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1.
Conserv Biol ; : e14259, 2024 Apr 04.
Artículo en Inglés | MEDLINE | ID: mdl-38571448

RESUMEN

Approximately one quarter of the earth's population directly harvests natural resources to meet their daily needs. These individuals are disproportionately required to alter their behaviors in response to increasing climatic variability and global biodiversity loss. Much of the ever-ambitious global conservation agenda relies on the voluntary uptake of conservation behaviors in such populations. Thus, it is critical to understand how such individuals perceive environmental change and use conservation practices as a tool to protect their well-being. We developed a participatory mapping activity to elicit spatially explicit perceptions of forest change and its drivers across 43 mangrove-dependent communities in Pemba, Tanzania. We administered this activity along with a questionnaire regarding conservation preferences and behaviors to 423 individuals across those 43 communities. We analyzed these data with a set of Bayesian hierarchical statistical models. Perceived cover loss in 50% of a community's mangrove area drove individuals to decrease proposed limits on fuelwood bundles from 2.74 (forest perceived as intact) to 2.37 if participants believed resultant gains in mangrove cover would not be stolen by outsiders. Conversely, individuals who believed their community mangrove forests were at high risk of theft loosened their proposed harvest limits from 1.26 to 2.75 bundles of fuelwood in response to the same perceived forest decline. High rates of intergroup competition and mangrove loss were thus driving a self-reinforcing increase in unsustainable harvesting preferences in community forests in this system. This finding demonstrates a mechanism by which increasing environmental decline may cause communities to forgo conservation practices, rather than adopt them, as is often assumed in much community-based conservation planning. However, we also found that when effective boundaries were present, individuals were willing to limit their own harvests to stem such perceived decline.


Efectos de las percepciones del cambio forestal y la competencia intergrupal en los comportamientos de conservación comunitarios Resumen Aproximadamente una cuarta parte de la población mundial aprovecha directamente los recursos naturales para satisfacer sus necesidades diarias. Estos individuos se ven desproporcionadamente obligados a alterar sus comportamientos en respuesta a la creciente variabilidad climática y la pérdida de biodiversidad global. Gran parte de la ambiciosa agenda de conservación global se basa en la adopción voluntaria de comportamientos de conservación en dichas poblaciones. Por lo tanto, es fundamental comprender cómo esas personas perciben el cambio ambiental y utilizan las prácticas de conservación como herramienta para proteger su bienestar. Desarrollamos una actividad de mapeo participativo para generar percepciones espacialmente explícitas del cambio forestal y sus causantes en 43 comunidades dependientes de manglares en Pemba, Tanzania. Administramos esta actividad junto con un cuestionario sobre preferencias y comportamientos de conservación a 423 personas en esas 43 comunidades. Analizamos estos datos mediante un conjunto de modelos estadísticos jerárquicos bayesianos. La pérdida de cobertura percibida en el 50% del área de manglares de una comunidad llevó a los individuos a reducir los límites propuestos para los paquetes de leña de 2.74 (bosque percibido como intacto) a 2.37 si los participantes creían que las ganancias resultantes en la cobertura de manglares no serían robadas por personas ajenas a la comunidad. Por el contrario, las personas que creían que los bosques de manglares de su comunidad corrían un alto riesgo de robo flexibilizaron los límites de cosecha propuestos de 1.26 a 2.75 haces de leña en respuesta a la misma disminución percibida del bosque. Por lo tanto, las altas tasas de competencia entre grupos y pérdida de manglares estaban impulsando un aumento, que se auto reforzaba, en las preferencias de aprovechamiento insostenibles en los bosques comunitarios de este sistema. Este hallazgo muestra un mecanismo por el cual el creciente deterioro ambiental puede hacer que las comunidades renuncien a las prácticas de conservación, en lugar de adoptarlas, como a menudo se supone en gran parte de la planificación de la conservación basada en la comunidad. Sin embargo, también encontramos que cuando existían límites efectivos, los individuos estaban dispuestos a restringir sus propias cosechas para frenar esa disminución percibida.

