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PubMed2006

Metamer-set-based approach to estimating surface reflectance from camera RGB.

We present an approach to estimating the reflectance of a surface given its camera response. In this approach we first solve the general form of this problem: we calculate the set of all possible surface reflectances, called the metamer set, and then choose a member from this set. Three possibilities in choosing a single reflectance are described here. First, we assume that all reflectances are equally likely and minimize worst-case error. Second, we adopt the assumption that reflectances follow a normal probability distribution and maximize this probability. Finally, we assume that reflectances are smooth and maximize this property. The results of our experiments show that there is significant benefit from the proposed approach in terms of the accuracy of the estimation compared with that of standard estimation methods. Moreover, the present approach introduces a notion of robustness of estimates in the form of error bars.

Journal Article↗

PubMed2005

Cross-polarized reflected light measurement of fast optical responses associated with neural activation.

We developed an optical probe for cross-polarized reflected light measurements and investigated optical signals associated with electrophysiological activation in isolated lobster nerves. The cross-polarized baseline light intensity (structural signal) and the amplitude of the transient response to stimulation (functional signal) measured in reflected mode were dependent on the orientation of the nerve axis relative to the polarization plane of incident light. The maximum structural signal and functional response amplitude were observed at 45 degrees , and the ratio of functional to structural signals was approximately constant across orientations. Functional responses were measured in single trials in both transmitted and reflected geometries and responses had similar waveforms. Both structural and functional signals were an order of magnitude smaller in reflected than in transmitted light measurements, but functional responses had similar signal/noise ratios. We propose a theoretical model based on geometrical optics that is consistent with experimental results. In the model, the cross-polarized structural signal results from light reflection from axonal fibers and the transient functional response arises from axonal swelling associated with neural activation. Polarization-sensitive reflected light measurements could greatly enhance in vivo imaging of neural activation since cross-polarized responses are much larger than scattering signals now employed for dynamic functional neuroimaging.

Animals↗

PubMed2003

Forest reflectance modeling: theoretical aspects and applications.

Forest reflectance models are able to contribute to the interpretation of satellite images over forested areas. A multipurpose forest reflectance model, its basic ideas, model input and output options are briefly described. The possibility to apply the model in forest remote sensing is demonstrated through the following simulation examples: the age dependence of forest reflectance, the seasonal course of forest reflectance, defoliation effects on forest reflectance, sensitivity of chlorophyll and water indices with respect to leaf chlorophyll and water content, respectively, and uncertainties in these indices introduced by the variation in stand parameters. When used together with the atmospheric radiative transfer and sensor calibration models, the forest reflectance model is applicable in satellite-imagery-aided forest ecology and health assessment, forest inventory and management.

Calibration↗

PubMed2000

Reflective and black mulch increase yield in pumpkins under virus disease pressure.

Experiments were conducted over a 4-yr period that examined the effect reflective, black, and no-mulch had on aphid populations, incidence of virus infected pumpkin plants, and yield of pumpkin. Three different planting dates and their effect on viral infection and yield were also investigated. The use of reflective mulches significantly reduced the number of alates landing in these rows compared with black- or no-mulch rows. The reduction in aphid numbers resulted in a reduction in the percent of plants infected with virus. Approximately 10 times more plants were infected with virus in the black and no-mulch plots than in the reflective mulch plots in mid- to late July. However, by the end of August, all treatments had near 100% of plants infected with virus. This delay in viral infection in reflective mulch plots resulted in a 45 and 120% increase in pumpkin yield compared with black mulch and no-mulch plots, respectively. First plantings always had greater yields than later plantings. The interaction between mulch type and planting time was significant. Reflective mulches increased yields overall, but significantly increased yields compared with black or no-mulch in second and third plantings. The use of reflective mulch combined with timely planting is a cost effective way of delaying virus problems and increasing pumpkin yields in midwestern United States.

Animals↗

PubMed2002

Wing colors of Chrysozephyrus butterflies (Lepidoptera; Lycaenidae): ultraviolet reflection by males.

Wing colors of the four species of Chrysozephyrus butterflies were analyzed by a spectrophotometer. As the dorsal wing surface of males showed a strong reflectance when the specimen was tilted, measurements were made by the tilting method. The dorsal wing surface of males which appears green to the human eye reflected UV (315-350 nm) as well as green light (530-550 nm). The reflectance rate of UV to visible green light varied among species with a higher rate for C. hisamatsusanus and C. ataxus, and a lower rate for C. smaragdinus and C. brillantinus. The peak wavelength and the peak height did not shift when the specimen was exposed to direct sunlight at least for 16 hr. Artificial removal of scales by scratching the wing surface decreased reflectance. Blue marks on the forewings of C. brillantinus, C. hisamatsusanus and C. ataxus females reflected UV to visible light of short wavelength, and orange marks on the dorsal surface of the forewing and the ventral surface of the hindwing of C. samaragdinus females showed a higher reflectance at longer wavelengths.

