NARROW LINE ABSORPTION IN CACO3.

DTIC Science & Technology

CARBONATES), (*CALCIUM COMPOUNDS, (*ABSORPTION SPECTRA, CALCITE), (*CALCITE, RADIATION EFFECTS), ELECTRON PARAMAGNETIC RESONANCE, SINGLE CRYSTALS , NEUTRONS, X RAYS, GAMMA RAYS, IONS, CRYSTAL DEFECTS, PARAMAGNETIC RESONANCE.

Quasiclassical Theory on Third-Harmonic Generation in Conventional Superconductors with Paramagnetic Impurities

NASA Astrophysics Data System (ADS)

Jujo, Takanobu

2018-02-01

We investigate the third-harmonic generation (THG) of s-wave superconductors under microwave pulse irradiation. We consider the effect of paramagnetic impurities on the THG intensity of dirty superconductors. The nonlinear response function is calculated using the method of the quasiclassical Green function. It is shown that the amplitude mode is included as the vertex correction and makes a predominant contribution to the THG intensity. When the effect of paramagnetic impurities is weak, the THG intensity shows a peak at the temperature at which the superconducting gap is about the same as the frequency of the incident pulse, similarly to in experiments. As the effect of paramagnetic impurities is strengthened, the peak of the THG intensity disappears. This indicates that time-reversal symmetry breaking due to paramagnetic impurities eliminates the well-defined amplitude mode. The result of our calculation shows that the existence of the amplitude mode can be confirmed through the THG intensity. The result of a semiquantitative calculation is in good agreement with the experimental result, and it also shows that the diamagnetic term is negligible.

Toxicity of Urban PM10 and Relation with Tracers of Biomass Burning

PubMed Central

Staelens, Jeroen; Koppen, Gudrun; Schoeters, Greet

2018-01-01

The chemical composition of particles varies with space and time and depends on emission sources, atmospheric chemistry and weather conditions. Evidence suggesting that particles differ in toxicity depending on their chemical composition is growing. This in vitro study investigated the biological effects of PM10 in relation to PM-associated chemicals. PM10 was sampled in ambient air at an urban traffic site (Borgerhout) and a rural background location (Houtem) in Flanders (Belgium). To characterize the toxic potential of PM10, airway epithelial cells (Beas-2B cells) were exposed to particles in vitro. Different endpoints were studied including cell damage and death (cell viability) and the induction of interleukin-8 (IL-8). The mutagenic capacity was assessed using the Ames II Mutagenicity Test. The endotoxin levels in the collected samples were analyzed and the oxidative potential (OP) of PM10 particles was evaluated by electron paramagnetic resonance (EPR) spectroscopy. Chemical characteristics of PM10 included tracers for biomass burning (levoglucosan, mannosan and galactosan), elemental and organic carbon (EC/OC) and polycyclic aromatic hydrocarbons (PAHs). Most samples displayed dose-dependent cytotoxicity and IL-8 induction. Spatial and temporal differences in PM10 toxicity were seen. PM10 collected at the urban site was characterized by increased pro-inflammatory and mutagenic activity as well as higher OP and elevated endotoxin levels compared to the background area. Reduced cell viability (−0.46 < rs < −0.35, p < 0.01) and IL-8 induction (−0.62 < rs < −0.67, p < 0.01) were associated with all markers for biomass burning, levoglucosan, mannosan and galactosan. Furthermore, direct and indirect mutagenicity were associated with tracers for biomass burning, OC, EC and PAHs. Multiple regression analyses showed levoglucosan to explain 16% and 28% of the variance in direct and indirect mutagenicity, respectively. Markers for biomass burning were associated with altered cellular responses and increased mutagenic activity. These findings may indicate a role of biomass burning in the observed adverse health effect of particulate matter. PMID:29439546

Effect of the lattice dynamics on the electronic structure of paramagnetic NiO within the disordered local moment picture

NASA Astrophysics Data System (ADS)

Mozafari, Elham; Alling, Björn; Belov, Maxim P.; Abrikosov, Igor A.

2018-01-01

Using the disordered local moments approach in combination with the ab initio molecular dynamics method, we simulate the behavior of a paramagnetic phase of NiO at finite temperatures to investigate the effect of magnetic disorder, thermal expansion, and lattice vibrations on its electronic structure. In addition, we study its lattice dynamics. We verify the reliability of our theoretical scheme via comparison of our results with available experiment and earlier theoretical studies carried out within static approximations. We present the phonon dispersion relations for the paramagnetic rock-salt (B1) phase of NiO and demonstrate that it is dynamically stable. We observe that including the magnetic disorder to simulate the paramagnetic phase has a small yet visible effect on the band gap. The amplitude of the local magnetic moment of Ni ions from our calculations for both antiferromagnetic and paramagnetic phases agree well with other theoretical and experimental values. We demonstrate that the increase of temperature up to 1000 K does not affect the electronic structure strongly. Taking into account the lattice vibrations and thermal expansion at higher temperatures have a major impact on the electronic structure, reducing the band gap from ˜3.5 eV at 600 K to ˜2.5 eV at 2000 K. We conclude that static lattice approximations can be safely employed in simulations of the paramagnetic state of NiO up to relatively high temperatures (˜1000 K), but as we get closer to the melting temperature vibrational effects become quite large and therefore should be included in the calculations.

Upper critical fields in Ba2Ti2Fe2As4O single crystals: Evidence for dominant Pauli paramagnetic effect

NASA Astrophysics Data System (ADS)

Abdel-Hafiez, M.; Brisbois, J.; Zhu, Z.; Adamski, A.; Hassen, A.; Vasiliev, A. N.; Silhanek, A. V.; Krellner, C.

2018-03-01

We report on magneto-optical imaging and the temperature dependency of the upper critical fields Hc2 c(T ) parallel to the c axis and Hc2 a b(T ) parallel to the a b plane in Ba2Ti2Fe2As4O single crystals. These data were inferred from the measurements of the temperature-dependent resistance in static magnetic fields up to 14 T and magnetoresistance in pulsed fields up to 60 T. Hc 2 values are found to be 52 and 50 T for H ∥a b and H ∥c , respectively. These values are 1.2-1.35 times larger than the weak-coupling Pauli paramagnetic limit (Hp˜1.84 Tc ), indicating that enhanced paramagnetic limiting is essential and this superconductor is unconventional. Our observations of strong bending in the Hc2 a b(T ) curves and a nearly isotropic maximum upper critical field Hc2 a b(0 ) ≈Hc2 c(0 ) support the presence of a strong Pauli paramagnetic effect. We show that the Werthamer-Helfand-Hohenberg (WHH) formula that includes the spin-orbit scattering can effectively describe the Hc2 a b(T ) curve, whereas Hc 2 deviates from the conventional WHH theoretical model without considering the spin paramagnetic effect for the H ∥c and H ∥a b directions. For H ∥c , a two-band model is required to fully reproduce the behavior of Hc 2, while for H ∥a b the spin paramagnetic effect is responsible for the behavior of Hc 2. The anisotropy of Hc 2 is close to 3 near Tc and decreases rapidly at lower temperatures.

Optimal-mass-transfer-based estimation of glymphatic transport in living brain

PubMed Central

Zhu, Liangjia; Kolesov, Ivan; Nedergaard, Maiken; Benveniste, Helene; Tannenbaum, Allen

2016-01-01

It was recently shown that the brain-wide cerebrospinal fluid (CSF) and interstitial fluid exchange system designated the ‘glymphatic pathway’ plays a key role in removing waste products from the brain, similarly to the lymphatic system in other body organs1,2. It is therefore important to study the flow patterns of glymphatic transport through the live brain in order to better understand its functionality in normal and pathological states. Unlike blood, the CSF does not flow rapidly through a network of dedicated vessels, but rather through para-vascular channels and brain parenchyma in a slower time-domain, and thus conventional fMRI or other blood-flow sensitive MRI sequences do not provide much useful information about the desired flow patterns. We have accordingly analyzed a series of MRI images, taken at different times, of the brain of a live rat, which was injected with a paramagnetic tracer into the CSF via the lumbar intrathecal space of the spine. Our goal is twofold: (a) find glymphatic (tracer) flow directions in the live rodent brain; and (b) provide a model of a (healthy) brain that will allow the prediction of tracer concentrations given initial conditions. We model the liquid flow through the brain by the diffusion equation. We then use the Optimal Mass Transfer (OMT) approach3 to derive the glymphatic flow vector field, and estimate the diffusion tensors by analyzing the (changes in the) flow. Simulations show that the resulting model successfully reproduces the dominant features of the experimental data. PMID:26877579

A combined positron emission tomography (PET)-electron paramagnetic resonance imaging (EPRI) system: initial evaluation of a prototype scanner

NASA Astrophysics Data System (ADS)

Tseytlin, Mark; Stolin, Alexander V.; Guggilapu, Priyaankadevi; Bobko, Andrey A.; Khramtsov, Valery V.; Tseytlin, Oxana; Raylman, Raymond R.

2018-05-01

The advent of hybrid scanners, combining complementary modalities, has revolutionized the application of advanced imaging technology to clinical practice and biomedical research. In this project, we investigated the melding of two complementary, functional imaging methods: positron emission tomography (PET) and electron paramagnetic resonance imaging (EPRI). PET radiotracers can provide important information about cellular parameters, such as glucose metabolism. While EPR probes can provide assessment of tissue microenvironment, measuring oxygenation and pH, for example. Therefore, a combined PET/EPRI scanner promises to provide new insights not attainable with current imagers by simultaneous acquisition of multiple components of tissue microenvironments. To explore the simultaneous acquisition of PET and EPR images, a prototype system was created by combining two existing scanners. Specifically, a silicon photomultiplier (SiPM)-based PET scanner ring designed as a portable scanner was combined with an EPRI scanner designed for the imaging of small animals. The ability of the system to obtain simultaneous images was assessed with a small phantom consisting of four cylinders containing both a PET tracer and EPR spin probe. The resulting images demonstrated the ability to obtain contemporaneous PET and EPR images without cross-modality interference. Given the promising results from this initial investigation, the next step in this project is the construction of the next generation pre-clinical PET/EPRI scanner for multi-parametric assessment of physiologically-important parameters of tissue microenvironments.

Susceptibility cancellation of a microcoil wound with a paramagnetic-liquid-filled copper capillary

NASA Astrophysics Data System (ADS)

Takeda, Kazuyuki; Takasaki, Tomoya; Takegoshi, K.

2015-09-01

Even though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-field inhomogeneity due to the bulk susceptibility effect of the coil material can cause serious resonance-line broadening. Here, we propose to fabricate the microcoil using a thin, hollow copper capillary instead of a wire and fill paramagnetic liquid inside the capillary, so as to cancel the diamagnetic contribution of the copper. Susceptibility cancellation is demonstrated using aqueous solution of NiSO4. In addition, the paramagnetic liquid serves as coolant when it is circulated through the copper capillary, effectively transferring the heat generated by radiofrequency pulses.

Dynamics of paramagnetic agents by off-resonance rotating frame technique

NASA Astrophysics Data System (ADS)

Zhang, Huiming; Xie, Yang

2006-12-01

Off-resonance rotating frame technique offers a novel tool to explore the dynamics of paramagnetic agents at high magnetic fields ( B0 > 3 T). Based on the effect of paramagnetic relaxation enhancement in the off-resonance rotating frame, a new method is described here for determining the dynamics of paramagnetic ion chelates from the residual z-magnetizations of water protons. In this method, the dynamics of the chelates are identified by the difference magnetization profiles, which are the subtraction of the residual z-magnetization as a function of frequency offset obtained at two sets of RF amplitude ω1 and pulse duration τ. The choices of ω1 and τ are guided by a 2-D magnetization map that is created numerically by plotting the residual z-magnetization as a function of effective field angle θ and off-resonance pulse duration τ. From the region of magnetization map that is the most sensitive to the alteration of the paramagnetic relaxation enhancement efficiency R1 ρ/ R1, the ratio of the off-resonance rotating frame relaxation rate constant R1 ρ verse the laboratory frame relaxation rate constant R1, three types of difference magnetization profiles can be generated. The magnetization map and the difference magnetization profiles are correlated with the rotational correlation time τR of Gd-DTPA through numerical simulations, and further validated by the experimental data for a series of macromolecule conjugated Gd-DTPA in aqueous solutions. Effects of hydration water number q, diffusion coefficient D, magnetic field strength B0 and multiple rotational correlation times are explored with the simulations of the magnetization map. This method not only provides a simple and reliable approach to determine the dynamics of paramagnetic labeling of molecular/cellular events at high magnetic fields, but also a new strategy for spectral editing in NMR/MRI based on the dynamics of paramagnetic labeling in vivo.

Optimal-mass-transfer-based estimation of glymphatic transport in living brain

NASA Astrophysics Data System (ADS)

Ratner, Vadim; Zhu, Liangjia; Kolesov, Ivan; Nedergaard, Maiken; Benveniste, Helene; Tannenbaum, Allen

2015-03-01

It was recently shown that the brain-wide cerebrospinal fluid (CSF) and interstitial fluid exchange system designated the `glymphatic pathway' plays a key role in removing waste products from the brain, similarly to the lymphatic system in other body organs . It is therefore important to study the flow patterns of glymphatic transport through the live brain in order to better understand its functionality in normal and pathological states. Unlike blood, the CSF does not flow rapidly through a network of dedicated vessels, but rather through para-vascular channels and brain parenchyma in a slower time-domain, and thus conventional fMRI or other blood-flow sensitive MRI sequences do not provide much useful information about the desired flow patterns. We have accordingly analyzed a series of MRI images, taken at different times, of the brain of a live rat, which was injected with a paramagnetic tracer into the CSF via the lumbar intrathecal space of the spine. Our goal is twofold: (a) find glymphatic (tracer) flow directions in the live rodent brain; and (b) provide a model of a (healthy) brain that will allow the prediction of tracer concentrations given initial conditions. We model the liquid flow through the brain by the diffusion equation. We then use the Optimal Mass Transfer (OMT) approach to derive the glymphatic flow vector field, and estimate the diffusion tensors by analyzing the (changes in the) flow. Simulations show that the resulting model successfully reproduces the dominant features of the experimental data. Keywords: inverse problem, optimal mass transport, diffusion equation, cerebrospinal fluid flow in brain, optical flow, liquid flow modeling, Monge Kantorovich problem, diffusion tensor estimation

The Effect of Electronic Paramagnetism on Nuclear Magnetic Resonance Frequencies in Metals

DOE R&D Accomplishments Database

Townes, C. H.; Herring, C.; Knight, W. D.

1950-09-22

Observations on the shifts of nuclear resonances in metals ( Li{sup 7}, Na{sup 23}, Cu {sup 63}, Be{sup 9}, Pb{sup 207}, Al{sup 27}, and Ca{sup 69} ) due to free electron paramagnetism; comparison with theoretical values.

The EPR of the triplet state of aryl cations in crystals of diazonium salts

NASA Astrophysics Data System (ADS)

Kondratenko, P. A.; Shrubovich, E. V.; Shulga, S. Z.

The spectra of the electron paramagnetic resonance (EPR) of aryl cations possessing a principle triplet ground-state and orientated in a monocrystal of diazonium salts is studied. It is shown that two nonequivalent paramagnetic centers, which differ in orientation are formed within the crystal. A theoretic description of experimental results is possible only when allowing for the effect of low symmetry. This symmetry is invoked by the interactivity of the paramagnetic center of symmetry C(sub 2v) with the crystal field of symmetry C(sub i).

Novel magnetic graphene quantum dot as dual modality fluorescence/MMOCT contrast agent for tracking epithelial cells

NASA Astrophysics Data System (ADS)

Li, Wei; Matcher, Stephen J.

2017-02-01

A novel nanoparticle, magnetic graphene quantum dot (MGQD), was synthesized by hydrothermally cutting graphene oxide-iron oxide sheet for contrast agent in magnetomotive optical coherence tomography (MMOCT) and confocal fluorescence microscopy (CFM). The MGQD has superparamagnetism, which allows the MGQD to be tracked and imaged using MMOCT. The MMOCT can display paramagnetic nanoparticle in vivo and provide an anatomical information with micron scale resolution and long imaging depth in clinic application. Moreover, the MGQD has excitation-depend fluorescence and emits visible fluorescence under the excitation of 360nm light, which allows the MGQD to be used as tracer in CFM. CFM can offer intracellular details due to higher resolution, while CFM is unsuitable for imaging anatomical structure because of the limited view of field. The use of MGQD for cell or tissue tracking realizes the combination of MMOCT and CFM, and gives a more comprehensive diagnosis.

Biomedical research applications of electromagnetically separated enriched stable isotopes

NASA Astrophysics Data System (ADS)

Lambrecht, R. M.

The current and projected annual requirements through 1985 for stable isotopes enriched by electromagnetic separation methods were reviewed for applications in various types of biomedical research: (1) medical radiosiotope production, labeled compounds, and potential radio-pharmaceuticals; (2) nutrition, food science, and pharmacology: (3) metallobiochemistry and environmental toxicology; (4) nuclear magnetic resonance, electron paramagnetic resonance, and moessbauer spectroscopy in biochemical, biophysical, and biomedical research; and (5) miscellaneous advances in radioactive and nonradioactive tracer technology. Radioisotopes available from commercial sources or routinely used in clinical nuclear medicine were excluded. Current requirements for enriched stable isotopes in biomedical research are not being satisfied. Severe shortages exist for Mg 26, Ca 43, Zn 70, Se 76, Se 77, Se 78, Pd 102, Cd 111, Cd 113, and Os 190. Many interesting and potentially important investigations in biomedical research require small quantities of specific elements at high isotopic enrichments.

Paramagnetic Europium Salen Complex and Sickle-Cell Anemia

NASA Astrophysics Data System (ADS)

Wynter, Clive I.; Ryan, D. H.; May, Leopold; Oliver, F. W.; Brown, Eugene; Hoffman, Eugene J.; Bernstein, David

2005-04-01

A new europium salen complex, Eu(salen)2NH4, was synthesized, and its composition was confirmed by chemical analysis and infrared spectroscopy. Further characterization was carried out by 151 Eu Mössbauer spectroscopy and magnetic susceptibility measurements. Mössbauer spectroscopic measurements were made at varying temperatures between 9 K and room temperature and a value of Debye temperature of 133 ±5 K was computed. Both Mössbauer and magnetic susceptibility measurements confirmed the paramagnetic behavior of this complex and the trivalent state of the europium ion. In view of the fact that the "odd" paramagnetic molecule NO has been shown to reverse sickling of red blood cells in sickle cell anemia, the interaction between the paramagnetic europium salen complex and sickle cells was examined after incubation with this europium complex and shown to have similar effects.

Electron paramagnetic resonance of natural and gamma-irradiated alunite and kaolin mineral powders

NASA Astrophysics Data System (ADS)

Koksal, F.; Koseoglu, R.; Saka, I.; Basaran, E.; Sener, F.

2004-06-01

Natural alunite and kaolin minerals obtained from West Anatolia were investigated by electron paramagnetic resonance (EPR) in natural and gamma-irradiated states at room temperature and at 113 K. The paramagnetic centres at ambient temperature in natural alunite were attributed to the (C) over dot H 2OH, (C) over dot O-3(-), (S) over dot O-2(-), (C) over dot O-2(-) and [AlO4 ](0) radicals. In natural kaolin, the paramagnetic centres were attributed to the (C) over dot O-3(-), (S) over dot O-2(-) (C) over dot O-2(-) and [AlO4](0) radicals. The gamma-irradiation does not produce any detectable effects on these radicals. At 113 K, the lines for (C) over dot H2OH could not be observed well, probably due to the anisotropic behaviour of the hyperfine interaction of the methylene protons, but the lines for [AlO4](0) centres were found to be perfectly observable at above 20 mW microwave power in both alunite and kaolin powders before and after gamma-irradiation. The EPR parameters of the observed paramagnetic centres were reported.

Nonlinear magnetoelectric effect and magnetostriction in piezoelectric CsCuCl{sub 3} in paramagnetic and antiferromagnetic states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharkovskiy, A. I., E-mail: akharkovskiy@inbox.ru; L.F. Vereshchagin Institute for High Pressure Physics RAS, 142190 Troitsk, Moscow; Shaldin, Yu. V.

2016-01-07

The direct nonlinear magnetoelectric (ME) effect and the magnetostriction of piezoelectric CsCuCl{sub 3} single crystals were comprehensively studied over a wide temperature range in stationary magnetic fields of up to 14 T. The direct nonlinear ME effect measurements were also performed in pulsed magnetic fields up to 31 T, at liquid helium temperature in the antiferromagnetic (AF) state for the crystallographic direction in which effect has the maximum value. The nonlinear ME effect was quadratic in the paramagnetic state for the whole range of magnetic fields. In the AF state the phase transition between different configurations of spins manifested itself as plateau-likemore » peculiarity on the nonlinear ME effect. The nonlinear ME effect was saturated by the phase transition to the spin-saturated paramagnetic state. Two contributions to the nonlinear ME effects in CsCuCl{sub 3} were extracted from the experimental data: the intrinsic ME effect originated from the magnetoelectric interactions, and the extrinsic one, which resulted from a magnetostriction-induced piezoelectric effect.« less

Dual excitation acoustic paramagnetic logging tool

DOEpatents

Vail, III, William B.

1989-01-01

New methods and apparatus are disclosed which allow measurement of the presence of oil and water in gelogical formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleous present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be preformed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described.

Dual excitation acoustic paramagnetic logging tool

DOEpatents

Vail, W.B. III.

1989-02-14

New methods and apparatus are disclosed which allow measurement of the presence of oil and water in geological formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleons present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be performed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described. 6 figs.

3-D numerical evaluation of density effects on tracer tests.

PubMed

Beinhorn, M; Dietrich, P; Kolditz, O

2005-12-01

In this paper we present numerical simulations carried out to assess the importance of density-dependent flow on tracer plume development. The scenario considered in the study is characterized by a short-term tracer injection phase into a fully penetrating well and a natural hydraulic gradient. The scenario is thought to be typical for tracer tests conducted in the field. Using a reference case as a starting point, different model parameters were changed in order to determine their importance to density effects. The study is based on a three-dimensional model domain. Results were interpreted using concentration contours and a first moment analysis. Tracer injections of 0.036 kg per meter of saturated aquifer thickness do not cause significant density effects assuming hydraulic gradients of at least 0.1%. Higher tracer input masses, as used for geoelectrical investigations, may lead to buoyancy-induced flow in the early phase of a tracer test which in turn impacts further plume development. This also holds true for shallow aquifers. Results of simulations with different tracer injection rates and durations imply that the tracer input scenario has a negligible effect on density flow. Employing model cases with different realizations of a log conductivity random field, it could be shown that small variations of hydraulic conductivity in the vicinity of the tracer injection well have a major control on the local tracer distribution but do not mask effects of buoyancy-induced flow.

Buckling of paramagnetic chains in soft gels

NASA Astrophysics Data System (ADS)

Huang, Shilin; Pessot, Giorgio; Cremer, Peet; Weeber, Rudolf; Holm, Christian; Nowak, Johannes; Odenbach, Stefan; Menzel, Andreas M.; Auernhammer, Günter K.

We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects.

Hyperfine Structure and Exchange Narrowing of Paramagnetic Resonance

DOE R&D Accomplishments Database

Townes, C. H.; Turkevich, J.

1950-01-01

Discussion of electronic paramagnetic resonance for the free radical ?, ?-diphenyl ?-picryl hydrazyl as observed by its effect on the transmission of microwave through a TE{sub 01} cavity with a small amount of the free radical placed approximately on the axis of the cavity; the half-width of this resonance at half maximum absorption was 1.45 oersteds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolff-Fabris, F.; Lei, Hechang; Wosnitza, J.

We have studied the temperature dependence of the upper critical fields μ 0 H c 2 of K x Fe 2 - y Se 2 - z S z single crystals up to 60 T. The μ 0 H c 2 for H ∥ a b and H ∥ c decrease with increasing sulfur content. The detailed analysis using Werthamer-Helfand-Hohenberg theory including the Pauli spin-paramagnetic effect shows that μ 0 H c 2 for H ∥ a b is dominated by the spin-paramagnetic effect, which diminishes with higher S content, whereas μ 0 H c 2 for H ∥ cmore » shows a linear temperature dependence with an upturn at high fields. The latter observation can be ascribed to multiband effects that become weaker for higher S content. This results in an enhanced anisotropy of μ 0 H c 2 for high S content due to the different trends of the spin-paramagnetic and multiband effect for H ∥ a b and H ∥ c , respectively.« less

Water fluxes in root-soil-systems investigated by Magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Haber-Pohlmeier, Sabina; Javaux, Mathieu; Pohlmeier, Andreas

2010-05-01

Water flux through soils is one of the most important control function with respect to the water supply for root and plant growth. The understanding of these processes bases generally on the interplay between experimental investigations and the development of theory and numerical models. In recent time detailed 3D models have been developed, but experimental information is mainly available from two-dimensional rhizotrons or only with coarse resolution from water content measurements by means of TDR probes and tensiometers. An emerging powerful tool for high resolution, non-invasive imaging of water content and fluxes in soils in saturated and unsaturated state is Nuclear Magnetic Resonance Imaging (MRI)[1,2]. With respect to water fluxes the slow flow velocities do not allow the direct monitoring by MRI flow imaging so indirect methods like transport of contrast agents should be applied. Therefore we have chosen Gd-DTPA [3], a negatively charged paramagnetic Gd-complex, as tracer for the investigation of water fluxes during i) infiltration and ii) injection experiments of unsaturated model soil with maize and lupin plants. The contrast of the NMR measurements was optimised using high resolution T1 weighted spin echo sequences. With respect to the infiltration experiment we observed that during rapid infiltration from the bottom the plume moved homogeneously into the bulk soil, but leaves out the immediate surrounding of the maize roots. After this initial period a continuously increasing enrichment of tracer in this region is monitored, but no uptake by the plant within one hour. Continuing these studies injection experiments have been performed where the tracer was placed in a small volume in the direct vicinity of the roots, and the entire water content changed only minimal even under quite dry conditions. For a well developed lupin root system we observed diffusive spreading followed by a very slow transporte of the plume to the root system over a period of two days. The important difference to the short term experiment is the observation of tracer uptake followed by an upward transport in the inner root tissues. This could also be proved by a following chemical analysis showing decreasing Gd content from the roots over the shoot to the leaves. In parallel a high resolution 3d image of the root system architecture was performed, in order to compare the experimentally observed motion of the plume with detailed 3D model calculations of water uptake and tracer transport. References: 1. Pohlmeier, A., et al., Imaging water fluxes in porous media by magnetic resonance imaging using D2O as a tracer. Mag. Res. Imag., 2008. 27(2): p. 285-292. 2. Pohlmeier, A., et al., Changes in Soil Water Content Resulting from Ricinus Root Uptake Monitored by Magnetic Resonance Imaging Vadose Zone Journal, 2008. 7: p. 1010-1017. 3. Haber-Pohlmeier, S., Stapf S. and Pohlmeier A., Waterflow monitored by tracer transport in natural porouse media using MRI. Vadose Zone Journal, submitted

Magnetic-field-induced effects in the electronic structure of itinerant d- and f-metal systems

NASA Astrophysics Data System (ADS)

Grechnev, G. E.

2009-08-01

A paramagnetic response of transition metals and itinerant d- and f-metal compounds in an external magnetic field is studied by employing ab initio full-potential LMTO method in the framework of the local spin density approximation. Within this method the anisotropy of the magnetic susceptibility in hexagonal close-packed transition metals is evaluated for the first time. This anisotropy is owing to the orbital Van Vleck-like paramagnetic susceptibility, which is revealed to be substantial in transition-metal systems due to hybridization effects in the electronic structure. It is demonstrated that compounds TiCo, Ni3Al, YCo2, CeCo2, YNi5, LaNi5, and CeNi5 are strong paramagnets close to the quantum critical point. For these systems the Stoner approximation underestimates the spin susceptibility, whereas the calculated field-induced spin moments provide a good description of the large paramagnetic susceptibilities and magnetovolume effects. It is revealed that an itinerant description of hybridized f electrons produces magnetic properties of the compounds CeCo2, CeNi5, UAl3, UGa3, USi3, and UGe3 in close agreement with experiment. In the uranium compounds UX3 the strong spin-orbit coupling together with hybridization effects give rise to peculiar magnetic states in which the field-induced spin moments are antiparallel to the external field, and the magnetic response is dominated by the orbital contribution.

Preparation of a Cobalt(II) Cage: An Undergraduate Laboratory Experiment That Produces a ParaSHIFT Agent for Magnetic Resonance Spectroscopy

ERIC Educational Resources Information Center

Burns, Patrick J.; Tsitovich, Pavel B.; Morrow, Janet R.

2016-01-01

Laboratory experiments that demonstrate the effect of paramagnetic complexes on chemical shifts and relaxation times of protons are a useful way to introduce magnetic resonance spectroscopy (MRS) probes or magnetic resonance imaging (MRI) contrast agents. In this undergraduate inorganic chemistry experiment, a paramagnetic Co(II) cage complex is…

Effects of iodinated contrast agent, xylocaine and gadolinium concentration on the signal emitted in magnetic resonance arthrography: a samples study*

PubMed Central

da Silva, Yvana Lopes Pinheiro; Costa, Rita Zanlorensi Visneck; Pinho, Kátia Elisa Prus; Ferreira, Ricardo Rabello; Schuindt, Sueliton Miyamoto

2015-01-01

Objective To investigate the effects of dilution of paramagnetic contrast agent with iodinated contrast and xylocaine on the signal intensity during magnetic resonance arthrography, and to improve the paramagnetic contrast agent concentration utilized in this imaging modality. Materials and Methods Samples specially prepared for the study with three different concentrations of paramagnetic contrast agent diluted in saline, iodinated contrast agent and xylocaine were imaged with fast spin echo T1-weighted sequences with fat saturation. The samples were placed into flasks and graphical analysis of the signal intensity was performed as a function of the paramagnetic contrast concentration. Results As compared with samples of equal concentrations diluted only with saline, the authors have observed an average signal intensity decrease of 20.67% for iodinated contrast agent, and of 28.34% for xylocaine. However, the increased gadolinium concentration in the samples caused decrease in signal intensity with all the dilutions. Conclusion Minimizing the use of iodinated contrast media and xylocaine and/or the use of a gadolinium concentration of 2.5 mmol/L diluted in saline will improve the sensitivity of magnetic resonance arthrography. PMID:25987746

Gigantic magnetoelectric effect caused by magnetic-field-induced canted antiferromagnetic-paramagnetic transition in quasi-two-dimensional Ca2CoSi2O7 crystal

NASA Astrophysics Data System (ADS)

Akaki, M.; Tozawa, J.; Akahoshi, D.; Kuwahara, H.

2009-05-01

We have investigated the magnetic and dielectric properties of Ca2CoSi2O7 crystal. The dielectricity and magnetism of Ca2CoSi2O7 are strongly coupled below a canted antiferromagnetic transition temperature (TN). Magnetic fields induce electric polarization below TN. Interestingly, the magnetic-field-induced electric polarization is detected even without poling electric fields. Below TN, a canted antiferromagnetic-paramagnetic transition is induced by magnetic fields. The large magnetocapacitance is observed around TN. The origin of the large magnetocapacitance is due to the magnetic-field-induced the canted antiferromagnetic-paramagnetic transition.

Bulk magnetic properties of La1-xCaxMnO3 (0⩽x⩽0.14) : Signatures of local ferromagnetic order

NASA Astrophysics Data System (ADS)

Terashita, Hirotoshi; Neumeier, J. J.

2005-04-01

We report the bulk magnetic properties of hole-doped La1-xCaxMnO3 (0⩽x⩽0.14) in the paramagnetic and antiferromagnetic regions; the Mn4+ concentration was determined with chemical analysis. Significant enhancement of the effective paramagnetic moment illustrates the existence of ferromagnetic clusters (polarons). The data reveal a distinct crossover in the paramagnetic region, signifying competition between ferromagnetic clusters and antiferromagnetic correlations associated with the low-temperature magnetically ordered state. The results suggest similarity in the magnetic properties at low temperatures between hole-doped LaMnO3 and electron-doped CaMnO3 .

Tracer tomography: design concepts and field experiments using heat as a tracer.

PubMed

Doro, Kennedy O; Cirpka, Olaf A; Leven, Carsten

2015-04-01

Numerical and laboratory studies have provided evidence that combining hydraulic tomography with tomographic tracer tests could improve the estimation of hydraulic conductivity compared with using hydraulic data alone. Field demonstrations, however, have been lacking so far, which we attribute to experimental difficulties. In this study, we present a conceptual design and experimental applications of tracer tomography at the field scale using heat as a tracer. In our experimental design, we improve active heat tracer testing by minimizing possible effects of heat losses, buoyancy, viscosity, and changing boundary conditions. We also utilize a cost-effective approach of measuring temperature changes in situ at high resolution. We apply the presented method to the 8 m thick heterogeneous, sandy gravel, alluvial aquifer at the Lauswiesen Hydrogeological Research Site in Tübingen, Germany. Results of our tomographic heat-tracer experiments are in line with earlier work on characterizing the aquifer at the test site. We demonstrate from the experimental perspective that tracer tomography is applicable and suitable at the field scale using heat as a tracer. The experimental results also demonstrate the potential of heat-tracer tomography as a cost-effective means for characterizing aquifer heterogeneity. © 2014, National Ground Water Association.

Fractured-rock hydrogeophysics with electrically conductive and neutrally buoyant tracers

NASA Astrophysics Data System (ADS)

Shakas, A.; Linde, N.; Baron, L.; Le Borgne, T.; Bour, O.; Lavenant, N.; Gerard, M. F.

2016-12-01

Artificial tracer tests help to characterize and understand the dynamics of groundwater systems. This remains a challenging task, especially when dealing with highly heterogeneous formations in which flow can be very localized and the interpretation of tracer breakthrough curves may be ambiguous. As a complement to tracer tests, ground-penetrating radar (GPR) and electrical resistivity tomography can map the space-time migration of electrically conductive tracers. In hydrogeophysics, the most common tracer is dissolved table salt in water. However, conventional salt tracers lead to density effects that are often ignored. Even less than 1% density variations can have a dramatic effect on transport behavior and affect tracer tests in complex ways. Such effects have been demonstrated in our previous experiments that used single-hole GPR to monitor saline push-pull tests in fractured granite. It is possible to model density effects, but this leads to computational complexity and field dynamics that are not necessarily representative of the natural responses of the system. To minimize density effects, we performed a new set of push-pull tests using a neutrally buoyant and electrically conductive tracer at the same test site located close to Ploemeur, France. This novel tracer consists of a mixture of salt (NaCl), water and pure ethanol. Ethanol has a density of 789 g/L at 20° C and is used to counter-act the salt-induced density increase. Our GPR time-lapse images and tracer breakthrough data indicate a largely reversible transport process that confirms the neutral buoyancy of the tracer. Ethanol is biodegradable and does not pose significant environmental issues. Furthermore, calibration of the neutral-buoyant mixture is straightforward to perform in the field using Archimedes principle. Based on these results, we argue that neutrally buoyant ethanol-salt-water mixtures are ideal for a wide variety of hydrogeophysical tracer tests in porous or fractured media.

Multiferroic composites for magnetic data storage beyond the super-paramagnetic limit

NASA Astrophysics Data System (ADS)

Vopson, M. M.; Zemaityte, E.; Spreitzer, M.; Namvar, E.

2014-09-01

Ultra high-density magnetic data storage requires magnetic grains of <5 nm diameters. Thermal stability of such small magnetic grain demands materials with very large magneto-crystalline anisotropy, which makes data write process almost impossible, even when Heat Assisted Magnetic Recording (HAMR) technology is deployed. Here, we propose an alternative method of strengthening the thermal stability of the magnetic grains via elasto-mechanical coupling between the magnetic data storage layer and a piezo-ferroelectric substrate. Using Stoner-Wohlfarth single domain model, we show that the correct tuning of this coupling can increase the effective magneto-crystalline anisotropy of the magnetic grains making them stable beyond the super-paramagnetic limit. However, the effective magnetic anisotropy can also be lowered or even switched off during the write process by simply altering the applied voltage to the substrate. Based on these effects, we propose two magnetic data storage protocols, one of which could potentially replace HAMR technology, with both schemes promising unprecedented increases in the data storage areal density beyond the super-paramagnetic size limit.

Blind identification of the kinetic parameters in three-compartment models

NASA Astrophysics Data System (ADS)

Riabkov, Dmitri Y.; Di Bella, Edward V. R.

2004-03-01

Quantified knowledge of tissue kinetic parameters in the regions of the brain and other organs can offer information useful in clinical and research applications. Dynamic medical imaging with injection of radioactive or paramagnetic tracer can be used for this measurement. The kinetics of some widely used tracers such as [18F]2-fluoro-2-deoxy-D-glucose can be described by a three-compartment physiological model. The kinetic parameters of the tissue can be estimated from dynamically acquired images. Feasibility of estimation by blind identification, which does not require knowledge of the blood input, is considered analytically and numerically in this work for the three-compartment type of tissue response. The non-uniqueness of the two-region case for blind identification of kinetic parameters in three-compartment model is shown; at least three regions are needed for the blind identification to be unique. Numerical results for the accuracy of these blind identification methods in different conditions were considered. Both a separable variables least-squares (SLS) approach and an eigenvector-based algorithm for multichannel blind deconvolution approach were used. The latter showed poor accuracy. Modifications for non-uniform time sampling were also developed. Also, another method which uses a model for the blood input was compared. Results for the macroparameter K, which reflects the metabolic rate of glucose usage, using three regions with noise showed comparable accuracy for the separable variables least squares method and for the input model-based method, and slightly worse accuracy for SLS with the non-uniform sampling modification.

Complexation of β-cyclodextrin with dual molecular probes bearing fluorescent and paramagnetic moieties linked by short polyether chains.

PubMed

Mocanu, S; Matei, I; Ionescu, S; Tecuceanu, V; Marinescu, G; Ionita, P; Culita, D; Leonties, A; Ionita, Gabriela

2017-10-18

Electron paramagnetic resonance (EPR) and fluorescence spectroscopies provide molecular-level insights on the interaction of paramagnetic and fluorescent species with the microenvironment. A series of dual molecular probes bearing fluorescent and paramagnetic moieties linked by flexible short polyether chains have been synthesized. These new molecular probes open the possibility to investigate various multi-component systems such as host-guest systems, polymeric micelles, gels and protein solutions by using EPR and fluorescence spectroscopies concertedly. The EPR and fluorescence spectra of these compounds show that the dependence of the rotational correlation time and fluorescence quantum yield on the chain length of the linker is not linear, due to the flexibility of the polyether linker. The quenching effect of the nitroxide moiety on the fluorescence intensity of the pyrene group varies with the linker length and flexibility. The interaction of these dual molecular probes with β-cyclodextrin, in solution and in polymeric gels, was evaluated and demonstrated by analysis of EPR and fluorescence spectra.

Acoustic paramagnetic logging tool

DOEpatents

Vail, III, William B.

1988-01-01

New methods and apparatus are disclosed which allow measurement of the presence of oil and water in geological formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleons present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth3 s magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation . The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be preformed in open boreholes and in cased well bores.

Application of Electron Paramagnetic Resonance Spectroscopy to Comparative Examination of Different Groups of Free Radicals in Thermal Injuries Treated with Propolis and Silver Sulphadiazine

PubMed Central

Olczyk, Pawel; Ramos, Pawel; Bernas, Marcin; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

2013-01-01

Different groups of free radicals expressed in burn wounds treated with propolis and silver sulphadiazine were examined. The thermal effect forms major types of free radicals in a wound because of the breaking of chemical bonds. Free radicals, located in the heated skin, were tested after 21 days of treating by these two substances. The aim of this work was to find the method for determination of types and concentrations of different groups of free radicals in wound after high temperature impact during burning. The effects of the therapy by propolis and silver sulphadiazine on free radicals were studied. Since the chemical methods of free radicals studies are destructive, the usefulness of the electron paramagnetic resonance spectroscopy was tested in this work. The electron paramagnetic resonance spectra measured with the microwave power of 2.2 mW were numerically fitted by theoretical curves of Gaussian and Lorentzian shapes. The experimental electron paramagnetic resonance spectra of tissue samples are best fitted by the sum of one Gauss and two Lorentz lines. An innovatory numerical procedure of spectroscopic skin analysis was presented. It is very useful in the alternative medicine studies. PMID:23762162

Paramagnetic Defects in Electron-Irradiated Yttria-Stabilized Zirconia: Effect of Yttria Content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costantini, Jean-Marc; Beuneu, Francois; Morrison-Smith, Sarah

2011-01-01

We have studied the effect of the yttria content on the paramagnetic centres in electron-irradiated yttria-stabilized zirconia (ZrO2: Y3+) or YSZ. Single crystals with 9.5 mol% or 18 mol% Y2O3 were irradiated with electrons of 1.0, 1.5, 2.0 and 2.5 MeV. The paramagnetic centre production was studied by X-band EPR spectroscopy. The same paramagnetic centres were identified for both chemical compositions, namely two electron centres, i.e. i) F+-type centres (involving singly ionized oxygen vacancies), and ii) so-called T centres (Zr3+ in a trigonal symmetry site), and hole-centres. A strong effect is observed on the production of hole-centres which are stronglymore » enhanced when doubling the yttria content. However, no striking effect is found on the electron centres (except the enhancement of an extra line associated to the F+-type centres). It is concluded that hole-centres are produced by inelastic interactions, whereas F+-type centres are produced by elastic collisions with no effect of the yttria content on the defect production rate. In the latter case, the threshold displacement energy (Ed) of oxygen is estimated from the electron-energy dependence of the F+-type centre production rate, with no significant effect of the yttria content on Ed. An Ed value larger than 120 eV is found. Accordingly, classical molecular dynamics (MD) simulations with a Buckingham-type potential show that Ed values for Y and O are likely to be in excess of 200 eV. Due to the difficulty in displacing O or Y atoms, the radiation-induced defects may alternatively be a result of Zr atom displacements for Ed = 80 1 eV with subsequent defect re-arrangement.« less

Models And Experiments Of Laminar Diffusion Flames In Non-Uniform Magnetic Fields

NASA Technical Reports Server (NTRS)

Baker, J.; Varagani, R.; Saito, K.

2003-01-01

Non-uniform magnetic fields affect laminar diffusion flames as a result of the paramagnetic and diamagnetic properties of the products and reactants. Paramagnetism is the weak attraction to a magnetic field a material exhibits as a result of permanent magnetic dipole moments in the atoms of the material. Diamagnetism is the weak repulsion to a magnetic field exhibited by a material due to the lack of permanent magnetic dipole moments in the atoms of a material. The forces associated with paramagnetic and diamagnetism are several orders of magnitude less than the forces associated with the more familiar ferromagnetism. A typical example of a paramagnetic gas is oxygen while hydrocarbon fuels and products of combustion are almost always diamagnetic. The fact that magnets can affect flame behavior has been recognized for more than one hundred years. Early speculation was that such behavior was due to the magnetic interaction with the ionized gases associated with a flame. Using a scaling analysis, it was later shown that for laminar diffusion flames the magnetic field/ionized gas interaction was insignificant to the paramagnetic and diamagnetic influences. In this effort, the focus has been on examining laminar diffusion slot flames in the presence of non-uniform upward decreasing magnetic fields produced using permanent magnets. The principal reason for choosing slot flames was mathematical models of such flames show an explicit dependence on gravitational body forces, in the buoyancy-controlled regime, and an applied magnetic field would also impose a body force. In addition, the behavior of such flames was more easily visualized while maintaining the symmetry of the two-dimensional problem whereas it would have been impossible to obtain a symmetric magnetic field around a circular flame and still visually record the flame height and shape along the burner axis. The motivation for choosing permanent magnets to produce the magnetic fields was the assumption that space-related technologies based on the knowledge gained during this investigation would more likely involve permanent magnets as opposed to electromagnets. While no analysis has been done here to quantify the impact that an electric field, associated with an electromagnetic, would have relative to the paramagnetic and diamagnetic interactions, by using permanent magnets this potential effect was completely eliminated and thus paramagnetic and diamagnetic effects were isolated.

Paramagnet induced signal quenching in MAS-DNP experiments in frozen homogeneous solutions

NASA Astrophysics Data System (ADS)

Corzilius, Björn; Andreas, Loren B.; Smith, Albert A.; Ni, Qing Zhe; Griffin, Robert G.

2014-03-01

The effects of nuclear signal quenching induced by the presence of a paramagnetic polarizing agent are documented for conditions used in magic angle spinning (MAS)-dynamic nuclear polarization (DNP) experiments on homogeneous solutions. In particular, we present a detailed analysis of three time constants: (1) the longitudinal build-up time constant TB for 1H; (2) the rotating frame relaxation time constant T1ρ for 1H and 13C and (3) T2 of 13C, the transverse relaxation time constant in the laboratory frame. These relaxation times were measured during microwave irradiation at a magnetic field of 5 T (140 GHz) as a function of the concentration of four polarizing agents: TOTAPOL, 4-amino-TEMPO, trityl (OX063), and Gd-DOTA and are compared to those obtained for a sample lacking paramagnetic doping. We also report the EPR relaxation time constants T1S and T2S, the DNP enhancements, ε, and the parameter E, defined below, which measures the sensitivity enhancement for the four polarizing agents as a function of the electron concentration. We observe substantial intensity losses (paramagnetic quenching) with all of the polarizing agents due to broadening mechanisms and cross relaxation during MAS. In particular, the monoradical trityl and biradical TOTAPOL induce ∼40% and 50% loss of signal intensity. In contrast there is little suppression of signal intensity in static samples containing these paramagnetic species. Despite the losses due to quenching, we find that all of the polarizing agents provide substantial gains in signal intensity with DNP, and in particular that the net enhancement is optimal for biradicals that operate with the cross effect. We discuss the possibility that much of this polarization loss can be regained with the development of instrumentation and methods to perform electron decoupling.

Effects of plasma proteins on sieving of tracer macromolecules in glomerular basement membrane.

PubMed

Lazzara, M J; Deen, W M

2001-11-01

It was found previously that the sieving coefficients of Ficoll and Ficoll sulfate across isolated glomerular basement membrane (GBM) were greatly elevated when BSA was present at physiological levels, and it was suggested that most of this increase might have been the result of steric interactions between BSA and the tracers (5). To test this hypothesis, we extended the theory for the sieving of macromolecular tracers to account for the presence of a second, abundant solute. Increasing the concentration of an abundant solute is predicted to increase the equilibrium partition coefficient of a tracer in a porous or fibrous membrane, thereby increasing the sieving coefficient. The magnitude of this partitioning effect depends on solute size and membrane structure. The osmotic reduction in filtrate velocity caused by an abundant, mostly retained solute will also tend to elevate the tracer sieving coefficient. The osmotic effect alone explained only about one-third of the observed increase in the sieving coefficients of Ficoll and Ficoll sulfate, whereas the effect of BSA on tracer partitioning was sufficient to account for the remainder. At physiological concentrations, predictions for tracer sieving in the presence of BSA were found to be insensitive to the assumed shape of the protein (sphere or prolate spheroid). For protein mixtures, the theoretical effect of 6 g/dl BSA on the partitioning of spherical tracers was indistinguishable from that of 3 g/dl BSA and 3 g/dl IgG. This suggests that for partitioning and sieving studies in vitro, a good experimental model for plasma is a BSA solution with a mass concentration matching that of total plasma protein. The effect of plasma proteins on tracer partitioning is expected to influence sieving not only in isolated GBM but also in intact glomerular capillaries in vivo.

Origin of negative resistivity slope in U-based ferromagnets

NASA Astrophysics Data System (ADS)

Havela, L.; Paukov, M.; Buturlim, V.; Tkach, I.; Mašková, S.; Dopita, M.

2018-05-01

Ultra-nanocrystalline UH3-based ferromagnets with TC ≈ 200 K exhibit a flat temperature dependence of electrical resistivity with a negative slope both in the ferromagnetic and paramagnetic range. The ordered state with randomness on atomic scale, equivalent to a non-collinear ferromagnetism, can be affected by magnetic field, supressing the static magnetic disorder, which reduces the resistivity and removes the negative slope. It is deduced that the dynamic magnetic disorder in the paramagnetic state can be conceived as continuation of the static disorder in the ordered state. The experiments, performed for (UH3)0.78Mo0.12Ti0.10, demonstrate that the negative resistivity slope, observed for numerous U-based intermetallics in the paramagnetic state, can be due to the strong disorder effect on resistivity. The resulting weak localization, as a quantum interference effect which increases resistivity, is gradually suppressed by enhanced temperature, contributing by electron-phonon scattering, inelastic in nature and removing the quantum coherence.

Adenosine receptor agonist NECA increases cerebral extravasation of fluorescein and low molecular weight dextran independent of blood-brain barrier modulation

PubMed Central

Cheng, Chih-Chung; Yang, Ya Lan; Liao, Kate Hsiurong; Lai, Ted Weita

2016-01-01

Conventional methods for therapeutic blood-brain barrier (BBB) disruption facilitate drug delivery but are cumbersome to perform. A previous study demonstrated that adenosine receptor (AR) stimulation by 5′-N-ethylcarboxamide adenosine (NECA) increased the extravasation of intravascular tracers into the brain and proposed that AR agonism may be an effective method for therapeutic BBB disruption. We attempted to confirm the extravasation of tracers into the brain and also investigated tracer extravasation into peripheral organs and tracer retention in the blood. We found that NECA not only increased the extravasation of intravascular fluorescein and low molecular weight dextran into the brain of mice but also increased the concentrations of these tracers in the blood. In fact, the brain:blood ratio-normalized BBB permeability for either tracer is actually decreased by NECA administration. Elevated blood urea nitrogen levels in mice following NECA treatment suggested that renal function impairment was a probable cause of tracer retention. Therefore, NECA has almost no effect on the extravasation of intravascular Evans blue dye (EBD), an albumin-binding tracer with little renal clearance. Rather than inducing BBB disruption, our study demonstrated that NECA increased tracer extravasation into the brain by increasing the concentration gradient of the tracer across the BBB. PMID:27025761

Adenosine receptor agonist NECA increases cerebral extravasation of fluorescein and low molecular weight dextran independent of blood-brain barrier modulation.

PubMed

Cheng, Chih-Chung; Yang, Ya Lan; Liao, Kate Hsiurong; Lai, Ted Weita

2016-03-30

Conventional methods for therapeutic blood-brain barrier (BBB) disruption facilitate drug delivery but are cumbersome to perform. A previous study demonstrated that adenosine receptor (AR) stimulation by 5'-N-ethylcarboxamide adenosine (NECA) increased the extravasation of intravascular tracers into the brain and proposed that AR agonism may be an effective method for therapeutic BBB disruption. We attempted to confirm the extravasation of tracers into the brain and also investigated tracer extravasation into peripheral organs and tracer retention in the blood. We found that NECA not only increased the extravasation of intravascular fluorescein and low molecular weight dextran into the brain of mice but also increased the concentrations of these tracers in the blood. In fact, the brain:blood ratio-normalized BBB permeability for either tracer is actually decreased by NECA administration. Elevated blood urea nitrogen levels in mice following NECA treatment suggested that renal function impairment was a probable cause of tracer retention. Therefore, NECA has almost no effect on the extravasation of intravascular Evans blue dye (EBD), an albumin-binding tracer with little renal clearance. Rather than inducing BBB disruption, our study demonstrated that NECA increased tracer extravasation into the brain by increasing the concentration gradient of the tracer across the BBB.

Demonstrating Paramagnetism Using Liquid Nitrogen.

ERIC Educational Resources Information Center

Simmonds, Ray; And Others

1994-01-01

Describes how liquid nitrogen is attracted to the poles of neodymium magnets. Nitrogen is not paramagnetic, so the attraction suggests that the liquid nitrogen contains a small amount of oxygen, which causes the paramagnetism. (MVL)

VARIATION OF THE VISCOSITY OF CERTAIN GAS-OXYGEN MIXTURES UNDER THE INFLUENCE OF MAGNETIC FIELD; Variatia Viscozitatii unor Amestecuri de Gaze cu Oxigen sub Influenta unui Cimp Magnetic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ursu, I.

1958-01-01

The paramagnetic effects of oxygen and gas-oxygen mixtures are discussed. One of the paramagnetic effect the varistion of viscosity during the viscous flow in a magnetic field. The viscosity of gaseous oxygen and certain gas-oxygen mixtures decreased when the flow occurred in a magnetic field. The dependence of this effect on the size of the capillaries and porous materials was investigated. The viscosity was also found to vary with the concentration of oxygen and the other components forming the mixture. The results of the investigations with various gas mixtures are graphically shown. (A.C.)

Spin injection and spin transport in paramagnetic insulators

DOE PAGES

Okamoto, Satoshi

2016-02-22

We investigate the spin injection and the spin transport in paramagnetic insulators described by simple Heisenberg interactions using auxiliary particle methods. Some of these methods allow access to both paramagnetic states above magnetic transition temperatures and magnetic states at low temperatures. It is predicted that the spin injection at an interface with a normal metal is rather insensitive to temperatures above the magnetic transition temperature. On the other hand below the transition temperature, it decreases monotonically and disappears at zero temperature. We also analyze the bulk spin conductance. We show that the conductance becomes zero at zero temperature as predictedmore » by linear spin wave theory but increases with temperature and is maximized around the magnetic transition temperature. These findings suggest that the compromise between the two effects determines the optimal temperature for spintronics applications utilizing magnetic insulators.« less

Upcycling: converting waste plastics into paramagnetic, conducting, solid, pure carbon microspheres.

PubMed

Pol, Vilas Ganpat

2010-06-15

The recent tremendous increase in the volume of waste plastics (WP) will have a harmful environmental impact on the health of living beings. Hundreds of years are required to degrade WP in atmospheric conditions. Hence, in coming years, in addition to traditional recycling services, innovative "upcycling" processes are necessary. This article presents an environmentally benign, solvent-free autogenic process that converts various WP [low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PET), polystyrene (PS), or their mixtures] into carbon microspheres (CMSs), an industrially significant, value-added product. The thermal dissociation of these individual or mixed WP in a closed reactor under autogenic pressure ( approximately 1000 psi) produced dry, pure powder of CMSs. In this paper, the optimization of process parameters such as the effect of mixing of WP with other materials, and the role of reaction temperature and time are reported. Employing advanced analytical techniques, the atomic structure, composition, and morphology of as-obtained CMSs were analyzed. The room-temperature paramagnetism in CMSs prepared from waste LDPE, HDPE, and PS was further studied by electron paramagnetic resonance (EPR). The conducting and paramagnetic nature of CMSs holds promise for their potential applications in toners, printers, paints, batteries, lubricants, and tires.

Point defects in crystalline zircon (zirconium silicate), ZrSiO4: electron paramagnetic resonance studies

NASA Astrophysics Data System (ADS)

Tennant, W. C.; Claridge, R. F. C.; Walsby, C. J.; Lees, N. S.

This article outlines the present state of knowledge of paramagnetic defects in crystalline zircon as obtained mainly, but not exclusively, from electron paramagnetic resonance (EPR) studies in crystalline zircon (zirconium silicate, ZrSiO4). The emphasis is on single-crystal studies where, in principle, unambiguous analysis is possible. Firstly, the crystallography of zircon is presented. Secondly, the relationships between available crystal-site symmetries and the symmetries of observed paramagnetic species in zircon, and how these observations lead to unambiguous assignments of point-group symmetries for particular paramagnetic species are detailed. Next, spin-Hamiltonian (SH) analysis is discussed with emphasis on the symmetry relationships that necessarily exist amongst the Laue classes of the crystal sites in zircon, the paramagnetic species occupying those sites and the SH itself. The final sections of the article then survey the results of EPR studies on zircon over the period 1960-2002.

Paramagnetic defects in electron-irradiated yttria-stabilized zirconia: Effect of yttria content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costantini, Jean-Marc; Beuneu, Francois; Morrison-Smith, Sarah E.

2011-12-20

We have studied the effect of the yttria content on the paramagnetic centres in electron-irradiated yttria-stabilized zirconia (ZrO2: Y3+) or YSZ. Single crystals with 9.5 mol% or 18 mol% Y2O3 were irradiated with electrons of 1.0, 1.5, 2.0 and 2.5 MeV. The paramagnetic centre production was studied by X-band EPR spectroscopy. The same paramagnetic centres were identified for both chemical compositions, namely two electron centres, i.e. i) F+-type centres (involving singly ionized oxygen vacancies), and ii) so-called T centres (Zr3+ in a trigonal symmetry site), and hole-centres. A strong effect is observed on the production of hole-centres which are stronglymore » enhanced when doubling the yttria content. However, no striking effect is found on the electron centres (except the enhancement of an extra line associated to the F+-type centres). It is concluded that hole-centres are produced by inelastic interactions, whereas F+-type centres are produced by elastic collisions with no effect of the yttria content on the defect production rate. In the latter case, the threshold displacement energy (Ed) of oxygen is estimated from the electron-energy dependence of the F+-type centre production rate, with no significant effect of the yttria content on Ed. An Ed value larger than 120 eV is found. Accordingly, classical molecular dynamics (MD) simulations with a Buckingham-type potential show that Ed values for Y and O are likely to be in excess of 200 eV. It is concluded that F+-type centres might be actually oxygen divacancies (F2+-type centres). Due to the difficulty in displacing O or Y atoms, the radiation-induced defects may alternatively be a result of Zr atom displacements for Ed = 80 ± 1 eV with subsequent defect re-arrangement.« less

Ambiguity in measuring matrix diffusion with single-well injection/recovery tracer tests

USGS Publications Warehouse

Lessoff, S.C.; Konikow, Leonard F.

1997-01-01

Single-well injection/recovery tracer tests are considered for use in characterizing and quantifying matrix diffusion in dual-porosity aquifers. Numerical modeling indicates that neither regional drift in homogeneous aquifers, nor heterogeneity in aquifers having no regional drift, nor hydrodynamic dispersion significantly affects these tests. However, when drift is coupled simultaneously with heterogeneity, they can have significant confounding effects on tracer return. This synergistic effect of drift and heterogeneity may help explain irreversible flow and inconsistent results sometimes encountered in previous single-well injection/recovery tracer tests. Numerical results indicate that in a hypothetical single-well injection/recovery tracer test designed to demonstrate and measure dual-porosity characteristics in a fractured dolomite, the simultaneous effects of drift and heterogeneity sometimes yields responses similar to those anticipated in a homogeneous dual-porosity formation. In these cases, tracer recovery could provide a false indication of the occurrence of matrix diffusion. Shortening the shut-in period between injection and recovery periods may make the test less sensitive to drift. Using multiple tracers having different diffusion characteristics, multiple tests having different pumping schedules, and testing the formation at more than one location would decrease the ambiguity in the interpretation of test data.

Numerical simulations to assess the tracer dilution method for measurement of landfill methane emissions.

PubMed

Taylor, Diane M; Chow, Fotini K; Delkash, Madjid; Imhoff, Paul T

2016-10-01

Landfills are a significant contributor to anthropogenic methane emissions, but measuring these emissions can be challenging. This work uses numerical simulations to assess the accuracy of the tracer dilution method, which is used to estimate landfill emissions. Atmospheric dispersion simulations with the Weather Research and Forecast model (WRF) are run over Sandtown Landfill in Delaware, USA, using observation data to validate the meteorological model output. A steady landfill methane emissions rate is used in the model, and methane and tracer gas concentrations are collected along various transects downwind from the landfill for use in the tracer dilution method. The calculated methane emissions are compared to the methane emissions rate used in the model to find the percent error of the tracer dilution method for each simulation. The roles of different factors are examined: measurement distance from the landfill, transect angle relative to the wind direction, speed of the transect vehicle, tracer placement relative to the hot spot of methane emissions, complexity of topography, and wind direction. Results show that percent error generally decreases with distance from the landfill, where the tracer and methane plumes become well mixed. Tracer placement has the largest effect on percent error, and topography and wind direction both have significant effects, with measurement errors ranging from -12% to 42% over all simulations. Transect angle and transect speed have small to negligible effects on the accuracy of the tracer dilution method. These tracer dilution method simulations provide insight into measurement errors that might occur in the field, enhance understanding of the method's limitations, and aid interpretation of field data. Copyright © 2016 Elsevier Ltd. All rights reserved.

Predictive value of tracer studies for /sup 131/I treatment in hyperthyroid cats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broome, M.R.; Turrel, J.M.; Hays, M.T.

In 76 cats with hyperthyroidism, peak thyroidal radioiodine (/sup 131/I) uptakes and effective half-lives were determined after administration of tracer and therapeutic activities of /sup 131/I. In 6 additional hyperthyroid cats, only peak thyroidal uptakes after administration of tracer and therapeutic activities of /sup 131/I were determined. Good correlation was found between peak thyroidal uptakes of tracer and therapeutic /sup 131/I; however, only fair correlation was observed between effective half-lives. In 79% of the cats, the effective half-life for therapeutic /sup 131/I was longer than that for tracer /sup 131/I. After administration of therapeutic activity of /sup 131/I, monoexponential andmore » biphasic decay curves were observed in 51 and 16 cats, respectively. Using therapeutic kinetic data, radiation doses to the thyroid gland were calculated retrospectively on the basis of 2 methods for determining the activity of /sup 131/I administered: (1) actual administration of tracer-compensated activity and (2) hypothetic administration of uniform activity (3 mCi). Because of the good predictive ability of tracer kinetic data for the therapeutic kinetic data, the tracer-compensated radiation doses came significantly (P = 0.008) closer to the therapeutic goal than did the uniform-activity doses. In addition, the use of tracer kinetic information reduced the extent of the tendency for consistently high uniform-activity doses. A manual method for acquiring tracer kinetic data was developed and was an acceptable alternative to computerized techniques. Adoption of this method gives individuals and institutions with limited finances the opportunity to characterize the iodine kinetics in cats before proceeding with administration of therapeutic activities of /sup 131/I.« less

A DNA Tracer System for Hydrological Environment Investigations.

PubMed

Liao, Renkuan; Yang, Peiling; Wu, Wenyong; Luo, Dan; Yang, Dayong

2018-02-20

To monitor and manage hydrological pollution effectively, tracing sources of pollutants is of great importance and also is in urgent need. A variety of tracers have been developed such as isotopes, silica, bromide, and dyes; however, practical limitations of these traditional tracers still exist such as lack of multiplexed, multipoint tracing and interference of background noise. To overcome these limitations, a new tracing system based on DNA nanomaterials, namely DNA tracer, has already been developed. DNA tracers possess remarkable advantages including sufficient species, specificity, environmental friendly, stable migration, and high sensitivity as well as allowing for multipoints tracing. In this review article, we introduce the molecular design, synthesis, protection and signal readout strategies of DNA tracers, compare the advantages and disadvantages of DNA tracer with traditional tracers, and summarize the-state-of-art applications in hydrological environment investigations. In the end, we provide our perspective on the future development of DNA tracers.

Magnetic properties of point defects in proton irradiated diamond

NASA Astrophysics Data System (ADS)

Makgato, T. N.; Sideras-Haddad, E.; Ramos, M. A.; García-Hernández, M.; Climent-Font, A.; Zucchiatti, A.; Muñoz-Martin, A.; Shrivastava, S.; Erasmus, R.

2016-09-01

We investigate the magnetic properties of ultra-pure type-IIa diamond following irradiation with proton beams of ≈1-2 MeV energy. SQUID magnetometry indicate the formation of Curie type paramagnetism according to the Curie law. Raman and Photoluminescence spectroscopy measurements show that the primary structural features created by proton irradiation are the centers: GR1, ND1, TR12 and 3H. The Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations together with SQUID observations show a strong correlation between vacancy production, proton fluence and the paramagnetic factor. At an average surface vacancy spacing of ≈1-1.6 nm and bulk (peak) vacancy spacing of ≈0.3-0.5 nm Curie paramagnetism is induced by formation of ND1 centres with an effective magnetic moment μeff~(0.1-0.2)μB. No evidence of long range magnetic ordering is observed in the temperature range 4.2-300 K.

Low-temperature anomalies in the dynamic elastic moduli of cubic AIIBVI crystals with 3d-transition metal impurities

NASA Astrophysics Data System (ADS)

Lonchakov, A. T.

2011-04-01

A negative paramagnetic contribution to the dynamic elastic moduli is identified in AIIBVI:3d wide band-gap compounds for the first time. It appears as a paramagnetic elastic, or, briefly, paraelastic, susceptibility. These compounds are found to have a linear temperature dependence for the inverse paraelastic susceptibility. This is explained by a contribution from the diagonal matrix elements of the orbit-lattice interaction operators in the energy of the spin-orbital states of the 3d-ion as a function of applied stress (by analogy with the Curie contribution to the magnetic susceptibility). The inverse paraelastic susceptibility of AIIBVI crystals containing non-Kramers 3d-ions is found to deviate from linearity with decreasing temperature and reaches saturation. This effect is explained by a contribution from nondiagonal matrix elements (analogous to the well known van Vleck contribution to the magnetic susceptibility of paramagnets).

Application of electron paramagnetic resonance imaging to the characterization of the Ultem(R) exposed to 1 MeV electrons. Correlation of radical density data to tiger code calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suleman, N.K.

1994-12-01

A major long-term goal of the Materials Division at the NASA Langley Research Center is the characterization of new high-performance materials that have potential applications in the aircraft industry, and in space. The materials used for space applications are often subjected to a harsh and potentially damaging radiation environment. The present study constitutes the application of a novel technique to obtain reliable data for ascertaining the molecular basis for the resilience and durability of materials that have been exposed to simulated space radiations. The radiations of greatest concern are energetic electrons and protons, as well as galactic cosmic rays. Presently,more » the effects of such radiation on matter are not understood in their entirety. It is clear however, that electron radiation causes ionization and homolytic bond rupture, resulting in the formation of paramagnetic spin centers in the polymer matrices of the structural materials. Since the detection and structure elucidation of paramagnetic species are most readily accomplished using Electron Paramagnetic Resonance (EPR) Spectroscopy, the NASA LaRC EPR system was brought back on-line during the 1991 ASEE term. The subsequent 1992 ASEE term was devoted to the adaptation of the EPR core system to meet the requirements for EPR Imaging (EPRI), which provides detailed information on the spatial distribution of paramagnetic species in bulk media. The present (1994) ASEE term was devoted to the calibration of this EPR Imaging system, as well as to the application of this technology to study the effects of electron irradiation on Ultem(exp R), a high performance polymer which is a candidate for applications in aerospace. The Ultem was exposed to a dose of 2.4 x 10(exp 9) Rads (1-MeV energy/electron) at the LaRC electron accelerator facility. Subsequently, the exposed specimens were stored in liquid nitrogen, until immediately prior to analyses by EPRI.« less

Non-input analysis for incomplete trapping irreversible tracer with PET.

PubMed

Ohya, Tomoyuki; Kikuchi, Tatsuya; Fukumura, Toshimitsu; Zhang, Ming-Rong; Irie, Toshiaki

2013-07-01

When using metabolic trapping type tracers, the tracers are not always trapped in the target tissue; i.e., some are completely trapped in the target, but others can be eliminated from the target tissue at a measurable rate. The tracers that can be eliminated are termed 'incomplete trapping irreversible tracers'. These incomplete trapping irreversible tracers may be clinically useful when the tracer β-value, the ratio of the tracer (metabolite) elimination rate to the tracer efflux rate, is under approximately 0.1. In this study, we propose a non-input analysis for incomplete trapping irreversible tracers based on the shape analysis (Shape), a non-input analysis used for irreversible tracers. A Monte Carlo simulation study based on experimental monkey data with two actual PET tracers (a complete trapping irreversible tracer [(11)C]MP4A and an incomplete trapping irreversible tracer [(18)F]FEP-4MA) was performed to examine the effects of the environmental error and the tracer elimination rate on the estimation of the k3-parameter (corresponds to metabolic rate) using Shape (original) and modified Shape (M-Shape) analysis. The simulation results were also compared with the experimental results obtained with the two PET tracers. When the tracer β-value was over 0.03, the M-Shape method was superior to the Shape method for the estimation of the k3-parameter. The simulation results were also in reasonable agreement with the experimental ones. M-Shape can be used as the non-input analysis of incomplete trapping irreversible tracers for PET study. Copyright © 2013 Elsevier Inc. All rights reserved.

Combining Step Gradients and Linear Gradients in Density.

PubMed

Kumar, Ashok A; Walz, Jenna A; Gonidec, Mathieu; Mace, Charles R; Whitesides, George M

2015-06-16

Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density.

Development of device for quantifying magnetic nanoparticle tracers accumulating in sentinel lymph nodes

NASA Astrophysics Data System (ADS)

Kuwahata, Akihiro; Kaneko, Miki; Chikaki, Shinichi; Kusakabe, Moriaki; Sekino, Masaki

2018-05-01

The developed device with electromagnetic coils and small permanent magnets quantifies the iron contents of superparamagnetic iron oxide nanoparticles for sentinel lymph node (SLN) biopsy. To remove diamagnetic and paramagnetic components and detect only superparamagnetic components, a 2nd harmonics signal is detected by a gradiometer under a moderate AC magnetic field (1-2 mT) with the fundamental frequency (2.944 kHz) of the coils and DC magnetic field (1-2 mT) of the magnets. The detection limit with a signal-to-noise ratio of 5 is approximately 0.28 μg of iron, and the device has a wide dynamic range of 104, 0.28 μg-2.8 mg. Additional coils and permanent magnets play an important role producing the optimum distribution of AC/DC magnetic fields for an iron distribution-independent and SLN size-independent quantification. We demonstrated the quantification of the iron in phantoms, which have a size of 3-20 mm with varied iron distributions and contain magnetic nanoparticles numerically. These results indicate that the developed device is useful for quantifying the magnetic nanoparticles accumulating in SLNs.

Paramagnetic fluorinated nanoemulsions for sensitive cellular fluorine-19 magnetic resonance imaging

PubMed Central

Kislukhin, Alexander A.; Xu, Hongyan; Adams, Stephen R.; Narsinh, Kazim H.; Tsien, Roger Y.; Ahrens, Eric T.

2016-01-01

Fluorine-19 magnetic resonance imaging (19F MRI) probes enable quantitative in vivo detection of cell therapies and inflammatory cells. Here, we describe the formulation of perfluorocarbon-based nanoemulsions with improved sensitivity for cellular MRI. Reduction of the 19F spin-lattice relaxation time (T1) enables rapid imaging and an improved signal-to-noise ratio, thereby improving cell detection sensitivity. We synthesized metal-binding β-diketones conjugated to linear perfluoropolyether (PFPE), formulated these fluorinated ligands as aqueous nanoemulsions, and then metalated them with various transition and lanthanide ions in the fluorous phase. Iron(III) tris-β-diketonate ('FETRIS') nanoemulsions with PFPE have low cytotoxicity (<20%) and superior MRI properties. Moreover, the 19F T1 can readily be reduced by an order of magnitude and tuned by stoichiometric modulation of the iron concentration. The resulting 19F MRI detection sensitivity is enhanced by 3-to-5 fold over previously used tracers at 11.7 T, and is predicted to increase by at least 8-fold at clinical field strength of 3 T. PMID:26974409

Experiments to Evaluate and Implement Passive Tracer Gas Methods to Measure Ventilation Rates in Homes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lunden, Melissa; Faulkner, David; Heredia, Elizabeth

2012-10-01

This report documents experiments performed in three homes to assess the methodology used to determine air exchange rates using passive tracer techniques. The experiments used four different tracer gases emitted simultaneously but implemented with different spatial coverage in the home. Two different tracer gas sampling methods were used. The results characterize the factors of the execution and analysis of the passive tracer technique that affect the uncertainty in the calculated air exchange rates. These factors include uncertainties in tracer gas emission rates, differences in measured concentrations for different tracer gases, temporal and spatial variability of the concentrations, the comparison betweenmore » different gas sampling methods, and the effect of different ventilation conditions.« less

Magnetic Ordering in Gold Nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrachev, Mikhail; Antonello, Sabrina; Dainese, Tiziano

Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au 25(SCH 2CH 2Ph) 18 0, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au 25(SCH 2CH 2Ph) 18 0 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. Onemore » or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena« less

Magnetic Ordering in Gold Nanoclusters

DOE PAGES

Agrachev, Mikhail; Antonello, Sabrina; Dainese, Tiziano; ...

2017-06-12

Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au 25(SCH 2CH 2Ph) 18 0, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au 25(SCH 2CH 2Ph) 18 0 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. Onemore » or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena« less

Investigations on the Crystal-Chemical Behavior of Transition-Metal-Bearing Aluminosilicate Garnet Solid Solutions Using 27Al and 29Si NMR Spectroscopy

NASA Astrophysics Data System (ADS)

Palke, A. C.; Geiger, C. A.; Stebbins, J. F.

2015-12-01

The petrological importance of silicate garnet is derived from the presence of three distinct cation sites of varying size and coordination number. This allows for a wide range of trace, minor, and major element substitutions. However, a full and precise crystal-chemical understanding of the nature of transition metals in garnet is not at hand. Possible mechanisms of various charge-balanced substitutions (e.g. octahedral Ti4+ or tetrahedral Al3+) and the structural state of solid solutions (i.e. short- to long-range ordering) need study. We report on ongoing efforts in these directions using 27Al and 29Si Magic-Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. Early work on synthetic and natural Fe- and Mn-bearing pyrope- and grossular-rich garnets focused on the effect these paramagnetic transition metals have in measuring and interpreting NMR spectra. These results have been expanded with NMR measurements on synthetic pyrope-rich garnets containing other paramagnetic transition metals including Cr3+, V3+, Co2+, and Ni2+ as well as diamagnetic Ti4+. NMR peaks are severely broadened in the presence of even small concentrations of Cr3+, Mn2+, and Fe3+ leading to a loss of spectral resolution. On the other hand, the spectra of garnet containing V3+, Fe2+, Co2+, and Ni2+ have better resolution and show separate paramagnetically shifted NMR peaks. In some cases, crystal-chemical information can be obtained because of the large frequency separations between the NMR peaks that can be assigned to various local atomic configurations around Al and Si. Furthermore, the 27Al NMR spectrum of a synthetic pyrope garnet with about 2% diamagnetic Ti4+ on the octahedral site showed the absence of any tetrahedral Al3+, which rules out the substitution mechanism VITi + IVAl = VIAl + IVSi in the solid solution. Our NMR investigations on garnet are now being made at the exploratory level. We think that NMR spectra of diamagnetic garnet can provide information on a number of crystal-chemical properties. Spectra of garnet containing various paramagnetic transition elements can also, in some cases, give local structural information. With a better understanding of paramagnetic effects in NMR spectroscopy, this type of study can possibly be expanded to other geologically important paramagnetic minerals and phases.

Safety of stable isotope use.

PubMed

Koletzko, B; Sauerwald, T; Demmelmair, H

1997-08-01

The increased employment of stable isotope tracers for diagnostic and research purposes frequently raises questions on potential risks associated with their use, which is of particular importance in the paediatric age group. Biological effects and the potential of adverse events has been evaluated in a large number of animal and, in part, also human studies. Possible differences in physical, chemical and biochemical behaviour resulting in kinetic and thermodynamic isotope effects between stable isotopes of the same element are related to the relative differences in atomic weight. Deuterium (2H), which differs markedly in mass from the predominant hydrogen isotope 1H, may induce serious side-effects at high concentrations in body fluids. The threshold dose for the occurrence of side-effects lies well above the usual tracer dosages for clinical use. In contrast to deuterium, heavier stable isotopes such as 13C, 15N or 18O that differ relatively little in mass from the predominant isotopes such as 12C, does not show any adverse biological effects even at highest enrichments. The doses of stable isotope tracer substances that are used for clinical diagnostic and research purposes appear safe and without any adverse effects. Stable isotope tracers should only be used in children if the trace is safe at the doses applied, and tracer is chemically pure and stable. In the case of intravenous application, the tracer preparation must also be sterile and pyrogen free.