2.
Commun Biol ; 7(1): 451, 2024 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-38622287

RESUMEN

This report presents an optical fibre-based endo-microscopic imaging tool that simultaneously measures the topographic profile and 3D viscoelastic properties of biological specimens through the phenomenon of time-resolved Brillouin scattering. This uses the intrinsic viscoelasticity of the specimen as a contrast mechanism without fluorescent tags or photoacoustic contrast mechanisms. We demonstrate 2 µm lateral resolution and 320 nm axial resolution for the 3D imaging of biological cells and Caenorhabditis elegans larvae. This has enabled the first ever 3D stiffness imaging and characterisation of the C. elegans larva cuticle in-situ. A label-free, subcellular resolution, and endoscopic compatible technique that reveals structural biologically-relevant material properties of tissue could pave the way toward in-vivo elasticity-based diagnostics down to the single cell level.


Asunto(s)
Imagenología Tridimensional , Microscopía , Animales , Microscopía/métodos , Imagenología Tridimensional/métodos , Caenorhabditis elegans , Elasticidad , Biología
3.
Sci Rep ; 13(1): 16228, 2023 09 27.
Artículo en Inglés | MEDLINE | ID: mdl-37758808

RESUMEN

There is a consensus about the strong correlation between the elasticity of cells and tissue and their normal, dysplastic, and cancerous states. However, developments in cell mechanics have not seen significant progress in clinical applications. In this work, we explore the possibility of using phonon acoustics for this purpose. We used phonon microscopy to obtain a measure of the elastic properties between cancerous and normal breast cells. Utilising the raw time-resolved phonon-derived data (300 k individual inputs), we employed a deep learning technique to differentiate between MDA-MB-231 and MCF10a cell lines. We achieved a 93% accuracy using a single phonon measurement in a volume of approximately 2.5 µm3. We also investigated means for classification based on a physical model that suggest the presence of unidentified mechanical markers. We have successfully created a compact sensor design as a proof of principle, demonstrating its compatibility for use with needles and endoscopes, opening up exciting possibilities for future applications.


Asunto(s)
Aprendizaje Profundo , Neoplasias , Fonones , Acústica , Línea Celular , Consenso
4.
Acta Biomater ; 166: 317-325, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37137402

RESUMEN

Microrheology, the study of fluids on micron length-scales, promises to reveal insights into cellular biology, including mechanical biomarkers of disease and the interplay between biomechanics and cellular function. Here a minimally-invasive passive microrheology technique is applied to individual living cells by chemically binding a bead to the surface of a cell, and observing the mean squared displacement of the bead at timescales ranging from milliseconds to 100s of seconds. Measurements are repeated over the course of hours, and presented alongside analysis to quantify changes in the cells' low-frequency elastic modulus, G0', and the cell's dynamics over the time window ∼10-2 s to 10 s. An analogy to optical trapping allows verification of the invariant viscosity of HeLa S3 cells under control conditions and after cytoskeletal disruption. Stiffening of the cell is observed during cytoskeletal rearrangement in the control case, and cell softening when the actin cytoskeleton is disrupted by Latrunculin B. These data correlate with conventional understanding that integrin binding and recruitment triggers cytoskeletal rearrangement. This is, to our knowledge, the first time that cell stiffening has been measured during focal adhesion maturation, and the longest time over which such stiffening has been quantified by any means. STATEMENT OF SIGNIFICANCE: Here, we present an approach for studying mechanical properties of live cells without applying external forces or inserting tracers. Regulation of cellular biomechanics is crucial to healthy cell function. For the first time in literature, we can non-invasively and passively quantify cell mechanics during interactions with functionalised surface. Our method can monitor the maturation of adhesion sites on the surface of individual live cells without disrupting the cell mechanics by applying forces to the cell. We observe a stiffening response in cells over tens of minutes after a bead chemically binds. This stiffening reduces the deformation rate of the cytoskeleton, although the internal force generation increases. Our method has potential for applications to study mechanics during cell-surface and cell-vesicle interactions.


Asunto(s)
Citoesqueleto , Pinzas Ópticas , Citoesqueleto/metabolismo , Membrana Celular/metabolismo , Módulo de Elasticidad , Citoesqueleto de Actina
5.
Photoacoustics ; 31: 100493, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37180958

RESUMEN

In this paper, we show a proof-of-concept method to parallelise phonon microscopy measurements for cell elasticity imaging by demonstrating a 3-fold increase in acquisition speed which is limited by current acquisition hardware. Phonon microscopy is based on time-resolved Brillouin scattering, which uses a pump-probe method with asynchronous optical sampling (ASOPS) to generate and detect coherent phonons. This enables access to the cell elasticity via the Brillouin frequency with sub-optical axial resolution. Although systems based on ASOPS are typically faster compared to the ones built with a mechanical delay line, they are still very slow to study real time changes at the cellular level. Additionally, the biocompatibility is reduced due to long light exposure and scanning time. Using a multi-core fibre bundle rather than a single channel for detection, we acquire 6 channels simultaneously allowing us to speed-up measurements, and open a way to scale-up this method.

