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Sample records for oxygen sensing properties

  1. Timeline: Cellular Oxygen Sensing.

    PubMed

    Szewczak, Lara

    2016-09-22

    Since the 1950s, researchers have recognized that red blood cell numbers expand or contract as needed, according to the amount of available oxygen. The later discoveries that erythropoietin and VEGF levels adapt to oxygen levels launched a new field aimed at understanding how cells sense and respond to normal- and low-oxygen environments. The 2016 Albert Lasker Basic Medical Research Award recognizes key discoveries about this global oxygen sensing pathway and its impacts on pathogenesis, including cancer and inflammation. PMID:27662095

  2. Oxygen Sensing and Homeostasis.

    PubMed

    Prabhakar, Nanduri R; Semenza, Gregg L

    2015-09-01

    The discovery of carotid bodies as sensory receptors for detecting arterial blood oxygen levels, and the identification and elucidation of the roles of hypoxia-inducible factors (HIFs) in oxygen homeostasis have propelled the field of oxygen biology. This review highlights the gas-messenger signaling mechanisms associated with oxygen sensing, as well as transcriptional and non-transcriptional mechanisms underlying the maintenance of oxygen homeostasis by HIFs and their relevance to physiology and pathology.

  3. Synthesis, photophysical and oxygen-sensing properties of a novel Eu 3+ complex incorporated in mesoporous MCM-41

    NASA Astrophysics Data System (ADS)

    Zuo, Qinghui; Li, Bin; Zhang, Liming; Wang, Yinghui; Liu, Yanhong; Zhang, Jun; Chen, Ying; Guo, Lifan

    2010-07-01

    A novel Eu 3+ complex of Eu(DPIQ)(TTA) 3 (DPIQ=10H-dipyrido [ f, h] indolo [3,2 -b] quinoxaline, TTA=2-thenoyltrifluoroacetonate) was synthesized and encapsulated in the mesoporous MCM-41, hoping to explore an oxygen-sensing system based on the long-lived Eu 3+ emitter. The Eu(DPIQ)(TTA) 3/MCM-41 composites were characterized by infrared spectra (IR) , ultraviolet-visible (UV-vis) absorption spectra, small-angle X-ray diffraction (SAXRD), luminescence intensity quenching upon various oxygen concentrations, and fluorescence decay analysis. The results indicated that the composites exhibited the characteristic emission of the Eu 3+ ion and the fluorescence intensity of 5D0- 7F2 obviously decreased with increasing oxygen concentrations. The oxygen sensing properties of the composites with different loading levels of Eu(DPIQ)(TTA) 3 complex were investigated. A sensitivity of 3.04, a short response time of 7 s, and good linearity were obtained for the composites with a loading level of 20 mg/g. These results are the best reported values for optical oxygen-sensing materials based on Eu 3+ complexes so far.

  4. Influence of oxygen depletion layer on the properties of tin oxide gas-sensing films fabricated by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Natarajan, Gomathi; Cameron, David C.

    2009-06-01

    In this paper we report on the influence of film thickness on the electrical and gas-sensing properties of tin oxide thin films grown by atomic layer deposition (ALD) technique. The nature of the carrier and post-flow gases used in ALD was found to have a dramatic influence on the electrical conductance of the deposited films. Up to a film thickness of 50 nm the sheet conductance of the films increased with the thickness, and above 50 nm the sheet conductance was not significantly influenced by the film thickness. This effect was attributed to oxygen depletion at the film surface. When the depth of oxygen depletion ( d dep) was greater than or equal to the film thickness ( t), the sheet conductance was thickness dependant. On the other hand, when d dep≤ t, the sheet conductance was independent of the film thickness but depended on the depth of the oxygen depletion. This proposed explanation was verified by subjecting the films to different lengths of post-annealing in an oxygen depleted atmosphere. Gas-sensing functionality of the films with various thicknesses was examined. It was observed that the film thickness had a significant influence on the gas-sensing property of the films. When the thickness was greater than 40 nm, the sensitivity of the films to ethanol was found to follow the widely reported trend, i.e., the sensitivity decreases when the film thickness increases. Below the film thickness of 40 nm the sensitivity decreases as film thickness decreases, and we propose a model to explain this observation based on the increase in resistance due to multiple grain boundaries.

  5. Oxygen sensing and metabolic homeostasis.

    PubMed

    Palmer, Biff F; Clegg, Deborah J

    2014-11-01

    Oxygen-sensing mechanisms have evolved to maintain cell and tissue homeostasis since the ability to sense and respond to changes in oxygen is essential for survival. The primary site of oxygen sensing occurs at the level of the carotid body which in response to hypoxia signals increased ventilation without the need for new protein synthesis. Chronic hypoxia activates cellular sensing mechanisms which lead to protein synthesis designed to alter cellular metabolism so cells can adapt to the low oxygen environment without suffering toxicity. The master regulator of the cellular response is hypoxia-inducible factor (HIF). Activation of this system under condition of hypobaric hypoxia leads to weight loss accompanied by increased basal metabolic rate and suppression of appetite. These effects are dose dependent, gender and genetic specific, and results in adverse effects if the exposure is extreme. Hypoxic adipose tissue may represent a unified cellular mechanism for variety of metabolic disorders, and insulin resistance in patients with metabolic syndrome.

  6. Oxygen and carbon dioxide sensing

    NASA Technical Reports Server (NTRS)

    Ren, Fan (Inventor); Pearton, Stephen John (Inventor)

    2012-01-01

    A high electron mobility transistor (HEMT) capable of performing as a CO.sub.2 or O.sub.2 sensor is disclosed, hi one implementation, a polymer solar cell can be connected to the HEMT for use in an infrared detection system. In a second implementation, a selective recognition layer can be provided on a gate region of the HEMT. For carbon dioxide sensing, the selective recognition layer can be, in one example, PEI/starch. For oxygen sensing, the selective recognition layer can be, in one example, indium zinc oxide (IZO). In one application, the HEMTs can be used for the detection of carbon dioxide and oxygen in exhaled breath or blood.

  7. Temperature and Oxygen Sensing Properties of Ru(II) Covalently-Grafted Sol-Gel Derived Ormosil Hybrid Materials.

    PubMed

    Zhang, Haoran; Lei, Bingfu; Dong, Hanwu; Liu, Yingliang; Zheng, Mingtao; Xiao, Yong

    2016-04-01

    In this article, oxygen and temperature-sensing hybrid materials consisting of [Ru(Phen)3]2+ portions covalently-grafted onto the sol-gel derived ormosil network were prepared by co-condensation of tetraethoxysilane (TEOS) using n-octyltriethoxysilane as the network modifier. For comparison purposes, the hybrid materials in which [Ru(Phen)3]2+ were conventionally physically-incorporated into the matrix were also prepared. The obtained hybrid materials were characterized by Fourier transform infrared (FT-IR), luminescence intensity oxygen quenching Stern-Volmer plots, temperature quenching plots and excited-state lifetime. The near linear Stern-Volmer plots can be attributed to the approximate heterogeneous environment of the luminophore within the ormosil materials. The results reveal that the. covalently-grafted sample is more sensitive to 02, and has a higher sensing sensitivity and a higher thermal activation energy compared to the physically-incorporated one, since these Ru(II) molecules are strongly covalently-grafted onto the Si-O network via the CH2-Si bonds and less -OH group. PMID:27451760

  8. Nanofibers doped with a novel red-emitting Europium complex: Synthesis, characterization, photophysical property and sensing activity toward molecular oxygen

    NASA Astrophysics Data System (ADS)

    Jianliang, SUN; Ge, HU; Qing, SHE; Zhaohong, ZUO; Lei, GUO

    2012-06-01

    In this paper, we synthesize a novel diamine ligand of DIQ-Et and its corresponding Eu(III) complex of Eu(TTA)3DIQ-Et, where DIQ-Et = N-ethyl-10H-dipyrido-[f,h]-indolo-[3,2-b]-quinoxaline, and TTA = 2-thenoyltrifluoroacetonate. The UV-vis absorption, photoluminescence, low temperature phosphorescence, energy transfer mechanism, and excited state lifetime of Eu(TTA)3DIQ-Et are investigated in detail. Data suggest that the emission of Eu(TTA)3DIQ-Et is quenchable by molecular oxygen due to the back-energy transfer process. By doping Eu(TTA)3DIQ-Et into a polymer matrix of poly(vinylpyrrolidone) (PVP), oxygen sensing performance of the resulted nanofibers is investigated. Finally, the 0.7 wt% doped sample exhibits a linear response toward molecular oxygen, with a sensitivity of 2.4 and response/recovery time of 12 s/16 s.

  9. Sensing properties of an oxygen sensor using BaCe{sub 0.8}Gd{sub 0.2}O{sub 3{minus}{alpha}} ceramics as electrolytes

    SciTech Connect

    Taniguchi, Noboru; Yasumoto, Eiichi; Nakagiri, Yasushi; Gamo, Takaharu

    1998-05-01

    Limiting-current-type oxygen sensors using BaCe{sub 0.8}Gd{sub 0.2}O{sub 3{minus}{alpha}} (BCG) ceramics as electrolytes were constructed on a trial basis and their sensing properties investigated in order to develop a new oxygen sensor to replace the zirconia type. BCG ceramics exhibited high conductivity in the temperature range 200--1,000 C, and it was verified that the oxide ion could be a conductive carrier in BCG in oxygen at low temperatures (300 C). The oxygen sensors using BCGs worked at 300 C, and their output currents linearly increased with an increase in oxygen concentration in the range 1--22%. They could respond within 30 s between 1 and 21%, and humidity only slightly affected sensing performance. BCG seems to be a promising electrolyte material for an oxygen sensor operating at low temperatures (300 C).

  10. Dissolved oxygen sensing based on fluorescence quenching of ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Shehata, Nader; Meehan, Kathleen; Leber, Donald

    2012-10-01

    The development of oxygen sensors has positively impacted the fields of medical science, bioengineering, environmental monitoring, solar cells, industrial process control, and a number of military applications. Fluorescent quenching sensors have an inherent high sensitivity, chemical selectivity, and stability when compared to other types of sensors. While cerium oxide thin films have been used to monitor oxygen in the gas phase, the potential of cerium oxide (ceria) nanoparticles as the active material in sensor for oxygen gas has only recently been investigated. Ceria nanoparticles are one of the most unique nanomaterials that are being studied today due to the diffusion and reactivity of its oxygen vacancies, which contributes to its high oxygen storage capability. The reactivity of the oxygen vacancies, which is also related to conversion of cerium ion from the Ce+4 to Ce+3 state, affects the fluorescence properties of the ceria nanoparticles. Our research demonstrates that the ceria nanoparticles (~7 nm in diameter) have application as a fluorescence quenching sensor to measure dissolved oxygen in water. We have found a strong inverse correlation between the amplitude of the fluorescence emission (λexcitation = 430 nm and λpeak = 520 nm) and the dissolved oxygen concentration between 5 - 13 mg/L. The Stern-Volmer constant, which is an indication of the sensitivity of gas sensing is 184 M-1 for the ceria nanoparticles. The results show that ceria nanoparticles can be used in an improved, robust fluorescence sensor for dissolved oxygen in a liquid medium.

  11. A miniature inexpensive, oxygen sensing element

    SciTech Connect

    Arenz, R.W.

    1991-10-07

    An exhaustive study was conducted to determine the feasibility of Nernst-type oxygen sensors based on ceramics containing Bi{sub 2}O{sub 3}. The basic sensor design consisted of a ceramic sensing module sealed into a metal tube. The module accommodated an internal heater and thermocouple. Thermal-expansion-matched metals, adhesives, and seals were researched and developed, consistent with sequential firings during sensor assembly. Significant effort was devoted to heater design/testing and to materials' compatibility with Pt electrodes. A systematic approach was taken to develop all sensor components which led to several design modifications. Prototype sensors were constructed and exhaustively tested. It is concluded that development of Nerst-type oxygen sensors based on Bi{sub 2}O{sub 3} will require much further effort and application of specialized technologies. However, during the course of this 3-year program much progress was reported in the literature on amperometric-type oxygen sensors, and a minor effort was devoted here to this type of sensor based on Bi{sub 2}O{sub 3}. These studies were made on Bi{sub 2}O{sub 3}-based ceramic samples in a multilayer-capacitor-type geometry and amperometric-type oxygen sensing was demonstrated at very low temperatures ({approximately} 160{degree}C). A central advantage here is that these types of sensors can be mass-produced very inexpensively ({approximately} 20--50 cents per unit). Research is needed, however, to develop an optimum diffusion-limiting barrier coating. In summary, the original goals of this program were not achieved due to unforeseen problems with Bi{sub 2}O{sub 3}-based Nernst sensors. However, a miniature amperometric sensor base on Bi{sub 2}O{sub 3} was demonstrated in this program, and it is now seen that this latter sensor is far superior to the originally proposed Nernst sensor. 6 refs., 24 figs.

  12. Evolution and physiology of neural oxygen sensing

    PubMed Central

    Costa, Kauê M.; Accorsi-Mendonça, Daniela; Moraes, Davi J. A.; Machado, Benedito H.

    2014-01-01

    Major evolutionary trends in animal physiology have been heavily influenced by atmospheric O2 levels. Amongst other important factors, the increase in atmospheric O2 which occurred in the Pre-Cambrian and the development of aerobic respiration beckoned the evolution of animal organ systems that were dedicated to the absorption and transportation of O2, e.g., the respiratory and cardiovascular systems of vertebrates. Global variations of O2 levels in post-Cambrian periods have also been correlated with evolutionary changes in animal physiology, especially cardiorespiratory function. Oxygen transportation systems are, in our view, ultimately controlled by the brain related mechanisms, which senses changes in O2 availability and regulates autonomic and respiratory responses that ensure the survival of the organism in the face of hypoxic challenges. In vertebrates, the major sensorial system for oxygen sensing and responding to hypoxia is the peripheral chemoreflex neuronal pathways, which includes the oxygen chemosensitive glomus cells and several brainstem regions involved in the autonomic regulation of the cardiovascular system and respiratory control. In this review we discuss the concept that regulating O2 homeostasis was one of the primordial roles of the nervous system. We also review the physiology of the peripheral chemoreflex, focusing on the integrative repercussions of chemoreflex activation and the evolutionary importance of this system, which is essential for the survival of complex organisms such as vertebrates. The contribution of hypoxia and peripheral chemoreflex for the development of diseases associated to the cardiovascular and respiratory systems is also discussed in an evolutionary context. PMID:25161625

  13. Transport properties of oxygen

    NASA Technical Reports Server (NTRS)

    Roder, H. M.

    1983-01-01

    Tables of viscosity, thermal conductivity, and thermal diffusivity of oxygen as a function of temperature and pressure from the triple point to 320 K and at pressures to 100 MPa are presented. Auxiliary tables in engineering units are also given. Viscosity and thermal conductivity are calculated from published correlations. Density and specific heat at constant pressure, required to calculate thermal diffusivity, are obtained from an equation of state. The Prandtl number can be obtained quite easily from the values tabulated.

  14. Oxygen Sensing by Protozoans: How They Catch Their Breath

    PubMed Central

    West, Christopher M.; Blader, Ira J.

    2015-01-01

    Cells must know the local levels of available oxygen and either alter their activities or relocate to more favorable environments. Prolyl 4-hydroxylases are emerging as universal cellular oxygen sensors. In animals, these oxygen sensors respond to decreased oxygen availability by up-regulating hypoxia-inducible transcription factors. In protists, the prolyl 4-hydroxylases appear to activate E3-SCF ubiquitin ligase complexes potentially to turn over their proteomes. Intracellular parasites respond to decreased oxygen by utilizing both types of oxygen-sensing pathways. Since parasites are exposed to diverse oxygen tensions during their life cycle, oxygen sensing is likely a critical process and this review will discuss how these oxygen-sensing mechanisms contribute to the behavior of these unicellular eukaryotes. PMID:25988702

  15. Spatially monitoring oxygen level in 3D microfabricated cell culture systems using optical oxygen sensing beads.

    PubMed

    Wang, Lin; Acosta, Miguel A; Leach, Jennie B; Carrier, Rebecca L

    2013-04-21

    Capability of measuring and monitoring local oxygen concentration at the single cell level (tens of microns scale) is often desirable but difficult to achieve in cell culture. In this study, biocompatible oxygen sensing beads were prepared and tested for their potential for real-time monitoring and mapping of local oxygen concentration in 3D micro-patterned cell culture systems. Each oxygen sensing bead is composed of a silica core loaded with both an oxygen sensitive Ru(Ph2phen3)Cl2 dye and oxygen insensitive Nile blue reference dye, and a poly-dimethylsiloxane (PDMS) shell rendering biocompatibility. Human intestinal epithelial Caco-2 cells were cultivated on a series of PDMS and type I collagen based substrates patterned with micro-well arrays for 3 or 7 days, and then brought into contact with oxygen sensing beads. Using an image analysis algorithm to convert florescence intensity of beads to partial oxygen pressure in the culture system, tens of microns-size oxygen sensing beads enabled the spatial measurement of local oxygen concentration in the microfabricated system. Results generally indicated lower oxygen level inside wells than on top of wells, and local oxygen level dependence on structural features of cell culture surfaces. Interestingly, chemical composition of cell culture substrates also appeared to affect oxygen level, with type-I collagen based cell culture systems having lower oxygen concentration compared to PDMS based cell culture systems. In general, results suggest that oxygen sensing beads can be utilized to achieve real-time and local monitoring of micro-environment oxygen level in 3D microfabricated cell culture systems.

  16. Mechanisms and meaning of cellular oxygen sensing in the organism.

    PubMed

    Acker, H

    1994-01-01

    Oxygen sensors in the body induce various cell activities to avoid any mismatch between oxygen demand and oxygen supply and to maintain an optimal level of oxygen partial pressure (PO2) in various organs. Oxygen sensing seems to be a well conserved process among procaryontic and eucaryontic cells. The molecular mechanism of oxygen sensing is unknown, but it has been suggested that a hemeprotein is involved that does not participate in the mitochondrial energy production. As examplified on the carotid body and on erythropoietin producing HepG2 cells, a cytochrome b was described for the NAD(P)H oxidase of neutrophiles might be an attractive candidate for this hemeprotein. It is hypothesised that hydrogen peroxide (H2O2) produced by this cytochrome b in direct correlation with cellular PO2, serves as a second messenger to regulate potassium channels or gene expression. One might forsee, that this new concept of oxygen sensing could have an impact on all processes in physiology and pathophysiology which are dealing with reactive oxygen intermediates.

  17. Sensing fuel properties with thermal microsensors

    NASA Astrophysics Data System (ADS)

    Bonne, Ulrich

    1996-05-01

    We report on measurements of combustion-relevant fuel properties for on-line, feedforward control with small, rugged and fully compensated microsensor-based systems. Such silicon microstructure sensor systems have been demonstrated to determine gaseous and liquid fuel properties such as stoichiometric oxygen demand, octane number, heating value, density and other properties of interest. The measurement approach consists of a three-step process: (1) Measurement of changes in electrical quantities when the sensing elements come in contact with the fluid, (2) Conversion of these quantities into primary sensor outputs, yi, such as thermal conductivity, specific heat, temperature and pressure, and (3) Correlation between these and the properties of interest, Y(yi). By coupling this property sensor to an equally rugged and small thermal flow microsensor, millisecond-range response time signals of mass or volume flow, or stoichiometric oxygen demand rate are provided for feed-forward control, without exposing any sensor to harsh exhaust gas environments. Having presented results with gaseous fuels elsewhere, we update these here but concentrate on the determination of octane and cetane number of liquid fuels. Analysis results show that the correlations between these combustion performance properties and physical fuel properties are as good as the ones between octane and critical compression ratio or between cetane and ignition delay. However, all those correlations appear to be limited presently by the accuracy or at least consistency of available data, which are needed for calibration of the sensor system. In checking the temperature dependence of one of the correlations for octane, we found the system output to shift by 15% when using hexadecane as a reference fuel, but only by 1% with iso-octane as reference, for a 10 degree(s)C shift in temperature.

  18. Nano-Enriched and Autonomous Sensing Framework for Dissolved Oxygen.

    PubMed

    Shehata, Nader; Azab, Mohammed; Kandas, Ishac; Meehan, Kathleen

    2015-01-01

    This paper investigates a nano-enhanced wireless sensing framework for dissolved oxygen (DO). The system integrates a nanosensor that employs cerium oxide (ceria) nanoparticles to monitor the concentration of DO in aqueous media via optical fluorescence quenching. We propose a comprehensive sensing framework with the nanosensor equipped with a digital interface where the sensor output is digitized and dispatched wirelessly to a trustworthy data collection and analysis framework for consolidation and information extraction. The proposed system collects and processes the sensor readings to provide clear indications about the current or the anticipated dissolved oxygen levels in the aqueous media. PMID:26287211

  19. Multifunctional mesoporous nanocomposites with magnetic, optical, and sensing features: synthesis, characterization, and their oxygen-sensing performance.

    PubMed

    Wang, Yanyan; Li, Bin; Zhang, Liming; Song, Hang

    2013-01-29

    In this paper, the fabrication, characterization, and application in oxygen sensing are reported for a novel multifunctional nanomaterial of [Ru(bpy)(2)phen-MMS] (bpy, 2,2'-bipyridyl; phen, phenathrolin) which was simply prepared by covalently grafting the ruthenium(II) polypyridyl compounds into the channels of magnetic mesoporous silica nanocomposites (MMS). Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, N(2) adsorption-desorption, a superconducting quantum interference device, UV-vis spectroscopy, and photoluminescence spectra were used to characterize the samples. The well-designed multifunctional nanocomposites show superparamagnetic behavior and ordered mesoporous characteristics and exhibit a strong red-orange metal-to-ligand charge transfer emission. In addition, the obtained nanocomposites give high performance in oxygen sensing with high sensitivity (I(0)/I(100) = 5.2), good Stern-Volmer characteristics (R(2) = 0.9995), and short response/recovery times (t↓ = 6 s and t↑ = 12 s). The magnetic, mesoporous, luminescent, and oxygen-sensing properties of this multifunctional nanostructure make it hold great promise as a novel multifunctional oxygen-sensing system for chemical/biosensor.

  20. Composite nanofibers doped with a phosphorescent Re(I) complex having restricted conjugation plane in its diamine ligand: Preparation, characterization, photophysical property and oxygen-sensing performance

    NASA Astrophysics Data System (ADS)

    Lin, Chen; Shaoyan, Wang; Qi, Wang; Jing, Li

    2013-10-01

    In this paper, we report a Re(I) complex of Re(CO)3(Cl-PYO)Br, where Cl-PYO stands for 2-(4-chlorophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole, including its synthesis, identification, molecular structure, theoretical calculation and photophysical character. Re(CO)3(Cl-PYO)Br is found to be a yellow emitter with long excited state lifetime in pure N2 atmosphere. Theoretical calculation result suggests that this emission comes from a triplet metal-to-ligand-charge-transfer excited state. By doping Re(CO)3(Cl-PYO)Br into a polymer supporting matrix of poly(vinylpyrrolidone), the emission of the resulted composite materials is found to be sensitive towards various oxygen concentrations. The maximum sensitivity is obtained to be 7.88. Owing to the porous structure of fibrous poly(vinylpyrrolidone) matrix, a short response time of 11 s towards molecular oxygen is also realized with high photostability.

  1. Quality assessment of packaged foods by optical oxygen sensing

    NASA Astrophysics Data System (ADS)

    Papkovsky, Dmitri B.; O'Mahony, Fiach C.; Kerry, Joe P.; Ogurtsov, Vladimir I.

    2005-11-01

    A phase-fluorometric oxygen sensor system has been developed, which allows non-destructive measurement of residual oxygen levels in sealed containers such as packaged foods. It operates with disposable solid-state sensors incorporated in each pack, and a portable detector which interrogates with the sensors through a (semi)transparent packaging material. The system has been optimized for packaging applications and validated in small and medium scale trials with different types of food, including MAP hams, cheese, convenience foods, smoked fish, bakery. It has demonstrated high efficiency in monitoring package integrity, oxygen profiles in packs, performance of packaging process and many other research and quality control tasks, allowing control of 100% of packs. The low-cost batch-calibrated sensors have demonstrated reliability, safety, stability including direct contact with food, high efficiency in the low oxygen range. Another system, which also employs the fluorescence-based oxygen sensing approach, provides rapid assessment of microbial contamination (total viable counts) in complex samples such as food homogenates, industrial waste, environmental samples, etc. It uses soluble oxygen-sensitive probes, standard microtitter plates and fluorescence measurements on conventional plate reader to monitor growth of aerobic bacteria in small test samples (e.g. food homogenates) via their oxygen respiration. The assay provides high sample through put, miniaturization, speed, and can serve as alternative to the established methods such as agar plate colony counts and turbidimetry.

  2. Highly sensitive humidity sensing properties of carbon quantum dots films

    SciTech Connect

    Zhang, Xing; Ming, Hai; Liu, Ruihua; Han, Xiao; Kang, Zhenhui; Liu, Yang; Zhang, Yonglai

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A humidity sensing device was fabricated based on carbon quantum dots (CQDs) films. ► The conductivity of the CQDs films shows a linear and rapid response to atmosphere humidity. ► The humidity sensing property was due to the hydrogen bonds between the functional groups on CQDs. -- Abstract: We reported the fabrication of a humidity sensing device based on carbon quantum dots (CQDs) film. The conductivity of the CQDs film has a linear and rapid response to relative humidity, providing the opportunity for the fabrication of humidity sensing devices. The mechanism of our humidity sensor was proposed to be the formation of hydrogen bonds between carbon quantum dots and water molecules in the humidity environment, which significantly promote the electrons migration. In a control experiment, this hypothesis was confirmed by comparing the humidity sensitivity of candle soot (i.e. carbon nanoparticles) with and without oxygen containing groups on the surfaces.

  3. Cytochromes and oxygen radicals as putative members of the oxygen sensing pathway.

    PubMed

    Ehleben, W; Bölling, B; Merten, E; Porwol, T; Strohmaier, A R; Acker, H

    1998-10-01

    This study applies biophysical methods like light absorption spectrophotometry of cytochromes, determination of NAD(P)H-dependent superoxide anion (O2-) formation and localisation of hydroxyl radicals (*OH) by 3-dimensional (3D) confocal laser scanning microscopy to reveal in human cells putative members of the oxygen sensing signal pathway leading to enhanced gene expression under hypoxia. A cell membrane localised non-mitochondrial cytochrome b558 seems to be involved as an oxygen sensor in the hepatoma cell line HepG2 in cooperation with the mitochondrial cytochrome b563 probably probing additionally metabolic changes. *OH the putative second messenger of the oxygen sensing pathway generated by a Fenton reaction could be visualized in the perinuclear space of the three human cell lines used. Substances like cobalt or the iron chelator desferrioxamine, which have been applied in HepG2 cells to mimic hypoxia induced gene expression, interact on various sides of the oxygen sensing pathway confirming the importance of b-type cytochromes and the Fenton reaction.

  4. Oxygen Sensing Coordinates Photomorphogenesis to Facilitate Seedling Survival

    PubMed Central

    Abbas, Mohamad; Berckhan, Sophie; Rooney, Daniel J.; Gibbs, Daniel J.; Vicente Conde, Jorge; Sousa Correia, Cristina; Bassel, George W.; Marín-de la Rosa, Nora; León, José; Alabadí, David; Blázquez, Miguel A.; Holdsworth, Michael J.

    2015-01-01

    Summary Successful emergence from the soil is essential for plant establishment in natural and farmed systems. It has been assumed that the absence of light in the soil is the preeminent signal perceived during early seedling development, leading to a distinct morphogenic plan (skotomorphogenesis) [1], characterized by traits providing an adaptive advantage until emergence and photomorphogenesis. These traits include suppressed chlorophyll synthesis, promotion of hypocotyl elongation, and formation of a closed apical hook that protects the stem cell niche from damage [2, 3]. However, absence of light by itself is not a sufficient environmental signal for early seedling development [4, 5]. Reduced oxygen levels (hypoxia) can occur in water-logged soils [6–8]. We therefore hypothesized that below-ground hypoxia may be an important, but thus far undiscovered, ecological component regulating seedling development. Here, we show that survival and establishment of seedlings following darkness depend on their ability to sense hypoxia, through enhanced stability of group VII Ethylene Response Factor (ERFVII) transcription factors. Hypoxia is perceived as a positive environmental component in diverse taxa of flowering plants, promoting maintenance of skotomorphogenic traits. Hypoxia greatly enhances survival once light is perceived, while oxygen is necessary for the subsequent effective completion of photomorphogenesis. Together with light perception, oxygen sensing therefore allows an integrated response to the complex and changing physical microenvironment encountered during early seedling growth. We propose that plants monitor the soil’s gaseous environment after germination, using hypoxia as a key external cue to protect the stem cell niche, thus ensuring successful rapid establishment upon emergence above ground. PMID:25981794

  5. Oxygen sensing coordinates photomorphogenesis to facilitate seedling survival.

    PubMed

    Abbas, Mohamad; Berckhan, Sophie; Rooney, Daniel J; Gibbs, Daniel J; Vicente Conde, Jorge; Sousa Correia, Cristina; Bassel, George W; Marín-de la Rosa, Nora; León, José; Alabadí, David; Blázquez, Miguel A; Holdsworth, Michael J

    2015-06-01

    Successful emergence from the soil is essential for plant establishment in natural and farmed systems. It has been assumed that the absence of light in the soil is the preeminent signal perceived during early seedling development, leading to a distinct morphogenic plan (skotomorphogenesis) [1], characterized by traits providing an adaptive advantage until emergence and photomorphogenesis. These traits include suppressed chlorophyll synthesis, promotion of hypocotyl elongation, and formation of a closed apical hook that protects the stem cell niche from damage [2, 3]. However, absence of light by itself is not a sufficient environmental signal for early seedling development [4, 5]. Reduced oxygen levels (hypoxia) can occur in water-logged soils [6-8]. We therefore hypothesized that below-ground hypoxia may be an important, but thus far undiscovered, ecological component regulating seedling development. Here, we show that survival and establishment of seedlings following darkness depend on their ability to sense hypoxia, through enhanced stability of group VII Ethylene Response Factor (ERFVII) transcription factors. Hypoxia is perceived as a positive environmental component in diverse taxa of flowering plants, promoting maintenance of skotomorphogenic traits. Hypoxia greatly enhances survival once light is perceived, while oxygen is necessary for the subsequent effective completion of photomorphogenesis. Together with light perception, oxygen sensing therefore allows an integrated response to the complex and changing physical microenvironment encountered during early seedling growth. We propose that plants monitor the soil's gaseous environment after germination, using hypoxia as a key external cue to protect the stem cell niche, thus ensuring successful rapid establishment upon emergence above ground.

  6. Ratiometric optical fiber sensor for dual sensing of copper ion and dissolved oxygen.

    PubMed

    Chu, Cheng-Shane; Chuang, Chih-Yung

    2015-12-20

    This paper develops a new ratiometric optical dual sensor for Cu2+ ions and dissolved oxygen (DO) incorporating a sol-gel matrix doped with palladium tetrakis pentafluorophenyl porphine as the oxygen-sensitive material, CdSe quantum dots as the Cu2+ ion-sensing material, and 7-amino-4-trifluoromethyl coumarin as the Cu2+ /DO practically independent fluorescent dye. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric optical fiber dual sensor is investigated. Using an LED with a central wavelength of 405 nm as an excitation source, it is shown that the emission wavelengths of the Cu2+ ion-sensitive, DO-sensitive dye and the reference dye have no spectral overlap and therefore permit Cu2+ ion and DO concentration to be measured using a ratiometric-based method. The ratiometric optical fiber dual sensor has been tested with regard to monitoring different Cu2+ ion (0-10 μM) and DO concentrations (0-38 mg/L). The results show that the luminescence properties of the Cu2+ ion sensor are independent of the presence of the oxygen sensor and have a uniquely good linear response in the 0-10 μM range. The proposed ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the intensity of the excitation source. PMID:26837033

  7. Synthesis and characterization of a new trifunctional magnetic photoluminescent oxygen-sensing nanomaterial

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Li, Bin; Ying, Jun; Wu, Xiudong; Zhao, Haifeng; Ren, Xinguang; Zhu, Dongxia; Su, Zhongmin

    2008-12-01

    Magnetic Fe2O3 nanoparticles coated with SiO2 chemically doped with a Ru(II) complex were prepared using a simple solution based method. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed that the Fe2O3 nanoparticles with a mean diameter of ~115 nm were successfully coated with Ru(II) complex-chemically doped SiO2 shell with a thickness of ~30 nm. The obtained nanocomposite material showed a strong magnetic response to a varying magnetic field, exhibited the bright red triplet metal-to-ligand charge transfer (3MLCT) emission, and its photoluminescent intensity was sensitive to oxygen concentration. Compared with the Ru(II) complex in silica gels, the Ru(II) complex in the magnetic-optical-oxygen-sensing nanocomposite demonstrated improved thermodynamic stability of emissions. These nanocomposites are also nontoxic and easily conjugated with biomolecules. Their magnetic, photoluminescent and oxygen-sensing properties make them promising candidates for cell separation, biomarkers and optical oxygen sensors, which can measure the O2 concentration in biological bodies.

  8. Study on an oxygen sensing rhenium(I) complex with enlarged sensing/active area: fabrication, photophysical parameters and molecular oxygen sensing performance.

    PubMed

    Xu, Guiying; Lu, Mang; Huang, Can; Wang, Yaoqiong; Ge, Shuping

    2014-04-01

    In this paper, we synthesize a novel 1,10-phenanthroline-derived (Phen-derived) diamine ligand of benzo[f][1,10]phenanthroline-6,7-dicarbonitrile (Phen-CN) with enlarged conjugation planar and its corresponding Re(I) complex of Re(CO)3Cl(Phen-CN), hoping to achieve an optical sensor owing large sensing/active area. Its geometric and electronic structures are investigated, which suggests that the effective sensing/active area of Re(CO)3Cl(Phen-CN) is enlarged by the successful formation of conjugation planar. The promising photophysical parameters of Re(CO)3Cl(Phen-CN), including large sensing/active area and long excited state lifetime, make it a potential probe for oxygen detection. By doping Re(CO)3Cl(Phen-CN) into a polymer matrix of poly(vinylpyrrolidone), oxygen sensing performances of the resulted composite materials are investigated. Finally, a high sensitivity of 17.1 is realized, with short response/recovery time of 9s/32s.

  9. The thermodynamic properties of organic oxygen compounds

    NASA Astrophysics Data System (ADS)

    Chirico, R. D.; Steele, W. V.; Hossenlopp, A.; Nguyen, A.; Archer, D. G.; Strube, M. M.

    1988-01-01

    The principles of group additivity are used to compare a series of cyclic hydrocarbons with the corresponding oxygen-containing analogs. The strengths and limitations of the group-additivity method are demonstrated and recommendations are made for measurements essential to the improvement of the accuracy of the predicted properties. The ideal-gas enthalpies of formation and ideal-gas entropies (which are used in combination to calculate Gibbs energies) are considered.

  10. Transport properties of ground state oxygen atoms

    NASA Technical Reports Server (NTRS)

    Holland, Paul M.; Biolsi, Louis

    1988-01-01

    The transport properties of dilute monatomic gases depend on the two-body interactions between like atoms. When two ground-state oxygen atoms interact, they can follow any of 18 potential energy curves corresponding to O2, all of which contribute to the transport properties of the ground-state atoms. Transport collision integrals have been calculated for those interactions with an attractive minimum in the potential, and repulsive ab initio potential-energy curves have been accurately represented. Results are given for viscosity, thermal conductivity, and diffusion and they are compared with previous theoretical calculations.

  11. Ratiometric optical oxygen sensing: a review in respect of material design.

    PubMed

    Feng, Yan; Cheng, Jinghui; Zhou, Li; Zhou, Xiangge; Xiang, Haifeng

    2012-11-01

    The quantitative determination of oxygen concentration is essential for a variety of applications ranging from life sciences to environmental sciences. Optical oxygen sensing allows non-invasive measurements with biological objects, parallel monitoring of multiple samples, and imaging. In general, ratiometric optical oxygen sensing is more desirable, due to its advantages of selectivity, insensitivity to ambient or scattered light, and elimination of instrumental fluctuation. Moreover, it can provide the perceived colour change, which would be useful not only for the ratiometric method of detection but also for rapid visual sensing. Mainly focusing on material design for ratiometric measurement, this review describes the overall progress made in the past ten years on ratiometric optical ground-state triplet oxygen sensing and offers a critical comparison of various methods reported in the literature. It also provides a development blueprint for ratiometric optical oxygen sensing.

  12. Symmetry properties in polarimetric remote sensing

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Yueh, S. H.; Kwok, R.; Li, F. K.

    1992-01-01

    This paper presents the relations among polarimetric backscattering coefficients from the viewpoint of symmetry groups. Symmetry of geophysical media encountered in remote sensing due to reflection, rotation, azimuthal, and centrical symmetry groups is considered for both reciprocal and nonreciprocal cases. On the basis of the invariance under symmetry transformations in the linear polarization basis, the scattering coefficients are related by a set of equations which restrict the number of independent parameters in the polarimetric covariance matrix. The properties derived under these transformations are general and apply to all scattering mechanisms in a given symmetrical configuration. The scattering coefficients calculated from theoretical models for layer random media and rough surfaces are shown to obey the derived symmetry relations. Use of symmetry properties in remote sensing of structural and environmental responses of scattering media is discussed. As a practical application, the results from this paper provide new methods for the external calibration of polarimetric radars without the deployment of man-made calibration targets.

  13. Reversed oxygen sensing using colloidal quantum wells towards highly emissive photoresponsive varnishes

    PubMed Central

    Lorenzon, Monica; Christodoulou, Sotirios; Vaccaro, Gianfranco; Pedrini, Jacopo; Meinardi, Francesco; Moreels, Iwan; Brovelli, Sergio

    2015-01-01

    Colloidal quantum wells combine the advantages of size-tunable electronic properties with vast reactive surfaces that could allow one to realize highly emissive luminescent-sensing varnishes capable of detecting chemical agents through their reversible emission response, with great potential impact on life sciences, environmental monitoring, defence and aerospace engineering. Here we combine spectroelectrochemical measurements and spectroscopic studies in a controlled atmosphere to demonstrate the ‘reversed oxygen-sensing’ capability of CdSe colloidal quantum wells, that is, the exposure to oxygen reversibly increases their luminescence efficiency. Spectroelectrochemical experiments allow us to directly relate the sensing response to the occupancy of surface states. Magneto-optical measurements demonstrate that, under vacuum, heterostructured CdSe/CdS colloidal quantum wells stabilize in their negative trion state. The high starting emission efficiency provides a possible means to enhance the oxygen sensitivity by partially de-passivating the particle surfaces, thereby enhancing the density of unsaturated sites with a minimal cost in term of luminescence losses. PMID:25910499

  14. Oxygen sensing neurons and neuropeptides regulate survival after anoxia in developing C. elegans.

    PubMed

    Flibotte, John J; Jablonski, Angela M; Kalb, Robert G

    2014-01-01

    Hypoxic brain injury remains a major source of neurodevelopmental impairment for both term and preterm infants. The perinatal period is a time of rapid transition in oxygen environments and developmental resetting of oxygen sensing. The relationship between neural oxygen sensing ability and hypoxic injury has not been studied. The oxygen sensing circuitry in the model organism C. elegans is well understood. We leveraged this information to investigate the effects of impairments in oxygen sensing on survival after anoxia. There was a significant survival advantage in developing worms specifically unable to sense oxygen shifts below their preferred physiologic range via genetic ablation of BAG neurons, which appear important for conferring sensitivity to anoxia. Oxygen sensing that is mediated through guanylate cyclases (gcy-31, 33, 35) is unlikely to be involved in conferring this sensitivity. Additionally, animals unable to process or elaborate neuropeptides displayed a survival advantage after anoxia. Based on these data, we hypothesized that elaboration of neuropeptides by BAG neurons sensitized animals to anoxia, but further experiments indicate that this is unlikely to be true. Instead, it seems that neuropeptides and signaling from oxygen sensing neurons operate through independent mechanisms, each conferring sensitivity to anoxia in wild type animals.

  15. Remote sensing application for property tax evaluation

    NASA Astrophysics Data System (ADS)

    Jain, Sadhana

    2008-02-01

    This paper presents a study for linking remotely sensed data with property tax related issues. First, it discusses the key attributes required for property taxation and evaluates the capabilities of remote sensing technology to measure these attributes accurately at parcel level. Next, it presents a detailed case study of six representative wards of different characteristics in Dehradun, India, that illustrates how measurements of several of these attributes supported by field survey can be combined to address the issues related to property taxation. Information derived for various factors quantifies the property taxation contributed by an average dwelling unit of the different income groups. Results show that the property tax calculated in different wards varies between 55% for the high-income group, 32% for the middle-income group, 12% for the low-income group and 1% for squatter units. The study concludes that higher spatial resolution satellite data and integrates social survey helps to assess the socio-economic status of the population for tax contribution purposes.

  16. Oxygen scrubbing and sensing in plant growth chambers using solid oxide electrolyzers

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; MacElroy, Robert D.

    1997-01-01

    The maintenance of optimal levels of oxygen in the gaseous environment of a plant growth chamber during light and dark periods is an essential criterion for the correct growth of plants. The use of solid oxide electrolyzers to control the oxygen levels by removing the excess gaseous oxygen during periods of illumination and full-scale photosynthesis is described. A part of the oxygen removed can be stored and supplied back to the plants during dark periods. The excess oxygen can be used by the crew. The electrolizer can be additionally used in its open circuit mode, to sense the oxygen concentrations in the plant chamber. The solid oxide electrolysis process is described.

  17. High sensitivity and accuracy dissolved oxygen (DO) detection by using PtOEP/poly(MMA-co-TFEMA) sensing film.

    PubMed

    Zhang, Ke; Zhang, Honglin; Wang, Ying; Tian, Yanqing; Zhao, Jiupeng; Li, Yao

    2017-01-01

    Fluorinated acrylate polymer has received great interest in recent years due to its extraordinary characteristics such as high oxygen permeability, good stability, low surface energy and refractive index. In this work, platinum octaethylporphyrin/poly(methylmethacrylate-co-trifluoroethyl methacrylate) (PtOEP/poly(MMA-co-TFEMA)) oxygen sensing film was prepared by the immobilizing of PtOEP in a poly(MMA-co-TFEMA) matrix and the technological readiness of optical properties was established based on the principle of luminescence quenching. It was found that the oxygen-sensing performance could be improved by optimizing the monomer ratio (MMA/TFEMA=1:1), tributylphosphate(TBP, 0.05mL) and PtOEP (5μg) content. Under this condition, the maximum quenching ratio I0/I100 of the oxygen sensing film is obtained to be about 8.16, Stern-Volmer equation is I0/I=1.003+2.663[O2] (R(2)=0.999), exhibiting a linear relationship, good photo-stability, high sensitivity and accuracy. Finally, the synthesized PtOEP/poly(MMA-co-TFEMA) sensing film was used for DO detection in different water samples. PMID:27450122

  18. Oxygen-sensing by arterial chemoreceptors: Mechanisms and medical translation.

    PubMed

    López-Barneo, José; Ortega-Sáenz, Patricia; González-Rodríguez, Patricia; Fernández-Agüera, M Carmen; Macías, David; Pardal, Ricardo; Gao, Lin

    2016-01-01

    Acute O2 sensing is necessary for the activation of cardiorespiratory reflexes (hyperventilation and sympathetic activation), which permit the survival of individuals under hypoxic environments (e.g. high altitude) or medical conditions presenting with reduced capacity for gas exchange between the lung alveoli and the blood. Changes in blood O2 tension are detected by the arterial chemoreceptors, in particular the carotid body (CB), which act in concert with the adrenal medulla (AM) to facilitate rapid adaptations to hypoxia. The field of arterial chemoreception has undergone a considerable expansion in recent years, with many of the fundamental observations made at the molecular and cellular levels serving to improve our understanding of the pathogenesis of numerous medical disorders, and even to propose advances in the treatment strategies. In this review, after a short historical preface, we describe the current model of chemosensory transduction based on the modulation of membrane K(+) channels by O2 in specialized chemoreceptor cells. Recent progress in elucidating the molecular mechanisms underlying the modulation of ion channels by O2 tension, which involves mitochondrial complex I, is also discussed. The discovery in the last few years of a specific population of neural crest-derived stem cells in the CB explains the reversible growth of this organ, an intriguing and unusual property of this type of neuronal tissue that contributes to acclimatization under chronic hypoxia. The essential homeostatic role of the CB-AM axis is clearly evident in newly generated mouse models that reach adulthood, albeit with CB and AM atrophy. These animals exhibit a marked intolerance to even mild hypoxia. CB inhibition or over-activation can have important medical consequences. Respiratory depression by general anesthetics or by opioid use is a common clinical condition that frequently causes death in susceptible individuals. An exaggerated sympathetic outflow due to over

  19. Mitochondrial complex III: an essential component of universal oxygen sensing machinery?

    PubMed

    Chandel, Navdeep S

    2010-12-31

    Oxygen is necessary for the survival of mammalian cells. In order to maintain adequate cellular oxygenation, mammals have evolved multiple acute and long-term adaptive responses to hypoxia. These include hypoxic increases in erythropoiesis, pulmonary vasoconstriction and carotid body neurosecretion. Collectively, these responses help maintain oxygen homeostasis as oxygen levels remain scarce. There are multiple effectors proposed to underlie these diverse responses to hypoxia including PHD2, AMPK, NADPH oxidases, and mitochondrial complex III. Here I propose a model wherein complex III is integral to oxygen sensing in regulating diverse response to hypoxia.

  20. A Pyrene@Micelle Sensor for Fluorescent Oxygen Sensing

    PubMed Central

    Yuan, Yan-xia; Peng, Hong-shang; Ping, Jian-tao; Wang, Xiao-hui; You, Fang-tian

    2015-01-01

    For most fluorescent oxygen sensors developed today, their fabrication process is either time-consuming or needs specialized knowledge. In this work, a robust fluorescent oxygen sensor is facilely constructed by dissolving pyrene molecules into CTAB aqueous solution. The as-prepared pyrene@micelle sensors have submicron-sized diameter, and the concentration of utilized pyrene can be reduced as low as 0.8 mM but still can exhibit dominant excimer emission. The excimer fluorescence is sensitive to dissolved oxygen in both intensity and lifetime, and the respective Stern-Volmer plot follows a nonlinear behavior justified by a two-site model. Because of the merits of large Stokes shift (~140 nm), easy fabrication, and robustness, the pyrene@micelle sensors are very attractive for practical determination of oxygen. PMID:26539471

  1. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization

    NASA Astrophysics Data System (ADS)

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-01

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~ 6 s.

  2. Oxygen and life on earth: an anesthesiologist's views on oxygen evolution, discovery, sensing, and utilization.

    PubMed

    Lindahl, Sten G E

    2008-07-01

    The advent of oxygenic photosynthesis and the accumulation of oxygen in our atmosphere opened up new possibilities for the development of life on Earth. The availability of oxygen, the most capable electron acceptor on our planet, allowed the development of highly efficient energy production from oxidative phosphorylation, which shaped the evolutionary development of aerobic life forms from the first multicellular organisms to the vertebrates.

  3. Luminescent sensing and imaging of oxygen: Fierce competition to the Clark electrode

    PubMed Central

    2015-01-01

    Luminescence‐based sensing schemes for oxygen have experienced a fast growth and are in the process of replacing the Clark electrode in many fields. Unlike electrodes, sensing is not limited to point measurements via fiber optic microsensors, but includes additional features such as planar sensing, imaging, and intracellular assays using nanosized sensor particles. In this essay, I review and discuss the essentials of (i) common solid‐state sensor approaches based on the use of luminescent indicator dyes and host polymers; (ii) fiber optic and planar sensing schemes; (iii) nanoparticle‐based intracellular sensing; and (iv) common spectroscopies. Optical sensors are also capable of multiple simultaneous sensing (such as O2 and temperature). Sensors for O2 are produced nowadays in large quantities in industry. Fields of application include sensing of O2 in plant and animal physiology, in clinical chemistry, in marine sciences, in the chemical industry and in process biotechnology. PMID:26113255

  4. Microwave remote sensing of snowpack properties

    NASA Technical Reports Server (NTRS)

    Rango, A. (Editor)

    1980-01-01

    Topic concerning remote sensing capabilities for providing reliable snow cover data and measurement of snow water equivalents are discussed. Specific remote sensing technqiues discussed include those in the microwave region of the electromagnetic spectrum.

  5. Glucose sensing molecules having selected fluorescent properties

    DOEpatents

    Satcher, Jr., Joe H.; Lane, Stephen M.; Darrow, Christopher B.; Cary, Douglas R.; Tran, Joe Anh

    2004-01-27

    An analyte sensing fluorescent molecule that employs intramolecular electron transfer is designed to exhibit selected fluorescent properties in the presence of analytes such as saccharides. The selected fluorescent properties include excitation wavelength, emission wavelength, fluorescence lifetime, quantum yield, photostability, solubility, and temperature or pH sensitivity. The compound comprises an aryl or a substituted phenyl boronic acid that acts as a substrate recognition component, a fluorescence switch component, and a fluorophore. The fluorophore and switch component are selected such that the value of the free energy for electron transfer is less than about 3.0 kcal mol.sup.-1. Fluorescent compounds are described that are excited at wavelengths greater than 400 nm and emit at wavelengths greater than 450 nm, which is advantageous for optical transmission through skin. The fluorophore is typically selected from transition metal-ligand complexes and thiazine, oxazine, oxazone, or oxazine-one as well as anthracene compounds. The fluorescent compound can be immobilized in a glucose permeable biocompatible polymer matrix that is implantable below the skin.

  6. Morphology impact on oxygen sensing ability of Ru(dpp)3Cl2 containing biocompatible polymers.

    PubMed

    Zhao, Susan Y; Harrison, Benjamin S

    2015-08-01

    Especially for tissue engineering applications, the diffusion of oxygen is a critical factor affecting spatial distribution and migration of cells. The cellular oxygen demand also fluctuates depending on tissue type and growth phase. Sensors that determine dissolved oxygen levels under biological conditions provide critical metabolic information about the growing cells as well as the state of the tissue culture within the tissue scaffold. This work focused on the effect of the scaffold morphology on the oxygen sensing response time. It was found that electrospun scaffolds had a faster oxygen-sensing response time than their bulk film counterparts. Tris-(4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride doped electrospun fiber mats of polycaprolactone (PCL) were found to be the most responsive to the presence of oxygen, followed by polyethylene (PEO) glycol mats. Systems containing poly vinyl alcohol were found to be the least responsive. This would suggest that, out of all the polymers tested, PCL and PEO are the most suitable biomaterials for oxygen-sensing applications. PMID:26042716

  7. Morphology impact on oxygen sensing ability of Ru(dpp)3Cl2 containing biocompatible polymers.

    PubMed

    Zhao, Susan Y; Harrison, Benjamin S

    2015-08-01

    Especially for tissue engineering applications, the diffusion of oxygen is a critical factor affecting spatial distribution and migration of cells. The cellular oxygen demand also fluctuates depending on tissue type and growth phase. Sensors that determine dissolved oxygen levels under biological conditions provide critical metabolic information about the growing cells as well as the state of the tissue culture within the tissue scaffold. This work focused on the effect of the scaffold morphology on the oxygen sensing response time. It was found that electrospun scaffolds had a faster oxygen-sensing response time than their bulk film counterparts. Tris-(4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride doped electrospun fiber mats of polycaprolactone (PCL) were found to be the most responsive to the presence of oxygen, followed by polyethylene (PEO) glycol mats. Systems containing poly vinyl alcohol were found to be the least responsive. This would suggest that, out of all the polymers tested, PCL and PEO are the most suitable biomaterials for oxygen-sensing applications.

  8. Molybdenum chloride incorporated sol-gel materials for oxygen sensing above room temperature

    NASA Astrophysics Data System (ADS)

    Osborn, D. J., III

    Maximizing the efficiency of the combustion process requires the ability to sense oxygen levels over a broad range of concentrations with fast response times under rapidly varying conditions of pressure and temperature to maintain the correct fuel/oxygen ratio in real-time. Quenching of the luminescence from organometallic compounds by oxygen has been used to develop a number of fiber-based sensors. A major drawback of these organometallic indicators for combustion applications is that the chromophores degrade with time, have a limited operational temperature range, typically room temperature +/-25°C, and lack long-term reliability. This work investigates luminescent molybdenum clusters based on Mo6Cl12 were as replacements for organometallic indicators. A study of the high temperature stability of Mo6Cl 12 in air revealed irreversible changes in the optical absorption spectrum at T >250°C and a loss of the red luminescence characteristic of the pristine clusters. Thermal aging experiments run in air and under nitrogen point to oxidation of the clusters as the cause of the change in optical properties. X-ray powder diffraction measurements on samples annealed at 300°C under controlled conditions are consistent with oxidation of Mo6Cl 12 to form MoO3. Optical and thermal aging experiments show that K2Mo6Cl14•1H2O, the alkali metal salt of Mo6Cl12, has higher thermal stability and remains luminescent after long-term aging in air at 280°C. Methods were developed for depositing K2Mo6Cl14•1H 2O-incorporated sol--gel films on planar and optical fiber substrates by dip coating and spray coating. The mechanical properties of the films depended on the film thickness; thin films were stable, but cracks often formed in the thicker films needed for sensors. This problem was addressed using two strategies: altering the components of the sol--gel solutions used to embed the clusters and by devising a composite approach to sensing layers where a slurry of fully cured sol

  9. Epidermal sensing of oxygen is essential for systemic hypoxic response.

    PubMed

    Boutin, Adam T; Weidemann, Alexander; Fu, Zhenxing; Mesropian, Lernik; Gradin, Katarina; Jamora, Colin; Wiesener, Michael; Eckardt, Kai-Uwe; Koch, Cameron J; Ellies, Lesley G; Haddad, Gabriel; Haase, Volker H; Simon, M Celeste; Poellinger, Lorenz; Powell, Frank L; Johnson, Randall S

    2008-04-18

    Skin plays an essential role, mediated in part by its remarkable vascular plasticity, in adaptation to environmental stimuli. Certain vertebrates, such as amphibians, respond to hypoxia in part through the skin; but it is unknown whether this tissue can influence mammalian systemic adaptation to low oxygen levels. We have found that epidermal deletion of the hypoxia-responsive transcription factor HIF-1alpha inhibits renal erythropoietin (EPO) synthesis in response to hypoxia. Conversely, mice with an epidermal deletion of the von Hippel-Lindau (VHL) factor, a negative regulator of HIF, have increased EPO synthesis and polycythemia. We show that nitric oxide release induced by the HIF pathway acts on cutaneous vascular flow to increase systemic erythropoietin expression. These results demonstrate that in mice the skin is a critical mediator of systemic responses to environmental oxygen.

  10. Spatiotemporal Oxygen Sensing Using Dual Emissive Boron Dye–Polylactide Nanofibers

    PubMed Central

    2015-01-01

    Oxygenation in tissue scaffolds continues to be a limiting factor in regenerative medicine despite efforts to induce neovascularization or to use oxygen-generating materials. Unfortunately, many established methods to measure oxygen concentration, such as using electrodes, require mechanical disturbance of the tissue structure. To address the need for scaffold-based oxygen concentration monitoring, a single-component, self-referenced oxygen sensor was made into nanofibers. Electrospinning process parameters were tuned to produce a biomaterial scaffold with specific morphological features. The ratio of an oxygen sensitive phosphorescence signal to an oxygen insensitive fluorescence signal was calculated at each image pixel to determine an oxygenation value. A single component boron dye–polymer conjugate was chosen for additional investigation due to improved resistance to degradation in aqueous media compared to a boron dye polymer blend. Standardization curves show that in fully supplemented media, the fibers are responsive to dissolved oxygen concentrations less than 15 ppm. Spatial (millimeters) and temporal (minutes) ratiometric gradients were observed in vitro radiating outward from the center of a dense adherent cell grouping on scaffolds. Sensor activation in ischemia and cell transplant models in vivo show oxygenation decreases on the scale of minutes. The nanofiber construct offers a robust approach to biomaterial scaffold oxygen sensing. PMID:25426706

  11. Oxygen Sensing for Industrial Safety — Evolution and New Approaches

    PubMed Central

    Willett, Martin

    2014-01-01

    The requirement for the detection of oxygen in industrial safety applications has historically been met by electrochemical technologies based on the consumption of metal anodes. Products using this approach have been technically and commercially successful for more than three decades. However, a combination of new requirements is driving the development of alternative approaches offering fresh opportunities and challenges. This paper reviews some key aspects in the evolution of consumable anode products and highlights recent developments in alternative technologies aimed at meeting current and anticipated future needs in this important application. PMID:24681673

  12. "Oxygen Sensing" by Na,K-ATPase: These Miraculous Thiols.

    PubMed

    Bogdanova, Anna; Petrushanko, Irina Y; Hernansanz-Agustín, Pablo; Martínez-Ruiz, Antonio

    2016-01-01

    Control over the Na,K-ATPase function plays a central role in adaptation of the organisms to hypoxic and anoxic conditions. As the enzyme itself does not possess O2 binding sites its "oxygen-sensitivity" is mediated by a variety of redox-sensitive modifications including S-glutathionylation, S-nitrosylation, and redox-sensitive phosphorylation. This is an overview of the current knowledge on the plethora of molecular mechanisms tuning the activity of the ATP-consuming Na,K-ATPase to the cellular metabolic activity. Recent findings suggest that oxygen-derived free radicals and H2O2, NO, and oxidized glutathione are the signaling messengers that make the Na,K-ATPase "oxygen-sensitive." This very ancient signaling pathway targeting thiols of all three subunits of the Na,K-ATPase as well as redox-sensitive kinases sustains the enzyme activity at the "optimal" level avoiding terminal ATP depletion and maintaining the transmembrane ion gradients in cells of anoxia-tolerant species. We acknowledge the complexity of the underlying processes as we characterize the sources of reactive oxygen and nitrogen species production in hypoxic cells, and identify their targets, the reactive thiol groups which, upon modification, impact the enzyme activity. Structured accordingly, this review presents a summary on (i) the sources of free radical production in hypoxic cells, (ii) localization of regulatory thiols within the Na,K-ATPase and the role reversible thiol modifications play in responses of the enzyme to a variety of stimuli (hypoxia, receptors' activation) (iii) redox-sensitive regulatory phosphorylation, and (iv) the role of fine modulation of the Na,K-ATPase function in survival success under hypoxic conditions. The co-authors attempted to cover all the contradictions and standing hypotheses in the field and propose the possible future developments in this dynamic area of research, the importance of which is hard to overestimate. Better understanding of the processes

  13. Remote sensing for quantification of agronomic properties

    NASA Astrophysics Data System (ADS)

    Sullivan, Dana Grace

    Remote sensing (RS) may be used to rapidly assess surface features and facilitate natural resource management, precision agriculture and soil survey. Information obtained in such a way would streamline data collection and improve diagnostic capabilities. Current RS technology has had limited testing, particularly within the Southeast. Our study was designed to evaluate RS as a rapid assessment tool in three different natural resource applications: nitrogen (N) management in a corn crop (Zea mays L.), assessment of in situ crop residue cover, and quantification of near-surface soil properties. In 2000, study sites were established in four physiographic provinces of Alabama: Tennessee Valley, Ridge and Valley, Appalachian Plateau, and Coastal Plain. Spectral measurements were acquired via spectroradiometer (350--1050 nm), airborne ATLAS multispectral scanner (400--12,500 nm), and IKONOS satellite (450--900 nm). Corn plots were established from fresh-tilled ground in a completely randomized design at the Appalachian Plateau and Coastal Plain study sites in 2000. Plots received four N rates (0, 56, 112, and 168 kg N ha-1 ), and were maintained for three consecutive growing seasons. Spectroradiometer data were acquired biweekly from V6-R2 and ATLAS and IKONOS were acquired per availability. Results showed vegetation indices derived from hand-held spectroradiometer measurements as early as V6-V8 were linearly related to yield and tissue N. ATLAS imagery showed promise at the AP site during the V6 stage (r2 = 0.66), but no significant relationships between plant N and IKONOS imagery were observed. Residue plots (15m x 15m) were established at the Appalachian Plateau and Coastal Plain in 2000 and 200. Residue treatments consisted of hand applied wheat straw cover (0, 10 20, 50, or 80%) arranged in a completely randomized design. Spectroradiometer data were acquired monthly and ATLAS and IKONOS were acquired per availability. Residue cover estimates were best with ATLAS

  14. Role Of Hif2α Oxygen Sensing Pathway In Bronchial Epithelial Club Cell Proliferation

    PubMed Central

    Torres-Capelli, Mar; Marsboom, Glenn; Li, Qilong Oscar Yang; Tello, Daniel; Rodriguez, Florinda Melendez; Alonso, Tamara; Sanchez-Madrid, Francisco; García-Rio, Francisco; Ancochea, Julio; Aragonés, Julián

    2016-01-01

    Oxygen-sensing pathways executed by the hypoxia-inducible factors (HIFs) induce a cellular adaptive program when oxygen supply becomes limited. However, the role of the HIF oxygen-sensing pathway in the airway response to hypoxic stress in adulthood remains poorly understood. Here we found that in vivo exposure to hypoxia led to a profound increase in bronchial epithelial cell proliferation mainly confined to Club (Clara) cells. Interestingly, this response was executed by hypoxia-inducible factor 2α (HIF2α), which controls the expression of FoxM1, a recognized proliferative factor of Club cells. Furthermore, HIF2α induced the expression of the resistin-like molecules α and β (RELMα and β), previously considered bronchial epithelial growth factors. Importantly, despite the central role of HIF2α, this proliferative response was not initiated by in vivo Vhl gene inactivation or pharmacological inhibition of prolyl hydroxylase oxygen sensors, indicating the molecular complexity of this response and the possible participation of other oxygen-sensing pathways. Club cells are principally involved in protection and maintenance of bronchial epithelium. Thus, our findings identify a novel molecular link between HIF2α and Club cell biology that can be regarded as a new HIF2α-dependent mechanism involved in bronchial epithelium adaptation to oxygen fluctuations. PMID:27150457

  15. Correlating defect induced ferromagnetism and gas sensing properties of undoped tin oxide sensors

    NASA Astrophysics Data System (ADS)

    Kamble, Vinayak B.; Umarji, Arun M.

    2014-06-01

    A correlation between gas sensing properties and defect induced Room Temperature Ferromagnetism (RTFM) is demonstrated in non-stoichiometric SnO2 prepared by solution combustion method. The presence of oxygen vacancies (VO), confirmed by RTFM is identified as the primary factor for enhanced gas sensing effect. The as-prepared SnO2 shows high saturation magnetization of ˜0.018 emu/g as compared to ˜0.002 and ˜0.0005 emu/g in annealed samples and SnO2 prepared by precipitation respectively. The SnO2 prepared by precipitation which is an equilibrium method of synthesis shows lesser defects compared to the combustion product and hence exhibits lesser sensitivity in spite of smaller crystallite size. The study utilizes RTFM as a potential tool to characterize metal oxide gas sensors and recognizes the significance of oxygen vacancies in sensing mechanism over the microstructure.

  16. Erythrocytes Are Oxygen-Sensing Regulators of the Cerebral Microcirculation.

    PubMed

    Wei, Helen Shinru; Kang, Hongyi; Rasheed, Izad-Yar Daniel; Zhou, Sitong; Lou, Nanhong; Gershteyn, Anna; McConnell, Evan Daniel; Wang, Yixuan; Richardson, Kristopher Emil; Palmer, Andre Francis; Xu, Chris; Wan, Jiandi; Nedergaard, Maiken

    2016-08-17

    Energy production in the brain depends almost exclusively on oxidative metabolism. Neurons have small energy reserves and require a continuous supply of oxygen (O2). It is therefore not surprising that one of the hallmarks of normal brain function is the tight coupling between cerebral blood flow and neuronal activity. Since capillaries are embedded in the O2-consuming neuropil, we have here examined whether activity-dependent dips in O2 tension drive capillary hyperemia. In vivo analyses showed that transient dips in tissue O2 tension elicit capillary hyperemia. Ex vivo experiments revealed that red blood cells (RBCs) themselves act as O2 sensors that autonomously regulate their own deformability and thereby flow velocity through capillaries in response to physiological decreases in O2 tension. This observation has broad implications for understanding how local changes in blood flow are coupled to synaptic transmission. PMID:27499087

  17. Oxygen-Sensing Methods in Biomedicine from the Macroscale to the Microscale.

    PubMed

    Roussakis, Emmanuel; Li, Zongxi; Nichols, Alexander J; Evans, Conor L

    2015-07-13

    Oxygen monitoring has been a topic of exhaustive study given its central role in the biochemistry of life. The ability to quantify the physiological distribution and real-time dynamics of oxygen from sub-cellular to macroscopic levels is required to fully understand the mechanisms associated with both normal physiology and disease states. This Review will present the most significant recent advances in the development of oxygen-sensing materials and techniques, including polarographic, nuclear medicine, magnetic resonance, and optical approaches, that can be applied specifically for the real-time monitoring of oxygen dynamics in cellular and tissue environments. As some of the most exciting recent advances in synthetic methods and biomedical applications have been in the field of optical oxygen sensors, a major focus will be on the development of these toolkits.

  18. Thickness Dependency of Thin Film Samaria Doped Ceria for Oxygen Sensing

    SciTech Connect

    Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Jiang, Weilin; Varga, Tamas; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

    2011-01-01

    High temperature oxygen sensors are widely used for exhaust gas monitoring in automobiles. This particular study explores the use of thin film single crystalline samaria doped ceria as the oxygen sensing material. Desired signal to noise ratio can be achieved in a material system with high conductivity. From previous studies it is established that 6 atomic percent samarium doping is the optimum concentration for thin film samaria doped ceria to achieve high ionic conductivity. In this study, the conductivity of the 6 atomic percent samaria doped ceria thin film is measured as a function of the sensing film thickness. Hysteresis and dynamic response of this sensing platform is tested for a range of oxygen pressures from 0.001 Torr to 100 Torr for temperatures above 673 K. An attempt has been made to understand the physics behind the thickness dependent conductivity behavior of this sensing platform by developing a hypothetical operating model and through COMSOL simulations. This study can be used to identify the parameters required to construct a fast, reliable and compact high temperature oxygen sensor.

  19. Cellular Oxygen and Nutrient Sensing in Microgravity Using Time-Resolved Fluorescence Microscopy

    NASA Technical Reports Server (NTRS)

    Szmacinski, Henryk

    2003-01-01

    Oxygen and nutrient sensing is fundamental to the understanding of cell growth and metabolism. This requires identification of optical probes and suitable detection technology without complex calibration procedures. Under this project Microcosm developed an experimental technique that allows for simultaneous imaging of intra- and inter-cellular events. The technique consists of frequency-domain Fluorescence Lifetime Imaging Microscopy (FLIM), a set of identified oxygen and pH probes, and methods for fabrication of microsensors. Specifications for electronic and optical components of FLIM instrumentation are provided. Hardware and software were developed for data acquisition and analysis. Principles, procedures, and representative images are demonstrated. Suitable lifetime sensitive oxygen, pH, and glucose probes for intra- and extra-cellular measurements of analyte concentrations have been identified and tested. Lifetime sensing and imaging have been performed using PBS buffer, culture media, and yeast cells as a model systems. Spectral specifications, calibration curves, and probes availability are also provided in the report.

  20. Effect of oxygenates blending with gasoline to improve fuel properties

    NASA Astrophysics Data System (ADS)

    Babazadeh Shayan, Soheil; Seyedpour, Seyed Morteza; Ommi, Fathollah

    2012-07-01

    The purpose of this paper is to study the effect of oxygenate additives into gasoline for the improvement of physicochemical properties of blends. Methyl Tertiary Butyl Ether (MTBE), Methanol, Tertiary butyl alcohol (TBA), and Tertiary amyl alcohol (TAA) blend into unleaded gasoline with various blended rates of 2.5%, 5%, 7.5%, 10%, 15%, and 20%. Physicochemical properties of blends are analyzed by the standard American Society of Testing and Materials (ASTM) methods. Methanol, TBA, and TAA increase density of the mixtures, but MTBE decreases density. The addition of oxygenates lead to a distortion of the base gasoline's distillation curves. The Reid vapor pressure (RVP) of gasoline is found to increase with the addition of the oxygenated compounds. All oxygenates improve both motor and research octane numbers. Among these four additives, TBA shows the best fuel properties.

  1. Properties of coherence-gated wavefront sensing.

    PubMed

    Rueckel, Markus; Denk, Winfried

    2007-11-01

    Coherence-gated wavefront sensing (CGWS) allows the determination of wavefront aberrations in strongly scattering tissue and their correction by adaptive optics. This allows, e.g., the restoration of the diffraction limit in light microscopy. Here, we develop a model, based on ray tracing of ballistic light scattered from a set of discrete scatterers, to characterize CGWS performance as it depends on coherence length, scatterer density, coherence-gate position, and polarization. The model is evaluated by using Monte Carlo simulation and verified against experimental measurements. We show, in particular, that all aberrations needed for adaptive wavefront restoration are correctly sensed if circularly polarized light is used. PMID:17975579

  2. Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

    NASA Astrophysics Data System (ADS)

    Rajyaguru, Bhargav; Gadani, Keval; Rathod, K. N.; Solanki, Sapana; Kansara, S. B.; Pandya, D. D.; Shah, N. A.; Solanki, P. S.

    2016-05-01

    In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are more capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.

  3. FIBER OPTICAL MICRO-DETECTORS FOR OXYGEN SENSING IN POWER PLANTS

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III; Po Zhang

    2005-07-01

    A reflection mode fiber optic oxygen sensor is being developed that can operate at high temperatures for power plant applications. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Two critical materials issues are the cluster's ability to withstand high temperatures when immobilized in a porous the sol-gel support, and whether after heating to high temperatures, the sol-gel matrix maintains a high and constant permeability to oxygen to support rapid quenching of luminescence. We used a composite materials approach to prepare stable sensing layers on optical fibers. We dispersed 60 w/w% of a pre-cured sol-gel composite containing the potassium salt of molybdenum clusters (K{sub 2}Mo{sub 6}Cl{sub 14}) into a sol-gel binder solution, and established the conditions necessary for deposition of sol-gel films on optical fibers and planar substrates. The fiber sensor has an output signal of 5 nW when pumped with an inexpensive commercial 365 nm ultraviolet light emitting diode (LED). Quenching of the sensor signal by oxygen was observed up to a gas temperature of 175 C with no degradation of the oxygen permeability of the composite after high temperature cycling. On planar substrates the cluster containing composite responds within <1 second to a gas exchange from nitrogen to oxygen, indicating the feasibility of real-time oxygen detection.

  4. Facet effects of palladium nanocrystals for oxygen reduction in ionic liquids and for sensing applications

    NASA Astrophysics Data System (ADS)

    Tang, Yongan; Chi, Xiaowei; Zou, Shouzhong; Zeng, Xiangqun

    2016-03-01

    Palladium nanocrystals enclosed by {100} and {110} crystal facets, were successfully synthesized through an aqueous one-pot synthesis method. A new thermal annealing approach was developed for fabricating these palladium nanocrystals as a working electrode on a gas permeable membrane to study the facet effects of the oxygen reduction process in an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]). Results were compared with the same processes at a conventional platinum electrode. Our study shows that the structural difference between the two facets of Pd nanocrystals has little effect on the oxygen reduction process but significantly affects the oxidation process of the superoxide. It is found that the Pd{110}/IL interface can better stabilize superoxide radicals revealed by a more positive oxidation potential compared to that of Pd{100}. In addition, the analytical characteristic of utilizing both palladium nanocrystals as electrodes for oxygen sensing is comparable with a polycrystal platinum oxygen sensor, in which Pd{110} presents the best sensitivity and lowest detection limit. Our results demonstrate the facet-dependence of oxygen reduction in an ionic liquid medium and provide the fundamental information needed to guide the applications of palladium nanocrystals in electrochemical gas sensor and fuel cell research.Palladium nanocrystals enclosed by {100} and {110} crystal facets, were successfully synthesized through an aqueous one-pot synthesis method. A new thermal annealing approach was developed for fabricating these palladium nanocrystals as a working electrode on a gas permeable membrane to study the facet effects of the oxygen reduction process in an ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Bmpy][NTf2]). Results were compared with the same processes at a conventional platinum electrode. Our study shows that the structural difference between the two facets of Pd

  5. A paradigm shift in oxygen sensing with a twist in the tale!

    PubMed

    O'Halloran, Ken D

    2016-09-01

    AMP-activated protein kinase (AMPK) is pivotal to metabolic homoeostasis in eukaryotes, serving as a critical energy sensor. Increased AMPK activity during oxygen deprivation (hypoxia) protects against potentially catastrophic deficits in ATP supply. Although the nervous system circuitry for elaboration of the complex cardiorespiratory response to hypoxia has been understood in some detail for many decades, there is continued and considerable interest in the molecular machinery underpinning the mechanism(s) of oxygen sensing. In this issue of the Biochemical Journal, Evans et al. [(2016) Biochem. J.] review their recent work, which points to a pivotal role for AMPK in the transduction of cellular hypoxic stress to integrated ventilatory behaviour, critical in the defence of whole-body oxygen homoeostasis. Of great surprise, there is profound blunting of the hyperventilatory response to hypoxic stress in AMPK deficient mice, with resultant dysregulated breathing arising in spite of normal peripheral oxygen sensing and appropriate sensory input to the brain! Their pointedly provocative review challenges current dogma, and in doing so raises intriguing questions that probe fundamental aspects of our understanding of the mammalian ventilatory response to hypoxic stress. The engaging review by Evans et al. [(2016) Biochem. J.] is an interesting read that is sure to encourage colourful debate. PMID:27574024

  6. Remote Sensing of Dissolved Oxygen and Nitrogen in Water Using Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Ganoe, Rene; DeYoung, Russell J.

