These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

X-Ray Absorption Spectroscopic Characterization of the Molybdenum Site of 'Escherichia Coli' Dimethyl Sulfoxide Reductase  

SciTech Connect

Structural studies of dimethyl sulfoxide (DMSO) reductases were hampered by modification of the active site during purification. We report an X-ray absorption spectroscopic analysis of the molybdenum active site of Escherichia coli DMSO reductase contained within its native membranes. The enzyme in these preparations is expected to be very close to the form found in vivo. The oxidized active site was found to have four Mo-S ligands at 2.43 angstroms, one Mo=O at 1.71 angstroms, and a longer Mo-O at 1.90 angstroms. We conclude that the oxidized enzyme is a monooxomolybdenum(VI) species coordinated by two molybdopterin dithiolenes and a serine. The bond lengths determined for E. coli DMSO reductase are very similar to those determined for the well-characterized Rhodobacter sphaeroides DMSO reductase, suggesting similar active site structures for the two enzymes. Furthermore, our results suggest that the form found in vivo is the monooxobis(molybdopterin) species.

George, G.N.; Doonan, C.J.; Rothery, R.A.; Boroumand, N.; Weiner, J.H.; /Saskatchewan U. /Alberta U.

2007-07-09

2

Spectroscopic characterization of Nd:Y2O3: application toward a differential absorption lidar system for remote sensing of ozone  

NASA Astrophysics Data System (ADS)

Neodymium-doped yttria (Nd:Y2O3) is investigated as a solid-state laser material for frequency-tripled generation of ultraviolet laser wavelengths for use in remote sensing of ozone. Emphasis is placed both on the spectroscopy of the fundamental wavelengths at ~0.914 ?m and ~0.946 ?m to assess their feasibility for laser oscillation and on the absorption spectroscopy in the 0.8-?m wavelength region for determination of suitable pump sources. The temperature dependence of the emission and absorption characteristics of Nd:Y2O3 are examined, since aggressive cooling may be required for efficient ~0.914-?m lasing due to its quasi four-level nature. Data for flash-lamp-pumped laser performance on the 4F3/2-->4I11/2 is presented for Nd:Y2O3 and compared with Nd:YAG. Diode-pumped threshold-fluence and threshold-pump energy estimates for Nd:Y2O3 lasing on the 4F3/2-->4I9/2 at 0.914 ?m and 0.946 ?m are calculated based on the data presented here. The measurements presented here for the Nd:Y2O3 indicate favorable absorption and emission properties. Favorable absorption properties in the ~0.8-?m pump wavelength are compatible with a variety of potential pump sources. Favorable emission properties at reduced temperatures near 150 K indicate that Nd:Y2O3 operating at 0.914 ?m and 0.946 ?m will have normal-mode laser thresholds similar to that of room-temperature Nd:YAG operating at 0.946 ?m. In Q-switched operation, however, Nd:Y2O3 is predicted to exceed the performance of Nd:YAG due to the lower 1.06/0.94 cross-section ratio, which helps to limit amplified spontaneous-emission effects. Although Nd:Y2O3 is not a new material, it has not been the topic of study due to growth problems associated with its high melting point. New advances in growth techniques and the favorable spectroscopic features of Nd:Y2O3 have inspired a new examination of this material.

Walsh, Brian M.; McMahon, John M.; Edwards, William C.; Barnes, Norman P.; Equall, Randy W.; Hutcheson, Ralph L.

2002-12-01

3

Ultraviolet-Absorption Spectroscopic Biofilm Monitor  

NASA Technical Reports Server (NTRS)

An ultraviolet-absorption spectrometer system has been developed as a prototype instrument to be used in continuous, real-time monitoring to detect the growth of biofilms. Such monitoring is desirable because biofilms are often harmful. For example, biofilms in potable-water and hydroponic systems act as both sources of pathogenic bacteria that resist biocides and as a mechanism for deterioration (including corrosion) of pipes. Biofilms formed from several types of hazardous bacteria can thrive in both plant-growth solutions and low-nutrient media like distilled water. Biofilms can also form in condensate tanks in air-conditioning systems and in industrial heat exchangers. At present, bacteria in potable-water and plant-growth systems aboard the space shuttle (and previously on the Mir space station) are monitored by culture-plate counting, which entails an incubation period of 24 to 48 hours for each sample. At present, there are no commercially available instruments for continuous monitoring of biofilms in terrestrial or spaceborne settings.

Micheels, Ronald H.

2004-01-01

4

Infrared spectroscopic characterization of mineralized tissues  

PubMed Central

Vibrational spectroscopy (Infrared and Raman), and in particular micro-spectroscopy and micro-spectroscopic imaging has been used to characterize developmental changes in bone and other mineralized tissues, to monitor these changes in cell cultures, and to detect disease and drug-induced modifications. Examples of the use of infrared micro-spectroscopy and micro-spectroscopic imaging are discussed in this review. PMID:16691288

Boskey, Adele L.; Mendelsohn, Richard

2006-01-01

5

PRECISION RADIAL VELOCITIES OF DOUBLE-LINED SPECTROSCOPIC BINARIES WITH AN IODINE ABSORPTION CELL  

E-print Network

PRECISION RADIAL VELOCITIES OF DOUBLE-LINED SPECTROSCOPIC BINARIES WITH AN IODINE ABSORPTION CELL October 15; accepted 2005 February 25 ABSTRACT A spectroscopic technique employing an iodine absorption the absorption cell technique to a new level by introducing an iodine (I2) absorption cell with the modeling

6

Characterization of the physico-chemical properties of polymeric materials for aerospace flight. [differential thermal and atomic absorption spectroscopic analysis of nickel cadmium batteries  

NASA Technical Reports Server (NTRS)

Electrodes and electrolytes of nickel cadmium sealed batteries were analyzed. Different thermal analysis of negative and positive battery electrodes was conducted and the temperature ranges of occurrence of endotherms indicating decomposition of cadmium hydroxide and nickel hydroxide are identified. Atomic absorption spectroscopy was used to analyze electrodes and electrolytes for traces of nickel, cadmium, cobalt, and potassium. Calibration curves and data are given for each sample analyzed. Instrumentation and analytical procedures used for each method are described.

Rock, M.

1981-01-01

7

Spectroscopic characterization of C7H3(+) and C7H3?: electronic absorption and fluorescence in 6 K neon matrices.  

PubMed

Mass selective deposition of C7H3(+) (m/z = 87) into solid neon reveals the 1(1)A1?X(1)A1 electronic absorption system of hepta-1,2,3,4,5,6-heptahexaenylium cation B(+) [H2CCCCCCCH](+) with an origin band at 441.3 nm, 1(1)A'?X(1)A' transition of 2,4-pentadiynylium,1-ethynyl cation C(+) [HCCCHCCCCH](+) starting at 414.6 nm and the 1(1)A1?X(1)A1 one of cyclopropenylium,1,3-butadiynyl cation A(+) [HCCCCC<(CH=CH)](+) with an onset at 322.2 nm. Vibrationally resolved fluorescence was observed for isomer B(+) upon laser excitation of the absorption bands in the 1(1)A1?X(1)A1 transition. After neutralization of the cations in the matrix five absorption systems of the C7H3 neutral radicals starting at 530.3, 479.4, 482.3, 325.0 and 302.5 nm were detected. These were identified as the 1(2)A'?X(2)A' and 2(2)A'?X(2)A' electronic transitions of 2-(buta-1,3-diynyl)cycloprop-2yl-1-1ylidene E? [HCCCCC<(C=CH2)]?, 1(2)B1?X(2)B1 of 1,2,3,4,5,6-heptahexaenyl B? [H2CCCCCCCH]?, 3(2)B1?X(2)B1 of 3-buta-1,3-diynyl-cyclopropenyl A? [HCCCCC<(CH=CH)]? and 2(2)B1?X(2)A2 transition of 1,2-divinylidene-cyclopropanyl radical F? [HCC-cyc-(CCHC)-CCH]?, respectively. The assignment is based on calculated vertical excitation energies using the CASPT2 method. Comparison of the calculated harmonic vibrational frequencies with those inferred from the spectra supports the assignment. PMID:24603977

Chakraborty, Arghya; Fulara, Jan; Dietsche, Rainer; Maier, John P

2014-04-21

8

Spectroscopic characterization of manganese minerals.  

PubMed

Manganese minerals ardenite, alleghanyite and leucopoenicite originated from Madhya Pradesh, India, Nagano prefecture Japan, Sussex Country and Parker Shaft Franklin, Sussex Country, New Jersey respectively are used in the present work. In these minerals manganese is the major constituent and iron if present is in traces only. An EPR study of on all of the above samples confirms the presence of Mn(II) with g around 2.0. Optical absorption spectrum of the mineral alleghanyite indicates that Mn(II) is present in two different octahedral sites and in leucophoenicite Mn(II) is also in octahedral geometry. Ardenite mineral gives only a few Mn(II) bands. NIR results of the minerals ardenite, leucophoenicite and alleghanyite are due to hydroxyl and silicate anions which confirming the formulae of the minerals. PMID:23995604

Lakshmi Reddy, S; Padma Suvarna, K; Udayabhaska Reddy, G; Endo, Tamio; Frost, R L

2014-01-01

9

Tunable fiber ring laser absorption spectroscopic sensors for gas detection  

NASA Astrophysics Data System (ADS)

Fiber-optic gas sensing techniques are commonly based on the recognition of a wide range of chemical species from characteristic absorption, fluorescence or Raman-scattering spectra signatures. By tuning over the vibrational lines of species in the path of laser beam, tunable diode laser gas sensors measure signal spectroscopic intensity, gas concentration, and other properties. However, they have limitations of bulk architecture, small change of signal on top of large background, and low sensitivity of direct absorption. Here we report the fabrication and optical measurements of tunable Er-doped fiber ring laser absorption spectroscopic sensor featuring a gas cell that is a segment of photonic crystal fiber (PCF) with a long-period grating (LPG) inscribed. The tunable laser beam is coupled into the cladding of the PCF by the LPG where the gas in air holes absorbs light. The light travels along the PCF cladding and reflects at the end of the fiber where a silver film is coated as a mirror at one end facet. The light propagates back within cladding and passes through the gas one more time thus increasing the interaction length. This light is finally recoupled into the fiber core for intensity measurement. The proposed fiber gas sensors have been experimentally used for ammonia (NH3) concentration detection. They show excellent sensitivity and selectivity, and are minimally affected by temperature and/or humidity changes. The sensors using PCF-LPG gas cell are simple to fabricate, cost-effective, and are deployed for a variety of applications not possible using conventional optical fibers.

Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

2013-04-01

10

Spectroscopic characterization of a titan plasma produced by a continuous-high-power CO2 laser  

Microsoft Academic Search

It is well known, metallic plasmas created during welding with high power lasers are very important for the welding process. During recent years, we have been trying to characterize these kinds of plasmas, in order to get a better comprehension of the absorption of laser light by a steel target during welding with a CO2 laser. A complete spectroscopic characterization

Angel M. de Frutos Baraja; Anne Poueyo-Verwaerde; G. Deshors; Remy Fabbro; Jose M. Orza

1993-01-01

11

Intrinsic Absorption Properties in Active Galaxies Observed with the Far Ultraviolet Spectroscopic Explorer  

E-print Network

In a continuing survey of active galactic nuclei observed by the Far Ultraviolet Spectroscopic Explorer, we provide a deeper analysis of intrinsic absorption features found in 35 objects. Our survey is for low-redshift and moderate-luminosity objects, mostly Seyfert galaxies. We find a strong correlation between maximum radial velocity and luminosity. We also examine the relationships between equivalent width (EW), full width at half maximum, velocity: and continuum flux. The correlation between velocity and luminosity has been explored previously by Laor & Brandt, but at a significantly higher redshift and heavily weighted by broad absorption line quasars. We also have examined each object with multiple observations for variability in each of the aforementioned quantities, and have characterized the variation of EW with the continuum flux. In our survey, we find that variability of O VI lambda1032, lambda1038 is less common than of the UV doublets of CIV and N V seen at longer wavelengths, because the O VI absorption is usually saturated. Lyman beta absorption variability is more frequent. In a target-by-target examination we find that broad absorption line absorption and narrow absorption line absorbers are related in terms of maximum outflow velocity and luminosity, and both can be exhibited in similar luminosity objects. We also find one object that shows radial velocity change, seven objects that show equivalent width variability, and two objects that show either transverse velocity changes or a change in ionization.

Jay P. Dunn; D. Michael Crenshaw; S. B. Kraemer; M. L. Trippe

2008-07-01

12

Start | View At a Glance | Author Index 348-3 An In Situ Real-Time Quick X-Ray Absorption Spectroscopic (Q-XAS) Investigation of  

E-print Network

Ni K-edge extended X-ray absorption fine structure spectroscopic data to characterize the mechanisms Spectroscopic (Q-XAS) Investigation of Ni Precipitation On Al-Rich Soil Minerals. See more from this Division: S, Street Level Matthew Siebecker1, Wei Li1 and Donald Sparks2, (1)Plant and Soil Sciences, University

Sparks, Donald L.

13

Spectroscopic Methods of Remote Sensing for Vegetation Characterization  

NASA Astrophysics Data System (ADS)

Imaging spectroscopy (IS), often referred to as hyperspectral remote sensing, is one of the latest innovations in a very long history of spectroscopy. Spectroscopic methods have been used for understanding the composition of the world around us, as well as, the solar system and distant parts of the universe. Continuous sampling of the electromagnetic spectrum in narrow bands is what separates IS from previous forms of remote sensing. Terrestrial imaging spectrometers often have hundreds of channels that cover the wavelength range of reflected solar radiation, including the visible, near-infrared (NIR), and shortwave infrared (SWIR) regions. In part due to the large number of channels, a wide variety of methods have been applied to extract information from IS data sets. These can be grouped into several broad classes, including: multi-channel indices, statistical procedures, full spectrum mixing models, and spectroscopic methods. Spectroscopic methods carry on the more than 150 year history of laboratory-based spectroscopy applied to material identification and characterization. Spectroscopic methods of IS relate the positions and shapes of spectral features resolved by airborne and spaceborne sensors to the biochemical and physical composition of vegetation in a pixel. The chlorophyll 680nm, water 980nm, water 1200nm, SWIR 1700nm, SWIR 2100nm, and SWIR 2300nm features have been the subject of study. Spectral feature analysis (SFA) involves isolating such an absorption feature using continuum removal (CR) and calculating descriptors of the feature, such as center position, depth, width, area, and asymmetry. SFA has been applied to quantify pigment and non-pigment biochemical concentrations in leaves, plants, and canopies. Spectral feature comparison (SFC) utilizes CR of features in each pixel's spectrum and linear regression with continuum-removed features in reference spectra in a library of known vegetation types to map vegetation species and communities. SFC has been applied to map the distributions of minerals in soils and rocks; however, its application to characterize vegetation cover has been less widespread than SFA. Using IS data and the USGS Processing Routines in IDL for Spectroscopic Measurements (PRISM; http://pubs.usgs.gov/of/2011/1155/), this talk will examine requirements for and limitations in applying SFA and SFC to characterize vegetation. A time series of Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) data collected in the marshes of Louisiana following the Deepwater Horizon oil spill will be used to examine the impact of varying leaf water content on the shapes of the SWIR 1700, 2100, and 2300 nm features and the implications of these changes on vegetation identification and biochemical estimation. The USGS collection of HyMap data over Afghanistan, the largest terrestrial coverage of IS data to date, will be used to demonstrate the characterization of vegetation in arid and semi-arid regions, in which chlorophyll absorption is often weak and soil and rock mineral absorption features overlap vegetation features. Hyperion data, overlapping the HyMap data, will be presented to illustrate the complications that arise when signal-to-noise is low. The benefits of and challenges to applying a spectroscopic remote sensing approach to imaging spectrometer data will be discussed.

Kokaly, R. F.

2013-12-01

14

Spectroscopic characterization of genetically modified flax fibers  

NASA Astrophysics Data System (ADS)

The principal goal of this paper is an analysis of flax fiber composition. Natural and genetically modified flax fibers derived from transgenic flax have been analyzed. Development of genetic engineering enables to improve the quality of fibers. Three transgenic plant lines with different modifications were generated based on fibrous flax plants as the origin. These are plants with: silenced cinnamyl alcohol dehydrogenase (CAD) gene; overexpression of polygalacturonase (PGI); and expression of three genes construct containing ?-ketothiolase (phb A), acetoacetyl-CoA reductase (phb B), and poly-3-hydroxybutyric acid synthase (phb C). Flax fibers have been studied by FT-IR spectroscopy. The integral intensities of the IR bands have been used for estimation of the chemical content of the normal and transgenic flaxes. The spectroscopic data were compared to those obtained from chemical analysis of flax fibers. X-ray studies have been used to characterize the changes of the crystalline structure of the flax cellulose fibers.

Dymi?ska, L.; G?gor, A.; Hanuza, J.; Kulma, A.; Preisner, M.; ?uk, M.; Szatkowski, M.; Szopa, J.

2014-09-01

15

Development of an infrared absorption spectroscope based on linear variable filters  

E-print Network

The objective of this thesis is to develop a low-cost infrared absorption spectroscope based on linear variable filter (LVF) technology for the automated detection of gases and vapors, and the semi-automated detection of liquids. This instrument...

Nogueira, Felipe Guimaraes

2009-05-15

16

Spectroscopic characterizations of organic/inorganic nanocomposites  

NASA Astrophysics Data System (ADS)

In the present study, pure and 0.3 wt%, 0.4 wt%, as well as 0.5 wt% L-arginine doped potassium dihydrogen phosphate (KDP) crystals were grown using solution growth techniques and further subjected to infrared (IR) absorption and Raman studies for confirmation of chemical group functionalization for investigating the incorporation mechanism of the L-arginine organic material into the KDP crystal structure. Infrared spectroscopic analysis suggests that structural changes are occurring for the L-arginine molecule as a result of its interaction with the KPD crystal. Infrared spectroscopic technique confirms the disturbance of the N-H, C-H and C-N bonds of the amino acid, suggesting successful incorporation of L-arginine into the KDP crystals. Raman analysis also reveals modification of the N-H, C-H and C-N bonds of the amino acid, implying successful inclusion of L-arginine into the KDP crystals. With the help of Gaussian software, a prediction of possible incorporation mechanisms of the organic material was obtained from comparison of the simulated infrared and Raman vibrational spectra with the experimental results. Furthermore, we also studied the effect of L-arginine doping on the thermal stability of the grown KDP crystal by employing Thermo gravimetric analysis (TGA). TGA suggests that increasing the level of L-arginine doping speeds the decomposition process and it weakens the KDP crystal, which indicates successful doping of the KDP crystals with L-arginine amino acid. Urinary stones are one of the oldest and most widely spread diseases in humans, animals and birds. Many remedies have been employed through the ages for the treatment of urinary stones. Recent medicinal measures reflect the modern advances, which are based on surgical removal, percutaneous techniques and extracorporeal shock wave lithotripsy (ESWL). Although these procedures are valuable, they are quite expensive for most people. Furthermore, recurrence of these diseases is awfully frequent with these procedures and the patients have to be subjected to careful follow up for several years. In contrast, in traditional therapeutic systems, most of the remedies were taken from plants and they proved to be helpful. However, the rationale behind their use is not thoroughly established through systematic pharmacological and clinical studies. In this regard, in the present investigation, with a view towards acquiring more insights, we have performed a detailed study of kidney stone formation and growth inhibition based on a traditional medicine approach with herbal extracts. The intricacy of calculi formation (i.e. nucleation, transformation, and aggregation) in a natural system such as urine is replicated to a certain extent in the present study by using a simplified single diffusion gel growth technique. Crystals were synthesized in a static gel environment without and with the presence of 1% and 2% concentration of Rotula Aquatica Lour (RAL) herbal extracts and further subjected to Raman, infrared absorption, X-ray photoelectron spectroscopy (XPS), and photoluminescence to analyze the effects of RAL on the growth of manganese-based calculi. Raman spectroscopy clearly provided an indication of the newberyite type of crystal as well as information on the chemical interaction between crystal and inhibitor. It also indicates the presence of organic components due to the RAL plant material. Infrared absorption spectroscopy indicates the presence of a strong reflecting component in the inhibitor as well as the newberyite type of crystal. XPS results indicated the presence of metallic zinc in the crystal with inhibitor. Furthermore, a considerable increase in the intensity of the magnesium and oxygen lines are noticed with the addition of the herbal extract, which suggest that the inhibitor chemical composition includes a substantial quantity of Mg and O. XPS analysis also demonstrates the presence of modified phosphorus oxidation states and suggest that they might make a contribution, too. The photoluminescence spectra of the crystal with inhibitor indicate the p

Govani, Jayesh R.

2009-12-01

17

Surface spectroscopic characterization of titanium implant materials  

NASA Astrophysics Data System (ADS)

Titanium is one of the most commonly used biomaterials for dental and orthopedic applications. Its excellent tissue compatibility is mainly due to the properties of the stable oxide layer which is present on the surface. This paper reports a detailed spectroscopic characterization of the surface composition of non-alloyed Ti implant materials, prepared according to procedures commonly used in clinical practice (machining, ultrasonic cleaning and sterilization). The main methods of characterization are XPS and AES, and complementary information is obtained by SIMS, EDX and NMA (nuclear microanalysis). The surface of the implants is found to consist of a thin surface oxide which is covered by a carbon-dominated contamination layer. By comparison with reference spectra from single crystal TiO 2 (rutile) the composition of the surface oxide is shown to be mainly TiO 2, with minor amounts of suboxides and TiN x. The thickness of the surface oxides is 2-6 nm, depending on the method of sterilization. The surface contamination layer is found to vary considerably from sample to sample and consists of mainly hydrocarbons with trace amounts of Ca, N, S, P, Cl. Some differences in surface composition between directly prepared surfaces, and some possible contamination sources, are identified and discussed shortly.

Lausmaa, Jukka; Kasemo, Bengt; Mattsson, Håkan

1990-04-01

18

Spectroscopic remote sensing for material identification, vegetation characterization, and mapping  

NASA Astrophysics Data System (ADS)

Identifying materials by measuring and analyzing their reflectance spectra has been an important procedure in analytical chemistry for decades. Airborne and space-based imaging spectrometers allow materials to be mapped across the landscape. With many existing airborne sensors and new satellite-borne sensors planned for the future, robust methods are needed to fully exploit the information content of hyperspectral remote sensing data. A method of identifying and mapping materials using spectral feature analyses of reflectance data in an expert-system framework called MICA (Material Identification and Characterization Algorithm) is described. MICA is a module of the PRISM (Processing Routines in IDL for Spectroscopic Measurements) software, available to the public from the U.S. Geological Survey (USGS) at http://pubs.usgs.gov/of/2011/1155/. The core concepts of MICA include continuum removal and linear regression to compare key diagnostic absorption features in reference laboratory/field spectra and the spectra being analyzed. The reference spectra, diagnostic features, and threshold constraints are defined within a user-developed MICA command file (MCF). Building on several decades of experience in mineral mapping, a broadly-applicable MCF was developed to detect a set of minerals frequently occurring on the Earth's surface and applied to map minerals in the country-wide coverage of the 2007 Afghanistan HyMap data set. MICA has also been applied to detect sub-pixel oil contamination in marshes impacted by the Deepwater Horizon incident by discriminating the C-H absorption features in oil residues from background vegetation. These two recent examples demonstrate the utility of a spectroscopic approach to remote sensing for identifying and mapping the distributions of materials in imaging spectrometer data.

Kokaly, Raymond F.

2012-06-01

19

Spectroscopic characterization of metallothionein from the terrestrial snail, Helix pomatia.  

PubMed

The Cd-sequestering metallothionein (MT) isoform isolated from the midgut gland of Roman snails exposed to Cd supplements in the feed was characterized by compositional and spectroscopic analysis. The preparations contained nearly 5 mol of Cd, small amounts of Cu and about 1 mol of Zn per chain mass of 6620 Da, in numerical agreement with the apoprotein's measured capacity of firmly binding a maximum of 6 equivalents of Cd per molecule. As with other Cd-containing MTs the occurrence of a prominent Cd-mercaptide-specific shoulder at 250 nm in its absorption spectrum showed that Cd is complexed in tetrahedral symmetry by the cysteine residues of the protein, and the multiphasic ellipticity profile in the CD spectrum revealed that these complexes are joined to form one or more oligonuclear Cd-mercapto clusters. Both spectral features vanished with the removal of the metal but were reconstituted to maximum amplitudes by readdition of Cd to the metal-free apoprotein, provided precautions were taken to prevent air oxidation of the latter. Quantitative analysis of snail MT reconstituted with Cd established that the 18 cysteine side chains bind the metal in a 3-to-1 ratio; spectroscopic studies on fractionally restored forms demonstrated that the six Cd ions were bound to the apoprotein molecule in succession in two sets of three Cd ions each. Thus, one can infer from the observed stoichiometry and the coordinating preferences of Cd that this gastropod MT, like the Cd-bearing MTs of marine crustaceans, harboured the metal in two separate cyclically constructed Cd3Cys9 clusters. The snail clusters differed, however, from other MTs in their response to acidification. Their protolytic dissociation proceeded through two separate protonation steps with the manifestation of spectroscopically distinguishable intermediate forms. Thus, this snail isoform displays in its metal composition and its chemical and spectroscopic features both similarities and differences to other animal kingdom MTs. Its properties suggest that it serves an important role in the protection of the terrestrial gastropod from Cd. PMID:11488904

Dallinger, R; Wang, Y; Berger, B; Mackay, E A; Kägi, J H

2001-08-01

20

Spectroscopic characterization of matrix isolated transient species  

NASA Astrophysics Data System (ADS)

Part I describes the electronic spectra of various actinide containing compounds isolated in solid Ar using laser induced fluorescence (LIF) spectroscopy. The IR spectra for many of the same molecules were also recorded to aid in the identification of the fluorescing species in the LIF spectra. LIF spectra of UO2 isolated in solid Ar were recorded to investigate the interactions between actinide compounds and the rare gas matrix host. At the time of the experiments, it had been proposed that for UO2 and CUO, the interactions between the actinide containing molecule and Ar were strong enough to reorder the low-lying electronic states of the molecule. The experiments presented here showed no evidence of a reordering of low-lying electronic states based on comparison of the matrix spectra with theoretical predictions and gas phase spectra. An attempt to observe fluorescence from higher order uranium oxides was undertaken. A matrix was made by ablating U metal in a 1.0% O2/Ar mixture. UO3 was a probable molecule formed in the experiment. And, while absorptions belonging to UO3 were observed in IR spectra, LIF from the same matrix provided evidence that another molecule was fluorescing. Two different vibrational frequencies observed in the U-O symmetric stretching region were indicative of at least two low-lying electronic states in fluorescing molecule. UO3 is a closed shell molecule, and it is unlikely that it has any low-lying electronic states. Instead, the fluorescence was attributed to the open shell species (UO2)+(O2) -. LIF and IR spectra of thermally vaporized UCl4 isolated in solid Ar were recorded. UCl4 contains U(IV), which is the most stable oxidation state other than U(VI). Before these experiments, no fluorescence had been recorded that could be attributed to UCl4. Based on the observed vibrational frequencies in the fluorescence bands and the lifetime of the fluorescence, it was determine that there was at least two different fluorescing species. The short lived fluorescence was assigned to UCl 4, and the long-lived fluorescence was assigned to UOCl x. A low resolution map for the electronic levels in UOCl x was created. One of the first LIF studies of actinide containing molecules was performed by Grzybowski and Andrews[1] for UF6. While, the same group later recorded IR spectra for the UFx fragements[2], no fluorescence spectra were recorded. Spectra were recorded here of UF x fragments trapped in solid formed by either passing UF 6 through a microwave discharge or ablating U atoms into an F2 /Ar mixture. At the time of these experiments, the IR spectrometer was not available, and the molecules producing the fluorescence could not be deduced solely from the LIF spectra. A comparison with previous IR spectra[2] gave some indication of possible candidates. In all the experiments that investigated uranium containing matrices with IR spectroscopy, UN2 was observed. A search was undertaken to observe fluorescence from UN2. To insure a good yield of UN 2, 1% N2 was added to the carrier gas. The fluorescence spectra observed in these experiments was very intriguing, but was determined not to be coming from UN2, rather it appears to be coming from U atom clusters. However further experiments are necessary to confirm how many atoms are in the clusters. The final part of this thesis focuses on the electronic spectra of Xe-OH isolated solid Ar. Rare gas radical systems (Rg-X) such as Rg-OH are a good model system for studying weak, long range intermolecular interactions. It is known that when Rg=Xe, the strength of the interaction is much larger. For most Rg-OH complexes, the spectroscopic constants have been determined previously[3]. However, the constants for Xe-OH ares currently undetermined. Gas-phase studies were undertaken to determined these constants.[4] However, these experiments were in conflict with previous LIF spectra recorded in a matrix in which Goodman and Brus[5] observed that the A ? X emission band for Xe-OH is redshifted approximately 5,000 cm-1, which is unusually large. Additionally, they found

Lue, Christopher J.

21

IR absorption spectroscopic study of mixed cobalt substituted lithium ferrites  

NASA Astrophysics Data System (ADS)

The IR spectra of Li0.5-(x/2)CoxFe2.5-(x/2)O4 ferrite samples (0?x?0.6) prepared by solution combustion method have been reported. The influence of Co substitution is verified. XRD studies confirm the spinel phase formation of ferrites. Lattice constant varies linearly from 8.31 Å (x=0) to 8.35 Å (x=0.6) with composition. Evidence of two absorption bands in the IR spectra (below 800 cm-1) reveals the characteristic feature of spinel ferrite. The IR spectra featured additional three absorption bands around 550, 670 and 705 cm-1 for the samples x=0.1 and x=0.6. Absence of bands splitting specifies that Fe ions do not exist in excess form. It is found that high frequency band (?1), due to tetrahedral (A) group, lies at around 600 cm-1 and low frequency band (?2), due to octahedral (B) group, around 450 cm-1. The positions of bands are found to be composition dependent. The IR bands due to tetrahedral complexes shift slightly towards high frequency side with composition upto x=0.4 where as that due to octahedral complexes shift towards lower frequency side with x. Based on the data of absorption bands, force constants (kt, ko) and bond lengths (RA, RB) were estimated. Compositional dependence of force constants is explained on the basis of cation-oxygen bond distances of respective sites and cation distribution.

Sawant, V. S.; Bagade, A. A.; Mohite, S. V.; Rajpure, K. Y.

2014-10-01

22

Spectroscopic characterization of nitroaromatic landmine signature explosives  

NASA Astrophysics Data System (ADS)

TNT and DNT are important explosives used as base charges of landmines and other explosive devices. They are often combined with RDX in specific explosive formulations. Their detection in vapor phase as well as in soil in contact with the explosives is important in landmine detection technology. The spectroscopic signatures of nitroaromatic compounds in neat forms: crystals, droplets, and recrystallized samples were determined by Raman Microspectroscopy (RS), Fourier Transform Infrared Microscopy (FTIR) and Fiber Optics Coupled - Fourier Transform Infrared Spectroscopy (FOC-FTIR) using a grazing angle (GA) probe. TNT exhibits a series of characteristic bands: vibrational signatures, which allow its detection in soil. The spectroscopic signature of neat TNT is dominated by strong bands about 1380 and 2970 cm-1. The intensity and position of these bands were found remarkably different in soil samples spiked with TNT. The 1380 cm-1 band is split into a number of bands in that region. The 2970 cm-1 band is reduced in intensity and new bands are observed about 2880 cm-1. The results are consistent with a different chemical environment of TNT in soil as compared to neat TNT. Interactions were found to be dependent on the physical source of the explosive. In the case of DNT-sand interactions, shifts in vibrational frequencies of the explosives as well as the substrates were found.

Hernandez-Rivera, Samuel P.; Manrique-Bastidas, Cesar A.; Blanco, Alejandro; Primera, Oliva M.; Pacheco, Leonardo C.; Castillo-Chara, Jairo; Castro, Miguel E.; Mina, Nairmen

2004-09-01

23

Spectroscopic characterization of novel polycyclic aromatic polymers.  

PubMed

A series of novel polyphenylenevinylene (PPV) derivative polymers were studied by absorption and photoluminescence spectroscopies. The effect of the sequential introduction of polycyclic aromatic ring substituents into the delocalized backbone was examined with relation to hypsochromatic and bathochromatic shifting. While the replacement of the phenyl units by naphthyl units results in a substantial hypsochromic shift of both the absorption and emission spectra, their subsequent substitution by anthryl units results in a bathochromic shift. The system is modeled according to, and is found to be consistent with, a previous study of donor-acceptor polyenes of varying length. The electronic structure of the backbone is found to be a balance between that of the high electron affinity polycyclic ring system and the contribution to conjugation across the linking vinyl unit. The model is adapted based on electron affinities of the constituent units, and a clear structure-property relationship for the absorption and emission properties of the system is elucidated. The Stokes shift is examined and is seen to be well-correlated with the vinyl contribution to the electron affinity total (EAtotal). The trends observed in the optical properties of the polymeric system are supported by Raman spectroscopy, whereby the spectral signature of the connecting vinyl bond is seen to soften in a fashion which is correlated with the modeled electron affinity parameters. PMID:17214468

O'Neill, Luke; Lynch, Patrick; McNamara, Mary; Byrne, Hugh J

2007-01-18

24

Vibrational Spectroscopic Characterization of Hematite, Maghemite, and Magnetite Thin  

E-print Network

Vibrational Spectroscopic Characterization of Hematite, Maghemite, and Magnetite Thin Films University, 100 West 18th Avenue, Columbus, Ohio 43210 ABSTRACT Thin films of three iron oxide polymorphs, hematite, maghemite, and magnetite, were produced on KBr substrates using a conventional electron beam

25

A Survey of Intrinsic Absorption in Active Galaxies using the Far Ultraviolet Spectroscopic Explorer  

E-print Network

We present a survey of 72 Seyfert galaxies and quasars observed by the it Far Ultraviolet Spectroscopic Explorer (FUSE). We have determined that 72 of 253 available active galactic nuclei (AGN) targets are viable targets for detection of intrinsic absorption lines. We examined these spectra for signs of intrinsic absorption in the O VI doublet (lambda 1031.9, 1037.6) and Lyman beta (lambda 1025.7). The fraction of Seyfert 1 galaxies and low-redshift quasars at z absorption is ~50%, which is slightly lower than Crenshaw et al. (1999) found (60%) based on a smaller sample of Seyfert 1 galaxies observed with the Hubble Space Telescope (HST). With this new fraction we find a global covering factor of the absorbing gas with respect to the central nucleus of ~0.4. Our survey is to date the largest searching for intrinsic UV absorption with high spectral resolution, and is the first step toward a more comprehensive study of intrinsic absorption in low-redshift AGN.

Jay P. Dunn; D. Michael Crenshaw; S. B. Kraemer; J. R. Gabel

2007-06-20

26

Crystallographic and X-ray absorption spectroscopic characterization of Helicobacter pylori UreE bound to Ni2+ and Zn2+ reveal a role for the disordered C-terminal arm in metal trafficking  

PubMed Central

The survival and growth of the pathogen Helicobacter pylori in the gastric acidic environment is ensured by the activity of urease, an enzyme containing two essential Ni2+ ions in the active site. The metallo-chaperone UreE facilitates in vivo Ni2+ insertion into the apo-enzyme. Crystals of apo-HpUreE and its Ni2+ and Zn2+ bound forms were obtained from protein solutions in the absence and presence of the metal ions. The crystal structures of the homodimeric protein, determined at 2.00 Å (apo), 1.59 Å (Ni) and 2.52 Å (Zn) resolution, show the conserved proximal and solvent-exposed His102 residues from two adjacent monomers invariably involved in metal binding. The C-terminal regions of the apo-protein are disordered in the crystal, but acquire significant ordering in the presence of the metal ions due to the binding of His152. The analysis of X-ray absorption spectral data obtained on solutions of Ni2+- and Zn2+-HpUreE provided accurate information of the metal ion environment in the absence of solid-state effects. These results reveal the role of the histidine residues at the protein C-terminus in metal ion binding, and the mutual influence of protein framework and metal ion stereo-electronic properties in establishing coordination number and geometry leading to metal selectivity. PMID:22010876

Banaszak, Katarzyna; Martin-Diaconescu, Vlad; Bellucci, Matteo; Zambelli, Barbara; Rypniewski, Wojciech; Maroney, Michael J.; Ciurli, Stefano

2012-01-01

27

Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar  

E-print Network

We use an airborne pulsed integrated path differential absorption lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric CO2 at the 1572.335 nm absorption line. We measure the absorption lineshape in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HITRAN shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations, and the absorption linewidth to within 0.6% of calculations.

Ramanathan, Anand; Allan, Graham R; Riris, Haris; Weaver, Clark J; Hasselbrack, William E; Browell, Edward V; Abshire, James B

2013-01-01

28

Spectroscopic characterization of femtosecond laser filament in argon gas  

SciTech Connect

We report a spectroscopic approach to measure the plasma density and electron temperature inside a filament created by an intense femtosecond laser pulse in atmospheric pressure argon gas. The technique relies on the proportionality between the Stark broadened argon fluorescence line width due to electron impact and the plasma density, while the electron temperature is determined from the well known Boltzmann plot. The obtained maximum plasma density is about 5.5x10{sup 16} cm{sup -3}, and the electron temperature is about 5800 K. Our method provides a promising and convenient way to characterize the filament for further understanding the fundamental physics and potential applications of filamentation.

Liu, W.; Bernhardt, J.; Theberge, F.; Chin, S. L.; Chateauneuf, M.; Dubois, J. [Institute of Modern Optics, Nankai University, Key Laboratory of Opto-electronic Information Science and Technology, Education Ministry of China, Tianjin 300071 (China); Centre d'Optique, Photonique et Laser (COPL) and Departement de physique, de genie physique et d'optique, Universite Laval, Quebec, Quebec G1K 7P4 (Canada); Defence Research and Development Canada--Valcartier, 2459 Pie-XI Blvd. North, Quebec, Quebec, G3J 1X5 Canada (Canada)

2007-08-01

29

Novel dipodal Schiff base compounds: Synthesis, characterization and spectroscopic studies  

NASA Astrophysics Data System (ADS)

Two novel dipodal Schiff base compounds 1,2-benzyloxy-bis-[2-(benzylideneamino)phenol, L1 and 1,2-benzyloxy-bis[3-(benzylideneamino)pyridine], L2 were synthesized. Their sensing actions were confirmed by UV-Vis absorbance and emission spectroscopic studies in presence of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II) in methanol medium (1 × 10-4 M). It was found that the dipodal compounds can selectively bind to Cu(II) and Pb(II) metal ions with a significant change in its emission and absorption spectra, while the addition of other metal ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II)) produces insignificant or minor changes. The host-guest complexes formed were determined by Job's plot method. As a chemosensor, L1 and L2 dipodal Schiff base compounds shows a specific selectivity towards Cu(II) and Pb(II) ions in according to all spectroscopic data.

Obali, Aslihan Yilmaz; Ucan, Halil Ismet

2015-02-01

30

Characterization of cytochrome c as marker for retinal cell degeneration by uv/vis spectroscopic imaging  

NASA Astrophysics Data System (ADS)

Retinal diseases like age-related macular degeneration have become an important cause of visual loss depending on increasing life expectancy and lifestyle habits. Due to the fact that no satisfying treatment exists, early diagnosis and prevention are the only possibilities to stop the degeneration. The protein cytochrome c (cyt c) is a suitable marker for degeneration processes and apoptosis because it is a part of the respiratory chain and involved in the apoptotic pathway. The determination of the local distribution and oxidative state of cyt c in living cells allows the characterization of cell degeneration processes. Since cyt c exhibits characteristic absorption bands between 400 and 650 nm wavelength, uv/vis in situ spectroscopic imaging was used for its characterization in retinal ganglion cells. The large amount of data, consisting of spatial and spectral information, was processed by multivariate data analysis. The challenge consists in the identification of the molecular information of cyt c. Baseline correction, principle component analysis (PCA) and cluster analysis (CA) were performed in order to identify cyt c within the spectral dataset. The combination of PCA and CA reveals cyt c and its oxidative state. The results demonstrate that uv/vis spectroscopic imaging in conjunction with sophisticated multivariate methods is a suitable tool to characterize cyt c under in situ conditions.

Hollmach, Julia; Schweizer, Julia; Steiner, Gerald; Knels, Lilla; Funk, Richard H. W.; Thalheim, Silko; Koch, Edmund

2011-07-01

31

Spectroscope  

NSDL National Science Digital Library

In this activity, learners construct their own spectroscope as they explore and observe spectra from familiar light sources. Learners can be challenged to make technological improvements to their spectroscopes and/or participate in extension activities that expand their understanding of different kinds of spectra and sharpen their observing skills.

2012-06-26

32

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin  

PubMed Central

Hemoglobin (Hb) is the heme-containing O2 transport protein essential for life in all vertebrates. The resting high-spin (S = 2) ferrous form, deoxy-Hb, combines with triplet O2, forming diamagnetic (S = 0) oxy-Hb. Understanding this electronic structure is the key first step in understanding transition metal–O2 interaction. However, despite intense spectroscopic and theoretical studies, the electronic structure description of oxy-Hb remains elusive, with at least three different descriptions proposed by Pauling, Weiss, and McClure-Goddard, based on theory, spectroscopy, and crystallography. Here, a combination of X-ray absorption spectroscopy and extended X-ray absorption fine structure, supported by density functional theory calculations, help resolve this debate. X-ray absorption spectroscopy data on solution and crystalline oxy-Hb indicate both geometric and electronic structure differences suggesting that two of the previous descriptions are correct for the Fe–O2 center in oxy-Hb. These results support the multiconfigurational nature of the ground state developed by theoretical results. Additionally, it is shown here that small differences in hydrogen bonding and solvation effects can tune the ground state, tipping it into one of the two probable configurations. These data underscore the importance of solution spectroscopy and show that the electronic structure in the crystalline form may not always reflect the true ground-state description in solution. PMID:24062465

Wilson, Samuel A.; Green, Evan; Mathews, Irimpan I.; Benfatto, Maurizio; Hodgson, Keith O.; Hedman, Britt; Sarangi, Ritimukta

2013-01-01

33

Characterization by spectroscopic Ellipsometry, the physical properties of silver nanoparticles.  

NASA Astrophysics Data System (ADS)

Physicists are able to change their minds through their experiments. I think it is time to go kick the curse and go further in research if we want a human future. I work in the Nano-Optics and Plasmonics research. I defined with ellipsomètrie the structure of new type of Nano particles of silver. It's same be act quickly to replace the old dirty leaded electronic-connexion chip and by the other hand to find a new way for the heath care of cancer disease by nanoparticles the next killers of bad cells. Silver nanoparticle layers are obtained by Spark Plasma Sintering are investigated as an alternative to lead alloy based material for solder joint in power mechatronics modules. These layers are characterized by mean of conventional techniques that is the dilatometry technique, the resistivity measurement through the van der Pauw method, and the flash laser technique. Furthermore, the nanoparticles of silver layer are deeply studied by UV-Visible spectroscopic ellipsometry. Spectroscopic angles parameters are determined in function of temperature and dielectric constants are deduced and analyzed through an optical model which takes into account a Drude and a Lorentz component within the Bruggeman effective medium approximation (EMA). The relaxation times and the electrical conductivity are plot in function of temperature. The obtained electrical conductivity give significant result in good agreement to those reported by four points electrical measurement method.

Coanga, Jean-Maurice

2013-04-01

34

Optical absorption and photoluminescence properties of Nd3+ doped mixed alkali phosphate glasses-spectroscopic investigations.  

PubMed

Spectroscopic investigations were performed on 68NH(4)H(2)PO(4).xLi(2)CO(3)(30-x)K(2)CO(3) and 68NH(4)H(2)PO(4).xNa(2)CO(3)(30-x)K(2)CO(3) (where x=5, 10, 15, 20 and 25) glasses containing 2 mol% Nd(2)O(3). Various spectroscopic parameters (Racah (E(1), E(2), E(3)), spin-orbit (xi(4f)) and configuration interaction (alpha)) are reported. Judd-Ofelt intensity parameters (Omega(2), Omega(4), Omega(6)) are calculated for Nd(3+) doped two mixed alkali phosphate glass matrices. From the magnitude of Judd-Ofelt parameters, covalency is studied as a function of x in the glass matrix. Using Judd-Ofelt intensity parameters, total radiative transition probabilities (A(T)), radiative lifetimes (tau(R)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been computed for certain excited states of Nd(3+) in these mixed alkali phosphate glasses. Emission cross sections (sigma(P)) are calculated for the two transitions, (4)G(7/2)-->(4)I(11/2) and (4)G(7/2)-->(4)I(13/2) of Nd(3+) in these mixed alkali phosphate glasses. Optical band gaps (E(opt)) for direct and indirect transitions are reported. PMID:19010718

Ratnakaram, Y C; Srihari, N V; Kumar, A Vijaya; Naidu, D Thirupathi; Chakradhar, R P S

2009-02-01

35

Spectroscopic characterization of a contemporary Indian miniature painting.  

PubMed

A case study on a contemporary Indian miniature was carried out through the application of different spectroscopic techniques. Painting support, pigments, and dyes were largely characterized by means of energy dispersive x-ray fluorescence and Raman microspectroscopy directly on the artwork. Regarding golden motifs and silvered areas, for which these techniques have not provided enough information, scanning electron microscopy coupled with energy dispersive x-ray spectroscopy was used as a complementary technique. The painting support was identified as the Bombyx mori silk. Among the colorant matters, several pigments were identified such as chrome yellow, lithopone, hematite, lamp black, mica-titania pearlescent pigment, and tin-based metallic silver, and dyes such as phthalocyanine blue and the recent synthetic pigment red PR9 naphthol AS. All this materials will provide evidence in the support of the contemporary production of the artwork for future studies. PMID:24359650

Cardeira, Ana Mafalda; Longelin, Stéphane; Le Gac, Agnès; Nogueira, Isabel; Carvalho, Maria Luísa; Manso, Marta

2013-12-01

36

Spectroscope  

NSDL National Science Digital Library

In this activity (posted on March 12, 2011), learners follow the steps to construct a spectroscope, a tool used to analyze light and color. First, learners use relatively simple materials to construct the device. Then, learners look through their spectroscopes at a variety of different light sources including incandescents, LEDs, compact fluorescents, sun light, etc. and compare what they observe. This resource includes a few examples of how certain chemicals form different colors of light.

Oakland Discovery Center

2011-01-01

37

Thermal and Spectroscopic Characterization of a Proton Pumping Rhodopsin from an Extreme Thermophile*  

PubMed Central

So far retinylidene proteins (?rhodopsin) have not been discovered in thermophilic organisms. In this study we investigated and characterized a microbial rhodopsin derived from the extreme thermophilic bacterium Thermus thermophilus, which lives in a hot spring at around 75 °C. The gene for the retinylidene protein, named thermophilic rhodopsin (TR), was chemically synthesized with codon optimization. The codon optimized TR protein was functionally expressed in the cell membranes of Escherichia coli cells and showed active proton transport upon photoillumination. Spectroscopic measurements revealed that the purified TR bound only all-trans-retinal as a chromophore and showed an absorption maximum at 530 nm. In addition, TR exhibited both photocycle kinetics and pH-dependent absorption changes, which are characteristic of rhodopsins. Of note, time-dependent thermal denaturation experiments revealed that TR maintained its absorption even at 75 °C, and the denaturation rate constant of TR was much lower than those of other proton pumping rhodopsins such as archaerhodopsin-3 (200 ×), Haloquadratum walsbyi bacteriorhodopsin (by 10-times), and Gloeobacter rhodopsin (100 ×). Thus, these results suggest that microbial rhodopsins are also distributed among thermophilic organisms and have high stability. TR should allow the investigation of the molecular mechanisms of ion transport and protein folding. PMID:23740255

Tsukamoto, Takashi; Inoue, Keiichi; Kandori, Hideki; Sudo, Yuki

2013-01-01

38

Near-infrared diode laser based spectroscopic detection of ammonia: a comparative study of photoacoustic and direct optical absorption methods  

NASA Technical Reports Server (NTRS)

A photoacoustic spectroscopic (PAS) and a direct optical absorption spectroscopic (OAS) gas sensor, both using continuous-wave room-temperature diode lasers operating at 1531.8 nm, were compared on the basis of ammonia detection. Excellent linear correlation between the detector signals of the two systems was found. Although the physical properties and the mode of operation of both sensors were significantly different, their performances were found to be remarkably similar, with a sub-ppm level minimum detectable concentration of ammonia and a fast response time in the range of a few minutes.

Bozoki, Zoltan; Mohacsi, Arpad; Szabo, Gabor; Bor, Zsolt; Erdelyi, Miklos; Chen, Weidong; Tittel, Frank K.

2002-01-01

39

Spectroscopic characterization of collagen cross-links in bone  

NASA Technical Reports Server (NTRS)

Collagen is the most abundant protein of the organic matrix in mineralizing tissues. One of its most critical properties is its cross-linking pattern. The intermolecular cross-linking provides the fibrillar matrices with mechanical properties such as tensile strength and viscoelasticity. In this study, Fourier transform infrared (FTIR) spectroscopy and FTIR imaging (FTIRI) analyses were performed in a series of biochemically characterized samples including purified collagen cross-linked peptides, demineralized bovine bone collagen from animals of different ages, collagen from vitamin B6-deficient chick homogenized bone and their age- and sex-matched controls, and histologically stained thin sections from normal human iliac crest biopsy specimens. One region of the FTIR spectrum of particular interest (the amide I spectral region) was resolved into its underlying components. Of these components, the relative percent area ratio of two subbands at approximately 1660 cm(-1) and approximately 1690 cm(-1) was related to collagen cross-links that are abundant in mineralized tissues (i.e., pyridinoline [Pyr] and dehydrodihydroxylysinonorleucine [deH-DHLNL]). This study shows that it is feasible to monitor Pyr and DHLNL collagen cross-links spatial distribution in mineralized tissues. The spectroscopic parameter established in this study may be used in FTIRI analyses, thus enabling the calculation of relative Pyr/DHLNL amounts in thin (approximately 5 microm) calcified tissue sections with a spatial resolution of approximately 7 microm.

Paschalis, E. P.; Verdelis, K.; Doty, S. B.; Boskey, A. L.; Mendelsohn, R.; Yamauchi, M.

2001-01-01

40

Spectroscopic characterization of collagen cross-links in bone.  

PubMed

Collagen is the most abundant protein of the organic matrix in mineralizing tissues. One of its most critical properties is its cross-linking pattern. The intermolecular cross-linking provides the fibrillar matrices with mechanical properties such as tensile strength and viscoelasticity. In this study, Fourier transform infrared (FTIR) spectroscopy and FTIR imaging (FTIRI) analyses were performed in a series of biochemically characterized samples including purified collagen cross-linked peptides, demineralized bovine bone collagen from animals of different ages, collagen from vitamin B6-deficient chick homogenized bone and their age- and sex-matched controls, and histologically stained thin sections from normal human iliac crest biopsy specimens. One region of the FTIR spectrum of particular interest (the amide I spectral region) was resolved into its underlying components. Of these components, the relative percent area ratio of two subbands at approximately 1660 cm(-1) and approximately 1690 cm(-1) was related to collagen cross-links that are abundant in mineralized tissues (i.e., pyridinoline [Pyr] and dehydrodihydroxylysinonorleucine [deH-DHLNL]). This study shows that it is feasible to monitor Pyr and DHLNL collagen cross-links spatial distribution in mineralized tissues. The spectroscopic parameter established in this study may be used in FTIRI analyses, thus enabling the calculation of relative Pyr/DHLNL amounts in thin (approximately 5 microm) calcified tissue sections with a spatial resolution of approximately 7 microm. PMID:11585346

Paschalis, E P; Verdelis, K; Doty, S B; Boskey, A L; Mendelsohn, R; Yamauchi, M

2001-10-01

41

Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin.  

PubMed

A second group of proteorhodopsin-encoding genes (blue-absorbing proteorhodopsin, BPR) differing by 20-30% in predicted primary structure from the first-discovered green-absorbing (GPR) group has been detected in picoplankton from Hawaiian deep sea water. Here we compare BPR and GPR absorption spectra, photochemical reactions, and proton transport activity. The photochemical reaction cycle of Hawaiian deep ocean BPR in cells is 10-fold slower than that of GPR with very low accumulation of a deprotonated Schiff base intermediate in cells and exhibits mechanistic differences, some of which are due to its glutamine residue rather than leucine at position 105. In contrast to GPR and other characterized microbial rhodopsins, spectral titrations of BPR indicate that a second titratable group, in addition to the retinylidene Schiff base counterion Asp-97, modulates the absorption spectrum near neutral pH. Mutant analysis confirms that Asp-97 and Glu-108 are proton acceptor and proton donor, respectively, in retinylidene Schiff base proton transfer reactions during the BPR photocycle as previously shown for GPR, but BPR contains an alternative acceptor evident in its D97N mutant, possibly the same as the second titratable group modulating the absorption spectrum. BPR, similar to GPR, carries out outward light-driven proton transport in Escherichia coli vesicles but with a reduced translocation rate attributable to its slower photocycle. In energized E. coli cells at physiological pH, the net effect of BPR photocycling is to generate proton currents dominated by a triggered proton influx, rather than efflux as observed with GPR-containing cells. Reversal of the proton current with the K+-ionophore valinomycin supports that the influx is because of voltage-gated channels in the E. coli cell membrane. These observations demonstrate diversity in photochemistry and mechanism among proteorhodopsins. Calculations of photon fluence rates at different ocean depths show that the difference in photocycle rates between GPR and BPR as well as their different absorption maxima may be explained as an adaptation to the different light intensities available in their respective marine environments. Finally, the results raise the possibility of regulatory (i.e. sensory) rather than energy harvesting functions of some members of the proteorhodopsin family. PMID:12821661

Wang, Wei-Wu; Sineshchekov, Oleg A; Spudich, Elena N; Spudich, John L

2003-09-01

42

Spectroscopic method for determination of the absorption coefficient in brain tissue  

NASA Astrophysics Data System (ADS)

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, ?a. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(?a)+d ln(Is)ln(?a), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.

Johansson, Johannes D.

2010-09-01

43

X-ray diffraction and absorption spectroscopic studies of copper mixed ligand complexes with aminophenol as one of the ligands  

Microsoft Academic Search

X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been conducted on two copper complexes, i.e., copper macrocyclic complex of succinic acid and ortho aminophenol (complex-1) and copper macrocyclic complex of pthalic acid and ortho aminophenol (complex-2). The diffraction pattern of the complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with rotating anode X-ray tube operated at

A Mishra; Garima Jain; H Patil

2012-01-01

44

PROCESSING OF HIGH LEVEL WASTE: SPECTROSCOPIC CHARACTERIZATION OF REDOX REACTIONS IN SUPERCRITICAL WATER  

EPA Science Inventory

Current efforts are focused on the oxidative dissolution of chromium compounds found in Hanford tank waste sludge. Samples of chromium oxides and hydroxides with varying degrees of hydration are being characterized using Raman, FTIR, and XPS spectroscopic techniques. Kinetics of ...

45

Confocal Light Absorption and Scattering Spectroscopic (CLASS) imaging: From cancer detection to sub-cellular function  

NASA Astrophysics Data System (ADS)

Light scattering spectroscopy (LSS), an optical technique that relates the spectroscopic properties of light elastically scattered by small particles to their size, refractive index and shape, has been recently successfully employed for sensing morphological and biochemical properties of epithelial tissues and cells in vivo. LSS does not require exogenous markers, is non-invasive, and, due to its multispectral nature, can sense biological structures well beyond the diffraction limit. All that makes LSS be a very good candidate to be used both in clinical medicine for in vivo detection of disease and in cell biology to monitor cell function on the organelle scale. Recently we developed two LSS-based imaging modalities: clinical Polarized LSS (PLSS) Endoscopic Technique for locating early pre-cancerous changes in GI tract and Confocal Light Absorption and Scattering Spectroscopic (CLASS) Microscopy for studying cells in vivo without exogenous markers. One important application of the clinical PLSS endoscopic instrument, a noncontact scanning imaging device compatible with the standard clinical endoscopes and capable of detecting dysplastic changes, is to serve as a guide for biopsy in Barrett's esophagus (BE). The instrument detects parallel and perpendicular components of the polarized light, backscattered from epithelial tissues, and determines characteristics of epithelial nuclei from the residual spectra. It also can find tissue oxygenation, hemoglobin content and other properties from the diffuse light component. By rapidly scanning esophagus the PLSS endoscopic instrument makes sure the entire BE portion is scanned and examined for the presence of dysplasia. CLASS microscopy, on the other hand, combines principles of light scattering spectroscopy (LSS) with confocal microscopy. Its main purpose is to image cells on organelle scale in vivo without the use of exogenous labels which may affect the cell function. The confocal geometry selects specific region and images are obtained by scanning the confocal volume across the sample. The new beam scanning CLASS microscope is a significant improvement over the previous proof-of-principle device. With this new device we have already performed experiments to monitor morphological changes in cells during apoptosis, differentiated fetal from maternal nucleated red blood cells, and detected plasmon scattering spectra of single gold nanorod.

Qiu, Le

46

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

E-print Network

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been

van Stokkum, Ivo

47

Recent advances in chromatographic separation and spectroscopic characterization of the higher fullerenes C76 and C84.  

