Single-fluorophore orientation determination with multiview polarized illumination : modeling and microscope design

Author Posting. © Optical Society of America, 2017. This article is posted here by permission of Optical Society of America for personal use, not for redistribution. The definitive version was published in Optics Express 25 (2017): 31309-31325, doi:10.1364/OE.25.031309.We investigate the use of polarized illumination in multiview microscopes for determining the orientation of single-molecule fluorescence transition dipoles. First, we relate the orientation of single dipoles to measurable intensities in multiview microscopes and develop an information-theoretic metric—the solid-angle uncertainty—to compare the ability of multiview microscopes to estimate the orientation of single dipoles. Next, we compare a broad class of microscopes using this metric—single- and dual-view microscopes with varying illumination polarization, illumination numerical aperture (NA), detection NA, obliquity, asymmetry, and exposure. We find that multi-view microscopes can measure all dipole orientations, while the orientations measurable with single-view microscopes is halved because of symmetries in the detection process. We also find that choosing a small illumination NA and a large detection NA are good design choices, that multiview microscopes can benefit from oblique illumination and detection, and that asymmetric NA microscopes can benefit from exposure asymmetry.National Institute of Health (NIH) (R01GM114274, R01EB017293)

Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory

Context. Debris discs are thought to be formed through the collisional grinding of planetesimals, and can be considered as the outcome of planet formation. Understanding the properties of gas and dust in debris discs can help us to comprehend the architecture of extrasolar planetary systems. Herschel Space Observatory far-infrared (IR) photometry and spectroscopy have provided a valuable dataset for the study of debris discs gas and dust composition. This paper is part of a series of papers devoted to the study of Herschel PACS observations of young stellar associations. Aims. This work aims at studying the properties of discs in the Beta Pictoris Moving Group (BPMG) through far-IR PACS observations of dust and gas. Methods. We obtained Herschel-PACS far-IR photometric observations at 70, 100 and 160 microns of 19 BPMG members, together with spectroscopic observations of four of them. Spectroscopic observations were centred at 63.18 microns and 157 microns, aiming to detect [OI] and [CII] emission. We incorporated the new far-IR observations in the SED of BPMG members and fitted modified blackbody models to better characterise the dust content. Results. We have detected far-IR excess emission toward nine BPMG members, including the first detection of an IR excess toward HD 29391.The star HD 172555, shows [OI] emission, while HD 181296, shows [CII] emission, expanding the short list of debris discs with a gas detection. No debris disc in BPMG is detected in both [OI] and [CII]. The discs show dust temperatures in the range 55 to 264 K, with low dust masses (6.6*10^{-5} MEarth to 0.2 MEarth) and radii from blackbody models in the range 3 to 82 AU. All the objects with a gas detection are early spectral type stars with a hot dust component.Comment: 12 pages, 7 figures, 6 table

Exocomet signatures around the A-shell star Φ\Phi Leo?

We present an intensive monitoring of high-resolution spectra of the Ca {\sc ii} K line in the A7IV shell star $\Phi$ Leo at very short (minutes, hours), short (night to night), and medium (weeks, months) timescales. The spectra show remarkable variable absorptions on timescales of hours, days, and months. The characteristics of these sporadic events are very similar to most that are observed toward the debris disk host star $\beta$ Pic, which are commonly interpreted as signs of the evaporation of solid, comet-like bodies grazing or falling onto the star. Therefore, our results suggest the presence of solid bodies around $\Phi$ Leo. To our knowledge, with the exception of $\beta$ Pic, our monitoring has the best time resolution at the mentioned timescales for a star with events attributed to exocomets. Assuming the cometary scenario and considering the timescales of our monitoring, our results indicate that $\Phi$ Leo presents the richest environment with comet-like events known to date, second only to $\beta$ Pic.Comment: A&A letters, proof-correcte

Beyond "the Relationship between the Individual and Society": broadening and deepening relational thinking in group analysis

The question of ‘the relationship between the individual and society’ has troubled group analysis since its inception. This paper offers a reading of Foulkes that highlights the emergent, yet evanescent, psychosocial ontology in his writings, and argues for the development of a truly psychosocial group analysis, which moves beyond the individual/society dualism. It argues for a shift towards a language of relationality, and proposes new theoretical resources for such a move from relational sociology, relational psychoanalysis and the ‘matrixial thinking’ of Bracha Ettinger which would broaden and deepen group analytic understandings of relationality

DZ Cha: a bona fide photoevaporating disc

DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright protoplanetary disc with evidence of inner disc clearing. Its narrow \Ha line and infrared spectral energy distribution suggest that DZ Cha may be a photoevaporating disc. We aim to analyse the DZ Cha star + disc system to identify the mechanism driving the evolution of this object. We have analysed three epochs of high resolution optical spectroscopy, photometry from the UV up to the sub-mm regime, infrared spectroscopy, and J-band imaging polarimetry observations of DZ Cha. Combining our analysis with previous studies we find no signatures of accretion in the \Ha line profile in nine epochs covering a time baseline of $\sim20$ years. The optical spectra are dominated by chromospheric emission lines, but they also show emission from the forbidden lines [SII] 4068 and [OI] 6300$\,\AA$ that indicate a disc outflow. The polarized images reveal a dust depleted cavity of $\sim7$ au in radius and two spiral-like features, and we derive a disc dust mass limit of M_\mathrm{dust} 80 \MJup) companions are detected down to 0\farcs07 ($\sim 8$ au, projected). The negligible accretion rate, small cavity, and forbidden line emission strongly suggests that DZ Cha is currently at the initial stages of disc clearing by photoevaporation. At this point the inner disc has drained and the inner wall of the truncated outer disc is directly exposed to the stellar radiation. We argue that other mechanisms like planet formation or binarity cannot explain the observed properties of DZ Cha. The scarcity of objects like this one is in line with the dispersal timescale ($\lesssim 10^5$ yr) predicted by this theory. DZ Cha is therefore an ideal target to study the initial stages of photoevaporation.Comment: A&A in press, language corrections include