    2013-01-01

    The health of an estuarine ecosystem is largely driven by the abundance of dissolved oxygen and nitrogen available for maintenance of plant and animal life. An investigation was conducted to quantify the concentration of dissolved molecular oxygen and nitrogen in water by means of Raman spectroscopy. This technique is proposed for the remote sensing of dissolved oxygen in the Chesapeake Bay, which will be utilized by aircraft in order to survey large areas in real-time. A proof of principle system has been developed and the specifications are being honed to maximize efficiency for the final application. The theoretical criteria of the research, components of the experimental system, and key findings are presented in this report

  7. Saccharide sensing molecules having enhanced fluorescent properties

    DOEpatents

    Satcher Jr., Joe H.; Lane, Stephen M.; Darrow, Christopher B.; Cary, Douglas R.; Tran, Joe Anh

    2004-01-06

    The present invention provides formulae for fluorescent compounds that have a number of properties which make them uniquely suited for use in sensors of analytes such as saccharides. The advantageous fluorescent properties include favorable excitation wavelengths, emission wavelengths, fluorescence lifetimes, and photostability. Additional advantageous properties include enhanced aqueous solubility, as well as temperature and pH sensitivity. The compound comprises an aryl or a substituted phenyl botonic acid that acts as a substrate recognition component, a fluorescence switch component, and a fluorophore. Fluorescent compounds are described that are excited at wavelengths greater than 400 nm and emit at wavelengths greater than 450 nm, which is advantageous for optical transmission through skin. The fluorophore is typically selected from transition metal-ligand complexes and thiazine, oxazine, oxazone, or oxazine-one as well as anthracene compounds. The fluorescent compound can be immobilized in a glucose permeable biocompatible polymer matrix that is implantable below the skin.

  8. Properties of reactive oxygen species by quantum Monte Carlo

    SciTech Connect

    Zen, Andrea; Trout, Bernhardt L.; Guidoni, Leonardo

    2014-07-07

    The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of chemistry, biology, and atmospheric science. Nevertheless, the electronic structure of such species is a challenge for ab initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution, and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular, we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as N{sup 3} − N{sup 4}, where N is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles.

  9. Properties of reactive oxygen species by quantum Monte Carlo.

    PubMed

    Zen, Andrea; Trout, Bernhardt L; Guidoni, Leonardo

    2014-07-01

    The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of chemistry, biology, and atmospheric science. Nevertheless, the electronic structure of such species is a challenge for ab initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution, and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular, we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as N(3) - N(4), where N is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles. PMID:25005287

  10. Properties of reactive oxygen species by quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Zen, Andrea; Trout, Bernhardt L.; Guidoni, Leonardo

    2014-07-01

    The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of chemistry, biology, and atmospheric science. Nevertheless, the electronic structure of such species is a challenge for ab initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution, and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular, we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as N3 - N4, where N is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles.

  11. Remote sensing of aerosol properties during CARES

    NASA Astrophysics Data System (ADS)

    Kassianov, Evgueni; Barnard, James; Pekour, Mikhail; Flynn, Connor; Ferrare, Richard; Hostetler, Chris; Hair, John; Jobson, Bertram T.

    2011-11-01

    One month of MFRSR data collected at two sites in the central California (USA) region during the CARES campaign are processed and the MFRSR-derived AODs at 500 nm wavelength are compared with available AODs provided by AERONET measurements. We find that the MFRSR and AERONET AODs are small (~0.05) and comparable. A reasonable quantitative agreement between column aerosol size distributions (up to 2 μm) from the MFRSR and AERONET retrievals is illustrated as well. Analysis of the retrieved (MFRSR and AERONET) and in situ measured aerosol size distributions suggests that the contribution of the coarse mode to aerosol optical properties is substantial for several days. The results of a radiative closure experiment performed for the two sites and one-month period show a favorable agreement between the calculated and measured broadband downwelling irradiances (bias does not exceed about 3 Wm-2), and thus imply that the MFRSR-derived aerosol optical properties are reasonable.

  12. Remote Sensing of Aerosol Properties during CARES

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Flynn, Connor J.; Ferrare, R.; Hostetler, Chris A.; Hair, John; Jobson, Bertram Thomas

    2011-10-01

    One month of MFRSR data collected at two sites in the central California (USA) region during the CARES campaign are processed and the MFRSR-derived AODs at 500 nm wavelength are compared with available AODs provided by AERONET measurements. We find that the MFRSR and AERONET AODs are small ({approx}0.05) and comparable. A reasonable quantitative agreement between column aerosol size distributions (up to 2 um) from the MFRSR and AERONET retrievals is illustrated as well. Analysis of the retrieved (MFRSR and AERONET) and in situ measured aerosol size distributions suggests that the contribution of the coarse mode to aerosol optical properties is substantial for several days. The results of a radiative closure experiment performed for the two sites and one-month period show a favorable agreement between the calculated and measured broadband downwelling irradiances (bias does not exceed about 3 Wm-2), and thus imply that the MFRSR-derived aerosol optical properties are reasonable.

  13. Optical oxygen sensing systems for drug discovery applications: Respirometric Screening Technology (RST)

    NASA Astrophysics Data System (ADS)

    Papkovsky, Dmitri B.; Hynes, James; Fernandes, Richard

    2005-11-01

    Quenched-fluorescence oxygen sensing allows non-chemical, reversible, real-time monitoring of molecular oxygen and rates of oxygen consumption in biological samples. Using this approach we have developed Respirometric Screening Technology (RST); a platform which facilitates the convenient analysis of cellular oxygen uptake. This in turn allows the investigation of compounds and processes which affect respiratory activity. The RST platform employs soluble phosphorescent oxygen-sensitive probes, which may be assessed in standard microtitter plates on a fluorescence plate reader. New formats of RST assays and time-resolved fluorescence detection instrumentation developed by Luxcel provide improvements in assay sensitivity, miniaturization and overall performance. RST has a diverse range of applications in drug discovery area including high throughput analysis of mitochondrial function; studies of mechanisms of toxicity and apoptosis; cell and animal based screening of compound libraries and environmental samples; and, sterility testing. RST has been successfully validated with a range of practical targets and adopted by several leading pharmaceutical companies.

  14. Effective Potential Energies and Transport Properties for Nitrogen and Oxygen

    NASA Technical Reports Server (NTRS)

    Stallcop, James R.; Partridge, Harry; Levin, Eugene; Kwak, Dochan (Technical Monitor)

    2001-01-01

    The results of recent theoretical studies for N--N2, O--O2, N2--N2 interactions are applied to the transport properties of nitrogen and oxygen gases. The theoretical results are used to select suitable oxygen interaction energies from previous work for determining the diffusion and viscosity coefficients at high temperatures. A universal formulation is applied to determine the collision integrals for O2--O2 interactions at high temperatures and to calculate certain ratios for determining higher-order collision integrals.

  15. Chlorine sensing properties of zigzag boron nitride nanoribbons

    NASA Astrophysics Data System (ADS)

    Srivastava, Pankaj; Jaiswal, Neeraj K.; Tripathi, Gagan Kant

    2014-05-01

    The density functional theory based first-principles calculations have been employed to explore the chlorine sensing properties of zigzag boron nitride nanoribbons (ZBNNR). The sensing was investigated by calculating electronic structures and current-voltage (I-V) behavior. Three different possibilities were considered for the chlorine adsorption on ZBNNR and the findings were compared with bare ribbons. It is revealed that presence of chlorine has a profound effect on the electronic and transport properties of ZBNNR. Bare ZBNNR are half-metallic in nature whereas chlorine adsorption turns them semiconducting irrespective of adsorption site. Further, the negative differential resistance has been observed in bare ribbons which disappear upon the chlorine adsorption. Enhanced sensing capability is predicted when chlorine is attached at the N edge or at both the edges of the ZBNNR.

  16. Study the gas sensing properties of boron nitride nanosheets

    SciTech Connect

    Sajjad, Muhammad; Feng, Peter

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized boron nitride nanosheets (BNNSs) on silicon substrate. • We analyzed gas sensing properties of BNNSs-based gas-sensor device. • CH{sub 4} gas is used to measure gas-sensing properties of the device. • Quick response and recovery time of the device is recorded. • BNNSs showed excellent sensitivity to the working gas. - Abstract: In the present communication, we report on the synthesis of boron nitride nanosheets (BNNSs) and study of their gas sensing properties. BNNSs are synthesized by irradiating pyrolytic hexagonal boron nitride (h-BN) target using CO{sub 2} laser pulses. High resolution transmission electron microscopic measurements (HRTEM) revealed 2-dientional honeycomb crystal lattice structure of BNNSs. HRTEM, electron diffraction, XRD and Raman scattering measurements clearly identified h-BN. Gas sensing properties of synthesized BNNSs were analyzed with prototype gas sensor using methane as working gas. A systematic response curve of the sensor is recorded in each cycle of gas “in” and “out”; suggesting excellent sensitivity and high performance of BNNSs-based gas-sensor.

  17. Metal oxide nanostructures and their gas sensing properties: a review.

    PubMed

    Sun, Yu-Feng; Liu, Shao-Bo; Meng, Fan-Li; Liu, Jin-Yun; Jin, Zhen; Kong, Ling-Tao; Liu, Jin-Huai

    2012-01-01

    Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given. PMID:22736968

  18. Metal oxide nanostructures and their gas sensing properties: a review.

    PubMed

    Sun, Yu-Feng; Liu, Shao-Bo; Meng, Fan-Li; Liu, Jin-Yun; Jin, Zhen; Kong, Ling-Tao; Liu, Jin-Huai

    2012-01-01

    Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

  19. Oxygen Sensing by Arterial Chemoreceptors Depends on Mitochondrial Complex I Signaling.

    PubMed

    Fernández-Agüera, M Carmen; Gao, Lin; González-Rodríguez, Patricia; Pintado, C Oscar; Arias-Mayenco, Ignacio; García-Flores, Paula; García-Pergañeda, Antonio; Pascual, Alberto; Ortega-Sáenz, Patricia; López-Barneo, José

    2015-11-01

    O2 sensing is essential for mammalian homeostasis. Peripheral chemoreceptors such as the carotid body (CB) contain cells with O2-sensitive K(+) channels, which are inhibited by hypoxia to trigger fast adaptive cardiorespiratory reflexes. How variations of O2 tension (PO2) are detected and the mechanisms whereby these changes are conveyed to membrane ion channels have remained elusive. We have studied acute O2 sensing in conditional knockout mice lacking mitochondrial complex I (MCI) genes. We inactivated Ndufs2, which encodes a protein that participates in ubiquinone binding. Ndufs2-null mice lose the hyperventilatory response to hypoxia, although they respond to hypercapnia. Ndufs2-deficient CB cells have normal functions and ATP content but are insensitive to changes in PO2. Our data suggest that chemoreceptor cells have a specialized succinate-dependent metabolism that induces an MCI state during hypoxia, characterized by the production of reactive oxygen species and accumulation of reduced pyridine nucleotides, which signal neighboring K(+) channels.

  20. Fiber-Based Laser Transmitter for Oxygen A-Band Spectroscopy and Remote Sensing

    NASA Technical Reports Server (NTRS)

    Stephen, Mark A.; Abshire, James B.

    2010-01-01

    A fiber-based laser transmitter has been designed for active remote-sensing spectroscopy. The transmitter uses a master-oscillator-power-amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled nonlinear crystal. The utility of this single-frequency, wavelength-tunable, power-scalable laser has been demonstrated in a spectroscopic measurement of the diatomic oxygen A-band.

  1. Diversity of Magneto-Aerotactic Behaviors and Oxygen Sensing Mechanisms in Cultured Magnetotactic Bacteria

    PubMed Central

    Lefèvre, Christopher T.; Bennet, Mathieu; Landau, Livnat; Vach, Peter; Pignol, David; Bazylinski, Dennis A.; Frankel, Richard B.; Klumpp, Stefan; Faivre, Damien

    2014-01-01

    Microorganisms living in gradient environments affect large-scale processes, including the cycling of elements such as carbon, nitrogen or sulfur, the rates and fate of primary production, and the generation of climatically active gases. Aerotaxis is a common adaptation in organisms living in the oxygen gradients of stratified environments. Magnetotactic bacteria are such gradient-inhabiting organisms that have a specific type of aerotaxis that allows them to compete at the oxic-anoxic interface. They biomineralize magnetosomes, intracellular membrane-coated magnetic nanoparticles, that comprise a permanent magnetic dipole that causes the cells to align along magnetic field lines. The magnetic alignment enables them to efficiently migrate toward an optimal oxygen concentration in microaerobic niches. This phenomenon is known as magneto-aerotaxis. Magneto-aerotaxis has only been characterized in a limited number of available cultured strains. In this work, we characterize the magneto-aerotactic behavior of 12 magnetotactic bacteria with various morphologies, phylogenies, physiologies, and flagellar apparatus. We report six different magneto-aerotactic behaviors that can be described as a combination of three distinct mechanisms, including the reported (di-)polar, axial, and a previously undescribed mechanism we named unipolar. We implement a model suggesting that the three magneto-aerotactic mechanisms are related to distinct oxygen sensing mechanisms that regulate the direction of cells’ motility in an oxygen gradient. PMID:25028894

  2. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D. J. Osborn; Po Zhang

    2006-09-30

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications has been developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. We report on a fiber optic technique for detection of gas phase oxygen up to 100 C based on the {sup 3}O{sub 2} quenching of the luminescence from molybdenum chloride clusters, K{sub 2}Mo{sub 6}Cl{sub 14}. The inorganic sensing film is a composite of sol-gel particles embedded in a thin, oxygen permeable sol-gel binder. The particles are comprised of thermally stable, luminescent K{sub 2}Mo{sub 6}Cl{sub 14} clusters dispersed in a fully equilibrated sol-gel matrix. From 40 to 100 C, the fiber sensor switches {approx}6x in intensity in response to alternating pulses of <0.001% O2 and 21% O{sub 2} between two well defined levels with a response time of 10 s. The sensor signal is a few nW for an input pump power of 250 {micro}W. The normalized sensor signal is linear with molar oxygen concentration and fits the theoretical Stern-Volmer relationship. Although the sensitivity decreases with temperature, sensitivity at 100 C is 160 [O{sub 2}]{sup -1}. These parameters are well suited for in-situ, real-time monitoring of oxygen for industrial process control applications.

  3. Relationship between the microscopic and macroscopic world in optical oxygen sensing: a luminescence lifetime microscopy study.

    PubMed

    López-Gejo, Juan; Haigh, David; Orellana, Guillermo

    2010-02-01

    An investigation based on confocal fluorescence lifetime imaging microscopy (FLIM) of silica-loaded silicone films doped with a molecular oxygen-sensitive ruthenium(II) polyazaheterocyclic complex is presented. The effect of the silica type (hydrophilic/hydrophobic), particle size and amount of silica filler on the luminescence decay of the immobilized indicator dye has thoroughly been studied. A higher amount of hydrophilic silica leads to both a higher solubility of molecular oxygen into the silicone film and to higher levels of the metal indicator dye. Thus, incorporation of 10% (by wt) pyrogenic silica into silicone shortens the mean luminescence lifetime from 1.4 to 0.9 micros. However, an excess of filler may lead to overloading of the dye into the film producing new phenomena such as triplet-triplet annihilation and excitation energy homotransfer, as observed from their influence on the emission lifetime of the metal complex. Those phenomena do not take place when trimethylated silica (hydrophobic filler) is used. In this case, no increase on the oxygen or dye concentration is observed after addition of the filler and no significant reduction of the luminescence lifetime is measured. Both the addition of silica and the possible precipitation of dye crystals lead to the appearance of microdomains where the molecular probe exhibits widely different excited state lifetimes. For the first time, such microdomains within the oxygen sensing layer are visualized and analyzed by means of FLIM, showing the potential of this technique and the usefulness of our conclusions to the future design and development of novel luminescent oxygen sensor films for environmental and process analysis.

  4. Oxygen sensing in neuroendocrine cells and other cell types: pheochromocytoma (PC12) cells as an experimental model.

    PubMed

    Spicer, Zachary; Millhorn, David E

    2003-01-01

    A steady supply of oxygen is an absolute requirement for mammalian cells to maintain normal cellular functions. To answer the challenge that oxygen deprivation represents, mammals have evolved specialized cell types that can sense changes in oxygen tension and alter gene expression to enhance oxygen delivery to hypoxic areas. These oxygensensing cells are rare and difficult to study in vivo. As a result, pheochromocytoma (PC12) cells have become a vital in vitro model system for deciphering the molecular events that confer the hypoxia-resistant and oxygen-sensing phenotypes. Research over the last few years has revealed that the hypoxia response in PC12 cells involves the interactions of several signal transduction pathways (Ca2+/calmodulin-dependent kinases, Akt, SAPKs, and MAPKs) and transcription factors (HIFs, CREB, and c-fos/junB). This review summarizes the current understanding of the role these signal transduction pathways and transcription factors play in determining the hypoxic response. PMID:14739486

  5. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn; Po Zhang

    2006-06-30

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Our approach towards immobilizing the potassium salt of the molybdenum cluster, K{sub 2}Mo{sub 6}Cl{sub 14}, at the far end of an optical fiber is to embed the cluster in a thermally cured sol-gel matrix particle. This particle-in-binder approach affords fibers with greatly improved mechanical properties, as compared to previous approaches. The sensor was characterized in 2-21% gas phase oxygen at 40, 70 and 100 C. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  6. Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Haas, Jon P.; Wilson, D. Bruce; Fries, Joseph (Technical Monitor)

    2000-01-01

    The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

  7. Oxygen transport properties estimation by DSMC-CT simulations

    SciTech Connect

    Bruno, Domenico; Frezzotti, Aldo; Ghiroldi, Gian Pietro

    2014-12-09

    Coupling DSMC simulations with classical trajectories calculations is emerging as a powerful tool to improve predictive capabilities of computational rarefied gas dynamics. The considerable increase of computational effort outlined in the early application of the method (Koura,1997) can be compensated by running simulations on massively parallel computers. In particular, GPU acceleration has been found quite effective in reducing computing time (Ferrigni,2012; Norman et al.,2013) of DSMC-CT simulations. The aim of the present work is to study rarefied Oxygen flows by modeling binary collisions through an accurate potential energy surface, obtained by molecular beams scattering (Aquilanti, et al.,1999). The accuracy of the method is assessed by calculating molecular Oxygen shear viscosity and heat conductivity following three different DSMC-CT simulation methods. In the first one, transport properties are obtained from DSMC-CT simulations of spontaneous fluctuation of an equilibrium state (Bruno et al, Phys. Fluids, 23, 093104, 2011). In the second method, the collision trajectory calculation is incorporated in a Monte Carlo integration procedure to evaluate the Taxman’s expressions for the transport properties of polyatomic gases (Taxman,1959). In the third, non-equilibrium zero and one-dimensional rarefied gas dynamic simulations are adopted and the transport properties are computed from the non-equilibrium fluxes of momentum and energy. The three methods provide close values of the transport properties, their estimated statistical error not exceeding 3%. The experimental values are slightly underestimated, the percentage deviation being, again, few percent.

  8. Substitutionally doped phosphorene: electronic properties and gas sensing

    NASA Astrophysics Data System (ADS)

    Suvansinpan, Nawat; Hussain, Fayyaz; Zhang, Gang; Hsin Chiu, Cheng; Cai, Yongqing; Zhang, Yong-Wei

    2016-02-01

    Phosphorene, a new elemental two-dimensional material, has attracted increasing attention owing to its intriguing electronic properties. In particular, pristine phospohorene, due to its ultrahigh surface-volume ratio and high chemical activity, has been shown to be promising for gas sensing (Abbas et al 2015 ACS Nano 9 5618). To further enhance its sensing ability, we perform first-principles calculations based on density functional theory to study substitutionally doped phosphorene with 17 different atoms, focusing on structures, energetics, electronic properties and gas sensing. Our calculations reveal that anionic X (X = O, C and S) dopants have a large binding energy and highly dispersive electronic states, signifying the formation of covalent X-P bonds and thus strong structural stability. Alkali atom (Li and Na) doping is found to donate most of the electrons in the outer s-orbital by forming ionic bonds with P, and the band gap decreases by pushing down the conduction band, suggesting that the optical and electronic properties of the doped phosphorene can be tailored. For doping with VIIIB-group (Fe, Co and Ni) elements, a strong affinity is predicted and the binding energy and charge transfer are correlated strongly with their electronegativity. By examining NO molecule adsorption, we find that these metal doped phosphorenes (MDPs) in general exhibit a significantly enhanced chemical activity compared with pristine phosphorene. Our study suggests that substitutionally doped phosphorene shows many intriguing electronic and optic properties different from pristine phosphorene and MDPs are promising in chemical applications involving molecular adsorption and desorption processes, such as materials growth, catalysis, gas sensing and storage.

  9. Substitutionally doped phosphorene: electronic properties and gas sensing.

    PubMed

    Suvansinpan, Nawat; Hussain, Fayyaz; Zhang, Gang; Chiu, Cheng Hsin; Cai, Yongqing; Zhang, Yong-Wei

    2016-02-12

    Phosphorene, a new elemental two-dimensional material, has attracted increasing attention owing to its intriguing electronic properties. In particular, pristine phospohorene, due to its ultrahigh surface-volume ratio and high chemical activity, has been shown to be promising for gas sensing (Abbas et al 2015 ACS Nano 9 5618). To further enhance its sensing ability, we perform first-principles calculations based on density functional theory to study substitutionally doped phosphorene with 17 different atoms, focusing on structures, energetics, electronic properties and gas sensing. Our calculations reveal that anionic X (X = O, C and S) dopants have a large binding energy and highly dispersive electronic states, signifying the formation of covalent X-P bonds and thus strong structural stability. Alkali atom (Li and Na) doping is found to donate most of the electrons in the outer s-orbital by forming ionic bonds with P, and the band gap decreases by pushing down the conduction band, suggesting that the optical and electronic properties of the doped phosphorene can be tailored. For doping with VIIIB-group (Fe, Co and Ni) elements, a strong affinity is predicted and the binding energy and charge transfer are correlated strongly with their electronegativity. By examining NO molecule adsorption, we find that these metal doped phosphorenes (MDPs) in general exhibit a significantly enhanced chemical activity compared with pristine phosphorene. Our study suggests that substitutionally doped phosphorene shows many intriguing electronic and optic properties different from pristine phosphorene and MDPs are promising in chemical applications involving molecular adsorption and desorption processes, such as materials growth, catalysis, gas sensing and storage.

  10. Gas Sensing Properties of ZnO-SnO2 Nanostructures.

    PubMed

    Chen, Weigen; Li, Qianzhu; Xu, Lingna; Zeng, Wen

    2015-02-01

    One-dimensional (1D) semiconductor metal oxide nanostructures have attracted increasing attention in electrochemistry, optics, magnetic, and gas sensing fields for the good properties. N-type low dimensional semiconducting oxides such as SnO2 and ZnO have been known for the detection of inflammable or toxic gases. In this paper, we fabricated the ZnO-SnO2 and SnO2 nanoparticles by hydrothermal synthesis. Microstructure characterization was performed using X-ray diffraction (XRD) and surface morphologies for both the pristine and doped samples were observed using field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Then we made thin film gas sensor to study the gas sensing properties of ZnO-SnO2 and SnO2 gas sensor to H2 and CO. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO2 and ZnO toward H2 and CO over that of the commonly applied undecorated SnO2 nanoparticles. The improved gas sensing properties are attributed to the size of grains and pronounced electron transfer between the compound nanostructures and the absorbed oxygen species as well as to the heterojunctions of the ZnO nanoparticles to the SnO2 nanoparticles, which provide additional reaction rooms. The results represent an advance of compound nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials, offering a new avenue and direction to detect gases of interest based on composite tin oxide nanoparticles. PMID:26353640

  11. Oxygenation properties and isoform diversity of snake hemoglobins.

    PubMed

    Storz, Jay F; Natarajan, Chandrasekhar; Moriyama, Hideaki; Hoffmann, Federico G; Wang, Tobias; Fago, Angela; Malte, Hans; Overgaard, Johannes; Weber, Roy E

    2015-11-01

    Available data suggest that snake hemoglobins (Hbs) are characterized by a combination of unusual structural and functional properties relative to the Hbs of other amniote vertebrates, including oxygenation-linked tetramer-dimer dissociation. However, standardized comparative data are lacking for snake Hbs, and the Hb isoform composition of snake red blood cells has not been systematically characterized. Here we present the results of an integrated analysis of snake Hbs and the underlying α- and β-type globin genes to characterize 1) Hb isoform composition of definitive erythrocytes, and 2) the oxygenation properties of isolated isoforms as well as composite hemolysates. We used species from three families as subjects for experimental studies of Hb function: South American rattlesnake, Crotalus durissus (Viperidae); Indian python, Python molurus (Pythonidae); and yellow-bellied sea snake, Pelamis platura (Elapidae). We analyzed allosteric properties of snake Hbs in terms of the Monod-Wyman-Changeux model and Adair four-step thermodynamic model. Hbs from each of the three species exhibited high intrinsic O2 affinities, low cooperativities, small Bohr factors in the absence of phosphates, and high sensitivities to ATP. Oxygenation properties of the snake Hbs could be explained entirely by allosteric transitions in the quaternary structure of intact tetramers, suggesting that ligation-dependent dissociation of Hb tetramers into αβ-dimers is not a universal feature of snake Hbs. Surprisingly, the major Hb isoform of the South American rattlesnake is homologous to the minor HbD of other amniotes and, contrary to the pattern of Hb isoform differentiation in birds and turtles, exhibits a lower O2 affinity than the HbA isoform. PMID:26354849

  12. Oxygenation properties and isoform diversity of snake hemoglobins.

    PubMed

    Storz, Jay F; Natarajan, Chandrasekhar; Moriyama, Hideaki; Hoffmann, Federico G; Wang, Tobias; Fago, Angela; Malte, Hans; Overgaard, Johannes; Weber, Roy E

    2015-11-01

    Available data suggest that snake hemoglobins (Hbs) are characterized by a combination of unusual structural and functional properties relative to the Hbs of other amniote vertebrates, including oxygenation-linked tetramer-dimer dissociation. However, standardized comparative data are lacking for snake Hbs, and the Hb isoform composition of snake red blood cells has not been systematically characterized. Here we present the results of an integrated analysis of snake Hbs and the underlying α- and β-type globin genes to characterize 1) Hb isoform composition of definitive erythrocytes, and 2) the oxygenation properties of isolated isoforms as well as composite hemolysates. We used species from three families as subjects for experimental studies of Hb function: South American rattlesnake, Crotalus durissus (Viperidae); Indian python, Python molurus (Pythonidae); and yellow-bellied sea snake, Pelamis platura (Elapidae). We analyzed allosteric properties of snake Hbs in terms of the Monod-Wyman-Changeux model and Adair four-step thermodynamic model. Hbs from each of the three species exhibited high intrinsic O2 affinities, low cooperativities, small Bohr factors in the absence of phosphates, and high sensitivities to ATP. Oxygenation properties of the snake Hbs could be explained entirely by allosteric transitions in the quaternary structure of intact tetramers, suggesting that ligation-dependent dissociation of Hb tetramers into αβ-dimers is not a universal feature of snake Hbs. Surprisingly, the major Hb isoform of the South American rattlesnake is homologous to the minor HbD of other amniotes and, contrary to the pattern of Hb isoform differentiation in birds and turtles, exhibits a lower O2 affinity than the HbA isoform.

  13. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III; Po Zhang

    2006-05-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Previously we described a particle-in-binder approach to immobilizing the potassium salt of the molybdenum cluster, K{sub 2}Mo{sub 6}Cl{sub 14}, at the tips of optical fibers. Compared to previous methods, the particle-in-binder approach affords fibers with greatly improved mechanical properties. The response of the sensor to oxygen at 40, 70 and 100 C was measured in 2-21% gas phase oxygen. The normalized sensor signal is linear with molar oxygen concentration and fits the theoretical Stern-Volmer relationship. Although the sensitivity decreases with temperature, at 100 C the sensitivity is 160 [O{sub 2}]{sup -1}. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  14. Hematite nanoplates: Controllable synthesis, gas sensing, photocatalytic and magnetic properties.

    PubMed

    Hao, Hongying; Sun, Dandan; Xu, Yanyan; Liu, Ping; Zhang, Guoying; Sun, Yaqiu; Gao, Dongzhao

    2016-01-15

    Uniform hematite (α-Fe2O3) nanoplates exposing {001} plane as basal planes have been prepared by a facile solvothermal method under the assistance of sodium acetate. The morphological evolution of the nanoplates was studied by adjusting the reaction parameters including the solvent and the amount of sodium acetate. The results indicated that both the adequate nucleation/growth rate and selective adsorption of alcohol molecules and acetate anions contribute to the formation of the plate-like morphology. In addition, the size of the nanoplates can be adjusted from ca. 180nm to 740nm by changing the reaction parameters. Three nanoplate samples with different size were selected to investigate the gas sensing performance, photocatalytic and magnetic properties. As gas sensing materials, all the α-Fe2O3 nanoplates exhibited high gas sensitivity and stability toward n-butanol. When applied as photocatalyst, the α-Fe2O3 nanoplates show high photodegradation efficiency towards RhB. Both the gas sensing performance and the photocatalytic property of the products exhibit obvious size-dependent effect. Magnetic measurements reveal that the plate-like α-Fe2O3 particles possess good room temperature magnetic properties. PMID:26476200

  15. Exfoliated black phosphorus gas sensing properties at room temperature

    NASA Astrophysics Data System (ADS)

    Donarelli, M.; Ottaviano, L.; Giancaterini, L.; Fioravanti, G.; Perrozzi, F.; Cantalini, C.

    2016-06-01

    Room temperature gas sensing properties of chemically exfoliated black phosphorus (BP) to oxidizing (NO2, CO2) and reducing (NH3, H2, CO) gases in a dry air carrier have been reported. To study the gas sensing properties of BP, chemically exfoliated BP flakes have been drop casted on Si3N4 substrates provided with Pt comb-type interdigitated electrodes in N2 atmosphere. Scanning electron microscopy and x-ray photoelectron spectroscopy characterizations show respectively the occurrence of a mixed structure, composed of BP coarse aggregates dispersed on BP exfoliated few layer flakes bridging the electrodes, and a clear 2p doublet belonging to BP, which excludes the occurrence of surface oxidation. Room temperature electrical tests in dry air show a p-type response of multilayer BP with measured detection limits of 20 ppb and 10 ppm to NO2 and NH3 respectively. No response to CO and CO2 has been detected, while a slight but steady sensitivity to H2 has been recorded. The reported results confirm, on an experimental basis, what was previously theoretically predicted, demonstrating the promising sensing properties of exfoliated BP.

  16. Hematite nanoplates: Controllable synthesis, gas sensing, photocatalytic and magnetic properties.

    PubMed

    Hao, Hongying; Sun, Dandan; Xu, Yanyan; Liu, Ping; Zhang, Guoying; Sun, Yaqiu; Gao, Dongzhao

    2016-01-15

    Uniform hematite (α-Fe2O3) nanoplates exposing {001} plane as basal planes have been prepared by a facile solvothermal method under the assistance of sodium acetate. The morphological evolution of the nanoplates was studied by adjusting the reaction parameters including the solvent and the amount of sodium acetate. The results indicated that both the adequate nucleation/growth rate and selective adsorption of alcohol molecules and acetate anions contribute to the formation of the plate-like morphology. In addition, the size of the nanoplates can be adjusted from ca. 180nm to 740nm by changing the reaction parameters. Three nanoplate samples with different size were selected to investigate the gas sensing performance, photocatalytic and magnetic properties. As gas sensing materials, all the α-Fe2O3 nanoplates exhibited high gas sensitivity and stability toward n-butanol. When applied as photocatalyst, the α-Fe2O3 nanoplates show high photodegradation efficiency towards RhB. Both the gas sensing performance and the photocatalytic property of the products exhibit obvious size-dependent effect. Magnetic measurements reveal that the plate-like α-Fe2O3 particles possess good room temperature magnetic properties.

  17. Optical Properties of Volcanic Ash: Improving Remote Sensing Observations

    NASA Astrophysics Data System (ADS)

    Whelley, P.; Colarco, P. R.; Aquila, V.; Krotkov, N. A.; Bleacher, J. E.; Garry, W. B.; Young, K. E.; Lima, A. R.; Martins, J. V.; Carn, S. A.

    2015-12-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation. Recent research has identified a wide range in volcanic ash optical properties among samples collected from the ground after different eruptions. The database of samples investigated remains relatively small, and measurements of optical properties at the relevant particle sizes and spectral channels are far from complete. Generalizing optical properties remains elusive, as does establishing relationships between ash composition and optical properties, which are essential for satellite retrievals. We are building a library of volcanic ash optical and microphysical properties. In this presentation we show

  18. Optical properties of volcanic ash: improving remote sensing observations.

    NASA Astrophysics Data System (ADS)

    Whelley, Patrick; Colarco, Peter; Aquila, Valentina; Krotkov, Nickolay; Bleacher, Jake; Garry, Brent; Young, Kelsey; Rocha Lima, Adriana; Martins, Vanderlei; Carn, Simon

    2016-04-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation.

  19. An algorithm for sensing venous oxygenation using ultrasound-modulated light enhanced by microbubbles

    NASA Astrophysics Data System (ADS)

    Honeysett, Jack E.; Stride, Eleanor; Deng, Jing; Leung, Terence S.

    2012-02-01

    Near-infrared spectroscopy (NIRS) can provide an estimate of the mean oxygen saturation in tissue. This technique is limited by optical scattering, which reduces the spatial resolution of the measurement, and by absorption, which makes the measurement insensitive to oxygenation changes in larger deep blood vessels relative to that in the superficial tissue. Acousto-optic (AO) techniques which combine focused ultrasound (US) with diffuse light have been shown to improve the spatial resolution as a result of US-modulation of the light signal, however this technique still suffers from low signal-to-noise when detecting a signal from regions of high optical absorption. Combining an US contrast agent with this hybrid technique has been proposed to amplify an AO signal. Microbubbles are a clinical contrast agent used in diagnostic US for their ability to resonate in a sound field: in this work we also make use of their optical scattering properties (modelled using Mie theory). A perturbation Monte Carlo (pMC) model of light transport in a highly absorbing blood vessel containing microbubbles surrounded by tissue is used to calculate the AO signal detected on the top surface of the tissue. An algorithm based on the modified Beer-Lambert law is derived which expresses intravenous oxygen saturation in terms of an AO signal. This is used to determine the oxygen saturation in the blood vessel from a dual wavelength microbubble-contrast AO measurement. Applying this algorithm to the simulation data shows that the venous oxygen saturation is accurately recovered, and this measurement is robust to changes in the oxygenation of the superficial tissue layer.

  20. Molecular packing and magnetic properties of lithium naphthalocyanine crystals: hollow channels enabling permeability and paramagnetic sensitivity to molecular oxygen.

    PubMed

    Pandian, Ramasamy P; Dolgos, Michelle; Marginean, Camelia; Woodward, Patrick M; Hammel, P Chris; Manoharan, Periakaruppan T; Kuppusamy, Periannan

    2009-01-01

    The synthesis, structural framework, magnetic and oxygen-sensing properties of a lithium naphthalocyanine (LiNc) radical probe are presented. LiNc was synthesized in the form of a microcrystalline powder using a chemical method and characterized by electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility, powder X-ray diffraction analysis, and mass spectrometry. X-Ray powder diffraction studies revealed a structural framework that possesses long, hollow channels running parallel to the packing direction. The channels measured approximately 5.0 × 5.4 Å(2) in the two-dimensional plane perpendicular to the length of the channel, enabling diffusion of oxygen molecules (2.9 × 3.9 Å(2)) through the channel. The powdered LiNc exhibited a single, sharp EPR line under anoxic conditions, with a peak-to-peak linewidth of 630 mG at room temperature. The linewidth was sensitive to surrounding molecular oxygen, showing a linear increase in pO(2) with an oxygen sensitivity of 31.2 mG per mmHg. The LiNc microcrystals can be further prepared as nano-sized crystals without the loss of its high oxygen-sensing properties. The thermal variation of the magnetic properties of LiNc, such as the EPR linewidth, EPR intensity and magnetic susceptibility revealed the existence of two different temperature regimes of magnetic coupling and hence differing columnar packing, both being one-dimensional antiferromagnetic chains but with differing magnitudes of exchange coupling constants. At a temperature of ∼50 K, LiNc crystals undergo a reversible phase transition. The high degree of oxygen-sensitivity of micro- and nano-sized crystals of LiNc, combined with excellent stability, should enable precise and accurate measurements of oxygen concentration in biological systems using EPR spectroscopy.

  1. Online Hemoglobin and Oxygen Saturation Sensing During Continuous Renal Replacement Therapy with Regional Citrate Anticoagulation.

    PubMed

    Yessayan, Lenar T; Yee, Jerry; Frinak, Stan; Szamosfalvi, Balazs

    2015-01-01

    Optical hemoglobin and oxygen saturation sensor (OHOS) monitor when used in combination with other hemodynamic tools may be useful for continuous hemodynamic monitoring during ultrafiltration. The stand-alone OHOS monitor can easily be deployed predialyzer into the extracorporeal circuit of continuous renal replacement therapy (CRRT) systems. To maximize the accuracy of the OHOS in 24 hr CRRT systems, clotting in the optical blood chamber and the presensor dilution incurred by replacement fluid should be minimized. Sustained low-efficiency dialysis (SLED) with regional citrate anticoagulation is a therapy that incorporates an OHOS and maintains the overall reliability of hemoglobin (Hb) and saturation sensing. The system operates at a blood flow rate of 60 ml/min and a fixed acid citrate infusion rate of 150 ml/hr. The presensor dilution incurred by concentrated citrate infusion would result in a minimal Hb dilution (<0.7 g/dl) while minimizing optical blood chamber clotting during 24 hr SLED.

  2. Room temperature alcohol sensing by oxygen vacancy controlled TiO2 nanotube array

    NASA Astrophysics Data System (ADS)

    Hazra, A.; Dutta, K.; Bhowmik, B.; Chattopadhyay, P. P.; Bhattacharyya, P.

    2014-08-01

    Oxygen vacancy (OV) controlled TiO2 nanotubes, having diameters of 50-70 nm and lengths of 200-250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH4F and ethylene glycol with selective H2O content. The structural evolution of TiO2 nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO2 nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO2 nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

  3. Excellent acetone sensing properties of porous ZnO

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Bai; Liu, Xing-Yi; Wang, Sheng-Lei

    2015-01-01

    Porous ZnO was obtained by hydrothermal method. The results of scanning electron microscope revealed the porous structure in the as-prepared materials. The acetone sensing test results of porous ZnO show that porous ZnO possesses excellent acetone gas sensing properties. The response is 35.5 at the optimum operating temperature of 320 °C to 100 ppm acetone. The response and recovery times to 50 ppm acetone are 2 s and 8 s, respectively. The lowest detecting limit to acetone is 0.25 ppm, and the response value is 3.8. Moreover, the sensors also exhibit excellent selectivity and long-time stability to acetone. Projected supported by the Project of Challenge Cup for College Students, China (Grant No. 450060497053).

  4. Role of distal arginine in early sensing intermediates in the heme domain of the oxygen sensor FixL.

    PubMed

    Jasaitis, Audrius; Hola, Klara; Bouzhir-Sima, Latifa; Lambry, Jean-Christophe; Balland, Veronique; Vos, Marten H; Liebl, Ursula

    2006-05-16

    FixL is a bacterial heme-based oxygen sensor, in which release of oxygen from the sensing PAS domain leads to activation of an associated kinase domain. Static structural studies have suggested an important role of the conserved residue arginine 220 in signal transmission at the level of the heme domain. To assess the role of this residue in the dynamics and properties of the initial intermediates in ligand release, we have investigated the effects of R220X (X = I, Q, E, H, or A) mutations in the FixLH heme domain on the dynamics and spectral properties of the heme upon photolysis of O(2), NO, and CO using femtosecond transient absorption spectroscopy. Comparison of transient spectra for CO and NO dissociation with steady-state spectra indicated less strain on the heme in the ligand dissociation species for all mutants compared to the wild type (WT). For CO and NO, the kinetics were similar to those of the wild type, with the exception of (1) a relatively low yield of picosecond NO rebinding to R220A, presumably related to the increase in the free volume of the heme pocket, and (2) substantial pH-dependent picosecond to nanosecond rebinding of CO to R220H, related to formation of a hydrogen bond between CO and histidine 220. Upon excitation of the complex bound with the physiological sensor ligand O(2), a 5-8 ps decay phase and a nondecaying (>4 ns) phase were observed for WT and all mutants. The strong distortion of the spectrum associated with the decay phase in WT is substantially diminished in all mutant proteins, indicating an R220-induced role of the heme in the primary intermediate in signal transmission. Furthermore, the yield of dissociated oxygen after this phase ( approximately 10% in WT) is increased in all mutants, up to almost unity in R220A, indicating a key role of R220 in caging the oxygen near the heme through hydrogen bonding. Molecular dynamics simulations corroborate these findings and suggest motions of O(2) and arginine 220 away from the heme

  5. A green-emitting Cu complex for oxygen-sensing purpose: Synthesis, characterization and photophysical features

    NASA Astrophysics Data System (ADS)

    Hui, Han; Wei, Li; Zhentao, Liu; Xiangen, Han

    2015-05-01

    In the present work, a green-emitting Cu(I) complex [Cu(BT-Et)(POP)]BF4 was synthesized and fully characterized, where BT-Et = 4-(1-ethyl-1H-benzo[d]imidazol-2-yl)thiazole, POP = bis(2-(diphenylphosphanyl)phenyl) ether, respectively. An ethyl group was connected onto the diamine ligand to breach π-π attraction within solid [Cu(BT-Et)(POP)]BF4, favoring O2 molecule attack and sensitivity improvement. Its molecular identity was confirmed by single crystal analysis and theoretical calculation. [Cu(BT-Et)(POP)]BF4 emitted long-lived green emission peaking at 521 nm upon photoexcitation which was vulnerable towards O2 molecule, making itself a potential oxygen sensing material. [Cu(BT-Et)(POP)]BF4 was then doped into a silica supporting matrix MCM-41. The resulting composite samples showed sensing behavior towards O2 molecule, with short response time of 10 s and sensitivity of 5.56.

  6. Mechanisms of oxygen sensing: a key to therapy of pulmonary hypertension and patent ductus arteriosus

    PubMed Central

    Weir, E K; Obreztchikova, M; Vargese, A; Cabrera, J A; Peterson, D A; Hong, Z

    2008-01-01

    Specialized tissues that sense acute changes in the local oxygen tension include type 1 cells of the carotid body, neuroepithelial bodies in the lungs, and smooth muscle cells of the resistance pulmonary arteries and the ductus arteriosus (DA). Hypoxia inhibits outward potassium current in carotid body type 1 cells, leading to depolarization and calcium entry through L-type calcium channels. Increased intracellular calcium concentration ([Ca++]i) leads to exocytosis of neurotransmitters, thus stimulating the carotid sinus nerve and respiration. The same K+ channel inhibition occurs with hypoxia in pulmonary artery smooth muscle cells (PASMCs), causing contraction and providing part of the mechanism of hypoxic pulmonary vasoconstriction (HPV). In the SMCs of the DA, the mechanism works in reverse. It is the shift from hypoxia to normoxia that inhibits K+ channels and causes normoxic ductal contraction. In both PA and DA, the contraction is augmented by release of Ca++ from the sarcoplasmic reticulum, entry of Ca++ through store-operated channels (SOC) and by Ca++ sensitization. The same three ‘executive' mechanisms are partly responsible for idiopathic pulmonary arterial hypertension (IPAH). While vasoconstrictor mediators constrict both PA and DA and vasodilators dilate both vessels, only redox changes mimic oxygen by having directly opposite effects on the K+ channels, membrane potential, [Ca++]i and tone in the PA and DA. There are several different hypotheses as to how redox might alter tone, which remain to be resolved. However, understanding the mechanism will facilitate drug development for pulmonary hypertension and patent DA. PMID:18641675

  7. Engineering the oxygen sensing regulation results in an enhanced recombinant human hemoglobin production by Saccharomyces cerevisiae.

    PubMed

    Martínez, José L; Liu, Lifang; Petranovic, Dina; Nielsen, Jens

    2015-01-01

    Efficient production of appropriate oxygen carriers for transfusions (blood substitutes or artificial blood) has been pursued for many decades, and to date several strategies have been used, from synthetic polymers to cell-free hemoglobin carriers. The recent advances in the field of metabolic engineering also allowed the generation of different genetically modified organisms for the production of recombinant human hemoglobin. Several studies have showed very promising results using the bacterium Escherichia coli as a production platform, reporting hemoglobin titers above 5% of the total cell protein content. However, there are still certain limitations regarding the protein stability and functionality of the recombinant hemoglobin produced in bacterial systems. In order to overcome these limitations, yeast systems have been proposed as the eukaryal alternative. We recently reported the generation of a set of plasmids to produce functional human hemoglobin in Saccharomyces cerevisiae, with final titers of active hemoglobin exceeding 4% of the total cell protein. In this study, we propose a strategy for further engineering S. cerevisiae by altering the oxygen sensing pathway by deleting the transcription factor HAP1, which resulted in an increase of the final recombinant active hemoglobin titer exceeding 7% of the total cellular protein.

  8. Early non-destructive biofouling detection and spatial distribution: Application of oxygen sensing optodes.

    PubMed

    Farhat, N M; Staal, M; Siddiqui, A; Borisov, S M; Bucs, Sz S; Vrouwenvelder, J S

    2015-10-15

    Biofouling is a serious problem in reverse osmosis/nanofiltration (RO/NF) applications, reducing membrane performance. Early detection of biofouling plays an essential role in an adequate anti-biofouling strategy. Presently, fouling of membrane filtration systems is mainly determined by measuring changes in pressure drop, which is not exclusively linked to biofouling. Non-destructive imaging of oxygen concentrations (i) is specific for biological activity of biofilms and (ii) may enable earlier detection of biofilm accumulation than pressure drop. The objective of this study was to test whether transparent luminescent planar O2 optodes, in combination with a simple imaging system, can be used for early non-destructive biofouling detection. This biofouling detection is done by mapping the two-dimensional distribution of O2 concentrations and O2 decrease rates inside a membrane fouling simulator (MFS). Results show that at an early stage, biofouling development was detected by the oxygen sensing optodes while no significant increase in pressure drop was yet observed. Additionally, optodes could detect spatial heterogeneities in biofouling distribution at a micro scale. Biofilm development started mainly at the feed spacer crossings. The spatial and quantitative information on biological activity will lead to better understanding of the biofouling processes, contributing to the development of more effective biofouling control strategies.

  9. EDTA-Decorated Nanostructured ZnO/CdS Thin Films for Oxygen Gas Sensing Applications

    NASA Astrophysics Data System (ADS)

    Arunraja, L.; Thirumoorthy, P.; Karthik, A.; Rajendran, V.; Edwinpaul, L.

    2016-08-01

    ZnO/CdS and ZnO/CdS-EDTA nanostructured thin films were prepared on a glass substrate using spin-coating and used for oxygen gas sensor applications. The structural properties of both ZnO/CdS and ZnO/CdS-EDTA nanostructured composites were comparatively characterized. The nanostructure thin film was found in a hexagonal structure with an average crystallite size reduced from 77 nm to 29 nm due to the influence of the EDTA. The optical absorption, photo luminescence, functional groups and surface morphology of the nanostructured thin films were comprehensively investigated. Oxygen was suitably tailored to verify the sensor response over a concentration range of 10-50 ppm at room temperature. Thus, the sensor studies reveal that the performance, response, and recovery time were enhanced in ZnO/CdS-EDTA nanostructured thin film compared with ZnO/CdS.

  10. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D. J. Osborn; Po Zhang

    2006-09-30

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Our approach towards immobilizing the potassium salt of the molybdenum cluster, K{sub 2}Mo{sub 6}Cl{sub 14}, at the far end of an optical fiber is to embed the cluster in a thermally cured sol-gel matrix particle. Due to the improved mechanical properties of this approach high temperature sensor measurements were performed up to 100 C. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  11. Investigation of gas sensing properties of InN nanoparticles

    SciTech Connect

    Madapu, Kishore K. E-mail: dhara@igcar.gov.in; Prasad, A. K.; Tyagi, A. K.; Dhara, S. E-mail: dhara@igcar.gov.in

    2015-06-24

    InN nanoparticles were grown by chemical vapor deposition technique using In{sub 2}O{sub 3} as precursor material. Raman spectroscopic studies show the presence of the wurtzite phase of as-grown InN. Size of the nanoparticles were in range from quantum dot (<8 nm) to larger sized particles (100 nm). We studied the gas sensing properties of InN nanoparticles with CH{sub 4} gas. Sensors substrates were fabricated with interdigitated Au electrodes. InN nanoparticles show high response towards CH{sub 4} with minimum detectable concentration of 50 ppm at 200 °C.

  12. Changes in Polymeric Tether Properties Due to Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Finckenor, Miria M.; Vaughn, Jason A.; Watts, Edward W.

    2003-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) mission is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster. A 5-km conductive tether is attached to the Delta II second stage and collects current fiom the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, which is then attached to an endmass containing several scientific instruments. Atomic oxygen (AO) erodes most organic materials. As the orbit of the Delta II second stage decas, the AO flux (atoms/sq cm sec) increases. A nominal AO fluence of 1 x l0(exp 21) atoms/sq cm was agreed upon by the investigators as an adequate level for evaluating the performance of the tether materials. A test series was performed to determine the effect of atomic oxygen (AO) on the mechanical integrity and possible strength loss of ProSEDS tether materials. The tether materials in this study were Dyneema, an ultra-high molecular weight polyethylene material used as the non-conducting portion of the ProSEDS tether, and the Kevlar core strength fiber used in the conductive tether. Samples of Dyneema and Kevlar were exposed to various levels of atomic oxygen up to 1.07 x 10(exp 21) atoms/sq cm in the Marshall Space Flight Center Atomic Oxygen Beam Facility (AOBF). Changes in mass were noted after AO exposure. The tethers were then tensile-tested until failure. AO affected both the Dyneema and Kevlar tether material strength. Dyneema exposed to 1.07 x 10(exp 21) atoms/sq cm of atomic oxygen failed due to normal handling when removed fiom the AOBF and was not tensile-tested. Another test series was performed to determine the effect of AO on the electrical properties of the ProSEDS conductive tether. The conductive tether consists of seven individually coated strands of 28 AWG 1350

  13. Improving the ethanol gas-sensing properties of porous ZnO microspheres by Co doping

    SciTech Connect

    Xiao, Qi Wang, Tao

    2013-08-01

    Graphical abstract: - Highlights: • Co-doped porous ZnO microspheres were synthesized. • 3 mol% Co-doped ZnO sensor showed the highest response to ethanol. • 3 mol% Co-doped ZnO sensor exhibited fast recovery property. • 3 mol% Co-doped ZnO sensor exhibited good selectivity and long-term stability. - Abstract: Porous Co-doped ZnO microspheres were prepared by a simple hydrothermal method combined with post-annealing. Co species existed as a form of divalent state in the sample and substituted Zn{sup 2+} sites in ZnO crystal lattice, which was affirmed by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The gas-sensing measurements demonstrated that the 3 mol% Co-doped ZnO sample showed the highest response value to 100 ppm ethanol at 350 °C, which were 5 folds higher than that of the pure ZnO sample. In addition, the 3 mol% Co-doped ZnO sensor exhibited fast recovery property, good quantitative determination, good selectivity and long-term stability. The superior sensing properties were contributed to high specific surface area combined with the large amount of oxygen vacancies originating from Co doping.

  14. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III; Po Zhang

    2006-01-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Previously we described a particle-in-binder approach to immobilizing the potassium salt of a molybdenum cluster, K{sub 2}Mo{sub 6}Cl{sub 14}, at the tips of optical fibers. Compared to previous methods, the particle-in-binder approach affords fibers with greatly improved mechanical properties. We have extensively characterized two fiber sensors at high temperature. We obtain quenching ratios between pure nitrogen and 21% oxygen as high as 3.9 x at 70 C. For the first sensor at 60 C we obtained a {+-} 1% variation in the quenching ratio over 6 cycles of measurement, and monitored the device performance over 23 days. We were able to operate the second sensor continuously for 14 hours at 70 C, and the sensor quenching ratio was stable to 5% over that time period. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  15. Luminescent sensing of dissolved oxygen based on Ru(II) complex embedded in sol-gel matrix

    NASA Astrophysics Data System (ADS)

    Bi, Yubing; Tao, Wei; Hu, Yanli; Mao, Yimei; Zhao, Hui

    2015-11-01

    In biological cells and tissues environment, real-time monitoring and controlling dissolved oxygen (DO) provides critical information for studying cellular metabolism process, health status and pathological features. This paper developed an optical DO sensor based on fluorescence quenching principle, prepared tris(4,7-diphenyl-1,10- phenanthroline)ruthenium(II) dichloride complex sol-gel sensing film, and studied its sensing performance. The principle of this sensor is that dissolved oxygen has quenching effect towards the fluorescence emitted by ruthenium complex. So the fluorescence intensity is reduced due to the existence of DO. The measurement limit of DO was 10- 100%, the response time was 20s, and the resolution was 0.02. Compared to traditional dissolved oxygen electrode probe, this luminescent fiber had many advantages, such as smaller size, shorter response time and higher stability.

  16. Generic properties of curvature sensing through vision and touch.

    PubMed

    Dresp-Langley, Birgitta

    2013-01-01

    Generic properties of curvature representations formed on the basis of vision and touch were examined as a function of mathematical properties of curved objects. Virtual representations of the curves were shown on a computer screen for visual scaling by sighted observers (experiment 1). Their physical counterparts were placed in the two hands of blindfolded and congenitally blind observers for tactile scaling. The psychophysical data show that curvature representations in congenitally blind individuals, who never had any visual experience, and in sighted observers, who rely on vision most of the time, are statistically linked to the same mathematical properties of the curves. The perceived magnitude of object curvature, sensed through either vision or touch, is related by a mathematical power law, with similar exponents for the two sensory modalities, to the aspect ratio of the curves, a scale invariant geometric property. This finding supports biologically motivated models of sensory integration suggesting a universal power law for the adaptive brain control and balance of motor responses to environmental stimuli from any sensory modality.

  17. Heteronuclear Ir(III)-Ln(III) Luminescent Complexes: Small-Molecule Probes for Dual Modal Imaging and Oxygen Sensing.

    PubMed

    Jana, Atanu; Crowston, Bethany J; Shewring, Jonathan R; McKenzie, Luke K; Bryant, Helen E; Botchway, Stanley W; Ward, Andrew D; Amoroso, Angelo J; Baggaley, Elizabeth; Ward, Michael D

    2016-06-01

    Luminescent, mixed metal d-f complexes have the potential to be used for dual (magnetic resonance imaging (MRI) and luminescence) in vivo imaging. Here, we present dinuclear and trinuclear d-f complexes, comprising a rigid framework linking a luminescent Ir center to one (Ir·Ln) or two (Ir·Ln2) lanthanide metal centers (where Ln = Eu(III) and Gd(III), respectively). A range of physical, spectroscopic, and imaging-based properties including relaxivity arising from the Gd(III) units and the occurrence of Ir(III) → Eu(III) photoinduced energy-transfer are presented. The rigidity imposed by the ligand facilitates high relaxivities for the Gd(III) complexes, while the luminescence from the Ir(III) and Eu(III) centers provide luminescence imaging capabilities. Dinuclear (Ir·Ln) complexes performed best in cellular studies, exhibiting good solubility in aqueous solutions, low toxicity after 4 and 18 h, respectively, and punctate lysosomal staining. We also demonstrate the first example of oxygen sensing in fixed cells using the dyad Ir·Gd, via two-photon phosphorescence lifetime imaging (PLIM). PMID:27219675

  18. Oxygen sensing by the carotid body: mechanisms and role in adaptation to hypoxia.

    PubMed

    López-Barneo, José; González-Rodríguez, Patricia; Gao, Lin; Fernández-Agüera, M Carmen; Pardal, Ricardo; Ortega-Sáenz, Patricia

    2016-04-15

    Oxygen (O2) is fundamental for cell and whole-body homeostasis. Our understanding of the adaptive processes that take place in response to a lack of O2(hypoxia) has progressed significantly in recent years. The carotid body (CB) is the main arterial chemoreceptor that mediates the acute cardiorespiratory reflexes (hyperventilation and sympathetic activation) triggered by hypoxia. The CB is composed of clusters of cells (glomeruli) in close contact with blood vessels and nerve fibers. Glomus cells, the O2-sensitive elements in the CB, are neuron-like cells that contain O2-sensitive K(+)channels, which are inhibited by hypoxia. This leads to cell depolarization, Ca(2+)entry, and the release of transmitters to activate sensory fibers terminating at the respiratory center. The mechanism whereby O2modulates K(+)channels has remained elusive, although several appealing hypotheses have been postulated. Recent data suggest that mitochondria complex I signaling to membrane K(+)channels plays a fundamental role in acute O2sensing. CB activation during exposure to low Po2is also necessary for acclimatization to chronic hypoxia. CB growth during sustained hypoxia depends on the activation of a resident population of stem cells, which are also activated by transmitters released from the O2-sensitive glomus cells. These advances should foster further studies on the role of CB dysfunction in the pathogenesis of highly prevalent human diseases.

  19. Cellular Oxygen Sensing: Crystal Structure of Hypoxia-Inducible Factor Prolyl Hydroxylase (PHD2)

    SciTech Connect

    McDonough,M.; Li, V.; Flashman, E.; Chowdhury, R.; Mohr, C.; Lienard, B.; Zondlo, J.; Oldham, N.; Clifton, I.; et al.

    2006-01-01

    Cellular and physiological responses to changes in dioxygen levels in metazoans are mediated via the posttranslational oxidation of hypoxia-inducible transcription factor (HIF). Hydroxylation of conserved prolyl residues in the HIF-{alpha} subunit, catalyzed by HIF prolyl-hydroxylases (PHDs), signals for its proteasomal degradation. The requirement of the PHDs for dioxygen links changes in dioxygen levels with the transcriptional regulation of the gene array that enables the cellular response to chronic hypoxia; the PHDs thus act as an oxygen-sensing component of the HIF system, and their inhibition mimics the hypoxic response. We describe crystal structures of the catalytic domain of human PHD2, an important prolyl-4-hydroxylase in the human hypoxic response in normal cells, in complex with Fe(II) and an inhibitor to 1.7 Angstroms resolution. PHD2 crystallizes as a homotrimer and contains a double-stranded {beta}-helix core fold common to the Fe(II) and 2-oxoglutarate-dependant dioxygenase family, the residues of which are well conserved in the three human PHD enzymes (PHD 1-3). The structure provides insights into the hypoxic response, helps to rationalize a clinically observed mutation leading to familial erythrocytosis, and will aid in the design of PHD selective inhibitors for the treatment of anemia and ischemic disease.

  20. Room temperature alcohol sensing by oxygen vacancy controlled TiO{sub 2} nanotube array

    SciTech Connect

    Hazra, A.; Dutta, K.; Bhowmik, B.; Bhattacharyya, P.; Chattopadhyay, P. P.

    2014-08-25

    Oxygen vacancy (OV) controlled TiO{sub 2} nanotubes, having diameters of 50–70 nm and lengths of 200–250 nm, were synthesized by electrochemical anodization in the mixed electrolyte comprising NH{sub 4}F and ethylene glycol with selective H{sub 2}O content. The structural evolution of TiO{sub 2} nanoforms has been studied by field emission scanning electron microscopy. Variation in the formation of OVs with the variation of the structure of TiO{sub 2} nanoforms has been evaluated by photoluminescence and X-ray photoelectron spectroscopy. The sensor characteristics were correlated to the variation of the amount of induced OVs in the nanotubes. The efficient room temperature sensing achieved by the control of OVs of TiO{sub 2} nanotube array has paved the way for developing fast responding alcohol sensor with corresponding response magnitude of 60.2%, 45.3%, and 36.5% towards methanol, ethanol, and 2-propanol, respectively.

  1. Electrochemical sensing chemical oxygen demand based on the catalytic activity of cobalt oxide film.

    PubMed

    Wang, Jinqi; Wu, Can; Wu, Kangbing; Cheng, Qin; Zhou, Yikai

    2012-07-29

    Cobalt oxide sensing film was in situ prepared on glassy carbon electrode surface via constant potential oxidation. Controlling at 0.8 V in NaOH solution, the high-valence cobalt catalytically oxidized the reduced compounds, decreasing its surface amount and current signal. The current decline was used as the response signal of chemical oxygen demand (COD) because COD represents the summation of reduced compounds in water. The surface morphology and electrocatalytic activity of cobalt oxide were readily tuned by variation of deposition potential, time, medium and Co(2+) concentration. As confirmed from the atomic force microscopy measurements, the cobalt oxide film, that prepared at 1.3 V for 40 s in pH 4.6 acetate buffer containing 10 mM Co(NO(3))(2), possesses large surface roughness and numerous three-dimensional structures. Electrochemical tests indicated that the prepared cobalt oxide exhibited high electrocatalytic activity to the reduced compounds, accompanied with strong COD signal enhancement. As a result, a novel electrochemical sensor with high sensitivity, rapid response and operational simplicity was developed for COD. The detection limit was as low as 1.1 mg L(-1). The analytical application was studied using a large number of lake water samples, and the accuracy was tested by standard method.

  2. Oxygen Sensing by T Cells Establishes an Immunologically Tolerant Metastatic Niche.

    PubMed

    Clever, David; Roychoudhuri, Rahul; Constantinides, Michael G; Askenase, Michael H; Sukumar, Madhusudhanan; Klebanoff, Christopher A; Eil, Robert L; Hickman, Heather D; Yu, Zhiya; Pan, Jenny H; Palmer, Douglas C; Phan, Anthony T; Goulding, John; Gattinoni, Luca; Goldrath, Ananda W; Belkaid, Yasmine; Restifo, Nicholas P

    2016-08-25

    Cancer cells must evade immune responses at distant sites to establish metastases. The lung is a frequent site for metastasis. We hypothesized that lung-specific immunoregulatory mechanisms create an immunologically permissive environment for tumor colonization. We found that T-cell-intrinsic expression of the oxygen-sensing prolyl-hydroxylase (PHD) proteins is required to maintain local tolerance against innocuous antigens in the lung but powerfully licenses colonization by circulating tumor cells. PHD proteins limit pulmonary type helper (Th)-1 responses, promote CD4(+)-regulatory T (Treg) cell induction, and restrain CD8(+) T cell effector function. Tumor colonization is accompanied by PHD-protein-dependent induction of pulmonary Treg cells and suppression of IFN-γ-dependent tumor clearance. T-cell-intrinsic deletion or pharmacological inhibition of PHD proteins limits tumor colonization of the lung and improves the efficacy of adoptive cell transfer immunotherapy. Collectively, PHD proteins function in T cells to coordinate distinct immunoregulatory programs within the lung that are permissive to cancer metastasis. PAPERCLIP. PMID:27565342

  3. Remote sensing of boundary layer properties using Infrared Sounding

    NASA Astrophysics Data System (ADS)

    Martins, J. P. A.; Teixeira, J.; Soares, P. M. M.; Miranda, P. M. A.; Santos, A. F.; Dang, V.; Irion, F. W.; Fetzer, E.; Fishbein, E. F.

    2010-09-01

    Several techniques have been used to measure Planetary Boundary Layer (PBL) properties, but none of them allows the spatial and temporal sampling properties of spaceborne remote sensing instruments. This work addresses the potential of diagnosing PBL height using an almost unexplored dataset from the Atmopheric InfraRed Sounder (AIRS) suite, known as the support product, which samples the atmospheric properties in a 100-level grid. This kind of vertical sampling allowed the use of a simple algorithm to detect strong gradients on the potential temperature and relative humidity profiles to determine the PBL height. A comparison of these estimates against rawinsonde data from the Rain in Cumulus over the Ocean (RICO) campaign was made and good agreement between the two datasets was found at the local scale. A global distribution of PBL height was also computed and compared against other datasets such as Radio Occultation measurements and model reanalysis. Temporal and spatial variability of this quantity can easily be discussed in light of well known large scale circulation features, revealing the true potential of this dataset has to provide important information useful to develop new parameterization schemes.

  4. Gas sensing properties of nanocrystalline diamond at room temperature

    PubMed Central

    Kulha, Pavel; Laposa, Alexandr; Hruska, Karel; Demo, Pavel; Kromka, Alexander

    2014-01-01

    Summary This study describes an integrated NH3 sensor based on a hydrogenated nanocrystalline diamond (NCD)-sensitive layer coated on an interdigitated electrode structure. The gas sensing properties of the sensor structure were examined using a reducing gas (NH3) at room temperature and were found to be dependent on the electrode arrangement. A pronounced response of the sensor, which was comprised of dense electrode arrays (of 50 µm separation distance), was observed. The sensor functionality was explained by the surface transfer doping effect. Moreover, the three-dimensional model of the current density distribution of the hydrogenated NCD describes the transient flow of electrons between interdigitated electrodes and the hydrogenated NCD surface, that is, the formation of a closed current loop. PMID:25551062

  5. Oxygen-sensing mechanisms and the regulation of redox-responsive transcription factors in development and pathophysiology

    PubMed Central

    Haddad, John J

    2002-01-01

    How do organisms sense the amount of oxygen in the environment and respond appropriately when the level of oxygen decreases? Oxygen sensing and the molecular stratagems underlying the process have been the focus of an endless number of investigations trying to find an answer to the question: "What is the identity of the oxygen sensor?" Dynamic changes in pO2 constitute a potential signaling mechanism for the regulation of the expression and activation of reduction-oxidation (redox)-sensitive and oxygen-responsive transcription factors, apoptosis-signaling molecules and inflammatory cytokines. The transition from placental to lung-based respiration causes a relatively hyperoxic shift or oxidative stress, which the perinatal, developing lung experiences during birth. This variation in ΔpO2, in particular, differentially regulates the compartmentalization and functioning of the transcription factors hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-κB (NF-κB). In addition, oxygen-evoked regulation of HIF-1α and NF-κB is closely coupled with the intracellular redox state, such that modulating redox equilibrium affects their responsiveness at the molecular level (expression/transactivation). The differential regulation of HIF-1α and NF-κB in vitro is paralleled by oxygen-sensitive and redox-dependent pathways governing the regulation of these factors during the transition from placental to lung-based respiration ex utero. The birth transition period in vivo and ex utero also regulates apoptosis signaling pathways in a redox-dependent manner, consistent with NF-κB being transcriptionally regulated in order to play an anti-apoptotic function. An association is established between oxidative stress conditions and the augmentation of an inflammatory state in pathophysiology, regulated by the oxygen- and redox-sensitive pleiotropic cytokines. PMID:12537605

  6. FIBER OPTICAL MICRO-DETECTORS FOR OXYGEN SENSING IN POWER PLANTS

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III

    2003-07-01

    Mo{sub 6}Cl{sub 12}, a cluster compound whose luminescence depends on the ambient concentration of oxygen, is the basis for a real-time oxygen sensor for combustion applications. Previously, the properties of Mo{sub 6}Cl{sub 12} have largely been studied at room temperature; these studies have now been extended to 200 C. Optical microscopy shows that Mo{sub 6}Cl{sub 12} undergoes a steady change in color as it is heated from room temperature to 200 C, changing from canary yellow to crimson and then back to canary yellow. Concurrent thermal gravimetric analyses show a small weight loss for Mo{sub 6}Cl{sub 12} that is consistent with loss of water or HCl from the clusters. These changes are reversible. Absorption and fluorescence emission spectroscopy of Mo{sub 6}Cl{sub 12} heated to 200 C for two hours shows no change in the photophysical parameters compared to the control sample that was not heat cycled.

  7. Synthesis, processing and characterization of calcia-stabilized zirconia solid electrolytes for oxygen sensing applications

    SciTech Connect

    Zhou Minghua . E-mail: mzhou@nrcan.gc.ca; Ahmad, Aftab

    2006-04-13

    Precursor powders of calcia-stabilized zirconia (CSZ) solid electrolytes have been synthesized by a sol-gel method. The phase evolution of the precursor powders after thermal treatments at different temperatures were analysized by X-ray diffraction technique. Disc-shaped sensor elements were fabricated via uniaxial pressing of the calcined powders and subsequently sintered at 1650 deg. C. Scanning electron microscopy (SEM) was used to analyze the microstructure of the sintered pellets. Platinum electrodes were applied to the sintered elements to produce potentiometric/electrochemical gas sensors. The electrical response of the gas sensors to oxygen and the complex impedance of the sensors in air were measured at various temperatures. Impedance analyses indicate that the sensor cell with 15 mol% CaO has much lower resistance (the sum of bulk and grain-boundary resistance) than the sensor cell with 22 mol% CaO. This is also reflected by the EMF responses of both sensor cells to various oxygen concentrations in the testing gas. The EMF deviation from the theoretical value of the CSZ sensor cell with 22 mol% CaO was larger than that of the CSZ sensor cell with 15 mol% CaO. The corrrelations between material compositions, microstructures of the sintered pellets and the electrical properties of the sensors are discussed.

  8. Synthesis and enhanced NO2 gas sensing properties of ZnO nanorods/TiO2 nanoparticles heterojunction composites.

    PubMed

    Zou, C W; Wang, J; Xie, W

    2016-09-15

    ZnO nanorods/TiO2 nanoparticles composites were synthesized and the effects of TiO2 concentrations on the NO2 sensing properties were studied in detail. The as-prepared composites were characterized by XRD, SEM, TEM, PL, I-V and gas sensing measurements. The gas sensing results demonstrated that all the sensors based on ZnO/TiO2 nanocomposites exhibited much higher response than that of sensors based on pure ZnO nanorods. At the optimum operating temperature of 180°C, the response values of the sensors based on ZnO/TiO2 nanocomposites decorated with TiO2 concentrations of 0, 3, 5, 8 and 10wt% were 50, 140, 310, 350 and 258, respectively. The PL and I-V results indicated that the increased charge transfer between the ZnO nanorods mediated by TiO2 nanoparticles enhanced the conductivity of the ZnO/TiO2 nanocomposites. The gas sensing mechanism was also carefully analyzed. The attachment of TiO2 nanoparticles onto ZnO nanorods induced more active sites for the adsorption of oxygen molecules (O(2)) and O(2) which can be more easily adsorbed on the surface of ZnO nanorods. Furthermore, the conduction channel of ZnO/TiO2 was much narrower as a result of the formation of heterojunction which may further contribute to the enhanced NO2 sensing properties.