Coarsening of physics for biogeochemical model in NEMO

NASA Astrophysics Data System (ADS)

Bricaud, Clement; Le Sommer, Julien; Madec, Gurvan; Deshayes, Julie; Chanut, Jerome; Perruche, Coralie

2017-04-01

Ocean mesoscale and submesoscale turbulence contribute to ocean tracer transport and to shaping ocean biogeochemical tracers distribution. Representing adequately tracer transport in ocean models therefore requires to increase model resolution so that the impact of ocean turbulence is adequately accounted for. But due to supercomputers power and storage limitations, global biogeochemical models are not yet run routinely at eddying resolution. Still, because the "effective resolution" of eddying ocean models is much coarser than the physical model grid resolution, tracer transport can be reconstructed to a large extent by computing tracer transport and diffusion with a model grid resolution close to the effective resolution of the physical model. This observation has motivated the implementation of a new capability in NEMO ocean model (http://www.nemo-ocean.eu/) that allows to run the physical model and the tracer transport model at different grid resolutions. In a first time, we present results obtained with this new capability applied to a synthetic age tracer in a global eddying model configuration. In this model configuration, ocean dynamic is computed at ¼° resolution but tracer transport is computed at 3/4° resolution. The solution obtained is compared to 2 reference setup ,one at ¼° resolution for both physics and passive tracer models and one at 3/4° resolution for both physics and passive tracer model. We discuss possible options for defining the vertical diffusivity coefficient for the tracer transport model based on information from the high resolution grid. We describe the impact of this choice on the distribution and one the penetration of the age tracer. In a second time we present results obtained by coupling the physics with the biogeochemical model PISCES. We look at the impact of this methodology on some tracers distribution and dynamic. The method described here can found applications in ocean forecasting, such as the Copernicus Marine service operated by Mercator-Ocean, and in Earth System Models for climate applications.

Upcycling : converting waste plastics into paramagnetic, conducting, solid, pure carbon microspheres.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pol, V.

2010-06-15

The recent tremendous increase in the volume of waste plastics (WP) will have a harmful environmental impact on the health of living beings. Hundreds of years are required to degrade WP in atmospheric conditions. Hence, in coming years, in addition to traditional recycling services, innovative 'upcycling' processes are necessary. This article presents an environmentally benign, solvent-free autogenic process that converts various WP [low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PET), polystyrene (PS), or their mixtures] into carbon microspheres (CMSs), an industrially significant, value-added product. The thermal dissociation of these individual or mixed WP in a closed reactormore » under autogenic pressure (1000 psi) produced dry, pure powder of CMSs. In this paper, the optimization of process parameters such as the effect of mixing of WP with other materials, and the role of reaction temperature and time are reported. Employing advanced analytical techniques, the atomic structure, composition, and morphology of as-obtained CMSs were analyzed. The room-temperature paramagnetism in CMSs prepared from waste LDPE, HDPE, and PS was further studied by electron paramagnetic resonance (EPR). The conducting and paramagnetic nature of CMSs holds promise for their potential applications in toners, printers, paints, batteries, lubricants, and tires.« less

Paramagnetic liposomes as innovative contrast agents for magnetic resonance (MR) molecular imaging applications.

PubMed

Terreno, Enzo; Delli Castelli, Daniela; Cabella, Claudia; Dastrù, Walter; Sanino, Alberto; Stancanello, Joseph; Tei, Lorenzo; Aime, Silvio

2008-10-01

This article illustrates some innovative applications of liposomes loaded with paramagnetic lanthanide-based complexes in MR molecular imaging field. When a relatively high amount of a Gd(III) chelate is encapsulated in the vesicle, the nanosystem can simultaneously affect both the longitudinal (R(1)) and the transverse (R(2)) relaxation rate of the bulk H2O H-atoms, and this finding can be exploited to design improved thermosensitive liposomes whose MRI response is not longer dependent on the concentration of the probe. The observation that the liposome compartmentalization of a paramagnetic Ln(III) complex induce a significant R(2) enhancement, primarily caused by magnetic susceptibility effects, prompted us to test the potential of such agents in cell-targeting MR experiments. The results obtained indicated that these nanoprobes may have a great potential for the MR visualization of cellular targets (like the glutamine membrane transporters) overexpressing in tumor cells. Liposomes loaded with paramagnetic complexes acting as NMR shift reagents have been recently proposed as highly sensitive CEST MRI agents. The main peculiarity of CEST probes is to allow the MR visualization of different agents present in the same region of interest, and this article provides an illustrative example of the in vivo potential of liposome-based CEST agents.

Trispyrazolylborate Complexes: An Advanced Synthesis Experiment Using Paramagnetic NMR, Variable-Temperature NMR, and EPR Spectroscopies

ERIC Educational Resources Information Center

Abell, Timothy N.; McCarrick, Robert M.; Bretz, Stacey Lowery; Tierney, David L.

2017-01-01

A structured inquiry experiment for inorganic synthesis has been developed to introduce undergraduate students to advanced spectroscopic techniques including paramagnetic nuclear magnetic resonance and electron paramagnetic resonance. Students synthesize multiple complexes with unknown first row transition metals and identify the unknown metals by…

Effects of thermal annealing on the radiation produced electron paramagnetic resonance spectra of bovine and equine tooth enamel: Fossil and modern

NASA Astrophysics Data System (ADS)

Weeks, Robert A.; Bogard, James S.; Elam, J. Michael; Weinand, Daniel C.; Kramer, Andrew

2003-06-01

The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 °C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 °C increments from 100 to 300 °C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300-1200 Gy from 60Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 °C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of the heat treated fossil sample. We conclude that the hyperfine components are due to sample heating to temperatures/times >100 °C/30 min and that similarities between fossil and MEQ spectra after the 300 °C/30 min MEQ anneal are also due to sample heating. We conclude that the presence of the hyperfine components in spectra of fossil tooth enamel indicate that such thermal events occurred either at the time of death, or during the postmortem history.

Estimates of tracer-based piston-flow ages of groundwater from selected sites-National Water-Quality Assessment Program, 1992-2005

USGS Publications Warehouse

Hinkle, Stephen R.; Shapiro, Stephanie D.; Plummer, Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.

2011-01-01

This report documents selected age data interpreted from measured concentrations of environmental tracers in groundwater from 1,399 National Water-Quality Assessment (NAWQA) Program groundwater sites across the United States. The tracers of interest were chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis primarily were from wells representing two types of NAWQA groundwater studies - Land-Use Studies (shallow wells, usually monitoring wells, in recharge areas under dominant land-use settings) and Major-Aquifer Studies (wells, usually domestic supply wells, in principal aquifers and representing the shallow, used resource). Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) associated with Land-Use Studies also were included. Tracer samples were collected between 1992 and 2005, although two networks sampled from 2006 to 2007 were included because of network-specific needs. Tracer data from other NAWQA Program components (Flow System Studies, which are assessments of processes and trends along groundwater flow paths, and various topical studies) were not compiled herein. Tracer data from NAWQA Land-Use Studies and Major-Aquifer Studies that previously had been interpreted and published are compiled herein (as piston-flow ages), but have not been reinterpreted. Tracer data that previously had not been interpreted and published are evaluated using documented methods and compiled with aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), estimates of tracer-based piston-flow ages, and selected ancillary data, such as redox indicators, well construction, and major dissolved gases (N2, O2, Ar, CH4, and CO2). Tracer-based piston-flow ages documented in this report are simplistic representations of the tracer data. Tracer-based piston-flow ages are a convenient means of conceptualizing groundwater age. However, the piston-flow model is based on the potentially limiting assumptions that tracer transport is advective and that no mixing occurs. Additional uncertainties can arise from tracer degradation, sorption, contamination, or fractionation; terrigenic (natural) sources of tracers; spatially variable atmospheric tracer concentrations; and incomplete understanding of mechanisms of recharge or of the conditions under which atmospheric tracers were partitioned to recharge. The effects of some of these uncertainties are considered herein. For example, degradation, contamination, or fractionation often can be identified or inferred. However, detailed analysis of the effects of such uncertainties on the tracer-based piston-flow ages is constrained by sparse data and an absence of complementary lines of evidence, such as detailed solute transport simulations. Thus, the tracer-based piston-flow ages compiled in this report represent only an initial interpretation of the tracer data.

Mechanical membrane for the separation of a paramagnetic constituent from a fluid

DOEpatents

Maurice, David

2017-05-02

The disclosure provides an apparatus and method for the separation of a paramagnetic component from a mixture using a mechanical membrane apparatus. The mechanical membrane comprises a supporting material having a plurality of pores where each pore is surrounded by a plurality of magnetic regions. The magnetic regions augment a magnetic field on one side of the supporting material while mitigating the field to near zero on the opposite side. In operation, a flow of fluid such as air comprising a paramagnetic component such as O.sub.2 is directed toward the mechanical membrane, and the paramagnetic component is typically attracted toward a magnetic field surrounding a pore while dimagnetic components such as N.sub.2 are generally repelled. As some portion of the fluid passes through the plurality of magnetic apertures to the opposite side of the mechanical membrane, the mechanical membrane generates a fluid enriched in the paramagnetic component. Alternately, the magnetic field may act to repel the paramagnetic component while diamagnetic components such as N.sub.2 are generally unaffected and pass to the opposite side of the mechanical membrane.

Tracing Injection Fluids in Engineered Geothermal Systems

NASA Astrophysics Data System (ADS)

Rose, P. E.; Leecaster, K.; Mella, M.; Ayling, B.; Bartl, M. H.

2011-12-01

The reinjection of produced fluids is crucial to the effective management of geothermal reservoirs, since it provides a mechanism for maintaining reservoir pressures while allowing for the disposal of a toxic byproduct. Tracers are essential to the proper location of injection wells since they are the only known tool for reliably characterizing the flow patterns of recirculated fluids. If injection wells are placed too close to production wells, then reinjected fluids do not have sufficient residence time to extract heat from the reservoir and premature thermal breakthrough results. If injection wells are placed too far away, then the reservoir risks unacceptable pressure loss. Several thermally stable compounds from a family of very detectable fluorescent organic compounds (the naphthalene sulfonates) were characterized and found to be effective for use as geothermal tracers. Through batch-autoclave reactions, their Arrhenius pseudo-first-order decay-rate constants were determined. An analytical method was developed that allows for the laboratory determination of concentrations in the low parts-per-trillion range. Field experiments in numerous geothermal reservoirs throughout the world have confirmed the laboratory findings. Whereas conservative tracers such as the naphthalene sulfonates are effective tools for indicating interwell flow patterns and for measuring reservoir pore volumes, 'reactive' tracers can be used to constrain fracture surface area, which is the effective area for heat extraction. This is especially important for engineered geothermal system (EGS) wells, since reactive tracers can be used to measure fracture surface area immediately after drilling and while the well stimulation equipment is still on site. The reactive properties of these tracers that can be exploited to constrain fracture surface area are reversible sorption, contrasting diffusivity, and thermal decay. Laboratory batch- and flow-reactor experiments in combination with numerical simulation studies have served to identify candidate compounds for use as reactive tracers. An emerging class of materials that show promise for use as geothermal and EGS tracers are colloidal nanocrystals (quantum dots). These are semiconductor particles that fluoresce as a function of particle size. Preliminary laboratory experimentation has demonstrated that these thermally stable, water-soluble particles can serve as conservative tracers for geothermal applications. Likewise, they show promise as potential reactive tracers, since their surfaces can be modified to be reversibly sorptive and their diameters are sufficiently large to allow for contrasts in diffusivity with solute tracers.

Effect of UV irradiation on Echinaceae purpureae interactions with free radicals examined by an X-band (9.3 GHz) EPR spectroscopy.

PubMed

Ramos, Paweł; Pilawa, Barbara

The effect of UVA (315-400 nm) irradiation on Echinaceae purpureae interactions with free radicals was examined by the use of electron paramagnetic resonance (EPR) spectroscopy. The changes of antioxidant properties of E. purpureae with time of UV irradiation from 10 to 110 min (10 min steps) were determined. DPPH as the paramagnetic reference was used in this study. Changes of EPR signals of the reference after interactions with nonirradiated and UV-irradiated E. purpureae were detected. Interactions of the tested E. purpureae samples caused decrease of the EPR signal of DPPH as the result of its antioxidant properties. The decrease of the amplitude of EPR line of DPPH was lower for interactions with UV-irradiated E. purpureae . EPR examination confirmed antioxidant properties of E. purpureae . The weaker antioxidant properties of E. purpureae after UV irradiation were pointed out. E. purpureae should be storage in the dark. The tests bring to light usefulness of electron paramagnetic resonance with microwave frequency of 9.3 GHz (an X-band) in examination of storage conditions of pharmacological herbs.

Spatiotemporal distribution modeling of PET tracer uptake in solid tumors.

PubMed

Soltani, Madjid; Sefidgar, Mostafa; Bazmara, Hossein; Casey, Michael E; Subramaniam, Rathan M; Wahl, Richard L; Rahmim, Arman

2017-02-01

Distribution of PET tracer uptake is elaborately modeled via a general equation used for solute transport modeling. This model can be used to incorporate various transport parameters of a solid tumor such as hydraulic conductivity of the microvessel wall, transvascular permeability as well as interstitial space parameters. This is especially significant because tracer delivery and drug delivery to solid tumors are determined by similar underlying tumor transport phenomena, and quantifying the former can enable enhanced prediction of the latter. We focused on the commonly utilized FDG PET tracer. First, based on a mathematical model of angiogenesis, the capillary network of a solid tumor and normal tissues around it were generated. The coupling mathematical method, which simultaneously solves for blood flow in the capillary network as well as fluid flow in the interstitium, is used to calculate pressure and velocity distributions. Subsequently, a comprehensive spatiotemporal distribution model (SDM) is applied to accurately model distribution of PET tracer uptake, specifically FDG in this work, within solid tumors. The different transport mechanisms, namely convention and diffusion from vessel to tissue and in tissue, are elaborately calculated across the domain of interest and effect of each parameter on tracer distribution is investigated. The results show the convection terms to have negligible effect on tracer transport and the SDM can be solved after eliminating these terms. The proposed framework of spatiotemporal modeling for PET tracers can be utilized to comprehensively assess the impact of various parameters on the spatiotemporal distribution of PET tracers.

Effect of body temperature on the pharmacokinetics of a triarylmethyl-type paramagnetic contrast agent used in EPR oximetry.

PubMed

Matsumoto, Ken-Ichiro; Hyodo, Fuminori; Mitchell, James B; Krishna, Murali C

2018-02-01

Pharmacokinetics of the tri[8-carboxy-2,2,6,6-tetrakis(2-hydroxymethyl)benzo[1,2-d:4,5-d']bis(1,3)dithio-4-yl]methyl radical (Oxo63) after a single bolus and/or continuous intravenous infusion was investigated in tumor-bearing C3H mice with or without body temperature control while under anesthesia. The in vivo time course of Oxo63 in blood was measured using X-band electron paramagnetic resonance spectroscopy. Distribution of Oxo63 in normal muscle and tumor tissues was obtained using a surface coil resonator and a 700-MHz electron paramagnetic resonance spectrometer. The whole-body distribution of Oxo63 was obtained by 300-MHz continuous-wave electron paramagnetic resonance imaging. The high-resolution 300-MHz time-domain electron paramagnetic resonance imaging was also carried out to probe the distribution of Oxo63. Urination of mice was retarded at low body temperature, causing the concentration of Oxo63 in blood to attain high levels. However, the concentration of Oxo63 in tumor tissue was lower with no control of body temperature than active body temperature control. The nonsystemized blood flow in the tumor tissues may pool Oxo63 at lower body temperature. Pharmacokinetics of the contrast agent were found to be significantly affected by body temperature of the experimental animal, and can influence the probe distribution and the image patterns. Magn Reson Med 79:1212-1218, 2018. © Published 2017. This article is a U.S. Government work and is in the public domain in the USA. © Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Lanthanide paramagnetic probes for NMR spectroscopic studies of fast molecular conformational dynamics and temperature control. Effective six-site proton exchange in 18-crown-6 by exchange spectroscopy.

PubMed

Babailov, Sergey P

2012-02-06

(1)H and (13)C NMR measurements are reported for the CDCl(3) and CD(2)Cl(2) solutions of [La(18-crown-6)(NO(3))(3)] (I), [Pr(18-crown-6) (NO(3))(3)] (II), [Ce(18-crown-6)(NO(3))(3)] (III), and [Nd(18-crown-6)(NO(3))(3)] (IV) complexes. Temperature dependencies of the (1)H NMR spectra of paramagnetic II-IV have been analyzed using the dynamic NMR (DNMR) methods for six-site exchange. Two types of conformational dynamic processes were identified (the first one is conditioned by interconversion of complex enantiomeric forms and pseudorotation of a macrocycle molecule upon the C(2) symmetry axis; the second one is conditioned by macrocycle molecule inversion). Application of exchange spectroscopy (2D-EXSY) of DNMR for investigation of this dynamic system (II-IV) simplifies the assignment of the NMR signals and represents the first experimental study of multisite exchange. In the present work, the methodology of paramagnetic 4f (Ce, Pr, and Nd) probe applications for the study of free-energy, enthalpy, and entropy changes in chemical exchange processes, as well as the advantages of this method in a comparison with DNMR studies of diamagnetic substances, is discussed. In particular, as a result of paramagnetic chemical shifts in 4f complexes, the range of measurable rate constants expands considerably compared to the analogous range in diamagnetic compounds. Coordination compounds investigated in the paper represent new types of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution.

Use of deuterated water as a conservative artificial ground water tracer

USGS Publications Warehouse

Becker, M.W.; Coplen, T.B.

2001-01-01

Conservative tracers are necessary to obtain groundwater transport velocities at the field scale. Deuterated water is an effective tracer for this purpose due to its similarity to water, chemical stability, non-reactivity, ease of handling and sampling, relatively neutral buoyancy, and reasonable price. Reliable detection limits of 0.1 mg deuterium/L may be obtained in field tests. A field example is presented in which deuterated water, bromide, and pentafluorobenzoic acid are used as groundwater tracers. Deuterated water appeared to be transported conservatively, producing almost identical breakthrough curves as that of other soluble tracers. ?? Springer-Verlag 2001.

Separation of diamagnetic and paramagnetic anisotropy by high-field, low-temperature torque measurements

NASA Astrophysics Data System (ADS)

Schmidt, Volkmar; Hirt, Ann M.; Rosselli, Pascal; Martín-Hernández, Fátima

2007-01-01

The anisotropy of magnetic susceptibility (AMS) of rocks can be composed of contributions from ferromagnetic, paramagnetic and diamagnetic minerals. However, in general the AMS of only one fraction is of interest. While there are several approaches to isolate the ferromagnetic contribution to the AMS, the separation of the diamagnetic from the paramagnetic contribution is still problematic. A new method for the separation of these two contributions based on high-field torque measurements at room and low-temperature is presented. The paramagnetic anisotropy increases at low temperature according to the Curie-Weiss law, whereas the diamagnetic contribution is temperature independent. If the paramagnetic AMS is due to perfectly oblate or prolate minerals and the ratio of the susceptibility differences at two temperatures is known, paramagnetic and diamagnetic AMS can be separated. When measuring in fields high enough to saturate the ferromagnetic phases all three contributions to the AMS can be separated. The separation of paramagnetic and diamagnetic AMS is demonstrated on natural crystals and synthetic calcite-muscovite aggregates. A high-field torque magnetometer, equipped with a cryostat for measurements at 77 K, allows sensitive measurements at two different temperatures. The sensitivity at 77 K is 3 × 10-7 J and standard-sized (palaeomagnetic) samples of 11.4 cm3 can be measured. This new method is especially suited for the investigation of diamagnetic fabrics of impure carbonate rocks.

Interactions of solvent with the heme region of methemoglobin and fluoro-methemoglobin.

PubMed

Koenig, S H; Brown, R D; Lindstrom, T R

1981-06-01

It is now more than 20 years since Davidson and collaborators (1957, Biochim. Biophys, Acta. 26:370-373; J. Mol. Biol. 1:190-191) applied the theoretical ideas of Bloembergen et al. (1948. Phys. Rev. 73:679-712) on outer sphere magnetic relaxation of solvent protons to studies of solutions of methemoglobin. From then on, there has been debate regarding the relative contributions to paramagnetic solvent proton relaxation by inner sphere (ligand-exchange) effects and by outer sphere (diffusional) effects in methemoglobin solutions. Gupta and Mildvan (1975. J. Biol. Chem 250:146-253) extended the early measurements, attributed the relatively small paramagnetic effects to exchange with solvent of the water ligand of the heme-Fe3+ ion, and interpreted their data to indicate cooperativity and an alkaline Bohr effect in the presence of inositol hexaphosphate. They neglected the earlier discussions entirely, and made no reference to outer sphere effects. We have measured the relaxation rate of solvent protons as a function of magnetic field for solutions of methemoglobin, under a variety of conditions of pH and temperature, and have given careful consideration to the relatively large diamagnetic corrections that are necessary by making analogous measurements on oxyhemoglobin, carbonmonoxyhemoglobin, and cyano- and azide-methemoglobin. (The latter two, because of their short electronic relaxation times, behave as though diamagnetic). We show that the paramagnetic contribution to solvent relaxation can be dominated by outer sphere effects, a result implying that many conclusions, including those of Gupta and Mildvan, require reexamination. Finally, we present data for fluoro-methemoglobin, which relaxes solvent protons an order of magnitude better than does methemoglobin. Here one has a startling breakdown of the dogma that has been the basis for interpreting many ligand-replacement studies; in contrast to the prevailing view that replacement of a water ligand of a protein-bound paramagnetic ion by another ligand should decrease relaxation rates, replacement of H2O by F- increases the relaxation rate drastically. The data can all be reconciled, however, with what is anticipated from knowledge of ligand interactions in the heme region.

Probing the Dipolar Coupling in a Heterospin Endohedral Fullerene-Phthalocyanine Dyad.

PubMed

Zhou, Shen; Yamamoto, Masanori; Briggs, G Andrew D; Imahori, Hiroshi; Porfyrakis, Kyriakos

2016-02-03

Paramagnetic endohedral fullerenes and phthalocyanine (Pc) complexes are promising building blocks for molecular quantum information processing, for which tunable dipolar coupling is required. We have linked these two spin qubit candidates together and characterized the resulting electron paramagnetic resonance properties, including the spin dipolar coupling between the fullerene spin and the copper spin. Having interpreted the distance-dependent coupling strength quantitatively and further discussed the antiferromagnetic aggregation effect of the CuPc moieties, we demonstrate two ways of tuning the dipolar coupling in such dyad systems: changing the spacer group and adjusting the solution concentration.

The tight binding model study of the role of band filling on the charge gap in graphene-on-substrate in paramagnetic state

NASA Astrophysics Data System (ADS)

Panda, Rudrashish; Sahu, Sivabrata; Rout, G. C.

2017-05-01

We communicate here a tight binding theoretical model study of the band filling effect on the charge gap in graphene-on-substrate. The Hamiltonian consists of nearest neighbor electron hopping and substrate induced gap. Besides this the Coulomb interaction is considered here within mean-field approximation in the paramagnetic limit. The electron occupancies at two sublattices are calculated by Green's function technique and are solved self consistently. Finally the charge gap i.e. Δ ¯=U [ < na > -< nb > ] is calculated and computed numerically. The results are reported.

Oxygen-17 NMR Shifts Caused by Cr{Sup ++} in Aqueous Solutions

DOE R&D Accomplishments Database

Jackson, J. A.; Lemons, J. F.; Taube, H.

1962-01-01

Cr{sup ++} in solution produces a paramagnetic shift in the NMR absorption of O{sup 17} in ClO{sub 4}{sup -}, as well as the expected paramagnetic shift for O{sup 17} in H{sub 2}O. As the concentration of ClO{sub 4}{sup -} increases, the shift in the H{sub 2}O{sup 17} absorption is diminished, and eventually changes sign. The effects are ascribed to preferential replacement by ClO{sub 4}{sup -} of water molecules from the axial positions in the first coordination sphere about Cr{sup ++}.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gorai, Prashun; Toberer, Eric S.; Stevanović, Vladan

Here, at room temperature and above, most magnetic materials adopt a spin-disordered (paramagnetic) state whose electronic properties can differ significantly from their low-temperature, spin-ordered counterparts. Yet computational searches for new functional materials usually assume some type of magnetic order. In the present work, we demonstrate a methodology to incorporate spin disorder in computational searches and predict the electronic properties of the paramagnetic phase. We implement this method in a high-throughput framework to assess the potential for thermoelectric performance of 1350 transition-metal sulfides and find that all magnetic systems we identify as promising in the spin-ordered ground state cease to bemore » promising in the paramagnetic phase due to disorder-induced deterioration of the charge carrier transport properties. We also identify promising non-magnetic candidates that do not suffer from these spin disorder effects. In addition to identifying promising materials, our results offer insights into the apparent scarcity of magnetic systems among known thermoelectrics and highlight the importance of including spin disorder in computational searches.« less

Nitroxide paramagnet-induced para-ortho conversion and nuclear spin relaxation of H2 in organic solvents.

PubMed

Sartori, Elena; Ruzzi, Marco; Lawler, Ronald G; Turro, Nicholas J

2008-09-24

The kinetics of para-ortho conversion and nuclear spin relaxation of H 2 in chloroform- d 1 were investigated in the presence of nitroxides as paramagnetic catalysts. The back conversion from para-hydrogen ( p-H 2) to ortho-hydrogen ( o-H 2) was followed by NMR by recording the increase in the intensity of the signal of o-H 2 at regular intervals of time. The nitroxides proved to be hundreds of times more effective at inducing relaxation among the spin levels of o-H 2 than they are in bringing about transitions between p-H 2 and the levels of o-H 2. The value of the encounter distance d between H 2 and the paramagnetic molecule, calculated from the experimental bimolecular conversion rate constant k 0, using the Wigner theory of para-ortho conversion, agrees perfectly with that calculated from the experimental relaxivity R 1 using the force free diffusion theory of spin-lattice relaxation.

Application of separable parameter space techniques to multi-tracer PET compartment modeling.

PubMed

Zhang, Jeff L; Michael Morey, A; Kadrmas, Dan J

2016-02-07

Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg-Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models.

Application of separable parameter space techniques to multi-tracer PET compartment modeling

NASA Astrophysics Data System (ADS)

Zhang, Jeff L.; Morey, A. Michael; Kadrmas, Dan J.

2016-02-01

Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg-Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models.

Study of the effects of hydroxyapatite nanocrystal codoping by pulsed electron paramagnetic resonance methods

NASA Astrophysics Data System (ADS)

Gafurov, M. R.; Biktagirov, T. B.; Mamin, G. V.; Shurtakova, D. V.; Klimashina, E. S.; Putlyaev, V. I.; Orlinskii, S. B.

2016-03-01

The effect of codoping of hydroxyapatite (HAP) nanocrystals with average sizes of 35 ± 15 nm during "wet" synthesis by CO 3 2- carbonate anions and Mn2+ cations on relaxation characteristics (for the times of electron spin-spin relaxation) of the NO 3 2- nitrate radical anion has been studied. By the example of HAP, it has been demonstrated that the electron paramagnetic resonance (EPR) is an efficient method for studying anion-cation (co)doping of nanoscale particles. It has been shown experimentally and by quantummechanical calculations that simultaneous introduction of several ions can be energetically more favorable than their separate inclusion. Possible codoping models have been proposed, and their energy parameters have been calculated.

Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

NASA Astrophysics Data System (ADS)

Knapp, Julia L. A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

2017-02-01

Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

USGS Publications Warehouse

Knapp, Julia L.A.; González-Pinzón, Ricardo; Drummond, Jennifer D.; Larsen, Laurel G.; Cirpka, Olaf A.; Harvey, Judson W.

2017-01-01

Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We present results of a tracer test where we injected the conservative tracer bromide together with the reactive tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer, which we found to be on average 2 cm thick in this study, ranging from one third to one half of the full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective reaction rates.

Evaluation of single- and dual-porosity models for reproducing the release of external and internal tracers from heterogeneous waste-rock piles.

PubMed

Blackmore, S; Pedretti, D; Mayer, K U; Smith, L; Beckie, R D

2018-05-30

Accurate predictions of solute release from waste-rock piles (WRPs) are paramount for decision making in mining-related environmental processes. Tracers provide information that can be used to estimate effective transport parameters and understand mechanisms controlling the hydraulic and geochemical behavior of WRPs. It is shown that internal tracers (i.e. initially present) together with external (i.e. applied) tracers provide complementary and quantitative information to identify transport mechanisms. The analysis focuses on two experimental WRPs, Piles 4 and Pile 5 at the Antamina Mine site (Peru), where both an internal chloride tracer and externally applied bromide tracer were monitored in discharge over three years. The results suggest that external tracers provide insight into transport associated with relatively fast flow regions that are activated during higher-rate recharge events. In contrast, internal tracers provide insight into mechanisms controlling solutes release from lower-permeability zones within the piles. Rate-limited diffusive processes, which can be mimicked by nonlocal mass-transfer models, affect both internal and external tracers. The sensitivity of the mass-transfer parameters to heterogeneity is higher for external tracers than for internal tracers, as indicated by the different mean residence times characterizing the flow paths associated with each tracer. The joint use of internal and external tracers provides a more comprehensive understanding of the transport mechanisms in WRPs. In particular, the tracer tests support the notion that a multi-porosity conceptualization of WRPs is more adequate for capturing key mechanisms than a dual-porosity conceptualization. Copyright © 2018 Elsevier B.V. All rights reserved.

Single-scan dual-tracer FLT+FDG PET tumor characterization.

PubMed

Kadrmas, Dan J; Rust, Thomas C; Hoffman, John M

2013-02-07

Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from the multi-tracer PET signal. The ability to rapidly and reliably image both (18)F-fluorodeoxyglucose (FDG) and (18)F-fluorothymidine (FLT) would provide complementary measures of tumor metabolism and proliferative activity, with important applications in guiding oncologic treatment decisions and assessing response. However, this tracer combination presents one of the most challenging dual-tracer signal-separation problems--both tracers have the same radioactive half-life, and the injection delay is short relative to the half-life and tracer kinetics. This work investigates techniques for single-scan dual-tracer FLT+FDG PET tumor imaging, characterizing the performance of recovering static and dynamic imaging measures for each tracer from dual-tracer datasets. Simulation studies were performed to characterize dual-tracer signal-separation performance for imaging protocols with both injection orders and injection delays of 10-60 min. Better performance was observed when FLT was administered first, and longer delays before administration of FDG provided more robust signal-separation and recovery of the single-tracer imaging measures. An injection delay of 30 min led to good recovery (R > 0.96) of static image values (e.g. SUV), K(net), and K(1) as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k(2), k(3)) was less robust, indicating that information regarding these parameters was harder to recover in the presence of statistical noise and dual-tracer effects. Performance of the dual-tracer FLT(0 min)+FDG(32 min) technique was further evaluated using PET/CT imaging studies in five patients with primary brain tumors where the data from separate scans of each tracer were combined to synthesize dual-tracer scans with known single-tracer components; results demonstrated similar dual-tracer signal recovery performance. We conclude that rapid dual-tracer FLT+FDG tumor imaging is feasible and can provide quantitative tumor imaging measures comparable to those from conventional separate-scan imaging.

Single-scan dual-tracer FLT+FDG PET tumor characterization

NASA Astrophysics Data System (ADS)

Kadrmas, Dan J.; Rust, Thomas C.; Hoffman, John M.

2013-02-01

Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from the multi-tracer PET signal. The ability to rapidly and reliably image both 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) would provide complementary measures of tumor metabolism and proliferative activity, with important applications in guiding oncologic treatment decisions and assessing response. However, this tracer combination presents one of the most challenging dual-tracer signal-separation problems—both tracers have the same radioactive half-life, and the injection delay is short relative to the half-life and tracer kinetics. This work investigates techniques for single-scan dual-tracer FLT+FDG PET tumor imaging, characterizing the performance of recovering static and dynamic imaging measures for each tracer from dual-tracer datasets. Simulation studies were performed to characterize dual-tracer signal-separation performance for imaging protocols with both injection orders and injection delays of 10-60 min. Better performance was observed when FLT was administered first, and longer delays before administration of FDG provided more robust signal-separation and recovery of the single-tracer imaging measures. An injection delay of 30 min led to good recovery (R > 0.96) of static image values (e.g. SUV), Knet, and K1 as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k2, k3) was less robust, indicating that information regarding these parameters was harder to recover in the presence of statistical noise and dual-tracer effects. Performance of the dual-tracer FLT(0 min)+FDG(32 min) technique was further evaluated using PET/CT imaging studies in five patients with primary brain tumors where the data from separate scans of each tracer were combined to synthesize dual-tracer scans with known single-tracer components; results demonstrated similar dual-tracer signal recovery performance. We conclude that rapid dual-tracer FLT+FDG tumor imaging is feasible and can provide quantitative tumor imaging measures comparable to those from conventional separate-scan imaging.

Single-scan dual-tracer FLT+FDG PET tumor characterization

PubMed Central

Kadrmas, Dan J; Rust, Thomas C; Hoffman, John M

2013-01-01

Rapid multi-tracer PET aims to image two or more tracers in a single scan, simultaneously characterizing multiple aspects of physiology and function without the need for repeat imaging visits. Using dynamic imaging with staggered injections, constraints on the kinetic behavior of each tracer are applied to recover individual-tracer measures from the multi-tracer PET signal. The ability to rapidly and reliably image both 18F-fluorodeoxyglucose (FDG) and 18F-fluorothymidine (FLT) would provide complementary measures of tumor metabolism and proliferative activity, with important applications in guiding oncologic treatment decisions and assessing response. However, this tracer combination presents one of the most challenging dual-tracer signal-separation problems—both tracers have the same radioactive half-life, and the injection delay is short relative to the half-life and tracer kinetics. This work investigates techniques for single-scan dual-tracer FLT+FDG PET tumor imaging, characterizing the performance of recovering static and dynamic imaging measures for each tracer from dual-tracer datasets. Simulation studies were performed to characterize dual-tracer signal-separation performance for imaging protocols with both injection orders and injection delays of 10–60 min. Better performance was observed when FLT was administered first, and longer delays before administration of FDG provided more robust signal-separation and recovery of the single-tracer imaging measures. An injection delay of 30 min led to good recovery (R > 0.96) of static image values (e.g. SUV), Knet, and K1 as compared to values from separate, single-tracer time-activity curves. Recovery of higher order rate parameters (k2, k3) was less robust, indicating that information regarding these parameters was harder to recover in the presence of statistical noise and dual-tracer effects. Performance of the dual-tracer FLT(0 min)+FDG(32 min) technique was further evaluated using PET/CT imaging studies in five patients with primary brain tumors where the data from separate scans of each tracer were combined to synthesize dual-tracer scans with known single-tracer components; results demonstrated similar dual-tracer signal recovery performance. We conclude that rapid dual-tracer FLT+FDG tumor imaging is feasible and can provide quantitative tumor imaging measures comparable to those from conventional separate-scan imaging. PMID:23296314

Neutrally buoyant tracers in hydrogeophysics: Field demonstration in fractured rock

NASA Astrophysics Data System (ADS)

Shakas, Alexis; Linde, Niklas; Baron, Ludovic; Selker, John; Gerard, Marie-Françoise; Lavenant, Nicolas; Bour, Olivier; Le Borgne, Tanguy

2017-04-01

Electrical and electromagnetic methods are extensively used to map electrically conductive tracers within hydrogeologic systems. Often, the tracers used consist of dissolved salt in water, leading to a denser mixture than the ambient formation water. Density effects are often ignored and rarely modeled but can dramatically affect transport behavior and introduce dynamics that are unrepresentative of the response obtained with classical tracers (e.g., uranine). We introduce a neutrally buoyant tracer consisting of a mixture of salt, water, and ethanol and monitor its movement during push-pull experiments in a fractured rock aquifer using ground-penetrating radar. Our results indicate a largely reversible transport process and agree with uranine-based push-pull experiments at the site, which is in contrast to results obtained using dense saline tracers. We argue that a shift toward neutrally buoyant tracers in both porous and fractured media would advance hydrogeophysical research and enhance its utility in hydrogeology.

Innovative techniques for the description of reservoir heterogeneity using tracers. Second technical annual progress report, October 1991--September 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pope, G.A.; Sepehrnoori, K.

1992-12-31

This second annual report on innovative uses of tracers for reservoir characterization contains four sections each describing a novel use of oilfield tracers. The first section describes and illustrates the use of a new single-well tracer test to estimate wettability. This test consists of the injection of brine containing tracers followed by oil containing tracers, a shut-in period to allow some of the tracers to react, and then production of the tracers. The inclusion of the oil injection slug with tracers is unique to this test, and this is what makes the test work. We adapted our chemical simulator, UTCHEM,more » to enable us to study this tracer method and made an extensive simulation study to evaluate the effects of wettability based upon characteristic curves for relative permeability and capillary pressure for differing wetting states typical of oil reservoirs. The second section of this report describes a new method for analyzing interwell tracer data based upon a type-curve approach. Theoretical frequency response functions were used to build type curves of ``transfer function`` and ``phase spectrum`` that have dimensionless heterogeneity index as a parameter to characterize a stochastic permeability field. We illustrate this method by analyzing field tracer data. The third section of this report describes a new theory for interpreting interwell tracer data in terms of channeling and dispersive behavior for reservoirs. Once again, a stochastic approach to reservoir description is taken. The fourth section of this report describes our simulation of perfluorocarbon gas tracers. This new tracer technology developed at Brookhaven National Laboratory is being tested at the Elk Hills Naval Petroleum Reserve No. 1 in California. We report preliminary simulations made of these tracers in one of the oil reservoirs under evaluation with these tracers in this field. Our compostional simulator (UTCOMP) was used for this simulation study.« less

Electron paramagnetic resonance of several lunar rock samples

NASA Technical Reports Server (NTRS)

Marov, P. N.; Dubrov, Y. N.; Yermakov, A. N.

1974-01-01

The results are presented of investigating lunar rock samples returned by the Luna 16 automatic station, using electron paramagnetic resonance (EPR). The EPR technique makes it possible to detect paramagnetic centers and investigate their nature, with high sensitivity. Regolith (finely dispersed material) and five particles from it, 0.3 mm in size, consisting mostly of olivine, were investigated with EPR.

Monitoring changes of paramagnetically-shifted 31P signals in phospholipid vesicles

NASA Astrophysics Data System (ADS)

Joyce, Rebecca E.; Williams, Thomas L.; Serpell, Louise C.; Day, Iain J.

2016-03-01

Phospholipid vesicles are commonly used as biomimetics in the investigation of the interaction of various species with cell membranes. In this letter we present a 31P NMR investigation of a simple vesicle system using a paramagnetic shift reagent to probe the inner and outer layers of the lipid bilayer. Time-dependent changes in the 31P NMR signal are observed, which differ whether the paramagnetic species is inside or outside the vesicle, and on the choice of buffer solution used. An interpretation of these results is given in terms of the interaction of the paramagnetic shift reagent with the lipids.

Waste Oil Burn-Off in Coast Guard Power Plants - Diesel Piston Ring Wear Study by Radioactive Tracer Techniques

DOT National Transportation Integrated Search

1976-07-01

This report covers the results of a study utilizing a radioactive tracer technique to determine wear effects on the upper compression rings of a two-stroke cycle diesel engine burning mixtures of waste lube oil in fuel oil. The radioactive tracer tec...

A Lagrangian model for the age of tracer in surface water

NASA Astrophysics Data System (ADS)

Ding, Yu; Liu, Haifei; Yi, Yujun

The age of tracer is a spatio-temporal scale, indicating the transition time of solute particles, which is helpful to monitor and manage the pollutant leakage accidents. In this study, an effective Lagrangian model for the age of tracer is developed based on the lattice Boltzmann method in D2Q5 lattices. A tracer age problem in an asymmetrical circular reservoir is then employed as a benchmark test to verify this method. Then it is applied to computing the age of tracers under two different reservoir operation schemes in the Danjiangkou Reservoir, the drinking water source for the Middle Route of South-to-North Water Transfer Project.

Spatial patterns in heavy-mineral concentrations along the Curonian Spit coast, southeastern Baltic Sea

NASA Astrophysics Data System (ADS)

Pupienis, Donatas; Buynevich, Ilya; Ryabchuk, Daria; Jarmalavičius, Darius; Žilinskas, Gintautas; Fedorovič, Julija; Kovaleva, Olga; Sergeev, Alexander; Cichoń-Pupienis, Anna

2017-08-01

The 98-km-long Curonian Spit is fronted by beaches mainly composed of quartz sand with minor high-density fractions. In this study heavy-mineral concentration (HMC) trends and grain-size statistical parameters were used to assess their role as indicators of natural processes, human activities, and patterns of longshore transport. A total of 92 surface sand samples were collected at 1 km intervals from the middle of the beach along the Baltic Sea shoreline of the spit between Klaipėda strait in Lithuania and Zelenogradsk in Russia. HMC contribution was assessed in the laboratory using bulk low-field magnetic susceptibility (MS) as a proxy for ferrimagnetic and paramagnetic mineral content. Quartz-dominated (background) sand is generally characterized by low MS values of κ < 50 μSI, whereas higher values κ > 150 μSI are typical for heavy-mineral-rich sand. The greatest MS values along the middle of the beach occur in the southern part of the spit and are 40 times higher than in the northern sector. This pattern suggests the existence of a longshore particle flux with HMC distribution having the potential as a useful tracer of longshore sediment transport. Local anomalously high MS excursions are associated with contribution of iron-rich materials from adjacent man-made structures. Therefore, temporally constrained HMC distribution along the middle of the beach reflects the cumulative effect of antecedent geologic framework, longshore sediment transfer, erosional and accretionary processes, wave and wind climate, and local coastal protective structures.

An electrochemical immunosensor for ochratoxin A determination in wines based on a monoclonal antibody and paramagnetic microbeads.

PubMed

Vidal, Juan C; Bonel, Laura; Ezquerra, Alba; Duato, Patricia; Castillo, Juan R

2012-06-01

We report a direct competitive immunosensor for the rapid determination of ochratoxin A (OTA) in wine samples. Magnetic beads (1 ± 0.5 μm diameter) covered with streptavidin were functionalized with a monoclonal antibody against OTA, and then left to incubate in a solution of tracer (ochratoxin conjugated to the enzyme peroxidase) and a range of OTA concentrations (10(-4) to 1,000 ng mL(-1)). After washing and separation steps helped with a magnetic field, a volume of the dispersion was put on screen-printed electrodes under a magnet, and after adding the substrate the p-benzoquinone generated enzymatically was detected by differential-pulse voltammetry. Wine samples (2 mL) were easily prepared simply by adjusting to pH = 7.5 with diluted NaOH and by adding polyvinylpyrrolidone for complexing polyphenols, without any other clean-up or preconcentration steps. The limit of detection for detecting OTA in wines was of 0.11 ± 0.01 ng L(-1), well below the permitted content of the mycotoxin by the European Union (<2 ng mL(-1)). Spiked wines were subjected to immunosensor calibrations to study the matrix effects. OTA concentrations measured with the immunosensor were compared with those obtained by high-performance liquid chromatography coupled to fluorescence detection (AOAC official method 2001.01). The OTA levels from two red wines of "Campo de Borja", Spain, ranged from about 0.027 to 0.033 ng mL(-1) of OTA.

Effects of Submesoscale Turbulence on Reactive Tracers in the Upper Ocean

NASA Astrophysics Data System (ADS)

Smith, Katherine Margaret

In this dissertation, Large Eddy Simulations (LES) are used to model the coupled turbulence-reactive tracer dynamics within the upper mixed layer of the ocean. Prior work has shown that LES works well over the spatial and time scales relevant to both turbulence and reactive biogeochemistry. Additionally, the code intended for use is able to carry an arbitrary number of tracer equations, allowing for easy expansion of the species reactions. Research in this dissertation includes a study of 15 idealized non-reactive tracers within an evolving large-scale temperature front in order determine and understand the fundamental dynamics underlying turbulence-tracer interaction in the absence of reactions. The focus of this study, in particular, was on understanding the evolution of biogeochemically-relevant, non-reactive tracers in the presence of both large ( 5 km) submesoscale eddies and smallscale ( 100 m) wave-driven Langmuir turbulence. The 15 tracers studied have different initial, boundary, and source conditions and significant differences are seen in their distributions depending on these conditions. Differences are also seen between regions where submesoscale eddies and small-scale Langmuir turbulence are both present, and in regions with only Langmuir turbulence. A second study focuses on the examination of Langmuir turbulence effects on upper ocean carbonate chemistry. Langmuir mixing time scales are similar to those of chemical reactions, resulting in potentially strong tracer-flow coupling effects. The strength of the Langmuir turbulence is varied, from no wave-driven turbulence (i.e., only shear-driven turbulence), to Langmuir turbulence that is much stronger than that found in typical upper ocean conditions. Three different carbonate chemistry models are also used in this study: time-dependent chemistry, equilibrium chemistry, and no-chemistry (i.e., non-reactive tracers). The third and final study described in this dissertation details the development of a reduced-order biogeochemical model with 17 state equations that can accurately reproduce the Bermuda Atlantic Time-series Study (BATS) ecosystem behavior, but that can also be integrated within high-resolution LES.

Application of separable parameter space techniques to multi-tracer PET compartment modeling

PubMed Central

Zhang, Jeff L; Morey, A Michael; Kadrmas, Dan J

2016-01-01

Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg–Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models. PMID:26788888

Evaluation of rapid dual-tracer 62Cu-PTSM + 62Cu-ATSM PET in dogs with spontaneously occurring tumors

NASA Astrophysics Data System (ADS)

Black, Noel F.; McJames, Scott; Rust, Thomas C.; Kadrmas, Dan J.

2008-01-01

We are developing methods for imaging multiple PET tracers in a single scan with staggered injections, where imaging measures for each tracer are separated and recovered using differences in tracer kinetics and radioactive decay. In this work, signal separation performance for rapid dual-tracer 62Cu-PTSM (blood flow) + 62Cu-ATSM (hypoxia) tumor imaging was evaluated in a large animal model. Four dogs with pre-existing tumors received a series of dynamic PET scans with 62Cu-PTSM and 62Cu-ATSM, permitting evaluation of a rapid dual-tracer protocol designed by previous simulation work. Several imaging measures were computed from the dual-tracer data and compared with those from separate, single-tracer imaging. Static imaging measures (e.g. SUV) for each tracer were accurately recovered from dual-tracer data. The wash-in (k1) and wash-out (k2) rate parameters for both tracers were likewise well recovered (r = 0.87-0.99), but k3 was not accurately recovered for PTSM (r = 0.19) and moderately well recovered for ATSM (r = 0.70). Some degree of bias was noted, however, which may potentially be overcome through further refinement of the signal separation algorithms. This work demonstrates that complementary information regarding tumor blood flow and hypoxia can be acquired by a single dual-tracer PET scan, and also that the signal separation procedure works effectively for real physiologic data with realistic levels of kinetic model mismatch. Rapid multi-tracer PET has the potential to improve tumor assessment for image-guide therapy and monitoring, and further investigation with these and other tracers is warranted.

Evaluation of Rapid Dual-Tracer 62Cu-PTSM + 62Cu-ATSM PET in Dogs with Spontaneously-Occurring Tumors

PubMed Central

Black, Noel F.; McJames, Scott; Rust, Thomas C.; Kadrmas, Dan J.

2013-01-01

We are developing methods for imaging multiple PET tracers in a single scan with staggered injections, where imaging measures for each tracer are separated and recovered using differences in tracer kinetics and radioactive decay. In this work, signal-separation performance for rapid dual-tracer 62Cu-PTSM (blood flow) + 62Cu-ATSM (hypoxia) tumor imaging was evaluated in a large animal model. Four dogs with pre-existing tumors received a series of dynamic PET scans with 62Cu-PTSM and 62Cu-ATSM, permitting evaluation of a rapid dual-tracer protocol designed by previous simulation work. Several imaging measures were computed from the dual-tracer data and compared with those from separate, single-tracer imaging. Static imaging measures (e.g. SUV) for each tracer were accurately recovered from dual-tracer data. The wash-in (k1) and wash-out (k2) rate parameters for both tracers were likewise well recovered (r = 0.87 – 0.99), but k3 was not accurately recovered for PTSM (r = 0.19) and moderately well recovered for ATSM (r = 0.70). Some degree of bias was noted, however, which may potentially be overcome through further refinement of the signal-separation algorithms. This work demonstrates that complementary information regarding tumor blood flow and hypoxia can be acquired by a single dual-tracer PET scan, and also that the signal-separation procedure works effectively for real physiologic data with realistic levels of kinetic model-mismatch. Rapid multi-tracer PET has the potential to improve tumor assessment for image-guide therapy and monitoring, and further investigation with these and other tracers is warranted. PMID:18182698

A novel fluorine-18 β-fluoroethoxy organophosphate positron emission tomography imaging tracer targeted to central nervous system acetylcholinesterase.

PubMed

James, Shelly L; Ahmed, S Kaleem; Murphy, Stephanie; Braden, Michael R; Belabassi, Yamina; VanBrocklin, Henry F; Thompson, Charles M; Gerdes, John M

2014-07-16

Radiosynthesis of a fluorine-18 labeled organophosphate (OP) inhibitor of acetylcholinesterase (AChE) and subsequent positron emission tomography (PET) imaging using the tracer in the rat central nervous system are reported. The tracer structure, which contains a novel β-fluoroethoxy phosphoester moiety, was designed as an insecticide-chemical nerve agent hybrid to optimize handling and the desired target reactivity. Radiosynthesis of the β-fluoroethoxy tracer is described that utilizes a [(18)F]prosthetic group coupling approach. The imaging utility of the [(18)F]tracer is demonstrated in vivo within rats by the evaluation of its brain penetration and cerebral distribution qualities in the absence and presence of a challenge agent. The tracer effectively penetrates brain and localizes to cerebral regions known to correlate with the expression of the AChE target. Brain pharmacokinetic properties of the tracer are consistent with the formation of an OP-adducted acetylcholinesterase containing the fluoroethoxy tracer group. Based on the initial favorable in vivo qualities found in rat, additional [(18)F]tracer studies are ongoing to exploit the technology to dynamically probe organophosphate mechanisms of action in mammalian live tissues.

Effect of ultraviolet irradiation on free radical scavenging activity of immunosuppressants used in lung transplantation and comparative electron paramagnetic resonance study of kinetics of their interactions with model free radicals.

PubMed

Stanjek-Cichoracka, A; Żegleń, S; Ramos, P; Pilawa, B; Wojarski, J

2018-06-01

The immunosuppressive drugs used in solid organ transplantation or autoimmunological processes were studied by electron paramagnetic resonance (EPR) spectroscopy to estimate their free radical scavenging activity. The interactions of immunosuppressants with free radicals were examined by an X-band (9.3 GHz) EPR spectroscopy and a model of DPPH free radicals. The EPR spectra of DPPH and DPPH interacting with individual drugs were compared. Kinetic studies were performed, and the effect of ultraviolet (UV) irradiation on the free radical scavenging activity of the tested drugs was determined. The free radical scavenging activity of non-irradiated drugs decreased in the order: rapamycin > mycophenolate mofetil > ciclosporin > tacrolimus. UV irradiation increased the free radical scavenging activity of all the tested immunosuppressive drugs, and the effect was highest for tacrolimus. For the non-irradiated samples, the speed of free radical interactions decreased in the order: ciclosporin > tacrolimus > mycophenolate mofetil > rapamycin. UV irradiation only slightly affected the speed of interactions of the immunosuppressive drugs with the model DPPH free radicals. Electron paramagnetic resonance spectroscopy is useful for obtaining information on interactions of immunosuppressive drugs with free radicals. We hypothesized that the long-term immunosuppressive effects of these drugs after transplantation or during autoimmune disorders may be mediated by anti-inflammatory action in addition to the known receptor/cell cycle inhibition. © 2018 John Wiley & Sons Ltd.

Sensitivity analysis of tracer transport in variably saturated soils at USDA-ARS OPE3 field site

USDA-ARS?s Scientific Manuscript database

The objective of this study was to assess the effects of uncertainties in hydrologic and geochemical parameters on the results of simulations of the tracer transport in variably saturated soils at the USDA-ARS OPE3 field site. A tracer experiment with a pulse of KCL solution applied to an irrigatio...

Modified expression for bulb-tracer depletion—Effect on argon dating standards

USGS Publications Warehouse

Fleck, Robert J.; Calvert, Andrew T.

2014-01-01

40Ar/39Ar geochronology depends critically on well-calibrated standards, often traceable to first-principles K-Ar age calibrations using bulb-tracer systems. Tracer systems also provide precise standards for noble-gas studies and interlaboratory calibration. The exponential expression long used for calculating isotope tracer concentrations in K-Ar age dating and calibration of 40Ar/39Ar age standards may provide a close approximation of those values, but is not correct. Appropriate equations are derived that accurately describe the depletion of tracer reservoirs and concentrations of sequential tracers. In the modified expression the depletion constant is not in the exponent, which only varies as integers by tracer-number. Evaluation of the expressions demonstrates that systematic error introduced through use of the original expression may be substantial where reservoir volumes are small and resulting depletion constants are large. Traditional use of large reservoir to tracer volumes and the resulting small depletion constants have kept errors well less than experimental uncertainties in most previous K-Ar and calibration studies. Use of the proper expression, however, permits use of volumes appropriate to the problems addressed.

Tuning Magnetic Order in Transition Metal Oxide Thin Films

NASA Astrophysics Data System (ADS)

Grutter, Alexander John

In recent decades, one of the most active and promising areas of condensed matter research has been that of complex oxides. With the advent of new growth techniques such as pulsed laser deposition and molecular beam epitaxy, a wealth of new magnetic and electronic ground states have emerged in complex oxide heterostructures. The wide variety of ground states in complex oxides is well known and generally attributed to the unprecedented variety of valence, structure, and bonding available in these systems. The tunability of this already diverse playground of states and interactions is greatly multiplied in thin films and heterostructures by the addition of parameters such as substrate induced strain and interfacial electronic reconstruction. Thus, recent studies have shown emergent properties such as the stabilization of ferromagnetism in a paramagnetic system, conductivity at the interface of two insulators, and even exchange bias at the interface between a paramagnet and a ferromagnet. Despite these steps forward, there remains remarkable disagreement on the mechanisms by which these emergent phenomena are stabilized. The contributions of strain, stoichiometry, defects, intermixing, and electronic reconstruction are often very difficult to isolate in thin films and superlattices. This thesis will present model systems for isolating the effects of strain and interfacial electronic interactions on the magnetic state of complex oxides from alternative contributions. We will focus first on SrRuO3, an ideal system in which to isolate substrate induced strain effects. We explore the effects of structural distortions in the simplest case of growth on (100) oriented substrates. We find that parameters including saturated magnetic moment and Curie temperature are all highly tunable through substrate induced lattice distortions. We also report the stabilization of a nonmagnetic spin-zero configuration of Ru4+ in tetragonally distorted films under tensile strain. Through growth on (110) and (111) oriented substrates we explore the effects of different distortion symmetries on SrRuO3 and demonstrate the first reported strain induced transition to a high-spin state of Ru 4+. Finally, we examine the effects of strain on SrRuO3 thin films and demonstrate a completely reversible universal out-of-plane magnetic easy axis on films grown on different substrate orientations. Having demonstrated the ability to tune nearly every magnetic parameter of SrRuO 3 through strain, we turn to magnetic properties at interfaces. We study the emergent interfacial ferromagnetism in superlattices of the paramagnetic metal CaRuO3 and the antiferromagnetic insulator CaMnO3 and demonstrate that the interfacial ferromagnetic layer in this system is confined to a single unit cell of CaMnO3 at the interface. We discuss the remarkable oscillatory dependence of the saturated magnetic moment on the thickness of the CaMnO3 layers and explore mechanisms by which this oscillation may be stabilized. We find long range coherence of the antiferromagnetism of the CaMnO3 layers across intervening layers of paramagnetic CaRuO3. Finally, we utilize the system of LaNiO3/CaMnO3 to separate the effects of intermixing and interfacial electronic reconstruction and conclusively demonstrate intrinsic interfacial ferromagnetism at the interface between a paramagnetic metal and an antiferromagnetic insulator. We find that the emergent ferromagnetism is stabilized through interfacial double exchange and that the leakage of conduction electrons from the paramagnetic metal to the antiferromagnetic insulator is critical to establishing the ferromagnetic ground state.

Tailoring the magnetostructural transition and magnetocaloric properties around room temperature: In-doped Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Zhang, Linfang; Wang, Jingmin; Hua, Hui; Jiang, Chengbao; Xu, Huibin

2014-09-01

Some off-stoichiometric Ni-Mn-Ga alloys undergo a coupled magnetostructural transition from ferromagnetic martensite to paramagnetic austenite, giving rise to the large magnetocaloric effect. However, the magnetostructural transitions of Ni-Mn-Ga alloys generally take place at temperatures higher than room temperature. Here, we report that by the partial substitution of In for Ga, the paramagnetic austenite phase is well stabilized, and the magnetostructural transition can be tailored around room temperature. Sizable magnetic entropy change and adiabatic temperature change were induced by magnetic field change in the vicinity of the magnetostructural transition of the In-doped Ni-Mn-Ga alloys.

Paramagnetic NMR Investigation of Dendrimer-Based Host-Guest Interactions

PubMed Central

Wang, Fei; Shao, Naimin; Cheng, Yiyun

2013-01-01

In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the 1H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH2, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and 1H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems. PMID:23762249

Analysis techniques for tracer studies of oxidation. M. S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Basu, S. N.

1984-01-01

Analysis techniques to obtain quantitative diffusion data from tracer concentration profiles were developed. Mass balance ideas were applied to determine the mechanism of oxide growth and to separate the fraction of inward and outward growth of oxide scales. The process of inward oxygen diffusion with exchange was theoretically modelled and the effect of lattice diffusivity, grain boundary diffusivity and grain size on the tracer concentration profile was studied. The development of the tracer concentration profile in a growing oxide scale was simulated. The double oxidation technique was applied to a FeCrAl-Zr alloy using 0-18 as a tracer. SIMS was used to obtain the tracer concentration profile. The formation of lacey oxide on the alloy was discussed. Careful consideration was given to the quality of data required to obtain quantitative information.

Retrospective Reconstruction of Radiation Doses of Chernobyl Liquidators by Electron Paramagnetic Resonance

DTIC Science & Technology

1997-12-01

Armed Forces Rad I Research Institute Retrospective Reconstruction of Radiation Doses of Chernobyl Liquidators by Electron Paramagnetic Resonance A...of Radiation Doses of Chernobyl Liquidators by Electron Paramagnetic Resonance Authored by Scientific Center of Radiation Medicine Academy of Medical...libraries associated with the U.S. Government’s Depository Library System. Preface On April 26, 1986, Reactor #4 at the Chernobyl Nuclear Power Plant near

Across North America tracer experiment (ANATEX): Sampling and analysis

NASA Astrophysics Data System (ADS)

Draxler, R. R.; Dietz, R.; Lagomarsino, R. J.; Start, G.

Between 5 January 1987 and 29 March 1987, there were 33 releases of different tracers from each of two sites: Glasgow, MT and St. Cloud, MN. The perfluorocarbon tracers were routinely released in a 3-h period every 2.5 days, alternating between daytime and night-time tracer releases. Ground-level air samples of 24-h duration were taken at 77 sites mostly located near rawinsonde stations east of 105°W and between 26°N and 55°N. Weekly air samples were taken at 12 remote sites between San Diego, CA and Pt. Barrow, AK and between Norway and the Canary Islands. Short-term 6-h samples were collected at ground level and 200 m AGL along an arc of five towers between Tulsa, OK and Green Bay, WI. Aircraft sampling within several hundred kilometers of both tracer release sites was used to establish the initial tracer path. Experimental design required improved sampler performance, new tracers with lower atmospheric backgrounds, and improvements in analytic precision. The advances to the perfluorocarbon tracer system are discussed in detail. Results from the tracer sampling showed that the average and peak concentrations measured over the daily ground-level sampling network were consistent with what would be calculated using mass conservative approaches. however, ground-level samples from individual tracer patterns showed considerable complexity due to vertical stability or the interaction of the tracer plumes with low pressure and frontal systems. These systems could pass right through the tracer plume without appreciable effect. Aircraft tracer measurements are used to confirm the initial tracer trajectory when the narrow plume may miss the coarser spaced ground-level sampling network. Tower tracer measurements showed a more complex temporal structure than evident from the longer duration ground-level sampling sites. Few above background plume measurements were evident in the more distant remote sampling network due to larger than expected uncertainties in the ambient background concentrations.

Application of multiple tracers (SF6 and chloride) to identify the transport by characteristics of contaminant at two separate contaminated sites

NASA Astrophysics Data System (ADS)

Lee, K. K.; Lee, S. S.; Kim, H. H.; Koh, E. H.; Kim, M. O.; Lee, K.; Kim, H. J.

2016-12-01

Multiple tracers were applied for source and pathway detection at two different sites. CO2 gas injected in the subsurface for a shallow-depth CO2 injection and leak test can be regarded as a potential contaminant source. Therefore, it is necessary to identify the migration pattern of CO2 gas. Also, at a DNAPL contaminated site, it is important to figure out the characteristics of plume evolution from the source zone. In this study, multiple tracers (SF6 and chloride) were used to evaluate the applicability of volatile and non-volatile tracers and to identify the characteristics of contaminant transport at each CO2 injection and leak test site and DNAPL contaminated site. Firstly, at the CO2 test site, multiple tracers were used to perform the single well push-drift-pull tracer test at total 3 specific depth zones. As results of tests, volatile and non-volatile tracers showed different mass recovery percentage. Most of chloride mass was recovered but less than half of SF6 mass was recovered due to volatile property. This means that only gaseous SF6 leak out to unsaturated zone. However, breakthrough curves of both tracers indicated similar peak time, effective porosity, and regional groundwater velocity. Also, at both contaminated sites, natural gradient tracer tests were performed with multiple tracers. With the results of natural gradient tracer test, it was possible to confirm the applicability of multiple tracers and to understand the contaminant transport in highly heterogeneous aquifer systems through the long-term monitoring of tracers. Acknowledgement: financial support was provided by the R&D Project on Environmental Management of Geologic CO2 Storage)" from the KEITI (Project Number: 2014001810003) and Korea Ministry of Environment as "The GAIA project (2014000540010)".

Utility of bromide and heat tracers for aquifer characterization affected by highly transient flow conditions

NASA Astrophysics Data System (ADS)

Ma, Rui; Zheng, Chunmiao; Zachara, John M.; Tonkin, Matthew

2012-08-01

A tracer test using both bromide and heat tracers conducted at the Integrated Field Research Challenge site in Hanford 300 Area (300A), Washington, provided an instrument for evaluating the utility of bromide and heat tracers for aquifer characterization. The bromide tracer data were critical to improving the calibration of the flow model complicated by the highly dynamic nature of the flow field. However, most bromide concentrations were obtained from fully screened observation wells, lacking depth-specific resolution for vertical characterization. On the other hand, depth-specific temperature data were relatively simple and inexpensive to acquire. However, temperature-driven fluid density effects influenced heat plume movement. Moreover, the temperature data contained "noise" caused by heating during fluid injection and sampling events. Using the hydraulic conductivity distribution obtained from the calibration of the bromide transport model, the temperature depth profiles and arrival times of temperature peaks simulated by the heat transport model were in reasonable agreement with observations. This suggested that heat can be used as a cost-effective proxy for solute tracers for calibration of the hydraulic conductivity distribution, especially in the vertical direction. However, a heat tracer test must be carefully designed and executed to minimize fluid density effects and sources of noise in temperature data. A sensitivity analysis also revealed that heat transport was most sensitive to hydraulic conductivity and porosity, less sensitive to thermal distribution factor, and least sensitive to thermal dispersion and heat conduction. This indicated that the hydraulic conductivity remains the primary calibration parameter for heat transport.

Utility of Bromide and Heat Tracers for Aquifer Characterization Affected by Highly Transient Flow Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Rui; Zheng, Chunmiao; Zachara, John M.

A tracer test using both bromide and heat tracers conducted at the Integrated Field Research Challenge site in Hanford 300 Area (300A), Washington, provided an instrument for evaluating the utility of bromide and heat tracers for aquifer characterization. The bromide tracer data were critical to improving the calibration of the flow model complicated by the highly dynamic nature of the flow field. However, most bromide concentrations were obtained from fully screened observation wells, lacking depth-specific resolution for vertical characterization. On the other hand, depth-specific temperature data were relatively simple and inexpensive to acquire. However, temperature-driven fluid density effects influenced heatmore » plume movement. Moreover, the temperature data contained “noise” caused by heating during fluid injection and sampling events. Using the hydraulic conductivity distribution obtained from the calibration of the bromide transport model, the temperature depth profiles and arrival times of temperature peaks simulated by the heat transport model were in reasonable agreement with observations. This suggested that heat can be used as a cost-effective proxy for solute tracers for calibration of the hydraulic conductivity distribution, especially in the vertical direction. However, a heat tracer test must be carefully designed and executed to minimize fluid density effects and sources of noise in temperature data. A sensitivity analysis also revealed that heat transport was most sensitive to hydraulic conductivity and porosity, less sensitive to thermal distribution factor, and least sensitive to thermal dispersion and heat conduction. This indicated that the hydraulic conductivity remains the primary calibration parameter for heat transport.« less

Can nanotechnology help advance glaciological research?

NASA Astrophysics Data System (ADS)

Dahlke, H. E.; McNew, C.; Wang, C.; McLaughlin, S.; Kocis, T. N.

2017-12-01

In a rapidly changing cryosphere, identifying sources, pathways, and residence times of snow and glacier meltwater is critical to developing improved understanding of watershed-stream connections and hydrological/glaciological melt models. Traditionally, glaciologists have used a variety of tracers, including chloride, microparticles, and dyes, to identify the structure and morphology of subglacial drainage systems. However, minimum detection limits, tracer expense, and the ability of watersheds to retain a memory of past tracer inputs have restricted both the scale of tracer application and the repeated or simultaneous use of most known tracers, thus limiting our ability to study complex glacial systems. These shortcomings in hydrologic tracers can be overcome by utilizing a tracer that allows for the unique identification between spatial and temporal inputs while maintaining identical transport characteristics. Here, we present the use of DNA-labeled nanoparticles, developed for nano-medicine and drug delivery, as environmental tracers. The DNA-labeled particle tracers consist of short DNA strands encapsulated within biodegradable polymer microspheres, which allow for repeatable production of numerous uniquely labelled tracers of pre-determined size and physical transport properties. Each batch of tracers are independently quantifiable; even a single DNA molecule can be detected with cost-effective quantitative polymerase chain reaction (qPCR). We have tested our tracer technology in complex systems such as valley glaciers in Sweden and Alaska and in both laboratory and field studies of channel flow, overland flow, and flow in porous media; these proof-of-concept studies indicate that nanotechnology allows for powerful characterization, description, and, ultimately, prediction of flow pathways in glacial systems and the environment.

Enhanced Wireless Power Transmission Using Strong Paramagnetic Response.

PubMed

Ahn, Dukju; Kiani, Mehdi; Ghovanloo, Maysam

2014-03-01

A method of quasi-static magnetic resonant coupling has been presented for improving the power transmission efficiency (PTE) in near-field wireless power transmission, which improves upon the state of the art. The traditional source resonator on the transmitter side is equipped with an additional resonator with a resonance frequency that is tuned substantially higher than the magnetic field excitation frequency. This additional resonator enhances the magnetic dipole moment and the effective permeability of the power transmitter, owing to a phenomenon known as the strong paramagnetic response. Both theoretical calculations and experimental results show increased PTE due to amplification of the effective permeability. In measurements, the PTE was improved from 57.8% to 64.2% at the nominal distance of 15 cm when the effective permeability was 2.6. The power delivered to load was also improved significantly, with the same 10 V excitation voltage, from 0.38 to 5.26 W.

Thermoelectricity in transition metal compounds: The role of spin disorder

DOE PAGES

Gorai, Prashun; Toberer, Eric S.; Stevanović, Vladan

2016-11-01

Here, at room temperature and above, most magnetic materials adopt a spin-disordered (paramagnetic) state whose electronic properties can differ significantly from their low-temperature, spin-ordered counterparts. Yet computational searches for new functional materials usually assume some type of magnetic order. In the present work, we demonstrate a methodology to incorporate spin disorder in computational searches and predict the electronic properties of the paramagnetic phase. We implement this method in a high-throughput framework to assess the potential for thermoelectric performance of 1350 transition-metal sulfides and find that all magnetic systems we identify as promising in the spin-ordered ground state cease to bemore » promising in the paramagnetic phase due to disorder-induced deterioration of the charge carrier transport properties. We also identify promising non-magnetic candidates that do not suffer from these spin disorder effects. In addition to identifying promising materials, our results offer insights into the apparent scarcity of magnetic systems among known thermoelectrics and highlight the importance of including spin disorder in computational searches.« less

Anisotropy reversal of the upper critical field at low temperatures and spin-locked superconductivity in K 2 Cr 3 As 3

DOE PAGES

Balakirev, F. F.; Kong, T.; Jaime, M.; ...

2015-06-23

We report measurements of the anisotropic upper critical field H c2(T) for K 2Cr 3As 3 single crystals up to 60 T and T>0.6K. Our results show that the upper critical field parallel to the Cr chains, H ∥ c2(T), exhibits a paramagnetically limited behavior, whereas the shape of the H ⊥ c2(T) curve (perpendicular to the Cr chains) has no evidence of paramagnetic effects. As a result, the curves H ⊥ c2(T) and H ∥ c2(T) cross at T≈4K, so that the anisotropy parameter γ H(T)=H ⊥ c2/H ∥ c2(T) increases from γ H(T c)≈0.35 near T c tomore » γ H(0)≈1.7 at 0.6 K. The paramagnetically limited behavior of H ∥ c2(T) is inconsistent with triplet superconductivity but suggests a form of singlet superconductivity with the electron spins locked onto the direction of Cr chains.« less

Observation of superconductivity in BaNb2S5

NASA Astrophysics Data System (ADS)

Smith, M. G.; Neumeier, J. J.

2018-06-01

Bulk superconductivity is reported in BaNb2S5 at the transition temperature Tc = 0.85(1) K. The electrical resistivity ρ versus T is metallic with ρ(2 K) = 42.4 μΩ cm. The magnetic susceptibility is paramagnetic, with temperature-independent contributions due to diamagnetism, Pauli paramagnetism, and Van Vleck paramagnetism; a Curie-Weiss contribution appears to be impurity related. Hall effect measurements show that the majority charge carriers are electrons with charge-carrier concentration n(3 K) = 2.40(2) × 1021 cm-3. Specific heat measurements reveal an electronic specific heat coefficient γ = 11.2(1) mJ/mol K2, a Debye temperature ΘD = 126.4(8) K, and an energy gap associated with the superconducting state of Eg = 0.184(4) meV. Measurements of ρ(T) in magnetic field provide the upper critical magnetic field of about 3055(74) Oe as T → 0 K, which was used to estimate the coherence length ξ = 6.21(15) nm. The results allow classification of BaNb2S5 as a Type II, BCS superconductor in the dirty limit.

Improving the method of low-temperature anisotropy of magnetic susceptibility (LT-AMS) measurements in air

NASA Astrophysics Data System (ADS)

Issachar, R.; Levi, T.; Lyakhovsky, V.; Marco, S.; Weinberger, R.

2016-07-01

This study examines the limitations of the method of low-temperature anisotropy of magnetic susceptibility (LT-AMS) measurements in air and presents technical improvements that significantly reduce the instrumental drift and measurement errors. We analyzed the temperature profile of porous chalk core after cooling in liquid nitrogen and found that the average temperature of the sample during the LT-AMS measurement in air is higher than 77K and close to 92K. This analysis indicates that the susceptibility of the paramagnetic minerals are amplified by a factor ˜3.2 relative to that of room temperature AMS (RT-AMS). In addition, it was found that liquid nitrogen was absorbed in the samples during immersing and contributed diamagnetic component of ˜-9 × 10-6 SI to the total mean susceptibility. We showed that silicone sheet placed around and at the bottom of the measuring coil is an effective thermal protection, preventing instrument drift by the cold sample. In this way, the measuring errors of LT-AMS reduced to the level of RT-AMS, allowing accurate comparison with standard AMS measurements. We examined the applicability of the LT-AMS measurements on chalk samples that consist <5% (weight) of paramagnetic minerals and showed that it helps to efficiently enhance the paramagnetic fabric. The present study offers a practical approach, which can be applied to various types of rocks to better delineate the paramagnetic phase using conventional equipment.

Hyperfine Interactions in the Electron Paramagnetic Resonance Spectra of Point Defects in Wide-Band-Gap Semiconductors

DTIC Science & Technology

2014-09-18

compensation) during growth due to their preferred trivalent charge states. The electron paramagnetic resonance spectrum of the singly ionized chromium ...neutral nitrogen acceptor in ZnO . . . . . . . . . . . . . . . . . . 45 16 Spectrum of the singly ionized chromium acceptor in TiO2 . . . . . . . . . 49...is a single crystal of magnesium oxide that has been doped with chromium . Chromium Cr3+ substitutes for magnesium Mg2+ and creates a paramagnetic

Relative Roles of Gap Junction Channels and Cytoplasm in Cell-to-Cell Diffusion of Fluorescent Tracers

NASA Astrophysics Data System (ADS)

Safranyos, Richard G. A.; Caveney, Stanley; Miller, James G.; Petersen, Nils O.

1987-04-01

Intercellular (tissue) diffusion of molecules requires cytoplasmic diffusion and diffusion through gap junctional (or cell-to-cell) channels. The rates of tissue and cytoplasmic diffusion of fluorescent tracers, expressed as an effective diffusion coefficient, De, and a cytoplasmic diffusion coefficient, Dcyt, have been measured among the developing epidermal cells of a larval beetle, Tenebrio molitor L., to determine the contribution of the junctional channels to intercellular diffusion. Tracer diffusion was measured by injecting fluorescent tracers into cells and quantitating the rate of subsequent spread into adjacent cells. Cytoplasmic diffusion was determined by fluorescence photobleaching. These experiments show that gap junctional channels constitute approximately 70-80% of the total cell-to-cell resistance to the diffusion of organic tracers at high concentrations in this tissue. At low concentrations, however, the binding of tracer to cytoplasm slows down the cytoplasmic diffusion, which may limit intercellular diffusion.

Simulation of soluble waste transport and buildup in surface waters using tracers

USGS Publications Warehouse

Kilpatrick, F.A.

1993-01-01

Soluble tracers can be used to simulate the transport and dispersion of soluble wastes that might have been introduced or are planned for introduction into surface waters. Measured tracer-response curves produced from the injection of a known quantity of soluble tracer can be used in conjunction with the superposition principle to simulate potential waste buildup in streams, lakes, and estuaries. Such information is particularly valuable to environmental and water-resource planners in determining the effects of proposed waste discharges. The theory, techniques, analysis, and presentation of results of tracer-waste simulation tests in rivers, lakes, and estuaries are described. This manual builds on other manuals dealing with dye tracing by emphasizing the expanded use of data from time-of-travel studies.

