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Sample records for measuring intrinsic fluorescence

  1. Intrinsic photosensitizer fluorescence measured using multi-diameter single-fiber spectroscopy in vivo

    NASA Astrophysics Data System (ADS)

    van Leeuwen-van Zaane, Floor; Gamm, Ute A.; van Driel, Pieter B. A. A.; Snoeks, Thomas J.; de Bruijn, Henriette S.; van der Ploeg-van den Heuvel, Angelique; Sterenborg, Henricus J. C. M.; Löwik, Clemens W.; Amelink, Arjen; Robinson, Dominic J.

    2014-01-01

    Quantification of fluorescence in vivo is complicated by the influence of tissue optical properties on the collected fluorescence signal. When tissue optical properties in the measurement volume are quantified, one can obtain the intrinsic fluorescence, which equals the product of fluorophore absorption coefficient and quantum yield. We applied this method to in vivo single-fiber fluorescence spectroscopy measurements on mouse tongue, skin, liver, and oral squamous cell carcinoma, where we detected intrinsic fluorescence spectra of the photosensitizers chlorin e6 and Bremachlorin at t=[3,4.5,6,24,48] h incubation time. We observed a tissue-dependent maximum of 35% variation in the total correction factor over the visible wavelength range. Significant differences in spectral shape over time between sensitizers were observed. Although the wavelength position of the fluorescence intensity maximum for ce6 shifted to the red, Bremachlorin showed a blue shift. Furthermore, the Bremachlorin peak appeared to be broader than the ce6 fluorescence peak. Intrinsic fluorescence intensity, which can be related to photosensitizer concentration, was decreasing for all time points but showed significantly more Bremachlorin present compared to ce6 at long incubation times. Results from this study can be used to define an optimal treatment protocol for Bremachlorin-based photodynamic therapy.

  2. A bio-aerosol detection technique based on tryptophan intrinsic fluorescence measurement

    NASA Astrophysics Data System (ADS)

    Cai, Shuyao; Zhang, Pei; Zhu, Linglin; Zhao, Yongkai; Huang, Huijie

    2011-12-01

    Based on the measurement of intrinsic fluorescence, a set of bio-aerosol including virus aerosols detection instrument is developed, with which a method of calibration is proposed using tryptophan as the target. The experimental results show a good linear relationship between the fluorescence voltage of the instrument and the concentration of the tryptophan aerosol. An excellent correlation (R2>=0.99) with the sensitivity of 4000PPL is obtained. The research demonstrates the reliability of the bio-aerosol detection by measuring the content of tryptophan. Further more the feasibility of prejudgment to the species of bio-aerosol particles with the multi-channel fluorescence detection technology is discussed.

  3. Simultaneous light scattering and intrinsic fluorescence measurement for the classification of airborne particles.

    PubMed

    Kaye, P H; Barton, J E; Hirst, E; Clark, J M

    2000-07-20

    We describe a prototype laboratory light-scattering instrument that integrates two approaches to airborne particle characterization: spatial light-scattering analysis and intrinsic fluorescence measurement, with the aim of providing an effective means of classifying biological particles within an ambient aerosol. The system uses a single continuous-wave 266-nm ultraviolet laser to generate both the spatial elastic scatter data (from which an assessment of particle size and shape is made) and the particle intrinsic fluorescence data from particles in the approximate size range of 1-10-mum diameter carried in a sample airflow through the laser beam. Preliminary results suggest that this multiparameter measurement approach can provide an effective means of classifying different particle types and can reduce occurrences of false-positive detection of biological aerosols. PMID:18349949

  4. Anisotropy measurements of intrinsic fluorescence of prenyllipids reveal much higher mobility of plastoquinol than alpha-tocopherol in model membranes.

    PubMed

    Jemioła-Rzemińska, Małgorzata; Kruk, Jerzy; Strzałka, Kazimierz

    2003-04-01

    As an alternative to a fluorescent probe approach, the intrinsic fluorescence of reduced forms of prenylquinones has been exploited, which offers a convenient means of determining directly motional properties of these molecules. The steady-state fluorescence anisotropy measurements of plastoquinols (PQH(2)) and alpha-tocopherol (alpha-Toc) incorporated into phospholipid liposomes have been performed. The effect of prenyllipid concentration, PQH(2) side chain length and the composition of the membranes has been studied. For the data interpretation, the fundamental anisotropy of alpha-Toc, PQH(2), ubiquinol-10 and alpha-tocopherolquinol, as well as the angles between the absorption and emission transition moments have been also determined. It was concluded that alpha-Toc shows very low mobility in the lipid bilayer, whereas PQH(2)-9 displays significant motional freedom in dipalmitoylphosphatidylcholine vesicles and even higher in egg yolk lecithin membranes. PMID:12691855

  5. Probing intrinsic anisotropies of fluorescence: Mueller matrix approach.

    PubMed

    Saha, Sudipta; Soni, Jalpa; Chandel, Shubham; Kumar, Uday; Ghosh, Nirmalya

    2015-08-01

    We demonstrate that information on “intrinsic” anisotropies of fluorescence originating from preferential orientation/organization of fluorophore molecules can be probed using a Mueller matrix of fluorescence. For this purpose, we have developed a simplified model to decouple and separately quantify the depolarization property and the intrinsic anisotropy properties of fluorescence from the experimentally measured fluorescence Mueller matrix. Unlike the traditionally defined fluorescence anisotropy parameter, the Mueller matrix-derived fluorescence polarization metrics, namely, fluorescence diattenuation and polarizance parameters, exclusively deal with the intrinsic anisotropies of fluorescence. The utility of these newly derived fluorescence polarimetry parameters is demonstrated on model systems exhibiting multiple polarimetry effects, and an interesting example is illustrated on biomedically important fluorophores, collagen. PMID:26301796

  6. Rapid identification of microorganisms by intrinsic fluorescence

    NASA Astrophysics Data System (ADS)

    Bhatta, Hemant; Goldys, Ewa M.; Learmonth, Robert

    2005-03-01

    Microbial contamination has serious consequences for the industries that use fermentation processes. Common contaminants such as faster growing lactic acid bacteria or wild yeast can rapidly outnumber inoculated culture yeast and produce undesirable end products. Our study focuses on a rapid method of identification of such contaminants based on autofluorescence spectroscopy of bacterial and yeast species. Lactic acid bacteria (Lac-tobacillus casei), and yeast (Saccharomyces cerevisiae) were cultured under controlled conditions and studied for variations in their autofluorescence. We observed spectral differences in the spectral range representative of tryptophan residues of proteins, with excitation at 290 nm and emission scanned in the 300 nm - 440 nm range. Excitation scans between 240 nm and 310 nm were also performed for the emission at 340 nm. Moreover, we observed clearly pronounced differences in the excitation and emission in the visible range, with 410 nm excitation. These results demonstrate that bacterial and yeast species can be differentiated using their intrinsic fluorescence both in UV and in the visible region. The comparative spectroscopic study of selected strains of Saccharomyces yeast showed clear differences between strains. Spectrally-resolved laser scanning microscopy was carried out to link the results obtained using ensembles of cells with spectral properties of individual cells. Strongly fluorescent subpopulation were observed for all yeast strains with excitation at 405 nm. The fluorescence spectra showed variations correlated with cell brightness. The presented results demonstrate that using autofluorescence, it is possible to differentiate between yeast and lactic acid bacteria and between different yeast species.

  7. Characterization and quantification of intact 26S proteasome proteins by real-time measurement of intrinsic fluorescence prior to top-down mass spectrometry.

    PubMed

    Russell, Jason D; Scalf, Mark; Book, Adam J; Ladror, Daniel T; Vierstra, Richard D; Smith, Lloyd M; Coon, Joshua J

    2013-01-01

    Quantification of gas-phase intact protein ions by mass spectrometry (MS) is impeded by highly-variable ionization, ion transmission, and ion detection efficiencies. Therefore, quantification of proteins using MS-associated techniques is almost exclusively done after proteolysis where peptides serve as proxies for estimating protein abundance. Advances in instrumentation, protein separations, and informatics have made large-scale sequencing of intact proteins using top-down proteomics accessible to the proteomics community; yet quantification of proteins using a top-down workflow has largely been unaddressed. Here we describe a label-free approach to determine the abundance of intact proteins separated by nanoflow liquid chromatography prior to MS analysis by using solution-phase measurements of ultraviolet light-induced intrinsic fluorescence (UV-IF). UV-IF is measured directly at the electrospray interface just prior to the capillary exit where proteins containing at least one tryptophan residue are readily detected. UV-IF quantification was demonstrated using commercially available protein standards and provided more accurate and precise protein quantification than MS ion current. We evaluated the parallel use of UV-IF and top-down tandem MS for quantification and identification of protein subunits and associated proteins from an affinity-purified 26S proteasome sample from Arabidopsis thaliana. We identified 26 unique proteins and quantified 13 tryptophan-containing species. Our analyses discovered previously unidentified N-terminal processing of the β6 (PBF1) and β7 (PBG1) subunit - such processing of PBG1 may generate a heretofore unknown additional protease active site upon cleavage. In addition, our approach permitted the unambiguous identification and quantification both isoforms of the proteasome-associated protein DSS1. PMID:23536786

  8. Intrinsic fluorescence of selenium nanoparticles for cellular imaging applications

    NASA Astrophysics Data System (ADS)

    Khalid, A.; Tran, Phong A.; Norello, Romina; Simpson, David A.; O'Connor, Andrea J.; Tomljenovic-Hanic, Snjezana

    2016-02-01

    Nanoparticles hold great potential in contributing to high-resolution bioimaging as well as for biomedical applications. Although, selenium (Se) nanoparticles (NPs) have been investigated owing to their potential roles in therapeutics, the imaging capability of these NPs has never been explored. This manuscript identifies the intrinsic fluorescence of Se NPs, which is highly beneficial for nanoscale imaging of biological structures. The emission of individual NPs and its evolution with time is explored. The photoluminescence spectra has revealed visible to near infrared emission for Se NPs. The work finally reflects on the role of this intrinsic fluorescence for in vitro imaging and tracking in fibroblast cells, without the need of any additional tags. This technique would overcome the limitations of the conventionally used methods of imaging with tagged fluorescent proteins and dyes, preventing possible adverse cellular effects or phototoxicity caused by the added fluorescent moieties.Nanoparticles hold great potential in contributing to high-resolution bioimaging as well as for biomedical applications. Although, selenium (Se) nanoparticles (NPs) have been investigated owing to their potential roles in therapeutics, the imaging capability of these NPs has never been explored. This manuscript identifies the intrinsic fluorescence of Se NPs, which is highly beneficial for nanoscale imaging of biological structures. The emission of individual NPs and its evolution with time is explored. The photoluminescence spectra has revealed visible to near infrared emission for Se NPs. The work finally reflects on the role of this intrinsic fluorescence for in vitro imaging and tracking in fibroblast cells, without the need of any additional tags. This technique would overcome the limitations of the conventionally used methods of imaging with tagged fluorescent proteins and dyes, preventing possible adverse cellular effects or phototoxicity caused by the added fluorescent

  9. Compact point-detection fluorescence spectroscopy system for quantifying intrinsic fluorescence redox ratio in brain cancer diagnostics

    PubMed Central

    Liu, Quan; Grant, Gerald; Li, Jianjun; Zhang, Yan; Hu, Fangyao; Li, Shuqin; Wilson, Christy; Chen, Kui; Bigner, Darell; Vo-Dinh, Tuan

    2011-01-01

    We report the development of a compact point-detection fluorescence spectroscopy system and two data analysis methods to quantify the intrinsic fluorescence redox ratio and diagnose brain cancer in an orthotopic brain tumor rat model. Our system employs one compact cw diode laser (407 nm) to excite two primary endogenous fluorophores, reduced nicotinamide adenine dinucleotide, and flavin adenine dinucleotide. The spectra were first analyzed using a spectral filtering modulation method developed previously to derive the intrinsic fluorescence redox ratio, which has the advantages of insensitivty to optical coupling and rapid data acquisition and analysis. This method represents a convenient and rapid alternative for achieving intrinsic fluorescence-based redox measurements as compared to those complicated model-based methods. It is worth noting that the method can also extract total hemoglobin concentration at the same time but only if the emission path length of fluorescence light, which depends on the illumination and collection geometry of the optical probe, is long enough so that the effect of absorption on fluorescence intensity due to hemoglobin is significant. Then a multivariate method was used to statistically classify normal tissues and tumors. Although the first method offers quantitative tissue metabolism information, the second method provides high overall classification accuracy. The two methods provide complementary capabilities for understanding cancer development and noninvasively diagnosing brain cancer. The results of our study suggest that this portable system can be potentially used to demarcate the elusive boundary between a brain tumor and the surrounding normal tissue during surgical resection. PMID:21456877

  10. Compact point-detection fluorescence spectroscopy system for quantifying intrinsic fluorescence redox ratio in brain cancer diagnostics

    NASA Astrophysics Data System (ADS)

    Liu, Quan; Grant, Gerald; Li, Jianjun; Zhang, Yan; Hu, Fangyao; Li, Shuqin; Wilson, Christy; Chen, Kui; Bigner, Darell; Vo-Dinh, Tuan

    2011-03-01

    We report the development of a compact point-detection fluorescence spectroscopy system and two data analysis methods to quantify the intrinsic fluorescence redox ratio and diagnose brain cancer in an orthotopic brain tumor rat model. Our system employs one compact cw diode laser (407 nm) to excite two primary endogenous fluorophores, reduced nicotinamide adenine dinucleotide, and flavin adenine dinucleotide. The spectra were first analyzed using a spectral filtering modulation method developed previously to derive the intrinsic fluorescence redox ratio, which has the advantages of insensitivty to optical coupling and rapid data acquisition and analysis. This method represents a convenient and rapid alternative for achieving intrinsic fluorescence-based redox measurements as compared to those complicated model-based methods. It is worth noting that the method can also extract total hemoglobin concentration at the same time but only if the emission path length of fluorescence light, which depends on the illumination and collection geometry of the optical probe, is long enough so that the effect of absorption on fluorescence intensity due to hemoglobin is significant. Then a multivariate method was used to statistically classify normal tissues and tumors. Although the first method offers quantitative tissue metabolism information, the second method provides high overall classification accuracy. The two methods provide complementary capabilities for understanding cancer development and noninvasively diagnosing brain cancer. The results of our study suggest that this portable system can be potentially used to demarcate the elusive boundary between a brain tumor and the surrounding normal tissue during surgical resection.

  11. Compact point-detection fluorescence spectroscopy system for quantifying intrinsic fluorescence redox ratio in brain cancer diagnostics.

    PubMed

    Liu, Quan; Grant, Gerald; Li, Jianjun; Zhang, Yan; Hu, Fangyao; Li, Shuqin; Wilson, Christy; Chen, Kui; Bigner, Darell; Vo-Dinh, Tuan

    2011-03-01

    We report the development of a compact point-detection fluorescence spectroscopy system and two data analysis methods to quantify the intrinsic fluorescence redox ratio and diagnose brain cancer in an orthotopic brain tumor rat model. Our system employs one compact cw diode laser (407 nm) to excite two primary endogenous fluorophores, reduced nicotinamide adenine dinucleotide, and flavin adenine dinucleotide. The spectra were first analyzed using a spectral filtering modulation method developed previously to derive the intrinsic fluorescence redox ratio, which has the advantages of insensitivity to optical coupling and rapid data acquisition and analysis. This method represents a convenient and rapid alternative for achieving intrinsic fluorescence-based redox measurements as compared to those complicated model-based methods. It is worth noting that the method can also extract total hemoglobin concentration at the same time but only if the emission path length of fluorescence light, which depends on the illumination and collection geometry of the optical probe, is long enough so that the effect of absorption on fluorescence intensity due to hemoglobin is significant. Then a multivariate method was used to statistically classify normal tissues and tumors. Although the first method offers quantitative tissue metabolism information, the second method provides high overall classification accuracy. The two methods provide complementary capabilities for understanding cancer development and noninvasively diagnosing brain cancer. The results of our study suggest that this portable system can be potentially used to demarcate the elusive boundary between a brain tumor and the surrounding normal tissue during surgical resection. PMID:21456877

  12. Intrinsic fluorescence spectra characteristics of vitamin B1, B2, and B6

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Xiao, Xue; Zhao, Xuesong; Hu, Lan; Lv, Caofang; Yin, Zhangkun

    2015-11-01

    This paper presents the intrinsic fluorescence characteristics of vitamin B1, B2 and B6 measured with 3D fluorescence Spectrophotometer. Three strong fluorescence areas of vitamin B2 locate at λex/λem=270/525nm, 370/525nm and 450/525nm, one fluorescence areas of vitamin B1 locates at λex/λem=370/460nm, two fluorescence areas of vitamin B6 locates at λex/λem=250/370nm and 325/370nm were found. The influence of pH of solution to the fluorescence profile was also discussed. Using the PARAFAC algorithm, 10 vitamin B1, B2 and B6 mixed solutions were successfully decomposed, and the emission profiles, excitation profiles, central wavelengths and the concentration of the three components were retrieved precisely through about 5 iteration times.

  13. Detecting cervical cancer progression through extracted intrinsic fluorescence and principal component analysis

    NASA Astrophysics Data System (ADS)

    Devi, Seema; Panigrahi, Prasanta K.; Pradhan, Asima

    2014-12-01

    Intrinsic fluorescence spectra of the human normal, cervical intraepithelial neoplasia 1 (CIN1), CIN2, and cervical cancer tissue have been extracted by effectively combining the measured polarized fluorescence and polarized elastic scattering spectra. The efficacy of principal component analysis (PCA) to disentangle the collective behavior from smaller correlated clusters in a dimensionally reduced space in conjunction with the intrinsic fluorescence is examined. This combination unambiguously reveals the biochemical changes occurring with the progression of the disease. The differing activities of the dominant fluorophores, collagen, nicotinamide adenine dinucleotide, flavins, and porphyrin of different grades of precancers are clearly identified through a careful examination of the sectorial behavior of the dominant eigenvectors of PCA. To further classify the different grades, the Mahalanobis distance has been calculated using the scores of selected principal components.

  14. Preliminary investigation of intrinsic UV fluorescence spectroscopic changes associated with proteolytic digestion of bovine articular cartilage

    NASA Astrophysics Data System (ADS)

    Lewis, William; Padilla-Martinez, Juan-Pablo; Ortega-Martinez, Antonio; Franco, Walfre

    2016-03-01

    Degradation and destruction of articular cartilage is the etiology of osteoarthritis (OA), an entity second only to cardiovascular disease as a cause of disability in the United States. Joint mechanics and cartilage biochemistry are believed to play a role in OA; an optical tool to detect structural and chemical changes in articular cartilage might offer benefit for its early detection and treatment. The objective of the present study was to identify the spectral changes in intrinsic ultraviolet (UV) fluorescence of cartilage that occur after proteolytic digestion of cartilage. Bovine articular cartilage samples were incubated in varying concentrations of collagenase ranging from 10ug/mL up to 5mg/mL for 18 hours at 37°C, a model of OA. Pre- and post-incubation measurements were taken of the UV excitation-emission spectrum of each cartilage sample. Mechanical tests were performed to determine the pre- and post-digestion force/displacement ratio associated with indentation of each sample. Spectral changes in intrinsic cartilage fluorescence and stiffness of the cartilage were associated with proteolytic digestion. In particular, changes in the relative intensity of fluorescence peaks associated with pentosidine crosslinks (330 nm excitation, 390 nm emission) and tryptophan (290 nm excitation, 340 nm emission) were found to correlate with different degrees of cartilage digestion and cartilage stiffness. In principle, it may be possible to use UV fluorescence spectral data for early detection of damage to articular cartilage, and as a surrogate measure for cartilage stiffness.

  15. Intrinsic Fluorescence as a Spectral Probe for Protein Denaturation Studies in the Presence of Honey

    NASA Astrophysics Data System (ADS)

    Wong, Y. H.; Kadir, H. A.; Tayyab, S.

    2015-11-01

    Honey was found to quench the intrinsic fluorescence of bovine serum albumin (BSA) in a concentration dependent manner, showing complete quenching in the presence of 5% (w/v) honey. Increasing the protein concentration up to 5.0 μM did not lead to the recovery of the protein fluorescence. Urea denaturation of BSA, which otherwise shows a two-step, three-state transition, using intrinsic fluorescence of the protein as the probe failed to produce any result in the presence of 5% (w/v) honey. Thus, intrinsic fluorescence cannot be used as a spectral probe for protein denaturation studies in the presence of honey.

  16. Importance and challenges of measuring intrinsic foot muscle strength

    PubMed Central

    2012-01-01

    Background Intrinsic foot muscle weakness has been implicated in a range of foot deformities and disorders. However, to establish a relationship between intrinsic muscle weakness and foot pathology, an objective measure of intrinsic muscle strength is needed. The aim of this review was to provide an overview of the anatomy and role of intrinsic foot muscles, implications of intrinsic weakness and evaluate the different methods used to measure intrinsic foot muscle strength. Method Literature was sourced from database searches of MEDLINE, PubMed, SCOPUS, Cochrane Library, PEDro and CINAHL up to June 2012. Results There is no widely accepted method of measuring intrinsic foot muscle strength. Methods to estimate toe flexor muscle strength include the paper grip test, plantar pressure, toe dynamometry, and the intrinsic positive test. Hand-held dynamometry has excellent interrater and intrarater reliability and limits toe curling, which is an action hypothesised to activate extrinsic toe flexor muscles. However, it is unclear whether any method can actually isolate intrinsic muscle strength. Also most methods measure only toe flexor strength and other actions such as toe extension and abduction have not been adequately assessed. Indirect methods to investigate intrinsic muscle structure and performance include CT, ultrasonography, MRI, EMG, and muscle biopsy. Indirect methods often discriminate between intrinsic and extrinsic muscles, but lack the ability to measure muscle force. Conclusions There are many challenges to accurately measure intrinsic muscle strength in isolation. Most studies have measured toe flexor strength as a surrogate measure of intrinsic muscle strength. Hand-held dynamometry appears to be a promising method of estimating intrinsic muscle strength. However, the contribution of extrinsic muscles cannot be excluded from toe flexor strength measurement. Future research should clarify the relative contribution of intrinsic and extrinsic muscles

  17. Passive fluorescence measurements during SIFLEX

    NASA Astrophysics Data System (ADS)

    Moya, I.; Ounis, A.; Louis, J.; Evain, S.; Ducruet, J.-M.

    The goal of the participation of the LURE team to the SIFLEX campaign was %to provide clear evidence of quantitative absolute measurements of natural fluorescence andfluorescence flux evaluation by passive methods in the Fraunhofer lines. More specifically, to quantify the fluorescence flux in A and B absorption bands of atmospheric oxygen. The measurements have been focus on: Testing specific passive fluorescence instrumentation recently developed at LURE for assessing the sun induced fluorescence radiance from vegetation. Investigating diurnal and seasonal change of fluorescence and its behaviour with respect to plant condition, pigment content, global radiation amount and its correlation against accumulated biomass during growing period, Cross-correlate the fluorescence signal with hyperspectral reflectance and thermal IR radiance. A special attention has been paid to diurnal cycle and seasonal variations. Comparing fluorescence fluxes with CO2 fluxes measured by the already existing gas exchange equipment of the site. Instrumentation PMFD (Passive Multiwavelength Fluorescence Detector) was the main instrument used to asses fluorescence fluxes. The instrument was based on the Fraunhofer line principle, applied in the atmospheric oxygen A and B bands (760nm and 687nm, respectively). The output parameters were two stationary fluorescence flux at 687nm and 760nm and the NDVI (NDVI = (R760-R687) / (R760+R687)) index. Two additional channels of the instrument are devoted to measure reflectance variations at 531nm and 570 nm in order to calculate the PRI (PRI = (R531-R570) / (R531+R570)) index. This instrument was installed on the main tower, 10 m above the crown of the trees and maintained in the same viewing direction during the campaign (towards the north direction). The zenith angle was set to about 50-65 degrees. The footprint of the instrument contained the crowns of several trees. BD was a second passive detector operating solely in the atmospheric oxygen A

  18. Studying Photosynthesis by Measuring Fluorescence

    ERIC Educational Resources Information Center

    Sanchez, Jose Francisco; Quiles, Maria Jose

    2006-01-01

    This paper describes an easy experiment to study the absorption and action spectrum of photosynthesis, as well as the inhibition by heat, high light intensity and the presence of the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on the photosynthetic process. The method involves measuring the chlorophyll fluorescence emitted by intact…

  19. The aggregation behavior of native collagen in dilute solution studied by intrinsic fluorescence and external probing

    NASA Astrophysics Data System (ADS)

    Wu, Kun; Liu, Wentao; Li, Guoying

    2013-02-01

    The aggregation behavior of type I collagen in acid solutions with the concentrations covering a range of 0.06-1.50 mg/mL was studied utilizing both of the fluorescence resonance energy transfer (FRET) between the phenylalanine and tyrosine residues and the external probing of 1,8-anilinonaphthalene sulfonate (ANS). FRET at 0.30 mg/mL showed the distance among collagen monomers was within 10 nm without the obvious aggregates formed. The predominance of tyrosine fluorescence in FRET in the range of 0.45-0.75 mg/mL identified the existence of collagen aggregates companied with the formation of hydrophobic microdomains revealed by the change of the fluorescence of ANS. The blue-shift of tyrosine fluorescence from 303 to 293 nm for 0.90-1.50 mg/mL dedicated the formation of high order aggregates. The results from the two-phase diagrams of the intrinsic fluorescence for the guanidine hydrochloride-induced unfolding of collagen confirmed these conclusions. By the two-dimensional correlation analysis for the intrinsic fluorescence of collagen solutions of 0.45, 0.75 and 1.05 mg/mL, the probable characteristic fluorescence peaks for the interactions of proline-aromatic (CH ˜ π) among the collagen molecules were found at 298 and 316 nm.

  20. Metal-enhanced intrinsic fluorescence of nucleic acids using platinum nanostructured substrates

    NASA Astrophysics Data System (ADS)

    Akbay, Nuriye; Mahdavi, Farhad; Lakowicz, Joseph R.; Ray, Krishanu

    2012-10-01

    We investigated the feasibility of using platinum nanostructures to accomplish the metal-enhanced fluorescence (MEF) in the UV spectral region. We examine the possibility for detection of the intrinsic fluorescence from nucleotides and G-quadruplex DNA on platinum nanoparticles. Guanosine monophosphate (GMP) showed significant increases (˜20-fold) in fluorescence intensities in the presence of platinum nanostructures when compared to quartz controls. G-quadruplex DNA demonstrated ˜5-fold increase in fluorescence intensity and higher photostability in the presence of Pt nanostructures. We performed Finite Element Method simulations to explore how Pt nanoparticles interact with plane waves and conformed that the Pt nanostructures are promising for enhancing the fluorescence emission in the UV region.

  1. Ligand-induced evolution of intrinsic fluorescence and catalytic activity from cobalt ferrite nanoparticles.

    PubMed

    Pal, Monalisa; Kundu, Anirban; Rakshit, Rupali; Mandal, Kalyan

    2015-06-01

    To develop CoFe(2)O(4) as magneto-fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe(2)O(4) NPs with Na-tartrate. Moreover, the functionalized CoFe(2)O(4) NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe(2)O(4) NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe(2)O(4) NPs hold great promise for advanced biomedical and technological applications. PMID:25867626

  2. Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation

    PubMed Central

    Zipfel, Warren R.; Williams, Rebecca M.; Christie, Richard; Nikitin, Alexander Yu; Hyman, Bradley T.; Webb, Watt W.

    2003-01-01

    Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces images with the resolution and detail of standard histology without the use of exogenous stains. Imaging of intrinsic indicators within tissue, such as nicotinamide adenine dinucleotide, retinol, indoleamines, and collagen provides crucial information for physiology and pathology. The efficient application of multiphoton microscopy to intrinsic imaging requires knowledge of the nonlinear optical properties of specific cell and tissue components. Here we compile and demonstrate applications involving a range of intrinsic molecules and molecular assemblies that enable direct visualization of tissue morphology, cell metabolism, and disease states such as Alzheimer's disease and cancer. PMID:12756303

  3. Experimental recovery of intrinsic fluorescence and fluorophore concentration in the presence of hemoglobin: spectral effect of scattering and absorption on fluorescence

    NASA Astrophysics Data System (ADS)

    Du Le, Vinh Nguyen; Patterson, Michael S.; Farrell, Thomas J.; Hayward, Joseph E.; Fang, Qiyin

    2015-12-01

    The ability to recover the intrinsic fluorescence of biological fluorophores is crucial to accurately identify the fluorophores and quantify their concentrations in the media. Although some studies have successfully retrieved the fluorescence spectral shape of known fluorophores, the techniques usually came with heavy computation costs and did not apply for strongly absorptive media, and the intrinsic fluorescence intensity and fluorophore concentration were not recovered. In this communication, an experimental approach was presented to recover intrinsic fluorescence and concentration of fluorescein in the presence of hemoglobin (Hb). The results indicated that the method was efficient in recovering the intrinsic fluorescence peak and fluorophore concentration with an error of 3% and 10%, respectively. The results also suggested that chromophores with irregular absorption spectra (e.g., Hb) have more profound effects on fluorescence spectral shape than chromophores with monotonic absorption and scattering spectra (e.g., black India ink and polystyrene microspheres).

  4. Direct measurement of the intrinsic ankle stiffness during standing.

    PubMed

    Vlutters, M; Boonstra, T A; Schouten, A C; van der Kooij, H

    2015-05-01

    Ankle stiffness contributes to standing balance, counteracting the destabilizing effect of gravity. The ankle stiffness together with the compliance between the foot and the support surface make up the ankle-foot stiffness, which is relevant to quiet standing. The contribution of the intrinsic ankle-foot stiffness to balance, and the ankle-foot stiffness amplitude dependency remain a topic of debate in the literature. We therefore developed an experimental protocol to directly measure the bilateral intrinsic ankle-foot stiffness during standing balance, and determine its amplitude dependency. By applying fast (40 ms) ramp-and-hold support surface rotations (0.005-0.08 rad) during standing, reflexive contributions could be excluded, and the amplitude dependency of the intrinsic ankle-foot stiffness was investigated. Results showed that reflexive activity could not have biased the torque used for estimating the intrinsic stiffness. Furthermore, subjects required less recovery action to restore balance after bilateral rotations in opposite directions compared to rotations in the same direction. The intrinsic ankle-foot stiffness appears insufficient to ensure balance, ranging from 0.93±0.09 to 0.44±0.06 (normalized to critical stiffness 'mgh'). This implies that changes in muscle activation are required to maintain balance. The non-linear stiffness decrease with increasing rotation amplitude supports the previous published research. With the proposed method reflexive effects can be ruled out from the measured torque without any model assumptions, allowing direct estimation of intrinsic stiffness during standing. PMID:25843262

  5. Identification of hematic cells by spectroscopic analysis of the intrinsic fluorescence

    NASA Astrophysics Data System (ADS)

    Monici, Monica; Agati, Giovanni; Fusi, Franco; Bernabei, Pietro A.; Caporale, Roberto; Ferrini, Pierluigi R.; Croce, Anna C.; Bottiroli, Giovanni F.; Cioncolini, Stefano; Innocenti, Alberto; Pratesi, Riccardo

    1994-12-01

    The determination of blood cell composition has been a valuable tool in diagnoses. In particular, both total and differential counts are considered the basic parameters that characterize the leukocyte population. Since 100 years ago, manual techniques were introduced that allow a morphological examination of blood smears. At present, the automated analysis has been proved to be particularly difficult to standardize. In fact, the identification and count of the five leukocyte populations are not completely solved problems in routine methods for hematological analysis. Optoelectronics could have a decisive role in the development of new techniques that can ensure characteristics of automation, reliability, accuracy and rapidity of execution. Fluorescence spectroscopy techniques could represent a valid approach. Recently, the evaluation of tissue and cell autofluorescence has been applied to the diagnosis of solid tissue neoplasies. In this work, we have considered the possibility to develop a reliable method of leukocyte analysis based on their intrinsic fluorescence emission properties. The study has been performed by applying both spectrofluorometric techniques to enriched suspensions of cells and microspectrofluorometric techniques to single leukocytes. The results obtained have shown the possibility to recognize some cell populations on the grounds of the intrinsic fluorescence characteristics.

  6. Fluorescence lifetime as a new parameter in analytical cytology measurements

    NASA Astrophysics Data System (ADS)

    Steinkamp, John A.; Deka, Chiranjit; Lehnert, Bruce E.; Crissman, Harry A.

    1996-05-01

    A phase-sensitive flow cytometer has been developed to quantify fluorescence decay lifetimes on fluorochrome-labeled cells/particles. This instrument combines flow cytometry (FCM) and frequency-domain fluorescence spectroscopy measurement principles to provide unique capabilities for making phase-resolved lifetime measurements, while preserving conventional FCM capabilities. Cells are analyzed as they intersect a high-frequency, intensity-modulated (sine wave) laser excitation beam. Fluorescence signals are processed by conventional and phase-sensitive signal detection electronics and displayed as frequency distribution histograms. In this study we describe results of fluorescence intensity and lifetime measurements on fluorescently labeled particles, cells, and chromosomes. Examples of measurements on intrinsic cellular autofluorescence, cells labeled with immunofluorescence markers for cell- surface antigens, mitochondria stains, and on cellular DNA and protein binding fluorochromes will be presented to illustrate unique differences in measured lifetimes and changes caused by fluorescence quenching. This innovative technology will be used to probe fluorochrome/molecular interactions in the microenvironment of cells/chromosomes as a new parameter and thus expand the researchers' understanding of biochemical processes and structural features at the cellular and molecular level.

  7. On the feasibility of using the intrinsic fluorescence of nucleotides for DNA sequencing.

    SciTech Connect

    Chowdhury, M. H.; Ray, K.; Johnson, R. L.; Gray, S. K.; Pond, J.; Lakowicz, J. R.; Univ. of Maryland; Univ. of Virginia; Lumerical Solutions, Inc.

    2010-04-29

    There is presently a worldwide effort to increase the speed and decrease the cost of DNA sequencing as exemplified by the goal of the National Human Genome Research Institute (NHGRI) to sequence a human genome for under $1000. Several high throughput technologies are under development. Among these, single strand sequencing using exonuclease appear very promising. However, this approach requires complete labeling of at least two bases at a time, with extrinsic high quantum yield probes. This is necessary because nucleotides absorb in the deep ultraviolet (UV) and emit with extremely low quantum yields. Hence intrinsic emission from DNA and nucleotides is not being exploited for DNA sequencing. In the present paper we consider the possibility of identifying single nucleotides using their intrinsic emission. We used the finite-difference time-domain (FDTD) method to calculate the effects of aluminum nanoparticles on nearby fluorophores that emit in the UV. We find that the radiated power of UV fluorophores is significantly increased when they are in close proximity to aluminum nanostructures. We show that there will be increased localized excitation near aluminum particles at wavelengths used to excite intrinsic nucleotide emission. Using FDTD simulation we show that a typical DNA base when coupled to appropriate aluminum nanostructures leads to highly directional emission. Additionally we present experimental results showing that a thin film of nucleotides show enhanced emission when in close proximity to aluminum nanostructures. Finally we provide Monte Carlo simulations that predict high levels of base calling accuracy for an assumed number of photons that is derived from the emission spectra of the intrinsic fluorescence of the bases. Our results suggest that single nucleotides can be detected and identified using aluminum nanostructures that enhance their intrinsic emission. This capability would be valuable for the ongoing efforts toward the $1000 genome.

  8. Intrinsic randomness as a measure of quantum coherence

    NASA Astrophysics Data System (ADS)

    Yuan, Xiao; Zhou, Hongyi; Cao, Zhu; Ma, Xiongfeng

    2015-08-01

    Based on the theory of quantum mechanics, intrinsic randomness in measurement distinguishes quantum effects from classical ones. From the perspective of states, this quantum feature can be summarized as coherence or superposition in a specific (classical) computational basis. Recently, by regarding coherence as a physical resource, Baumgratz et al. [Phys. Rev. Lett. 113, 140401 (2014), 10.1103/PhysRevLett.113.140401] presented a comprehensive framework for coherence measures. Here, we propose a quantum coherence measure essentially using the intrinsic randomness of measurement. The proposed coherence measure provides an answer to the open question in completing the resource theory of coherence. Meanwhile, we show that the coherence distillation process can be treated as quantum extraction, which can be regarded as an equivalent process of classical random number extraction. From this viewpoint, the proposed coherence measure also clarifies the operational aspect of quantum coherence. Finally, our results indicate a strong similarity between two types of quantumness—coherence and entanglement.