  9. The effects of low earth orbit atomic oxygen on the properties of Polytetrafluoroethylene

    NASA Astrophysics Data System (ADS)

    Hooshangi, Zhila; Hossein Feghhi, Seyed Amir; Saeedzadeh, Rezgar

    2016-02-01

    Polymers are widely used in space systems as the structural materials. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen. Exposure of polymeric materials to atomic oxygen results in destructive effects on the chemical, electrical, thermal, optical and mechanical properties as well as surface degradation. In the present work, the effects of atomic oxygen on the mechanical, thermal, and optical properties of Polytetrafluoroethylene film have been investigated. The atomic oxygen density was calculated by SPENVIS tool. After the atomic oxygen exposure by using radio-frequency (RF) plasma source, the appearance of the samples changed, and the mass of the samples reduced because of outgassing. The results of thermal analysis showed that atomic oxygen flux does not affect thermal degradation of samples regarding TGA diagrams. By increasing the atomic oxygen flux, the amount of absorbance increased showing that atomic oxygen had damaged the surface of Polytetrafluoroethylene, and it had oxidized the surface of the polymer.

  10. Biological oxygen sensing via two-photon absorption by an Ir(III) complex using a femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Moritomo, Hiroki; Fujii, Akinari; Suzuki, Yasutaka; Yoshihara, Toshitada; Tobita, Seiji; Kawamata, Jun

    2016-09-01

    Near-infrared two-photon absorption of the phosphorescent Ir(III) complex (2,4-pentanedionato-κO 2,κO 4)bis[2-(6-phenanthridinyl-κN)benzo[b]thien-3-yl-κC]iridium (BTPHSA) was characterized. It exhibited a 800-1200 nm two-photon absorption band, and thus could be electronically excited by 1030-nm femtosecond Ti:sapphire and Yb-doped fiber lasers. By using BTPHSA, oxygen concentrations in human embryonic kidney 293 (HEK293) cells were imaged. These results demonstrate two-photon oxygen sensing of live tissues via easily operable excitation sources.

  11. Biological oxygen sensing via two-photon absorption by an Ir(III) complex using a femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Moritomo, Hiroki; Fujii, Akinari; Suzuki, Yasutaka; Yoshihara, Toshitada; Tobita, Seiji; Kawamata, Jun

    2016-09-01

    Near-infrared two-photon absorption of the phosphorescent Ir(III) complex (2,4-pentanedionato-κO 2,κO 4)bis[2-(6-phenanthridinyl-κN)benzo[b]thien-3-yl-κC]iridium (BTPHSA) was characterized. It exhibited a 800–1200 nm two-photon absorption band, and thus could be electronically excited by 1030-nm femtosecond Ti:sapphire and Yb-doped fiber lasers. By using BTPHSA, oxygen concentrations in human embryonic kidney 293 (HEK293) cells were imaged. These results demonstrate two-photon oxygen sensing of live tissues via easily operable excitation sources.

  12. Solubility and thermodynamic properties of oxygen in solid molybdenum

    NASA Technical Reports Server (NTRS)

    Srivastava, S. C.; Seigle, L. L.

    1974-01-01

    A formula is obtained for the solubility of oxygen in solid Mo, determined in the range from 1400 to 1900 C by equilibrating rods of zone-refined Mo with mixtures of Mo and MoO2 powders. Using the known value of the free energy of formation of MoO2, a formula is obtained for the chemical potential of oxygen in the dilute solid solution. The heat of solution of oxygen in solid Mo and the excess entropy for the interstitial solid solution are also determined, assuming that the oxygen atoms reside in the octahedral interstices of bcc Mo.

  13. Effect of high-pressure oxygen on the mechanical properties of alloys

    NASA Technical Reports Server (NTRS)

    Schwartzberg, F. R.; Shepic, J. A.

    1977-01-01

    Unnotched and notched tensile properties of stressed and unstressed specimens of wrought 316 stainless steel, Incology 903, Monel K-500, and cast specimens of Inconel 718 were examined. Environmental tests were performed in atmospheric pressure air, high pressure nitrogen, and high pressure oxygen. Results show that oxygen did not alter the tensile properties of any of the alloys studied.

  14. TiO2 Nanotubes: Recent Advances in Synthesis and Gas Sensing Properties

    PubMed Central

    Galstyan, Vardan; Comini, Elisabetta; Faglia, Guido; Sberveglieri, Giorgio

    2013-01-01

    Synthesis—particularly by electrochemical anodization-, growth mechanism and chemical sensing properties of pure, doped and mixed titania tubular arrays are reviewed. The first part deals on how anodization parameters affect the size, shape and morphology of titania nanotubes. In the second part fabrication of sensing devices based on titania nanotubes is presented, together with their most notable gas sensing performances. Doping largely improves conductivity and enhances gas sensing performances of TiO2 nanotubes. PMID:24184919

  15. Surface doping of La ions into ZnO nanocrystals to lower the optimal working temperature for HCHO sensing properties.

    PubMed

    Tian, Shouqin; Zhang, Yupeng; Zeng, Dawen; Wang, Hao; Li, Neng; Xie, Changsheng; Pan, Chunxu; Zhao, Xiujian

    2015-11-01

    Lowering the working temperature without sacrificing other good gas-sensing properties is of particular interest to gas sensors for an excellent performance. In this work, La surface doped ZnO nanocrystals were successfully prepared by a facile thermal treatment with lanthanum nitrate (La(NO3)3) solution injected into ZnO thick films, which exhibited a remarkable decrease in the optimal working temperature for formaldehyde (HCHO) sensing properties. This was probably attributed to the formation of surface LaZn defects in the ZnO nanocrystals which was evidenced by XRD, XPS results and DFT calculations. The surface LaZn defects can introduce a shallower donor level than oxygen vacancies, and probably facilitate the charge transfer from oxygen species to ZnO for producing chemisorbed oxygen species more easily. This was in good agreement with the DFT results that the absorption energy of oxygen molecules on the surface of La doped ZnO was only -10.61 eV, much lower than that of pure ZnO. Moreover, the optimal working temperature of the La doped ZnO based sensor was significantly decreased from 350 to 250 °C without sacrificing the high and quick response to HCHO gas as the content of surface LaZn defects was increased gradually. Therefore, the behavior of the surface LaZn defects in the optimal working temperature revealed a HCHO response mechanism in ZnO, which can provide new insights into the enhanced HCHO sensing performance of gas sensors. PMID:26421631

  16. F-box and leucine-rich repeat protein 5 (FBXL5): sensing intracellular iron and oxygen.

    PubMed

    Ruiz, Julio C; Bruick, Richard K

    2014-04-01

    Though essential for many vital biological processes, excess iron results in the formation of damaging reactive oxygen species (ROS). Therefore, iron metabolism must be tightly regulated. F-box and leucine-rich repeat protein 5 (FBXL5), an E3 ubiquitin ligase subunit, regulates cellular and systemic iron homeostasis by facilitating iron regulatory protein 2 (IRP2) degradation. FBXL5 possesses an N-terminal hemerythrin (Hr)-like domain that mediates its own differential stability by switching between two different conformations to communicate cellular iron availability. In addition, the FBXL5-Hr domain also senses O2 availability, albeit by a distinct mechanism. Mice lacking FBXL5 fail to sense intracellular iron levels and die in utero due to iron overload and exposure to damaging levels of oxidative stress. By closely monitoring intracellular levels of iron and oxygen, FBLX5 prevents the formation of conditions that favor ROS formation. These findings suggest that FBXL5 is essential for the maintenance of iron homeostasis and is a key sensor of bioavailable iron. Here, we describe the iron and oxygen sensing mechanisms of the FBXL5 Hr-like domain and its role in mediating ROS biology.

  17. Silicon-on-glass pore network micromodels with oxygen-sensing fluorophore films for chemical imaging and defined spatial structure

    SciTech Connect

    Grate, Jay W.; Kelly, Ryan T.; Suter, Jonathan D.; Anheier, Norman C.

    2012-11-21

    Pore network microfluidic models were fabricated by a silicon-on-glass technique that provides the precision advantage of dry etched silicon while creating a structure that is transparent across all microfluidic channels and pores, and can be imaged from either side. A silicon layer is bonded to an underlying borosilicate glass substrate and thinned to the desired height of the microfluidic channels and pores. The silicon is then patterned and through-etched by deep reactive ion etching (DRIE), with the underlying glass serving as an etch stop. After bonding on a transparent glass cover plate, one obtains a micromodel in oxygen impermeable materials with water wet surfaces where the microfluidic channels are transparent and structural elements such as the pillars creating the pore network are opaque. The micromodel can be imaged from either side. The advantageous features of this approach in a chemical imaging application are demonstrated by incorporating a Pt porphyrin fluorophore in a PDMS film serving as the oxygen sensing layer and a bonding surface, or in a polystyrene film coated with a PDMS layer for bonding. The sensing of a dissolved oxygen gradient was demonstrated using fluorescence lifetime imaging, and it is shown that different matrix polymers lead to optimal use in different ranges dissolved oxygen concentration. Imaging with the opaque pillars in between the observation direction and the continuous fluorophore film yields images that retain spatial information in the sensor image.

  18. Silicon-on-glass pore network micromodels with oxygen-sensing fluorophore films for chemical imaging and defined spatial structure.

    PubMed

    Grate, Jay W; Kelly, Ryan T; Suter, Jonathan; Anheier, Norm C

    2012-11-21

    Pore network microfluidic models were fabricated by a silicon-on-glass technique that provides the precision advantage of dry etched silicon while creating a structure that is transparent across all microfluidic channels and pores, and can be imaged from either side. A silicon layer is bonded to an underlying borosilicate glass substrate and thinned to the desired height of the microfluidic channels and pores. The silicon is then patterned and through-etched by deep reactive ion etching (DRIE), with the underlying glass serving as an etch stop. After bonding on a transparent glass cover plate, one obtains a micromodel in oxygen impermeable materials with water-wet surfaces where the microfluidic channels are transparent and structural elements such as the pillars creating the pore network are opaque. The advantageous features of this approach in a chemical imaging application are demonstrated by incorporating a Pt porphyrin fluorophore in a PDMS film serving as the oxygen-sensing layer and a bonding surface, or in a polystyrene film coated with a PDMS layer for bonding. The sensing of a dissolved oxygen gradient was demonstrated using fluorescence lifetime imaging, and it is shown that different matrix polymers lead to optimal use in different ranges of oxygen concentration. Imaging with the opaque pillars in between the observation direction and the continuous fluorophore film yields images that retain defined spatial structure in the sensor image.

  19. Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

    NASA Astrophysics Data System (ADS)

    Lettieri, S.; Pallotti, D. K.; Gesuele, F.; Maddalena, P.

    2016-07-01

    We show that mixed-phase titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting, and ratiometric optical sensor of O2. Simultaneous availability of rutile and anatase TiO2 photoluminescence (PL) and their peculiar "anti-correlated" PL responses to O2 allow using their ratio as a measurement parameter associated with the O2 concentration, leading to an experimental responsivity being by construction larger than the one obtainable for single-phase PL detection. A proof of this concept is given, showing a two-fold enhancement of the optical responsivity provided by the ratiometric approach. Besides the peculiar ratiometric-enhanced responsivity, other characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely (a) low production costs, (b) absence of heterogeneous components, and (c) self-supporting properties. These characteristics encourage experimenting with its use for applications requiring high indicator quantities at a competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing.

  20. Satellite remote sensing of aerosol and cloud properties over Eurasia

    NASA Astrophysics Data System (ADS)

    Sogacheva, Larisa; Kolmonen, Pekka; Saponaro, Giulia; Virtanen, Timo; Rodriguez, Edith; Sundström, Anu-Maija; Atlaskina, Ksenia; de Leeuw, Gerrit

    2015-04-01

    Satellite remote sensing provides the spatial distribution of aerosol and cloud properties over a wide area. In our studies large data sets are used for statistical studies on aerosol and cloud interaction in an area over Fennoscandia, the Baltic Sea and adjacent regions over the European mainland. This area spans several regimes with different influences on aerosol cloud interaction such as a the transition from relative clean air over Fennoscandia to more anthropogenically polluted air further south, and the influence maritime air over the Baltic and oceanic air advected from the North Atlantic. Anthropogenic pollution occurs in several parts of the study area, and in particular near densely populated areas and megacities, but also in industrialized areas and areas with dense traffic. The aerosol in such areas is quite different from that produced over the boreal forest and has different effects on air quality and climate. Studies have been made on the effects of aerosols on air quality and on the radiation balance in China. The aim of the study is to study the effect of these different regimes on aerosol-cloud interaction using a large aerosol and cloud data set retrieved with the (Advanced) Along Track Scanning Radiometer (A)ATSR Dual View algorithm (ADV) further developed at Finnish Meteorological Institute and aerosol and cloud data provided by MODIS. Retrieval algorithms for aerosol and clouds have been developed for the (A)ATSR, consisting of a series of instruments of which we use the second and third one: ATSR-2 which flew on the ERS-2 satellite (1995-2003) and AATSR which flew on the ENVISAT satellite (2002-2012) (both from the European Space Agency, ESA). The ADV algorithm provides aerosol data on a global scale with a default resolution of 10x10km2 (L2) and an aggregate product on 1x1 degree (L3). Optional, a 1x1 km2 retrieval products is available over smaller areas for specific studies. Since for the retrieval of AOD no prior knowledge is needed on

  1. Germanium implanted with high dose oxygen and its optical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Qi-Chu; Kelly, J. C.; Kenny, M. J.

    1990-05-01

    Single crystal n-type Ge samples are implanted with 1 × 10 17 to 1.5 × 10 18 cm -2 oxygen ions at 45 keV. Infrared and Rutherford backscattering measurements indicate that germanium dioxide is formed. The atomic ratio of oxygen to germanium is near the GeO 2 stoichiometric value of 2.0 from the surface down to a depth of 550 Å for germanium samples implanted to 1.5 × 10 18 cm -2. The excess oxygen is redistributed during the implantation. The results of optical reflectivity measurements indicate that the reflectivity of germanium in the 0.2-1.4 μm wavelength region is greatly reduced after high dose oxygen ion implantation. The reflectivity value at about 0.7 μm is near zero for germanium implanted to a dose of 1.5 × 10 18 cm -2.

  2. Examining the Reinforcing Properties of Making Sense: A Preliminary Investigation

    ERIC Educational Resources Information Center

    Wray, Alisha M.; Dougher, Michael J.; Hamilton, Derek A.; Guinther, Paul M.

    2012-01-01

    Acceptance and commitment therapy asserts that in clinical problems such as rumination and depression, making sense continues despite accompanying aversive consequences, because sense-making is reinforcing, particularly when it leads to experiential avoidance. The following series of experiments aimed to provide preliminary empirical evidence for…

  3. Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes: A comparative study

    SciTech Connect

    Singh, Ram Sevak

    2015-11-15

    Influence of oxygen impurity on electronic properties of carbon and boron nitride nanotubes (CNTs and BNNTs) is systematically studied using first principle calculations based on density functional theory. Energy band structures and density of states of optimized zigzag (5, 0), armchair (3, 3), and chiral (4, 2) structures of CNT and BNNT are calculated. Oxygen doping in zigzag CNT exhibits a reduction in metallicity with opening of band gap in near-infrared region while metallicity is enhanced in armchair and chiral CNTs. Unlike oxygen-doped CNTs, energy bands are drastically modulated in oxygen-doped zigzag and armchair BNNTs, showing the nanotubes to have metallic behaviour. Furthermore, oxygen impurity in chiral BNNT induces narrowing of band gap, indicating a gradual modification of electronic band structure. This study underscores the understanding of different electronic properties induced in CNTs and BNNTs under oxygen doping, and has potential in fabrication of various nanoelectronic devices.

  4. Raman-lidar technique for tropospheric and stratospheric sensing of aerosol optical and microphysical properties

    SciTech Connect

    Wandinger, U.

    1995-01-01

    Tropospheric and stratospheric aerosols and clouds are known to influence the earth`s radiation budget as well as chemical processes of the atmosphere. Thus, remote sensing of optical and microphysical properties of atmospheric particles has important applications in weather and climate research, pollution monitoring, and atmospheric chemistry. During the last few years Raman lidars have become very important tools in this field of research. The development of powerful light sources such as Nd:YAG and excimer lasers, of interference filters with narrow bandwidth and high transmission, and of low-noise photomultiplier tubes and counting systems has improved the Raman-lidar technique during the past decade significantly. The technique is based on the detection of two signals resulting from elastic backscattering by air molecules and particles and inelastic (Raman) backscattering by a gas of known number density, i.e., nitrogen or oxygen. The technique has been successfully applied to cirrus-cloud studies. In this presentation, the capability of the Raman-lidar technique for tropospheric and stratospheric profiling of aerosol and cloud properties will be discussed on the basis of measurement examples.

  5. Global Oxygen Sensing and Visualization in Water using Luminescent Probe on Anodized Aluminum

    NASA Astrophysics Data System (ADS)

    Ozaki, Tatsuya; Ishikawa, Hitoshi; Iijima, Yoshimi; Sakaue, Hirotaka

    2008-11-01

    The extension of pressure-sensitive paint (PSP) technique as a wind tunnel technology to a global oxygen visualization and detection in water is presented. The topic includes the development of anodized-aluminum pressure-sensitive paint (AA-PSP) as a global oxygen sensor in water as well as its calibration and demonstration. Based on the luminophore study, platinum porphyrin is selected as a luminophore, because it is not dissolved in water. It is found that the luminescent increase is over 20 percent after 8 days immersed in water. Even though the signal increases after water immersion, its oxygen sensitivity is the same, which is 0.4. This AA-PSP is used to visualize oxygen rich water (20 mg/l) impinged in less oxygen water (3 mg/l). Even though the difference of water is only the amount of oxygen, we can visualize the water jet with its mixing process using a fast frame rate camera at the frame rate of 100 Hz. In the final version, we will include the oxygen map combined with the visualization result.

  6. FIBER OPTICAL MICRO-DETECTORS FOR OXYGEN SENSING IN POWER PLANTS

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III; Po Zhang

    2005-04-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. One of the critical materials issues is to demonstrate that the luminescent cluster immobilized in the sol-gel porous support can withstand high temperature. At the same time the sol-gel matrix must have a high permeability to oxygen. Using a potassium salt of the molybdenum clusters, K{sub 2}Mo{sub 6}Cl{sub 14}, we have established the conditions necessary for deposition of optical quality sol-gel films. From spectroscopic measurements of the film we have shown that the cluster luminescence is stable following heat cycling of 54 hours at 200 C. Quenching of a factor of 1.5X between pure nitrogen and 21% oxygen was observed from in-situ measurements of films heated directly at 200 C. An automated system for characterizing fiber optic oxygen sensors up to 220 C with a temporal resolution better than 10 s is under construction. We estimate a signal of 6 x 10{sup 8} photons/s after complete quenching in 21% oxygen. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  7. Optical properties of oxygenated CdTe thin films

    NASA Astrophysics Data System (ADS)

    Zapata-Navarro, A.; Peña-Chapa, J. L.; Villagrán De León, J. C.

    1996-07-01

    Cadmium telluride oxide films (CdTe-O) were grown by a radio frequency sputtering technique on glass slide substrates using a controlled plasma (Ar-N2O). The films were studied by Auger electron spectroscopy (AES) and optical transmission. We demonstrate that the oxidation process enhances the transmittance of the films into the visible part of the spectrum depending on the oxygen concentration.

  8. Thermodynamic, transport, and flow properties of gaseous products resulting from combustion of methane-air-oxygen

    NASA Technical Reports Server (NTRS)

    Klich, G. F.

    1976-01-01

    Results of calculations to determine thermodynamic, transport, and flow properties of combustion product gases are presented. The product gases are those resulting from combustion of methane-air-oxygen and methane-oxygen mixtures. The oxygen content of products resulting from the combustion of methane-air-oxygen mixtures was similiar to that of air; however, the oxygen contained in products of methane-oxygen combustion ranged from 20 percent by volume to zero for stoichiometric combustion. Calculations were made for products of reactant mixtures with fuel percentages, by mass, of 7.5 to 20. Results are presented for specific mixtures for a range of pressures varying from 0.0001 to 1,000 atm and for temperatures ranging from 200 to 3,800 K.

  9. Stoichiometry dependent electron transport and gas sensing properties of indium oxide nanowires.

    PubMed

    Gali, Pradeep; Sapkota, Gopal; Syllaios, A J; Littler, Chris; Philipose, U

    2013-06-01

    The effect of stoichiometry of single crystalline In2O3 nanowires on electrical transport and gas sensing was investigated. The nanowires were synthesized by vapor phase transport and had diameters ranging from 80 to 100 nm and lengths between 10 and 20 μm, with a growth direction of [001]. Transport measurements revealed n-type conduction, attributed to the presence of oxygen vacancies in the crystal lattice. As-grown In2O3 nanowires were shown to have a carrier concentration of ≈5 × 10(17) cm(-3), while nanowires that were annealed in wet O2 showed a reduced carrier concentration of less than 10(16) cm(-3). Temperature dependent conductivity measurements on the as-grown nanowires and analysis of the thermally activated Arrhenius conduction for the temperature range of 77-350 K yielded an activation energy of 0.12 eV. This is explained on the basis of carrier exchange that occurs between the surface states and the bulk of the nanowire, resulting in a depleted surface layer of thickness of the order of the Debye length (LD), estimated to be about 3-4 nm for the as-grown nanowires and about 10 times higher for the more stoichiometric nanowires. Significant changes in the electrical conductance of individual In2O3 nanowires were also observed within several seconds of exposure to NH3 and O2 gas molecules at room temperature, thus demonstrating the potential use of In2O3 nanowires as efficient miniaturized chemical sensors. The sensing mechanism is dominated by the nanowire channel conductance, and a simple energy band diagram is used to explain the change in conductivity when gas molecules adsorbed on the nanowire surface influence its electrical properties. Less stoichiometric nanowires were found to be more sensitive to oxidizing gases while more stoichiometric nanowires showed significantly enhanced response to reducing gases.

  10. Improved in vivo performance of amperometric oxygen (PO2) sensing catheters via electrochemical nitric oxide generation/release.

    PubMed

    Ren, Hang; Coughlin, Megan A; Major, Terry C; Aiello, Salvatore; Rojas Pena, Alvaro; Bartlett, Robert H; Meyerhoff, Mark E

    2015-08-18

    A novel electrochemically controlled release method for nitric oxide (NO) (based on electrochemical reduction of nitrite ions) is combined with an amperometric oxygen sensor within a dual lumen catheter configuration for the continuous in vivo sensing of the partial pressure of oxygen (PO2) in blood. The on-demand electrochemical NO generation/release method is shown to be fully compatible with amperometric PO2 sensing. The performance of the sensors is evaluated in rabbit veins and pig arteries for 7 and 21 h, respectively. Overall, the NO releasing sensors measure both venous and arterial PO2 values more accurately with an average deviation of -2 ± 11% and good correlation (R(2) = 0.97) with in vitro blood measurements, whereas the corresponding control sensors without NO release show an average deviation of -31 ± 28% and poor correlation (R(2) = 0.43) at time points >4 h after implantation in veins and >6 h in arteries. The NO releasing sensors induce less thrombus formation on the catheter surface in both veins and arteries (p < 0.05). This electrochemical NO generation/release method could offer a new and attractive means to improve the biocompatibility and performance of implantable chemical sensors. PMID:26201351

  11. Amphiphilic Fluorinated Polymer Nanoparticle Film Formation and Dissolved Oxygen Sensing Application

    NASA Astrophysics Data System (ADS)

    Gao, Yu; Zhu, Huie; Yamamoto, Shunsuke; Miyashita, Tokuji; Mitsuishi, Masaya

    2016-04-01

    Fluorinated polymer nanoparticle films were prepared by dissolving amphiphilic fluorinated polymer, poly (N-1H, 1H-pentadecafluorooctylmethacrylamide) (pC7F15MAA) in two miscible solvents (AK-225 and acetic acid). A superhydrophobic and porous film was obtained by dropcasting the solution on substrates. With higher ratios of AK-225 to acetic acid, pC7F15MAA was densified around acetic acid droplets, leading to the formation of pC7F15MAA nanoparticles. The condition of the nanoparticle film preparation was investigated by varying the mixing ratio or total concentration. A highly sensitive dissolved oxygen sensor system was successfully prepared utilizing a smart surface of superhydrophobic and porous pC7F15MAA nanoparticle film. The sensitivity showed I0/I40 = 126 in the range of dissolved oxygen concentration of 0 ~ 40 mg L-1. The oxygen sensitivity was compared with that of previous reports.

  12. Properties of turbulence in natural gas-oxygen diffusion flames

    SciTech Connect

    Sautet, J.C.; Ditaranto, M. ); Samaniego, J.M.; Charon, O. )

    1999-07-01

    Measurements of turbulent flow field velocities, including first and second order velocity moments and the shear stress are carried out by laser Doppler velocimetry in five different, 25 kW, turbulent natural gas-oxygen diffusion flames. The mean flow behavior is described including the velocity half value radius as well as centerline velocity. Mean radial velocity profiles are fitted by a Gaussian function. According to the initial momentum ratio, different jet dynamic behaviors are pointed out by the description of the fluctuating velocity field.

  13. Acene-doped polymer films: singlet oxygen dosimetry and protein sensing.

    PubMed

    Koylu, Damla; Sarrafpour, Syena; Zhang, Jingjing; Ramjattan, Sanya; Panzer, Matthew J; Thomas, Samuel W

    2012-10-01

    This paper describes thin films comprising acenes dispersed in a conjugated polymeric host that have a ratiometric photoluminescence response to singlet oxygen. These films also respond to irradiation of protein-bound sensitizers, which represents a solution to the problem of protein-conjugated polymer non-specific interactions. PMID:22899174

  14. Functional properties of opsins and their contribution to light-sensing physiology.

    PubMed

    Terakita, Akihisa; Nagata, Takashi

    2014-10-01

    Many animals have developed systems for sensing environmental conditions during evolution. In sensory cells, receptor molecules are responsible for their sensing abilities. In light sensing, most animals capture light information via rhodopsin-like photoreceptive proteins known as opsin-based pigments. A body of evidence from comparisons of amino acid sequences and in vitro experiments demonstrates that opsins have phylogenetically and functionally diversified during evolution and suggests that the phylogenetic diversity in opsins correlates with the variety of molecular properties of opsin-based pigments. In this review, we discuss the various molecular properties of opsin-based pigments and their contribution to light-sensing ability by providing two examples: i) contribution of photoregeneration ability and Chromophore retinal binding property of an Opn3 homolog to non-visual photoreception, and ii) contribution of an absorption characteristic of a visual pigment to depth perception in jumping spiders. PMID:25284384

  15. Hydrothermal synthesis of self-assembled hierarchical tungsten oxides hollow spheres and their gas sensing properties.

    PubMed

    Li, Jinwei; Liu, Xin; Cui, Jiashan; Sun, Jianbo

    2015-05-20

    Hierarchical self-assembled hollow spheres (HS) of tungsten oxide nanosheets have been synthesized via a template-free hydrothermal method. Morphology evolution of the products is determined by the amount of H2C2O4 (oxalic acid) which serves as chelating agent. Structural features of the products were characterized by X-ray diffraction (XRD), and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the porous structure was analyzed using the Brunauer-Emmett-Teller (BET) approach. The synthesis mechanism of the products with self-assembled hierarchical structures was proposed. The NO2 gas sensing properties of self-assembled hierarchical WO3 HS materials were investigated, the gas sensing properties of WO3 synthesized by a variety of formulations were compared, and the possible gas sensing mechanism was discussed. The obvious enhancement of the gas sensing properties was ascribed to the structure of the hierarchical HS.

  16. Human oxygen sensing may have origins in prokaryotic elongation factor Tu prolyl-hydroxylation.

    PubMed

    Scotti, John S; Leung, Ivanhoe K H; Ge, Wei; Bentley, Michael A; Paps, Jordi; Kramer, Holger B; Lee, Joongoo; Aik, WeiShen; Choi, Hwanho; Paulsen, Steinar M; Bowman, Lesley A H; Loik, Nikita D; Horita, Shoichiro; Ho, Chia-hua; Kershaw, Nadia J; Tang, Christoph M; Claridge, Timothy D W; Preston, Gail M; McDonough, Michael A; Schofield, Christopher J

    2014-09-16

    The roles of 2-oxoglutarate (2OG)-dependent prolyl-hydroxylases in eukaryotes include collagen stabilization, hypoxia sensing, and translational regulation. The hypoxia-inducible factor (HIF) sensing system is conserved in animals, but not in other organisms. However, bioinformatics imply that 2OG-dependent prolyl-hydroxylases (PHDs) homologous to those acting as sensing components for the HIF system in animals occur in prokaryotes. We report cellular, biochemical, and crystallographic analyses revealing that Pseudomonas prolyl-hydroxylase domain containing protein (PPHD) contain a 2OG oxygenase related in structure and function to the animal PHDs. A Pseudomonas aeruginosa PPHD knockout mutant displays impaired growth in the presence of iron chelators and increased production of the virulence factor pyocyanin. We identify elongation factor Tu (EF-Tu) as a PPHD substrate, which undergoes prolyl-4-hydroxylation on its switch I loop. A crystal structure of PPHD reveals striking similarity to human PHD2 and a Chlamydomonas reinhardtii prolyl-4-hydroxylase. A crystal structure of PPHD complexed with intact EF-Tu reveals that major conformational changes occur in both PPHD and EF-Tu, including a >20-Å movement of the EF-Tu switch I loop. Comparison of the PPHD structures with those of HIF and collagen PHDs reveals conservation in substrate recognition despite diverse biological roles and origins. The observed changes will be useful in designing new types of 2OG oxygenase inhibitors based on various conformational states, rather than active site iron chelators, which make up most reported 2OG oxygenase inhibitors. Structurally informed phylogenetic analyses suggest that the role of prolyl-hydroxylation in human hypoxia sensing has ancient origins.

  17. Human oxygen sensing may have origins in prokaryotic elongation factor Tu prolyl-hydroxylation.

    PubMed

    Scotti, John S; Leung, Ivanhoe K H; Ge, Wei; Bentley, Michael A; Paps, Jordi; Kramer, Holger B; Lee, Joongoo; Aik, WeiShen; Choi, Hwanho; Paulsen, Steinar M; Bowman, Lesley A H; Loik, Nikita D; Horita, Shoichiro; Ho, Chia-hua; Kershaw, Nadia J; Tang, Christoph M; Claridge, Timothy D W; Preston, Gail M; McDonough, Michael A; Schofield, Christopher J

    2014-09-16

    The roles of 2-oxoglutarate (2OG)-dependent prolyl-hydroxylases in eukaryotes include collagen stabilization, hypoxia sensing, and translational regulation. The hypoxia-inducible factor (HIF) sensing system is conserved in animals, but not in other organisms. However, bioinformatics imply that 2OG-dependent prolyl-hydroxylases (PHDs) homologous to those acting as sensing components for the HIF system in animals occur in prokaryotes. We report cellular, biochemical, and crystallographic analyses revealing that Pseudomonas prolyl-hydroxylase domain containing protein (PPHD) contain a 2OG oxygenase related in structure and function to the animal PHDs. A Pseudomonas aeruginosa PPHD knockout mutant displays impaired growth in the presence of iron chelators and increased production of the virulence factor pyocyanin. We identify elongation factor Tu (EF-Tu) as a PPHD substrate, which undergoes prolyl-4-hydroxylation on its switch I loop. A crystal structure of PPHD reveals striking similarity to human PHD2 and a Chlamydomonas reinhardtii prolyl-4-hydroxylase. A crystal structure of PPHD complexed with intact EF-Tu reveals that major conformational changes occur in both PPHD and EF-Tu, including a >20-Å movement of the EF-Tu switch I loop. Comparison of the PPHD structures with those of HIF and collagen PHDs reveals conservation in substrate recognition despite diverse biological roles and origins. The observed changes will be useful in designing new types of 2OG oxygenase inhibitors based on various conformational states, rather than active site iron chelators, which make up most reported 2OG oxygenase inhibitors. Structurally informed phylogenetic analyses suggest that the role of prolyl-hydroxylation in human hypoxia sensing has ancient origins. PMID:25197067

  18. Protein kinase G–regulated production of H2S governs oxygen sensing

    PubMed Central

    Yuan, Guoxiang; Vasavda, Chirag; Peng, Ying-Jie; Makarenko, Vladislav V.; Raghuraman, Gayatri; Nanduri, Jayasri; Gadalla, Moataz M.; Semenza, Gregg L.; Kumar, Ganesh K.; Snyder, Solomon H.; Prabhakar, Nanduri R.

    2015-01-01

    Reflexes initiated by the carotid body, the principal O2-sensing organ, are critical for maintaining cardio-respiratory homeostasis during hypoxia. O2 sensing by the carotid body requires carbon monoxide (CO) generation by heme oxygenase-2 (HO-2) and hydrogen sulfide (H2S) synthesis by cystathionine-γ-lyase (CSE). We report that O2 stimulated the generation of CO, but not that of H2S, and required two cysteine residues in the heme regulatory motif (Cys265 and Cys282) of HO-2. CO stimulated protein kinase G (PKG)–dependent phosphorylation of Ser377 of CSE, inhibiting the production of H2S. Hypoxia decreased the inhibition of CSE by reducing CO generation resulting in increased H2S, which stimulated carotid body neural activity. In carotid bodies from mice lacking HO-2, compensatory increased abundance of nNOS (neuronal nitric oxide synthase) mediated O2 sensing through PKG-dependent regulation of H2S by nitric oxide. These results provide a mechanism for how three gases work in concert in the carotid body to regulate breathing. PMID:25900831

  19. THE OXYGEN PERMEATION PROPERTIES OF NANO CRYSTALLINE CEO2 THIN FILMS

    SciTech Connect

    Brinkman, K.

    2010-09-27

    The measurement of oxygen flux across nanocrystalline CeO{sub 2} cerium oxide thin films at intermediate temperature (650 to 800 C) is presented. Porous ceria support substrates were fabricated by sintering with carbon additions. The final dense film was deposited from an optimized sol-gel solution resulting in a mean grain size of 50 nm which displayed oxygen flux values of up to 0.014 {micro}mol/cm{sup 2}s over the oxygen partial pressure range from air to helium gas used in the measurement at 800 C. The oxygen flux characteristics confirm mixed ionic and electronic conductivity in nanocrystalline ceria films and demonstrate the role of size dependent materials properties as a design parameter in functional membranes for oxygen separation.

  20. Determination of atomic oxygen density and temperature of the thermosphere by remote sensing

    NASA Astrophysics Data System (ADS)

    Sharma, Ramesh D.; Harlow, Harry B.; Riehl, James P.

    1988-06-01

    Measurement of emission from the earth's atmosphere in the far infrared due to transitions between fine structure levels of the ground state (3P) of atomic oxygen at 63 microns, (3P1 to 3P2) and 147 microns (3P0 to 3P1) is proposed. These magnetic-dipole allowed transitions with long radiative lifetimes (about 3.2 h for the 63 micron transition and about 16.3 h for the 147 micron transition) are assumed to be in equilibrium with the local translational temperature. A one-dimensional onion-peel inversion of the limb emissions at 63 and 147 microns from a model atmosphere is shown to yield reasonable results for both the temperature and atomic oxygen density in the 90-250 km altitude range.

  1. The disulfide relay of the intermembrane space of mitochondria: an oxygen-sensing system?

    PubMed

    Bihlmaier, Karl; Mesecke, Nikola; Kloeppel, Christine; Herrmann, Johannes M

    2008-12-01

    The intermembrane space of mitochondria contains many proteins that lack classical mitochondrial targeting sequences. Instead, these proteins often show characteristic patterns of cysteine residues that are critical for their accumulation in the organelle. Import of these proteins is catalyzed by two essential components, Mia40 and Erv1. Mia40 is a protein in the intermembrane space that directly binds newly imported proteins via disulfide bonds. By reorganization of these bonds, intramolecular disulfide bonds are formed in the imported proteins, which are thereby released from Mia40 into the intermembrane space. Because folded proteins are unable to traverse the import pore of the outer membrane, this leads to a permanent location of these proteins within the mitochondria. During this reaction, Mia40 becomes reduced and needs to be re-oxidized to regain its activity. Oxidation of Mia40 is carried out by Erv1, a conserved flavine adenine dinucleotide (FAD)-binding sulfhydryl oxidase. Erv1 directly interacts with Mia40 and shuttles electrons from reduced Mia40 to oxidized cytochrome c, from whence they flow through cytochrome oxidase to molecular oxygen. The connection of the disulfide relay with the respiratory chain not only significantly increases the efficiency of the oxidase activity, but also prevents the formation of potentially deleterious hydrogen peroxide. The oxidative activity of Erv1 strongly depends on the oxygen concentration in mitochondria. Erv1, therefore, may function as a molecular switch that adapts mitochondrial activities to the oxygen levels in the cell.

  2. Memristive properties of hexagonal WO3 nanowires induced by oxygen vacancy migration.

    PubMed

    He, Xiongwu; Yin, Yanling; Guo, Jie; Yuan, Huajun; Peng, Yuehua; Zhou, Yong; Zhao, Ding; Hai, Kuo; Zhou, Weichang; Tang, Dongsheng

    2013-01-01

    Tungsten trioxide (WO3) is always oxygen-deficient or non-stoichiometric under atmospheric conditions. Positively charged oxygen vacancies prefer to drift as well as electrons when the electric field is strong enough, which will alter the distribution of oxygen vacancies and then endow WO3 with memristive properties. In Au/WO3 nanowire/Au sandwich structures with two ohmic contacts, the axial distribution of oxygen vacancies and then the electrical transport properties can be more easily modulated by bias voltage. The threshold electric field for oxygen vacancy drifting in single-crystal hexagonal WO3 nanowire is about 106 V/m, one order of magnitude less than that in its granular film. At elevated temperatures, the oxygen vacancy drifts and then the memristive effect can be enhanced remarkably. When the two metallic contacts are asymmetric, the WO3 nanowire devices even demonstrate good rectifying characteristic at elevated temperatures. Based on the drift of oxygen vacancies, nanoelectronic devices such as memristor, rectifier, and two-terminal resistive random access memory can be fabricated on individual WO3 nanowires. PMID:23347429

  3. Performance and properties of atomic oxygen protective coatings for polymeric materials

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Lamoreaux, Cynthia

    1992-01-01

    Such large LEO spacecraft as the Space Station Freedom will encounter high atomic oxygen fluences which entail the use of protective coatings for their polymeric structural materials. Such coatings have demonstrated polymer mass losses due to oxidation that are much smaller than those of unprotected materials. Attention is here given to protective and/or electrically conductive coatings of SiO(x), Ge, and indium-tin oxide which have been exposed to atomic oxygen in order to ascertain mass loss, electrical conductivity, and optical property dependence on atomic oxygen exposure.

  4. Enhanced Gas-Sensing Properties of the Hierarchical TiO₂ Hollow Microspheres with Exposed High-Energy {001} Crystal Facets.

    PubMed

    Yang, Yong; Liang, Yan; Wang, Guozhong; Liu, Liangliang; Yuan, Cailei; Yu, Ting; Li, Qinliang; Zeng, Fanyan; Gu, Gang

    2015-11-11

    Anatase hierarchical TiO2 with innovative designs (hollow microspheres with exposed high-energy {001} crystal facets, hollow microspheres without {001} crystal facets, and solid microspheres without {001} crystal facets) were synthesized via a one-pot hydrothermal method and characterized. Based on these materials, gas sensors were fabricated and used for gas-sensing tests. It was found that the sensor based on hierarchical TiO2 hollow microspheres with exposed high-energy {001} crystal facets exhibited enhanced acetone sensing properties compared to the sensors based on the other two materials due to the exposing of high-energy {001} crystal facets and special hierarchical hollow structure. First-principle calculations were performed to illustrate the sensing mechanism, which suggested that the adsorption process of acetone molecule on TiO2 surface was spontaneous, and the adsorption on high-energy {001} crystal facets would be more stable than that on the normally exposed {101} crystal facets. Further characterization indicated that the {001} surface was highly reactive for the adsorption of active oxygen species, which was also responsible for the enhanced sensing performance. The present studies revealed the crystal-facets-dependent gas-sensing properties of TiO2 and provided a new insight into improving the gas sensing performance by designing hierarchical hollow structure with special-crystal-facets exposure.

  5. Pulsation Properties of Carbon and Oxygen Red Giants

    NASA Astrophysics Data System (ADS)

    Percy, J. R.; Huang, D. J.

    2015-07-01

    We have used up to 12 decades of AAVSO visual observations, and the AAVSO VSTAR software package to determine new and/or improved periods of 5 pulsating biperiodic carbon (C-type) red giants, and 12 pulsating biperiodic oxygen (M-type) red giants. We have also determined improved periods for 43 additional C-type red giants, in part to search for more biperiodic C-type stars, and also for 46 M-type red giants. For a small sample of the biperiodic C-type and M-type stars, we have used wavelet analysis to determine the time scales of the cycles of amplitude increase and decrease. The C-type and M-type stars do not differ significantly in their period ratios (first overtone to fundamental). There is a marginal difference in the lengths of their amplitude cycles. The most important result of this study is that, because of the semiregularity of these stars, and the presence of alias, harmonic, and spurious periods, the periods which we and others derive for these stars—especially the smaller-amplitude ones—must be determined and interpreted with great care and caution. For instance: spurious periods of a year can produce an apparent excess of stars, at that period, in the period distribution.

  6. Synthesis, characterization and gas sensing properties of tin oxide nanopowder

    NASA Astrophysics Data System (ADS)

    Choudhary, Meenakshi; Mishra, V. N.; Dwivedi, R.

    2013-06-01

    In the present work, tin oxide nanopowder has been synthesized by solid-state reaction technique. The as-prepared pure and palladium doped (0.5 and 1%) powders have been used for the fabrication of thick film sensors. The influence of particle size of powders and morphology of the thick films has been studied on the sensing performance of thick film sensor. It is observed that the sensors produced from the SnO2 doped with 1% palladium have an excellent ability for the detection of hydrogen gas.

  7. Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

    PubMed Central

    Galvin, C. O. T.; Cooper, M. W. D.; Rushton, M. J. D.; Grimes, R. W.

    2016-01-01

    Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Thx,Pu1−x)O2 (0 ≤ x ≤ 1) between 300–3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Thx,Pu1−x)O2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Thx,Pu1−x)O2 is explained in terms of lower oxygen defect formation enthalpies for (Thx,Pu1−x)O2 than PuO2 and ThO2, while links are drawn between the superionic transition temperature and oxygen Frenkel disorder. PMID:27796314

  8. Room temperature NO2-sensing properties of WO3 nanoparticles/porous silicon

    NASA Astrophysics Data System (ADS)

    Yan, Wenjun; Hu, Ming; Zeng, Peng; Ma, Shuangyun; Li, Mingda

    2014-02-01

    WO3 nanoparticles were synthesized by sol-gel method with tungsten hexachloride (WCl6) as precursor and deposited onto porous silicon and alumina substrates by dip-coating. The morphology and crystal structure of samples were investigated by means of field emission scanning electron microscope and X-ray diffractometer. It is the experimental results demonstrated by gas sensing tests that WO3 nanoparticles combining with the substrate of porous silicon presented an improved NO2-sensing property at room temperature. Compared to WO3 deposited on alumina working above 100 °C, the WO3 nanoparticles/porous silicon exhibited higher properties upon exposure to sub-ppm concentrations of NO2 gas at room temperature. Additionally, the NO2-sensing performance of WO3 nanoparticles/porous silicon was enhanced markedly, in comparison to pure porous silicon. The mechanism of WO3/porous silicon composite structure on the NO2 sensing was explained in detail.

  9. FIBER OPTICAL MICRO-DETECTORS FOR OXYGEN SENSING IN POWER PLANTS

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III

    2004-10-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. High temperature measurements of the emission of clusters in sol gel films show that the luminescence intensity from the films follow a 1/T relationship from room temperature to 150 C, and then declines at a slower rate at higher temperatures. The large number of photons available at 230 C is consistent with simple low cost optics for fiber optic probes based on the emission from clusters in sol gel films.

  10. Hydrazine sensing properties of microwave synthesized graphene/ZnO composites

    NASA Astrophysics Data System (ADS)

    Sreejesh, M.; Nagaraja, H. S.; Udaya Bhat, K.

    2016-05-01

    This paper reports the synthesis of graphene/ ZnO nanocomposite using microwave method and its application in sensing of hydrazine. The morphological characteristics of the samples are studied using Scanning Electron Microscope (SEM). The formation of the composite is further confirmed by the X-ray Diffraction (XRD). Energy Dispersive X-ray Analysis (EDAX) shows the presence of carbon indicating the presence of graphene. The hydrazine sensing property of the electrode is studied using cyclic voltammometry (CV) and Chronoamperometry (CA) studeis.

  11. Properties of Aluminum Deposited by a High-Velocity Oxygen-Fueled Process

    SciTech Connect

    Chow, R; Decker, T A; Gansert, R V; Gansert, D; Lee, D

    2001-06-12

    Aluminum coatings deposited by a HVOF process have been demonstrated and relevant coating properties evaluated according to two deposition parameters, the spray distance and the oxygen-to-fuel flow ratio. The coating porosity, surface roughness, and microhardness are measured. The coating properties are fairly insensitive to spray distance, the distance between the nozzle and the workpiece, and fuel ratios, the oxygen-to-fuel flow. Increasing the fuel content does appear to improve the process productivity in terms of surface roughness. Minimization of nozzle loading is discussed.

  12. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    SciTech Connect

    Mene, Ravindra U.; Mahabole, Megha P.; Mohite, K.C.; Khairnar, Rajendra S.

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  13. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    SciTech Connect

    Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2014-01-28

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  14. Cirrus Mammatus Properties Derived from an Extended Remote Sensing Dataset.

    NASA Astrophysics Data System (ADS)

    Wang, Likun; Sassen, Kenneth

    2006-02-01

    The first quantitative and statistical evaluation of cirrus mammatus clouds based on wavelet analysis of remote sensing data is made by analyzing the University of Utah Facility for Atmospheric Remote Sensing (FARS) 10-yr high-cloud dataset. First, a case study of cirrus mammata combining a high-resolution lidar system and a W-band Doppler radar is presented, yielding an assessment of the thermodynamic environment and dynamic mechanisms. Then, 25 cirrus mammatus cases selected from the FARS lidar dataset are used to disclose their characteristic environmental conditions, and vertical and length scales. The results show that cirrus mammata occur in the transition zone from moist (cloudy) to dry air layers with weak wind shear, which suggests that cloud-induced thermal structures play a key role in their formation. Their maximum vertical and horizontal length scales vary from 0.3 to 1.1 km and 0.5 to 8.0 km, respectively. It is also found that small-scale structures develop between the large-scale protuberances. The spectral slopes of the lidar-returned power and mean radar Doppler velocity data extracted from the cirrus cloud-base region further indicate the presence of developed three-dimensional, locally isotropic, homogeneous turbulence generated by buoyancy. Finally, comparisons of anvil and cirrus mammata are made. Although both are generated in a similar environment, cirrus mammata generally do not form fallout fronts like their anvil counterparts, and so do not have their smooth and beautiful outlines.


  15. Singlet oxygen-induced photodegradation of the polymers and dyes in optical sensing materials and the effect of stabilizers on these processes.

    PubMed

    Enko, Barbara; Borisov, Sergey M; Regensburger, Johannes; Bäumler, Wolfgang; Gescheidt, Georg; Klimant, Ingo

    2013-09-12

    A comprehensive study of photodegradation processes in optical sensing materials caused by photosensitized singlet oxygen in different polymers is presented. The stabilities of the polymers are accessed in the oxygen consumption measurements performed with help of optical oxygen sensors. Polystyrene and poly(phenylsilesquioxane) are found to be the most stable among the polymers investigated, whereas poly(2,6-dimethyl-p-phenylene oxide) and particularly poly(methyl methacrylate) and their derivatives show the fastest oxygen consumption. The effect of the stabilizers (singlet oxygen quenchers) on the oxygen consumption rates, the photostability of the sensitizer, and the total photon emission (TPE) by singlet oxygen is studied. 1,4-Diazabicyclo[2.2.2]octane (DABCO) was found to significantly reduce both the TPE and the oxygen consumption rates, indicating its role as a physical quencher of singlet oxygen. The addition of DABCO also significantly improved the photostability of the sensitizer. The N-alkylated derivative of DABCO and DABCO covalently grafted to the polystyrene backbone are prepared in an attempt to overcome the volatility and water solubility of the quencher. These derivatives as well as other tertiary amines investigated were found to be inefficient as stabilizing agents, and some of them even negatively affected the oxygen consumption rates.

  16. Thermophysical properties and oxygen transport in the (Ux,Pu1-x)O2 lattice

    NASA Astrophysics Data System (ADS)

    Cooper, M. W. D.; Murphy, S. T.; Rushton, M. J. D.; Grimes, R. W.

    2015-06-01

    Using molecular dynamics, the thermophysical properties of the (Ux,Pu1-x)O2 system have been investigated between 300 and 3200 K. The variation with temperature of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure, are explained in terms of defect formation and diffusivity on the oxygen sublattice. Vegard's Law is approximately observed for the thermal expansion of the solid solutions below 2000 K. Deviation from Vegard's Law above this temperature occurs due to the different superionic transition temperatures of the solid solutions (2200-2900 K). Similarly, a spike in the specific heat, associated with the superionic transition, occurs at lower temperatures in solid solutions that have a high Pu content. While oxygen diffusivity is higher in pure PuO2 than in pure UO2, lower oxygen defect enthalpies in (Ux,Pu1-x)O2 solid solutions cause higher oxygen mobility than would be expected by interpolation between the diffusivities of the end members. In comparison to UO2 and PuO2 there is considerable variety of oxygen vacancy and oxygen interstitial sites in solid solutions generating a wide range of property values. Trends in the defect enthalpies are discussed in terms of composition and the lattice parameter of (Ux,Pu1-x)O2. Comparison is made with previous work on (Ux,Th1-x)O2.

  17. Iodine-mediated etching of gold nanorods for plasmonic sensing of dissolved oxygen and salt iodine.

    PubMed

    Zhang, Zhiyang; Chen, Zhaopeng; Cheng, Fangbin; Zhang, Yaowen; Chen, Lingxin

    2016-05-10

    Here, we have carefully investigated iodine-mediated etching of gold nanorods (AuNRs) in the presence of iodate and applied this phenomenon to on-site detection of dissolved oxygen (DO). Under given conditions, the quantitative conversion of target analytes DO to iodine leads to the etching of AuNRs along the longitudinal direction with the aid of cetyltrimethylammonium. As a result, the longitudinal localized surface plasmon resonance shifts to a short wavelength. The peak-shift can be used for quantitative determination of DO and iodate by a spectrophotometer. The satisfactory results from DO detection in different water samples and iodate detection in table salt indicate the feasibility of the proposed methods. Moreover, the as-prepared colorimetric test paper would make the detection more economical and simpler. PMID:27049138

  18. A Potassium-Dependent Oxygen Sensing Pathway Regulates Plant Root Hydraulics.

    PubMed

    Shahzad, Zaigham; Canut, Matthieu; Tournaire-Roux, Colette; Martinière, Alexandre; Boursiac, Yann; Loudet, Olivier; Maurel, Christophe

    2016-09-22

    Aerobic organisms survive low oxygen (O2) through activation of diverse molecular, metabolic, and physiological responses. In most plants, root water permeability (in other words, hydraulic conductivity, Lpr) is downregulated under O2 deficiency. Here, we used a quantitative genetics approach in Arabidopsis to clone Hydraulic Conductivity of Root 1 (HCR1), a Raf-like MAPKKK that negatively controls Lpr. HCR1 accumulates and is functional under combined O2 limitation and potassium (K(+)) sufficiency. HCR1 regulates Lpr and hypoxia responsive genes, through the control of RAP2.12, a key transcriptional regulator of the core anaerobic response. A substantial variation of HCR1 in regulating Lpr is observed at the Arabidopsis species level. Thus, by combinatorially integrating two soil signals, K(+) and O2 availability, HCR1 modulates the resilience of plants to multiple flooding scenarios.

  19. A Potassium-Dependent Oxygen Sensing Pathway Regulates Plant Root Hydraulics.

    PubMed

    Shahzad, Zaigham; Canut, Matthieu; Tournaire-Roux, Colette; Martinière, Alexandre; Boursiac, Yann; Loudet, Olivier; Maurel, Christophe

    2016-09-22

    Aerobic organisms survive low oxygen (O2) through activation of diverse molecular, metabolic, and physiological responses. In most plants, root water permeability (in other words, hydraulic conductivity, Lpr) is downregulated under O2 deficiency. Here, we used a quantitative genetics approach in Arabidopsis to clone Hydraulic Conductivity of Root 1 (HCR1), a Raf-like MAPKKK that negatively controls Lpr. HCR1 accumulates and is functional under combined O2 limitation and potassium (K(+)) sufficiency. HCR1 regulates Lpr and hypoxia responsive genes, through the control of RAP2.12, a key transcriptional regulator of the core anaerobic response. A substantial variation of HCR1 in regulating Lpr is observed at the Arabidopsis species level. Thus, by combinatorially integrating two soil signals, K(+) and O2 availability, HCR1 modulates the resilience of plants to multiple flooding scenarios. PMID:27641502

  20. FIBER OPTICAL MICRO-DETECTORS FOR OXYGEN SENSING IN POWER PLANTS

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III

    2004-07-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Alkali salts of Mo{sub 6}Cl{sub 12} were synthesized and heated to 280 C for one hour in air. Optical measurements of the thermally treated material confirm the potential of the salts as lumophores in high temperature fiber optic sensors. In addition sol-gel films containing Mo{sub 6}Cl{sub 12} were dip coated on quartz substrates and heated at 200 C for one hour. Conditions were developed for successfully immobilizing monomeric complexes that are compatible with sol-gel processing.

  1. TASK channels in arterial chemoreceptors and their role in oxygen and acid sensing.

    PubMed

    Buckler, Keith J

    2015-05-01

    Arterial chemoreceptors play a vital role in cardiorespiratory control by providing the brain with information regarding blood oxygen, carbon dioxide, and pH. The main chemoreceptor, the carotid body, is composed of sensory (type 1) cells which respond to hypoxia or acidosis with a depolarising receptor potential which in turn activates voltage-gated calcium entry, neurosecretion and excitation of adjacent afferent nerves. The receptor potential is generated by inhibition of Twik-related acid-sensitive K(+) channel 1 and 3 (TASK1/TASK3) heterodimeric channels which normally maintain the cells' resting membrane potential. These channels are thought to be directly inhibited by acidosis. Oxygen sensitivity, however, probably derives from a metabolic signalling pathway. The carotid body, isolated type 1 cells, and all forms of TASK channel found in the type 1 cell, are highly sensitive to inhibitors of mitochondrial metabolism. Moreover, type1 cell TASK channels are activated by millimolar levels of MgATP. In addition to their role in the transduction of chemostimuli, type 1 cell TASK channels have also been implicated in the modulation of chemoreceptor function by a number of neurocrine/paracrine signalling molecules including adenosine, GABA, and serotonin. They may also be instrumental in mediating the depression of the acute hypoxic ventilatory response that occurs with some general anaesthetics. Modulation of TASK channel activity is therefore a key mechanism by which the excitability of chemoreceptors can be controlled. This is not only of physiological importance but may also offer a therapeutic strategy for the treatment of cardiorespiratory disorders that are associated with chemoreceptor dysfunction.

  2. Fiber Optical Micro-detectors for Oxygen Sensing in Power Plants

    SciTech Connect

    Gregory L. Baker; Ruby N. Ghosh; D.J. Osborn III; Po Zhang

    2005-10-01

    A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. Previously we immobilized the potassium salt of a molybdenum cluster, K{sub 2}M{sub 6}Cl{sub 14}, in a sol-gel matrix and showed that the luminescence is stable after 54 hours at 200 C, but the quenching ratios were low and the films delaminated after thermal cycling due to densification of the matrix. Three new approaches to solve decreased quenching over time and delamination of films off fiber tips were investigated. In the first approach K{sub 2}Mo{sub 6}Cl{sub 14} embedded in cured sol-gel particles were incorporated into a TEOS based sol-gel. These gave enhanced quenching (6x), but delaminated. Our second approach was to use a commercial cyanoacrylate glue to immobilize the particles onto the tip of an optical fiber. This gave better adhesion and good quenching initially, but eventually the glue degraded upon heating. Our third approach was to use a 55% OtMOS/ TEOS sol-gel binder. Films based on this new sol-gel binder show high quenching ({approx}6x) and superior mechanical stability even after thermal cycling. Sensor measurements on an optical fiber containing K{sub 2}Mo{sub 6}Cl{sub 14} embedded in cured sol-gel particles were obtained from 100 to 25 C. The signal intensity in nitrogen was stable at 2.8 {+-} 0.2 nW, and the quenching ratio (ratio of signal in N{sub 2} vs. 21 % O{sub 2}) varied from 4.4 to 6.9X. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

  3. Haemoglobin polymorphisms affect the oxygen-binding properties in Atlantic cod populations.

    PubMed

    Andersen, Oivind; Wetten, Ola Frang; De Rosa, Maria Cristina; Andre, Carl; Carelli Alinovi, Cristiana; Colafranceschi, Mauro; Brix, Ole; Colosimo, Alfredo

    2009-03-01

    A major challenge in evolutionary biology is to identify the genes underlying adaptation. The oxygen-transporting haemoglobins directly link external conditions with metabolic needs and therefore represent a unique system for studying environmental effects on molecular evolution. We have discovered two haemoglobin polymorphisms in Atlantic cod populations inhabiting varying temperature and oxygen regimes in the North Atlantic. Three-dimensional modelling of the tetrameric haemoglobin structure demonstrated that the two amino acid replacements Met55beta1Val and Lys62beta1Ala are located at crucial positions of the alpha1beta1 subunit interface and haem pocket, respectively. The replacements are proposed to affect the oxygen-binding properties by modifying the haemoglobin quaternary structure and electrostatic feature. Intriguingly, the same molecular mechanism for facilitating oxygen binding is found in avian species adapted to high altitudes, illustrating convergent evolution in water- and air-breathing vertebrates to reduction in environmental oxygen availability. Cod populations inhabiting the cold Arctic waters and the low-oxygen Baltic Sea seem well adapted to these conditions by possessing the high oxygen affinity Val55-Ala62 haplotype, while the temperature-insensitive Met55-Lys62 haplotype predominates in the southern populations. The distinct distributions of the functionally different haemoglobin variants indicate that the present biogeography of this ecologically and economically important species might be seriously affected by global warming.

  4. Haemoglobin polymorphisms affect the oxygen-binding properties in Atlantic cod populations

    PubMed Central

    Andersen, Øivind; Wetten, Ola Frang; De Rosa, Maria Cristina; Andre, Carl; Carelli Alinovi, Cristiana; Colafranceschi, Mauro; Brix, Ole; Colosimo, Alfredo

    2008-01-01

    A major challenge in evolutionary biology is to identify the genes underlying adaptation. The oxygen-transporting haemoglobins directly link external conditions with metabolic needs and therefore represent a unique system for studying environmental effects on molecular evolution. We have discovered two haemoglobin polymorphisms in Atlantic cod populations inhabiting varying temperature and oxygen regimes in the North Atlantic. Three-dimensional modelling of the tetrameric haemoglobin structure demonstrated that the two amino acid replacements Met55β1Val and Lys62β1Ala are located at crucial positions of the α1β1 subunit interface and haem pocket, respectively. The replacements are proposed to affect the oxygen-binding properties by modifying the haemoglobin quaternary structure and electrostatic feature. Intriguingly, the same molecular mechanism for facilitating oxygen binding is found in avian species adapted to high altitudes, illustrating convergent evolution in water- and air-breathing vertebrates to reduction in environmental oxygen availability. Cod populations inhabiting the cold Arctic waters and the low-oxygen Baltic Sea seem well adapted to these conditions by possessing the high oxygen affinity Val55–Ala62 haplotype, while the temperature-insensitive Met55–Lys62 haplotype predominates in the southern populations. The distinct distributions of the functionally different haemoglobin variants indicate that the present biogeography of this ecologically and economically important species might be seriously affected by global warming. PMID:19033139

  5. Effects of oxygen content on the microstructures and optical properties of thermochromic vanadium oxide thin films

    NASA Astrophysics Data System (ADS)

    Luo, Zhenfei; Wu, Zhiming; Wang, Tao; Li, Weizhi; Jiang, Yadong

    2012-02-01

    Reactive direct current magnetron sputtering and in situ thermal oxidation were used to prepare vanadium oxide (VO X ) thin films with different oxygen contents. X-ray diffraction, Fourier transform infrared spectroscopy and a field emission scanning electron microscope were employed to characterize the films. The optical properties of the VO X films at room temperature and 90 °C were investigated by applying an spectroscopic ellipsometer with a three-layer model of BEMA/Brendel-Bormann oscillator/substrate. It was demonstrated that the vanadium-oxygen bonds were strengthened, the film thickness and roughness decreased, while the grain size increased with increasing oxygen content. The increase in oxygen content had the effect of decreasing the near-infrared reflectance and free-electron concentration of the film at 90°C due to the decrease in the amount of VO2.

  6. Oxygen binding properties of hemoglobin from the white rhinoceros (beta 2-GLU) and the tapir.

    PubMed

    Baumann, R; Mazur, G; Braunitzer, G

    1984-04-01

    The beta-chain of rhinoceros hemoglobin contains glutamic acid at position beta 2, and important site for the binding of organic phosphates. We have investigated the oxygen binding properties of this hemoglobin and its interaction with ATP, 2,3-diphosphoglycerate, CO2 and chloride. The results show that the presence of GLU at position beta 2 nearly abolishes the effect of organic phosphates and CO2, whereas the oxygen-linked binding of chloride is not affected. Thus rhinoceros hemoglobin has only protons and chloride anions as major allosteric effectors for the control of its oxygen affinity. From the results obtained with hemoglobin solutions it can be calculated that the blood oxygen affinity of the rhinoceros must be rather high with a P50 of about 20 torr at pH 7.4 and 37 degrees C, which conforms with observations obtained for other large mammals.

  7. Effects of dissolved oxygen on electrochemical and semiconductor properties of 316L stainless steel

    NASA Astrophysics Data System (ADS)

    Feng, Zhicao; Cheng, Xuequn; Dong, Chaofang; Xu, Lin; Li, Xiaogang

    2010-12-01

    The effects of dissolved oxygen on the electrochemical behavior and semiconductor properties of passive film formed on 316L SS in three solutions with different dissolved oxygen were studied by using polarization curve, Mott-Schottky analysis and the point defect model (PDM). The results show that higher dissolved oxygen accelerates both anodic and cathodic process. Based on Mott-Schottky analysis and PDM, the key parameters for passive film, donor density Nd, flat-band potential Efb and diffusivity of defects D0 were calculated. The results display that Nd(1-7 × 10 27 m -3) and D0(1-18 × 10 -16 cm 2/s) increase and Efb value reduces with the dissolved oxygen in solution.

  8. Sugar and water contents of honey with dielectrc property sensing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The dielectric properties of pure yellow locust, jujube and rape flower honey and their water-adulterated products with water content from 18% to 42.6% were measured with open-ended coaxial-line probe technology and a network analyzer from 10 to 4500 MHz at 25oC. Dielectric constants of pure honeys ...

  9. Blood oxygen binding properties for the burrowing owl, Athene cunicularia.

    PubMed

    Maginniss, L A; Kilgore, D L

    1989-05-01

    Isocapnic O2 equilibrium curves (O2ECs) were generated for whole blood of 4 adult burrowing owls (Athene cunicularia) using thin film techniques. At in vivo pHa (7.49 +/- 0.02; mean +/- 1 SEM) and 41 degrees C, the PO2 at half saturation (P50) was 42.3 +/- 0.8 Torr. CO2 and fixed acid (H+) Bohr slopes (delta log P50/delta pH) were -0.46 +/- 0.01 and -0.42 +/- 0.02, respectively, demonstrating a small specific CO2 effect. CO2 and H+ Bohr slopes were saturation-independent between 0.1 and 0.9 S. Hill plots for Athene blood were non-linear; the Hill coefficient (n) increased from 2.6 below 0.4 S to 3.4 above 0.6 S. Owl equilibrium data were accurately described by the equation: S = [(7.7 x 10(6]/(P4 + 44P3 - 108P2 + 3.5 x 10(4)P) + 1]-1. This complex O2EC shape may result from Hb heterogeneity; isoelectric focusing showed 4 isoHbs with a molar ratio of 9:1:1:1. This study revealed no apparent adaptations of Athene blood for hypoxic and hypercapnic conditions. We conclude that the observed blood O2 binding properties promote tissue O2 delivery during periods of surface activity. While occupying its burrow, the owl compensates for moderate alterations in inspired gas composition partly through increased ventilation. PMID:2749025

  10. Blood oxygen binding properties for the burrowing owl, Athene cunicularia.

    PubMed

    Maginniss, L A; Kilgore, D L

    1989-05-01

    Isocapnic O2 equilibrium curves (O2ECs) were generated for whole blood of 4 adult burrowing owls (Athene cunicularia) using thin film techniques. At in vivo pHa (7.49 +/- 0.02; mean +/- 1 SEM) and 41 degrees C, the PO2 at half saturation (P50) was 42.3 +/- 0.8 Torr. CO2 and fixed acid (H+) Bohr slopes (delta log P50/delta pH) were -0.46 +/- 0.01 and -0.42 +/- 0.02, respectively, demonstrating a small specific CO2 effect. CO2 and H+ Bohr slopes were saturation-independent between 0.1 and 0.9 S. Hill plots for Athene blood were non-linear; the Hill coefficient (n) increased from 2.6 below 0.4 S to 3.4 above 0.6 S. Owl equilibrium data were accurately described by the equation: S = [(7.7 x 10(6]/(P4 + 44P3 - 108P2 + 3.5 x 10(4)P) + 1]-1. This complex O2EC shape may result from Hb heterogeneity; isoelectric focusing showed 4 isoHbs with a molar ratio of 9:1:1:1. This study revealed no apparent adaptations of Athene blood for hypoxic and hypercapnic conditions. We conclude that the observed blood O2 binding properties promote tissue O2 delivery during periods of surface activity. While occupying its burrow, the owl compensates for moderate alterations in inspired gas composition partly through increased ventilation.

  11. Oxygen permeability and mechanical properties of films from hydrolyzed whey protein.

    PubMed

    Sothornvit, R; Krochta, J M

    2000-09-01

    The effects of whey protein hydrolysis on film oxygen permeability (OP) and mechanical properties at several glycerol-plasticizer levels were studied. Both 5.5% and 10% degree of hydrolysis (DH) whey protein isolate (WPI) had significant effect (p properties compared to unhydrolyzed WPI. Hydrolyzed WPI required less glycerol to achieve the same mechanical properties compared to those of unhydrolyzed WPI. Little or no significant difference (p > 0.05) occurred for film OP between unhydrolyzed WPI, 5.5% DH WPI, and 10% DH WPI films at the same glycerol content. Hydrolyzed WPI films of mechanical properties similar to those of WPI films had better oxygen barrier. Therefore, use of hydrolyzed WPI allowed achievement of desired film flexibility with less glycerol and with smaller increase in OP.

  12. Mechanical properties of chiral and achiral silicon carbide nanotubes under oxygen chemisorption.

    PubMed

    Ansari, R; Mirnezhad, M; Hosseinzadeh, M

    2015-03-01

    In this paper, the mechanical properties of fully oxygenated silicon carbide nanotubes (O2-SiCNTs) are explored using a molecular mechanics model joined with the density functional theory (DFT). The closed-form analytical expressions suggested in this study can easily be adapted for nanotubes with different chiralities. The force constants of molecular mechanics model proposed herein are derived through DFT within a generalized gradient approximation. Moreover, the mechanical properties of fully oxygenated silicon carbide (O2-SiC) sheet are evaluated for the case that the oxygen atoms are adsorbed on one side of the SiC sheet. According to the results obtained for the bending stiffness of O2-SiC sheet, one can conclude that the O2-SiC sheet has isotropic characteristics.

  13. Ocean color remote sensing using polarization properties of reflected sunlight

    NASA Technical Reports Server (NTRS)

    Frouin, R.; Pouliquen, E.; Breon, F.-M.

    1994-01-01

    The effects of the atmosphere and surface on sunlight backscattered to space by the ocean may be substantially reduced by using the unpolarized component of reflectance instead of total reflectance. At 450 nm, a wavelength of interest in ocean color remote sensing, and for typical conditions, 45% of the unpolarized reflectance may originate from the water body instead of 20% of the total reflectance, which represents a gain of a factor 2.2 in useful signal for water composition retrieval. The best viewing geometries are adjacent to the glitter region; they correspond to scattering angles around 100 deg, but they may change slightly depending on the polarization characteristics of the aerosols. As aerosol optical thickness increases, the atmosphere becomes less efficient at polarizing sunlight, and the enhancement of the water body contribution to unpolarized reflectance is reduced. Since the perturbing effects are smaller on unpolarized reflectance, at least for some viewing geometries, they may be more easily corrected, leading to a more accurate water-leaving signal and, therefore, more accurate estimates of phytoplankton pigment concentration.

  14. Tin dioxide nanoparticles: Reverse micellar synthesis and gas sensing properties

    SciTech Connect

    Ahmed, Jahangeer; Vaidya, Sonalika; Ahmad, Tokeer; Sujatha Devi, P.; Das, Dipankar; Ganguli, Ashok K.

    2008-02-05

    Tin dioxide (SnO{sub 2}) nanoparticles have been synthesized by reverse micellar route using cetyltrimethyl ammoniumbromide (CTAB) as the surfactant. Monophasic tin dioxide (SnO{sub 2}) was obtained using NaOH as the precipitation agent at 60 deg. C, however, when liquor NH{sub 3} was used as precipitating agent then crystalline SnO{sub 2} nanoparticles are obtained at 500 deg. C. SnO{sub 2} prepared using NaOH show crystallite size of 4 and 12 nm after heating at 60 and 500 deg. C respectively using X-ray line broadening studies. Transmission electron microscopy (TEM) studies show agglomerated particles of sizes 70 and 150 nm, respectively. The grain size was found to be 6-8 nm after heating the precursor obtained (using liquor NH{sub 3}) at 500 deg. C by X-ray line broadening and the TEM studies. Dynamic light-scattering (DLS) studies show the aggregates of SnO{sub 2} nanoparticles with uniform size distribution. Moessbauer studies show an increase of s-electron density at the Sn sites compared to bulk SnO{sub 2} and a finite quadrupole splitting indicative of lowering of symmetry around tin atoms. The gas sensing characteristics have also been investigated using n-butane which show high sensitivity and fast recovery time.

  15. Air separation and oxygen storage properties of hexagonal rare-earth manganites

    NASA Astrophysics Data System (ADS)

    Abughayada, Castro

    This dissertation presents evaluation results of hexagonal Y1-x RxMnO3+delta (R = Er, Y, Dy, Pr, La, Tb and Ho) rare-earth manganites for prospective air separation applications. In these materials, oxygen content is sensitively dependent on the surrounding conditions of temperature and/or oxygen partial pressure, and therefore they exhibit the ability to selectively absorb, store, and release significant amounts of separated oxygen from air. This study presents a full characterization of their thermogravimetric characteristics and air separation capabilities. With the expected potential impact of oxygen content on the physical properties of these materials, the scope of this work is expanded to explore other relevant properties such as magnetic, transport, and dilatometric characteristics. Single-phase polycrystalline samples of these materials were achieved in the hexagonal P63cm phase through solid state reaction at elevated temperatures. Further annealings under reducing conditions were required for samples with large rare-earth cations in order to suppress the competing perovskite structure and form in the anticipated hexagonal phase. Thermogravimetric measurements in oxygen atmospheres demonstrated that samples with the larger R ionic radii show rapid and reversible incorporation of significant amounts of excess oxygen (0.41 > delta > 0) at an unusual low temperature range ~190-325 °C. The reversible oxygen storage characteristics of HoMnO3+delta and related materials shown by the fast incorporation and release of interstitial oxygen at easily accessible elevated temperatures of ~300 °C demonstrate the feasibility and potential for low-cost thermal swing adsorption TSA process for oxygen separation and enrichment from air. Neutron and X-ray powder diffraction measurements confirmed the presence of three line compounds RMnO3+delta, the oxygen stoichiometric P6 3cm (delta = 0 for all R), the intermediate oxygen content superstructure phase R3c (delta ~ 0

  16. Regulation of gene expression and secretory functions in oxygen-sensing pheochromocytoma cells.

    PubMed

    Conforti, L; Kobayashi, S; Beitner-Johnson, D; Conrad, P W; Freeman, T; Millhorn, D E

    1999-04-01

    The cellular response to hypoxia is complex. Specialized oxygen chemosensitive cells that are excitable respond to reduced O2 by membrane depolarization, altered gene expression, and neurotransmitter secretion. We have used the O2-sensitive pheochromocytoma (PC12) cell line to investigate the cellular response to hypoxia. Here, we present evidence that membrane depolarization and increased intracellular free Ca2+ are major regulatory events in these cells. Membrane depolarization is mediated by the inhibition of a slow-inactivating voltage-dependent potassium (K) channel. Evidence from molecular biology and patch-clamp studies indicate that the O2-sensitive K channel is a member of the Kv1 family. We also reviewed findings on the regulation of gene expression in PC12 cells during hypoxia. An increase in intracellular free Ca2+ is required for hypoxia-induced transcription of a number of genes including tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamine neurotransmitters, and several of the immediate early genes. We also reviewed the role of dopamine (DA) and adenosine (ADO) receptors in regulation of membrane depolarization and gene expression. PMID:10385038

  17. Oxygen sensing glucose biosensors based on alginate nano-micro systems

    NASA Astrophysics Data System (ADS)

    Chaudhari, Rashmi; Joshi, Abhijeet; Srivastava, Rohit

    2014-04-01

    Clinically glucose monitoring in diabetes management is done by point-measurement. However, an accurate, continuous glucose monitoring, and minimally invasive method is desirable. The research aims at developing fluorescence-mediated glucose detecting biosensors based on near-infrared radiation (NIR) oxygen sensitive dyes. Biosensors based on Glucose oxidase (GOx)-Rudpp loaded alginate microspheres (GRAM) and GOx-Platinum-octaethylporphyrin (PtOEP)-PLAalginate microsphere system (GPAM) were developed using air-driven atomization and characterized using optical microscopy, CLSM, fluorescence spectro-photometry etc. Biosensing studies were performed by exposing standard solutions of glucose. Uniform sized GRAM and GPAM with size 50+/-10μm were formed using atomization. CLSM imaging of biosensors suggests that Rudpp and PtOEP nanoparticles are uniformly distributed in alginate microspheres. The GRAM and GPAM showed a good regression constant of 0.974 and of 0.9648 over a range of 0-10 mM of glucose with a high sensitivity of 3.349%/mM (625 nm) and 2.38%/mM (645 nm) at 10 mM of glucose for GRAM and GPAM biosensor. GRAM and GPAM biosensors show great potential in development of an accurate and minimally invasive glucose biosensor. NIR dye based assays can aid sensitive, minimally-invasive and interference-free detection of glucose in diabetic patients.

