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1.
Radiol Technol ; 94(4): 269-286, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36973017

RESUMEN

PURPOSE: To investigate the educational effect of the COVID-19 pandemic on virtual technology use in the radiologic technology classroom by comparing virtual technology use and perceived barriers for use from before the COVID-19 pandemic through the spring 2021 semester. METHODS: An explanatory mixed-method, cross-sectional survey design was used to evaluate radiologic technology educators' integration of virtual technology and continuance intention to use (CITU) virtual technology in the radiologic technology classroom. A pseudoqualitative component also was used to add meaning to the quantitative data. RESULTS: A total of 255 educators completed the survey. Educators with associate degrees scored significantly lower in CITU compared with participants with master's degrees (P = .04) and doctoral or professional degrees (P = .01). Virtual technology use significantly increased from before COVID-19 to spring 2021 (P < .001). Educators' perceptions of barriers to technology integration significantly decreased from before COVID-19 to spring 2021 (P < .001). In this report, radiologic technology educators indicated intentions for increased virtual technology use in the future compared with their use during the spring 2021 semester (P = .001). DISCUSSION: Virtual technology use was low before COVID-19, and although it increased during the spring 2021 semester, it remained relatively low. Future intentions for virtual technology use indicate an increase from spring 2021, suggesting a change in future delivery of radiologic science education. Instructors' levels of education had a significant effect on CITU scores. Cost and funding was consistently the highest reported barrier to virtual technology use, whereas student resistance to technology was consistently the lowest reported barrier. Narratives of participants' challenges, current and future use, and rewards related to virtual technology also added pseudoqualitative meaning to the quantitative findings. CONCLUSION: The educators in this study demonstrated low virtual technology use before the COVID-19 pandemic, increased virtual technology use because of the pandemic, and significantly positive CITU scores. Radiologic science educators' responses regarding their challenges, current and future use, and rewards might be helpful in facilitating more effective technology integration.


Asunto(s)
COVID-19 , Tecnología Radiológica , Humanos , Tecnología Radiológica/educación , Pandemias , Estudios Transversales , Tecnología
2.
medRxiv ; 2023 Feb 08.
Artículo en Inglés | MEDLINE | ID: mdl-36798392

RESUMEN

Background: Intraepidermal nerve fiber density (IENFD) has become an important biomarker for neuropathy diagnosis and research. The consequences of reduced IENFD can include sensory dysfunction, pain, and a significant decrease in quality of life. We examined the extent to which IENFD is being used as a tool in human and mouse models and compared the degree of fiber loss between diseases to gain a broader understanding of the existing data collected using this common technique. Methods: We conducted a scoping review of publications that used IENFD as a biomarker in human and non-human research. PubMed was used to identify 1,004 initial articles that were then screened to select articles that met the criteria for inclusion. Criteria were chosen to standardize publications so they could be compared rigorously and included having a control group, measuring IENFD in a distal limb, and using protein gene product 9.5 (PGP9.5). Results: We analyzed 397 articles and collected information related to publication year, the condition studied, and the percent IENFD loss. The analysis revealed that the use of IENFD as a tool has been increasing in both human and non-human research. We found that IENFD loss is prevalent in many diseases, and metabolic or diabetes-related diseases were the most studied conditions in humans and rodents. Our analysis identified 74 human diseases in which IENFD was affected, with 71 reporting IENFD loss and an overall average IENFD change of -47%. We identified 28 mouse and 21 rat conditions, with average IENFD changes of -31.6 % and - 34.7% respectively. Additionally, we present data describing sub-analyses of IENFD loss according to disease characteristics in diabetes and chemotherapy treatments in humans and rodents. Interpretation: Reduced IENFD occurs in a surprising number of human disease conditions. Abnormal IENFD contributes to important complications, including poor cutaneous vascularization, sensory dysfunction, and pain. Our analysis informs future rodent studies so they may better mirror human diseases impacted by reduced IENFD, highlights the breadth of diseases impacted by IENFD loss, and urges exploration of common mechanisms that lead to substantial IENFD loss as a complication in disease.

