Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “dynamic range”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed1994

Comparative analysis of spectro-temporal receptive fields, reverse correlation functions, and frequency tuning curves of auditory-nerve fibers.

The tuning properties of single auditory-nerve fibers (ANFs) are characterized with spectro-temporal receptive fields (STRFs), reverse correlation functions (revcors), and frequency tuning curves (FTCs). Measures of tuning and latency from the STRFs and revcors are largely comparable to the traditional measures of tuning from FTCs and measures of latency from peristimulus time histograms (PSTHs), but several important differences are found. As is well known, revcors can only characterize low (< 6 kHz) best frequency (BF) units, whereas STRFs are able to characterize all units studied (BFs ranging from 0.26-23 kHz), except for a few very low-BF examples. Whereas tuning bandwidth derived from revcor exceeds that measured from FTCs at all BFs and increases with sound level. STRF bandwidth is comparable to FTC bandwidth, except at low BFs, and is stable with sound level. The STRF may reflect nonlinear properties of auditory-nerve fibers such as refractoriness and two-tone suppression that are absent in the FTC and revcor characterizations. The principal drawback of the STRF is its narrow dynamic range.

Animals↗
PubMed2000

Background-free, high sensitivity staining of proteins in one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gels using a luminescent ruthenium complex.

SYPRO Ruby dye is a permanent stain comprised of ruthenium as part of an organic complex that interacts noncovalently with proteins. SYPRO Ruby Protein Gel Stain provides a sensitive, gentle, fluorescence-based method for detecting proteins in one-dimensional and two-dimensional sodium dodecyl sulfate-polyacrylamide gels. Proteins are fixed, stained from 3h to overnight and then rinsed in deionized water or dilute methanol/acetic acid solution for 30 min. The stain can be visualized using a wide range of excitation sources commonly used in image analysis systems including a 302 nm UV-B transilluminator, 473 nm second harmonic generation (SHG) laser, 488 nm argon-ion laser, 532 nm yttrium-aluminum-garnet (YAG) laser, xenon arc lamp, blue fluorescent light bulb or blue light-emitting diode (LED). The sensitivity of SYPRO Ruby Protein Gel Stain is superior to colloidal Coomassie Brilliant Blue (CBB) stain or monobromobimane labeling and comparable with the highest sensitivity silver or zinc-imidazole staining procedures available. The linear dynamic range of SYPRO Ruby Protein Gel stain extends over three orders of magnitude, which is vastly superior to silver, zinc-imidazole, monobromobimane and CBB stain. The fluorescent stain does not contain superfluous chemicals (formaldehyde, glutaraldehyde, Tween-20) that frequently interfere with peptide identification in mass spectrometry. While peptide mass profiles are severely altered in protein samples prelabeled with monobromobimane, successful identification of proteins by peptide mass profiling using matrix-assisted laser desorption/ionization mass spectrometry was easily performed after protein detection with SYPRO Ruby Protein Gel stain.

Dextrans↗
PubMed1999

A luminescent ruthenium complex for ultrasensitive detection of proteins immobilized on membrane supports.

SYPRO Ruby protein blot stain provides a sensitive, gentle, fluorescence-based method for detecting proteins on nitrocellulose or polyvinylidene difluoride (PVDF) membranes. SYPRO Ruby dye is a permanent stain composed of ruthenium as part of an organic complex that interacts noncovalently with proteins. Stained proteins can be excited by ultraviolet light of about 302 nm or with visible light of about 470 nm. Fluorescence emission of the dye is approximately 618 nm. The stain can be visualized using a wide range of excitation sources utilized in image analysis systems including a UV-B transilluminator, 488-nm argon-ion laser, 532-nm yttrium-aluminum-garnet (YAG) laser, blue fluorescent light bulb, or blue light-emitting diode (LED). The detection sensitivity of SYPRO Ruby protein blot stain (0.25-1 ng protein/mm(2)) is superior to that of amido black, Coomassie blue, and india ink staining and nearly matches colloidal gold staining. SYPRO Ruby protein blot stain visualizes proteins more rapidly than colloidal gold stain and the linear dynamic range is more extensive. Unlike colloidal gold stain, SYPRO Ruby protein blot stain is fully compatible with subsequent biochemical applications including colorimetric and chemiluminescent immunoblotting, Edman-based sequencing and mass spectrometry.