  9. Caffeine Consumption Contributes to Skin Intrinsic Fluorescence in Type 1 Diabetes

    PubMed Central

    Eny, Karen M.; Orchard, Trevor J.; Miller, Rachel Grace; Maynard, John; Grant, Denis M.; Costacou, Tina; Cleary, Patricia A.; Braffett, Barbara H.

    2015-01-01

    Abstract Background: A variant (rs1495741) in the gene for the N-acetyltransferase 2 (NAT2) protein is associated with skin intrinsic fluorescence (SIF), a noninvasive measure of advanced glycation end products and other fluorophores in the skin. Because NAT2 is involved in caffeine metabolism, we aimed to determine whether caffeine consumption is associated with SIF and whether rs1495741 is associated with SIF independently of caffeine. Materials and Methods: SIF was measured in 1,181 participants with type 1 diabetes from the Epidemiology of Diabetes Interventions and Complications study. Two measures of SIF were used: SIF1, using a 375-nm excitation light-emitting diode (LED), and SIF14 (456-nm LED). Food frequency questionnaires were used to estimate mean caffeine intake. To establish replication, we examined a second type 1 diabetes cohort. Results: Higher caffeine intake was significantly associated with higher SIF1LED 375 nm[0.6, 0.2] (P=2×10−32) and SIF14LED 456 nm[0.4, 0.8] (P=7×10−31) and accounted for 4% of the variance in each after adjusting for covariates. When analyzed together, caffeine intake and rs1495741 both remained highly significantly associated with SIF1LED 375 nm[0.6, 0.2] and SIF14LED 456 nm[0.4, 0.8]. Mean caffeinated coffee intake was also positively associated with SIF1LED 375 nm[0.6, 0.2] (P=9×10−12) and SIF14LED 456 nm[0.4, 0.8] (P=4×10−12), but no association was observed for decaffeinated coffee intake. Finally, caffeine was also positively associated with SIF1LED 375 nm[0.6, 0.2] and SIF14LED 456 nm[0.4, 0.8] (P<0.0001) in the replication cohort. Conclusions: Caffeine contributes to SIF. The effect of rs1495741 on SIF appears to be partially independent of caffeine consumption. Because SIF and coffee intake are each associated with cardiovascular disease, our findings suggest that accounting for coffee and/or caffeine intake may improve risk prediction models for SIF and cardiovascular

  10. Efficient Chlorophyll Fluorescence Measurements of Sugarcane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As with many crops, chlorophyll fluorescence emission is a promising tool for measuring responses of sugarcane (Saccharum spp.) to biotic and abiotic stresses. Chlorophyll fluorescence can be easily measured using portable fluorometers. However, several factors should be considered in order to op...

  11. Development of in-vitro models to elucidate mechanisms of intrinsic cellular and tissue fluorescence

    NASA Astrophysics Data System (ADS)

    Savage, Howard E.; Kolli, Venkateswara; Saha, Sanjoy; Zhang, Jian C.; Glasgold, Mark; Sacks, Peter G.; Alfano, Robert R.; Schantz, Stimson P.

    1995-04-01

    In vitro cell model systems have been used to study the mechanisms of intrinsic cellular and tissue fluorescence as a potential biomarker for cancer. Phenotypic characteristics of cancer that are different from normal tissue include changes in histoarchitecture, proliferation rates and differentiation. a nitrosmethlybenzylamine (NMBA)/rat esophageal carcinogenesis model (NMBA), a transforming growth factor beta (TGF- (beta) )/normal epithelial cell model, and a retinoic acid (RA)/multicellular tumor spheroid model (RAMTS) were used to assess fluorescence changes associated respectively with changes in histoarchitecture, proliferation rates and differentiation. A xenon based fluorescence spectrophotometer (Mediscience Corp.) was used to collect excitation and emission spectra. Two excitation scans ((lambda) Ex 200-360 nm, (lambda) Em 380 nm; (lambda) Ex 240-430 nm, (lambda) Em 450 nm) and two emission scans ((lambda) Ex 300 nm, (lambda) Em 320-580 nm; (lambda) Ex 340 nm, (lambda) Em 360-660 nm) were used to analyze the three model systems. Using the NMBA model. Differences were seen in the excitation scan ((lambda) Ex 200-360 nm, (lambda) Em 380 nm) and the emission scan ((lambda) Ex 340 nm, (lambda) Em 360-660 nm) when normal rat esophageal tissue was compared to hyperplastic and tumor tissue. In the (TGF-(beta) ) model, differences were seen in the excitation scan ((lambda) Ex 240-430 nm, (lambda) Em 450 nm) when comparing proliferation slowed (TGF-(beta) treated) epithelial cells to their untreated controls. In the RAMTS model, differences were seen with all four scans when RA treated multicellular tumor spheroids (nondifferentiating) were compared to untreated control cells (differentiating). The data indicate that fluorescence changes seen in these model systems may relate to changes in histoarchitecture, proliferation rates and differentiation. Their relationship to in vivo fluorescence changes seen in cancer patients remains to be elucidated.

  12. The intrinsic fluorescence of isolated central-nervous-system myelin-sheath preparations.

    PubMed Central

    Crang, A J; Rumsby, M G

    1979-01-01

    The intrinsic fluorescence characteristics of tyrosine and tryptophan residues in the proteins of isolated central-nervous-system myelin were investigated to gain information concerning the location of these residues within the intact membrane system. Tryptophan fluorescence from isolated myelin has an emission maximum at 325 nm that appears to arise from at least two different populations of tryptophan residues. Further evidence for heterogeneity of tryptophan location in the membrane is obtained from quenching studies with chloroform and acrylamide. It is speculated that one tryptophan population is hydrophobically situated and may be derived from the proteolipid protein of myelin, whereas the other tryptophan population is located at the membrane surface and may arise from the extrinsic basic protein. A significant tyrosine fluorescence is detected from isolated myelin, indicating that some of these residues are not quenched by structural interactions within the lipid--protein membrane system. Studies with freeze-dried resuspended myelin suggest that the structural arrangement of protein components in the dried rehydrated membrane system differs significantly from that of the freshly isolated myelin membrane. PMID:435264

  13. Improvements in intrinsic feature pose measurement for awake animal imaging

    SciTech Connect

    J.S. Goddard, J.S. Baba, S.J. Lee, A.G. Weisenberger, A. Stolin, J. McKisson, M.F. Smith

    2011-06-01

    Development has continued with intrinsic feature optical motion tracking for awake animal imaging to measure 3D position and orientation (pose) for motion compensated reconstruction. Prior imaging results have been directed towards head motion measurement for SPECT brain studies in awake unrestrained mice. This work improves on those results in extracting and tracking intrinsic features from multiple camera images and computing pose changes from the tracked features over time. Previously, most motion tracking for 3D imaging has been limited to measuring extrinsic features such as retro-reflective markers applied to an animal's head. While this approach has been proven to be accurate, the use of external markers is undesirable for several reasons. The intrinsic feature approach has been further developed from previous work to provide full pose measurements for a live mouse scan. Surface feature extraction, matching, and pose change calculation with point tracking and accuracy results are described. Experimental pose calculation and 3D reconstruction results from live images are presented.

  14. Improvements in Intrinsic Feature Pose Measurement for Awake Animal Imaging

    SciTech Connect

    Goddard Jr, James Samuel; Baba, Justin S; Lee, Seung Joon; Weisenberger, A G; McKisson, J; Smith, M F; Stolin, Alexander

    2010-01-01

    Development has continued with intrinsic feature optical motion tracking for awake animal imaging to measure 3D position and orientation (pose) for motion compensated reconstruction. Prior imaging results have been directed towards head motion measurement for SPECT brain studies in awake unrestrained mice. This work improves on those results in extracting and tracking intrinsic features from multiple camera images and computing pose changes from the tracked features over time. Previously, most motion tracking for 3D imaging has been limited to measuring extrinsic features such as retro-reflective markers applied to an animal s head. While this approach has been proven to be accurate, the use of external markers is undesirable for several reasons. The intrinsic feature approach has been further developed from previous work to provide full pose measurements for a live mouse scan. Surface feature extraction, matching, and pose change calculation with point tracking and accuracy results are described. Experimental pose calculation and 3D reconstruction results from live images are presented.

  15. Single-molecule spectroscopic study of enhanced intrinsic phycoerythrin fluorescence on silver nanostructured surfaces.

    PubMed

    Ray, Krishanu; Chowdhury, Mustafa H; Lakowicz, Joseph R

    2008-09-15

    In this paper, we report on steady-state and time-resolved single-molecule fluorescence measurements performed on a phycobiliprotein, R-phycoerythrin (RPE), assembled on silver nanostructures. Single-molecule measurements clearly show that RPE molecules display a 10-fold increase in fluorescence intensity, with a 7-fold decrease in lifetime when they are assembled on silver nanostructured surfaces, as compared to control glass slides. The emission spectrum of individual RPE molecules also displays a significant fluorescence enhancement on silver nanostructures as compared to glass. From intensity and lifetime histograms, it is clear that the intensities as well as lifetimes of individual RPE molecules on silver nanostructures are more heterogeneously distributed than that on glass. This single-molecule study provides further insight on the heterogeneity in the fluorescence intensity and lifetimes of the RPE molecules on both glass and SiFs surfaces, which is otherwise not possible to observe using ensemble measurements. Finite-difference time-domain calculations have been performed to study the enhanced near-fields induced around silver nanoparticles by a radiating excited-state fluorophore, and the effect of such enhanced fields on the fluorescence enhancement observed is discussed. PMID:18690697

  16. New Locus for Skin Intrinsic Fluorescence in Type 1 Diabetes Also Associated With Blood and Skin Glycated Proteins.

    PubMed

    Roshandel, Delnaz; Klein, Ronald; Klein, Barbara E K; Wolffenbuttel, Bruce H R; van der Klauw, Melanie M; van Vliet-Ostaptchouk, Jana V; Atzmon, Gil; Ben-Avraham, Danny; Crandall, Jill P; Barzilai, Nir; Bull, Shelley B; Canty, Angelo J; Hosseini, S Mohsen; Hiraki, Linda T; Maynard, John; Sell, David R; Monnier, Vincent M; Cleary, Patricia A; Braffett, Barbara H; Paterson, Andrew D

    2016-07-01

    Skin fluorescence (SF) noninvasively measures advanced glycation end products (AGEs) in the skin and is a risk indicator for diabetes complications. N-acetyltransferase 2 (NAT2) is the only known locus influencing SF. We aimed to identify additional genetic loci influencing SF in type 1 diabetes (T1D) through a meta-analysis of genome-wide association studies (N = 1,359) including Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) and Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR). A locus on chromosome 1, rs7533564 (P = 1.9 × 10(-9)), was associated with skin intrinsic fluorescence measured by SCOUT DS (excitation 375 nm, emission 435-655 nm), which remained significant after adjustment for time-weighted HbA1c (P = 1.7 × 10(-8)). rs7533564 was associated with mean HbA1c in meta-analysis (P = 0.0225), mean glycated albumin (P = 0.0029), and glyoxal hydroimidazolones (P = 0.049), an AGE measured in skin biopsy collagen, in DCCT. rs7533564 was not associated with diabetes complications in DCCT/EDIC or with SF in subjects without diabetes (nondiabetic [ND]) (N = 8,721). In conclusion, we identified a new locus associated with SF in T1D subjects that did not show similar effect in ND subjects, suggesting a diabetes-specific effect. This association needs to be investigated in type 2 diabetes. PMID:27207532

  17. Transgenic mice expressing the Peripherin-EGFP genomic reporter display intrinsic peripheral nervous system fluorescence.

    PubMed

    McLenachan, Samuel; Goldshmit, Yona; Fowler, Kerry J; Voullaire, Lucille; Holloway, Timothy P; Turnley, Ann M; Ioannou, Panos A; Sarsero, Joseph P

    2008-12-01

    The development of homologous recombination methods for the precise modification of bacterial artificial chromosomes has allowed the introduction of disease causing mutations or fluorescent reporter genes into human loci for functional studies. We have introduced the EGFP gene into the human PRPH-1 locus to create the Peripherin-EGFP (hPRPH1-G) genomic reporter construct. The hPRPH1-G reporter was used to create transgenic mice with an intrinsically fluorescent peripheral nervous system (PNS). During development, hPRPH1-G expression was concomitant with the acquisition of neuronal cell fate and growing axons could be observed in whole embryo mounts. In the adult, sensory neurons were labeled in both the PNS and central nervous system, while motor neurons in the spinal cord had more limited expression. The fusion protein labeled long neuronal processes, highlighting the peripheral circuitry of hPRPH1-G transgenic mice to provide a useful resource for a range of neurobiological applications. PMID:18709437

  18. Steady-State and Time-Resolved Studies into the Origin of the Intrinsic Fluorescence of G-Quadruplexes.

    PubMed

    Sherlock, Madeline E; Rumble, Christopher A; Kwok, Chun Kit; Breffke, Jens; Maroncelli, Mark; Bevilacqua, Philip C

    2016-06-16

    Stretches of guanines in DNA and RNA can fold into guanine quadruplex structures (GQSs). These structures protect telomeres in DNA and regulate gene expression in RNA. GQSs have an intrinsic fluorescence that is sensitive to different parameters, including loop sequence and length. However, the dependence of GQS fluorescence on solution and sequence parameters and the origin of this fluorescence are poorly understood. Herein we examine effects of dangling nucleotides and cosolute conditions on GQS fluorescence using both steady-state and time-resolved fluorescence spectroscopy. The quantum yield of dGGGTGGGTGGGTGGG, termed "dG3T", is found to be modest at ∼2 × 10(-3). Nevertheless, dG3T and its variants are significantly brighter than the common nucleic acid fluorophore 2-aminopurine (2AP) largely due to their sizable extinction coefficients. Dangling 5'-end nucleotides generally reduce emission and blue-shift the resultant spectrum, whereas dangling 3'-end nucleotides slightly enhance fluorescence, particularly on the red side of the emission band. Time-resolved fluorescence decays are broadly distributed in time and require three exponential components for accurate fits. Time-resolved emission spectra suggest the presence of two emitting populations centered at ∼330 and ∼390 nm, with the redder component being a well-defined long-lived (∼1 ns) entity. Insights into GQS fluorescence obtained here should be useful in designing brighter intrinsic RNA and DNA quadruplexes for use in label-free biotechnological applications. PMID:27267433

  19. Intrinsic Tryptophan Fluorescence in the Detection and Analysis of Proteins: A Focus on Förster Resonance Energy Transfer Techniques

    PubMed Central

    Ghisaidoobe, Amar B. T.; Chung, Sang J.

    2014-01-01

    Förster resonance energy transfer (FRET) occurs when the distance between a donor fluorophore and an acceptor is within 10 nm, and its application often necessitates fluorescent labeling of biological targets. However, covalent modification of biomolecules can inadvertently give rise to conformational and/or functional changes. This review describes the application of intrinsic protein fluorescence, predominantly derived from tryptophan (λEX ∼ 280 nm, λEM ∼ 350 nm), in protein-related research and mainly focuses on label-free FRET techniques. In terms of wavelength and intensity, tryptophan fluorescence is strongly influenced by its (or the protein’s) local environment, which, in addition to fluorescence quenching, has been applied to study protein conformational changes. Intrinsic Förster resonance energy transfer (iFRET), a recently developed technique, utilizes the intrinsic fluorescence of tryptophan in conjunction with target-specific fluorescent probes as FRET donors and acceptors, respectively, for real time detection of native proteins. PMID:25490136

  20. Intrinsic Feature Pose Measurement for Awake Animal SPECT Imaging

    SciTech Connect

    Goddard Jr, James Samuel; Baba, Justin S; Lee, Seung Joon; Weisenberger, A G; Stolin, A; McKisson, J; Smith, M F

    2009-01-01

    New developments have been made in optical motion tracking for awake animal imaging that measures 3D position and orientation (pose) for a single photon emission computed tomography (SPECT) imaging system. Ongoing SPECT imaging research has been directed towards head motion measurement for brain studies in awake, unrestrained mice. In contrast to previous results using external markers, this work extracts and tracks intrinsic features from multiple camera images and computes relative pose from the tracked features over time. Motion tracking thus far has been limited to measuring extrinsic features such as retro-reflective markers applied to the mouse s head. While this approach has been proven to be accurate, the additional animal handling required to attach the markers is undesirable. A significant improvement in the procedure is achieved by measuring the pose of the head without extrinsic markers using only the external surface appearance. This approach is currently being developed with initial results presented here. The intrinsic features measurement extracts discrete, sparse natural features from 2D images such as eyes, nose, mouth and other visible structures. Stereo correspondence between features for a camera pair is determined for calculation of 3D positions. These features are also tracked over time to provide continuity for surface model fitting. Experimental results from live images are presented.

  1. Fluorescence lifetime measurements in flow cytometry

    NASA Astrophysics Data System (ADS)

    Beisker, Wolfgang; Klocke, Axel

    1997-05-01

    Fluorescence lifetime measurements provide insights int eh dynamic and structural properties of dyes and their micro- environment. The implementation of fluorescence lifetime measurements in flow cytometric systems allows to monitor large cell and particle populations with high statistical significance. In our system, a modulated laser beam is used for excitation and the phase shift of the fluorescence signal recorded with a fast computer controlled digital oscilloscope is processed digitally to determine the phase shift with respect to a reference beam by fast fourier transform. Total fluorescence intensity as well as other parameters can be determined simultaneously from the same fluorescence signal. We use the epi-illumination design to allow the use of high numerical apertures to collect as much light as possible to ensure detection of even weak fluorescence. Data storage and processing is done comparable to slit-scan flow cytometric data using data analysis system. The results are stored, displayed, combined with other parameters and analyzed as normal listmode data. In our report we discuss carefully the signal to noise ratio for analog and digital processed lifetime signals to evaluate the theoretical minimum fluorescence intensity for lifetime measurements. Applications to be presented include DNA staining, parameters of cell functions as well as different applications in non-mammalian cells such as algae.

  2. Fluorescence lifetime measurements in heterogeneous scattering medium

    NASA Astrophysics Data System (ADS)

    Nishimura, Goro; Awasthi, Kamlesh; Furukawa, Daisuke

    2016-07-01

    Fluorescence lifetime in heterogeneous multiple light scattering systems is analyzed by an algorithm without solving the diffusion or radiative transfer equations. The algorithm assumes that the optical properties of medium are constant in the excitation and emission wavelength regions. If the assumption is correct and the fluorophore is a single species, the fluorescence lifetime can be determined by a set of measurements of temporal point-spread function of the excitation light and fluorescence at two different concentrations of the fluorophore. This method is not dependent on the heterogeneity of the optical properties of the medium as well as the geometry of the excitation-detection on an arbitrary shape of the sample. The algorithm was validated by an indocyanine green fluorescence in phantom measurements and demonstrated by an in vivo measurement.

  3. Ultrasonic resonant piezoelectric actuator with intrinsic torque measurement.

    PubMed

    Pott, Peter P; Matich, Sebastian; Schlaak, Helmut F

    2012-11-01

    Piezoelectric ultrasonic actuators are widely used in small-scale actuation systems, in which a closed-loop position control is usually utilized. To save an additional torque sensor, the intrinsic measurement capabilities of the piezoelectric material can be employed. To prove feasibility, a motor setup with clearly separated actuation for the friction and driving forces is chosen. The motor concept is based on resonant ultrasonic vibrations. To assess the effects of the direct piezoelectric effect, a capacitance bridge-type circuit has been selected. Signal processing is done by a measurement card with an integrated field-programmable gate array. The motor is used to drive a winch, and different torques are applied by means of weights to be lifted. Assessing the bridge voltage, a good proportionality to the applied torque of 1.47 mV/mN·m is shown. A hysteresis of 1% has been determined. The chosen motor concept is useful for intrinsic torque measurement. However, it provides drawbacks in terms of limited mechanical performance, wear, and thermal losses because of the soft piezoelectric material. Future work will comprise the application of the method to commercially available piezoelectric actuators as well as the implementation of the measurement circuit in an embedded system. PMID:23192814

  4. Rapid Intrinsic Fluorescence Method for Direct Identification of Pathogens in Blood Cultures

    PubMed Central

    Walsh, John D.; Hyman, Jay M.; Borzhemskaya, Larisa; Bowen, Ann; McKellar, Caroline; Ullery, Michael; Mathias, Erin; Ronsick, Christopher; Link, John; Wilson, Mark; Clay, Bradford; Robinson, Ron; Thorpe, Thurman; van Belkum, Alex; Dunne, W. Michael

    2013-01-01

    ABSTRACT A positive blood culture is a critical result that requires prompt identification of the causative agent. This article describes a simple method to identify microorganisms from positive blood culture broth within the time taken to perform a Gram stain (<20 min). The method is based on intrinsic fluorescence spectroscopy (IFS) of whole cells and required development of a selective lysis buffer, aqueous density cushion, optical microcentrifuge tube, and reference database. A total of 1,121 monomicrobial-positive broth samples from 751 strains were analyzed to build a database representing 37 of the most commonly encountered species in bloodstream infections or present as contaminants. A multistage algorithm correctly classified 99.6% of unknown samples to the Gram level, 99.3% to the family level, and 96.5% to the species level. There were no incorrect results given at the Gram or family classification levels, while 0.8% of results were discordant at the species level. In 8/9 incorrect species results, the misidentified isolate was assigned to a species of the same genus. This unique combination of selective lysis, density centrifugation, and IFS can rapidly identify the most common microbial species present in positive blood cultures. Faster identification of the etiologic agent may benefit the clinical management of sepsis. Further evaluation is now warranted to determine the performance of the method using clinical blood culture specimens. PMID:24255123

  5. Following intracellular cholesterol transport by linear and non-linear optical microscopy of intrinsically fluorescent sterols.

    PubMed

    Wüstner, Daniel

    2012-02-01

    Elucidation of intracellular cholesterol transport is important for understanding the molecular basis of several metabolic and neuronal diseases, like atheroclerosis or lysosomal storage disorders. Progress in this field depends crucially on the development of new technical approaches to follow the cellular movement of this essential lipid molecule. In this article, a survey of the various methods being used for analysis of sterol trafficking is given. Various classical biochemical methods are presented and their suitability for analysis of sterol trafficking is assessed. Special emphasis is on recent developments in imaging technology to follow the intracellular fate of intrinsically fluorescent sterols as faithful cholesterol markers. In particular, UV-sensitive wide field and multiphoton microscopy of the sterol dehydroergosterol, DHE, is explained and new methods of quantitative image analysis like pixel-wise bleach rate fitting and multiphoton image correlation spectroscopy are introduced. Several applications of the new technology including observation of vectorial sterol trafficking in polarized human hepatoma cells for investigation of reverse cholesterol transport are presented. PMID:21470123

  6. Intrinsic oxygen fugacity measurements of some Allende Type B inclusions

    NASA Technical Reports Server (NTRS)

    Kozul, Jean M.; Hewins, Roger H.; Ulmer, Gene C.

    1988-01-01

    The intrinsic oxygen fugacities (IOFs) of two type B Ca-rich and Al-rich inclusions (CAI) from the Allende meteorite were measured using the solid-electrolyte double-cell IOF technique of Ulmer et al. (1976). The measurements were compared to calculated and experimentally extrapolated fO2 of type B phases. It was found that the IOFs of the type B are 6-8 orders of magnitude more oxidized (H2/H2O = 1-10) than the canonical solar nebular gas (H2/H2O = 100-2000). It is suggested that some local fO2 enhancing mechanism, such as dust or gas concentrations, or the release of oxygen-rich vapors during CAI volatilization in the type B inclusions was in operation at temperatures higher than 700 C.

  7. Fluorescence anisotropy measurements under shock compression

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Bassett, Will; Banishev, Alexandr; Dlott, Dana

    2015-06-01

    Fluorescence anisotropy measurements, where the parallel and perpendicular polarized emissions from probe molecules are acquired simultaneously, provide direct measurement of molecular rotational dynamics. In our experiments, the fluorescence from rhodamine 6G dye in various materials under GPa shocks produced by laser-driven flyer plates is collected, separated into two orthogonally-polarized beams using a Wollaston prism and detected with a streak camera. In liquids, the molecular rotations result from rotational diffusion and in solids from shear flow. The rotation rates can be used to determine the viscosity of the shocked medium.

  8. Precise Measurement of the Absolute Fluorescence Yield

    NASA Astrophysics Data System (ADS)

    Ave, M.; Bohacova, M.; Daumiller, K.; Di Carlo, P.; di Giulio, C.; San Luis, P. Facal; Gonzales, D.; Hojvat, C.; Hörandel, J. R.; Hrabovsky, M.; Iarlori, M.; Keilhauer, B.; Klages, H.; Kleifges, M.; Kuehn, F.; Monasor, M.; Nozka, L.; Palatka, M.; Petrera, S.; Privitera, P.; Ridky, J.; Rizi, V.; D'Orfeuil, B. Rouille; Salamida, F.; Schovanek, P.; Smida, R.; Spinka, H.; Ulrich, A.; Verzi, V.; Williams, C.

    2011-09-01

    We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources--the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

  9. Brain Mechanical Property Measurement Using MRE with Intrinsic Activation

    PubMed Central

    Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2013-01-01

    Problem Addressed Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. Methodology A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. Results, Significance and Potential Impact The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of 6 asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when

  10. Brain mechanical property measurement using MRE with intrinsic activation

    NASA Astrophysics Data System (ADS)

    Weaver, John B.; Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2012-11-01

    Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of six asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when the MRE procedures were repeated on the same day. Cardiac pulsation

  11. Intrinsic motivation inventory: an adapted measure for schizophrenia research.

    PubMed

    Choi, Jimmy; Mogami, Tamiko; Medalia, Alice

    2010-09-01

    This article describes the psychometric validation of a scale designed to measure intrinsic motivation (IM) in schizophrenia. Recent studies have highlighted the relationship between motivation and functional outcome in schizophrenia and identified IM as an important mediating factor between neurocognition and psychosocial outcome. It therefore becomes imperative to have validated measures of IM for empirical use. To that end, we validated a self-report IM scale that gauges the central motivational structures identified by Self-determinism Theory as pertinent to cognitive task engagement, skill acquisition, treatment compliance, and remediation outcome. Participants were schizophrenia outpatients involved in a cognitive remediation study (n = 58), a convenience subsample of clinically stable schizophrenia outpatients (n = 15), and a group of healthy normals (n = 22). The Intrinsic Motivation Inventory for Schizophrenia Research (IMI-SR) is a concise instrument, possessing good internal consistency (alpha = .92) and test-retest reliability (intraclass correlation = .77). Data were analyzed to abridge the original 54 items into a final 21-item questionnaire comprised of 3 domains relevant to motivation for treatments (interest/enjoyment, perceived choice, value/usefulness). The scale was highly associated with germane constructs of motivation for health-related behaviors, including perceived competency for attempting challenging tasks and autonomous treatment engagement. Importantly, the scale was able to distinguish improvers and nonimprovers on a cognitive task and actual learning exercises, delineate high vs low treatment attendance, and demonstrate sensitivity to motivational changes due to intervention variation. The IMI-SR is a viable instrument to measure IM in schizophrenia as part of a cognitive remediation protocol or psychosocial rehabilitation program. PMID:19386577

  12. Measurements of intrinsic shot noise in a 35 GHz gyroklystron

    NASA Astrophysics Data System (ADS)

    Calame, J. P.; Danly, B. G.; Garven, M.

    1999-07-01

    Experimental measurements of electron beam shot noise in a 35 GHz, 225 kW, three-cavity gyroklystron have been obtained from both the input and output cavities. This intrinsic noise was studied in the absence of an applied carrier (i.e., at zero drive power). The spectrum of the noise emitted by the input cavity is found to have a Lorentzian shape, with peak noise power densities from the input cavity typically reaching 6.3×10-15 W/Hz (-112 dBm/Hz), and typical 3 dB bandwidths of 160 MHz. The output cavity noise spectrum is found to be equal to the input cavity noise spectrum multiplied by the measured linear frequency response of the gyroklystron. The measured noise levels at the input cavity are 0-5 dB lower than theoretical predictions for shot noise unaltered by collective effects. Furthermore, the input cavity noise power exhibits complex variations as a function of beam current, beam velocity ratio, and circuit magnetic field that are not predicted by present theory. Noise-to-carrier ratios expected in the input cavity during full power amplifier operation are inferred from the noise measurements and known values of drive power required to saturate the gyroklystron. The noise-to-carrier ratio, with typical values of -90 to -80 dBc, is found to be a strong function of the operating parameters.

  13. Fluorescence lifetime measurements of NADH and tryptophan in intact ischemic, intact rabbit myocardium

    NASA Astrophysics Data System (ADS)

    Hamburger, Adrian; Gryczynski, Zygmunt; Lakowicz, Joseph R.; Sommers, Keith

    1999-07-01

    Ischemia-reperfusion injury is the leading cause of early dysfunction following transplantation. Currently, there are no techniques available to accurately measure ischemic changes during organ storage. Therefore, the interest exists in developing non-invasive monitoring techniques. We used NADH and tryptophan as fluorescent markers, since both are intrinsic fluorophores and excellent indicators for levels of hypoxia and protein denaturation, respectively.

  14. Measurement of fluorescent white effects and whiteness.

    PubMed

    Anders, G

    1975-01-01

    This report surveys the literature and describes various techniques of whiteness measurement and evaluation in current use. Measuring techniques are described for dealing separately with the effects obtained by bleaching, blueing and fluorescent whitening, and an example is given of the direct quantitative estimation of a fluorescent whitening agents (FWAs) on a substrate by measuring reflectance in the ultraviolet region. Another chapter deals with the colorimetric estimation of the whiteness and the shade of a fluorescent white using modern apparatus in conjunction with a programmable minicomputer. A new simple and universally applicab,e formula was worked out: W=D-Y+P-x+Q-y+C which has been successfully used in routine tests and which for the first time gives different weight to whiteness values corresponding to all shade preferences existing in theory. Each user can match the formula to his own preference by appropriate adjustment of the D, P, Q andC values. Y,x and y are the customary colorimetric values as standardized by the CIE (Commission Internationale de l'Eclairage). It was also found that with another formula the shades of fluorescent whitening effects (green to red tints) may be defined in a simple way. PMID:1064551

  15. Intrinsic feature-based pose measurement for imaging motion compensation

    SciTech Connect

    Baba, Justin S.; Goddard, Jr., James Samuel

    2014-08-19

    Systems and methods for generating motion corrected tomographic images are provided. A method includes obtaining first images of a region of interest (ROI) to be imaged and associated with a first time, where the first images are associated with different positions and orientations with respect to the ROI. The method also includes defining an active region in the each of the first images and selecting intrinsic features in each of the first images based on the active region. Second, identifying a portion of the intrinsic features temporally and spatially matching intrinsic features in corresponding ones of second images of the ROI associated with a second time prior to the first time and computing three-dimensional (3D) coordinates for the portion of the intrinsic features. Finally, the method includes computing a relative pose for the first images based on the 3D coordinates.

  16. Fluorescence depolarization measurements on oriented membranes.

    PubMed Central

    Adler, M; Tritton, T R

    1988-01-01

    We describe the theory and experimental application of fluorescence depolarization measurements on small molecules bound to oriented phospholipid bilayers. The results yield insight into both the orientation and the rotational motion of fluorophores in a membrane environment. To accomplish this the angular distribution of polarized fluorescence intensities is measured on a membrane preparation consisting of stacked phospholipid bilayers oriented in a known coordinate system. Considerably more information is available from this data than in comparable solution phase measurements. Three parameters are derived from the data: the rate of rotational diffusion and the second and fourth degree order parameters. These latter two parameters provide an assessment of the average distribution of fluorophore orientation in the membrane bilayer. The data have been carefully examined for systematic experimental artifacts and new protocols are presented which help to eliminate errors that have not been amply treated in the past. We present data for two types of fluorescent molecules: (a) conventional membrane probes like diphenylhexatriene, perylene and anthroyloxy fatty acids; and (b) the anticancer agent adriamycin and several congeneric anthracycline antibiotics. The results show that the hydrocarbon core of membranes is more rigid than previously thought, particularly above the thermal phase transition temperature. We also show that the orientation of small molecules is sensitive to both the phospholipid composition and to the interaction of specific functional groups with the lipid bilayer. The results are discussed in terms of energetic models describing the general patterns for the binding of small molecules to biological membranes. Images FIGURE 1 PMID:3165033

  17. Potato tuber pyrophosphate-dependent phosphofructokinase: effect of thiols and polyalcohols on its intrinsic fluorescence, oligomeric structure, and activity in dilute solutions.

    PubMed

    Podestá, F E; Moorhead, G B; Plaxton, W C

    1994-08-15

    The effect of dilution of homogeneous potato tuber pyrophosphate:fructose-6-phosphate 1-phosphotransferase (EC 2.7.1.90; PFP) on the enzyme's intrinsic fluorescence, activity, and oligomeric structure has been examined. A rapid decrease in PFP's intrinsic fluorescence occurred in response to dilution. The decay follows double-exponential kinetics and was accompanied by a reduction in catalytic activity (measured in the glycolytic direction). Gel filtration-HPLC indicated a concomitant deaggregation of the native alpha 4 beta 4 heterooctamer into the inactive free alpha- and beta-subunits, followed by random aggregation of the subunits into an inactive, high M(r) conglomerate. The addition of 2 mM dithiothreitol, 2 mM 2-mercaptoethanol, or 5% (w/v) polyethylene glycol, but not any of the substrates, Mg2+, or fructose 2,6-bisphosphate, prevented this process. When purified PFP was stored for 1 week at -20 degrees C in the presence of 50% (v/v) glycerol partial degradation of its alpha-subunit occurred. This resulted in a labile enzyme that was more susceptible to subunit dissociation. The intrinsic fluorescence of the degraded PFP could be stabilized by 5% (w/v) polyethylene glycol, but not by 2 mM dithiothreitol or 2-mercaptoethanol. It is proposed that the current assay procedures for PFP, which normally involve considerable dilution in the absence of added sulfhydryl reducing agents or polyhydroxy compounds, may underestimate the actual activity of the enzyme. This has important implications for the assessment of the functions and regulation of PFP in vivo. PMID:8053686

  18. Plant stress detection by remote measurement of fluorescence

    USGS Publications Warehouse

    McFarlane, J. C.; Watson, Robert D.; Theisen, Arnold F.; Jackson, R. D.; Ehrler, W. L.; Pinter, P. J., Jr.; Idso, S. B.; Reginato, R. J.

    1980-01-01

    Chlorophyll fluorescence of mature lemon trees was measured with a Fraunhofer line discriminator (FLD). An increase in fluorescence was correlated with plant water stress as measured by stomatal resistance and twig water potential.

  19. Laser-excited fluorescence for measuring atmospheric pollution

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1975-01-01

    System measures amount of given pollutant at specific location. Infrared laser aimed at location has wavelength that will cause molecules of pollutant to fluoresce. Detector separates fluorescence from other radiation and measures its intensity to indicate concentration of pollutant.

  20. Measurement of Rydberg positronium fluorescence lifetimes

    NASA Astrophysics Data System (ADS)

    Deller, A.; Alonso, A. M.; Cooper, B. S.; Hogan, S. D.; Cassidy, D. B.

    2016-06-01

    We report measurements of the fluorescence lifetimes of positronium (Ps) atoms with principal quantum numbers n =10 -19 . Ps atoms in Rydberg-Stark states were produced via a two-color two-step 1 3S→2 3P→n 3S/n measured time-of-flight distributions were used to determine the mean lifetimes of the Rydberg levels, yielding values ranging from 3 μ s to 26 μ s . Our data are in accord with the expected radiative lifetimes of Rydberg-Stark states of Ps.

  1. High-performance liquid chromatography combined with intrinsic fluorescence detection to analyse melittin in individual honeybee (Apis mellifera) venom sac.

