Changes In Light Absorption Research Articles

Comparison of Optical Rhinometry and Active Anterior Rhinomanometry Using Nasal Provocation Testing

To investigate whether there is a correlation between active anterior rhinomanometry (RMM) and optical rhinometry (ORM) data in the detection of changes in nasal congestion. In 70 subjects both ORM and RMM were performed. Changes in nasal congestion were induced by nasal provocation with histamine, allergens, solvent, and xylometazoline hydrochloride, 0.1%. Using visual analog scales, subjects rated the degree of nasal congestion and how comfortable each of the 2 measures was. In total, 136 measurements were evaluated. Seventy subjects were included in the study. All had a normal otorhinolaryngologic status with no acute or chronic infections. Nasal provocation tests with allergens, histamine, control solution, or xylometazoline were performed. Congestion or decongestion of the nasal mucosa was measured via nasal resistance (RMM), changes in light absorption of the nasal tissue (ORM), and visual analog scale. When comparing the relative change in light extinction in ORM with nasal airflow in RMM, we found correlation coefficients up to r = -0.69. Results from RMM were correlated with the subjects' ratings of nasal congestion (r = -0.63). In comparison, the correlation coefficient between these ratings and ORM was r = 0.84. In addition, ORM was rated to be more comfortable than RMM. The subjects' ratings of nasal congestion correlated to a higher degree with the results from ORM than with those from RMM. In addition, ORM was rated as more comfortable than RMM. Overall, ORM appeared to be a valid technique for the assessment of changes in nasal congestion.

Laser-Induced Transient Grating Analysis of Dynamics of Interaction between Sensory Rhodopsin II D75N and the HtrII Transducer

The interaction between sensory rhodopsin II (SRII) and its transducer HtrII was studied by the time-resolved laser-induced transient grating method using the D75N mutant of SRII, which exhibits minimal visible light absorption changes during its photocycle, but mediates normal phototaxis responses. Flash-induced transient absorption spectra of transducer-free D75N and D75N joined to 120 amino-acid residues of the N-terminal part of the SRII transducer protein HtrII (ΔHtrII) showed only one spectrally distinct K-like intermediate in their photocycles, but the transient grating method resolved four intermediates ( K 1– K 4) distinct in their volumes. D75N bound to HtrII exhibited one additional slower kinetic species, which persists after complete recovery of the initial state as assessed by absorption changes in the UV-visible region. The kinetics indicate a conformationally changed form of the transducer portion (designated Tr*), which persists after the photoreceptor returns to the unphotolyzed state. The largest conformational change in the ΔHtrII portion was found to cause a ΔHtrII-dependent increase in volume rising in 8 μs in the K 4 state and a drastic decrease in the diffusion coefficient ( D) of K 4 relatively to those of the unphotolyzed state and Tr*. The magnitude of the decrease in D indicates a large structural change, presumably in the solvent-exposed HAMP domain of ΔHtrII, where rearrangement of interacting molecules in the solvent would substantially change friction between the protein and the solvent.

Synthesis and characterization of nanocrystalline NaTaO 3

Tantalum pentoxide reacts actively with concentrated NaOH solution under hydrothermal conditions at 180 °C. In the reaction between NaOH solution and Ta 2O 5, the structure and composition of the tantalates depend on the reaction time, and the structure evolution results in a remarkable change in light absorption. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) diffused reflection spectrum were used to characterize various properties of the obtained solid products. At 180 °C, the reaction proceeds rapidly. With the increase of time, the reflection peaks of unreacted Ta 2O 5 in the XRD patterns becomes weaker and weaker. Pure NaTaO 3 is obtained after 60 min, which is well crystallized with a uniform cubic morphology.

