Change In Intensity Ratio Research Articles

Assessment of high precision, high accuracy Inductively Coupled Plasma-Optical Emission Spectroscopy to obtain concentration uncertainties less than 0.2% with variable matrix concentrations

The ability to obtain high precision, high accuracy measurements in samples with complex matrices using High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy (HP-ICP-OES) was investigated. The Common Analyte Internal Standard (CAIS) procedure was incorporated into the High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy method to correct for matrix-induced changes in emission intensity ratios. Matrix matching and standard addition approaches to minimize matrix-induced errors when using High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy were also assessed. The High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy method was tested with synthetic solutions in a variety of matrices, alloy standard reference materials and geological reference materials.

Effects of Sustained Length-Dependent Activation on In Situ Cross-Bridge Dynamics in Rat Hearts

The cellular basis of the length-dependent increases in contractile force in the beating heart has remained unclear. Our aim was to investigate whether length-dependent mediated increases in contractile force are correlated with myosin head proximity to actin filaments, and presumably the number of cross-bridges activated during a contraction. We therefore employed x-ray diffraction analyses of beat-to-beat contractions in spontaneously beating rat hearts under open-chest conditions simultaneous with recordings of left ventricle (LV) pressure-volume. Regional x-ray diffraction patterns were recorded from the anterior LV free wall under steady-state contractions and during acute volume loading (intravenous lactate Ringers infusion at 60 ml/h, <5 min duration) to determine the change in intensity ratio ( I 1,0/ I 1,1) and myosin interfilament spacing ( d 1,0). We found no significant change in end-diastolic (ED) intensity ratio, indicating that the proportion of myosin heads in proximity to actin was unchanged by fiber stretching. Intensity ratio decreased significantly more during the isovolumetric contraction phase during volume loading than under baseline contractions. A significant systolic increase in myosin head proximity to actin filaments correlated with the maximum rate of pressure increase. Hence, a reduction in interfilament spacing at end-diastole (∼0.5 nm) during stretch increased the proportion of cross-bridges activated. Furthermore, our recordings suggest that d 1,0 expansion was inversely related to LV volume but was restricted during contraction and sarcomere shortening to values smaller than the maximum during isovolumetric relaxation. Since ventricular volume, and presumably sarcomere length, was found to be directly related to interfilament spacing, these findings support a role for interfilament spacing in modulating cross-bridge formation and force developed before shortening.

Visualization of maturation of the corpus callosum during childhood and adolescence using T2 relaxometry

Previous studies have shown that maturation of the white matter in terms of its relative signal intensity changes on MRI is almost complete at 2–3 years of age. We hypothesized that quantitative analysis may show maturation of the white matter during childhood and adolescence. In the present study we performed multi-echo T2 relaxometry in 33 healthy subjects (girls, 15; boys, 18) aged 3–15 years. T2 relaxation times of the genu and splenium were measured. In healthy subjects, the T2 relaxation times were significantly correlated with age in both girls (r=0.611, p=.016) and boys (r=0.721, p=.001) in the splenium, but not in the genu (p>.05). To further confirm genu-to-splenium signal intensity ratio changes, a total of 389 brain MRIs were retrospectively selected from the patients who had normal results (189 girls/women, 200 boys/men; age range, 3–20 years). The genu-to-splenium signal intensity ratio was obtained from the T2-weighted images. In patients with normal MRI, the genu-to-splenium signal intensity ratio was significantly decreased with age (p<.001) by 16 years. The T2 relaxation times gradually increase in the splenium during childhood and adolescence, suggestive of maturation.

Microscale enzymatic optical biosensors using mass transport limiting nanofilms. 1. Fabrication and characterization using glucose as a model analyte.