6.
Eur Radiol ; 32(10): 7237-7247, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-36006428

RESUMEN

OBJECTIVES: Relapse occurs in ~20% of patients with classical Hodgkin lymphoma (cHL) despite treatment adaption based on 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography response. The objective was to evaluate pre-treatment FDG PET/CT-derived machine learning (ML) models for predicting outcome in patients with cHL. METHODS: All cHL patients undergoing pre-treatment PET/CT at our institution between 2008 and 2018 were retrospectively identified. A 1.5 × mean liver standardised uptake value (SUV) and a fixed 4.0 SUV threshold were used to segment PET/CT data. Feature extraction was performed using PyRadiomics with ComBat harmonisation. Training (80%) and test (20%) cohorts stratified around 2-year event-free survival (EFS), age, sex, ethnicity and disease stage were defined. Seven ML models were trained and hyperparameters tuned using stratified 5-fold cross-validation. Area under the curve (AUC) from receiver operator characteristic analysis was used to assess performance. RESULTS: A total of 289 patients (153 males), median age 36 (range 16-88 years), were included. There was no significant difference between training (n = 231) and test cohorts (n = 58) (p value > 0.05). A ridge regression model using a 1.5 × mean liver SUV segmentation had the highest performance, with mean training, validation and test AUCs of 0.82 ± 0.002, 0.79 ± 0.01 and 0.81 ± 0.12. However, there was no significant difference between a logistic model derived from metabolic tumour volume and clinical features or the highest performing radiomic model. CONCLUSIONS: Outcome prediction using pre-treatment FDG PET/CT-derived ML models is feasible in cHL patients. Further work is needed to determine optimum predictive thresholds for clinical use. KEY POINTS: • A fixed threshold segmentation method led to more robust radiomic features. • A radiomic-based model for predicting 2-year event-free survival in classical Hodgkin lymphoma patients is feasible. • A predictive model based on ridge regression was the best performing model on our dataset.


Asunto(s)
Enfermedad de Hodgkin , Tomografía Computarizada por Tomografía de Emisión de Positrones , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Fluorodesoxiglucosa F18/metabolismo , Enfermedad de Hodgkin/diagnóstico por imagen , Enfermedad de Hodgkin/terapia , Humanos , Aprendizaje Automático , Masculino , Persona de Mediana Edad , Recurrencia Local de Neoplasia , Tomografía Computarizada por Tomografía de Emisión de Positrones/métodos , Tomografía de Emisión de Positrones/métodos , Estudios Retrospectivos , Adulto Joven
7.
ACS Photonics ; 9(6): 1919-1925, 2022 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-35726241

RESUMEN

In this paper, we show for the first time the polarization-sensitive super-resolution phononic reconstruction of multiple nanostructures in a liquid environment by overcoming the diffraction limit of the optical system (1 µm). By using time-resolved pump-probe spectroscopy, we measure the acoustic signature of nanospheres and nanorods at different polarizations. This enables the size, position, and orientation characterization of multiple nanoparticles in a single point spread function with the precision of 5 nm, 3 nm, and 1.4°, respectively. Unlike electron microscopy where a high vacuum environment is needed for imaging, this technique performs measurements in liquids at ambient pressure, ideal to study the insights of living specimens. This is a potential path toward super-resolution phononic imaging where the acoustic signatures of multiple nanostructures could act as an alternative to fluorescent labels. In this context, phonons also offer the opportunity to extract information about the mechanical properties of the surrounding medium as well as access to subsurface features.