  18. Remote sensing of optical properties in continuously stratified waters

    NASA Technical Reports Server (NTRS)

    Gordon, H. R.

    1978-01-01

    The radiative transfer equation is solved by Monte Carlo methods for natural waters in which the optical properties are distributed with depth. It is demonstrated that interpreting the reflectance of a continuously stratified ocean in terms of an equivalent homogeneous ocean yields the average of a particular combination of the water's optical properties over the dimensionless penetration depth. Although in general the dimensionless penetration depth cannot be remotely measured, a method is presented for estimating the actual penetration depth from the remote observations if the medium's absorption coefficient is known, independent of depth, and sufficiently large. The application of this to the remote measurement of the vertical distribution of suspended sediments is discussed in detail.

  19. The Enhanced Formaldehyde-Sensing Properties of P3HT-ZnO Hybrid Thin Film OTFT Sensor and Further Insight into Its Stability

    PubMed Central

    Tai, Huiling; Li, Xian; Jiang, Yadong; Xie, Guangzhong; Du, Xiaosong

    2015-01-01

    A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles' hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology. PMID:25608214

  20. Discrimination of soil hydraulic properties by combined thermal infrared and microwave remote sensing

    NASA Technical Reports Server (NTRS)

    Vandegriend, A. A.; Oneill, P. E.

    1986-01-01

    Using the De Vries models for thermal conductivity and heat capacity, thermal inertia was determined as a function of soil moisture for 12 classes of soil types ranging from sand to clay. A coupled heat and moisture balance model was used to describe the thermal behavior of the top soil, while microwave remote sensing was used to estimate the soil moisture content of the same top soil. Soil hydraulic parameters are found to be very highly correlated with the combination of soil moisture content and thermal inertia at the same moisture content. Therefore, a remotely sensed estimate of the thermal behavior of the soil from diurnal soil temperature observations and an independent remotely sensed estimate of soil moisture content gives the possibility of estimating soil hydraulic properties by remote sensing.

  1. Pyruvate modifies metabolic flux and nutrient sensing during extracorporeal membrane oxygenation in an immature swine model

    SciTech Connect

    Ledee, Dolena R.; Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Olson, Aaron; Isern, Nancy G.; Robillard Frayne, Isabelle; Des Rosiers, Christine; Portman, Michael A.

    2015-07-01

    Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support for infants and children with postoperative cardiopulmonary failure. Nutritional support is mandatory during ECMO, although specific actions for substrates on the heart have not been delineated. Prior work shows that enhancing pyruvate oxidation promotes successful weaning from ECMO. Accordingly, we closely examined the role of prolonged systemic pyruvate supplementation in modifying metabolic parameters during the unique conditions of ventricular unloading provided by ECMO. Twelve male mixed breed Yorkshire piglets (age 30-49 days) received systemic infusion of either normal saline (Group C) or pyruvate (Group P) during ECMO for 8 hours. Over the final hour piglets received [2-13C] pyruvate, and [13C6]-L-leucine, as an indicator for oxidation and protein synthesis. A significant increase in lactate and pyruvate concentrations occurred, along with an increase in the absolute concentration of all measured CAC intermediates. Group P showed greater anaplerotic flux through pyruvate carboxylation although pyruvate oxidation relative to citrate synthase flux was similar to Group C. The groups demonstrated similar leucine fractional contributions to acetyl-CoA and fractional protein synthesis rates. Pyruvate also promoted an increase in the phosphorylation state of several nutrient sensitive enzymes, such as AMPK and ACC, and promoted O-GlcNAcylation through the hexosamine biosynthetic pathway (HBP). In conclusion, prolonged pyruvate supplementation during ECMO modified anaplerotic pyruvate flux and elicited changes in important nutrient and energy sensitive pathways, while preserving protein synthesis. Therefore, the observed results support the further study of nutritional supplementation and its downstream effects on cardiac adaptation during ventricular unloading.

  2. Remote Sensing of Spectral Aerosol Properties: A Classroom Experience

    NASA Technical Reports Server (NTRS)

    Levy, Robert C.; Pinker, Rachel T.

    2006-01-01

    Bridging the gap between current research and the classroom is a major challenge to today s instructor, especially in the sciences where progress happens quickly. NASA Goddard Space Flight Center and the University of Maryland teamed up in designing a graduate class project intended to provide a hands-on introduction to the physical basis for the retrieval of aerosol properties from state-of-the-art MODIS observations. Students learned to recognize spectral signatures of atmospheric aerosols and to perform spectral inversions. They became acquainted with the operational MODIS aerosol retrieval algorithm over oceans, and methods for its evaluation, including comparisons with groundbased AERONET sun-photometer data.

  3. Hyperspectral Remote Sensing of Atmosphere and Surface Properties

    NASA Technical Reports Server (NTRS)

    Liu, Xu; Zhou, Daniel K.; Larar, Allen M.; Yang, Ping

    2011-01-01

    Atmospheric Infrared Sounder (AIRS), Infrared Atmospheric Sounding Interferometer (IASI), and Cross-track Infrared Sounder (CrIS) are all hyper-spectral satellite sensors with thousands of spectral channels. Top of atmospheric radiance spectra measured by these sensors contain high information content on atmospheric, cloud, and surface properties. Exploring high information content contained in these high spectral resolution spectra is a challenging task due to computation e ort involved in modeling thousands of spectral channels. Usually, only very small fractions (4{10 percent) of the available channels are included in physical retrieval systems or numerical weather forecast (NWP) satellite data assimilations. We will describe a method of simultaneously retrieving atmospheric temperature, moisture, cloud, and surface properties using all available spectral channels without sacrificing computational speed. The essence of the method is to convert channel radiance spectra into super-channels by an Empirical Orthogonal Function (EOF) transformation. Because the EOFs are orthogonal to each other, about 100 super-channels are adequate to capture the information content of the radiance spectra. A Principal Component-based Radiative Transfer Model (PCRTM) developed at NASA Langley Research Center is used to calculate both the super-channel magnitudes and derivatives with respect to atmospheric profiles and other properties. There is no need to perform EOF transformations to convert super channels back to spectral space at each iteration step for a one-dimensional variational retrieval or a NWP data assimilation system. The PCRTM forward model is also capable of calculating radiative contributions due to multiple-layer clouds. The multiple scattering effects of the clouds are efficiently parameterized. A physical retrieval algorithm then performs an inversion of atmospheric, cloud, and surface properties in super channel domain directly therefore both reducing the

  4. Comparison of the macroscopic properties of field-accelerated electrons in dry air and in pure oxygen

    NASA Astrophysics Data System (ADS)

    Fournier, G.; Bonnet, J.; Pigache, D.

    1980-06-01

    The numerical solution of the Boltzmann equation for an ionized gas yields the macroscopic properties of electrons accelerated by an electric field in dry air and in pure oxygen. For the purpose of ozone generation, the stronger the field, the better the efficiency of oxygen dissociation. In air, the oxygen dissociation is found to be much less easy than that at the same amount of pure oxygen.

  5. Electrical conduction and NO2 gas sensing properties of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Şahin, Yasin; Öztürk, Sadullah; Kılınç, Necmettin; Kösemen, Arif; Erkovan, Mustafa; Öztürk, Zafer Ziya

    2014-06-01

    Thermally stimulated current (TSC), photoresponse and gas sensing properties of zinc oxide (ZnO) nanorods were investigated depending on heating rates, illumination and dark aging times with using sandwich type electrode system. Vertically aligned ZnO nanorods were grown on indium tin oxide (ITO) coated glass substrate by hydrothermal process. TSC measurements were performed at different heating rates under constant potential. Photoresponse and gas sensing properties were investigated in dry air ambient at 200 °C. For gas sensing measurements, ZnO nanorods were exposed to NO2 (100 ppb to 1 ppm) in dark and illuminated conditions and the resulting resistance transient was recorded. It was found from dark electrical measurements that the dependence of the dc conductivity on temperature followed Mott's variable range hopping (VRH) model. In addition, response time and recovery times of ZnO nanorods to NO2 gas decreased by exposing to white light.

  6. Preparation and gas sensing property of Ag-supported vanadium oxide nanotubes

    NASA Astrophysics Data System (ADS)

    Jin, Wei; Yan, Shilin; Chen, Wen; Yang, Shuang; Zhao, Chunxia; Dai, Ying

    2014-03-01

    A facile microwave irradiation was used to synthesize Ag nanoparticle supported on vanadium oxide nanotubes (VONTs) in this paper. The VONTs on alumina tube installed with Pt electrodes were tested for gas sensing towards C2H5OH, NH3 and C6H5CH3 gases. Detailed studies showed that the sensing capabilities were greatly enhanced in comparison to those of pure nanotubes. It was found that the Ag nanoparticles supported on VONTs sensing films exhibited a high C2H5OH selectivity compared with NH3 and C6H5CH3 gases. When the sensor is exposed to C2H5OH, the ethanol molecules interact with the preadsorbed oxygen ions on the Ag nanoparticles surface. The ethanol oxidation on the Ag nanoparticles leads to the transfer of electrons into the semiconducting VONTs and this is reflected as the change in conductance of sensor. The presence of Ag nanoparticles on the surface of VONTs serves to enhance the C2H5OH oxidation due to a higher oxygen ion-chemisorption on the conductive Ag nanoparticle surfaces.

  7. Physical characterization of functionalized spider silk: electronic and sensing properties

    NASA Astrophysics Data System (ADS)

    Steven, Eden; Park, Jin Gyu; Paravastu, Anant; Branco Lopes, Elsa; Brooks, James S.; Englander, Ongi; Siegrist, Theo; Kaner, Papatya; Alamo, Rufina G.

    2011-10-01

    This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of β-sheet (crystalline) and amorphous (helical) structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 °C, has a strong effect on the morphology of silk bundles (increasing their size), on the process of pyrolization (suppressing mass loss rates) and on the resulting carbonized fiber structure (that becomes more robust against bending and strain). The effects of iodine doping and other functional parameters (vacuum and thin film coating) motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR) to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and β-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR) spectroscopy, revealing a partial transformation of β-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof-of-concept applications of

  8. Psychometric Properties of the Teachers' Sense of Efficacy Scale within the Greek Educational Context

    ERIC Educational Resources Information Center

    Tsigilis, Nikolaos; Koustelios, Athanasios; Grammatikopoulos, Vasilios

    2010-01-01

    Many concerns have been raised about the validity of the existing instruments measuring teachers' efficacy. Recently, a new instrument to measure teachers' perceived efficacy has been presented, namely, the Teachers' Sense of Efficacy Scale (TSES). The purpose of the present study is to examine the psychometric properties of the TSES in the Greek…

  9. Historical development of grain moisture measurement and other food quality sensing through electrical properties.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A review of the use of electrical properties of agricultural products for sensing moisture content and other qualities shows that their use for rapid measurements of the moisture content in grain and seed has been the most successful application. Discovery of useful correlations between the moistur...

  10. Estimating crop biophysical properties from remote sensing data by inverting linked radiative transfer and ecophysiological models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Remote sensing technology can rapidly provide spatial information on crop growth status, which ideally could be used to invert radiative transfer models or ecophysiological models for estimating a variety of crop biophysical properties. However, the outcome of the model inversion procedure will be ...

  11. Transport properties for the oxygen system - O2, O, O(+), and e

    NASA Technical Reports Server (NTRS)

    Biolsi, Louis

    1988-01-01

    The transport properties of the oxygen system, O2, O, O(+), and the electron, e, are calculated and their applications are discussed. The possible two-body interactions in the oxygen system are examined and the exponential repulsive potential is used to determine collision integrals for these interactions. Values are presented for the viscosity of the pure gases, the self-diffusion coefficient of the pure gases at 1 atm pressure, the translational thermal conductivity of the pure gases, and the internal thermal conductivity of O2.

  12. Enhanced Gas Sensing Properties of SnO2 Hollow Spheres Decorated with CeO2 Nanoparticles Heterostructure Composite Materials.

    PubMed

    Liu, Jiangyang; Dai, Mingjun; Wang, Tianshuang; Sun, Peng; Liang, Xishuang; Lu, Geyu; Shimanoe, Kengo; Yamazoe, Noboru

    2016-03-01

    CeO2 decorated SnO2 hollow spheres were successfully synthesized via a two-step hydrothermal strategy. The morphology and structures of as-obtained CeO2/SnO2 composites were analyzed by various kinds of techniques. The SnO2 hollow spheres with uniform size around 300 nm were self-assembled with SnO2 nanoparticles and were hollow with a diameter of about 100 nm. The CeO2 nanoparticles on the surface of SnO2 hollow spheres could be clearly observed. X-ray photoelectron spectroscopy results confirmed the existence of Ce(3+) and the increased amount of both chemisorbed oxygen and oxygen vacancy after the CeO2 decorated. Compared with pure SnO2 hollow spheres, such composites revealed excellent enhanced sensing properties to ethanol. When the ethanol concentration was 100 ppm, the sensitivity of the CeO2/SnO2 composites was 37, which was 2.65-times higher than that of the primary SnO2 hollow spheres. The sensing mechanism of the enhanced gas sensing properties was also discussed.

  13. Sputtering temperature dependent growth kinetics and CO2 sensing properties of ZnO deposited over porous silicon

    NASA Astrophysics Data System (ADS)

    Martínez, L.; Holguín-Momaca, J. T.; Karthik, T. V. K.; Olive-Méndez, S. F.; Campos-Alvarez, J.; Agarwal, V.

    2016-10-01

    We report the growth kinetics and sensing properties of ZnO deposited over macro-porous silicon substrates at 400 and 600 °C using magnetron-sputtering technique. Scanning electron microscopy was employed to investigate the morphology and the particle size of the ZnO nanoparticles (NPs). The grain growth kinetics was analyzed with the help of the phenomenological equation rn =k0 texp(- Q / RT) finding an activation energy Q = 13.92 kJ/mol. The grain growth exponent (n = 2.85) for the growth at 400 °C corresponds to an Ostwald ripening process, while the growth at 600 °C is described by n = 1.66 implying a higher growth rate attributed to a high surface diffusion of add-atoms contributing to the formation of larger grains. The sensing response of the complete structure has been tested at different temperatures. The highest sensitivity, S ∼10, was obtained at a sensor temperature of 300 °C on the ZnO NPs sputtered on to the porous silicon substrate at 400 °C. The high response is attributed to the infiltration, uniform and homogenous distribution of the ZnO NPs into the pores. ZnO NPs sputtered at 400 °C are found to be smaller than those grown at 600 °C, exhibiting a larger surface-area/volume ratio and hence increasing the oxygen adsorption resulting in an enhanced CO2 sensitivity.

  14. Investigation on the Electrical and Methane Gas-Sensing Properties of ZnO Thin Films Produced by Different Methods

    NASA Astrophysics Data System (ADS)

    Teimoori, F.; Khojier, K.; Dehnavi, N. Z.

    2016-10-01

    In this work, the influence of deposition method on the structural, electrical, and methane gas-sensing properties of ZnO thin films is investigated. Sol-gel spin coating, direct current (DC) magnetron sputtering, and e-beam evaporation techniques are employed for production of Zn thin films post-annealed at 500°C with a constant flow of oxygen. Detailed morphological, chemical, and structural investigations are carried out on all samples by field emission electron microscopy (FESEM) and x-ray diffraction (XRD) analyses. DC electrical resistivity of the samples was measured using a four-point probe instrument while a Hall effect instrument was used for the Hall effect measurements. The sensing performance was optimized with respect to the deposition method as well as the operating temperature. Detection limit, reproducibility, and stability of all samples produced using different methods are also identified. An optimum operating temperature of 350°C is obtained. The best sensitivity was attributed to the deposited film by the e-beam evaporation method due to its different surface morphology, which provided a larger ratio of surface-to-bulk area, and a lower carrier concentration, which caused higher electrical resistance. All ZnO thin films deposited by different methods also showed good reproducibility and stability.

  15. Study on fabrication of smart FRP-OFBG composite laminates and their sensing properties

    NASA Astrophysics Data System (ADS)

    Wang, Yanlei; Zhou, Zhi; Ou, Jinping

    2007-01-01

    Fiber reinforced polymer (FRP) has gained much attention in civil engineering due to its high strength-to-weight and stiffness-to-weight ratios, corrosion resistance and good fatigue resistance. Optical Fiber Bragg Grating (OFBG) is now widely accepted as smart sensor due to its advantages of electric-magnetic resistance, small size, distributed sensing, durability, and so on. Combined the FRP with OFBG, new kind of smart FRP-OFBG composite laminates was developed. Fabrication method of the smart composite laminates was introduced in this paper. The study presented the basic principle of OFBG sensors. Then the strain and temperature sensing properties of the proposed smart FRP-OFBG composite laminates were experimentally studied on material test system and under hot water, respectively. The experimental results indicate the strain sensing properties of the smart FRP-OFBG composite laminates are nearly the same as that of bare OFBG, however, the temperature sensing abilities of the smart FRP-OFBG composite laminates are improved and the sensitivity coefficient is nearly 3.2 times as much as that of bare OFBG. The strain and temperature sensing precisions of the smart FRP-OFBG composite laminates are 1 μ\\Vegr and 0.03 °C, respectively. The smart FRYOFBG composite laminates are very proper for application in civil engineering.

  16. Optical gas sensing properties of nanoporous Nb2O5 films.

    PubMed

    Ab Kadir, Rosmalini; Rani, Rozina Abdul; Alsaif, Manal M Y A; Ou, Jian Zhen; Wlodarski, Wojtek; O'Mullane, Anthony P; Kalantar-Zadeh, Kourosh

    2015-03-01

    Nanoporous Nb2O5 has been previously demonstrated to be a viable electrochromic material with strong intercalation characteristics. Despite showing such promising properties, its potential for optical gas sensing applications, which involves the production of ionic species such as H(+), has yet to be explored. Nanoporous Nb2O5 can accommodate a large amount of H(+) ions in a process that results in an energy bandgap change of the material which induces an optical response. Here, we demonstrate the optical hydrogen gas (H2) sensing capability of nanoporous anodic Nb2O5 with a large surface-to-volume ratio prepared via a high temperature anodization method. The large active surface area of the film provides enhanced pathways for efficient hydrogen adsorption and dissociation, which are facilitated by a thin layer of Pt catalyst. We show that the process of H2 sensing causes optical modulations that are investigated in terms of response magnitudes and dynamics. The optical modulations induced by the intercalation process and sensing properties of nanoporous anodic Nb2O5 shown in this work can potentially be used for future optical gas sensing systems. PMID:25685899

  17. Solvothermal, chloroalkoxide-based synthesis of monoclinic WO(3) quantum dots and gas-sensing enhancement by surface oxygen vacancies.

    PubMed

    Epifani, Mauro; Comini, Elisabetta; Díaz, Raül; Andreu, Teresa; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Faglia, Guido; Morante, Joan R

    2014-10-01

    We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 °C in oleic acid of W chloroalkoxide solutions was employed. It was shown that the bulk monoclinic crystallographic phase is the stable one even for the nanosized regime (mean size 4 nm). The nanocrystals were characterized by X-ray diffraction, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis, Fourier transform infrared and Raman spectroscopy. It was concluded that they were constituted by a core of monoclinic WO3, surface covered by unstable W(V) species, slowly oxidized upon standing in room conditions. The WO3 nanocrystals could be easily processed to prepare gas-sensing devices, without any phase transition up to at least 500 °C. The devices displayed remarkable response to both oxidizing (nitrogen dioxide) and reducing (ethanol) gases in concentrations ranging from 1 to 5 ppm and from 100 to 500 ppm, at low operating temperatures of 100 and 200 °C, respectively. The analysis of the electrical data showed that the nanocrystals were characterized by reduced surfaces, which enhanced both nitrogen dioxide adsorption and oxygen ionosorption, the latter resulting in enhanced ethanol decomposition kinetics.

  18. DEVICE FOR CONTROL OF OXYGEN PARTIAL PRESSURE

    DOEpatents

    Bradner, H.; Gordon, H.S.

    1957-12-24

    A device is described that can sense changes in oxygen partial pressure and cause a corresponding mechanical displacement sufficient to actuate meters, valves and similar devices. A piston and cylinder arrangement contains a charge of crystalline metal chelate pellets which have the peculiar property of responding to variations in the oxygen content of the ambient atmosphere by undergoing a change in dimension. A lever system amplifies the relative displacement of the piston in the cylinder, and actuates the controlled valving device. This partial pressure oxygen sensing device is useful in controlled chemical reactions or in respiratory devices such as the oxygen demand meters for high altitude aircraft.

  19. [Biooptical properties of marine phytoplankton as they apply to satellite remote sensing

    NASA Technical Reports Server (NTRS)

    Yentsch, Charles S.

    1992-01-01

    This final report covers research performed over a period of 10 years from 1982 to 1992. During this time, Grant #NAGW410 was funded under three titles through a series of Supplements. The original proposal was entitled 'Photoecology, optical properties and remote sensing of warm core rings'; the second and major portion was entitled 'Continuation of studies of biooptical properties of phytoplankton and the study of mesoscale and submesoscale features using fluorescence and colorimetry'; with the final portion named 'Studies of biooptical properties of phytoplankton, with reference to identification of spectral types associated with meso- and submesoscale features in the ocean'. The focus of these projects was to try to expand our knowledge of the biooptical properties of marine phytoplankton as they apply to satellite remote sensing. We used a variety of techniques, new and old, to better measure these optical properties at appropriate scales, in some cases at the level of individual cells. We also exploited the specialized oceanic conditions that occur within certain regions and features of the ocean around the world in order to explain the tremendous variability one sees in a single remote sensing image. This document strives to provide as complete a summary as possible for this large body of work, including the pertinent publications supported by this funding.

  20. [A nondestructive method to measure the oxygen binding and releasing properties of biodegradable polymers microcapsules intented for blood substitutes].

    PubMed

    Zhang, Xiaolan; Yuan, Yuan; Wang, Kai; Shan, Xiaoqian; Zhao, Jian; Sheng, Yan; Liu, Changsheng

    2008-10-01

    P50 is an important parameter reflecting the binding and releasing oxygen properties of blood substitutes. In this study, based on the strong penetrating property of near infrared light and the mechanism involved in the pulsatile oxygen meter in clinic as well as on the ability for penetrating biodegradable polymers and detecting bovine hemoglobin encapsulated within the microcapsules, we have made an airproof and equilibrium apparatus to measure oxygen saturation and oxygen partial pressure. Subsequently, we have obtained the oxygen dissociation curve and P50 of the microcapsules loaded bovine hemoglobin in the light of oxyHemoglobin and deoxyHemoglobin with different spectrum in the near infrared region. The above-mentioned apparatus and method are not destructive to the microcapsules, and the process is simple and nondestructive. So it is practical to take in-situ measurements of the oxygen binding and releasing property of biodegradable polymer microcapsules intented for the blood substitute.

  1. Synthesis and oxygen content dependent properties of hexagonal DyMnO[subscript 3+delta

    SciTech Connect

    Remsen, S.; Dabrowski, B.; Chmaissem, O.; Mais, J.; Szewczyk, A.

    2011-10-28

    Oxygen deficient polycrystalline samples of hexagonal P6{sub 3}cm (space group No.185) DyMnO{sub 3+{delta}} ({delta} < 0) were synthesized in Ar by intentional decomposition of its perovskite phase obtained in air. The relative stability of these phases is in accord with our previous studies of the temperature and oxygen vacancy dependent tolerance factor. Thermogravimetric measurements have shown that hexagonal samples of DyMnO{sub 3+{delta}} (0 {le} {delta} {le} 0.4) exhibit unusually large excess oxygen content, which readily incorporates on heating near 300 C in various partial-pressures of oxygen atmospheres. Neutron and synchrotron diffraction data show the presence of two new structural phases at {delta} {approx} 0.25 (Hex{sub 2}) and {delta} {approx} 0.40 (Hex{sub 3}). Rietveld refinements of the Hex{sub 2} phase strongly suggest it is well modeled by the R3 space group (No.146). These phases were observed to transform back to P6{sub 3}cm above {approx} 350 C when material becomes stoichiometric in oxygen content ({delta} = 0). Chemical expansion of the crystal lattice corresponding to these large changes of oxygen was found to be 3.48 x 10{sup -2} mol{sup -1}. Thermal expansion of stoichiometric phases were determined to be 11.6 x 10{sup -6} and 2.1 x 10{sup -6} K{sup -1} for the P6{sub 3}cm and Hex{sub 2} phases, respectively. Our measurements also indicate that the oxygen non-stoichiometry of hexagonal RMnO{sub 3+{delta}} materials may have important influence on their multiferroic properties.

  2. Synthesis and oxygen content dependent properties of hexagonal DyMnO{sub 3 + sub delta}.

    SciTech Connect

    Remsen, S.; Dabrowski, B.; Chmaissem, O.; Mais, J.; Szewczyk, A.

    2011-07-01

    Oxygen deficient polycrystalline samples of hexagonal P6{sub 3}cm (space group No.185) DyMnO{sub 3+{delta}} ({delta} < 0) were synthesized in Ar by intentional decomposition of its perovskite phase obtained in air. The relative stability of these phases is in accord with our previous studies of the temperature and oxygen vacancy dependent tolerance factor. Thermogravimetric measurements have shown that hexagonal samples of DyMnO{sub 3+{delta}} (0 {<=} {delta} {<=} 0.4) exhibit unusually large excess oxygen content, which readily incorporates on heating near 300 C in various partial-pressures of oxygen atmospheres. Neutron and synchrotron diffraction data show the presence of two new structural phases at {delta} {approx} 0.25 (Hex{sub 2}) and {delta} {approx} 0.40 (Hex{sub 3}). Rietveld refinements of the Hex{sub 2} phase strongly suggest it is well modeled by the R3 space group (No.146). These phases were observed to transform back to P6{sub 3}cm above {approx}350 C when material becomes stoichiometric in oxygen content ({delta} = 0). Chemical expansion of the crystal lattice corresponding to these large changes of oxygen was found to be 3.48 x 10{sup -2} mol{sup -1}. Thermal expansion of stoichiometric phases were determined to be 11.6 x 10{sup -6} and 2.1 x 10{sup -6} K{sup -1} for the P6{sub 3}cm and Hex{sub 2} phases, respectively. Our measurements also indicate that the oxygen non-stoichiometry of hexagonal RMnO{sub 3+{delta}} materials may have important influence on their multiferroic properties.

  3. The physical properties of the blast wave produced by a stoichiometric propane/oxygen explosion

    NASA Astrophysics Data System (ADS)

    Dewey, M. C.; Dewey, J. M.

    2014-07-01

    The trajectory of the primary shock produced by the explosion of a nominal 18.14 t (20 tn) hemispherical propane/oxygen charge was analysed previously to provide the physical properties immediately behind the shock, but gave no information about the time-resolved properties throughout the blast wave. The present study maps all the physical properties of the wave throughout and beyond the positive durations for a range of distances from about 1.6-18 m scaled to a 1 kg charge at NTP. The physical properties were calculated using a hydro-code to simulate the flow field produced by a spherical piston moving with a specific trajectory. This technique has been used extensively to determine the physical properties of blast waves from a variety of sources for which the piston path was determined by high-speed photography of smoke tracers established close to the charges immediately before detonation. In the case of the propane/oxygen explosion, smoke tracer data were not available to determine the trajectory of the spherical piston. An arbitrary piston path was used and its trajectory iteratively adjusted until it produced a blast wave with a primary shock whose trajectory exactly matched the measured trajectory from the propane/oxygen explosion. Throughout the studied flow field the time histories of hydrostatic pressure, density and particle velocity are well described by fits to the modified Friedlander equation. The properties are presented as functions of scaled radius and are compared with the properties of the blast wave from a 1 kg TNT surface burst explosion, and with other measurements of the same explosion.

  4. The physical properties of the blast wave produced by a stoichiometric propane/oxygen explosion

    NASA Astrophysics Data System (ADS)

    Dewey, M. C.; Dewey, J. M.

    2014-11-01

    The trajectory of the primary shock produced by the explosion of a nominal 18.14 t (20 tn) hemispherical propane/oxygen charge was analysed previously to provide the physical properties immediately behind the shock, but gave no information about the time-resolved properties throughout the blast wave. The present study maps all the physical properties of the wave throughout and beyond the positive durations for a range of distances from about 1.6-18 m scaled to a 1 kg charge at NTP. The physical properties were calculated using a hydro-code to simulate the flow field produced by a spherical piston moving with a specific trajectory. This technique has been used extensively to determine the physical properties of blast waves from a variety of sources for which the piston path was determined by high-speed photography of smoke tracers established close to the charges immediately before detonation. In the case of the propane/oxygen explosion, smoke tracer data were not available to determine the trajectory of the spherical piston. An arbitrary piston path was used and its trajectory iteratively adjusted until it produced a blast wave with a primary shock whose trajectory exactly matched the measured trajectory from the propane/oxygen explosion. Throughout the studied flow field the time histories of hydrostatic pressure, density and particle velocity are well described by fits to the modified Friedlander equation. The properties are presented as functions of scaled radius and are compared with the properties of the blast wave from a 1 kg TNT surface burst explosion, and with other measurements of the same explosion.

  5. Investigation into the optoelectrical properties of tungsten oxide thin films annealed in an oxygen air

    SciTech Connect

    Arfaoui, A.; Ouni, B. Touihri, S.; Mannoubi, T.

    2014-12-15

    Tungsten oxide (WO{sub x}) thin film have been deposited onto glass substrates using the thermal vacuum evaporation technique, monitored by an annealing process in a variable oxygen atmosphere. Analysis by X-ray diffraction and Raman spectroscopy showed the structural changes from orthorhombic to monoclinic which depend on the annealing temperature and the oxygen content. AFM study shows that the increase of oxygen content leads to a decrease of the root-mean-square from 94.64 nm to 2 nm. Ellipsometric measurements have been used to evaluate the optical constants. Further, it is found that when the oxygen content increases, the band gap of the annealed layer varies from 3.01 eV to 3.52 eV by against, the Urbach energy decreases. The AC conductivity plot showed a universal power law according to the Jonscher model. Moreover, at high frequency semiconductor-to-metallic behavior has been observed. Finally, the effect of annealing in oxygen atmosphere on their structural modifications, morphological, optical properties and electrical conductivity are reported.

  6. Protoporphyrin IX nanoparticle carrier: preparation, optical properties, and singlet oxygen generation.

    PubMed

    Rossi, Liane M; Silva, Paulo R; Vono, Lucas L R; Fernandes, Adjaci U; Tada, Dayane B; Baptista, Maurício S

    2008-11-01

    The present study is focused on developing a nanoparticle carrier for the photosensitizer protoporphyrin IX for use in photodynamic therapy. The entrapment of protoporphyrin IX (Pp IX) in silica spheres was achieved by modification of Pp IX molecules with an organosilane reagent. The immobilized drug preserved its optical properties and the capacity to generate singlet oxygen, which was detected by a direct method from its characteristic phosphorescence decay curve at near-infrared and by a chemical method using 1,3-diphenylisobenzofuran to trap singlet oxygen. The lifetime of singlet oxygen when a suspension of Pp IX-loaded particles in acetonitrile was excited at 532 nm was determined as 52 micros, which is in good agreement with the value determined for methylene blue in acetonitrile solution under the same conditions. The Pp IX-loaded silica particles have an efficiency of singlet oxygen generation (eta Delta) higher than the quantum yield of free porphyrins. This high efficiency of singlet oxygen generation was attributed to changes on the monomer-dimer equilibrium after photosentisizer immobilization. PMID:18834155

  7. A comparative study of the temperature dependence of the oxygen-binding properties of mammalian hemoglobins.

    PubMed

    Coletta, M; Clementi, M E; Ascenzi, P; Petruzzelli, R; Condò, S G; Giardina, B

    1992-03-15

    The effect of temperature on the oxygen-binding properties of hemoglobin (Hb) from ruminants, such as ox, reindeer, musk ox, mouflon and egyptian water buffalo is compared to that of human adult Hb (HbA). A striking difference emerges where in the presence of chloride ions and in the absence of 2,3-diphosphoglycerate [Gri(2,3)P2] a strongly reduced exothermic oxygenation process is observed for all ruminant Hb investigated with respect to HbA. Next, in the presence of physiological concentrations of Gri(2,3)P2, HbA displays a less exothermic oxygenation process, with values tending toward those observed in ruminant Hb [where Gri(2,3)P2 is not a physiological effector and for which the addition of Gri(2,3)P2 has essentially no effect on the oxygenation enthalpy]. Different from HbA, the intrinsically less exothermic oxygen binding seems to be independent of the experimental conditions for ruminant Hb, underlying specific structural characteristics which might be responsible for this feature.

  8. Controlling the electronic properties of Er2O3 thin film by oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Wang, Aaron; Yost, Andrew; Jain, Vivek; Dai, Qilin; Tang, Jinke; Chien, Teyu

    With a high dielectric constant and wide bandgap, Er2O3 is suitable for applications in electronic and optical devices. It is known that in many oxide materials, oxygen vacancy concentration plays a decisive role in engineering the properties of the oxides. To address the oxygen vacancy concentration effects on the properties of Er2O3, here we present Scanning Tunneling Microscopy and Spectroscopy (STM/S) and X-Ray Diffraction (XRD) studies of the Er2O3 thin film made by Pulsed Laser Deposition (PLD). XRD shows Er2O3 thin film deposited at 700oC in high vacuum (HV) (sample 1) has broader peaks compared to that of the one deposited at room temperature (RT) in HV followed by 400oC annealing in air (sample 2). This indicates that, for sample 1, the loss of long range periodicity in crystal structure is mainly due to oxygen vacancies. Moreover, a relatively rough surface with 2 to 5 nm nanoclusters were observed in sample 1 by STM; while sample 2 is too resistive for STM measurements. In addition, Scanning Tunneling Spectroscopy (STS) analysis for sample 1 revealed the bandgap as well as features in the conduction band which may be related to the oxygen vacancies.

  9. Sensing, Control, and In Situ Measurement of Coating Properties: An Integrated Approach Toward Establishing Process-Property Correlations

    NASA Astrophysics Data System (ADS)

    Sampath, S.; Srinivasan, V.; Valarezo, A.; Vaidya, A.; Streibl, T.

    2009-06-01

    Over the last decade there has been an explosion in terms of available tools for sensing the particle spray stream in thermal spray processes. This has led to considerable enhancement in our understanding of process reproducibility and reliability. Despite these advances, the linkage to coating properties has continued to be an enigma. This is partially due to the complex nature of the build-up process and the associated issues with measuring properties of these complex coatings. In this paper, we identify critical issues in processing-structure-property relations particularly with respect to the linkage to particle properties. Our goal is to demonstrate an integrated strategy, one that combines particle state sensing, with process mapping and extracting coating properties in situ through the development of robust and advanced curvature-based techniques. These techniques allow estimation of coating modulus, residual stress and, non-linear response of thermal sprayed ceramic coatings all within minutes of the deposition process. Finally, the integrated strategy examines the role of process maps for control of the spray stream as well as tailoring properties of thermal spray coatings. Examples of such studies for yttria-stabilized zirconia thermal barrier coatings are discussed.

  10. A comparison of the ethanol sensing properties of α-iron oxide nanostructures prepared via the sol-gel and electrospinning techniques

    NASA Astrophysics Data System (ADS)

    Leonardi, S. G.; Mirzaei, A.; Bonavita, A.; Santangelo, S.; Frontera, P.; Pantò, F.; Antonucci, P. L.; Neri, G.

    2016-02-01

    Haematite (α-Fe2O3) nanostructures were synthesized via a Pechini sol-gel method (PSG) and an electrospinning (ES) technique. Their texture and morphology were investigated by scanning and transmission electron microscopy. α-Fe2O3 nanoparticles were obtained by the PSG method, whereas fibrous structures consisting of interconnected particles were synthesized through the ES technique. The crystallinity of the α-Fe2O3 nanostructures was also studied by means of x-ray diffraction and Raman spectroscopy. Gas-sensing devices were fabricated by printing the synthesized samples on ceramic substrates provided with interdigitated Pt electrodes. The sensors were tested towards low concentrations of ethanol in air in the temperature range (200-400°C). The results show that the α-Fe2O3 nanostructures exhibit somewhat different gas-sensing properties and, interestingly, their sensing behaviour is strongly temperature-dependent. The availability of active sites for oxygen chemisorption and the diffusion of the analyte gas within the sensing layer structure are hypothesized to be the key factors responsible for the different sensing behaviour observed.

  11. Effects of Oxygen Vacancy on Optical and Electrical Properties of ZnO Bulks and Nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Xiao-Xia; Zheng, Hong-Mei; Fang, Xiao-Yong; Jin, Hai-Bo; Cao, Mao-Sheng

    2014-11-01

    Based on the generalized gradient approximation (GGA) in density functional theory (DFT) and using the first-principle plane wave ultrasoft pseudopotential method, we construct and optimize the structures of intrinsic and oxygen vacancy (VO) ZnO bulks and nanowires (NWs) in the Castep module. Moreover, the calculation of band structures and the optical properties are carried out. The calculated results exhibit that the oxygen vacancy exerts a more significant influence on the electronic structures of the ZnO bulks instead of the NWs. What is more, the influences of the VO on the optical properties are mainly embodied in the ultraviolet region, and the main optical parameters of ZnO bulks and NWs with VO are anisotropic.

  12. Water-soluble nanocrystalline cellulose films with highly transparent and oxygen barrier properties

    NASA Astrophysics Data System (ADS)

    Cheng, Shaoling; Zhang, Yapei; Cha, Ruitao; Yang, Jinliang; Jiang, Xingyu

    2015-12-01

    By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food.By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07647a

  13. Properties of solid polymer electrolyte fluorocarbon film. [used in hydrogen/oxygen fuel cells

    NASA Technical Reports Server (NTRS)

    Alston, W. B.

    1973-01-01

    The ionic fluorocarbon film used as the solid polymer electrolyte in hydrogen/oxygen fuel cells was found to exhibit delamination failures. Polarized light microscopy of as-received film showed a lined region at the center of the film thickness. It is shown that these lines were not caused by incomplete saponification but probably resulted from the film extrusion process. The film lines could be removed by an annealing process. Chemical, physical, and tensile tests showed that annealing improved or sustained the water contents, spectral properties, thermo-oxidative stability, and tensile properties of the film. The resistivity of the film was significantly decreased by the annealing process.

  14. BOMBER: A tool for estimating water quality and bottom properties from remote sensing images

    NASA Astrophysics Data System (ADS)

    Giardino, Claudia; Candiani, Gabriele; Bresciani, Mariano; Lee, Zhongping; Gagliano, Stefano; Pepe, Monica

    2012-08-01

    BOMBER (Bio-Optical Model Based tool for Estimating water quality and bottom properties from Remote sensing images) is a software package for simultaneous retrieval of the optical properties of water column and bottom from remotely sensed imagery, which makes use of bio-optical models for optically deep and optically shallow waters. Several menus allow the user to choose the model type, to specify the input and output files, and to set all of the variables involved in the model parameterization and inversion. The optimization technique allows the user to retrieve the maps of chlorophyll concentration, suspended particulate matter concentration, coloured dissolved organic matter absorption and, in case of shallow waters, bottom depth and distributions of up to three different types of substrate, defined by the user according to their albedo. The software requires input image data that must be atmospherically corrected to remote sensing reflectance values. For both deep and shallow water models, a map of the relative error involved in the inversion procedure is also given. The tool was originally intended to estimate water quality in lakes; however thanks to its general design, it can be applied to any other aquatic environments (e.g., coastal zones, estuaries, lagoons) for which remote sensing reflectance values are known. BOMBER is fully programmed in IDL (Interactive Data Language) and uses IDL widgets as graphical user interface. It runs as an add-on tool for the ENVI+IDL image processing software and is available on request.

  15. Remote-Sensing Reflectance and Inherent Optical Properties for Optically Deep Waters: A Revisit

    NASA Technical Reports Server (NTRS)

    Lee, Zhong-Ping; Carder, Kendall L.; Du, Ke-Ping

    2001-01-01

    Remote-sensing reflectance (r(rs)) is defined as the ratio of upwelling radiance to downwelling irradiance. Relationships between remote-sensing reflectance and inherent optical properties serve as the basis for ocean-color modeling, as well as for spectral deduction of oceanic constituents through analytical/semi-analytical models of ocean color. A decade ago, a simple and concise formula based on Monte Carlo simulations was developed by relating rrs to a property u, the ratio of backscattering (b(b)) to the sum of absorption (a) and backscattering (u = b(b)/(a+b(b))). This relationship generally ignored the shape differences in phase functions between molecular scattering and particle scattering. In this study, the relationship is updated with separate parameters for molecular and particle scattering, based on the Radiative Transfer Equation through use of Hydrolight numerical solutions. The new approach fits r(rs) better than an earlier traditional formula, for both clear and turbid waters.

  16. Monochloramine-sensitive amperometric microelectrode: optimization of gold, platinum, and carbon fiber sensing materials for removal of dissolved oxygen interference

    EPA Science Inventory

    Amperometric monochloramine detection using newly fabricated gold, platinum, and carbon-fiber microsensors was investigated to optimize sensor operation and eliminate oxygen interference. Gold and platinum microsensors exhibited no oxygen interference during monochloramine measu...

  17. Growth conditions effects on the H2 and CO2 gas sensing properties of Indium Tin Oxide

    NASA Astrophysics Data System (ADS)

    Isik, S.; Coban, O.; Shafai, C.; Tuzemen, S.; Gur, E.

    2016-04-01

    Indium Tin Oxide (ITO) thin films are transparent conducting wide bandgap oxide. In this study investigated optical, structural and morphological properties of sputtered ITO thin films using X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDX) and optical absorption techniques. These measurements revealed that the oxygen gas percentage present in the ITO film deposited by RF magnetron sputter deposition showed systematic variation of its band gap, crystal orientation, growth rate, figure of merit (FOM) and dominant XRD peaks. All the thin films deposited at room temperature (RT). Once characterization of the films carried out, H2 and CO2 resistive gas sensors fabricated by depositing the ITO film on top of aluminium interdigitated contacts/electrode (IDE), that fabricated following lithography and etching processes. These devices showed reasonable sensitivity for pure H2 and CO2 at elevated temperature. A correlation found between the thin film properties of the ITO and its sensing capability for H2 and CO2, which these gases are important in many fields such as automotive, energy, biological and health-related applications.

  18. Room temperature ammonia and VOC sensing properties of CuO nanorods

    NASA Astrophysics Data System (ADS)

    Bhuvaneshwari, S.; Gopalakrishnan, N.

    2016-05-01

    Here, we report a NH3 and Volatile Organic Compounds (VOCs) sensing prototype of CuO nanorods with peculiar sensing characteristics at room temperature. High quality polycrystalline nanorods were synthesized by a low temperature hydrothermal method. The rods are well oriented with an aspect ratio of 5.71. Luminescence spectrum of CuO nanorods exhibited a strong UV-emission around 415 nm (2.98 eV) which arises from the electron-hole recombination phenomenon. The absence of further deep level emissions establishes the lack of defects such as oxygen vacancies and Cu interstitials. At room temperature, the sensor response was recorded over a range of gas concentrations from 100-600 ppm of ammonia, ethanol and methanol. The sensor response showed power law dependence with the gas concentration. This low temperature sensing can be validated by the lower value of calculated activation energy of 1.65 eV observed from the temperature dependent conductivity measurement.

  19. Synthesis of nestlike ZnO hierarchically porous structures and analysis of their gas sensing properties.

    PubMed

    Wang, Xinzhen; Liu, Wei; Liu, Jiurong; Wang, Fenglong; Kong, Jing; Qiu, Song; He, Cuizhu; Luan, Liqiang

    2012-02-01

    Nestlike 3D ZnO porous structures with size of 1.0-3.0 μm have been synthesized through annealing the zinc hydroxide carbonate precursor, which was obtained by a one-pot hydrothermal process with the assistance of glycine, Na(2)SO(4), and polyvinyl pyrrolidone (PVP). The nestlike 3D ZnO structures are built of 2D nanoflakes with the thickness of ca. 20 nm, which exhibit the nanoporous wormhole-like characteristic. The measured surface area is 36.4 m(2)g(-1) and the pore size is ca. 3-40 nm. The unique nestlike 3D ZnO porous structures provided large contacting surface area for electrons, oxygen and target gas molecules, and abundant channels for gas diffusion and mass transport. Gas sensing tests showed that the nestlike 3D ZnO porous structures exhibit excellent gas sensing performances such as high sensitivity and fast response and recovery speed, suggesting the potential applications as advanced gas sensing materials.

  20. Electrochemical sensing property of Mn doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Giribabu, K.; Manigandan, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2013-02-01

    The Mn doped Fe3O4 nanoparticles were synthesized by hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD) analysis, UV-Visible spectroscopy (UV-Vis) and field emission scanning electron microscopy (FE-SEM). The electrochemical sensing property of pure and Mn doped Fe3O4 nanoparticles were examined using uric acid (UA) as an analyte. The obtained results indicated that the Mn doped Fe3O4 nanoparticles exhibited higher electrocatalytic activity towards UA.

  1. Oxygen partial pressure dependent magnetic properties of manganese-zinc ferrite polycrystals

    SciTech Connect

    Byeon, S.C.; Hong, K.S.; Je, H.J.

    1997-05-01

    A systematic variation in initial permeability with oxygen partial pressure during post sintering cooling was observed in Mn{sub 0.47}Zn{sub 0.47}Fe{sub 2.06}O{sub 4} polycrystalline samples. The initial permeability increased from 6,300 to 8,600 when the atmospheric parameter decreased from 8.4 to 6.4. Here atmospheric parameter is the degree of oxygen partial pressure engaged in the cooling stage of the sample preparation. The origins of this systematic variation were investigated by measuring the saturation magnetization under high fields (10 kOe) and by observing microstructure changes as well as the magnetic properties under small applied fields (0.15 mOe). It was found that saturation magnetization of samples under high fields was almost unchanged in the range of oxygen partial pressures through which Fe{sup 2+} concentration varied by up to 0.5%. The systematic changes in saturated magnetization and saturation time under small applied fields suggest that the permeability is strongly dependent on domain mobility. This increase in domain mobility was attributed to increased grain growth with decreasing oxygen partial pressure.

  2. Integrating Remote Sensing Data with Socioeconomic Data: Sensitivity, Confidentiality, Privacy, and Intellectual Property Challenges

    NASA Astrophysics Data System (ADS)

    Downs, R. R.; Adamo, S. B.

    2014-12-01

    The integration of remote sensing data with socioeconomic data presents new opportunities for scientific discovery and analysis that can improve understanding of the environmental sustainability issues that society faces today. Such integrated data products and services can be used to study interdisciplinary issues by investigators representing various disciplines. In addition to the scientific benefits that can be attained by integrating remote sensing data with socioeconomic data, the integration of these data also present challenges that reflect the complex issues that arise when sharing and integrating different types of science data. When integrating one or more datasets that contain sensitive information, data producers need to be aware of the limitations that have been placed upon the data to protect private property, species or other inhabitants that reside on the property, or restricted information about a particular location. Similarly, confidentiality and privacy issues are a concern for data that have been collected about individual humans and families who have volunteered to serve as human research subjects or whose personal information may have been collected without their knowledge. In addition, intellectual property rights that are associated with a particular dataset may prevent integration with other data or pose constraints on the use of the resulting data products or services. These challenges will be described along with approaches that can be applied to address them when planning projects that involve the integration of remote sensing data with socioeconomic data.

  3. Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Pan, Xiaoyang; Yang, Min-Quan; Fu, Xianzhi; Zhang, Nan; Xu, Yi-Jun

    2013-04-01

    Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the

  4. Real-time endoscopic oxygenation imaging using single snapshot of optical properties (SSOP) imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Angelo, Joseph P.; van de Giessen, Martijn; Gioux, Sylvain

    2016-03-01

    With 50% of all interventional procedures in the US being minimally invasive, there is a need for objective tools to help guide surgeons in this challenging environment. Tissue oxygenation is a useful biomarker of tissue viability and suitable for surgical guidance. Here we present our efforts to perform real-time quantitative optical imaging through a rigid endoscope using Single Snapshot of Optical Properties (SSOP) imaging. In particular, in this work we introduce for the first time 3 dimensionally-corrected dual wavelength optical properties imaging using SSOP through an endoscope, allowing accurate oxygenation maps to be obtained on tissue simulating phantoms and in vivo samples. We compared the results with state-of-the-art wide-field spatial frequency domain imaging (SFDI). Overall, results from the novel endoscopic imaging system agreed within 10% in absorption, reduced scattering, and oxygenation. Moreover, we introduce here real-time, video-rate quantitative optical imaging with 3D profile correction through an endoscope. These results demonstrate the potential of endoscopic SSOP as an objective surgical guidance tool for the clinic.

  5. Reduced-Gravity Measurements of the Effect of Oxygen on Properties of Zirconium

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Lee, J.; Wunderlich, R.; Fecht, H.-J.; Schneider, S.; SanSoucie, M.; Rogers, J.; Hyers, R.

    2016-01-01

    The influence of oxygen on the thermophysical properties of zirconium is being investigated using MSL-EML (Material Science Laboratory - Electromagnetic Levitator) on ISS (International Space Station) in collaboration with NASA, ESA (European Space Agency), and DLR (German Aerospace Center). Zirconium samples with different oxygen concentrations will be put into multiple melt cycles, during which the density, viscosity, surface tension, heat capacity, and electric conductivity will be measured at various undercooled temperatures. The facility check-up of MSL-EML and the first set of melting experiments have been successfully performed in 2015. The first zirconium sample will be tested near the end of 2015. As part of ground support activities, the thermophysical properties of zirconium and ZrO were measured using a ground-based electrostatic levitator located at the NASA Marshall Space Flight Center. The influence of oxygen on the measured surface tension was evaluated. The results of this research will serve as reference data for those measured in ISS.

  6. Effect of Oxygen Annealing on the Electrical Properties of PBLZST Anti-ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Yi, Jinqiao; Xiong, Xue; Liu, Sisi; Jiang, Shenglin

    2015-11-01

    The effect of oxygen annealing on the electrical properties of (Pb0.97- x Ba x La0.02)(Zr0.6Sn0.32Ti0.08)O3 (PBLZST) anti-ferroelectric (AFE) ceramics has been investigated through measuring its phase structure, electric field-induced polarization and dielectric properties. The oxygen annealing process can significantly improve the stability of the AFE phase and decrease the dielectric constant peaks. The saturation polarization of the PBLZST samples annealed in O2 increases gradually when x < 0.085, but it decreases when x > 0.085. Compared with the conventional sintering method, the hysteresis switch fields of samples annealed in O2 maintains the consistent stability, and the dielectric constant peaks drop drastically and are simultaneously broadened, except at x = 0.095. The Curie temperature decreases greatly after oxygen annealing when x is smaller than 0.08, but increases slightly when x is greater than 0.08. When x = 0.085, the difference of c/a ratios between the samples processed by the two methods reaches a maximum of about 0.00614, and the increment of the saturation polarization is 7 μC/cm2.

  7. Instrumented impact properties of zircaloy-oxygen and zircaloy-hydrogen alloys

    SciTech Connect

    Garde, A.M.; Kassner, T.F.

    1980-04-01

    Instrumented-impact tests were performed on subsize Charpy speciments of Zircaloy-2 and -4 with up to approx. 1.3 wt % oxygen and approx. 2500 wt ppM hydrogen at temperatures between 373 and 823/sup 0/K. Self-consistent criteria for the ductile-to-brittle transition, based upon a total absorbed energy of approx. 1.3 x 10/sup 4/ J/m/sup 2/, a dynamic fracture toughness of approx. 10 MPa.m/sup 1/2/, and a ductility index of approx. 0, were established relative to the temperature and oxygen concentration of the transformed BETA-phase material. The effect of hydrogen concentration and hydride morphology, produced by cooling Zircaloy-2 specimens through the temperature range of the BETA ..-->.. ..cap alpha..' = hydride phase transformation at approx. 0.3 and 3 K/s, on the impact properties was determined at temperatures between 373 and 673 K. On an atom fraction basis, oxygen has a greater effect than hydrogen on the impact properties of Zircaloy at temperatures between approx. 400 and 600 K. 34 figures.

  8. Investigation of dynamic properties of erbium fiber laser for ultrasonic sensing.

    PubMed

    Wu, Qi; Okabe, Yoji; Sun, Junqiang

    2014-04-01

    Dynamic properties of an erbium fiber laser (EFL) is researched and demonstrated for ultrasonic sensing in this research. The EFL has ring cavity incorporated with a phase-shifted fiber Bragg grating. A numerical model is used to analyze its dynamic responses to quasi-static change, continuous wave and burst wave. The ultrasonic behavior of the EFL resembles the forced single degree of freedom vibration with damping. Corresponding experimental results fit the simulation results well, showing some interesting ultrasonic properties of this EFL. After certain data process method, this EFL can be used in practical ultrasonic nondestructive testing.

  9. Investigation of dynamic properties of erbium fiber laser for ultrasonic sensing.

    PubMed

    Wu, Qi; Okabe, Yoji; Sun, Junqiang

    2014-04-01

    Dynamic properties of an erbium fiber laser (EFL) is researched and demonstrated for ultrasonic sensing in this research. The EFL has ring cavity incorporated with a phase-shifted fiber Bragg grating. A numerical model is used to analyze its dynamic responses to quasi-static change, continuous wave and burst wave. The ultrasonic behavior of the EFL resembles the forced single degree of freedom vibration with damping. Corresponding experimental results fit the simulation results well, showing some interesting ultrasonic properties of this EFL. After certain data process method, this EFL can be used in practical ultrasonic nondestructive testing. PMID:24718214

  10. The Properties of Oxygen Investigated with Easily Accessible Instrumentation: The "One-Photon-Two-Molecule" Mechanism Revisited

    ERIC Educational Resources Information Center

    Adelhelm, Manfred; Aristov, Natasha; Habekost, Achim

    2010-01-01

    The physical properties of oxygen, in particular, the blue color of the liquid phase, the red glow of its chemiluminescence, and its paramagnetism as shown by the entrapment or deflection of liquid oxygen by a magnetic field, can be investigated in a regular school setting with hand-held spectrophotometers and digital cameras. In college-level…

  11. Oxygen Sensing via the Ethylene Response Transcription Factor RAP2.12 Affects Plant Metabolism and Performance under Both Normoxia and Hypoxia.

    PubMed

    Paul, Melanie Verena; Iyer, Srignanakshi; Amerhauser, Carmen; Lehmann, Martin; van Dongen, Joost T; Geigenberger, Peter

    2016-09-01

    Subgroup-VII-ethylene-response-factor (ERF-VII) transcription factors are involved in the regulation of hypoxic gene expression and regulated by proteasome-mediated proteolysis via the oxygen-dependent branch of the N-end-rule pathway. While research into ERF-VII mainly focused on their role to regulate anoxic gene expression, little is known on the impact of this oxygen-sensing system in regulating plant metabolism and growth. By comparing Arabidopsis (Arabidopsis thaliana) plants overexpressing N-end-rule-sensitive and insensitive forms of the ERF-VII-factor RAP2.12, we provide evidence that oxygen-dependent RAP2.12 stability regulates central metabolic processes to sustain growth, development, and anoxic resistance of plants. (1) Under normoxia, overexpression of N-end-rule-insensitive Δ13RAP2.12 led to increased activities of fermentative enzymes and increased accumulation of fermentation products, which were accompanied by decreased adenylate energy states and starch levels, and impaired plant growth and development, indicating a role of oxygen-regulated RAP2.12 degradation to prevent aerobic fermentation. (2) In Δ13RAP2.12-overexpressing plants, decreased carbohydrate reserves also led to a decrease in anoxic resistance, which was prevented by external Suc supply. (3) Overexpression of Δ13RAP2.12 led to decreased respiration rates, changes in the levels of tricarboxylic acid cycle intermediates, and accumulation of a large number of amino acids, including Ala and γ-amino butyric acid, indicating a role of oxygen-regulated RAP2.12 abundance in controlling the flux-modus of the tricarboxylic acid cycle. (4) The increase in amino acids was accompanied by increased levels of immune-regulatory metabolites. These results show that oxygen-sensing, mediating RAP2.12 degradation is indispensable to optimize metabolic performance, plant growth, and development under both normoxic and hypoxic conditions. PMID:27372243

  12. Oxygen Sensing via the Ethylene Response Transcription Factor RAP2.12 Affects Plant Metabolism and Performance under Both Normoxia and Hypoxia1[OPEN

    PubMed Central

    Paul, Melanie Verena; Iyer, Srignanakshi; Lehmann, Martin

    2016-01-01

    Subgroup-VII-ethylene-response-factor (ERF-VII) transcription factors are involved in the regulation of hypoxic gene expression and regulated by proteasome-mediated proteolysis via the oxygen-dependent branch of the N-end-rule pathway. While research into ERF-VII mainly focused on their role to regulate anoxic gene expression, little is known on the impact of this oxygen-sensing system in regulating plant metabolism and growth. By comparing Arabidopsis (Arabidopsis thaliana) plants overexpressing N-end-rule-sensitive and insensitive forms of the ERF-VII-factor RAP2.12, we provide evidence that oxygen-dependent RAP2.12 stability regulates central metabolic processes to sustain growth, development, and anoxic resistance of plants. (1) Under normoxia, overexpression of N-end-rule-insensitive Δ13RAP2.12 led to increased activities of fermentative enzymes and increased accumulation of fermentation products, which were accompanied by decreased adenylate energy states and starch levels, and impaired plant growth and development, indicating a role of oxygen-regulated RAP2.12 degradation to prevent aerobic fermentation. (2) In Δ13RAP2.12-overexpressing plants, decreased carbohydrate reserves also led to a decrease in anoxic resistance, which was prevented by external Suc supply. (3) Overexpression of Δ13RAP2.12 led to decreased respiration rates, changes in the levels of tricarboxylic acid cycle intermediates, and accumulation of a large number of amino acids, including Ala and γ-amino butyric acid, indicating a role of oxygen-regulated RAP2.12 abundance in controlling the flux-modus of the tricarboxylic acid cycle. (4) The increase in amino acids was accompanied by increased levels of immune-regulatory metabolites. These results show that oxygen-sensing, mediating RAP2.12 degradation is indispensable to optimize metabolic performance, plant growth, and development under both normoxic and hypoxic conditions. PMID:27372243

  13. Structural and optical properties of solid-phase singlet oxygen photosensitizers based on fullerene aqueous suspensions

    NASA Astrophysics Data System (ADS)

    Belousova, I. M.; Belousov, V. P.; Kiselev, V. M.; Murav'eva, T. D.; Kislyakov, I. M.; Sirotkin, A. K.; Starodubtsev, A. M.; Kris'ko, T. K.; Bagrov, I. V.; Ermakov, A. V.

    2008-11-01

    The relationship between the structural and photosensitizing properties of solid-phase particles of fullerene C60 in aqueous suspensions is studied using the methods of absorption spectroscopy, electron spin resonance spectroscopy (ESR), X-ray diffraction, and spectrophotometry of solutions of singlet oxygen chemical traps—histidine in combination with p-nitrosodimethylaniline. Two new variants are proposed for obtaining aqueous suspensions of particles of solid-phase fullerene whose structures are disordered and whose degrees of amorphization are 67 and 40%, respectively. It is shown that an increase in the disorder of the structure of particles in suspensions and a decrease in their average size facilitate an increase in the formation efficiency of singlet oxygen by solid-phase fullerene presumably due to an in increase in the concentration of surface localized excitons.

  14. Determination of mechanical properties from depth-sensing indentation data and results of finite element modeling

    NASA Astrophysics Data System (ADS)

    Isaenkova, M. G.; Perlovich, Yu A.; Krymskaya, O. A.; Zhuk, D. I.

    2016-04-01

    3D finite element model of indentation process with Berkovich tip was created. Using this model with different type of test materials, several series of calculations were made. These calculations lead to determination of material behavior features during indentation. Relations between material properties and its behavior during instrumented indentation were used for construction of dimensionless functions required for development the calculation algorithm, suitable to determine mechanical properties of materials by results of the depth-sensing indentation. Results of mechanical properties determination using elaborated algorithm for AISI 1020 steel grade were compared to properties obtained with standard compression tests. These two results differ by less than 10% for yield stress that evidence of a good accuracy of the proposed technique.

  15. Field Collection Efforts of Snowpack Properties in Support of Remote Sensing Applications

    NASA Astrophysics Data System (ADS)

    Deeb, E. J.; Marshall, H.; Deems, J. S.; Finnegan, D. C.; Painter, T. H.; Landry, C.; Bryant, A. C.; Skiles, S.

    2010-12-01

    Over the past several decades remote sensing techniques have been developed to estimate snowpack properties (e.g., snow covered area) over various scales. In addition, newer techniques are still being formulated to characterize other important snowpack properties (e.g., snow water equivalent) over basin scales for snow hydrology modeling efforts. Estimating these essential properties are often difficult based on the high spatial variability of snowpack caused by terrain, wind, vegetation, and local climate. The sparsity of ground-based observations, due to their time-consuming nature, has made it difficult to accurately validate these new remote sensing techniques. Through collective collaboration with Boise State University, the US Army Corps Cold Regions Research and Engineering Laboratory, Center for Snow and Avalanche Studies, National Snow and Ice Data Center, and JPL/Snow Optics Laboratory, a rich data set of coordinated field-based and remote sensing observations was collected within Senator Beck Basin, San Juan Mountains, Colorado during April 2010. Manual snow pit and snowfork measurements are compared to ground-based radar profiles. High-resolution (1-3m) satellite-based radar backscatter (X-Band SAR) is compared to co-located ground-based radar observations. Field spectra and measurements of dust concentrations are compared to AVIRIS and MODIS retrievals. Ground-based, full waveform scanning LiDAR provides a high resolution snow surface model of the lower elevation study plot, and the intensity and range of a LiDAR pit face scan is compared to grain size stratigraphy from contact spectroscopy. Along with its existing infrastructure (i.e., snow hydrology study plots and instrumentation), the basin provides a unique laboratory for data collection and comparison of various snow products derived from field-based and remote sensing techniques.

  16. Effect of Oxygen on the Structural/Electrical Properties of NIZO Films on Transparent Flexible Substrates.

    PubMed

    Lim, Byung-Wook; Lee, Young-Jun; Kim, Joo-Hyung; Jeong, Hyeon-Taek; Ha, Tae-Won; Kim, Eun-Mi; Heo, Gi-Seok; Kim, Young-Baek; Kim, Hyeon-Ju; Lee, Ho-Saeng

    2015-10-01

    Thin film transparent oxides have attracted considerable attention over the last few decades for transparent electronic applications, such as flat panel displays, solar cells, touch-pads, and mobile devices. Metallic doped InZnO (IZO) films have been suggested for the transparent layer exhibiting semiconducting or metallic properties because of its controllable mobility and excellent electrical properties, but they show a degradation of the electrical performance under bending conditions. This study assessed Ni doped IZO (NIZO) films as a flexible transparent electrode on different flexible transparent substrates for flexible electronic applications. Thin NIZO films were deposited on cellulose, PES and glass substrates using a sputtering system with a single NIZO target (In2O3 73.8/ZnO 15.7/NiO 10.5 mol.%) at room temperature. During deposition of the NIZO films, the total flow rate of the carrier gas was maintained using a regulating system. The effects of the oxygen content in the carrier gas on the structural, electrical and optical properties of the thin films deposited on flexible substrates was characterized. The results highlight the feasibility of the transparent NIZO oxide layer on flexible substrates as a flexible electrode with a relatively high sheet resistance, which is strongly related to the crystallographic structure and oxygen content during the film deposition process. PMID:26726363

  17. Effect of Oxygen on the Structural/Electrical Properties of NIZO Films on Transparent Flexible Substrates.

    PubMed

    Lim, Byung-Wook; Lee, Young-Jun; Kim, Joo-Hyung; Jeong, Hyeon-Taek; Ha, Tae-Won; Kim, Eun-Mi; Heo, Gi-Seok; Kim, Young-Baek; Kim, Hyeon-Ju; Lee, Ho-Saeng

    2015-10-01

    Thin film transparent oxides have attracted considerable attention over the last few decades for transparent electronic applications, such as flat panel displays, solar cells, touch-pads, and mobile devices. Metallic doped InZnO (IZO) films have been suggested for the transparent layer exhibiting semiconducting or metallic properties because of its controllable mobility and excellent electrical properties, but they show a degradation of the electrical performance under bending conditions. This study assessed Ni doped IZO (NIZO) films as a flexible transparent electrode on different flexible transparent substrates for flexible electronic applications. Thin NIZO films were deposited on cellulose, PES and glass substrates using a sputtering system with a single NIZO target (In2O3 73.8/ZnO 15.7/NiO 10.5 mol.%) at room temperature. During deposition of the NIZO films, the total flow rate of the carrier gas was maintained using a regulating system. The effects of the oxygen content in the carrier gas on the structural, electrical and optical properties of the thin films deposited on flexible substrates was characterized. The results highlight the feasibility of the transparent NIZO oxide layer on flexible substrates as a flexible electrode with a relatively high sheet resistance, which is strongly related to the crystallographic structure and oxygen content during the film deposition process.

  18. Examination of two methods of describing the thermodynamic properties of oxygen near the critical point

    NASA Technical Reports Server (NTRS)

    Rees, T. H.; Suttles, J. T.

    1972-01-01

    A computer study was conducted to compare the numerical behavior of two approaches to describing the thermodynamic properties of oxygen near the critical point. Data on the relative differences between values of specific heats at constant pressure (sub p) density, and isotherm and isochor derivatives of the equation of state are presented for selected supercritical pressures at temperatures in the range 100 to 300 K. The results of a more detailed study of the sub p representations afforded by the two methods are also presented.

  19. Effect of oxygen and associated residual stresses on the mechanical properties of high growth rate Czochralski silicon

    NASA Astrophysics Data System (ADS)

    Youssef, Khaled; Shi, Meirong; Radue, Chantelle; Good, Ethan; Rozgonyi, George

    2013-04-01

    The mechanical properties of Czochralski silicon (Cz-Si) crystals grown in vacancy rich regimes with elevated axial oxygen concentrations ranging from ˜6 × 1017 to ˜12 × 1017 atoms/cm3 have been investigated using nano- and micro-indentation techniques. Both hardness and fracture toughness were found to decrease with increasing oxygen concentration, while major differences in mechanical properties were found between the central core and the edge of the high oxygen concentration wafers. Photoluminescence imaging and Nomarski optical microscopy of high-oxygen wafers revealed the presence of a ring and swirl-like distributions of micro defects, including oxidation induced stacking faults. Micro-Raman analysis was used to measure local residual stress profiles associated with these characteristic defects. These results provide a quantitative understanding of the influence of the oxygen content and the associated defects resulting from the sub-optimal growth regimes within the Cz-Si process.

  20. On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow

    NASA Astrophysics Data System (ADS)

    Khojier, K.; Savaloni, H.; Zolghadr, S.

    2014-11-01

    Nitrogen and carbon oxides (CO, NO and NO2), released from combustion facilities and automobiles, are known to be extremely harmful to the human body and also are the main cause of air pollution. Therefore, effective methods to monitor and suppress the carbon and nitrogen oxides have been highly demanded for atmospheric environmental measurements and controls. It is known that molybdenum oxide (MoO3) can be a good semiconductor material for use as a gas sensor in monitoring CO, NO and NO2. In this paper we report the structural characteristics and sensing properties of the sputtered MoO3 thin films as a function of argon gas flow. MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrates at different argon gas flows in the range of 5-20 sccm. X-ray diffraction (XRD) analysis was used for studying crystallographic structure. XRD results showed that all of our films were of polycrystalline structure and of α-MoO3 stable orthorhombic phase. Results also showed that crystallite size increases while compressive nano-strain in the structure of the films decreases with increasing the argon gas flow. Atomic force microscope and the field emission scanning electron microscope studies showed granular structures for all samples, which increased in size consistent with the XRD results, with argon gas flow, while the surface roughness of the films also increased with argon gas flow. Chemical composition study showed optimum reaction between oxygen and molybdenum atoms for films produced at 15 sccm flow of argon gas. The electrical response of samples was measured in the vacuum and the CO environments in the temperature range of 150-350 K. All samples showed Ohmic behavior and the electrical resistances of the films measured in the CO environment were lower than those measured in vacuum. This study showed that the sensing ability of MoO3 for CO improves with increasing the argon gas flow.

  1. A survey of natural aggregate properties and characteristics important in remote sensing and airborne geophysics

    USGS Publications Warehouse

    Knepper, D.H.; Langer, W.H.; Miller, S.

    1995-01-01

    Natural aggregate is vital to the construction industry. Although natural aggregate is a high volume/low value commodity that is abundant, new sources are becoming increasingly difficult to find and develop because of rigid industry specifications, political considerations, development and transportation costs, and environmental concerns. There are two primary sources of natural aggregate: (1) exposed or near-surface bedrock that can be crushed, and (2) deposits of sand and gravel. Remote sensing and airborne geophysics detect surface and near-surface phenomena, and may be useful for detecting and mapping potential aggregate sources; however, before a methodology for applying these techniques can be developed, it is necessary to understand the type, distribution, physical properties, and characteristics of natural aggregate deposits. The distribution of potential aggregate sources is closely tied to local geologic history. Conventional exploration for natural aggregate deposits has been largely a ground-based operation, although aerial photographs and topographic maps have been extensively used to target possible deposits. Today, the exploration process also considers factors such as the availability of the land, space and water supply for processing, political and environmental factors, and distance from the market; exploration and planning cannot be separated. There are many physical properties and characteristics by which to judge aggregate material for specific applications; most of these properties and characteristics pertain only to individual aggregate particles. The application of remote sensing and airborne geophysical measurements to detecting and mapping potential aggregate sources, however, is based on intrinsic bulk physical properties and extrinsic characteristics of the deposits that can be directly measured, mathematically derived from measurement, or interpreted with remote sensing and geophysical data. ?? 1995 Oxford UniversityPress.