Simulation of soluble waste transport and buildup in surface waters using tracers

USGS Publications Warehouse

Kilpatrick, Frederick A.

1992-01-01

Soluble tracers can be used to simulate the transport and dispersion of soluble wastes that might have been introduced or are planned for introduction into surface waters. Measured tracer-response curves produced from the injection of a known quantity of soluble tracer can be used in conjunction with the superposition principle to simulate potential waste buildup in streams, lakes, and estuaries. Such information is particularly valuable to environmental and water-resource planners in determining the effects of proposed waste discharges.The theory, techniques, analysis, and presentation of results of tracer-waste simulation tests in rivers, lakes, and estuaries are described. This manual builds on other manuals on dye tracing with emphasis on the expanded use of time-of-travel type data.

Emergent Interfacial Ferromagnetism in CaMnO3-based Superlattices

NASA Astrophysics Data System (ADS)

Grutter, Alexander

2014-03-01

Interfaces of complex oxide materials provide a rich playground not only for the exploration of properties not found in the bulk constituents but also for the development of functional interfaces to be incorporated in spintronic applications. Emergent interfacial magnetic phenomena have been of great interest but surprisingly there have been few examples of emergent interfacial ferromagnetism. In this talk, I will describe our recent work on the stabilization of ferromagnetism in CaMnO3-based superlattices. We have demonstrated ferromagnetism at the interface between the antiferromagnetic insulator CaMnO3 and a paramagnetic metallic layer, including CaRuO3 and LaNiO3. Theoretically the ferromagnetism has been attributed to an interfacial double exchange interaction among the interfacial Mn ions that is mediated by itinerant electrons from the paramagnetic metallic layer. Through polarized neutron reflectivity and observation of exchange bias, we have demonstrated that the ferromagnetism comes from Mn ions in a single unit cell at the interfaces just as theory has predicted. We have also demonstrated that the metallicity of the paramagnetic layer is critical in stabilizing ferromagnetism at the interface and that the interfacial ferromagnetism can be suppressed by suppressing the metallicity of the paramagnetic layer. Despite the agreement with theory, there remain open questions as to the magnetic interactions among the interfacial ferromagnetic layers. For example, the saturated magnetic moment modulates as a function of the thickness of both the CaMnO3 and paramagnetic metal layers. The origins of this oscillation are not well understood and may stem from either structural effects or long-range oscillatory magnetic coupling interactions reminiscent of RKKY interactions. Evidence of the doubling of the unit cell and long range antiferromagnetic correlations support these speculations. This work was supported by the U.S. Department of Energy, Office of Science, Division of Materials Sciences and Engineering, under Contract # DE-AC05-76RL01830 and DE-SC0008505.

Tracer SWIW tests in propped and un-propped fractures: parameter sensitivity issues, revisited

NASA Astrophysics Data System (ADS)

Ghergut, Julia; Behrens, Horst; Sauter, Martin

2017-04-01

Single-well injection-withdrawal (SWIW) or 'push-then-pull' tracer methods appear attractive for a number of reasons: less uncertainty on design and dimensioning, and lower tracer quantities required than for inter-well tests; stronger tracer signals, enabling easier and cheaper metering, and shorter metering duration required, reaching higher tracer mass recovery than in inter-well tests; last not least: no need for a second well. However, SWIW tracer signal inversion faces a major issue: the 'push-then-pull' design weakens the correlation between tracer residence times and georeservoir transport parameters, inducing insensitivity or ambiguity of tracer signal inversion w. r. to some of those georeservoir parameters that are supposed to be the target of tracer tests par excellence: pore velocity, transport-effective porosity, fracture or fissure aperture and spacing or density (where applicable), fluid/solid or fluid/fluid phase interface density. Hydraulic methods cannot measure the transport-effective values of such parameters, because pressure signals correlate neither with fluid motion, nor with material fluxes through (fluid-rock, or fluid-fluid) phase interfaces. The notorious ambiguity impeding parameter inversion from SWIW test signals has nourished several 'modeling attitudes': (i) regard dispersion as the key process encompassing whatever superposition of underlying transport phenomena, and seek a statistical description of flow-path collectives enabling to characterize dispersion independently of any other transport parameter, as proposed by Gouze et al. (2008), with Hansen et al. (2016) offering a comprehensive analysis of the various ways dispersion model assumptions interfere with parameter inversion from SWIW tests; (ii) regard diffusion as the key process, and seek for a large-time, asymptotically advection-independent regime in the measured tracer signals (Haggerty et al. 2001), enabling a dispersion-independent characterization of multiple-scale diffusion; (iii) attempt to determine both advective and non-advective transport parameters from one and the same conservative-tracer signal (relying on 'third-party' knowledge), or from twin signals of a so-called 'dual' tracer pair, e. g.: using tracers with contrasting reactivity and partitioning behavior to determine residual saturation in depleted oilfields (Tomich et al. 1973), or to determine advective parameters (Ghergut et al. 2014); using early-time signals of conservative and sorptive tracers for propped-fracture characterization (Karmakar et al. 2015); using mid-time signals of conservative tracers for a reservoir-borne inflow profiling in multi-frac systems (Ghergut et al. 2016), etc. The poster describes new uses of type-(iii) techniques for the specific purposes of shale-gas reservoir characterization, productivity monitoring, diagnostics and engineering of 're-frac' treatments, based on parameter sensitivity findings from German BMWi research project "TRENDS" (Federal Ministry for Economic Affairs and Energy, FKZ 0325515) and from the EU-H2020 project "FracRisk" (grant no. 640979).

Viscosity scaling in concentrated dispersions and its impact on colloidal aggregation.

PubMed

Nicoud, Lucrèce; Lattuada, Marco; Lazzari, Stefano; Morbidelli, Massimo

2015-10-07

Gaining fundamental knowledge about diffusion in crowded environments is of great relevance in a variety of research fields, including reaction engineering, biology, pharmacy and colloid science. In this work, we determine the effective viscosity experienced by a spherical tracer particle immersed in a concentrated colloidal dispersion by means of Brownian dynamics simulations. We characterize how the effective viscosity increases from the solvent viscosity for small tracer particles to the macroscopic viscosity of the dispersion when large tracer particles are employed. Our results show that the crossover between these two regimes occurs at a tracer particle size comparable to the host particle size. In addition, it is found that data points obtained in various host dispersions collapse on one master curve when the normalized effective viscosity is plotted as a function of the ratio between the tracer particle size and the mean host particle size. In particular, this master curve was obtained by varying the volume fraction, the average size and the polydispersity of the host particle distribution. Finally, we extend these results to determine the size dependent effective viscosity experienced by a fractal cluster in a concentrated colloidal system undergoing aggregation. We include this scaling of the effective viscosity in classical aggregation kernels, and we quantify its impact on the kinetics of aggregate growth as well as on the shape of the aggregate distribution by means of population balance equation calculations.

Simultaneous Analyses and Applications of Multiple Fluorobenzoate and Halide Tracers in Hydrologic Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Q; Moran, J E

2004-01-22

An analytical method that employs ion chromatography has been developed to more fully exploit the use of fluorobenzoic acids (FBAs) and halides as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g., nitrate and sulfate). The usefulness of this ion chromatographic (IC) analytical method is demonstrated in both field and laboratory tracer experiments. Field experiments in unsaturated tuff featuring fractures or a fault show that this efficient and cost-effective method helps achieve the objectives ofmore » tracer studies that use multiple FBAs and/or diffusivity tracers (simultaneous use of one or more FBA and halide). The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the United States--mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need--reveal several insights about tracer transport behavior: (1) Bromide and FBAs are not always transported conservatively. (2) The delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy. (3) Any use of iodine as a hydrologic tracer should take into account the different sorption behaviors of iodide and iodate and the possible conversion of iodine's initial chemical form. (4) The transport behavior of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments.« less

Investigating the effect of compression on solute transport through degrading municipal solid waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woodman, N.D., E-mail: n.d.woodman@soton.ac.uk; Rees-White, T.C.; Stringfellow, A.M.

2014-11-15

Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to themore » presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.« less

Optical detection of paramagnetic centres: From crystals to glass-ceramics

NASA Astrophysics Data System (ADS)

Rogulis, Uldis

2016-07-01

An unambiguous attribution of the absorption spectra to definite paramagnetic centres identified by the EPR techniques in the most cases is problematic. This problem may be solved by applying of a direct measurement techniques—the EPR detected via the magnetic circular dichroism, or briefly MCD-EPR. The present survey reports on the advantages and disadvantages applying the MCD-EPR techniques to simple and complex paramagnetic centres in crystals as well as glasses and glass-ceramics.

Application of Electron Paramagnetic Resonance to Study of Gallstones

NASA Astrophysics Data System (ADS)

Kiselev, S. A.; Tsyro, L. V.; Afanasiev, D. A.; Unger, F. G.; Soloviev, M. M.

2014-03-01

We present the results of an electron paramagnetic resonance (EPR) study of mixed cholesterol gallstones. We have established that free radicals are distributed nonuniformly within the interior of the stone. The type and number of paramagnetic centers depend on the pigment content in the selected layer. We show that the parameters of the sextet lines in the EPR spectrum of the pigment are close to the parameters of lines in the spectrum of a brown pigment stone.

CW EPR and 9 GHz EPR imaging investigation of stable paramagnetic species and their antioxidant activities in dry shiitake mushroom (Lentinus edodes).

PubMed

Nakagawa, Kouichi; Hara, Hideyuki

2016-01-01

We investigated the antioxidant activities and locations of stable paramagnetic species in dry (or drying) shiitake mushroom (Lentinus edodes) using continuous wave (CW) electron paramagnetic resonance (EPR) and 9 GHz EPR imaging. CW 9 GHz EPR detected paramagnetic species (peak-to-peak linewidth (ΔHpp) = 0.57 mT) in the mushroom. Two-dimensional imaging of the sharp line using a 9 GHz EPR imager showed that the species were located in the cap and shortened stem portions of the mushroom. No other location of the species was found in the mushroom. However, radical locations and concentrations varied along the cap of the mushroom. The 9 GHz EPR imaging determined the exact location of stable paramagnetic species in the shiitake mushroom. Distilled water extracts of the pigmented cap surface and the inner cap of the mushroom showed similar antioxidant activities that reduced an aqueous solution of 0.1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The present results suggest that the antioxidant activities of the edible mushroom extracts are much weaker than those of ascorbic acid. Thus, CW EPR and EPR imaging revealed the location and distribution of stable paramagnetic species and the antioxidant activities in the shiitake mushroom for the first time.

Effects of crude oil on water and tracer movement in the unsaturated and saturated zones.

PubMed

Delin, Geoffrey N; Herkelrath, William N

2017-05-01

A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the periphery of the oil. Preferential flow resulted in reduced tracer interaction with the soil, adsorption, and dispersion and faster tracer movement in the oily zone than expected. Tracers were freely transported through the oily zone to the water table. Recharge calculations support the idea that the oil does not substantially affect recharge in the oily zone. This is an important result indicating that previous model-based assumptions of decreased recharge beneath the oil were incorrect. Results have important implications for modeling the fate and transport of dissolved contaminants at hydrocarbon spill sites. Published by Elsevier B.V.

In situ monitoring of tracer tests: how to distinguish tracer recovery from natural background

NASA Astrophysics Data System (ADS)

Bailly-Comte, V.; Durepaire, X.; Batiot-Guilhe, C.; Schnegg, P.-A.

2018-03-01

Hydrogeological tracer tests are primarily conducted with fluorescent tracers. Field fluorometers make it possible to monitor tracers at very low concentrations (<1 ppb) and at high frequency. However, changes in natural fluorescence at a site resulting from variations of dissolved and suspended inorganic and organic material may compromise the measurement of useful signals, thereby limiting the chances of identifying or quantifying the real tracer recovery. An elevated natural signal can mask small concentrations of the tracer while its variability can give the impression of a false recovery. This article shows how the use of a combination of several continuous measurements at different wavelengths allows a better extraction of the natural signal. Field multispectral fluorometers were installed at two Mediterranean karst outlets; both drain carbonate systems but have different environmental conditions. The fluorometers functioned over several hydrologic cycles, in periods affected or not by artificial tracers, making it possible to observe natural signal variations at these sites. The optical properties of this type of field fluorometer were used to calculate the spectral response of the different optics of the measuring probe. These responses, superimposed on three-dimensional excitation/emission matrices produced from laboratory fluorescence measurements, allowed an understanding of what the fluorometer sees under natural flow conditions. The result is an innovative method for correcting artificial tracer results. This type of correction makes it possible to fine-tune the effect of natural background variation on tracer recovery curves for a clear identification of the tracer presence and a more precise quantification of its recovery.

Chemical disorder influence on magnetic state of optimally-doped La0.7Ca0.3MnO3

NASA Astrophysics Data System (ADS)

Rozenberg, E.; Auslender, M.; Shames, A. I.; Jung, G.; Felner, I.; Tsindlekht, M. I.; Mogilyansky, D.; Sominski, E.; Gedanken, A.; Mukovskii, Ya. M.; Gorodetsky, G.

2011-10-01

X-band electron magnetic resonance and dc/ac magnetic measurements have been employed to study the effects of chemical disorder on magnetic ordering in bulk and nanometer-sized single crystals and bulk ceramics of optimally-doped La0.7Ca0.3MnO3 manganite. The magnetic ground state of bulk samples appeared to be ferromagnetic with the lower Curie temperature and higher magnetic homogeneity in the vicinity of the ferromagnetic-paramagnetic phase transition in the crystal, as compared with those characteristics in the ceramics. The influence of technological driven "macroscopic" fluctuations of Ca-dopant level in crystal and "mesoscopic" disorder within grain boundary regions in ceramics was proposed to be responsible for these effects. Surface spin disorder together with pronounced inter-particle interactions within agglomerated nano-sample results in well defined core/shell spin configuration in La0.7Ca0.3MnO3 nano-crystals. The analysis of the electron paramagnetic resonance data enlightened the reasons for the observed difference in the magnetic order. Lattice effects dominate the first-order nature of magnetic phase transition in bulk samples. However, mesoscale chemical disorder seems to be responsible for the appearance of small ferromagnetic polarons in the paramagnetic state of bulk ceramics. The experimental results and their analysis indicate that a chemical/magnetic disorder has a strong impact on the magnetic state even in the case of mostly stable optimally hole-doped manganites.

Physicochemical characterization, and relaxometry studies of micro-graphite oxide, graphene nanoplatelets, and nanoribbons.

PubMed

Paratala, Bhavna S; Jacobson, Barry D; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn(2+) ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

PubMed Central

Paratala, Bhavna S.; Jacobson, Barry D.; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents. PMID:22685555

A tracer dose of technetium-99m-labeled liposomes can estimate the effect of hyperthermia on intratumoral doxil extravasation.

PubMed

Kleiter, Miriam M; Yu, Daohai; Mohammadian, Lenore A; Niehaus, Nelsen; Spasojevic, Ivan; Sanders, Linda; Viglianti, Benjamin L; Yarmolenko, Pavel S; Hauck, Marlene; Petry, Neil A; Wong, Terence Z; Dewhirst, Mark W; Thrall, Donald E

2006-11-15

A noninvasive method to monitor intratumoral Doxil delivery in individual patients during targeted tumor therapy is important to predict treatment response. The purpose of this study was to determine if a small tracer dose of technetium-99m (99mTc)-labeled liposomes could be used to quantify the effect of local hyperthermia on intratumoral Doxil extravasation. Experiments were carried out in a rat fibrosarcoma model with transplanted thigh tumors. Liposomes of approximately same size and composition as Doxil were radiolabeled using [technetium-99m (99mTc)]exametazime. Eight treatment groups received either Doxil, a tracer dose or a large dose of 99mTc-labeled liposomes, or a combination of tracer and Doxil, with or without hyperthermia. This design was chosen to assure that coadministration of both liposomal formulations did not influence their intratumoral distribution. Hyperthermia was done for 45 minutes. Scintigraphic images were obtained at 5 and 18 hours. At 18 hours, tumors were removed and gamma counts as well as doxorubicin concentrations were measured. Intratumoral extravasation of the 99mTc-labeled tracer could be imaged scintigraphically under normothermic and hyperthermic conditions. The thermal enhancement ratio was slightly higher for radiolabeled liposomes than for doxorubicin concentration. However, there was a significant positive correlation of intratumoral doxorubicin concentration and intratumoral uptake of the radiolabeled tracer (expressed as percentage of the injected dose per gram of tissue). Coadministration of radiolabeled liposomes did not negatively influence the amount of drug delivered with Doxil. The use of a radiolabeled tracer has potential value to monitor drug delivery and estimate the effect of an intervention aimed to increase liposomal accumulation, such as local hyperthermia.

EPR Characterization of Dinitrosyl Iron Complexes with Thiol-Containing Ligands as an Approach to Their Identification in Biological Objects: An Overview.

PubMed

Vanin, Anatoly F

2018-06-01

The overview demonstrates how the use of only one physico-chemical approach, viz., the electron paramagnetic resonance method, allowed detection and identification of dinitrosyl iron complexes with thiol-containing ligands in various animal and bacterial cells. These complexes are formed in biological objects in the paramagnetic (electron paramagnetic resonance-active) mononuclear and diamagnetic (electron paramagnetic resonance-silent) binuclear forms and control the activity of nitrogen monoxide, one of the most universal regulators of metabolic processes in the organism. The analysis of electronic and spatial structures of dinitrosyl iron complex sheds additional light on the mechanism whereby dinitrosyl iron complex with thiol-containing ligands function in human and animal cells as donors of nitrogen monoxide and its ionized form, viz., nitrosonium ions (NO + ).

Bed load tracer mobility in a mixed bedrock/alluvial channel

NASA Astrophysics Data System (ADS)

Ferguson, R. I.; Sharma, B. P.; Hodge, R. A.; Hardy, R. J.; Warburton, J.

2017-04-01

The presence of bare or partially covered rock in an otherwise alluvial river implies a downstream change in transport capacity relative to supply. Field investigations of this change and what causes it are lacking. We used two sets of magnet-tagged tracer clasts to investigate bed load transport during the same sequence of floods in fully alluvial, bare rock, and partial-cover reaches of an upland stream. High-flow shear stresses in different reaches were calculated by using stage loggers. Tracers seeded in the upstream alluvial channel moved more slowly than elsewhere until the frontrunners reached bare rock and sped up. Tracers seeded on bare rock moved rapidly off it and accumulated just upstream from, and later in, a partial-cover zone with many boulders. The backwater effect of the boulder-rich zone is significant in reducing tracer mobility. Tracer movement over full or partial sediment cover was size selective but dispersion over bare rock was not. Along-channel changes in tracer mobility are interpreted in terms of measured differences in shear stress and estimated differences in threshold stress.

Theoretical foundation for measuring the groundwater age distribution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardner, William Payton; Arnold, Bill Walter

2014-01-01

In this study, we use PFLOTRAN, a highly scalable, parallel, flow and reactive transport code to simulate the concentrations of 3H, 3He, CFC-11, CFC-12, CFC-113, SF6, 39Ar, 81Kr, 4He and themean groundwater age in heterogeneous fields on grids with an excess of 10 million nodes. We utilize this computational platform to simulate the concentration of multiple tracers in high-resolution, heterogeneous 2-D and 3-D domains, and calculate tracer-derived ages. Tracer-derived ages show systematic biases toward younger ages when the groundwater age distribution contains water older than the maximum tracer age. The deviation of the tracer-derived age distribution from the true groundwatermore » age distribution increases with increasing heterogeneity of the system. However, the effect of heterogeneity is diminished as the mean travel time gets closer the tracer age limit. Age distributions in 3-D domains differ significantly from 2-D domains. 3D simulations show decreased mean age, and less variance in age distribution for identical heterogeneity statistics. High-performance computing allows for investigation of tracer and groundwater age systematics in high-resolution domains, providing a platform for understanding and utilizing environmental tracer and groundwater age information in heterogeneous 3-D systems. Groundwater environmental tracers can provide important constraints for the calibration of groundwater flow models. Direct simulation of environmental tracer concentrations in models has the additional advantage of avoiding assumptions associated with using calculated groundwater age values. This study quantifies model uncertainty reduction resulting from the addition of environmental tracer concentration data. The analysis uses a synthetic heterogeneous aquifer and the calibration of a flow and transport model using the pilot point method. Results indicate a significant reduction in the uncertainty in permeability with the addition of environmental tracer data, relative to the use of hydraulic measurements alone. Anthropogenic tracers and their decay products, such as CFC11, 3H, and 3He, provide significant constraint oninput permeability values in the model. Tracer data for 39Ar provide even more complete information on the heterogeneity of permeability and variability in the flow system than the anthropogenic tracers, leading to greater parameter uncertainty reduction.« less

Assessing the Accuracy of the Tracer Dilution Method with Atmospheric Dispersion Modeling

NASA Astrophysics Data System (ADS)

Taylor, D.; Delkash, M.; Chow, F. K.; Imhoff, P. T.

2015-12-01

Landfill methane emissions are difficult to estimate due to limited observations and data uncertainty. The mobile tracer dilution method is a widely used and cost-effective approach for predicting landfill methane emissions. The method uses a tracer gas released on the surface of the landfill and measures the concentrations of both methane and the tracer gas downwind. Mobile measurements are conducted with a gas analyzer mounted on a vehicle to capture transects of both gas plumes. The idea behind the method is that if the measurements are performed far enough downwind, the methane plume from the large area source of the landfill and the tracer plume from a small number of point sources will be sufficiently well-mixed to behave similarly, and the ratio between the concentrations will be a good estimate of the ratio between the two emissions rates. The mobile tracer dilution method is sensitive to different factors of the setup such as placement of the tracer release locations and distance from the landfill to the downwind measurements, which have not been thoroughly examined. In this study, numerical modeling is used as an alternative to field measurements to study the sensitivity of the tracer dilution method and provide estimates of measurement accuracy. Using topography and wind conditions for an actual landfill, a landfill emissions rate is prescribed in the model and compared against the emissions rate predicted by application of the tracer dilution method. Two different methane emissions scenarios are simulated: homogeneous emissions over the entire surface of the landfill, and heterogeneous emissions with a hot spot containing 80% of the total emissions where the daily cover area is located. Numerical modeling of the tracer dilution method is a useful tool for evaluating the method without having the expense and labor commitment of multiple field campaigns. Factors tested include number of tracers, distance between tracers, distance from landfill to transect path, and location of tracers with respect to the hot spot. Results show that location of the tracers relative to the hot spot of highest landfill emissions makes the largest difference in accuracy of the tracer dilution method.

Van vleck paramagnetism in orthorhombic TiO2 (Brookite)

USGS Publications Warehouse

Senftle, F.E.; Thorpe, A.N.

1968-01-01

The magnetic susceptibility of the orthorhombic form of titanium dioxide has been measured from 5 to 300??K. After deducting the temperature-dependent component, which is probably due to defects or impurities, and the free-ion diamagnetic component, the Van Vleck paramagnetism was estimated to be 33??10-6 emu/mole. Comparison is made between this value and the Van Vleck paramagnetism of strontium titanate and the two tetragonal forms of titanium dioxide: rutile and anatase. ?? 1968 The American Physical Society.

The effect of wind and currents on gas exchange in an estuarine system

NASA Technical Reports Server (NTRS)

Broecker, W. S.; Ledwell, J. R.; Bopp, R.

1987-01-01

The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF6, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF6, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF6 and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

A line source tracer test - a better method for assessing high groundwater velocity

NASA Astrophysics Data System (ADS)

Magal, E.; Weisbrod, N.; Yakirevich, A.; Kurtzman, D.; Yechieli, Y.

2009-12-01

A line source injection is suggested as an effective method for assessing groundwater velocities and flow directions in subsurface characterized by high water fluxes. Modifying the common techniques of injecting a tracer into a well was necessary after frequently-used methods of natural and forced gradient tracer tests ended with no reliable information on the local groundwater flow. In a field experiment, tracers were injected into 8-m long line injection system constructed below the water table almost perpendicular to the assumed flow direction. The injection system was divided to four separate segments (each 2 m long) enabling the injection of four different tracers along the line source. An array of five boreholes located in an area of 10x10 m downstream was used for monitoring the tracers' transport. Two dye tracers (Uranine and Na Naphthionate) were injected in a long pulse of several hours into two of the injection pipe segments and two tracers (Rhenium oxide and Gd-DTPA) were instantaneously injected to the other two segments. The tracers were detected 0.7 to 2.3 hours after injection in four of the five observation wells, located 2.3 to 10 m from the injection system, respectively. Groundwater velocities were calculated directly from the tracers' arrival times and by fitting the observed breakthrough curves to simulations with one and two dimensions analytical solutions for conservative tracer transport. The groundwater velocity was determined to be ~100 m/d. The longitudinal dispersivity value, generated from fitting the tracer breakthrough curves, was in a range of 0.2-3m. The groundwater flow direction was derived based on the arrival of the tracers and was found to be consistent with the apparent direction of the hydraulic gradient. The hydraulic conductivity derived from the groundwater velocity was ~1200 m/d, which is in the upper range of gravel sediment.

EVALUATION OF LEAKAGE FROM FUME HOODS USING TRACER GAS, TRACER NANOPARTICLES AND NANOPOWDER HANDLING TEST METHODOLOGIES

PubMed Central

Dunn, Kevin H.; Tsai, Candace Su-Jung; Woskie, Susan R.; Bennett, James S.; Garcia, Alberto; Ellenbecker, Michael J.

2015-01-01

The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the hood opening. These containment tests were conducted across a range of hood face velocities (60, 80, and 100 feet/minute) and with the room ventilation system turned off and on. For the tracer gas and tracer nanoparticle tests, leakage was much more prominent on the left side of the hood (closest to the room supply air diffuser) although some leakage was noted on the right side and in the BZ sample locations. During the tracer gas and tracer nanoparticle tests, leakage was primarily noted when the room air conditioner was on for both the low and medium hood exhaust air flows. When the room air conditioner was turned off, the static tracer gas tests showed good containment across most test conditions. The tracer gas and nanoparticle test results were well correlated showing hood leakage under the same conditions and at the same sample locations. The impact of a room air conditioner was demonstrated with containment being adversely impacted during the use of room air ventilation. The tracer nanoparticle approach is a simple method requiring minimal setup and instrumentation. However, the method requires the reduction in background concentrations to allow for increased sensitivity. PMID:25175285

Evaluation of leakage from fume hoods using tracer gas, tracer nanoparticles and nanopowder handling test methodologies.

PubMed

Dunn, Kevin H; Tsai, Candace Su-Jung; Woskie, Susan R; Bennett, James S; Garcia, Alberto; Ellenbecker, Michael J

2014-01-01

The most commonly reported control used to minimize workplace exposures to nanomaterials is the chemical fume hood. Studies have shown, however, that significant releases of nanoparticles can occur when materials are handled inside fume hoods. This study evaluated the performance of a new commercially available nano fume hood using three different test protocols. Tracer gas, tracer nanoparticle, and nanopowder handling protocols were used to evaluate the hood. A static test procedure using tracer gas (sulfur hexafluoride) and nanoparticles as well as an active test using an operator handling nanoalumina were conducted. A commercially available particle generator was used to produce sodium chloride tracer nanoparticles. Containment effectiveness was evaluated by sampling both in the breathing zone (BZ) of a mannequin and operator as well as across the hood opening. These containment tests were conducted across a range of hood face velocities (60, 80, and 100 ft/min) and with the room ventilation system turned off and on. For the tracer gas and tracer nanoparticle tests, leakage was much more prominent on the left side of the hood (closest to the room supply air diffuser) although some leakage was noted on the right side and in the BZ sample locations. During the tracer gas and tracer nanoparticle tests, leakage was primarily noted when the room air conditioner was on for both the low and medium hood exhaust airflows. When the room air conditioner was turned off, the static tracer gas tests showed good containment across most test conditions. The tracer gas and nanoparticle test results were well correlated showing hood leakage under the same conditions and at the same sample locations. The impact of a room air conditioner was demonstrated with containment being adversely impacted during the use of room air ventilation. The tracer nanoparticle approach is a simple method requiring minimal setup and instrumentation. However, the method requires the reduction in background concentrations to allow for increased sensitivity.

Impact of community tracer teams on treatment outcomes among tuberculosis patients in South Africa.

PubMed

Bronner, Liza E; Podewils, Laura J; Peters, Annatjie; Somnath, Pushpakanthi; Nshuti, Lorna; van der Walt, Martie; Mametja, Lerole David

2012-08-07

Tuberculosis (TB) indicators in South Africa currently remain well below global targets. In 2008, the National Tuberculosis Program (NTP) implemented a community mobilization program in all nine provinces to trace TB patients that had missed a treatment or clinic visit. Implementation sites were selected by TB program managers and teams liaised with health facilities to identify patients for tracing activities. The objective of this analysis was to assess the impact of the TB Tracer Project on treatment outcomes among TB patients. The study population included all smear positive TB patients registered in the Electronic TB Registry from Quarter 1 2007-Quarter 1 2009 in South Africa. Subdistricts were used as the unit of analysis, with each designated as either tracer (standard TB program plus tracer project) or non-tracer (standard TB program only). Mixed linear regression models were utilized to calculate the percent quarterly change in treatment outcomes and to compare changes in treatment outcomes from Quarter 1 2007 to Quarter 1 2009 between tracer and non-tracer subdistricts. For all provinces combined, the percent quarterly change decreased significantly for default treatment outcomes among tracer subdistricts (-0.031%; p < 0.001) and increased significantly for successful treatment outcomes among tracer subdistricts (0.003%; p = 0.03). A significant decrease in the proportion of patient default was observed for all provinces combined over the time period comparing tracer and non-tracer subdistricts (p = 0.02). Examination in stratified models revealed the results were not consistent across all provinces; significant differences were observed between tracer and non-tracer subdistricts over time in five of nine provinces for treatment default. Community mobilization of teams to trace TB patients that missed a clinic appointment or treatment dose may be an effective strategy to mitigate default rates and improve treatment outcomes. Additional information is necessary to identify best practices and elucidate discrepancies across provinces; these findings will help guide the NTP in optimizing the adoption of tracing activities for TB control.

Impact of meteorological inflow uncertainty on tracer transport and source estimation in urban atmospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucas, Donald D.; Gowardhan, Akshay; Cameron-Smith, Philip

2015-08-08

Here, a computational Bayesian inverse technique is used to quantify the effects of meteorological inflow uncertainty on tracer transport and source estimation in a complex urban environment. We estimate a probability distribution of meteorological inflow by comparing wind observations to Monte Carlo simulations from the Aeolus model. Aeolus is a computational fluid dynamics model that simulates atmospheric and tracer flow around buildings and structures at meter-scale resolution. Uncertainty in the inflow is propagated through forward and backward Lagrangian dispersion calculations to determine the impact on tracer transport and the ability to estimate the release location of an unknown source. Ourmore » uncertainty methods are compared against measurements from an intensive observation period during the Joint Urban 2003 tracer release experiment conducted in Oklahoma City.« less

Sensitivity models and design protocol for partitioning tracer tests in alluvial aquifers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, M.; Butler, G.W.; Jackson, R.E.

1997-11-01

Zones of dense, nonaqueous phase liquids (DNAPLs) are difficult to characterize as to their volume, composition, and spatial distribution using conventional ground-water extraction and soil-sampling methods. Such incompletely characterized sites have negative consequences for those responsible for their remedial design, e.g., the uncertainties in the optimal placement of ground-water extraction wells and in the duration of remediation. However, the recent use of the partitioning interwell tracer test (PITT) to characterize DNAPL zones at sites in New Mexico [unsaturated alluvium] and in Ohio, Texas, and Utah [saturated alluvium] demonstrates that the volume and spatial distribution of residual DNAPL can be determinedmore » with accuracy. The PITT involves injection of a suite of tracers which reversibly partition to different degrees between the DNAPL and the ground water or soil air resulting in the chromatographic separation of the tracer signals observed at the extraction well(s). The design of a PITT requires careful consideration of the hydrostratigraphic, hydraulic, and certain geochemical properties of the alluvium being tested. A three-dimensional, numerical model of a heterogeneous alluvial aquifer containing DNAPL has been developed for use with the UTCHEM simulator to demonstrate partitioning tracer testing and to address questions that are frequently raised in its application. The simulations include (1) the estimation of DNAPL volume for the simple case where only residual DNAPL is present in heterogeneous alluvium, (2) sensitivity studies to demonstrate the effect of increasingly low residual DNAPL saturation on the tracer signal, and (3) the effect of free-phase DNAPL on the estimation of the volume of DNAPL present. Furthermore, the potential interference of sedimentary organic carbon as a DNAPL surrogate on the tracer signal is considered and shown to be readily resolved by the careful choice of tracers.« less

Determining the Orientation and Localization of Membrane-Bound Peptides

PubMed Central

Hohlweg, Walter; Kosol, Simone; Zangger, Klaus

2012-01-01

Many naturally occurring bioactive peptides bind to biological membranes. Studying and elucidating the mode of interaction is often an essential step to understand their molecular and biological functions. To obtain the complete orientation and immersion depth of such compounds in the membrane or a membrane-mimetic system, a number of methods are available, which are separated in this review into four main classes: solution NMR, solid-state NMR, EPR and other methods. Solution NMR methods include the Nuclear Overhauser Effect (NOE) between peptide and membrane signals, residual dipolar couplings and the use of paramagnetic probes, either within the membrane-mimetic or in the solvent. The vast array of solid state NMR methods to study membrane-bound peptide orientation and localization includes the anisotropic chemical shift, PISA wheels, dipolar waves, the GALA, MAOS and REDOR methods and again the use of paramagnetic additives on relaxation rates. Paramagnetic additives, with their effect on spectral linewidths, have also been used in EPR spectroscopy. Additionally, the orientation of a peptide within a membrane can be obtained by the anisotropic hyperfine tensor of a rigidly attached nitroxide label. Besides these magnetic resonance techniques a series of other methods to probe the orientation of peptides in membranes has been developed, consisting of fluorescence-, infrared- and oriented circular dichroism spectroscopy, colorimetry, interface-sensitive X-ray and neutron scattering and Quartz crystal microbalance. PMID:22044140

Spectral analysis of paramagnetic centers induced in human tooth enamel by x-rays and gamma radiation

NASA Astrophysics Data System (ADS)

Kirillov, V. A.; Kuchuro, I. I.

2010-03-01

Based on study of spectral and relaxation characteristics, we have established that paramagnetic centers induced in tooth enamel by x-rays and gamma radiation are identical in nature. We show that for the same exposure dose, the intensity of the electron paramagnetic resonance (EPR) signal induced by x-radiation with effective energy 34 keV is about an order of magnitude higher than the amplitude of the signal induced by gamma radiation. We have identified a three-fold attenuation of the EPR signal along the path of the x-radiation from the buccal to the lingual side of a tooth, which is evidence that the individual had undergone diagnostic x-ray examination of the dentition or skull. We have shown that the x-ray exposure doses reconstructed from the EPR spectra are an order of magnitude higher than the applied doses, while the dose loads due to gamma radiation are equal to the applied doses. The data obtained indicate that for adequate reconstruction of individual absorbed doses from EPR spectra of tooth enamel in the population subjected to the combined effect of x-radiation and accidental external gamma radiation as a result of the disaster at the Chernobyl nuclear power plant, we need to take into account the contribution to the dose load from diagnostic x-rays in examination of the teeth, jaw, or skull.

Multiple injected and natural conservative tracers quantify mixing in a stream confluence affected by acid mine drainage near Silverton, Colorado

NASA Astrophysics Data System (ADS)

Schemel, Laurence E.; Cox, Marisa H.; Runkel, Robert L.; Kimball, Briant A.

2006-08-01

The acidic discharge from Cement Creek, containing elevated concentrations of dissolved metals and sulphate, mixed with the circumneutral-pH Animas River over a several hundred metre reach (mixing zone) near Silverton, CO, during this study. Differences in concentrations of Ca, Mg, Si, Sr, and SO42- between the creek and the river were sufficiently large for these analytes to be used as natural tracers in the mixing zone. In addition, a sodium chloride (NaCl) tracer was injected into Cement Creek, which provided a Cl- reference tracer in the mixing zone. Conservative transport of the dissolved metals and sulphate through the mixing zone was verified by mass balances and by linear mixing plots relative to the injected reference tracer. At each of seven sites in the mixing zone, five samples were collected at evenly spaced increments of the observed across-channel gradients, as determined by specific conductance. This created sets of samples that adequately covered the ranges of mixtures (mixing ratios, in terms of the fraction of Animas River water, %AR). Concentratis measured in each mixing zone sample and in the upstream Animas River and Cement Creek were used to compute %AR for the reference and natural tracers. Values of %AR from natural tracers generally showed good agreement with values from the reference tracer, but variability in discharge and end-member concentrations and analytical errors contributed to unexpected outlier values for both injected and natural tracers. The median value (MV) %AR (calculated from all of the tracers) reduced scatter in the mixing plots for the dissolved metals, indicating that the MV estimate reduced the effects of various potential errors that could affect any tracer.

High-gradient permanent magnet apparatus and its use in particle collection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Mengdawn; Ludtka, Gerard Michael; Avens, Larry R.

A high-gradient permanent magnet apparatus for capturing paramagnetic particles, the apparatus comprising: (i) at least two permanent magnets positioned with like poles facing each other; (ii) a ferromagnetic spacer separating the like poles; and (iii) a magnetizable porous filling material in close proximity to the at least two permanent magnets. Also described is a method for capturing paramagnetic particles in which a gas or liquid sample containing the paramagnetic particles is contacted with the high-gradient permanent magnet apparatus described above; wherein, during the contacting step, the gas or liquid sample contacts the magnetizable porous filling material of the high-gradient permanentmore » magnet apparatus, and at least a portion of the paramagnetic particles in the gas or liquid sample is captured on the magnetizable porous filling material.« less

Electron Paramagnetic Resonance (EPR) Spectroscopy in Studies of the Protective Effects of 24-Epibrasinoide and Selenium against Zearalenone-Stimulation of the Oxidative Stress in Germinating Grains of Wheat.

PubMed

Filek, Maria; Łabanowska, Maria; Kurdziel, Magdalena; Sieprawska, Apolonia

2017-05-27

These studies concentrate on the possibility of using selenium ions and/or 24-epibrassinolide at non-toxic levels as protectors of wheat plants against zearalenone, which is a common and widespread mycotoxin. Analysis using the UHPLC-MS technique allowed for identification of grains having the stress-tolerant and stress-sensitive wheat genotype. When germinating in the presence of 30 µM of zearalenone, this mycotoxin can accumulate in both grains and hypocotyls germinating from these grains. Selenium ions (10 µM) and 24-epibrassinolide (0.1 µM) introduced together with zearalenone decreased the uptake of zearalenone from about 295 to 200 ng/g and from about 350 to 300 ng/g in the grains of tolerant and sensitive genotypes, respectively. As a consequence, this also resulted in a reduction in the uptake of zearalenone from about 100 to 80 ng/g and from about 155 to 128 ng/g in the hypocotyls from the germinated grains of tolerant and sensitive wheat, respectively. In the mechanism of protection against the zearalenone-induced oxidative stress, the antioxidative enzymes-mainly superoxide dismutase (SOD) and catalase (CAT)-were engaged, especially in the sensitive genotype. Electron paramagnetic resonance (EPR) studies allowed for a description of the chemical character of the long-lived organic radicals formed in biomolecular structures which are able to stabilize electrons released from reactive oxygen species as well as the changes in the status of transition paramagnetic metal ions. The presence of zearalenone drastically decreased the amount of paramagnetic metal ions-mainly Mn(II) and Fe(III)-bonded in the organic matrix. This effect was particularly found in the sensitive genotype, in which these species were found at a smaller level. The protective effect of selenium ions and 24-epibrassinolide originated from their ability to inhibit the destruction of biomolecules by reactive oxygen species. An increased ability to defend biomolecules against zearalenone action was observed for 24-epibrassinolide.

Bioturbation, advection, and diffusion of a conserved tracer in a laboratory flume

NASA Astrophysics Data System (ADS)

Work, P. A.; Moore, P. R.; Reible, D. D.

2002-06-01

Laboratory experiments indicating the relative influences of advection, diffusion, and bioturbation on transport of NaCl tracer between a stream and streambed are described. Data were collected in a recirculating flume housing a box filled with test sediments. Peclet numbers ranged from 0 to 1.5. Sediment components included a medium sand (d50 = 0.31 mm), kaolinite, and topsoil. Lumbriculus variegatus were introduced as bioturbators. Conductivity probes were employed to document the flux of the tracer solution out of the bed. Measurements are compared to one-dimensional effective diffusion models assuming one or two horizontal sediment layers. These simple models provide a good indication of tracer half-life in the bed if a suitable effective diffusion coefficient is chosen but underpredict initial flux and overpredict flux at long times. Organism activity was limited to the upper reaches of the sediment test box but eventually exerts a secondary influence on flux from deeper regions.

Resonance magnetoplasticity in ultralow magnetic fields

NASA Astrophysics Data System (ADS)

Alshits, V. I.; Darinskaya, E. V.; Koldaeva, M. V.; Petrzhik, E. A.

2016-09-01

Resonance relaxation displacements of dislocations in NaCl crystals placed in crossed static and alternating ultralow magnetic fields in the electron paramagnetic resonance scheme are discussed. The Earth's magnetic field B Earth ≈ 50μT and other fields in the range of 26-261 μT are used as the static field. New strongly anisotropic properties of the effect have been revealed. Frequency spectra including numerous peaks of paths at low pump frequencies beginning with 10 kHz, as well as the quartet of equidistant peaks at high frequencies ( 1.4 MHz at B= B Earth), have been measured. The effect is also observed in the pulsed pump field with a resonance duration of 0.5 μs. Resonance changes have been detected in the microhardness of ZnO, triglycine sulfate, and potassium hydrogen phthalate crystals after their exposure in the Earth's magnetic field in the same electron paramagnetic resonance scheme.

Quantum tunneling of magnetization and related phenomena in molecular materials.

PubMed

Gatteschi, Dante; Sessoli, Roberta

2003-01-20

Molecules comprising a large number of coupled paramagnetic centers are attracting much interest because they may show properties which are intermediate between those of simple paramagnets and classical bulk magnets and provide unambiguous evidence of quantum size effects in magnets. To date, two cluster families, usually referred to as Mn12 and Fe8, have been used to test theories. However, it is reasonable to predict that other classes of molecules will be discovered which have similar or superior properties. To do this it is necessary that synthetic chemists have a good understanding of the correlation between the structure and properties of the molecules, for this it is necessary that concepts such as quantum tunneling, quantum coherence, quantum oscillations are understood. The goal of this article is to review the fundamental concepts needed to understand quantum size effects in molecular magnets and to critically report what has been done in the field to date.

Fermionic spin liquid analysis of the paramagnetic state in volborthite

NASA Astrophysics Data System (ADS)

Chern, Li Ern; Schaffer, Robert; Sorn, Sopheak; Kim, Yong Baek

2017-10-01

Recently, thermal Hall effect has been observed in the paramagnetic state of volborthite, which consists of distorted kagome layers with S =1 /2 local moments. Despite the appearance of magnetic order below 1 K , the response to external magnetic field and unusual properties of the paramagnetic state above 1 K suggest possible realization of exotic quantum phases. Motivated by these discoveries, we investigate possible spin liquid phases with fermionic spinon excitations in a nonsymmorphic version of the kagome lattice, which belongs to the two-dimensional crystallographic group p 2 g g . This nonsymmorphic structure is consistent with the spin model obtained in the density functional theory calculation. Using projective symmetry group analysis and fermionic parton mean field theory, we identify twelve distinct Z2 spin liquid states, four of which are found to have correspondence in the eight Schwinger boson spin liquid states we classified earlier. We focus on the four fermionic states with bosonic counterpart and find that the spectrum of their corresponding root U (1 ) states features spinon Fermi surface. The existence of spinon Fermi surface in candidate spin liquid states may offer a possible explanation of the finite thermal Hall conductivity observed in volborthite.

Electron interactions, spin-orbit coupling, intersite correlations in pyrochlore iridates: a comparison of single-site and cluster calculations

NASA Astrophysics Data System (ADS)

Wang, Runzhi; Go, Ara; Millis, Andrew

Pyrochlore iridates (R2 Ir2O7) are studied using density functional theory plus single-site and cluster dynamical mean-field theory (DFT+DMFT). The calculations include spin-orbit coupling. Significant differences between the single-site and cluster calculations are found. The single-site approximation fails to account for the properties of the paramagnetic insulator phase, in particular predicting a larger gap than found in experiments, while cluster calculations yield gaps consistent with transport data. A ground-state phase diagram is computed. Paramagnetic metal, metallic all-in/all-out (AIAO) and insulating AIAO phases are found. Tilted Weyl cones are observed in the AIAO metallic phase for a relatively wide range of interaction strength. Our paramagnetic calculations predict almost identical behaviors for the Y and Eu compound, conflicting with the strong material dependence reported in experiments. Inclusion of magnetic order restores the material difference. The physical origin of the difference is discussed. The results indicate that intersite effects, most likely of antiferromagnetic origin, play an important role in studying the physics of pyrochlore iridates. This work is supported by DOE-ER046169.

Magnetic properties of Cu80Co20 and Cu80Co15Fe5 melt-spun ribbons

NASA Astrophysics Data System (ADS)

Rubinstein, Mark; Harris, V. G.; Das, B. N.; Koon, N. C.

1994-11-01

The magnetic properties of granular, annealed, melt-spun ribbons of the ``giant'' magnetoresistors, Cu80Co20 and Cu80Co15Fe5, have been studied by a variety of techniques. These include x-ray dfiffraction, electron microscopy, ferromagnetic resonance, SQUID magnetometry, Mössbauer-effect spectroscopy, and magnetoresistance. We utilize each of these measurements to reveal different aspects of the particle size distribution as a function of annealing temperatures. These melt-spun alloys require large magnetic fields for magnetic saturation, impairing their utility as magnetic sensors. However, the properties of melt-spun ribbons provide an understanding of why all granular magnetic materials are difficult to saturate. The magnetoresistance ratio of these alloys is maximized by a 500 °C anneal with Δρ/ρ~=14% at 4.2 K. The paramagnetic fraction determined by SQUID magnetometry at 4.2 K is 33% for this annealing temperature. The paramagnetic fraction determined by Mössbauer spectroscopy is 14% for samples annealed by 500 °C, and vanishes when the sample is annealed at 900 °C. The discrepancy between the two measurements of the paramagnetic fraction is due to the vastly different averaging times of the two techniques.

Characterisation of β-tricalcium phosphate-based bone substitute materials by electron paramagnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Matković, Ivo; Maltar-Strmečki, Nadica; Babić-Ivančić, Vesna; Dutour Sikirić, Maja; Noethig-Laslo, Vesna

2012-10-01

β-TCP based materials are frequently used as dental implants. Due to their resorption in the body and direct contact with tissues, in order to inactivate bacteria, fungal spores and viruses, they are usually sterilized by γ-irradiation. However, the current literature provides little information about effects of the γ-irradiation on the formation and stability of the free radicals in the bone graft materials during and after sterilization procedure. In this work five different bone graft substitution materials, composed of synthetic beta tricalcium phosphate (β-TCP) and hydroxyapatite (HAP) present in the market were characterized by electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Paramagnetic species Mn2+, Fe3+, trapped H-atoms and CO2- radicals were detected in the biphasic material (60% HAP, 40% β-TCP), while in β-TCP materials only Mn2+ andor trapped hydrogen atoms were detected. EPR analysis revealed the details of the structure of these materials at the atomic level. The results have shown that EPR spectroscopy is a method which can be used to improve the quality control of bone graft materials after syntering, processing and sterilization procedure.

Magnetocaloric effect and magnetic properties in SmFe1-xMnxO3 perovskite: Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Erchidi Elyacoubi, A. S.; Masrour, R.; Jabar, A.

2018-03-01

We have used Monte Carlo simulation to study the magnetocaloric effect on SmFe1-xMnxO3 perovskite. The temperature-dependent magnetization shows that the Néel temperature of the weak-ferromagnetic SmFeO3 decreases as Fe ions are substituted by Mn ions. A paramagnetic-to-weak-antiferromagnetic transition with decreasing the temperature is observed and the corresponding Néel temperature essentially decreases as the Mn content increases. The magnetocaloric effect shows two peaks related to magnetic behavior changes, at paramagnetic-like behavior TK(K) and at Néel temperature TN(K) of SmFe1-xMnxO3. The second phase transition is established. The magnetic entropy change is given for a several magnetic fields. We have also determined the relative cooling power for dilution x = 0.5 and for a several external magnetic fields. Finally, the magnetic hysteresis cycles have been obtained with different dilutions x and temperatures values.

Lethal effect of uv and $gamma$ irradiation on some species of Dematiaceae (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhdanova, N.N.; Gavryushina, A.I.; Bondar, A.I.

1972-01-01

A comparative study was conducted of relation of four species of Dematiaceae and a mutant with lowered content of melanine to gamma and uv rays. Under uv irradiation, survival iate of all studied species was characterized by a complex exponential curve with a large, sharply pronounced resistant area. An assumption is advanced that a sharp fall of survival rate during the first minutes of uv irradiation is conditioned by specificity of the protective effect of melanine pigment tint needs time for transition into the active state. Species resistant to gamma irradiation had sygmoid curves of survival rate and sensitive speciesmore » had the exponential ones. Increased resistance to gamma rays was accompanied by an increase in concentration of paramagnetic-particles that were determined by the method of electronic paramagnetic resonance. Analysis of the data obtained makes it possible to suppose that the protective effect of fungal melanine is various under gamma and uv irradiation. (auth)« less

Large magnetoresistance and Hall effect in paramagnetic black phosphorus synthesized from red phosphorus

NASA Astrophysics Data System (ADS)

Jiang, X. H.; Xiong, F.; Zhang, X. W.; Hua, Z. H.; Wang, Z. H.; Yang, S. G.

2018-05-01

Black phosphorus (BP) is an important material, which can be used in the fabrication of phosphorene. In this manuscript, a systematic study was described on the high-pressure synthesis of BP from red phosphorus. For physical characterization, the bulk BP was synthesized under the high pressure of 1.6 GPa and high temperature of 700 °C for 2 h. X-ray diffraction and Raman studies illustrated the formation of high-quality pure phase pleomorphic BP. A nonlinear Hall effect was observed in the BP sample. Magnetoresistance (MR) in the bulk BP reached 90% at 40 K, and positive-to-negative crossover in MR was measured. A paramagnetic feature was found in the prepared bulk BP, and the MR results were attributed to the combination of the effect of classical resistor network and magnetic polaron. The conduction tensors were analyzed by a two-band model to determine the carrier concentration and mobility at several temperatures.

TRANSFORMER APPARATUS

DOEpatents

Wolfgang, F.; Nicol, J.

1962-11-01

Transformer apparatus is designed for measuring the amount of a paramagnetic substance dissolved or suspended in a diamagnetic liquid. The apparatus consists of a cluster of tubes, some of which are closed and have sealed within the diamagnetic substance without any of the paramagnetic material. The remaining tubes are open to flow of the mix- ture. Primary and secondary conductors are wrapped around the tubes in such a way as to cancel noise components and also to produce a differential signal on the secondaries based upon variations of the content of the paramagnetic material. (AEC)

Measurement of electron paramagnetic resonance using terahertz time-domain spectroscopy.

PubMed

Kozuki, Kohei; Nagashima, Takeshi; Hangyo, Masanori

2011-12-05

We present a frequency-domain electron spin resonance (ESR) measurement system using terahertz time-domain spectroscopy. A crossed polarizer technique is utilized to increase the sensitivity in detecting weak ESR signals of paramagnets caused by magnetic dipole transitions between magnetic sublevels. We demonstrate the measurements of ESR signal of paramagnetic copper(II) sulfate pentahydrate with uniaxial anisotropy of the g-factor under magnetic fields up to 10 T. The lineshape of the obtained ESR signals agrees well with the theoretical predictions for a powder sample with the uniaxial anisotropy.

The project MOHAVE tracer study: study design, data quality, and overview of results

NASA Astrophysics Data System (ADS)

Green, Mark C.

In the winter and summer of 1992, atmospheric tracer studies were conducted in support of project MOHAVE, a visibility study in the southwestern United States. The primary goal of project MOHAVE is to determine the effects of the Mohave power plant and other sources upon visibility at Grand Canyon National Park. Perfluorocarbon tracers (PFTs) were released from the Mohave power plant and other locations and monitored at about 30 sites. The tracer data are being used for source attribution analysis and for evaluation of transport and dispersion models and receptor models. Collocated measurements showed the tracer data to be of high quality and suitable for source attribution analysis and model evaluation. The results showed strong influences of channeling by the Colorado River canyon during both winter and summer. Flow from the Mohave power plant was usually to the south, away from the Grand Canyon in winter and to the northeast, toward the Grand Canyon in summer. Tracer released at Lake Powell in winter was found to often travel downstream through the entire length of the Grand Canyon. Data from summer tracer releases in southern California demonstrated the existence of a convergence zone in the western Mohave Desert.

A Lagrangian View of Stratospheric Trace Gas Distributions

NASA Technical Reports Server (NTRS)

Schoeberl, M. R.; Sparling, L.; Dessler, A.; Jackman, C. H.; Fleming, E. L.

1998-01-01

As a result of photochemistry, some relationship between the stratospheric age-of-air and the amount of tracer contained within an air sample is expected. The existence of such a relationship allows inferences about transport history to be made from observations of chemical tracers. This paper lays down the conceptual foundations for the relationship between age and tracer amount, developed within a Lagrangian framework. In general, the photochemical loss depends not only on the age of the parcel but also on its path. We show that under the "average path approximation" that the path variations are less important than parcel age. The average path approximation then allows us to develop a formal relationship between the age spectrum and the tracer spectrum. Using the relation between the tracer and age spectra, tracer-tracer correlations can be interpreted as resulting from mixing which connects parts of the single path photochemistry curve, which is formed purely from the action of photochemistry on an irreducible parcel. This geometric interpretation of mixing gives rise to constraints on trace gas correlations, and explains why some observations are do not fall on rapid mixing curves. This effect is seen in the ATMOS observations.

Use of hydrochemistry as a standalone and complementary groundwater age tracer

NASA Astrophysics Data System (ADS)

Beyer, Monique; Jackson, Bethanna; Daughney, Chris; Morgenstern, Uwe; Norton, Kevin

2016-12-01

Groundwater age or residence time is the time water has resided in the subsurface since recharge. This can provide information on groundwater mixing and flow, and volumes of groundwater and recharge, etc. Groundwater age can be inferred from environmental tracers, such as SF6 and tritium that have a known input to groundwater and/or undergo known alteration processes in groundwater. Multiple tracers are often applied complementarily in order to increase the robustness of age interpretations. To this end, it is desirable to develop cost-effective and easily applicable age tracers/techniques to supplement the existing ones. A number of hydrochemical parameters are spatially and temporally widely available due to national and regional groundwater monitoring programmes. Their determination is cost-effective and relatively simple compared to existing age tracers. Hydrochemistry has been used as an age proxy but its use as an independent age tracer has only been demonstrated for water recharged weeks to months ago (relying on seasonal changes). This study focuses on the Lower Hutt Groundwater Zone, New Zealand, and assesses whether hydrochemistry can be used as an independent indicator of groundwater age, or if not, whether hydrochemistry can be used to complement groundwater age measurements based on other tracers. This study also examines the use of hydrochemistry as an indicator for recharge sources and weathering processes. This study shows that, when used independently, hydrochemistry could only be used as an age proxy, but in combination with tritium measurements, hydrochemistry provided useful additional constraint on age of groundwater recharged days to ∼100 years ago.

Measurement of variation in soil solute tracer concentration across a range of effective pore sizes

USGS Publications Warehouse

Harvey, Judson W.

1993-01-01

Solute transport concepts in soil are based on speculation that solutes are distributed nonuniformly within large and small pores. Solute concentrations have not previously been measured across a range of pore sizes and examined in relation to soil hydrological properties. For this study, modified pressure cells were used to measure variation in concentration of a solute tracer across a range of pore sizes. Intact cores were removed from the site of a field tracer experiment, and soil water was eluted from 10 or more discrete classes of pore size. Simultaneous changes in water content and unsaturated hydraulic conductivity were determined on cores using standard pressure cell techniques. Bromide tracer concentration varied by as much as 100% across the range of pore sizes sampled. Immediately following application of the bromide tracer on field plots, bromide was most concentrated in the largest pores; concentrations were lower in pores of progressively smaller sizes. After 27 days, bromide was most dilute in the largest pores and concentrations were higher in the smaller pores. A sharp, threefold decrease in specific water capacity during elution indicated separation of two major pore size classes at a pressure of 47 cm H2O and a corresponding effective pore diameter of 70 μm. Variation in tracer concentration, on the other hand, was spread across the entire range of pore sizes investigated in this study. A two-porosity characterization of the transport domain, based on water retention criteria, only broadly characterized the pattern of variation in tracer concentration across pore size classes during transport through a macroporous soil.

Growth Kinetics of the S Sub H Center on Magnesium Oxide Using Electron Paramagnetic Resonance

NASA Technical Reports Server (NTRS)

Jayne, J. P.

1971-01-01

Electron paramagnetic resonance spectroscopy was used to study the growth of S sub H centers on magnesium oxide powder which had hydrogen adsorbed on its surface. The centers were produced by ultraviolet radiation. The effects of both radiation intensity and hydrogen pressure were also studied. At constant hydrogen pressure and radiation dose, the initial S sub H center growth rate was found to be zero order. Beyond the initial region the growth rate deviated from zero order and finally approached saturation. The results are interpreted in terms of a model which assumes that the S sub H center is a hydrogen atom associated with a surface vacancy. Saturation appears to result from a limited supply of surface vacancies.

Negative electric susceptibility and magnetism from translational invariance and rotational invariance

NASA Astrophysics Data System (ADS)

Koo, Je Huan

2015-02-01

In this work we investigate magnetic effects in terms of the translational and rotational invariances of magnetisation. Whilst Landau-type diamagnetism originates from translational invariance, a new diamagnetism could result from rotational invariance. Translational invariance results in only conventional Landau-type diamagnetism, whereas rotational invariance can induce a paramagnetic susceptibility for localised electrons and also a new kind of diamagnetism that is specific to conducting electrons. In solids, the moving electron shows a paramagnetic susceptibility but the surrounding screening of electrons may produce a new diamagnetic response by Lenz's law, resulting in a total susceptibility that tends to zero. For electricity, similar behaviours are obtained. We also derive the DC-type negative electric susceptibility via two methods in analogy with Landau diamagnetism.

Dual-porosity analysis of conservative tracer testing in saturated volcanic rocks at Yucca Mountain in Nye County, Nevada

USGS Publications Warehouse

Fahy, M.F.

1997-01-01

A radially convergent conservative tracer injection test was conducted between boreholes UE-25 #2 and UE-25 c #3 of the C-hole complex at Yucca Mountain to determine effective porosity and longitudinal dispersivity. Approximately 47% of the tracer mass was recovered and a dual-porosity analytical model replicates the breakthrough curve. Fractured-rock analyses focus on the fracture-porosity and geometry as the controlling factors in transport.

Single well surfactant test to evaluate surfactant floods using multi tracer method

DOEpatents

Sheely, Clyde Q.

1979-01-01

Data useful for evaluating the effectiveness of or designing an enhanced recovery process said process involving mobilizing and moving hydrocarbons through a hydrocarbon bearing subterranean formation from an injection well to a production well by injecting a mobilizing fluid into the injection well, comprising (a) determining hydrocarbon saturation in a volume in the formation near a well bore penetrating formation, (b) injecting sufficient mobilizing fluid to mobilize and move hydrocarbons from a volume in the formation near the well bore, and (c) determining the hydrocarbon saturation in a volume including at least a part of the volume of (b) by an improved single well surfactant method comprising injecting 2 or more slugs of water containing the primary tracer separated by water slugs containing no primary tracer. Alternatively, the plurality of ester tracers can be injected in a single slug said tracers penetrating varying distances into the formation wherein the esters have different partition coefficients and essentially equal reaction times. The single well tracer method employed is disclosed in U.S. Pat. No. 3,623,842. This method designated the single well surfactant test (SWST) is useful for evaluating the effect of surfactant floods, polymer floods, carbon dioxide floods, micellar floods, caustic floods and the like in subterranean formations in much less time and at much reduced cost compared to conventional multiwell pilot tests.

Investigating the Distribution of Stable Paramagnetic Species in an Apple Seed Using X-Band EPR and EPR Imaging.

PubMed

Nakagawa, Kouichi; Epel, Boris

2017-03-01

This study investigated the location and distribution of paramagnetic species in apple seeds using electron paramagnetic resonance (EPR) and X-band (9 GHz) EPR imaging (EPRI). EPR primarily detected two paramagnetic species per measured seed. These two different radical species were assigned as stable radicals and Mn 2+ species based on the g values and hyperfine components. The signal from the stable radical was noted at g ≈ 2.00 and was strong and relatively stable. The subsequent noninvasive EPRI of the radical present in each seed revealed that the stable radicals were located primarily in the seed coat, with very few radicals observed in the cotyledon of the seed. These results indicate that the stable radical species were only found within the seed coat, and few radical species were found in other seed parts.

Paramagnetic resonance and susceptibility of ilmenite, FeTiO3 crystal

NASA Technical Reports Server (NTRS)

Mcdonald, P. F.; Parasiris, A.; Pandey, R. K.; Gries, B. L.; Kirk, W. P.

1991-01-01

Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and X-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Neel temperature of about 59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

[Detection of the lethal process in plankton noctiluca by means of a forbidden transition of ESR of Mn2+ ion].

PubMed

Kamenev, S E; Kopvillem, U Kh; Pasynkov, A S; Sharipov, R Z

1981-01-01

A forbidden ESR line of Mn2+ that is connected with the penetration of Mn into the plancton organism and binding it to a marcomolecule is selected from the experiment. A method for saturating the plancton organism with paramagnetic ions is proposed. It is shown that the constant of the axial electric field in the spin hamiltonian of Mn2+ ion described the dynamics of a selforganizing system. It is tested that the lethal process in the plancton with paramagnetic ion enrichment originated from boson avalanche. Experiments are performed with plancton noctiluca which illustrate the occurrence of avalancheline lethal process in the case of paramagnetic ion enrichment with limiting concentration. The meaning of these results for the problems of oceanology and pollution-ocean inhabitants interaction in the case of paramagnetic ions is discussed.

Impact of community tracer teams on treatment outcomes among tuberculosis patients in South Africa

PubMed Central

2012-01-01

Background Tuberculosis (TB) indicators in South Africa currently remain well below global targets. In 2008, the National Tuberculosis Program (NTP) implemented a community mobilization program in all nine provinces to trace TB patients that had missed a treatment or clinic visit. Implementation sites were selected by TB program managers and teams liaised with health facilities to identify patients for tracing activities. The objective of this analysis was to assess the impact of the TB Tracer Project on treatment outcomes among TB patients. Methods The study population included all smear positive TB patients registered in the Electronic TB Registry from Quarter 1 2007-Quarter 1 2009 in South Africa. Subdistricts were used as the unit of analysis, with each designated as either tracer (standard TB program plus tracer project) or non-tracer (standard TB program only). Mixed linear regression models were utilized to calculate the percent quarterly change in treatment outcomes and to compare changes in treatment outcomes from Quarter 1 2007 to Quarter 1 2009 between tracer and non-tracer subdistricts. Results For all provinces combined, the percent quarterly change decreased significantly for default treatment outcomes among tracer subdistricts (−0.031%; p < 0.001) and increased significantly for successful treatment outcomes among tracer subdistricts (0.003%; p = 0.03). A significant decrease in the proportion of patient default was observed for all provinces combined over the time period comparing tracer and non-tracer subdistricts (p = 0.02). Examination in stratified models revealed the results were not consistent across all provinces; significant differences were observed between tracer and non-tracer subdistricts over time in five of nine provinces for treatment default. Conclusions Community mobilization of teams to trace TB patients that missed a clinic appointment or treatment dose may be an effective strategy to mitigate default rates and improve treatment outcomes. Additional information is necessary to identify best practices and elucidate discrepancies across provinces; these findings will help guide the NTP in optimizing the adoption of tracing activities for TB control. PMID:22871071

Effects of soft interactions and bound mobility on diffusion in crowded environments: a model of sticky and slippery obstacles

NASA Astrophysics Data System (ADS)

Stefferson, Michael W.; Norris, Samantha L.; Vernerey, Franck J.; Betterton, Meredith D.; E Hough, Loren

2017-08-01

Crowded environments modify the diffusion of macromolecules, generally slowing their movement and inducing transient anomalous subdiffusion. The presence of obstacles also modifies the kinetics and equilibrium behavior of tracers. While previous theoretical studies of particle diffusion have typically assumed either impenetrable obstacles or binding interactions that immobilize the particle, in many cellular contexts bound particles remain mobile. Examples include membrane proteins or lipids with some entry and diffusion within lipid domains and proteins that can enter into membraneless organelles or compartments such as the nucleolus. Using a lattice model, we studied the diffusive movement of tracer particles which bind to soft obstacles, allowing tracers and obstacles to occupy the same lattice site. For sticky obstacles, bound tracer particles are immobile, while for slippery obstacles, bound tracers can hop without penalty to adjacent obstacles. In both models, binding significantly alters tracer motion. The type and degree of motion while bound is a key determinant of the tracer mobility: slippery obstacles can allow nearly unhindered diffusion, even at high obstacle filling fraction. To mimic compartmentalization in a cell, we examined how obstacle size and a range of bound diffusion coefficients affect tracer dynamics. The behavior of the model is similar in two and three spatial dimensions. Our work has implications for protein movement and interactions within cells.

Quantifying the distribution of tracer discharge from boreal catchments under transient flow using the kinematic pathway approach

NASA Astrophysics Data System (ADS)

Soltani, S. S.; Cvetkovic, V.

2017-07-01

This focuses on solute discharge from boreal catchments with relatively shallow groundwater table and topography-driven groundwater flow. We explore whether a simplified semianalytical approach can be used for predictive modeling of the statistical distribution of tracer discharge. The approach is referred to as the "kinematic pathways approach" (KPA). This approach uses hydrological and tracer inputs and topographical and hydrogeological information; the latter regards average aquifer depth to the less permeable bedrock. A characteristic velocity of water flow through the catchment is further obtained from the overall water balance in the catchment. For the waterborne tracer transport through the catchment, morphological dispersion is accounted for by topographical analysis of the distribution of pathway lengths to the catchment outlet. Macrodispersion is accounted for heuristically by assuming an effective Péclet number. Distribution of water travel times through the catchment reflect the dispersion on both levels and are derived in both a forward mode (transit time from input to outlet) and a backward mode (water age when arriving at outlet arrival). The forward distribution of water travel times is further used for the tracer discharge modeling by convolution. The approach is applied to modeling of a 23 year long chloride data series for a specific catchment Kringlan (Sweden), and for generic modeling to better understand the dependence of the tracer discharge distribution on different dispersion aspects. The KPA is found to provide reasonable estimates of tracer discharge distribution, and particularly of extreme values, depending on method for determining the pathway length distribution. As a possible alternative analytical model of tracer transport through a catchment, the reservoir approach generally results in large tracer dispersion. This implies that tracer discharge distributions obtained from a mixed reservoir approach and from KPA are only compatible under large dispersion conditions.

Three-Dimensional Bayesian Geostatistical Aquifer Characterization at the Hanford 300 Area using Tracer Test Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xingyuan; Murakami, Haruko; Hahn, Melanie S.

2012-06-01

Tracer testing under natural or forced gradient flow holds the potential to provide useful information for characterizing subsurface properties, through monitoring, modeling and interpretation of the tracer plume migration in an aquifer. Non-reactive tracer experiments were conducted at the Hanford 300 Area, along with constant-rate injection tests and electromagnetic borehole flowmeter (EBF) profiling. A Bayesian data assimilation technique, the method of anchored distributions (MAD) [Rubin et al., 2010], was applied to assimilate the experimental tracer test data with the other types of data and to infer the three-dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of themore » Hanford formation. In this study, the Bayesian prior information on the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using the constant-rate injection tests and the EBF data. The posterior distribution of the conductivity field was obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells. MAD was implemented with the massively-parallel three-dimensional flow and transport code PFLOTRAN to cope with the highly transient flow boundary conditions at the site and to meet the computational demands of MAD. A synthetic study proved that the proposed method could effectively invert tracer test data to capture the essential spatial heterogeneity of the three-dimensional hydraulic conductivity field. Application of MAD to actual field data shows that the hydrogeological model, when conditioned on the tracer test data, can reproduce the tracer transport behavior better than the field characterized without the tracer test data. This study successfully demonstrates that MAD can sequentially assimilate multi-scale multi-type field data through a consistent Bayesian framework.« less

Toxicological and ecotoxicological assessment of water tracers

NASA Astrophysics Data System (ADS)

Behrens, H.; Beims, U.; Dieter, H.; Dietze, G.; Eikmann, T.; Grummt, T.; Hanisch, H.; Henseling, H.; Käß, W.; Kerndorff, H.; Leibundgut, C.; Müller-Wegener, U.; Rönnefahrt, I.; Scharenberg, B.; Schleyer, R.; Schloz, W.; Tilkes, F.

2001-06-01

Uncertainties regarding possible negative effects on the environment or on human health of authorizing tracing experiments in groundwater and surface waters led to the establishment of a Working Group at the German Federal Environmental Agency (Umweltbundesamt - UBA) for conducting a toxicological and ecotoxicological assessment. A total of 17 water tracers was assessed by the Working Group on the basis of the results of toxicological tests, the available literature, and the group's expert knowledge. In the future, tracers that pose a risk to the environment or to human health should no longer be used. Nevertheless, there are a number of tracers that could be used in hydrogeological and hydrological investigations for water-pollution-control purposes with no adverse environmental impact.

Tracer-monitored flow titrations.

PubMed

Sasaki, Milton K; Rocha, Diogo L; Rocha, Fábio R P; Zagatto, Elias A G

2016-01-01

The feasibility of implementing tracer-monitored titrations in a flow system is demonstrated. A dye tracer is used to estimate the instant sample and titrant volumetric fractions without the need for volume, mass or peak width measurements. The approach was applied to spectrophotometric flow titrations involving variations of sample and titrant flow-rates (i.e. triangle programmed technique) or concentration gradients established along the sample zone (i.e. flow injection system). Both strategies required simultaneous monitoring of two absorbing species, namely the titration indicator and the dye tracer. Mixing conditions were improved by placing a chamber with mechanical stirring in the analytical path aiming at to minimize diffusional effects. Unlike most of flow-based titrations, the innovation is considered as a true titration, as it does not require a calibration curve thus complying with IUPAC definition. As an application, acidity evaluation in vinegars involving titration with sodium hydroxide was selected. Phenolphthalein and brilliant blue FCF were used as indicator and dye tracer, respectively. Effects of sample volume, titrand/titrant concentrations and flow rates were investigated aiming at improved accuracy and precision. Results were reliable and in agreement with those obtained by a reference titration procedure. Copyright © 2015 Elsevier B.V. All rights reserved.

Design of a perfluorocarbon tracer based monitoring network to support monitoring verification and accounting of sequestered CO2

NASA Astrophysics Data System (ADS)

Watson, T.; Sullivan, T.

2013-05-01

The levels of CO2 in the atmosphere have been growing since the beginning of the industrial revolution. The current level is 391 ppm. If there are no efforts to mitigate CO2 emissions, the levels will rise to 750 ppm by 2100. Geologic carbon sequestration is one strategy that may be used to begin to reduce emissions. Sequestration will not be effective unless reservoir leak rates are significantly less than 1%. There must be rigorous monitoring protocols in place to ensure sequestration projects meet regulatory and environmental goals. Monitoring for CO2 leakage directly is difficult because of the large background levels and variability of CO2 in the atmosphere. Using tracers to tag the sequestered CO2 can mitigate some of the difficulties of direct measurement but a tracer monitoring network and the levels of tagging need to be carefully designed. Simple diffusion and dispersion models are used to predict the surface and atmospheric concentrations that would be seen by a network monitoring a sequestration site. Levels of tracer necessary to detect leaks from 0.01 to 1% are presented and suggestions for effective monitoring and protection of global tracer utility are presented.

Measuring air-water interfacial area for soils using the mass balance surfactant-tracer method.

PubMed

Araujo, Juliana B; Mainhagu, Jon; Brusseau, Mark L

2015-09-01

There are several methods for conducting interfacial partitioning tracer tests to measure air-water interfacial area in porous media. One such approach is the mass balance surfactant tracer method. An advantage of the mass-balance method compared to other tracer-based methods is that a single test can produce multiple interfacial area measurements over a wide range of water saturations. The mass-balance method has been used to date only for glass beads or treated quartz sand. The purpose of this research is to investigate the effectiveness and implementability of the mass-balance method for application to more complex porous media. The results indicate that interfacial areas measured with the mass-balance method are consistent with values obtained with the miscible-displacement method. This includes results for a soil, for which solid-phase adsorption was a significant component of total tracer retention. Copyright © 2015 Elsevier Ltd. All rights reserved.

Getting Things Sorted With Lagrangian Coherent Structures

NASA Astrophysics Data System (ADS)

Atis, Severine; Peacock, Thomas; Environmental Dynamics Laboratory Team

2014-11-01

The dispersion of a tracer in a fluid flow is influenced by the Lagrangian motion of fluid elements. Even in laminar regimes, the irregular chaotic behavior of a fluid flow can lead to effective stirring that rapidly redistributes a tracer throughout the domain. For flows with arbitrary time-dependence, the modern approach of Lagrangian Coherent Structures (LCSs) provide a method for identifying the key material lines that organize flow transport. When the advected tracer particles possess a finite size and nontrivial shape, however, their dynamics can differ markedly from passive tracers, thus affecting the dispersion phenomena. We present details of numerical simulations and laboratory experiments that investigate the behavior of finite size particles in 2-dimensional chaotic flows. We show that the shape and the size of the particles alter the underlying LCSs, facilitating segregation between tracers of different shape in the same flow field.

Traveltime and reaeration characteristics for a reach of the Rio Grande, Albuquerque, New Mexico, October 1991

USGS Publications Warehouse

Waltemeyer, S.D.

1994-01-01

Traveltime characteristics were determined using stream-velocity data and tracer-dye data for a reach of the Rio Grande. Traveltimes determined by the stream-velocity method were virtually the same as those determined by the tracer-dye and tracer-gas technique. The mean velocity of the stream was 1.12 miles per hour at a flow of about 300 cubic feet per second. Reaeration characteristics were determined using a propane tracer gas and a tracer-dye (rhodamine WT). Reaeration coefficients were adjusted for water temperature and the effects of wind movement on the water surface. The peak method-adjusted reaeration-coefficient mean value for the reach was 7.0 per day and ranged from 4.6 to 8.3 per day. The area method-adjusted reaeration- coefficient mean value for the reach was 7.7 per day and ranged from 5.5 to 10.4 per day.

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocker, J.; Cornu, D.; Kieseritzky, E.