PubMed

The basic and the higher fullerenes were chromatographically isolated from the obtained series of carbon soot extracts, in increased yields, by the new, advanced methods, on Al2O3 columns. The elution was performed continuously, in one phase of each process, at ambient conditions, with the several different original hexane-toluene gradients. Various separation systems were used previously. The unique and the main, dominant absorption maxima of the purified higher fullerenes were registered in the spectral regions where they intensively absorb, applying the IR and UV/VIS techniques. All the observed absorption bands are in excellent agreement with theoretical calculations, indicating the achieved advancement in chromatographic separation and spectroscopic characterization. The isolated fullerenes are important for investigation of their remarkable optical and electronic properties, as well as for the numerous possible applications in chemistry, physics, biomedicine, diagnostic and therapeutic agents, sensors, polymers, nanophotonic materials, special lenses, optical limiting, organic field effect transistors, solar cells etc. PMID:24635208

Jovanovic, T; Koruga, Dj

2014-01-01

48

Growth and spectroscopic characterization of Fe 2O 3 highly doped near-stoichiometric LiNbO 3 single crystals  

Microsoft Academic Search

In this paper, a series of Fe2O3 doped near-stoichiometric LiNbO3 crystals was grown by the top seeded solution growth method using K2O as flux. X-ray powder diffraction, ultraviolet–visible absorption and the infrared spectrum were measured and are discussed in terms of the spectroscopic characterization, the defect structure and the occupation mechanism of Fe ions in near-stoichiometric Fe:LiNbO3 crystals. The results

Hongtao Li; Yexia Fan; Fengyun Guo; Yangyi Xu; Liancheng Zhao

2007-01-01

49

New advances in the use of infrared absorption spectroscopy for the characterization of heterogeneous catalytic reactions.  

PubMed

Infrared absorption spectroscopy has proven to be one of the most powerful spectroscopic techniques available for the characterization of catalytic systems. Although the history of IR absorption spectroscopy in catalysis is long, the technique continues to provide key fundamental information about a variety of catalysts and catalytic reactions, and to also offer novel options for the acquisition of new information on both reaction mechanisms and the nature of the solids used as catalysts. In this review, an overview is provided of the main contributions that have been derived from IR absorption spectroscopy studies of catalytic systems, and a discussion is included on new trends and new potential directions of research involving IR in catalysis. We start by briefly describing the power of Fourier-transform IR (FTIR) instruments and the main experimental IR setups available, namely, transmission (TIR), diffuse reflectance (DRIFTS), attenuated total reflection (ATR-IR), and reflection-absorption (RAIRS), for advancing research in catalysis. We then discuss the different environments under which IR characterization of catalysts is carried out, including in situ and operando studies of typical catalytic processes in gas-phase, research with model catalysts in ultrahigh vacuum (UHV) and so-called high-pressure cell instruments, and work involving liquid/solid interfaces. A presentation of the type of information extracted from IR data follows in terms of the identification of adsorbed intermediates, the characterization of the surfaces of the catalysts themselves, the quantitation of IR intensities to extract surface coverages, and the use of probe molecules to identify and titrate specific catalytic sites. Finally, the different options for carrying out kinetic studies with temporal resolution such as rapid-scan FTIR, step-scan FTIR, and the use of tunable lasers or synchrotron sources, and to obtain spatially resolved spectra, by sample rastering or by 2D imaging, are introduced. PMID:24424375

Zaera, Francisco

2014-11-21

50

Characterization of Spectroscopic and Laser Properties of Pr3+ in S-FAP Crystal  

NASA Astrophysics Data System (ADS)

Spectroscopic and laser properties have been characterized for Pr3+ in Sr5(PO4)3F (S-FAP). The standard Judd-Ofelt analysis has been applied to the measured optical absorption intensities to determine the radiative decay rates, branching ratios, and emission cross sections of principal intermanifold transitions of Pr3+. The Judd-Ofelt parameters Omega(2), Omega(4), and Omega(6) are smaller than those reported for Pr3+ in other laser host crystals. The measured room temperature fluorescence lifetimes of the 1D2 -> 3H4 and 3P0 -> 3F2 transitions are 325 and 105 microseconds, while the Judd-Ofelt analysis predicts the radiative lifetimes for the 1D2 and 3P0 states to be 822 and 116 ms, resulting in the fluorescence quantum efficiencies of 40 and 91sections of the 1D2 -> 3H4 and 3P0 -> 3F2 intermanifold transitions have been also determined to be 0.54 x 10-20 and 4.15 x 10-20 cm2, respectively. *Supported by the NSF grant No. DMR-0099479

Castano, Francisco; Sardar, Dhiraj

2001-10-01

51

Spectroscopic characterization of alkali modified zinc-tellurite glasses doped with neodymium.  

PubMed

Neodymium doped zinc-tellurite glasses of composition TeO(2)-ZnO-Na(2)O-Li(2)O have been prepared and characterized for their thermal, structural and optical properties. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section for (4)F(3/2)-->(4)I(9/2, 11/2, 13/2) transitions. The quantum efficiency of the (4)F(3/2) level is comparable to the typical values obtained for the Nd(2)O(3)-doped glasses. The decay properties for higher concentration of Nd(2)O(3) were analyzed using Inokuti-Hirayama model to investigate the non-radiative relaxation of the (4)F(3/2) emitting level. The experimental values of branching ratio and saturation intensity of (4)F(3/2)-->(4)I(11/2) transition and calculated spectroscopic quality factor indicate the favourable lasing action in these glasses. PMID:20570210

Rajeswari, R; Babu, S Surendra; Jayasankar, C K

2010-09-15

52

Characterization of water molecular state in in-vivo thick tissues using diffuse optical spectroscopic imaging  

NASA Astrophysics Data System (ADS)

Structural changes in water molecules are related to physiological, anatomical and pathological properties of tissues. Near infrared (NIR) optical absorption methods are sensitive to water; however, detailed characterization of water in thick tissues is difficult to achieve because subtle spectral shifts can be obscured by multiple light scattering. In the NIR, a water absorption peak is observed around 975 nm. The precise NIR peak's shape and position are highly sensitive to water molecular disposition. A bound water index (BWI) was developed that quantifies the spectral shift and shape changes observed in tissue water absorption spectra measured by broadband diffuse optical spectroscopic imaging (DOSI). DOSI quantitatively measures light absorption and scattering spectra in cm-deep tissues and therefore reveals bound water spectral shifts. BWI as a water state index was validated by comparing broadband DOSI to MRI and a conductivity cell using bound water phantoms. Non-invasive BWI measurements of malignant and normal tissues in 18 subjects showed a significantly higher fraction of free water in malignant tissues (p<0.0001) compared to normal tissues. BWI showed potential as a prognostic index based on high correlations with tumor grade and size. An algorithm for absolute temperature measurements in deep tissues was developed based on resolving opposing effects of water vibrational frequency shifts due to macromolecular binding. DOSI measures absolute temperature with a difference of 1.1+/-0.91°C from a thermistor. Deep tissue temperature measured in forearms during cold-stress was consistent with previously reported invasively-measured deep tissue temperature. Finally, the BWI was compared to Apparent Diffusion Coefficient (ADC) of diffusion weighted MRI in 9 breast cancer patients. The BWI and ADC correlated (R=0.8, p=<0.01) and both parameters decreased with increasing bulk water content in cancer tissues. Although BWI and ADC are positively correlated in vivo, BWI appears to be more sensitive to free water in the extracellular matrix while ADC reflects increased tumor cellularity. The relationship between ADC, BWI and bulk water concentration suggests that both parameters have potential for assessing tumor histopathological grade. My results confirm the importance of water as a critical tissue component that can potentially provide unique insight into the molecular pathophysiology of cancer.

Chung, So Hyun

53

Nanofluid optical property characterization: towards efficient direct absorption solar collectors  

PubMed Central

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

2011-01-01

54

Nanofluid optical property characterization: towards efficient direct absorption solar collectors.  

PubMed

Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 ?m). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ?10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

2011-01-01

55

Spectroscopic characterization of novel multilayer mirrors intended for astronomical and laboratory applications  

NASA Astrophysics Data System (ADS)

We report measurements of the reflection spectra of (i) concave (spherical and parabolic) Mo/Si, Mg/Si, and Al/Zr multilayer mirrors (MMs) intended for imaging solar spectroscopy in the framework of the TESIS/CORONAS-FOTON Satellite Project and of (ii) an aperiodic Mo/Si MM optimized for maximum uniform reflectivity in the 125-250 Å range intended for laboratory applications. The reflection spectra were measured in the configuration of a transmission grating spectrometer employing the radiation of a tungsten laser-driven plasma as the source. The function of detectors was fulfilled by backside-illuminated CCDs coated with Al or Zr/Si multilayer absorption filters. High-intensity second-order interference reflection peaks at wavelengths of about 160 Å were revealed in the reflection spectra of the 304-Å Mo/Si MMs. By contrast, the second-order reflection peak in the spectra of the new-generation narrow-band (~12 Å FWHM) 304-Å Mg/Si MMs is substantially depressed. Manifestations of the NEXAFS structure of the L2, 3 absorption edges of Al and Al2O3 were observed in the spectra recorded. The broadband Mo/Si MM was employed as the focusing element of spectrometers in experiments involving (i) the charge exchange of multiply charged ions with the donor atoms of a rare-gas jet; (ii) the spectroscopic characterization of a debris-free soft X-ray radiation source excited by Nd laser pulses in a Xe jet (iii) near-IR-to-soft-X-ray frequency conversion (double Doppler effect) occurring in the retroreflection from the relativistic electron plasma wake wave (flying mirror) driven by a multiterawatt laser in a pulsed helium jet.

Ragozin, Eugene N.; Mednikov, Konstantin N.; Pertsov, Andrei A.; Pirozhkov, Alexander S.; Reva, Anton A.; Shestov, Sergei V.; Ul'yanov, Artem S.; Vishnyakov, Eugene A.

2009-05-01

56

Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene  

PubMed Central

Photolysis (? > 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and ?-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm?1, |E/hc| = 0.0554 cm?1; |D/hc| = 0.579 cm?1, |E/hc| = 0.0315 cm?1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding ? orbital between sulfur and the neighboring carbon—an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (?max = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively). PMID:22463599

Pharr, Caroline R.; Kopff, Laura A.; Bennett, Brian; Reid, Scott A.; McMahon, Robert J.

2014-01-01

57

Characterization of vanadium, manganese and iron model clusters by vibrational and optical spectroscopic methods  

NASA Astrophysics Data System (ADS)

The active ferryl intermediates in the catalytic cycles of heme proteins are subject to interactions from the proximal and distal amino acid residues which control their activities and affect the ?(FeIVO) frequency. The effects of sixth axial ligation, hydrogen bonding, and solvent induced polarization on the resonance Raman (RR) spectra of the ferryl porphyrin analogs, vanadyl (VIVO) porphyrins and their ?-cation radicals, are characterized. ?(VIVO) stretching bands for (VO)TMPyP and (VO)PPIX are observed to be sensitive to the pH value of the aqueous solutions, and reveal a number of coexisting 5-coordinate (c) and 6- c vanadyl porphyrins in solution. Moreover, the ?(VIVO) bands for (VO)TMP and (VO)TPP porphyrins upshift to higher frequencies with the formation of their ?-cation radicals, in agreement with that of the (VO)OEP radical. For both a1u (OEP) and a2u (TPP, TMP) type radicals, an increased positive charge on the porphyrin reduces the porphyrin --> vanadium electron donation, but enhances the oxo --> V donation. The UV-Vis absorption and RR spectroscopic studies on a series of oxo-bridged vanadium(III) and manganese (III, IV) complexes established spectrostructural correlations that are useful as monitors of the structure of vanadium(III) and manganese(III, IV) centers in biological systems. The linear and bent V-O-V dimers display distinctive RR and absorption spectra. The linear V-O-V bridge displays an intense ?-O --> V charge transfer (CT) absorption band and a strongly enhanced symmetric (?s) or antisymmetric (?as) V-O-V stretching band in RR spectra, depending upon terminal ligands. In contrast, the bent bridge shows two ?-O --> V CT bands and both ?s and ?as V- O-V stretches are observed in RR spectra. These ?s and ?as vibrations are used to indicate that the vanadium(III) oxo-bridged dimer intercalates with DNA. The Mn-O-Mn vibrational frequencies in the 400-700 cm -1 region of the oxo-bridged manganese(III, IV) dimers, trimers, and tetramers are characterized and show dependence on the cluster geometry and manganese and oxygen modes of coordination. The Raman frequencies and intensities provide a good estimate of the ground and excited structural states and electronic dynamics mediated by the oxo-bridges.

Ji, Wenbin

1999-12-01

58

X-ray diffraction and absorption spectroscopic studies of copper mixed ligand complexes with aminophenol as one of the ligands  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been conducted on two copper complexes, i.e., copper macrocyclic complex of succinic acid and ortho aminophenol (complex-1) and copper macrocyclic complex of pthalic acid and ortho aminophenol (complex-2). The diffraction pattern of the complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with rotating anode X-ray tube operated at 40 kV and 100 mA. The X-ray absorption spectra of the complexes have been recorded at the K-edge of copper on Cauchois type bent crystal spectrograph having radius 0.4 m employing a mica crystal, oriented to reflect from (100) planes, for dispersion. The X-ray absorption near edge structure (XANES) parameters, viz., chemical shift, energy position of the principal absorption maximum and edge-width have been determined and discussed. From the extended X-ray absorption fine structure (EXAFS) data, the bond lengths have been calculated using three methods, namely, Levy's method, Lytle, Sayers and Stern's (LSS) method and Fourier transformation method. The results obtained have been compared with each other and discussed.

Mishra, A.; Jain, Garima; Patil, H.

2012-05-01

59

X-ray absorption fine structure spectroscopic study of uranium nitrides  

SciTech Connect

Uranium mononitride (UN), sesquinitride (U2N3) and dinitride (UN2) were characterized by extended X-Ray absorption fine structure spectroscopy. Analysis on UN indicate the presence of three uranium shells at distances of 3.46(3), 4.89(5) and 6.01(6) A and a nitrogen shell at a distance of 2.46(2) A . For U2N3, two absorbing uranium atoms at different crystallographic positions are present in the structure. One of the uranium atoms is surrounded by nitrogen atoms at 2.28(2) A and by uranium atoms at 3.66(4) and 3.95(4) A . The second type of uranium atom is surrounded by nitrogen atoms at 2.33(2) and 2.64(3) A and by uranium atoms at 3.66(4), 3.95(4) and 5.31(5) A . Results on UN2 indicate two uranium shells at 3.71(4) and 5.32(5) A and two nitrogen shells at 2.28(2).

Poineau, Frederic [University of Nevada, Las Vegas; Yeamans, Charles B. [University of California, Berkeley; Cerefice, Gary S. [University of Nevada, Las Vegas; Sattelberger, Alfred P [Argonne National Laboratory (ANL); Czerwinski, Ken R. [University of Nevada, Las Vegas

2012-01-01

60

Characterization of the energy-dependent response of riometer absorption  

NASA Astrophysics Data System (ADS)

Ground-based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth's ionosphere. The energy-dependent relationship between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth's magnetosphere. In this study, statistical and event-based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time-lagged correlation analysis of trapped to precipitating fluxes shows that daily averaged absorption best correlates with ˜60 keV trapped electron flux at zero-time lag, although large variability is observed across different phases of the solar cycle. High-time resolution statistical cross-correlation analysis between signatures observed by riometer stations, and assuming electron motion due to gradient and curvature drift, results in inferred energies of 10-100 keV, with a clear maximum in occurrence for 40-60 keV electrons. One event is considered in detail utilizing riometer absorption signatures obtained from several stations. The mean inferred energies for the initial rise time and peak of the absorption after correction for electric field effects were ˜70 keV and ˜60 keV, respectively. The analyses presented provide a means to characterize the energy of electrons to which riometers are responding in both a statistical sense and during the evolution of individual events.

Kellerman, A. C.; Shprits, Y. Y.; Makarevich, R. A.; Spanswick, E.; Donovan, E.; Reeves, G.

2015-01-01

61

Raman spectroscopic characterization and differentiation of seminal plasma  

NASA Astrophysics Data System (ADS)

Raman spectroscopy (RS) was applied for the analysis of seminal plasma in order to detect spectral parameters, which might be used for differentiating the normal and abnormal semen samples. Raman spectra of seminal plasma separated from normal and abnormal semen samples, showed a distinct difference in peak ratios between 1449 and 1418 cm-1 (P < 0.05). More efficient alternative method of using principal component analysis-linear discriminate analysis based on Raman spectroscopic data yielded a diagnostic sensitivity of 73% and specificity of 82%. The results suggest that RS combined with the multivariate analysis method has the potential for differentiating semen samples by examination of the corresponding seminal plasma.

Huang, Zufang; Chen, Xiwen; Chen, Yanping; Chen, Jinhua; Dou, Min; Feng, Shangyuan; Zeng, Haishan; Chen, Rong

2011-11-01

62

Spectroscopic Characterization and Detection of Ethyl Mercaptan in Orion  

NASA Astrophysics Data System (ADS)

New laboratory data of ethyl mercaptan, CH3CH2SH, in the millimeter- and submillimeter-wave domains (up to 880 GHz) provided very precise values of the spectroscopic constants that allowed the detection of gauche-CH3CH2SH toward Orion KL. This identification is supported by 77 unblended or slightly blended lines plus no missing transitions in the range 80-280 GHz. A detection of methyl mercaptan, CH3SH, in the spectral survey of Orion KL is reported as well. Our column density results indicate that methyl mercaptan is sime 5 times more abundant than ethyl mercaptan in the hot core of Orion KL. This work was based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Kolesniková, L.; Tercero, B.; Cernicharo, J.; Alonso, J. L.; Daly, A. M.; Gordon, B. P.; Shipman, S. T.

2014-03-01

63

Spectroscopic characterization of laser-induced tin plasma S. S. Harilal,a  

E-print Network

efficiency. Laser-induced plasma LIP tech- niques are also used in space applications such as in chemi- cal as in the detection of bio- logical molecules.3,4 Other important applications of LIP in- clude pulsed laserSpectroscopic characterization of laser-induced tin plasma S. S. Harilal,a Beau O'Shay, and Mark. S

Harilal, S. S.

64

Absorption spectroscopic probe to investigate the interaction between Nd(III) and calf-thymus DNA  

Microsoft Academic Search

The interaction between Nd(III) and Calf Thymus DNA (CT-DNA) in physiological buffer (pH 7.4) has been studied using absorption spectroscopy involving 4f–4f transition spectra in different aquated organic solvents. Complexation with CT-DNA is indicated by the changes in absorption intensity following the subsequent changes in the oscillator strengths of different 4f–4f bands and Judd–Ofelt intensity (T?) parameters. The other spectral

Ch. Victory Devi; N. Rajmuhon Singh

2011-01-01

65

Impedance spectroscopic characterization of gadolinium substituted cobalt ferrite ceramics  

SciTech Connect

Gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2?x}Gd{sub x}O{sub 4}, referred to CFGO) with variable Gd content (x?=?0.0–0.4) have been synthesized by solid state ceramic method. The crystal structure and impedance properties of CFGO compounds have been evaluated. X-ray diffraction measurements indicate that CFGO crystallize in the inverse spinel phase. The CFGO compounds exhibit lattice expansion due to substitution of larger Gd ions into the crystal lattice. Impedance spectroscopy analysis was performed under a wide range of frequency (f?=?20?Hz–1?MHz) and temperature (T?=?303–573?K). Electrical properties of Gd incorporated Co ferrite ceramics are enhanced compared to pure CoFe{sub 2}O{sub 4} due to the lattice distortion. Impedance spectroscopic analysis illustrates the variation of bulk grain and grain-boundary contributions towards the electrical resistance and capacitance of CFGO materials with temperature. A two-layer heterogeneous model consisting of moderately conducting grain interior (ferrite-phase) regions separated by insulating grain boundaries (resistive-phase) accurately account for the observed temperature and frequency dependent electrical characteristic of CFGO ceramics.

Rahman, Md. T., E-mail: mrahman5@miners.utep.edu; Ramana, C. V. [Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2014-10-28

66

Vibrational spectroscopic characterization of wild growing mushrooms and toadstools  

NASA Astrophysics Data System (ADS)

Recently, there has been increase of general interest in fungi because of the possible medical applications of their polysaccharide constituents called glucans, some of which are reported to have immunomodulatory properties. Since an extraction method can change the chemical composition of a substance, especially a delicate one such as fungal thallus, it is necessary and useful to know more about the studied matter in advance in order to choose the chemical procedure properly. We demonstrated the usefulness of vibrational spectroscopy in identifying different glucan types in various parts of intact fruiting bodies of Asco- and Basidiomycetes. Fourier transform-infrared (FT-IR) spectroscopy was used for obtaining vibrational spectra of spores and fruiting bodies of more than 70 species belonging to 37 different genera of wild growing mushrooms. The list of the bands in 750-950 cm -1 interval, assigned to ?- and ?-glucans, is provided for all species studied. Vibrational spectra in the interval 1000-1200 cm -1 could serve as an indicator of mushroom genus, although particular species cannot be identified spectroscopically. Great similarities in spectra of spores of the same genus, but different species, e.g. Tricholoma album and Trichloma sulphureum, were observed. On the other hand, spectra of cap, stalk and spores of the same mushroom show great differences, indicating variety in the chemical composition of different parts of the same fruiting body.

Moha?ek-Grošev, Vlasta; Božac, Romano; Puppels, Gerwin J.

2001-12-01

67

Impedance spectroscopic characterization of gadolinium substituted cobalt ferrite ceramics  

NASA Astrophysics Data System (ADS)

Gadolinium (Gd) substituted cobalt ferrites (CoFe2-xGdxO4, referred to CFGO) with variable Gd content (x = 0.0-0.4) have been synthesized by solid state ceramic method. The crystal structure and impedance properties of CFGO compounds have been evaluated. X-ray diffraction measurements indicate that CFGO crystallize in the inverse spinel phase. The CFGO compounds exhibit lattice expansion due to substitution of larger Gd ions into the crystal lattice. Impedance spectroscopy analysis was performed under a wide range of frequency (f = 20 Hz-1 MHz) and temperature (T = 303-573 K). Electrical properties of Gd incorporated Co ferrite ceramics are enhanced compared to pure CoFe2O4 due to the lattice distortion. Impedance spectroscopic analysis illustrates the variation of bulk grain and grain-boundary contributions towards the electrical resistance and capacitance of CFGO materials with temperature. A two-layer heterogeneous model consisting of moderately conducting grain interior (ferrite-phase) regions separated by insulating grain boundaries (resistive-phase) accurately account for the observed temperature and frequency dependent electrical characteristic of CFGO ceramics.

Rahman, Md. T.; Ramana, C. V.

2014-10-01

68

Photomask CD and LER characterization using Mueller matrix spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Critical dimension and line edge roughness on photomask arrays are determined with Mueller matrix spectroscopic ellipsometry. Arrays with large sinusoidal perturbations are measured for different azimuth angels and compared with simulations based on rigorous coupled wave analysis. Experiment and simulation show that line edge roughness leads to characteristic changes in the different Mueller matrix elements. The influence of line edge roughness is interpreted as an increase of isotropic character of the sample. The changes in the Mueller matrix elements are very similar when the arrays are statistically perturbed with rms roughness values in the nanometer range suggesting that the results on the sinusoidal test structures are also relevant for "real" mask errors. Critical dimension errors and line edge roughness have similar impact on the SE MM measurement. To distinguish between both deviations, a strategy based on the calculation of sensitivities and correlation coefficients for all Mueller matrix elements is shown. The Mueller matrix elements M13/M31 and M34/M43 are the most suitable elements due to their high sensitivities to critical dimension errors and line edge roughness and, at the same time, to a low correlation coefficient between both influences. From the simulated sensitivities, it is estimated that the measurement accuracy has to be in the order of 0.01 and 0.001 for the detection of 1 nm critical dimension error and 1 nm line edge roughness, respectively.

Heinrich, A.; Dirnstorfer, I.; Bischoff, J.; Meiner, K.; Ketelsen, H.; Richter, U.; Mikolajick, T.

2014-10-01

69

Accurate Spectroscopic Characterization of Protonated Oxirane: A Potential Prebiotic Species in Titan's Atmosphere  

NASA Astrophysics Data System (ADS)

An accurate spectroscopic characterization of protonated oxirane has been carried out by means of state-of-the-art computational methods and approaches. The calculated spectroscopic parameters from our recent computational investigation of oxirane together with the corresponding experimental data available were used to assess the accuracy of our predicted rotational and IR spectra of protonated oxirane. We found an accuracy of about 10 cm-1 for vibrational transitions (fundamentals as well as overtones and combination bands) and, in relative terms, of 0.1% for rotational transitions. We are therefore confident that the spectroscopic data provided herein are a valuable support for the detection of protonated oxirane not only in Titan's atmosphere but also in the interstellar medium.

Puzzarini, Cristina; Ali, Ashraf; Biczysko, Malgorzata; Barone, Vincenzo

2014-09-01

70

Spectroscopic characterization of monometallic and bimetallic model catalysts  

E-print Network

is the characterization of the surface composition, morphology, and electronic/geometric structure of the following catalysts: Au/TiOx, Au-Pd/Mo(110), Au- Pd/SiO2, Cu-Pd/Mo(110), and Sn/Pd(100). Structure-reactivity correlations during surface-alloy formation...

Luo, Kai

2009-06-02

71

Spectroscopic Characterization of Mineralogy Across Vesta: Evidence of Different Lithologies  

NASA Technical Reports Server (NTRS)

The average spectrum of Vesta, obtained by VIR in the range 0.25-5.1 microns, shows clear evidence of absorption bands due to pyroxenes and thermal emissions beyond 3.5 11m. Vesta shows considerable variability across its surface in terms of spectral reflectance and emission, band depths, bands widths and bands centers, reflecting a complex geological history. Vesta's average spectrum and inferred mineralogy resemble those of howardite meteorites. On a regional scale, significant deviations are seen: the south polar 500km Rheasilvia impact crater has a higher diogenitic component, and equatorial regions show a higher eucritic component. This lithologic distribution, with a concentration of Mg-pyroxenes in the Rheasilvia area, reinforces the hypothesis of a deeper diogenitic crust excavated by the impact that formed the Rheasilvia crater, and an upper eucritic crust, whose remnants are seen in the equatorial region. This scenario has implications for Vesta differentiation, consistent with magma ocean models. However, serial magmatism models could also have concentrated pyroxene cumulates in plutons emplaced within the lower crust,

De Sanotis, M. C.; Ammannito, E.; Filacchione, G.; Capria, M. T.; Tosi, F.; Capaccioni, F.; Zambon, F.; Carraro, F.; Fonte, S.; Frigeri, A.; Jaumann, R.; Magni, G.; Marchi, S.; McCord, T. B.; McFadden, L. A.; McSween, H. Y.; Mittlefehldt, D. W.; Nathues, A.; Palomba, E.; Pieters, C. M.; Raymond, C. A.; Russell, C. T.; Turrini, D.

2012-01-01

72

Single-Molecule Spectroscopic Characterization of Light-Harvesting 2 Complexes Reconstituted into Model Membranes  

PubMed Central

The spectroscopic properties of the light-harvesting 2 complexes (LH2) from the purple bacterium Rhodopseudomonas acidophila (strain 10050) in detergent micelles and reconstituted into lipid membranes have been studied by single-molecule spectroscopy. When LH2 complexes are solubilized from their host biological membranes by nondenaturing detergents, such as LDAO, there is a small 2-nm spectral shift of the B850 absorption band in the ensemble spectrum. This is reversed when the LH2 complexes are put back into phospholipid vesicles, i.e., into a more native-like environment. The spectroscopic properties on the single-molecule level of the detergent-solubilized LH2 complexes were compared with those reconstituted into the lipid membranes to see if their detailed spectroscopic behavior was influenced by these small changes in the position of the B850 absorption band. A detailed analysis of the low-temperature single-molecule fluorescence-excitation spectra of the LH2 complexes in these two different conditions showed no significant differences. In particular, the distribution of the spectral splitting between the circular k = ±1 exciton states of the B850 absorption band and the distribution of the mutual angle between the k = ±1 exciton states are identical in both cases. It can be concluded, therefore, that the LH2 complexes from Rps. acidophila are equally stable when solubilized in detergent micelles as they are when membrane reconstituted. Moreover, when they are solubilized in a suitable detergent and spin coated onto a surface for the single-molecule experiments they do not display any more structural disorder than when in a phospholipid membrane. PMID:17416626

Richter, Martin F.; Baier, Jürgen; Cogdell, Richard J.; Köhler, Jürgen; Oellerich, Silke

2007-01-01

73

X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes  

SciTech Connect

Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s{yields}3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

Westre, T.E.

1996-01-01

74

Spectroscopic investigation of amber color silicate glasses and factors affecting the amber related absorption bands.  

PubMed

The effects of carbon, Fe2O3 and Na2SO4 contents on the amber color of glass with composition (wt%) 64.3 SiO2, 25.7 CaO, 10 Na2O were studied. The effect of some additives that could be found in glass batch or cullets on the amber related absorption band(s) was also studied. An amber related absorption band due to the chromophore Fe(3+)O3S(2-) was recorded at 420nm with shoulder at 440nm. A second amber related band recorded at 474nm with shoulder at 483nm was assigned to FeS. Increasing melting time at 1400°C up to 6h caused fainting of the amber color, decreases the intensities of the amber related bands and shifted the first band to 406nm. Addition of ZnO, Cu2O and NaNO3 to the glass produced decolorizing effect and vanishing of the amber related bands. The effects of melting time and these additives were explained on the bases of destruction the amber chromophore and its conversion into Fe(3+) in tetrahedral sites or ZnS. Addition of Se intensifies the amber related bands and may cause dark coloration due to the formation of Se° and polyselenide. Amber color can be monitored through measuring the absorption in the range 406-420nm. PMID:25795612

Morsi, Morsi M; El-Sherbiny, Samya I; Mohamed, Karam M

2015-06-15

75

Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments of a Brazilian subtropical microbasin  

E-print Network

;2 Abstract Humic substances (HS) perform a fundamental role in aquatic environments, exhibiting different and spectroscopic analyses. insu-00508976,version1-10Aug2010 #12;3 1. Introduction Humic substances (HS1 Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments

Paris-Sud XI, Université de

76

Resonance Raman spectroscopic characterization of compound III of lignin peroxidase  

SciTech Connect

Resonance Raman (RR) spectra of several compounds III of lignin peroxidase (LiP) have been measured at 90 K with Soret and visible excitation wavelengths. The samples include LiPIIIa (or oxyLiP) prepared by oxygenation of the ferrous enzyme, LiPIIIb generated by reaction of the native ferric enzyme with superoxide, LiPIIIc prepared from native LiP plus H{sub 2}O{sub 2} followed by removal of excess peroxide with catalase, and LiPIII made by addition of excess H{sub 2}O{sub 2} to the native enzyme. The RR spectra of these four products appear to be similar and, thus, indicate that the environments of these hexacoordinate, low-spin ferriheme species must also be very similar. Nonetheless, the Soret absorption band of LiPIII is red-shifted by 5 nm from the 414-nm maximum common to LiPIIIa, -b, and -c. Analysis of the iron-porphyrin vibrational frequencies indicates that the electronic structures for the various compounds III are consistent with an Fe{sup III}O{sub 2}{sup {center dot}-}formulation. The spectral changes observed between the oxygenated complex and the ferrous heme of lignin peroxidase are similar to those between oxymyoglobin and deoxymyoglobin. The contraction in the core sizes in compound III relative to the native peroxidase is analyzed and compared with that of other heme systems. The Fe-O{sub 2} stretching vibration of the oxygenated peroxidase is observed at 563 cm{sup {minus}1} and shifts of 538 cm{sup {minus}1} with {sup 18}O isotope. The Fe-histidine stretching vibration is observed at 245 cm{sup {minus}1} in ferrous peroxidase and appears to shift to 276 cm{sup {minus}1} in the oxygenated complex.

Mylrajan, M.; Valli, K.; Wariishi, Gold, M.H.; Loehr, T.M. (Oregon Graduate Institute of Science and Technology, Beaverton (USA))

1990-10-01

77

FTIR Spectroscopic Characterization Of II-VI Semiconductors  

NASA Technical Reports Server (NTRS)

Combination of commercial Fourier-transform infrared (FTIR) spectrometer with computer and special-purpose software constitutes highly automated facility for acquisition and processing of infrared transmission or reflection spectral image data. Intended principally to acquire transmission spectra of some compounds of elements in groups II and VI of periodic table. System used to characterize specimens of II/VI alloy semiconductors grown by directional solidification and quenching. Transmission-edge maps helpful in studies of flows, gradients of temperature, and coefficients of diffusion in solidifying melts. Data acquired by system include optical characteristics, and they both verify and complement data obtained by such other techniques as measurements of density and x-ray-dispersion analysis.

Perry, G. L. E.; Szofran, F. R.

1991-01-01

78

Thermal sintering of solution-deposited nanoparticle silver ink films characterized by spectroscopic ellipsometry  

Microsoft Academic Search

Low-temperature sintering of metal nanoparticle inks is a promising technique in realizing large area and flexible electronics. It is demonstrated in this letter that spectroscopic ellipsometry in the spectral region of 0.75-3.5 eV can be employed to characterize the sintering process manifested by the evolution of film thickness, effective dielectric function, and percolation transition. A two-oscillator model can be used

Heng Pan; Seung H. Ko; Costas P. Grigoropoulos

2008-01-01

79

Thermal sintering of solution-deposited nanoparticle silver ink films characterized by spectroscopic ellipsometry  

Microsoft Academic Search

Low-temperature sintering of metal nanoparticle inks is a promising technique in realizing large area and flexible electronics. It is demonstrated in this letter that spectroscopic ellipsometry in the spectral region of 0.75–3.5 eV can be employed to characterize the sintering process manifested by the evolution of film thickness, effective dielectric function, and percolation transition. A two-oscillator model can be used

Heng Pan; Seung H. Ko; Costas P. Grigoropoulos

2008-01-01

80

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL  

E-print Network

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL Ido Ben in the absorption profile of a medium containing system atoms. Moreover, the change leads to a very narrow spectra: the VCSEL output and the absorption. Two modulation side bands, separated by fhfs owe to coincide

Eisenstein, Gadi

81

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone. The optimizations of various experimental conditions were described. Optimum concentration ranges for the determination of GTF, MXF and SPF were 5.0-150, 40-440 ?g mL -1 and 0.10-1.5 mg mL -1 using atomic absorption (AAS), conductometric and colorimetric methods, respectively. Detection and quantification limits are ranges from 1.5 to 2.3 ?g mL -1 using AAS method or 30-45 ?g mL -1 using colorimetric method. The proposed procedures have been applied successfully to the analysis of these drugs in pharmaceutical formulations and the results are favourably comparable to the reference methods.

Al-Ghannam, Sheikha M.

2008-04-01

82

Flash spectroscopic characterization of photosynthetic electron transport in isolated heterocysts  

SciTech Connect

Electron transport was studied in heterocysts of the filamentous cyanobacterium Anabaena 7120 using spectral and kinetic analysis of absorbance transients elicited by single turnover flashes. Consistent photosynthetic turnovers were observed only in the presence of an exogenous source of reductant; therefore measurements were routinely made under a gas phase containing H2. Prominent absorbance changes corresponding to the oxidation of cytochrome c (554 nm) and the reduction of cytochrome b563 (563 nm) were observed. Under the most reducing conditions (99% H2/1% O2) cytochrome b563 was partially reduced between flashes in a slow, dark reaction. At 10-15% O2, the slow, dark reduction of cytochrome b563 was eliminated. Cytochrome turnover ceased entirely at high O2 concentrations (30%) but was restored by the addition of 25 microM KCN, demonstrating an interaction between the photosynthetic and respiratory electron transfer chains. Strobilurin A slowed the re-reduction of cytochrome c and eliminated the appearance of reduced cytochrome b563 by blocking electron transfer between reduced plastoquinone and the cytochrome b/f complex. Inhibition at a second site was apparent with 2-(n-heptyl)-4-hydroxyquinoline N-oxide, which blocked the reoxidation of cytochrome b563 but had little effect on cytochrome c relaxation. In uncoupled heterocysts, the rates of cytochrome c re-reduction and cytochrome b563 reduction were equal. Additional unassigned absorbance changes at 475 nm, 515 nm, and 572 nm were partially characterized. No absorbance change corresponding to an electrochromic shift was observed.

Houchins, J.P.; Hind, G.

1983-07-01

83

Synthesis and spectroscopic characterization of copper zinc aluminum nanoferrite particles.  

PubMed

Copper doped zinc aluminum ferrites CuxZn1-x.(AlxFe2-x)O4 are synthesized by the solid-state reaction route and characterized by XRD, TEM, EPR and non linear optical spectroscopy techniques. The average particle size is found to be from 35 to 90nm and the unit cell parameter "a" is calculated as from 8.39 to 8.89Å. The cation distributions are estimated from X-ray diffraction intensities of various planes. The XRD studies have verified the quality of the synthesis of compounds and have shown the differences in the positions of the diffraction peaks due to the change in concentration of copper ions. TEM pictures clearly indicating that fundamental unit is composed of octahedral and tetrahedral blocks and joined strongly. The selected area electron diffraction (SAED) of the ferrite system shows best crystallinity is obtained when Cu content is very. Some of the d-plane spacings are exactly coinciding with XRD values. EPR spectra is compositional dependent at lower Al/Cu concentration EPR spectra is due to Fe(3+) and at a higher content of Al/Cu the EPR spectra is due to Cu(2+). Absence of EPR spectra at room temperature indicates that the sample is perfectly ferromagnetic. EPR results at low temperature indicate that the sample is paramagnetic, and that copper is placed in the tetragonal elongation (B) site with magnetically non-equivalent ions in the unit cell having strong exchange coupling between them. This property is useful in industrial applications. Nonlinear optical properties of the samples studied using 5ns laser pulses at 532nm employing the open aperture z-scan technique indicate that these ferrites are potential candidates for optical limiting applications. PMID:24632431

Lakshmi Reddy, S; Ravindra Reddy, T; Roy, Nivya; Philip, Reji; Montero, Ovidio Almanza; Endo, Tamio; Frost, Ray L

2014-06-01

84

Spectroscopic characterization of triplet forming states in photosystem II.  

PubMed

Fluorescence and electron paramagnetic resonance (EPR) measurements have been applied to characterize chlorophyll triplet formation in the reaction center of photosystem II (PSII). A highly triplet forming state was generated in PSII membranes by chemical double reduction of the primary electron acceptor QA. In triplet forming PSII centers, the steady-state yield of chlorophyll fluorescence decreased to about 70% of the maximal fluorescence yield observed in closed PSII centers in which QA is singly reduced. The results are well interpreted in the framework of a model where the charge state of QA electrostatically controls the yield of primary charge separation [Schatz, G. H., Brock, H., & Holzwarth, A. R. (1988) Biophys. J. 54, 397-405]. Thus, high triplet yield and decreased, although still quite high, fluorescence indicate a charge-neutralized state of PSII in which QA is singly or doubly reduced and protonated or absent. The EPR signal of the triplet primary chlorophyll donor, 3P680, is suppressed by illumination at 77 K concomitant with the formation of a cationic radical (g = 2.0025-2.0027, and 0.92 mT wide) that is stable in the dark. This is attributed to the oxidation of an accessory chlorophyll (Chl) in the vicinity of P680. Electrostatic repulsion between Chl+ and P680+ is likely to prevent primary charge separation, and in turn triplet formation, providing a further example of electrostatic control of primary charge separation. The triplet P680 EPR signal is also suppressed in the presence of oxygen. This effect, which is almost completely reversible by removing the oxygen, is attributed to the interaction of triplet P680 with triplet O2. PMID:1320926

Vass, I; Styring, S

1992-07-01

85

Spectroscopic and Functional Characterization of Iron-Bound Forms of Azotobacter vinelandiiNifIscA†  

PubMed Central

The ability of Azotobacter vinelandii NifIscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. NifIscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, CD and VTMCD, EPR, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5cm?1) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm?1) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound NifIscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ±15 mV at pH 7.8 (versus NHE). L-cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of NifIscA. Fe(III)-bound NifIscA was also shown to a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results. PMID:23003563

Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

2012-01-01

86

In Situ Polarization Modulation Infrared Reflection Absorption Spectroscopic and Kinetic Investigations of Heterogeneous Catalytic Reactions  

E-print Network

below the temperature previously reported. Characterizations of highly catalytically active Au films have also been carried out. Electronic and chemical properties of (1 x 1)- and (1 x 3)-Au/TiOx/Mo(112) films are investigated by PM-IRAS using CO as a...

Cai, Yun

2010-01-14

87

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF; )

2002-09-26

88

Spectrum of excess partial molar absorptivity. I. Near infrared spectroscopic study of aqueous acetonitrile and acetone.  

PubMed

We study the mixing schemes or the molecular processes occurring in aqueous acetonitrile (ACN) and acetone (ACT) by near-infrared spectroscopy (NIR). Both solutions (any other aqueous solutions) are not free from strong and complex intermolecular interactions. To tackle such a many-body problem, we first use the concept of the excess molar absorptivity, epsilonE, which is a function of solute mole fraction in addition to that of wavenumber, nu. The plots of epsilonE calculated from NIR spectra for both aqueous solutions against nu showed two clearly separated bands at 5020 and 5230 cm(-1); the former showed negative and the latter positive peaks. At zero and unity mole fractions of solute, epsilonE is identically zero independent of nu. Similar to the thermodynamic excess functions, both negative and positive bands grow in size from zero to the minimum (or the maximum) and back to zero, as the mole fraction varies from 0 to 1. Since the negative band's nu-locus coincides with the NIR spectrum of ice, and the positive with that of liquid H(2)O, we suggest that on addition of solute the "ice-likeness" decreases and the "liquid-likeness" increases, reminiscent of the two-mixture model for liquid H(2)O. The modes of these variations, however, are qualitatively different between ACN-H(2)O and ACT-H(2)O. The former ACN is known to act as a hydrophobe and ACT as a hydrophile from our previous thermodynamic studies. To see the difference more clearly, we introduced and calculated the excess partial molar absorptivity of ACN and ACT, epsilon(E)(N) and epsilon(E)(T), respectively. The mole fraction dependences of epsilon(E)(N) and epsilon(E)(T) show qualitatively different behavior and are consistent with the detailed mixing schemes elucidated by our earlier differential thermodynamic studies. Furthermore, we found in the H(2)O-rich region that the effect of hydrophobic ACN is acted on the negative band at 5020 cm(-1), while that of hydrophilic ACT is on the positive high-energy band. Thus, the present method of analysis adds more detailed insight into the difference between a hydrophobe and a hydrophile in their effects on H(2)O. PMID:19678652

Koga, Yoshikata; Sebe, Fumie; Minami, Takamasa; Otake, Keiko; Saitow, Ken-ichi; Nishikawa, Keiko

2009-09-01

89

X-ray absorption spectroscopic studies on novel microporous copper containing catalytic systems  

Microsoft Academic Search

Novel copper metal modified microporous aluminosilicate and aluminophosphate catalysts with the high phase purity were synthesized and characterized. CuK-edge XAS measurements were carried out over a series of copper containing SAPO-34 and ZSM-5 catalysts. EXAFS technique was used to obtain specific climacteric information related to the copper atomic distances, coordination and near neighbour environments. EXAFS studies indicated the presence of

Suresh K. Bhargava; Deepak B. Akolekar; Garry Foran

2006-01-01

90

Spectroscopic characterization approach to study surfactants effect on ZnO 2 nanoparticles synthesis by laser ablation process  

NASA Astrophysics Data System (ADS)

Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H 2O 2. The effect of surfactants on the optical and structure of ZnO 2 was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H 2O 2, and H 2O 2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO 2 nanoparticles prepared with and without surfactants show a characteristic ZnO 2 absorption at 435-445 cm -1. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm -1.

Drmosh, Q. A.; Gondal, M. A.; Yamani, Z. H.; Saleh, T. A.

2010-05-01

91

Spectroscopic characterization of both aqueous and solid-state diacerhein/hydroxypropyl-?-cyclodextrin inclusion complexes  

NASA Astrophysics Data System (ADS)

Diacerhein, a poorly water soluble antirheumatic prodrug, was spectroscopically characterized to form inclusion complexes with hydroxypropyl-?-cyclodextrin (HP?CD) in both aqueous solution and in solid phase. Complexation with the hydrophilic carriers was used to improve the solubility and dissolution rate of the compound. The kinetics of the prodrug degradation to the active rhein in aqueous buffer solution were also investigated as a function of HP?CD concentration. The solid complexes prepared by different methods such as physical mixture, kneading, co-evaporation method and freeze dried method in 1:1 M ratio, were characterized by DSC and FTIR. The dissolution profiles of solid complexes were determined and compared with diacerhein alone and their physical mixture, in the simulated intestinal fluid at 37 °C. The accurate molecular spectroscopic characterization of diacerhein in the presence of different amounts of aqueous cyclodextrins was essential to determine the correct binding constants for the diacerhein/HP?CD system. The binding constants were also validated by UV spectrometry and HPLC procedure in order to compare the values from the different methods. Higuchi-Connors phase solubility method has proved not suitable when either the free or/and the complexed prodrug degrade in aqueous solution.

Petralito, Stefania; Zanardi, Iacopo; Spera, Romina; Memoli, Adriana; Travagli, Valter

2014-06-01

92

Spectroscopic characterization of both aqueous and solid-state diacerhein/hydroxypropyl-?-cyclodextrin inclusion complexes.  

PubMed

Diacerhein, a poorly water soluble antirheumatic prodrug, was spectroscopically characterized to form inclusion complexes with hydroxypropyl-?-cyclodextrin (HP?CD) in both aqueous solution and in solid phase. Complexation with the hydrophilic carriers was used to improve the solubility and dissolution rate of the compound. The kinetics of the prodrug degradation to the active rhein in aqueous buffer solution were also investigated as a function of HP?CD concentration. The solid complexes prepared by different methods such as physical mixture, kneading, co-evaporation method and freeze dried method in 1:1M ratio, were characterized by DSC and FTIR. The dissolution profiles of solid complexes were determined and compared with diacerhein alone and their physical mixture, in the simulated intestinal fluid at 37°C. The accurate molecular spectroscopic characterization of diacerhein in the presence of different amounts of aqueous cyclodextrins was essential to determine the correct binding constants for the diacerhein/HP?CD system. The binding constants were also validated by UV spectrometry and HPLC procedure in order to compare the values from the different methods. Higuchi-Connors phase solubility method has proved not suitable when either the free or/and the complexed prodrug degrade in aqueous solution. PMID:24632430

Petralito, Stefania; Zanardi, Iacopo; Spera, Romina; Memoli, Adriana; Travagli, Valter

2014-06-01

93

Processing of High Level Waste: Spectroscopic Characterization of Redox Reactions in Supercritical Water - Final Report  

SciTech Connect

Current efforts are focused on the oxidative dissolution of chromium compounds found in Hanford tank waste sludge. Samples of chromium oxides and hydroxides with varying degrees of hydration are being characterized using Raman, FTIR, and XPS spectroscopic techniques. Kinetics of oxidation reactions at subcritical and supercritical temperatures are being followed by Raman spectroscopy using a high temperature stainless steel cell with diamond windows. In these reactions both hydrogen peroxide and nitrate anions are used as the oxidizing species with Cr(III) compounds and organic compounds as reducing agents.

Arrington Jr., C. A.

2000-11-15

94

Replacement of the axial histidine heme ligand with cysteine in nitrophorin 1: spectroscopic and crystallographic characterization  

Microsoft Academic Search

To evaluate the potential of using heme-containing lipocalin nitrophorin 1 (NP1) as a template for protein engineering, we\\u000a have replaced the native axial heme-coordinating histidine residue with glycine, alanine, and cysteine. We report here the\\u000a characterization of the cysteine mutant H60C_NP1 by spectroscopic and crystallographic methods. The UV\\/vis, resonance Raman,\\u000a and magnetic circular dichroism spectra suggest weak thiolate coordination of

Stefan W. Vetter; Andrew C. Terentis; Robert L. Osborne; John H. Dawson; David B. Goodin

2009-01-01

95

Direct spectroscopic characterization of aqueous actinyl(VI) species: a comparative study of Np and U.  

PubMed

The hydrolysis reactions of Np(VI) were investigated under an ambient atmosphere by attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy, NIR absorption spectroscopy, and speciation modeling applying the updated NEA thermodynamic database. For the first time, spectroscopic results of Np(VI) hydrolysis reactions are provided in the submillimolar concentration range and at pH values up to 5.3. The calculated speciation pattern and the results from FT-IR spectroscopy are comparatively discussed with results obtained from the U(VI) system under identical conditions. For both actinides, the formation of similar species can be derived from infrared spectroscopic results at pH values < or = 4, namely, the free cation AnO(2)(2+) (An = U, Np) and monomeric hydrolysis products. At higher pH, the infrared spectra evidence structurally different species contributing to the speciation of both actinides. At pH 5, the formation of a carbonate-containing dimeric complex, that is, (NpO(2))(2)CO(3)(OH)(3)(-), probably occurs during the hydrolysis reactions of neptunium, which is supported by the calculated speciation and results from NIR spectroscopy. For uranium, the presence of additional hydroxo complexes is assumed in this pH range. However, an unequivocal assignment of the spectral features to distinct species remains difficult. In particular, in the concentration range (0.5 mM) that constitutes the lower limit for the spectroscopic investigations of Np(VI) in the present work, monomeric and polymeric species obviously contribute to the U(VI) speciation considerably increasing the complexity of the spectral data. PMID:19514785

Müller, Katharina; Foerstendorf, Harald; Tsushima, Satoru; Brendler, Vinzenz; Bernhard, Gert

2009-06-18

96

Spectroscopic characterization of biological agents using FTIR, normal Raman and surface-enhanced Raman spectroscopies  

NASA Astrophysics Data System (ADS)

FTIR, Raman spectroscopy and Surface Enhanced Raman Scattering (SERS) requires a minimum of sample allows fast identification of microorganisms. The use of this technique for characterizing the spectroscopic signatures of these agents and their stimulants has recently gained considerable attention due to the fact that these techniques can be easily adapted for standoff detection from considerable distances. The techniques also show high sensitivity and selectivity and offer near real time detection duty cycles. This research focuses in laying the grounds for the spectroscopic differentiation of Staphylococcus spp., Pseudomonas spp., Bacillus spp., Salmonella spp., Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae, and E. coli, together with identification of their subspecies. In order to achieve the proponed objective, protocols to handle, cultivate and analyze the strains have been developed. Spectroscopic similarities and marked differences have been found for Spontaneous or Normal Raman spectra and for SERS using silver nanoparticles have been found. The use of principal component analysis (PCA), discriminate factor analysis (DFA) and a cluster analysis were used to evaluate the efficacy of identifying potential threat bacterial from their spectra collected on single bacteria. The DFA from the bacteria Raman spectra show a little discrimination between the diverse bacterial species however the results obtained from the SERS demonstrate to be high discrimination technique. The spectroscopic study will be extended to examine the spores produced by selected strains since these are more prone to be used as Biological Warfare Agents due to their increased mobility and possibility of airborne transport. Micro infrared spectroscopy as well as fiber coupled FTIR will also be used as possible sensors of target compounds.

Luna-Pineda, Tatiana; Soto-Feliciano, Kristina; De La Cruz-Montoya, Edwin; Pacheco Londoño, Leonardo C.; Ríos-Velázquez, Carlos; Hernández-Rivera, Samuel P.

2007-04-01

97

Spectroscopic characterization of stress-induced leakage current in sub 5-nm-thick silicon oxide film  

Microsoft Academic Search

This article proposes a spectroscopic characterization technique for examining the stress-induced leakage current in sub 5-nm-thick silicon oxide films. The fluctuation power of stress-induced leakage currents suggests that defects have a single, dominant energy level. Monte Carlo simulations are carried out to verify the defect model and stress-induced leakage current characteristics. It is clearly demonstrated using simulations and spectroscopic analyses

Kenji Komiya; Yasuhisa Omura

2002-01-01

98

Reactivity of Chromium(III) Nutritional Supplements in Biological Media: An X-Ray Absorption Spectroscopic Study  

SciTech Connect

Chromium(III) nutritional supplements are widely used due to their purported ability to enhance glucose metabolism, despite growing evidence on low activity and the potential genotoxicity of these compounds. Reactivities of Cr(III) complexes used in nutritional formulations, including [Cr3O(OCOEt)6(OH2)3]+ (A), [Cr(pic)3] (pic) = 2-pyridinecarboxylato(-) (B), and trans-[CrCl2(OH2)4]+ (CrCl3 {center_dot} 6H2O; C), in a range of natural and simulated biological media (artificial digestion systems, blood and its components, cell culture media, and intact L6 rat skeletal muscle cells) were studied by X-ray absorption near-edge structure (XANES) spectroscopy. The XANES spectroscopic data were processed by multiple linear-regression analyses with the use of a library of model Cr(III) compounds, and the results were corroborated by the results of X-ray absorption fine structure spectroscopy and electrospray mass spectrometry. Complexes A and B underwent extensive ligand-exchange reactions under conditions of combined gastric and intestinal digestion (in the presence of a semisynthetic meal, 3 h at 310 K), as well as in blood serum and in a cell culture medium (1-24 h at 310 K), with the formation of Cr(III) complexes with hydroxo and amino acid/protein ligands. Reactions of compounds A-C with cultured muscle cells led to similar ligand-exchange products, with at least part of Cr(III) bound to the surface of the cells. The reactions of B with serum greatly enhanced its propensity to be converted to Cr(VI) by biological oxidants (H2O2 or glucose oxidase system), which is proposed to be a major cause of both the insulin-enhancing activity and toxicity of Cr(III) compounds (Mulyani, I.; Levina, A.; Lay, P. A. Angew. Chem. Int. Ed. 2004, 43, 4504-4507). This finding enhances the current concern over the safety of consumption of large doses of Cr(III) supplements, particularly [Cr(pic)3].

Nguyen, A.; Mulyani, I.; Levina, A.; Lay, P.A.

2009-05-22

99

Spectroscopic Characterization of the Water Oxidation Intermediates in the Blue Dimer Ru-Based Catalyst for Artificial Photosynthesis  

NASA Astrophysics Data System (ADS)

Utilization of sunlight requires solar capture, light-to-energy conversion and storage. One effective way to store energy is to convert it into chemical energy by fuel-forming reactions, such as water splitting into hydrogen and oxygen. Ruthenium complexes are among few molecular-defined catalysts capable of water splitting. Mechanistic insights about such catalysts can be acquired by spectroscopic analysis of short-lived intermediates of catalytic water oxidation. Use of techniques such as EPR and X-ray absorption spectroscopy (XAS) are used to determine electronic requirements of catalytic water oxidation. About 30 years ago Meyer and coworkers reported first ruthenium-based catalyst for water oxidation, the ``blue dimer''. We performed EPR studies and characterized structures and electronic configurations of intermediates of water oxidation by the ``blue dimer''. Intermediates were prepared chemically by oxidation of Ru-complexes with defined number of Ce (IV) equivalents and freeze-quenched at controlled times. Changes in oxidation state of Ru atom were detected by XANES at Ru K-edges. K-edges are sensitive to changes in Ru oxidation state for Blue Dimer [3,3]^4+, [3,4]^4+, [3,4]'^4+ and [4,5]^3+ allowing a clear assignment of Ru oxidation state in intermediates. EXAFS demonstrated structural changes.

Moonshiram, Dooshaye; Pushkar, Yulia; Jurss, Jonah; Concepcion, Javier; Meyer, Thomas; Zakharova, Taisiya; Alperovich, Igor

2012-02-01

100

Silver sulfadoxinate: Synthesis, structural and spectroscopic characterizations, and preliminary antibacterial assays in vitro  

NASA Astrophysics Data System (ADS)

The sulfa drug sulfadoxine (SFX) reacted with Ag+ ions in aqueous solution, affording a new silver(I) complex (AgSFX), which was fully characterized by chemical, spectroscopic and structural methods. Elemental, ESI-TOF mass spectrometric and thermal analyses of AgSFX suggested a [Ag(C12H13N4O2S)] empirical formula. Infrared spectroscopic measurements indicated ligand coordination to Ag(I) through the nitrogen atoms of the (deprotonated) sulfonamide group and by the pyrimidine ring, as well as through oxygen atom(s) of the sulfonamide group. These hypotheses were corroborated by 13C and 15N SS-NMR spectroscopy and by an unconventional structural characterization based on X-ray powder diffraction data. The latter showed that AgSFX crystallizes as centrosymmetric dimers with a strong Ag⋯Ag interaction of 2.7435(6) Å, induced by the presence of exo-bidentate N,N? bridging ligands and the formation of an eight-membered ring of [AgNCN]2 sequence, nearly planar. Participation of oxygen atoms of the sulfonamide residues generates in the crystal a 1D coordination polymer, likely responsible for its very limited solubility in all common solvents. Besides the analytical, spectroscopic and structural description, the antibacterial properties of AgSFX were assayed using disc diffusion methods against Escherichia coli and Pseudomonas aeruginosa (Gram-negative), and Staphylococcus aureus (Gram-positive) bacterial strains. The AgSFX complex showed to be active against Gram-positive and Gram-negative bacterial strains, being comparable to the activities of silver sulfadiazine.

Zanvettor, Nina T.; Abbehausen, Camilla; Lustri, Wilton R.; Cuin, Alexandre; Masciocchi, Norberto; Corbi, Pedro P.

