0.94(Bi0.5Na0.5TiO3)–0.06(BaTiO3) (BNTBT) is a potential lead-free piezoelectric candidate to replace lead-based PZT ceramics. The thermal depoling temperature sets the upper limit for the high ...temperature application of piezoelectric materials. Recently, an interface model was proposed to explain the good resistance to thermal depoling of BNTBT-ZnO composite. However, we found that the presence of ZnO was not limited to the interface, but contributed intrinsically to the BNTBT lattice. This played a critical role in the structural changes of BNTBT, confirmed by a unit volume change supported by XRD, which was further proved by Raman, EDS, and dielectric characterization at different temperatures. The previous interface model is not correct because BNTBT shows thermally stable piezoelectric properties, even though there is no interface between BNTBT and ZnO. The thermal depoling behavior of BNTBT-based materials is directly related to the transition temperature from the rhombohedral phase to the tetragonal phase in our phase transition model, which is consistent with four current peaks in their ferroelectric loops close to the depoling temperature.
Shaped around the stories of one extended family, their friends, neighbours, and community, Pandemic Kinship provides an intimate portrait of everyday life in Botswana's time of AIDS. It challenges ...assumptions about a 'crisis of care' unfolding in the wake of the pandemic, showing that care - like other aspects of Tswana kinship - is routinely in crisis, and that the creative ways families navigate such crises make them kin. In Setswana, conflict and crisis are glossed as dikgang, and negotiating dikgang is an ethical practice that generates and reorients kin relations over time. Governmental and non-governmental organisations often misread the creativity of crisis, intervening in ways that may prove more harmful than the problems they set out to solve. Moving between family discussions, community events, and the daily work of orphan care projects and social work offices, Pandemic Kinship provides provocative insights into how we manage change in pandemic times.
Cryogels consisting of polyvinyl alcohol and iron (II, III) oxide magnetic nanoparticles coated with a model drug-acetaminophen, were developed as a tunable platform for thermally triggered drug ...release, based on shape-selective heat transfer. Two different shapes of cryogels; discs and spherical caps, were formed via adding polymer-nanoparticle-drug mixtures into 3D printed molds, followed by freeze-thawing five times. No additional chemical crosslinking agents were used for gel formation and the iron oxide nanoparticles were coated with acetaminophen using only citric acid as a hydrogen-bonding linker. The two gel shapes displayed varying levels of acetaminophen release within 42-50 °C, which are ideal temperatures for hyperthermia induced drug delivery. The amount and time of drug-release were shown to be tunable by changing the temperature of the medium and the shape of the gels, while keeping all other factors (ex. gel volume, surface area, polymer/nanoparticle concentrations and drug-loading) constant. The discs displayed higher drug release at all temperatures while being particularly effective at lower temperatures (42-46 °C), in contrast to the spherical caps, which were more effective at higher temperatures (48-50 °C). Magnetic hyperthermia-mediated thermal imaging and temperature profiling studies revealed starkly different heat transfer behavior from the two shapes of gels. The disc gels retained their structural integrity up to 51 °C, while the spherical caps were stable up to 59 °C, demonstrating shape-dependent robustness. The highly customizable physicochemical features, facile synthesis, biocompatibility and tunable drug release ability of these cryogels offer potential for their application as a low cost, safe and effective platform for hyperthermia-mediated drug delivery, for external applications such as wound care/muscle repair or internal applications such as melanoma treatment.
Review of graphene-ceramic matrix composites Porwal, H.; Grasso, S.; Reece, M. J.
Advances in applied ceramics,
11/1/2013, 20131100, 2013-11-00, 20131101, Letnik:
112, Številka:
8
Journal Article
Recenzirano
Graphene has remarkable mechanical properties, which makes it potentially a good reinforcement in ceramic composites. It also has unique electrical and thermal properties, which makes it an ...attractive filler for producing multifunctional ceramics for a wide range of applications. In the past few years, relatively little attention has been focused on graphene ceramic matrix composites (GCMC) in comparison to polymer composites. This review gives a comprehensive overview on the state of the art of GCMC, including materials synthesis, densification and characterisation. The published literature allows us to define the critical steps for processing GCMC, and identify its influence on the multifunctional and mechanical properties of the composites. Finally, the potential future applications and current research trends in GCMC are presented.