2014-08-01

A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of themore » resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic species with a density of approximately 5 × 10{sup 11} spins/cm{sup 2}, which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology.« less

Modified Perfluorocarbon Tracer Method for Measuring Effective Multizone Air Exchange Rates

PubMed Central

Shinohara, Naohide; Kataoka, Toshiyuki; Takamine, Koichi; Butsugan, Michio; Nishijima, Hirokazu; Gamo, Masashi

2010-01-01

A modified procedure was developed for the measurement of the effective air exchange rate, which represents the relationship between the pollutants emitted from indoor sources and the residents’ level of exposure, by placing the dosers of tracer gas at locations that resemble indoor emission sources. To measure the 24-h-average effective air exchange rates in future surveys based on this procedure, a low-cost, easy-to-use perfluorocarbon tracer (PFT) doser with a stable dosing rate was developed by using double glass vials, a needle, a polyethylene-sintered filter, and a diffusion tube. Carbon molecular sieve cartridges and carbon disulfide (CS2) were used for passive sampling and extraction of the tracer gas, respectively. Recovery efficiencies, sampling rates, and lower detection limits for 24-h sampling of hexafluorobenzene, octafluorotoluene, and perfluoroallylbenzene were 40% ± 3%, 72% ± 5%, and 84% ± 6%; 10.5 ± 1.1, 14.4 ± 1.4, and 12.2 ± 0.49 mL min−1; and 0.20, 0.17, and 0.26 μg m−3, respectively. PMID:20948928

Modified perfluorocarbon tracer method for measuring effective multizone air exchange rates.

PubMed

Shinohara, Naohide; Kataoka, Toshiyuki; Takamine, Koichi; Butsugan, Michio; Nishijima, Hirokazu; Gamo, Masashi

2010-09-01

A modified procedure was developed for the measurement of the effective air exchange rate, which represents the relationship between the pollutants emitted from indoor sources and the residents' level of exposure, by placing the dosers of tracer gas at locations that resemble indoor emission sources. To measure the 24-h-average effective air exchange rates in future surveys based on this procedure, a low-cost, easy-to-use perfluorocarbon tracer (PFT) doser with a stable dosing rate was developed by using double glass vials, a needle, a polyethylene-sintered filter, and a diffusion tube. Carbon molecular sieve cartridges and carbon disulfide (CS₂) were used for passive sampling and extraction of the tracer gas, respectively. Recovery efficiencies, sampling rates, and lower detection limits for 24-h sampling of hexafluorobenzene, octafluorotoluene, and perfluoroallylbenzene were 40% ± 3%, 72% ± 5%, and 84% ± 6%; 10.5 ± 1.1, 14.4 ± 1.4, and 12.2 ± 0.49 mL min⁻¹; and 0.20, 0.17, and 0.26 μg m⁻³, respectively.

Pre-clinical and Clinical Evaluation of High Resolution, Mobile Gamma Camera and Positron Imaging Devices

DTIC Science & Technology

2009-10-01

Field-of-View, Mobile PET/SPECT System for Bedside Environments: A Dynamic Cardiac Phantom Study using 99mTc and 18F- FDG . Presented at the American...using Tc-99m tracers and viability imaging using F- 18 tracers [3]-[7]. For cardiac F-18 imaging in a bedside environment, the 511 keV SPECT approach...SPECT system may have difficulty imaging subtle myocardial defects with F-18 tracers , but it may effectively image moderate to severe defects. The

Magnetocaloric effect in Heusler alloys Ni50Mn34In16 and Ni50Mn34Sn16

NASA Astrophysics Data System (ADS)

Sharma, V. K.; Chattopadhyay, M. K.; Kumar, Ravi; Ganguli, Tapas; Tiwari, Pragya; Roy, S. B.

2007-12-01

We present results of detailed ac susceptibility, magnetization and specific heat measurements in Heusler alloys Ni50Mn34In16 and Ni50Mn34Sn16. These alloys undergo a paramagnetic to ferromagnetic transition around 305 K, which is followed by a martensitic transition in the temperature regime around 220 K. Inside the martensite phase both the alloys show signatures of field-induced transition from martensite to austenite phase. Both field- and temperature-induced martensite-austenite transitions are relatively sharp in Ni50Mn34In16. We estimate the isothermal magnetic entropy change and adiabatic temperature change across the various phase transitions in these alloys and investigate the possible influence of these transitions on the estimated magnetocaloric effect. The sharp martensitic transition in Ni50Mn34In16 gives rise to a comparatively large inverse magnetocaloric effect across this transition. On the other hand the magnitudes of the conventional magnetocaloric effect associated with the paramagnetic to ferromagnetic transition are quite comparable in these alloys.

The effect of entrapped nonaqueous phase liquids on tracer transport in heterogeneous porous media: Laboratory experiments at the intermediate scale

USGS Publications Warehouse

Barth, Gilbert R.; Illangasekare, T.H.; Rajaram, H.

2003-01-01

This work considers the applicability of conservative tracers for detecting high-saturation nonaqueous-phase liquid (NAPL) entrapment in heterogeneous systems. For this purpose, a series of experiments and simulations was performed using a two-dimensional heterogeneous system (10??1.2 m), which represents an intermediate scale between laboratory and field scales. Tracer tests performed prior to injecting the NAPL provide the baseline response of the heterogeneous porous medium. Two NAPL spill experiments were performed and the entrapped-NAPL saturation distribution measured in detail using a gamma-ray attenuation system. Tracer tests following each of the NAPL spills produced breakthrough curves (BTCs) reflecting the impact of entrapped NAPL on conservative transport. To evaluate significance, the impact of NAPL entrapment on the conservative-tracer breakthrough curves was compared to simulated breakthrough curve variability for different realizations of the heterogeneous distribution. Analysis of the results reveals that the NAPL entrapment has a significant impact on the temporal moments of conservative-tracer breakthrough curves. ?? 2003 Elsevier B.V. All rights reserved.

Accuracy of travel time distribution (TTD) models as affected by TTD complexity, observation errors, and model and tracer selection

USGS Publications Warehouse

Green, Christopher T.; Zhang, Yong; Jurgens, Bryant C.; Starn, J. Jeffrey; Landon, Matthew K.

2014-01-01

Analytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic datasets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for one public-supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer (NO3−) concentrations. Analytical models included a new, scale-dependent dispersivity model (SDM) for two-dimensional transport from the watertable to a well, and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for NO3− and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.

Subcellular storage and release mode of the novel 18F-labeled sympathetic nerve PET tracer LMI1195.

PubMed

Chen, Xinyu; Werner, Rudolf A; Lapa, Constantin; Nose, Naoko; Hirano, Mitsuru; Javadi, Mehrbod S; Robinson, Simon; Higuchi, Takahiro

2018-02-06

18 F-N-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine ( 18 F-LMI1195) is a new class of PET tracer designed for sympathetic nervous imaging of the heart. The favorable image quality with high and specific neural uptake has been previously demonstrated in animals and humans, but intracellular behavior is not yet fully understood. The aim of the present study is to verify whether it is taken up in storage vesicles and released in company with vesicle turnover. Both vesicle-rich (PC12) and vesicle-poor (SK-N-SH) norepinephrine-expressing cell lines were used for in vitro tracer uptake studies. After 2 h of 18 F-LMI1195 preloading into both cell lines, effects of stimulants for storage vesicle turnover (high concentration KCl (100 mM) or reserpine treatment) were measured at 10, 20, and 30 min. 131 I-meta-iodobenzylguanidine ( 131 I-MIBG) served as a reference. Both high concentration KCl and reserpine enhanced 18 F-LMI1195 washout from PC12 cells, while tracer retention remained stable in the SK-N-SH cells. After 30 min of treatment, 18 F-LMI1195 releasing index (percentage of tracer released from cells) from vesicle-rich PC12 cells achieved significant differences compared to cells without treatment condition. In contrast, such effect could not be observed using vesicle-poor SK-N-SH cell lines. Similar tracer kinetics after KCl or reserpine treatment were also observed using 131 I-MIBG. In case of KCl exposure, Ca 2 +-free buffer with the calcium chelator, ethylenediaminetetracetic acid (EDTA), could suppress the tracer washout from PC12 cells. This finding is consistent with the tracer release being mediated by Ca 2 + influx resulting from membrane depolarization. Analogous to 131 I-MIBG, the current in vitro tracer uptake study confirmed that 18 F-LMI1195 is also stored in vesicles in PC12 cells and released along with vesicle turnover. Understanding the basic kinetics of 18 F-LMI1195 at a subcellular level is important for the design of clinical imaging protocols and imaging interpretation.

Characterization of an alluvial aquifer with thermal tracer tomography

NASA Astrophysics Data System (ADS)

Somogyvári, Márk; Bayer, Peter

2017-04-01

In the summer of 2015, a series of thermal tracer tests was performed at the Widen field site in northeast Switzerland. At this site numerous hydraulic, tracer, geophysical and hydrogeophysical field tests have been conducted in the past to investigate a shallow alluvial aquifer. The goals of the campaign in 2015 were to design a cost-effective thermal tracer tomography setup and to validate the concept of travel time-based thermal tracer tomography under field conditions. Thermal tracer tomography uses repeated thermal tracer injections with different injection depths and distributed temperature measurements to map the hydraulic conductivity distribution of a heterogeneous aquifer. The tracer application was designed with minimal experimental time and cost. Water was heated in inflatable swimming pools using direct sunlight of the warm summer days, and it was injected as low temperature pulses in a well. Because of the small amount of injected heat, no long recovery times were required between the repeated heat tracer injections and every test started from natural thermal conditions. At Widen, four thermal tracer tests were performed during a period of three days. Temperatures were measured in one downgradient well using a distributed temperature measurement system installed at seven depth points. Totally 12 temperature breakthrough curves were collected. Travel time based tomographic inversion assumes that thermal transport is dominated by advection and the travel time of the thermal tracer can be related to the hydraulic conductivities of the aquifer. This assumption is valid in many shallow porous aquifers where the groundwater flow is fast. In our application, the travel time problem was treated by a tomographic solver, analogous to seismic tomography, to derive the hydraulic conductivity distribution. At the test site, a two-dimensional cross-well hydraulic conductivity profile was reconstructed with the travel time based inversion. The reconstructed profile corresponds well with the findings of the earlier hydraulic and geophysical experiments at the site.

Microscale Demonstration of the Paramagnetism of Liquid Oxygen with a Neodymium Magnet

ERIC Educational Resources Information Center

Mattson, Bruce

2007-01-01

A microscale classroom demonstration of the paramagnetic behavior of various samples of liquid oxygen with neodymium magnet is being presented. The experiment should be done with extreme caution, as liquid oxygen reacts violently with organic matters.

Ferromagnetic clusters induced by a nonmagnetic random disorder in diluted magnetic semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bui, Dinh-Hoi; Physics Department, Hue University’s College of Education, 34 Le Loi, Hue; Phan, Van-Nham, E-mail: phanvannham@dtu.edu.vn

In this work, we analyze the nonmagnetic random disorder leading to a formation of ferromagnetic clusters in diluted magnetic semiconductors. The nonmagnetic random disorder arises from randomness in the host lattice. Including the disorder to the Kondo lattice model with random distribution of magnetic dopants, the ferromagnetic–paramagnetic transition in the system is investigated in the framework of dynamical mean-field theory. At a certain low temperature one finds a fraction of ferromagnetic sites transiting to the paramagnetic state. Enlarging the nonmagnetic random disorder strength, the paramagnetic regimes expand resulting in the formation of the ferromagnetic clusters.

Magnetic resonance force microscopy with a paramagnetic probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berman, G. P.; Gorshkov, V. N.; Tsifrinovich, V. I.

Here, we consider theoretically extension of magnetic resonance force microscopy (MRFM) replacing a ferromagnetic probe on a cantilever tip (CT) with a paramagnetic one (PMRFM). The dynamics of the interaction between the paramagnetic probe and a local magnetic moment in a sample is analyzed, using a quasi-classical approach. We show that the application of a proper sequence of electromagnetic pulses provides a significant deflection of the CT from the initial equilibrium position. Periodic application of these sequences of pulses results in quasi-periodic CT deflections from the equilibrium, which can be used for detection of the magnetic moment in a sample.

Dedicated Co-deposition System for Metallic Paramagnetic Films

DOE PAGES

Jaeckel, F.; Kotsubo, V.; Hall, J. A.; ...

2012-01-27

Here, we describe a dedicated co-sputtering/ion-mill system developed to study metallic paramagnetic films for use in magnetic microcalorimetry. Small-diameter sputtering guns allow study of several precious-metal-based paramagnetic alloy systems within a reasonable budget. We demonstrated safe operation of a 1" sputtering gun at >5x the rated maximum power, achieving deposition rates up to ~900 Å/min/gun (Cu) in our co-sputtering geometry. Demonstrated co-sputtering deposition ratios up to 100:1 allow accurate tuning of magnetic dopant concentration and eliminate the difficulty of preparing homogeneous alloy targets of extreme dilution.

Magnetic resonance force microscopy with a paramagnetic probe

NASA Astrophysics Data System (ADS)

Berman, G. P.; Gorshkov, V. N.; Tsifrinovich, V. I.

2017-04-01

We consider theoretically extension of magnetic resonance force microscopy (MRFM) replacing a ferromagnetic probe on a cantilever tip (CT) with a paramagnetic one (PMRFM). The dynamics of the interaction between the paramagnetic probe and a local magnetic moment in a sample is analyzed, using a quasi-classical approach. We show that the application of a proper sequence of electromagnetic pulses provides a significant deflection of the CT from the initial equilibrium position. Periodic application of these sequences of pulses results in quasi-periodic CT deflections from the equilibrium, which can be used for detection of the magnetic moment in a sample.

Improved paramagnetic chelate for molecular imaging with MRI

NASA Astrophysics Data System (ADS)

Winter, Patrick; Athey, Phillip; Kiefer, Garry; Gulyas, Gyongyi; Frank, Keith; Fuhrhop, Ralph; Robertson, David; Wickline, Samuel; Lanza, Gregory

2005-05-01

The relaxivity and transmetallation of two lipophilic paramagnetic chelates incorporated onto perfluorocarbon nanoparticles, i.e., gadolinium-methoxy-tetraazacyclododecane-tetraacetic acid phosphatidylethanolamine (Gd-MeO-DOTA-PE) and gadolinium-methoxy-tetraazacyclododecane-tetraacetic acid triglycine phosphatidylethanolamine (Gd-MeO-DOTA-triglycine-PE (Gd-MeO-DOTA-triglycine-PE)), were compared to a prototypic gadolinium-diethylene-triamine-pentaacetic acid bis-oleate (Gd-DTPA-BOA) paramagnetic formulation. Nanoparticles with MeO-DOTA-based chelates demonstrated higher relaxivity (40% higher for Gd-MeO-DOTA-PE and 55% higher for Gd-MeO-DOTA-triglycine-PE) and less transmetallation than the original Gd-DTPA-BOA-based agent.

Magnetic resonance force microscopy with a paramagnetic probe

DOE PAGES

Berman, G. P.; Gorshkov, V. N.; Tsifrinovich, V. I.

2017-04-01

Here, we consider theoretically extension of magnetic resonance force microscopy (MRFM) replacing a ferromagnetic probe on a cantilever tip (CT) with a paramagnetic one (PMRFM). The dynamics of the interaction between the paramagnetic probe and a local magnetic moment in a sample is analyzed, using a quasi-classical approach. We show that the application of a proper sequence of electromagnetic pulses provides a significant deflection of the CT from the initial equilibrium position. Periodic application of these sequences of pulses results in quasi-periodic CT deflections from the equilibrium, which can be used for detection of the magnetic moment in a sample.

Cancer detection based on Raman spectra super-paramagnetic clustering

NASA Astrophysics Data System (ADS)

González-Solís, José Luis; Guizar-Ruiz, Juan Ignacio; Martínez-Espinosa, Juan Carlos; Martínez-Zerega, Brenda Esmeralda; Juárez-López, Héctor Alfonso; Vargas-Rodríguez, Héctor; Gallegos-Infante, Luis Armando; González-Silva, Ricardo Armando; Espinoza-Padilla, Pedro Basilio; Palomares-Anda, Pascual

2016-08-01

The clustering of Raman spectra of serum sample is analyzed using the super-paramagnetic clustering technique based in the Potts spin model. We investigated the clustering of biochemical networks by using Raman data that define edge lengths in the network, and where the interactions are functions of the Raman spectra's individual band intensities. For this study, we used two groups of 58 and 102 control Raman spectra and the intensities of 160, 150 and 42 Raman spectra of serum samples from breast and cervical cancer and leukemia patients, respectively. The spectra were collected from patients from different hospitals from Mexico. By using super-paramagnetic clustering technique, we identified the most natural and compact clusters allowing us to discriminate the control and cancer patients. A special interest was the leukemia case where its nearly hierarchical observed structure allowed the identification of the patients's leukemia type. The goal of this study is to apply a model of statistical physics, as the super-paramagnetic, to find these natural clusters that allow us to design a cancer detection method. To the best of our knowledge, this is the first report of preliminary results evaluating the usefulness of super-paramagnetic clustering in the discipline of spectroscopy where it is used for classification of spectra.

Apparatus for magnetic separation of paramagnetic and diamagnetic material

DOEpatents

Doctor, Richard D.

1988-01-01

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadropole magnet. The open gradient magnetic field further segregates the paramagnetic particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin.

Apparatus for magnetic separation of paramagnetic and diamagnetic material

DOEpatents

Doctor, R.D.

1988-10-18

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadrupole magnet. The open gradient magnetic field further segregates the paramagnetic particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin. 5 figs.

Apparatus for magnetic separation of paramagnetic and diamagnetic material

DOEpatents

Doctor, R.D.

1986-07-24

The present invention relates to methods and apparatus for segregating paramagnetic from diamagnetic particles in particulate material and, in particular, to the open gradient magnetic separation of ash producing components and pyritic sulfur from coal. The apparatus includes a vertical cylinder and a rotatable vertical screw positioned within the cylinder, the screw having a helical blade angled downwardly and outwardly from the axis. Rotation of the vertical screw causes denser particles, which in the case of coal include pyritic sulfur and ash, which are paramagnetic, to migrate to the outside of the screw, and less dense particles, such as the low sulfur organic portion of the coal, which are diamagnetic, to migrate towards the center of the screw. A vibration mechanism attached to the screw causes the screw to vibrate during rotation, agitating and thereby accommodating further segregation of the particles. An open gradient magnetic field is applied circumferentially along the entire length of the screw by a superconducting quadrupole magnet. The open gradient magnetic field further segregates the paramagnetic-particles from the diamagnetic particles. The paramagnetic particles may then be directed from the cylinder into a first storage bin, and the diamagnetic particles, which are suitable for relatively clean combustion, may be directed into a second storage bin. 5 figs.

Development of a Hybrid EPR/NMR Coimaging System

PubMed Central

Samouilov, Alexandre; Caia, George L.; Kesselring, Eric; Petryakov, Sergey; Wasowicz, Tomasz; Zweier, Jay L.

2010-01-01

Electron paramagnetic resonance imaging (EPRI) is a powerful technique that enables spatial mapping of free radicals or other paramagnetic compounds; however, it does not in itself provide anatomic visualization of the body. Proton magnetic resonance imaging (MRI) is well suited to provide anatomical visualization. A hybrid EPR/NMR coimaging instrument was constructed that utilizes the complementary capabilities of both techniques, superimposing EPR and proton-MR images to provide the distribution of paramagnetic species in the body. A common magnet and field gradient system is utilized along with a dual EPR and proton-NMR resonator assembly, enabling coimaging without the need to move the sample. EPRI is performed at ~1.2 GHz/~40 mT and proton MRI is performed at 16.18 MHz/~380 mT; hence the method is suitable for whole-body coimaging of living mice. The gradient system used is calibrated and controlled in such a manner that the spatial geometry of the two acquired images is matched, enabling their superposition without additional postprocessing or marker registration. The performance of the system was tested in a series of phantoms and in vivo applications by mapping the location of a paramagnetic probe in the gastrointestinal (GI) tract of mice. This hybrid EPR/NMR coimaging instrument enables imaging of paramagnetic molecules along with their anatomic localization in the body. PMID:17659621

Paramagnetic particles coupled with an automated flow injection analysis as a tool for influenza viral protein detection.

PubMed

Krejcova, Ludmila; Dospivova, Dana; Ryvolova, Marketa; Kopel, Pavel; Hynek, David; Krizkova, Sona; Hubalek, Jaromir; Adam, Vojtech; Kizek, Rene

2012-11-01

Currently, the influenza virus infects millions of individuals every year. Since the influenza virus represents one of the greatest threats, it is necessary to develop a diagnostic technique that can quickly, inexpensively, and accurately detect the virus to effectively treat and control seasonal and pandemic strains. This study presents an alternative to current detection methods. The flow-injection analysis-based biosensor, which can rapidly and economically analyze a wide panel of influenza virus strains by using paramagnetic particles modified with glycan, can selectively bind to specific viral A/H5N1/Vietnam/1203/2004 protein-labeled quantum dots. Optimized detection of cadmium sulfide quantum dots (CdS QDs)-protein complexes connected to paramagnetic microbeads was performed using differential pulse voltammetry on the surface of a hanging mercury drop electrode (HMDE) and/or glassy carbon electrode (GCE). Detection limit (3 S/N) estimations based on cadmium(II) ions quantification were 0.1 μg/mL or 10 μg/mL viral protein at HMDE or GCE, respectively. Viral protein detection was directly determined using differential pulse voltammetry Brdicka reaction. The limit detection (3 S/N) of viral protein was estimated as 0.1 μg/mL. Streptavidin-modified paramagnetic particles were mixed with biotinylated selective glycan to modify their surfaces. Under optimized conditions (250 μg/mL of glycan, 30-min long interaction with viral protein, 25°C and 400 rpm), the viral protein labeled with quantum dots was selectively isolated and its cadmium(II) content was determined. Cadmium was present in detectable amounts of 10 ng per mg of protein. Using this method, submicrogram concentrations of viral proteins can be identified. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elucidating the design principles of photosynthetic electron-transfer proteins by site-directed spin labeling EPR spectroscopy.

PubMed

Ishara Silva, K; Jagannathan, Bharat; Golbeck, John H; Lakshmi, K V

2016-05-01

Site-directed spin labeling electron paramagnetic resonance (SDSL EPR) spectroscopy is a powerful tool to determine solvent accessibility, side-chain dynamics, and inter-spin distances at specific sites in biological macromolecules. This information provides important insights into the structure and dynamics of both natural and designed proteins and protein complexes. Here, we discuss the application of SDSL EPR spectroscopy in probing the charge-transfer cofactors in photosynthetic reaction centers (RC) such as photosystem I (PSI) and the bacterial reaction center (bRC). Photosynthetic RCs are large multi-subunit proteins (molecular weight≥300 kDa) that perform light-driven charge transfer reactions in photosynthesis. These reactions are carried out by cofactors that are paramagnetic in one of their oxidation states. This renders the RCs unsuitable for conventional nuclear magnetic resonance spectroscopy investigations. However, the presence of native paramagnetic centers and the ability to covalently attach site-directed spin labels in RCs makes them ideally suited for the application of SDSL EPR spectroscopy. The paramagnetic centers serve as probes of conformational changes, dynamics of subunit assembly, and the relative motion of cofactors and peptide subunits. In this review, we describe novel applications of SDSL EPR spectroscopy for elucidating the effects of local structure and dynamics on the electron-transfer cofactors of photosynthetic RCs. Because SDSL EPR Spectroscopy is uniquely suited to provide dynamic information on protein motion, it is a particularly useful method in the engineering and analysis of designed electron transfer proteins and protein networks. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson. Copyright © 2016. Published by Elsevier B.V.

Interaction of Spin-Labeled Lipid Membranes with Transition Metal Ions

PubMed Central

2015-01-01

The large values of spin relaxation enhancement (RE) for PC spin-labels in the phospholipid membrane induced by paramagnetic metal salts dissolved in the aqueous phase can be explained by Heisenberg spin exchange due to conformational fluctuations of the nitroxide group as a result of membrane fluidity, flexibility of lipid chains, and, possibly, amphiphilic nature of the nitroxide label. Whether the magnetic interaction occurs predominantly via Heisenberg spin exchange (Ni) or by the dipole–dipole (Gd) mechanism, it is essential for the paramagnetic ion to get into close proximity to the nitroxide moiety for efficient RE. For different salts of Ni the RE in phosphatidylcholine membranes follows the anionic Hofmeister series and reflects anion adsorption followed by anion-driven attraction of paramagnetic cations on the choline groups. This adsorption is higher for chaotropic ions, e.g., perchlorate. (A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules.) However, there is no anionic dependence of RE for model membranes made from negatively charged lipids devoid of choline groups. We used Ni-induced RE to study the thermodynamics and electrostatics of ion/membrane interactions. We also studied the effect of membrane composition and the phase state on the RE values. In membranes with cholesterol a significant difference is observed between PC labels with nitroxide tethers long enough vs not long enough to reach deep into the membrane hydrophobic core behind the area of fused cholesterol rings. This study indicates one must be cautious in interpreting data obtained by PC labels in fluid membranes in terms of probing membrane properties at different immersion depths when it can be affected by paramagnetic species at the membrane surface. PMID:26490692

Optimization of 13C dynamic nuclear polarization: isotopic labeling of free radicals

NASA Astrophysics Data System (ADS)

Niedbalski, Peter; Parish, Christopher; Kiswandi, Andhika; Lumata, Lloyd

Dynamic nuclear polarization (DNP) is a physics technique that amplifies the nuclear magnetic resonance (NMR) signals by transferring the high polarization of the electrons to the nuclear spins. Thus, the choice of free radical is crucial in DNP as it can directly affect the NMR signal enhancement levels, typically on the order of several thousand-fold in the liquid-state. In this study, we have investigated the efficiency of four variants of the well-known 4-oxo-TEMPO radical (normal 4-oxo-TEMPO plus its 15N-enriched and/or perdeuterated variants) for use in DNP of an important metabolic tracer [1-13C]acetate. Though the variants have significant differences in electron paramagnetic resonance (EPR) spectra, we have found that changing the composition of the TEMPO radical through deuteration or 15N doping yields no significant difference in 13C DNP efficiency at 3.35 T and 1.2 K. On the other hand, deuteration of the solvent causes a significant increase of 13C polarization that is consistent over all the 4-oxo-TEMPO variants. These findings are consistent with the thermal mixing model of DNP. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and the Robert A. Welch Foundation Grant No. AT-1877.

Application of electron paramagnetic resonance imaging to the characterization of the Ultem(R) exposed to 1 MeV electrons. Correlation of radical density data to tiger code calculations

NASA Technical Reports Server (NTRS)

Suleman, Naushadalli K.

1994-01-01

A major long-term goal of the Materials Division at the NASA Langley Research Center is the characterization of new high-performance materials that have potential applications in the aircraft industry, and in space. The materials used for space applications are often subjected to a harsh and potentially damaging radiation environment. The present study constitutes the application of a novel technique to obtain reliable data for ascertaining the molecular basis for the resilience and durability of materials that have been exposed to simulated space radiations. The radiations of greatest concern are energetic electrons and protons, as well as galactic cosmic rays. Presently, the effects of such radiation on matter are not understood in their entirety. It is clear however, that electron radiation causes ionization and homolytic bond rupture, resulting in the formation of paramagnetic spin centers in the polymer matrices of the structural materials. Since the detection and structure elucidation of paramagnetic species are most readily accomplished using Electron Paramagnetic Resonance (EPR) Spectroscopy, the NASA LaRC EPR system was brought back on-line during the 1991 ASEE term. The subsequent 1992 ASEE term was devoted to the adaptation of the EPR core system to meet the requirements for EPR Imaging (EPRI), which provides detailed information on the spatial distribution of paramagnetic species in bulk media. The present (1994) ASEE term was devoted to the calibration of this EPR Imaging system, as well as to the application of this technology to study the effects of electron irradiation on Ultem(exp R), a high performance polymer which is a candidate for applications in aerospace. The Ultem was exposed to a dose of 2.4 x 10(exp 9) Rads (1-MeV energy/electron) at the LaRC electron accelerator facility. Subsequently, the exposed specimens were stored in liquid nitrogen, until immediately prior to analyses by EPRI. The intensity and dimensions of the EPR Images that were generated for the irradiated specimens showed that the electrons penetrated the material to a depth of approximately 0.125 inch. These data show a very high degree of correlation to the energy deposition profile as predicted by the Tiger Code, a Monte Carlo code that provides guidelines for the transport of electrons in matter. Subsequent efforts will focus on delineating the transport properties of energetic protons in Ultem(R).

Rejuvenating the Largest Treatment Wetland in Florida: Tracer Moment and Model Analysis of Wetland Hydraulic Performance

NASA Astrophysics Data System (ADS)

White, J. R.; Wang, H.; Jawitz, J. W.; Sees, M. D.

2004-12-01

The Orlando Easterly Wetland (OEW), the largest municipal treatment wetland in Florida, began operation in 1987 mainly for reducing nutrient loads in tertiary treated domestic wastewater produced by the city of Orlando. After more than ten years of operation, a decrease in total P removal effectiveness has occurred since 1999, even though the effluent concentration of the wetland has remained below the permitted limit of 0.2 mg/L,. Hydraulic inefficiency in the wetland, especially in the front-end cells of the north flow train, was identified as a primary cause of the reduced treatment effectiveness. In order to improve the hydraulic performance of the OEW and maintain its efficient phosphorus treatment, a rejuvenation program (including muck removal followed by re-vegetation) was initiated on the front-end cells of the north flow train in 2002. The effectiveness of this activity for the improvement of hydraulic performance was evaluated with a tracer test and subsequent moment and model analyses for the tracer resident time distribution (RTDs). Results were compared to similar tracer tests conducted prior to rejuvenation activities. The models included one-path tank-in-series (TIS), two-path TIS, one-dimensional transport with inflow and storage (OTIS), plug flow with dispersion (PFD), and plug flow with fractional dispersion (PFFD). The hydraulic performance was characterized by both wetland hydraulic efficiency and the spreading of tracers. The results demonstrated that the rejuvenation considerably improved the hydraulic performance in the restored area. Also presented is a comparison of the wetland response between both bromide and lithium tracers, and the determination of the complete moments of residence time distributions (RTD) in cell-network wetlands.

Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA

USGS Publications Warehouse

Day-Lewis, F. D.; Lane, J.W.; Gorelick, S.M.

2006-01-01

An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock. ?? Springer-Verlag 2004.

Tracing wastewater effluents in surface and groundwaters: a couple approach with organic/inorganic tracers and isotopes

NASA Astrophysics Data System (ADS)

Petelet-Giraud, Emmanuelle; Baran, Nicole; Soulier, Coralie

2017-04-01

In the context of land use change, the origins of contamination of water resources are often multiple, including for a single chemical element or molecule. For instance, excess of nitrates in both surface and groundwater can originate from agricultural practices and wastewater effluents. The discrimination of the origins and vectors of contamination in the environment is both an environmental and societal issue in order to define an integrated water resources management at the catchment or water body scale by implementing appropriate measures to effectively struggle against pollution. The objective of this study is to define a methodology for the identification of a "domestic wastewater" contamination within surface waters and groundwater. An ideal tracer should be conservative, persistent in the different water compartments, present in quantity above the detection limit and originate from a single type of pollution source. There is, however, no ideal tracer in the strict sense. Indeed, even chloride which is present in quantity in wastewater, and which behaves conservatively in the environment, is not an univocal tracer of wastewater, as it may come from atmospheric inputs, from the dissolution of evaporitic rocks, from the salting of roads or from fertilizers. To overcome this limitation, in this study, we propose a multi-tracer approach (chemical and isotopic) to identify and validate the relevance of foreseen tracers. Among the relevant tracers of wastewater, the following may be used for their intrinsic or combined discriminant power: 1) organic effluent tracers: nitrogen contents and isotopic ratios of nitrogen and oxygen of nitrates; 2) tracer of detergents: boron contents and boron isotopes; 3) pharmaceuticals tracers: e.g. carbamazepine, ibuprofen, paracetamol, gadolinium anomaly; 4) life-style tracers: e.g. caffeine. The originality of the study relies on small capacities wastewater treatment plants without tertiary treatment process. Results on a catchment impacted both by diffuse agricultural pollution and punctual wastewater inputs are presented. Investigations concern wastewater effluents resulting from different type of treatment plants, surface and groundwater. Potential combination of suitable tracers is discussed.

Microbubbles and Microparticles are Not Faithful Tracers of Turbulent Acceleration

NASA Astrophysics Data System (ADS)

Mathai, Varghese; Calzavarini, Enrico; Brons, Jon; Sun, Chao; Lohse, Detlef

2016-07-01

We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St ≪1 in turbulent flow. At a decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles; i.e., they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere. They also question the common usage of microbubbles and microdroplets as tracers in turbulence research.

Effect of morphology and discharge on hyporheic exchange flows in two small streams in the Cascade Mountains of Oregon, USA.

Treesearch

Steven M. Wondzell

2006-01-01

Stream-tracer injections were used to examine the effect of channel morphology and changing stream discharge on hyporheic exchange flows. Direct observations were made from well networks to follow tracer movement through the hyporheic zone. The reach-integrated influence of hyporheic exchange was evaluated using the transient storage model (TSM) OTIS-P. Transient...

Separation of Diamagnetic and Paramagnetic Fabrics Reveals Strain Directions in Carbonate Rocks

NASA Astrophysics Data System (ADS)

Issachar, R.; Levi, T.; Marco, S.; Weinberger, R.

2018-03-01

We present a new procedure for separating magnetic fabrics in coccolith-bearing chalk samples, demonstrated in the case studies of three sites located within the Dead Sea Fault (DSF) plate boundary. The separation is achieved by combining measurements of room temperature and low-temperature anisotropy of magnetic susceptibility (RT-AMS and LT-AMS, respectively) with anisotropy of anhysteretic remanence magnetization (AARM). The LT-AMS, measured at 77 K, enhances the fabric of paramagnetic clay minerals. The AARM represents the fabric of ferromagnetic Fe oxides. By subtracting the paramagnetic and ferromagnetic fabrics from the RT-AMS, the diamagnetic fabric is separated. In the studied samples, we found that the ferromagnetic contribution to the bulk magnetic fabric is negligible and could be excluded from the subtraction procedure. Our analysis indicates that in chalks with a negligible ferromagnetic contribution, diamagnetic fabric predominates the rock bulk magnetic fabric, if the mean susceptibility is <-6 × 10-6 SI, whereas with a mean susceptibility >11 × 10-6 SI, paramagnetic fabric predominates. In the studied rocks, the paramagnetic clay minerals preserve the original depositional fabric, whereas the diamagnetic minerals show a tectonic fabric. We propose a mechanism by which coccolith rotation under tectonic strain contributes to the development of the diamagnetic fabric parallel to the shortening direction. We infer that the diamagnetic fabrics of the studied rocks indicate strain regime of approximately N-S horizontal shortening near strands of the DSF system. This suggests a deflection of the regional principal strain axes near the DSF. The diamagnetic fabric is more sensitive to tectonic strain than paramagnetic fabric in chalks and provides a valuable strain indicator near major faults.

Change in the Magnetocapacity in the Paramagnetic Region in a Cation-Substituted Manganese Selenide

NASA Astrophysics Data System (ADS)

Aplesnin, S. S.; Sitnikov, M. N.; Zhivul'ko, A. M.

2018-04-01

The capacity and the dielectric loss tangent of a Gd x Mn1- x Se ( x ≤ 0.2) solid solution have been measured in the frequency range 1-300 kHz without a magnetic field and in a magnetic field of 8 kOe in the temperature range 100-450 K, and the magnetic moment of the solid solution has been measured in a field of 8.6 kOe. The magnetocapacity effect and the change in the magnetocapacity sign have been observed in room temperature in the paramagnetic region. A correlation of the changes in the dielectric permittivity and the magnetic susceptibility with temperature has been revealed. The magnetocapacity is described using the model with orbital electron ordering and the Maxwell-Wagner model.

Magnetic properties of Zn1-xNixO

NASA Astrophysics Data System (ADS)

Mondal, A.; Giri, N.; Sarkar, S.; Ray, Ruma

2018-05-01

Ni doped ZnO (Zn1-xNixO for 0.01 ≤ x ≤ 0.11) have been prepared by chemical precipitation method. X-ray diffraction corroborates a hexagonal wurzite structure without any impurity phases upto 11% Ni doping. Morphology of the particles is investigated by FE-SEM which exhibits either rod or tube like structure depending on the dopant concentration. Magnetization of Zn1-xNixO for 0.03 ≤ x ≤ 0.11 measured at room temperature infers the paramagnetic behavior. Zero field cooled and field cooled magnetization for x = 0.11 follows Curie-Weiss behavior above 122 K with effective paramagnetic moment 3.9μB. The non-linear magnetic hysteresis loop at 2 K with a small coercivity (300 Oe) indicates signature of ferromagnetic ordering.

The dual role of paramagnetic particles for integrated lysis and measurement in a rapid immunoassay for intracellular proteins.

PubMed

Sharif, Elham; Kiely, Janice; Wraith, Patrick; Luxton, Richard

2013-05-01

A novel, integrated lysis and immunoassay methodology and system for intracellular protein measurement are described. The method uses paramagnetic particles both as a lysis agent and assay label resulting in a rapid test requiring minimal operator intervention, the test being homogeneous and completed in less than 10 min. A design study highlights the critical features of the magnetic detection system used to quantify the paramagnetic particles and a novel frequency-locked loop-based magnetometer is presented. A study of paramagnetic particle enhanced lysis demonstrates that the technique is more than twice as efficient at releasing intracellular protein as ultrasonic lysis alone. Results are presented for measurements of intracellular prostate specific antigen in an LNCAP cell line. This model was selected to demonstrate the rapidity and efficiency of intracellular protein quantification. It was shown that, on average, LNCAP cells contained 0.43 fg of prostate specific antigen. This system promises an attractive solution for applications that require a rapid determination of intracellular proteins.

Fe–Ni solid solutions in nano-size dimensions: Effect of hydrogen annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Asheesh, E-mail: asheeshk@barc.gov.in; Meena, S.S.; Banerjee, S.

Highlights: • Fe–Ni solid solution with nano-size dimensions were prepared and characterized. • Both as prepared and hydrogenated solid solutions have FCC structure of Ni. • Paramagnetic and ferromagnetic domains coexist in these samples. - Abstract: Nanoparticles of Ni{sub 0.50}Fe{sub 0.50} and Ni{sub 0.75}Fe{sub 0.25} alloys were prepared by chemical reduction in ethylene glycol medium. XRD and {sup 57}Fe Mössbauer studies have confirmed the formation of Fe–Ni solid solution in nano-size dimensions with FCC structure. These samples consist of both ferromagnetic and paramagnetic domains which have been attributed to the coexistence of large and small particles as confirmed by atomicmore » force microscopic (AFM) and {sup 57}Fe Mössbauer spectroscopic studies. Improved extent of Fe–Fe exchange interaction existing in Ni{sub 0.50}Fe{sub 0.50} alloy compared to Ni{sub 0.75}Fe{sub 0.25} alloy explains the observed increase in the relative extent of ferromagnetic domains compared to paramagnetic domains in the former sample. Increase in the relative extent of ferromagnetic domains for hydrogenated alloys is due to increase in particle size brought about by the high temperature activation prior to hydrogenation.« less

Dynamic Structural Changes of SiO₂ Supported Pt-Ni Bimetallic Catalysts over Redox Treatments Revealed by NMR and EPR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Suochang; Walter, Eric D.; Zhao, Zhenchao

2015-08-18

SiO 2 supported Pt-Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin-lattice relaxation of Q 4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q 3 species, which are in close contact with the paramagnetic nickel ions,more » are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. However, in the reduced samples, the superparamagnetic or ferromagnetic metallic Ni particles were inside the PtNi NPs, making their influence on the 29Si relaxation in the SiO 2 support weaker than the oxidized samples.« less

Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y)

PubMed Central

Jarý, Vítězslav; Havlák, Lubomír; Bárta, Jan; Buryi, Maksym; Mihóková, Eva; Rejman, Martin; Laguta, Valentin; Nikl, Martin

2015-01-01

Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED) lighting. Samples were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic resonance, and X-ray excited fluorescence. Corresponding characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra, and decay kinetics curves, were measured and evaluated in a broad temperature range (8–800 K). Calculations including quantum local crystal field potential and spin-Hamiltonian for a paramagnetic particle in D3d local symmetry and phenomenological model dealing with excited state dynamics were performed to explain the experimentally observed features. Based on the results, an energy diagram of lanthanide energy levels in KLuS2 is proposed. Color model xy-coordinates are used to compare effects of dopants on the resulting spectrum. The application potential of the mentioned compounds in the field of white LED solid state lighting or X-ray phosphors is thoroughly discussed. PMID:28793612

The Src SH2 domain interacts dynamically with the focal adhesion kinase binding site as demonstrated by paramagnetic NMR spectroscopy.

PubMed

Lindfors, Hanna E; Drijfhout, Jan Wouter; Ubbink, Marcellus

2012-06-01

The interaction between the tyrosine kinases Src and focal adhesion kinase (FAK) is a key step in signaling processes from focal adhesions. The phosphorylated tyrosine residue 397 in FAK is able to bind the Src SH2 domain. To establish the extent of the FAK binding motif, the binding affinity of the SH2 domain for phosphorylated and unphosphorylated FAK-derived peptides of increasing length was determined and compared with that of the internal Src SH2 binding site. It is shown that the FAK peptides have higher affinity than the internal binding site and that seven negative residues adjacent to the core SH2 binding motif increase the binding constant 30-fold. A rigid spin-label incorporated in the FAK peptides was used to establish on the basis of paramagnetic relaxation enhancement whether the peptide-protein complex is well defined. A large spread of the paramagnetic effects on the surface of the SH2 domain suggests that the peptide-protein complex exhibits dynamics, despite the high affinity of the peptide. The strong electrostatic interaction between the positive side of the SH2 domain and the negative peptide results in a high affinity but may also favor a dynamic interaction. Copyright © 2012 Wiley Periodicals, Inc.

Isotope dilution technique for quantitative analysis of endogenous trace element species in biological systems

NASA Astrophysics Data System (ADS)

Schaumlöffel, Dirk; Lobinski, Ryszard

2005-04-01

The aim of this study was to develop an inductively coupled plasma mass spectrometry (ICPMS) method for the determination of enriched species-specific mercury tracers at ng L-1 levels (ppt) in zooplankton and aquatic samples from biological tracer experiments. Applying a cold vapor sector field ICPMS method a high sensitivity was obtained, i.e., 106 cps for 1 [mu]g L-1 of natural mercury measured on 202Hg+, which in turn enabled the measurement of mercury isotope ratios with a 0.6-1.4%R.S.D. precision for a 50 ng L-1 standard. This method was used to quantify CH3201Hg+ and 200Hg2+ tracers in zooplankton from a biological tracer experiment with the aim of investigating the effects of algal density and zooplankton density on mercury bioaccumulation in zooplankton in a fresh water system. For quantification purposes a known amount of 199Hg+ was added to the zooplankton samples before digestion. The digested samples were analyzed and the resulting ICPMS spectra split into four spectra one for each of the four sources of mercury present in the sample (CH3201Hg+, 200Hg2+, 199Hg2+ and natural mercury) using algebraic de-convoluting. The CH3201Hg+ and 200Hg2+ tracers were quantified using an isotope dilution approach with the added 199Hg+. Detection limits were 0.6 and 0.2 ng L-1 for 200Hg+ and CH3201Hg+, respectively. The coefficient of variation on the tracer determinations was approximately 18% CV estimated from the analysis of real samples with tracer concentrations in the <0.1-100 ng L-1 range. The developed method was successfully applied for the determination of species-specific mercury tracers in zooplankton samples from a biological tracer experiment.

Time series measurements of transient tracers and tracer-derived transport in the Deep Western Boundary Current between the Labrador Sea and the subtropical Atlantic Ocean at Line W

NASA Astrophysics Data System (ADS)

Smith, John N.; Smethie, William M.; Yashayev, Igor; Curry, Ruth; Azetsu-Scott, Kumiko

2016-11-01

Time series measurements of the nuclear fuel reprocessing tracer 129I and the gas ventilation tracer CFC-11 were undertaken on the AR7W section in the Labrador Sea (1997-2014) and on Line W (2004-2014), located over the US continental slope off Cape Cod, to determine advection and mixing time scales for the transport of Denmark Strait Overflow Water (DSOW) within the Deep Western Boundary Current (DWBC). Tracer measurements were also conducted in 2010 over the continental rise southeast of Bermuda to intercept the equatorward flow of DSOW by interior pathways. The Labrador Sea tracer and hydrographic time series data were used as input functions in a boundary current model that employs transit time distributions to simulate the effects of mixing and advection on downstream tracer distributions. Model simulations of tracer levels in the boundary current core and adjacent interior (shoulder) region with which mixing occurs were compared with the Line W time series measurements to determine boundary current model parameters. These results indicate that DSOW is transported from the Labrador Sea to Line W via the DWBC on a time scale of 5-6 years corresponding to a mean flow velocity of 2.7 cm/s while mixing between the core and interior regions occurs with a time constant of 2.6 years. A tracer section over the southern flank of the Bermuda rise indicates that the flow of DSOW that separated from the DWBC had undergone transport through interior pathways on a time scale of 9 years with a mixing time constant of 4 years.

Long residence times - bad tracer tests?

NASA Astrophysics Data System (ADS)

Ghergut, Julia; Behrens, Horst; Sauter, Martin

2015-04-01

Tracer tests conducted at geothermal well doublets or triplets in the Upper Rhine Rift Valley [1] all face, with very few exceptions so far, one common issue: lack of conclusive tracer test results, or tracer signals still undetectable for longer than one or two years after tracer injection. While the reasons for this surely differ from site to site (Riehen, Landau, Insheim, Bruchsal, ...), its effects on how the usefulness of tracer tests is perceived by the non-tracer community are pretty much the same. The 'poor-signal' frustration keeps nourishing two major 'alternative' endeavours : (I) design and execute tracer tests in single-well injection-withdrawal (push-pull), 'instead of' inter-well flow-path tracing configurations; (II) use 'novel' tracer substances instead of the 'old' ones which have 'obviously failed'. Frustration experienced with most inter-well tracer tests in the Upper Rhine Rift Valley has also made them be regarded as 'maybe useful for EGS' ('enhanced', or 'engineered' geothermal systems, whose fluid RTD typically include a major share of values below one year), but 'no longer worthwhile a follow-up sampling' in natural, large-scale hydrothermal reservoirs. We illustrate some of these arguments with the ongoing Bruchsal case [2]. The inter-well tracer test conducted at Bruchsal was (and still is!) aimed at assessing inter-well connectivity, fluid residence times, and characterizing the reservoir structure [3]. Fluid samples taken at the geothermal production well after reaching a fluid turnover of about 700,000 m3 showed tracer concentrations in the range of 10-8 Minj per m3, in the liquid phase of each sample (Minj being the total quantity of tracer injected as a short pulse at the geothermal re-injection well). Tracer signals might actually be higher, owing to tracer amounts co-precipitated and/or adsorbed onto the solid phase whose accumulation in the samples was unavoidable (due to pressure relief and degassing during the very sampling process, and later on during sample aeration); the adsorbed and/or co-precipitated tracer amounts appear to be non-zero, but their accurate metering was not completed to date. Thus, a conservative estimate of cumulative tracer recovery amounts to (at least) 2 parts-per-thousand for the first 700,000 m3 of fluid turnover within the geothermal well doublet. Neither do such recovery values automatically imply 'bad news' (poor inter-well connectivity), nor do they appear as implausibly low (cf. fig. 2 of [3]), considering the possibility of major vertical drainage along the large-scale fault zone that isolates the 'aquifer basin' around the re-injection well from the 'aquifer catchment' around the production well, along with the prospect of transport-effective porosity and/or thickness within these 'aquifers' being rather high, due to extensive fissuring/fracturing. In more general terms, we argue that (a) inter-well flow-path spikings are still worthwhile being conducted even in large-scale hydrothermal reservoirs; (b) results gained from single-well tests [3] can never serve as a substitute for the kind of information (primarily: residence time distribution RTD, or flow-storage repartition FSR) being expected from inter-well tests; (c) tracer species that are 'novel' in terms of thermo-/reactivity/sorptivity/exchange at phase interfaces and thus involve some transport-retarding process cannot alleviate the frustration associated with long RT; (d) augmenting the tracer quantity Minj to use for inter-well spiking might render the tracer signal detectable, say, one or two years earlier, but it does not make FSR available sooner, since Minj cannot alter the RTD of fluids traveling through the reservoir; moreover, for inter-well configurations and reservoir structures typical of the Upper Rhine Rift Valley, the Minj augmenting factors necessary to render tracer signals detectable 1 or 2 years earlier mostly range beyond the limits of the reasonably-recommendable (e. g., for Bruchsal: 2 tons, instead of 100 kg of a particular tracer). Acknowledgements: We gratefully acknowledge financial support from Energie Baden-Württemberg (EnBW), from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, and from the Federal Ministry for Economic Affairs and Energy (BMU and BMWi, Germany), within research projects with grant nos. 0327579, 0325111B, 0325515. References: [1] www.bfe.admin.ch/forschunggeothermie/02484/02766/index.html?lang=de&dossier_id=06049 [2] http://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/0619.pdf [3] presentations.copernicus.org/EGU2012-13687_presentation.pdf

Application of fluorescently labeled tracer technique for detection of natural active macromolecules in Chinese medicine.

PubMed

Zeng, Qiao-Hui; Zhang, Xue-Wu; Xu, Kai-Peng; Jiang, Jian-Guo

2014-02-01

Active substances in traditional Chinese Medicine (TCM) contain not only a variety of small molecules, but also many other macromolecules (TCMMs), such as proteins, peptides and polysaccharides. Active TCMM can achieve good therapeutic effects by regulating the body's overall function with lower side effects. This review summarized the literatures published in recent years on the application of fluorescently labeled tracer technique for detection of natural active macromolecules in TCM. Classified by fluorescent markers, applications of fluorescein, rhodamine, and quantum dots (QDs) in TCMM active tracer are reviewed, and the methods and principles of TCMM fluorescent marker are illustrated. Studies on active TCMMs and their action mechanism are quite difficult due to a multitarget, multicomponent, and multipath system of TCM. However, the development of fluorescently labeled active tracer technique (FLATT) provides this research with new tools. Traditional fluorescent markers have many deficiencies, such as easily quenched, short luminous cycle, and intrinsic toxicity. Relatively, FLATT has many obvious advantages, and its application in TCMM is still at the early stage. In order to improve the overall level of fluorescence labeling in TCMM active tracer, the improvement on FLATT's detection sensitivity and biological affinity is urgent and critical to allow study of these interesting molecules.

Tracer methodology: an appropriate tool for assessing compliance with accreditation standards?

PubMed

Bouchard, Chantal; Jean, Olivier

2017-10-01

Tracer methodology has been used by Accreditation Canada since 2008 to collect evidence on the quality and safety of care and services, and to assess compliance with accreditation standards. Given the importance of this methodology in the accreditation program, the objective of this study is to assess the quality of the methodology and identify its strengths and weaknesses. A mixed quantitative and qualitative approach was adopted to evaluate consistency, appropriateness, effectiveness and stakeholder synergy in applying the methodology. An online questionnaire was sent to 468 Accreditation Canada surveyors. According to surveyors' perceptions, tracer methodology is an effective tool for collecting useful, credible and reliable information to assess compliance with Qmentum program standards and priority processes. The results show good coherence between methodology components (appropriateness of the priority processes evaluated, activities to evaluate a tracer, etc.). The main weaknesses are the time constraints faced by surveyors and management's lack of cooperation during the evaluation of tracers. The inadequate amount of time allowed for the methodology to be applied properly raises questions about the quality of the information obtained. This study paves the way for a future, more in-depth exploration of the identified weaknesses to help the accreditation organization make more targeted improvements to the methodology. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution

NASA Astrophysics Data System (ADS)

Rasa, Ehsan; Foglia, Laura; Mackay, Douglas M.; Scow, Kate M.

2013-11-01

Conservative tracer experiments can provide information useful for characterizing various subsurface transport properties. This study examines the effectiveness of three different types of transport observations for sensitivity analysis and parameter estimation of a three-dimensional site-specific groundwater flow and transport model: conservative tracer breakthrough curves (BTCs), first temporal moments of BTCs ( m 1), and tracer cumulative mass discharge ( M d) through control planes combined with hydraulic head observations ( h). High-resolution data obtained from a 410-day controlled field experiment at Vandenberg Air Force Base, California (USA), have been used. In this experiment, bromide was injected to create two adjacent plumes monitored at six different transects (perpendicular to groundwater flow) with a total of 162 monitoring wells. A total of 133 different observations of transient hydraulic head, 1,158 of BTC concentration, 23 of first moment, and 36 of mass discharge were used for sensitivity analysis and parameter estimation of nine flow and transport parameters. The importance of each group of transport observations in estimating these parameters was evaluated using sensitivity analysis, and five out of nine parameters were calibrated against these data. Results showed the advantages of using temporal moment of conservative tracer BTCs and mass discharge as observations for inverse modeling.

Partitioning Tracer Test for Detection, Estimation, and Remediation Performance Assessment of Subsurface Nonaqueous Phase Liquids

NASA Astrophysics Data System (ADS)

Jin, Minquan; Delshad, Mojdeh; Dwarakanath, Varadarajan; McKinney, Daene C.; Pope, Gary A.; Sepehrnoori, Kamy; Tilburg, Charles E.; Jackson, Richard E.

1995-05-01

In this paper we present a partitioning interwell tracer test (PITT) technique for the detection, estimation, and remediation performance assessment of the subsurface contaminated by nonaqueous phase liquids (NAPLs). We demonstrate the effectiveness of this technique by examples of experimental and simulation results. The experimental results are from partitioning tracer experiments in columns packed with Ottawa sand. Both the method of moments and inverse modeling techniques for estimating NAPL saturation in the sand packs are demonstrated. In the simulation examples we use UTCHEM, a comprehensive three-dimensional, chemical flood compositional simulator developed at the University of Texas, to simulate a hypothetical two-dimensional aquifer with properties similar to the Borden site contaminated by tetrachloroethylene (PCE), and we show how partitioning interwell tracer tests can be used to estimate the amount of PCE contaminant before remedial action and as the remediation process proceeds. Tracer tests results from different stages of remediation are compared to determine the quantity of PCE removed and the amount remaining. Both the experimental (small-scale) and simulation (large-scale) results demonstrate that PITT can be used as an innovative and effective technique to detect and estimate the amount of residual NAPL and for remediation performance assessment in subsurface formations.

Partitioning tracer test for detection, estimation, and remediation performance assessment of subsurface nonaqueous phase liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, M.; Delshad, M.; Dwarakanath, V.

1995-05-01

In this paper we present a partitioning interwell tracer test (PITT) technique for the detection, estimation, and remediation performance assessment of the subsurface contaminated by nonaqueous phase liquids (NAPLs). We demonstrate the effectiveness of this technique by examples of experimental and simulation results. The experimental results are from partitioning tracer experiments in columns packed with Ottawa sand. Both the method of moments and inverse modeling techniques for estimating NAPL saturation in the sand packs are demonstrated. In the simulation examples we use UTCHEM, a comprehensive three-dimensional, chemical flood compositional simulator developed at the University of Texas, to simulate a hypotheticalmore » two-dimensional aquifer with properties similar to the Borden site contaminated by tetrachloroethylene (PCE), and we show how partitioning interwell tracer tests can be used to estimate the amount of PCE contaminant before remedial action and as the remediation process proceeds. Tracer test results from different stages of remediation are compared to determine the quantity of PCE removed and the amount remaining. Both the experimental (small-scale) and simulation (large-scale) results demonstrate that PITT can be used as an innovative and effective technique to detect and estimate the amount of residual NAPL and for remediation performance assessment in subsurface formations. 43 refs., 10 figs., 1 tab.« less

CoAs: The line of 3 d demarcation

NASA Astrophysics Data System (ADS)

Campbell, Daniel J.; Wang, Limin; Eckberg, Chris; Graf, Dave; Hodovanets, Halyna; Paglione, Johnpierre

2018-05-01

Transition metal-pnictide compounds have received attention for their tendency to combine magnetism and unconventional superconductivity. Binary CoAs lies on the border of paramagnetism and the more complex behavior seen in isostructural CrAs, MnP, FeAs, and FeP. Here we report the properties of CoAs single crystals grown with two distinct techniques along with density functional theory calculations of its electronic structure and magnetic ground state. While all indications are that CoAs is paramagnetic, both experiment and theory suggest proximity to a ferromagnetic instability. Quantum oscillations are seen in torque measurements up to 31.5 T and support the calculated paramagnetic Fermiology.

Paramagnetic and Diamagnetic Materials

ERIC Educational Resources Information Center

Thompson, Frank

2011-01-01

Paramagnetic and diamagnetic materials are now generally known as the "Cinderella" materials of the magnetic world. However, susceptibility measurements made on these materials in the past have revealed many details about the molecular bonding and the atomic structure of the so-called "transition" elements. Indeed, the magnetic moment of neodymium…

System Validation Experiments for Obtaining Tracer Laser-Induced Fluorescence Data at Elevated Pressure and Temperature.

PubMed

Hartwig, Jason; Mittal, Gaurav; Kumar, Kamal; Sung, Chih-Jen

2018-04-01

This paper presents a set of system validation experiments that can be used to qualify either static or flow experimental systems for gathering tracer photophysical data or conducting laser diagnostics at high pressure and temperature in order to establish design and operation limits and reduce uncertainty in data interpretation. Tests demonstrated here quantify the effect of tracer absorption at the test cell walls, stratification, photolysis, pyrolysis, adequacy of mixing and seeding, and reabsorption of laser light using acetone as the tracer and 282 nm excitation. Results show that acetone exhibits a 10% decrease in fluorescence signal over 36 000 shots at 127.4 mJ/cm 2 , and photolysis is negligible below 1000 shots collected. Meanwhile, appropriately chosen gas residence times can mitigate risks due to pyrolysis and inadequate mixing and seeding; for the current work 100 ms residence time ensured <0.5% alteration of tracer number density due to thermal destruction. Experimental results here are compared to theoretical values from the literature.

Optimization of 18 F-syntheses using 19 F-reagents at tracer-level concentrations and liquid chromatography/tandem mass spectrometry analysis: Improved synthesis of [18 F]MDL100907.

PubMed

Zhang, Xiang; Dunlow, Ryan; Blackman, Burchelle N; Swenson, Rolf E

2018-05-15

Traditional radiosynthetic optimization faces the challenges of high radiation exposure, cost, and inability to perform serial reactions due to tracer decay. To accelerate tracer development, we have developed a strategy to simulate radioactive 18 F-syntheses by using tracer-level (nanomolar) non-radioactive 19 F-reagents and LC-MS/MS analysis. The methodology was validated with fallypride synthesis under tracer-level 19 F-conditions, which showed reproducible and comparable results with radiosynthesis, and proved the feasibility of this process. Using this approach, the synthesis of [ 18 F]MDL100907 was optimized under 19 F-conditions with greatly improved yield. The best conditions were successfully transferred to radiosynthesis. A radiochemical yield of 19% to 22% was achieved with the radiochemical purity >99% and the molar activity 38.8 to 53.6 GBq/ μmol (n = 3). The tracer-level 19 F-approach provides a high-throughput and cost-effective process to optimize radiosynthesis with reduced radiation exposure. This new method allows medicinal and synthetic chemists to optimize radiolabeling conditions without the need to use radioactivity. Copyright © 2018 John Wiley & Sons, Ltd.

TU-AB-202-11: Tumor Segmentation by Fusion of Multi-Tracer PET Images Using Copula Based Statistical Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lapuyade-Lahorgue, J; Ruan, S; Li, H

Purpose: Multi-tracer PET imaging is getting more attention in radiotherapy by providing additional tumor volume information such as glucose and oxygenation. However, automatic PET-based tumor segmentation is still a very challenging problem. We propose a statistical fusion approach to joint segment the sub-area of tumors from the two tracers FDG and FMISO PET images. Methods: Non-standardized Gamma distributions are convenient to model intensity distributions in PET. As a serious correlation exists in multi-tracer PET images, we proposed a new fusion method based on copula which is capable to represent dependency between different tracers. The Hidden Markov Field (HMF) model ismore » used to represent spatial relationship between PET image voxels and statistical dynamics of intensities for each modality. Real PET images of five patients with FDG and FMISO are used to evaluate quantitatively and qualitatively our method. A comparison between individual and multi-tracer segmentations was conducted to show advantages of the proposed fusion method. Results: The segmentation results show that fusion with Gaussian copula can receive high Dice coefficient of 0.84 compared to that of 0.54 and 0.3 of monomodal segmentation results based on individual segmentation of FDG and FMISO PET images. In addition, high correlation coefficients (0.75 to 0.91) for the Gaussian copula for all five testing patients indicates the dependency between tumor regions in the multi-tracer PET images. Conclusion: This study shows that using multi-tracer PET imaging can efficiently improve the segmentation of tumor region where hypoxia and glucidic consumption are present at the same time. Introduction of copulas for modeling the dependency between two tracers can simultaneously take into account information from both tracers and deal with two pathological phenomena. Future work will be to consider other families of copula such as spherical and archimedian copulas, and to eliminate partial volume effect by considering dependency between neighboring voxels.« less

Three-Dimensional Bayesian Geostatistical Aquifer Characterization at the Hanford 300 Area using Tracer Test Data

NASA Astrophysics Data System (ADS)

Chen, X.; Murakami, H.; Hahn, M. S.; Hammond, G. E.; Rockhold, M. L.; Rubin, Y.

2010-12-01

Tracer testing under natural or forced gradient flow provides useful information for characterizing subsurface properties, by monitoring and modeling the tracer plume migration in a heterogeneous aquifer. At the Hanford 300 Area, non-reactive tracer experiments, in addition to constant-rate injection tests and electromagnetic borehole flowmeter (EBF) profiling, were conducted to characterize the heterogeneous hydraulic conductivity field. A Bayesian data assimilation technique, method of anchored distributions (MAD), is applied to assimilate the experimental tracer test data and to infer the three-dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of the Hanford formation. In this study, the prior information of the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using the constant-rate injection tests and the EBF data. The posterior distribution of the random field is obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells. The parallel three-dimensional flow and transport code PFLOTRAN is implemented to cope with the highly transient flow boundary conditions at the site and to meet the computational demand of the proposed method. The validation results show that the field conditioned on the tracer test data better reproduces the tracer transport behavior compared to the field characterized previously without the tracer test data. A synthetic study proves that the proposed method can effectively assimilate tracer test data to capture the essential spatial heterogeneity of the three-dimensional hydraulic conductivity field. These characterization results will improve conceptual models developed for the site, including reactive transport models. The study successfully demonstrates the capability of MAD to assimilate multi-scale multi-type field data within a consistent Bayesian framework. The MAD framework can potentially be applied to combine geophysical data with other types of data in site characterization.

Tracer Studies In A Laboratory Beach Subjected To Waves

EPA Science Inventory

This work investigated the washout of dissolved nutrients from beaches due to waves by conducting tracer studies in a laboratory beach facility. The effects of waves were studied in the case where the beach was subjected to the tide, and that in which no tidal action was present...

Effects of intermediate-energy electrons on mechanical and molecular properties of a polyetherimide

NASA Technical Reports Server (NTRS)

Long, S. A. T.; Long, E. R., Jr.

1984-01-01

An experiment, using 100-keV electrons and 10 to the 9th -rad doses, was conducted on Ultem polyetherimide film. Mechanical, electron paramagnetic resonance, and infrared spectroscopic data suggested that the radiation produced crosslinking and embrittlement of the material.

Short-term fluid, heat, and solute transport in deep 'georeservoirs' likely to become 'EGS': some challenges to ICDP hydrogeologists who might like using artificial tracers

NASA Astrophysics Data System (ADS)

Ghergut, Julia; Behrens, Horst; Huenges, Ernst; Rose, Peter; Sauter, Martin

2014-05-01

During Fall 2013, the Integrated Continental Scientific Drilling Programme (ICDP) set out to define a new Science Plan that shall replace its past-decade version (Harms et al., eds., 2005) for the decade to come. Geoscientists worldwide were welcomed to suggest new imaging and exploration methods, new sites to drill, new challenges to be addressed with a view at new 'societal needs' (Harms and Wiersberg 2013). Save for two outstanding exceptions at the Mutnovsky volcano in Russia and the KTB site in Germany, the use of artificial tracers, especially within forced-gradient tests, has not been on the agenda of most ICDP projects so far (other than for purposes of monitoring microbial contamination in conjunction with drilling activities); deep-reservoir exploration and characterization efforts were restrained to non-fluid-invasive techniques on the one hand, and to sites featuring some unique earth-historical traits, on the other hand. Surely, this was not for lack of interest in quantifying fluid transport in the deep subsurface in general, but mainly due to operational, technical, and financial constraints (lack of resources / lack of opportunity for significant fluid turnover within the target, deep-seated georeservoirs, and fear of persistent, large-scale georeservoir contamination by non-pristine fluids). - This is likely to change during the forthcoming decade(s), owing to worldwide increased interest in some 'georesource' or 'georeservoir' play types (Moeck 2013) that have not been in the ICDP focus so far, including non-volcanogenic geothermal, and allowing for man-made design and intervention into how those 'georesources' or 'georeservoirs' shall work for us. Among the latter, petrothermal systems (Jung 2013, Huenges and Jung 2004) acquire growing recognition as a promising (and maybe unique) option for baseload energy supply in vast areas of the Northern hemisphere, at very low emissions and (in the long run) moderate costs. With petrothermal coming into play, forced-gradient turnover of significant fluid amounts shall be on the agenda, and with it also a more comprehensive use of artificial tracers, for far more ambitious tasks than just the monitoring of drilling-related contamination. Since any ICDP project is likely to start (and mostly also end) with not more than one deep well, single-well forced-gradient test experience gained within the non-ICDP areas of hydrocarbon and geothermal exploration and engineering seem predestined for a specific knowledge transfer. Single-well 'push-then-pull' (SW) tracer methods appear as attractive for a number of reasons: less uncertainty of design and dimensioning, and lower tracer quantities required, than for inter-well (IW) tests; stronger tracer signals, enabling easier and cheaper metering, and shorter metering duration required, reaching higher tracer mass recovery, than in IW tests; last not least: no need for a second well! However, SW tracer signal inversion faces a major issue: the 'push-then-pull' design weakens the correlation between tracer residence time distribution (RTD) and fluid transport parameters, inducing insensitivity or ambiguity of tracer signal inversion against some of those georeservoir parameters that are supposed to be the target of tracer tests par excellence: pore velocity, transport-effective porosity, fracture aperture and spacing or density (where applicable), fluid/solid or fluid/fluid phase interface density. Hydraulic and geophysical methods cannot measure the transport-effective values of such parameters, because the signals they detect correlate neither with fluid motion, nor with material fluxes through (fluid-rock, or fluid-fluid) phase interfaces. Typically, pressure signals obtained in hydraulic tests do not enable to distinguish between geological formations with equal permeability, but different transport-effective porosity, nor between formations with equal permeability, equal transport-effective porosity, but different fluid-rock interface area. The ability to measure this latter parameter is crucial to lifetime predictability for geothermal, gas storage, waste disposal, or hydrocarbon reservoirs (especially in advanced depletion stages). From IW tracer signals, fluid RTD can be derived, whose statistical moments relate to major hydrogeological properties of target georeservoirs. By contrast, SW tests can be used to quantify processes other than advection-dispersion: typically, the exchange of some extensive quantity (mass, energy) between fluid and solid/fluid phases by matrix diffusion or sorption/partitioning, whose rate or amount depends on the phase saturation and/or interface area density. Flow-field reversal during the 'pull' stage of a SW test is supposed to largely compensate the effects of flow path heterogeneity, and to enhance the effects of tracer exchange processes at phase interfaces. However, it always destroys the equivalence between fluid RT and reservoir size; transport-effective porosities, closely relating to fluid RT, can only be measured reliably by means of conservative-tracer IW tests. The SW inability to determine porosity also (indirectly) impedes the SW-based ability to determine those complementary, non-advective parameters: increased sensitivity comes along with increased ambiguity. Reactive tracers can aid overcoming some of the limitations to parameter determinability associated with the SW design. Specific use of reactive tracers has first been made by Tomich et al. (1973), for a SW-based measurement of residual-oil saturation in (depleted) oil reservoirs; later on by Robinson (1985), for tracking temperature fronts in laboratory-scale geothermal-reservoir IW-test 'analogues'; more recently by Schaffer et al. (2013), for tracking brine-(sc)CO2 interfaces during CO2 injection within CCS research projects. The paper discusses some lessons derived from a twelve-year experience using artificial tracers in various IW and SW field tests in Germany, aimed at deep-georeservoir characterization and/or short- to mid-term process monitoring during reservoir operation: - if those tests have been successful to a certain extent, it was primarily owing to ascertainedly conservative tracer transport behavior; - if those tests have been of limited success, it was because of lack of reactive tracer species with well-defined, and reasonable properties (reasonable means: sensitive to 'something', but not to 'everything' that may 'happen' within the target georeservoir). If the artificial-tracer-based quantification of deep-georeservoir hydrogeology and of induced (short- to mid-term) transport processes therein is to become a task for some future ICDP projects, they will need to effectively address this dilemma. Further, if EGS, and especially the petrothermal type shall be on the agenda, then SW tests will be 'unavoidable'. Finally, if the most is to be made out of a SW test, then tailored reactive tracer pairs (Tomich et al. 1973, Ghergut et al. 2013) are a must: not just reactive, not just retarded, but: conservative alongside with reactive, and with contrasting retardation behavior between product and reactant. Selected references: Harms U, Koeberl C, Zoback M, eds (2005) Continental Scientific Drilling: A Decade of Progress, and Challenges for the Future. Springer, 366 pp. Harms U, Wiersberg T (2013) Conference on ICDP's New Science Plan. Scientific Drilling, 15: 77. Huenges E, Jung R (2004) Technologies for the Utilisation of Enhanced Geothermal Systems (www.bgr.de/ veransta/renewables_2004/presentations_DGP/Block1Introduction_pdf/2_Huenges_Jung.pdf) Jung R (2013) EGS - Goodbye or Back to the Future. Chapter 5, dx.doi.org/10.5772/56458 (www.intechopen.com/ books/effective-and-sustainable-hydraulic-fracturing) Moeck I (2013) Classification of geothermal plays according to geological habitats. IGA Academy Report 0101-2013 (www.geothermal-energy.org/iga_service_gmbh/projects/ifc_project/workshop_izmir.html) Robinson B A (1985) Non-reactive and chemically reactive tracers: Theory and applications. Ph D Thesis, MIT, Cambridge, MA, 551 pp. Rose P, Mella M, Kasteler C, Johnson S (2004) The estimation of reservoir pore volume from tracer data. Procs 29th Workshop on Geothermal Reservoir Engineering, Stanford University, SGP-TR-175 (pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2004/Rose.pdf) Schaffer M, Maier F, Licha T, Sauter M (2013) A new generation of tracers for the characterization of interfacial areas during supercritical carbon dioxide injections into deep saline aquifers: kinetic interface-sensitive (KIS) tracers. Intl J Greenhouse Gas Control, 14: 200-208. Tomich J F, Dalton R L Jr, Deans H A, Shallenberger L K (1973) Single-Well Tracer Method to Measure Residual Oil Saturation. J Petrol Technol Transact, 255: 211-218. Ghergut I, Behrens H, Sauter M (2013) Can Peclet numbers depend on tracer species? going beyond SW test insensitivity to advection or equilibrium exchange. Procs 38th Workshop on Geothermal Reservoir Engineering, Stanford University, SGP-TR-198 (pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2013/Ghergut5.pdf) Acknowledgements: The Göttingen group gratefully acknowledges financial support (to developing tracer SW methods for petrothermal-reservoir testing) from Baker Hughes (Celle) and the Lower-Saxonian Government within the interdisciplinary research project 'gebo' ('Geothermal Energy and High-Performance Drilling').

Peculiarities of magnetic and spin effects in a biradical/stable radical complex (three-spin system). Theory and comparison with experiment.

PubMed

Magin, Ilya M; Purtov, Petr A; Kruppa, Alexander I; Leshina, Tatiana V

2005-08-25

The field dependencies of biradical recombination probability in the presence of paramagnetic species with spins S(3) = 1 and S(3) = (1)/(2) have been calculated in the framework of the density matrix formalism. To describe the effect of the "third" spin on the spin evolution in biradical, we have also considered the spin exchange interaction between the added spin and one of the paramagnetic biradical centers. A characteristic feature of the calculated field dependencies is the existence of several extrema with positions and magnitudes depending on the signs and values of the exchange integrals in the system. The method proposed can be used to describe the effect of spin catalysis. It is shown that for the system with the third spin S(3) = 1 spin catalysis manifests itself stronger than in the case of spin S(3) = (1)/(2). The dependence of spin catalysis efficiency on the exchange interaction with the third spin has an extremum with position independent of the value of the spin added.

A multislice gradient echo pulse sequence for CEST imaging.

PubMed

Dixon, W Thomas; Hancu, Ileana; Ratnakar, S James; Sherry, A Dean; Lenkinski, Robert E; Alsop, David C

2010-01-01

Chemical exchange-dependent saturation transfer and paramagnetic chemical exchange-dependent saturation transfer are agent-mediated contrast mechanisms that depend on saturating spins at the resonant frequency of the exchangeable protons on the agent, thereby indirectly saturating the bulk water. In general, longer saturating pulses produce stronger chemical and paramagnetic exchange-dependent saturation transfer effects, with returns diminishing for pulses longer than T1. This could make imaging slow, so one approach to chemical exchange-dependent saturation transfer imaging has been to follow a long, frequency-selective saturation period by a fast imaging method. A new approach is to insert a short frequency-selective saturation pulse before each spatially selective observation pulse in a standard, two-dimensional, gradient-echo pulse sequence. Being much less than T1 apart, the saturation pulses have a cumulative effect. Interleaved, multislice imaging is straightforward. Observation pulses directed at one slice did not produce observable, unintended chemical exchange-dependent saturation transfer effects in another slice. Pulse repetition time and signal-to noise ratio increase in the normal way as more slices are imaged simultaneously. Copyright (c) 2009 Wiley-Liss, Inc.

Fusion of multi-tracer PET images for dose painting.

PubMed

Lelandais, Benoît; Ruan, Su; Denœux, Thierry; Vera, Pierre; Gardin, Isabelle

2014-10-01

PET imaging with FluoroDesoxyGlucose (FDG) tracer is clinically used for the definition of Biological Target Volumes (BTVs) for radiotherapy. Recently, new tracers, such as FLuoroThymidine (FLT) or FluoroMisonidazol (FMiso), have been proposed. They provide complementary information for the definition of BTVs. Our work is to fuse multi-tracer PET images to obtain a good BTV definition and to help the radiation oncologist in dose painting. Due to the noise and the partial volume effect leading, respectively, to the presence of uncertainty and imprecision in PET images, the segmentation and the fusion of PET images is difficult. In this paper, a framework based on Belief Function Theory (BFT) is proposed for the segmentation of BTV from multi-tracer PET images. The first step is based on an extension of the Evidential C-Means (ECM) algorithm, taking advantage of neighboring voxels for dealing with uncertainty and imprecision in each mono-tracer PET image. Then, imprecision and uncertainty are, respectively, reduced using prior knowledge related to defects in the acquisition system and neighborhood information. Finally, a multi-tracer PET image fusion is performed. The results are represented by a set of parametric maps that provide important information for dose painting. The performances are evaluated on PET phantoms and patient data with lung cancer. Quantitative results show good performance of our method compared with other methods. Copyright © 2014 Elsevier B.V. All rights reserved.

