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1.
Neuropsychol Rehabil ; : 1-37, 2023 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-37310032

RESUMO

Mobile phone reminding apps can be used by people with acquired brain injury (ABI) to compensate for memory impairments. This pilot feasibility trial aimed to establish the feasibility of a randomized controlled trial comparing reminder apps in an ABI community treatment setting. Adults with ABI and memory difficulty who completed the three-week baseline were randomized (n = 29) and allocated to Google Calendar or ApplTree app. Those who attended an intervention session (n = 21) watched a 30-minute video tutorial of the app then completed reminder setting assignments to ensure they could use the app. Guidance was given if needed from a clinician or researcher. Those who passed the app assignments (n = 19) completed a three-week follow up. Recruitment was lower than target (n = 50), retention rate was 65.5%, adherence rate was 73.7%. Qualitative feedback highlighted issues that may impact usability of reminding apps introduced within community brain injury rehabilitation. Feasibility results indicate a full trial would require 72 participants to demonstrate the minimally clinically important efficacy difference between apps, should a difference exist. Most participants (19 of 21) given an app could learn to use it with the short tutorial. Design features implemented in ApplTree have potential to improve the uptake and utility of reminding apps.

2.
J Med Internet Res ; 25: e45181, 2023 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-37058337

RESUMO

BACKGROUND: Colonoscopy is the gold standard for lower gastrointestinal diagnostics. The procedure is invasive, and its demand is high, resulting in long waiting times. Colon capsule endoscopy (CCE) is a procedure that uses a video capsule to investigate the colon, meaning that it can be carried out in a person's own home. This type of "hospital-at-home" service could potentially reduce costs and waiting times, and increase patient satisfaction. Little is currently understood, however, about how CCE is actually experienced and accepted by patients. OBJECTIVE: The aim of this study was to capture and report patient experiences of the CCE technology (the capsule and associated belt and recorder) and of the new clinical pathway for the CCE service being rolled out as part of routine service in Scotland. METHODS: This was a mixed methods service evaluation of patient experiences of a real-world, deployed, managed service for CCE in Scotland. Two hundred and nine patients provided feedback via a survey about their experiences of the CCE service. Eighteen of these patients took part in a further telephone interview to capture more in-depth lived experiences to understand the barriers and opportunities for the further adoption and scaling up of the CCE service in a way that supports the patient experience and journey. RESULTS: Patients overall perceived the CCE service to be of significant value (eg, mentioning reduced travel times, reduced waiting times, and freedom to complete the procedure at home as perceived benefits). Our findings also highlighted the importance of clear and accessible information (eg, what to expect and how to undertake the bowel preparation) and the need for managing expectations of patients (eg, being clear about when results will be received and what happens if a further colonoscopy is required). CONCLUSIONS: The findings led to recommendations for future implementations of managed CCE services in National Health Service (NHS) Scotland that could also apply more widely (United Kingdom and beyond) and at a greater scale (with more patients in more contexts). These include promoting CCE with, for, and among clinical teams to ensure adoption and success; capturing and understanding reasons why patients do and do not opt for CCE; providing clear information in a variety of appropriate ways to patients (eg, around the importance of bowel preparation instructions); improving the bowel preparation (this is not specific to CCE alone); providing flexible options for issuing and returning the kit (eg, dropping off at a pharmacy); and embedding formative evaluation within the service itself (eg, capturing patient-reported experiences via surveys in the information pack when the equipment is returned).


Assuntos
Endoscopia por Cápsula , Endoscopia por Cápsula/métodos , Endoscopia por Cápsula/normas , Escócia , Inquéritos e Questionários , Entrevistas como Assunto , Medicina Estatal/tendências , Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Idoso de 80 Anos ou mais , Neoplasias Colorretais/diagnóstico
3.
Disabil Rehabil Assist Technol ; 17(3): 338-348, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-32633592