2015-02-01

101

The Reaction Coordinate of a Functional Model of Tyrosinase: Spectroscopic and Computational Characterization  

PubMed Central

The ?-?2:?2-peroxodicopper(II) complex synthesized by reacting the Cu(I) complex of the bis-diamine ligand N,N?-di-tert-butyl-ethylenediamine (DBED) with O2 is a functional and spectroscopic model of the coupled binuclear copper protein tyrosinase. This complex reacts with 2,4-di-tert-butylphenolate at low temperature to produce a mixture of the catechol and quinone products, which proceeds through three intermediates (A – C) that have been characterized. A, stabilized at 153K, is characterized as a phenolate-bonded bis-?-oxo dicopper(III) species, which proceeds at 193K to B, presumably a catecholate-bridged coupled bis-copper(II) species via an electrophilic aromatic substitution mechanism wherein aromatic ring distortion is the rate-limiting step. Isotopic labeling shows that the oxygen inserted into the aromatic substrate during hydroxylation derives from dioxygen, and a late-stage ortho-H+ transfer to an exogenous base is associated with C-O bond formation. Addition of a proton to B produces C, determined from resonance Raman spectra to be a Cu(II)-semiquinone complex. The formation of C (the oxidation of catecholate and reduction to Cu(I)) is governed by the protonation state of the distal bridging oxygen ligand of B. Parallels and contrasts are drawn between the spectroscopically and computationally supported mechanism of the DBED system, presented here, and the experimentally-derived mechanism of the coupled binuclear copper protein tyrosinase. PMID:19368383

Op’t Holt, Bryan T.; Vance, Michael A.; Mirica, Liviu M.; Stack, T. Daniel P.; Solomon, Edward I.

2009-01-01

102

Direct characterization and removal of interfering absorption trends in two-layer turbid media  

E-print Network

Direct characterization and removal of interfering absorption trends in two-layer turbid media Rolf confined to the lower layer of a two-layer turbid medium, as is desired in near-infrared spectroscopy (NIRS

Berger, Andrew J.

103

Quantitative Ultrasound Spectroscopic Imaging for Characterization of Disease Extent in Prostate Cancer Patients1  

PubMed Central

Three-dimensional quantitative ultrasound spectroscopic imaging of prostate was investigated clinically for the noninvasive detection and extent characterization of disease in cancer patients and compared to whole-mount, whole-gland histopathology of radical prostatectomy specimens. Fifteen patients with prostate cancer underwent a volumetric transrectal ultrasound scan before radical prostatectomy. Conventional-frequency (~ 5 MHz) ultrasound images and radiofrequency data were collected from patients. Normalized power spectra were used as the basis of quantitative ultrasound spectroscopy. Specifically, color-coded parametric maps of 0-MHz intercept, midband fit, and spectral slope were computed and used to characterize prostate tissue in ultrasound images. Areas of cancer were identified in whole-mount histopathology specimens, and disease extent was correlated to that estimated from quantitative ultrasound parametric images. Midband fit and 0-MHz intercept parameters were found to be best associated with the presence of disease as located on histopathology whole-mount sections. Obtained results indicated a correlation between disease extent estimated noninvasively based on midband fit parametric images and that identified histopathologically on prostatectomy specimens, with an r2 value of 0.71 (P < .0001). The 0-MHz intercept parameter demonstrated a lower level of correlation with histopathology. Spectral slope parametric maps offered no discrimination of disease. Multiple regression analysis produced a hybrid disease characterization model (r2 = 0.764, P < .05), implying that the midband fit biomarker had the greatest correlation with the histopathologic extent of disease. This work demonstrates that quantitative ultrasound spectroscopic imaging can be used for detecting prostate cancer and characterizing disease extent noninvasively, with corresponding gross three-dimensional histopathologic correlation. PMID:25749174

Sadeghi-Naini, Ali; Sofroni, Ervis; Papanicolau, Naum; Falou, Omar; Sugar, Linda; Morton, Gerard; Yaffe, Martin J.; Nam, Robert; Sadeghian, Alireza; Kolios, Michael C.; Chung, Hans T.; Czarnota, Gregory J.

2015-01-01

104

Quantitative ultrasound spectroscopic imaging for characterization of disease extent in prostate cancer patients.  

PubMed

Three-dimensional quantitative ultrasound spectroscopic imaging of prostate was investigated clinically for the noninvasive detection and extent characterization of disease in cancer patients and compared to whole-mount, whole-gland histopathology of radical prostatectomy specimens. Fifteen patients with prostate cancer underwent a volumetric transrectal ultrasound scan before radical prostatectomy. Conventional-frequency (~5MHz) ultrasound images and radiofrequency data were collected from patients. Normalized power spectra were used as the basis of quantitative ultrasound spectroscopy. Specifically, color-coded parametric maps of 0-MHz intercept, midband fit, and spectral slope were computed and used to characterize prostate tissue in ultrasound images. Areas of cancer were identified in whole-mount histopathology specimens, and disease extent was correlated to that estimated from quantitative ultrasound parametric images. Midband fit and 0-MHz intercept parameters were found to be best associated with the presence of disease as located on histopathology whole-mount sections. Obtained results indicated a correlation between disease extent estimated noninvasively based on midband fit parametric images and that identified histopathologically on prostatectomy specimens, with an r(2) value of 0.71 (P<.0001). The 0-MHz intercept parameter demonstrated a lower level of correlation with histopathology. Spectral slope parametric maps offered no discrimination of disease. Multiple regression analysis produced a hybrid disease characterization model (r(2)=0.764, P<.05), implying that the midband fit biomarker had the greatest correlation with the histopathologic extent of disease. This work demonstrates that quantitative ultrasound spectroscopic imaging can be used for detecting prostate cancer and characterizing disease extent noninvasively, with corresponding gross three-dimensional histopathologic correlation. PMID:25749174

Sadeghi-Naini, Ali; Sofroni, Ervis; Papanicolau, Naum; Falou, Omar; Sugar, Linda; Morton, Gerard; Yaffe, Martin J; Nam, Robert; Sadeghian, Alireza; Kolios, Michael C; Chung, Hans T; Czarnota, Gregory J

2015-02-01

105

Spectroscopic, orbital, and physical properties of the binary Feige 24 and detection of transient He II absorption in the system  

NASA Astrophysics Data System (ADS)

We have obtained new high-dispersion optical spectroscopy at Kitt Peak National Observatory (KPNO) and new International Ultraviolet Explorer (IUE) spectroscopy of the white dwarf+red dwarf binary system Feige 24. The optical range shows a composite DA+dM spectrum, together with H I Balmer and He I emission. The orbital phase dependence of the emission shows that it results from extreme ultraviolet (EUV) light reprocessing in the red dwarf upper atmosphere. The systems close enough and hot enough to show this reprocessing signature only recently emerged from common-envelope evolution. The ultraviolet spectrum exclusively emanates from the white dwarf and shows numerous heavy element absorption lines. We measured accurate radial velocities of the red dwarf component motion, traced by both optical absorption and emission lines, and new radial velocities of the white dwarf, traced by ultraviolet Fe V lines. Combining these measurements, we refined the orbital parameters presented by Vennes et al. (1991), and we confirmed that the white dwarf gravitational redshift is exceptionally small with 9 +/- 2 km/s. From this we deduced that the interior is either pure helium or carbon with a thick hydrogen layer, and we derived, for the combined interior compositions, a white dwarf mass and radius of MWD = 0.44-050 solar mass and RWD = 0.028-0.036 solar radius. We suggest that Feige 24 could be a typical case of close binary evolution leading to the formation of a low-mass helium white dwarf. The mass of the red dwarf and the inclination of the system naturally follow: MdM = 0.26-0.33 solar mass, i greater than or equal to 75 deg. High-dispersion H-alpha line profiles are asymmetrical, strongly enhanced toward the blue, suggesting a moving atmosphere possibly linked to a mass loss rate of 10-10 solar mass/yr. The IUE spectra taken when the system is near inferior conjunction show strong He II 1640 A absorption. The profile is highly variable in width and intensity. Because it is correlated with the passage of the white dwarf at inferior conjunction, the absorption may occur in some foreground plasma emanated by the red dwarf and accumulating near a Lagrangian point or, alternatively, it may originate in an accretion spot on the white dwarf surface coaligned with the major orbital axis. Either way, the He II detection may imply substantial mass loss from the red dwarf with a corollary reclassification of Feige 24 as a mixed He/H DAO white dwarf resulting from accretion of secondary mass-loss material. Feige 24 is the prototype of a class of young, EUV-emitting, binary systems comprising a late main sequence secondary and a hot H-rich white dwarf; the class is characterized by optical and ultraviolet photospheric He II absorption, circumstellar C IV lambda (1550) absorption, and by the presence of EUV-induced, phase-dependent Balmer fluorescence. These young systems present the best opportunity to constrain theory of common-envelope evolution.

Vennes, S.; Thorstensen, J. R.

1994-11-01

106

Optical characterization of ferroelectric PZT thin films by variable angle spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

Ferroelectric thin films are used as high dielectric constant capacitors, infrared detectors, piezoelectric transducers, optical modulators, optical waveguides, and nonvolatile memory chips for dynamic random access memory (DRAM) etc. While ferroelectric and dielectric properties of these films have been extensively investigated, their optical properties have been comparatively less studied and of limited use in quantitative evaluation of multilayer thin films. In this work we explored the variable angle spectroscopic ellipsometry (VASE) technique for its effectiveness in physical property characterization. The VASE combined with its computer modeling tool enables nondestructive, nonintrusive, and contactless optical means for optical characterization. Crystalline Lead Zirconium Titanate PbZr0.52Ti0.48O3 (PZT) thin films, fabricated on SrTiO3 layer atop of Si substrates, were characterized using VASE (J.A. Woollam; Lincoln, NE, USA) by determining the ellipsometric parameters ? and ? as a function of wavelengths (200-1000 nm) and incident angles (65°, 70°,75°) at room temperature. A physical representation of the multilayer system was constructed by a six layer model (analysis software WVASE32, J.A. Woollam) through a step-by-step method. Other physical properties characterized by several well-known techniques on structure, morphology and topographical features correspond well with the models developed using VASE alone. The technique and the methodology developed have shown promises in identifying the respective thickness and optical properties of multilayer thin film system, with limited input of processing or composition information.

Rahman, Md. Shafiqur; Garcia, Carlos D.; Bhalla, Amar; Guo, Ruyan

2014-09-01

107

FT-IR spectroscopic, thermal analysis of human urinary stones and their characterization  

NASA Astrophysics Data System (ADS)

In the present study, FT-IR, XRD, TGA-DTA spectral methods have been used to investigate the chemical compositions of urinary calculi. Multi-components of urinary calculi such as calcium oxalate, hydroxyl apatite, struvite and uric acid have been studied. The chemical compounds are identified by FT-IR spectroscopic technique. The mineral identification was confirmed by powder X-ray diffraction patterns as compared with JCPDS reported values. Thermal analysis techniques are considered the best techniques for the characterization and detection of endothermic and exothermic behaviors of the urinary stones. The percentages of each hydrate (COM and COD) are present together, in the presences of MAPH or UA. Finally, the present study suggests that the Urolithiasis is significant health problem in children, and is very common in some parts of the world, especially in India. So that present study is so useful and helpful to the scientific community for identification of latest human health problems and their remedies using spectroscopic techniques.

Selvaraju, R.; Raja, A.; Thiruppathi, G.

2015-02-01

108

FT-IR spectroscopic, thermal analysis of human urinary stones and their characterization.  

PubMed

In the present study, FT-IR, XRD, TGA-DTA spectral methods have been used to investigate the chemical compositions of urinary calculi. Multi-components of urinary calculi such as calcium oxalate, hydroxyl apatite, struvite and uric acid have been studied. The chemical compounds are identified by FT-IR spectroscopic technique. The mineral identification was confirmed by powder X-ray diffraction patterns as compared with JCPDS reported values. Thermal analysis techniques are considered the best techniques for the characterization and detection of endothermic and exothermic behaviors of the urinary stones. The percentages of each hydrate (COM and COD) are present together, in the presences of MAPH or UA. Finally, the present study suggests that the Urolithiasis is significant health problem in children, and is very common in some parts of the world, especially in India. So that present study is so useful and helpful to the scientific community for identification of latest human health problems and their remedies using spectroscopic techniques. PMID:25306135

Selvaraju, R; Raja, A; Thiruppathi, G

2015-02-25

109

Spectroscopic characterization of recently excavated archaeological potsherds from Tamilnadu, India with multi-analytical approach  

NASA Astrophysics Data System (ADS)

A combined analytical study of potsherds excavated from different archaeological sites of Tamilnadu (Kavalapatti, Nattapuraki and Thamaraikulam villages), India are analyzed by spectroscopic techniques such as FTIR, X-ray diffraction, thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) coupled with Energy Dispersive Spectrometer (EDS). FTIR and XRD techniques have been attempted to characterize the mineralogical composition, firing temperature and firing conditions of the archaeological potsherds. Thermogravimetric analysis (TGA) is the complementary study to estimate the firing temperature from characteristic thermal reactions in potsherds under controlled firing in inert gas atmosphere. Further, Scanning Electron Microscopy (SEM) equipped and coupled with an Energy Dispersive Spectrometer (EDS) to analyze internal morphology and chemical composition of the potsherds was used. From the results of the above techniques, the firing temperatures of potsherds were found to be greater than 650 °C.

Raja Annamalai, G.; Ravisankar, R.; Rajalakshmi, A.; Chandrasekaran, A.; Rajan, K.

2014-12-01

110

Raman spectroscopic and ESI-MS characterization of uranyl peroxide cage clusters.  

PubMed

Strategies for interpreting mass spectrometric and Raman spectroscopic data have been developed to study the structure and reactivity of uranyl peroxide cage clusters in aqueous solution. We demonstrate the efficacy of these methods using the three best-characterized uranyl peroxide clusters, {U24}, {U28}, and {U60}. Specifically, we show a correlation between uranyl-peroxo-uranyl dihedral bond angles and the position of the Raman band of the symmetric stretching mode of the peroxo ligand, develop methods for the assignment of the ESI mass spectra of uranyl peroxide cage clusters, and show that these methods are generally applicable for detecting these clusters in the solid state and solution and for extracting information about their bonding and composition without crystallization. PMID:24422479

McGrail, Brendan T; Sigmon, Ginger E; Jouffret, Laurent J; Andrews, Christopher R; Burns, Peter C

2014-02-01

111

Spectroscopic characterization of recently excavated archaeological potsherds from Tamilnadu, India with multi-analytical approach.  

PubMed

A combined analytical study of potsherds excavated from different archaeological sites of Tamilnadu (Kavalapatti, Nattapuraki and Thamaraikulam villages), India are analyzed by spectroscopic techniques such as FTIR, X-ray diffraction, thermogravimetric analysis (TGA) and Scanning Electron Microscope (SEM) coupled with Energy Dispersive Spectrometer (EDS). FTIR and XRD techniques have been attempted to characterize the mineralogical composition, firing temperature and firing conditions of the archaeological potsherds. Thermogravimetric analysis (TGA) is the complementary study to estimate the firing temperature from characteristic thermal reactions in potsherds under controlled firing in inert gas atmosphere. Further, Scanning Electron Microscopy (SEM) equipped and coupled with an Energy Dispersive Spectrometer (EDS) to analyze internal morphology and chemical composition of the potsherds was used. From the results of the above techniques, the firing temperatures of potsherds were found to be greater than 650°C. PMID:24929323

Raja Annamalai, G; Ravisankar, R; Rajalakshmi, A; Chandrasekaran, A; Rajan, K

2014-12-10

112

Chemical vapor deposition synthesis and Raman spectroscopic characterization of large-area graphene sheets.  

PubMed

We present a chemical vapor deposition (CVD) method to catalytically synthesize large-area, transferless, single- to few-layer graphene sheets using hexamethyldisilazane (HMDS) on a SiO2/Si substrate as a carbon source and thermally evaporated alternating Ni/Cu/Ni layers as a catalyst. The as-synthesized graphene films were characterized by Raman spectroscopic imaging to identify single- to few-layer sheets. This HMDS-derived graphene layer is continuous over the entire growth substrate, and single- to trilayer mixed sheets can be up to 30 ?m in the lateral dimension. With the synthetic CVD method proposed here, graphene can be grown into tailored shapes directly on a SiO2/Si surface through vapor priming of HMDS onto predefined photolithographic patterns. The transparent and conductive HMDS-derived graphene exhibits its potential for widespread electronic and opto-electronic applications. PMID:23461419

Liao, Chun-Da; Lu, Yi-Ying; Tamalampudi, Srinivasa Reddy; Cheng, Hung-Chieh; Chen, Yit-Tsong

2013-10-01

113

Metal ion binding by a bicyclic diamide: Deep UV Raman spectroscopic characterization  

SciTech Connect

Deep UV resonance Raman spectroscopy was used for characterizing ligand-metal ion complexes. The obtained results demonstrated a strong intrinsic sensitivity and selectivity of a Raman spectroscopic signature of a bicyclic diamide, a novel chelating agent for lanthanides and actinides (Lumetta, G. J.; Rapko, B. M.; Garza, P. A.; Hay, B. P.; Gilbertson, R. D.; Weakley, T. J. R.; Hutchison, J. E. J. Am. Chem. Soc. 2002, 124, 5644). Molecular modeling, which included structure optimization and calculation of Raman frequencies and resonance intensities, allowed for assigning all strong Raman bands of the bicyclic diamide as well as predicting the band shifts observed because of complex formation with metal ions. A comparative analysis of Raman spectra and the results of the molecular modeling could be used for elucidating the structure of complexes in solution.

Shashilov, Victor A.; Ermolenkov, Vladimir V.; Levitskaia, Tatiana G.; Lednev, Igor K.

2005-08-18

114

Spectroscopic Characterization of a Green Copper Site in a Single-Domain Cupredoxin  

PubMed Central

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded ?-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought. PMID:24932914

Roger, Magali; Biaso, Frédéric; Castelle, Cindy J.; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2014-01-01

115

Spectroscopic characterization of a green copper site in a single-domain cupredoxin.  

PubMed

Cupredoxins are widespread copper-binding proteins, mainly involved in electron transfer pathways. They display a typical rigid greek key motif consisting of an eight stranded ?-sandwich. A fascinating feature of cupredoxins is the natural diversity of their copper center geometry. These geometry variations give rise to drastic changes in their color, such as blue, green, red or purple. Based on several spectroscopic and structural analyses, a connection between the geometry of their copper-binding site and their color has been proposed. However, little is known about the relationship between such diversity of copper center geometry in cupredoxins and possible implications for function. This has been difficult to assess, as only a few naturally occurring green and red copper sites have been described so far. We report herein the spectrocopic characterization of a novel kind of single domain cupredoxin of green color, involved in a respiratory pathway of the acidophilic organism Acidithiobacillus ferrooxidans. Biochemical and spectroscopic characterization coupled to bioinformatics analysis reveal the existence of some unusual features for this novel member of the green cupredoxin sub-family. This protein has the highest redox potential reported to date for a green-type cupredoxin. It has a constrained green copper site insensitive to pH or temperature variations. It is a green-type cupredoxin found for the first time in a respiratory pathway. These unique properties might be explained by a region of unknown function never found in other cupredoxins, and by an unusual length of the loop between the second and the fourth copper ligands. These discoveries will impact our knowledge on non-engineered green copper sites, whose involvement in respiratory chains seems more widespread than initially thought. PMID:24932914

Roger, Magali; Biaso, Frédéric; Castelle, Cindy J; Bauzan, Marielle; Chaspoul, Florence; Lojou, Elisabeth; Sciara, Giuliano; Caffarri, Stefano; Giudici-Orticoni, Marie-Thérèse; Ilbert, Marianne

2014-01-01

116

Synthesis, characterization and spectroscopic behavior of novel 2-oxo-1,4-disubstituted-1,2,5,6-tetrahydrobenzo[h]quinoline-3-carbonitrile dyes  

NASA Astrophysics Data System (ADS)

Two synthetic pathways were adopted to synthesize the target 2-oxo-1,4-disubstituted-1,2,5,6-tetrahydro-benzo[h]quinoline-3-carbonitriles. Structure of the synthesized compounds has been characterized based on FT-IR, 1H NMR, 13C NMR and elemental analyses. UV-Vis and fluorescence spectroscopy measurements provided that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including singlet absorption, extinction coefficient, Stokes shift, oscillator strength and dipole moment were investigated in order to explore the analytical potential of synthesized compounds.

Khan, Salman A.; Asiri, Abdullah M.; Al-Thaqafy, Saad H.; Faidallah, Hassan M.; El-Daly, Samy A.

2014-12-01

117

Electrochemical and resonance Raman spectroscopic characterization of polyaniline and polyaniline-metalloporphyrin electrode films  

SciTech Connect

Characteristics of electropolymerized aniline and metallotetrakis(2-aminophenyl)porphine (metallo-2-TAPP) films are described. Aniline polymerized from methylene chloride solution by oxidative cycling at a platinum electrode shows characteristic two-wave or one-wave cycle voltammograms when scanned in pH 1 aqueous solution, depending on the positive potential sweep limit. Similar CV's are produced when the solution contains metallo-TAPP's, except that additional waves associated with metalloporphyrin redox processes are superimposed. The absorption spectra of the films formed on transparent SnO/sub 2/ electrodes showed characteristic metalloporphyrin Soret absorption bands, with red shifts relative to the solution spectra, due to axial coordination and/or excitonic effects. Raman spectra are reported for films polymerized from aniline, aniline-/sup 15/N, aniline-N,N-d/sub 2/, and aniline-d/sub 5/. The replacement of strong aniline bands at 1000 and 1029 cm/sup -1/ with bands in the films at 1190 and 1200 cm/sup -1/ is diagnostic for para-substituted aniline units in the polymer. The films show a strong /sup 15/N-sensitive band at 1525 cm/sup -1/, which is absent in aniline but present in p-phenylenediamine. Thus the electrochemical and spectroscopic characteristics of the TAPP films are fully consistent with unmodified porphyrin units contained within a polyaniline polymer. Porphyrin radical cation formation is insufficient to induce polymerization if the potential is lower than that required for aniline oxidation. Films containing Mn(2-TAPP) show a Mn/sup 3+/2+/ wave at approx.-0.2 V, negative of the polyaniline redox waves, when the electrode is in contact with nonaqueous or aqueous electrolyte. The metalloporphyrin redox process does not require electronic conduction through the polyaniline framework. 21 references. 8 figures.

Macor, K.A.; Su, Y.O.; Miller, L.A.; Spiro, T.G.

1987-08-12

118

Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations  

NASA Technical Reports Server (NTRS)

The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

2012-01-01

119

New meso-substituted corroles possessing pentafluorophenyl groups - synthesis and spectroscopic characterization.  

PubMed

The investigation presented in this paper deals with new free-base corroles substituted with different peripheral groups. These aromatic macrocycles were efficiently synthesized by a [2+1] approach from dipyrromethanes. Moreover, the basic spectroscopic studies of the dyes in chloroform were conducted, and the UV-Vis absorption, fluorescence and ESR parameters were estimated. The experimental data were supported by quantum chemical calculations. The presence of monomeric dye structures is concentration independent (10(-6)-10(-4) M), as expected for dyes in a solvent of low polarity, and rules out aggregate formation of corroles dissolved in chloroform. The excitation emission and fluorescence life-time values confirm the monomeric structure of the corroles. The spectra were compared with the time-dependent density functional theory (TD-DFT) results for the HOMO-LUMO states. The ESR examinations strongly show that for any type of studied fluorine corrole an unpaired electron is localized on the corrole macroring but not on the substituents both before and after light illumination. Laser illumination creates additional radicals, however with different effectiveness depending on the sample. PMID:25704213

Bursa, Bartosz; Barszcz, Boles?aw; Bednarski, Waldemar; Lewtak, Jan Pawe?; Koszelewski, Dominik; Vakuliuk, Olena; Gryko, Daniel T; Wróbel, Danuta

2015-03-01

120

Optical and spectroscopic characterization of Er3+-Yb3+co-doped tellurite glasses and fibers  

NASA Astrophysics Data System (ADS)

Optical and spectroscopic properties of Er3+-Yb3+ co-doped TeO2-WO3-Nb2O5-Na2O-Al2O3 glasses and fibers were investigated. Emission spectra and fluorescence lifetimes of 4I13/2 level of Er3+ion as a function of rare earth concentration and fiber length were measured in glasses. Results show that the self-absorption effect broadens the spectral bandwidth of 4I13/2?4I15/2 transition and lengthens the lifetime significantly from 3.5 to 4.6 ms. Fibers were fabricated by the rod-in-tube technique using a Heathway drawing tower. The emission power of these Er3+-Yb3+ co-doped Step Index Tellurite Fibers (SITFs; lengths varying from 2 to 60 cm) were generated by a 980 nm diode laser pump and then the emission power spectra were acquired with an OSA. The maximum emission power spectra, within the 1530-1560 nm region, were observed for fiber lengths ranging from 3 to 6 cm. The highest bandwidth obtained was 108 nm for 8 cm fiber length around 1.53 µm.

Narro-García, R.; Desirena, H.; Chillcce, E. F.; Barbosa, L. C.; Rodriguez, E.; De la Rosa, E.

2014-04-01

121

Optical and spectroscopic characterization of Er/Yb-activated planar waveguides  

NASA Astrophysics Data System (ADS)

Soda-lime silicate glasses doped with different percentages of Er- and Yb-oxides were produced by melting, and both planar and channel waveguides were fabricated by diluted silver ion exchange. Their optical and spectroscopic properties have been investigated, and some results are reported here. The optical parameters such as refractive index, diffusion depth and number of modes were measured by m-line technique. Absorption and fluorescence spectra were also measured; particular attention was focused on upconversion phenomena. The upconversion luminescence spectra of an Er/Yb-activated waveguide were obtained by continuous-wave excitation at 514.5 nm, as a function of the excitation power. The weak upconversion bands are assigned to the 2H9/2 yields 4I15/2 and 4G11/2 yields 4I15/2 transitions of the Er3+ ion. The upconversion mechanism is found to be a two-photon process. Preliminary results of gain measurements in channel waveguides showed signal enhancement at 1.5 micrometers , for high input signal intensities, upon pumping at 0.98 micrometers .

Pelli, Stefano; Brenci, Massimo; Fossi, Matteo; Righini, Giancarlo C.; Duverger, Claire; Montagna, Maurizio; Rolli, Raffaella; Ferrari, Maurizio

2000-04-01

122

Transient Spectroscopic Characterization of the Genesis of a Ruthenium Complex Catalyst Supported on Zeolite Y  

SciTech Connect

A mononuclear ruthenium complex anchored to dealuminated zeolite HY, Ru(acac)(C{sub 2}H{sub 4}){sup 2+} (acac = acetylacetonate, C{sub 5}H{sub 7}O{sup 2}{sup -}), was characterized in flow reactors by transient infrared (IR) spectroscopy and Ru K edge X-ray absorption spectroscopy. The combined results show how the supported complex was converted into a form that catalyzes ethene conversion to butene. The formation of these species resulted from the removal of acac ligands from the ruthenium (as shown by IR and extended X-ray absorption fine structure (EXAFS) spectra) and the simultaneous decrease in the symmetry of the ruthenium complex, with the ruthenium remaining mononuclear and its oxidation state remaining essentially unchanged (as shown by EXAFS and X-ray absorption near-edge structure spectra). The removal of anionic acac ligands from the ruthenium was evidently compensated by the bonding of other anionic ligands, such as hydride from H2 in the feed stream, to form species suggested to be Ru(H)(C{sub 2}H{sub 4}){sub 2}{sup +}, which is coordinatively unsaturated and inferred to react with ethene, leading to the observed formation of butene in a catalytic process.

Ogino, Isao; Gates, Bruce C.; (UCD)

2010-01-12

123

Absorption  

NSDL National Science Digital Library

This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÂ?s 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

Katherine M Knudson (Polson Middle School)

1998-04-01

124

Characterization of the oral absorption of several aminopenicillins: determination of intrinsic membrane absorption parameters in the rat intestine in situ  

NASA Technical Reports Server (NTRS)

The absorption mechanism of several penicillins was characterized using in situ single-pass intestinal perfusion in the rat. The intrinsic membrane parameters were determined using a modified boundary layer model (fitted value +/- S.E.): Jmax* = 11.78 +/- 1.88 mM, Km = 15.80 +/- 2.92 mM, Pm* = 0, Pc* = 0.75 +/- 0.04 for ampicillin; Jmax* = 0.044 +/- 0.018 mM, Km = 0.058 +/- 0.026 mM, Pm* = 0.558 +/- 0.051, Pc* = 0.757 +/- 0.088 for amoxicillin; and Jmax* = 16.30 +/- 3.40 mM, Km = 14.00 +/- 3.30 mM, Pm* = 0, Pc* = 1.14 +/- 0.05 for cyclacillin. All of the aminopenicillins studied demonstrated saturable absorption kinetics as indicated by their concentration-dependent wall permeabilities. Inhibition studies were performed to confirm the existence of a nonpassive absorption mechanism. The intrinsic wall permeability (Pw*) of 0.01 mM ampicillin was significantly lowered by 1 mM amoxicillin and the Pw* of 0.01 mM amoxicillin was reduced by 2 mM cephradine consistent with competitive inhibition.

Sinko, P. J.; Amidon, G. L.

1992-01-01

125

FTIR spectroscopic characterization of Cu(II) coordination compounds with exopolysaccharide pullulan and its derivatives  

NASA Astrophysics Data System (ADS)

Pullulan is a water-soluble, extracellular neutral polysaccharide with a linear flexible chain of ?-(1 ? 6)-linked maltotriose units, the structure of which is intermediate between pullulan and amylose structures because of the co-existence of both ?-(1 ? 6) and ?-(1 ? 4)-glycosidic linkages in single compounds. In alkali solutions Cu(II) ion forms complexes with reduced low-molar pullulan (RLMP). The metal content and the solution composition depends on pH. The complexing process begins in a weak alkali solution (pH > 7), and involves OH groups in C(2) and C(3) or C(6) pullulan monomer units (?- D-glucopyranose). Complexes of Cu(II) ion with reduced low-molar pullulan were synthesized in the water solutions, at the boiling temperature and at different pH values (7.512). Fourier-Transform Infrared (FTIR) spectroscopic data of synthesized complexes are rare in literature. FTIR spectroscopic characterization (FTIR, LNT-FTIR, ATR-FTIR, and FTIR microspectroscopy) of Cu(II) ion complexes with RLMP ( M w 6000 g mol -1) was carried out in this work. The similarities of the ?(C sbnd H) range in a part of FTIR spectra indicate that there is no difference in the conformation of the C 1 glucopyranose (Glc) unit in the RLMP and synthesized Cu(II) complexes. The complexing Cu(II) ion with RLMP in the dependence from the pH form different types of complex (pH 7-8: Cu(II)(Glc) 2(H 2O) 2, pH 8-10: Cu(II)(Glc) 2(H 2O)(OH), pH 10-12: Cu(II)(Glc) 2(OH) 2).

Miti?, Ž.; Nikoli?, G. S.; Caki?, M.; Premovi?, P.; Ili?, Lj.

2009-04-01

126

Toward the characterization of biological toxins using field-based FT-IR spectroscopic instrumentation  

NASA Astrophysics Data System (ADS)

IR spectroscopy is a broadly applicable technique for the identification of covalent materials. Recent advances in instrumentation have made Fourier Transform infrared (FT-IR) spectroscopy available for field characterization of suspect materials. Presently, this instrumentation is broadly deployed and used for the identification of potential chemical hazards. This discussion concerns work towards expanding the analytical utility of field-based FT-IR spectrometry in the characterization of biological threats. Two classes of materials were studied: biologically produced chemical toxins which were non-peptide in nature and peptide toxin. The IR spectroscopic identification of aflatoxin-B1, trichothecene T2 mycotoxin, and strychnine was evaluated using the approach of spectral searching against large libraries of materials. For pure components, the IR method discriminated the above toxins at better than the 99% confidence level. The ability to identify non-peptide toxins in mixtures was also evaluated using a "spectral stripping" search approach. For the mixtures evaluated, this method was able to identify the mixture components from ca. 32K spectral library entries. Castor bean extract containing ricin was used as a representative peptide toxin. Due to similarity in protein spectra, a SIMCA pattern recognition methodology was evaluated for classifying peptide toxins. In addition to castor bean extract the method was validated using bovine serum albumin and myoglobin as simulants. The SIMCA approach was successful in correctly classifying these samples at the 95% confidence level.

Schiering, David W.; Walton, Robert B.; Brown, Christopher W.; Norman, Mark L.; Brewer, Joseph; Scott, James

2004-12-01

127

Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption  

NASA Technical Reports Server (NTRS)

The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

2003-01-01

128

Raman Spectroscopic Characterization of the Feldspars: Implications for Surface Mineral Characterization in Planetary Exploration  

NASA Technical Reports Server (NTRS)

The availability in the last decade of improved Raman instrumentation using small, stable, intense lasers, sensitive CCD array detectors, and advanced fast grating systems enabled us to develop the Mars Microbeam Raman Spectrometer (MMRS), a field-portable Raman spectrometer with precision and accuracy capable of identifying minerals and their different compositions. For example, we can determine Mg cation ratios in pyroxenes and olivines to +/-0.1 on the basis of Raman peak positions. Feldspar is another major mineral formed in igneous systems whose characterization is important for determining rock petrogenesis and alteration. From their Raman spectral pattern, feldspars can be readily distinguished from ortho- and chain-silicates and from other tecto-silicates such as quartz and zeolites. We show here how well Raman spectral analysis can distinguish among members within the feldspar group.

Freeman, J. J.; Wang, Alian; Kuebler, K. E.; Haskin, L. A.

2003-01-01

129

Development of Cellular Absorptive Tracers (CATs) for a Quantitative Characterization of Microbial Mass in Flow Systems  

SciTech Connect

We report on a new Cellular Absorptive Tracers (CATs) method, for a simple, non-destructive characterization of bacterial mass in flow systems. Results show that adsorption of a CAT molecule into the cellular mass results in its retardation during flow, which is a good, quantitative measure of the biomass quantity and distribution. No such methods are currently available for a quantitative characterization of cell mass.

Saripalli, Prasad; Brown, Christopher F.; Lindberg, Michael J.

2005-03-16

130

Spectroscopic analysis of a laser-induced NaCl–water plasma. The influence of self-absorption  

Microsoft Academic Search

A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical\\u000a emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of\\u000a the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line

R. Hannachi; S. Boussaïdi; P. Teulet; G. Taieb; Y. Cressault; A. Gleizes; Zohra Ben Lakhdar

2008-01-01

131

Optical characterization of the nematic lyotropic chromonic liquid crystals: Light absorption, birefringence, and scalar order parameter  

E-print Network

Optical characterization of the nematic lyotropic chromonic liquid crystals: Light absorption report on the optical properties of the nematic N phase formed by lyotropic chromonic liquid crystals.70.Md, 61.30.Gd, 61.30.Pq I. INTRODUCTION Lyotropic chromonic liquid crystals LCLCs represent a special

Lavrentovich, Oleg D.

132

Growth and Raman spectroscopic characterization of As 4S 4 (II) single crystals  

NASA Astrophysics Data System (ADS)

As described by Kutoglu (1976 [16]), single crystals of As 4S 4 (II) phase have been grown using a new two-step synthesis that drastically increases the reproducibility that is attainable in synthetic experiments. First, through photo-induced phase transformation, pararealgar powder is prepared as a precursor instead of AsS melt. Then it is dissolved and recrystallized from CS 2 solvent. Results show that single crystals of the As 4S 4 (II) phase were obtained reproducibly through the dissolution-recrystallization process. Single crystals of As 4S 4 (II) obtained using this method were translucent and showed a uniform yellow-orange color. The crystal exhibits a platelet-like shape as a thin film with well-developed faces (0 1 0) and (0 1¯ 0). The grown crystals are as large as 0.50×0.50×0.01 mm. They were characterized using powder and single crystal X-ray diffraction techniques to confirm the phase identification and the lattice parameters. The As 4S 4 (II) phase crystallizes in monoclinic system with cell parameters a=11.202(4) Å, b=9.954(4) Å, c=7.142(4) Å, ?=92.81(4)°, V=795.4(6) Å 3, which shows good agreement with the former value. Raman spectroscopic studies elucidated the behavior of the substance and the relation among phases of tetra-arsenic tetrasulfide.

Kyono, Atsushi

2010-11-01

133

13C-METHYL Formate in Orion-Kl Alma Observations and Spectroscopic Characterization  

NASA Astrophysics Data System (ADS)

Determination of elemental isotopic ratios is valuable for understanding the chemical evolution of interstellar material. Until now the 12C/13C ratio has predominantly been measured in simple species such as CO, CN and H2CO and, becomes larger with increasing distance from the Galactic Center. We have investigated the carbon isotopic ratio for methyl formate HCOOCH3, and its isotopologues H13COOCH3 and HCOO13CH3 addressing the issue whether the 12C/13C ratio is the same for both simple and large molecules. Using ALMA science verification observations of Orion-KL and the spectroscopic characterization of the complex H13COOCH3 and HCOO13CH3 species that we have performed, we have 1) confirmed the detection of the 13C-methyl formate species in Orion-KL and, 2) image for the first time their spatial distribution. I will present some of these results. In particular, our analysis shows that the 12C/13C isotope ratio in methyl formate toward the Compact Ridge and Hot Core-SW components that are associated with Orion-KL are, for both the 13C-methyl formate isotopologues, commensurate with the well-known 12C/13C ratio of the simple species CO. Our findings suggest that grain surface chemistry very likely prevails in the formation of methyl formate main and 13C isotopologues.

Favre, Cécile; Carvajal, Miguel; Field, David; Bergin, Edwin; Neill, Justin; Crockett, Nathan; Jørgensen, Jes; Bisschop, Suzanne; Brouillet, Nathalie; Despois, Didier; Baudry, Alain; Kleiner, Isabelle; Margulès, L.; Huet, T. R.; Demaison, Jean

2014-06-01

134

Spectroscopic ellipsometric characterization of Si/Si(1-x)Ge(x) strained-layer superlattices  

NASA Technical Reports Server (NTRS)

Spectroscopic ellipsometry (SE) was employed to characterize Si/Si(1-x)Ge(x) strained-layer superlattices. An algorithm was developed, using the available optical constants measured at a number of fixed x values of Ge composition, to compute the dielectric function spectrum of Si(1-x)Ge(x) at an arbitrary x value in the spectral range 17 to 5.6 eV. The ellipsometrically determined superlattice thicknesses and alloy compositional fractions were in excellent agreement with results from high-resolution x ray diffraction studies. The silicon surfaces of the superlattices were subjected to a 9:1 HF cleaning prior to the SE measurements. The HF solution removed silicon oxides on the semiconductor surface, and terminated the Si surface with hydrogen-silicon bonds, which were monitored over a period of several weeks, after the HF cleaning, by SE measurements. An equivalent dielectric layer model was established to describe the hydrogen-terminated Si surface layer. The passivated Si surface remained unchanged for greater than 2 h, and very little surface oxidation took place even over 3 to 4 days.

Yao, H.; Woollam, J. A.; Wang, P. J.; Tejwani, M. J.; Alterovitz, S. A.

1993-01-01

135

Spectroscopic and Electrochemical Characterization of Nanostructured Optically-Transparent Carbon Electrodes  

PubMed Central

The present paper describes the results related to the optical and electrochemical characterization of thin carbon films fabricated by spin coating and pyrolysis of AZ P4330-RS photoresist. The goal of this paper is to provide comprehensive information allowing for the rational the selection of the conditions to fabricate optically-transparent carbon electrodes (OTCE) with specific electro-optical properties. According to our results, these electrodes could be appropriate choices as electrochemical transducers to monitor electrophoretic separations. At the core of this manuscript is the development and critical evaluation of a new optical model to calculate the thickness of the OTCE by variable angle spectroscopic ellipsometry (VASE). Such data was complemented with topography and roughness (obtained by AFM), electrochemical properties (obtained by cyclic voltammetry), electrical properties (obtained by electrochemical impedance spectroscopy), and structural composition (obtained by Raman spectroscopy). Although the described OTCE were used as substrates to investigate the effect of electrode potential on the real-time adsorption of proteins by ellipsometry, these results could enable the development of other biosensors that can be then integrated into various CE platforms. PMID:23595607

Benavidez, Tomas E.; Garcia, Carlos D.

2013-01-01

136

Sensitivity analysis for OMOG and EUV photomasks characterized by UV-NIR spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

We investigated the potentials, applicability and advantages of spectroscopic ellipsometry (SE) for the characterization of high-end photomasks. The SE measurements were done in the ultraviolet-near infrared (UVNIR) wavelength range from 300 nm to 980 nm, at angle of incidences (AOI) between 10 and 70° and with a microspot size of 45 x 10 ?m2 (AOI=70°). The measured ? and 𝛥 spectra were modeled using the rigorous coupled wave analysis (RCWA) to determine the structural parameters of a periodic array, i.e. the pitch and critical dimension (CD). Two different types of industrial photomasks consisting of line/space structures were evaluated, the reflecting extreme ultraviolet (EUV) and the transmitting opaque MoSi on glass (OMOG) mask. The ? and 𝛥 spectra of both masks show characteristic differences, which were related to the Rayleigh singularities and the missing transmission diffraction in the EUV mask. In the second part of the paper, a simulation based sensitivity analysis of the Fourier coefficients ? and ? is presented, which is used to define the required measurement precision to detect a CD deviation of 1%. This study was done for both mask types to investigate the influence of the stack transmission. It was found that sensitivities to CD variations are comparable for OMOG and EUV masks. For both masks, the highest sensitivities appear close to the Rayleigh singularities and significantly increase at very low AOI. To detect a 1% CD deviation for pitches below 150 nm a measurement precision in the order of 0.01 is required. This measurement precision can be realized with advanced optical hardware. It is concluded that UV-NIR ellipsometry is qualified to characterize photomasks down to the 13 nm technology node in 2020.

Heinrich, A.; Dirnstorfer, I.; Bischoff, J.; Meiner, K.; Richter, U.; Mikolajick, T.

2013-09-01

137

Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR, Raman and fluorescence  

Microsoft Academic Search

Natural organic materials used to prepare pharmaceutical mixtures including ointments and balsams have been characterized\\u000a by a combined non-destructive spectroscopic analytical approach. Three classes of materials which include vegetable oils (olive,\\u000a almond and palm tree), gums (Arabic and Tragacanth) and beeswax are considered in this study according to their widespread\\u000a use reported in ancient recipes. Micro-FTIR, micro-Raman and fluorescence spectroscopies

L. Brambilla; C. Riedo; C. Baraldi; A. Nevin; M. C. Gamberini; C. D’Andrea; O. Chiantore; S. Goidanich; L. Toniolo

138

Chemical Characterization of Riverine Dissolved Organic Matter Using a Combination of Spectroscopic and Pyrolytic Methods  

NASA Astrophysics Data System (ADS)

It is now well established that riverine dissolved organic matter (DOM) play a major role in environmental processes. However natural organic matter exhibit different properties depending on their sources and the fractions considered. As a result chemical characterization of DOM has appeared essential for a better understanding of their reactivity. The purpose of this work was to characterize all of the DOM at molecular level, including the non-hydrolysable fraction, which is a major part of this OM. To this aim a new analytical approach had to be considered. A combination of spectroscopic and pyrolytic methods has been applied to various fractions of DOM originating from different catchments (French and Amazonian rivers). The fractions were termed hydrophilic, transphilic and colloids according to the IHSS fractionation procedure, and account for at least 70% of the total dissolved organic carbon. Solid state 13C NMR and FTIR afford information on the nature and relative abundance of the chemical functions occurring in macromolecules. Differential thermogravimetric analysis allows to determine the thermal behaviour of the studied material and hence to optimize analytical pyrolysis conditions. Curie point pyrolysis combined to gas chromatography and mass spectrometry leads to identification of characteristic pyrolysis products, some of them being specific of a macromolecular source. Additional information can be provided by thermochemolysis with tetramethylammonium hydroxide (TMAH). TMAH was shown to allow an increase in the efficiency of the cracking of macromolecular structures and an enhancement of the detection of the polar pyrolysis products especially due to methylation of the alcohol, phenol and acid groups. The results obtained have established the importance of terrestrial contribution to DOM. Hydrophobic fractions mainly originate from lignin-derived units, whereas transphilic fractions mostly contain cellulose units together with lignin derived ones and substantial amount of nitrogen-containing moieties. Characterization of colloidal fraction has indicated the presence of compounds from bacterial origin, especially specific nitrogen-containing molecules that are characteristic pyrolysis products of peptidoglycans, along with lignin-derived units. However pyrolysis has revealed significant differences in the detection of nitrogen-containing molecules, which do not parallel nitrogen content of the fractions. Moreover in hydrophobic and transphilic fractions the molecular structure of these compounds, which are mainly nitrogen- and oxygen- containing molecules, has not allowed to ascertain their origin. As the major biological sources of organic nitrogen (proteins, amino sugars, or tetrapyrrole pigments) involve differences in the main nitrogen functionality, two additional spectroscopic methods, namely X-ray photoelectron spectroscopy (XPS) and solid state 15N NMR, have been used to determine the nitrogen functional groups (amide, amine, and N-heterocycle) present in the different fractions of DOM. The combination of these two methods has revealed the occurrence of different functionality of nitrogen, with relative contributions depending on the considered fraction. It has also appeared that Curie point pyrolysis does not account for the presence of nitrogen in macromolecules with the same efficiency depending on the functional group involved. This study has highlighted the importance of combining different analytical approaches to obtain a whole insight into chemical structure of OM and avoid biased information.

Templier, J.; Derenne, S.

2006-12-01

139

Spectroscopic analysis of a laser-induced NaCl water plasma. The influence of self-absorption  

NASA Astrophysics Data System (ADS)

A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have been constructed for concentrations ranging up to 1.5%.

Hannachi, R.; Boussaïdi, S.; Teulet, P.; Taieb, G.; Cressault, Y.; Gleizes, A.; Lakhdar, Zohra Ben

2008-09-01

140

Characterization of dissolved organic matter during reactive transport: A column experiment with spectroscopic detection  

NASA Astrophysics Data System (ADS)

Al and Fe oxy-hydroxide minerals have been implicated in dissolved organic matter (DOM) stabilization. DOM solutions from a Pinus ponderosa forest floor (PPDOM) were used to irrigate polypropylene columns, 3.2 cm long by 0.9 cm diameter (total volume 2.0 cm3), that were packed with quartz sand (QS), gibbsite-quartz sand (Al-QS), and goethite-quartz sand (Fe-QS) mixtures. To investigate the mobilization and fractionation of DOM during reactive transport, effluent solutions were characterized by UV-Vis absorbance and excitation-emission matrix (EEM) fluorescence spectroscopies. Magnitude of PPDOM sorption followed the trend Al-QS > Fe-QS > QS during the initial transport. Effluent pH values suggest that ligand exchange is a primary mechanism for PPDOM sorption onto oxy-hydroxide minerals. Low molar absorptivity values were observed in effluent solutions of early pore volumes, indicating preferential mobilization of compounds with low aromatic character. Compounds traditionally characterized by EEM spectroscopy as being more highly humified were favorably absorbed onto the gibbsite and goethite surfaces. Humification index values (HIX) were also correlated with DOM aromaticity. HIX results suggest that the presence of low mass fractions of oxy-hydroxide minerals affect the preferential uptake of high molar mass constituents of PPDOM during reactive transport.

Vazquez, A.; Hernández, S.; Rasmussen, C.; Chorover, J.

2010-12-01

141

Adsorption and Reaction of NO on Cu(100): An Infrared Reflection Absorption Spectroscopic Study at 25 K  

E-print Network

at 25 K C. M. Kim, C.-W. Yi, and D. W. Goodman* Department of Chemistry, Texas A&M UniVersity, College oxide (NO) on a Cu(100) surface at 25 K has been studied using infrared reflection absorption, dimerization of NO occurs. Further dosing of NO at 25 K produces a multilayer of the NO dimer. Annealing

Goodman, Wayne

142

Spectroscopic characterization of fluorescein- and tetramethylrhodamine-labeled oligonucleotides and their complexes with a DNA template  

NASA Astrophysics Data System (ADS)

We measured absorption and emission spectra, fluorescence quantum yield, anisotropy, fluorescence resonance energy transfer (FRET), and melting temperature to characterize fluorescein- and tetramethylrhodamine (TMR)-labeled oligonucleotides in solution and when hybridized to a common DNA template. Upon hybridization to the template, both the absorption and emission spectra of TMR-labeled duplexes exhibited a shift with respect to those of labeled oligonucleotides, depending on the location of the TMR on the oligonucleotide. Measurements of quantum yield, anisotropy, and melting temperature indicated that TMR interacted with nucleotides within the duplexes in the order (T1>T5>T11, T16) that the oligonucleotide with TMR labeled at the 5' end (T1) is stronger than that labeled at position 5 from the 5' end (T5), which is also stronger than those labeled at the positions, 11 and 16, from the 5' end (T11, T16). In the case of the duplex formed between T1 and the template, fluorescence quenching was observed, which is attributed to the interaction between the dye molecule and guanosines located at the single-stranded portion of the template. A two-state model was suggested to describe the conformational states of TMR in the duplex. The melting temperatures of the four FRET complexes show the same pattern as those of TMR-labeled duplexes. We infer that the interactions between TMR and guanosine persist in the FRET complexes. This interaction may bring the donor and the acceptor molecules closely together, which could cause interaction between the two dye molecules shown in absorbance measurements of the FRET complexes.

Wang, L.; Gaigalas, A. K.; Blasic, J.; Holden, M. J.

2004-10-01

143

Preparation and characterization of silver nanoparticles on localized surface plasmon-enhanced optical absorption  

NASA Astrophysics Data System (ADS)

Self-assembly silver nanoparticles were successfully prepared on indium tin oxide coated glass substrates by means of a vacuum vapor evaporation method followed by thermal annealing. The nanoparticles were characterized using a field-emission scanning election microscopy with an energy dispersive X-ray analyzer and a UV-vis spectrometer. It was found that the particle morphology was drastically changed depending both on the evaporated silver mass thickness and the length of time of the thermal annealing. Some absorption peaks were observed in the UV-vis spectra and the peaks showed red-shift with the average particle size increase. These facts suggest that the absorption peaks may arise from the localized surface plasmon resonance. These controllable absorptions may be suitable for photon management in dye sensitized solar cells.

Mijanur Rahman, Md.; Hattori, Nampei; Nakagawa, Yuta; Lin, Xu; Yagai, Shiki; Sakai, Masatoshi; Kudo, Kazuhiro; Yamamoto, Kazunuki

2014-11-01

144

X-ray-absorption-spectroscopic evidence for a novel iron cluster in hydrogenase II from Clostridium pasteurianum.  

PubMed Central

Hydrogenase II from Clostridium pasteurianum contains three different iron-sulphur clusters. Two are [4Fe-4S](2+.1+) clusters, whereas the other, which is thought to be the site of interaction with H2 and is known as the 'H cluster', is of unknown structure and possesses unusual spectroscopic properties. Analysis of the iron e.x.a.f.s. spectra shows that the H cluster contains iron co-ordinated mostly to sulphur and possesses 2.8 A (1 A = 0.1 nm) Fe--Fe separations when oxidized and 3.3 A Fe--Fe separations when reduced with H2. The data suggest that the reduced H cluster represents a new structural type of iron-sulphur cluster. PMID:2655584

George, G N; Prince, R C; Stokley, K E; Adams, M W; Stockley, K E

1989-01-01

145

An X-ray absorption spectroscopic structural investigation of the nickel site in Escherichia coli NikA protein  

SciTech Connect

Since the discovery of the involvement of Ni in the active site of the enzyme urease in 1975, the role of Ni in biology has been rapidly expanding. The list of nickel-dependent metalloenzymes now includes acetyl coenzyme A synthase/carbon monoxide dehydrogenase, methyl coenzyme M reductase, Ni/Fe hydrogenases, and superoxide dismutases from Streptomyces. Each of these enzymes appears to be dependent on several gene products that constitute a Ni-specific transport and metallocenter assembly system. The authors report here the results of an X-ray spectroscopic structural investigation of the Ni site in a Ni transport protein, the periplasmic Ni-binding protein, NikA, from Escherichia coli.

Allan, C.B.; Gu, Z.; Choudhury, S.B.; Al-Mjeni, F.; Sharma, M.L.; Maroney, M.J. [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry] [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemistry; Wu, L.F.; Mandrand-Berthelot, M.A. [CNRS-URA, Villeurbanne (France). Lab. de Genetique Moleculaire des Microorganismes] [CNRS-URA, Villeurbanne (France). Lab. de Genetique Moleculaire des Microorganismes

1998-11-02

146

Nuclear Magnetic Resonance and X-Ray Absorption Spectroscopic Studies of Lithium Insertion in Silver Vanadium Oxide Cathodes  

Microsoft Academic Search

Structural studies have been carried out on AgVO (silver vanadium oxide, SVO) and LiAgVO, lithiated SVO with x=0.72, 2.13, and 5.59 using nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS). Lithium-7 NMR indicates the formation of a solid electrolyte interphase layer on the x=0.72 sample and lithium intercalation into both octahedral and tetrahedral sites in the SVO lattice, and

N. D. Leifer; A. Colon; k. Martocci; S. G. Greenbaum; F. M. Alamgir; T. B. Reddy; N. R. Gleason; R. A. Leising; E. S. Takeuchi

2007-01-01

147

Characterisation of Bhringaraj and Guduchi herbs by ICP-MS Analysis, Optical absorption and EPR spectroscopic methods  

Microsoft Academic Search

Bhringaraj and Guduchi herb of Kadapa district of Andhra Pradesh, India are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II) Optical absorption spectrum of guduchi indicates that Cu(II) is

S. Lakshmi Reddy; Adeel Ahmad; G. Siva Reddy; P. Sambasiva Rao; B. Jagannatha Reddy; R. L. Frost

148

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods  

Microsoft Academic Search

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that

S. Lakshmi Reddy; N. C. G. Reddy; Adeel Ahmad; G. Siva Reddy; P. Sambasiva Rao; B. Jagannatha Reddy; R. L. Frost

2008-01-01

149

X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins  

SciTech Connect

X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it, from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.

Tan, G.O.

1993-06-01

150

Synthesis, spectroscopic characterization and molecular modeling of a tetranuclear platinum(II) complex with thiazolidine-4-carboxylic acid  

NASA Astrophysics Data System (ADS)

The synthesis, spectroscopic characterization and molecular modeling of a novel tetranuclear platinum(II) complex with thiazolidine-4-carboxylic acid (THC) are described. Elemental analysis is consistent with the composition PtCl2C4H7NO2S·H2O. Infrared (IR) spectroscopic results and solid-state 13C and 15N nuclear magnetic resonance (NMR) data indicate coordination of the ligand to Pt(II) through the nitrogen and sulfur atoms. The square planar geometry of the platinum(II) complex is completed by chlorine atoms. Density functional theory (DFT) suggests the formation of a tetrameric cluster as the most probable structure, where each THC molecule bridges between two metal centers. The compound is insoluble in water.

Corbi, Pedro P.; Formiga, André L. B.; Bonk, Fábio A.; Quintão, Frederico A.; Ferraresi, Diego K. D.; Lustri, Wilton R.; Massabni, Antonio C.

2012-07-01

151

Tissue characterization with ballistic photons: counting scattering and/or absorption centres  

NASA Astrophysics Data System (ADS)

We describe a new method to separate ballistic from the scattered photons for optical tissue characterization. It is based on the hypothesis that the scattered photons acquire a phase delay. The photons passing through the sample without scattering or absorption preserve their coherence so they may participate in interference. We implement a Mach-Zehnder experimental setup where the ballistic photons pass through the sample with the delay caused uniquely by the sample indices of refraction. We incorporate a movable mirror on the piezoelectric actuator in the sample arm to detect the amplitude of the modulation term. We present the theory that predicts the path-integrated (or total) concentration of the scattering and absorption centres. The proposed technique may characterize samples with transmission attenuation of ballistic photons by a factor of 10-14.

Corral, F.; Strojnik, M.; Paez, G.

2015-03-01

152

Infrared spectroscopic characterization of organic matter associated with microbial bioalteration textures in basaltic glass.  

PubMed

Microorganisms have been found to etch volcanic glass within volcaniclastic deposits from the Ontong Java Plateau, creating micron-sized tunnels and pits. The fossil record of such bioalteration textures is interpreted to extend back ?3.5 billion years to include meta-volcanic glass from ophiolites and Precambrian greenstone belts. Bioalteration features within glass clasts from Leg 192 of the Ocean Drilling Program were investigated through optical microscopy and Fourier transform infrared (FTIR) spectroscopy of petrographic thin sections. Extended depth of focus optical microscopic imaging was used to identify bioalteration tubules within the samples and later combined with FTIR spectroscopy to study the organic molecules present within tubule clusters. The tubule-rich areas are characterized by absorption bands indicative of aliphatic hydrocarbons, amides, esters, and carboxylic groups. FTIR analysis of the tubule-free areas in the cores of glass clasts indicated that they were free of organics. This study further constrains the nature of the carbon compounds preserved within the tubules and supports previous studies that suggest the tubules formed through microbial activity. PMID:21848422

Preston, L J; Izawa, M R M; Banerjee, N R

2011-09-01

153

Spectroscopic and structural characterization of reduced technetium species in acetate media  

SciTech Connect

The reduction of ammonium pertechnetate by sodium borohydride in 0.1 M NaOH/glacial acetic acid has been studied. The reduction products (solids and solutions) have been characterized by UV-Visible spectroscopy, Scanning Electron Microscopy/Energy-dispersive X-ray emission spectroscopy (SEM/EDS), and X-ray absorption fine structure (XAFS) spectroscopy. UV-Visible spectra of the solution, after reduction, exhibit bands at 350 and 500 nm that have been attributed to the formation of polymeric Tc(IV) species. SEM/EDS on the solid (X-ray amorphous) indicates the absence of metallic Tc and the presence of oxygen. EXAFS measurements further indicate that the precipitate exhibits a [Tc({mu}-O){sub 2}Tc] core structure. XANES is consistent with the formation of Tc(III) and/or Tc(IV). Results infer that reduction of aqueous Tc(VII) by borohydride in the presence of acetic acid does not produce metallic Tc, but a mixture of various oxidation states of Tc near Tc(III) and Tc(IV).

