (and thereby the nanometre and micrometre length-scale structure of the hydrogel). Both alcohol-modified chitosan and subsequently reacetylated chitin scaffolds were then mineralised with a combined soaking mineralisation method in the presence of poly(acrylic acid), the latter of which mimics the role of the acidic proteins in the native system. The effects of these structural variations of the hydrogel, induced by the presence of alcohol during fabrication, on (1) the formation of a polyelectrolyte complex between the chitosan or chitin and the poly(acrylic acid) and (2) the subsequent polymorph and morphology of calcium carbonate crystals mineralised within the hydrogel scaffold were investigated. Increasing the amount of the alcohols 1,2-propanediol or 1,3-propanediol led to increased disruption of the hydrogen bonding of the hydrogel scaffold and significant changes to, or reduced formation of, the polyelectrolyte complex formed between the scaffold carbohydrate and the poly(acrylic acid). The disruption of the polyelectrolyte complex in turn led to a loss of control over which polymorph of calcium carbonate is nucleated. These results show that the physical form of the polymer scaffold in these organic/inorganic composites, and the formation of the polyelectrolyte complex play a crucial role in determining the final composite structure and the calcium carbonate polymorphs and morphologies.


Assuntos
Materiais Biomiméticos/química , Biomimética/métodos , Quitosana/química , Eletrólitos/química , Etanol/química
11.
Chem Commun (Camb) ; 49(33): 3407-9, 2013 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-23508225

RESUMO

Continuous self-assembled growth of both the organic and inorganic components of materials with nacre-like structure is achieved upon mineralisation of chitin and chitosan scaffolds using a combined soaking method and the inclusion of poly(acrylic acid) and chitosan oligomers as additives.


Assuntos
Materiais Biomiméticos/química , Quitina/química , Quitosana/química , Nácar/química , Resinas Acrílicas/química , Materiais Biomiméticos/metabolismo , Cristalização
12.
J Colloid Interface Sci ; 394: 243-51, 2013 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-23347996

RESUMO

Resistive pulse sensing (RPS) with tunable pores (TPs) has been used to investigate an oil-in-water emulsion stabilised with ß-lactoglobulin (BLG). The mode of the droplet size distribution steadily increased over four months, from less than 150 nm to more than 200 nm. Results suggest that the dominant growth mechanism was migration of oil to relatively large droplets, as in Ostwald ripening. In contrast, the growth dynamics for salt-induced aggregation suggest flocculation and coalescence of droplets coming into contact. The charge measurement method recently developed by Vogel et al. was also applied to the emulsion. The two data analysis methods used yielded average droplet ζ-potentials of -18.9 mV and -21.8 mV, compared with -27.6 mV obtained using light scattering. Methods for measuring emulsion droplet deformation and the charge on individual droplets are under development. Tunable pores are a useful tool for improved characterisation of submicrometre emulsions, as well as other synthetic and biological particles, as they provide better precision than light scattering for particle number distributions.

13.
J Colloid Interface Sci ; 381(1): 48-58, 2012 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-22709624

RESUMO

The concentrated (dispersed phase 50-70 wt%) composition space of Na-caseinate, a family of milk proteins, stabilised emulsions was investigated for three different oils: soybean oil, palm olein and tetradecane with pH 6.8 phosphate buffer continuous phase. The variation of emulsion stability and microstructure were explored using static light scattering, diffusion nuclear magnetic resonance, cryo-scanning electron microscopy, rheology and the time varying macroscopic phase separation of the emulsions. For soybean oil and palm olein a rich diversity of emulsion microstructures and stabilities are realised. Five emulsion domains, each having a different microstructure and macroscopic stability have been identified within the composition space probed. For the lowest concentrations of emulsifier bridging flocculation is evident and emulsions are of low stability. Increasing Na-caseinate concentration leads to an increased stability and the existence of distinct individual oil droplets, visualised using cryo-scanning electron microscopy. Further increases in Na-caseinate concentration reduce emulsion stability due to depletion flocculation. Na-caseinate self-assembly is then initiated. At sufficiently high Na-caseinate and/or oil concentrations the continuous phase of the emulsion is a three-dimensional protein network and emulsion stability is again enhanced. At the limits of the emulsion composition space a gel-like paste is formed. The diversity of emulsion microstructure is reduced when tetradecane is the discrete phase. Na-caseinate self-assembly is limited and there is no evidence for formation of a protein network.