    PubMed

    Dong, Jiangtao; Ying, Bihua; Huang, Shaokang; Ma, Shuangqin; Long, Peng; Tu, Xijuan; Yang, Wenchao; Wu, Zhenhong; Chen, Wenbin; Miao, Xiaoqing

    2015-10-01

    Melittin is the major toxin peptide in bee venom, which has diverse biological effects. In the present study, melittin was separated by reverse-phase high-performance liquid chromatography, and was then detected using intrinsic fluorescence signal of tryptophan residue. The accuracy, linearity, limit of quantitation (LOQ), intra-day and inter-day precision of the method were carefully validated in this study. Results indicate that the intrinsic fluorescence signal of melittin has linear range from 0.04μg/mL to 20μg/mL with LOQ of 0.04μg/mL. The recovery range of spiked samples is between 81.93% and 105.25%. The precision results are expressed as relative standard deviation (RSD), which is in the range of 2.1-7.4% for intra-day precision and 6.2-10.8% for inter-day precision. Because of the large linear dynamic range and the high sensitivity, intrinsic fluorescence detection (IFD) can be used for analyzing melittin contents in individual venom sac of honeybee (Apis mellifera). The detected contents of melittin in individual bee venom sac are 0.18±0.25μg for one-day old honeybees (n=30), and 114.98±43.51μg for 25-day old (n=30) honeybees, respectively. Results indicate that there is large bee-to-bee difference in melittin contents. The developed method can be useful for discovering the melittin related honeybee biology information, which might be covered in the complex samples. PMID:26319802

  2. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    NASA Astrophysics Data System (ADS)

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-08-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses.

  3. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function

    PubMed Central

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P.; Georgakoudi, Irene

    2016-01-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses. PMID:27491409

  4. Two-photon excited fluorescence of intrinsic fluorophores enables label-free assessment of adipose tissue function.

    PubMed

    Alonzo, Carlo Amadeo; Karaliota, Sevasti; Pouli, Dimitra; Liu, Zhiyi; Karalis, Katia P; Georgakoudi, Irene

    2016-01-01

    Current methods for evaluating adipose tissue function are destructive or have low spatial resolution. These limit our ability to assess dynamic changes and heterogeneous responses that occur in healthy or diseased subjects, or during treatment. Here, we demonstrate that intrinsic two-photon excited fluorescence enables functional imaging of adipocyte metabolism with subcellular resolution. Steady-state and time-resolved fluorescence from intracellular metabolic co-factors and lipid droplets can distinguish the functional states of excised white, brown, and cold-induced beige fat. Similar optical changes are identified when white and brown fat are assessed in vivo. Therefore, these studies establish the potential of non-invasive, high resolution, endogenous contrast, two-photon imaging to identify distinct adipose tissue types, monitor their functional state, and characterize heterogeneity of induced responses. PMID:27491409

  5. Different Ligands of the TRPV3 Cation Channel Cause Distinct Conformational Changes as Revealed by Intrinsic Tryptophan Fluorescence Quenching*

    PubMed Central

    Billen, Bert; Brams, Marijke; Debaveye, Sarah; Remeeva, Alina; Alpizar, Yeranddy A.; Waelkens, Etienne; Kreir, Mohamed; Brüggemann, Andrea; Talavera, Karel; Nilius, Bernd; Voets, Thomas; Ulens, Chris

    2015-01-01

    TRPV3 is a thermosensitive ion channel primarily expressed in epithelial tissues of the skin, nose, and tongue. The channel has been implicated in environmental thermosensation, hyperalgesia in inflamed tissues, skin sensitization, and hair growth. Although transient receptor potential (TRP) channel research has vastly increased our understanding of the physiological mechanisms of nociception and thermosensation, the molecular mechanics of these ion channels are still largely elusive. In order to better comprehend the functional properties and the mechanism of action in TRP channels, high-resolution three-dimensional structures are indispensable, because they will yield the necessary insights into architectural intimacies at the atomic level. However, structural studies of membrane proteins are currently hampered by difficulties in protein purification and in establishing suitable crystallization conditions. In this report, we present a novel protocol for the purification of membrane proteins, which takes advantage of a C-terminal GFP fusion. Using this protocol, we purified human TRPV3. We show that the purified protein is a fully functional ion channel with properties akin to the native channel using planar patch clamp on reconstituted channels and intrinsic tryptophan fluorescence spectroscopy. Using intrinsic tryptophan fluorescence spectroscopy, we reveal clear distinctions in the molecular interaction of different ligands with the channel. Altogether, this study provides powerful tools to broaden our understanding of ligand interaction with TRPV channels, and the availability of purified human TRPV3 opens up perspectives for further structural and functional studies. PMID:25829496

  6. Integrating fluorescence and interactance measurements to improve apple maturity assessment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fluorescence and interactance are promising techniques for measuring fruit quality and condition. Our previous research showed that a hyperspectral imaging technique integrating fluorescence and reflectance could improve predictions of selected quality parameters compared to single sensing technique...

  7. Mathematical modeling of reflectance and intrinsic fluorescence for cancer detection in human pancreatic tissue

    NASA Astrophysics Data System (ADS)

    Wilson, Robert H.; Chandra, Malavika; Scheiman, James; Simeone, Diane; McKenna, Barbara; Purdy, Julianne; Mycek, Mary-Ann

    2009-02-01

    Pancreatic adenocarcinoma has a five-year survival rate of only 4%, largely because an effective procedure for early detection has not been developed. In this study, mathematical modeling of reflectance and fluorescence spectra was utilized to quantitatively characterize differences between normal pancreatic tissue, pancreatitis, and pancreatic adenocarcinoma. Initial attempts at separating the spectra of different tissue types involved dividing fluorescence by reflectance, and removing absorption artifacts by applying a "reverse Beer-Lambert factor" when the absorption coefficient was modeled as a linear combination of the extinction coefficients of oxy- and deoxy-hemoglobin. These procedures demonstrated the need for a more complete mathematical model to quantitatively describe fluorescence and reflectance for minimally-invasive fiber-based optical diagnostics in the pancreas.

  8. Intrinsic alignments of BOSS LOWZ galaxies - II. Impact of shape measurement methods

    NASA Astrophysics Data System (ADS)

    Singh, Sukhdeep; Mandelbaum, Rachel

    2016-04-01

    Measurements of intrinsic alignments of galaxy shapes with the large-scale density field, and the inferred intrinsic alignments model parameters, are sensitive to the shape measurement methods used. In this paper, we measure the intrinsic alignments of the Sloan Digital Sky Survey-III (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) low redshift (LOWZ) galaxies using three different shape measurement methods (re-Gaussianization, isophotal, and de Vaucouleurs), identifying a variation in the inferred intrinsic alignments amplitude at the 40 per cent level between these methods, independent of the galaxy luminosity or other properties. We also carry out a suite of systematics tests on the shapes and their two-point correlation functions, identifying a pronounced contribution from additive point spread function systematics in the de Vaucouleurs shapes. Since different methods measure galaxy shapes at different effective radii, the trends we identify in the intrinsic alignments amplitude are consistent with the interpretation that the outer regions of galaxy shapes are more responsive to tidal fields, resulting in isophote twisting and stronger alignments for isophotal shapes. We observe environment dependence of ellipticity, with brightest galaxies in groups being rounder on average compared to satellite and field galaxies. We also study the anisotropy in intrinsic alignments measurements introduced by projected shapes, finding effects consistent with predictions of the non-linear alignment model and hydrodynamic simulations. The large variations seen using the different shape measurement methods have important implications for intrinsic alignments forecasting and mitigation with future surveys.

  9. An optical microsensor to measure fluorescent light intensity in biofilms.

    PubMed

    Beyenal, Haluk; Yakymyshyn, Chris; Hyungnak, Jeon; Davis, Catherine C; Lewandowski, Zbigniew

    2004-09-01

    We have developed an optical microsensor to quantify fluorescent light intensity distribution in biofilms. The optical system consisted of a beam splitter, light couplers, filters and a spectrophotometer able to accept the fiberoptic cable to measure fluorescent light intensity. The emitted light, fluorescence from the biofilm, was collected at the tip of the optical microsensor and was transferred to a spectrophotometer via a fiberoptic cable. The total fluorescent light intensity was evaluated from the emission spectrum by numerical integration. The newly developed fiberoptic microsensor was tested using a Staphylococcus aureus strain producing yellow fluorescent protein (YFP) grown as biofilm. We used a 405-nm violet laser diode for excitation, and measured the emission intensity between 480 nm and 540 nm. The optical microsensor that quantifies fluorescent light intensity is a promising tool in biofilm research which often requires detection and quantification of fluorescent light intensity distribution generated by various fluorescent proteins. PMID:15279941

  10. Fluorescent nanosensors for intracellular measurements: synthesis, characterization, calibration, and measurement

    PubMed Central

    Desai, Arpan S.; Chauhan, Veeren M.; Johnston, Angus P. R.; Esler, Tim; Aylott, Jonathan W.

    2013-01-01

    Measurement of intracellular acidification is important for understanding fundamental biological pathways as well as developing effective therapeutic strategies. Fluorescent pH nanosensors are an enabling technology for real-time monitoring of intracellular acidification. The physicochemical characteristics of nanosensors can be engineered to target specific cellular compartments and respond to external stimuli. Therefore, nanosensors represent a versatile approach for probing biological pathways inside cells. The fundamental components of nanosensors comprise a pH-sensitive fluorophore (signal transducer) and a pH-insensitive reference fluorophore (internal standard) immobilized in an inert non-toxic matrix. The inert matrix prevents interference of cellular components with the sensing elements as well as minimizing potentially harmful effects of some fluorophores on cell function. Fluorescent nanosensors are synthesized using standard laboratory equipment and are detectable by non-invasive widely accessible imaging techniques. The outcomes of studies employing this technology are dependent on reliable methodology for performing measurements. In particular, special consideration must be given to conditions for sensor calibration, uptake conditions and parameters for image analysis. We describe procedures for: (1) synthesis and characterization of polyacrylamide and silica based nanosensors, (2) nanosensor calibration and (3) performing measurements using fluorescence microscopy. PMID:24474936

  11. Apparatus for eliminating background interference in fluorescence measurements

    DOEpatents

    Martin, John C.; Jett, James H.

    1986-01-01

    The disclosure is directed to an apparatus for eliminating background interference during fluorescence measurements in a multiple laser flow cytometer. A biological particle stained with fluorescent dyes is excited by a laser. A fluorescence detector detects the fluorescence. The particle scatters light and a gate signal is generated and delayed until the biological particle reaches the next laser. The delayed signal turns on this next laser, which excites a different stained component of the same biological particle.

  12. Apparatus for eliminating background interference in fluorescence measurements

    DOEpatents

    Martin, J.C.; Jett, J.H.

    1984-01-06

    The disclosure is directed to an apparatus for eliminating background interference during fluorescence measurements in a multiple laser flow cytometer. A biological particle stained with fluorescent dyes is excited by a laser. A fluorescence detector detects the fluorescence. The particle scatters light and a gate signal is generated and delayed until the biological particle reaches the next laser. The delayed signal turns on this next laser which excites a different stained component of the same biological particle.

  13. Apparatus for eliminating background interference in fluorescence measurements

    DOEpatents

    Martin, J.C.; Jett, J.H.

    1986-03-04

    The disclosure is directed to an apparatus for eliminating background interference during fluorescence measurements in a multiple laser flow cytometer. A biological particle stained with fluorescent dyes is excited by a laser. A fluorescence detector detects the fluorescence. The particle scatters light and a gate signal is generated and delayed until the biological particle reaches the next laser. The delayed signal turns on this next laser, which excites a different stained component of the same biological particle. 8 figs.

  14. Direct measurement of the intrinsic linewidth of a resonant state

    NASA Astrophysics Data System (ADS)

    Kobos, Zachary; Reed, Mark

    2015-03-01

    We have applied inelastic electron tunneling spectroscopy (IETS) techniques to a resonantly-coupled system to determine quantitative differences in resonant versus non-resonant IETS. We use as a model system a set of GaAs-AlGaAs resonant tunneling diodes (RTDs)(footnote: with different barrier widths to tune resonant state linewidths and transmission coefficients. Modulation-broadening studies confirm theoretical predictions; however, the thermal dependence is markedly different than expected from classical IETS theory. An analysis of resonance shut-off reveals that the thermal dependence reflects the thermal broadening of the injector and resonant state density of states. Using this analysis, we show that one can extract both the transmission coefficient and the intrinsic linewidth of the resonant state. This is compared for RTDs of different tunneling barrier widths, and we observe the expected increase in resonance width for thinner barriers. This work was supported by the National Science Foundation.

  15. Dissolved-oxygen quenching of in-situ fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Chudyk, Wayne; Tonaszuck, David; Pohlig, Kenneth

    1993-04-01

    In-situ fluorescence measurements of aromatic organic ground water contaminants do not always agree with gas chromatographic methods. Dissolved oxygen quenching of fluorescence may be an interferant in field measurements. Two standard fluorescent aromatics, quinine sulfate and naphthalene, were evaluated in this study. Over the range of dissolved oxygen concentrations expected to be encountered in the field, no effects of oxygen quenching on fluorescence of these compounds was observed. Quenching of quinine sulfate fluorescence by sodium chloride was observed using this system. Sodium chloride quenching was shown to follow the Stern-Volmer relation.

  16. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, C.; Steinkamp, J.A.

    1999-06-01

    Time-resolved fluorescence decay measurements are disclosed for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated CW laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes. 12 figs.

  17. Time-resolved fluorescence decay measurements for flowing particles

    DOEpatents

    Deka, Chiranjit; Steinkamp, John A.

    1999-01-01

    Time-resolved fluorescence decay measurements for flowing particles. An apparatus and method for the measurement and analysis of fluorescence for individual cells and particles in flow are described, wherein the rapid measurement capabilities of flow cytometry and the robust measurement and analysis procedures of time-domain fluorescence lifetime spectroscopy are combined. A pulse-modulated cw laser is employed for excitation of the particles. The characteristics and the repetition rate of the excitation pulses can be readily adjusted to accommodate for fluorescence decays having a wide range of lifetimes.

  18. Fluorescent pH probes, fluorescent proteins, and intrinsic cellular fluorochromes are tools to study cytosolic pH (pHcyt) in mammalian cells.

    NASA Astrophysics Data System (ADS)

    Martinez, Gloria M.; Gollahon, Lauren S.; Shafer, Keri; Oomman, Sowmini K.; Busch, Christian; Martinez-Zaguilan, Raul

    2001-07-01

    Our understanding of intracellular pH homeostatis in eukaryotic systems has been enhanced since the introduction of carboxyfluorescein diacetate as a useful pH probe more than 20 years ago. BCECF, a derivative of this earlier fluoroprobe has dominated the field. In the past 10 years, SNARF-1 has emerged as an alternative pH probe. Recently, a novel derivative of BCECF, BCPCF has been developed. Green Fluorescent Proteins (GFPs) have also been used recently to monitor pH in a non invasive manner in several cell types. Here, we report that human mammary epithelial cells can be transfected with the gene encoding for cyan (CFP), green (GFP), and yellow (YFP), to study cytosolic pH. The novel red fluorescent protein (DsRed) is not sensitive to pH. Multidrug resistance (MDR) has been associated with altered cytosolic pH homeostasis. We show that experimental maneuvers that decrease pHin enhance the efficacy of chemotherapeutic drugs. We also show that short pulses of UV-B light elicited acidosis in cells, as evaluated by ratio ion cell imaging, and confocal/spectral imaging microscopy. During the course of these experiments we noticed that cells exhibit intrinsic fluorochromes that can be used to monitor pH in living cells.

  19. [Monitoring the Redox States of Thioredoxin in Protein-Protein Interaction Using Intrinsic Fluorescence Probe].

    PubMed

    Wang, Pan; Guo, Ai-yu; Chang, Guan-xiao; Ran, Xia; Zhang, Yu; Guo, Li-jun

    2015-10-01

    The cellular redox states directly affect cell proliferation, differentiation and apoptosis, and the redox states changes is particularly important to the regulation of cell survival or death. Thioredoxin is a kind of oxidation regulatory protein which is widely exists in organisms, and the change of redox states is also an important process in redox regulation. In this work, we have used the site-directed mutagenesis of protein, SDS-polyacrylamide gel electrophoresis fluorescence spectroscopy and circular dichroism etc., to investigate redox states changes between TRX (E. coli) and glutathione peroxidase(GPX3) during their interaction. By observing the fluorescence spectra of TRX and its mutants, we have studied the protein interactions as well as the redox states switching between oxidation state TRX and the reduced state GPX3. The results demonstrate the presence of interactions and electron exchanges occurring between reduced GPX3 and oxidized TRX, which is of significance for revealing the physical and chemical mechanism of TRX in intracellular signal transduction. PMID:26904821

  20. Multiplexed fluorescence tomography with spectral and temporal data: demixing with intrinsic regularization.

    PubMed

    Pera, Vivian; Brooks, Dana H; Niedre, Mark

    2016-01-01

    We consider the joint use of spectral and temporal data for multiplexed fluorescence molecular tomography to enable high-throughput imaging of multiple fluorescent targets in bulk tissue. This is a challenging problem due to the narrow near-infrared diagnostic window and relatively broad emission spectra of common fluorophores, and the distortion ("redshift") that the fluorophore signals undergo as they propagate through tissue. We show through a Cramér-Rao lower bound analysis that demixing with spectral-temporal data could result in an order of magnitude improvement in performance over either modality alone. To cope with the resulting large data set, we propose a novel two-stage algorithm that decouples the demixing and tomographic reconstruction operations. In this work we concentrate on the demixing stage. We introduce an approach which incorporates ideas from sparse subspace clustering and compressed sensing and does not require a regularization parameter. We report on simulations in which we simultaneously demixed four fluorophores with closely overlapping spectral and temporal profiles in a 25 mm diameter cross-sectional area with a root-mean-square error of less than 3% per fluorophore, as well as on studies of sensitivity of the method to model mismatch. PMID:26819822

  1. Multiplexed fluorescence tomography with spectral and temporal data: demixing with intrinsic regularization

    PubMed Central

    Pera, Vivian; Brooks, Dana H.; Niedre, Mark

    2015-01-01

    We consider the joint use of spectral and temporal data for multiplexed fluorescence molecular tomography to enable high-throughput imaging of multiple fluorescent targets in bulk tissue. This is a challenging problem due to the narrow near-infrared diagnostic window and relatively broad emission spectra of common fluorophores, and the distortion (“redshift”) that the fluorophore signals undergo as they propagate through tissue. We show through a Cramér-Rao lower bound analysis that demixing with spectral-temporal data could result in an order of magnitude improvement in performance over either modality alone. To cope with the resulting large data set, we propose a novel two-stage algorithm that decouples the demixing and tomographic reconstruction operations. In this work we concentrate on the demixing stage. We introduce an approach which incorporates ideas from sparse subspace clustering and compressed sensing and does not require a regularization parameter. We report on simulations in which we simultaneously demixed four fluorophores with closely overlapping spectral and temporal profiles in a 25 mm diameter cross-sectional area with a root-mean-square error of less than 3% per fluorophore, as well as on studies of sensitivity of the method to model mismatch. PMID:26819822

  2. Suitability of fluorescence measurements to quantify sulfate-reducing bacteria.

    PubMed

    Barton, Larry L; Carpenter, Claire M

    2013-06-01

    Fluorescence activity has been used to identify Desulfovibrio and has been termed the 'desulfoviridin test'. This fluorescence is attributed to the prosthetic group of bisulfite reductase, a key enzyme in dissimilatory sulfate reduction. We have pursued the use of fluorescence measurements to quantify sulfate-reducing bacteria. Cells of D. desulfuricans and D. gigas were treated with NaOH and produced two fluorescence spectra: one with maximum fluorescence with an excitation at 395 nm and an emission at 605 nm and another with an excitation at 320 nm and emission at 360 nm. Using the fluorescence with excitation at 395 nm and emission at 605 nm, we explored a series of parameters to measure Desulfovibrio in pure cultures and environmental samples. Fluorescence measurements are reliable provided the cells are treated with 1.75 N NaOH and the chromophore released from the cells is not exposed to strong light intensity, and is not exposed to temperatures greater than 20 °C, and measurements are done within a few minutes of extraction. Bleaching of fluorescence was attributed to metal ions in solution which was not observed until metal concentrations reached 1.5mM. We propose that D. desulfuricans is appropriate as the reference organism for measurement of sulfate-reducing bacteria by fluorescence and by using fluorescence intensity, 10(5) cells/ml can be readily detected in environmental samples. PMID:23566827

  3. Fluorescent Protein Based FRET Pairs with Improved Dynamic Range for Fluorescence Lifetime Measurements.

    PubMed

    George Abraham, Bobin; Sarkisyan, Karen S; Mishin, Alexander S; Santala, Ville; Tkachenko, Nikolai V; Karp, Matti

    2015-01-01

    Fluorescence Resonance Energy Transfer (FRET) using fluorescent protein variants is widely used to study biochemical processes in living cells. FRET detection by fluorescence lifetime measurements is the most direct and robust method to measure FRET. The traditional cyan-yellow fluorescent protein based FRET pairs are getting replaced by green-red fluorescent protein variants. The green-red pair enables excitation at a longer wavelength which reduces cellular autofluorescence and phototoxicity while monitoring FRET. Despite the advances in FRET based sensors, the low FRET efficiency and dynamic range still complicates their use in cell biology and high throughput screening. In this paper, we utilized the higher lifetime of NowGFP and screened red fluorescent protein variants to develop FRET pairs with high dynamic range and FRET efficiency. The FRET variations were analyzed by proteolytic activity and detected by steady-state and time-resolved measurements. Based on the results, NowGFP-tdTomato and NowGFP-mRuby2 have shown high potentials as FRET pairs with large fluorescence lifetime dynamic range. The in vitro measurements revealed that the NowGFP-tdTomato has the highest Förster radius for any fluorescent protein based FRET pairs yet used in biological studies. The developed FRET pairs will be useful for designing FRET based sensors and studies employing Fluorescence Lifetime Imaging Microscopy (FLIM). PMID:26237400

  4. Models of fluorescence and photosynthesis for interpreting measurements of solar-induced chlorophyll fluorescence

    PubMed Central

    van der Tol, C; Berry, J A; Campbell, P K E; Rascher, U

    2014-01-01

    We have extended a conventional photosynthesis model to simulate field and laboratory measurements of chlorophyll fluorescence at the leaf scale. The fluorescence paramaterization is based on a close nonlinear relationship between the relative light saturation of photosynthesis and nonradiative energy dissipation in plants of different species. This relationship diverged only among examined data sets under stressed (strongly light saturated) conditions, possibly caused by differences in xanthophyll pigment concentrations. The relationship was quantified after analyzing data sets of pulse amplitude modulated measurements of chlorophyll fluorescence and gas exchange of leaves of different species exposed to different levels of light, CO2, temperature, nitrogen fertilization treatments, and drought. We used this relationship in a photosynthesis model. The coupled model enabled us to quantify the relationships between steady state chlorophyll fluorescence yield, electron transport rate, and photosynthesis in leaves under different environmental conditions. Key Points Light saturation of photosynthesis determines quenching of leaf fluorescence We incorporated steady state leaf fluorescence in a photosynthesis model PMID:27398266

  5. Mammalian pharmacokinetics of carbon nanotubes using intrinsic near-infrared fluorescence

    PubMed Central

    Cherukuri, Paul; Gannon, Christopher J.; Leeuw, Tonya K.; Schmidt, Howard K.; Smalley, Richard E.; Curley, Steven A.; Weisman, R. Bruce

    2006-01-01

    Individualized, chemically pristine single-walled carbon nanotubes have been intravenously administered to rabbits and monitored through their characteristic near-infrared fluorescence. Spectra indicated that blood proteins displaced the nanotube coating of synthetic surfactant molecules within seconds. The nanotube concentration in the blood serum decreased exponentially with a half-life of 1.0 ± 0.1 h. No adverse effects from low-level nanotube exposure could be detected from behavior or pathological examination. At 24 h after i.v. administration, significant concentrations of nanotubes were found only in the liver. These results demonstrate that debundled single-walled carbon nanotubes are high-contrast near-infrared fluorophores that can be sensitively and selectively tracked in mammalian tissues using optical methods. In addition, the absence of acute toxicity and promising circulation persistence suggest the potential of carbon nanotubes in future pharmaceutical applications. PMID:17135351

  6. Dissecting the Catalytic Mechanism of Betaine-Homocysteine S-Methyltransferase Using Intrinsic Tryptophan Fluorescence and Site-Directed Mutagenesis

    SciTech Connect

    Castro, C.; Gratson, A.A.; Evans, J.C.; Jiracek, J.; Collinsova, M.; Ludwig, M.L.; Garrow, T.A.

    2010-03-05

    Betaine-homocysteine S-methyltransferase (BHMT) is a zinc-dependent enzyme that catalyzes the transfer of a methyl group from glycine betaine (Bet) to homocysteine (Hcy) to form dimethylglycine (DMG) and methionine (Met). Previous studies in other laboratories have indicated that catalysis proceeds through the formation of a ternary complex, with a transition state mimicked by the inhibitor S-({delta}-carboxybutyl)-l-homocysteine (CBHcy). Using changes in intrinsic tryptophan fluorescence to determine the affinity of human BHMT for substrates, products, or CBHcy, we now demonstrate that the enzyme-substrate complex reaches its transition state through an ordered bi-bi mechanism in which Hcy is the first substrate to bind and Met is the last product released. Hcy, Met, and CBHcy bind to the enzyme to form binary complexes with K{sub d} values of 7.9, 6.9, and 0.28 {micro}M, respectively. Binary complexes with Bet and DMG cannot be detected with fluorescence as a probe, but Bet and DMG bind tightly to BHMT-Hcy to form ternary complexes with K{sub d} values of 1.1 and 0.73 {micro}M, respectively. Mutation of each of the seven tryptophan residues in human BHMT provides evidence that the enzyme undergoes two distinct conformational changes that are reflected in the fluorescence of the enzyme. The first is induced when Hcy binds, and the second, when Bet binds. As predicted by the crystal structure of BHMT, the amino acids Trp44 and Tyr160 are involved in binding Bet, and Glu159 in binding Hcy. Replacing these residues by site-directed mutagenesis significantly reduces the catalytic efficiency (V{sub max}/K{sub m}) of the enzyme. Replacing Tyr77 with Phe abolishes enzyme activity.

  7. Superresolution intrinsic fluorescence imaging of chromatin utilizing native, unmodified nucleic acids for contrast.

    PubMed

    Dong, Biqin; Almassalha, Luay M; Stypula-Cyrus, Yolanda; Urban, Ben E; Chandler, John E; Nguyen, The-Quyen; Sun, Cheng; Zhang, Hao F; Backman, Vadim

    2016-08-30

    Visualizing the nanoscale intracellular structures formed by nucleic acids, such as chromatin, in nonperturbed, structurally and dynamically complex cellular systems, will help expand our understanding of biological processes and open the next frontier for biological discovery. Traditional superresolution techniques to visualize subdiffractional macromolecular structures formed by nucleic acids require exogenous labels that may perturb cell function and change the very molecular processes they intend to study, especially at the extremely high label densities required for superresolution. However, despite tremendous interest and demonstrated need, label-free optical superresolution imaging of nucleotide topology under native nonperturbing conditions has never been possible. Here we investigate a photoswitching process of native nucleotides and present the demonstration of subdiffraction-resolution imaging of cellular structures using intrinsic contrast from unmodified DNA based on the principle of single-molecule photon localization microscopy (PLM). Using DNA-PLM, we achieved nanoscopic imaging of interphase nuclei and mitotic chromosomes, allowing a quantitative analysis of the DNA occupancy level and a subdiffractional analysis of the chromosomal organization. This study may pave a new way for label-free superresolution nanoscopic imaging of macromolecular structures with nucleotide topologies and could contribute to the development of new DNA-based contrast agents for superresolution imaging. PMID:27535934

  8. Photon-counting technique for rapid fluorescence-decay measurement.

    PubMed

    Pack, S D; Renfro, M W; King, G B; Laurendeau, N M

    1998-08-01

    We report on a novel laser-induced fluorescence triple-integration method (LIFTIME) that is capable of making rapid, continuous fluorescence lifetime measurements by a unique photon-counting technique. The LIFTIME has been convolved with picosecond time-resolved laser-induced fluorescence, which employs a high-repetition-rate mode-locked laser, permitting the eventual monitoring of instantaneous species concentrations in turbulent flames. We verify the technique by application of the LIFTIME to two known fluorescence media, diphenyloxazole (PPO) and quinine sulfate monohydrate (QSM). PPO has a fluorescence lifetime of 1.28 ns, whereas QSM has a fluorescence lifetime that can be varied from 1.0 to 3.0 ns. From these liquid samples we demonstrate that fluorescence lifetime can currently be monitored at a sampling rate of up to 500 Hz with less than 10% uncertainty (1 sigma) . PMID:18087478

  9. Understanding the contributions of NADH and collagen to cervical tissue fluorescence spectra: modeling, measurements, and implications

    NASA Astrophysics Data System (ADS)

    Drezek, Rebekah A.; Sokolov, Konstantin V.; Utzinger, Urs; Boiko, Iouri; Malpica, Anais; Follen, Michele; Richards-Kortum, Rebecca R.

    2001-10-01

    Objective: At 380 nm excitation, cervical tissue fluorescence spectra demonstrate characteristic changes with both patient age and the presence of dysplasia. A Monte Carlo model was developed in order to quantitatively examine how intrinsic NADH and collagen fluorescence, in combination with tissue scattering and absorption properties, yield measured tissue spectra. Methods: Excitation-emission matrices were measured for live cervical cells and collagen gel phantoms. Fluorescence microscopy of fresh tissue sections was performed to obtain the location and density of fluorophores as a function of patient age and the presence of dysplasia. A Monte Carlo model was developed which incorporated measurements of fluorophore line shapes and spatial distributions. Results: Modeled spectra were consistent with clinical measurements and indicate that an increase in NADH fluorescence and decrease in collagen fluorescence create clinically observed differences between normal and dysplastic tissue spectra. Model predictions were most sensitive to patient age and epithelial thickness. Conclusions: Monte Carlo techniques provide an important means to investigate the combined contributions of multiple fluorophores to measured emission spectra. The approach will prove increasingly valuable as a more sophisticated understanding of in vivo optical properties is developed.

  10. SIMULTANEOUS MEASUREMENT OF CIRCULAR DICHROISM AND FLUORESCENCE POLARIZATION ANISOTROPY.

    SciTech Connect

    SUTHERLAND,J.C.

    2002-01-19

    Circular dichroism and fluorescence polarization anisotropy are important tools for characterizing biomolecular systems. Both are used extensively in kinetic experiments involving stopped- or continuous flow systems as well as titrations and steady-state spectroscopy. This paper presents the theory for determining circular dichroism and fluorescence polarization anisotropy simultaneously, thus insuring the two parameters are recorded under exactly the same conditions and at exactly the same time in kinetic experiments. The approach to measuring circular dichroism is that used in almost all conventional dichrographs. Two arrangements for measuring fluorescence polarization anisotropy are described. One uses a single fluorescence detector and signal processing with a lock-in amplifier that is similar to the measurement of circular dichroism. The second approach uses classic ''T'' format detection optics, and thus can be used with conventional photon-counting detection electronics. Simple extensions permit the simultaneous measurement of the absorption and excitation intensity corrected fluorescence intensity.

  11. Time-resolved spectroscopy of the intrinsic fluorescence of nucleic acid species

    NASA Astrophysics Data System (ADS)

    Daniels, Malcolm; Hart, Lucas P.; Ho, Paul S.; Ballini, Jean-Pierre; Vigny, Paul

    1990-05-01

    Polarization and lifetime studies have shown that the fluorescence from nucleic acid species is complex, both at the individual chromophore level and because of the effect of stacking interactions on the electronic states. Recent work aimed at elucidating some aspects of this behavior by decay analysis and time-resolved spectroscopy is surveyed. Experimental work has been carried out using the ACO synchrotron at LURE, France) with time-correlated single photon counting, or a frequency-doubled N2-pumped dye laser, pulse width 700 ps, with fast-gated (100 ps width) analog detection and signal averaging. Decay curves are treated by global analysis using the Marquardt non-linear least-squares algorithm (synchrotron data) or the SPLMOD program (EMBO), which carries out a non-linear leastsquares minimization using cubic splines, for the laser data. Resolution of the decay data gives a model-based estimate of the number of components and their lifetimes. This information is then used to deconvolute timewindowed spectra (time-delayed spectra) into the time-resolved spectra. It is a particular feature of the combination of delayed photon counting with the continuous wavelength distribution of pulsed synchrotron radiation that excitation spectra correlating with emissions of different lifetimes can be obtained by uninterrupted repetitive scanning over a wide range of exciting wavelengths, in the present work from 230 nm to 354 urn. Such time-delayed excitation spectra can also be deconvoluted into components corresponding to the various time-resolved emission spectra. Examples of these three types of information viz resolved lifetimes, time-resolved emission spectra and their excitation spectra are presented and discussed for the following systems. I. adenosine; 6N, 6N-dimethyladenosine; protonated adenosine; this work shows the role of rotamers in the excited state behavior of this chromophore and demonstrates the forbidden nature of the lowest excited state. II. d(AT); d

  12. Intracellular distribution of fluorescent copper and zinc bis(thiosemicarbazonato) complexes measured with fluorescence lifetime spectroscopy.

    PubMed

    Hickey, James L; James, Janine L; Henderson, Clare A; Price, Katherine A; Mot, Alexandra I; Buncic, Gojko; Crouch, Peter J; White, Jonathan M; White, Anthony R; Smith, Trevor A; Donnelly, Paul S

    2015-10-01

    The intracellular distribution of fluorescently labeled copper and zinc bis(thiosemicarbazonato) complexes was investigated in M17 neuroblastoma cells and primary cortical neurons with a view to providing insights into the neuroprotective activity of a copper bis(thiosemicarbazonato) complex known as Cu(II)(atsm). Time-resolved fluorescence measurements allowed the identification of the Cu(II) and Zn(II) complexes as well as the free ligand inside the cells by virtue of the distinct fluorescence lifetime of each species. Confocal fluorescent microscopy of cells treated with the fluorescent copper(II)bis(thiosemicarbazonato) complex revealed significant fluorescence associated with cytoplasmic puncta that were identified to be lysosomes in primary cortical neurons and both lipid droplets and lysosomes in M17 neuroblastoma cells. Fluorescence lifetime imaging microscopy confirmed that the fluorescence signal emanating from the lipid droplets could be attributed to the copper(II) complex but also that some degree of loss of the metal ion led to diffuse cytosolic fluorescence that could be attributed to the metal-free ligand. The accumulation of the copper(II) complex in lipid droplets could be relevant to the neuroprotective activity of Cu(II)(atsm) in models of amyotrophic lateral sclerosis and Parkinson's disease. PMID:26397162

  13. Measuring initiator caspase activation by bimolecular fluorescence complementation.

    PubMed

    Parsons, Melissa J; Bouchier-Hayes, Lisa

    2015-01-01

    Initiator caspases, including caspase-2, -8, and -9, are activated by the proximity-driven dimerization that occurs after their recruitment to activation platforms. Here we describe the use of caspase bimolecular fluorescence complementation (caspase BiFC) to measure this induced proximity. BiFC assays rely on the use of a split fluorescent protein to identify protein-protein interactions in cells. When fused to interacting proteins, the fragments of the split fluorescent protein (which do not fluoresce on their own) can associate and fluoresce. In this protocol, we use the fluorescent protein Venus, a brighter and more photostable variant of yellow fluorescent protein (YFP), to detect the induced proximity of caspase-2. Plasmids encoding two fusion products (caspase-2 fused to either the amino- or carboxy-terminal halves of Venus) are transfected into cells. The cells are then treated with an activating (death) stimulus. The induced proximity (and subsequent activation) of caspase-2 in the cells is visualized as Venus fluorescence. The proportion of Venus-positive cells at a single time point can be determined using fluorescence microscopy. Alternatively, the increase in fluorescence intensity over time can be evaluated by time-lapse confocal microscopy. The caspase BiFC strategy described here should also work for other initiator caspases, such as caspase-8 or -9, as long as the correct controls are used. PMID:25561623

  14. Laser-fluorescence measurement of marine algae

    NASA Technical Reports Server (NTRS)

    Browell, E. V.