Mausolf, Edward; Poineau, Frederic; Droessler, Janelle; Czerwinski, Kenneth R. (UNLV)

2011-11-17

154

Infrared Spectroscopic, X-ray and Nanoscale Characterization of Strontium Titanate Thin Films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the v{sub 3} and v{sub 4} phonon absorption bands in thin strontium titanate films deposited on single-crystal yttrium-barium copper oxide (YBCO), lanthanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequencies above 400 cm-1. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of strontium titanate and the substrates for comparison. Softening in the frequency of the v{sub 4} transverse optical phonon in the lattice-mismatched films below the established value of 544 cm-1 is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J. D.; Moutinho, H. R.; Kazmerski, L. L.; Mueller, C. H.; Rivkin, T. V.; Treece, R. E.; Dalberth, M.; Rogers, C. T.

1997-01-01

155

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the v{sub 3} and v{sub 4} phonon absorption bands in thin Sr titanate films deposited on single-crystal Y-Ba Cu oxide (YBCO), La aluminate, Mg oxide, and Sr titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements at frequencies above 400 cm{sup -1}. Atomic force microscopy (AFM) and x-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of Sr titanate and the substrates for comparison. Softening in the frequency of the v{sub 4} transverse optical phonon in the lattice-mismatched films below the established value of 544 cm{sup -1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-06-01

156

Infrared spectroscopic, x-ray, and nanoscale characterization of strontium titanate thin films  

SciTech Connect

Attenuated total reflectance (ATR) measurements were performed using Fourier transform infrared (FTIR) spectroscopy in the ATR mode with a thallium iodobromide (KRS-5) crystal to measure the frequencies of the {nu}{sub 3} and {nu}{sub 4} phonon absorption bands in thin strontium titanate films deposited on single-crystal yttrium-barium copper oxide (YBCO), lanthanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequencies above 400 cm{sup {minus}1}. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements were also made to further characterize the films. The measurements were repeated on single-crystal specimens of strontium titanate and the substrates for comparison. Softening in the frequency of the {nu}{sub 4} transverse optical phonon in the lattice- mismatched films below the established value of 544 cm{sup {minus}1} is indicative of the highly textured, polycrystalline ceramic nature of the films and is consistent with the XRD and AFM results.

Webb, J.D.; Moutinho, H.R.; Kazmerski, L.L. [National Renewable Energy Lab., Golden, CO (United States); Mueller, C.H.; Rivkin, T.V.; Treece, R.E. [Superconducting Core Technologies, Inc., Golden, CO (United States); Dalberth, M.; Rogers, C.T. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

1996-04-01

157

X-ray absorption fine structure spectroscopic determination of plutonium speciation at the Rocky Flats environmental technology  

SciTech Connect

X-ray Absorption Fine Structure spectroscopy was used to probe the speciation of the ppm level Pu in thirteen soil and concrete samples from the Rocky Flats Environmental Technology Site in support of the site remediation effort that has been successfully completed since these measurements. In addition to X-ray Absorption Near Edge Spectra, two of the samples yielded Extended X-ray Absorption Fine Structure spectra that could be analyzed by curve-fits. Most of these spectra exhibited features consistent with PU(IV), and more specificaJly, PuO{sub 2+x}-type speciation. Two were ambiguous, possibly indicating that Pu that was originally present in a different form was transforming into PuO{sub 2+x}, and one was interpreted as demonstrating the presence of an unusual Pu(VI) compound, consistent with its source being spills from a PUREX purification line onto a concrete floor and the resultant extreme conditions. These experimental results therefore validated models that predicted that insoluble PuO{sub 2+x} would be the most stable form of Pu in equilibrium with air and water even when the source terms were most likely Pu metal with organic compounds or a Pu fire. A corollary of these models' predictions and other in situ observations is therefore that the minimal transport of Pu that occurred on the site was via the resuspension and mobilization of colloidal particles. Under these conditions, the small amounts of diffusely distributed Pu that were left on the site after its remediation pose only a negligible hazard.

Lezama-pacheco, Juan S [Los Alamos National Laboratory; Conradson, Steven D [Los Alamos National Laboratory; Clark, David L [Los Alamos National Laboratory

2008-01-01

158

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods.  

PubMed

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals. PMID:18280774

Reddy, S Lakshmi; Fayazuddin, Md; Reddy, N C G; Ahmad, Adeel; Reddy, G Siva; Rao, P Sambasiva; Reddy, B Jagannatha; Frost, R L

2008-11-01

159

Characterisation of bhringaraj and guduchi herb by ICP-MS analysis, optical absorption, infrared and EPR spectroscopic methods  

NASA Astrophysics Data System (ADS)

Leaves of bhringaraj and guduchi herb of Kadapa district of Andhra Pradesh, India, are dried and powdered. ICP-MS analysis of samples indicates that copper is present in both the samples. An EPR study of guduchi sample also confirms the presence of Fe(III) whereas Eclipta alba confirms the presence of Fe(III), Mn(II) and Cu(II). Optical absorption spectrum of guduchi indicates that Cu(II) is present in rhombically distorted octahedral environment. NIR and IR results are due to carbonate fundamentals.

Reddy, S. Lakshmi; Fayazuddin, Md.; Reddy, N. C. G.; Ahmad, Adeel; Reddy, G. Siva; Rao, P. Sambasiva; Reddy, B. Jagannatha; Frost, R. L.

2008-11-01

160

Nuclear Magnetic Resonance and X-Ray Absorption Spectroscopic Studies of Lithium Insertion in Silver Vanadium Oxide Cathodes  

SciTech Connect

Structural studies have been carried out on Ag{sub 2}V{sub 4}O{sub 11} (silver vanadium oxide, SVO) and Li{sub x}Ag{sub 2}V{sub 4}O{sub 11}, lithiated SVO with x=0.72, 2.13, and 5.59 using nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS). Lithium-7 NMR indicates the formation of a solid electrolyte interphase layer on the x=0.72 sample and lithium intercalation into both octahedral and tetrahedral sites in the SVO lattice, and that most but not all of the Ag (I) is reduced prior to initiation of V(V) reduction. Vanadium-51 NMR studies of SVO and lithiated SVO show decreased crystallinity with increased lithiation, as previously reported. Silver XAS studies indicate the formation of metallic silver crystallites in all the lithiated samples. A comparison of X-ray absorption near edge spectroscopy spectra for vanadium in these samples with those of reference compounds shows that some reduction of vanadium (V) occurs in the lithiated SVO with x=0.72 and increases with further lithiation leading to the formation of V(IV) and V(III) species. The results of this study indicate that vanadium(V) reduction occurs in parallel with silver (I) reduction during the initial stages of SVO lithiation, leading ultimately to the formation of vanadium (IV) and (III) species with further lithiation.

Leifer,N.; Colon, A.; Martocci, k.; Greenbaum, S.; Alamgir, F.; Reddy, T.; Gleason, N.; Leising, R.; Takeuchi, E.

2007-01-01

161

Tiny peaks vs mega backgrounds: a general spectroscopic method with applications in resonant Raman scattering and atmospheric absorptions.  

PubMed

A simple method using standard spectrometers with charge-coupled device (CCD) detectors is described to routinely measure background-corrected spectra in situations where the signal is composed of weak spectral features (such as Raman peaks or absorption lines) engulfed in a much stronger (by as much as ?10(5)) broad background. The principle of the method is to subtract the dominant fixed-structure noise and obtain a shot-noise limited spectrum. The final noise level can therefore be reduced as desired by sufficient integration time. The method requires multiple shifts of the diffraction gratings to extract the pixel-dependent noise structure, which is then used as a flat-field correction. An original peak-retrieval procedure is proposed, demonstrating accurate determination of peak lineshapes and linewidths and robustness on practical examples where conventional methods would not be applicable. Examples are discussed to illustrate the potential of the technique to perform routine resonant Raman measurements of fluorescent dyes with high quantum yield, using conventional Raman systems. The method can equally be applied to other situations where small features are masked by a broad overwhelming background. An explicit example is given with the measurement of weak absorption lines in atmospheric gases. PMID:22894881

Auguié, Baptiste; Reigue, Antoine; Le Ru, Eric C; Etchegoin, Pablo G

2012-09-18

162

Probing the Fermi Bubbles in Ultraviolet Absorption: A Spectroscopic Signature of the Milky Way's Biconical Nuclear Outflow  

E-print Network

Giant lobes of plasma extend 55 degrees above and below the Galactic Center, glowing in emission from gamma rays (the Fermi Bubbles) to microwaves (the WMAP haze) and polarized radio waves. We use ultraviolet absorption-line spectra from the Hubble Space Telescope to constrain the velocity structure of the outflowing gas within these regions, targeting the quasar PDS 456 (Galactic coordinates l,b=10.4, +11.2 degrees). This sightline passes through a clear biconical structure seen in hard X-ray and gamma-ray emission near the base of the northern Fermi Bubble. We report two high-velocity metal absorption components, at v_LSR=-235 and +250 km/s, which cannot be explained by co-rotating gas in the Galactic disk or halo. Their velocities are suggestive of an origin on the front and back side of an expanding biconical outflow emanating from the Galactic Center. We develop simple kinematic biconical outflow models that can explain these observed profiles with an outflow velocity of ~900 km/s and a full opening angl...

Fox, Andrew J; Savage, Blair D; Lockman, Felix J; Jenkins, Edward B; Wakker, Bart P; Bland-Hawthorn, Joss; Hernandez, Svea; Kim, Tae-Sun; Benjamin, Robert A; Bowen, David V; Tumlinson, Jason

2014-01-01

163

Synthesis and spectroscopic characterization of super-stable rhenium(V)porphyrins  

NASA Astrophysics Data System (ADS)

The preparation of rhenium(V) porphyrin complexes {?-oxo-bis[(oxo)(5,10,15,20-tetraphenyl-21H,23H-porphinato)rhenium(V)] [OReTPP]2O (1), (oxo)(phenoxo)(2,3,7,8,12,13,17,18-octaethyl-5-monophenyl-21H,23H-porphinato)rhenium(V) ORe(PhO)MPOEP (2), (cloro)(oxo)(2,3,7,8,12,13,17,18-octaethyl-5,15-diphenyl-21H,23H-porphinato)rhenium(V) ORe(Cl)5,15DPOEP (4), and (oxo)(phenoxo)(2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphinato)rhenium(V) ORe(PhO)OEP (5)} by the interaction of H2ReCl6 with corresponding porphyrin in boiling phenol is described. (Cloro)(oxo)(2,3,7,8,12,13,17,18-octaethyl-5-monophenyl-21H,23H-porphinato)rhenium(V) ORe(Cl)MPOEP (3) and (oxo)(chloro)(2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphinato)rhenium(V) ORe(Cl)OEP (6) have been prepared by the reaction of axial-ligand substitution from (2) and (5), respectively. Compounds (2-4) were newly synthesized. Characterization of the compounds (1-6) reported herein was made mainly by UV-Visible, IR, 1? NMR, 1H1H 2D COSY, 1H1H 2D DOSY, 1H1H 2D ROESY, 1H1H 2D TOCSY spectroscopic techniques and elemental analysis. The stability of the complexes in solutions when exposed to strong acids at the presence of atmospheric oxygen has been estimated. Compounds (2-4) and (6) show them super-stable since they do not undergo dissociation along MN bonds in concentrated H2SO4 under heating up to 363 K. Compounds (3) and (4) undergo one-electron oxidation to form stable ?-cation radicals ORe(HSO)P under these conditions. The products of the reaction between all studied porphyrins and concentrated H2SO4 were isolated in CHCl3 by reprecipitation onto ice and proved to be rhenium(V) complexes ORe(HSO4)P.

Bichan, N. G.; Tyulyaeva, E. Yu.; Khodov, I. A.; Lomova, T. N.

2014-03-01

164

Crystal structure, complexation, spectroscopic characterization and antimicrobial evaluation of 3,4-dihydroxybenzylidene isonicotinyl-hydrazone.  

PubMed

A single crystal of 3,4-dihydroxybenzylidene isonicotinylhydrazone, HBINH, has been grown and solved by X-ray crystallography. The VO(2+), Zr(4+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pd(2+) complexes of HBINH have been prepared and spectroscopically characterized. The data confirmed the formulae [Co(HBINH)(H2O)Cl]Cl·H2O, [Pd(HBINH)Cl2], [Zn(HBINH)2Cl2], [Cd(HBINH)(H2O)2Cl2]·1½H2O, [(VO)2(HBINH-3H)(OH)(H2O)], [Ni2(HBINH)(H2O)6Cl2]Cl2, [Cu2(HBINH-3H)(H2O)2(OAc)]·3H2O, [Zr2(HBINH-3H)Cl4]Cl, [Hg2(HBINH)Cl4] and the dimer {[Cu(HBINH)Cl]Cl}2. Most of the complexes have intense colors and high melting points and some are electrolytes in DMSO solution. The ligand behaves as a neutral bidentate in the Co(II), Cu(II), Pd(II), Zn(II) and Cd(II) complexes; dibasic tetradentate in [Ni2(HBINH)(H2O)6Cl2]Cl2 and tribasic tetradentate in [Cu2(HBINH-3H)(OAc)]·5H2O, [(VO)2(HBINH-3H)(OH)(H2O)] and [Zr2(HBINH-3H)Cl4]Cl by the loss of 3H(+) due to the deprotonation of the two hydroxyl groups and the enolization of the amide (OCNH) group. A tetrahedral geometry was proposed for the Co(II), Cu(II), Zn(II) and Hg(II) complexes; square-planar for the Pd(II) complex; square-pyramid for the VO(2+) complex and octahedral for the Ni(II) and Cd(II) complexes. The complexes [Cd(HBINH)(H2O)2Cl2]·1½H2O, [(VO)2(HBINH-3H)(OH)(H2O)] and [Cu2(HBINH-3H)-(H2O)2(OAc)]·3H2O have activities against Bacillus sp. M3010, Candida albicans, Escherichia coli, Staphylococcus aureus and Slamonella sp. PA393. PMID:25791887

Jeragh, Bakir; Ali, Mayada S; El-Asmy, Ahmed A

2015-06-15

165

Calibration method for spectroscopic systems  

DOEpatents

Calibration spots of optically-characterized material placed in the field of view of a spectroscopic system allow calibration of the spectroscopic system. Response from the calibration spots is measured and used to calibrate for varying spectroscopic system operating parameters. The accurate calibration achieved allows quantitative spectroscopic analysis of responses taken at different times, different excitation conditions, and of different targets. 3 figs.

Sandison, D.R.

1998-11-17

166

Calibration method for spectroscopic systems  

DOEpatents

Calibration spots of optically-characterized material placed in the field of view of a spectroscopic system allow calibration of the spectroscopic system. Response from the calibration spots is measured and used to calibrate for varying spectroscopic system operating parameters. The accurate calibration achieved allows quantitative spectroscopic analysis of responses taken at different times, different excitation conditions, and of different targets.

Sandison, David R. (Edgewood, NM)

1998-01-01

167

Probing the Fermi Bubbles in Ultraviolet Absorption: A Spectroscopic Signature of the Milky Way's Biconical Nuclear Outflow  

NASA Astrophysics Data System (ADS)

Giant lobes of plasma extend ?55° above and below the Galactic center, glowing in emission from gamma rays (the Fermi Bubbles) to microwaves and polarized radio waves. We use ultraviolet absorption-line spectra from the Hubble Space Telescope to constrain the velocity of the outflowing gas within these regions, targeting the quasar PDS 456 (l, b = 10.°4, +11.°2). This sightline passes through a clear biconical structure seen in hard X-ray and gamma-ray emission near the base of the northern Fermi Bubble. We report two high-velocity metal absorption components, at v LSR = –235 and +250 km s–1, which cannot be explained by co-rotating gas in the Galactic disk or halo. Their velocities are suggestive of an origin on the front and back side of an expanding biconical outflow emanating from the Galactic center. We develop simple kinematic biconical outflow models that can explain the observed profiles with an outflow velocity of gsim900 km s–1 and a full opening angle of ?110° (matching the X-ray bicone). This indicates Galactic center activity over the last ?2.5-4.0 Myr, in line with age estimates of the Fermi Bubbles. The observations illustrate the use of UV spectroscopy to probe the properties of swept-up gas venting into the Fermi Bubbles. Based on observations taken under program 13448 of the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, and under program 14B-299 of the NRAO Green Bank Telescope, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Fox, Andrew J.; Bordoloi, Rongmon; Savage, Blair D.; Lockman, Felix J.; Jenkins, Edward B.; Wakker, Bart P.; Bland-Hawthorn, Joss; Hernandez, Svea; Kim, Tae-Sun; Benjamin, Robert A.; Bowen, David V.; Tumlinson, Jason

2015-01-01

168

Infrared spectroscopic characterization of dehydration and accompanying phase transition behaviors in NAT-topology zeolites  

SciTech Connect

Relative humidity (PH2O, partial pressure of water)-dependent dehydration and accompanying phase transitions in NAT-topology zeolites (natrolite, scolecite, and mesolite) were studied under controlled temperature and known PH2O conditions by in situ diffuse-reflectance infrared Fourier transform spectroscopy and parallel X-ray powder diffraction. Dehydration was characterized by the disappearance of internal H2O vibrational modes. The loss of H2O molecules caused a sequence of structural transitions in which the host framework transformation path was coupled primarily via the thermal motion of guest Na?/Ca2? cations and H2O molecules. The observation of different interactions of H2O molecules and Na?/Ca2? cations with host aluminosilicate frameworks under highand low-PH2O conditions indicated the development of different local strain fields, arising from cation H2O interactions in NAT-type channels. These strain fields influence the Si O/Al O bond strength and tilting angles within and between tetrahedra as the dehydration temperature is approached. The newly observed infrared bands (at 2,139 cm-1 in natrolite, 2,276 cm-1 in scolecite, and 2,176 and 2,259 cm-1 in mesolite) result from strong cation H2O Al Si framework interactions in NAT-type channels, and these bands can be used to evaluate the energetic evolution of Na?/Ca2? cations before and after phase transitions, especially for scolecite and mesolite. The 2,176 and 2,259 cm-1 absorption bands in mesolite also appear to be related to Na?/Ca2? order disorder that occur when mesolite loses its Ow4 H2O molecules.

Wang, Hsiu-Wen [ORNL; Bishop, David [ORNL

2012-01-01

169

Synthesis and spectroscopic characterization of site-specific 2-amino-1-methyl-6-phenylimidazo.  

PubMed

The aim of the present study is to determine the chemical structure and conformation of DNA adducts formed by incubation of the bioactive form of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), N-acetoxy-PhIP, with a single-stranded 11mer oligodeoxyribonucleotide. Using conditions optimized to give the C8-dG-PhIP adduct as the major product, sufficient material was synthesized for NMR solution structure determination. The NMR data indicate that in duplex DNA this adduct exists in equilibrium between two different conformational states. In the main conformer, the covalently bound PhIP molecule intercalates in the helix, whilst in the minor conformation the PhIP ligand is probably solvent exposed. In addition to the C8-dG-PhIP adduct, at least eight polar adducts are found after reaction of N-acetoxy-PhIP with the oligonucleotide. Three of these were purified for further characterization and shown to exhibit lowest energy UV absorption bands in the range 342-347 nm, confirming the presence of PhIP or PhIP derivative. Accurate mass determination of two of the polar adducts by negative ion MALDI-TOF MS revealed ions consistent with a spirobisguanidino-PhIP derivative and a ring-opened adduct. The third adduct, which has the same mass as the C8-dG-PhIP oligonucleotide adduct, may contain PhIP bound to the N2 position of guanine. PMID:11328879

Brown, K; Guenther, E A; Dingley, K H; Cosman, M; Harvey, C A; Shields, S J; Turteltaub, K W

2001-05-01

170

Compressed shell conditions extracted from spectroscopic analysis of Ti K-shell absorption spectra with evaluation of line self-emission  

SciTech Connect

Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n?=?1–2 transitions in F- through Li-like Ti ions in the 4400–4800?eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature T{sub e} and density N{sub e} to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of T{sub e} and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed T{sub e}, N{sub e} conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range T{sub e}?=?400–600?eV and N{sub e}?=?3.0–10.0?×?10{sup 24} cm{sup ?3} for all but the most distant Ti-doped layer, with error bars ?5% T{sub e} value and ?10% N{sub e} on average. The T{sub e}, N{sub e} conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T. [Physics Department, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557 (United States); Smalyuk, V. A.; Regan, S. P.; Delettrez, J. [Laboratory for Laser Energetics, University of Rochester, 250 E. River Road, Rochester, New York 14623 (United States)

2014-08-15

171

Compressed shell conditions extracted from spectroscopic analysis of Ti K-shell absorption spectra with evaluation of line self-emission  

NASA Astrophysics Data System (ADS)

Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n = 1-2 transitions in F- through Li-like Ti ions in the 4400-4800 eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature Te and density Ne to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of Te and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed Te, Ne conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range Te = 400-600 eV and Ne = 3.0-10.0 × 1024 cm-3 for all but the most distant Ti-doped layer, with error bars ˜5% Te value and ˜10% Ne on average. The Te, Ne conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J.

2014-08-01

172

Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands  

NASA Astrophysics Data System (ADS)

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. Microanalytical data, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA data and ESR spectral studies were used to confirm the structures of the complexes. Electronic absorption and IR spectra of the complexes suggest a square-planar geometry around the central metal ion. The interaction of complexes with pET30a plasmid DNA was investigated by spectroscopic measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the copper(II) complexes can cleave circular plasmid DNA to nicked and linear forms.

Vyas, Komal M.; Joshi, Rushikesh G.; Jadeja, R. N.; Ratna Prabha, C.; Gupta, Vivek K.

2011-12-01

173

Structural characterization of nickel oxide nanowires by X-ray absorption near-edge structure spectroscopy.  

PubMed

Nickel oxide nanowires modified by poly(vinylpyrrolidone) (PVP) were synthesized via a simple chemical pattern. For the first time NiO nanowires with diameters ranging from 40 to 100 nm with the expected ratio (length vs diameter) ranging from 54 to 90 were grown using a simple solution-phase approach (mild method). These nickel nanowires exhibited unique photoluminescence features and displayed a significant UV luminescence. X-ray absorption near-edge spectroscopy has been used to characterize the local Ni environment and identify the electronic structure. Comparing experimental and theoretical spectra at the Ni and O K edges, we determine the lattice distortion via the analysis of the characteristic preedge features and the multiple-scattering structures detected in the X-ray absorption near-edge structure spectra. The correlation between experimental features and the disordered or distorted local structures is also discussed. PMID:16851250

Wu, Z Y; Liu, C M; Guo, L; Hu, R; Abbas, M I; Hu, T D; Xu, H B

2005-02-24

174

Soft X-ray absorption spectroscopic studies with different probing depths: Effect of an electrolyte additive on electrode surfaces  

NASA Astrophysics Data System (ADS)

A solid electrolyte interphase (SEI) formed on a model LiCoO2 electrode was analyzed by the ultra-soft X-ray absorption spectroscopy (XAS). The data of Li K-, B K-, C K-, O K-, and Co L-edges spectra for the SEI film on the electrode were collected using three detection methods with different probing depths. The electrode was prepared by a pulsed laser deposition method. All the spectral data consistently indicated that the SEI film containing lithium carbonate was instantly formed just after the soak of the electrode into the electrolyte solution and that it decomposed during the repeated charge-discharge reactions. The decomposition of the SEI film seems to cause the deterioration in lithium ion battery cycle performance. By adding lithium bis(oxalate) borate (LiBOB) to the electrolyte the decomposition could be suppressed leading to longer cycle life. It was found that some of the Co ions at the electrode surface were reduced to Co(II) during the charge-discharge reactions and this reaction could also be suppressed by the addition of LiBOB.

Yogi, Chihiro; Takamatsu, Daiko; Yamanaka, Keisuke; Arai, Hajime; Uchimoto, Yoshiharu; Kojima, Kazuo; Watanabe, Iwao; Ohta, Toshiaki; Ogumi, Zenpachi

2014-02-01

175

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation  

NASA Astrophysics Data System (ADS)

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 ?g ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

Ragab, Gamal H.; Amin, Alaa S.

2004-03-01

176

X-ray absorption spectroscopic evidence for the complexation of Hg(II) by reduced sulfur in soil humic substances  

SciTech Connect

Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligands by Hg(II) in the complexation with humic substances.

Xia, K. [Kansas State Univ., Manhattan, KS (United States). Dept. of Agronomy] [Kansas State Univ., Manhattan, KS (United States). Dept. of Agronomy; Skyllberg, U.L. [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Ecology] [Swedish Univ. of Agricultural Sciences, Umeaa (Sweden). Dept. of Forest Ecology; Bleam, W.F.; Helmke, P.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Soil Science] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Soil Science; Bloom, P.R.; Nater, E.A. [Univ. of Minnesota, St. Paul, MN (United States). Dept. of Soil, Water, and Climate] [Univ. of Minnesota, St. Paul, MN (United States). Dept. of Soil, Water, and Climate

1999-01-15

177

On the mechanism of NO selective catalytic reduction by hydrocarbons over Cu-ZSM-5 via X-ray absorption spectroscopic study  

SciTech Connect

An understanding of the catalytic mechanism of NO{sub x} reduction is critical for the development of next-generation high-fuel efficiency, low-emission vehicles. This paper compiles the investigations in recent years on the mechanism of NO selective catalytic reduction (SCR) by hydrocarbon over Cu-ZSM-5. The studies were focused on the oxidation state and coordination chemistry of the exchanged Cu as the active site during the catalytic reaction using X-ray absorption spectroscopic (XAS) techniques, mainly XANES and EXAFS. Their experiment demonstrated the existence of a redox mechanism which involves cyclic switching of the oxidation states between Cu(II) and Cu(I) in an oxygen-rich gas mixture under elevated temperature. The authors also observed the coordination structural change of copper ion in ZSM-5 accompanying the change of oxidation state. A correlation between cuprous ion concentration and catalytic activity was found in NO SCR by propene. The impact of another two hydrocarbons, propane and methane, on the copper redox behavior also appears to correlate to catalytic activities in the respective mixtures. Discussions on the nature of the active sites and the mechanism of SCR are presented based on the XAS data analysis. The similarity and difference of the physical properties of copper ion between NO catalytic decomposition and NO SCR are also discussed.

Liu, D.J. [AlliedSignal Inc., Des Plaines, IL (United States)] [AlliedSignal Inc., Des Plaines, IL (United States); Robota, H.J. [ASEC, Tulsa, OK (United States)] [ASEC, Tulsa, OK (United States)

1999-04-08

178

Optical properties of large-area polycrystalline chemical vapor deposited graphene by spectroscopic ellipsometry  

Microsoft Academic Search

Spectroscopic ellipsometry was used to characterize the complex refractive index of chemical vapor deposition (CVD) graphene grown on copper foils and transferred to glass substrates. Two ellipsometers, with respective wavelength ranges extending into the ultraviolet and infrared (IR), have been used to characterize the CVD graphene optical functions. The optical absorption follows the same relation to the fine structure constant

F. J. Nelson; V. K. Kamineni; T. Zhang; E. S. Comfort; J. U. Lee; A. C. Diebold

2010-01-01

179

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites  

NASA Astrophysics Data System (ADS)

Rare-earth orthoferrites, REFeO3 (RE=rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO3 compounds (RE=La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is.

Hayes, J. R.; Grosvenor, A. P.

2011-11-01

180

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites.  

PubMed

Rare-earth orthoferrites, REFeO? (RE D rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO? compounds (RE D La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is. PMID:22056809

Hayes, J R; Grosvenor, A P

2011-11-23

181

An x-ray absorption spectroscopic study of the electronic structure and bonding of rare-earth orthoferrites  

SciTech Connect

Rare-earth orthoferrites, REFeO{sub 3} (RE=rare earth; Y), are tremendously adaptable compounds that are being investigated for use in a wide variety of applications including gas sensors, vehicle catalytic converters, and solid-oxide fuel cells. They also exhibit interesting magnetic properties such as high-temperature antiferromagnetism, making them useful for data storage applications. The compounds adopt a distorted perovskite-type structure where the tilt angle of the octahedra increases (Fe-O-Fe bond angle decreases) as the size of the rare-earth atom decreases. Despite intensive study of the physical properties of these compounds, very few studies have investigated how the bonding and electronic structure of these systems change with substitution of the RE. X-ray absorption near-edge spectroscopy (XANES) is a technique well-suited for such a study, and, in view of this, Fe L-, Fe K- and O K-edge spectra from a series of REFeO{sub 3} compounds (RE=La, Pr, Nd, Sm, Eu, Gd, Ho, Yb, Y) have been collected, and are presented here. Fe L-edge spectra show that Fe is octahedrally coordinated and that the Fe-centered octahedra do not appear to distort with changes in the identity of the RE. The Fe K-edge spectra contain an intersite hybrid peak, which is an ill-studied feature that is attributed to non-local transitions of 1s electrons to 3d states on the next-nearest-neighbor atom that are hybridized with 4p states on the absorbing atom through O 2p states. In this study, it is shown that the intensity of this feature is strongly dependent on the Fe-O-Fe bond angle; the lower the Fe-O-Fe bond angle, the less intense the intersite hybrid peak is.

Hayes, J.R.; Grosvenor, A.P. (Saskatchewan)

2011-11-07

182

Synthesis, spectroscopic, and molecular structure characterizations of some azo derivatives of 2-hydroxyacetophenone  

Microsoft Academic Search

Some novel azo compounds were prepared by the reaction of 2-hydroxyacetophenone with aniline and its substituted derivatives. The structures of synthesized azo compounds were determined by IR, UV–Vis, 1H NMR and 13C NMR spectroscopic techniques and the structures of some of these compounds were also determined by X-ray diffraction studies. Structural analysis using IR in solid state shows that the

Çigdem Albayrak; ?smail E. Gümrükçüo?lu; Mustafa Odabasoglu; Nazan Ocak ?skeleli; Erbil Agar

2009-01-01

183

Anion pairs in room temperature ionic liquids predicted by molecular dynamics simulation, verified by spectroscopic characterization  

SciTech Connect

Molecular-level spectroscopic analyses of an aprotic and a protic room-temperature ionic liquid, BMIM OTf and BMIM HSO4, respectively, have been carried out with the aim of verifying molecular dynamics simulations that predict anion pair formation in these fluid structures. Fourier-transform infrared spectroscopy, Raman spectroscopy and nuclear magnetic resonance spectroscopy of various nuclei support the theoretically-determined average molecular arrangements.

Schwenzer, Birgit; Kerisit, Sebastien N.; Vijayakumar, M.

2014-01-01

184

Spectroscopic ellipsometry characterization of (InGa)N on GaN  

Microsoft Academic Search

Pseudodielectric function spectra of hexagonal (InGa)N epitaxial layers on GaN were obtained by spectroscopic ellipsometry and compared with photoreflection spectra. Composition and thickness of the InxGa1-xN layers grown by metalorganic chemical vapor deposition, were varied between 0.04<=x<=0.10 and 15-60 nm, respectively. The pseudodielectric function exhibits a clear maximum at the fundamental gap energy of the (InGa)N, which allows a determination

J. Wagner; A. Ramakrishnan; D. Behr; H. Obloh; M. Kunzer; K.-H. Bachem

1998-01-01

185

Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation.  

PubMed

The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage. PMID:25511126

Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

2015-02-01

186

X-ray absorption spectroscopic study of new high-Tc superconducting intercalation compound of (HgX2)0.5Bi2Sr2CaCu2Oy(X=Br,I)  

Microsoft Academic Search

We have systematically performed x-ray absorption spectroscopic (XAS) studies on the new mercuric halide intercalated superconductors, (HgX2)0.5Bi2Sr2CaCu2Oy with X equals Br and I, in order to investigate the electronic and crystal structure of these compounds. The present Hg LIII-edge EXAFS results indicate that the mercury is coordinated with two bromide or iodide ligands with bond length of 2.46 angstrom for

Jin-Ho Choy; Nam-Gyu Park; Seong-Ju Hwang; Sung-Ho Hwang; Dong-Hoon Kim

1996-01-01

187

Nanoflaky MnO2/functionalized carbon nanotubes for supercapacitors: an in situ X-ray absorption spectroscopic investigation  

NASA Astrophysics Data System (ADS)

The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage.The surfaces of acid- and amine-functionalized carbon nanotubes (C-CNT and N-CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. C-CNT was found to have a lower edge plane structure and fewer defect sites than N-CNT. MnO2/C-CNT with a highly developed surface area exhibited favorable electrochemical performance. To determine the atomic/electronic structures of the MnO2/functionalized CNTs (MnO2/C-CNT and MnO/N-CNT) during the charge/discharge process, in situ X-ray absorption spectroscopy (XAS) measurements were made at the Mn K-edge. Both C-CNT and N-CNT are highly conductive. The effect of the scan rate on the capacitance behavior was also examined, revealing that the ?* state of CNT and the size of the tunnels in pseudo-capacitor materials (which facilitate conduction and the transport of electrolyte ions) are critical for the capacitive performance, and their role depends on the scan rate. In the slow charge/discharge process, MnO2/N-CNT has a more symmetrical rectangular cyclic voltammetry (CV) curve. In the fast charge/discharge process, MnO2/C-CNT with a highly developed surface provides fast electronic and ionic channels that support a reversible faradaic redox reaction between MnO2 nanoflakes and the electrolyte, significantly enhancing its capacitive performance over that of MnO2/N-CNT. The MnO2/C-CNT architecture has great potential for supercapacitor applications. The information that was obtained herein helps to elucidate CNT surface modification and the design of the MnO2/functionalized CNT interface with a view for the further development of supercapacitors. This work, and especially the combination of CV with in situ XAS measurements, will be of value to readers with an interest in nanomaterial, nanotechnology and their applications in energy storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06439a

Chang, Han-Wei; Lu, Ying-Rui; Chen, Jeng-Lung; Chen, Chi-Liang; Lee, Jyh-Fu; Chen, Jin-Ming; Tsai, Yu-Chen; Chang, Chien-Min; Yeh, Ping-Hung; Chou, Wu-Ching; Liou, Ya-Hsuan; Dong, Chung-Li

2015-01-01

188

Characterization of a new modular decay total absorption gamma-ray spectrometer (DTAS) for FAIR  

SciTech Connect

Beta-decay studies are one of the main goals of the DEcay SPECtroscopy experiment (DESPEC) to be installed at the future Facility for Antiproton and Ion Research (FAIR). DESPEC aims at the study of nuclear structure of exotic nuclei. A new modular Decay Total Absorption gamma-ray Spectrometer (DTAS) is being built at IFIC and is specially adapted to studies at fragmentation facilities such as the Super Fragment Separator (Super-FRS) at FAIR. The designed spectrometer is composed of 16 identical NaI(Tl) scintillation crystals. This work focuses on the characterization of these independent modules, as an initial step for the characterization of the full spectrometer. Monte Carlo simulations have been performed in order to understand the detector response.

Montaner Piza, A.; Tain, J. L.; Agramunt, J.; Algora, A.; Guadilla, V.; Marin, E.; Rice, S.; Rubio, B. [Instituto de Fisica Corpuscular, CSIC-Univ. de Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain)

2013-06-10

189

Characterization of Liquid Crystal Layer and Cholesteric Film by Renormalized Spectroscopic Ellipsometry  

NASA Astrophysics Data System (ADS)

Renormalized transmission spectroscopic ellipsometry (RTSE) is used to evaluate the device parameters of liquid crystal display (LCD). To determine the reduced dielectric and elastic constants, threshold voltage, pretilt angle, cell gap, and surface polar anchoring energy coefficient, symmetrically oblique incidence transmission ellipsometry (SOITE) was applied to vertical-alignment (VA) LCD. It is suggested that the rubbing process on the alignment films for VA LCD does not disturb the measurement of the genuine surface polar anchoring energy coefficient. RTSE is also applicable to the determination of the total twist angle of the cholesteric film.

Kimura, Munehiro; Kamada, Hirokazu; Onuma, Toshihiko; Akahane, Tadashi

2009-03-01

190

Spectroscopic characterization of genetically modified flax fibres enhanced with poly-3-hydroxybutyric acid  

NASA Astrophysics Data System (ADS)

Genetically modified flax fibres, derived from transgenic flax with expression of three bacterial genes necessary for synthesis of poly-3-hydroxybutyric acid (PHB), have been analysed. These transgenic flaxes, enhanced with different amount of the PHB, have been studied by FT-IR spectroscopy. The integral intensities of the IR bands have been used for estimation of the chemical content of the normal and transgenic flaxes as well as the differences between the natural and genetically modified flax fibres. The spectroscopic data were compared to those obtained from chemical analysis of flax fibres.

Wróbel-Kwiatkowska, Magdalena; Szopa, Jan; Dymi?ska, Lucyna; M?czka, Miros?aw; Hanuza, Jerzy

2009-02-01

191

X-ray Absorption Spectroscopic and Theoretical Studies on (L)2[Cu2(S2)n]2+ Complexes: Disulfide Versus Disulfide(•1?) Bonding  

PubMed Central

Cu K-, L- and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{(TMPA)Cu}2S2](ClO4)2 (1), [{Cu[HB(3,5-Pri2pz)3]}2(S2)] (2) and [{(TMEDA)Cu}2(S2)2](OTf)2 (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63% and 37% Cu d-character in the ground state of 1 and 2, respectively while the S K-pre-edge intensities reflect 20% and 48% S character in their ground states. These data indicate a more than two-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu-S bonds in 2 (µ-?2:?2 S22? bridge) compared to 1 ((µ-?1:?1 S22? bridge), dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the CuII/(S2?)2 nature of 3. The two disulfide(•1?)’s in 3 undergo strong bonding interactions which destabilize the resultant filled antibonding ?* orbitals of the (S2?)2 fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide(•1?) complex. PMID:18076173

Sarangi, Ritimukta; York, John T.; Helton, Matthew E.; Fujisawa, Kiyoshi; Karlin, Kenneth D.; Tolman, William B.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.

2008-01-01

192

Electrochemical Kinetics and X-ray Absorption Spectroscopic Investigations of Oxygen Reduction on Chalcogen-Modified Ruthenium Catalysts in Alkaline Media  

SciTech Connect

The oxygen reduction reaction (ORR) in alkaline media has been investigated on chalcogen-modified ruthenium nanoparticles (Ru/C, Se/Ru/C, Se/RuMo/C, S/Ru/C, S/RuMo/C) synthesized in-house via aqueous routes. In acidic medium, it is well known that modification by a chalcogen prevents the oxidation of the underlying transition-metal (Ru) surface, thereby promoting direct molecular O{sub 2} adsorption on the Ru metal. On an unmodified Ru catalyst in alkaline media, the surface oxides on Ru mediate the 2e{sup -} reduction of molecular O{sub 2} to a stable peroxide anion (HO{sub 2}{sup -}) intermediate via an outer-sphere electron-transfer mechanism. This increases the activity of HO{sub 2}{sup -} near the electrode surface and decreases the overpotential for ORR by effectively carrying out the reduction of HO{sub 2}{sup -} to OH{sup -} at the oxide-free ruthenium metal site. An increase in ORR activity of Ru is observed by modification with a chalcogen; however, the increase is not as significant as observed in acidic media. Ternary additives, such as Mo, were found to significantly improve the stability of the chalcogen-modified catalysts. Detailed investigations of the ORR activity of this class of catalyst have been carried out in alkaline media along with comparisons to acidic media wherever necessary. A combination of electrochemical and X-ray absorption spectroscopic (EXAFS, XANES, {Delta}{mu}) studies has been performed in order to understand the structure/property relationships of these catalysts within the context of ORR in alkaline electrolytes.

N Ramaswamy; R Allen; S Mukerjee; Y

2011-12-31

193

Combined Mössbauer, multi-edge X-ray absorption spectroscopic, and density functional theoretical study of the radical SAM enzyme spore photoproduct lyase  

PubMed Central

Spore photoproduct lyase (SPL), a member of the radical SAM superfamily, catalyzes the direct reversal of the spore photoproduct (SP), a thymine dimer specific to bacterial spores, to two thymines. SPL requires S-adenosyl-L-methionine (SAM) and a redox active [4Fe-4S] cluster for catalysis. Mössbauer analysis of anaerobically purified SPL indicates the presence of a mixture of cluster states with the majority (40%) as [2Fe-2S]2+ and a smaller amount (15%) as [4Fe-4S]2+ clusters. Upon reduction, the cluster content changes to primarily (60%) [4Fe-4S]+. The speciation information from Mössbauer data allowed us to deconvolute iron and sulfur K-edge X-ray absorption spectra to uncover electronic (XANES) and geometric (EXAFS) structural features of the Fe-S clusters, and their interactions with SAM. The Fe K-edge EXAFS provide evidence for elongation of a [2Fe-2S] rhomb of the [4Fe-4S] cluster upon binding SAM on the basis of an Fe…Fe scatterer at 3.0 Å. The XANES spectra of reduced SPL in the absence and presence of SAM overlay, indicating that SAM is not undergoing reductive cleavage. The XAS data for SPL samples and data for model complexes from literature allowed for the deconvolution of contributions from [2Fe-2S] and [4Fe-4S] clusters to the sulfur K-edge XANES spectra. The analysis of pre-edge features revealed electronic changes in the Fe-S clusters as a function of SAM presence. The spectroscopic findings were further corroborated by density functional theory calculations that provided insights into structural and electronic perturbations that can be correlated by considering the role of SAM as a catalyst or substrate. PMID:24532333

Silver, Sunshine C.; Gardenghi, David J.; Naik, Sunil G.; Shepard, Eric M.; Huynh, Boi Hanh

2014-01-01

194

X-Ray Absorption Spectroscopic And Theoretical Studies on (L)(2)[Cu-2(S-2)N](2+) Complexes: Disulfide Versus Disulfide(Center Dot 1-) Bonding  

SciTech Connect

Cu K-, Cu L-, and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{l_brace}(TMPA)Cu{r_brace}{sub 2}S{sub 2}](ClO{sub 4}){sub 2} (1), [{l_brace}Cu[HB(3,5-Pr{sub 2}{sup i}pz){sub 3}]{r_brace}{sub 2}(S{sub 2})] (2), and [{l_brace}(TMEDA)Cu{r_brace}{sub 2}(S{sub 2}){sub 2}](OTf){sub 2} (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63 and 37% Cu d-character in the ground state of 1 and 2, respectively, whereas the S K-pre-edge intensities reflect 20 and 48% S character in their ground states, respetively. These data indicate a more than 2-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu?S bonds in 2 ({mu}-{eta}{sup 2}:{eta}{sup 2} S{sub 2}{sup 2-} bridge) compared to 1 ({mu}-{eta}{sup 1}:{eta}{sup 1} S{sub 2}{sup 2-} bridge) dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the Cu{sup II}/(S{sub 2}{sup -}){sub 2} nature of 3. The two disulfide({center_dot}1?)'s in 3 undergo strong bonding interactions that destabilize the resultant filled antibonding {pi}* orbitals of the (S{sub 2}{sup -}){sub 2} fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand-based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide({center_dot}1?) complex.

Sarangi, R.; York, J.T.; Helton, M.E.; Fujisawa, K.; Karlin, K.D.; Tolman, W.B.; Hodgson, K.O.; Hedman, B.; Solomon, E.I.; /Stanford U., Chem. Dept. /SLAC, SSRL /Minnesota U. /Johns Hopkins U. /Tsukuba U.

2009-04-30

195

X-ray absorption spectroscopic and theoretical studies on (L)2[Cu2(S2)n]2+ complexes: disulfide versus disulfide(*1-) bonding.  

PubMed

Cu K-, Cu L-, and S K-edge X-ray absorption spectroscopic (XAS) data have been combined with density functional theory (DFT) calculations on [{(TMPA)Cu}2S2](ClO4)2 (1), [{Cu[HB(3,5-Pr(i)2pz)3]}2(S2)] (2), and [{(TMEDA)Cu}2(S2)2](OTf)2 (3) to obtain a quantitative description of their ground state wavefunctions. The Cu L-edge intensities give 63 and 37% Cu d-character in the ground state of 1 and 2, respectively, whereas the S K-pre-edge intensities reflect 20 and 48% S character in their ground states, respectively. These data indicate a more than 2-fold increase in the total disulfide bonding character in 2 relative to 1. The increase in the number of Cu-S bonds in 2 (mu-eta(2):eta(2) S2(2-) bridge) compared to 1 ((mu-eta(1):eta(1) S2(2-) bridge) dominantly determines the large increase in covalency and Cu-disulfide bond strength in 2. Cu K- and L- and S K-pre-edge energy positions directly demonstrate the Cu(II)/(S2(-))2 nature of 3. The two disulfide(*1-)'s in 3 undergo strong bonding interactions that destabilize the resultant filled antibonding pi* orbitals of the (S2(-))2 fragment relative to the Cu 3d levels. This leads to an inverted bonding scheme in 3 with dominantly ligand-based holes in its ground state, consistent with its description as a dicopper(II)-bis-disulfide(*1-) complex. PMID:18076173

Sarangi, Ritimukta; York, John T; Helton, Matthew E; Fujisawa, Kiyoshi; Karlin, Kenneth D; Tolman, William B; Hodgson, Keith O; Hedman, Britt; Solomon, Edward I

2008-01-16

196

Cyanide/isocyanide abundances in the interstellar medium - I. Theoretical spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Modelling molecular abundances in the interstellar medium requires accurate molecular data. In this work, structural and spectroscopic properties of a series of metal cyanides/isocyanide species containing Na, Mg, Al and Si are calculated and compared using highly correlated ab initio calculations. The metal substitution effect on molecular properties is discussed. Isomerization pathways and transitions states are detailed. NaCN shows three isomeric structures, one T shaped and two linear forms, whereas the remaining compounds display two linear minimum energy geometries. For the first time, NaCN secondary minima are described. Second-order perturbation theory spectroscopic parameters are determined from an anharmonic RCCSD(T)/aug-cc-pV5Z force field. Very accurate rotational constants are calculated using a complete basis set and taking into account vibrational effects and the structure variation with core electron correlation. For l-SiCN and l-SiNC, spin-orbit parameters are also provided. Present theoretical results are compared with available experimental data attaining a good agreement.

Senent, M. L.; Dumouchel, F.; Lique, F.

2012-02-01

197

Time-resolved spectroscopic characterization of a novel photodecarboxylation reaction mediated by homolysis of a carbon ?-bond in flurbiprofen.  

PubMed

Flurbiprofen (Fp), a nonsteroidal anti-inflammatory drug (NSAID) currently in use for arthritis pain relief and in clinical trials for metastatic prostate cancer, can induce photosensitization and phototoxicity upon exposure to sunlight. The mechanisms responsible for Fp phototoxicity are poorly understood and deserve investigation. In this study, the photodecarboxylation reaction of Fp, which has been assumed to underpin its photoinduced side effects, was explored by femtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopic techniques in pure acetonitrile (MeCN) solvent. Density functional theory (DFT) calculations were also performed to facilitate the assignments of transient species. The resonance Raman and DFT calculation results reveal that the neutral form of Fp was the predominant species present in MeCN. Analysis of the ultraviolet/visible absorption spectrum and results from TD-DFT calculations indicate that the second excited singlet (S2) can be excited by 266 nm light. Due to its intrinsic instability, S2 rapidly underwent internal conversion (IC) to decay to the lowest lying excited singlet (S1), which was observed in the fs-TA spectra at very early delay times. Intriguingly, three distinct pathways for S1 decay seem to coexist. Specifically, other than fluorescence emission back to the ground state and transformation to the lowest triplet state T1 through intersystem crossing (ISC), the homolysis of the carbon ?-bond decarboxylation reaction proceeded simultaneously to give rise to two radical species, one being carboxyl and another being the residual, denoted as FpR. The coexistence of the triplet Fp (T1) and FpR species was verified by means of TR(3) spectra along with ns-TA spectra. As a consequence of its apparent high reactivity, the FpR intermediate was observed to undergo oxidation under oxygen-saturated conditions to yield another radical species, denoted as FOR, which subsequently underwent intramolecular hydrogen transfer (IHT) and dehydroxylation (DHO) to form a final product, which could react with the carboxyl from the decarboxylation reaction to generate a minor final product. TD-DFT and transient state (TS) calculations for predicting the absorption bands and activation energies of the transient species produced in the photodecarboxylation reaction have provided valuable mechanistic insights for the assignment of the intermediate species observed in the time-resolved spectroscopy experiments reported here. The results of the time-resolved spectroscopy experiments and DFT calculations were used to elucidate the reaction mechanisms and intermediates involved in the photochemistry of Fp. PMID:23750456

Su, Tao; Ma, Jiani; Wong, Naikei; Phillips, David Lee

2013-07-18

198

Synthesis and characterization of Cu(In, Ga)Se2 absorption/scattering layers by electrodeposition method  

NASA Astrophysics Data System (ADS)

We propose a Cu(In, Ga)Se2 double absorption layer structure with both absorption and scattering effects. We synthesized CIGS absorption layers by electro-deposition using different electrical potentials. Structural properties were characterized by x-ray diffraction and field-emission scanning electron microscopy. Optical properties were measured using UV/VIS spectrometry. Grain size and surface roughness were controlled by manipulation of the electrical potential. From these results, the currently typical, single CIGS absorption layer, was replaced with two CIGS layers: a top CIGS layer of smaller grain size and a bottom CIGS layer of larger grain size. We found that the larger-grain CIGS layer provides better scattering effect, so that the CIGS double layer structure provides enhanced light absorption performance in visible light. By applying this new CIGS double layer structure, it is expected that conversion efficiency will be increased.

Jeong, Soochang; Choi, Hyonkwang; Hwang, Junghwan; Park, Juntae; Im, Ki Hong; Jung, Yongil; Jeon, Minhyon

2013-11-01

199

Synthesis, spectroscopic characterization and crystal structure of novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands  

NASA Astrophysics Data System (ADS)

Novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands with different substituents (CF3, N(CH3)2 or OH groups) were synthesized by the condensation reaction of triethylenetetramine with 4-substituted benzaldehydes. Triethylenetetramine tris(4-trifluoromethylbenzylidene) (TTFMB), triethylenetetramine tris(4-dimethylaminobenzylidene) (TTDMB) and triethylenetetramine tris(2,4-dihydroxybenzylidene) (TTDHB) were formed as N4 donor ligands. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine ligand. The structure of the TTFMB and TTDMB were determined by single crystal X-ray crystallography. The synthesized ligands have been characterized on the basis of the results of cyclic voltammetry (CV) and spectroscopic studies viz. FT-IR spectroscopy (FT-IR), mass spectroscopy (MS) and UV-Vis spectroscopy (UV-Vis).

Habibi, Mohammad Hossein; Shojaee, Elahe; Nichol, Gary S.

2012-12-01

200

Synthesis, spectroscopic characterization and crystal structure of novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands.  

PubMed

Novel NNNN-donor ?-bis(bidentate) tetraaza acyclic Schiff base ligands with different substituents (CF(3), N(CH(3))(2) or OH groups) were synthesized by the condensation reaction of triethylenetetramine with 4-substituted benzaldehydes. Triethylenetetramine tris(4-trifluoromethylbenzylidene) (TTFMB), triethylenetetramine tris(4-dimethylaminobenzylidene) (TTDMB) and triethylenetetramine tris(2,4-dihydroxybenzylidene) (TTDHB) were formed as N(4) donor ligands. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging unit gives rise to a new type of imidazolidine ligand. The structure of the TTFMB and TTDMB were determined by single crystal X-ray crystallography. The synthesized ligands have been characterized on the basis of the results of cyclic voltammetry (CV) and spectroscopic studies viz. FT-IR spectroscopy (FT-IR), mass spectroscopy (MS) and UV-Vis spectroscopy (UV-Vis). PMID:23010628

Habibi, Mohammad Hossein; Shojaee, Elahe; Nichol, Gary S

2012-12-01

201

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin 1  

NASA Astrophysics Data System (ADS)

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm-1. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I. H. M.; van Grondelle, Rienk; Moffat, Keith; Kennis, John T. M.

2004-09-01

202

Low-temperature and time-resolved spectroscopic characterization of the LOV2 domain of Avena sativa phototropin  

SciTech Connect

The phototropins are plant blue-light receptors that base their light-dependent action on the reversible formation of a covalent bond between a flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in light, oxygen or voltage (LOV) domains. The spectroscopic properties of the LOV2 domain of phototropin 1 of Avena sativa (oat) have been investigated by means of low-temperature absorption and fluorescence spectroscopy and by time-resolved fluorescence spectroscopy. The low-temperature absorption spectrum of the LOV2 domain showed a fine structure around 473 nm, indicating heterogeneity in the flavin binding pocket. The fluorescence quantum yield of the flavin cofactor increased from 0.13 to 0.41 upon cooling the sample from room temperature to 77 K. A pronounced phosphorescence emission around 600 nm was observed in the LOV2 domain between 77 and 120 K, allowing for an accurate positioning of the flavin triplet state in the LOV2 domain at 16900 cm{sup -1}. Fluorescence from the cryotrapped covalent adduct state was extremely weak, with a fluorescence spectrum showing a maximum at 440 nm. Time-resolved fluorescence experiments utilizing a synchroscan streak camera revealed a singlet-excited state lifetime of the LOV2 domain of 2.4 ns. FMN dissolved in aqueous solution showed a pH-dependent lifetime ranging between 2.9 ns at pH 2.0 to 4.7 ns at pH 8.0. No spectral shifting of the flavin emission was observed in the LOV2 domain nor in FMN in aqueous solution.

Gauden, Magdalena; Crosson, Sean; van Stokkum, I.H.; Grondelle, Rienkvan; Moffat, Keith; Kennis, John T. (UC)

2004-12-13

203

Synthesis and Spectroscopic Characterization of Water-Soluble Fluorescent Ag Nanoclusters  

PubMed Central

Water-soluble fluorescent Ag nanoclusters (NCs) were synthesized at room temperature with sodium dodecyl sulfonate (SDS) as a protective agent. The effects of synthetic conditions on the fluorescence properties of Ag NCs were investigated. The results show that the fluorescence intensity of Ag NCs strongly depends on the synthetic conditions, such as the molar ratio of AgNO3 versus SDS and sodium borohydride (NaBH4), the reaction time, and the pH value of the reaction solution. Under the optimum conditions, the as-prepared Ag NCs exist in face-centered-cubic phase with an average size of 2?nm. Fluorescence spectra of Ag NCs show emission peaks at 365?nm for different excitation wavelength. Resonant absorptions are observed at 203?nm and 277?nm in the absorption spectrum, which can be used to establish the electronic levels in the Ag NCs system. PMID:23762779

Zheng, Chengzhi; Wang, Huiping; Liu, Lingzhi; Zhang, Manjun; Liang, Jiangong; Han, Heyou

2013-01-01

204

SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite  

NASA Astrophysics Data System (ADS)

The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH)?H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm-1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm-1. A very sharp band is observed at 3668 cm-1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm-1 are assigned to water stretching vibrations.

Frost, Ray L.; López, Andrés; Scholz, Ricardo; Theiss, Frederick L.; Romano, Antônio Wilson

2015-02-01

205

Spectroscopic characterization and quantitative determination of atorvastatin calcium impurities by novel HPLC method  

NASA Astrophysics Data System (ADS)

Seven process related impurities were identified by LC-MS in the atorvastatin calcium drug substance. These impurities were identified by LC-MS. The structure of impurities was confirmed by modern spectroscopic techniques like 1H NMR and IR and physicochemical studies conducted by using synthesized authentic reference compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. These impurities were detected by newly developed gradient, reverse phase high performance liquid chromatographic (HPLC) method. The system suitability of HPLC analysis established the validity of the separation. The analytical method was validated according to International Conference of Harmonization (ICH) with respect to specificity, precision, accuracy, linearity, robustness and stability of analytical solutions to demonstrate the power of newly developed HPLC method.

Gupta, Lokesh Kumar

2012-11-01

206

Characterization of Arsenic Ultra-Shallow Junctions in Silicon Using Photocarrier Radiometry and Spectroscopic Ellipsometry  

NASA Astrophysics Data System (ADS)

Photocarrier radiometry (PCR) and spectroscopic ellipsometry (SE) techniques were employed to measure ultra-shallow junction (USJ) wafers. These USJ wafers were prepared by As+ ion implantation at energies of 0.5 keV to 5 keV, at a dose of 1 × 1015 As+/cm2 and spike annealing. The experimental data showed that the PCR signal versus implantation energy exhibits a monotonic behavior. The damaged layer of the as-implanted wafer and the recrystallization and activation of the post-annealed wafer were evaluated by SE in the spectral range from 0.27 ?m to 20 ?m. PCR and SE were shown to provide non-destructive metrology tools for process monitoring in USJ fabrication.

Huang, Qiuping; Li, Bincheng; Gao, Weidong

2012-11-01

207

SEM, EDX, infrared and Raman spectroscopic characterization of the silicate mineral yuksporite.  

