Shape-from-focus for real-time terahertz 3D imaging.

Thanks to significant advances in real-time terahertz imaging in terms of resolution and image quality, adapting and extending optical methods for 3D imaging at the millimeter scale is now promising. The shape-from-focus algorithm is a post-processing tool used in optical microscopy to reconstruct the external shape surface of a convex surface object. Images acquired at different distances from the object-side focal plane are implemented in this algorithm. We localize the best focus position in the stack of images for each pixel and then reconstruct the object in 3D due to the short depth of field. In this Letter, we propose an application of this algorithm in active and real-time terahertz imaging. We achieve the experimental reconstruction in 3D with a terahertz waves imaging system composed of a powerful source and a real-time terahertz camera.

Liquid index matching for 2D and 3D terahertz imaging.

Two-dimensional (2D) terahertz imaging and 3D visualization suffer from severe artifacts since an important part of the terahertz beam is reflected, diffracted, and refracted at each interface. These phenomena are due to refractive index mismatch and reflection in the case of non-orthogonal incidence. This paper proposes an experimental procedure that reduces these deleterious optical refraction effects for a cylinder and a prism made with polyethylene material. We inserted these samples in a low absorption liquid medium to match the sample index. We then replaced the surrounding air with a liquid with an optimized refractive index, with respect to the samples being studied. Using this approach we could more accurately recover the original sample shape by time-of-flight tomography.

Terahertz imaging and tomography as efficient instruments for testing polymer additive manufacturing objects.

Additive manufacturing (AM) technology is not only used to make 3D objects but also for rapid prototyping. In industry and laboratories, quality controls for these objects are necessary though difficult to implement compared to classical methods of fabrication because the layer-by-layer printing allows for very complex object manufacturing that is unachievable with standard tools. Furthermore, AM can induce unknown or unexpected defects. Consequently, we demonstrate terahertz (THz) imaging as an innovative method for 2D inspection of polymer materials. Moreover, THz tomography may be considered as an alternative to x-ray tomography and cheaper 3D imaging for routine control. This paper proposes an experimental study of 3D polymer objects obtained by additive manufacturing techniques. This approach allows us to characterize defects and to control dimensions by volumetric measurements on 3D data reconstructed by tomography.

Ordered subsets convex algorithm for 3D terahertz transmission tomography.

We investigate in this paper a new reconstruction method in order to perform 3D Terahertz (THz) tomography using a continuous wave acquisition setup in transmission mode. This method is based on the Maximum Likelihood for TRansmission tomography (ML-TR) first developed for X-ray imaging. We optimize the Ordered Subsets Convex (OSC) implementation of the ML-TR by including the Gaussian propagation model of THz waves and take into account the intensity distributions of both blank calibration scan and dark-field measured on THz detectors. THz ML-TR reconstruction quality and accuracy are discussed and compared to other tomographic reconstructions.

Integration and application of the Rainfall Runoff Library.

The Rainfall Runoff Library (RRL) provides a convenient platform for implementing environment modelling components such as rainfall runoff models, calibration tools, and objective functions. A rainfall-runoff model widely known and used in South Korea, TANK, is added to the RRL, and used along with the models AWBM and SIMHYD to reproduce the historical time series of daily and monthly runoff at the Soyanggang Dam and Youngcheon Dam catchments located in South Korea. The features of the RRL allow for an easy comparison of different models in a standardised and common framework. Three optimisation methods (Genetic algorithm, Rosenbrock method and Shuffled Complex Evolution algorithm) were applied to calibrate the model parameters using three different objective functions. The applicability of each model to these catchments is discussed based on the resulting statistics.

Chemical morphogenesis: turing patterns in an experimental chemical system.

Patterns resulting from the sole interplay between reaction and diffusion are probably involved in certain stages of morphogenesis in biological systems, as initially proposed by Alan Turing. Self-organization phenomena of this type can only develop in nonlinear systems (i.e. involving positive and negative feedback loops) maintained far from equilibrium. We present Turing patterns experimentally observed in a chemical system. An oscillating chemical reaction, the CIMA reaction, is operated in an open spatial reactor designed in order to obtain a pure reaction-diffusion system. The two types of Turing patterns observed, hexagonal arrays of spots and parallel stripes, are characterized by an intrinsic wavelength. We identify the origin of the necessary diffusivity between activator and inhibitor. We also describe a pattern growth mechanism by spot splitting that recalls cell division.