    1980-01-01

    Progress in remote sensing of algae by laser-induced fluorescence is subject of comprehensive report. Existing single-wavelength and four-wavelength systems are reviewed, and new expression for power received by airborne sensor is derived. Result differs by as much as factor of 10 from those previously reported. Detailed error analysis evluates factors affecting accuracy of laser-fluorosensor systems.

  15. Measurement of Fluorescence Spectra from Ambient Aerosol Particles Using Laser-induced Fluorescence Technique

    NASA Astrophysics Data System (ADS)

    Taketani, F.; Kanaya, Y.; Nakamura, T.; Moteki, N.; Takegawa, N.

    2011-12-01

    To obtain the information of composition of organic aerosol particles in atmosphere, we developed an instrument using laser-induced fluorescence (LIF) technique. To measure the fluorescence from a particle, we employed two lasers. Scattering light signal derived from a single particle upon crossing the 635nm-CW laser triggers the 266nm-pulsed laser to excite the particle. Fluorescence from the particle in the wavelength range 300-600nm is spectrally dispersed by a grating spectrometer and then detected by a 32-Ch photo-multiplier tube(PMT). The aerosol stream is surrounded by a coaxial sheath air flow and delivered to the optical chamber at atmospheric pressure. Using PSL particles with known sizes, we made a calibration curve to estimate particle size from scattering light intensity. With the current setup of the instrument we are able to detect both scattering and fluorescence from particles whose diameters are larger than 0.5um. Our system was able to differentiate particles composed of mono-aromatic species (e.g. Tryptophan) from those of Riboflavin, by their different fluorescence wavelengths. Also, measurements of fluorescence spectra of ambient particles were demonstrated in our campus in Yokosuka city, facing Tokyo bay in Japan. We obtained several types of florescence spectra in the 8 hours. Classification of the measured fluorescence spectra will be discussed in the presentation.

  16. Double-excitation fluorescence spectral imaging: eliminating tissue auto-fluorescence from in vivo PPIX measurements

    NASA Astrophysics Data System (ADS)

    Torosean, Sason; Flynn, Brendan; Samkoe, Kimberley S.; Davis, Scott C.; Gunn, Jason; Axelsson, Johan; Pogue, Brian W.

    2012-02-01

    An ultrasound coupled handheld-probe-based optical fluorescence molecular tomography (FMT) system has been in development for the purpose of quantifying the production of Protoporphyrin IX (PPIX) in aminolevulinic acid treated (ALA), Basal Cell Carcinoma (BCC) in vivo. The design couples fiber-based spectral sampling of PPIX fluorescence emission with a high frequency ultrasound imaging system, allowing regionally localized fluorescence intensities to be quantified [1]. The optical data are obtained by sequential excitation of the tissue with a 633nm laser, at four source locations and five parallel detections at each of the five interspersed detection locations. This method of acquisition permits fluorescence detection for both superficial and deep locations in ultrasound field. The optical boundary data, tissue layers segmented from ultrasound image and diffusion theory are used to estimate the fluorescence in tissue layers. To improve the recovery of the fluorescence signal of PPIX, eliminating tissue autofluorescence is of great importance. Here the approach was to utilize measurements which straddled the steep Qband excitation peak of PPIX, via the integration of an additional laser source, exciting at 637 nm; a wavelength with a 2 fold lower PPIX excitation value than 633nm.The auto-fluorescence spectrum acquired from the 637 nm laser is then used to spectrally decouple the fluorescence data and produce an accurate fluorescence emission signal, because the two wavelengths have very similar auto-fluorescence but substantially different PPIX excitation levels. The accuracy of this method, using a single source detector pair setup, is verified through animal tumor model experiments, and the result is compared to different methods of fluorescence signal recovery.

  17. Fluorescence spectroscopy: a rapid, noninvasive method for measurement of skin surface thickness of topical agents.

    PubMed

    Rhodes, L E; Diffey, B L

    1997-01-01

    We report the quantification of skin surface thickness of topical agents by in vivo fluorescence spectroscopy, and demonstrate its potential uses for assessment of application technique and substantivity. A series of studies were performed on forearm skin of eight normal subjects using three creams which have intrinsic fluorescence: a sunscreen (Neutrogena SPF15 waterproof cream), an antiseptic (Hewlett's cream) and a steroid (Trimovate (clobetasone butyrate) cream). Initially, the dose-response relationship was established for each agent by applying a series of five doses (0.5-8 microliters/cm2) and measuring cream fluorescence using appropriate excitation and emission wavelengths. Next, the influence of application technique was examined by comparing light application of cream with firm rubbing. Substantivity of the three creams was assessed on dry skin by taking fluorescence measurements over 8 h. Finally, water resistance of 2 microliters/cm2 of sunscreen and antiseptic cream were compared by measuring fluorescence after each of four water immersions. The fluorescence intensity was strongly correlated with the logarithm of surface density. r = 1.0, 0.92 and 0.98 for sunscreen, antiseptic and steroid creams, respectively, allowing derivation of a simple expression for equivalent thickness. Surface thickness of each cream was lower following firm rubbing compared with light application (P < 0.01). The rate constants for reduction of surface density of the three creams with time on dry skin were not significantly different. However, on washed skin, the rate constant was higher for Hewlett's than Neutrogena cream (0.503 and 0.243 h. respectively, P = 0.02), with a higher rate for each cream on wet compared with dry skin (P < 0.001). Hence, fluorescence spectroscopy is a simple, rapid method for measurement of cream thickness in vivo. The many potential applications in dermatology include quantitative assessment of application technique and substantivity of topical

  18. On intrinsic time measure in the modeling of cyclic behavior of a Nitinol cubic block

    NASA Astrophysics Data System (ADS)

    Chiroiu, Veturia; Florinel Ionescu, Marius; Sireteanu, Tudor; Ioan, Rodica; Munteanu, Ligia

    2015-03-01

    In this paper, the cyclic behavior of a superelastic-plastic nitinol cubic block is described by using the Bouc-Wen model coupled to an intrinsic time measure other than clock time, which governs the behavior of the materials. As a consequence, the thermodynamic admissibility of the Bouc-Wen model is provided by the endochronic theory of plasticity. The role of the intrinsic time measure is described by capturing the stiffness and strength degradation and the opposite phenomena. Such behavior is due to the permanent-strain addition of residual martensite and alterations in the properties of the texture during phase transformation.

  19. Observation of spectrum effect on the measurement of intrinsic error field on EAST

    NASA Astrophysics Data System (ADS)

    Wang, Hui-Hui; Sun, You-Wen; Qian, Jin-Ping; Shi, Tong-Hui; Shen, Biao; Gu, Shuai; Liu, Yue-Qiang; Guo, Wen-Feng; Chu, Nan; He, Kai-Yang; Jia, Man-Ni; Chen, Da-Long; Xue, Min-Min; Ren, Jie; Wang, Yong; Sheng, Zhi-Cai; Xiao, Bing-Jia; Luo, Zheng-Ping; Liu, Yong; Liu, Hai-Qing; Zhao, Hai-Lin; Zeng, Long; Gong, Xian-Zu; Liang, Yun-Feng; Wan, Bao-Nian; The EAST Team

    2016-06-01

    Intrinsic error field on EAST is measured using the ‘compass scan’ technique with different n  =  1 magnetic perturbation coil configurations in ohmically heated discharges. The intrinsic error field measured using a non-resonant dominated spectrum with even connection of the upper and lower resonant magnetic perturbation coils is of the order {{b}r2,1}/{{B}\\text{T}}≃ {{10}-5} and the toroidal phase of intrinsic error field is around {{60}{^\\circ}} . A clear difference between the results using the two coil configurations, resonant and non-resonant dominated spectra, is observed. The ‘resonant’ and ‘non-resonant’ terminology is based on vacuum modeling. The penetration thresholds of the non-resonant dominated cases are much smaller than that of the resonant cases. The difference of penetration thresholds between the resonant and non-resonant cases is reduced by plasma response modeling using the MARS-F code.

  20. System and method for measuring fluorescence of a sample

    DOEpatents

    Riot, Vincent J

    2015-03-24

    The present disclosure provides a system and a method for measuring fluorescence of a sample. The sample may be a polymerase-chain-reaction (PCR) array, a loop-mediated-isothermal amplification array, etc. LEDs are used to excite the sample, and a photodiode is used to collect the sample's fluorescence. An electronic offset signal is used to reduce the effects of background fluorescence and the noises from the measurement system. An integrator integrates the difference between the output of the photodiode and the electronic offset signal over a given period of time. The resulting integral is then converted into digital domain for further processing and storage.

  1. Models of fluorescence and photosynthesis for interpreting measurements of solar-induced chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Tol, C.; Berry, J. A.; Campbell, P. K. E.; Rascher, U.

    2014-12-01

    We have extended a conventional photosynthesis model to simulate field and laboratory measurements of chlorophyll fluorescence at the leaf scale. The fluorescence paramaterization is based on a close nonlinear relationship between the relative light saturation of photosynthesis and nonradiative energy dissipation in plants of different species. This relationship diverged only among examined data sets under stressed (strongly light saturated) conditions, possibly caused by differences in xanthophyll pigment concentrations. The relationship was quantified after analyzing data sets of pulse amplitude modulated measurements of chlorophyll fluorescence and gas exchange of leaves of different species exposed to different levels of light, CO2, temperature, nitrogen fertilization treatments, and drought. We used this relationship in a photosynthesis model. The coupled model enabled us to quantify the relationships between steady state chlorophyll fluorescence yield, electron transport rate, and photosynthesis in leaves under different environmental conditions.

  2. Fluorescence cross section measurements of biological agent simulants

    SciTech Connect

    Stephens, J.R.

    1996-11-01

    Fluorescence is a powerful technique that has potential uses in detection and characterization of biological aerosols both in the battlefield and in civilian environments. Fluorescence techniques can be used with ultraviolet (UV) light detection and ranging (LIDAR) equipment to detect biological aerosol clouds at a distance, to provide early warning of a biological attack, and to track an potentially noxious cloud. Fluorescence can also be used for detection in a point sensor to monitor biological materials and to distinguish agents from benign aerosols. This work is part of a continuing program by the Army`s Chemical and Biological Defense Command to characterized the optical properties of biological agents. Reported here are ultraviolet fluorescence measurements of Bacillus megaterium and Bacillus Globigii aerosols suspended in an electrodynamic particle trap. Fluorescence spectra of a common atmospheric aerosol, pine pollen, are also presented.

  3. Laser-saturated fluorescence measurements in laminar sooting diffusion flames

    NASA Technical Reports Server (NTRS)

    Wey, Changlie

    1993-01-01

    The hydroxyl radical is known to be one of the most important intermediate species in the combustion processes. The hydroxyl radical has also been considered a dominant oxidizer of soot particles in flames. In this investigation the hydroxyl concentration profiles in sooting diffusion flames were measured by the laser-saturated fluorescence (LSF) method. The temperature distributions in the flames were measured by the two-line LSF technique and by thermocouple. In the sooting region the OH fluorescence was too weak to make accurate temperature measurements. The hydroxyl fluorescence profiles for all four flames presented herein show that the OH fluorescence intensities peaked near the flame front. The OH fluorescence intensity dropped sharply toward the dark region of the flame and continued declining to the sooting region. The OH fluorescence profiles also indicate that the OH fluorescence decreased with increasing height in the flames for all flames investigated. Varying the oxidizer composition resulted in a corresponding variation in the maximum OH concentration and the flame temperature. Furthermore, it appears that the maximum OH concentration for each flame increased with increasing flame temperature.

  4. An all-fiber partial discharge monitoring system based on both intrinsic fiber optic interferometry sensor and fluorescent fiber

    NASA Astrophysics Data System (ADS)

    Yin, Zelin; Zhang, Ruirui; Tong, Jie; Chen, Xi

    2013-12-01

    Partial discharges (PDs) are an electrical phenomenon that occurs within a transformer whenever the voltage stress is sufficient to produce ionization in voids or inclusions within a solid dielectric, at conductor/dielectric interfaces, or in bubbles within liquid dielectrics such as oil; high-frequency transient current discharges will then appear repeatedly and will progressively deteriorate the insulation, ultimately leading to breakdown. Fiber sensor has great potential on the partial discharge detection in high-voltage equipment for its immunity to electromagnetic interference and it can take direct measurement in the high voltage equipment. The energy released in PDs produces a number of effects, resulting in flash, chemical and structural changes and electromagnetic emissions and so on. Acoustic PD detection is based on the mechanical pressure wave emitted from the discharge and fluorescent fiber PD detection is based on the emitted light produced by ionization, excitation and recombination processes during the discharge. Both of the two methods have the shortage of weak anti-interference capacity in the physical environment, like thunder or other sound source. In order to avoid the false report, an all-fiber combined PD detection system of the two methods is developed in this paper. In the system the fluorescent fiber PD sensor is considered as a reference signal, three F-P based PD detection sensors are used to both monitor the PD intensity and calculate the exact position of the discharge source. Considering the wave band of the F-P cavity and the fluorescent probe are quite different, the reflection spectrum of the F-P cavity is in the infrared region, however the fluorescent probe is about 600nm to 700nm, thus the F-P sensor and fluorescent fiber probe can be connected in one fiber and the reflection light can be detected by two different detectors without mutual interference. The all-fiber partial discharge monitoring system not only can detect the PDs

  5. Measurement of Sun Induced Chlorophyll Fluorescence Using Hyperspectral Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Irteza, S. M.; Nichol, J. E.

    2016-06-01

    Solar Induced Chlorophyll Fluorescence (SIF), can be used as an indicator of stress in vegetation. Several scientific approaches have been made and there is considerable evidence that steady state Chlorophyll fluorescence is an accurate indicator of plant stress hence a reliable tool to monitor vegetation health status. Retrieval of Chlorophyll fluorescence provides an insight into photochemical and carbon sequestration processes within vegetation. Detection of Chlorophyll fluorescence has been well understood in the laboratory and field measurement. Fluorescence retrieval methods were applied in and around the atmospheric absorption bands 02B (Red wavelength) approximately 690 nm and 02A (Far red wavelengths) 740 nm. Hyperion satellite images were acquired for the years 2012 to 2015 in different seasons. Atmospheric corrections were applied using the 6S Model. The Fraunhofer Line Discrimanator (FLD) method was applied for retrieval of SIF from the Hyperion images by measuring the signal around the absorption bands in both vegetated and non vegetated land cover types. Absorption values were extracted in all the selected bands and the fluorescence signal was detected. The relationships between NDVI and Fluorescence derived from the satellite images are investigated to understand vegetation response within the absorption bands.

  6. Measuring and Sorting Cell Populations Expressing Isospectral Fluorescent Proteins with Different Fluorescence Lifetimes

    PubMed Central

    Naivar, Mark; Houston, Jessica P.; Brent, Roger

    2014-01-01

    Study of signal transduction in live cells benefits from the ability to visualize and quantify light emitted by fluorescent proteins (XFPs) fused to different signaling proteins. However, because cell signaling proteins are often present in small numbers, and because the XFPs themselves are poor fluorophores, the amount of emitted light, and the observable signal in these studies, is often small. An XFP's fluorescence lifetime contains additional information about the immediate environment of the fluorophore that can augment the information from its weak light signal. Here, we constructed and expressed in Saccharomyces cerevisiae variants of Teal Fluorescent Protein (TFP) and Citrine that were isospectral but had shorter fluorescence lifetimes, ∼1.5 ns vs ∼3 ns. We modified microscopic and flow cytometric instruments to measure fluorescence lifetimes in live cells. We developed digital hardware and a measure of lifetime called a “pseudophasor” that we could compute quickly enough to permit sorting by lifetime in flow. We used these abilities to sort mixtures of cells expressing TFP and the short-lifetime TFP variant into subpopulations that were respectively 97% and 94% pure. This work demonstrates the feasibility of using information about fluorescence lifetime to help quantify cell signaling in living cells at the high throughput provided by flow cytometry. Moreover, it demonstrates the feasibility of isolating and recovering subpopulations of cells with different XFP lifetimes for subsequent experimentation. PMID:25302964

  7. Protein rotational motion in solution measured by polarized fluorescence depletion.

    PubMed Central

    Yoshida, T M; Barisas, B G

    1986-01-01

    A microscope-based system is described for directly measuring protein rotational motion in viscous environments such as cell membranes by polarized fluorescence depletion (PFD). Proteins labeled with fluorophores having a high quantum yield for triplet formation, such as eosin isothiocyanate (EITC), are examined anaerobically in a fluorescence microscope. An acousto-optic modulator generates a several-microsecond pulse of linearly polarized light which produces an orientationally-asymmetric depletion of ground state fluorescence in the sample. When the sample is then probed with light polarized parallel to the excitation pulse, fluorescence recovers over 0-1,000 microseconds as the sum of two exponentials. One exponential corresponds to triplet decay and the other to the rotational relaxation. An exciting pulse perpendicular to the probe beam is then applied. Fluorescence recovery following this pulse is the difference of the same two exponentials. Equations for fluorescence recovery kinetics to be expected in various experimentally significant cases are derived. Least-squares analysis using these equations then permits the triplet lifetime and rotational correlation time to be determined directly from PFD data. Instrumentation for PFD measurements is discussed that permits photobleaching recovery measurements of lateral diffusion coefficients using the same microscope system. With this apparatus, both rotational and translational diffusion coefficients (Dr, Dt) were measured for EITC-labeled bovine serum albumin in glycerol solutions. Values obtained for Dr and Dt are discussed in light of both the PFD models and the experimental system. PMID:3730506

  8. Synthesis and Characterization of Fluorescently Labeled Diblock Copolymers for Location-Specific Measurements of The Glass Transition Temperature

    NASA Astrophysics Data System (ADS)

    Christie, Dane; Register, Richard; Priestley, Rodney

    Interfaces play a determinant role in the size dependence of the glass transition temperature (Tg) of polymers confined to nanometric length scales. Interfaces are intrinsic in diblock copolymers, which, depending on their molecular weight and composition, are periodically nanostructured in the bulk. As a result diblock copolymers are model systems for characterizing the effect of interfaces on Tg in bulk nanostructured materials. Investigating the effect of intrinsic interfaces on Tg in diblock copolymers has remained unexplored due to their small periodic length scale. By selectively incorporating trace amounts of a fluorescent probe into a diblock copolymer, Tg can be characterized relative to the diblock copolymer's intrinsic interface using fluorescence spectroscopy. Here, pyrene is selectively incorporated into the poly(methyl methacrylate) (PMMA) block of lamellar forming diblock copolymers of poly(butyl- b-methyl methacrylate) (PBMA-PMMA). Preliminary results show a correlation of Tg as measured by fluorescence with the onset of Tg as measured by calorimetry in labeled homopolymers of PMMA. This result is consistent with previous characterizations of Tg using fluorescence spectroscopy. In selectively labeled diblock copolymers Tg is found to vary systematically depending on the distance of the probe from the PBMA-PMMA interface. We acknowledge funding from the Princeton Center for Complex Materials, a MRSEC supported by NSF Grant DMR 1420541.

  9. N-methyl-D-aspartate receptor encephalitis mediates loss of intrinsic activity measured by functional MRI.

    PubMed

    Brier, Matthew R; Day, Gregory S; Snyder, Abraham Z; Tanenbaum, Aaron B; Ances, Beau M

    2016-06-01

    Spontaneous brain activity is required for the development and maintenance of normal brain function. Many disease processes disrupt the organization of intrinsic brain activity, but few pervasively reduce the amplitude of resting state blood oxygen level dependent (BOLD) fMRI fluctuations. We report the case of a female with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, longitudinally studied during the course of her illness to determine the contribution of NMDAR signaling to spontaneous brain activity. Resting state BOLD fMRI was measured at the height of her illness and 18 weeks following discharge from hospital. Conventional resting state networks were defined using established methods. Correlation and covariance matrices were calculated by extracting the BOLD time series from regions of interest and calculating either the correlation or covariance quantity. The intrinsic activity was compared between visits, and to expected activity from 45 similarly aged healthy individuals. Near the height of the illness, the patient exhibited profound loss of consciousness, high-amplitude slowing of the electroencephalogram, and a severe reduction in the amplitude of spontaneous BOLD fMRI fluctuations. The patient's neurological status and measures of intrinsic activity improved following treatment. We conclude that NMDAR-mediated signaling plays a critical role in the mechanisms that give rise to organized spontaneous brain activity. Loss of intrinsic activity is associated with profound disruptions of consciousness and cognition. PMID:27025853

  10. Fluorescent-Antibody Measurement Of Cancer-Cell Urokinase

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R.

    1993-01-01

    Combination of laboratory techniques provides measurements of amounts of urokinase in and between normal and cancer cells. Includes use of fluorescent antibodies specific against different forms of urokinase-type plasminogen activator, (uPA), fluorescence microscopy, quantitative analysis of images of sections of tumor tissue, and flow cytometry of different uPA's and deoxyribonucleic acid (DNA) found in suspended-tumor-cell preparations. Measurements provide statistical method for indicating or predicting metastatic potentials of some invasive tumors. Assessments of metastatic potentials based on such measurements used in determining appropriate follow-up procedures after surgical removal of tumors.

  11. Breast cancer: in vitro measurements of native fluorescence

    NASA Astrophysics Data System (ADS)

    Lohmann, Wolfgang; Bohle, Rainer M.; Dreyer, Thomas; Haas, Sabine; Wallenfels, Heike; Schwemmle, Konrad; Schill, Wolf-Bernhard

    1996-12-01

    Unfixed, HE stained cryosections of breast tissue obtained from 67 patients during surgery were illuminated with 395 - 440 nm and their fluorescence response as well as the 2- dimensional fluorophore distribution were measured. The histological evaluation of the same cryosection, illuminated as usual with a transmitted light obtained from a halogen lamp, revealed 9 patients with healthy tissue, 11 with benign epithelial hyperplasia, 4 with ductal carcinoma in situ, 35 with invasive ductal carcinoma, 7 with invasive lobular carcinoma, and one with invasive tubular carcinoma. A comparison between the fluorescence and the HE images shows that both match very nicely and that the fluorescence images are also characteristic for the different pathological condition of the biopsy sample. Moreover, benign tumors e.g. fibroadenomas, exhibit a fluorescence response different from cancer and healthy tissue.

  12. Measuring and interpreting X-ray fluorescence from planetary surfaces.

    PubMed

    Owens, Alan; Beckhoff, Burkhard; Fraser, George; Kolbe, Michael; Krumrey, Michael; Mantero, Alfonso; Mantler, Michael; Peacock, Anthony; Pia, Maria-Grazia; Pullan, Derek; Schneider, Uwe G; Ulm, Gerhard

    2008-11-15

    As part of a comprehensive study of X-ray emission from planetary surfaces and in particular the planet Mercury, we have measured fluorescent radiation from a number of planetary analog rock samples using monochromatized synchrotron radiation provided by the BESSY II electron storage ring. The experiments were carried out using a purpose built X-ray fluorescence (XRF) spectrometer chamber developed by the Physikalisch-Technische Bundesanstalt, Germany's national metrology institute. The XRF instrumentation is absolutely calibrated and allows for reference-free quantitation of rock sample composition, taking into account secondary photon- and electron-induced enhancement effects. The fluorescence data, in turn, have been used to validate a planetary fluorescence simulation tool based on the GEANT4 transport code. This simulation can be used as a mission analysis tool to predict the time-dependent orbital XRF spectral distributions from planetary surfaces throughout the mapping phase. PMID:18855420

  13. Single-particle spectroscopic measurements of fluorescent graphene quantum dots.

    PubMed

    Xu, Qinfeng; Zhou, Qi; Hua, Zheng; Xue, Qi; Zhang, Chunfeng; Wang, Xiaoyong; Pan, Dengyu; Xiao, Min

    2013-12-23

    We have performed the first single-particle spectroscopic measurements on individual graphene quantum dots (GQDs) and revealed several intriguing fluorescent phenomena that are otherwise hidden in the optical studies of ensemble GQDs. First, despite noticeable differences in the size and the number of layers from particle to particle, all of the GQDs studied possess almost the same spectral lineshapes and peak positions. Second, GQDs with more layers are normally brighter emitters but are associated with shorter fluorescent lifetimes. Third, the fluorescent spectrum of GQDs was red-shifted upon being aged in air, possibly due to the water desorption effect. Finally, the missing emission of single photons and stable fluorescence without any intermittent behavior were observed from individual GQDs. PMID:24251867

  14. Marine fluorescence from high spectrally resolved satellite measurements

    NASA Astrophysics Data System (ADS)

    Wolanin, Aleksandra; Dinter, Tilman; Rozanov, Vladimir; Noël, Stefan; Vountas, Marco; Burrows, John P.; Bracher, Astrid

    2014-05-01

    When chlorophyll molecules absorb light, most of this energy is transformed into chemical energy in a process of photosynthesis. However, a fraction of the energy absorbed is reemitted as fluorescence. As a result of its relationship to photosynthetic e?ciency, information about chlorophyll fluorescence can be used to assess the physiological state of phytoplankton (Falkowski and Kolber,1995). In-situ measurements of chlorophyll fluorescence are widespread in physiological and ecophysiological studies. When retrieved from space, chlorophyll fluorescence can improve our knowledge of global biogeochemical cycles and phytoplankton productivity (Behrenfeld et al., 2009; Huot et al., 2013) by providing high coverage and periodicity. So far, the only satellite retrieval of sun-induced marine fluorescence, Fluorescence Line Height (FLH), was designed for MODIS (Abbott and Letelier, 1999), and later also applied to the similar sensor MERIS (Gower et al., 2004). However, it could so far not be evaluated on global scale. Here, we present a different approach to observe marine chlorophyll fluorescence, based on the Differential Optical Absorption Spectroscopy (DOAS) technique (Perner and Platt, 1979) applied to the hyperspectral data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Global Ozone Monitoring Experiment-2 (GOME-2). Since fluorescence, as a trans-spectral process, leads to the shift of the wavelength of the radiation, it can be observed in the filling-in of Fraunhofer lines. In our retrieval, we evaluate the filling-in of the Zeeman triplet Fraunhofer line FeI at 684.3 nm, which is located very close to the emission peak of marine fluorescence (~685 nm). In order to conduct the chlorophyll fluorescence retrieval with the DOAS method, we calculated the reference spectra for chlorophyll fluorescence, based on simulations performed with the coupled ocean-atmosphere radiative transfer model SCIATRAN (Rozanov et al., 2014

  15. Fluorescence lifetime measurements of boronate derivatives to determine glucose concentration

    SciTech Connect

    Gable, J H

    2000-06-01

    A novel investigation into the fluorescence lifetimes of molecules, both established and newly designed, was performed. These molecules are the basis of a continuous, minimally invasive, glucose sensor based on fluorescence lifetime measurements. This sensor, if coupled with an automated insulin delivery device, would effectively create an artificial pancreas allowing for the constant monitoring and control of glucose levels in a person with diabetes. The proposed sensor includes a fluorescent molecule that changes its' fluorescence properties upon binding selectively and reversibly to glucose. One possible sensor molecule is N-methyl-N-(9-methylene anthryl)-2-methylenephenylboronic acid (AB). The fluorescence intensity of AB was shown to change in response to changing glucose concentrations. (James, 1994) James proposed that when glucose binds to AB the fluorescence intensity increases due to an enhancement of the N{yields}B dative bond which prevents photoinduced electron transfer (PET). PET from the amine (N) to the fluorophore (anthracene) quenches the fluorescence. The dative bond between the boron and the amine can prevent PET by involving the lone pair of electrons on the amine in interactions with the boron rather than allowing them to be transferred to the fluorophore. Results of this research show the average fluorescence lifetime of AB also changes with glucose concentration. It is proposed that fluorescence is due to two components: (1) AB with an enhanced N{yields}B interaction, and no PET, and (2) AB with a weak N{yields}B interaction, resulting in fluorescence quenching by PET. Lifetime measurements of AB as a function of both the pH of the solvent and glucose concentration in the solution were made to characterize this two component system and investigate the nature of the N{yields}B bond. Measurements of molecules similar to AB were also performed in order to isolate behavior of specific AB constituents. These molecules are 9-(Methylaminomethyl

  16. Biochip Image Grid Normalization Absolute Signal Fluorescence Measurement Using

    Energy Science and Technology Software Center (ESTSC)

    2001-04-17

    This software was developed to measure absolute fluorescent intensities of gel pads on a microchip in units defined by a standard fluorescent slide. It can accomodate varying measurement conditions (e.g. exposure time, sensitivity of detector, resolution of detector, etc.) as well as fluorescent microscopes with non-uniform sensitivity across their field of view allowing the user to compare measurements done on different detectors with varying exposure times, sensitivities, and resolutions. The software is designed both tomore » operate Roper Scientific, Inc. cameras and to use image files produced by the program supplied with that equipment for its calculations. the intensity of the gel pad signal is computed so as to reduce background influence.« less

  17. Redox-Sensitive and Intrinsically Fluorescent Photoclick Hyaluronic Acid Nanogels for Traceable and Targeted Delivery of Cytochrome c to Breast Tumor in Mice.

    PubMed

    Li, Shuai; Zhang, Jian; Deng, Chao; Meng, Fenghua; Yu, Lin; Zhong, Zhiyuan

    2016-08-24

    In spite of their high specificity and potency, few protein therapeutics are applied in clinical cancer therapy owing to a lack of safe and efficacious delivery systems. Here, we report that redox-sensitive and intrinsically fluorescent photoclick hyaluronic acid nanogels (HA-NGs) show highly efficient loading and breast tumor-targeted delivery of cytochrome c (CC). HA-NGs were obtained from hyaluronic acid-graft-oligo(ethylene glycol)-tetrazole (HA-OEG-Tet) via inverse nanoprecipitation and catalyst-free photoclick cross-linking with l-cystine dimethacrylamide (MA-Cys-MA). HA-NGs exhibited a superb CC loading content of up to 40.6 wt %, intrinsic fluorescence (λem = 510 nm), and a small size of ca. 170 nm. Notably, CC-loaded nanogels (CC-NGs) showed a fast glutathione-responsive protein release behavior. Importantly, released CC maintained its bioactivity. MTT assays revealed that CC-NGs were highly potent with a low IC50 of 3.07 μM to CD44+ MCF-7 human breast tumor cells. Confocal microscopy observed efficient and selective internalization of fluorescent HA-NGs into MCF-7 cells. Interestingly, HA-NGs exhibited also effective breast tumor penetration. The therapeutic results demonstrated that CC-NGs effectively inhibited the growth of MCF-7 breast tumor xenografts at a particularly low dose of 80 or 160 nmol CC equiv./kg. Moreover, CC-NGs did not cause any change in mice body weight, corroborating their low systemic side effects. Redox-sensitive and intrinsically fluorescent photoclick hyaluronic acid nanogels have appeared as a "smart" protein delivery nanoplatform enabling safe, efficacious, traceable, and targeted cancer protein therapy in vivo. PMID:27509045

  18. First Measurement of the Intrinsic Noise of a HEMT at Sub-Kelvin Temperatures

    NASA Astrophysics Data System (ADS)

    Torres, L.; Arcambal, C.; Delisle, C.; Dong, Q.; Jin, Y.; Rodriguez, L.; Cara, C.

    2016-07-01

    The increasing sensitivity of high impedance cryogenic detectors demands amplification stages closer to detectors to guarantee high performance. We have developed a cryogenic installation to measure the intrinsic noise, the gain, and the DC characteristics of HEMTs or MOSFETs at low temperature. Components under test are mounted in a helium cryostat containing a double stage 3He/4He sorption cooler to perform sub-kelvin measurements. In this work, we describe this installation and present the encouraging first results that have revealed a level of intrinsic input voltage noise of a HEMT, developed by CNRS/LPN, of 0.44 nV/sqrt(Hz) at 1 kHz at 480 mK (Cin = 100 pF).

  19. Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

    NASA Technical Reports Server (NTRS)

    Domonkos, Matthew T.; Stevens, Richard E.

    2001-01-01

    Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

  20. Fluorescence molecular tomographic image reconstruction based on reduced measurement data

    NASA Astrophysics Data System (ADS)

    Zou, Wei; Wang, Jiajun; Feng, David Dagan; Fang, Erxi

    2015-07-01

    The analysis of fluorescence molecular tomography is important for medical diagnosis and treatment. Although the quality of reconstructed results can be improved with the increasing number of measurement data, the scale of the matrices involved in the reconstruction of fluorescence molecular tomography will also become larger, which may slow down the reconstruction process. A new method is proposed where measurement data are reduced according to the rows of the Jacobian matrix and the projection residual error. To further accelerate the reconstruction process, the global inverse problem is solved with level-by-level Schur complement decomposition. Simulation results demonstrate that the speed of the reconstruction process can be improved with the proposed algorithm.

  1. Mercury mass measurement in fluorescent lamps via neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Viererbl, L.; Vinš, M.; Lahodová, Z.; Fuksa, A.; Kučera, J.; Koleška, M.; Voljanskij, A.

    2015-11-01

    Mercury is an essential component of fluorescent lamps. Not all fluorescent lamps are recycled, resulting in contamination of the environment with toxic mercury, making measurement of the mercury mass used in fluorescent lamps important. Mercury mass measurement of lamps via instrumental neutron activation analysis (NAA) was tested under various conditions in the LVR-15 research reactor. Fluorescent lamps were irradiated in different positions in vertical irradiation channels and a horizontal channel in neutron fields with total fluence rates from 3×108 cm-2 s-1 to 1014 cm-2 s-1. The 202Hg(n,γ)203Hg nuclear reaction was used for mercury mass evaluation. Activities of 203Hg and others induced radionuclides were measured via gamma spectrometry with an HPGe detector at various times after irradiation. Standards containing an Hg2Cl2 compound were used to determine mercury mass. Problems arise from the presence of elements with a large effective cross section in luminescent material (europium, antimony and gadolinium) and glass (boron). The paper describes optimization of the NAA procedure in the LVR-15 research reactor with particular attention to influence of neutron self-absorption in fluorescent lamps.

  2. Measurements of extrinsic fluorescence in Intralipid and polystyrene microspheres

    PubMed Central

    Du Le, Vinh Nguyen; Nie, Zhaojun; Hayward, Joseph E.; Farrell, Thomas J.; Fang, Qiyin

    2014-01-01

    The fluorescence of Intralipid and polystyrene microspheres with sphere diameter of 1 µm at a representative lipid and microsphere concentration for simulation of mucosal tissue scattering has not been a subject of extensive experimental study. In order to elucidate the quantitative relationship between lipid and microsphere concentration and the respective fluorescent intensity, the extrinsic fluorescence spectra between 360 nm and 650 nm (step size of 5 nm) were measured at different lipid concentrations (from 0.25% to 5%) and different microsphere concentrations (0.00364, 0.0073, 0.0131 spheres per cubic micrometer) using laser excitation at 355 nm with pulse energy of 2.8 µJ. Current findings indicated that Intralipid has a broadband emission between 360 and 650 nm with a primary peak at 500 nm and a secondary peak at 450 nm while polystyrene microspheres have a single peak at 500 nm. In addition, for similar scattering properties the fluorescence of Intralipid solutions is approximately three-fold stronger than that of the microsphere solutions. Furthermore, Intralipid phantoms with lipid concentrations ~2% (simulating the bottom layer of mucosa) produce up to seven times stronger fluorescent emission than phantoms with lipid concentration ~0.25% (simulating the top layer of mucosa). The fluoresence decays of Intralipid and microsphere solutions were also recorded for estimation of fluorescence lifetime. PMID:25136497

  3. Fluorescence Rise Time Measurements for High Temperature Fluorescence-Based Thermometry

    SciTech Connect

    Allison, S.W.

    2005-03-24

    Certain ceramic-like phosphor materials exhibit bright fluorescence with a pronounced temperature dependence over a range which spans the cryogenic to 1700 C, depending on the specific phosphor. To measure temperature, a surface, for instance a turbine blade, is coated with the material. An optical system, sometimes including optical fibers, conveys stimulating light and collects the emission for analysis. Either emission intensity or decay time may indicate temperature. Previously fielded tests have involved surfaces such as blades, vanes, pistons, in-take valves, sheets of galvanneal steel, etc. The fluorescent coatings may be applied to small parts via sputtering methods or to large areas by mixture with inorganic binders. Presented here are results characterizing fluorescence rise times as a means of determining temperature from ambient to 700 C for Y{sub 2}O{sub 3}:Eu.

