1,453 research outputs found
Variable optical elements for fast focus control
In this Review, we survey recent developments in the emerging field of high-speed variable-z-focus optical elements, which are driving important innovations in advanced imaging and materials processing applications. Three-dimensional biomedical imaging, high-throughput industrial inspection, advanced spectroscopies, and other optical characterization and materials modification methods have made great strides forward in recent years due to precise and rapid axial control of light. Three state-of-the-art key optical technologies that enable fast z-focus modulation are reviewed, along with a discussion of the implications of the new developments in variable optical elements and their impact on technologically relevant applications
Flow Assessment Using Optical Coherence Microscopy Based Particle Image Velocimetry
Congenital heart diseases (CHDs) are the most common forms of congenital malformation in newborns. Among all types of CHDs, a large portion is contributed by malformation of endocardial cushion malformation during early heart development. Although the etiology of endocardial cushion malformation is unclear, it is a result of interactions between genetic and environmental factors has been confirmed. There is hypothesis indicating that malformation of endocardial cushion is caused by altered shear stress conditions where in cushion forming area the shear stress is supposed to be high compare with other area in congenital heart. However it is difficult to justify due to lack of in vivo imaging modality that is able to monitor structure and hemodynamic conditions simultaneously and over long time period. To address this problem, we present an optical coherence microscopy based particle image velocimetry system. This system is capable of invasively imaging biological sample structures at micrometer resolution and providing velocity information at the same time. With this imaging set up we successfully assessed velocity profile in a microfluidic system with simultaneous structure details demonstration of the microfluidic channel. Both flow measurement and structural information were verified using conventional microscopy. As a result, OCM-based PIV imaging modality not only makes it feasible to study in detail the process of congenital heart remodeling in response to environmental alterations, but also provides new options for measuring fluid flow in live tissue
Acousto-optic systems for advanced microscopy
Acoustic waves in an optical medium cause rapid periodic changes in the refraction index, leading to diffraction effects. Such acoustically controlled diffraction can be used to modulate, deflect, and focus light at microsecond timescales, paving the way for advanced optical microscopy designs that feature unprecedented spatiotemporal resolution. In this article, we review the operational principles, optical properties, and recent applications of acousto-optic (AO) systems for advanced microscopy, including random-access scanning, ultrafast confocal and multiphoton imaging, and fast inertia-free light-sheet microscopy. As AO technology is reaching maturity, designing new microscope architectures that utilize AO elements is more attractive than ever, providing new exciting opportunities in fields as impactful as optical metrology, neuroscience, embryogenesis, and high-content screening
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CA1-projecting subiculum neurons facilitate object-place learning.
Recent anatomical evidence suggests a functionally significant back-projection pathway from the subiculum to the CA1. Here we show that the afferent circuitry of CA1-projecting subicular neurons is biased by inputs from CA1 inhibitory neurons and the visual cortex, but lacks input from the entorhinal cortex. Efferents of the CA1-projecting subiculum neurons also target the perirhinal cortex, an area strongly implicated in object-place learning. We identify a critical role for CA1-projecting subicular neurons in object-location learning and memory, and show that this projection modulates place-specific activity of CA1 neurons and their responses to displaced objects. Together, these experiments reveal a novel pathway by which cortical inputs, particularly those from the visual cortex, reach the hippocampal output region CA1. Our findings also implicate this circuitry in the formation of complex spatial representations and learning of object-place associations
Data-driven microscopy: placing high-fidelity data in a population-wide context
