Photoelastic sphenoscopic analysis of crystals.

Birefringent crystals are at the basis of various devices used in many fields, from high energy physics to biomedical imaging for cancer detection. Since crystals are the main elements of those devices, a great attention is paid on their quality and properties. Here, we present a methodology for the photoelastic analysis of birefringent crystals, based on a modified polariscope. Polariscopes using conoscopic observation are used to evaluate crystals residual stresses in a precise but time consuming way; in our methodology, the light beam shape, which impinges on the crystal surface, has been changed from a solid cone (conoscopy) to a wedge (sphenoscopy). Since the polarized and coherent light is focused on a line rather than on a spot, this allows a faster analysis which leads to the observation, at a glance, of a spatial distribution of stress along a line. Three samples of lead tungstate crystals have been observed using this technique, and the obtained results are compared with the conoscopic observation. The samples have been tested both in unloaded condition and in a loaded configuration induced by means of a four points bending device, which allows to induce a known stress distribution in the crystal. The obtained results confirm, in a reliable manner, the sensitivity of the methodology to the crystal structure and stress.

A photoelastic measurement system for residual stress analysis in scintillating crystals by conoscopic imaging.

The assessment of the stress state of scintillating crystals is an important issue for producers as well as users of such materials, because residual stress may arise during growth process. In this paper, a measurement system, based on the use of a photoelastic, conoscopic optical setup, is proposed for the assessment of stress state in scintillating crystals. Local stress values can be measured on the crystal in order to observe their spatial distribution. With the proposed system, it is possible to vary the dimensions of the inspected measurement volume. It has been validated with reference to a known stress state induced in a birefringent crystal sample and it has been tested for the case of loaded and unloaded samples, showing sub-millimetric spatial resolution and stress uncertainty ≤0.25 MPa. The proposed measurement system is a valid method for the inspection of scintillating crystals required by producers and users of such materials.

Karyometry and quantitative immunohistochemical analysis of the urothelium in tissue sections: a feasibility study based on chromatin remodeler DAXX immunostaining.

The aim of this study was to investigate the feasibility of applying a software traditionally used in the field of engineering to pathology, in particular to tissue sections from normal urothelium (NU) immuno-stained for the chromatin remodeler DAXX (death domain-associated protein). The study included 5 cases of NU. Images were recorded with a Nikon digital camera. The nuclear area and the intensity of nuclear staining were analyzed with a software package developed in LabVIEW environment. The nuclear size is 14.8 plus or minus 6.5 square microns. The nuclei in the cells adjacent to the stroma are slightly smaller than in the intermediate cells by a factor of 0.86. The mean nuclear area of the nuclei in the superficial cell layer in NU is identical to the nuclei in the intermediate cell layers. For each nucleus intensity of nuclear staining is calculated based on the gray value of the individual picture elements in the green color plane. The mean and standard deviation of nuclear gray value are 106 plus or minus 15. The mean value in the nuclei adjacent to the stroma is slightly greater by a factor 1.02 and 1.04 compared to the intermediate and superficial cell layers. In conclusion, this exploratory study shows that karyometry and quantitative immunohistochemical analysis can be done accurately by using a digital camera commonly available to pathologists and an image analysis software routinely used in the field of engineering.

Agent-based station for on-line diagnostics by self-adaptive laser Doppler vibrometry.

A self-adaptive diagnostic system based on laser vibrometry is proposed for quality control of mechanical defects by vibration testing; it is developed for appliances at the end of an assembly line, but its characteristics are generally suited for testing most types of electromechanical products. It consists of a laser Doppler vibrometer, equipped with scanning mirrors and a camera, which implements self-adaptive bahaviour for optimizing the measurement. The system is conceived as a Quality Control Agent (QCA) and it is part of a Multi Agent System that supervises all the production line. The QCA behaviour is defined so to minimize measurement uncertainty during the on-line tests and to compensate target mis-positioning under guidance of a vision system. Best measurement conditions are reached by maximizing the amplitude of the optical Doppler beat signal (signal quality) and consequently minimize uncertainty. In this paper, the optimization strategy for measurement enhancement achieved by the down-hill algorithm (Nelder-Mead algorithm) and its effect on signal quality improvement is discussed. Tests on a washing machine in controlled operating conditions allow to evaluate the efficacy of the method; significant reduction of noise on vibration velocity spectra is observed. Results from on-line tests are presented, which demonstrate the potential of the system for industrial quality control.

Estimating mechanical blood trauma in a centrifugal blood pump: laser Doppler anemometer measurements of the mean velocity field.

A laser Doppler anemometer (LDA) was used to obtain the mean velocity and the Reynolds stress fields in the inner channels of a well-known centrifugal vaneless pump (Bio-pump). Effects of the excessive flow resistance against which an occlusive pump operates in some surgical situations, such as cardiopulmonary bypass, are illustrated. The velocity vector field obtained from LDA measurements reveals that the constraint-forced vortex provides pumping action in a restricted area in the core of the pump. In such situations, recirculating zones dominate the flow and consequently increase the damage to blood cells and raise the risk of thrombus formation in the device. Reynolds normal and shear stress fields were obtained in the entry flow for the channel formed by two rotating cones to illustrate the effects of flow disturbances on the potential for blood cell damage.