  4. Excitation-emission matrices measurements of human cutaneous lesions: tool for fluorescence origin

    NASA Astrophysics Data System (ADS)

    Zhelyazkova, A.; Borisova, E.; Angelova, L.; Pavlova, E.; Keremedchiev, M.

    2013-11-01

    The light induced fluorescence (LIF) technique has the potential of providing real-time diagnosis of malignant and premalignant skin tissue; however, human skin is a multilayered and inhomogeneous organ with different optical properties that complicate the analysis of cutaneous fluorescence spectra. In spite of the difficulties related to the detection and analysis of fluorescent data from skin lesions, this technique is among the most widely applied techniques in laboratorial and pre-clinical investigations for early skin neoplasia diagnosis. The important point is to evaluate all sources of intrinsic fluorescence and find any significant alterations distinguishing the normal skin from a cancerous state of the tissue; this would make the autofluorescence signal obtained useful for the development of a non-invasive diagnostic tool for the dermatological practice. Our investigations presented here were based on ex vivo point-by-point measurements of excitation-emission matrices (EEM) from excised tumor lesions and the surrounding skin taken during the daily clinical practice of Queen Jiovanna- ISUL University Hospital, Sofia, the local Ethical Committee's approval having already been obtained. The fluorescence emission was measured between 300 nm and 800 nm using excitation in the 280-440 nm spectral range. In the process of excitation-emission matrices (EEM) measurements we could establish the origin of the autofluorescence and the compounds related by assigning the excitation and emission maxima obtained during the experiments. The EEM were compared for normal human skin, basal cell carcinoma, squamous cell carcinoma, benign nevi and malignant melanoma lesions to obtain information for the most common skin malignancies and their precursors. The main spectral features and the applicability of the technique of autofluorescent spectroscopy of human skin in general as an initial diagnostic tool are discussed as well.

  5. Velocity measurements by laser resonance fluorescence. [single atom diffusional motion

    NASA Technical Reports Server (NTRS)

    She, C. Y.; Fairbank, W. M., Jr.

    1980-01-01

    The photonburst correlation method was used to detect single atoms in a buffer gas. Real time flow velocity measurements with laser induced resonance fluorescence from single or multiple atoms was demonstrated and this method was investigated as a tool for wind tunnel flow measurement. Investigations show that single atoms and their real time diffusional motion on a buffer gas can be measured by resonance fluorescence. By averaging over many atoms, flow velocities up to 88 m/s were measured in a time of 0.5 sec. It is expected that higher flow speeds can be measured and that the measurement time can be reduced by a factor of 10 or more by careful experimental design. The method is clearly not ready for incorporation in high speed wind tunnels because it is not yet known whether the stray light level will be higher or lower, and it is not known what detection efficiency can be obtained in a wind tunnel situation.

  6. Kr II laser-induced fluorescence for measuring plasma acceleration.

    PubMed

    Hargus, W A; Azarnia, G M; Nakles, M R

    2012-10-01

    We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d(4)D(7/2) to the 5p(4)P(5/2)(∘) state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d(4)D(7/2)-5p(4)P(5/2)(∘) transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume. PMID:23126755

  7. Raman/Rayleigh/fluorescence lidar for atmosphere measurement

    NASA Astrophysics Data System (ADS)

    Gong, Shunsheng; Zheng, Wengang; Li, Hongjun; Yang, Guotao

    1998-08-01

    A Raman/Rayleigh/Fluorescence Lidar established in the Wuhan Institute of Physics & Mathematics, China for the measurements of the atmosphere is described, and the preliminary observation results for the lower, upper atmosphere and the sodium layer over Wuhan, China obtained by this lidar are presented in this paper.

  8. Photoinhibition of Photosystems I and II Using Chlorophyll Fluorescence Measurements

    ERIC Educational Resources Information Center

    Quiles, Maria Jose

    2005-01-01

    In this study the photoinhibition of photosystems (PS) I and II caused by exposure to high intensity light in oat ("Avena sativa," var Prevision) is measured by the emission of chlorophyll fluorescence in intact leaves adapted to darkness. The maximal quantum yield of PS II was lower in plants grown under high light intensity than in plants grown…

  9. Temperature Dependent Fluorescence Lifetime Measurements in a Phosphor

    NASA Astrophysics Data System (ADS)

    Nettles, Charles J.; Smith, R. Seth; Heath, Jonathan J.

    2012-03-01

    This poster will describe an undergraduate senior research project involving fluorescence lifetime measurements in a LaSO4:Eu phosphor compound. Specifically, this project seeks to determine the temperature dependence of the lifetime. The temperature of the phosphor will be varied using a heater block with temperature control. The phosphor will be excited with the 337 nm output of a Nitrogen Laser. An Oriel Monochromator will be used to disperse the fluorescence, and the lifetime for a particular wavelength will be determined from a photomultiplier tube signal. At the time of the presentation, this project will be nearing completion; and I will discuss my progress, successes, and challenges.

  10. Confidence intervals for concentration and brightness from fluorescence fluctuation measurements.

    PubMed

    Pryse, Kenneth M; Rong, Xi; Whisler, Jordan A; McConnaughey, William B; Jiang, Yan-Fei; Melnykov, Artem V; Elson, Elliot L; Genin, Guy M

    2012-09-01

    The theory of photon count histogram (PCH) analysis describes the distribution of fluorescence fluctuation amplitudes due to populations of fluorophores diffusing through a focused laser beam and provides a rigorous framework through which the brightnesses and concentrations of the fluorophores can be determined. In practice, however, the brightnesses and concentrations of only a few components can be identified. Brightnesses and concentrations are determined by a nonlinear least-squares fit of a theoretical model to the experimental PCH derived from a record of fluorescence intensity fluctuations. The χ(2) hypersurface in the neighborhood of the optimum parameter set can have varying degrees of curvature, due to the intrinsic curvature of the model, the specific parameter values of the system under study, and the relative noise in the data. Because of this varying curvature, parameters estimated from the least-squares analysis have varying degrees of uncertainty associated with them. There are several methods for assigning confidence intervals to the parameters, but these methods have different efficacies for PCH data. Here, we evaluate several approaches to confidence interval estimation for PCH data, including asymptotic standard error, likelihood joint-confidence region, likelihood confidence intervals, skew-corrected and accelerated bootstrap (BCa), and Monte Carlo residual resampling methods. We study these with a model two-dimensional membrane system for simplicity, but the principles are applicable as well to fluorophores diffusing in three-dimensional solution. Using simulated fluorescence fluctuation data, we find the BCa method to be particularly well-suited for estimating confidence intervals in PCH analysis, and several other methods to be less so. Using the BCa method and additional simulated fluctuation data, we find that confidence intervals can be reduced dramatically for a specific non-Gaussian beam profile. PMID:23009839

  11. Highly versatile nanohydrogel platform based on riboflavin-polysaccharide derivatives useful in the development of intrinsically fluorescent and cytocompatible drug carriers.

    PubMed

    Di Meo, Chiara; Montanari, Elita; Manzi, Lucio; Villani, Claudio; Coviello, Tommasina; Matricardi, Pietro

    2015-01-22

    In this work we describe a new nanohydrogel platform, based on polysaccharides modified with the hydrophobic and fluorescent molecule riboflavin tetrabutyrate, which leads to innovative structures useful for drug delivery applications. Hyaluronic acid and pullulan were chosen as representative of anionic and neutral polysaccharides, respectively, and the bromohexyl derivative of riboflavin tetrabutyrate was chemically linked to these polymer chains. Because of such derivatization, polymer chains were able to self-assemble in aqueous environment thus forming nanohydrogels, with mean diameters of about 312 and 210 nm, for hyaluronan and pullulan, respectively. These new nanohydrogels showed low polydispersity index, and negative ζ-potential. Moreover, the nanohydrogels, which can be easily loaded with model drugs, showed long-term stability in water and physiological conditions and excellent cytocompatibility. All these properties allow to consider these intrinsically fluorescent nanohydrogels suitable for the formulation of innovative drug dosage forms. PMID:25439925

  12. TOP-IDP-Scale: A New Amino Acid Scale Measuring Propensity for Intrinsic Disorder

    PubMed Central

    Campen, Andrew; Williams, Ryan M.; Brown, Celeste J.; Meng, Jingwei; Uversky, Vladimir N.; Dunker, A. Keith

    2009-01-01

    Intrinsically disordered proteins carry out various biological functions while lacking ordered secondary and/or tertiary structure. In order to find general intrinsic properties of amino acid residues that are responsible for the absence of ordered structure in intrinsically disordered proteins we surveyed 517 amino acid scales. Each of these scales was taken as an independent attribute for the subsequent analysis. For a given attribute value X, which is averaged over a consecutive string of amino acids, and for a given data set having both ordered and disordered segments, the conditional probabilities P(so | x) and P(sd | x) for order and disorder, respectively, can be determined for all possible values of X. Plots of the conditional probabilities P(so | x) and P(sd | x) versus X give a pair of curves. The area between these two curves divided by the total area of the graph gives the area ratio value (ARV), which is proportional to the degree of separation of the two probability curves and, therefore, provides a measure of the given attribute’s power to discriminate between order and disorder. As ARV falls between zero and one, larger ARV corresponds to the better discrimination between order and disorder. Starting from the scale with the highest ARV, we applied a simulated annealing procedure to search for alternative scale values and have managed to increase the ARV by more than 10%. The ranking of the amino acids in this new TOP-IDP scale is as follows (from order promoting to disorder promoting): W, F, Y, I, M, L, V, N, C, T, A, G, R, D, H, Q, K, S, E, P. A web-based server has been created to apply the TOP-IDP scale to predict intrinsically disordered proteins (http://www.disprot.org/dev/disindex.php). PMID:18991772

  13. Diffusion measurement of fluorescence-labeled amphiphilic molecules with a standard fluorescence microscope.

    PubMed Central

    Dietrich, C; Merkel, R; Tampé, R

    1997-01-01

    The lateral diffusion of fluorescence-labeled amphiphilic tracer molecules dissolved within a two-dimensional matrix of lipids was measured by continuous illumination of an elongated rectangular region. The resulting spatial concentration profile of unbleached tracer molecules was observed with a standard epifluorescence microscope and analyzed with digital image-processing techniques. These concentration profiles are governed by the mobility of the tracers, their rate of photolysis, and the geometry of the illuminated area. For the case of a long and narrow illuminated stripe, a mathematical analysis of the process is given. After prolonged exposure, the concentration profile can be approximated by a simple analytical function. This fact was used to measure the quotient of the rate of photolysis, and the diffusion constant of the fluorescent probe. With an additional measurement of the rate of photolysis, the mobility of the tracer was determined. As prototype experiments we studied the temperature dependence of the lateral diffusion of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-dipalmitoylphosphatidyl++ + ethanolamine in glass-supported bilayers of L-alpha-dimyristoylphosphatidylcholine. Because of its simple experimental setup, this technique represents a very useful method of determining the lateral diffusion of fluorescence-labeled membrane molecules. Images FIGURE 5 PMID:9083674

  14. On the reliable measurement of specific absorption rates and intrinsic loss parameters in magnetic hyperthermia materials

    NASA Astrophysics Data System (ADS)

    Wildeboer, R. R.; Southern, P.; Pankhurst, Q. A.

    2014-12-01

    In the clinical application of magnetic hyperthermia, the heat generated by magnetic nanoparticles in an alternating magnetic field is used as a cancer treatment. The heating ability of the particles is quantified by the specific absorption rate (SAR), an extrinsic parameter based on the clinical response characteristic of power delivered per unit mass, and by the intrinsic loss parameter (ILP), an intrinsic parameter based on the heating capacity of the material. Even though both the SAR and ILP are widely used as comparative design parameters, they are almost always measured in non-adiabatic systems that make accurate measurements difficult. We present here the results of a systematic review of measurement methods for both SAR and ILP, leading to recommendations for a standardised, simple and reliable method for measurements using non-adiabatic systems. In a representative survey of 50 retrieved datasets taken from published papers, the derived SAR or ILP was found to be more than 5% overestimated in 24% of cases and more than 5% underestimated in 52% of cases.

  15. Measuring Exocytosis Rate Using Corrected Fluorescence Recovery After Photoconversion.

    PubMed

    Luo, Nan; Yan, An; Yang, Zhenbiao

    2016-05-01

    Exocytosis plays crucial roles in regulating the distribution and function of plasma membrane (PM) and extracellular matrix proteins. However, measuring the exocytosis rate of a specific protein by conventional methods is very difficult because of exocytosis-independent trafficking such as endocytosis, which also affects membrane protein distribution. Here, we describe a novel method, corrected fluorescence recovery after photoconversion, in which exocytosis-dependent and -independent trafficking events are measured simultaneously to accurately determine exocytosis rate. In this method, the protein-of-interest is tagged with Dendra2, a green-to-red photoconvertible fluorescent protein. Following the photoconversion of PM-localized Dendra2, both the recovery of the green signal and the changes in the photoconverted red signal are measured, and the rate of exocytosis is calculated from the changing rates of these two signals. PMID:26822068

  16. Measurements of Solar Induced Chlorophyll Fluorescence at 685 nm by Airborne Plant Fluorescence Sensor (APFS)

    NASA Astrophysics Data System (ADS)

    Morgan, F.; Yee, J. H.; Boldt, J.; Cook, W. B.; Corp, L. A.

    2015-12-01

    Solar-induced chlorophyll fluorescence (ChlF) by terrestrial vegetation is linked closely to photosynthetic efficiency that can be exploited to monitor the plant health status and to assess the terrestrial carbon budget from space. The weak, broad continuum ChlF signal can be detected from the fill-in of strong O2 absorption lines or solar Fraunhofer lines in the reflected spectral radiation. The Johns Hopkins University, Applied Physics Laboratory (JHU/APL) Airborne Plant Fluorescence Sensor (APFS) is a triple etalon Fabry-Perot interferometer designed and optimized specifically for the ChlF sensing from an airborne platform using this line fill-in technique. In this paper, we will present the results of APFS ChlF measurements obtained from a NASA Langley King Air during two airborne campaigns (12/12 in 2014 and 5/20 in 2015) over various land, river, and vegetated targets in Virginia during stressed and growth seasons.

  17. High-accuracy direct ZT and intrinsic properties measurement of thermoelectric couple devices.

    PubMed

    Kraemer, D; Chen, G

    2014-04-01

    Advances in thermoelectric materials in recent years have led to significant improvements in thermoelectric device performance and thus, give rise to many new potential applications. In order to optimize a thermoelectric device for specific applications and to accurately predict its performance ideally the material's figure of merit ZT as well as the individual intrinsic properties (Seebeck coefficient, electrical resistivity, and thermal conductivity) should be known with high accuracy. For that matter, we developed two experimental methods in which the first directly obtains the ZT and the second directly measures the individual intrinsic leg properties of the same p/n-type thermoelectric couple device. This has the advantage that all material properties are measured in the same sample direction after the thermoelectric legs have been mounted in the final device. Therefore, possible effects from crystal anisotropy and from the device fabrication process are accounted for. The Seebeck coefficients, electrical resistivities, and thermal conductivities are measured with differential methods to minimize measurement uncertainties to below 3%. The thermoelectric couple ZT is directly measured with a differential Harman method which is in excellent agreement with the calculated ZT from the individual leg properties. The errors in both the directly measured and calculated thermoelectric couple ZT are below 5% which is significantly lower than typical uncertainties using commercial methods. Thus, the developed technique is ideal for characterizing assembled couple devices and individual thermoelectric materials and enables accurate device optimization and performance predictions. We demonstrate the methods by measuring a p/n-type thermoelectric couple device assembled from commercial bulk thermoelectric Bi2Te3 elements in the temperature range of 30 °C-150 °C and discuss the performance of the couple thermoelectric generator in terms of its efficiency and materials

  18. Measurements of Fluorescent Bioaerosol Particles in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Perring, A. E.; Emerson, J. B.; Fierer, N.; Schwarz, J. P.; Fahey, D. W.

    2013-12-01

    Bioaerosols are of atmospheric interest due to their potential importance as cloud condensation and heterogeneous ice nuclei and because they represent a sizeable fraction of coarse mode aerosol in some locations. Relatively little data exists, however, regarding diurnal, seasonal and annual cycles of bioaerosols and the meteorological processes that control them. Newly developed real-time instrumentation allows for sensitive, high time resolution detection of fluorescent bioaerosols and is uniquely suited to address key uncertainties in the sources, distributions and behavior of these particles in the atmosphere. Here we present observations of ambient fluorescent biological aerosol made on the Front Range of Colorado using a custom-modified Wideband Integrated Bioaerosol Sensor (WIBS) during the summer and fall of 2013. The summertime measurements were made from the roof of the NOAA ESRL David Skaggs Research Center in Boulder and the fall measurements were made both at the surface and aloft at the Boulder Atmospheric Observatory Tall Tower. We examine diurnal variations in loading and size distribution of fluorescent bioaerosol at the two locations. We also investigate the relationship between meteorological events and fluorescent bioaerosol. For example, we observe higher concentrations and markedly different number distributions associated with precipitation events. Simultaneous filter samples were collected for DNA sequencing and flow cytometry. To our knowledge this represents the first such comparison for the WIBS under ambient conditions and the microbial identification accomplished with the filters adds significantly to the analysis. This data set will provide useful insight into the sources, loadings and properties of fluorescent bioaerosol and the local and regional processes that drive them.

  19. Blind deconvolution estimation of fluorescence measurements through quadratic programming

    NASA Astrophysics Data System (ADS)

    Campos-Delgado, Daniel U.; Gutierrez-Navarro, Omar; Arce-Santana, Edgar R.; Skala, Melissa C.; Walsh, Alex J.; Jo, Javier A.

    2015-07-01

    Time-deconvolution of the instrument response from fluorescence lifetime imaging microscopy (FLIM) data is usually necessary for accurate fluorescence lifetime estimation. In many applications, however, the instrument response is not available. In such cases, a blind deconvolution approach is required. An iterative methodology is proposed to address the blind deconvolution problem departing from a dataset of FLIM measurements. A linear combination of a base conformed by Laguerre functions models the fluorescence impulse response of the sample at each spatial point in our formulation. Our blind deconvolution estimation (BDE) algorithm is formulated as a quadratic approximation problem, where the decision variables are the samples of the instrument response and the scaling coefficients of the basis functions. In the approximation cost function, there is a bilinear dependence on the decision variables. Hence, due to the nonlinear nature of the estimation process, an alternating least-squares scheme iteratively solves the approximation problem. Our proposal searches for the samples of the instrument response with a global perspective, and the scaling coefficients of the basis functions locally at each spatial point. First, the iterative methodology relies on a least-squares solution for the instrument response, and quadratic programming for the scaling coefficients applied just to a subset of the measured fluorescence decays to initially estimate the instrument response to speed up the convergence. After convergence, the final stage computes the fluorescence impulse response at all spatial points. A comprehensive validation stage considers synthetic and experimental FLIM datasets of ex vivo atherosclerotic plaques and human breast cancer cell samples that highlight the advantages of the proposed BDE algorithm under different noise and initial conditions in the iterative scheme and parameters of the proposal.

  20. Uncertainty analysis of planar laser-induced fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Tavoularis, Stavros; Vanderwel, Christina

    2014-11-01

    We present a thorough analysis of the uncertainty of the planar laser-induced fluorescence (PLIF) method. We consider the measurement of concentration maps in cross-sections parallel to and normal to the axis of a slender plume containing Rhodamine 6G as a passive scalar tracer and transported by a turbulent shear flow. In particular, we identify two previously unexplored sources of error contributed by non-uniformity of the concentration across the laser sheet and by secondary fluorescence. We propose new methods to evaluate and correct for these sources of error and demonstrate that the corrected concentration measurements accurately determined the injected dye mass flow rate of the plume in the far field. Supported by NSERC.

  1. Measurement of Nanoparticle Magnetic Hyperthermia Using Fluorescent Microthermal Imaging

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaowan; van Keuren, Edward

    Nanoparticle magnetic hyperthermia uses the application of an AC magnetic field to ferromagnetic nanoparticles to elevate the temperature of cancer cells. The principle of hyperthermia as a true cell-specific therapy is that tumor cells are more sensitive to high temperature, so it is of great importance to control the locality and magnitude of the temperature differences. One technique to measure temperature variations on microscopic length scales is fluorescent microthermal imaging (FMI). Since it is the local temperature that is measured in FMI, effects such as heating due to nearby field coils can be accounted for. A dye, the rare earth chelate europium thenoyltrifluoroacetonate (Eu:TTA), with a strong temperature-dependent fluorescence emission has been incorporated into magnetic nanoparticles dispersed in a polymer films. FMI experiments were carried out on these samples under an applied high frequency magnetic field. Preliminary results show that FMI is a promising technique for characterizing the local generation of heat in nanoparticle magnetic hyperthermia.

  2. Kr II laser-induced fluorescence for measuring plasma acceleration

    SciTech Connect

    Hargus, W. A. Jr.

    2012-10-15

    We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d{sup 4}D{sub 7/2} to the 5p{sup 4}P{sub 5/2}{sup Ring-Operator} state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d{sup 4}D{sub 7/2}-5p{sup 4}P{sub 5/2}{sup Ring-Operator} transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume.

  3. Near-infrared spark source excitation for fluorescence lifetime measurements

    NASA Astrophysics Data System (ADS)

    Birch, D. J. S.; Hungerford, G.; Imhof, R. E.

    1991-10-01

    We have extended the range of excitation wavelengths from spark sources used in single photon timing fluorometry into the near infrared by means of the all-metal coaxial flashlamp filled with an argon-hydrogen gas mixture. At 750 nm this mixture gives ˜15 times the intensity available from pure hydrogen for a comparable pulse duration. Measurements are demonstrated by using the laser dye IR-140 in acetone, for which a fluorescence lifetime of 1.20 ns is recorded.

  4. Scattering versus intrinsic attenuation in the near surface: Measurements from permanent down-hole geophones

    NASA Astrophysics Data System (ADS)

    Mangriotis, Maria-Daphne

    The study of attenuation, equivalently of the quality (Q) factor, in the near-surface has three main applications. Firstly, low Q values, which are fairly common in near-surface materials, aside from decreasing seismic energy, also distort the waveforms; treatment of this disturbance effect with inverse-Q filters requires reliable Q estimates. Secondly, attenuation is a seismic parameter which improves interpretation of seismograms, as it is correlated with lithological properties. Thirdly, establishing near-surface Q is important in assessing site effects on strong ground motion events in applications of earthquake modeling and seismic engineering design. In view of these applications, theoretical treatments of attenuation, as well as laboratory and field tests, aim at estimating Q as a function of frequency and strain level. To determine the applicability of using different types of Q measurements, laboratory vs. in-situ measurements, to predict Q behavior across the different frequency bands and strain-levels of interest, it is necessary to model and separate the attenuation mechanisms into scattering (heterogeneity of elastic properties causing energy to be redistributed in space) and intrinsic (energy absorption due to conversion to heat) components. The objective of the presented study was to separate scattering versus intrinsic attenuation in the near-surface from a shallow VSP experiment conducted in the Lawrence Livermore National Laboratory (LLNL) facility using permanent down-hole geophones and a vertical impact source. Given that the VSP array was above the watertable, the Q characterization lies within the vadose zone. The first arrival of the vertically-incident transmitted P-wave was used to estimate the P-wave attenuation in the field data. Scattering attenuation estimates were established for a selected range of elastic models, which addressed both the effect of the variance of the elastic properties (density and velocity), as well as the effect of

  5. Solvent-induced multicolour fluorescence of amino-substituted 2,3-naphthalimides studied by fluorescence and transient absorption measurements.

    PubMed

    Fujii, Mayu; Namba, Misa; Yamaji, Minoru; Okamoto, Hideki

    2016-07-01

    A series of amino-2,3-naphthalimide derivatives having the amino functionality at 1-, 5- and 6-positions (, and , respectively) were prepared, and their photophysical properties were systematically investigated based on the measurements of steady-state absorption and fluorescence spectra, fluorescence lifetimes as well as transient absorption spectra. The s efficiently fluoresced in solution, and the emission spectra appreciably shifted depending on the solvent polarity. displayed only a slight fluorescence red-shift upon increasing the solvent polarity. In contrast, and showed marked positive solvatofluorochromism with large Stokes shifts displaying multicolour fluorescence; the fluorescence colours of and varied from violet-blue in hexane to orange-red in methanol. and , thus, serve as micro-environment responding fluorophores. In methanol, the intensity of the fluorescence emission band of and significantly reduced. Based on the fluorescence quantum yields and lifetimes, and transient absorption measurements, it has been revealed that internal conversion from the S1 state of s to the ground state was accelerated by the protic medium, resulting in a reduction in their fluorescence efficiency, while intersystem crossing from the S1 state to a triplet state was not responsible for the decrease of fluorescence intensity. PMID:27251860

  6. In vivo track the development of melanoma with the intrinsic third harmonic generation and two-photon fluorescence contrasts of melanin

    NASA Astrophysics Data System (ADS)

    Wu, Pei-Chun; Chen, Yu-Shing; Hsieh, Tsung-Yuan; Liu, Han-Wen; Lin, Wen-Li; Liu, Tzu-Ming

    2012-03-01

    The understanding of the interaction between tumors and surrounding microenvironment in vivo is an important first step and basis for pathway-targeting cancer therapy. To in vivo observe the dynamic development of tumor cells and validate the efficacy of therapy in microscopic scales, people commonly performed multi-photon fluorescence microscopy through an invasive window chamber setup. However, under such system, the cancer cells can't be identified and long-term tracked without a fluorescence labeling. Exploiting the intrinsic third harmonic generation (THG) and two-photon fluorescence (2PF) contrasts of melanin, we demonstrated in vivo identification of melanoma and tracked its development without labeling. It was achieved with a least invasive femtosecond Cr:forsterite laser and a laser scanning nonlinear microscopy system with 3D sub-micron spatial resolution. Combined with molecular probes or reporters, we anticipate thus developed platform a powerful tool to reveal molecular insights of tumor microenvironments, enhance our understanding of tumor biology, and trigger new therapeutic approaches.

  7. Intrinsic heating in optically trapped Au nanoparticles measured by dark-field spectroscopy

    PubMed Central

    Andres-Arroyo, Ana; Wang, Fan; Toe, Wen Jun; Reece, Peter

    2015-01-01

    Assessing the degree of heating present when a metal nanoparticle is trapped in an optical tweezers is critical for its appropriate use in biological applications as a nanoscale force sensor. Heating is necessarily present for trapped plasmonic particles because of the non-negligible extinction which contributes to an enhanced polarisability. We present a robust method for characterising the degree of heating of trapped metallic nanoparticles, using the intrinsic temperature dependence of the localised surface plasmon resonance (LSPR) to infer the temperature of the surrounding fluid at different incident laser powers. These particle specific measurements can be used to infer the rate of heating and local temperature of trapped nanoparticles. Our measurements suggest a considerable amount of a variability in the degree of heating, on the range of 414–673 K/W, for different 100 nm diameter Au nanoparticles, and we associated this with variations in the axial trapping position. PMID:26417530

  8. Surmounting intrinsic quantum-measurement uncertainties in Gaussian-state tomography with quadrature squeezing

    PubMed Central

    Řeháček, Jaroslav; Teo, Yong Siah; Hradil, Zdeněk; Wallentowitz, Sascha

    2015-01-01

    We reveal that quadrature squeezing can result in significantly better quantum-estimation performance with quantum heterodyne detection (of H. P. Yuen and J. H. Shapiro) as compared to quantum homodyne detection for Gaussian states, which touches an important aspect in the foundational understanding of these two schemes. Taking single-mode Gaussian states as examples, we show analytically that the competition between the errors incurred during tomogram processing in homodyne detection and the Arthurs-Kelly uncertainties arising from simultaneous incompatible quadrature measurements in heterodyne detection can often lead to the latter giving more accurate estimates. This observation is also partly a manifestation of a fundamental relationship between the respective data uncertainties for the two schemes. In this sense, quadrature squeezing can be used to overcome intrinsic quantum-measurement uncertainties in heterodyne detection. PMID:26195198

  9. Containerless high temperature property measurements by atomic fluorescence

    NASA Technical Reports Server (NTRS)

    Nordine, P. C.; Schiffman, R. A.

    1982-01-01

    Laser induced fluorescence techniques were developed for the containerless study of high temperature processes, material properties, levitation, and heating techniques for containerless earth-based experimentation. Experiments were performed in which fluorescence of atomic aluminum, mercury, or tungsten were studied. These experiments include measurements of: (1) Al atom evaporation from CW CO2 laser heated and aerodynamically levitated sapphire and alumina spheres, and self-supported sapphire filaments, (2) Al atom reaction with ambient oxygen in the wake of a levitated specimen, (3) Hg atom concentrations in the wake of levitated alumina and sapphire spheres, relative to the ambient Hg atom concentration, (4) Hg atom concentrations in supersonic levitation jets, and (5) metastable, electronically excited W atom concentrations produced by evaporation of an electrically heated tungsten filament.

  10. A SAURON study of M32: measuring the intrinsic flattening and the central black hole mass

    NASA Astrophysics Data System (ADS)

    Verolme, E. K.; Cappellari, M.; Copin, Y.; van der Marel, R. P.; Bacon, R.; Bureau, M.; Davies, R. L.; Miller, B. M.; de Zeeuw, P. T.

    2002-09-01

    We present dynamical models of the nearby compact elliptical galaxy M32, using high-quality kinematic measurements, obtained with the integral-field spectrograph SAURON mounted on the William Herschel Telescope on La Palma. We also include STIS data obtained previously by Joseph et al. We find a best-fitting black hole mass of M•= (2.5 +/- 0.5) × 106 Msolar and a stellar I-band mass-to-light ratio of (1.85 +/- 0.15) Msolar/Lsolar. For the first time, we are also able to constrain the inclination along which M32 is observed to 70°+/- 5°. Assuming that M32 is indeed axisymmetric, the averaged observed flattening of 0.73 then corresponds to an intrinsic flattening of 0.68 +/- 0.03. These tight constraints are mainly caused by the use of integral-field data. We show this quantitatively by comparing with models that are constrained by multiple slits only. We show the phase-space distribution and intrinsic velocity structure of the best-fitting model and investigate the effect of regularization on the orbit distribution.

  11. Bloodstain age analysis: toward solid state fluorescent lifetime measurements

    NASA Astrophysics Data System (ADS)

    Guo, Kevin; Zhegalova, Natalia; Achilefu, Samuel; Berezin, Mikhail Y.

    2013-03-01

    One of the most pressing unsolved challenges in forensic science is the determination of time since deposition (TSD) of bloodstains at crime scenes. Despite a number of high profile cases over the past couple hundred years involving controversy over TSD methods, no reliable quantitative method has been established. We present here an approach that has yet to be explored by forensic scientist: measuring the fluorescence lifetime of solid-state blood. Such a method would allow for on-site measurements of bloodstains utilizing the appropriate device, and would allow for rapid results returned in real-time to investigators.

  12. Laser-induced fluorescence measurement of combustion chemistry intermediates

    NASA Technical Reports Server (NTRS)

    Crosley, David R.

    1986-01-01

    Laser-induced fluorescence (LIF) can measure the trace (often free radical) species encountered as intermediates in combustion chemistry; OH, CS, NH, NS, and NCO are typical of the species detected in flames by LIF. Attention is given to illustrative experiments designed to accumulate a quantitative data base for LIF detection in low pressure flow systems and flames, as well as to flame measurements conducted with a view to the detection of new chemical intermediaries that may deepen insight into the chemistry of combustion.

  13. An Intrinsic Fiber-Optic Sensor for Structure Lightning Current Measurement

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.; Mata, Carlos T.; Mata, Angel. G.; Snyder, Gary P.

    2014-01-01

    An intrinsic optical-fiber sensor based on Faraday Effect is developed that is highly suitable for measuring lightning current on aircraft, towers and complex structures. Originally developed specifically for aircraft installations, it is light-weight, non-conducting, structure conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can measure total current down to DC. When used on lightning towers, the sensor can help validate other sensors and lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. A broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with a 60 dB dynamic range. Two systems were built that are similar in design but with slightly different sensitivities. The 1310nm laser system can measure 300 A - 300 kA, and has a 15m long sensing fiber. It was used in laboratory testing, including measuring current on an aluminum structure simulating an aircraft fuselage or a lightning tower. High current capabilities were demonstrated up to 200 kA at a lightning test facility. The 1550nm laser system can measure 400 A - 400 kA and has a 25m fiber length. Used in field measurements, excellent results were achieved in the summer of 2012 measuring rocket-triggered lightning at the International Center for Lightning Research and Testing (ICLRT), Camp Blanding, Florida. In both systems increased sensitivity can be achieved with multiple fiber loops. The fiber optic sensor provides many unique capabilities not currently possible with traditional sensors. It represents an important new tool for lightning current measurement where low weight

  14. Correlating molar masses of nitrocelluloses with their intrinsic viscosities measured using capillary electrophoresis instrumentation.

    PubMed

    Alinat, Elodie; Delaunay, Nathalie; Archer, Xavier; Gareil, Pierre

    2015-09-01

    Specific viscosities for a set of six nitrocellulose (NC) standards comprising three different mass-average molar masses (between 20,000 and 300,000 g mol(-1)) of two different nitrogen contents (11.2 and 12.1%) were measured at 20 °C in tetrahydrofuran, using capillary electrophoresis instrumentation as a bench-top viscometer in frontal mode. Intrinsic viscosities were derived applying Huggins' and Kraemer's models, showing excellent convergence of both models at infinitely diluted polymer concentration. Good overall consistency was shown between viscosity data experimentally acquired by this new protocol and the mass-average molar masses provided by the manufacturers. This simple protocol should be of interest for a better understanding of the solvent interaction given by this complex polymer, and beyond this, for tailoring NC solutions devoted to film deposition, and for the determination of mass-average molar masses of unknown NC samples. PMID:26005144

  15. Measurement of cation movement in primary cultures using fluorescent dyes.

    PubMed

    Reynolds, I J

    2001-05-01

    Ca(2+), Na(+), K(+), and Mg(2+) have a central role in neuronal excitability. The concentration of these cations in the cytoplasm of neurons (generically termed [ion(+)]i) provides a marker of the excitation state of the neurons, and may also illuminate the activity of specific signaling mechanisms that involve Ca(2+)- or Mg(2+)-activated enzymes. The measurement of [ion(+)]i in cultured neurons is achieved with the use of an ion-sensitive fluorescent dye in combination with equipment designed to quantitatively measure fluorescence. Specificity is obtained by choosing dyes with the appropriate selectivity for the ion of interest. Measurements of steady state ion concentrations can be made, as well as measurements of the net difference between ion movement into the cytoplasm (in response to a stimulus) and the physiological buffering of that ion. The procedures in this unit for loading and recording from dyes are broadly similar for each ion when ratiometric dyes are used as described, and can readily be modified for use with single-wavelength dyes. Support protocols are provided for calibration of individual dyes, which can be more problematic. PMID:18428522

  16. Measuring Phagosome pH by Ratiometric Fluorescence Microscopy.

    PubMed

    Nunes, Paula; Guido, Daniele; Demaurex, Nicolas

    2015-01-01

    Phagocytosis is a fundamental process through which innate immune cells engulf bacteria, apoptotic cells or other foreign particles in order to kill or neutralize the ingested material, or to present it as antigens and initiate adaptive immune responses. The pH of phagosomes is a critical parameter regulating fission or fusion with endomembranes and activation of proteolytic enzymes, events that allow the phagocytic vacuole to mature into a degradative organelle. In addition, translocation of H(+) is required for the production of high levels of reactive oxygen species (ROS), which are essential for efficient killing and signaling to other host tissues. Many intracellular pathogens subvert phagocytic killing by limiting phagosomal acidification, highlighting the importance of pH in phagosome biology. Here we describe a ratiometric method for measuring phagosomal pH in neutrophils using fluorescein isothiocyanate (FITC)-labeled zymosan as phagocytic targets, and live-cell imaging. The assay is based on the fluorescence properties of FITC, which is quenched by acidic pH when excited at 490 nm but not when excited at 440 nm, allowing quantification of a pH-dependent ratio, rather than absolute fluorescence, of a single dye. A detailed protocol for performing in situ dye calibration and conversion of ratio to real pH values is also provided. Single-dye ratiometric methods are generally considered superior to single wavelength or dual-dye pseudo-ratiometric protocols, as they are less sensitive to perturbations such as bleaching, focus changes, laser variations, and uneven labeling, which distort the measured signal. This method can be easily modified to measure pH in other phagocytic cell types, and zymosan can be replaced by any other amine-containing particle, from inert beads to living microorganisms. Finally, this method can be adapted to make use of other fluorescent probes sensitive to different pH ranges or other phagosomal activities, making it a generalized

  17. Containerless high temperature property measurements by atomic fluorescence

    NASA Technical Reports Server (NTRS)

    Schiffman, R. A.; Walker, C. A.

