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PubMed1987

Brain mechanism of selective listening reflected by event-related potentials.

Stimulus selection during selective listening on the basis of simple physical stimulus features is reflected by an event-related potential (ERP) component called the processing negativity (PN). PN has been proposed to indicate a matching or comparison process between the physical features of the stimulus and an 'attentional trace,' an actively formed and maintained temporary neuronal representation of the features defining the relevant stimuli. According to this theory, the smaller is the difference between the eliciting stimulus and that represented by the attentional trace, the longer time is the stimulus processed, and thus the larger in amplitude and longer in duration is the PN elicited. The relevant stimuli, perfectly matching with the attentional trace, and therefore eliciting the largest and longest-duration PN, are selected for further processing. In the present study, the relevant and irrelevant stimuli differed in pitch, and the magnitude of this pitch separation was varied between different stimulus blocks. The results support the afore-mentioned matching or comparison hypothesis of selective attention by showing that PN is not elicited only by the relevant stimuli but even by irrelevant stimuli, and further that the latter PN is larger in amplitude and longer in duration the more similar the irrelevant stimuli are to the relevant stimuli. This PN, however, was smaller than that to the relevant stimuli even for very small separations, reflecting high accuracy of the discrimination function of the attentional trace mechanism proposed to underly selective listening. The termination of the PN to the irrelevant stimuli was followed by a positivity which thus partly explained the difference (Nd) between the ERPs to the relevant and irrelevant stimuli.

Adult↗

PubMedDate not supplied

Acoustic versus phonetic representation of speech as reflected by the mismatch negativity event-related potential.

The concept of categorical perception of speech and speech-like sounds has been central to models of speech perception for decades. Event-related potentials (ERPs) provide a neurophysiologic perspective of this important phenomenon. In the present experiment the mismatch negativity (MMN) event-related potential, which is sensitive to fine acoustic differences, was recorded in adults. Of interest was whether the MMN reflects the acoustic or categorical perception of speech. The MMN was elicited by stimulus pairs (along a continuum varying in place of articulation from /da/ to /ga/) which had been identified as the same phoneme /da/ (within category condition) and as different phonemes /da/ and /ga/ (across categories condition). The acoustic differences between these two pairs of stimuli were equivalent. The MMN was observed in all subjects both in the within and across category conditions. Furthermore, the MMN did not differ in latency, amplitude or area within and across categories. That is, the MMN indicated equal discrimination both across and within categories. These results suggest that the MMN appears to reflect the processing of acoustic aspects of the speech stimulus, but not phonetic processing into categories. The MMN appears to be an extremely sensitive electrophysiologic index of minimal acoustic differences in speech stimuli.

Acoustic Stimulation↗

PubMed1992

Evaluation of the use of the reflectance meter by several operators in field screening for diabetes mellitus.

The performance of reflectance meters for measuring blood glucose concentrations was evaluated in other studies previously and was found to be satisfactory. In the present study, we have evaluated the reliability of one brand of such meters (Glucometer II), when used by several operators, for blood glucose measurements during an epidemiological survey. We have compared the results obtained by the meter with those obtained by a standard hospital laboratory procedure for the same samples. A high and statistically significant degree of correlation (r = 0.901) was observed between the two groups of measurements. The linear regression equation was Y = 0.9X + 13.4. We conclude that the Glucometer II is an accurate and practical instrument even when used by several operators in epidemiological surveys provided that adequate training is given to those operators prior to using the instrument. This is important since the use of reflectance meters in epidemiological surveys is becoming increasingly widespread especially in the third world countries.

Adult↗

PubMed1994

Serum 7 alpha-hydroxycholesterol reflects hepatic bile acid synthesis in patients with obstructive jaundice after external biliary drainage.