RESUMO

BACKGROUND: Smartphone reminding applications can help overcome memory difficulties experienced by people with acquired brain injury (ABI). Cognitive difficulties with memory and attention make entering reminders into a device, and remembering to set reminders, challenging for this group. ApplTree is a reminding app with features that aim to address challenges. One app feature was push notifications (asking "Do you need to set any reminders?") to support people to initiate use of the app to set reminders. Another app feature was a customisable user interface design to support attention and short term memory during reminder setting. METHODS: In a mixed-methods user study, five people with self or other reported memory impairment following ABI used ApplTree for at least 4 months. They received push notifications for at least 2 months and no push notifications for at least 2 months. Monthly participant interviews provided insight into user interface preference, app use, and push notification acceptability. RESULTS: Receiving four Push notifications per day doubled number of daily reminders set and four of the five participants found receiving them to be acceptable. This long-term field study uncovered issues relevant for clinicians and designers, including insights into the potential benefits of different user interface designs, the impact of family members on app use, and the importance of perceived need influencing use and acceptance. CONCLUSIONS: Feedback provided insight into future considerations when designing reminding apps and using them in neuropsychological rehabilitation. This work highlights the benefit of user-led research into accessible design and use of assistive technologies.IMPLICATIONS FOR REHABILITATION"Unsolicited" push prompts are an easy to implement feature of reminding technology that is useful and acceptable for people with ABI in community rehabilitation.Observations provide insights about how people with ABI make use of reminding apps over time. This can inform those designing apps or providing reminding technology as part of neuropsychological rehabilitation.Participants differed on their preference of the two user-interface designs available in ApplTree. This highlights an area for future research because currently available reminding apps have a broad-shallow design which may not always be appropriate for people with ABI.


Assuntos
Disfunção Cognitiva , Aplicativos Móveis , Humanos
4.
Int J Life Cycle Assess ; 28: 156-171, 2022 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-36891065

RESUMO

Purpose: Electricity production is one of the largest sources of environmental emissions-especially greenhouse gases (GHGs)-in the USA. Emission factors (EFs) vary from region to region, which requires the use of spatially relevant EF data for electricity production while performing life cycle assessments (LCAs). Uncertainty information, which is sought by LCA practitioners, is rarely supplied with available life cycle inventories (LCIs). Methods: To address these challenges, we present a method for collecting data from different sources for electricity generation and environmental emissions; discuss the challenges involved in agglomerating such data; provide relevant suggestions and solutions to merge the information; and calculate EFs for electricity generation processes from various fuel sources for different spatial regions and spatial resolutions. The EFs from the US 2016 Electricity Life Cycle Inventory (eLCI) are analyzed and explored in this study. We also explore the method of uncertainty information derivation for the EFs. Results and discussion: We explore the EFs from different technologies across Emissions & Generation Resource Integrated Database (eGRID) regions in the USA. We find that for certain eGRID regions, the same electricity production technology may have worse emissions. This may be a result of the age of the plants in the region, the quality of fuel used, or other underlying factors. Region-wise life cycle impact assessment (LCIA) ISO 14040 impacts for total generation mix activities provide an overview of the total sustainability profile of electricity production in a particular region, rather than only global warming potential (GWP). We also find that, for different LCIA impacts, several eGRID regions are consistently worse than the US average LCIA impact for every unit of electricity generated. Conclusion: This work describes the development of an electricity production LCI at different spatial resolutions by combining and harmonizing information from several databases. The inventory consists of emissions, fuel inputs, and electricity and steam outputs from different electricity production technologies located across various regions of the USA. This LCI for electricity production in the USA will prove to be an enormous resource for all LCA researchers-considering the detailed sources of the information and the breadth of emissions covered by it.

5.
Disabil Rehabil Assist Technol ; 15(4): 453-466, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-30985193

RESUMO

Background: Cognitive and behavioural difficulties after acquired brain injury (ABI) may lead to reduced engagement in leisure and social activities. Increasing participation is a goal of neuropsychological rehabilitation and assistive and behaviour change technology can play an important role in this. Focus groups and interviews were conductive with brain injury rehabilitation stakeholders (n = 24): people with ABI (n = 9), family members (n = 3) and care providers (n = 12) in order to understand the barriers to engaging in meaningful activities and what helps to overcome these barriers. A collaborative thematic analysis was performed by a multi-disciplinary research team using an approach based on Grounded Theory. Results: Four central, interlinked, barriers were found: Access, Cognitive Difficulties, Anticipation (of Physical or Cognitive Difficulties) and Motivation. To overcome these barriers, participants cited themes such as External Motivation from both Other People and Technology, Maintaining Momentum and different aspects of Being Planful. Conclusions: The results point to future directions for the purposeful development of effective assistive technology for this user group. Technology that is social, persuasive, adapts to individual needs and supports people to plan activities are likely to be particularly useful within neuropsychological rehabilitation.Implications For RehabilitationAdults with ABI and their carers describe problems accessing activities, cognitive difficulties, anticipationof physical or cognitive difficulties and low motivation as the key barriers to undertaking meaningfulactivities.Current solutions are external prompting, maintaining momentum and being planful.This detailed qualitative analysis of a diverse group of carers and service users allows insight into theassistive technologies that could aid rehabilitation.