8.
Conserv Biol ; 36(4): e13918, 2022 08.
Artículo en Inglés | MEDLINE | ID: mdl-35554972

RESUMEN

The pink pigeon (Nesoenas mayeri) is an endemic species of Mauritius that has made a remarkable recovery after a severe population bottleneck in the 1970s to early 1990s. Prior to this bottleneck, an ex situ population was established from which captive-bred individuals were released into free-living subpopulations to increase population size and genetic variation. This conservation rescue led to rapid population recovery to 400-480 individuals, and the species was twice downlisted on the International Union for the Conservation of Nature (IUCN) Red List. We analyzed the impacts of the bottleneck and genetic rescue on neutral genetic variation during and after population recovery (1993-2008) with restriction site-associated sequencing, microsatellite analyses, and quantitative genetic analysis of studbook data of 1112 birds from zoos in Europe and the United States. We used computer simulations to study the predicted changes in genetic variation and population viability from the past into the future. Genetic variation declined rapidly, despite the population rebound, and the effective population size was approximately an order of magnitude smaller than census size. The species carried a high genetic load of circa 15 lethal equivalents for longevity. Our computer simulations predicted continued inbreeding will likely result in increased expression of deleterious mutations (i.e., a high realized load) and severe inbreeding depression. Without continued conservation actions, it is likely that the pink pigeon will go extinct in the wild within 100 years. Conservation rescue of the pink pigeon has been instrumental in the recovery of the free-living population. However, further genetic rescue with captive-bred birds from zoos is required to recover lost variation, reduce expression of harmful deleterious variation, and prevent extinction. The use of genomics and modeling data can inform IUCN assessments of the viability and extinction risk of species, and it helps in assessments of the conservation dependency of populations.


La paloma rosada (Nesoenas mayeri) es una especie endémica de Mauricio que se ha recuperado impresionantemente después de un grave cuello de botella poblacional a principios de la década de 1970 que duró hasta inicios de la década de 1990. Antes de este cuello de botella se había establecido una población ex situ de la cual se liberaban individuos reproducidos en cautiverio a las subpoblaciones en libertad para incrementar la variación genética y el tamaño poblacional. Este rescate de conservación derivó en una recuperación rápida de la población (400-480 individuos) y la especie cambió positivamente de categoría dos veces en la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza (UICN). Analizamos los impactos del cuello de botella y el rescate genético sobre la variación genética neutral durante y después de la recuperación poblacional (de 1993 a 2008) mediante secuenciación RAD, análisis de microsatélites y análisis genéticos cuantitativos de los datos del libro genealógico de 1112 aves ubicadas en zoológicos de Europa y los Estados Unidos. Usamos simulaciones por computadora para estudiar los cambios pronosticados en la variación genética y en la viabilidad poblacional del pasado hacia el futuro. La variación genética declinó rápidamente, a pesar de la recuperación poblacional, y el tamaño efectivo de la población fue aproximadamente un orden de magnitud más pequeño que el tamaño del censo. La especie contó con una carga genética elevada de casi 15 equivalentes letales para la longevidad. Nuestras simulaciones pronostican que la endogamia continua probablemente resultará en un incremento en la expresión de mutaciones deletéreas (es decir, una carga realizada elevada) y en una depresión endogámica severa. Sin acciones continuas para la conservación, es probable que la paloma rosada esté extinta en vida libre dentro de cien años. El rescate de conservación de la paloma rosada ha sido fundamental en la recuperación de la población silvestre; sin embargo, se requiere de un rescate genético adicional con las aves de reproducción en cautiverio de los zoológicos para recuperar la variación perdida, reducir la expresión de la variación deletérea dañina y prevenir la extinción. El uso de la genómica y los datos modelados puede orientar las valoraciones de la UICN sobre la viabilidad y el riesgo de extinción de las especies, además de que ayuda en la evaluación de la dependencia que tienen las poblaciones de la conservación.


Asunto(s)
Aves , Conservación de los Recursos Naturales , Animales , Aves/genética , Especies en Peligro de Extinción , Europa (Continente) , Variación Genética , Genómica , Densidad de Población
9.
Light Sci Appl ; 10(1): 91, 2021 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-33907178

RESUMEN

We show for the first time that a single ultrasonic imaging fibre is capable of simultaneously accessing 3D spatial information and mechanical properties from microscopic objects. The novel measurement system consists of two ultrafast lasers that excite and detect high-frequency ultrasound from a nano-transducer that was fabricated onto the tip of a single-mode optical fibre. A signal processing technique was also developed to extract nanometric in-depth spatial measurements from GHz frequency acoustic waves, while still allowing Brillouin spectroscopy in the frequency domain. Label-free and non-contact imaging performance was demonstrated on various polymer microstructures. This singular device is equipped with optical lateral resolution, 2.5 µm, and a depth-profiling precision of 45 nm provided by acoustics. The endoscopic potential for this device is exhibited by extrapolating the single fibre to tens of thousands of fibres in an imaging bundle. Such a device catalyses future phonon endomicroscopy technology that brings the prospect of label-free in vivo histology within reach.