"Smart tattoo" sensors-fluorescent microspheres that can be implanted intradermally and interrogated noninvasively using light-are being developed as potential tools for in vivo biochemical monitoring. In this work, a platform for enzymatic tattoo-type sensors is described and prototype devices evaluated using glucose as a model analyte. Sensor particles were prepared by immobilizing Pt(II) octaethylporphine (PtOEP), a phosphorescent dye readily quenched by molecular oxygen, into hybrid silicate microspheres, followed by loading and subsequent covalent immobilization of glucose oxidase. Rhodamine B-doped multilayer nanofilms were subsequently assembled on the surfaces of the particles to provide a reference signal and provide critical control of glucose transport into the particle. The enzymatic oxidation of glucose within the sensor results in the glucose concentration-dependent depletion of local oxygen levels, enabling indirect monitoring of glucose by measuring relative changes in PtOEP emission. A custom testing apparatus was used to monitor the dynamic sensor response to varying bulk oxygen and glucose levels, respectively. For the prototypes tested, dynamic test results indicate that the sensors respond rapidly (t(95) = 84 s) and reversibly to changes in bulk glucose levels, while demonstrating high baseline stability. The sensitivity (change in intensity ratio) of these devices was determined to be 4.16 +/- 0.57%/mg dL(-1). The analytical range for the prototypes was determined to be 2-120 mg/dl, though this can be extended to cover the physiologically relevant range by tailoring the nanofilm coatings. These findings confirm the potential for enzymatic microscale optical and pave the way for extension of this initial demonstration with glucose to target other biochemical species relevant to metabolic monitoring.

MRI investigation of normal fetal lung maturation using signal intensities on different imaging sequences

To purpose of this paper is to study the relation between normal lung maturation signal and changes in intensity ratios (SIR) and to determine which magnetic resonance imaging sequence provides the strongest correlation of normal lung SIs with gestational age. 126 normal singleton pregnancies (20-37 weeks) were examined with a 1.5 Tesla unit. Mean SIs for lungs, liver, and gastric fluid were assessed on six different sequences, and SIRs of lung/liver (LLSIR) and lung/gastric fluid (LGSIR) were correlated with gestational age for each sequence. To evaluate the feasibility of SIRs in the prediction of the state of the lung maturity, accuracy of the predicted SIRs (D*) was measured by calculating relative residuals (D*-D)/D for each sequence. LLSIRs showed significant changes in every sequence (p<0.05), while LGSIRs only on two sequences. Significant differences were shown for the mean of absolute residuals for both LLSIRs (p<0.001) and for LGSIRs (p=0.003). Relative residuals of LLSIRs were significantly smaller on T1-weighted sequence, whereas they were significantly higher for LGSIRs on FLAIR sequence. Fetal liver seems to be adequate reference for the investigation of lung maturation. T1-weighted sequence was the most accurate for the measurement of the lung SIs; thus, we propose to determine LLSIR on T1-weighted sequence when evaluating lung development.

Structural investigations of aluminum-chromium-nitride hard coatings by Raman micro-spectroscopy

Arc-evaporated aluminum-chromium-nitride (AlxCr1−xN) hard coatings were characterized using Raman micro-spectroscopy. The main Raman bands were assigned to vibrational modes. Changes in Raman intensities were attributed to incorporation of aluminum in the CrN structure and possibly to resonance enhancement. Raman shifts decreased with the Al-content caused by lattice contractions and compressive stress in the coatings. Transition from phases with dominating cubic to dominating hexagonal structure at x>0.71 was indicated by downshift of all modes and changes in relative intensity ratios. Increased intensity of the transversal acoustic mode at 633 nm excitation was potentially caused by resonance enhancement. Phase content and structure were found to be substrate independent down to 0.5 μm below the coating surface. Increasing bias voltages during coating deposition resulted in considerable high residual stress up to several GPa. No preferential orientation of coating crystallites was found in substrate parallel planes.

Glucose Sensors Based on Microcapsules Containing an Orange/Red Competitive Binding Resonance Energy Transfer Assay

Fluorescent sensing systems offer the potential for noninvasive monitoring with implantable devices, but they require carrier technologies that provide suitable immobilization, accessibility, and biocompatibility while maintaining adequate response characteristics. A recent development towards this goal is a highly specific and sensitive competitive binding assay for glucose using apo-glucose oxidase (apo-GOx) as the recognition element and dextran as the competing ligand; this has been demonstrated as a glucose sensor system by encapsulating the competitive binding assay in semipermeable microcapsule carriers. This paper describes the extension of this sensor design to longer wavelengths in an attempt to increase the applicability to in vivo monitoring. The glucose sensitivity of the tetramethylrhodamine isothiocyanate-dextran (TD) and cyanine Cy5-apo-GOx (CAG) complexes showed five to 10 times greater specificity for beta-D-glucose over other sugars. Microcapsules loaded with TD/CAG complexes exhibited a linear, totally reversible response in the range of 0-720 mg/dL, with a sensitivity (percent change in intensity ratio) of 0.06%/(mg/dL). The decrease in sensitivity observed with the use of longer-wavelength dyes is most likely to be compensated with the deeper penetration of light and reduced tissue scattering. These findings imply that the encapsulation of sensing assay elements in microcapsules is a simple and translatable method for the fabrication of stable biosensors, and optimization of resonance energy transfer pairs and assay component preparation will further improve the response to approach clinically relevant performance.