Assuntos
Lesões Encefálicas/reabilitação , Atividades de Lazer , Motivação , Tecnologia Assistiva , Participação Social , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pesquisa Qualitativa
6.
Environ Sci Technol ; 53(4): 2238-2248, 2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30717588

RESUMO

This study updates the Petroleum Refinery Life Cycle Inventory Model (PRELIM) to provide a more complete gate-to-gate life cycle inventory and to allow for the calculation of a full suite of impact potentials commonly used in life cycle assessment (LCA) studies. Prior to this update, PRELIM provided results for energy use and greenhouse gas emissions from petroleum refineries with a level of detail suitable for most LCA studies in support of policy decisions. We updated the model to add criteria air pollutants, hazardous air pollutants, releases to water, releases to land, and managed wastes reflecting 2014 reported releases and waste management practices using data from the U.S. Environmental Protection Agency Greenhouse Gas Reporting Program, National Emissions Inventory, Discharge Monitoring Reports, and Toxic Release Inventory together with process unit capacities and fuel consumption data from the U.S. Energy Information Administration (U.S. EIA). The variability of refinery subprocess release factors is characterized using log-normal distributions with parameters set based on the distribution of release factors across facilities. The U.S. EPA Tool for the Reduction and Assessment of Chemical and Environmental Impacts life cycle impact assessment (LCIA) method is used together with the updated inventory data to provide impact potentials in the PRELIM dashboard interface. Release inventories at the subprocess level enable greater responsiveness to variable selection within PRELIM, such as refinery configuration, and allocation to specific refinery products. The updated version also provides a template to allow users to import PRELIM inventory results into the openLCA software tool as unit process data sets. Here we document and validate the model updates. Impact potentials from the national crude mix in 2014 are compared to impacts from the 2005 mix to demonstrate the impact of assay and configuration on the refining sector over time. The expanded version of PRELIM offers users a reliable, transparent, and streamlined tool for estimating the effect of changes in petroleum refineries on LCIA results in the context of policy analysis.


Assuntos
Poluentes Atmosféricos , Petróleo , Meio Ambiente , United States Environmental Protection Agency
7.
Neuropsychol Rehabil ; 29(4): 513-533, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-28425328

RESUMO

Prompting-based memory compensation is a potential application for smartwatches. This study investigated the usability and efficacy of a Moto360 smartwatch as a memory aid. Four community dwelling adults with memory difficulties following acquired brain injury (ABI) were included in an A-B-A single case experimental design study. Performance of everyday memory tasks was tested over six weeks with the smartwatch and software provided during weeks three and four. Participants were asked to use their usual memory aids and strategies during the control phases (weeks 1-2, 5-6). Three participants successfully used the smartwatch throughout the intervention weeks and gave positive usability ratings. A fourth participant experienced a seizure and subsequently left the study before the intervention phase. Three participants showed improved memory performance when using the smartwatch. Nonoverlap of all pairs (NAP) analysis showed a non-significant small increase in memory performance between baseline and intervention phases (mean NAP = 0.1, p = .84). There was a larger, significant decline between the intervention and return to baseline (mean NAP = 0.58, p < .01). The use of an off-the-shelf smartwatch device and software was feasible for people with ABI in the community. It was effective compared to practice as usual, although this was only apparent on withdrawal of the device.


Assuntos
Lesões Encefálicas/reabilitação , Transtornos da Memória/reabilitação , Aplicativos Móveis , Sistemas de Alerta , Tecnologia Assistiva , Smartphone , Adulto , Lesões Encefálicas/complicações , Estudos de Viabilidade , Feminino , Humanos , Masculino , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Projetos de Pesquisa , Resultado do Tratamento
8.
Environ Sci Technol ; 51(2): 977-987, 2017 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-28092937

