1,720,985 research outputs found
Quantum Dot Blueing and Blinking Enables Fluorescence Nanoscopy
No full textWe demonstrate superresolution fluorescence imaging of cells using bioconjugated CdSe/ZnS quantum dot markers. Fluorescence blueing of quantum dot cores facilitates separation of blinking markers residing closer than the diffraction barrier. The high number of successively emitted photons enables ground state depletion microscopy followed by individual marker return with a resolving power of the size of a single dot (similar to 12 nm). Nanoscale imaging is feasible with a simple webcam
STED nanoscopy with mass-produced laser diodes.
No full textWe show that far-field fluorescence nanoscopy by stimulated emission depletion (STED) can be realized with compact off-the-shelf laser diodes, such as those used in laser pointers and DVDs. A spatial resolution of 40-50 nm is attained by pulsing a 660 nm DVD-diode. The efficacy of these low-cost STED microscopes in biological imaging is demonstrated by differentiating between clusters of the synaptic protein bassoon and transport vesicles in hippocampal neurons, based on the feature diameter. Our results facilitate the implementation of this all-molecular-transition based superresolution method in many applications ranging from nanoscale fluorescence imaging to nanoscale fluorescence sensing
2,2 '-thiodiethanol: A new water soluble mounting medium for high resolution optical microscopy
No full textThe use of high numerical aperture immersion lenses in optical microscopy is compromised by spherical aberrations induced by the refractive index mismatch between the immersion system and the embedding medium of the sample. Especially when imaging >10 mu m deep into the specimen, the refractive index mismatch results in a noticeable loss of image brightness and resolution. A solution to this problem is to adapt the index of the embedding medium to that of the immersion system. Unfortunately, not many mounting media are known that are both index tunable as well as compatible with fluorescence imaging. Here we introduce a nontoxic embedding medium, 2,2'-thiodiethanol (TDE), which, by being miscible with water at any ratio, allows fine adjustment of the average refractive index of the sample ranging from that of water (1.33) to that of immersion oil (1.52). TDE thus enables high resolution imaging deep inside fixed specimens with objective lenses of the highest available aperture angles and has the potential to render glycerol embedding redundant. The refractive index changes due to larger cellular structures, such as nuclei, are largely compensated. Additionally, as an antioxidant, TDE preserves the fluorescence quantum yield of most of the fluorophores. We present the optical and chemical properties of this new medium as well as its application to a variety of differently stained cells and cellular substructures
4Pi microscopy with negligible sidelobes.
No full textThe coherent addition of the wavefronts of two opposing highangle lenses provides an axial (z) resolution improvement by 5 - 7-fold in farfield fluorescence microscopy. However, all microscopy concepts based on this principle have so far required mathematical deconvolution of the acquired data. This stems from the fact that the decrease of the axial width of the effective point spread function (EPSF) is accompanied by a substantial elevation of the side maxima of the EPSF along the optical axis. Here, we realize an EPSF with negligible lobes and gain axially superresolved images just through the physical phenomena involved. The constructive interference of the added wavefronts can be controlled through the image brightness which greatly simplifies the operation of the system
Fluoreszenznanoskopie einzelner DNA-Moleküle mit Fluoreszenzverhinderung durch stimulierte Emission (STED)
No full textScharfe Aufnahmen: STED-Nanoskopie (STED=stimulierte Fluoreszenzverhinderung) von einzelnen DNA-Strängen visualisiert Strukturen mit einer 5- bis 6fach höheren Auflösung als konfokale Mikroskopie (Konf), wie aus dem linken bzw. rechten Bild ersichtlich ist. Die STED-Technik enthüllt Strukturen der Größenordnung der DNA-Persistenzlänge (ca. 50 nm), ohne dabei in maßgeblicher Weise Photoschäden wie Bleichen oder DNA-Bruch zu verursachen
Molecular Orientation Affects Localization Accuracy in Superresolution Far-Field Fluorescence Microscopy
No full textWe investigate the cooperative effect of molecular tilt and defocus on fluorophore localization by centroid calculation in far-held superresolution microscopy based on stochastic single molecule switching, If tilt angle and defocus are unknown, the localization contains systematic errors up to about +/-125 nm. When imaging rotation-impaired fluorophores of unknown random orientation, the average localization accuracy in three-dimensional samples is typically limited to about +/-32 nm, restricting the attainable resolution accordingly
Direct light-driven modulation of luminescence from Mn-doped ZnSe quantum dots.
No full textUnlimited possibilities: Light-driven modulation of the fluorescence from Mn-doped ZnSe quantum nanocrystals has been established through excited-state absorption and its direct competition with spontaneous emission. Such optical control over electronic transitions enables far-field fluorescence microscopy analysis with diffraction-unlimited resolution (45 nm, red) based on quantum dots (confocal imaging has a resolution of 200 nm, blue)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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