To examine the hypothesis that serum levels of 7 alpha-hydroxycholesterol reflect bile acid synthesis in the liver, we analyzed serum 7 alpha-hydroxycholesterol and bile acid output in 13 patients with obstructive jaundice after relief of biliary obstruction. Before biliary drainage, the serum level of 7 alpha-hydroxycholesterol was 92 +/- 12 pmol/ml (mean +/- S.E.M.) and was significantly lower than the control value (226 +/- 26 pmol/ml, p < 0.01). After biliary drainage, serum 7 alpha-hydroxycholesterol level and biliary bile acid outputs began to rise in some patients, indicating reversible liver dysfunction. In other patients, serum 7 alpha-hydroxycholesterol levels and bile acid outputs did not increase, suggesting severe or irreversible liver dysfunction. On and after the third day of biliary decompression, serum 7 alpha-hydroxycholesterol levels correlated well with bile acid excretion (p < 0.01, r = 0.93). Other liver function parameters, such as serum bilirubin, serum bile acids, albumin, and bile flow, also revealed significant correlation with serum 7 alpha-hydroxycholesterol levels. We conclude that the serum 7 alpha-hydroxycholesterol level clearly reflects bile acid synthesis in the liver and that it may serve as a useful parameter for the assessment of hepatic functional recovery in patients with obstructive jaundice after biliary drainage.

Aged↗

PubMed1994

Analysis of remote reflection spectroscopy to monitor plant health.

Remote non-contact reflection spectroscopy is examined as a method for detecting stress in Controlled Ecological Life Support System CELSS type crops. Lettuce (Lactuca [correction of Latuca] Sativa L. cv. Waldmans Green) and wheat (Triticum Aestivum L. cv. Yecora Rojo) were grown hydroponically. Copper and zinc treatments provided toxic conditions. Nitrogen, phosphorous, and potassium treatments were used for deficiency conditions. Water stress was also induced in test plants. Reflectance spectra were obtained in the visible and near infrared (400nm to 2600nm) wavebands. Numerous effects of stress conditions can be observed in the collected spectra and this technique appears to have promise as a remote monitor of plant health, but significant research remains to be conducted to realize the promise.

Algorithms↗

PubMed1989

The American dominative medical system as a reflection of social relations in the larger society.

Expanding upon Navarro's analysis of the American biomedical sector, I argue that the phenomenon of medical pluralism has historically and continues to reflect class, racial/ethnic, and gender relations in American society. The evolution of the American medical system is traced from a relatively pluralistic one in the nineteenth century to a dominative one in the twentieth century. While legitimation and even professionalization of various alternative medical systems supports the assertion that the dominance of biomedicine is delegated rather than absolute, these processes reflect the growing accommodation on the part of alternative practitioners to the reductionist disease theory which is compatible with capitalist ideology.

Chiropractic↗

PubMed1995

Locus of control and socioeconomic status: does internal locus of control reflect real resources and opportunities or personal coping abilities?

The present study attempts to provide answers to the following questions: Does locus of control reflect real opportunities and resources such as higher income and education, or internal strengths and coping abilities? Is it locus of control, socioeconomic status or the interaction between these two variables that affects depression level and life satisfaction? Data was obtained from a stratified random sample of 150 Israeli widows, under the age of 54. Multiple regressional analysis was followed by analysis of variance in order to examine the interaction hypothesis. The results, providing no support for the interaction hypothesis, indicate that both locus of control and socioeconomic status are related to depression and life satisfaction independently, and that locus of control reflects more than socioeconomic resources.

Adult↗

PubMed1986

Total internal reflection fluorescence. Measurement of spatial and orientational distributions of fluorophores near planar dielectric interfaces.

The fluorescence collected from a fluorophore which is near a planar interface and is excited by a laser beam that is totally internally reflected at the interface depends on the direction of the absorption and emission transition dipole moments of the fluorophore with respect to the interface, on the distance from the fluorophore to the interface, on the angle of incidence and polarization direction of the exciting beam, and on properties of the collection optics. Expressions are derived for the excitation and subsequent emission and collection of fluorescence from a population of fluorophores near a planar interface. Presented is a general model-independent method of obtaining characteristic parameters of the spatial and orientational distribution of the population of fluorophores, from a measure of the fluorescence collected as a function of the polarization and the incidence angle of the totally internally reflected laser beam. The method is illustrated with several simulation calculations.