RESUMO

The National Energy Technology Laboratory produced a well-to-wheels (WTW) life cycle greenhouse gas analysis of petroleum-based fuels consumed in the U.S. in 2005, known as the NETL 2005 Petroleum Baseline. This study uses a set of engineering-based, open-source models combined with publicly available data to calculate baseline results for 2014. An increase between the 2005 baseline and the 2014 results presented here (e.g., 92.4 vs 96.2 g CO2e/MJ gasoline, + 4.1%) are due to changes both in modeling platform and in the U.S. petroleum sector. An updated result for 2005 was calculated to minimize the effect of the change in modeling platform, and emissions for gasoline in 2014 were about 2% lower than in 2005 (98.1 vs 96.2 g CO2e/MJ gasoline). The same methods were utilized to forecast emissions from fuels out to 2040, indicating maximum changes from the 2014 gasoline result between +2.1% and -1.4%. The changing baseline values lead to potential compliance challenges with frameworks such as the Energy Independence and Security Act (EISA) Section 526, which states that Federal agencies should not purchase alternative fuels unless their life cycle GHG emissions are less than those of conventionally produced, petroleum-derived fuels.


Assuntos
Efeito Estufa , Petróleo , Previsões , Gasolina , Modelos Teóricos , Estados Unidos
9.
Neuropsychol Rehabil ; 27(6): 919-936, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26509889

RESUMO

Evans, Wilson, Needham, and Brentnall ( 2003 ) investigated memory aid use by people with acquired brain injury (ABI) and found little use of technological memory aids. The present study aims to investigate use of technological and other memory aids and strategies 10 years on, and investigate what predicts use. People with ABI and self-reported memory impairments (n = 81) completed a survey containing a memory aid checklist, demographic questions and memory questionnaires. Chi-square analysis showed that 10 of 18 memory aids and strategies were used by significantly more people in the current sample than in Evans et al. ( 2003 ). The most commonly used strategies were leaving things in noticeable places (86%) and mental retracing of steps (77%). The most commonly used memory aids were asking someone to remind you (78%), diaries (77%), lists (78%), and calendars (79%) and the most common technologies used were mobile phone reminders (38%) and alarms/timers (38%). Younger people who used more technology prior to their injury and who use more non-technological memory aids currently were more likely to use technology. Younger people who used more memory aids and strategies prior to their injury and who rated their memory as poorer were more likely to use all types of memory aids and strategies.


Assuntos
Lesões Encefálicas/reabilitação , Transtornos da Memória/reabilitação , Tecnologia Assistiva/estatística & dados numéricos , Adulto , Idoso , Lesões Encefálicas/complicações , Feminino , Humanos , Masculino , Transtornos da Memória/complicações , Pessoa de Meia-Idade
10.
Behav Modif ; 39(5): 691-720, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26149395

RESUMO

Single-case data analysis still relies heavily on visual inspection, and, at the same time, it is not clear to what extent the results of different quantitative procedures converge in identifying an intervention effect and its magnitude when applied to the same data; this is the type of evidence provided here for two procedures. One of the procedures, included due to the importance of providing objective criteria to visual analysts, is a visual aid fitting and projecting split-middle trend while taking into account data variability. The other procedure converts several different metrics into probabilities making their results comparable. In the present study, we expore to what extend these two procedures coincide in the magnitude of intervention effect taking place in a set of studies stemming from a recent meta-analysis. The procedures concur to a greater extent with the values of the indices computed and with each other and, to a lesser extent, with our own visual analysis. For distinguishing smaller from larger effects, the probability-based approach seems somewhat better suited. Moreover, the results of the field test suggest that the latter is a reasonably good mechanism for translating different metrics into similar labels. User friendly R code is provided for promoting the use of the visual aid, together with a quantification based on nonoverlap and the label provided by the probability approach.


Assuntos
Recursos Audiovisuais , Probabilidade , Projetos de Pesquisa/normas , Estatística como Assunto/métodos , Resultado do Tratamento , Humanos , Metanálise como Assunto
11.
Neuropsychol Rehabil ; 24(3-4): 419-44, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-23957379

RESUMO

Technology can compensate for memory impairment. The efficacy of assistive technology for people with memory difficulties and the methodology of selected studies are assessed. A systematic search was performed and all studies that investigated the impact of technology on memory performance for adults with impaired memory resulting from acquired brain injury (ABI) or a degenerative disease were included. Two 10-point scales were used to compare each study to an ideally reported single case experimental design (SCED) study (SCED scale; Tate et al., 2008 ) or randomised control group study (PEDro-P scale; Maher, Sherrington, Herbert, Moseley, & Elkins, 2003 ). Thirty-two SCED (mean = 5.9 on the SCED scale) and 11 group studies (mean = 4.45 on the PEDro-P scale) were found. Baseline and intervention performance for each participant in the SCED studies was re-calculated using non-overlap of all pairs (Parker & Vannest, 2009 ) giving a mean score of 0.85 on a 0 to 1 scale (17 studies, n = 36). A meta-analysis of the efficacy of technology vs. control in seven group studies gave a large effect size (d = 1.27) (n = 147). It was concluded that prosthetic technology can improve performance on everyday tasks requiring memory. There is a specific need for investigations of technology for people with degenerative diseases.