    1984-01-01

    Laser induced fluorescence (LIF) techniques for containerless study of high temperature processes and material properties was studied. Gas jet and electromagnetic levitation and electromagnetic and laser heating techniques are used with LIF in earth-based containerless high temperature experiments. Included are the development of an apparatus and its use in the studies of (1) chemical reactions on Al2O3, molybdenum, tungsten and LaB6 specimens, (2) methods for noncontact specimen temperature measurement, (3) levitation jet properties and (4) radiative lifetime and collisional energy transfer rates for electronically excited atoms.

  18. Containerless high temperature property measurements by atomic fluorescence

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The use of laser induced fluorescence (LIF) techniques for containerless study of high temperature processes and material properties is studied. Gas jet and electromagnetic levitation and electromagnetic and laser heating techniques are used with LIF in Earth-based containerless high temperature experiments. The work to date includes development of an apparatus and its use in studies of chemical reactions on Al2O3, molybdenum, and tungsten specimens, novel methods for noncontact specimen temperature measurement, and levitation jet properties. Brief summaries of these studies are given. The apparatus is described and detailed results for the current reporting period are presented.

  19. Assessment of Vegetation Stress Using Reflectance or Fluorescence Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, P. K. E.; Middleton, E. M.; McMurtrey, J. E.; Corp, L. A.; Chappelle, E. W.

    2007-01-01

    Current methods for large-scale vegetation monitoring rely on multispectral remote sensing, which has serious limitation for the detection of vegetation stress. To contribute to the establishment of a generalized spectral approach for vegetation stress detection, this study compares the ability of high-spectral resolution reflectance (R) and fluorescence (F) foliar measurements to detect vegetation changes associated with common environmental factors affecting plant growth and productivity. To obtain a spectral dataset from a broad range of species and stress conditions, plant material from three experiments was examined, including (i) corn, nitrogen (N) deficiency/excess; (ii) soybean, elevated carbon dioxide, and ozone levels; and (iii) red maple, augmented ultraviolet irradiation. Fluorescence and R spectra (400-800 nm) were measured on the same foliar samples in conjunction with photosynthetic pigments, carbon, and N content For separation of a wide range of treatment levels, hyperspectral (5-10 nm) R indices were superior compared with F or broadband R indices, with the derivative parameters optimal results. For the detection of changes in vegetation physiology, hyperspectral indices can provide a significant improvement over broadband indices. The relationship of treatment levels to R was linear, whereas that to F was curvilinear. Using reflectance measurements, it was not possible to identify the unstressed vegetation condition, which was accomplished in all three experiments using F indices. Large-scale monitoring of vegetation condition and the detection of vegetation stress could be improved by using hyperspectral R and F information, a possible strategy for future remote sensing missions.

  20. Measurements of Intrinsic Shot Noise in a Ka-Band Gyroklystron

    NASA Astrophysics Data System (ADS)

    Calame, J. P.; Danly, B. G.; Antonsen, T. M., Jr.; Garven, M.

    1998-11-01

    Experimental measurements of electron beam shot noise in a 35 GHz, 225 kW, 3-cavity gyroklystron have been obtained in both the input and output cavities. This intrinsic amplitude noise was studied in the absence of an applied carrier (i.e. at zero drive power). The noise power spectrum of the input cavity is found to have a lorentzian shape, with peak noise power densities from the input cavity typically reaching 6.3x10-15 W/Hz (-112 dBm/Hz). (This level would correspond to -165 dBc/Hz when referenced to the 200 W of input power required to saturate the amplifier). The output noise spectrum is generally found to be equal to the input cavity noise spectrum multiplied by the linear frequency response of the gyroklystron. The overall measured noise levels at the input cavity are 0 to 5 dB lower than theoretical predictions [1] for shot noise unaltered by collective effects. The measured input cavity noise power exhibits complex variations as a function of beam current and pitch angle. Data illustrating these various effects and possible explanations will be presented. [1] T.M. Antonsen, Jr. and W.M. Manheimer, IEEE Trans. Plasma Sci. 26, 444 (1998).

  1. Strain measurements in thermally grown alumina scales using ruby fluorescence

    SciTech Connect

    Veal, B.W.; Natesan, K.; Koshelev, I.; Grimsditch, M.; Renusch, D. Hou, P.Y.

    1996-12-31

    We have measured strains in alumina scales thermally grown on Fe-Cr- Al alloys by exploiting the strain dependence of the ruby luminescence line. Measurements were done on Fe-5Cr-28Al and Fe-18Cr-10Al (at.%, bal. Fe) oxidized between 300-1300 C with periodic cycling to room temperature. Significantly different levels of strain buildup were observed in scales on these alloys. Results on similar alloys containing a dilute reactive element (Zr or Hf) are also presented. We observe that scales on alloys containing a reactive element (RE) can support higher strains than scales on RE-free alloys. With the luminescence technique, strain relief associated with spallation thresholds is readily observed. In early stage oxidation, the evolution of transition phases is monitored using Raman and fluorescence spectroscopies. The fluorescence technique also provides a sensitive probe of early stage formation of {alpha}-Al{sub 2}O{sub 3}. It appears that, in presence of Cr{sub 2}O{sub 3} or Fe{sub 2}O{sub 3}, the {alpha}-alumina phase can form at anomalously low temperatures.

  2. Rapid measurements of intracellular calcium using a fluorescence plate reader.

    PubMed

    Lin, K; Sadée, W; Quillan, J M

    1999-02-01

    Intracellular calcium is a universal second messenger that can serve as a broad-based measure of receptor activity. Recent developments in multi-well plate fluorescence readers facilitate measurement of intracellular free-calcium levels and reduce reliance on slower, more cumbersome or expensive data collection methods. In this report, we describe a rapid and sensitive method to assay intracellular calcium ions in human embryonic kidney (HEK293) and Chinese hamster ovary (CHO) cells from multi-well plates using a fluorometer equipped with on-line injectors. We examine the compatibility of visible-light excitable dyes Calcium Green-1 and Oregon Green 488 BAPTA-1. Using this assay, we were able to detect and quantify activity from muscarinic and beta-adrenergic receptors endogenous to HEK293 cells and detect calcium signals generated by activation of Gi-coupled recombinant mu-opioid and dopamine D2L receptors, and the Gs-coupled melanocortin subtype 4 (MC4) receptor. Fluorescence signals, stable in HEK293 cells, required the use of Oregon Green 488 BAPTA-1 and an inhibitor of organic anion transport in CHO cells. Under appropriate conditions, both cell types can be used to collect complete concentration-response data for a variety of receptors (including a recombinant muscarinic M1 receptor expressed in CHO cells) from a single plate of dye-loaded cells. PMID:10023544

  3. The Relationships among Measures of Intrinsic Motivation, Instructional Design, and Learning in Computer-Based Instruction.

    ERIC Educational Resources Information Center

    Rezabek, Randy

    The intent of this study was to explore the intrinsic aspects of motivation, and to see if the design of instruction could positively affect learners' levels of intrinsic motivation toward the subject matter. The following questions were addressed: (1) Will different computer-based instructional treatments which have been designed to reflect…

  4. Microscopic imaging of glyceraldehyde-induced tissue glycation with intrinsic second harmonic generation and two-photon fluorescence contrasts

    NASA Astrophysics Data System (ADS)

    Hwang, Yu Jer; Granelli, Joseph; Tirumalasetty, Manasa; Lyubovitsky, Julia

    2013-02-01

    The bioinspired approaches to tissue strengthening and preservation rely on non-toxic cross-linking agents one of which is glyceraldehyde. In this study we used multiphoton microscopy that employs second harmonic generation (SHG) contrast to evaluate collagen microstructures and two-photon fluorescence (TPF) contrast to monitor progression of cross-linking upon treatment of tissues with glyceraldehyde. We examined collagen hydrogels assembled at 37 °C and 27 °C, bovine scleral and corneal tissues, skin as well as rat tail tendons. The results show a different effect of glyceraldehyde on collagen microstructures within the above tissues. This effect depends on the original microstructural assembly of collagen within a specific tissue. Our data suggests that epidermis (in skin and cornea) will protect collagen from cross-linking with glyceraldehyde. The work highlights benefits of monitoring progression of collagen cross-linking and effects of cross-linking on fiber microstructures as imaged with SHG and TPF signals.

  5. Radiometric calibration to consider in quantitative clinical fluorescence imaging measurements

    NASA Astrophysics Data System (ADS)

    Litorja, M.; Urbas, A.; Zong, Y.

    2015-03-01

    The fluorescent light detected by a clinical imager is assumed to be proportional only to the amount of fluorescent substance present in the sample and the level of excitation. Unfortunately, there are many factors that can add or subtract to the light signal directly attributable to the desired fluorescence emission, especially with fluorescence from inside the body imaged remotely. The quantification of fluorescence emission is feasible by calibrating the imager using international system of units (SI)-traceable physical and material calibration artifacts such that the detector's digital numbers (DN) can be converted to radiometric units. Here we discuss three calibration methods for quantitative clinical fluorescence imaging systems.

  6. Measurement of the tradeoff between intrinsic emittance and quantum efficiency from a NaKSb photocathode near threshold

    SciTech Connect

    Maxson, Jared Cultrera, Luca; Gulliford, Colwyn; Bazarov, Ivan

    2015-06-08

    We measure the tradeoff between the quantum efficiency and intrinsic emittance from a NaKSb photocathode at three increasing wavelengths (635, 650, and 690 nm) at or below the energy of the bandgap plus the electron affinity, hν≤E{sub g}+E{sub a}. These measurements were performed using a high voltage dc gun for varied photocathode surface fields of 1.4−4.4 MV/m. Measurements of intrinsic emittance are performed using two different methods and were found to agree. At the longest wavelength available, 690 nm, the intrinsic emittance was 0.26 μm/mm-rms with a quantum efficiency of ∼10{sup −4}. The suitability of NaKSb emitting at threshold for various low emittance applications is discussed.

  7. Containerless high temperature property measurements by atomic fluorescence

    NASA Technical Reports Server (NTRS)

    Nordine, Paul C.; Shiffman, Robert A.

    1987-01-01

    Containerless high temperature processing and material property measurements are discussed. Researchers developed methods for non-contact suspension, heating, and property measurement for materials at temperatures up to 3,680K, the melting point of tungsten. New, scientifically interesting results were obtained in Earth-based research. These results and the demonstration of new methods and techniques form a basis for further advances under the low gravity environment of space where containerless conditions are more easily achieved. Containerless high temperature material property investigations that have been completed in this and our earlier projects include measurements of fluorine LaB sub 6 reaction kinetics at 1,000 to 1,500K; optical property measurements on sapphire (Al2O3) at temperatures up to the melting point (2,327K); and vapor pressure measurements for LaB sub 6 at 2,000 to 2,500K, for molybdenum up to 2,890K and for tungsten up to 3,680K. Gas jet levitation which is applicable to any solid material, and electromagnetic levitation of electrical conductors were used to suspend the materials of interest. Non-contact heating and property measurements were achieved by optical techniques, i.e., laser heating, laser induced fluorescence measurements of vapor concentrations, and optical pyrometry for specimen temperatures.

  8. Fluorescent measurements of Zn2+ on a smartphone

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Arafat; Ast, Sandra; Canning, John; Cook, Kevin; Rutledge, Peter J.; Jamalipour, Abbas

    2015-07-01

    Using a smartphone-based portable spectrofluorimeter, measurement of metal ion concentration in water is reported. A UV LED (λex ~ 370 nm), which is powered by the internal source of the smartphone was implemented to function as the excitation source. The emission peak of the UV LED overlaps well with the absorption peak of the Zn2+-responsive molecular probe 6-(1,4,8,11-cyclam-1-yl)ethyl-1,2,3-triazol-4-yl)2-ethyl-naphthalimide fluoro-ionophore (λabs ~ 358 nm). The fluorescence emission of this dye at λem ~ 458 nm is enhanced upon coordination of Zn2+. A customized Android application digitally processes the image from a nano-imprinted polymer diffraction grating and analyses the spectral changes. Zn2+ concentration in water samples were measured with a detection limit of δ ~ 5 μM.

  9. A mesospheric airglow multichannel photometer and an optical method to measure mesospheric AGW intrinsic parameters

    NASA Astrophysics Data System (ADS)

    Mangognia, Anthony; Swenson, Gary; Vargas, Fabio; Liu, Alan

    2016-05-01

    A multichannel photometer (MCP) instrument, designed with filters for three specific airglow emissions, OH Meinel (5-1), (6-2), 840 nm; O2 (b) (0,1), 865 nm; and O(1S), 557.7 nm, as well as background, is used to observe atmospheric wave perturbations to layers in the local zenith with high temporal resolution (∼5 s). By measuring the relative phase of propagating waves through the layers, with known altitude separation, we deduce the vertical wavelength. We describe here the instrument attributes, a unique background subtraction technique, and the validation of a new method for determining intrinsic wave parameters via MCP and imager data that can be taken from various platforms, including ground-based and spacecraft platforms. Vertical wavelengths deduced using this method are in close agreement with those measured using LIDAR temperatures as well as those calculated with the dispersion relation using a combination of all-sky imager (horizontal wavelength) and meteor radar (winds) data.

  10. Intrinsic Line Shape Measurements of the XRS Instrument on Astro-E2

    NASA Technical Reports Server (NTRS)

    Porter, F. Scott

    2004-01-01

    The XRS instrument on the Astro-E2 observatory contains a substantially improved microcalorimeter array over the Astro-E mission. In addition to roughly a factor of 2 improvement in the detector resolution at 6 keV, the detector response is shown to be almost perfectly gaussian. We have made measurements of the detector response of the flight instrument, using a double crystal monochrometer at 4 and 8 keV, a 55-Fe internal conversion source, and x-ray induced fluorescence from a number of targets including Ti, Cu, and GaAs. The detector response has been measured to be entirely gaussian to at least 2 orders of magnitude down from the peak of the line or line complex. This is in sharp contrast to the results from the XRS on Astro-E where many channels exhibited excess counts on the high energy side of the spectral lines. Here we present details of the line shape measurement as well as the detector response as measured during the XRS ground calibration including details of the line fits and line models.

  11. Multiparameter single-molecule fluorescence measurements of DNA intercalating fluorophores

    NASA Astrophysics Data System (ADS)

    Bowen, Benjamin P.; Enderlein, Jorg; Woodbury, Neal W. T.

    2003-06-01

    Experiments using single-molecules of TOTO-1 intercalated into dsDNA were performed to investigate the DNA sequence dependence on the fluorescence detectable with single-molecule fluorescence spectroscopy. Previous work has shown that there is a difference in the fluorescence lifetime when TOTO-1 is intercalated in poly-AT DNA or in poly-GC DNA. The fluorescence detected from single-molecules in this work for poly-GC and poly-AT DNA showed fluorescence lifetimes of 2.1 and 1.8 nsec, respectively. Analysis of the fluorescence intensity detected from single-molecules of TOTO-1 was performed by fluorescence cross-correlation spectroscopy. TOTO-1 is shown to spend large amounts of time in dark states. These dark states reduce the detectable fluorescence intensity to approximately 10 photons per millisecond on average.

  12. Limitation of fluorescence spectrophotometry in the measurement of naphthenic acids in oil sands process water.

    PubMed

    Lu, Weibing; Ewanchuk, Andrea; Perez-Estrada, Leonidas; Sego, Dave; Ulrich, Ania

    2013-01-01

    Fluorescence spectrophotometry has been proposed as a quick screening technique for the measurement of naphthenic acids (NAs). To evaluate the feasibility of this application, the fluorescence emission spectra of NAs extracted from three oil sands process water sources were compared with that of commercial NAs. The NAs resulting from the bitumen extraction process cannot be differentiated because of the similarity of the fluorescence spectra. Separation of the fluorescent species in NAs using high performance liquid chromatography with fluorescence detector proved unsuccessful. The acidic fraction of NAs is fluorescent but the basic fraction of NAs is not fluorescent, implying that aromatic acids in NAs give rise to the fluorescent signals. The concentrations of NAs in oil sands process water were measured by Fourier transform infrared spectroscopy (FTIR), fluorescence spectrophotometry and ultra high performance liquid chromatography-time of flight/mass spectrometry (UPLC-TOF/MS). Commercial Merichem and Kodak NAs are the best standards to use when measuring NAs concentration with FTIR and fluorescence spectrophotometry. In addition, the NAs concentrations measured by fluorescence spectrophotometry are about 30 times higher than those measured by FTIR and UPLC-TOF/MS. The findings in this study underscore the limitation of fluorescence spectrophotometry in the measurement of NAs. PMID:23379948

  13. Investigation of the structural determinants of the intrinsic fluorescence emission of the trp repressor using single tryptophan mutants.

    PubMed Central

    Royer, C A

    1992-01-01

    The fluorescence decay properties of wild-type trp repressor (TR) have been characterized by carrying out a multi-emission wavelength study of the frequency response profiles. The decay is best analyzed in terms of a single exponential decay near 0.5 ns and a distribution of lifetimes centered near 3-4 ns. By comparing the recovered decay associated spectra and lifetime values with the structure of the repressor, tentative assignments of the two decay components recovered from the analysis to the two tryptophan residues, W19 and W99, of the protein have been made. These assignments consist of linking the short, red emitting component to emission from W99 and most of the longer bluer emitting lifetime distribution to emission from W19. Next, single tryptophan mutants of the repressor in which one of each of the tryptophan residues was substituted by phenylalanine were used to confirm the preliminary assignments, inasmuch as the 0.5-ns component is clearly due to emission from tryptophan 99, and much of the decay responsible for the recovered distribution emanates from tryptophan 19. The data demonstrate, however, that the decay of the wild-type protein is not completely resolvable due both to the large number of components in the wild-type emission (at least five) as well as to the fact that three of the five lifetime components are very close in value. The fluorescence decay of the wild-type decay is well described as a combination of the components found in each of the mutants. However, whereas the linear combination analysis of the 15 data sets (5 from the wild-type and each mutant) yields a good fit for the components recovered previously for the two mutants, the amplitudes of these components in the wild-type are not recovered in the expected ratios. Because of the dominance of the blue shifted emission in the wild-type protein, it is most likely that subtle structural differences in the wild-type as compared with the mutants, rather than energy transfer from

  14. Prolonged irradiation of enhanced cyan fluorescent protein or Cerulean can invalidate Forster resonance energy transfer measurements.

    PubMed

    Hoffmann, Birgit; Zimmer, Thomas; Klöcker, Nikolaj; Kelbauskas, Laimonas; König, Karsten; Benndorf, Klaus; Biskup, Christoph

    2008-01-01

    Since its discovery, green fluorescent protein (GFP) and its variants have proven to be a good and convenient fluorescent label for proteins: GFP and other visible fluorescent proteins (VFPs) can be fused selectively to the protein of interest by simple cloning techniques and develop fluorescence without additional cofactors. Among the steadily growing collection of VFPs, several pairs can be chosen that can serve as donor and acceptor fluorophores in Forster resonance energy transfer (FRET) experiments. Among them, the cyan fluorescent proteins (ECFP/Cerulean) and the enhanced yellow fluorescent protein (EYFP) are most commonly used. We show that ECFP and Cerulean have some disadvantages despite their common use: Upon irradiation with light intensities that are commonly used for intensity- and lifetime-based FRET measurements, both the fluorescence intensity and the fluorescence lifetime of ECFP and Cerulean decrease. This can hamper both intensity- and lifetime-based FRET measurements and emphasizes the need for control measurements to exclude these artifacts. PMID:18601529

  15. Localization of subsurface fluorescent lesions using surface spectral measurements

    NASA Astrophysics Data System (ADS)

    Kolste, Kolbein

    Localization of Subsurface Fluorescent Lesions using Surface Spectral Measurements Sponsored by the National Institute of Health, Bethesda, Maryland Kolbein Kolste, Ph.D. Keith Paulsen In neurosurgical tumor resection, maximizing extent of resection plays a major role in the care of cancer patients. To date, ALA is being researched as a technique to guide tumor resection by inducing the accumulation of the endogenous fluorophore PpIX. Most research has focused on the use of blue light excitation of PpIX to visual the tumor. However, due to the high attenuation of blue light by in vivo chromophores, such as oxy- and deoxy-hemoglobin, the source of collected fluorescence emissions is confined to the top layer of cells, and the signal is subject to masking by blood on the surface of the surgical field of view. This issue is particularly a problem at the end of the resection, when the surgeon is evaluating the margin for remaining tumor, but the blue-signal is insensitive to residual tumor that may be located several millimeters beneath the surface. PpIX has an absorption band in the near infrared (NIR), where the absorption due to blood is orders of magnitude lower, enabling the excitation of a fluorophore at depth. In this work, we created a hyperspectral imaging system that attaches to a neurosurgical microscope and is capable of detecting PpIX fluorescence that has been excited at 635 nm. We utilize a dual-waveband technique from the hyperspectral to estimate depth of fluorescence origin and characterize the inherent limitations of the estimated depth. One of the major benefits of this technique is that the estimation is independent of the concentration and size of the fluorophore. This is first demonstrated in phantom studies, where the depths of multiple separate inclusions at various depths are accurately estimated. The technique is verified in animal tumor models and translated into the clinical theater, with pilot data showing the first estimation of depth of

  16. Quantitative fluorescent speckle microscopy (QFSM) to measure actin dynamics.

    PubMed

    Mendoza, Michelle C; Besson, Sebastien; Danuser, Gaudenz

    2012-10-01

    Quantitative fluorescent speckle microscopy (QFSM) is a live-cell imaging method to analyze the dynamics of macromolecular assemblies with high spatial and temporal resolution. Its greatest successes were in the analysis of actin filament and adhesion dynamics in the context of cell migration and microtubule dynamics in interphase and the meiotic/mitotic spindle. Here, focus is on the former application to illustrate the procedures of FSM imaging and the computational image processing that extracts quantitative information from these experiments. QFSM is advantageous over other methods because it measures the movement and turnover kinetics of the actin filament (F-actin) network in living cells across the entire field of view. Experiments begin with the microinjection of fluorophore-labeled actin into cells, which generate a low ratio of fluorescently labeled to endogenously unlabeled actin monomers. Spinning disk confocal or wide-field imaging then visualizes fluorophore clusters (two to eight actin monomers) within the assembled F-actin network as speckles. QFSM software identifies and computationally tracks and utilizes the location, appearance, and disappearance of speckles to derive network flows and maps of the rate of filament assembly and disassembly. PMID:23042526

  17. Error analysis for intrinsic quality factor measurement in superconducting radio frequency resonators

    NASA Astrophysics Data System (ADS)

    Melnychuk, O.; Grassellino, A.; Romanenko, A.

    2014-12-01

    In this paper, we discuss error analysis for intrinsic quality factor (Q0) and accelerating gradient (Eacc) measurements in superconducting radio frequency (SRF) resonators. The analysis is applicable for cavity performance tests that are routinely performed at SRF facilities worldwide. We review the sources of uncertainties along with the assumptions on their correlations and present uncertainty calculations with a more complete procedure for treatment of correlations than in previous publications [T. Powers, in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27]. Applying this approach to cavity data collected at Vertical Test Stand facility at Fermilab, we estimated total uncertainty for both Q0 and Eacc to be at the level of approximately 4% for input coupler coupling parameter β1 in the [0.5, 2.5] range. Above 2.5 (below 0.5) Q0 uncertainty increases (decreases) with β1 whereas Eacc uncertainty, in contrast with results in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27], is independent of β1. Overall, our estimated Q0 uncertainty is approximately half as large as that in Powers [in Proceedings of the 12th Workshop on RF Superconductivity, SuP02 (Elsevier, 2005), pp. 24-27].

  18. An advanced fluorescence LIDAR system for the acquisition of interleaved active (LIF) and passive (SIF) fluorescence measurements on vegetation

    NASA Astrophysics Data System (ADS)

    Raimondi, Valentina; Palombi, Lorenzo; Di Ninni, Paola

    2015-10-01

    Fluorescence is regarded as a valuable tool to investigate the eco-physiological status of vegetation. Chlorophyll a, which emits a typical fluorescence in the red/far-red region of the e.m. spectrum, plays a key role in the photosynthetic process and its fluorescence is considered an effective proxy of photosynthetic activity of plants. Laser Induced Fluorescence (LIF) has been studied for several decades both at leaf- and canopy-level by means of optical fibers-coupled instrumentation and fluorescence LIDAR systems. On the other hand, Solar-Induced Fluorescence (SIF) has been the object of several scientific studies quite recently, with the aim to investigate the feasibility of measuring the fluorescence of vegetation using passive spectroradiometers in view of global scale monitoring from satellite platforms. This paper presents the main technical features and preliminary tests of a fluorescence LIDAR, recently upgraded to acquire maps of interleaved LIF and SIF measurements at canopy level. In-house developed electronics and software permits the acquisition of interleaved LIF and SIF spectra by switching on/off the laser, the selection of the suitable grating, the setting of the integration time and the synchronization of the Intensified CCD (ICCD) gate opening time. For each pixel of the map, a fluorescence dataset can be acquired containing a LIF spectrum - from 570 nm to 830 nm with a spectral resolution of 0.5 nm - and radiance spectra from 685.53 nm to 690.30 nm with subnanometric spectral resolution containing the molecular oxygen O2-B telluric absorption band. The latter can be exploited for polynomial regression data fit and SIF retrieval.

  19. Measuring Agarwood Formation Ratio Quantitatively by Fluorescence Spectral Imaging Technique.

    PubMed

    Huang, Botao; Nguyen, Duykien; Liu, Tianyi; Jiang, Kaibin; Tan, Jinfen; Liu, Chunxin; Zhao, Jing; Huang, Shaowei

    2015-01-01

    Agarwood is a kind of important and precious traditional Chinese medicine. With the decreasing of natural agarwood, artificial cultivation has become more and more important in recent years. Quantifying the formation of agarwood is an essential work which could provide information for guiding cultivation and controlling quality. But people only can judge the amount of agarwood qualitatively by experience before. Fluorescence multispectral imaging method is presented to measure the agarwood quantitatively in this paper. A spectral cube from 450 nm to 800 nm was captured under the 365 nm excitation sources. The nonagarwood, agarwood, and rotten wood in the same sample were distinguished based on analyzing the spectral cube. Then the area ratio of agarwood to the whole sample was worked out, which is the quantitative information of agarwood area percentage. To our knowledge, this is the first time that the formation of agarwood was quantified accurately and nondestructively. PMID:26089935

  20. Fluorescent Measurement of Synaptic Activity Using SynaptopHluorin in Isolated Hippocampal Neurons

    PubMed Central

    Li, Hongmei; Park, Han-A; Jonas, Elizabeth A.

    2016-01-01

    This protocol comprises the entire process of fluorescent measurement of vesicle recycling using the probe SynaptopHluorin, a pH-dependent GFP variant whose fluorescence increases at the synapse upon vesicle release due to fluorescence quenching in acidic vesicles. This technique provides a genetic tool to monitor synaptic vesicle recycling in real time in cultured hippocampal neurons.

  1. Improved method for measuring vitamin B12 in serum using intrinsic factor, 57CoB12, and coated charcoal

    PubMed Central

    Raven, J. L.; Robson, M. B.; Walker, P. L.; Barkhan, P.

    1969-01-01

    An improved and simplified method is described for the measurement of vitamin B12 in serum using intrinsic factor, 57CoB12, and coated charcoal. The extraction of serum in the presence of cyanide and the incorporation of B12-deficient serum into the intrinsic factor control has increased the accuracy of the method for both sera and crystalline B12 solutions. There are interesting differences between the results obtained for some sera by the isotope and L. leichmannii methods and the reasons for these differences are discussed. PMID:5776552

  2. Laser induced fluorescence measurements of the cylindrical Hall thruster plume

    SciTech Connect

    Spektor, R.; Diamant, K. D.; Beiting, E. J.; Raitses, Y.; Fisch, N. J.

    2010-09-15

    An investigation of a fully cylindrical Hall thruster was performed using laser induced fluorescence (LIF) to measure ion velocity profiles in the plume. The measurements confirm a previously reported 9% increase in the exhaust energy when the cathode keeper draws an excess current (overrun mode). Furthermore, the velocity directions in the plume remain relatively unchanged for the cusped and direct magnetic field configuration in both overrun and nonoverrun modes. Previously reported plume narrowing in the overrun mode was confirmed and found to be due to the shift of the acceleration and ionization regions toward the anode. The electric field inferred from the LIF measurements allowed calculation of the electron ExB drift. Close to the centerline of the thruster, electrons drift azimuthally with velocity decreasing away from the centerline, thus creating shear. This shear can be a source of plasma instabilities and influence electron transport. Further away from the centerline, electrons drift in the opposite direction with their velocity increasing with increasing radius. In that region, electrons rotate without shear.

  3. Measurement uncertainty in Total Reflection X-ray Fluorescence

    NASA Astrophysics Data System (ADS)

    Floor, G. H.; Queralt, I.; Hidalgo, M.; Marguí, E.

    2015-09-01

    Total Reflection X-ray Fluorescence (TXRF) spectrometry is a multi-elemental technique using micro-volumes of sample. This work assessed the components contributing to the combined uncertainty budget associated with TXRF measurements using Cu and Fe concentrations in different spiked and natural water samples as an example. The results showed that an uncertainty estimation based solely on the count statistics of the analyte is not a realistic estimation of the overall uncertainty, since the depositional repeatability and the relative sensitivity between the analyte and the internal standard are important contributions to the uncertainty budget. The uncertainty on the instrumental repeatability and sensitivity factor could be estimated and as such, potentially relatively straightforward implemented in the TXRF instrument software. However, the depositional repeatability varied significantly from sample to sample and between elemental ratios and the controlling factors are not well understood. By a lack of theoretical prediction of the depositional repeatability, the uncertainty budget can be based on repeat measurements using different reflectors. A simple approach to estimate the uncertainty was presented. The measurement procedure implemented and the uncertainty estimation processes developed were validated from the agreement with results obtained by inductively coupled plasma - optical emission spectrometry (ICP-OES) and/or reference/calculated values.

  4. Azadioxatriangulenium: exploring the effect of a 20 ns fluorescence lifetime in fluorescence anisotropy measurements

    NASA Astrophysics Data System (ADS)

    Bogh, Sidsel A.; Bora, Ilkay; Rosenberg, Martin; Thyrhaug, Erling; Laursen, Bo W.; Just Sørensen, Thomas

    2015-12-01

    Azaoxatriangulenium (ADOTA) has been shown to be highly emissive despite a moderate molar absorption coefficient of the primary electronic transition. As a result, the fluorescence lifetime is ~20 ns, longer than all commonly used red fluorescent organic probes. The electronic transitions in ADOTA are highly polarised (r 0  =  0.38), which in combination with the long fluorescence lifetime extents the size-range of biomolecular weights that can be detected in fluorescence polarisation-based experiments. Here, the rotational dynamics of bovine serum albumin (BSA) are monitored with three different ADOTA derivatives, differing only in constitution of the reactive linker. A detailed study of the degree of labelling, the steady-state anisotropy, and the time-resolved anisotropy of the three different ADOTA-BSA conjugates are reported. The fluorescence quantum yields (ϕ fl) of the free dyes in PBS solution are determined to be ~55%, which is reduced to ~20% in the ADOTA-BSA conjugates. Despite the reduction in ϕ fl, a ~20 ns intensity averaged lifetime is maintained, allowing for the rotational dynamics of BSA to be monitored for up to 100 ns. Thus, ADOTA can be used in fluorescence polarisation assays to fill the gap between commonly used organic dyes and the long luminescence lifetime transition metal complexes. This allows for efficient steady-state fluorescence polarisation assays for detecting binding of analytes with molecular weights of up to 100 kDa.

  5. Monitoring Ras Interactions with the Nucleotide Exchange Factor Son of Sevenless (Sos) Using Site-specific NMR Reporter Signals and Intrinsic Fluorescence*

    PubMed Central

    Vo, Uybach; Vajpai, Navratna; Flavell, Liz; Bobby, Romel; Breeze, Alexander L.; Embrey, Kevin J.; Golovanov, Alexander P.

    2016-01-01

    The activity of Ras is controlled by the interconversion between GTP- and GDP-bound forms partly regulated by the binding of the guanine nucleotide exchange factor Son of Sevenless (Sos). The details of Sos binding, leading to nucleotide exchange and subsequent dissociation of the complex, are not completely understood. Here, we used uniformly 15N-labeled Ras as well as [13C]methyl-Met,Ile-labeled Sos for observing site-specific details of Ras-Sos interactions in solution. Binding of various forms of Ras (loaded with GDP and mimics of GTP or nucleotide-free) at the allosteric and catalytic sites of Sos was comprehensively characterized by monitoring signal perturbations in the NMR spectra. The overall affinity of binding between these protein variants as well as their selected functional mutants was also investigated using intrinsic fluorescence. The data support a positive feedback activation of Sos by Ras·GTP with Ras·GTP binding as a substrate for the catalytic site of activated Sos more weakly than Ras·GDP, suggesting that Sos should actively promote unidirectional GDP → GTP exchange on Ras in preference of passive homonucleotide exchange. Ras·GDP weakly binds to the catalytic but not to the allosteric site of Sos. This confirms that Ras·GDP cannot properly activate Sos at the allosteric site. The novel site-specific assay described may be useful for design of drugs aimed at perturbing Ras-Sos interactions. PMID:26565026

  6. Monitoring Ras Interactions with the Nucleotide Exchange Factor Son of Sevenless (Sos) Using Site-specific NMR Reporter Signals and Intrinsic Fluorescence.

    PubMed

    Vo, Uybach; Vajpai, Navratna; Flavell, Liz; Bobby, Romel; Breeze, Alexander L; Embrey, Kevin J; Golovanov, Alexander P

    2016-01-22

    The activity of Ras is controlled by the interconversion between GTP- and GDP-bound forms partly regulated by the binding of the guanine nucleotide exchange factor Son of Sevenless (Sos). The details of Sos binding, leading to nucleotide exchange and subsequent dissociation of the complex, are not completely understood. Here, we used uniformly (15)N-labeled Ras as well as [(13)C]methyl-Met,Ile-labeled Sos for observing site-specific details of Ras-Sos interactions in solution. Binding of various forms of Ras (loaded with GDP and mimics of GTP or nucleotide-free) at the allosteric and catalytic sites of Sos was comprehensively characterized by monitoring signal perturbations in the NMR spectra. The overall affinity of binding between these protein variants as well as their selected functional mutants was also investigated using intrinsic fluorescence. The data support a positive feedback activation of Sos by Ras·GTP with Ras·GTP binding as a substrate for the catalytic site of activated Sos more weakly than Ras·GDP, suggesting that Sos should actively promote unidirectional GDP → GTP exchange on Ras in preference of passive homonucleotide exchange. Ras·GDP weakly binds to the catalytic but not to the allosteric site of Sos. This confirms that Ras·GDP cannot properly activate Sos at the allosteric site. The novel site-specific assay described may be useful for design of drugs aimed at perturbing Ras-Sos interactions. PMID:26565026

  7. Characterization and measurement results of fluorescence in absorption optical filter glass

    NASA Astrophysics Data System (ADS)

    Reichel, S.; Biertümpfel, R.; Engel, A.

    2015-09-01

    Optical filter glasses (absorption filters) are for example used for spectroscopy. The filter glass absorbs the unwanted light and has a nearly angle independent spectral characteristic. The absorbed light can lead to (self-) fluorescence, i. e. the filter glass itself re-emits fluorescence light at a different wavelength - compared to the incident (excitation) light. This fluorescence light can disturb the measurement signal. In order to obtain an optimized optical design the fluorescence properties of the glasses must be known. By knowing fluorescence properties one can design a system with a good signal-to-noise ratio. We will present our measurement set-up for fluorescence measurements of optical filter glass. This set-up was used to obtain fluorescence measurement results for different optical filter glasses. For the first time we present results on the fluorescence level for different optical filter glasses. In addition the effect of excitation wavelength on the fluorescence level will be studied. Besides other factors, fluorescence depends on impurities of the raw material of the glass melt. Due to small fluctuations of the raw material used for the glass production the fluorescence of the same filter glass type can fluctuate from melt-to-melt. Thus, results from different melts will be shown for the same filter glass type.