Lasers↗

PubMed1991

Combined reflection and transmission ultrasound imaging.

Reflex transmission imaging (RTI) is a method for producing orthographic ultrasound transmission images, which depict focal-plane transmittance, by using a single transducer rather than an opposed transducer pair. RTI can be implemented using modified B-scan equipment, and a bidirectional scan probe. It has the further advantage of enabling simultaneous generation of integrated reflection C-scan (IRCS) images, which depict backscatter from the focal plane, in perfect registration with the transmission images. We describe these methods, demonstrate a new process by which the reflection and transmission images can be combined to produce a new image of superior quality, and demonstrate the applicability of this technique to improved visualization of kidney stones, with potential application to lithotripsy.

Humans↗

PubMed1983

Sharp vibration maximum in the cochlea without wave reflection.

The recently discovered sharp vibration maximum of the basilar membrane at the best frequency is difficult to reconcile with the reflectionless traveling wave that is implied by the empirical data. The apparent paradox is resolved by representing the cochlea as a transmission line and investigating its characteristic impedance. The appropriate differential equation has been derived previously (Zwislocki, J. (1953); J. Acoust. Soc. Am. 25, 986-989). It is valid for both long and short wave lengths found in the cochlea. The investigation reveals that, in the presence of sufficiently short waves prevailing around the vibration maximum, the characteristic impedance remains practically constant, independent of the rapid variation of the impedance of the basilar membrane. Since wave reflection depends on variation of the characteristic impedance, no wave reflection should be expected. The constancy of the characteristic impedance also enhances the vibration maximum.

Basilar Membrane↗

PubMed1993

Voluntary contraction of middle ear muscles: effects on input impedance, energy reflectance and spontaneous otoacoustic emissions.

Two types of measurements were performed on a subject able to voluntarily contract her middle ear muscles (MEM). First, wideband measurements (0-11 kHz) of middle ear input impedance and energy reflectance were obtained when the subject was relaxed and when she contracted her MEM. The changes in impedance observed with voluntary MEM contraction were similar to those reported in the literature for acoustically-elicited MEM contractions. The energy reflectance increased for frequencies below about 4 kHz. Second, the effects of voluntary MEM contraction on the frequencies and levels of spontaneous otoacoustic emissions (SOAEs) were measured and compared to effects evoked by contralateral acoustic stimulation. Effects on SOAEs appear to be a more sensitive indicator of MEM activity than changes in impedance, and the effects due to voluntary MEM contraction were qualitatively similar to those evoked by contralateral acoustic stimulation. These results suggest that in subjects with normally-functioning middle ears, only some effects on otoacoustic emissions caused by contralateral stimuli whose levels are below the contralateral acoustic reflex threshold can be unequivocally attributed to the action of cochlear efferents. The temporal aspects of SOAE frequency shifts caused by voluntary contraction of MEM show that voluntary contraction fatigues rapidly over a time period of tens of seconds.

Acoustic Impedance Tests↗

PubMed1995

Recovery of the compound action potential following prior stimulation: evidence for a slow component that reflects recovery of low spontaneous-rate auditory neurons.

Relkin and Doucet (1991) have shown that recovery of single auditory-nerve neurons from the effects of prior stimulation by a 100 ms pure tone varies with the spontaneous activity of the neuron. Recovery of thresholds for low spontaneous-rate (SR) neurons takes up to 2.0 s, a factor of 10 times greater than the 200 ms required for recovery of high SR neurons. The purpose of this study was to see if the different recovery rates for the two classes of neurons is reflected in recovery of the amplitude of the compound and potential (CAP) recorded in response to a brief probe tone with similar prior stimulation. We present evidence for two components in the recovery of the CAP amplitude, a slow and fast component, that have time courses similar to those for the recovery of responses for single low and high SR neurons, respectively. Thus, we conclude that the recovery of the CAP amplitude does indeed reflect the underlying recovery processes of single auditory-nerve neurons.

Acoustic Stimulation↗

PubMed1992

Real-time measurement of microcirculation of skin by reflectance spectrophotometry.