  2. Hydrothermal Synthesis and Acetylene Sensing Properties of Variety Low Dimensional Zinc Oxide Nanostructures

    PubMed Central

    Chen, Weigen; Peng, Shudi; Zeng, Wen

    2014-01-01

    Various morphologies of low dimensional ZnO nanostructures, including spheres, rods, sheets, and wires, were successfully synthesized using a simple and facile hydrothermal method assisted with different surfactants. Zinc acetate dihydrate was chosen as the precursors of ZnO nanostructures. We found that polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycine, and ethylene glycol (EG) play critical roles in the morphologies and microstructures of the synthesized nanostructures, and a series of possible growth processes were discussed in detail. Gas sensors were fabricated using screen-printing technology, and their sensing properties towards acetylene gas (C2H2), one of the most important arc discharge characteristic gases dissolved in oil-filled power equipments, were systematically measured. The ZnO nanowires based sensor exhibits excellent C2H2 sensing behaviors than those of ZnO nanosheets, nanorods, and nanospheres, indicating a feasible way to develop high-performance C2H2 gas sensor for practical application. PMID:24672324

  3. Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles.

    PubMed

    Noel, J L; Udayabhaskar, R; Renganathan, B; Muthu Mariappan, S; Sastikumar, D; Karthikeyan, B

    2014-11-11

    We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample.

  4. Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Noel, J. L.; Udayabhaskar, R.; Renganathan, B.; Muthu Mariappan, S.; Sastikumar, D.; Karthikeyan, B.

    2014-11-01

    We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample.

  5. LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

    NASA Astrophysics Data System (ADS)

    Bagul, Sagar B.; Upadhye, Deepak S.; Sharma, Ramphal

    2016-05-01

    Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology of Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.

  6. Synthesis, formation mechanism and sensing properties of WO{sub 3} hydrate nanowire netted-spheres

    SciTech Connect

    Yan, Aihua; Xie, Changsheng; Zeng, Dawen; Cai, Shuizhou; Hu, Mulin

    2010-10-15

    Tungsten oxide hydrate nanowire netted-spheres were successfully synthesized in the glycol solution using a facile solvothermal approach. The nanowires with uniform diameter of 4-6 nm are actually a kind of tungsten oxide hydrate/surfactant hybrid materials. The influence of surfactant, solvent, time and temperature on tailoring morphology was investigated in detail. The possible formation process of WO{sub 3} hydrate nanowire netted-sphere was proposed. Sensing properties of such WO{sub 3} hydrate sensor show that the desirable sensing characteristics towards 100 ppm ammonia gas at 320 {sup o}C were obtained, such as rapid response (18.3 s), high sensitivity, good reproducibility and stability.

  7. Preparation and Gas Sensing Properties of Hollow ZnS Microspheres.

    PubMed

    Xiao, Jingkun; Song, Chengwen; Song, Mingyan; Dong, Wei; Li, Chen; Yin, Yanyan

    2016-03-01

    Hollow ZnS microspheres are synthesized by a facile hydrothermal method. Morphology and structure of the ZnS microspheres are analyzed by SEM, TEM, XRD and N2 sorption technique, Gas sensing properties of the as-prepared ZnS sensor are also systematically investigated. The results show that the ZnS microspheres have well-developed porous and hollow nanostructure. The sensor based on the ZnS microspheres exhibits ultra-fast response (1-2 s) and fast recovery time (7-34 s) towards ethanol at the optimal operating temperature of 160 degrees C. Moreover, the ZnS sensor also demonstrates high selectivity to other gases such as methanol, benzene, dichloromethane and hexane, suggesting that it is a promising candidate for ethanol sensing applications. PMID:27455754

  8. Single-crystal Au microflakes modulated by amino acids and their sensing and catalytic properties.

    PubMed

    Li, Mingjie; Wu, Xiaochen; Zhou, Jiyu; Kong, Qingshan; Li, Chaoxu

    2016-04-01

    Single-crystal Au microflakes with the planar area over 10(3)μm(2) (i.e. being accessible to the human eye resolution) were synthesized in an environment-friendly route by directing two-dimensional growth of Au nanocrystals into macroscopic scales with amino acids as both reducing agents and capping agents. Side groups of amino acids were found to be a determinant parameter to tune the dimension and size of Au single crystals. The successful synthesis of Au microflakes provides an unprecedented opportunity to bridge nanotechnology and macroscopic devices, and hereby to start a new scenario of exploring their unique properties and applications in optoelectronic devices and bio-sensing fields across multiple length scales. For example, Au microflakes respond to air humidity upon depositing on films of chitin nanofibrils, and sense various physiological molecules as electrode materials of biosensors.

  9. Impact of 100 MeV Ag7+ SHI irradiation fluence and N incorporation on structural, optical, electrical and gas sensing properties of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Balakrishnan, L.; Gokul Raj, S.; Meher, S. R.; Asokan, K.; Alex, Z. C.

    2015-06-01

    In the present study, we have investigated the influence of Ag7+ ion irradiation fluence and N incorporation on structural, optical, electrical and gas sensing properties of ZnO thin films. The X-ray diffraction analysis reveals the retainment of ZnO wurtzite structure even at higher fluence irradiation with slight decrease in crystallinity. Photoluminescence and Hall effect measurement analysis showed an increase in density of defects for high ion fluence irradiation. Atomic force microscope analysis shows that the films irradiated at high ion fluence have vertical standing needle-like morphology and also have high value of roughness compared with the films irradiated at low ion fluence. The ammonia and methanol gas sensing properties of the films have been studied at different operating temperature and gas concentration. It conveys that the films have selectivity towards ammonia than methanol and also that the films irradiated at high ion fluence exhibit better sensitivity, low response and recovery times compared with the films irradiated at low ion fluence. The film grown in oxygen ambience and irradiated at high ion fluence showed good sensing characteristics at all temperatures even at room temperature.

  10. Remote sensing of cloud, aerosol, and water vapor properties from the moderate resolution imaging spectrometer (MODIS)

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Kaufman, Yoram J.; Menzel, W. Paul; Tanre, Didier D.

    1992-01-01

    The authors describe the status of MODIS-N and its companion instrument MODIS-T (tilt), a tiltable cross-track scanning spectrometer with 32 uniformly spaced channels between 0.410 and 0.875 micron. They review the various methods being developed for the remote sensing of atmospheric properties using MODIS, placing primary emphasis on the principal atmospheric applications of determining the optical, microphysical, and physical properties of clouds and aerosol particles from spectral reflection and thermal emission measurements. In addition to cloud and aerosol properties, MODIS-N will be used for determining the total precipitable water vapor and atmospheric stability. The physical principles behind the determination of each of these atmospheric products are described, together with an example of their application to aircraft and/or satellite measurements.

  11. Crystal plane-dependent gas-sensing properties of zinc oxide nanostructures: experimental and theoretical studies.

    PubMed

    Kaneti, Yusuf V; Zhang, Zhengjie; Yue, Jeffrey; Zakaria, Quadir M D; Chen, Chuyang; Jiang, Xuchuan; Yu, Aibing

    2014-06-21

    The sensitivity of a metal oxide gas sensor is strongly dependent on the nature of the crystal surface exposed to the gas species. In this study, two types of zinc oxide (ZnO) nanostructures: nanoplates and nanorods with exposed (0001) and (10̄10) crystal surfaces, respectively, were synthesized through facile solvothermal methods. The gas-sensing results show that sensitivity of the ZnO nanoplates toward ethanol is two times higher than that of the ZnO nanorods, at an optimum operating temperature of 300 °C. This could be attributed to the higher surface area and the exposed (0001) crystal surfaces. DFT (Density Functional Theory) simulations were carried out to study the adsorption of ethanol on the ZnO crystal planes such as (0001), (10̄10), and (11̄20) with adsorbed O(-) ions. The results reveal that the exposed (0001) planes of the ZnO nanoplates promote better ethanol adsorption by interacting with the surface oxygen p (O2p) orbitals and stretching the O-H bond to lower the adsorption energy, leading to the sensitivity enhancement of the nanoplates. These findings will be useful for the fabrication of metal oxide nanostructures with specifically exposed crystal surfaces for improved gas-sensing and/or catalytic performance. PMID:24801357

  12. Flickering Analysis of Erythrocyte Mechanical Properties: Dependence on Oxygenation Level, Cell Shape, and Hydration Level

    PubMed Central

    Yoon, Young-Zoon; Hong, Ha; Brown, Aidan; Kim, Dong Chung; Kang, Dae Joon; Lew, Virgilio L.; Cicuta, Pietro

    2009-01-01

    Erythrocytes (red blood cells) play an essential role in the respiratory functions of vertebrates, carrying oxygen from lungs to tissues and CO2 from tissues to lungs. They are mechanically very soft, enabling circulation through small capillaries. The small thermally induced displacements of the membrane provide an important tool in the investigation of the mechanics of the cell membrane. However, despite numerous studies, uncertainties in the interpretation of the data, and in the values derived for the main parameters of cell mechanics, have rendered past conclusions from the fluctuation approach somewhat controversial. Here we revisit the experimental method and theoretical analysis of fluctuations, to adapt them to the case of cell contour fluctuations, which are readily observable experimentally. This enables direct measurements of membrane tension, of bending modulus, and of the viscosity of the cell cytoplasm. Of the various factors that influence the mechanical properties of the cell, we focus here on: 1), the level of oxygenation, as monitored by Raman spectrometry; 2), cell shape; and 3), the concentration of hemoglobin. The results show that, contrary to previous reports, there is no significant difference in cell tension and bending modulus between oxygenated and deoxygenated states, in line with the softness requirement for optimal circulatory flow in both states. On the other hand, tension and bending moduli of discocyte- and spherocyte-shaped cells differ markedly, in both the oxygenated and deoxygenated states. The tension in spherocytes is much higher, consistent with recent theoretical models that describe the transitions between red blood cell shapes as a function of membrane tension. Cell cytoplasmic viscosity is strongly influenced by the hydration state. The implications of these results to circulatory flow dynamics in physiological and pathological conditions are discussed. PMID:19751665

  13. Massive stars on the verge of exploding: the properties of oxygen sequence Wolf-Rayet stars

    NASA Astrophysics Data System (ADS)

    Tramper, F.; Straal, S. M.; Sanyal, D.; Sana, H.; de Koter, A.; Gräfener, G.; Langer, N.; Vink, J. S.; de Mink, S. E.; Kaper, L.

    2015-09-01

    Context. Oxygen sequence Wolf-Rayet (WO) stars are a very rare stage in the evolution of massive stars. Their spectra show strong emission lines of helium-burning products, in particular highly ionized carbon and oxygen. The properties of WO stars can be used to provide unique constraints on the (post-)helium burning evolution of massive stars, and their remaining lifetimes and the expected properties of their supernovae. Aims: We aim to homogeneously analyze the currently known presumed-single WO stars to obtain the key stellar and outflow properties and to constrain their evolutionary state. Methods: We use the line-blanketed non-local thermal equilibrium atmosphere code cmfgen to model the X-Shooter spectra of the WO stars and to deduce the atmospheric parameters. We calculate dedicated evolutionary models to determine the evolutionary state of the stars. Results: The WO stars have extremely high temperatures that range from 150 kK to 210 kK, and very low surface helium mass fractions that range from 44% down to 14%. Their properties can be reproduced by evolutionary models with helium zero-age main sequence masses of MHe,ini = 15-25 M⊙ that exhibit a fairly strong (a few times 10-5M⊙ yr-1), homogeneous (fc> 0.3) stellar wind. Conclusions: WO stars represent the final evolutionary stage of stars with estimated initial masses of Mini = 40-60 M⊙. They are post core-helium burning and predicted to explode as type Ic supernovae within a few thousand years. Based on observations obtained at the European Southern Observatory under program IDs 091.C-0934 and 093.D-0591.Appendices are available in electronic form at http://www.aanda.org

  14. Oxygen transport properties estimation by classical trajectory–direct simulation Monte Carlo

    SciTech Connect

    Bruno, Domenico; Frezzotti, Aldo Ghiroldi, Gian Pietro

    2015-05-15

    Coupling direct simulation Monte Carlo (DSMC) simulations with classical trajectory calculations is a powerful tool to improve predictive capabilities of computational dilute gas dynamics. The considerable increase in computational effort outlined in early applications of the method can be compensated by running simulations on massively parallel computers. In particular, Graphics Processing Unit acceleration has been found quite effective in reducing computing time of classical trajectory (CT)-DSMC simulations. The aim of the present work is to study dilute molecular oxygen flows by modeling binary collisions, in the rigid rotor approximation, through an accurate Potential Energy Surface (PES), obtained by molecular beams scattering. The PES accuracy is assessed by calculating molecular oxygen transport properties by different equilibrium and non-equilibrium CT-DSMC based simulations that provide close values of the transport properties. Comparisons with available experimental data are presented and discussed in the temperature range 300–900 K, where vibrational degrees of freedom are expected to play a limited (but not always negligible) role.

  15. Oxygen transport properties estimation by classical trajectory-direct simulation Monte Carlo

    NASA Astrophysics Data System (ADS)

    Bruno, Domenico; Frezzotti, Aldo; Ghiroldi, Gian Pietro

    2015-05-01

    Coupling direct simulation Monte Carlo (DSMC) simulations with classical trajectory calculations is a powerful tool to improve predictive capabilities of computational dilute gas dynamics. The considerable increase in computational effort outlined in early applications of the method can be compensated by running simulations on massively parallel computers. In particular, Graphics Processing Unit acceleration has been found quite effective in reducing computing time of classical trajectory (CT)-DSMC simulations. The aim of the present work is to study dilute molecular oxygen flows by modeling binary collisions, in the rigid rotor approximation, through an accurate Potential Energy Surface (PES), obtained by molecular beams scattering. The PES accuracy is assessed by calculating molecular oxygen transport properties by different equilibrium and non-equilibrium CT-DSMC based simulations that provide close values of the transport properties. Comparisons with available experimental data are presented and discussed in the temperature range 300-900 K, where vibrational degrees of freedom are expected to play a limited (but not always negligible) role.

  16. Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

    NASA Astrophysics Data System (ADS)

    Sahin, Bünyamin; Kaya, Tolga

    2016-01-01

    In this study, un-doped, Na-doped, and K-doped nanostructured CuO films were successfully synthesized by the successive ionic layer adsorption and reaction (SILAR) technique and then characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and current-voltage (I-V) measurements. Structural properties of the CuO films were affected from doping. The XRD pattern indicates the formation of polycrystalline CuO films with no secondary phases. Furthermore, doping affected the crystal structure of the samples. The optimum conductivity values for both Na and K were obtained at 4 M% doping concentrations. The comparative hydration level sensing properties of the un-doped, Na-doped, and K-doped CuO nanoparticles were also investigated. A significant enhancement in hydration level sensing properties was observed for both 4 M% Na and K-doped CuO films for all concentration levels. Detailed discussions were reported in the study regarding atomic radii, crystalline structure, and conductivity.

  17. An Airborne A-Band Spectrometer for Remote Sensing Of Aerosol and Cloud Optical Properties

    NASA Technical Reports Server (NTRS)

    Pitts, Michael; Hostetler, Chris; Poole, Lamont; Holden, Carl; Rault, Didier

    2000-01-01

    Atmospheric remote sensing with the O2 A-band has a relatively long history, but most of these studies were attempting to estimate surface pressure or cloud-top pressure. Recent conceptual studies have demonstrated the potential of spaceborne high spectral resolution O2 A-band spectrometers for retrieval of aerosol and cloud optical properties. The physical rationale of this new approach is that information on the scattering properties of the atmosphere is embedded in the detailed line structure of the O2 A-band reflected radiance spectrum. The key to extracting this information is to measure the radiance spectrum at very high spectral resolution. Instrument performance requirement studies indicate that, in addition to high spectral resolution, the successful retrieval of aerosol and cloud properties from A-band radiance spectra will also require high radiometric accuracy, instrument stability, and high signal-to-noise measurements. To experimentally assess the capabilities of this promising new remote sensing application, the NASA Langley Research Center is developing an airborne high spectral resolution A-band spectrometer. The spectrometer uses a plane holographic grating with a folded Littrow geometry to achieve high spectral resolution (0.5 cm-1) and low stray light in a compact package. This instrument will be flown in a series of field campaigns beginning in 2001 to evaluate the overall feasibility of this new technique. Results from these campaigns should be particularly valuable for future spaceborne applications of A-band spectrometers for aerosol and cloud retrievals.

  18. Preparation and gas-sensing properties of α-Fe2O3 thin films

    NASA Astrophysics Data System (ADS)

    Chai, C. C.; Peng, J.; Yan, B. P.

    1995-07-01

    Haematite (α-Fe2O3) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe2O3 films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.

  19. On the radiative properties of ice clouds: Light scattering, remote sensing, and radiation parameterization

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Liou, Kuo-Nan; Bi, Lei; Liu, Chao; Yi, Bingqi; Baum, Bryan A.

    2015-01-01

    Presented is a review of the radiative properties of ice clouds from three perspectives: light scattering simulations, remote sensing applications, and broadband radiation parameterizations appropriate for numerical models. On the subject of light scattering simulations, several classical computational approaches are reviewed, including the conventional geometric-optics method and its improved forms, the finite-difference time domain technique, the pseudo-spectral time domain technique, the discrete dipole approximation method, and the T-matrix method, with specific applications to the computation of the single-scattering properties of individual ice crystals. The strengths and weaknesses associated with each approach are discussed. With reference to remote sensing, operational retrieval algorithms are reviewed for retrieving cloud optical depth and effective particle size based on solar or thermal infrared (IR) bands. To illustrate the performance of the current solar- and IR-based retrievals, two case studies are presented based on spaceborne observations. The need for a more realistic ice cloud optical model to obtain spectrally consistent retrievals is demonstrated. Furthermore, to complement ice cloud property studies based on passive radiometric measurements, the advantage of incorporating lidar and/or polarimetric measurements is discussed. The performance of ice cloud models based on the use of different ice habits to represent ice particles is illustrated by comparing model results with satellite observations. A summary is provided of a number of parameterization schemes for ice cloud radiative properties that were developed for application to broadband radiative transfer submodels within general circulation models (GCMs). The availability of the single-scattering properties of complex ice habits has led to more accurate radiation parameterizations. In conclusion, the importance of using nonspherical ice particle models in GCM simulations for climate

  20. Enhanced ethanol gas sensing properties of SnO₂-core/ZnO-shell nanostructures.

    PubMed

    Tharsika, T; Haseeb, A S M A; Akbar, Sheikh A; Sabri, Mohd Faizul Mohd; Hoong, Wong Yew

    2014-01-01

    An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ~5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures.

  1. Application of symmetry properties to polarimetric remote sensing with JPL AIRSAR data

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Yueh, Simon H.; Kwok, R.; Li, F. K.

    1992-01-01

    Based on symmetry properties, polarimetric remote sensing of geophysical media is studied. From the viewpoint of symmetry groups, media with reflection, rotation, azimuthal, and centrical symmetries are considered. The symmetries impose relations among polarimetric scattering coefficients, which are valid to all scattering mechanisms in the symmetrical configurations. Various orientation distributions of non-spherical scatterers can be identified from the scattering coefficients by a comparison with the symmetry calculations. Experimental observations are then analyzed for many geophysical scenes acquired with the Jet Propulsion Laboratory (JPL) airborne polarimetric SAR at microwave frequencies over sea ice and vegetation. Polarimetric characteristics of different ice types are compared with symmetry behaviors. The polarimetric response of a tropical rain forest reveals characteristics close to the centrical symmetry properties, which can be used as a distributed target to relatively calibrate polarimetric radars without any deployment of manmade calibration targets.

  2. Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

    PubMed Central

    Penza, Michele; Alvisi, Marco; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa

    2016-01-01

    Summary A one-step electrochemical method based on sacrificial anode electrolysis (SAE) was used to deposit stabilized gold nanoparticles (Au NPs) directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C) on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO) was investigated. Transmission and scanning electron microscopy (TEM and SEM), as well as X-ray photoelectron spectroscopy (XPS), revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties. PMID:26925349

  3. Application of Multitemporal Remotely Sensed Soil Moisture for the Estimation of Soil Physical Properties

    NASA Technical Reports Server (NTRS)

    Mattikalli, N. M.; Engman, E. T.; Jackson, T. J.; Ahuja, L. R.

    1997-01-01

    This paper demonstrates the use of multitemporal soil moisture derived from microwave remote sensing to estimate soil physical properties. The passive microwave ESTAR instrument was employed during June 10-18, 1992, to obtain brightness temperature (TB) and surface soil moisture data in the Little Washita watershed, Oklahoma. Analyses of spatial and temporal variations of TB and soil moisture during the dry-down period revealed a direct relationship between changes in T and soil moisture and soil physical (viz. texture) and hydraulic (viz. saturated hydraulic conductivity, K(sat)) properties. Statistically significant regression relationships were developed for the ratio of percent sand to percent clay (RSC) and K(sat), in terms of change components of TB and surface soil moisture. Validation of results using field measured values and soil texture map indicated that both RSC and K(sat) can be estimated with reasonable accuracy. These findings have potential applications of microwave remote sensing to obtain quick estimates of the spatial distributions of K(sat), over large areas for input parameterization of hydrologic models.

  4. Excellent ethanol sensing properties based on Er2O3-Fe2O3 nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Bai; He, Ying; Wang, Sheng-Lei

    2015-11-01

    In this work, pure α-Fe2O3 and Er2O3-Fe2O3 nanotubes were synthesized by a simple single-capillary electrospinning technology followed by calcination treatment. The morphologies and crystal structures of the as-prepared samples were characterized by scanning electron microscopy and x-ray diffraction, respectively. The gas-sensing properties of the as-prepared samples have been researched, and the result shows that the Er2O3-Fe2O3 nanotubes exhibit much better sensitivity to ethanol. The response value of Er2O3-Fe2O3 nanotubes to 10 ppm ethanol is 21 at the operating temperature 240°, which is 14 times larger than that of pure α-Fe2O3 nanotubes (response value is 1.5). The ethanol sensing properties of α-Fe2O3 nanotubes are remarkably enhanced by doping Er, and the lowest detection limit of Er2O3-Fe2O3 nanotubes is 300 ppb, to which the response value is about 2. The response and recovery times are about 4 s and 70 s to 10 ppm ethanol, respectively. In addition, the Er2O3-Fe2O3 nanotubes possess good selectivity and long-term stability. Project supported by Jilin Provincial Science and Technology Department, China (Grant No. 20140204027GX) and the Challenge Cup for College Students, China (Grant No. 450060497053).

  5. Spectral properties of water ice and contaminants. [of importance to remote sensing of ice in solar system

    NASA Technical Reports Server (NTRS)

    Lucey, P. G.; Clark, R. N.

    1985-01-01

    For remote sensing studies of ices in the solar system, it is important to understand the optical properties of water ice, and mixtures of ice and particulate materials. The present paper has the objective to review the current understanding of the spectral properties of ice, and mixtures of ice and particulates. The review is to provide a basis for the understanding of the remote sensing of ice. It is found that reflectance spectra of ice-soil intimate mixtures are complex, nonlinear functions of the optical and physical properties of the components which comprise the surface.

  6. Effect of the oxygen balance on ignition and detonation properties of liquid explosive mixtures

    NASA Astrophysics Data System (ADS)

    Genetier, Marc; Osmont, Antoine; Baudin, Gerard

    2013-06-01

    The objective is to compare ignition and detonation properties of various liquid high explosives having negative up to positive oxygen balance (OB): nitromethane (OB < 0), saccharose and hydrogen peroxide based mixture (quasi nil OB), hydrogen peroxide with more than 90% purity (OB > 0). The decomposition kinetic rates and the equations of state (EOS) for the liquid mixtures and detonation products (DP) are the input data for a detonation model. EOS are theoretically determined using the Woolfolk et al universal liquid polar shock law and thermochemical computations for DP. The decomposition kinetic rate laws are determined to reproduce the shock to detonation transition for the mixtures submitted to planar plate impacts. Such a model is not sufficient to compute open field explosions. The aerial overpressure is well reproduced in the first microseconds, however, after it becomes worse at large expansion of the fireball and the impulse is underestimated. The problem of the DP EOS alone is that it takes into account only the detonation, the secondary combustion DP - air being not considered. To solve this problem a secondary combustion model has been developed to take into account the OB effect. The detonation model has been validated on planar plate impact experiments. The secondary combustion parameters were deduced from thermochemical computations. The whole model has been used to predict the effects of the oxygen balance on open air blast effects of spherical charges.

  7. Effect of the oxygen balance on ignition and detonation properties of liquid explosive mixtures

    NASA Astrophysics Data System (ADS)

    Genetier, M.; Osmont, A.; Baudin, G.

    2014-05-01

    The objective is to compare the ignition and detonation properties of various liquid high explosives having negative up to positive oxygen balance (OB): nitromethane (OB < 0), saccharose and hydrogen peroxide based mixture (quasi nil OB), hydrogen peroxide with more than 90% purity (OB > 0). The decomposition kinetic rates and the equations of state (EOS) for the liquid mixtures and detonation products (DP) are the input data for a detonation model. EOS are theoretically determined using the Woolfolk et al. universal liquid polar shock law and thermochemical computations for DP. The decomposition kinetic rate laws are determined to reproduce the shock to detonation transition for the mixtures submitted to planar plate impacts. Such a model is not sufficient to compute open field explosions. The aerial overpressure is well reproduced in the first few microseconds, however, after it becomes worse at large expansion of the fireball and the impulse is underestimated. The problem of the DP EOS alone is that it takes only the detonation into account, the secondary combustion DP - air is not considered. To solve this problem a secondary combustion model has been developed to take the OB effect into account. The detonation model has been validated on planar plate impact experiments. The secondary combustion parameters were deduced from thermochemical computations. The whole model has been used to predict the effects of the oxygen balance on open air blast effects of spherical charges.

  8. Cellulose nanobiocomposites with reinforcement of boron nitride: study of thermal, oxygen barrier and chemical resistant properties.

    PubMed

    Swain, Sarat K; Dash, Satyabrata; Behera, Chandini; Kisku, Sudhir K; Behera, Lingaraj

    2013-06-20

    A series of cellulose based nanobiocomposites (cellulose/BN) were prepared with incorporation of various percentage of nano boron nitride (BN). The interaction between cellulose and boron nitride was studied by Fourier transform infrared spectroscopy (FTIR). The structure of cellulose/BN nanobiocomposites was investigated by XRD, FESEM, and HRTEM. It was observed that the boron nitride nanoparticles were dispersed within cellulose matrix due to intercalation and partial exfoliation. The quantitative identification of nanobiocomposites was investigated by selected area electron diffraction (SAED). Thermal stabilities of the prepared nanobiocomposites were measured by thermo gravimetric analysis (TGA) and it was found that thermal stability of the nanobiocomposites was higher than the virgin cellulose. The oxygen barrier property of cellulose/BN nanobiocomposites was measured using a gas permeameter and a substantial reduction in oxygen permeability due to increase in boron nitride loading was observed. Further it was noticed that the chemical resistance of the nanobiocomposites was more than the virgin cellulose. Hence, the prepared nanobiocomposite may be widely used for insulating and temperature resistant packaging materials. PMID:23648034

  9. Enhancing the photoelectrochemical properties of titanium dioxide by thermal treatment in oxygen deficient environment

    NASA Astrophysics Data System (ADS)

    Singh, Aadesh P.; Kodan, Nisha; Mehta, Bodh R.

    2016-05-01

    The effect of thermal treatment on TiO2 thin films under oxygen deficient environment (5% H2 in Ar) at partial pressure of 2 × 10-2 Torr have been studied for photoelectrochemical (PEC) water splitting application. Thermal treatment in anatase TiO2 thin films exhibits a shift in optical absorption from UV to visible region and activates TiO2 for water splitting application under visible light. X-ray photoelectron spectroscopy results showed that the thermal treated thin films contain oxygen vacancies, which suggests improved charge transport. Optical absorption, X-ray spectroscopy (XPS) and Kelvin probe force microscope (KPFM) studies show reduction in band gap by 0.36 eV, shift in valence band maximum by 0.49 eV towards the Fermi level and work function values by 0.3 eV towards the vacuum level. The pristine TiO2 thin films exhibit very less photoactivity in terms of photocurrent density, whereas thermally treated thin films displayed a markedly enhanced photocurrent density of ∼2.41 mA/cm2 at 0.23 V vs. Ag/AgCl. Higher values of photocurrent density in thermal treated TiO2 films have been explained in terms of change in the optical and electrical properties along with energy band diagram.

  10. Oxygen vacancy assisted multiferroic property of Cu doped ZnO films.

    PubMed

    Liu, Hongyan; Wang, Yonglin; Wu, Jianhua; Zhang, Guanli; Yan, Yue

    2015-04-14

    Exploring multi-functional properties in a single material is the focus for future material design and applications. In this work, we investigated the multiferroic property of Cu doped ZnO films using a combination of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), classical magnetometry and electric measurements. The results show that the texture of Cu doped ZnO films is deteriorated with an increase in Cu contents, whereas the dielectric property is improved due to the introduction of Cu ions. The XAS result reveals that the Cu atoms occupy the substitutional Zn sites in the ZnO host, and thus induce local electric dipoles owing to the displacement of the Cu-O bond. The presence of oxygen vacancies together with Cu ions facilitates the movement of the ferroelectric domain boundary, and contributes to the ferromagnetism due to the indirect exchange between Cu atoms and large-sized vacancy orbitals. The Cu doped ZnO film is a feasible promising candidate for applications in multiferroic devices.

  11. Drug-induced reactive oxygen species (ROS) rely on cell membrane properties to exert anticancer effects

    PubMed Central

    Molavian, Hamid R.; Goldman, Aaron; Phipps, Colin J.; Kohandel, Mohammad; Wouters, Bradly G.; Sengupta, Shiladitya; Sivaloganathan, Sivabal

    2016-01-01

    Pharmacological concentrations of small molecule natural products, such as ascorbic acid, have exhibited distinct cell killing outcomes between cancer and normal cells whereby cancer cells undergo apoptosis or necrosis while normal cells are not adversely affected. Here, we develop a mathematical model for ascorbic acid that can be utilized as a tool to understand the dynamics of reactive oxygen species (ROS) induced cell death. We determine that not only do endogenous antioxidants such as catalase contribute to ROS-induced cell death, but also cell membrane properties play a critical role in the efficacy of ROS as a cytotoxic mechanism against cancer cells vs. normal cells. Using in vitro assays with breast cancer cells, we have confirmed that cell membrane properties are essential for ROS, in the form of hydrogen peroxide (H2O2), to induce cell death. Interestingly, we did not observe any correlation between intracellular H2O2 and cell survival, suggesting that cell death by H2O2 is triggered by interaction with the cell membrane and not necessarily due to intracellular levels of H2O2. These findings provide a putative mechanistic explanation for the efficacy and selectivity of therapies such as ascorbic acid that rely on ROS-induced cell death for their anti-tumor properties. PMID:27278439

  12. Optical Properties of Oxygen Plasma-Treated Carbon Nanowalls Grown on Glass Substrates.

    PubMed

    Jung, Yong Ho; Choi, Won Seok

    2016-05-01

    In this paper, we investigated the effect of oxygen (02) plasma treatment on a synthesized carbon nanowall (CNW). A microwave plasma-enhanced chemical vapor deposition (PECVD) system was facilitated to grow CNWs on a glass, using a mixture of CH4 and H2 gases. First, the CNWs were post-plasma-treated for different treatment durations, and then their optical properties were analyzed. In addition, the cross-sectional and planar images of the CNWs were examined via field-emission scanning electron microscopy (FE-SEM) depending on the different post-plasma-treatment durations. Then the structural characteristics were analyzed via Raman spectroscopy, and the changes in the light transmittance depending on the O2 plasma treatment durations were analyzed using UV-Vis spectroscopy. The effects of the post-plasma treatments on the synthesized CNWs were evaluated. The results confirmed that O2 gas is effective for plasma etching of CNWs. PMID:27483919

  13. Hybrid Gas Sensing and Transport Properties of Few-Walled CNTs Decorated with Discrete SnO₂ Nanoparticles.

    PubMed

    Ranganathan, Kamalakannan; Shanmugam, Ilango; Kamruddin, Mohammed; Tyagi, Ashok K

    2016-01-01

    CVD grown, few walled carbon nanotubes (FWCNTs) were quasi decorated with SnO₂nanoparticles (FWCNTs-SnO₂) and its gas sensing properties were analyzed with ammonia and ethanol. At room temperature FWCNTs-SnO₂show enhanced 'p type' gas sensing response than FWCNTs. Activation of SnO₂at high temperatures led to systematic changes in the sensing behavior towards 'n type' response. Temperature dependent transport behavior was found to be a one dimensional variable range hopping mechanism (1 D-VRH) for the FWCNTs and a 3D-VRH mechanism for the FWCNTs-SnO2. These temperature dependent gas transport and sensing properties elucidate the hybrid nature of the nanocomposite with novel characteristics. This also implies its importance as a potential gas sensor material. PMID:27398589

  14. Dispersion of SiC nanoparticles in cellulose for study of tensile, thermal and oxygen barrier properties.

    PubMed

    Kisku, Sudhir K; Dash, Satyabrata; Swain, Sarat K

    2014-01-01

    Cellulose/silicon carbide (cellulose/SiC) nanobiocomposites were prepared by solution technique. The interaction of SiC nanoparticles with cellulose were confirmed by Fourier transformed infrared (FTIR) spectroscopy. The structure of cellulose/SiC nanobiocomposites was investigated by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The tensile properties of the nanobiocomposites were improved as compared with virgin cellulose. Thermal stabilities of cellulose/SiC nanobiocomposites were studied by thermogravimetric analysis (TGA). The cellulose/SiC nanobiocomposites were thermally more stable than the raw cellulose. It may be due to the delamination of SiC with cellulose matrix. The oxygen barrier properties of cellulose composites were measured using gas permeameter. A substantial reduction in oxygen permeability was obtained with increase in silicon carbide concentrations. The thermally resistant and oxygen barrier properties of the prepared nanobiocomposites may enable the materials for the packaging applications. PMID:24274511

  15. Assimilation of remotely-sensed optical properties to improve marine biogeochemistry modelling

    NASA Astrophysics Data System (ADS)

    Ciavatta, Stefano; Torres, Ricardo; Martinez-Vicente, Victor; Smyth, Timothy; Dall'Olmo, Giorgio; Polimene, Luca; Allen, J. Icarus

    2014-09-01

    In this paper we evaluate whether the assimilation of remotely-sensed optical data into a marine ecosystem model improves the simulation of biogeochemistry in a shelf sea. A localized Ensemble Kalman filter was used to assimilate weekly diffuse light attenuation coefficient data, Kd(443) from SeaWiFs, into an ecosystem model of the western English Channel. The spatial distributions of (unassimilated) surface chlorophyll from satellite, and a multivariate time series of eighteen biogeochemical and optical variables measured in situ at one long-term monitoring site were used to evaluate the system performance for the year 2006. Assimilation reduced the root mean square error and improved the correlation with the assimilated Kd(443) observations, for both the analysis and, to a lesser extent, the forecast estimates, when compared to the reference model simulation. Improvements in the simulation of (unassimilated) ocean colour chlorophyll were less evident, and in some parts of the Channel the simulation of this data deteriorated. The estimation errors for the (unassimilated) in situ data were reduced for most variables with some exceptions, e.g. dissolved nitrogen. Importantly, the assimilation adjusted the balance of ecosystem processes by shifting the simulated food web towards the microbial loop, thus improving the estimation of some properties, e.g. total particulate carbon. Assimilation of Kd(443) outperformed a comparative chlorophyll assimilation experiment, in both the estimation of ocean colour data and in the simulation of independent in situ data. These results are related to relatively low error in Kd(443) data, and because it is a bulk optical property of marine ecosystems. Assimilation of remotely-sensed optical properties is a promising approach to improve the simulation of biogeochemical and optical variables that are relevant for ecosystem functioning and climate change studies.

  16. Influence of oxygen partial pressure on optical and structural properties of RF sputtered ZnO thin films

    NASA Astrophysics Data System (ADS)

    Murkute, P.; Saha, S.; Pandey, S. K.; Chatterjee, A.; Datta, D.; Chakrabarti, S.

    2016-02-01

    In this paper we report a detailed investigation of ZnO thin film properties deposited on Si<100> substrate at 400°C using RF sputtering. To reduce oxygen induced vacancies and interstitial defects in samples, variable oxygen flow rate during deposition followed by post growth annealing in oxygen ambient were carried out. Four samples were deposited under constant temperature condition but with variable oxygen partial pressure of 0%, 20%, 50% and 80% in Argon and Oxygen mixture, namely sample S1, S2 , S3 and S4 respectively. Deposited films were further annealed at 700, 800, 900 and 1000°C in oxygen ambient for 10s. Photoluminescence (PL) measurements carried at low temperature (18K) demonstrated near band edge emission peak of ZnO at 3.37eV. Increment in PL intensity was observed with increasing annealing temperature and a particular sample S4 annealed at 900 measured narrowest full width half maxima (FWHM) of ~0.1272eV. Defects peaks observed at lower energies were suppressed with increasing oxygen flow and post growth annealing, indicating improvement in film quality. From HRXRD measurement it was observed S4 sample annealed at 900°C has the highest peak intensity and narrowest FWHM compared to other samples, demonstrating the best crystalline property of annealed film at 900°C. Highest XRD peak intensity measured at 34.53° corresponds to (002) crystal orientation reveals that the films were highly caxis oriented. AFM results show increase in grain size with increasing oxygen flow and annealing temperature which ensures improvement in morphological properties of the film.

  17. Enhanced Ethanol Gas Sensing Properties of SnO2-Core/ZnO-Shell Nanostructures

    PubMed Central

    Tharsika, T.; Haseeb, A. S. M. A.; Akbar, Sheikh A.; Sabri, Mohd Faizul Mohd; Hoong, Wong Yew

    2014-01-01

    An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ∼5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures. PMID:25116903

  18. Plasmonic Properties of Bimetallic Nanostructures and Their Applications in Hydrogen Sensing and Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Jiang, Ruibin

    Noble metal nanocrystals have attracted great interest from a wide range of research fields because of their intriguing properties endowed by their localized surface plasmon resonances, which are the collective oscillations of free electrons. Under resonant excitation, metal nanostructures exhibit very large scattering and absorption cross sections and large near-field enhancement. These extraordinary properties can be used in different applications, such as plasmonic sensing and imaging, plasmon-controlled optics, photothermal therapy, photocatalysis, solar cells, and so on. Gold and Silver nanocrystals have plasmon resonances in the visible and near-infrared regions. However, gold and silver are not suitable for some applications. For example, they are generally inactive for catalyzing chemical reactions. The integration of plasmonic metals with other metals can offer superior or new physical/chemical properties. In this thesis, I prepared Au/Ag and Au/Pd bimetallic nanostructures and studied their plasmonic properties and applications in hydrogen sensing and photocatalysis. Seeds have a crucial importance in the synthesis of bimetallic nanostructures. I therefore first studied the roles of the crystalline structure and shape of seeds on the overgrowth of bimetallic nanostructures. The overgrowth of silver and palladium on single crystalline Au nanorods, multicrystalline Au nanorods, and nanobipyramids were studied under the same conditions for each metal. The growths of silver and palladium on single crystalline Au nanorods gave cuboidal nanostructures, while rod-shaped nanostructures were obtained from the growths of silver and palladium on multicrystalline Au nanorods and nanobipyramids. Moreover, the growths of silver and palladium on multicrystalline Au nanobipyramids started at the stepped side facets, while the growths started at the twin boundaries on multicrystalline Au nanorods. These results unambiguously indicate that the crystalline structure of

  19. Enhancing dissolved oxygen control using an on-line hybrid fuzzy-neural soft-sensing model-based control system in an anaerobic/anoxic/oxic process.

    PubMed

    Huang, Mingzhi; Wan, Jinquan; Hu, Kang; Ma, Yongwen; Wang, Yan

    2013-12-01

    An on-line hybrid fuzzy-neural soft-sensing model-based control system was developed to optimize dissolved oxygen concentration in a bench-scale anaerobic/anoxic/oxic (A(2)/O) process. In order to improve the performance of the control system, a self-adapted fuzzy c-means clustering algorithm and adaptive network-based fuzzy inference system (ANFIS) models were employed. The proposed control system permits the on-line implementation of every operating strategy of the experimental system. A set of experiments involving variable hydraulic retention time (HRT), influent pH (pH), dissolved oxygen in the aerobic reactor (DO), and mixed-liquid return ratio (r) was carried out. Using the proposed system, the amount of COD in the effluent stabilized at the set-point and below. The improvement was achieved with optimum dissolved oxygen concentration because the performance of the treatment process was optimized using operating rules implemented in real time. The system allows various expert operational approaches to be deployed with the goal of minimizing organic substances in the outlet while using the minimum amount of energy. PMID:24052227

  20. Ratiometric Molecular Probes Based on Dual Emission of a Blue Fluorescent Coumarin and a Red Phosphorescent Cationic Iridium(III) Complex for Intracellular Oxygen Sensing.

    PubMed

    Yoshihara, Toshitada; Murayama, Saori; Tobita, Seiji

    2015-06-09

    Ratiometric molecular probes RP1 and RP2 consisting of a blue fluorescent coumarin and a red phosphorescent cationic iridium complex connected by a tetra- or octaproline linker, respectively, were designed and synthesized for sensing oxygen levels in living cells. These probes exhibited dual emission with good spectral separation in acetonitrile. The photorelaxation processes, including intramolecular energy transfer, were revealed by emission quantum yield and lifetime measurements. The ratios (R(I) = (I(p)/I(f))) between the phosphorescence (I(p)) and fluorescence (I(f)) intensities showed excellent oxygen responses; the ratio of R(I) under degassed and aerated conditions ( R(I)(0) was 20.3 and 19.6 for RP1 and RP2. The introduction of the cationic Ir (III) complex improved the cellular uptake efficiency compared to that of a neutral analogue with a tetraproline linker. The emission spectra of the ratiometric probes internalized into living HeLa or MCF-7 cells could be obtained using a conventional microplate reader. The complex RP2 with an octaproline linker provided ratios comparable to the ratiometric measurements obtained using a microplate reader: the ratio of the R(I)) value of RP2 under hypoxia (2.5% O2) to that under normoxia (21% O2) was 1.5 and 1.7 for HeLa and MCF-7 cells, respectively. Thus, the intracellular oxygen levels of MCF-7 cells could be imaged by ratiometric emission measurements using the complex RP2.

  1. Photopatternable Polymeric Membranes for Optical Oxygen Sensors

    PubMed Central

    Ambekar, Raghu; Park, Jongwon; Henthorn, David B.; Kim, Chang-Soo

    2009-01-01

    A new class of optical oxygen sensor that can be photopatternable by traditional UV lithography is presented. They are fabricated using photopatternable spin-on silicone (polydimethyl-siloxane, PDMS) with oxygen sensitive luminescent dyes. It has a good adhesion property and can be applied on glass or on photopolymer (SU-8) without any additional surface treatments. The optimum mixture composition for patternable oxygen sensitive membranes is investigated and its optical properties are characterized. Proof-of-concepts for two applications, intensity-based oxygen sensing with SU-8 based structure and self-calibration fluidic oxygen sensor, are described. These photopatternable optical membranes will find many applications wherever small patterns of oxygen sensitive membranes are required. PMID:19554206

  2. Remote sensing of atmospheric properties with the Modular Optical Scanner (MOS)

    NASA Astrophysics Data System (ADS)

    Krawczyk, Harald; Pflug, Bringfried M.; Gerasch, Birgit

    1998-12-01

    Satellite remote sensing of atmospheric properties is important for investigation of atmospheric pollution and also for remote sensing of the underlying surface, where an atmospheric correction is needed. For the proof of new methodological concepts the multispectral imaging spectrometer MOS was developed in the DLR Institute of Space Sensor Technology and launched on the Indian satellite IRS- P3. It has 13 bands in the VIS/NIR region with 10nm bandwidth. MOS successfully provides data for more than 2 years over European and Northern African coasts. The paper will introduce a standard atmospheric correction scheme for MOS data over water regions using measurements in the near IR form 685 nm to 1000 nm. This method is based on a 2- channel correction, estimating the aerosol optical depth and the Angstrom coefficient for the spectral behavior of the optical thickness. After extrapolation of the visible region the atmospheric correction is applied. Examples will be shown from the Baltic and North Sea regions. The obtained result will be compared and discussed with available in situ measurements taken simultaneously with MOS overflights. Lastly, this algorithm is applied to an observation of forest fire smoke over Malaysia.

  3. Ultrasonic guided wave sensing properties of PVDF thin film with inter digital electrodes

    NASA Astrophysics Data System (ADS)

    Rathod, Vivek T.; Roy Mahapatra, D.

    2014-04-01

    Ultrasonic strain sensing performance of the large area PVDF with Inter Digital Electrodes (IDE) is studied in this work. Procedure to obtain IDE on a beta-phase PVDF is explained. PVDF film with IDE is bonded on a plate structure and is characterized for its directional sensitivity at different frequencies. Guided waves are induced on the IDE-PVDF sensor from different directions by placing a piezoelectric wafer actuator at different angles. Strain induced on the IDE-PVDF sensor by the guided waves in estimated by using a Laser Doppler Vibrometer (LDV) and a wave propagation model. Using measured voltage response from IDE-PVDF sensor and the strain measurements from LDV the piezoelectric coefficient is estimated in various directions. The variation of ℯ11 e at different angles shows directional sensitivity of the IDE-PVDF sensor to the incident guided waves. The present study provides an effective technique to characterize thin film piezoelectric sensors for ultrasonic strain sensing at very high frequencies of 200 kHz. Often frequency of the guided wave is changed to alter the wavelength to interrogate damages of different sizes in Structural Health Monitoring (SHM) applications. The unique property of directional sensitivity combined with frequency tunability makes the IDEPVDF sensor most suitable for SHM of structures.

  4. Synthesis and Gas Sensing Properties of Single La-Doped SnO2 Nanobelts

    PubMed Central

    Wu, Yuemei; Zhang, Heng; Liu, Yingkai; Chen, Weiwu; Ma, Jiang; Li, Shuanghui; Qin, Zhaojun

    2015-01-01

    Single crystal SnO2 nanobelts (SnO2 NBs) and La-SnO2 nanobelts (La-SnO2 NBs) were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC) liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed. PMID:26087374

  5. Synthesis and Gas Sensing Properties of Single La-Doped SnO₂ Nanobelts.

    PubMed

    Wu, Yuemei; Zhang, Heng; Liu, Yingkai; Chen, Weiwu; Ma, Jiang; Li, Shuanghui; Qin, Zhaojun

    2015-06-16

    Single crystal SnO2 nanobelts (SnO2 NBs) and La-SnO2 nanobelts (La-SnO2 NBs) were synthesized by thermal evaporation. Both a single SnO2 NB sensor and a single La-SnO2 NB sensor were developed and their sensing properties were investigated. It is found that the single La-SnO2 NB sensor had a high sensitivity of 8.76 to ethanediol at a concentration of 100 ppm at 230 °C, which is the highest sensitivity of a single SnO2 NB to ethanediol among three kinds of volatile organic (VOC) liquids studied, including ethanediol, ethanol, and acetone. The La-SnO2 NBs sensor also exhibits a high sensitivity, good selectivity and long-term stability with prompt response time to ethanediol. The mechanism behind the enhanced sensing performance of La-doped SnO2 nanobelts is discussed.

  6. Chemical mechanisms of the toxicological properties of nanomaterials: generation of intracellular reactive oxygen species.

    PubMed

    Yan, Liang; Gu, Zhanjun; Zhao, Yuliang

    2013-10-01

    As more and more nanomaterials with novel physicochemical properties or new functions are created and used in different research fields and industrial sectors, the scientific and public concerns about their toxic effects on human health and the environment are also growing quickly. In the past decade, the study of the toxicological properties of nanomaterials/nanoparticles has formed a new research field: nanotoxicology. However, most of the data published relate to toxicological phenomena and there is less understanding of the underlying mechanism for nanomaterial-induced toxicity. Nanomaterial-induced reactive oxygen species (ROS) play a key role in cellular and tissue toxicity. Herein, we classify the pathways for intracellular ROS production by nanomaterials into 1) the direct generation of ROS through nanomaterial-catalyzed free-radical reactions in cells, and 2) the indirect generation of ROS through disturbing the inherent biochemical equilibria in cells. We also discuss the chemical mechanisms associated with above pathways of intracellular ROS generation, from the viewpoint of the high reactivity of atoms on the nanosurface. We hope to aid in the understanding of the chemical origin of nanotoxicity to provide new insights for chemical and material scientists for the rational design and creation of safer and greener nanomaterials.

  7. Flotation properties of some oxygen-containing compounds of the acyclic series

    SciTech Connect

    Shreider, E.M.; Para, S.F.; Galanov, M.E.; Trachik, T.L.; Lagutina, L.V.

    1981-01-01

    In the monatomic alcohols series, maximum flotation activity is reached at 6 to 8 carbon atoms in the radical. It was decided to investigate the reagent properties of some other substances containing hydroxyl radicals which have not previously been considered. Oxygen-containing compounds in the acyclic series were examined, including alcohols: I - ethanol, ethylene-glycol, glycerol, pentaerythrytol, D-mannitol; II - dulcitol, D-sorbitol, D-mannitol, xylitol; glycols - monoethyleneglycol, diethyleneglycol, triethyleneglycol, polyethyleneglycol; and ethanolamines - ethanolamine, triethanolamine. The flotation properties of the reagents were determined in a Mekhanobr laboratory flotation machine with a chamber volume of 1.5 liter and an impeller speed of 1800 rpm. The materials tested were the <1 mm size fractions from run-of-plant charge and slurry from the radial thickeners. The samples were first dried and averaged. The pulp density was 200 g/l. The reagent conditions were kept constant throughout (50% of the total added at the start of a test, 25% after 2 min and 25% after 4 min from the start). The reagent additions were 1.0 to 1.4 kg/ton. All of these compounds had a very weak flotation activity.

  8. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus_minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus_minus} 6 MPa and a fracture toughness of 3.3 {plus_minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  9. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus minus} 6 MPa and a fracture toughness of 3.3 {plus minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  10. Cellular Response to Non-contacting Nanoscale Sublayer: Cells Sense Several Nanometer Mechanical Property.

    PubMed

    Azuma, Tomoyuki; Teramura, Yuji; Takai, Madoka

    2016-05-01

    Cell adhesion is influenced not only from the surface property of materials but also from the mechanical properties of the nanometer sublayer just below the surface. In this study, we fabricated a well-defined diblock polymer brush composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate (AEMA). The underlying layer of poly(MPC) is a highly viscous polymer, and the surface layer of poly(AEMA) is a cell-adhesive cationic polymer. The adhesion of L929 mouse fibroblasts was examined on the diblock polymer brush to see the effect of a non-contacting underlying polymer layer on the cell-adhesion behavior. Cells could sense the viscoelasticity of the underlying layers at the nanometer level, although the various fabricated diblock polymer brushes had the same surface property and the functional group. Thus, we found a new factor which could control cell spread at the nanometer level, and this insight would be important to design nanoscale biomaterials and interfaces. PMID:27064435

  11. Growth and toxic gas sensing properties of poly(urethaneimide) thin films.

    PubMed

    Youssef, Ismail Ben; Sarry, Frederic; Nysten, Bernard; Alexieva, Gergana; Strashilov, Vesselin; Kolev, Iliyan; Alem, Halima

    2016-06-01

    In this work we present a study on the growth and the gas sensing properties of poly(urethane imide) thin films. We first deeply characterized by atomic force microscopy (AFM) the nanostructuration of the poly(urethane imide) holding different amine groups. We further studied the interaction between highly toxic gases such as hexamethyleneimine (HMI) and pyridine and the polymer by using an unconventional method based on Quartz Crystal Microbalance (QCM) measurement. We showed for the first time that weak interactions, i.e. hydrogen bonding between the gas molecules and the polymer film allow the diffusion of the gas molecule deep in the polymeric film and the recovery of the film once the gas molecules leave the sensor. This first work paves a new way for the design of a completely recoverable sensor able to detect highly toxic gases for environmental concern.

  12. Synthesis, magnetic and ethanol gas sensing properties of semiconducting magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Al-Ghamdi, Ahmed A.; Al-Hazmi, Faten; Al-Tuwirqi, R. M.; Alnowaiser, F.; Al-Hartomy, Omar A.; El-Tantawy, Farid; Yakuphanoglu, F.

    2013-05-01

    The superparamagnetic magnetite (Fe3O4) nanoparticles with an average size of 7 nm were synthesized using a rapid and facile microwave hydrothermal technique. The structure of the magnetite nanoparticles was characterized by X-ray diffraction (X-ray), field effect scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The prepared Fe3O4 was shown to have a cubic phase of pure magnetite. Magnetization hysteresis loop shows that the synthesized magnetite exhibits no hysteretic features with a superparamagnetic behavior. The ethanol gas sensing properties of the synthesized magnetite were investigated, and it was found that the responsibility time is less than 10 s with good reproducibility for ethanol sensor. Accordingly, it is evaluated that the magnetite nanoparticles can be effectively used as a solid state ethanol sensor in industrial commercial product applications.

  13. Synthesis of metal oxide composite nanosheets and their pressure sensing properties

    NASA Astrophysics Data System (ADS)

    Tariq Saeed Chani, Muhammad; Bahadar Khan, Sher; Karimov, Kh. S.; Abid, M.; Asiri, Abdullah M.; Akhtar, Kalsoom

    2015-02-01

    This study presents the synthesis of metal oxides composite nanosheets (oxides of cobalt, zinc and iron) and their pressure sensing properties. A transducer has been fabricated to directly measure the resistance—pressure and impedance—pressure relationships of pristine nanopowder. At the initial stage, a nanopowder sample of 10 mm diameter and 1 mm height was placed in the transducer and by applying pressure of up to 8.15 kN/m2; the DC resistance and the impedance are reduced by 44% on average. It can be explained by the densification of the samples and a decrease in porosity due to the effect of pressure. It was also observed that the DC resistance increases with time and saturated within 8 min. It is considered that this phenomenon is based on the effect of displacement currents of bound charges. The dependences of the impedance phase (θ) on frequency and pressure have also been investigated.

  14. Martian lavas: Three complementary remote sensing techniques to derive flow properties

    NASA Technical Reports Server (NTRS)

    Lopes-Gautier, R.; Bruno, B. C.; Taylor, G. J.; Rowland, S.; Kilburn, C. R. J.

    1993-01-01

    Several remote sensing techniques have been developed to determine various properties of lava flows. We are currently focusing on three such techniques to interpret Martian lava flows on Alba Patera, which are based on measurements of distal flow lobe widths which can be used to infer silica content; convolution of flow margins which can distinguish between pahoehoe and a'a types of basaltic flows; final flow field dimensions which can be combined with ground slope to derive effusion duration and average effusion rate. These methods are extremely complementary and together provide a more significant and complete understanding of extra-terrestrial lava flows. However, each of these techniques have specific and distinct data requirements.

  15. Four new lanthanide-organic frameworks: selective luminescent sensing and magnetic properties.

    PubMed

    Ning, Yan; Wang, Lu; Yang, Guo-Ping; Wu, Yunlong; Bai, Nannan; Zhang, Wenyan; Wang, Yao-Yu

    2016-08-01

    Four new isostructural lanthanide-organic frameworks, [Ln(L)(H2O)2]·H2O·CH3CN (1-Ln) (Ln = Eu, Tb, Dy, and Gd), have been successfully synthesized via solvothermal reactions with a semi-rigid V-shaped multicarboxylate ligand 2-(2',4'-dicarboxylphenoxy) benzoic acid (H3L) and Ln(NO3)3·6H2O. 1-Ln shows 2D layer-by-layer frameworks with interlayer channels decorated by carboxylate groups. 1-Eu exhibits excellent luminescence properties, and therefore, is chosen as a probe for sensing different metal ions and anions. Consequently, 1-Eu displays high selectivity and sensitivity for Fe(3+) and Cr(6+) ions, simultaneously, through the luminescence quenching effect, and thus, should be an excellent candidate for probing these pollutant metal ions. In addition, antiferromagnetic exchange interactions also exist between the Dy(3+) ions in 1-Dy. PMID:27464998

  16. Sensing Properties of a Fabry-Perot Dielectric Structure and Dimer Nanoparticles

    DOE PAGESBeta

    Polemi, A.; Shuford, K. L.

    2012-01-01

    We investigate the use of a Fabry-Perot dielectric structure combined with differently shaped nanoparticles for Surface Enhanced Raman Scattering. In particular, we show how an ideal two-layer Fabry-Perot configuration enhances the local surface field of silver nanoparticles positioned on the surface of the structure. We develop the concept using disc dimers and then extend the discussion to bowtie nanoparticles. The structure is excited by a single emitter, which couples to the nanoparticles through the dielectric layers, producing a wide aperture field that can be used to excite multiple dimers. We show how an array of nanoparticles can be properly arrangedmore » in order to increase the total scattering signal generated from the structure. The layered geometry produces robust field properties in between nanoparticles, making the overall sensing characteristics less sensitive to the interparticle seperation distance and incident polarization.« less

  17. Piper nigrum, Piper betle and Gnetum gnemon- Natural Food Sources with Anti-Quorum Sensing Properties

    PubMed Central

    Tan, Li Ying; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    Various parts of Piper nigrum, Piper betle and Gnetum gnemon are used as food sources by Malaysians. The purpose of this study is to examine the anti-quorum sensing (anti-QS) properties of P. nigrum, P. betle and G. gnemon extracts. The hexane, chloroform and methanol extracts of these plants were assessed in bioassays involving Pseudomonas aeruginosa PA01, Escherichia coli [pSB401], E. coli [pSB1075] and Chromobacterium violaceum CV026. It was found that the extracts of these three plants have anti-QS ability. Interestingly, the hexane, chloroform and methanol extracts from P. betle showed the most potent anti-QS activity as judged by the bioassays. Since there is a variety of plants that serve as food sources in Malaysia that have yet to be tested for anti-QS activity, future work should focus on identification of these plants and isolation of the anti-QS compounds. PMID:23519352

  18. Highly sensitive and selective electrochemical dopamine sensing properties of multilayer graphene nanobelts

    NASA Astrophysics Data System (ADS)

    Karthick Kannan, Padmanathan; Moshkalev, Stanislav A.; Sekhar Rout, Chandra

    2016-02-01

    In the present study, we report the electrochemical sensing property of multi-layer graphene nanobelts (GNBs) towards dopamine (DA). GNBs are synthesized from natural graphite and characterized by using techniques like field-emission scanning electron microscopy, atomic force microscopy and Raman spectroscopy. An electrochemical sensor based on GNBs is developed for the detection of DA. From the cyclic voltammetry and amperometry studies, it is found that GNBs possess excellent electrocatalytic activity towards DA molecules. The developed DA sensor showed a sensitivity value of 0.95 μA μM-1 cm-2 with a linear range of 2 μM to 0.2 mM. The interference data exhibited that GNB is highly selective to DA even in the presence of common interfering species like ascorbic acid, uric acid, glucose and lactic acid.

  19. Porous Nd-doped In2O3 nanotubes with excellent formaldehyde sensing properties

    NASA Astrophysics Data System (ADS)

    Wang, Xuesong; Zhang, Jinbao; He, Yue; Wang, Lianyuan; Liu, Li; Wang, Han; Guo, Xuexin; Lian, Hongwei

    2016-08-01

    Pure and Nd-doped porous In2O3 nanotubes have been successfully synthesized by single-capillary electrospinning method. The SEM images displays the novel structure of Nd-doped In2O3 which has pores distributed on the surface of nanotubes. The subsequent test results demonstrate that Nd-doped porous In2O3 nanotubes possess excellent gas-sensing properties to formaldehyde. The response of Nd-doped porous In2O3 nanotubes to 100 ppm formaldehyde is 44.6 at the optimum operating temperature of 240 °C, which is 3.6 times larger than that of pure porous In2O3 nanotubes (12.5), and the response and recovery times to 100 ppm formaldehyde are 15 and 50 s, respectively.

  20. NH3 sensing properties polyaniline: TiO2 nanorods heterostructure

    NASA Astrophysics Data System (ADS)

    Patil, U. V.; Ramgir, Niranjan S.; Debnath, A. K.; Karmakar, N.; Aswal, D. K.; Kothari, D. C.; Gupta, S. K.

    2016-05-01

    NH3 sensing properties of polyaniline: TiO2 nanorods heterostructures have been investigated. TiO2 nanorods were synthesized using hydrothermal method. Thin layer of polyanilene was deposited by in-situ oxidative polymerization of aniline over TiO2 nanorods film. The heterostructure film exhibited an enhanced sensor response towards NH3 at room temperature. For example, heterostructure films exhibited a sensor response of 610% towards 100 ppm of NH3 with a response and recovery times of 40 and 60 s, respectively. This response and response kinetics is better than pure PANI films that exhibited a response of 210% with a response and recovery time of 21 and 160 s, respectively.

  1. Growth and toxic gas sensing properties of poly(urethaneimide) thin films.

    PubMed

    Youssef, Ismail Ben; Sarry, Frederic; Nysten, Bernard; Alexieva, Gergana; Strashilov, Vesselin; Kolev, Iliyan; Alem, Halima

    2016-06-01

    In this work we present a study on the growth and the gas sensing properties of poly(urethane imide) thin films. We first deeply characterized by atomic force microscopy (AFM) the nanostructuration of the poly(urethane imide) holding different amine groups. We further studied the interaction between highly toxic gases such as hexamethyleneimine (HMI) and pyridine and the polymer by using an unconventional method based on Quartz Crystal Microbalance (QCM) measurement. We showed for the first time that weak interactions, i.e. hydrogen bonding between the gas molecules and the polymer film allow the diffusion of the gas molecule deep in the polymeric film and the recovery of the film once the gas molecules leave the sensor. This first work paves a new way for the design of a completely recoverable sensor able to detect highly toxic gases for environmental concern. PMID:27130101

  2. Room temperature ammonia vapor sensing properties of transparent single walled carbon nanotube thin film

    NASA Astrophysics Data System (ADS)

    Shobin, L. R.; Manivannan, S.

    2014-10-01

    Carbon nanotube (CNT) networks are identified as potential substitute and surpass the conventional indium doped tin oxide (ITO) in transparent conducting electrodes, thin-film transistors, solar cells, and chemical sensors. Among them, CNT based gas sensors gained more interest because of its need in environmental monitoring, industrial control, and detection of gases in warfare or for averting security threats. The unique properties of CNT networks such as high surface area, low density, high thermal conductivity and chemical sensitivity making them as a potential candidate for gas sensing applications. Commercial unsorted single walled carbon nanotubes (SWCNT) were purified by thermal oxidation and acid treatment processes and dispersed in organic solvent N-methyl pyrolidone using sonication process in the absence of polymer or surfactant. Optically transparent SWCNT networks are realized on glass substrate by coating the dispersed SWCNT with the help of dynamic spray coating process at 200ºC. The SWCNT random network was characterized by scanning electron microscopy and UV-vis-NIR spectroscopy. Gas sensing property of transparent film towards ammonia vapor is studied at room temperature by measuring the resistance change with respect to the concentration in the range 0-1000 ppm. The sensor response is increased logarithmically in the concentration range 0 to 1000 ppm with the detection limit 0.007 ppm. The random networks are able to detect ammonia vapor selectively because of the high electron donating nature of ammonia molecule to the SWCNT. The sensor is reversible and selective to ammonia vapor with response time 70 seconds and recovery time 423 seconds for 62.5 ppm with 90% optical transparency at 550 nm.

  3. UV and humidity sensing properties of ZnO nanorods prepared by the arc discharge method.

    PubMed

    Fang, F; Futter, J; Markwitz, A; Kennedy, J

    2009-06-17

    The UV and humidity sensing properties of ZnO nanorods prepared by arc discharge have been studied. Scanning electron microscopy and photoluminescence spectroscopy were carried out to analyze the morphology and optical properties of the as-synthesized ZnO nanorods. Proton induced x-ray emission was used to probe the impurities in the ZnO nanorods. A large quantity of high purity ZnO nanorod structures were obtained with lengths of 0.5-1 microm. The diameters of the as-synthesized ZnO nanorods were found to be between 40 and 400 nm. The nanorods interlace with each other, forming 3D networks which make them suitable for sensing application. The addition of a polymeric film-forming agent (BASF LUVISKOL VA 64) improved the conductivity, as it facilitates the construction of conducting networks. Ultrasonication helped to separate the ZnO nanorods and disperse them evenly through the polymeric agent. Improved photoconductivity was measured for a ZnO nanorod sensor annealed in air at 200 degrees C for 30 min. The ZnO nanorod sensors showed a UV-sensitive photoconduction, where the photocurrent increased by nearly four orders of magnitude from 2.7 x 10(-10) to 1.0 x 10(-6) A at 18 V under 340 nm UV illumination. High humidity sensitivity and good stability were also measured. The resistance of the ZnO nanorod sensor decreased almost linearly with increasing relative humidity (RH). The resistance of the ZnO nanorods changed by approximately five orders of magnitude from 4.35 x 10(11) Omega in dry air (7% RH) to about 4.95 x 10(6) Omega in 95% RH air. It is experimentally demonstrated that ZnO nanorods obtained by the arc discharge method show excellent performance and promise for applications in both UV and humidity sensors. PMID:19468159

  4. Exploring the electronic, vibrational, and chemical sensing properties of graphene, nanotubes, nanoparticles, and other nanomaterials

    NASA Astrophysics Data System (ADS)

    Sussman, Allen

    Some might view the "nano revolution" as one of the most important developments of our time, as nanomaterials have been and continue to be a seemingly endless source of new and exciting physics and have found application in almost every imaginable aspect of our lives. Carbon allotropes such as graphene, which is a single atomic layer of carbon atoms in a hexagonal lattice, carbon nanotubes (CNTs), which can be thought of as graphene sheets rolled up into cylinders, and graphene nanoribbons (GNRs) have garnered massive attention in recent years due to their remarkable properties and many potential uses. This work investigates the fundamental properties and applications of certain nanomaterials such as carbon allotropes, semiconducting metal oxide (SMO) nanoparticles, and others in the exciting fields of gas sensing, nanoelectromechanical oscillation, and optical near field enhancement. It also introduces a novel GNR synthesis technique. Chapter 1 of this work is a brief introduction to the nanomaterials that will be investigated here. Chapter 2 presents experimental investigations into the interaction between gases and certain nanomaterials, including SMO nanoparticles, gold nanowires and thin films, CNTs, bare graphene, and graphene functionalized by a novel electrodeposition technique. New findings on the sensing mechanism of tungsten oxide nanoparticles for hydrogen sulfide gas are discussed. These findings suggest that previous models were incorrect or incomplete. Chapter 3 discusses sustained self-oscillations of a singly-clamped CNT under constant bias, a phenomenon which obviates the need for large external sources to drive nanomechanical oscillations. A model of the phenomenon is presented and used to guide scalable, top-down fabrication of self-oscillators. In chapter 4, a novel, clean technique for synthesizing GNRs with desired dimensions is demonstrated. It is shown that this method allows for transmission electron microscopy and electronic

  5. Remote Sensing of Cloud, Aerosol, and Land Properties from MODIS: Applications to the East Asia Region

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Chu, D. Allen; Moody, Eric G.

    2001-01-01

    MODIS is an earth-viewing cross-track scanning spectroradiometer launched on the Terra satellite in December 1999. MODIS scans a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, sun-synchronous platform at an altitude of 705 km, and provides images in 36 spectral bands between 0.415 and 14.235 microns with spatial resolutions of 250 m (two bands), 500 m (five bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean, and atmospheric processes. In this presentation we review the comprehensive set of remote sensing algorithms that have been developed for the remote sensing of atmospheric properties using MODIS data, placing primary emphasis on the principal atmospheric applications of (i) developing a cloud mask for distinguishing clear sky from clouds, (ii) retrieving global cloud radiative and microphysical properties, including cloud top pressure and temperature, effective emissivity, cloud optical thickness, thermodynamic phase, and effective radius, (iii) monitoring tropospheric aerosol optical thickness over the land and ocean and aerosol size distribution over the ocean, (iv) determining atmospheric profiles of moisture and temperature, and (v) estimating column water amount. The physical principles behind the determination of each of these atmospheric products will be described, together with an example of their application using MODIS observations to the east Asian region in Spring 2001. All products are archived into two categories: pixel-level retrievals (referred to as Level-2 products) and global gridded products at a latitude and longitude resolution of 1 degree (Level-3 products). An overview of the MODIS atmosphere algorithms and products, status, validation activities, and early level-2 and -3 results will be presented.

  6. Remote Sensing of Cloud, Aerosol, and Water Vapor Properties from MODIS

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Menzel, W. Paul; Kaufman, Yoram J.; Ackerman, Steven A.; Tanre, Didier; Gao, Bo-Cai

    2001-01-01

    MODIS is an earth-viewing cross-track scanning spectroradiometer launched on the Terra satellite in December 1999. MODIS scans a swath width sufficient to provide nearly complete global coverage every two days from a polar orbiting, sun-synchronous, platform at an altitude of 705 kilometers, and provides images in 36 spectral bands between 0.415 and 14.235 micrometers with spatial resolutions of 250 meters (2 bands), 500 meters (5 bands) and 1000 meters (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean, and atmospheric processes. In this presentation we review the comprehensive set of remote sensing algorithms that have been developed for the remote sensing of atmospheric properties using MODIS data, placing primary emphasis on the principal atmospheric applications of (i) developing a cloud mask for distinguishing clear sky from clouds, (ii) retrieving global cloud radiative and microphysical properties, including cloud top pressure and temperature, effective emissivity, cloud optical thickness, thermodynamic phase, and effective radius, (iii) monitoring tropospheric aerosol optical thickness over the land and ocean and aerosol size distribution over the ocean, (iv) determining atmospheric profiles of moisture and temperature, and (v) estimating column water amount. The physical principles behind the determination of each of these atmospheric products will be described, together with an example of their application using MODIS observations. All products are archived into two categories: pixel-level retrievals (referred to as Level-2 products) and global gridded products at a latitude and longitude resolution of 1 degree (Level-3 products). An overview of the MODIS atmosphere algorithms and products, status, validation activities, and early level-2 and -3 results will be presented.

  7. Surrounding Sensitive Electronic Properties of Bi2Te3 Nanoplates—Potential Sensing Applications of Topological Insulators

    PubMed Central

    Liu, Bin; Xie, Wuyuan; Li, Han; Wang, Yanrong; Cai, Daoping; Wang, Dandan; Wang, Lingling; Liu, Yuan; Li, Qiuhong; Wang, Taihong

    2014-01-01

    Significant efforts have been paid to exploring the fundamental properties of topological insulators (TIs) in recent years. However, the investigation of TIs as functional materials for practical device applications is still quite limited. In this work, electronic sensors based on Bi2Te3 nanoplates were fabricated and the sensing performance was investigated. On exposure to different surrounding environments, significant changes in the conducting properties were observed by direct electrical measurements. These results suggest that nanostructured TIs hold great potential for sensing applications. PMID:24717774

  8. Digital phosphorimeter with frequency domain signal processing: Application to real-time fiber-optic oxygen sensing

    NASA Astrophysics Data System (ADS)

    Alcala, J. Ricardo; Yu, Clement; Yeh, Gong Jong

    1993-06-01

    An instrument to measure the excited-state lifetimes of phosphorescent materials in real time is described. This apparatus uses pulsed and frequency-doubled Nd:YAG solid-state laser for excitation, sampler for data acquisition, and frequency domain methods for data fitting. The instrument amplifies the ac components of the detector output and band limits the signal to 25 kHz. The fundamental frequency of the excitation is then set to obtain a desired number of harmonics. This band limited signal is sampled and averaged over few thousand cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic is then computed. Ten to a hundred values of the phase and modulations are averaged before computing the sensor lifetime. The instrument is capable of measuring precise and accurate excited-state lifetimes from subpicowatt luminescent signals in 100 μm optical fibers. To monitor oxygen for biomedical applications the response time of the system is decreased by collecting only 8 or 16 harmonics. A least-squares fit yields the lifetimes of single exponentials. A component of zero lifetime is introduced to account for the backscatter excitation. The phosphorescence lifetimes measured reproducibly to three parts in a thousand are used to monitor oxygen. Oxygen concentrations are computed employing empirical polynomials. The system drift is less than 1% over 100 h of continuous operation. This instrument is used to measure oxygen concentrations in vitro and in vivo with 2 s update times and 90 s full response times. Examples of measurements in saline solutions and in dogs are presented.