Collodion↗
PubMed2002

Pediatric high KV/filtered airway radiographs: comparison of CR and film-screen systems.

The imaging of pediatric airways presents a challenge because of the superimposition of the airway over the bone of the spine on the AP view. In recent years, some radiology departments have replaced conventional X-ray films by computed radiography (CR). The effect of the various changes upon image quality and radiation doses has not been clearly demonstrated. The goal of this paper was to investigate and identify potential improvements and/or degradations to pediatric airways imaging from the application of new technology, in particular to high KV/filtered radiographs; a new filter was designed. Two modern film-screen combinations and a CR system were evaluated for a range of tube potentials from 60 to 140 kVp. The spatial resolutions were measured for different geometrical magnifications. Relative radiation doses were also determined. Clinical airway images of children taken with the different imaging methods were subjectively compared. Our study confirmed that the visualization of the pediatric airways is enhanced by using high X-ray tube potentials with proper X-ray beam filtration. For CR systems, the selection of the cassette size, cassette type, focal spot, and geometrical magnification impact upon the image quality. Despite the increased dynamic range and image processing advantage with CR systems, CR techniques need to be improved to be more comparable with high kVp filtered magnification radiographs using film screens and small X-ray tube focal spots. With appropriate X-ray beam filtration and high kVp's, CR image receptors can provide adequate image quality for pediatric airway imaging. However, the transition to digital radiography involves certain caveats. In general, radiation doses with CR systems are greater than typical doses with film-screen systems.

Child↗
PubMed2003

Structural behavior of nanometric carbohydrate films transduced by a resonant technique.

New optical nanoresonance effects enabled us to study the effect of ions on nanometric carbohydrate thin layers on chips. Immobilization was done via spin coating of the derivatized carbohydrate polymer at a metallized chip surface forming ultrathin films (about 50-300 nm thick) followed by photochemical cross-linking. Deposition of metal-nanoclusters, synthesized by chemical means and sputter coating on top of the polymer, induced an optical resonance effect, which transduced changes of polymer structure quantitatively into an optical signal that can be observed directly as resonance shift of a narrow optical peak. The response of the sensor chip even visible to the eye was quantified spectroscopically in the visible and ir range of the spectrum. The lifetime of thin film was good, and thus application as a sensor was limited only by the mechanical stability of the reactive matrix, but not by photobleaching or molecular leakage. Due to the inherent hydrophilic nature of the alginate polymer, the response time of this new sensor is governed by simple aqueous diffusion of the ionic calcium for up to 300 nm completed within less than one second. Monitoring of calcium fluctuations in a high background of magnesium and even serum was demonstrated with a dynamic range optimal for physiological measurements and a linear response up to 5 mM. Surface and alignment of polymer chain were influenced by the nanostructure of the supporting metal film-contrary to alginic acid, chitosan was deposited well aligned to the nanocrystals of the support.

Absorption↗
PubMed2003

On-line monitoring of solutes in dialysate using wavelength-dependent absorption of ultraviolet radiation.

The aim of the study was to assess the wavelength dependence of the UV absorbance during monitoring of different compounds in the dialysate. UV absorbance was determined by using a double-beam spectrophotometer on dialysate samples taken at pre-determined times during dialysis, over a wavelength range of 180-380 nm. Concentrations of several removed substances, such as urea, creatinine, uric acid, phosphate and beta2-microglobulin, were determined in the blood and in the spent dialysate samples using standard laboratory techniques. Millimolar extinction coefficients, for urea, creatinine, monosodium phosphate and uric acid were determined during laboratory bench experiments. The correlation between UV absorbance and substances both in the dialysate and in the blood was calculated at all wavelengths. A time-dependent UV absorbance was determined on the collected dialysate samples from a single dialysis session over a wavelength range of 200-330 nm. The highest contribution from observed compounds relative to the mean value of the absorbance was found around 300 nm and was approximately 70%. The main contribution to the total absorbance from uric acid was confirmed at this wavelength. The highest correlation for uric acid, creatinine and urea was obtained at wavelengths from 280 nm to 320 nm, both in the spent dialysate and in the blood. The wavelength region with the highest correlation for phosphate and beta2-microglobulin, with a suitable UV-absorbance dynamic range, was from 300 to 330 nm. In the wavelength range of 220-270 nm the highest absorbance sensitivity for the observed substances was obtained. A suitable wavelength range for instrumental design seems to be around 290-330 nm. The relatively high correlation between UV absorbance and the substances in the spent dialysate and in the blood indicates that the UV-absorbance technique can estimate the removal of several retained solutes known to accumulate in dialysis patients.