Relevance of depth resolution for cerebral blood flow monitoring by near-infrared spectroscopic bolus tracking during cardiopulmonary bypass

Noninvasive near-infrared spectroscopy (NIRS) is increasingly used to monitor cerebral oxygenation and blood flow status, which is also of high relevance during cardiovascular surgical interventions with cardiopulmonary bypass. Contamination of the cerebral signal by contamination from overlaying extracerebral tissue, however, has been proposed to reduce sensitivity and cerebral selectivity of this promising technique. We evaluated a novel depth-resolved approach for the determination of cerebral hemodynamics by near-infrared spectroscopic tracking of intravenously administered indocyanine green boluses. A frequency domain technique was applied, allowing simultaneous determination of light absorption changes and time of flight of single photons and enabling the differentiation between extracerebral and intracerebral tracer kinetics. Depth-resolved near-infrared spectroscopy was tested in 4 patients undergoing cardiopulmonary bypass and compared with data derived by conventional continuous-wave near-infrared spectroscopy. Depth resolution extracted the differential responses of extracerebral and intracerebral blood vessels from near-infrared bolus tracking signals. Postoperative blood flow indices derived from the intracerebral time course exceeded preoperative values by 1.5 +/- 0.2 times, indicating a significant increase of cerebral blood flow not detectable by conventional near-infrared spectroscopy. The depth-resolved approach provides additional and relevant data for the interpretation of intraoperative cerebral perfusion during cardiothoracic surgery. The validity of this approach for patients with preexisting risk factors for cerebral hypoperfusion remains to be determined in larger clinical trials.

Down co-regulation of light absorption, photochemistry, and carboxylation in Fe-deficient plants growing in different environments

The regulation of photosynthesis through changes in light absorption, photochemistry, and carboxylation efficiency has been studied in plants grown in different environments. Iron deficiency was induced in sugar beet (Beta vulgaris L.) by growing plants hydroponically in controlled growth chambers in the absence of Fe in the nutrient solution. Pear (Pyrus communis L.) and peach (Prunus persica L. Batsch) trees were grown in field conditions on calcareous soils, in orchards with Fe deficiency-chlorosis. Gas exchange parameters were measured in situ with actual ambient conditions. Iron deficiency decreased photosynthetic and transpiration rates, instantaneous transpiration efficiencies and stomatal conductances, and increased sub-stomatal CO(2) concentrations in the three species investigated. Photosynthesis versus CO(2) sub-stomatal concentration response curves and chlorophyll fluorescence quenching analysis revealed a non-stomatal limitation of photosynthetic rates under Fe deficiency in the three species investigated. Light absorption, photosystem II, and Rubisco carboxylation efficiencies were down-regulated in response to Fe deficiency in a coordinated manner, optimizing the use of the remaining photosynthetic pigments, electron transport carriers, and Rubisco.

Visible foliar injury caused by ozone alters the relationship between SPAD meter readings and chlorophyll concentrations in cutleaf coneflower

The ability of the SPAD-502 chlorophyll meter to quantify chlorophyll amounts in ozone-affected leaves of cutleaf coneflower (Rudbeckia laciniata var. digitata) was assessed in this study. When relatively uninjured leaves were measured (percent leaf area affected by stipple less than 6%), SPAD meter readings were linearly related to total chlorophyll with an adjusted R (2) of 0.84. However, when leaves with foliar injury (characterized as a purple to brownish stipple on the upper leaf surface affecting more than 6% of the leaf area) were added, likelihood ratio tests showed that it was no longer possible to use the same equation to obtain chlorophyll estimations for both classes of leaves. Either an equation with a common slope or a common intercept was necessary. We suspect several factors are involved in altering the calibration of the SPAD meter for measuring chlorophyll amounts in visibly ozone-injured leaves, with the most likely being changes in either light absorption or scattering resulting from tissue necrosis.

Pyrrolidine-Containing Polypyridines: New Ligands for Improved Visible Light Absorption by Ruthenium Complexes

[reaction: see text] A range of new electron-releasing pyrrolidine-containing bipyridines and terpyridines has been prepared via selective metalation-cross-coupling sequences. The obtained ligands have been involved in microwave-assisted ruthenium complexation leading to homoleptic complexes in high yield. The electron-donor effect of the pyrrolidine nucleus led to a notable improvement of visible light absorption and strong changes in the electrochemical behavior, opening new opportunities for the design of photovoltaic devices.