  8. Electron beam fluorescence measurements in the Boeing hypersonic shock tunnel

    NASA Technical Reports Server (NTRS)

    Price, Linwood L.; Williams, W. Dan; Powell, H. M.

    1992-01-01

    The Calspan electron beam fluorescence (EBF) measurement system is described along with the results of measurements made in hypersonic flow. Numerous self-emitting metallic species were identified, many of which may be associated with an aging/erosion process within the B30HST. Because there were only 16 tunnel runs, it was only possible to obtain spectral measurements over a limited range of wavelengths and time sampling periods. Many spectral features of the flow remain uninvestigated. Because flow self-emission is important to all optical diagnostic techniques, it is recommended that additional spectral studies by performed. The three electron beam-excited species that were identified are nitrogen, helium, and nitric oxide. The high metallic radiation background interfered with attempts to obtain the time-wise variation of N2 density and He radiation with the optical fiber/PMT channels. In the case of the N2 density measurements the result of interference was increased uncertainty. Unfortunately, the interference caused the time-wise He measurements to fail completely. It is recommended that the electron beam be modulated to provide discrimination against the background radiation in future N2 density measurements. Careful data reduction produced useful measurements of N2 vibrational temperature, even though the high background from metallic species significantly increased measurement uncertainty. Perhaps the recommended additional spectral studies would reveal N2(+) First Negative System band-pair regions having less background. Detection of the He arrival was easily accomplished with the spectrometer/array detector system. Because of this, it is recommended that this means of detecting He arrival be used in the future. With proper calibrations of the system an He number density could be obtained. Although the flow conditions were out of limits for the run in which the NO spectrum was recorded, the usefulness of the NO spectrum for determination of free

  9. Phytoplankton photocompensation from space-based fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Morrison, J. Ruairidh; Goodwin, Deborah S.

    2010-03-01

    Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.

  10. A multi-view time-domain non-contact diffuse optical tomography scanner with dual wavelength detection for intrinsic and fluorescence small animal imaging.

    PubMed

    Lapointe, Eric; Pichette, Julien; Bérubé-Lauzière, Yves

    2012-06-01

    We present a non-contact diffuse optical tomography (DOT) scanner with multi-view detection (over 360°) for localizing fluorescent markers in scattering and absorbing media, in particular small animals. It relies on time-domain detection after short pulse laser excitation. Ultrafast time-correlated single photon counting and photomultiplier tubes are used for time-domain measurements. For light collection, seven free-space optics non-contact dual wavelength detection channels comprising 14 detectors overall are placed around the subject, allowing the measurement of time point-spread functions at both excitation and fluorescence wavelengths. The scanner is endowed with a stereo camera pair for measuring the outer shape of the subject in 3D. Surface and DOT measurements are acquired simultaneously with the same laser beam. The hardware and software architecture of the scanner are discussed. Phantoms are used to validate the instrument. Results on the localization of fluorescent point-like inclusions immersed in a scattering and absorbing object are presented. The localization algorithm relies on distance ranging based on the measurement of early photons arrival times at different positions around the subject. This requires exquisite timing accuracy from the scanner. Further exploiting this capability, we show results on the effect of a scattering hetereogenity on the arrival time of early photons. These results demonstrate that our scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step. Through its free-space optics design and the short pulse laser used, our scanner shows unprecedented timing resolution compared to other multi-view time-domain scanners. PMID:22755630

  11. A multi-view time-domain non-contact diffuse optical tomography scanner with dual wavelength detection for intrinsic and fluorescence small animal imaging

    NASA Astrophysics Data System (ADS)

    Lapointe, Eric; Pichette, Julien; Bérubé-Lauzière, Yves

    2012-06-01

    We present a non-contact diffuse optical tomography (DOT) scanner with multi-view detection (over 360°) for localizing fluorescent markers in scattering and absorbing media, in particular small animals. It relies on time-domain detection after short pulse laser excitation. Ultrafast time-correlated single photon counting and photomultiplier tubes are used for time-domain measurements. For light collection, seven free-space optics non-contact dual wavelength detection channels comprising 14 detectors overall are placed around the subject, allowing the measurement of time point-spread functions at both excitation and fluorescence wavelengths. The scanner is endowed with a stereo camera pair for measuring the outer shape of the subject in 3D. Surface and DOT measurements are acquired simultaneously with the same laser beam. The hardware and software architecture of the scanner are discussed. Phantoms are used to validate the instrument. Results on the localization of fluorescent point-like inclusions immersed in a scattering and absorbing object are presented. The localization algorithm relies on distance ranging based on the measurement of early photons arrival times at different positions around the subject. This requires exquisite timing accuracy from the scanner. Further exploiting this capability, we show results on the effect of a scattering hetereogenity on the arrival time of early photons. These results demonstrate that our scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step. Through its free-space optics design and the short pulse laser used, our scanner shows unprecedented timing resolution compared to other multi-view time-domain scanners.

  12. Laser-induced fluorescence, dispersed fluorescence and lifetime measurements of jet-cooled chloro-substituted benzyl radicals

    NASA Astrophysics Data System (ADS)

    Hamatani, Satoshi; Tsuji, Kazuhide; Kawai, Akio; Shibuya, Kazuhiko

    2002-07-01

    We measured the laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled α-, o- and m-chlorobenzyl radicals after they were generated by the 193 nm photolysis of the corresponding parent molecules. The vibronically resolved spectra were obtained to analyze their D1-D0 transitions. The fluorescence lifetimes of α-, o-, m- and p-chlorobenzyls in the zeroth vibrational levels of the D1 states were measured to estimate the oscillator strengths of a series of benzyl derivatives. It was found that the α-substitution is inefficient to break the `accidental forbiddenness' of the D1-D0 transition of benzyl, while the ring-substitution enhances the oscillator strength by 50%.

  13. Fluorescence measurements of the thermal control experiments coatings on LDEF S0069 and A0114

    NASA Technical Reports Server (NTRS)

    Zwiener, J. M.; Mell, R. J.; Peters, P. N.; Gregory, J. C.; Wilkes, D. R.; Miller, E. R.

    1993-01-01

    Fluorescence measurements were made on the thermal control coatings from the Long Duration Experiment Facility (LDEF) S0069, Thermal Control Surfaces Experiment (TCSE); and the A0114, Interaction of Atomic Oxygen with Material Surfaces in Low Earth orbit. Fluorescence was observed in two types of thermal control coatings and is attributed to pigments or binders. In addition, fluorescence measurement on the silver Teflon from the front cover of TCSE led to confirmation of damage (cracking) to the metal layers during application.

  14. In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics

    PubMed Central

    Leeuw, Thomas; Boss, Emmanuel S.; Wright, Dana L.

    2013-01-01

    Chlorophyll a fluorometry has long been used as a method to study phytoplankton in the ocean. In situ fluorometry is used frequently in oceanography to provide depth-resolved estimates of phytoplankton biomass. However, the high price of commercially manufactured in situ fluorometers has made them unavailable to some individuals and institutions. Presented here is an investigation into building an in situ fluorometer using low cost electronics. The goal was to construct an easily reproducible in situ fluorometer from simple and widely available electronic components. The simplicity and modest cost of the sensor makes it valuable to students and professionals alike. Open source sharing of architecture and software will allow students to reconstruct and customize the sensor on a small budget. Research applications that require numerous in situ fluorometers or expendable fluorometers can also benefit from this study. The sensor costs US$150.00 and can be constructed with little to no previous experience. The sensor uses a blue LED to excite chlorophyll a and measures fluorescence using a silicon photodiode. The sensor is controlled by an Arduino microcontroller that also serves as a data logger. PMID:23783738

  15. Quantum dots fluorescence quantum yield measured by Thermal Lens Spectroscopy.

    PubMed

    Estupiñán-López, Carlos; Dominguez, Christian Tolentino; Cabral Filho, Paulo E; Fontes, Adriana; de Araujo, Renato E

    2014-01-01

    An essential parameter to evaluate the light emission properties of fluorophores is the fluorescence quantum yield, which quantify the conversion efficiency of absorbed photons to emitted photons. We detail here an alternative nonfluorescent method to determine the absolute fluorescence quantum yield of quantum dots (QDs). The method is based in the so-called Thermal Lens Spectroscopy (TLS) technique, which consists on the evaluation of refractive index gradient thermally induced in the fluorescent material by the absorption of light. Aqueous dispersion carboxyl-coated cadmium telluride (CdTe) QDs samples were used to demonstrate the Thermal Lens Spectroscopy technical procedure. PMID:25103802

  16. Naphthalene laser-induced fluorescence measurements at low temperature and pressure.

    PubMed

    Combs, Christopher S; Clemens, Noel T

    2016-05-01

    Few studies on naphthalene vapor fluorescence have been conducted at low temperature and pressure conditions. The current study focuses on conducting measurements of naphthalene quenching and absorption cross section in a temperature- and pressure-regulated test cell with 266 nm laser excitation. The test-cell measurements were of the naphthalene-fluorescence lifetime and integrated fluorescence signal over the temperature range of 100 to 525 K and pressure range of 1 to 40 kPa in air. These data enabled the calculation of naphthalene-fluorescence quantum yield and absorption cross section over the range of temperatures and pressures tested, which were then fit to simple functional forms for future use in the calibration of naphthalene laser-induced fluorescence (LIF) measurements. Furthermore, the variation of naphthalene-fluorescence signal with respect to temperature was investigated for four different excitation wavelengths, demonstrating that a two-line naphthalene LIF thermometry technique may be feasible. PMID:27140385

  17. [Study on fluorescence measurement system of wastewater treatment process].

    PubMed

    Wu, Zhi-Xiang; Wang, Jun-Bo; Li, Zhan-Feng; Deng, Hu

    2011-06-01

    The present paper, focusing on the relationship between the fluorescence characteristics of fluorescent substances produced by the anaerobic reactors in process of the wastewater treatment status, aims to build an online detection platform of anaerobic wastewater treatment process for the wastewater treatment process parameter control, to provide effective, credible and stable technical basis, and to a certain extent can improve the efficiency of wastewater treatment. The results showed that it is feasible for this system to use fluorescence spectroscopy of wastewater treatment anaerobic reactor during the test; compared with the conventional detection method, it has simple structure, high sensitivity, and less time-consuming advantages; for other fluorescent substances in waste water treatment, it has broad application prospects. PMID:21847935

  18. Color measurements on prints containing fluorescent whitening agents

    NASA Astrophysics Data System (ADS)

    Andersson, Mattias; Norberg, Ole

    2007-01-01

    Papers with a slightly blue shade are, at least among a majority of observers being perceived as whiter than papers having a more neutral color1. Therefore, practically all commercially available printing papers contain bluish dyes and fluorescent whitening agents (FWA) to give the paper a whiter appearance. Furthermore, in the paper industry, the most frequently used measure for paper whiteness is the CIE-whiteness. The CIE Whiteness formula, does in turn, also favor slightly bluish papers. Excessive examples of high CIE-whiteness values can be observed in the office-paper segment where a high CIE-whiteness value is an important sales argument. As an effect of the FWA, spectrophotometer measurements of optical properties such as paper whiteness are sensitive to the ultraviolet (UV) content of the light source used in the instrument. To address this, the standard spectrophotometers used in the paper industry are equipped with an adjustable filter for calibrating the UV-content of the illumination. In the paper industry, spectrophotometers with d/0 measurement geometry and a light source of type C are used. The graphical arts industry on the other hand, typically measures with spectrophotometers having 45/0 geometry and a light source of type A. Moreover, these instruments have only limited possibilities to adjust the UV-content by the use of different weighting filters. The standard for color measurements in the paper industry governs that measurements should be carried out using D65 standard illumination and the 10 ° standard observer. The corresponding standard for the graphic arts industry specify D50 standard illumination and the 2 ° standard observer. In both cases, the standard illuminants are simulated from the original light source by spectral weighting functions. However, the activation of FWA, which will impact the measured spectral reflectance, depends on the actual UV-content of the illumination used. Therefore, comparisons between measurements on

  19. Solvation of deoxynucleosides in aqueous mixtures of organic solvents probed through their intrinsic fluorescence: Implications for open base pair states in DNA

    NASA Astrophysics Data System (ADS)

    Ababneh, Anas Mohammad

    Because of the importance of solvation in the function of DNA, there is considerable interest in understanding the solvation network of its constituent components. This is of particular importance in connection with the closing of base pairs that have been disrupted as a result of structural fluctuations. Following the opening of a base pair, the open base is exposed to a heterogeneous environment which involves polar as well as nonpolar interactions. Toward the goal of understanding how the open bases interact with such a heterogeneous environment, we have studied the intrinsic fluorescence properties of the purine and pyrimidine nucleosides (dG, dA, dT, and dC) in organic solvents in the presence of small amounts of water. Exposure of the nucleoside to water was done by preparing solutions in three different ways: (i) "premixed" solution in which the nucleoside is dissolved in a water-organic solvent mixture, (ii) "carry its own water" solution in which the nucleoside is first dissolved in water and then diluted in the organic solvent, and (iii) "injected" solution in which water is added to a solution of the nucleoside in the organic solvent. The organic solvents used in the present study were: n-butanol, acetonitrile, methanol, n-propanol, isopropanol, and isobutanol. We find that for n-butanol and acetonitrile, which have a high degree of amphiphilicity and weak hydrogen bonding ability, respectively, the fluorescence spectral properties of the purines are found to depend on the sequence of the steps in which the aqueous mixture was formed. By contrast, no such dependence was observed in the other organic solvents. On the other hand, no such dependence was observed for the pyrimidines in any of the organic solvents used in the present study. These findings suggest that the final solvation network around the purines is dependent on the nature of the environment to which they were initially exposed. This would tend to present an impediment to the closing of

  20. Determination of biological activity from fluorescence-lifetime measurements in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Rudek, F.; Baselt, T.; Lempe, B.; Taudt, C.; Hartmann, P.

    2015-03-01

    The importance of fluorescence lifetime measurement as an optical analysis tool is growing. Many applications already exist in order to determine the fluorescence lifetime, but the majority of these require the addition of fluorescence-active substances to enable measurements. Every usage of such foreign materials has an associated risk. This paper investigates the use of auto-fluorescing substances in Saccharomyces cerevisiae (Baker's yeast) as a risk free alternative to fluorescence-active substance enabled measurements. The experimental setup uses a nitrogen laser with a pulse length of 350 ps and a wavelength of 337 nm. The excited sample emits light due to fluorescence of NADH/NADPH and collagen. A fast photodiode collects the light at the output of an appropriate high-pass edge-filter at 400 nm. Fluorescence lifetimes can be determined from the decay of the measurement signals, which in turn characterizes the individual materials and their surrounding environment. Information about the quantity of the fluorescence active substances can also be measured based on the received signal intensity. The correlation between the fluorescence lifetime and the metabolic state of Saccharomyces cerevisiae was investigated and is presented here.

  1. Analysis of laser-induced-fluorescence carbon monoxide measurements in turbulent nonpremixed flames.

    PubMed

    Mokhov, A V; Levinsky, H B; van der Meij, C E; Jacobs, R A

    1995-10-20

    The influence of fluctuating concentrations and temperature on the laser-induced-fluorescence (LIF) measurement of CO in turbulent flames is described, under conditions in which the fluorescence and the temperature are measured independently. The analysis shows that correlations between CO concentration and temperature can bias the averaged mole fraction extracted from LIF measurements. The magnitude of the bias can exceed the order of the average CO mole fraction. Further, LIF measurements of CO concentrations in a turbulent, nonpremixed, natural gas flame are described. The averaged CO mole fractions are derived from the fluorescence measurements by the use of flame temperatures independently measured by coherent anti-Stokes Raman spectroscopy. Analysis of the fluctuations in measured temperature and fluorescence indicates that temperature and CO concentrations in flame regions with intensive mixing are indeed correlated. In the flame regions where burnout of CO has ceased, the LIF measurements of the CO mole fraction correspond to the probe measurements in exhaust. PMID:21060569

  2. Dual-channel red/blue fluorescence dosimetry with broadband reflectance spectroscopic correction measures protoporphyrin IX production during photodynamic therapy of actinic keratosis

    NASA Astrophysics Data System (ADS)

    Kanick, Stephen Chad; Davis, Scott C.; Zhao, Yan; Hasan, Tayyaba; Maytin, Edward V.; Pogue, Brian W.; Chapman, M. Shane

    2014-07-01

    Dosimetry for aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy of actinic keratosis was examined with an optimized fluorescence dosimeter to measure PpIX during treatment. While insufficient PpIX generation may be an indicator of incomplete response, there exists no standardized method to quantitate PpIX production at depths in the skin during clinical treatments. In this study, a spectrometer-based point probe dosimeter system was used to sample PpIX fluorescence from superficial (blue wavelength excitation) and deeper (red wavelength excitation) tissue layers. Broadband white light spectroscopy (WLS) was used to monitor aspects of vascular physiology and inform a correction of fluorescence for the background optical properties. Measurements in tissue phantoms showed accurate recovery of blood volume fraction and reduced scattering coefficient from WLS, and a linear response of PpIX fluorescence versus concentration down to 1.95 and 250 nM for blue and red excitations, respectively. A pilot clinical study of 19 patients receiving 1-h ALA incubation before treatment showed high intrinsic variance in PpIX fluorescence with a standard deviation/mean ratio of >0.9. PpIX fluorescence was significantly higher in patients reporting higher pain levels on a visual analog scale. These pilot data suggest that patient-specific PpIX quantitation may predict outcome response.

  3. Measuring thermodynamic details of DNA hybridization using fluorescence

    PubMed Central

    You, Yong; Tataurov, Andrey V; Owczarzy, Richard

    2011-01-01

    Modern real-time PCR systems make it easy to monitor fluorescence while temperature is varied for hundreds of samples in parallel, permitting high-throughput studies. We employed such system to investigate melting transitions of ordered nucleic acid structures into disordered random coils. Fluorescent dye and quencher were attached to oligonucleotides in such a way that changes of fluorescence intensity with temperature indicated progression of denaturation. When fluorescence melting data were compared with traditional ultraviolet optical experiments, commonly used dye/quencher combinations, like fluorescein and tetramethylrhodamine, showed substantial discrepancies. We have therefore screened 22 commercially available fluorophores and quenchers for their ability to reliably report annealing and melting transitions. Dependence of fluorescence on temperature and pH was also investigated. The optimal performance was observed using Texas Red or ROX dyes with Iowa Black RQ or Black Hole quenchers. These labels did not alter two-state nature of duplex melting process and provided accurate melting temperatures, free energies, enthalpies, and entropies. We also suggest a new strategy for determination of DNA duplex thermodynamics where concentration of a dye-labeled strand is kept constant and its complementary strand modified with a quencher is added at increasing excess. These methodological improvements will help build predictive models of nucleic acid hybridization. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 472–486, 2011. PMID:21384337

  4. Frequency domain fluorescence lifetime microwell-plate platform for respirometry measurements

    NASA Astrophysics Data System (ADS)

    Chatni, M. R.; Yale, G.; Van Ryckeghem, A.; Porterfield, D. M.

    2010-04-01

    Traditionally micro-well plate based platforms used in biology utilize fluorescence intensity based methods to measure processes of biological relevance. However, fluorescence intensity measurements suffer from calibration drift due to a variety of factors. Photobleaching and self-quenching of the fluorescent dyes cause the intensity signal to drop over the lifetime of sensor immobilized inside the well. Variation in turbidity of the sample during the course of the measurement affects the measured fluorescence intensity. In comparison, fluorescence lifetime measurements are not significantly affected by these factors because fluorescence lifetime is a physico-chemical property of the fluorescent dye. Reliable and inexpensive frequency domain fluorescence lifetime instrumentation platforms are possible because the greater tolerance for optical alignment, and because they can be performed using inexpensive light sources such as LEDs. In this paper we report the development of a frequency domain fluorescence lifetime well-plate platform utilizing an oxygen sensitive transition-metal ligand complex fluorophore with a lifetime in the microsecond range. The fluorescence lifetime dye is incorporated in a polymer matrix and immobilized on the base of micro-well of a 60 well micro-well plate. Respiration measurements are performed in both aqueous and non-aqueous environment. Respirometry measurements were recorded from single Daphnia magna egg in hard water. Daphnia is an aquatic organism, important in environmental toxicology as a standard bioassay and early warning indicator for water quality monitoring. Also respirometry measurements were recorded from Tribolium castaneum eggs, which are common pests in the processed flour industry. These eggs were subjected to mitochondrial electron transport chain inhibitor such as potassium cyanide (KCN) and its effects on egg respiration were measured in real-time.

  5. Measurement of protein-like fluorescence in river and waste water using a handheld spectrophotometer.

    PubMed

    Baker, Andy; Ward, David; Lieten, Shakti H; Periera, Ryan; Simpson, Ellie C; Slater, Malcolm

    2004-07-01

    Protein-like fluorescence intensity in rivers increases with increasing anthropogenic DOM inputs from sewerage and farm wastes. Here, a portable luminescence spectrophotometer was used to investigate if this technology could be used to provide both field scientists with a rapid pollution monitoring tool and process control engineers with a portable waste water monitoring device, through the measurement of river and waste water tryptophan-like fluorescence from a range of rivers in NE England and from effluents from within two waste water treatment plants. The portable spectrophotometer determined that waste waters and sewerage effluents had the highest tryptophan-like fluorescence intensity, urban streams had an intermediate tryptophan-like fluorescence intensity, and the upstream river samples of good water quality the lowest tryptophan-like fluorescence intensity. Replicate samples demonstrated that fluorescence intensity is reproducible to +/- 20% for low fluorescence, 'clean' river water samples and +/- 5% for urban water and waste waters. Correlations between fluorescence measured by the portable spectrophotometer with a conventional bench machine were 0.91; (Spearman's rho, n = 143), demonstrating that the portable spectrophotometer does correlate with tryptophan-like fluorescence intensity measured using the bench spectrophotometer. PMID:15223288

  6. Direct measurement of human ankle stiffness during quiet standing: the intrinsic mechanical stiffness is insufficient for stability

    PubMed Central

    Loram, Ian D; Lakie, Martin

    2002-01-01

    During quiet standing the human ‘inverted pendulum’ sways irregularly. In previous work where subjects balanced a real inverted pendulum, we investigated what contribution the intrinsic mechanical ankle stiffness makes to achieve stability. Using the results of a plausible model, we suggested that intrinsic ankle stiffness is inadequate for providing stability. Here, using a piezo-electric translator we applied small, unobtrusive mechanical perturbations to the foot while the subject was standing freely. These short duration perturbations had a similar size and velocity to movements which occur naturally during quiet standing, and they produced no evidence of any stretch reflex response in soleus, or gastrocnemius. Direct measurement confirms our earlier conclusion; intrinsic ankle stiffness is not quite sufficient to stabilise the body or pendulum. On average the directly determined intrinsic stiffness is 91 ± 23 % (mean ± s.d.) of that necessary to provide minimal stabilisation. The stiffness was substantially constant, increasing only slightly with ankle torque. This stiffness cannot be neurally regulated in quiet standing. Thus we attribute this stiffness to the foot, Achilles’ tendon and aponeurosis rather than the activated calf muscle fibres. Our measurements suggest that the triceps surae muscles maintain balance via a spring-like element which is itself too compliant to guarantee stability. The implication is that the brain cannot set ankle stiffness and then ignore the control task because additional modulation of torque is required to maintain balance. We suggest that the triceps surae muscles maintain balance by predictively controlling the proximal offset of the spring-like element in a ballistic-like manner. PMID:12482906

  7. Mapping cropland GPP in the north temperate region with space measurements of chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Guanter, L.; Zhang, Y.; Jung, M.; Joiner, J.; Voigt, M.; Huete, A. R.; Zarco-Tejada, P.; Frankenberg, C.; Lee, J.; Berry, J. A.; Moran, S. M.; Ponce-Campos, G.; Beer, C.; Camps-Valls, G.; Buchmann, N. C.; Gianelle, D.; Klumpp, K.; Cescatti, A.; Baker, J. M.; Griffis, T.

    2013-12-01

    Monitoring agricultural productivity is important for optimizing management practices in a world under a continuous increase of food and biofuel demand. We used new space measurements of sun-induced chlorophyll fluorescence (SIF), a vegetation parameter intrinsically linked to photosynthesis, to capture photosynthetic uptake of the crop belts in the north temperate region. The following data streams and procedures have been used in this analysis: (1) SIF retrievals have been derived from measurements of the MetOp-A / GOME-2 instrument in the 2007-2011 time period; (2) ensembles of process-based and data-driven biogeochemistry models have been analyzed in order to assess the capability of global models to represent crop gross primary production (GPP); (3) flux tower-based GPP estimates covering the 2007-2011 time period have been extracted over 18 cropland and grassland sites in the Midwest US and Western Europe from the Ameriflux and the European Fluxes Database networks; (4) large-scale NPP estimates have been derived by the agricultural inventory data sets developed by USDA-NASS and Monfreda et al. The strong linear correlation between the SIF space retrievals and the flux tower-based GPP, found to be significantly higher than that between reflectance-based vegetation indices (EVI, NDVI and MTCI) and GPP, has enabled the direct upscaling of SIF to cropland GPP maps at the synoptic scale. The new crop GPP estimates we derive from the scaling of SIF space retrievals are consistent with both flux tower GPP estimates and agricultural inventory data. These new GPP estimates show that crop productivity in the US Western Corn Belt, and most likely also in the rice production areas in the Indo-Gangetic plain and China, is up to 50-75% higher than estimates by state-of-the-art data-driven and process-oriented biogeochemistry models. From our analysis we conclude that current carbon models have difficulties in reproducing the special conditions of those highly productive

  8. Intrinsically safe laser-based system for continuous measurement of low-frequency vibration of mine shaft installations

    NASA Astrophysics Data System (ADS)

    Szade, Adam; Passia, Henryk; Lipowczan, Adam; Bochenek, Wojciech

    1998-06-01

    Proper condition of the mine shaft equipment is of vital importance both in view of production and safety. In some cases, this state can be adversely by the changing geological conditions in the shaft surroundings so that special precautions are necessary for reliable operation of the shaft. In the paper, an intrinsically-safe measuring system, approved for gassy mine use, based on the laser vibration sensor has been presented including its construction and operational characteristics. Examples of application have also been given related to measurements of low-frequency vibration events and of displacements both in the surface and underground parts of the shafts.

  9. Photonic reagents for concentration measurement of flu-orescent proteins with overlapping spectra.

    PubMed

    Goun, Alexei; Bondar, Denys I; Er, Ali O; Quine, Zachary; Rabitz, Herschel A

    2016-01-01

    By exploiting photonic reagents (i.e., coherent control by shaped laser pulses), we employ Optimal Dynamic Discrimination (ODD) as a novel means for quantitatively characterizing mixtures of fluorescent proteins with a large spectral overlap. To illustrate ODD, we simultaneously measured concentrations of in vitro mixtures of Enhanced Blue Fluorescent Protein (EBFP) and Enhanced Cyan Fluorescent Protein (ECFP). Building on this foundational study, the ultimate goal is to exploit the capabilities of ODD for parallel monitoring of genetic and protein circuits by suppressing the spectral cross-talk among multiple fluorescent reporters. PMID:27181496

  10. Photonic reagents for concentration measurement of flu-orescent proteins with overlapping spectra

    PubMed Central

    Goun, Alexei; Bondar, Denys I.; Er, Ali O.; Quine, Zachary; Rabitz, Herschel A.

    2016-01-01

    By exploiting photonic reagents (i.e., coherent control by shaped laser pulses), we employ Optimal Dynamic Discrimination (ODD) as a novel means for quantitatively characterizing mixtures of fluorescent proteins with a large spectral overlap. To illustrate ODD, we simultaneously measured concentrations of in vitro mixtures of Enhanced Blue Fluorescent Protein (EBFP) and Enhanced Cyan Fluorescent Protein (ECFP). Building on this foundational study, the ultimate goal is to exploit the capabilities of ODD for parallel monitoring of genetic and protein circuits by suppressing the spectral cross-talk among multiple fluorescent reporters. PMID:27181496

  11. Measurement of the fluorescence lifetime in scattering media by frequency-domain photon migration.

    PubMed

    Mayer, R H; Reynolds, J S; Sevick-Muraca, E M

    1999-08-01

    A method is presented to determine fluorescence decay lifetimes within tissuelike scattering media. Fluorescence lifetimes are determined for micromolar concentrations of the dyes 3,3'-Diethylthiatricarbocyanine Iodide and Indocyanine Green by frequency-domain investigations of light propagating in turbid media. Dual-wavelength photon-migration measurements that use intensity-modulated sources at excitation and emission wavelengths of the fluorophores provide optical parameters of the media as well as fluorescence properties of the dyes. The deduction of fluorescence lifetimes requires no calibration with reference fluorophores, and the results are shown to be independent of dye concentration. PMID:18323983

  12. Photonic reagents for concentration measurement of flu-orescent proteins with overlapping spectra

    NASA Astrophysics Data System (ADS)

    Goun, Alexei; Bondar, Denys I.; Er, Ali O.; Quine, Zachary; Rabitz, Herschel A.

    2016-05-01

    By exploiting photonic reagents (i.e., coherent control by shaped laser pulses), we employ Optimal Dynamic Discrimination (ODD) as a novel means for quantitatively characterizing mixtures of fluorescent proteins with a large spectral overlap. To illustrate ODD, we simultaneously measured concentrations of in vitro mixtures of Enhanced Blue Fluorescent Protein (EBFP) and Enhanced Cyan Fluorescent Protein (ECFP). Building on this foundational study, the ultimate goal is to exploit the capabilities of ODD for parallel monitoring of genetic and protein circuits by suppressing the spectral cross-talk among multiple fluorescent reporters.

  13. Intestine pH measurements using fluorescence imaging: an in-vivo preliminary study

    NASA Astrophysics Data System (ADS)

    Marechal, Xavier-Marie; Mordon, Serge R.; Devoisselle, Jean-Marie; Begu, Sylvie; Mathieu, D.; Buys, Bruno; Dhelin, Guy; Lesage, Jean C.; Neviere, Remi; Chopin, Claude

    1999-02-01

    Measurement of gastrointestinal intramucosal pH has been recognized as an important factor in the detection of hypoxia-induced dysfunctions. However, current pH measurement techniques are limited in terms of time and spatial resolution. A major advance in accurate pH measurement was the development of the ratiometric fluorescent indicator dye, 2',7'-bis(carboxyethyl)-4,5- carboxyfluorescein (BCECF). This study aimed to demonstrate the feasibility of fluorescence imaging technique to measure in vivo the pH of intestine. The intestine was inserted in an optical chamber placed under a microscope. Animals were injected i.v. with the pH-sensitive fluorescent dye BCECF. Fluorescence was visualized by illuminating the intestine alternately at 490 and 470 nm. The emitted fluorescence was directed to an intensified camera. The ratio of emitted fluorescence at excitation wavelengths of 490 and 470 nm was measured, corrected and converted to pH by constructing a calibration curve. The pH controls were performed with a pH microelectrode correlated with venous blood gas sampling. We concluded that accurate pH measurements of rat intestine can be obtained by fluorescence imaging using BCECF. This technology could be easily adapted for endoscopic pH measurement.

  14. Droplet temperature measurement based on 2-color laser-induced exciplex fluorescence

    NASA Astrophysics Data System (ADS)

    Zhang, Yuyin; Zhang, Gaoming; Xu, Min; Wang, Jianxin

    2013-08-01

    Measurements of liquid phase temperature distributions in liquid-vapor co-existing conditions (such as in evaporating sprays) are important to understand the physics of droplet evaporation. The techniques based on laser-induced fluorescence are not suitable for evaporating case since both liquid and vapor phases emit fluorescence with the same wavelength. In this study, the fluorescence from liquid and vapor phases was separated by use of laser-induced exciplex fluorescence (LIEF) technique. Two fluorescence bands from the liquid phase fluorescence spectra were detected simultaneously, and their intensity ratio was correlated to the liquid phase temperature. For the LIEF imaging system, FB-DEMA- n-hexane was selected as it was a typical LIEF system for the vapor concentration diagnostic, and thus easily to be extended to a simultaneous diagnostic on the vapor concentration and the droplet temperature. The fluorescence spectra were obtained in the temperature range from 303 to 423 K. The effects of liquid temperature, liquid pressure, dopant concentration and laser energy on the temperature measurement were investigated. The results show a good linear relationship between the fluorescence ratio and the temperature function. Increasing the dopant concentration can raise the signal-to-noise ratio but deteriorate temperature sensitivity. The optimal range of the dopant concentration was found between 0.1 % and 0.5 %. After calibration, the technique was applied to a monosized droplet stream, and the measurement results demonstrated excellent measurement accuracy with error below 1 % in the range of 303-423 K.

  15. Temperature dependent steady state and picosecond kinetic fluorescence measurements of a photosystem I preparation from spinach

    SciTech Connect

    Mukerji, I.; Sauer, K.

    1988-08-01

    The fluorescence properties of a photosystem I (PSI) preparation from spinach containing approximately 200 chlorophyll (Chl) per reaction center were investigated. The preparation, characterized both spectroscopically and biochemically, contained the peripheral light harvesting antenna associated with PSI. In this study steady state fluorescence measurements were performed as a function of temperature. An emission maximum at 690 nm and a long wavelength shoulder from 710 to 740 nm were observed. The fluorescence yield at 690 nm is temperature independent, while the yield of the long wavelength shoulder increases dramatically with decreasing temperature. Additionally, kinetic measurements using the technique of single photon counting were done at room temperature and 77K. At 295K a four component fit was needed to describe the fluorescence decay; whereas at 77K, an additional 40-50 ps rise component indicative of fluorescence induction was necessary. 28 refs., 13 figs., 1 tab.

  16. Red and far red Sun-induced chlorophyll fluorescence as a measure of plant photosynthesis

    NASA Astrophysics Data System (ADS)

    Rossini, M.; Nedbal, L.; Guanter, L.; Ač, A.; Alonso, L.; Burkart, A.; Cogliati, S.; Colombo, R.; Damm, A.; Drusch, M.; Hanus, J.; Janoutova, R.; Julitta, T.; Kokkalis, P.; Moreno, J.; Novotny, J.; Panigada, C.; Pinto, F.; Schickling, A.; Schüttemeyer, D.; Zemek, F.; Rascher, U.

    2015-03-01

    Remote estimation of Sun-induced chlorophyll fluorescence emitted by terrestrial vegetation can provide an unparalleled opportunity to track spatiotemporal variations of photosynthetic efficiency. Here we provide the first direct experimental evidence that the two peaks of the chlorophyll fluorescence spectrum can be accurately mapped from high-resolution radiance spectra and that the signal is linked to variations in actual photosynthetic efficiency. Red and far red fluorescence measured using a novel airborne imaging spectrometer over a grass carpet treated with an herbicide known to inhibit photosynthesis was significantly higher than the corresponding signal from an equivalent untreated grass carpet. The reflectance signal of the two grass carpets was indistinguishable, confirming that the fast dynamic changes in fluorescence emission were related to variations in the functional status of actual photosynthesis induced by herbicide application. Our results from a controlled experiment at the local scale illustrate the potential for the global mapping of terrestrial photosynthesis through space-borne measurements of chlorophyll fluorescence.

  17. Measurements of the Ultraviolet Fluorescence Cross Sections and Spectra of Bacillus Anthracis Simulants

    SciTech Connect

    Stephens, J.R.

