Refractive index measurement through image analysis with an optofluidic device.

We present a novel optical method, to our knowledge, to measure the refractive index of liquids by means of the images produced by an optofluidic lens. In addition we propose a new method to make optofluidic lenses.

Illumination, background luminance, and perceptual learning in perception of achromatic colors.

Plateau's experiment, in which the bisection method was introduced, is recognized as the first psychophysical experiment ever done. That experiment was replicated and extended using modem imaging devices. First, participants with professional training in visual arts painted grayscales with no control on illumination. Then, the trained participants and the nontrained participants generated grayscales using a personal computer in three different conditions: a white background of a linearized monitor, a black background of that monitor, and a white background but without linearizing the monitor. Analyses showed that with artificial illumination, scales with steps more evenly spread were produced than with natural illumination. Humans do not seem to have a natural ability to use the bisection method properly. Experts seem to be able to judge the reflectance of distal stimuli, and perceptual learning played an important role in the perception of achromatic colors as found in prior literature.

Optofluidic compound microlenses made by emulsion techniques.

Here we present a new method to make liquid lenses. It is based on the microfluidics method and involves the preparation of emulsions one drop at a time. Tests of lenses by image formation are presented. Experimental results are compared with results of an optical design program. We also present a new type of lens that we call a Compound Lens which consists of two spherical lenses, one inside the other.

Pressure measurements through image analysis.

Here we propose a new optical method, to our knowledge, to measure the pressure in liquids or gases by means of a flexible lens. Images of an object given by the dynamical lens are analyzed, and through the visibility of those images pressure is inferred.

Novel approach to assess the emissivity of the human skin.

To study the radiation emitted by the human skin, the emissivity of its surface must be known. We present a new approach to measure the emissivity of the human skin in vivo. Our method is based on the calculation of the difference of two infrared images: one acquired before projecting a CO(2) laser beam on the surface of the skin and the other after such projection. The difference image contains the radiation reflected by the skin, which is used to calculate the emissivity, making use of Kirchhoff's law and the Helmholtz reciprocity relation. With our method, noncontact measurements are achieved, and the determination of the skin temperature is not needed, which has been an inconvenience for other methods. We show that it is possible to make determinations of the emissivity at specific wavelengths. Last, our results confirm that the human skin obeys Lambert's law of diffuse reflection and that it behaves almost like a blackbody at a wavelength of 10.6 microm.

Optofluidic variable focus lenses.

Here we propose optofluidic spherical microlenses that can change their focal distance by varying the refractive index of the liquid that composes them. These lenses are fabricated in the bulk of a polymeric mixture. Results of a characterization study of the profile of the lenses, the image forming capability, and the behavior of the focal distance as a function of the refractive index are presented. Ionic liquids are suggested as a source of liquids useful for fabricating this type of lens.

A psychophysical test of the visual pathway of children with autism.

Signal detection psychophysical experiments were conducted to investigate the visual path of children with autism. Computer generated images with Gaussian noise were used. Simple signals, still and in motion were embedded in the background noise. The computer monitor was linearized to properly display the contrast changes. To our knowledge, this is the first time that experiments of this type have been done with observers with autism. Our results show that the visual capabilities of typically developed children were superior to those of the children with autism, and that the related problems of children with autism are sensation related only in a reduced proportion. There is no evidence that they are disabled in detecting simple visual stimuli, still and in motion.

Pressure sensor with optofluidic configuration.

We present a new kind of compact, simple, and low cost optical pressure sensor. The physical principle on which the sensor is based, components, layout of the system, and characterization are described. The range of pressures in which the sensor works is from about 0.5 to 3 psi (1 psi=6.895 kPa).

Effect of alendronate on periodontal disease in postmenopausal women: a randomized placebo-controlled trial.

BACKGROUND: We investigated the effect of oral alendronate (ALN) treatment on radiological and clinical measurements of periodontal disease in postmenopausal women without hormone replacement therapy. METHODS: We evaluated the effect of 6 months of ALN treatment in 40 postmenopausal women, 55 to 65 years old with established periodontal disease, in a controlled, double-masked, prospective study. Volunteers were paired by age and randomized to receive ALN (10 mg/day) or placebo for the study period. Periodontal mechanical treatment was carried out in both groups. At baseline and after treatment, clinical evaluation, hormone blood levels, distance from the crestal alveolar bone (CAB) to the cemento-enamel junction (CEJ), calcaneus bone mineral density (BMD), hormone levels, serum N-telopeptide (NTx), and bone-specific alkaline phosphatase (BSAP) were assessed. RESULTS: Periodontal disease conditions improved in both groups, but greater improvement in probing depth (-0.8 +/- 0.3 mm versus -0.4 +/- 0.4 mm, P = 0.02) and gingival bleeding (-0.3% +/- 0.13% versus -0.2% +/- 0.06%, P = 0.006) was found in the ALN treated group. Calcaneus BMD increased in the ALN treated group (68 +/- 47 mm3 versus -26 +/- 81 mm3, P = 0.0006). CAB-CEJ distance diminished in the ALN group (-0.4 +/- 0.40 mm versus 0.60 +/- 0.53 mm, P = 0.00008). Marginal reduction in both NTx and BSAP levels was found in the ALN group (-9.4 +/- 6.6 nmol versus -4.3 +/- 4.7 nmol bone collagen equivalents, P = 0.08, and -7.7 +/- 8.4 versus -1.5 +/- 5.0 U/l, P = 0.1, respectively). Hormone levels were unchanged after treatment. Similar improvement of calcaneus BMD and CAB-CEJ distance with ALN treatment was found in obese and non-obese women. CONCLUSION: ALN treatment improved periodontal disease and bone turnover in postmenopausal women.