Animals↗

PubMed2003

Does the regional oxygen uptake measured by near infrared spectroscopy reflect the phase II pulmonary oxygen uptake at the onset of exercise?

It has been hypothesized that the signals of near infrared spectroscopy (NIRS) would reflect muscle O(2) uptake (mVO(2)). Although it is not definite that NIRS signals accurately reflect mVO(2), there is every possibility that NIRS signals at least reflect regional O(2) uptake (rVO(2)). The phase II kinetics of pulmonary oxygen uptake (pVO(2)) is regarded as reflecting mVO(2) at the onset of exercise. To examine whether the rVO(2) on-kinetics measured by NIRS reflects the mVO(2) on-kinetics at the onset of exercise, we compared the rVO(2) as measured by NIRS with the phase II kinetics of pVO(2) at the onset of exercise. Twelve healthy male subjects cycled a Monark ergometer at three different intensities: below the ventilatory threshold (VT) level (below-VT), on the VT level (on-VT), and above the VT level (above-VT), for 6 minutes on three separate occasions. The rVO(2) was calculated from the concentration of oxyhemoglobin and deoxyhemoglobin, as measured by NIRS every 3 seconds. The pVO(2) was determined by the breath-by-breath method. A significant relationship between the amount of increases of pVO(2) and rVO(2) from rest to the end of exercise among all levels of exercise intensity was found (r=0.935, P<0.001). The time constants of rVO(2) (rVO(2)-Tc: below-VT: 6.514+/-2.159 s, on-VT: 7.760+/-2.035 s, above-VT: 9.532+/-2.342 s) were significantly faster than the time constants of pVO(2) (pVO(2)-Tc: below-VT: 23.8+/-4.4 s, on-VT: 25.9+/-5.1 s, above-VT: 26.3+/-5.7 s) (P<0.001). There was no significant relationship between rVO(2)-Tc and pVO(2)-Tc for each intensity (P>0.05). We conclude that the rVO(2) on-kinetics measured by NIRS does not necessarily reflect the mVO(2) kinetics at the onset of exercise.

Adult↗

PubMed1997

Impulsive-reflective cognitive style, metacognition, and emotion in adolescence.

The study investigated the relationship between reflective or impulsive cognitive style, metacognitive functioning, and depression in young adolescents. Metacognitive functioning (metacognitive knowledge about reading and memory, monitoring of text comprehension) and self-reported depressive feelings were analyzed in a group of subjects who showed a Reflective or Impulsive cognitive style. The sample consisted of 56 junior high-school students (Grades 6, 7, and 8) selected from a larger original group of 61 subjects. We excluded from the original group those with an IQ below 75 on both the Verbal and Performance subscales on the short form of the WISC-R, those reported by teachers to have a severe learning disability, and those that did not complete the test battery due to long absences from school. The reflective-impulsive cognitive style was identified with the Matching Familiar Figures Test-20. Using the median of the distribution for both Latency (17 sec. per item) and Errors (9 errors) on this task, the sample was divided in four partially overlapping subgroups: 16 with Impulsive cognitive style (Latency below the median, Errors above the median), 13 with Reflective cognitive style (Latency above the median, Error below the median), 4 fast and accurate (both scores below the median), and 11 slow and inaccurate (both scores above the median). Twelve subjects with one or both scores coinciding with the critical value (median) were excluded. Analysis showed that subjects with Impulsive cognitive style had significantly lower scores than those with Reflective cognitive style in monitoring of comprehension of text. No differences were found on monitoring by eighth graders, irrespective of cognitive style. No differences between the two groups were found in metacognitive knowledge. Subjects with Impulsive cognitive style had significantly higher scores than subjects with Reflective cognitive style on a self-rating scale for childhood depression, the Children's Depression Inventory. The implications of these data are discussed.

Adolescent↗

PubMed1988

Erythrocyte aggregate rheology by transmitted and reflected light.