  9. Microstructure, mechanical and optical properties of TiAlON coatings sputter-deposited with varying oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Schalk, Nina; Thierry Simonet Fotso, J. F.; Holec, David; Fian, Alexander; Jakopic, Georg; Terziyska, Velislava L.; Daniel, Rostislav; Mitterer, Christian

    2016-01-01

    Due to their excellent mechanical and optical properties as well as chemical stability, the synthesis of transition metal oxynitride thin films has attracted growing interest in the last years. Within this work, the evolution of the structure and properties of TiAlON coatings over a wide compositional range, from the nitride to the oxide side, was investigated. The coatings were grown on Si substrates in a laboratory-scale unbalanced magnetron dc sputtering system from powder metallurgical TiAl targets with an Al/Ti atomic ratio of 60/40, using a constant level of nitrogen with rising oxygen partial pressure. Coating composition and microstructure were investigated by energy- and wavelength-dispersive x-ray spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. Furthermore, the mechanical and optical properties were evaluated using nanoindentation and spectroscopic ellipsometry, respectively. Oxygen concentrations of up to 49 at.% within the films could be obtained, at the expense of the nitrogen content. The oxygen-free coating exhibited a single-phase fcc-Ti1-x Al x N structure. With increasing oxygen content the structure remained fcc-Ti1-x Al x N based, but additional fractions of amorphous oxides were formed. The structural evolution was corroborated by ab initio calculations. Decreasing coating hardness could be observed with increasing oxygen concentration. The refraction index and extinction coefficient were lower for coatings with higher oxygen content, but the behavior of the optical properties remained Ti1-x Al x N-like over the investigated spectral range.

  10. Terahertz Remote Sensing of Ice Clouds - Sensitivity on Ice Dielectric Properties

    NASA Astrophysics Data System (ADS)

    Mendrok, J.; Baron, P.; Kasai, Y.

    2007-12-01

    Initiated by current developments in terahertz sensor technology the application of instruments operating in the spectral region between 0.1 - 30 THz is considered for a number of remote sensing issues. Accounting for more than 50 percent of the outgoing longwave radiation and with the major component of cirrus radiative forcing in the far-infrared, satellite measurements in this spectral region will significantly support the determination of the radiation budget of the Earth. Furthermore, spanning the whole range of particle sizes found in tropospheric ice clouds, the Terahertz region bears the potential to complement existing methods and improve our knowlegde and understanding of those clouds. Both, determination of the Earth's radiation budget as well as retrieving ice cloud properties require appropriately accurate calculations of radiative transfer. Hence, a good knowledge of the input parameters to the radiative transfer models is needed. In particular, this includes spectrally dependent properties of the molecular as well as particulate atmospheric matter, i.e., spectroscopic parameters of the molecular absorption lines and continua as well as the dielectric properties of aerosol and cloud particle material. Due to the lack of Terahertz light source and receiver technology in the past, measurements of these parameters have been sparse and the knowledge about them is rather poor. In preparation to evaluate the feasibility of monitoring tropospheric ice clouds using passive Terahertz observations, we study the modeling uncertainties due to the unconfident knowledge of the complex refractive index of ice. We give an overview of the consistency and discrepancies, respectively, of the existing measurements and models for ice refractive index in the Terahertz region. Using calculations of particle optical properties according to Mie theory as well as the radiative transfer models Moliere and SARTre, we estimate the deviations in particle optical properties and

  11. Effect of CSA Concentration on the Ammonia Sensing Properties of CSA-Doped PA6/PANI Composite Nanofibers

    PubMed Central

    Pang, Zengyuan; Fu, Jiapeng; Lv, Pengfei; Huang, Fenglin; Wei, Qufu

    2014-01-01

    Camphor sulfonic acid (CSA)-doped polyamide 6/polyaniline (PA6/PANI) composite nanofibers were fabricated using in situ polymerization of aniline under different CSA concentrations (0.02, 0.04, 0.06, 0.08 and 0.10 M) with electrospun PA6 nanofibers as templates. The structural, morphological and ammonia sensing properties of the prepared composite nanofibers were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), four-point probe techniques, X-ray diffraction (XRD) and a home-made gas sensing test system. All the results indicated that the CSA concentration had a great influence on the sensing properties of CSA-doped PA6/PANI composite nanofibers. The composite nanofibers doped with 0.02 M CSA showed the best ammonia sensing properties, with a significant sensitivity toward ammonia (NH3) at room temperature, superior to that of the composite nanofibers doped with 0.04–0.10 mol/L CSA. It was found that for high concentrations of CSA, the number of PANI–H+ reacted with NH3 would not make up a high proportion of all PANI–H+ within certain limits. As a result, within a certain range even though higher CSA-doped PA6/PANI nanofibers had better conductivity, their ammonia sensing performance would degrade. PMID:25401687

  12. Effect of CSA concentration on the ammonia sensing properties of CSA-doped PA6/PANI composite nanofibers.

    PubMed

    Pang, Zengyuan; Fu, Jiapeng; Lv, Pengfei; Huang, Fenglin; Wei, Qufu

    2014-01-01

    Camphor sulfonic acid (CSA)-doped polyamide 6/polyaniline (PA6/PANI) composite nanofibers were fabricated using in situ polymerization of aniline under different CSA concentrations (0.02, 0.04, 0.06, 0.08 and 0.10 M) with electrospun PA6 nanofibers as templates. The structural, morphological and ammonia sensing properties of the prepared composite nanofibers were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), four-point probe techniques, X-ray diffraction (XRD) and a home-made gas sensing test system. All the results indicated that the CSA concentration had a great influence on the sensing properties of CSA-doped PA6/PANI composite nanofibers. The composite nanofibers doped with 0.02 M CSA showed the best ammonia sensing properties, with a significant sensitivity toward ammonia (NH3) at room temperature, superior to that of the composite nanofibers doped with 0.04-0.10 mol/L CSA. It was found that for high concentrations of CSA, the number of PANI-H+ reacted with NH3 would not make up a high proportion of all PANI-H+ within certain limits. As a result, within a certain range even though higher CSA-doped PA6/PANI nanofibers had better conductivity, their ammonia sensing performance would degrade. PMID:25401687

  13. Nitrogen dioxide sensing properties of sprayed tungsten oxide thin film sensor: Effect of film thickness.

    PubMed

    Ganbavle, V V; Mohite, S V; Agawane, G L; Kim, J H; Rajpure, K Y

    2015-08-01

    We report a study on effect of film thickness on NO2 sensing properties of sprayed WO3 thin films. WO3 thin films varying in thicknesses are deposited onto the glass substrates by simple spray pyrolysis technique by varying the volume of spray solution.Thin film gas sensors are characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) techniques to study their physical properties. Film having thickness 745nm has shown highest gas response of 97% with 12 and 412s response and recovery times, respectively towards 100ppm NO2 concentration. Gas response of 20% is observed towards 10ppm NO2 at 200°C operating temperature. Sensitivity of the optimal sensor is 0.83%/ppm when operating at 200°C with 10ppm lower detection limit. The response of the sensor is reproducible and WO3 films are highly selective towards NO2 in presence of mist of various interfering gases viz. H2S, NH3, LPG, CO and SO2. PMID:25898119

  14. Numerical and experimental investigation of plasmonic properties of silver nanocrescent structures for sensing applications

    NASA Astrophysics Data System (ADS)

    Abumazwed, Ahmed; Kirk, A. G.; Kubo, W.; Tanaka, T.

    2015-02-01

    A novel technique to fabricate metallic nanocrescents is presented. Their optical response is simulated using the finite difference time domain (FDTD) method and validated via experimental investigation and surface characterization. Nanocrescents support multiresonance extinction spectra, making them good candidates for sensing applications. In this work, silver nanocrescents are arrayed on a glass substrate. A silicon mold was used to imprint an array of polymer nanopillars that were coated using obliquely evaporated silver in order to introduce a wedge angle to the wall thickness around the pillars. The thin part of the silver wall and the inner pillars were then removed under a vertical hydrogen plasma shower and nanocrescents were formed. Scanning electron microscopy (SEM) was used to characterize the surface morphology, and the optical properties have been investigated by using spectroscopy. We then performed a FDTD analysis of the nanocrescent structures to investigate their plasmonic properties emphasizing the multiresonance behavior. A comparison between the measured and simulated extinction spectra for two different polarizations of the incident plane wave showed a slight redshift in the case of the simulated spectra in both polarization states. This slight discrepancy is attributed to the roughness of the fabricated nanostructures. The existence of multiple resonances was clearly seen in the case of measured spectra.

  15. Multifunctional Benzothiadiazole-Based Small Molecules Displaying Solvatochromism and Sensing Properties toward Nitroarenes, Anions, and Cations**

    PubMed Central

    Alfonso, María; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2014-01-01

    Aryl or heteroaryl 5-substituted imidazo-benzothiadiazole derivatives were synthesized and shown to display remarkable solvatofluorochromism and selectively sense mercury(II) cations, acetate anions, and nitroaromatic derivatives, with discrimination between p-nitrophenol and picric acid. These novel sensors are of importance these days, as the detection of explosives is a high priority in issues of national security and environmental protection. To determine the ion binding properties of the sensors, their absorption and fluorescence emission spectra upon binding different cations and anions were compared. Significant shifts in the spectra were only observed for mercury(II) and acetate. The binding of these two ions was further studied using 1H NMR. The binding properties of different nitroaromatic compounds were also determined, and the results showed the importance of the presence of a phenol group in the guest molecule. Specifically, the two sensors were shown to discriminate between p-nitrophenol and picric acid. Finally, the mechanism of fluorescence quenching upon addition of nitrophenols was determined by computational methods. PMID:25558442

  16. Remote Sensing of Cloud, Aerosol, and Land Properties from MODIS: Applications to the East Asia Region

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Moody, Eric G.

    2002-01-01

    MODIS is an earth-viewing cross-track scanning spectroradiometer launched on the Terra satellite in December 1999 and the Aqua satellite in May 2002. MODIS scans a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, sun-synchronous, platform at an altitude of 705 km, and provides images in 36 spectral bands between 0.415 and 14.235 microns with spatial resolutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean, and atmospheric processes. In this paper we will describe the various methods being used for the remote sensing of cloud, aerosol, and surface properties using MODIS data, focusing primarily on (i) the MODIS cloud mask used to distinguish clouds, clear sky, heavy aerosol, and shadows on the ground, (ii) cloud optical properties, especially cloud optical thickness and effective radius of water drops and ice crystals, (iii) aerosol optical thickness and size characteristics both over land and ocean, and (iv) ecosystem classification and surface spectral reflectance. The physical principles behind the determination of each of these products will be described, together with an example of their application using MODIS observations to the east Asian region. All products are archived into two categories: pixel-level retrievals (referred to as Level-2 products) and global gridded products at a latitude and longitude resolution of 1 min (Level-3 products).

  17. Mechanical properties and cytocompatibility of oxygen-modified β-type Ti-Cr alloys for spinal fixation devices.

    PubMed

    Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Narita, Kengo; Şen, Mustafa; Shiku, Hitoshi; Matsue, Tomokazu

    2015-01-01

    In this study, various amounts of oxygen were added to Ti-10Cr (mass%) alloys. It is expected that a large changeable Young's modulus, caused by a deformation-induced ω-phase transformation, can be achieved in Ti-10Cr-O alloys by the appropriate oxygen addition. This "changeable Young's modulus" property can satisfy the otherwise conflicting requirements for use in spinal implant rods: high and low moduli are preferred by surgeons and patients, respectively. The influence of oxygen on the microstructures and mechanical properties of the alloys was examined, as well as the bending springback and cytocompatibility of the optimized alloy. Among the Ti-10Cr-O alloys, Ti-10Cr-0.2O (mass%) alloy shows the largest changeable Young's modulus following cold rolling for a constant reduction ratio. This is the result of two competing factors: increased apparent β-lattice stability and decreased amounts of athermal ω phase, both of which are caused by oxygen addition. The most favorable balance of these factors for the deformation-induced ω-phase transformation occurred at an oxygen concentration of 0.2mass%. Ti-10Cr-0.2O alloy not only exhibits high tensile strength and acceptable elongation, but also possesses a good combination of high bending strength, acceptable bending springback and great cytocompatibility. Therefore, Ti-10Cr-0.2O alloy is a potential material for use in spinal fixture devices. PMID:25449914

  18. Tensile properties of V-Cr-Ti alloys after exposure in helium and low-partial-pressure oxygen environments

    SciTech Connect

    Natesan, K.; Soppet, W.K.

    1997-04-01

    A test program is in progress to evaluate the effect of oxygen at low pO{sub 2} on the tensile properties of V-(4-5)wt% Cr-(4-5)wt% Ti alloys. Some of the tensile specimens were precharged with oxygen at low pO{sub 2} at 500{degrees}C and reannealed in vacuum at 500{degrees}C in environments with various pO{sub 2} levels and subsequently tensile tested at room temperature. The preliminary results indicate that both approaches are appropriate for evaluating the effect of oxygen uptake on the tensile properties of the alloys. The data showed that in the relatively short-time tests conducted thus far, the maximum engineering stress slightly increased after oxygen exposure but the uniform and total elongation values exhibited significant decrease after exposure in oxygen-containing environments. The data for a specimen exposed to a helium environment were similar to those obtained in low pO{sub 2} environments.

  19. Oxygen adsorption and electronic transport properties of Fe-substituted YBaCo{sub 4}O{sub 7} compounds

    SciTech Connect

    Hao, Haoshan; He, Qinglin; Cheng, Yongguang; Zhao, Limin

    2014-05-01

    Graphical abstract: - Highlights: • The conduction mechanism of YBaCo{sub 4}O{sub 7} system was established. • The effect of Fe substitution on the electronic transport was discussed. • The effect of oxygen adsorption/desorption processes on the transport properties was investigated. - Abstract: YBaCo{sub 4−x}Fe{sub x}O{sub 7} (0.0 ≤ x ≤ 0.8) samples were prepared by the solid-state reaction method and the effect of Fe substitution and oxygen adsorption/desorption on the electronic transport properties was investigated from room temperature to 900 °C. Fe for Co substitution results in a slight decline in the oxygen storage capacity at lower temperature (200–400 °C) and an increase of the phase-decomposition temperature at higher temperature (700–900 °C). Both the hole concentration and mobility are reduced in the Fe-containing compositions. Electrical resistivity, Seebeck coefficient, and conduction activation energy increase with the increasing Fe content. A close correlativity between oxygen adsorption and electronic transport behavior was observed in YBaCo{sub 4−x}Fe{sub x}O{sub 7} system. Oxygen adsorption decreases the electrical resistivity and Seebeck coefficients because of the increase of hole concentration at lower temperature and the phase decomposition at higher temperature.

  20. Mechanical properties and cytocompatibility of oxygen-modified β-type Ti-Cr alloys for spinal fixation devices.

    PubMed

    Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Narita, Kengo; Şen, Mustafa; Shiku, Hitoshi; Matsue, Tomokazu

    2015-01-01

    In this study, various amounts of oxygen were added to Ti-10Cr (mass%) alloys. It is expected that a large changeable Young's modulus, caused by a deformation-induced ω-phase transformation, can be achieved in Ti-10Cr-O alloys by the appropriate oxygen addition. This "changeable Young's modulus" property can satisfy the otherwise conflicting requirements for use in spinal implant rods: high and low moduli are preferred by surgeons and patients, respectively. The influence of oxygen on the microstructures and mechanical properties of the alloys was examined, as well as the bending springback and cytocompatibility of the optimized alloy. Among the Ti-10Cr-O alloys, Ti-10Cr-0.2O (mass%) alloy shows the largest changeable Young's modulus following cold rolling for a constant reduction ratio. This is the result of two competing factors: increased apparent β-lattice stability and decreased amounts of athermal ω phase, both of which are caused by oxygen addition. The most favorable balance of these factors for the deformation-induced ω-phase transformation occurred at an oxygen concentration of 0.2mass%. Ti-10Cr-0.2O alloy not only exhibits high tensile strength and acceptable elongation, but also possesses a good combination of high bending strength, acceptable bending springback and great cytocompatibility. Therefore, Ti-10Cr-0.2O alloy is a potential material for use in spinal fixture devices.

  1. Properties of Carbon–Oxygen White Dwarfs From Monte Carlo Stellar Models

    NASA Astrophysics Data System (ADS)

    Fields, C. E.; Farmer, R.; Petermann, I.; Iliadis, C.; Timmes, F. X.

    2016-05-01

    We investigate properties of carbon–oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using the stellar evolution toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the probability density functions in the reaction rate library STARLIB. These are the first Monte Carlo stellar evolution studies that use complete stellar models. Focusing on 3 {M}ȯ models evolved from the pre main-sequence to the first thermal pulse, we survey the remnant core mass, composition, and structure properties as a function of 26 STARLIB reaction rates covering hydrogen and helium burning using a Principal Component Analysis and Spearman Rank-Order Correlation. Relative to the arithmetic mean value, we find the width of the 95% confidence interval to be {{Δ }}{M}{{1TP}} ≈ 0.019 {M}ȯ for the core mass at the first thermal pulse, Δ{t}{{1TP}} ≈ 12.50 Myr for the age, {{Δ }}{log}({T}{{c}}/{{K}}) ≈ 0.013 for the central temperature, {{Δ }}{log}({ρ }{{c}}/{{g}} {{cm}}-3) ≈ 0.060 for the central density, {{Δ }}{Y}{{e,c}} ≈ 2.6 × 10‑5 for the central electron fraction, {{Δ }}{X}{{c}}{(}22{{Ne}}) ≈ 5.8 × 10‑4, {{Δ }}{X}{{c}}{(}12{{C}}) ≈ 0.392, and {{Δ }}{X}{{c}}{(}16{{O}}) ≈ 0.392. Uncertainties in the experimental 12C(α ,γ {)}16{{O}}, triple-α, and 14N({\\text{}}p,γ {)}15{{O}} reaction rates dominate these variations. We also consider a grid of 1–6 {M}ȯ models evolved from the pre main-sequence to the final white dwarf to probe the sensitivity of the initial–final mass relation to experimental uncertainties in the hydrogen and helium reaction rates.

  2. Properties of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models

    NASA Astrophysics Data System (ADS)

    Fields, C. E.; Farmer, R.; Petermann, I.; Iliadis, C.; Timmes, F. X.

    2016-05-01

    We investigate properties of carbon-oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using the stellar evolution toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the probability density functions in the reaction rate library STARLIB. These are the first Monte Carlo stellar evolution studies that use complete stellar models. Focusing on 3 {M}⊙ models evolved from the pre main-sequence to the first thermal pulse, we survey the remnant core mass, composition, and structure properties as a function of 26 STARLIB reaction rates covering hydrogen and helium burning using a Principal Component Analysis and Spearman Rank-Order Correlation. Relative to the arithmetic mean value, we find the width of the 95% confidence interval to be {{Δ }}{M}{{1TP}} ≈ 0.019 {M}⊙ for the core mass at the first thermal pulse, Δ{t}{{1TP}} ≈ 12.50 Myr for the age, {{Δ }}{log}({T}{{c}}/{{K}}) ≈ 0.013 for the central temperature, {{Δ }}{log}({ρ }{{c}}/{{g}} {{cm}}-3) ≈ 0.060 for the central density, {{Δ }}{Y}{{e,c}} ≈ 2.6 × 10-5 for the central electron fraction, {{Δ }}{X}{{c}}{(}22{{Ne}}) ≈ 5.8 × 10-4, {{Δ }}{X}{{c}}{(}12{{C}}) ≈ 0.392, and {{Δ }}{X}{{c}}{(}16{{O}}) ≈ 0.392. Uncertainties in the experimental 12C(α ,γ {)}16{{O}}, triple-α, and 14N({\\text{}}p,γ {)}15{{O}} reaction rates dominate these variations. We also consider a grid of 1-6 {M}⊙ models evolved from the pre main-sequence to the final white dwarf to probe the sensitivity of the initial-final mass relation to experimental uncertainties in the hydrogen and helium reaction rates.

  3. Enhancing photoluminescence properties of SiC/SiO2 coaxial nanocables by making oxygen vacancies.

    PubMed

    Liu, Wenna; Chen, Junhong; Yang, Tao; Chou, Kuo-Chih; Hou, Xinmei

    2016-09-14

    Coaxial nanocables (CNs) with an SiC core and a SiO2 shell were fabricated at a large scale by a simple and low cost method. The thickness of the SiO2 shell could be controlled by etching in 1 M NaOH aqueous solution for different amounts of time. XRD, SEM, TEM, HRTEM, PL and UV-Vis spectra were adopted to investigate the morphology and optical properties of the obtained SiC/SiO2CNs. Blue photoluminescence was observed at room temperature from the coaxial structure. The intensity of the single emission band at 468 nm (2.65 eV) exhibited a strong dependence on the thickness of the SiO2 layer and was significantly enhanced when the outer SiO2 shell had a thickness of 2.8 nm. The enhancement effect was attributed to oxygen vacancies (OV) and this was verified by deliberately enriching the surface OV through hydrogen treatment. PMID:27503431

  4. Synthesis and high sensing properties of a single Pd-doped SnO2 nanoribbon

    PubMed Central

    2014-01-01

    Monocrystal SnO2 and Pd-SnO2 nanoribbons have been successfully synthesized by thermal evaporation, and novel ethanol sensors based on a single Pd-SnO2 nanoribbon and a single SnO2 nanoribbon were fabricated. The sensing properties of SnO2 nanoribbon (SnO2 NB) and Pd-doped SnO2 nanoribbon (Pd-SnO2 NB) sensors were investigated. The results indicated that the SnO2 NB showed a high sensitivity to ethanol and the Pd-SnO2 NB has a much higher sensitivity of 4.3 at 1,000 ppm of ethanol at 230°C, which is the highest sensitivity for a SnO2-based NB. Pd-SnO2 NB can detect ethanol in a wide range of concentration (1 ~ 1,000 ppm) with a relatively quick response (recovery) time of 8 s (9 s) at a temperature from 100°C to 300°C. In the meantime, the sensing capabilities of the Pd-SnO2 NB under 1 ppm of ethanol at 230°C will help to promote the sensitivity of a single nanoribbon sensor. Excellent performances of such a sensor make it a promising candidate for a device design toward ever-shrinking dimensions because a single nanoribbon device is easily integrated in the electronic devices. PMID:25278819

  5. Effects of aging on mechanical properties of composite restoratives: a depth-sensing microindentation approach.

    PubMed

    Yap, Adrian U J; Chung, S M; Rong, Y; Tsai, K T

    2004-01-01

    This study investigated the effects of aging on the hardness and modulus of two composites (Tetric Ceram [TC], Vivadent; Esthet X [EX], Dentsply), a conventional (Compoglass [CG], Vivadent) and a posterior compomer (Dyract Posterior [DP], Dentsply) using a depth-sensing microindentation approach. Seven specimens (3-mm wide x 3-mm long x 2-mm deep) of each material were made and conditioned in distilled water at 37 degrees C. Hardness and modulus of the materials were determined at seven and 30 days using depth-sensing microindentation testing with the Instron MicroTester. Hardness was determined by dividing the peak load over the maximum projected contact area while effective modulus was calculated by analysis of the loading/unloading P-h curves and the analytical model according to Oliver and Pharr (1992). Results were analyzed using one-way ANOVA/Scheffe's post-hoc test and Independent Samples t-test at significance level 0.05. Mean Vickers Hardness (HV) ranged from 46.60 to 58.67 and 44.44 to 59.41 at seven and 30 days, respectively. Mean indentation modulus ranged from 9.57 to 9.95 and 9.19 to 10.03 for the same time periods. At both time periods, EX was significantly harder than all the other materials and HV values for TC were significantly greater than CG. No significant difference in hardness and modulus was observed between seven and 30 days for all materials with the exception of CG. For the latter, a significant decrease in mechanical properties was detected over time.

  6. Surface Properties and Characteristics of Mars Landing Sites from Remote Sensing Data and Ground Truth

    NASA Astrophysics Data System (ADS)

    Golombek, M. P.; Haldemann, A. F.; Simpson, R. A.; Furgason, R. L.; Putzig, N. E.; Huertas, A.; Arvidson, R. E.; Heet, T.; Bell, J. F.; Mellon, M. T.; McEwen, A. S.

    2008-12-01

    Surface characteristics at the six sites where spacecraft have successfully landed on Mars can be related favorably to their signatures in remotely sensed data from orbit and from the Earth. Comparisons of the rock abundance, types and coverage of soils (and their physical properties), thermal inertia, albedo, and topographic slope all agree with orbital remote sensing estimates and show that the materials at the landing sites can be used as ground truth for the materials that make up most of the equatorial and mid- to moderately high-latitude regions of Mars. The six landing sites sample two of the three dominant global thermal inertia and albedo units that cover ~80% of the surface of Mars. The Viking, Spirit, Mars Pathfinder, and Phoenix landing sites are representative of the moderate to high thermal inertia and intermediate to high albedo unit that is dominated by crusty, cloddy, blocky or frozen soils (duricrust that may be layered) with various abundances of rocks and bright dust. The Opportunity landing site is representative of the moderate to high thermal inertia and low albedo surface unit that is relatively dust free and composed of dark eolian sand and/or increased abundance of rocks. Rock abundance derived from orbital thermal differencing techniques in the equatorial regions agrees with that determined from rock counts at the surface and varies from ~3-20% at the landing sites. The size-frequency distributions of rocks >1.5 m diameter fully resolvable in HiRISE images of the landing sites follow exponential models developed from lander measurements of smaller rocks and are continuous with these rock distributions indicating both are part of the same population. Interpretation of radar data confirms the presence of load bearing, relatively dense surfaces controlled by the soil type at the landing sites, regional rock populations from diffuse scattering similar to those observed directly at the sites, and root-mean-squared slopes that compare favorably

  7. Gas sensing in nematodes.

    PubMed

    Carrillo, M A; Hallem, E A

    2015-01-01

    Nearly all animals are capable of sensing changes in environmental oxygen (O2) and carbon dioxide (CO2) levels, which can signal the presence of food, pathogens, conspecifics, predators, or hosts. The free-living nematode Caenorhabditis elegans is a powerful model system for the study of gas sensing. C. elegans detects changes in O2 and CO2 levels and integrates information about ambient gas levels with other internal and external cues to generate context-appropriate behavioral responses. Due to its small nervous system and amenability to genetic and genomic analyses, the functional properties of its gas-sensing microcircuits can be dissected with single-cell resolution, and signaling molecules and natural genetic variations that modulate gas responses can be identified. Here, we discuss the neural basis of gas sensing in C. elegans, and highlight changes in gas-evoked behaviors in the context of other sensory cues and natural genetic variations. We also discuss gas sensing in other free-living nematodes and parasitic nematodes, focusing on how gas-sensing behavior has evolved to mediate species-specific behavioral requirements. PMID:24906953

  8. Cellular oxygen sensing: Importins and exportins are mediators of intracellular localisation of prolyl-4-hydroxylases PHD1 and PHD2

    SciTech Connect

    Steinhoff, Amrei; Pientka, Friederike Katharina; Moeckel, Sylvia; Kettelhake, Antje; Hartmann, Enno; Koehler, Matthias; Depping, Reinhard

    2009-10-02

    Hypoxia-inducible factors are crucial in the regulatory process of oxygen homeostasis of vertebrate cells. Inhibition of prolyl hydroxylation of HIF-{alpha} subunits by prolyl-hydroxylases (PHD1, PHD2 and PHD3) leads to transcription of a greater number of hypoxia responsive genes. We have investigated the subcellular distribution and the molecular mechanisms regulating the intracellular allocation of PHD1 and PHD2. As reported earlier we find PHD1 located exclusively in the nucleus. We demonstrate that nuclear import of PHD1 occurs importin {alpha}/{beta} dependently and relies on a nuclear localisation signal (NLS). By contrast PHD2 is cycling between nucleus and cytoplasm, and nuclear import seems to be independent of 'classical' importin {alpha}/{beta} receptors. Furthermore, we reveal that the exit of PHD2 from the nucleus requires CRM1 and the N-terminal 100 amino acids of the protein. Our findings provide new insights into the mechanisms of the regulation of the oxygen sensor cascade of PHDs in different cellular compartments.

  9. A low-volume platform for cell-respirometric screening based on quenched-luminescence oxygen sensing.

    PubMed

    Alderman, John; Hynes, James; Floyd, Suzanne M; Krüger, Jan; O'Connor, Rosemary; Papkovsky, Dmitri B

    2004-06-15

    Cell viability assays represent an important technology in modern cell biology, drug discovery and biotechnology, where currently there is a high demand for simple, sensitive and cost-effective screening methods. We have developed a new methodology and associated tools for cell-based screening assays, which are based on the measurement of the rates of oxygen uptake in cells by luminescence quenching. Sealable microchamber devices matching the footprint of a standard 96-well plate were developed and used in conjunction with long-decay phosphorescent oxygen probes. These devices permit cell non-invasive, real-time monitoring of cellular respiration and a rapid, one-step, kinetic assessment of multiple samples for cell viability, drug/effector action. These assays can be carried out on conventional fluorescence plate readers, they are suitable for different types of cells, including adherent and slow-respiring cells, require small sample volumes and cell numbers, and are amenable for high throughput screening. Monitoring of as little as 300 mammalian cells in 3 microl volume has been demonstrated.

  10. Novel perspectives on the PHD-HIF oxygen sensing pathway in cardioprotection mediated by IPC and RIPC

    PubMed Central

    Martin-Puig, Silvia; Tello, Daniel; Aragonés, Julián

    2015-01-01

    Reperfusion of ischemic cardiac tissue is the standard treatment for improving clinical outcome following myocardial infarction but is inevitably associated with ischemia-reperfusion injury (IRI). Ischemic myocardial injury can be alleviated by exposing the heart to brief episodes of sublethal ischemia-reperfusion prior to the ischemic insult, a phenomenon that has been termed ischemic preconditioning (IPC). Similarly, remote IPC (RIPC) is defined as transient episodes of ischemia at a distant site before a subsequent prolonged injury of the target organ. In this setting, adaptive responses to hypoxia/ischemia in peripheral tissues include the release of soluble factors that have the potential to protect cardiomyocytes remotely. Oxygen fluctuations is a hallmark of insufficient tissue perfusion and ischemic episodes. Emerging evidence indicates that prolyl hydroxylase oxygen sensors (PHDs) and hypoxia-inducible transcription factors (HIFs) are critical regulators of IPC and RIPC. In this review, we discuss recent findings concerning the role of the PHD-HIF axis in IPC and RIPC-mediated cardioprotection and examine molecular pathways and cell types that might be involved. We also appraise the therapeutic value of targeting the PHD-HIF axis to enhance cardiac tolerance against IRI. PMID:26042040

  11. Using Remote Sensing Platforms to Estimate Near-Surface Soil Properties

    NASA Technical Reports Server (NTRS)

    Sullivan, D. G.; Shaw, J. N.; Rickman, D.; Mask, P. L.; Wersinger, J. M.; Luvall, J.

    2003-01-01

    Evaluation of near-surface soil properties via remote sensing (RS) could facilitate soil survey mapping, erosion prediction, fertilization regimes, and allocation of agrochemicals. The objective of this study was to evaluate the relationship between soil spectral signature and near surface soil properties in conventionally managed row crop systems. High resolution RS data were acquired over bare fields in the Coastal Plain, Appalachian Plateau, and Ridge and Valley provinces of Alabama using the Airborne Terrestrial Applications Sensor (ATLAS) multispectral scanner. Soils ranged from sandy Kandiudults to fine textured Rhodudults. Surface soil samples (0-1 cm) were collected from 163 sampling points for soil water content, soil organic carbon (SOC), particle size distribution (PSD), and citrate dithionite extractable iron (Fed) content. Surface roughness, soil water content, and crusting were also measured at sampling. Results showed RS data acquired from lands with less than 4 % surface soil water content best approximated near-surface soil properties at the Coastal Plain site where loamy sand textured surfaces were predominant. Utilizing a combination of band ratios in stepwise regression, Fed (r2 = 0.61), SOC (r2 = 0.36), sand (r2 = 0.52), and clay (r2 = 0.76) were related to RS data at the Coastal Plain site. In contrast, the more clayey Ridge and Valley soils had r-squares of 0.50, 0.36, 0.17, and 0.57. for Fed, SOC, sand and clay, respectively. Use of estimated eEmissivity did not generally improve estimates of near-surface soil attributes.

  12. Remote sensing and the optical properties of the narrow cylindrical leaves of Juncus roemerianus

    USGS Publications Warehouse

    Ramsey, Elijah W.; Rangoonwala, A.

    2004-01-01

    To develop a more complete foundation for remote sensing of the marsh grass Juncus roemerianus, we measured the optical properties of its cylindrical leaves at sites of different canopy height, biomass composition and amount, and connectivity to ocean flushing. To measure the leaf optical properties, we adapted a technique used for conifer needles. After establishing the reliability and limits of the adapted technique to the wider J.roemerianus leaves, mean transmittance and reflectance spectra were compared to associated leaf diameters from two dates in 1999 and 2002 and at each site. Transmittance was inversely related to leaf diameter. Mean transmittance and reflectance generated from reoccupation of many field sites in 2002 indicated little or no difference in transmittance between years, a slight reflectance difference in the visible (<2%) and a slightly higher reflectance difference in the near infrared (NIR) (<4%). Site comparison indicated limited ability to separate leaf transmittance but not reflectance by marsh type (e.g., low, medium, high) or biomass. Excluding one outlier, we found leaf transmittances could be adequately represented as 1% ?? 0.2% in the visible and 9% ?? 1% in the NIR and leaf reflectances represented from 14% to 16% in the visible and 71% to 75% in the NIR (the reflectance ranges represent 1999 and 2002 means). Reflectance and transmittance spectra associated with the dead J. roemerianus leaves displayed a spectrally flat increase from the visible to the NIR wavelengths. In total, we documented the atypical optical properties of the cylindrical J. roemerianus leaves and showed that to a first approximation, single means could represent leaf transmittance and visible leaf reflectance across all marsh zones and, after accounting for sample standardization, possibly the NIR reflectance as well.

  13. Remote sensing of cloud, aerosol and water vapor properties from the Moderate Resolution Imaging Spectrometer (MODIS)

    NASA Technical Reports Server (NTRS)

    King, M. D.

    1992-01-01

    The Moderate Resolution Imaging Spectrometer (MODIS) is an Earth-viewing sensor being developed as a facility instrument for the Earth Observing System (EOS) to be launched in the late 1990s. MODIS consists of two separate instruments that scan a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, Sun-synchronous, platform at an altitude of 705 km. Of primary interest for studies of atmospheric physics is the MODIS-N (nadir) instrument which will provide images in 36 spectral bands between 0.415 and 14.235 micrometers with spatial resoulutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean and atmosperhic processes. The intent of this lecture is to describe the current status of MODIS-N and its companion instrument MODIS-T (tilt), a tiltable cross-track scanning radiometer with 32 uniformly spaced channels between 0.410 and 0.875 micrometers, and to describe the physical principles behind the development of MODIS for the remote sensing of atmospheric properties. Primary emphasis will be placed on the main atmospheric applications of determining the optical, microphysical and physical properties of clouds and aerosol particles form spectral-reflection and thermal-emission measurements. In addition to cloud and aerosol properties, MODIS-N will be utilized for the determination of the total precipitable water vapor over land and atmospheric stability. The physical principles behind the determination of each of these atmospheric products will be described herein.

  14. Influence of heat treatment and oxygen doping on the mechanical properties and biocompatibility of titanium-niobium binary alloys.

    PubMed

    da Silva, Luciano Monteiro; Claro, Ana Paula Rosifini Alves; Donato, Tatiani Ayako Goto; Arana-Chavez, Victor E; Moraes, João Carlos Silos; Buzalaf, Marília Afonso Rabelo; Grandini, Carlos Roberto

    2011-05-01

    The most commonly used titanium (Ti)-based alloy for biological applications is Ti-6Al-4V, but some studies associate the vanadium (V) with the cytotoxic effects and adverse reactions in tissues, while aluminum (Al) has been associated with neurological disorders. Ti-Nb alloys belong to a new class of Ti-based alloys with no presence of Al and V and with elasticity modulus values that are very attractive for use as a biomaterial. It is well known that the presence of interstitial elements (such as oxygen, for example) changes the mechanical properties of alloys significantly, particularly the elastic properties, the same way that heat treatments can change the microstructure of these alloys. This article presents the effect of heat treatment and oxygen doping in some mechanical properties and the biocompatibility of three alloys of the Ti-Nb system, characterized by density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, in vitro cytotoxicity, and mechanical spectroscopy.

  15. Enhancement of electrical property by oxygen doping to copper phthalocyanine in inverted top emitting organic light emitting diodes

    SciTech Connect

    Hong, Kihyon; Kim, Kisoo; Lee, Jong-Lam

    2009-11-23

    We reported the evidence of oxygen doping to copper-phthalocyanine (CuPc) by O{sub 2}-plasma treatment to inverted top-emitting organic light-emitting diodes (ITOLEDs). In situ synchrotron-radiation photoelectron spectroscopy results showed that a new Cu-O bond appeared and the energy difference between the highest-occupied molecular orbital and E{sub F} is lowered by 0.15 eV after plasma treatment. The oxygen ions chemically interacted with Cu atoms and transferred charges to the CuPc. Thus the hole injection barrier was lowered, enhancing the electroluminescent property of ITOLEDs.

  16. Effect of low oxygen pressure on structural and magnetic properties of quenched SrFe12O19 thin films

    NASA Astrophysics Data System (ADS)

    Katlakunta, S.; Praveena, K.; Singh, R.

    2013-10-01

    Strontium hexaferrite thin films have been grown on glass substrates at room temperature in oxygen environment by pulsed laser deposition method. The effect of oxygen pressure (po2) on the structural and magnetic properties has been investigated. The as-deposited films were found to be amorphous in nature. The crystallization of these films was achieved by annealing at a temperature of 850 °C in air. The thickness of the film increased with po2. The film grown at po2 = 0.455 Pa had a clear hexagonal structure. The values of coercivity for the films were found to increase with po2.

  17. Remote sensing reflectance and inherent optical properties in the mid Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Tzortziou, Maria; Subramaniam, Ajit; Herman, Jay R.; Gallegos, Charles L.; Neale and, Patrick J., Jr.; Harding, Lawrence W.

    2007-03-01

    We used an extensive set of bio-optical data to examine the relationships between inherent optical properties and remotely sensed quantities in an optically complex and biologically productive region of the Chesapeake Bay. Field observations showed that the chlorophyll algorithms used by the MODIS (MODerate resolution Imaging Spectroradiometer) ocean color sensor (i.e. Chlor_a, chlor_MODIS, chlor_a_3 products) do not perform accurately in these Case 2 waters. This is because, at high concentrations of chlorophyll, all MODIS algorithms are based on empirical relationships between chlorophyll concentration and blue:green wavelength remote sensing reflectance ( Rrs) ratios that do not account for the typically strong blue-wavelength absorption by non-covarying, dissolved and non-algal particulate components. We found stronger correlation between chlorophyll concentration and red:green Rrs ratios (i.e. Rrs(677)/ Rrs(554)). Regionally-specific algorithms that are based on the phytoplankton optical properties in the red wavelength region provide a better basis for satellite monitoring of phytoplankton blooms in these Case 2 waters. Our estimates of f/ Q (proportionality factor in the relationship between Rrs and the ratio of water backscattering, bb, and absorption, a, coefficients, bb/( a + bb)) were not considerably different from f/ Q previously estimated for same measurement geometry but Case 1 waters. Variation in surface bb significantly affected Rrs magnitude across the visible spectrum and was most strongly correlated ( R2 = 0.88) with observed variability in Rrs at 670 nm. Surface values of particulate backscattering were strongly correlated with non-algal particulate absorption, anap ( R2 = 0.83). These results, along with the measured backscattering fraction and non-algal particulate absorption spectral slope, indicate that suspended non-algal particles with high inorganic content are the major water constituents regulating bb variability in the studied region

  18. Development of Satellite Remote Sensing Techniques for Quantifying Volcanic Ash Cloud Properties

    NASA Astrophysics Data System (ADS)

    Pavolonis, Michael J.

    Novel new approaches to automatically detect and characterize volcanic ash using satellite data are presented. The Spectrally Enhanced Cloud Objects (SECO) ash detection algorithm, combines radiative transfer theory, Bayesian methods, and image processing/computer vision concepts to identify volcanic ash clouds in satellite data with skill that is generally comparable to a human expert, especially with respect to false alarm rate. The SECO method is globally applicable and can be applied to virtually any low earth orbit or geostationary satellite sensor. The new ash detection approach was quantitatively proven to be significantly more skillful than traditional pixel based approaches, including the commonly used "split-window" technique. The performance of the SECO approach is extremely promising and well suited for a variety of new and improved applications. A new approach to retrieve volcanic ash cloud properties from infrared satellite measurements was also developed. The algorithm utilizes an optimal estimation framework to retrieve ash cloud height, mass loading, and effective particle radius. Optimal estimation allows uncertainties in the measurements and forward model to be taken into account and uncertainty estimates for each of the retrieved parameters to be determined. Background atmospheric water vapor, surface temperature, and surface emissivity are explicitly accounted for on a pixel-by-pixel basis, so the algorithm is globally applicable. In addition, the ash cloud retrieval algorithm is unique because it allows the cloud temperature/height to be a free parameter. Volcanic ash clouds are a major aviation hazard. Fine-grained ash from explosive eruptions can be transported long distances (>1000 km) from the source volcano by atmospheric winds, severely disrupting aviation operations. Volcanic ash clouds are complex and the background environment in which they reside can be as well. Thus, sophisticated satellite remote sensing techniques for extracting

  19. Remote Sensing of Cloud, Aerosol, and Water Vapor Properties from MODIS

    NASA Technical Reports Server (NTRS)

    King, Michael D.

    2001-01-01

    MODIS is an earth-viewing cross-track scanning spectroradiometer launched on the Terra satellite in December 1999. MODIS scans a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, sun-synchronous, platform at an altitude of 705 km, and provides images in 36 spectral bands from 0.415 to 14.235 microns with spatial resolutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean, and atmospheric processes. In this presentation I will review the comprehensive set of remote sensing algorithms that have been developed for the remote sensing of atmospheric properties using MODIS data, placing primary emphasis on the principal atmospheric applications of: (1) developing a cloud mask for distinguishing clear sky from clouds, (2) retrieving global cloud radiative and microphysical properties, including cloud top pressure and temperature, effective emissivity, cloud optical thickness, thermodynamic phase, and effective radius, (3) monitoring tropospheric aerosol optical thickness over the land and ocean and aerosol size distribution over the ocean, (4) determining atmospheric profiles of moisture and temperature, and (5) estimating column water amount. The physical principles behind the determination of each of these atmospheric products will be described, together with an example of their application using MODIS observations. All products are archived into two categories: pixel-level retrievals (referred to as Level-2 products) and global gridded products at a latitude and longitude resolution of 1 deg (Level-3 products). An overview of the MODIS atmosphere algorithms and products, status, validation activities, and early level-2 and -3 results will be presented. Finally, I will present some highlights from the land and ocean algorithms developed for processing global MODIS observations, including: (1) surface reflectance, (2

  20. In-airway molecular flow sensing: A new technology for continuous, noninvasive monitoring of oxygen consumption in critical care.

    PubMed

    Ciaffoni, Luca; O'Neill, David P; Couper, John H; Ritchie, Grant A D; Hancock, Gus; Robbins, Peter A

    2016-08-01

    There are no satisfactory methods for monitoring oxygen consumption in critical care. To address this, we adapted laser absorption spectroscopy to provide measurements of O2, CO2, and water vapor within the airway every 10 ms. The analyzer is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. The precision is illustrated by integrating the balance gas (N2 plus Ar) flow and showing that this exchange was near zero. Measured O2 consumption changed by <5% between air and O2 breathing. Clinical capability was illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible.

  1. SDS-assisted hydrothermal synthesis of NiO flake-flower architectures with enhanced gas-sensing properties

    NASA Astrophysics Data System (ADS)

    Miao, Ruiyang; Zeng, Wen; Gao, Qi

    2016-10-01

    A facile hydrothermal route was developed for the preparation of well-aligned hierarchical flower-like NiO nanostructure with the assistance of SDS that served as a structure-directing agent as well as a capping agent in the process of aggregation and assembly. Notably, the NiO sensors exhibit enhanced gas-sensing performance towards ethanol, which could be explained in association with the ultrathin nanosheets that are close to Debye length (LD) scale and thus get the majority carriers fully depleted due to the ionization of adsorbed oxygen, abundant effective gas diffusion paths as well as high surface-to-volume ratio to promote sufficient contact and reaction between the NiO sample and ethanol molecules, and numerous miniature reaction rooms assembled with nanosheets to make the test gas molecules stay long enough for completed gas-sensing reactions. Besides, a novel growth mechanism with the passage of reaction time was also proposed in detail.

  2. Effect of oxygen plasma on the properties of tantalum oxide films

    SciTech Connect

    Kalygina, V. M. Zarubin, A. N.; Novikov, V. A.; Petrova, Yu. S.; Skakunov, M. S.; Tolbanov, O. P.; Tyazhev, A. V.; Yaskevich, T. M.

    2010-09-15

    The effect of oxygen plasma on the leakage current, permittivity, and the dielectric loss tangent of Ta{sub 2}O{sub 5} thin layers (300-400 nm) is studied. It is suggested to treat tantalum oxide films in oxygen plasma to control their electrical and dielectric characteristics.

  3. Effects of oxygen incorporation in GeSbTe films on electrical properties and thermal stability

    SciTech Connect

    Jang, Moon Hyung; Park, Seung Jong; Lim, Dong Hyeok; Park, Sung Jin; Cho, Mann-Ho; Cho, Seong Jin; Cho, Yoon Ho; Lee, Jong-Heun

    2010-03-01

    Oxygen incorporated Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) films were prepared by an ion beam sputtering deposition method. I-V curves of the oxygen incorporated GST active layer showed that the threshold voltage (V{sub th}) varied, depending on the level of incorporated oxygen. In the case of a GST film with an elevated oxygen content of 30.8%, the GST layer melted at 9.02 V due to the instability conferred by the high oxygen content. The formation of Ge-deficient hexagonal phases such as GeSb{sub 2}Te{sub 4} and Sb{sub 2}Te{sub 3} appear to be responsible for the V{sub th} variation. Impedance analyses indicated that the resistance in GST films with oxygen contents of 16.7% and 21.7% had different origins. Thermal desorption spectroscopy data indicate that moisture and hydrocarbons were more readily desorbed at higher oxygen content because the oxygen incorporated GST films are more hydrophilic than undoped GST films.

  4. Oxygen-Induced Degradation in C60-Based Organic Solar Cells: Relation Between Film Properties and Device Performance.

    PubMed

    Bastos, João P; Voroshazi, Eszter; Fron, Eduard; Brammertz, Guy; Vangerven, Tim; Van der Auweraer, Mark; Poortmans, Jef; Cheyns, David

    2016-04-20

    Fullerene-based molecules are the archetypical electron-accepting materials for organic photovoltaic devices. A detailed knowledge of the degradation mechanisms that occur in C60 layers will aid in the development of more stable organic solar cells. Here, the impact of storage in air on the optical and electrical properties of C60 is studied in thin films and in devices. Atmospheric exposure induces oxygen-trap states that are 0.19 eV below the LUMO of the fullerene C60. Moreover, oxygen causes a 4-fold decrease of the exciton lifetime in C60 layers, resulting in a 40% drop of short-circuit current from optimized planar heterojunction solar cells. The presence of oxygen-trap states increases the saturation current of the device, resulting in a 20% loss of open-circuit voltage. Design guidelines are outlined to improve air stability for fullerene-containing devices.

  5. Oxygen self-diffusion in ThO2 under pressure: Connecting point defect parameters with bulk properties

    DOE PAGESBeta

    Cooper, Michael William D.; Fitzpatrick, M. E.; Tsoukalas, L. H.; Chroneos, A.

    2016-06-06

    ThO2 is a candidate material for use in nuclear fuel applications and as such it is important to investigate its materials properties over a range of temperatures and pressures. In the present study molecular dynamics calculations are used to calculate elastic and expansivity data. These are used in the framework of a thermodynamic model, the cBΩ model, to calculate the oxygen self-diffusion coefficient in ThO2 over a range of pressures (–10–10 GPa) and temperatures (300–1900 K). As a result, increasing the hydrostatic pressure leads to a significant reduction in oxygen self-diffusion. Conversely, negative hydrostatic pressure significantly enhances oxygen self-diffusion.

  6. Gas sensing properties of magnesium doped SnO{sub 2} thin films in relation to AC conduction

    SciTech Connect

    Deepa, S.; Skariah, Benoy Thomas, Boben; Joseph, Anisha

    2014-01-28

    Conducting magnesium doped (0 to 1.5 wt %) tin oxide thin films prepared by Spray Pyrolysis technique achieved detection of 1000 ppm of LPG. The films deposited at 304 °C exhibit an enhanced response at an operating temperature of 350 °C. The microstructural properties are studied by means of X-ray diffraction. AC conductivity measurements are carried out using precision LCR meter to analyze the parameters that affect the variation in sensing. The results are correlated with compositional parameters and the subsequent modification in the charge transport mechanism facilitating an enhanced LPG sensing action.

  7. In situ precipitation preparation of ZnO hollow spheres and their photocatalysis and gas-sensing properties

    NASA Astrophysics Data System (ADS)

    Jia, Xiaohua; Tian, Minggang; Liu, Yingying; Wu, Xiangyang; Song, Haojie

    2015-06-01

    ZnO hollow spheres were synthesized by in situ precipitation method in the presence of surfactant polyvinylpyrrolidone combined with subsequent calcination. The prepared ZnO was characterized using scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy. The results indicated that the prepared ZnO hollow spheres were well crystalline with wurtzite hexagonal phase. The formation mechanism of ZnO hollow spheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas and photocatalytic activities for the degradation of rhodamine B (RhB) of the prepared ZnO hollow spheres were investigated. The results indicated that the prepared ZnO hollow spheres exhibited superior photocatalysis properties on decomposition of RhB and high gas-sensing properties for detection of acetone gas.

  8. Remote-sensing based technique to account for sub-grid scale variability of land surface properties

    NASA Technical Reports Server (NTRS)

    Crosson, William L.; Laymon, Charles A.

    1995-01-01

    A method has been presented for the representation of sub-grid scale variability of surface properties within a land surface processes model. The method uses remotely-sensed data to directly or indirectly estimate probability density functions (PDF's) or key surface variables. Application of this technique in a coupled land surface-atmosphere model requires only grid-scale values of the variables of interest, obtained from low-resolution satellite imagery or surface/remote sensing data assimilation. The PDF's of each controlling surface property are superimposed on the respective grid-scale values to simulate sub-grid scale heterogeneity. Sensitivity studies will be carried out to ascertain the relative importance of the heterogeneity of several variables, and the degree to which non-linear property-process interactions impact large-scale fluxes.

  9. Remote Sensing Reflectance and Inherent Optical Properties in the Mid-mesohaline Chesapeake Bay

    NASA Technical Reports Server (NTRS)

    Tzortziou, Maria; Subramaniam, Ajit; Herman, Jay R.; Gallegos, Charles L.; Neal, Patrick J.; Harding, Lawrence W., Jr.

    2006-01-01

    We used an extensive set of bio-optical data and radiative transfer (RT) model simulations of radiation fields to investigate relationships between inherent optical properties and remotely sensed quantities in the optically complex, mid-mesohaline Chesapeake Bay waters. Field observations showed that the chlorophyll algorithms used by the MODIS (MODerate resolution Imaging Spectroradiometer) ocean color sensor (i.e. Chlor_a, chlor_MODIS, chlor_a_3 products) do not perform accurately in these Case 2 waters. This is because, when applied to waters with high concentrations of chlorophyll, all MODIS algorithms are based on empirical relationships between chlorophyll concentration and blue-green wavelength remote sensing reflectance (Rrs) ratios that do not account for the typically strong blue-wavelength absorption by non-covarying, dissolved and non-algal particulate components. Stronger correlation was observed between chlorophyll concentration and Rrs ratios in the red (i.e. Rrs(677)/Rrs(554)) where dissolved and non-algal particulate absorption become exponentially smaller. Regionally-specific algorithms that are based on the phytoplankton optical properties in the red wavelength region provide a better basis for satellite monitoring of phytoplankton blooms in these Case 2 waters. Good optical closure was obtained between independently measured Rrs spectra and the optical properties of backscattering, b(sub b), and absorption, a, over the wide range of in-water conditions observed in the Chesapeake Bay. Observed variability in the quantity f/Q (proportionality factor in the relationship between Rrs and the water inherent optical properties ratio b(sub b)/(a+b(sub b)) was consistent with RT model calculations for the specific measurement geometry and water bio-optical characteristics. Data and model results showed that f/Q values in these Case 2 coastal waters are not considerably different from those estimated in previous studies for Case 1 waters. Variation in

  10. Frequency-Stabilized Cavity Ring-Down Spectroscopy of Oxygen and Carbon Dioxide to Support Atmospheric Remote Sensing

    NASA Astrophysics Data System (ADS)

    Long, David Alexander

    Recent remote-sensing satellite missions have aimed to measure global greenhouse gas concentrations with precisions as demanding as 0.25%. These high-resolution measurements should allow for the quantification of carbon sources and sinks, thus, allowing for a considerable reduction in present carbon cycle uncertainties. To achieve these unprecedented measurement goals will require the most precise body of spectroscopic reference data (i.e., laboratory measurements) ever assembled. In order to aid these missions, we have measured ultraprecise spectroscopic parameters for the (30012)←(00001) CO2 band at 1.57 microm and the O2 A-band at 0.76 microm. These near-infrared transitions are utilized in recent greenhouse gas monitoring missions, with the A-band being employed to derive pressure and temperature profiles. In these investigations we have employed frequency-stabilized cavity ring-down spectroscopy (FS-CRDS), a novel ultrasensitive spectroscopic technique. In the O2 A-band we have measured magnetic dipole line parameters for 16O 2 as well as each of the rare isotopologues and have produced calculated, HITRAN-style line lists. Due to the clear presence of collisional narrowing in the spectra, we have utilized the Galatry line profile in these studies and have reported narrowing parameters under self- and air-broadened conditions. We anticipate that the use of these spectral parameters will greatly reduce the uncertainties of atmospheric remote-sensing retrievals. In addition, the spectral fidelity of FS-CRDS allowed us to observe and quantify unresolved hyperfine structure for the 17O-containing isotopologues. Furthermore, the high sensitivity of FS-CRDS enabled measurements of ultraweak (S˜10 -30 cm molec.-1) electric quadrupole transitions in the A-band, many of which had not previously been observed. Recently we have begun a series of studies of the near-infrared CO2 transitions. Measurements at low pressures (<40 kPa) have revealed the simultaneous presence

  11. Reactive oxygen species alters the electrophysiological properties and raises [Ca2+]i in intracardiac ganglion neurons.

    PubMed

    Dyavanapalli, Jhansi; Rimmer, Katrina; Harper, Alexander A

    2010-07-01

    We have investigated the effects of the reactive oxygen species (ROS) donors hydrogen peroxide (H(2)O(2)) and tert-butyl hydroperoxide (t-BHP) on the intrinsic electrophysiological characteristics: ganglionic transmission and resting [Ca(2+)](i) in neonate and adult rat intracardiac ganglion (ICG) neurons. Intracellular recordings were made using sharp microelectrodes filled with either 0.5 M KCl or Oregon Green 488 BAPTA-1, allowing recording of electrical properties and measurement of [Ca(2+)](i). H(2)O(2) and t-BHP both hyperpolarized the resting membrane potential and reduced membrane resistance. In adult ICG neurons, the hyperpolarizing action of H(2)O(2) was reversed fully by Ba(2+) and partially by tetraethylammonium, muscarine, and linopirdine. H(2)O(2) and t-BHP reduced the action potential afterhyperpolarization (AHP) amplitude but had no impact on either overshoot or AHP duration. ROS donors evoked an increase in discharge adaptation to long depolarizing current pulses. H(2)O(2) blocked ganglionic transmission in most ICG neurons but did not alter nicotine-evoked depolarizations. By contrast, t-BHP had no significant action on ganglionic transmission. H(2)O(2) and t-BHP increased resting intracellular Ca(2+) levels to 1.6 ( +/- 0.6, n = 11, P < 0.01) and 1.6 ( +/- 0.3, n = 8, P < 0.001), respectively, of control value (1.0, approximately 60 nM). The ROS scavenger catalase prevented the actions of H(2)O(2), and this protection extended beyond the period of application. Superoxide dismutase partially shielded against the action of H(2)O(2), but this was limited to the period of application. These data demonstrate that ROS decreases the excitability and ganglionic transmission of ICG neurons, attenuating parasympathetic control of the heart. PMID:20445155

  12. Using Remote Sensing Data to Evaluate Surface Soil Properties in Alabama Ultisols

    NASA Technical Reports Server (NTRS)

    Sullivan, Dana G.; Shaw, Joey N.; Rickman, Doug; Mask, Paul L.; Luvall, Jeff

    2005-01-01

    Evaluation of surface soil properties via remote sensing could facilitate soil survey mapping, erosion prediction and allocation of agrochemicals for precision management. The objective of this study was to evaluate the relationship between soil spectral signature and surface soil properties in conventionally managed row crop systems. High-resolution RS data were acquired over bare fields in the Coastal Plain, Appalachian Plateau, and Ridge and Valley provinces of Alabama using the Airborne Terrestrial Applications Sensor multispectral scanner. Soils ranged from sandy Kandiudults to fine textured Rhodudults. Surface soil samples (0-1 cm) were collected from 163 sampling points for soil organic carbon, particle size distribution, and citrate dithionite extractable iron content. Surface roughness, soil water content, and crusting were also measured during sampling. Two methods of analysis were evaluated: 1) multiple linear regression using common spectral band ratios, and 2) partial least squares regression. Our data show that thermal infrared spectra are highly, linearly related to soil organic carbon, sand and clay content. Soil organic carbon content was the most difficult to quantify in these highly weathered systems, where soil organic carbon was generally less than 1.2%. Estimates of sand and clay content were best using partial least squares regression at the Valley site, explaining 42-59% of the variability. In the Coastal Plain, sandy surfaces prone to crusting limited estimates of sand and clay content via partial least squares and regression with common band ratios. Estimates of iron oxide content were a function of mineralogy and best accomplished using specific band ratios, with regression explaining 36-65% of the variability at the Valley and Coastal Plain sites, respectively.

  13. Aging influence on sensing properties of porous silica films sensitized toward ammonia

    NASA Astrophysics Data System (ADS)

    Tyszkiewicz, Cuma; Rogoziński, Roman

    2015-12-01

    The sol-gel technology allows preparation of thin silica films ranging in porosity from dense to highly porous. These films can function as a matrix binding molecules of the pH-sensitive dyes and can be utilized as the sensitive films for intensity based planar evanescent wave chemical sensors. Sensitive properties of these dyes decreases in time due to aging processes. We report characterization of weakening of sensing properties of highly porous silica films doped with the bromocresole purple (BCP). In the presence of the gaseous ammonia, the absorption band (AB) of protonated BCP centered at λ=430 nm, is shifted toward λ=591 nm due to deprotonation, resulting in the increase of sensitive films absorption in the range of wavelengths of shifted AB. Two sets of films were investigated. Films from the first one were cyclically exposed to the ammonia and stored isolated from the daylight. Films from the second set weren't exposed to the ammonia and were stored in a staining jar exposed to the daylight. A depth of the AB at λ=430 nm was measured using a spectrophotometer. A sensitivity of the films toward ammonia was measured using LED emitting at center wavelength λ=610 nm. As was shown, the sensitivity of these films exposed to the ammonia diluted in dry air, and isolated from the daylight, decreases in time exponentially. The magnitude of that decrease monotonically depends on the ammonia concentration. It was also shown that the daylight causes quick aging of films not exposed to the ammonia. A depth of the AB centered at λ=430 nm relatively quickly decreased when compared with films isolated from the daylight and exposed to the ammonia.

  14. A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part III: Radiative Properties

    SciTech Connect

    Sassen, K.; Comstock, Jennifer M.

    2001-08-01

    In Part III of a series of papers describing the extended time high-cloud observations from the University of Utah Facility for Atmospheric Remote Sensing (FARS) supporting the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment, the visible and infrared radiative properties of cirrus clouds over Salt Lake City, Utah, are examined. Using {approx}860 h of combined ruby (0.694 {micro}m) lidar and midinfrared (9.5-11.5 {micro}m) radiometer data collected between 1992 and 1999 from visually identified cirrus clouds, the visible optical depths {tau} and infrared layer emittance epsilon of the varieties of midlatitude cirrus are characterized. The mean and median values for the cirrus sample are 0.75 {+-} 0.91 and 0.61 for {tau}, and 0.30 {+-} 0.22 and 0.25 for epsilon. Other scattering parameters studied are the visible extinction and infrared absorption coefficients, and their ratio, and the lidar backscatter-to-extinction ratio, which has a mean value of 0.041 sr{sup -1}. Differences among cirrus clouds generated by general synoptic (e.g., jet stream), thunderstorm anvil, and orographic mechanisms are found, reflecting basic cloud microphysical effects. The authors draw parameterizations in terms of midcloud temperature T{sub m} and physical cloud thickness {Delta}z for epsilon and {tau}: both macrophysical variables are needed to adequately address the impact of the adiabatic process on ice cloud content, which modulates radiative transfer as a function of temperature. For the total cirrus dataset, the authors find epsilon = 1 -exp [-8.5 x 10{sup -5} (T{sub m} + 80 C) {Delta}z]. These parameterizations, based on a uniquely comprehensive dataset, hold the potential for improving weather and climate model predictions, and satellite cloud property retrieval methods.

  15. Optical properties of copper oxide thin films as selective sensing principle for hydrogen sulfide detection

    NASA Astrophysics Data System (ADS)

    Kneer, Janosch; Boxberg, Manuel; Wöllenstein, Jürgen

    2013-05-01

    Semiconducting cuprous (Cu2O) and cupric oxide (CuO) have been subject to intense research efforts, mainly because of the materials' potential for photovoltaic applications and as doping material. In this work, the impact of hydrogen sulfide (H2S) exposure on thin film samples of CuO and Cu2O has been investigated, focusing on alterations in the optical properties. The materials composition was verified using Raman spectroscopy. The samples were exposed to well-defined dosages of H2S and the transmission and reflection characteristics in the expanded UV/Vis regime (350-1100 nm) were recorded. Cu2O films showed an explicit increase in transmissivity for the wavelength region l = 550-900 nm, besides a general decrease in reflectivity of all samples within the considered spectral range. Optical band gaps were determined using Tauc's plotting, revealing a shift in the slope of a2 of CuO after gas exposure. The observed effects can be exploited as sensing effect, which was examined in a thin film total-internal-reflection (TIR) set-up to transiently monitor surface-gas interactions, yielding reproducible changes in response to 20 min exposure to5 ppm H2S.

  16. Microwave Remote Sensing of Soil Moisture for Estimation of Soil Properties

    NASA Technical Reports Server (NTRS)

    Mattikalli, Nandish M.; Engman, Edwin T.; Jackson, Thomas J.

    1997-01-01

    Surface soil moisture dynamics was derived using microwave remote sensing, and employed to estimate soil physical and hydraulic properties. The L-band ESTAR radiometer was employed in an airborne campaign over the Little Washita watershed, Oklahoma during June 10-18, 1992. Brightness temperature (TB) data were employed in a soil moisture inversion algorithm which corrected for vegetation and soil effects. Analyses of spatial TB and soil moisture dynamics during the dry-down period revealed a direct relationship between changes in TB, soil moisture and soil texture. Extensive regression analyses were carried out which yielded statistically significant quantitative relationships between ratio of percent sand to percent clay (RSC, a term derived to quantify soil texture) and saturated hydraulic conductivity (Ksat) in terms of change components of TB and surface soil moisture. Validation of results indicated that both RSC and Ksat can be estimated with reasonable accuracy. These findings have potential applications for deriving spatial distributions of RSC and Ksat over large areas.

  17. Unique chloride-sensing properties of WNK4 permit the distal nephron to modulate potassium homeostasis.

    PubMed

    Terker, Andrew S; Zhang, Chong; Erspamer, Kayla J; Gamba, Gerardo; Yang, Chao-Ling; Ellison, David H

    2016-01-01

    Dietary potassium deficiency activates thiazide-sensitive sodium chloride cotransport along the distal nephron. This may explain, in part, the hypertension and cardiovascular mortality observed in individuals who consume a low-potassium diet. Recent data suggest that plasma potassium affects the distal nephron directly by influencing intracellular chloride, an inhibitor of the with-no-lysine kinase (WNK)-Ste20p-related proline- and alanine-rich kinase (SPAK) pathway. As previous studies used extreme dietary manipulations, we sought to determine whether the relationship between potassium and NaCl cotransporter (NCC) is physiologically relevant and clarify the mechanisms involved. We report that modest changes in both dietary and plasma potassium affect NCC in vivo. Kinase assay studies showed that chloride inhibits WNK4 kinase activity at lower concentrations than it inhibits activity of WNK1 or WNK3. Also, chloride inhibited WNK4 within the range of distal cell chloride concentration. Mutation of a previously identified WNK chloride-binding motif converted WNK4 effects on SPAK from inhibitory to stimulatory in mammalian cells. Disruption of this motif in WNKs 1, 3, and 4 had different effects on NCC, consistent with the three WNKs having different chloride sensitivities. Thus, potassium effects on NCC are graded within the physiological range, which explains how unique chloride-sensing properties of WNK4 enable it to mediate effects of potassium on NCC in vivo.

  18. Structural, optical and ethanol sensing properties of Cu-doped SnO{sub 2} nanowires

    SciTech Connect

    Johari, Anima Sharma, Manish; Johari, Anoopshi; Bhatnagar, M. C.

    2014-04-24

    In present work, one-dimensional nanostructure of Cu-doped Tin oxide (SnO{sub 2}) was synthesized by using thermal evaporation method in a tubular furnace under Nitrogen (N{sub 2}) ambience. The growth was carried out at atmospheric pressure. SEM and TEM images reveal the growth of wire-like nanostructures of Cu-doped SnO{sub 2} on Si substrate. The XRD analysis confirms that the synthesized SnO{sub 2} nanowires have tetragonal rutile structure with polycrystalline nature and X-ray diffraction pattern also showed that Cu gets incorporated into the SnO{sub 2} lattice. EDX spectra confirm the doping of Cu into SnO{sub 2} nanowires and atomic fraction of Cu in nanowires is ∼ 0.5 at%. The Vapor Liquid Solid (VLS) growth mechanism for Cu-doped SnO{sub 2} nanowires was also confirmed by EDX spectra. The optical properties of as grown Cu-doped SnO{sub 2} nanowires were studied by using UV-vis spectra which concludes the band gap of about 3.7 eV. As synthesized single Cu-doped SnO{sub 2} nanowire based gas sensor exhibit relatively good performance to ethanol gas. This sensing behaviour offers a suitable application of the Cu-doped SnO{sub 2} nanowire sensor for detection of ethanol gas.

  19. Investigation on strain sensing properties of carbon-based nanocomposites for structural aircraft applications

    NASA Astrophysics Data System (ADS)

    Lamberti, Patrizia; Spinelli, Giovanni; Tucci, Vincenzo; Guadagno, Liberata; Vertuccio, Luigi; Russo, Salvatore

    2016-05-01

    The mechanical and electrical properties of a thermosetting epoxy resin particularly indicated for the realization of structural aeronautic components and reinforced with multiwalled carbon nanotubes (MWCNTs, at 0.3 wt%) are investigated for specimens subjected to cycles and different levels of applied strain (i.e. ɛ) loaded both in axial tension and flexural mode. It is found that the piezoresistive behavior of the resulting nanocomposite evaluated in terms of variation of the electrical resistance is strongly affected by the applied mechanical stress mainly due to the high sensibility and consequent rearrangement of the electrical percolating network formed by MWCNTs in the composite at rest or even under a small strain. In fact, the variations in electrical resistance that occur during the mechanical stress are correlated to the deformation exhibited by the nanocomposites. In particular, the overall response of electrical resistance of the composite is characterized by a linear increase with the strain at least in the region of elastic deformation of the material in which the gauge factor (i.e. G.F.) of the sensor is usually evaluated. Therefore, the present study aims at investigating the possible use of the nanotechnology for application of embedded sensor systems in composite structures thus having capability of self-sensing and of responding to the surrounding environmental changes, which are some fundamental requirements especially for structural aircraft monitoring applications.

  20. Enhanced physical properties of porous silicon for improved hydrogen gas sensing

    NASA Astrophysics Data System (ADS)

    Naderi, N.; Hashim, M. R.; Amran, T. S. T.

    2012-05-01

    In the current communication, porous silicon samples were prepared by pulsed photoelectrochemical etching using a hydrofluoric acid-based solution. The structural and gas-sensing properties of the samples were studied. Apart from the cycle time T and pause time Toff of the pulsed current, a novel parameter, in the shape of the current named 'delay time Td' was introduced. Our results showed that by optimization of delay time, the porosity of samples can be controlled due to the chemical preparation of silicon surface prior to electrochemical anodization. The fourier-transform infrared measurements of porous silicon (PS) layers on Si substrate showed that the typical PS surface was characterized by chemical species like Si-H and Si-O-Si terminations. The two-minute delay before applying electrical current was considered sufficient for the fabrication of higher porosity (83%), more uniform, and more stable structures. The photoluminescence (PL) peak of the optimized sample showed higher intensity than the other samples. An obvious PL blue shift also revealed a change in the crystallographic characteristics of silicon due to quantum confinement effects. Metal-semiconductor-metal diodes with Schottky contacts of nickel were fabricated on PS samples and the potential application of optimized substrates for the improved sensitivity, stability, response time and recovery time of hydrogen gas sensors was subsequently studied.

  1. Photoinduced green synthesis of silver nanoparticles with highly effective antibacterial and hydrogen peroxide sensing properties.

    PubMed

    Kumar, Vijay; Gundampati, Ravi Kumar; Singh, Devendra K; Bano, Daraksha; Jagannadham, Medicherla V; Hasan, Syed Hadi

    2016-09-01

    In this study, an eco-friendly and sustainable green route was employed for the synthesis of stable silver nanoparticles (AgNPs) using aqueous leaf extract of Euphorbia hirta (AEE) as both reducing as well as a stabilizing agent. The synthesis of AgNPs was confirmed by UV-visible spectroscopy which produced a prominent SPR band at λmax 425nm after 25min of sunlight exposure. The AgNPs thus synthesized were optimized using one factor at a time approach, and these optimized conditions were 25min of sunlight exposure time, 5.0% (v/v) of AEE inoculum dose and 3.0mM of AgNO3 concentration. The Field Emission Scanning Electron Microscopy (FE-SEM) and High Resolution Transmission Electron Microscopy (HRTEM) analysis confirmed the presence of spherical AgNPs with average size 15.5nm. The crystallinity was determined by X-ray Diffractometer (XRD) and Selected Area Electron Diffraction (SAED) pattern. Chemical and elemental compositions were determined by Fourier Transformed Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) respectively. The Atomic Force Microscopy (AFM) images with average roughness 1.15nm represented the lateral and 3D topological characteristic of AgNPs. The AgNPs thus synthesized showed effective antibacterial activity against gram negative and gram positive bacteria as well as hydrogen peroxide sensing property with a minimum detection limit of 10(-7)M. PMID:27424098

  2. Electrical and gas sensing properties of self-aligned copper-doped zinc oxide nanoparticles

    SciTech Connect

    Sonawane, Yogesh S.; Kanade, K.G.; Kale, B.B. Aiyer, R.C.

    2008-10-02

    Electrical and gas sensing properties of nanocrystalline ZnO:Cu, having Cu X wt% (X = 0.0, 0.5, 1.0, and 1.5) in ZnO, in the form of pellet were investigated. Copper chloride and zinc acetate were used as precursors along with oxalic acid as a precipitating reagent in methanol. Material characterization was done by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and inductive coupled plasma with optical emission spectrometry (ICP-OES). FE-SEM showed the self-aligned Cu-doped ZnO nano-clusters with particles in the range of 40-45 nm. The doping of 0.5% of copper changes the electrical conductivity by an order of magnitude whereas the temperature coefficient of resistance (TCR) reduces with increase in copper wt% in ZnO. The material has shown an excellent sensitivity for the H{sub 2}, LPG and CO gases with limited temperature selectivity through the optimized operating temperature of 130, 190 and 220 deg. C for H{sub 2}, LPG and CO gases, respectively at 625 ppm gas concentration. The %SF was observed to be 1460 for H{sub 2} at 1% Cu doping whereas the 0.5% Cu doping offered %SF of 950 and 520 for CO and LPG, respectively. The response and recovery time was found to be 6 to 8 s and 16 s, respectively.

  3. Photoinduced green synthesis of silver nanoparticles with highly effective antibacterial and hydrogen peroxide sensing properties.

