Practical use of digital cameras for microphotography through the operating microscope

A practical use of personal digital cameras for taking digital photographs in the microsurgical field through an operating microscope is described. This inexpensive and practical method for acquiring microscopic images at the desired magnification combines the advantages of the digital camera and the operating microscope.

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Aims. Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P’s nucleus. Methods. Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results. Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P1 = 12.76129 ± 0.00005 h and P2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates λ = 65° ± 15°, β = + 59° ± 15°, corresponding to equatorial coordinates RA = 22°, Dec = + 76°. However, we find that the mirror solution, also prograde, at λ = 275° ± 15°, β = + 50° ± 15° (or RA = 274°, Dec = + 27°), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane.

Synchronization of two independently moving cameras without feature correspondences

In this work, a method that synchronizes two video sequences is proposed. Unlike previous methods, which require the existence of correspondences between features tracked in the two sequences, and/or that the cameras are static or jointly moving, the proposed approach does not impose any of these constraints. It works when the cameras move independently, even if different features are tracked in the two sequences. The assumptions underlying the proposed strategy are that the intrinsic parameters of the cameras are known and that two rigid objects, with independent motions on the scene, are visible in both sequences. The relative motion between these objects is used as clue for the synchronization. The extrinsic parameters of the cameras are assumed to be unknown. A new synchronization algorithm for static or jointly moving cameras that see (possibly) different parts of a common rigidly moving object is also proposed. Proof-of-concept experiments that illustrate the performance of these methods are presented, as well as a comparison with a state-of-the-art approach.

Cloud observations in Switzerland using hemispherical sky cameras

We present observations of total cloud cover and cloud type classification results from a sky camera network comprising four stations in Switzerland. In a comprehensive intercomparison study, records of total cloud cover from the sky camera, long-wave radiation observations, Meteosat, ceilometer, and visual observations were compared. Total cloud cover from the sky camera was in 65–85% of cases within ±1 okta with respect to the other methods. The sky camera overestimates cloudiness with respect to the other automatic techniques on average by up to 1.1 ± 2.8 oktas but underestimates it by 0.8 ± 1.9 oktas compared to the human observer. However, the bias depends on the cloudiness and therefore needs to be considered when records from various observational techniques are being homogenized. Cloud type classification was conducted using the k-Nearest Neighbor classifier in combination with a set of color and textural features. In addition, a radiative feature was introduced which improved the discrimination by up to 10%. The performance of the algorithm mainly depends on the atmospheric conditions, site-specific characteristics, the randomness of the selected images, and possible visual misclassifications: The mean success rate was 80–90% when the image only contained a single cloud class but dropped to 50–70% if the test images were completely randomly selected and multiple cloud classes occurred in the images.

CHARACTERIZATION OF THE COUNT RATE PERFORMANCE AND EVALUATION OF THE EFFECTS OF HIGH COUNT RATES ON MODERN GAMMA CAMERAS

CHARACTERIZATION OF THE COUNT RATE PERFORMANCE AND EVALUATION OF THE EFFECTS OF HIGH COUNT RATES ON MODERN GAMMA CAMERAS Michael Stephen Silosky, B.S. Supervisory Professor: S. Cheenu Kappadath, Ph.D. Evaluation of count rate performance (CRP) is an integral component of gamma camera quality assurance and measurement of system dead time (τ) is important for quantitative SPECT. The CRP of three modern gamma cameras was characterized using established methods (Decay and Dual Source) under a variety of experimental conditions. For the Decay method, input count rate was plotted against observed count rate and fit to the paralyzable detector model (PDM) to estimate τ (Rates method). A novel expression for observed counts as a function of measurement time interval was derived and the observed counts were fit to this expression to estimate τ (Counts method). Correlation and Bland-Altman analysis were performed to assess agreement in estimates of τ between methods. The dependencies of τ on energy window definition and incident energy spectrum were characterized. The Dual Source method was also used to estimate τ and its agreement with the Decay method under identical conditions and the effects of total activity and the ratio of source activities were investigated. Additionally, the effects of count rate on several performance metrics were evaluated. The CRP curves for each system agreed with the PDM at low count rates but deviated substantially at high count rates. Estimates of τ for the paralyzable portion of the CRP curves using the Rates and Counts methods were highly correlated (r=0.999) but with a small (~6%) difference. No significant difference was observed between the highly correlated estimates of τ using the Decay or Dual Source methods under identical experimental conditions (r=0.996). Estimates of τ increased as a power-law function with decreasing ratio of counts in the photopeak to the total counts and linearly with decreasing spectral effective energy. Dual Source method estimates of τ varied as a quadratic with the ratio of the single source to combined source activities and linearly with total activity used across a large range. Image uniformity, spatial resolution, and energy resolution degraded linearly with count rate and image distorting effects were observed. Guidelines for CRP testing and a possible method for the correction of count rate losses for clinical images have been proposed.