Creatinine↗
PubMed1986

[Electric stimulation of a sensory nerve with 70-micrometer electrodes].

Using the device of an implant (Fig. 1) for direct stimulation of the eighth cranial nerve (Zwicker et al., 1986) measurements have been performed after implantation of one electrode in the nervus suralis of the first author. The results show that threshold of sensation is reached at voltage amplitudes of about 600 mV for sinusoidal stimuli almost frequency independent in the range between 100 Hz and 3 kHz (Fig. 2). The impedance of the electrode (Fig. 3) was found to be remarkably smaller compared with values measured by Zollner (1982) in Ringer's solution. No clear relation between threshold value or impedance and active electrode area could be detected. However, there was a clear dependence of the threshold voltage on the angle between the direction of puncture of the electrode and the direction of the nerve. Parallel puncturing resulted in a 13 dB less sensitive threshold in relation to perpendicular puncturing. The practical dynamic range between the threshold of sensation and the threshold of pain was found to be 10 to 12 dB.

Auditory Perception↗
PubMed2005

Time-resolved imaging of the plume dynamics in infrared matrix-assisted laser desorption/ionization with a glycerol matrix.

The dynamics of the expanding material plume after irradiation of a matrix sample with two different infrared (IR) lasers, an Er:YAG laser of ca. 100 ns and an optical parametric oscillator (OPO) laser system of 6 ns pulse duration, were investigated by imaging the plumes with nanosecond time resolution. Both lasers emitted at an identical wavelength of 2.94 microm. Laser exposure parameters were typical for infrared matrix-assisted laser desorption/ionization mass spectrometry (IR-MALDI-MS); glycerol was employed as a liquid matrix to provide a homogeneous sample and reproducible plume formation. A Nd:YAG laser (532 nm; 8 ns) was used as the illumination source and a CMOS camera with a ten-bit dynamic range served for recording of the images. Dark-field as well as scattered light illumination was employed to preferentially image the gaseous and particulate components of the plume, respectively. During the initial phase of its expansion (ca. 1 micros) the plume appears to consist of a continuous cloud of material of varying density. At later times after exposure, individual particles of several micrometers in size dominate the images. For both laser pulse durations material ejection was observed for times as long as 100 micros postexposure. Subtle but distinct differences in the plume dynamics are observed for the two different pulse durations. They are related to a transition between the regimes below and above acoustic confinement. The experimental findings are compared to results obtained in two previous studies by photoacoustic analysis of the desorption process and IR-laser postionization of the plume.

Glycerol↗
PubMed1997

Psychometric functions and temporal integration in electric hearing.

Temporal-integration functions and psychometric functions for detection were obtained in eight users of the Nucleus 22-electrode cochlear implant. Stimuli were 100-Hz, 200-microseconds/phase trains of biphasic pulses with durations ranging from 0.44 to 630.4 ms (1 to 64 pulses). Temporal-integration functions were measured for 21 electrodes. Slopes of these functions were considerably shallower than the 2.5 dB/doubling slopes typically observed in acoustic hearing. They varied widely across subjects and for different electrodes in a given subject, ranging from 0.06 to 1.94 dB/doubling of stimulus pulses, with a mean [standard deviation (s.d.)] value of 0.42 (0.38). Psychometric functions were measured for 11 of the same 21 electrodes. Slopes of psychometric functions also varied across subjects and electrodes, and were 2-20 times steeper than those reported by other investigators for normal-hearing and cochlear-impaired acoustic listeners. Slopes of individual psychometric functions for 1-, 2-, 4-, and 8-pulse stimuli ranged from 0.20 to 1.84 log d'/dB with a mean (s.d.) value of 0.77 (0.45). Psychometric-function slopes did not vary systematically with stimulus duration in most cases. A clear inverse relation between slopes of psychometric functions and slopes of temporal-integration functions was observed. This relation was reasonably well described by a hyperbolic function predicted by the multiple-looks model of temporal integration [Viemeister and Wakefield, J. Acoust. Soc. Am. 90, 858-865 (1991)]. Psychometric-function slopes tended to increase with absolute threshold and were inversely correlated with dynamic range, suggesting that observed differences in psychometric-function slopes across subjects and electrodes may reflect underlying differences in neural survival.