Polar Smectic Films

We report on a new experimental procedure for forming and studying polar smectic liquid crystal films. A free standing smectic film is put in contact with a liquid drop, so that the film has one liquid crystal/liquid interface and one liquid crystal/air interface. This polar environment results in changes in the textures observed in the film, including a boojum texture and a previously unobserved spiral texture in which the winding direction of the spiral reverses at a finite radius from its center. Some aspects of these textures are explained by the presence of a Ksb term in the bulk elastic free energy density that favors a combination of splay and bend deformations.Comment: 4 pages, REVTeX, 3 figures, submitted to PR

Dissection of Molecular Assembly Dynamics by Tracking Orientation and Position of Single Molecules in Live Cells

Regulation of order, such as orientation and conformation, drives the function of most molecular assemblies in living cells but remains difficult to measure accurately through space and time. We built an instantaneous fluorescence polarization microscope, which simultaneously images position and orientation of fluorophores in living cells with single-molecule sensitivity and a time resolution of 100 ms. We developed image acquisition and analysis methods to track single particles that interact with higher-order assemblies of molecules. We tracked the fluctuations in position and orientation of molecules from the level of an ensemble of fluorophores down to single fluorophores. We tested our system in vitro using fluorescently labeled DNA and F-actin, in which the ensemble orientation of polarized fluorescence is known. We then tracked the orientation of sparsely labeled F-actin network at the leading edge of migrating human keratinocytes, revealing the anisotropic distribution of actin filaments relative to the local retrograde flow of the F-actin network. Additionally, we analyzed the position and orientation of septin-GFP molecules incorporated in septin bundles in growing hyphae of a filamentous fungus. Our data indicate that septin-GFP molecules undergo positional fluctuations within ∼350 nm of the binding site and angular fluctuations within ∼30° of the central orientation of the bundle. By reporting position and orientation of molecules while they form dynamic higher-order structures, our approach can provide insights into how micrometer-scale ordered assemblies emerge from nanoscale molecules in living cells

Anomalous diffusion in polymers: long-time behaviour

We study the Dirichlet boundary value problem for viscoelastic diffusion in polymers. We show that its weak solutions generate a dissipative semiflow. We construct the minimal trajectory attractor and the global attractor for this problem.Comment: 13 page

Analyse des délais de prise en charge des cancers thoraciques : étude prospective

RésuméIntroductionLe cancer broncho-pulmonaire est la première cause de décès par cancer en France. Son diagnostic est le plus souvent tardif, alors que le délai entre le début des symptômes et la prise en charge est considéré comme un facteur aggravant.Matériel et méthodesNotre étude prospective a recueilli les différentes dates de prise en charge de 139 patients consécutifs bénéficiant d’un traitement primaire pour un cancer thoracique dans notre hôpital entre novembre 2008 et mai 2009. L’objectif de cette étude était d’évaluer différents délais de prise en charge des patients porteurs d’un cancer thoracique quelle que soit sa prise en charge thérapeutique (médicale ou chirurgicale) et de déterminer la cause de ces délais.RésultatsLe délai médian entre la première imagerie pathologique et le traitement est de 9,6 semaines. Les délais étaient significativement plus courts dans les stades tardifs et les carcinomes à petites cellules (p=0,001). Il existait une tendance à des délais plus courts pour les femmes et des délais plus longs pour les classes d’âge les plus élevées.ConclusionL’évaluation des délais de prise en charge, en particulier pour les stades précoces, s’intègre dans le contrôle de la qualité de prise en charge de ces pathologies.SummaryIntroductionLung cancer is the main cause of cancer death in France. The diagnosis is often late and the delay between the onset of symptoms and management is considered an aggravating factor.Material and methodsOur prospective study collected the dates of the start of management of 139 consecutive patients receiving first line treatment for thoracic cancer in our hospital between November 2008 and May 2009. The aim of this study was to evaluate the delays in medical or surgical treatments in patients with thoracic cancer and to determine the cause of these delays.ResultsThe median delay between the first abnormal chest X-ray and treatment was 9.6 weeks. The delays were significantly shorter in the late stages and in small cell cancer (P=0.001). There was a tendency for shorter delays in women and for longer delays in older patients.ConclusionEvaluation of the delays in treatment, particularly in the early stages, is part of the quality control of management of these diseases

Radio emission of extensive air shower at CODALEMA: Polarization of the radio emission along the v*B vector

Cosmic rays extensive air showers (EAS) are associated with transient radio emission, which could provide an efficient new detection method of high energy cosmic rays, combining a calorimetric measurement with a high duty cycle. The CODALEMA experiment, installed at the Radio Observatory in Nancay, France, is investigating this phenomenon in the 10^17 eV region. One challenging point is the understanding of the radio emission mechanism. A first observation indicating a linear relation between the electric field produced and the cross product of the shower axis with the geomagnetic field direction has been presented (B. Revenu, this conference). We will present here other strong evidences for this linear relationship, and some hints on its physical origin.Comment: Contribution to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009. 4 pages, 8 figures. v2: Typo fixed, arxiv references adde