Magnetorefractive cell on basis of the Salisbury screen

Recently, it has been shown that the magnetorefractive effect (MRE) can be significantly enhanced if a layer of material exhibiting MRE is placed inside a photonic crystal to form a defect mode. We propose to use for the MRE enhancement the Salisbury screen as a competitive and much more simple scheme. Since MRE is mostly due to a change of light absorption under magnetization the three-layer Salisbury structure optimized for highest possible absorption inside magnetic layer provides MRE at least two orders of magnitude greater than that for single layer and of the same value or even greater than that for 37-layer photonic crystal.

A simple empirical optical model for simulating light attenuation variability in a partially mixed estuary

Representation of the subsurface light field is a crucial component of pelagic ecosystem and water quality models. Modeling the light field in estuaries is a particularly complicated problem due to the significant influence of high concentrations of dissolved and particulate matter that are derived from both terrestrial and estuarine sources. The goal of this study was to develop a relatively simple but effective way to model light attenuation variability in a turbuid estuary (Chesapeake Bay, United States) in a coupled physical-biological model. We adopted a simple, nonspectral empirical approach. Surface water quality data (salinity was used as a proxy of chromophoric dissolved organic matter [CDOM]) and light measurements from the Chesapeake Bay Program were used to determine the absorption coefficients in a linear attenuation model using regression methods. This model predicts Kc (specific attenuation due to phytoplankton/chlorophylla [chla]), Kt (specific attenuation due to total suspended solids), and Ks (a function of specific attenuation coefficients of CDOM in relation to salinity). The Bay-wide fitted relation between the light attenuation coefficient and water quality concentrations gives generally good estimates of total light attenuation, Kd. The direct inclusion of salinity in the relationship has one disadvantage: it can yield negative values for Kd at high salinities. We developed two separate models for two different salinity regimes. This approach, in addition to solving the negative Kd problem, also accounts for some changes in specific light absorption by chla, seston (nonphytoplankton particulate matter), and CDOM that apparently occur in different salinity regimes in Chesapeake Bay. The resulting model predicts the statistical characteristics (i.e., the mean and variance) of Kd quite accurately in most regions of Chesapeake Bay. We also discuss in this paper the feasibility and caveats of using Kd converted from Secchi depth in the empirical method.

Spectrophotometric measurement of swelling of polymer films by very poor solvents

AbstractSolvent swelling of polymers is important for many applications, but can be difficult to measure when thin films or very poor solvents are involved. A novel spectrophotometric method is presented that is well suited for measuring swelling of thick or thin polymer films by very poor solvents. In this method, the solvent is stained with iodine, and solvent uptake is measured by observing the change in visible light absorption of the polymer using a spectrophotometer. Using this method, swelling can be accurately measured in thin (< 2 μm) polymer films and with poor solvents that cause little swelling, even water. Results are presented for PMMA films of varying molecular weights swelled by water, by water–alcohol mixtures, and by undiluted alcohols. Swelling of these films is more rapid and more Fickian than has been reported for bulk samples, probably due to differences in PMMA molecular weight and processing. The properties of the iodine–PMMA complex are also explored. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1082–1089, 2005

Supramolecular Optical Chemosensors for Organic Analytes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Molecular Adsorption‐Mediated Control over the Electrical Characteristics of Polycrystalline CdTe/CdS Solar Cells

The effect of surface treatments on p-CdTe/n-CdS solar cell performance was examined. Adsorption of organic molecules with various magnitudes and directions of the dipole moment on p-CdTe resulted in controlled changes in electron affinity and surface bond bending. Similar adsorption on CdTe in state-of-the-art p-CdTe/n-CdS solar cells changes the cell performance, and we explain this by a combination of increased series resistance and changes in light absorption and in cell photovoltage. While at this stage no improvement in performance has been found with these cell structures, which are the result of years of empirical optimization, the molecular effect on the photovoltage shows that it is possible in this way to control the photovoltaic effect at this junction. Separate optimization may well lead to improvement by inserting a dipole layer near the photovoltaic interface. Our results also show that this is even possible when dipole adsorption is performed on the complete polycrystalline thin-film cell.