Assuntos
Lesões Encefálicas/reabilitação , Transtornos da Memória/reabilitação , Doenças Neurodegenerativas/reabilitação , Tecnologia Assistiva , Lesões Encefálicas/complicações , Humanos , Transtornos da Memória/complicações , Doenças Neurodegenerativas/complicações
12.
Mol Pharm ; 10(5): 1815-23, 2013 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-23514109

RESUMO

Photothermal Fourier transform infrared (FTIR) microspectroscopy (PTMS), involving the combination of FTIR spectroscopy with atomic force microscopy, has been used to examine compacts of amorphous and crystalline salbutamol sulfate in order to assess the ability of the technique to distinguish between different physical forms in a multicomponent material. Samples of amorphous and crystalline material were assessed using modulated temperature differential scanning calorimetry (DSC), atomic force microscopy, microthermal analysis, and conventional FTIR. Mixed compacts were then prepared such that verification of the location of the forms present was possible via topography and localized thermal analysis. PTMS studies were then performed on selected interrogation points, with spectra obtained which were largely intermediate between those corresponding to the two individual forms. Calculation of the thermal diffusivity indicated a resolution for the technique corresponding to a hemisphere of a major diameter in the region of 40 µm, which is large in relation to the particle sizes involved. However, distinction into amorphous, crystalline, and indeterminate categories was possible using chemometric analysis (hierarchical cluster analysis and principal component analysis). Good agreement was found between the identification methods for the mixed systems. The study has therefore shown the potential, as well as identifying the limitations, of using PTMS as a means of spatially identifying components in complex materials.


Assuntos
Albuterol/química , Microscopia de Força Atômica/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Agonistas de Receptores Adrenérgicos beta 2/química , Fenômenos Químicos , Química Farmacêutica , Cristalização , Temperatura Alta , Propriedades de Superfície , Condutividade Térmica
13.
Int J Pharm ; 422(1-2): 220-8, 2012 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-22100976

RESUMO

An investigation into the effect of water uptake on the glass transition of spray dried and milled salbutamol sulphate has been performed, with a particular view to exploring how the water uptake, T(g) value and recrystallization behaviour correlate. Samples of milled and spray dried drug were stored under controlled humidity conditions and the T(g) measured as a function of time. The T(g) was measured using modulated temperature differential scanning calorimetry (MTDSC) while the water content was measured using thermogravimetric analysis (TGA). A correlation was found between time of storage, water content and T(g) in that the samples showed time dependent equilibration with the storage environment (either gaining or losing water depending on the RH). The relationship between water content and stability, based on the concept of T(g) lowering, was modelled using the semi-empirical approach of Royall et al. (1999) as well as a derivation of the Kwei equation which allowed the interaction between the water and substrate to be accounted for. A method for predicting stability based on two simple DSC runs is proposed. In addition, we discuss the observation of a double glass transition for the spray dried samples.


Assuntos
Albuterol/química , Broncodilatadores/química , Modelos Químicos , Água/química , Varredura Diferencial de Calorimetria , Química Farmacêutica , Cristalização , Dessecação , Estabilidade de Medicamentos , Armazenamento de Medicamentos , Umidade , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Tecnologia Farmacêutica/métodos , Termogravimetria , Fatores de Tempo , Temperatura de Transição
14.
J Pharm Sci ; 100(8): 3114-3129, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21456029

RESUMO

A study has been undertaken using a range of established and novel approaches to examine the effects of milling on the structure and crystallization behavior of salbutamol sulfate. A combination of modulated temperature differential scanning calorimetry, attenuated total reflectance Fourier-transform infrared spectroscopy, powder X-ray diffraction, and gravimetric vapor sorption analysis have been employed, with a particular view to examining the validity of using spray-dried material as a comparator. Although the expected increase in amorphization with milling time was observed, several unexpected observations were made including an apparently anomalous relationship between glass transition temperature and water content; this was used as the basis for the development of a novel method of quantifying amorphous content. Reasonable agreement was found between the data obtained from the spectroscopic and thermal methods, particularly those latter approaches that do not rely on recrystallization for quantification. The activation energy for the onset process was determined and found to be similar for all materials studied. The study has indicated that when using spray-dried material as a standard, the associated limitations must be appreciated, particularly in terms of the assumption of comparability of the recrystallization process between materials that is embedded in many quantification techniques.