Adult↗
PubMed1999

A chaos-based model for low complexity predictive coding scheme for compression and transmission of electroencephalogram data.

A method for low complexity, low bit rate transmission of EEG (electroencephalogram) data, based on chaotic principles, is presented. The EEG data is assumed to be generated by a non-linear dynamical system of E dimensions. The E dynamical variables are reconstructed from the one-dimensional time series by the process of time-delay embedding. A model of the form X[n + 1] = F(X[n], X[n - 1], ... , X[n - p]) is fitted for the data in the E-dimensional space and this model is used as predictor in the predictive coding scheme for transmission. This model is able to give a reduction of nearly 50% of the dynamic range of the error signal to be transmitted, with a reduced complexity, when compared to the conventionally used linear prediction method. This implies that a reduced bit rate of transmission with a reduced complexity can be obtained. The effects of variation of model parameters on the complexity and bit rate are discussed.

Adult↗
PubMed2005

Reduction of the concentration difference of proteins in biological liquids using a library of combinatorial ligands.

The discovery of polypeptides and proteins with relevance to a particular biological state is complicated by their vast number and concentration range in most biological mixtures. Depletion methodologies are frequently used to remove the most abundant species; however, this removal not only fails significantly to enrich trace proteins, it may also nonspecifically deplete them due to their interactions with the removed high-abundance proteins. Here we report a simple-to-use methodology that reduces the protein concentration range of a complex mixture like whole serum through the simultaneous dilution of high-abundance proteins and the concentration of low-abundance proteins. This methodology utilizes solid-phase ligand libraries of immense diversity, generated by "split, couple, recombine" combinatorial chemistry, that are used for affinity-based binding to the proteins of a given mixture. With a controlled sample-to-ligand ratio it is possible to modulate the relative concentration of proteins such that many peptides or proteins that are undetectable by classical analytical methods become easily accessible. The reduction in the dynamic range of unfractionated serum is specifically described along with treatment of other proteomes such as extracts from Escherichia coli, chicken egg white and cell culture supernatant. Mono- and bi-dimensional electrophoresis (1-DE and 2-DE respectively) and surface-enhanced laser desorption/ionization-mass spectrometry (SELDI-TOF-MS) technology demonstrate the reduction in protein concentration range. Combining this approach with additional fractionation methods further increased the number of detectable species.

Adsorption↗
PubMed1990

Background-induced flicker enhancement in cat retinal horizontal cells. I. Temporal and spectral properties.

1. Dim backgrounds can enhance small-spot flicker responses of cat retinal horizontal cells by a factor of 2 or more. 2. Intracellular marking with horseradish peroxidase (HRP) reveals that this enhancement effect occurs in--but is not necessarily limited to--the cone-connected, A-type horizontal cell. 3. Flicker amplitudes decrease over a frequency range from 3 to 36 Hz of square-wave photic stimulation. There is little evidence of flicker-response enhancement at 3 Hz. Flicker-response enhancement is typically 2-6 times larger at 35 than at 6 Hz. 4. Inspection of flicker waveforms indicates both a scaling-up of response signals with backgrounds and a distortion composed of 2- to 5-ms-latency decrease, expressed primarily within a quick component of OFF-repolarization. 5. Flicker enhancement first increases as a function of background irradiance and then decreases. The increasing limb has the dynamic range and spectral sensitivity of cat rods (507-nm peak). Enhancement is maintained during rod after-effects. The decreasing limb of the background-versus-intensity function results from light adaptation of cat, long-wavelength (red) cones. 6. The flicker responses themselves peak spectrally at approximately 555 nm and reflect only the activity of cat long-wavelength (red) cones, without evidence of intermixing of other photoreceptor mechanisms. 7. Thus within the first synaptic layer of the cat visual system, rod signals interact with the flicker responses of red cones, both increasing cone-signal amplitudes and modifying cone-signal waveforms. 8. The results are closely analogous to "suppressive rod-cone interaction" (SRCI) as described in human psychophysics. 9. An outer-plexiform-layer circuit involving rods, horizontal cells and cones may mediate rod-induced enhancement of cone flicker. This being the case, notions of horizontal-cell feedback interactions with cones may have to be modified and extended. A specific feedback model is elaborated in the companion paper.