Assuntos
Alcanos/química , Caseínas/química , Óleo de Soja/química , Água/metabolismo , Microscopia Crioeletrônica , Difusão , Emulsões , Floculação , Concentração de Íons de Hidrogênio , Luz , Espectroscopia de Ressonância Magnética , Reologia , Espalhamento de Radiação , Triglicerídeos/análise , Viscosidade
14.
Chem Commun (Camb) ; 48(39): 4716-8, 2012 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-22473223

RESUMO

Biomimetic materials which display the complexity of biominerals like nacre are synthetically difficult to prepare. The formation of chitin/calcium carbonate composites, where CaCO(3) is present as aragonite, was achieved via reacetylation of preformed chitosan scaffolds followed by the combination of presoaking of chitin templates with mineral solutions in the presence of poly(acrylic acid). The as-synthesised composites are comprised of well-ordered ribbons of aragonite crystals held within an organic matrix, mimicking the structure of nacre.


Assuntos
Biomimética , Carbonato de Cálcio/síntese química , Quitina/síntese química , Resinas Acrílicas/química , Carbonato de Cálcio/química , Quitina/química , Microscopia Eletrônica de Varredura
15.
J Perinat Educ ; 21(2): 72-9, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23449834

RESUMO

Childbirth educator Kathryn McGrath reflects on fear and courage and comes to see some levels of fear as a normal part of the process of pregnancy and birth and not something to be brushed aside. In this article, originally presented as a keynote address in 2005 at the Lamaze International Annual Conference, McGrath discusses fear during pregnancy and birth and presents ways in which the childbirth educator can acknowledge and accept women's fears, and help find the courage they need to give birth.

16.
Dalton Trans ; 40(36): 9259-68, 2011 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-21829841

RESUMO

Chitosan hydrogels are of considerable interest in synthetic biomimetic mineralisation strategies due to their favourable characteristics such as the presentation of a large surface area for crystal nucleation within a structured yet responsive scaffold. Chitosan hydrogels were prepared and subsequently calcium carbonate mineralisation was initiated using a method which combines alternate soaking of the films with precursor solutions followed by treatment with Kitano solution. This combined approach allows for increased extent of mineralisation, inducement of mineralisation uniformly throughout the hydrogel rather than only at the peripheral surface and ready scalability and shape manipulation. The base synthetic system is readily modified through the introduction of additives that manipulate the nucleation and growth of the calcium carbonate. Addition of poly(acrylic acid) inhibits nucleation and induces tangential crystal growth along the internal and external interfaces of the hydrogel. The resulting composite is comprised of stacked overlapping plates of calcium carbonate intercalated with carbohydrate. The method is applicable in combination with a variety of hydrogels including macroporous chitosan, chitosan-alginate bilayers and pure alginate hydrogels. The composite materials were analysed by SEM, XRD, microRaman spectroscopy and mechanical strength testing.


Assuntos
Materiais Biomiméticos/química , Carbonato de Cálcio/química , Quitosana/química , Hidrogéis/química , Alginatos/química , Materiais Biocompatíveis/química , Cristalização , Ácido Glucurônico/química , Ácidos Hexurônicos/química
17.
Dalton Trans ; 40(36): 9269-75, 2011 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-21829842

RESUMO

Biomimetic strategies which utilise hydrogels have been targeted due to favourable hydrogel characteristics such as the presentation of a large surface area for crystal nucleation within a structured yet responsive scaffold. Chitosan hydrogels were prepared and mineralised using a combined method which involves alternate soaking of the films with precursor solutions, followed by treatment with saturated mineral solution. This method has been shown to be effective for the synthesis of calcium carbonate-chitosan composite materials with tensile strength comparable to nacre. The ratio of organic to inorganic is readily controlled through the presoaking solution concentrations. The ubiquity of this method is shown here with respect to switching out both the anion (CaHPO(4)) and the cation (BaSO(4)). Cation doping is also readily achieved allowing formation of Mg-rich CaCO(3). Poly(acrylic acid) added to (Mg,Ca)CO(3)-chitosan systems induces the formation of two polymorphs (vaterite and calcite) which coexist within the composite material. The mineralised scaffolds were analysed by SEM and powder XRD. The successful mineralisation of chitosan templates with various inorganic compounds shows that this combined approach is widely applicable as a biomimetic approach.