Principal wavelengths in the formation of spectral images of natural scenes.

Considering the high degree of correlation in the visible spectrum, the principal wavelengths from spectral measurements of radiance recorded in spectral images were selected using a method based on principal components analysis (PCA). It seems to be that this is the first time that, instead of using spectra, data is taken directly from the "slices" of spectral images; the method has the advantage of preserving the structure of the original data in the reduced data set. A "true" dimensionality of five wavelengths resulted for all the analyzed images. The averages of the selected wavelengths for 10 spectral images produced good results for a human observer. These results were possible using only four wavelengths. Though PCA by itself is not able to include the impact of specific sensors on the selection of basis functions, results suggest that the variable selection method used in this work (which is not just PCA) yielded objective information of the structure of the physical stimuli (i.e., the spectral structures) that have been shaping the visual systems of animals and insects since many years ago.

Simple reaction times and performance in the detection of visual stimuli of patients with diabetes.

Simple reaction times (SRT) to visual stimuli were investigated through reactions to computer simulations of changes of traffic lights. The performance in the detection of visual stimuli, implying decision processes, was also assessed using the two alternative forced choice (2AFC) method. Subjects were patients affected by diabetes type 2, and observers without diabetes. Results indicated that mean SRT was longer in the group of diabetic patients but was not correlated with age, diabetes duration or fasting glucose. The performance index (d') was correlated with age and with diabetes duration. Unexpectedly, the correlation between fasting glucose and d' was not negative.

[Skills and requirements of residents. Teaching resources to help tutors in a situation of change]. / Capacidad y necesidades del residente. Recursos docentes para ayudar al tutor en una situación de cambio.

OBJECTIVE: To determine indicators of the skills and expectations of family and community medicine (FMC) residents (MIR). To construct teaching resources to value skills and expectations individually and continuously. DESIGN: Qualitative study, based on workshops and work conferences. SETTING: Health centres and functions room of primary health care management, Murcia, Spain. PARTICIPANTS: Thirty tutors from 7 teaching health centres in Murcia, 2 pedagogues, and the coordinator of the FCM teaching unit of Murcia, selected by means of voluntary request. MEASUREMENTS: Brainstorming and discussion in a large group to determine indicators. Meetings to coordinate work and to construct the teaching resources. MAIN RESULTS: Tutors were concerned about the strengths and weaknesses of the residents, in areas such as health care communication, clinical reasoning, care management, information systems, bioethics, research, and attitudes relating to trust, respect, responsibility, and dialogue. There were also expectations and personal needs to do with training and integration into the health centre. Therefore, 2 teaching resources were constructed for systematic investigation. CONCLUSIONS: The skills and requirements of both tutors and residents need to be known, if training is to be in the interests of both. This study contributes instruments that aid teaching work and an opportunity for collaboration by gathering questions that concern tutors.

A simple procedure for simulating samples of tissue using Voronoi diagrams.

OBJECTIVE: To describe a simple and quick procedure for modeling samples of tissue with Voronoi diagrams. STUDY DESIGN: Instead of calculating the centers of the so-called Dirichlet domains (i.e., the polygonal areas occupied by individual cells), the centroid of such areas is used to generate Voronoi diagrams. The coordinates of the centroids are calculated by simply averaging the coordinates of the points of the cell contours; that is much simpler and faster than any geometric procedure for locating the Dirichlet centers. Using the centroids as centers, circles are allowed to grow until no space on the surface is available. With this procedure it is easy to control the rate of growth of individual cells or groups of cells according to any rule or rules. It is also possible to simulate the effects of removing > or = 1 cells from the sample. CONCLUSION: The procedure was successfully applied to modeling some of the changes that can occur in a real sample of human corneal endothelium. The procedure is simple, completely automated, efficient and flexible and can be easily implemented on a personal computer. It can be used to test growth or communication strategies among cells.

Rod and spherical silica microlenses fabricated by CO2 laser melting.

The fabrication and testing of glass microlenses with rod and spherical shapes are described. The sizes of the lenses range from tens of micrometers to several millimeters. The surfaces of the lenses were fabricated by the melting method. These surfaces have been studied by several methods. The theoretical behavior of the lenses was investigated by ray tracing. Some applications of the lenses are presented.