Animals↗
PubMed1996

Quantitative long-term imaging of the functional representation of a whisker in rat barrel cortex.

In this study, we implement chronic optical imaging of intrinsic signals in rat barrel cortex and repeatedly quantify the functional representation of a single whisker over time. The success of chronic imaging for more than 1 month enabled an evaluation of the normal dynamic range of this sensory representation. In individual animals for a period of several weeks, we found that: (i) the average spatial extent of the quantified functional representation of whisker C2 is surprisingly large--1.71 mm2 (area at half-height); (ii) the location of the functional representation is consistent; and (iii) there are ongoing but nonsystematic changes in spatiotemporal characteristics such as the size, shape, and response amplitude of the functional representation. These results support a modified description of the functional organization of barrel cortex, where although a precisely located module corresponds to a specific whisker, this module is dynamic, large, and overlaps considerably with the modules of many other whiskers.

Animals↗
PubMedDate not supplied

Detection of deterministic behavior within the tissue injury-induced persistent firing of nociceptive neurons in the dorsal horn of the rat spinal cord.

To unravel the temporal features of the peripheral tissue injury induced persistent nociceptive discharge, single wide dynamic range (WDR) unit activity was recorded extracellularly in lumbar dorsal horn of anesthetized rats and interspike interval (ISI) series were obtained. Subcutaneous (s.c.) bee venom (BV) injection induced persistent discharge of spinal WDR neurons and has been well established to be a good model in evaluation of tissue injury induced pain. By applying a more novel approach, i.e., the unstable periodic orbit (UPO) identification method, we detected a family of significant separate UPOs (period-1, 2 and 3 orbits) within the ISI series of BV-induced nociceptive discharge, but not spontaneous background activity of spinal WDR neuron. Furthermore, temporally dynamic changes of UPOs at lower period-1, 2 and 3 for 4 successive time segments within 1 h time course of WDR unit firing showed temporally dynamic changes, i.e., new orbits with longer ISIs emerged and those with shorter ISIs vanished with time change. By using this method we suggest that BV-induced nociceptive discharge of spinal WDR neuron be a kind of deterministic activity and various UPOs may play some role in temporal coding of sensory information.

Action Potentials↗
PubMed2007

Effects of adaptation in maintaining high sensitivity over a wide range of backgrounds for Escherichia coli chemotaxis.

An allosteric model is developed to study the cooperative kinase response of wild-type (wt) Escherichia coli cells to the chemoattractant MeAsp in different ambient MeAsp concentrations. The model, together with wt dose response data, reveals the underlying mechanism for E. coli's ability to maintain high sensitivity over a wide range of backgrounds. We find: 1), Adaptation tunes the system to the steepest part of the dose response curve, where the sensitivity to a given type of stimulus is amplified by the number of corresponding receptors in the (mixed) functional receptor complex. A lower bound on the number of Tar receptor dimers (Na) in the complex Na>approximately 6 is obtained from the measured sensitivity. 2), Accurate adaptation synchronizes the kinase activities from different (uncoupled) receptor complexes in a single cell and is crucial in maintaining the high Hill coefficient in the (population averaged) kinase response curve. 3), The wide dynamic range of the high sensitivity can be explained in our model by either having a very small ratio between ligand dissociation constants of the inactive and the active receptors C=0.006, Na=6, and a (methylation level independent) dissociation constant for the inactive Tar receptor K=18.2 microM or by having K and/or Na increase with receptor methylation level together with a larger value of C>0.01. Specific experiments are suggested to distinguish these two scenarios. 4), The receptor occupancy in a wt cell should also adapt and exhibit a slow (approximately logarithmic) dependence on the ligand concentration in the adapted state; this general prediction can be tested experimentally to verify/falsify our model.