PubMed

The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH)?H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm(-1) and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm(-1). A very sharp band is observed at 3668 cm(-1) and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm(-1) are assigned to water stretching vibrations. PMID:25240833

Frost, Ray L; López, Andrés; Scholz, Ricardo; Theiss, Frederick L; Romano, Antônio Wilson

2015-02-25

208

Spectroscopic and computational characterization of laccases and their substrate radical intermediates.  

PubMed

Laccases are multicopper oxidases which oxidize a wide variety of aromatic compounds with the concomitant reduction of oxygen to water as by-product. Due to their high stability and biochemical versatility, laccases are key enzymes to be used as eco-friendly biocatalyst in biotechnological applications. The presence of copper paramagnetic species in the catalytic site paired with the substrate radical species produced in the catalytic cycle makes laccases particularly attractive to be studied by spectroscopic approaches. In this review, the potentiality of a combined multifrequency electron paramagnetic spectroscopy /computational approach to gain information on the nature of the catalytic site and radical species is presented. The knowledge at molecular level of the enzyme oxidative process can be of great help to model new enzymes with increased efficiency and robustness. PMID:25595303

Pogni, Rebecca; Baratto, Maria Camilla; Sinicropi, Adalgisa; Basosi, Riccardo

2015-03-01

209

Characterization of the SEI on a carbon film electrode by combinedEQCM and spectroscopic ellipsometry  

SciTech Connect

The electrochemical quartz crystal microbalance (EQCM) andcyclic voltammetry have been applied simultaneously to characterizeelectron-beam deposited carbon film electrodes in LiClO4 orLiPF6-containing mixed electrolytes of ethylene carbonate (EC) anddimethyl carbonate (DMC). The structure of the carbon electrode was foundto be amorphous/disordered using Raman spectroscopy. Cyclic voltammetryin LiClO4 / EC+DMC demonstrated features typical of Liintercalation/deintercalation into/from the disordered carbon electrode,and EQCM showed a corresponding mass increase/decrease. Contrary to thecase of LiClO4 / EC+DMC electrolyte, LiPF6/EC+DMC electrolyte showed noLi deintercalation out of the thin-film carbon electrode. Combined EQCMand spectroscopic ellipsometry data were compared, and the solidelectrolyte interphase density after the first cycle in LiClO4 /EC+DMCwas estimated to be 1.3 g/cm3.

evans@socrates.berkeley.edu

2002-01-01

210

Practical photoluminescence and photoreflectance spectroscopic system for optical characterization of semiconductor devices  

NASA Astrophysics Data System (ADS)

We present a practical experimental design for performing photoluminescence (PL) and photoreflectance (PR) measurements of semiconductors with only one PL spectroscopic system. The measurement setup is more cost efficient than typical PL-plus-PR systems. The design of the experimental setup of the PL-PR system is described in detail. Measurements of two actual device structures, a high-electron-mobility transistor (HEMT) and a double heterojunction-bipolar transistor (DHBT), are carried out by using this design. The experimental PL and PR spectra of the HEMT device, as well as polarized-photoreflectance (PPR) spectra of the DHBT structure, are analyzed in detailed and discussed. The experimental analyses demonstrate the well-behaved performance of this PL-PR design.

Ho, Ching-Hwa; Huang, Kuo-Wei; Lin, Yu-Shyan; Lin, Der-Yuh

2005-05-01

211

Spectroscopic characterization of dissolved organic matter isolates from sediments and the association with phenanthrene binding affinity.  

PubMed

In this study, selected spectroscopic characteristics of sediment organic matter (SOM) were compared and discussed with respect to their different isolation methods, the source discrimination capabilities, and the association with the extent of phenanthrene binding. A total of 16 sediments were collected from three categorized locations including a costal lake, industrial areas, and upper streams, each of which is likely influenced by the organic sources of algal production, industrial effluent, and terrestrial input, respectively. The spectroscopic properties related to aromatic structures and terrestrial humic acids were more pronounced for alkaline extractable organic matter (AEOM) isolates than for the SOM isolates based on water soluble extracts and pore water. The three categorized sampling locations were the most differentiated in the AEOM isolates, suggesting AEOM may be the most representative SOM isolates in terms of describing the chemical properties and the organic sources of SOM. Parallel factor analysis (PARAFAC) based on fluorescence excitation-emission matrix (EEM) showed that a combination of three fluorescent groups could represent all the fluorescence features of SOM. The three categorized sampling locations were well discriminated by the percent distributions of humic-like fluorescent groups of the AEOM isolates. The relative distribution of terrestrial humic-like fluorophores was well correlated with the extent of phenanthrene binding (r=0.571; p<0.05), suggesting that the presence of humic acids in SOM may contribute to the enhancement of binding with hydrophobic organic contaminants in sediments. Principal component analysis (PCA) further demonstrated that the extent of SOM's binding affinity might be affected by the degree of biogeochemical transformation in SOM. PMID:24997951

Hur, Jin; Lee, Bo-Mi; Shin, Kyung-Hoon

2014-09-01

212

Green preparation and spectroscopic characterization of plasmonic silver nanoparticles using fruits as reducing agents  

PubMed Central

Summary Chemicals typically available in plants have the capability to reduce silver and gold salts and to create silver and gold nanoparticles. We report the preparation of silver nanoparticles with sizes between 10 and 300 nm from silver nitrate using fruit extract collected from pineapples and oranges as reducing agents. The evolvement of a characteristic surface plasmon extinction spectrum in the range of 420 nm to 480 nm indicates the formation of silver nanoparticles after mixing silver nitrate solution and fruit extract. Shifts in plasmon peaks over time indicate the growth of nanoparticles. Electron microscopy shows that the shapes of the nanoparticles are different depending on the fruit used for preparation. The green preparation process can result in individual nanoparticles with a very poor tendency to form aggregates with narrow gaps even when aggregation is forced by the addition of NaCl. This explains only modest enhancement factors for near-infrared-excited surface enhanced Raman scattering. In addition to the surface plasmon band, UV–visible absorption spectra show features in the UV range which indicates also the presence of small silver clusters, such as Ag4 2+. The increase of the plasmon absorption correlates with the decrease of absorption band in the UV. This confirms the evolution of silver nanoparticles from silver clusters. The presence of various silver clusters on the surface of the “green” plasmonic silver nanoparticles is also supported by a strong multicolor luminesce signal emitted by the plasmonic particles during 473 nm excitation.

Ærøe Hyllested, Jes; Espina Palanco, Marta; Hagen, Nicolai; Mogensen, Klaus Bo

2015-01-01

213

FTIR spectroscopic, thermal and XRD characterization of hydroxyapatite from new natural sources.  

PubMed

The inorganic constituents of 5 different plants (leaves and stalks) were investigated by using Fourier transformer infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis including thermal gravimetric analysis (TGA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). These plants are Catha edulis (Khat), basil, mint, green tea and trifolium. The absorption bands of carbonate ions CO(3)(2-) was exhibited at 1446 cm(-1), and the phosphate ions PO(4)(3-) was assigned at 1105 and 1035 cm(-1). At high temperatures (600, 700 and 600°C) further absorption bands of the phosphate ions PO(4)(3-) was assigned at the frequencies 572, 617, 962, 1043 and 1110 cm(-1) and the vibrational absorption band of the carbonate ions CO(3)(2-) was assigned at 871, 1416 and 1461 cm(-1). X-ray diffraction and thermal analysis confirm the obtained results of FITR. Results showed that the main inorganic constituents of C. edulis and basil leaves are hydroxyapatite whereas the hydroxyapatite content in the other plant samples is less than that in case of C. edulis and basil plant leaves. PMID:21903453

Shaltout, Abdallah A; Allam, Moussa A; Moharram, Mohamed A

2011-12-01

214

Green preparation and spectroscopic characterization of plasmonic silver nanoparticles using fruits as reducing agents.  

PubMed

Chemicals typically available in plants have the capability to reduce silver and gold salts and to create silver and gold nanoparticles. We report the preparation of silver nanoparticles with sizes between 10 and 300 nm from silver nitrate using fruit extract collected from pineapples and oranges as reducing agents. The evolvement of a characteristic surface plasmon extinction spectrum in the range of 420 nm to 480 nm indicates the formation of silver nanoparticles after mixing silver nitrate solution and fruit extract. Shifts in plasmon peaks over time indicate the growth of nanoparticles. Electron microscopy shows that the shapes of the nanoparticles are different depending on the fruit used for preparation. The green preparation process can result in individual nanoparticles with a very poor tendency to form aggregates with narrow gaps even when aggregation is forced by the addition of NaCl. This explains only modest enhancement factors for near-infrared-excited surface enhanced Raman scattering. In addition to the surface plasmon band, UV-visible absorption spectra show features in the UV range which indicates also the presence of small silver clusters, such as Ag4 (2+). The increase of the plasmon absorption correlates with the decrease of absorption band in the UV. This confirms the evolution of silver nanoparticles from silver clusters. The presence of various silver clusters on the surface of the "green" plasmonic silver nanoparticles is also supported by a strong multicolor luminesce signal emitted by the plasmonic particles during 473 nm excitation. PMID:25821667

Ærøe Hyllested, Jes; Espina Palanco, Marta; Hagen, Nicolai; Mogensen, Klaus Bo; Kneipp, Katrin

2015-01-01

215

A Complete Spectroscopic Characterization of SO and its Isotopologues up to the Terahertz Domain  

NASA Astrophysics Data System (ADS)

In order to obtain accurate terahertz center frequencies for SO and its isotopologues, we have studied the absorption spectrum of SO, 34SO, and 33SO up to 2.5 THz using continuous-wave terahertz photomixing based on a frequency comb providing an accuracy down to 10 kHz. Sulfur monoxide was produced in a radio frequency discharge of air in a cell containing pure sulfur. Together with the strong absorption signal of the main isotopologue, transitions of 34SO (34S: 4.21%) and 33SO (33S: 0.75%) were observed in natural abundance. The newly observed transitions constitute an extension of the observed rotational quantum numbers of the molecule toward higher N values, allowing an improvement of the molecular parameters for the three species. An isotopically invariant fit has been performed based on pure rotational and ro-vibrational transitions of all SO isotopologues, enabling their accurate line position prediction at higher frequencies. Thanks to this new set of parameters, it is now possible to predict with very high accuracy the frequencies of the ro-vibrational lines. This should enable the research of SO in the mid-IR using ground-based IR telescopes, space-based telescope archives (Infrared Space Observatory, Spitzer), and future space missions such as the James Webb Space Telescope. This set of parameters is particularly well adapted for the detection of SO lines in O-rich evolved stars or in molecular clouds in absorption against bright IR sources.

Martin-Drumel, M. A.; Hindle, F.; Mouret, G.; Cuisset, A.; Cernicharo, J.

2015-02-01

216

An in situ cell for characterization of solids by soft x-ray absorption  

NASA Astrophysics Data System (ADS)

A cell has been designed and fabricated for in situ characterization of catalysts and environmental materials using soft x-ray absorption spectroscopy and spectromicroscopy at photon energies above 250 eV. "Lab-on-a-chip" technologies were used to fabricate the cell on a glass wafer. The sample compartment is 1.0 mm in diameter and has a gas path length of 0.8 mm to minimize x-ray absorption in the gas phase. The sample compartment can be heated to 533 K by an Al resistive heater and gas flows up to 5.0 cm3 min-1 can be supplied to the sample compartment through microchannels. The performance of the cell was tested by acquiring Cu L3-edge x-ray appearance near-edge structure (XANES) data during the reduction and oxidation of a silica-supported Cu catalyst using the beam line 11.0.2 scanning transmission x-ray microscope (STXM) at the Advanced Light Source of Lawrence Berkeley National Laboratory (Berkeley, CA). Two-dimensional images of individual catalyst particles were recorded at photon energies between 926 and 937 eV, the energy range in which the Cu(II) and Cu(I) L3 absorption edges are observed. Oxidation state specific images of the catalyst clearly show the disappearance of Cu(II) species during the exposure of the oxidized sample to 4% CO in He while increasing the temperature from 308 to 473 K. Reoxidation restores the intensity of the image associated with Cu(II). Cu L3-edge XANES spectra obtained from stacks of STXM images show that with increasing temperature the Cu(II) peak intensity decreases as the Cu(I) peak intensity increases.

Drake, Ian J.; Liu, Teris C. N.; Gilles, Mary; Tyliszczak, Tolek; Kilcoyne, A. L. David; Shuh, David K.; Mathies, Richard A.; Bell, Alexis T.

2004-10-01

217

The role of terahertz polariton absorption in the characterization of crystalline iron sulfate hydrates.  

PubMed

Iron sulfate compounds have been used extensively to produce iron gall ink, a widely used writing ink in the western world from the 12th-20th centuries. Iron gall ink is well known to corrode writing supports, so detection of iron species is important for the preservation of historical artwork and documents. Iron(ii) sulfate readily changes hydration states and oxidizes in ambient conditions, forming compounds that contribute to this deterioration. In this study, five forms of iron sulfate are characterized by terahertz spectroscopy and solid-state density functional theory (DFT). The results have revealed that the room temperature spectra of FeSO4·7H2O and FeSO4·4H2O are remarkably similar, differing by only a single absorption feature. The identifying terahertz spectra provide an unambiguous metric to determine the relative concentrations of the most common hydrates FeSO4·7H2O and FeSO4·4H2O in a mixed sample. Complete spectral assignments of these species were accomplished by quantum mechanical simulations, with the exception being a single anomalous feature at approximately 40 cm(-1) in the heptahydrate. This peak is believed to be due to polariton absorption, brought about by the particular coordination structure of FeSO4·7H2O that results in a greater charge separation relative to the other iron sulfate crystals. PMID:25760695

Ruggiero, Michael T; Bardon, Tiphaine; Strli?, Matija; Taday, Philip F; Korter, Timothy M

2015-04-14

218

Silica-coated iron nanocubes: preparation, characterization and application in microwave absorption.  

PubMed

Novel cubic nanocapsules consisting of metallic iron core and amorphous silica shell were fabricated through a simple chemical reduction route followed by a Stöber process. Thus-prepared Fe@SiO(2) nanocubes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectrometer (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), vibrating sample magnetometer (VSM) and scalar network analysis (SNA). Comparing with that of pure iron counterparts, silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance. A reflection loss (RL) exceeding -12 dB was obtained in the frequency range of 8-14 GHz for an absorber thickness of 2 mm, with an optimal RL of -18.2 dB at 9 GHz. Mechanism of the improved microwave absorption properties of the Fe@SiO(2) composite was discussed based on their magnetic properties and electromagnetic theory. PMID:19833348

Ni, Xiaomin; Zheng, Zhong; Hu, Xiang; Xiao, Xiukun

2010-01-01

219

Synthesis, characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite  

NASA Astrophysics Data System (ADS)

Sm-doped strontium ferrite nanopowders (SrSm0.3Fe11.7O19) and their composites of polyaniline (PANI)/SrSm0.3Fe11.7O19 with 10 wt% and 20 wt% ferrite were prepared by a sol-gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm0.3Fe11.7O19 was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm0.3Fe11.7O19 possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2-18 GHz. The value of the maximum reflection loss (RL) were -26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and -24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.

Luo, Juhua; Xu, Yang; Gao, Duoduo

2014-11-01

220

Instrument for x-ray absorption spectroscopy with in situ electrical control characterizations  

SciTech Connect

We report a synchrotron-based setup capable of performing x-ray absorption spectroscopy and x-ray magnetic circular dichroism with simultaneous electrical control characterizations. The setup can enable research concerning electrical transport, element- and orbital-selective magnetization with an in situ fashion. It is a unique approach to the real-time change of spin-polarized electronic state of a material/device exhibiting magneto-electric responses. The performance of the setup was tested by probing the spin-polarized states of cobalt and oxygen of Zn{sub 1-x}Co{sub x}O dilute magnetic semiconductor under applied voltages, both at low (?20 K) and room temperatures, and signal variations upon the change of applied voltage were clearly detected.

Huang, Chun-Chao; Chang, Shu-Jui; Yang, Chao-Yao; Tseng, Yuan-Chieh [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China)] [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Chou, Hsiung [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)] [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

2013-12-15

221

Absorption in the Cosmic Web: Characterizing the Intergalactic Medium in Cosmological Filaments  

NASA Astrophysics Data System (ADS)

We propose to observe and characterize the IGM associated with cosmological filaments in a statistical manner up to redshift ~0.4. For this purpose, we have used a published cluster catalog (Hao et al. 2010) to identify massive nodes in the cosmic web. We used cluster-pairs separated by < 20 Mpc (transverse) and < 2000 km/s (along the LOS) to identify zones where filaments should reside with high probabilities. We have selected a single QSO whose sightline passess through a total of 9 independent cluster-pairs (8 of which having spectroscopic redshifts) at impact parameters <10 Mpc (7 of which at < 5 Mpc). We propose to observe the QSO with HST/COS using the G130M and G160M gratings to cover the full FUV spectral range at medium resolution (R~20000). We require observations at S/N>10 to ensure a full characterization of HI and OVI lines at column densities N~10^13 cm^-2. This setup will allow us to detect broad and shallow HI and OVI lines (if any) at the redshifts of these filaments, believed to trace portions of the warm-hot intergalactic medium (WHIM). Combining these new observations with those from our pilot study carried out in cycle 20 (ID 12958, PI Tejos), we aim to provide a firm detection of the WHIM in cosmological filaments, at the 95% confidence level. Our findings will test our understanding of galaxy formation and the role of AGN/supernova feedback by comparing them with state-of-the-art hydrodynamical simulations. We will also test the the hypothesis which states that the majority of OVI absorbers at low-z are confined within <300 kpc from galaxies (i.e. circumgalactic medium) thus not related to the WHIM (Prochaska et al. 2011; Tumlinson et al. 2011).

Tejos, Nicolas

2014-10-01

222

Applied quantum chemistry: Spectroscopic detection and characterization of the F2BS and Cl2BS free radicals in the gas phase  

NASA Astrophysics Data System (ADS)

In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X2BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F2BS and Cl2BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor mixtures of BF3 or BCl3 and CS2 vapor to an electric discharge at the exit of a pulsed molecular beam valve. The B ˜ 2 A 1 - X ˜ 2 B 2 laser-induced fluorescence spectra were found within 150 cm-1 of their theoretically predicted positions with vibronic structure consistent with our Franck-Condon simulations. The B ˜ 2 A 1 state emits down to the ground state and to the low-lying A ˜ 2 B 1 excited state and the correspondence between the observed and theoretically derived SVL emission Franck-Condon profiles was used to positively identify the radicals and make assignments. Excited state Coriolis coupling effects complicate the emission spectra of both radicals. In addition, a forbidden component of the electronically allowed B ˜ - X ˜ band system of Cl2BS is evident, as signaled by the activity in the b2 modes in the spectrum. Symmetry arguments indicate that this component gains intensity due to a vibronic interaction of the B ˜ 2 A 1 state with a nearby electronic state of 2B2 symmetry.

Jin, Bing; Sheridan, Phillip M.; Clouthier, Dennis J.

2015-03-01

223

Comparative in vitro characterization of moxidectin and doramectin percutaneous absorption through bovine skin.  

PubMed

Topical formulations have achieved worldwide acceptance in veterinary medicine because their administration is an easy, less labor-intensive and nonstressing form. Any chemical compound that comes in contact with the skin has the potential to be locally and/or systemically absorbed. However, many factors related to the features of animal skin, composition of the topical formulation and to the drug itself can determine marked differences in the percutaneous absorption process. The aim of the current work was to characterize the pattern of in vitro percutaneous absorption for moxidectin (MXD) and doramectin (DRM), two of the most worldwide used topical macrocyclic lactone antiparasitic compounds in cattle. The work included the development of a simple and inexpensive in vitro assay useful to predict in vivo drug percutaneous absorption in cattle. Both drugs were administered as the commercial formulations intended for their topical administration to cattle. The in vitro studies were carried out using modified Franz-type vertical diffusion cells. Cattle skin slices of 500 ?m thickness were prepared using a dermatome to separate the stratum corneum and upper epidermis from dermis and subcutaneous tissue. The receptor medium was sampled up to 72 h postadministration and drug concentrations were measured by HPLC. The parameters used to estimate the comparative in vitro skin permeation showed marked differences between DRM and MXD. A 5.29-fold longer lag time (T(lag)) was observed for DRM. Similarly, the flux (J) (2.93-fold) and the permeation coefficients (K(p) ) (2.95-fold) in cattle skin were significantly higher (P < 0.05) for DRM compared to those obtained for MXD. Additionally, the data obtained from the in vitro permeation studies was correlated with the plasma concentrations of both compounds achieved in vivo in cattle treated with the same topical formulations. Correlation coefficients between percentage of drug permeated in vitro vs. percentage of drug absorbed in vivo (up to 48 h post-treatment) were 0.856-0.887 (MXD) and 0.976-0.990 (DRM). However, the highest in vitro-in vivo correlations for both molecules were observed up to 24 h post-treatment A rapid screening method for testing different topical formulations can be achieved with the simple in vitro cattle skin permeation technique described here, which has been successfully adapted to test the comparative percutaneous absorption of MXD and DRM. PMID:21521238

Sallovitz, J M; Nejamkin, P; Lifschitz, A L; Virkel, G L; Imperiale, F A; Lanusse, C E

2012-04-01

224

Micro-spectroscopic techniques applied to characterization of varnished archeological findings  

NASA Astrophysics Data System (ADS)

This work reports an analysis on terracotta varnished finding recovered in east Sicily area (Messina). We have performed FTIR micro-spectroscopy and electronic microscopy (SEM)measurements in order to recognize the elemental constituents of the varnished surfaces. Furthermore, for all the samples, a study on the bulk has been performed by Fourier Transform Infrared Absorption. The analyzed samples consist of a number of pottery fragments belonging to archaic and classical ages, varnished in black and red colors. The obtained data furnished useful information about composition of decorated surfaces and bulk matrixes, about baking temperature, manufacture techniques and alteration mechanisms of findings due to the long burial.

Barone, G.; Ioppolo, S.; Majolino, D.; Migliardo, P.; Ponterio, R.

2000-04-01

225

Minerals from Macedonia XXIII. Spectroscopic and structural characterization of schorl and beryl cyclosilicates.  

PubMed

IR and Raman spectroscopy study on two collected cyclosilicate species: schorl (from tourmaline group), Na(Fe,Mg)(3)Al(6)(BO(3))(3)Si(6)O(18)(OH,F)(4) and beryl (Be,Mg,Fe)(3)Al(2)Si(6)O(18) were carried out. Although beryl is nominally anhydrous mineral, vibrational results strongly indicate that H(2)O molecules exist in the structural channels. The number of vibrational bands and their frequencies revealed the presence of H(2)O type II, in which C(2) symmetry axis of the water molecule is parallel to the structural channel (and to the c-axis of beryl). On the other hand, it was found that observed bands in the IR and Raman OH stretching region of the other tourmaline varieties appear as a result of the cation combinations involving dominant presence of Mg and Fe cations in the Y structural sites. The strong indication derived from the vibrational spectroscopic results that the studied mineral represents a schorl variety, coincide very well with the results obtained by powder X-ray diffraction and X-ray microprobe analysis. Both minerals show IR spectral similarities in the region below 1500 cm(-1), whereas the resemblance between the Raman spectra (1500-100 cm(-1)) is less expressed confirming that these spectra are more sensitive to compositional changes and to structural disorder. The identification of both minerals was additionally supported by studying the powder X-ray diffraction diagrams. PMID:18722809

Makreski, Petre; Jovanovski, Gligor

2009-08-01

226

Spectroscopic and chromatographic characterization of wastewater organic matter from a biological treatment plant.  

PubMed

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation. PMID:22315538

Park, Min-Hye; Lee, Tae-Hwan; Lee, Bo-Mi; Hur, Jin; Park, Dae-Hee

2010-01-01

227

Molecular structure and spectroscopic characterization of Carbamazepine with experimental techniques and DFT quantum chemical calculations.  

PubMed

A systematic vibrational spectroscopic assignment and analysis of Carbamazepine has been carried out by using FT-IR, FT-Raman and UV spectral data. The vibrational analysis were aided by electronic structure calculations - ab initio (RHF) and hybrid density functional methods (B3LYP) performed with standard basis set 6-31G(d,p). Molecular equilibrium geometries, electronic energies, natural bond order analysis, harmonic vibrational frequencies and IR intensities have been computed. A detailed interpretation of the vibrational spectra of the molecule has been made on the basis of the calculated Potential Energy Distribution (PED) by VEDA program. UV-visible spectrum of the compound was also recorded and the electronic properties, such as HOMO and LUMO energies and ?max were determined by HF/6-311++G(d,p) Time-Dependent method. The thermodynamic functions of the title molecule were also performed using the RHF and DFT methods. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance (NMR) calculation procedure was also performed, and it was used for assigning the (13)C and (1)H NMR chemical shifts of Carbamazepine. PMID:25682215

Suhasini, M; Sailatha, E; Gunasekaran, S; Ramkumaar, G R

2015-04-15

228

Synthesis and Spectroscopic Characterization of Some New Axially Ligated Indium(III) Macrocyclic Complexes and Their Biological Activities  

PubMed Central

The synthesis and spectroscopic characterization of new axially ligated indium(III) porphyrin complexes were reported. Chloroindium(III) porphyrin (TPPIn-Cl) was obtained in good yield by treating the corresponding free base with indium trichloride. The action of the different phenols on chloroderivatives (TPPIn-Cl) led to the corresponding phenolato complexes (TPPIn-X). These derivatives were characterized on the basis of mass spectrometry, 1H-NMR, IR, and UV-visible data. The separation and isolation of these derivatives have been achieved through chromatography. The spectral properties of free base porphyrin and its corresponding metallated and axially ligated indium(III) porphyrin compounds were compared with each other. A detailed analysis of UV-Vis, 1H-NMR, and IR suggested the transformation from free base porphyrin to indium(III) porphyrin. Besides, 13C-NMR and fluorescence spectra were also reported and interpreted. The stability of these derivatives has also been studied through thermogravimetry. The complexes were also screened for anticancerous activities. Among all the complexes, 4-MePhO-InTPP shows highest anticancerous activity. The title complexe, TPPIn-X (where X = different phenolates), represents a five-coordinate indium(III) porphyrin complex in a square-pyramidal geometry with the phenolate anion as the axial ligand. PMID:25140121

Bajju, Gauri D.; Gupta, Deepmala; Kapahi, Ashu

2014-01-01

229

Synthesis, spectroscopic, structural and thermal characterizations of vanadyl(IV) adenine complex prospective as antidiabetic drug agent.  

PubMed

The vanadyl(IV) adenine complex; [VO(Adn)2]?SO4; was synthesized and characterized. The molar conductivity of this complex was measured in DMSO solution that showed an electrolyte nature. Spectroscopic investigation of the green solid complex studied here indicate that the adenine acts as a bidentate ligand, coordinated to vanadyl(IV) ions through the nitrogen atoms N7 and nitrogen atom of amino group. Thus, from the results presented the vanadyl(IV) complex has square pyramid geometry. Further characterizations using thermal analyses and scanning electron techniques was useful. The aim of this paper was to introduce a new drug model for the diabetic complications by synthesized a novel mononuclear vanadyl(IV) adenine complex to mimic insulin action and reducing blood sugar level. The antidiabetic ability of this complex was investigated in STZ-induced diabetic mice. The results suggested that VO(IV)/adenine complex has antidiabetic activity, it improved the lipid profile, it improved liver and kidney functions, also it ameliorated insulin hormone and blood glucose levels. The vanadyl(IV) complex possesses an antioxidant activity and this was clear through studying SOD, CAT, MDA, GSH and methionine synthase. The current results support the therapeutic potentiality of vanadyl(IV)/adenine complex for the management and treatment of diabetes. PMID:25150436

El-Megharbel, Samy M; Hamza, Reham Z; Refat, Moamen S

2015-01-25

230

Synthesis, spectroscopic, structural and thermal characterizations of vanadyl(IV) adenine complex prospective as antidiabetic drug agent  

NASA Astrophysics Data System (ADS)

The vanadyl(IV) adenine complex; [VO(Adn)2]?SO4; was synthesized and characterized. The molar conductivity of this complex was measured in DMSO solution that showed an electrolyte nature. Spectroscopic investigation of the green solid complex studied here indicate that the adenine acts as a bidentate ligand, coordinated to vanadyl(IV) ions through the nitrogen atoms N7 and nitrogen atom of amino group. Thus, from the results presented the vanadyl(IV) complex has square pyramid geometry. Further characterizations using thermal analyses and scanning electron techniques was useful. The aim of this paper was to introduce a new drug model for the diabetic complications by synthesized a novel mononuclear vanadyl(IV) adenine complex to mimic insulin action and reducing blood sugar level. The antidiabetic ability of this complex was investigated in STZ-induced diabetic mice. The results suggested that VO(IV)/adenine complex has antidiabetic activity, it improved the lipid profile, it improved liver and kidney functions, also it ameliorated insulin hormone and blood glucose levels. The vanadyl(IV) complex possesses an antioxidant activity and this was clear through studying SOD, CAT, MDA, GSH and methionine synthase. The current results support the therapeutic potentiality of vanadyl(IV)/adenine complex for the management and treatment of diabetes.

El-Megharbel, Samy M.; Hamza, Reham Z.; Refat, Moamen S.

2015-01-01

231

Spectroscopic investigation and optical characterization of Eu3+ ions in K-Nb-Si glasses.  

PubMed

This paper reports on the effect of concentration of Eu(3+) ions in K2O-Nb2O5-SiO2-Eu2O3 (KNbSiEu) glasses prepared by the melt quenching technique. By using the Judd-Ofelt (JO) theory, the intensity parameters ?? (?=2, 4, 6) have been determined from the absorption and emission spectra of Eu(3+) ions under different constraints. The radiative properties of some of the excited states of Eu(3+) ions have been calculated. The decay curves of (5)D0 level exhibited single exponential for all the Eu(3+) ions concentrations. From these results, it is suggested that the strong red emission at 616 nm corresponding to the (5)D0?(7)F2 transition could be used for the development of optical display devices. PMID:24161859

Murali Mohan, M; Rama Moorthy, L; Ramachari, D; Jayasankar, C K

2014-01-24

232

Structural, spectroscopic and magnetic characterization of undoped, Ni2+ doped ZnO nanopowders  

NASA Astrophysics Data System (ADS)

Structural, magnetic and optical properties of undoped and Ni2+ doped ZnO nanopowders have been prepared by sonochemical assistance. Powder XRD studies confirm the hexagonal structure of both undoped and Ni2+ doped of ZnO nanopowders and its average crystallite sizes are evaluated. Optical absorption and Electron Paramagnetic Resonance spectral data confirmed the site symmetry for Ni2+ ions as octahedral. Photoluminescence spectra exhibited the emission bands in ultraviolet and blue regions at an excitation wavelength of 328 nm. FT-IR spectra showed the characteristic vibrational bands of Zn-O. Vibrating sample magnetometer was used for the magnetic property investigations and indicates room temperature ferromagnetism which is intrinsic in nature and attributed to oxygen and/or Zn deficiencies.

Babu, B.; Sundari, G. Rama; Ravindranadh, K.; Yadav, M. Rajesh; Ravikumar, R. V. S. S. N.

2014-12-01

233

Biochemical and spectroscopic characterization of a novel metalloprotease, cotinifolin from an antiviral plant shrub: Euphorbia cotinifolia.  

PubMed

A high molecular mass novel metalloprotease, cotinifolin is purified from the latex of Euphorbia cotinifolia by a combination of anion exchange and hydrophobic interaction chromatography. The nonglycosylated enzyme has a molecular mass of 79.76 kDa (ESI-MS) and the isoelectric point of the enzyme is pH 7.7. Cotinifolin hydrolyzes denatured natural substrates such as casein, azoalbumin, and hemoglobin with high specific activity. The K(m) value of the enzyme was found to be 20 ?M with azocasein. The enzyme is not prone to autolysis even at very low concentrations. Polyclonal antibodies specific to enzyme was raised and immunodiffusion reveals that the enzyme has unique antigenic determinants. Maximum caseinolytic activity of cotinifolin is observed in the range of pH 7.0-8.0 and temperature of 50 °C. Using 0.2 mL of 1 mM solution of each metal ion, the purified protease was inhibited slightly by Ba²? and Mn²?, moderately by Mg²?, Ca²? and Cs²? and significantly by Zn²?, Cu²? and Co²?. On the other hand, substantial activation in caseinolytic activity was achieved by Ni²?. The enzyme activity was also inhibited by EDTA and o-phenanthroline but not by any other protease inhibitors. Perturbation studies by temperature, pH, and chaotrophs of the enzyme also reveal its high stability as seen by CD, fluorescence and proteolytic activity. Spectroscopic studies reveal that cotinifolin has secondary structural features with ?/? type with approximately 9% of ?-helicity. Easy availability and simple purification procedure makes the enzyme a good system for biophysical study, biotechnological and industrial applications. PMID:21531144

Kumar, Reetesh; Singh, Kunwar Awaneesh; Tomar, Ritu; Jagannadham, Medicherla V

2011-07-01

234

Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate  

NASA Astrophysics Data System (ADS)

Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH3-S-CHO (MSCHO) and O-methyl thioformate CH3-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH3-S-CHO represents the most stable structure lying 4372.2 cm-1 below cis-CH3-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm-1) than for MOCHS (1963.6 cm-1). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V3(cis) are determined to be 139.7 cm-1 (CH3-S-CHO) and 670.4 cm-1 (CH3-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm-1 for CH3-S-CHO and negligible for CH3-O-CHS.

Senent, M. L.; Puzzarini, C.; Hochlaf, M.; Domínguez-Gómez, R.; Carvajal, M.

2014-09-01

235

Theoretical spectroscopic characterization at low temperatures of S-methyl thioformate and O-methyl thioformate  

SciTech Connect

Highly correlated ab initio methods are employed to determine spectroscopic properties at low temperatures of two S-analogs of methyl formate: S-methyl thioformate CH{sub 3}-S-CHO (MSCHO) and O-methyl thioformate CH{sub 3}-O-CHS (MOCHS). Both species are detectable and they are expected to play an important role in Astrochemistry. Molecular properties are compared with those of the O-analog, methyl formate. Both isomers present two conformers cis and trans. cis-CH{sub 3}-S-CHO represents the most stable structure lying 4372.2 cm{sup ?1} below cis-CH{sub 3}-O-CHS. The energy difference between the cis and trans forms is drastically lower for MSCHO (1134 cm{sup ?1}) than for MOCHS (1963.6 cm{sup ?1}). Harmonic and anharmonic fundamentals and the corresponding intensities, as well as the rotational constants for the ground vibrational and first excited torsional states and the centrifugal distortions constants, are provided. Low torsional energy levels have been obtained by solving variationally a two dimensional Hamiltonian expressed in terms of the two torsional degrees of freedom. The corresponding 2D potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The methyl torsional barriers V{sub 3}(cis) are determined to be 139.7 cm{sup ?1} (CH{sub 3}-S-CHO) and 670.4 cm{sup ?1} (CH{sub 3}-O-CHS). The A/E splitting of ground torsional state has been estimated to be 0.438 cm{sup ?1} for CH{sub 3}-S-CHO and negligible for CH{sub 3}-O-CHS.

Senent, M. L., E-mail: senent@iem.cfmac.csic.es [Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-C.S.I.C., Serrano 121, Madrid 28006 (Spain); Puzzarini, C., E-mail: cristina.puzzarini@unibo.it [Dipartimento di Chimica G. Ciamician, Università di Bologna, Via F. Selmi 2, I-40126 Bologna (Italy); Hochlaf, M., E-mail: hochlaf@univ-mlv.fr [Laboratoire de Modélisation et Simulation Multi Echelle, Université Paris-Est, MSME UMR 8208 CNRS, 5 boulevard Descartes, 77454 Marne-la-Vallée (France); Domínguez-Gómez, R., E-mail: rosa.dominguez@upm.es [Departamento de Ingeniería Civil, Cátedra de Química, E.U.I.T. Obras Públicas, Universidad Politécnica de Madrid, Madrid (Spain); Carvajal, M., E-mail: miguel.carvajal@dfa.uhu.es [Departamento de Física Aplicada, Facultad de Ciencias Experimentales, Unidad Asociada IEM-CSIC-U.Huelva, Universidad de Huelva, 21071 Huelva (Spain)

2014-09-14

236

Spectroscopic characterization of the chemical composition of the potent sweetener Vartamil  

NASA Astrophysics Data System (ADS)

The chemical composition of the potent sweetener Vartamil was characterized using spectral methods. It was demonstrated that Vartamil is a mixture of saccharose chloro derivatives, the main one of which is 4,1',6'-trichloro-4,1',6'-trideoxygalactosaccharose (Sucralose).

Kolosova, T. E.; Prokhodchenko, L. K.; Pilipenko, V. V.; Suboch, V. P.

2008-03-01

237

Pretreatments and filiform corrosion resistance of cataphoretic painted aluminium characterization by EIS and spectroscopic ellipsometry  

Microsoft Academic Search

Aluminium alloys are widely used in architectural, aeronautic and car industries. They are usually protected by the formation of a thick oxide layer (anodization) or by applying an organic coating. In the latter case, a particular type of corrosion called filiform corrosion can occur. This corrosion is characterized by a paint adhesion loss and the occurrence of threads at the

V. Poulain; J.-P. Petitjean; E. Dumont; B. Dugnoille

1996-01-01

238

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

Microsoft Academic Search

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger

Janel S. Uejio; Craig P. Schwartz; Andrew M. Duffin; Walter S. Drisdell; Ronald C. Cohen; Richard J. Saykally

2008-01-01

239

Steady state and time-resolved fluorescence spectroscopic characterization of normal and cancerous urine  

NASA Astrophysics Data System (ADS)

Urine is one of the diagnostically important bio fluids, as it has many metabolites and some of them are native fluorophores. There may be a variation in the distribution and the physiochemical properties of the fluorophores during any metabolic change and pathologic conditions. Native fluorescence spectroscopy has been considered as a promising tool to characterize the fluorophores present in the urine. In this study, we aimed at characterizing the urine of both normal and patients with confirmed cancer using steady state and time-resolved fluorescence spectroscopy at 280 nm and 350 nm excitation. It is observed that the metabolites indoxyl sulphate and neopterin and its derivatives are responsible for altered spectral signatures at 280 nm, and 350 nm excitation. The overall spectral data were subjected to Principal Component Analysis and the resultant components were used as input in the linear discriminant analysis. As a total, 84% and 81.8% of samples were correctly classified at 280 nm and 350 nm respectively.

Rajasekaran, Ramu; Aruna, Prakasa Rao; Balu David, Munusamy; Koteeswaran, Dornadula; Muthuvelu, Kulandaivel; Rai, R.; Ganesan, Singaravelu

2013-03-01

240

Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas  

NASA Astrophysics Data System (ADS)

Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the Sisbnd Osbnd Si bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric Sisbnd Osbnd Si stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials.

Capeletti, Larissa B.; Baibich, Ione M.; Butler, Ian S.; dos Santos, João H. Z.

2014-12-01

241

Infrared and Raman spectroscopic characterization of some organic substituted hybrid silicas.  

PubMed

Nine hybrid silicas bearing the organic substituent groups methyl, octyl, octadecyl, vinyl, phenyl, mercaptopropyl, isocyanatopropyl, chloropropyl and glycidoxypropyl were synthesized by an acid-catalyzed, hydrolytic sol-gel process. The resulting solid materials were characterized by their absorbance and attenuated total reflection (ATR) IR and Raman spectra. The latter technique proved to be particularly useful in the identification of the organic moieties in the hybrid silicas. The effect of the presence of the organic groups on the silica networks was also investigated - there were increases observed in both the SiOSi bond angles and bond lengths. Moreover, deconvolution of the IR-active antisymmetric SiOSi stretching bands permitted detection of the four- and six-membered siloxane rings present in the silicas. There proved to be a greater number of four-membered rings on the surfaces of the particles. Both IR and Raman spectroscopy proved to be invaluable in the characterization of these hybrid materials. PMID:24992921

Capeletti, Larissa B; Baibich, Ione M; Butler, Ian S; dos Santos, João H Z

2014-12-10

242

Purification and Spectroscopic Characterization of the Human Protein Tyrosine Kinase6 SH3 Domain  

Microsoft Academic Search

The human protein tyrosine kinase-6 (PTK6) polypeptide that is deduced from the cDNA sequence contains a Src homology (SH) 3 domain, SH2 domain, and catalytic domain of tyrosine kinase. We initiated biochemical and NMR characterization of PTK6 SH3 domain in order to correlate the structural role of the PTK6 using circular dichroism and heteronuclear NMR techniques. The circular dichroism data

Bon-Kyung Koo; Min-Hyung Kim; Seung-Taek Lee; Weontae Lee

2002-01-01

243

Spectroscopic characterization of fluorinated\\/hydrogenated mixed vesicles containing fluorinated Mn(III)-porphyrin  

Microsoft Academic Search

Mixed fluorinated\\/hydrogenated vesicles prepared with n-dodecylbetaine and the ammonium salt of a perfluoropolyiber carboxylate were able to be loaded with 5, 10, 15, 20-tetrakis 4-perfluorooctylphenyl)porphyrin and with its Mn(III) salt. The synthesis and the characterization of both long chain tetrapyrrole compounds are described. The structural features of the loaded vesicle systems were studied by light scattering and small angle neutron

Simona Rossi; Sandra Ristori; Gianluca Pozzi; Giacomo Martini

1998-01-01

244

Characterization of interaction of calf thymus DNA with gefitinib: Spectroscopic methods and molecular docking.  

PubMed

The binding interaction of gefitinib with calf thymus DNA (ct-DNA) under the simulated physiological pH condition was studied employing UV absorption, fluorescence, circular dichroism (CD), viscosity measurement and molecular docking methods. The experimental results revealed that gefitinib preferred to bind to the minor groove of ct-DNA with the binding constant (Kb) of 1.29×10(4)Lmol(-1) at 298K. Base on the signs and magnitudes of the enthalpy change (?H(0)=-60.4kJmol(-1)) and entropy change (?S(0)=-124.7Jmol(-1)K(-1)) in the binding process and the results of molecular docking, it can be concluded that the main interaction forces between gefitinib and ct-DNA in the binding process were van der Waals force and hydrogen bonding interaction. The results of CD experiments revealed that gefitinib did not disturb native B-conformation of ct-DNA. And, the significant change in the conformation of gefitinib in gefitinib-ct-DNA complex was observed from the molecular docking results and the change was close relation with the structure of B-DNA fragments, indicating that the flexibility of gefitinib molecule also plays an important role in the formation of the stable gefitinib-ct-DNA complex. PMID:25839749

Shi, Jie-Hua; Liu, Ting-Ting; Jiang, Min; Chen, Jun; Wang, Qi

2015-06-01

245

Characterization of the interactions between tetracycline antibiotics and microbial extracellular polymeric substances with spectroscopic approaches.  

PubMed

The antibiotics have attracted global attentions for their impact on aquatic ecosystem. The knowledge about the fate of antibiotics encountering extracellular polymeric substances (EPS) is, however, limited. In this study, we investigated the interacting mechanisms of tetracycline (TC) to EPS extracted from aerobic activated sludge. The contributions of the main components of EPS, extracellular proteins, and polysaccharides were evaluated using bovine serum albumin and alginate sodium, respectively. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance indicated that hydroxyl, carboxyl, and amino groups were the domain chemical groups involved in the interaction between TC and EPS, and the binding of TC onto EPS changed the structure of these chemical groups, thus causing shifts in their UV-visible absorption spectra. In addition, we found that extracellular proteins, rather than polysaccharides, were the major active contents involved in the interaction. Three-dimensional excitation-emission matrix fluorescence spectroscopy showed that the fluorophores in EPS were clearly quenched by TC and the static quenching process was observed, implying the complex formation of TC and EPS. Furthermore, thermodynamic analysis indicated that the binding of TC with EPS is spontaneous and dominated by electrostatic forces. PMID:23979850

Song, Chao; Sun, Xue-Fei; Xing, Su-Fang; Xia, Peng-Fei; Shi, Yi-Jing; Wang, Shu-Guang

2014-02-01

246

Spectroscopic Characterization of Intermediates in the Iron Catalyzed Activation of Alkanes  

SciTech Connect

The present report begins with a brief survey of recent hypervalent iron chemistry and mentions two previously reported ferrate papers funded by the DOE/BES grant. The focus is then shifted to the seven publications acknowledging support of the grant that have not been reported since the last Progress Report, DOE/ER/14340-9, was prepared. These papers deal with: (a) the successful use of an ATR element in a stopped-flow infrared spectrometer, (b) the rationalization of a depolarization of a LiClO4 solution in polyethylene oxide high polymer, (c) an analysis of several coupled ultrasonic relaxations observed in solutions of pentoses undergoing isomerization, (d) the combination of ultrasonic absorption and Raman scattering measurements to elucidate zinc thiocyanate solutions in water, (e) the use of NMR to determine stability constants when LiClO4:12-crown-4 is dissolved in acetonitrile and in methanol, (f) the possible existence of triple ions in low permittivity solutions, and (g) the properties of a high surface area ceria aerogel. Collectively, these papers illustrate advantages of bringing several modern experimental techniques to bear on complex chemical systems.

Edward M. Eyring

2007-05-28

247

Synchronous luminescence spectroscopic characterization of blood elements of normal and patients with cervical cancer  

NASA Astrophysics Data System (ADS)

In this study the diagnostic potential of synchronous luminescence spectroscopy (SLS) technique for the characterization of normal and different pathological condition of cervix viz., moderately differentiated squamous cell carcinoma (MDSCC), poorly differentiated squamous cell carcinoma (PDSCC) and well differentiated squamous cell carcinoma (WDSSC). Synchronous fluorescence spectra were measured for 70 abnormal cases and 30 normal subjects. Characteristic, highly resolved peaks and significant spectral differences between normal and MDSCC, PDSCC and WDSCC cervical blood formed elements were obtained. The synchronous luminescence spectra of formed elements of normal and abnormal cervical cancer patients were subjected to statistical analysis. Synchronous luminescence spectroscopy provides 90% sensitivity and 92.6% specificity.

Muthuvelu, K.; Shanmugam, Sivabalan; Koteeswaran, Dornadula; Srinivasan, S.; Venkatesan, P.; Aruna, Prakasarao; Ganesan, Singaravelu

2011-03-01

248

Raman Spectroscopic Characterization of Rare Earth Ions Doped Bismuth-Based Glasses  

SciTech Connect

The xReO(1-x)[3Bi2O3{center_dot}PbO] glass systems with diferent rare earth ions (ReO = CeO2, Tb4O7) have been prepared and examined with the aim of determining their structural characteristics. Raman sprectroscopy and density measurements were used to characterize the samples. Raman spectroscopy data permitted to identify some of the structural units that built up the lead bismuthate vitreous network. Density data were used to calculate the Poisson's ratio in terms of the Makishima-Mackenzie model.

Pop, L.; Culea, E.; Bosca, M. [Department of Physics, Technical University of Cluj-Napoca (Romania); Culea, M. [Faculty of Physics, Babes-Bolyai University of Cluj-Napoca (Romania)

2007-04-23

249

Theoretical spectroscopic characterization at low temperatures of methyl hydroperoxide and three S-analogs  

NASA Astrophysics Data System (ADS)

The low temperature spectra of the detectable species methyl hydroperoxide (CH3OOH) and three sulfur analogs, the two isomers of methanesulfenic acid (CH3SOH and CH3OSH) and the methyl hydrogen disulfide (CH3SSH), are predicted from highly correlated ab initio methods (CCSD(T) and CCSD(T)-F12). Rotational parameters, anharmonic frequencies, torsional energy barriers, torsional energy levels, and their splittings are provided. Our computed parameters should help for the characterization and the identification of these organic compounds in laboratory and in the interstellar medium.

Dalbouha, S.; Senent, M. L.; Komiha, N.

2015-02-01

250

Theoretical spectroscopic characterization at low temperatures of methyl hydroperoxide and three S-analogs.  

PubMed

The low temperature spectra of the detectable species methyl hydroperoxide (CH3OOH) and three sulfur analogs, the two isomers of methanesulfenic acid (CH3SOH and CH3OSH) and the methyl hydrogen disulfide (CH3SSH), are predicted from highly correlated ab initio methods (CCSD(T) and CCSD(T)-F12). Rotational parameters, anharmonic frequencies, torsional energy barriers, torsional energy levels, and their splittings are provided. Our computed parameters should help for the characterization and the identification of these organic compounds in laboratory and in the interstellar medium. PMID:25702012

Dalbouha, S; Senent, M L; Komiha, N

2015-02-21

251

UV spectroscopic characterization of an alkyl substituted Criegee intermediate CH3CHOO.  

PubMed

Ozonolysis of alkenes in the troposphere proceeds through a Criegee intermediate, or carbonyl oxide, which has only recently been detected in the gas phase. The present study focuses on the production of an alkyl-substituted Criegee intermediate, CH3CHOO, in a pulsed supersonic expansion, and then utilizes VUV photoionization at 118 nm and UV-induced depletion of the m?z = 60 signal to probe the B (1)A(') ? X (1)A(') transition. The UV-induced depletion approaches 100% near the peak of the profile at 320 nm, indicating rapid dynamics in the B state, and corresponds to a peak absorption cross section of ?5 × 10(-17) cm(2) molecule(-1). The electronic spectrum for CH3CHOO is similar to that reported recently for CH2OO, but shifted 15 nm to shorter wavelength, which will result in a longer tropospheric lifetime for CH3CHOO with respect to solar photolysis. Complementary electronic structure calculations (EOM-CCSD) are carried out for the B and X potentials of these Criegee intermediates along the O-O coordinate. An intramolecular interaction stabilizes the ground state of the syn-conformer of CH3CHOO relative to anti-CH3CHOO, and indicates that the syn-conformer will be the more abundant species in the expansion. The excited B electronic state of syn-CH3CHOO is also predicted to be destabilized relative to that for anti-CH3CHOO and CH2OO, in accord with the shift in the B-X transition observed experimentally. Hydroxyl radicals produced concurrently with the generation of the Criegee intermediates are detected by 1+1(') resonance enhanced multiphoton ionization. The OH yield observed with CH3CHOO is 4-fold larger than that from CH2OO, consistent with prior studies of OH generation from alkene ozonolysis. PMID:23822244

Beames, Joseph M; Liu, Fang; Lu, Lu; Lester, Marsha I

2013-06-28

252

Synthesis, characterization and multi-spectroscopic DNA interaction studies of a new platinum complex containing the drug metformin  

NASA Astrophysics Data System (ADS)

A new platinum(II) complex; [Pt(Met)(DMSO)Cl]Cl in which Met = metformin and DMSO: dimethylsulfoxide, was synthesized and characterized by 1H NMR, IR, UV-Vis spectra, molar conductivity and computational methods. Binding interaction of this complex with calf thymus (CT) DNA has been investigated by using absorption, emission, circular dichroism, viscosity measurements, differential pulse voltammetry and cleavage studies by agarose gel electrophoresis. UV-Vis absorption studies showed hyperchromism. CD studies showed less perturbation on the base stacking and helicity bands in the CD spectrum of CT-DNA (B ? C structural transition). In fluorimeteric studies, the Pt(II) complex can bind with DNA-NR complex and forms a new non-fluorescence adduct. The anodic peak current in the differential pulse voltammogram of the Pt(II) complex decreased gradually with the addition of DNA. Cleavage experiments showed that the Pt(II) complex does not induce any cleavage under the experimental setup. Finally all results indicated that Pt(II) complex interact with DNA via groove binding mode.

Shahabadi, Nahid; Heidari, Leila

2014-07-01

253

Spectroscopic, molecular structure characterizations and quantum chemical computational studies of ( E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol  

NASA Astrophysics Data System (ADS)

The molecular structure and spectroscopic properties of ( E)-5-(diethylamino)-2-[(2-fluorophenylimino)methyl]phenol were characterized by X-ray diffraction, IR and UV/Vis spectroscopy. These properties of title compound were also investigated from calculative point of view. Geometry optimization in gas phase was performed using DFT method with B3LYP applying 6-311G(d,p) basis set and geometry optimizations in solvent media were performed with the same level of theory by the polarizable continuum model (PCM). TD-DFT calculations starting from optimized geometry were carried out in both gas and solution phase to calculate excitation energies of title compound. In addition, while the non-linear optical properties were computed, thermodynamic properties were obtained at the optimized geometry with the same level of theory. The intramolecular proton transfer process from enol form to keto form was investigated using DFT method with B3LYP applying 6-311G(d,p) basis set. Transition state structure in EtOH was performed with the same level of theory by the polarizable continuum model (PCM).

Albayrak, Çi?dem; Frank, Rene

2010-12-01

254

Structures and spectroscopic characterization of calcium chloride-nicotinamide, -isonicotinamide, -picolinamide and praseodymium bromide-nicotinamide complexes.  

PubMed

The coordination structures formed by calcium complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) and praseodymium bromide-na are reported. The structures of CaCl2·(C6H6N2O)2·2H2O (Ca-na), CaCl2·(C6H6N2O)2·4H2O (Ca-ina), CaCl2·(C6H6N2O)2·5H2O (Ca-pa) and PrBr3·(C6H6N2O)2·6H2O (PrBr-na) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Raman spectroscopies. Carbonyl oxygen of nicotinamide is coordinated to Ca(2+), but it is O-monodentate (carbonyl oxygen) and N,O-bidentate ligand (pyridyl nitrogen and carbonyl oxygen) for Pr(3+) to form a chain structure in PrBr-na. For isonicotinamide, only carbonyl oxygen atom is coordinated to Ca(2+). Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Ca(2+) to form a five-membered ring structure. The crystal structure and spectroscopic results indicate the differences of the coordination of Ca and Pr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation. Unlike transition metal ions, Sr(2+) or lanthanide ions, Ca(2+) is inclined to coordinate to carbonyl oxygen atoms of the ligands. PMID:25280333

Xue, Junhui; Jiang, Ye; Li, Weihong; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Zhang, Gaohui; Bu, Xiaoxia; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

2015-02-25

255

Structures and spectroscopic characterization of calcium chloride-nicotinamide, -isonicotinamide, -picolinamide and praseodymium bromide-nicotinamide complexes  

NASA Astrophysics Data System (ADS)

The coordination structures formed by calcium complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) and praseodymium bromide-na are reported. The structures of CaCl2·(C6H6N2O)2·2H2O (Ca-na), CaCl2·(C6H6N2O)2·4H2O (Ca-ina), CaCl2·(C6H6N2O)2·5H2O (Ca-pa) and PrBr3·(C6H6N2O)2·6H2O (PrBr-na) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Raman spectroscopies. Carbonyl oxygen of nicotinamide is coordinated to Ca2+, but it is O-monodentate (carbonyl oxygen) and N,O-bidentate ligand (pyridyl nitrogen and carbonyl oxygen) for Pr3+ to form a chain structure in PrBr-na. For isonicotinamide, only carbonyl oxygen atom is coordinated to Ca2+. Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Ca2+ to form a five-membered ring structure. The crystal structure and spectroscopic results indicate the differences of the coordination of Ca and Pr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation. Unlike transition metal ions, Sr2+ or lanthanide ions, Ca2+ is inclined to coordinate to carbonyl oxygen atoms of the ligands.

Xue, Junhui; Jiang, Ye; Li, Weihong; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Zhang, Gaohui; Bu, Xiaoxia; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

2015-02-01

256

Synthesis, spectroscopic characterization and biological activity of cis-[Ru(hesperidin)(1,10?-phenanthroline)2](PF6) complex  

NASA Astrophysics Data System (ADS)

The new complex cis-[Ru(phen)2(hesperidin)](PF6), complex 1, was synthesized and characterized by analytical (ESI-MS+, EA (C, H, N)) and spectroscopic (FTIR, UV-vis, 1H and 13C NMR) techniques and cyclic voltammetry. Complex 1 is chemically stable in the solid state and in organic solvents such as ethanol, methanol, acetone, and acetonitrile, as shown by spectrophotometric analysis. 1 is also photochemically and chemically stable (pH effects) and more hydrosoluble (518.83 ± 0.91 g mL-1) than free hesperidin (5.92 g mL-1). In accordance with this, the lipophilicity value in aqueous-octanol solution for 1 was -1.28, indicating its high hydrophilic characteristic. Although complex 1 showed to be essentially noncytotoxic, IC50 > 1.0 mmol L-1 as evaluated in the human cervical cancer cells line HeLa, it exhibited a moderate capacity of inhibiting the catalytic activity of the acetylcholinaesterase enzyme, IC50 = 63.6 mol L-1. The Lineweaver-Burk plot and the respective secondary replot indicated that the AChE inhibition was noncompetitive and reversible. These findings shows that complexation of the hesperidin improves physicochemical characteristics and increases the perspectives for development and medical applications of new bioactive-metal complexes.

Oliveira, Regina M. M.; de Souza Daniel, Juliana F.; Carlos, Rose M.

2013-01-01

257

Spectroscopic characterization of metal complexes of novel Schiff base. Synthesis, thermal and biological activity studies  

NASA Astrophysics Data System (ADS)

Novel Schiff base (HL) ligand is prepared via condensation of 4-aminoantipyrine and 2-aminobenzoic acid. The ligand is characterized based on elemental analysis, mass, IR and 1H NMR spectra. Metal complexes are reported and characterized based on elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance and thermal analyses (TGA, DrTGA and DTA). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that HL is coordinated to the metal ions in a uninegatively tridentate manner with NNO donor sites of the azomethine N, amino N and deprotonated caroxylic-O. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral. The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ?H*, ?S* and ?G* are calculated from the DrTG curves using Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes also were screened for their antibacterial activity against bacterial species, Escherichia Coli, Pseudomonas aeruginosa, Staphylococcus Pyogones and Fungi (Candida). The activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species.