    1998-09-01

    Measurements of the ultraviolet autofluorescence spectra and absolute cross sections of the Bacillus anthracis (Ba) simulants Bacillus globigii (Bg), Bacillus megaterium (Bm), Bacillus subtilis (Bs), and Bacillus cereus (Bc) were measured. Fluorescence spectra and cross sections of pine pollen (Pina echinata) were measured for comparison. Both dried vegetative cells and spores separated from the sporulated vegetative material were studied. The spectra were obtained by suspending a small number (<10) of particles in air in our Single Particle Spectroscopy Apparatus (SPSA), illuminating the particles with light from a spectrally filtered arc lamp, and measuring the fluorescence spectra of the particles. The illumination was 280 nm (20 nm FWHM) and the fluorescence spectra was measured between 300 and 450 nm. The fluorescence cross section of vegetative Bg peaks at 320 nm with a maximum cross section of 5 X 10{sup -14} cm{sup 2}/sr-nm-particle while the Bg spore fluorescence peaks at 310 nm with peak fluorescence of 8 X 10{sup -15} cm{sup 2}/sr-nm-particle. Pine pollen particles showed a higher fluorescence peaking at 355 nm with a cross section of 1.7 X 10{sup -13} cm{sup 2}/sr-nm-particle. Integrated cross sections ranged from 3.0 X 10{sup -13} for the Bg spores through 2.25 X 10{sup -12} (cm{sup 2}/sr-particle) for the vegetative cells.

  18. 5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence in Meningioma: Qualitative and Quantitative Measurements In Vivo

    PubMed Central

    Valdes, Pablo A.; Bekelis, Kimon; Harris, Brent T.; Wilson, Brian C.; Leblond, Frederic; Kim, Anthony; Simmons, Nathan E.; Erkmen, Kadir; Paulsen, Keith D.; Roberts, David W.

    2014-01-01

    BACKGROUND The use of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence has shown promise as a surgical adjunct for maximizing the extent of surgical resection in gliomas. To date, the clinical utility of 5-ALA in meningiomas is not fully understood, with most descriptive studies using qualitative approaches to 5-ALA-PpIX. OBJECTIVE To assess the diagnostic performance of 5-ALA-PpIX fluorescence during surgical resection of meningioma. METHODS ALA was administered to 15 patients with meningioma undergoing PpIX fluorescence-guided surgery at our institution. At various points during the procedure, the surgeon performed qualitative, visual assessments of fluorescence by using the surgical microscope, followed by a quantitative fluorescence measurement by using an intra-operative probe. Specimens were collected at each point for subsequent neuropathological analysis. Clustered data analysis of variance was used to ascertain a difference between groups, and receiver operating characteristic analyses were performed to assess diagnostic capabilities. RESULTS Red-pink fluorescence was observed in 80% (12/15) of patients, with visible fluorescence generally demonstrating a strong, homogenous character. Quantitative fluorescence measured diagnostically significant PpIX concentrations (CPpIx) in both visibly and nonvisibly fluorescent tissues, with significantly higher CPpIx in both visibly fluorescent (P < .001) and tumor tissue (P = .002). Receiver operating characteristic analyses also showed diagnostic accuracies up to 90% for differentiating tumor from normal dura. CONCLUSION ALA-induced PpIX fluorescence guidance is a potential and promising adjunct in accurately detecting neoplastic tissue during meningioma resective surgery. These results suggest a broader reach for PpIX as a biomarker for meningiomas than was previously noted in the literature. PMID:23887194

  19. Direct determination of fluorescent whitening agents by absorption measurement in situ on thin layer chromatograms.

    PubMed

    Theidel, H

    1975-01-01

    The measuring technique for the chromatogram spectrophotometer (Zeiss) to determine the reflectance curves, the analysis according to the Kubelka-Munck function, and the basic outlines of the quantitative determination of stilbene fluorescent whitening agents (FWAs) are explained. PMID:1064527

  20. A unified planar measurement technique for compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1992-01-01

    A unified laser-induced fluorescence technique for conducting planar measurements of temperature, pressure and velocity in nonreacting, highly compressible flows has been developed, validated and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled CCD camera. In the measurement technique, temperature is determined from the fluorescence induced with the laser operated broad band. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum which is measured with the laser operated narrow band. The measurement approach described herein provides a means of obtaining accurate, spatially-complete maps of the primary flow field parameters in a wide variety of cold supersonic and transonic flows.

  1. INTER-LABORATORY STUDY OF CELLULAR FLUORESCENCE INTENSITY MEASUREMENTS WITH FLUORESCEIN-LABELED MICROBEAD STANDARDS

    EPA Science Inventory

    To determine the precision of cellular fluorescence intensity (FI) measurements derived from labeled microbead standards, FI results were compared from 43 different flow cytometers in 34 laboratories. ll laboratories analyzed prepared aliquots of fluoresceinated calf thymocyte nu...

  2. Measurement of the Fluorescence Quantum Yield Using a Spectrometer With an Integrating Sphere Detector.

    PubMed

    Gaigalas, Adolfas K; Wang, Lili

    2008-01-01

    A method is proposed for measuring the fluorescence quantum yield (QY) using a commercial spectrophotometer with a 150 mm integrating sphere (IS) detector. The IS detector is equipped with an internal cuvette holder so that absorbance measurements can be performed with the cuvette inside the IS. In addition, the spectrophotometer has a cuvette holder outside the IS for performing conventional absorbance measurements. It is shown that the fluorescence quantum yield can be obtained from a combination of absorbance measurements of the buffer and the analyte solution inside and outside the IS detector. Due to the simultaneous detection of incident and fluorescent photons, the absorbance measurements inside the IS need to be adjusted for the wavelength dependence of the photomultiplier detector and the wavelength dependence of the IS magnification factor. An estimate of the fluorescence emission spectrum is needed for proper application of the wavelength-dependent adjustments. Results are presented for fluorescein, quinine sulfate, myoglobin, rhodamine B and erythrosin B. The QY of fluorescein in 0.1 mol/L NaOH was determined as 0.90±0.02 where the uncertainty is equal to the standard deviation of three independent measurements. The method provides a convenient and rapid estimate of the fluorescence quantum yield. Refinements of the measurement model and the characteristics of the IS detector can in principle yield an accurate value of the absolute fluorescence quantum yield. PMID:27096110

  3. Optical fiber sensor system for oil contamination measurement based on 3D fluorescence spectrum parameterization

    NASA Astrophysics Data System (ADS)

    Shang, Liping; Shi, Jinshan

    2000-10-01

    In recent years oil contamination in water is more serious and destroys the mode of life and relation to water body environments. Excitation fluorescence method is one of the main approaches to monitor oil contamination on line. But average intensity of oil fluorescence only indicates its density, not indicates the type of contamination oil. Two-dimensional fluorescence spectrum is more difficult to determine the kind of oil, because the different oil has fluorescence spectrum overlapping to a great extent. In this paper, the 3D fluorescence spectrum parameterization is introduced. It can extract several characteristic parameters to measure the kid of oil to be measured. A prototype of optical fiber 3D fluorescence spectrum meter we developed carries out the identification of different oil types, such as crude oil, diesel oil and kerosene. The experiment arrangement conceived to measure pulse xenon lamp induced of oil component in water. The experiment results state clearly that the 3D fluorescence spectrum parameterization and software are successful to measure oil density and identify the type of oil in situ.

  4. A double filtering method for measuring the translational velocity of fluorescently stained cells

    SciTech Connect

    Yasokawa, Toshiki; Ishimaru, Ichirou; Kuriyama, Shigeki; Masaki, Tsutomu; Takegawa, Kaoru; Tanaka, Naotaka

    2007-09-24

    The authors propose a double filtering method to measure translational velocity for tracking fluorescently stained cells. This method employs two diffraction gratings installed in the infinity space through which the parallel pencil beam of the fluorescence passes. With this method, the change in light intensity whose period is proportional to the translational velocity of the sample can be obtained at the imaging surface. By using a sample that has a random distribution of fluorescence intensity, the authors verified that translational velocity measurements could be achieved using the proposed method.

  5. On the Uncertainty in Single Molecule Fluorescent Lifetime and Energy Emission Measurements

    NASA Technical Reports Server (NTRS)

    Brown, Emery N.; Zhang, Zhenhua; McCollom, Alex D.

    1996-01-01

    Time-correlated single photon counting has recently been combined with mode-locked picosecond pulsed excitation to measure the fluorescent lifetimes and energy emissions of single molecules in a flow stream. Maximum likelihood (ML) and least squares methods agree and are optimal when the number of detected photons is large, however, in single molecule fluorescence experiments the number of detected photons can be less than 20, 67 percent of those can be noise, and the detection time is restricted to 10 nanoseconds. Under the assumption that the photon signal and background noise are two independent inhomogeneous Poisson processes, we derive the exact joint arrival time probability density of the photons collected in a single counting experiment performed in the presence of background noise. The model obviates the need to bin experimental data for analysis, and makes it possible to analyze formally the effect of background noise on the photon detection experiment using both ML or Bayesian methods. For both methods we derive the joint and marginal probability densities of the fluorescent lifetime and fluorescent emission. The ML and Bayesian methods are compared in an analysis of simulated single molecule fluorescence experiments of Rhodamine 110 using different combinations of expected background noise and expected fluorescence emission. While both the ML or Bayesian procedures perform well for analyzing fluorescence emissions, the Bayesian methods provide more realistic measures of uncertainty in the fluorescent lifetimes. The Bayesian methods would be especially useful for measuring uncertainty in fluorescent lifetime estimates in current single molecule flow stream experiments where the expected fluorescence emission is low. Both the ML and Bayesian algorithms can be automated for applications in molecular biology.

  6. On the uncertainty in single molecule fluorescent lifetime and energy emission measurements

    NASA Technical Reports Server (NTRS)

    Brown, Emery N.; Zhang, Zhenhua; Mccollom, Alex D.

    1995-01-01

    Time-correlated single photon counting has recently been combined with mode-locked picosecond pulsed excitation to measure the fluorescent lifetimes and energy emissions of single molecules in a flow stream. Maximum likelihood (ML) and least square methods agree and are optimal when the number of detected photons is large however, in single molecule fluorescence experiments the number of detected photons can be less than 20, 67% of those can be noise and the detection time is restricted to 10 nanoseconds. Under the assumption that the photon signal and background noise are two independent inhomogeneous poisson processes, we derive the exact joint arrival time probably density of the photons collected in a single counting experiment performed in the presence of background noise. The model obviates the need to bin experimental data for analysis, and makes it possible to analyze formally the effect of background noise on the photon detection experiment using both ML or Bayesian methods. For both methods we derive the joint and marginal probability densities of the fluorescent lifetime and fluorescent emission. the ML and Bayesian methods are compared in an analysis of simulated single molecule fluorescence experiments of Rhodamine 110 using different combinations of expected background nose and expected fluorescence emission. While both the ML or Bayesian procedures perform well for analyzing fluorescence emissions, the Bayesian methods provide more realistic measures of uncertainty in the fluorescent lifetimes. The Bayesian methods would be especially useful for measuring uncertainty in fluorescent lifetime estimates in current single molecule flow stream experiments where the expected fluorescence emission is low. Both the ML and Bayesian algorithms can be automated for applications in molecular biology.

  7. Measurement of intrinsic and laser heating-induced stress in microcrystalline silicon thin films

    NASA Astrophysics Data System (ADS)

    Kalampounias, A. G.; Farsari, E.; Amanatides, E.; Papatheodorou, G. N.; Mataras, D.

    2016-05-01

    In this work we employed a relatively simple experimental procedure to separate the mechanisms that contribute to the total stress of partially crystalline silicon thin films. Raman spectroscopy has been utilized to elucidate the influence of the laser irradiation (λ0 = 441.6 nm) on the μc-Si:H thin film by analyzing the observed peak shift of the Si-Si TO phonon mode in an effort to separate the different mechanisms that impose spectral changes after the applied laser treatment. When external mechanical stress is not applied, only two distinct mechanisms contribute to the frequency shift of the Raman band, namely the heating-induced stress and the internal stress due to the deposition conditions. The use of the appropriate fitting procedure of the experimental spectrum allows the estimation of the observed frequency shift, which is attributed to both local heating due to the laser irradiation and the intrinsic tensile stress of the μc-Si:H films. In the limit where the laser is highly attenuated, the induced heating is negligible and we are able to isolate and evaluate tensile stress directly from the spectroscopic data in the context of current theoretical models. Beyond this limit, the values of internal and total stress have been used to calculate the laser-induced stress. Crystallinity seems to be the key factor to control the volume change induced by the displacement of the surrounding atoms, which is spread over medium in long-range order.

  8. A research on measuring and analyzing the optical properties of fluorescent whitening agent in soybean milk

    NASA Astrophysics Data System (ADS)

    Zhu, Xingyue; Zhao, Zhimin; Zhang, Lin; Qian, Kun; Wang, Lexin; Lan, Xiufeng

    2015-03-01

    A research on measuring and analyzing the fluorescence spectra of fluorescent whitening agent in soybean milk was explained in this paper. At the temperature of 30 °C, linear relationship was found good between fluorescence intensity and concentration of fluorescent whitening agent in the range of 0.015-0.25 mg/mL when the emission wavelength was 437 nm and excitation wavelength was 347 nm. Modeling analysis showed that the correlation coefficient was 0.996, the relative standard deviation (RSD) ranged from 0.45% to 0.73% and the recovery of standard addition ranged from 96.80% to 102.67%, which testified the validity of the method. This research provided a new way for detecting the unedible fluorescent whitening agent content in food production.

  9. Detecting and Quantifying Biomolecular Interactions of a Dendritic Polyglycerol Sulfate Nanoparticle Using Fluorescence Lifetime Measurements.

    PubMed

    Boreham, Alexander; Pikkemaat, Jens; Volz, Pierre; Brodwolf, Robert; Kuehne, Christian; Licha, Kai; Haag, Rainer; Dernedde, Jens; Alexiev, Ulrike

    2015-01-01

    Interactions of nanoparticles with biomaterials determine the biological activity that is key for the physiological response. Dendritic polyglycerol sulfates (dPGS) were found recently to act as an inhibitor of inflammation by blocking selectins. Systemic application of dPGS would present this nanoparticle to various biological molecules that rapidly adsorb to the nanoparticle surface or lead to adsorption of the nanoparticle to cellular structures such as lipid membranes. In the past, fluorescence lifetime measurements of fluorescently tagged nanoparticles at a molecular and cellular/tissue level have been proven to reveal valuable information on the local nanoparticle environment via characteristic fluorescent lifetime signatures of the nanoparticle bound dye. Here, we established fluorescence lifetime measurements as a tool to determine the binding affinity to fluorescently tagged dPGS (dPGS-ICC; ICC: indocarbocyanine). The binding to a cell adhesion molecule (L-selectin) and a human complement protein (C1q) to dPGS-ICC was evaluated by the concentration dependent change in the unique fluorescence lifetime signature of dPGS-ICC. The apparent binding affinity was found to be in the nanomolar range for both proteins (L-selectin: 87 ± 4 nM and C1q: 42 ± 12 nM). Furthermore, the effect of human serum on the unique fluorescence lifetime signature of dPGS-ICC was measured and found to be different from the interactions with the two proteins and lipid membranes. A comparison between the unique lifetime signatures of dPGS-ICC in different biological environments shows that fluorescence lifetime measurements of unique dPGS-ICC fluorescence lifetime signatures are a versatile tool to probe the microenvironment of dPGS in cells and tissue. PMID:26712722

  10. A novel pretreatment method of three-dimensional fluorescence data for quantitative measurement of component contents in mixture.

    PubMed

    Xu, Jing; Wang, Yu-Tian; Liu, Xiao-Fei

    2015-04-01

    Three-dimensional fluorescence technique is commonly used for the determination of component contents in the mixture. Fluorescence intensity data are used directly in the fluorescent spectrum data processing method. The relationship between fluorescence intensity values and concentrations is linear. Random noise is inevitable in the process of measuring due to fluorescence spectrometer. The measurement accuracy is reduced due to the existence of noise. To reduce random noise and improve the measurement sensitivity, a novel pretreatment method of three-dimensional fluorescence data is proposed. The method is based on Quasi-Monte-Carlo integral. Due to the increased slope of fluorescence intensity data during the integral, the measurement sensitivity is improved. At the same time, the sum of different exponentials of fluorescence intensity at the points reduces the random noise, so the measurement sensitivity is improved more. The recovery rates of the mixture mixed by gasoline, kerosene and diesel oil are calculated to validate the effectiveness of the method. PMID:25638431

  11. Accurate modeling of fluorescence line narrowing difference spectra: Direct measurement of the single-site fluorescence spectrum

    NASA Astrophysics Data System (ADS)

    Reppert, Mike; Naibo, Virginia; Jankowiak, Ryszard

    2010-07-01

    Accurate lineshape functions for modeling fluorescence line narrowing (FLN) difference spectra (ΔFLN spectra) in the low-fluence limit are derived and examined in terms of the physical interpretation of various contributions, including photoproduct absorption and emission. While in agreement with the earlier results of Jaaniso [Proc. Est. Acad. Sci., Phys., Math. 34, 277 (1985)] and Fünfschilling et al. [J. Lumin. 36, 85 (1986)], the derived formulas differ substantially from functions used recently [e.g., M. Rätsep et al., Chem. Phys. Lett. 479, 140 (2009)] to model ΔFLN spectra. In contrast to traditional FLN spectra, it is demonstrated that for most physically reasonable parameters, the ΔFLN spectrum reduces simply to the single-site fluorescence lineshape function. These results imply that direct measurement of a bulk-averaged single-site fluorescence lineshape function can be accomplished with no complicated extraction process or knowledge of any additional parameters such as site distribution function shape and width. We argue that previous analysis of ΔFLN spectra obtained for many photosynthetic complexes led to strong artificial lowering of apparent electron-phonon coupling strength, especially on the high-energy side of the pigment site distribution function.

  12. Measurements of Intrinsic Ion Bernstein Waves in a Tokamak by Collective Thomson Scattering

    NASA Astrophysics Data System (ADS)

    Korsholm, S. B.; Stejner, M.; Bindslev, H.; Furtula, V.; Leipold, F.; Meo, F.; Michelsen, P. K.; Moseev, D.; Nielsen, S. K.; Salewski, M.; de Baar, M.; Delabie, E.; Kantor, M.; Bürger, A.

    2011-04-01

    In this Letter we report measurements of collective Thomson scattering (CTS) spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas. The measured spectra are in accordance with theoretical predictions and show clear sensitivity to variation in the density ratio of the main ion species in the plasma. Measurements with this novel diagnostic demonstrate that CTS can be used as a fuel ion ratio diagnostic in burning fusion plasma devices.

  13. Intrinsic nonlinearity probed by intermodulation distortion microwave measurements on high quality MgB2 thin films

    NASA Astrophysics Data System (ADS)

    Cifariello, G.; Aurino, M.; Di Gennaro, E.; Lamura, G.; Andreone, A.; Orgiani, P.; Xi, X. X.; Villégier, J.-C.

    2006-04-01

    The two-tone intermodulation distortion arising in MgB2 thin films synthesized by hybrid physical-chemical vapor deposition is studied in order to probe the influence of the two bands on the nonlinear response of this superconductor. The measurements are carried out by using a dielectrically loaded copper cavity operating at 7GHz. Microwave data on samples having critical temperatures above 41K, very low resistivity values, and residual resistivity ratio larger than 10 are shown. The dependence of the nonlinear surface losses and of the third order intermodulation products on the power feeding the cavity and on the temperature is analyzed. At low power, the signal arising from distortion versus temperature shows the intrinsic s-wave behavior expected for this compound. Data are compared with measurements performed on Nb and YBa2Cu3O7-δ thin films using the same technique.

  14. DAPI-fluorescent fading: a problem in microscopy or a way to measure nuclear DNA content?

    NASA Astrophysics Data System (ADS)

    Gallardo-Escárate, Cristian; Álvarez-Borrego, Josué; Kober, V.; del Río-Portilla, Miguel Á.

    2006-01-01

    In observation by confocal or conventional fluorescence microscopy, the retardation of the lost in fluorescence, from highest signal of fluorescence to lowest intensity are important factors in order to obtain accurate images. This problem is very common in fluorochromes for nuclear DNA and especially for DAPI stain. The fluorescence of DAPI is rapidly lost when it is exposure to excitation by ultra violet (UV) light, and especially under optimal condition of observation. Although the fading process could be retardate by using of mounting medium with antifading solutions, the photochemical process underlying the fluorescence decay has not yet been fully explained. In addiction, neither relationship has been tested between the fluorescence fading and nuclear DNA content. However, the capacity of the DNA to absorb UV light is knows. In order to test this relationship we measured by means of image analysis the fluorescence intensity in several nuclei types during a fading period. The analysis was performed by an algorithm specifically built in MATLAB software. The relationship between nuclear DNA content and DAPI-fluorescence fading was found equal to 99%. This study demonstrates the feasibility for estimates genome size by quantification of fluorescence fading. In this context, the present method allows to measure nuclear DNA content in several medical applications (cancer, HIV, organ transplants, etc). Nowadays, for measuring DNA content, flow cytometry is widely used; however, with the flow cytometry method it is not possible to select a specific group of cells, such as from a specific region of a tumor. Moreover, the using of image analysis allows automatizing diagnostics procedures.

  15. Standard reference for instrument response function in fluorescence lifetime measurements in visible and near infrared

    NASA Astrophysics Data System (ADS)

    Chib, Rahul; Shah, Sunil; Gryczynski, Zygmunt; Fudala, Rafal; Borejdo, Julian; Zelent, Bogumil; Corradini, Maria G.; Ludescher, Richard D.; Gryczynski, Ignacy

    2016-02-01

    Allura red (AR) fluorophore, a common dye in the food industry, displays a broad emission spectrum in water (visible-to-near infrared region of the electromagnetic spectrum) and has a remarkably short fluorescence lifetime of about 10 ps. This short lifetime does not depend on the emission (observation) wavelength. We examined time responses of AR fluorescence across emission wavelengths from 550 nm to 750 nm and found that it is an ideal candidate for impulse response functions in fluorescence lifetime measurements.

  16. Measurement of intrinsic radioactive backgrounds from the 137Cs and U/Th chains in CsI(Tl) crystals

    NASA Astrophysics Data System (ADS)

    Liu, Shu-Kui; Yue, Qian; Lin, Shin-Ted; Li, Yuan-Jing; Tang, Chang-Jian; Wong Tsz-King, Henry; Xing, Hao-Yang; Yang, Chao-Wen; Zhao, Wei; Zhu, Jing-Jun

    2015-04-01

    The inorganic CsI(Tl) crystal scintillator is a candidate anti-compton detector for the China Dark matter Experiment. Studying the intrinsic radiopurity of the CsI(Tl) crystal is an issue of major importance. The timing, energy and spatial correlations, as well as the capability of pulse shape discrimination provide powerful methods for the measurement of intrinsic radiopurities. The experimental design, detector performance and event-selection algorithms are described. A total of 359×3 kg-days data from three prototypes of CsI(Tl) crystals were taken at China Jinping Underground Laboratory (CJPL), which offers a good shielding environment. The contamination levels of internal isotopes from 137Cs, 232Th and 238U series, as well as the upper bounds of 235U series are reported. Identification of the whole α peaks from U/Th decay chains and derivation of those corresponding quenching factors are achieved. Supported by National Natural Science Foundation of China (11275107, 11175099)

  17. Precise measurement of the absolute fluorescence yield of the 337 nm band in atmospheric gases

    NASA Astrophysics Data System (ADS)

    Ave, M.; Bohacova, M.; Curry, E.; Di Carlo, P.; Di Giulio, C.; Facal San Luis, P.; Gonzales, D.; Hojvat, C.; Hörandel, J.; Hrabovsky, M.; Iarlori, M.; Keilhauer, B.; Klages, H.; Kleifges, M.; Kuehn, F.; Li, S.; Monasor, M.; Nozka, L.; Palatka, M.; Petrera, S.; Privitera, P.; Ridky, J.; Rizi, V.; Rouille D'Orfeuil, B.; Salamida, F.; Schovanek, P.; Smida, R.; Spinka, H.; Ulrich, A.; Verzi, V.; Williams, C.

    2013-02-01

    A measurement of the absolute fluorescence yield of the 337 nm nitrogen band, relevant to ultra-high energy cosmic ray (UHECR) detectors, is reported. Two independent calibrations of the fluorescence emission induced by a 120 GeV proton beam were employed: Cherenkov light from the beam particle and calibrated light from a nitrogen laser. The fluorescence yield in air at a pressure of 1013 hPa and temperature of 293 K was found to be Y337=5.61±0.06stat±0.22syst photons/MeV. When compared to the fluorescence yield currently used by UHECR experiments, this measurement improves the uncertainty by a factor of three, and has a significant impact on the determination of the energy scale of the cosmic ray spectrum.

  18. Ultrafast solvent dynamics: Connection between time resolved fluorescence and optical Kerr measurements

    NASA Astrophysics Data System (ADS)

    Cho, Minhaeng; Rosenthal, Sandra J.; Scherer, Norbert F.; Ziegler, Lawrence D.; Fleming, Graham R.

    1992-04-01

    The vibrational characteristics of liquid dynamics are used to describe the ultrafast relaxations observed in time-dependent fluorescence Stokes shift [J. Chem. Phys. 95, 4715 (1991)] and heterodyne detected optical Kerr effect measurements on acetonitrile, via a Brownian oscillator model. Introducing a frequency distribution of vibrational modes makes it possible to compare the two experiments. The ultrafast decays observed in the fluorescence Stokes shift and optical Kerr signals are produced by destructive superposition of the high frequency, underdamped modes.

  19. Simultaneous measurement of Raman scattering and laser-induced OH fluorescence in nonpremixed turbulent jet flames.

    PubMed

    Barlow, R S; Dibble, R W; Lucht, R P

    1989-03-01

    Spontaneous Raman scattering and laser-induced fluorescence are combined to perform simultaneous point measurements of major species concentrations, temperature, and hydroxyl radical concentration in turbulent nonpremixed flames. The Raman-scattering data for major species concentrations and temperature characterize the instantaneous, local, collisional quenching environment of the OH molecule. Collisional quenching corrections are applied for each laser shot so that absolute hydroxyl concentrations are obtained in turbulent flames using linear laser-induced fluorescence. PMID:19749889

  20. On-line measurement of lignin in wood pulp by color shift of fluorescence

    DOEpatents

    Jeffers, Larry A.; Malito, Michael L.

    1996-01-01

    Lignin concentrations from wood pulp samples are measured by applying an excitation light at a selected wavelength to the samples in order to cause the lignin to emit fluorescence. A spectral distribution of the fluorescence emission is then determined. The lignin concentration is then calculated based on the spectral distribution signal. The spectral distribution is quantified by either a wavelength centroid method or a band ratio method.

  1. On-line measurement of lignin in wood pulp by color shift of fluorescence

    DOEpatents

    Jeffers, L.A.; Malito, M.L.

    1996-01-23

    Lignin concentrations from wood pulp samples are measured by applying an excitation light at a selected wavelength to the samples in order to cause the lignin to emit fluorescence. A spectral distribution of the fluorescence emission is then determined. The lignin concentration is then calculated based on the spectral distribution signal. The spectral distribution is quantified by either a wavelength centroid method or a band ratio method. 6 figs.

  2. Quenching-independent measurement of species concentrations in flames by laser-induced fluorescence

    SciTech Connect

    Salmon, J.T.; Carter, C.D.; Laurendeau, N.M.

    1990-09-01

    This report describes work accomplished in the last two years on measurement of species concentrations in flames via laser-induced fluorescence. During this period, we have published absolute number densities of atomic hydrogen in subatmospheric, premixed C{sub 2}H{sub 4}/O{sub 2}/Ar flames at equivalence ratios of 1.0 and 1.7 via two-photon excited fluorescence. This work has led to the development of a new single-laser, two-step fluorescence method for the detection of atomic hydrogen in flames. Using photoionization controlled-loss spectroscopy (PICLS), we have verified the T{sup {minus}1/2} dependence of quenching on temperature for atomic hydrogen, in agreement with kinetic theory. Previous work on pyrometry using laser-saturated fluorescence (LSF) and the anomalous fluorescence from pyrene has evolved into publication of a major review paper on temperature measurements by light-scattering methods. Finally, we have demonstrated the feasibility of quantitative LSF measurements of NO concentration by obtaining relative saturation curves and NO fluorescence profiles. 25 refs.

  3. Spectrally resolved fluorescence lifetime imaging of Nile red for measurements of intracellular polarity

    NASA Astrophysics Data System (ADS)

    Levitt, James A.; Chung, Pei-Hua; Suhling, Klaus

    2015-09-01

    Spectrally resolved confocal microscopy and fluorescence lifetime imaging have been used to measure the polarity of lipid-rich regions in living HeLa cells stained with Nile red. The emission peak from the solvatochromic dye in lipid droplets is at a shorter wavelength than other, more polar, stained internal membranes, and this is indicative of a low polarity environment. We estimate that the dielectric constant, ɛ, is around 5 in lipid droplets and 25<ɛ<40 in other lipid-rich regions. Our spectrally resolved fluorescence lifetime imaging microscopy (FLIM) data show that intracellular Nile red exhibits complex, multiexponential fluorescence decays due to emission from a short lifetime locally excited state and a longer lifetime intramolecular charge transfer state. We measure an increase in the average fluorescence lifetime of the dye with increasing emission wavelength, as shown using phasor plots of the FLIM data. We also show using these phasor plots that the shortest lifetime decay components arise from lipid droplets. Thus, fluorescence lifetime is a viable contrast parameter for distinguishing lipid droplets from other stained lipid-rich regions. Finally, we discuss the FLIM of Nile red as a method for simultaneously mapping both polarity and relative viscosity based on fluorescence lifetime measurements.

  4. Laser Induced Fluorescence For Measurement Of Lignin Concentrations In Pulping Liquors

    NASA Astrophysics Data System (ADS)

    Horvath, J. J.; Semerjian, H. G.; Biasca, K. L.; Attala, R.

    1988-11-01

    Laser excited fluorescence of pulping liquors was investigated for use in the pulp and paper industry for process measurement and control applications. Liquors from both mill and laboratory cooks were studied. A Nd-YAG pumped dye laser was used to generate the excitation wavelength of 280 nm; measurements were also performed using a commercially available fluorometer. Measurements on mill pulping liquors gave strong signals and showed changes in the fluorescence intensity during the cook. Absorption spectra of diluted mill liquor samples showed large changes during the cook. Samples from well controlled and characterized laboratory cooks showed fluorescence to be linear with concentration over two decades with an upper limit of approximately 1000 ppm dissolved lignin. At the end of these cooks a possible chemical change was indicated by an increase in the observed fluorescence intensity. Results indicate that lignin concentrations in pulping liquors can be accurately determined with fluorescence in the linear optical region over a greater dynamic range than absorption spectroscopy. Laser induced fluorescence may also provide an indication of chemical changes occurring in the lignin structure during a cook.

  5. DEVELOPMENT OF EVALUATION OF A QUANTITATIVE VIDEO-FLUORESCENCE IMAGING SYSTEM AND FLUORESCENT TRACER FOR MEASURING TRANSFER OF PESTICIDE RESIDUES FROM SURFACES TO HANDS WITH REPEATED CONTACTS

    EPA Science Inventory

    A video imaging system and the associated quantification methods have been developed for measurement of the transfers of a fluorescent tracer from surfaces to hands. The highly fluorescent compound riboflavin (Vitamin B2), which is also water soluble and non-toxic, was chosen as...

  6. Validation of fluorescent-labeled microspheres for measurement of relative blood flow in severely injured lungs

    NASA Technical Reports Server (NTRS)

    Hubler, M.; Souders, J. E.; Shade, E. D.; Hlastala, M. P.; Polissar, N. L.; Glenny, R. W.

    1999-01-01

    The aim of the study was to validate a nonradioactive method for relative blood flow measurements in severely injured lungs that avoids labor-intensive tissue processing. The use of fluorescent-labeled microspheres was compared with the standard radiolabeled-microsphere method. In seven sheep, lung injury was established by using oleic acid. Five pairs of radio- and fluorescent-labeled microspheres were injected before and after established lung injury. Across all animals, 175 pieces were selected randomly. The radioactivity of each piece was determined by using a scintillation counter. The fluorescent dye was extracted from each piece with a solvent without digestion or filtering. The fluorescence was determined with an automated fluorescent spectrophotometer. Perfusion was calculated for each piece from both the radioactivity and fluorescence and volume normalized. Correlations between flow determined by the two methods were in the range from 0.987 +/- 0.007 (SD) to 0.991 +/- 0.002 (SD) after 9 days of soaking. Thus the fluorescent microsphere technique is a valuable tool for investigating regional perfusion in severely injured lungs and can replace radioactivity.

  7. Measuring diffusion coefficients via two-photon fluorescence recovery after photobleaching.

    PubMed

    Sullivan, Kelley D; Brown, Edward B

    2010-01-01

    Multi-fluorescence recovery after photobleaching is a microscopy technique used to measure the diffusion coefficient (or analogous transport parameters) of macromolecules, and can be applied to both in vitro and in vivo biological systems. Multi-fluorescence recovery after photobleaching is performed by photobleaching a region of interest within a fluorescent sample using an intense laser flash, then attenuating the beam and monitoring the fluorescence as still-fluorescent molecules from outside the region of interest diffuse in to replace the photobleached molecules. We will begin our demonstration by aligning the laser beam through the Pockels Cell (laser modulator) and along the optical path through the laser scan box and objective lens to the sample. For simplicity, we will use a sample of aqueous fluorescent dye. We will then determine the proper experimental parameters for our sample including, monitor and bleaching powers, bleach duration, bin widths (for photon counting), and fluorescence recovery time. Next, we will describe the procedure for taking recovery curves, a process that can be largely automated via LabVIEW (National Instruments, Austin, TX) for enhanced throughput. Finally, the diffusion coefficient is determined by fitting the recovery data to the appropriate mathematical model using a least-squares fitting algorithm, readily programmable using software such as MATLAB (The Mathworks, Natick, MA). PMID:20190730

  8. The Academic Motivation Scale: A Measure of Intrinsic, Extrinsic, and Amotivation in Education.

    ERIC Educational Resources Information Center

    Vallerand, Robert J.; And Others

    1992-01-01

    A French measure of motivation toward education was cross-culturally validated in English with 745 Canadian university students. Results demonstrate satisfactory internal consistency and temporal stability for the English version, the Academic Motivation Scale (AMS). A LISREL confirmatory factor analysis confirms the seven-factor structure of the…

  9. Leaf vein length per unit area is not intrinsically dependent on image magnification: avoiding measurement artifacts for accuracy and precision.

    PubMed

    Sack, Lawren; Caringella, Marissa; Scoffoni, Christine; Mason, Chase; Rawls, Michael; Markesteijn, Lars; Poorter, Lourens

    2014-10-01

    Leaf vein length per unit leaf area (VLA; also known as vein density) is an important determinant of water and sugar transport, photosynthetic function, and biomechanical support. A range of software methods are in use to visualize and measure vein systems in cleared leaf images; typically, users locate veins by digital tracing, but recent articles introduced software by which users can locate veins using thresholding (i.e. based on the contrasting of veins in the image). Based on the use of this method, a recent study argued against the existence of a fixed VLA value for a given leaf, proposing instead that VLA increases with the magnification of the image due to intrinsic properties of the vein system, and recommended that future measurements use a common, low image magnification for measurements. We tested these claims with new measurements using the software LEAFGUI in comparison with digital tracing using ImageJ software. We found that the apparent increase of VLA with magnification was an artifact of (1) using low-quality and low-magnification images and (2) errors in the algorithms of LEAFGUI. Given the use of images of sufficient magnification and quality, and analysis with error-free software, the VLA can be measured precisely and accurately. These findings point to important principles for improving the quantity and quality of important information gathered from leaf vein systems. PMID:25096977

  10. Measurement of the intrinsic variability within protein crystals: implications for sample-evaluation and data-collection strategies

    PubMed Central

    Bowler, Michael G.; Bowler, Matthew W.

    2014-01-01

    The advent of micro-focused X-ray beams has led to the development of a number of advanced methods of sample evaluation and data collection. In particular, multiple-position data-collection and helical oscillation strategies are now becoming commonplace in order to alleviate the problems associated with radiation damage. However, intra-crystal and inter-crystal variation means that it is not always obvious on which crystals or on which region or regions of a crystal these protocols should be performed. For the automation of this process for large-scale screening, and to provide an indication of the best strategy for data collection, a metric of crystal variability could be useful. Here, measures of the intrinsic variability within protein crystals are presented and their implications for optimal data-collection strategies are discussed. PMID:24419635