Under ice shelf photographs from Drescher Inlet (Riiser Larsen Ice Shelf) taken by seal mounted cameras during expedition DRE2003

While modern sampling techniques, such as autonomous underwater vehicles, are increasing our knowledge of the fauna beneath Antarctic sea ice of only a few meters in depth, greater sampling difficulties mean that little is known about the marine life underneath Antarctic ice shelves over 100 m thick. In this study, we present underwater images showing the underside of an Antarctic ice shelf covered by aggregated invertebrate communities, most likely cnidarians and isopods. These images, taken at an average depth of 145 m, were obtained with a digital still camera system attached to Weddell seals Leptonychotes weddellii foraging just beneath the ice shelf. Our observations indicate that, similar to the sea floor, ice shelves serve as an important habitat for a remarkable amount of marine invertebrate fauna in Antarctica.

"Si llega a ocurrir de vuelta los vecinos los matamos" : Anotaciones sobre entrevistas a vecinas de un ex CCD. Responsabilidad, justicia y/o derecho

Los últimos diez años han visto reaparecer la pregunta en torno al comportamiento de la sociedad civil durante la última dictadura. Esta pregunta, heterogénea en su interior -los comportamientos eclesiásticos, empresariales, partidarios, sindicales y, finalmente, del hombre común y corriente-, no es sin embargo una novedad en el campo argentino de los derechos humanos y la memoria: en la misma dictadura algunas voces preguntaron por ella (Rokkind, 2004:238). Este trabajo, enmarcado en nuestra tesis doctoral en curso sobre responsabilidad colectiva y pequeñas resistencias para con la última dictadura a partir de memorias de vecinos de CCD en sus representaciones literarias y cinematográficas en articulación con una etnografía sobre las vecindades de un ex CCD en particular, intentará volver sobre esta pregunta de dos modos distintos pero articulados. Por un lado, repasando dos trabajos clásicos sobre derecho transicional y responsabilidad de dos autores de destacada participación en el Juicio a las Juntas (Nino, 1997; MalamudGoti, 2000). Por el otro, rastreando el modo en que aquellas responsabilidades y justicias aparecen en dos entrevistas realizadas a vecinas de un ex CCD en particular, la Seccional 1o de Santa Rosa-La Pampa, durante nuestro trabajo de campo. En esta dirección intentará orientarse este trabajo

"Si llega a ocurrir de vuelta los vecinos los matamos" : Anotaciones sobre entrevistas a vecinas de un ex CCD. Responsabilidad, justicia y/o derecho