3.
Compr Rev Food Sci Food Saf ; 20(4): 3438-3463, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-34151512

RESUMEN

Meat is one of the most consumed agro-products because it contains proteins, minerals, and essential vitamins, all of which play critical roles in the human diet and health. Meat is a perishable food product because of its high moisture content, and as such there are concerns about its quality, stability, and safety. There are two widely used methods for monitoring meat quality attributes: subjective sensory evaluation and chemical/instrumentation tests. However, these methods are labor-intensive, time-consuming, and destructive. To overcome the shortfalls of these conventional approaches, several researchers have developed fast and nondestructive techniques. Recently, electronic nose (e-nose), computer vision (CV), spectroscopy, hyperspectral imaging (HSI), and multispectral imaging (MSI) technologies have been explored as nondestructive methods in meat quality and safety evaluation. However, most of the studies on the application of these novel technologies are still in the preliminary stages and are carried out in isolation, often without comprehensive information on the most suitable approach. This lack of cohesive information on the strength and shortcomings of each technique could impact their application and commercialization for the detection of important meat attributes such as pH, marbling, or microbial spoilage. Here, we provide a comprehensive review of recent nondestructive technologies (e-nose, CV, spectroscopy, HSI, and MSI), as well as their applications and limitations in the detection and evaluation of meat quality and safety issues, such as contamination, adulteration, and quality classification. A discussion is also included on the challenges and future outlooks of the respective technologies and their various applications.


Asunto(s)
Contaminación de Alimentos , Carne , Nariz Electrónica , Contaminación de Alimentos/análisis , Humanos , Carne/análisis , Análisis Espectral
4.
Phys Med Biol ; 66(5)2021 02 25.
Artículo en Inglés | MEDLINE | ID: mdl-33535191

RESUMEN

There has been a recent revival of interest in the FLASH effect, after experiments have shown normal tissue sparing capabilities of ultra-high-dose-rate radiation with no compromise on tumour growth restraint. A model has been developed to investigate the relative importance of a number of fundamental parameters considered to be involved in the oxygen depletion paradigm of induced radioresistance. An example eight-dimensional parameter space demonstrates the conditions under which radiation may induce sufficient depletion of oxygen for a diffusion-limited hypoxic cellular response. Initial results support experimental evidence that FLASH sparing is only achieved for dose rates on the order of tens of Gy s-1or higher, for a sufficiently high dose, and only for tissue that is slightly hypoxic at the time of radiation. We show that the FLASH effect is the result of a number of biological, radiochemical and delivery parameters. Also, the threshold dose for a FLASH effect occurring would be more prominent when the parameterisation was optimised to produce the maximum effect. The model provides a framework for further FLASH-related investigation and experimental design. An understanding of the mechanistic interactions producing an optimised FLASH effect is essential for its translation into clinical practice.


Asunto(s)
Neoplasias , Oxígeno , Humanos , Neoplasias/radioterapia , Dosificación Radioterapéutica
5.
Sci Rep ; 11(1): 3341, 2021 02 08.
Artículo en Inglés | MEDLINE | ID: mdl-33558553

RESUMEN

This paper presents the first plasmid DNA irradiations carried out with Very High Energy Electrons (VHEE) over 100-200 MeV at the CLEAR user facility at CERN to determine the Relative Biological Effectiveness (RBE) of VHEE. DNA damage yields were measured in dry and aqueous environments to determine that ~ 99% of total DNA breaks were caused by indirect effects, consistent with other published measurements for protons and photons. Double-Strand Break (DSB) yield was used as the biological endpoint for RBE calculation, with values found to be consistent with established radiotherapy modalities. Similarities in physical damage between VHEE and conventional modalities gives confidence that biological effects of VHEE will also be similar-key for clinical implementation. Damage yields were used as a baseline for track structure simulations of VHEE plasmid irradiation using GEANT4-DNA. Current models for DSB yield have shown reasonable agreement with experimental values. The growing interest in FLASH radiotherapy motivated a study into DSB yield variation with dose rate following VHEE irradiation. No significant variations were observed between conventional and FLASH dose rate irradiations, indicating that no FLASH effect is seen under these conditions.