Surface morphology effects on the optical phonon modes in InAsxSb1–x epilayers on GaAs(001)

AbstractWe have studied Raman scattering from longitudinal‐ and transverse‐optical (LO and TO) phonon modes in InAsxSb1–x epilayers grown on GaAs(001) substrates with various arsenic compositions (x). InSb‐like and InAs‐like LO and TO phonon modes of the epilayers are observed. We find that the peak intensity ratio of the InAs‐like LO to TO‐mode decreases for x &lt; 0.6 while it increases for x &gt; 0.6. This intensity ratio change is attributed to two‐ and three‐dimensional (2D and 3D) growth mode of the epilayers using atomic force microscopy. Further, the intensity ratio depends on the root mean square surface roughness of the alloy. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Sum-Frequency Spectroscopy of a Monolayer of Zinc Arachidate at the Solid−Solid Interface

Infrared-visible sum-frequency spectroscopy has been used to record the vibrational spectrum of a zinc arachidate monolayer at the interface between a sapphire prism and a fused silica lens. Spectra have been recorded for the monolayer deposited on the prism before, during, and after contact, and as a function of increasing pressure. Sum-frequency spectra are reported of the monolayer under sliding contact. The monolayer is found to be resistant to pressure- and shear-induced conformational disorder. However, frequency shifts, drops in peak intensities, and changes in peak intensity ratios have been observed as the monolayer is placed in contact between the prism and the lens. Transfer of monolayer material between the two surfaces is observed and is confirmed by spectra obtained with a monolayer deposited on the surface of the lens rather than the prism. On one face of the sapphire prism, the monolayer reconstructs to a low symmetry layer, probably due to epitaxy. The epitaxial structure disappeared in contact. Existing models for calculating sum-frequency spectra have been extended to include unit cells containing two molecules and torsion about the terminal C-C bond. This model can explain some, but not all, of the experimental observations.

Microcapsule Biosensors Using Competitive Binding Resonance Energy Transfer Assays Based on Apoenzymes

This paper reports the first demonstration of a fluorescence resonance energy transfer based glucose sensor, wherein a competitive binding (CB) assay is encapsulated into polyelectrolyte microcapsules. The work supports the concept that microcapsules are superior to hydrogel systems or other matrixes for competitive-binding-based system, as they provide free movement of the sensing elements within the capsule interior while constant total sensing assay concentration is maintained. The transduction approach employed in these preliminary experiments is also a novel CB system based on a model apoenzyme, apo-glucose oxidase (AG), which is highly specific to beta-d-glucose, as the model target-binding protein. The glucose sensitivity of the fluorescein isothiocyanate (FITC)-dextran and tetramethylrhodamine isothiocyanate-AG encapsulated in microcapsules showed 5 times greater specificity for beta-D-glucose over other sugars, with sensitivity (change in intensity ratio) in the range of 2-6%/mM. It was observed that the sensitivity and range of the response can be tailored by controlling the assay concentration using different FITC-dextran molecular weight and total capsule concentration. The findings support the concepts of using microcapsules to encapsulate CB assays for reversible and stable sensors and the use of apoenzymes as specific molecular recognition elements in CB assays. Further, characterization results for microcapsule glucose sensors demonstrate their suitability for monitoring physiological glucose levels.