Both the transmission of light through a confined layer of blood and the reflection from the surface of that layer have been utilized for studying the rheology of erythrocyte aggregates. The two methods do not necessarily provide the same information. The light reflected from the blood layer relates to the rheological behavior of erythrocytes near the blood surface, whereas the light transmitted relates more to the properties of blood in bulk. This investigation makes direct comparison between the transmitted and reflected light methods with regard to the kinetics of aggregation in thin and thick layers of blood as well as following shear flow excitation steps of different sizes. Also, the transmission and reflection for static blood layers of varying thicknesses were determined. The kinetics of aggregation from transmitted and reflected light measurements are compared both graphically and by equations containing multiple characteristic aggregation times. The number of characteristic times required for accurate description increases with the time over which the aggregation process is monitored. The first 40 seconds of the aggregation process are precisely described by two characteristic times. For normal blood the characteristic times from reflection measurements are shorter than those from transmission measurements.

Erythrocyte Aggregation↗

PubMed1989

[The unbalanced polarity of response flexibility and cognitive preference between reflective and impulsive children].

Two experiments investigated the unbalanced polarity of response flexibility and cognitive preference between reflective and impulsive children. In experiment I, Cairns and Cammock's Matching Familiar Figures Test was readministered to 186 reflective and impulsive children in the first and fourth grades under one of three instructions: standard, accuracy-emphasized, or speed-emphasized instructions. Reflective children controlled their responses flexibly even if the task demand was opposite to their accustomed manners. But impulsive children could not accommodate their responses to the unaccustomed, accuracy-emphasized demand. In experiment II, 96 reflective and impulsive children in the first and fourth grades were asked about their expert, preferred task demand. Most reflective children answered that they were successful in the accuracy-demanded condition and preferred it. A half of impulsive children selected the speed-demanded condition; the others replied the same as the reflective.

Adaptation, Psychological↗

PubMedDate not supplied

Color measurement of rosemary honey in the solid state by reflectance spectroscopy with black background.

A colorimetric method was developed to measure the color of rosemary honeys in the solid state, without liquefaction. The color of 20 solid samples of rosemary honeys was measured by reflectance spectroscopy with white and black background in cells of 1 cm pathlength. The Kulbelka-Munk theory of turbid media was applied to calculate the spectral distribution of reflectivity, internal transmittance, and coefficients of absorbance and scattering of light. From these spectral distributions, 2 different types of honey were found. The honey colors measured from reflectivity and internal transmittance are well grouped. The colors obtained from reflectivity and those obtained from reflectance with black background show high linear correlation (r2 > 0.99). As a practical application, measurements of reflectance with black background in cells of 1 cm pathlength can be used to determine the color of these honeys in the solid state.

Colorimetry↗

PubMed2000

The thickness of the human precorneal tear film: evidence from reflection spectra.

PURPOSE: Interferometric methods have considerable potential for studying the thickness of layers of the human tear film and cornea because of their ability to make noninvasive, accurate, and rapid measurements. However, previous interferometric studies by Prydal and Danjo yielded tear thickness values near 40 and 11 microm, respectively, considerably greater than estimates made by invasive methods of 4 to 8 microm. Using a modified version of Danjo's method, interference effects from the tear film and cornea were studied, with the aim of correlation with known structure and optical properties of the cornea and hence determining the most probable value of tear film thickness. METHODS: Reflectance spectra from the human cornea were measured at normal incidence. These spectra show oscillations whose maxima correspond to constructive interference between light reflected from the air surface and from some deeper surface. The frequency of these spectral oscillations is proportional to the thickness of the layer between the air surface and the second surface. Therefore, Fourier analysis of reflectance spectra can be used to determine the thickness of layers of the tear film and cornea. In the main experiment, 36 low-resolution spectra were obtained from six normal eyes for measuring thickness up to 100 microm. Control experiments included measurements of the time course of thickness changes and high-resolution spectra for measuring thickness up to 1000 microm. RESULTS: For the main experiment, in the thickness range 1 to 100 microm, the strongest peak in the Fourier transform was near 3 microm (range, 1.5-4.7 microm) beneath the air surface. In the range 20 to 100 microm, the strongest peak was near 55 microm (range, 50-59 microm) for all 36 spectra; none were in Prydal's range near 40 microm. This 55-microm peak is consistent with a reflection from the basement membrane of the epithelium. Time course measurements after a blink show that the 3-microm peak is not an artifact. High-resolution spectra gave a peak near 510 microm, corresponding to the complete thickness of the cornea (plus tear film). This peak had a contrast similar to that of the 3-microm peak. CONCLUSIONS: These studies did not confirm Prydal's estimate of approximately 40 microm. Nor were there prominent peaks near Danjo's value of approximately 11 microm, except in cases of probable reflex tears. Because the reflection at the aqueous-mucus boundary would be expected to be weaker than that from the epithelial surface, the 3-microm peak is unlikely to correspond to the aqueous layer (rather than the complete tear film). The proposal that the 3-microm peak corresponds to a reflection from the front of the cornea is supported by the demonstration of a peak of similar contrast from the back of the cornea. Thus, the current evidence consistently supports a value of approximately 3 microm for the thickness of the human precorneal tear film.