Asunto(s)
Partículas beta , Roturas del ADN de Doble Cadena , Modelos Químicos , Plásmidos/química
6.
Foods ; 9(7)2020 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-32674380

RESUMEN

In the last two decades, food scientists have attempted to develop new technologies that can improve the detection of insect infestation in fruits and vegetables under postharvest conditions using a multitude of non-destructive technologies. While consumers' expectations for higher nutritive and sensorial value of fresh produce has increased over time, they have also become more critical on using insecticides or synthetic chemicals to preserve food quality from insects' attacks or enhance the quality attributes of minimally processed fresh produce. In addition, the increasingly stringent quarantine measures by regulatory agencies for commercial import-export of fresh produce needs more reliable technologies for quickly detecting insect infestation in fruits and vegetables before their commercialization. For these reasons, the food industry investigates alternative and non-destructive means to improve food quality. Several studies have been conducted on the development of rapid, accurate, and reliable insect infestation monitoring systems to replace invasive and subjective methods that are often inefficient. There are still major limitations to the effective in-field, as well as postharvest on-line, monitoring applications. This review presents a general overview of current non-destructive techniques for the detection of insect damage in fruits and vegetables and discusses basic principles and applications. The paper also elaborates on the specific post-harvest fruit infestation detection methods, which include principles, protocols, specific application examples, merits, and limitations. The methods reviewed include those based on spectroscopy, imaging, acoustic sensing, and chemical interactions, with greater emphasis on the noninvasive methods. This review also discusses the current research gaps as well as the future research directions for non-destructive methods' application in the detection and classification of insect infestation in fruits and vegetables.

7.
Sci Rep ; 9(1): 19870, 2019 12 27.
Artículo en Inglés | MEDLINE | ID: mdl-31882690

RESUMEN

There is strong in vitro cell survival evidence that the relative biological effectiveness (RBE) of protons is variable, with dependence on factors such as linear energy transfer (LET) and dose. This is coupled with the growing in vivo evidence, from post-treatment image change analysis, of a variable RBE. Despite this, a constant RBE of 1.1 is still applied as a standard in proton therapy. However, there is a building clinical interest in incorporating a variable RBE. Recently, correlations summarising Monte Carlo-based mechanistic models of DNA damage and repair with absorbed dose and LET have been published as the Manchester mechanistic (MM) model. These correlations offer an alternative path to variable RBE compared to the more standard phenomenological models. In this proof of concept work, these correlations have been extended to acquire RBE-weighted dose distributions and calculated, along with other RBE models, on a treatment plan. The phenomenological and mechanistic models for RBE have been shown to produce comparable results with some differences in magnitude and relative distribution. The mechanistic model found a large RBE for misrepair, which phenomenological models are unable to do. The potential of the MM model to predict multiple endpoints presents a clear advantage over phenomenological models.


Asunto(s)
Daño del ADN/genética , Reparación del ADN/genética , Adulto , Algoritmos , Daño del ADN/fisiología , Reparación del ADN/fisiología , Femenino , Humanos , Transferencia Lineal de Energía/genética , Transferencia Lineal de Energía/fisiología , Método de Montecarlo , Adulto Joven
8.
Sci Rep ; 9(1): 6359, 2019 04 23.
Artículo en Inglés | MEDLINE | ID: mdl-31015540

RESUMEN

Following radiation induced DNA damage, several repair pathways are activated to help preserve genome integrity. Double Strand Breaks (DSBs), which are highly toxic, have specified repair pathways to address them. The main repair pathways used to resolve DSBs are Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR). Cell cycle phase determines the availability of HR, but the repair choice between pathways in the G2 phases where both HR and NHEJ can operate is not clearly understood. This study compares several in silico models of repair choice to experimental data published in the literature, each model representing a different possible scenario describing how repair choice takes place. Competitive only scenarios, where initial protein recruitment determines repair choice, are unable to fit the literature data. In contrast, the scenario which uses a more entwined relationship between NHEJ and HR, incorporating protein co-localisation and RNF138-dependent removal of the Ku/DNA-PK complex, is better able to predict levels of repair similar to the experimental data. Furthermore, this study concludes that co-localisation of the Mre11-Rad50-Nbs1 (MRN) complexes, with initial NHEJ proteins must be modeled to accurately depict repair choice.