The primary purpose of the present study is to determine if an organized control scheme exists for the antagonist muscle during steady isometric torque. A secondary focus is to better understand how ...firing rates of the antagonist muscle change from a moderate- to higher-contraction intensity. Fourteen subjects performed two submaximal isometric trapezoid muscle actions of the forearm flexors that included a linearly increasing, steady force at both 40% and 70% maximum voluntary contraction, and linearly decreasing segments. Surface electromyographic signals of the biceps and triceps brachii were collected and decomposed into constituent motor unit action potential trains. Motor unit firing rate versus recruitment threshold, motor unit action potential amplitude versus recruitment threshold, and motor unit firing rate versus action potential amplitude relationships of the biceps brachii (agonist) and triceps brachii (antagonist) muscles were analyzed. Moderate- to-strong relationships (|
| ≥ 0.69) were present for the agonist and antagonist muscles for each relationship with no differences between muscles (
= 0.716, 0.428, 0.182). The
-intercepts of the motor unit firing rate versus recruitment threshold relationship of the antagonist did not increase from 40% to 70% maximal voluntary contractions (
= 0.96), unlike for the agonist (
= 0.009). The antagonist muscle exhibits a similar motor unit control scheme to the agonist. Unlike the agonist, however, the firing rates of the antagonist did not increase with increasing intensity. Future research should investigate how antagonist firing rates adapt to resistance training and changes in antagonist firing rates in the absence of peripheral feedback.
This is the first study to explore a potential motor unit control scheme and quantify changes in firing rates with increasing intensity of an antagonist muscle during isometric contractions. We demonstrate that the antagonist muscle possesses an organized motor unit firing rate and recruitment scheme similar to the agonist muscle during isometric forearm flexion, but unlike the agonist muscle, there was no significant increase in firing rates from a moderate- to higher-intensity isometric contraction.
Deficient ophthalmologic care is costly to patients, making the identification of groups not receiving adequate care of vital importance. The current landscape of equity in ophthalmic care has yet to ...be thoroughly investigated and is important to ensure inclusivity and patient-centered care.
To perform a scoping review of the literature pertaining to health care inequities in the field of ophthalmology.
A comprehensive database search using MEDLINE (via PubMed) and Ovid Embase was done in July 2022. English-language articles published from 2016 to 2021 were included and encompassed all article types except commentaries or correspondence. The search modeled the National Institutes of Health list of designated US health inequity populations, which includes income, education level, occupational status, rural and underresourced area, sex and gender, lesbian, gay, bisexual, transgender, and queer (LGBTQ) identity, and race and ethnicity. A total of 8170 abstracts and titles were screened by 2 independent investigators, and 189 studies were assessed in full text for eligibility. For inclusion, articles needed to be an ophthalmic study discussing health inequities. In a masked, duplicate fashion, 2 independent investigators screened 75 full-text studies for data extraction using a pilot-tested form. Data extraction included general publication characteristics and health inequity data based on the National Institutes of Health's defined inequity groups.
A total of 75 publications were included. Notable inequities were found among Black and Hispanic patients associated with negative ophthalmic outcomes and mixed associations regarding sex or gender. Overall, lower-income patients were more likely to have vision impairment, use eye care services less, and have lower adherence to eye examinations. No articles within our sample examined LGBTQ inequities among ophthalmology patients since the 2016 National Institutes of Health classification of sexual and gender minority populations. Substantial research gaps were observed within the ophthalmic literature pertaining to the LGBTQ community, race and ethnicity, and rural and underresourced areas.
This scoping review found substantial findings associated with the LGBTQ community, race and ethnicity, and the role of telemedicine in rural and underresourced areas. Because of the importance of ophthalmic care in overall patient health, it is vital to understand the various inequities present and strive to improve the current gaps in the literature. Future studies should (1) examine barriers to clinical study and medical trainee recruitment as well as patient values and preference studies and (2) investigate the implementation of telemedicine in underresourced areas.