10.
Sci Rep ; 11(1): 3301, 2021 02 08.
Artículo en Inglés | MEDLINE | ID: mdl-33558575

RESUMEN

Brillouin light scattering (BLS) is an emerging method for cell imaging and characterisation. It allows elasticity-related contrast, optical resolution and label-free operation. Phonon microscopy detects BLS from laser generated coherent phonon fields to offer an attractive route for imaging since, at GHz frequencies, the phonon wavelength is sub-optical. Using phonon fields to image single cells is challenging as the signal to noise ratio and acquisition time are often poor. However, recent advances in the instrumentation have enabled imaging of fixed and living cells. This work presents the first experimental characterisation of phonon-based axial resolution provided by the response to a sharp edge. The obtained axial resolution is up to 10 times higher than that of the optical system used to take the measurements. Validation of the results are obtained with various polymer objects, which are in good agreement with those obtained using atomic force microscopy. Edge localisation, and hence profilometry, of a phantom boundary is measured with accuracy and precision of approximately 60 nm and 100 nm respectively. Finally, 3D imaging of fixed cells in culture medium is demonstrated.

11.
Ultrasonics ; 111: 106306, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33290959

RESUMEN

In this work we employ additive manufacturing to print a circular array of micropillars on an aluminium slab turning its top surface into a graded index metasurface for surface acoustic waves (SAW). The graded metasurface reproduces a Luneburg lens capable of focusing plane SAWs to a point. The graded index profile is obtained by exploiting the dispersion properties of the metasurface arising from the well-known resonant coupling between the micropillars (0.5 mm diameter and variable length ∼3 mm) and the surface waves propagating in the substrate. From the analytical formulation of the metasurface's dispersion curves, a slow phase velocity mode is shown to arise from the hybridisation of the surface wave with the pillar resonance. This is used to compute the radial height profile corresponding to the refractive index given by Luneburg's equation. An initial validation of the lens design, achieved through ray theory, shows that ray trajectories have a strong frequency dependence, meaning that the lens will only work on a narrow band. An ultrasonic experiment at 500 kHz where plane SAWs are generated with a piezoelectric transducer and a laser scanner measures the out of plane displacement on the metasurface, validates the actual lens performance and the manufacturing technique. Finally, comparison between the ray analysis and experimental results offers insight into the behaviour of this type of metasurface especially in the proximity of the acoustic bandgaps and highlights the possibility for acoustic shielding.

12.
Heredity (Edinb) ; 125(6): 396-416, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-32616877

RESUMEN

Crop populations derived from experimental crosses enable the genetic dissection of complex traits and support modern plant breeding. Among these, multi-parent populations now play a central role. By mixing and recombining the genomes of multiple founders, multi-parent populations combine many commonly sought beneficial properties of genetic mapping populations. For example, they have high power and resolution for mapping quantitative trait loci, high genetic diversity and minimal population structure. Many multi-parent populations have been constructed in crop species, and their inbred germplasm and associated phenotypic and genotypic data serve as enduring resources. Their utility has grown from being a tool for mapping quantitative trait loci to a means of providing germplasm for breeding programmes. Genomics approaches, including de novo genome assemblies and gene annotations for the population founders, have allowed the imputation of rich sequence information into the descendent population, expanding the breadth of research and breeding applications of multi-parent populations. Here, we report recent successes from crop multi-parent populations in crops. We also propose an ideal genotypic, phenotypic and germplasm 'package' that multi-parent populations should feature to optimise their use as powerful community resources for crop research, development and breeding.


Asunto(s)
Productos Agrícolas , Genómica , Fitomejoramiento , Mapeo Cromosómico , Productos Agrícolas/genética , Genoma de Planta , Sitios de Carácter Cuantitativo
13.
Nanoscale ; 12(26): 14230-14236, 2020 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-32608440

RESUMEN

The characterisation of metallic nano-structures is of great importance as their optical properties are strongly dependent on their size and shape. Inaccurate size or shape characterisation can result in misleading measurements in applications such as bio-imaging and sensing. Characterisation techniques such as dynamic light scattering, electron microscopy or atomic force microscopy are commonly used; however, performing sub-surface measurements (inside semi-transparent objects) or in liquid media are very challenging. Here, we use time-resolved pump-probe spectroscopy to characterise the size and shape of metallic nano-structures in a water surrounding medium by using their vibrational modes. We show that this technique can achieve size measurements with a precision of 3 nm for the largest nano-structures which are in agreement with electron microscopy images. Furthermore, we demonstrate the ability to probe individual nano-structures despite being located in the same optical point spread function (PSF). Combining the high precision and sub-optical measurements provided by this technique with the ability to insert metallic nano-structures inside biological samples might open a way to perform 3D characterisation measurements.