Assuntos
Biomimética/métodos , Carbonato de Cálcio/química , Quitosana/química , Hidrogéis/química , Cristalização , Microscopia Eletrônica de Varredura , Minerais/química , Sais/química
18.
Langmuir ; 27(8): 4430-8, 2011 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-21417341

RESUMO

2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.


Assuntos
Eletrólitos/química , Membranas Artificiais , Transição de Fase , Ácidos Esteáricos/química , Cálcio , Carbonatos , Cristalização , Ligação de Hidrogênio , Eletricidade Estática
19.
Dalton Trans ; 39(28): 6524-31, 2010 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-20544110

RESUMO

We report a soft and straightforward method for synthesizing two- and three-dimensionally patterned silicate materials by phase separation using nonionic emulsion templates. Our liquid-state method involves, under controlled atmosphere, the mixing of a condensed silica solution with an oil-in-water emulsion in the presence of a solution of a nonionic emulsifier, Triton X-100. The preparation is stabilized using an organic solvent. The morphology of the silicate materials is significantly modified by changing the reaction conditions or the concentration of the reagents. Three-dimensionally macro and nanoporous continuous films and nanoporous individual spherical particles, both made of amorphous silica, are obtained. The structure of the films and particles is defined by the emulsion template. Films were on average 20 microm thick with a volume-based porosity of approximately 7 x 10(-2) cm(3) g(-1), with pore size correlating well with the size of the oil droplets in the templating emulsion. The siliceous films are bicontinuous leading to large surface areas and openly accessible pores. Individual spheres ranged in size from approximately 1 to 6 microm in diameter with nanoporous openings of 300 nm in diameter. The porosity and integrity of all materials are maintained upon calcination.


Assuntos
Silicatos/química , Emulsões/química , Nanoestruturas/química , Octoxinol/química , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier
20.
J Colloid Interface Sci ; 342(2): 399-406, 2010 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-19942228

RESUMO

The self-diffusion coefficients of water and casein aggregates in aqueous Na-caseinate dispersions were measured using a pulsed gradient stimulated echo nuclear magnetic resonance technique (PGSTE-NMR). The results for water self-diffusion are discussed in terms of the cell model. The influence of Na-caseinate concentration on water self-diffusion can be explained by obstruction and tortuosity effects arising due to the presence of casein aggregates. Unrestricted diffusion of casein aggregates was measured for all concentrations at short observation times ( approximately 20ms). Despite a near uniform size distribution on increasing Na-caseinate concentration the measured unrestricted diffusion coefficient was a decreasing function of Na-caseinate concentration. Enhanced packing interaction between the aggregates and the slight augmentation of the large tail in the size distribution is the main reason for this observed decrease. On increasing the experimental observation times restricted diffusion of the aggregates is measured. The rheological response of the dispersions was investigated. The stress evolution of the sample with time exhibits three distinct behaviours, irrespective of Na-caseinate concentration and applied shear rate: a spontaneous increase of stress at very short times (<1s), followed by a plateau with fine structure superposed and lastly a sharp increase in stress attributed to irreversible gelation. The latter occurs at significantly reduced times on increasing Na-caseinate concentration. Linear rheology measurements indicate that the dispersions are predominantly locally liquid-like while being macroscopically in a gelled state.


Assuntos
Caseínas/química , Géis/química , Animais , Bovinos , Difusão , Leite/química , Ressonância Magnética Nuclear Biomolecular , Tamanho da Partícula , Reologia , Água/química
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