Mikroskopi Àr idag ett fundamentalt verktyg inom forskning, dÀr det tillÄter oss att skÄda in och utforska vÄra prover i hög detalj. Mycket utav utvecklingen av nya mikroskopimetoder har strÀvat efter att öka den detaljnivÄ vi kan uppnÄ. Samtidigt har utvecklingen inom hÄrdvara, med tillgÄng till bÀttre och mer kraftfulla instrument, lett till utveckligen av metoder dÀr fokuset Àr att studera en hel population av celler. Till skillnad frÄn nÀr vi studerar ett fÄtal celler i hög detalj, tillÄter det oss att sÀtta perspektiv pÄ det vi ser. Det ger oss en förmÄga att sÀga vad det normala beteendet som man kan förvÀnta sig Àr, och vilka celler som sticker ut i en population. Med andra ord, vad som Àr intressant.Samtidigt finns det ett stort intresse av att veta hur varje individuell cell beter sig. Varje cell Àr, precis som oss mÀnniskor, unik. De har olika historia, olika Älder och befinner sig i olika tillstÄnd. Precis som vÄra celler i kroppen Àr unika, Àr Àven de cellerna som kan orsaka sjukdom unika. För att förstÄ varför vissa personer Àr mer kÀnsliga mot sjukdom, och hur en infektion svarar pÄ vÄra behandlingar behövs en förstÄelse och an förmÄga att studera celler pÄ individuell nivÄ, samtidigt som vi bibehÄller ett perspektiv utifrÄn populations-nivÄ.Denna brist pÄ perspektiv har lÀnge varit ett problem inom mikroskopi. Den vanliga lösningen pÄ detta problem Àr att vi, som mÀnniskor, kan tolka en bild och peka pÄ vad det Àr som Àr intressant eller inte. Vi Àr, trots allt, extremt duktiga pÄ att tolka visuell information. Men detta Àr inte en helt felfri lösning. Som mÀnniskor kan vi vara relativt okonsekventa, vi tolkar oftast utifrÄn hur vi vill att datan ser ut. Med andra ord, vi saknar förmÄgan att vara objektiva i vÄr metodik för att samla in bilder i hög detalj.Min avhandling har till stor del handlat om att utveckla ett verktyg som tillÄter oss att sÀtta perspektiv pÄ det vi studerar med mikroskopi. Detta har lett till Arbete 1, dÀr vi presenterar en allmÀn strategi (data-styrd mikroskopi) för hur vi kan arbeta med mikroskopi för att samla in data pÄ en hel population, samtidigt som vi kan samla in data med hög detalj pÄ relevanta fynd i populationen. Vi presenterar Àven hÀr en teknisk lösning, och utför metoden i tre olika scenarion: ett för att studera en population av celler mer allmÀnt, ett för att fÄnga det ögonblick som bakterier infekterar mÀnskliga celler, och ett dÀr vi studerar och fÄngar in data pÄ relevanta (frÄn ett populations-kontext) cancerceller och följer dem över tid. Denna metod tillÄter oss att samla in data i hög detalj pÄ ett objektivt sÀtt, och att sÀtta perspektiv pÄ det vi studerar.I Arbete 2 har vi vidare utvecklat pÄ vÄr metod, dÀr vi försöker lösa problemet att hitta en och samma cell i flera olika mikroskop. Eftersom vi, genom mikroskopi, jobbar pÄ en sÄ ofantligt liten skala, Àr det oftast vÀldigt svÄrt att orientera sig och hitta rÀtt inom ett prov. Det Àr lite som att spela PÄ spÄret och gissa vart man Àr, fast utan alla ledtrÄdar man fÄr pÄ varje nivÄ. Eftersom vi har tillgÄng till data pÄ en hel population, sÄ utgick vi frÄn att det borde finnas samband mellan celler och deras grannar i ett prov som Àr unika för just dem. Genom att anvÀnda sig av dessa unika samband kom vi fram med en lösning dÀr vi snabbt kan kalibrera ett prov pÄ ett nytt mikroskop. Det öppnar dörrarna för oss forskare att ÄteranvÀnda prov, att lÀttare justera provet med nya markörer (för det vi vill visualisera inom cellerna), och att kunna tolka ett prov med data insamlat frÄn flera system.COVID-19 pandemin var en stor omstÀllning för samhÀllet och vÄrden. LikvÀl var det en stor omstÀllning för mÄnga forskningslabb, dÀr en kapplöpning startade för att sÄ snabbt som möjligt förstÄ sig pÄ hur viruset fungerar och hur vÄrt immunförsvar svarar pÄ dess infektion. Det var i detta kontext som mitt tredje arbete utfördes. Genom den erfarenhet jag samlat pÄ mig inom mikroskopi och att analysera bilder pÄ stora dataset, bidrog jag med hjÀlp för att studera hur framtagna antikroppar kan förhindra bindningen av virus-lika partiklar till celler. Antikroppar Àr ett protein som immunförsvaret producerar i respons mot en patogen. En bÀttre förstÄelse kring hur antikroppar verkar, och vad skillnaden mellan en bra och en dÄlig antikropp Àr kan leda till framtagningen av bÀttre vaccin-program och behandlingar inom sjukvÄrden.I Arbete 4 medverkade jag i ett arbete dÀr bakterien Streptococcus pyogenes var i fokus. S. pyogenes enda vÀrd Àr mÀnniskor, och ansvarar för över 600 miljoner infektionsfall per Är globalt. PÄ bakteriens yta dominerar ett protein, M-proteinet, ett multi-funktionellt protein som bakterien (bland annat) anvÀnder sig för att binda till ytor och förhindra immunförsvarets förmÄga att göra sig av med bakterien. I arbetet upptÀckte vi att fibronektin binder till bakterien (specifikt M-proteinet) olika mycket beroende pÄ mÀngden antikroppar som finns i miljön. Fibronektin Àr ett protein som vi mÀnniskor producerar, och bidrar (bland annat) till att skapa den miljön som celler befinner sig i. MÀngden fibronektin varierar beroende pÄ var i kroppen man kollar. Till exempel, i saliv har du en relativt lÄg mÀngd fibronektin jÀmfört med i blodet. Detta ledde till hypotesen att bakterien Àr special-anpassad för olika miljöer i dess förmÄga att undkomma immunförsvaret. En bÀttre förstÄelse kring hur bakterien Àr anpassad till vÄra olika miljöer och dess infektionsförlopp kan leda till bÀttre och mer anpassade behandlingar inom sjukvÄrden
Temporal and Spatial Coherence: chronological and affective narrative within holographic and lenticular space.