Asunto(s)
Roturas del ADN de Doble Cadena , Reparación del ADN , Modelos Biológicos , Simulación por Computador , Reparación del ADN por Unión de Extremidades
9.
RSC Adv ; 9(12): 6845-6858, 2019 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-35518487

RESUMEN

Relative Biological Effectiveness (RBE), the ratio of doses between radiation modalities to produce the same biological endpoint, is a controversial and important topic in proton therapy. A number of phenomenological models incorporate variable RBE as a function of Linear Energy Transfer (LET), though a lack of mechanistic description limits their applicability. In this work we take a different approach, using a track structure model employing fundamental physics and chemistry to make predictions of proton and photon induced DNA damage, the first step in the mechanism of radiation-induced cell death. We apply this model to a proton therapy clinical case showing, for the first time, predictions of DNA damage on a patient treatment plan. Our model predictions are for an idealised cell and are applied to an ependymoma case, at this stage without any cell specific parameters. By comparing to similar predictions for photons, we present a voxel-wise RBE of DNA damage complexity. This RBE of damage complexity shows similar trends to the expected RBE for cell kill, implying that damage complexity is an important factor in DNA repair and therefore biological effect.

10.
Neuropsychologia ; 128: 209-214, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-29154901

RESUMEN

Translucence is an important property of natural materials, and human observers are adept at perceiving changes in translucence. Perceptions of different material properties appear to arise from different cortical regions, and it is therefore plausible that the perception of translucence is dependent on specialised regions, separate from those important for colour and texture processing. To test for anatomical independence between areas necessary for colour, texture and translucence perception we assessed translucency perception in a cortically colour blind observer, who performs at chance on tasks of colour and texture discrimination. Firstly, in order to establish that MS has shown no significant recovery, we assessed his colour perception performance on the Farnsworth-Munsell 100 Hue Test. Secondly, we tested him with two translucence ranking tasks. In one task, stimuli were images of glasses of tea varying in tea strength. In the other, stimuli were glasses of tea varying only in milkiness. MS was able to systematically rank both strength and milkiness, although less consistently than controls, and for tea strength his rankings were in the opposite order. An additional group of controls tested with greyscale versions of the images succeeded at the tasks, albeit slightly less consistently on the milkiness task, showing that the performance of normal observers cannot be transformed into the performance of MS simply by removing colour information from the stimuli. The systematic performance of MS suggests that some aspects of translucence perception do not depend on regions critical for colour and texture processing.


Asunto(s)
Corteza Cerebral/fisiología , Percepción de Color/fisiología , Percepción Visual/fisiología , Anciano , Mapeo Encefálico , Pruebas de Percepción de Colores , Visión de Colores , Defectos de la Visión Cromática/fisiopatología , Defectos de la Visión Cromática/psicología , Hemianopsia/fisiopatología , Hemianopsia/psicología , Humanos , Masculino , Desempeño Psicomotor
11.
J Intensive Care Soc ; 16(4): 312-325, 2015 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-28979437

RESUMEN

Chest drains are common on intensive care units for a wide variety of clinical conditions. Despite this, there are no published data on their use within the intensive care unit and minimal published literature to guide decision making regarding the timing of their removal. Therefore, we undertook an audit to review our experience over one year, as to the degree of variability in when chest drains were removed. Using our electronic observation records, we assessed the length of stay of our chest drains against their functionality by whether they remained swinging (i.e. in connection with the pleural space) and whether they had a pathological fluid output (>150 mL/24 h). We found that our drains had a mean duration of 5.89 days, and that one-quarter remained in place for three days despite being non-functional. To conclude, we have devised a three-stage assessment (using the acronym I-T-U), to help guide an intensivist in the safe and timely removal of a chest drain.

12.
Vision Res ; 109: 221-35, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25448119

RESUMEN

Gloss is a relatively little studied visual property of objects' surfaces. The earliest recorded scientific reference to gloss appears to have been by Ingersoll in 1921: studies at this time were based on the assumption that gloss could be understood as an inherent physical property of a surface, and the priority was to devise a satisfactory method and scale to measure it reliably. As awareness of the complexity of perception grew, efforts were made to distinguish different types of gloss, although these generally still took the form of a search for objective physical measures to be solved within the visual system by means of inverse optics. It became more widely recognised approximately 20 years ago that models of gloss perception based on inverse optics were intractable and failed to explain experimental findings adequately. A temporary decline in the number of published studies followed; however the last decade or so has seen a renewal of interest in the perception of gloss, in an effort to map what is now understood to be a complex interaction of variables including illumination, surface properties and observer. This appears to have been driven by a number of factors, as the study of gloss re-emerged from research into other surface properties such as colour and texture, with technological advances paving the way for new experimental techniques and measurements. This review describes the main strands of research, tracking the changes in approach and theory which have triggered new avenues of research, to the current state of knowledge.