Secondary organic aerosol (SOA) formation during photo-oxidation of primary emissions from cookstoves used in developing countries may make important contributions to their climate and air quality ...impacts. We present results from laboratory experiments with a field portable oxidation flow reactor (F-OFR) to study the evolution of emissions over hours to weeks of equivalent atmospheric aging. Lab tests, using dry red oak, measured fresh and aged emissions from a 3 stone fire (TSF), a “rocket” natural draft stove (NDS), and a forced draft gasifier stove (FDGS), in order of increasing modified combustion efficiency (MCE) and decreasing particulate matter emission factors (EF). SOA production was observed for all stoves/tests; organic aerosol (OA) enhancement factor ranged from 1.2 to 3.1, decreasing with increased MCE. In primary emissions, OA mass spectral fragments associated with oxygenated species (primary biomass burning markers) increased (decreased) with MCE; fresh OA from FDGS combustion was especially oxygenated. OA oxygenation increased with further oxidation for all stove emissions, even where minimal enhancement was observed. More efficient stoves emit particles with greater net direct specific warming than TSFs, with the difference increasing with aging. Our results show that the properties and evolution of cookstove emissions are a strong function of combustion efficiency and atmospheric aging.
The extent to which motor vehicles contribute to ambient secondary organic aerosol (SOA) remains uncertain. Here, we present in situ measurements of SOA formation at a near-highway site with ...substantial tree-cover 10 m from Interstate 40 near Durham, North Carolina. In July 2015 (summer) and February 2016 (winter), we exposed ambient air to a range of oxidant (O3 and OH) concentrations in an oxidation flow reactor (OFR), resulting in hours to weeks of equivalent atmospheric aging. We observed substantial seasonal variation in SOA formation upon OFR aging; diurnally varying OA enhancements of ∼3–8 μg m–3 were observed in summer and significantly lower enhancements (∼0.5–1 μg m–3) in winter. Measurements in both seasons showed consistent changes in bulk OA properties (chemical composition; volatility) with OFR aging. Mild increases in traffic-related SOA precursors during summer partly explains the seasonal variation. However, biogenic emissions, with sharp temperature dependence, appear to dominate summer OFR-SOA. Our analysis indicates that SOA observed in the OFR is similar (within a factor of 2) to that predicted to form from traffic and biogenic precursors using literature yields, especially in winter. This study highlights the utility of the OFR for studying the prevalence of SOA precursors in complex real-world settings.
Genetic and environmental manipulations, such as dietary restriction, can improve both health span and lifespan in a wide range of organisms, including humans. Changes in nutrient intake trigger ...often overlapping metabolic pathways that can generate distinct or even opposite outputs depending on several factors, such as when dietary restriction occurs in the lifecycle of the organism or the nature of the changes in nutrients. Due to the complexity of metabolic pathways and the diversity in outputs, the underlying mechanisms regulating diet-associated pro-longevity are not yet well understood. Adult reproductive diapause (ARD) in the model organism Caenorhabditis elegans is a dietary restriction model that is associated with lengthened lifespan and reproductive potential. To explore the metabolic pathways regulating ARD in greater depth, we performed a candidate-based genetic screen analyzing select nutrient-sensing pathways to determine their contribution to the regulation of ARD. Focusing on the three phases of ARD (initiation, maintenance, and recovery), we found that ARD initiation is regulated by fatty acid metabolism, sirtuins, AMPK, and the O-linked N-acetyl glucosamine (O-GlcNAc) pathway. Although ARD maintenance was not significantly influenced by the nutrient sensors in our screen, we found that ARD recovery was modulated by energy sensing, stress response, insulin-like signaling, and the TOR pathway. Further investigation of downstream targets of NHR-49 suggest the transcription factor influences ARD initiation through the fatty acid beta-oxidation pathway. Consistent with these findings, our analysis revealed a change in levels of neutral lipids associated with ARD entry defects. Our findings identify conserved genetic pathways required for ARD entry and recovery and uncover genetic interactions that provide insight into the role of OGT and OGA.
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