Adaptation, Physiological↗
PubMed2004

Secondary motions of the knee during weight bearing and non-weight bearing activities.

The objective of this study was to test the hypothesis that during a weight bearing activity such as walking, a dynamic range (envelope of motion) exists in the relationship between the secondary knee motions (anterior-posterior (AP) translation, internal-external (IE) rotation, and abduction-adduction (Ab-Adduction)) and knee flexion angle. In addition differences in the envelope of motion between a weight bearing and non-weight bearing activity were tested. The hypothesis was evaluated by testing for differences (offsets) in secondary displacements at specific knee flexion angles during the walking cycle and seated leg extension (non-weight bearing). Kinematic measurements were obtained using a previously developed point cluster technique to analyze the six-degrees of freedom movement of the knee. During walking, phase plots of the IE rotation and AP translation versus knee flexion demonstrated significant offsets from one phase of the gait cycle to another at the same flexion angle. During the non-weight bearing activity, no significant offset in the secondary movement was found; the knee followed the same pathway of motion during the flexion and extension phase of this activity. The characteristics of the secondary motions during walking indicated that secondary knee movements are caused by the external forces (muscle, inertial and gravitational) that act on the knee during the various phases of the walking cycle. The boundaries of the envelope appear to reflect the characteristics of the passive restraints. The weight bearing secondary motion AP and IE rotation seen during a walking activity demonstrated an envelope of dynamic laxity that could potentially be used to evaluate functional instabilities at the knee.

Adult↗
PubMed2003

Profiling core proteomes of human cell lines by one-dimensional PAGE and liquid chromatography-tandem mass spectrometry.

Protein expression profiles vary considerably between human cell lines and tissues, which is in part a reflection of their specialized roles within an organism. It is of considerable practical use to establish which proteins constitute the primary components of the respective proteomes. When compiled into databases, such information can facilitate the assessment of selectivity and specificity of a wide range of proteomic experiments. Here we describe the major constituents of proteomes of six human immortalized cell lines. By employing a combination of one-dimensional SDS-PAGE and nanocapillary liquid chromatography-tandem mass spectrometry (LC-MS/MS), we identified up to 1785 non-redundant cytoplasmic and nuclear proteins from a single cell line using 50 and 30 microg of total protein from the corresponding fractions. Up to 38 proteins could be identified from a single band in one liquid chromatography-MS/MS experiment. When combined with systematic gridding of gel lanes into 48 slices, a dynamic range for protein identification of approximately 1:2000 can be envisaged for this approach. Identified proteins range from 4-553 kDa in size, cover the pI range between 3.4 and 12.8, and include 255 proteins with predicted transmembrane domains. Repeated analysis of peptides derived from the same gel band showed that the reproducibility of nanocapillary liquid chromatography-MS/MS of such complex mixtures is about 60-70% suggesting that a particular analytical experiment would need to be repeated about three times to arrive at a representative estimate of the set of highly abundant proteins in a given proteome. Given its technical simplicity, sensitivity, and wealth of generated information, we have adopted this experimental approach to characterize every cell line and tissue that is the subject of experimentation in our laboratory. The combined dataset for the six cell lines consists of 2341 non-redundant human proteins and thus constitutes one of the largest collections of human proteomic data published to date.

Cell Line↗
PubMed1990

The Edridge-Green lecture vision at low light levels: role of spatial, temporal and contrast filters.

One of the most impressive features of our vision is the fact that we see with good sensitivity over such a large range of light levels. This process is usually termed light adaptation by which it is meant that the sensitivity of individual neurones within the retina automatically adapts to suit the prevailing lighting conditions. Although this is usually thought about in terms of single neurones, its effectiveness is greatly enhanced by the fact that individual neurones have distinctive properties. The fact that individual neurones can be considered as acting as neural filters along the dimensions of size, time, orientation and contrast means that visual information is distributed across the whole neuronal population which in turn plays an important role in extending our dynamic range. In this paper the distributed nature of visual processing is emphasized and its role in extending the range of light levels over which we can see is highlighted.

Adaptation, Ocular↗