14.
Nat Commun ; 11(1): 3267, 2020 Jun 29.
Artículo en Inglés | MEDLINE | ID: mdl-32601307

RESUMEN

Elastic waves guided along surfaces dominate applications in geophysics, ultrasonic inspection, mechanical vibration, and surface acoustic wave devices; precise manipulation of surface Rayleigh waves and their coupling with polarised body waves presents a challenge that offers to unlock the flexibility in wave transport required for efficient energy harvesting and vibration mitigation devices. We design elastic metasurfaces, consisting of a graded array of rod resonators attached to an elastic substrate that, together with critical insight from Umklapp scattering in phonon-electron systems, allow us to leverage the transfer of crystal momentum; we mode-convert Rayleigh surface waves into bulk waves that form tunable beams. Experiments, theory and simulation verify that these tailored Umklapp mechanisms play a key role in coupling surface Rayleigh waves to reversed bulk shear and compressional waves independently, thereby creating passive self-phased arrays allowing for tunable redirection and wave focusing within the bulk medium.

15.
Ultrasonics ; 108: 106171, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-32497903

RESUMEN

Throughout our engineered environment, many materials exhibit a crystalline lattice structure. The orientation of such lattices is crucial in determining functional properties of these structures, including elasticity and magnetism. Hence, tools for determining orientation are highly sought after. Surface acoustic wave velocities in multiple directions can not only highlight the microstructure contrast, but also determine the crystallographic orientation by comparison to a pre-calculated velocity model. This approach has been widely used for the recovery of orientation in cubic materials, with accurate results. However, there is a demand to probe the microstructure in anisotropic crystals - such as hexagonal close packed titanium. Uniquely, hexagonal structure materials exhibit transverse isotropic linear elasticity. In this work, both experimental and simulation results are used to study the discrete effects of both experimental parameters and varying lattice anisotropy across the orientation space, on orientation determination accuracy. Results summarise the theoretical and practical limits of hexagonal orientation determination by linear SAW measurements. Experimental results from a polycrystalline titanium specimen, obtained by electron back scatter diffraction and spatially resolved acoustic spectroscopy show good agreement (errors of ϕ1=5.14° and Φ=6.99°). Experimental errors are in accordance with those suggested by simulation, according to the experimental parameters. Further experimental results demonstrate dramatically improved orientation results (Φ error <1°). Demonstrating the possibility of achieving results near the theoretical limit by strict control of the experimental parameters.

16.
Photoacoustics ; 19: 100180, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32489857

RESUMEN

Understanding the mechanical properties of biological cells is a challenging problem for the life sciences partly because there are limited methods for mapping elasticity with high resolution. Phonon microscopy is a form of Brillouin light scattering which uses coherent phonons for imaging with elasticity-related contrast, phonon resolution and without labels. It can measure material properties such as sound velocity, acoustic impedance and attenuation. To use it as a contrast mechanism in microscopy, high numerical aperture (NA) lenses are key to high resolution. However, increasing NA induces apparent attenuation, a premature decay of the detected signal. To reduce signal decay and quantify the sound attenuation coefficient in cells, it is necessary to understand the mechanisms that affect signal decay. Here we define opto-acoustic defocus as a signal decay mechanism and propose methods to achieve quantitative sound attenuation measurements, and to optimise in-depth imaging at high resolution which is crucial for cell imaging.

17.
Opt Express ; 27(18): 25064-25071, 2019 Sep 02.
Artículo en Inglés | MEDLINE | ID: mdl-31510385

RESUMEN

This report introduces a novel time resolved Brillouin spectrometer, consisting of an opto-acoustic transducer which resides on the tip of a single-mode optical fiber of arbitrary length with 125 µm outer diameter and 5 µm sensing diameter. Demonstrated here are proof of concept spectroscopic measurements - shifts in Brillouin frequency - with sensitivities of 41±3MHz/%wt and 2.5±0.6 MHz/°C for changes in water-salinity and water-temperature, respectively, and an interpolated frequency resolution of 9±2 MHz. The technique benefits from low-cost raw materials, scalable fabrication, scalable pixel density, easy alignment, and data acquisition speeds down to 0.4 s: traits which make this compatible with in vivo applications.