A comparison between tracer gas and aerosol particles distribution indoors: The impact of ventilation rate, interaction of airflows, and presence of objects.

PubMed

Bivolarova, M; Ondráček, J; Melikov, A; Ždímal, V

2017-11-01

The study investigated the separate and combined effects of ventilation rate, free convection flow produced by a thermal manikin, and the presence of objects on the distribution of tracer gas and particles in indoor air. The concentration of aerosol particles and tracer gas was measured in a test room with mixing ventilation. Three layouts were arranged: an empty room, an office room with an occupant sitting in front of a table, and a single-bed hospital room. The room occupant was simulated by a thermal manikin. Monodisperse particles of three sizes (0.07, 0.7, and 3.5 μm) and nitrous oxide tracer gas were generated simultaneously at the same location in the room. The particles and gas concentrations were measured in the bulk room air, in the breathing zone of the manikin, and in the exhaust air. Within the breathing zone of the sitting occupant, the tracer gas emerged as reliable predictor for the exposure to all different-sized test particles. A change in the ventilation rate did not affect the difference in concentration distribution between tracer gas and larger particle sizes. Increasing the room surface area did not influence the similarity in the dispersion of the aerosol particles and the tracer gas. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Prediction of Down-Gradient Impacts of DNAPL Source Depletion Using Tracer Techniques

NASA Astrophysics Data System (ADS)

Basu, N. B.; Fure, A. D.; Jawitz, J. W.

2006-12-01

Four simplified DNAPL source depletion models that have been discussed in the literature recently are evaluated for the prediction of long-term effects of source depletion under natural gradient flow. These models are simple in form (a power function equation is an example) but are shown here to serve as mathematical analogs to complex multiphase flow and transport simulators. One of the source depletion models, the equilibrium streamtube model, is shown to be relatively easily parameterized using non-reactive and reactive tracers. Non-reactive tracers are used to characterize the aquifer heterogeneity while reactive tracers are used to describe the mean DNAPL mass and its distribution. This information is then used in a Lagrangian framework to predict source remediation performance. In a Lagrangian approach the source zone is conceptualized as a collection of non-interacting streamtubes with hydrodynamic and DNAPL heterogeneity represented by the variation of the travel time and DNAPL saturation among the streamtubes. The travel time statistics are estimated from the non-reactive tracer data while the DNAPL distribution statistics are estimated from the reactive tracer data. The combined statistics are used to define an analytical solution for contaminant dissolution under natural gradient flow. The tracer prediction technique compared favorably with results from a multiphase flow and transport simulator UTCHEM in domains with different hydrodynamic heterogeneity (variance of the log conductivity field = 0.2, 1 and 3).

Using predictive uncertainty analysis to optimise tracer test design and data acquisition

NASA Astrophysics Data System (ADS)

Wallis, Ilka; Moore, Catherine; Post, Vincent; Wolf, Leif; Martens, Evelien; Prommer, Henning

2014-07-01

Tracer injection tests are regularly-used tools to identify and characterise flow and transport mechanisms in aquifers. Examples of practical applications are manifold and include, among others, managed aquifer recharge schemes, aquifer thermal energy storage systems and, increasingly important, the disposal of produced water from oil and shale gas wells. The hydrogeological and geochemical data collected during the injection tests are often employed to assess the potential impacts of injection on receptors such as drinking water wells and regularly serve as a basis for the development of conceptual and numerical models that underpin the prediction of potential impacts. As all field tracer injection tests impose substantial logistical and financial efforts, it is crucial to develop a solid a-priori understanding of the value of the various monitoring data to select monitoring strategies which provide the greatest return on investment. In this study, we demonstrate the ability of linear predictive uncertainty analysis (i.e. “data worth analysis”) to quantify the usefulness of different tracer types (bromide, temperature, methane and chloride as examples) and head measurements in the context of a field-scale aquifer injection trial of coal seam gas (CSG) co-produced water. Data worth was evaluated in terms of tracer type, in terms of tracer test design (e.g., injection rate, duration of test and the applied measurement frequency) and monitoring disposition to increase the reliability of injection impact assessments. This was followed by an uncertainty targeted Pareto analysis, which allowed the interdependencies of cost and predictive reliability for alternative monitoring campaigns to be compared directly. For the evaluated injection test, the data worth analysis assessed bromide as superior to head data and all other tracers during early sampling times. However, with time, chloride became a more suitable tracer to constrain simulations of physical transport processes, followed by methane. Temperature data was assessed as the least informative of the solute tracers. However, taking costs of data acquisition into account, it could be shown that temperature data when used in conjunction with other tracers was a valuable and cost-effective marker species due to temperatures low cost to worth ratio. In contrast, the high costs of acquisition of methane data compared to its muted worth, highlighted methanes unfavourable return on investment. Areas of optimal monitoring bore position as well as optimal numbers of bores for the investigated injection site were also established. The proposed tracer test optimisation is done through the application of common use groundwater flow and transport models in conjunction with publicly available tools for predictive uncertainty analysis to provide modelers and practitioners with a powerful yet efficient and cost effective tool which is generally applicable and easily transferrable from the present study to many applications beyond the case study of injection of treated CSG produced water.

Evaluating 10B-enriched Boric Acid, Bromide, and Heat as Tracers of Recycled Groundwater Flow near MAR Operations

NASA Astrophysics Data System (ADS)

Becker, T.; Clark, J. F.

2012-12-01

Coupled with the unpredictability of a changing climate, the projected growth in human population over the next century requires new and innovative ways to augment already-depleted water supplies. An increasingly popular and promising development is managed aquifer recharge (MAR), a cost-effective method of intentionally storing potable water in groundwater aquifers at engineered sites worldwide. Reclaimed (or recycled) water, defined as cleaned and treated wastewater, will account for a larger portion of MAR water in future years. A crucial component for managing groundwater recharged with reclaimed water is its subsurface travel time. The California Department of Public Health (CDPH), with the most recent draft of regulations issued on November 21, 2011, requires the application of groundwater tracers to demonstrate subsurface residence time. Residence time increases the quality of reclaimed water via soil-aquifer treatment (SAT), which includes mechanisms such as sorption, biological degradation, and microbial inactivation to remove potential contaminants or pathogens. This study addresses the need for an appropriate tracer to determine groundwater residence times near MAR facilities. Standard shallow groundwater dating techniques, such as T/3He and chlorofluorocarbon (CFC) methods, cannot be used because their uncertainties are typically ± 2 years, longer than the target CDPH retention time of ~6 months. These methods also cannot map preferential flow paths. Sulfur hexafluoride (SF6), a nonreactive synthetic gas, is well-established as a deliberate tracer for determining subsurface travel time; however, SF6 is a very strong greenhouse gas and the California Air Resources Board (CARB) is regulating its emission. Other tracers, such as noble gas isotopes, that have successfully determined subsurface retention times are impractical due to their high cost. A multi-tracer experiment at the San Gabriel Spreading Grounds test basin (Montebello Forebay, Los Angeles County, CA, USA) has been in progress since September 6, 2011, following injection of boric acid enriched in boron-10 (10B) and bromide (Br-) tracers. Tracer concentrations are collected at 9 monitoring wells that have pre-experiment estimated travel times between 0.5 to 180 days. Results indicate that 10B-enriched boric acid is an effective deliberate tracer at MAR sites; however, the ion's movement is slightly retarded relative to bromide by the substrate. 10B/Br- travel time ratios range from 1 to 1.4. In addition to the two deliberate geochemical tracers, heat is being evaluated as a possible intrinsic tracer at MAR sites. At the time of the experiment (late summer), reclaimed water was significantly warmer (~20°F) than the native groundwater as it entered the system. Time series are developed from loggers outfitted at each monitoring well, with measurements recorded hourly accurate to one thousandth of a degree. Results are similar to 10B & Br- travel times and validate the potential of heat as an intrinsic tracer.

Quantitative Visualization of Dynamic Tracer Transportation in the Extracellular Space of Deep Brain Regions Using Tracer-Based Magnetic Resonance Imaging.

PubMed

Hou, Jin; Wang, Wei; Quan, Xianyue; Liang, Wen; Li, Zhiming; Chen, Deji; Han, Hongbin

2017-09-03

BACKGROUND This study assessed an innovative tracer-based magnetic resonance imaging (MRI) system to visualize the dynamic transportation of tracers in regions of deep brain extracellular space (ECS) and to measure transportation ability and ECS structure. MATERIAL AND METHODS Gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) was the chosen tracer and was injected into the caudate nucleus and thalamus. Real-time dynamic transportation of Gd-DTPA in ECS was observed and the results were verified by laser scanning confocal microscopy. Using Transwell assay across the blood-brain barrier, a modified diffusion equation was further simplified. Effective diffusion coefficient D* and tortuosity λ were calculated. Immunohistochemical staining and Western blot analysis were used to investigate the extracellular matrix contributing to ECS structure. RESULTS Tracers injected into the caudate nucleus were transported to the ipsilateral frontal and temporal cortices away from the injection points, while both of them injected into the thalamus were only distributed on site. Although the caudate nucleus was closely adjacent to the thalamus, tracer transportation between partitions was not observed. In addition, D* and the λ showed statistically significant differences between partitions. ECS was shown to be a physiologically partitioned system, and its division is characterized by the unique distribution territory and transportation ability of substances located in it. Versican and Tenascin R are possible contributors to the tortuosity of ECS. CONCLUSIONS Tracer-based MRI will improve our understanding of the brain microenvironment, improve the techniques for local delivery of drugs, and highlight brain tissue engineering fields in the future.

Three-dimensional Bayesian geostatistical aquifer characterization at the Hanford 300 Area using tracer test data

NASA Astrophysics Data System (ADS)

Chen, Xingyuan; Murakami, Haruko; Hahn, Melanie S.; Hammond, Glenn E.; Rockhold, Mark L.; Zachara, John M.; Rubin, Yoram

2012-06-01

Tracer tests performed under natural or forced gradient flow conditions can provide useful information for characterizing subsurface properties, through monitoring, modeling, and interpretation of the tracer plume migration in an aquifer. Nonreactive tracer experiments were conducted at the Hanford 300 Area, along with constant-rate injection tests and electromagnetic borehole flowmeter tests. A Bayesian data assimilation technique, the method of anchored distributions (MAD) (Rubin et al., 2010), was applied to assimilate the experimental tracer test data with the other types of data and to infer the three-dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of the Hanford formation.In this study, the Bayesian prior information on the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using constant-rate injection and borehole flowmeter test data. The posterior distribution of the conductivity field was obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells. MAD was implemented with the massively parallel three-dimensional flow and transport code PFLOTRAN to cope with the highly transient flow boundary conditions at the site and to meet the computational demands of MAD. A synthetic study proved that the proposed method could effectively invert tracer test data to capture the essential spatial heterogeneity of the three-dimensional hydraulic conductivity field. Application of MAD to actual field tracer data at the Hanford 300 Area demonstrates that inverting for spatial heterogeneity of hydraulic conductivity under transient flow conditions is challenging and more work is needed.

Prediction of iodine-131 biokinetics and radiation doses from therapy on the basis of tracer studies: an important question for therapy planning in nuclear medicine.

PubMed

Willegaignon, José; Pelissoni, Rogério A; Lima, Beatriz C G D; Sapienza, Marcelo T; Coura-Filho, George B; Buchpiguel, Carlos A

2016-05-01

This study aimed to present a comparison of iodine-131 (I) biokinetics and radiation doses to red-marrow (rm) and whole-body (wb), following the administration of tracer and therapeutic activities, as a means of confirming whether I clearance and radiation doses for therapy procedures can be predicted by tracer activities. Eleven differentiated thyroid cancer patients were followed after receiving tracer and therapeutic I activity. Whole-body I clearance was estimated using radiation detectors and OLINDA/EXM software was used to calculate radiation doses to rm and wb. Tracer I activity of 86 (±14) MBq and therapeutic activity of 8.04 (±1.18) GBq were administered to patients, thereby producing an average wb I effective half-time and residence time of, respectively, 13.51 (±4.05) and 23.13 (±5.98) h for tracer activities and 13.32 (±3.38) and 19.63 (±4.77) h for therapy. Radiation doses to rm and wb were, respectively, 0.0467 (±0.0208) and 0.0589 (±0.0207) mGy/MBq in tracer studies and 0.0396 (±0.0169) and 0.0500 (±0.0163) mGy/MBq in therapy. Although the differences were not considered statistically significant between averages, those between the values of effective half-times (P=0.906), residence times (P=0.145), and radiation doses to rm (P=0.393) and to wb (P=0.272), from tracer and therapy procedures, large differences of up to 80% in wb I clearance, and up to 50% in radiation doses were observed when patients were analyzed individually, thus impacting on the total amount of I activity calculated to be safe for application in individual therapy. I biokinetics and radiation doses to rm and wb in therapy procedures are well predicted by diagnostic activities when average values of a group of patients are compared. Nonetheless, when patients are analyzed individually, significant differences may be encountered, thus implying that nuclear medicine therapy-planning requires due consideration of changes in individual patient-body status from initial tracer to final therapy procedures to thus provide appropriate adjustments in therapeutic activities.

The effect of physical back-diffusion of 13CO2 tracer on the coupling between photosynthesis and soil CO2 efflux in grassland.

PubMed

Burri, Susanne; Sturm, Patrick; Baur, Thomas; Barthel, Matti; Knohl, Alexander; Buchmann, Nina

2014-01-01

Pulse labelling experiments provide a common tool to study short-term processes in the plant-soil system and investigate below-ground carbon allocation as well as the coupling of soil CO(2) efflux to photosynthesis. During the first hours after pulse labelling, the measured isotopic signal of soil CO(2) efflux is a combination of both physical tracer diffusion into and out of the soil as well as biological tracer release via root and microbial respiration. Neglecting physical back-diffusion can lead to misinterpretation regarding time lags between photosynthesis and soil CO(2) efflux in grassland or any ecosystem type where the above-ground plant parts cannot be labelled in gas-tight chambers separated from the soil. We studied the effects of physical (13)CO(2) tracer back-diffusion in pulse labelling experiments in grassland, focusing on the isotopic signature of soil CO(2) efflux. Having accounted for back-diffusion, the estimated time lag for first tracer appearance in soil CO(2) efflux changed from 0 to 1.81±0.56 h (mean±SD) and the time lag for maximum tracer appearance from 2.67±0.39 to 9.63±3.32 h (mean±SD). Thus, time lags were considerably longer when physical tracer diffusion was considered. Using these time lags after accounting for physical back-diffusion, high nocturnal soil CO(2) efflux rates could be related to daytime rates of gross primary productivity (R(2)=0.84). Moreover, pronounced diurnal patterns in the δ(13)C of soil CO(2) efflux were found during the decline of the tracer over 3 weeks. Possible mechanisms include diurnal changes in the relative contributions of autotrophic and heterotrophic soil respiration as well as their respective δ(13)C values. Thus, after accounting for physical back-diffusion, we were able to quantify biological time lags in the coupling of photosynthesis and soil CO(2) efflux in grassland at the diurnal time scale.

Characterization of thermal tracer tests and heat exchanges in fractured media

NASA Astrophysics Data System (ADS)

de La Bernardie, Jérôme; Bour, Olivier; Guihéneuf, Nicolas; Chatton, Eliot; Labasque, Thierry; Longuevergne, Laurent; Le Lay, Hugo; Koch, Florian; Gerard, Marie-Françoise; Lavenant, Nicolas; Le Borgne, Tanguy

2016-04-01

Geothermal energy is a renewable energy source particularly attractive due to associated low greenhouse gas emission rates. Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (< 100m), because of the low permeability of the medium. In some cases, fractures may enhance permeability, but thermal energy storage at these shallow depths is still remaining very challenging because of the low storativity of the medium. Within this framework, the purpose of this study is to test the possibility of efficient thermal energy storage in shallow fractured rocks with a single well semi open loop heat exchanger (standing column well). For doing so, several heat tracer tests have been achieved along a borehole between two connected fractures. The heat tracer tests have been achieved at the experimental site of Ploemeur (H+ observatory network). The tracer tests consist in monitoring the temperature in the upper fracture while injecting hot water in the deeper one thanks to a field boiler. For such an experimental setup, the main difficulty to interpret the data comes from the requirement for separating the temperature advective signal of the tracer test (temperature recovery) from the heat increase due to injection of hot water through the borehole which induces heat losses all along the injection tube in the water column. For doing so, in addition to a double straddle packer used for isolating the injection chamber, the particularity of the experimental set up is the use of fiber optic distributed temperature sensing (FO-DTS); an innovative technology which allows spatial and temporal monitoring of the temperature all along the well. Thanks to this tool, we were able to estimate heat increases coming from diffusion along the injection tube which is found much lower than localized temperature increases resulting from tracer test recovery. With local temperatures probes, separating both effects would not have been feasible. We also show through signal processing how diffusive and advective effects may be differentiated. This allowed us to estimate temperature recovery for different heat tracer durations and setups. In particular we show that temperature recovery is highly dependent on hydraulic configuration such as perfect dipole or fully convergent heat tracer tests.

Free Radicals in Precision Cut Bovine Testicle Slices: Effects of 1,3,5 Trinitrobenzene Measured by Electron Paramagnetic Resonance.

DTIC Science & Technology

1996-04-01

toluene or dinitrotoluene and toluene diamine have oligoasthenoteratozoospermia ( Radike , 1985). Oligoasthenoteratozoospermiais a condition of...transfer interations between Superoxide ion and organic compounds. J. Phys Chem 77: 1722-1724. Radike , M. Reproductive Toxicology Chpterl6 In

Study of free radicals in gamma irradiated cellulose of cultural heritage materials using Electron Paramagnetic Resonance

NASA Astrophysics Data System (ADS)

Kodama, Yasko; Rodrigues, Orlando, Jr.; Garcia, Rafael Henrique Lazzari; Santos, Paulo de Souza; Vasquez, Pablo A. S.

2016-07-01

Main subject of this article was to study room temperature stable radicals in Co-60 gamma irradiated contemporary paper using Electron Paramagnetic Resonance spectrometer (EPR). XRD was used to study the effect of ionizing radiation on the morphology of book paper. SEM images presented regions with cellulose fibers and regions with particles agglomeration on the cellulose fibers. Those agglomerations were rich in calcium, observed by EDS. XRD analysis confirmed presence of calcium carbonate diffraction peaks. The main objective of this study was to propose a method using conventional kinetics chemical reactions for the observed radical formed by ionizing radiation. Therefore, further analyses were made to study the half-life and the kinetics of the free radical created. This method can be suitably applied to study radicals on cultural heritage objects.

Classical topological paramagnetism

NASA Astrophysics Data System (ADS)

Bondesan, R.; Ringel, Z.

2017-05-01

Topological phases of matter are one of the hallmarks of quantum condensed matter physics. One of their striking features is a bulk-boundary correspondence wherein the topological nature of the bulk manifests itself on boundaries via exotic massless phases. In classical wave phenomena, analogous effects may arise; however, these cannot be viewed as equilibrium phases of matter. Here, we identify a set of rules under which robust equilibrium classical topological phenomena exist. We write simple and analytically tractable classical lattice models of spins and rotors in two and three dimensions which, at suitable parameter ranges, are paramagnetic in the bulk but nonetheless exhibit some unusual long-range or critical order on their boundaries. We point out the role of simplicial cohomology as a means of classifying, writing, and analyzing such models. This opens an experimental route for studying strongly interacting topological phases of spins.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herojit Singh, L.; Govindaraj, R., E-mail: govind@igcar.gov.in; Rajagopalan, S.

Mössbauer spectroscopic studies have been carried out at different temperatures across ferromagnetic to paramagnetic transition in Ni{sub 50}Fe{sub 35}Co{sub 15} and the evolution of hyperfine parameters such as centre shift and magnetic hyperfine fields with temperature has been studied. Mössbauer spectrum obtained at 300 K in Ni{sub 50}Fe{sub 35}Co{sub 15} exhibiting fcc crystal structure is a six line pattern with the mean value of the hyperfine field close to 33 Tesla. Ferromagnetic to paramagnetic transition has been observed to occur in this system around 895 K matching with that of magnetization results. Debye temperature of this nickel rich alloy ismore » deduced to be around 470 K matching with that of Ni. Effect of prolonged annealing at 750 K on the magnetic property is also investigated with respect to the thermal stability of the alloy.« less

Magnetization and transport properties of single RPd2P2 (R=Y, La-Nd, Sm-Ho, Yb)

NASA Astrophysics Data System (ADS)

Drachuck, Gil; Boehmer, Anna; Bud'Ko, Sergey L.; Canfield, Paul

Single crystals of RPd2P2 (R=Y, La-Nd, Sm-Ho, Yb) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction, anisotropic temperature and field dependent magnetization and temperature dependent in-plane resistivity. Anisotropic magnetic properties, arising mostly from crystal electric field (CEF) effects, were observed for most magnetic rare earths. The experimentally estimated CEF parameters B02 were calculated from the anisotropic paramagnetic θab and θcvalues. Ordering temperatures, as well as the polycrystalline averaged paramagnetic Curie-Weiss temperature, θave, were extracted from magnetization and resistivity measurements. Work done at Ames Laboratory was supported by US Department of Energy, Basic Energy Sciences, Division of Materials Sciences and Engineering under Contract No. DE-AC02-07CH111358.

Assessing antibody microarrays for space missions: effect of long-term storage, gamma radiation, and temperature shifts on printed and fluorescently labeled antibodies.

PubMed

de Diego-Castilla, Graciela; Cruz-Gil, Patricia; Mateo-Martí, Eva; Fernández-Calvo, Patricia; Rivas, Luis A; Parro, Víctor

2011-10-01

Antibody microarrays are becoming frequently used tools for analytical purposes. A key factor for optimal performance is the stability of the immobilized (capturing) antibodies as well as those that have been fluorescently labeled to achieve the immunological test (tracers). This is especially critical for long-distance transport, field testing, or planetary exploration. A number of different environmental stresses may affect the antibody integrity, such as dryness, sudden temperature shift cycles, or, as in the case of space science, exposure to large quantities of the highly penetrating gamma radiation. Here, we report on the effect of certain stabilizing solutions for long-term storage of printed antibody microarrays under different conditions. We tested the effect of gamma radiation on printed and freeze- or vacuum-dried fluorescent antibodies at working concentrations (tracer antibodies), as well as the effect of multiple cycles of sudden and prolonged temperature shifts on the stability of fluorescently labeled tracer antibody cocktails. Our results show that (i) antibody microarrays are stable at room temperature when printed on stabilizing spotting solutions for at least 6 months, (ii) lyophilized and vacuum-dried fluorescently labeled tracer antibodies are stable for more than 9 months of sudden temperature shift cycles (-20°C to 25°C and 50°C), and (iii) both printed and freeze- or vacuum-dried fluorescent tracer antibodies are stable after several-fold excess of the dose of gamma radiation expected during a mission to Mars. Although different antibodies may exhibit different susceptibilities, we conclude that, in general, antibodies are suitable for use in planetary exploration purposes if they are properly treated and stored with the use of stabilizing substances.

Basic magnetic properties of bituminous coal

USGS Publications Warehouse

Alexander, C.C.; Thorpe, A.N.; Senftle, F.E.

1979-01-01

Magnetic susceptibility and other static magnetic parameters have been measured on a number of bituminous coals from various locations in the United States. The paramagnetic Curie constant correlates negatively with carbon concentration on a moisture-free basis. The major contribution to the total paramagnetism comes from the mineral matter rather than from free radicals or broken bonds. Analysis of the data indicates that the specific paramagnetism is generally lower in the mineral matter found in high-ash compared to low-ash coal. A substantial number of the coal specimens tested also had a ferromagnetic susceptibility which appeared to be associated with magnetite. Magnetite and ??-iron spherules, possibly of meteoritic or volcanic origin, were found in several specimens. ?? 1979.

Excess-Si related defect centers in buried SiO2 thin films

NASA Astrophysics Data System (ADS)

Warren, W. L.; Fleetwood, D. M.; Shaneyfelt, M. R.; Schwank, J. R.; Winokur, P. S.; Devine, R. A. B.

1993-06-01

Using electron paramagnetic resonance (EPR) and capacitance-voltage measurements we have investigated the role of excess-silicon related defect centers as charge traps in separation by the implantation of oxygen materials. Three types of EPR-active centers were investigated: oxygen vacancy Eγ' centers (O3≡Si• +Si≡O3), delocalized Eδ' centers, and D centers (Si3≡Si•). It was found that all of these paramagnetic centers are created by selective hole injection, and are reasonably ascribed as positively charged when paramagnetic. These results provide the first experimental evidence for (1) the charge state of the Eδ' center, and (2) that the D center is an electrically active point defect in these materials.

Single crystal EPR and optical studies of paramagnetic ions doped zinc potassium phosphate hexahydrate—Part I: Cu(II)—a case of orthorhombic symmetry

NASA Astrophysics Data System (ADS)

Sambasiva Rao, P.; Rajendiran, T. M.; Venkatesan, R.; Madhu, N.; Chandrasekhar, A. V.; Reddy, B. J.; Reddy, Y. P.; Ravikumar, R. V. S. S. N.

2001-12-01

Single crystal electron paramagnetic resonance (EPR) studies on Cu(II) doped zinc potassium phosphate hexahydrate (ZPPH) were carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice substitutionally in place of Zn(II) and the spin Hamiltonian parameters calculated from these spectra are gxx=2.188, gyy=2.032, gzz=2.373, Axx=50 G, Ayy=65.0 G and Azz=80 G. The g and A tensors were coincident and these values matched fairly well with the values obtained from powder spectrum. The bonding parameters have also been calculated.

Ionic liquids and solids with paramagnetic anions.

PubMed

Krieger, Brenna M; Lee, Heather Y; Emge, Thomas J; Wishart, James F; Castner, Edward W

2010-08-21

Four paramagnetic ionic compounds have been prepared and their magnetic, structural and thermal properties have been investigated. The four compounds are methylbutylpyrrolidinium tetrachloroferrate(III) ([Pyrr(14)](+)/[FeCl(4)](-)), methyltributylammonium tetrachloroferrate(III) ([N(1444)](+)/[FeCl(4)](-)), butylmethylimidazolium tetrachloroferrate(III) ([bmim](+)/[FeCl(4)](-)) and tetrabutylammonium bromotrichloroferrate(III) ([N(4444)](+)/[FeBrCl(3)](-)). Temperature-dependent studies of their magnetic behaviors show that all four compounds are paramagnetic at ambient temperatures. Glass transitions are observed for only two of the four compounds, [Pyrr(14)](+)/[FeCl(4)](-) and [bmim](+)/[FeCl(4)](-). Crystal structures for [Pyrr(14)](+)/[FeCl(4)](-) and [N(1444)](+)/[FeCl(4)](-) are compared with the previously reported [N(4444)](+)/[FeBrCl(3)](-).

The porphyrin-fullerene nanoparticles to promote the ATP overproduction in myocardium: 25Mg2+-magnetic isotope effect.

PubMed

Rezayat, S M; Boushehri, S V S; Salmanian, B; Omidvari, A H; Tarighat, S; Esmaeili, S; Sarkar, S; Amirshahi, N; Alyautdin, R N; Orlova, M A; Trushkov, I V; Buchachenko, A L; Liu, K C; Kuznetsov, D A

2009-04-01

This is a first case ever reported on the fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexyl fullerene-C(60)) designed for targeted delivery of the paramagnetic magnesium stable isotope to the heart muscle providing a sharp clinical effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 h after a single injection (0.03-0.1 LD(50)). A whole principle of this therapy is novel: (25)Mg(2+)-magnetic isotope effect selectively stimulates the ATP overproduction in the oxygen-depleted cells due to (25)Mg(2+) released by the nanoparticles. Being membranotropic cationites, these "smart nanoparticles" release the overactivating paramagnetic cations only in response to the metabolic acidic shift. The resulting positive changes in the heart cell energy metabolism may help to prevent and/or treat the local myocardial hypoxic disorders and, hence, protect the heart muscle from a serious damage in a vast variety of the hypoxia-caused clinical situations including both doxorubicin and 1-methylnicotineamide cardiotoxic side effects. Both pharmacokinetics and pharmacodynamics of the drug proposed make it suitable for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes.

Localization and diffusion of tracer particles in viscoelastic media with active force dipoles

NASA Astrophysics Data System (ADS)

Yasuda, Kento; Okamoto, Ryuichi; Komura, Shigeyuki; Mikhailov, Alexander S.

2017-02-01

Optical tracking in vivo experiments reveal that diffusion of particles in biological cells is strongly enhanced in the presence of ATP and the experimental data for animal cells could previously be reproduced within a phenomenological model of a gel with myosin motors acting within it (Fodor É. et al., EPL, 110 (2015) 48005). Here, the two-fluid model of a gel is considered where active macromolecules, described as force dipoles, cyclically operate both in the elastic and the fluid components. Through coarse-graining, effective equations of motions for idealized tracer particles displaying local deformations and local fluid flows are derived. The equation for deformation tracers coincides with the earlier phenomenological model and thus confirms it. For flow tracers, diffusion enhancement caused by active force dipoles in the fluid component, and thus due to metabolic activity, is found. The latter effect may explain why ATP-dependent diffusion enhancement could also be observed in bacteria that lack molecular motors in their skeleton or when the activity of myosin motors was chemically inhibited in eukaryotic cells.

Scale-by-scale contributions to Lagrangian particle acceleration

NASA Astrophysics Data System (ADS)

Lalescu, Cristian C.; Wilczek, Michael

2017-11-01

Fluctuations on a wide range of scales in both space and time are characteristic of turbulence. Lagrangian particles, advected by the flow, probe these fluctuations along their trajectories. In an effort to isolate the influence of the different scales on Lagrangian statistics, we employ direct numerical simulations (DNS) combined with a filtering approach. Specifically, we study the acceleration statistics of tracers advected in filtered fields to characterize the smallest temporal scales of the flow. Emphasis is put on the acceleration variance as a function of filter scale, along with the scaling properties of the relevant terms of the Navier-Stokes equations. We furthermore discuss scaling ranges for higher-order moments of the tracer acceleration, as well as the influence of the choice of filter on the results. Starting from the Lagrangian tracer acceleration as the short time limit of the Lagrangian velocity increment, we also quantify the influence of filtering on Lagrangian intermittency. Our work complements existing experimental results on intermittency and accelerations of finite-sized, neutrally-buoyant particles: for the passive tracers used in our DNS, feedback effects are neglected such that the spatial averaging effect is cleanly isolated.

Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

USGS Publications Warehouse

Shapiro, Stephanie D.; Plummer, Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.; Runkle, Donna L.

2012-01-01

Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N2, O2, Ar, CH4, and CO2) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N2-Ar-based) where available. The N2-Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N2-Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages compiled in this report are provided as a consistent means of reporting the tracer data. The tracer-based piston-flow ages may provide an initial interpretation of age in cases in which mixing is minimal and may aid in developing a basic conceptualization of groundwater age in an aquifer. These interpretations are based on the assumption that tracer transport is by advection only and that no mixing occurs. In addition, it is assumed that other uncertainties are minimized, including tracer degradation, sorption, contamination, or fractionation, and that terrigenic (natural) sources of tracers, and spatially variable atmospheric tracer concentrations are constrained.

Tracer-based quantification of individual frac discharge in single-well multiple-frac backflow: sensitivity study

NASA Astrophysics Data System (ADS)

Ghergut, Julia; Behrens, Horst; Sauter, Martin

2014-05-01

Within the deep-geothermal research project at GroßSchönebeck in the NE German Basin, targeting volcanic rocks (Lower Rotliegend) and siliciclastics (Upper Rotliegend) in the Lower Permian by means of a well doublet with several screening intervals between 3815 and 4247 m b.s.l., several artificial fractures with different geometric and hydraulic characteristics were created at each well, aiming to increase reservoir performance [1], [2]. It could not be told a priori which of the various fracturing treatments was to prove as most promising in terms of future reservoir productivity. At the intended-production well (GS-4), one large-area waterfrac was created in the low-permeability volcanic rocks, and two gel-proppant fractures in selected sandstone layers. Each fracturing treatment was accompanied by the injection of a water-dissolved tracer slug, followed by a defined volume of tracer-free ('chaser') fluid [3]. Each frac received a different species of a sulfonated aromatic acid salt, as a conservative water tracer. During subsequent backflow tests (either gas-based lifting, or production by means of a downhole submersible pump), each frac can contribute a certain (more or less constant) amount to the measured total discharge (also depending on whether and when each frac 'starts' contributing, and which effective aperture and area it actually 'manifests' during the process). Since these individual-frac discharge amounts cannot be measured directly, it was endeavoured to indirectly determine ('resolve') them from tracer signals as detectable in the overall backflow discharge. Therefore, we need to examine how these tracer signals depend on local discharge values and on local hydrogeologic parameters (matrix porosity, permeability distribution; frac transmissivity, thickness, effective area and aperture), and to what extent hydrogeological uncertainty will impede the inversion of local discharge values. To this end, a parameter sensitivity study was conducted on a simplified flow and tracer transport model (using FEOW and assuming Darcian flow within the matrix, Hagen-Poiseuille flow within the waterfrac, and either D or H-P flow within the gel-proppant fracs), whose main findings are: (1) late tracer signals are almost independent on matrix porosity, permeability distribution, frac area (length), thickness and effective aperture, while being highly sensitive to local discharge values; 'late' means a backflow or production volume at least fivefold the injected chaser volume; (2a) early tracer signals (concentration 'peak' intervals) may exhibit slight 'acceleration' and 'damping' with increasing matrix porosity or increasing frac aperture (a 'paradoxical' behaviour which is not really surprising for single-well 'push-then-backflow' tests, actually owing to flow-field dispersion[4]), and (2b) a non-monotonous response to varying frac area, being almost insensitive to frac area as long as the linear-flow regime prevails against the radial-flow regime (effects of the latter only becoming visible at very low frac areas); (2c) the effects of these various factors on early-time tracer signals are not unambiguously discernible from each other, and this ambiguity would persist even if frac-resolved (in-situ) discharge metering were feasible. For each of the three fracs (k=1,2,3), a 'type-curve' set Ck(Q,t) (parametrized by discharge values Q) can be generated. Since every frac received a different tracer, tracer signals measured within the overall backflow will differ from individual-frac type-curves by mere dilution (no 'superposition'). Type-curve dilution by factor Qk/Qtotal can be compared to measured tracer concentrations in the total discharge, ck(ti), (i = 1, ..., no. of tracer samplings). From a formal point of view, the unknown discharge values Qk can be determined as the solution of a linear optimization task subject to the constraint Q1 + Q2 + Q3 = Qtotal (the latter being a measured value). It is recommendable to perform 'optimization' manually, rather than by resorting to automated solutions provided by some linear programming software. The first items to inspect are the late-time height and slope of measured tracer signal 'tailings': their height yields a first approximation to dilution factors, and thus a first estimate for Qk, while late-time consistency of observed tailing slopes can be taken as indicative of the applicability of model presuppositions. To be noted, dilution factors associated with individual fracs can vary with time, since a steady-state discharge pattern might not be reached simultaneously at all fracs. The paper also discusses some reasons why early-time tracer signals are generally unsuited for frac discharge inversion. References: [1] Blöcher M G, Zimmermann G, Moeck I, Brandt W, Hassanzadegan A, Magri F (2010) 3D numerical modeling of hydrothermal processes during the lifetime of a deep geothermal reservoir. Geofluids, 10, 406-421. [2] Zimmermann G, Blöcher G, Reinicke A, Brandt W (2011) Rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system - Concepts and field results. Tectonophysics, 503, 146-154. [3] http://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2007/ghergut.pdf [4] http://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2013/Ghergut3.pdf ; ~Ghergut5.pdf Acknowledgements: Tracer tests at the GroßSchönebeck site were conducted with financial and operational support from the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and from the Helmholtz Research Centre GeoForschungsZentrum (GFZ) Potsdam. Modelling work was conducted within the 'gebo' project ('Geothermal Energy and High-Performance Drilling', www.gebo-nds.de), funded by the Lower-Saxonian government and by Baker Hughes (Celle), Germany.

Introduction to Spin Label Electron Paramagnetic Resonance Spectroscopy of Proteins

ERIC Educational Resources Information Center

Melanson, Michelle; Sood, Abha; Torok, Fanni; Torok, Marianna

2013-01-01

An undergraduate laboratory exercise is described to demonstrate the biochemical applications of electron paramagnetic resonance (EPR) spectroscopy. The beta93 cysteine residue of hemoglobin is labeled by the covalent binding of 3-maleimido-proxyl (5-MSL) and 2,2,5,5-tetramethyl-1-oxyl-3-methyl methanethiosulfonate (MTSL), respectively. The excess…

Method of manufacturing a high temperature superconductor with improved transport properties

DOEpatents

Balachandran, Uthamalingam; Siegel, Richard W.; Askew, Thomas R.

2001-01-01

A method of preparing a high temperature superconductor. A method of preparing a superconductor includes providing a powdered high temperature superconductor and a nanophase paramagnetic material. These components are combined to form a solid compacted mass with the paramagnetic material disposed on the grain boundaries of the polycrystaline high temperature superconductor.

THE INTERACTION OF PARAMAGNETIC RELAXATION REAGENTS WITH INTRA- AND INTERMOLECULAR HYDROGEN BONDED PHENOLS

EPA Science Inventory

Intermolecular electron-nuclear 13-C relaxation times (T(1)sup e's) from solutions containing the paramagnetic relaxation reagent (PARR), Cr(acac)3, used in conjunction with 13-C T(1)'s in diamagnetic solutions (intramolecular 13-C - (1)H dipolar T(1)'s) provide a significant inc...

Locations of radical species in black pepper seeds investigated by CW EPR and 9 GHz EPR imaging

NASA Astrophysics Data System (ADS)

Nakagawa, Kouichi; Epel, Boris

2014-10-01

In this study, noninvasive 9 GHz electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate the locations of paramagnetic species in black pepper seeds without further irradiation. First, lithium phthalocyanine (LiPC) phantom was used to examine 9 GHz EPR imaging capabilities. The 9 GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2 mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe3+, and Mn2+ complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1 h. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species were mostly located at the seed surface. Fewer radicals were found inside the seed. We demonstrated that the CW EPR and 9 GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds.

Locations of radical species in black pepper seeds investigated by CW EPR and 9GHz EPR imaging.

PubMed

Nakagawa, Kouichi; Epel, Boris

2014-10-15

In this study, noninvasive 9GHz electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate the locations of paramagnetic species in black pepper seeds without further irradiation. First, lithium phthalocyanine (LiPC) phantom was used to examine 9GHz EPR imaging capabilities. The 9GHz EPR-imager easily resolved the LiPC samples at a distance of ∼2mm. Then, commercially available black pepper seeds were measured. We observed signatures from three different radical species, which were assigned to stable organic radicals, Fe(3+), and Mn(2+) complexes. In addition, no EPR spectral change in the seed was observed after it was submerged in distilled H2O for 1h. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species were mostly located at the seed surface. Fewer radicals were found inside the seed. We demonstrated that the CW EPR and 9GHz EPR imaging were useful for the determination of the spatial distribution of paramagnetic species in various seeds. Copyright © 2014 Elsevier B.V. All rights reserved.

EPR investigation of electronic excitations in rare gas solids (Review Article)

NASA Astrophysics Data System (ADS)

Zhitnikov, R. A.; Dmitriev, Yu. A.

1998-10-01

The methods are described for producing unstable paramagnetic excited states in rare gas cryocrystals Ne, Ar, Kr, and Xe through the trapping, in the cryocrystals growing from the gas phase, the products of the gas discharge taking place in the same or other rare gas. The paper presents a technique and results of an observation and investigation of excited states in rare gas cryocrystals with electron paramagnetic resonance (EPR). The discovered unstable paramagnetic centers are interpreted as being local metastable excited np5(n+1)s atomic-type states in rare gas cryocrystals which are subject to the action of the anisotropic electric field resulted from the crystal surroundings distorted by the center. An account is given of the mechanisms for formation of observed paramagnetic excited states in cryocrystals which arise owing to the excitation energy of the metastable 3P2 atoms of Ne, Ar, Kr, Xe and He 23S1 and 21S0 atoms that form in the discharge in an appropriate gas and trap in the growing cryocrystal.

High-frequency EPR of surface impurities on nanodiamond

NASA Astrophysics Data System (ADS)

Peng, Zaili; Stepanov, Viktor; Takahashi, Susumu

Diamond is a fascinating material, hosting nitrogen-vacancy (NV) defect centers with unique magnetic and optical properties. There have been many reports that suggest the existence of paramagnetic impurities near surface of various kinds of diamonds. Electron paramagnetic resonance (EPR) investigation of mechanically crushed nanodiamonds (NDs) as well as detonation NDs revealed g 2 like signals that are attributed to structural defects and dangling bonds near the diamond surface. In this presentation, we investigate paramagnetic impurities in various sizes of NDs using high-frequency (HF) continuous wave (cw) and pulsed EPR spectroscopy. Strong size dependence on the linewidth of HF cw EPR spectra reveals the existence of paramagnetic impurities in the vicinity of the diamond surface. We also study the size dependence of the spin-lattice and spin-spin relaxation times (T1 and T2) of single substitutional nitrogen defects in NDs Significant deviations from the temperature dependence of the phonon-assisted T1 process were observed in the ND samples, and were attributed to the contribution from the surface impurities. This work was supported by the Searle Scholars Program and the National Science Foundation (DMR-1508661 and CHE-1611134).

Equation of state of paramagnetic CrN from ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Steneteg, Peter; Alling, Björn; Abrikosov, Igor A.

2012-04-01

The equation of state for chromium nitride has been debated in the literature in connection with a proposed collapse of its bulk modulus following the pressure-induced transition from the paramagnetic cubic phase to the antiferromagnetic orthorhombic phase [F. Rivadulla , Nature Mater.1476-112210.1038/nmat2549 8, 947 (2009); B. Alling , Nature Mater.1476-112210.1038/nmat2722 9, 283 (2010)]. Experimentally the measurements are complicated due to the low transition pressure, while theoretically the simulation of magnetic disorder represents a major challenge. Here a first-principles method is suggested for the calculation of thermodynamic properties of magnetic materials in their high-temperature paramagnetic phase. It is based on ab initio molecular dynamics and simultaneous redistributions of the disordered but finite local magnetic moments. We apply this disordered local moments molecular dynamics method to the case of CrN and simulate its equation of state. In particular the debated bulk modulus is calculated in the paramagnetic cubic phase and is shown to be very similar to that of the antiferromagnetic orthorhombic CrN phase for all considered temperatures.

Effect of perfusate hematocrit on urea permeability-surface area in isolated dog lung

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, R.E.; Roselli, R.J.; Haselton, F.R.

1986-10-01

Seven dog lower left lung lobes were statically inflated and perfused at a constant rate for each lobe with a perfusate in which the hematocrit was altered over a wide range. The permeability-surface area of urea was calculated from multiple indicator dilution curves using two separate injectates for each hematocrit level. One injectate contained only /sup 125/I-albumin as the vascular reference tracer and the other contained both /sup 51/Cr-erythrocytes and /sup 125/I-albumin as the vascular reference tracers; both contained (/sup 14/C)urea as the permeating tracer. The results strongly indicate that the phenomenon of erythrocyte trapping of urea does not affectmore » the calculation of urea permeability-surface area product provided the appropriate albumin-erythrocyte composite reference tracer is utilized in its calculation.« less

Simultaneous 3D tracking of passive tracers and microtubule bundles in an active gel

NASA Astrophysics Data System (ADS)

Fan, Yi; Breuer, Kenneth S.; Fluids Team

Kinesin-driven microtubule bundles generate a spontaneous flow in unconfined geometries. They exhibit properties of active matter, including the emergence of collective motion, reduction of apparent viscosity and consumption of local energy. Here we present results from 3D tracking of passive tracers (using Airy rings and 3D scanning) synchronized with 3D measurement of the microtubule bundles motion. This technique is applied to measure viscosity variation and collective flow in a confined geometry with particular attention paid to the self-pumping system recently reported by Wu et al. (2016). Results show that the viscosity in an equilibrium microtubule network is around half that of the isotropic unbundled microtubule solution. Cross-correlations of the active microtubule network and passive tracers define a neighborhood around microtubule bundles in which passive tracers are effectively transported. MRSEC NSF.

Simultaneous measurement of ventilation using tracer gas techniques and VOC concentrations in homes, garages and vehicles.

PubMed

Batterman, Stuart; Jia, Chunrong; Hatzivasilis, Gina; Godwin, Chris

2006-02-01

Air exchange rates and interzonal flows are critical ventilation parameters that affect thermal comfort, air migration, and contaminant exposure in buildings and other environments. This paper presents the development of an updated approach to measure these parameters using perfluorocarbon tracer (PFT) gases, the constant injection rate method, and adsorbent-based sampling of PFT concentrations. The design of miniature PFT sources using hexafluorotoluene and octafluorobenzene tracers, and the development and validation of an analytical GC/MS method for these tracers are described. We show that simultaneous deployment of sources and passive samplers, which is logistically advantageous, will not cause significant errors over multiday measurement periods in building, or over shorter periods in rapidly ventilated spaces like vehicle cabins. Measurement of the tracers over periods of hours to a week may be accomplished using active or passive samplers, and low method detection limits (<0.025 microg m(-3)) and high precisions (<10%) are easily achieved. The method obtains the effective air exchange rate (AER), which is relevant to characterizing long-term exposures, especially when ventilation rates are time-varying. In addition to measuring the PFT tracers, concentrations of other volatile organic compounds (VOCs) are simultaneously determined. Pilot tests in three environments (residence, garage, and vehicle cabin) demonstrate the utility of the method. The 4 day effective AER in the house was 0.20 h(-1), the 4 day AER in the attached garage was 0.80 h(-1), and 16% of the ventilation in the house migrated from the garage. The 5 h AER in a vehicle traveling at 100 km h(-1) under a low-to-medium vent condition was 92 h(-1), and this represents the highest speed test found in the literature. The method is attractive in that it simultaneously determines AERs, interzonal flows, and VOC concentrations over long and representative test periods. These measurements are practical, cost-effective, and helpful in indoor air quality and other investigations.

Feasibility of using sodium chloride as a tracer for the characterization of the distribution of matter in complex multi-compartment 3D bioreactors for stem cell culture.

PubMed

Gerlach, Jörg C; Witaschek, Tom; Strobel, Catrin; Brayfield, Candace A; Bornemann, Reinhard; Catapano, Gerardo; Zeilinger, Katrin

2010-06-01

The experimental characterization of the distribution of matter in complex multi-compartment three-dimensional membrane bioreactors for human cell culture is complicated by tracer interactions with the membranes and other bioreactor constituents. This is due to the fact that membranes with a high specific surface area often feature a hydrophobic chemical backbone that may adsorb tracers often used to this purpose, such as proteins and dyes. Membrane selectivity, and its worsening caused by protein adsorption, may also hinder tracer transfer across neighboring compartments, thus preventing effective characterization of the distribution of matter in the whole bioreactor. Tracer experiments with sodium chloride (NaCl) may overcome some of these limitations and be effectively used to characterize the distribution of matter in complex 3D multi-compartments membrane bioreactors for stem cell culture. NaCl freely permeates most used membranes, it does not adsorb on uncharged membranes, and its concentration may be accurately measured in terms of solution conductivity. In this preliminary study, the feasibility of complex multi-compartment membrane bioreactors was investigated with a NaCl concentration pulse challenge to characterize how their distribution of matter changes when they are operated under different conditions. In particular, bioreactors consisting of three different membrane types stacked on top of one another to form a 3D network were characterized under different feed conditions.

Magnetic anisotropy of some phyllosilicates

NASA Astrophysics Data System (ADS)

Borradaile, Graham J.; Werner, Tomasz

1994-08-01

Magnetic susceptibility, anisotropy of susceptibility and hysteresis of single microcrystals of chlorite, biotite, phlogopite, muscovite, zinnwaldite and fuchsite were measured in low and high magnetic fields with an alternating gradient force magnetometer (Micromag). Their properties are sufficient to account for the low field susceptibility (AMS) of most micaceous rocks. Nearly all samples show some ferromagnetic contribution at low fields due to inclusions of pseudosingle domain and multidomain magnetite. The paramagnetic contribution isolated at high fields usually exceeds the ferromagnetic contribution. The paramagnetic susceptibility is intrinsic to the silicate lattice and agrees with values predicted from chemical composition within the limits of error. The minimum susceptibility is nearly parallel to c, another axis is parallel to b and the third susceptibility (usually the maximum) is close to a. The paramagnetic susceptibility has a disk-shaped magnitude ellipsoid with strong anisotropy ( P' < 2). The ferromagnetic contributions at low fields have more variably shaped ellipsoids with greater eccentricity ( P' < 5). The silicate lattice does not constrain their orientation. Our technique cannot determine the principal axes of the ferromagnetic component. However, its principal values usually correspond with the paramagnetic principal susceptibilities in order of magnitude. Thus, the combined paramagnetic-ferromagnetic anisotropy recognised in routine studies of AMS should faithfully represent the petrofabric of most micaceous rocks. Nevertheless, nearly 10% of our samples have incompatible anisotropy ellipsoids for the silicate host and magnetite inclusions. These yield a net inverse AMS that does not correctly represent the orientation of the silicate lattice. Therefore, some caution is necessary in petrofabric-AMS studies of micaceous rocks.

Diffusional mechanisms augment the fluorine magnetic resonance relaxation in paramagnetic perfluorocarbon nanoparticles that provides a “relaxation switch” for detecting cellular endosomal activation

PubMed Central

Hu, Lingzhi; Zhang, Lei; Chen, Junjie; Lanza, Gregory M.; Wickline, Samuel A.

2011-01-01

Purpose To develop a physical model for the 19F relaxation enhancement in paramagnetic perfluorocarbon nanoparticles (PFC NP) and demonstrate its application in monitoring cellular endosomal functionality through a “19F relaxation switch” phenomenon. Materials and Methods An explicit expression for 19F longitudinal relaxation enhancement was derived analytically. Monte-Carlo simulation was performed to confirm the gadolinium induced magnetic field inhomogenity inside the PFC NP. Field dependent T1 measurements for three types of paramagnetic PFC NPs were carried out to validate the theoretical prediction. Based on the physical model, 19F and 1H relaxation properties of macrophage internalized paramagnetic PFC NPs were measured to evaluate the intracellular process of NPs by macrophages in vitro. Results The theoretical description was confirmed experimentally by field-dependent T1 measurements. The shortening of 19F T1 was found to be attributed to the Brownian motion of PFC molecules inside the NP in conjunction with their ability to permeate into the lipid surfactant coating. A dramatic change of 19F T1 was observed upon endocytosis, revealing the transition from intact bound PFC NP to processed constituents. Conclusion The proposed first-principle analysis of 19F spins in paramagnetic PFC NP relates their structural parameters to the special MR relaxation features. The demonstrated “19F relaxation switch” phenomenon is potentially useful for monitoring cellular endosomal functionality. PMID:21761488

Dynamic nuclear polarization of (1)H, (13)C, and (59)Co in a tris(ethylenediamine)cobalt(III) crystalline lattice doped with Cr(III).

PubMed

Corzilius, Björn; Michaelis, Vladimir K; Penzel, Susanne A; Ravera, Enrico; Smith, Albert A; Luchinat, Claudio; Griffin, Robert G

2014-08-20

The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that (1)H, (13)C, and (59)Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins.

Dynamic Nuclear Polarization of 1H, 13C, and 59Co in a Tris(ethylenediamine)cobalt(III) Crystalline Lattice Doped with Cr(III)

PubMed Central

2015-01-01

The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that 1H, 13C, and 59Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins. PMID:25069794

Effect of ferroelastic domain pattern changes on the EPR spectra in TDM

NASA Astrophysics Data System (ADS)

Zapart, W.; Zapart, M. B.

2011-09-01

This article presents polarized light microscopy studies of the ferroelastic domain structure and the analysis of electron paramagnetic resonance spectra of Cr3+ admixture ions in trigonal double molybdates. The correlation has been found between abnormal EPR lineshape and domain structure in ferroelastic phases of these crystals.

Rapid Multi-Tracer PET Tumor Imaging With F-FDG and Secondary Shorter-Lived Tracers.

PubMed

Black, Noel F; McJames, Scott; Kadrmas, Dan J

2009-10-01

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer (62)Cu - PTSM (blood flow) + (62)Cu - ATSM (hypoxia) tumor imaging. In this work, the feasibility of rapidly imaging (18)F-FDG plus one or two of these shorter-lived secondary tracers was evaluated in the same tumor model. Dynamic PET imaging was performed in four dogs with pre-existing tumors, and the raw scan data was combined to emulate 60 minute long dual- and triple-tracer scans, using the single-tracer scans as gold standards. The multi-tracer data were processed for static (SUV) and kinetic (K(1), K(net)) endpoints for each tracer, followed by linear regression analysis of multi-tracer versus single-tracer results. Static and quantitative dynamic imaging measures of FDG were both accurately recovered from the multi-tracer scans, closely matching the single-tracer FDG standards (R > 0.99). Quantitative blood flow information, as measured by PTSM K(1) and SUV, was also accurately recovered from the multi-tracer scans (R = 0.97). Recovery of ATSM kinetic parameters proved more difficult, though the ATSM SUV was reasonably well recovered (R = 0.92). We conclude that certain additional information from one to two shorter-lived PET tracers may be measured in a rapid multi-tracer scan alongside FDG without compromising the assessment of glucose metabolism. Such additional and complementary information has the potential to improve tumor characterization in vivo, warranting further investigation of rapid multi-tracer techniques.

Rapid Multi-Tracer PET Tumor Imaging With 18F-FDG and Secondary Shorter-Lived Tracers

PubMed Central

Black, Noel F.; McJames, Scott; Kadrmas, Dan J.

2009-01-01

Rapid multi-tracer PET, where two to three PET tracers are rapidly scanned with staggered injections, can recover certain imaging measures for each tracer based on differences in tracer kinetics and decay. We previously showed that single-tracer imaging measures can be recovered to a certain extent from rapid dual-tracer 62Cu – PTSM (blood flow) + 62Cu — ATSM (hypoxia) tumor imaging. In this work, the feasibility of rapidly imaging 18F-FDG plus one or two of these shorter-lived secondary tracers was evaluated in the same tumor model. Dynamic PET imaging was performed in four dogs with pre-existing tumors, and the raw scan data was combined to emulate 60 minute long dual- and triple-tracer scans, using the single-tracer scans as gold standards. The multi-tracer data were processed for static (SUV) and kinetic (K1, Knet) endpoints for each tracer, followed by linear regression analysis of multi-tracer versus single-tracer results. Static and quantitative dynamic imaging measures of FDG were both accurately recovered from the multi-tracer scans, closely matching the single-tracer FDG standards (R > 0.99). Quantitative blood flow information, as measured by PTSM K1 and SUV, was also accurately recovered from the multi-tracer scans (R = 0.97). Recovery of ATSM kinetic parameters proved more difficult, though the ATSM SUV was reasonably well recovered (R = 0.92). We conclude that certain additional information from one to two shorter-lived PET tracers may be measured in a rapid multi-tracer scan alongside FDG without compromising the assessment of glucose metabolism. Such additional and complementary information has the potential to improve tumor characterization in vivo, warranting further investigation of rapid multi-tracer techniques. PMID:20046800

Evaluation of groundwater residence time in a high mountain aquifer system (Sacramento Mountains, USA): insights gained from use of multiple environmental tracers

NASA Astrophysics Data System (ADS)

Land, Lewis; Timmons, Stacy

2016-06-01

The New Mexico Bureau of Geology and Mineral Resources (USA) has conducted a regional investigation of groundwater residence time within the southern Sacramento Mountains aquifer system using multiple environmental tracers. Results of the tracer surveys indicate that groundwater in the southern Sacramento Mountains ranges in age from less than 1 year to greater than 50 years, although the calculated ages contain uncertainties and vary significantly depending on which tracer is used. A distinctive feature of the results is discordance among the methods used to date groundwater in the study area. This apparent ambiguity results from the effects of a thick unsaturated zone, which produces non-conservative behavior among the dissolved gas tracers, and the heterogeneous character and semi-karstic nature of the aquifer system, which may yield water from matrix porosity, fractures, solution-enlarged conduits, or a combination of the three. The data also indicate mixing of groundwater from two or more sources, including recent recharge originating from precipitation at high elevations, old groundwater stored in the matrix, and pre-modern groundwater upwelling along fault zones. The tracer data have also been influenced by surface-water/groundwater exchange via losing streams and lower elevation springs (groundwater recycling). This study highlights the importance of using multiple tracers when conducting large-scale investigations of a heterogeneous aquifer system, and sheds light on characteristics of groundwater flow systems that can produce discrepancies in calculations of groundwater age.

Control of mixing hotspots over the vertical turbulent flux in the Southern Ocean

NASA Astrophysics Data System (ADS)

Mashayek, Ali; Ferrari, Raffaele; Ledwell, Jim; Merrifield, Sophia; St. Laurent, Louis

2015-11-01

Vertical turbulent mixing in the Southern Ocean is believed to play a role in setting the rate of the ocean Meridional Overturning Circulation (MOC), one of the key regulators of the climate system. The extent to which mixing influences the MOC, however, depends on its strength and is still under debate. To address this, a passive tracer was released upstream of the Drake Passage in 2009 as a part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). Vertical dispersion of the tracer was measured in subsequent years to estimate vertical mixing. The inferred effective turbulent diffusivity values have proven larger than those obtained from localized measurements of shear made at various locations along the path of the tracer. While the values inferred from tracer imply a key role played by mixing in setting the MOC, those based on localized measurements suggest otherwise. In this work we employ the tracer data and localized turbulence measurements from DIMES in combination with a high resolution numerical ocean model to investigate whether these discrepancies are the result of different sampling strategies: the microstructure profiles sampled mixing only in a few regions, while the tracer sampled mixing over a much wider area as it spread spatially.

Ambient changes in tracer concentrations from a multilevel monitoring system in Basalt

USGS Publications Warehouse

Bartholomay, Roy C.; Twining, Brian V.; Rose, Peter E.

2014-01-01

Starting in 2008, a 4-year tracer study was conducted to evaluate ambient changes in groundwater concentrations of a 1,3,6-naphthalene trisulfonate tracer that was added to drill water. Samples were collected under open borehole conditions and after installing a multilevel groundwater monitoring system completed with 11 discrete monitoring zones within dense and fractured basalt and sediment layers in the eastern Snake River aquifer. The study was done in cooperation with the U.S. Department of Energy to test whether ambient fracture flow conditions were sufficient to remove the effects of injected drill water prior to sample collection. Results from thief samples indicated that the tracer was present in minor concentrations 28 days after coring, but was not present 6 months after coring or 7 days after reaming the borehole. Results from sampling the multilevel monitoring system indicated that small concentrations of the tracer remained in 5 of 10 zones during some period after installation. All concentrations were several orders of magnitude lower than the initial concentrations in the drill water. The ports that had remnant concentrations of the tracer were either located near sediment layers or were located in dense basalt, which suggests limited groundwater flow near these ports. The ports completed in well-fractured and vesicular basalt had no detectable concentrations.

Cosmological constraints from multiple tracers in spectroscopic surveys

NASA Astrophysics Data System (ADS)

Alarcon, Alex; Eriksen, Martin; Gaztanaga, Enrique

2018-01-01

We use the Fisher matrix formalism to study the expansion and growth history of the Universe using galaxy clustering with 2D angular cross-correlation tomography in spectroscopic or high-resolution photometric redshift surveys. The radial information is contained in the cross-correlations between narrow redshift bins. We show how multiple tracers with redshift space distortions cancel sample variance and arbitrarily improve the constraints on the dark energy equation of state ω(z) and the growth parameter γ in the noiseless limit. The improvement for multiple tracers quickly increases with the bias difference between the tracers, up to a factor ∼4 in FoMγω. We model a magnitude limited survey with realistic density and bias using a conditional luminosity function, finding a factor 1.3-9.0 improvement in FoMγω - depending on global density - with a split in a halo mass proxy. Partly overlapping redshift bins improve the constraints in multiple tracer surveys a factor ∼1.3 in FoMγω. This finding also applies to photometric surveys, where the effect of using multiple tracers is magnified. We also show large improvement on the FoM with increasing density, which could be used as a trade-off to compensate some possible loss with radial resolution.

A tracer experiment to study flow paths of water in a forest soil

NASA Astrophysics Data System (ADS)

Feyen, H.; Wunderli, H.; Wydler, H.; Papritz, A.

1999-12-01

This contribution discusses a tracer experiment, which was performed to study the flow paths of water in a macroporous forest soil. The experiment was performed in the framework of a study on the cycling of nitrogen in forested Prealpine catchments, in which losses of nitrate from virtually pristine areas were observed. Two soil plots with distinct micro-topography and top-soil were investigated: a well drained mor humus on a mound and a wet muck humus in a small depression. To reveal the effect of the soil horizons on the flow regime, tracers were applied both onto the soil surface and injected into the sub-soil. Tracers injected directly into the gleyic sub-soil reached the outlet (at a distance of 3.3 m) about 1000 times faster than could be expected from the saturated hydraulic conductivity of the soil matrix. Peak concentrations were observed after 18 (muck humus, tracer recovery 31%) to 70 min (mor humus, tracer recovery 40%). The peak concentration was 10 times smaller on the drier mor humus plot as compared to the muck humus. The mobile water content of the sub-soil varied between 0.5 (muck humus) and 1.3% (mor humus) of the total available soil water. The discrepancy in residence time, peak concentration and volume of mobile water between both sub-soils can be attributed to the differently structured sub-soil (longer travel distance and mixing volume in the drier mor humus). Tracers applied onto the soil surface resulted in a much slower breakthrough (tracer peaks after 400-700 min). Thus, in contrast to the sub-soil, flow through the matrix was the predominating transport process in the upper humus layers of both plots.

Heat tracer test in an alluvial aquifer: Field experiment and inverse modelling

NASA Astrophysics Data System (ADS)

Klepikova, Maria; Wildemeersch, Samuel; Hermans, Thomas; Jamin, Pierre; Orban, Philippe; Nguyen, Frédéric; Brouyère, Serge; Dassargues, Alain

2016-09-01

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in an injection well and monitoring the evolution of groundwater temperature and tracer concentration in the pumping well and in measurement intervals. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells closely spaced along three transects were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume is explained by the groundwater flow gradient on the site and heterogeneities in the hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with a pilot point approach for inversion of the hydraulic conductivity field, the main preferential flow paths were delineated. The successful application of a field heat tracer test at this site suggests that heat tracer tests is a promising approach to image hydraulic conductivity field. This methodology could be applied in aquifer thermal energy storage (ATES) projects for assessing future efficiency that is strongly linked to the hydraulic conductivity variability in the considered aquifer.

Kinetic limitations on tracer partitioning in ganglia dominated source zones.

PubMed

Ervin, Rhiannon E; Boroumand, Ali; Abriola, Linda M; Ramsburg, C Andrew

2011-11-01

Quantification of the relationship between dense nonaqueous phase liquid (DNAPL) source strength, source longevity and spatial distribution is increasingly recognized as important for effective remedial design. Partitioning tracers are one tool that may permit interrogation of DNAPL architecture. Tracer data are commonly analyzed under the assumption of linear, equilibrium partitioning, although the appropriateness of these assumptions has not been fully explored. Here we focus on elucidating the nonlinear and nonequilibrium partitioning behavior of three selected alcohol tracers - 1-pentanol, 1-hexanol and 2-octanol in a series of batch and column experiments. Liquid-liquid equilibria for systems comprising water, TCE and the selected alcohol illustrate the nonlinear distribution of alcohol between the aqueous and organic phases. Complete quantification of these equilibria facilitates delineation of the limits of applicability of the linear partitioning assumption, and assessment of potential inaccuracies associated with measurement of partition coefficients at a single concentration. Column experiments were conducted under conditions of non-equilibrium to evaluate the kinetics of the reversible absorption of the selected tracers in a sandy medium containing a uniform entrapped saturation of TCE-DNAPL. Experimental tracer breakthrough data were used, in conjunction with mathematical models and batch measurements, to evaluate alternative hypotheses for observed deviations from linear equilibrium partitioning behavior. Analyses suggest that, although all tracers accumulate at the TCE-DNAPL/aqueous interface, surface accumulation does not influence transport at concentrations typically employed for tracer tests. Moreover, results reveal that the kinetics of the reversible absorption process are well described using existing mass transfer correlations originally developed to model aqueous boundary layer resistance for pure-component NAPL dissolution. Copyright © 2011 Elsevier B.V. All rights reserved.

Field-scale Prediction of Enhanced DNAPL Dissolution Using Partitioning Tracers and Flow Pattern Effects

NASA Astrophysics Data System (ADS)

Wang, F.; Annable, M. D.; Jawitz, J. W.

2012-12-01

The equilibrium streamtube model (EST) has demonstrated the ability to accurately predict dense nonaqueous phase liquid (DNAPL) dissolution in laboratory experiments and numerical simulations. Here the model is applied to predict DNAPL dissolution at a PCE-contaminated dry cleaner site, located in Jacksonville, Florida. The EST is an analytical solution with field-measurable input parameters. Here, measured data from a field-scale partitioning tracer test were used to parameterize the EST model and the predicted PCE dissolution was compared to measured data from an in-situ alcohol (ethanol) flood. In addition, a simulated partitioning tracer test from a calibrated spatially explicit multiphase flow model (UTCHEM) was also used to parameterize the EST analytical solution. The ethanol prediction based on both the field partitioning tracer test and the UTCHEM tracer test simulation closely matched the field data. The PCE EST prediction showed a peak shift to an earlier arrival time that was concluded to be caused by well screen interval differences between the field tracer test and alcohol flood. This observation was based on a modeling assessment of potential factors that may influence predictions by using UTCHEM simulations. The imposed injection and pumping flow pattern at this site for both the partitioning tracer test and alcohol flood was more complex than the natural gradient flow pattern (NGFP). Both the EST model and UTCHEM were also used to predict PCE dissolution under natural gradient conditions, with much simpler flow patterns than the forced-gradient double five spot of the alcohol flood. The NGFP predictions based on parameters determined from tracer tests conducted with complex flow patterns underestimated PCE concentrations and total mass removal. This suggests that the flow patterns influence aqueous dissolution and that the aqueous dissolution under the NGFP is more efficient than dissolution under complex flow patterns.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raffel, D.M.; Rosario, R.B. del; Tluczek, L.

Elimination of the {alpha}-carbon CH{sub 3} group from C-11 hydroxyephedrine (HED) yields a new radiotracer for cardiac sympathetic neurons: C-11 phenylephrine (PHEN). This small structural change has profound effects on the tracer kinetics - HED is not metabolized by neuronal monoamine oxidase (MAO), while PHEN is an excellent MAO substrate. To assess the influence of MAO metabolism and vesicular storage on PHEN kinetics a series of constant infusion studies were performed. Isolated working rat hearts were perfused under control conditions for 25 min, then switched to a second perfusate circuit containing PHEN at tracer concentrations. PHEN was infused for 10more » min then the heart switched back to normal perfusate to effect washout of PHEN. The amount of PHEN in the heart was externally measured using coinsidence detection. The data between 1 and 4 min were used to estimate an uptake constant, K{sub up} (ml/min/g wet). Washout data were fit to multiple exponentials. Several studies were done: (1) To slow MAO metabolism, the dideuterium substituted analog C-11 D{sub 2-}PHEN was made and studied as described above. (2) For both tracers, the effect of age on washout kinetics was studied as rat heart MAO levels steadily increase throughout the animal`s life. (3) The effect of MAO inhibition was studied using 100 {mu}M pargyline throughout the experiment. (4) Reserpine pretreated rats were used to assess the influence of vesicular storage on tracer kinetics.« less

Tracer Movement in a Single Fissure in Granitic Rock: Some Experimental Results and Their Interpretation

NASA Astrophysics Data System (ADS)

Neretnieks, Ivars; Eriksen, Tryggve; TäHtinen, PäIvi

1982-08-01

Radionuclide migration was studied in a natural fissure in a granite core. The fissure was oriented parallel to the axis in a cylindrical core 30 cm long and 20 cm in diameter. The traced solution was injected at one end of the core and collected at the other. Breakthrough curves were obtained for the nonsorbing tracers, tritiated water, and a large-molecular-weight lignosulphonate molecule and for the sorbing tracers, cesium and strontium. From the breakthrough curves for the nonsorbing tracers it could be concluded that channeling occurs in the single fissure. A `dispersion' model based on channeling is presented. The results from the sorbing tracers indicate that there is substantial diffusion into and sorption in the rock matrix. Sorption on the surface of the fissure also accounts for a part of the retardation effect of the sorbing species. A model which includes the mechanisms of channeling, surface sorption, matrix diffusion, and matrix sorption is presented. The experimental breakthrough curves can be fitted fairly well by this model by use of independently obtained data on diffusivities and matrix sorption.

Using DNA-labelled nano- and microparticles to track particle transport in the environment

NASA Astrophysics Data System (ADS)

McNew, Coy; Wang, Chaozi; Dahlke, Helen; Lyon, Steve; Walter, Todd

2017-04-01

By utilizing bio-molecular nanotechnology developed for nano-medicines and drug delivery, we are able to produce DNA-labelled nano- and microparticle tracers for use in a myriad of environmental systems. The use of custom sequenced DNA allows for the fabrication of an enormous number of uniquely labelled tracers with identical transport properties (approximately 1.61 x 1060 unique sequences), each independently quantifiable, that can be applied simultaneously in any hydrologic system. By controlling the fabrication procedure to produce particles of custom size and charge, we are able to tag each size-charge combination uniquely in order to directly probe the effect of these variables on the transport properties of the particles. Here we present our methods for fabrication, extraction, and analysis of the DNA nano- and microparticle tracers, along with results from several successful applications of the tracers, including transport and retention analysis at the lab, continuum, and field scales. To date, our DNA-labelled nano- and microparticle tracers have proved useful in surface and subsurface water applications, soil retention, and even subglacial flow pathways. The range of potential applications continue to prove nearly limitless.

Hydrochemical evidence for mixing of river water and groundwater during high-flow conditions, lower Suwannee River basin, Florida, USA

USGS Publications Warehouse

Crandall, C.A.; Katz, B.G.; Hirten, J.J.

1999-01-01

Karstic aquifers are highly susceptible to rapid infiltration of river water, particularly during periods of high flow. Following a period of sustained rainfall in the Suwannee River basin, Florida, USA, the stage of the Suwannee River rose from 3.0 to 5.88 m above mean sea level in April 1996 and discharge peaked at 360 m3/s. During these high-flow conditions, water from the Suwannee River migrated directly into the karstic Upper Floridan aquifer, the main source of water supply for the area. Changes in the chemical composition of groundwater were quantified using naturally occurring geochemical tracers and mass-balance modeling techniques. Mixing of river water with groundwater was indicated by a decrease in the concentrations of calcium, silica, and 222Rn; and by an increase in dissolved organic carbon (DOC), tannic acid, and chloride, compared to low-flow conditions in water from a nearby monitoring well, Wingate Sink, and Little River Springs. The proportion (fraction) of river water in groundwater ranged from 0.13 to 0.65 at Wingate Sink and from 0.5 to 0.99 at well W-17258, based on binary mixing models using various tracers. The effectiveness of a natural tracer in quantifying mixing of river water and groundwater was related to differences in tracer concentration of the two end members and how conservatively the tracer reacted in the mixed water. Solutes with similar concentrations in the two end-member waters (Na, Mg, K, Cl, SO4, SiO2) were not as effective tracers for quantifying mixing of river water and groundwater as those with larger differences in end-member concentrations (Ca, tannic acid, DOC, 222Rn, HCO3). ?? Springer-Verlag.

Changes in mitochondrial functioning with electromagnetic radiation of ultra high frequency as revealed by electron paramagnetic resonance methods.

PubMed

Burlaka, Anatoly; Selyuk, Marina; Gafurov, Marat; Lukin, Sergei; Potaskalova, Viktoria; Sidorik, Evgeny

2014-05-01

To study the effects of electromagnetic radiation (EMR) of ultra high frequency (UHF) in the doses equivalent to the maximal permitted energy load for the staffs of the radar stations on the biochemical processes that occur in the cell organelles. Liver, cardiac and aorta tissues from the male rats exposed to non-thermal UHF EMR in pulsed and continuous modes were studied during 28 days after the irradiation by the electron paramagnetic resonance (EPR) methods including a spin trapping of superoxide radicals. The qualitative and quantitative disturbances in electron transport chain (ETC) of mitochondria are registered. A formation of the iron-nitrosyl complexes of nitric oxide (NO) radicals with the iron-sulphide (FeS) proteins, the decreased activity of FeS-protein N2 of NADH-ubiquinone oxidoreductase complex and flavo-ubisemiquinone growth combined with the increased rates of superoxide production are obtained. (i) Abnormalities in the mitochondrial ETC of liver and aorta cells are more pronounced for animals radiated in a pulsed mode; (ii) the alterations in the functioning of the mitochondrial ETC cause increase of superoxide radicals generation rate in all samples, formation of cellular hypoxia, and intensification of the oxide-initiated metabolic changes; and (iii) electron paramagnetic resonance methods could be used to track the qualitative and quantitative changes in the mitochondrial ETC caused by the UHF EMR.

An Analytical Model for Non-Uniform Magnetic Field Effects on Two-Dimensional Laminar Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Calvert, M. E.; Baker, J.; Saito, K.; VanderWal, R. L.

2001-01-01

In 1846, Michael Faraday found that permanent magnets could cause candle flames to deform into equatorial disks. He believed that the change in flame shape was caused by the presence of charged particles within the flames interacting with the magnetic fields. Later researchers found that the interaction between the flame ions and the magnetic fields were much too small to cause the flame deflection. Through a force analysis, von Engel and Cozens showed that the change in the flame shape could be attributed to the diamagnetic flame gases in the paramagnetic atmosphere. Paramagnetism occurs in materials composed of atoms with permanent magnetic dipole moments. In the presence of magnetic field gradients, the atoms align with the magnetic field and are drawn into the direction of increasing magnetic field. Diamagnetism occurs when atoms have no net magnetic dipole moment. In the presence of magnetic gradient fields, diamagnetic substances are repelled towards areas of decreasing magnetism. Oxygen is an example of a paramagnetic substance. Nitrogen, carbon monoxide and dioxide, and most hydrocarbon fuels are examples of diamagnetic substances. In order to evaluate the usefulness of these magnets in altering flame behavior, a study has been undertaken to develop an analytical model to describe the change in the flame length of a laminar diffusion jet in the presence of a nonuniform magnetic field.

The NMR contribution to protein-protein networking in Fe-S protein maturation.