The thesis for this practice-based study maintains that the Z and X axes of lenticular and holographic space can be used to store images chronologically, providing an audience with a new experience with affective and authentic impact. My contribution to knowledge has been to create a new element to the lenticular, analogue and digitally animated holographic artform. My research presents my familyâs archival material â photographs, film, text and objects â in a sequential order within the Z and X axes of holographic space, creating an animated four-dimensional (4-D) family album in which my ancestors recede into holographic space and members of the current generation float in front of the surface of the media. Audience experience of the artwork has been gathered and evaluated, providing evidence of the research studyâs contribution to knowledge.University of Southampto
Development of a Three-Dimensional Trap for Single-Molecule Studies with a Four-Focus Confocal Fluorescence Microscope
This dissertation presents the development of an instrument based on a confocal fluorescence microscope for feedback-driven trapping of a single molecule or nanoparticle in three-dimensions as it undergoes Brownian diffusion within an aqueous medium. Such trapping enables prolonged observation of a molecule while untethered and free from collisions with surfaces, which is needed to improve various studies, such as investigations of protein folding dynamics, molecular heterogeneities, and interactions. In the experiment, a dilute solution (~100 pM) of fluorescent nano-objects is inserted into a microfluidic device, which achieves trapping by control of electroosmotic flows in two crossed channels. The geometry, which is designed using COMSOL Multiphysics, funnels the flows to achieve sufficient electroosmotic speed to counteract Brownian diffusion while maintaining a 4:1 width-to-depth for wide-angle light collection by the microscope objective from the center of the crossing region. A fluorescence excitation volume centered at this point is defined by four overlapping focused laser beams, each with ~0.5 ÎŒm beam waist but with centers offset in a tetrahedral arrangement. The beams are derived from a mode-locked laser using a series of beam splitters with the pulses in each beam delayed to provide pulse-interleaved excitation at 304 MHz. Fluorescence is collected through a pinhole and split to two single-photon detectors, which provide signals for an FPGA (Field Programmable Gate Array) for time-gated counting into four channels synchronous with the pulses in each of the laser beams. The FPGA also bins the counts and applies an algorithm to estimate the direction of the position offset of the nano-object and to adjust four voltages. These are applied at the four fluid inlets of the microfluidic cross-channel to electroosmotically drive the fluid to keep the nano-object at the midpoint of the four foci. Movies of camera imaging of trapped nano-objects were acquired. Results show trapping of 40 nm FluoSpheres for ~4 minutes, 20 nm FluoSpheres for ~25 seconds, and 5 nm protein molecules of Streptavidin-Alexa Fluorâą 647 for ~1.5 seconds. In addition, Maximum Likelihood Estimation of positions from binned photons was conducted for the FluoSphere experiments to estimate effective spring constants of the trap
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Development and applications of high speed and hyperspectral nonlinear microscopy
Nonlinear microscopy refers to a range of laser scanning microscopy techniques that are based on nonlinear optical processes such as two-photon excited fluorescence and second harmonic generation. Nonlinear microscopy techniques are powerful because they enable the visualization of highly scattering biological samples with subcellular resolution. This capability is especially valuable for in vivo and live tissue imaging since it can provide both structural and functional information about tissues in their native environment. With the use of a range of exogenous dyes and intrinsic contrast, in vivo nonlinear microscopy can be used to characterize and measure dynamic processes of tissues in their normal environment. These advances have been particularly relevant in neuroscience, where truly understanding the function of the brain requires that its neural and vascular networks be observed while undisturbed. Despite these advantages, in vivo nonlinear microscopy still faces several major challenges.
First, observing dynamics that occur in large areas over short time scales, such as neuronal signaling and blood flow, is challenging because nonlinear microscopy generally requires scanning to create an image. This limits the study of dynamic behavior to either a single plane or to a small subset of regions within a volume. Second, applications that rely on the use of exogenous dyes can be limited by the need to stain tissues before imaging, the availability of dyes, and specificity that can be achieved.
Usually considered a nuisance, endogenous tissue contrast from autofluorescence or structures exhibiting second harmonic generation can produce stunning images for visualizing subcellular morphology. Imaging endogenous contrast can also provide valuable information about the chemical makeup and metabolic state of the tissue. Few methods have been developed to carefully and quantitatively examine endogenous fluorescence in living tissues. In this thesis, these two challenges in nonlinear microscopy are addressed. The development of a novel hyperspectral two-photon microscopy method to acquire spectroscopic data from tissues and increase the information available from endogenous contrast is presented. This system was applied to visualize and identify sources of endogenous contrast in gastrointestinal tissues, providing robust references for the assessment of normal and diseased tissues.
Secondly, three methods for high speed volumetric imaging using laser scanning nonlinear microscopy were developed to address the need for improved high-speed imaging in living tissues. A spectrally-encoded high-speed imaging method that can provide simultaneous imaging of multiple regions of the living brain in parallel is presented and used to study spontaneous changes in vascular tone in the brain. This technique is then extended for use with second harmonic generation microscopy, which has the potential to greatly increase the degree of multiplexing. Finally, a complete system design capable of volumetric scan rates >1Hz is shown, offering improved performance and versatility to image brain activity
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