Omar, M. M.; Mohamed, Gehad G.; Ibrahim, Amr A.

2009-07-01

258

Solvate Structures and Computational/Spectroscopic Characterization of LiBF4 Electrolytes  

SciTech Connect

Crystal structures have been determined for both LiBF4 and HBF4 solvates?(acetonitrile)2:LiBF4, (ethylene glycol diethyl ether)1:LiBF4, (diethylene glycol diethyl ether)1:LiBF4, (tetrahydrofuran)1:LiBF4, (methyl methoxyacetate)1:LiBF4, (suc-cinonitrile)1:LiBF4, (N,N,N',N",N"-pentamethyldiethylenetriamine)1:HBF4, (N,N,N',N'-tetramethylethylenediamine)3/2:HBF4 and (phenanthroline)2:HBF4. These, as well as other known LiBF4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4-...Li+ cation coordination. In addition, complementary DFT calculations of BF4-...Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.

Seo, D. M.; Boyle, Paul D.; Allen, Joshua L.; Han, Sang D.; Jonsson , Erlendur; Johansson, Patrik; Henderson, Wesley A.

2014-07-21

259

Synthesis, spectroscopic characterization, biological screenings, DNA binding study and POM analyses of transition metal carboxylates.  

PubMed

This article contains the synthesis of a novel carboxylic acid derivative, its transition metal complexes and evaluation of biological applications. Six carboxylate complexes of transition metals, Zn(II) and Hg(II), have been successfully synthesized and characterized by FT-IR and NMR ((1)H, (13)C). The ligand, HL, (4-[(2,6-Diethylphenyl)amino]-4-oxobutanoic acid) was also characterized by single crystal X-ray analysis. The complexation occurs via oxygen atoms of the carboxylate moiety. FT-IR date show the bidentate nature of the carboxylate moiety of the ligand as the ?? value in all complexes is less than that of the free ligand. The ligand and its complexes were screened for antifungal and antileishmanial activities. The results showed that the ligand and its complexes are active with few exceptions. UV-visible spectroscopy and viscometry results reveal that the ligand and its complexes interact with the DNA via intercalative mode of interaction. A new and efficient strategy to identify the pharmacophores and anti-pharmacophores sites in carboxylate derivatives for the antibacterial/antifungal activity using Petra, Osiris and Molinspiration (POM) analyses was also carried out. PMID:25646895

Uddin, Noor; Sirajuddin, Muhammad; Uddin, Nizam; Tariq, Muhammad; Ullah, Hameed; Ali, Saqib; Tirmizi, Syed Ahmed; Khan, Abdur Rehman

2015-04-01

260

Spectroscopic and chromatographic characterization of triflusal delivery systems prepared by using supercritical impregnation technologies.  

PubMed

This study describes the development and evaluation of an analytical method for the characterization of triflusal (2-acetoxy-4-(trifluoromethyl) benzoic acid) dispersed in sustained delivery systems prepared using supercritical fluid impregnation technology. Characterization assays comprised the determination of the percentage of triflusal and its degradation product impregnated in polymeric supports and further monitoring of the releases of the two drug components over time in physiological conditions. Preliminary delivery profiles were monitored spectrophotometrically using a continuous-flow system. In this case, no selective wavelength for discriminating between triflusal and metabolite was found so that measurements at 225 nm provided overall profiles corresponding to the two compounds. For a more accurate study, a chromatographic method was developed for monitoring the evolution of the concentration of the two components independently. Triflusal and metabolite were separated in a C(18) column and 25 mM acetic acid/acetate (pH 5.0)+methanol (40/60v/v) mobile phase. Several triflusal-polymer samples were prepared under different experimental conditions and release features were evaluated. Excellent delivery systems were obtained with poly(methyl)methacrylate beads treated at 40 degrees C and 190 bar for 48 h using supercritical carbon dioxide as a solvent. These samples showed a constant sustained release of drug for several weeks. PMID:18093783

Argemí, Anna; López-Periago, Ana; Domingo, Concepción; Saurina, Javier

2008-02-13

261

Full elastic characterization of absorptive rubber using laser excited guided ultrasonic waves  

NASA Astrophysics Data System (ADS)

Because of the highly damping nature of rubber, it is difficult to characterize its dynamic elastic properties using classical methods. In this paper, an experimental approach employing laser excited guided acoustic waves is proposed to accurately determine the real and imaginary part of the longitudinal and shear elastic modulus of a rubber layer. From the spatiotemporal evolution of a propagating laser excited Lamb wave measured by a laser Doppler vibrometer, which is scanning along a line perpendicular to a line of excitation, the phase velocity dispersion curves in the wave number - frequency domain are obtained. The results are interpreted in the framework of a detailed semianalytical study, analyzing the influence of elastic damping on the Lamb dispersion curves. This analysis is exploited to adequately fit the experimental dispersion curves and thus extract information about the elastic moduli and absorption coefficients of the rubber plate. The results are validated by a pulse-echo measurement, and by guided wave propagation results with the rubber layer connected in a bi-layer plate configuration to non-damping plates.

Verstraeten, Bert; Xu, Xiadong; Martinez, Loïc; Glorieux, Christ

2012-05-01

262

X-ray absorption spectroscopic study of new high-Tc superconducting intercalation compound of (HgX2)0.5Bi2Sr2CaCu2Oy(X=Br,I)  

NASA Astrophysics Data System (ADS)

We have systematically performed x-ray absorption spectroscopic (XAS) studies on the new mercuric halide intercalated superconductors, (HgX2)0.5Bi2Sr2CaCu2Oy with X equals Br and I, in order to investigate the electronic and crystal structure of these compounds. The present Hg LIII-edge EXAFS results indicate that the mercury is coordinated with two bromide or iodide ligands with bond length of 2.46 angstrom for the HgBr2-intercalate and 2.65 angstrom for the HgI2-one. This is the first example of linear molecular salt of HgX2 stabilized in the solid lattice. According to the I LI- and Br K-edge x-ray absorption near edge structure (XANES) spectroscopic studies, a small amount of electron transfer from the intercalant HgX2 to the host lattice could be observed upon intercalation, resulting in the negatively charged state of (HgX2)(delta -). The Cu K-edge EXAFS analysis reveals that the bond distance of Cu-Oaxial is slightly shortened upon intercalation, reflecting the oxidation of (Cu-O) layer, which is well consistent with the I LI- and Br K-edge XANES results.

Choy, Jin-Ho; Park, Nam-Gyu; Hwang, Seong-Ju; Hwang, Sung-Ho; Kim, Dong-Hoon

1996-06-01

263

Spectroscopic and morphological characterization of inflow cannulas of left ventricular assist devices.  

PubMed

Despite the consistent clinical data on the positive effects of left ventricular assist devices (LVADs) in the treatment of refractory heart failure, unfortunately these devices yet show some limitations such as the risk of stroke, infection, and device malfunction. The complex interplay between blood and the foreign material has a major role in the occurrence of these complications and biocompatibility of the inflow cannula would be pivotal in these terms. In this study, we carried out an in-depth physicochemical characterization of two commercially available LVADs by means of field emission gun scanning electron microscopy, energy dispersive X-ray, and X-ray photoelectron spectra. Our results show that, despite both pumps share the same physicochemical concepts, major differences can be identified in the surface nature, morphology, and chemical composition of their inflow cannulas. PMID:25396275

Pappalardo, Federico; Cristaldi, Domenico A; Fragalà, Ignazio L; Millesi, Salvatrice; De Bonis, Michele; Gulino, Antonino

2015-01-01

264

Spectroscopic characterization of magnetic Fe3O4@Au core shell nanoparticles.  

PubMed

The magnetic nanoparticles iron oxide (Fe3O4) nanoparticles and iron oxide/gold core-shell (Fe3O4/Au) nanoparticles were synthesized and their catalytic photo-degradation activity towards malathion as example of organophosphorus pesticides were reported. Iron oxide (Fe3O4) magnetic nanoparticle was successfully prepared through co-precipitation method by the reduction of ferric chloride (FeCl3) using ascorbic acid. The morphology of the prepared nanoparticles was characterized by the TEM and XRD (X-ray diffraction) techniques. Degradation of 10 ppm of malathion in the presence of these nanoparticles under UV radiation was monitored using (HPLC) and UV-visible spectra. Fe3O4/Au nanoparticles showed higher efficiency in photo-degradation of malathion than Fe3O4 ones. PMID:25617979

Fouad, Dina M; El-Said, Waleed A; Mohamed, Mona B

2015-04-01

265

Spectroscopic characterization of 1450 nm semiconductor pump laser structures for Raman amplifiers  

NASA Astrophysics Data System (ADS)

In order to characterize various different epilayer designs for semiconductor Raman amplifier pump lasers, combined electromodulated reflectance (ER) and photoluminescence (PL) studies were performed on wafer samples of InP / InGaAsP / InGaAsP edge-emitter laser structures in the infrared spectral region. Information about the quantum well (QW) transitions is obtained primarily from the ER, with additional corroboration provided by the PL. The ER spectra are fitted with a line shape model to obtain the ground-state and higher-order QW transition energies, which are found to agree well with theoretically calculated values. The ER spectra also provide the waveguide core and barrier compositions and built-in electric fields in the laser structures. The information provided by ER studies on the prefabrication wafers is found to corroborate well with diagnostic spontaneous emission measurements performed on actual laser devices fabricated from the same wafer batches.

Constant, S. B.; Tomi?, S.; Lock, D.; Sale, T. E.; Sweeney, S. J.; Hosea, T. J. C.

2003-06-01

266

Structural and spectroscopic characterizations of tetra-nuclear niobium(V) complexes of quinolinol derivatives.  

PubMed

Reactions between niobium ethoxide and 8-hydroxy-2-methylquinoline or 5-chloro-8-hydroxyquinoline have been explored. Two new tetranuclear heteroleptic niobium complexes containing oxo, ethoxo, and quinolinate chelate rings have been synthesized and characterized by (1)H, (13)C and (93)Nb NMR, UV-Vis, and FT-IR spectroscopies, and single-crystal X-ray diffraction. The molecular structures of the niobium complexes, [Nb4(?-O)4(?-OEt)2(ONC10H8)2(OEt)8] (I) and [Nb4(?-O)4(?-OEt)2(ONC9H5Cl)2(OEt)8] (II), are composed of a pair of edge-sharing bioctahedral moieties in which connected via two almost linear oxo-bridges, with a large difference in the NbO distances. Single-crystal structures showed both complexes are centrosymmetric and contain two distinct Nb centers, and results confirmed by observation of two niobium signals in the (93)Nb NMR spectra of complexes. PMID:25756687

Amini, Mostafa M; Fazaeli, Yousef; Mohammadnezhad, Gholamhossein; Khavasi, Hamid Reza

2015-06-01

267

Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes  

NASA Astrophysics Data System (ADS)

Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M = Cr(III) and Fe(III) and X = Cl-, CH3COO- or NO3-, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities.

Rathi, Parveen; Sharma, Kavita; Singh, Dharam Pal

2014-09-01

268

Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics  

NASA Astrophysics Data System (ADS)

Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

Jannotti, Phillip; Subhash, Ghatu; Zheng, James Q.; Halls, Virginia; Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K.

2015-01-01

269

Synthesis and spectroscopic characterization of gallic acid and some of its azo complexes  

NASA Astrophysics Data System (ADS)

A series of gallic acid and azo gallic acid complexes were prepared and characterized by elemental analysis, IR, electronic spectra and magnetic susceptibility. The complexes were of different geometries: Octahedral, Tetrahedral and Square Planar. ESR was studied for copper complexes. All of the prepared complexes were of isotropic nature. The thermal analyses of the complexes were studied by DTA and DSC techniques. The thermodynamic parameters and the thermal transitions, such as glass transitions, crystallization and melting temperatures for some ligands and their complexes were evaluated and discussed. The entropy change values, ?S#, showed that the transition states are more ordered than the reacting complexes. The biological activities of some ligands and their complexes are tested against Gram positive and Gram negative bacteria. The results showed that some complexes have a well considerable activity against different organisms.

Masoud, Mamdouh S.; Hagagg, Sawsan S.; Ali, Alaa E.; Nasr, Nessma M.

2012-04-01

270

Spectroscopic characterization of a masterpiece: the Manueline foral charter of Sintra.  

PubMed

The foral charter attributed by D. Manuel I of Portugal, in 1514, to the village of Sintra was studied using Energy Dispersive X-ray Fluorescence spectrometry, Raman and Infrared micro-spectroscopies. A complete characterization of the pictorial materials used in the production of this masterpiece allowed the identification of iron gall inks used in the written text; pigments such as malachite, azurite, lead white, cinnabar, yellow ochre, gold, silver and carbon black in the illuminations and letterings; filler and binder used in the production of coloring materials and inks. Gum and calcium carbonate were the most recurrent binder and filler identified in this study. Silvering and gilding were mostly obtained by applying ground silver and gold on parchment. PMID:23318772

Manso, Marta; Le Gac, Agnès; Longelin, Stéphane; Pessanha, Sofia; Frade, José Carlos; Guerra, Mauro; Candeias, António José; Carvalho, Maria Luísa

2013-03-15

271

Spectroscopic characterization of a masterpiece: The Manueline foral charter of Sintra  

NASA Astrophysics Data System (ADS)

The foral charter attributed by D. Manuel I of Portugal, in 1514, to the village of Sintra was studied using Energy Dispersive X-ray Fluorescence spectrometry, Raman and Infrared micro-spectroscopies. A complete characterization of the pictorial materials used in the production of this masterpiece allowed the identification of iron gall inks used in the written text; pigments such as malachite, azurite, lead white, cinnabar, yellow ochre, gold, silver and carbon black in the illuminations and letterings; filler and binder used in the production of coloring materials and inks. Gum and calcium carbonate were the most recurrent binder and filler identified in this study. Silvering and gilding were mostly obtained by applying ground silver and gold on parchment.

Manso, Marta; Gac, Agnès Le; Longelin, Stéphane; Pessanha, Sofia; Frade, José Carlos; Guerra, Mauro; Candeias, António José; Carvalho, Maria Luísa

2013-03-01

272

Spectroscopic characterization and the coordination behavior of isonicotinamide with lanthanide ions  

NASA Astrophysics Data System (ADS)

The coordination of amide groups to metal ions is important because it may be involved in the interactions between metal ions and proteins. The synthesis and characterization of nine novel lanthanide-isonicotinamide (ina) complexes, including LaCl3, PrCl3, NdCl3, SmCl3, EuCl3, GdCl3, TbCl3, ErCl3 and PrBr3 complexes are reported. The structures of these complexes in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Luminescence spectroscopy. Isonicotinamide has only one coordination mode in four structures as O-monodentate ligand to coordinate to metal ions, but four kinds of topological structures are observed for lanthanide-isonicotinamide complexes, including LnCl3?(C6H6N2O)2?4H2O (La, Pr, Nd and Sm), EuCl3?(C6H6N2O)2?7H2O, LnCl3?(C6H6N2O)2?6H2O (Gd, Tb and Er) and PrBr3?(C6H6N2O)2?7H2O. Chloride ions can coordinate to metal ions or hydrogen-bonded. FTIR spectra indicate the formation of four kinds of lanthanide-ina complexes, the extensive hydrogen bond networks after complexation and the coordinations and the changes of the conformation of the ligand. FIR and THz spectra also confirm the formation of lanthanide ion-ina complexes. Luminescence spectra of Eu and Tb-ina complexes have the characteristics of Eu and Tb ions.

Xue, Junhui; Hua, Xiaohui; Yang, Limin; Xu, Yizhuang; Li, Weihong; Zhao, Guozhong; Zhang, Gaohui; Wu, Jinguang

2013-11-01

273

Absorption of Carbon Dioxide Characterized by Using the Absorbent Composed of Piperazine and Triethanolamine  

Microsoft Academic Search

This work studies the CO2 absorption of alkanolamine, piperazine, and TEA (triethanolamine), and the chemical reaction kinetics of CO2 by using the mixed solution of piperazine and TEA in polyvinylidine?fluoride hollow fiber membrane contactor?stripper hybrid process. Absorption was studied from 303K to 382K in the mixed solution of piperazine 0.26 M, 0.64 M, and TEA 0.38 M, 1.13 M, 2.26 M. Also, absorption rates were

Bongkuk Sea

2004-01-01

274

Spectroscopic characterization of extracellular polymeric substances from a mixed culture dominated by ammonia-oxidizing bacteria.  

PubMed

Extracellular polymeric substances (EPS) of aerobic (AerAOB) and anaerobic ammonium-oxidizing bacteria (AnAOB) are expected to have a significant impact on the performance of autotrophic nitrogen removal in engineered systems. However, there are a few investigations of the EPS of AerAOB and AnAOB, and the results are contradictory. In this study, photometric measurements indicated that the EPS of AerAOB- (31.74 ± 1.48 mg/g-VSS, volatile suspended solids) and AnAOB-enriched cultures (30.12 ± 1.52 mg/g-VSS) contained more polysaccharides than did conventional activated sludge from a municipal wastewater treatment facility (10.76 ± 0.83 mg/g-VSS). In addition, the EPS of the AnAOB-enriched culture was dominated by proteins, leading to a considerably higher protein/polysaccharide ratio (2.64 ± 0.12) than those of the AerAOB-enriched culture (0.56 ± 0.03) and conventional activated sludge (1.96 ± 0.09). Characterization using Fourier transform infrared spectroscopy (FTIR) revealed the dominance of amide bands and/or polysaccharide-associated bands in the EPS of AnAOB and AerAOB. These results corroborate the data from the photometric measurements. In addition, the EPS of AnAOB (23.1% ± 1.2%) and AerAOB (21.9% ± 1.1%) had a higher portion of ?-helices, which is the key protein secondary structure that determines flocculation or cell aggregation, in the amide I band than that of activated sludge (16.7% ± 0.8%). X-ray photoelectron spectroscopy (XPS) characterization also revealed significantly different functionalities among the EPS of the three mixed cultures; e.g., O-(C,H), which indicates the presence of polysaccharides, was richer in the EPS of AerAOB, whereas protonated amines, which are commonly found in amino acids and amino sugars, accounted for a large portion of the EPS of AnAOB. The results of this study can potentially expand our knowledge of the microbial aggregates responsible for autotrophic nitrogen removal. PMID:25462778

Yin, Cuiqin; Meng, Fangang; Chen, Guang-Hao

2015-01-01

275

Synthesis and microwave absorption characterization of SiO2 coated Fe3O4-MWCNT composites.  

PubMed

This study investigated the microwave absorption properties of core-shell composites containing; iron oxide decorated carbon nanotubes (CNTs) and silica (SiO2@Fe3O4-MWCNTs) with various thicknesses of silica shells (7, 20 and 50 nm). Transmission electron microscopy (TEM) and X-ray diffraction results confirmed the formation of these core-shell structures. Microwave absorption characterization of the samples at the ranging band under consideration (the X-band) showed increased absorption and shifting of the peaks to lower frequencies compared to the uncoated sample (Fe3O4-MWCNTs). The minimum reflection loss decreased with increasing SiO2 thickness. The minimum reflection loss of the composite with an optimized thickness of the silica shell (7 nm) exceeded -41 dB at 8.7-9 GHz. PMID:25288483

Hekmatara, Hoda; Seifi, Majid; Forooraghi, Keyvan; Mirzaee, Sharareh

2014-11-21

276

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: Spectroscopic and thermal characterization  

NASA Astrophysics Data System (ADS)

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic- OH, -NH and carbonyl- O, while VMA is coordinated with OO donor sites of the phenolic- OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Mohamed, Gehad G.; Nour El-Dien, F. A.; El-Nahas, R. G.

2011-10-01

277

Spectroscopic characterization of B/KNO3 diode-laser induced combustion.  

PubMed

The combustion of a B/KNO3 pyrotechnic mixture was characterized by its chemiluminescence for the first time. The reaction was initiated by a continuous wave (cw) diode laser inside a novel multipurpose reaction cell, whose design and construction are described. As in the case of the extensively studied oxidation of boron by O2, the most intense luminescence, recorded in the 400-600 nm range, is assigned to BO2. Its appearance delay time (10(-2) to 10(-1) s) equals that measured for the pressure increase and is shortened as the laser power is increased. A band observed at 355 nm appears at longer delay times than the BO2 bands. The band, and some weaker ones, may be assigned to BO, although some bands expected for BO (based on reaction between B atoms and O2) are absent from the spectra. This observation is discussed in the text, and possible emission from BN is discussed. If the band is assigned to BO, the absence of known bands may be due to specific E-V resonance energy transfer. Possible oxidation mechanisms consistent with the different delay ignition times are discussed. PMID:23679891

Sivan, J; Haas, Y

2013-11-21

278

Characterization of Functionalized Self-Assembled Monolayers and Surface-Attached Interlocking Molecules Using Near-Edge X-ray Absorption Fine Structure Spectroscopy  

SciTech Connect

Quantitative knowledge of the fundamental structure and substrate binding, as well as the direct measurement of conformational changes, are essential to the development of self-assembled monolayers (SAMs) and surface-attached interlocking molecules, catenanes and rotaxanes. These monolayers are vital to development of nano-mechanical, molecular electronic, and biological/chemical sensor applications. This dissertation investigates properties of functionalized SAMs in sulfur-gold based adsorbed molecular monolayers using quantitative spectroscopic techniques including near-edge x-ray absorption fine structure spectroscopy (NEXAFS) and x-ray photoelectron spectroscopy (XPS). The stability of the gold-thiolate interface is addressed. A simple model SAM consisting of dodecanethiol adsorbed on Au(111) degrades significantly in less than 24 hours under ambient laboratory air. S 2p and O 1s XPS show the gold-bound thiolates oxidize to sulfinates and sulfonates. A reduction of organic material on the surface and a decrease in order are observed as the layer degrades. The effect of the carboxyl vs. carboxylate functionalization on SAM structure is investigated. Carboxyl-terminated layers consisting of long alkyl-chain thiols vs. thioctic acid with short, sterically separated, alkyl groups are compared and contrasted. NEXAFS shows a conformational change, or chemical switchability, with carboxyl groups tilted over and carboxylate endgroups more upright. Surface-attached loops and simple surface-attached rotaxanes are quantitatively characterized, and preparation conditions that lead to desired films are outlined. A dithiol is often insufficient to form a molecular species bound at each end to the substrate, while a structurally related disulfide-containing polymer yields surface-attached loops. Similarly, spectroscopic techniques show the successful production of a simple, surface-attached rotaxane that requires a ''molecular riveting'' step to hold the mechanically attached crown ether rings in place until disulfides in the molecules adsorb onto the gold. Finally, by introducing an aldehyde into the crown ether portion of this well-characterized surface-attached rotaxane, conformational changes are directly measured when the aldehyde is reacted with aniline. These fundamental results have implications for the creation of nanoscale functional surfaces using molecular monolayers.

Willey, T; Willey, T

2004-03-24

279

(TAML)Fe**IV=O Complex in Aqueous Solution: Synthesis And Spectroscopic And Computational Characterization  

SciTech Connect

Recently, we reported the characterization of the S = 1/2 complex [Fe{sup V}(O)B*]{sup -}, where B* belongs to a family of tetraamido macrocyclic ligands (TAMLs) whose iron complexes activate peroxides for environmentally useful applications. The corresponding one-electron reduced species, [Fe{sup IV}(O)B*]{sup 2-} (2), has now been prepared in >95% yield in aqueous solution at pH > 12 by oxidation of [Fe{sup III}(H{sub 2}O)B*]{sup -} (1), with tert-butyl hydroperoxide. At room temperature, the monomeric species 2 is in a reversible, pH-dependent equilibrium with dimeric species [B*Fe{sup IV}?O?Fe{sup IV}B*]{sup 2-} (3), with a pK{sub a} near 10. In zero field, the Moessbauer spectrum of 2 exhibits a quadrupole doublet with {Delta}E{sub Q} = 3.95(3) mm/s and {delta} = ?0.19(2) mm/s, parameters consistent with a S = 1 Fe{sup IV} state. Studies in applied magnetic fields yielded the zero-field splitting parameter D = 24(3) cm{sup -1} together with the magnetic hyperfine tensor A/g{sub n}{beta}{sub n} = (?27, ?27, +2) T. Fe K-edge EXAFS analysis of 2 shows a scatterer at 1.69 (2) {angstrom}, a distance consistent with a Fe{sup IV} = O bond. DFT calculations for [Fe{sup IV}(O)B*]{sup 2-} reproduce the experimental data quite well. Further significant improvement was achieved by introducing hydrogen bonding of the axial oxygen with two solvent-water molecules. It is shown, using DFT, that the {sup 57}Fe hyperfine parameters of complex 2 give evidence for strong electron donation from B* to iron.

Chanda, A.; Shan, X.; Chakrabarti, M.; Ellis, W.C.; Popescu, D.L.; Oliveira, F.Tiago de; Wang, D.; Que, L.; Jr.; Collins, T.J.; Munck, E.; Bominaar, E.L.

2009-05-12

280

A new heterometallic (Ni 2+ and Cr 3+) complex - Crystal structure and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

A new heterometallic complex, of the composition [Ni(bpy) 3] 2[Cr(C 2O 4) 3]NO 3·10H 2O (bpy = 2,2'-bipyridine) ( 1), was synthesized and characterized by elemental and TG/DTA analyses, IR, UV/vis and EPR spectroscopy and by a single-crystal X-ray diffraction study. The compound crystallizes in the monoclinic P2 1/ c space group, with the unit cell parameters: a = 23.201(7), b = 13.562(4), c = 22.350(7) Å, ? = 92.782(5)°, V = 7024(4) Å 3 and Z = 4. The molecular structure of 1 consists of two symmetry independent [Ni(bpy) 3] 2+ cations, one [Cr(C 2O 4) 3] 3- anion, one nitrate anion and 10 molecules of water. Due to the rigidity of the didentate ligands, both [Ni(bpy) 3] 2+ and [Cr(C 2O 4) 3] 3- ions possess a trigonally distorted octahedral geometry. Analysis of crystal packing revealed the existence of a specific type of supramolecular contact comprising four bipyridine ligands from two neighbouring [Ni(bpy) 3] 2+ units - a quadruple aryl embrace (QAE) contact. The electronic spectrum showed superposition of bands characteristic for both nickel(II) and chromium(III) six-coordinated ions. The X-band EPR spectra were recorded on a single crystal and on a powdered sample of 1 in the temperature range 300-5 K. From the obtained spectra, the spin-Hamiltonian parameters for Cr 3+ were deduced. Throughout the investigated temperature range, Ni 2+ was EPR silent.

Juri?, Marijana; Planini?, Pavica; Žili?, Dijana; Rakvin, Boris; Prugove?ki, Biserka; Matkovi?-?alogovi?, Dubravka

2009-04-01

281

Raman, infrared and near-infrared spectroscopic characterization of the herderite-hydroxylherderite mineral series.  

PubMed

Natural single-crystal specimens of the herderite-hydroxylherderite series from Brazil, with general formula CaBePO4(F,OH), were investigated by electron microprobe, Raman, infrared and near-infrared spectroscopies. The minerals occur as secondary products in granitic pegmatites. Herderite and hydroxylherderite minerals show extensive solid solution formation. The Raman spectra of hydroxylherderite are characterized by bands at around 985 and 998 cm(-1), assigned to ?1 symmetric stretching mode of the HOPO3(3-) and PO4(3-) units. Raman bands at around 1085, 1128 and 1138 cm(-1) are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 563, 568, 577, 598, 616 and 633 cm(-1) are assigned to the ?4 out of plane bending modes of the PO4 and H2PO4 units. The OH Raman stretching vibrations of hydroxylherderite were observed ranging from 3626 cm(-1) to 3609 cm(-1). The infrared stretching vibrations of hydroxylherderites were observed between 3606 cm(-1) and 3599 cm(-1). By using a Libowitzky type function, hydrogen bond distances based upon the OH stretching bands were calculated. Characteristic NIR bands at around 6961 and 7054 cm(-1) were assigned to the first overtone of the fundamental, whilst NIR bands at 10,194 and 10,329 cm(-1) are assigned to the second overtone of the fundamental OH stretching vibration. Insight into the structure of the herderite-hydroxylherderite series is assessed by vibrational spectroscopy. PMID:24076459

Frost, Ray L; Scholz, Ricardo; López, Andrés; Xi, Yunfei; Queiroz, Camila de Siqueira; Belotti, Fernanda M; Cândido Filho, Mauro

2014-01-24

282

Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units  

NASA Astrophysics Data System (ADS)

Single crystals of Zn4(OH)2[(UO2)(PO4)2(OH)2(H2O)] (UZnP), Cs[(UO2)(HPO4)NO3] (UCsP), and In3[(UO2)2(PO4)4OH(H2O)6].2H2O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) Å; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) Å, ?=72.974(2), ?=74.261(2), ?=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) Å ?=101.289(1), ?=114.642(1), ?=99.203(2). The U6+ cations are present as (UO2)2+ uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry.

Wylie, Ernest M.; Dawes, Colleen M.; Burns, Peter C.

2012-12-01

283

Synthesis, spectroscopic characterization and antimicrobial activity of binuclear metal complexes of a new asymmetrical Schiff base ligand: DNA binding affinity of copper(II) complexes  

NASA Astrophysics Data System (ADS)

The 1:1 condensation of o-acetoacetylphenol and 1,2-diaminopropane under condition of high dilution gives the mono-condensed Schiff base, (E)-3-(1-aminopropan-2-ylimino)-1-(2-hydroxyphenyl)butan-1-one. The mono-condensed Schiff base has been used for further condensation with isatin to obtain the new asymmetrical dicompartmental Schiff base ligand, (E)-3-(2-((E)-4-(2-hydroxyphenyl)-4-oxobutan-2-ylideneamino) propylimino)indolin-2-one (H3L) with a N2O3 donor set. Reactions of the ligand with metal salts give a series of new binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [(HL)(VO)2(SO4)(H2O)]·4H2O, [(HL)Fe2Cl4(H2O)3]·EtOH, [(HL)Fe2(ox)Cl2(H2O)3]·2H2O, [(L)M2(OAc)(H2O)m]·nH2O; M = Co, Ni or Cu, m = 4, 0 and n = 2, 3, [(HL)Cu2Cl]Cl·6H2O and [(L)(UO2)2(OAc)(H2O)3]·6H2O. The metal complexes exhibited octahedral geometrical arrangements except copper complexes that exhibited tetrahedral geometries and uranyl complex in which the metal ion is octa-coordinated. The Schiff base and its metal complexes were evaluated for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli) and fungi (Candida albicans and Aspergillus flavus). The ligand and some of its complexes were found to be biologically active. The DNA-binding properties of the copper complexes (6 and 7) have been investigated by electronic absorption, fluorescence and viscosity measurements. The results obtained indicate that these complexes bind to DNA via an intercalation binding mode with an intrinsic binding constant, Kb of 1.34 × 104 and 2.5 × 104 M-1, respectively.

Shebl, Magdy

2014-01-01

284

Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units  

SciTech Connect

Single crystals of Zn{sub 4}(OH){sub 2}[(UO{sub 2})(PO{sub 4}){sub 2}(OH){sub 2}(H{sub 2}O)] (UZnP), Cs[(UO{sub 2})(HPO{sub 4})NO{sub 3}] (UCsP), and In{sub 3}[(UO{sub 2}){sub 2}(PO{sub 4}){sub 4}OH(H{sub 2}O){sub 6}].2H{sub 2}O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) A; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) A, {alpha}=72.974(2), {beta}=74.261(2), {gamma}=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) A {alpha}=101.289(1), {beta}=114.642(1), {gamma}=99.203(2). The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry. - Graphical abstract: Three new uranyl phosphates with unique structural units are reported. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Three new uranyl phosphates have been synthesized hydrothermally. Black-Right-Pointing-Pointer Single crystal analyses reveal unique structural units. Black-Right-Pointing-Pointer The dimensionality of these compounds deviate from typical U{sup 6+} layered structures.

Wylie, Ernest M.; Dawes, Colleen M. [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States)] [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

2012-12-15

285

Spectroscopic characterizations of a mixed surfactant mesophase and its application in materials synthesis  

NASA Astrophysics Data System (ADS)

A viscous lyotropic crystalline mesophase containing bis (2-ethylhexyl) sodium sulfosuccinate (AOT), alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water was characterized by Fourier-transform 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. Shear alignment on the reverse hexagonal mesophase was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures became macroscopically aligned after Couette shear and the alignment retained for a long period of time. 31P NMR chemical shift anisotropy characteristics were used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR of the water, methyl and methylene groups exhibited spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. A reverse hexagonal to lamellar phase transition was manifested as an expanding of the expressed 31P NMR chemical shift anisotropy and an apparent reversal of the powder pattern with increasing water content and/or temperature. Correspondingly, 1H NMR spectra also experienced a spectral pattern transition as the water content or temperature was increased. These observations complement the findings of mesophase alignment obtained using small angle neutron scattering (SANS) and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. The mesophase retains its alignment for extended periods allowing materials synthesis to be decoupled from the application of shear. Highly aligned string-like silica nanostructures were obtained through templated synthesis in the columnar hexagonal structure of the viscous lyotropic crystalline mesophase. A two-step procedure was used to first shear-align the surfactant mesophase, and then conduct synthesis under quiescent conditions in the mesophase. Polystyrene was post-grafted to the silica surface without disturbing its nanostring morphology. The coupling of materials synthesis in surfactant mesophases with processing techniques (e.g. extrusion) may result in functional materials, such as new catalyst support and membrane nanoarchitectures.

Liu, Limin

286

Spectroscopic studies of copper enzymes  

SciTech Connect

Several spectroscopic methods, including absorption, circular dichroism (CD), magnetic CD (MCD), X-ray absorption, resonance Raman, EPR, NMR, and quasi-elastic light-scattering spectroscopy, have been used to probe the structures of copper-containing amine oxidases, nitrite reductase, and nitrous oxide reductase. The basic goals are to determine the copper site structure, electronic properties, and to generate structure-reactivity correlations. Collectively, the results on the amine oxidases permit a detailed model for the Cu(II) sites in these enzymes to be constructed that, in turn, rationalizes the ligand-binding chemistry. Resonance Raman spectra of the phenylhydrazine and 2,4-dinitrophenyl-hydrazine derivatives of bovine plasma amine oxidase and models for its organic cofactor, e.g. pyridoxal, methoxatin, are most consistent with methoxatin being the intrinsic cofactor. The structure of the Cu(I) forms of the amine oxidases have been investigated by X-ray absorption spectroscopy (XAS); the copper coordination geometry is significantly different in the oxidized and reduced forms. Some anomalous properties of the amine oxidases in solution are explicable in terms of their reversible aggregation, which the authors have characterized via light scattering. Nitrite and nitrous oxide reductases display several novel spectral properties. The data suggest that new types of copper sites are present.

Dooley, D.M.; Moog, R.; Zumft, W.; Koenig, S.H.; Scott, R.A.; Cote, C.E.; McGuirl, M.

1986-05-01

287

Observation of a cw Dark-Field Signal in an Absorption Spectroscopic Experiment Using a Phase Locked Free-Electron Laser  

NASA Astrophysics Data System (ADS)

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 ?m, using phase-locked pulses from the Mark III FEL, clearly reveal an interpulse beat signal due to absorption by adjacent molecular rotational lines which is generated only in the presence of interpulse phase coherence.

Szarmes, Eric B.; Madey, John M. J.; Straub, Karl D.

2000-03-01

288

Observation of a cw dark-field signal in an absorption spectroscopic experiment using a phase locked free-electron laser  

PubMed

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 &mgr;m, using phase-locked pulses from the Mark III FEL, clearly reveal an interpulse beat signal due to absorption by adjacent molecular rotational lines which is generated only in the presence of interpulse phase coherence. PMID:11018958

Szarmes; Madey; Straub

2000-03-27

289

Aminophenyl double decker silsesquioxanes: Spectroscopic elucidation, physical and thermal characterization, and their applications  

NASA Astrophysics Data System (ADS)

The incorporation of cage-like silsesquioxanes (SQ) to form polymers has demonstrated property enhancements in areas such as: thermal and mechanical characteristics, flame retardance, dielectric properties, and oxidative resistance. However, with most hybrid polymers investigated, the attached SQs are pendant with respect to the polymer backbone. A recently developed class of these nano-structured, cage-like silsesquioxanes, formally known as double decker silsesquioxanes (DDSQ), offers the opportunity to form hybrid polymers with SQ cages as a part of the polymer backbone. However, during the capping reaction, these functionalized DDSQs generate cis and trans isomers with respect to the 3D Si-O core. Therefore, it is logical to characterize properties, which will allow for optimization of capping reaction parameters, particularly if one isomer is favored over the other. Moreover, these characteristics are also relevant when reacting or incorporating these isomers, or mixtures thereof, with other molecules to form novel materials. In this dissertation, three aminophenyl DDSQs were synthesized. More specifically, two meta- aminophenyl DDSQs, which were differentiated according to the moiety attached to the D-Si (methyl or cyclohexyl), and one para-aminophenyl DDSQ with a methyl moiety were used. Chemical, physical, and thermal characteristics were evaluated for individual isomers as well as binary mixtures of different cis/trans ratios. The 1H NMR spectra of the cis and trans isomers of these DDSQ had not previously been assigned to a degree that allowed for quantification, which was necessary for these studies. Thus, 1H-29Si HMBC correlations were applied to facilitate 1H spectral assignments and also to confirm previous 29Si assignments. Using 1H NMR not only saves time and material over 29Si NMR, but also provides a more accurate quantification, thus allowing for the ratio of cis and trans isomers present in each compound to be determined. Solubility behavior was investigated for the individual isomers, such that separation techniques could be developed. It was found that cis isomers were 33 times more soluble than trans isomers for para-aminophenyl (R = methyl), and 22 times more soluble for the analogous meta-aminophenyl in a solution of THF and hexanes. For a more sterically hindered meta-aminophenyl (R = cyclohexyl), cis isomers were only 3.5 times more soluble, and the overall solubility was also the lowest. Phase diagrams representing solid-liquid melt equilibria of the binary cis/trans mixtures were developed. Single crystal x-ray diffraction data of isolated isomers helped to interpret the phase behavior. Both compounds with a methyl moiety exhibited eutectic phase diagrams. Their trans isomers were higher melting and exhibited larger packing density. Changing from para- to meta-aminophenyl shifted the solid-liquid equilibrium further from ideal, with decreased activity coefficients. Cyclohexyl DDSQ exhibited an isomorphic phase diagram (a complete solid-solution), attributed to cyclohexyl being more similar in size to the phenyl moieties. A specific application that was chosen for these DDSQ was high performance thermosetting oligoimides. They displayed advantages over their organic counterparts in areas such as the liquid to solid transition and viscosity, which improves the processing window. Additionally, they increased the overall degree of cross-linking leading to improved oxidative stability at elevated temperatures.

Schoen, Beth Whitney

290

Elastic characterization of closed cell foams from impedance tube absorption tests.  

PubMed

A method is presented to determine the bulk elastic properties of isotropic elastic closed-cell foams from impedance tube sound absorption tests. For such foams, a resonant sound absorption is generally observed, where acoustic energy is transformed into mechanical vibration, which in turn is dissipated into heat due to structural damping. This article shows how the bulk Young's modulus, Poisson's ratio, and damping loss factor can be deduced from the resonant absorption. Also, an optimal damping loss factor yielding 100% of absorption at the first resonance is defined from the developed theory. The method is introduced for a sliding edge condition which is an ideal condition. Then, the method is extended to a bonded edge condition which is more easily achievable and additionally enables the identification of the Poisson's ratio. The method is experimentally tested on expanding closed-cell foams to find their elastic properties in both cases. Using the found properties, sound absorption predictions using an equivalent solid model with and without surface absorption are compared to measurements. Good correlations are obtained when considering surface absorption. PMID:18189557

Chevillotte, F; Panneton, R

2007-11-01

291

Observation of a cw Dark-Field Signal in an Absorption Spectroscopic Experiment Using a Phase Locked Free-Electron Laser  

Microsoft Academic Search

We introduce a technique for ultrasensitive absorption spectroscopy using the GHz-rate pulse train from a phase-locked free-electron laser (FEL), in which the fractional power absorbed from one or more laser lines reappears as a signal on the dark background between the pulses emerging from the sample. Preliminary absorption experiments in 15 Torr cm of methane at 3.25 mum, using phase-locked

Eric B. Szarmes; John M. J. Madey; Karl D. Straub

2000-01-01

292

Accurate Spectroscopic Characterization of Oxirane: A Valuable Route to its Identification in Titan's Atmosphere and the Assignment of Unidentified Infrared Bands  

NASA Astrophysics Data System (ADS)

In an effort to provide an accurate spectroscopic characterization of oxirane, state-of-the-art computational methods and approaches have been employed to determine highly accurate fundamental vibrational frequencies and rotational parameters. Available experimental data were used to assess the reliability of our computations, and an accuracy on average of 10 cm-1 for fundamental transitions as well as overtones and combination bands has been pointed out. Moving to rotational spectroscopy, relative discrepancies of 0.1%, 2%-3%, and 3%-4% were observed for rotational, quartic, and sextic centrifugal-distortion constants, respectively. We are therefore confident that the highly accurate spectroscopic data provided herein can be useful for identification of oxirane in Titan's atmosphere and the assignment of unidentified infrared bands. Since oxirane was already observed in the interstellar medium and some astronomical objects are characterized by very high D/H ratios, we also considered the accurate determination of the spectroscopic parameters for the mono-deuterated species, oxirane-d1. For the latter, an empirical scaling procedure allowed us to improve our computed data and to provide predictions for rotational transitions with a relative accuracy of about 0.02% (i.e., an uncertainty of about 40 MHz for a transition lying at 200 GHz).

Puzzarini, Cristina; Biczysko, Malgorzata; Bloino, Julien; Barone, Vincenzo

2014-04-01

293

Isolation, characterization, spectroscopic properties and quantum chemical computations of an important phytoalexin resveratrol as antioxidant component from Vitis labrusca L. and their chemical compositions  

NASA Astrophysics Data System (ADS)

In this study, isolation and characterization of trans-resveratrol (RES) as an antioxidant compound were carried out from VLE, VLG and VLS. Furthermore, antioxidant activities were evaluated by using six different methods. Finally, total phenolic, flavonoid, ascorbic acid, anthocyanin, lycopene, ?-carotene and vitamin E contents were carried out. In addition, the FT-IR, 13C and 1H NMR chemical shifts and UV-vis. spectra of trans-resveratrol were experimentally recorded. Quantum chemical computations such as the molecular geometry, vibrational frequencies, UV-vis. spectroscopic parameters, HOMOs-LUMOs energies, molecular electrostatic potential (MEP), natural bond orbitals (NBO) and nonlinear optics (NLO) properties of title molecule have been calculated by using DFT/B3PW91 method with 6-311++G(d,p) basis set in ground state for the first time. The obtained results show that the calculated spectroscopic data are in a good agreement with experimental data.

Güder, Aytaç; Korkmaz, Halil; Gökce, Halil; Alpaslan, Yelda Bingöl; Alpaslan, Gökhan

2014-12-01

294

Characterization of the Inhibition of K+ Absorption in Oat Roots by Salicylic Acid 1  

PubMed Central

The phenolic compounds salicylic acid (o-hydroxybenzoic acid) and ferulic acid (4-hydroxy-3-methoxycinnamic acid) inhibited K+ (86Rb+) absorption in excised oat (Avena sativa L. cv. Goodfield) root tissue. Salicylic acid was the most inhibitory. The degree of inhibition was both concentration- and pH-dependent. With decreasing pH, the inhibitory effect of the phenolic increased. During the early stages of incubation, the time required to inhibit K+ absorption was also pH- and concentration-dependent. At pH 4.0, 5×10?4 molar salicylic acid inhibited K+ absorption about 60% within 1 minute; whereas, at pH 6.5, this concentration affected absorption only after 10 to 15 minutes. However, at 5 × 10?3 molar and pH 6.5, salicylic acid was inhibitory within 1 minute. The capacity of the tissue to recover following a 1-hour treatment in 5 × 10?4 molar salicylic acid ranged from no recovery at pH 4.5 to complete recovery at pH 7.5. The absorption of salicylic acid was pH-dependent, also. As pH decreased, more of the phenolic compound was absorbed by the tissue. The increased absorption of the compound at low pH most likely contributed to apparent tissue damage at pH 4.5 and might have accounted for the lack of recovery of K+ absorption as pH decreased. Under the proper conditions of pH and concentration, phenolic acids such as salicylic acid could significantly affect mineral absorption by plants in the field. PMID:16662106

Harper, James R.; Balke, Nelson E.

1981-01-01

295

Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation  

NASA Technical Reports Server (NTRS)

The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.

Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)

2002-01-01

296

Ultra-violet and visible absorption characterization of explosives by differential reflectometry.  

PubMed

This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and ?-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials. PMID:23299022

Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

2013-03-15

297

Characterization of multiple-photon absorption and dissociation of polyatomic molecules  

SciTech Connect

A quantitative comparison of multiple-photon absorption (MPA) and dissociation (MPD) has been performed for experiments with a number of different polyatomic molecules. Appropriate normalization techniques for the absorption and dissociation parameters are formulated to account for the different conditions of the experiment and the molecular parameters. This procedure in a first approximation, accounts for the effects of independent variables such as gas pressure, optical bandwidth, optical pulse duration, excitation frequency, spectral width of the optical absorption band, absorption strength of the transition, bond strength, and the density of states in the molecule. The theoretical description of the dynamics of the absorbing ground state is considered and used to provide the rationale for the normalization procedure. The results of this analysis indicate that the functional dependence of the number of photons absorbed per molecule with fluence is qualitatively the same for the most molecules. Similarly, the probability for dissociation of most molecules can be related to the density of vibrational states, the bond strength, the number of photons absorbed per molecule, and the width of the absorbing transition. The functional relationships derived for MPA and MPD can be related to several theoretical aspects of the optical interaction process. In particular, the implications for the basic absorption mechanisms and the distribution of vibrational energy in the molecule will be addressed.

Judd, O.P.

1980-01-01

298

Development of a UV extended real time spectroscopic ellipsometer and its use for characterization of boron nitride thin films  

NASA Astrophysics Data System (ADS)

A rotating polarizer multichannel ellipsometer has been optimized for operation well into the ultraviolet (uv) spectral range. With this instrument, 132 spectral points in the ellipsometric parameters (psi, Delta) over the photon energy range from 1.5 eV (827 nm) to 6.5 eV (191 nm) can be collected in a minimum acquisition time of 24.5 ms, corresponding to one optical cycle of the rotating polarizer. Averages over two and eighty optical cycles (obtained in 49 ms and 1.96 s, respectively) give standard deviations in (psi, Delta) less than (0.04°, 0.08°) and (0.007°, 0.015°) respectively, for the energy range from 3.5 to 6.0 eV, as determined from successive measurements of a stable thermally oxidized silicon wafer. The key modifications that enable the extended spectral range include (i) a tandem in-line Xe/D2 source configuration, (ii) MgF2 Rochon polarizers, (iii) a spectrograph with a grating blazed at 250 nm and two stages of internally-mounted order-sorting filters, and (iv) non-uniform grouping of the pixels of the photodiode array detector. These modifications can be readily incorporated in other real time ellipsometer designs, including the rotating compensator and dual rotating compensator. The new instrument is well suited for real time characterization of wide band gap materials including boron nitride (BN), amorphous silicon oxy nitrides (a-SiOxNy), tantalum oxide (Ta2O5) among others. As an example of the application of this instrument, results of real time spectroscopic ellipsometry studies are reported for the deposition of boron nitride films grown by reactive magnetron sputtering from targets of BN and boron carbide. With the aid of the extended spectral range, crystallographic phase determination of the layered structure of the BN films has been possible. We have study the effect of deposition conditions on the nucleation of cBN and its optical properties.

Zapien, Juan Antonio

299

Spectroscopic characterization of the coordination chemistry and hydrolysis of gallium(III) in the presence of aquatic organic matter  

NASA Astrophysics Data System (ADS)

Interactions between metals and natural organic matter (NOM) are of great environmental importance and one of the key factors influencing hydrolysis, solubility, and speciation of the metals. However, studying geochemically relevant metals like Al, Fe, and Cu is sometimes associated with analytical problems; for example Fe and Cu are both redox active. Gallium (Ga) is a non-redox active metal that usually occurs at very low concentrations in environmental samples and therefore a wide concentration range of metal(III)-NOM species can be explored by adding Ga(III) to such samples. This makes Ga(III) a good probe and analogue for other metal ions, in particular Al. In addition, due to the increased usage of Ga in society, a better understanding of how Ga interacts with NOM is of importance but such studies are scarce. In this work, Ga(III) interactions with two different organic materials (Suwannee River natural organic matter and Suwannee River fulvic acid) were studied using infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy in a large experimental range (101-84,076 ?g Ga g-1 dry weight; pH 3-8). Our IR spectroscopic results showed that Ga(III) is bonded mainly to carboxylic functional groups and suggested that only a fraction of the total number of carboxylic sites in the samples was actively involved in the bonding. Modeling of the EXAFS data revealed that Ga(III) formed mononuclear chelate complexes with NOM that strongly suppressed the hydrolysis and polymerization of Ga(III). At low Ga(III) concentrations (1675-16,649 ?g g-1) organic complexes, consisting of 1-3 chelate ring structures, were the dominating species in the entire pH range while at higher concentrations (67,673-84,076 ?g g-1, pH 3.0-7.0) we detected mixtures of mononuclear organic Ga(III) complexes, Ga(III) (hydr)oxide, and free Ga(III) (here defined as the hydrated Ga(III) ion and its soluble hydrolysis products). Moreover, the EXAFS results showed significantly higher contribution from second-shell C atoms (9-11) for the Ga(III)-organic complexes at the lowest concentration (101-125 ?g g-1, pH 4.9-5.1), indicating formation of cage-like structures similar to Ga(III)-EDTA. Our combined results showed that Ga(III)-NOM interactions can be of importance for the solubility and speciation of Ga in environmental systems. Furthermore, the similarities between Ga(III) and previous Fe(III) results demonstrate that Ga(III) can be utilized as a probe for metal(III)-NOM interactions over an extended experimental range (e.g., pH and metal concentration) and thereby improve our knowledge about these interactions in general.

Hagvall, Kristoffer; Persson, Per; Karlsson, Torbjörn

2014-12-01

300

Description of the Role of Shot Noise in Spectroscopic Absorption and Emission Measurements with Photodiode and Photomultiplier Tube Detectors: Information for an Instrumental Analysis Course  

ERIC Educational Resources Information Center

A description of shot noise and the role it plays in absorption and emission measurements using photodiode and photomultiplier tube detection systems is presented. This description includes derivations of useful forms of the shot noise equation based on Poisson counting statistics. This approach can deepen student understanding of a fundamental…

McClain, Robert L.; Wright, John C.

2014-01-01

301

Photoelectron spectroscopic characterization of titanium-containing amorphous hydrogenated silicon–carbon films (aSi1-xCx:H\\/Ti)  

Microsoft Academic Search

.   Titanium-containing amorphous hydrogenated silicon–carbon films (aSi1-xCx:H\\/Ti) have been deposited by reactive magnetron cosputtering. Core-level photoelectron spectroscopy (XPS) and valence-band\\u000a photoelectron spectroscopy (UPS) have served as means for the characterization of these films. The spectroscopic data are\\u000a interpreted by a structural model on the basis of a nanocomposite containing clusters of a Ti-C-Si alloy being embedded in\\u000a an amorphous hydrogenated

A. Schüler; P. Oelhafen

2001-01-01

302

A novel mixed valence copper(I) copper(II) bis(antipyryl-methyl)-piperazine complex: synthesis, molecular structure and spectroscopic characterization  

NASA Astrophysics Data System (ADS)

This paper describes a new case of the bis(antipyryl-methyl)-piperazine [BAMP] ligand being in the "boat"-conformation and acting as a tetradentate. But unlike in Co(BAMP)(NCS) 2, which is the only complex with BAMP acting as tetradentate known so far, the coordinated copper(II) is connected via a iodo-bridge to a Cu II 2-moiety. The synthesis, elemental analysis, spectroscopic (far- and mid-FTIR, UV-Vis) and structural characterization (X-ray diffraction) as well as magnetochemical and conductivity data of this novel mixed valence binuclear complex Cu ICu II(BAMP)I 3 are presented.

Weinberger, P.; Costisor, O.; Tudose, R.; Baumgartner, O.; Linert, W.

2000-02-01

303

Synthesis and spectroscopic characterization of nickel(II) complexes of 1-benzotriazol-1-yl-[( p-X-phenyl)hydrazone]propan-2-one  

Microsoft Academic Search

The reaction of NiCl2·H2O with 1-benzotriazol-1-yl-[(p-X-phenyl)hydrazone]propan-2-one, X=H (HL1), X=Cl (HL2), X=Br (HL3) and X=Me (HL4), gave the complexes [(HL)NiCl2]·nH2O and [LNi(OH)]2, where L is the monobasic anion of HL2 or HL3. The nature of the products is solvent and ligand dependent. The complexes are characterized by elemental analyses, molar conductivity, magnetic moments and spectroscopic (IR and UV\\/vis) measurements. The IR

Nouria Al-Awadi; Nadia M. Shuaib; Ali El-Dissouky

2006-01-01

304

Spectroscopic characterization of iron ores formed in different geological environments using FTIR, XPS, Mössbauer spectroscopy and thermoanalyses  

NASA Astrophysics Data System (ADS)

Application of thermoanalyses, FTIR, XPS and Mössbauer spectroscopic methods can differentiate between iron ores formed in different geological environments. Two types of iron ore are formed in shallow marine environments in the Bahariya Depression, Egypt, yellowish brown ooidal ironstones (type 1) and black mud and fossiliferous ironstones (type 2). Both types were subjected to subaerial weathering, producing a dark brown lateritic (pedogenic) iron ore (type 3). Microscopic investigation indicates goethite is the main mineral in types 1 and 3, while hematite is the main mineral in type 2 and also occurs in type 3. Thermoanalyses indicated the dehydroxylation endothermic peak of goethite of type 1 occurs between 329 and 345 °C, while in type 3 occurs between 284 and 330 °C. This variation can be attributed to the nanocrystalline nature of the pedogenic goethite. The presence of an exothermic peak at 754 °C in type 3 is probably attributed to goethite-hematite phase transformation. FTIR spectroscopy indicated that goethite of type 1 is characterized by the presence of the ?-OH band between 799 and 802 cm-1, the ?-OH between 898 and 904 cm-1 and the bulk hydroxyl stretch between 3124 and 3133 cm-1. Goethite of type 3 is characterized by the absence of the bulk hydroxyl stretch band and the ?-OH and ?-OH are shifted to higher Wavenumbers that can attributed to a relative Al-for Fe-substitution. Hematite is identified by two IR bands; the first is between 464 and 475 cm-1 and at the second is between 540 and 557 cm-1. Quartz is identified in all iron ore types, nitrates are identified in types 1 and 2, but absent in type 3 and Kaolinite is identified in type 2. The Mössbauer spectrum of type 1 is fitted with one magnetic sextet corresponding to goethite with an isomer shift (IS) = 0.374 mm s-1, a quadruple splitting (QS) = -0.27 mm s-1 and a hyperfine magnetic field (BHF) = ?37. The Mössbauer spectrum of type 2 is fitted with one magnetic sextet corresponding to hematite with IS = 0.363 mm s-1, QS = -0.23 mm s-1 and BHF = ?50. The Mössbauer spectrum of type 3 is best fitted with a single doublet corresponding to ferrihydrite and one sextet corresponding to hematite. The XPS survey scans and the high resolution of the Fe 2p3/2 can differentiate between the yellowish-brown and green ooidal laminae of type 1. The XPS survey scans indicate the presence of Fe, O, C, N, Na, Cl, Ca and Si in all laminae, while S, Zn, Ti and P are only restricted to the green laminae. The high resolution of the Fe 2p3/2 indicates that Fe is linked to OH- ligand in the yellowish-brown laminae that correspond to goethite, while Fe is linked to SO42- ligand in the green laminae. The XPS survey scans of types 2 and 3 indicate that Fe is linked to O2- ligand that corresponds to hematite.

Salama, Walid; El Aref, Mourtada; Gaupp, Reinhard

2015-02-01

305

Spectroscopic characterization of iron ores formed in different geological environments using FTIR, XPS, Mössbauer spectroscopy and thermoanalyses.  