Supramolecular optical chemosensors for organic analytes

Supramolecular optical chemosensors are abiotic molecular devices that bind analytes by noncovalent interactions, producing a change in light absorption or fluorescence. This review summarizes recent progress in the development of such chemosensors for organic analytes based on artificial receptors. Important design considerations, such as analyte affinity, choice of chromophore or fluorophore, binding selectivity, and optical signaling mechanism are briefly discussed. Chemists have fashioned chemosensors from a wide range of molecular structures, including polyalcohols, crown ethers, calixarenes, helicenes, sterically geared tripods, metal complexes, pinwheels, porphyrins, and fused-ring heterocycles. Analytes of interest include amines, carboxylic acids, amino acids, hydroquinones, alkaloids, carbohydrates, peptides, urea and creatinine.

Biosensing based on light absorption of nanoscaled gold and silver particles.

The absorption spectrum of noble metal spherical nanoparticles is known to be strongly influenced by the dielectric constant of the surrounding material, and as such, these particles are well suited for biosensing applications. To perform biosensing using nanoparticles on a substrate, the metal particles are covalently attached onto quartz using an organic adhesion layer of mercaptosilanes. The particles in solution are characterized by UV-vis spectroscopy and transmission electron microscopy, while those attached to the quartz are characterized with UV-vis spectroscopy and atomic force microscopy. Antibodies are attached to the metal nanoparticles, and the antigen recognition is monitored via the change of light absorption when this binding event occurs. Not only is the absorbance originating from plasmon resonances of the particles influenced by the dielectric properties of molecules attached to the nanospheres but also the interband absorption of the particles changes, which will be demonstrated in this report. A light absorption change is detected when a molecular recognition occurs between the bioreceptor molecules attached to the nanoparticle and a biomolecular counterpart. This change in absorption can be very large when adhered molecules are at resonance (interband transitions). In addition, the presented type of biosensing can be a cost-effective and easy to use alternative to conventional biosensing techniques.

Effects of corticotropin-releasing factor on plasticity of optically recorded neuronal activity in the substantia gelatinosa of rat spinal cord slices

We examined the effects of corticotropin-releasing factor (CRF) on plasticity of optically recorded neuronal activity in the substantia gelatinosa (lamina II) of 12–18-day-old rat spinal cord slices stained with a voltage-sensitive dye. Single-pulse test stimulation to the dorsal root that activated A and C fibres evoked prolonged (>100 ms) light-absorption change in the lamina II. This response represents the gross membrane potential change of all elements along the slice depth. After conditioning high-frequency stimulation of A-fibre-activating strength, test stimulus elicited less neuronal activity [−27±1% (7), (average±SE ( n)), P<0.01 (*) at 45–60 min after conditioning]. When CRF (1 μM, 10 min) was applied during conditioning, the neuronal activity was facilitated rather than suppressed [+20±3% (5), P<0.05]. CRF alone exhibited insignificant effect [−5±1% (4), P=0.2]. In the presence of the inhibitory amino acid antagonists bicuculline (1 μM) and strychnine (0.3 μM) in the perfusate, in contrast, the conditioning facilitated it [+27±1% (12)*], and CRF treatment during conditioning inhibited the facilitation dose-dependently [0.1 μM: +18±2% (5)*, 1 μM: +13±1% (7)*]. Although interneuronal actions might contribute, these results suggest that CRF may have dual effects on excitatory synaptic transmission within the lamina II depending upon cellular conditions: a conversion from the induction of long-term depression to long-term potentiation (LTP), and inhibition of LTP induction. Since the LTP is thought to be responsible at least in part for the persistent pain, CRF could regulate the induction.