Los últimos diez años han visto reaparecer la pregunta en torno al comportamiento de la sociedad civil durante la última dictadura. Esta pregunta, heterogénea en su interior -los comportamientos eclesiásticos, empresariales, partidarios, sindicales y, finalmente, del hombre común y corriente-, no es sin embargo una novedad en el campo argentino de los derechos humanos y la memoria: en la misma dictadura algunas voces preguntaron por ella (Rokkind, 2004:238). Este trabajo, enmarcado en nuestra tesis doctoral en curso sobre responsabilidad colectiva y pequeñas resistencias para con la última dictadura a partir de memorias de vecinos de CCD en sus representaciones literarias y cinematográficas en articulación con una etnografía sobre las vecindades de un ex CCD en particular, intentará volver sobre esta pregunta de dos modos distintos pero articulados. Por un lado, repasando dos trabajos clásicos sobre derecho transicional y responsabilidad de dos autores de destacada participación en el Juicio a las Juntas (Nino, 1997; MalamudGoti, 2000). Por el otro, rastreando el modo en que aquellas responsabilidades y justicias aparecen en dos entrevistas realizadas a vecinas de un ex CCD en particular, la Seccional 1o de Santa Rosa-La Pampa, durante nuestro trabajo de campo. En esta dirección intentará orientarse este trabajo

"Si llega a ocurrir de vuelta los vecinos los matamos" : Anotaciones sobre entrevistas a vecinas de un ex CCD. Responsabilidad, justicia y/o derecho

Los últimos diez años han visto reaparecer la pregunta en torno al comportamiento de la sociedad civil durante la última dictadura. Esta pregunta, heterogénea en su interior -los comportamientos eclesiásticos, empresariales, partidarios, sindicales y, finalmente, del hombre común y corriente-, no es sin embargo una novedad en el campo argentino de los derechos humanos y la memoria: en la misma dictadura algunas voces preguntaron por ella (Rokkind, 2004:238). Este trabajo, enmarcado en nuestra tesis doctoral en curso sobre responsabilidad colectiva y pequeñas resistencias para con la última dictadura a partir de memorias de vecinos de CCD en sus representaciones literarias y cinematográficas en articulación con una etnografía sobre las vecindades de un ex CCD en particular, intentará volver sobre esta pregunta de dos modos distintos pero articulados. Por un lado, repasando dos trabajos clásicos sobre derecho transicional y responsabilidad de dos autores de destacada participación en el Juicio a las Juntas (Nino, 1997; MalamudGoti, 2000). Por el otro, rastreando el modo en que aquellas responsabilidades y justicias aparecen en dos entrevistas realizadas a vecinas de un ex CCD en particular, la Seccional 1o de Santa Rosa-La Pampa, durante nuestro trabajo de campo. En esta dirección intentará orientarse este trabajo

"Si llega a ocurrir de vuelta los vecinos los matamos" : Anotaciones sobre entrevistas a vecinas de un ex CCD. Responsabilidad, justicia y/o derecho

Los últimos diez años han visto reaparecer la pregunta en torno al comportamiento de la sociedad civil durante la última dictadura. Esta pregunta, heterogénea en su interior -los comportamientos eclesiásticos, empresariales, partidarios, sindicales y, finalmente, del hombre común y corriente-, no es sin embargo una novedad en el campo argentino de los derechos humanos y la memoria: en la misma dictadura algunas voces preguntaron por ella (Rokkind, 2004:238). Este trabajo, enmarcado en nuestra tesis doctoral en curso sobre responsabilidad colectiva y pequeñas resistencias para con la última dictadura a partir de memorias de vecinos de CCD en sus representaciones literarias y cinematográficas en articulación con una etnografía sobre las vecindades de un ex CCD en particular, intentará volver sobre esta pregunta de dos modos distintos pero articulados. Por un lado, repasando dos trabajos clásicos sobre derecho transicional y responsabilidad de dos autores de destacada participación en el Juicio a las Juntas (Nino, 1997; MalamudGoti, 2000). Por el otro, rastreando el modo en que aquellas responsabilidades y justicias aparecen en dos entrevistas realizadas a vecinas de un ex CCD en particular, la Seccional 1o de Santa Rosa-La Pampa, durante nuestro trabajo de campo. En esta dirección intentará orientarse este trabajo