PubMed

Application of thermoanalyses, FTIR, XPS and Mössbauer spectroscopic methods can differentiate between iron ores formed in different geological environments. Two types of iron ore are formed in shallow marine environments in the Bahariya Depression, Egypt, yellowish brown ooidal ironstones (type 1) and black mud and fossiliferous ironstones (type 2). Both types were subjected to subaerial weathering, producing a dark brown lateritic (pedogenic) iron ore (type 3). Microscopic investigation indicates goethite is the main mineral in types 1 and 3, while hematite is the main mineral in type 2 and also occurs in type 3. Thermoanalyses indicated the dehydroxylation endothermic peak of goethite of type 1 occurs between 329 and 345°C, while in type 3 occurs between 284 and 330°C. This variation can be attributed to the nanocrystalline nature of the pedogenic goethite. The presence of an exothermic peak at 754°C in type 3 is probably attributed to goethite-hematite phase transformation. FTIR spectroscopy indicated that goethite of type 1 is characterized by the presence of the ?-OH band between 799 and 802cm(-1), the ?-OH between 898 and 904cm(-1) and the bulk hydroxyl stretch between 3124 and 3133cm(-1). Goethite of type 3 is characterized by the absence of the bulk hydroxyl stretch band and the ?-OH and ?-OH are shifted to higher Wavenumbers that can attributed to a relative Al-for Fe-substitution. Hematite is identified by two IR bands; the first is between 464 and 475cm(-1) and at the second is between 540 and 557cm(-1). Quartz is identified in all iron ore types, nitrates are identified in types 1 and 2, but absent in type 3 and Kaolinite is identified in type 2. The Mössbauer spectrum of type 1 is fitted with one magnetic sextet corresponding to goethite with an isomer shift (IS)=0.374mms(-1), a quadruple splitting (QS)=-0.27mms(-1) and a hyperfine magnetic field (BHF)=?37. The Mössbauer spectrum of type 2 is fitted with one magnetic sextet corresponding to hematite with IS=0.363mms(-1), QS=-0.23mms(-1) and BHF=?50. The Mössbauer spectrum of type 3 is best fitted with a single doublet corresponding to ferrihydrite and one sextet corresponding to hematite. The XPS survey scans and the high resolution of the Fe 2p3/2 can differentiate between the yellowish-brown and green ooidal laminae of type 1. The XPS survey scans indicate the presence of Fe, O, C, N, Na, Cl, Ca and Si in all laminae, while S, Zn, Ti and P are only restricted to the green laminae. The high resolution of the Fe 2p3/2 indicates that Fe is linked to OH(-) ligand in the yellowish-brown laminae that correspond to goethite, while Fe is linked to SO4(2-) ligand in the green laminae. The XPS survey scans of types 2 and 3 indicate that Fe is linked to O(2-) ligand that corresponds to hematite. PMID:25467675

Salama, Walid; El Aref, Mourtada; Gaupp, Reinhard

2014-10-31

306

Spectroscopic Characterization of AN Alkyl-Substituted Criegee Intermediate CH_{3}CHOO and its OH Radical Products  

NASA Astrophysics Data System (ADS)

In the atmosphere, cycloaddition of ozone to the double bond of alkenes produces energized Criegee intermediates, which undergo subsequent decay processes to yield OH radicals. In this laboratory, a simple alkyl-substituted Criegee intermediate CH_{3}CHOO is produced by 248 nm photolysis of CH_{3}CHI_{2} and subsequent reaction of CH_{3}CHI with O_{2} in a quartz capillary tube reactor, following the same approach utilized for CH_{2}OO. The CH_{3}CHOO intermediate (m/z=60) and other products are detected following supersonic expansion using 118 nm VUV ionization in a time-of-flight mass spectrometer. The OH radical products from decomposition of the CH_{3}CHOO intermediate are also directly detected at m/z=17 using a new UV+VUV ionization scheme, combining UV excitation on the OH A ^2?^+-X ^2? (1,0) transition with fixed-frequency VUV at 118 nm, or alternatively by UV laser-induced fluorescence on the OH A-X transition; OH products are also observed from CH_{2}OO. The CH_{3}CHOO intermediate is characterized by a strong B ^1A'-X ^1A' electronic transition, in which UV excitation near the peak of a broad absorption profile centered at 320 nm results in significant depletion of the CH_{3}CHOO photoionization signal. The mechanism proposed for OH generation from energized CH_{3}CHOO and many larger Criegee intermediates is a 1,4 H-atom shift to form vinylhydroperoxide species that decay to produce OH. This reaction scheme provides a non-photolytic source of OH radicals in the atmosphere during night and winter times. J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. {134}, 20045 (2012). J. M. Beames, F. Liu, M. I. Lester and C. Murray, J. Chem. Phys. {134}, 241102 (2011).

Beames, Joseph M.; Liu, Fang; Lu, Lu; Lester, Marsha I.

2013-06-01

307

Spectroscopic and potentiometric characterization of oxovanadium(IV) complexes formed by 3-hydroxy-4-pyridinones. Rationalization of the influence of basicity and electronic structure of the ligand on the properties of V(IV)O species in aqueous solution.  

PubMed

Aqueous solution studies regarding the identification and characterization of complexes formed by the VIVO ion and 11 3-hydroxy-4-pyridinone derivatives have been performed using EPR and UV/vis spectroscopic techniques. For the three ligands (HL) adequately soluble in water (1-methyl-3-hydroxy-4-pyridinone, 1-methyl-2-ethyl-3-hydroxy-4-pyridinone, and 1,2-diethyl-3-hydroxy-4-pyridinone), potentiometric titrations were performed; the results are consistent with the formation of [V(IV)OL]+, [V(IV)OL2], [V(IV)OL2H(-1)]-, [(V(IV)O)2L2H(-2)], and [V(IV)L3]+ species. Bis chelated complexes are characterized by a cis-trans isomerism, the trans isomer being strongly favored with respect to the cis arrangement. Tris chelated non-oxo V(IV) species were prepared in CH3COOH; their spectroscopic features point to a d(z2) ground state and a geometry intermediate between an octahedron and a trigonal prism, related to the steric requirements of the substituent on the carbon atom in position 2 of the pyridinone ring. Four new solid derivatives, [V(IV)O(1,2-diethyl-3-hydroxy-4-pyridinonato)2], [V(IV)O(1-(p-tolyl)-2-ethyl-3-hydroxy-4-pyridinonato)2], [V(IV)O(1-(p-(n-butyl)phenyl)-2-ethyl-3-hydroxy-4-pyridinonato)2], and [V(IV)O(1-(p-(n-hexyl)phenyl)-2-ethyl-3-hydroxy-4-pyridinonato)2], were isolated and characterized; they exhibited a five-coordinate geometry close to square-pyramid. A criterion for establishing the degree of distortion toward the trigonal-bipyramid on the basis of the electronic absorption spectra is provided. Relationships between the pKa of the -OH group in position 3 of the ring and (i) log K of mono and bis chelated complexes, (ii) pK of the water molecule in cis-[V(IV)OL2(H2O)], (iii) log K of tris chelated species [V(IV)L3]+, and (iv) 51V hyperfine coupling constant (Az) have been established and discussed for a number of pyrone, pyridinone, and catechol ligands. The results are rationalized by assuming for pyridinones an electronic structure intermediate between that of pyrones and catechols. The relationships are valuable to the understanding of the behavior of VIVO species in aqueous solution. PMID:16999406

Rangel, Maria; Leite, Andreia; João Amorim, M; Garribba, Eugenio; Micera, Giovanni; Lodyga-Chruscinska, Elzbieta

2006-10-01

308

Mn L2,3-edge X-ray absorption spectroscopic studies on charge-discharge mechanism of Li2MnO3  

NASA Astrophysics Data System (ADS)

The redox reaction of Mn in Li2MnO3 was studied by X-ray absorption spectroscopy and ab initio multiplet calculation. Associated with the de-intercalation of Li-ion, small but clear spectral changes were observed in Mn-L2,3 X-ray absorption near edge structure (XANES). The systematic ab initio multiplet calculations of Mn-L2,3 XANES revealed that the spectral changes in the experiment could not simply be ascribed to the change of the valency from Mn4+ to Mn5+ but can be explained well by the changes of local atomic structures around Mn4+ due to the Li de-intercalation. Our results suggest that the electronic state of oxygen should change during charging in Li2MnO3.

Kubobuchi, Kei; Mogi, Masato; Ikeno, Hidekazu; Tanaka, Isao; Imai, Hideto; Mizoguchi, Teruyasu

2014-02-01

309

Local structure and speciation of platinum in fresh and road-aged North American sourced vehicle emissions catalysts: an X-ray absorption spectroscopic study.  

PubMed

Given emerging concerns about the bioavailability and toxicity of anthropogenic platinum compounds emitted into the environment from sources including vehicle emission catalysts (VEC), the platinum species present in selected North American sourced fresh and road-aged VEC were determined by Pt and Cl X-ray absorption spectroscopy. Detailed analysis of the Extended X-ray Absorption Fine Structure at the Pt L3 and L2 edges of the solid phase catalysts revealed mainly oxidic species in the fresh catalysts and metallic components dominant in the road-aged catalysts. In addition, some bimetallic components (Pt-Ni, Pt-Pd, Pt-Rh) were observed in the road-aged catalysts from supporting Ni-, Pd-, and Rh-K edge XAS studies. These detailed analyses allow for the significant conclusion that this study did not find any evidence for the presence of chloroplatinate species in the investigated solid phase of a Three Way Catalyst or Diesel Oxidation Catalysts. PMID:24568168

Ash, Peter W; Boyd, David A; Hyde, Timothy I; Keating, Jonathan L; Randlshofer, Gabriele; Rothenbacher, Klaus; Sankar, Gopinathan; Schauer, James J; Shafer, Martin M; Toner, Brandy M

2014-04-01

310

Ground-based infrared spectroscopic measurements of carbonyl sulfide: Free tropospheric trends from a 24-year time series of solar absorption measurements  

Microsoft Academic Search

Solar absorption spectra recorded over a 24-year time span have been analyzed to retrieve average free tropospheric mixing ratios of carbonyl sulfide (OCS). The measurements were recorded with the Fourier transform spectrometer located in the U.S. National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, lat. 31.9°N, long. 111.6°W), southwest of Tucson, Arizona, and were obtained

C. P. Rinsland; A. Goldman; E. Mahieu; R. Zander; J. Notholt; N. B. Jones; D. W. T. Griffith; T. M. Stephen; L. S. Chiou

2002-01-01

311

Electronic absorption and luminescence spectroscopic studies of kyanite single crystals: differentiation between excitation of FeTi charge transfer and Cr 3+ dd transitions  

Microsoft Academic Search

A selected set of five different kyanite samples was analysed by electron microprobe and found to contain chromium between <0.001 and 0.055 per formula unit (pfu). Polarized electronic absorption spectroscopy on oriented single crystals,\\u000a R1, R2-sharp line luminescence and spectra of excitation of ?3- and ?4-components of R1-line of Cr3+-emission had the following results: (1) The Fe2+–Ti4+ charge transfer in

A. N. Platonov; A. N. Tarashchan; K. Langer; M. Andrut; G. Partzsch; S. S. Matsyuk

1998-01-01

312

X-ray absorption spectroscopic studies of the blue copper site: Metal and ligand Kedge studies to probe the origin of the EPR hyperfine splitting in plastocyanin  

Microsoft Academic Search

X-ray absorption spectra for the oxidized blue copper protein plastocyanin and several Cu(II) model complexes have been measured at both the Cu K-edge and the ligand K-edges (Cl and S) in order to elucidate the source of the small parallel hyperfine splitting in the EPR spectra of blue copper centers. Assignment and analysis of a feature in the Cu K-edge

Susan E. Shadle; James E. Penner-Hahn; Harvey J. Schugar; Britt Hedman; Keith O. Hodgson; Edward I. Solomon

1993-01-01

313

The role of Pd2+/Pd0 in hydrogenation by [Pd(2-pymo)2]n: an X-ray absorption and IR spectroscopic study.  

PubMed

The metal-organic framework (MOF) [Pd(2-pymo)(2)](n) (2-pymo=2-pyrimidinolate) was used as catalyst in the hydrogenation of 1-octene. During catalytic hydrogenation, the changes at the metal nodes and linkers of the MOF were investigated by in situ X-ray absorption spectroscopy (XAS) and IR spectroscopy. With the help of extended X-ray absorption fine structure and X-ray absorption near edge structure data, Quick-XAS, and IR spectroscopy, detailed insights into the catalytic relevance of Pd(2+)/Pd(0) in the hydrogenation of 1-octene could be achieved. Shortly after exposure of the catalyst to H(2) and simultaneously with the hydrogenation of 1-octene, the aromatic rings of the linker molecules are hydrogenated rapidly. Up to this point, the MOF structure remained intact. After completion of linker hydrogenation, the linkers were also protonated. When half of the linker molecules were protonated, the onset of reduction of the Pd(2+) centers to Pd(0) was observed and the hydrogenation activity decreased, followed by fast reduction of the palladium centers and collapse of the MOF structure. Major fractions of Pd(0) are only observed when the hydrogenation of 1-octene is almost finished. Consequently, the Pd(2+) nodes of the MOF [Pd(2-pymo)(2)](n) are identified as active centers in the hydrogenation of 1-octene. PMID:23074097

Schuster, Sabine; Klemm, Elias; Bauer, Matthias

2012-12-01

314

Spectroscopic Study of Solvent Effects on the Electronic Absorption Spectra of Flavone and 7-Hydroxyflavone in Neat and Binary Solvent Mixtures  

PubMed Central

The solvatochromic characteristics of flavone and 7-hydroxyflavone were investigated in neat and binary solvent mixtures. The spectral shifts of these solutes were correlated with the Kamlet and Taft parameters (?, ? and ?*) using linear solvation energy relationships. The multiparametric analysis indicates that both specific hydrogen bond donor ability and non-specific dipolar interactions of the solvents play an important role in absorption maxima of flavone in pure solvents. The hydrogen bond acceptor ability of the solvent was the main parameter affecting the absorption maxima of 7-hydroxyflavone. The simulated absorption spectra using a TD-DFT method were in good agreement with the experimental ones for both flavones. Index of preferential solvation was calculated as a function of solvent composition. Preferential solvation by ethanol was detected in cyclohexane-ethanol and acetonitrile-ethanol mixtures for flavone and in acetonitrile-ethanol mixtures for 7-hydroxyflavone. These results indicate that intermolecular hydrogen bonds between solute and solvent are responsible for the non-linear variation of the solvatochromic shifts on the mole fraction of ethanol in the analyzed binary mixtures. PMID:22272110

Sancho, Matias I.; Almandoz, Maria C.; Blanco, Sonia E.; Castro, Eduardo A.

2011-01-01

315

Synthesis and characterizations of star-shaped octupolar triazatruxenes-based two-photon absorption chromophores.  

PubMed

A series of star-shaped octupolar triazatruxenes (TATs, 1-6) with intramolecular "push-pull" structure were synthesized and their photophysical properties have been systematically investigated. These chromophores showed obvious solvatochromic effect, i.e., significant bathochromic shift of the emission spectra and larger Stokes shifts were observed in more polar solvents mainly due to photoinduced intramolecular charge transfer (ICT). The two-photon absorption (2PA) cross-section values were determined by two-photon excited fluorescence (2PEF) measurements in toluene and THF. These chromophores exhibited large two-photon absorption cross-sections ranging from 280 to 1620 GM in the near-infrared (NIR) region. Compound 6 showed the largest 2PA action cross-section (?(2)?) of 564 GM and could be a potential two-photon fluorescent (2PF) probe. In addition, compounds 1-6 all displayed good thermal stability and photostability. PMID:21210649

Shao, Jinjun; Guan, Zhenping; Yan, Yongli; Jiao, Chongjun; Xu, Qing-Hua; Chi, Chunyan

2011-02-01

316

Performance characterization and ground testing of an airborne CO2 differential absorption lidar system (phase II)  

Microsoft Academic Search

The Air Force Research Laboratory (AFRL) Active Remote Sensing Branch has developed the Laser Airborne Remote Sensing (LARS) system for chemical detection using the differential absorption lidar (DIAL) technique. The system is based on a high-power CO2 laser which can use either the standard 12C16O2 or the 13C16O2 carbon dioxide isotopes as the lasing medium, and has output energies of

Daniel C. Senft; Marsha J. Fox; Carla M. Hamilton; Dale A. Richter; N. S. Higdon; Brian T. Kelly

1999-01-01

317

Interaction of cholesterol with sphingosine: physicochemical characterization and impact on intestinal absorption.  

PubMed

Molecular associations between sphingomyelin and cholesterol provide a molecular basis for the colocalization of these lipids in plasma membrane microdomains (lipid rafts) and for the inhibitory effect of sphingomyelin on the intestinal absorption of cholesterol. Using surface pressure measurements at the air-water interface, we showed that sphingosine, the common sphingoid backbone of most sphingolipids, formed condensed lipid complexes with cholesterol. Structure-activity relationship studies with long-chain analogs of sphingosine, together with molecular mechanics simulations, were consistent with a specific interaction between sphingosine and the alpha face of cholesterol. The uptake of micellar cholesterol and the effect of sphingosine on cholesterol absorption were studied with two human model intestinal epithelial cell lines, Caco-2 and HT-29-D4. Real-time PCR quantifications of the putative cholesterol transporter Niemann-Pick C1 like 1 (NPC1L1) mRNA revealed that, in these cell lines, the activity of cholesterol transport correlated with the level of NPC1L1 expression. In both cell lines, sphingosine induced a dose-dependent decrease of cholesterol absorption. Yet the effect of sphingosine was more dramatic in Caco-2 cells, which also displayed the highest expression of NPC1L1 mRNA. Altogether, these data suggested that sphingosine interacts specifically with cholesterol and inhibits the intestinal NPC1L1-dependent transport of micellar cholesterol. PMID:15520452

Garmy, Nicolas; Taïeb, Nadira; Yahi, Nouara; Fantini, Jacques

2005-01-01

318

Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.  

PubMed

Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary. PMID:24245312

Ryu, Seongwoo; Mo, Chan Bin; Lee, Haeshin; Hong, Soon Hyung

2013-11-01

319

Preformulation characterization and in vivo absorption in beagle dogs of JFD, a novel anti-obesity drug for oral delivery.  

PubMed

Abstract JFD (N-isoleucyl-4-methyl-1,1-cyclopropyl-1-(4-chlorine)phenyl-2-amylamine·HCl) is a novel investigational anti-obesity drug without obvious cardiotoxicity. The objective of this study was to characterize the key physicochemical properties of JFD, including solution-state characterization (ionization constant, partition coefficient, aqueous and pH-solubility profile), solid-state characterization (particle size, thermal analysis, crystallinity and hygroscopicity) and drug-excipient chemical compatibility. A supporting in vivo absorption study was also carried out in beagle dogs. JFD bulk powders are prismatic crystals with a low degree of crystallinity, particle sizes of which are within 2-10??m. JFD is highly hygroscopic, easily deliquesces to an amorphous glass solid and changes subsequently to another crystal form under an elevated moisture/temperature condition. Similar physical instability was also observed in real-time CheqSol solubility assay. pKa (7.49?±?0.01), log?P (5.10?±?0.02) and intrinsic solubility (S0) (1.75??g/ml) at 37?°C of JFD were obtained using potentiometric titration method. Based on these solution-state properties, JFD was estimated to be classified as BCS II, thus its dissolution rate may be an absorption-limiting step. Moreover, JFD was more chemically compatible with dibasic calcium phosphate, mannitol, hypromellose and colloidal silicon dioxide than with lactose and magnesium stearate. Further, JFD exhibited an acceptable pharmacokinetic profiling in beagle dogs and the pharmacokinetic parameters Tmax, Cmax, AUC0-t and absolute bioavailability were 1.60?±?0.81?h, 0.78?±?0.47??g/ml, 3.77?±?1.85??g·h/ml and 52.30?±?19.39%, respectively. The preformulation characterization provides valuable information for further development of oral administration of JFD. PMID:24694186

Fan, Yunzhou; Yang, Meiyan; Wang, Yuli; Li, Yanyou; Zhou, Yuanda; Chen, Xiaoping; Shan, Li; Wei, Jun; Gao, Chunsheng

2014-04-01

320

Light Absorption Properties of Brown Carbon from Fresh and Aged Biomass Burning Aerosols Characterized in a Smog Chamber  

NASA Astrophysics Data System (ADS)

Black carbon is an important particulate phase light absorber in the atmosphere. Recent studies have shown that some organic matter also absorb visible light, especially at short wavelengths. These organic compounds are referred to as "brown carbon". Biomass burning is a major contributor to brown carbon in atmospheric particulate matter; however, its optical properties are poorly characterized. We have conducted smog chamber experiments to investigate light absorption properties of brown carbon in primary and aged biomass burning emissions, namely the imaginary refractive index. The aging was performed in a smog chamber, where dilute emissions were exposed to UV lights to initiate photo-oxidation, which often produced substantial secondary organic aerosol. The experiments took place at Carnegie Mellon University (CMU) and at the US Fire Science Laboratory in Missoula, MT as part of the Fire Lab at Missoula field campaign (FLAME 2009). The CMU experiments simulated household wood burning (oak), and the FLAME experiments simulated wildland fires with fuels including gallberry, lodgepole pine, black spruce and ponderosa pine. Absorption coefficients were measured using an Aethalometer (Magee Scientific) at 7 different wavelengths ranging between 370 nm and 950 nm. The black carbon size distributions were measured using a Single Particle Soot Photometer (SP2, DMT), and total aerosol size distributions were measured using a Scanning Mobility Particle Sizer (SMPS, TSI). The absorption coefficients of both the fresh and aged aerosol were significantly larger, and had stronger wavelength dependence than what would be expected for black carbon alone, and for a black carbon core with a non-absorbing shell. This indicates that biomass burning organic aerosol should be classified as brown carbon. A (black carbon) core - (brown carbon) shell absorption model based on Mie theory was optimized to determine the shell imaginary refractive index which produces model outputs that fit measured absorption coefficients. The fresh and aged aerosol had similar optical properties, with shell imaginary refractive index ranging between 0.2 and 0.4 at 550 nm, and wavelength dependence between ?-2 and ?-3. These values correspond to absorption efficiencies comparable to black carbon at short visible wavelengths. Assuming a clear (non-absorbing) shell overestimates the single scattering albedo by up to a factor of 2, and underestimates the simple forcing efficiency by up to an order of magnitude.

Saleh, R.; Chuang, W.; Hennigan, C.; McMeeking, G. R.; Coe, H.; Donahue, N. M.; Robinson, A. L.

2011-12-01

321

Spectroscopic characterization of soft x-ray multilayer optics using a broadband laser-plasma radiation source  

NASA Astrophysics Data System (ADS)

We present the spectroscopic techniques for studying imaging, spectral, and polarizing properties of multilayer optics intended for solar astronomy and laboratory applications. The measurements were performed using line or quasicontinuous radiation (15 - 400 angstrom) of a point-like source driven by 0.15-J, 5-ns laser pulses at 0.54 micrometer. The imaging quality of focusing normal-incidence multilayer mirrors (MMs) in the subarcsecond resolution range was evaluated from small- source imaging tests employing a high-resolution photographic film. The spectral properties of focusing and plane MMs were measured using the configuration of a transmission grating spectrograph with a medium dispersion, the plate scale typically lying in the range 10 - 30 angstroms/mm. This technique allowed us to measure: (1) the resonance wavelengths versus MM aperture (evaluation of lateral uniformity of the d- spacing); (2) the spectral shape of the primary resonance reflection peak; (3) outside-resonance reflection and higher- order reflection maxima revealed under irradiation by a broad spectrum; (4) for plane MMs, the reflectivities at arbitrary angles of incidence. In the evaluation of plane MMs, the function of focusing radiation was transferred to grazing- incidence toroidal mirrors. About 40 MMs ranging in resonance wavelength from 45 to 310 angstroms, synthesized in different laboratories, were studied using these techniques. A broadband spectrograph comprising a grazing-incidence toroidal mirror and a transmission grating proved to be inherently suited for characterizing the laser-plasma source itself. Two versions of tungsten-coated toroidal mirrors were used, which operated at grazing angles of 7.6 degrees and 4 degrees and had the respective practical short-wave cutoffs at about 40 and 15 angstroms. A source of collimated polarized quasimonochromatic radiation in the 170 to 180 angstrom band was implemented around MMs and our laser-plasma source. The peak polarizance of plane Mo-Si MMs with a d-spacing of 120 angstroms, measured around 175 angstroms at 41 degrees off normal, proved to be 98.2%, which was consistent with the calculated value (98.75%). Two high-resolution high-throughput stigmatic spectrographs were implemented, each comprising a couple of identical concave normal-incidence MMs and a plane grating at grazing incidence. Space-resolved line spectra of laser- produced plasma were obtained and analyzed. The spectrograph for the 130 - 140 angstrom range had a practical resolving power of at least 4000, a plate scale of 0.7 angstroms/mm, and measured 0.6 m. These parameters for the 170 - 190 angstrom range instrument were respectively 24,000, 0.35 angstrom/mm, and 1.1 m. A highly dispersive spectroheliograph was put to a test using a laser-plasma source; the configuration was closely related to that of the spectrograph but involved a reversed ray propagation.

Ragozin, Eugene N.; Kolachevsky, Nikolai N.; Mitropolsky, Mikhail M.; Pokrovsky, Yurii Y.

1997-07-01

322

Time-resolved characterization of a filamentary argon discharge at atmospheric pressure in a capillary using emission and absorption spectroscopy  

NASA Astrophysics Data System (ADS)

An argon/nitrogen (0.999/0.001) filamentary pulsed discharge operated at atmospheric pressure in a quartz tube is characterized using voltage-current measurements, microphotography, optical emission spectroscopy (OES) and absorption spectroscopy. Nitrogen is applied as a sensor gas for the purpose of OES diagnostic. The density of argon metastable atoms Ar(3P2) is determined using tunable diode laser absorption spectroscopy (TDLAS). Using a plasma chemical model the measured OES data are applied for the characterization of the plasma conditions. Between intense positive pulses the discharge current oscillates with a damped amplitude. It is established that an electric current flows in this discharge not only through a thin plasma filament that is observed in the discharge image but also through the whole cross section of the quartz tube. A diffuse plasma fills the quartz tube during a time between intense current pulses. Ionization waves are propagating in this plasma between the spike and the grounded area of the tube producing thin plasma channels. The diameter of these channels increases during the pause between the propagation of ionization waves probably because of thermal expansion and diffusion. Inside the channels electron densities of ˜2 × 1013 cm-3, argon metastable densities ˜1014 cm-3 and a reduced electric field about 10 Td are determined.

Schröter, Sandra; Pothiraja, Ramasamy; Awakowicz, Peter; Bibinov, Nikita; Böke, Marc; Niermann, Benedikt; Winter, Jörg

2013-11-01

323

A femtosecond transient absorption spectroscopic study on a carbonyl-containing carotenoid analogue, 2-(all-trans-retinylidene)-indan-1,3-dione  

PubMed Central

The photophysical properties of a carbonyl-containing carotenoid analogue in an s-cis configuration, relative to the conjugated ? system, 2-(all-trans-retinylidene)-indan-1,3-dione (C20Ind), were investigated by femtosecond time-resolved spectroscopy in various solvents. The lifetime of the optically forbidden S1 state of C20Ind becomes long as solvent polarity increases. This trend is completely opposite to the situation of S1-ICT dynamics of carbonyl-containing carotenoids, such as peridinin and fucoxanthin. Excitation energy dependence of the transient absorption measurements shows that the transient absorption spectra in non-polar solvents were originated from two distinct transient species, while those in polar and protic solvents are due to a single transient species. By referring to the results of MNDO-PSDCI (modified neglect of differential overlap with partial single- and double-configuration interaction) calculations, we conclude: (1) In polar and protic solvents, the S1 state is generated following excitation up to the S2 state; (2) In non-polar solvents, however, both the S1 and 1n?* states are generated; and (3) C20Ind does not generate the S1-ICT state, despite the fact that it has two conjugated carbonyl groups. PMID:21361262

Kusumoto, Toshiyuki; Kosumi, Daisuke; Uragami, Chiasa; Frank, Harry A.; Birge, Robert R.; Cogdell, Richard J.; Hashimoto, Hideki

2011-01-01

324

Effects of oxidation state on metal ion binding by Medicago sativa (alfalfa): Atomic and X-ray absorption spectroscopic studies with Fe(II) and Fe(III)  

SciTech Connect

The authors present here experimental results that investigate the effects of metal-ion binding on iron-ion sorption to and recovery from alfalfa biomass. Fe(II)- and Fe(III)-ion binding were measured in order to ascertain the differences in binding strengths due to changes in oxidation state. Stronger binding was found for iron(III)-biomass as compared to iron(II)-biomass. The optimal pH for iron uptake was determined to be 5. The results of pH binding profile, orion desorption, and temperature-dependent binding experiments as well as X-ray spectroscopic (XAS) measurements all suggest that binding of iron by alfalfa biomass may be occurring through carboxyl ligands. The XAS experiments further demonstrate that the metal binding proceeds without an oxidation state change, and both iron(II) and iron(III) have similar coordination environments. The information presented will assist in understanding the binding of other metals to alfalfa biomass and in developing methods for their recovery.

Tiemann, K.J.; Gardea-Torresdey, J.L.; Gamez, G.; Dokken, K.; Cano-Aguilera, I.; Renner, M.W.; Furenlid, L.R.

2000-02-15

325

GaAs nano-pillars for solar power absorption: Electromagnetic characterization  

Microsoft Academic Search

The characterization of GaAs nano-pillars in the optical frequency range was investigated using HFSS. Important parameters such as optical material properties were compiled and organized to allow accurate simulation of GaAs nano-pillars to observe total reflection in comparison to flat GaAs pn-junction. This characterization exercise was essential in providing a platform for further investigation of these nano-pillars. It is now

Timothy Brockett; Harish Rajagopalan; Yahya Rahmat-Samii

2010-01-01

326

Spectroscopic studies of copper enzymes  

Microsoft Academic Search

Several spectroscopic methods, including absorption, circular dichroism (CD), magnetic CD (MCD), X-ray absorption, resonance Raman, EPR, NMR, and quasi-elastic light-scattering spectroscopy, have been used to probe the structures of copper-containing amine oxidases, nitrite reductase, and nitrous oxide reductase. The basic goals are to determine the copper site structure, electronic properties, and to generate structure-reactivity correlations. Collectively, the results on the

D. M. Dooley; R. Moog; W. Zumft; S. H. Koenig; R. A. Scott; C. E. Cote; M. McGuirl

1986-01-01

327

Halo-substituted thiosemicarbazones and their copper(II), nickel(II) complexes: Detailed spectroscopic characterization and study of antitumour activity against HepG2 human hepatoblastoma cells  

NASA Astrophysics Data System (ADS)

Copper(II) and nickel(II) complexes of two different halogen substituted thiosemicarbazone ligands were synthesized. The ligands 3,4-difluoroacetophenone thiosemicarbazone (1) and 2-bromo-4'-chloroacetophenone thiosemicarbazone (2) were characterized and confirmed spectroscopically by FT-IR, FT-Raman, UV-vis and fluorescence spectral analysis, while the respective copper(II) complexes [Cu(C9H9N3F2S)2Cl2] (1a), [Cu(C9H9N3ClBrS)2Cl2] (2a) and nickel(II) complexes [Ni(C9H9N3F2S)2] (1b), [Ni(C9H9N3ClBrS)2] (2b) were characterized by FT-IR, UV-vis and electron paramagnetic spectroscopy (EPR). The EPR spectra of the Cu(II) complexes provided the rhombic octahedral and axial symmetry of the complexes 1a and 2a respectively. For the complex 1a, the g values calculated as g1 = 2.1228, g2 = 2.0706 and g3 = 2.001 between 2900 and 3300 G. While for the complex 2a, a set of two resonance absorptions were observed. The synthesized compounds were tested for antitumor activity and showed that the ability to kill liver cancer cells significantly. Out of all the synthesized compounds, copper(II) complexes 1a and 2a showed high cytotoxic effect on liver cancer cells with 67.51% and 42.77% of cytotoxicity respectively at 100 ?M.

Jagadeesh, M.; Kalangi, Suresh K.; Sivarama Krishna, L.; Reddy, A. Varada

2014-01-01

328

Enhancement of oral bioavailability of tripterine through lipid nanospheres: preparation, characterization, and absorption evaluation.  

PubMed

Oral delivery of anticancer drugs remains challenging because of limited water-solubility and/or poor permeability. Here, we aimed to enhance the oral bioavailability of tripterine (TRI, a plant-derived anticancer compound) using lipid nanospheres (LNs) and to determine the mechanisms of oral absorption. TRI-loaded LNs (TRI-LNs) were prepared by rapid dispersion of an ethanol mixture of TRI, lecithin, sodium oleate, and soybean oil into water. The obtained LNs were 150 nm in size with a high value of entrapment efficiency (99.95%). TRI-LNs were fairly stable and the drug release was negligible (<0.2%) in simulated physiological fluid. The pharmacokinetic results showed that LNs significantly enhanced the oral bioavailability of TRI with a relative bioavailability of 224.88% (TRI suspensions was used as a reference). The mechanistic studies demonstrated that improved intestinal permeability and post-enterocyte lymphatic transport were mainly responsible for the enhanced oral absorption. Our findings suggested that LNs may be a viable oral carrier for poorly bioavailable drugs. PMID:24700417

Zhang, Xingwang; Zhang, Tianpeng; Zhou, Xiaotong; Liu, Hongming; Sun, Hua; Ma, Zhiguo; Wu, Baojian

2014-06-01

329

Absorption spectra and photovoltaic characterization of chlorophyllins as sensitizers for dye-sensitized solar cells.  

PubMed

Dye-sensitized solar cells (DSSCs) based on Chlorine-e6 (Chl-e6), a Chlorophyll a derivative, and Chl-e6 containing Cu, have been investigated by carrying out incident photon to current efficiency (IPCE) and current-voltage (I-V) measurements. The effect of the metallic ion and the influence of the solvent polarity on the dye aggregation and their absorption bands have been analysed by performing electronic absorption measurements. The dependence of the photoelectrochemical parameters of these DSSCs on the electrolyte by the addition of pyrimidine and/or pyrrole has been discussed in details. For the first time I-V curves for a DSSC based on copper Chl-e6 dye have been shown and compared with Zn based chlorophyllin. Furthermore, the performance of a Cu-Chl-e6 based DSSC has been deeply improved by a progressive optimization of the TiO2 multilayer photoanode overcoming the best data reported in literature so far for this dye. It's worth to emphasize that, the analysis reported in this paper supplies very useful information which paves the way to further detailed studies turned to the employment of natural pigments as sensitizers for solar cells. PMID:24892526

Calogero, Giuseppe; Citro, Ilaria; Crupi, Cristina; Di Marco, Gaetano

2014-11-11

330

Large-scale synthesis, characterization and microwave absorption properties of carbon nanotubes of different helicities  

NASA Astrophysics Data System (ADS)

Carbon nanotubes of high helicity (H-HCNTs, Sample A) have been synthesized in large-scale by pyrolysis of acetylene at 450 °C over Fe nanoparticles derived from coprecipitation/hydrogen reduction method. With controlled introduction of hydrogen during acetylene pyrolysis, CNTs of low helicity (L-HCNTs, Sample B) and worm-like CNTs (Sample C) were obtained in large quantities. The yields of the CNTs products are high, especially that of H-HCNTs (ca. 7474%). The complex permittivity and permeability of Composites A, B, and C that contain Samples A, B and C (30 wt%) were measured in the 2-18 GHz frequency range. Good absorption of electromagnetic wave (reflection loss<-20 dB) was observed in the 7.18-10.68 and 7.5-10.7 GHz range over Composites B and C (2.0-3.0 mm thickness), respectively. Thus, through the suggested route, CNTs can be produced easily and selectively in large quantities. The lightweight materials can be utilized for microwave absorption.

Qi, Xiaosi; Yang, Yi; Zhong, Wei; Deng, Yu; Au, Chaktong; Du, Youwei

2009-10-01

331

X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials  

SciTech Connect

The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 [Angstrom]. The Fe-Fe distance was determined to be 3.4 [Angstrom]. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

DeWitt, J.G.

1992-12-01

332

X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials  

SciTech Connect

The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 {Angstrom}. The Fe-Fe distance was determined to be 3.4 {Angstrom}. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

DeWitt, J.G.

1992-12-01

333

Distinguishing Förster Resonance Energy Transfer and solvent-mediated charge-transfer relaxation dynamics in a zinc(II) indicator: a femtosecond time-resolved transient absorption spectroscopic study.  

PubMed

A bifluorophoric molecule (1) capable of intramolecular Förster Resonance Energy Transfer (FRET) is reported. The emission intensity of the FRET acceptor in 1 depends on the molar absorptivity of the donor, which is a function of zinc(II) complexation. The FRET dynamics of [Zn(1)](ClO4)2 is characterized by femtosecond time-resolved transient absorption spectroscopy. The solvent-mediated relaxation of the charge-transfer (CT) state of the isolated donor and the FRET process of the donor–acceptor conjugate are on similar time scales (40–50 ps in CH3CN), but distinguishable by the opposite solvent polarity dependency. As the solvent polarity increases, the efficiency of Columbic-based FRET is reduced, whereas CT relaxation is accelerated. In addition to revealing a method to distinguish CT and FRET dynamics, this work provides a photophysical foundation for developing indicators based on the FRET strategy. PMID:24504046

Sreenath, Kesavapillai; Yi, Chongyue; Knappenberger, Kenneth L; Zhu, Lei

2014-03-21

334

Multi-steps infrared spectroscopic characterization of the effect of flowering on medicinal value of Cistanche tubulosa  

NASA Astrophysics Data System (ADS)

Multi-steps infrared spectroscopic methods, including conventional Fourier transform infrared spectroscopy (FT-IR), second derivative spectroscopy and two-dimensional infrared (2D-IR) correlation spectroscopy, have been proved to be effective methods to examine complicated mixture system such as Chinese herbal medicine. The focus of this paper is the investigation on the effect of flowering on the pharmaceutical components of Cistanche tubulosa by using the Multi-steps infrared spectroscopic method. Power-spectrum analysis is applied to improve the resolution of 2D-IR contour maps and much more details of overlapped peaks are detected. According to the results of FT-IR and second derivative spectra, the peak at 1732 cm -1 assigned to C dbnd O is stronger before flowering than that after flowering in the stem, while more C dbnd O groups are found in the top after flowering. The spectra of root change a lot in the process of flowering for the reason that many peaks shift and disappear after flowering. Seven peaks in the spectra of stem, which are assigned to different kinds of glycoside components, are distinguished by Power-spectra in the range of 900-1200 cm -1. The results provide a scientific explanation to the traditional experience that flowering consumes the pharmaceutical components in stem and the seeds absorb some nutrients of stem after flowering. In conclusion, the Multi-steps infrared spectroscopic method combined with Power-spectra is a promising method to investigate the flowering process of C. tubulosa and discriminate various parts of the herbal medicine.

Lai, Zuliang; Xu, Peng; Wu, Peiyi

2009-01-01

335

Spectroscopic Observations  

NSDL National Science Digital Library

This is a series of three activities about light and spectra. First, learners will construct their own spectroscope, observe common light sources, record the observed spectra, and compare their findings. Next, learners will use their spectroscopes to observe the spectra from different gas tubes and compare each observed spectrum to known spectra. Finally, they will observe a solar spectrum created by a prism, view a solar spectrum on paper, and attempt to determine the elements present in the Sun. This activity requires spectroscope posters and gratings available from the Stanford Solar Center (http://solar-center.stanford.edu/posters/), fluorescent and incandescent light sources, and emission lamps and power sources. This activity is from the Stanford Solar Center's All About the Sun: Sun and Stars activity guide for Grades 5-8 and can also accompany the Stanford Solar Center's Build Your Own Spectroscope activity.

336

Characterization of Thermal Radiative Properties of Nanofluids for Selective Absorption of Solar Radiation  

NASA Astrophysics Data System (ADS)

Nanofluids are used in device cooling, heat pipes, and other applications. Researchers in thermal engineering have extensively investigated the thermal conductivity and enhanced heat transfer of nanofluids. This study investigates the thermal radiative properties of nanofluids and discusses the characteristics of the selective absorption of solar radiation of nanofluids. Several kinds of nanoparticles are prepared using the two-step method, and the effects of dispersants, mass fractions, and nanoparticle materials on the radiative properties of nanofluids within the wavelength range of 300 nm to 2500 nm are analyzed. Dispersants can reduce the transmittance of water by <5 % within the visible spectrum. ZnO- and AlN-water nanofluids selectively absorb solar radiation, whereas ZrC- and TiN-water nanofluids absorb most of the solar radiation applied to them. The findings of this study are beneficial to research on the application of nanofluids in solar energy utilization.

Zhu, Qunzhi; Cui, Yun; Mu, Lijuan; Tang, Liqing

2013-12-01

337

Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy  

NASA Technical Reports Server (NTRS)

Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

Finklea, H. O.; Vithanage, R.

1982-01-01

338

Characterization of metalloproteins by high-throughput X-ray absorption spectroscopy  

PubMed Central

High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal- binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function. PMID:21482623

Shi, Wuxian; Punta, Marco; Bohon, Jen; Sauder, J. Michael; D'Mello, Rhijuta; Sullivan, Mike; Toomey, John; Abel, Don; Lippi, Marco; Passerini, Andrea; Frasconi, Paolo; Burley, Stephen K.; Rost, Burkhard; Chance, Mark R.

2011-01-01

339

Characterization of Metalloproteins by High-throughput X-ray Absorption Spectroscopy  

SciTech Connect

High-throughput X-ray absorption spectroscopy was used to measure transition metal content based on quantitative detection of X-ray fluorescence signals for 3879 purified proteins from several hundred different protein families generated by the New York SGX Research Center for Structural Genomics. Approximately 9% of the proteins analyzed showed the presence of transition metal atoms (Zn, Cu, Ni, Co, Fe, or Mn) in stoichiometric amounts. The method is highly automated and highly reliable based on comparison of the results to crystal structure data derived from the same protein set. To leverage the experimental metalloprotein annotations, we used a sequence-based de novo prediction method, MetalDetector, to identify Cys and His residues that bind to transition metals for the redundancy reduced subset of 2411 sequences sharing <70% sequence identity and having at least one His or Cys. As the HT-XAS identifies metal type and protein binding, while the bioinformatics analysis identifies metal-binding residues, the results were combined to identify putative metal-binding sites in the proteins and their associated families. We explored the combination of this data with homology models to generate detailed structure models of metal-binding sites for representative proteins. Finally, we used extended X-ray absorption fine structure data from two of the purified Zn metalloproteins to validate predicted metalloprotein binding site structures. This combination of experimental and bioinformatics approaches provides comprehensive active site analysis on the genome scale for metalloproteins as a class, revealing new insights into metalloprotein structure and function.

W Shi; M Punta; J Bohon; J Sauder; R DMello; M Sullivan; J Toomey; D Abel; M Lippi; et al.

2011-12-31

340

Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy  

USGS Publications Warehouse

Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg-1 (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of ??25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites. (C) 2000 Elsevier Science B.V.

Kim, C.S.; Brown, G.E., Jr.; Rytuba, J.J.

2000-01-01

341

Optical characterization of the nematic lyotropic chromonic liquid crystals: Light absorption, birefringence, and scalar order parameter  

NASA Astrophysics Data System (ADS)

We report on the optical properties of the nematic (N) phase formed by lyotropic chromonic liquid crystals (LCLCs) in well aligned planar samples. LCLCs belong to a broad class of materials formed by one-dimensional molecular self-assembly and are similar to other systems such as “living polymers” and “wormlike micelles.” We study three water soluble LCLC forming materials: disodium chromoglycate, a derivative of indanthrone called Blue 27, and a derivative of perylene called Violet 20. The individual molecules have a planklike shape and assemble into rodlike aggregates that form the N phase once the concentration exceeds about 0.1M . The uniform surface alignment of the N phase is achieved by buffed polyimide layers. According to the light absorption anisotropy data, the molecular planes are on average perpendicular to the aggregate axes and thus to the nematic director. We determined the birefringence of these materials in the N and biphasic N -isotropic (I) regions and found it to be negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic low-molecular-weight nematic materials. In the absorbing materials Blue 27 and Violet 20, the wavelength dependence of birefringence is nonmonotonic because of the effect of anomalous dispersion near the absorption bands. We describe positive and negative tactoids formed as the nuclei of the new phase in the biphasic N-I region (which is wide in all three materials studied). Finally, we determined the scalar order parameter of the N phase of Blue 27 and found it to be relatively high, in the range 0.72-0.79, which puts the finding into the domain of general validity of the Onsager model. However, the observed temperature dependence of the scalar order parameter points to the importance of factors not accounted for in the athermal Onsager model, such as interaggregate interactions and the temperature dependence of the aggregate length.

Nastishin, Yu. A.; Liu, H.; Schneider, T.; Nazarenko, V.; Vasyuta, R.; Shiyanovskii, S. V.; Lavrentovich, O. D.

2005-10-01

342

Optical characterization of the nematic lyotropic chromonic liquid crystals: light absorption, birefringence, and scalar order parameter.  

PubMed

We report on the optical properties of the nematic (N) phase formed by lyotropic chromonic liquid crystals (LCLCs) in well aligned planar samples. LCLCs belong to a broad class of materials formed by one-dimensional molecular self-assembly and are similar to other systems such as "living polymers" and "wormlike micelles." We study three water soluble LCLC forming materials: disodium chromoglycate, a derivative of indanthrone called Blue 27, and a derivative of perylene called Violet 20. The individual molecules have a planklike shape and assemble into rodlike aggregates that form the phase once the concentration exceeds about 0.1 M. The uniform surface alignment of the N phase is achieved by buffed polyimide layers. According to the light absorption anisotropy data, the molecular planes are on average perpendicular to the aggregate axes and thus to the nematic director. We determined the birefringence of these materials in the N and biphasic N-isotropic (I) regions and found it to be negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic low-molecular-weight nematic materials. In the absorbing materials Blue 27 and Violet 20, the wavelength dependence of birefringence is nonmonotonic because of the effect of anomalous dispersion near the absorption bands. We describe positive and negative tactoids formed as the nuclei of the new phase in the biphasic N-I region (which is wide in all three materials studied). Finally, we determined the scalar order parameter of the phase of Blue 27 and found it to be relatively high, in the range 0.72-0.79, which puts the finding into the domain of general validity of the Onsager model. However, the observed temperature dependence of the scalar order parameter points to the importance of factors not accounted for in the athermal Onsager model, such as interaggregate interactions and the temperature dependence of the aggregate length. PMID:16383406

Nastishin, Yu A; Liu, H; Schneider, T; Nazarenko, V; Vasyuta, R; Shiyanovskii, S V; Lavrentovich, O D

2005-10-01

343

Synthesis, spectroscopic characterization, DFT studies, and antibacterial and antitumor activities of a novel water soluble Pd(II) complex with L-alliin  

NASA Astrophysics Data System (ADS)

A new water soluble Pd(II) complex with L-alliin (S-allyl-L-cysteine sulfoxide) was obtained and characterized by a set of chemical and spectroscopic measurements. Elemental and mass spectrometric data are consistent with the formula [Pd(C6H10NO3S)2]. The 1H and 13C nuclear magnetic resonance (NMR) data, [1H-15N] two dimensional (2D) NMR and infrared spectroscopic measurements indicate coordination of the ligand to Pd(II) through N and O atoms. DFT studies showed that the trans isomer is the most stable and preferred geometry for the complex. The complex is soluble in water and dimethylsulfoxide. An antibiogram assay revealed that the complex possess antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus bacterial strains in the range 125-500 ?g mL-1. Antitumor assays revealed that the complex presents cytotoxic activity over HeLa cells with an estimated IC50 of 20 ?mol L-1.

Abbehausen, Camilla; Sucena, Suelen F.; Lancellotti, Marcelo; Heinrich, Tassiele A.; Abrão, Emiliana P.; Costa-Neto, Claudio M.; Formiga, André L. B.; Corbi, Pedro P.

2013-03-01

344

X-Ray Absorption Fine Structure Spectroscopic Studies of Octakis(DMSO)Lanthanoid(III) Complexes in Solution And in the Solid Iodides  

SciTech Connect

Octakis(DMSO)lanthanoid(III) iodides (DMSO = dimethylsulfoxide), [Ln(OS(CH{sub 3}){sub 2}){sub 8}]I{sub 3}, of most lanthanoid(III) ions in the series from La to Lu have been studied in the solid state and in DMSO solution by extended X-ray absorption fine structure (EXAFS) spectroscopy. L{sub 3}-edge and also some K-edge spectra were recorded, which provided mean Ln-O bond distances for the octakis(DMSO)lanthanoid(III) complexes. The agreement with the average of the Ln-O bond distances obtained in a separate study by X-ray crystallography was quite satisfactory. The crystalline octakis(DMSO)lanthanoid(III) iodide salts have a fairly broad distribution of Ln-O bond distances, ca. 0.1 {angstrom}, with a few disordered DMSO ligands. Their EXAFS spectra are in excellent agreement with those obtained for the solvated lanthanoid(III) ions in DMSO solution, both of which show slightly asymmetric distributions of the Ln-O bond distances. Hence, all lanthanoid(III) ions are present as octakis(DMSO)lanthanoid(III) complexes in DMSO solution, with the mean Ln-O distances centered at 2.50 (La), 2.45 (Pr), 2.43 (Nd), 2.41 (Sm), 2.40 (Eu), 2.39 (Gd), 2.37 (Tb), 2.36 (Dy), 2.34 (Ho), 2.33 (Er), 2.31 (Tm), and 2.29 {angstrom} (Lu). This decrease in the Ln-O bond distances is larger than expected from the previously established ionic radii for octa-coordination. This indicates increasing polarization of the Ln{sup III}-O(DMSO) bonds with increasing atomic number. However, the S(1s) electron transition energies in the sulfur K-edge X-ray absorption near-edge structure (XANES) spectra, probing the unoccupied molecular orbitals of lowest energy of the DMSO ligands for the [Ln(OS(CH{sub 3}){sub 2}){sub 8}]{sup 3+} complexes, change only insignificantly from Ln = La to Lu. This indicates that there is no appreciable change in the ?-contribution to the S-O bond, probably due to a corresponding increase in the contribution from the sulfur lone pair to the bonding.

Persson, I.; Risberg, E.Damian; D'Angelo, P.; Panfilis, S.De; Sandstrom, M.; Abbasi, A.

2009-06-04

345

An X-ray absorption spectroscopic study of the metal site preference in Al{sub 1-x}Ga{sub x}FeO{sub 3}  

SciTech Connect

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO{sub 3} (Pna2{sub 1}; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al{sub 1-x}Ga{sub x}FeO{sub 3} was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L{sub 2,3}-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al{sub 1-x}Ga{sub x}FeO{sub 3} indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO{sub 3} than in GaFeO{sub 3}, implying more anti-site disorder is present in AlFeO{sub 3}. - Graphical abstract: Al{sub 1-x}Ga{sub x}FeO{sub 3} has been investigated by XANES. Through examination of Al L{sub 2,3}-, Ga K-, and Fe K-edge XANES spectra, it was found that more anti-site disorder of the Fe atoms is present in AlFeO{sub 3} compared to in GaFeO{sub 3}. Highlights: Black-Right-Pointing-Pointer Al{sub 1-x}Ga{sub x}FeO{sub 3} was investigated by X-ray absorption spectroscopy. Black-Right-Pointing-Pointer Ga prefers to occupy the tetrahedral site in Al{sub 1-x}Ga{sub x}FeO{sub 3}. Black-Right-Pointing-Pointer Fe prefers to occupy the octahedral sites in Al{sub 1-x}Ga{sub x}FeO{sub 3} as x increases. Black-Right-Pointing-Pointer More anti-site disorder is present in AlFeO{sub 3} compared to in GaFeO{sub 3.}.

Walker, James D.S. [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 (Canada); Grosvenor, Andrew P., E-mail: andrew.grosvenor@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C9 (Canada)

2013-01-15

346

Constraining the N2O5 UV absorption cross section from spectroscopic trace gas measurements in the tropical mid-stratosphere  

NASA Astrophysics Data System (ADS)

The absorption cross section of N2O5, ?N2O5(?, T), which is known from laboratory measurements with the uncertainty of a factor of 2 (Table 4-2 in (Jet Propulsion Laboratory) JPL-2011; the spread in laboratory data, however, points to an uncertainty in the range of 25 to 30%, Sander et al., 2011), was investigated by balloon-borne observations of the relevant trace gases in the tropical mid-stratosphere. The method relies on the observation of the diurnal variation of NO2 by limb scanning DOAS (differential optical absorption spectroscopy) measurements (Weidner et al., 2005; Kritten et al., 2010), supported by detailed photochemical modelling of NOy (NOx(= NO + NO2) + NO3 + 2N2O5 + ClONO2 + HO2NO2 + BrONO2 + HNO3) photochemistry and a non-linear least square fitting of the model result to the NO2 observations. Simulations are initialised with O3 measured by direct sun observations, the NOy partitioning from MIPAS-B (Michelson Interferometer for Passive Atmospheric Sounding - Balloon-borne version) observations in similar air masses at night-time, and all other relevant species from simulations of the SLIMCAT (Single Layer Isentropic Model of Chemistry And Transport) chemical transport model (CTM). Best agreement between the simulated and observed diurnal increase of NO2 is found if the ?N2O5(?, T) is scaled by a factor of 1.6 ± 0.8 in the UV-C (200-260 nm) and by a factor of 0.9 ± 0.26 in the UV-B/A (260-350 nm), compared to current recommendations. As a consequence, at 30 km altitude, the N2O5 lifetime against photolysis becomes a factor of 0.77 shorter at solar zenith angle (SZA) of 30° than using the recommended ?N2O5(?, T), and stays more or less constant at SZAs of 60°. Our scaled N2O5 photolysis frequency slightly reduces the lifetime (0.2-0.6%) of ozone in the tropical mid- and upper stratosphere, but not to an extent to be important for global ozone.

Kritten, L.; Butz, A.; Chipperfield, M. P.; Dorf, M.; Dhomse, S.; Hossaini, R.; Oelhaf, H.; Prados-Roman, C.; Wetzel, G.; Pfeilsticker, K.

2014-09-01

347

Spectral characterization of a tunable alexandrite laser by rubidium absorption at 780 nm  

Microsoft Academic Search

Rubidium vapor was used to characterize the output of a tunable, pulsed alexandrite laser operating at 780 nm. Rubidium spectra were obtained at temperatures of 23, 50, 110, and 140 C. Excellent agreement was obtained with computer-synthesized spectra which yielded values for the effective laser bandwidth at different operating conditions. The model assumed a Voigt profile for the rubidium 5

A. V. Nowak; B. J. Krohn

1985-01-01

348

Spectroscopic characterization of co-precipitated arsenic- and iron-bearing sulfide phases at circum-neutral pH  

NASA Astrophysics Data System (ADS)

Precipitation of arsenic- and iron-sulfide phases from porewaters is an important mechanism for removing arsenic and other contaminant metals from solution, thus reducing their bioaccessibility and potential toxicity. Although sulfide phases form readily at low pH, the identity, crystallinity, and local structure of arsenic and iron co-precipitated phases that form at circum-neutral pH are less well known. In this study, co-precipitated As+Fe sulfide phases and end-member As-sulfides and Fe-sulfides were synthesized in batch experiments and in a gas-tight reaction vessel at 25°C. Reduced conditions were maintained by keeping a constant flow of a 95%N2 /5%H2 mixture gas. Fresh saturated solutions of 0.3 M Fe(II) or Fe(III), 0.3 M S2- and 0.2 M As(III) ions were mixed and pH was maintained at pH 4, 6 and 8 by small additions of concentrated HCl or NaOH. At different time intervals, aliquots were extracted from suspensions aged from hours to 1 month and analyzed for total iron, arsenic and sulfur (by ICP-OES and ICP-MS). The Fe-S-As precipitates were characterized by X-ray diffraction (XRD) and synchrotron X-ray absorption spectroscopy (XAS). X-ray diffraction and Fe k-edge EXAFS showed the precipitation of amorphous to poorly crystalline iron sulfide when Fe(II) was co-precipitated with sulfide (no arsenic) at pH 4, 6, and 8. The precipitate that formed in ~1-4 h was nanoparticle-sized and disordered mackinawite (FeS), which showed a characteristic broad, low-intensity Bragg peaks in the XRD patterns. After aging for ~7 d, XRD patterns showed a change to more crystalline mackinawite. In contrast, co-precipitation of As(III) with Fe(II) and sulfide resulted in x-ray amorphous (both synchrotron and laboratory XRD) precipitates for all pH and aging times (~4 h to 1 m). Arsenic and iron XANES and EXAFS spectra of precipitates at pH 4 showed a mixture of amorphous orpiment-type (As2S3) and mackinawite-type (FeS) phases. At pH 6 and 8, XANES showed As sulfide and a fraction of As(III) coordinated by oxygen, with a higher proportion of As(III)-O at pH 8 with arsenic EXAFS data showing two distinct coordination environments: oxygen atoms at 1.79 Å and sulfur atoms at 2.3, 3.2, and 3.5 Å, the latter consistent with the local structure of orpiment. When Fe(II) was co-precipitated with arsenic and sulfide, Fe EXAFS and XRD showed a mackinawite-type structure with evidence for formation of magnetite at pH 8. Arsenic EXAFS showed a mixture of arsenic sulfide and As(III)-O, with a higher proportion of As(III)-O at pH 8 than at pH 6. Also, analyses of the pH 6 and 8 supernatant solutions showed that ~95% of the iron, and 96-99% of arsenic and sulfur were precipitated with the highest arsenic uptake associated with the Fe(II) mixtures. Thus, at circum-neutral pH arsenic is effectively removed when combined with both iron and sulfide. A complicated mechanism of arsenic sequestration occurs through both rapid precipitation of amorphous arsenic sulfide phases and surface complexation. This differs from the precipitation dominated arsenic removal at low pH mixtures.

Illera, V.; Rivera, N. A.; O'Day, P. A.

2009-12-01

349

Characterization of fine particulate matter in ambient air by combining TEM and multiple spectroscopic techniques - NMR, FTIR and Raman spectroscopy.  