Immobilization of multi-enzyme microreactors inside microfluidic devices

A simple method to fabricate enzyme-containing microscopic hydrogel structures in microfluidic devices for the potential use in micro total analysis systems (μ-TAS) is described. Poly(ethylene glycol)-based hydrogel microstructures were prepared inside microchannels by photolithography and enzymes conjugated to a pH sensitive fluorophore (SNAFL-1) were incorporated into these hydrogel microstructures. Because of the ratiometric pH-dependent nature of SNAFL fluorescence, hydrogel microstructures exhibited a different emission intensity ratio with pH and this intensity ratio changed almost linearly between pH 7 and 12. When alkaline phosphatase-containing microreactors were exposed to p-nitrophenylphosphate (pNPP) as a substrate, phosphoric acid was produced inside the microstructure by enzymatic-catalyzed hydrolysis of the substrate and subsequently decreased the microenvironment pH. Because of the relatively rapid mass transport of analyte through the hydrogel, enzyme-catalyzed reaction was easily detected by change in emission intensity ratio before and after exposure to substrates. Enzyme-catalyzed reactions were quite fast and reached 90% of maximum value within 10 min. Data were analyzed using a modified Michaelis–Menten equation and apparent Michaelis constants could be obtained. This system was also successfully applied to urea hydrolysis by urease.

Formation and annealing effect for close-packed Ge/Cu(111) layers

Growth and annealing effects of Ge/Cu(111) ultrathin films as deposited at ambient temperature have been studied using Auger electron spectroscopy and low-energy electron diffraction techniques. Ge/Cu(111) system shows a 1×1 structure up to 5 monolayers as deposited at 300 K. The kinetic energy of Cu L3M45M45 Auger electrons shifts to a lower value upon deposition of Ge overlayers. This could be explained by the electric charge transfer between Ge and Cu atoms. From the intensity ratio change of Auger signals (IGe/ICu), significant interdiffusion of Ge/Cu(111) films occurs around 375 K. Owing to the formation of a Cu-rich surface layer, the Cu L3M45M45 peak restores to the initial kinetic energy of a clean Cu(111) surface at 500 K.

Spectroscopic studies of the interaction of ferrous bleomycin with DNA.

Bleomycin is an antibiotic used in cancer chemotherapy for its ability to achieve both single- and double-strand cleavage of DNA through abstraction of the deoxyribose C4'-H. Magnetic circular dichroism (MCD) and X-ray absorption (XAS) spectroscopies have been used to study the interaction of the biologically relevant FeIIBLM complex with DNA. Calf thymus DNA was used as the substrate as well as short oligonucleotides, including one with a preferred 5'-G-pyrimidine-3' cleavage site [d(GGAAGCTTCC)2] and one without [d(GGAAATTTCC)2]. DNA binding to FeIIBLM significantly perturbs the FeII active site, resulting in a change in intensity ratio of the d d transitions and a decrease in excited-state orbital splitting (5Eg). Although this effect is somewhat dependent on length and composition of the oligonucleotide, it is not correlated to the presence of a 5'-G-pyrimidine-3' cleavage site. No effect is observed on the charge-transfer transitions, indicating that the H-bonding recognition between the pyrimidine and guanine base does not perturb Fe-pyrimidine backbonding. Azide binding studies indicate that FeIIBLM bound to either oligomer has the same affinity for N3-. Parallel studies of BLM structural derivatives indicate that FeIIiso-PEPLM, in which the carbamoyl group is shifted on the mannose sugar, forms the same DNA-bound species as FeIIBLM. In contrast, FeIIDP-PEPLM, in which the -aminoalanine group is absent, forms a new species upon DNA binding. These data are consistent with a model in which the primary amine from the -aminoalanine is an FeII ligand and the mannose carbamoyl provides either a ligand to the FeII or significant second-sphere effects on the FeII site; intercalation of the bithiazole tail into the double helix likely brings the metal-bound complex close enough to the DNA to create steric interactions that remove the sugar groups from interaction with the FeII. The fact that the FeII active site is perturbed regardless of DNA sequence is consistent with the fact that cleavage is observed for both 5'-GC-3' and nonspecific oligomers and indicates that different reaction coordinates may be active, depending on orientation of the deoxyribose C4'-H.