Adult↗

PubMed2001

[Effect of rice canopy structural changes on bidirectional reflectance].

The study of vegetation bidirectional reflectance is useful for remote sensing data interpretation. Vegetation canopies information such as leaf area index, mean leaf inclination, mean plant height, and coverage, can be inverted from vegetation bidirectional reflectance. This paper discussed the dynamics of vegetation canopies reflectance with vegetation canopy structures by measuring rice canopy structure and bidirectional reflectance at 26, 35, 41, 49, 62, 67 and 86 days after transplanting. It is concluded that the sensitivity of vegetation canopies to directional reflectance variations varied with canopy structures, and hence, through bidirectional reflectance, more information about canopy structure can be know.

Light↗

PubMed2002

Proportional (fractional) displacement of the Hirschberg corneal light reflection (test): a new easily memorized aid for strabometry; photogrammetric standardization (calibration).

PURPOSE: To improve the usefulness of the Hirschberg Corneal Light Reflection Test (CLRT), using a photogrammetric technique independent of the size of the pupil, and to devise an easily remembered sequence of numbers corresponding to the fractional displacement of the reflection in various approximate angles of esotropia. METHOD: Photographs (slides) were taken of the right eye of 25 young adults using a centered strobe light source to produce the corneal light reflection in 5 prism diopters (PD) increments of adduction from 0 to 90 PD to standardize the Hirschberg CLRT for esodeviations. On a large, dual-projection screen, the eye of the subject looking straight ahead (primary position) was projected on one side and the various slides of the same eye of that subject looking into various degrees of adduction were projected on the other side of the screen. Measurements of the distance between the lateral limbus and the corneal reflection were made with a centimeter rule on the screen. The displacement (shift) of the corneal light reflection was expressed as a fraction of the distance between the lateral limbus and the position of the reflection (in relation to the lateral margins of the pupil) with the eye fixing in the primary position. RESULTS: The values found were 1/4 = 30 +/- 3 PD; 1/3 = 41 +/- 4 PD; 1/2 = 59 +/- 4 PD; 2/3 = 75 +/- 6 PD; and 3/4 = 80 +/- 6 PD. CONCLUSIONS: An easily memorized similar series of values is 30, 40 60, 75 and 80 PD corresponding to 1/4, 1/3, 1/2, 2/3 and 3/4 PD. This is useful to know which prism to pick up to begin the prism alternate cover test efficiently in a small child.

Blinking↗

PubMed2002

Reflective self-awareness and conscious states: PET evidence for a common midline parietofrontal core.

A recent meta-analysis has shown precuneus, angular gyri, anterior cingulate gyri, and adjacent structures to be highly metabolically active in support of resting consciousness. We hypothesize that these regions constitute a functional network of reflective self-awareness thought to be a core function of consciousness. Seven normal volunteers were asked to think intensely on how they would describe the personality traits and physical appearance of themselves and a neutral reference person known to all the subjects (the Danish Queen). During each of the four conditions cerebral blood flow distribution was measured by the intravenous H(2)(15)O PET scanning technique. During scanning, no sensory or motor activity was intended. After each scan, the subjects reported the contents of their thoughts during the scan to ascertain that the instructions had been followed. The results confirmed our hypothesis: Statistical parametric mapping showed differential activity in precuneus and angular gyri during reflection on own personality traits and in anterior cingulate gyri during reflection on own physical traits. Connectivity analysis of synchrony showed these regions to be functionally connected during reflective self-awareness. The commonality between the neural networks of the resting conscious state and self-awareness reflects the phenomenological concept of a fundamental contribution of reflective self-awareness to the contents and coherence of the conscious state.

Adult↗

PubMed2002

[Reflected wave and isolated systolic hypertension: problems of pathogenesis and therapy].