Assuntos
Albuterol/análise , Albuterol/química , Composição de Medicamentos/métodos , Água/química , Adsorção , Varredura Diferencial de Calorimetria , Cristalização , Microscopia Eletrônica de Varredura , Modelos Químicos , Tamanho da Partícula , Transição de Fase , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura de Transição , Volatilização , Difração de Raios X
15.
J Am Chem Soc ; 128(24): 7718-9, 2006 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-16771468

RESUMO

We have obtained both porous and dendritic, intricate morphology crystals of beta-glycine by the novel and simple method of emulsion droplet adhesion and encapsulation. By using octanoic acid emulsified with nonionic surfactants, the adhesion of the emulsion droplets can be so strong that, remarkably, crystal growth often proceeds around the droplets, leading to their inclusion within the single crystals. Consequently, porous single crystals can be produced with the pore diameters ( approximately 10-25 mum) corresponding to the emulsion droplet sizes. Highly intricate, dendritic morphologies for glycine were obtained by increasing the surfactant concentration in the emulsions to 50%. In this case, partial droplet encapsulation results in crystal dendrites growing on either side of adsorbed droplets, with the complex morphologies developing due to the high density of dendritic branches that can occur. These intricate morphologies are in stark contrast to the facetted crystals that normally develop at these low supersaturations in the absence of octanoic acid droplets. This study demonstrates that complex architectures can be attained by using simple emulsion systems and tuning the degree of droplet adhesion.


Assuntos
Caprilatos/química , Cristalização/métodos , Glicina/química , Água/química , Emulsões , Soluções/química , Propriedades de Superfície , Tensoativos/química , Temperatura , Aderências Teciduais
16.
J Am Chem Soc ; 127(34): 11894-5, 2005 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-16117500

RESUMO

Highly anomalous crystallization behavior has been achieved in phase-inverting emulsion systems by using nonionic surfactants that induce nucleation. In particular, nucleation can be inhibited at the phase inversion, allowing systems held at, or near, this temperature to undergo crystallization either on heating or cooling. This new phenomenon is demonstrated for 27.4 wt % aqueous glycine solutions emulsified in decane using Span 20 Tween 20 blends. The inhibitory effect on interfacial nucleation at/near the phase inversion is readily shown by the maximum in the induction time for crystallization found in systems at/near the phase-inversion temperature. These findings are unprecedented. An extremely rapid rise in nucleation rate is expected on cooling glycine solutions, owing to the associated increase in supersaturation, the driving force for crystallization. The origin of this highly anomalous behavior is thought to be the low droplet interfacial tension, gammaow, that occurs at the phase-inversion temperature, which results primarily in a substantially increased contact angle between the glycine critical nucleus and the droplet interface. This may present a paradigm shift in crystallization strategies through the use of tunable contact-angle nucleators.

17.
Langmuir ; 20(9): 3593-600, 2004 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-15875388

RESUMO

The crystallization of DL-aspartic acid beneath nylon 6 spread films has been studied for 150% supersaturated systems using neutron reflectivity and external reflection FTIR. The neutron reflectivity data showed the gradual incorporation of DL-aspartic acid within a nylon 6 spread film layer over a period of 6-8 h, culminating in over 50 vol % of the "film" layer comprising DL-aspartic acid. Accumulation of further DL-aspartic acid material to produce microscopic/macroscopic surface crystals occurred, but on a more limited scale, resulting in approximately 1-5% surface coverage of crystals over the same period. External reflection FTIR studies revealed very weak bands attributable to DL-aspartic acid in surface regions devoid of visible crystals, in agreement with the neutron reflectivity studies. In regions with visible crystals, much larger and sharper DL-aspartic acid bands were seen. Changes in the intensity of the nylon 6 NH stretch band were often observed during the visible crystallization and dissolution of DL-aspartic acid and were consistent with the reversible accumulation of nylon 6 around the growing crystals.


Assuntos
Ácido Aspártico/química , Caprolactama/análogos & derivados , Nêutrons , Polímeros/química , Caprolactama/química , Cristalização , Espectroscopia de Infravermelho com Transformada de Fourier
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