PubMed

Banci, Lucia; Camponeschi, Francesca; Ciofi-Baffoni, Simone; Piccioli, Mario

2018-03-22

Iron-sulfur proteins were among the first class of metalloproteins that were actively studied using NMR spectroscopy tailored to paramagnetic systems. The hyperfine shifts, their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues are an efficient fingerprint of the nature and the oxidation state of the Fe-S cluster. NMR significantly contributed to the analysis of the magnetic coupling patterns and to the understanding of the electronic structure occurring in [2Fe-2S], [3Fe-4S] and [4Fe-4S] clusters bound to proteins. After the first NMR structure of a paramagnetic protein was obtained for the reduced E. halophila HiPIP I, many NMR structures were determined for several Fe-S proteins in different oxidation states. It was found that differences in chemical shifts, in patterns of unobserved residues, in internal mobility and in thermodynamic stability are suitable data to map subtle changes between the two different oxidation states of the protein. Recently, the interaction networks responsible for maturing human mitochondrial and cytosolic Fe-S proteins have been largely characterized by combining solution NMR standard experiments with those tailored to paramagnetic systems. We show here the contribution of solution NMR in providing a detailed molecular view of "Fe-S interactomics". This contribution was particularly effective when protein-protein interactions are weak and transient, and thus difficult to be characterized at high resolution with other methodologies.

A novel method for the induction of experimental glaucoma using magnetic microspheres.

PubMed

Samsel, Paulina A; Kisiswa, Lilian; Erichsen, Jonathan T; Cross, Stephen D; Morgan, James E

2011-03-25

The development of a method for the sustained elevation of intraocular pressure in experimental glaucoma based on the anterior chamber injection of paramagnetic microbeads. Unilateral glaucoma was induced in adult male Norwegian Brown rats by the injection of paramagnetic polystyrene microspheres. A handheld 0.45 Tesla magnet was used to draw the beads into the iridocorneal angle to impede aqueous drainage via the trabecular meshwork. Elevated intraocular pressures (IOPs) were induced in 61 rats, resulting in a mean elevation of 5.8 mm Hg ± 1.0 (SEM) relative to the contralateral control eye. The mean duration of sustained IOP elevation (defined as >5 mm Hg relative to the control eye for at least 7 consecutive days) after a single injection was 12.8 days ± 0.9 (SEM, maximum duration 27 days). In all eyes, the visual axis remained clear from the time of injection, with minimal inflammation after injection. Retinal ganglion cell loss was determined in 21 animals (mean integral IOP, 194.5 mm Hg days ± 87.5 [SEM]) as 36.4% ± 2.4 (SEM) compared with the contralateral, untreated eye. The use of paramagnetic microbeads for the occlusion of the iridocorneal angle produces a sustained elevation of IOP with fewer injections and avoids the risk of visual axis occlusion. It represents a simple and effective method for the induction of experimental glaucoma.

New pharmacokinetic methods. III. Two simple test for deep pool effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Browne, T.R.; Greenblatt, D.J.; Schumacher, G.E.

1990-08-01

If a portion of administered drug is distributed into a deep peripheral compartment, the drug's actual elimination half-life during the terminal exponential phase of elimination may be longer than determined by a single dose study or a tracer dose study (deep pool effect). Two simple methods of testing for deep pool effect applicable to drugs with either linear or nonlinear pharmacokinetic properties are described. The methods are illustrated with stable isotope labeled (13C15N2) tracer dose studies of phenytoin. No significant (P less than .05) deep pool effect was detected.

TB tracer teams in South Africa: knowledge, practices and challenges of tracing TB patients to improve adherence.

PubMed

Bristow, Claire C; Podewils, Laura Jean; Bronner, Liza Ellen; Bantubani, Nonkqubela; Walt, Martie van der; Peters, Annatjie; Mametja, David

2013-09-04

In 2008-2009 the South African National Tuberculosis (TB) Program (NTP) implemented a national pilot project, the TB Tracer Project, aiming to decrease default rates and improve patient outcomes. The current study aimed to inform the NTP by describing the knowledge, attitudes, and practices of TB program personnel involved with tracing activities. A self-administered written questionnaire was sent to TB staff, managers and tracer team leaders to assess basic TB knowledge, attitudes and practices. Descriptive statistics were used to summarize results and the chi-squared statistic was used to compare responses of staff at facilities that participated in the TB Tracer Project (tracer) and those that followed standard NTP care (non-tracer). Of 560 total questionnaires distributed, 270 were completed and returned (response rate 48%). Total TB knowledge ranged from 70.8-86.3% correct across all response groups. However, just over half (range 50-59.3%) of each respondent group was able to correctly identify the four components of a DOT encounter. A patient no longer feeling sick was cited by 72.1% of respondents as the reason patients fail to adhere to treatment. Tracer teams were viewed as an effective means to get patients to return to treatment by 96.3% of health facility level respondents. Tracer team leaders reported concerns including lack of logistical support (41.7%), insufficient physical safety precautions (41.7%), and inadequate protection from contracting TB (39.1%). Upon patients returning to treatment at the clinic, facilities included in the TB Tracer Project were significantly more likely to discuss alternate DOTS arrangements than non-tracer facilities (79.2 vs. 66.4%, p = 0.03). This study identified key components of knowledge, attitudes, and practices regarding TB patient tracing activities in South Africa. Educating patients on the essential need to complete treatment irrespective of clinical symptoms may help improve treatment adherence. Future scale-up and integration of TB tracing activities as part of standard TB management should include provisions for standardized training of personnel on the critical elements of DOTS, and for ensuring appropriate supervision, logistical support, and physical safety and TB transmission protection of tracing teams.

Effects of Langmuir Turbulence on Reactive Tracers in the Upper Ocean

NASA Astrophysics Data System (ADS)

Smith, K.; Hamlington, P.; Niemeyer, K.; Fox-Kemper, B.; Lovenduski, N. S.

2017-12-01

Reactive tracers such as carbonate chemical species play important roles in the oceanic carbon cycle, allowing the ocean to hold 60 times more carbon than the atmosphere. However, uncertainties in regional ocean sinks for anthropogenic CO2 are still relatively high. Many carbonate species are non-conserved, flux across the air-sea interface, and react on time scales similar to those of ocean turbulent processes, such as small-scale wave-driven Langmuir turbulence. All of this complexity gives rise to heterogeneous tracer distributions that are not fully understood and can greatly affect the rate at which CO2 fluxes across the air-sea interface. In order to more accurately model the biogeochemistry of the ocean in Earth system models (ESMs), a better understanding of the fundamental interactions between these reactive tracers and relevant turbulent processes is required. Research on reacting flows in other contexts has shown that the most significant tracer-flow couplings occur when coherent structures in the flow have timescales that rival reaction time scales. Langmuir turbulence, a 3D, small-scale, wave-driven process, has length and time scales on the order of O(1-100m) and O(1-10min), respectively. Once CO2 transfers across the air-sea interface, it reacts with seawater in a series of reactions whose rate limiting steps have time scales of 10-25s. This similarity in scales warrants further examination into interactions between these small-scale physical and chemical processes. In this presentation, large eddy simulations are used to examine the evolution of reactive tracers in the presence of realistic upper ocean wave- and shear-driven turbulence. The reactive tracers examined are those specifically involved in non-biological carbonate chemistry. The strength of Langmuir turbulence is varied in order to determine a relationship between the degree of enhancement (or reduction) of carbon that is fluxed across the air-sea interface due to the presence of Langmuir turbulence. By examining different reaction chemistry and surface forcing scenarios, the coupled turbulence-reactive tracer dynamics are connected with spatial and statistical properties of the resulting tracer fields. These results, along with implications for development of reduced order reactive tracer models, are discussed.

Electron paramagnetic resonance and FT-IR spectroscopic studies of glycine anhydride and betaine hydrochloride

NASA Astrophysics Data System (ADS)

Halim Başkan, M.; Kartal, Zeki; Aydın, Murat

2015-12-01

Gamma irradiated powders of glycine anhydride and betaine hydrochloride have been investigated at room temperature by electron paramagnetic resonance (EPR). In these compounds, the observed paramagnetic species were attributed to the R1 and R2 radicals, respectively. It was determined that the free electron interacted with environmental protons and 14N nucleus in both radicals. The EPR spectra of gamma irradiated powder samples remained unchanged at room temperature for two weeks after irradiation. Also, the Fourier Transform Infrared (FT-IR), FT-Raman and thermal analyses of both compounds were investigated. The functional groups in the molecular structures of glycine anhydride and betaine hydrochloride were identified by vibrational spectroscopies (FT-IR and FT-Raman).

Single crystal EPR and optical studies of paramagnetic ions doped zinc potassium phosphate hexahydrate--part I: Cu(II)--a case of orthorhombic symmetry.

PubMed

Sambasiva Rao, P; Rajendiran, T M; Venkatesan, R; Madhu, N; Chandrasekhar, A V; Reddy, B J; Reddy, Y P; Ravikumar, R V

2001-12-01

Single crystal electron paramagnetic resonance (EPR) studies on Cu(II) doped zinc potassium phosphate hexahydrate (ZPPH) were carried out at room temperature. The angular variation spectra in the three orthogonal planes indicate that the paramagnetic impurity has entered the lattice substitutionally in place of Zn(II) and the spin Hamiltonian parameters calculated from these spectra are g(xx) = 2.188, g(yy) = 2.032, g(zz) = 2.373, Axx = 50 G, Ayy = 65.0 G and Azz = 80 G. The g and A tensors were coincident and these values matched fairly well with the values obtained from powder spectrum. The bonding parameters have also been calculated.

Feasibility of Rapid Multitracer PET Tumor Imaging

NASA Astrophysics Data System (ADS)

Kadrmas, D. J.; Rust, T. C.

2005-10-01

Positron emission tomography (PET) can characterize different aspects of tumor physiology using various tracers. PET scans are usually performed using only one tracer since there is no explicit signal for distinguishing multiple tracers. We tested the feasibility of rapidly imaging multiple PET tracers using dynamic imaging techniques, where the signals from each tracer are separated based upon differences in tracer half-life, kinetics, and distribution. Time-activity curve populations for FDG, acetate, ATSM, and PTSM were simulated using appropriate compartment models, and noisy dual-tracer curves were computed by shifting and adding the single-tracer curves. Single-tracer components were then estimated from dual-tracer data using two methods: principal component analysis (PCA)-based fits of single-tracer components to multitracer data, and parallel multitracer compartment models estimating single-tracer rate parameters from multitracer time-activity curves. The PCA analysis found that there is information content present for separating multitracer data, and that tracer separability depends upon tracer kinetics, injection order and timing. Multitracer compartment modeling recovered rate parameters for individual tracers with good accuracy but somewhat higher statistical uncertainty than single-tracer results when the injection delay was >10 min. These approaches to processing rapid multitracer PET data may potentially provide a new tool for characterizing multiple aspects of tumor physiology in vivo.

Field-scale effective matrix diffusion coefficient for fractured rock: results from literature survey.

PubMed

Zhou, Quanlin; Liu, Hui-Hai; Molz, Fred J; Zhang, Yingqi; Bodvarsson, Gudmundur S

2007-08-15

Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D(m)(e), a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D(m)(e) values were calculated, either directly using data reported in the literature, or by reanalyzing the corresponding field tracer tests. The reanalysis was conducted for the selected tracer tests using analytic or semi-analytic solutions for tracer transport in linear, radial, or interwell flow fields. Surveyed data show that the scale factor of the effective matrix diffusion coefficient (defined as the ratio of D(m)(e) to the lab-scale matrix diffusion coefficient, D(m), of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate, on average trend toward systematic increase in the scale factor with observation scale. This trend suggests that the effective matrix diffusion coefficient is likely to be statistically scale-dependent. The scale-factor value ranges from 0.5 to 884 for observation scales from 5 to 2000 m. At a given scale, the scale factor varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different geologic sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal and contaminant remediation.

Multi-Scale Thermal Heat Tracer Tests for Characterizing Transport Processes and Flow Channelling in Fractured Media: Theory and Field Experiments

NASA Astrophysics Data System (ADS)

de La Bernardie, J.; Klepikova, M.; Bour, O.; Le Borgne, T.; Dentz, M.; Guihéneuf, N.; Gerard, M. F.; Lavenant, N.

2017-12-01

The characterization of flow and transport in fractured media is particularly challenging because hydraulic conductivity and transport properties are often strongly dependent on the geometric structure of the fracture surfaces. Here we show how thermal tracer tests may be an excellent complement to conservative solute tracer tests to infer fracture geometry and flow channeling. We performed a series of thermal tracer tests at different scales in a crystalline rock aquifer at the experimental site of Ploemeur (H+ observatory network). The first type of thermal tracer tests are push-pull tracer tests at different scales. The temporal and spatial scaling of heat recovery, measured from thermal breakthrough curves, shows a clear signature of flow channeling. In particular, the late time tailing of heat recovery under channeled flow is shown to diverge from the T(t) α t-1,5 behavior expected for the classical parallel plate model and follow the scaling T(t) α 1/t(logt)2 for a simple channel modeled as a tube. Flow channeling is also manifested on the spatial scaling of heat recovery as flow channeling affects the decay of the thermal breakthrough peak amplitude and the increase of the peak time with scale. The second type of thermal tracer tests are flow-through tracer tests where a pulse of hot water was injected in a fracture isolated by a double straddle packer while pumping at the same flow rate in another fracture at a distance of about 10 meters to create a dipole flow field. Comparison with a solute tracer test performed under the same conditions also present a clear signature of flow channeling. We derive analytical expressions for the retardation and decay of the thermal breakthrough peak amplitude for different fracture geometries and show that the observed differences between thermal and solute breakthrough can be explained only by channelized flow. These results suggest that heat transport is much more sensitive to fracture heterogeneity and flow channeling than conservative solute transport. These findings, which bring new insights on the effect of flow channeling on heat transfer in fractured rocks, show how heat recovery in geothermal systems may be controlled by fracture geometry. This highlights the interest of thermal tracer tests as a complement to solute tracers tests to infer fracture aperture and geometry.

Electron paramagnetic resonance investigation on modulatory effect of 17beta-estradiol on membrane fluidity of erythrocytes in postmenopausal women.

PubMed

Tsuda, K; Kinoshita, Y; Kimura, K; Nishio, I; Masuyama, Y

2001-08-01

Many studies have shown that estrogen may exert cardioprotective effects and reduce the risk of hypertension and coronary events. On the other hand, it has been proposed that cell membrane abnormalities play a role in the pathophysiology of hypertension, although it is not clear whether estrogen would influence membrane function in essential hypertension. The present study was performed to investigate the effects of 17beta-estradiol (E(2)) on membrane fluidity of erythrocytes in normotensive and hypertensive postmenopausal women. We determined the membrane fluidity of erythrocytes by means of an electron paramagnetic resonance and spin-labeling method. In an in vitro study, E(2) significantly decreased the order parameter for 5-nitroxide stearate and the peak height ratio for 16-nitroxide stearate obtained from electron paramagnetic resonance spectra of erythrocyte membranes in normotensive postmenopausal women. The finding indicates that E(2) might increase the membrane fluidity of erythrocytes. The effect of E(2) was significantly potentiated by the NO donor, S-nitroso-N-acetylpenicillamine, and a cGMP analogue, 8-bromo-cGMP. In contrast, the change in the membrane fluidity evoked by E(2) was attenuated in the presence of the NO synthase inhibitor, N(G)-nitro-L-arginine methyl ester, and asymmetric dimethyl-L-arginine. In hypertensive postmenopausal women, the membrane fluidity of erythrocytes was significantly lower than that in normotensive postmenopausal women. The effect of E(2) on membrane fluidity was significantly more pronounced in the erythrocytes of hypertensive postmenopausal women than in the erythrocytes of normotensive postmenopausal women. The results of the present study showed that E(2) significantly increased the membrane fluidity and improved the microviscosity of erythrocyte membranes, partially mediated by an NO- and cGMP-dependent pathway. Furthermore, the greater action of E(2) in hypertension might be consistent with the hypothesis that E(2) could have a beneficial effect in regulating rheological behavior of erythrocytes and could have a crucial role in the improvement of the microcirculation in hypertension.

Fundamentals of thinking, patterns

NASA Astrophysics Data System (ADS)

Gafurov, O. M.; Gafurov, D. O.; Syryamkin, V. I.

2018-05-01

The authors analyze the fundamentals of thinking and propose to consider a model of the brain based on the presence of magnetic properties of gliacytes (Schwann cells) because of their oxygen saturation (oxygen has paramagnetic properties). The authors also propose to take into account the motion of electrical discharges through synapses causing electric and magnetic fields as well as additional effects such as paramagnetic resonance, which allows combining multisensory object-related information located in different parts of the brain. Therefore, the events of the surrounding world are reflected and remembered in the cortex columns, thus, creating isolated subnets with altered magnetic properties (patterns) and subsequently participate in recognition of objects, form a memory, and so on. The possibilities for the pattern-based thinking are based on the practical experience of applying methods and technologies of artificial neural networks in the form of a neuroemulator and neuromorphic computing devices.

Systematic approach to cutoff frequency selection in continuous-wave electron paramagnetic resonance imaging

NASA Astrophysics Data System (ADS)

Hirata, Hiroshi; Itoh, Toshiharu; Hosokawa, Kouichi; Deng, Yuanmu; Susaki, Hitoshi

2005-08-01

This article describes a systematic method for determining the cutoff frequency of the low-pass window function that is used for deconvolution in two-dimensional continuous-wave electron paramagnetic resonance (EPR) imaging. An evaluation function for the criterion used to select the cutoff frequency is proposed, and is the product of the effective width of the point spread function for a localized point signal and the noise amplitude of a resultant EPR image. The present method was applied to EPR imaging for a phantom, and the result of cutoff frequency selection was compared with that based on a previously reported method for the same projection data set. The evaluation function has a global minimum point that gives the appropriate cutoff frequency. Images with reasonably good resolution and noise suppression can be obtained from projections with an automatically selected cutoff frequency based on the present method.

Physical and Instrumental Considerations in the Use of Lithium Phthalocyanine for Measurements of the Concentration of the Oxygen

NASA Astrophysics Data System (ADS)

Smirnov, A. I.; Norby, S. W.; Walczak, T.; Liu, K. J.; Swartz, H. M.

The use of crystals of lithium phthalocyanine (LiPc) to measure the concentration of oxygen in vivo and in vitro by electron paramagnetic resonance leads to experimental constraints due to the very narrow EPR lines that may occur (as narrow as 11-13 mG in the absence of O 2), distortions induced by the automatic frequency control system, anisotropy in the spectra (orientation-dependent linewidth is 11-17 mG in the absence of O 2), microwave power saturation, and the effect of physiological motion. These constraints can be overcome if recognized. This article highlights the experimental and theoretical basis of these properties of the EPR signal of LiPc and suggests some technical solutions. It is most important to recognize that paramagnetic species such as LiPc present problems that are not commonly encountered in EPR spectroscopy.

Carbon-related platinum defects in silicon: An electron paramagnetic resonance study of high spin states

NASA Astrophysics Data System (ADS)

Scheerer, O.; Höhne, M.; Juda, U.; Riemann, H.

1997-10-01

In this article, we report about complexes in silicon investigated by electron paramagnetic resonance (EPR). In silicon doped with C and Pt we detected two different complexes: cr-1Pt (cr: carbon-related, 1Pt: one Pt atom) and cr-3Pt. The complexes have similar EPR properties. They show a trigonal symmetry with effective g-values geff,⊥=2g⊥≈4 and geff,‖=g‖≈2 (g⊥, g‖ true g-values). The g-values can be explained by a spin Hamiltonian with large fine-structure energy (electron spin S=3/2) and smaller Zeeman interaction. The participation of platinum in the complexes is proved by the hyperfine interaction. From experiments with varying carbon concentration we conclude that the complexes contain carbon. Atomistic models based on the Watkins vacancy-model for substitutional Pt were developed.

Study of ultrasonic attenuation in f-electron systems in the paramagnetic limit of Coulomb interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shadangi, Asit Ku., E-mail: asitshad@iopb.res.in; Rout, G. C., E-mail: gcr@iopb.res.in

2015-05-15

We report here a microscopic model study of ultrasonic attenuation in f-electron systems based on Periodic Anderson Model in which Coulomb interaction is considered within a mean-field approximation for a weak interaction. The Phonon is coupled to the conduction band and f-electrons. The phonon Green's function is calculated by Zubarev's technique of the Green's function method. The temperature dependent ultrasonic attenuation co-efficient is calculated from the imaginary part of the phonon self-energy in the dynamic and long wave length limit. The f-electron occupation number is calculated self-consistently in paramagnetic limit of Coulomb interaction. The effect of the Coulomb interaction onmore » ultrasonic attenuation is studied by varying the phonon coupling parameters to the conduction and f-electrons, hybridization strength, the position of f-level and the Coulomb interaction Strength. Results are discussed on the basis of experimental results.« less

MRI-guided targeting delivery of doxorubicin with reduction-responsive lipid-polymer hybrid nanoparticles.

PubMed

Wu, Bo; Lu, Shu-Ting; Deng, Kai; Yu, Hui; Cui, Can; Zhang, Yang; Wu, Ming; Zhuo, Ren-Xi; Xu, Hai-Bo; Huang, Shi-Wen

2017-01-01

In recent years, there has been increasing interest in developing a multifunctional nanoscale platform for cancer monitoring and chemotherapy. However, there is still a big challenge for current clinic contrast agents to improve their poor tumor selectivity and response. Herein, we report a new kind of Gd complex and folate-coated redox-sensitive lipid-polymer hybrid nanoparticle (Gd-FLPNP) for tumor-targeted magnetic resonance imaging and therapy. Gd-FLPNPs can simultaneously accomplish diagnostic imaging, and specific targeting and controlled release of doxorubicin (DOX). They exhibit good monodispersity, excellent size stability, and a well-defined core-shell structure. Paramagnetic nanoparticles based on gadolinium-diethylenetriaminepentaacetic acid-bis-cetylamine have paramagnetic properties with an approximately two-fold enhancement in the longitudinal relaxivity compared to clinical used Magnevist. For targeted and reduction-sensitive drug delivery, Gd-FLPNPs released DOX faster and enhanced cell uptake in vitro, and exhibited better antitumor effect both in vitro and in vivo.

Large dielectric permittivity and possible correlation between magnetic and dielectric properties in bulk BaFeO{sub 3−δ}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sagdeo, Archna; Gautam, Kamini; Singh, M. N.

2014-07-28

We report structural, magnetic, and dielectric properties of oxygen deficient hexagonal BaFeO{sub 3−δ}. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO{sub 3−δ}. Magnetization measurements indicate magnetic inhomogeneity and the system shows a paramagnetic to antiferromagnetic transition at ∼160 K. Remarkably, the temperature, at which paramagnetic to antiferromagnetic transition occurs, around this temperature, a huge drop in the dissipation factor takes place and resistivity shoots up; this indicates the possible correlation among magnetic and dielectric properties. First principle simulations reveal that some of these behaviors may be explained in terms of many body electron correlationmore » effect in the presence of oxygen vacancy present in BaFeO{sub 3−δ} indicating its importance in both fundamental science as well as in applications.« less

Magnetic phase composition of strontium titanate implanted with iron ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dulov, E.N., E-mail: evgeny.dulov@ksu.ru; Ivoilov, N.G.; Strebkov, O.A.

2011-12-15

Highlights: Black-Right-Pointing-Pointer The origin of RT-ferromagnetism in iron implanted strontium titanate. Black-Right-Pointing-Pointer Metallic iron nanoclusters form during implantation and define magnetic behaviour. Black-Right-Pointing-Pointer Paramagnetic at room temperature iron-substituted strontium titanate identified. -- Abstract: Thin magnetic films were synthesized by means of implantation of iron ions into single-crystalline (1 0 0) substrates of strontium titanate. Depth-selective conversion electron Moessbauer spectroscopy (DCEMS) indicates that origin of the samples magnetism is {alpha}-Fe nanoparticles. Iron-substituted strontium titanate was also identified but with paramagnetic behaviour at room temperature. Surface magneto-optical Kerr effect (SMOKE) confirms that the films reveal superparamagnetism (the low-fluence sample) or ferromagnetism (themore » high-fluence sample), and demonstrate absence of magnetic in-plane anisotropy. These findings highlight iron implanted strontium titanate as a promising candidate for composite multiferroic material and also for gas sensing applications.« less

Phase diagram and re-entrant fermionic entanglement in a hybrid Ising-Hubbard ladder

NASA Astrophysics Data System (ADS)

Sousa, H. S.; Pereira, M. S. S.; de Oliveira, I. N.; Strečka, J.; Lyra, M. L.

2018-05-01

The degree of fermionic entanglement is examined in an exactly solvable Ising-Hubbard ladder, which involves interacting electrons on the ladder's rungs described by Hubbard dimers at half-filling on each rung, accounting for intrarung hopping and Coulomb terms. The coupling between neighboring Hubbard dimers is assumed to have an Ising-like nature. The ground-state phase diagram consists of four distinct regions corresponding to the saturated paramagnetic, the classical antiferromagnetic, the quantum antiferromagnetic, and the mixed classical-quantum phase. We have exactly computed the fermionic concurrence, which measures the degree of quantum entanglement between the pair of electrons on the ladder rungs. The effects of the hopping amplitude, the Coulomb term, temperature, and magnetic fields on the fermionic entanglement are explored in detail. It is shown that the fermionic concurrence displays a re-entrant behavior when quantum entanglement is being generated at moderate temperatures above the classical saturated paramagnetic ground state.

Strength and scales of itinerant spin fluctuations in 3 d paramagnetic metals

DOE PAGES

Wysocki, Aleksander L.; Kutepov, Andrey; Antropov, Vladimir P.

2016-10-10

The full spin density fluctuations (SDF) spectra in 3d paramagnetic metals are analyzed from first principles using the linear response technique. Using the calculated complete wave vector and energy dependence of the dynamic spin susceptibility, we obtain the most important, but elusive, characteristic of SDF in solids: on-site spin correlator (SC). We demonstrate that the SDF have a mixed character consisting of interacting collective and single-particle excitations of similar strength spreading continuously over the entire Brillouin zone and a wide energy range up to femtosecond time scales. These excitations cannot be adiabatically separated and their intrinsically multiscale nature should alwaysmore » be taken into account for a proper description of metallic systems. Altogether, in all studied systems, despite the lack of local moment, we found a very large SC resulting in an effective fluctuating moment of the order of several Bohr magnetons.« less

Strength and scales of itinerant spin fluctuations in 3 d paramagnetic metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wysocki, Aleksander L.; Kutepov, Andrey; Antropov, Vladimir P.

The full spin density fluctuations (SDF) spectra in 3d paramagnetic metals are analyzed from first principles using the linear response technique. Using the calculated complete wave vector and energy dependence of the dynamic spin susceptibility, we obtain the most important, but elusive, characteristic of SDF in solids: on-site spin correlator (SC). We demonstrate that the SDF have a mixed character consisting of interacting collective and single-particle excitations of similar strength spreading continuously over the entire Brillouin zone and a wide energy range up to femtosecond time scales. These excitations cannot be adiabatically separated and their intrinsically multiscale nature should alwaysmore » be taken into account for a proper description of metallic systems. Altogether, in all studied systems, despite the lack of local moment, we found a very large SC resulting in an effective fluctuating moment of the order of several Bohr magnetons.« less

Kondo destruction in a quantum paramagnet with magnetic frustration

NASA Astrophysics Data System (ADS)

Zhang, Jiahao; Zhao, Hengcan; Lv, Meng; Hu, Sile; Isikawa, Yosikazu; Yang, Yi-feng; Si, Qimiao; Steglich, Frank; Sun, Peijie

2018-06-01

We report results of isothermal magnetotransport and susceptibility measurements at elevated magnetic fields B down to very low temperatures T on single crystals of the frustrated Kondo-lattice system CePdAl. They reveal a B*(T ) line within the paramagnetic part of the phase diagram. This line denotes a thermally broadened "small"-to-"large" Fermi-surface crossover which substantially narrows upon cooling. At B0 *=B*(T =0 ) =(4.6 ±0.1 ) T , this B*(T ) line merges with two other crossover lines, viz. Tp(B ) below and TFL(B ) above B0 *. Tp characterizes a frustration-dominated spin-liquid state, while TFL is the Fermi-liquid temperature associated with the lattice Kondo effect. Non-Fermi-liquid phenomena which are commonly observed near a "Kondo-destruction" quantum-critical point cannot be resolved in CePdAl. Our observations reveal a rare case where Kondo coupling, frustration, and quantum criticality are closely intertwined.

Coupling Surfactants/Cosolvents with Oxidants: Effects on Site Characterization and DNAPL Remediation

NASA Astrophysics Data System (ADS)

Dugan, P. J.; Siegrist, R. L.; Crimi, M. L.

2004-12-01

Within the last decade, surfactant-enhanced aquifer remediation \\(SEAR\\), and more recently, in-situ chemical oxidation \\(ISCO\\) show promise for remediation of dense nonaqueous phase liquid \\(DNAPL\\) contamination in the subsurface. DNAPL removal is typically difficult to achieve with one remedial technique; however, coupling of treatments can be a highly effective method for remediation of DNAPL contamination. Little research has been completed to date to evaluate such coupling and the factors that impact appropriate engineering design and remediation performance assessment. Partitioning tracer tests (PTTs) are a promising method for estimating the volume and distribution of DNAPL. PTTs have several useful purposes: locating subsurface DNAPL zones, estimating NAPL saturation or volume within these contaminated zones, and providing a quantitative and qualitative means of assessing remediation performance. PTT theory permits direct calculation of the NAPL saturation from the chromatographic separation of a tracer pulse consisting of suites of partitioning and non-partitioning tracers that travel with the advecting groundwater. The PTT has been used with limited success after surfactant/cosolvent recovery but has not been assessed as a performance assessment tool after ISCO. There are several factors that could potentially impact the feasibility of the PTT after ISCO. First, previous batch experiments indicate that partitioning tracers degrade in the presence of the oxidant potassium permanganate. Secondly, tracer partitioning could be inhibited by manganese dioxide film formation after chemical oxidation of DNAPL. Both of these factors have potential to influence partitioning tracer transport, which could lead to inaccurate estimates of the post-remediation NAPL saturation, and therefore remediation efficiency. There is a need for researching PTTs after surfactant/cosolvent coupling with ISCO. In general, DNAPL-zone characterization methods have significant uncertainty, and assessing remediation efficiency is difficult. Effluent concentrations can be monitored in the extraction fluid during surfactant/cosolvent flushing, as an independent measure of mass removed. However, a challenge with ISCO in terms of performance assessment is that there is no way to directly measure mass destroyed, except through post-remediation characterization (i.e., PTTs or soil cores). Column and 2-D cell studies were conducted to investigate removal of DNAPL with surfactant/cosolvent flushing coupled with ISCO using the oxidant potassium permanganate. Partitioning and non-partitioning tracers were used in the pre- and post-remediation studies to investigate the effect of these remedial techniques on the viability of PTT.

Time-resolved luminescence measurements of the magnetic field effect on paramagnetic photosensitizers in photodynamic reactions

NASA Astrophysics Data System (ADS)

Mermut, O.; Bouchard, J.-P.; Cormier, J.-F.; Desroches, P.; Diamond, K. R.; Fortin, M.; Gallant, P.; Leclair, S.; Marois, J.-S.; Noiseux, I.; Morin, J.-F.; Patterson, M. S.; Vernon, M.

2008-02-01

The development of multimodal molecular probes and photosensitizing agents for use in photodynamic therapy (PDT) is vital for optimizing and monitoring cytotoxic responses. We propose a combinatorial approach utilizing photosensitizing molecules that are both paramagnetic and luminescent with multimodal functionality to perturb, control, and monitor molecular-scale reaction pathways in PDT. To this end, a time-domain single photon counting lifetime apparatus with a 400 nm excitation source has been developed and integrated with a variable low field magnet (0- 350mT). The luminescence lifetime decay function was measured in the presence of a sweeping magnetic field for a custom designed photosensitizing molecule in which photoinduced electron transfer was studied The photosensitizer studied was a donor-acceptor complex synthesized using a porphyrin linked to a fullerene molecule. The magneto-optic properties were investigated for the free-base photosensitizer complex as well as those containing either diamagnetic (paired electron) or paramagnetic (unpaired electron) metal centers, Zn(II) and Cu(II). The magnetic field was employed to affect and modify the spin states of radical pairs of the photosensitizing agents via magnetically induced hyperfine and Zeeman effects. Since the Type 1 reaction pathway of an excited triplet state photosensitizer involves the production of radical species, lifetime measurements were conducted at low dissolved oxygen concentration (0.01ppm) to elucidate the dependence of the magnetic perturbation on the photosensitization mechanistic pathway. To optimize the magnetic response, a solvent study was performed examining the dependence of the emission properties on the magnetic field in solutions of varying dielectric constants. Lastly, the cytotoxicity in murine tumor cell suspensions was investigated for the novel porphyrin-fullerene complex by inducing photodynamic treatments and determining the associated cell survival.

Uniform magnetic targeting of magnetic particles attracted by a new ferromagnetic biological patch.

PubMed

Pei, Ning; Cai, Lanlan; Yang, Kai; Ma, Jiaqi; Gong, Yongyong; Wang, Qixin; Huang, Zheyong

2018-02-01

A new non-toxic ferromagnetic biological patch (MBP) was designed in this paper. The MBP consisted of two external layers that were made of transparent silicone, and an internal layer that was made of a mixture of pure iron powder and silicon rubber. Finite-element analysis showed that the local inhomogeneous magnetic field (MF) around the MBP was generated when MBP was placed in a uniform MF. The local MF near the MBP varied with the uniform MF and shape of the MBP. Therefore, not only could the accumulation of paramagnetic particles be adjusted by controlling the strength of the uniform MF, but also the distribution of the paramagnetic particles could be improved with the different shape of the MBP. The relationship of the accumulation of paramagnetic particles or cells, magnetic flux density, and fluid velocity were studied through in vitro experiments and theoretical considerations. The accumulation of paramagnetic particles first increased with increment in the magnetic flux density of the uniform MF. But when the magnetic flux density of the uniform MF exceeded a specific value, the magnetic flux density of the MBP reached saturation, causing the accumulation of paramagnetic particles to fall. In addition, the adsorption morphology of magnetic particles or cells could be improved and the uniform distribution of magnetic particles could be achieved by changing the shape of the MBP. Also, MBP may be used as a new implant to attract magnetic drug carrier particles in magnetic drug targeting. Bioelectromagnetics. 39:98-107, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agosta, C. C.; Jin, J.; Coniglio, W. A.

We present upper critical field data for {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} with the magnetic field close to parallel and parallel to the conducting layers. We show that we can eliminate the effect of vortex dynamics in these layered materials if the layers are oriented within 0.3-inch of parallel to the applied magnetic field. Eliminating vortex effects leaves one remaining feature in the data that corresponds to the Pauli paramagnetic limit (H{sub p}). We propose a semiempirical method to calculate the H{sub p} in quasi-2D superconductors. This method takes into account the energy gap of each of the quasi-2D superconductors, which ismore » calculated from specific-heat data, and the influence of many-body effects. The calculated Pauli paramagnetic limits are then compared to critical field data for the title compound and other organic conductors. Many of the examined quasi-2D superconductors, including the above organic superconductors and CeCoIn{sub 5}, exhibit upper critical fields that exceed their calculated H{sub p} suggesting unconventional superconductivity. We show that the high-field low-temperature state in {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} is consistent with the Fulde-Ferrell-Larkin-Ovchinnikov state.« less

Quantum fluctuations of a fullerene cage modulate its internal magnetic environment.

PubMed

Kawatsu, Tsutomu; Tachikawa, Masanori

2018-01-17

To investigate the effect of quantum fluctuations on the magnetic environment inside a C 60 fullerene cage, we have calculated the nuclear magnetic shielding constant of protons in H 2 @C 60 and HD@C 60 systems by on-the-fly ab initio path integral simulation, including both thermal and nuclear quantum effects. The most dominant upfield from an isolated hydrogen molecule occurs due to the diamagnetic current of the C 60 cage, which is partly cancelled by the paramagnetic current, where the paramagnetic contribution is enlarged by the zero-point vibrational fluctuation of the C 60 carbon backbone structure via a widely distributed HOMO-LUMO gap. This quantum modulation mechanism of the nuclear magnetic shielding constant is newly proposed. Because this quantum effect is independent of the difference between H 2 and HD, the H 2 /HD isotope shift occurs in spite of the C 60 cage. The nuclear magnetic constants computed for H 2 @C 60 and HD@C 60 are 32.047 and 32.081 ppm, respectively, which are in reasonable agreement with the corresponding values of 32.19 and 32.23 ppm estimated from the experimental values of the chemical shifts.

Joint Use of ERT, Tracer, and Numerical Techniques to Image Preferential Flow Paths in a Fractured Granite Aquifer

NASA Astrophysics Data System (ADS)

Sanaga, S.; Vijay, S.; Kbvn, P.; Peddinti, S. R.; P S L, S.

2017-12-01

Fractured geologic media poses formidable challenges to hydrogeologists due of the strenuous mapping of fracture-matrix system and quantification of flow and transport processes. In this research, we demonstrated the efficacy of tracer-ERT studies coupled with numerical simulations to delineate preferential flow paths in a fractured granite aquifer of Deccan traps in India. A series of natural gradient saline tracer experiments were conducted from a depth window of 18 to 22 m in an injection well located inside the IIT Hyderabad campus. Tracer migration was monitored in a time-lapse mode using two cross-sectional surface ERT profiles placed in the direction of flow gradient. Dynamic changes in sub-surface electrical properties inferred via resistivity anomalies were used to highlight preferential flow paths of the study area. ERT-derived tracer breakthrough curves were in agreement with geochemical sample measurements (R2=0.74). Fracture geometry and hydraulic properties derived from ERT and pumping tests were then used to evaluate two mathematical conceptualizations that are relevant to fractured aquifers. Results of numerical analysis conclude that a dual continuum model that combines matrix and fracture systems through a flow exchange term has outperformed equivalent continuum model in reproducing tracer concentrations at the monitoring wells (evident by decrease in RMSE from 199 mg/l to 65 mg/l). A sensitivity analysis of the model parameters reveals that spatial variability in hydraulic conductivity, local-scale dispersion, and flow exchange at fracture-matrix interface have a profound effect on model simulations. Keywords: saline tracer, ERT, fractured granite, groundwater, preferential flow, numerical simulation

Paramagnetism Paradoxes: Projectable Demonstrations

ERIC Educational Resources Information Center

Sauls, Frederick C.; Vitz, Ed

2008-01-01

Drops of oil in Mn(SO[subscript 4])(aq) and drops of the solution in oil show opposite effects when brought near a rare earth magnet. Oxygen, nitrogen, and air bubbles atop water show expected attraction, repulsion, and null behavior, respectively. Air bubbles atop aqueous Mn(SO[subscript 4]) show paradoxical behavior because the magnet's…

A Simple Demonstration of the Curie-Weiss Law and a Spin-Crossover Compound.

ERIC Educational Resources Information Center

Hutchinson, Bennett; And Others

1980-01-01

Discusses an addition to an apparatus which allows the effect of temperature on a paramagnetic compound to be measured, therefore demonstrating the Curie-Weiss law. The experiment can be used as a demonstration or student experiment to stimulate discussion of magnetic susceptibility and ligand field trips. (Author/JN)

Small cause - big effect: improvement in interface design results in improved data quality - a multicenter crossover study.

PubMed

Ahlbrandt, Janko; Henrich, Michael; Hartmann, Bernd A; Bundschuh, Bettina B; Schwarz, Julia; Klasen, Joachim; Röhrig, Rainer

2012-01-01

In Germany the core data set for anesthesia version 3.0 was recently introduced for external quality assurance, which includes five surgical tracer procedures. We found a low rate of correctly documented tracers when compared to procedure data (OPS-Codes) documented separately. Examination revealed that the graphical user interface (GUI) contravened the dialogue principles as defined in EN ISO 9241-110. We worked with the manufacturer to implement small improvements and roll out the software. A crossover study was conducted at a university hospital and a municipal hospital chain with five hospitals. All study sites and surgical tracer procedures combined, we found an improvement from 42% to 65% (p<0.001; N=34,610) correctly documented anesthesias. We also saw improvements for most of the observed surgical tracer procedures at all hospitals. Our results show the big effect small changes to the GUI can have on data quality. They also raise the question, if highly flexible and parameterized clinical documentation systems are suited to achieve high usability. Finding the right balance between GUIs designed by usability experts and the flexibility of parameterization by administrators will be a difficult task for the future and subject to further research.

Monte Carlo simulations of protein micropatterning in biomembranes: effects of immobile sticky obstacles

NASA Astrophysics Data System (ADS)

Arnold, Andreas M.; Sevcsik, Eva; Schütz, Gerhard J.

2016-09-01

Single molecule trajectories of lipids and proteins can yield valuable information about the nanoscopic organization of the plasma membrane itself. The interpretation of such trajectories, however, is complicated, as the mobility of molecules can be affected by the presence of immobile obstacles, and the transient binding of the tracers to these obstacles. We have previously developed a micropatterning approach that allows for immobilizing a plasma membrane protein and probing the diffusional behavior of a putative interaction partner in living cells. Here, we provide guidelines on how this micropatterning approach can be extended to quantify interaction parameters between plasma membrane constituents in their natural environment. We simulated a patterned membrane system and evaluated the effect of different surface densities of patterned immobile obstacles on the relative mobility as well as the surface density of diffusing tracers. In the case of inert obstacles, the size of the obstacle can be assessed from its surface density at the percolation threshold, which in turn can be extracted from the diffusion behavior of the tracer. For sticky obstacles, 2D dissociation constants can be determined from the tracer diffusion or surface density.

Paramagnetic or diamagnetic persistent currents? A topological point of view

NASA Astrophysics Data System (ADS)

Waintal, Xavier

2009-03-01

A persistent current flows at low temperatures in small conducting rings when they are threaded by a magnetic flux. I will discuss the sign of this persistent current (diamagnetic or paramagnetic response) in the special case of N electrons in a one dimensional ring [1]. One dimension is very special in the sense that the sign of the persistent current is entirely controlled by the topology of the system. I will establish lower bounds for the free energy in the presence of arbitrary electron-electron interactions and external potentials. Those bounds are the counterparts of upper bounds derived by Leggett using another topological argument. Rings with odd (even) numbers of polarized electrons are always diamagnetic (paramagnetic). The situation is more interesting with unpolarized electrons where Leggett upper bound breaks down: rings with N=4n exhibit either paramagnetic behavior or a superconductor-like current-phase relation. The topological argument provides a rigorous justification for the phenomenological Huckel rule which states that cyclic molecules with 4n + 2 electrons like benzene are aromatic while those with 4n electrons are not. [4pt] [1] Xavier Waintal, Geneviève Fleury, Kyryl Kazymyrenko, Manuel Houzet, Peter Schmitteckert, and Dietmar Weinmann Phys. Rev. Lett.101, 106804 (2008).

Two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

NASA Astrophysics Data System (ADS)

Hagmann, C.; Richards, P. L.

We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites, as well as to cool cryogenic X-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic caesium alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium gallium garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar cords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10-100 h. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

Rapid detection of Bacillus anthracis spores using a super-paramagnetic lateral-flow immunological detection system.

PubMed

Wang, Dian-Bing; Tian, Bo; Zhang, Zhi-Ping; Deng, Jiao-Yu; Cui, Zong-Qiang; Yang, Rui-Fu; Wang, Xu-Ying; Wei, Hong-Ping; Zhang, Xian-En

2013-04-15

There is an urgent need for convenient, sensitive, and specific methods to detect the spores of Bacillus anthracis, the causative agent of anthrax, because of the bioterrorism threat posed by this bacterium. In this study, we firstly develop a super-paramagnetic lateral-flow immunological detection system for B. anthracis spores. This system involves the use of a portable magnetic assay reader, super-paramagnetic iron oxide particles, lateral-flow strips and two different monoclonal antibodies directed against B. anthracis spores. This detection system specifically recognises as few as 400 pure B. anthracis spores in 30 min. This system has a linear range of 4×10³-10⁶ CFU ml⁻¹ and reproducible detection limits of 200 spores mg⁻¹ milk powder and 130 spores mg⁻¹ soil for simulated samples. In addition, this approach shows no obvious cross-reaction with other related Bacillus spores, even at high concentrations, and has no significant dependence on the duration of the storage of the immunological strips. Therefore, this super-paramagnetic lateral-flow immunological detection system is a promising tool for the rapid and sensitive detection of Bacillus anthracis spores under field conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

On the bispectra of very massive tracers in the Effective Field Theory of Large-Scale Structure

DOE PAGES

Nadler, Ethan O.; Perko, Ashley; Senatore, Leonardo

2018-02-01

The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a consistent perturbative framework for describing the statistical distribution of cosmological large-scale structure. In a previous EFTofLSS calculation that involved the one-loop power spectra and tree-level bispectra, it was shown that the k-reach of the prediction for biased tracers is comparable for all investigated masses if suitable higher-derivative biases, which are less suppressed for more massive tracers, are added. However, it is possible that the non-linear biases grow faster with tracer mass than the linear bias, implying that loop contributions could be the leading correction to the bispectra. To check this,more » we include the one-loop contributions in a fit to numerical data in the limit of strongly enhanced higher-order biases. Here, we show that the resulting one-loop power spectra and higher-derivative plus leading one-loop bispectra fit the two- and three-point functions respectively up to k≃0.19 h Mpc -1 and ksime 0.14 h Mpc -1 at the percent level. We find that the higher-order bias coefficients are not strongly enhanced, and we argue that the gain in perturbative reach due to the leading one-loop contributions to the bispectra is relatively small. Thus, we conclude that higher-derivative biases provide the leading correction to the bispectra for tracers of a very wide range of masses.« less

On the bispectra of very massive tracers in the Effective Field Theory of Large-Scale Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadler, Ethan O.; Perko, Ashley; Senatore, Leonardo

The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a consistent perturbative framework for describing the statistical distribution of cosmological large-scale structure. In a previous EFTofLSS calculation that involved the one-loop power spectra and tree-level bispectra, it was shown that the k-reach of the prediction for biased tracers is comparable for all investigated masses if suitable higher-derivative biases, which are less suppressed for more massive tracers, are added. However, it is possible that the non-linear biases grow faster with tracer mass than the linear bias, implying that loop contributions could be the leading correction to the bispectra. To check this,more » we include the one-loop contributions in a fit to numerical data in the limit of strongly enhanced higher-order biases. Here, we show that the resulting one-loop power spectra and higher-derivative plus leading one-loop bispectra fit the two- and three-point functions respectively up to k≃0.19 h Mpc -1 and ksime 0.14 h Mpc -1 at the percent level. We find that the higher-order bias coefficients are not strongly enhanced, and we argue that the gain in perturbative reach due to the leading one-loop contributions to the bispectra is relatively small. Thus, we conclude that higher-derivative biases provide the leading correction to the bispectra for tracers of a very wide range of masses.« less

Spin relaxation measurements of electrostatic bias in intermolecular exploration

NASA Astrophysics Data System (ADS)

Teng, Ching-Ling; Bryant, Robert G.

2006-04-01

We utilize the paramagnetic contribution to proton spin-lattice relaxation rate constants induced by freely diffusing charged paramagnetic centers to investigate the effect of charge on the intermolecular exploration of a protein by the small molecule. The proton NMR spectrum provided 255 resolved resonances that report how the explorer molecule local concentration varies with position on the surface. The measurements integrate over local dielectric constant variations, and, in principle, provide an experimental characterization of the surface free energy sampling biases introduced by the charge distribution on the protein. The experimental results for ribonuclease A obtained using positive, neutral, and negatively charged small nitroxide radicals are qualitatively similar to those expected from electrostatic calculations. However, while systematic electrostatic trends are apparent, the three different combinations of the data sets do not yield internally consistent values for the electrostatic contribution to the intermolecular free energy. We attribute this failure to the weakness of the electrostatic sampling bias for charged nitroxides in water and local variations in effective translational diffusion constant at the water-protein interface, which enters the nuclear spin relaxation equations for the nitroxide-proton dipolar coupling.

Optimized co-solute paramagnetic relaxation enhancement for the rapid NMR analysis of a highly fibrillogenic peptide.

PubMed

Oktaviani, Nur Alia; Risør, Michael W; Lee, Young-Ho; Megens, Rik P; de Jong, Djurre H; Otten, Renee; Scheek, Ruud M; Enghild, Jan J; Nielsen, Niels Chr; Ikegami, Takahisa; Mulder, Frans A A

2015-06-01

Co-solute paramagnetic relaxation enhancement (PRE) is an attractive way to speed up data acquisition in NMR spectroscopy by shortening the T 1 relaxation time of the nucleus of interest and thus the necessary recycle delay. Here, we present the rationale to utilize high-spin iron(III) as the optimal transition metal for this purpose and characterize the properties of its neutral chelate form Fe(DO3A) as a suitable PRE agent. Fe(DO3A) effectively reduces the T 1 values across the entire sequence of the intrinsically disordered protein α-synuclein with negligible impact on line width. The agent is better suited than currently used alternatives, shows no specific interaction with the polypeptide chain and, due to its high relaxivity, is effective at low concentrations and in 'proton-less' NMR experiments. By using Fe(DO3A) we were able to complete the backbone resonance assignment of a highly fibrillogenic peptide from α1-antitrypsin by acquiring the necessary suite of multidimensional NMR datasets in 3 h.

Deproteinization assessment using isotopically enriched compounds to trace the coprecipitation of low-molecular-weight selenium species with proteins.

PubMed

Godin, Simon; Bouzas-Ramos, Diego; Fontagné-Dicharry, Stéphanie; Bouyssière, Brice; Bueno, Maïté

2017-08-01

Studies have shown that information related to the presence of low-molecular-weight metabolites is frequently lost after deproteinization of complex matrices, such as blood and plasma, during sample preparation. Therefore, the effect of several deproteinization reagents on low-molecular-weight selenium species has been compared by species-specific isotope labeling. Two isotopically enriched selenium tracers were used to mimic models of small inorganic anionic ( 77 Se-selenite) and organic zwitterionic ( 76 Se-selenomethionine) species. The results presented here show that the use of a methanol-acetonitrile-acetone (1:1:1 v/v/v) mixture provided approximately two times less tracer loss from plasma samples in comparison with the classic procedure using acetonitrile, which may not be optimal as it leads to important losses of low-molecular-weight selenium species. In addition, the possible interactions between selenium tracers and proteins were investigated, revealing that both coprecipitation phenomena and association with proteins were potentially responsible for selenite tracer losses during protein precipitation in blood samples. However, coprecipitation phenomena were found to be fully responsible for losses of both tracers observed in plasma samples and of the selenomethionine tracer in blood samples. This successfully applied strategy is anticipated to be useful for more extensive future studies in selenometabolomics. Copyright © 2017 Elsevier Inc. All rights reserved.

Combining 3D Hydraulic Tomography with Tracer Tests for Improved Transport Characterization.

PubMed

Sanchez-León, E; Leven, C; Haslauer, C P; Cirpka, O A

2016-07-01

Hydraulic tomography (HT) is a method for resolving the spatial distribution of hydraulic parameters to some extent, but many details important for solute transport usually remain unresolved. We present a methodology to improve solute transport predictions by combining data from HT with the breakthrough curve (BTC) of a single forced-gradient tracer test. We estimated the three dimensional (3D) hydraulic-conductivity field in an alluvial aquifer by inverting tomographic pumping tests performed at the Hydrogeological Research Site Lauswiesen close to Tübingen, Germany, using a regularized pilot-point method. We compared the estimated parameter field to available profiles of hydraulic-conductivity variations from direct-push injection logging (DPIL), and validated the hydraulic-conductivity field with hydraulic-head measurements of tests not used in the inversion. After validation, spatially uniform parameters for dual-domain transport were estimated by fitting tracer data collected during a forced-gradient tracer test. The dual-domain assumption was used to parameterize effects of the unresolved heterogeneity of the aquifer and deemed necessary to fit the shape of the BTC using reasonable parameter values. The estimated hydraulic-conductivity field and transport parameters were subsequently used to successfully predict a second independent tracer test. Our work provides an efficient and practical approach to predict solute transport in heterogeneous aquifers without performing elaborate field tracer tests with a tomographic layout. © 2015, National Ground Water Association.

Lattice-Boltzmann simulations of microswimmer-tracer interactions

NASA Astrophysics Data System (ADS)

de Graaf, Joost; Stenhammar, Joakim

2017-02-01

Hydrodynamic interactions in systems composed of self-propelled particles, such as swimming microorganisms and passive tracers, have a significant impact on the tracer dynamics compared to the equivalent "dry" sample. However, such interactions are often difficult to take into account in simulations due to their computational cost. Here, we perform a systematic investigation of swimmer-tracer interaction using an efficient force-counterforce-based lattice-Boltzmann (LB) algorithm [De Graaf et al., J. Chem. Phys. 144, 134106 (2016), 10.1063/1.4944962] in order to validate its ability to capture the relevant low-Reynolds-number physics. We show that the LB algorithm reproduces far-field theoretical results well, both in a system with periodic boundary conditions and in a spherical cavity with no-slip walls, for which we derive expressions here. The force-lattice coupling of the LB algorithm leads to a "smearing out" of the flow field, which strongly perturbs the tracer trajectories at close swimmer-tracer separations, and we analyze how this effect can be accurately captured using a simple renormalized hydrodynamic theory. Finally, we show that care must be taken when using LB algorithms to simulate systems of self-propelled particles, since its finite momentum transport time can lead to significant deviations from theoretical predictions based on Stokes flow. These insights should prove relevant to the future study of large-scale microswimmer suspensions using these methods.

EGS in sedimentary basins: sensitivity of early-flowback tracer signals to induced-fracture parameters

NASA Astrophysics Data System (ADS)

Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

2015-04-01

Artificial-fracture design, and fracture characterization during or following stimulation treatment is a central aspect of many EGS ('enhanced' or 'engineered' geothermal system) projects. During the creation or stimulation of an EGS, the injection of fluids, followed by flowback and production stages offers the opportunity for conducting various tracer tests in a single-well (SW) configuration, and given the typical operational and time limitations associated with such tests, along with the need to assess treatment success in real time, investigators mostly favour using short-time tracer-test data, rather than awaiting long-term 'tailings' of tracer signals. Late-time tracer signals from SW injection-flowback and production tests have mainly been used for the purpose of multiple-fracture inflow profiling in multi-layer reservoirs [1]. However, the potential of using SW short-term tracer signals for fracture characterization [2, 3] remained little explored as yet. Dealing with short-term flowback signals, we face a certain degree of parameter interplay, leading to ambiguity in fracture parameter inversion from the measured signal of a single tracer. This ambiguity can, to a certain extent, be overcome by - combining different sources of information (lithostratigraphy, and hydraulic monitoring) in order to constrain the variation range of hydrogeologic parameters (matrix and fracture permeability and porosity, fracture size), - using different types of tracers, such as conservative tracer pairs with contrasting diffusivity, or tracers pairs with contrasting sorptivity onto target surfaces. Fracture height is likely to be constrained by lithostratigraphy, while fracture length is supposed to be determinable from hydraulic monitoring (pressure recordings); the flowback rate can be assumed as a known (measurable) quantity during individual-fracture flowback. This leaves us with one or two unknown parameters to be determined from tracer signals: - the transport-effective aperture, in a water fracture (WF), or - fracture thickness and porosity, for a gel-proppant fracture (GPF). We find that parameter determination from SW early signals can significantly be improved by concomitantly using a number of solute tracers with different transport and retardation behaviour. We considered tracers of different sorptivity to proppant coatings, and to matrix rock surfaces, for GPF, as well as contrasting-diffusivity or -sorptivity tracers, for WF. An advantage of this SW approach is that it requires only small chaser volumes (few times the fracture volume), not relying on advective penetration into the rock matrix. Thus, selected tracer species are to be injected during the very last stage of the fracturing process, when fracture sizes and thus target parameters are supposed to attain more or less stable values. We illustrate the application of these tracer test design principles using hydro- and lithostratigraphy data from the Geothermal Research Platform at Groß Schönebeck [4], targeting a multi-layer reservoir (sedimentary and crystalline formations in 4-5 km depth) in the NE-German Sedimentary Basin. Acknowledgments: This work benefited from long-term support from Baker Hughes (Celle) and from the Lower-Saxonian Science and Culture Ministry (MWK Niedersachsen) within the applied research project gebo (Geothermal Energy and High-Performance Drilling, 2009-2014). The first author gratefully acknowledges continued financial support from the DAAD (German Academic Exchange Service) to pursuing Ph. D. work. References: [1] http://www.sciencedirect.com/science/article/pii/S1876610214017391 [2] http://www.geothermal-energy.org/cpdb/record_detail.php?id=7215 [3] http://www.geothermal-energy.org/cpdb/record_detail.php?id=19034 [4] http://www.gfz-potsdam.de/en/scientific-services/laboratories/gross-schoenebeck/

TracerLPM (Version 1): An Excel® workbook for interpreting groundwater age distributions from environmental tracer data

USGS Publications Warehouse

Jurgens, Bryant C.; Böhlke, J.K.; Eberts, Sandra M.

2012-01-01

TracerLPM is an interactive Excel® (2007 or later) workbook program for evaluating groundwater age distributions from environmental tracer data by using lumped parameter models (LPMs). Lumped parameter models are mathematical models of transport based on simplified aquifer geometry and flow configurations that account for effects of hydrodynamic dispersion or mixing within the aquifer, well bore, or discharge area. Five primary LPMs are included in the workbook: piston-flow model (PFM), exponential mixing model (EMM), exponential piston-flow model (EPM), partial exponential model (PEM), and dispersion model (DM). Binary mixing models (BMM) can be created by combining primary LPMs in various combinations. Travel time through the unsaturated zone can be included as an additional parameter. TracerLPM also allows users to enter age distributions determined from other methods, such as particle tracking results from numerical groundwater-flow models or from other LPMs not included in this program. Tracers of both young groundwater (anthropogenic atmospheric gases and isotopic substances indicating post-1940s recharge) and much older groundwater (carbon-14 and helium-4) can be interpreted simultaneously so that estimates of the groundwater age distribution for samples with a wide range of ages can be constrained. TracerLPM is organized to permit a comprehensive interpretive approach consisting of hydrogeologic conceptualization, visual examination of data and models, and best-fit parameter estimation. Groundwater age distributions can be evaluated by comparing measured and modeled tracer concentrations in two ways: (1) multiple tracers analyzed simultaneously can be evaluated against each other for concordance with modeled concentrations (tracer-tracer application) or (2) tracer time-series data can be evaluated for concordance with modeled trends (tracer-time application). Groundwater-age estimates can also be obtained for samples with a single tracer measurement at one point in time; however, prior knowledge of an appropriate LPM is required because the mean age is often non-unique. LPM output concentrations depend on model parameters and sample date. All of the LPMs have a parameter for mean age. The EPM, PEM, and DM have an additional parameter that characterizes the degree of age mixing in the sample. BMMs have a parameter for the fraction of the first component in the mixture. An LPM, together with its parameter values, provides a description of the age distribution or the fractional contribution of water for every age of recharge contained within a sample. For the PFM, the age distribution is a unit pulse at one distinct age. For the other LPMs, the age distribution can be much broader and span decades, centuries, millennia, or more. For a sample with a mixture of groundwater ages, the reported interpretation of tracer data includes the LPM name, the mean age, and the values of any other independent model parameters. TracerLPM also can be used for simulating the responses of wells, springs, streams, or other groundwater discharge receptors to nonpoint-source contaminants that are introduced in recharge, such as nitrate. This is done by combining an LPM or user-defined age distribution with information on contaminant loading at the water table. Information on historic contaminant loading can be used to help evaluate a model's ability to match real world conditions and understand observed contaminant trends, while information on future contaminant loading scenarios can be used to forecast potential contaminant trends.

On magnetic structure of CuFe 2Ge 2: Constrains from the 57Fe Mössbauer spectroscopy

DOE PAGES

Bud’ko, Sergey L.; Jo, Na Hyun; Downing, Savannah S.; ...

2017-09-20

57Fe Mössbauer spectroscopy measurements were performed on a powdered CuFe 2Ge 2 sample that orders antiferromagnetically at ~175 K. Whereas a paramagnetic doublet was observed above the Néel temperature, a superposition of paramagnetic doublet and magnetic sextet (in approximately 0.5:0.5 ratio) was observed in the magnetically ordered state, suggesting a magnetic structure similar to a double-Q spin density wave with half of the Fe paramagnetic and another half bearing static moment of ~0.5–1μ B. Lastly, these results call for a re-evaluation of the recent neutron scattering data and band structure calculations, as well as for deeper examination of details ofmore » sample preparation techniques.« less

Speeding up NMR by in Situ Photo-Induced Reversible Acceleration of T1 -Relaxation (PIRAT).

PubMed

Stadler, Eduard; Dommaschk, Marcel; Frühwirt, Philipp; Herges, Rainer; Gescheidt, Georg

2018-03-05

Increasing the signal-to-noise ratio is one of the major goals in the field of NMR spectroscopy. In this proof of concept, we accelerate relaxation during an NMR pulse sequence using photo-generated paramagnetic states of an inert sensitizer. For the follow-up acquisition period, the system is converted to a diamagnetic state. The reversibility of the photo-induced switching allows extensive repetition required for multidimensional NMR. We thus eliminate the obstacle of line-broadening by the presence of paramagnetic species. In this contribution, we show how cycling of synchronized light/pulse sequences leads to an enhanced efficiency in multidimensional NMR. Our approach utilizes a molecular spin switch reversibly altering between a paramagnetic and diamagnetic state. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of radiation-induced damage in high performance polymers by electron paramagnetic resonance imaging spectroscopy

NASA Technical Reports Server (NTRS)

Suleman, Naushadalli K.

1992-01-01

The potential for long-term human activity beyond the Earth's protective magnetosphere is limited in part by the lack of detailed information on the effectiveness and performance of existing structural materials to shield the crew and spacecraft from highly penetrating space radiations. The two radiations of greatest concern are high energy protons emitted during solar flares and galactic cosmic rays which are energetic ions ranging from protons to highly oxidized iron. Although the interactions of such high-energy radiations with matter are not completely understood at this time, the effects of the incident radiation are clearly expected to include the formation of paramagnetic spin centers via ionization and bond-scission reactions in the molecular matrices of structural materials. Since this type of radiation damage is readily characterized by Electron Paramagnetic Resonance (EPR) spectroscopy, the NASA Langley Research Center EPR system was repaired and brought on-line during the 1991 ASEE term. A major goal of the 1992 ASEE term was to adapt the existing core of the LaRC EPR system to meet the requirements for EPR Imaging--a powerful new technique which provides detailed information on the internal structure of materials by mapping the spatial distribution of unpaired spin density in bulk media. Major impetus for this adaptation arises from the fact that information derived from EPRI complements other methods such as scanning electron microscopy which primarily characterize surface phenomena. The modification of the EPR system has been initiated by the construction of specially designed, counterwound Helmholtz coils which will be mounted on the main EPR electromagnet. The specifications of the coils have been set to achieve a static linear magnetic field gradient of 10 gauss/mm/amp along the principal (Z) axis of the Zeeman field. Construction is also in progress of a paramagnetic standard in which the spin distribution is known in all three dimensions. This sample will be used to assess the linearity of the magnetic field gradient and to ensure authentic image reconstruction. A second major task was to secure the computer capability to enable image reconstruction from projection data generated by the magnetic field gradients. To this end, commercially available and public domain software packages which perform inverse Fourier Transform and convoluted (filtered) back projection functions are being integrated into the existing EPR data processing system.

Journal: A Review of Some Tracer-Test Design Equations for Tracer-Mass Estimation and Sample Collection Frequency

EPA Science Inventory

Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estima...

Micro-bubbles and Micro-particles are Not Faithful Tracers of Turbulent Acceleration

NASA Astrophysics Data System (ADS)

Sun, Chao; Mathai, Varghese; Calzavarini, Enrico; Brons, Jon; Lohse, Detlef

2016-11-01

We report on the Lagrangian statistics of acceleration of small (sub-Kolmogorov) bubbles and tracer particles with Stokes number St <<1 in turbulent flow. At decreasing Reynolds number, the bubble accelerations show deviations from that of tracer particles, i.e. they deviate from the Heisenberg-Yaglom prediction and show a quicker decorrelation despite their small size and minute St. Using direct numerical simulations, we show that these effects arise due the drift of these particles through the turbulent flow. We theoretically predict this gravity-driven effect for developed isotropic turbulence, with the ratio of Stokes to Froude number or equivalently the particle drift-velocity governing the enhancement of acceleration variance and the reductions in correlation time and intermittency. Our predictions are in good agreement with experimental and numerical results. The present findings are relevant to a range of scenarios encompassing tiny bubbles and droplets that drift through the turbulent oceans and the atmosphere.

Bioelimination of /sup 51/Cr and /sup 85/Sr by cockroaches, Gromphadorhina portentosa (Orthoptera: Blaberidae), as affected by mites, Gromphadorholaelaps schaeferi (parasitiformes: laelapidae)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schowalter, T.D.; Crossley, D.A. Jr.

1982-03-01

This paper describes rates of Chromium-51 and Strontium-85 assimilation and bioelimination by the hissing cockroach, Gromphadorhina portentosa (Schaum), when the symbiotic mite, Gromphadorholaelaps schaeferi Till, was present or removed. Mite-infested cockroaches had significantly higher rates of /sup 51/Cr elimination relative to mite-free cockroaches, implying more rapid gut clearance times. We did not find a significant mite effect on /sup 85/Sr elimination by the host, but mite effects could have been masked by the apparently unique process of nutrient assimilation and elimination by G. portentosa. Conventional models of radioactive tracer bioelimination predict a rapid initial loss of tracer due to gutmore » clearance, followed by a slower loss due to excretion of assimilated tracer. Our results indicated that assimilated /sup 85/Sr was eliminated earlier than unassimilated /sup 85/Sr was lost by defecation.« less

Ocean Turbulence V: Mesoscale Modeling in Level Coordinates. The Effect of Random Nature of Density

NASA Technical Reports Server (NTRS)

Canuto, V. M.; Dubovikov, M. S.

1998-01-01

The main result of this paper is the derivation of a new expression for the tracer subgrid term in level coordinates S(l) to be employed in O-GCM. The novel feature is the proper account of the random nature of the density field which strongly affects the transformation from isopycnal to level coordinates of the variables of interest, velocity and tracer fields, their correlation functions and ultimately the subgrid terms. In deriving our result we made use of measured properties of vertical ocean turbulence. The major new results are: 1) the new subgrid expression is different from that of the heuristic GM model, 2) u++(tracer)=1/2u+(thickness), where u++ and u+ are the tracer and thickness bolus velocities. In previous models, u++ = u+, 2) the subgrid for a tracer tau is not the same as that for the density rho even when one accounts for the obvious absence of a diffusion term in the latter. The difference stems from a new treatment of the stochastic nature of the density, 3) the mesoscale diffusivity enters both locally and non-locally, as the integral over all z's from the bottom of the ocean to the level z.

Radio-tracer techniques for the study of flow in saturated porous materials

USGS Publications Warehouse

Skibitzke, H.E.; Chapman, H.T.; Robinson, G.M.; McCullough, Richard A.

1961-01-01

An experiment was conducted by the U.S. Geological Survey to determine the feasibility of using a radioactive substance as a tracer in the study of microscopic flow in a saturated porous solid. A radioactive tracer was chosen in preference to dye or other chemical in order to eliminate effects of the tracer itself on the flow system such as those relating to density, viscosity and surface tension. The porous solid was artificial "sandstone" composed of uniform fine grains of sand bonded together with an epoxy adhesive. The sides of the block thus made were sealed with an epoxy coating compound to insure water-tightness. Because of the chemical inertness of the block it was possible to use radioactive phosphorus (P32). Ion-exchange equilibrium was created between the block and nonradioactive phosphoric acid. Then a tracer tagged with P32 was injected into the block in the desired geometric configuration, in this case, a line source. After equilibrium in isotopic exchange was reached between the block and the line source, the block was rinsed, drained and sawn into slices. It was found that a quantitative analysis of the flow system may be made by assaying the dissected block. ?? 1961.

Trajectory-based modeling of fluid transport in a medium with smoothly varying heterogeneity

DOE PAGES

Vasco, D. W.; Pride, Steven R.; Commer, Michael

2016-03-04

Using an asymptotic methodology, valid in the presence of smoothly varying heterogeneity and prescribed boundaries, we derive a trajectory-based solution for tracer transport. The analysis produces a Hamilton-Jacobi partial differential equation for the phase of the propagating tracer front. The trajectories follow from the characteristic equations that are equivalent to the Hamilton-Jacobi equation. The paths are determined by the fluid velocity field, the total porosity, and the dispersion tensor. Due to their dependence upon the local hydrodynamic dispersion, they differ from conventional streamlines. This difference is borne out in numerical calculations for both uniform and dipole flow fields. In anmore » application to the computational X-ray imaging of a saline tracer test, we illustrate that the trajectories may serve as the basis for a form of tracer tomography. In particular, we use the onset time of a change in attenuation for each volume element of the X-ray image as a measure of the arrival time of the saline tracer. In conclusion, the arrival times are used to image the spatial variation of the effective hydraulic conductivity within the laboratory sample.« less

An evaluation of tracer dilution techniques for gauging of rivers in flood

NASA Astrophysics Data System (ADS)

Airey, P. L.; Calf, G. E.; Davison, A.; Easey, J. F.; Morley, A. W.

1984-10-01

The use of the tracer dilution technique to gauge flow over broad shallow floodplains is examined. Because of the long mixing lengths, it sometimes takes several days for the passage of the laterally dispersed pulse. Tracer methods can be used if the flow rates vary linearly during the passage of the pulse. The measured flow rate is related to the time at which the first moment of the concentration profile (∫ tc( z, t)d t) is zero. An experimental verification is presented. By analysing the tracer pulse shapes before the establishment of complete mixing, it was demonstrated that the effective dispersion coefficients were independent of the scale of turbulence over the range 10 m to ˜1 km. This is consistent with the establishment of isotropic turbulence on the floodplain in contrast to oceanic surfaces. The velocity of the tracer is a factor of 2 less than that of an advancing wave front, which is in acceptable agreement with prediction. It is concluded that the transport of a non-interacting contaminant across the floodplain can be predicted from the wave front velocity and the dispersion coefficients measured close to the release point.

Observations of axisymmetric tracer particle orientation during flow through a dilute fixed bed of fibers

NASA Astrophysics Data System (ADS)

Frattini, Paul L.; Shaqfeh, Eric S. G.; Levy, Jeffrey L.; Koch, Donald L.

1991-11-01

Direct microstructural evidence for net tracer particle orientation induced solely by hydrodynamic interactions in a dilute, disordered, fibrous media is reported. A dilute fixed bed of randomly placed fibers was constructed and glycerol/water suspensions of either synthetic akaganeite (βFeOOH, average aspect ratio 6.3) or hematite (αFe2O3, average aspect ratio 1.6) tracer particles were made to flow axially through the bed at prescribed flow rates. Conservative linear dichroism, a noninvasive light scattering technique, was employed to provide a direct measure of the orientational order parameter for the tracer particle population at the end of the bed. The effect of Brownian motion on the hydrodynamically induced order in the suspensions was studied over three orders of magnitude in scaled rotary Peclet number, 5

Carbonaceous aerosol tracers in ice-cores record multi-decadal climate oscillations

PubMed Central

Seki, Osamu; Kawamura, Kimitaka; Bendle, James A. P.; Izawa, Yusuke; Suzuki, Ikuko; Shiraiwa, Takayuki; Fujii, Yoshiyuki

2015-01-01

Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (μg/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (μg/m3) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research. PMID:26411576

Reciprocating magnetic refrigerator employing tandem porous matrices within a reciprocating displacer

NASA Technical Reports Server (NTRS)

Johnson, D. L. (Inventor)

1985-01-01

Disclosed is a method and apparatus for a magnetic refrigeration system. A continuously reciprocating displacer houses at least a pair of paramagnetic substances each of which is alternately driven into and out of a magnetic field. Two separate bidirectional pumping systems flow helium gas through the displacer and through both paramagnetic substances to create heat exchange conditions at two separate temperature extremes.

Environmental effects of dredging. Documentation of the dyecon module for ADDAMS: Determining the hydraulic retention and efficiency of confined disposal facilities. Technical note

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, D.F.; Schroeder, P.R.; Engler, R.M.

This technical note describes procedures for determining mean hydraulic retention time and efficiency of a confined disposal facility (CDF) from a dye tracer slug test. These parameters are required to properly design a CDF for solids retention and for effluent quality considerations. Detailed information on conduct and analysis of dye tracer studies can be found in Engineer Manual 1110-2-5027, Confined Dredged Material Disposal. This technical note documents the DYECON computer program which facilitates the analysis of dye tracer concentration data and computes the hydraulic efficiency of a CDF as part of the Automated Dredging and Disposal Alternatives Management System (ADDAMS).

Effect of antecedent soil moisture on preferential flow in a texture-contrast soil

NASA Astrophysics Data System (ADS)

Hardie, Marcus A.; Cotching, William E.; Doyle, Richard B.; Holz, Greg; Lisson, Shaun; Mattern, Kathrin

2011-02-01

SummaryThe effect of soil moisture status on preferential flow in a texture-contrast soil was investigated by applying 25 mm Brilliant Blue dye tracer to soil profiles at high and low antecedent soil moisture. Differences in soil morphology and chemistry between soil profiles had little effect on the depth of dye infiltration and dye distribution down the profile. Antecedent soil moisture strongly influenced the type, depth and rate of dye tracer movement. In the wet treatment, the dye tracer infiltrated to depths between 0.24 and 0.40 m, at an average rate of 120 mm h -1. Whilst in the dry treatment, the same volume of dye tracer infiltrated to between 0.85 and 1.19 m depth at an average rate of 1160 mm h -1. In dry antecedent conditions, finger flow developed in the A1 horizon as a result of water repellency. In the wet treatment, the wetting front developed permutations but did not break into fingers. Despite similar particle size distributions, flow in the A2 e was slower than the A1 horizon, due to the absence of macropores. In the dry treatment, the dye tracer ponded on the upper surface of the B21 horizon, which then spilled down the sides of the large clay columns as rivulets, at rates of between 2000 and 3000 mm h -1. The dye tracer accumulated at the base of the columns resulting in backfilling of the inter column shrinkage cracks, at an estimated rate of 750 mm h -1. In the subsoil, water movement occurred via shrinkage cracks which resulted in flow by-passing 99% of the soil matrix in the B21 horizon and 94% of the soil matrix in the B22 horizon. Evidence of rapid and deep infiltration in 'dry' texture-contrast soils has implications for water and solute management. This knowledge could be used to: (i) improve irrigation and fertilizer efficiency (ii) explain variations in crop yield (iii) reduce salinity through improved leaching practices, (iv) reduce the risk of agrochemicals contaminating shallow groundwater.