A reflectance spectrophotometric measurement was developed to analyze the microcirculation of the skin in real time. The relative absorption (RA) spectra were obtained from skin tissue 10 times per second using a spectro-multi-channel-photodetector system. In this system, white light was projected onto the skin of the back of the anesthetized rat and the spectrum of the reflected light between 450 and 643 nm was analyzed. Two absorption peaks at wavelengths of about 540 and 577 nm were observed, corresponding to the absorption peaks in the oxyhemoglobin (HbO2) spectrum. Either phlebotomy or the i.v. injection of norepinephrine (NE) reduced the RA spectrum. Peaks of the reduction in spectrum [(RA spectrum before the treatment) - (RA spectrum after the treatment)] were observed at about 540 and 577 nm. Injection of NE (0.75-48 ng/100 g B.W., i.v.) reduced the RA value at 577 nm dose-dependently, suggesting a decrease in the skin blood flow due to vasoconstriction. In addition, the content of HbO2 and capillary permeation were measured at the same time after the i.v. injection of Evans blue (EB) dye. As indices of HbO2 content and capillary permeation, RA changes at 540 and 610 nm (the latter is an absorption peak in the EB spectrum) were measured in real time, respectively. Both RA values increased dose-dependently after the intradermal injection of histamine (0.3-100 micrograms/site), suggesting the presence of vasodilation and an increase in permeability. The time at which the RA value for HbO2 reached a maximum was shorter than that for EB. These observations suggest that the method described here can detect changes in the HbO2 content and permeation of skin microcirculation at the same time, and in real time.

Animals↗

PubMedDate not supplied

Radical reflection as a theoretical framework in nursing using acquired immunodeficiency syndrome as example.

The purpose of this article is to present a critical theoretical analysis of society's view of the acquired immunodeficiency syndrome (AIDS) epidemic. The method of radical reflection that was developed by Jan Thompson in 1983 is used as the framework of analysis. Through the five steps of Thompson's method (bracketing, historical recovery, critique, dialectical imagination, and negotiation), the dominant societal ideology of AIDS is identified, placed in an historical context, and examined through the process of Habermasian critique. From this knowledge, a more liberating type of social reality can be envisioned, allowing for the forging of a more egalitarian health care system. Radical reflection can be used by both professional and student nurses to explore and evaluate other health issues. Illness must not be approached and thought of outside of and detached from the major problems of society.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Metal-enhanced fluorescence immunoassays using total internal reflection and silver island-coated surfaces.

We present a generic immunoassay platform that uses enhanced total internal reflection fluorescence in the proximity of silver island films (SIFs), a surface coating consisting of metal (silver) particles. This platform is used with a model immunoassay where a protein antigen, rabbit immunoglobulin G, was immobilized on the SIF-coated glass surface. The signal from a fluorescent dye-labeled anti-rabbit antibody binding to the surface antigen was detected; different color dyes have been tested. Close placement of the fluorophore to surface-bound silver nanostructures results in dramatic signal enhancement (up to 40-fold) on the SIFs as compared with the glass slides. Use of the total internal reflection mode of excitation has significant advantages (over classic front-face excitation) for practical assay development. The limited evanescent wave excitation volume makes it possible to minimize the background signal and use the immunoassay with no need for any washing steps.

Antibodies↗

PubMed2005

C-mode real-time tomographic reflection for a matrix array ultrasound sonic flashlight.