Effect of 17β-estradiol on gene expression in lumbar spinal cord following sciatic nerve crush injury in ovariectomized mice

Previously, we observed that estrogen treatment enhances regeneration of the sciatic nerve after crush injury [Brain Res. 943 (2002) 283]. In this research, we studied expression of estrogen receptors and effects of estrogen on gene expression in the lumbar spinal cord, following sciatic nerve crush injury. Using the Atlas Mouse 1.2 Array, changes in the expression of 267 of 1176 genes were registered 4 days after nerve injury. Those genes that exhibited a change in signal intensity ratios of 2-fold or greater were selected as up-regulated (42) or down-regulated (21). In estrogen treated mice, we have observed up-regulation of the genes known to control apoptosis, cell proliferation, and growth, which might account for the positive effects of estrogen on the regeneration of motor neurons. Immunohistochemical staining revealed estrogen receptor-α and estrogen receptor-β localized in the nucleus and cytoplasm of lumbar motor neurons, and in the regenerating neurites of the sciatic nerve. Expression of estrogen receptor-α and estrogen receptor-β mRNA in lumbar spinal cord was shown by traditional RT-PCR. Using real-time quantitative RT-PCR, we demonstrated increased expression of estrogen receptors-α and -β mRNA on the injured side of the lumbar spinal cord. Western blot analysis showed the accumulation of ERs in regenerating sciatic nerve, and revealed a 40% increase of activated ERK1/2 in estrogen treated mice, compared to placebo. Our findings indicate that: (i) axotomized motor neurons increase expression of estrogen receptors-α and -β mRNA, (ii) estrogen mediates the expression of genes which accelerate the growth and maturation of axons, and (iii) estrogen receptors are transported from the perikaryon into regenerating neurites, and estrogen promotes regeneration locally through the non-genomic ERK-activated signaling pathway.

Coalescence during Emulsification: 1. Method Development

A new method of measuring the amount of coalescence that occurs between drops during the emulsification process is proposed. The method uses a hydrophobic fluorescent probe, which is introduced into a fraction of the oil phase that is to be homogenized. The ratio of the intensity of the excimer peak to the intensity of the monomer peak in the fluorescent emission spectrum is sensitive to the concentration of the probe in the oil phase. Random coalescence events between oil drops lead to redistribution of the probe and its effective dilution in the oil phase. Coalescence results in a decrease in the intensity ratio in the fluorescence spectrum obtained from the ensemble of drops. Monte Carlo simulation is used to relate the change in intensity ratio to the coalescence rate. It is experimentally verified that the signal change is only due to coalescence and is not affected by the drop size of the distribution.

Effect of Polarization on Deformation and Fracture of Tetragonal PZT

Four-point bending tests were conducted with smooth specimens of poled and non-poled lead zirconate titanate (PZT) ceramics with a tetragonal structure. The specimens poled in the longitudinal, transverse and short-transverse directions were called PL, PT and PS specimens, respectively. The non-poled specimens were called NP specimens. The true stress-strain relation showed nonlinearity and was different between tension and compression. The nonlinearity of the stress and strain relation resulted from domain switching induced by external loading, and the degree of nonlinearity increased with easiness of domain switching under bending. The fracture strength expressed in terms of the nominal and true stresses followed the Weibull distribution. The shape parameter took a large value around 18 to 22 for PT and PS specimens, while it was the smallest around 7 to 8 for PL specimens. NP specimens took values in between. The mean strength was the largest for NP specimen and was the lowest for PL specimen. Domain switching during loading will relieve local stress concentrations of defects within the material, thus increases the strength and the shape parameter. The change in intensity ratio of the 002 to 200 diffractions can be used to assess the degree of domain switching caused by external straining.

Interactions of Phosphors in Glucose Glasses for Solid-Matrix Phosphorescence

Quenching of the room-temperature solid-matrix phosphorescence (SMP), near-infrared spectrometry, differential scanning calorimetry, and a polarity probe were used to study interactions of heterocyclic aromatic amines in glucose glasses prepared using crystalline glucose and a glucose melt. A near-infrared spectrometry method was developed to determine the wt % moisture in the glucose glasses. The wt % moisture of the glucose glasses was then related to phosphorescence intensities and lifetime ratios of the heterocyclic aromatic amines. A modified form of the Stern–Volmer equation was used to describe the changes in phosphorescence intensity and lifetime ratios. In other experiments, the glass transition temperatures of the glucose glasses were determined using differential scanning calorimetry. The glass transition temperatures were then correlated to the SMP of the heterocyclic aromatic amines in the glucose glasses. Lastly, the micro-environmental polarities of the glucose glasses were studied using a polarity probe. From these results a model was developed that described the effects of several parameters on the glucose glass matrices. For example, water was able to diffuse through channels in the glucose glasses and cause dynamic quenching of the phosphorescence. Also, the hydrogen bonding network in the glucose glasses was disrupted by water. This resulted in matrix quenching of the phosphorescence signals.