The value of reflected (tidal) wave amplitude in the pathogenesis of isolated systolic hypertension (ISH) is discussed and main characteristics of elastic properties of arteries (compliance, distensibility, rigidity, pulse wave velocity, and amplitude of reflected wave) are considered. In ISH systolic and pulse blood pressures are associated with augmentation of the reflected wave amplitude. Increased pulse wave velocity characteristic of ISH leads to displacement of reflected wave from diastole to systole. Summation of two waves (primary and reflected) causes elevation of systolic blood pressure. Choice of antihypertensive drugs for the treatment of ISH is determined by their action on pulse wave velocity, delay of reflected wave and arterial compliance. Preferable agents are angiotensin converting enzyme inhibitors, calcium antagonists, diuretics and beta-blockers with vasodilating properties. In bradycardia with high stroke volume normalization of heart rate can be achieved by M-anticholinergic drugs and theophylline.

Antihypertensive Agents↗

PubMedDate not supplied

Reflections on caring narratives: enhancing patterns of knowing.

The purpose of this study was to provide graduate students with the opportunity to enrich their esthetic knowing and acquire the meaning of caring in their practice by reflecting on their caring narratives. Content analysis examining for context, process, and fulfillment was used to analyze 68 caring encounters written by five classes of graduate nursing students over five semesters of course work. This article focuses on the value of reflection in knowing and the fulfillment identified by the students through the reflective process. Student fulfillment included reflecting on the need to care for self, knowing that emotional attachment can be dangerous, recognizing caring as a moral responsibility, attending to caring teaches one about caring, and reflecting on caring encounters engages one in defining caring. It is concluded that graduate nursing students can enhance multiple ways of knowing and their understanding of caring through the process of reflecting on caring encounters.

Adolescent↗

PubMed2003

[A study on multicomponent bidirectional reflectance model for rice].

In this paper, the bidirectional reflectance factor (BRF) of rice measured in field experiment in 1999 and 2000 was compared with the BRF computed from the rice multicomponent bidirectional reflectance model that based on the radiative transfer theory, rice canopy geometric structural factors and different characteristics of the different growth period for rice in detail. The contribution of some sensitive factors such as the average inclination angle of all components belonged to rice and LAI was accurately specified. The results showedthat the rice multicomponent bidirectional reflectance model described above could basically simulate the angular distribution characteristic of reflectance spectrum of rice canopies, and the different peak point of the hotspot effect of rice canopies reached under different conditions. In addition, the regulation of the first-order scattering reflectance by soil and water and the multiple scattering reflectance by foliage, stem, fringe and soil changing with the average inclination angle of all components, as well as the contribution of LAI to BRF were analyzed. All of these laid a foundation to monitor rice growth and estimate its yield. Meanwhile, it also implied that some rice canopy parameters could be accurately estimated by the model through selecting the suitable image bands.

Light↗

PubMedDate not supplied

Noninvasive measurement of arterial oxyhemoglobin saturation with a heated and a non-heated skin reflectance pulse oximeter sensor.

The feasibility of measuring arterial oxyhemoglobin saturation (SaO2) noninvasively using a skin reflectance pulse oximeter sensor attached to the scalp, neck, and thigh regions of anesthetized swine was investigated. The optical reflectance sensor used consisted of a pair of red and infrared light-emitting diodes and a concentric array of six identical photodiodes. Two prototype sensor assemblies were evaluated: one assembly housed only the optical sensor, whereas the other also included a miniature heater. Measurements made from the scalp and neck regions were obtained with the non-heated skin reflectance sensor, and measurements from the thigh were made with the heated prototype. Each sensor was interfaced to a commercial transmittance pulse oximeter adapted to perform as a reflectance pulse oximeter. SaO2 values obtained by the reflectance pulse oximeters (SpO2(r) were compared simultaneously with SaO2 values obtained from arterial blood samples and analyzed in vitro with a CO-oximeter. The equations for the best-fitted linear regression lines describing the relationships between SpO2(r) and SaO2 values in the range between 30 and 100% were: SpO2(r) = 10.7 + 0.90 (SaO2), n = 321, r = 0.97; SpO2(r) = 16.72 + 0.82 (SaO2), n = 217, r = 0.95; and SpO2(r) = 20.21 + 0.77 (SaO2), n = 37, r = 0.97 for the neck, thigh, and scalp measurements, respectively. The regression analysis revealed significant correlation and a relatively small standard error of estimate (SEE = 4.05% for the neck, 4.79% for the thigh, and 3.50% for the scalp measurements). This study demonstrated the feasibility of measuring SaO2 noninvasively over a wide range of values utilizing the principle of reflectance pulse oximetry.

Animals↗