PubMed

This paper reports a systematic study of the microstructures and spectroscopic characteristics of PM2.5 and its potential sources in Beijing by combining transmission electron microscopy and multiple spectroscopic techniques: nuclear magnetic resonance, Fourier transform infrared and Raman spectroscopy. TEM images showed that dominant components of PM2.5 are airborne organic substances with many trace metal elements which are associated with combustion sources. NMR spectra precisely determined the percentage of carbonaceous speciation in both PM2.5 (with spatial and temporal distribution) and its potential sources, and distinguished the similarities and differences among them. In FTIR spectra, a remarkable peak at 1390 cm(-1) that appeared only in PM2.5 samples was attributed to NH4NO3, representing the occurrence of secondary processes. Raman spectra revealed certain inorganic compounds including sulfate and nitrate ions. Based on the analysis of the decomposition of Raman spectra, spectral parameters provided structural information and helped to find potential sources of PM2.5. In the space of carbon aromaticity index and ID1/IG, PM2.5 points followed a linear distribution which may also be useful in source tracing. The result shows that the combined non-destructive methods are efficient to trace the sources of PM2.5. PMID:25597896

Ji, Zhurun; Dai, Rucheng; Zhang, Zengming

2015-03-11

350

Spectroscopic ellipsometry study of Si nanocrystals embedded in a SiOx matrix: Modeling and optical characterization  

NASA Astrophysics Data System (ADS)

In this work, we report on a spectroscopic ellipsometry study of thin films of silicon nanocrystals embedded in a SiOx matrix that is performed to better understand how substoichiometric SiOx species affect the optical properties of these systems. The silicon nanocrystals are fabricated in a SiOx matrix by thermal annealing of magnetron-sputtered thin films in a wide range of x values (0 < x < 2) in order to produce every possible substoichiometric SiOx species in various fractions. A generic optical model to describe the thin film content with various SiOx volumetric fractions is developed and used to analyze the data obtained from the spectroscopic ellipsometry. Tauc-Lorentz and Bruggeman effective medium approximation models are employed to determine the ellipsometric angles (? and ?) and the complex dielectric function. We show that the optical properties of the nc-Si embedded in a SiOx matrix are highly dependent on the value of x and on the volumetric fractions of the substoichiometric SiOx species present in the system.

Ilday, Serim; Nogay, Gizem; Turan, Rasit

2014-11-01

351

Structural characterization of 1,1,3,3-tetramethylguanidinium chloride ionic liquid by reversible SO2 gas absorption.  

PubMed

A unique new ionic liquid-gas adduct solid state compound formed between 1,1,3,3-tetramethylguanidinium chloride ([tmgH]Cl) and sulfur dioxide has been characterized by X-ray diffraction and Raman spectroscopy. The structure contains SO2 molecules of near normal structure kept at their positions by Cl-S interactions. The crystals belong in the orthorhombic system, space group Pbcn, with unit cell dimensions of a = 15.6908(10) Å, b = 9.3865(6) Å, and c = 14.1494(9) Å, angles ? = ? = ? = 90°, and Z = 8 at 120 K. The [tmgH]Cl has a very high absorption capacity of nearly 3 mol of SO2 per mol of [tmgH]Cl at 1 bar of SO2 and at room temperature. However, part of the absorbed SO2 was liberated during the crystallization, probably because the crystal only accommodates one molecule of SO2 per [tmgH]Cl. The nature of the high absorption capacity of [tmgH]Cl as well as of the homologous compounds with bromide and iodide are discussed. Some of these salts may prove useful as reversible absorbents of SO2 in industrial flue gases. PMID:24088034

Berg, Rolf W; Harris, Pernille; Riisager, Anders; Fehrmann, Rasmus

2013-11-01

352

An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3  

NASA Astrophysics Data System (ADS)

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.

Walker, James D. S.; Grosvenor, Andrew P.

2013-01-01

353

Spectroscopic verification of zinc absorption and distribution in the desert plant Prosopis juliflora-velutina (velvet mesquite) treated with ZnO nanoparticles  

PubMed Central

The impact of metal nanoparticles (NPs) on biological systems, especially plants, is still not well understood. The aim of this research was to determine the effects of zinc oxide (ZnO) NPs in velvet mesquite (Prosopis juliflora-velutina). Mesquite seedlings were grown for 15 days in hydroponics with ZnO NPs (10 nm) at concentrations varying from 500 to 4000 mg L?1. Zinc concentrations in roots, stems and leaves were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Plant stress was examined by the specific activity of catalase (CAT) and ascorbate peroxidase (APOX); while the biotransformation of ZnO NPs and Zn distribution in tissues was determined by X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (?XRF), respectively. ICP-OES results showed that Zn concentrations in tissues (2102 ± 87, 1135 ± 56, and 628 ± 130 mg kg?1 d wt in roots, stems, and leaves, respectively) were found at 2000 mg ZnO NPs L?1. Stress tests showed that ZnO NPs increased CAT in roots, stems, and leaves, while APOX increased only in stems and leaves. XANES spectra demonstrated that ZnO NPs were not present in mesquite tissues, while Zn was found as Zn(II), resembling the spectra of Zn(NO3)2. The ?XRF analysis confirmed the presence of Zn in the vascular system of roots and leaves in ZnO NP treated plants. PMID:22820414

Hernandez-Viezcas, J.A.; Castillo-Michel, H.; Servin, A.D.; Peralta-Videa, J.R.; Gardea-Torresdey, J.L.

2012-01-01

354

X-ray absorption spectroscopic analysis of reductive [2Fe-2S] cluster degradation in hyperthermophilic archaeal succinate:caldariellaquinone oxidoreductase subunits.  

PubMed

The biological [2Fe-2S] clusters play important roles in electron transfer and cellular signaling for a variety of organisms from archaea, bacteria to eukarya. The two recombinant hyperthermophilic archaeal [2Fe-2S] cluster-binding proteins, SdhC and the N-terminal domain fragment of SdhB, of Sulfolobus tokodaii respiratory complex II overproduced in Escherichia coli are thermostable as isolated, but moderately sensitive to reduction with excess dithionite. We used iron K-edge X-ray absorption spectroscopy to monitor the structural changes of their Fe sites in the irreversible [2Fe-2S] cluster degradation process. Regardless of the differences in the cluster-ligating cysteine motifs and the XAS-detectable [2Fe-2S](2+) cluster environments, a complete reductive breakdown of the [2Fe-2S] clusters resulted in the appearance of a new Fourier transform (FT) peak at approximately 3.3 A with a concomitant loss of the Fe-Fe interaction at ca. 2.7 A for both proteins. On the basis of the unambiguous assignment of the 3.3 A FT peak, our results suggest that a biological [2Fe-2S] cluster breakdown under reducing conditions generally releases Fe(2+) from the polypeptide chain into the aqueous solution, and the Fe(2+) might then be recruited as a secondary ferrous iron source for de novo biosynthesis and/or regulation of iron-binding enzymes in the cellular system. PMID:14674777

Li, Zhongrui; Shokes, Jacob E; Kounosu, Asako; Imai, Takeo; Iwasaki, Toshio; Scott, Robert A

2003-12-23

355

Transmission electron microscopic and X-ray absorption fine structure spectroscopic investigation of U repartition and speciation after accumulation in renal cells.  

PubMed

After environmental contamination, U accumulates in the kidneys and in bones, where it causes visible damage. Recent in vitro data prove that the occurrence of citrate increases U bioavailability without changing its speciation. Two hypotheses can explain the role of citrate: it either modifies the U intracellular metabolization pathway, or it acts on the transport of U through cell membrane. To understand which mechanisms lead to increased bioavailability, we studied the speciation of U after accumulation in NRK-52E kidney cells. U speciation was first identified in various exposure media, containing citrate or not, in which U was supplied as U carbonate. The influence of serum proteins was analyzed in order to detect the formation of macromolecular complexes of U. Transmission electron microscopy (TEM) was employed to follow the evolution of the U species distribution among precipitated and soluble forms. Finally, extended X-ray absorption fine structure spectroscopy (EXAFS) enabled the precipitates observed to be identified as U-phosphate. It also demonstrated that the intracellular soluble form of U is U carbonate. These results suggest that citrate does not change U metabolization but rather plays a role in the intracellular accumulation pathway. U speciation inside cells was directly and clearly identified for the first time. These results elucidate the role of U speciation in terms of its bioavailability and consequent health effects. PMID:18273650

Carrière, Marie; Proux, Olivier; Milgram, Sarah; Thiebault, Céline; Avoscan, Laure; Barre, Nicole; Den Auwer, Christophe; Gouget, Barbara

2008-06-01

356

In situ X-ray absorption spectroscopic investigation of the electrochemical conversion reactions of CuF{sub 2}-MoO{sub 3} nanocomposite  

SciTech Connect

We have used X-ray absorption spectroscopy at the Cu K-edge to investigate the electrochemical conversion reaction of 20 nm size 85 wt% CuF{sub 2}-15 wt% MoO{sub 3} nanocomposite under in situ conditions. The nanocomposite was prepared by high energy milling. Upon discharge, the lithiation reaction with the nanocomposite resulted in the formation of nanophase metallic Cu, which is consistent with the conversion of CuF{sub 2} into Cu and LiF. Based on XANES and Fourier transforms of EXAFS spectra, we show that the discharge process proceeded via the formation of highly dispersed Cu particles. Based on the coordination number of the first shell of Cu, the average size of the Cu particles was estimated to be in the 1-3 nm range in the fully discharged state. -- Graphical Abstract: Comparison of Fourier transform of in situ Cu K-edge EXAFS spectra for a fully discharged CuF{sub 2{center_dot}}MoO{sub 3} nanocomposite in a nonaqueous Li cell with that of a Cu foil. Quantitative analysis of the Fourier transforms confirmed that the discharge mechanism for the nanocomposite proceeds via the reaction CuF{sub 2}+2Li{yields}Cu+2LiF. The discharge product of Cu is in the form of highly dispersed nanoparticles. Display Omitted

Mansour, A.N., E-mail: Azzam.Mansour@navy.mi [Systems and Materials for Power and Protection Branch, Naval Surface Warfare Center, Carderock Division, 9500 MacArthur Boulevard, West Bethesda, MD 20817-5700 (United States); Badway, F. [Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ 08902 (United States); Yoon, W.-S. [School of Advanced Materials Eng., Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Chung, K.Y. [Battery Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Amatucci, G.G. [Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, North Brunswick, NJ 08902 (United States)

2010-12-15

357

Spectroscopic analysis of small organic molecules: a comprehensive near-edge x-ray-absorption fine-structure study of C6-ring-containing molecules.  

PubMed

We report high-resolution C 1s near-edge x-ray-absorption fine-structure (NEXAFS) spectra of the C6-ring-containing molecules benzene (C6H6), 1,3- and 1,4-cyclohexadiene (C6H8), cyclohexene (C6H10), cyclohexane (C6H12), styrene (C8H8), and ethylbenzene (C8H10) which allow us to examine the gradual development of delocalization of the corresponding pi electron systems. Due to the high experimental resolution, vibrational progressions can be partly resolved in the spectra. The experimental spectra are compared with theoretical NEXAFS spectra obtained from density-functional theory calculations where electronic final-state relaxation is accounted for. The comparison yields very good agreement between theoretical spectra and experimental results. In all cases, the spectra can be described by excitations to pi*- and sigma*-type final-state orbitals with valence character, while final-state orbitals of Rydberg character make only minor contributions. The lowest C 1s-->1pi* excitation energy is found to agree in the (experimental and theoretical) spectra of all molecules except for 1,3-cyclohexadiene (C6H8) where an energy smaller by about 0.6 eV is obtained. The theoretical analysis can explain this result by different binding properties of this molecule compared to the others. PMID:16438578

Kolczewski, C; Püttner, R; Martins, M; Schlachter, A S; Snell, G; Sant'anna, M M; Hermann, K; Kaindl, G

2006-01-21

358

X-ray absorption spectroscopic evidence on the partial formation of copper(III) in the superconducting La{sub 2}CuO{sub 4.08}  

SciTech Connect

In the present work, we suggest for the first time the contribution of the unoccupied Cu 3d states to the newly formed holes using the bulk sensitive X-ray absorption spectroscopy at the Cu K edge for nonsuperconducting La{sub 2}CuO{sub 4} and two superconducting La{sub 2}CuO{sub 4-{delta}} phases prepared electrochemically and chemically, respectively, on the basis of the previous XAS study for the Cu{sup III} compounds. In summary, it has been clearly confirmed by XAS that the same doping effect on the stoichiometric La{sub 2}CuO{sub 4} could be induced by chemical and electrochemical methods. Comparing the Cu K edge XANES spectra between the present compounds and the chemically well defined Cu{sup III} references, it is concluded that a Cu{sup III} contribution is present in the ground state of the oxidized phase, La{sub 2}CuO{sub 4.08}. 19 refs., 2 figs., 1 tab.

Choy, J.H.; Kim, D.K.; Hwang, S.H. [Seoul National Univ. (Korea, Republic of); Park, J.C. [Pusan Women`s Univ. (Korea, Republic of)

1995-07-19

359

X-ray absorption spectroscopic and computational investigation of a possible S···S interaction in the [Cu3S2]3+ core.  

PubMed

The electronic structure of the [Cu(3)S(2)](3+) core of [(LCu)(3)(S)(2)](3+) (L = N,N,N',N'-tetramethyl-2R,3R-cyclohexanediamine) is investigated using a combination of Cu and S K-edge X-ray absorption spectroscopy and calculations at the density functional and multireference second-order perturbation levels of theory. The results show that the [Cu(3)S(2)](3+) core is best described as having all copper centers close to but more oxidized than Cu(2+), while the charge on the S(2) fragment is between that of a sulfide (S(2-)) and a subsulfide (S(2)(3-)) species. The [Cu(3)S(2)](3+) core thus is different from a previously described, analogous [Cu(3)O(2)](3+) core, which has a localized [(Cu(3+)Cu(2+)Cu(2+))(O(2-))(2)](3+) electronic structure. The difference in electronic structure between the two analogues is attributed to increased covalent overlap between the Cu 3d and S 3p orbitals and the increased radial distribution function of the S 3p orbital (relative to O 2p). These features result in donation of electron density from the S-S ?* to the Cu and result in some bonding interaction between the two S atoms at ~2.69 Å in [Cu(3)S(2)](3+), stabilizing a delocalized S = 1 ground state. PMID:21923178

Sarangi, Ritimukta; Yang, Lei; Winikoff, Stuart G; Gagliardi, Laura; Cramer, Christopher J; Tolman, William B; Solomon, Edward I

2011-11-01

360

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

PubMed Central

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings. PMID:18463292

Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-01

361

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets.  

PubMed

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings. PMID:18463292

Uejio, Janel S; Schwartz, Craig P; Duffin, Andrew M; Drisdell, Walter S; Cohen, Ronald C; Saykally, Richard J

2008-05-13

362

Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study  

SciTech Connect

The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm{sup 3} foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhofer et al., J. Phys.: Conf. Ser. 244, 032010 (2010)] long pulse beam with an energy of 1.2 kJ and 3.5 ns pulselength. The plasma temperatures were inferred with the accuracy of 5 eV from the fits to the measurements using an atomic physics code. The results show that the inferred temperature is sustained at 40-45 eV between 6 and 7 ns and decreases to 25 eV at 8 ns. 2-D radiation hydrodynamic simulations show a good agreement with the measurements. Application of the shock-heated foam plasma platform toward fast electron transport experiments is discussed.

Yabuuchi, T.; Sawada, H.; Wei, M. S.; Beg, F. N. [Center for Energy Research, University of California, San Diego, La Jolla, California 92093 (United States); Regan, S. P.; Anderson, K.; Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Hund, J.; Paguio, R. R.; Saito, K. M.; Stephens, R. B. [General Atomics, San Diego, California 92186 (United States); Key, M. H.; Mackinnon, A. J.; McLean, H. S.; Patel, P. K.; Wilks, S. C. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2012-09-15

363

Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study  

NASA Astrophysics Data System (ADS)

The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm3 foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhofer et al., J. Phys.: Conf. Ser. 244, 032010 (2010)] long pulse beam with an energy of 1.2 kJ and 3.5 ns pulselength. The plasma temperatures were inferred with the accuracy of 5 eV from the fits to the measurements using an atomic physics code. The results show that the inferred temperature is sustained at 40-45 eV between 6 and 7 ns and decreases to 25 eV at 8 ns. 2-D radiation hydrodynamic simulations show a good agreement with the measurements. Application of the shock-heated foam plasma platform toward fast electron transport experiments is discussed.

Yabuuchi, T.; Sawada, H.; Regan, S. P.; Anderson, K.; Wei, M. S.; Betti, R.; Hund, J.; Key, M. H.; Mackinnon, A. J.; McLean, H. S.; Paguio, R. R.; Patel, P. K.; Saito, K. M.; Stephens, R. B.; Wilks, S. C.; Beg, F. N.

2012-09-01

364

Characterization of selective binding of alkali cations with carboxylate by x-ray absorption spectroscopy of liquid microjets  

SciTech Connect

We describe an approach for characterizing selective binding between oppositely charged ionic functional groups under biologically relevant conditions. Relative shifts in K-shell x-ray absorption spectra of aqueous cations and carboxylate anions indicate the corresponding binding strengths via perturbations of carbonyl antibonding orbitals. XAS spectra measured for aqueous formate and acetate solutions containing lithium, sodium, and potassium cations reveal monotonically stronger binding of the lighter metals, supporting recent results from simulations and other experiments. The carbon K-edge spectra of the acetate carbonyl feature centered near 290 eV clearly indicate a preferential interaction of sodium versus potassium, which was less apparent with formate. These results are in accord with the Law of Matching Water Affinities, relating relative hydration strengths of ions to their respective tendencies to form contact ion pairs. Density functional theory calculations of K-shell spectra support the experimental findings.

Saykally, Richard J; Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; Drisdell, Walter S.; Cohen, Ronald C.; Saykally, Richard J.

2008-01-08

365

The purple Codex Rossanensis: spectroscopic characterization and first evidence of the use of the elderberry lake in a 6th century manuscript  

E-print Network

The Codex Rossanensis is a 6th century Bizantine illuminated manuscript written on purple parchment and conserved at the Museo Diocesano in Rossano Calabro, Italy. It is one of the oldest surviving illuminated manuscripts of the New Testament. The challenge of the analysis of the Codex Rossanensis lies in the lack of analytical information on the pictorial media used in the Early Middle Ages. Even though old-medieval illuminated manuscripts have been deeply studied from the historical standpoint, they have been rarely described in their material composition. This paper presents the results obtained during the measurements campaign (June 2012 - November 2013). The spectroscopic analyses performed by Raman, micro-FTIR and XRF allowed for the complete characterization of the pictorial palette, the inks, the support and the material used in a previous restoration treatment. To the author knowledge the article shows the first experimental evidence of the usage of the elderberry lake in a 6th century illuminated ma...

Bicchieri, Marina

2014-01-01

366

Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion  

NASA Astrophysics Data System (ADS)

The study deals with the XPS, Raman and EDX characterization of a series of structured catalysts composed of cobalt oxides promoted by palladium and cerium oxides. The aim of the work was to relate the information gathered from spectroscopic analyses with the ones from kinetic tests of methane combustion to establish the basic structure-activity relationships for the catalysts studied. The most active catalyst was the cobalt oxide doped with little amount of palladium and wins a confrontation with pure palladium oxide catalyst which is commercially used in converters for methane. The analyses Raman and XPS analyses showed that this catalyst is composed of a cobalt spinel and palladium oxide. The quantitative approach to the composition of the catalysts by XPS and EDX methods revealed that the surface of palladium doped cobalt catalyst is enriched with palladium oxide which provides a great number of active centres for methane combustion indicated by kinetic parameters.

Jod?owski, P. J.; J?drzejczyk, R. J.; Rogulska, A.; Wach, A.; Ku?trowski, P.; Sitarz, M.; ?ojewski, T.; Ko?odziej, A.; ?ojewska, J.

2014-10-01

367

Spectroscopic characterization of Co3O4 catalyst doped with CeO2 and PdO for methane catalytic combustion.  

PubMed

The study deals with the XPS, Raman and EDX characterization of a series of structured catalysts composed of cobalt oxides promoted by palladium and cerium oxides. The aim of the work was to relate the information gathered from spectroscopic analyses with the ones from kinetic tests of methane combustion to establish the basic structure-activity relationships for the catalysts studied. The most active catalyst was the cobalt oxide doped with little amount of palladium and wins a confrontation with pure palladium oxide catalyst which is commercially used in converters for methane. The analyses Raman and XPS analyses showed that this catalyst is composed of a cobalt spinel and palladium oxide. The quantitative approach to the composition of the catalysts by XPS and EDX methods revealed that the surface of palladium doped cobalt catalyst is enriched with palladium oxide which provides a great number of active centres for methane combustion indicated by kinetic parameters. PMID:24913565

Jod?owski, P J; J?drzejczyk, R J; Rogulska, A; Wach, A; Ku?trowski, P; Sitarz, M; ?ojewski, T; Ko?odziej, A; ?ojewska, J

2014-10-15

368

Study of a sample of faint Be stars in the exofield of CoRoT. I. Spectroscopic characterization  

NASA Astrophysics Data System (ADS)

Context. Be stars are probably the most rapid rotators among stars in the main sequence (MS) and, as such, are excellent candidates to study the incidence of the rotation on the characteristics of their non-radial pulsations, as well as on their internal structure. Pulsations are also thought to be possible mechanisms that help the mass ejection needed to build up the circumstellar disks of Be stars. Aims: The purpose of this paper is to identify a number of faint Be stars observed with the CoRoT satellite and to determine their fundamental parameters, which will enable us to study their pulsation properties as a function of the location in the HR diagram and to search for correlations with the light outbursts, which are possibly produced by discrete mass ejections. Methods: We identified those objects in the exofields of CoRoT presenting the Be phenomenon using H? surveys, as well as automated methods based on pulsation properties that we finally confirmed with FLAMES/GIRAFFE and X-shooter spectroscopic observations at VLT/ESO, and with near-IR photometry. The spectra were 1) corrected for the veiling effect, 2) treated with the GIRFIT code to determine apparent fundamental parameters, and 3) corrected with the FASTROT code for effects induced by the rapid rotation. Results: A list of 41 Be star candidates were found from photometric and spectroscopic criteria. The spectral coverage useful for determining the fundamental parameters was obtained for only about half of them. We then spectroscopically identified 21 Be stars, two probable Be stars, and two B stars contaminated by the Sh 2-284 nebulosity. A short description of the spectral characteristics of each star is given. The fundamental parameters and, in particular, the rotation frequency ?r (cycles per day) were all corrected for rotational effects at rotation rates ranging from ?/?c = 0.8 to 1.0. We have determined the positions of Be stars in the HR diagram and find two of them located beyond the MS phase. Conclusions: The well-determined fundamental parameters presented in this paper for a statistically reliable sample of Be stars will enable us in forthcoming papers to compare the properties of stars as pulsators either according to their location in different regions of the HR diagram or with those predicted from theory. Appendices are only available in electronic form at http://www.aanda.org

Semaan, T.; Hubert, A. M.; Zorec, J.; Martayan, C.; Frémat, Y.; Gutiérrez-Soto, J.; Fabregat, J.

2013-03-01

369

Spectroscopic remote sensing of plant stress at leaf and canopy levels using the chlorophyll 680 nm absorption feature with continuum removal  

NASA Astrophysics Data System (ADS)

This paper explores the use of spectral feature analysis to detect plant stress in visible/near infrared wavelengths. A time series of close range leaf and canopy reflectance data of two plant species grown in hydrocarbon-contaminated soil was acquired with a portable spectrometer. The ProSpecTIR-VS airborne imaging spectrometer was used to obtain far range hyperspectral remote sensing data over the field experiment. Parameters describing the chlorophyll 680 nm absorption feature (depth, width, and area) were derived using continuum removal applied to the spectra. A new index, the Plant Stress Detection Index (PSDI), was calculated using continuum-removed values near the chlorophyll feature centre (680 nm) and on the green-edge (560 and 575 nm). Chlorophyll feature's depth, width and area, the PSDI and a narrow-band normalised difference vegetation index were evaluated for their ability to detect stressed plants. The objective was to analyse how the parameters/indices were affected by increasing degrees of plant stress and to examine their utility as plant stress indicators at the remote sensing level (e.g. airborne sensor). For leaf data, PSDI and the chlorophyll feature area revealed the highest percentage (67-70%) of stressed plants. The PSDI also proved to be the best constraint for detecting the stress in hydrocarbon-impacted plants with field canopy spectra and airborne imaging spectroscopy data. This was particularly true using thresholds based on the ASD canopy data and considering the combination of higher percentage of stressed plants detected (across the thresholds) and fewer false-positives.

Sanches, Ieda Del'Arco; Souza Filho, Carlos Roberto; Kokaly, Raymond Floyd

2014-11-01

370

An X-ray absorption near-edge spectroscopic study of the structure of passive films on amorphous Al-Fe-Ce alloys  

SciTech Connect

The authors report on the composition and structure of passive oxide films of melt-spun ribbons of amorphous Al{sub 90}Fe{sub 10{minus}x}Ce{sub x} (x = 3, 5, and 7) alloys using x-ray absorption near-edge structure (XANES) spectroscopy. The passive films were formed in an aerated solution of 0.9 weight percent (w/o) NaCl at constant potential in the passive region at {minus}0.5 V vs. a saturated calomel electrode (SCE) for 60 min. The oxidation state of Fe in the passive films of these alloys is mainly +3, such as in {alpha}-Fe{sub 2}O{sub 3} and/or {gamma}-Fe{sub 2}O{sub 3}. Cerium in the passive film of Al{sub 90}Fe{sub 7}Ce{sub 3} alloy is present mainly in the +3 oxidation state as Ce{sub 2}O{sub 3} and/or Ce(OH){sub 3}, with only a small fraction as Ce{sup 4+}. In the passive film of Al{sub 90}Fe{sub 5}Ce{sub 5} alloy it is present in the +3 and +4 oxidation states (as Ce{sub 2}O{sub 3} and/or Ce(OH){sub 3} and CeO{sub 2}) while in Al{sub 90}Fe{sub 3}Ce{sub 7} alloy the passive film contains cerium in the +4 oxidation state as CeO{sub 2}. The fact that the passive film may consist of mixed oxide phases containing Al, Fe, and Ce cannot be ruled out.

Mansour, A.N. [Naval Surface Warfare Center, Silver Spring, MD (United States). Carderock Div.; Melendres, C.A. [Argonne National Lab., IL (United States); Poon, S.J.; He, Y.; Shiflet, G.J. [Univ. of Virginia, Charlottesville, VA (United States)

1996-02-01

371

The Phoenix Deep Survey: spectroscopic catalog  

E-print Network

The Phoenix Deep Survey is a multi-wavelength survey based on deep 1.4 GHz radio imaging, reaching well into the sub-100 microJy level. One of the aims of this survey is to characterize the sub-mJy radio population, exploring its nature and evolution. In this paper we present the catalog and results of the spectroscopic observations aimed at characterizing the optically ``bright'' (R<~ 21.5 mag) counterparts of faint radio sources. Out of 371 sources with redshift determination, 21% have absorption lines only, 11% show AGN signatures, 32% are star-forming galaxies, 34% show narrow emission lines that do not allow detailed spectral classification (due to poor signal-to-noise ratio and/or lack of diagnostic emission lines) and the remaining 2% are identified with stars. For the star-forming galaxies with a Balmer decrement measurement we find a median extinction of A(Ha)=1.9 mag, higher than that of optically selected samples. This is a result of the radio selection, which is not biased against dusty systems. Using the available spectroscopic information, we estimate the radio luminosity function of star-forming galaxies in two independent redshift bins at z~0.1 and 0.3 respectively. We find direct evidence for strong luminosity evolution of these systems consistent with L(1.4 GHz) ~ (1+z)^(2.7).

J. Afonso; A. Georgakakis; C. Almeida; A. M. Hopkins; L. E. Cram; B. Mobasher; M. Sullivan

2005-05-06

372

Characterization of the Electronic Structure of Silicon Nanoparticles Using X-ray Absorption and Emission  

SciTech Connect

Resolving open questions regarding transport in nanostructures can have a huge impact on a broad range of future technologies such as light harvesting for energy. Silicon has potential to be used in many of these applications. Understanding how the band edges of nanostructures move as a function of size, surface termination and assembly is of fundamental importance in understanding the transport properties of these materials. In this thesis work I have investigated the change in the electronic structure of silicon nanoparticle assemblies as the surface termination is changed. Nanoparticles are synthesized using a thermal evaporation technique and sizes are determined using atomic force microscopy (AFM). By passivating the particles with molecules containing alcohol groups we are able to modify the size dependent band edge shifts. Both the valence and conduction bands are measured using synchrotron based x-ray absorption spectroscopy (XAS) and soft x-ray fluorescence (SXF) techniques. Particles synthesized via recrystallization of amorphous silicon/SiO{sub 2} multilayers of thicknesses below 10 nm are also investigated using the synchrotron techniques. These samples also show quantum confinement effects but the electronic structure is different from those synthesized via evaporation methods. The total bandgap is determined for all samples measured. The origins of these differences in the electronic structures are discussed.

Vaverka, A M

2008-07-15

373

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution  

SciTech Connect

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm Multiplication-Sign 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45 Degree-Sign beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

Laroche, G. [Laboratoire d'Ingenierie de Surface, Centre de Recherche sur les Materiaux Avances, Departement de genie des mines, de la metallurgie et des materiaux, Universite Laval, 1065, avenue de la Medecine, Quebec G1V 0A6 (Canada); Centre de recherche du CHUQ, Hopital St Francois d'Assise, 10, rue de l'Espinay, local E0-165, Quebec G1L 3L5 (Canada); Vallade, J. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Agence de l'environnement et de la Ma Latin-Small-Letter-Dotless-I -carettrise de l'Energie, 20, avenue du Gresille, BP 90406, F-49004 Angers Cedex 01 (France); Bazinette, R.; Hernandez, E.; Hernandez, G.; Massines, F. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Nijnatten, P. van [OMT Solutions bv, High Tech Campus 9, 5656AE Eindhoven (Netherlands)

2012-10-15

374

Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide  

NASA Astrophysics Data System (ADS)

Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg-1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (˜0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13- coordination environment (e.g. >90%) and no (<10%) Am(IV) or (V) can be detected in the rim zone. The occurrence of americium dioxide is avoided by the redox buffering activity of the uranium dioxide matrix.

Degueldre, Claude; Cozzo, Cedric; Martin, Matthias; Grolimund, Daniel; Mieszczynski, Cyprian

2013-06-01

375

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution.  

PubMed

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm × 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45° beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma. PMID:23126767

Laroche, G; Vallade, J; Bazinette, R; van Nijnatten, P; Hernandez, E; Hernandez, G; Massines, F

2012-10-01

376

Plutonium-uranium mixed oxide characterization by coupling micro-X-ray diffraction and absorption investigations  

NASA Astrophysics Data System (ADS)

Plutonium-uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The potential differences of metal redox state and microstructural developments of the matrix before and after irradiation are commonly analysed by electron probe microanalysis. In this work the structure and next-neighbor atomic environments of Pu and U oxide features within unirradiated homogeneous MOX and irradiated (60 MW d kg -1) MOX samples was analysed by micro-X-ray fluorescence (?-XRF), micro-X-ray diffraction (?-XRD) and micro-X-ray absorption fine structure (?-XAFS) spectroscopy. The grain properties, chemical bonding, valences and stoichiometry of Pu and U are determined from the experimental data gained for the unirradiated as well as for irradiated fuel material examined in the center of the fuel as well as in its peripheral zone (rim). The formation of sub-grains is observed as well as their development from the center to the rim (polygonization). In the irradiated sample Pu remains tetravalent (>95%) and no (<5%) Pu(V) or Pu(VI) can be detected while the fuel could undergo slight oxidation in the rim zone. Any slight potential plutonium oxidation is buffered by the uranium dioxide matrix while locally fuel cladding interaction could also affect the redox of the fuel.

Degueldre, C.; Martin, M.; Kuri, G.; Grolimund, D.; Borca, C.

2011-09-01

377

Spectroscopic characterization of different structural forms of the new promising energetic material FOX-7 in different solvents  

NASA Astrophysics Data System (ADS)

UV-vis, IR and NMR spectroscopy were utilized as direct monitoring techniques for structure changes of a new promising energetic material FOX-7 in different protic and aprotic solvents. The dissolved FOX-7 indicates changes in molecular structure as compared with that in solid-state. The push-pull properties of the molecule together with the effects of solvents result in charge separated zwitterion formed in solution. By combination of different spectroscopic techniques, structural changes of charge-separated molecule of FOX-7 were described in dependence on the solvent properties, temperature, proton activity and concentration. From the analytical point of view, the lowest detectable concentration of FOX-7 using UV-vis spectra was determined to approximately 6 × 10-7 mol L-1.

Šimková, Ludmila; Šoral, Michal; Lušpai, Karol; Ludvík, Ji?í

2015-03-01

378

Subzero-temperature stabilization and spectroscopic characterization of homogeneous oxyferrous complexes of the cytochrome P450 BM3 (CYP102) oxygenase domain and holoenzyme  

SciTech Connect

We describe herein for the first time the formation and spectroscopic characterization of homogeneous oxyferrous complexes of the cytochrome P450 BM3 (CYP102) holoenzyme and heme domain (BMP) at -55 {sup o}C using a 70/30 (v/v) glycerol/buffer cryosolvent. The choice of buffer is a crucial factor with Tris [tris(hydroxymethyl)aminomethane] buffer being significantly more effective than phosphate. The oxyferrous complexes have been characterized with magnetic circular dichroism spectroscopy and the resulting spectra compared to those of the more well-characterized oxyferrous cytochrome P450-CAM. The formation of a stable substrate-bound oxyferrous CYP BM3 holoenzyme, despite the fact that it has the necessary reducing equivalents for turnover, indicates that electron transfer from the flavin domain to the oxyferrous center is very slow at this temperature. The ability to prepare stable homogeneous oxyferrous derivatives of both BMP and the CYP BM3 holoenzyme will enable these species to be used as starting materials for mechanistic investigation of dioxygen activation.

Perera, Roshan [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States); Sono, Masanori [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States); Raner, Gregory M. [Department of Chemistry and Biochemistry, University of North Carolina, Greensboro, NC 27402 (United States); Dawson, John H. [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States) and School of Medicine, University of South Carolina, Columbia, SC 29208 (United States)]. E-mail: dawson@sc.edu

2005-12-09

379

The Time Domain Spectroscopic Survey: Spectroscopic Variability Investigations Within SDSS-IV/eBOSS  

NASA Astrophysics Data System (ADS)

The Time Domain Spectroscopic Survey (TDSS) is an SDSS-IV subproject that began summer 2014 and will continue for 4-6 years. Besides its main program to obtain initial characterization spectra of about 220,000 optical variables selected from PanSTARRS-1, the TDSS includes 9 separate smaller programs to study spectroscopic variability. We describe each of these Few-Epoch Spectroscopy (FES) programs, which target objects with existing SDSS spectroscopy amongst classes of quasars and stars of particular astrophysical interest. These include, in approximate order of decreasing sample size: Broad Absorption Line Quasars (BALQSOs), the most photometrically variable ("HyperVariable") quasars, high S/N normal broad line quasars, quasars with double-peaked or very asymmetric broad emission line profiles, Hypervariable stars, active ultracool (late-M and L-type) dwarf stars with Halpha emission, dwarf carbon stars, white dwarf/M dwarf spectroscopic binaries with Halpha emission, and binary supermassive black hole candidates from MgII broad line velocity shift analysis. We summarize herein the unique and diverse astrophysical investigations facilitated by these TDSS FES programs.

Green, Paul J.; Anderson, Scott F.; Morganson, Eric; Eracleous, Michael; Shen, Yue; Brandt, W. Niel; Ruan, John J.; Schmidt, Sarah J.; Badenes, Carles; West, Andrew A.; Ju, Wenhua; Greene, Jenny E.; Tdss, Panstarrs-1, Sdss-Iv

2015-01-01

380

Morphological and spectroscopic investigation of the behavior of permanent iridium modifier deposited on pyrolytic graphite coated and zirconium treated platforms in electrothermal atomic absorption spectrometry  

NASA Astrophysics Data System (ADS)

In order to better characterise a permanent modifier based on iridium deposited on zirconium or tungsten treated platforms of transversely heated graphite atomizer, and to gain additional information about its chemical behavior directed to an eventual further optimization, a series of experiments were carried out, both by surface techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS or ESCA) and X-ray fluorescence (XRF) and by electrothermal atomic absorption spectrometry on the iridium release from unmodified and various other modified pyrolytic graphite platforms. Special attention was paid to the influence of the amount of iridium, zirconium carbide coating of the platform surface and the presence of citric acid on the iridium vaporization during pyrolysis and atomization. The processes of iridium losses during pyrolysis and atomization and peak maximum alignment depend on the amount of the iridium deposited on the pyrolytic graphite coated platforms in the presence of nitric acid. A fractional order of release which suggests an atom vaporization from the surface or edges of the iridium islands was estimated. In the presence of citric acid, mass independence and zero order of the atom release were found. The zirconium treatment of the platform results in change of the spatial distribution of iridium and hence its vaporization. Vaporization temperatures as high as 2100°C, and first order of the process of atom generation were obtained. While it was possible to study the iridium atomization from uncoated and zirconium coated surfaces, evidencing a different order for the release process, the same was not possible for the tungsten coated platforms due to an 'overstabilization' that brought the iridium atomization temperature out of the working range of the instrument used. The different chemical behavior of tungsten and zirconium was also confirmed by XPS investigations. With tungsten, evidence of both W?C and W?O bonding was found, while zirconium on the contrary shows only Zr?O bonding and no evidence of carbide bonding. The SEM revealed a highly dispersed distribution of spot-like features whose smallest average diameter was of the order of 0.1 ?m. The XRF asserted the confinement of iridium in these features and a strict association with zirconium in the case of zirconium treated surfaces. It is worth mentioning that such structure was preserved also after 400 thermal cycles simulating an atomization step at 1900°C despite a quite evident deterioration of the graphite surface, thus confirming the excellent durability of this modifier.

Slaveykova, Vera I.; Lampugnani, Leonardo; Tsalev, Dimiter L.; Sabbatini, L.

1997-12-01

381

Infra-red reflection absorption spectroscopic study on adsorption structures of acrolein on polycrystalline gold and Au(111) surfaces under ultra-high vacuum conditions  

NASA Astrophysics Data System (ADS)

Infra-red reflection absorption (IRA) spectra were measured at 80 K under ultra-high vacuum conditions for acrolein adsorbed on two kinds of gold films; Au(111) and polycrystalline gold surfaces. Upon increasing the amount of exposure from 0.02 to 200 L (1 L=1×10 -6 Torr·s), the adsorbate at Au(111) gave rise to a series of sharp IRA bands due to a CH 2 out-of-plane wagging vibration [ ?(CH 2)] successively, indicating discrete adsorption states, i.e. 964 (type 1)?978(type 1')?991(type 2)?1003 cm -1(type 3). All these states have the molecular plane parallel to the surface; type 1 is in an isolated state, and type 2 is in an associated state with a two-dimensional arrangement, whereas type 3 forms an ordered multilayered structure. Type 1' was tentatively assigned either to a trapped state at step sites or to an associated state forming small oligomers at the surface. Only type 3 gives rise to IRA bands due to ?(C?O), which appears at 1677 cm -1 as a singlet at relatively small exposure levels and splits into doublets, giving the 1686 and 1672 cm -1 components at 2.0 L. The doublets were explained as being due to a crystal field splitting, which conforms to the fact that the adsorbate forms an ordered three-dimensional arrangement. The IRA spectrum of type 3 is readily converted to that of a more stable polycrystalline state upon increasing the temperature from 80 to 100 K. Thus, type 3 is a thermodynamically metastable state. Acrolein adsorbed on a polycrystalline gold film assumes an amorphous state in the exposure level of 0.06-4.8 L, giving broad IRA bands due to ?(C?O) and ?(CH 2) in the 1686-1699 and 974-991 cm -1 regions, respectively. The IRA spectra of acrolein adsorbed on Ag(111) were also measured, which indicated that the adsorbates exist in a less ordered state than those on Au(111), although a multilayered structure gives IRA features that are almost identical with those of type 3.

Akita, M.; Osaka, N.; Itoh, K.

1998-05-01

382

Electronic structures of organometallic complexes of f elements. LIII. Comparison of the experimental spectroscopic splitting factors of a magnetically diluted tetrahydrofuran adduct derived from tris(? 5-cyclopentadienyl)erbium with calculated values based on wavefunctions obtained from a parametric analysis of the absorption spectrum  

Microsoft Academic Search

The absorption spectrum of (?5-Cp)3Er·MeTHF (1) has been measured at room and low temperatures. Fitting the experimental energy levels to those obtained by the diagonalization of the energy matrices obtained from a parametric Hamiltonian resulted in 47 crystal field assignments with an r.m.s. deviation of 27.6 cm?1. The averaged values of the spectroscopic splitting factors ?g??=8.07 and ?g??=4.41 (extracted from

H. Reddmann; S. Jank; H. Schultze; H.-D. Amberger; N. M. Edelstein

2003-01-01

383

Monothiol Glutaredoxins Can Bind Linear [Fe3S4]+ and [Fe4S4]2+ Clusters in Addition to [Fe2S2]2+ Clusters: Spectroscopic Characterization and Functional Implications  

PubMed Central

Saccharomyces cerevisiae mitochondrial glutaredoxin 5 (Grx5) is the archetypical member of a ubiquitous class of monothiol glutaredoxins with a strictly conserved CGFS active-site sequence that has been shown to function in biological [Fe2S2]2+ cluster trafficking. In this work, we show that recombinant S. cerevisiae Grx5 purified aerobically after prolonged exposure of the cell-free extract to air or after anaerobic reconstitution in the presence of glutathione, predominantly contains a linear [Fe3S4]+ cluster. The excited state electronic properties and ground state electronic and vibrational properties of the linear [Fe3S4]+ cluster have been characterized using UV-visible absorption/CD/MCD, EPR, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic S = 5/2 linear [Fe3S4]+ cluster with properties similar to those reported for synthetic linear [Fe3S4]+ clusters and the linear [Fe3S4]+ clusters in purple aconitase. Moreover, the results indicate that the Fe-S cluster content previously reported for many monothiol Grxs has been misinterpreted exclusively in terms of [Fe2S2]2+ clusters, rather than linear [Fe3S4]+ clusters or mixtures of linear [Fe3S4]+ and [Fe2S2]2+ clusters. In the absence of GSH, anaerobic reconstitution of Grx5 yields a dimeric form containing one [Fe4S4]2+ cluster that competent for in vitro activation of apo-aconitase, via intact cluster transfer. The ligation of the linear [Fe3S4]+ and [Fe4S4]2+ clusters in Grx5 has been assessed by spectroscopic, mutational and analytical studies. Potential roles for monothiol Grx5 in scavenging and recycling linear [Fe3S4]+ clusters released during protein unfolding under oxidative stress conditions and in maturation of [Fe4S4]2+ cluster-containing proteins are discussed in light of these results. PMID:24032439

Zhang, Bo; Bandyopadhyay, Sibali; Shakamuri, Priyanka; Naik, Sunil G.; Huynh, Boi Hanh; Couturier, Jérémy; Rouhier, Nicolas; Johnson, Michael K.

2013-01-01

384

One-dimensional WO{sub 3} and its hydrate: One-step synthesis, structural and spectroscopic characterization  

SciTech Connect

We report on a one-step hydrothermal growth of one-dimensional (1D) WO{sub 3} nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO{sub 3} nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO{sub 3} nanostructures, which increased two-fold in a hydrated WO{sub 3} phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO{sub 3}, while protons are responsible or contribute significantly to the same in the hydrated phase. - Graphical abstract: The figure illustrates the role of pH in morphological and absorption edge evolution of WO{sub 3} (hydrate) as well as the variation in the concentration of defect electrons between anhydrous and hydrated WO{sub 3}. Highlights: Black-Right-Pointing-Pointer WO{sub 3} nanorods prepared in a one step procedure. Black-Right-Pointing-Pointer HCl (aq) enables phase pure WO{sub 3} nanorods. Black-Right-Pointing-Pointer HCl (aq) induces significant reduction in dimension of and red shift in absorption edge of nanorods. Black-Right-Pointing-Pointer W{sup 5+} detected in hydrothermal WO{sub 3} phase, the concentration of which increases in the hydrated phase. Black-Right-Pointing-Pointer W{sup 5+} from the two phases due to different positive defects.

Iwu, Kingsley O., E-mail: k.o.iwu@smn.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway); Galeckas, Augustinas, E-mail: augustinas.galeckas@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Rauwel, Protima, E-mail: protima.singh@fys.uio.no [Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1126 Blindern, NO-0318 Oslo (Norway); Kuznetsov, Andrej Y., E-mail: andrej.kuznetsov@fys.uio.no [Department of Physics, University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, NO-0316 Oslo (Norway); Norby, Truls, E-mail: truls.norby@kjemi.uio.no [Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo (Norway)

2012-01-15

385

Single molecule spectroscopic characterization of a far-red fluorescent protein (HcRed) from the Anthozoa coral Heteractis crispa  

NASA Astrophysics Data System (ADS)

We report on the photophysical properties of a far-red intrinsic fluorescent protein by means of single molecule and ensemble spectroscopic methods. The green fluorescent protein (GFP) from Aequorea victoria is a popular fluorescent marker with genetically encoded fluorescence and which can be fused to any biological structure without affecting its function. GFP and its variants provide emission colors from blue to yellowish green. Red intrinsic fluorescent proteins from Anthozoa species represent a recent addition to the emission color palette provided by GFPs. Red intrinsic fluorescent markers are on high demand in protein-protein interaction studies based on fluorescence-resonance energy transfer or in multicolor tracking studies or in cellular investigations where autofluorescence possesses a problem. Here we address the photophysical properties of a far-red fluorescent protein (HcRed), a mutant engineered from a chromoprotein cloned from the sea anemone Heteractis crispa, by using a combination of ensemble and single molecule spectroscopic methods. We show evidence for the presence of HcRed protein as an oligomer and for incomplete maturation of its chromophore. Incomplete maturation results in the presence of an immature (yellow) species absorbing/fluorescing at 490/530-nm. This yellow chromophore is involved in a fast resonance-energy transfer with the mature (purple) chromophore. The mature chromophore of HcRed is found to adopt two conformations, a Transoriented form absorbing and 565-nm and non-fluorescent in solution and a Cis-oriented form absorbing at 590-nm and emitting at 645-nm. These two forms co-exist in solution in thermal equilibrium. Excitation-power dependence fluorescence correlation spectroscopy of HcRed shows evidence for singlet-triplet transitions in the microseconds time scale and for cis-trans isomerization occurring in a time scale of tens of microseconds. Single molecule fluorescence data recorded from immobilized HcRed proteins, all point to the presence of two classes of molecules: proteins with Cis and Trans-oriented chromophores. Immobilization of HcRed in water-filled pores of polyvinyl alcohol leads to a polymer matrix - protein barrel interaction which results in a 'freezing' of the chromophore in a stable conformation for which non-radiative deactivation pathways are either suppressed or reduced. As a result, proteins with both Cis- and Trans-oriented chromophores can be detected at the single molecule level. Polymer chain motion is suggested as a mediator for an eventual cis-trans isomerization of the chromophore in the case of single immobilized proteins.

Cotlet, Mircea; Habuchi, Satoshi; Whitier, Jennifer E.; Werner, James H.; De Schryver, Frans C.; Hofkens, Johan; Goodwin, Peter M.

2006-02-01

386

Optical characterization of CuIn3Se5, CuGa3Se5 and CuGa5Se8 crystals by spectroscopic ellipsometry  

NASA Astrophysics Data System (ADS)

The ellipsometric spectra of CuIn3Se5, CuGa3Se5 and CuGa5Se8 ordered vacancy compounds (OVC) have been studied in the spectral range from 0.8 to 4.4 eV. The structures observed in the measured spectra were analyzed by fitting the second derivative of the experimental spectrum to analytical line shapes. The energies corresponding to different electronic transitions were determined. The lowest direct gap (E 0) is characterized by 3-dimensional critical points, while higher energy structures are characterized by 2D critical points. Optical constants related to dielectric function, such as the complex refractive index n *( ), extinction coefficient k ( ), absorption coefficient ? ( ), and normal-incidence reflectivity R ( ), of studied OVC were determined.

León, M.; Serna, R.; Levcenko, S.; Nateprov, A.; Nicorici, A.; Merino, J. M.; Arushanov, E.

2006-09-01

387

Characterization of Copper(II) Interactions with Sinefungin, a Nucleoside Antibiotic: Combined Potentiometric, Spectroscopic and DFT Studies  

PubMed Central

Interactions between sinefungin and copper(II) ions were investigated. Stoichiometry and stability constants of the metal-free system and two mononuclear complexes present in solution were determined on the basis of potentiometric data analysis. The results were compared to the Cu(II)-ornithine system due to structural similarities between both molecules. Combined spectroscopic and theoretical studies allowed for determination of coordination pattern for the Cu(II)-sinefungin complexes. At acidic pH, copper is bound in “glycine-like” coordination mode, identical with that of ornithine. This involves ?-amino group and the carboxyl oxygen. At higher pH, a “bis-complex” is formed by two sinefungin molecules. The second ligand binds in equatorial position displacing two water molecules, what results in the stable {2N,2O} coordination. Both axial positions are supposed to be occupied by N1 nitrogen donors of adenine moiety, what is confirmed by DFT calculations. They interact indirectly with copper(II) through water molecules as the result of dominant syn conformation of purine. PMID:18273386

Jaworska, Maria; Lodowski, Piotr; Mucha, Ariel; Szczepanik, Wojciech; Valensin, Gianni; Cappannelli, Massimo; Je?owska-Bojczuk, Ma?gorzata

2007-01-01

388

A combined spectroscopic and molecular docking approach to characterize binding interaction of megestrol acetate with bovine serum albumin.  

PubMed

The binding interactions between megestrol acetate (MA) and bovine serum albumin (BSA) under simulated physiological conditions (pH?7.4) were investigated by fluorescence spectroscopy, circular dichroism and molecular modeling. The results revealed that the intrinsic fluorescence of BSA was quenched by MA due to formation of the MA-BSA complex, which was rationalized in terms of a static quenching procedure. The binding constant (Kb ) and number of binding sites (n) for MA binding to BSA were 2.8?×?10(5) ?L/mol at 310?K and about 1 respectively. However, the binding of MA with BSA was a spontaneous process due to the negative ?G(0) in the binding process. The enthalpy change (?H(0) ) and entropy change (?S(0) ) were - 124.0?kJ/mol and -295.6?J/mol per K, respectively, indicating that the major interaction forces in the binding process of MA with BSA were van der Waals forces and hydrogen bonding. Based on the results of spectroscopic and molecular docking experiments, it can be deduced that MA inserts into the hydrophobic pocket located in subdomain IIIA (site II) of BSA. The binding of MA to BSA leads to a slight change in conformation of BSA but the BSA retained its secondary structure, while conformation of the MA has significant change after forming MA-BSA complex, suggesting that flexibility of the MA molecule supports the binding interaction of BSA with MA. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24852109

Shi, Jie-Hua; Zhu, Ying-Yao; Wang, Jing; Chen, Jun

2015-02-01

389

CD Spectroscope  

NSDL National Science Digital Library

In this activity, learners use an old CD to construct a spectroscope, a device that separates light into its component colors. Learners will hold it up to various light sources to examine how different light has different color strengths. Use this activity to introduce learners to the color spectrum and the tools scientists use to study it.

2012-06-26

390

13C-Methyl Formate: Observations of a Sample of High-mass Star-forming Regions Including orion-KL and Spectroscopic Characterization  

NASA Astrophysics Data System (ADS)

We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic center for methyl formate, HCOOCH3, and its isotopologues H13COOCH3 and HCOO13CH3. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4 GHz. Based on the APEX observations, we report tentative detections of the 13C-methyl formate isotopologue HCOO13CH3 toward the following four massive star-forming regions: Sgr B2(N-LMH), NGC 6334 IRS 1, W51 e2, and G19.61-0.23. In addition, we have used the 1 mm ALMA science verification observations of Orion-KL and confirm the detection of the 13C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the 12C/13C isotope ratio in methyl formate toward the Orion-KL Compact Ridge and Hot Core-SW components (68.4 ± 10.1 and 71.4 ± 7.8, respectively) are, for both the 13C-methyl formate isotopologues, commensurate with the average 12C/13C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the 12C/13C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H13COOCH3 and HCOO13CH3 species. New spectroscopic data for both isotopomers H13COOCH3 and HCOO13CH3, presented in this study, have made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory (under program ID 089.F-9319).

Favre, Cécile; Carvajal, Miguel; Field, David; Jørgensen, Jes K.; Bisschop, Suzanne E.; Brouillet, Nathalie; Despois, Didier; Baudry, Alain; Kleiner, Isabelle; Bergin, Edwin A.; Crockett, Nathan R.; Neill, Justin L.; Margulès, Laurent; Huet, Thérèse R.; Demaison, Jean

2014-12-01

391

Reactions of Highly Uniform Zeolite H-Supported Rhodium Complexes: Transient Characterization by Infrared and X-ray Absorption Spectroscopies  

SciTech Connect

A zeolite H-{beta}-supported mononuclear rhodium diethene complex (Rh(C{sub 2}H{sub 4}){sub 2}{l_brace}O{sub 2}Al{r_brace}, where the braces indicate a part of the zeolite) was formed by the reaction of Rh(acac)({eta}{sub 2}-C{sub 2}H{sub 4}){sub 2} (acac = acetylacetonate, C{sub 5}H{sub 7}O{sub 2}{sup -}) with the zeolite. Transient characterization of the sample by X-ray absorption near edge structure (XANES) and infrared (IR) spectroscopies (combined with mass spectrometry of the effluent gas) while the sample was in contact with flowing CO indicates a simple stoichiometric conversion of the supported metal complex into another species, identified by the spectra as the zeolite-supported rhodium gem-dicarbonyl (Rh(CO){sub 2}{l_brace}O{sub 2}Al{r_brace}). The sharpness of the v{sub CO} bands in the IR spectrum indicates a high degree of uniformity of the supported rhodium gem-dicarbonyl, and isosbestic points in the XANES spectra as the transformation was occurring imply that the rhodium diethene complex was also highly uniform. Spectra similarly show that treatment of the supported rhodium gem-dicarbonyl with flowing C{sub 2}H{sub 4} resulted in another stoichiometrically simple transformation, giving a species suggested to be Rh(C{sub 2}H{sub 4})(CO){sub 2}{l_brace}O{sub 2}Al{r_brace}. The intermediate was ultimately transformed when the sample was purged with helium into another highly uniform supported species, inferred on the basis of IR spectra to be Rh(C{sub 2}H{sub 4})(CO){l_brace}O{sub 2}Al{r_brace}. Extended X-ray absorption fine structure spectra characterizing the supported rhodium diethene complex and the species formed from it show how the Rh-O bond distance at the Rh-support interface varied in response to the changes in the ligands bonded to the rhodium.

Ogino, I.; Gates, B

2010-01-01

392

CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE AGNs. I. SPECTROSCOPIC PROPERTIES AND SERENDIPITOUS DISCOVERY OF NEW DUAL AGNs  

SciTech Connect

A sample of 10 nearby intermediate-type active galactic nuclei (AGNs) drawn from the Sloan Digital Sky Survey is presented. The aim of this work is to provide estimations of the black hole (BH) mass for the sample galaxies from the dynamics of the broad-line region. For this purpose, a detailed spectroscopic analysis of the objects was done. Using Baldwin-Phillips-Terlevich diagnostic diagrams, we have carefully classified the objects as true intermediate-type AGNs and found that 80%{sup +7.2%} {sub -17.3%} are composite AGNs. The BH mass estimated for the sample is within 6.54 {+-} 0.16 < log M {sub BH} < 7.81 {+-} 0.14. Profile analysis shows that five objects (J120655.63+501737.1, J121607.08+504930.0, J141238.14+391836.5, J143031.18+524225.8, and J162952.88+242638.3) have narrow double-peaked emission lines in both the red (H{alpha}, [N II] {lambda}{lambda}6548,6583 and [S II] {lambda}{lambda}6716, 6731) and the blue (H{beta} and [O III] {lambda}{lambda}4959, 5007) regions of the spectra, with velocity differences ({Delta}V) between the double peaks within 114 km s{sup -1} < {Delta}V < 256 km s{sup -1}. Two of them, J121607.08+504930.0 and J141238.14+391836.5, are candidates for dual AGNs since their double-peaked emission lines are dominated by AGN activity. In searches of dual AGNs, type 1, type II, and intermediate-type AGNs should be carefully separated, due to the high serendipitous number of narrow double-peaked sources (50% {+-} 14.4%) found in our sample.

Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni; Jimenez-Bailon, Elena [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F. 04510 (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F. 04510 (Mexico); Mendez-Abreu, Jairo; Lopez-Martin, Luis [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain)] [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Fuentes-Carrera, Isaura [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional (ESFM-IPN), U.P. Adolfo Lopez Mateos, Mexico D.F. 07730 (Mexico)] [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional (ESFM-IPN), U.P. Adolfo Lopez Mateos, Mexico D.F. 07730 (Mexico); Leon-Tavares, Jonathan [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FI-02540, Kylmaelae (Finland)] [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FI-02540, Kylmaelae (Finland); Chavushyan, Vahram H., E-mail: erika@astro.unam.mx [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51-216, 72000 Puebla (Mexico)

2013-01-20