RESUMEN

Imaging using scintillators is a widespread and cost-effective approach in radiography. While different types of scintillator and sensor configurations exist, it can be stated that the detection efficiency and resolution of a scintillator-based system strongly depend on the scintillator material and its thickness. Recently developed event-driven detectors are capable of registering spots of light emitted by the scintillator after a particle interaction, allowing to reconstruct the Center-of-Mass of the interaction within the scintillator. This results in a more precise location of the event and therefore provides a pathway to overcome the scintillator thickness limitation and increase the effective spatial resolution of the system. Utilizing this principle, we present a detector capable of Time-of-Flight imaging with an adjustable field-of-view, ad-hoc binning and re-binning of data based on the requirements of the experiment including the possibility of particle discrimination via the analysis of the event shape in space and time. It is considered that this novel concept might replace regular cameras in neutron imaging detectors as it provides superior detection capabilities with the most recent results providing an increase by a factor 3 in image resolution and an increase by up to a factor of 7.5 in signal-to-noise for thermal neutron imaging.

RESUMEN

Dinosaur nesting biology has been an intriguing research topic, though dinosaur behaviors were relatively less illuminated because of the constraints of the fossil record. For instance, hatching asynchrony, where eggs in a single clutch hatch at different times, is unique to modern neoavian birds but was also suggested to be present in oviraptorid dinosaurs based on a possible partial clutch of four embryo-containing eggs from Mongolia. Unfortunately, unequivocal evidence for the origination of these eggs from a single clutch is lacking. Here we report a new, better preserved partial oviraptorid clutch with three embryo-containing eggs-a single egg (Egg I) and a pair (Egg II/III)-from the Late Cretaceous Nanxiong Group of Jiangxi Province, China. Geopetal features indicate that the pair of eggs was laid prior to the single egg. Neutron tomographic images in combination with osteological features indicate that the embryo of the single egg is less developed than those of the paired eggs. Eggshell histology suggests that the embryo-induced erosion in the paired eggs is markedly more pronounced than in the single egg, providing a new line of evidence for hatching asynchrony. The inferred hatching asynchrony in combination with previously surmised thermoregulatory incubation and communal nesting behaviors very likely suggests that oviraptorid dinosaurs presented a unique reproductive biology lacking modern analogs, which is contrary to the predominant view that their reproductive biology was intermediate between that of modern crocodiles and birds.

A biologia de nidificação de dinossauros tem sido um tópico de pesquisa intrigante, embora o comportamentos do dinossauros tenham sido relativamente menos compreendidos devido às restrições do registro fóssil. Por exemplo, eclosão assincrônica, onde os ovos em uma única ninhada eclodem em momentos diferentes, é exclusiva em aves neoavianas modernas, tem-se sugerido estar presente em dinossauros oviraptorídeos com base em uma possível ninhada parcial de quatro ovos da Mongólia contendo embriões. Infelizmente, faltam evidências inequívocas para a origem desses ovos a partir de uma única embreagem. Relatamos aqui uma nova parcial ninhada oviraptoroide melhor preservada, com três ovos contendo embriões­um único ovo (ovo I) e um par (ovo II/III)­do Grupo de Nanxiong Cretáceo Final da Província de Jiangxi, China. A erosão induzida pelo embrião nos ovos emparelhados é significativamente maior que a do ovo único, fornecendo uma evidência inequívoca de eclosão assincrônica. A inferida de eclosão assincrônica, em combinação com as linhas de evidência anteriores, sugere que os dinossauros oviraptorídeos apresentavam uma biologia reprodutiva muito singular, sem análogos modernos, contrariando a visão predominante de que sua biologia reprodutiva era intermediária entre a dos crocodilos e pássaros modernos. Translated to Portuguese by Diego Vaz (dbistonvaz@vims.edu).

RESUMEN

When in situ techniques became available in recent years this led to a breakthrough in accurately determining diffusion coefficients for liquid alloys. Here we discuss how neutron radiography can be used to measure chemical diffusion in a ternary AlCuAg alloy. Neutron radiography hereby gives complementary information to x-ray radiography used for measuring chemical diffusion and to quasielastic neutron scattering used mainly for determining self-diffusion. A novel Al(2)O(3) based furnace that enables one to study diffusion processes by means of neutron radiography is discussed. A chemical diffusion coefficient of Ag against Al around the eutectic composition Al(68.6)Cu(13.8)Ag(17.6) at.% was obtained. It is demonstrated that the in situ technique of neutron radiography is a powerful means to study mass transport properties in situ in binary and ternary alloys that show poor x-ray contrast.

RESUMEN

Using conventional methods, three-dimensional imaging of the lung is challenging because of the low contrast between air and tissue and the large differences in dimensions between various pulmonary structures. The small distal airway structures and the high air-to-tissue ratio of lung tissue require an imaging technique which reliably discriminates between air and water. The objective of this study was to assess whether neutron computed tomography would satisfy such a requirement. This method utilizes the unique characteristic of neutrons of directly interacting with the atomic nucleus rather than being scattered by the atomic shell. Neutron computed tomography was tested in rats and allowed differentiation of larger lung structures (e.g., lobes) and distal airways. Airways could be identified reliably down to the sixth bronchial generation, in some cases even down to the tenth generation. The lung could be stabilized for sufficiently long exposure times to achieve an image resolution of 50-60 µm, which is the current physical resolution limit of the neutron computed tomography facility. Neutron computed tomography allowed excellent lung imaging without the need for additional tissue preparation or contrast media. The enhanced structural resolution obtained by applying this new research technique may improve understanding of lung physiology and respiratory therapy.

Asunto(s)

RESUMEN

At Agfa Medical Imaging Systems, a new type of image plate scanner is being developed. Instead of scanning the irradiated image plate with a single laser and reading the luminescence information with a single light collector and photomultiplier, the new system employs a whole line of laser diodes and a set of CCD line sensors. This technique allows for virtually unlimited detection areas and a very fast readout.

Asunto(s)

RESUMEN

One of the very interesting applications at Munich's New Neutron Source will be neutron tomography. It will be used both for research and industry. The D2O moderated high flux reactor will provide thermal neutrons for the structural analysis of specimen up to the size of 1 m. A central problem is the design of the beam geometry, especially the layout of the collimator and the aperture. Calculations were carried out in order to get an optimal beam geometry, taking into consideration an extended source, low beam divergency and high flux in the detector plane.

RESUMEN

For many neutron tomography setups, the maximum sample size for tomography is limited by a comparatively small beam cross section. However, it is not well known outside the medical field that it is possible to perform region-of-interest tomography of sections inside the object that fit into the beam and detector area. Approximately valid reconstruction data appear in a circle with a diameter of approximately the detector width, but with incomplete data and strong artifacts outside that circle. These artifacts can be removed either by mathematical means or by simple geometrical cutting of the reconstructed data, enabling the examination of samples bigger than the detector or beam area.

RESUMEN

The new reactor FRM-II of Technical University Munich will offer a professional radiography and tomography facility for industrial use. The concept of the instrument and the optimization under the conditions imposed by the surrounding instruments are described for the first installment and for a second stage in an external experimental hall in about 5 years. Several detector systems for different applications will be employed and a short description of their possibilities is given.

RESUMEN

The skin manifestations associated with boric acid intoxication are particularly striking. We present a case report of a 44-year-old black woman who, following a suicide attempt, demonstrated the classic features of acute boric acid poisoning. She developed generalized erythema creating a "boiled lobster" appearance with massive areas of desquamation. A discussion of the history of the use of boric acid by the medical profession follows the patient presentation.

Asunto(s)

Asunto(s)