TB tracer teams in South Africa: knowledge, practices and challenges of tracing TB patients to improve adherence

PubMed Central

2013-01-01

Background In 2008–2009 the South African National Tuberculosis (TB) Program (NTP) implemented a national pilot project, the TB Tracer Project, aiming to decrease default rates and improve patient outcomes. The current study aimed to inform the NTP by describing the knowledge, attitudes, and practices of TB program personnel involved with tracing activities. Methods A self-administered written questionnaire was sent to TB staff, managers and tracer team leaders to assess basic TB knowledge, attitudes and practices. Descriptive statistics were used to summarize results and the chi-squared statistic was used to compare responses of staff at facilities that participated in the TB Tracer Project (tracer) and those that followed standard NTP care (non-tracer). Results Of 560 total questionnaires distributed, 270 were completed and returned (response rate 48%). Total TB knowledge ranged from 70.8-86.3% correct across all response groups. However, just over half (range 50–59.3%) of each respondent group was able to correctly identify the four components of a DOT encounter. A patient no longer feeling sick was cited by 72.1% of respondents as the reason patients fail to adhere to treatment. Tracer teams were viewed as an effective means to get patients to return to treatment by 96.3% of health facility level respondents. Tracer team leaders reported concerns including lack of logistical support (41.7%), insufficient physical safety precautions (41.7%), and inadequate protection from contracting TB (39.1%). Upon patients returning to treatment at the clinic, facilities included in the TB Tracer Project were significantly more likely to discuss alternate DOTS arrangements than non-tracer facilities (79.2 vs. 66.4%, p = 0.03). Conclusions This study identified key components of knowledge, attitudes, and practices regarding TB patient tracing activities in South Africa. Educating patients on the essential need to complete treatment irrespective of clinical symptoms may help improve treatment adherence. Future scale-up and integration of TB tracing activities as part of standard TB management should include provisions for standardized training of personnel on the critical elements of DOTS, and for ensuring appropriate supervision, logistical support, and physical safety and TB transmission protection of tracing teams. PMID:24007294

In vitro and in vivo comparison of a tailored magnetic particle imaging blood pool tracer with Resovist.

PubMed

Kaul, Michael Gerhard; Mummert, Tobias; Jung, Caroline; Salamon, Johannes; Khandhar, Amit P; Ferguson, R Matthew; Kemp, Scott J; Ittrich, Harald; Krishnan, Kannan M; Adam, Gerhard; Knopp, Tobias

2017-05-07

Optimizing tracers for individual imaging techniques is an active field of research. The purpose of this study was to perform in vitro and in vivo magnetic particle imaging (MPI) measurements using a new monodisperse and size-optimized tracer, LS-008, and to compare it with the performance of Resovist, the standard MPI tracer. Magnetic particle spectroscopy (MPS) and in vitro MPI measurements were performed in concerns of concentration and amount of tracer in a phantom. In vivo studies were carried out in healthy FVB mice. The first group (n  =  3) received 60 µl LS-008 (87 mM) and the second (n  =  3) diluted Resovist of the same concentration and volume. Tracer injections were performed with a syringe pump during a dynamic MPI scan. For anatomic referencing MRI was applied beforehand of the MPI measurements. Summing up MPS examinations and in vitro MPI experiments, LS-008 showed better sensitivity and spatial resolution than Resovist. In vivo both tracers can visualize the propagation of the bolus through the inferior vena cava. MPI with LS-008 did show less temporal fluctuation artifacts and the pulsation of blood due to respiratory and cardiac cycle was detectable. With LS-008 the aorta was distinguishable from the caval vein while with Resovist this failed. A liver vessel and a vessel structure leading cranially could only be observed with LS-008 and not with Resovist. Beside these structural advantages both tracers showed very different blood half-life. For LS-008 we found 88 min. Resovist did show a fast liver accumulation and a half-life of 13 min. Only with LS-008 the perfusion fraction in liver and kidney was measureable. MPI for angiography can be significantly improved by applying more effective tracers. LS-008 shows a clear improvement concerning the delineation while resolving a larger number of vessels in comparison to Resovist. Therefore, in aspects of quality and quantity LS-008 is clearly favorable for angiographic and perfusion studies.

Towards tracer dose reduction in PET studies: Simulation of dose reduction by retrospective randomized undersampling of list-mode data.

PubMed

Gatidis, Sergios; Würslin, Christian; Seith, Ferdinand; Schäfer, Jürgen F; la Fougère, Christian; Nikolaou, Konstantin; Schwenzer, Nina F; Schmidt, Holger

2016-01-01

Optimization of tracer dose regimes in positron emission tomography (PET) imaging is a trade-off between diagnostic image quality and radiation exposure. The challenge lies in defining minimal tracer doses that still result in sufficient diagnostic image quality. In order to find such minimal doses, it would be useful to simulate tracer dose reduction as this would enable to study the effects of tracer dose reduction on image quality in single patients without repeated injections of different amounts of tracer. The aim of our study was to introduce and validate a method for simulation of low-dose PET images enabling direct comparison of different tracer doses in single patients and under constant influencing factors. (18)F-fluoride PET data were acquired on a combined PET/magnetic resonance imaging (MRI) scanner. PET data were stored together with the temporal information of the occurrence of single events (list-mode format). A predefined proportion of PET events were then randomly deleted resulting in undersampled PET data. These data sets were subsequently reconstructed resulting in simulated low-dose PET images (retrospective undersampling of list-mode data). This approach was validated in phantom experiments by visual inspection and by comparison of PET quality metrics contrast recovery coefficient (CRC), background-variability (BV) and signal-to-noise ratio (SNR) of measured and simulated PET images for different activity concentrations. In addition, reduced-dose PET images of a clinical (18)F-FDG PET dataset were simulated using the proposed approach. (18)F-PET image quality degraded with decreasing activity concentrations with comparable visual image characteristics in measured and in corresponding simulated PET images. This result was confirmed by quantification of image quality metrics. CRC, SNR and BV showed concordant behavior with decreasing activity concentrations for measured and for corresponding simulated PET images. Simulation of dose-reduced datasets based on clinical (18)F-FDG PET data demonstrated the clinical applicability of the proposed data. Simulation of PET tracer dose reduction is possible with retrospective undersampling of list-mode data. Resulting simulated low-dose images have equivalent characteristics with PET images actually measured at lower doses and can be used to derive optimal tracer dose regimes.

In vitro and in vivo comparison of a tailored magnetic particle imaging blood pool tracer with Resovist

NASA Astrophysics Data System (ADS)

Kaul, Michael Gerhard; Mummert, Tobias; Jung, Caroline; Salamon, Johannes; Khandhar, Amit P.; Ferguson, R. Matthew; Kemp, Scott J.; Ittrich, Harald; Krishnan, Kannan M.; Adam, Gerhard; Knopp, Tobias

2017-05-01

Optimizing tracers for individual imaging techniques is an active field of research. The purpose of this study was to perform in vitro and in vivo magnetic particle imaging (MPI) measurements using a new monodisperse and size-optimized tracer, LS-008, and to compare it with the performance of Resovist, the standard MPI tracer. Magnetic particle spectroscopy (MPS) and in vitro MPI measurements were performed in concerns of concentration and amount of tracer in a phantom. In vivo studies were carried out in healthy FVB mice. The first group (n  =  3) received 60 µl LS-008 (87 mM) and the second (n  =  3) diluted Resovist of the same concentration and volume. Tracer injections were performed with a syringe pump during a dynamic MPI scan. For anatomic referencing MRI was applied beforehand of the MPI measurements. Summing up MPS examinations and in vitro MPI experiments, LS-008 showed better sensitivity and spatial resolution than Resovist. In vivo both tracers can visualize the propagation of the bolus through the inferior vena cava. MPI with LS-008 did show less temporal fluctuation artifacts and the pulsation of blood due to respiratory and cardiac cycle was detectable. With LS-008 the aorta was distinguishable from the caval vein while with Resovist this failed. A liver vessel and a vessel structure leading cranially could only be observed with LS-008 and not with Resovist. Beside these structural advantages both tracers showed very different blood half-life. For LS-008 we found 88 min. Resovist did show a fast liver accumulation and a half-life of 13 min. Only with LS-008 the perfusion fraction in liver and kidney was measureable. MPI for angiography can be significantly improved by applying more effective tracers. LS-008 shows a clear improvement concerning the delineation while resolving a larger number of vessels in comparison to Resovist. Therefore, in aspects of quality and quantity LS-008 is clearly favorable for angiographic and perfusion studies.

Nocturnal Glucose Metabolism in Type 1 Diabetes: A Study Comparing Single Versus Dual Tracer Approaches.

PubMed

Mallad, Ashwini; Hinshaw, Ling; Dalla Man, Chiara; Cobelli, Claudio; Basu, Rita; Lingineni, Ravi; Carter, Rickey E; Kudva, Yogish C; Basu, Ananda

2015-08-01

Understanding the effect size, variability, and underlying physiology of the dawn phenomenon is important for next-generation closed-loop control algorithms for type 1 diabetes (T1D). We used an iterative protocol design to study 16 subjects with T1D on individualized insulin pump therapy for two successive nights. Endogenous glucose production (EGP) rates at 3 a.m. and 7 a.m. were measured with [6,6-(2)H(2)]glucose as a single tracer, infused from midnight to 7 a.m. in all subjects. To explore possibility of tracer recycling due to prolonged [6,6-(2)H(2)]glucose infusion, which was highly probable after preplanned interim data analyses, we infused a second tracer, [6-(3)H]glucose, from 4 a.m. to 7 a.m. in the last seven subjects to measure EGP at 7 a.m. Cortisol concentrations increased during both nights, but changes in glucagon and insulin concentration were inconsistent. Although the plasma glucose concentrations rose from midnight to 7 a.m. during both nights, EGP measured with [6,6-(2)H(2)]glucose between 3 a.m. and 7 a.m. did not differ during Night 1 but fell in Night 2. However, EGP measured with [6-(3)H]glucose at 7 a.m. was higher than that measured with [6,6-(2)H(2)]glucose during both nights, thereby suggesting tracer recycling probably underestimating EGP calculated at 7 a.m. with [6,6-(2)H(2)]glucose. Likewise, EGP was higher at 7 a.m. with [6-(3)H]glucose than at 3 a.m. with [6,6-(2)H(2)]glucose during both nights. The data demonstrate a consistent overnight rise in glucose concentrations through increased EGP, mediated likely by rising cortisol concentrations. The observations with the dual tracer approach imply significant tracer recycling leading to underestimation of EGP measured by longer-duration tracer infusion.

Evaluating Contaminants of Emerging Concern as tracers of wastewater from septic systems.

PubMed

James, C Andrew; Miller-Schulze, Justin P; Ultican, Shawn; Gipe, Alex D; Baker, Joel E

2016-09-15

Bacterial and nutrient contamination from anthropogenic sources impacts fresh and marine waters, reducing water quality and restricting recreational and commercial activities. In many cases the source of this contamination is ambiguous, and a tracer or set of tracers linking contamination to source would be valuable. In this work, the effectiveness of utilizing a suite of Contaminants of Emerging Concern (CECs) as tracers of bacteria from human septic system effluent is investigated. Field sampling was performed at more than 20 locations over approximately 18 months and analyzed for a suite of CECs and fecal coliform bacteria. The sampling locations included seeps and small freshwater discharges to the shoreline. Sites were selected and grouped according to level of impact by septic systems as determined by previous field sampling programs. A subset of selected locations had been positively identified as being impacted by effluent from failing septic systems through dye testing. The CECs were selected based on their predominant use, their frequency of use, and putative fate and transport properties. In addition, two rounds of focused sampling were performed at selected sites to characterize short-term variations in CEC and fecal coliform concentrations, and to evaluate environmental persistence following source correction activities. The results indicate that a suite of common use compounds are suitable as generalized tracers of bacterial contamination from septic systems and that fate and transport properties are important in tracer selection. Highly recalcitrant or highly labile compounds likely follow different loss profiles in the subsurface compared to fecal bacteria and are not suitable tracers. The use of more than one tracer compound is recommended due to source variability of septic systems and to account for variations in the subsurface condition. In addition, concentrations of some CECs were measured in receiving waters at levels which suggested the potential for environmental harm, indicating that the possible risk presented from these sources warrants further investigation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Combined use of fluorescence with a magnetic tracer and dilution effect upon sentinel node localization in a murine model.

PubMed

Kuwahata, Akihiro; Ahmed, Muneer; Saeki, Kohei; Chikaki, Shinichi; Kaneko, Miki; Qiu, Wenqi; Xin, Zonghao; Yamaguchi, Shinji; Kaneko, Akiko; Douek, Michael; Kusakabe, Moriaki; Sekino, Masaki

2018-01-01

Sentinel node biopsy using radioisotope and blue dye remains a gold standard for axillary staging in breast cancer patients with low axillary burden. However, limitations in the use of radioisotopes have resulted in emergence of novel techniques. This is the first in vivo study to assess the feasibility of combining the two most common novel techniques of using a magnetic tracer and indocyanine green (ICG) fluorescence. A total of 48 mice were divided into eight groups. Groups 1 and 2, the co-localization groups, received an injection of magnetic tracers (Resovist ® and Sienna+ ® , respectively) and ICG fluorescence; distilled water was used as the solvent of ICG. Groups 3 and 4, the diluted injection groups, received an injection of magnetic tracers (Resovist and Sienna+, respectively) and saline for dilution. Groups 5, 6, and 7, the control groups, received magnetic tracer (Resovist, Sienna+) and ICG alone, respectively. Fluorescent intensity assessment and iron quantification of excised popliteal lymph nodes were performed. Group 1', a co-localization group, received an injection of magnetic tracers (Resovist) and ICG' fluorescence: saline was used as the solvent for ICG. Lymphatic uptake of all tracers was confined to the popliteal nodes only, with co-localization confirmed in all cases and no significant difference in fluorescent intensity or iron content of ex vivo nodes between the groups (except for Group 1'). There was no impact of dilution on the iron content in the diluted Sienna+ group, but it significantly enhanced Resovist uptake ( P =0.005). In addition, there was a significant difference in iron content ( P =0.003) in Group 1'. The combination of a magnetic tracer (Resovist or Sienna+) and ICG fluorescence is feasible for sentinel node biopsy and will potentially allow for precise transcutaneous node identification, in addition to accurate intraoperative assessment. This radioisotope-free "combined technique" warrants further assessment within a clinical trial.

The Five-Year Fate of a 15N Tracer in a Mixed Deciduous Forest: Retention, Redistribution, and Differences by Mycorrhizal Association

NASA Astrophysics Data System (ADS)

Goodale, C. L.

2015-12-01

The impact of nitrogen deposition on forest ecosystems depends in large part on its fate: uptake by trees can stimulate growth, while gaseous or leaching losses contribute to air and water pollution and represent the loss of a limiting nutrient. Past tracer studies have shown that soils dominate the short-term fate of added 15N, but its longer-term term fate remains uncertain. This study examined how much 15N tracer moved plant or soil pools or was lost over 5-6 years. In 2007, a 15N tracer (0.21 kg/ha as 99% enriched 15N-KNO3) was added to 0.25 ha mixed hardwood forest in central NY. All of the tracer was recovered in the days after its addition, but recovery fell to 78% by the end of this year (25% surface litter, 48% 0-10 cm soil, 5% roots). One year later, recovery in these pools fell (to 51%), with losses from surface litter (-11%) and the 0-10 cm soils (-15%), including losses from the "heavy" soil fraction. Additional tracer moved to other plant pools (+5%) and to deeper soil (+13%; up to 30 cm), for a total recovery of 69% of the added tracer. Between years 1 and 5-6, only total tracer recovery decreased by only 1.4%. Recovery decreased in foliage (-0.2%), all roots (-3.5%), and surface litter (-9.8%), while increasing in woody biomass (+0.9%), 0-10 cm soil (+8.9%), and deep soil (+2.3%; up to 50 cm). Tracer recovery in live and dead plant N pools (11%) did not change, as 3% moved from roots into aboveground plant tissues and 3% moved from live plant pools into leaf litter; these results imply no net transfer of 15N from soil to plants during this period. Over all 5-6 years, only 1.6% of the tracer moved into bark or wood, a small but important sink because of its high C:N ratio; however, roughly one-third of this total was in wood formed prior to the start of the tracer addition. Tree species differed in their recovery of 15N: the six species with ectomycorrhizal associations showed more enrichment than the four species with arbuscular mycorrhizae. It is not yet apparent whether ectomycorrhizal species were more effective at scavenging 15N at the time of tracer addition, or if they were better at acquiring 15N from its initial fate in litter and soil. Only continued long-term resampling can distinguish between these alternatives, and to what extent 15N initially retained in soil eventually moves into plants over decadal timescales.

Evolution of the electrical resistivity anisotropy during saline tracer tests: insights from geoelectrical milli-fluidic experiments

NASA Astrophysics Data System (ADS)

Jougnot, D.; Jimenez-Martinez, J.; Legendre, R.; Le Borgne, T.; Meheust, Y.; Linde, N.

2017-12-01

The use of time-lapse electrical resistivity tomography has been largely developed in environmental studies to remotely monitor water saturation and contaminant plumes migration. However, subsurface heterogeneities, and corresponding preferential transport paths, yield a potentially large anisotropy in the electrical properties of the subsurface. In order to study this effect, we have used a newly developed geoelectrical milli-fluidic experimental set-up with a flow cell that contains a 2D porous medium consisting of a single layer of cylindrical solid grains. We performed saline tracer tests under full and partial water saturations in that cell by jointly injecting air and aqueous solutions with different salinities. The flow cell is equipped with four electrodes to measure the bulk electrical resistivity at the cell's scale. The spatial distribution of the water/air phases and the saline solute concentration field in the water phase are captured simultaneously with a high-resolution camera by combining a fluorescent tracer with the saline solute. These data are used to compute the longitudinal and transverse effective electrical resistivity numerically from the measured spatial distributions of the fluid phases and the salinity field. This approach is validated as the computed longitudinal effective resistivities are in good agreement with the laboratory measurements. The anisotropy in electrical resistivity is then inferred from the computed longitudinal and transverse effective resistivities. We find that the spatial distribution of saline tracer, and potentially air phase, drive temporal changes in the effective resistivity through preferential paths or barriers for electrical current at the pore scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical resistivity, especially for partially saturated conditions. Therefore, considering the electrical resistivity as a tensor could improve our understanding of transport properties from field-scale time-lapse ERT.

Utilizing tagged paramagnetic shift reagents to monitor protein dynamics by NMR.

PubMed

Ye, Libin; Van Eps, Ned; Li, Xiang; Ernst, Oliver P; Prosser, R Scott

2017-11-01

Calmodulin is a ubiquitous calcium sensor protein, known to serve as a critical interaction hub with a wide range of signaling partners. While the holo form of calmodulin (CaM-4Ca 2+ ) has a well-defined ground state structure, it has been shown to undergo exchange, on a millisecond timescale, to a conformation resembling that of the peptide bound state. Tagged paramagnetic relaxation agents have been previously used to identify long-range dipolar interactions through relaxation effects on nuclear spins of interest. In the case of calmodulin, this lead to the determination of the relative orientation of the N- and C-terminal domains and the presence of a weakly populated peptide bound like state. Here, we make use of pseudocontact shifts from a tagged paramagnetic shift reagent which allows us to define minor states both in 13 C and 15 N NMR spectra and through 13 C- and 15 N-edited 1 H-CPMG relaxation dispersion measurements. This is validated by pulsed EPR (DEER) spectroscopy which reveals an ensemble consisting of a compact peptide-bound like conformer, an intermediate peptide-bound like conformer, and a (dumbbell-like) extended ground state conformer of CaM-4Ca 2+ , where addition of the MLCK peptide increases the population of the peptide-bound conformers. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

Aerosol pollution potential from major population centers

NASA Astrophysics Data System (ADS)

Kunkel, D.; Tost, H.; Lawrence, M. G.

2012-09-01

Major population centers (MPCs) or mega-cities represent the largest of growing urban agglomerations with major societal and environmental implications. In terms of air quality they are seen as localized but strong emission sources of aerosols and trace gases which in turn affect air pollution levels in the city or in downwind regions. In the state-of-the-art atmospheric chemistry general circulation model EMAC, generic aerosol and gas phase tracers with equal emission source strengths at 46 MPC locations are used to study the balance between local pollution build up and pollution export, either vertically into the upper troposphere or horizontally, but remaining in the lower atmosphere. The insoluble gas phase tracers with fixed lifetimes are transported with the atmospheric circulation, while the aerosol tracers also undergo gravitational sedimentation as well as dry and wet deposition processes. The strength of low-level tracer export depends on the location of the emission source and prevailing meteorology, in particular on atmospheric stability and the height of the boundary layer and the mixing out of this layer. In contrast, vertical transport of tracer mass depends on the tracer's solubility: the more soluble a tracer is the less mass reaches altitudes above five kilometers. Hence, the mass of insoluble gas phase tracer above five kilometers can be up to ten times higher than the hydrophilic aerosol mass from the same source. In the case of aerosol tracers, pollution build up around the source is determined by meteorological factors which have only indirect effects on tracer lifetime, like surface wind, boundary layer height, and turbulent mixing as well as those which affect the lifetime of the tracers such as precipitation. The longer a tracer stays in the atmosphere, the lower is the relative importance of the location of the source to the atmospheric mass and thus the lower is the relative local pollution build up. We further use aerosol deposition fields to estimate regions with high deposition, that is more than 1% or more than 5% of the corresponding tracer emission deposited in this region. In doing so, we find that the high deposition areas are larger for larger aerosols, and these differ less between the MPCs than for smaller aerosols due to faster deposition. Furthermore, cities in regions with high precipitation rates or unfavorable geographic location, e.g. in a basin, suffer most of this high deposition. Most of the high deposition occurs over land, although about 50% of the MPCs are located along coastlines. By folding the aerosol deposition fields with geographical distributions of cropland, pasture, and forest, the impact on different land ecosystems is assessed. In general, forest are exhibited most to deposition from MPCs while pasture land is least affected. Moreover, the impact on humans, measured with a threshold exceedance of pollutant surface mixing ratios, is more dependent on population densities than on the size of the area holding a certain mixing ratio.

Aerosol pollution potential from major population centers

NASA Astrophysics Data System (ADS)

Kunkel, D.; Tost, H.; Lawrence, M. G.

2013-04-01

Major population centers (MPCs), or megacities, represent the largest of growing urban agglomerations with major societal and environmental implications. In terms of air quality, they are seen as localized but strong emission sources of aerosols and trace gases which in turn affect air pollution levels in the city or in downwind regions. In the state-of-the-art atmospheric chemistry general circulation model EMAC, generic aerosol and gas-phase tracers with equal emission source strengths at 46 MPC locations are used to study the balance between local pollution build-up and pollution export, either vertically into the upper troposphere or horizontally in the lower troposphere. The insoluble gas-phase tracers with fixed lifetimes are transported with the atmospheric circulation, while the aerosol tracers also undergo gravitational sedimentation as well as dry and wet deposition processes. The strength of low-level tracer export depends on the location of the emission source and prevailing meteorology, in particular on atmospheric stability and the height of the boundary layer and the mixing out of this layer. In contrast, vertical transport of tracer mass depends on the tracer's solubility: the more soluble a tracer is, the less mass reaches altitudes above five kilometers. Hence, the mass of insoluble gas-phase tracer above five kilometers can be up to ten times higher than the hydrophilic aerosol mass from the same source. In the case of aerosol tracers, pollution build-up around the source is determined by meteorological factors which have only indirect effects on tracer lifetime, like surface wind, boundary layer height, and turbulent mixing, as well as those which affect the lifetime of the tracers such as precipitation. The longer a tracer stays in the atmosphere, the lower is the relative importance of the location of the source to the atmospheric mass, and thus the lower is the relative local pollution build-up. We further use aerosol deposition fields to estimate regions with high deposition, that is more than 1% or more than 5% of the corresponding tracer emission deposited in this region. In doing so, we find that the high deposition areas are larger for aerosols with diameters of 10.0 μm, and these differ less between the MPCs than for aerosols with diameters smaller than 2.5 μm due to faster deposition. Furthermore, cities in regions with high precipitation rates or unfavorable geographic locations, e.g., in a basin, suffer most of this high deposition. Most of the high deposition occurs over land, although about 50% of the MPCs are located along coastlines. By folding the aerosol deposition fields with geographical distributions of cropland, pasture, and forest, the impact on different land ecosystems is assessed. In general, forest is exposed most to deposition from MPCs while pastureland is least affected. Moreover, the impact on humans, measured with a threshold exceedance of pollutant surface mixing ratios, is more dependent on population densities than on the size of the area with a certain mixing ratio.

Mechanism for the occurrence of paramagnetic planes within magnetically ordered cerium systems

NASA Astrophysics Data System (ADS)

Kioussis, Nicholas; Cooper, Bernard R.; Banerjea, Amitava

1988-11-01

Hybridization of moderately delocalized f electrons with band electrons gives rise to a highly anisotropic two-ion interaction. Previously it has been shown that such an interaction explains the experimentally observed unusual magnetic behavior of CeBi, yielding a phase transition from a higher-temperature type-I (↑↓) to a lower-temperature type-IA (↑↑↓↓) antiferromagnetic structure. If the hybridization-mediated interaction is the key to understanding the magnetic behavior of such moderately delocalized f-electron systems, we should expect to be able to understand on this basis the even more unusual magnetic behavior of CeSb. In CeSb, there is a sequence of magnetic structures in which the higher-temperature structures involve a periodic stacking of paramagnetic \\{001\\} planes alternating with magnetically ordered \\{001\\} planes of [001]-moment alignment. In this paper we show that such a coexistence of paramagnetic and magnetically ordered Ce3+ sites can be understood on the basis of the hybridization-mediated interionic interaction when there are cubic crystal-field (CF) interactions of comparable strength. The tendency to form paramagnetic planes is found to increase with increasing CF strength (Γ7 ground state); and the stability of the up-down paramagnetic plane arrangement at high temperatures is shown to arise from the reconciliation of the magnetic ordering with the CF interactions. We also find that for a certain range of parameters a different novel situation occurs, with a fully nonmagnetic (singlet) ground state for the Ce3+ ion. This singlet state is not Kondo-like, and occurs in such a way that the system would be expected to fluctuate between two differently polarized states, one of which is the singlet state.

Recover Act. Verification of Geothermal Tracer Methods in Highly Constrained Field Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, Matthew W.

2014-05-16

The prediction of the geothermal system efficiency is strong linked to the character of the flow system that connects injector and producer wells. If water flow develops channels or “short circuiting” between injection and extraction wells thermal sweep is poor and much of the reservoir is left untapped. The purpose of this project was to understand how channelized flow develops in fracture geothermal reservoirs and how it can be measured in the field. We explored two methods of assessing channelization: hydraulic connectivity tests and tracer tests. These methods were tested at a field site using two verification methods: ground penetratingmore » radar (GPR) images of saline tracer and heat transfer measurements using distributed temperature sensing (DTS). The field site for these studies was the Altona Flat Fractured Rock Research Site located in northeastern New York State. Altona Flat Rock is an experimental site considered a geologic analog for some geothermal reservoirs given its low matrix porosity. Because soil overburden is thin, it provided unique access to saturated bedrock fractures and the ability image using GPR which does not effectively penetrate most soils. Five boreholes were drilled in a “five spot” pattern covering 100 m2 and hydraulically isolated in a single bedding plane fracture. This simple system allowed a complete characterization of the fracture. Nine small diameter boreholes were drilled from the surface to just above the fracture to allow the measurement of heat transfer between the fracture and the rock matrix. The focus of the hydraulic investigation was periodic hydraulic testing. In such tests, rather than pumping or injection in a well at a constant rate, flow is varied to produce an oscillating pressure signal. This pressure signal is sensed in other wells and the attenuation and phase lag between the source and receptor is an indication of hydraulic connection. We found that these tests were much more effective than constant pumping tests in identifying a poorly connected well. As a result, we were able to predict which well pairs would demonstrate channelized flow. The focus of the tracer investigation was multi-ionic tests. In multi-ionic tests several ionic tracers are injected simultaneously and the detected in a nearby pumping well. The time history of concentration, or breakthrough curve, will show a separation of the tracers. Anionic tracers travel with the water but cationic tracer undergo chemical exchange with cations on the surface of the rock. The degree of separation is indicative of the surface area exposed to the tracer. Consequently, flow channelization will tend to decrease the separation in the breakthrough. Estimation of specific surface area (the ration of fracture surface area to formation volume) is performed through matching the breakthrough curve with a transport model. We found that the tracer estimates of surface area were confirmed the prediction of channelized flow between well pairs produced by the periodic hydraulic tests. To confirm that the hydraulic and tracer tests were correctly predicting channelize flow, we imaged the flow field using surface GPR. Saline water was injected between the well pairs which produced a change in the amplitude and phase of the reflected radar signal. A map was produced of the migration of saline tracer from these tests which qualitatively confirmed the flow channelization predicted by the hydraulic and tracer tests. The resolution of the GPR was insufficient to quantitatively estimate swept surface area, however. Surface GPR is not applicable in typical geothermal fields because the penetration depths do not exceed 10’s of meters. Nevertheless, the method of using of phase to measure electrical conductivity and the assessment of antennae polarization represent a significant advancement in the field of surface GPR. The effect of flow character on fracture / rock thermal exchange was evaluated using heated water as a tracer. Water elevated 30 degrees C above the formation water was circulated between two wells pairs. One well pair had been identified in hydraulic and tracer testing as well connected and the other poorly connected. Temperature rise was measured in the adjacent rock matrix using coiled fiber optic cable interrogated for temperature using a DTS. This experimental design produced over 4000 temperature measurements every hour. We found that heat transfer between the fracture and the rock matrix was highly impacted by the character of the flow field. The strongly connected wells which had demonstrated flow channelization produced heat rise in a much more limited area than the more poorly connected wells. In addition, the heat increase followed the natural permeability of the fracture rather than the induced flow field. The primary findings of this work are (1) even in a single relatively planar fracture, the flow field can be highly heterogeneous and exhibit flow channeling, (2) channeling results from a combination of fracture permeability structure and the induced flow field, and (3) flow channeling leads to reduced heat transfer. Multi-ionic tracers effectively estimate relative surface area but an estimate of ion-exchange coefficients are necessary to provide an absolute measure of specific surface area. Periodic hydraulic tests also proved a relative indicator of connectivity but cannot prove an absolute measure of specific surface area.« less

A Multiple-Tracer Approach for Identifying Sewage Sources to an Urban Stream System

USGS Publications Warehouse

Hyer, Kenneth Edward

2007-01-01

The presence of human-derived fecal coliform bacteria (sewage) in streams and rivers is recognized as a human health hazard. The source of these human-derived bacteria, however, is often difficult to identify and eliminate, because sewage can be delivered to streams through a variety of mechanisms, such as leaking sanitary sewers or private lateral lines, cross-connected pipes, straight pipes, sewer-line overflows, illicit dumping of septic waste, and vagrancy. A multiple-tracer study was conducted to identify site-specific sources of sewage in Accotink Creek, an urban stream in Fairfax County, Virginia, that is listed on the Commonwealth's priority list of impaired streams for violations of the fecal coliform bacteria standard. Beyond developing this multiple-tracer approach for locating sources of sewage inputs to Accotink Creek, the second objective of the study was to demonstrate how the multiple-tracer approach can be applied to other streams affected by sewage sources. The tracers used in this study were separated into indicator tracers, which are relatively simple and inexpensive to apply, and confirmatory tracers, which are relatively difficult and expensive to analyze. Indicator tracers include fecal coliform bacteria, surfactants, boron, chloride, chloride/bromide ratio, specific conductance, dissolved oxygen, turbidity, and water temperature. Confirmatory tracers include 13 organic compounds that are associated with human waste, including caffeine, cotinine, triclosan, a number of detergent metabolites, several fragrances, and several plasticizers. To identify sources of sewage to Accotink Creek, a detailed investigation of the Accotink Creek main channel, tributaries, and flowing storm drains was undertaken from 2001 to 2004. Sampling was conducted in a series of eight synoptic sampling events, each of which began at the most downstream site and extended upstream through the watershed and into the headwaters of each tributary. Using the synoptic sampling approach, 149 sites were sampled at least one time for indicator tracers; 52 of these sites also were sampled for confirmatory tracers at least one time. Through the analysis of multiple-tracer levels in the synoptic samples, three major sewage sources to the Accotink Creek stream network were identified, and several other minor sewage sources to the Accotink Creek system likely deserve additional investigation. Near the end of the synoptic sampling activities, three additional sampling methods were used to gain better understanding of the potential for sewage sources to the watershed. These additional sampling methods included optical brightener monitoring, intensive stream sampling using automated samplers, and additional sampling of several storm-drain networks. The samples obtained by these methods provided further understanding of possible sewage sources to the streams and a better understanding of the variability in the tracer concentrations at a given sampling site. Collectively, these additional sampling methods were a valuable complement to the synoptic sampling approach that was used for the bulk of this study. The study results provide an approach for local authorities to use in applying a relatively simple and inexpensive collection of tracers to locate sewage sources to streams. Although this multiple-tracer approach is effective in detecting sewage sources to streams, additional research is needed to better detect extremely low-volume sewage sources and better enable local authorities to identify the specific sources of the sewage once it is detected in a stream reach.

A survey of techniques for refrigeration, reliquefaction, and production of slush for hydrogen

NASA Technical Reports Server (NTRS)

Overcash, Dan R.

1990-01-01

Several techniques were surveyed for the refrigeration, reliquefaction and production of slush from hydrogen. The techniques included auger; bubbling helium gas; Simon desorption; the Petlier effect; Joule-Kelvin expansion using Stirling, Brayton, and Viulleumirer approaches; rotary reciprocating; a dilution refrigerator; adiabatic demagnetization of a paramagnetic salt; and adiabatic magnetization of a superconductor.

Electronic correlation in magnetic contributions to structural energies

NASA Astrophysics Data System (ADS)

Haydock, Roger

For interacting electrons the density of transitions [see http://arxiv.org/abs/1405.2288] replaces the density of states in calculations of structural energies. Extending previous work on paramagnetic metals, this approach is applied to correlation effects on the structural stability of magnetic transition metals. Supported by the H. V. Snyder Gift to the University of Oregon.

Nitrogen-containing species in the structure of the synthesized nano-hydroxyapatite

NASA Astrophysics Data System (ADS)

Gafurov, M.; Biktagirov, T.; Yavkin, B.; Mamin, G.; Filippov, Y.; Klimashina, E.; Putlayev, V.; Orlinskii, S.

2014-04-01

Synthesized by the wet chemical precipitation technique, hydroxyapatite (HAp) powders with the sizes of the crystallites of 20-50 nm and 1 μm were analyzed by different analytical methods. By means of electron paramagnetic resonance (EPR) it is shown that during the synthesis process nitrate anions from the reagents (byproducts) could incorporate into the HAp structure. The relaxation times and EPR parameters of the stable axially symmetric NO{3/2-} paramagnetic centers detected after X-ray irradiation are measured with high accuracy. Analyses of high-frequency (95 GHz) electron-nuclear double resonance spectra from 1H and 31P nuclei and ab initio density functional theory calculations allow suggesting that the paramagnetic centers and nitrate anions as the precursors of NO{3/2-} radicals preferably occupy PO{4/3-} site in the HAp structure.

Electron paramagnetic resonance study of radiation-induced paramagnetic centers in succinic anhydride single crystal

NASA Astrophysics Data System (ADS)

Caliskan, Betul; Caliskan, Ali Cengiz; Er, Emine

2017-09-01

Succinic anhydride single crystals were exposed to 60Co-gamma irradiation at room temperature. The irradiated single crystals were investigated at 125 K by Electron Paramagnetic Resonance (EPR) Spectroscopy. The investigation of EPR spectra of irradiated single crystals of succinic anhydride showed the presence of two succinic anhydride anion radicals. The anion radicals observed in gamma-irradiated succinic anhydride single crystal were created by the scission of the carbon-oxygen double bond. The structure of EPR spectra demonstrated that the hyperfine splittings arise from the same radical species. The reduction of succinic anhydride was identified which is formed by the addition of an electron to oxygen of the Csbnd O bond. The g values, the hyperfine structure constants and direction cosines of the radiation damage centers observed in succinic anhydride single crystal were obtained.

Imaging single spin probes embedded in a conductive diamagnetic layer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messina, P.; Fradin, F.

2009-01-01

The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been substantially improved by the work presented by Komeda and Manassen (Komeda, T.; Manassen, Y. Appl. Phys. Lett. 2008, 92, 212506). The application of this technique to molecular paramagnets requires the positioning and anchoring of paramagnetic molecules at surfaces. It also requires the possibility of tunneling high current densities into the STM-molecule-substrate tunneling junction. In this letter, we exploit the self-assembly of 1,10-phenantroline on the Au(111) surface to form a diamagnetic matrix that hosts individual molecules and dimers of diphenyl-2-picryl-hydrazyl (DPPH). STM measurements are used tomore » characterize the molecular layer. Electron spin resonance (ESR) measurements elucidate the role of thermal annealing in the preservation of the paramagnetic nature of the DPPH molecules.« less

On the Paramagnetic Inelastic Scattering of Neutrons due to Ions in the Anisotropic Crystalline Field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, Yasusada

1960-03-15

The paramagnetic inelastic scattering of neutrons due to ions of3d transition elements in the anisotropic crystalline field was considered. When the orbital momentum of the paramagnetic tons is not quenched, the spin states are no longer degenerate but split into discrete levels. The transition between these levels can occur by mugnetic dipole interaction of ions with neutrons. In the special case of FeCl/sub 2/, an antiferromagnetic crystal whose Neel temperature is 24 deg K, the calculation of the forward scuttering cross-sections of neutrons at various temperatures and wave lengths was carried out which showed that it is possible, under ordinarymore » conditions, to observe the inelastically scattered neutrons and hence to obtain information about the energy level scheme of the atomic spin in the cry stal. (auth)« less

Regional-scale analysis of karst underground flow deduced from tracing experiments: examples from carbonate aquifers in Malaga province, southern Spain

NASA Astrophysics Data System (ADS)

Barberá, J. A.; Mudarra, M.; Andreo, B.; De la Torre, B.

2018-02-01

Tracer concentration data from field experiments conducted in several carbonate aquifers (Malaga province, southern Spain) were analyzed following a dual approach based on the graphical evaluation method (GEM) and solute transport modeling to decipher flow mechanisms in karst systems at regional scale. The results show that conduit system geometry and flow conditions are the principal factors influencing tracer migration through the examined karst flow routes. Solute transport is mainly controlled by longitudinal advection and dispersion throughout the conduit length, but also by flow partitioning between mobile and immobile fluid phases, while the matrix diffusion process appears to be less relevant. The simulation of tracer breakthrough curves (BTCs) suggests that diffuse and concentrated flow through the unsaturated zone can have equivalent transport properties under extreme recharge, with high flow velocities and efficient mixing due to the high hydraulic gradients generated. Tracer mobilization within the saturated zone under low flow conditions mainly depends on the hydrodynamics (rather than on the karst conduit development), which promote a lower longitudinal advection and retardation in the tracer migration, resulting in a marked tailing effect of BTCs. The analytical advection-dispersion equation better approximates the effective flow velocity and longitudinal dispersion estimations provided by the GEM, while the non-equilibrium transport model achieves a better adjustment of most asymmetric and long-tailed BTCs. The assessment of karst underground flow properties from tracing tests at regional scale can aid design of groundwater management and protection strategies, particularly in large hydrogeological systems (i.e. transboundary carbonate aquifers) and/or in poorly investigated ones.

Protein binding of isofluorophate in vivo after coexposure to multiple chemicals.

PubMed Central

Vogel, John S; Keating, Garrett A; Buchholz, Bruce A

2002-01-01

Full toxicologic profiles of chemical mixtures, including dose-response extrapolations to realistic exposures, is a prohibitive analytical problem, even for a restricted class of chemicals. We present an approach to probing in vivo interactions of pesticide mixtures at relevant low doses using a monitor compound to report the response of biochemical pathways shared by mixture components. We use accelerator mass spectrometry (AMS) to quantify [14C]-diisopropylfluorophosphate as a tracer at attomole levels with 1-5% precision after coexposures to parathion (PTN), permethrin (PER), and pyridostigmine bromide separately and in conjunction. Pyridostigmine shows an overall protective effect against tracer binding in plasma, red blood cells, muscle, and brain that is not explained as competitive protein binding. PTN and PER induce a significant 25-30% increase in the amount of tracer reaching the brain with or without pyridostigmine. The sensitivity of AMS for isotope-labeled tracer compounds can be used to probe the physiologic responses of specific biochemical pathways to multiple compound exposures. PMID:12634135

Nitrogen-to-oxygen as a tracer of the chemical evolution of the Local and young Universe

NASA Astrophysics Data System (ADS)

Pérez-Montero, E.

2013-05-01

Oxygen optical emission-lines are used exhaustively as tracers of the metal content in gaseous nebulae ionized during different episodes of massive star formation. The high luminosity of these lines make them to be detected from the Local Universe up to starbursts at high redshift. Occasionally, in those cases where these lines cannot be measured due to the spectral coverage or to the redshift, nitrogen emission-lines are used instead. However, both nitrogen and oxygen have different nucleosynthetic origins, so the study of chemical abundances from nitrogen emission-lines introduces variables depending on the star formation history of each galaxy that must be taken into account. This contribution summarizes those risks involved in using metallicity tracers based on optical nitrogen emission lines and also describes the advantages of using instead the nitrogen-to-oxygen ratio as a tracer itself, based mainly on its independence on star formation rate, avoiding selection effects at high redshift.

A rapid method for the measurement of sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), and Halon 1211 (CF2ClBr) in hydrologic tracer studies

USGS Publications Warehouse

Busenberg, Eurybiades; Plummer, Niel

2010-01-01

A rapid headspace method for the simultaneous laboratory determination of intentionally introduced hydrologic tracers, sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), Halon 1211 (CF2ClBr), and other halocarbons in water and gases is described. The high sensitivity of the procedure allows for introduction of minimal tracer mass (a few grams) into hydrologic systems with a large dynamic range of analytical detection (dilutions to 1:108). Analysis times by gas chromatography with electron capture detector are less than 1 min for SF6; about 2 min for SF6 and SF5CF3; and 4 min for SF6, SF5CF3, and Halon 1211. Many samples can be rapidly collected, preserved in stoppered septum bottles, and analyzed at a later time in the laboratory. Examples are provided showing the effectiveness of the gas tracer test studies in varied hydrogeological settings.

A rapid method for the measurement of sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), and Halon 1211 (CF2ClBr) in hydrologic tracer studies

NASA Astrophysics Data System (ADS)

Busenberg, Eurybiades; Plummer, L. Niel

2010-11-01

A rapid headspace method for the simultaneous laboratory determination of intentionally introduced hydrologic tracers, sulfur hexafluoride (SF6), trifluoromethyl sulfur pentafluoride (SF5CF3), Halon 1211 (CF2ClBr), and other halocarbons in water and gases is described. The high sensitivity of the procedure allows for introduction of minimal tracer mass (a few grams) into hydrologic systems with a large dynamic range of analytical detection (dilutions to 1:108). Analysis times by gas chromatography with electron capture detector are less than 1 min for SF6; about 2 min for SF6 and SF5CF3; and 4 min for SF6, SF5CF3, and Halon 1211. Many samples can be rapidly collected, preserved in stoppered septum bottles, and analyzed at a later time in the laboratory. Examples are provided showing the effectiveness of the gas tracer test studies in varied hydrogeological settings.

Accounting for pharmacokinetic differences in dual-tracer receptor density imaging

PubMed Central

Tichauer, K M; Diop, M; Elliott, J T; Samkoe, K S; Hasan, T; St. Lawrence, K; Pogue, B W

2014-01-01

Dual-tracer molecular imaging is a powerful approach to quantify receptor expression in a wide range of tissues by using an untargeted tracer to account for any nonspecific uptake of a molecular-targeted tracer. This approach has previously required the pharmacokinetics of the receptor-targeted and untargeted tracers to be identical, requiring careful selection of an ideal untargeted tracer for any given targeted tracer. In this study, methodology capable of correcting for tracer differences in arterial input functions, as well as binding-independent delivery and retention, is derived and evaluated in a mouse U251 glioma xenograft model using an Affibody tracer targeted to epidermal growth factor receptor (EGFR), a cell membrane receptor overexpressed in many cancers. Simulations demonstrated that blood, and to a lesser extent vascular-permeability, pharmacokinetic differences between targeted and untargeted tracers could be quantified by deconvolving the uptakes of the two tracers in a region of interest devoid of targeted tracer binding, and therefore corrected for, by convolving the uptake of the untargeted tracer in all regions of interest by the product of the deconvolution. Using fluorescently labelled, EGFR-targeted and untargeted Affibodies (known to have different blood clearance rates), the average tumor concentration of EGFR in 4 mice was estimated using dual-tracer kinetic modelling to be 3.9 ± 2.4 nM compared to an expected concentration of 2.0 ± 0.4 nM. However, with deconvolution correction a more equivalent EGFR concentration of 2.0 ± 0.4 nM was measured. PMID:24743262

Impact of solvent granularity and layering on tracer hydrodynamics in confinement.

PubMed

Bollinger, Jonathan A; Carmer, James; Jain, Avni; Truskett, Thomas M

2016-11-28

Classic hydrodynamic arguments establish that when a spherical tracer particle is suspended between parallel walls, tracer-wall coupling mediated by the solvent will cause the tracer to exhibit position-dependent diffusivity. We investigate how the diffusivity profiles of confined tracers are impacted by the diameter size-ratio of the tracer to solvent: starting from the classic limit of infinite size-ratio (i.e., continuum solvent), we consider size-ratios of four or less to examine how hydrodynamic predictions are disrupted for systems where the tracer and solvent are of similar scale. We use computer simulations and techniques based on the Fokker-Planck formalism to calculate the diffusivity profiles of hard-sphere tracer particles in hard-sphere solvents, focusing on the dynamics perpendicular to the walls. Given wall separations of several tracer diameters, we first consider confinement between hard walls, where anisotropic structuring at the solvent lengthscale generates inhomogeneity in the tracer free-energy landscape and undermines hydrodynamic predictions locally. We then introduce confining planes that we term transparent walls, which restrict tracer and solvent center-accessibilities while completely eliminating static anisotropy, and reveal position-dependent signatures in tracer diffusivity solely attributable to confinement. With or without suppressing static heterogeneity, we find that tracer diffusivity increasingly deviates on a local basis from hydrodynamic predictions at smaller size-ratios. However, hydrodynamic theory still approximately captures spatially-averaged dynamics across the pores even for very small tracer-solvent size-ratios over a wide range of solvent densities and wall separations.

Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow.

PubMed

Ghim, Mean; Alpresa, Paola; Yang, Sung-Wook; Braakman, Sietse T; Gray, Stephen G; Sherwin, Spencer J; van Reeuwijk, Maarten; Weinberg, Peter D

2017-11-01

Transport of macromolecules across vascular endothelium and its modification by fluid mechanical forces are important for normal tissue function and in the development of atherosclerosis. However, the routes by which macromolecules cross endothelium, the hemodynamic stresses that maintain endothelial physiology or trigger disease, and the dependence of transendothelial transport on hemodynamic stresses are controversial. We visualized pathways for macromolecule transport and determined the effect on these pathways of different types of flow. Endothelial monolayers were cultured under static conditions or on an orbital shaker producing different flow profiles in different parts of the wells. Fluorescent tracers that bound to the substrate after crossing the endothelium were used to identify transport pathways. Maps of tracer distribution were compared with numerical simulations of flow to determine effects of different shear stress metrics on permeability. Albumin-sized tracers dominantly crossed the cultured endothelium via junctions between neighboring cells, high-density lipoprotein-sized tracers crossed at tricellular junctions, and low-density lipoprotein-sized tracers crossed through cells. Cells aligned close to the angle that minimized shear stresses across their long axis. The rate of paracellular transport under flow correlated with the magnitude of these minimized transverse stresses, whereas transport across cells was uniformly reduced by all types of flow. These results contradict the long-standing two-pore theory of solute transport across microvessel walls and the consensus view that endothelial cells align with the mean shear vector. They suggest that endothelial cells minimize transverse shear, supporting its postulated proatherogenic role. Preliminary data show that similar tracer techniques are practicable in vivo. NEW & NOTEWORTHY Solutes of increasing size crossed cultured endothelium through intercellular junctions, through tricellular junctions, or transcellularly. Cells aligned to minimize the shear stress acting across their long axis. Paracellular transport correlated with the level of this minimized shear, but transcellular transport was reduced uniformly by flow regardless of the shear profile. Copyright © 2017 the American Physiological Society.

Water sources and mixing in riparian wetlands revealed by tracers and geospatial analysis.

PubMed

Lessels, Jason S; Tetzlaff, Doerthe; Birkel, Christian; Dick, Jonathan; Soulsby, Chris

2016-01-01

Mixing of waters within riparian zones has been identified as an important influence on runoff generation and water quality. Improved understanding of the controls on the spatial and temporal variability of water sources and how they mix in riparian zones is therefore of both fundamental and applied interest. In this study, we have combined topographic indices derived from a high-resolution Digital Elevation Model (DEM) with repeated spatially high-resolution synoptic sampling of multiple tracers to investigate such dynamics of source water mixing. We use geostatistics to estimate concentrations of three different tracers (deuterium, alkalinity, and dissolved organic carbon) across an extended riparian zone in a headwater catchment in NE Scotland, to identify spatial and temporal influences on mixing of source waters. The various biogeochemical tracers and stable isotopes helped constrain the sources of runoff and their temporal dynamics. Results show that spatial variability in all three tracers was evident in all sampling campaigns, but more pronounced in warmer dryer periods. The extent of mixing areas within the riparian area reflected strong hydroclimatic controls and showed large degrees of expansion and contraction that was not strongly related to topographic indices. The integrated approach of using multiple tracers, geospatial statistics, and topographic analysis allowed us to classify three main riparian source areas and mixing zones. This study underlines the importance of the riparian zones for mixing soil water and groundwater and introduces a novel approach how this mixing can be quantified and the effect on the downstream chemistry be assessed.

The use of an ordinary colour scanner to fingerprint sediment sources in the South African Karoo.

PubMed

Pulley, Simon; Rowntree, Kate

2016-01-01

The widespread adoption of sediment fingerprinting methodologies for the purpose of catchment management has been restricted by the high cost of tracer analysis as well as the potential for significant uncertainties to be present in results. Sediment colour has shown potential to be an inexpensive tracer able to discriminate between sediment sources. However, at present colour has not been demonstrated to be conservative during sediment erosion and transport. Sediment particle size and organic matter have been shown to strongly affect sediment colour, introducing significant uncertainties associated with its use. This study aimed to assess the suitability of colour as a tracer when it is measured using a commercially available colour scanner. The use of hydrogen peroxide (H2O2) to decompose sediment-associated organic matter was assessed as a means of minimising uncertainty. The impact of particle size on the accurate use of colour signatures as a tracer was also assessed. It was concluded that colour performed comparably to mineral magnetic signatures and showed good potential for use as a tracer. The use of H2O2 pre-treatment and limitation of the analysis to either the <32 μm or the >32 μm fraction of the samples were indicated to be important methods to limit uncertainties associated with organic matter and particle size. The methods used were considerably more time and cost effective than the measurement of most conventional tracers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of an electron paramagnetic resonance methodology for studying the photo-generation of reactive species in semiconductor nano-particle assembled films

NASA Astrophysics Data System (ADS)

Twardoch, Marek; Messai, Youcef; Vileno, Bertrand; Hoarau, Yannick; Mekki, Djamel E.; Felix, Olivier; Turek, Philippe; Weiss, Jean; Decher, Gero; Martel, David

2018-06-01

An experimental approach involving electron paramagnetic resonance is proposed for studying photo-generated reactive species in semiconductor nano-particle-based films deposited on the internal wall of glass capillaries. This methodology is applied here to nano-TiO2 and allows a semi-quantitative analysis of the kinetic evolutions of radical production using a spin scavenger probe.

A two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

NASA Astrophysics Data System (ADS)

Hagmann, C.; Richards, P. L.

1993-02-01

We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites as well as to cool cryogenic x-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic-cesium-alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium-gallium-garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar chords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10 to 100 hours. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

Structural, magnetic, and magnetocaloric properties of bilayer manganite La1.38Sr1.62Mn2O7

NASA Astrophysics Data System (ADS)

Yang, Yu-E.; Xie, Yunfei; Xu, Lisha; Hu, Dazhi; Ma, Chunlan; Ling, Langsheng; Tong, Wei; Pi, Li; Zhang, Yuheng; Fan, Jiyu

2018-04-01

In this study, we investigated the structural, magnetic phase transition, and magnetocaloric properties of bilayer perovskite manganite La1.38Sr1.62Mn2O7 based on X-ray diffraction, electron paramagnetic resonance, and temperature-/magnetic field-dependent magnetization measurements. The structural characterization results showed the prepared sample had a tetragonal structure with the space group I4/mmm. The Curie temperature was determined as 114 K in the magnetization studies and a second-order paramagnetic-ferromagnetic transition was confirmed by the Arrott plot, which showed that the slopes were positive for all the curves. According to the variation in the electron paramagnetic resonance spectrum, we detected obvious electronic phase separation across a broad temperature range from 220 to 80 K in this magnetic material, thereby indicating that the paramagnetic and ferromagnetic phases coexist above as well as below the Curie temperature. Based on a plot of the isothermal magnetization versus the magnetic applied field, we deduced the maximum magnetic entropy change, which only reached 1.89 J/kg.K under an applied magnetic field of 7.0 T. These theoretical investigations indicated that in addition to the magnetoelastic couplings and electron interaction, electronic phase separation and anisotropic exchange interactions also affect the magnetic entropy changes in this bilayer manganite.

A two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

NASA Technical Reports Server (NTRS)

Hagmann, C.; Richards, P. L.

1993-01-01

We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites as well as to cool cryogenic x-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic-cesium-alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium-gallium-garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar chords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10 to 100 hours. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

Effects of water on fingernail electron paramagnetic resonance dosimetry.

PubMed

Zhang, Tengda; Zhao, Zhixin; Zhang, Haiying; Zhai, Hezheng; Ruan, Shuzhou; Jiao, Ling; Zhang, Wenyi

2016-09-01

Electron paramagnetic resonance (EPR) is a promising biodosimetric method, and fingernails are sensitive biomaterials to ionizing radiation. Therefore, kinetic energy released per unit mass (kerma) can be estimated by measuring the level of free radicals within fingernails, using EPR. However, to date this dosimetry has been deficient and insufficiently accurate. In the sampling processes and measurements, water plays a significant role. This paper discusses many effects of water on fingernail EPR dosimetry, including disturbance to EPR measurements and two different effects on the production of free radicals. Water that is unable to contact free radicals can promote the production of free radicals due to indirect ionizing effects. Therefore, varying water content within fingernails can lead to varying growth rates in the free radical concentration after irradiation-these two variables have a linear relationship, with a slope of 1.8143. Thus, EPR dosimetry needs to be adjusted according to the water content of the fingernails of an individual. When the free radicals are exposed to water, the eliminating effect will appear. Therefore, soaking fingernail pieces in water before irradiation, as many researchers have previously done, can cause estimation errors. In addition, nails need to be dehydrated before making accurately quantitative EPR measurements. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Methodology for quantitative rapid multi-tracer PET tumor characterizations.

PubMed

Kadrmas, Dan J; Hoffman, John M

2013-10-04

Positron emission tomography (PET) can image a wide variety of functional and physiological parameters in vivo using different radiotracers. As more is learned about the molecular basis for disease and treatment, the potential value of molecular imaging for characterizing and monitoring disease status has increased. Characterizing multiple aspects of tumor physiology by imaging multiple PET tracers in a single patient provides additional complementary information, and there is a significant body of literature supporting the potential value of multi-tracer PET imaging in oncology. However, imaging multiple PET tracers in a single patient presents a number of challenges. A number of techniques are under development for rapidly imaging multiple PET tracers in a single scan, where signal-recovery processing algorithms are employed to recover various imaging endpoints for each tracer. Dynamic imaging is generally used with tracer injections staggered in time, and kinetic constraints are utilized to estimate each tracers' contribution to the multi-tracer imaging signal. This article summarizes past and ongoing work in multi-tracer PET tumor imaging, and then organizes and describes the main algorithmic approaches for achieving multi-tracer PET signal-recovery. While significant advances have been made, the complexity of the approach necessitates protocol design, optimization, and testing for each particular tracer combination and application. Rapid multi-tracer PET techniques have great potential for both research and clinical cancer imaging applications, and continued research in this area is warranted.

Methodology for Quantitative Rapid Multi-Tracer PET Tumor Characterizations

PubMed Central

Kadrmas, Dan J.; Hoffman, John M.

2013-01-01

Positron emission tomography (PET) can image a wide variety of functional and physiological parameters in vivo using different radiotracers. As more is learned about the molecular basis for disease and treatment, the potential value of molecular imaging for characterizing and monitoring disease status has increased. Characterizing multiple aspects of tumor physiology by imaging multiple PET tracers in a single patient provides additional complementary information, and there is a significant body of literature supporting the potential value of multi-tracer PET imaging in oncology. However, imaging multiple PET tracers in a single patient presents a number of challenges. A number of techniques are under development for rapidly imaging multiple PET tracers in a single scan, where signal-recovery processing algorithms are employed to recover various imaging endpoints for each tracer. Dynamic imaging is generally used with tracer injections staggered in time, and kinetic constraints are utilized to estimate each tracers' contribution to the multi-tracer imaging signal. This article summarizes past and ongoing work in multi-tracer PET tumor imaging, and then organizes and describes the main algorithmic approaches for achieving multi-tracer PET signal-recovery. While significant advances have been made, the complexity of the approach necessitates protocol design, optimization, and testing for each particular tracer combination and application. Rapid multi-tracer PET techniques have great potential for both research and clinical cancer imaging applications, and continued research in this area is warranted. PMID:24312149

Methionine kinetics in adult men: effects of dietary betaine on L-(2H3-methyl-1-13C)methionine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Storch, K.J.; Wagner, D.A.; Young, V.R.

1991-08-01

The effects of a daily 3-g supplement of betaine on kinetic aspects of L-(2H3-methyl-1-13C)methionine (MET) metabolism in healthy young adult men were explored. Four groups of four subjects each were given a control diet, based on an L-amino acid mixture supplying 29.5 and 21.9 mg.kg-1.d-1 of L-methionine and L-cystine for 4 d before the tracer study, conducted on day 5 during the fed state. Two groups received the control diet and two groups received the betaine supplement. Tracer was given intravenously (iv) or orally. The transmethylation rate of MET (TM), homocysteine remethylation (RM), and oxidation of methionine were estimated frommore » plasma methionine labeling and 13C enrichment of expired air. RM tended to increase (P = 0.14) but the TM and methionine oxidation were significantly (P less than 0.05) higher after betaine supplementation when estimated with the oral tracer. No differences were detected with the intravenous tracer. Methionine concentration in plasma obtained from blood taken from subjects in the fed state was higher (P less than 0.01) with betaine supplementation. These results suggest that excess methyl-group intake may increase the dietary requirement for methionine.« less

Determination of the Isotopic Enrichment of 13C- and 2H-Labeled Tracers of Glucose Using High-Resolution Mass Spectrometry: Application to Dual- and Triple-Tracer Studies.

PubMed

Trötzmüller, Martin; Triebl, Alexander; Ajsic, Amra; Hartler, Jürgen; Köfeler, Harald; Regittnig, Werner

2017-11-21

Multiple-tracer approaches for investigating glucose metabolism in humans usually involve the administration of stable and radioactive glucose tracers and the subsequent determination of tracer enrichments in sampled blood. When using conventional, low-resolution mass spectrometry (LRMS), the number of spectral interferences rises rapidly with the number of stable tracers employed. Thus, in LRMS, both computational effort and statistical uncertainties associated with the correction for spectral interferences limit the number of stable tracers that can be simultaneously employed (usually two). Here we show that these limitations can be overcome by applying high-resolution mass spectrometry (HRMS). The HRMS method presented is based on the use of an Orbitrap mass spectrometer operated at a mass resolution of 100 000 to allow electrospray-generated ions of the deprotonated glucose molecules to be monitored at their exact masses. The tracer enrichment determination in blood plasma is demonstrated for several triple combinations of 13 C- and 2 H-labeled glucose tracers (e.g., [1- 2 H 1 ]-, [6,6- 2 H 2 ]-, [1,6- 13 C 2 ]glucose). For each combination it is shown that ions arising from 2 H-labeled tracers are completely differentiated from those arising from 13 C-labeled tracers, thereby allowing the enrichment of a tracer to be simply calculated from the observed ion intensities using a standard curve with curve parameters unaffected by the presence of other tracers. For each tracer, the HRMS method exhibits low limits of detection and good repeatability in the tested 0.1-15.0% enrichment range. Additionally, due to short sample preparation and analysis times, the method is well-suited for high-throughput determination of multiple glucose tracer enrichments in plasma samples.

Journal: Efficient Hydrologic Tracer-Test Design for Tracer ...

EPA Pesticide Factsheets

Hydrological tracer testing is the most reliable diagnostic technique available for the determination of basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed to facilitate the design of tracer tests by root determination of the one-dimensional advection-dispersion equation (ADE) using a preset average tracer concentration which provides a theoretical basis for an estimate of necessary tracer mass. The method uses basic measured field parameters (e.g., discharge, distance, cross-sectional area) that are combined in functional relatipnships that descrive solute-transport processes related to flow velocity and time of travel. These initial estimates for time of travel and velocity are then applied to a hypothetical continuous stirred tank reactor (CSTR) as an analog for the hydrological-flow system to develop initial estimates for tracer concentration, tracer mass, and axial dispersion. Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be necessary for descri

Accounting for pharmacokinetic differences in dual-tracer receptor density imaging.

PubMed

Tichauer, K M; Diop, M; Elliott, J T; Samkoe, K S; Hasan, T; St Lawrence, K; Pogue, B W

2014-05-21

Dual-tracer molecular imaging is a powerful approach to quantify receptor expression in a wide range of tissues by using an untargeted tracer to account for any nonspecific uptake of a molecular-targeted tracer. This approach has previously required the pharmacokinetics of the receptor-targeted and untargeted tracers to be identical, requiring careful selection of an ideal untargeted tracer for any given targeted tracer. In this study, methodology capable of correcting for tracer differences in arterial input functions, as well as binding-independent delivery and retention, is derived and evaluated in a mouse U251 glioma xenograft model using an Affibody tracer targeted to epidermal growth factor receptor (EGFR), a cell membrane receptor overexpressed in many cancers. Simulations demonstrated that blood, and to a lesser extent vascular-permeability, pharmacokinetic differences between targeted and untargeted tracers could be quantified by deconvolving the uptakes of the two tracers in a region of interest devoid of targeted tracer binding, and therefore corrected for, by convolving the uptake of the untargeted tracer in all regions of interest by the product of the deconvolution. Using fluorescently labeled, EGFR-targeted and untargeted Affibodies (known to have different blood clearance rates), the average tumor concentration of EGFR in four mice was estimated using dual-tracer kinetic modeling to be 3.9 ± 2.4 nM compared to an expected concentration of 2.0 ± 0.4 nM. However, with deconvolution correction a more equivalent EGFR concentration of 2.0 ± 0.4 nM was measured.

Chemical Tracer Methods: Chapter 7

USGS Publications Warehouse

Healy, Richard W.

2017-01-01

Tracers have a wide variety of uses in hydrologic studies: providing quantitative or qualitative estimates of recharge, identifying sources of recharge, providing information on velocities and travel times of water movement, assessing the importance of preferential flow paths, providing information on hydrodynamic dispersion, and providing data for calibration of water flow and solute-transport models (Walker, 1998; Cook and Herczeg, 2000; Scanlon et al., 2002b). Tracers generally are ions, isotopes, or gases that move with water and that can be detected in the atmosphere, in surface waters, and in the subsurface. Heat also is transported by water; therefore, temperatures can be used to trace water movement. This chapter focuses on the use of chemical and isotopic tracers in the subsurface to estimate recharge. Tracer use in surface-water studies to determine groundwater discharge to streams is addressed in Chapter 4; the use of temperature as a tracer is described in Chapter 8.Following the nomenclature of Scanlon et al. (2002b), tracers are grouped into three categories: natural environmental tracers, historical tracers, and applied tracers. Natural environmental tracers are those that are transported to or created within the atmosphere under natural processes; these tracers are carried to the Earth’s surface as wet or dry atmospheric deposition. The most commonly used natural environmental tracer is chloride (Cl) (Allison and Hughes, 1978). Ocean water, through the process of evaporation, is the primary source of atmospheric Cl. Other tracers in this category include chlorine-36 (36Cl) and tritium (3H); these two isotopes are produced naturally in the Earth’s atmosphere; however, there are additional anthropogenic sources of them.

Travel-time-based thermal tracer tomography

NASA Astrophysics Data System (ADS)

Somogyvári, Márk; Bayer, Peter; Brauchler, Ralf

2016-05-01

Active thermal tracer testing is a technique to get information about the flow and transport properties of an aquifer. In this paper we propose an innovative methodology using active thermal tracers in a tomographic setup to reconstruct cross-well hydraulic conductivity profiles. This is facilitated by assuming that the propagation of the injected thermal tracer is mainly controlled by advection. To reduce the effects of density and viscosity changes and thermal diffusion, early-time diagnostics are used and specific travel times of the tracer breakthrough curves are extracted. These travel times are inverted with an eikonal solver using the staggered grid method to reduce constraints from the pre-defined grid geometry and to improve the resolution. Finally, non-reliable pixels are removed from the derived hydraulic conductivity tomograms. The method is applied to successfully reconstruct cross-well profiles as well as a 3-D block of a high-resolution fluvio-aeolian aquifer analog data set. Sensitivity analysis reveals a negligible role of the injection temperature, but more attention has to be drawn to other technical parameters such as the injection rate. This is investigated in more detail through model-based testing using diverse hydraulic and thermal conditions in order to delineate the feasible range of applications for the new tomographic approach.

MapMaker and PathTracer for tracking carbon in genome-scale metabolic models

PubMed Central

Tervo, Christopher J.; Reed, Jennifer L.

2016-01-01

Constraint-based reconstruction and analysis (COBRA) modeling results can be difficult to interpret given the large numbers of reactions in genome-scale models. While paths in metabolic networks can be found, existing methods are not easily combined with constraint-based approaches. To address this limitation, two tools (MapMaker and PathTracer) were developed to find paths (including cycles) between metabolites, where each step transfers carbon from reactant to product. MapMaker predicts carbon transfer maps (CTMs) between metabolites using only information on molecular formulae and reaction stoichiometry, effectively determining which reactants and products share carbon atoms. MapMaker correctly assigned CTMs for over 97% of the 2,251 reactions in an Escherichia coli metabolic model (iJO1366). Using CTMs as inputs, PathTracer finds paths between two metabolites. PathTracer was applied to iJO1366 to investigate the importance of using CTMs and COBRA constraints when enumerating paths, to find active and high flux paths in flux balance analysis (FBA) solutions, to identify paths for putrescine utilization, and to elucidate a potential CO2 fixation pathway in E. coli. These results illustrate how MapMaker and PathTracer can be used in combination with constraint-based models to identify feasible, active, and high flux paths between metabolites. PMID:26771089

ELECTRON MICROSCOPY OF ABSORPTION OF TRACER MATERIALS BY TOAD URINARY BLADDER EPITHELIUM

PubMed Central

Choi, Jae Kwon

1965-01-01

The absorption of Thorotrast and saccharated iron oxide by the epithelium of the toad urinary bladder was studied by electron microscopy. Whether the toads were hydrated, dehydrated, or given Pitressin, no significant differences in transport of colloidal particles by epithelial cells were observed. This implies that these physiological factors had little effect on the transport of the tracer particles. Tracer particles were encountered in three types of epithelial cells which line the bladder lumen, but most frequently in the mitochondria-rich cells. Tracer materials were incorporated into the cytoplasm of epithelial cells after being adsorbed to the coating layer covering the luminal surface of the cells. In the intermediate stage (1 to 3 hours after introducing tracer) particles were present in small vesicles, tubules, and multivesicular bodies. In the later stages (up to 65 hours), the particles were more commonly seen to be densely packed within large membrane-bounded bodies which were often found near the Golgi region. These large bodies probably were formed by the fusion of small vesicles. Irrespective of the stages of absorption, no particles were found in the intercellular spaces or in the submucosa. Particles apparently did not penetrate the intercellular spaces of the epithelium beyond the level of the tight junction. PMID:14287173

Numerical Simulations of Airflows and Tracer Transport in the Southwestern United States.

NASA Astrophysics Data System (ADS)

Yamada, Tetsuji

2000-03-01

Project MOHAVE (Measurement of Haze and Visual Effects) produced a unique set of tracer data over the southwestern United States. During the summer of 1992, a perfluorocarbon tracer gas was released from the Mohave Power Project (MPP), a large coal-fired facility in southern Nevada. Three-dimensional atmospheric models, the Higher-Order Turbulence Model for Atmospheric Circulation-Random Puff Transport and Diffusion (HOTMAC-RAPTAD), were used to simulate the concentrations of tracer gas that were observed during a portion of the summer intensive period of Project MOHAVE. The study area extended from northwestern Arizona to southern Nevada and included Lake Mead, the Colorado River Valley, the Grand Canyon National Park, and MPP. The computational domain was 368 km in the east-west direction by 252 km in the north-south direction. Rawinsonde and radar wind profiler data were used to provide initial and boundary conditions to HOTMAC simulations. HOTMAC with a horizontal grid spacing of 4 km was able to simulate the diurnal variations of drainage and upslope flows along the Grand Canyon and Colorado River Valley. HOTMAC also captured the diurnal variations of turbulence, which played important roles for the transport and diffusion simulations by RAPTAD. The modeled tracer gas concentrations were compared with observations. The model's performance was evaluated statistically.

Determination of water saturation using gas phase partitioning tracers and time-lapse electrical conductivity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy C.; Oostrom, Martinus; Truex, Michael J.

2013-05-21

Water saturation is an important indicator of contaminant distribution and plays a governing role in contaminant transport within the vadose zone. Understanding the water saturation distribution is critical for both remediation and contaminant flux monitoring in unsaturated environments. In this work we propose and demonstrate a method of remotely determining water saturation levels using gas phase partitioning tracers and time-lapse bulk electrical conductivity measurements. The theoretical development includes the partitioning chemistry for the tracers we demonstrate (ammonia and carbon dioxide), as well as a review of the petrophysical relationship governing how these tracers influence bulk conductivity. We also investigate methodsmore » of utilizing secondary information provided by electrical conductivity breakthrough magnitudes induced by the tracers. We test the method on clean, well characterized, intermediate-scale sand columns under controlled conditions. Results demonstrate the capability to predict partitioning coefficients and accurately monitor gas breakthrough curves along the length of the column according to the corresponding electrical conductivity response, leading to accurate water saturation estimates. This work is motivated by the need to develop effective characterization and monitoring techniques for contaminated deep vadose zone environments, and provides a proof-of-concept toward uniquely characterizing and monitoring water saturation levels at the field scale and in three-dimensions using electrical resistivity tomography.« less

Estriol improves membrane fluidity of erythrocytes by the nitric oxide-dependent mechanism: an electron paramagnetic resonance study.

PubMed

Tsuda, K; Shimamoto, Y; Kimura, K; Nishio, I; Masuyama, Y

2001-05-01

The present in vitro study was performed to investigate the effects of estriol (E3) on membrane fluidity of erythrocytes by means of an electron paramagnetic resonance (EPR) and spin-labeling method. E3 was shown to significantly decrease the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-NS obtained from EPR spectra of erythrocyte membranes. This finding indicated that E3 might increase the membrane fluidity of erythrocytes. The effect of E3 was significantly potentiated by the nitric oxide (NO) donor, S-nitroso-N-acetylpenicillamine (SNAP), and a cyclic guanosine 3',5'-monophosphate (cGMP) analog, 8-bromo-cGMP. In contrast, the change in the membrane fluidity induced by E3 was antagonized by the NO synthase inhibitor, L-NG-nitroarginine-methyl-ester (L-NAME), and asymmetric dimethyl-L-arginine (ADMA). The results of the present study showed that E3 significantly increased the membrane fluidity and improved the microviscosity of erythrocyte membranes, partially mediated by an NO- and cGMP-dependent pathway. Furthermore, the data might be consistent with the hypothesis that E3 could have a beneficial effect on the rheological behavior of erythrocytes and may play a crucial role in the regulation of microcirculation.

Ordered phases in the Holstein-Hubbard model: Interplay of strong Coulomb interaction and electron-phonon coupling

NASA Astrophysics Data System (ADS)

Murakami, Yuta; Werner, Philipp; Tsuji, Naoto; Aoki, Hideo

2013-09-01

We study the Holstein-Hubbard model at half filling to explore ordered phases including superconductivity (SC), antiferromagnetism (AF), and charge order (CO) in situations where the electron-electron and electron-phonon interactions are strong (comparable to the electronic bandwidth). The model is solved in the dynamical mean-field approximation with a continuous-time quantum Monte Carlo impurity solver. We determine the superconducting transition temperature Tc and the SC order parameter and show that the phonon-induced retardation or the strong Coulomb interaction leads to a significant reduction and shift of the Tc dome against the effective electron-electron interaction Ueff given by the Hubbard U reduced by the phonon-mediated attraction in the static limit. This behavior is analyzed by comparison to an effective static model in the polaron representation with a renormalized bandwidth. In addition, we discuss the superconducting gap Δ and 2Δ/Tc to reveal the effect of the retardation and the Coulomb interaction. We also determine the finite-temperature phase diagram including AF and CO. In the moderate-coupling regime, there is a hysteretic region of AF and CO around Ueff=0, while the two phases are separated by a paramagnetic metal in the weak-coupling regime and a paramagnetic insulator in the strong-coupling regime.

Role of crystal field in mixed alkali metal effect: electron paramagnetic resonance study of mixed alkali metal oxyfluoro vanadate glasses.

PubMed

Honnavar, Gajanan V; Ramesh, K P; Bhat, S V

2014-01-23

The mixed alkali metal effect is a long-standing problem in glasses. Electron paramagnetic resonance (EPR) is used by several researchers to study the mixed alkali metal effect, but a detailed analysis of the nearest neighbor environment of the glass former using spin-Hamiltonian parameters was elusive. In this study we have prepared a series of vanadate glasses having general formula (mol %) 40 V2O5-30BaF2-(30 - x)LiF-xRbF with x = 5, 10, 15, 20, 25, and 30. Spin-Hamiltonian parameters of V(4+) ions were extracted by simulating and fitting to the experimental spectra using EasySpin. From the analysis of these parameters it is observed that the replacement of lithium ions by rubidium ions follows a "preferential substitution model". Using this proposed model, we were able to account for the observed variation in the ratio of the g parameter, which goes through a maximum. This reflects an asymmetric to symmetric changeover of the alkali metal ion environment around the vanadium site. Further, this model also accounts for the variation in oxidation state of vanadium ion, which was confirmed from the variation in signal intensity of EPR spectra.

Using the tracer-dilution discharge method to develop streamflow records for ice-affected streams in Colorado

USGS Publications Warehouse

Capesius, Joseph P.; Sullivan, Joseph R.; O'Neill, Gregory B.; Williams, Cory A.