    PubMed

    Kumar, Vijay; Gundampati, Ravi Kumar; Singh, Devendra K; Bano, Daraksha; Jagannadham, Medicherla V; Hasan, Syed Hadi

    2016-09-01

    In this study, an eco-friendly and sustainable green route was employed for the synthesis of stable silver nanoparticles (AgNPs) using aqueous leaf extract of Euphorbia hirta (AEE) as both reducing as well as a stabilizing agent. The synthesis of AgNPs was confirmed by UV-visible spectroscopy which produced a prominent SPR band at λmax 425nm after 25min of sunlight exposure. The AgNPs thus synthesized were optimized using one factor at a time approach, and these optimized conditions were 25min of sunlight exposure time, 5.0% (v/v) of AEE inoculum dose and 3.0mM of AgNO3 concentration. The Field Emission Scanning Electron Microscopy (FE-SEM) and High Resolution Transmission Electron Microscopy (HRTEM) analysis confirmed the presence of spherical AgNPs with average size 15.5nm. The crystallinity was determined by X-ray Diffractometer (XRD) and Selected Area Electron Diffraction (SAED) pattern. Chemical and elemental compositions were determined by Fourier Transformed Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) respectively. The Atomic Force Microscopy (AFM) images with average roughness 1.15nm represented the lateral and 3D topological characteristic of AgNPs. The AgNPs thus synthesized showed effective antibacterial activity against gram negative and gram positive bacteria as well as hydrogen peroxide sensing property with a minimum detection limit of 10(-7)M.

  4. Remote Sensing of Mycorrhizae? Detection of Mycorrhizal Association from Canopy Spectral Properties.

    NASA Astrophysics Data System (ADS)

    Fisher, J. B.; Sweeney, S.; Brzostek, E. R.; Evans, T. P.; Bourg, N. A.; Phillips, R.

    2014-12-01

    Nearly all tree species form symbiotic relationships with one of two types of mycorrzhae—arbuscular mycorrhizae (AM) and ectomycorrhizal (ECM) fungi. AM- and ECM-dominated forests often have distinct nutrient economies, and there is strong interest in mapping or detecting mycorrhizae over large areas. We explored remotely sensed tree canopy spectral properties to "detect" underlying mycorrhizal association across a gradient of AM- and ECM-dominated forest plots. We used a combination of principal components analysis and statistical mining of reflectance and band differencing across moderate/high-resolution Landsat data in conjunction with phenological signals from stitched seasonal time series and topographic features. This approach was trained and validated against measurements of tree species and mycorrhizal association across more than 60,000 trees throughout the central and eastern US. Using this approach, we were able to predict 81% of the variation in mycorrhizal association (p<0.001). Differences in phenological characteristics between AM- and ECM-associated trees drove the relatively high prediction skill.

  5. In situ growth of copper nanocrystals from carbonaceous microspheres with electrochemical glucose sensing properties

    SciTech Connect

    Zhou, Xiaoliang; Yan, Zhengguang Han, Xiaodong

    2014-02-01

    Graphical abstract: In situ growth of copper nanoparticles from hydrothermal copper-containing carbonaceous microspheres was induced by annealing or electron beam irradiation. Obtained micro-nano carbon/copper composite microspheres show electrochemical glucose sensing properties. - Highlights: • We synthesized carbonaceous microspheres containing non-nanoparicle copper species through a hydrothermal route. • By annealing or electron beam irradiation, copper nanoparticles would form from the carbonaceous microspheres in situ. • By controlling the annealing temperature, particle size of copper could be controlled in the range of 50–500 nm. • The annealed carbon/copper hierarchical composite microspheres were used to fabricate an electrochemical glucose sensor. - Abstract: In situ growth of copper nanocrystals from carbon/copper microspheres was observed in a well-controlled annealing or an electron beam irradiation process. Carbonaceous microspheres containing copper species with a smooth appearance were yielded by a hydrothermal synthesis using copper nitrate and ascorbic acid as reactants. When annealing the carbonaceous microspheres under inert atmosphere, copper nanoparticles were formed on carbon microspheres and the copper particle sizes can be increased to a range of 50–500 nm by altering the heating temperature. Similarly, in situ formation of copper nanocrystals from these carbonaceous microspheres was observed on the hydrothermal product carbonaceous microspheres with electron beam irradiation in a vacuum transmission electron microscopy chamber. The carbon/copper composite microspheres obtained through annealing were used to modify a glassy carbon electrode and tested as an electrochemical glucose sensor.

  6. Advancement in polarimetric glucose sensing: simulation and measurement of birefringence properties of cornea

    NASA Astrophysics Data System (ADS)

    Malik, Bilal H.; Coté, Gerard L.

    2011-03-01

    Clinical guidelines dictate that frequent blood glucose monitoring in diabetic patients is critical towards proper management of the disease. Although, several different types of glucose monitors are now commercially available, most of these devices are invasive, thereby adversely affecting patient compliance. To this end, optical polarimetric glucose sensing through the eye has been proposed as a potential noninvasive means to aid in the control of diabetes. Arguably, the most critical and limiting factor towards successful application of such a technique is the time varying corneal birefringence due to eye motion artifact. We present a spatially variant uniaxial eye model to serve as a tool towards better understanding of the cornea's birefringence properties. The simulations show that index-unmatched coupling of light is spatially limited to a smaller range when compared to the index-matched situation. Polarimetric measurements on rabbits' eyes indicate relative agreement between the modeled and experimental values of corneal birefringence. In addition, the observed rotation in the plane of polarized light for multiple wavelengths demonstrates the potential for using a dual-wavelength polarimetric approach to overcome the noise due to timevarying corneal birefringence. These results will ultimately aid us in the development of an appropriate eye coupling mechanism for in vivo polarimetric glucose measurements.

  7. Synthesis, characterization and humidity sensing properties of Cu-Sr-Al mixed metal oxide composites

    SciTech Connect

    Vijaya, J. Judith Kennedy, L. John; Sekaran, G.; Nagaraja, K.S.

    2008-02-05

    Copper-strontium-aluminum mixed metal oxide composites prepared by sol-gel technique was investigated for humidity sensing properties. X-ray diffraction, scanning electron microscopy (SEM), FT-IR spectroscopy and nitrogen adsorption/desorption isotherm at 77 K was employed, respectively, to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the composites. The composites were prepared with the mole ratios of Cu:Sr as (0.0:1.0, 0.2:0.8, 0.4:06, 0.6:0.4, 0.8:0.2 and 1.0:0.0) keeping the aluminium mole ratio as constant and were labeled as CuSA1, CuSA2, CuSA3, CuSA4, CuSA5 and CuSA6, respectively. The samples sintered at 900 deg. C for 5 h, were subjected to dc resistance measurements as a function of relative humidity (RH) in the range 5-98% and the results revealed that the sensitivity factor of CuSA5 possessed the highest humidity sensitivity of 42,000 while the pure composite copper aluminate (CuSA1) and strontium aluminate (CuSA6) possessed comparatively low sensitivities 10,000 and 20,000, respectively. The response and recovery characteristics of the composites CuSA1, CuSA5 and CuSA6 were studied.

  8. Thickness and UV irradiation effects on the gas sensing properties of Te thin films

    SciTech Connect

    Manouchehrian, M.; Larijani, M.M.; Elahi, S.M.

    2015-02-15

    Highlights: • Tellurium thin films were prepared by thermal evaporation technique. • Tellurium thin films showed excellent gas-sensing properties to H{sub 2}S at room temperature. • Tellurium showed a remarkably enhanced response to H{sub 2}S gas under UV irradiation. • The reason of the enhanced response by UV irradiation was discussed. - Abstract: In this research, tellurium thin films were investigated for use as hydrogen sulfide gas sensors. To this end, a tellurium thin film has been deposited on Al{sub 2}O{sub 3} substrates by thermal evaporation, and the influence of thickness on the sensitivity of the tellurium thin film for measuring H{sub 2}S gas is studied. XRD patterns indicate that as the thickness increases, the crystallization improves. Observing the images obtained by SEM, it is seen that the grain size increases as the thickness increases. Studying the effect of thickness on H{sub 2}S gas measurement, it became obvious that as the thickness increases, the sensitivity decreases and the response and recovery times increase. To improve the response and recovery times of the tellurium thin film for measuring H{sub 2}S gas, the influence of UV radiation while measuring H{sub 2}S gas was also investigated. The results indicate that the response and recovery times strongly decrease using UV radiation.

  9. Unique chloride-sensing properties of WNK4 permit the distal nephron to modulate potassium homeostasis

    PubMed Central

    Terker, Andrew S.; Zhang, Chong; Erspamer, Kayla J.; Gamba, Gerardo; Yang, Chao-Ling; Ellison, David H.

    2015-01-01

    Dietary potassium deficiency activates thiazide-sensitive sodium chloride cotransport along the distal nephron. This may explain, in part, the hypertension and cardiovascular mortality observed in individuals who consume a low potassium diet. Recent data suggest plasma potassium affects the distal nephron directly by influencing intracellular chloride, an inhibitor of the With no lysine kinase (WNK)-Ste20p-related proline-and alanine-rich kinase (SPAK) pathway. Since previous studies used extreme dietary manipulations, we sought to determine if the relationship between potassium and NCC is physiologically relevant and clarify the mechanisms involved. We report that modest changes in both dietary and plasma potassium affect the thiazide-sensitive sodium-chloride cotransporter, NCC, in vivo. Kinase assay studies showed that chloride inhibits WNK4 kinase activity at lower concentrations than it inhibits activity of WNK1 or WNK3. Also, chloride inhibited WNK4 within the range of distal cell chloride. Mutation of a previously identified WNK chloride-binding motif converted WNK4 effects on SPAK from inhibitory to stimulatory in mammalian cells. Disruption of this motif in WNKs 1, 3 and 4 had different effects on NCC, consistent with the three WNKs having different chloride sensitivities. Thus, potassium effects on NCC are graded within the physiological range, which explains how unique chloride-sensing properties of WNK4 enable kinase mediating effects of potassium on NCC in vivo. PMID:26422504

  10. Effect of HCl doping on optoelectrical and LPG sensing properties of nanostructured polyaniline thin films

    NASA Astrophysics Data System (ADS)

    Upadhye, Deepak S.; Huse, Nanasaheb P.; Sharma, Ramphal

    2016-05-01

    Nanostructure Polyaniline thin films doped with 0.5 M, 0.7 M, and 1 M of HCL were synthesized by simple and inexpensive chemical oxidative polymerization technique at room temperature. All prepared thin films of Polyaniline were characterized by optical absorbance study by UV-visible spectroscopy. The absorbance spectrum of Polyaniline shows three fundamental peaks at 356, 419 and 820 nm with increase in absorption intensity. The electrical study shows magnitude of resistance of HCL doped Polyaniline is dependent on doping level. Furthermore, the thin film of Polyaniline was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents irregular granular morphology. In order to investigate LPG sensing properties, I-V characteristics of the Polyaniline films doped with 0.5 M, 0.7 M, and 1 M of HCL were recorded at room temperature in presence of air and 100 ppm of LPG. The observed values of sensitivity found to be 7.21%, 9.85% and 17.46 % for 0.5 M, 0.75 M, and 1.0 M of HCL doped Polyaniline thin films respectively

  11. Influences of oxygen incorporation on the structural and optoelectronic properties of Cu2ZnSnS4 thin films

    NASA Astrophysics Data System (ADS)

    Yu, Ruei-Sung; Hung, Ta-Chun

    2016-02-01

    This study used the sol-gel method to prepare Cu2ZnSnS4 thin films containing oxygen and explored the composition, structural, and optoelectronic properties of the films. The non-vacuum process enabled the oxygen content of the Cu2ZnSnS4 films to be 8.89 at% and 10.30 at% for two different annealing conditions. In the crystal structure, oxygen was substituted at the positions of sulfur and appeared in the interstitial sites of the lattice. The compositions of the thin films deviated from the stoichiometric ratio. Both films had kesterite structures with no secondary phase structure. The kesterite CZTS film possessed a composite microstructure of crystallite and crystalline states. The microstructure of the Cu2ZnSnS4 film with higher oxygen content was denser and the average grain size was smaller. Incorporating oxygen atoms into crystalline Cu2ZnSnS4 changed the energy band structure: the direct energy band gaps were, respectively, 2.75 eV and 2.84 eV; the thin films mainly adsorbed photons with wavelengths less than 500 nm; and the absorption coefficients increased from 104 cm-1 to 105 cm-1. The films had a comparatively high absorptive capacity for photons less than 350 nm. Increasing the oxygen content of the film lowered the resistivity. Thus, the oxygen-containing Cu2ZnSnS4 thin film could be a candidate for the p-type absorber layer material required in multi-junction solar cells.

  12. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    PubMed Central

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-01-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction. PMID:27079897

  13. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction.

    PubMed

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-01-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd(2+) ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction. PMID:27079897

  14. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-04-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction.

  15. Electrocatalytic Properties of Nanocrystalline Calcium-Doped Lanthanum Cobalt Oxide for Bifunctional Oxygen Electrodes

    SciTech Connect

    Malkhandi, S; Yang, B; Manohar, AK; Manivannan, A; Prakash, GKS; Narayanan, SR

    2012-04-19

    Calcium-doped lanthanum cobalt oxide is a promising electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal air batteries and water electrolyzers operating with alkaline electrolyte. Nanocrystalline perovskite of composition La0.6Ca0.4CoO3 with a unique cellular internal structure was prepared at 350 degrees C and then annealed in air at progressively higher temperatures in the range of 600-750 degrees C. The samples were characterized by electrochemical techniques and X-ray photoelectron spectroscopy. The area-specific electrocatalytic activity for oxygen evolution/oxygen reduction, the oxidation state of cobalt, and the crystallite size increased with annealing temperature, while the Tafel slope remained constant. These trends provide new insights into the role of the cobalt center in oxygen evolution and oxygen reduction, and how preparation conditions can be altered to tune the activity of the cobalt center for electrocatalysis. We expect these findings to guide the design of electrocatalysts for bifunctional oxygen electrodes, in general.

  16. In-airway molecular flow sensing: A new technology for continuous, noninvasive monitoring of oxygen consumption in critical care

    PubMed Central

    Ciaffoni, Luca; O’Neill, David P.; Couper, John H.; Ritchie, Grant A. D.; Hancock, Gus; Robbins, Peter A.

    2016-01-01

    There are no satisfactory methods for monitoring oxygen consumption in critical care. To address this, we adapted laser absorption spectroscopy to provide measurements of O2, CO2, and water vapor within the airway every 10 ms. The analyzer is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. The precision is illustrated by integrating the balance gas (N2 plus Ar) flow and showing that this exchange was near zero. Measured O2 consumption changed by <5% between air and O2 breathing. Clinical capability was illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible. PMID:27532048

  17. The IRP1-HIF-2α axis coordinates iron and oxygen sensing with erythropoiesis and iron absorption.

    PubMed

    Anderson, Sheila A; Nizzi, Christopher P; Chang, Yuan-I; Deck, Kathryn M; Schmidt, Paul J; Galy, Bruno; Damnernsawad, Alisa; Broman, Aimee T; Kendziorski, Christina; Hentze, Matthias W; Fleming, Mark D; Zhang, Jing; Eisenstein, Richard S

    2013-02-01

    Red blood cell production is a finely tuned process that requires coordinated oxygen- and iron-dependent regulation of cell differentiation and iron metabolism. Here, we show that translational regulation of hypoxia-inducible factor 2α (HIF-2α) synthesis by iron regulatory protein 1 (IRP1) is critical for controlling erythrocyte number. IRP1-null (Irp1(-/-)) mice display a marked transient polycythemia. HIF-2α messenger RNA (mRNA) is derepressed in kidneys of Irp1(-/-) mice but not in kidneys of Irp2(-/-) mice, leading to increased renal erythropoietin (Epo) mRNA and inappropriately elevated serum Epo levels. Expression of the iron transport genes DCytb, Dmt1, and ferroportin, as well as other HIF-2α targets, is enhanced in Irp1(-/-) duodenum. Analysis of mRNA translation state in the liver revealed IRP1-dependent dysregulation of HIF-2α mRNA translation, whereas IRP2 deficiency derepressed translation of all other known 5' iron response element (IRE)-containing mRNAs expressed in the liver. These results uncover separable physiological roles of each IRP and identify IRP1 as a therapeutic target for manipulating HIF-2α action in hematologic, oncologic, and other disorders. PMID:23395174

  18. In-airway molecular flow sensing: A new technology for continuous, noninvasive monitoring of oxygen consumption in critical care.

    PubMed

    Ciaffoni, Luca; O'Neill, David P; Couper, John H; Ritchie, Grant A D; Hancock, Gus; Robbins, Peter A

    2016-08-01

    There are no satisfactory methods for monitoring oxygen consumption in critical care. To address this, we adapted laser absorption spectroscopy to provide measurements of O2, CO2, and water vapor within the airway every 10 ms. The analyzer is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. The precision is illustrated by integrating the balance gas (N2 plus Ar) flow and showing that this exchange was near zero. Measured O2 consumption changed by <5% between air and O2 breathing. Clinical capability was illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible. PMID:27532048

  19. Oxygen: A Fundamental Property Regulating Pelagic Ecosystem Structure in the Coastal Southeastern Tropical Pacific

    PubMed Central

    Bertrand, Arnaud; Chaigneau, Alexis; Peraltilla, Salvador; Ledesma, Jesus; Graco, Michelle; Monetti, Florian; Chavez, Francisco P.

    2011-01-01

    Background In the southeastern tropical Pacific anchovy (Engraulis ringens) and sardine (Sardinops sagax) abundance have recently fluctuated on multidecadal scales and food and temperature have been proposed as the key parameters explaining these changes. However, ecological and paleoecological studies, and the fact that anchovies and sardines are favored differently in other regions, raise questions about the role of temperature. Here we investigate the role of oxygen in structuring fish populations in the Peruvian upwelling ecosystem that has evolved over anoxic conditions and is one of the world's most productive ecosystems in terms of forage fish. This study is particularly relevant given that the distribution of oxygen in the ocean is changing with uncertain consequences. Methodology/Principal Findings A comprehensive data set is used to show how oxygen concentration and oxycline depth affect the abundance and distribution of pelagic fish. We show that the effects of oxygen on anchovy and sardine are opposite. Anchovy flourishes under relatively low oxygen conditions while sardine avoid periods/areas with low oxygen concentration and restricted habitat. Oxygen consumption, trophic structure and habitat compression play a fundamental role in fish dynamics in this important ecosystem. Conclusions/Significance For the ocean off Peru we suggest that a key process, the need to breathe, has been neglected previously. Inclusion of this missing piece allows the development of a comprehensive conceptual model of pelagic fish populations and change in an ocean ecosystem impacted by low oxygen. Should current trends in oxygen in the ocean continue similar effects may be evident in other coastal upwelling ecosystems. PMID:22216315

  20. Relationship of oxygen dose to angiogenesis induction in irradiated tissue

    SciTech Connect

    Marx, R.E.; Ehler, W.J.; Tayapongsak, P.; Pierce, L.W. )

    1990-11-01

    This study was accomplished in an irradiated rabbit model to assess the angiogenic properties of normobaric oxygen and hyperbaric oxygen as compared with air-breathing controls. Results indicated that normobaric oxygen had no angiogenic properties above normal revascularization of irradiated tissue than did air-breathing controls (p = 0.89). Hyperbaric oxygen demonstrated an eight- to ninefold increased vascular density over both normobaric oxygen and air-breathing controls (p = 0.001). Irradiated tissue develops a hypovascular-hypocellular-hypoxic tissue that does not revascularize spontaneously. Results failed to demonstrate an angiogenic effect of normobaric oxygen. It is suggested that oxygen in this sense is a drug requiring hyperbaric pressures to generate therapeutic effects on chronically hypovascular irradiated tissue.

  1. Metal nanoparticle-graphene oxide composites: Photophysical properties and sensing applications

    NASA Astrophysics Data System (ADS)

    Murphy, Sean J.

    Composite nanomaterials allow for attractive properties of multiple functional components to be combined. Fundamental understanding of the interaction between different nanomaterials, their surroundings, and nearby molecular species is pertinent for implementation into devices. Metal nanoparticles have been used for their optical properties in many applications including stained glass, cancer therapy, solar steam generation, surface enhanced Raman spectroscopy (SERS), and catalysis. Carbon-based nanomaterials such as graphene and carbon nanotubes show potential for a wide variety of applications including solar energy harvesting, chemical sensors, and electronics. Combining useful and in some cases new properties of composite nanomaterials offers exciting opportunities in fundamental science and device development. In this dissertation, I aim to address understanding photoinduced interaction between porphyrin and silver nanoparticles, inter-sheet interaction between stacked graphene oxide (GO) sheets in thin films, complexation of reduced GO with Raman active target molecule in SERS applications, and efficacy of graphene-metal nanoparticle composites for sensing applications. Molecule-metal nanoparticle composite material made up of photoactive porphyrin and silver nanoparticles was studied using various spectroscopic tools. UV-visible absorption and surface enhanced Raman spectroscopic results suggest formation of a charge-transfer complex for porphyrin-silver nanoparticle composite. Ultrafast transient absorption and fluorescence upconversion spectroscopies further corroborate electronic interaction by providing evidence for excited state electron transfer between porphyrin and silver nanoparticles. Understanding electronic interaction between adsorbed photoactive molecules and metal nanoparticles may be of use for applications in photocatalysis or light-energy harvesting. Graphene oxide (GO) thin films have been prepared and studied using transient absorption

  2. Microdistribution of oxygen in silicon and its effects on electronic properties

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Mao, B. Y.; Nauka, K.; Lagowski, J.

    1982-01-01

    The effects of interstitial oxygen on the electrical characteristics of Czochralski-grown silicon crystals were investigated for the first time on a microscale. It was found that the generation of thermal donors is not a direct function of the oxygen concentration. It was further found that the minority carrier life-time decreases with increasing oxygen concentration, on a microscale in as-grown crystals. It was thus shown, again for the first time, that oxygen in as grown crystals is not electronically inert as generally believed. Preannealing at 1200 C commonly employed in device fabrication, was found to suppress the donor generation at 450 C and to decrease the deep level concentrations.

  3. The effect of oxygen vacancies on the electrical properties of TiO2-x Re-RAM switching devices

    NASA Astrophysics Data System (ADS)

    Benkraouda, Maamar

    2014-03-01

    The main goal of this work is to contribute toward an accurate determination of the electronic properties of Resistance random access memory (Re-RAM) using the density functional theory, which is the current state of the art method that employs high accuracy, it can treat a few hundred atoms on medium sized PC. All the fundamental properties are studied as a function of the mole fraction. The density of states arising from vacancy distribution, the electron transport and formation energy are analyzed. Using controllable mole fraction, various intermediate resistance states are induced. Oxygen vacancy has a considerable effect on the electrical properties of most transition metal oxides such as TiOx Re-RAM devices. The presence of oxygen vacancies is linked to the on-state conduction and resistance switching mechanism. Hydrogen is a ubiquitous impurity in most semiconductors, insertion of hydrogen atoms will remove some of defect states which were induced by oxygen vacancies; this will obviously have an effect on the conductive path, because hydrogen in the vacancy site results in the rupture of conductive channel by localizing electrons, the conductivity may decrease in this case.

  4. Synergistic catalytic properties of bifunctional nanoalloy catalysts in rechargeable lithium-oxygen battery

    NASA Astrophysics Data System (ADS)

    Kang, Ning; Ng, Mei Shan; Shan, Shiyao; Wu, Jinfang; Zhao, Wei; Yin, Jun; Fang, Weiqing; Luo, Jin; Petkov, Valeri; Zhong, Chuan-Jian

    2016-09-01

    The understanding of factors influencing the performance of catalysts in the air cathode of a rechargeable lithium-oxygen battery, including overpotentials for oxygen reduction/evolution and discharge capacity, is essential for exploration of its ultimate application. This report describes new findings of an investigation of PdCu nanoalloys as cathode catalysts. Alloying Pd with oxophilic base metals such as Cu leads to reduction of the overpotentials and increase of the discharge capacity. The nanoalloy structures depend on the bimetallic composition, with an atomic ratio near 50:50 featuring mixed bcc and fcc structures. The discharge potential exhibits a maximum while the charge potential display a minimum in the range of 20-50% Cu, closer to 25% Cu, both of which correspond to a maximum reduction of the discharge-charge overpotentials. The discharge capacity displays a gradual increase with Cu%. This type of catalytic synergy is believed to be associated with a combination of ensemble and ligand effects. In particular, the activation of oxygen on Pd sites and oxygen oxophilicity at the alloyed Cu sites in the catalyst may have played an important role in effectively activating oxygen and maneuvering surface superoxide/peroxide species. These findings have implications for the design of multifunctional cathode catalysts in rechargeable lithium-oxygen batteries.

  5. Oxygen binding properties of backswimmer (Notonectidae, Anisops) haemoglobin, determined in vivo.

    PubMed

    Matthews, Philip G D; Seymour, Roger S

    2011-12-01

    Aquatic backswimmers (Anisops spp.) collect oxygen from the atmosphere in order to breathe underwater, carrying it within a bubble of air on the ventral surface of their body and bound within haemoglobin-filled cells inside their abdomen. These oxygen stores are interconnected via the abdominal spiracles and the tracheal system. Fibre optic oxygen probes were used to measure PO(2) changes within the air bubbles of submerged backswimmers (Anisops deanei) and these measurements were transformed into in vivo haemoglobin-oxygen equilibrium curves (OECs) using a biotonometric approach. The haemoglobin displayed a triphasic, highly sigmoid OEC with a P(50) of 3.90 kPa. Comparisons made with a previous in vitro analysis of Anisops haemoglobin demonstrate that while the apparent cooperativity and oxygen affinity are considerably higher in vivo, both measurements share unusual Hb-O(2) binding characteristics. The affinity and cooperativity of the backswimmers' haemoglobin appears adaptive as it lengthens dives and promotes neutral buoyancy. While there are limitations associated with biotonometry, the in vivo OEC accurately represents the loading and unloading of biologically available oxygen within the backswimmers' haemoglobin cells. Potential errors associated with determining the OEC are small, as evaluated with sensitivity analyses in numerical models.

  6. Influence of texture coefficient on surface morphology and sensing properties of W-doped nanocrystalline tin oxide thin films.

    PubMed

    Kumar, Manjeet; Kumar, Akshay; Abhyankar, A C

    2015-02-18

    For the first time, a new facile approach based on simple and inexpensive chemical spray pyrolysis (CSP) technique is used to deposit Tungsten (W) doped nanocrystalline SnO2 thin films. The textural, optical, structural and sensing properties are investigated by GAXRD, UV spectroscopy, FESEM, AFM, and home-built sensing setup. The gas sensing results indicate that, as compared to pure SnO2, 1 wt % W-doping improves sensitivity along with better response (<2 s) and recovery time (<25 s) toward NO2 gas at operating temperatures of ∼225 °C. The optimal composition of 1 wt % W-doped films exhibit lowest crystallite size of the order of ∼8-10 nm with reduced energy band gap and large roughness values of 3.82 eV and 3.01 nm, respectively. Reduction in texture coefficient along highly dense (110) planes with concomitant increase along loosely packed (200) planes is found to have prominent effect on gas sensing properties of W-doped films. PMID:25603393

  7. Comparative analysis of property taxation policies within Greece and Cyprus evaluating the use of GIS, CAMA, and remote sensing techniques

    NASA Astrophysics Data System (ADS)

    Dimopoulos, Thomas; Labropoulos, Tassos; Hadjimitsis, Diofantos G.

    2014-08-01

    This paper aims to examine how CAMA, GIS and Remote Sensing are integrated to assist property taxation. Real property tax apart from its fiscal dimension is directly linked to geographic location. The value of the land and other immovable features such as buildings and structures is determined from specific parameters. All these immovable assets are visible and have specific geographic location & coordinates, materials, occupied area, land-use & utility, ownership & occupancy status and finally a specific value (ad valorem property taxation system) according to which the property tax is levied to taxpayers. Of high importance in the tax imposing procedure is that the use of CAMA, GIS and Remote Sensing tools is capable of providing effective and efficient collection of this property value determining data. Furthermore, these tools can track changes during a property's lifecycle such parcel subdivision into plots, demolition of a building and development of a new one or track a change in the planning zone. The integration of these systems also supports a full range of business processes on revenue mobilization ranging from billing to taxpayers objections management.

  8. Optical remote sensing of properties and concentrations of atmospheric trace constituents

    NASA Astrophysics Data System (ADS)

    Vladutescu, Daniela Viviana

    The effect of human activities on the global climate may lead to large disturbances of the economic, social and political circumstances in the middle and long term. Understanding the dynamics of the Earth's climate is therefore of high importance and one of the major scientific challenges of our time. The estimation of the contribution of the Earth's climate system components needs observation and continuous monitoring of various atmospheric physical and chemical parameters. Temperature, water vapor and greenhouse gases concentration, aerosol and clouds loads, and atmospheric dynamics are parameters of particular importance in this respect. The quantification of the anthropogenic influence on the dynamics of these above-mentioned parameters is of crucial importance nowadays but still affected by significant uncertainties. In the present context of these huge uncertainties in our understanding of how these different atmospheric compounds contribute to the radiative forcing, a significant part of my research interest is related to the following topics: (1) Development of lidar (Light Detection and Ranging)-based remote sensing techniques for monitoring atmospheric compounds and processes; (2) Aerosols hygroscopic properties and atmospheric modeling; (3) Water vapor mixing ratio and relative humidity estimation in the troposphere; (4) Characterization of the long-range transported aerosols; (5) Ambient gases detection using Fourier Transform Interferometers (FTIR); (6) Design of inexpensive Fabry Perot Interferometer for visible and near infrared for land and ocean surface remote sensing applications. The lidar-based remote sensing measurement techniques for the monitoring of climate change parameters where implemented at the City College of the City University of New York (CCNY/CUNY) LIDAR station and are presented in the second section of the paper. The geographical location of the CCNY lidar station is 40.86N, -73.86W. Among the lidar retrievals one important

  9. Effect of oxygen on growth and properties of diamond thin film deposited at low surface temperature

    SciTech Connect

    Das, D.; Singh, Raj N.; Barney, I. T.; Jackson, A. G.; Mukhopadhyay, S. M.

    2008-11-15

    Polycrystalline diamond thin films are grown on a p-type Si (100) single crystal substrate at a low surface deposition temperature of 455 deg. C using a microwave plasma enhanced chemical vapor deposition process in an Ar-rich Ar/H{sub 2}/CH{sub 4} plasma containing different oxygen levels from 0% to 0.75%. The surface deposition temperatures are measured and monitored by an IR thermometer capable of working in a plasma environment without any interference from the plasma emissions. The lower surface deposition temperature at high microwave power of 1300 W and higher gas pressure of 95 torr is achieved by active cooling of the substrate from the backside using a specially designed cooling stage. An enhanced growth rate from 0.19 to 0.63 {mu}m/h is observed with varying oxygen from 0% to 0.75% in the plasma. Diamond grain size also increased from 0.69 {mu}m for the sample with no oxygen to 1.74 {mu}m for the sample with 0.75% oxygen. The diamond films are characterized using x-ray diffraction, environmental scanning electron microscopy field emission gun, Raman spectroscopy, and x-ray photoelectron spectroscopy. The enhanced growth rate is correlated with the enhanced atomic hydrogen to C{sub 2} ratio with increasing oxygen concentration in the plasma, which is measured by an in situ optical emission spectroscopy.

  10. The surface properties of fluorinated polyimides exposed to VUV and atomic oxygen

    NASA Technical Reports Server (NTRS)

    Forsythe, John S.; George, Graeme A.; Hill, David J. T.; Odonnell, James H.; Pomery, Peter J.; Rasoul, Firas A.

    1995-01-01

    The effect of atomic oxygen flux and VUV radiation alone and in combination on the surface of fluorinated polyimide films was studied using XPS spectroscopy. Exposure of fluorinated polyimides to VUV radiation alone caused no observable damage to the polymer surface, while an atomic oxygen flux resulted in substantial oxidation of the surface. On the other hand, exposure to VUV radiation and atomic oxygen in combination caused extensive oxidation of the polymer surface after only 2 minutes of exposure. The amount of oxidized carbon on the polymer surface indicated that there is aromatic ring opening oxidation. The changes in the O1s/C1s, N1s/C1s, and F1s/C1s ratios suggested that an ablative degradation process is highly favorable. A synergistic effect of VUV radiation in the presence of atomic oxygen is clearly evidenced from the XPS study. The atomic oxygen could be considered as the main factor in the degradation process of fluorinated polyimide films exposed to a low earth orbit environment.

  11. Sensing Properties of Multiwalled Carbon Nanotubes Grown in MW Plasma Torch: Electronic and Electrochemical Behavior, Gas Sensing, Field Emission, IR Absorption

    PubMed Central

    Majzlíková, Petra; Sedláček, Jiří; Prášek, Jan; Pekárek, Jan; Svatoš, Vojtěch; Bannov, Alexander G.; Jašek, Ondřej; Synek, Petr; Eliáš, Marek; Zajíčková, Lenka; Hubálek, Jaromír

    2015-01-01

    Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 μm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‐modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures. PMID:25629702

  12. Sensing properties of multiwalled carbon nanotubes grown in MW plasma torch: electronic and electrochemical behavior, gas sensing, field emission, IR absorption.

    PubMed

    Majzlíková, Petra; Sedláček, Jiří; Prášek, Jan; Pekárek, Jan; Svatoš, Vojtěch; Bannov, Alexander G; Jašek, Ondřej; Synek, Petr; Eliáš, Marek; Zajíčková, Lenka; Hubálek, Jaromír

    2015-01-01

    Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 µm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‑modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures. PMID:25629702

  13. Effect of Remote Oxygen Scavenging on Electrical Properties of Ge-Based Metal-Oxide-Semiconductor Capacitors

    NASA Astrophysics Data System (ADS)

    Fadida, Sivan; Nyns, Laura; Van Elshocht, Sven; Eizenberg, Moshe

    2016-08-01

    Remote oxygen scavenging has been studied in a metal/high-k dielectric/GeO2/Ge stack, where a thin Ti layer inserted into the metal/high-k dielectric interface serves as the scavenger. First, we established that remote oxygen scavenging indeed occurs specifically in the studied HfO2/Al2O3/GeO2/Ge stack. It was also established that the source for oxygen is decomposition of the GeO2 layer. Then, the effect of remote oxygen scavenging of the GeO2 layer on the electrical characteristics of the metal/oxide/Ge capacitors was investigated. The electrical properties were studied in comparison with identical gate stacks with a Pt electrode, before and after annealing. Although a decrease in effective oxide thickness was demonstrated as a result of this process, clear degradation of the interface electrical quality was observed after scavenging. Initiation of the scavenging process was witnessed upon deposition of Ti at room temperature, emphasizing that this process could not be controlled.

  14. Oxygen partial pressure influenced structural and optical properties of DC magnetron sputtered ZrO{sub 2} films

    SciTech Connect

    Kondaiah, P.; Madhavi, V.; Uthanna, S.

    2013-02-05

    Thin films of zirconium oxide (ZrO{sub 2}) were deposited on (100) p-silicon and quartz substrates by sputtering of metallic zirconium target under different oxygen partial pressures in the range 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa. The effect of oxygen partial pressure on the structural and optical properties of the deposited films was systematically investigated. The deposition rate of the films decreased from 3.3 to 1.83 nm/min with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively. The X-ray diffraction profiles revealed that the films exhibit (111) refection of zirconium oxide in monoclinic phase. The optical band gap of the films increased from 5.62 to 5.80 eV and refractive index increased from 2.01 to 2.08 with the increase of oxygen partial pressure from 8 Multiplication-Sign 10{sup -3}-6 Multiplication-Sign 10{sup -2}Pa respectively.

  15. Tuning the magnetic properties of L a0.67S r0.33Co O3-δ films by oxygen pressure

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Wang, Yiqian; Liu, Guiju; Feng, Honglei; Yang, Huaiwen; Xue, Xuyan; Sun, Jirong

    2016-03-01

    In this paper, oxygen-deficient L a0.67S r0.33Co O3 (LSCO) thin films are prepared by adjusting the oxygen pressure during the deposition. As oxygen vacancies are introduced into the LSCO films, the out-of-plane lattices are elongated, as revealed by x-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Modulated bright and dark stripes observed in the HRTEM images of the oxygen-deficient LSCO films are induced by cation ordering and oxygen vacancy ordering, respectively. Magnetic measurements and first-principles calculations show that the oxygen vacancies depress the magnetism of the LSCO films greatly. We also demonstrate that doping Sr into LaCo O3 and removing oxygen from LSCO have a similar effect on the magnetic properties, which is correlated with a derived formula.

  16. Phytoglobin: a novel nomenclature for plant globins accepted by the globin community at the 2014 XVIII conference on Oxygen-Binding and Sensing Proteins.

    PubMed

    Hill, Robert; Hargrove, Mark; Arredondo-Peter, Raúl

    2016-01-01

    Hemoglobin (Hb) is a heme-containing protein found in the red blood cells of vertebrates. For many years, the only known Hb-like molecule in plants was leghemoglobin (Lb). The discovery that other Hb-like proteins existed in plants led to the term "nonsymbiotic Hbs (nsHbs)" to differentiate them from the Lbs. While this terminology was adequate in the early stages of research on the protein, the complexity of the research in this area necessitates a change in the definition of these proteins to delineate them from red blood cell Hb. At the 2014 XVIII Conference on Oxygen-Binding and Sensing Proteins, the group devoted to the study of heme-containing proteins, this issue was discussed and a consensus was reached on a proposed name change. We propose Phytoglobin (Phytogb) as a logical, descriptive name to describe a heme-containing (Hb-like) protein found in plants. It will be readily recognized by the research community without a prolonged explanation of the origin of the term. The classification system that has been established can essentially remain unchanged substituting Phytogb in place of nsHb. Here, we present a guide to the new nomenclature, with reference to the existing terminology and a phylogenetic scheme, placing the known Phytogbs in the new nomenclature. PMID:26998237

  17. Phytoglobin: a novel nomenclature for plant globins accepted by the globin community at the 2014 XVIII conference on Oxygen-Binding and Sensing Proteins

    PubMed Central

    Hill, Robert; Hargrove, Mark; Arredondo-Peter, Raúl

    2016-01-01

    Hemoglobin (Hb) is a heme-containing protein found in the red blood cells of vertebrates. For many years, the only known Hb-like molecule in plants was leghemoglobin (Lb). The discovery that other Hb-like proteins existed in plants led to the term “nonsymbiotic Hbs (nsHbs)” to differentiate them from the Lbs. While this terminology was adequate in the early stages of research on the protein, the complexity of the research in this area necessitates a change in the definition of these proteins to delineate them from red blood cell Hb. At the 2014 XVIII Conference on Oxygen-Binding and Sensing Proteins, the group devoted to the study of heme-containing proteins, this issue was discussed and a consensus was reached on a proposed name change. We propose Phytoglobin (Phytogb) as a logical, descriptive name to describe a heme-containing (Hb-like) protein found in plants. It will be readily recognized by the research community without a prolonged explanation of the origin of the term. The classification system that has been established can essentially remain unchanged substituting Phytogb in place of nsHb. Here, we present a guide to the new nomenclature, with reference to the existing terminology and a phylogenetic scheme, placing the known Phytogbs in the new nomenclature. PMID:26998237

  18. Therapeutic targeting of oxygen-sensing prolyl hydroxylases abrogates ATF4-dependent neuronal death and improves outcomes after brain hemorrhage in several rodent models.

    PubMed

    Karuppagounder, Saravanan S; Alim, Ishraq; Khim, Soah J; Bourassa, Megan W; Sleiman, Sama F; John, Roseleen; Thinnes, Cyrille C; Yeh, Tzu-Lan; Demetriades, Marina; Neitemeier, Sandra; Cruz, Dana; Gazaryan, Irina; Killilea, David W; Morgenstern, Lewis; Xi, Guohua; Keep, Richard F; Schallert, Timothy; Tappero, Ryan V; Zhong, Jian; Cho, Sunghee; Maxfield, Frederick R; Holman, Theodore R; Culmsee, Carsten; Fong, Guo-Hua; Su, Yijing; Ming, Guo-li; Song, Hongjun; Cave, John W; Schofield, Christopher J; Colbourne, Frederick; Coppola, Giovanni; Ratan, Rajiv R

    2016-03-01

    Disability or death due to intracerebral hemorrhage (ICH) is attributed to blood lysis, liberation of iron, and consequent oxidative stress. Iron chelators bind to free iron and prevent neuronal death induced by oxidative stress and disability due to ICH, but the mechanisms for this effect remain unclear. We show that the hypoxia-inducible factor prolyl hydroxylase domain (HIF-PHD) family of iron-dependent, oxygen-sensing enzymes are effectors of iron chelation. Molecular reduction of the three HIF-PHD enzyme isoforms in the mouse striatum improved functional recovery after ICH. A low-molecular-weight hydroxyquinoline inhibitor of the HIF-PHD enzymes, adaptaquin, reduced neuronal death and behavioral deficits after ICH in several rodent models without affecting total iron or zinc distribution in the brain. Unexpectedly, protection from oxidative death in vitro or from ICH in vivo by adaptaquin was associated with suppression of activity of the prodeath factor ATF4 rather than activation of an HIF-dependent prosurvival pathway. Together, these findings demonstrate that brain-specific inactivation of the HIF-PHD metalloenzymes with the blood-brain barrier-permeable inhibitor adaptaquin can improve functional outcomes after ICH in several rodent models.

  19. Oxygen safety

    MedlinePlus

    COPD - oxygen safety; Chronic obstructive pulmonary disease - oxygen safety; Chronic obstructive airways disease - oxygen safety; Emphysema - oxygen safety; Heart failure - oxygen-safety; Palliative care - oxygen safety; ...

  20. More than a signal: non-signaling properties of quorum sensing molecules.

    PubMed

    Schertzer, Jeffrey W; Boulette, Megan L; Whiteley, Marvin

    2009-05-01

    Quorum sensing in bacteria serves as an example of the adaptation of single-celled organisms to engage in cooperative group behaviors. This phenomenon is much more widespread than originally thought, with many different species 'speaking' through various secreted small molecules. Despite some variation in signaling molecules, the principles of quorum sensing are conserved across a wide range of organisms. Small molecules, secreted into the environment, are detected by neighbors who respond by altering gene expression and, as a consequence, behavior. However, it is not known whether these systems evolved specifically for this purpose, or even if their role is exclusive to information trafficking. Rather, clues exist that many quorum sensing molecules function as more than just signals. Here, we discuss non-signaling roles for quorum sensing molecules in such important processes as nutrient scavenging, ultrastructure modification and competition.

  1. Oxygen vacancies induced DX center and persistent photoconductivity properties of high quality ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Xie, Yong; Madel, Manfred; Feneberg, Martin; Neuschl, Benjamin; Jie, Wanqi; Hao, Yue; Ma, Xiaohua; Thonke, Klaus

    2016-04-01

    Ultraviolet sensors based on homoepitaxially grown ZnO nanorods were fabricated using clean room technology. We study the spectral dependence and frequency dependence of the photoresponse of these rods at different temperatures and ambient conditions. Whereas the response for above-bandgap light is fast, we find a slow response to light below band gap and clear signatures of persistent photoconductivity. These findings are explained by switching oxygen vacancies by light from nonconductive to conductive state, whereas the oxygen vacancies undergo a large lattice relaxation. The threshold photon energy for this process is found to be 2.6 eV at room temperature.

  2. Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

    2008-01-01

    Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

  3. Role of Oxygen Defects on the Photocatalytic Properties of Mg-Doped Mesoporous Ta3 N5.

    PubMed

    Xie, Yinghao; Wang, Yawei; Chen, Zuofeng; Xu, Xiaoxiang

    2016-06-22

    Tantalum nitride (Ta3 N5 ) highlights an intriguing paradigm for converting solar energy into chemical fuels. However, its photocatalytic properties are strongly governed by various intrinsic/extrinsic defects. In this work, we successfully prepared a series of Mg-doped mesoporous Ta3 N5 using a simple method. The photocatalytic and photoelectrochemical properties were investigated from the viewpoint of how defects such as accumulation of oxygen and nitrogen vacancies contribute to the catalytic activity. Our findings suggest that Mg doping is accompanied by an accumulation of oxygen species and a simultaneous elimination of nitrogen vacancies in Ta3 N5 . These oxygen species in Ta3 N5 induce delocalized shallow donor states near the conduction band minimum and are responsible for high electron mobility. The superior photocatalytic activity of Mg-doped Ta3 N5 can then be understood by the improved electron-hole separation as well as the lack of nitrogen vacancies, which often serve as charge-recombination centers. PMID:27100134

  4. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma

    NASA Astrophysics Data System (ADS)

    Islam, Muhammad R.; Kang, Narae; Bhanu, Udai; Paudel, Hari P.; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N.; Khondaker, Saiful I.

    2014-08-01

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2

  5. Effect of platinum-nanodendrite modification on the glucose-sensing properties of a zinc-oxide-nanorod electrode

    NASA Astrophysics Data System (ADS)

    Abdul Razak, Khairunisak; Neoh, Soo Huan; Ridhuan, N. S.; Mohamad Nor, Noorhashimah

    2016-09-01

    The properties of ZnO nanorods (ZnONRs) decorated with platinum nanodendrites (PtNDs) were studied. Various sizes of PtNDs were synthesized and spin coated onto ZnONRs, which were grown on indium-titanium-oxide (ITO) substrates through a low-temperature hydrothermal method. Scanning electron microscopy and X-ray diffraction analyses were conducted to analyze the morphology and structural properties of the electrodes. The effects of PtND size, glucose concentration, and Nafion amount on glucose-sensing properties were investigated. The glucose-sensing properties of electrodes with immobilized glucose oxidase (GOx) were measured using cyclic voltammetry. The bio-electrochemical properties of Nafion/GOx/42 nm PtNDs/ZnONRs/ITO glucose sensor was observed with linear range within 1-18 mM, with a sensitivity value of 5.85 μA/mM and a limit of detection of 1.56 mM. The results of this study indicate that PtNDs/ZnONRs/ITO has potential in glucose sensor applications.

  6. Changing the magnetic and optical properties of (Ga, Fe)N and (Ga, Co)N by alloying with oxygen

    NASA Astrophysics Data System (ADS)

    El Maalam, K.; Salmani, E.; Mounkachi, O.; Hamedoun, M.; Benyoussef, A.

    2016-04-01

    Systematic density functional theory studies and model analyses have been used to show that the magnetic properties of (Ga0.94Fe0.06)N and (Ga0.94Co0.06)N can be changed from disorder local moment state to ferromagnetic state by replacing ~2 % of the nitrogen atoms with oxygen atoms. The estimated curie temperatures are much higher than the room temperature which indicates the room temperature ferromagnetism can be realized by oxygen doping. Moreover, the optical absorption spectra obtained by ab initio calculations confirm the ferromagnetic stability based on the charge state of magnetic impurities. (Ga0.94Fe0.06)N0.98O0.02 and (Ga0.94Co0.06)N0.98O0.02 ferromagnetic DMS exhibits half-metallic behavior, which is suitable for spintronics applications.

  7. Effect of oxygen incorporation in a-plane GaN on p-type ohmic contact property

    NASA Astrophysics Data System (ADS)

    Jung, Ki-Chang; Lee, Inwoo; Park, Jaehyoung; Bae, Hyojung; Kim, Chung Yi; Shin, Hui-Youn; Kim, Hyung-Gu; Jeon, Jina; Jung, S.; Choi, Yoon-Ho; Lee, Jung-Soo; Ha, Jun-Seok

    2014-09-01

    We report on the origin of the non-ohmic behavior of Ni/Au-based p-type contacts on a nonpolar a-plane GaN layer. The contact properties of Ga-polar c-plane GaN and nonpolar a-plane GaN are compared. While the Ga-polar c-plane shows ohmic-contact properties in the Ni/Au contact after heat treatment, the nonpolar a-plane shows rectifying characteristics both before and after heat treatment. We determined the reasons why the two planes show substantial differences in contact properties using various tools. We conclude that the differences originated from the oxygen incorporation preference resulting in gallium oxide formation at the interface of nonpolar a-plane GaN.

  8. Structure and properties of oxygen-containing thin films and bulk MgB2

    NASA Astrophysics Data System (ADS)

    Prikhna, T.; Shapovalov, A.; Goldacker, W.; Eisterer, M.; Kozyrev, A.; Shaternik, V.; Boutko, V.; Gusev, A.; Weber, H. W.; Karpets, M.; Basyuk, T.; Sverdun, V.; Moshchil, V.; Belogolovskiy, M.; Sergienko, N.

    2015-12-01

    A structural Auger spectroscopy study of MgB2 thin (∼140 nm) oxygen-containing polycrystalline films produced by magnetron sputtering and 99% dense MgB2 bulks synthesized at 2 GPa allows us to conclude that jc of MgB2 depends to a high extent on the amount and distribution of oxygen in the material matrix. jc reached 7.8-2.7 MA/cm2 below 1T at 20 K in the films and 0.3-0.9 MA/cm2 (depending on the boron used) in the bulks. The higher jc in MgB2 thin films can be associated with finer oxygen-enriched Mg-B-O inclusions and their higher density in the film structure compared to the bulk. Calculations of the total electron density of states (DOS) in MgB2, MgB1.75O0.25, MgB1.5O0.5 and MgBO showed that all the compounds are conductors with metal-like behaviour. The DOS is even higher in MgB1.5O0 5 than in MgB2 and the binding energy is similar. So, the experimentally found presence of some dissolved oxygen in MgB2 does not contradict its high SC performance. The introduction of a high amount of oxygen into the MgB2 structure does not dramatically reduce the material's Tc and allows obtaining highjc as observed in our MgB2 films and bulks.

  9. Remote sensing in dryland cotton: relation to yield potential and soil properties

    NASA Astrophysics Data System (ADS)

    Read, John J.; Iqbal, Javed; Thomasson, John A.; Willers, Jeffrey L.; Jenkins, Johnie N.

    2004-01-01

    The use of soil and topography information to explain crop yield variation across fields is often applied for crop management purposes. Remote sensed data is a potential source of information for site-specific crop management, providing both spatial and temporal information about soil and crop condition. Studies were conducted in a 104-acre (42-hectare) dryland cotton field in 2001 and 2002 in order to (1) qualitatively assess the spatial variability of soil physical properties from kriged estimates, (2) compare actual yields with normalized difference vegetation reflectance indices (NDVI) obtained from multispectral imagery and from in situ radiometer data, and (3) predict site-specific cotton yields using a crop simulation model, GOSSYM. An NDVI map of soybean in 2000 obtained from a multispectral image was used to establish four sites in each low, medium and high NDVI class. These 12 sites were studied in 2001 and 12 more sites selected at random were studied in 2002 (n = 24). Site-specific measurements included leaf area index (LAI), canopy hyperspectral reflectance, and three-band multispectral image data for green, red, and near-infrared reflectance wavebands at spatial resolutions of 2 m in 2001 and 0.5 m in 2002. Imagery was imported into the image analysis software Imagine (ERDAS, v. 8.5) for georegistration and image analysis. A 6x6 pixels (144 m2) area of interest was established on top of each field plot site and digital numbers (DN) from reflectance imagery were extracted from each band for derivation of NDVI maps for each of four sampling dates. Lint yield from each plot site was collected by hand and also by a cotton picker equipped with AgLeader yield monitor and OmniStar differential global positioning system. We found plant height, leaf area index, and lint yield were closely associated with NDVI maps and with NIR band values acquired from either an aircraft or handheld (GER-1500) sensor during peak bloom in mid July. Results indicate NDVI and NIR

  10. Inference of effective river properties from remotely sensed observations of water surface

    NASA Astrophysics Data System (ADS)

    Garambois, Pierre-André; Monnier, Jérôme

    2015-05-01

    The future SWOT mission (Surface Water and Ocean Topography) will provide cartographic measurements of inland water surfaces (elevation, widths and slope) at an unprecedented spatial and temporal resolution. Given synthetic SWOT like data, forward flow models of hierarchical-complexity are revisited and few inverse formulations are derived and assessed for retrieving the river low flow bathymetry, roughness and discharge (A0, K, Q) . The concept of an effective low flow bathymetry A0 (the real one being never observed) and roughness K , hence an effective river dynamics description, is introduced. The few inverse models elaborated for inferring (A0, K, Q) are analyzed in two contexts: (1) only remotely sensed observations of the water surface (surface elevation, width and slope) are available; (2) one additional water depth measurement (or estimate) is available. The inverse models elaborated are independent of data acquisition dynamics; they are assessed on 91 synthetic test cases sampling a wide range of steady-state river flows (the Froude number varying between 0.05 and 0.5 for 1 km reaches) and in the case of a flood on the Garonne River (France) characterized by large spatio-temporal variabilities. It is demonstrated that the most complete shallow-water like model allowing to separate the roughness and bathymetry terms is the so-called low Froude model. In Case (1), the resulting RMSE on infered discharges are on the order of 15% for first guess errors larger than 50%. An important feature of the present inverse methods is the fairly good accuracy of the discharge Q obtained, while the identified roughness coefficient K includes the measurement errors and the misfit of physics between the real flow and the hypothesis on which the inverse models rely; the later neglecting the unobserved temporal variations of the flow and the inertia effects. A compensation phenomena between the indentifiedvalues of K and the unobserved bathymetry A0 is highlighted, while the

  11. Optical properties and remote sensing of optically diverse waters in Pomeranian Region (Poland)

    NASA Astrophysics Data System (ADS)

    Ficek, Dariusz

    2015-04-01

    This work presents the large set of empirical examples of upward and downward spectral irradiance fields, along with their associated coefficients of reflectance and transmittance in the waters in Pomeranian Region. On the one hand, the light field prevailing in a water body is one of the main factors governing life in it, affecting as it does a number of processes of great significance for this ecosystem. On the other, it is an important source of information used, among other things, for the remote assessment of the state of structural characteristics, including the composition and concentration of OACs, and the changes taking place in this environment. In this age of remote sensing, be this from on board a satellite or an aircraft, the light field is a highly topical issue. The 235 optical measurements performed in Pomeranian Region enabled a range of characteristic features of the vertical spectral distributions of the downward and upward irradiance, and irradiance transmittance to be defined. Based on these measurements, spectra of the diffusional coefficient of the downward irradiance attenuation in different types of lacustrine waters were determined. The underwater irradiance fields are governed by absorption and scattering, and these processes, in turn, depend on the type and concentration of OACs contained in the water. Later in this work, I show the influence of these constituents on the spatial and spectral characteristics of underwater light fields in trophically and optically diverse waters; I also analyse the possibilities of utilizing this modified light field to determine the OAC concentration in the waters under study here. The magnitude that is used to monitor the state of the water in natural bodies using remote sensing is the reflectanceR(λ), a function of the reflection of the downward daytime irradiance. Because the spectra of this reflectance differ in shape (the positions and values of their maxima and minima), three types of spectra have

  12. Assessing three different ranges of amounts of silver nanoparticle dopants on the ethanol sensing properties of zinc oxide

    NASA Astrophysics Data System (ADS)

    Mohammadrezaei, Ameneh; Afzalzadeh, Reza; Mohsen Hosseini-Golgoo, Seyed

    2012-03-01

    The effects of silver nanoparticle (SNP) dopants on the ethanol sensing properties of zinc oxide (ZnO) bulk sensors were investigated. ZnO powder was mixed with various weight percentages of SNPs in the range of 0-1.8 wt% and then all samples were sintered at 860 °C. X-ray diffractometry was used to determine the crystal structure of the doped samples. Scanning electron microscopy was used to characterize the structure of the specimens. The electrical and gas-sensing properties of the specimens were assessed at different temperatures. Three different ranges of additive amount were distinguished based on the sensing behavior of the samples as a result of the solubility of SNPs in ZnO samples. In the first range, a tiny amount of the SNPs (˜0.025 wt%) can be dissolved in the ZnO lattice, so the resistance and response of the bulk ZnO sensors are decreased. In the second range (0.025% < wt% <0.7%), those parameters are increased, revealing that Ag cannot be dissolved in ZnO at higher concentration. Best recovery time is achieved in this range at 0.7 wt% of SNP dopants. In the third range (wt% > 0.7%), the resistance is observed to increase and the response to decrease with a high accumulation of Ag clusters on the grain surfaces. Moreover, the working temperature is reduced by increasing the amount of SNPs.

  13. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates

    PubMed Central

    Cho, Byungjin; Yoon, Jongwon; Lim, Sung Kwan; Kim, Ah Ra; Choi, Sun-Young; Kim, Dong-Ho; Lee, Kyu Hwan; Lee, Byoung Hun; Ko, Heung Cho; Hahm, Myung Gwan

    2015-01-01

    We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D) molybdenum disulfide (MoS2) flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO2 gas molecules (>1.2 ppm) as well as NH3 (>10 ppm). Metal nanoparticles (NPs) could tune the electronic properties of the 2D graphene/MoS2 device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS2, electronically sensitizing NH3 gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO2 sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS2 flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms. PMID:26404279

  14. First principles study of oxygen vacancies and iron impurities on electrical and optical properties of NiO

    NASA Astrophysics Data System (ADS)

    Petersen, John; Fidele, Twagirayezu; Borges, Pablo; Scolfaro, Luisa; Geerts, Wilhelmus

    We are studying the properties of iron doped NiO by Density Functional Theory. NiO is being considered for use in RRAM, based on the reversible switching of a thin transition metal oxide (TMO) layer between a low and high resistance state using the mechanism of soft breakdown. RRAM's high integration density, its high endurance and good retention, its low energy use, and its high speed make it a potential candidate for replacing Flash memory. Switching between the high and low resistance state is inhomogeneous, and low resistance nano-filaments are formed. Fe impurities are introduced to optimize the switching properties. The effects of oxygen vacancies and iron on the electronic structure and optical properties of NiO are calculated and compared with experiment. Antiferromagnetic rhombohedral 108 atom cells with 1.85% Fe concentration are considered. Due to the highly-correlated nature of d orbitals in TMOs, a Hubbard U correction is applied to calculations in this work via the GGA + U method of DFT using VASP. Hybrid HSE06 calculations will also be considered. Localized energy levels from iron and from oxygen vacancies are identified, and their effects on dielectric permittivity are presented. Texas State University (Research Enhancement grant) and DOD (HBCU/MI Grant W911NF-15-1-0394).

  15. Study on structural, morphological and thermal properties of surface modified polyvinylchloride (PVC) film under air, argon and oxygen discharge plasma

    NASA Astrophysics Data System (ADS)

    Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Serra Rodríguez, Carmen

    2016-09-01

    The effect of air, argon, oxygen DC glow discharge plasma on the polyvinylchloride (PVC) film synthesized by solution casting technique, were evaluated via changes in physio-chemical properties such as structural, morphological, crystalline, thermal properties. The PVC film was plasma treated as a function of exposure time and different plasma forming gases, while other operating parameters such as power and pressure remained constant at 100 W and 2 Pa respectively. The plasma treated PVC were characterized by static contact angle, ATR-FTIR, XPS, AFM and T-peel analysis. It was found that various gaseous plasma treatments have improved the polar components, surface roughness on the surface of PVC which was confirmed by XPS, AFM, resulting in highly enhanced wettability and adhesion. X-ray diffraction study showed that plasma treatment does not persuade considerable change, even though it vaguely induces the crystallinity. The thermal properties of plasma treated PVC were evaluated by Differential Scanning Calorimetry and it was observed that O2 plasma treatment gives higher glass transition temperature of 87.21 °C compared with the untreated one. The glass transition temperature slightly increased for Oxygen plasma treated material due to the presence of higher concentration of the polar functional groups on the PVC surface due to strong intramolecular bonding.

  16. Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties.

    PubMed

    Fortunelli, Alessandro; Goddard, William A; Sementa, Luca; Barcaro, Giovanni

    2015-03-14

    Electrochemical water-based energy cycles provide a most promising alternative to fossil-fuel sources of energy. However, current electrocatalysts are not adequate (high overpotential, lack of selectivity toward O2 production, catalyst degradation). We propose here mechanistic guidelines for experimental examination of modified catalysts based on the dependence of kinetic rates on the solvent dielectric constant. To illustrate the procedure we consider the fcc(111) platinum surface and show that the individual steps for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) change systematically with the polarizability of the medium. Thus changing this environmental variable can be used to tune the rate determining steps and the barriers, providing a means for screening and validating new systems to optimize the rate determining steps for the ORR and OER reaction pathways.

  17. Optimizing the oxygen evolution reaction for electrochemical water oxidation by tuning solvent properties

    NASA Astrophysics Data System (ADS)

    Fortunelli, Alessandro; Goddard, William A., III; Sementa, Luca; Barcaro, Giovanni

    2015-02-01

    Electrochemical water-based energy cycles provide a most promising alternative to fossil-fuel sources of energy. However, current electrocatalysts are not adequate (high overpotential, lack of selectivity toward O2 production, catalyst degradation). We propose here mechanistic guidelines for experimental examination of modified catalysts based on the dependence of kinetic rates on the solvent dielectric constant. To illustrate the procedure we consider the fcc(111) platinum surface and show that the individual steps for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) change systematically with the polarizability of the medium. Thus changing this environmental variable can be used to tune the rate determining steps and the barriers, providing a means for screening and validating new systems to optimize the rate determining steps for the ORR and OER reaction pathways.

  18. Effects of hyperbaric oxygen on the growth and properties of Pseudomonas aeruginosa.

    PubMed

    Kenward, M A; Alcock, S R; Brown, M R

    1980-01-01

    Growth of Pseudomonas aeruginosa in 2 atmospheres absolute of 100% oxygen at 37 degrees C produced two types of abnormal colonies--stunted, rough colonies, termed dwarfs, and large, domed, mucoid colonies, termed giants. The occurrence of these variants depended upon the partial pressure of oxygen and the inoculum size. Subculture of dwarf or giant colonies produced a mixture of both colony types after incubation in hyperbaric oxygen, and colonies of normal appearance after incubation in air. Electron micrographs of ultrathin sections showed that cells from dwarf colonies had a more clearly defined envelope region than cells from normal colonies. Giant colony and normal colony-derived cells were of similar appearance. Whole cells from giant colonies contained more carbohydrate, readily extractable lipid, neutral lipid and free fatty acid than cells from normal colonies; the two cell types showed similar contents of 2-keto,3-deoxyoctonic acid and total phospholipid, but different proportions of individual phospholipids. Cells from dwarf, giant and normal (air-grown) colonies were incubated in air on nutrient agar containing either polymyxin, tetracycline or phenoxyethanol. Relative to cells from normal colonies, cells from dwarf colonies showed enhanced resistance to all three agents and cells from giant colonies showed enhanced resistance to polymyxin and tetracycline only. The resistance of cells from variant colonies was lost following a single subculture in air in the absence of antibacterial agents. It was concluded that the envelopes of cells from dwarf and giant colonies differed both from each other and from those of normal cells. These differences, and the formation of variant colonies, appeared to result from bacterial adaptation to hyperbaric oxygen rather than from mutation.

  19. The Optical Property of Core-Shell Nanosensors and Detection of Atrazine Based on Localized Surface Plasmon Resonance (LSPR) Sensing

    PubMed Central

    Yang, Shaobo; Wu, Tengfei; Zhao, Xinhua; Li, Xingfei; Tan, Wenbin

    2014-01-01

    Three different nanosensors with core-shell structures were fabricated by molecular self-assembly and evaporation techniques. Such closely packed nanoparticles exhibit fine optical properties which are useful for biochemical sensing. The refractive index sensitivity (RIS) of nanosensors was detected by varying the refractive index of the surrounding medium and the decay length of nanosensors was investigated using a layer-by-layer polyelectrolyte multilayer assembly. The results showed that the thickness of the Au shell plays an important role in determining the RIS and the decay length. A system based on localized surface plasmon resonances (LSPR) sensing was constructed in our study. The core-shell nanosensors can detect 10 ng/mL atrazine solutions and are suitable for pesticide residue detection. PMID:25057137

  20. The optical property of core-shell nanosensors and detection of atrazine based on localized surface plasmon resonance (LSPR) sensing.

    PubMed

    Yang, Shaobo; Wu, Tengfei; Zhao, Xinhua; Li, Xingfei; Tan, Wenbin

    2014-01-01

    Three different nanosensors with core-shell structures were fabricated by molecular self-assembly and evaporation techniques. Such closely packed nanoparticles exhibit fine optical properties which are useful for biochemical sensing. The refractive index sensitivity (RIS) of nanosensors was detected by varying the refractive index of the surrounding medium and the decay length of nanosensors was investigated using a layer-by-layer polyelectrolyte multilayer assembly. The results showed that the thickness of the Au shell plays an important role in determining the RIS and the decay length. A system based on localized surface plasmon resonances (LSPR) sensing was constructed in our study. The core-shell nanosensors can detect 10 ng/mL atrazine solutions and are suitable for pesticide residue detection. PMID:25057137

  1. Co(II)-doped MOF-5 nano/microcrystals: Solvatochromic behaviour, sensing solvent molecules and gas sorption property

    SciTech Connect

    Yang, Ji-Min; Liu, Qing; Sun, Wei-Yin

    2014-10-15

    Co(II)-doped MOF-5 nano/microcrystals with controllable morphology and size were successfully obtained by solvothermal method. The products were characterized by powder X-ray diffraction (PXRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), inductively coupled plasma optical emission spectrometer (ICP-OES), elemental analysis, UV–vis and infrared (IR) spectroscopy. The factors influencing the crystal morphology and size were investigated. The gas sorption measurements reveal that highly crystalline particles have large Langmuir surface area. It was found that the Co(II)-doped MOF-5 shows enhanced hydrostability and the sorption profiles of the Co(II)-doped MOF-5 nano/microcrystals are dependent on the morphology and size of the particles. Porous Co(II)-doped MOF-5 is stable upon the removal of guest molecules and exhibits different colour with accommodating different solvent molecule, which means that it can act as solvatochromic sensing materials for recognition of solvent molecules. - Graphical abstract: Co(II)-doped MOF-5 nano/microcrystals with different shapes and sizes were synthesized by a facile hydrothermal method, which not only enhance gas sorption properties and structural stability of MOFs towards moisture, but also act as new sensing materials for sensing small molecules. - Highlights: • Co(II)-doped MOF-5 nano/microcrystals with controllable morphology and size were obtained. • Co(II)-doped MOF-5 nano/microcrystals enhance the structural stability towards moisture. • Co(II)-doped MOF-5 can act as new sensing material for sensing small molecules.

  2. An assessment of optical properties and primary production derived from remote sensing in the Southern Ocean (SO GasEx)

    NASA Astrophysics Data System (ADS)

    Lee, Zhongping; Lance, Veronica P.; Shang, Shaoling; Vaillancourt, Robert; Freeman, Scott; Lubac, Bertrand; Hargreaves, Bruce R.; Del Castillo, Carlos; Miller, Richard; Twardowski, Michael; Wei, Guomei

    2011-04-01

    Optical properties and primary production were measured during the Southern Ocean (SO) Gas Exchange Experiment (GasEx) (March-April 2008). To assess and evaluate these properties derived from remote sensing, absorption coefficients derived from remote sensing reflectance (Rrs) with the quasi-analytical algorithm were compared with those from in situ measurements from both an ac-9 optical instrument deployed on a profiling package and from discrete water samples analyzed using filter pad spectrophotometry. Total absorption coefficients from Rrs retrievals were found, on average, to be ˜12% less than ac-9 measurements and ˜15% less than filter pad measurements. Absorption coefficients of gelbstoff-detritus and phytoplankton pigments (at 443 nm) derived from Rrs were ˜15% and ˜25% less than ac-9 measurements, respectively. The difference can be well explained based on the determination methods and these results indicate general consistency between remote sensing retrievals and in situ measurements for these waters. Further, incorporating measured surface radiation data, water column primary production (PPeu) was estimated using chlorophyll concentration based models (Chl-PP) and a phytoplankton absorption based model (Aph-PP), where remote-sensing Chl was retrieved with an operational empirical algorithm. These estimated PPeu values were then compared with primary productivity measured using 14C incubation techniques, and coefficient of determination (R2, N = 13) of 0.74 were found for the Aph-PP results, while the R2 of the Chl-PP results were less than 0.5. Such a contrast further highlights the importance of analytically retrieving phytoplankton absorption from measurement of ocean color and the advantage of using phytoplankton absorption to represent the role of phytoplankton in photosynthesis. Spatial distribution and contrast of PPeu in the greater SO GasEx region estimated from satellite data are also presented.

  3. Physical vapor deposited thin films of lignins extracted from sugar cane bagasse: morphology, electrical properties, and sensing applications.

    PubMed

    Volpati, Diogo; Machado, Aislan D; Olivati, Clarissa A; Alves, Neri; Curvelo, Antonio A S; Pasquini, Daniel; Constantino, Carlos J L

    2011-09-12

    The concern related to the environmental degradation and to the exhaustion of natural resources has induced the research on biodegradable materials obtained from renewable sources, which involves fundamental properties and general application. In this context, we have fabricated thin films of lignins, which were extracted from sugar cane bagasse via modified organosolv process using ethanol as organic solvent. The films were made using the vacuum thermal evaporation technique (PVD, physical vapor deposition) grown up to 120 nm. The main objective was to explore basic properties such as electrical and surface morphology and the sensing performance of these lignins as transducers. The PVD film growth was monitored via ultraviolet-visible (UV-vis) absorption spectroscopy and quartz crystal microbalance, revealing a linear relationship between absorbance and film thickness. The 120 nm lignin PVD film morphology presented small aggregates spread all over the film surface on the nanometer scale (atomic force microscopy, AFM) and homogeneous on the micrometer scale (optical microscopy). The PVD films were deposited onto Au interdigitated electrode (IDE) for both electrical characterization and sensing experiments. In the case of electrical characterization, current versus voltage (I vs V) dc measurements were carried out for the Au IDE coated with 120 nm lignin PVD film, leading to a conductivity of 3.6 × 10(-10) S/m. Using impedance spectroscopy, also for the Au IDE coated with the 120 nm lignin PVD film, dielectric constant of 8.0, tan δ of 3.9 × 10(-3), and conductivity of 1.75 × 10(-9) S/m were calculated at 1 kHz. As a proof-of-principle, the application of these lignins as transducers in sensing devices was monitored by both impedance spectroscopy (capacitance vs frequency) and I versus time dc measurements toward aniline vapor (saturated atmosphere). The electrical responses showed that the sensing units are sensible to aniline vapor with the process being

  4. Growth properties and reactivity of oxygen phases on platinum (111) and palladiium (111)

    NASA Astrophysics Data System (ADS)

    Devarajan, Sunil Poondi

    Oxidation reactions of Pt and Pd under lean burn or oxygen rich conditions are crucial to heterogeneous catalysis systems used in oxidation of hydrocarbons, fabrication of specialty chemicals, power generation through catalytic oxidation, fuel cells and most significantly pollution control through remediation of industrial and automotive exhaust. In spite of their tremendous appeal and widespread use in many important applications, knowledge used to formulate catalytic systems based on the transition metals has chiefly been derived from empirical data, because of their low reactivity towards molecular oxygen under experimental conditions of Ultra High Vacuum (UHV). Thanks to recent advances in surface science techniques, path breaking research through innovative experimental methods coupled with a renewed vigor towards computational ab-initio simulations, have opened avenues for fundamental understanding of this important class of reactions. We utilized strong oxidizing agents like nitrogen di-oxide and atomic oxygen beams to grow oxygen phases on platinum and palladium single crystals and studied their characteristics using various surface analytic techniques. Our STM work on Pt(111), ends a long standing debate on whether the oxygen atoms continue filling up fcc hollow sites or start filling up hcp hollow sites beyond the well understood 0.25 ML coverage. We also present evidence to demonstrate formation of a Pt oxide chain compound which appears as protrusions on the surface and arrange themselves into a well networked superstructure during initial oxidation. Our work on Pd(111) using TPRS, reveals for the first time that C-H bond cleavage of propane occurs on a PdO(101) thin film at temperatures below 200 K under UHV conditions. It is also observed that the hydrogen, and propyl fragments resulting from the bond cleavage react with the thin film oxide to undergo complete oxidation releasing H2O and CO2 at higher temperatures. The C-H bond cleavage occurs only

  5. Low-temperature anomalies in the magnetic and thermal properties of molecular cryocrystals doped with oxygen impurity

    NASA Astrophysics Data System (ADS)

    Freiman, Yu. A.; Tretyak, S. M.; JeŻowski, A.