18.
Obes Surg ; 29(12): 4036-4042, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31346983

RESUMEN

BACKGROUND: The combination of intragastric balloons (IGB) with comprehensive lifestyle and behavioral changes is critical for ongoing weight loss. Many community and rural practices do not have access to robust obesity resources, limiting the use of IGBs. Online aftercare programs were developed in response to this need, delivering lifestyle coaching to maximize effectiveness. How these programs compare to traditional follow-up is currently unknown. METHODS: Using propensity scoring (PS) methods, two large prospective databases of patients undergoing IGB therapy were compared to estimate the difference in percent total body weight loss (%TBWL) between groups while identifying predictors of response. RESULTS: Seven hundred fifty-eight unique patients across 78 different participating practices (online n = 437; clinical registry n = 321) was analyzed. The mean %TBWL at balloon removal was 11% ± 6.9 with an estimated treatment difference (ETD) between online and traditional follow-up of - 1.5% TBWL (95% CI - 3-0.4%; p = 0.125). Three months post-balloon removal, the combined %TBWL was 12.2% ± 8.3 with an ETD of only 1% TBWL (95%CI - 3-3%; p = 0.08). On multivariable linear regression, each incremental follow-up was associated with increased %TBWL (ß = 0.6% p = 0.002). CONCLUSION: Online IGB aftercare programs provide similar weight loss compared with traditional programs. Increased lifestyle coaching whether in person or remotely is associated with more %TBWL at removal and during follow-up. Close follow-up for clinical symptoms is still warranted.


Asunto(s)
Cuidados Posteriores , Balón Gástrico , Terapia Asistida por Computador , Estudios de Cohortes , Femenino , Conductas Relacionadas con la Salud , Humanos , Estilo de Vida , Masculino , Análisis por Apareamiento , Persona de Mediana Edad , Obesidad Mórbida/cirugía , Estados Unidos , Pérdida de Peso
19.
J Environ Manage ; 243: 88-94, 2019 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-31082755

RESUMEN

In recent years, visitation to U.S. National Parks has been increasing, with the majority of this increase occurring in a subset of parks. As a result, managers in these parks must respond quickly to increasing visitor-related challenges. Improved visitation forecasting would allow managers to more proactively plan for such increases. In this study, we leverage internet search data that is freely available through Google Trends to create a forecasting model. We compare this Google Trends model to a traditional autoregressive forecasting model. Overall, our Google Trends model accurately predicted 97% of the total visitation variation to all parks one year in advance from 2013 to 2017 and outperformed the autoregressive model by all metrics. While our Google Trends model performs better overall, this was not the case for each park unit individually; the accuracy of this model varied significantly from park to park. We hypothesized that park attributes related to trip planning would correlate with the accuracy of our Google Trends model, but none of the variables tested produced overly compelling results. Future research can continue exploring the utility of Google Trends to forecast visitor use in protected areas, or use methods demonstrated in this paper to explore alternative data sources to improve visitation forecasting in U.S. National Parks.


Asunto(s)
Parques Recreativos , Predicción
20.
Biomed Opt Express ; 10(5): 2399-2408, 2019 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-31143495

RESUMEN

The single cell eukaryotic protozoan Acanthamoeba castellanii exhibits a remarkable ability to switch from a vegetative trophozoite stage to a cystic form, in response to stressors. This phenotypic switch involves changes in gene expression and synthesis of the cell wall, which affects the ability of the organism to resist biocides and chemotherapeutic medicines. Given that encystation is a fundamental survival mechanism in the life cycle of A. castellanii, understanding of this process should have significant environmental and medical implications. In the present study, we investigated the mechanism of A. castellanii encystation using a novel phonon microscopy technique at the single cell level. Phonon microscopy is an emerging technique to image cells using laser-generated sub-optical wavelength phonons. This imaging modality can image with contrast underpinned by mechanical properties of cells at an optical or higher resolution. Our results show that the Brillouin frequency, a shift of the colour of light induced by phonons, evolves in three well defined frequency bands instead of a simple shift in frequency. These observations confirm previous results from literature and provide new insights into the capacity of A. castellanii cyst to react quickly in harsh environments.

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