2005-01-01

Accurate ice-affected streamflow records are difficult to obtain for several reasons, which makes the management of instream-flow water rights in the wintertime a challenging endeavor. This report documents a method to improve ice-affected streamflow records for two gaging stations in Colorado. In January and February 2002, the U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board, conducted an experiment using a sodium chloride tracer to measure streamflow under ice cover by the tracer-dilution discharge method. The purpose of this study was to determine the feasibility of obtaining accurate ice-affected streamflow records by using a sodium chloride tracer that was injected into the stream. The tracer was injected at two gaging stations once per day for approximately 20 minutes for 25 days. Multiple-parameter water-quality sensors at the two gaging stations monitored background and peak chloride concentrations. These data were used to determine discharge at each site. A comparison of the current-meter streamflow record to the tracer-dilution streamflow record shows different levels of accuracy and precision of the tracer-dilution streamflow record at the two sites. At the lower elevation and warmer site, Brandon Ditch near Whitewater, the tracer-dilution method overestimated flow by an average of 14 percent, but this average is strongly biased by outliers. At the higher elevation and colder site, Keystone Gulch near Dillon, the tracer-dilution method experienced problems with the tracer solution partially freezing in the injection line. The partial freezing of the tracer contributed to the tracer-dilution method underestimating flow by 52 percent at Keystone Gulch. In addition, a tracer-pump-reliability test was conducted to test how accurately the tracer pumps can discharge the tracer solution in conditions similar to those used at the gaging stations. Although the pumps were reliable and consistent throughout the 25-day study period, the pumps underdischarged the tracer by 5.8-15.9 percent as compared to the initial pumping rate setting, which may explain some of the error in the tracer-dilution streamflow record as compared to current-meter streamflow record.

Detection of Nitric Oxide by Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Hogg, Neil

2010-01-01

Electron paramagnetic resonance (EPR) spectroscopy has been used in a number of ways to study nitric oxide chemistry and biology. As an intrinsically stable and relatively unreactive diatomic free radical, the challenges for detecting this species by EPR are somewhat different than those for transient radical species. This review gives a basic introduction to EPR spectroscopy and discusses its uses to assess and quantify nitric oxide formation in biological systems. PMID:20304044

The Demonstration of the Feasibility of the Tuning and Stimulation of Nuclear Radiation.

DTIC Science & Technology

1988-10-31

line, or the center of a resonance pattern, is called the isomer shift. It is due to the electrostatic interaction of the nucleus with the electron ...magnetic moment due to the presence of unpaired electrons , the material is either paramagnetic or ferromagnetic. In paramagnetic materials these moments...capture and fission.4,5,8 A very fertile interdisciplinary area of nuclear quantum electronics 7 appeared to be developing, encouraged by the

Dynamics of structures in active suspensions of paramagnetic particles and applications to artificial micro-swimmers

NASA Astrophysics Data System (ADS)

Keaveny, Eric Edward

Micron-size paramagnetic particles suspended in viscous fluid will aggregate to form linear chains when subject to a uniform magnetic field. This process provides a way of changing the rheological properties of a suspension or building structures for microfluidic devices. We present a method to efficiently and accurately quantify the magnetic interactions between these particles. With this model and the force-coupling method, we perform simulations of both small ensembles and suspensions of thousands of paramagnetic particles subject to shear flows or rotating applied magnetic fields and demonstrate that in these situations an accurate representation of the fluid forces is necessary to estimate chain length. The artificial micro-swimmer is a device constructed from a flagellum-like tail of chemically linked paramagnetic beads tethered to a human red blood cell. To simulate this device, we develop an elastic coupling model that treats each chemical link as an inextensible, flexible rod. We demonstrate that when this device is subject to a rotating applied magnetic field, the filament tail will deform into a helical shape rotating with the field and propel the swimmer through the viscous fluid. Using a continuous elastica/resistive force model, we explore further the dependence of the swimming speed on the magnetic forces and swimmer geometry in the low frequency limit. We then examine the interactions between two comoving swimmers and ascertain at what separation distance a far-field approximation of the hydrodynamics is sufficient to reproduce the swimmers' dynamics. We also provide simulations of a single swimmer near a rigid surface and demonstrate that under certain conditions the presence of a wall can enhance the swimming speed. We determine further the height dependence of the repulsion from the surface, and, in the case of the spiral swimmer, the lateral drift speed. Finally, we consider a "squirmer" model for a swimming microorganism, appropriate for ciliary propulsion on time-scales much larger than the period of ciliary beating. We show that the "squirmer" model within the force-coupling method framework provides an effective simulation tool for studying low volume fraction suspensions of microorganisms.

Molecular modeling of biomolecules by paramagnetic NMR and computational hybrid methods.

PubMed

Pilla, Kala Bharath; Gaalswyk, Kari; MacCallum, Justin L

2017-11-01

The 3D atomic structures of biomolecules and their complexes are key to our understanding of biomolecular function, recognition, and mechanism. However, it is often difficult to obtain structures, particularly for systems that are complex, dynamic, disordered, or exist in environments like cell membranes. In such cases sparse data from a variety of paramagnetic NMR experiments offers one possible source of structural information. These restraints can be incorporated in computer modeling algorithms that can accurately translate the sparse experimental data into full 3D atomic structures. In this review, we discuss various types of paramagnetic NMR/computational hybrid modeling techniques that can be applied to successful modeling of not only the atomic structure of proteins but also their interacting partners. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of the oxidized and non- oxidized bitumen modified with additive «Adgezolin» by using electron paramagnetic resonance

NASA Astrophysics Data System (ADS)

Mukhamatdinov, I.; Gafurov, M.; Kemalov, A.; Rodionov, A.; Mamin, G.; Fakhretdinov, P.

2018-05-01

Cationic surfactant (adhesion additive) «Adgezolin» has been developed. It is shown that introduction of «Adgezolin» into the oxidized bitumen increases the relative amount of asphaltenes and monocyclearomatic hydrocarbons. By means of electron paramagnetic resonance (EPR) it is demonstrated that the introduction of additive «Adgezolin» increases the number of paramagnetic «free» carbon radicals (FR) in the oxidized bitumen and decreases that in the unoxidized species. In both types of bitumen shift from the Lorentzian to Gaussian EPR lineshape of FR is obtained that could be connected with as an increase of the samples homogeneity. It is supposed that while in the oxygenated bitumens introduction of additives leads to the disaggregation of asphaltene-resins compounds, in the unoxidized samples the balance is shifted towards formation of di-radicals.

Combined multifrequency EPR and DFT study of dangling bonds in a-Si:H

NASA Astrophysics Data System (ADS)

Fehr, M.; Schnegg, A.; Rech, B.; Lips, K.; Astakhov, O.; Finger, F.; Pfanner, G.; Freysoldt, C.; Neugebauer, J.; Bittl, R.; Teutloff, C.

2011-12-01

Multifrequency pulsed electron paramagnetic resonance (EPR) spectroscopy using S-, X-, Q-, and W-band frequencies (3.6, 9.7, 34, and 94 GHz, respectively) was employed to study paramagnetic coordination defects in undoped hydrogenated amorphous silicon (a-Si:H). The improved spectral resolution at high magnetic field reveals a rhombic splitting of the g tensor with the following principal values: gx=2.0079, gy=2.0061, and gz=2.0034, and shows pronounced g strain, i.e., the principal values are widely distributed. The multifrequency approach furthermore yields precise 29Si hyperfine data. Density functional theory (DFT) calculations on 26 computer-generated a-Si:H dangling-bond models yielded g values close to the experimental data but deviating hyperfine interaction values. We show that paramagnetic coordination defects in a-Si:H are more delocalized than computer-generated dangling-bond defects and discuss models to explain this discrepancy.

Biocompatible Collagen Paramagnetic Scaffold for Controlled Drug Release.

PubMed

Bettini, Simona; Bonfrate, Valentina; Syrgiannis, Zois; Sannino, Alessandro; Salvatore, Luca; Madaghiele, Marta; Valli, Ludovico; Giancane, Gabriele

2015-09-14

A porous collagen-based hydrogel scaffold was prepared in the presence of iron oxide nanoparticles (NPs) and was characterized by means of infrared spectroscopy and scanning electron microscopy. The hybrid scaffold was then loaded with fluorescein sodium salt as a model compound. The release of the hydrosoluble species was triggered and accurately controlled by the application of an external magnetic field, as monitored by fluorescence spectroscopy. The biocompatibility of the proposed matrix was also tested by the MTT assay performed on 3T3 cells. Cell viability was only slightly reduced when the cells were incubated in the presence of the collagen-NP hydrogel, compared to controls. The economicity of the chemical protocol used to obtain the paramagnetic scaffolds as well as their biocompatibility and the safety of the external trigger needed to induce the drug release suggest the proposed collagen paramagnetic matrices for a number of applications including tissue engeneering and drug delivery.

Dependence of Van-Vleck paramagnetism on the size of nanocrystals in superstoichiometric TiO{sub y}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valeeva, A. A., E-mail: valeeva@ihim.uran.ru; Nazarova, S. Z.; Rempel, A. A.

2016-04-15

In situ measurements of the magnetic susceptibility of titanium monoxide nanocrystals with superstoichiometric composition TiO{sub y} (y > 1) in the 300–1200 K temperature range showed that this value depends not only on the structural state of a sample, but also on the size of crystals. Analysis of data obtained for both ordered and disordered TiO{sub y} showed that the Van-Vleck paramagnetism is inversely proportional to the nanocrystal size because of breakage of the symmetry of local environment of the near-surface atoms of titanium and oxygen. The Van-Vleck paramagnetism contribution due to atomic-vacancy disorder in superstoichiometric titanium monoxide nanocrystals, asmore » well as in the stoichiometric composition, is proportional to a deviation of the degree of long-range order from its maximum value.« less

Time-dependent broken-symmetry density functional theory simulation of the optical response of entangled paramagnetic defects: Color centers in lithium fluoride

NASA Astrophysics Data System (ADS)

Janesko, Benjamin G.

2018-02-01

Parameter-free atomistic simulations of entangled solid-state paramagnetic defects may aid in the rational design of devices for quantum information science. This work applies time-dependent density functional theory (TDDFT) embedded-cluster simulations to a prototype entangled-defect system, namely two adjacent singlet-coupled F color centers in lithium fluoride. TDDFT calculations accurately reproduce the experimental visible absorption of both isolated and coupled F centers. The most accurate results are obtained by combining spin symmetry breaking to simulate strong correlation, a large fraction of exact (Hartree-Fock-like) exchange to minimize the defect electrons' self-interaction error, and a standard semilocal approximation for dynamical correlations between the defect electrons and the surrounding ionic lattice. These results motivate application of two-reference correlated ab initio approximations to the M-center, and application of TDDFT in parameter-free simulations of more complex entangled paramagnetic defect architectures.

Studying the Structure and Dynamics of Biomolecules by Using Soluble Paramagnetic Probes

PubMed Central

Hocking, Henry G; Zangger, Klaus; Madl, Tobias

2013-01-01

Characterisation of the structure and dynamics of large biomolecules and biomolecular complexes by NMR spectroscopy is hampered by increasing overlap and severe broadening of NMR signals. As a consequence, the number of available NMR spectroscopy data is often sparse and new approaches to provide complementary NMR spectroscopy data are needed. Paramagnetic relaxation enhancements (PREs) obtained from inert and soluble paramagnetic probes (solvent PREs) provide detailed quantitative information about the solvent accessibility of NMR-active nuclei. Solvent PREs can be easily measured without modification of the biomolecule; are sensitive to molecular structure and dynamics; and are therefore becoming increasingly powerful for the study of biomolecules, such as proteins, nucleic acids, ligands and their complexes in solution. In this Minireview, we give an overview of the available solvent PRE probes and discuss their applications for structural and dynamic characterisation of biomolecules and biomolecular complexes. PMID:23836693

Pumping Liquid Oxygen by Use of Pulsed Magnetic Fields

NASA Technical Reports Server (NTRS)

Youngquist, Robert; Lane, John; Immer, Christopher; Simpson, James

2004-01-01

An effort is underway to develop a method of pumping small amounts of liquid oxygen by use of pulsed magnetic fields. This development is motivated by a desire to reduce corrosion and hazards of explosion and combustion by eliminating all moving pump parts in contact with the pumped oxygen. The method exploits the known paramagnetism of liquid oxygen. Since they both behave similarly, the existing theory of ferrofluids (liquids with colloidally suspended magnetic particles) is directly applicable to paramagnetic liquid oxygen. In general, the force density of the paramagnetic interaction is proportional to the magnetic susceptibility multiplied by the gradient of the square of the magnitude of the magnetic field. The local force is in the direction of intensifying magnetic field. In the case of liquid oxygen, the magnetic susceptibility is large enough that a strong magnetic-field gradient can lift the liquid in normal Earth gravitation.

Ionic Liquids and Solids with Paramagnetic Anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castner, Jr., E.W.; Wishart, J.; Krieger, B.M.

2010-06-18

Four paramagnetic ionic compounds have been prepared and their magnetic, structural and thermal properties have been investigated. The four compounds are methylbutylpyrrolidinium tetrachloroferrate(III) ([Pyrr{sub 14}]{sup +}/[FeCl{sub 4}]{sup -}), methyltributylammonium tetrachloroferrate(III) ([N{sub 1444}]{sup +}/[FeCl{sub 4}]{sup -}), butylmethylimidazolium tetrachloroferrate(III) ([bmim]{sup +}/[FeCl{sub 4}]{sup -}) and tetrabutylammonium bromotrichloroferrate(III) ([N{sub 4444}]{sup +}/[FeBrCl{sub 3}]{sup -}). Temperature-dependent studies of their magnetic behaviors show that all four compounds are paramagnetic at ambient temperatures. Glass transitions are observed for only two of the four compounds, [Pyrr{sub 14}]{sup +}/[FeCl{sub 4}]{sup -} and [bmim]{sup +}/[FeCl{sub 4}]{sup -}. Crystal structures for [Pyrr{sub 14}]{sup +}/[FeCl{sub 4}]{sup -} and [N{sub 1444}]{sup +}/[FeCl{sub 4}]{sup -}more » are compared with the previously reported [N{sub 4444}]{sup +}/[FeBrCl{sub 3}]{sup -}.« less

On the use of flow-storage repartitions derived from artificial tracer tests for geothermal reservoir characterization in the Malm-Molasse basin: a theoretical study

NASA Astrophysics Data System (ADS)

Dewi, Dina Silvia; Osaigbovo Enomayo, Augustine; Mohsin, Rizwan; Karmakar, Shyamal; Ghergut, Julia; Sauter, Martin

2016-04-01

Flow-storage repartition (FSR) analysis (Shook 2003) is a versatile tool for characterizing subsurface flow and transport systems. FSR can be derived from measured signals of inter-well tracer tests, if certain requirements are met - basically, the same as required for equivalence between fluid residence time distribution (RTD) and a measured inter-well tracer signal (pre-processed and de-convolved if necessary). Nominally, a FSR is derived from a RTD as a trajectory in normalized {1st, 0th}-order statistical moment space; more intuitively, as a parametric plot of 0th-order against 1st-order statistical moments of RTD truncated at time t, with t as a parameter running from the first tracer input to the latest available tracer sampling; 0th-order moments being normalized by the total tracer recovery, and 1st-order moments by the mean RT. Fracture-dominated systems plot in the upper left (high F , low S) region of FSR diagrams; a homogeneous single-continuum with no dispersion (infinite Peclet number) displays a straight line from {F ,S}={0,0} to {F ,S}={1,1}. This analysis tool appears particularly attractive for characterizing markedly-heterogeneous, porous-fissured-fractured (partly karstified) formations like those targeted by geothermal exploration in the Malm-Molasse basin in Southern Germany, and especially for quantifying flow and transport contributions from contrasting facies types ('reef' versus 'bedded'). However, tracer tests conducted in such systems with inter-well distances of some hundreds of metres (as required by economic considerations on geothermal reservoir sizing) face the problem of very long residence times - and thus the need to deal with incomplete (truncated) signals. For the geothermal well triplet at the Sauerlach site near Munich, tracer peak arrival times exceeding 2 years have been predicted, and signal tails decreasing by less than 50% over >10 years, which puts great uncertainty on the (extrapolation-based) normalizing factors needed to calculate FSR. Looking at the Sauerlach example, we find that premature interruption of tracer sampling systematically leads to overestimating the reservoir's storage capacity and underestimating its flow capacity, with misestimation generally increasing as the bedded/reef interfacial area per volume is increased. It is interesting to correlate these findings with the tracer-based approach to facies identification for the shallower Malm aquifers of the Southern Franconian Alb, proposed by Seiler et al. (1989, 1995) and with expectations from the direct (i. e., distributed-parameter) modeling of matrix-diffusive effects (Maloszewski and Zuber 1985) on measured tracer signals. References: Maloszewski P, Zuber A (1985) On the theory of tracer experiments in fissured rocks with a porous matrix, Journal of Hydrology, 79, 333-358 Seiler K-P, Behrens H, Wolf M (1995) Use of artificial and environmental tracers to study storage and drainage of groundwater in the Franconian Alb, Germany, and the consequences for groundwater protection, Proc Isotopes in Water Resources Management, 2, 135-146 (IAEA, Vienna) Seiler K-P, Maloszewski P, Behrens H (1989) Hydrodynamic dispersion in karstified limestones and dolomites in the Upper Jurassic of the Franconian Alb, FRG, Journal of Hydrology, 108, 235-247 Shook G M (2003) A Simple, Fast Method of Estimating Fractured Reservoir Geometry from Tracer Tests, Geothermal Resources Council Transactions, 27, 407-411 Financial support from the German Federal Ministry for Economic Affairs and Energy is gratefully acknowledged. - Gefördert durch BMWi aufgrund eines Beschlusses des Deutschen Bundestages (FKZ 0325515 "TRENDS").

Effect of magnetic coupling on non-radiative relaxation time of Fe3+ sites on LaAl1-xFexO3 pigments

NASA Astrophysics Data System (ADS)

Novatski, A.; Somer, A.; Maranha, F. G.; de Souza, E. C. F.; Andrade, A. V. C.; Antunes, S. R. M.; Borges, C. P. F.; Dias, D. T.; Medina, A. N.; Astrath, N. G. C.

2018-02-01

Inorganic pigments of the system LaAl1-xFexO3 were prepared by the Pechini and the Solid State Reaction (SSR) methods. Magnetic interactions and non-radiative relaxation time were analyzed by means of phase-resolved photoacoustic spectroscopy and electron paramagnetic resonance (EPR) techniques. EPR results show a change in the magnetic behavior from paramagnetic (x = 0.2 and 0.4) to antiferromagnetic (x = 1.0), which is believed to be a result of the SSR preparation method. Trends in the optical absorption bands of the Fe3+ are attributed to their electronic transitions, and the increase in the band's intensity at 480 and 550 nm was assigned to the increase in the magnetic coupling between Fe-Fe. The phase-resolved method is capable of distinguishing between the two preparation methods, and it is possible to infer that SSR modifies the magnetic coupling of Fe-Fe with x.

NOTE: The effects of paramagnetic contrast agents on metabolite protons in aqueous solution

NASA Astrophysics Data System (ADS)

Murphy, Philip S.; Leach, Martin O.; Rowland, Ian J.

2002-03-01

The longitudinal (R1) and transverse (R2) relaxivities of the clinically used contrast agents Gd(DTPA)2-, Gd(DOTA)- and Gd(DTPA-BMA) have been determined in mixed aqueous metabolite solutions for choline, creatine and N-acetylaspartate. Measurements were performed at 1.5 T using a STEAM sequence on 25 mM metabolite solutions at pH = 7.4 and 22 °C. The data showed that for all the contrast agents and metabolites, R1 ~ R2. The largest range of relaxivity values was found for Gd(DTPA)2-, where R2 = 6.8 +/- 0.3 mM-1 s-1 for choline and 1.5 +/- 0.4 mM-1 s-1 for N-acetylaspartate. Variation in relaxivity values was attributed primarily to differences between the charges of the paramagnetic agent and metabolite. The maximum potential influence of the contrast agents on in vivo metabolite signals was calculated using the measured relaxivities.

Electron spin resonance (ESR) dose measurement in bone of Hiroshima A-bomb victim.

PubMed

Kinoshita, Angela; Baffa, Oswaldo; Mascarenhas, Sérgio

2018-01-01

Explosion of the bombs in Hiroshima and Nagasaki corresponds to the only historical moment when atomic bombs were used against civilians. This event triggered countless investigations into the effects and dosimetry of ionizing radiation. However, none of the investigations has used the victims' bones as dosimeter. Here, we assess samples of bones obtained from fatal victims of the explosion by Electron Spin Resonance (ESR). In 1973, one of the authors of the present study (SM) traveled to Japan and conducted a preliminary experiment on the victims' bone samples. The idea was to use the paramagnetism induced in bone after irradiation to measure the radiation dose. Technological advances involved in the construction of spectrometers, better knowledge of the paramagnetic center, and improvement in signal processing techniques have allowed us to resume the investigation. We obtained a reconstructed dose of 9.46 ± 3.4 Gy from the jawbone, which was compatible with the dose distribution in different locations as measured in non-biological materials such as wall bricks and roof tiles.

Effect of the next-nearest-neighbor hopping on the charge collective modes in the paramagnetic phase of the Hubbard model

NASA Astrophysics Data System (ADS)

Dao, Vu Hung; Frésard, Raymond

2017-10-01

The charge dynamical response function of the t-t'-U Hubbard model is investigated on the square lattice in the thermodynamical limit. The correlation function is calculated from Gaussian fluctuations around the paramagnetic saddle-point within the Kotliar and Ruckenstein slave-boson representation. The next-nearest-neighbor hopping only slightly affects the renormalization of the quasiparticle mass. In contrast a negative t'/t notably decreases (increases) their velocity, and hence the zero-sound velocity, at positive (negative) doping. For low (high) density n ≲ 0.5 (n ≳ 1.5) we find that it enhances (reduces) the damping of the zero-sound mode. Furthermore it softens (hardens) the upper-Hubbard-band collective mode at positive (negative) doping. It is also shown that our results differ markedly from the random-phase approximation in the strong-coupling limit, even at high doping, while they compare favorably with existing quantum Monte Carlo numerical simulations.

Positive Effect of Propolis on Free Radicals in Burn Wounds

PubMed Central

Olczyk, Pawel; Ramos, Pawel; Komosinska-Vassev, Katarzyna; Stojko, Jerzy; Pilawa, Barbara

2013-01-01

Concentration and properties of free radicals in the burn wounds treated with propolis were examined by the use of electron paramagnetic resonance spectroscopy. Magnetic spin-spin interactions and complex free radicals structures in wound beds were studied. The results were compared to those obtained for silver sulphadiazine used as a standard pharmaceutical agent. The changes of free radicals in the matrix of injury with time of exposition on these substances were tested. The aim of this study was to check the hypothesis about the best influence of propolis on the burn wounds healing. It was confirmed that a relatively lower concentration of free radicals exists in the burn wounds treated with propolis. The homogeneously broadened spectra and a complex free radical system characterize the tested tissue samples. The fastening of spin-lattice relaxation processes in the matrix of injury after treatment with propolis and silver sulphadiazine was observed. Practical usefulness of electron paramagnetic resonance spectroscopy in alternative medicine was proved. PMID:23762125

Probing α -RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

NASA Astrophysics Data System (ADS)

Winter, Stephen M.; Riedl, Kira; Kaib, David; Coldea, Radu; Valentí, Roser

2018-02-01

Recent studies have brought α -RuCl3 to the forefront of experimental searches for materials realizing Kitaev spin-liquid physics. This material exhibits strongly anisotropic exchange interactions afforded by the spin-orbit coupling of the 4 d Ru centers. We investigate the dynamical response at finite temperature and magnetic field for a realistic model of the magnetic interactions in α -RuCl3 . These regimes are thought to host unconventional paramagnetic states that emerge from the suppression of magnetic order. Using exact diagonalization calculations of the quantum model complemented by semiclassical analysis, we find a very rich evolution of the spin dynamics as the applied field suppresses the zigzag order and stabilizes a quantum paramagnetic state that is adiabatically connected to the fully polarized state at high fields. At finite temperature, we observe large redistributions of spectral weight that can be attributed to the anisotropic frustration of the model. These results are compared to recent experiments and provide a road map for further studies of these regimes.

Strong-coupling phases of the spin-orbit-coupled spin-1 Bose-Hubbard chain: Odd-integer Mott lobes and helical magnetic phases

NASA Astrophysics Data System (ADS)

Pixley, J. H.; Cole, William S.; Spielman, I. B.; Rizzi, Matteo; Das Sarma, S.

2017-10-01

We study the odd-integer filled Mott phases of a spin-1 Bose-Hubbard chain and determine their fate in the presence of a Raman induced spin-orbit coupling which has been achieved in ultracold atomic gases; this system is described by a quantum spin-1 chain with a spiral magnetic field. The spiral magnetic field initially induces helical order with either ferromagnetic or dimer order parameters, giving rise to a spiral paramagnet at large field. The spiral ferromagnet-to-paramagnet phase transition is in a universality class with critical exponents associated with the divergence of the correlation length ν ≈2 /3 and the order-parameter susceptibility γ ≈1 /2 . We solve the effective spin model exactly using the density-matrix renormalization group, and compare with both a large-S classical solution and a phenomenological Landau theory. We discuss how these exotic bosonic magnetic phases can be produced and probed in ultracold atomic experiments in optical lattices.

Proton in SRF Niobium

NASA Astrophysics Data System (ADS)

Wallace, John Paul

2011-03-01

Hydrogen is a difficult impurity to physically deal with in superconducting radio frequency (SRF) niobium, therefore, its properties in the metals should be well understood to allow the metal's superconducting properties to be optimized for minimum loss in the construction of resonant accelerator cavities. It is known that hydrogen is a paramagnetic impurity in niobium from NMR studies. This paramagnetism and its effect on superconducting properties are important to understand. To that end analytical induction measurements aimed at isolating the magnetic properties of hydrogen in SRF niobium are introduced along with optical reflection spectroscopy which is also sensitive to the presence of hydrogen. From the variety, magnitude and rapid kinetics found in the optical and magnetic properties of niobium contaminated with hydrogen forced a search for an atomic model. This yielded quantum mechanical description that correctly generates the activation energy for diffusion of the proton and its isotopes not only in niobium but the remaining metals for which data is available. This interpretation provides a frame work for understanding the individual and collective behavior of protons in metals.

Influence of Molecular Oxygen on Ortho-Para Conversion of Water Molecules

NASA Astrophysics Data System (ADS)

Valiev, R. R.; Minaev, B. F.

2017-07-01

The mechanism of influence of molecular oxygen on the probability of ortho-para conversion of water molecules and its relation to water magnetization are considered within the framework of the concept of paramagnetic spin catalysis. Matrix elements of the hyperfine ortho-para interaction via the Fermi contact mechanism are calculated, as well as the Maliken spin densities on water protons in H2O and O2 collisional complexes. The mechanism of penetration of the electron spin density into the water molecule due to partial spin transfer from paramagnetic oxygen is considered. The probability of ortho-para conversion of the water molecules is estimated by the quantum chemistry methods. The results obtained show that effective ortho-para conversion of the water molecules is possible during the existence of water-oxygen dimers. An external magnetic field affects the ortho-para conversion rate given that the wave functions of nuclear spin sublevels of the water protons are mixed in the complex with oxygen.

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging.

PubMed

Epel, Boris; Halpern, Howard J

2015-05-01

Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage. Copyright © 2015 Elsevier Inc. All rights reserved.

Atomic-scale control of magnetic anisotropy via novel spin–orbit coupling effect in La 2/3Sr 1/3MnO 3/SrIrO 3 superlattices

DOE PAGES

Yi, Di; Liu, Jian; Hsu, Shang-Lin; ...

2016-05-19

Magnetic anisotropy (MA) is one of the most important material properties for modern spintronic devices. Conventional manipulation of the intrinsic MA, i.e., magnetocrystalline anisotropy (MCA), typically depends upon crystal symmetry. Extrinsic control over the MA is usually achieved by introducing shape anisotropy or exchange bias from another magnetically ordered material. Here we demonstrate a pathway to manipulate MA of 3d transition-metal oxides (TMOs) by digitally inserting nonmagnetic 5d TMOs with pronounced spin-orbit coupling (SOC). High-quality superlattices comprising ferromagnetic La 2/3Sr 1/3MnO 3 (LSMO) and paramagnetic SrIrO 3 (SIO) are synthesized with the precise control of thickness at the atomic scale.more » Magnetic easy-axis reorientation is observed by controlling the dimensionality of SIO, mediated through the emergence of a novel spin-orbit state within the nominally paramagnetic SIO.« less

Comparison of magnetic and thermoelectric properties of (Nd,Ca)BaCo2O5.5 and (Nd,Ca)CoO3

NASA Astrophysics Data System (ADS)

Kolesnik, S.; Dabrowski, B.; Chmaissem, O.; Wojciechowski, K.; Świerczek, K.

2012-04-01

Magnetic and thermoelectric properties of Nd1-xCaxBaCo2O5.5 and Nd1-xCaxCoO3 have been studied. Ca doping in Nd1-xCaxBaCo2O5.5 (x ≤ 0.2) preserves the metal to insulator transition (MIT) at 340-360 K. While the antiferromagnetic state disappears upon doping, the Curie temperature is increasing and becomes close to MIT for x > 0.12. The magnetic susceptibility of Nd1-xCaxCoO3 is paramagnetic for x up to 0.2, similar to the parent compound, with some indication of cluster-glass-like behavior at temperatures below 30 K. The increasing effective paramagnetic moments with doping suggest a low spin state of Co3+ and a high spin state of Co4+. Maximum observed ZT reaches a value close to 0.2 for x = 0.15 at 800 K, which is one of the highest values for perovskite cobaltites.

REVIEW ARTICLE: Unconventional isotope effects in the high-temperature cuprate superconductors

NASA Astrophysics Data System (ADS)

Zhao, Guo-meng; Keller, H.; Conder, K.

2001-07-01

We review various isotope effects in the high-Tc cuprate superconductors to assess the role of the electron-phonon interaction in the basic physics of these materials. Of particular interest are the unconventional isotope effects on the supercarrier mass, on the charge-stripe formation temperature, on the pseudogap formation temperature, on the electron paramagnetic resonance (EPR) linewidth, on the spin-glass freezing temperature and on the antiferromagnetic ordering temperature. The observed unconventional isotope effects strongly suggest that lattice vibrations play an important role in the microscopic pairing mechanism of high-temperature superconductivity.

Direct Parametric Image Reconstruction in Reduced Parameter Space for Rapid Multi-Tracer PET Imaging.

PubMed

Cheng, Xiaoyin; Li, Zhoulei; Liu, Zhen; Navab, Nassir; Huang, Sung-Cheng; Keller, Ulrich; Ziegler, Sibylle; Shi, Kuangyu

2015-02-12

The separation of multiple PET tracers within an overlapping scan based on intrinsic differences of tracer pharmacokinetics is challenging, due to limited signal-to-noise ratio (SNR) of PET measurements and high complexity of fitting models. In this study, we developed a direct parametric image reconstruction (DPIR) method for estimating kinetic parameters and recovering single tracer information from rapid multi-tracer PET measurements. This is achieved by integrating a multi-tracer model in a reduced parameter space (RPS) into dynamic image reconstruction. This new RPS model is reformulated from an existing multi-tracer model and contains fewer parameters for kinetic fitting. Ordered-subsets expectation-maximization (OSEM) was employed to approximate log-likelihood function with respect to kinetic parameters. To incorporate the multi-tracer model, an iterative weighted nonlinear least square (WNLS) method was employed. The proposed multi-tracer DPIR (MTDPIR) algorithm was evaluated on dual-tracer PET simulations ([18F]FDG and [11C]MET) as well as on preclinical PET measurements ([18F]FLT and [18F]FDG). The performance of the proposed algorithm was compared to the indirect parameter estimation method with the original dual-tracer model. The respective contributions of the RPS technique and the DPIR method to the performance of the new algorithm were analyzed in detail. For the preclinical evaluation, the tracer separation results were compared with single [18F]FDG scans of the same subjects measured 2 days before the dual-tracer scan. The results of the simulation and preclinical studies demonstrate that the proposed MT-DPIR method can improve the separation of multiple tracers for PET image quantification and kinetic parameter estimations.

Evaluation of N-[(11)C]methyl-AMD3465 as a PET tracer for imaging of CXCR4 receptor expression in a C6 glioma tumor model.

PubMed

Hartimath, S V; van Waarde, A; Dierckx, R A J O; de Vries, E F J

2014-11-03

The chemokine receptor CXCR4 and its ligand CXCL12 play an important role in tumor progression and metastasis. CXCR4 receptors are expressed by many cancer types and provide a potential target for treatment. Noninvasive detection of CXCR4 may aid diagnosis and improve therapy selection. It has been demonstrated in preclinical studies that positron emission tomography (PET) with a radiolabeled small molecule could enable noninvasive monitoring of CXCR4 expression. Here, we prepared N-[(11)C]methyl-AMD3465 as a new PET tracer for CXCR4. N-[(11)C]Methyl-AMD3465 was readily prepared by N-methylation with [(11)C]CH3OTf. The tracer was obtained in a 60 ± 2% yield (decay corrected), the purity of the tracer was >99%, and specific activity was 47 ± 14 GBq/μmol. Tracer stability was tested in vitro using liver microsomes and rat plasma; excellent stability was observed. The tracer was evaluated in rat C6 glioma and human PC-3 cell lines. In vitro cellular uptake of N-[(11)C]methyl-AMD3465 was receptor mediated. The effect of transition metal ions (Cu(2+), Ni(2+), and Zn(2+)) on cellular binding was examined in C6 cells, and the presence of these ions increased the cellular binding of the tracer 9-, 7-, and 3-fold, respectively. Ex vivo biodistribution and PET imaging of N-[(11)C]methyl-AMD3465 were performed in rats with C6 tumor xenografts. Both PET and biodistribution studies demonstrated specific accumulation of the tracer in the tumor (SUV 0.6 ± 0.2) and other CXCR4 expressing organs, such as lymph node (1.5 ± 0.2), liver (8.9 ± 1.0), bone marrow (1.0 ± 0.3), and spleen (1.0 ± 0.1). Tumor uptake was significantly reduced (66%, p < 0.01) after pretreatment with Plerixafor (AMD3100). Biodistribution data indicates a tumor-to-muscle ratio of 7.85 and tumor-to-plasma ratio of 1.14, at 60 min after tracer injection. Our data demonstrated that N-[(11)C]methyl-AMD3465 is capable of detecting physiologic CXCR4 expression in tumors and other CXCR4 expressing tissues. These results warrant further evaluation of N-[(11)C]methyl-AMD3465 as a potential PET tracer for CXCR4 receptor imaging.

Effect of analytical proton beam irradiation on lead-white pigments, characterized by EPR spectroscopy

NASA Astrophysics Data System (ADS)

Gourier, Didier; Binet, Laurent; Gonzalez, Victor; Vezin, Hervé; Touati, Nadia; Calligaro, Thomas

2018-01-01

Analytical techniques using proton beams with energy in the MeV range are commonly used to study archeological artefact and artistic objects. However ion beams can induce alteration of fragile materials, which is notably the case of easel paintings, limiting the use of these techniques. We used continuous wave EPR and pulse EPR spectroscopy to reveal the effect of 3 MeV proton irradiation on lead carbonates, which were extensively employed as white pigments from the antiquity to the 20th century. Two kinds of paramagnetic centers were identified in cerussite (PbCO3): the first one is CO3- radicals formed by hole trapping by CO32- ions, and the second one is NO32- radical resulting from electron trapping by NO3- impurities. Hydrocerussite (2PbCO3·Pb(OH)2) is the most darkened material under proton beam, however it exhibits no NO32- radicals and 20 times less CO3- radicals than cerussite. Consequently these paramagnetic centers are not directly responsible for the darkening of lead-white pigments. We proposed that their higher instability in hydrocerussite might be at the origin of the formation of color centers in this material.

Magnetocaloric Effect in Layered Organic Conductor λ-(BETS)2FeCl4

NASA Astrophysics Data System (ADS)

Sugiura, Shiori; Shimada, Kazuo; Tajima, Naoya; Nishio, Yutaka; Terashima, Taichi; Isono, Takayuki; Kato, Reizo; Zhou, Biao; Uji, Shinya

2018-04-01

Magnetocaloric effect (MCE) and magnetic torque measurements have been carried out in the π-d system λ-(BETS)2FeCl4 [BETS = bis(ethylenedithio)tetraselenafulvalene], which shows an antiferromagnetic insulating (AFI) phase below ˜8.5 K. In the magnetic torque curve, a sharp structure at ˜1.2 T and a step at ˜10 T are observed at low temperatures, which are caused by the spin-flop (SF) transition and the transition from the AFI to paramagnetic metallic (PM) phase, respectively. The MCE, directly related to the magnetic entropy, shows a small sharp peak at the SF transition and a sharp dip at the AFI-PM transition. The overall feature above 3 K is qualitatively interpreted by a simple picture: antiferromagnetic (AF) π spins and paramagnetic 3d spins at the Fe sites. However, a broad dip in the MCE is additionally found at ˜5 T below ˜3 K, which is not explained by the above picture. The results are compared with those of κ-(BETS)2FeBr4, which shows an AF order of the 3d spins at the Fe sites.

The influence of genistein on free radicals in normal dermal fibroblasts and keloid fibroblasts examined by EPR spectroscopy.

PubMed

Jurzak, Magdalena; Ramos, Paweł; Pilawa, Barbara

2017-01-01

Normal and keloid fibroblasts were examined using X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The effect of genistein on the concentration of free radicals in both normal dermal and keloid fibroblasts after ultraviolet irradiation was investigated. The highest concentration of free radicals was seen in keloid fibroblasts, with normal fibroblasts containing a lower concentration. The concentration of free radicals in both normal and keloid fibroblasts was altered in a concentration-dependent manner by the presence of genistein. The change in intra-cellular free radical concentration after the ultraviolet irradiation of both normal and keloid fibroblasts is also discussed. The antioxidant properties of genistein, using its 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging activity as a model, were tested, and the effect of ultraviolet irradiation on its interaction with free radicals was examined. The electron paramagnetic resonance spectra of DPPH showed quenching by genistein. The interaction of genistein with DPPH free radicals in the absence of ultraviolet irradiation was shown to be slow, but this interaction was much faster under ultraviolet irradiation. Ultraviolet irradiation enhanced the free radical-scavenging activity of genistein.

Ultrasonic assisted rapid synthesis of high uniform super-paramagnetic microspheres with core-shell structure and robust magneto-chromatic ability

NASA Astrophysics Data System (ADS)

Zhang, Wenyan; Chen, Jiahua; Wang, Wei; Lu, GongXuan; Hao, Lingyun; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

2017-03-01

Super-paramagnetic core-shell microspheres were synthesized by ultrasonic assisted routine under low ultrasonic irradiation powers. Compared with conventional routine, ultrasonic effect could not only improve the uniformity of the core-shell structure of Fe3O4@SiO2, but shorten the synthesis time in large scale. Owing to their hydrophilicity and high surface charge, the Fe3O4@SiO2 microspheres could be dispersed well in distilled water to form homogeneous colloidal suspension. The suspensions have favorable magneto-chromatic ability that they sensitively exhibit brilliant colorful ribbons by magnetic attraction. The colorful ribbons, which distributed along the magnetic lines, make morphology of the magnetic fields become "visible" to naked eyed. Those colorful ribbons originate from strong magnetic interaction between the microspheres and magnetic fields. Furthermore, the magneto-chromatic performance is reversible as the colorful ribbons vanished rapidly with the removing of magnetic fields. The silica layer effectively enhanced the acid resistance and surface-oxidation resistance of theFe3O4@SiO2 microspheres, so they could exhibit stable magnetic nature and robust magneto-chromatic property in acid environment.

Antiferromagnetic coupling between rare earth ions and semiquinones in a series of 1:1 complexes.

PubMed

Caneschi, Andrea; Dei, Andrea; Gatteschi, Dante; Poussereau, Sandrine; Sorace, Lorenzo

2004-04-07

We use the strategy of diamagnetic substitution for obtaining information on the crystal field effects in paramagnetic rare earth ions using the homologous series of compounds with the diamagnetic tropolonato ligand, Ln(Trp)(HBPz(3))(2), and the paramagnetic semiquinone ligand, Ln(DTBSQ)(HBPz(3))(2), (DTBSQ = 3,5-di-tert-butylsemiquinonato, Trp = tropolonate, HBPz(3)= hydrotrispyrazolylborate) for Ln = Sm(iii), Eu(iii), Gd(iii), Tb(iii), Dy(iii), Ho(iii), Er(iii) or Yb(iii). The X-ray crystal structure of a new form of tropolonate derivative is presented, which shows, as expected, a marked similarity with the structure of the semiquinonate derivative. The Ln(Trp)(HBPz(3))(2) derivatives were then used as a reference for the qualitative determination of crystal field effects in the exchange coupled semiquinone derivatives. Through magnetisation and susceptibility measurements this empirical diamagnetic substitution method evidenced for Er(iii), Tb(iii), Dy(iii) and Yb(iii) derivatives a dominating antiferromagnetic coupling. The increased antiferromagnetic contribution compared to other radical-rare earth metal complexes formed by nitronyl nitroxide ligands may be related to the increased donor strength of the semiquinone ligand.

The leap-frog effect of ring currents in benzene.

PubMed

Ligabue, Andrea; Soncini, Alessandro; Lazzeretti, Paolo

2002-03-06

Symmetry arguments show that the ring-current model proposed by Pauling, Lonsdale, and London to explain the enhanced diamagnetism of benzene is flawed by an intrinsic drawback. The minimal basis set of six atomic 2p orbitals taken into account to develop such a model is inherently insufficient to predict a paramagnetic contribution to the perpendicular component of magnetic susceptibility in planar ring systems such as benzene. Analogous considerations can be made for the hypothetical H(6) cyclic molecule. A model allowing for extended basis sets is necessary to rationalize the magnetism of aromatics. According to high-quality coupled Hartree-Fock calculations, the trajectories of the current density vector field induced by a magnetic field perpendicular to the skeletal plane of benzene in the pi electrons are noticeably different from those typical of a Larmor diamagnetic circulation, in that (i) significant deformation of the orbits from circular to hexagonal symmetry occurs, which is responsible for a paramagnetic contribution of pi electrons to the out-of-plane component of susceptibility, and (ii) a sizable component of the pi current density vector parallel to the inducing field is predicted. This causes a waving motion of pi electrons; streamlines are characterized by a "leap-frog effect".

Two-dimensional Anderson-Hubbard model in the DMFT + {Sigma} approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuchinskii, E. Z., E-mail: kuchinsk@iep.uran.ru; Kuleeva, N. A.; Nekrasov, I. A.

The density of states, the dynamic (optical) conductivity, and the phase diagram of the paramagnetic two-dimensional Anderson-Hubbard model with strong correlations and disorder are analyzed within the generalized dynamical mean field theory (DMFT + {Sigma} approximation). Strong correlations are accounted by the DMFT, while disorder is taken into account via the appropriate generalization of the self-consistent theory of localization. We consider the two-dimensional system with the rectangular 'bare' density of states (DOS). The DMFT effective single-impurity problem is solved by numerical renormalization group (NRG). The 'correlated metal,' Mott insulator, and correlated Anderson insulator phases are identified from the evolution ofmore » the density of states, optical conductivity, and localization length, demonstrating both Mott-Hubbard and Anderson metal-insulator transitions in two-dimensional systems of finite size, allowing us to construct the complete zero-temperature phase diagram of the paramagnetic Anderson-Hubbard model. The localization length in our approximation is practically independent of the strength of Hubbard correlations. But the divergence of the localization length in a finite-size two-dimensional system at small disorder signifies the existence of an effective Anderson transition.« less

Evaluation of synergistic antioxidant potential of complex mixtures using oxygen radical absorbance capacity (ORAC) and electron paramagnetic resonance (EPR).

PubMed

Parker, Tory L; Miller, Samantha A; Myers, Lauren E; Miguez, Fernando E; Engeseth, Nicki J

2010-01-13

Previous research has demonstrated that certain combinations of compounds result in a decrease in toxic or pro-oxidative effects, previously noted when compounds were administered singly. Thus, there is a need to study many complex interactions further. Two in vitro techniques [electron paramagnetic resonance (EPR) and oxygen radical absorbance capacity (ORAC) assays] were used in this study to assess pro- and antioxidant capacity and synergistic potential of various compounds. Rutin, p-coumaric acid, abscisic acid, ascorbic acid, and a sugar solution were evaluated individually at various concentrations and in all 26 possible combinations at concentrations found in certain foods (honey or papaya), both before and after simulated digestion. EPR results indicated sugar-containing combinations provided significantly higher antioxidant capacity; those combinations containing sugars and ascorbic acid demonstrated synergistic potential. The ORAC assay suggested additive effects, with some combinations having synergistic potential, although fewer combinations were significantly synergistic after digestion. Finally, ascorbic acid, caffeic acid, quercetin, and urate were evaluated at serum-achievable levels. EPR analysis did not demonstrate additive or synergistic potential, although ORAC analysis did, principally in combinations containing ascorbic acid.

Lanthanide binding and IgG affinity construct: Potential applications in solution NMR, MRI, and luminescence microscopy

PubMed Central

Barb, Adam W; Ho, Tienhuei Grace; Flanagan-Steet, Heather; Prestegard, James H

2012-01-01

Paramagnetic lanthanide ions when bound to proteins offer great potential for structural investigations that utilize solution nuclear magnetic resonance spectroscopy, magnetic resonance imaging, or optical microscopy. However, many proteins do not have native metal ion binding sites and engineering a chimeric protein to bind an ion while retaining affinity for a protein of interest represents a significant challenge. Here we report the characterization of an immunoglobulin G-binding protein redesigned to include a lanthanide binding motif in place of a loop between two helices (Z-L2LBT). It was shown to bind Tb3+ with 130 nM affinity. Ions such as Dy3+, Yb3+, and Ce3+ produce paramagnetic effects on NMR spectra and the utility of these effects is illustrated by their use in determining a structural model of the metal-complexed Z-L2LBT protein and a preliminary characterization of the dynamic distribution of IgG Fc glycan positions. Furthermore, this designed protein is demonstrated to be a novel IgG-binding reagent for magnetic resonance imaging (Z-L2LBT:Gd3+ complex) and luminescence microscopy (Z-L2LBT: Tb3+ complex). PMID:22851279

Bioelimination of /sup 51/Cr and /sup 85/Sr by cockroaches, Gromphadorhina portentosa (orthoptera: blaberidae), as affected by mites, Gromphadorholaelaps schaeferi (parasitiformes: laelapidae)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schowalter, T.D.; Crossley, D.A. Jr.

1982-03-01

The rates of Chromium-51 and Strontium-85 assimilation and bioelimination by the hissing cockroach, Gromphadorhina portentosa (Schaum) are described when the symbiotic mite, Gromphadorholaelaps schaeferi Till, was present or removed. Mite-infested cockroaches had significantly higher rates of /sup 51/Cr elimination relative to mite-free cockroaches, implying more rapid gut clearance times. The authors did not find a significant mite effect on /sup 85/Sr elimination by the host, but mite effects could have been masked by the apparently unique process of nutrient assimilation and elimination by G. portentosa. Conventional models of radioactive tracer bioelimination predict a rapid initial loss of tracer due tomore » gut clearance, followed by a slower loss due to excretion of assimilated tracer. The results indicated that assimilated /sup 85/Sr was eliminated earlier than unassimilated /sup 85/Sr, which was lost by defecation.« less

Effect of Polydispersity on Diffusion in Random Obstacle Matrices

NASA Astrophysics Data System (ADS)

Cho, Hyun Woo; Kwon, Gyemin; Sung, Bong June; Yethiraj, Arun

2012-10-01

The dynamics of tracers in disordered matrices is of interest in a number of diverse areas of physics such as the biophysics of crowding in cells and cell membranes, and the diffusion of fluids in porous media. To a good approximation the matrices can be modeled as a collection of spatially frozen particles. In this Letter, we consider the effect of polydispersity (in size) of the matrix particles on the dynamics of tracers. We study a two dimensional system of hard disks diffusing in a sea of hard disk obstacles, for different values of the polydispersity of the matrix. We find that for a given average size and area fraction, the diffusion of tracers is very sensitive to the polydispersity. We calculate the pore percolation threshold using Apollonius diagrams. The diffusion constant, D, follows a scaling relation D˜(ϕc-ϕm)μ-β for all values of the polydispersity, where ϕm is the area fraction and ϕc is the value of ϕm at the percolation threshold.

Effect of polydispersity on diffusion in random obstacle matrices.

PubMed

Cho, Hyun Woo; Kwon, Gyemin; Sung, Bong June; Yethiraj, Arun

2012-10-12

The dynamics of tracers in disordered matrices is of interest in a number of diverse areas of physics such as the biophysics of crowding in cells and cell membranes, and the diffusion of fluids in porous media. To a good approximation the matrices can be modeled as a collection of spatially frozen particles. In this Letter, we consider the effect of polydispersity (in size) of the matrix particles on the dynamics of tracers. We study a two dimensional system of hard disks diffusing in a sea of hard disk obstacles, for different values of the polydispersity of the matrix. We find that for a given average size and area fraction, the diffusion of tracers is very sensitive to the polydispersity. We calculate the pore percolation threshold using Apollonius diagrams. The diffusion constant, D, follows a scaling relation D~(φ(c)-φ(m))(μ-β) for all values of the polydispersity, where φ(m) is the area fraction and φ(c) is the value of φ(m) at the percolation threshold.

3-D Modelling the effect of river excavation on surface water and groundwater relation in a bank filtration system - comparing electrical conductivity and heat as tracer

NASA Astrophysics Data System (ADS)

Wang, Weishi; Oswald, Sascha; Munz, Matthias; Strasser, Daniel

2017-04-01

As a pretreatment for conventional drinking water supply, bank filtration (BF) is widely used in Europe, while in Germany it contributes 16% of potable water supply. There are usually two crucial issues for BF influencing its treatment effect, which are separately the spatial and temporal distribution of travelling times and distinguishing between the flow contribution of BF versus inflow from the ambient groundwater. Modelling is a strong tool for analyzing the behavior and development of the flow field, especially for quantification of the river recharge rate of BF and estimation of travel time distribution. Though 3-D modelling of the flow field as a comprehensive tool has been used in several studies, many simulations are limited to pure water flow. Since heads are only partially able to constrain the flow field, model non-uniqueness might lead to misinterpretation of the real flow field, especially in complex geological conditions. Some studies have shown that by including tracers, the model non-uniqueness could be reasonably constrained and the accuracy of flux estimation could be improved. Natural tracers thus are used in groundwater modelling, while differences in their properties or input may cause dissimilar behavior during the transport process. In this study, we have set up a numerical 3-D groundwater flow model of a bank filtration site with strong geological heterogeneity and used the data of several years monitoring activities as the data basis. We were particularly interested in the seasonal dynamics but also structural changes induced by a reconstruction of the surface water including excavation and rebuilding the bank construction. By combining separately electrical conductivity and heat as tracers in the model we were able to i) understand flow field mechanisms and its changes caused by the excavation ii) conclude from the deviations of the tracer concentrations and dynamics simulated compared to the measurements on deficiencies of the flow field; and thus by the tracer study flow field could be improved iii) compare the individual behavior of the tracers in this realistic setting of transport processes also relevant for judging water quality in the pumping wells now and in the future.

On the pathways and timescales of intercontinental air pollution transport

NASA Astrophysics Data System (ADS)

Stohl, Andreas; Eckhardt, Sabine; Forster, Caroline; James, Paul; Spichtinger, Nicole

2002-12-01

This paper presents results of a 1-year simulation of the transport of six passive tracers, released over the continents according to an emission inventory for carbon monoxide (CO). Lagrangian concepts are introduced to derive age spectra of the tracer concentrations on a global grid in order to determine the timescales and pathways of pollution export from the continents. Calculating these age spectra is equivalent to simulating many (quasi continuous) plumes, each starting at a different time, which are subsequently merged. Movies of the tracer dispersion have been made available on an Internet website. It is found that emissions from Asia experience the fastest vertical transport, whereas European emissions have the strongest tendency to remain in the lower troposphere. European emissions are transported primarily into the Arctic and appear to be the major contributor to the Arctic haze problem. Tracers from an upwind continent first arrive over a receptor continent in the upper troposphere, typically after some 4 days. Only later foreign tracers also arrive in the lower troposphere. Assuming a 2-day lifetime, the domestic tracers dominate total tracer columns over all continents except over Australia where foreign tracers account for 20% of the tracer mass. In contrast, for a 20-day lifetime even continents with high domestic emissions receive more than half of their tracer burden from foreign continents. Three special regions were identified where tracers are transported to, and tracer dilution is slow. Future field studies therefore should be deployed in the following regions: (1) In the winter, the Asia tracer accumulates over Indonesia and the Indian Ocean, a region speculated to be a stratospheric fountain. (2) In the summer, the highest concentrations of the Asia tracer are found in the Middle East. (3) In the summer, the highest concentrations of the North America tracer are found in the Mediterranean.

Ellipsoidal Brownian self-driven particles in a magnetic field

NASA Astrophysics Data System (ADS)

Fan, Wai-Tong Louis; Pak, On Shun; Sandoval, Mario

2017-03-01

We study the two-dimensional Brownian dynamics of an ellipsoidal paramagnetic microswimmer moving at a low Reynolds number and subject to a magnetic field. Its corresponding mean-square displacement, showing the effect of a particles's shape, activity, and magnetic field on the microswimmer's diffusion, is analytically obtained. Comparison between analytical and computational results shows good agreement. In addition, the effect of self-propulsion on the transition time from anisotropic to isotropic diffusion of the ellipse is investigated.

Biological tracer method

DOEpatents

Strong-Gunderson, Janet M.; Palumbo, Anthony V.

1998-01-01

The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer.

Biological tracer method

DOEpatents

Strong-Gunderson, J.M.; Palumbo, A.V.

1998-09-15

The present invention is a biological tracer method for characterizing the movement of a material through a medium, comprising the steps of: introducing a biological tracer comprising a microorganism having ice nucleating activity into a medium; collecting at least one sample of the medium from a point removed from the introduction point; and analyzing the sample for the presence of the biological tracer. The present invention is also a method for using a biological tracer as a label for material identification by introducing a biological tracer having ice nucleating activity into a material, collecting a sample of a portion of the labelled material and analyzing the sample for the presence of the biological tracer. 2 figs.

Relativistically corrected nuclear magnetic resonance chemical shifts calculated with the normalized elimination of the small component using an effective potential-NMR chemical shifts of molybdenum and tungsten

NASA Astrophysics Data System (ADS)

Filatov, Michael; Cremer, Dieter

2003-07-01

A new method for relativistically corrected nuclear magnetic resonance (NMR) chemical shifts is developed by combining the individual gauge for the localized orbital approach for density functional theory with the normalized elimination of a small component using an effective potential. The new method is used for the calculation of the NMR chemical shifts of 95Mo and 183W in various molybdenum and tungsten compounds. It is shown that quasirelativistic corrections lead to an average improvement of calculated NMR chemical shift values by 300 and 120 ppm in the case of 95Mo and 183W, respectively, which is mainly due to improvements in the paramagnetic contributions. The relationship between electronic structure of a molecule and the relativistic paramagnetic corrections is discussed. Relativistic effects for the diamagnetic part of the magnetic shielding caused by a relativistic contraction of the s,p orbitals in the core region concern only the shielding values, however, have little consequence for the shift values because of the large independence from electronic structure and a cancellation of these effects in the shift values. It is shown that the relativistic corrections can be improved by level shift operators and a B3LYP hybrid functional, for which Hartree-Fock exchange is reduced to 15%.

Lanthanide-labeled clay: A new method for tracing sediment transport in Karst

USGS Publications Warehouse

Mahler, B.J.; Bennett, P.C.; Zimmerman, M.

1998-01-01

Mobile sediment is a fundamental yet poorly characterized aspect of mass transport through karst aquifers. Here the development and field testing of an extremely sensitive particle tracer that may be used to characterize sediment transport in karst aquifers is described. The tracer consists of micron-size montmorillonite particles homoionized to the lanthanide form; after injection and retrieval from a ground water system, the lanthanide ions are chemically stripped from the clay and quantified by high performance liquid chromatography. The tracer meets the following desired criteria: low detection limit; a number of differentiable signatures; inexpensive production and quantification using standard methods; no environmental risks; and hydrodynamic properties similar to the in situ sediment it is designed to trace. The tracer was tested in laboratory batch experiments and field tested in both surface water and ground water systems. In surface water, arrival times of the tracer were similar to those of a conservative water tracer, although a significant amount of material was lost due to settling. Two tracer tests were undertaken in a karst aquifer under different flow conditions. Under normal flow conditions, the time of arrival and peak concentration of the tracer were similar to or preceded that of a conservative water tracer. Under low flow conditions, the particle tracer was not detected, suggesting that in low flow the sediment settles out of suspension and goes into storage.Mobile sediment is a fundamental yet poorly characterized aspect of mass transport through karst aquifers. Here the development and field testing of an extremely sensitive particle tracer that may be used to characterize sediment transport in karst aquifers is described. The tracer consists of micron-size montmorillonite particles homoionized to the lanthanide form; after injection and retrieval from a ground water system, the lanthanide ions are chemically stripped from the clay and quantified by high performance liquid chromatography. The tracer meets the following desired criteria: low detection limit; a number of differentiable signatures; inexpensive production and quantification using standard methods; no environmental risks; and hydrodynamic properties similar to the in situ sediment it is designed to trace. The tracer was tested in laboratory batch experiments and field tested in both surface water and ground water systems. In surface water, arrival times of the tracer were similar to those of a conservative water tracer, although a significant amount of material was lost due to settling. Two tracer tests were undertaken in a karst aquifer under different flow conditions. Under normal flow conditions, the time of arrival and peak concentration of the tracer were similar to or preceded that of a conservative water tracer. Under low flow conditions, the particle tracer was not detected, suggesting that in low flow the sediment settles out of suspension and goes into storage.

Emission quantification using the tracer gas dispersion method: The influence of instrument, tracer gas species and source simulation.

PubMed

Delre, Antonio; Mønster, Jacob; Samuelsson, Jerker; Fredenslund, Anders M; Scheutz, Charlotte

2018-09-01

The tracer gas dispersion method (TDM) is a remote sensing method used for quantifying fugitive emissions by relying on the controlled release of a tracer gas at the source, combined with concentration measurements of the tracer and target gas plumes. The TDM was tested at a wastewater treatment plant for plant-integrated methane emission quantification, using four analytical instruments simultaneously and four different tracer gases. Measurements performed using a combination of an analytical instrument and a tracer gas, with a high ratio between the tracer gas release rate and instrument precision (a high release-precision ratio), resulted in well-defined plumes with a high signal-to-noise ratio and a high methane-to-tracer gas correlation factor. Measured methane emission rates differed by up to 18% from the mean value when measurements were performed using seven different instrument and tracer gas combinations. Analytical instruments with a high detection frequency and good precision were established as the most suitable for successful TDM application. The application of an instrument with a poor precision could only to some extent be overcome by applying a higher tracer gas release rate. A sideward misplacement of the tracer gas release point of about 250m resulted in an emission rate comparable to those obtained using a tracer gas correctly simulating the methane emission. Conversely, an upwind misplacement of about 150m resulted in an emission rate overestimation of almost 50%, showing the importance of proper emission source simulation when applying the TDM. Copyright © 2018 Elsevier B.V. All rights reserved.

MRI-Based Computational Model of Heterogeneous Tracer Transport following Local Infusion into a Mouse Hind Limb Tumor

PubMed Central

Magdoom, Kulam Najmudeen; Pishko, Gregory L.; Rice, Lori; Pampo, Chris; Siemann, Dietmar W.; Sarntinoranont, Malisa

2014-01-01

Systemic drug delivery to solid tumors involving macromolecular therapeutic agents is challenging for many reasons. Amongst them is their chaotic microvasculature which often leads to inadequate and uneven uptake of the drug. Localized drug delivery can circumvent such obstacles and convection-enhanced delivery (CED) - controlled infusion of the drug directly into the tissue - has emerged as a promising delivery method for distributing macromolecules over larger tissue volumes. In this study, a three-dimensional MR image-based computational porous media transport model accounting for realistic anatomical geometry and tumor leakiness was developed for predicting the interstitial flow field and distribution of albumin tracer following CED into the hind-limb tumor (KHT sarcoma) in a mouse. Sensitivity of the model to changes in infusion flow rate, catheter placement and tissue hydraulic conductivity were investigated. The model predictions suggest that 1) tracer distribution is asymmetric due to heterogeneous porosity; 2) tracer distribution volume varies linearly with infusion volume within the whole leg, and exponentially within the tumor reaching a maximum steady-state value; 3) infusion at the center of the tumor with high flow rates leads to maximum tracer coverage in the tumor with minimal leakage outside; and 4) increasing the tissue hydraulic conductivity lowers the tumor interstitial fluid pressure and decreases the tracer distribution volume within the whole leg and tumor. The model thus predicts that the interstitial fluid flow and drug transport is sensitive to porosity and changes in extracellular space. This image-based model thus serves as a potential tool for exploring the effects of transport heterogeneity in tumors. PMID:24619021

A new look at ocean ventilation time scales and their uncertainties

NASA Astrophysics Data System (ADS)

Fine, Rana A.; Peacock, Synte; Maltrud, Mathew E.; Bryan, Frank O.

2017-05-01

A suite of eddy-resolving ocean transient tracer model simulations are first compared to observations. Observational and model pCFC-11 ages agree quite well, with the eddy-resolving model adding detail. The CFC ages show that the thermocline is a barrier to interior ocean exchange with the atmosphere on time scales of 45 years, the measureable CFC transient, although there are exceptions. Next, model simulations are used to quantify effects on tracer ages of the spatial dependence of internal ocean tracer variability due to stirring from eddies and biases from nonstationarity of the atmospheric transient when there is mixing. These add to tracer age uncertainties and biases, which are large in frontal boundary regions, and small in subtropical gyre interiors. These uncertainties and biases are used to reinterpret observed temporal trends in tracer-derived ventilation time scales taken from observations more than a decade apart, and to assess whether interpretations of changes in tracer ages being due to changes in ocean ventilation hold water. For the southern hemisphere subtropical gyres, we infer that the rate of ocean ventilation 26-27.2 σθ increased between the mid-1990s and the decade of the 2000s. However, between the mid-1990s and the decade of the 2010s, there is no significant trend—perhaps except for South Atlantic. Observed age/AOU/ventilation changes are linked to a combination of natural cycles and climate change, and there is regional variability. Thus, for the future it is not clear how strong or steady in space and time ocean ventilation changes will be.

Assessment of key transport parameters in a karst system under different dynamic conditions based on tracer experiments: the Jeita karst system, Lebanon

NASA Astrophysics Data System (ADS)

Doummar, Joanna; Margane, Armin; Geyer, Tobias; Sauter, Martin

2018-03-01

Artificial tracer experiments were conducted in the mature karst system of Jeita (Lebanon) under various flow conditions using surface and subsurface tracer injection points, to determine the variation of transport parameters (attenuation of peak concentration, velocity, transit times, dispersivity, and proportion of immobile and mobile regions) along fast and slow flow pathways. Tracer breakthrough curves (TBCs) observed at the karst spring were interpreted using a two-region nonequilibrium approach (2RNEM) to account for the skewness in the TBCs' long tailings. The conduit test results revealed a discharge threshold in the system dynamics, beyond which the transport parameters vary significantly. The polynomial relationship between transport velocity and discharge can be related to the variation of the conduit's cross-sectional area. Longitudinal dispersivity in the conduit system is not a constant value (α = 7-10 m) and decreases linearly with increasing flow rate because of dilution effects. Additionally, the proportion of immobile regions (arising from conduit irregularities) increases with decreasing water level in the conduit system. From tracer tests with injection at the surface, longitudinal dispersivity values are found to be large (8-27 m). The tailing observed in some TBCs is generated in the unsaturated zone before the tracer actually arrives at the major subsurface conduit draining the system. This work allows the estimation and prediction of the key transport parameters in karst aquifers. It shows that these parameters vary with time and flow dynamics, and they reflect the geometry of the flow pathway and the origin of infiltrating (potentially contaminated) recharge.

Anomalous, non-Gaussian tracer diffusion in crowded two-dimensional environments

NASA Astrophysics Data System (ADS)

Ghosh, Surya K.; Cherstvy, Andrey G.; Grebenkov, Denis S.; Metzler, Ralf

2016-01-01

A topic of intense current investigation pursues the question of how the highly crowded environment of biological cells affects the dynamic properties of passively diffusing particles. Motivated by recent experiments we report results of extensive simulations of the motion of a finite sized tracer particle in a heterogeneously crowded environment made up of quenched distributions of monodisperse crowders of varying sizes in finite circular two-dimensional domains. For given spatial distributions of monodisperse crowders we demonstrate how anomalous diffusion with strongly non-Gaussian features arises in this model system. We investigate both biologically relevant situations of particles released either at the surface of an inner domain or at the outer boundary, exhibiting distinctly different features of the observed anomalous diffusion for heterogeneous distributions of crowders. Specifically we reveal an asymmetric spreading of tracers even at moderate crowding. In addition to the mean squared displacement (MSD) and local diffusion exponent we investigate the magnitude and the amplitude scatter of the time averaged MSD of individual tracer trajectories, the non-Gaussianity parameter, and the van Hove correlation function. We also quantify how the average tracer diffusivity varies with the position in the domain with a heterogeneous radial distribution of crowders and examine the behaviour of the survival probability and the dynamics of the tracer survival probability. Inter alia, the systems we investigate are related to the passive transport of lipid molecules and proteins in two-dimensional crowded membranes or the motion in colloidal solutions or emulsions in effectively two-dimensional geometries, as well as inside supercrowded, surface adhered cells.

Field-scale sulfur hexafluoride tracer experiment to understand long distance gas transport in the deep unsaturated zone

USGS Publications Warehouse

Walvoord, Michelle Ann; Andraski, Brian J.; Green, Christopher T.; Stonestrom, David A.; Striegl, Robert G.

2014-01-01

A natural gradient SF6 tracer experiment provided an unprecedented evaluation of long distance gas transport in the deep unsaturated zone (UZ) under controlled (known) conditions. The field-scale gas tracer test in the 110-m-thick UZ was conducted at the U.S. Geological Survey’s Amargosa Desert Research Site (ADRS) in southwestern Nevada. A history of anomalous (theoretically unexpected) contaminant gas transport observed at the ADRS, next to the first commercial low-level radioactive waste disposal facility in the United States, provided motivation for the SF6 tracer study. Tracer was injected into a deep UZ borehole at depths of 15 and 48 m, and plume migration was observed in a monitoring borehole 9 m away at various depths (0.5–109 m) over the course of 1 yr. Tracer results yielded useful information about gas transport as applicable to the spatial scales of interest for off-site contaminant transport in arid unsaturated zones. Modeling gas diffusion with standard empirical expressions reasonably explained SF6 plume migration, but tended to underpredict peak concentrations for the field-scale experiment given previously determined porosity information. Despite some discrepancies between observations and model results, rapid SF6 gas transport commensurate with previous contaminant migration was not observed. The results provide ancillary support for the concept that apparent anomalies in historic transport behavior at the ADRS are the result of factors other than nonreactive gas transport properties or processes currently in effect in the undisturbed UZ.

First-in-Human Assessment of the Novel PDE2A PET Radiotracer 18F-PF-05270430

PubMed Central

Waterhouse, Rikki N.; Nabulsi, Nabeel; Lin, Shu-Fei; Labaree, David; Ropchan, Jim; Tarabar, Sanela; DeMartinis, Nicholas; Ogden, Adam; Banerjee, Anindita; Huang, Yiyun; Carson, Richard E.

2016-01-01

This was a first-in-human study of the novel phosphodiesterase-2A (PDE2A) PET ligand 18F-PF-05270430. The primary goals were to determine the appropriate tracer kinetic model to quantify brain uptake and to examine the within-subject test–retest variability. Methods: In advance of human studies, radiation dosimetry was determined in nonhuman primates. Six healthy male subjects participated in a test–retest protocol with dynamic scans and metabolite-corrected input functions. Nine brain regions of interest were studied, including the striatum, white matter, neocortical regions, and cerebellum. Multiple modeling methods were applied to calculate volume of distribution (VT) and binding potentials relative to the nondisplaceable tracer in tissue (BPND), concentration of tracer in plasma (BPP), and free tracer in tissue (BPF). The cerebellum was selected as a reference region to calculate binding potentials. Results: The dosimetry study provided an effective dose of less than 0.30 mSv/MBq, with the gallbladder as the critical organ; the human target dose was 185 MBq. There were no adverse events or clinically detectable pharmacologic effects reported. Tracer uptake was highest in the striatum, followed by neocortical regions and white matter, and lowest in the cerebellum. Regional time–activity curves were well fit by multilinear analysis-1, and a 70-min scan duration was sufficient to quantify VT and the binding potentials. BPND, with mean values ranging from 0.3 to 0.8, showed the best intrasubject and intersubject variability and reliability. Test–retest variability in the whole brain (excluding the cerebellum) of VT, BPND, and BPP were 8%, 16%, and 17%, respectively. Conclusion: 18F-PF-05270430 shows promise as a PDE2A PET ligand, albeit with low binding potential values. PMID:27103022

Tracer-Test Planning Using the Efficient Hydrologic Tracer ...

EPA Pesticide Factsheets

Hydrological tracer testing is the most reliable diagnostic technique available for establishing flow trajectories and hydrologic connections and for determining basic hydraulic and geometric parameters necessary for establishing operative solute-transport processes. Tracer-test design can be difficult because of a lack of prior knowledge of the basic hydraulic and geometric parameters desired and the appropriate tracer mass to release. A new efficient hydrologic tracer-test design (EHTD) methodology has been developed that combines basic measured field parameters (e.g., discharge, distance, cross-sectional area) in functional relationships that describe solute-transport processes related to flow velocity and time of travel. The new method applies these initial estimates for time of travel and velocity to a hypothetical continuously stirred tank reactor as an analog for the hydrologic flow system to develop initial estimates for tracer concentration and axial dispersion, based on a preset average tracer concentration. Root determination of the one-dimensional advection-dispersion equation (ADE) using the preset average tracer concentration then provides a theoretical basis for an estimate of necessary tracer mass.Application of the predicted tracer mass with the hydraulic and geometric parameters in the ADE allows for an approximation of initial sample-collection time and subsequent sample-collection frequency where a maximum of 65 samples were determined to be

Journal: A Review of Some Tracer-Test Design Equations for ...

EPA Pesticide Factsheets

Determination of necessary tracer mass, initial sample-collection time, and subsequent sample-collection frequency are the three most difficult aspects to estimate for a proposed tracer test prior to conducting the tracer test. To facilitate tracer-mass estimation, 33 mass-estimation equations are reviewed here, 32 of which were evaluated using previously published tracer-test design examination parameters. Comparison of the results produced a wide range of estimated tracer mass, but no means is available by which one equation may be reasonably selected over the others. Each equation produces a simple approximation for tracer mass. Most of the equations are based primarily on estimates or measurements of discharge, transport distance, and suspected transport times. Although the basic field parameters commonly employed are appropriate for estimating tracer mass, the 33 equations are problematic in that they were all probably based on the original developers' experience in a particular field area and not necessarily on measured hydraulic parameters or solute-transport theory. Suggested sampling frequencies are typically based primarily on probable transport distance, but with little regard to expected travel times. This too is problematic in that tends to result in false negatives or data aliasing. Simulations from the recently developed efficient hydrologic tracer-test design methodology (EHTD) were compared with those obtained from 32 of the 33 published tracer-

Test of synthetic DNA tracers in a periodic hydrodynamic system for time-variable transit time distribution assessment

NASA Astrophysics Data System (ADS)

Dahlke, H. E.; Wang, C.; McNew, C.; McLaughlin, S.; Lyon, S. W.

2016-12-01

Recent research on time-varying transport through hydrologic systems proposed using decomposed over-printed tracer breakthrough curves to directly observe transport through complex flow systems. This method, also known as the PERTH (Periodic Tracer Hierarchy) method requires periodic flow and multiple tracer injections to reveal changes in flow pathways and transport behavior. Time-variable transit time distributions (TTD) estimated from tracer breakthrough curves often vary with the storage state of the system, which in turn is influenced by internal and external variabilities, such as the arrangement of flow pathways and fluctuations in system inputs. Deciphering internal from external variabilities in TTDs might help to advance the use of TTDs for estimating the physical state of a system; however, thus far the finite number of unique conservative tracers available for tracing has limited deeper insights. Synthetic DNA tracers consisting of short strands of synthetic DNA encapsulated by polylactic acid (PLA) microspheres could potentially provide multiple unique tracers with identical transport properties needed to explore time varying transport through hydrologic systems in more detail. An experiment was conducted on the miniLeo hillslope, a 1 m3 sloping lysimeter, within the Biosphere 2 Landscape Evolution Observatory near Tucson, AZ to investigate transit time variability. The goal of the experiment was to 1) test the suitability of using synthetic DNA tracers for estimating TTDs in a hydrologic system and 2) to determine the TTDs of individual tracer pulses under periodic steady-state conditions. Five DNA tracers, consisting of four unique, encapsulated DNA sequences and one free/non-encapsulated DNA sequence, were applied as reference and probe tracers together with deuterium, using the PERTH method. The lysimeter received three 2-hour pulses of rainfall at a rate of 30 mm/hr for 10 days. Initial results show that both the encapsulated and free DNA tracers were successfully transported in a pulsed manner through the system, but had overall longer breakthrough times than the reference deuterium tracer. Comparison of the DNA probe tracers indicate differences in transit times, likely related to differences in tracer mobilization in response to the time-variant rainfall input.

Technical Note: Coupling of chemical processes with the Modular Earth Submodel System (MESSy) submodel TRACER

NASA Astrophysics Data System (ADS)

Jöckel, P.; Kerkweg, A.; Buchholz-Dietsch, J.; Tost, H.; Sander, R.; Pozzer, A.

2008-03-01

The implementation of processes related to chemistry into Earth System Models and their coupling within such systems requires the consistent description of the chemical species involved. We provide a tool (written in Fortran95) to structure and manage information about constituents, hereinafter referred to as tracers, namely the Modular Earth Submodel System (MESSy) generic (i.e., infrastructure) submodel TRACER. With TRACER it is possible to define a multitude of tracer sets, depending on the spatio-temporal representation (i.e., the grid structure) of the model. The required information about a specific chemical species is split into the static meta-information about the characteristics of the species, and its (generally in time and space variable) abundance in the corresponding representation. TRACER moreover includes two submodels. One is TRACER_FAMILY, an implementation of the tracer family concept. It distinguishes between two types: type-1 families are usually applied to handle strongly related tracers (e.g., fast equilibrating species) for a specific process (e.g., advection). In contrast to this, type-2 families are applied for tagging techniques. Tagging means the artificial decomposition of one or more species into parts, which are additionally labelled (e.g., by the region of their primary emission) and then processed as the species itself. The type-2 family concept is designed to conserve the linear relationship between the family and its members. The second submodel is TRACER_PDEF, which corrects and budgets numerical negative overshoots that arise in many process implementations due to the numerical limitations (e.g., rounding errors). The submodel therefore guarantees the positive definiteness of the tracers and stabilises the integration scheme. As a by-product, it further provides a global tracer mass diagnostic. Last but not least, we present the submodel PTRAC, which allows the definition of tracers via a Fortran95 namelist, as a complement to the standard tracer definition by application of the TRACER interface routines in the code. TRACER with its submodels and PTRAC can readily be applied to a variety of models without further requirements. The code and a documentation are included in the electronic supplement.

LARGE-SCALE NATURAL GRADIENT TRACER TEST IN SAND AND GRAVEL, CAPE COD, MASSACHUSETTS - 1. EXPERIMENTAL DESIGN AND OBSERVED TRACER MOVEMENT

EPA Science Inventory

A large-scale natural gradient tracer experiment was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. The nonreactive tracer, bromide, and the reactive tracers, lithium and molybdate, were injected as a pulse i...