Asunto(s)
Propiedades de Superficie , Percepción Visual/fisiología , Señales (Psicología) , Humanos , Modelos Teóricos , Psicofísica
13.
Nature ; 507(7493): 471-4, 2014 Mar 27.
Artículo en Inglés | MEDLINE | ID: mdl-24670765

RESUMEN

The observable Solar System can be divided into three distinct regions: the rocky terrestrial planets including the asteroids at 0.39 to 4.2 astronomical units (AU) from the Sun (where 1 AU is the mean distance between Earth and the Sun), the gas giant planets at 5 to 30 AU from the Sun, and the icy Kuiper belt objects at 30 to 50 AU from the Sun. The 1,000-kilometre-diameter dwarf planet Sedna was discovered ten years ago and was unique in that its closest approach to the Sun (perihelion) is 76 AU, far greater than that of any other Solar System body. Formation models indicate that Sedna could be a link between the Kuiper belt objects and the hypothesized outer Oort cloud at around 10,000 AU from the Sun. Here we report the presence of a second Sedna-like object, 2012 VP113, whose perihelion is 80 AU. The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort cloud, whose objects could outnumber all other dynamically stable populations in the Solar System.

14.
Technol Health Care ; 21(3): 191-7, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23792793

RESUMEN

The aim of this study is to describe the process of staff and patient adoption and compliance of a real-time locating system (RTLS) across two health care settings and present lessons learned. While previous work has examined the technological feasibility of tracking staff and patients in a health care setting in real-time, these studies have not described the critical adoption issues that must be overcome for deployment. The ability to track and monitor individual staff and patients presents new opportunities for improving workflow, patient health and reducing health care costs. A RTLS is introduced in both a long-term care and a polytrauma transitional rehabilitation program (PTRP) in a Veterans Hospital to track staff and patient locations and five lessons learned are presented from our experiences and responses to emergent technological, work-related and social barriers to adoption. We conclude that successful tracking in a health care environment requires time and careful consideration of existing work, policies and stakeholder needs which directly impact the efficacy of the technology.


Asunto(s)
Personal de Enfermería en Hospital/organización & administración , Cooperación del Paciente , Dispositivo de Identificación por Radiofrecuencia , Carga de Trabajo , Adulto , Anciano , Estudios de Factibilidad , Hospitales de Veteranos , Humanos , Cuidados a Largo Plazo , Centros de Rehabilitación , Estados Unidos
15.
Science ; 329(5997): 1304, 2010 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-20705814

RESUMEN

The orbits of small Solar System bodies record the history of our Solar System. Here, we report the detection of 2008 LC18, which is a Neptune Trojan in the trailing (L5) Lagrangian region of gravitational equilibrium within Neptune's orbit. We estimate that the leading and trailing Neptune Trojan regions have similarly sized populations and dynamics, with both regions dominated by high-inclination objects. Similar populations and dynamics at both Neptune Lagrangian regions indicate that the Trojans were likely captured by a migrating, eccentric Neptune in a dynamically excited planetesimal population.

16.
IEEE Comput Graph Appl ; 30(2): 71-85, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-20669534

RESUMEN

The Nintendo Wii Remote (Wiimote) has served as an input device in 3D user interfaces (3DUIs) but differs from the general-purpose input hardware typically found in research labs and commercial applications. Despite this, no one has systematically evaluated the device in terms of what it offers 3DUI designers. Experience with the Wiimote indicates that it's an imperfect harbinger of a new class of spatially convenient devices, classified in terms of spatial data, functionality, and commodity design. This tutorial presents techniques for using the Wiimote in 3DUIs. It discusses the device's strengths and how to compensate for its limitations, with implications for future spatially convenient devices.