    2000-09-01

    The magnetic properties of oxygen pair clusters are investigated theoretically for different cluster geometries which can be realized by doping molecular cryomatrices with oxygen. Anomalous temperature and pressure behavior of the magnetic susceptibility, heat capacity, and entropy is predicted. It is proposed to use these anomalies for studying the parameters characterizing the oxygen clusters and the parameters of the host matrix: the effective spin-figure interaction constant D for the molecule in the matrix, the exchange parameter J, and the number of pair clusters Np, which can deviate markedly from the purely random value Np=6Nc2 (N is Avogadro's number, and c is the molar concentration of the impurity). The data on the magnetic susceptibility may be used to analyze the character of the positional and orientational short-range order in the solid solution. The value of D contains information about the orientational order parameter; the distance and angular dependence of the exchange interaction parameter are still subject to discussion in the literature. The temperature dependence of Np contains information about diffusion and clusterization processes in the system.

  6. [Studies of the blood antioxidant system and oxygen-transporting properties of human erythrocytes during 105-day isolation].

    PubMed

    Brazhe, N A; Baĭzhumanov, A A; Parshina, E Iu; Iusipovich, A I; Akhalaia, M Ia; Iarlykova, Iu V; Labetskaia, O I; Ivanova, S M; Morukov, B V; Maksimov, G V

    2011-01-01

    Effects of strict 105-d isolation on blood antioxidant status, erythrocyte membrane processes and oxygen-binding properties of hemoglobin were studied in 6 male volunteers (25 to 40 y.o.) in ground-based simulation of a mission to Mars (experiment Mars-105). The parameters were measured using venous blood samples collected during BDC, on days 35, 70 and 105 of the experiment and on days 7 and 14-15 after its completion. Methods of biochemistry (determination of enzyme activity and thin-layer chromatography) and biophysical (laser interference microscopy, Raman spectroscopy) showed changes in relative content of lipid and phospholipid fractions suggesting growth of membrane microviscosity and increase in TBA-AP (active products of lipids peroxidation interacting with thiobarbituric acid). A significant increase in glucose-6-phosphate dehydrogenase and superoxide dismutase activities against reduction of catalase activity points to both reparative processes in erythrocytes and disbalance between the number of evolving active forms of oxygen and antioxidant protection mechanisms in cells. Hemoglobin sensitivity of oxygen and blood level of oxyhemoglobin were found to increase, too. It is presumed that adaptation of organism to stresses experienced during and after the experiment may destroy balance of the antioxidant protection systems which is conducive to oxidation of membrane phospholipids, alteration of their content, increase of membrane microviscosity and eventual failure of the gas-exchange function of erythrocytes. PMID:21675192

  7. The influence of intercalated oxygen on the properties of graphene on polycrystalline Cu under various environmental conditions.

    PubMed

    Blume, Raoul; Kidambi, Piran R; Bayer, Bernhard C; Weatherup, Robert S; Wang, Zhu-Jun; Weinberg, Gisela; Willinger, Marc-Georg; Greiner, Mark; Hofmann, Stephan; Knop-Gericke, Axel; Schlögl, Robert

    2014-12-21

    Intercalation of oxygen at the interface of graphene grown by chemical vapour deposition and its polycrystalline copper catalyst can have a strong impact on the electronic, chemical and structural properties of both the graphene and the Cu. This can affect the oxidation resistance of the metal as well as subsequent graphene transfer. Here, we show, using near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), X-ray absorption near edge spectroscopy (XANES), energy dispersive X-ray spectroscopy (EDX) and (environmental) scanning electron microscopy (ESEM) that both the oxygen intercalation and de-intercalation are kinetically driven and can be clearly distinguished from carbon etching. The obtained results reveal that a charge transfer between as grown graphene and Cu can be annulled by intercalating oxygen creating quasi-free-standing graphene. This effect is found to be reversible on vacuum annealing proceeding via graphene grain boundaries and defects within the graphene but not without loss of graphene by oxidative etching for repeated (de-)intercalation cycles. PMID:25356600

  8. Blue Light-excited Light-Oxygen-Voltage-sensing Domain 2 (LOV2) Triggers a Rearrangement of the Kinase Domain to Induce Phosphorylation Activity in Arabidopsis Phototropin1.

    PubMed

    Oide, Mao; Okajima, Koji; Kashojiya, Sachiko; Takayama, Yuki; Oroguchi, Tomotaka; Hikima, Takaaki; Yamamoto, Masaki; Nakasako, Masayoshi

    2016-09-16

    Phototropin1 is a blue light (BL) receptor in plants and shows BL-dependent kinase activation. The BL-excited light-oxygen-voltage-sensing domain 2 (LOV2) is primarily responsible for the activation of the kinase domain; however, the molecular mechanism by which conformational changes in LOV2 are transmitted to the kinase domain remains unclear. Here, we investigated BL-induced structural changes of a minimum functional fragment of Arabidopsis phototropin1 composed of LOV2, the kinase domain, and a linker connecting the two domains using small-angle x-ray scattering (SAXS). The fragment existed as a dimer and displayed photoreversible SAXS changes reflected in the radii of gyration of 42.9 Å in the dark and 48.8 Å under BL irradiation. In the dark, the molecular shape reconstructed from the SAXS profiles appeared as two bean-shaped lobes in a twisted arrangement that was 170 Å long, 80 Å wide, and 50 Å thick. The molecular shape under BL became slightly elongated from that in the dark. By fitting the crystal structure of the LOV2 dimer and a homology model of the kinase domain to their inferred shapes, the BL-dependent change could be interpreted as the positional shift in the kinase domain relative to that of the LOV2 dimer. In addition, we found that lysine 475, a functionally important residue, in the N-terminal region of LOV2 plays a critical role in transmitting the structural changes in LOV2 to the kinase domain. The interface between the domains is critical for signaling, suitably changing the structure to activate the kinase in response to conformational changes in the adjoining LOV2. PMID:27484797

  9. Heme-independent Redox Sensing by the Heme-Nitric Oxide/Oxygen-binding Protein (H-NOX) from Vibrio cholerae.

    PubMed

    Mukhopadyay, Roma; Sudasinghe, Nilusha; Schaub, Tanner; Yukl, Erik T

    2016-08-19

    Heme nitric oxide/oxygen (H-NOX)-binding proteins act as nitric oxide (NO) sensors among various bacterial species. In several cases, they act to mediate communal behavior such as biofilm formation, quorum sensing, and motility by influencing the activity of downstream signaling proteins such as histidine kinases (HisKa) in a NO-dependent manner. An H-NOX/HisKa regulatory circuit was recently identified in Vibrio cholerae, and the H-NOX protein has been spectroscopically characterized. However, the influence of the H-NOX protein on HisKa autophosphorylation has not been evaluated. This process may be important for persistence and pathogenicity in this organism. Here, we have expressed and purified the V. cholerae HisKa (HnoK) and H-NOX in its heme-bound (holo) and heme-free (apo) forms. Autophosphorylation assays of HnoK in the presence of H-NOX show that the holoprotein in the Fe(II)-NO and Fe(III) forms is a potent inhibitor of HnoK. Activity of the Fe(III) form and aerobic instability of the Fe(II) form suggested that Vibrio cholerae H-NOX may act as a sensor of the redox state as well as NO. Remarkably, the apoprotein also showed robust HnoK inhibition that was dependent on the oxidation of cysteine residues to form disulfide bonds at a highly conserved zinc site. The importance of cysteine in this process was confirmed by mutagenesis, which also showed that holo Fe(III), but not Fe(II)-NO, H-NOX relied heavily upon cysteine for activation. These results highlight a heme-independent mechanism for activation of V. cholerae H-NOX that implicates this protein as a dual redox/NO sensor.

  10. Blue Light-excited Light-Oxygen-Voltage-sensing Domain 2 (LOV2) Triggers a Rearrangement of the Kinase Domain to Induce Phosphorylation Activity in Arabidopsis Phototropin1.

    PubMed

    Oide, Mao; Okajima, Koji; Kashojiya, Sachiko; Takayama, Yuki; Oroguchi, Tomotaka; Hikima, Takaaki; Yamamoto, Masaki; Nakasako, Masayoshi

    2016-09-16

    Phototropin1 is a blue light (BL) receptor in plants and shows BL-dependent kinase activation. The BL-excited light-oxygen-voltage-sensing domain 2 (LOV2) is primarily responsible for the activation of the kinase domain; however, the molecular mechanism by which conformational changes in LOV2 are transmitted to the kinase domain remains unclear. Here, we investigated BL-induced structural changes of a minimum functional fragment of Arabidopsis phototropin1 composed of LOV2, the kinase domain, and a linker connecting the two domains using small-angle x-ray scattering (SAXS). The fragment existed as a dimer and displayed photoreversible SAXS changes reflected in the radii of gyration of 42.9 Å in the dark and 48.8 Å under BL irradiation. In the dark, the molecular shape reconstructed from the SAXS profiles appeared as two bean-shaped lobes in a twisted arrangement that was 170 Å long, 80 Å wide, and 50 Å thick. The molecular shape under BL became slightly elongated from that in the dark. By fitting the crystal structure of the LOV2 dimer and a homology model of the kinase domain to their inferred shapes, the BL-dependent change could be interpreted as the positional shift in the kinase domain relative to that of the LOV2 dimer. In addition, we found that lysine 475, a functionally important residue, in the N-terminal region of LOV2 plays a critical role in transmitting the structural changes in LOV2 to the kinase domain. The interface between the domains is critical for signaling, suitably changing the structure to activate the kinase in response to conformational changes in the adjoining LOV2.

  11. Detection of reactive oxygen species (ROS) by the oxidant-sensing probe 2',7'-dichlorodihydrofluorescein diacetate in the cyanobacterium Anabaena variabilis PCC 7937

    SciTech Connect

    Rastogi, Rajesh P.; Singh, Shailendra P.; Haeder, Donat-P.; Sinha, Rajeshwar P.

    2010-07-02

    The generation of reactive oxygen species (ROS) under simulated solar radiation (UV-B: 0.30 Wm{sup -2}, UV-A: 25.70 Wm{sup -2} and PAR: 118.06 Wm{sup -2}) was studied in the cyanobacterium Anabaena variabilis PCC 7937 using the oxidant-sensing fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). DCFH-DA is a nonpolar dye, converted into the polar derivative DCFH by cellular esterases that are nonfluorescent but switched to highly fluorescent DCF when oxidized by intracellular ROS and other peroxides. The images obtained from the fluorescence microscope after 12 h of irradiation showed green fluorescence from cells covered with 295, 320 or 395 nm cut-off filters, indicating the generation of ROS in all treatments. However, the green/red fluorescence ratio obtained from fluorescence microscopic analysis showed the highest generation of ROS after UV-B radiation in comparison to PAR or UV-A radiation. Production of ROS was also measured by a spectrofluorophotometer and results obtained supported the results of fluorescence microscopy. Low levels of ROS were detected at the start (0 h) of the experiment showing that they are generated even during normal metabolism. This study also showed that UV-B radiation causes the fragmentation of the cyanobacterial filaments which could be due to the observed oxidative stress. This is the first report for the detection of intracellular ROS in a cyanobacterium by fluorescence microscopy using DCFH-DA and thereby suggesting the applicability of this method in the study of in vivo generation of ROS.

  12. The Skp1 protein from Toxoplasma is modified by a cytoplasmic prolyl 4-hydroxylase associated with oxygen sensing in the social amoeba Dictyostelium.

    PubMed

    Xu, Yuechi; Brown, Kevin M; Wang, Zhuo A; van der Wel, Hanke; Teygong, Crystal; Zhang, Dongmei; Blader, Ira J; West, Christopher M

    2012-07-20

    In diverse types of organisms, cellular hypoxic responses are mediated by prolyl 4-hydroxylases that use O(2) and α-ketoglutarate as substrates to hydroxylate conserved proline residues in target proteins. Whereas in metazoans these enzymes control the stability of the HIFα family of transcription factor subunits, the Dictyostelium enzyme (DdPhyA) contributes to O(2) regulation of development by a divergent mechanism involving hydroxylation and subsequent glycosylation of DdSkp1, an adaptor subunit in E3(SCF) ubiquitin ligases. Sequences related to DdPhyA, DdSkp1, and the glycosyltransferases that cap Skp1 hydroxyproline occur also in the genomes of Toxoplasma and other protists, suggesting that this O(2) sensing mechanism may be widespread. Here we show by disruption of the TgphyA locus that this enzyme is required for Skp1 glycosylation in Toxoplasma and that disrupted parasites grow slowly at physiological O(2) levels. Conservation of cellular function was tested by expression of TgPhyA in DdphyA-null cells. Simple gene replacement did not rescue Skp1 glycosylation, whereas overexpression not only corrected Skp1 modification but also restored the O(2) requirement to a level comparable to that of overexpressed DdPhyA. Bacterially expressed TgPhyA protein can prolyl hydroxylate both Toxoplasma and Dictyostelium Skp1s. Kinetic analyses showed that TgPhyA has similar properties to DdPhyA, including a superimposable dependence on the concentration of its co-substrate α-ketoglutarate. Remarkably, however, TgPhyA had a significantly higher apparent affinity for O(2). The findings suggest that Skp1 hydroxylation by PhyA is a conserved process among protists and that this biochemical pathway may indirectly sense O(2) by detecting the levels of O(2)-regulated metabolites such as α-ketoglutarate.

  13. Role of oxygen vacancies in magnetic properties of LaAlO{sub 3}/SrTiO{sub 3} interface

    SciTech Connect

    Mohanta, N.; Taraphder, A.

    2014-04-24

    The interface of two band-insulators SrTiO{sub 3} and LaAlO{sub 3} exhibits a highly conducting two-dimensional electron gas which shows low-temperature superconductivity, ferromagnetism and many other novel properties. Several studies reveal that the oxygen vacancies at the interface have strong influence on the electronic and magnetic properties of the interface electrons. Here, we develop an insight into the effects of oxygen vacancies on the magnetic properties of the system; the oxygen vacancies help in establishing ferromagnetism which competes with superconductivity at low temperatures. Simulated Monte-Carlo annealing suggests an ordering of the oxygen vacant sites and sheds light on the experimental observation of the quenching of magnetic moment on annealing. A possible explanation for the coexistence of superconductivity and ferromagnetism is also discussed.

  14. Cold Oxygen Plasma Treatments for the Improvement of the Physicochemical and Biodegradable Properties of Polylactic Acid Films for Food Packaging.

    PubMed

    Song, Ah Young; Oh, Yoon Ah; Roh, Si Hyeon; Kim, Ji Hyeon; Min, Sea C

    2016-01-01

    The effects of cold plasma (CP) treatment on the physicochemical and biodegradable properties of polylactic acid (PLA) films were studied. The PLA films were exposed to CP for 40 min at 900 W and 667 Pa using oxygen as the plasma-forming gas. The tensile, optical, and dynamic mechanical thermal properties, surface morphology, printability, water contact angle, chemical structure, weight change, and biodegradability properties of the films were evaluated during storage for up to 56 d. The tensile and optical properties of the PLA films were not significantly affected by CP treatment (CPT; P > 0.05). The surface roughness and water contact angle of PLA films increased by CPT and further increased during storage for 56 d. The printability of the PLA films increased following CPT and remained stable throughout the storage period. CP-induced hydrophilicity was also sustained during the storage period. The PLA films lost 1.9% of their weight after CPT, but recovered 99.5% of this loss after 14 d in storage. Photodegradation, thermal, and microbial biodegradable properties of the films were significantly improved by CPT (P < 0.05). Accelerated biodegradation of CP-treated PLA sachets with and without cheese was observed in compost. These results demonstrate the potential of CPT for modifying the stiffness, water contact angle, and chemical structure of PLA films and improving the printability and biodegradability of the films for food packaging.

  15. Oxygen vacancy formation, crystal structures, and magnetic properties of three SrMnO3-δ films

    NASA Astrophysics Data System (ADS)

    Wang, F.; Zhang, Y. Q.; Bai, Y.; Liu, W.; Zhang, H. R.; Wang, W. Y.; Li, S. K.; Ma, S.; Zhao, X. G.; Sun, J. R.; Wang, Z. H.; Wang, Z. J.; Zhang, Z. D.

    2016-08-01

    The crystal structures and magnetic properties of the 40 nm brownmillerite SrMnO2.5 film, perovskite SrMnO3-δ film, and mixed-phase film have been systematically investigated. The features of the oxygen vacancy ordering superstructure in the brownmillerite SrMnO2.5 film are observed from HRSTEM as follows: the dark stripes with a periodicity of four (110) planes of the cubic perovskite appearing at an angle of 45° with the substrate-film interface and extra reflection spots in fast Fourier transformation patterns along the (001) plane. When annealing the brownmillerite SrMnO2.5 film under higher oxygen pressure, the top portion undergoes structure transition into perovskite SrMnO3-δ as seen in the mixed-phase film consisting of the perovskite SrMnO3-δ phase dominating at the top part and the brownmillerite SrMnO2.5 phase dominating at the bottom part. The magnetic properties and Mn valences of the brownmillerite SrMnO2.5 film indicate that this film, similar to the bulk, is antiferromagnetic with TN at 375 K. However, the strained tetragonal perovskite SrMnO3-δ film exhibits ferromagnetic behavior with Curie temperature at 75 K and a saturation magnetization of 2.5μB/Mn at 2 K. Moreover, the top perovskite SrMnO3-δ phase of the mixed-phase film also exhibits ferromagnetic behavior evidenced by the existence of the exchange bias. We propose that the ferromagnetic properties in both the perovskite SrMnO3-δ film and the top perovskite SrMnO3-δ phase in the mixed-phase film originate from Mn3+-Mn4+ double exchange coupling. However, the formation of Mn3+ differs for the two samples in that it is caused by oxygen vacancies in the former and the distribution of oxygen content across the film during annealing in the latter.

  16. Preparation and spectroscopic properties of multiluminophore luminescent oxygen and temperature sensor films.

    PubMed

    Köse, Muhammet Erkan; Carroll, Bruce F; Schanze, Kirk S

    2005-09-27

    A new luminescent oxygen and temperature sensor has been developed that utilizes two luminescent dyes, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin platinum(II) (PtTFPP, the oxygen sensor) and tris(1,10-phenanthroline)ruthenium(II) dichloride (Ruphen, the temperature sensor). The two dyes are dispersed in an oxygen-permeable polymer binder consisting of a copolymer of 4-tert-butylstyrene (tBS) and 2,2,2-trifluoroethyl methacrylate (p-tBS-co-TFEM). To alleviate energy transfer and other quenching interactions between the two luminescent dyes in the p-tBS-co-TFEM binder, the Ruphen temperature sensor is encapsulated in polyacrylonitrile (PAN) polymer nanospheres that are prepared by coprecipitation of PAN and Ruphen from N,N-dimethylformamide solution. The temperature and air-pressure response of the emission from the sensor film is fully characterized by using emission spectroscopy. The emission from the two luminescent dyes is spectrally well-separated. The intensity of the Ruphen emission varies strongly with temperature (approximately 1.4% degrees C(-1)), whereas the intensity of the PtTFPP emission varies with temperature and air pressure. The two-dye luminescent coating is useful as a pressure-sensitive paint (PSP), where the emission from the Ruphen temperature sensor is used to correct for the temperature dependence of the pressure response of the PtTFPP sensor. To demonstrate the PSP application, a coupon coated with the sensor was imaged using a CCD camera, and the CCD images were analyzed by intensity ratio methods. Spectroscopic studies were also carried out on a sensor that contains three dyes in order to demonstrate the feasibility of including an intensity reference dye along with the temperature and pressure dyes into the sensor.

  17. Spatiotemporal Variability of Soil Hydraulic Properties from Field Data and Remote Sensing in the Walnut Gulch Experimental Watershed

    NASA Astrophysics Data System (ADS)

    Becker, R.; Gebremichael, M.; Marker, M.

    2015-12-01

    Soil moisture is one of the main input variables for hydrological models. However due to the high spatial and temporal variability of soil properties it is often difficult to obtain accurate soil information at the required resolution. The new satellite SMAP promises to deliver soil moisture information at higher resolutions and could therefore improve the results of hydrological models. Nevertheless it still has to be investigated how precisely the SMAP soil moisture data can be used to delineate rainfall-runoff generation processes and if SMAP imagery can significantly improve the results of surface runoff models. Important parameters to understand the spatiotemporal distribution of soil humidity are infiltration and hydraulic conductivities apart from soil texture and macrostructure. During the SMAPVEX15-field campaign data on hydraulic conductivity and infiltration rates is collected in the Walnut Gulch Experimental Watershed (WGEW) in Southeastern Arizona in order to analyze the spatiotemporal variability of soil hydraulic properties. A Compact Constant Head Permeameter is used for in situ measurements of saturated hydraulic conductivity within the soil layers and a Hood Infiltrometer is used to determine infiltration rates at the undisturbed soil surface. Sampling sites were adjacent to the USDA-ARS meteorological and soil moisture measuring sites in the WGEW to take advantage of the long-term database of soil and climate data. Furthermore a sample plot of 3x3km was selected, where the spatial variability of soil hydraulic properties within a SMAP footprint was investigated. The results of the ground measurement based analysis are then compared with the remote sensing data derived from SMAP and aircraft-based microwave data to determine how well these spatiotemporal variations are captured by the remotely sensed data with the final goal of evaluating the use of future satellite soil moisture products for the improvement of rainfall runoff models. The results

  18. Evaluate humidity sensing properties of novel TiO{sub 2}–WO{sub 3} composite material

    SciTech Connect

    Lin, Wang-De; Lai, De-Sheng; Chen, Min-Hung; Wu, Ren-Jang; Chen, Fu-Chou

    2013-10-15

    Graphical abstract: TiO{sub 2}–WO{sub 3} (1:1) showed better humidity sensing properties than others within the range of 12–90% relative humidity (RH), the response and recovery time were about 20 s and 160 s, respectively. Compared to the previous studies, the prepared sensor exhibits higher sensitivity (S = 451) and the low hysteresis value was around 0.13% at 32% RH. - Highlights: • Novel TiO{sub 2}–WO{sub 3} composite material was prepared for humidity sensor. • The sensor exhibits higher sensitivity (S = 451). • Low hysteresis value was around 0.13% at 32% RH. - Abstract: A novel TiO{sub 2}–WO{sub 3} composite material was prepared using a different proportion of TiO{sub 2} and WO{sub 3} to that investigated in previous studies. The obtained mesoporous material was characterized using X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, energy dispersive X-ray spectroscopy, and N{sub 2} adsorption-desorption techniques. The humidity-sensing properties were measured using an inductance, capacitance and resistance analyzer. The results demonstrated that the TiO{sub 2}–WO{sub 3} sample with a ratio of 1:1 showed better humidity sensing properties. Compared to previous studies, the prepared sensor exhibited higher sensitivity (S = 451) and the lower hysteresis value was around 0.13% at 32% RH. Complex impedance analysis indicated that the enhanced humidity sensitivity was probably due to spherical Brunauer–Emmett–Teller surface area and the hetero-junction between TiO{sub 2}–WO{sub 3} thin films, while the impedance varied about three orders of magnitude. Our results demonstrated the potential application of TiO{sub 2}–WO{sub 3} composite for fabricating high performance humidity sensors.

  19. Thermodynamic properties of diosgenin determined by oxygen-bomb calorimetry and DSC

    NASA Astrophysics Data System (ADS)

    Zhao, Ming-Rui; Wang, Hong-Jie; Wang, Shu-Yu; Yue, Xiao-Xin

    2014-12-01

    The combustion enthalpy of diosgenin was determined by oxygen-bomb calorimetry. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be -16098.68 and -528.52 kJ mol-1, respectively. Fusion enthalpy and melting temperature for diosgenin were also measured to be -34.43 kJ mol-1 and 212.33°C, respectively, according to differential scanning calorimetry (DSC) data. These studies can provide useful thermodynamic data for this compound.

  20. [Fat-stabilizing properties of phosphatides. 1. Response of selected phosphatides to oxygen].

    PubMed

    Linow, F; Mieth, G

    1975-01-01

    The authors investigated the formation of hydroperoxides and carbonyl compounds in raw phosphatides from soya-beans and rape-seeds during storage at 50 degrees C. According to the results obtained, the chemical deterioration of the raw phosphatides depends upon their intrinsic contents of prooxidative and antioxidative compounds and upon the consituent fatty acids. Purified preparations are considerably more stable as comparable fatty acid methyl esters; and phosphatides containing nitrogenous bases are less sensitive to atmospheric oxygen than their nitrogen-free analogues. PMID:1171372

  1. The effect of 75% glycerol on the oxygen binding properties of carp hemoglobin.

    PubMed

    Kwiatkowski, L D; Noble, R W

    1993-09-30

    At pH 6 in the presence of inositol hexaphosphate, IHP, conditions where ligand-saturated carp hemoglobin is already in the low affinity T state, the addition of glycerol has little effect on affinity and ligand binding remains noncooperative. At all other pH values examined, with and without IHP, the effect of glycerol is to lower oxygen affinity possibly by shifting the equilibrium between the T state and the high affinity R state in the direction of the T state. Although glycerol does not appear to have an appreciable effect on the T state itself, a small effect on the R state cannot be excluded by our data.

  2. Physical Properties of Silver Oxide Thin Film Prepared by DC Magnetron Sputtering: Effect of Oxygen Partial Pressure During Growth

    NASA Astrophysics Data System (ADS)

    Entezar Mehdi, Hamid; Hantehzadeh, M. R.; Valedbagi, Sh.

    2013-02-01

    In this paper the physical properties of silver oxide thin film have been prepared on BK7 substrate at room temperature by reactive DC magnetron sputtering technique using pure silver metal target by varying oxygen partial pressure during growth at reported. The reactive sputter gas was a mixture of Ar (99.999%) and N2 (99.999%) with the different ratio Ar and N2 by volume at the constant pressure of the growth chamber. The X-ray diffraction measurements showed that by increasing O2 volume during the Growth, change in crystalline structure will occur. The Atomic Force Microscope images shown by increasing O2 volume, the RMS roughness decreasing consistently. The thickness of the thin films decreases (from 353 to 230 nm) with increasing oxygen partial pressure in chamber. The reflectivity of thin films was investigated with a spectrophotometer system, and the surface reflectivity measurements indicate that by increasing O2 volume growth, the optical properties of the films changes.

  3. Tuning the electrical property via defect engineering of single layer MoS2 by oxygen plasma.

    PubMed

    Islam, Muhammad R; Kang, Narae; Bhanu, Udai; Paudel, Hari P; Erementchouk, Mikhail; Tetard, Laurene; Leuenberger, Michael N; Khondaker, Saiful I

    2014-09-01

    We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.

  4. Structural and Electrocatalytic Properties of PtIrCo/C Catalysts for Oxygen Reduction Reaction

    SciTech Connect

    Loukrakpam, Rameshwori; Wanjala, Bridgid N.; Yin, Jun; Fang, Bin; Luo, Jin; Shao, Minhua; Protsailo, Lesia; Kawamura, Tetsuo; Chen, Yongsheng; Petkov, Valeri; Zhong, Chuan-Jian

    2015-10-15

    This paper describes the results of an investigation of the synthesis of PtIrCo nanoparticles (2-3 nm) for electrocatalytic oxygen reduction reaction. The carbon-supported PtIrCo catalysts (PtIrCo/C) were thermally treated at temperatures ranging from 400 to 900 C. The size, composition, and atomic-scale structures of the PtIrCo/C catalysts were characterized for establishing their correlation with the electrocatalytic activity toward oxygen reduction reaction. The specific activity was found to increase by a factor of 3-5 for the PtIrCo/C catalysts in comparison with Pt/C catalysts. A correlation was identified between the specific activity and the nanoparticle's fcc-type lattice parameter. The specific activity increases whereas the fcc-type lattice parameter decreases with the thermal treatment temperature. This correlation was further substantiated by analyzing the interatomic spatial parameters in the trimetallic nanoparticles based on X-ray absorption fine structure spectroscopic and high-energy XRD experiments. Implications of these findings, along with the durability of the catalysts, to the design of active electrocatalysts were also discussed.

  5. Oxygen emission line properties from analysis of MAVEN-IUVS Echellograms of the Martian atmosphere

    NASA Astrophysics Data System (ADS)

    Mayyasi, Majd A.; Clarke, John T.; Stewart, Ian; McClintock, William; Schneider, Nicholas M.; Jakosky, Bruce; IUVS Team

    2016-10-01

    The high resolution echelle mode of the Mars Atmosphere and Volatile Evolution (MAVEN) mission Imaging Ultraviolet Spectrograph (IUVS) instrument has been used to spectrally image the sunlit limb of Mars during the spacecraft periapse orbital segments. When multiple images are co-added over a few hours, there are detectable spectral emission features that have been identified to originate from atomic and molecular neutral species such as H, D, N, O, CO as well as from C+ ions. The echelle detector has a localized spectral resolution of ~0.008 Angstrom and is therefore capable of spectrally resolving the oxygen resonant triplet (130.217, 130.486 and 130.603 nm) and forbidden doublet (135.560 and 135.851 nm) emission lines. The brightness of each of these emission lines has been determined and will be compared with detected brightnesses of other species. The emission line integrated brightness ratios are being analyzed for insights into the abundance, excitation, and variability of oxygen in the martian atmosphere.

  6. Fabrication and NO2 gas-sensing properties of reduced graphene oxide/WO3 nanocomposite films.

    PubMed

    Su, Pi-Guey; Peng, Shih-Liang

    2015-01-01

    One-pot polyol process was combined with the metal organic decomposition (MOD) method to fabricate a room-temperature NO2 gas sensor based on tungsten oxide and reduced graphene oxide (RGO/WO3) nanocomposite films. Fourier Transform infrared spectrometer (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the microstructure and morphology of the fabricated films. The electrical and NO2 gas-sensing properties of WO3 to which various amounts of RGO were added were measured in detail as a function of concentration of NO2 gas at room temperature, to elucidate the contribution of RGO to the NO2 gas-sensing capacity. The NO2 gas-sensing mechanism of the RGO/WO3 nanocomposite films were explained by considering their composition and microstructures. The sensor that was based on a nanocomposite film of RGO/WO3 exhibited a strong response to low concentrations of NO2 gas at room temperature, satisfactory linearity and favorable long-term stability. PMID:25476324

  7. Fabrication and NO2 gas-sensing properties of reduced graphene oxide/WO3 nanocomposite films.

    PubMed

    Su, Pi-Guey; Peng, Shih-Liang

    2015-01-01

    One-pot polyol process was combined with the metal organic decomposition (MOD) method to fabricate a room-temperature NO2 gas sensor based on tungsten oxide and reduced graphene oxide (RGO/WO3) nanocomposite films. Fourier Transform infrared spectrometer (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the microstructure and morphology of the fabricated films. The electrical and NO2 gas-sensing properties of WO3 to which various amounts of RGO were added were measured in detail as a function of concentration of NO2 gas at room temperature, to elucidate the contribution of RGO to the NO2 gas-sensing capacity. The NO2 gas-sensing mechanism of the RGO/WO3 nanocomposite films were explained by considering their composition and microstructures. The sensor that was based on a nanocomposite film of RGO/WO3 exhibited a strong response to low concentrations of NO2 gas at room temperature, satisfactory linearity and favorable long-term stability.

  8. Hopc: a Novel Similarity Metric Based on Geometric Structural Properties for Multi-Modal Remote Sensing Image Matching

    NASA Astrophysics Data System (ADS)

    Ye, Yuanxin; Shen, Li

    2016-06-01

    Automatic matching of multi-modal remote sensing images (e.g., optical, LiDAR, SAR and maps) remains a challenging task in remote sensing image analysis due to significant non-linear radiometric differences between these images. This paper addresses this problem and proposes a novel similarity metric for multi-modal matching using geometric structural properties of images. We first extend the phase congruency model with illumination and contrast invariance, and then use the extended model to build a dense descriptor called the Histogram of Orientated Phase Congruency (HOPC) that captures geometric structure or shape features of images. Finally, HOPC is integrated as the similarity metric to detect tie-points between images by designing a fast template matching scheme. This novel metric aims to represent geometric structural similarities between multi-modal remote sensing datasets and is robust against significant non-linear radiometric changes. HOPC has been evaluated with a variety of multi-modal images including optical, LiDAR, SAR and map data. Experimental results show its superiority to the recent state-of-the-art similarity metrics (e.g., NCC, MI, etc.), and demonstrate its improved matching performance.

  9. Synthesis of Highly Stable Silver-Loaded Vertical ZnO Nanowires Array and its Acetylene Sensing Properties

    NASA Astrophysics Data System (ADS)

    Uddin, Abu Sadat Mohammad Iftekhar; Chung, Gwiy-Sang

    2016-09-01

    A silver-loaded one-dimensional (1D) vertical ZnO nanowires (NWs) array synthesized by a facile seed mediated hydrothermal-RF magnetron sputtering method has been investigated for the fabrication of a highly stable and reproducible acetylene (C2H2) gas sensor. Successful immobilization of silver nanoparticles (NPs) as a sensitizer on the ZnO NWs array significantly enhanced the C2H2 sensing properties and showed a stable sensing performance. The grown structure exhibited high response magnitude (30.8 at 1000ppm), short response time (43s) and excellent selectivity at 220∘C. The enhanced performance can probably be accounted for the effect of combining the highly orientated ZnO NWs and catalytically active silver-based network. The superior sensing features toward C2H2 along with broad detection range (1-1000ppm), outstanding stability and excellent reproducibility indicate that the sensor is a promising candidate for practical applications.

  10. Impact of oxygen dissolved at bottling and transmitted through closures on the composition and sensory properties of a Sauvignon Blanc wine during bottle storage.

    PubMed

    Lopes, Paulo; Silva, Maria A; Pons, Alexandre; Tominaga, Takatoshi; Lavigne, Valérie; Saucier, Cédric; Darriet, Philippe; Teissedre, Pierre-Louis; Dubourdieu, Denis

    2009-11-11

    This work outlines the results from an investigation to determine the effect of the oxygen dissolved at bottling and the specific oxygen barrier properties of commercially available closures on the composition, color and sensory properties of a Bordeaux Sauvignon Blanc wine during two years of storage. The importance of oxygen for wine development after bottling was also assessed using an airtight bottle ampule. Wines were assessed for the antioxidants (SO(2) and ascorbic acid), varietal thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol), hydrogen sulfide and sotolon content, and color throughout 24 months of storage. In addition, the aroma and palate properties of wines were also assessed. The combination of oxygen dissolved at bottling and the oxygen transferred through closures has a significant effect on Sauvignon Blanc development after bottling. Wines highly exposed to oxygen at bottling and those sealed with a synthetic, Nomacorc classic closure, highly permeable to oxygen, were relatively oxidized in aroma, brown in color, and low in antioxidants and volatile compounds compared to wines sealed with other closures. Conversely, wines sealed under more airtight conditions, bottle ampule and screw cap Saran-tin, have the slowest rate of browning, and displayed the greatest contents of antioxidants and varietal thiols, but also high levels of H(2)S, which were responsible for the reduced dominating character found in these wines, while wines sealed with cork stoppers and screw cap Saranex presented negligible reduced and oxidized characters.

  11. Hydrothermal synthesis of h-MoO3 microrods and their gas sensing properties to ethanol

    NASA Astrophysics Data System (ADS)

    Liu, Yueli; Yang, Shuang; Lu, Yu; Podval'naya, Natal'ya V.; Chen, Wen; Zakharova, Galina S.

    2015-12-01

    Hexagonal molybdenum trioxide (h-MoO3) microrods were successfully synthesized via a novel and facile hydrothermal route from peroxomolybdate solution with the presence of NH4Cl as the mineralizer. A variety of the techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry combined with the thermal gravimetric analysis (DSC-TG) were used to characterize the product. The gas sensing test indicates that h-MoO3 microrods have a good response to 5-500 ppm ethanol in the range of 273-380 °C, and the optimum operating temperature is 332 °C with a high sensitivity of 8.24 to 500 ppm ethanol. Moreover, it also has a good selectivity toward ethanol gas if compared with other gases, such as ammonia, methanol and toluene. The sensing mechanism of h-MoO3 microrods to ethanol was also discussed.

  12. Au sensitized ZnO nanorods for enhanced liquefied petroleum gas sensing properties

    NASA Astrophysics Data System (ADS)

    Nakate, U. T.; Bulakhe, R. N.; Lokhande, C. D.; Kale, S. N.

    2016-05-01

    The zinc oxide (ZnO) nanorods have grown on glass substrate by spray pyrolysis deposition (SPD) method using zinc acetate solution. The phase formation, surface morphology and elemental composition of ZnO films have been investigated using X-ray diffraction, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and energy dispersive X-ray (EDX) techniques. The liquefied petroleum gas (LPG) sensing response was remarkably improved by sensitization of gold (Au) surface noble metal on ZnO nanorods film. Maximum LPG response of 21% was observed for 1040 ppm of LPG, for pure ZnO nanorods sample. After Au sensitization on ZnO nanorods film sample, the LPG response greatly improved up to 48% at operating temperature 623 K. The improved LPG response is attributed Au sensitization with spill-over mechanism. Proposed model for LPG sensing mechanism discussed.

  13. Effects of Surface and Morphological Properties of Zeolite on Impedance Spectroscopy-Based Sensing Performance

    PubMed Central

    Zhang, Jianwei; Li, Xiaogan; White, Jeremy; Dutta, Prabir K.

    2012-01-01

    Measurement by impedance spectroscopy of the changes in intrazeolitic cation motion of pressed pellets of zeolite particles upon adsorption of dimethylmethylphosphonate (DMMP) provides a strategy for sensing DMMP, a commonly used simulant for highly toxic organophosphate nerve agents. In this work, two strategies for improving the impedance spectroscopy based sensing of DMMP on zeolites were investigated. The first one is the use of cerium oxide (CeO2) coated on the zeolite surface to neutralize acidic groups that may cause the decomposition of DMMP, and results in better sensor recovery. The second strategy was to explore the use of zeolite Y membrane. Compared to pressed pellets, the membranes have connected supercages of much longer length scales. The zeolite membranes resulted in higher sensitivity to DMMP, but recovery of the device was significantly slower as compared to pressed zeolite pellets. PMID:23201996

  14. Au clustering formation by implantation in silica: optical, magnetic and sensing properties

    NASA Astrophysics Data System (ADS)

    Mazzoldi, P.; Mattei, G.; Battaglin, G.; Bello, V.; Cesca, T.; Carturan, S.; Fernandez, C. de Julian; Maurizio, C.; Pellegrini, G.; Scian, C.

    2013-06-01

    This paper gives a review, within the contributions presented at the REM5 Conference, of the activity developed in the last years by the research Group of Nanotechnologies of the Department of Physics and Astronomy, Padova University, in cooperation with Venice and Florence Universities, concerning the chemical and physical aspects of Au nanoparticles, formed by ion implantation in the silica matrix, applied in three different scientific areas: magnetism, optics and sensing.

  15. Synthesis of hierarchical SnO2 nanoflowers with enhanced acetic acid gas sensing properties

    NASA Astrophysics Data System (ADS)

    Jin, W. X.; Ma, S. Y.; Tie, Z. Z.; Li, W. Q.; Luo, J.; Cheng, L.; Xu, X. L.; Wang, T. T.; Jiang, X. H.; Mao, Y. Z.

    2015-10-01

    Different morphologies hierarchical flower-like tin dioxide (SnO2) nanostructures were fabricated by changing the volume ratio of glycol and de-ionized water (Vg:Vw = 0, 1:2, 1:1 and 2:1) under a template-free and low-cost hydrothermal method and subsequent calcinations. The architectures, morphologies and gas sensing performances of the products were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and gas-sensing measurement device. It can be observed that all the nanoflowers were composed of two-dimensional (2D) nanosheets, and the thickness of nanosheets is only about 9 nm when Vg:Vw = 1:1. The sensor based on the product of Vg:Vw = 1:1 exhibited excellent gas sensing performance toward 500 ppm acetic acid at 260 °C, and the response value of this sensor was about 153.6, which was above 7.5 times higher than that of ammonia (about 20.3). In addition, the 3D flower-like SnO2 nanostructures exhibited not only high response and selectivity to ppm level acetone, but also fast response and recovery time within 10 s, demonstrating it can be used as a potential candidate for detecting acetic acid. Finally, the possible formation mechanism was proposed, too.

  16. Synthesis, characterization and gas sensing properties of novel homo and hetero dinuclear ball-type phthalocyanines.

    PubMed

    Kakı, Esra; Altındal, Ahmet; Salih, Bekir; Bekaroğlu, Özer

    2015-05-01

    New ball-type homodinuclear Co(ii)-Co(ii) phthalocyanine () and ball-type heterodinuclear Co(ii)-Fe(ii) phthalocyanine () were synthesized from the corresponding [2,10,16,24-tetrakis{4,4'-cyclohexylidenebis(2-cyclohexyphenoxyphthalonitrile)}phthalocyaninatocobalt(ii)] (). The novel compounds have been characterized by elemental analysis, IR, UV-Vis and MALDI-TOF mass spectroscopy. Gas sensing capability of the spin coated film of and were studied using amperometric technique at various temperatures. For a better understanding of the interaction of and films with organic compounds, two different groups of compounds (aromatics and alcohols) were selected as test analytes. It was observed that the operating temperature had a considerable effect on the gas sensing performance of the sensors investigated. The experimental results show that film offers a promising perspective as a sensing material for the detection of relatively low aromatic vapours even at room temperature. This suggests that aromatics might be distinguished from alcohols. The obtained data were analysed using two different adsorption kinetic models: the pseudo first order equation and Elovich equation to determine the best fit equation for the adsorption of toluene vapor onto and films. The first-order equation was the best of the various kinetic models studied to describe the adsorption kinetic of toluene on Pc films at higher concentrations, as evidenced by the highest correlation coefficients. In addition, it was observed that Elovich equation generates a straight line that best fit to the data of adsorption of lower concentrations of toluene.

  17. Oxygen deficiency induced deterioration in microstructure and magnetic properties at Y3Fe5O12/Pt interface

    NASA Astrophysics Data System (ADS)

    Song, Dongsheng; Ma, Li; Zhou, Shiming; Zhu, Jing

    2015-07-01

    Transport efficiency of pure spin current across the ferromagnetic films adjacent with a nonmagnetic metal is strongly dependent on the spin mixing conductance, which is very sensitive to atomic-level interface conditions. Here, by the means of advanced electron microscopy techniques, atomic structure, electronic structure, and magnetic properties at Y3Fe5O12 (YIG)/Pt interface are detailed characterized to correlate the microstructure and magnetic properties with interfacial transport properties. It is found that the order-disorder structure transformation at the interface is accompanied with oxygen deficiency, thus the reduced iron valence and the break of magnetic atom-O-magnetic atom bridges, which is responsible for superexchange interaction and magnetic order. It is also found that the magnetic moment of interfacial iron ions is decreased. The disorder interfacial layer with suppressed magnetism finally contributes to the declined spin transport efficiency. Our results provide the knowledge to control and manipulate the interfacial structure and properties in order to obtain higher spin transport efficiency.

  18. Investigations on the effect of gamma-ray irradiation on the gas sensing properties of SnO2 nanoparticles.

    PubMed

    Lavanya, N; Sekar, C; Anithaa, A C; Sudhan, N; Asokan, K; Bonavita, A; Leonardi, S G; Neri, G

    2016-09-23

    In recent years, SnO2 nanoparticles (NPs) have been subjected to various modifications in order to improve their performance in sensing and other applications. Here, we report the synthesis of SnO2 NPs by microwave irradiation, and subsequent exposure to gamma (γ) radiation at different doses (0-150 kGy) to induce desirable physico-chemical properties. The irradiated samples were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM and HR-TEM), and photoluminescence (PL) to evaluate the effect of γ-ray irradiation on their morphology and microstructure. The results revealed that the bulk crystal structure remained unchanged after irradiation, while the existence of defects and a damaged over-layer have been confirmed by PL and HR-TEM respectively. The influence of γ-irradiation on the electrical and CO sensing characteristics was also investigated in the temperature range between 150 and 400 °C. γ-irradiated SnO2 NP based resistive sensors showed better CO sensing characteristics (i.e. higher response and lower working temperature) compared to non-irradiated SnO2. Upon optimizing the γ-ray dose irradiation level and working temperature, a ten-fold enhancement in the response to CO has been achieved (R/R 0 = 12 to 50 ppm of CO in air) in 50 kGy irradiated SnO2 NP based sensors operating at 150 °C. A possible mechanism for the enhanced sensing performance of γ-irradiated SnO2 NPs has been proposed. PMID:27532479

  19. Investigations on the effect of gamma-ray irradiation on the gas sensing properties of SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Lavanya, N.; Sekar, C.; Anithaa, A. C.; Sudhan, N.; Asokan, K.; Bonavita, A.; Leonardi, S. G.; Neri, G.

    2016-09-01

    In recent years, SnO2 nanoparticles (NPs) have been subjected to various modifications in order to improve their performance in sensing and other applications. Here, we report the synthesis of SnO2 NPs by microwave irradiation, and subsequent exposure to gamma (γ) radiation at different doses (0–150 kGy) to induce desirable physico-chemical properties. The irradiated samples were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM and HR-TEM), and photoluminescence (PL) to evaluate the effect of γ-ray irradiation on their morphology and microstructure. The results revealed that the bulk crystal structure remained unchanged after irradiation, while the existence of defects and a damaged over-layer have been confirmed by PL and HR-TEM respectively. The influence of γ-irradiation on the electrical and CO sensing characteristics was also investigated in the temperature range between 150 and 400 °C. γ-irradiated SnO2 NP based resistive sensors showed better CO sensing characteristics (i.e. higher response and lower working temperature) compared to non-irradiated SnO2. Upon optimizing the γ-ray dose irradiation level and working temperature, a ten-fold enhancement in the response to CO has been achieved (R/R 0 = 12 to 50 ppm of CO in air) in 50 kGy irradiated SnO2 NP based sensors operating at 150 °C. A possible mechanism for the enhanced sensing performance of γ-irradiated SnO2 NPs has been proposed.

  20. Investigations on the effect of gamma-ray irradiation on the gas sensing properties of SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Lavanya, N.; Sekar, C.; Anithaa, A. C.; Sudhan, N.; Asokan, K.; Bonavita, A.; Leonardi, S. G.; Neri, G.

    2016-09-01

    In recent years, SnO2 nanoparticles (NPs) have been subjected to various modifications in order to improve their performance in sensing and other applications. Here, we report the synthesis of SnO2 NPs by microwave irradiation, and subsequent exposure to gamma (γ) radiation at different doses (0-150 kGy) to induce desirable physico-chemical properties. The irradiated samples were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM and HR-TEM), and photoluminescence (PL) to evaluate the effect of γ-ray irradiation on their morphology and microstructure. The results revealed that the bulk crystal structure remained unchanged after irradiation, while the existence of defects and a damaged over-layer have been confirmed by PL and HR-TEM respectively. The influence of γ-irradiation on the electrical and CO sensing characteristics was also investigated in the temperature range between 150 and 400 °C. γ-irradiated SnO2 NP based resistive sensors showed better CO sensing characteristics (i.e. higher response and lower working temperature) compared to non-irradiated SnO2. Upon optimizing the γ-ray dose irradiation level and working temperature, a ten-fold enhancement in the response to CO has been achieved (R/R 0 = 12 to 50 ppm of CO in air) in 50 kGy irradiated SnO2 NP based sensors operating at 150 °C. A possible mechanism for the enhanced sensing performance of γ-irradiated SnO2 NPs has been proposed.

  1. Auxiliary field diffusion Monte Carlo calculation of properties of oxygen isotopes

    SciTech Connect

    Gandolfi, S.; Pederiva, F.

    2006-04-15

    The ground state and some low-lying excited states of oxygen isotopes {sup 18}O-{sup 22}O were simulated by means of auxiliary field diffusion Monte Carlo techniques. We performed the calculations by replacing the {sup 16}O core with a mean-field self-consistent potential we computed by using Skyrme interactions. The external neutrons were included in the Monte Carlo calculations, building a wave function with the orbitals computed in the self-consistent external potential. The shell considered was the 1D{sub 5/2}. The NN interactions employed included tensor, spin-orbit, and three-body forces. While absolute binding energies are too deep compared with those of experimental data, the differences between the energies for nearly all isotopes and excitations are in very good agreement with the experiments. The exception is the 4{sup +} state of the {sup 18}O isotope, which shows a larger discrepancy.

  2. Optoelectronics and formaldehyde sensing properties of tin-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Prajapati, C. S.; Kushwaha, Ajay; Sahay, P. P.

    2013-11-01

    Sn-doped ZnO thin films were deposited on clean glass substrates using the chemical spray pyrolysis technique. XRD analyses confirm stable ZnO hexagonal wurtzite structure of the films with crystallite size in the range of 20-28 nm. The surface roughness of the films increases on Sn doping, which favors to higher adsorption of oxygen species on the film surface, resulting in higher gas response. Optical studies reveal that the band gap decreases on Sn doping. All the films show near band edge emission, and on Sn doping the luminescence peak intensity has been found to increase. Photocurrent in the 1.5 at.% doped film enhances about three times to that observed in the undoped ZnO film. Among all the films examined, the 1.5 at.% Sn-doped film exhibits the maximum response (˜94.5 %) at the operating temperature of 275 °C for 100 ppm concentration of formaldehyde, which is much higher than the response (˜35 %) in the undoped film. The gas response of the film is attributed to the chemisorption of oxygen on the film surface and the subsequent reaction between the adsorbed oxygen species and the formaldehyde molecules.

  3. Synthesis, Charaterization and Electrochemical Sensing Properties of PANI—Cobalt doped α-Fe2O3 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Suresh, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2011-07-01

    The PANI-NSA/(4%Co)α-Fe2O3 composite was prepared by a template free method in the presence of β-Napthalene sulphonic acid (β-NSA) as a dopant for PANI. The FTIR spectroscopy was used to confirm the formation of the composite. The structural property of the composite was characterized by XRD. The morphological property of the composite was characterized by SEM. The SEM image of composite showed that the particles are homogenous. The electrochemical sensing ability of ascorbic acid (AA) by PANI-NSA and composite modified GCE exhibited higher anodic current response than the bare GCE. Compared with the bare and PANI-NSA modified GCE, PANI-NSA/(4%Co)α-Fe2O3 composite modified GCE showed larger current response with shift towards less positive potential.

  4. Influence of CHx thickness layer on the sensing properties of CHx/PS/Si structure against CO2 gas

    NASA Astrophysics Data System (ADS)

    Zouadi, N.; Belhousse, S.; Bradaî, D.; Cheraga, H.; Ouchabane, M.; Keffous, A.; Sam, S.; Gabouze, N.

    2013-11-01

    In this work, we report a study on the influence of hydrocarbon groups (CHx) thickness layer on sensing properties of CHx/Porous Silicon (PS)/Si structures against CO2 gas. The hydrocarbon groups were deposited by plasma of methane-argon mixture. The properties of these structures are investigated by current-voltage, current-time and capacitance-voltage measurements from where a different behaviour depending on CHx layer thickness has been observed. The results show that current-voltage and impedance-voltage characteristics are modified by the gas reactivity on the CHx/PS surface. As the CHx layer thickness increases, the series resistance and the ideality factor of the structure increase. In addition, the response and recovery times of the sensor decrease with increasing the CHx thickness. Finally, the results point out the effect of CHx coating on the sensitivity of the CHx/PS/Si sensor.

  5. Monitoring Intracellular Oxygen Concentration: Implications for Hypoxia Studies and Real-Time Oxygen Monitoring.

    PubMed

    Potter, Michelle; Badder, Luned; Hoade, Yvette; Johnston, Iain G; Morten, Karl J

    2016-01-01

    The metabolic properties of cancer cells have been widely accepted as a hallmark of cancer for a number of years and have shown to be of critical importance in tumour development. It is generally accepted that tumour cells exhibit a more glycolytic phenotype than normal cells. In this study, we investigate the bioenergetic phenotype of two widely used cancer cell lines, RD and U87MG, by monitoring intracellular oxygen concentrations using phosphorescent Pt-porphyrin based intracellular probes. Our study demonstrates that cancer cell lines do not always exhibit an exclusively glycolytic phenotype. RD demonstrates a reliance on oxidative phosphorylation whilst U87MG display a more glycolytic phenotype. Using the intracellular oxygen sensing probe we generate an immediate readout of intracellular oxygen levels, with the glycolytic lines reflecting the oxygen concentration of the environment, and cells with an oxidative phenotype having significantly lower levels of intracellular oxygen. Inhibition of oxygen consumption in lines with high oxygen consumption increases intracellular oxygen levels towards environmental levels. We conclude that the use of intracellular oxygen probes provides a quantitative assessment of intracellular oxygen levels, allowing the manipulation of cellular bioenergetics to be studied in real time.

  6. Temperature-dependent H{sub 2} gas-sensing properties of fabricated Pd nanowires using highly oriented pyrolytic graphite

    SciTech Connect

    Sennik, Erdem; Kilinc, Necmettin; Oeztuerk, Zafer Ziya

    2010-09-15

    Horizontal palladium (Pd) nanowires and Pd nanoparticles were successfully fabricated directly on highly oriented pyrolytic graphite depending on the electrodeposition time using palladium nitrate [Pd(NO{sub 2}){sub 3}] solution at room temperature, and the temperature-dependent hydrogen (H{sub 2}) sensing properties of these structures were investigated in the concentration range of 50-5000 ppm. Pd nanowires and Pd nanoparticles were fabricated on a graphite surface by applying triple-pulsed potential with varying the electrodeposition time from 400 to 600 s. The fabricated Pd nanowires were characterized by scanning electron microscopy and energy-dispersive x-ray spectroscopy. It was found that the nanowire arrays were continuous, parallel to each other and ordered after an electrodeposition time of 600 s. The diameters of the Pd nanowires and Pd nanoparticles are observed in the range of 70-180 nm. The H{sub 2} sensing properties of these structures were determined with variation in resistance measurements. It was observed that the limit of detection is lower than 50 ppm H{sub 2}, the sensor response was approximately 2% for 1000 ppm H{sub 2} at room temperature, and the sensor response was decreased with increasing temperature.

  7. Low Temperature Sensing Properties of a Nano Hybrid Material Based on ZnO Nanotetrapods and Titanyl Phthalocyanine

    PubMed Central

    Coppedè, Nicola; Villani, Marco; Mosca, Roberto; Iannotta, Salvatore; Zappettini, Andrea; Calestani, Davide

    2013-01-01

    ZnO nanotetrapods have recently been exploited for the realization of high-sensitivity gas sensors, but they are affected by the typical drawbacks of metal-oxides, i.e., poor selectivity and a relatively high working temperature. On the other hand, it has been also demonstrated that the combined use of nanostructured metal oxides and organic molecules can improve the gas sensing performance sensitivity or selectivity, even at lower temperatures. A gas sensor device, based on films of interconnected ZnO nanotetrapods properly functionalized by titanyl phthalocyanine (TiOPc), has been realized in order to combine the high surface to volume ratio and structural stability of the crystalline ZnO nanostructures with the enhanced sensitivity of the semiconducting TiOPc molecule, especially at low temperature. The electronic properties of the resulting nanohybrid material are different from those of each single component. The response of the hybrid nanostructure towards different gases has been compared with that of ZnO nanotetrapod without functionalization in order to highlight the peculiar properties of the hybrid interaction(s). The dynamic response in time has been studied for different gases and temperatures; in particular, an increase in the response to NO2 has been observed, even at room temperature. The formation of localized p-n heterojunctions and the possibility of exchanging charge carriers at the hybrid interface is shown to be crucial for the sensing mechanism. PMID:23486215

  8. Low temperature sensing properties of a nano hybrid material based on ZnO nanotetrapods and titanyl phthalocyanine.

    PubMed

    Coppedè, Nicola; Villani, Marco; Mosca, Roberto; Iannotta, Salvatore; Zappettini, Andrea; Calestani, Davide

    2013-03-13

    ZnO nanotetrapods have recently been exploited for the realization of high-sensitivity gas sensors, but they are affected by the typical drawbacks of metal-oxides, i.e., poor selectivity and a relatively high working temperature. On the other hand, it has been also demonstrated that the combined use of nanostructured metal oxides and organic molecules can improve the gas sensing performance sensitivity or selectivity, even at lower temperatures. A gas sensor device, based on films of interconnected ZnO nanotetrapods properly functionalized by titanyl phthalocyanine (TiOPc), has been realized in order to combine the high surface to volume ratio and structural stability of the crystalline ZnO nanostructures with the enhanced sensitivity of the semiconducting TiOPc molecule, especially at low temperature. The electronic properties of the resulting nanohybrid material are different from those of each single component. The response of the hybrid nanostructure towards different gases has been compared with that of ZnO nanotetrapod without functionalization in order to highlight the peculiar properties of the hybrid interaction(s). The dynamic response in time has been studied for different gases and temperatures; in particular, an increase in the response to NO2 has been observed, even at room temperature. The formation of localized p-n heterojunctions and the possibility of exchanging charge carriers at the hybrid interface is shown to be crucial for the sensing mechanism.

  9. Synthesis of ZnO Nanoparticles-Reduced Graphene Oxide Composites and Their Intrinsic Gas Sensing Properties

    NASA Astrophysics Data System (ADS)

    Uddin, Abu Sadat Mohammad Iftekhar; Phan, Duy-Thach; Chung, Gwiy-Sang

    2014-09-01

    A ZnO nanoparticles (NPs)/reduced graphene oxide (rGO) composite was fabricated via a simple one-step solvothermal method with graphene oxide (GO) and Zn(NO3)2 ṡ 6H2O as the precursors. The morphology, crystal structure and optical properties of the synthesized materials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) spectroscopy. The synthesized composite exhibited rGO layers assorted with tiny ZnO NPs. rGO supposedly acted as a template in the solvothermal process, that may promote the preferential attachment of ZnO NPs and prevented the agglomeration of ZnO NPs in the synthesized composite. It was also found that the electrical properties of the composite improved markedly with bare ZnO NPs, without significantly changing the morphology and crystal structure of the ZnO NPs. The main aim of this research is to develop an efficient sensor and to understand the effect of graphene in sensing characteristics. The synthesized composite was exposed to H2, CO and C2H2 gases to confirm its feasibility for gas sensing, and the results showed preferential detection of reducing gases at low temperature.

  10. Effect of thickness on surface morphology, optical and humidity sensing properties of RF magnetron sputtered CCTO thin films

    NASA Astrophysics Data System (ADS)

    Ahmadipour, Mohsen; Ain, Mohd Fadzil; Ahmad, Zainal Arifin

    2016-11-01

    In this study, calcium copper titanate (CCTO) thin films were deposited on ITO substrates successfully by radio frequency (RF) magnetron sputtering method in argon atmosphere. The CCTO thin films present a polycrystalline, uniform and porous structure. The surface morphology, optical and humidity sensing properties of the synthesized CCTO thin films have been studied by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV-vis spectrophotometer and current-voltage (I-V) analysis. XRD and AFM confirmed that the intensity of peaks and pore size of CCTO thin films were enhanced by increasing the thin films. Tauc plot method was adopted to estimate the optical band gaps. The surface structure and energy band gaps of the deposited films were affected by film thickness. Energy band gap of the layers were 3.76 eV, 3.68 eV and 3.5 eV for 200 nm, 400 nm, and 600 nm CCTO thin films layer, respectively. The humidity sensing properties were measured by using direct current (DC) analysis method. The response times were 12 s, 22 s, and 35 s while the recovery times were 500 s, 600 s, and 650 s for 200 nm, 400 nm, and 600 nm CCTO thin films, respectively at humidity range of 30-90% relative humidity (RH).

  11. Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO₃ films.

    PubMed

    Onbaşlı, Mehmet C; Goto, Taichi; Tang, Astera; Pan, Annia; Battal, Enes; Okyay, Ali K; Dionne, Gerald F; Ross, C A

    2015-05-18

    Cobalt-substituted SrTiO3 films (SrTi0.70Co0.30O(3-δ)) were grown on SrTiO3 substrates using pulsed laser deposition under oxygen pressures ranging from 1 μTorr to 20 mTorr. The effect of oxygen pressure on structural, magnetic, optical, and magneto-optical properties of the films was investigated. The film grown at 3 μTorr has the highest Faraday rotation (FR) and magnetic saturation moment (M(s)). Increasing oxygen pressure during growth reduced M(s), FR and optical absorption in the near-infrared. This trend is attributed to decreasing Co2+ ion concentration and oxygen vacancy concentration with higher oxygen partial pressure during growth. PMID:26074589

  12. Resistive switching properties of epitaxial BaTiO(3-δ) thin films tuned by after-growth oxygen cooling pressure.

    PubMed

    Heo, Yooun; Kan, Daisuke; Shimakawa, Yuichi; Seidel, Jan

    2016-01-01

    BaTiO3-δ, i.e. oxygen-deficient barium titanate (BaTiO3), thin films grown on GdScO3(110) substrates with SrRuO3 conductive electrodes by pulsed laser deposition are studied by X-ray diffraction and conductive AFM to characterize their structure and nanoscale electronic properties. Bias- and time-dependent resistive switching measurements reveal a strong dependence on the oxygen vacancy concentration, which can be tuned by after-growth oxygen cooling conditions of thin films. The results indicate that the resistive switching properties of BaTiO3-δ can be enhanced by controlling oxygen deficiency and provide new insight for potential non-volatile resistive random-access memory (RRAM) applications.

  13. Ba{sub 3}Fe{sub 2}WO{sub 9-{delta}}: Effect of oxygen non-stoichiometry on structural and magnetic properties

    SciTech Connect

    Ivanov, S.A. . E-mail: ivan@cc.nifhi.ac.ru; Eriksson, S.-G. . E-mail: stene@chalmers.se; Tellgren, R. . E-mail: rte@mkem.uu.se; Rundlof, H.; Nordblad, P.; Eriksen, J.

    2006-08-15

    The magnetic and structural properties of oxygen-deficient perovskites with composition Ba{sub 3}Fe{sub 2}WO{sub 9-{delta}} (BFWO) have been systematically studied for two different oxygen contents corresponding to {delta}=0.00 and 0.55 in the chemical formula in order to determine and correlate their chemical composition, structural and magnetic properties. The evolution of nuclear and magnetic structures with temperature has been investigated by neutron powder diffraction. It was shown that at room temperature the stoichiometric compound ({delta}=0.00) adopts a hexagonal 6H-perovskite structure (space group P6{sub 3}/mmc). This phase, when heated at high temperature under a stream of Ar gas, transforms to an oxygen-deficient phase {delta}=0.55), which is an ordered cubic perovskite structure (space group Fm-3m). The crystallographic and magnetic properties of the obtained phases are compared, and it is clear that the magnetic properties are significantly affected by oxygen non-stoichiometry. These changes of magnetic properties for such a slight decrease in oxygen content are interpreted as a result of structural transformations. Together with the experimental results based on neutron powder diffraction data a discussion of some aspects of the structural transformation (P6{sub 3}/mmc->Fm-3m) is presented.

  14. Trimethylamine sensing properties of graphene quantum Dots/α-Fe2O3 composites

    NASA Astrophysics Data System (ADS)

    Hu, Tao; Chu, Xiangfeng; Gao, Feng; Dong, Yongping; Sun, Wenqi; Bai, Linshan

    2016-05-01

    Graphene quantum dots (GQDs) were prepared by pyrolysis of citric acid. The sizes of the as-prepared GQDs were in the range of 2-4 nm. The GQDs/α-Fe2O3 composites were prepared by loading GQDs with α-Fe2O3 via a one-step facile hydrothermal method. The GQDs/α-Fe2O3 composites were characterized by XRD, TGA, FTIR, Raman, SEM and TEM, respectively. The sensor devices were fabricated using the GQDs/α-Fe2O3 composites as sensing materials. The effect of the amount of GQDs in the composites on the gas-sensing responses of the materials and the gas-sensing selectivity was investigated. The experimental results revealed that the sensor based on GQDs/α-Fe2O3 (S-15) composite exhibited high sensitivity and good selectivity to TMA vapor. The responses of the sensor based on GQDs/α-Fe2O3 (S-15) composite to 1000 ppm and 0.01 ppm TMA vapor attained 1033.0 and 1.9 at 270 °C, respectively. The response time and recovery time for 0.01 ppm TMA vapor were only 6 s and 4 s, respectively. (2) The responses of the sensor based on GQDs/α-Fe2O3 (S-15) composite to 0.01, 0.1, 1, 10, 100 and 1000 ppm TMA vapor at 270 °C are 1.9, 2.9, 5.5, 15.4, 293.0 and 1033.0, respectively, and the detection limit can reach 0.01 ppm.

  15. Study on the fabricating process monitoring of thermoplastic based materials packaged OFBG and their sensing properties

    NASA Astrophysics Data System (ADS)

    Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

    2007-04-01

    As common materials or engineering materials, thermoplastic resin based materials can be used not only directly fabricating products but also FRTP(fiber reinforced thermoplastic polymer) materials for other uses. As one kind of FRTP material, GFRPP(glass fiber reinforced polypropylene) has lots of merits, such as: light weight, high strength, high tenacity, high elongation percentage, good durability, reshaping character and no environmental pollution characters. And they also can be conveniently formed hoop rebar in civil engineering. While a new kind of GFRPP-OFBG smart rod which combined GFRPP and OFBG together can be used as not only structure materials but also sensing materials. Meanwhile, PP packaged OFBG strain sensor can be expected for its low modulus, good sensitivity and good durability. Furthermore, it can be used for large strain measuring. In this paper, we have successfully fabricated a new kind of GFRPP-OFBG(Glass Fiber Reinforced Polypropylene-Optic Fiber Bragg Grating) rod by our own thermoplastic pultrusion production line and a new kind of PP packaged OFBG strain sensor by extruding techniques. And we monitored the inner strain and temperature changes with tow OFBG simultaneously of the fabricating process. The results show that: OFBG can truly reflect the strain and temperature changes in both the GFRPP rod and the PP packaged OFBG, these are very useful to modify our processing parameters. And we also find that because of the shrinkage of PP, this new kind of PP packaged OFBG have -13000μɛ storage, and the strain sensing performance is still very well, so which can be used for large strain measuring. Besides these, GFRPP-OFBG smart rod has good sensing performance in strain sensing just like that of FRSP-OFBG rod, the strain sensitivity coefficient is about1.19pm/μɛ. Besides these, the surface of GFRPP-OFBG rods can be handled just as steel bars and also can be bended and reshaped. These are all very useful and very important for the use

  16. Sensing Properties of GO and Amine-Silica Nanoparticles Functionalized QCM Sensors for Detection of Formaldehyde

    NASA Astrophysics Data System (ADS)

    Wang, Zhenqiang; Yang, Mingqing; He, Junhui

    2014-12-01

    In the current work, graphene oxides (GO) and Amine-Functionalized Silica Nanoparticles (NH2-SNs) were used as sensing layer on quart crystal microbalance (QCM) for detection of HCHO gas. The GO and NH2-SNs functionalized QCM resonators all had a significant response to HCHO gas. The sensitivity of GO functionalized QCM resonator is 0.04 Hz/(μgṡppm), which is four times as high as that of NH2-SNs functionalized QCM resonator (0.01 Hz/(μgṡppm)). The GO functionalized QCM resonators would be of benefit in area of environmental applications.

  17. Properties of reactively sputtered oxygenated cadmium sulfide (CdS:O) and their impact on CdTe solar cell performance

    SciTech Connect

    Meysing, Daniel M. Wolden, Colin A.; Griffith, Michelle M.; Mahabaduge, Hasitha; Pankow, Joel; Reese, Matthew O.; Burst, James M.; Rance, William L.; Barnes, Teresa M.

    2015-03-15

    Oxygenated cadmium sulfide (CdS:O) is commonly used as the n-type window layer in high-performance CdTe heterojunction solar cells. This layer is deposited by reactive sputtering, but the optimal amount of oxygen in the sputtering ambient is highly dependent on the specific system and process employed. In this work, the intrinsic properties of CdS:O were measured as a function of the oxygen content (0%–10%) in the sputtering ambient and correlated to device performance with the goal of better defining optimal CdS:O properties for CdTe solar cells. Optimal performance was found using CdS:O films that contained ∼40 at. % oxygen as measured by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy confirmed these results and showed that oxygen is incorporated primarily as oxygenated sulfur compounds (SO{sub x}). Device efficiency improved from 10.5% using CdS to >14% with CdS:O due largely to increases in short-circuit current density as well as a modest improvement in open-circuit voltage. The transparency of the CdS:O films was well correlated with observed improvements in blue quantum efficiency with increasing oxygen content. The optical bandgap of as-deposited CdS:O was identified as a simple metric for process optimization and transfer, with 2.8 eV being ideal for the device architecture employed.

  18. Transport properties and metal-insulator transition in oxygen deficient LaNiO3: a density functional theory study

    NASA Astrophysics Data System (ADS)

    Misra, D.; Kundu, T. K.

    2016-09-01

    Density functional theory with appropriate functional has been employed to investigate the metal to insulator transition in oxygen deficient LaNiO3-x (x = 0.0, 0.25, 0.5, 1.0) compounds. While the metallic nature of LaNiO3 is characterized by the low temperature Fermi liquid behavior of resistivity and a finite density of states at the Fermi level, the density of states and the transport properties clearly identify LaNiO2.75 as a semiconductor, and LaNiO2.5 as an insulator, which is followed by another insulator to semiconductor transition with further increase of x to ‘1’ in LaNiO2. This oxygen vacancy controlled metal to insulator transition is explained on the basis of non-adiabatic polaronic transport. From the covalency metric calculation of the chemical bonding and the Bader charge transfer analysis, this metal to insulator transition is attributed to the enhanced covalent part in the chemical bonding and reduced charge transfer from Ni to O atoms in LaNiO3-x compounds.

  19. Influence of oxygen octahedral tilting on the properties of low-dimensional lead-zirconium-titanate systems

    NASA Astrophysics Data System (ADS)

    Sichuga, David Leybovich

    In this thesis, we investigate low-dimensional Pb(Zr,Ti)O3 (PZT) systems in the presence of antiferrodistortive (AFD) oxygen octahedral tilting. In Chapter 1, some basic concepts and definitions useful for the following discussion are brought in. Chapter 2 addresses a question of AFD influence on epitaxial strain induced phase transitions in PZT ultrathin films under the short-circuit (SC) electrical boundary conditions, as a function of applied strain and alloy composition. Chapter 3 considers the same two-dimensional system under the open-circuit (OC) electrical boundary conditions leading to a formation of stripe domains. More precisely, properties of multi-domain system under the influence of AFD degrees of freedom using the Monte Carlo techniques are studied in Chapter 3. Chapter 4 deals with novel phenomena which appear in the zero-dimensional stress-free cubic nanodot made of PZT disordered solid solution under the OC electrical boundary conditions in the ground state. The consequences of coupling between the electric dipoles organized in vortices and AFD oxygen octahedral tilting is investigated and new order parameter to describe the new state of the system is introduced. In Chapter 5, the same zero-dimensional system under the SC conditions is examined which reveals the Curie temperature dependence on Ti content in the PZT alloy and the size of a nanodot enhanced by the influence of AFD displacements. Chapter 6 briefly lists the main achievements of the research discussed in the Thesis.

  20. La and Sr substituted Pr{sub 2}NiO{sub 4+{delta}}: Oxygenation and electrical properties

    SciTech Connect

    Allancon, C.; Odier, P.; Loup, J.P.; Bassat, J.M.

    1997-06-01

    We report herein results concerning the solid solutions Pr{sub 2-x}M{sub x}NiO{sub 4+{delta}}, M = La, Sr. These two cations are larger than praseodymium and lead to a structural stabilization. The oxygen excess {delta} decreases with x for La and Sr substituted Pr{sub 2}NiO{sub 4+{delta}}. Both cases suggest that structural strain is a leading factor for the oxygenation ability of the title compounds. From the evolution of cell parameters, we suggest a phase transition for La substituted compounds occurring for x {approximately} 1-1.2. Surprisingly, this transition has a negligible effect on transport properties. On the other hand, a charge localization linked to the presence of praseodymium is observed. Owing to charge compensation, the Sr substituted compounds have a quasi-constant hole concentration (formally 50%) for x < 0.5. The Pr{sub 2-x}Sr{sub x}NiO{sub 4+{delta}} solid solution shows an anomalous behavior for x = 0.5 corresponding to Ni{sup 2+}/Ni{sup 3+} = 1. This anomaly combines an enhancement of the c/a ratio, a larger resistivity, and a peak for the activation energy of the resistivity versus T.