RATIONALE AND OBJECTIVES: Real-time tomographic reflection (RTTR) permits in situ visualization of tomographic images so that natural hand-eye coordination can be used directly during invasive procedures. The method uses a half-silvered mirror to merge the visual outer surface of the patient with a simultaneous scan of the patient's interior without requiring a head-mounted display or tracking. A viewpoint-independent virtual image is reflected precisely into its actual location. When applied to ultrasound, we call the resulting RTTR device the sonic flashlight. We previously implemented the sonic flashlight using conventional two-dimensional ultrasound scanners that produce B-mode slices. Real-time three-dimensional (RT3D) ultrasound scanners recently have been developed that permit RTTR to be applied to slices with other orientations, including C-mode (parallel to the face of the transducer). Such slice orientation may offer advantages for image-guided intervention. MATERIALS AND METHODS: Using a prototype scanner developed at Duke University (Durham, NC) with a matrix array that electronically steers an ultrasound beam at high speed in 3D, we implemented a sonic flashlight capable of displaying C-mode images in situ in real time. RESULTS: We present the first images from the C-mode sonic flashlight, showing bones in the hand and the cardiac ventricles. CONCLUSION: The extension of RTTR to matrix array RT3D ultrasound offers the ability to visualize in situ slices other than the conventional B-mode slice, including C-mode slices parallel to the face of the transducer. This orientation may provide a broader target, facilitating certain interventional procedures. Future work is discussed, including display of slices with arbitrary orientation and use of a holographic optical element instead of a mirror.

Calibration↗

PubMed2005

Effects of high intensity resistance training on arterial stiffness and wave reflection in women.

BACKGROUND: Cross-sectional studies reported that chronic resistance training is associated with arterial stiffening in men. These findings are in marked contrast to those found with aerobic exercise and may have important clinical relevance with regard to cardiovascular disease risk. However, the effect of resistance training on arterial stiffness has not been confirmed by interventional studies nor has this relation been investigated in women. METHODS: To determine whether a strength training program increases regional and central arterial stiffness in women, 23 healthy young women (29+/-1 years; mean+/-SD) participated in a high-intensity strength and power training program for 11 weeks. Ten other women (27+/-2 years) served as time controls. RESULTS: In the intervention group, one repetition maximal strength increased 12% to 17% (P<.0001), and leg fat-free mass (via DEXA) increased significantly. Brachial blood pressure (BP) and fasting plasma lipid and lipoprotein concentrations did not change across the 11 weeks. Carotid augmentation index, a measure of arterial wave reflection and arterial stiffness, increased from -8%+/-13% to 1%+/-18% (P<.05), and carotid-femoral pulse wave velocity increased (791+/-88 v 833+/-96 cm/sec; P<.05). There were no changes in femoral-ankle pulse wave velocity, a segmental measure of peripheral arterial stiffness. CONCLUSIONS: We concluded that a high-intensity resistance training program increases arterial stiffness and wave reflection in young healthy women. Our present interventional results are consistent with the previous cross-sectional studies in men in which high-intensity strength training is associated with arterial stiffening.

Absorptiometry, Photon↗

PubMed2005

C-reactive protein is related to arterial wave reflection and stiffness in asymptomatic subjects from the community.

BACKGROUND: Emerging data suggest that C-reactive protein (CRP), a marker of inflammation, is associated with functional properties of arteries. We investigated the relationship of CRP to measures of arterial wave reflection and stiffness (aortic augmentation index [AIX], carotid-femoral pulse wave velocity [PWV], and pulse pressure) in asymptomatic individuals from the community. METHODS: Subjects (n = 214) had a mean age of 59 years and 53% were men. CRP was measured by a high-sensitivity assay and values were log-transformed to reduce skewness. Radial artery waveforms were obtained by applanation tonometry, a validated transfer function was used to derive an ascending aortic pressure waveform, and AIX calculated. PWV was calculated from electrocardiogram-gated waveforms of the right carotid and right femoral artery obtained by applanation tonometry. RESULTS: Log CRP was correlated with AIX (r = 0.24, P = .0005), PWV (r = 0.25, P = .0002), and pulse pressure (r = 0.29, P < or = .0001). In separate backward elimination multiple regression analyses, log CRP was significantly associated with AIX (P = .038) and pulse pressure (P = .036), and marginally significantly associated with PWV (P = .054), after adjustment for heart rate, height, and coronary heart disease (CHD) risk factors (age, sex, body mass index, mean arterial pressure, total cholesterol, HDL cholesterol, diabetes, hypertension, and history of smoking). CONCLUSIONS: These results suggest that CRP, a marker of systemic inflammation, is related to measures of arterial wave reflection and stiffness in asymptomatic subjects from the community. Further studies are needed to understand the mechanisms underlying this association and the implications for assessment and management of CHD risk.

Aged↗