Effects of tioconazole on parturition and serum levels of 17 beta-oestradiol, progesterone, LH and PRL in the rat.

Tioconazole, an imidazole antifungal agent, was administered orally at 100 mg/kg/day to pregnant rats according to two regimens; in one, treatment started on day 15 post-insemination (p.i.) and in the other it started on day 18 p.i. The first regimen caused a delay in onset of parturition and a prolongation of labour. Serum progesterone was decreased from days 17 to 21 p.i., 17 beta-oestradiol decreased on day 21 p.i., LH increased on day 17 p.i., and the normal surge of prolactin on day 21 p.i. abolished. The parturition disorders disappeared when 17 beta-oestradiol (0.125 microgram/animal/day s.c.) was given with tioconazole from day 15 p.i. In the second regimen, tioconazole treatment advanced by about 24 hours the onset of parturition and the normal fall in serum progesterone and the surge in prolactin. Serum 17 beta-oestradiol was unaffected, but LH was raised on days 19 and 20 p.i. In animals receiving progesterone (2.5 mg/animal/day, s.c.) and tioconazole from day 18 p.i. parturition was no longer advanced. In conclusion, the parturition disorders observed in rats during tioconazole treatment are associated with a modification of progesterone and 17 beta-oestradiol serum levels. These findings have questionable relevance for the human situation as the roles of these steroid hormones in parturition in women are different from those in rats.

A method for the routine observation of sexual behaviour in rats.

In seeking a method for the routine observation of copulatory behaviour in rats we compared the use of a standard rectangular Makrolon cage, commonly used in toxicology studies, with a Plexiglas cylinder that provided 2.5 times more floor area. The cylinder resulted in a much higher incidence of copulation, either once or for multiple series, within 30 min. This was not affected by whether oestrus was natural or induced. Using the cylinder and 4 h observation periods, we found that the dark phase of a 12-12 h inverse light cycle resulted in many more copulations than occurred during the light phase of a natural cycle. The incidence increased from the first to the second to the last 4 h of the dark phase. We found that placing a virgin receptive female and a naive male together in a Plexiglas cylinder for 1 h towards the end of the dark phase is a useful tool in reproductive toxicology studies in which it is important to know the precise time of insemination.

Reproductive studies with the anti-inflammatory agent, piroxicam: modification of classical protocols.

Reproductive toxicology studies were conducted in rabbits and rats given piroxicam, a non-steroidal anti-inflammatory agent (NSAI), orally at 2, 5 and 10 mg/kg/day. In teratology studies there was neither drug-related embryotoxicity nor teratogenicity. As piroxicam, like other NSAI, affects parturition in rats and leads to a progressive toxicity in lactating females, standard protocols were modified: dams of the female fertility study were treated from 2 weeks prior to mating until day 6 of gestation and females of the post-natal toxicity study were treated from parturition until day 12 of lactation. No other adverse effects on reproduction, fertility and postnatal development were observed.

Use of the New Zealand white rabbit in teratology: incidence of spontaneous and drug-induced malformations.

Cumulative data are presented on the occurrence of external, skeletal and visceral abnormalities in foetuses from teratology studies conducted in New Zealand White rabbits over a 10-yr period. The data, based on examinations of over 5500 control foetuses and 19,000 foetuses from treated dams, are derived from studies involving 58 compounds, five of which were judged to be teratogenic.

Levels of spontaneous malformations in the CD rat and the CD-1 mouse.

Extensive information was supplied about the frequencies and types of spontaneous skeletal and visceral malformations in control and test fetuses which may be encountered during teratological assays. Data were also provided on fertility, agerage body weights, water consumption as a function of diet, and food consumption. The two strains used, Crl:COBS CD (SD) BR (France) rats and Crl:CD-1 (ICR) BR (France) mice, are valuable research tools since they are prolific, have a low rate of spontaneous malformations, and are responsive to teratogenic agents. The difficulties of determining the significance of infrequent anomalies were discussed.