17.
Anim Reprod Sci ; 119(3-4): 205-11, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20193992

RESUMEN

In seasonally anoestrous ewes of many breeds, the introduction of rams triggers an increase in gonadotrophin secretion that induces ovulation, a phenomenon known as the 'ram effect'. The ram effect is a practical method for mating ewes outside the natural breeding season, and also can provide synchronised lambing, but the variability of the response, especially in young animals, reduces its potential for widespread application. The aim of our study was to assess two factors that are thought to contribute to the variability in young ewes: temperament and sexual experience. We used anovulatory ewes from a flock that had been genetically selected for 'calm' or 'nervous' temperament and compared the endocrine and ovarian responses to the ram effect in four groups (each n=15): 'calm' and parous (3-6 years old); 'calm' and nulliparous (2 years old); 'nervous' and parous; and 'nervous' and nulliparous. Parous ewes, independently of their temperament, exhibited a faster endocrine response and a higher proportion of females cycling after ram introduction than nulliparous ewes. 'Nervous' ewes exhibited a higher proportion of females cycling after ram introduction than calm ewes, but only in the nulliparous group. We conclude that temperament exerts little influence on the response to the ram effect in sexually experienced ewes, and that females of 'nervous' temperament appear to respond better when sexually 'naive'. Both sexual experience and temperament need to be taken into consideration when flock management involves the ram effect. Finally, some ewes were cyclic at ram introduction, yet exhibited an increase in LH secretion even in the presence of high concentrations of progesterone. The mechanism by which the inhibitory effect of progesterone on LH secretion was bypassed needs to be clarified.


Asunto(s)
Anestro/fisiología , Paridad , Estaciones del Año , Conducta Sexual Animal/fisiología , Ovinos/fisiología , Animales , Cruzamiento , Femenino , Hormona Luteinizante/metabolismo , Masculino , Ovulación/fisiología , Inducción de la Ovulación/veterinaria , Embarazo , Progesterona/sangre , Temperamento/fisiología
18.
Dev Psychobiol ; 51(5): 429-38, 2009 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-19530256

RESUMEN

Temperament influences maternal behavior and lamb survival in Merino sheep selected for calm or nervous temperament. The impact of this selection on mother-young recognition and early expression of temperament in lambs is unknown. We tested the ability of multiparous ewes selected for calm (n = 16) or nervous (n = 18) temperament to recognize their own lambs 6 hr after parturition, the ability of the lambs to display a preference for their own mother at 18 hr, and the temperament of the lambs at 1 and 16 weeks of age. Ewes and lambs from both genotypes showed a similar preference for their familiar kin. In contrast, differences in temperament were detectable at 1 and 16 weeks of age. Nervous lambs showed higher vocal and locomotor activity than calm lambs. Thus, temperament did not affect the early process of ewe-lamb bonding but might affect the quality of the mother-young relationship under more challenging situations.


Asunto(s)
Conducta de Elección , Apego a Objetos , Temperamento , Animales , Conducta Animal , Conducta Materna , Pruebas Psicológicas , Reconocimiento en Psicología , Ovinos
19.
Solid State Nucl Magn Reson ; 31(4): 169-73, 2007 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17560090

RESUMEN

(27)Al MAS NMR has been used to study a sol-gel prepared alumina annealed at various temperatures. Two-field simulation of the sample heated to 1200 degrees C confirmed the presence of corundum, as suggested by XRD, and also the presence of nanocrystalline theta-Al(2)O(3). (27)Al MAS NMR chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites within theta-Al(2)O(3).


Asunto(s)
Óxido de Aluminio , Aluminio , Espectroscopía de Resonancia Magnética , Física Nuclear
20.
Faraday Discuss ; 134: 83-102; discussion 103-18, 415-9, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17326564

RESUMEN

Alumina and silica Zener pinning particles in sol-gel prepared nanocrystalline ZrO2 and MgO have been characterised using 27Al and 29Si MAS NMR after annealing at various temperatures up to 1200 degrees C. The structures of the pinning phases were found to differ not just between the two metal oxide systems but also depending on the exact method of manufacture. Three distinct transitional alumina phases have been observed in different alumina-pinned samples annealed at 1200 degrees C, one in particular identified by a peak at a shift of 95 ppm in the 27Al NMR spectrum. Both the alumina and silica pinning phases reacted with the MgO nanocrystals, forming spinel in the case of alumina, and enstatite and forsterite in the case of silica. Despite reacting readily with the MgO, the silica pinning particles were effective at restricting grain growth, with 11 nm MgO nanocrystals remaining after annealing at 1000 degrees C.

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