Detection of Karenia mikimotoi by spectral absorption signatures

This study investigated the performance of a spectral similarity index and a multivariate partial least-squares regression technique for detecting the presence of the gyroxanthin-diester-carrying toxic dinoflagellate Karenia mikimotoi from measurements of spectral light absorption. The methods were applied to fourth-derivative absorption spectra of K. mikimotoi mixed with the toxic dinoflagellate Prorocentrum minimum, which does not contain gyroxanthin-diester. Acclimating the cultures to different light and nutrient conditions allowed us to evaluate the sensitivity of the methods to changes in pigmentation and intracellular light absorption (pigment packaging) of the algae. Both methods were able to determine the fraction of K. mikimotoi and the gyroxanthin-diester concentration. However, whereas the partial least-squares predictions were almost insensitive to the induced variability in optical properties of the algae, predictions based on the similarity index differed significantly depending on the acclimation of the algae. Furthermore, discriminating K. mikimotoi from natural phytoplankton assemblages indicated a significant influence of cell-size composition, through pigment packaging, on the accuracy of the similarity index. Our results suggest that optical discrimination of phytoplankton species from spectral absorption signatures will improve significantly by applying the partial least-squares regression technique.

Polymer Gel Light‐Modulation Materials Imitating Pigment Cells

Novel light‐modulation materials composed of stimuli‐responsive gel particles with an added high concentration of colorants, which can modulate light due to an induced volume phase transition, have been obtained (see Figure). The light‐modulation mechanism and constitution of this material are similar to those of pigment cells existing in cephalopods, and the light absorption change is based on diffusion and aggregation of the colorants.

Multi-sensor fusion for robust computation of breathing rate

Respiratory information can be obtained from the changes in electrical impedance across the chest, the electrocardiogram or the changes in light absorption across the finger. Running estimates of the breathing rate from each of these can be obtained from independent Kalman filters. A robust estimate of breathing rate is derived by fusing the outputs of these independent Kalman filters using a weighting calculated from the squared differences between each prediction from the filters and the corresponding measurements.

A simulation study on the importance of size-related changes in leaf morphology and physiology for carbon gain in an epiphytic bromeliad.

This study addresses the question of how size-related changes in leaf morphology and physiology influence light absorption and carbon gain of the epiphytic bromeliad Vriesea sanguinolenta. A geometrically based computer model, Y-plant, was used for the three-dimensional reconstruction of entire plants and for calculation of whole plant light interception and carbon gain. Plants of different sizes were reconstructed, and morphological and physiological attributes of young and old leaves, and small and large plants were combined to examine the individual effects of each factor on light absorption and carbon gain of the plant. The influence of phyllotaxis on light absorption was also explored. Departure of measured divergence angles between successive leaves from the ideal 137.5 degrees slightly decreased light absorption. The only morphological parameter that consistently changed with plant size was leaf shape: larger plants produced more slender foliage, which substantially reduced self-shading. Nevertheless, self-shading increased with plant size. While the maximum rate of net CO(2) uptake of leaves increased linearly with plant size by a factor of two from the smallest to the largest individual, the potential plant carbon gain (based on total foliage area) showed a curvilinear relationship, but with similar numerical variation. We conclude that leaf physiology has a greater impact on plant carbon gain than leaf and plant morphology in this epiphytic bromeliad.

Temporal cortex activation during speech recognition: an optical topography study

Cortical activity during speech recognition was examined using optical topography (OT), a recently developed non-invasive technique. To assess relative changes in hemoglobin oxygenation, local changes in near-infrared light absorption were measured simultaneously from 44 points in both hemispheres. A dichotic listening paradigm was used in this experiment, in which target stimuli and non-target stimuli were presented to different ears. Subjects were asked to track targets and to press a button when targets shifted from one ear to the other. We compared three tasks: (i) a control task, in which a tone was used as the target; (ii) a repeat task, in which the target was one repeated sentence; (iii) a story task, in which the targets were continuous sentences of a story. The activity for the story task, compared with the repeat task, was localized in the left superior temporal cortex. Relative to the control task, we observed in this region a larger increase in oxyhemoglobin concentration and a decrease in deoxyhemoglobin concentration in the story task than those in the repeat task. These results suggest that the activity in the left temporal association area reflects the load of auditory, memory, and language information processing.