Estrogens decrease reperfusion-associated cortical ischemic damage: an MRI analysis in a transient focal ischemia model.

Early identification of irreversible cerebral ischemia is critical in defining strategies that influence neuronal survival after stroke. We used MRI to investigate the effects of 17beta-estradiol (E2) on the temporal evolution of focal ischemia. Female rats were ovariectomized and divided into 1 of 2 groups: ovariectomy alone (OVX; n=4) or ovariectomy with estrogen replacement (OVX+E2; n=3). Both groups were then subjected to 1-hour middle cerebral artery occlusion (MCAO), with the use of a standardized endovascular monofilament model, followed by reperfusion. Sequential diffusion-weighted (DWI) and T2-weighted (T2WI) MRI were obtained during and after the MCAO. In separate groups of animals (n=5 for OVX and OVX+E2), cerebral blood flow (CBF) was measured by laser-Doppler methods before, during, and after occlusion. DWI detected similar lesion characteristics during MCAO in both groups. In the OVX group, lesion size did not change during reperfusion, but the signal intensity ratio increased early and stabilized during the latter stages. In contrast, DWI lesion size decreased during reperfusion in OVX+E2 rats by 50% to 60% (P<0.05), a size reduction almost exclusively limited to cortical regions. During MCAO, the signal intensity ratio in OVX+E2 rats was reduced compared with OVX rats. Reperfusion further attenuated the signal intensity ratio in cortical but not subcortical regions (P<0.05 versus OVX). T2WI revealed no lesions in either group during MCAO, but it detected lesion sizes similar to that of DWI during reperfusion. Furthermore, similar patterns and magnitudes of estrogen treatment-related decrease in lesion size were noted after reperfusion. T2WI demonstrated less intense signal intensity ratio changes in both groups compared with DWI. There were no differences in CBF between groups either during occlusion, early reperfusion, or 1 day after reperfusion. This study strongly suggests that estrogens selectively protect cortical tissue from ischemic damage during MCAO and that this protection is exerted during both the occlusion and reperfusion phases of ischemia and does not involve an estrogen-related change in CBF.

Deformation and Fracture of Piezoelectric Ceramics(Student Poster Session)

The true stress-strain relation calculated from the relations of load against tensile and compressive surface strains under the Bernoulli's assumption of deformation of beam show nonlinearity and is different between tension and compression. The nonlinearity of the stress and strain relation comes from domain switching induced by external loading. The degree of nonlinearity increased with the easiness of domain switching in bent specimens. The fracture strength in terms of the nominal and true stresses follows the Weibull distribution. The shape parameter takes a large value around, 18 to 22, for PT and PS specimens, while it is the smallest, 7 to 8, for PL specimens. NP specimens take a value in between. The mean strength is the largest for NP specimen and is the lowest for PL specimen. Domain switching during loading will relive local stress concentrations of defects within the material, thus increase the strength and the shape parameter. The change in intensity ratio of the 002 to 200 diffractions can be used to assess the degree of domain switching caused by external straining.

Change in the Orientational Distribution of Non-Isomerizing Diphenyldiacetylene Chromophores in LB-Films

LB-films of an amphiphile containing diphenyldiacetylene moieties as chromophore have been prepared. Compared to the solution the LB-films show a different intensity ratio between the two diacetylene bands in the UV/Vis spectrum due to the dense packing of the chromophores. Irradiation with polarized light at 360 nm causes an angle dependent increase in the absorbance in the π-band region, which previously has been interpreted to be due to a photoreorientation process. However, a decrease of the π′-band in the UV/Vis spectra and the C≡C vibration band in the grazing angle reflectance IR-spectra indicate a photoreaction of the chromophores, which nature remains elusive. The increase in absorbance in the π-band region is conjectured to be to partial reversal of the intensity ratio changes due to a less dense packing of intact chromophores. From experiments, in which the irradiated LB-film is dissolved, the amount of reacted chromophores can be estimated to less than 20%.